US8833975

US008833975B2
(12) United States Patent (10) Patent No.: US 8,833,975 B2

Kishimoto et al. (45) Date of Patent: Sep. 16, 2014
(54) LIGHT-EMITTING DEVICE, ILLUMINATING (56) References Cited
DEVICE, VEHICLE HEADLAMP, AND
METHOD FOR PRODUCING U.S. PATENT DOCUMENTS
LIGHT-EMITTING DEVICE
7,588,351 B2* 9/2009 Meyer ........................... 362,294
2005, 01 05301 A1 5/2005 Takeda et al.
(75) Inventors: Katsuhiko Kishimoto, Osaka (JP); 2006/027995.0 A1 12/2006 Hama et al.
Hidenori Kawanishi, Osaka (JP) 2007, 0080362 A1 4/2007 Scotch et al.
2007/O131954 A1 6/2007 Murayama et al.
(73) Assignee: Sharp Kabushiki Kaisha, Osaka-shi 2008.O290357 A1 11/2008 Lin et al.
2009/004O781 A1 2, 2009 to
(JP) 2009/0095960 A1 4/2009 Murayama
2011/0051449 A1 3/2011 Bieblet al.
(*) Notice: Subject to any disclaimer, the term of this 2012fOO39072 A1 2/2012 Lell et al.
patent is extended or adjusted under 35
U.S.C. 154(b) by 464 days. FOREIGN PATENT DOCUMENTS
(21) Appl. No.: 13/222,772 JP 2005-150041 6, 2005

JP 2005-294.185 10/2005
JP 2007-27688 2, 2007
(22) Filed: Aug. 31, 2011 JP 2007-294.754 11, 2007
JP 2007-335514 12/2007
(65) Prior Publication Data
US 2012/OO57364 A1 Mar. 8, 2012
(Continued)
OTHER PUBLICATIONS
(30) Foreign Application Priority Data Sasaki, M. (2005). "Applications of White LED Lighting to Automo
Sep. 7, 2010 (JP) ................................. 2010-199958 bile Onboard Devices.” Oyo Buturi 74(11): 1463-1466.
Sep. 7, 2010 (JP) ................................. 2010-199959 Primary Examiner — Stephen F Husar
Dec. 28, 2010 (JP) ................................. 2010-294098 (74) Attorney, Agent, or Firm — Morrison & Foerster LLP
Dec. 28, 2010 (JP) ................................. 2010-294.100
(57) ABSTRACT
(51) Int. Cl.
F2IV 29/00 (2006.01) A headlamp disclosed includes: a laser diode for emitting a
F2IV 9/16 (2006.01) laser beam; a light emitting section including a fluorescent
F2IS 8/10 (2006.01) material which emits light in response to excitation light
F2I Y IOI/O2 (2006.01) emitted from the laser diode; a light-transmitting heat con
ducting member which is provided so as to face a laser beam
(52) U.S. Cl. irradiation Surface of the light emitting section and receive
CPC ................. F2IV 9/16 (2013.01); F2IS 48/321 heat of the light emitting section; and an adhesive layer filling
(2013.01); F2IS 48/115 (2013.01); F2IS a gap between the heat conducting member and the laser
48/1241 (2013.01); F2IV 29/004 (2013.01); beam irradiation Surface. This arrangement improves effi
F2IY 2101/025 (2013.01) ciency of the heat conducting member in absorbing the heat of
USPC .............. 362/294; 362/84; 362/260; 362/373 the light emitting section, and consequently cools the light
(58) Field of Classification Search emitting section efficiently.
USPC ............................ 362/84, 259,260, 294,373
See application file for complete search history. 13 Claims, 22 Drawing Sheets
US 8,833,975 B2
Page 2
(56) References Cited JP 2008-294438 12/2008

JP 2009-394.38 2, 2009
JP 2009-513003 3, 2009
FOREIGN PATENT DOCUMENTS WO WO-2009,089.903 T 2009
WO WO-2010/069282 6, 2010
JP 2008-28245 2, 2008
JP 2008-53477 3, 2008 * cited by examiner
U.S. Patent Sep. 16, 2014 Sheet 1 of 22 US 8,833,975 B2
FIG. 1
§2
4,2€.
FIG. 2
CONDUCTION OF HEAT
FIG. 3
15 16 J 17
$4717.
:
:-
13
FIG. 4
FIG. 5
6 LASER BEAM E.
(EXCITATION LIGHT)f
D
CONDUCTION OF HEAT
FIG. 6
FIG. 7
FIG. 8
FIG. 9
<!Z2,
FIG 10
FIG. 11
N
N
U.S. Patent Sep. 16, 2014 Sheet 10 Of 22 US 8,833,975 B2
FIG, 12
FIG. 13
LASER BEAM ::g

(EXCITATION LIGHT):
N:
Ži 3 ( )
FIG. 14
, ,,, ,
6 LASER BEAM :::::

(EXCITATION LIGHT):0::
:: G
H2
'' ' %
FIG. 15
FIG 16
- DIRECTION
Ø@ - DIRECTION
OWER DIRECTION
NN)
FIG. 17
FIG. 18
LASER BEAM :
(EXCITATION LIGHT)
O MCONDUCTION
OF HEAT
7a-1:
CONDUCTION OF HEAT
FIG. 19
FIG. 20
LASER BEAM
314a
314b
(EXCITATIONLIGHT)
D CONDUCTION > 141
7a-1, OF HEAT
314
CONDUCTION OF HEAT
FIG. 21
BON) HOO MEBER

O HEA CONDUCNG MEMBER
FIG. 23
FIG. 24
410 5 601
O ...TOLD LIGHT
SOURCE UNIT 420
JLIGHT JLIGHT ULIGHT 600
FIG. 25
400
t g A
411
Z / 2' total oil

41243 J LGHT
600 602 5
E:
:::::::
411 412 15 7 13 410
-----> ELECTRICAL OUTET

h 600
FIG. 28
LED DOWNLIGHT LASER DOWNLIGHT

500 400
EXTERNAL DIMENSION DIAMETER 117 x 9mm DAMETER 60 x 20mm
DMENSION OF INSERTONHOLE DIAMETER 100m
HEIGHT OF UNEXPOSED PORTION

US 8,833,975 B2
1. 2
LIGHT-EMITTING DEVICE, ILLUMINATING is thermally connected to the ferrule. This arrangement
DEVICE, VEHICLE HEADLAMP, AND reduces heat generated by the wavelength converting mem
METHOD FOR PRODUCING ber.
LIGHT-EMITTING DEVICE Patent Literature 4 discloses an invention which includes a
heat dissipating member having a passage for allowing a
This Nonprovisional application claims priority under 35 refrigerant to flow. The heat dissipating member is disposed at
U.S.C. S 119(a) on (i) Patent Application No. 2010-199958 Such a location as to face a Surface of a light converting
filed in Japan on Sep. 7, 2010, (ii) Patent Application No. member (corresponding to a light emitting section) which
2010-199959 filed in Japan on Sep. 7, 2010, (iii) Patent Appli Surface is present on a side on which a semiconductor light
cation No. 2010-294098 filed in Japan on Dec. 28, 2010, and
10 emitting element is present. This arrangement cools the light
(iv) Patent Application No. 2010-294.100 filed in Japan on converting member.
Dec. 28, 2010, the entire contents of all of which are hereby Patent Literature 5 discloses an arrangement of thermally
incorporated by reference. connecting a light-transmitting heat sink to a Surface of a
high-output LED chip serving as a light source. This arrange
TECHNICAL FIELD
15 ment cools the high-output LED chip.
CITATION LIST
The present invention relates to (i) a light emitting device
functioning as a high-luminance light source and (ii) an illu Patent Literature 1
minating device and a vehicle headlamp each including the Japanese Patent Application Publication, Tokukai, No.
light emitting device. 2005-150041 A (Publication Date: Jun. 9, 2005)
Patent Literature 2
BACKGROUND ART
Japanese Patent Application Publication, Tokukai, No.
2007-27688A (Publication Date: Feb. 1, 2007)
In recent years, studies have been intensively carried out 25 Patent Literature 3
for a light emitting device that uses, as illumination light, Japanese Patent Application Publication, Tokukai, No.
fluorescence emitted from a light emitting section (wave 2007-335514 A (Publication Date: Dec. 27, 2007)
length converting member) which includes a fluorescent Patent Literature 4
material. The light emitting section emits the fluorescence Japanese Patent Application Publication, Tokukai, No.
upon irradiation with excitation light which is emitted from 30 2005-294.185 A (Publication Date: Oct. 20, 2005)
an excitation light Source. The excitation light Source is a Patent Literature 5
semiconductor light emitting element such as a light emitting Japanese Patent Application Publication (Translation of
diode (LED) and a laser diode (LD). PCT Application), Tokuhyo, No. 2009-513003 (Publication
Patent Literature 1 discloses a lamp as an example tech Date: Mar. 26, 2009)
35
nique related to Such a light emitting device. In order to SUMMARY OF INVENTION
produce a high-luminance light source, the lamp disclosed in
Patent Literature 1 includes a laser diode as the excitation
Technical Problem
light source. Laser beams emitted from the laser diode are
coherent light: These laser beams have strong directivity, and 40 In a case where a light emitting section with no heat con
therefore can be converged and used as the excitation light ducting member provided is irradiated with excitation light
without waste. A light emitting device (hereinafter referred to having a high output and a highlight density, a portion of the
as “LD light-emitting device') including Such a laser diode as light emitting section which portion is irradiated with the
the excitation light source is suitably applicable for vehicle excitation light will locally have a raised temperature. In
headlamps. The use of a laser diode as an excitation light 45 comparison, in a case where a light emitting section is in
Source allows production of a high-luminance light Source contact with a light-transmitting heat conducting member and
which could not otherwise be produced with use of an LED. is irradiated with excitation light via the light-transmitting
In a case where such laser beams are used as excitation heat conducting member, it is possible to prevent a tempera
light, the excitation light irradiates and is thus absorbed by a ture rise in the vicinity of an excitation light irradiation Sur
minute light emitting section, that is, a light emitting section 50 face, that is, a portion of the light emitting section which
having an extremely small Volume. The excitation light, how portion would have a temperature that has been raised most.
ever, includes a component which is not converted into fluo Patent Literatures 2 through 5 each disclose an arrange
rescence by a fluorescent material and which is instead con ment that thermally connects (i) a first member in which a
Verted into heat. Such a component easily raises a temperature rise occurs, the first member being, for example,
temperature of the light emitting section, and consequently 55 a wavelength converting member, a light converting member,
impaired properties of the light emitting section or thermally or a high-output LED (hereinafter collectively referred to as
damages the light emitting section. “light emitting section') to (ii) a second member which con
To solve the above problem, Patent Literature 2 discloses ducts heat generated by the light emitting section, the second
an invention which includes a light-transmitting heat con member being, for example, a heat conducting member, a
ducting member that is in a shape of a thin film and that is 60 heat dissipating member, or a heat sink (hereinafter collec
thermally connected to a wavelength converting member tively referred to as “heat conducting member'). This
(corresponding to a light emitting section). The heat conduct arrangement reduces heat generated by the light emitting
ing member reduces heat generated by the wavelength con section.
Verting member. However, in an arrangement in which (i) a light emitting
Patent Literature 3 discloses an invention which includes 65 section is a member separate from a heat conducting member
(i) a cylindrical ferrule that Supports a wavelength converting and (ii) the heat conducting member is in contact with a
member and (ii) a wire-shaped heat conducting member that Surface of the light emitting section, the heat conducting
US 8,833,975 B2
3 4
member has a decreased heat absorption efficiency because emitting section. This is because if the heat conducting mem
the light emitting section is separated from the heat conduct ber has a shape, such as a film shape and a layer shape, which
ing member by a gap. The inventors of the present invention renders the heat conducting member easily breakable by an
have found this problem as a result of diligent studies, and external force, the pressure applied as above will break the
none of the above Patent Literatures teaches a method for heat conducting member.
Solving this problem. The inventors of the present invention have further found
The invention of Patent Literature 2, for example, forms a the following problem: A light emitting section has a heat
heat conductive layer as the heat conducting member on a dissipation efficiency which greatly varies at different por
Surface of the light emitting section by a method such as tions depending on where a light-transmitting heat conduct
sputtering, deposition, and plating. Thus, the light emitting 10 ing member is positioned. In a case where the light emitting
section and the heat conducting member are not provided section is irradiated with intense excitation light, a portion of
separately from each other. Further, Patent Literature 2 states the light emitting section which portion is farther away from
that the heat conductive layer is preferably approximately the heat conducting member has a higher temperature. This
from 1 um to 100 um in thickness. This indicates an insuffi may lead to a significant decrease in luminous efficiency of
cient heat dissipation effect. In addition, the invention of 15 the light emitting section or a reduction in life of the light
Patent Literature 2 includes an optical fiber as an essential emitting section.
constituent. In particular, in the invention of Patent Literature 2, the
The invention of Patent Literature 4 forms the light emit light emitting section is inseparable from the heat conducting
ting section (light converting member) on a Surface of the heat member having a film shape or a layer shape. It is thus difficult
dissipating memberby, for example, screen printing or inkjet to fix the light emitting section with use of Such a heat con
application. Thus, the light emitting section and the heat ducting member so that the light emitting section is Supported
conducting member are not provided separately from each by the heat conducting member. This is because the heat
other. conducting member (i) has a shape, such as a film shape and
In a case where a light emitting section is repeatedly irra a layer shape, which renders the heat conducting member
diated with excitation light over time, the light emitting sec 25 easily breakable by an external force, and (ii) is thus too
tion may generate heat in an extremely large amount. In this fragile to support the light emitting section.
case, however much the heat generated by the wavelength The above conventional arrangements each focus on how
converting member is dissipated via a heat conducting mem to cool a light emitting section. None of the above Patent
ber, Such heat generated by the light emitting section may not Literatures discloses a technical idea of utilizing heat gener
be reduced sufficiently if an amount of the heat generation 30 ated by a light emitting section.
greatly exceeds an amount of the heat dissipation. The invention of Patent Literature 1 pays attention to heat
Such a situation gives rise to a difference in thermal expan dissipation for a laser diode element, but pays no attention to
sion between the light emitting section and the heat conduct heat dissipation for a light emitting section. Further, the
ing member, the difference arising from a difference in coef invention of Patent Literature 1 includes a light-transmitting
ficient of thermal expansion between them. The difference in 35 member which fixes a light emitting section, the light-trans
thermal expansion weakens close contact between the light mitting member being positioned outside the light emitting
emitting section and the heat conducting member in a case section as viewed from the laser diode element. Patent Lit
where they are adhered to each other via an adhesive. Further, erature 1 thus fails to disclose an arrangement in which a laser
in a case where the light emitting section is provided, on a beam is emitted to a light emitting section through a light
surface thereof, with a heat conducting member formed in the 40 transmitting heat conducting member.
shape of a thin film, the heat conducting member may be The invention of Patent Literature 3 includes (i) a ferrule
detached from the light emitting section. provided at an endofan optical fiberand (ii) aheat conducting
Such weakening in close contact between the light emitting member thermally connected to the ferrule. Patent Literature
section and the heat conducting member naturally impairs 3 thus fails to disclose the arrangement in which a laser beam
reliability of thermal connection between them. Further, in a 45 is emitted to a light emitting section through a light-transmit
case where, for example, the light emitting section is Sup ting heat conducting member.
ported by the heat conducting member, the above reduction The invention of Patent Literature 4 involves no light
makes it difficult to keep Supporting the light emitting section transmitting heat conducting member.
at a predetermined location. In other words, the reduction The invention of Patent Literature 5 is related to heat dis
results in a positional shift of the light emitting section. 50 sipation of an LED chip. Patent Literature 5 thus fails to
A light emitting section is positioned relative to an excita disclose the arrangement in which a laser beam is emitted to
tion light source Such as a laser diode so that the light emitting a light emitting section through a light-transmitting heat con
section is efficiently irradiated with excitation light emitted ducting member.
by the excitation light source. A positional shift of the light The present invention has been accomplished to solve the
emitting section will thus greatly reduce efficiency in irradia 55 above problems. It is a first object of the present invention to
tion with excitation light. provide a light-emitting device, an illuminating device, and a
In a case where a light emitting section closely contacts a vehicle headlamp, in each of which, in an arrangement in
heat conducting member and is thus fixed at a location, a which a light emitting section is provided separately from a
difference in thermal expansion will weaken close contact heat conducting member for absorbing heat of the light emit
between the light emitting section and the heat conducting 60 ting section, the heat conducting member has an improved
member as described above, and may further cause the light heat absorption efficiency so that the light emitting section
emitting section to drop. can be cooled efficiently.
In the invention of Patent Literature 2, in particular, the It is a second object of the present invention to provide a
light emitting section is inseparable from the heat conducting light-emitting device, an illuminating device, and a vehicle
member having the shape of a thin film Such as a film shape or 65 headlamp in each of which a light emitting section closely
a layer shape. Thus, if the heat conducting member has been contacting and thus Supported by a Supporting member can
detached, it becomes difficult to keep Supporting the light keep Supported by the Supporting member even if close con
US 8,833,975 B2
5 6
tact between the light emitting section and the Supporting light, a portion of the excitation light is converted not into
member weakens due to heat generated by the light emitting fluorescence but into heat, which in turn raises a temperature
section. of the light emitting section. The heat is first conducted to the
It is a third object of the present invention to provide a first heat conducting member, connected to the light emitting
light-emitting device, an illuminating device, a vehicle head section so that heat can be conducted thereto, and is then
lamp, and a method for producing a light-emitting device in conducted to a member different from the first heat conduct
each of which a heat conducting member that absorbs heat of ing member for use in the different member. The heat is used
a light emitting section is positioned so as to improve its heat to, for example, (i) prevent or remove dew condensation, (ii)
absorption efficiency and to prevent a temperature rise in the prevent freezing or unfreeze, or (iii) thaw Snow.
light emitting section. 10 The above arrangement allows effective use of heat of the
It is a fourth object of the present invention to provide a light emitting section, and thus eliminates the need to con
light-emitting device and a vehicle headlamp each of which Sume extra energy in order to, for example, thaw Snow.
effectively utilizes heat of a light emitting section. In order to solve the above problem, a light-emitting device
of the present invention includes: a light emitting section for
Solution to Problem 15 emitting illumination light in response to excitation light
emitted from an excitation light source: a Supporting member
In order to solve the above problem, a light-emitting device for Supporting the light emitting section at Such a location that
of the present invention includes: an excitation light Source the light emitting section is irradiated with the excitation
for emitting excitation light; a light emitting section including light; and a fall preventing mechanism which is in contact
a fluorescent material which emits light in response to the with at least part of an outer Surface of the light emitting
excitation light, the light emitting section having an excita section and which, in a case where the Supporting member has
tion light irradiation surface which is irradiated with the exci become unable to support the light emitting section, prevents
tation light; a light-transmitting heat conducting member the light emitting section from falling off the Supporting
which is provided so as to (i) face the excitation light irradia member.
tion Surface and (ii) receive heat of the light emitting section; 25 The light emitting section, which emits light upon receipt
and a gap layer which fills a gap between the heat conducting of excitation light, generates heat while emitting light as it is
member and the excitation light irradiation Surface. irradiated with the excitation light. In a case where the light
The above arrangement achieves the following: The light emitting section is repeatedly irradiated with the excitation
emitting section emits light in response to excitation light, a light, the light emitting section generates an increasing
portion of which is converted into heat. The light emitting 30 amount of heat. This leads to a difference in thermal expan
section thus generates heat. The heat conducting member, sion between the Supporting member and the light emitting
provided so as to face the excitation light irradiation surface section due to a difference in coefficient of thermal expansion
of the light emitting section, absorbs heat of the light emitting between them.
section so as to cool the light emitting section. Since the heat Thus, in a case where the light emitting section closely and
conducting member transmits light, the excitation light 35 fixedly contacts the Supporting member via an adhesive or a
passes through the heat conducting member and reaches the close contact material Such as grease without use of the fall
light emitting section. preventing mechanism, the above difference in thermal
The fluorescent material included in the light emitting sec expansion causes a mechanical stress to a portion at which the
tion has a diameter ranging from 1 to 20 Jum. In a case where Supporting member and the light emitting section closely
the fluorescent material is present along the excitation light 40 contact each other, and thus weakens close contact at the close
irradiation Surface of the light emitting section, bringing the contact portion. This makes it difficult for the Supporting
excitation light irradiation Surface into contact with a Surface member to keep Supporting the light emitting section, possi
of the light-transmitting heat conducting member (made of bly letting the light emitting section fall.
Sapphire, for example) leaves a relatively large gap between In view of this, the above arrangement causes the fall
them. The gap Substantially reduces a region (area of contact) 45 preventing mechanism to be in contact with at least a portion
by which the excitation light irradiation Surface is in contact of the outer Surface of the light emitting section so as to
with the heat conducting member. The present invention pro prevent the light emitting section from falling off the Support
vides a gap layer between the heat conducting member and ing member.
the excitation light irradiation Surface So as to fill the gap. The Thus, even in the case where the difference in thermal
gap layer Substantially increases the area of contact between 50 expansion between the Supporting member and the light emit
the heat conducting member and the excitation light irradia ting section causes a mechanical stress, which in turn weak
tion Surface. ens close contact at the above-mentioned portion at which the
The above arrangement thus allows heat generated by the Supporting member and the light emitting section closely
light emitting section to be efficiently dissipated with use of contact each other, the above arrangement prevents the light
the heat conducting member (that is, improves heat absorp 55 emitting section from falling off the Supporting member. The
tion efficiency of the heat conducting member). Supporting member can thus keep Supporting the light emit
In order to solve the above problem, a light-emitting device ting section.
of the present invention includes: an excitation light Source In order to solve the above problem, a light-emitting device
for emitting excitation light; a light emitting section which of the present invention includes: an excitation light Source
emits light in response to the excitation light; and a first heat 60 for emitting excitation light; a light emitting section including
conducting member connected to the light emitting section so a fluorescent material which emits light in response to the
as to receive heat from the light emitting section, the first heat excitation light, the light emitting section having an excita
conducting member being provided so as to conduct the heat tion light irradiation surface which is irradiated with the exci
to a member different from the first heat conducting member tation light; a first heat conducting member which is provided
for use in the different member. 65 So as to (i) face the excitation light irradiation Surface and (ii)
The above arrangement achieves the following: When the receive heat of the light emitting section; and a second heat
light emitting section emits light in response to excitation conducting member which is provided so as to (i) face an
US 8,833,975 B2
7 8
opposite Surface of the light emitting section which opposite a problem of a positional shift of the heat conducting mem
Surface is opposite to the excitation light irradiation Surface bers relative to each other and (ii) a problem of a fall of either
and (ii) receive heat of the light emitting section. of the heat conducting members.
The above arrangement achieves the following: The light
emitting section emits light upon receipt of excitation light Advantageous Effects of Invention
emitted from the excitation light source. The excitation light
is partially converted into heat. The light emitting section thus As described above, a light-emitting device of the present
generates heat. The light emitting section has a temperature invention includes: an excitation light source for emitting
rise over the excitation light irradiation surface, from which excitation light; a light emitting section including a fluores
the first heat conducting member receives heat. 10
cent material which emits light in response to the excitation
The first heat conducting member is lower in heat dissipa light, the light emitting section having an excitation light
tion efficiency for a portion of the light emitting section which irradiation surface which is irradiated with the excitation
portion is farther away from the excitation light irradiation light; a light-transmitting heat conducting member which is
Surface. However, the second heat conducting member provided so as to (i) face the excitation light irradiation Sur
receives heat from the opposite Surface of the light emitting 15
face and (ii) receive heat of the light emitting section; and a
section, the opposite Surface beingaportion which is opposite
to the excitation light irradiation surface and for which the gap layer which fills a gap between the heat conducting mem
first heat conducting member is lowest in heat dissipation ber and the excitation light irradiation Surface.
efficiency. The above arrangement allows heat generated by the light
As described above, the heat conducting members can be emitting section to be efficiently dissipated with use of the
used to efficiently dissipate heat generated by the light emit heat conducting member.
ting section (that is, improve heat absorption efficiency of the As described above, a light-emitting device of the present
heat conducting members). This makes it possible to prevent invention includes: an excitation light source for emitting
a temperature rise in the light emitting section. excitation light; a light emitting section which emits light in
The excitation light irradiation Surface and the opposite 25 response to the excitation light; and a first heat conducting
Surface opposite to the excitation light irradiation Surface are member connected to the light emitting section so as to
each a flat Surface in a case where, for example, the light receive heat from the light emitting section, the first heat
emitting section is in a cuboid or cube shape. The light emit conducting member being provided so as to conduct the heat
ting section is naturally not limited in shape to a cuboid or a to a second member for use in the second member.
cube, and may be in any shape as long as the light emitting 30
The above arrangement allows effective use of heat of the
section has a Solid body having a three dimensional spatial light emitting section, and thus eliminates the need to con
extent. In a case where, for example, the light emitting section Sume extra energy in order to, for example, thaw Snow.
is in a spherical shape, the above Surfaces are each a spherical As described above, a light-emitting device of the present
surface. The above surfaces, as described above, each vary invention includes: a light emitting section for emitting illu
according to the shape of the light emitting section. 35
mination light in response to excitation light emitted from an
In order to solve the above problem, a method of the excitation light source; a Supporting member for Supporting
present invention for producing a light-emitting device
includes the steps of forming a heat conducting member in a the light emitting section at Such a location that the light
shape of a cup; sintering inside the cup-shaped heat conduct emitting section is irradiated with the excitation light; and a
ing member a combination of (i) a fluorescent material and 40 fall preventing mechanism which is in contact with at least
(ii) a fluorescent material retention Substance, having a melt part of an outer Surface of the light emitting section and
ing point lower than a melting point of the cup-shaped heat which, in a case where the Supporting member has become
conducting member, so as to form a light emitting section; unable to Support the light emitting section, prevents the light
polishing the light emitting section and the cup-shaped heat emitting section from falling off the Supporting member.
conducting member to make a planar Surface including an 45 With the above arrangement, a light emitting section
opening of the cup-shaped heat conducting member, and adhered to and thus Supported by a Supporting member can
bonding (i) the cup-shaped heat conducting member to (ii) a keep Supported by the Supporting member even if close con
second heat conducting member, having a planar Surface at tact between the light emitting section and the Supporting
least at a portion, so that the respective planar Surfaces of the member weakens due to heat generated by the light emitting
cup-shaped heat conducting member and the second heat 50 section.
conducting member face each other. As described above, a light-emitting device of the present
According to the above method, the forming step forms a invention includes: an excitation light source for emitting
heat conducting member in a desired cup shape so that the excitation light; a light emitting section including a fluores
sintering step automatically forms a light emitting section cent material which emits light in response to the excitation
which closely contacts an inner Surface of the cup. The 55 light, the light emitting section having an excitation light
method thus improves a thermal bond of the light emitting irradiation surface which is irradiated with the excitation
section to the cup-shaped heat conducting member, and sim light; a first heat conducting member which is provided so as
plifies a production process. This remarkably improves a to (i) face the excitation light irradiation Surface and (ii)
production yield as a result. receive heat of the light emitting section; and a second heat
Further, the polishing step and the bonding step cause the 60 conducting member which is provided so as to (i) face an
light emitting section to strongly bond to a second heat con opposite surface of the light emitting section which opposite
ducting member via a surface including an opening of the Surface is opposite to the excitation light irradiation Surface
cup-shaped heat conducting member. This improves heat dis and (ii) receive heat of the light emitting section.
sipation efficiency of the second heat conducting member With the above arrangement, a heat conducting member
with respect to the light emitting section. 65 that absorbs heat of a light emitting section is positioned so as
In addition, the above method causes the heat conducting to improve its heat absorption efficiency and to prevent a
members to bond strongly to each other, and thus prevents (i) temperature rise in the light emitting section.
US 8,833,975 B2
9 10
BRIEF DESCRIPTION OF DRAWINGS downlight of an embodiment of the present invention and (ii)
a conventional LED downlight.
FIG. 1 is a cross-sectional view illustrating a configuration FIG. 24 is a cross sectional view illustrating a ceiling on
of a headlamp in accordance with a first embodiment of the which the laser downlight is disposed.
present invention. FIG.25 is a cross sectional view illustrating the laser down
FIG. 2 is a structural view illustrating how a light emitting light.
section and a heat conducting member both included in the FIG. 26 is a cross sectional view illustrating a variation of
headlamp are adhered to each other with use of an adhesive how to dispose the laser downlight.
layer. 10
FIG. 27 is a cross sectional view illustrating a ceiling on
FIG. 3 is a cross-sectional view illustrating a preferable which the LED downlight is disposed.
example of a diffusing agent. FIG. 28 is a table comparing specifications of the laser
FIG.4(a)is a diagram schematically illustrating a circuit of downlight and those of the LED downlight.
a laser diode, and (b) is a perspective view illustrating a basic
configuration of the laser diode. DESCRIPTION OF EMBODIMENTS
15
FIG. 5 is a cross-sectional view illustrating a variation of
the light emitting section. Embodiment 1
FIG. 6 is a view illustrating specific examples of the light
emitting section and the heat conducting member both The following describes a first embodiment of the present
included in the headlamp. invention with reference to FIGS. 1 through 6. In the first
FIG. 7 is a view schematically illustrating a configuration embodiment, a vehicle headlamp (light emitting device; illu
ofaheadlamp in accordance with a second embodiment of the minating device; vehicle headlamp) 1 is described as an
present invention. example of an illuminating device of the present invention.
FIG. 8(a) through (c) are each a view illustrating a variation The illuminating device of the present invention may, how
of a fixing section, and (d) is a view illustrating a configura 25 ever, be in the form of (i) aheadlamp for a vehicle or a moving
tion in which a light emitting section is connected to a heat object other than a vehicle (e.g., a human, a ship, an aircraft,
conducting member via an adhesive layer. a Submarine, and a rocket), or (ii) other illuminating devices.
FIG.9 is a cross-sectional view illustrating a configuration The other illuminating devices encompass, for example, a
of a headlamp in accordance with a third embodiment of the searchlight, a projector, a streetlight, a traffic light, and a
present invention. 30 home illuminating device.
FIG. 10 is a view schematically illustrating a configuration The headlamp 1 may comply with (i) a light distribution
of a headlamp in accordance with a fourth embodiment of the characteristic standard of a running headlamp (high beam) or
present invention. (ii) a light distribution characteristic standard of a dipped
FIG. 11 is a cross-sectional view illustrating a configura headlamp (low beam).
tion of a headlamp in accordance with a fifth embodiment of 35 (Configuration of Headlamp 1)
the present invention. The description below first deals with a configuration of the
FIG. 12 is a structural view illustrating how a light emitting headlamp 1 with reference to FIG. 1. FIG. 1 is a cross
section and a Supporting member both included in the head sectional view illustrating the configuration of the headlamp
lamp closely contacts each other with use of a gap layer and 1. As illustrated in FIG. 1, the headlamp 1 includes a laser
SCCWS. 40 diode array 2, aspherical lenses 4, an optical fiber 5, a ferrule
FIG. 13 is a view schematically illustrating a first variation 6, a light emitting section 7, a reflecting mirror 8, a transparent
of the headlamp. plate 9, a housing 10, an extension 11, a lens 12, a heat
FIG. 14 is a view schematically illustrating a second varia conducting member 13, a cooling section 14, and an adhesive
tion of the headlamp. layer 15. The adhesive layer 15 functions as a gap layer filling
FIG. 15 is a view schematically illustrating a third variation 45 a gap between the heat conducting member 13 and the light
of the headlamp. emitting section 7. Further, as illustrated in FIG. 2, the adhe
FIG.16 is a view schematically illustrating a configuration sive layer 15 includes a diffusing agent 16. FIG. 2 is a struc
of a headlamp in accordance with a sixth embodiment of the tural diagram illustrating how the light emitting section 7 and
present invention. the heat conducting member 13 are adhered to each other with
FIG. 17 is a cross-sectional view illustrating a configura 50 use of the adhesive layer 15.
tion of a headlamp in accordance with a seventh embodiment (Laser Diode Array 2 and Laser Diode 3)
of the present invention. The laser diode array 2 functions as an excitation light
FIG. 18 is a structural view illustrating how a light emitting Source which emits excitation light, and includes a plurality
section and a heat conducting member both included in the of laser diodes (excitation light sources) 3 that are provided
headlamp are adhered to each other with use of a hollow 55 on a substrate. Each of the laser diodes 3 emits a laser beam as
member, where (a) is a cross-sectional view illustrating the excitation light. It is not always necessary to use a plurality of
structure, and (b) is a perspective view of the structure. the laser diodes 3 as the excitation light source: The laser
FIG. 19 is a cross-sectional view illustrating a first varia diode array 2 may alternatively include a single laser diode 3.
tion of the hollow member. It is, however, easier to use a plurality of laser diodes 3 in
FIG. 20 is a cross-sectional view illustrating a second 60 order to obtain a high-output laser beam.
variation of the hollow member. The laser diodes 3 each have a single light emitting point
FIG. 21(a) through (c) are each a perspective view illus per chip and emit a laser beam of for example, 405 nm
trating a variation of the hollow member. (violet). The laser diode 3 has an output of 1.0 W, an operating
FIG.22 is a flowchart showing steps of a process involved Voltage of 5 V, and an operating current of 0.6 A, and is
in a method for producing the headlamp. 65 contained in a package that has a diameter of 5.6 mm. The
FIG. 23 is a view schematically illustrating external laser beam emitted from the laser diode 3 is not limited to a
appearances of (i) a light emitting unit included in a laser laser beam of 405 nm, and may be any laser beam as long as
US 8,833,975 B2
11 12
the laser beam has a peak wavelength in a wavelength range hardly has any absorption loss of a laser beam. The clad
of not less than 380 nm but not more than 470 nm. includes, as its main component, quartz glass or a synthetic
If it is possible to produce a high-quality shortwavelength resin material, each of which has a refractive index lower than
laser diode which can emit a laser beam having a wavelength that of the core. The optical fiber 5 is made of, for example,
smaller than 380 nm, the laser diode 3 of the present embodi quartz having a core diameter of 200 um, a clad diameter of
ment can be a laser diode which is designed to emit a laser 240 um, and a numerical aperture NA of 0.22. The optical
beam having a wavelength smaller than 380 nm. fiber 5 are, however, not limited in configuration, thickness or
The present embodiment uses laser diodes as the excitation material to the foregoing values. Further, the optical fiber 5
light source. The laser diodes may, however, be replaced with may be rectangular along a cross section perpendicular to its
light emitting diodes. 10 long axis direction.
(Aspherical Lens 4) The optical fiber 5 is flexible, which makes it easy to
The aspherical lenses 4 are each a lens for causing the laser change how to dispose the emitting ends 5a relative to the
beam (excitation light) emitted from a laser diode 3 to enteran laser beam irradiation Surface 7a of the light emitting section
entering end 5b, which is one end of the optical fiber 5. The 7. The emitting ends 5a can thus be disposed so as to extend
aspherical lens 4 may be, for example, a FLKN1405 manu 15 along the shape of the laser beam irradiation surface 7a of the
factured by ALPS ELECTRICCO.,LTD. The aspherical lens light emitting section 7. This makes it possible to mildly
4 is not particularly limited in its shape or material as long as irradiate the entire laser beam irradiation surface 7a of the
the lens has the foregoing function. It is, however, preferable light emitting section 7 with the laser beams.
that the material have a high transmittance for a wavelength in The flexibility of the optical fiber 5 further makes it pos
the vicinity of 405 nm, which is a wavelength of the excitation sible to easily change a relative positional relationship of the
light, and have a high heat resistance. laser diode 3 with the light emitting section 7. In addition,
(Optical Fiber 5) adjusting a length of the optical fiber 5 allows the laser diode
(Disposition of Optical Fiber 5) 3 to be disposed at a location far from the light emitting
The optical fiber 5 is a light guiding member which guides section 7.
to the light emitting section 7 the laser beams emitted by the 25 The above arrangement thus increases the freedom in
laser diodes 3, and is a bundle of a plurality of optical fibers. design of the headlamp 1, for example, the laser diodes 3 can
The optical fiber 5 has (i) a plurality of entering ends 5b each be disposed at Such a location as to be cooled replaced easily.
of which receives a laser beam, and (ii) a plurality of emitting In other words, the freedom in design of the headlamp 1 can
ends 5a each of which emits a laser beam entered via a be improved because it is possible to easily change (i) a
corresponding one of the entering ends 5b. The plurality of 30 positional relation between the entering ends 5b and the emit
emitting ends 5a emit laser beams to respective regions on a ting ends 5a and thus (ii) the positional relation between the
laser beam irradiation surface (excitation light irradiation laser diodes 3 and the light emitting section 7.
surface) 7a of the light emitting section 7. The light guiding member may alternatively be (i) a mem
For example, the plurality of emittingends 5a of the optical ber other than the optical fibers or (ii) a combination of the
fiber 5 are aligned on a plane that is parallel to the laser beam 35 optical fibers and another member. For example, the light
irradiation surface 7a. With such an alignment, the respective guiding member may alternatively be a single or a plurality of
laser beams emitted from the plurality of emitting ends 5a to light guiding members each of which (i) has an entering end
the laser beam irradiation surface 7a of the light-emitting and an emitting end for a laser beam and (ii) has a shape of a
section 7 can be dispersed on a two-dimensional plane. This conical frustum or a square frustum.
is because respective first components of the laser beams 40 (Ferrule 6)
irradiate different regions of the laser beam irradiation sur The ferrule 6 supports the plurality of emitting ends 5a of
face 7a of the light-emitting section 7. A first component of a the optical fiber 5 in a predetermined pattern with respect to
laser beam is a component which falls upon a central portion the laser beam irradiation surface 7a of the light emitting
(peak portion in light intensity) of an irradiation region section 7. The ferrule 6 may (i) have holes formed in a pre
formed by the laser beam on the laser beam irradiation surface 45 determined pattern for inserting the respective emitting ends
7a. 5a, or (ii) include separable upper and lower parts each of
The above arrangement prevents a part of the light emitting which has, on a bonding Surface, grooves formed for sand
section 7 from remarkable impairment (property change and wiching the emitting ends 5a.
life reduction) due to local irradiation of the light emitting The ferrule 6 may be fixed with respect to (i) the reflecting
section 7 with the laser beam. 50 mirror 8 by use of, for example, a bar-shaped or tube-shaped
The optical fiber 5 is not necessarily required to include a member that extends out from the reflecting mirror 8, or (ii)
bundle of optical fibers (that is, a plurality of emitting ends the heat conducting member 13. The ferrule 6 is not particu
5a), and may thus include a single emitting end 5a. larly limited in terms of material, and may be stainless steel,
The emitting ends 5a may be in contact with the laser beam for example. Alternatively, a plurality of ferrules 6 may be
irradiation Surface 7a, or may be disposed so that a slight gap 55 provided for each light emitting section 7.
is secured therebetween. In particular, in a case where the The ferrule 6 can be omitted in the case where the optical
emitting ends 5a are disposed so that a gap is secured between fiber 5 includes a single emitting end 5a. However, the ferrule
the emitting ends 5a and the laser beam irradiation surface 7a, 6 is preferably provided in such a case as well so as to
the gap is preferably set so that a laser beam emitted from accurately fix the emitting end 5a at a position relative to the
each emitting end 5a and spreading in a shape of a circular 60 laser beam irradiation surface 7a.
cone falls in its entirely onto the laser beam irradiation surface (Light Emitting Section 7)
7a. (Composition of Light Emitting Section 7)
(Material and Configuration of Optical Fiber 5) The light emitting section (wavelength conversion mem
The optical fiber 5 has a double-layered structure in which ber) 7 emits light upon receipt of the laser beams emitted via
a center core is covered with a clad having a refractive index 65 the emitting ends 5a, and is provided in the vicinity of a focal
lower than that of the core. The core includes quartz glass point of the reflecting mirror 8. The light emitting section 7
(silicon oxide) as its main component, which quartz glass includes a fluorescent material which emits light upon receipt
US 8,833,975 B2
13 14
of the laser beams. More specifically, the light emitting sec the extremely intense laser beam (that is, its output and light
tion 7 is a member in which a fluorescent material is dispersed density) emitted by the laser diode 3, and are thus suitable for
inside silicone resin that serves as a fluorescent material a laser illumination source.
retention Substance (sealing material). The silicone resin and The oxynitride fluorescent material can be what is com
the fluorescent material are present in a ratio of approxi- 5 monly called sialon fluorescent material. Sialon fluorescent
mately 10:1. The light emitting section 7 may alternatively be material is a Substance in which (i) silicon atoms of silicon
made up by pressing the fluorescent material together into a nitride are partially Substituted with aluminum atoms and (ii)
solid. The fluorescent material retention substance is not lim nitrogen atoms of the silicon nitride are partially substituted
with
ited to a resin material Such as silicone resin, and may be what 10 preparedoxygen atoms. The sialon fluorescent material may be
is called organic-inorganic hybrid glass or inorganic glass. as a Solid Solution by combining alumina (Al2O),
In a case where, for example, the fluorescent material silica (SiO), rare earth elements and the like into silicon
retention Substance is inorganic glass, the light emitting sec nitride (SiN).
One feature of the semiconductor nanoparticle fluorescent
tion 7 can be a sintered body obtained by first (i) mixing the material is that even in a case where only a single type of
inorganic glass with the fluorescent material and then (ii) 15 compound semiconductor (e.g., indium phosphide: InP) is
sintering a resulting mixture at a predetermined temperature. used, it is possible to change its luminous color by quantum
In a case where the sintering temperature is above a melting size effect by changing its particle diameter to a nanometer
point of the inorganic glass serving as the fluorescent material size diameter. For instance, InP emits red light when the
retention Substance, it is possible to disperse the fluorescent particle size is around 3 nm to 4 nm. The particle size is
material uniformly in the inorganic glass by first melting the 20 measured under a transmission electron microscope (TEM).
inorganic glass temporarily. The semiconductor nanoparticle fluorescent material has a
The above inorganic glass can be, for example, a material short fluorescence duration since it is semiconductor-based.
which is normally referred to as low melting glass and which The fluorescent material is, on the other hand, highly resistant
has a melting point of 600° C. or lower. The mixture of the to high power excitation light since it can rapidly emit fluo
inorganic glass and the fluorescent material is sintered typi- 25 rescence with use of power of the excitation light. This is
cally with use of a mold for forming as a sintered body serving because the light emission duration of the semiconductor
as the light emitting section 7. Specifically, the mixture of the nanoparticle fluorescent material is around 10 nanoseconds,
inorganic glass and the fluorescent material is filled in the which duration is five digits smaller than that of a normal
fluorescent material which includes a rare earth as a lumines
mold and is then sintered. The sintered body serving as the 30 Cence Center.
light emitting section 7 is formed so as to have a shape that fits
an inner shape of the mold. Naturally, the inorganic glass above, Since the light emission duration is short as described
preferably has a melting point which is lower than a melting can rapidly the semiconductor nanoparticle fluorescent material
point of the mold. repeat absorption of a laser beam and light emis
sion of the fluorescent
The fluorescent material is, for example, an oxynitride 35 maintain a high efficiency material. As a result, it is possible to (i)
fluorescent material or a nitride fluorescent substance which
with respect to a strong laser beam
and (ii) reduce heat generated by the fluorescent material.
includes, dispersed in silicone resin, at least one of (i) a This further prevents the light emitting section 7 from
fluorescent material emitting blue light, (ii) a fluorescent impairment (discoloring and deformation) caused by heat.
material emitting green light, and (iii) a fluorescent material Accordingly, in a case where a light emitting element having
emitting red light. The laser diodes 3 each emit a laser beam 40 a high optical output is used as a light source, it is possible to
of 405 nm (violet), thereby causing a mixture of a plurality of prevent the life of the light emitting device from shortening.
colors and generation of white light upon irradiation of the (Shape and Size of Light Emitting Section 7)
light emitting section 7 with the laser beam. On this account, The light emitting section 7 is, for example, a cylindrical
it can be said that the light emitting section 7 is a wavelength column in shape, and is either (i) 3.2 mm in diameter and 1
converting material. 45 mm in thickness or (ii) 2 mm in diameter and 0.5 mm in
The laser diode 3 may emit a laser beam of 450 nm (blue) thickness. The light emitting section 7 receives laser beams
(or a laser beam close to what is called “blue' having a peak from the emitting ends 5a at the laser beam irradiation surface
wavelength in a wavelength range from not less than 440 nm 7a, which corresponds to a bottom surface of the cylindrical
to not more than 490 nm). In this case, the fluorescent material column.
is a yellow fluorescent material or a mixture of a green fluo- 50 The light emitting section 7 may alternatively be a cuboid
rescent material and a red fluorescent material. The yellow in shape instead of a cylindrical column. The cuboid is, for
fluorescent material is a fluorescent material which emits example, a 3 mmx1 mmx1 mm cuboid. In this case, the laser
light having a peak wavelength in a wavelength range of not beam irradiation surface at which the laser beams from the
less than 560 nm to not more than 590 nm. The green fluo laser diode 3 are received is 3 mm in area. A light distribution
rescent material is a fluorescent material which emits light 55 pattern (light distribution) of a vehicle headlamp lawfully
having a peak wavelength in a wavelength range of not less stipulated domestically in Japan is narrow in a vertical direc
than 510 nm to not more than 560 nm. The red fluorescent tion and broad in a horizontal direction; hence, in order to
material is a fluorescent material which emits light having a easily achieve the light distribution pattern, the shape of the
peak wavelength in a wavelength range of not less than 600 light emitting section 7 is made wide in the horizontal direc
nm to not more than 680 nm. 60 tion (cross section being Substantially rectangular shaped).
(Kind of Fluorescent Material) A required thickness of the light-emitting section 7 is var
The fluorescent material included in the light emitting sec ied in accordance with a ratio of the fluorescent material
tion 7 can be a nitride fluorescent material, an oxynitride retention substance of the light-emitting section 7 to the fluo
fluorescent material, or a III-V compound semiconductor rescent material thereof. The more the fluorescent material is
nanoparticle fluorescent material. In particular, an oxynitride 65 contained in the light-emitting section 7, the higher a conver
fluorescent material and a III-V compound semiconductor sion efficiency of the laser light to the white light becomes.
nanoparticle fluorescent material are both highly resistant to Thus, an increase in a content of the fluorescent material in the
US 8,833,975 B2
15 16
light-emitting-section 7 allows a reduction in thickness of the The transparent plate 9 may be used to fix the light emitting
light-emitting section 7. Reducing the thickness of the light section 7 in combination with the heat conducting member
emitting section 7 increases an effect of dissipating heat 13. In other words, the light emitting section 7 may be sand
toward the heat conducting member 13. Reducing the thick wiched between the heat conducting member 13 and the
ness excessively may, however, cause the laser beams to be transparent plate 9. The transparent plate 9 in this case func
emitted to the outside without being converted into fluores tions as a fixing section for fixing a relative positional rela
cence. From the viewpoint of excitation light absorption by tionship between the light emitting section 7 and the heat
the fluorescent material, the light emitting section 7 prefer conducting member 13. Sandwiching the light emitting sec
ably has a thickness which is at least 10 times as large as a tion 7 between the heat conducting member 13 and the trans
particle size of the fluorescent material. From this viewpoint, 10
parent plate 9 more reliably fixes the light emitting section 7
the light emitting section 7 is simply required to have a at a location even if the adhesive layer 15 has a low adhesive
thickness of not less than 0.01um in the case where it includes strength.
a nanoparticle fluorescent material. The thickness in this case In a case where the transparent plate 9 is made of a material
is, however, preferably not less than 10 Lum (not less than 0.01 which is higher in thermal conductivity than the light emitting
mm) for ease of production steps such as dispersing the nano 15
particle fluorescent material into the sealing material. section 7 (e.g., glass, in the case where the light emitting
Increasing the thickness of the light emitting section 7 will, on section 7 includes a sealing material made of silicone resin),
the other hand, increase a shift from a focus point of the the transparent plate 9 can produce an effect of cooling the
reflecting mirror 8, and consequently blur the light distribu light emitting section 7.
tion pattern. The transparent plate 9 may be omitted in a case where the
Thus, the light emitting section 7 preferably has a thickness light emitting section 7 is fixed with use of only the heat
which is not less than 0.2 mm and not greater than 2 mm in a conducting member 13.
case where the light emitting section 7 includes an oxynitride (Housing 10)
fluorescent material. The lower limit of the thickness does not The housing 10 forms the body of the headlamp 1, and
apply to a case in which the fluorescent material has an 25 stores members such as the reflecting mirror 8. The optical
extremely large content (typically, in a case where the light fiber 5 penetrates through the housing 10, whereas the laser
emitting section 7 contains 100% fluorescent material). diode array 2 is disposed outside the housing 10. Although the
The laser beam irradiation surface 7a of the light emitting laser diode array 2 generates heat when emitting laser beams,
section 7 is not necessarily required to be a flat surface, and since the laser diode array 2 is provided outside the housing
may be a curved surface. The laser beam irradiation surface 30 10, it is possible to efficiently cool the laser diode array 2. This
7a is, however, preferably a flat surface in order to control in turn prevents the light emitting section 7 from, for example,
reflection of the laser beam. having decreased properties or being thermally damaged due
The light emitting section 7 is, as illustrated in FIGS. 1 and to heat generated by the laser diode array 2.
2, fixed via the adhesive layer 15 to a surface of the heat In case the laser diode 3 should possibly break down, it is
conducting member 13 which Surface is opposite to a Surface 35 preferable to dispose the laser diodes 3 at such a location as to
which is irradiated with the laser beam. be replaced easily. If these points can be ignored, the laser
(Reflecting Mirror 8) diode array 2 may be stored inside the housing 10.
The reflecting mirror 8 reflects the light emitted from the (Extension 11)
light emitting section 7, and thus forms a pencil of rays which The extension 11 is disposed at a location away from the
travels within a predetermined solid angle. In other words, the 40 reflection mirror 8 in the forward direction. The extension 11
reflecting mirror 8 reflects the light from the light emitting hides the inner configuration of the headlamp 1 so as to (i)
section 7 so as to form a pencil of rays which travels in a improve appearance of the headlamp 1 and (ii) improve a
direction of a front of the headlamp 1. The reflecting mirror 8 sense of unity between the reflecting mirror 8 and the vehicle
is, for example, a (cup-shaped) member which has a curved body. This extension 11 also has a metal thin film formed on
surface provided with a metal thin film formed thereon. 45 its surface, as with the reflecting mirror 8.
The reflection mirror 8 may alternatively be a hemispheri (Lens 12)
cal mirror, an ellipsoidal mirror, a parabolic mirror, or a The lens 12 is disposed at the opening of the housing 10,
mirror which has a hemispherical, ellipsoidal, or parabolic and hermetically seals the headlamp 1. Light emitted from the
portion. In other words, the reflection mirror 8 is simply light emitting section 7 and reflected off the reflecting mirror
required to include, in its reflection Surface, at least a portion 50 8 is emitted towards the front of the headlamp 1 through the
having a curved surface formed by rotating a shape (an lens 12. In other words, the lens 12 is a light-transmitting
ellipse, a circle, or a parabola) about a rotation axis. member which transmits fluorescence emitted from the light
(Transparent Plate 9) emitting section 7 as illumination light and which thus emits
The transparent plate 9 is a transparent resin plate which is the fluorescence to the outside of the vehicle headlamp.
provided at an opening of the reflecting mirror 8 and which 55 (Heat Conducting Member 13)
transmits fluorescence emitted from the light emitting section The heat conducting member (highly heat conducting
7 as illumination light. The transparent plate 9 is preferably member) 13 is provided so as to face the laser beam irradia
made of a material which (i) blocks the laser beams emitted tion surface (excitation light irradiation surface) 7a of the
from the laser diodes 3, and (ii) transmits fluorescence (for light emitting section 7. The laser beam irradiation surface 7a
example, white light) that is generated by converting the laser 60 is a surface which is irradiated with excitation light. The heat
beams in the light emitting section 7. With the light emitting conducting member 13 is a light-transmitting member which
section 7, most of the coherent laser beams is converted to receives heat of the light emitting section 7, and is thus ther
incoherent light. There may be, however, cases where a por mally connected to the light emitting section 7 (that is, con
tion of the laser beams is not converted due to some kind of nected so that thermal energy can be transferred from the light
cause. Even in Such a case, it is possible, by blocking the laser 65 emitting section 7). Specifically, the heat conducting member
beams with the transparent plate 9, to prevent the laser beams 13 and the light emitting section 7 are, as illustrated in FIG.2,
from leaking outside. adhered to each other via the adhesive layer (gap layer) 15.
US 8,833,975 B2
17 18
FIG. 2 is a diagram illustrating how the light emitting section (Cooling Section 14)
7 is adhered to the heat conducting member 13 via the adhe The cooling section 14 is a member for cooling the heat
sive layer 15. conducting member 13. The cooling section 14 is, for
The heat conducting member 13 is a plate-shaped member example, a heat dissipating block which is made of a metal
which has (i) a first end in thermal contact with the laser beam 5 Such as aluminum and copper and which is thus high in heat
irradiation surface 7a of the light emitting section 7 and (ii) a conductivity. In a case where the reflecting mirror 8 is made of
second end in thermal connection with the cooling section 14. a metal, the reflecting mirror 8 may further serve the function
The heat conducting member 13, shaped and connected as of the cooling section 14. The cooling section 14 may alter
above, (i) holds the minute light emitting section 7 at a light natively be (i) a cooling device which cools the heat conduct
emitting section fixing location and (ii) dissipates, to the 10 ing member 13 by circulating a coolant inside itself, or (ii) a
outside of the headlamp 1, heat generated by the light emit cooling device (fan) which air-cools the heat conducting
ting section 7. member 13.
The heat conducting member 13 preferably has a thermal In a case where the cooling section 14 is a metal block, the
conductivity of not less than 20 W/mK so as to efficiently metal block may include on a top surface a plurality of heat
dissipate heat of the light emitting section 7. Since the laser 15 dissipating fins. This arrangement increases a Surface area of
beam emitted from the laser diode 3 passes through the heat the metal block, and thus improves efficiency in heat dissipa
conducting member 13 before reaching the light emitting tion from the metal block.
section 7, the heat conducting member 13 is preferably made The cooling section 14 is not essential to the headlamp 1.
of a material which is highly light-transmitting property. Heat received by the heat conducting member 13 from the
In view of the above preferable points, the heat conducting light emitting section 7 may alternatively be allowed to dis
member 13 is preferably made of a material such as Sapphire sipate spontaneously from the heat conducting member 13.
(Al2O), magnesia (MgO), gallium nitride (GaN), and spinel Providing the cooling section 14, however, allows heat to
(MgAlO4). Using one of the above materials achieves a efficiently dissipate from the heat conducting member 13.
thermal conductivity of 20 W/mK or greater. The cooling section 14 is particularly useful in a case where
The heat conducting member 13 preferably has a thickness 25 an amount of heat from the light emitting section 7 is 3 Wor
13c (see FIG. 2) which is not less than 0.3 mm and not greater greater.
than 3.0 mm. The thickness 13c refers to a thickness along a Adjusting a length of the heat conducting member 13
direction extending from a first surface 13a of the heat con allows the cooling section 14 to be disposed at a location away
ducting member 13 to a second surface 13b of the heat con from the light emitting section 7. In this case, the cooling
ducting member 13, the first surface 13a facing the laser beam 30 section 14 is not necessarily contained in the housing 10 as
irradiation surface 7a and the second surface 13b being oppo illustrated in FIG.1. The cooling section 14 may be disposed
site to the first surface 13a. If the thickness is less than 0.3 outside the housing 10 with the heat conducting member 13
mm, the heat conducting member 13 cannot sufficiently dis penetrating the housing 10.
sipate heat of the light emitting section 7, and the light emit This arrangement (i) allows the cooling section 14 to be
ting section 7 may thus be impaired. If the thickness is greater 35 disposed at Such a location that it can be easily repaired or
than 3.0 mm, the heat conducting member 13 will absorb replaced if broken down, and (ii) increases the freedom in
more of the laser beam emitted thereto, and efficiency in use design of the headlamp 1.
of excitation light will in consequence decrease significantly. (Adhesive Layer 15)
With an arrangement in which the heat conducting member The adhesive layer 15 is a layer of an adhesive filling a gap
13 having an appropriate thickness is in contact with the light 40 between the heat conducting member 13 and the laser beam
emitting section 7, it is possible to dissipate heat of the light irradiation surface 7a. The fluorescent material included in
emitting section 7 rapidly and efficiently, particularly in a the light emitting section 7 is approximately from 1 to 20 um
case where a laser beam irradiating the light emitting section in diameter. The gap is thus relatively large in a case where,
7 is so extreme in intensity, for example, greater than 1 W. The for example, (i) the heat conducting member 13 is made of
above arrangement thus prevents the light emitting section 7 45 Sapphire and has a polished Surface and (ii) the light emitting
from being damaged (impaired). section 7 is disposed in contact with the polished surface. The
The heat conducting member 13 may be in a shape of a gap can be filled by providing the adhesive layer 15 between
plate with no bend, or have a bent portion and/or a curved the heat conducting member 13 and the laser beam irradiation
portion. The heat conducting member 13 is, however, prefer surface 7a of the light emitting section 7.
ably flat (in the plate shape) at a portion to which the light 50 Providing the adhesive layer 15 substantially increases an
emitting section 7 is adhered. This allows the light emitting area by which the heat conducting member 13 and the laser
section 7 to be adhered securely. beam irradiation surface 7a are in contact with each other, and
(Variation of Heat Conducting Member 13) thus improves heat absorption efficiency of the heat conduct
The heat conducting member 13 may alternatively include ing member 13. The heat conducting member 13 can have a
a portion which is light-transmitting (light-transmitting sec 55 higher heat absorption efficiency in a case where the adhesive
tion) and a portion which is not light-transmitting (light layer 15 has a thermal conductivity which is equivalent to or
blocking section). In this case, the light-transmitting section greater than that of the light emitting section 7.
is disposed so as to cover the laser beam irradiation Surface 7a The adhesive layer 15 can be formed of, for example,
of the light emitting section 7, whereas the light blocking Epixacolle EP433 (visible light polymerizable optical adhe
section is disposed so as to Surround the light-transmitting 60 sive manufactured by Adell Corporation). The thermal con
section. ductivity of Epixacolle EP433 is not disclosed, but is pre
The light blocking section may be a heat dissipating mem sumed to fall within a range approximately from 0.1 to 0.3
ber made of a metal (for example, copper or aluminum). The W/mK since Epixacolle EP433 is an acrylic adhesive.
light blocking section may alternatively be made of a light The adhesive layer 15 preferably has a flexibility (or a
transmitting material having a Surface that is provided with a 65 viscosity) sufficient to absorb a difference in coefficient of
film, such as a film made of aluminum or silver, which reflects thermal expansion between the light emitting section 7 and
illumination light. the heat conducting member 13. Since the light emitting
US 8,833,975 B2
19 20
section 7 and the heat conducting member 13 are different (Combination of Material of Gap Layer and Light Emitting
from each other in coefficient of thermal expansion, the light Section 7)
emitting section 7 may become detached from the heat con The adhesive layer 15, as described above, preferably has a
ducting member 13 due to the difference in coefficient of thermal conductivity which is equivalent to or greater than
thermal expansion in a case where the light emitting section 7 5 that of the light emitting section 7. Since the adhesive layer 15
generates heat. is an example of the gap layer of the present invention which
In a case where the adhesive layer 15 has a flexibility (or a example includes an adhesive, the following description uses
viscosity) sufficient to absorb the difference in coefficient of the term "gap layer,” which is broader in concept, to deal with
thermal expansion between the light emitting section 7 and 10
an example material of the adhesive layer 15.
the heat conducting member 13, it is possible to prevent the Table 1 shows example materials for the gap layer and the
light emitting section 7 from becoming detached from the light emitting section 7. Examples for the gap layer include a
heat conducting member 13 due to heat generated by the light material which, in order to improve the thermal conductivity
emitting section 7. of the gap layer, contains a highly heat conductive filler
The adhesive layer 15 preferably has a thickness (a thick 15 (highly heat conductive additive) made of a material similar
ness between the heat conducting member 13 and the laser to that of the diffusing agent 16. The highly heat conductive
beam irradiation Surface 7a) which is not less than 1 um and filler refers to light-transmitting particles including a material
not greater than 30 um. In a case where the adhesive layer 15 having a high heat conductivity.
has a thickness which is not less than 1 um and not greater The description below uses (i) the term “highly heat con
than 30 lum, even if the adhesive layer 15 is lower in thermal ductive filler A' to refer to a portion of the highly heat con
conductivity than the light emitting section 7, it is possible to ductive filler which portion is higher in thermal conductivity
reduce a thermal resistance of the adhesive layer 15 and thus than resin and (ii) the term “highly heat conductive filler B to
to efficiently transfer heat generated by the light emitting refer to a portion of the highly heat conductive filler A which
section 7 to the heat conducting member 13 via the adhesive portion is higher in thermal conductivity than glass.
layer 15. The thermal resistance is identical between, for 25 Example materials of the highly heat conductive filler A
example, (i) a case in which the adhesive layer 15 has a include SiO beads, Al-O beads, and diamond beads.
Example materials of the highly heat conductive filler B
thermal conductivity of 1 W/mK and a thickness of 0.1 mm include Al-O beads and diamond beads.
and (ii) a case in which the adhesive layer 15 has a thermal
conductivity of 0.2 W/mK and a thickness of 20 Lum (=0.02 30 TABLE 1
mm).
Note that embodiments below may refer to the adhesive Gap layer Light emitting Section
layer 15 as a gap layer 15. Thermal Material for Thermal
(Dispersing Agent 16) conductivity sealing conductivity
The adhesive layer 15 may include a diffusing agent 16. 35
Material (W/mK) material (W/mK)
Since the laser beam has an extremely small light emitting Acrylic O.1-0.3 Resin O.1 to O.3
point and is coherent light, it may harm the human body if it adhesive
is emitted directly to the outside without being converted into Acrylic O.3<
adhesive +
fluorescence or diffused by the light emitting section 7. The highly heat
diffusing agent 16 included in the adhesive layer 15 diffuses 40 conductive
the laser beam emitted from the optical fiber 5 so that the light filler A
Glass paste 1.O Inorganic 1.O
emitting point is expanded and the laser beam is converted glass
into incoherent light. Glass paste + 1.O<
Thus, even if the laser beam is not entirely converted into highly heat
conductive
fluorescence or diffused by the light emitting section 7, the 45
filler B
diffusing agent 16, which diffuses the laser beam in advance,
reduces the possibility of coherent light leaking to the outside.
The diffusing agent 16 is preferably made of a material In a case where, for example, (i) the gap layer is formed of
such as SiO beads, Al-O beads, and diamond beads. The an acrylic adhesive and (ii) the sealing material of the light
SiO beads are in a perfectly spherical shape, and have a 50 emitting section 7 is a resin material (for example, epoxy
particle size which ranges from several nanometers to several resin or silicone resin) or HBG (organic-inorganic hybrid
micrometers. The SiO beads are mixed in the adhesive layer glass), the gap layer is equivalent in thermal conductivity to
15 at 0.1 to several percent. The diffusing agent 16 is prefer the light emitting section 7.
ably contained in an amount which falls within a range The two instances below each exemplify a combination of
approximately from 1 mg to 30 mg per gram of the adhesive 55 the gap layer and the light emitting section 7 where the gap
layer 15 because containing an excessive amount of the dif layer is higher in thermal conductivity than the light emitting
fusing agent 16 reduces an amount of the laser beam which section 7.
reaches the light emitting section 7. (1) In a case where the sealing material of the light emitting
Containing a transparent, inorganic Substance Such as the section 7 is a resin material, the gap layer can be formed of (i)
above also improves the thermal conductivity of the adhesive 60 an acrylic adhesive, (ii) an acrylic adhesive prepared by
layer 15. SiO, has a thermal conductivity of 1.38 W/mK, kneading an acrylic adhesive with the highly heat conductive
which is higher than that of acrylic resin. The diamond beads filler A, (iii) a glass paste (typically including low melting
have a thermal conductivity which ranges from 800 to 2000 glass), or (iv) a glass paste prepared by kneading a glass paste
W/mK, which is significantly higher than that of acrylic resin. with either the highly heat conductive filler A or the highly
Containing a transparent, inorganic Substance as above sig 65 heat conductive filler B.
nificantly improves the thermal conductivity of the adhesive In this combination, the highly heat conductive filler A is
layer 15 in consequence. formed of beads which are more highly heat conductive than
US 8,833,975 B2
21 22
an acrylic adhesive. Such beads being (i)SiO (silica) beads, The diffusing agent 16 may alternatively be provided in a
which have a thermal conductivity of approximately 1 plurality of layers as long as a fixed distance is maintained
W/mK, (ii) Al-O (sapphire) beads, which have a thermal between the heat conducting member 13 and the light emit
conductivity ranging approximately from 20 to 40 W/mK, or ting section 7.
(iii) diamond beads, which have a thermal conductivity rang As illustrated in FIG. 3, a reflective film 17 may be pro
ing approximately from 1000 to 2000 W/mK. vided not only to a side surface of the adhesive layer 15, but
(2) In a case where the sealing material of the light emitting also to a side surface of the light emitting section 7. This
section 7 is inorganic glass, the gap layer can be formed of (i) arrangementallows the reflective film 17 to also cool the light
a glass paste including low melting glass or (ii) a glass paste emitting section 7. This effect can be improved by making the
prepared by mixing a glass paste with the highly heat con 10 reflective film 17 of a material which is higher in heat con
ductive filler B. ductivity than the light emitting section 7.
Although low melting glass is used, it is necessary to heat (Configuration of Laser Diode 3)
a glass paste to at least 400° C. in order to melt it and adhere Next described is a basic configuration of the laser diodes
3. FIG. 4(a) is a circuit diagram Schematically illustrating a
the gap layer to the light emitting section 7. The highly heat 15 laser diode 3, and FIG. 4(b) is a perspective view illustrating
conductive filler is thus required to not melt or change in the basic configuration of the laser diode 3. As illustrated in
quality at a fusing temperature of a glass paste in use. FIG. 4(b), the laser diode 3 is made up by stacking a cathode
The above examples of the highly heat conductive filler, electrode 23, a substrate 22, a clad layer 113, an active layer
namely SiO beads (silica), Al2O beads, and diamond beads, 111, a clad layer 112, and an anode electrode 21 in this order.
have their respective melting points of 1713°C. 2030° C. The substrate 22 is a semiconductor substrate, and in order
and 3550°C. The above examples of the highly heat conduc to obtain a blue to ultraviolet excitation light for exciting a
tive filler thus do not melt or change in quality at the fusing fluorescent material as in the present application, it is prefer
temperature of low melting glass. able to use GaN. sapphire, or SiC as a material of the substrate
In either (1) or (2), it is simply necessary to select a highly 22. Generally, other examples of a substrate for use in a laser
heat conductive filler for mixture in the gap layer so that the 25 diode encompass Substrates made of a material Such as: IV
gap layer is higher in thermal conductivity than the light semiconductors such as Si, Ge, and SiC; III-V compound
emitting section 7. semiconductors such as GaAs, GaP, InP, AlAs. GaN. InN,
The thermal conductivity of the gap layer, however, InSb, GaSb, and AlN; II-VI compound semiconductors such
depends not only on the material of the highly heat conductive as ZnTe ZeSe, ZnS, and ZnO, oxide insulators such as ZnO,
filler to be mixed, but also on its concentration. The thermal 30 Al-O, SiO, TiO, CrO3, and CeO2, and nitride insulators
conductivity is higher in, for example, (i) a case where sap such as SiN.
phire beads are mixed in a relatively large number than (ii) a The anode electrode 21 is provided for injecting current
case where diamond paste is mixed in an extremely small into the active layer 111 via the clad layer 112.
number. The thermal conductivity of the gap layer canthus be The cathode electrode 23 is provided for injecting current
simply adjusted by (i) selecting a material of the highly heat 35 into the active layer 111 via the clad layer 113 from under the
conductive filler to be mixed in the gap layer and (ii) adjusting substrate 22. The current is injected by applying a forward
an amount of the highly heat conductive filler. bias to the anode electrode 21 and the cathode electrode 23.
Alternatively, a plurality of kinds of the highly heat con The active layer 111 is sandwiched between the clad layer
ductive filler may be mixed in the gap layer. 113 and the clad layer 112.
(Shape of Dispersing Agent 16) 40 In order to obtain a blue to ultraviolet excitation light, a
The description above cites SiO beads and the like as mixed crystal semiconductor including AlInGaN is used as a
examples of the highly heat conductive filler. The highly heat material of the active layer 111 and the clad layers 112 and
conductive filler is, however, not necessarily spherical, and 113. Generally, a mixed crystal semiconductor whose main
may thus be in a bar shape or an indefinite shape. The highly component is Al. Ga, In, AS, P. N. or Sb is optionally used as
heat conductive filler is preferably perfectly spherical and 45 the active layer 111 and clad layers 112 and 113 of the laser
identical in diameter in order to control the thickness of the diode. Alternatively, the active layer 111 and the clad layers
gap layer. 112 and 113 may be made up of a II-VI compound semicon
FIG. 3 is a cross-sectional view illustrating a preferable ductor such as Zn, Mg, S, Se, Te, or ZnO.
example of the diffusing agent 16. As illustrated in FIG.3, the The active layer 111 is a region which emits light upon the
diffusing agent 16 is made of particles (heat conducting par 50 injection of the current. The light emitted is trapped within the
ticles) which are each substantially spherical (preferably, per active layer 111 due to the difference in refractive index
fectly spherical) and have a predetermined diameter. The between the clad layer 112 and the clad layer 113.
diffusing agent 16 thus maintains a fixed distance between the The active layer 111 is further formed so as to have a front
light emitting section 7 and the heat conducting member 13. cleaved surface 114 and a rear cleaved surface 115 which are
Further, the diffusing agent 16 is in contact with the heat 55 disposed opposite to each other so as to trap the light ampli
conducting member 13 and the light emitting section 7 So as fied by stimulated emission. The front cleaved surface 114
to conduct heat of the light emitting section 7 to the heat and rear cleaved surface 115 serve as mirrors.
conducting member 13. As different from a case of a mirror which completely
The diffusing agent 16 is preferably present only in a single reflects light, a portion of the light amplified by the stimulated
layer between the heat conducting member 13 and the light 60 emission is emitted from the front cleaved surface 114 and the
emitting section 7, and a gap filler (an adhesive or a glass rear cleaved surface 115 (in the present embodiment, from the
paste, for example) fills gaps between the particles of the front cleaved surface 114, for convenience) of the active layer
diffusing agent 16. Providing the diffusing agent 16 arranged 111. The light thus emitted serves as the excitation light L0.
as such allows efficient conduction of heat of the light emit The active layer 111 may have a multilayer quantum well
ting section 7 to the heat conducting member 13 even in a case 65 Structure.
where the gap filler is made of a material. Such as an acrylic The rear cleaved surface 115 opposite to the front cleaved
adhesive, which is low in thermal conductivity. surface 114 has a reflective film (not shown) provided
US 8,833,975 B2
23 24
thereon, which reflective film is used for laser emission. A The reflective film 17 is simply required to cover the side
difference in reflectance between the front cleaved surface surface of at least the adhesive layer 15, and is thus not
114 and the rear cleaved surface 115 causes most of the necessarily required to cover the side Surface of the light
excitation light L0 to be emitted from a low-reflectance edge emitting section 7 as well. Covering the side surface of the
surface, for example the front cleaved surface 114, via a light light emitting section 7 with the reflective film 17, however,
emitting point 103. allows the reflective film 17 to cool the light emitting section
The clad layer 113 and the clad layer 112 may each be 7. This effect can be improved by making the reflective film
made up of a semiconductor of any one of (i) III-V compound 17 of a material which is higher in heat conductivity than the
semiconductors represented by GaAs, GaP. InP, AlAs. GaN. light emitting section 7.
InN, InSb, GaSb, and MN and (ii) II-VI compound semicon 10 (Advantage of Headlamp 1)
ductors such as ZnTe ZeSe, ZnS, and ZnO, each of which is The inventors of the present invention have found that the
ofan n-type or a p-type. Applying a forward bias to the anode light emitting section 7 is remarkably impaired in a case
electrode 21 and the cathode electrode 23 can cause current to where the light emitting section 7 is excited with a high
be injected into the active layer 111. power laser beam. Impairment of the light emitting section 7
Film formation of the semiconductor layers such as the 15 is mainly caused by (i) impairment of the fluorescent material
clad layer 113, clad layer 112, and active layer 111, may be itself included in the light emitting section 7 and further by (ii)
carried out by a general film forming method such as impairment of the sealing material (for example, silicone
MOCVD (metal-organic chemical vapor deposition), MBE resin) that Surrounds the fluorescent material. The foregoing
(molecular beam epitaxy), CVD (chemical vapor deposition), sialon fluorescent material and nitride fluorescent material
laserablasion, sputtering, or like method. The film formation each emit light with an efficiency of 60% to 80% upon irra
of the metal layers may be carried out by a general film diation with the laser beams. However, the remainder merely
forming method such as vacuum deposition, plating, laser serves as a cause for generation and discharging of heat. It is
ablasion, Sputtering or like method. thought that the material Surrounding the fluorescent material
(Light Emitting Principle of Light Emitting Section 7) is impaired due to this heat.
Next described is a principle on which a laser beam emitted 25 In the headlamp 1, which includes the adhesive layer 15
from a laser diode 3 causes a fluorescent material to emit light. between the light emitting section 7 and the heat conducting
First, laser beams emitted from the laser diodes 3 are emit member 13, the adhesive layer 15 fills the gap between the
ted to the fluorescent material included in the light emitting light emitting section 7 and the heat conducting member 13
section 7. This causes electrons existing inside the fluorescent and allows the heat conducting member 13 to cool the light
material to be excited from a low energy state to a high energy 30 emitting section 7 more effectively. As such, it is possible to
state (excited State). (i) lengthen a life of a headlamp serving as a light Source
Since this excited state is unstable, the energy state of the which uses a laser beam as excitation light and which has an
electrons inside the fluorescent material thereafter switches extremely high luminance, and thus (ii) improve reliability of
back to the original low energy state (ground level energy the headlamp.
state or metastable level energy state between excitation level 35
and ground level) after elapse of a given time. Example
AS Such, the fluorescent material emits light upon a tran
sition of electrons in the excited, high energy state back to the The following description deals with an Example of the
low energy state. present invention with reference to FIG. 6. FIG. 6 is a view
White light can be made up by a mixture of three colors 40 illustrating specific examples of the light emitting section 7
which meet an isochromatic principle or by a mixture of two and the heat conducting member 13.
colors which have a relation of complementary colors for The Example used as the light emitting section 7a wave
each other. It is possible to emit white light by as above length conversion member including (i) a sealing material
combining, based on the principle and the relation, (i) the and (ii) an oxynitride fluorescent material (CaC.-SiAlON:Ce)
color of the laser beam emitted from the laser diode with (ii) 45 and a nitride fluorescent material dispersed in the sealing
the color of light emitted from the fluorescent material. material. The light emitting section 7 had a discoid shape, and
(Variation) was 3 mm in diameter and 1.5 mm in thickness.
FIG. 5 is a cross-sectional view illustrating a variation of The Example used as the heat conducting member 13 a
the light emitting section 7. As illustrated in FIG. 5, a reflec sapphire plate (thermal conductivity: 42 W/mK) having a
tive film 17 may be provided on a side surface of the light 50 thickness of 0.5 mm. The light emitting section 7 was
emitting section 7 and the adhesive layer 15. The reflective adhered, as illustrated in FIG. 6, to the heat conducting mem
film 17 is a light-reflecting film which covers at least a portion ber 13 by using Epixacole EP433 (visible light polymeriz
of an outward surface of the adhesive layer 15 (the outward able optical adhesive manufactured by Adell Corporation) as
surface being a surface which is in contact with neither the the adhesive layer 15.
light emitting section 7 nor the heat conducting member 13). 55 A light emitting section including CaO.-SiAlON:Ce and
The reflective film 17 is, for example, a metal thin film such as CASN:Eu has an efficiency of approximately 70% in convert
an aluminum thin film. ing excitation light into illumination light (fluorescence).
Since the adhesive layer 15 includes the diffusing agent 16, Thus, in a case where 10W of excitation light is emitted to the
the laser beam is diffused by the diffusing agent 16. This light emitting section, 3 W out of the 10 W is converted not
results in generation of a laser beam (hereinafter referred to as 60 into illumination light but into heat.
“stray light') which does not travel in a direction of the light The sealing material that encloses the fluorescent material
emitting section 7 and which instead leaks out from the side has a thermal conductivity which (i) in a case of silicone resin
surface of the adhesive layer 15. With the above arrangement, or organic-inorganic hybridglass, ranges approximately from
the stray light is reflected by the reflective film 17, provided 0.1 to 0.2 W/mK or (ii) in a case of inorganic glass, ranges
on the side surface of the adhesive layer 15, and thus remains 65 approximately from 1 to 2 W/mK. According to calculation
inside the adhesive layer 15. This improves efficiency in use based on a simulation, a temperature of 500° C. or higher
of the laser beam. (555.6°C.) is reached for a heat generating body which, for
US 8,833,975 B2
25 26
example, (i) is 3 mm in height, 3 mm in width, and 1 mm in mechanism) 83. The light emitting section of the headlamp 30
thickness, (ii) has a thermal conductivity of 0.2W/mK, (iii) is is sandwiched between the heat conducting member 13 and
thermally insulated from the outside, and (iv) generates heat the transparent plate 18.
of 1 Wata 3 mmx3 mm surface. The reflecting mirror 81 is similar in function to the reflect
If the thermal conductivity of the sealing material is 2 ing mirror 8. The reflecting mirror 81 has a shape which is
W/mK, the temperature rises by 55.6°C. for a heat generating formed Substantially by cutting the reflecting mirror 8 along a
body which is identical in size and heat generation amount to plane which is (i) at a location near a focal point of the
the above heat generating body. This indicates that the ther reflecting mirror 81 and (ii) perpendicular to an optical axis.
mal conductivity of the sealing material is an extremely The reflecting mirror 81 is not particularly limited in terms of
important factor. Further, if (i) the thermal conductivity of the 10 material. To achieve a sufficient reflectance, however, the
sealing material is 2 W/mK and (ii) the heat generating body reflecting mirror 81 is preferably produced by (i) making a
is 3 mm in height, 1 mm in width, and 1 mm in thickness, the reflecting mirror of copper or SUS (stainless steel) and then
temperature rises by 166.7°C. Thus, reducing the size of the (ii) providing silver plating, chromate coating and the like to
light emitting section 7 to increase its luminance increases the the reflecting mirror. Alternatively, the reflecting mirror 81
temperature rise even with the same heat generation amount, 15 may be produced by (i) making a reflecting mirror of alumi
and imposes a heavier load on the light emitting section 7 as num and (ii) providing an antioxidant film to a Surface of the
a result. reflecting mirror. The reflecting mirror 81 may further alter
In contrast, in a case where a heat conducting plate (3 mm natively be produced by (i) making a reflecting mirror of resin
in height, 10 mm in width, and 0.5 mm in thickness) having a and (ii) forming a metal thin film on a surface of the reflecting
thermal conductivity of 40 W/mK is thermally adhered to the mirror.
above heat generating body (3 mm in height, 3 mm in width, The metal ring 19 is a ring in a shape of a mortar having an
and 1 mm in thickness; thermal conductivity: 0.2 W/mK), the opening in a bottom section. The metal ring 19 (i) Supple
temperature rise of the heat generating body is reduced to ments the reflecting mirror 81 to constitute a complete reflect
approximately 170° C. Increasing the thickness of the heat ing mirror and (ii) corresponds in shape to a part near a focal
conducting plate from 0.5 mm to 1.0 mm reduces the tem 25 point of the complete reflecting mirror. The mortar shape of
perature rise to approximately 85°C., which is half the above the metal ring 19 is surrounded by an inclined sidewall sur
temperature rise. Further, reducing the thickness of the heat face with which the opening is larger in area as farther away
generating body from 1 mm to a smaller value (for example, from the bottom section. The light emitting section 7 is pro
to 0.5 mm) allows heat to be more efficiently dissipated to the vided in the opening of the bottom section.
heat conducting plate, and further reduces the temperature 30 The metal ring 19 includes a mortar-shaped portion having
rise of the heat generating body as a result. a Surface which functions as a reflecting mirror. The metal
In a case where (i) the light emitting section including a ring 19 combines with the reflecting mirror 81 to constitute a
fluorescent material has a set temperature of approximately reflecting mirror which is complete in shape. The metal ring
200° C. and (ii) the fluorescent material is an oxynitride 19 is thus a partial reflecting mirror which functions as a part
fluorescent material, a nitride fluorescent material, or a III-V 35 of a reflecting mirror. In a case where the reflecting mirror 81
compound semiconductor nanoparticle fluorescent material, is referred to as “first partial reflecting mirror,” the metal ring
heat is dissipated rapidly and efficiently even if, in particular, 19 can be referred to as “second partial reflecting mirror
the light emitting section 7 is irradiated with excitation light corresponding to the part near the focal point. When the light
so extremely intense that the light emitting section 7 gener emitting section 7 emits fluorescence, a portion of the fluo
ates heat of greater than 1 W. The above arrangement thus 40 rescence is reflected by the surface of the metal ring 19, and is
prevents the light emitting section 7 from being damaged thus emitted as illumination light in a direction of a front of
(impaired). the headlamp 30.
The sealing material included in the light emitting section The metal ring 19 is not particularly limited in terms of
7 is preferably organic-inorganic hybrid glass or inorganic material, but is preferably made of a material Such as silver,
glass. In a case where the sealing material is silicone resin, it 45 copper, and aluminum for Sufficient heat dissipation. The
is preferable to keep the temperature rise at approximately metal ring 19 is, in the case where it is made of silver or
150° C. or lower on the basis of close simulation for heat. aluminum, preferably produced by (i) providing a mirror
Organic-inorganic hybrid glass tolerates temperatures finish to the mortar-shaped portion and then (ii) providing a
approximately from 250° C. to 300°C. Inorganic glass toler protecting layer (for example, chromate coating or a resin
ates temperatures of even 500° C. and above. 50 layer) to the mortar-shaped portion for protection against
blackening and oxidation. The metal ring 19 is, in the case
Embodiment 2 where it is made of copper, preferably produced by (i) carry
ing out silver plating or aluminum deposition and then (ii)
The following describes a second embodiment of the providing thereto the above protecting layer.
present invention with reference to FIGS. 7 and 8. Members 55 The light emitting section 7 is adhered to (or closely con
similar to their respective equivalents in Embodiment 1 are tacts) the heat conducting member 13 via the adhesive layer
each assigned the same reference numeral, and are thus not 15 (not shown in FIG.7; alternatively, a close contact material
described here. The present embodiment describes another such as grease). The metal ring 19 is in contact with the heat
example member which is used in combination with the heat conducting member 13 as well. The metal ring 19, in contact
conducting member 13 to Sandwich the light emitting section 60 with the heat conducting member 13, produces an effect of
7. cooling the heat conducting member 13. In other words, the
FIG. 7 is a view schematically illustrating a configuration metal ring 19 also functions as a cooling section for cooling
of a headlamp 30 of the present embodiment. As illustrated in the heat conducting member 13.
FIG. 7, the headlamp 30 includes a transparent plate (fixing The metal ring 19 and the reflecting mirror 81 sandwich the
section; pressure applying mechanism; facing member) 18, a 65 transparent plate 18. The transparent plate 18 is in contact
metal ring (storing member) 19, a reflecting mirror (reflecting with a surface of the light emitting section 7 which surface is
member) 81, a Substrate 82, and screws (pressure applying opposite to the laser beam irradiation surface 7a. The trans
US 8,833,975 B2
27 28
parent plate 18thus serves to press the light emitting section the pressure caused by fixing the reflecting mirror 81 to the
7 against the heat conducting member 13 so that the light substrate 82 with the screws 83. The metal ring 19 may be
emitting section 7 will not be detached from the heat conduct replaced with a ring which is not made of a metal. The metal
ing member 13. The mortar-shaped portion of the metal ring ring 19 may be replaced with, for example, a resin ring which
19 has a depth which is substantially identical to a height of 5 withstands the above pressure and which has a surface that is
the light emitting section 7. The transparent plate 18 is thus in provided with a metal thin film.
contact with the light emitting section 7 while the transparent (Advantage of Headlamp 30)
plate 18 is separated from the heat conducting member 13 by In the headlamp 30, the light emitting section 7 is sand
a fixed distance. As such, there is no possibility that the light wiched between the heat conducting member 13 and the
emitting section 7 will be crushed by the heat conducting 10
transparent plate 18. This allows the light emitting section 7
member 13 and the transparent plate 18, which sandwich the and the heat conducting member 13 to have a fixed relative
light emitting section 7. positional relationship. As such, even if (i) the adhesive layer
The transparent plate 18 may be made of any material that
is at least light-transmitting. The transparent plate 18 is, how 15 is low in adhesiveness or (ii) there is a difference in
ever, preferably has a high thermal conductivity (20 W/mKor 15 coefficient of thermal expansion between the light emitting
greater) as with the heat conducting member 13. The trans section 7 and the heat conducting member 13, it is possible to
parent plate 18 preferably includes, for example, Sapphire, prevent the light emitting section 7 from being detached from
gallium nitride, magnesia, or diamond. The transparent plate the heat conducting member 13.
18 is in this case higher in thermal conductivity than the light (Another Example of Fixing Section)
emitting section 7. The transparent plate 18 thus efficiently The fixing section for fixing a location of the light emitting
absorbs heat generated by the light emitting section 7, and section 7 relative to the heat conducting member 13 is not
consequently cools the light emitting section 7. necessarily a plate-shaped member. The fixing section is sim
The heat conducting member 13 and the transparent plate ply required to have (i) a pressing Surface which presses and
18 each preferably have a thickness which is approximately is in contact with at least a part of a Surface (hereinafter
not less than 0.3 mm and not greater than 3.0 mm. If the 25 referred to as “fluorescence emitting surface') opposite to the
thickness is less than 0.3 mm, the heat conducting member 13 laser beam irradiation Surface 7a of the light emitting section
and the transparent plate 18 cannot sandwich the light emit 7 and (ii) a pressing Surface fixing section which fixes a
ting section 7 and the metal ring 19 with a force sufficient to relative positional relationship between the pressing Surface
fix them. If the thickness is greater than 3.0 mm, the heat and the heat conducting member 13.
conducting member 13 and the transparent plate 18 will (i) 30 The light emitting section 7 can be fixed to the heat con
absorb more than an ignorable level of the laser beam and (ii) ducting member 13 by (i) fixing respective relative positions
be more expensive as well. of the pressing surface and the heat conducting member 13
The Substrate 82 is a plate-shaped member having an open and (ii) pressing the pressing Surface against the fluorescence
ing 82a through which the laser beam emitted from the laser emitting Surface of the light emitting section 7 (that is, caus
diode 3 passes. The reflecting mirror 81 is fixed to the sub 35 ing the pressing Surface to be in contact with the fluorescence
strate 82 with the screws 83. The reflecting mirror 81 is emitting Surface with Some pressure).
disposed away from the substrate 82 as separated by the heat FIGS. 8(a) through (c) are each a view illustrating a varia
conducting member 13, the metal ring 19, and the transparent tion of the fixing section. In a case where the light emitting
plate 18. The opening 82a has a center which substantially section 7 is, for example, a cylindrical column in shape as
coincides with a center of the opening in the bottom section of 40 illustrated in FIG. 8(a), the fixing section may be a cylinder
the metal ring 19. As such, the laser beam emitted from the shaped hollow member 20a which has a surface that is in
laser diode 3 passes through the opening 82a of the substrate contact with the fluorescence emitting Surface of the light
82, the heat conducting member 13, and the opening of the emitting section 7 and which is connected (that is, adhered or
metal ring 19 to reach the light emitting section 7. welded) to the heat conducting member 13. In a case where
The substrate 82 is not particularly limited in terms of 45 the light emitting section 7 is a cuboid or a cube in shape as
material. However, in a case where the substrate 82 is made of illustrated in FIG. 8(b), the fixing section may be a hollow
a metal which is high in thermal conductivity, the substrate 82 member 20b in a shape of a cuboid or a cube. The hollow
can also function as a cooling section for cooling the heat members 20a and 20b each have a surface connected to the
conducting member 13. The heat conducting member 13 is in heat conducting member 13, the Surface having an opening.
contact in its entirety with the substrate 82. Thus, in a case 50 Alternatively, the fixing section may be a fixing section 20c
where the substrate 82 is made of a metal such as iron and which has, as illustrated in FIG. 8(c), a surface that is in
copper, it is possible to more efficiently cool the heat con contact with the fluorescence emitting Surface and that is
ducting member 13 and consequently cool the light emitting partially open (particularly, in a central portion). This con
section 7. figuration prevents fluorescence loss which is caused by the
The metal ring 19 is preferably securely fixed to the heat 55 fixing section absorbing fluorescence emitted from the light
conducting member 13. The metal ring 19 can be fixed to the emitting section 7. The fixing section is preferably a light
heat conducting member 13 to a certain extent with use of transmitting member, but may be made of a material which is
pressure caused by fixing the reflecting mirror 81 to the sub not light-transmitting (for example, a metal) as long as the
strate 82 with the screws 83. However, the risk of the light fixing section is open at the central portion.
emitting section 7 being detached due to a positional shift of 60 The fixing section may alternatively include a plurality of
the metal ring 19 can be avoided by securely fixing the metal wires each of which has (i) a first end that is connected to the
ring 19 by a method of, for example, (i) adhering the metal light emitting section 7 and (ii) a second end connected to the
ring 19 to the heat conducting member 13 with use of an heat conducting member 13.
adhesive or (ii) screwing the metal ring 19 to the substrate 82 Further alternatively, the light emitting section 7 may be
via the heat conducting member 13. 65 connected to the heat conducting member 13 with use of the
The metal ring 19 is simply required to (i) function as the adhesive layer 15, as illustrated in FIG. 8(d), instead of a
above-mentioned partial reflecting mirror and (ii) withstand fixing section 20.
US 8,833,975 B2
29 30
Embodiment 3 cates that increasing respective thermal conductivities of the
light emitting section 7 and the gap layer causes their respec
The following describes a third embodiment of the present tive thermal resistances to decrease.
invention with reference to FIG. 9. The present embodiment The thermal resistance can be decreased by a method, other
is described as a headlamp 100 which serves as an example of 5 than increasing the thermal conductivity, such as (i) increas
the illuminating device of the present invention. Members ing respective heat dissipation areas (that is, an area by which
similar to their respective equivalents in Embodiments 1 and a member is in contact with another) of the light emitting
2 are each assigned the same reference numeral, and are thus section 7 and the gap layer and (ii) reducing respective thick
not described here. nesses of the light emitting section 7 and the gap layer.
(Configuration of Headlamp 100) 10 The thermal resistance simply needs to be a value indica
FIG. 9 is a cross-sectional view illustrating the configura tive of difficulty in heat conduction. Thus, the present inven
tion of the headlamp 100. As illustrated in FIG. 9, the head tion may be implemented on the basis of a thermal resistance
lamp 100 includes a laser diode array 2, aspherical lenses 4, concept other than the concept represented by Formula (1).
an optical fiber 5, a ferrule 6, a light emitting section 7, a (Advantage of Headlamp 100)
reflecting mirror 8, a transparent plate (first light-transmitting 15 The headlamp 100 is configured such that the heat con
member) 9, a housing 10, an extension 11, a lens (second ducting member 13 (i) is disposed so as to face the excitation
light-transmitting member) 12, a heat conducting member light irradiation Surface of the light emitting section 7 and (ii)
(first heat conducting member) 13, and an adhesive layer 15. absorbs heat of the light emitting section 7 so as to cool the
The headlamp 100 differs from the headlamp 1 in that it does light emitting section 7. The light emitting section 7 generates
not include a cooling section 14. most heat on the excitation light irradiation Surface. Thus,
In the headlamp 100, the light emitting section 7 may be thermally connecting the heat conducting member 13 to the
caused to contact the heat conducting member 13 by a physi excitation light irradiation surface effectively cools the light
cal force. In this case, the adhesive layer 15 is not necessarily emitting section 7.
required. AS Such, it is possible to (i) lengthen a life of a headlamp
The heat conducting member 13 is a plate-shaped member 25 serving as a light Source which uses a laser beam as excitation
which has (i) a first end in thermal contact with the laser beam light and which has an extremely high luminance, and thus
irradiation surface 7a of the light emitting section 7 and (ii) a (ii) improve reliability of the headlamp.
second end connected to the reflecting mirror 8. In other The heat conducting member 13 receives heat from the
words, the heat conducting member 13 is provided so as to (i) light emitting section 7, and the heat is utilized to (i) prevent
receive heat from the light emitting section 7 and (ii) conduct 30 or remove dew condensation inside the headlamp 100 (par
it to another member so that the heat can be utilized. ticularly, on the surface of the reflecting mirror 8) or (ii)
The heat conducting member 13, shaped and connected as prevent the headlamp 100 from freezing or unfreeze it.
above, (i) holds the minute light emitting section 7 at a light The above arrangement allows effective use of heat of the
emitting section fixing location and (ii) conducts heat gener light emitting section 7, and thus eliminates the need to con
ated by the light emitting section 7 to the reflecting mirror 8. 35 Sume extra energy in order to, for example, prevent dew
This arrangement warms the reflecting mirror 8 so as to condensation. As a result, it is possible to reduce power con
prevent or remove dew condensation on a Surface of the sumption of the headlamp 100.
reflecting mirror 8.
Since the heat conducting member 13 is warmed by the Embodiment 4
light emitting section 7, the above arrangement removes dew 40
condensation (cloudiness) on the heat conducting member 13 The following describes a fourth embodiment of the
itself as well. present invention with reference to FIG. 10. Members similar
The reflecting mirror 8 is preferably made of a metal so that to their respective equivalents in Embodiment 1 are each
heat of the heat conducting member 13 is efficiently con assigned the same reference numeral, and are thus not
ducted to the entire reflecting mirror 8. In a case where the 45 described here. FIG. 10 is a view schematically illustrating a
reflecting mirror 8 is made of a resin so as to be light in configuration of a headlamp 110 in accordance with the
weight, the reflecting mirror 8 may be provided, on the sur present embodiment of the present invention.
face thereof, with a wire thermally connected to the heat In the headlamp 110 of the present embodiment, the heat
conducting member 13. This allows heat of the heat conduct conducting member 13 has an end connected to the reflecting
ing member 13 to be conducted to the entire reflecting mirror 50 mirror 8 and extending from the reflecting mirror 8, the end
8. The heat conducting member 13 preferably has a thermal being connected to a first end of a heat pipe (second heat
conductivity of 20 W/mk or greater so as to efficiently con conducting member) 116.
duct heat of the light emitting section 7. The heat pipe 116 includes (i) a pipe made of a highly heat
(Thermal Resistance) conductive metal such as copper and (ii) an operating fluid
The description above deals with respective materials of 55 encased in the pipe. The heat pipe 116 may further include
the members of the present invention with regard to thermal capillaries so that the operating fluid flows rapidly by capil
conductivity. The present invention can, however, also be lary phenomenon.
described from a viewpoint of thermal resistance. The heat pipe 116 has a second end which extends through
The term “thermal resistance' as used in the present speci an opening of the extension 11 to be connected to the lens 12
fication refers to a value indicative of difficulty in heat con 60 so that heat can be conducted to the lens 12.
duction, and is represented by the following Formula (1): The heat pipe 116 allows heat of the light emitting section
7 which heat has been received by the heat conducting mem
thermal resistance=(1?thermal conductivity) (length of ber 13 to be conducted to the lens 12. This arrangement
heat dissipation path sectional area for heat dissi warms the lens 12 and dissipates heat of the light emitting
pation) (1) 65 section 7 to outside air.
Increasing the thermal conductivity decreases the thermal Since the lens 12 is directly exposed to outside air, snow
resistance if the other parameters are unchanged. This indi may lie on the lens 12 in a cold district. The headlamp 110
US 8,833,975 B2
31 32
warms the lens 12 with use ofheat of the light emitting section makes it possible to reliably keep Supporting the light emit
7, and can thus thaw such snow on the lens 12. While it is ting section 7 in position even in a case where the gap layer 15
possible to thaw such snow on the lens 12 with use of a has a weakened close contact.
different heat Source, using heat of the light emitting section The transparent plate 9 may be adhered, contacted, or fused
7 as Such can save energy. 5 (hereinafter collectively referred to as close contact) to the
The heat conducting member for conducting heat of the light emitting section 7. Such close contact allows heat gen
heat conducting member 13 to the lens 12 is not limited to a erated by the light emitting section 7 to be conducted to the
heat pipe, and may alternatively be, for example, a thin wire. transparent plate 9 more effectively.
(Supporting Member 213)
Embodiment 5 10 The supporting member 213 is provided so as to face the
laser beam irradiation Surface 7a of the light emitting section
The following describes a fifth embodiment of the present 7. The laser beam irradiation surface 7a is a surface which is
invention with reference to FIGS. 11 through 15. The present irradiated with excitation light. The supporting member 213
embodiment is described as a headlamp 200 which serves as 15 is a light-transmitting member which receives heat of the light
an example of the illuminating device of the present inven emitting section 7, and is thus thermally connected to the light
tion. emitting section 7 (that is, connected so that thermal energy
(Configuration of Headlamp 200) can be transferred from the light emitting section 7). Specifi
The description below first deals with a configuration of the cally, the Supporting member 213 and the light emitting sec
headlamp 200 with reference to FIG. 11. FIG. 11 is a cross tion 7, as illustrated in FIG. 12, closely contact each other via
sectional view illustrating a configuration of the headlamp the gap layer 15.
200. As illustrated in FIG. 11, the headlamp 200 includes a The Supporting member 213 has opposite ends through
laser diode array 2, aspherical lenses 4, an optical fiber 5, a which, for example, two respective screws 214 penetrate, and
ferrule 6, a light emitting section 7, a reflecting mirror 8, a thus fixes the screws 214. The screws 214 have respective
transparent plate (fall preventing mechanism; pressure apply- 25 front ends buried in the transparent plate 9. Naturally, the
ing mechanism; facing member)9, a housing 10, an extension number of the screws 214 is not limited to two. The support
11, a lens 12, a supporting member 213, a screw 214 (fall ing member 213 may alternatively have, for example, four
preventing mechanism; pressure applying mechanism), and a corners through which four respective Screws penetrate, and
gap layer 15. thus fix the four screws. This alternative arrangement presses
The light emitting section 7, as illustrated in FIG. 12, 30 the light emitting section 7 against the Supporting member
closely contacts the Supporting member 213 via the gap layer 213 more strongly.
15, and is thus supported by the supporting member 213 in Since the laser beam emitted from the laser diode 3 passes
position. Specifically, the light emitting section 7 closely and through the supporting member 213 before reaching the light
fixedly contacts, via the gap layer 15, a Surface of the Sup emitting section 7, the supporting member 213 is preferably
porting member 213 which surface is opposite to a surface 35 made of a material which is highly light-transmitting.
irradiated with a laser beam.
The Supporting member 213 has opposite ends through The supporting member 213 can be made of a material such
which, for example, two screws 214 penetrate, and fixes the as Sapphire (Al2O), magnesia (MgO). gallium nitride (GaN),
screws 214. The screws 214 have respective frontends buried and spinel (MgAlO4).
in the transparent plate 9. FIG. 12 is a structural diagram 40 The Supporting member 213 may be in a shape of a plate
illustrating how the light emitting section 7 and the Support with no bend, or have a bent portion and/or a curved portion.
ing member 213 closely contact each other with use of the gap The supporting member 213 is, however, preferably flat (in
layer 15 and the two screws 214. The gap layer 15 may be not the plate shape) at a portion to which the light emitting section
only a layer of cured transparent adhesive, but also a layer of 7 closely contacts the supporting member 213. This allows
a material which itself is not cured such as transparent heat 45 the light emitting section 7 to closely contact the Supporting
dissipating grease. member 213 in a secure manner.
The ferrule 6 may be fixed with respect to (i) the reflecting The supporting member 213 preferably has a thickness
mirror 8 by use of, for example, a bar-shaped or tube-shaped which is not less than 0.3 mm and not greater than 3.0 mm. If
member that extends out from the reflecting mirror 8 or (ii) the thickness is less than 0.3 mm, the supporting member 213
the supporting member 213. 50 cannot sufficiently dissipate heat of the light emitting section
The transparent plate 9 may be used to press the light 7, and the light emitting section 7 may thus be impaired. If the
emitting section 7 against the Supporting member 213. In thickness is greater than 3.0 mm, the Supporting member 213
other words, the light emitting section 7 may be sandwiched will absorb more of the laser beam emitted thereto, and effi
between the supporting member 213 and the transparent plate ciency in use of excitation light will in consequence decrease
9. As described above, the two screws 214 fixedly penetrate 55 significantly.
through the respective opposite ends of the Supporting mem (Variation of Supporting Member 213)
ber 213, and have the respective front ends buried in the The supporting member 213 may alternatively include a
transparent plate 9. With this arrangement, the transparent portion which is light-transmitting (light-transmitting sec
plate 9 can apply a pressure that causes the light emitting tion) and a portion which is not light-transmitting (light
section 7 and the supporting member 213 to press each other. 60 blocking section). In this case, the light-transmitting section
In other words, the transparent plate 9, in which the screws is disposed so as to cover the laser beam irradiation Surface 7a
214 fixed by the supporting member 213 are inserted, func of the light emitting section 7, whereas the light blocking
tions as a pressure applying mechanism for applying a pres section is disposed so as to Surround the light-transmitting
Sure to press the light emitting section 7 against the Support section.
ing member 213. 65 The light blocking section may be a heat dissipating mem
Pressing the light emitting section 7 against the Supporting ber made of a metal (for example, copper or aluminum). The
member 213 with use of the transparent plate 9 as above light blocking section may alternatively be made of a light
US 8,833,975 B2
33 34
transmitting material having a Surface that is provided with a The pins 231 further penetrate through respective through
film which reflects illumination light such as a film made of holes of the supporting member 213 in a manner in which
aluminum or silver. play remains. The pins 231 each have a tip which sticks out
The present embodiment uses the gap layer 15, which is an from the corresponding through hole. The tip is provided with
adhesive layer, to adhere the light emitting section 7 to the 5 (i) a spring 232 (pressure applying mechanism) through
supporting member 213. The present embodiment may be which the tip is inserted and (ii) a nut 233 (pressure applying
varied such that the light emitting section 7, as described mechanism) which is threadedly engaged with the tip.
above, closely contacts the supporting member 213 with As described above, Variation 1 is configured such that the
simple use of a close contact material Such as grease. Such light emitting section 7 is fixedly pressed against the Support
variation is possible because the present embodiment, as 10
ing member 213 with use of the transparent plate 9, the pins
described above, allows a pressure for pressing the light emit 231, the springs 232, and the nuts 233 so that a pressure is
ting section 7 against the Supporting member 213 to be applied to the light emitting section 7 and the Supporting
applied to the light emitting section 7. This arrangement member 213 in the direction toward each other.
eliminates the need to use an adhesive having a high adhesive
strength, and thus simply requires close contact. Further, 15 The number of the pins 231 may be two as with the screws
since it is possible to use a relatively inexpensive close con 214 of Embodiment 5. The number may alternatively be four
tact material Such as grease, the cost of producing the head or naturally any other number.
lamp 200 can be reduced. The above grease may be replaced Variation 1 allows application of a pressure having a mag
by, for example, a highly viscous oil or a transparent Substrate nitude which more appropriately corresponds to a change in
provided on both sides with an adhesive (for example, trans thermal expansion of the light emitting section 7 and the
parent double-faced tape). Supporting member 213.
(Advantage of Headlamp 200) Variation 1 as well as Variations 2 and 3 described below
The light emitting section 7, which emits light upon receipt includes a diffusing agent 16 in the gap layer 15. Since the
of a laser beam, generates heat while emitting light as it is laser beam has an extremely small light emitting point and is
irradiated with the laser beam. In a case where the light 25 coherent light, it may harm the human body if it is emitted
emitting section 7 is repeatedly irradiated with the laser beam, directly to the outside without being converted into fluores
the light emitting section 7 generates an increasing amount of cence or diffused by the light emitting section 7. The diffusing
heat. This leads to a difference in thermal expansion between agent 16 included in the gap layer 15 diffuses the laser beam
the supporting member 213 and the light emitting section 7 emitted from the optical fiber 5 so that the light emitting point
due to a difference in coefficient of thermal expansion 30
is expanded and the laser beam is converted into incoherent
between them.
light.
Thus, in a case where the light emitting section 7 is fixed to Thus, even if the laser beam is not entirely converted into
the supporting member 213 via the gap layer 15, which is an fluorescence or diffused by the light emitting section 7, the
adhesive layer, or a close contact material Such as grease diffusing agent 16, which diffuses the laser beam in advance,
without use of the above-described pressure applying mecha 35
nism including the transparent plate 9 and the screws 214, the reduces the possibility of coherent light leaking to the outside.
above difference in thermal expansion causes a mechanical The reflective film 17 covers at least a portion of a surface
stress to a portion at which the Supporting member 213 and of the gap layer 15 which surface is in contact with neither the
the light emitting section 7 closely contact each other, and light emitting section 7 nor the Supporting member 213.
thus weakens close contact at the close contact portion. This 40 (Variation 2)
makes it difficult for the supporting member 213 to keep FIG. 14 is a view schematically illustrating a configuration
Supporting the light emitting section 7, possibly letting the of Variation 2 of the headlamp 200 inaccordance with the fifth
light emitting section 7 fall. embodiment. As illustrated in FIG. 14.Variation 2 is arranged
The headlamp 200 uses the transparent plate 9 and the Such that the Supporting member 213 has through holes and
screws 214 to apply a pressure to the light emitting section 7 45 that pins 231a (pressure applying mechanism) are hooked on
and the supporting member 213 in the direction toward each the supporting member 213. Specifically, the pins 231a each
other. The pressure thus applied causes the light emitting have (i) a discoid head and (ii) a neck, which is fitted in one of
section 7 to be pressed against the Supporting member 213. the through holes of the supporting member 213 so that the
Thus, even in the case where the difference in thermal pins 231a are attached to and fitted in the Supporting member
expansion between the Supporting member 213 and the light 50 213.
emitting section 7 causes a mechanical stress, which in turn The pins 231a furtherpenetrate through respective through
weakens close contact at the above-mentioned portion at holes of the transparent plate 9 in a manner in which play
which the Supporting member 213 and the light emitting remains. The pins 231a each have a tip which sticks out from
section 7 closely contact each other, the above arrangement the corresponding through hole. The tip is provided with (i) a
presses the light emitting section 7 against the Supporting 55 spring 232a (pressure applying mechanism) through which
member 213. The supporting member 213 can thus keep the tip is inserted and (ii) a nut 233a (pressure applying
Supporting the light emitting section 7. mechanism) which is threadedly engaged with the tip.
(Variation 1) As described above, Variation 2 is configured such that the
FIG. 13 is a view schematically illustrating a configuration light emitting section 7 is fixedly pressed against the Support
of Variation 1 of the headlamp 200 inaccordance with the fifth 60 ing member 213 with use of the transparent plate 9, the pins
embodiment. As illustrated in FIG. 13, Variation 1 is arranged 231a, the springs 232a, and the nuts 233a so that a pressure is
such that the transparent plate 9 has through holes and that applied to the light emitting section 7 and the Supporting
pins 231 (pressure applying mechanism) are hooked on the member 213 in the direction toward each other.
transparent plate 9. Specifically, the pins 231 each have (i) a Variation 2 allows application of a pressure having a mag
discoid head and (ii) a neck, which is fitted in one of the 65 nitude which more appropriately corresponds to a change in
through holes of the transparent plate 9 so that the pins 231 are thermal expansion of the light emitting section 7 and the
attached to and fitted in the transparent plate 9. Supporting member 213.
US 8,833,975 B2
35 36
(Variation 3) preventing mechanism), that is, a Supporting member 253
FIG. 15 is a view schematically illustrating a configuration having a lower end with a projection. The Supporting member
of Variation 3 of the headlamp 200 inaccordance with the fifth 253 is provided, at its lower end, with, e.g., a plate-shaped
embodiment. As illustrated in FIG.15. Variation3 is arranged member which is similar to the fall preventing plate 252
such that (i) the supporting member 213 has through holes described above and which serves as the above projection.
235, (ii) the transparent plate 9 has through holes 236, and (iii) With this configuration, the light emitting section 7 is dis
a spring 234 (pressure applying mechanism) penetrates posed on a bottom of a box constituted by the Supporting
through both the through holes 235 and 236 in a manner in member 253 and the transparent plate 9. The configuration
which play remains. The spring 234 presses the light emitting reliably prevents a fall of the light emitting section 7 even in
section 7 against the Supporting member 213 So as to fix the 10 the case where close contact between the light emitting sec
light emitting section 7. This configuration applies a pressure tion and the supporting member 253 is weakened. This con
to the light emitting section 7 and the supporting member 213 figuration eliminates the need itself to adhere the light emit
in the direction toward each other. ting section 7 to the supporting member 253, and reliably
Variation 3 allows application of a pressure having a mag fixes the light emitting section 7 to the Supporting member
nitude which more appropriately corresponds to a change in 15 253.
thermal expansion of the light emitting section 7 and the Naturally, the above projection may alternatively be pro
Supporting member 213. vided at a lower end of the transparent plate 9.
The present embodiment includes, in addition to the screws
Embodiment 6 214 of Embodiment 5, the metal ring 251, the fall preventing
plate 252, or the light emitting section fixing structure.
The following describes a sixth embodiment of the present Instead of the screws 214 of Embodiment 5, a gap layer may
invention with reference to FIG. 16. Members similar to their be provided between the light emitting section 7 and the
respective equivalents in Embodiments 1 through 5 are each transparent plate 9 as in the case where the gap layer 15 is
assigned the same reference numeral, and are thus not provided between the light emitting section 7 and the Sup
described here. 25 porting member 213. In this case, even if (i) close contact of
Embodiment 5 above is configured such that (i) the Sup the gap layer 15 between the light emitting section 7 and the
porting member 213 has opposite ends through which the two supporting member 213 or 253 is weakened and (ii) close
respective screws 214 penetrate and that (ii) the screws 214 contact of the gap layer between the light emitting section 7
have their respective frontends buried in the transparent plate and the transparent plate 9 is weakened so that neither of the
9. 30 supporting member 253 and the transparent plate 9 can sup
The present embodiment, in contrast, includes a member port the light emitting section 7 any longer, the above-de
described below, specifically a metal ring, a fall preventing scribed member, namely the metal ring 251, the fall prevent
plate, or a light emitting section fixing structure, in addition to ing plate 252, or the light emitting section fixing structure,
the screws 214 of Embodiment 5 (see FIG.16). The use of the prevents the light emitting section 7 from falling.
member Such as a metal ring prevents the light emitting sec 35
tion 7 from falling off the supporting member 213, even in a Embodiment 7
case where close contact between the light emitting section 7
and the supporting member 213 is weakened. FIG. 16 omits The following describes a seventh embodiment of the
the screws 214 for ease of view. present invention with reference to FIGS. 17 through 22. The
FIG.16(a), for example, illustrates a configuration includ 40 present embodiment is described as a headlamp 300 which
ing a metal ring 251 (fall preventing mechanism) in addition serves as an example of the illuminating device of the present
to the screws 214 of Embodiment 5. With this configuration, invention.
the metal ring 251 reliably prevents a fall of the light emitting (Configuration of Headlamp 300)
section 7 even in the case where close contact between the The description below first deals with a configuration of the
light emitting section 7 and the Supporting member 213 is 45 headlamp 300 with reference to FIG. 17. FIG. 17 is a cross
weakened. The metal ring 251 is not necessarily required to sectional view illustrating a configuration of the headlamp
contact the light emitting section 7 along the entire periphery 300. As illustrated in FIG. 17, the headlamp 300 includes a
of the light emitting section 7. In a case where, for example, laser diode array 2, aspherical lenses 4, an optical fiber 5, a
the light emitting section 7 is in a cuboid or cube shape, the ferrule 6, a light emitting section 7, a reflecting mirror 8, a
metal ring 251 may be in contact with the light emitting 50 transparent plate 9, a housing 10, an extension 11, a lens 12,
section 7 at three or four points thereof. Naturally, the metal aheat conducting member (first heat conducting member) 13,
ring 251 is fixed in advance between the supporting member a hollow member (second heat conducting member) 314, and
213 and the transparent plate 9. a cooling section 14. FIG. 18 is a structural diagram illustrat
FIG.16(b) illustrates a configuration including a fall pre ing how the heat conducting member 13 and the hollow
venting plate 252 (fall preventing mechanism) in addition to 55 member 314 are connected (adhered or welded) to each other.
the screws 214 of Embodiment 5. With this configuration, the FIG. 18 illustrates in (a) a cross-sectional view of the struc
fall preventing plate 252 reliably prevents a fall of the light ture and in (b) a perspective view thereof.
emitting section 7 even in the case where close contact (Optical Fiber 5)
between the light emitting section 7 and the Supporting mem (Disposition of Optical Fiber 5)
ber 213 is weakened. The light emitting section 7 is simply 60 The optical fiber 5 is a light guiding member which guides
required to be disposed on a top surface of the fall preventing to the light emitting section 7 the laser beams emitted by the
plate 252. Naturally, the fall preventing plate 252 is fixed in laser diodes 3, and is a bundle of a plurality of optical fibers.
advance between the supporting member 213 and the trans The optical fiber 5 has (i) a plurality of entering ends 5b each
parent plate 9. of which receives a laser beam, and (ii) a plurality of emitting
FIG. 16(c) illustrates a configuration which includes, in 65 ends 5a each of which emits a laser beam entered via a
addition to the screws 214 and the transparent plate 9 of corresponding one of the entering ends 5b. The plurality of
Embodiment 5, a light emitting section fixing structure (fall emitting ends 5a emit laser beams to respective regions on a
US 8,833,975 B2
37 38
laser beam irradiation Surface (excitation light irradiation The opposite surface 7b generates, as illustrated in FIG.
surface) 7a of the light emitting section 7. 18(a), (i) its most amount of heat in the vicinity of its center
The laser beam irradiation surface 7a is, as illustrated in and (ii) a Smaller amount of heat at a portion farther away
FIGS. 17 and 18, a flat surface in a case where the light from the vicinity of the center. This is because the light
emitting section 7 is in a cuboid or cube shape. The light emitting section 7 is irradiated with excitation light at the
emitting section 7 is naturally not limited in shape to a cuboid laser beam irradiation surface 7a, that is, in the vicinity of a
ora cube, and may be in any shape as long as the light emitting center of a side surface facing the emitting ends 5a, and the
section 7 has a Solid body having a three dimensional spatial excitation light is thus mostly directed to the vicinity of the
extent. In a case where, for example, the light emitting section center of the opposite surface 7b.
7 is in a spherical shape, the laser beam irradiation surface 7a 10 The hollow member 314 is a hollow member in a cuboid or
is naturally a spherical Surface. cube shape in the case where the light emitting section 7 is in
The laser beam irradiation surface 7a illustrated in FIG. the cuboid or cube shape (see FIG. 18(b)). The hollow mem
18(a) is for a case in which the laser beam irradiates only a ber 314 has a surface connected to the heat conducting mem
central portion of the light emitting section 7. In a case where ber 13, the Surface having an opening. This causes the laser
the laser beam irradiates a first surface of the light emitting 15 beam irradiation surface 7a of the light emitting section 7.
section 7 in its entirety which first surface faces the optical fitted in the hollow member 314, to be adhered to the heat
fiber 5, the laser beam irradiation surface 7a naturally corre conducting member 13.
sponds to the entire first Surface of the light emitting section In other words, the hollow member 314 both covers the
7. light emitting section 7 and causes the laser beam irradiation
(Heat Conducting Member 13) surface 7a of the light emitting section 7 to be adhered to the
The heat conducting member 13 is provided so as to face heat conducting member 13. Further, the hollow member 314
the laser beam irradiation Surface (excitation light irradiation causes its inner wall to be adhered to (i) the opposite surface
surface) 7a of the light emitting section 7. The laser beam 7b of the light emitting section 7, the opposite surface 7b
irradiation surface 7a is a surface which is irradiated with being opposite to the laser beam irradiation Surface 7a, and
excitation light. The heat conducting member 13 is a light 25 (ii) each of four perpendicular surfaces 7c of the light emitting
transmitting member which receives heat of the light emitting section 7, the perpendicular surfaces 7c being perpendicular
section 7, and is thus thermally connected to the light emitting to the laser beam irradiation surface 7a.
section 7 (that is, connected so that thermal energy can be The hollow member 314, shaped and connected as above,
transferred from the light emitting section 7). Specifically, the dissipates to the outside of the headlamp 300 heat generated
heat conducting member 13 and the light emitting section 7 30 by the light emitting section 7. Specifically, the light emitting
are, as illustrated in FIG. 18(a), adhered to each other with use section 7 dissipates heat to the hollow member 314, the heat
of the hollow member 314. The light emitting section 7 is then being conducted through the inside of the hollow mem
fitted in the hollow member 314. The heat conducting mem ber 314 to reach a connection portion at which the heat con
ber 13 and the hollow member 314 are, as described above, ducting member 13 is connected to the hollow member 314.
connected (adhered or welded) to each other so that the light 35 The heat is transferred from the hollow member 314 to the
emitting section 7 is adhered to the heat conducting member heat conducting member 13 at the connection portion.
13. The hollow member 314 preferably has a thermal conduc
The heat conducting member 13 is preferably a light-trans tivity of 20 W/mK or greater in order to dissipate heat of the
mitting member. The heat conducting member 13 may alter light emitting section 7 efficiently. Further, the hollow mem
natively be made of a material which is not light-transmitting 40 ber 314 is preferably made of a highly light-transmitting
(for example, a metal) as long as the heat conducting member material because fluorescence emitted from the light emitting
13 has an opening through which the laser beam passes. section 7 passes through the hollow member 314 to travel
(Hollow Member 314) toward the lens 12.
The hollow member 314 is provided so as to face an oppo In view of the above preferable points, the hollow member
site surface 7b of the light emitting section 7, the opposite 45 314 is preferably made of a material Such as Sapphire (Al2O),
surface 7b being opposite to the laser beam irradiation surface magnesia (MgO), gallium nitride (GaN), and spinel
7a, which is a surface irradiated with excitation light. The (MgAl2O). Using one of the above materials achieves a
hollow member 314 is a light-transmitting member which thermal conductivity of 20 W/mK or greater.
receives heat of the light emitting section 7, and is thus ther The hollow member 314 preferably has a thickness 314c
mally connected to the light emitting section 7 (that is, con 50 (see FIG. 18(a)) which is not less than 0.3 mm and not greater
nected so that thermal energy can be transferred from the light than 3.0 mm. The thickness 314c refers to a thickness along a
emitting section 7). Specifically, the light emitting section 7 is direction extending from a first surface 314a of the hollow
fitted in the hollow member 314 as illustrated in FIG. 18(a). member 314 to a second surface 314b of the hollow member
The hollow member 314 is, as described above, connected 314, the first surface 314.a facing the light emitting section 7
(adhered or welded) to the heat conducting member 13 so that 55 and the second surface 314b being opposite to the first surface
the light emitting section 7 inside the hollow member 314 is 314a. If the thickness is less than 0.3 mm, the hollow member
adhered to the heat conducting member 13. 314 cannot sufficiently dissipate heat of the light emitting
The opposite surface 7b, located opposite to the laser beam section 7, and the light emitting section 7 may thus be
irradiation surface 7a, is a flat surface as with the laser beam impaired. If the thickness is greater than 3.0 mm, the hollow
irradiation surface 7a in the case where the light emitting 60 member 314 will absorb more of fluorescence emitted from
section 7 is in the cuboid or cube shape (see FIGS. 17 and 18). the light emitting section 7, and efficiency in use of excitation
The light emitting section 7 is naturally not limited in shape to light will in consequence decrease significantly.
a cuboid or a cube, and may be in any shape as long as the light With an arrangement in which the hollow member 314
emitting section 7 has a Solid body having a three dimensional having an appropriate thickness is in contact with the light
spatial extent. In a case where, for example, the light emitting 65 emitting section 7, it is possible to dissipate heat rapidly and
section 7 is in a spherical shape, the opposite surface 7b is efficiently, particularly in a case where a laser beam irradiat
naturally a spherical Surface. ing the light emitting section 7 is so extreme in intensity that
US 8,833,975 B2
39 40
the light emitting section 7 generates heat of for example, are in a perfectly spherical shape, and have a particle size
greater than 1 W. The above arrangement thus prevents the which ranges from several nanometers to several microme
light emitting section 7 from being damaged (impaired). ters. The SiO, beads are mixed in each of the heat conducting
In a case where, in particular, the laser beam is intense, the member 13 and the hollow member 314 at 0.1 to several
light emitting section 7 generates heat in an amount which percent. The diffusing agent is preferably contained in an
greatly exceeds an amount of heat dissipated from the heat amount which falls within a range approximately from 1 mg
conducting member 13. This indicates that the heat conduct to 30 mg per gram of each of the heat conducting member 13
ing member 13 is lower in heat dissipation efficiency for a and the hollow member 314 because containing an excessive
portion farther away from the laser beam irradiation surface amount of the diffusing agent reduces a portion of the laser
7a, which is adhered to the heat conducting member 13. The 10 beam which portion reaches the light emitting section 7.
heat dissipation efficiency is lowest at a portion near the Containing a transparent, inorganic Substance Such as the
opposite surface 7b, located farthest away from the laser above also improves the thermal conductivity of each of the
beam irradiation Surface 7a, which faces the heat conducting heat conducting member 13 and the hollow member 314.
member 13. The hollow member 314 has an inner wall closely SiO, has a thermal conductivity of 1.38 W/mK, which is
contacting the opposite Surface 7b, and is thus capable of 15 higher than that of acrylic resin. The diamond beads have a
receiving heat from the opposite surface 7b. thermal conductivity which ranges from 800 to 2000 W/mk,
The inner wall of the hollow member 314 is, needless to which is significantly higher than that of acrylic resin. Con
say, also adhered to each of the four surfaces 7c perpendicular taining a transparent, inorganic Substance as above signifi
to the laser beam irradiation surface 7a. The hollow member cantly improves the thermal conductivity of each of the heat
314 is thus capable of receiving heat of the light emitting conducting member 13 and the hollow member 314 in con
section 7 via the four surfaces 7c as well. Sequence.
The hollow member 314 produces its effect in a case (Variation of Hollow Member 314)
where, for example, (i) among fluorescent materials included FIG. 20 is a cross-sectional view illustrating a variation of
in the light emitting section 7, a fluorescent material with a the hollow member 314. As illustrated in FIG. 20, the hollow
highest conversion efficiency has a conversion efficiency of 25 member 314 is roughly divided into (i) an opposite surface
90%, (ii) the laser beam irradiation surface 7a of the light close contact section (second heat conducting member) 141
emitting section 7 is 2 mm in area, and (iii) the laserbeam has closely contacting the opposite surface 7b of the light emit
an intensity of 1 W or greater. In other words, the hollow ting section 7, the opposite surface 7b being opposite to the
member 314 provided in addition to the heat conducting laser beam irradiation Surface 7a, and (ii) a perpendicular
member 13 effectively prevents a temperature rise in the light 30 Surface close contact section (third heat conducting member)
emitting section 7 in a case where the light emitting section 7 142 closely contacting apart of the perpendicular surfaces 7c,
generates heat in an amount of 0.1 W or greater. which are perpendicular to the laser beam irradiation surface
(Variation in Which Hollow Member 314 is Connected to 7a.
Transparent Plate 9) The hollow member 314 illustrated in FIGS. 17 and 18 is an
The transparent plate 9 may be used to cool the hollow 35 example including a portion corresponding to the perpen
member 314 as illustrated in FIG. 19. Specifically, the hollow dicular surface close contact section 142 illustrated in FIG.
member 314 may be thermally connected to the transparent 20, the portion (i) closely contacting all the perpendicular
plate 9 (that is, connected so that thermal energy can be surfaces 7c perpendicular to the laser beam irradiation surface
transferred from the hollow member 314). This allows heat 7a and (ii) being connected to the heat conducting member
dissipated from the light emitting section 7 to the hollow 40 13. This configuration causes the light emitting section 7 to
member 314 to be in turn dissipated via the transparent plate closely contact the heat conducting member 13.
9. The transparent plate 9, which is large in volume as com In contrast, the perpendicular surface close contact section
pared to the hollow member 314, has a heat capacity larger 142 of the variation illustrated in FIG. 20 closely contacts a
than that of the hollow member 314. Thus, in a case where the part of the perpendicular surfaces 7c perpendicular to the
hollow member 314 is connected to the transparent plate 9 at 45 laser beam irradiation surface 7a. In other words, such a part
a connection portion, there occurs a thermal gradient at the of the perpendicular surfaces 7c perpendicular to the laser
connection portion. The thermal gradient causes heat to be beam irradiation surface 7a is not covered by the hollow
transferred from the hollow member 314 to the transparent member 314 and is thus exposed.
plate 9. The transparent plate 9 is normally fixed to the hous The perpendicular Surface close contact section 142 is
ing 10 or the like (not shown). The heat transferred from the 50 connected to the heat conducting member 13 at a portion of
hollow member 314 to the transparent plate 9 is dissipated via the perimeter of the laser beam irradiation surface 7a, via
the housing 10 or the like to the outside of the headlamp 300. which the light emitting section 7 closely contacts the heat
(Dispersing Agent) conducting member 13. In this case, the perpendicular Sur
The heat conducting member 13 and the hollow member face close contact section 142 is preferably connected to the
314 may each include a diffusing agent (not shown). Since the 55 heat conducting member 13 at a location vertically under the
laser beam is coherent light, it may harm the human body if it light emitting section 7 So as to prevent the light emitting
is emitted directly to the outside without being converted into section 7 from falling in the vertical direction. This configu
fluorescence or diffused by the light emitting section 7. ration fixes a relative positional relationship between the heat
Including the diffusing agent in the heat conducting member conducting member 13 and the hollow member 314.
13 and the hollow member 314 allows diffusion of the laser 60 The variation illustrated in FIG. 20 can reduce an amount
beam emitted from the optical fiber 5. of a material of the hollow member 314 as compared to the
Thus, even if the laser beam is not entirely converted into hollow member 314 illustrated in FIGS. 17 and 18. The varia
fluorescence or diffused by the light emitting section 7, the tion can thus reduce a material cost for the hollow member
diffusing agent, which diffuses the laser beam in advance, 314, and consequently reduce the cost of producing the head
reduces the possibility of coherent light leaking to the outside. 65 lamp 300.
The diffusing agent is preferably made of beads such as FIGS. 21(a) through 21(c) are each a perspective view
SiO beads. Al-O beads, and diamond beads. The SiO beads illustrating a different variation of the hollow member 314.
US 8,833,975 B2
41 42
In a case where, for example, the light emitting section 7 is that it does not have a definite melting point or softening
a cylindrical column in shape as illustrated in FIG. 21(a), the point. Quartz gradually decreases in Viscosity with a tempera
hollow member 314 may be varied to a cylindrical hollow ture rise above 1550° C.
member 30a which has a surface in contact with the fluores The process next fills the transparent, cup-shaped hollow
cence emitting surface of the light emitting section 7 and 5 member 314, made by a method such as CIM and carving,
which is connected (adhered or welded) to the heat conduct with (i) inorganic glass frit serving as a sealing material and
ing member 13. The hollow member 30a has a surface via (ii) a mixture containing a fluorescent material dispersed
which it is connected to the heat conducting member 13, the therein (step S102).
Surface having an opening. The process then heats the filling to a temperature slightly
Alternatively, the hollow member 314 may be varied to a 10 higher than a melting point of the inorganic glass so as to (i)
hollow member 30b which has, as illustrated in FIG. 21(b), a thus disperse the fluorescent material in the inorganic glass and
Surface that is in contact with the fluorescence emitting Sur serving (ii) make, inside the hollow member 314, a sintered body
face and that is partially open (particularly, at a central por as a light emitting section 7 (step S103).
tion). This configuration prevents fluorescence loss which is 15 referred to as lowglass
The inorganic is suitably a material which is normally
melting glass and which has a melting point
caused by the hollow member 30b absorbing fluorescence of 600° C. or lower. The material may, however, have a
emitted from the light emitting section 7. The hollow member melting point lower than a melting point of the transparent
30b is preferably a light-transmitting member, but may be cup as long as the fluorescent material does not suffer from,
made of a material which is not light-transmitting (for for example, a change or impairment in quality.
example, a metal) as long as the hollow member 30b is open 20 The process next polishes the light emitting section 7.
at the central portion. sintered inside the hollow member 314, together with the
A further alternative variation may include, as illustrated in hollow member 314 to form a planar surface (step S104). In a
FIG. 21(c), a light emitting section fixing member 31 which case where the hollow member 314 is made of sapphire, the
includes (i) a first section 32 corresponding to the heat con polishing uses a diamond slurry.
ducting member 13 of FIG. 18(b) and (ii) a second section 33 25 The process finally bonds the hollow member 314, having
corresponding to the hollow member 314 of FIG. 18(b). The a planar Surface formed above, to the heat conducting mem
light emitting section fixing member 31 is a member formed ber 13 in such a manner that the respective planar surfaces
by integrating the heat conducting member 13 of FIG. 18(b) face each other (step S105).
with the hollow member 314 of FIG. 18(b) with use of, for The above steps produce the headlamp 300, particularly
example, a mold. 30 the light emitting section 7, the heat conducting member 13,
In the above variation, the light emitting section 7 is fitted and the hollow member 314.
into the second section.33 as illustrated in FIG. 21(c) through (Advantage of Headlamp 300)
an opening 33a of the second section 33. Naturally, even in The headlamp 300, when the light emitting section 7 gen
the variation of FIG. 21(c), the light emitting section 7 may erates heat, allows the heat conducting member 13 to receive
alternatively be disposed inside the second section 33 by (i) 35 heat from the laser beam irradiation surface 7a of the light
filling the second section 33 with the materials of the light emitting section 7, the laser beam irradiation surface 7a being
emitting section 7, namely the fluorescent material and the a portion having the highest temperature rise.
fluorescent material retention Substance, and (ii) sintering the In the headlamp 300, the heat conducting member 13 is
materials. lower in heat dissipation efficiency for a portion of the light
In the variation illustrated in FIG. 21(c), the first section 32 40 emitting section 7 which portion is farther away from the heat
and the second section 33 constituting the light emitting sec conducting member 13. However, the hollow member 314
tion fixing member 31 are integrated with each other, and are receives heat from the opposite surface 7b of the light emit
naturally in an extremely strong connection with each other. ting section 7, the opposite surface 7b being a portion which
This configuration consequently prevents (i) a problem of is opposite to the laser beam irradiation surface 7a and for
a positional shift of the first section 32 and the second section 45 which the heat conducting member 13 is lowest in heat dis
33 relative to each other and (ii) a problem of a fall of either sipation efficiency.
of the first section 32 and the second section 33. As described above, the headlamp 300 can use the heat
(Method for Producing Headlamp 300) conducting member 13 and the hollow member 314 to effi
The following describes an example method for producing ciently dissipate heat generated by the light emitting section 7
the headlamp 300. FIG. 22 is a flowchart showing steps of a 50 (that is, improve heat absorption efficiency of the heat con
process involved in the method for producing the headlamp ducting members). This makes it possible to cool the light
3OO. emitting section 7 more effectively. As such, it is possible to
The process of FIG. 22 first makes, of sapphire (alumina) (i) lengthen a life of a headlamp serving as a light Source
or quartz, a hollow member 314 in a shape of a transparent which uses a laser beam as excitation light and which has an
cup by ceramic injection molding (CIM) (step S101). 55 extremely high luminance, and thus (ii) improve reliability of
The hollow member 314 is 3 mm in outer diameter and 1 the headlamp.
mm in height, and has at one of end portions of the hollow
member 314 an inside hollow which is 2 mm in diameter and Embodiment 8
0.5 mm in depth. The transparent cup may be made by carving
instead of injection molding. In this case, the transparent cup 60 The following describes an eighth embodiment of the
can Suitably be made of magnesia in addition to Sapphire and present invention with reference to FIGS. 23 through 27.
quartZ. Members similar to their respective equivalents in Embodi
The hollow member 314 is required to be made of a mate ments 1 through 7 are each assigned the same reference
rial having a high melting point, which is at least 1000°C., or numeral, and are thus not described here.
preferably 1500° C. or higher. Sapphire, quartz, and magnesia 65 The present embodiment describes a laser downlight 400
have their respective melting points of 2050° C., 1550° C., as an example of an illuminating device of the present inven
and 2850° C. Quartz is different from the other materials in tion. The laser downlight 400 is an illuminating device which
US 8,833,975 B2
43 44
is disposed on a ceiling of a structure Such as a building, tions on the shape, size and disposition of the light emitting
vehicle or the like, and uses fluorescence as illumination light, section 7 are fewer than those on the headlamp.
which fluorescence is emitted upon irradiation of the light (Configuration of Light Source Unit 420)
emitting section 7 with laser beams emitted from the laser The LD light source unit 420 includes a laser diode 3, an
diodes 3. aspherical lens 4, and an optical fiber 5.
The present embodiment is an example laser downlight The entering end 5b, which is one end of the optical fiber 5,
including a basic configuration of the headlamp 1 of Embodi is connected to the LD light source unit 420. The laser beam
ment 1. The laser downlight may alternatively include a basic emitted from the laser diode 3 enters the entering end5b of the
configuration of the headlamp of any of Embodiments 2 to 7. 10
optical fiber 5 via the aspherical lens 4.
Moreover, an illuminating device having a similar configu Only one pair of the laser diode 3 and the aspherical lens 4
ration to the laser downlight 400 may be disposed on a side is illustrated inside the LD light source unit 420 of FIG. 25.
wall or a floor of the structure. Where the illuminating device However, in a case where a plurality of light emitting units
is disposed is not particularly limited. 410 are provided, a bundle of the optical fibers 5, each of
FIG. 23 is a view schematically illustrating an external 15 which extends from a respective one of the light emitting units
appearance of a light emitting unit 410 and a conventional 410, may be guided to a single LD light source unit 420. In
LED downlight 500. FIG. 24 is a cross sectional view illus this case, a plurality of pairs of the laser diode 3 and the
trating a ceiling on which the laser downlight 400 is disposed. aspherical lens 4 are stored in one LD light source unit 420,
FIG. 25 is a cross sectional view illustrating the laser down and the LD light source unit 420 functions as a centralized
light 400. As illustrated in FIGS. 23 to 25, the laser downlight power source box.
400 is embedded in a top panel 600, and includes (i) a light (Variation of how to Dispose Laser Downlight 400)
emitting unit 410 which emits illumination light and (ii) an FIG. 26 is a cross sectional view illustrating a variation of
LD light source unit 420 which supplies a laser beam to the how to dispose the laser downlight 400. As illustrated in FIG.
light emitting unit 410 via the optical fiber 5. The LD light 26, the variation of how to dispose the laser downlight 400
Source unit 420 is disposed not on the ceiling, but at a location 25 may be one in which the top panel 600 simply has a small hole
where the user can easily touch (e.g., on a side wall of the 602 opened for passing through the optical fiber 5, and the
building). The LD light source unit 420 can be freely posi laser downlight itself (light emitting unit 410) is adhered to
tioned as such since the LD light source unit 420 and the light the top panel 600, with full utilization of the thin and light
emitting unit 410 are connected to each other via the optical weight characteristics of the laser downlight 400. In this case,
fiber 5. The optical fiber 5 is disposed in a gap between the top 30
restrictions on disposing the laser downlight 400 are reduced,
panel 600 and a heat insulating material 401. and construction costs can advantageously be reduced in
(Configuration of Light Emitting Unit 410) amount to a remarkable extent.
The light emitting unit 410 includes, as illustrated in FIG. In this configuration, the heat conducting member 13 is
25, a housing 411, the optical fiber 5, the light emitting
section 7, aheat conducting member 13, and a light transmit 35 disposed so as to have a Surface which the laser beam enters,
ting plate 413. The light emitting section 7 is adhered to the the surface being in contact in its entirety with the bottom
heat conducting member 13 via an adhesive layer 15. As in the surface of the concave section 412. Thus, in a case where the
above Embodiments, heat of the light emitting section 7 is housing 411 is made of a material which is high in thermal
conducted to the heat conducting member 13, so that the light conductivity, the housing 411 can function as a cooling sec
emitting section 7 is cooled. 40 tion for cooling the heat conducting member 13.
The housing 411 has a concave section 412, and the light (Comparison of Laser Downlight 400 and Conventional
emitting section 7 is disposed on a bottom surface of the LED Downlight 500)
concave section 412. The concave section 412 has a metal thin As illustrated in FIG. 23, the conventional LED downlight
film formed on its surface, and therefore the concave section 500 includes a plurality of light transmitting plates 501, from
412 functions as a reflecting mirror. 45 each of which illumination light is emitted. In other words,
The housing 411 includes a path 414 formed through the LED downlight 500 includes a plurality of light emitting
which the optical fiber 5 passes. The optical fiber 5 passes points. Due to the relatively small luminous flux of light
through the path 414 and extends to the heat conducting emitted from each of the light emitting points, aluminous flux
member 13. The optical fiber 5 emits laser beams from its Sufficient as illumination light cannot be achieved unless a
emitting ends 5a which laser beams pass through the heat 50 plurality of the light emitting points are provided. This is why
conducting member 13 and the adhesive layer 15 to reach the the LED downlight 500 includes the plurality of the light
light emitting section 7. emitting points.
The light transmitting plate 413 is a transparent or semi In comparison, the laser downlight 400 is an illuminating
transparent plate disposed so as to close an opening of the device that has a high luminous flux. Hence, the laser down
concave section 412. The light transmitting plate 413 func 55 light 400 may have a single light emitting point. This attains
tions similarly to the transparent plate 9: Fluorescence emit an effect that a clear shadow is generated by use of the
ted from the light emitting section 7 is emitted through the illumination light. Moreover, use of a high color rendering
light transmitting plate 413 as illumination light. The light fluorescent material (e.g., a combination of several types of
transmitting plate 413 may be detachable from the housing oxynitride fluorescent material) as the fluorescent material of
411, or may be omitted from the configuration. 60 the light emitting section 7 improves color rendering proper
Although the light emitting unit 410 in FIG. 23 has a ties of the illumination light.
circular outer edge, the shape of the light emitting unit 410 The above arrangement achieves color rendering proper
(more specifically, the housing 411) is not particularly limited ties almost as high as those of an incandescent bulb down
in shape. light. Combining a high color rendering fluorescent material
As different from the case of the headlamp, the downlight 65 with the laser diode 3 produces light having high color ren
does not require an ideal point light Source, and is merely dering properties which light cannot easily be produced by an
required to have a single light emitting point. Hence, restric LED downlight or a fluorescent lamp downlight. The light
US 8,833,975 B2
45 46
has, for example, not only a general color rendering index Ra the LED downlight 500 and the laser downlight 400 in terms
of 90 or greater but also a special color rendering index R9 of of electricity consumption. Consequently, the laser downlight
95 or greater. 400 is capable of achieving the foregoing various advantages
FIG. 27 is a cross sectional view illustrating a ceiling on while consuming the same amount of electricity as the LED
which the LED downlight 500 is disposed. As illustrated in downlight 500.
FIG. 27, in the LED downlight 500, a housing 502 is embed As described above, the laser downlight 400 includes: an
ded in the top panel 600. This housing 502 contains an LED LD light source unit 420 including at least one laser diode 3
chip, a power source, and a cooling unit. The housing 502 is that emits a laser beam; at least one light emitting unit 410
relatively large, and a concave section is formed at a part of including a light emitting section 7 and a concave section 412
the heat insulating material 601 in which part the housing 502 10 that serves as a reflecting mirror; and an optical fiber 5 guid
is disposed, so that the heat insulating material 601 fits with ing the laser beam to the light emitting unit 410.
the shape of the housing 502. A power source line 503 extends (Other Variations)
from the housing 502 to be connected to a plug socket (not The present invention is not limited to the description of the
shown). embodiments above, but may be altered in various ways by a
Such a configuration causes the following problems: First, 15 skilled person within the scope of the claims. Any embodi
a light source (LED chip) and a power source, each of which ment based on a proper combination of technical means dis
is a heat generating source, are provided between the top closed in different embodiments is also encompassed in the
panel 600 and the heat insulating material 601. When the LED technical scope of the present invention.
downlight 500 is used, the temperature of the ceiling For instance, a high-output LED may be used as the exci
increases due to these heat generating Sources, thereby caus tation light Source. In this case, a light emitting device which
ing a decrease in cooling efficiency of the room. emits white light can be produced by combining (i) an LED
Further, a power source and a cooling unit are required for which emits light having a wavelength of 450 nm (blue color)
each of the LED downlight 500 provided. This increases the with (ii) a yellow fluorescent material or with green and red
total amount of costs. fluorescent materials.
In addition, since the housing 502 is a relatively large-sized 25 A solid laser other than the laser diode may be used as the
member, it is often difficult to dispose the LED downlight 500 excitation light source. It is, however, preferable that the laser
between the top panel 600 and the heat insulating material diode be used since the laser diode makes it possible to reduce
601. size of the excitation light source.
In comparison, the laser downlight 400 does not include a The present invention can alternatively be described as
large heat-generating source in the light emitting unit 410. 30 follows:
Therefore, the cooling efficiency of the room does not The light-emitting device may preferably be arranged such
decrease. Consequently, it is possible to avoid an increase in that the gap layer adheres the light emitting section and the
the costs required for cooling the room. heat conducting member to each other.
Since there is no need to provide the power source and the The above arrangement fixes the light emitting section to
cooling unit per light emitting unit 410, it is possible to reduce 35 the heat conducting member with use of the gap layer.
the size and thickness of the laser downlight 400. As a result, The light-emitting device may preferably be arranged such
restrictions on the space for disposing the laser downlight 400 that the gap layer is so flexible as to absorb a difference in
are reduced, thereby making it easy to dispose the laser down coefficient of thermal expansion between the light emitting
light 400 in already-built houses. section and the heat conducting member.
The laser downlight 400 is small and thin, and the light 40 The light emitting section and the heat conducting member
emitting unit 410 can thereby be disposed on the surface of are different from each other in coefficient of thermal expan
the top panel 600. As compared to the LED downlight 500, it Sion. Thus, in the arrangement in which the light emitting
is possible to reduce restrictions on disposition, which also section and the heat conducting member are adhered to each
allows for a remarkable reduction in construction fees. other with use of a gap layer, the light emitting section may
FIG. 28 is a graph that compares specifications of the laser 45 become detached from the heat conducting member due to
downlight 400 and those of the LED downlight 500. As the difference in coefficient of thermal expansion in a case
shown in FIG. 28, with the laser downlight 400 of this where the light emitting section generates heat.
example, the volume is reduced by 94% and the mass is According to the above arrangement, the gap layer is so
reduced by 86%, as compared to the LED downlight 500. flexible (or viscous) as to absorb the difference in coefficient
Since the LD light source unit 420 can be disposed at a 50 of thermal expansion between the light emitting section and
location which the user can reach easily, a laser diode 3 can be the heat conducting member. The arrangement thus prevents
easily replaced, in a case where it breaks down, without any the light emitting section from being detached from the heat
difficulty. Further, the optical fibers 5 extending from the conducting member due to heat generated by the light emit
plurality of light emitting units 410 are guided to a single LD ting section.
light source unit 420. This allows collective management of 55 The light-emitting device may preferably further include: a
the plurality of laser diodes 3. Accordingly, even if a plurality fixing section for fixing a relative positional relationship
of laser diodes 3 are to be replaced, the replacement can be between the light emitting section and the heat conducting
carried out easily. member.
In a case where the LED downlight 500 is of a type includ The above arrangement provides a fixing section that fixes
ing the high color rendering fluorescent material, a luminous 60 a relative positional relationship between the light emitting
flux of approximately 500 um is emitted with an electricity section and the heat conducting member. The arrangement
consumption of 10 W. In order to produce light of the same thus prevents the light emitting section from being detached
brightness with the laser downlight 400, an optical output of from the heat conducting member even in a case where the
3.3 W is required. With an LD efficiency of 35%, this optical gap layer is low in adhesiveness or a case where there has
output is equivalent to the electricity consumption of 10 W. 65 occurred a difference in coefficient of thermal expansion
Since the electricity consumption of the LED downlight 500 between the light emitting section and the heat conducting
is also 10 W, there is not much remarkable difference between member.
US 8,833,975 B2
47 48
The light-emitting device may preferably be arranged such the excitation light irradiation Surface, the thickness being at
that the fixing section is higher in thermal conductivity than least 10 times a particle size of the fluorescent material and
the light emitting section. not greater than 2 mm.
According to the above arrangement, the fixing section is In a case where the light emitting section is thin, heat
higher in thermal conductivity than the light emitting section. 5 thereof can be conducted to the heat conducting member
The fixing section thus efficiently absorbs heat generated by efficiently as compared to a case where the light emitting
the light emitting section, and consequently cools the light section is thick. If, however, the light emitting section is too
emitting section. thin, the excitation light may not be converted into fluores
The light-emitting device may preferably be arranged such cence, and may instead be emitted directly to the outside. If,
that the gap layer includes aheat conducting particle which is 10 on the other hand, the light emitting section is toothick, it may
in contact with the light emitting section and the heat con not only reduce heat dissipation efficiency of the heat con
ducting member. ducting member for the light emitting section, but also blura
The above arrangement causes heat of the light emitting light distribution pattern of the light-emitting device.
section to be conducted to the heat conducting member with The light emitting section thus preferably has a thickness
use of the heat conducting particle. The arrangement thus 15 which is at least 10 times the particle size of the fluorescent
allows heat of the light emitting section to be efficiently material and not greater than 2 mm. A simulation has shown
conducted to the heat conducting member with use of the heat that in a case where the light emitting section has a thickness
conducting particle even in a case where the gap layer which is at least 10 times the particle size of the fluorescent
includes a main component which is not so high in thermal material, nearly all the excitation light is converted into fluo
conductivity. 2O CSCCC.
The light-emitting device may preferably be arranged such The light-emitting device may preferably be arranged such
that the gap layer includes a diffusing agent for diffusing the that the heat conducting member has a thickness of not
excitation light. smaller than 0.3 mm and not greater than 3.0 mm between (i)
Since the excitation light is coherent light, it may harm the a first Surface facing the excitation light irradiation Surface
human body if it is emitted directly to the outside without 25 and (ii) a second Surface opposite to the first Surface.
being converted into fluorescence or diffused by the light If the heat conducting member has a thickness which is less
emitting section. than 0.3 mm, it may not be able to dissipate heat of the light
According to the above arrangement, the gap layer emitting section Sufficiently, and the light emitting section
includes a diffusing agent, which diffuses the excitation light. may be impaired as a result. If, on the other hand, the heat
Thus, even if the excitation light is not entirely converted into 30 conducting member has a thickness which is greater than 3.0
fluorescence or diffused by the light emitting section, the gap mm, it will absorb a larger proportion of the excitation light
layer, which diffuses the excitation light in advance, reduces irradiating the light emitting section, and efficiency in use of
the possibility of coherent light leaking to the outside. the excitation light will be decreased significantly as a result.
The light-emitting device may preferably further include: a The heat conducting member thus preferably has a thickness
reflective film at least partially covering a surface of the gap 35 of not smaller than 0.3 mm and not greater than 3.0 mm.
layer which surface is in contact with neither the light emit The technical scope of the present invention further
ting section nor the heat conducting member. encompasses an illuminating device and a vehicle headlamp
In the case where the gap layer includes a diffusing agent, each including the light-emitting device.
the excitation light, as diffused by the diffusing agent, The light-emitting device may preferably be arranged such
includes a component (stray light) which travels not toward 40 that the first heat conducting member is provided so as to face
the light emitting section but toward a side of the gap layer an excitation light irradiation Surface of the light emitting
(that is, within a predetermined angle with a central axis section, the excitation light irradiation Surface being irradi
extending in a direction perpendicular to the optical axis of ated with the excitation light, and transmits the excitation
the excitation light irradiating the light emitting section). light.
The above arrangement includes a reflective film which 45 According to the above arrangement, the first heat conduct
partially covers a Surface of the gap layer which Surface is in ing member is provided so as to face the excitation light
contact with neither the light emitting section nor the heat irradiation Surface of the light emitting section, and absorbs
conducting member. The arrangement thus prevents at least a heat of the light emitting section to cool it. Since the first heat
portion of the stray light to be emitted from the gap layer, so conducting member is light-transmitting, the excitation light
that such at least a portion of the stray light remains inside the 50 can pass through the first heat conducting member to reach
gap layer. the light emitting section. The light emitting section generates
The above arrangement consequently improves efficiency most heat on the excitation light irradiation surface. The first
in use of excitation light in the case where the gap layer heat conducting member, provided so as to face the excitation
includes a diffusing agent. light irradiation Surface, consequently cools the light emitting
The light-emitting device may preferably be arranged such 55 section effectively.
that the gap layer has a thickness of 30 um or less between the The light-emitting device may preferably be arranged such
heat conducting member and the excitation light irradiation that the heat received by the first heat conducting member is
Surface. conducted to a reflecting mirror serving as the different mem
The gap layer having a thickness of 30 um or less is low in ber.
thermal resistance even in a case where the gap layer is lower 60 According to the above arrangement, heat of the light emit
in thermal conductivity than the light emitting section. The ting section is conducted via the first heat conducting member
above arrangement thus allows heat generated by the light to the reflecting mirror, so that the reflecting mirror is
emitting section to be efficiently conducted to the heat con warmed. The arrangement thus prevents or removes dew con
ducting member via the gap layer. densation (or freezing) on a Surface of the reflecting mirror.
The light-emitting device may preferably be arranged such 65 The light-emitting device may preferably further include: a
that the light emitting section has a thickness between the first light-transmitting member which is provided at an open
excitation light irradiation Surface and a Surface opposite to ing of a reflecting mirror and which transmits fluorescence
US 8,833,975 B2
49 50
emitted from the light emitting section as illumination light, emitting section is sandwiched between the Supporting mem
wherein: the heat received by the first heat conducting mem ber and the facing member and which is in contact with at
ber is conducted to the first light-transmitting member Serv least part of a portion of the outer Surface of the light emitting
ing as the different member. section, the portion being opposite to the Supporting member;
According to the above arrangement, heat of the light emit and the pressure applying mechanism applies a pressure that
ting section warms the first light-transmitting member. The causes the Supporting member and the facing member to press
first light-transmitting member is provided at an opening of a each other so that the light emitting section is fixed between
reflecting mirror, and transmits the illumination light so as to the Supporting member and the facing member.
emit the illumination light to the outside of the light-emitting The above arrangement positions the Supporting member
device. Since the first light-transmitting member is warmed, it 10
and the facing member so that they face each other so as to
is possible to, for example, prevent dew condensation on the sandwich the light emitting section, and applies a pressure
first light-transmitting member. that causes the Supporting member and the facing member to
The technical scope of the present invention further press each other. The pressure thus applied presses the Sup
encompasses a vehicle headlamp including the light-emitting
device. In such a vehicle headlamp, it is possible with use of 15 porting member and the facing member in Such a direction as
heat of the light emitting section to (i) prevent or remove dew to press the light emitting section on both sides against each
condensation, (ii) prevent freezing or unfreeze, or (iii) thaw other.
snow, for the vehicle headlamp. With the above arrangement, it is possible to fix the light
The vehicle headlamp may preferably further include: a emitting section between the Supporting member and the
second light-transmitting member for transmitting illumina facing member even if there has occurred a mechanical stress
tion light, emitted by the light-emitting device, so as to emit due to a difference in thermal expansion between the support
the illumination light to an outside of the vehicle headlamp: ing member and the light emitting section, and close contact
and a second heat conducting member for conducting heat, is consequently weakened as described above at a portion at
received by the first heat conducting member, to the second which the Supporting member and the light emitting section
light-transmitting member. 25 closely contact each other.
According to the above arrangement, the vehicle headlamp The light-emitting device may preferably further include: a
includes a second light-transmitting member, through which storing member which includes a concave section for storing
illumination light emitted from the light-emitting device the light emitting section, the concave section having a bot
passes so as to be emitted to the outside of the vehicle head tom section that is open and allowing the excitation light,
lamp. The second light-transmitting member is connected to 30 directed from the excitation light Source to the light emitting
the first heat conducting member via the second heat conduct section, to pass through the bottom section, wherein: the
ing member so that heat can be transferred from the first heat storing member is sandwiched between the supporting mem
conducting member to the second light-transmitting member. ber and the facing member so as to maintainagap between the
Heat generated by the light emitting section and then received Supporting member and the facing member.
by the first heat conducting member is thus conducted to the 35 According to the above arrangement, the light emitting
second light-transmitting member. The above arrangement section is stored inside the concave section of the storing
consequently warms the second light-transmitting member member, and is sandwiched, together with the storing mem
with use of Such heat of the light emitting section. ber, between the Supporting member and the facing member.
AS Such, it is possible to (i) prevent or remove dew con The bottom section of the concave section is open, and exci
densation, (ii) prevent freezing or unfreeze, or (iii) thaw Snow, 40 tation light emitted from the excitation light source thus
for the second light-transmitting member. Heat of the light passes through the bottom section to irradiate the light emit
emitting section can thus be used effectively. ting section.
The light-emitting device may preferably be arranged such Since there is a pressure applied to the Supporting member
that the fall preventing mechanism is a pressure applying and the facing member in the direction toward each other, the
mechanism which is in contact with the at least part of the 45 pressure will be applied directly to the light emitting section
outer Surface of the light emitting section and which applies a without the use of the storing member. Under such a pressure
pressure that causes said at least part of the outer Surface and applied constantly for an extended period of time, the light
the Supporting member to press each other so that the light emitting section may be crushed by the pressure, and may be
emitting section is pressed against the Supporting member. damaged as a result.
According to the above arrangement, the pressure applying 50 In view of this, the above arrangement stores the light
mechanism is in contact with at least part of the outer Surface emitting section in the storing member, which maintains the
of the light emitting section, and applies a pressure that causes gap between the Supporting member and the facing member,
the at least part of the outer Surface and the Supporting mem so that the pressure applied to the Supporting member and the
ber to press each other. The pressure thus applied presses the facing member in the direction toward each other is not
light emitting section against the Supporting member. 55 directly applied to only the light emitting section.
Since the light emitting section is pressed against the Sup In a case where, for example, the storing member has a
porting member in the above arrangement, the Supporting thickness Substantially equal to a thickness of the light emit
member can keep Supporting the light emitting section even if ting section, the light emitting section is sandwiched between
there has occurred a mechanical stress due to a difference in the Supporting member and the facing member while a fixed
thermal expansion between the Supporting member and the 60 gap is maintained therebetween. The respective thicknesses
light emitting section, and close contact is consequently of the light emitting section and the storing member can each
weakened as described above at a portion at which the Sup be defined by a distance thereof extending from the support
porting member and the light emitting section closely contact ing member to the facing member.
each other. The above arrangement makes it possible to fix the light
The light-emitting device may preferably be arranged such 65 emitting section between the Supporting member and the
that the pressure applying mechanism includes a facing mem facing member while preventing the light emitting section
ber which faces the supporting member so that the light from being crushed and thus damaged.
US 8,833,975 B2
51 52
The light-emitting device may preferably be arranged such between the reflecting member and the transmitting member.
that the concave section is defined by an inclined sidewall The pressure is applied in Such a manner that the reflecting
Surface having a shape of a mortar which has an opening area member and the transmitting member press the combination
that is larger as farther away from the bottom section; and the of the Supporting member and the facing member on both
inclined sidewall surface reflects the illumination light. 5 sides against each other. The pressure in turn causes the
In the above arrangement, the light emitting section emits, Supporting member and the facing member to press the light
in response to excitation light, illumination light in all direc emitting section on both sides against each other.
tions with itself as a center. The above arrangement keeps applying a constant pressure
The storing member, which stores the light emitting sec to the light emitting section Sandwiched between the Support
tion, has a concave section that is defined by an inclined 10 ing member and the facing member, and consequently fixes
sidewall Surface having the shape of a mortar which has an the light emitting section between the Supporting member and
opening area that is larger as farther away from the bottom the facing member.
section. The light-emitting device may preferably further include: a
This arrangement causes light emitted from the light emit transmitting member which faces the light emitting section so
ting section to, except for a portion of the light, reach the 15 that the Supporting member is sandwiched between the light
inclined sidewall surface so as to be reflected. emitting section and the transmitting member and which
The above arrangement thus forms, from illumination light allows the excitation light, directed from the excitation light
emitted in all directions with the light emitting section as a Source to the light emitting section, to pass through the trans
center, a pencil of rays that travels within a predetermined mitting member, wherein: the Supporting member closely
Solid angle. 2O contacts the light emitting section via a first gap layer,
The light-emitting device may preferably further include: a whereas the transmitting member closely contacts the light
reflecting member which faces the light emitting section so emitting section via a second gap layer, and the fall prevent
that the facing member is sandwiched between the light emit ing mechanism prevents the light emitting section from fall
ting section and the reflecting member and which reflects the ing off the Supporting member in a case where close contact
illumination light that has passed through the facing member, 25 of both the first and second gap layers has been so weakened
wherein: the reflecting member is continuous with respect to that neither of the Supporting member and the transmitting
the inclined sidewall Surface via the facing member, and has member is able to Support the light emitting section.
a reflecting Surface having a shape of a mortar which has an According to the above arrangement, the fall preventing
opening area that is larger as farther away from the facing mechanism prevents the light emitting section from falling in
member. 30 the case where close contact of both the first and second gap
The above arrangement achieves an alignment in which the layers has been so weakened that neither of the Supporting
inclined sidewall surface, which defines the concave section member and the transmitting member is able to support the
of the storing member, is continuous with respect to the light emitting section.
reflecting Surface of the reflecting member. The arrangement The technical scope of the present invention further
thus forms a large, mortar-shaped reflecting Surface from the 35 encompasses an illuminating device and a vehicle headlamp
inclined sidewall surface of the concave section and the each including the light-emitting device.
reflecting surface of the reflecting member. The light-emitting device may preferably further include: a
The above arrangement allows such a large, mortar-shaped third heat conducting member which is provided so as to (i)
reflecting Surface to Surround the light emitting section, and face a first surface of the light emitting section which first
thus causes illumination light emitted from the light emitting 40 Surface is a Surface other than the excitation light irradiation
section to be reflected by a reflecting surface a larger number surface and the opposite surface and (ii) receive heat of the
of times. light emitting section.
The above arrangement consequently forms a pencil of The above arrangement makes it possible to dissipate heat
rays that travels within a small solid angle as compared to the of the light emitting section from the first surface, which is a
case in which illumination light is reflected with use of only 45 Surface other than the excitation light irradiation Surface and
the storing member. the opposite Surface. The arrangement thus prevents a tem
The light-emitting device may preferably further include: a perature rise in the light emitting section more effectively.
transmitting member which faces the light emitting section so The light-emitting device may preferably be arranged such
that the Supporting member is sandwiched between the light that the first heat conducting member, the second heat con
emitting section and the transmitting member and which 50 ducting member, and the third heat conducting member are
allows the excitation light, directed from the excitation light each higher in thermal conductivity than the light emitting
Source to the light emitting section, to pass through the trans section.
mitting member, wherein: the pressure applying mechanism According to the above arrangement, the first heat conduct
further includes a screw which penetrates through a first one ing member, the second heat conducting member, and the
of the reflecting member and the transmitting member and 55 third heat conducting member are each higher in thermal
which has an end buried in a second one of the reflecting conductivity than the light emitting section. The arrangement
member and the transmitting member. thus prevents a temperature rise in the light emitting section.
The above arrangement causes the Supporting member and The light-emitting device may preferably be arranged such
the facing member, which sandwich the light emitting sec that the second heat conducting member and the third heat
tion, to be in turn sandwiched between the reflecting member 60 conducting member are integrally combined with each other.
and the transmitting member. The reflecting member and the According to the above arrangement, the second heat con
transmitting member are fixed with use of a screw which ducting member and the third heat conducting member are
penetrates through a first one of the reflecting member and the integrally combined with each other. This arrangement fixes a
transmitting member and which has an end buried in a second relative positional relationship between the second heat con
one of the reflecting member and the transmitting member. 65 ducting member and the third heat conducting member.
The above arrangement applies a pressure to the Supporting The above arrangement consequently prevents (i) a prob
member and the facing member, which are Sandwiched lem of a positional shift of the second heat conducting mem
US 8,833,975 B2
53 54
ber and the third heat conducting member relative to each The light-emitting device may preferably be arranged such
other and (ii) a problem of a fall of either of the second heat that the first heat conducting member includes a diffusing
conducting member and the third heat conducting member. agent for diffusing the excitation light.
The light-emitting device may preferably be arranged such Since the excitation light is coherent light, it may harm the
that the first heat conducting member and the third heat con human body if it is emitted directly to the outside without
ducting member are integrally combined with each other. being converted into fluorescence or diffused by the light
According to the above arrangement, the first heat conduct emitting section.
ing member and the third heat conducting member are inte According to the above arrangement, the diffusing agent
grally combined with each other. This arrangement fixes a diffuses the excitation light. Thus, even if the excitation light
relative positional relationship between the first heat conduct 10
is not entirely converted into fluorescence or diffused by the
ing member and the third heat conducting member. light emitting section, the first heat conducting member,
The above arrangement consequently prevents (i) a prob
lem of a positional shift of the first heat conducting member which diffuses the excitation light in advance, reduces the
and the third heat conducting member relative to each other possibility of coherent light leaking to the outside.
and (ii) a problem of a fall of either of the first heat conducting 15 The light-emitting device may preferably be arranged such
member and the third heat conducting member. that the second heat conducting member includes a diffusing
The light-emitting device may preferably be arranged such agent for diffusing the excitation light.
that the third heat conducting member fixes the relative posi Since the excitation light is coherent light, it may harm the
tional relationship between the first heat conducting member human body if it is emitted directly to the outside without
and the second heat conducting member. being converted into fluorescence or diffused by the light
The above arrangement uses the third heat conducting emitting section.
member to fix a relative positional relationship between the According to the above arrangement, the diffusing agent
first heat conducting member and the second heat conducting diffuses excitation light which has passed through the light
member. emitting section without being converted into fluorescence or
In the case where, for example, the second heat conducting 25 diffused. This reduces the possibility of coherent light leaking
member and the third heat conducting member are integrally to the outside.
combined with each other, the third heat conducting member The light-emitting device may preferably be arranged such
may be further combined with the first heat conducting mem that the light emitting section has a thickness between the
ber. In the case where the first heat conducting member and excitation light irradiation Surface and the opposite surface,
the third heat conducting member are integrally combined 30 the thickness being at least 10 times as large as a particle size
with each other, the third heat conducting member may be of the fluorescent material and not greater than 2 mm.
further combined with the second heat conducting member. In a case where the light emitting section is thin, heat
The above combination fixes the relative positional rela thereof can be conducted to, for example, the first heat con
tionship between the first heat conducting member and the ducting member and the second heat conducting member
second heat conducting member. 35 efficiently as compared to a case where the light emitting
The above arrangement consequently prevents (i) a prob section is thick. If, however, the light emitting section is too
lem of a positional shift of the first heat conducting member thin, the excitation light may not be converted into fluores
and the second heat conducting member relative to each other cence, and may instead be emitted directly to the outside. If,
and (ii) a problem of a fall of either of the first heat conducting on the other hand, the light emitting section is toothick, it may
member and the second heat conducting member. 40 not only reduce heat dissipation efficiency of for example,
The light-emitting device may preferably be arranged such the first heat conducting member and the second heat con
that the light emitting section is a sintered body obtained by ducting member for the light emitting section, but also blura
(i) mixing a fluorescent material retention Substance with a light distribution pattern of the light-emitting device.
fluorescent material which is dispersed in the fluorescent The light emitting section thus preferably has a thickness
material retention Substance and which emits light upon irra 45 which is at least 10 times the particle size of the fluorescent
diation of a laser beam and (ii) sintering a resulting mixture; material and not greater than 2 mm. A simulation has shown
and the sintered body closely contacts at least one of the first that in a case where the light emitting section has a thickness
heat conducting member, the second heat conducting mem which is at least 10 times the particle size of the fluorescent
ber, and the third heat conducting member. material, nearly all the excitation light is converted into fluo
According to the above arrangement, the light emitting 50 CSCCC.
section as a sintered body closely contacts at least one of the The light-emitting device may preferably be arranged such
first heat conducting member, the second heat conducting that the first heat conducting member, the second heat con
member, and the third heat conducting member. The arrange ducting member, and the third heat conducting member each
ment thus improves heat dissipation efficiency over a Surface have a thickness of not Smaller than 0.3 mm and not greater
of the close contact, and consequently cools the light emitting 55 than 3.0 mm between (i) a first surface in contact with the light
section more effectively. emitting section and (ii) a second Surface opposite to the first
Since the fluorescent material included in the light emitting Surface.
section is fragile, there has been a need to pay attention in If any of the first heat conducting member, the second heat
handling the light emitting section as a separate member. The conducting member, and the third heat conducting member
above arrangement, in view of this, causes the light emitting 60 has a thickness which is less than 0.3 mm, it may not be able
section to integrally and closely contact at least one of the first to dissipate heat of the light emitting section Sufficiently, and
heat conducting member, the second heat conducting mem the light emitting section may be impaired as a result. If, on
ber, and the third heat conducting member. The arrangement the other hand, any of the first heat conducting member, the
thus facilitates handling the light emitting section during second heat conducting member, and the third heat conduct
production, and further prevents (i) a problem of a positional 65 ing member has a thickness which is greater than 3.0 mm, it
shift of the light emitting section and (ii) a problem of a fall of will absorb a larger proportion of for example, the excitation
the light emitting section. light irradiating the light emitting section and fluorescence
US 8,833,975 B2
55 56
generated by the light emitting section. Efficiency in use of -continued
the excitation light will be decreased significantly as a result.
Thus, the first heat conducting member, the second heat Reference Signs List
conducting member, and the third heat conducting member 7 light emitting section
each preferably have a thickness of not smaller than 0.3 mm 5
7a. laser beam irradiation Surface (excitation light
and not greater than 3.0 mm. 8
irradiation Surface)
reflecting mirror
9 transparent plate (fixing section; first
INDUSTRIAL APPLICABILITY light-transmitting member; fall preventing mechanism;
pressure applying mechanism; facing member; transmitting
The present invention is applicable to a light-emitting 10 member)
12 lens (second light-transmitting member)
device and an illuminating device each having a high lumi 13 heat conducting member (first heat conducting
nance and a long life. In particular, the present invention is member)
applicable to a headlamp for, for example, a vehicle. 15 adhesive layer (gap layer)
16 diffusing agent (heat conducting particle)
REFERENCE SIGNS LIST 15 17 reflective film
18 transparent plate (fixing section)
20a hollow member (fixing section)
1 headlamp (light-emitting device; vehicle headlamp) 2Ob hollow member (fixing section)
2 laser diode array (excitation light source) 20c
30
fixing section
headlamp (light-emitting device; vehicle
3 laser diode (excitation light source) headlamp)
7 light emitting section 51 metal ring (fall preventing mechanism)
7a laser beam irradiation surface (excitation light irradia 52 fall preventing plate (fall preventing mechanism)
tion Surface) 53 Supporting member (fall preventing mechanism)
8 reflecting mirror 81 reflecting mirror (reflecting member)
82 Substrate
9 transparent plate (fixing section; first light-transmitting 83 Screw (fall preventing mechanism; pressure
member, fall preventing mechanism; pressure applying 25 applying mechanism)
mechanism; facing member, transmitting member) 100 headlamp (light-emitting device; vehicle
headlamp)
12 lens (second light-transmitting member) 110 headlamp (light-emitting device; vehicle
13 heat conducting member (first heat conducting mem headlamp)
ber) 116 heat pipe (second heat conducting member)
15 adhesive layer (gap layer) 30 141 opposite surface close contact section (second
16 diffusing agent (heat conducting particle) heat conducting member)
17 reflective film 142 perpendicular surface close contact section (third
heat conducting member)
18 transparent plate (fixing section) 200 headlamp (light-emitting device; vehicle
20a hollow member (fixing section) headlamp)
20b hollow member (fixing section) 35 213 Supporting member
214 Screw (fall preventing mechanism; pressure
20c fixing section applying mechanism)
30 headlamp (light-emitting device; vehicle headlamp) 300 headlamp (light-emitting device; vehicle
51 metal ring (fall preventing mechanism) headlamp)
52 fall preventing plate (fall preventing mechanism) 314 hollow member (second heat conducting member)
400 aser downlight (light-emitting device;
53 Supporting member (fall preventing mechanism) 40
illuminating device)
81 reflecting mirror (reflecting member)
82 substrate
83 screw (fall preventing mechanism; pressure applying
mechanism) The invention claimed is:
100 headlamp (light-emitting device; vehicle headlamp) 45 1. A light-emitting device, comprising:
110 headlamp (light-emitting device; vehicle headlamp) an excitation light source for emitting excitation light;
116 heat pipe (second heat conducting member) a light emitting section including a fluorescent material
141 opposite Surface close contact section (second heat which emits light in response to the excitation light, the
conducting member) light emitting section having an excitation light irradia
142 perpendicular Surface close contact section (third heat 50
conducting member) tion surface which is irradiated with the excitation light;
200 headlamp (light-emitting device; vehicle headlamp) a light-transmitting heat conducting member which is pro
213 supporting member vided so as to (i) face the excitation light irradiation
214 screw (fall preventing mechanism; pressure applying Surface and (ii) receive heat of the light emitting section;
55 and
mechanism) a gap layer which fills a gap between the heat conducting
300 headlamp (light-emitting device; vehicle headlamp)
314 hollow member (second heat conducting member) member and the excitation light irradiation Surface.
400 laser downlight (light-emitting device; illuminating 2. The light-emitting device according to claim 1,
device) wherein:
60
the gap layer adheres the light emitting section and the heat
conducting member to each other.
Reference Signs List
3. The light-emitting device according to claim 2,
1 headlamp (light-emitting device; vehicle wherein:
headlamp)
2 laser diode array (excitation light source) 65 the gap layer is so flexible as to absorb a difference in
3 laser diode (excitation light source) coefficient of thermal expansion between the light emit
ting section and the heat conducting member.
US 8,833,975 B2
57 58
4. The light-emitting device according to claim 1, further 9. The light-emitting device according to claim 1,
comprising: wherein:
a fixing section for fixing a relative positional relationship the gap layer has a thickness of 30 um or less between the
between the light emitting section and the heat conduct heat conducting member and the excitation light irradia
ing member. tion Surface.
5. The light-emitting device according to claim 4. 10. The light-emitting device according to claim 1,
wherein: wherein:
the fixing section is higher in thermal conductivity than the the light emitting section has a thickness between the exci
light emitting section. tation light irradiation Surface and a Surface opposite to
6. The light-emitting device according to claim 1, 10 the excitation light irradiation Surface, the thickness
wherein: being at least 10 times a particle size of the fluorescent
the gap layer includes aheat conducting particle which is in material and not greater than 2 mm.
contact with the light emitting section and the heat con 11. The light-emitting device according to claim 1,
wherein:
ducting member.
7. The light-emitting device according to claim 1, 15 the heat conducting member has a thickness of not smaller
wherein: than 0.3 mm and not greater than 3.0 mm between (i) a
the gap layer includes a diffusing agent for diffusing the first Surface facing the excitation light irradiation Surface
excitation light. and (ii) a second Surface opposite to the first Surface.
8. The light-emitting device according to claim 7, further 12. A illuminating device, comprising:
comprising: the light emitting device recited in claim 1.
a reflective film at least partially covering a surface of the 13. A vehicle headlamp, comprising:
gap layer which surface is in contact with neither the the light-emitting device recited in claim 1.
light emitting section nor the heat conducting member. k k k k k

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US008833975B2

(12) United States Patent (10) Patent No.: US 8,833,975 B2

(21) Appl. No.: 13/222,772 JP 2005-150041 6, 2005

(56) References Cited JP 2008-294438 12/2008

LASER BEAM ::g

6 LASER BEAM :::::

BON) HOO MEBER

Z / 2' total oil

411 412 15 7 13 410

-----> ELECTRICAL OUTET

LED DOWNLIGHT LASER DOWNLIGHT

EXTERNAL DIMENSION DIAMETER 117 x 9mm DAMETER 60 x 20mm

DMENSION OF INSERTONHOLE DIAMETER 100m

HEIGHT OF UNEXPOSED PORTION

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