JP3622713B2 - Short arc type ultra high pressure discharge lamp - Google Patents

Description

[0001]
[Technical field to which the invention belongs]
The present invention relates to a short arc type ultra-high pressure discharge lamp having a mercury vapor pressure of 15 MPa or more when lit, and particularly to a projector device such as a liquid crystal display device or a DLP (digital light processor) using a DMD (digital mirror device). The present invention relates to a short arc type super high pressure discharge lamp used as a backlight.
[0002]
[Prior art]
Projection-type projector devices are required to illuminate an image with a uniform and sufficient color rendering property on a rectangular screen. Therefore, a metal halide lamp in which mercury or a metal halide is enclosed as a light source. Is used. In addition, these metal halide lamps have recently been further miniaturized and made point light sources, and those having an extremely small distance between electrodes have been put into practical use.
[0003]
Under such circumstances, recently, a lamp having an unprecedented high mercury vapor pressure, for example, 15 MPa, has been proposed in place of the metal halide lamp. This is to increase the mercury vapor pressure to suppress (narrow) the spread of the arc and further improve the light output.
Such an ultra-high pressure discharge lamp is disclosed in, for example, Japanese Patent Laid-Open Nos. 2-148561 and 6-52830.
[0004]
By the way, in such a super high pressure discharge lamp, the pressure in the arc tube becomes extremely high at the time of lighting. Therefore, in the side tube portion that extends on both sides of the arc tube portion, the quartz glass, the electrode, and the power supply constituting the side tube portion It is necessary to adhere the metal foil for use sufficiently and firmly. In particular, since the electrode is generally cylindrical and the metal foil is flat, a minute gap is always generated at the boundary with the quartz glass when the two are joined, and the high gas pressure in the light emitting space is caused by the electrode shaft rod. There is a possibility that the cracks are generated, grown and developed from this space by being applied to the minute space through the voids around.
For this reason, how to reduce the gap is an important issue in preventing cracks. However, by reducing the cross-sectional area of the electrode shaft, an attempt is made to reduce the small gap around the gap. It has been broken. For the gap formed around the electrode axis, refer to, for example, Japanese Patent Laid-Open No. 3-201357.
[0005]
On the other hand, the short arc type ultra-high pressure discharge lamp used in a projector device, even though the arc tube volume is very small as about 80 mm ^3, lit inside pressure is higher 15 MPa, the tube wall load value 0.8 W / mm is ² extremely severe thermal conditions that above, therefore, during the lighting of the discharge lamp, it is necessary to take the heat dissipation measures to prevent the high temperature of the discharge vessel for preventing devitrification sufficiently.
As a heat dissipation measure, cooling air or the like can be blown from the outside of the discharge vessel. However, heat dissipation due to the heat transfer action of the electrode (electrode shaft) is also an important factor.
Then, if only discussing conduction heat dissipation of heat in the discharge space, the thicker electrode shaft (that is, the larger the cross-sectional area) is, the better the heat dissipation effect is.
[0006]
In summary, the gas pressure during lighting in the discharge vessel is extremely high (for example, 15 MPa or more), the arc tube inner volume is 80 mm ³ or less, and the tube wall load is 0.8 W / mm ² or more. In short arc type ultra-high pressure mercury lamps for projectors that have strict requirements,
First, because of the high enclosed gas pressure at the time of lighting, cracks that do not occur in normal discharge lamps (those with a gas pressure at the time of lighting of about several MPa) may occur and grow in the side tube portion. For this reason, it is preferable to reduce the minute space that causes cracks by reducing the diameter of the electrode shaft.
Secondly, since the thermal conditions during lighting are extremely severe, it is necessary to quickly dissipate the high temperature in the discharge space. For this reason, it is important to use the heat transfer action by the electrode shaft. As a general configuration, it is preferable to make the electrode shaft thick.
[0007]
As means for solving such a problem, for example, there is one disclosed in JP-A-10-289690.
In this publication, the diameter of the electrode shaft is smaller than the portion where the discharge arc is held, and the portion welded to the glass is smaller. It is disclosed that the diameter of the electrode shaft is gradually reduced or continuously reduced as it goes.
[0008]
This structure should be able to solve both of the above two problems qualitatively, but the discharge lamp disclosed in this publication has an internal pressure of 0.1 MPa or more (paragraph number 0001 in the specification). For example, a discharge lamp having an internal pressure as large as two orders of magnitude of 15 MPa or more, such as a short arc type discharge lamp that is a subject of the present invention, does not necessarily achieve a complete problem. There wasn't.
[0009]
[Problems to be solved by the invention]
The problem to be solved by the present invention is to provide a structure having sufficiently high pressure resistance in an ultra-high pressure mercury lamp that operates at an extremely high mercury vapor pressure.
[0010]
[Means for Solving the Problems]
In order to solve the above-described problems, a short arc type ultra-high pressure discharge lamp of the present invention has a pair of electrodes mainly composed of tungsten facing each other and encloses 0.15 mg / mm ³ or more of mercury. In a short arc type ultra-high pressure discharge lamp composed of an arc tube portion made of quartz glass and a side tube portion made of quartz glass extending on both sides and having a metal foil inside, the electrode containing tungsten as a main component is: In a portion facing the side tube portion, a minute gap is formed between the quartz glass constituting the side tube portion and φ0 of the portion facing the quartz glass constituting the side tube portion. .6 to 1.5 mm large diameter portion and a portion to be joined to the metal foil, φ0.1 to 0.5 mm small diameter portion, and from the arc tube portion along the electrode, the metal Foil and front With extends to the joining portion between the small-diameter portion of the electrode, characterized in that the gap is 6Myu～16myuemu.
[0011]
[Action]
In the short arc type ultra-high pressure discharge lamp according to the present invention, the electrode extends as a large diameter portion at a portion facing the side tube portion. As a result, the electrode (electrode shaft) escapes from the outer periphery of the electrode shaft to the side tube portion through the constituent material of the side tube portion, for example, quartz glass, through the high temperature of the discharge space as conduction heat to the side tube portion. It can dissipate heat.
And since the electrode has a small diameter at the welded portion with the metal foil at the tip of the electrode, the inevitable gap generated during welding of the electrode and the metal foil can be made small, whereby the pressure resistance at the side tube portion can be reduced. Can be improved.
In addition, if it shows with a numerical value, a large diameter part is (phi) 0.6-1.5mm, and a small diameter part is (phi) 0.1-0.5mm.
[0012]
Further, the portion where the electrode (electrode axis) faces the side tube portion has a minute gap between the electrode surface and the material constituting the side tube portion. Thus, after the side tube portion is heated at a high temperature in the sealing step, the relative temperature generated by the difference in thermal expansion coefficient between the material constituting the electrode and the material constituting the side tube portion in the stage where the temperature gradually decreases. Difference in the amount of expansion and contraction can be prevented, and as a result, the occurrence of cracks in the contact portion due to the difference can be satisfactorily suppressed.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows the overall configuration of a short arc type ultra-high pressure discharge lamp (hereinafter also simply referred to as “discharge lamp”) of the present invention.
The discharge lamp 10 has a substantially spherical discharge space portion 12 formed by a discharge vessel 11 made of quartz glass, and a cathode 13 and an anode 14 are disposed in the discharge space portion 12 so as to face each other. . Further, side tube portions 15 are formed so as to extend from both end portions of the discharge space portion 12, and a conductive metal foil 16 usually made of molybdenum is embedded in the side tube portions 15 in an airtight manner, for example, by a pinch seal. The base end portion of the electrode rod having the cathode 13 and the anode 14 at the tip thereof is welded and electrically connected in a state of being disposed at one end portion of the conductive metal foil 16, and the other end An external lead bar 18 protruding to the outside is welded to the part.
The cathode 13 and the anode 14 are referred to as “electrodes” including the electrode axis, and these are composed mainly of tungsten.
Further, as will be described later, the cathode 13 and the anode 14 form a minute gap between the side tube portion 15, but FIG. 1 omits this gap from the viewpoint of showing the entire structure of the lamp.
[0014]
Mercury, rare gas, and halogen gas are enclosed in the discharge space 12. Mercury is used to obtain a necessary visible light wavelength, for example, radiated light having a wavelength of 360 to 780 nm, and 0.15 mg / mm ³ or more is enclosed. Although the amount of sealing varies depending on temperature conditions, the vapor pressure becomes extremely high at 15 MPa or more during lighting. Further, by enclosing a larger amount of mercury (for example, 0.20, 0.25, 0.30 mg / mm ³ ), a discharge lamp having a high mercury vapor pressure such as a mercury vapor pressure of 20 MPa or more and 30 MPa or more at the time of lighting is produced. The light source suitable for the projector device can be realized as the mercury vapor pressure increases.
For example, the rare gas is filled with about 13 kPa of argon gas to improve the lighting startability.
Halogen is encapsulated with bromine, chlorine, iodine or the like in the form of a compound with mercury or other metal, and the amount of halogen encapsulated can be selected from the range of 10 ⁻⁶ to 10 ⁻² μmol / mm ³ , for example. Its function is to extend the life for the purpose of preventing white turbidity of the discharge vessel. However, an extremely small and high internal pressure such as the discharge lamp of the present invention can enclose such a halogen, It affects the phenomenon of container breakage and devitrification prevention.
[0015]
The perfect load of the discharge lamp is 0.8 W / mm ² or more. This is because a large amount of mercury is sealed in the discharge vessel, and this mercury is used to achieve a thermal condition for sufficiently vaporizing the mercury during lamp operation.
Further, the discharge lamp has a small internal volume of 80 mm ³ or less. This is because it is required to make the discharge lamp itself as small as possible in response to the miniaturization of the liquid crystal projector apparatus.
[0016]
As an example of such a discharge lamp, for example, the maximum outer diameter of the light emitting part is 9.5 mm, the distance between the electrodes is 1.5 mm, the arc tube inner volume is 75 mm ³ , the tube wall load is 1.5 W / mm ³ , and the rated voltage is 80 V. The rated power is 150W.
The discharge lamp is mounted on a presentation device such as the projector device or the overhead projector, and can provide radiant light with good color rendering.
[0017]
2A and 2B are enlarged views of the anode. The electrode 14 includes a large diameter portion 14a of the discharge space and a small diameter portion 14b on the metal foil side. These are formed by processing from one piece.
And it has joined to the metal foil 16 in the small diameter part 14b.
Further, the surface of the large diameter portion 14a, the inner surface of the side tube portion 15 made of quartz glass, and the minute gap A are formed.
In FIG. 2 (a), the electrode 14 has a large-diameter portion 14a and a small-diameter portion 14b formed in stages, and (b) in FIG. 2B, the small-diameter portion 14b following the large-diameter portion 14a is gradually reduced in a tapered shape. .
As a numerical example, the large diameter portion 14a has a diameter of 0.6 to 1.5 mm, and the small diameter portion 14b has a diameter of 0.1 to 0.5 mm.
[0018]
As described above, since the large-diameter portion of the electrode shaft extends to face the inner surface of the side tube portion, the electrode shaft escapes to the side tube portion using the high temperature of the discharge space as conduction heat, and from the electrode shaft outer peripheral surface. Heat can be dissipated well through the constituent material of the side tube, for example, quartz glass.
And since the small diameter part of the electrode shaft is welded to the metal foil, the inevitable gap generated during welding of the electrode and the metal foil can be made small, thereby improving the pressure resistance in the side tube part. be able to.
FIG. 3 shows the air gap B inevitably generated when the metal foil 16 and the electrode shaft 14b are joined. As is apparent from the figure, the gap B is reduced when the outer diameter of the electrode shaft is small.
[0019]
FIG. 4 shows an enlarged view of the cathode of the ultrahigh pressure discharge lamp of the present invention. Unlike FIG. 2, metal foil and quartz glass are omitted.
The cathode 13 is also composed of a large diameter portion 13a and a small diameter portion 13b, and the large diameter portion 13a extends from the light emitting space portion to the side tube portion. For this reason, the high temperature in the arc tube portion can be induced by conducting heat and radiated from the side tube portion.
Moreover, it joins with metal foil in the small diameter part 13b, and the inevitable space | gap produced at the time of joining can be made small like an anode.
As for the cathode, unlike the anode, the electrode and the electrode axis are not distinguished from each other, and they are collectively referred to as an electrode. A structure in which a diameter electrode head is provided may be used.
Note that the coil 13c wound around the cathode tip is for improving the lighting startability.
[0020]
Returning to FIG. 2, the ultra-high pressure mercury lamp of the present invention has a minute gap A between the electrode shaft and the inner surface of the side tube portion. This gap A is determined from the viewpoint that the electrode can be freely expanded and contracted in the axial direction without being constrained by the difference in expansion coefficient between the constituent material of the electrode and the material constituting the side tube portion. When the tube portion is made of quartz glass, the width of the gap A is selected from the range of 6 to 16 μm, and 3 to 5 mm exists in the length direction of the electrode of the gap A.
By creating such a gap A, it is possible to satisfactorily prevent the occurrence of cracks due to the relative movement of the electrode and the quartz glass. In the figure, the gap A is exaggerated and expressed greatly.
In terms of the effects of the invention, it is preferable to provide the gap A in both the cathode and anode electrodes, but this does not exclude embodiments provided in either one of the electrodes.
[0021]
Finally, numerical examples of the short arc type discharge lamp according to the present invention will be introduced.
Side pipe outer diameter: 6.0 mm
Lamp total length: 65.0mm
Side tube length: 25.0mm
Internal volume of arc tube: 0.08cc
Distance between electrodes: 2.0mm
Rated lighting voltage: 200w
Rated lighting current: 2.5A
Encapsulated mercury content: 0.15 mg / mm ³
Noble gas: 13 kPa of argon
[0022]
As described above, in the short arc type ultra high pressure mercury lamp of the present invention, the electrode has a large diameter portion and a small diameter portion, and the large diameter portion extends in a portion facing the side tube portion. High temperature can be transferred to the side tube portion as conduction heat, and heat can be radiated well from the outer peripheral surface of the electrode shaft through the constituent material of the side tube portion, for example, quartz glass.
In addition, since the electrode has a small diameter in the welded portion with the metal foil at the tip of the electrode, the inevitable gap generated during welding of the electrode and the metal foil can be made small, and thereby the pressure resistance in the side tube portion. Can be improved.
Further, the portion where the electrode (electrode axis) faces the side tube portion has a minute gap between the electrode surface and the material constituting the side tube portion. Thus, after the side tube portion is heated at a high temperature in the sealing step, the relative temperature generated by the difference in thermal expansion coefficient between the material constituting the electrode and the material constituting the side tube portion in the stage where the temperature gradually decreases. Difference in the amount of expansion and contraction can be prevented, and as a result, the occurrence of cracks in the contact portion due to the difference can be satisfactorily suppressed.
[Brief description of the drawings]
FIG. 1 is an overall view of a short arc type ultrahigh pressure discharge lamp of the present invention.
FIG. 2 is an enlarged view of an anode of a short arc type ultra-high pressure discharge lamp of the present invention.
FIG. 3 is an enlarged view of a metal foil welded portion of the short arc type ultra-high pressure discharge lamp of the present invention.
FIG. 4 is an enlarged view of the cathode of the short arc type ultra-high pressure discharge lamp of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Discharge lamp 11 Light emission tube part 12 Light emission space 13 Cathode 14 Anode 15 Side tube part 16 Metal foil 17 Electrode shaft 18 External lead

Claims (1)

A pair of electrodes containing tungsten as a main component inside, and an arc tube portion made of quartz glass in which mercury of 0.15 mg / mm ³ or more is sealed, and extending on both sides of the metal foil inside In a short arc type ultra-high pressure discharge lamp consisting of a side tube made of quartz glass
The electrode containing tungsten as a main component is disposed in a portion facing the side tube portion so as to form a microscopic gap with the quartz glass constituting the side tube portion. Consists of a large diameter portion of φ0.6 to 1.5 mm of the portion facing the quartz glass to constitute, and a small diameter portion of φ0.1 to 0.5 mm of the portion to be joined to the metal foil,
The short gap extends from the arc tube portion along the electrode to a joint portion between the metal foil and the small diameter portion of the electrode, and the gap is 6 μm to 16 μm. Type ultra-high pressure discharge lamp.

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