JP4555250B2 - Light guide plate and planar illumination device using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light guide plate which has a low-profile and large-area light outgoing surface and a capability of emitting the incoming light as a high-luminance light with no or less luminance variation from the light outgoing surface. <P>SOLUTION: The light guide plate has a flat light outgoing surface, a surface facing the light outgoing surface, and many parallel grooves formed in parallel with each other at a predetermined spacing interval on the surface facing the light outgoing surface. The surface facing the light outgoing surface takes the inclined shape, such that the thickness in the direction perpendicular to the light outgoing surface gets smaller as it separates from the parallel grooves in the direction orthogonal to the extending direction of the parallel grooves, while the thickness in the direction perpendicular to the light outgoing surface gets greater as it separates from the end of the light outgoing surface in the direction parallel to the extending direction of the parallel grooves. <P>COPYRIGHT: (C)2008,JPO&amp;INPIT

Description

  The present invention relates to a light guide plate that diffuses light emitted from a light source and emits illumination light from a light exit surface, and a planar illumination device that includes the light guide plate to illuminate indoors and outdoors, or a liquid crystal display panel or an advertisement panel The present invention relates to a planar lighting device used as a backlight for advertising towers and billboards.

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

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

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

Therefore, various methods using a light guide plate have been proposed as thin backlight units.
For example, Patent Document 1 provides a backlight of a liquid crystal display device that can realize a reduction in size and weight and reduction in cost and power consumption of the liquid crystal display device without reducing the amount of backlight irradiation. For this purpose, a rectangular irradiation surface, a rectangular cross section grooved in parallel with the long side in the center of the short side, and both sides of the long side across this groove There is described a light guide plate having a back surface formed so that the plate thickness gradually decreases in the direction.
Patent Document 2 discloses a width of a recess for disposing a light source for the purpose of obtaining a bright backlight unit that can reduce the frame thickness of the liquid crystal display device and reduce the thickness thereof and has high light utilization efficiency. A light guide (light guide plate) is described in which the cross-sectional shape parallel to the direction is a parabolic shape with the depth direction as the main axis.
Further, in Patent Document 3, in order to improve the liquid crystal backlight for a large-sized liquid crystal display surface of a wall-mounted television, a large number of strip-shaped light guide plates formed with protruding edges at both ends in the width direction are arranged in parallel. There is described a liquid crystal backlight unit configured by arranging a linear light source in each fitting groove formed by butt contact.
Further, in Patent Document 4, in order to keep the in-plane brightness of the display panel uniform and to provide high-intensity illumination, a plurality of refractive indexes are sequentially increased on the C-shaped highly reflective layer. A light guide plate is described in which the plate-like optical waveguide layers are stacked and the light diffusion layer is brightened by the light emitted from the respective light emission end faces. Here, the recess for arranging the light source has a triangular shape.

JP-A-8-62426 JP 10-1333027 A JP 2001-42327 A JP-A-5-249320

However, each of the planar illumination devices using the light guide plate described in Patent Documents 1 to 4 has a limit on the amount of light that can be supplied from the light source, and in order to increase the amount of light incident on the light guide plate, Need to be larger. Thus, when the light incident part is enlarged, the light guide plate becomes thick, and there is a problem that it cannot be thinned.
In addition, even with a light guide plate that forms a groove for placing a light source on the surface opposite to the illumination surface (light emission surface), the light emitted from the light source does not reach the end of the light guide plate when the size is increased, and light is emitted. There is also a problem that uneven brightness occurs in the light emitted from the surface.

Further, in the light guide plate described in Patent Document 3, in order to suppress an increase in luminance in the portion directly above the linear light source, a transmission suppression pattern for suppressing transmission of light from the linear light source must be provided, The light from the linear light source is transmitted in the in-plane direction from one end to the other end inside the light guide plate, so that the amount of light gradually attenuates, which is insufficient for increasing the brightness. It was.
In addition, the light guide plate described in Patent Document 4 has a complicated structure in which a plurality of plate-like optical waveguide plates are laminated. Therefore, it is possible to obtain a uniform brightness with less attenuation of brightness than in the past. However, there is a problem that the manufacturing cost becomes high.

The first problem of the present invention is to solve the problems based on the above prior art, have a thin and large area light emission surface, and make the incident light as light with high luminance and no luminance unevenness or less. It is in providing the light-guide plate which can be made to inject from.
Further, the second problem of the present invention is to solve the problems based on the above prior art, and to emit light with high brightness and no luminance unevenness or little light from the light exit surface, which is a large and thin surface shape. The object is to provide a lighting device.

  In order to solve the first problem, a first form of the first aspect of the present invention includes a flat light exit surface, a surface facing the light exit surface, and a surface facing the light exit surface. A plurality of parallel grooves formed parallel to each other at a predetermined interval, and the surface facing the light exit surface is the light exit surface as the distance from the parallel groove increases in a direction perpendicular to the extending direction of the parallel grooves. In a shape that is thin so that the thickness in the direction perpendicular to the light exit surface increases in the direction parallel to the extending direction of the parallel grooves and from the end surface toward the center. There is provided a light guide plate characterized by being.

Furthermore, it has a scattering particle which scatters the light which propagates an inside, and it is preferable that the said scattering particle satisfy | fills following formula (1).
1.1 ≦ Φ · N _p · L _G · K _C ≦ 8.2 Formula (1)
(However, the scattering cross section of scattering particles [Phi, distance L _G to face from the end face of the light guide _plate, the density of the scattering particles N _p, a correction coefficient is K _C, 0.005 ≦ K _C ≦ 0.1)
Here, the distance from the end surface of the light guide plate to the opposite surface is the distance from one end surface of the light guide plate to the surface facing the end surface, that is, the other end surface.

  In order to solve the second problem, a first aspect of the second aspect of the present invention includes the light guide plate according to any one of the above and a plurality of light sources, and the light source includes the light guide. The present invention provides a planar illumination device that is disposed on end faces in the extending direction of the parallel grooves of the light plate and the light guide plate and allows light to enter the light guide plate from the parallel grooves and the end face.

  Here, the light source arranged on the end surface of the light guide plate in the extending direction of the parallel grooves is a plurality of LED elements arranged in a row, and the LED elements are arranged in the parallel grooves. It is preferable that they are arranged at different intervals according to the luminance of light emitted from a light source and incident on the light guide plate and emitted from the light exit surface.

  In order to solve the first problem, the second mode of the first aspect of the present invention is that a flat light exit surface, a surface facing the light exit surface, and a surface facing the light exit surface are mutually connected. A plurality of parallel grooves formed parallel to each other at a predetermined interval, and the surface facing the light exit surface is the light exit surface as the distance from the parallel groove increases in a direction perpendicular to the extending direction of the parallel grooves. So that the thickness in the direction perpendicular to the light exit surface increases in the direction parallel to the extending direction of the parallel grooves from one end surface to the other end surface. A light guide plate having an inclined shape.

Furthermore, it has a scattering particle which scatters the light which propagates an inside, and it is preferable that the said scattering particle satisfy | fills following formula (1).
1.1 ≦ Φ · N _p · L _G · K _C ≦ 8.2 Formula (1)
(However, the scattering cross section of the scattering particles [Phi, distance L _G to face from the end face of the light guide _plate, the density of the scattering particles N _p, a correction coefficient is K _C, 0.005 said K _C ≦ K _C ≦ 0.1)

  In order to solve the second problem, a second form of the second aspect of the present invention includes a light guide plate according to any one of the second aspects of the first form, and a plurality of light sources. The light source is disposed on an end surface of the light guide plate in a direction perpendicular to the light exit surface in the extending direction of the parallel groove of the light guide plate and the parallel groove of the light guide plate. The present invention provides a planar illumination device that allows light to enter the light guide plate from an end surface.

  The light source disposed on the end face of the light guide plate in the extending direction of the parallel grooves is a plurality of LED elements arranged in a row, and the LED elements are the light sources disposed in the parallel grooves. It is preferable that they are arranged at different intervals according to the luminance of the light emitted from the light and incident on the light guide plate and emitted from the light exit surface.

  ADVANTAGE OF THE INVENTION According to this invention, the light incident from the parallel groove | channel and both end surfaces of a light-guide plate can reach | attain far more efficiently, and the incident light can be uniformly inject | emitted from a light-projection surface. That is, light with high luminance and little or no luminance unevenness can be emitted from the light exit surface. Furthermore, it is possible to increase the light exit surface while maintaining the thin shape.

In addition, according to the present invention, it is possible to provide a planar lighting device that is thin, has a large light exit surface, has high brightness from the light exit surface, and can emit light with little or no brightness unevenness. it can.
Furthermore, by adjusting the arrangement interval of the light sources, it is possible to further reduce the luminance unevenness, particularly the luminance unevenness in the direction perpendicular to the extending direction of the parallel grooves, and there is less luminance unevenness or no luminance unevenness. Light can be emitted from the light exit surface.

  A light guide plate according to the present invention and a planar illumination device of the present invention using the same will be described in detail based on embodiments shown in the accompanying drawings.

  FIG. 1 is a schematic perspective view showing an embodiment of the surface illumination device of the present invention and showing an appearance viewed from a light exit surface. FIG. 2 is a partial cross-sectional view of the planar illumination device 10 shown in FIG. FIG. 3 is a schematic perspective view showing only the periphery of the unit light guide plate 23 having one parallel groove 22b constituting the light guide plate 22 of the illumination device body 14 of the planar illumination device 10 shown in FIG. 4 is a schematic perspective view showing the light guide plate 22, FIG. 5A is a front view of one unit light guide plate 23 of the light guide plate 22, and FIG. 5B is a diagram of the unit light guide plate 23. FIG. 5C is a side view in the longitudinal direction, and FIG. 5C is a side view in the short direction of the unit light guide plate 23.

  As shown in FIG. 1, the planar illumination device 10 includes a plurality of light sources 12, an illumination device body 14 that emits uniform light from a rectangular light emission surface, and the illumination device body 14 inside. A housing 16 having a rectangular opening 16a formed on the light emitting surface 14a side (front surface side), and a plurality of linear shapes attached to the light emitting surface 14a opposite to the light emitting surface 14a (back surface side). A power source 18 is used to turn on each of the light sources 12.

Here, the illuminating device main body 14 is for emitting uniform light from the rectangular light emitting surface 14a, and basically includes a plurality of light sources as shown in FIGS. 12 and a flat and rectangular light exit surface 22a is formed on the light exit surface 14a side, and a plurality of parallel grooves 22b for accommodating the plurality of light sources 12 are formed on the back side thereof, and between the adjacent parallel grooves 22b. The thinnest portion 22c having the thinnest thickness from the light exit surface 22a toward the back side is formed, and from the end surface 22e in the extending direction of the parallel groove 22b toward the center, and from the end surface 22f toward the center, The light guide plate 22 is formed with a back surface 22d having an inclination such that the thickness in the direction perpendicular to the light output surface 22a is increased, and the light output surface 22a side of the light guide plate 22 is disposed to form a rectangular light output surface 14a. Rectangular flat It comprises the optical member unit 24, and a reflecting member 26 disposed along the rear surface 22d of the light guide plate 22 with.
3 shows only the unit light guide plate 23 having one parallel groove 22b which is one unit constituting the light guide plate 22, the illumination device main body 14 shown in FIG. As shown, the illuminating device main body 14 is a light guide plate 22 composed of a plurality of unit light guide plates 23, and the optical member unit 24 arranged on the upper portion of the light guide plate 22 is also connected to the light emitting surface 22 a of the light guide plate 22. It goes without saying that they have substantially the same size (area).

As shown in FIGS. 3 and 4, the light source 12 includes a first LED array 12 a disposed in the plurality of parallel grooves 22 b of the light guide plate 22, and a second LED array disposed to face the end surface 22 e of the light guide plate 22. 12b and a third LED array 12c disposed to face the end face 22f of the light guide plate 22.
The first LED array 12 a has a plurality of LED (light emitting diode) chips (LED elements) 13 a, and the LED chips 13 a are arranged in rows in the parallel grooves 22 b of the light guide plate 22 at a predetermined interval. That is, the first LED array 12a is arranged along the extending direction of the parallel grooves 22b.
The second LED array 12b includes a plurality of LED chips 13b, and the plurality of LED chips 13b are arranged in a row at a predetermined interval so as to face the end surface 22e of the light guide plate 22. That is, the 2nd LED array 12b is arrange | positioned along the longitudinal direction of the end surface 22e (parallel to one side of the light emission surface 22a).
The third LED array 12c has a plurality of LED chips 13c, and the plurality of LED chips 13c are arranged in a row and opposed to the end surface 22f of the light guide plate 22 at a predetermined interval. That is, the third LED array 12c is arranged along the longitudinal direction of the end face 22f (parallel to one side of the light exit surface 22a).
The LED chips 13a to 13c constituting the first LED array 12a, the second LED array 12b, and the third LED array 12c are each connected to a power source 18 (see FIG. 1).
The LED array and LED chip will be described in detail later.

As shown in FIG. 4, the light guide plate 22 includes a plurality of unit light guide plates 23.
4 and 5, the unit light guide plate 23 has a rectangular flat light exit surface 22a and a surface facing the light exit surface 22a (individual light exit surface 23a) in the extending direction of the parallel grooves 22b. And an end surface 22e and a back surface 22d having an inclination such that the thickness (thickness) in the direction perpendicular to the light exit surface 22a increases toward the center from the end surface 22f. That is, as shown in FIG. 5B, the unit light guide plate 23 has a shape perpendicular to the light exit surface 23a and parallel to the parallel grooves, with the end surface 22e and the end surface 22f parallel, and the back surface 22d facing the center. It is a pentagonal shape that becomes convex. That is, the back surface 22d has a shape that protrudes in a direction away from the light emission surface 23a on a surface perpendicular to the light emission surface 23a and parallel to the parallel grooves.
Further, as shown in FIG. 5C, the cross-sectional shape in the direction perpendicular to the parallel grooves 22b is a slope in which the light exit surface 22a is a flat straight line, and the back surface 22d becomes thinner as the distance from the parallel grooves 22b increases. It is the shape which has.
That is, as shown in FIGS. 5A to 5C, the unit light guide plate 23 includes a rectangular and flat individual light emitting surface 23a, a thick portion 23b parallel to one side thereof, and the thick wall. The thin end portions 23c formed in parallel to one side on both sides of the portion 23b, and the thickness is reduced from the thick portion 23b toward the thin end portions 23c on both sides in a direction orthogonal to one side, and the back surface 22d of the light guide plate 22 And a parallel groove 22b for accommodating the light source 12 formed parallel to one side of the thick part 23b. The parallel groove 22b The inclined surface 23d is inclined in the direction away from the individual light exit surface 23a (the direction in which the thickness of the unit light guide plate 23 is increased) from the end surface 22e and the end surface 22f toward the center.
That is, the unit light guide plate 23 includes one parallel groove 22b, and has an individual light exit surface 23a having the same length as the light exit surface 14a of the light guide plate 22 in a direction parallel to the parallel groove 22b. . The shape formed by the contour line of the cross section of the parallel groove 22a and the line connecting the end portions on the back surface side (hereinafter also referred to as “the shape of the parallel groove 22a”) is a triangle.

The light guide plate 22 (unit light guide plate 23) 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 22 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 22, Atsipearl, thin cone, silica, zirconia, dielectric polymer, or the like can be used. By including such scattering particles in the light guide plate 22, it is possible to emit uniform illumination light with little unevenness in brightness from the light exit surface.
Such a light guide plate 22 can be manufactured using an extrusion molding method or an injection molding method.

The scattering cross-sectional area of the scattering particles contained in the light guide plate 22 is Φ, the distance from the end surface of the light guide plate to the opposite surface, that is, from one end surface of the light guide plate to the other end surface in the direction in which the light emitted from the light source is incident ( The distance to the end face, that is, in the present embodiment, the direction in which light enters (the direction perpendicular to the end face 22e and the end face 22f of the unit light guide plate 23, exit from the second LED array 12b or the third LED array 12c). L _{G is} the length of the light guide plate in the optical axis direction of the light incident on the end face 22e or the end face 22f), N _p is the density (number of particles per unit volume) of the scattering particles contained in the light guide plate 22, and the correction coefficient is When K _C is set, the relationship that the value of Φ · N _p · L _G · K _C is 1.1 or more and 8.2 or less is satisfied. Since the light guide plate 22 includes scattering particles that satisfy such a relationship, it is possible to emit illumination light that is uniform and has less luminance unevenness from the light exit surface.

In the light guide plate 22 having the structure shown in FIGS. 4 and 5, the light emitted from the first LED array 12a arranged in the parallel groove 22d is incident on the inside of the light guide plate 22 from the side surface forming the parallel groove 22d. The reflected light is reflected by the inclined surface 23d of the light guide plate 22 and then emitted from the light exit surface 22a. At this time, a part of the light leaks from the lower surface of the light guide plate 22, but the leaked light is reflected by the reflecting member 26 formed on the inclined surface 23 d side of the light guide plate 22 and again inside the light guide plate 22. And exits from the light exit surface 22a.
Further, among the light emitted from the second LED array 12b and the third LED array 12c disposed on the end surface 22e and the end surface 22f, the light that has entered the light guide plate 22 from the end surface 22e and the end surface 22f enters the light guide plate 22 inside. While being scattered by the included scatterer (details will be described later), the light passes through the inside of the light guide plate 22 and is reflected from the inclined surface 23d as it is, and then exits from the light exit surface 22a. At this time, a part of the light may leak from the inclined surface 23d, but the leaked light is reflected by the reflecting member 26 arranged so as to cover the inclined surface 23d of the light guide plate 22, and again inside the light guide plate 22 Is incident on.
As described above, the light emitted from the light source 12 is incident from the parallel grooves 22b, the end surface 22e, and the end surface 22f, and is emitted as uniform light from the light exit surface 22a.

  In the present invention, in order to make the light emitted from the light exit surface 22a uniform, the angle of the inclined surface 23d (taper) so that the light beam can effectively reach the light exit surface 22a at a right angle and in a parallel direction (depth direction). ) Is restricted. That is, the angle (taper) of the inclined surface 23d in the direction perpendicular to the parallel groove 22d is set so that a part of the light beam emitted from the first LED array 12a and incident on the light guide plate 22 is totally reflected by the light exit surface 22a (back surface). At an angle.

  The optical member unit 24 makes the uniform illumination light emitted from the light emission surface 22a of the light guide plate 22 more uniform, and emits the illumination light with further improved uniformity from the light emission surface 14a of the illumination device body 14. 2 and 3, a microprism array parallel to the parallel grooves 22b of the light guide plate 22 constituting the light output surface 14a is formed and emitted from the light output surface 22a of the light guide plate 22. A prism sheet 24a that improves the light collection property of the illumination light and improves the brightness, and a microprism array perpendicular to the parallel grooves 22b of the light guide plate 22 are formed, and the collection of the illumination light emitted from the light exit surface 22a of the light guide plate 22 It has a prism sheet 24b that enhances lightness and improves luminance, and a diffusion sheet 24c that diffuses and equalizes the illumination light emitted from the light exit surface 22a of the light guide plate 22.

  The prism sheets 24a and 24b are transparent sheets formed by arranging a plurality of prisms in parallel. The prism sheets 24a and 24b can improve the luminance by improving the condensing property of light emitted from the light exit surface 22a of the light guide plate 22. it can. The prism sheet 24a is arranged so that the extending direction of the prism row is parallel to the parallel grooves 22b of the light guide plate 22, and the prism sheet 24b is arranged to be vertical. That is, the prism sheets 24a and 24b are arranged so that the extending directions of the prism rows are perpendicular to each other. The prism sheet 24 a is arranged so that the apex angle of the prism faces the light exit surface 22 a of the light guide plate 22. Here, the arrangement order of the prism sheets 24a and 24b is such that a prism sheet 24b having a prism extending in a direction orthogonal to the parallel groove 22b of the light guide plate 22 is disposed immediately above the light guide plate, and the prism sheet 24b is placed on the prism sheet 24b. Alternatively, a prism sheet 24 a having a prism extending in a direction parallel to the parallel groove 22 b of the light guide plate 22 may be disposed.

  In the illustrated example, a prism sheet is used, but a sheet in which optical elements similar to prisms are regularly arranged may be used instead of the prism sheet. In addition, a sheet that regularly includes an optical element such as a lens effect, for example, a lenticular lens, a concave lens, a convex lens, or a pyramid type can be used instead of the prism sheet.

As shown in FIGS. 2 and 3, the diffusion sheet 24c is disposed on the surface of the prism sheet 24b opposite to the surface on the light guide plate 22 side. The diffusion sheet 24c is formed by imparting light diffusibility to a film-like member. The film-like member is optically transparent, such as PET (polyethylene terephthalate), PP (polypropylene), PC (polycarbonate), PMMA (polymethyl methacrylate), benzyl methacrylate, MS resin, or COP (cycloolefin polymer). Can be formed into a material.
Although the manufacturing method of the diffusion sheet 24c is not particularly limited, for example, the surface of the film-like member is subjected to surface roughening by fine unevenness processing or polishing to impart diffusibility, or a pigment such as silica, titanium oxide, or zinc oxide, Alternatively, a material for scattering light such as resin, glass or beads such as zirconia is coated on the surface together with a binder, or the above pigment or beads for scattering light is mixed in the transparent resin. Formed with. In addition, it is possible to use a material having high reflectance and low light absorption, for example, using a metal such as Ag or Al.
In the present invention, as the diffusion sheet 24c, a mat type or coating type diffusion sheet can be used.

The diffusion sheet 24c may be arranged at a predetermined distance from the light exit surface 22a (or the prism sheet 24b) of the light guide plate 22, and the distance is appropriately determined according to the light amount distribution from the light exit surface 22a of the light guide plate 22. Can be changed.
Thus, by separating the diffusion sheet 24c from the light exit surface 22a of the light guide plate 22 by a predetermined distance, light emitted from the light exit surface 22a of the light guide plate 22 is further mixed between the light exit surface 22a and the diffusion sheet 24c. (Mixed). Thereby, the brightness | luminance of the light which permeate | transmits the diffusion sheet 24c and illuminates the liquid crystal display panel 4 can be made further uniform.
As a method of separating the diffusion sheet 24 c from the light exit surface 22 a of the light guide plate 22 by a predetermined distance, for example, a method of providing a spacer between the diffusion sheet 24 c and the light guide plate 22 can be used.

  In addition to the arrangement of the optical member 24, or in place of the arrangement of the optical member 24, it is preferable to process the light exit surface 22a of the light guide plate 22 so that the light exit surface 22a has a light diffusion effect. Specifically, light uniformity is further improved by forming fine irregularities such as prisms on the light exit surface 22a, making the light exit surface 22a a sand-printed surface, and printing halftone dots on the light exit surface 22a. Can be made.

The reflecting member 26 used in the illuminating device main body 14 is disposed along the back surface 22 d of the light guide plate 22 to improve the utilization efficiency of the illumination light emitted from the light source 12, and the parallel grooves 22 b of the light guide plate 22. Is disposed along the back surface 22d of the light guide plate 22 excluding the parallel grooves 22b on the back side where the light guide plate 22 is formed, and reflects the light leaking from the back surface of the light guide plate 22 so as to be incident on the light guide plate 22 again. The light guide plate 22 is disposed on the back surface of the light source 12 so as to block the parallel grooves 22b of the light guide plate 22 between the reflecting sheets 26a. The light is reflected from the lower surface of the light source 12, and is reflected from the side wall surfaces of the parallel grooves 22b of the light guide plate 22. And a reflector 26b for allowing light to enter.
The illumination device body 14 is basically configured as described above.

  On the other hand, as shown in FIG. 3, the housing 16 accommodates and supports the illuminating device main body 14, and is sandwiched and fixed from the light emitting surface 14a side and the reflecting member 26 side, and the upper surface is open. The lighting device main body 14 is housed and supported from above, and the lower housing 30 that covers the four side surfaces thereof, and the opening 16a on the upper surface that is smaller than the rectangular light emitting surface 14a of the lighting device main body 14 are provided. A rectangular opening is formed, the lower surface is opened, and the upper housing 32 is covered from above so as to cover the light guide plate assembly 14 and the lower housing 30 in which the light guide plate assembly 14 is housed, including its four side surfaces. A concave (U-shaped) folding member 34 fitted between the side wall of the lower housing 30 and the side wall of the upper housing 32, and the rear surface 22 d of the light guide plate 22. Is supported by the reflecting member 26, and the lighting device is And a light guide plate supporting member 36 which also supports the entire body 14. Although not shown in FIG. 3, a power source 18 is attached to the back side of the lower housing 30.

Here, as a method for joining the lower housing 30 and the folding member 34, and a method for joining the folding member 34 and the upper housing 32, various methods such as a method using bolts and nuts, a method using an adhesive, and the like can be used. Can be used.
The upper housing 32 is larger than the lower housing 30 and at least outer wall surfaces at both ends of the lower housing 30 parallel to the parallel grooves 22b of the light guide plate 22 of the illuminating device body 14 or the linear light source 12 housed therein. The folding member 34 needs to be disposed in each gap between the inner wall surface of the upper casing 32 and the upper casing 32 opposed to the lower casing 30 on the four side surfaces of the casing 16. It may be arranged between the side wall of the upper housing 32 and the side wall of the upper housing 32. Moreover, it is preferable to attach the reinforcement member which reinforces the recessed part of the concave folding member 34. FIG.
By disposing the folding member 34 in this way, the rigidity of the housing 16 can be increased, and light can be emitted uniformly and efficiently. On the other hand, the light guide plate 22 is likely to warp due to the presence of the parallel grooves 22b. Even so, it is possible to correct the warp or prevent the light guide plate 22 from warping, and to obtain good optical characteristics without causing uneven brightness. Moreover, the rigidity of the housing | casing 16 can be made higher by attaching the reinforcement member which reinforces the recessed part of the folding | turning member 34, and it can prevent more appropriately that the light guide plate 22 warp. Thereby, better optical characteristics can be obtained.

  The light guide plate support portion 36 is formed of a resin such as polycarbonate. In the illustrated example, the light guide plate support portion 36 is a convex member having a shape obtained by reversing the shape of the back surface 22d of the thinnest portion 22c of the light guide plate 22, It is arranged along the back surface 22 d of the light guide plate 22 at the bottom of the body 30.

Note that the housing 16 is provided with a fastener such as an L-shaped metal fitting that joins the four corners, or between the diffusion sheet 24 c of the planar device main body 14 and the peripheral edge of the opening 16 a of the upper housing 30. An elastic member made of an elastic material such as rubber or a protective member for protecting the entire upper surface of the diffusion sheet 24c of the planar apparatus main body 14 may be provided.
The housing 16 is basically configured as described above.

The power source 18 is connected to the LED chips 13a, 13b, 13c of the first to third LED arrays 12a, 12b, 12c of the light source 12, and supplies a predetermined voltage to the LED chips 13a, 13b, 13c.
The planar illumination device 10 that is the planar illumination device of the present invention using the light guide plate of the present invention is basically configured as described above.

  This planar illumination device 10 is emitted from the light source 12, and light incident on the light guide plate 22 through the parallel grooves 22b, the side surface 22e, and the side surface 22f is emitted from the light exit surface 22a. The light emitted from the light exit surface 22a of the light guide plate 22 passes through the optical member unit 24, and high-luminance and uniform light is emitted from the light exit surface 14a.

Thus, the light guide plate 22 has a shape in which the parallel grooves 22b are formed on the surface facing the light exit surface, the thickness is reduced as the distance from the parallel grooves increases, and the thickness is increased from the end surface toward the center, The first to third LED arrays 12a, 12b, and 12c are arranged in the parallel grooves 22b, the end surface 22e, and the end surface 22f of the light guide plate 22, respectively. In addition, light with no uneven brightness can be emitted from the light exit surface.
In addition, by increasing the thickness of the light guide plate from the end face toward the center, the light incident from the end face can reach a farther position, and by reducing the thickness as the distance from the parallel groove increases, the parallel groove Can be reliably emitted from the light exit surface.

  In the present embodiment, the shape of the parallel groove is a triangle, but is not limited to this, and can be various shapes such as a hyperbola, an ellipse, a parabola, a U-shape or a combination thereof, and the present application relates to the application. Those disclosed in [0040] to [0058] of JP-A-2005-23497 can also be applied.

  In addition, the shape of the inclined surface of the light guide plate may be formed as a curved surface as in the present embodiment as long as the thickness decreases as the distance from the parallel groove increases, and the inclination angle with respect to the individual light exit surface is constant. It may be formed from a plurality of planes whose inclination angle gradually changes.

In addition, if the back surface of the light guide plate in the direction parallel to the extending direction of the parallel grooves and perpendicular to the light emitting surface is shaped so as to increase in thickness from the end surface toward the center, the individual light emitting is performed as in this embodiment. It may be formed by two straight lines having a constant inclination angle with respect to the surface, may be formed by two curved lines, or may be formed by a plurality of straight lines whose inclination angles gradually change.
It is preferable that the back surface has a symmetrical shape with an axis passing through the center of the light guide plate and perpendicular to the extending direction of the parallel grooves. By making the back surface symmetrical, more uniform light can be emitted from the light exit surface.

  In addition, although the scattering particles are kneaded and dispersed on the light guide plate 22, the present invention is not limited to this, and prisms are formed on the light exit surface 22 a and / or the back surface 22 d of the light guide plate 22 to form the light guide plate 22. Even if the incident light is scattered, a dot pattern such as a halftone dot sheet may be formed on the light exit surface 22a and / or the back surface 22d of the light guide plate 22 by printing to scatter the light incident on the light guide plate 22.

  In this embodiment, the light guide plate has a shape in which two unit light guide plates are connected, but the number of unit light guide plates to be connected is not particularly limited. By increasing the number of unit light guide plates to be connected, it is possible to increase the size without increasing the thickness of the light guide plate.

In the present embodiment, the LED chips of the second LED array and the third LED array arranged on the end face of the light guide plate are arranged at equal intervals. However, the luminance of the light incident from the parallel groove and emitted from the light exit surface is increased. Accordingly, it is preferable to adjust the arrangement interval, that is, to arrange them at different intervals.
By adjusting the arrangement interval of the LED chips arranged on the end face of the light guide plate, the luminance unevenness of the light emitted from the light exit surface can be further reduced.

Further, the light source is not limited to the LED array using the LED chip, and a light source in which semiconductor lasers are arranged in a row can also be used.
Further, the light source is not limited to a light source in which a plurality of light emitting elements are arranged in a line, and a linear light source such as a cold cathode tube (CCFL), a normal fluorescent tube, a hot cathode tube (HCFL), an external electrode tube (EEFL) is also used. be able to.
Here, when a linear light source such as a cold-cathode tube is used as the light source, the incident light amount adjusting member such as a film whose transmittance is adjusted according to the luminance of the light incident from the parallel groove and emitted from the light exit surface By sticking to the linear light source or arranging it on the end face, the luminance unevenness of the light emitted from the light exit surface can be further reduced in the same manner as described above.

Moreover, in the said embodiment, although the shape of the light-guide plate 22 was made into the shape which thickness becomes thick as it goes to the center from the end surface 22e and the end surface 22f, it is not limited to this.
FIG. 6 is a schematic perspective view showing a configuration example of the illuminating device main body 62 in which the light source is arranged only in the parallel groove and one end surface of the light guide plate. The illuminating device main body 62 shown in FIG. 6 includes a light source 64, a light guide plate 66, an optical member unit 68, and a reflecting member 70.

The light guide plate 66 is formed with a back surface 66d which is a surface opposite to the light exit surface 66a and a plurality of parallel grooves 66b which are formed in parallel with each other at a predetermined interval on a surface opposite to the light output surface 66a. That is, the light guide plate 66 is configured by connecting a plurality of unit light guide plates 67 having one parallel groove 66b in the same manner as the light guide plate 22 described above.
The cross-sectional shape of the unit light guide plate 67 in the direction perpendicular to the parallel grooves 66b is the same shape as the light guide plate 22 described above, and the shape of the unit light guide plate 67 in the extending direction of the parallel grooves 66d is the extension of the parallel grooves 66d. The back surface 66d is inclined so that the thickness in the direction perpendicular to the light exit surface 66a increases from one end surface 66e in the direction parallel to the existing direction to the other end surface 66f. That is, the sectional shape of the unit light guide plate 67 (light guide plate 66) in the direction perpendicular to the light exit surface 66a and parallel to the parallel groove 66b is such that the end surface 66e and the end surface 66f are parallel, and the angle formed by the end surface 66e and the light output surface 66a. In addition, each of the angles formed by the end surface 66f and the light exit surface 66a is a trapezoidal shape that is a right angle.

  The light source 64 includes a plurality of first LED arrays 64a and second LED arrays 64b. The first LED array 64a is disposed in the parallel groove 66b, and the second LED array 64b is disposed to face the end surface 66e.

  The optical member unit 68 includes two prism sheets 68a and 68b and a diffusion sheet 68c. Since the optical member unit 68 has the same configuration as the optical member unit 24 described above, a detailed description thereof will be omitted.

The reflection member 70 is for improving the utilization efficiency of the illumination light emitted from the light source 64 as in the case of the reflection member 26 described above. The reflection member 70 is a reflection disposed along the back surface 64d of the light guide plate 64 excluding the parallel grooves 64b. The film 70a and the reflector 70b arrange | positioned at the back surface of the light source 12 so that each parallel groove | channel 64b of the light-guide plate 22 may be plugged up are provided.
Although not shown, the planar lighting device 60 further includes a housing that houses and supports the lighting device main body 62 and a power source connected to the light source. This is the same as the lighting device 10.
The illumination device main body 62 is basically configured as described above.

Of the light emitted from the first LED array 64a, the light incident on the inside of the light guide plate 66 from the side surface forming the parallel groove 66d is reflected by the inclined surface of the light guide plate 66 and then emitted from the light exit surface 66a. At this time, a part of the light leaks from the lower surface of the light guide plate 66, but the leaked light is reflected by the reflecting member 70 formed on the inclined surface side of the light guide plate 66 and again enters the light guide plate 66. Incident light is emitted from the light exit surface 66a.
Further, among the light emitted from the second LED array 64b disposed on the end surface 66e, the light incident on the light guide plate 66 from the end surface 66e is scattered by a scatterer (details will be described later) included in the light guide plate 66. The light passes through the inside of the light guide plate 66 while being scattered, and is emitted from the light exit surface 66a as it is or after being reflected by an inclined surface. At this time, a part of light may leak from the inclined surface, but the leaked light is reflected by the reflecting member 70 arranged so as to cover the inclined surface of the light guide plate 66 and is incident on the inside of the light guide plate 66 again. To do.
As described above, the light emitted from the light source 64 enters the parallel groove 66b and the end face 66e, and is emitted as uniform light from the light exit surface 66a.

Here, in the light guide plate of the present embodiment, scattering particles are kneaded and dispersed in transparent resin, the scattering cross-sectional area of the scattering particles contained in the light guide plate 66 is Φ, the distance from the end surface of the light guide plate to the opposite surface, that is, the light source The distance from one end surface of the light guide plate to the other end surface (the surface facing the end surface) in the direction in which the light emitted from the light enters, that is, in this embodiment, the direction in which the light enters (of the unit light guide plate 67 The length of the light guide plate in the direction perpendicular to the end face 66e and the end face 66f, the optical axis direction of the light emitted from the second LED array 64b and incident on the end face 66e) is L _G , and the density (unit) of the scattering particles contained in the light guide plate 66 When the number of particles per volume) is N _p and the correction coefficient is K _C , the value of Φ · N _p · L _G · K _C is 1.1 or more and 8.2 or less. Satisfies. Since the light guide plate 66 includes scattering particles that satisfy such a relationship, it is possible to emit illumination light that is uniform and has less luminance unevenness from the light exit surface.

  As described above, the planar illumination device in which the light source is disposed only in the parallel groove and one end face can also emit uniform and high-luminance light from the light exit surface.

In the illuminating device main body 62 shown in FIG. 6, a light source is disposed only on one end surface 66e, and a light source is not disposed on the other end surface 66f. That is, since LED light is incident only from one end face 66e, not from both end faces, a part of the light from the LED that has passed through the light guide 66 reaches the opposite end face 66f. Become.
In order to reflect the light from such an LED at its end face 66f and make it enter the light guide again, the end face 66f is processed into a mirror surface, or a reflection plate is provided so as to cover the end face 66f. Also good.

Next, the LED array that can be used for the light source 12 of the planar illumination device 10 will be described in detail.
7A is a schematic perspective view of the configuration of the second LED array 12b, FIG. 7B is a schematic top view of the configuration of the LED chip 13b, and FIG. 7C is a configuration of the multilayer LED array 82. FIG. 7D is a schematic side view of an embodiment of the heat sink 80.
The LED chip 13b is a monochromatic LED configured to convert light emitted from the LED into white light using a fluorescent material. For example, when a GaN blue LED is used as a single color LED, white light can be obtained by using a YAG (yttrium, aluminum, garnet) fluorescent material.

The heat sink 80 is a plate-like member parallel to one side of the light guide plate 22, and is disposed to face the light guide plate 22. The heat sink 80 supports a plurality of LED chips 13 b on the surface facing the light guide plate 22. The heat sink 80 is formed of a metal having good thermal conductivity such as copper or aluminum, and absorbs heat generated from the LED chip 13b and dissipates it to the outside.
The heat sink 80 preferably has a shape in which the length in the direction perpendicular to the surface facing the light guide plate 22 is longer than the length in the short side direction of the surface facing the light guide plate 22 as in this embodiment. . Thereby, the cooling efficiency of LED chip 13b can be improved.
Here, the heat sink 80 preferably has a large surface area. For example, as shown in FIG. 7D, the heat sink 80 may be composed of a base portion 80a that supports the LED chip 13b and a plurality of fins 80b connected to the base portion 80a.
By providing a plurality of fins 80b, the surface area can be increased and the heat dissipation effect can be enhanced. Thereby, the cooling efficiency of LED chip 13b can be improved.
The heat sink is not limited to the air cooling method, and a water cooling method can also be used.
In this embodiment, the heat sink is used as the support portion of the LED chip. However, the present invention is not limited to this, and when cooling of the LED chip is not necessary, a plate-like member having no heat dissipation function is used as the support portion. It may be used.

Here, as shown in FIG. 7B, the LED chip 13b 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 in the arrangement direction of the LED chip 13b, that is, described later. The light guide plate 22 has a rectangular shape in which the thickness direction (direction perpendicular to the light exit surface 22a) is a short side. In other words, the LED chip 13b has a shape in which b> a, where a is the length perpendicular to the light exit surface 22a of the light guide plate 22 and b is the length in the arrangement direction. Further, when the arrangement interval of the LED chips 13b is p, p> b. As described above, the relationship between the length a in the direction perpendicular to the light exit surface 22a of the light guide plate 22 of the LED chip 13b, the length b in the arrangement direction, and the arrangement interval p of the LED chips 13b satisfies p>b> a. preferable.
By making the LED chip 13b rectangular, 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, since the LED chip can make the LED array thinner, it is preferable that the LED chip has a rectangular shape with a short side in the thickness direction of the light guide plate. However, the present invention is not limited to this, and the square shape, circular shape, LED chips having various shapes such as a rectangular shape and an elliptical shape can be used.

  In the present embodiment, the LED array is a single layer, but the present invention is not limited to this, and as shown in FIG. 7C, a multilayer LED array 82 having a configuration in which a plurality of LED arrays 24 are stacked. Can also be used as a light source. Even when LEDs are stacked in this way, more LED arrays can be stacked by making the LED chip rectangular and thinning the LED array. By stacking the multilayer LED arrays, that is, by increasing the filling rate of the LED arrays (LED chips), a larger amount of light can be output. 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.

A ball lens is disposed as a coupling lens 28 on the light emission side of each LED chip 13 b of the LED array 24. The coupling lens 28 is disposed corresponding to each LED chip 13b. The light emitted from each LED chip 13b is collimated by the coupling lens 28 and enters a light mixing portion (not shown) of the light guide plate 22.
Here, the ball lens is used as the coupling lens. However, the present invention is not limited to this, and the coupling lens is not particularly limited as long as the light emitted from the LED can be converted into parallel light. As the coupling lens, for example, a cylindrical lens, a lenticular, a kamaboko type lens, a Fresnel lens, or the like can be used.

  In the said embodiment, although LED which light-emits white light was used, this invention is not limited to this. For example, white light can be obtained by using LEDs of three colors of red, green, and blue and mixing the light emitted from each LED by a coupling lens.

Below, an example of the light source using the LED array comprised by LED of three colors is demonstrated. FIG. 8 is a schematic configuration diagram of a light source using an LED array composed of three color LEDs.
The light source 90 includes an LED array 92 and a coupling lens 94. In the LED array 92, a plurality of RGB-LEDs 94 formed by using three types of light-emitting diodes of red, green, and blue (hereinafter referred to as R-LED 96, G-LED 98, and B-LED 99, respectively) are arranged in a line. It is configured. FIG. 8 schematically shows how the plurality of RGB-LEDs 94 are arranged. As shown in FIG. 8, R-LED 96, G-LED 98, and B-LED 99 are regularly arranged.
Further, as shown in FIG. 9, the RGB-LED 94 includes three types of LEDs (R-LED 96, G-type) so that light emitted from the R-LED 96, G-LED 98, and B-LED 100 intersects at predetermined positions. -The orientation of the optical axis of the LED 98 and B-LED 99) is adjusted. By adjusting the three types of LEDs in this way, the light from these LEDs is mixed into white light.
The RGB-LED 94 constituted by using three primary color LEDs (R-LED 96, G-LED 98 and B-LED 99) has a color reproduction region as compared with a cold cathode tube (CCFL) conventionally used as a light source for a backlight. Therefore, when this RGB-LED 94 is used as a light source for backlight, color reproducibility is higher than in the prior art and a vivid color image can be displayed.

As shown in FIGS. 8 and 9, three ball lenses 102, 104, and 106 are arranged as coupling lenses 100 on the light emission side of each LED of the RGB-LED 94. Ball lenses 102, 104, and 106 are arranged corresponding to the respective LEDs. That is, three ball lenses 102, 104, and 106 are used in combination for one RGB-LED 94. Light emitted from each LED (R-LED 96, G-LED 98 and B-LED 99) is collimated by ball lenses 102, 104 and 106. Then, after intersecting at a predetermined position to be white light, it is incident on a light mixing portion (not shown) of the light guide plate 22. A coupling lens using a combination of the three ball lenses 102, 104, and 106 is a lens having three axes, and the light of each LED of RGB-LED can be narrowed down to one point and mixed.
Here, the ball lens is used as the coupling lens. However, the present invention is not limited to this, and the coupling lens is not particularly limited as long as the light emitted from the LED can be converted into parallel light. As the coupling lens, for example, a cylindrical lens, a lenticular, a kamaboko type lens, a Fresnel lens, or the like can be used.

Further, the light emitted from each LED or each LED chip of the LED array may be guided to the light guide plate using the light guide without arranging the LED array so as to face the end surface 22e and / or the end surface 22f of the light guide plate 22. Good. The light guide can be configured using an optical fiber, a light guide made of a transparent resin, or the like.
When an LED array is used as the light source and the LED array is disposed in the vicinity of the side surface of the light guide plate 22, the light guide plate 22 may be deformed or melted by the heat generated by the LEDs constituting the LED array. Therefore, the LED array is disposed at a position away from the side surface of the light guide plate 22, and light emitted from the LEDs is guided to the light guide plate 22 using a light guide, thereby preventing the light guide plate 22 from being deformed and melted due to the heat generated by the LEDs. be able to.

Here, in the above-described embodiment, the LED array is described as the LED array 12b in which the LED array is disposed on the end surface of the light guide plate. However, in the case of the LED array disposed in the parallel groove of the light guide plate, the LED array having the same configuration may be used. it can.
When the LED array having the above configuration is arranged in the parallel groove, it is possible to reduce the arrangement space by reducing the size of the heat sink or making it wide in the direction parallel to the light emitting surface. Can be made thin.
In addition, the LED array arrange | positioned in the parallel groove | channel of a light-guide plate is not limited above, LED of various characteristics can be used.

  As described above, the light guide plate and the planar lighting device using the light guide plate according to the present invention have been described in detail. However, the present invention is not limited to the above-described embodiments, and various improvements and modifications can be made without departing from the gist of the present invention. Of course, you may do it.

It is a schematic perspective view which shows the external appearance seen from the light-projection surface side of one Embodiment of the planar illuminating device of this invention. It is a fragmentary sectional view of one Embodiment of the planar illuminating device shown in FIG. It is a schematic perspective view of the illuminating device main body corresponding to one unit light-guide plate used for the planar illuminating device shown in FIG. It is a schematic perspective view which shows the light source and light-guide plate of the planar illuminating device shown in FIG. (A)-(C) are the front views, the side view of a longitudinal direction, and the side view of a transversal direction of one unit light guide plate of the light guide plate shown in FIG. 4, respectively. It is a schematic diagram of the illuminating device main body corresponding to one unit light-guide plate used for the planar illuminating device of other embodiment of this invention. (A) is a schematic perspective view which shows one Example of a structure of the LED array used for the light source of the planar illuminating device shown in FIG. 2, (B) is the LED chip of the LED array shown to (A) FIG. 2C is a schematic front view showing a configuration of a multilayer LED array using the LED array of FIG. 1A, and FIG. 3D is a schematic side view showing an embodiment of a heat sink. . It is a figure which shows typically the mode of arrangement | positioning of several RGB-LED comprised using three types of light emitting diodes of red, green, and blue. It is a schematic diagram of RGB-LED and a coupling lens.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10, 60 Planar illuminating device 12, 64 Light source 12a, 64a 1st LED array 12b, 64b 2nd LED array 12c 3rd LED array 13a, 13b, 13c LED chip 14, 62 Illuminating device main body 14a Light-emitting surface 16 Housing | casing 16a Opening part 18 Power supply 22, 66 Light guide plate 22a, 66a Light exit surface 22b, 66b Parallel groove 22c, 66c Thinnest part 22d, 66d Back surface 22e, 22f, 66e, 66f End face 23 Unit light guide plate 23a, 67a Individual light exit surface 23b Thick part 23c Thin end portion 23d Inclined surface 23e Inclined back surface portion 24, 68 Optical member unit 24a Diffusion sheet 24b, 24c Prism sheet 26, 70 Reflective member 26a Reflective film 26b Reflector 30 Lower housing 32 Upper housing 34 Folding member 36 Light guide plate support Element

Claims (8)

A flat light exit surface,
A surface facing the light exit surface;
A plurality of parallel grooves formed in parallel to be spaced apart from each other by a predetermined distance on a surface facing the light exit surface;
In the direction orthogonal to the extending direction of the parallel grooves, the surface facing the light emitting surface becomes thinner in the direction perpendicular to the light emitting surface as the distance from the parallel grooves increases, and the extending direction of the parallel grooves The light guide plate has a shape that is inclined so that the thickness in the direction perpendicular to the light exit surface increases from the end face toward the center in a direction parallel to the end face. Furthermore, it has scattering particles that scatter light propagating inside,
The light guide plate according to claim 1, wherein the scattering particles satisfy the following formula (1).
1.1 ≦ Φ · N _p · L _G · K _C ≦ 8.2 Formula (1)
(However, the scattering cross section of the scattering particles [Phi, distance L _G to face from the end face of the light guide _plate, the density of the scattering particles N _p, a correction coefficient is K _C, 0.005 said K _C ≦ K _C ≦ 0.1) The light guide plate according to claim 1 or 2,
A plurality of light sources,
The said light source is a planar illuminating device which is arrange | positioned at the end surface of the extension direction of the parallel groove of the said light guide plate and the said light guide plate, and makes light inject into the said light guide plate from the said parallel groove and the said end surface. The light source arranged on the end face of the light guide plate in the extending direction of the parallel grooves is a plurality of LED elements arranged in a row,
4. The surface according to claim 3, wherein the LED elements are arranged at different intervals according to the luminance of light emitted from the light source arranged in the parallel groove, incident on the light guide plate, and emitted from the light exit surface. Illuminator. A flat light exit surface,
A surface facing the light exit surface;
A plurality of parallel grooves formed in parallel to be spaced apart from each other by a predetermined distance on a surface facing the light exit surface;
In the direction orthogonal to the extending direction of the parallel grooves, the surface facing the light emitting surface becomes thinner in the direction perpendicular to the light emitting surface as the distance from the parallel grooves increases, and the extending direction of the parallel grooves The light guide plate has a shape that is inclined so that the thickness in the direction perpendicular to the light exit surface increases from one end face to the other end face in a direction parallel to the first end face. Furthermore, it has scattering particles that scatter light propagating inside,
The light guide plate according to claim 5, wherein the scattering particles satisfy the following formula (1).
1.1 ≦ Φ · N _p · L _G · K _C ≦ 8.2 Formula (1)
(However, the scattering cross section of the scattering particles [Phi, distance L _G to face from the end face of the light guide _plate, the density of the scattering particles N _p, a correction coefficient is K _C, 0.005 said K _C ≦ K _C ≦ 0.1) The light guide plate according to claim 5 or 6,
A plurality of light sources,
The light source is disposed on an end surface on a side where the thickness in the direction perpendicular to the light exit surface is thin in the extending direction of the parallel groove of the light guide plate and the parallel groove of the light guide plate, and the parallel groove and the one end surface A planar illumination device that makes light incident on a light guide plate. The light source arranged on the end face of the light guide plate in the extending direction of the parallel grooves is a plurality of LED elements arranged in a row,
8. The surface according to claim 7, wherein the LED elements are arranged at different intervals according to the luminance of light emitted from the light source arranged in the parallel groove, incident on the light guide plate, and emitted from the light exit surface. Illuminator.

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