JP4963592B2 - Surface lighting device - Google Patents

Description

  The present invention relates to a planar illumination device having a light guide plate that diffuses light emitted from a light source and emits illumination light from a light exit surface, and more particularly, to a planar illumination device that illuminates indoors and outdoors, and a liquid crystal display device. The present invention relates to a planar lighting device used as a backlight of a liquid crystal panel, an advertising panel, an advertising tower, or a signboard.

  In the liquid crystal display device, a backlight unit that irradiates light from the back side of the liquid crystal display panel and illuminates the liquid crystal display panel is used. The backlight unit is configured by using components such as a light guide plate that diffuses light emitted from a light source for illumination and irradiates the liquid crystal display panel, a prism sheet that diffuses light emitted from the light guide plate, and a diffusion sheet. .

  At present, a backlight unit of a large-sized liquid crystal television mainly uses a so-called direct type in which an optical member such as a diffusion plate is disposed immediately above a light source for illumination. In this system, a plurality of cold-cathode tubes, which are light sources, are arranged on the back surface of the liquid crystal display panel, and a uniform light quantity distribution and necessary luminance are ensured with the inside as a white reflecting surface.

  However, in the direct type backlight unit, in order to make the light quantity distribution uniform, the thickness in the direction perpendicular to the liquid crystal display panel is required to be about 30 mm. In the future, a thinner backlight unit will be desired. However, it is considered difficult to realize a backlight unit having a thickness of 10 mm or less from the standpoint of unevenness in the amount of light in the direct type.

Therefore, a backlight unit using a light guide plate in which scattering particles for scattering light in a transparent resin are mixed has been proposed (see, for example, Patent Documents 1 to 4).
For example, Patent Document 1 includes a light-scattering light guide having at least one light incident region and at least one light extraction surface region, and light source means for performing light incidence from the light incident surface region. The light-scattering light-guide light source device is characterized in that the light-scattering light guide has a region that tends to decrease in thickness as the distance from the light incident surface increases.
Patent Document 2 includes a light scattering light guide, a prism sheet disposed on the light extraction surface side of the light scattering light guide, and a reflector disposed on the back side of the light scattering light guide. A surface light source device is described. Patent Document 3 discloses a liquid crystal including a light emitting direction correcting element made of a plate-like optical material having a light incident surface having repetitive undulations in a prism array and a light emitting surface provided with light diffusibility. A display is described, and Patent Document 4 describes a light source device that includes a light scattering light guide provided with scattering ability therein, and a light supply unit that supplies light from an end surface of the light scattering light guide. Has been.

In such a planar illumination device, light emitted from a light source and entering the light-scattering light guide from a light incident surface propagates through the interior at a constant rate once or multiple scattering actions. Receive. In addition, a substantial part of the light reaching the both surfaces of the light scattering light guide or the surface of the reflector is reflected and returned to the light scattering light guide.
Through such a complex process, a light beam emitted with high efficiency from the light extraction surface is generated with directivity in the obliquely forward direction when viewed from the direction of the light source. That is, the light emitted from the light source is emitted from the light extraction surface of the light scattering light guide.
Thus, it is described that uniform light can be emitted with high emission efficiency by using a light guide plate mixed with scattering particles.

  In addition to the wedge-shaped light guide plate, a plate-shaped light guide plate and a light guide plate shaped by attaching a wedge-shaped light guide plate are described as the light guide plate mixed with scattering particles.

JP 07-36037 A JP 08-248233 A Japanese Patent Application Laid-Open No. 08-271739 JP-A-11-153963

  In the wedge-shaped sidelight-type light guide plate as described above (type having a light incident surface on the side end surface), the range of light from the light source, that is, the light guide length is limited, and the light emitting surface increases as the distance from the light source increases. The luminance of the light emitting element becomes weak, and the uniformity of the light emitting surface luminance cannot be sufficiently ensured. Further, the sidelight type light guide plate has a limit in the arrangement pitch of the light sources and the light emission density, so that it is difficult to obtain a necessary incident light amount, and therefore, it is difficult to obtain a necessary light emitting surface luminance.

In other words, the shape described in Patent Documents 1 to 4 that has a tendency to reduce the thickness as it goes away from the incident position of the light source, or the flat plate shape has a limit in the reach of light, and therefore there is a limit to enlargement. There is a problem.
Moreover, in the planar illumination device using the light guide plate described in Patent Documents 1 to 4, it is necessary to increase the thickness of the light guide plate itself in order to make the light reach a position farther from the light source in order to increase the size. . That is, there is a problem that the planar illumination device cannot be reduced in thickness and weight.

  An object of the present invention is to provide a planar lighting device that solves the above-mentioned problems based on the prior art, is thin, lightweight, can emit uniform and uniform illumination light, and can be increased in size. There is to do. Furthermore, another object of the present invention is to provide a planar illumination device that can efficiently use light emitted from a light source and can emit light with higher luminance from a light exit surface. It is in.

In order to solve such a problem, the present applicant has intensively studied and has an inclined surface which is an opposite surface of the light emitting surface and is inclined so as to move away from the light emitting surface as the distance from the light incident surface at the side end increases. A planar illumination device provided with a light guide plate (hereinafter also referred to as “reverse wedge light guide plate”) has been proposed (Japanese Patent Application No. 2006-167926).
By using an inverted wedge-shaped light guide plate as the light guide plate of the planar illumination device, the light can reach a position farther from the light source with a single light scattering light guide plate, realizing a uniform light quantity distribution. In addition, it has an excellent function such that the size can be increased and the efficiency of extracting incident light from the light guide plate (light utilization efficiency) can be increased.

  The Applicant has further studied diligently, and it is possible to emit light with high brightness from the light exit surface more efficiently without increasing the thickness of the light guide plate due to the arrangement relationship between the light source and the light guide plate, etc. I found out that

Specifically, in order to solve the above-described problem, the present invention provides a light emitting surface that emits planar light, the edge formed on the light emitting surface, and the direction from the direction substantially orthogonal to the light emitting surface. A light incident surface for entering light traveling in a direction parallel to the light exit surface, and a surface opposite to the light exit surface, and tilts away from the light exit surface as the distance from the light entrance surface increases. A transparent light guide plate having an inclined surface;
The light guide plate has a light emitting surface longer than the length of the effective cross section of the light incident surface in a direction substantially orthogonal to the light incident surface on the edge side of the light emitting surface on which the light incident surface is formed, A light source disposed opposite to the light incident surface of the light guide plate and inclined at a predetermined angle with respect to a direction substantially orthogonal to the light incident surface;
A light guide reflector disposed on the light exit surface side and the inclined surface side of the light incident surface of the light guide plate, and guiding the light emitted from the light source to the light incident surface;
A planar illumination device, wherein light emitted from a light emitting surface of the light source is incident on the light incident surface of the light guide plate, converted into planar light, and emitted from the light emitting surface. provide.

Here, it is preferable that the light incident surface of the light guide plate is a plane substantially orthogonal to the light emitting surface of the light source, and the effective cross section of the light incident surface corresponds to the substantially orthogonal plane.
Further, the light incident surface of the light guide plate is a flat surface that is inclined so as to face the light emitting surface of the light source in a direction substantially orthogonal to the light emitting surface, and an effective cross section of the light incident surface. Preferably corresponds to a cross section in a direction substantially orthogonal to the light exit surface at a contact point between the light entrance surface and the light exit surface.
The inclination angle of the light emitting surface of the light source with respect to the direction substantially orthogonal to the light exit surface is preferably 15 degrees to 90 degrees, and more preferably 15 degrees to 75 degrees.

  Further, the light source includes a plurality of light emitting diodes or semiconductor lasers arranged in an array along the longitudinal direction of the light incident surface of the light guide plate, and the light emission for attaching these light emitting diodes or semiconductor lasers. A planar or linear light source having an mounting surface inclined parallel to the surface and an array substrate is preferable.

  The guide reflection plate is attached to an end portion of the light guide surface of the light guide plate, and is attached to an end portion of the inclined surface of the light guide plate. It is preferable to have a second guide reflector having an extended portion that is extended to the first guide reflector.

  The light incident surface includes two light incident surfaces formed at two opposite sides of the light exit surface, and the inclined surface is centered from the two light incident surfaces facing each other. It is preferable that the two light-incidence surfaces are inclined so as to move away from the light exit surface as they go, and the light-incident surface has the smallest thickness and the thickness at the position where the two slant surfaces intersect is the largest.

  In the light guide plate, the light exit surface has a rectangular shape, the light incident surface is composed of one light incident surface formed at one end of the light exit surface, and the inclined surface is , Composed of one inclined surface that inclines away from the light emitting surface as it goes from the light incident surface to the other end surface facing the light incident surface, and is the thinnest at the light incident surface and the thickest at the other end surface It is preferable.

  In the light guide plate, the light exit surface has a rectangular shape, and the light incident surface includes four light incident surfaces formed on four end sides of the light exit surface, respectively, and the inclined surface. Is composed of four inclined surfaces that are inclined so as to move away from the light exit surface from the four light incident surfaces toward the center, and the light incident surface has the smallest thickness, and the four intersecting positions intersect. It is preferable that the thickness is a shape with the largest thickness.

Further, the light guide plate includes a large number of scattering particles therein, the scattering cross section of the scattering particles is Φ, the density of the scattering particles is N _p , the correction coefficient is K _C , and the light guide plate has a light incident direction. When the length from the light incident surface to the position where the thickness in the direction perpendicular to the light exit surface is the thickest is L _G , the inequality 1.1 ≦ Φ · N _p · L _G · K _C ≦ It is preferable that 8.2 and 0.005 ≦ K _C ≦ 0.1 are satisfied.

Furthermore, another aspect of the present invention is a light emitting surface for emitting planar light, and an angle formed between the light emitting surface and the light emitting surface is inclined at an angle larger than 90 °, and is formed at an edge of the light emitting surface. A side surface that is opposite to the light exit surface and is inclined so as to move away from the light exit surface as the distance from the side surface is increased. A transparent light guide plate having a light incident surface;
The light incident surface has a light emitting surface longer than the length of the cross section of the light guide plate in a direction substantially orthogonal to the light exit surface at the inclined surface side edge, and the light emitting surface is opposed to the light incident surface of the light guide plate. A light source disposed at a predetermined angle with respect to a direction substantially orthogonal to the light exit surface,
Guided reflection that is disposed so as to cover a part of the light exit surface on the side surface side of the light guide plate, the side surface, and the inclined surface, and guides light incident from the light incident surface toward the center of the light guide plate. With a board,
A planar illumination device, wherein light emitted from a light emitting surface of the light source is incident on the light incident surface of the light guide plate, converted into planar light, and emitted from the light emitting surface. It is to provide.

Here, it is preferable that the light incident surface of the light guide plate is formed in parallel with the light emitting surface, and the light source is disposed at an angle at which the light emitting surface is parallel to the light emitting surface.
The light guide plate includes a large number of scattering particles therein, a scattering cross section of the scattering particles is Φ, a density of the scattering particles is N _p , a correction coefficient is K _C , and the side surface and the light incident surface are When the length from the contact point to the position where the thickness in the direction perpendicular to the light emitting surface is maximum is L _G , the inequality, 1.1 ≦ Φ · N _p · L _G · K _C ≦ 8.2 And 0.005 ≦ K _C ≦ 0.1 is preferably satisfied.

According to the present invention, the light incident from the light incident surface can be delivered farther, and the light emission surface can be made thin and large.
In addition, by inclining the light emitting surface of the light source, light can be efficiently incident even when a light source having a large area of the light emitting surface is used with respect to the light guide plate having a small light incident surface. That is, the light use efficiency can be increased. Furthermore, the amount of light emitted from the light emitting surface can be increased by increasing the area of the light emitting surface.
That is, according to the present invention, light with high luminance or illuminance can be efficiently emitted from the light exit surface, and the device can be further thinned.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of a planar illumination device according to the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a perspective view showing an embodiment of a planar illumination device according to the present invention, FIG. 2 is a cross-sectional view taken along the line II-II of the planar illumination device shown in FIG. 1, and FIG. It is an expanded sectional view which expands and shows a part of planar lighting apparatus shown in FIG.
As shown in each drawing, the planar illumination device 10 houses a light source 12, an illumination device body 14 that emits uniform light from a rectangular light emitting surface 14a, and the illumination device body 14 and the light source 12 therein. And a housing 16. As will be described later, the housing 16 includes a main body portion 16a and a frame portion 16b.

First, the light source 12 will be described.
4A is a schematic perspective view showing a schematic configuration of the light source 12 of the planar illumination device 10 shown in FIGS. 1 and 2, and FIG. 4B is a diagram of the light source 12 shown in FIG. It is a schematic perspective view which expands and shows only one LED chip, and FIG.4 (C) is sectional drawing of the light source 12 shown to FIG. 4 (A).
As shown in FIG. 4A, the light source 12 includes a plurality of light emitting diode chips (hereinafter referred to as “LED chips”) 40 and a light source support portion 41.

The LED chip 40 has a light emitting surface 40 a having a predetermined area, and emits white light from the light emitting surface 40.
The LED chip 40 of the present embodiment is a monochromatic LED configured to convert light emitted from the LED into white light using a fluorescent material. For example, when a GaN blue LED is used as the monochromatic LED, Can obtain white light by using a YAG (yttrium, aluminum, garnet) fluorescent material.

  As shown in FIG. 4B, the light source support portion 41 includes an array support 42 and a plurality of fins 44. The plurality of LED chips 40 described above are arranged on the array substrate 42 in a row at a predetermined interval. Specifically, the plurality of LED chips 40 are arranged along the longitudinal direction of the first light incident surface 18d or the second light incident surface 18e of the light guide plate 18 to be described later, in other words, the light emitting surface 18a and the first light incident. They are arranged in an array parallel to a line where the surface 18d intersects or a line where the light exit surface 18a and the second light incident surface 18e intersect.

The array substrate 42 is a plate-like member whose one surface is disposed to face the thinnest side end surface of the light guide plate 18, and the first light incident surface 18 d or the second light incident surface 18 e that is the side end surface of the light guide plate 18. It is arranged to face. The array substrate 42 supports the LED chip 40 on a side surface that is a surface facing the light incident surface 18 b of the light guide plate 18.
Here, the array substrate 42 of the present embodiment is formed of a metal having good thermal conductivity such as copper or aluminum, and also has a function as a heat sink that absorbs heat generated from the LED chip 40 and dissipates it to the outside. .

Each of the plurality of fins 44 is a plate-like member made of a metal having good thermal conductivity such as copper or aluminum, and is adjacent to the surface of the array substrate 42 opposite to the surface on which the LED chip 40 is disposed. The fins 44 are connected with a predetermined distance.
By providing a plurality of fins 44 on the light source support portion 41, the surface area can be increased and the heat dissipation effect can be enhanced. Thereby, the cooling efficiency of LED chip 40 can be improved.
The heat sink is not limited to the air cooling method, and a water cooling method can also be used.
In this embodiment, the array substrate 42 of the light source support portion 41 is used as a heat sink. However, when cooling of the LED chip is not necessary, a plate-like member having no heat dissipation function is used as the array substrate instead of the heat sink. Also good.

Here, as shown in FIG. 4C, the LED chip 40 of the present embodiment has a rectangular shape whose length in the direction orthogonal to the arrangement direction is shorter than the length of the LED chip 40 in the arrangement direction, that is, described later. The light guide plate 18 has a rectangular shape with a short side in the thickness direction (direction perpendicular to the light exit surface 18a). In other words, the LED chip 40 has a shape in which b> a, where a is a length in the direction perpendicular to the light exit surface 18a of the light guide plate 18 and b is a length in the arrangement direction. Further, q> b, where q is the arrangement interval of the LED chips 40. Thus, the relationship between the length a in the direction perpendicular to the light exit surface 18a of the light guide plate 18 of the LED chip 40, the length b in the arrangement direction, and the arrangement interval q of the LED chips 40 satisfies q>b> a. It is preferable.
By making the LED chip 40 into a rectangular shape, a thin light source can be obtained while maintaining a large light output. By reducing the thickness of the light source, the planar illumination device can be reduced in thickness.

  Since the LED chip 40, that is, the light source can be made thinner, the LED chip 40 is preferably a rectangular shape having a short side in the thickness direction of the light guide plate 18, but the present invention is not limited to this, and the square shape, LED chips having various shapes such as a circular shape, a polygonal shape, and an elliptical shape can be used.

Here, as shown in FIGS. 2 and 3, the LED chip 40 and the array substrate 42 are arranged so as to be inclined at a predetermined angle with respect to a direction perpendicular to a light exit surface 18 a of the light guide plate 18 described later. That is, the LED chip 40 is arranged in a direction in which the light emitting surface 40a is inclined at a predetermined angle with respect to a direction perpendicular to a light emitting surface 18a of the light guide plate 18 described later.
This point will be described in detail later.

As shown in FIG. 2, the illuminating device main body 14 basically includes a light guide plate 18, a prism sheet 20, a diffusion film 22, a reflection plate 24, an upper guide reflection plate 34, and a lower guide reflection plate 36. Have
Hereinafter, these optical components constituting the illumination device body 14 will be described in detail.

First, the light guide plate 18 will be described.
As shown in FIG. 2, the light guide plate 18 has a substantially rectangular flat light emission surface 18a and two light incidents formed on both ends of the light emission surface 18a substantially perpendicular to the light emission surface 18a. Surfaces (first light incident surface 18d and second light incident surface 18e) and opposite to the light emitting surface 18a, parallel to the first light incident surface 18d and the second light incident surface 18e, and the light emitting surface 18a. The two inclined surfaces (first inclined surface 18b and second inclined surface) that are symmetrical with each other about the bisector α (see FIG. 1) that bisects the light and are inclined at a predetermined angle with respect to the light exit surface 18a Surface 18c). The first inclined surface 18b and the second inclined surface 18c are arranged such that the distance from the light emitting surface 18a increases (becomes larger) as the distance from the first light incident surface 18d and the second light incident surface 18e increases. As the distance from the light incident surface 18d and the second light incident surface 18e toward the center of the light guide plate is increased, the thickness in the direction perpendicular to the light exit surface of the light guide plate is increased. That is, the light guide plate 18 has the thinnest thickness at both end portions, that is, the first light incident surface 18d and the second light incident surface 18e, and the central portion, that is, the first inclined surface 18b and the second inclined surface 18c intersect. The thickness is maximized at the position of the isoline α. The inclination angles of the first inclined surface 18b and the second inclined surface 18c with respect to the light exit surface 18a are not particularly limited.
Further, the above-described light source 12 is disposed to face the first light incident surface 18d and the second light incident surface 18e of the light guide plate 18, respectively. That is, the planar illumination device 10 is arranged so that the two light sources 12 sandwich the light guide plate 18. In other words, the light guide plate 18 is disposed between the two light sources 12 disposed to face each other with a predetermined distance therebetween.

  In the light guide plate 18 shown in FIG. 2, the light incident from the first light incident surface 18d and the second light incident surface 18e is scattered by a scatterer (details will be described later) included in the light guide plate 18 while being guided. The light passes through the inside of the optical plate 18 and is reflected from the first inclined surface 18b and the second inclined surface 18c, and then emitted from the light exit surface 18a. At this time, a part of light may leak from the first inclined surface 18b and the second inclined surface 18c, but the leaked light covers the first inclined surface 18b and the second inclined surface 18c of the light guide plate 18. The light is reflected by 24 and enters the light guide plate 18 again.

  The light guide plate 18 is formed by kneading and dispersing scattering particles for scattering light in a transparent resin. Examples of the transparent resin material used for the light guide plate 18 include PET (polyethylene terephthalate), PP (polypropylene), PC (polycarbonate), PMMA (polymethyl methacrylate), benzyl methacrylate, MS resin, or COP (cycloolefin polymer). An optically transparent resin such as As scattering particles kneaded and dispersed in the light guide plate 18, Atsipearl, thin cone, silica, zirconia, dielectric polymer, or the like can be used. By including such scattering particles in the light guide plate 18, it is possible to emit illumination light that is uniform and has less luminance unevenness from the light exit surface. Such a light guide plate 18 can be manufactured using an extrusion molding method or an injection molding method.

Further, the scattering cross section of the scattering particles contained in the light guide plate 18 is Φ, the light incident direction (the direction parallel to the traveling direction of the light incident on the light guide plate, parallel to the light exit surface, the light exit surface and the light entrance Perpendicular to the light exit surface 18a from the first light incident surface 18d or the second light incident surface 18e of the light guide plate 18 in the direction perpendicular to the tangent to the surface (the first light incident surface or the second light incident surface). The length up to the position where the thickness of the direction becomes the maximum, in this embodiment, the light incident direction of the light guide plate (in this embodiment, the direction perpendicular to the first light incident surface 18d of the light guide plate 18, hereinafter "light L _{G is} the half length (length to the position of the bisector α), and the density of scattering particles (number of particles per unit volume) contained in the light guide plate 18 is N _p. , when the correction coefficient and _{K C,} the value of _{Φ · N p · L G ·} K C is 1.1 or more, One 8.2 or less, further, the value of the correction coefficient _{K C} is better to satisfy the relationship of 0.005 to 0.1. Since the light guide plate 18 includes scattering particles that satisfy such a relationship, the illumination light can be emitted from the light exit surface 18a with uniform brightness and less unevenness in luminance.

In general, the transmittance T when a parallel light beam is incident on an isotropic medium is expressed by the following formula (1) according to the Lambert-Beer rule.
T = I / I ₀ = exp (−ρ · x) (1)
Here, x is a distance, I ₀ is incident light intensity, I is outgoing light intensity, and ρ is an attenuation constant.

The attenuation constant ρ is expressed by the following equation (2) using the scattering cross-sectional area Φ of particles and the number of particles N _p per unit volume contained in the medium.
ρ = Φ · N _p (2)
Therefore, from the incident surface of the light guide plate in a direction parallel to the traveling direction of light of the light guide plate to the thickest position thickness length, the length of the half of the optical axis direction of the light guide plate when the L _G, light extraction The efficiency E _out is given by the following formula (3). Here, half the length L _G of the optical axis of the light guide plate, the length from one of the light incident surface of the light guide plate 18 in the direction perpendicular to the light incident surface of the light guide plate 18 to the center of the light guide plate 18 .

Furthermore, the light extraction efficiency and are, with respect to the incident light, the fraction of light reaching the position spaced the length L _G in the optical axis direction from the light incident surface of the light guide plate, for example, the light guide plate 18 shown in FIG. 2 In this case, it is a ratio of light reaching the center of the light guide plate (a position having a half length in the optical axis direction of the light guide plate) with respect to light incident on the end face.
E _out ∝exp (−Φ · N _p · L _G ) (3)

Here the formula (3) applies to a space of limited size, to introduce a correction coefficient K _C for correcting the relationship between the expression (1). The compensation coefficient K _C is a dimensionless compensation coefficient empirically obtained where light optical medium of limited dimensions propagates. Then, the light extraction efficiency E _out is expressed by the following formula (4).
_{E out = exp (-Φ · N} p · L G · K C) ··· (4)

According to the equation (4), when the value of Φ · N _p · L _G · K _C is 3.5, the light extraction efficiency E _out is 3%, and Φ · N _p · L _G · K _C When the value of is 4.7, the light extraction efficiency E _out is 1%.
From this result, it is understood that the light extraction efficiency E _out decreases as the value of Φ · N _p · L _G · K _C increases. Since light is scattered as it travels in the direction of the optical axis of the light guide plate, the light extraction efficiency E _out is considered to be low.

Therefore, it can be seen that the larger the value of Φ · N _p · L _G · K _C is, the more preferable property is for the light guide plate. In other words, by increasing the value of Φ · N _p · L _G · K _C , it is possible to reduce the light emitted from the surface facing the light incident surface and increase the light emitted from the light emission surface. it can. That is, by increasing the value of _{Φ · N p · L G ·} K C, ( hereinafter also referred to as "light use efficiency".) Ratio of light emitted through the light exit plane to the light incident on the incident surface of the high can do. Specifically, by setting 1.1 or the value of _{Φ · N p · L G ·} K C, the light use efficiency can be 50% or more.

Here, when the value of Φ · N _p · L _G · K _C is increased, the illuminance unevenness of the light emitted from the light exit surface 18a of the light guide plate 18 becomes remarkable, but Φ · N _p · L _G · K _C By making the value of 8.2 or less, the illuminance unevenness can be suppressed to a certain value (within an allowable range). Note that the illuminance and the luminance can be handled in substantially the same manner. Therefore, in the present invention, it is presumed that luminance and illuminance have the same tendency.

Thus, the value of _{Φ · N p · L G ·} K C of the light guide plate 18 of the present invention preferably satisfies the relationship of 1.1 or more and 8.2 or less, 2.0 or more and 8. More preferably, it is 0 or less. The value of _{Φ · N p · L G ·} K C is more preferably as long as 3.0 or more, most preferably, not less than 4.7.
The correction coefficient K _C is preferably 0.005 or more and 0.1 or less (0.005 ≦ K _C ≦ 0.1).

Hereinafter, the light guide plate 18 will be described in more detail with specific examples.
First, the scattering cross section Φ, particle density N _p , half length L _G of the light guide plate in the optical axis direction, and correction coefficient K _C are set to various values, and the values of Φ · N _p · L _G · K _C are different. About each light-guide plate, the light use efficiency was calculated | required by computer simulation, and also illumination intensity nonuniformity was evaluated. Here, the illuminance unevenness [%] is the maximum illuminance of light emitted through the light exit plane of the light guide plate and I _Max, a minimum illuminance and I _Min, Average illuminance when the I _Ave [(I _Max - I _Min ) / I _Ave ] × 100.
The measured results are shown in Table 1. The determination in Table 1 is indicated by ◯ when the light use efficiency is 50% or more and the illuminance unevenness is 150% or less, and when the light use efficiency is less than 50% or the illuminance unevenness is more than 150%.

Further, in FIG. 5, measuring a relationship between _{Φ · N p · L G ·} K C values and light use efficiency (ratio of light emitted through the light exit plane 18a to light incident on the light incident surface) The results are shown.
As shown in Table 1 and FIG. 5, by a _{Φ · N p · L G ·} K C to 1.1 or more, increasing the light use efficiency, specifically 50% or more of light use efficiency and It can be seen that by setting it to 8.2 or less, the illuminance unevenness can be reduced to 150% or less.
In addition, when Kc is set to 0.005 or more, the light use efficiency can be increased, and when it is set to 0.1 or less, the illuminance unevenness of light emitted from the light guide plate can be reduced. Recognize.

Then, the particle density N _p of the particles which kneaded or dispersed in the light guide plate creates various values of the light guide plate was measured illuminance distribution of light emitted from the respective positions of the light emitting surface of each light guide plate . In this exemplary embodiment, other conditions except for the particle density N _p, specifically, the scattering cross section [Phi, half the length of the optical axis direction of the light guide plate L _G, the correction coefficient K _C, the light guide plate The shape and the like were the same value. Accordingly, in the present _{embodiment, Φ · N p · L G} · K C changes in proportion to the particle density _{N p.}
FIG. 6 shows the result of measuring the illuminance distribution of the light emitted from the light exit surface for the light guide plates having various particle densities in this way. In FIG. 6, the vertical axis represents illuminance [lx], and the horizontal axis represents the distance (light guide length) [mm] from one light incident surface of the light guide plate.

Further, the uneven illuminance when the maximum illuminance of light emitted from the side wall of the light guide plate having the measured illuminance distribution is I _Max , the minimum illuminance is I _Min , and the average illuminance is I _Ave [(I _Max −I _Min ) / I _Ave ] × 100 [%] was calculated.
FIG. 7 shows the relationship between the calculated illuminance unevenness and the particle density. In FIG. 7, the vertical axis represents illuminance unevenness [%], and the horizontal axis represents particle density [pieces / m ³ ]. FIG. 7 also shows the relationship between the light utilization efficiency and the particle density, where the horizontal axis is similarly the particle density and the vertical axis is the light utilization efficiency [%].

As shown in FIGS. 6 and 7, when the particle density is increased, that is, Φ · N _p · L _G · K _C is increased, the light use efficiency is increased, but the illuminance unevenness is also increased. It can also be seen that when the particle density is lowered, that is, when Φ · N _p · L _G · K _C is reduced, the light utilization efficiency is reduced, but the illuminance unevenness is reduced.
Here, by the _{Φ · N p · L G ·} K C less than 1.1 and not greater than 8.2, the light use efficiency of 50% or more, and the illuminance unevenness of 150% or less. By setting the illuminance unevenness to 150% or less, the illuminance unevenness can be made inconspicuous.
_{That, Φ · N p · L G} · K C to be to less than 1.1 and not greater than 8.2 yields light use efficiency above a certain level, and illuminance unevenness also seen that it is possible to reduce.

In addition, the light guide plate is not limited to the above shape, and may have various shapes as long as the thickness of the light guide plate increases as the distance from the light incident surface increases.
For example, prism rows may be formed on the first inclined surface 18b and the second inclined surface 18c in a direction parallel to the first light incident surface 18d and the second light incident surface 18e. Further, instead of such a prism array, an optical element similar to a prism can be regularly formed. For example, an optical element having a lens effect, such as a lenticular lens, a concave lens, a convex lens, or a pyramid type, can be formed on the inclined surface of the light guide plate.

The shape of the light guide plate is not limited to the shape of the present embodiment. For example, the shape of the light guide plate shown in FIG. 2 cut in half along the bisector α, that is, the light incident surface is only one surface. The shape in which the thickness of the light guide plate increases as the distance from the light incident surface increases, in other words, the light incident surface is composed of one light incident surface formed on one end side of the light exit surface, and the inclined surface is It may be composed of one inclined surface that inclines away from the light exit surface as it goes from the light incident surface toward the other end surface facing the light incident surface, and may be the thinnest at the light incident surface and the thickest at the other end surface. In addition, the light source is arranged on any one of the side surfaces of the light guide plate, the four side surfaces are light incident surfaces, and the thickness increases from the four light incident surfaces toward the center, that is, the light emission of the light guide plate The surface opposite to the surface has a quadrangular pyramid shape, in other words, the light incident surface is composed of four light incident surfaces respectively formed on the four end sides of the light exit surface, and the inclined surface is Each of the four light incident surfaces is composed of four inclined surfaces that are inclined so as to move away from the light exit surface toward the center. The thickness of the light incident surface is the thinnest, and the thickness at the position where the four inclined surfaces intersect is the thickest. It is good also as a shape.
Again, with the light guide plate having the above shape, the length of the direction of incidence of light from the light incident surface of the light guide plate to a position where the direction of thickness perpendicular to the light exit surface is maximum and L _G, above Φ · N _p · L _G · K _C preferably satisfies 1.1 or more and 8.2 or less. By satisfying the above range, illuminance unevenness can be reduced and light with high light utilization efficiency can be emitted from the light exit surface.

Next, the prism sheet 20 will be described.
As shown in FIG. 2, one prism sheet 20 is provided between the light guide plate 18 and the diffusion film 22, that is, the prism sheet 20 is disposed to face the light exit surface 18 a of the light guide plate 18. Has been. The prism sheet 20 is an optical member formed by arranging a plurality of elongate prisms in parallel with each other on the surface of a transparent sheet, and improves the condensing property of light emitted from the light exit surface of the light guide plate 18. The brightness can be improved. The apex of each prism 20a of the prism sheet 20 is disposed so as to face the light exit surface 18a of the light guide plate 18, that is, downward in the drawing. As another aspect, a second prism sheet having the same structure can be disposed on the prism sheet 16 so that the prism intersects the prism 16a. As another prism sheet, a prism sheet having a configuration in which a large number of triangular pyramid (pyramid) prisms are arranged on the transparent sheet surface may be used.

Next, the diffusion film 22 will be described.
The diffusion film 22 is disposed on the surface of the prism sheet 20 opposite to the light guide plate 18 side. That is, the prism sheet 20 and the diffusion film 22 are laminated in this order on the light exit surface 18a of the light guide plate 18 from the light exit surface 18a side.
The diffusion film 22 is formed by imparting light diffusibility to a film-like member. The film-like member is optically transparent, such as PET (polyethylene terephthalate), PP (polypropylene), PC (polycarbonate), PMMA (polymethyl methacrylate), benzyl methacrylate, MS resin, or COP (cycloolefin polymer). Can be formed into a material.

Although the manufacturing method of the diffusion film 22 is not particularly limited, for example, the surface of the film-like member is subjected to surface roughening by fine unevenness processing or polishing to impart diffusibility, or silica, titanium oxide that scatters light on the surface, It can be formed by coating a pigment such as zinc oxide or beads such as resin, glass or zirconia together with a binder, or kneading the pigment or beads in the transparent resin. In addition, it is possible to use a material having high reflectance and low light absorption, for example, using a metal such as Ag or Al.
In the present invention, as the diffusion film 22, a mat type or coating type diffusion film can be used.
In FIG. 2, the diffusion film 22 is arranged on the prism sheet 20, but the arrangement position of the diffusion film 22 is not particularly limited, and may be arranged between the light guide plate 18 and the prism sheet 20.

Next, the reflecting plate 24 of the lighting device main body will be described.
The reflection plate 24 is provided to reflect light leaking from the first inclined surface 18b and the second inclined surface 18c of the light guide plate 18 so as to enter the light guide plate 18 again, thereby improving the light use efficiency. be able to. The reflecting plate 24 has a shape corresponding to the first inclined surface 18b and the second inclined surface 18c of the light guide plate 18, and is formed so as to cover the first inclined surface 18b and the second inclined surface 18c. In the present embodiment, in FIG. 2, since the first inclined surface 18b and the second inclined surface 18c of the light guide plate 18 are formed in a triangular cross section, the reflecting plate 24 is also formed in a shape that complements this. .

  The reflection plate 24 may be formed of any material as long as it can reflect light leaking from the inclined surface of the light guide plate 18. For example, the reflection plate 24 may be stretched after kneading a filler in PET, PP (polypropylene), or the like. Resin sheet with increased reflectivity by forming voids, a sheet with a mirror surface formed by vapor deposition of aluminum on the surface of a transparent or white resin sheet, a resin sheet carrying a metal foil or metal foil such as aluminum, or sufficient on the surface It can be formed of a thin metal plate having excellent reflectivity.

The upper guide reflection plate 34 is disposed between the light guide plate 18 and the prism sheet 20, that is, on the light emission surface 18 a side of the light guide plate 18, and at the end of the light emission surface 18 a of the light source 12 and the light guide plate 18 (first light incident). An end on the surface 18d side and an end on the second light incident surface 18e side) are disposed so as to cover each other. In other words, the upper guide reflection plate 34 is disposed so as to cover a part of the light exit surface 18a of the light guide plate 18 to a part of the array substrate 42 of the light source 12 in a direction parallel to the optical axis direction. That is, the two upper guide reflectors 34 are disposed at both ends of the light guide plate 18, respectively.
The lower guide reflection plate 36 is disposed so as to cover a part of the light source 12 on the side opposite to the light exit surface 18a side of the light guide plate 18, that is, on the first inclined surface 18b and the second inclined surface 18c side. . In addition, the end portion of the lower guide reflection plate 36 on the center side of the light guide plate is connected to the reflection plate 24.
Here, as the upper guide reflector 34 and the lower guide reflector 36, various materials used for the reflector 24 described above can be used.

Thus, by arranging the upper guide reflection plate 34, it is possible to prevent the light emitted from the light source 12 from leaking to the light exit surface 18 side without entering the light guide plate 18.
Thereby, the light emitted from the LED chip 40 of the light source 12 can be efficiently incident on the first light incident surface 18d and the second light incident surface 18e of the light guide plate 18, and the light use efficiency can be improved. it can.
Similarly, the lower guide reflector 36 prevents light emitted from the light source 12 from entering the light guide plate 18 and leaking to the first inclined surface 18b and the second inclined surface 18c side of the light guide plate 18. it can.
Thereby, the light emitted from the LED chip 40 of the light source 12 can be efficiently incident on the first light incident surface 18d and the second light incident surface 18e of the light guide plate 18, and the light use efficiency can be improved. it can.

  Here, the upper guide reflector 34 and the lower guide reflector 36 reflect the light emitted from the light source 12 toward the first light incident surface 18d or the second light incident surface 18e, and the light emitted from the light source 12. Can be incident on the first light incident surface 18d and the second light incident surface 18e, and the shape and width thereof are not particularly limited as long as the light incident on the light guide plate 18 can be guided to the center side of the light guide plate 18.

Next, the housing 16 will be described.
The housing 16 houses and supports the light source 12 and the lighting device main body 14, and basically includes a main body portion 16a and a frame portion 16b.
The main body portion 16a has an open top surface, and stores and supports the lighting device main body 14 from above, and covers the four side surfaces of the lighting device main body 14. Further, the four side surfaces include A reverse concave (U-shaped) folded portion 26 is integrally formed.
The frame portion 16b has a rectangular opening 28 smaller than the rectangular light exit surface 14a of the illuminating device main body 14 formed on the upper surface, the lower surface is opened, and the illuminating device main body 14 and the main body portion 16a in which the illuminating device main body 16a is housed are disposed. It covers from the light emission surface 14a side of the illuminating device main body 14 so as to cover the four side surfaces, and is attached to the main body portion 16a.

The folded portion 26 supports the side surfaces of the light guide plate 18, the reflective plate 24, and a light guide plate support portion 30 described later on the inner surface, and the outer surface of the folded member 26 is fitted with the frame portion 16 b.
As a method for joining the folded portion 26 of the main body portion 16a and the frame portion 16b, various known methods such as bolts and nuts, adhesives, and welding can be used. The housing 16 is basically configured as described above.

In the planar illumination device 10 of the present embodiment, a light guide plate support 30 is further disposed between the main body 16a and the reflector 24. The light guide plate support portion 30 is made of a resin such as polycarbonate and is in contact with the main body portion 16 a and the reflection plate 24.
A power storage unit 32 (see FIG. 1) that stores a power source (not shown) of the light source 12 is attached to the back side of the main body 16a.
The planar illumination device 10 is basically configured as described above.

Here, as shown in FIGS. 2 and 3, the LED chip 40 and the array substrate 42 of the light source 12 of the planar illumination device 10 are perpendicular to the light exit surface 18 a of the light guide plate 18, and the first light incident surface 18 d. Alternatively, the second light incident surface 18e is disposed so as to be inclined by a predetermined angle θ with respect to a surface S (hereinafter also referred to as “reference surface S”) parallel to the long side direction side. Specifically, the light emitting surface 40 a of the LED chip 40 is arranged with an angle θ inclined with respect to the reference surface S. That is, the light emitting surface 40a is arranged at a position rotated by an angle θ from the reference surface S toward the light emitting surface 18a.
In this way, by arranging the light source 12 to be inclined, light emitted from the light source having a large light emitting surface can be efficiently incident on the light guide plate. By using the light source having a large light emitting surface, the light is emitted from the light source. The amount of light to be increased can be increased. In other words, high-intensity light can be emitted from the light emission surface of the light guide plate by efficiently making the light emitted from the light source having a large light emitting surface incident on the light guide plate.
In addition, by arranging the upper guide reflection plate and the lower guide reflection plate and reflecting the light emitted from the light source, the light emitted from the light source is reflected even when the light emitting surface is inclined at a predetermined angle. The light emitted from the light source can be efficiently incident on the first light incident surface and the second light incident surface of the light guide plate.

Here, the LED chip 40 of the light source 12 is the length of the light emitting surface 40a in the inclination direction, that is, the length a of the light emitting surface 40a of the LED chip 40 in the direction orthogonal to the arrangement direction of the LED chips 40 in this embodiment ( 4) is the length of the cross section of the first light incident surface in the direction orthogonal to the light exit surface 18a on the edge side of the light exit surface 18a of the first light entrance surface 18d, in this embodiment, the light guide plate 18 The length d1 of the first light incident surface 18d or the second light incident surface 18e of the light guide plate 18 in the direction perpendicular to the light exit surface 18a (hereinafter referred to as “the effective section length d1 of the light incident surface”), that is, It is preferable that the first light incident surface 18d or the second light incident surface 18e is longer than the length of the light guide plate in the thickness direction.
By making the length a of the light emitting surface 40a longer than the length d1 of the effective cross section of the light incident surface, more light can be emitted from the light emitting surface.
Further, by arranging the light emitting surface 40a to be inclined at a predetermined angle θ with respect to the reference surface S, even when the length a of the light emitting surface 40a is larger than the length d1 of the effective cross section of the light incident surface, it is efficiently performed. Light can be incident on the light guide plate, and as described above, light with high luminance can be efficiently emitted from the light exit surface of the light guide plate.

Here, the inclination angle θ of the light emitting surface 40a with respect to the reference surface S is preferably 15 ° or more and 90 ° or less, that is, 15 ° ≦ θ ≦ 90 °, and 15 ° or more and 75 ° or less, that is, 15 ° ≦ More preferably, θ ≦ 75 °. Here, the inclination angle θ is an angle obtained by inclining the light emitting surface 40a toward the light emitting surface 18a with respect to the reference surface S. When θ = 90 °, the light emitting surface 40a is parallel to the light emitting surface 18a. Light is emitted from the light emitting surface 40a in the same direction as the light emitted from the light emitting surface 18a of the light guide plate 18.
By making the inclination angle θ of the light emitting surface 40a 15 ° ≦ θ ≦ 90 °, the light use efficiency can be further increased, and the light emitted from the light emitting surface can be made uniform, By setting 15 ° ≦ θ ≦ 75 °, the light utilization efficiency can be further increased and made more uniform.
Note that the light source 12 is preferably disposed with the light emitting surface 40 facing the light exit surface as in the present embodiment, but the present invention is not limited to this, and the light emitting surface 40a of the light source 12 has the first inclined surface. You may arrange | position toward the surface 18b or the 2nd inclined surface 18c.

Hereinafter, the planar illumination device 10 will be described in more detail with specific examples. Here, since the planar illumination device of the present embodiment has a symmetrical shape with the above-described bisecting line α as an axis, it will be described using the first light incident surface side as a representative.
In the surface illumination device of this embodiment, the length a of the light emitting surface 40a of the LED chip 40 in the direction orthogonal to the arrangement direction of the LED chips 40 is 2.5 mm, the thickness w1 of the LED chip 40 is 0.5 mm, and the LED chip. The length d2 of the array support 42 in the direction orthogonal to the arrangement direction of 40 is 3.0 mm, the thickness w2 of the array support 42 is 0.5 mm, and the length of the effective cross section of the first light incident surface 18d of the light guide plate 18 d1 is 2.0 mm, and the length of the upper guide reflector 34 and the light exit surface 18a of the light guide plate 18 is overlapped, that is, the light incident surface 18d and the end of the upper guide reflector 34 on the center side of the light guide plate 18 The distance L was 5 mm. Further, a reflective film having a thickness of 0.1 mm and a reflectivity of 98% is used for the reflector 24 and the lower guide reflector 36, and a reflection having a thickness of 0.1 mm and a reflectivity of 90% is used for the upper guide reflector 34. A film was used. Here, the reflecting plate 24 and the lower guiding reflecting plate 36 are formed of a single reflecting film. Further, the reflecting plate 24 and the lower guiding reflecting plate 36 are bent at a position corresponding to the connecting portion, that is, the first light incident surface 18 d at the end of the light guide plate 18.
When the inclination angle θ of the light emitting surface 40a of the LED chip 40 of the light source 12 of the planar illumination device having such a shape is θ = 15 °, 30 °, 45 °, 60 °, 75 °, The light utilization efficiency of the light source was measured.
For comparison, as a comparative example 1, as shown in FIG. 8A, θ = 0 °, that is, a planar illumination device in which the light emitting surface 40a is arranged at a position or an angle parallel to the reference plane S. The light utilization efficiency of the light source was measured. Furthermore, as Comparative Example 2, as shown in FIG. 8B, the length a of the light emitting surface 40a of the LED chip 40 in the direction orthogonal to the arrangement direction of the LED chips 40 is 1.45 mm, and θ = 0 °. The light use efficiency of the light source of the arranged planar lighting device was measured.
The measurement results are shown in Table 2 below and FIG.

As shown in Table 2 and FIG. 9, the light emitting surface of the light source is inclined at a predetermined angle, and in this embodiment, the light emitting surface 40 a is parallel to the reference surface S by 15 ° ≦ θ ≦ 75 °. It can be seen that the light use efficiency can be made higher than that in the case where the light is arranged at a position, that is, an angle. That is, more light can be incident on the light guide plate, and the luminance or illuminance of the light emitted from the light source can be further increased.
Further, in the present embodiment, by setting the inclination angle θ of the light emitting surface 40a to 15 ° ≦ θ ≦ 45 ° or less, the direction orthogonal to the arrangement direction of the LED chips 40 rather than the length of the effective cross section of the light incident surface. It can be seen that the light utilization efficiency can be made higher than in Comparative Example 2 in which the LED chip 40 in which the length a of the light emitting surface 40a of the LED chip 40 is shortened is arranged.
That is, by adjusting the inclination angle θ of the light emitting surface, light emitted from the light source can be made to enter the light guide plate more efficiently, and light with higher luminance and illuminance can be emitted from the light emitting surface.

Next, another embodiment of the planar lighting device will be described.
FIG. 10 is a schematic cross-sectional view showing another embodiment of the planar illumination device of the present invention, and FIG. 11 is an enlarged cross-sectional view of a part of the planar illumination device shown in FIG.
The planar illumination device 100 shown in FIGS. 10 and 11 has the planar illumination shown in FIGS. 1 to 3 except for the shapes of the first light incident surface 18d ′ and the second light incident surface 18e ′ of the light guide plate 18 ′. The configuration is the same as that of the device 10. Therefore, the same components are denoted by the same reference numerals in both, and the detailed description thereof is omitted, and hereinafter, the points peculiar to the planar illumination device 100 will be mainly described.

  The planar illumination device 100 includes a light source 12, an illumination device body 14 ′ that emits uniform light from a rectangular light emission surface 14a, and a housing 16 that houses the illumination device body 14 ′ and the light source 12 therein. I have. The illumination device main body 14 ′ includes a light guide plate 18 ′, a prism sheet 20, a diffusion film 22, a reflection plate 24, an upper guide reflection plate 34, and a lower guide reflection plate 36. Here, the light source 12, the casing 16, the prism sheet 20, the diffusing film 22, the reflecting plate 24, the upper guiding reflecting plate 34, and the lower guiding reflecting plate 36 have the same configuration as that of the planar lighting device 10 described above. Detailed description is omitted.

As shown in FIGS. 10 and 11, the light guide plate 18 ′ has a substantially rectangular flat light exit surface 18a, and both ends of the light exit surface 18a with respect to a reference surface S perpendicular to the light exit surface 18a. Two light incident surfaces (first light incident surface 18d ′ and second light incident surface 18e ′) formed at a predetermined angle θ1 are positioned opposite to the light exit surface 18a, and the first light incident surface 18d. 'And parallel to the second light incident surface 18e', symmetric with respect to the bisector α (see FIG. 1) that bisects the light emitting surface 18a as a central axis, and at a predetermined angle with respect to the light emitting surface 18a It has two inclined surfaces (the 1st inclined surface 18b and the 2nd inclined surface 18c) inclined by. The first inclined surface 18b and the second inclined surface 18c are arranged such that the distance from the light exit surface 18a increases (increases) as the distance from the first light incident surface 18d ′ and the second light incident surface 18e ′ increases. As the distance from the first light incident surface 18d ′ and the second light incident surface 18e ′ toward the center of the light guide plate 18 ′ is increased, the thickness in the direction perpendicular to the light exit surface of the light guide plate is increased. That is, the light guide plate 18 ′ has the thinnest thickness at both end portions, that is, the first light incident surface 18d ′ and the second light incident surface 18e ′, and the central portions, that is, the first inclined surface 18b and the second inclined surface 18c. The thickness is maximum at the position of the intersecting bisector α. The inclination angles of the first inclined surface 18b and the second inclined surface 18c with respect to the light exit surface 18a are not particularly limited.
Further, the light source 12 is disposed to face the first light incident surface 18d ′ and the second light incident surface 18e ′ of the light guide plate 18 ′, respectively. That is, in the planar lighting device 10, the two light sources 12 are arranged so as to sandwich the light guide plate 18 ′. In other words, the light guide plate 18 ′ is disposed between the two light sources 12 disposed to face each other with a predetermined distance therebetween.
Here, the planar illumination device 100 also has a symmetrical shape with the bisector α as the central axis in the same manner as the planar illumination device 10 described above, and therefore, the first illumination surface side will be described as a representative.

  As shown in FIG. 11, the planar illumination device 100 according to the present embodiment includes a light source disposed so as to face the inclination angle θ <b> 1 of the first light incident surface 18 d ′ with respect to the reference surface S and the first light incident surface 18 d ′. The inclination angle θ with respect to the reference plane S of the issue surface 40a of the 12 LED chips 40 is arranged at the same angle. That is, the first light incident surface 18d 'and the light emitting surface 40a are arranged in parallel.

By tilting the first light incident surface 18d ′ of the light guide plate 18 with respect to the reference plane S by a predetermined angle θ1, the surface area of the first light incident surface 18 ′ is made larger than the surface area of the effective cross section of the first light incident surface 18 ′. Can be increased. Thereby, the light emitted from the light emitting surface 40a of the light source 12 can be efficiently incident on the light guide plate 18 ′.
Here, when the first light incident surface 18d ′ is inclined as in the present embodiment, the edge side of the light exit surface 18a of the first light incident surface 18d ′, that is, the first light incident surface 18d. A cross section in a direction substantially orthogonal to the light exit surface 18a at a contact point (tangent, that is, a connecting position) between the light exit surface 18a is an effective cross section of the light entrance surface.
Further, as in the present embodiment, the first light incident surface 18d ′ of the light guide plate 18 is made parallel to the light emitting surface 40a of the light source 12, that is, the inclination angle of the first light incident surface with respect to the reference surface S is set. The light emitted from the light emitting surface 40 a can be efficiently incident on the first light incident surface 18 d ′ of the light guide plate 18 by setting the same angle as the inclination angle of the light emitting surface of the light source disposed facing each other. .

  Here, the inclination angle θ1 of the first light incident surface 18d ′ is preferably the same as the inclination angle θ of the light emitting surface 40a of the light source as in this embodiment, but the present invention is not limited to this. The inclination angle θ1 and the inclination angle θ may be different from each other. That is, the light emitting surface 40a may be disposed at a predetermined angle with respect to the first light incident surface 18d '.

Hereinafter, the planar illumination device 100 will be described in more detail with specific examples.
In the planar illumination device 100 of this embodiment, the length a of the light emitting surface 40a of the LED chip 40 in the direction orthogonal to the arrangement direction of the LED chips 40 is 2.5 mm, the thickness w1 of the LED chip 40 is 0.5 mm, and the LED The length d2 of the array support 42 in the direction orthogonal to the arrangement direction of the chips 40 is 3.0 mm, the thickness w2 of the array support 42 is 0.5 mm, and the effective cross section of the first light incident surface 18d ′ of the light guide plate 18 ′. The length d1 of the first light exit surface 18d ′ is 2.0 mm, that is, the length d3 of the first light exit surface 18d ′ connecting the light exit surface 18a and the first inclined surface 18b is (2. 0 / cos θ1), a length in which the upper guide reflector 34 and the light exit surface 18a of the light guide plate 18 ′ overlap, that is, the first light incident surface 18d ′ and the light guide plate 18 ′ center side of the upper guide reflector 18 The distance L from the end of the was 5 mm. Further, a reflective film having a thickness of 0.1 mm and a reflectivity of 98% is used for the reflector 24 and the lower guide reflector 36, and a reflection having a thickness of 0.1 mm and a reflectivity of 90% is used for the upper guide reflector 34. A film was used. Here, the reflecting plate 24 and the lower guiding reflecting plate 36 are formed of a single reflecting film. Further, the reflecting plate 24 and the lower guiding reflecting plate 36 are bent at a position corresponding to the connecting portion, that is, the first light incident surface 18d ′ of the light guide plate 18 ′.
The light emitting surface 40a of the light source 12 and the first light incident surface 18d ′ of the light guide plate 18 are parallel to each other, that is, the inclination angle θ of the light emitting surface 40a and the inclination angle θ1 of the first light incident surface 18d ′ are the same. It was an angle.
When the inclination angle θ and the first light incident surface θ1 of the light emitting surface 40a of the planar lighting device having such a shape are θ = θ1, and θ = 15 °, 30 °, 45 °, 60 °, 75 ° The light utilization efficiency of the light source of the planar lighting device was measured.
For comparison, as in the above example, as Comparative Example 1, as shown in FIG. 8A, θ = 0 °, that is, the position and angle at which the light emitting surface 40a is parallel to the reference surface S. The light use efficiency of the light source of the planar illumination device arranged in (1) was measured. Furthermore, as Comparative Example 2, as shown in FIG. 8B, the length a of the light emitting surface 40a of the LED chip 40 in the direction orthogonal to the arrangement direction of the LED chips 40 is 1.45 mm, and θ = 0 °. The light use efficiency of the light source of the arranged planar lighting device was measured.
The measured results are shown in Table 3 below and FIG.

As shown in Table 3 and FIG. 12, the light emitting surface of the light source and the light incident surface of the light guide plate are inclined by a predetermined angle, so that the light emitting surface 40a is arranged at a position parallel to the reference surface S, that is, at an angle. Alternatively, it can be seen that the light utilization efficiency can be made higher than when the light emitting surface 40a is arranged at a position parallel to the reference surface S. In the present embodiment, the light sources having the same length a are compared. However, by arranging the light sources at an inclination, the area of the light emitting surface of the light source can be increased. That is, more light can be incident on the light guide plate, and the luminance or illuminance of the light emitted from the light source can be further increased.
Further, in the present embodiment, the effective angle of the light incident surface is reduced by setting the inclination angle θ of the light emitting surface 40a and the inclination angle θ1 of the light guide plate to θ = θ1 and 15 ° ≦ θ ≦ 60 ° or less. It can be seen that the light utilization efficiency can be made higher than that of Comparative Example 2 in which the LED chip 40 in which the length a of the light emitting surface 40a of the LED chip 40 in the direction orthogonal to the arrangement direction of the LED chips 40 is shortened is arranged.
In other words, by adjusting the inclination angle θ of the light emitting surface and the inclination angle θ1 of the light guide plate, the light emitted from the light source is incident on the light guide plate more efficiently, and light with higher luminance and illuminance is emitted from the light emission surface. Can be made.

Next, another specific embodiment will be described.
In the present embodiment, θ = 45 °, and a specific example of the above-described planar illumination device 10 in which the distance L between the first light incident surface 18d and the end of the upper guide reflection plate 34 on the light guide plate 18 center side is 5 mm. Luminance (cd / m ² ), illuminance (lx), light utilization efficiency (%), and average luminance (%) at each position emitted from the light exit surfaces of two planar illumination devices having substantially the same configuration as the example. cd / m ² ) was measured.
Further, θ = θ1 = 45 °, and the surfaces described above except that the distance L between the first light incident surface 18d ′ and the end of the upper guide reflector 34 on the center side of the light guide plate 18 is 5 mm and 10 mm, respectively. Brightness (cd / m ² ), illuminance (lx), and light at each position emitted from the light exit surfaces of two planar illumination devices having substantially the same configuration as the specific example of the illumination device 100 Utilization efficiency (%) and average luminance (cd / m ² ) were measured. In addition, for comparison, as Comparative Example 3, each of the light emitted from the light emitting surface of the planar illumination device in which the reflecting plate is not disposed and the light incident surface of the light guide plate and the light emitting surface of the light source are parallel to the reference surface is provided. The luminance (cd / m ² ), illuminance (lx), light utilization efficiency (%), and average luminance (cd / m ² ) of the position were also measured.
The measured luminance distribution is shown in FIG. 13, and the illuminance distribution is shown in FIG. Here, in FIG. 13, the vertical axis represents luminance (cd / m ² ), and the horizontal axis represents distance (mm) from the center of the light guide plate. In FIG. 14, the vertical axis represents illuminance (lx), and the horizontal axis represents distance (mm) from the center of the light guide plate.
Table 4 shows the measured light utilization efficiency (%) and average luminance (cd / m ² ).

As shown in Table 4, it can be seen that the example of the present invention can increase the average luminance and the light utilization efficiency as compared with Comparative Example 3.
As shown in FIGS. 13 and 14, it can be seen that the embodiment of the present invention can increase the luminance and illuminance at each position on the light guide plate center side as compared with Comparative Example 3.
It can also be seen that the average luminance can be increased by setting the length L of the upper guide reflector to 5 mm.
From the above, the effects of the present invention are clear.

Next, still another embodiment of the planar lighting device of the present invention will be described.
FIGS. 15A and 15B are enlarged sectional views showing other embodiments of the planar lighting device of the present invention. Here, the planar illumination device 110 illustrated in FIG. 15A and the planar illumination device 150 illustrated in FIG. 15B also have a bilaterally symmetric shape, similar to the planar illumination device 10 and the planar illumination device 100 described above. Therefore, only one end is shown.

The planar illumination device 110 shown in FIG. 15 (A) is basically the same as the planar illumination device 10 except that the inclination angle θ of the light emitting surface 40a with respect to the reference plane S is 90 °. It is the composition.
The light source 12 of the planar illumination device 110 is disposed at a position where the inclination angle θ of the light emitting surface 40a of the LED chip 40 is 90 °, that is, the light emitting surface 40a is perpendicular to the first light incident surface 18d. The LED chip 40 is disposed on the first inclined surface 18b side of the first light incident surface 18d.
The upper guide reflection plate 112 is a plate-like member that is bent at the end of the light emission surface of the light guide plate 18, and the first light emitting surface 40 a of the LED chip 40 is partly formed from a part of the light emission surface 18 a of the light guide plate 18. It is arranged to cover up to the end farther from the light incident surface 18d. As the upper guide reflector 112, the same material as that of the upper guide reflector 34 described above can be used.

In the planar illumination device 110 having such a configuration, the light emitted from the light source 12 is incident on the light guide plate 18 from the first light incident surface 18d after being directly or after being reflected by the upper guide reflector 112. The light that has entered the light guide plate 18 is emitted from the light exit surface in the same manner as the planar illumination device 10 described above.
Thus, even when the inclination angle θ of the light emitting surface 40a is set to 90 °, light emitted from a light source having a large light emitting surface, for example, a light source having a light emitting surface longer than the length of the effective cross section of the light incident surface can be efficiently obtained. The light can be incident on the light exit surface well, and the light use efficiency can be improved. In addition, since the area of the light emitting surface can be increased by setting the inclination angle θ to 90 °, light with high luminance or illuminance can be emitted from the light emitting surface.

A planar illumination device 150 illustrated in FIG. 15B has the same configuration as the planar illumination device 110 illustrated in FIG. 15A except for the shape of the light guide plate 152.
The light guide plate 152 has a flat light emission surface 152a having a substantially rectangular shape and two side surfaces (first side surface 152f and first side surface) formed at both ends of the light emission surface 152a with a predetermined angle with respect to the light emission surface 152a. Two side surfaces (not shown)) and a bisector α (see FIG. 1) that bisects the light exit surface 152a are symmetric with respect to the central axis, and are inclined at a predetermined angle with respect to the light exit surface 152a. Two inclined surfaces (a first inclined surface 152b and a second inclined surface (not shown)), and two light incident surfaces (first surfaces) formed between the end portions of the inclined surfaces and the end portions of the side surfaces. It has a light incident surface 152d and a second light incident surface (not shown). Here, the light guide plate 152 has a shape in which an angle formed by the light exit surface 152a and the first side surface 152d is larger than 90 °, and an angle formed by the first light incident surface 152d and the first side surface 152f is smaller than 90 °. The light incident surface 152d is formed with an inclination angle θ1 of 90 ° with respect to the reference surface S.
In this embodiment, the cross section in the direction substantially orthogonal to the light exit surface 152a of the light guide plate 152 at the edge of the first light incident surface 152d on the first inclined surface 152b side is the effective cross section of the light incident surface.
Note that, since the planar lighting device 150 has a symmetrical shape, only the end portion on the first side surface 152d side is shown in FIG. 15B as described above.

The light source 12 includes a plurality of LED chips 40 and a light source support 41, and is disposed to face a first light incident surface 152d formed between the first inclined surface 152b and the first side surface 152f of the light guide plate 152. Has been.
The light source 12 is disposed at a position where the inclination angle θ of the light emitting surface 40a with respect to the reference surface S is 90 °. Therefore, the light emitting surface 40a of the light source 12 and the first light incident surface 152d are arranged in parallel.

The upper guide reflection plate 112 is disposed so as to cover the light guide plate 152 along a part of the light emission surface 152a on the first side surface 152f side and the shape of the first side surface 152f. Further, the end of the upper light guide plate 112 on the first side surface 152 f side of the light guide plate 152 is connected to the light source 12.
In addition, the reflection plate 24 is disposed on the first inclined surface 152 b side of the light guide plate 152.
That is, the light guide plate 152 includes a light emitting surface 152a, a first side surface 152f, a first light incident surface 152d, and a first inclined surface 152b on the first side surface 152d side by the upper guide reflection plate 112, the light source 12, and the reflection plate 24. Covered without gaps. Here, in this embodiment, the reflecting plate 24 also has a function as a lower guiding reflecting plate.

The light emitted from the light emitting surface 40a of the light source 12 enters from the first light incident surface 152d of the light guide plate 152 and directly enters the center side of the light guide plate 152 or the first side surface 152f or the upper guide reflector 112. The reflected light travels toward the center of the light guide plate 152.
The light traveling toward the center of the light guide plate 152 passes through the light guide plate 152 while being scattered by a scatterer (details will be described later) included in the light guide plate 152, as in the light guide plate 18 described above. The light exits from the light exit surface 152a directly or after being reflected by the first inclined surface 152b and the second inclined surface.

As described above, the light emitting surface of the light source is inclined at a predetermined angle with respect to the reference surface, the light incident surface of the light guide plate is also inclined at a predetermined angle, and a side surface is provided between the light incident surface and the light emitting surface of the light guide plate. Even in this case, the light emitted from the light source can be efficiently incident on the light guide plate, and the light utilization efficiency can be increased.
Further, by providing a side surface on the light guide plate and disposing the light emission surface on the inclined surface side, the area of the light emission surface of the light source can be increased, and light with high luminance or illuminance can be emitted from the light emission surface. it can. In addition, by reflecting the light incident from the light incident surface on the side surface inclined by a predetermined angle, even when light is incident from the light incident surface provided on the inclined surface side, light with no unevenness is emitted from the light emission surface. Can do.

Also, by providing the side surface, the light incident from the light incident surface can be reflected by the side surface, and even when the inclination angle of the light incident surface with respect to the reference surface is increased, the light incident from the light incident surface can be easily guided. It can be guided toward the center of the light plate.
Further, as in the present embodiment, the inclination angle θ1 of the first light incident surface 152d with respect to the reference surface S is set to 90 °, that is, the first light incident surface 152 and the light emitting surface are parallel to each other. The area of the surface can be increased.

Even in the case of a planar illumination device in which light is incident from the end of the inclined surface of the light guide plate, the scattering cross-sectional area of the scattering particles contained in the light guide plate 152 is Φ, parallel to the light exit surface 152a, and light. In the direction perpendicular to the tangent line between the exit surface 152a and the side surface (the first side surface 152f or the second side surface), the thickness of the light guide plate 152 from the contact between the side surface of the light guide plate 152 and the light incident surface, that is, the end of the light guide plate (light the distance in the vertical direction of the thickness on the exit surface (length)) to a position of maximum and L _G, the density of the scattering particles contained in the light guide plate 152 (number of particles per unit volume) N _p, a correction coefficient the when the _{K C,} the value of _{Φ · N p · L G ·} K C is not less than 1.1, and is 8.2 or less, further, the value of the correction coefficient _{K C} is 0.005 or more 0 It is preferable that the relationship of .1 or less is satisfied. Since the light guide plate 18 includes scattering particles that satisfy such a relationship, it is possible to emit illumination light that is uniform and has less unevenness in brightness from the light exit surface 152a.
Also, when the side surfaces are formed, the preferred mode is the same as that of the above-described embodiment. For example, the inclination angle θ = θ1 is preferably 15 ° ≦ θ ≦ 90 °.

Hereinafter, the surface illumination device of the present invention will be described in more detail with specific examples.
In this embodiment, θ = 90 °, that is, the inclination angle of the light emitting surface 40a of the LED chip of the light source, the shape of the upper guide reflector is set to the shape shown in the planar illumination device 110, and the upper guide reflector Except that the length L is 10 mm, the size and configuration are substantially the same as those of the above-described planar illumination device 10. The illuminance (lx) at each position emitted from the light exit surface of the planar illumination device 110 and the light utilization efficiency (%) were measured. For comparison, θ is 45 °, and the light incident surface of the light guide plate and the light emission surface of the light source are parallel to the reference surface of the planar illumination device in which the length L of the upper guide reflector is 10 mm. The illuminance (lx) and light utilization efficiency (%) at each position emitted from the light exit surface of the illuminating device were also measured.
The measurement results are shown in FIG. Here, in FIG. 16, the vertical axis is the illuminance (lx), and the horizontal axis is the distance (mm) from the center of the light guide plate.

As shown in FIG. 16 and Table 5, it can be seen that even when θ = 90 °, the light use efficiency can be increased as in the case of θ = 45 °. Moreover, as shown in FIG. 16, it turns out that uniform light can be inject | emitted from the center part of a light-guide plate.
From the above, the effects of the present invention are clear.

  The planar lighting device according to the present invention has been described in detail above. However, the present invention is not limited to the above-described embodiments, and various improvements and modifications may be made without departing from the gist of the present invention. Of course.

Here, in any of the above-described embodiments, as shown in FIG. 2, the light guide plate support portion 30 formed of a resin or the like is disposed between the main body portion 16 a and the reflection plate 24, and the first light guide plate 18. The reflector 24 is supported from the inclined surfaces 18b and the second inclined surfaces 18c, and the light guide plate 18 and the reflector 24 are brought into close contact with each other. However, the present invention is not limited to this.
Here, it is preferable to arrange a buffer member between the surface of the reflection plate 24 opposite to the light guide plate 18 side, that is, between the main body portion 16a and the reflection plate 24 of the present embodiment. Here, the buffer member is a member having rigidity lower than that of the light guide plate deformed along the shape of the light guide plate, such as a sponge.
By supporting the first inclined surface 18b and the second inclined surface 18c side of the reflecting plate 24 and the light guide plate 18 with the buffer member, the reflecting plate 24 can be brought into close contact with the light guide plate 18, and the reflecting plate 24 bends. Can be prevented. Further, by using the support as a buffer member, the light guide plate and the reflection plate can be brought into contact with each other without unevenness. As a result, only a part of the reflecting plate comes into contact, diffuses the light, prevents the light from being viewed as a bright portion of the light emitted from the light emitting surface, and allows uniform light to be emitted from the light emitting surface. it can.
Here, FIGS. 17A to 17D are exploded cross-sectional views illustrating an example of a schematic configuration of a buffer member that supports the light guide plate and the reflection plate, respectively.
For example, as shown in FIG. 17A, a rectangular buffer member 202 may be disposed on the surface of the reflecting plate 24 opposite to the light guide plate 18. Here, as the buffer member 202, the maximum stress acting on the light guide plate 18 from the buffer member 202 when assembled as a planar lighting device is a connecting portion between the first inclined surface and the second inclined surface in this embodiment. It is preferable to use a material having a stress acting on the surface of 5 [N / cm ² ] or less.
Also, as shown in FIG. 17B, a buffer member 212 made up of multilayer buffer materials 212a, 212b, and 212c is disposed on the surface of the reflector 24 opposite to the light guide plate 18, and the light guide plate 18 The thickness of the buffer member 212 may be different depending on the position depending on the shape. Thus, by changing the thickness of the buffer member 212 according to the position, the compression rate of the buffer member can be reduced, and the maximum stress acting on the light guide plate can be reduced. Thereby, the force which acts on a light guide plate can be made more uniform, and a light guide plate and a reflecting plate can be made to closely_contact | adhere.
Further, as shown in FIG. 17C, the buffer member 222 may have a shape along the inclined surface of the light guide plate 18. That is, the buffer member 222 has a shape in which the first inclined surface 222a and the second inclined surface 222b having the same inclination angle as the first inclined surface and the second inclined surface of the light guide plate 18 are formed on the surface on the light guide plate 18 side. .
In this way, the light guide plate and the reflection plate can be evenly adhered even when the buffer member has a shape along the inclined surface of the light guide plate.
Furthermore, as shown in FIG. 17D, the buffer member 232 is shaped along the inclined surface of the light guide plate 18, and the light guide plate 18 is inclined on the surface opposite to the light guide plate 18 side of the buffer member 232. It is good also as a structure which provided the sheet-metal member 234 along the shape of the surface.
By providing the sheet metal member 234 along the shape of the inclined surface of the light guide plate 18 on the surface opposite to the light guide plate 18 side of the buffer member 232, the compression rate of the buffer member can be made uniform, and the buffer member By supporting the reflection plate via the light guide plate, the light guide plate and the reflection plate can be brought into close contact.

In the present embodiment, a YAG (yttrium, aluminum, garnet) phosphor is disposed on the surface of the blue LED as the light source. However, the light source is a combination of infrared, red, green, and blue phosphors. Can also be used.
In the above embodiments, the LED chips are arranged in a single row in one direction as the light source. However, the present invention is not limited to this. Good.
In addition, instead of the LED chip shown in the above-described embodiment, the light source is a three-color LED of R, G, and B as one element, and the light of these three-color LEDs is mixed to become white light. RGB-LEDs configured as described above may be used. Furthermore, as the light source, an LD (laser diode) can be used instead of the LED chip or RGB-LED.
Moreover, it is not limited to arrange | positioning the fluorescent layer in the light emission surface of LED, and emitting white light, White light can be inject | emitted from a light emission surface also by mixing a fluorescent substance in a light-guide plate.
Moreover, it can replace with or arrange | position in addition to arrange | positioning fluorescent substance on the light emission surface of LED, and the structure which has arrange | positioned the optical sheet which apply | coated or mixed fluorescent substance on the light emission surface of a light-guide plate can also be used.

It is a schematic perspective view which shows one Embodiment of the planar illuminating device which concerns on this invention. It is the II-II sectional view taken on the line of the planar illuminating device shown in FIG. It is an expanded sectional view which expands and shows a part of planar illumination apparatus shown in FIG. (A) is a perspective view which shows schematic structure of the light source of the planar illuminating device shown in FIG.1 and FIG.2, (B) is sectional drawing of the light source shown to (A), (C) is It is a schematic perspective view which expands and shows one LED of the light source shown to (A). It is a diagram showing the results of measuring the relationship between _{Φ · N p · L G ·} K C and light use efficiency. It is a figure which shows the result of having measured the illumination intensity of the light inject | emitted from each light guide from which particle density differs, respectively. It is a figure which shows the relationship between light use efficiency, illumination intensity nonuniformity, and particle density. (A) And (B) is an expanded sectional view which shows schematic structure of an example of the planar illuminating device used for the comparison with the planar illuminating device of this invention, respectively. It is a graph which shows the result of having measured the light utilization efficiency of the planar illuminating device which made the inclination angle (theta) of the light emission surface various values. It is sectional drawing which shows schematic structure of other embodiment of the planar illuminating device of this invention. It is an expanded sectional view which expands and shows a part of planar illumination apparatus shown in FIG. It is a graph which shows the result of having measured the light utilization efficiency of the planar illuminating device which made the inclination angle (theta) of the light emission surface various values. It is a graph which shows the luminance distribution of the light inject | emitted from the light emission surface of the planar illuminating device which made the inclination angle of the light emission surface of a light source and the light-incidence surface, and the attachment length of an upper induction | guidance | derivation reflection plate into various values. It is a graph which shows the illumination intensity distribution of the light inject | emitted from the light emission surface of the planar illuminating device which made the inclination angle of the light emission surface of a light source and the light-incidence surface, and the attachment length of an upper induction | guidance | derivation reflection plate into various values. (A) And (B) is an expanded sectional view which shows schematic structure of the other example of the planar illuminating device of this invention, respectively. It is a graph which shows the illumination intensity distribution of the light inject | emitted from the light emission surface of the planar illuminating device shown to FIG. 15 (A). (A)-(D) are the decomposition | disassembly block diagrams which show an example of the buffer member which each supports a light-guide plate and a reflecting plate.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Planar illuminating device 12 Light source 12a Light emitting surface 14 Illuminating device main body 14a Light emission surface 15 Diffusion film 16 Housing | casing 16a Main body part 16b Frame part 18 Light guide plate 18a Light emission surface 18b 1st inclined surface 18c 2nd inclined surface 18d, 18d '1st light incident surface 18e 2nd light incident surface 20 Prism sheet 22 Diffusion film 24 Reflector plate 26 Folding part 28 Opening part 32 Power supply accommodating part 34 Upper guide reflector 36 Lower guide reflector 40 LED chip 42 Array substrate

Claims (13)

A light exit surface that emits planar light, and light that is formed on an edge of the light exit surface and makes light that travels in a direction parallel to the light exit surface from a direction substantially orthogonal to the light exit surface A transparent light guide plate having an incident surface and an inclined surface that is an opposite surface of the light exit surface and is inclined so as to be away from the light exit surface as it is away from the light entrance surface;
The length of the edge in the direction orthogonal to the longitudinal direction of the light incident surface is the direction of the light guide plate in the direction substantially orthogonal to the light exit surface on the edge side of the light exit surface on which the light incident surface is formed. The light emitting surface has a flat light emitting surface longer than the effective cross section of the light incident surface, and the light emitting surface is opposed to the light incident surface of the light guide plate, and is inclined at a predetermined angle with respect to a direction substantially orthogonal to the light emitting surface. A light source arranged in a
A light guide reflector disposed on the light exit surface side and the inclined surface side of the light incident surface of the light guide plate, and guiding the light emitted from the light source to the light incident surface;
A planar illumination device, wherein light emitted from a light emitting surface of the light source is incident on the light incident surface of the light guide plate, converted into planar light, and emitted from the light emitting surface.   The planar illumination device according to claim 1, wherein the light incident surface of the light guide plate is a plane substantially orthogonal to the light emitting surface of the light source, and an effective cross section of the light incident surface corresponds to the substantially orthogonal plane.   The light incident surface of the light guide plate is a plane inclined so as to face the light emitting surface of the light source in a direction substantially orthogonal to the light exit surface, and an effective cross section of the light incident surface is: The planar illumination device according to claim 1, corresponding to a cross section in a direction substantially orthogonal to the light exit surface at a contact point between the light entrance surface and the light exit surface. Angle of inclination with respect to the direction substantially orthogonal to the light exit plane of the light emitting surface of the light source, Ri 15 to 90 degrees der, the light exit plane and said light incident surface direction of the height of the light emitting surface substantially perpendicular a spread illuminating apparatus according to any one of the tilted Ru claims 1-3 so as to be shorter than the length of the effective cross section of the.   The light source includes a plurality of light emitting diodes or semiconductor lasers arranged in an array along the longitudinal direction of the light incident surface of the light guide plate, and the light emitting surface for mounting these light emitting diodes or semiconductor lasers. The planar illumination device according to any one of claims 1 to 4, wherein the planar illumination device is a planar or linear light source having an array substrate having a mounting surface inclined in parallel.   The guide reflection plate is attached to an end portion of the light guide surface of the light guide plate, and is attached to an end portion of the inclined surface of the light guide plate. The planar illumination device according to any one of claims 1 to 5, further comprising: a second guide reflection plate having an extended portion that is extended to the surface. In the light guide plate, the light exit surface is rectangular.
The light incident surface is composed of two light incident surfaces respectively formed on two opposite sides of the light emitting surface,
The inclined surface is composed of two inclined surfaces inclined so as to move away from the light exit surface as they go from the two light incident surfaces facing each other toward the center,
The planar illumination device according to any one of claims 1 to 6, wherein the planar illumination device has a thinnest thickness at the light incident surface and a thickest thickness at a position where the two inclined surfaces intersect. In the light guide plate, the light exit surface is rectangular.
The light incident surface is composed of one light incident surface formed on one end side of the light emitting surface,
The inclined surface is composed of one inclined surface that is inclined so as to be away from the light exit surface as it goes from the light incident surface to the other end surface facing the light incident surface,
The planar illumination device according to claim 1, wherein the planar illumination device has the thinnest shape on the light incident surface and the thickest shape on the other end surface. In the light guide plate, the light exit surface is rectangular.
The light incident surface is composed of four light incident surfaces respectively formed on four end sides of the light emitting surface,
The inclined surface is composed of four inclined surfaces that are inclined so as to move away from the light emitting surface toward the center from the four light incident surfaces,
The planar illumination device according to any one of claims 1 to 6, wherein the thickness of the light incident surface is the thinnest, and the thickness is the thickest at a position where the four inclined surfaces intersect. The light guide plate is
The light exit from the light incident surface of the light guide plate in the light incident direction includes a large number of scattering particles inside, the scattering cross section of the scattering particles is Φ, the density of the scattering particles is Np, the correction coefficient is KC, When the length to the position where the thickness in the direction perpendicular to the surface is the largest is LG, the following inequality 1.1 ≦ Φ · Np · LG · KC ≦ 8.2
0.005 ≦ KC ≦ 0.1
The planar illumination device according to any one of claims 1 to 9, wherein: A light emitting surface for emitting planar light, an angle formed by the light emitting surface with an angle greater than 90 °, a side surface formed at an edge of the light emitting surface, and a side opposite to the light emitting surface A transparent light guide plate having a light incident surface on which light is incident, which is formed between the side surface and the inclined surface, and an inclined surface that is inclined so as to move away from the light exit surface as the distance from the side surface increases. When,
The length of the edge in the direction orthogonal to the longitudinal direction of the light incident surface is longer than the length of the effective cross section of the light guide plate in the direction substantially orthogonal to the light exit surface at the inclined surface side edge of the light incident surface. A light source having a planar light emitting surface, the light emitting surface facing the light incident surface of the light guide plate, and being inclined at a predetermined angle with respect to a direction substantially orthogonal to the light emitting surface;
Guided reflection that is disposed so as to cover a part of the light exit surface on the side surface side of the light guide plate, the side surface, and the inclined surface, and guides light incident from the light incident surface toward the center of the light guide plate. With a board,
A planar illumination device, wherein light emitted from a light emitting surface of the light source is incident on the light incident surface of the light guide plate, converted into planar light, and emitted from the light emitting surface. The light guide plate has the light incident surface formed in parallel with the light exit surface,
The planar illumination device according to claim 11, wherein the light source is disposed at an angle at which the light emitting surface is parallel to the light emitting surface. The light guide plate is
It contains a large number of scattering particles inside, the scattering cross section of the scattering particles is Φ, the density of the scattering particles is Np, the correction coefficient is KC, and the contact point between the side surface and the light incident surface is perpendicular to the light exit surface. When the length to the position where the thickness in the direction is the maximum is LG, the following inequality 1.1 ≦ Φ · Np · LG · KC ≦ 8.2
0.005 ≦ KC ≦ 0.1
The planar illumination device according to claim 11 or 12, wherein:

Images