JP5403938B2 - Surface lighting device - Google Patents

Description

  The present invention relates to a planar illumination device that illuminates an interior or exterior having a light source and a light guide plate that receives light emitted from the light source and exits from a light exit surface, or a backlight that illuminates a liquid crystal panel of a liquid crystal display device, The present invention relates to a planar lighting device used as a backlight for advertising panels, advertising towers, billboards, and the like.

  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 using a light guide plate that diffuses light emitted from a light source for illumination and irradiates the liquid crystal display panel, or an optical member such as a prism sheet or a diffusion sheet.

  At present, a backlight unit of a large-sized liquid crystal television is mainly a so-called direct type in which an optical member such as a diffusion plate is disposed immediately above a light source for illumination without a light guide plate. 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 needs to be a predetermined thickness, for example, about 30 mm. In the future, a thinner backlight unit will be desired. However, it is difficult to realize a backlight unit having a thickness of, for example, 10 mm or less in the direct type from the viewpoint of unevenness in the amount of light.

Here, as a backlight unit that can be reduced in thickness, light emitted from a light source for illumination and guided incident light is guided in a predetermined direction and emitted from a light emitting surface that is different from the surface on which the light is incident. There is a backlight unit using a light guide plate.
As such a backlight unit using a light guide plate, a backlight unit using a light guide plate in which scattering particles for scattering light in a transparent resin are mixed has been proposed (for example, Patent Document 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, and the light 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 the planar illumination device including the light scatterer light guide plate mixed with the light scatterers described in Patent Documents 1 to 4, the light emitted from the light source and entering the light scatter light guide from the light incident surface In the process of propagating the light, it undergoes a single or multiple scattering action at a certain rate. 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.

  As the light guide plate, besides the light guide plate having a shape having a tendency to reduce the thickness as the distance from the light incident surface increases, the thickness decreases as the distance from the light incident surface increases. There is described a planar illumination device having a light guide plate in a shape in which light guide plates having a shape having a tendency are attached.

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

However, a planar illumination device using such a light guide plate has a problem that the light guide plate expands and contracts due to the influence of temperature and humidity. Since the expansion and contraction of the light guide plate increases as the size of the light guide plate increases, the influence of the expansion and contraction of the light guide plate becomes more remarkable when an attempt is made to increase the size of the planar illumination device using the light guide plate.
For this reason, when the light guide plate and a light source, for example, an LED (light emitting diode) disposed adjacent to the light incident end face are separately fixed to a support such as a housing, the adjacent LED or the like is extended when the light guide plate is extended. However, there is a problem that the light guide plate inflating the light source may be pressed to destroy the light source.
In addition, when the light guide plate contracts, the distance between the light incident end surface of the light guide plate and the light exit end surface of the light source such as an LED becomes longer, and light incident from the light source incident on the light incident surface of the light guide plate. There is a problem that the efficiency is lowered and the utilization efficiency of the light emitted from the light source is lowered.

  On the other hand, in the planar illuminating devices described in Patent Documents 1 to 4, problems due to expansion and contraction of the light guide plate are not considered at all, and these problems cannot be solved.

  The object of the present invention is to solve the above-mentioned problems in the prior art, and even if the light guide plate expands and contracts, the distance between the light incident end surface of the light guide plate and the light output end surface of a light source such as an LED can be kept constant, It is an object of the present invention to provide a planar lighting device that can be reduced in thickness, weight, and size without causing destruction of a light source, lowering of incident efficiency, and nonuniform brightness of light emitted from a light exit surface of a light guide plate.

  In order to solve the above-described problems, in the present invention, a light source that emits light, a light incident surface that is disposed adjacent to the light source and that allows light emitted from the light source to enter, and light incident from the light incident surface are provided. A light guide plate having a light exit surface that emits as planar light, and the light source and the light guide plate are integrally fixed with a fixed distance between the light source and the light incident surface of the light guide plate. Fixing means, a housing for housing the light source and the light guide plate integrated by the fixing means, and provided between the housing and the fixing means, from the light incident surface of the light guide plate In the direction toward the light source, the light source and the light guide plate are integrated according to the expansion and contraction of the light guide plate, and the distance between the light source and the light incident surface of the light guide plate is kept constant. All means for sliding the fixing means relative to the housing. Providing planar lighting device characterized by having a mechanism.

  The fixing means is slidably integrated with the fixing means in accordance with expansion and contraction of the light guide plate in a direction orthogonal to the direction from the light incident surface of the light guide plate toward the light source. It is preferable that

It is preferable that the sliding mechanism can change a frictional force between the sliding mechanism and the fixing unit according to the expansion and contraction of the light guide plate.
The sliding mechanism includes a sliding member that sandwiches the fixing means by a stress that screws the housing, and a static friction coefficient between the sliding member and the fixing means is μ, and a distance from the screwing position. If the stress distribution due to the screwing at a position separated by x is G (x), the frictional force T (x) between the sliding member and the fixing means at a position separated by a distance x from the screwing position is: Represented by the following formula:
T (x) = μ · G (x)
Further, when the Young's modulus of the light guide plate is Y, the average cross-sectional area of the light guide plate is Aave, the length of the light guide plate is L, and the extension length of the light guide plate is ΔL, the extension / contraction of the light guide plate When the force F is expressed by the following equation,
F = Y · Aave · (ΔL / L)
The sliding member has the following formula from the position where the housing is screwed:
T (x) = μ · G (x) <F = Y · Aave · (ΔL / L)
It is preferable to arrange at a position x that satisfies

The light guide plate preferably has a linear expansion coefficient satisfying 1/1000 <ΔL / L <5/1000 and a Young's modulus satisfying 1.5MN / m ² <Y <3MN / m ² .
Further, the light guide plate is formed on the rectangular flat light emission surface and a pair of opposing edges of the light emission surface, respectively, for even incident light traveling parallel to the light emission surface, A pair of the light incident surfaces facing each other and a surface opposite to the light emission surface are formed, and the thickness in a direction perpendicular to the light emission surface increases as the distance from the pair of light incident surfaces increases. The light source is disposed so as to face the pair of light incident surfaces of the light guide plate, respectively. And a pair of light sources that allow light to enter the pair of light incident surfaces, each light source including a plurality of LED chips and a support that supports the LED chips, and the plurality of LED chips. On the surface of the support opposite to the light incident surface, Be arranged in rows along the longitudinal direction of the entrance surface are preferred.

  Further, the remaining pair of light incident surfaces formed on the opposite pair of opposite sides of the light emitting surface of the light guide plate and orthogonal to the pair of light incident surfaces, and the remaining pair of light incident surfaces. It is preferable to have a pair of the light sources that are respectively disposed to face the light incident surfaces and allow the light to be incident on the remaining pair of light incident surfaces.

  The LED chip preferably satisfies the inequality b <a, where a is the length in the thickness direction of the light guide plate and b is the length in the direction perpendicular to the thickness direction of the light guide plate.

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 of the light guide plate in the light incident direction. the length from the incident surface to the thickest position the thickness of the light guide plate is taken as _{L G,} the inequality _{1.1 ≦ Φ · N p · L} G · K C ≦ 8.2
0.005 ≦ K _C ≦ 0.1
Is preferably satisfied.
Furthermore, the light emission surface and the one in a direction perpendicular to the light emission surface are provided between the housing and the one light source disposed to face the pair of light incident surfaces of the light guide plate. While keeping the distance between the light source and the housing constant, according to the expansion and contraction of the light guide plate, the one light source is directed toward the light source from the light incident surface of the light guide plate with respect to the housing. It is preferable to have guide means for movement.

Further, it is preferable that the one light source is disposed on the lower side in the vertical direction with respect to the other light source disposed to face the pair of light incident surfaces of the light guide plate.
Further, the fixing means includes a protrusion fixed to a light source disposed to face the pair of light incident surfaces of the light guide plate, and at least one of the light exit surface and the inclined surface of the light guide plate. It is a plate-like member fixed to the surface, and is preferably constituted by a reinforcing member that engages with the protrusion and engages the light guide plate with the protrusion.
The fixing means includes a fixing member that covers a surface other than the light emitting surface of the light source disposed to face the pair of light incident surfaces of the light guide plate and supports the light source, and the guide means It is preferable that the light source is movably supported by supporting the fixing member movably in a direction from the light incident surface of the light guide plate toward the light source with respect to the housing.
Moreover, it is preferable that the said guide means are two guide parts each arrange | positioned on both surfaces orthogonal to the longitudinal direction of the said light source.
Moreover, it is preferable that all of the members interposed between the light source and the housing are in contact with each other through heat radiation grease.

  According to the present invention, the distance between the light incident end face of the light guide plate and the light exit end face of the light source, that is, the light source, by integrating and fixing the light source such as the LED and the light guide plate in an integrated manner. By keeping the optical axis distance and the optical axis vertical distance to the light guide plate constant, it is possible to prevent the light source from being destroyed due to the expansion and contraction of the light guide plate and the light incident efficiency from the light source to the light guide plate from being lowered. In addition, according to the present invention, since the light guide plate can be freely expanded and contracted in the housing, the light guide plate is not warped, so that uneven brightness of light emitted from the light exit surface of the light guide plate can be prevented, and the liquid crystal display device Even when used as a backlight, the light guide plate does not push the liquid crystal panel, and display unevenness and brightness unevenness do not occur on the display screen. In addition, according to the present invention, since the influence of expansion and contraction of the light guide plate can be prevented even when a large light guide plate is used, the planar illumination device can be enlarged and applied to a large liquid crystal display device. be able to.

The planar lighting device according to the present invention will be described below in detail based on preferred embodiments shown in the accompanying drawings.
In the following description, a two-sided incidence type planar illumination device that makes light from a light source incident on two sides of a light guide plate is a representative example, but it goes without saying that the present invention is not limited to this. That is.
FIG. 1 is a perspective view showing an outline of a liquid crystal display device including a planar illumination device according to the present invention, and FIG. 2 is a cross-sectional view taken along line II-II of the liquid crystal display device shown in FIG. 3 is an enlarged view of the vicinity of the light source unit of the planar illumination device (hereinafter also referred to as “backlight unit”) shown in FIG. 4A is a partially omitted plan view showing a light guide plate of the planar illumination device shown in FIG. 2 and light sources arranged on two sides thereof, and FIG. 4B is a cross-sectional view taken along line BB in FIG. It is line sectional drawing.

  As shown in FIG. 1, the liquid crystal display device 10 includes a backlight unit 20, a liquid crystal display panel 12 disposed on the light emission surface side of the backlight unit 20, and a drive unit 14 that drives the liquid crystal display panel 12. Have In FIG. 1, a part of the liquid crystal display panel 12 is not shown in order to show the configuration of the planar lighting device.

The liquid crystal display panel 12 applies a partial electric field to liquid crystal molecules arranged in a specific direction in advance to change the arrangement of the molecules, and uses the change in the refractive index generated in the liquid crystal cell to make a liquid crystal display. Characters, figures, images, etc. are displayed on the surface of the display panel 12.
The drive unit 14 applies a voltage to the transparent electrode in the liquid crystal display panel 12, changes the direction of the liquid crystal molecules, and controls the transmittance of light transmitted through the liquid crystal display panel 12.

  The backlight unit 20 is an illuminating device that irradiates light from the back surface of the liquid crystal display panel 12 to the entire surface of the liquid crystal display panel 12, and has a light emission surface 24 a having substantially the same shape as the image display surface of the liquid crystal display panel 12.

As shown in FIG. 1, FIG. 2, FIG. 3, FIG. 4 (A) and FIG. 4 (B), the backlight unit 20 according to the present invention includes two light sources 28, a light guide plate 30, fixing means 31, and an optical member. The lighting device main body 24 having the unit 32 and the reflecting plate 34, and the housing 40 having the lower housing 42, the upper housing 44, the reinforcing member 46, and the sliding mechanism 48 are configured. In the illustrated example, a heat sink 64 and a heat pipe 66 are further provided between the reflecting plate 34 and the lower housing 42.
Further, as shown in FIG. 1, a power storage unit 49 that stores a plurality of power supplies for supplying power to the light source 28 is attached to the back side of the lower housing 42 (see FIG. 2) of the housing 40.
Hereinafter, each component which comprises the backlight unit 20 is demonstrated.

The illuminating device body 24 includes a light source 28 that emits light, a light guide plate 30 that emits light emitted from the light source 28 as planar light, and an optical axis distance and an optical axis vertical distance between the light guide plate 30 and the light source 28. A fixing means 31 that keeps the light constant, an optical member unit 32 that scatters and diffuses light emitted from the light guide plate 30 to make the light more uniform, and reflects light leaked from the light guide plate 30 A reflecting plate 34 that is incident again on the light guide plate.
Here, the optical axis distance between the light guide plate 30 and the light source 28 is the distance between the light exit surface of the light source 28 and the light incident surface (30d, 30e) of the light guide plate 30 as shown in FIG. Refers to the distance c. The optical axis vertical distance between the light guide plate 30 and the light source 28 refers to the distance between the respective optical axes in the thickness direction of the light guide plate 30 and the light source 28.

  First, an outline of the fixing means 31 and the sliding mechanism 48 which are characteristic configurations of the present invention will be described. The fixing means 31 fixes the light source 28, the light guide plate 30, the optical member unit 32, and the reflection plate 34 by the fixing member 31a, the plurality of screws 31b and 31c, and the plurality of fixing pins 31d and 31e. The optical axis distance and the optical axis vertical distance between 30 are kept constant. The sliding mechanism 48 includes a spring material 47, sliding member fixing members 48a and 48d, an upper sliding member 48b, and a lower sliding member 48c, and a fixing member 31a that integrally fixes the light source 28 and the light guide plate 30. Is slid within the housing 40 in response to the expansion and contraction of the light guide plate 30.

  First, an outline of the fixing means 31 and the sliding mechanism 48 which are characteristic configurations of the present invention will be described. The fixing means 31 fixes the light source 28, the light guide plate 30, the optical member unit 32, and the reflection plate 34 by the fixing member 31a, the plurality of screws 31b and 31c, and the plurality of fixing pins 31d and 31e. The optical axis distance and the optical axis vertical distance between 30 are kept constant. The sliding mechanism 48 includes a spring material 47, sliding member fixing members 48a and 48d, an upper sliding member 48b, and a lower sliding member 48c, and a fixing member 31a that integrally fixes the light source 28 and the light guide plate 30. Is slid within the housing 40 in response to the expansion and contraction of the light guide plate 30.

First, the light source 28 will be described.
5A is a schematic perspective view showing a schematic configuration of the light source 28 of the planar illumination device 20 shown in FIGS. 1 and 2, and FIG. 5B is a diagram of the light source 28 shown in FIG. FIG. 5C is a schematic perspective view showing only one LED (light emitting diode) chip 50 constituting the light source 28 shown in FIG. 5A in an enlarged manner.
As illustrated in FIG. 5A, the light source 28 includes a plurality of LED chips 50 and a light source support portion 52.

The LED chip 50 is a chip in which a fluorescent material is coated on the surface of a light emitting diode that emits blue light. The LED chip 50 has a light emitting surface 58 having a predetermined area, and emits white light from the light emitting surface 58.
That is, when the blue light emitted from the surface of the light emitting diode of the LED chip 50 passes through the fluorescent material, the fluorescent material fluoresces. Accordingly, when the blue light emitted from the LED chip 50 is transmitted, white light is generated and emitted by the blue light emitted from the light emitting diode and the light emitted by the fluorescent substance being fluorescent.
Here, the LED chip 50 is exemplified by a chip in which a YAG (yttrium / aluminum / garnet) fluorescent material is applied to the surface of a GaN-based light-emitting diode, InGaN-based light-emitting diode, or the like.

  As shown in FIG. 5B, the light source support portion 52 includes an array substrate 54 and a plurality of fins 56. The plurality of LED chips 50 described above are arranged on the array substrate 54 in a line at a predetermined interval. Specifically, the plurality of LED chips 50 constituting the light source 28 are arranged along the longitudinal direction of the first light incident surface 30d or the second light incident surface 30e of the light guide plate 30 to be described later, in other words, the light emitting surface 30a. Are arranged in an array parallel to the line where the first light incident surface 30d intersects or parallel to the line where the light emitting surface 30a and the second light incident surface 30e intersect, and are fixed on the array substrate 54. .

The array substrate 54 is a plate-like member that is disposed so as to face the light incident surface (30 d, 30 e) whose one surface is the thinnest side end surface of the light guide plate 30. The LED chip 50 is supported on the side surface of the array substrate 54 which is the surface facing the light incident surface (30d, 30e) of the light guide plate 30.
Here, the array substrate 54 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 50 and dissipates it to the outside. .

Each of the plurality of fins 56 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 54 opposite to the surface on which the LED chip 50 is disposed. The fins 56 are connected to each other at a predetermined distance.
By providing a plurality of fins 56 on the light source support 52, the surface area can be increased and the heat dissipation effect can be enhanced. Thereby, the cooling efficiency of LED chip 50 can be improved.
In this embodiment, the array substrate 54 of the light source support 52 is used as a heat sink. However, when cooling of the LED chip is not necessary, a plate-like member that does not have a heat dissipation function is used as the array substrate instead of the heat sink. Also good.

  Further, as shown in FIG. 5A, screw holes 52c are provided at two positions on both ends of the upper surface 52a of the light source support 52. Further, the lower surface 52b of the light source support 52 is provided with a screw hole 52d at a position corresponding to the screw hole 52c of the upper surface 52a. As will be described later, the screw holes 52c and 52d are used to fix the light source 28 to the fixing means 31 with screws 31b and 31c, respectively, as shown in FIG.

Here, as shown in FIG. 5C, the LED chip 50 of the present embodiment has a rectangular shape in which the length in the direction orthogonal to the arrangement direction is shorter than the length of the LED chip 50 in the arrangement direction, that is, described later. The light guide plate 30 has a rectangular shape with a short side in the thickness direction (direction perpendicular to the light exit surface 30a). In other words, the LED chip 50 has a shape in which b> a when the length in the direction perpendicular to the light exit surface 30a of the light guide plate 30 is a and the length in the arrangement direction is b. Further, q> b, where q is the arrangement interval of the LED chips 50. Thus, the relationship between the length a in the direction perpendicular to the light exit surface 30a of the light guide plate 30 of the LED chip 50, the length b in the arrangement direction, and the arrangement interval q of the LED chips 50 satisfies q>b> a. It is preferable.
By making the LED chip 50 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. In addition, the number of LED chips can be reduced.

  In addition, since the LED chip 50 can make a light source thinner, it is preferable that the light guide plate 30 has a rectangular shape having a short side in the thickness direction. However, the present invention is not limited to this, and a square shape, a circular shape, LED chips having various shapes such as a polygonal shape and an elliptical shape can be used.

  In this embodiment, the LED chips are arranged in a single row to form a single layer structure. However, the present invention is not limited to this, and a plurality of LED arrays having a plurality of LED chips 50 arranged on an array support are provided. A multilayer LED array having a laminated structure can also be used as a light source. Even when LED arrays are stacked in this manner, more LED arrays can be stacked by making the LED chip 50 rectangular and thinning the LED array. In this manner, a larger amount of light can be output by stacking multiple LED arrays, that is, by increasing the filling rate of the LED array (LED chip). In addition, the LED chip of the LED array in the layer adjacent to the LED chip of the LED array preferably has the arrangement interval satisfying the above formula as described above. In other words, the LED array is preferably laminated with the LED chip and the LED chip of the LED array in the adjacent layer separated by a predetermined distance.

Next, the light guide plate 30 will be described.
FIG. 6 is a schematic perspective view showing the shape of the light guide plate 30.
As shown in FIGS. 2, 4 and 6, the light guide plate 30 is formed in a substantially rectangular flat light emission surface 30a and at both ends of the light emission surface 30a substantially perpendicular to the light emission surface 30a. The two light incident surfaces (the first light incident surface 30d and the second light incident surface 30e) and the opposite side of the light emitting surface 30a, that is, on the back side of the light guide plate, the first light incident surface 30d and Parallel to the second light incident surface 30e, symmetrical with respect to a bisector α (see FIGS. 1 and 4) that bisects the light emitting surface 30a, and a predetermined angle with respect to the light emitting surface 30a. The two inclined surfaces (the first inclined surface 30b and the second inclined surface 30c) that are inclined at the angle of (2) and the opposite ends (the intersection of the light emitting surface 30a and the light incident surface) of the light emitting surface 30a where the light incident surface is not formed. Two side surfaces (first side) formed substantially perpendicular to the light exit surface 30a on two sides orthogonal to the line 30f and has a second side face 30g) and. The two first inclined surfaces 30b and the second inclined surface 30c intersect to form a ridge line 30h corresponding to the bisector α of the light exit surface 30a.

Further, the corners 30i of the light exit surface 30a where the first light incident surface 30d and the first side surface 30f intersect, and the corners 30j where the second light incident surface 30e and the first side surface 30f intersect are respectively located near the inside. A first round hole 60a and a second round hole 60c for fixing the light guide plate 30 to the fixing member 31a are provided. A first round hole 60b and a second round hole 60d are provided at positions corresponding to the first round hole 60a and the second round hole 60c on the back side of the light guide plate 30, respectively.
Further, the corner 30k where the first light incident surface 30d and the second side surface 30g of the light exit surface 30a intersect, and the inner corner of the corner 30l where the second light incident surface 30e and the second side surface 30f intersect each other. The first long hole 62a and the second long hole 62c, which are long in the direction parallel to the light incident surfaces 30d and 30e, are provided for connecting the light guide plate 30 to the fixing member 31a. In addition, a first elongated hole 62b and a second elongated hole 62d are provided at positions corresponding to the first elongated hole 62a and the second elongated hole 62c on the back side of the light guide plate 30, respectively.

The light guide plate 30 is connected to the upper housing 42 and the lower housing 44 of the housing 40 in the vicinity of the inside of the corner 30 i where the first round hole 60 a is provided, in proximity to the first round hole 60 a. A third round hole 61a is provided.
Further, in the vicinity of the inside of each corner 30j and 30k provided with the first elongated hole 62a and the second round hole 60c, the light guide plate 30 is adjacent to the first elongated hole 62a and the second round hole 60c, respectively. Are connected to the upper housing 42 and the lower housing 44 of the housing 40. The third elongated hole 63a is long in the direction parallel to the light incident surface 30d and the fourth elongated hole is long in the direction perpendicular to the light incident surface 30e. 63b is provided.

The first inclined surface 30b and the second inclined surface 30c are arranged such that the distance from the light exit surface 30a increases (becomes larger) as the distance from the first light incident surface 30d and the second light incident surface 30e increases. The first light incident surface 30d and the second light incident surface 30e are inclined so as to increase in thickness in a direction perpendicular to the light emitting surface 30a of the light guide plate 30 toward the center of the light guide plate.
That is, the light guide plate 30 has the smallest thickness at both end portions, that is, the first light incident surface 30d and the second light incident surface 30e, and the central portion, that is, the first inclined surface 30b and the second inclined surface 30c intersect each other. The thickness is maximum at the position corresponding to the equipartition line α. In other words, the light guide plate 30 has a shape in which the thickness in the direction perpendicular to the light exit surface 30a of the light guide plate increases as the distance from the first light incident surface 30d or the second light incident surface 30e increases. The inclination angles of the first inclined surface 30b and the second inclined surface 30c with respect to the light exit surface 30a are not particularly limited.

Here, the two light sources 28 described above are disposed to face the first light incident surface 30d and the second light incident surface 30e of the light guide plate 30, respectively. Here, in the present embodiment, the length of the light emitting surface 58 of the LED chip 50 of the light source 28 is substantially the same as the length of the first light incident surface 30d and the second light incident surface 30e in the direction perpendicular to the light emitting surface 30a. Length.
Thus, the planar illumination device 20 is arranged such that the two light sources 28 sandwich the light guide plate 30. That is, the light guide plate 30 is disposed between the two light sources 28 disposed to face each other at a predetermined interval.

  In the light guide plate 30 shown in FIG. 2, the light emitted from the light source 28 and incident from the first light incident surface 30 d and the second light incident surface 30 e is scattered by a scatterer (details will be described later) included in the light guide plate 30. The light passes through the light guide plate 30 while being scattered, and is reflected from the first inclined surface 30b and the second inclined surface 30c, and then emitted from the light emitting surface 30a. At this time, some light may leak from the first inclined surface 30b and the second inclined surface 30c, but the leaked light is disposed on the first inclined surface 30b and the second inclined surface 30c side of the light guide plate 30. The light is reflected by the reflecting plate 34 and enters the light guide plate 30 again. The reflector 34 will be described in detail later.

  In this way, the light guide plate 30 has a shape in which the thickness in the direction perpendicular to the light exit surface 30a increases as the distance from the first light incident surface 30d or the second light incident surface 30e at which the light source 28 is disposed at an opposing position. By doing so, the light incident from the light incident surface can be delivered to a position farther from the light incident surface, and the light exit surface can be enlarged. Moreover, since the light incident from the light incident surface can be suitably delivered to a distant position, the light guide plate can be thinned.

  The light guide plate 30 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 30 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 to be kneaded and dispersed in the light guide plate 30, Atsipearl, thin cone, silica, zirconia, dielectric polymer, or the like can be used. By including such scattering particles in the light guide plate 30, 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 30 can be manufactured using an extrusion molding method or an injection molding method.

In addition, the scattering cross-sectional area of the scattering particles contained in the light guide plate 30 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 The first light incident surface 30d or the second light incident surface 30e of the light guide plate 30 in the direction perpendicular to the tangent to the surface (the first light incident surface or the second light incident surface) is orthogonal to the light emitting surface 30a. 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 30d of the light guide plate 30, hereinafter “light L _{G is} the half length (length up to the position of the bisector α), and the density of scattered particles (number of particles per unit volume) included in the light guide plate 30 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 30 includes scattering particles that satisfy such a relationship, the illumination light can be emitted from the light exit surface 30a evenly and with little 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 an incident light intensity, I is an emitted 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, the length from the incident surface of the light guide plate in the direction parallel to the traveling direction of the light incident on the light guide plate to the position where the thickness is the thickest, in this embodiment, the half length in the optical axis direction of the light guide plate is L _{Assuming G} , the light extraction efficiency E _out is given by the following equation (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 30 in a direction perpendicular to the light incident surface of the light guide plate 30 to the center of the light guide plate 30 .

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 30 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 30a of the light guide plate 30 becomes significant, 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 30 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 30 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. 7, measures the relationship between _{Φ · N p · L G ·} K C values and light use efficiency (ratio of light emitted through the light exit plane 30a to light incident on the light incident surface) The results are shown.
As shown in Table 1 and FIG. 7, by setting Φ · N _p · L _G · K _C to 1.1 or more, the light use efficiency is increased, specifically, the light use efficiency is set to 50% or more. 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 to create a variety of 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. 8 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. 8, the vertical axis is illuminance [lx], and the horizontal axis is the distance (light guide length) [mm] from one light incident surface of the light guide plate.

Furthermore, the illuminance unevenness when the maximum illuminance of light emitted from the side wall of the light guide plate of 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. 9 shows the relationship between the calculated illuminance unevenness and the particle density. In FIG. 9, the vertical axis is illuminance unevenness [%], and the horizontal axis is particle density [pieces / m ³ ]. FIG. 9 also shows the relationship between light utilization efficiency and particle density, where the horizontal axis is the particle density and the vertical axis is the light utilization efficiency [%].

As shown in FIGS. 8 and 9, when the particle density is increased, that is, Φ · N _p · L _G · K _C is increased, the light utilization 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.

Next, the optical member unit 32 will be described.
The optical member unit 32 converts the illumination light emitted from the light exit surface 30a of the light guide plate 30 into light with no uneven brightness, and emits illumination light with more uniform brightness from the light exit surface 24a of the illumination device body 24. As shown in FIG. 2, a diffusion sheet 32a that diffuses illumination light emitted from the light exit surface 30a of the light guide plate 30 to reduce luminance unevenness, and a tangent line between the light incident surface and the light exit surface It has a prism sheet 32b on which parallel microprism arrays are formed, and a diffusion sheet 32c that diffuses illumination light emitted from the prism sheet 32b to reduce luminance unevenness.
The optical member unit 32 includes a first round hole 60a and a second round hole provided in the light exit surface 30a of the light guide plate 30 in order to fix the light source 28 and the light guide plate 30 to a fixing member 31a. It is preferable that similar round holes and elongated holes are provided at positions corresponding to the hole 60c, the first elongated hole 62a, and the second elongated hole 62c. Although not shown, the optical member unit 32 is provided on the light exit surface 30 a of the light guide plate 30 in order to connect the light guide plate 30 to the upper housing 42 and the lower housing 44 of the housing 40. It is preferable that similar round holes and long holes are provided at positions corresponding to the third round hole 61a, the third long hole 63a, and the fourth long hole 63b.

  As the diffusion sheets 32a and 32c and the prism sheet 32b, those disclosed in [0028] to [0033] of Japanese Patent Application Laid-Open No. 2005-23497 related to the applicant's application can be applied.

In the present embodiment, the optical member unit is constituted by the two diffusion sheets 32a and 32c and the prism sheet 32b disposed between the two diffusion sheets. However, the arrangement order and arrangement of the prism sheets and the diffusion sheets are not limited. The number is not particularly limited, and is also not particularly limited as a prism sheet or a diffusion sheet, as long as the luminance unevenness of the illumination light emitted from the light exit surface 30a of the light guide plate 30 can be further reduced, Various optical members can be used.
For example, as the optical member, in addition to or in place of the above-described diffusion sheet and prism sheet, a transmittance adjusting member in which a large number of transmittance adjusting bodies made of a diffusive reflector are arranged in accordance with luminance unevenness can also be used.

Next, the reflecting plate 34 of the lighting device main body will be described.
The reflection plate 34 is provided to reflect light leaking from the first inclined surface 30b and the second inclined surface 30c of the light guide plate 30 and to make it incident on the light guide plate 30 again, thereby improving the light utilization efficiency. be able to. The reflection plate 34 has a shape corresponding to the first inclined surface 30b and the second inclined surface 30c of the light guide plate 30, and is formed so as to cover the first inclined surface 30b and the second inclined surface 30c. In the present embodiment, as shown in FIG. 2, the first inclined surface 30 b and the second inclined surface 30 c of the light guide plate 30 are formed in a triangular cross section, so that the reflecting plate 34 is also formed in a shape that complements this. ing.

  The reflecting plate 34 may be formed of any material as long as it can reflect light leaking from the inclined surface of the light guide plate 30. For example, the reflecting plate 34 is 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 36 is disposed between the light guide plate 30 and the diffusion sheet 32a, that is, on the light emission surface 30a side of the light guide plate 30, and the end of the light emission surface 30a of the light guide plate 30 and the light emission surface 30a (first light incident). The end portion on the surface 30d side and the end portion on the second light incident surface 30e side) are respectively arranged inside the fixing member 31a so as to cover them. In other words, the upper guide reflection plate 36 is disposed so as to cover from a part of the light exit surface 30a of the light guide plate 30 to a part of the array substrate 54 of the light source 28 in a direction parallel to the optical axis direction. That is, the two upper guide reflectors 36 are disposed at both ends of the light guide plate 30, respectively.
As described above, by arranging the upper guide reflection plate 36, it is possible to prevent the light emitted from the light source 28 from leaking to the light emitting surface 30 side without entering the light guide plate 30.
Thereby, the light emitted from the LED chip 50 of the light source 28 can be efficiently incident on the first light incident surface 30d and the second light incident surface 30e of the light guide plate 30, and the light utilization efficiency can be improved. .

The lower guide reflector 38 is formed on the fixing member 31a so as to cover a part of the light source 28 on the side opposite to the light exit surface 30a side of the light guide plate 30, that is, on the first inclined surface 30b and the second inclined surface 30c side. Arranged inside. The end of the lower guide reflector 38 on the center side of the light guide plate is connected to the reflector 34.
By providing the lower guide reflection plate 38, the light emitted from the light source 28 can be prevented from leaking to the first inclined surface 30b and the second inclined surface 30c side of the light guide plate 30 without entering the light guide plate 30. .
Thereby, the light emitted from the LED chip 50 of the light source 28 can be efficiently incident on the first light incident surface 30d and the second light incident surface 30e of the light guide plate 30, and the light utilization efficiency can be improved. .
Here, as the upper guide reflector 36 and the lower guide reflector 38, various materials used for the reflector 34 described above can be used.
In the present embodiment, the reflecting plate 34 and the lower guiding reflecting plate 38 are connected. However, the present invention is not limited to this, and each may be a separate member.

  The upper guide reflector 36 and the lower guide reflector 38 are provided on the light exit surface 30a of the light guide plate 30 in order to fix the light source 28 and the light guide plate 30 to the fixing member 31a. Similar round holes and long holes are provided at positions corresponding to the first round holes 60a and 60b, the second round holes 60c and 60d, the first long holes 62a and 62b, and the second long holes 62c and 62d. It is good to be. Although not shown in the drawing, the upper guide reflector 36 and the lower guide reflector 38 are coupled to the light guide plate 30 in order to connect the light guide plate 30 to the upper housing 42 and the lower housing 44 of the housing 40. It is preferable that similar round holes and long holes are provided at positions corresponding to the third round hole 61a, the third long hole 63a, and the fourth long hole 63b provided on the emission surface 30a.

Here, the upper guide reflector 36 and the lower guide reflector 38 reflect the light emitted from the light source 28 toward the first light incident surface 30d or the second light incident surface 30e, and the light emitted from the light source 28 is reflected. The shape and width are not particularly limited as long as the light can be incident on the first light incident surface 30d and the second light incident surface 30e and the light incident on the light guide plate 30 can be guided to the center side of the light guide plate 30.
In the present embodiment, the upper guide reflector 36 is disposed between the light guide plate 30 and the diffusion sheet 32a. However, the position of the upper guide reflector 36 is not limited to this, and constitutes the optical member unit 32. You may arrange | position between sheet-like members, and may arrange | position between the optical member unit 32 and the fixing member 31a.

Next, the fixing means 31 will be described.
The fixing means 31 fixes the light source 28 and the light guide plate 30 and fixes them together, a plurality of screws 31b and 31c for fixing the light source 28 to the fixing member 31a, and the light guide plate 30 fixed to the fixing member 31a. And a plurality of fixing pins 31d and 31e.
The fixing member 31a fixes and integrates the light source 28 and the light guide plate 30 while keeping the optical axis distance and the optical axis vertical distance between the light source 28 and the light guide plate 30 constant. The sliding mechanism 48 slides on the upper sliding member 48b and the lower sliding member 48c fixed to the housing 40 by the sliding member fixing member 48a. The fixing member 31a is a columnar member having a U-shaped cross section.

The fixing member 31a is in sliding contact with the upper sliding member 48b and the lower sliding member 48c, so that even if the light guide plate 30 expands and contracts in the direction perpendicular to the light incident surfaces 30d and 30e of the light guide plate 30, Prevent warping.
Here, if the contact area between the fixed member 31a and the upper sliding member 48b and the lower sliding member 48c is large, the frictional force of the sliding portion increases, and if the contact area between the two is small, the sliding partial friction occurs. The power is reduced. Therefore, the shape of the fixing member 31a is such that when the light guide plate 30 extends, the contact area between the fixing member 31a, the upper sliding member 48b and the lower sliding member 48c increases, and the frictional force of the sliding portion increases. Is increased to suppress sliding of the fixing member 31a and the light guide plate 30 is contracted, the contact area between the fixing member 31a, the upper sliding member 48b and the lower sliding member 48c is reduced and slides. It is desirable that the frictional force of the portion be reduced to facilitate the sliding of the fixing member 31a.

As shown in FIG. 2, in the light source 28, the light guide plate 30, the optical member unit 32, and the reflecting plate 34 are integrally fixed to the fixing means 31 by fixing pins 31d and 31e.
That is, the light source 28 is positioned and fixed to the fixing member 31a by screwing the screws 31b and 31c into the screw holes 52c and 52d and the screw holes of the fixing member 31a, respectively.

  On both sides of the light guide plate 30 on the first side face 30f side, the first round holes 60a and 60b and the second round holes 60c and 60d respectively provided on the light exit surface 30a and the back surface of the light guide plate 30 are fixed members. By fitting the fixing pins 31d and 31e fitted in the fitting holes provided in 31a, the light guide plate 30 is positioned and fixed to the fixing member 31a. The diameters of the first round holes 60a and 60b and the second round holes 60c and 60d are substantially the same as the outer diameters of the fixing pins 31d and 31e. Therefore, the light guide plate 30 is positioned by the fixing member 31a on the first side face 30f side in both the direction perpendicular to and parallel to the first and second light incident faces 30d and 30e. The As a result, the light source 28 and the light guide plate 30 are integrated and fixed by the fixing member 31a, and the distance between the light emitting surface of the light source 28 and the first and second light incident surfaces 30d and 30e of the light guide plate 30 is increased. Kept constant.

  On the other hand, on both sides of the light guide plate 30 on the second side face 30g side, the first long holes 62a and 62b and the second long holes 62c and 62d provided on the light exit surface 30a and the back surface of the light guide plate 30, respectively, Fixing pins 31d and 31e fitted in fitting holes provided in the fixing member 31a are inserted. The first elongated holes 62a and 62b and the second elongated holes 62c and 62d are elongated holes that are long in a direction parallel to the first and second light incident surfaces 30d and 30e of the light guide plate 30, and are perpendicular to each other. The hole diameter is substantially the same as the outer diameter of the fixing pins 31d and 31e. Therefore, the fixing pins 31d and 31e are in the direction perpendicular to the first and second light incident surfaces 30d and 30e of the light guide plate 30 with respect to the first elongated holes 62a and 62b and the second elongated holes 62c and 62d, respectively. It is fixed without being moved (fitted), and is inserted so as to be movable in a parallel direction.

Therefore, the light guide plate 30 is positioned and fixed to the fixing member 31a in both directions on the second side surface 30g side with respect to the direction perpendicular to the first and second light incident surfaces 30d and 30e. In any direction, it is movable without being positioned with respect to the fixing member 31a.
As a result, in the direction perpendicular to the first and second light incident surfaces 30d and 30e of the light guide plate 30, the light source 28 and the light guide plate 30 are integrated and fixed by the fixing member 31a. The distance between the surface and the first and second light incident surfaces 30d and 30e of the light guide plate 30 is kept constant.
On the other hand, with respect to the direction parallel to the first and second light incident surfaces 30d and 30e of the light guide plate 30, the fixing pins 31d and 31e are respectively connected to the first long holes 62a and 62b according to the expansion and contraction of the light guide plate 30. In addition, it is possible to prevent the warp due to the expansion and contraction of the light guide plate 30 by moving (sliding) in the second elongated holes 62c and 62d.

  From the above, the light source 28 and the light guide plate 30 are integrated and fixed by the fixing member 31a both on the first side face 30f side and the second side face 30g side of the light guide plate 30. The distance between the first and second light incident surfaces 30d and 30e of the light guide plate 30 is kept constant. By doing so, the light source 28 arranged on the first and second light incident surfaces 30 d and 30 e side is not broken by the expansion and contraction of the light guide plate 30. Further, the light incident efficiency of the light incident on the first and second light incident surfaces 30d and 30e of the light guide plate 30 from the light source 28 is not reduced.

Even if the light source 28 and the light guide plate 30 are fixed and integrated in this way, if the light guide plate 30 expands and contracts in a direction parallel to the light incident surface (30d, 30e) of the light guide plate 30, the light guide plate 30 is guided. Since the positions of the fixing pins 31d and 31e move in the long axis direction in accordance with the expansion and contraction of the light plate 30, the light guide plate 30 can freely expand and contract, and the warpage of the light guide plate 30 is suppressed. In other words, luminance unevenness of light emitted from the light guide plate 30 can be suppressed.
Moreover, even if the light guide plate 30 is enlarged, the light guide plate 30 can be prevented from warping in the light guide plate 30 by freely expanding and contracting in a direction parallel to the light incident surfaces (30d, 30e) of the light guide plate. .

  Corresponding to the round holes 60a to 60d and the long holes 62a to 62d provided in the light guide plate 30, the round holes provided in the optical member unit 32 and the reflecting plate 34 (the upper guiding reflecting plate 38 and the lower guiding reflecting plate 36). The long holes are provided for passing pins 31 and 31e for fixing the fixing member 31a and the light guide plate 30, the optical member unit 32 and the reflection plate 34, respectively.

The round holes 60a, 60b and 60c, 60d are provided in the vicinity of the inside of the corners 30i and 30k of the light guide plate 30. By doing so, even when the liquid crystal display device 10, and thus the backlight unit 20, is installed with the direction parallel to the light incident surfaces 30d and 30e in the vertical direction, the position of the light guide plate 30 is shifted in the vertical direction. Thus, the light guide plate 30 can be prevented from being damaged.
The arrangement configuration of the round holes is not limited to this, and by arranging the round holes at positions where the position of the light guide plate 30 is not shifted according to the arrangement of the liquid crystal display device 10 and therefore the backlight unit 20 and the direction thereof, It is possible to prevent the light guide plate 30 from being damaged.

In the present embodiment, the light source 28 and the fixing member 31a are fixed by providing the screw holes 52c and 52d at two locations on the upper surface 52a and the lower surface 52b of the light source support 52 of the light source 28. The arrangement and the number of screw holes are not limited to this as long as the fixing member 31a can be fixed.
In this embodiment, a screw is used to fix the light source 28 and the fixing member 31a. However, the fixing tool for the light source 28 and the fixing member 31a is not limited to this, and various known fixing tools can be used. Can be used. For example, the light source 28 and the fixing member 31a may be fixed using an adhesive. By doing in this way, since it is not necessary to provide a screw hole in the light source support part 52, it can be set as a simpler structure.
Further, the method of fixing the light guide plate 30 and the fixing member 31a is not limited to the round hole and the pin. For example, instead of round holes and pins, an adhesive may be attached to the inside of the light exit surface 30a of the light guide plate 30 and the back side corners of the light guide plate 30 to fix the light guide plate 30 and the fixing member 31a.

Next, the housing 40 will be described.
As shown in FIG. 2, the housing 40 accommodates and supports the lighting device main body 24, and is sandwiched between the light emission surface 30a side and the first inclined surface 30b and second inclined surface 30c side of the light guide plate 30. And a lower casing 42, an upper casing 44, a reinforcing member 46, and a sliding mechanism 48.

  The lower housing 42 has an open top surface, and has a shape composed of a bottom surface portion and four side surfaces of the bottom surface portion and a side surface portion perpendicular to the bottom surface portion. That is, it is a substantially rectangular parallelepiped box shape with one surface open. As shown in FIG. 2, the lower housing 42 supports the illuminating device main body 24 housed from above with a bottom surface portion and a side surface portion, and also a surface other than the light emitting surface 24 a of the illuminating device main body 24, that is, the illuminating device. The main body 24 covers the surface (back surface) and the side surface opposite to the light exit surface 24a.

The upper housing 44 is formed with a rectangular opening on the upper surface, which becomes the rectangular light emitting surface 24a of the illuminating device body 24, which is smaller than the rectangular light emitting surface 30a of the light guide plate 30, and the lower surface is opened. It has a rectangular parallelepiped box shape.
As shown in FIG. 2, the upper housing 44 includes the lighting device main body 24 and the lower housing 42 in which the lighting device main body 24 and the lower housing 42 are housed from above the planar lighting device main body 24 and the lower housing 42. The other side surface portion 22b is also placed so as to cover it.

The reinforcing member 46 is a rod-shaped member having a square cross section provided between the upper housing 44 and the lower housing 42.
As shown in FIG. 2, the reinforcing member is connected to the upper housing 44 and the lower housing 42 by screws 46 a and 46 b.

Thus, by arranging the reinforcing member 46 between the lower housing 42 and the upper housing 44, the rigidity of the housing 40 can be increased, and the light guide plate 30 can be prevented from warping. Thus, for example, light can be emitted efficiently with little or no luminance unevenness, but even when using a light guide plate that is likely to warp, the warp can be corrected more reliably, or the light guide plate can be warped. It is possible to more reliably prevent the occurrence of light, and to emit light from the light exit surface with no or reduced brightness unevenness.
Further, by fastening and fixing the lower casing 42 and the upper casing 44 and the reinforcing member 46 with the screws 46a and 46b, it is possible to generate a stress that tightens the fixing means 31, particularly the fixing member 31a, in the sliding mechanism 48. .

  Note that various materials such as metal and resin can be used for the lower housing 42, the upper housing 44, and the reinforcing member 46 of the housing 40. In addition, as a material, it is preferable to use a lightweight and high-strength material.

  The sliding mechanism 48 is for enabling the fixing member 31a of the fixing means 31 to slide in accordance with expansion and contraction in a direction perpendicular to the light incident surfaces 30d and 30e of the light guide plate 30, and includes a spring material 47 and a sliding member. The fixing members 48a and 48d, the upper sliding member 48b, and the lower sliding member 48c are configured.

The spring material 47 is provided between the sliding member fixing member 48a and the fixing member 31a, and the fixing members 31a provided on the first and second light incident surfaces 30d and 30e side are respectively connected to the first and second light beams. The light is biased toward the center of the light guide plate 30 from the incident surfaces 30d and 30e, and the fixing member 31a is positioned with respect to the housing 40 in the direction perpendicular to the light incident surfaces 30d and 30e of the light guide plate 30. is there.
The spring material 47 is similarly provided between the first side surface 30g and the second side surface 30f of the light guide plate 30 and the housing 40, and the housing in a direction parallel to the light incident surfaces 30d and 30e of the light guide plate 30. Positioning relative to the body 40 is performed.

The sliding member fixing members 48a and 48d are for holding the upper sliding member 48b and the lower sliding member 48c for sliding the fixing means 31 (fixing member 31a). The sliding member fixing members 48a and 48d are provided between the lower housing 42 and the upper housing 44. The upper sliding member 48b is disposed on the back side of the sliding member fixing member 48d, and the sliding member fixing member 48a. A lower sliding member 48c is disposed on the upper surface of the.
The upper sliding member 48b and the lower sliding member 48c sandwich the fixing means 31 (fixing member 31a), and the fixing means 31 (fixing member 31a) corresponds to expansion and contraction in a direction perpendicular to the light incident surface of the light guide plate 30. To slide. The upper sliding member 48b and the lower sliding member 48c are plate-like members as shown in FIG.

  Although not shown in FIGS. 2 and 3, as a preferred embodiment of the present invention, as shown in FIGS. 4A and 6, the three corners 30i, 30j and 30k of the light guide plate 30 are used. Are provided with a third round hole 61a, a third slot 63a and a fourth slot 63b for connecting the light guide plate 30 to the upper casing 42 and the lower casing 44 of the casing 40, As described above, the optical member unit 32 including the diffusion sheet 32a, the prism sheet 32b, the diffusion sheet 32c, and the like corresponding to the third round hole 61a, the third elongated hole 63a, and the fourth elongated hole 63b of the light guide plate 30, In addition, the upper guide reflector 36 and the lower guide reflector 38 are also provided with similar round holes and long holes (not shown). On the other hand, the upper housing 42 and the lower housing 44 of the housing 40 are located at positions corresponding to the third round hole 61a, the third long hole 63a, and the fourth long hole 63b of the light guide plate 30 housed therein. A round hole (not shown) for fixing the pin is drilled. The third round hole 61a, the third long hole 63a and the fourth long hole 63b of the light guide plate 30 and the corresponding round holes and long holes of the optical member unit 32, the upper guide reflection plate 36 and the lower guide reflection plate 38 are provided. Are inserted into pins (not shown) substantially equal to the hole diameter (short diameter in the case of long holes), and these pins are formed in round holes drilled in the upper housing 42 and the lower housing 44 of the housing 40. Is also fitted and fixed.

At this time, as shown in FIG. 4A and FIG. 6, since the corner hole 30a of the light guide plate 30 is provided with a round hole 61a, the light guide plate 30 has a housing 40 at the corner 30i. It is fixed so as not to move with respect to the housing 40 by a pin (not shown) fixed to.
However, since the long corner 63a is provided in the corner 30j of the light guide plate 30 in a direction parallel to the light incident surfaces 30d and 30e, and the hole for connecting to the casing 40 is not provided in the corner 30l. The pin (not shown) fixed to the body 40 can move in the long hole 63a in the direction parallel to the light incident surfaces 30d and 30e even if the pin is fitted in the long hole 63a. The body 40 can move in a direction parallel to the light incident surfaces 30d and 30e, and can be expanded and contracted. As a result, warpage due to expansion and contraction of the light guide plate 30 can be prevented.
In addition, a long hole 63b is provided in the corner 30k of the light guide plate 30 in a direction perpendicular to the light incident surfaces 30d and 30e, and a hole for connecting to the casing 40 is not provided in the corner 30l. Even if a pin (not shown) fixed to the body 40 is fitted in the elongated hole 63b, the light guide plate 30 can be moved in the elongated hole 63b in a direction perpendicular to the light incident surfaces 30d and 30e. 40 can move in a direction perpendicular to the light incident surfaces 30d and 30e, and can expand and contract. As a result, warpage due to expansion and contraction of the light guide plate 30 can be prevented.

In this way, the light guide plate 30 can be held in the casing 40 so as to be extendable and contractible.
Further, as described above, the optical member unit including the diffusion sheet 32a, the prism sheet 32b, the diffusion sheet 32c, and the like corresponding to the third round hole 61a, the third elongated hole 63a, and the fourth elongated hole 63b of the light guide plate 30. 32, and the upper guide reflector 36 and the lower guide reflector 38 are also provided with similar round holes and long holes (not shown), so that the light guide plate 30, the diffusion sheet 32a, the prism sheet 32b, and the diffusion sheet are provided. Even if the expansion / contraction ratios of the optical member unit 32 such as 32c are different, it is possible to realize a holding mechanism that does not bend or warp.

As described above, the light guide plate 30 is held in the housing 40 so as to be extendable and contractible, and the sliding mechanism 48 is provided between the housing 40 and the fixing member 31a in which the light guide plate 30 and the light source 28 are integrated. Therefore, when the light guide plate 30 expands and contracts in a direction perpendicular to the light incident surfaces 30 d and 30 e of the light guide plate 30, the fixing member 31 a can slide by the sliding mechanism 48 according to the expansion and contraction of the light guide plate 30. it can. By doing in this way, the curvature of the light guide plate 30 by the light guide plate 30 expanding and contracting in the direction perpendicular to the light incident surface can be suppressed, and the luminance of light emitted from the light exit surface 30a of the light guide plate 30 is reduced. Unevenness can be suppressed. Furthermore, even in a large-sized light guide plate, the light guide plate 30 can freely expand and contract in a direction perpendicular to the light incident surface of the light guide plate 30, thereby suppressing uneven brightness of light emitted from the light exit surface 30 a of the light guide plate 30. it can.
Further, since the light guide plate 30 and the light source 28 are fixed to the fixing member 31a so as to keep the optical axis distance and the optical axis vertical distance constant, even if the fixing member 31a slides, the light guide plate 30 and the light source 28 The optical axis distance is kept constant. By doing so, the light guide plate 30 expands and contracts in the direction perpendicular to the light incident surface, and the light incident surfaces 30d and 30e of the light guide plate 30 compress and destroy the light source 28, or the light guide plate 30 is guided from the light source 28. It can prevent that the light-incidence efficiency of the light which injects into the optical plate 30 falls.

In the present embodiment, the sliding mechanism 48 has the upper sliding member 48b and the lower sliding member 48c having the shape shown in FIG. 2, so that the upper sliding member 48b, the lower sliding member 48c, and the fixing member 31a are interposed between them. A frictional force corresponding to the expanding and contracting force of the light guide plate 30 can be generated.
The contact area between the light guide plate 30 and the upper sliding member 48b and the lower sliding member 48c of the sliding mechanism 48 is small when the expansion and contraction of the light guide plate is small, and the contact area when the expansion and contraction of the light guide plate 30 is large. Becomes larger. The frictional force acting between the upper sliding member 48b and lower sliding member 48c and the fixing member 31a is small when the contact area is small, and is large when the contact area is large. Therefore, the frictional force acting between the light guide plate 30 and the upper sliding member 48b and the lower sliding member 48c of the sliding mechanism 48 is small when the light guide plate 30 is small in expansion and contraction, and the light guide plate 30 is large in expansion and contraction. Will be bigger.
Thus, by making the shapes of the upper sliding member 48b and the lower sliding member 48c of the sliding mechanism 48 as shown in FIG. 2, the frictional force corresponding to the expanding and contracting force of the light guide plate 30 is applied to the upper sliding member of the sliding mechanism 48. 48 b and the lower sliding member 48 c are generated between the fixing member 31 a and can act as a resistance against the extension of the light guide plate 30.

In the present embodiment, the frictional force corresponding to the expanding and contracting force of the light guide plate 30 is generated using the plate-like upper sliding member 48b and lower sliding member 48c as shown in FIG. The shape of 48b and the lower sliding member 48c is not limited to this. For example, as shown in FIG. 10, the upper sliding member 48b and the lower sliding member 48c may have a triangular cross section.
As shown in FIG. 10, when the cross section of the upper sliding member 48b and the lower sliding member 48c is triangular, the width between the upper sliding member 48b and the lower sliding member 48c when the expansion and contraction of the light guide plate 30 is small. Therefore, the frictional force acting between the upper and lower sliding members 48b and 48c and the fixing member 31a is small. When the expansion and contraction of the light guide plate 30 is increased, the fixing member 31a has to slide where the width between the upper sliding member 48b and the lower sliding member 48c is narrow, so that the upper sliding member 48b and the lower sliding member 48c The frictional force acting between the fixing means 31 is increased. That is, even if the cross sections of the upper sliding member 48b and the lower sliding member 48c are triangular, the frictional force corresponding to the expanding and contracting force of the light guide plate 30 is applied to the upper sliding member 48b, the lower sliding member 48c, and the fixing member. Can occur between 31a. In the embodiment shown in FIG. 10, the sliding mechanism 48 is like the sliding mechanism 48 shown in FIG. 3 because the urging force to the fixing member 31a acts by the triangular upper sliding member 48b and the lower sliding member 48c. The spring material 47 may not be provided.

  In the illustrated example, various materials such as Teflon and metal can be used for the upper sliding member 48b and the lower sliding member 48c. Further, without providing the upper sliding member 48b and the lower sliding member 48c separately, the upper sliding member 48b and the lower sliding member 48c may be formed by applying oil to the lower casing 42 and the upper casing 44.

  In this embodiment, the upper sliding member 48b and the lower sliding member 48c are provided on the back surface of the upper housing 44 and the upper surface of the lower housing 42, but the present invention is not limited to this. For example, a structure provided only on the upper sliding member 48b or only on the lower sliding member 48c may be employed. By doing in this way, the structure of the housing | casing 40 can be made into a simpler structure.

  The lower housing 42, the upper housing 44, and the reinforcing member 46 are connected by screws 46a and 46b. The stress by which the fixing means 31 (fixing member 31a) is sandwiched by the upper sliding member 48b and the lower sliding member 48c is determined by the stress caused by screwing the screws 46a and 46b. Further, the frictional force generated between the fixing member 31a, the upper sliding member 48b, and the lower sliding member 48c can be controlled by the screw tightening stress.

Here, when the frictional force between the fixing member 31a and the upper sliding member 48b and the lower sliding member 48c is larger than the force by which the light guide plate 30 expands and contracts, the fixing member 31a The sliding member 48c cannot be slid, and the warp generated in the light guide plate 30 when the light guide plate 30 expands or contracts cannot be suppressed.
Further, the stress applied to the upper sliding member 48b and the lower sliding member 48c by the screws 46a and 46b differs depending on the location because there is a stress distribution even if the force pressed by the screws 46a and 46b is constant.
Therefore, it is desirable to determine the positions where the upper sliding member 48b and the lower sliding member 48c are arranged according to the magnitude of stress by the screws 46a and 46b and the stress distribution. Hereinafter, a method for determining the positions of the upper sliding member 48b and the lower sliding member 48c will be described in detail.

When the Young's modulus of the light guide plate 30 is Y, the length is L, the elongation is ΔL, and the average cross-sectional area is Aave, the pushing force F due to the expansion and contraction of the light guide plate 30 is F = Y · Aave · (ΔL / L)
It becomes.
If the force that holds the light guide plate 30 is concentrated in the form of being concentrated on the ends of the upper sliding member 48b and the lower sliding member 48c, G is assumed, and the static friction coefficient of the contact surface is μ.
F> μ · G
Is a condition in which the fixing member 31a for fixing the light guide plate 30 starts to slide relative to the upper sliding member 48b and the lower sliding member 48c.

Here, an example of the force F due to the expansion and contraction of the light guide plate 30 in an actual shape will be given. When acrylic is used as the material of the light guide plate 30 and Teflon is used as the upper sliding member 48b and the lower sliding member 48c, the Young's modulus of the light guide plate 30 is 1.5 to 3 MPa = 1.5 to 3 MN / m ^2. The static friction coefficient of the upper sliding member 48b and the lower sliding member 48c is 0.01. Here, the value of the static friction coefficient is a value when the upper sliding member 48b and the lower sliding member 48c of the fixed member 31a are provided. The volume expansion coefficient of the light guide plate 30 in 24 hours is set to 0.3%. The width of the light incident portion of the light guide plate 30 in the direction perpendicular to the light exit surface 30a is 2 mm, and the width of the light guide plate 30 at the bisector α in the direction perpendicular to the light exit surface 30a is 3.6 mm. Table 2 shows the size and average cross-sectional area Aave of the light guide plate, and the force F due to the expansion and contraction of the light guide plate 30.

Next, the conditions under which the fixing member 31a starts to slide relative to the upper sliding member 48b and the lower sliding member 48c when the stress distribution is taken into consideration will be described.
When the screws 46a and 46b are M3 screws and the fixing member 31a is tightened, the tightening force is about 60 kg. This is a force directly applied to the screw thread, and the force is distributed near the screw by a washer or the like. Actually, the tightening force of the screws 46a and 46b is not directly applied to the object to be bonded, but a pressure with distribution is applied to a minute region, which is considered to be a normal force. When the stress distribution is considered to be G (x) in one dimension, the position of x = 0 is considered to be approximately the screw tightening force. The frictional force T (x) at a distance x away from the screws 46a, 46b is
T (x) = μ · G (x)
And
T (x) = μ · G (x) <F = Y · Aave · (ΔL / L) (5)
However, there is a condition that the fixing member 31a that fixes the light guide plate 30 and the light source 28 can slide with respect to the upper sliding member 48b and the lower sliding member 48c.

  FIG. 11 shows the result of measuring the stress distribution when screwing and fixing at the positions of x = 0 and x = 25. The vertical axis represents the magnitude of stress, and the horizontal axis represents the distance from the screwed position. Two solid lines indicate the case where the material of the fixed member 31a, the upper sliding member 48b and the lower sliding member 48c are both aluminum, and the case where the material of one member is aluminum and the material of the other member is resin. Show. As shown in FIG. 11, in the stress distribution G (x), the stress decreases from the screwed position, has a retaining portion at the center, and increases again toward the other screwed position. The sliding mechanism 48 is disposed in a portion where this stress becomes a stationary value. In this way, the upper sliding member 48b and the lower sliding member 48c are arranged at a location where the stress is small, so that the force of expanding and contracting the light guide plate 30 and the frictional force acting between the fixed member 31a and the sliding mechanism 48 are obtained. However, it becomes easy to satisfy the above-mentioned formula (5). Further, since the stress is constant in the stationary part, the positioning of the upper sliding member 48b and the lower sliding member 48c is facilitated, and the fixing member 31a can be slid more reliably by the sliding mechanism 48.

  As described above, the positions of the upper sliding member 48b and the lower sliding member 48c of the sliding mechanism 48 are determined in consideration of the force due to the expansion and contraction of the light guide plate, the tightening stress of the screws 46a and 46b, and the stress distribution. In this way, the fixing member 31a can surely slide on the upper sliding member 48b and the lower sliding member 48c by the sliding mechanism 48 according to the force due to the expansion and contraction of the light guide plate 30.

The planar lighting device 10 of the present embodiment further includes a heat sink 64 that is coupled to the lower part of the sliding member fixing member 48 a and absorbs heat from the light source 28, and a heat sink 64 between the reflector 34 and the lower housing 42. A heat pipe 66 that dissipates heat and is provided in a connected manner.
The heat sink 64 absorbs the heat radiated from the light source 28 through the sliding member fixing member 48 a and transfers the heat to the heat radiating or heat pipe 66.
The heat pipe 66 radiates heat transferred from the heat sink 64 connected to one end of the heat pipe 66 from the other end of the heat pipe 66.
By providing such a heat sink 64 and a heat pipe 66, heat generated from the light source 28 can be efficiently transferred to the heat pipe 66 and radiated from the heat pipe 66. Therefore, since the light source is cooled even when the light emission efficiency of the light source is low, the amount of light emitted from the light source can be increased, and a large backlight unit can be realized. On the contrary, by cooling the light source, the amount of light emitted from the light source can be further increased, and a large backlight unit can be realized.
The heat sink is not limited to the air cooling method, and a water cooling method can also be used.
In addition, a power storage unit 49 (see FIG. 1) for storing a power source (not shown) of the light source is attached to the back side of the lower housing 42.

The planar lighting device 20 is basically configured as described above.
In the planar illumination device 20, light emitted from the light sources 28 disposed at both ends of the light guide plate 30 is incident on the light incident surfaces (the first light incident surface 30 d and the second light incident surface 30 e) of the light guide plate 30. Furthermore, the light emitted from the sub-light sources 29 disposed at the other ends of the light guide plate 30 is incident on the side surfaces (the first side surface 30f and the second side surface 30g). Light incident from each surface passes through the light guide plate 30 while being scattered by the scatterers included in the light guide plate 30, and directly or after being reflected by the first inclined surface 30b and the second inclined surface 30c. The light exits from the light exit surface 30a. At this time, part of the light leaking from the first inclined surface 30 b and the second inclined surface 30 c is reflected by the reflecting plate 34 and enters the light guide plate 30 again.
In this way, the light emitted from the light exit surface 30 a of the light guide plate 30 passes through the optical member 32 and is emitted from the light exit surface 24 a of the illumination device body 24 to illuminate the liquid crystal display panel 12.
The liquid crystal display panel 12 displays characters, figures, images, and the like on the surface of the liquid crystal display panel 12 by controlling the light transmittance according to the position by the drive unit 14.

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 30b and the second inclined surface 30c in a direction parallel to the first light incident surface 30d and the second light incident surface 30e. 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.

  In addition, in the present embodiment, since light with higher luminance can be efficiently emitted from the light exit surface, the side where the light incident surface 30a of the light guide plate 30 intersects the light incident surface is a long side, and the side which intersects the side surface However, the present invention is not limited to this, and the light emission surface may be a square shape, the light incident surface side may be a short side, and the side surface side may be a long side.

  Here, the light guide plate 30 preferably has an R shape at the connection portion between the first inclined surface and the second inclined surface. By connecting the first inclined surface and the second inclined surface to an R shape and smoothly connecting the two surfaces, uneven brightness such as bright lines occurs at the intersection of the first inclined surface and the second inclined surface. This can be prevented.

Here, in this embodiment, the inclined surface of the light guide plate has a shape with a straight section, but the shape of the first inclined surface and the second inclined surface (that is, the back surface) is not particularly limited, and may be a curved surface. The first inclined surface and the second inclined surface may each be composed of a plurality of inclined portions. That is, the inclined surface may have a shape with a different inclination angle depending on the position. Further, the inclined surface may be a convex shape on the light exit surface side, a concave shape, or a shape in which the concave and convex portions are combined.
Here, it is preferable that the inclined surface has a shape in which the inclination angle of the inclined surface with respect to the light exit surface becomes gentler from the light incident surface toward the center of the light guide plate (or the position where the thickness of the light guide plate is the thickest). . By gradually reducing the inclination angle of the inclined surface, it is possible to emit light with no uneven brightness from the light emitting surface.
Furthermore, the inclined surface is more preferably an aspherical shape whose cross-sectional shape can be expressed by a tenth order polynomial. By setting the inclined surface to the above-described shape, it is possible to emit light without uneven brightness regardless of the thickness of the light guide plate.

In addition, the shape of the light guide plate is not limited to the shape of the present embodiment, and for example, the first inclined surface and the second inclined surface may have different inclinations. The distance from the first light incident surface to the position where the thickness of the light guide plate is maximized may be different from the distance from the second light incident surface to the position where the thickness of the light guide plate is maximized. That is, the length of the first inclined surface in the optical axis direction may be different from the length of the second inclined surface in the optical axis direction.
Even if the light guide plate has such a shape, light can reach a position far from the light incident surface while maintaining a thin shape. Thereby, the light guide plate can be thinned and the light emission surface can be enlarged.
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 and satisfies 0.005 ≦ K _C ≦ 0.1. 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.

Moreover, you may produce a light-guide plate by mixing a plasticizer in said transparent resin.
Thus, by producing a light guide plate with a material in which a transparent material and a plasticizer are mixed, the light guide plate can be made flexible, that is, a flexible light guide plate. It can be deformed into a shape. Therefore, the surface of the light guide plate can be formed into various curved surfaces.
By making the light guide plate flexible in this way, for example, when using a light guide plate or a planar lighting device using the light guide plate as a display plate for illumination, the wall having a curvature is also used. It becomes possible to mount the light guide plate, and it is possible to use the light guide plate for more types, wider use range of electrical decoration, POP (POP advertisement) and the like.

Here, as the plasticizer, phthalate ester, specifically, dimethyl phthalate (DMP), diethyl phthalate (DEP), dibutyl phthalate (DBP), di-2-ethylhexyl phthalate (DOP (DEHP)) ), Di-normal octyl phthalate (DnOP), diisononyl phthalate (DINP), dinonyl phthalate (DNP), diisodecyl phthalate (DIDP), phthalic acid mixed ester (C _{6 to} C ₁₁ ) (610P, 711P, etc.) And butylbenzyl phthalate (BBP). In addition to the phthalate ester, dioctyl adipate (DOA), diisononyl adipate (DINA), dinormal alkyl adipate (C6, _{8, 10} ) (610A), dialkyl adipate (C7, ₉ ) ( 79A), dioctyl azelate (DOZ), dibutyl sebacate (DBS), dioctyl sebacate (DOS), tricresyl phosphate (TCP), tributyl acetylcitrate (ATBC), epoxidized soybean oil (ESBO), trimellitic acid Examples include trioctyl (TOTM), polyester, and chlorinated paraffin.

  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 embodiment, and various improvements and modifications are made without departing from the gist of the present invention. May be.

  For example, in the above-described embodiment, the two fixing means 31 (fixing members 31 a) provided on the first incident surface side and the second incident surface side of the light guide plate 30 are provided in the sliding mechanism 48 provided in the housing 40. However, the fixing means 31 and the sliding mechanism 48 on one side may be integrated into a fixed end 74 and fixed to the housing 40 as shown in FIG. By doing in this way, positioning with respect to the housing | casing 40 of the light-guide plate 30 can be made easy.

Here, in the planar illumination device 10, it is preferable to install the light guide plate 30 so that the first light incident surface 30d is vertically above the second light incident surface 30e, and the light emitting surface 30a is in the vertical direction. More preferably, the light guide plate 30 is installed so that the first light incident surface 30d is parallel to the second light incident surface 30e in the vertical direction.
Thus, by installing the light guide plate 30 so that the first light incident surface 30d is on the upper side in the vertical direction than the second light incident surface 30e, the end fixed to the housing 40 is set to the upper side in the vertical direction. The end supported by the fixing member that slides relative to the housing can be the lower side in the vertical direction. By arranging the portion that moves relative to the housing in this manner on the lower side in the vertical direction, the movement of each member can be made smoother. Further, even when the light guide plate 30 is extended by heat or its own weight, a force acts downward in the vertical direction, so that it is possible to more reliably prevent the light guide plate from warping and bending, and uneven brightness. Etc. can be prevented more reliably.

In this embodiment, the light source 28 is disposed only on the light incident surfaces 30d and 30e. However, the present invention is not limited to this, and is disposed to face the light incident surfaces 30d and 30e as shown in FIG. The light source 28 is a main light source, a sub-light source 29 is provided to face the first side surface 30g and the second side surface 30f, and the first side surface 30g and the second side surface 30f are a third light incident surface and a fourth light incident surface, respectively. Also good. By doing in this way, the brightness | luminance of the light inject | emitted from a light-projection surface can be made higher.
Here, also in the case of providing the sub-light source 29, the fixing means 31 and the sliding mechanism 48 are provided in the same manner as in the case of the light source 28 shown in FIG. 2, and further, as shown in FIG. , 52d, in order to keep the distance between the main light source 28 and the light incident surfaces 30d, 30e of the light guide plate 30 and the distance between the sub light source 29 and the light incident surfaces 30f, 30g of the light guide plate 30 constant. The first round hole 60a, the first elongated hole 62a, and the second elongated hole 62c are provided at the corners 30i, 30j, and 30l of the 30 light exit surfaces 30a, respectively, and the corners 30k of the light guide plate 30 are provided. Instead of the second circular hole 60c, a first elongated hole 62a and a fifth elongated hole 62e having substantially the same shape as the second elongated hole 62c are provided, and in addition to these, the corners 30k, 30j of the light guide plate 30 and 30 liters, first By providing the sixth long hole 70a, the seventh long hole 71a, and the eighth long hole 72a having a long diameter in a direction orthogonal to the long diameter direction of the hole 62a, the second long hole 62c, and the fifth long hole 62e, the light guide plate 30 is provided. Simultaneously preventing destruction of the main light source 28 and the sub light source 29 due to expansion and contraction of the light, a decrease in light incident efficiency on the side surfaces by the main light source 28 and the sub light source 29, and generation of uneven brightness of light emitted from the light exit surface 30a. Can do. In addition, although illustration is abbreviate | omitted also to the inclined surfaces 30b and 30c of the back surface of the light-guide plate 30, a round hole and a long hole are similarly provided in the position corresponding to the round hole and a long hole of the light-projection surface 30a of the light-guide plate 30. Needless to say, is formed.

Although not shown in the example shown in FIG. 13, in order to connect the light guide plate 30 to the upper housing 42 and the lower housing 44 of the housing 40, the example shown in FIG. Similarly, of course, the light guide plate 30 may be provided with a third round hole 61a, a third elongated hole 63a, and a fourth elongated hole 63b. Here, the third round hole 61a, the third elongated hole 63a, and the fourth elongated hole 63b of the light guide plate 30 shown in FIGS. 4A and 6 are through holes, but the light emitting surface 30a of the light guide plate 30 is provided. It may be separated on the side and the back side.
In addition, the above-described one round hole 60a, six long holes 62a, 62c, 62e, 70a, 71a and 72a, and one round hole on the back side corresponding to these one round hole and six long holes and 6 The two long holes fix the light guide plate 30 to the fixing member 31 a and are integrated with the main light source 28 and the sub light source 29, the distance between the main light source 28 and the light incident surfaces 30 d and 30 e of the light guide plate 30, and the sub light source 29. Since it is a round hole and a long hole for keeping the distance from the light incident surfaces 30f and 30g of the light guide plate 30 constant, if there is a function, a round hole and a long hole on the light emitting surface 30a side and a round on the back side The hole and the long hole may be penetrated.

  Further, in the above embodiment, even when the light guide plate is deformed, the sliding mechanism 48 and the fixing means 31 so that the position of the light source 28 and the position of the light emitting surface 30a are the same in the direction perpendicular to the light emitting surface. The light guide plate 30 is supported by the fixing pin 31d, but the present invention is not limited to this. Instead of or in addition to the sliding mechanism and the fixing pin, guide means for supporting one light source may be provided so as not to shift in a direction perpendicular to the light emitting surface 30a.

Hereinafter, another embodiment of the present invention will be described in detail with reference to FIG.
FIG. 14A is a partially omitted plan view schematically showing a light source, a light guide plate, each reinforcing member, and guide means of a planar illumination device 130 according to another embodiment of the present invention, and FIG. FIG. 15 is a sectional view taken along line BB in FIG. Here, in the planar illumination device 130 of the present embodiment, the left side in FIG. 14A is vertically above, and the right side is vertically below.

  14 includes an upper main light source 210 and a lower main light source 212, a light guide plate 30, a first fixing means (upper fixing means) 214, and a second fixing means (lower fixing means) 216. , And guide means 218. Although not shown, the planar illumination device 130 also includes an optical member unit, a reflector, a lower housing, an upper housing, and a reinforcing member (housing reinforcing member), like the planar illumination device 10. The light guide plate 30 basically has the same configuration and shape as the light guide plate 30 of the backlight unit 20 described above, and a detailed description thereof will be omitted. Further, as shown in FIG. 14A, the light guide plate 30 is arranged in a direction in which the first light incident surface 30d is on the upper side in the vertical direction from the second light incident surface 30e.

The upper main light source 210 is disposed to face the first light incident surface 30 d of the light guide plate 30, and the lower main light source 212 is disposed to face the second light incident surface 30 e of the light guide plate 30. Here, since the light guide plate 30 is arranged in a direction in which the first light incident surface 30d is vertically above the second light incident surface 30e, the upper main light source 210 is more vertical than the lower main light source 214. Arranged above.
The upper main light source 210 includes a plurality of LED chips 50 and a light source support 220, and the plurality of LED chips 50 are arranged in a row on the surface of the light source support 220 that faces the first light incident surface 30d. ing.
The lower main light source 214 includes a plurality of LED chips 50 and a light source support portion 222, and the plurality of LED chips 50 are arranged in a row on the surface of the light source support portion 222 that faces the second light incident surface 30e. ing. In addition, the light source support portions 220 and 222 of the present embodiment are plate-like members. In the upper main light source 210 and the lower main light source 212, LEDs are arranged from the end portions of the light source support portions 220 and 222 to the end portions (regions corresponding to reinforcing members described later).
The light source support unit 220 also has a round hole 220a and two long holes 220b and 220c that engage with three fixing pins fixed to the casing described later. The round hole 220a is formed at the center of a plane parallel to the light exit surface 30a. In addition, the two long holes 220b and 220c are formed at positions spaced apart from the round hole 210a by a predetermined distance so that the longitudinal direction of the light source support portion 220 is the long axis direction. Further, the long hole 220b and the long hole 220c are formed symmetrically with respect to a plane passing through the round hole 220a and orthogonal to the bisector α of the light guide plate.
The light source support 220 has a round hole 220d that engages with a fixing pin 236 described later at one end in the longitudinal direction, and a round hole that engages with a fixing pin 238 described later at the other end in the longitudinal direction. 220e is formed.
The light source support 222 has a round hole 220d that engages with a fixing pin 246, which will be described later, at one end in the longitudinal direction, and a round hole that engages with a fixing pin 238, which will be described later, at the other end in the longitudinal direction. 220e is formed.

The first fixing means 214 includes a fixed end 224, first reinforcing members 226 and 228, and fixing pins 230, 232, 234, 236 and 238.
Similarly to the fixed end 74 described above, the fixed end 224 is a columnar member having a U-shaped cross section, and is fixed to the casing by being pressed against the lower casing and the upper casing. The fixed end 224 is fixed to the lower casing and the upper casing in a slidable state in the longitudinal direction.
The fixed end 224 has the upper main light source 210 disposed inside the U-shape, and corresponds to each of the round holes 220a, 220d, 220e and the long holes 220b, 220c of the light source support part 220 of the upper main light source 210. , Round holes 224a, 224d, 224e, and long holes 224b, 224c are formed.

The first reinforcing member 226 is a plate-like member, and the light emitting surface 30a near the corner 30i of the light guide plate 30 in a state where a part on the first light incident surface 30d side protrudes outside the light emitting surface 30a. It is fixed on the top. Further, the first reinforcing member 226 has a portion protruding outward from the light emitting surface 30a extending to a position facing the light source support 220, and a round hole 226a is formed at a position facing the round hole 220d. Yes.
The first reinforcing member 228 is a plate-like member and emits light near the corner 30j of the light guide plate 30 with a part of the first light incident surface 30d side protruding outward from the light emitting surface 30a. It is fixed on the surface 30a. Further, the first reinforcing member 228 has a portion protruding outward from the light emitting surface 30a extending to a position facing the light source support 220, and in the longitudinal direction of the light source support 220 at a position facing the round hole 220e. A long hole 228a is formed in a direction in which is in the long axis direction.
In addition, the 1st reinforcement member 226 and the 1st reinforcement member 228 are being fixed to the light-guide plate by making it adhere | attach with an adhesive agent in this embodiment. The first reinforcing member is preferably formed of super engineer plastic or metal. Here, examples of the metal include aluminum alloy and stainless steel. By forming the reinforcing member with a super engineer plastic or metal, the rigidity can be increased, the deformation can be made difficult, and the deformation due to humidity and heat can be reduced.
Here, in this embodiment, the reinforcing member is provided on the light exit surface of the light guide plate, but the present invention is not limited to this, and on the back surface of the light guide plate (that is, on the first inclined surface and the second inclined surface). ) May be provided with a reinforcing member. Moreover, you may provide a reinforcement member in both surfaces on a light-projection surface and a back surface. By providing the reinforcing member on both the light emitting surface and the back surface, the light guide plate can be more reliably supported by the reinforcing member, and the light guide plate can be more reliably prevented from being deformed or damaged. it can.

The fixing pin 230 is fixed to the housing, and is inserted into the round hole 220 a of the light source support part 220 and the round hole 224 a of the fixed end 224.
The fixing pin 232 is fixed to the housing, and is inserted through the long hole 220b of the light source support portion 220 and the long hole 224b of the fixed end 224. Furthermore, it is fixed to the fixing pin 234 and the casing, and is inserted into the long hole 220 c of the light source support part 220 and the long hole 224 c of the fixed end 224.

The fixing pin 236 is inserted into and fixed to the round hole 220d of the light source support part 220 and the round hole 224d of the fixed end 224, and is further inserted between the light source support part 220 and the fixed end 224. The reinforcing member 226 is inserted into the round hole 226a.
The fixing pin 238 is inserted into and fixed to the round hole 220e of the light source support part 220 and the round hole 224e of the fixed end 224, and is further inserted between the light source support part 220 and the fixed end 224. The long hole 226a of the reinforcing member 226 is inserted.

The first fixing means 214 is configured as described above, and the first reinforcing member 226 that is joined to the light guide plate 30 by inserting the fixing pin 236 into the round hole 226a of the first reinforcing member 226 is used as the first light. The position in the direction parallel to the tangent line between the incident surface 30d and the light exit surface 30a is fixed, and the fixing pin 238 is inserted into the elongated hole 226a of the first reinforcing member 228 joined to the light guide plate 30 to obtain the first reinforcement. By allowing the member 228 to move in a direction parallel to the tangent line between the first light incident surface 30d and the light emitting surface 30a, the light guide plate 30 can be moved toward the upper main light source 210 and the fixed end 224 by the first light incident surface. It can be supported in a state in which it can expand and contract in a direction parallel to the tangent line between 30d and the light exit surface 30a. Further, the distance between the upper main light source 210 and the light incident surface 30d can be made constant by making the distance in the direction perpendicular to the light incident surface 30d constant by the first reinforcing member 226 and the first reinforcing member 228. it can.
Moreover, the light source support part 220 and the fixed end 224 have round holes formed in the holes through which the fixing pins 230 are inserted, and long holes formed in the holes through which the fixed pins 232 and 234 are inserted. 224 can be fixed to the housing in a state in which it can expand and contract in a direction parallel to the tangent line between the first light incident surface 30d and the light emitting surface 30a with respect to the housing. By fixing the light source support part 220 and the fixed end 224 to the housing in a state where the light source support part 220 and the fixed end 224 can be expanded and contracted, the expansion and contraction is suppressed, and the light source support part 220 and the fixed end 224 can be prevented from warping.
In the present embodiment, the fixed end is fixed to the casing. However, since the fixing end can be fixed via a fixing pin, the fixed end may be fixed to the casing other than the fixing pin.
Further, the fixing pin may be changed in thickness, tapered, or provided with a stopper so that the light source support, the first reinforcing member, and the solid end are not displaced relative to the fixing pin. The fixing pin may be slidably engaged with the elongated hole and may be fitted so as not to be displaced from the round hole.

Next, the second fixing means 216 includes a fixing member 240, second reinforcing members 242 and 244, and fixing pins 246 and 248.
The fixing member 240 is disposed so as to be movable with respect to the housing. The fixing member 240 is a columnar member having a U-shaped cross section, and the lower main light source 212 is disposed therein. The fixing member 240 fixes the lower main light source 212 at a predetermined position in the fixing member 240 through fixing pins 246 and 248 described later.
The fixing member 240 is formed with round holes 240a and 240b corresponding to the round holes 220a and 220b of the light source support portion 222 of the lower main light source 212, respectively.
The second reinforcing member 242 is a plate-like member, and a light emitting surface 30a near the corner 30k of the light guide plate 30 in a state where a part on the second light incident surface 30e side protrudes outside the light emitting surface 30a. It is fixed on the top. Further, the second reinforcing member 242 has a portion protruding outward from the light emitting surface 30a extending to a position facing the light source support 222, and a round hole 242a is formed at a position facing the round hole 222a. Yes.
The second reinforcing member 244 is a plate-like member, and the light emission near the corner 30l of the light guide plate 30 with a part on the first light incident surface 30e side protruding outward from the light emission surface 30a. It is fixed on the surface 30a. In addition, the second reinforcing member 244 has a portion protruding outward from the light emitting surface 30a extending to a position facing the light source support 222, and in the longitudinal direction of the light source support 222 at a position facing the round hole 222b. A long hole 244a is formed in a direction in which the long axis direction becomes.
In addition, the 2nd reinforcement member 242 and the 2nd reinforcement member 244 are the structures similar to the 1st reinforcement member mentioned above, and are being fixed to the light-guide plate by making it adhere with an adhesive agent in this embodiment.

The fixing pin 246 is inserted into and fixed to the round hole 222a of the light source support part 222 and the round hole 240a of the fixing member 240, and is further inserted between the light source support part 222 and the fixing member 240. The reinforcing member 242 is inserted into the round hole 242a.
The fixing pin 248 is inserted and fixed in the round hole 222b of the light source support part 222 and the round hole 240b of the fixing member 240, and is further inserted between the light source support part 222 and the fixed end 240. The reinforcing member 242 is inserted into the long hole 242a.

The second fixing means 216 has the above-described configuration, and the second light of the second reinforcing member 242 joined to the light guide plate 30 by inserting the fixing pin 246 into the round hole 242a of the second reinforcing member 242. A second reinforcing member in which the position in the direction parallel to the tangent line between the incident surface 30 e and the light emitting surface 30 a is fixed, and the fixing pin 248 is inserted into the elongated hole 244 a of the second reinforcing member 244 and joined to the light guide plate 30. By allowing the member 244 to move in a direction parallel to the tangent line between the second light incident surface 30e and the light emitting surface 30a, the light guide plate 30 is moved toward the lower main light source 212 and the fixed member 240. It can support in the state which can be expanded-contracted in the direction parallel to the tangent of 30e and the light-projection surface 30a. Further, the distance between the lower main light source 212 and the second light incident surface 30e is made constant by making the distance in the direction perpendicular to the second light incident surface 30e constant by the second reinforcing member 242 and the second reinforcing member 244. Can be.
Further, by allowing the second fixing means 218 that supports the lower main light source 212 to move with respect to the housing, the lower main light source 212 and the second fixing means 218 are placed on the second light incident surface 30 e of the light guide plate 30. Even when the vertical direction (in this embodiment, the hanging direction) expands and contracts, the distance between the second light incident surface 30e and the lower main light source 212 can be moved according to the expansion and contraction of the light guide plate while maintaining a constant distance. it can. Thereby, expansion / contraction of the light guide plate is suppressed, stress is applied to the light guide plate, and the distance between the light source and the light incident surface can be kept constant while preventing the light guide plate from warping.
As a result, even when the light guide plate extends downward in the vertical direction due to its own weight, heat, etc., the second fixing means 218 can move in accordance with the expansion and contraction, so that the expansion is suppressed and bending and warping occur. Can be prevented.

The guide means 218 has four guide portions 250. The four guide portions 250 are disposed so as to face the two surfaces serving as the end portions in the longitudinal direction of the light source support portion 220 and the two surfaces serving as the end portions in the longitudinal direction of the light source support portion 222. .
The guide part 250 is in contact with the surface of the light source support part at the opposite position, and the light source support part at the opposite position is slidable in a direction parallel to the light emission surface and is perpendicular to the light emission surface. In the direction, the light source support part is supported in a state where it cannot move.
Each guide member 250 is fixed at a predetermined position of the casing.

Hereinafter, the guide member 250 will be described. Here, since the four guide members have the same shape and the same function, the four guide members are representatively disposed to face one surface which is an end portion in the longitudinal direction of the light source support portion 222. The guide member 250 is described.
15A is a side view of the lower main light source 214 viewed from the longitudinal direction, and FIG. 15B is a partial rear view of the lower main light source 214 shown in FIG. 15A viewed from the a direction. is there. FIG. 16A is a front view of the guide member 250, and FIG. 16B is a side view of the guide member 250 shown in FIG.

First, as shown in FIGS. 15A and 15B, the region corresponding to the guide member 250 on the side surface of the light source support portion 222 of the lower main light source 214 has an optical axis direction (a direction orthogonal to the light incident surface). A guide groove 222c is formed in the direction in which the groove extends.
Next, as shown in FIGS. 16A and 16B, the guide member 250 includes a plate-like base 252 and a spring member 254 disposed on the surface of the base 252 that faces the light source support portion 222.
The spring member 254 is an elastic body that can expand and contract only in the tangential direction (left and right direction in FIG. 16B) between the light emitting surface 30a and the second light incident surface 30e, and engages with the guide groove 222c to be slidable. ing.

As described above, the spring member 254 of the guide member 250 fixed to the casing is configured to be able to expand and contract only in the tangential direction between the light emitting surface 30a and the second light incident surface 30e, and the spring member 254 has the optical axis direction in the optical axis direction. By engaging with the guide groove 222c, which is the extending direction of the groove, the light source support 222 can be moved in the optical axis direction and can be expanded and contracted in the tangential direction between the light emitting surface 30a and the second light incident surface 30e. In this state, it is possible to prevent the light source support 222 from moving in a direction orthogonal to the exit surface.
Further, the portion of the guide member 250 that engages with the light source support portion can be expanded and contracted in the tangential direction between the light emitting surface 30a and the second light incident surface 30e, so that even when the light source support portion expands and contracts, It is possible to maintain the engagement between the formed groove and the guide member 250, and it is also possible to prevent the light source support portion from being stressed more than necessary.

As described above, the planar illumination device 130 is the guide means 218 that can move the light source support portion in the optical axis direction and extend and contract in the tangential direction between the light exit surface 30a and the second light incident surface 30e. Thus, by providing guide members 250 that prevent the light source support part 222 from moving in a direction orthogonal to the emission surface, the light source support part 220 is provided at four locations on the side surface of the light source support part 220 and the side surface of the light source support part 222. , 222 can be prevented from moving in a direction perpendicular to the light exit surface.
This prevents the first fixing means 214 supporting the light source support portion 220 and the second fixing means 216 supporting the light source support portion 222 from moving in the direction perpendicular to the light exit surface, and the first fixing. It is possible to prevent the light exit surface of the light guide plate engaged with the means 214 and the second fixing means 216 from moving in a direction perpendicular to the light exit surface.
Thereby, the position of the light emission surface in a housing | casing in the direction orthogonal to a light emission surface can be fixed. The distance between the light emission surface and the liquid crystal display panel can be made constant, and a suitable image without uneven brightness can be displayed. Further, it is possible to prevent the light emission surface 30a from warping and the light emission surface 30a from protruding in a direction perpendicular to the light emission surface 30a, and the surface illumination device 130 can be made thin. Thereby, the liquid crystal display device can be thinned.

Here, in the planar illumination device 130, the guide member is provided at four places. However, when the upper main light source is fixed to the housing by the fixed end as in this embodiment, at least the light source of the lower main light source. What is necessary is just to provide a guide member in two places corresponding to a support part.
On the upper main light source side, there is almost no displacement of the light exit surface, so by providing guide members at two locations corresponding to the light source support portion of the lower main light source, the light exit surface protrudes in the direction perpendicular to the light exit surface 30a. Can be prevented.

Further, the configuration of the guide member is not limited to the guide member shown in FIG.
Here, FIG. 17A is a front view showing a schematic configuration of another example of the guide member, and FIG. 17B is a side view of the guide member shown in FIG. FIG. 18A is a front view illustrating a schematic configuration of another example of the guide member, and FIG. 18B is a side view of the guide member illustrated in FIG.
For example, the guide member 260 illustrated in FIG. 17 includes a plate-like base portion 262 and a plurality of plungers 264 disposed on a surface of the base portion 262 facing the light source support portion 222.
The plunger 264 is a member that can be expanded and contracted only in the tangential direction (left and right direction in FIG. 17B) between the light emitting surface 30a and the second light incident surface 30e, and in a direction parallel to the extending direction of the guide groove 222c. It is arranged in a straight line. Each plunger 264 is engaged with the guide groove 222c. In this way, when the plunger is provided instead of the spring plate, the same effect as described above can be obtained.

Next, a guide member 270 shown in FIG. 18 has a plate-like base 272, a spring 274 disposed on the surface of the base 272 facing the light source support 222, and an end of the spring 274 on the light source support 222 side. And a supported linear guide 276.
The linear guide 276 is urged by a spring 274 in the tangential direction (the left-right direction in FIG. 18B) between the light emitting surface 30a and the second light incident surface 30e. The linear guide 276 is engaged with the guide groove 222c. Thus, also when the combination of a linear guide and a spring is used, the effect similar to the above can be acquired.

  In the above-described embodiments, the guide member is a convex portion and is configured to be engaged with the groove portion of the light source support portion. However, the present invention is not limited to this, and the guide member is provided with the convex portion of the light source support portion. It is good also as a structure which provides a groove part in this. In this case, the convex part of the light source support part is set to a height higher than a certain level (greater than the expansion width of the light source support part), and the convex part of the light source support part causes the groove part of the guide member to extend from the light emitting surface 30a by the expansion and contraction of the light source support part. What is necessary is just to make it move to the tangent direction with the 2 light-incidence surface 30e.

Moreover, in the said embodiment, although the light source support part and the guide member were engaged, this invention is not limited to this, A groove | channel is formed in the longitudinal direction edge part of a fixing member, or the longitudinal direction edge part of a fixing edge. The fixing member and the guide member may be engaged, or the fixing member and the guide member may be engaged.
If the light source, the fixing means, and the light guide plate can be prevented from moving in a direction perpendicular to the light exit surface with respect to the housing and can be supported in a movable state in other directions, the guide The arrangement position is not particularly limited. For example, the fixing member may be supported from the surface of the fixing member opposite to the light guide plate.

Further, in the planar illumination device 130, the light source is fixed to the fixed end and the fixing member via the fixing pin, but the present invention is not limited to this, and the light source may be directly connected to the fixed end or the fixing member and fixed. . Further, since the upper main light source is fixed to the housing by the fixing pin and the position in the direction perpendicular to the light emitting surface can be set to the predetermined position by the guide, the fixing end and the fixing member need not be provided. Thus, when a fixed end and a fixing member are not provided, a reinforcing member and a fixing pin serve as each fixing means.
In addition, the fixing pin does not need to penetrate through the light source support part, and if the housing and the fixed end and the light source support part, or the fixed end (fixing member), the reinforcing member, and the light source support part can be locked, the light source support is provided. Only one of the parts may be engaged, or separate fixing pins may be provided on the light emitting surface side and the inclined surface side.
Further, by providing the above-described sliding mechanism, it is possible to more reliably prevent the light emission surface, the light source, and the like from moving in a direction perpendicular to the light emission surface.

  Further, in the planar illumination device 130, the case where two light sources, ie, the upper main light source and the lower main light source are provided has been described. A secondary light source may be provided so that light is incident from four sides.

FIG. 19A is a partially omitted plan view schematically showing a light source, a light guide plate, each reinforcing member, and guide means of a planar illumination device of another example, and FIG. It is B line sectional drawing.
A planar illumination device 300 shown in FIG. 19 has an upper main light source 210 and a lower main light source 214 arranged as opposed to the light incident surfaces 30d and 30e as main light sources, and faces the first side surface 30f and the second side surface 30g. The sub-light sources 310 and 312 are provided, and the first side surface 30f and the second side surface 30g serve as a third light incident surface and a fourth light incident surface, respectively. By doing in this way, this invention can make the brightness | luminance of the light inject | emitted from a light-projection surface higher.

The planar lighting device 300 shown in FIG. 19 has two third fixing means 314 and 316 that make the two sub-light sources 310 and 312 and the light guide plate 30 a constant distance, and excludes the guide means 318. Since the other configuration is the same as that of the planar illumination device 130, the same members are denoted by the same reference numerals, and the description thereof will be omitted. Hereinafter, the features specific to the planar illumination device 300 will be described.
The planar illumination device 300 includes an upper main light source 210 and a lower main light source 212, sub-light sources 310 and 312, a light guide plate 30, a first fixing unit 214, a second fixing unit 216, a third fixing unit 314, 316 and guide means 318. Although not shown, the planar illumination device 300 also includes an optical member unit, a reflector, a lower housing, an upper housing, and a reinforcing member (housing reinforcing member), like the planar illumination device 130.

  The sub light source 310 and the third fixing means 314 are disposed to face the side surface 30 f of the light guide plate 30, and the sub light source 312 and the third fixing means 316 are disposed to face the side surface 30 g of the light guide plate 30. Here, the sub-light source 210 and the third fixing unit 314 and the sub-light source 312 and the third fixing unit 316 are the same in basic configuration except for the surface arranged with respect to the light guide plate 30. Therefore, the sub light source 310 and the third fixing means 314 will be described below as a representative.

The sub-light source 310 includes a plurality of LED chips 50 and a light source support 320 as in the case of the main light source. The light source support 320 is a plate-like member, and a plurality of LED chips 50 are arranged in a row on the surface facing the side surface 30f.
The light source support 320 includes a round hole 320a that engages with a fixing pin 328 described later at an end on the upper side in the longitudinal direction (on the first light incident surface 30d side), and a lower side in the vertical direction in the longitudinal direction (second A round hole 320b that engages with a fixing pin 330, which will be described later, is formed at the end of the light incident surface 30e side.

The third fixing means 314 includes a fixing member 322, fourth reinforcing members 324 and 326, and fixing pins 328 and 330.
The fixing member 322 is disposed so as to be movable with respect to the housing. The fixing member 322 is a columnar member having a U-shaped cross section, and the auxiliary light source 310 is disposed inside. The fixing member 322 fixes the auxiliary light source 310 at a predetermined position in the fixing member 322 via fixing pins 328 and 330 described later.
The fixing member 322 has round holes 322a and 322b corresponding to the round holes 320a and 320b of the light source support 320 of the sub light source 310, respectively.
The fourth reinforcing member 324 is a plate-like member, and is fixed on the light emitting surface 30a in the vicinity of the corners 30i of the light guide plate 30 with a part on the side surface 30f protruding outward from the light emitting surface 30a. ing. In addition, the fourth reinforcing member 324 has a portion protruding outward from the light emitting surface 30a extending to a position facing the light source support 320, and in the longitudinal direction of the light source support 320 at a position facing the round hole 320a. A round hole 324a is formed in a direction in which the direction becomes the major axis direction.
The fourth reinforcing member 326 is a plate-like member, and is fixed on the light emitting surface 30a near the corner 30k of the light guide plate 30 with a part of the side surface 30f protruding outward from the light emitting surface 30a. ing. Further, the fourth reinforcing member 326 has a portion protruding outward from the light emitting surface 30a extending to a position facing the light source support 320, and the longitudinal direction of the light source support 320 at a position facing the round hole 322b. A long hole 326a is formed in a direction in which the long axis direction becomes.
The fourth reinforcing members 324 and 326 have the same configuration as the first reinforcing member and the second reinforcing member described above. In the present embodiment, the fourth reinforcing members 324 and 326 are fixed to the light guide plate by being bonded with an adhesive.

The fixing pin 328 is inserted into and fixed to the round hole 320a of the light source support part 320 and the round hole 322a of the fixing member 322, and is further inserted between the light source support part 320 and the fixing member 322. The reinforcing member 324 is inserted into the round hole 324a.
The fixing pin 330 is inserted into and fixed to the round hole 320b of the light source support part 320 and the round hole 322b of the fixing member 322, and is further inserted between the light source support part 320 and the fixing member 322. The reinforcing member 326 is inserted into the elongated hole 326a.

The third fixing means 314 is configured as described above, and includes a side surface 30f of the fourth reinforcing member 324 that is inserted into the round hole 324a of the fourth reinforcing member 324 through the fixing pin 328 and joined to the light guide plate 30. The position in the direction parallel to the tangent to the light emitting surface 30a is fixed, the fixing pin 330 is inserted into the elongated hole 324a of the fourth reinforcing member 324, and the fourth reinforcing member 324 that is joined to the light guide plate 30 is connected to the side surface. A state in which the light guide plate 30 can be expanded and contracted in a direction (hanging direction) parallel to the tangent line between the side surface 30f and the light emission surface 30a by enabling movement in a direction parallel to the tangent line between the light emission surface 30a and 30f. It can be supported. Further, the distance between the lower main light source 212 and the second light incident surface 30e can be made constant by making the distance in the direction perpendicular to the side surface 30f constant by the fourth reinforcing member 324 and the fourth reinforcing member 326. it can.
In addition, a round hole 324a is formed in the fourth reinforcing member 324 on the upper side in the vertical direction to fix the relative position between the light source and the light guide plate, and a long hole 326a is formed in the fourth reinforcing member 326 on the lower side in the vertical direction. By making the fourth reinforcing member 326 joined to the optical plate movable in the hanging direction, the lower surface in the vertical direction can be easily extended. Thereby, the load concerning a light-guide plate can be made smaller.
Further, since the third fixing means 314 is movable with respect to the housing, even when the light guide plate extends in the width direction (tangential direction between the light incident surface and the light emitting surface), the third fixing means is As the light guide plate expands and contracts, it moves in the width direction together with the light guide plate while keeping the distance between the side surface and the sub-light source constant.
Thus, by providing the third fixing means, the sub-light source can also maintain a constant distance between the side surface and the sub-light source without suppressing warpage of the light guide plate.

The guide means 318 has six guide members 250, and the side of the light source support part 220 of the first fixing means 214 on the corner corner 30 i side of the light guide plate 30 and the third fixing on the corner corner 30 j side of the light guide plate 30. The surface of the fixing member 322 of the means 316 opposite to the light guide plate side, the side surface of the light source support portion 222 of the second fixing means on the corner 30k side of the light guide plate 30, and the light guide plate of the fixing member 240 of the second fixing means The surface of the third fixing means 316 of the third fixing means 316 on the corner 30l side of the light guide plate 30 is disposed on the surface opposite to the light guide plate side.
Since the guide member 250 has the same configuration as the guide member 250 of the planar illumination device 130 described above, detailed description thereof is omitted.
Further, a groove corresponding to the guide member 250 is formed in the opposing member of the guide member 250, and the convex portion of the guide member 250 is engaged with the groove.
The guide members 250 are movable in the optical axis direction and the tangential direction between the light emitting surface 30a and the second light incident surface 30e, respectively, so that the light source support 222 cannot move in the direction perpendicular to the emitting surface. The member engaged with is supported.
Thus, by providing the guide member at positions corresponding to the four corners of the light guide plate, it is possible to prevent the light exit surface of the light guide plate from moving in a direction orthogonal to the light exit surface.
In the case of this embodiment, the guide means 318 only needs to arrange the guide member 250 at least at two corners 30 k and 30 l of the light guide plate.

Here, in the planar lighting device, it is preferable that members interposed between the light source and the housing are brought into contact with each other through heat radiation grease. That is, it is preferable to apply the heat radiation grease to the contact surface between the members interposed between the light source and the housing (form a heat radiation grease layer).
Specifically, the contact surface between the light source (light source support portion thereof) and the fixing means, the contact surface between the members constituting the fixing means, the contact surface between the fixing means and the housing (upper housing, lower housing) It is preferable to apply a heat dissipation grease to each member and bring each member into contact with the heat dissipation grease.
Here, as the heat radiation grease, silicon grease or silicon grease containing a metal filler can be used.

In this way, each member is brought into contact with the heat dissipation grease, so that heat can be easily transferred from the light source to the housing while maintaining the state in which the fixing member is slidable. Efficiency can be improved and temperature rise of the light source can be prevented. Thus, the luminous efficiency of a light source can be made high by preventing the temperature rise of a light source.
Moreover, since the brightness | luminance inject | emitted with the same power consumption can be raised by suppressing the temperature rise of a light source and preventing the fall of the light emission efficiency of LED, the power consumption of a planar illuminating device can be reduced. it can.
Further, it is possible to prevent the members around the light source, particularly the light guide plate, from being deformed by the heat of the light source, and to prevent the device from being deformed. Occurrence of missing or the like can be prevented. Further, since the warpage can be suppressed, it is unnecessary or less necessary to provide a space assuming a warp and a cushioning material, so that the device configuration can be simplified and the device can be thinned.
In addition, since heat can be efficiently radiated, it is not necessary or less necessary to provide expensive heat radiating means such as a heat pipe, and the apparatus can be made inexpensive.
Moreover, the movable part can be smoothly slid by applying the heat radiation grease.

Here, the heat dissipating grease preferably has a thermal conductivity of 0.6 W / m · k or more.
By making the thermal conductivity 0.6 W / m · k or more, heat can be transferred efficiently, and metal particles mixed / dispersed grease heat dissipation is also efficiently generated by the light source even when thick grease is applied. Heat can be dissipated.
Moreover, it is preferable that the consistency is 300 or more and 400 or less.
By setting the consistency to 300 or more, it is possible to apply a thin heat-dissipating grease, and by setting it to 400 or less, it is possible to prevent the operability of the sliding portion from being lowered. Can be moved.

Moreover, it is preferable to apply the heat dissipating grease over the entire contact surface.
By applying heat radiation grease to the entire contact surface, the heat of the light source can be more efficiently transferred to the housing.
Further, in order to transfer heat at each contact surface, it is necessary to apply heat radiation grease to at least a part of each contact surface, but a certain degree of effect can be obtained even if it is not applied to the entire surface. .

Hereinafter, it explains in detail with a concrete example.
In this measurement example, have use a planar illumination device configured as shown in FIG. 2, the contact portion entirely between the light source 28 and the fixing member 31a, the contact surface between the fixed member 31a and the lower sliding member 48c, the lower sliding member 48c The contact surface between the sliding member fixing member 48a, the contact surface between the sliding member fixing member 48a and the lower housing 42, the contact surface between the fixing member 31a and the heat sink 64, and the contact surface between the heat sink 64 and the lower housing 42. The heat radiation grease was applied to the contact surface between the heat sink 64 and the heat pipe 66 and the entire contact portion between the heat pipe 66 and the lower housing 42 so that the thickness became 50 to 100 μm. The application of the heat dissipating grease was performed on each side of the two light incident surfaces of the light guide plate 30. Here, the heat radiation grease used for the measurement is a heat radiating silicone oil compound (trade name). The thermal conductivity of this grease is 0.84 W / (m / k) and the consistency is 300. Moreover, a plate-shaped member was used as the light source support part. As the light guide plate, a light guide plate used for a 52-inch planar illumination device was used. In addition, the planar lighting device was arranged in a direction in which the planar lighting device was suspended such that one fixing member 31a was above and the other fixing member 31a was below.

  Using the planar illumination device configured as described above, the temperature of the light source 28, and the planarity and luminance of the planar illumination device were measured. In addition, for comparison, regarding the planar illumination device having the same configuration except that no heat dissipation grease is applied, the temperature of the light source 28, the flatness of the light guide plate, and the luminance of light emitted from the light exit surface Was measured.

Here, the temperature of the light source was measured with a thermocouple at the position of the central portion in the longitudinal direction of the light source 28 of the light source support portion 50 of the upper light source 28 and 5 mm directly below the LED chip 50 mounting portion.
In addition, the flatness of the light guide plate was determined by measuring the amount of (skoya) deformation with respect to the reference gauge with respect to the upper and lower frame portions of the planar illumination device by stereo imaging.
Moreover, the brightness | luminance of the light inject | emitted from an emission surface measured the brightness | luminance of the center position of a light emission surface with the luminance meter (brand name: spectroradiometer SR-3).

The measurement results are shown in FIGS.
Here, FIG. 20 is a graph showing a measurement result representing the flatness of the liquid crystal panel module, and FIG. 21 is a measurement result of the relationship between the irradiation time, the temperature of the light source, and the luminance of the light emitted from the light exit surface. It is a graph which shows. Here, in FIG. 20, the vertical axis is the amount of deformation, and the horizontal axis is the longitudinal direction of the upper and lower frame. In FIG. 21, the vertical axis represents the temperature [° C.] and the luminance [cd] of the light source, and the horizontal axis represents the irradiation time [min].

As shown in FIG. 20, when the heat-dissipating grease is not applied, the displacement amount of the upper frame portion of the planar lighting device (shown as the upper side (no grease) in FIG. 20) is 3.7 mm at the maximum, and the lower frame portion (in FIG. 20). The maximum displacement amount (denoted as “no grease”) was 3.1 mm. On the other hand, when heat-dissipating grease is applied, the displacement amount of the upper frame portion (shown as the upper side (with grease) in FIG. 20) of the planar illumination device is 1.2 mm at the maximum, and the lower frame portion (lower side in FIG. 20). The displacement amount (denoted with grease) was 1.0 mm at the maximum. From this, it can be seen that by applying heat radiation grease, the amount of displacement of the frame portion of the planar lighting device can be reduced to about 1/3 of the amount of displacement when heat radiation grease is not applied.
From the above, it can be seen that by applying the heat radiation grease to the contact surface, the deformation of the light guide plate can be prevented and the flatness can be enhanced.

Further, as shown in FIG. 21, when the heat radiation grease is applied, the temperature of the light source 28 can be lowered by 8 ° C. and the luminance can be improved by 15% after 55 minutes compared to the case where no heat radiation grease is applied. I understand.
From the above, the effects of the present invention are clear.

In addition, for example, the LED chip of the light source has a configuration in which a YAG fluorescent material is applied to the light emitting surface of a blue LED. However, the present invention is not limited to this, and the fluorescent material is applied to the light emitting surface of another single color LED such as a red LED or a green LED. You may use the LED chip of the structure which has arrange | positioned.
Moreover, the LED unit of the structure which combined three types of LED of red LED, green LED, and blue LED as a light source can also be used. In this case, white light can be obtained by mixing light emitted from the three types of LEDs.
Further, a semiconductor laser (LD) can be used instead of the LED.

Further, a confusion portion made of a material having a refractive index close to that of the light guide plate 30 may be disposed between the light guide plate 30 and the light source (the light source 28 and / or the sub light source 29). Further, a part of the light incident surface and / or side surface of the light guide plate may be formed of a material having a smaller refractive index than other portions.
By making the refractive index of the portion where the light emitted from the light source is incident smaller than the other portions, the light emitted from the light source can be incident more efficiently, and the light utilization efficiency can be further increased. .

  Further, for example, a plurality of light guide plates may be arranged in parallel at the positions where the side surfaces of the light guide plates face each other, and one light emission surface may be formed by the plurality of light guide plates. In this case, it is good also as a structure which arrange | positions a sublight source only to the side surface of the light-guide plate of both ends.

It is a schematic perspective view which shows one Embodiment of the liquid crystal display device using the planar illuminating device which concerns on this invention. It is the II-II sectional view taken on the line of the liquid crystal display device shown in FIG. FIG. 3 is a partial enlarged cross-sectional view of the vicinity of a light incident surface of a light source and a light guide plate of the planar illumination device of the liquid crystal display device shown in FIG. 2. (A) is a partial omission plan view of a light source and a light guide plate of the planar illumination device shown in FIG. 2, and (B) is a cross-sectional view taken along line BB of (A). (A) is a perspective view which shows schematic structure of the light source of the planar illuminating device shown in FIG. 2, (B) is sectional drawing of the light source shown to (A), (C) is (A). It is a schematic perspective view which expands and shows one LED which comprises the light source shown in FIG. It is a schematic perspective view which shows the shape of the light-guide plate shown in FIG. 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. It is a partial expanded sectional view of the light-incidence surface vicinity of the light source and light-guide plate of other embodiment of the planar illuminating device concerning this invention. It is a figure which shows the result of having measured the stress distribution from a screwing position. It is sectional drawing which shows schematic structure of other embodiment of the planar illuminating device concerning this invention. It is a schematic plan view which shows other embodiment of the shape of the light-guide plate and light source used for the planar illuminating device concerning this invention. (A) is a partial abbreviated plan view schematically showing a light source, a light guide plate, each reinforcing member and guide means of another example of a planar lighting device, and (B) is a BB line in (A). It is sectional drawing. (A) is the side view which looked at the lower main light source from the longitudinal direction, (B) is the partial rear view which looked at the lower main light source shown to (A) from a direction. (A) is a front view which shows schematic structure of an example of a guide member, (B) is a side view of the guide member shown to (A). (A) is a front view which shows schematic structure of another example of a guide member, (B) is a side view of the guide member shown to (A). (A) is a front view which shows schematic structure of another example of a guide member, (B) is a side view of the guide member shown to (A). (A) is a partially omitted plan view schematically showing a light source, a light guide plate, each reinforcing member, and a guide member of another example of a planar illumination device, and (B) is a BB line in (A). It is sectional drawing. It is a figure which shows the measurement result showing the planarity of a liquid crystal panel module. It is a figure which shows the relationship between the brightness | luminance of the center position of a planar illuminating device, the temperature of a light source, and the light emission time of a light source.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Liquid crystal display device 12 Liquid crystal display panel 14 Drive unit 20, 130, 300 Backlight unit (planar illumination device) 22b Side surface part 24 Illumination device main body 24a, 30a Light emission surface 28 Main light source 210 Upper main light source 212 Lower main light source 220 , 222 Light source support 222c Guide grooves 29, 310, 312 Sub-light source 30 Light guide plate 30b First inclined surface 30c Second inclined surface 30d First light incident surface 30e Second light incident surface 30f First side surface 30g Second side surface 31 Fixed Means (second fixing means)
31a, 240 fixing member 214 first fixing means 74, 224 fixing end 216 second fixing means 31b, 31c, 46a, 46b screws 31d, 31e, 230, 232, 234, 236, 238 fixing pin 32 optical member unit 32a diffusion sheet 32b Prism sheet 32c Diffusion sheet 34 Reflector plate 36 Upper guide reflector 38 Lower guide reflector 40 Housing 42 Lower housing 44 Upper housing 46 Reinforcement member 47 Spring material 48 Sliding mechanism 48a, 48d Slide member fixing member 48b Upper slide Moving member 48c Lower sliding member 49 Power supply accommodating portion 50 LED chip 52 Light source support portion 52a Light source support portion upper surface 52b Light source support portion lower surface 52c, 52d, 53 Screw hole 53 Screw hole 54 Array substrate 56 Fin 58 Light emitting surface 60a, 60b, 61a Round holes 62a, 62b, 62c, 62d, 62e, 2f, 70a, 71a, 72a Slot 63a, 63b Slot 64 Heat sink 66 Heat pipe 226, 228 First reinforcement member 242, 244 Second reinforcement member 250, 260, 270 Guide member 252, 262, 272 Base 264 Plunger 254 Spring Member 274 Spring 276 Linear guide α bisector c Optical axis distance between light source and light guide plate

Claims (12)

A light source that emits light;
A light guide plate that is disposed facing the light source and includes a light incident surface on which light emitted from the light source is incident and a light emission surface that emits light incident from the light incident surface as planar light;
A fixing means for fixing and integrating the light source and the light guide plate with a constant distance between the light source and the light incident surface of the light guide plate;
A housing for housing the light source and the light guide plate integrated by the fixing means;
In the direction from the light incident surface of the light guide plate toward the light source provided between the housing and the fixing means, the light source and the light guide plate are integrated according to the expansion and contraction of the light guide plate, A sliding mechanism that slides the fixing means with respect to the housing while maintaining a constant distance between the light source and the light incident surface of the light guide plate;
The light guide plate and the fixing means are formed in one of the light guide plate and the fixing means at one end in the longitudinal direction of the light incident surface. The light guide plate is fixed to the light guide plate in accordance with the expansion and contraction of the light guide plate in the longitudinal direction of the light incident surface. The member can slide ,
The sliding mechanism has two sliding members that sandwich the fixing means in a direction perpendicular to the light emitting surface by screwing the housing.
The sliding member is disposed at a position where the frictional force between the fixing means and the sliding member is smaller than the force due to expansion and contraction of the light guide plate with respect to the screwing position of the housing,
As the sliding mechanism moves away from the light guide plate in a direction perpendicular to the light incident surface, the gap between the two sliding members becomes narrower, so that the light guide plate is oriented in a direction perpendicular to the light incident surface. When the light guide plate expands and contracts, the sliding mechanism and the fixed member are fixed so that the frictional force between the fixing means and the sliding member increases when the light guide plate extends and the frictional force decreases when the member contracts. A planar illumination device characterized by changing a frictional force with the means. The light guide plate has a linear expansion coefficient satisfying 1/1000 <ΔL / L <5/1000, and a Young's modulus satisfies 1.5MN / m ² <Y <3MN / m ^2. The planar illumination device according to claim 1 . The light guide plates are respectively formed on the rectangular flat light emission surface and a pair of opposing edges of the light emission surface, and are opposed to each other for allowing light traveling parallel to the light emission surface to enter. A pair of the light incident surfaces and a surface opposite to the light exit surface, and the thickness in a direction perpendicular to the light exit surface increases as the distance from the pair of light entrance surfaces increases. A back surface comprising a pair of inclined surfaces that are inclined and joined at the center of the pair of light incident surfaces;
The light sources are arranged to face the pair of light incident surfaces of the light guide plate, respectively, and consist of a pair of light sources that allow light to enter the pair of light incident surfaces, respectively.
Each light source has a plurality of LED chips and a support that supports the LED chips,
The planar illumination device according to claim 1 or 2 , wherein the plurality of LED chips are arranged in a line along a longitudinal direction of the light incident surface on a surface of the support that faces the light incident surface. Further, the remaining pair of light incident surfaces formed on the remaining pair of opposing edges of the light exit surface of the light guide plate and orthogonal to the pair of light incident surfaces;
4. The planar illumination device according to claim 3 , further comprising: a pair of the light sources that are disposed to face the remaining pair of light incident surfaces, respectively, and allow light to enter the remaining pair of light incident surfaces, respectively. . The LED chip, a thickness direction length of the light guide plate is a, the length in the direction perpendicular to the thickness direction of the light guide plate when is b, claim 3 or 4 satisfying the inequality b <a The surface illumination device described in 1. 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 of the light guide plate in the light incident direction. the length from the incident surface to the thickest position the thickness of the light guide plate is taken as L _G, the inequality _{1.1 ≦ Φ · N p · L} G · K C ≦ 8.2
0.005 ≦ K _C ≦ 0.1
The planar illumination device according to any one of claims 1 to 5 , which satisfies the following conditions. Furthermore, the light emission surface and the one in a direction perpendicular to the light emission surface are provided between the housing and the one light source disposed to face the pair of light incident surfaces of the light guide plate. While keeping the distance between the light source and the housing constant, according to the expansion and contraction of the light guide plate, the one light source is directed toward the light source from the light incident surface of the light guide plate with respect to the housing. The planar illumination device according to any one of claims 1 to 6 , further comprising guide means for movement. The planar illumination device according to claim 7 , wherein the one light source is disposed on the lower side in the vertical direction with respect to the other light source disposed to face the pair of light incident surfaces of the light guide plate. The fixing means includes a protrusion fixed to a light source disposed to face the pair of light incident surfaces of the light guide plate;
A plate-like member fixed to at least one surface of the light exit surface and the inclined surface of the light guide plate, and a reinforcing member that engages with the protrusion and engages the light guide plate with the protrusion. The planar illumination device according to claim 7 or 8 , wherein the planar illumination device is configured. The fixing means includes a fixing member that covers the surface other than the light emitting surface of the light source disposed to face the pair of light incident surfaces of the light guide plate and supports the light source,
Said guide means, said fixing member, wherein the relative housing from the light incident surface of the light guide plate be movable in the direction toward the light source, according to claim 7 for movably supporting said light source The planar illuminating device in any one of -9 . The planar illumination device according to any one of claims 7 to 10 , wherein the guide means are two guide portions respectively disposed on both surfaces orthogonal to the longitudinal direction of the light source. The planar illumination device according to any one of claims 1 to 11 , wherein a contact surface between the light source and the fixing unit and a contact surface between the fixing unit and the housing are in contact with each other through heat radiation grease. .

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