JP2006318754A - Transmissivity adjuster unit, planar illumination device, and liquid crystal display device using planer illumination device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thin and light transmissivity adjuster unit capable of reducing unevenness of brightness without reducing average brightness of incident light and without generating color irregularity. <P>SOLUTION: The transmissivity control unit has a light transmissive optical member and many transmissivity control units arranged on a surface of the optical member, of which transmissivity of the incident light is different in correspondence with its position. The transmissivity adjustor units are distributed on the surface of the optical member with a prescribed pattern, and a* and b* at C1EL*a*b* color space fulfills -2.0≤a*≤2.0, and b*=k×ln(T)+17. In formula, k fulfills -2.0≤k≤-1.7, and T is a color temperature of the incident light. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a transmittance adjusting body unit in which the transmittance of incident light differs depending on the position, a planar illumination device that emits light emitted from a light source from a light exit surface, and a liquid crystal display device using the same.

  A liquid crystal display device uses a backlight unit that irradiates light from the back side of a liquid crystal panel (LCD) to illuminate the liquid crystal panel. As the backlight unit, a light source for illumination, a light guide plate that diffuses light emitted from the light source and irradiates the liquid crystal panel, and a prism sheet or a diffusion sheet that uniformizes light emitted from the light guide plate are used. The configuration is known (see Patent Document 1, Patent Document 2, Patent Document 3 and Patent Document 4).

FIG. 20 is a schematic sectional view showing the surface light source device disclosed in Patent Document 1.
In the surface light source device (backlight unit) shown in the figure, after the fluorescent lamp 102 is embedded in the light guide plate 100, the reflection sheet 104 is disposed on the back surface of the light guide plate 100, and the transmitted light amount correction sheet is provided on the exit surface of the light guide plate 100. 106, a light diffusion plate 108, and a prism sheet 110 are laminated.
The light guide plate 100 has a substantially rectangular shape and is formed using a resin in which fine particles that diffuse illumination light are dispersed and mixed. In addition, the upper surface of the light guide plate 100 is flat and assigned to the exit surface. Further, a groove 100a having a U-shaped cross-section for embedding the fluorescent lamp 102 is formed on the back surface (surface opposite to the emission surface) of the light guide plate 100, and the emission surface of the light guide plate 100 is directly above the fluorescent lamp 102. Avoiding this, a light amount correction surface 100b that prompts emission of illumination light is formed.

  As described above, in Patent Document 1, the light guide plate 100 is formed by mixing fine particles, and the illumination light is corrected by the light amount correction surface 100b formed on a part or all of the emission surface except directly above the fluorescent lamp 102. It is described that by promoting the emission, the entire thickness can be reduced and unnatural luminance unevenness of the emitted light can be reduced.

Patent Document 2 discloses a backlight of a liquid crystal display device that can realize a reduction in size and weight of the liquid crystal display device and reduction in cost and power consumption 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 at the center of the short side, and a groove with a rectangular cross-section for inserting the light source, facing both sides of the long side across this groove A light guide plate having a back surface formed so that the plate thickness is gradually reduced is disclosed.
Further, in Patent Document 3, the frame of the liquid crystal display device can be narrowed and the thickness can be reduced, and in order to obtain a bright backlight unit with good light utilization efficiency, the width direction of the concave portion for arranging the light source is described. A light guide (light guide plate) is disclosed in which the parallel cross-sectional shape is a parabolic shape with the depth direction as the main axis.

  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 disclosed 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.

However, in any of the above light guide plates, uneven brightness occurs in the illumination light emitted from the emission surface.
For example, in the light guide plate 100 disclosed in Patent Document 1, a light source (fluorescent lamp) 102 is embedded in a groove 100a having a circular cross-sectional shape, and a luminance peak due to the light source 102 remains as it is as shown in FIG.
Therefore, for use as a planar light source device, an unnatural luminance unevenness on the exit surface is obtained using the transmitted light amount correction sheet 106, the light diffusion plate 108, the prism sheet 110, and the like disposed on the exit surface side of the light guide plate 100. Has been removed.

The transmitted light amount correction sheet 106 is formed by forming a fine metal film dot pattern on a transparent polyester film. Further, this dot pattern is formed so as to be densest right above the fluorescent lamp 102 and to decrease as the distance from the fluorescent lamp increases. Thereby, the transmitted light amount correction is partially reflected and returned to the inside of the light guide plate, and the light amount distribution of the transmitted light is made uniform.
The light diffusion plate 108 is formed of a translucent milky white acrylic plate, diffuses the light emitted from the transmitted light amount correction sheet 106, and emits the light with a desired light amount distribution.
The prism sheet 110 is a light control member that corrects the directivity of emitted light, and is formed of a translucent sheet material such as polycarbonate. A prism surface is formed on the side surface opposite to the light guide plate 100. This prism surface is formed by repeating protrusions having a triangular cross section extending substantially parallel to one direction. Thereby, the prism sheet 110 corrects the main emission direction of the emitted light to the front direction of the emission surface at the slope of the triangular protrusion.

  As described above, in Patent Literature 1, uniform emission light emitted from the emission surface of the light guide plate 100 is diffused using the light amount correction sheet 106, the light diffusion plate 108, and the prism sheet 110. It is said that it can emit light.

Various methods have been proposed as methods for reducing the uneven brightness of light emitted from the light guide plate (see Patent Document 5, Patent Document 6, Patent Document 7, Patent Document 8, and Patent Document 9).
For example, in Patent Document 5, as shown in FIG. 14, a dot-like printing portion that blocks light transmission is formed on the surface, and the cold cathode fluorescent lamp 36 is positioned directly below the density of the printing portion. There is disclosed a liquid crystal display device having a diffusion plate that is dense in a region 39A and is made sparse as it gets away from the region 39A. With such a diffusion plate, the amount of light emitted to the diffusion plate side is supposed to be uniform over the entire surface of the diffusion plate.

Patent Document 6 discloses a surface light source device in which a light amount adjustment layer for reflecting and scattering a part of light emitted from the upper surface on a surface facing a line light source and returning it to the light guide plate is disclosed. Yes. It is described that the light amount adjustment layer may be formed so that the area ratio decreases as the distance from the line light source increases, or may be formed only in the vicinity of the line light source. In addition, as a material for the transparent flat plate, a translucent resin or film is used, but a light diffusion plate may be used to smooth the intensity distribution of light emitted from the light guide plate and the line light source to the upper surface. It is said to be good.
Patent Document 7 discloses a light diffusing plate in which a continuous mesh pattern white or white translucent ink layer is provided on one surface.

  Further, in Patent Document 8, at least the luminance distribution of the light exit surface of the backlight unit without the bright line prevention unit is measured, and the data obtained by reversing the gradation of the measurement data is used as the bright line prevention unit. An optical member in which an inverted image of the luminance distribution is printed on a light guide plate or in an optical sheet shape is disclosed. Also disclosed is an optical member on which an inverted image formed by reversing the gradation of data obtained by simultaneously measuring the chromaticity distribution in addition to the luminance distribution is printed as the bright line prevention unit. It is also disclosed that white ink is used for the bright line distribution image.

  Further, Patent Document 9 includes titanium dioxide and barium sulfate as main components as a diffusion plate for a direct backlight with little luminance unevenness and a low color temperature reduction rate, and the titanium dioxide and the barium sulfate. A diffusion plate is disclosed in which an ink layer using an ink having a weight ratio of 5: 1 to 1: 1 is formed.

Japanese Patent Laid-Open No. 9-304623 JP-A-8-62426 JP 10-1333027 A JP-A-5-249320 JP-A-5-127156 JP-A-6-235823 JP-A-6-138308 JP 2004-170698 A JP 2000-164411 A

  Generally, luminance unevenness generated in light emitted from the exit surface of the light guide plate can be reduced by adding a diffusion plate. However, in order to reduce luminance unevenness, it is necessary to use a sufficiently thick (about 5 mm) plate-like thing, and as a result, it becomes thick and heavy as a planar lighting device.

On the other hand, the light amount correction sheet 106 disclosed in Patent Document 1, the dot-shaped printing unit that blocks light transmission on the surface disclosed in Patent Document 5, the light amount adjustment layer disclosed in Patent Document 6, and Patent Document The luminance unevenness can be reduced to some extent by partially disposing members having different transmittances such as the continuous mesh ink layer disclosed in FIG.
However, when a member having a different transmittance is partially disposed on the light exit surface, there is a problem that uneven color may occur in the emitted light.

  Further, Patent Document 8 creates a tone-reversed image based on data obtained by reversing the tone of measurement data, that is, creates a tone-reversed image using a complementary color for the chromaticity distribution. Although the non-uniformity is reduced, a specific method for creating a reverse image using white ink is not described. In addition, the bright line prevention unit (gradation reversal image) in which the complementary color for the chromaticity distribution is created with white ink has a problem that the color unevenness cannot be sufficiently reduced. As described above, the method of Patent Document 8 has a problem that even if the bright line prevention portion is formed using white ink, the color unevenness cannot be sufficiently reduced.

  Further, the light diffusing plate of Patent Document 9 may cause uneven color depending on the color temperature of the light source used. In addition, it can be used for direct-type backlight units by separating the distance from the light source to some extent, but when creating a thin backlight unit, the diffusion effect due to space (distance) cannot be used, and color There is a problem that uneven brightness and uneven brightness cannot be prevented.

  The first problem of the present invention is to solve the above-mentioned problems of the prior art, is thin and lightweight, and reduces brightness unevenness without reducing the average brightness of incident light and without causing color unevenness. It is in providing the transmittance | permeability adjustment body unit which can do.

In addition, the second problem of the present invention is to solve the above-mentioned problems of the prior art, to be thin and lightweight, to be manufactured at low cost, to be more uniform, less uneven brightness and less uneven color, and higher An object of the present invention is to provide a planar illumination device that can emit bright illumination light and can be applied to a liquid crystal display device such as a wall-mounted television.
The third problem of the present invention is to solve the above-mentioned problems of the prior art, to be thin and lightweight, to be manufactured at a lower cost, to be more uniform and less uneven in brightness and color, and more An object of the present invention is to provide a liquid crystal lighting device that can perform display with high luminance and can be a wall-hanging type such as a wall-mounted television.

In order to solve the first problem, a first aspect of the present invention includes an optical member having light transmittance, and a large number of transmittance adjusting bodies disposed on the surface of the optical member. A transmittance adjuster unit in which the transmittance of incident light varies depending on the position, the transmittance adjuster being arranged in a predetermined pattern on the surface of the optical member, and ClEL ^* a ^* b ^* color A ^* and b ^* in the space are represented by the following formula: −2.0 ≦ a ^* ≦ 2.0
b ^* = k × ln (T) +17
(Wherein k satisfies −2.0 ≦ k ≦ −1.7, and T is the color temperature of incident light)
The transmittance adjusting body unit that satisfies the above requirements is provided.
Here, the a ^* preferably satisfies −1.0 ≦ a ^* ≦ 1.0.
The k preferably satisfies −2.0 ≦ k ≦ −1.9.

Furthermore, the pattern density of the transmittance adjusting body at a predetermined position (x, y) is ρ (x, y), and the light emitted from the transmittance adjusting body unit when the transmittance adjusting body is not provided. When the maximum brightness F _max is 1, and the relative brightness of the light emitted from the predetermined position (x, y) with respect to the maximum brightness F _max is F (x, y), the relative brightness F (x, y) and the above The relationship with the pattern density ρ (x, y) is
ρ (x, y) = c {F (x, y) −F _min } / (F _max −F _min )
(Where c is 0.5 ≦ c ≦ 1 and F _min is the minimum luminance of relative luminance F (x, y))
Is preferably satisfied.
The optical member is preferably a transparent film, a light guide plate, a diffusion film, or a prism sheet.

In order to solve the second problem, a first form of the second aspect of the present invention includes a light source, a flat light guide plate that emits light incident from the light source from a light exit surface, A reflection sheet disposed on a surface facing the light exit surface of the light guide plate, a reflector disposed on a surface facing the light guide plate through the light source, and the above described disposed on the light exit surface of the light guide plate The planar illuminating device which has the transmittance | permeability adjustment body unit in any one of these is provided.
Here, the optical member is preferably at least one of a transparent film, a diffusion film, and a prism sheet.

In order to solve the second problem, a second form of the second aspect of the present invention includes a light source, a light guide plate on a flat plate that emits light incident from the light source from a light exit surface, and A reflection sheet disposed on a surface of the light guide plate facing the light exit surface, a reflector disposed on a surface of the light guide plate facing the light source through the light source, and a plurality of light guide plates disposed on the light exit surface of the light guide plate The transmittance adjuster is arranged in a predetermined pattern on the surface of the optical member, and a ^* and b ^* in the ClEL ^* a ^* b ^* color space are represented by the following formula: 2.0 ≦ a ^* ≦ 2.0
b ^* = k × ln (T) +17
(Wherein k satisfies −2.0 ≦ k ≦ −1.7, and T is the color temperature of incident light)
A planar illumination device that satisfies the above requirements is provided.

Furthermore, it has a diffusion film arranged on the light exit surface side of the light guide plate,
The diffusion film preferably has a haze of 85% or less.
The light guide plate includes a thick portion that is parallel to one side of the light guide plate and is positioned at a substantially central portion of the light emitting surface, a thin end portion that is formed in parallel to the thick portion, and a substantially central portion of the thick portion. A parallel groove for accommodating the light source formed parallel to the one side, and an axis of the rod-shaped light source on both sides of the parallel groove, which is symmetric with respect to a plane perpendicular to the light emitting surface. It is preferable that the thick wall portion is configured by an inclined back surface portion that forms a sloping back surface with a thickness decreasing toward the thin end portions on both sides in a direction orthogonal to the one side.
Furthermore, it is preferable that a plurality of minute prisms are engraved on at least one of the light exit surface and the pair of inclined back surface portions.

  In order to solve the third problem, a third aspect of the present invention is a planar illumination device including any one of the planar illumination devices described above, and is disposed on the light emission surface side of the planar illumination device. The present invention provides a liquid crystal display device comprising: a liquid crystal display panel to be driven; and a planar lighting device and a drive unit for driving the liquid crystal display panel.

According to the first aspect of the present invention, by using a transmittance adjusting body in which a ^* and b ^* satisfy the above formula, the average luminance of incident light is not reduced and color unevenness is not caused. Uneven brightness can be reduced. As a result, it is possible to emit light having no luminance unevenness and color unevenness.
Further, by arranging the transmittance adjusting body so that the pattern density ρ (x, y) satisfies the above formula, the luminance unevenness can be further reduced without reducing the average luminance. Furthermore, since uneven brightness can be efficiently reduced, even when a diffusion film is used, the diffusion film can be made thinner and lighter.

Moreover, according to the 2nd aspect of this invention, brightness nonuniformity can be reduced efficiently and color diffusion film can be made thin, without generating color nonuniformity. Further, by preventing the occurrence of color unevenness, various members for reducing the color unevenness, for example, a diffusion film can be provided or made thinner. Thereby, a lighter and cheaper planar lighting device can be provided.
Further, the luminance unevenness can be efficiently reduced, so that the emission efficiency can be increased, and light with high luminance can be emitted even when a low-luminance light source is used.
As a result, it is thin and lightweight, can be manufactured at a lower cost, can emit more uniform illumination light with less color unevenness and brightness unevenness, and higher brightness. A planar illumination device that can be applied to the device can be provided.

  Further, according to the third aspect of the present invention, by using the planar illumination device of the second aspect, it is thin and lightweight, can be manufactured at a lower cost, is more uniform and has uneven color. It is possible to provide a liquid crystal lighting device that can perform display with higher luminance with less unevenness of brightness and can be a wall-mounted type such as a wall-mounted television.

Hereinafter, the transmittance adjusting unit, the planar illumination device, and the liquid crystal display device using the same according to the present invention will be described in detail based on preferred embodiments shown in the accompanying drawings.
FIG. 1 is a schematic cross-sectional view of a planar illumination device 2 (hereinafter also referred to as a backlight unit) according to a second aspect of the present invention having the transmittance adjusting body unit 28 according to the first aspect of the present invention. Such a planar illumination device 2 is used as a planar illumination device of the liquid crystal display device according to the third aspect of the present invention. 2A and 2B, a part of one light guide plate unit 18 of the planar illumination device 2 shown in FIG. 1 and a schematic partial perspective view of a liquid crystal display device 10 using the planar illumination device 2 are shown. Figure and schematic partial cross-sectional view are shown. As shown in FIGS. 1, 2 (a) and 2 (b), the liquid crystal display device 10 basically includes a planar illumination device 2 and a liquid crystal display disposed on the light emission surface side of the planar illumination device 2. It has the panel 4 and the drive unit 6 (a connection part with the planar illuminating device 2 is not shown) for driving them.

  The liquid crystal display panel 4 includes, for example, GH, PC, TN, STN, ECB, PDLC, IPS (In-Plane Switching), VA (Vertical Aligned) type (MVA, PVA, EVA), OCB, ferroelectric A liquid crystal display panel according to a liquid crystal display mode such as liquid crystal or antiferroelectric liquid crystal can be used. The driving method of the liquid crystal display panel 4 is not particularly limited, and a known driving method such as a simple matrix method or an active matrix method can be used.

  The planar illumination device 2 is a planar illumination device for irradiating the entire surface of the liquid crystal display panel 4 with uniform light from behind the liquid crystal display panel 4, and has substantially the same light as the image display surface of the liquid crystal display panel 4. It has an emission surface (light emitting surface). As shown in FIG. 1, the surface illumination device 2 basically includes a light source 12, a diffusion film 14, two prism sheets 16 and 17, a light guide plate 19, a reflector 20, and a reflection sheet 22. And a transmittance adjusting unit 28. Further, as shown in FIG. 1, the light guide plate 19 used in the planar illumination device 2 of the present embodiment includes a plurality of light guide plate units 18.

  The driving method of the planar illumination device 2 is not particularly limited. For example, the planar lighting device 2 may be driven so as to perform luminance modulation by monitoring the surrounding environment. For example, the brightness may be modulated according to the brightness or temperature by providing an ambient light sensor to detect ambient brightness, or providing a temperature sensor to detect ambient temperature. Further, the driving method of the surface illumination device 2 is not particularly limited, and for example, each light source (for example, LED light source) of R (red), G (green), and B (blue) is used, and each of the light sources is liquid crystal. It may be driven by a field sequential method of sequentially lighting in accordance with the display on the display panel 4, or may be driven by an intermittent lighting method of emitting or turning off sequentially or simultaneously according to the liquid crystal scanning display. If the backlight unit 2 is driven using the field sequential method, the R, G, and B color filters can be removed, so that the loss of light quantity due to the color filters can be eliminated. In addition, if the light source is turned on for a short time according to the intermittent lighting method, the display performance of the moving image can be improved.

2A and 2B, a light source 12 is a thin rod-like cold cathode tube, and is used for illuminating the liquid crystal display panel 4. The light source 12 is disposed in a parallel groove 18f formed in the light guide plate unit 18, and is connected to the drive unit 6 (not shown). Here, a cold cathode tube is used as the light source 12, but the present invention is not limited to this, and any rod-shaped light source may be used. As the light source 12, for example, a normal fluorescent tube, an LED (light emitting diode), or the like can also be used.
For example, an LED light source having a columnar or prismatic transparent light guide having a length equivalent to the parallel groove 18 f of the light guide plate unit 18 and LEDs arranged on the top and bottom surfaces of the light guide 12 is used as the light source 12. It may be used instead. Such an LED light source can emit LED light from the side surface of the light guide by entering LED light from the top and bottom surfaces of the light guide.

  The light guide plate unit 18 includes a rectangular light exit surface 18a, a thick portion 18b parallel to one side thereof, thin end portions 18c formed in parallel to the one side on both sides of the thick portion 18b, In the direction perpendicular to the one side from the portion 18b, the thickness decreases toward the thin end portions 18c on both sides, and the inclined back surface portion 18e forming the inclined surface 18d and the thick portion 18b are formed in parallel to the one side. And a parallel groove 18f for accommodating the light source 12. That is, the light guide plate unit 18 is a flat plate having a rectangular outer shape on the surface, and is formed of a transparent resin. The light guide plate unit 18 has one surface that is flat, and the other surface is inclined with respect to one surface so that the plate thickness becomes thinner toward one side. Here, the inclined surface 18d is formed as a flat surface, but may be a curved surface.

  As shown in FIG. 1, the light guide plate unit 18 has a symmetrical shape with respect to a center line perpendicular to the light exit surface 18a of the light guide plate unit 18 through the center of the parallel groove 18f. The light guide plate 19 is formed by connecting a plurality of light guide plate units 18 with the thin-walled portion as a joint.

  On the side opposite to the light exit surface 18a of the thick portion 18b of the light guide plate unit 18, a parallel groove 18f for accommodating the light source 12 is formed extending in the longitudinal direction. The depth of the parallel groove 18f is preferably determined so that a part of the light source 12 does not protrude from the lower surface of the light guide plate unit 18. It is preferable to determine in consideration. Further, the thickness of the thick portion 18 b and the thin end portion 18 c of the light guide plate unit 18 can be arbitrarily changed according to the dimensions of the light source 12. Here, although the parallel groove 18f of the light guide plate unit 18 may be formed in a direction perpendicular to the longitudinal direction of the light guide plate unit 18, the light use efficiency from the light source 12 accommodated in the parallel groove 18f is increased. Therefore, it is preferable to form in the longitudinal direction.

  In the light guide plate unit 18 having the structure shown in FIGS. 2A and 2B, among the light emitted from the light source 12 arranged in the parallel groove 18f, the light guide plate starts from the side wall forming the parallel groove 18f. The light incident on the inside of the unit 18 is reflected by the inclined surface 18d of the light guide plate unit 18 and then exits from the light exit surface 18a. At this time, a part of the light leaks from the lower surface of the light guide plate unit 18, but the leaked light is reflected by a later-described reflection sheet 22 formed on the inclined surface 18 b side of the light guide plate unit 18 and again the light guide plate. The light enters the inside of the unit 18 and exits from the light exit surface 18a. Thus, uniform light is emitted from the light exit surface 18a of the light guide plate unit 18.

  The light guide plate 19 can be manufactured using, for example, a method in which a heated raw material resin is molded by extrusion molding or injection molding, a casting polymerization method in which a monomer, an oligomer, or the like is polymerized in a mold. Examples of the material of the light guide plate 19 include acrylic resins such as polycarbonate and PMMA (polymethyl methacrylate), PET (polyethylene terephthalate), PP (polypropylene), PC (polycarbonate), PMMA (polymethyl methacrylate), benzyl methacrylate, A transparent resin such as MS resin, other acrylic resin, or COP (cycloolefin polymer) can be used. The transparent resin may be mixed with fine particles for scattering light, whereby the light emission efficiency from the light exit surface 18a can be further increased.

  In the present embodiment, the parallel grooves 18f of the light guide plate unit 18 are formed such that a cross-sectional shape perpendicular to the length direction of the parallel grooves 18f (hereinafter simply referred to as a cross-sectional shape of the parallel grooves) is a triangular shape. . The shape of the parallel groove is not limited to a triangular shape, and may be various shapes such as a hyperbolic shape, an elliptical shape, and a catenary shape. The shape of the parallel groove 18f will be described in detail later.

  The prism sheets 16 and 17 are transparent sheets formed by arranging a plurality of prisms in parallel. The prism sheets 16 and 17 improve the light collecting property of the light emitted from the light exit surface 18a of the light guide plate unit 18 and improve the luminance. be able to. One of the prism sheets 16 and 17 is disposed so that the extending direction of the prism row is parallel to the parallel groove 18 f of the light guide plate unit 18, and the other is disposed vertically. That is, the prism sheets 16 and 17 are arranged so that the extending directions of the prism rows are perpendicular to each other. The prism sheet 16 is arranged so that the apex angle of the prism faces the liquid crystal display panel 4. Here, the order of arrangement of the prism sheets 16 and 17 is that a prism sheet 16 having a prism extending in a direction parallel to the parallel groove of the light guide plate is arranged immediately above the light guide plate, and on the prism sheet 16, A prism sheet having prisms extending in a direction perpendicular to the parallel grooves 18f of the light guide plate unit 18 may be disposed, or vice versa.

  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.

  In the present invention, as shown in FIGS. 3A and 3B, a prism sheet 23 is also provided between the reflection sheet 22 and the inclined surface 18d opposite to the light exit surface 18a of the light guide plate unit 18. It is preferable to provide it. 3A is a schematic cross-sectional view showing a state in which the prism sheet 23 is disposed between the reflection sheet 22 and the inclined surface 18d of the light guide plate unit 18, and FIG. FIG. 6 is a schematic plan view and a schematic cross-sectional view of the prism sheet 23 disposed between the light guide plate unit 18 and the inclined surface 18d of the light guide plate unit 18 as viewed from the light guide plate side. The prism sheet 23 provided between the reflection sheet 22 and the inclined surface 18d of the light guide plate unit 18 is arranged so that the extending direction of the prism 23a is perpendicular to the parallel grooves 18f of the light guide plate unit 18, and It is preferable to arrange the prism 23 a so that the apex angle of the prism 23 a faces the inclined surface 18 b of the light guide plate unit 18.

Although a prism sheet is used here, an optical element having the same effect as the prism sheet may be used, and an optical element having a lens effect, for example, an optical element such as a lenticular lens, a concave lens, a convex lens, or a pyramid type is regular. You may provide the sheet | seat arrange | positioned.
In the illustrated example, the prism sheets 16 and 17 and more preferably the prism sheet 23 are used. However, when the luminance on the light exit surface 18a by the parallel grooves 18f of the light guide plate unit 18 is made more uniform. Of course, the prism sheet 23 is unnecessary, and either one or both of the prism sheets 16 and 17 may not be used. The cost of the apparatus can be reduced by reducing the number of expensive prism sheets used or by stopping the use of prism sheets.

Here, in the embodiment shown in FIGS. 1 to 3, the prism sheet is disposed on the light exit surface side of the light guide plate unit and / or between the inclined surface of the light guide plate unit and the reflection sheet. However, the prisms parallel to the axis of the rod-shaped light source may be directly engraved on the surface of the light guide plate excluding the side surfaces of the parallel grooves, for example, the light exit surface and / or the inclined surface.
For example, the prism 25 may be formed directly on the inclined surface 18d of the light guide plate unit 18 as shown in FIGS. 4 (a) and 4 (b), and on the light exit surface 18a of the light guide plate unit 18 as shown in FIG. The prism 26 may be formed, and the prism 25 may be formed on the inclined surface 18d.
In this way, by forming the prism directly on the surface of the light guide plate unit excluding the side surfaces of the parallel grooves, the same effect as when the prism sheet is arranged can be obtained. Furthermore, since it is not necessary to provide a prism sheet, it is possible to eliminate light attenuation (decrease in luminance) caused by the gap formed by arranging the prism sheet. As a result, the light use efficiency as the planar illumination device, that is, the light emission efficiency can be made higher than when the prism sheet is disposed. Furthermore, since it is not necessary to provide a prism sheet, the apparatus can be further downsized (thinned).
Here, the prism is not limited to be formed on the entire light exit surface and / or the inclined surface of the light guide plate unit, and the prism is formed only on a part of the light exit surface and / or the inclined surface of the light guide plate unit. May be.

Further, the prism engraved on the inclined surface preferably has an apex angle θ _p1 of 100 ° ≦ θ _p1 ≦ 140 °. Further, the prism formed on the light exit surface preferably has an apex angle θ _p2 of 40 ° ≦ θ _p2 ≦ 70 °. By setting the apex angle θ _p1 and apex angle θ _p2 of the prism to be formed within the above ranges, the emission efficiency as the planar illumination device can be improved more suitably.

The prism preferably has a base length of 0.1 mm or less in a direction perpendicular to the parallel grooves.
By setting the length of the base of the prism to 0.1 mm or less, the visibility of the prism structure can be almost ignored.

Returning to FIG. 2, the description of the planar illumination device will be continued.
In FIG. 2, the reflection sheet 22 is for reflecting light leaking from the back surface (the lower surface in the figure) of the light guide plate unit 18 so as to enter the light guide plate unit 18 again, thereby improving the light use efficiency. Can be made. The reflection sheet 22 is formed so as to cover the inclined surface 18 d of the light guide plate unit 18. The reflector 20 is provided behind the light source 12 so as to close the parallel grooves 18 f of the light guide plate unit 18. The reflector 20 can reflect light from the lower surface of the light source 12 and make the light incident from the side wall surface of the parallel groove 18 f of the light guide plate unit 18.

  The reflection sheet 22 may be formed of any material as long as it can reflect light leaking from the inclined surface 18d of the light guide plate unit 18. For example, a filler is used for PET, PP (polypropylene), or the like. Resin sheet with increased reflectivity by forming voids by stretching after kneading, transparent or white resin sheet surface with mirror surface formed by vapor deposition of aluminum, etc., metal foil such as aluminum or metal foil It can be formed of a supported resin sheet or a thin metal plate having sufficient reflectivity on the surface. In addition, the reflector 20 can be formed of, for example, the same material as that of the reflection sheet, that is, a resin material, a metal foil, or a metal plate having sufficient reflectivity on the surface.

In FIG. 2, the diffusion film 14 is for diffusing and uniformizing the light emitted from the light exit surface 18a of the light guide plate unit 18. For example, PET (polyethylene terephthalate), PP (polypropylene), PC ( Polyamide), PMMA (polymethyl methacrylate), benzyl methacrylate, MS resin, other acrylic resins, or film-like members made of optically transparent resin such as COP (cycloolefin polymer). Formed. The method is not particularly limited. For example, the surface of the flat plate member is subjected to surface roughening by fine unevenness processing or polishing (hereinafter, the surface on which these are applied is referred to as “sand-rubbed surface”) to impart diffusibility. Or pigments such as silica, titanium oxide, zinc oxide, etc., or beads such as glass and zirconia are coated on the surface together with a binder, or the above-mentioned pigments that scatter light into the transparent resin. It is formed by kneading beads. In the present invention, the diffusion film 14 may be a mat type or coating type diffusion film.
In the present invention, as the diffusion film 14, it is preferable to use a film-like member having a thickness of 500 μm or less that uses the above-mentioned material and imparts light diffusibility.

  The diffusion film 14 is preferably arranged at a predetermined distance from the light exit surface 18a of the light guide plate unit 18, and the distance is appropriately changed according to the light amount distribution from the light exit surface 18a of the light guide plate unit 18. obtain. Thus, by separating the diffusion film 14 from the light exit surface 18 a of the light guide plate unit 18 by a predetermined distance, light emitted from the light exit surface 18 a of the light guide plate unit 18 is between the light exit surface 18 a and the diffusion film 14. And further mixing (mixing). Thereby, the brightness | luminance of the light which permeate | transmits the diffusion film 14 and illuminates the liquid crystal display panel 4 can be made further uniform. As a method of separating the diffusion film 14 from the light exit surface 18a of the light guide plate unit 18 by a predetermined distance, for example, a method of providing a spacer between the diffusion film 14 and the light guide plate unit 18 can be used.

  In particular, when the thickness of the planar lighting device 2 may be slightly increased, the luminance at the light exit surface 18a of the light guide plate unit 18 corresponding to the parallel grooves 18f is determined by the cross-sectional shape of the parallel grooves 18f of the light guide plate unit 18. It is not necessary to sufficiently reduce the peak value of the illumination light, and it is partially reduced and a gap is provided between the diffusion film 14 and the light exit surface 18a of the light guide plate unit 18 to reduce the illumination light emitted from the diffusion film 14. The luminance distribution may be made uniform. Further, there is a limit to the improvement of the cross-sectional shape of the parallel groove 18f of the light guide plate unit 18 (the taper of the tip portion of the parallel groove), and the luminance peak value on the light exit surface 18a of the light guide plate unit 18 corresponding to the parallel groove 18f. In the case where it is not possible to completely reduce or sufficiently reduce the luminance distribution of the illumination light emitted from the diffusion film 14 by providing a gap between the diffusion film 14 and the light exit surface 18a of the light guide plate unit 18. It may be uniform.

Next, the transmittance adjusting body unit of the present invention will be described.
The transmittance adjuster unit 28 according to the present embodiment reduces unevenness in luminance of light emitted from the light guide plate unit 18, and includes a transparent film 29 and a large number of transmittance adjustments arranged on the surface of the transparent film 29. And a body 26. The transmittance adjusting unit 28 is disposed between the light guide plate unit 18 and the diffusion film 14.

  The transparent film 29 is made of an optical material such as PET (polyethylene terephthalate), PP (polypropylene), PC (polycarbonate), PMMA (polymethyl methacrylate), benzyl methacrylate, MS resin, other acrylic resins, or COP (cycloolefin polymer). It is formed of a transparent member.

  The transmittance adjusting body 26 is a dot of various sizes having a predetermined transmittance, and has a shape such as a quadrangle, a circle, or a hexagon, and has a predetermined pattern, for example, a dot size or a dot according to a position. Are formed on the entire surface of the transparent film 29 on the light guide plate unit 18 side by printing or the like.

FIG. 6 shows an example in which the transmittance adjusting bodies 26 are arranged in a halftone dot pattern. Here, FIG. 6A is a schematic diagram showing an example of an arrangement pattern of the transmittance adjusting body 26 laid on the transparent film 29, and FIG. 6B is a transmittance adjustment of FIG. 6A. FIG. 6 is an enlarged schematic view showing a portion corresponding to one light guide plate unit 18 in the arrangement pattern of the body 26 in an enlarged manner. In FIGS. 6A and 6B, the center of the light guide plate unit 18, that is, the center of the parallel groove 18f is indicated by a one-dot chain line.
Thus, by arranging a large number of transmittance adjusting bodies 26 in a predetermined pattern on the surface of the transparent film 29 on the light guide plate unit 18 side, the pattern density of the transmittance adjusting body 26 changes according to the position on the surface. . The arrangement pattern of the transmittance adjusting body 26 will be described later.

By providing the transmittance adjusting body unit 28 in which the transmittance adjusting body 26 is arranged in this way, luminance unevenness can be reduced.
However, as described above, when the transmittance adjusting unit 28 is provided, color unevenness may occur in the light emitted from the planar illumination device 2.

As a result of intensive studies on the color unevenness, the present inventors have found that the relationship between the light incident on the transmittance adjusting body 26 and a ^* and b ^* in the CIELab color space of the transmittance adjusting body 26 is affected. I found it.
Furthermore, as a result of intensive studies, a transmittance adjuster in which a ^* and b ^* in the CIELab color space satisfy the following expressions 1 and 2 when the color temperature of light incident on the transmittance adjuster unit 28 is T. It was found that the use of No. 26 can prevent the occurrence of color unevenness.
−2.0 ≦ a ^* ≦ 2.0 Formula 1
b ^* = k × ln (T) +17 Equation 2
Note that k is −2.0 ≦ k ≦ −1.7.

Here, the color temperature T [K] of light incident on the transmittance adjuster unit 28 (hereinafter simply referred to as the color temperature T [K]) is, for example, the light of the light guide plate unit 18 by the transmittance adjuster unit 28. When arranged on the exit surface, it is obtained by measuring the light emitted from the light exit surface of the light guide plate unit 18.
In the present invention, a transmittance adjusting body unit is configured using a transmittance adjusting body in which a ^* and b ^* in the color space of CIELab satisfy the above formulas 1 and 2.
Here, a ^* and b ^* in the CIELab color space are determined as follows. First, a material (sample) used as a transmittance adjusting body is screen-printed on transparent PET having a predetermined size with a dot density of 100%. That is, the material constituting the transmittance adjusting body is formed on the entire surface of the transparent PET.
Next, using a color difference meter (TC1800, manufactured by Tokyo Denshoku Co., Ltd.), the color of light transmitted through the transparent PET having the material constituting the transmittance adjusting body formed on the entire surface is measured. That is, the transmittance for every 5 nm is measured in the wavelength range of 380 nm to 780 nm. Thereafter, a ^* and b ^* in the CIELab color space of the material to be measured are calculated using a high color rendering day white fluorescent lamp as the light source. In this way, the calculated values are set as a ^* and b ^* of the transmittance adjusting body. In the CIELab color space, a ^* and b ^* were calculated using the CIE 1976 (L ^* , a ^* , b ^* ) uniform perceptual color space (“New Color Science Handbook”, University of Tokyo Press (1980). (See Chapter 4, etc.)).
Here, a ^* is more preferably −1.0 ≦ a ^* ≦ 1.0. By setting a ^* of the transmittance adjusting body within the above range, it is possible to more reliably prevent the occurrence of color unevenness.
Further, k in the above formula 1 is more preferably −2.0 ≦ k ≦ −1.9. By setting k within the above range, the occurrence of color unevenness can be more reliably prevented.

By configuring the transmittance adjusting body of the transmittance adjusting body unit so as to satisfy the above formulas 1 and 2, the occurrence of color unevenness can be prevented. Further, by arranging the transmittance adjusting body in a predetermined pattern, it is possible to reduce the luminance unevenness without reducing the average luminance.
As described above, the transmittance adjusting body unit according to the present invention can emit uniform light having neither luminance unevenness nor color unevenness and high average luminance.
Further, by preventing the occurrence of color unevenness, various members for reducing the color unevenness, for example, a diffusion film can be provided or made thinner. Thereby, a lighter and cheaper planar lighting device can be provided.

The transmittance adjusting body 26 is not particularly limited as long as it satisfies the above formulas 1 and 2, and examples thereof include pigments or resins such as silica, titanium oxide, and zinc oxide that scatter light, glass, and the like. What coated beads, such as zirconia, with a binder can also be used.
In addition, as a material that can be used as the transmittance adjusting body 26, general white ink used in screen printing, offset printing, and the like can be used. Examples include inks in which titanium oxide, zinc oxide, zinc sulfate, barium sulfate, etc. are dispersed in acrylic binders, polyester binders, vinyl chloride binders, etc., and inks in which silica is mixed with titanium oxide to impart diffusibility. Can be used.
The transmittance adjusting body 26 may be composed of a single material or a plurality of materials. When a transmittance adjusting body is configured using a single material, a ^* and b ^* of the single material only need to satisfy the above formulas 1 and 2. Further, when the transmittance adjusting body 26 is configured by mixing a plurality of materials, it is only necessary that a ^* and b ^* of the mixed materials satisfy the above formulas 1 and 2.

Next, the arrangement pattern of the transmittance adjusting body will be described in detail.
Here, an arbitrary position (x on the light emission surface (surface on the liquid crystal display panel 4 side) of the planar illumination device 2 when the transmittance adjusting body 26 is not disposed, that is, when the transmittance adjusting body unit 28 is not provided. , Y) is assumed to be F (x, y). When the transmittance adjusting body 26 is not provided, the maximum luminance of light emitted from the light exit surface of the planar illumination device 2 is F _max , the minimum luminance is F _min , and the relative luminance F (x, y) is The maximum brightness F _max is set as a reference point (F _max = 1).
At this time, when the pattern density at an arbitrary position (x, y) of the transmittance adjusting unit 28 is ρ (x, y), the pattern density ρ (x, y) of the transmittance adjusting unit 28 and the relative luminance F The relationship with (x, y) preferably satisfies the following formula 3.
ρ (x, y) = c {F (x, y) −F _min } / (F _max −F _min ) Equation 3
Here, c is the maximum density, and is preferably 0.5 ≦ c ≦ 1.

  In the present invention, the pattern density ρ (x, y) is an occupation ratio per predetermined area of the transmittance adjusting body 26, and when ρ (x, y) = 1, the transmittance adjusting body 26 is within the predetermined area. When ρ (x, y) = 0, no arrangement is made within a predetermined area.

Further, when the transmittance adjusting body 26 is disposed on the entire surface, the transmittance adjusting body 26 has a transmittance of 10% or more and 50% or less when the pattern density ρ (x, y) is 1 in the above formula 3. It is preferably 20% or more and 40% or less.
By setting the transmittance to 10% or more, luminance unevenness can be suitably reduced, and by setting the transmittance to 50% or less, luminance unevenness can be reduced without reducing the average luminance.
Furthermore, the said effect can be acquired more suitably by making the transmittance | permeability into 20% or more and 40% or less.

By arranging the transmittance adjusting body 26 of the transmittance adjusting body unit 28 so as to satisfy the pattern density ρ (x, y) of the above equation 3, the light is emitted from the light exit surface of the planar illumination device 2 more preferably. It is possible to suppress a decrease in average luminance of light and reduce luminance unevenness. In this way, by using the transmittance adjusting unit 28, the luminance unevenness can be reduced, so that the diffusion film 14 can be made thinner, the use of the prism sheet can be stopped, or The number of prism sheets used can be reduced, and a lighter and cheaper planar lighting device can be provided.
Here, as described above, the maximum density c is preferably 0.5 ≦ c ≦ 1. By setting the maximum density c to 0.5 or more, it is possible to suppress a reduction in average luminance, and it is possible to emit uniform light with high luminance.

In the present embodiment, the transmittance adjuster unit is configured by arranging a rectangular transmittance adjuster on a transparent film. However, the present invention is not limited to this, and the shape of the transmittance adjuster is a triangle or a hexagon. Any shape such as circular, elliptical, etc.
Further, when the linear light source and the uniaxially extended light guide plate unit as in the present embodiment are used for the planar illumination device, the transmittance adjusting body may have a long strip shape parallel to the linear light source. .

In this embodiment, the pattern density distribution is adjusted by changing the size of the transmittance adjusting body. However, the present invention is not limited to this, and the arrangement interval of the transmittance adjusting bodies having a fixed shape is adjusted. By doing so, the pattern density can also be adjusted. For example, various methods such as an FM screening method and an AM core method can be used as a method for arranging the transmittance adjusting body according to the pattern density.
Here, the transmittance adjusting body is preferably arranged by the FM screening method. Thereby, the transmittance adjusting body can be dispersed and arranged as fine and uniform dots, and the arrangement pattern of the transmittance adjusting body can be made difficult to visually recognize from the light exit surface of the planar illumination device. That is, the arrangement pattern of the transmittance adjusting body is projected from the light emission surface of the planar illumination device, and uneven light can be prevented from being emitted, and more uniform light can be emitted. In addition, it is possible to prevent the dot size from becoming too small to make it difficult to form the transmittance adjusting body.

Here, the transmittance adjusting body has a maximum dimension of 500 μm or less. For example, in the case of a rectangular shape, the length of one side is preferably 500 μm or less, and in the case of an elliptical shape, the major axis is preferably 500 μm or less, and 200 μm or less. It is more preferable. By setting the maximum dimension of the transmittance adjusting body to 500 μm or less, the shape of the transmittance adjusting body becomes difficult to see, and by setting the maximum dimension to 200 μm or less, the shape of the transmittance adjusting body becomes invisible. When used as a liquid crystal display device, the shape of the transmittance adjusting body is not projected onto the light exit surface of the surface proof device, resulting in uneven brightness, and the uneven brightness can be reduced efficiently.
Further, it is more preferable that the transmittance adjusting body has a maximum dimension of 100 μm or less. By setting the maximum dimension to 100 μm or less, the dimension can be more surely less than the discrimination ability of the naked eye, and when actually used as a liquid crystal display device, the shape of the transmittance adjusting body is the light of the surface proof device. Luminance unevenness can be reduced more reliably and efficiently without being unevenly projected onto the exit surface.

  Moreover, as a method of printing the transmittance adjusting body on the surface of the transparent member, various printing methods such as screen printing, offset printing, and gravure printing can be used.

In the present embodiment, the transmittance adjusting unit is provided between the light guide plate unit and the diffusion film. However, the arrangement position is not limited to this, and may be arranged between the diffusion film and the prism sheet.
Moreover, although the transmittance | permeability adjustment body unit was provided by arrange | positioning the transmittance | permeability adjustment body to a transparent film, this invention is not limited to this, The transmittance | permeability adjustment body on the surface of a diffusion film, a prism sheet, or a light-guide plate It is good also as what the transmittance | permeability adjustment body unit arrange | positioned. Specifically, the transmittance adjusting body is arranged on at least one of the surface of the diffusion film on the light guide plate side (light incident surface) and the surface of the diffusion film opposite to the light guide plate side (light output surface). May be. Further, the transmittance adjusting body may be disposed on at least one of the surface of the prism sheet on the light guide plate side (light incident surface) and the surface of the prism sheet opposite to the light guide plate side (light emission surface). Good. Furthermore, a transmittance adjusting body may be disposed directly on the light exit surface of the light guide plate.
Thus, by providing the transmittance adjusting body on the surface of the diffusion film, the prism sheet or the light guide plate, the transmittance adjusting body unit can be formed without using a transparent film, and the layer configuration is further simplified. be able to.
Further, by arranging the transmittance adjusting body directly on the light exit surface of the light guide plate, in addition to the above effects, the luminance unevenness of the light emitted from the light guide plate can be obtained without taking alignment when the planar lighting device is assembled. In contrast, the transmittance adjusting body can be arranged at an accurate position.

  Moreover, it is preferable to arrange | position the transmittance | permeability adjustment body in several places, ie, several optical members, for example, the surface of a light-guide plate unit, a diffusion film back surface, etc., and to form several transmittance | permeability adjustment body units. By disposing the transmittance adjusting body on a plurality of optical members in this way, it is possible to widen the allowable amount of positional deviation between the arrangement pattern of the transmittance adjusting body and the incident light at each position, and uneven brightness and color. Uniform and uniform light can be emitted. Here, when the transmittance adjusting bodies are arranged at a plurality of locations, the arrangement patterns of the transmittance adjusting bodies may be the same arrangement pattern or different arrangement patterns.

  Moreover, although this embodiment set it as the structure laminated | stacked in order of the transmittance | permeability adjustment body unit, the diffusion film, and the prism sheet on the output surface side of the light-guide plate, this invention is not limited to this, The output-surface side of a light-guide plate unit There is no particular limitation on the arrangement order of the members. For example, the transmittance adjusting unit, the prism sheet, and the diffusion film may be laminated in this order on the light exit surface side of the light guide plate unit.

Moreover, when using a diffusion film as a planar illuminating device, it is preferable that the haze of the diffusion film shall be 85% or less.
By setting the haze of the diffusion film to 85% or less, the emission efficiency as the planar illumination device can be increased. Further, as described above, the present invention can prevent the occurrence of color unevenness in the transmittance adjusting body and does not need to reduce the color unevenness with the diffusion film. Therefore, a diffusion film having a haze of 85% or less is preferably used. Can be used.
As described above, by using a diffusion film having a haze of 85% or less, it is possible to provide a planar lighting device that can further increase the emission efficiency without causing uneven color and uneven brightness.

Hereinafter, together with specific examples, the transmittance adjusting unit unit and the planar lighting device including the same will be described in more detail.
As shown in FIG. 7A, the planar illumination device 30 of the present embodiment includes a light source 12, a light guide plate unit 18, a reflector 20, a reflective film 22, and a transmittance adjusting body unit 32. The Here, the transmittance adjusting body unit 32 of the present embodiment uses a diffusion film 34 in which the transmittance adjusting body 26 is arranged.
FIG. 7A shows only one light guide plate unit 18, but in this embodiment, a light guide plate 19 in which a plurality of light guide plate units 18 are connected is used. Here, the cross-sectional shape of the parallel groove 18f of the light guide plate unit 18 is as shown in FIG. 7B when the line passing through the center of the light guide plate unit 18 is the Y axis and the light exit surface is the X axis. , Y = − (1 + X ² /0.3) ^0.5 . In the light guide plate unit, a prism 25 is formed on the inclined surface, and a prism 27 is formed on the light exit surface. In addition, prisms are formed on the light exit surface and the inclined surface so that the direction of the grooves is parallel to the direction of the parallel grooves.

In this embodiment, the light guide plate unit 18 has a distance L from the center of the light guide plate unit 18 to the surface where the thickness of the light guide plate unit 18 is the thinnest, that is, the joint surface with the adjacent light guide plate unit 18 is 15 mm. The thickness D of the thickest portion 18b of the light guide plate unit 18 is set to 4.5 mm, the distance d ₁ between the tip portion of the parallel groove 18f and the light exit surface is set to 1 mm, and the thickness of the light guide plate unit is set. The thickness d ₂ of the surface with the smallest thickness is 1.5 mm, the width G ₁ of the end of the parallel groove 18 f opposite to the light exit surface 18 a is 4 mm, and the inclined rear surface of the joint with the adjacent light guide plate is smooth The curvature radius was set to 15 mm as a curved surface shape, the tip portion of the parallel groove was curved as a curved shape, and the curvature radius r was set to 0.5 mm.
The prism 27 has a shape with an apex angle of 70 degrees and a width (base length) of 0.1 mm, and is ± 1 mm in the direction perpendicular to the parallel groove from the center of the light guide plate unit on the light exit surface. Formed in part. The prism 25 has a shape with an apex angle of 120 degrees and a width (base length) of 0.1 mm, and is formed on the entire inclined surface. Further, a cold cathode tube (CCFL) having a diameter φ of 2.4 mm was used as the light source 12, and D121 manufactured by Tsujimoto Electric Co. was used as the diffusion film 34.

Next, the arrangement pattern of the transmittance adjusting body of the transmittance adjusting body unit was determined as follows.
First, in the planar lighting device having the above-described configuration, in order to calculate the pattern density ρ (x, y) of the transmittance adjusting body unit 32 that satisfies the above Expression 3, the transmittance adjusting body 26 is not provided. The relative luminance F (x, y) of the light emitted from the light exit surface of the planar illumination device when the planar illumination device 31 (see FIG. 8) having the same configuration and shape is used and the transmittance adjusting body unit is not provided. ) Was measured.

Here, the relative luminance F (x, y) was measured as follows.
First, the light emission surface of the planar illumination device 31 is fixed to an XY stage, and the luminance meter is fixed so as to be perpendicular to the light emission surface of the planar illumination device 31. And the brightness | luminance in the position of the light-projection surface of the planar illuminating device 31 was measured with the luminance meter, and the brightness | luminance information regarding the specific position of the light-projection surface of the light-guide plate unit 18 was obtained.
Thereafter, by moving the XY stage, the relationship between the position on the light exit surface of the planar illumination device 31 and the luminance was obtained, and the calculated maximum luminance was F _max and the minimum luminance was F _min . The maximum luminance F _max was set to 1, and the ratio of the luminance at each position to the maximum luminance F _max was set as the relative luminance F (x, y) at the position (x, y). The measurement results thus measured are shown in FIG. Here, in FIG. 9, the vertical axis represents relative luminance, and the horizontal axis represents the distance from the center of the light guide plate (the center of the parallel groove).

Next, the pattern density ρ (x, y) corresponding to the relative luminance F (x, y) is calculated from the measured maximum luminance F _max and the minimum luminance F _min using the above equation 3. Here, in this embodiment, the relationship between the relative luminance F (x, y) and the pattern density ρ (x, y) when the maximum density c is c = 1 is calculated. Here, the relationship between the relative luminance F (x, y) and the pattern density ρ (x, y) is a proportional relationship, and when the relative luminance F (x, y) is the minimum luminance F _min , the pattern density ρ (x , Y) is 0, and the maximum density F is the pattern density ρ (x, y) when the maximum brightness F _max is reached.

  Next, based on the relationship between the calculated relative luminance F (x, y) and the pattern density ρ (x, y), the relative luminance F (x, y) of the planar illumination device of the present embodiment shown in FIG. ) Distribution of the pattern density ρ (x, y) corresponding to. FIG. 10 shows the distribution of the pattern density ρ (x, y) calculated for the case where the maximum density c is c = 1. In FIG. 10, the vertical axis represents the pattern density ρ (x, y), and the horizontal axis represents the distance from the center of the light guide plate (the center of the parallel groove).

Next, when the calculated maximum density c is c = 1, the arrangement pattern of the transmittance adjusting body to be arranged on the diffusion film 34 is based on the distribution of the pattern density ρ (x, y) that satisfies Equation 1. Were determined.
Specifically, the distribution of the pattern density ρ (x, y) is calculated every 0.5 mm in the width direction (lateral direction in FIG. 7A), and according to the calculated pattern density ρ (x, y). Thus, the transmittance adjusting body unit 28 was created by appropriately arranging the transmittance adjusting body 26 having a size in the width direction larger than 0 and 1 mm or less. That is, L1 and L4 of the transmittance adjusting body unit shown in FIG. 6B are L1 = L4 = 1.0 mm, L2 and L3 are L2 = L3 = 0.5 mm, and w1 to w4 are 0 mm <w ≦ 1 mm. The arrangement pattern of the transmittance adjusting body 26 was determined.

In this example, the transmittance adjusting body 26 was arranged on the surface of the diffusion film 34 according to the above pattern by screen printing, and the transmittance adjusting body unit 32 was produced. As the transmittance adjusting body 26, a sample in which Jujo Reicure 4707M high-density white, Jujo Reicure 4746M indigo, and Teikoku UV FIL-135TC magenta were appropriately mixed was used. Furthermore, in this example, a plurality of samples (transmittance adjusters) having different a ^* and b ^* are prepared by changing the mixing ratio of the above samples, and the transmittance adjusters for each sample are the same as described above. In addition, a plurality of transmittance adjusting body units were prepared by arranging on a diffusion film in a predetermined pattern. Such a transmittance adjusting body unit is disposed such that the surface on which the transmittance adjusting body is disposed faces the light guide plate unit when incorporated in the planar lighting device.

A surface illumination device having the structure shown in FIG. 7A is manufactured by combining various transmittance adjustment unit units thus manufactured and various light sources, and the color difference of the emitted light is obtained, and color unevenness is visually observed. The sensitivity was evaluated by
Here, the color difference of the light emitted from the light exit surface of the planar illumination device is obtained by using the spectroradiometer (SR-3) manufactured by Topcon Corporation as the light emitted from the light exit surface of the planar illumination device. Light emitted from the exit surface from the center of the light exit surface in the direction orthogonal to the light source at intervals of 1 mm from end to end of the light guide plate unit, that is, exit light from the center of the light source to ± 15 mm at intervals of 1 mm, The chromaticity value of the emitted light was measured.
Then, the maximum value of a ^* of the measured chromaticity value (a ^* max), the minimum value (a ^* min), b ^* maximum value (b ^* max), since the minimum value (b ^* min), ( (A ^* max−a ^* min) ² + (b ^* max−b ^* min) ² ) ^0.5 was calculated, and the calculated value was defined as a color difference.

The measurement results thus measured are shown in Table 1 below. Table 1 shows the measured a ^* and b ^* of the sample of each planar illumination device (Experimental Examples 1 to 14), the color temperature of light incident on the transmittance adjusting unit (color temperature T), and the measurement results. Color difference and sensitivity evaluation are shown. Here, the sensitivity evaluation is indicated by ◎ when no color unevenness is felt, ◯ when almost no color unevenness is felt, and × when the color unevenness is generated.

Here, the color temperature T of the light incident on the transmittance adjuster unit is the light emitted from the light exit surface of the planar illumination device in which the transmittance adjuster unit is not arranged, that is, from the light exit surface of the light guide plate. This is a value obtained by measuring the color temperature T of the emitted light.
Specifically, the light emission of the light guide plate unit of the planar illumination device in which the transmittance adjusting unit unit is not arranged, that is, the planar illumination device including the light source, the light guide plate, the reflector, and the reflection film. The light is emitted from the surface, and the light emitted from the light exit surface is emitted from the center of the light exit surface in the direction perpendicular to the light source by using a spectroradiometer (SR-3) manufactured by Topcon Corporation at intervals of 1 mm. Measurement was performed from end to end. Since the light guide plate unit used in this example has a width of 30 mm, the emitted light from the center of the light source to ± 15 mm is measured at intervals of 1 mm, and the average value of the measured color temperature of the emitted light is the color temperature. T.

FIG. 11 shows the relationship between b ^* and color temperature T of the transmittance adjusting body of each experimental example. In FIG. 11, the vertical axis represents b ^* of the transmittance adjusting body, and the horizontal axis represents the color temperature T [K] of light incident on the transmittance adjusting body unit. Further, in order to clearly show the range of b ^* of the transmittance adjusting body that can be suitably used for the color temperature T, k is set to −1.7, −1 at b ^* = k × ln (T) +17. The relationship between b ^* and T when .8, -2.0 is indicated by a solid line.
As shown in FIG. 11 and Table 1, Experimental Example 1, Experimental Examples 3 to 6, Experimental Example 10 and Experimental Example 11 satisfying both of the above Expression 3 and Expression 1 have a color difference of 2.0 or less, and also visually. Almost no color unevenness was felt. In particular, in Experimental Example 3 and Experimental Example 4 in which −1 ≦ a ^* ≦ 1 and −1.8 ≦ k ≦ −2.0 in Equation 1, the color difference is 1 or less, and color unevenness is also observed visually. I couldn't feel it.
Thus, the occurrence of uneven color can be prevented by selecting and arranging the appropriate a ^* and b ^* transmittance adjusting bodies according to the color temperature of the light incident on the transmittance adjusting body. I understand.
From the above, the effects of the present invention are clear.

  Here, in the present embodiment, the cross-sectional shape of the parallel groove 18f of the light guide plate unit 18 is triangular, but the cross-sectional shape of the parallel groove 18f passes through the deepest part or center of the parallel groove 18f. Any shape that is symmetric with respect to the center line perpendicular to the light exit surface and that becomes narrower toward the light exit surface 18a may be used. For example, the specific embodiment shown in FIGS. As shown in FIG. 12, it can have a hyperbolic shape or an elliptical shape as shown in FIG. Alternatively, the cross-sectional shape of the parallel groove 18f of the light guide plate unit 18 may be a catenary line shape.

  Moreover, in the cross-sectional shape of a parallel groove, it can also be set as the shape where the deepest part (connection part of the side wall which forms a parallel groove) of a parallel groove becomes a cusp. That is, two curved lines or straight lines that are symmetrical with respect to a center line that passes through the center of the parallel groove and is perpendicular to the light exit surface of the light guide plate, the cross-sectional shape of the tip portion of the parallel groove having one sharp intersection that intersects each other It can form from a part of. In the present invention, even if the cross-sectional shape of the parallel groove of the light guide plate is any of the above shapes, uniform light can be emitted from the light exit surface of the light guide plate.

  In FIG. 14, the cross-sectional shape of the tip portion of the parallel groove is 2 symmetrical with respect to the center line perpendicular to the light exit surface of the light guide plate through the center of the parallel groove 18 f having one sharp intersection that intersects each other. An example of the case of consisting of a part of two curves is shown. In the light guide plate 50 shown in FIG. 14, two curves 54 a and 54 b that are symmetric with respect to the center line X passing through the center of the parallel groove and perpendicular to the light exit surface 52 of the light guide plate 50 are circular arcs. In this case, as shown in FIG. 14, the center position of the arc 54a corresponding to one side wall forming the parallel groove 18f is different from the center position of the arc 54b corresponding to the other side wall. As a result, the portion 56 where the arc-shaped side walls meet has a sharp shape as shown in FIG.

  Further, FIG. 15 shows that the cross-sectional shape of the tip portion of the parallel groove is symmetrical with respect to the center line perpendicular to the light exit surface of the light guide plate through the center of the parallel groove having one sharp intersection that intersects each other. Still another example in the case of consisting of a part of two curves is shown. The light guide plate 60 shown in FIG. 15 is a case where two curves 64a and 64b that are symmetric with respect to the center line X passing through the center of the parallel groove 18f and perpendicular to the light exit surface of the light guide plate are parabolas. In FIG. 15, the side wall of the parallel groove 18f is formed so that the focal point of the parabola 64a corresponding to one side wall of the parallel groove 18f and the focal point of the parabola 64b corresponding to the other side wall 22b are different from each other.

  As shown in FIG. 15, in the case where the cross-sectional shape of the tip portion of the parallel groove is formed by two curves 64a and 64b that intersect at the intersection 64, the intersection of the curves 64a corresponding to one side wall of the parallel groove 18f ( The angle θ between the tangent line at the cusp 64 and the tangent line at the intersection 64 of the curve 64b corresponding to the other side wall is preferably 90 degrees or less, and more preferably 60 degrees or less.

  FIGS. 1 to 15 show examples of the light guide plate in which the curves forming the side walls of the parallel grooves are concave toward the center of the parallel grooves in the cross-sectional shape of the parallel grooves. Another embodiment of the light plate is shown in FIGS. FIG. 16 shows an example of the light guide plate 70 in which the cross-sectional shape of the parallel groove 18f is formed by two curves 72a and 72b that protrude toward the center of the parallel groove 18f. FIG. 18 shows the cross-sectional shape of the parallel groove 18f. Is an example of the light guide plate 80 formed from a curve obtained by combining convex curves 82a and 82b and concave curves 84a and 84b toward the center of the parallel groove 18f. The light guide plates 70 and 80 having parallel grooves having a cross-sectional shape as shown in FIGS. 16 and 17 can also emit light with sufficient illuminance from the light exit surface while suppressing generation of bright lines.

  Thus, in the cross-sectional shape of the parallel groove of the light guide plate, the portion corresponding to the parallel groove can be a convex or concave curve or straight line toward the center of the parallel groove, and a combination thereof. Also good. These curves are not limited to the arc in the illustrated example, and may be any part of a curve such as an ellipse, a parabola, or a hyperbola that is convex or concave toward the center of the parallel groove. In the present invention, if the cross-sectional shape of the tip portion of the parallel groove is tapered as will be described later, the curve constituting the parallel groove is a circle that is convex or concave toward the center of the parallel groove, It may be a part of a curve such as an ellipse, a parabola, or a hyperbola, and is preferably a curve that can be approximated by a tenth-order function.

  Also, if the cross-sectional shape of the top (deepest part) of the tip of the parallel groove is only one chamfered flat shape or rounded circular shape with one sharp intersection symmetrically with respect to the center line of the parallel groove Of course, it may be oval, parabolic, or hyperbolic. In addition to this, as described above, the peak value of the illuminance may be reduced by using a top portion (deepest portion) of the tip portion of the parallel groove as a rubbing surface.

  Furthermore, illuminance and luminance can be handled in substantially the same manner on the surface of the light guide plate. Therefore, it is considered that the luminance of the light exit surface of the light guide plate can be made uniform by designing the light guide plate to have the above-described shape.

  Here, in the first embodiment of the light guide plate used in the backlight unit (planar illumination device) of the present invention, the portion corresponding to the inclined back surface 18d other than the parallel grooves 18f in the light exit surface 18a of the light guide plate unit 18. The peak value of the bright line formed in the portion (first portion) corresponding to the parallel groove 18f in the light exit surface 18a of the light guide plate unit 18 with respect to the average value of the illuminance formed in the (second portion) (peak value of illuminance) ) Of the tip of the parallel groove 18f of the light guide plate unit 18 is tapered, that is, the degree of taper of the tip of the parallel groove 18f of the light guide plate unit 18 according to the value of this ratio. Is preferably controlled. In this case, as in the case of the second embodiment to be described later, this ratio is preferably 3 or less, more preferably 2 or less.

  This ratio is the thickness of the planar illumination device 2 (the distance between the light exit surface 18a of the light guide plate unit 18 and the diffusion film 14) and the diffusion efficiency of the diffusion film 14 used in the planar illumination device 2. It is preferable to set according to the number of sheets, the diffusion efficiency of the prism sheets 16, 17 and 23, the number of sheets used, and the like. That is, the thickness of the planar illumination device 2 (the distance between the light exit surface 18a of the light guide plate unit 18 and the diffusion film 14) can be increased to some extent (or larger), or the diffusion used in the planar illumination device 2 can be used. When the diffusion efficiency of the film 14 is high and the number of used sheets can be increased, or when the diffusion efficiency of the prism sheets 16, 17 and 23 is high and the number of used sheets can be increased, the light is emitted from the light exit surface 18 a of the light guide plate unit 18. The illumination light can be sufficiently diffused (mixing, etc.), so that the cost is high, but the light guide plate unit 18 has an average value of the illuminance of the second portion of the light exit surface 18a of the light guide plate unit 18. The ratio of the peak value of the illuminance at the first portion of the light exit surface 18a can be set large to some extent. However, if this is not the case, the cost can be reduced, but the value of this ratio needs to be set small.

On the other hand, in the 2nd form of the light-guide plate used for the planar illuminating device of this invention, the peak value of the illumination intensity of the 1st part of the light-projection surface 18a of the light-guide plate unit 18 is the light-projection surface 18a of the light-guide plate unit 18. The tip shape of the parallel groove 18f of the light guide plate unit 18 is tapered so that the average value of the illuminance of the second portion is 3 times or less, more preferably 2 times or less. Here, the peak value of the illuminance of the first portion of the light exit surface 18a of the light guide plate unit 18 is set to be not more than three times the average value of the illuminance of the second portion of the light exit surface 18a of the light guide plate unit 18. Thus, the illuminance distribution of the illumination light emitted from the light exit surface 18a of the light guide plate unit 18 is made more uniform than before.
As a result, it is not necessary to sufficiently diffuse (mix, etc.) the illumination light emitted from the light exit surface 18a of the light guide plate unit 18.
By using such a light guide plate, the planar illumination device of the present invention can use a low-cost diffusion film 14 having a low diffusion efficiency, can reduce the number of sheets used, and is expensive. The use of the prism sheets 16, 17 and 23 itself can be stopped, or the use of the low-cost prism sheets 16, 17 and 23 which are not so high in diffusion efficiency can be used, or the number of used sheets can be reduced. Thereby, a lighter and cheaper planar lighting device can be provided.

  In the light guide plate used in the planar illumination device of the present invention, the tip portion of the parallel groove 18f that tapers in the cross-sectional shape of the parallel groove 18f of the light guide plate unit 18 is the light exit surface 18a from the center of the rod-shaped light source 12. It is preferable that the angle with respect to the vertical line (X) heading toward is a portion that is within 90 degrees on both sides, more preferably a portion that is within 60 degrees. That is, in the present invention, in order to reduce the peak value of the illuminance of the first portion corresponding to the parallel groove 18f of the light exit surface 18a of the light guide plate unit 18, the portion where the parallel groove 18f is tapered is the parallel groove 18f. However, if the peak value can be reduced, a predetermined tip portion may be used.

Here, the light guide plate used in the planar illumination device of the present invention is not limited to the above-described form, and light guide plates having various shapes can be used.
For example, in the present invention, as shown in FIG. 18, a plurality of light guide plate units 94, 96 are arranged in parallel so that the light exit surfaces 94a, 96a of the light guide plate units 94, 96 all form the same plane. A large light guide plate can also be configured. In this way, when the light guide plate units 94 and 96 are arranged in parallel, the inclined surface 94d of one light guide plate unit 94 and the inclined surface 96d of the other light guide plate unit 96 connected to the light guide plate unit 94 do not intersect, that is, The inclination angles of the inclined surfaces 94d and 96d of the light guide plate units 94 and 96 can be adjusted so that a smooth flat surface or curved surface is formed at the connecting portion of the inclined surfaces. The light guide plate shown in FIG. 18 is formed such that the surfaces formed by the inclined surfaces 94d and 96d of the light guide plate units 94 and 96 are arched. The light guide plate units 94 and 96 shown in FIG. 18 have basically the same configuration as that of the light guide plate unit 18 shown in FIGS. 1 to 3 and will not be described in detail.
By using such a light guide plate having large-sized light exit surfaces 94a and 96a, a planar illumination device having a large-sized light irradiation surface can be obtained, so a liquid crystal display device having a large-sized display screen In particular, the present invention can be applied to a wall-mounted liquid crystal display device such as a wall-mounted television.

  As described above, the light guide plate according to the present invention is formed by connecting thin portions of separately formed light guide plate units in order to connect a plurality of light guide plate units to form a large light guide plate. In addition to this, from the viewpoint of manufacturing efficiency, it is preferable to integrally form the number of light guide plate units necessary for forming a light guide plate corresponding to a required screen size.

  Moreover, in the light guide plate of the present invention, as shown in FIG. 19, the reflector 24 may be arranged on the side surface of the light guide plate unit 18 arranged on the outermost side. By disposing such a reflector 24 on the side surface, light leakage from the side surface of the light guide plate unit 18 can be prevented, and the light utilization efficiency can be further enhanced. In addition, the reflecting plate 24 can be formed using the same material as the reflecting sheet or reflector described above.

  Here, the transmittance adjusting body unit of the present invention is not limited to the above-mentioned shape, and can be used for a planar lighting device and a liquid crystal display device using light guide plates of various shapes such as a tandem type and a direct type.

  As mentioned above, although the diffusion film of this invention, the planar illuminating device provided with it, and the liquid crystal display device were demonstrated in detail, this invention is not limited to the said embodiment, In the range which does not deviate from the main point of this invention, it is various. Of course, improvements and changes may be made.

For example, in the planar illumination device of the present invention, a diffusion plate may be further disposed on the light exit surface side of the prism sheet, that is, the surface on the liquid crystal display panel side.
Examples of the diffusion plate include PET (polyethylene terephthalate), PP (polypropylene), PC (polycarbonate), PMMA (polymethyl methacrylate), benzyl methacrylate, MS resin, other acrylic resins, or COP (cycloolefin polymer). It is formed by imparting light diffusibility to such a film-like member made of an optically transparent resin. The method is not particularly limited. For example, the surface of the flat plate member is subjected to surface roughening by fine unevenness processing or polishing (hereinafter, the surface on which these are applied is referred to as “sand-rubbed surface”) to impart diffusibility. Or a pigment or resin such as silica, titanium oxide, or zinc oxide that scatters light, or a bead such as glass or zirconia on the surface together with a binder, or the aforementioned pigment that scatters light in the transparent resin, It is formed by kneading beads. As the diffusion plate 48, a mat type or coating type diffusion plate can be used.

  By providing the diffusion plate, the average luminance decreases due to the decrease in directivity, but the luminance unevenness can be further improved. Further, in the present invention, since the luminance unevenness is efficiently reduced by providing the transmittance adjusting unit, uniform light can be emitted even with a diffusion plate that is thinner and less diffuse than the prior art.

  Here, the light guide plate used in the planar illumination device includes the rectangular light exit surface shown in the above embodiment, a thick wall portion that is parallel to one side of the light guide plate, and that is positioned at a substantially rectangular central portion, and the thick wall plate. A thin-walled end portion formed in parallel to the portion and a parallel groove for accommodating the rod-shaped light source are formed in the center of the thick-walled portion in parallel with the one side, and the rod-shaped light source is formed on both sides of the parallel groove. The wall is symmetric with respect to a plane perpendicular to the rectangular light exit surface, and the thickness decreases from the thick portion toward the thin end portion on both sides in a direction perpendicular to the one side, It is preferable to use a light guide plate having a shape having an inclined back surface forming an inclined back surface. By using the light guide plate having such a shape, luminance unevenness of light emitted from the light guide plate is reduced, so that a planar illumination device with less luminance unevenness can be provided.

  Moreover, in the said Example, all are a rectangular-shaped light-projection surface, the thick part parallel to the one side, the thin end part formed in parallel with the said one side on both sides of this thick part, and the thick part In order to house the light source, the thickness is reduced toward the thin end portions on both sides in the direction perpendicular to the one side, and the inclined rear surface portion that forms the inclined surface and the thick portion that is formed in parallel to the one side. A planar illuminating device using a so-called bridge-type light guide plate having a plurality of parallel grooves, but a so-called tandem-type planar illuminating device in which a plurality of units each having a light guide plate arranged on the side surface of an illumination light source are arranged. It can also be used.

It is a schematic structure sectional view at the time of arranging a plurality of light guide plates used in a planar lighting device of the present invention in parallel. (A) And (b) is the schematic perspective view and schematic sectional drawing of a liquid crystal display device using the planar illuminating device which has a diffusion film of this invention, respectively. (A) is a schematic sectional drawing which shows a mode that the prism sheet is arrange | positioned between a reflective sheet and the inclined surface of a light-guide plate, (b) is between a reflective sheet and the inclined surface of a light-guide plate. It is the schematic plan view and schematic cross section which looked at the arrange | positioned prism sheet from the light-guide plate side. (A) is a schematic sectional drawing which shows a mode that the prism is formed in the inclined surface of a light-guide plate, (b) looked at the inclined surface of the light-guide plate in which the prism was formed from the light-projection surface side. It is a schematic plan view and a schematic cross-sectional view. It is a schematic sectional drawing which shows a mode that the prism is formed in the inclined surface and light-projection surface of a light-guide plate. (A) is a figure which shows an example of the arrangement pattern of the transmittance adjustment body which forms the transmittance adjustment body unit of this invention, (b) is one of the arrangement patterns of the transmittance adjustment body of (a). FIG. 4 is an enlarged view showing a portion corresponding to the light guide plate unit 18 in an enlarged manner. (A) is a schematic block diagram of an example of the specific example of this invention, (b) is an enlarged view of the parallel groove periphery of (a). It is a schematic block diagram at the time of removing only the transmittance | permeability adjustment body from Fig.7 (a). It is a graph of the relative brightness | luminance of the light radiate | emitted from the light emission surface of the planar illuminating device shown in FIG. It is a graph which shows the calculation result which computed distribution of the pattern density of the transmittance | permeability adjustment body unit which satisfies this invention when the maximum density c is set to 1 based on the relative luminance calculated in FIG. It is a graph which shows the relationship between b ^* and the color temperature T of a transmittance adjusting body. It is a schematic sectional drawing of the light-guide plate in case the cross-sectional shape perpendicular | vertical to the length direction of a parallel groove is a hyperbola. It is a schematic sectional drawing of a light-guide plate in case the cross-sectional shape perpendicular | vertical to the length direction of a parallel groove is an ellipse. The cross-sectional shape perpendicular to the length direction of the parallel grooves is formed of a part of two circular arc curves that are symmetric with respect to a center line that passes through the center of the parallel grooves and is perpendicular to the light exit surface of the light guide plate. It is a schematic sectional drawing. Outline of the light guide plate in which the cross-sectional shape perpendicular to the length direction of the parallel grooves is formed from a part of two parabolas symmetrical to the center line passing through the center of the parallel grooves and perpendicular to the light exit surface of the light guide plate It is sectional drawing. It is a schematic sectional drawing of the light-guide plate in which the cross-sectional shape perpendicular | vertical to the length direction of a parallel groove | channel is formed from two curves convex toward the center of a parallel groove | channel. It is a schematic sectional drawing of the light-guide plate in which the cross-sectional shape perpendicular | vertical to the length direction of a parallel groove is formed from the curve which combined the convex curve and the concave curve toward the center of a parallel groove. It is a schematic diagram which shows another example of the shape of a light-guide plate. It is the structural example which has arrange | positioned the reflecting plate in the side surface of the light guide plate, when the light guide plate of this invention is arrange | positioned in parallel. It is a disassembled perspective view of the surface light source device which has the conventional light-guide plate. It is a graph of the brightness | luminance in the output surface of the light-guide plate of the surface light source device of FIG.

Explanation of symbols

2, 30, 31 Planar illumination device 4 Liquid crystal display panel 6 Drive unit 10 Liquid crystal display device 12 Light source 14, 34 Diffusion film 16, 17, 23 Prism sheet 18, 42, 46, 50, 60, 70, 80, 94, 96 Light guide plate unit 18a, 52 Light exit surface 18b Thick portion 18c Thin end portion 18d Inclined surface 18e Inclined back portion 18f Parallel groove 19, 100 Light guide plate 20 Reflector 22, 44 Reflective sheet 24 Reflector 26 Transmissivity adjuster 28, 32 Transmittance adjusting body unit 29 Transparent film 48 Diffuser plate 54a, 54b Arc curve 56 Intersection 64a, 64b Parabola 72a, 72b, 82a, 82b, 84a, 84b Curve

Claims (12)

A transmittance adjuster unit having an optical member having light transmittance and a large number of transmittance adjusters arranged on the surface of the optical member, and the transmittance of incident light varies depending on the position. ,
The transmittance adjusting body is arranged in a predetermined pattern on the surface of the optical member, and a ^* and b ^* in a ClEL ^* a ^* b ^* color space have the following formula: −2.0 ≦ a ^* ≦ 2.0
b ^* = k × ln (T) +17
(Wherein k satisfies −2.0 ≦ k ≦ −1.7, and T is the color temperature of incident light)
Transmittance adjuster unit that satisfies the requirements. The transmittance adjuster unit according to claim 1, wherein the a ^* satisfies −1.0 ≦ a ^* ≦ 1.0.   The transmittance adjuster unit according to claim 1, wherein the k satisfies −2.0 ≦ k ≦ −1.9. The pattern density of the transmittance adjusting body at a predetermined position (x, y) is ρ (x, y),
When the transmittance adjusting body is not provided, the maximum luminance F _{max of} light emitted from the transmittance adjusting body unit is set to 1, and relative to the maximum luminance F _max of light emitted from a predetermined position (x, y). If the luminance is F (x, y),
The relationship between the relative luminance F (x, y) and the pattern density ρ (x, y) is expressed by the following equation:
ρ (x, y) = c {F (x, y) −F _min } / (F _max −F _min )
(Where c is 0.5 ≦ c ≦ 1 and F _min is the minimum luminance of relative luminance F (x, y))
The transmittance adjuster unit according to any one of claims 1 to 3, which satisfies:   The transmittance adjusting body unit according to claim 1, wherein the optical member is a transparent film, a light guide plate, a diffusion film, or a prism sheet.   A light source, a flat light guide plate that emits light incident from the light source from a light exit surface, a reflection sheet disposed on a surface facing the light exit surface of the light guide plate, and the light source of the light guide plate A planar illumination device comprising: a reflector disposed on a surface opposed to the light guide plate; and a transmittance adjusting body unit according to any one of claims 1 to 4 disposed on a light exit surface of the light guide plate.   The planar illumination device according to claim 6, wherein the optical member is at least one of a transparent film, a diffusion film, and a prism sheet. A light source, a light guide plate on a flat plate for emitting light incident from the light source from a light exit surface, a reflection sheet disposed on a surface facing the light exit surface of the light guide plate, and the light source of the light guide plate And a plurality of transmittance adjusting bodies arranged in a predetermined pattern on the light exit surface of the light guide plate,
In the transmittance adjusting body, a ^* and b ^* in the ClEL ^* a ^* b ^* color space have the following formula: −2.0 ≦ a ^* ≦ 2.0
b ^* = k × ln (T) +17
(Wherein k satisfies −2.0 ≦ k ≦ −1.7, and T is the color temperature of incident light)
A planar lighting device that satisfies the requirements. Furthermore, it has a diffusion film arranged on the light exit surface side of the light guide plate,
The planar illumination device according to any one of claims 6 to 8, wherein the diffusion film has a haze of 85% or less. The light guide plate is
A thick wall portion that is parallel to the one side and located at a substantially central portion of the light exit surface;
A thin end formed in parallel to the thick portion;
A parallel groove for accommodating the light source, which is formed in parallel with the one side at the approximate center of the thick part;
The axis of the rod-shaped light source is included on both sides of the parallel groove and is symmetric with respect to a plane perpendicular to the light emitting surface, and is directed from the thick portion to the thin end portions on both sides in a direction perpendicular to the one side. The planar illumination device according to any one of claims 6 to 9, wherein the planar illumination device is configured with an inclined back surface portion that has a reduced thickness and forms an inclined back surface.   The planar illumination device according to claim 10, wherein a plurality of minute prisms are engraved on at least one of the light exit surface and the pair of inclined back surface portions. A planar illumination device comprising the planar illumination device according to any one of claims 6 to 11,
A liquid crystal display device comprising: a liquid crystal display panel disposed on a light emission surface side of the planar illumination device; and a drive unit for driving the planar illumination device and the liquid crystal display panel.

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