CN101968203A - Light control plate, surface light source device and transmissive image display device - Google Patents

Abstract

The invention provides a light control board, a surface light source device and a transmissive image display device. The light diffusion plate (light control plate) (40) is a light control plate capable of emitting light incident from the first surface (40a) from the second surface (40b). A plurality of convex portions (41) extending in the first direction and arranged side by side in a second direction perpendicular to the first direction are formed on the second surface. In the cross section perpendicular to the first direction of the convex portion, the axis passing through both ends of the cross section in the second direction is defined as the x-axis, and the axis perpendicular to the x-axis passing through the centers of both ends on the x-axis is defined as z In the case of axis, the contour shape z(x) of the convex part in the above cross-section satisfies: 0.95×z ₀ (x)≤z(x)≤1.05×z ₀ (x), where z ₀ (x) is expressed as follows expression:

Here, w _a is the length of the convex portion in the x-axis direction, h _a = _0.525wa , k _a =-0.4.

Description

Light control board, surface light source device, and transmissive image display device

technical field

The present invention relates to a light control board, a surface light source device and a transmissive image display device.

Background technique

In a transmissive image display device such as a liquid crystal display device, a direct-type surface light source device is used as an example of backlight output from the liquid crystal display portion. As a typical surface light source device, a device in which a plurality of light sources are arranged on the back side of a light control plate such as a light diffusion plate is used. In such a surface light source device, the luminance of the light-emitting surface can be easily increased by increasing the number of arranged light sources, but there is a problem of low luminance uniformity. In particular, the periodic luminance non-uniformity (luminance non-uniformity) caused by the increase in luminance in the vicinity of the light source becomes a problem, and the number of light sources is reduced due to thinning of the surface light source device or low power consumption. , which would make the aforementioned periodic brightness non-uniformity a bigger problem.

Therefore, in order to ensure brightness uniformity, for example, in Japanese Patent Application Laid-Open No. 6-273760 (Patent Document 1), a light amount compensation pattern is formed corresponding to the distance from the light source on a light diffusion plate as an example of a light control plate. Similarly, in Japanese Unexamined Patent Application Publication No. 2004-127680 (Patent Document 2), a prism with a sawtooth-shaped cross section is provided on a part of the surface of the light source side of the light diffusing plate near directly above the light source, thereby increasing the amount of light received. Light is scattered near the light source directly above it.

However, in the structure of the backlight that depends on the distance from the position of the light source like the light quantity compensation mode of Patent Document 1 and the prism with a saw-toothed cross section in Patent Document 2, misalignment of a light control plate such as a light diffusion plate, Or due to heat deformation, etc., the brightness uniformity is deteriorated.

Contents of the invention

Therefore, an object of the present invention is to provide a light control panel, a surface light source device, and a transmissive image display device using the surface light source device that can more stably suppress brightness non-uniformity.

The light control board according to the present invention is a light control board capable of emitting light incident from a first surface from a second surface opposite to the first surface, and a plurality of convex portions are formed on the second surface. The plurality of convex portions extend in the first direction and are arranged side by side in a second direction orthogonal to the first direction, and in a cross section perpendicular to the first direction of the convex portion, passing through the second When the axes at both ends of the cross-section in two directions are defined as the x-axis, and the axis passing through the centers of the two ends on the x-axis and perpendicular to the x-axis is defined as the z-axis, the contour shape of the convex portion in the cross-section Expressed by z(x) satisfying the following formula (1),

0.95×z ₀ (x)≤z(x)≤1.05×z ₀ (x)···(1)

Among them, in the above formula (1),

${\mathrm{<span\; class="notranslate">\; z</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; -</span>\frac{{\mathrm{<span\; class="notranslate">\; 8</span>}\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}{<span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; x</span>}}{{\mathrm{<span\; class="notranslate">\; w</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; k</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; +</span>\sqrt{{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; k</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 16</span>}{\mathrm{<span\; class="notranslate">\; k</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}{<span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; x</span>}}{{\mathrm{<span\; class="notranslate">\; w</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}}<span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

In formula (2), w _a is the length of the x-axis direction of the said convex-shaped part, h _a =0.525wa _, k _a =-0.4.

In this configuration, since the convex portion has a cross-sectional shape represented by the aforementioned z(x), it is possible to more stably reduce the non-uniformity in brightness of the light emitted from the light control plate of the present invention.

A surface light source device according to the present invention includes: the light control plate according to the present invention; and a plurality of light sources arranged at intervals from each other and supplying light to the first surface of the light control plate.

Since this surface light source device includes the light control plate according to the present invention, it is possible to more stably reduce the luminance non-uniformity of the light emitted from the light control plate.

A transmissive image display device according to the present invention includes: the light control panel according to the present invention; a plurality of light sources arranged at intervals from each other and supplying light to the first surface of the light control panel; and a transmissive image display unit. An image is illuminated and displayed by light output from a plurality of the above-mentioned light sources and passing through the above-mentioned light diffusion plate.

Since this transmissive image display device includes the light control plate according to the present invention, it is possible to illuminate the transmissive image display portion with stable light with suppressed luminance non-uniformity. Therefore, an image excellent in luminance uniformity can be stably displayed.

According to the present invention, it is possible to provide a more stable light control panel that suppresses non-uniformity in luminance, and a surface light source device and a transmissive image display device including the light control panel.

Description of drawings

FIG. 1 is a cross-sectional view schematically showing the configuration of an embodiment of a transmissive image display device according to the present invention.

2 is a cross-sectional view of a light diffusion plate (light control plate) used in the transmissive image display device shown in FIG. 1 .

Fig. 3 is a view showing a cross-sectional shape of a convex portion included in a light diffusion plate (light control plate).

FIG. 4 is a diagram showing conditions that a contour line represented by a cross-sectional shape of a convex portion satisfies.

Explanation of reference symbols:

1...Transmissive image display device; 10...Transmissive image display unit; 20...Surface light source device; 30...Light source unit; 31...Light source; 40...Light diffusion plate (light control panel); 40a...first face; 40b...second face; 41c, 41d...a pair of side faces; 41...convex portion; 41a...end of protruding portion; 41b ...the top of the convex portion.

Detailed ways

Hereinafter, embodiments of a light control panel, a surface light source device, and a transmissive image display device according to the present invention will be described with reference to the drawings. Here, in the description of the drawings, the same reference numerals are assigned to the same elements, and overlapping descriptions are omitted. In addition, the dimensional ratios in the drawings do not necessarily match those in the description.

FIG. 1 is a cross-sectional view schematically showing the configuration of an embodiment of a transmissive image display device according to the present invention. FIG. 1 is an exploded view of a transmissive image display device. 2 is an enlarged view of a light diffusion plate (light control plate) included in the surface light source device included in the transmissive image display device shown in FIG. 1 .

As the transmissive image display unit 10 , for example, a liquid crystal display panel in which linear polarizing plates 12 and 13 are arranged on both surfaces of a liquid crystal cell 11 is exemplified. In this case, the transmissive image display device 1 is a liquid crystal display device (or a liquid crystal television). For the liquid crystal cell 11 and the polarizing plates 12 and 13, elements used in transmissive image display devices such as conventional liquid crystal display devices can be used. As the liquid crystal cell 11, well-known liquid crystal cells, such as a TFT type and an STN type, can be illustrated.

The surface light source device 20 is a so-called direct type surface light source device 20 and has a light source unit 30 including a plurality of light sources 31 arranged in parallel. Each light source 31 is a linear light source extending in a direction perpendicular to the direction in which the plurality of light sources 31 are arranged, and examples thereof include straight tube-shaped lamps such as fluorescent lamps (cold cathode tubes). The plurality of light sources 31 are arranged at intervals so that the central axes of the respective light sources 31 are located on the same plane P1, and when the distance between the central axes of two adjacent light sources 31, 31 is L, The distance L is, for example, 10 mm to 150 mm. Here, the light source 31 is linear, but a point light source such as LED may also be used. In addition, the plane P1 shown in FIG. 1 is a virtual plane for convenience of description.

As shown in FIG. 1 , a plurality of light sources 31 are preferably arranged in a light box 32, and the inner surface 32a of the light box 32 is preferably formed as a light reflecting surface. As a result, the light output from each light source 31 is reliably output to the transmissive image display unit 10 side, and thus the light from each light source 31 can be effectively used. In the present embodiment, the light source unit 30 will be described as a device having the light box 32 with the above-mentioned preferred configuration.

The surface light source device 20 has a light diffusion plate 40 as a light control plate on the front side of the light source portion 30 (upper side in FIG. configure. As described later, when the separation distance between the light diffusion plate 40 and the plurality of light sources 31 is D, the separation distance D is, for example, 3 mm to 50 mm. In order to achieve thinning in the surface light source device 20 , the distance L between two adjacent light sources 31 , 31 and the separation distance D are selected so that the L/D is 2 or more, preferably 2.5 or more.

The light diffusion plate 40 is for not projecting the image of each light source 31 to the transmissive image display unit 10, but for the light from the light source unit 30, that is, the direct light from each light source 31 and the light reflected by the inner surface 32a of the light box 32. The reflected light is diffusely irradiated toward the transmissive image display unit 10 . The thickness _d1 of the light diffusion plate 40 can be illustrated as about 2 mm.

The light diffusion plate 40 is made of a transparent material. The refractive index of a transparent material is 1.56-1.62 normally, and a transparent resin material and a transparent glass material are illustrated as a transparent material. In addition, examples of transparent resin materials include polycarbonate resin (refractive index: 1.59), MS resin (methyl methacrylate-styrene copolymer resin) (refractive index: 1.56 to 1.59), polystyrene resin (refractive index : 1.59) and the like, polystyrene resin is preferred in terms of cost and low moisture absorption.

When a transparent resin material is used as the transparent material, additives such as ultraviolet absorbers, antistatic agents, antioxidants, processing stabilizers, flame retardants, and lubricants may be added to the transparent resin materials. These additives may be used alone or in combination of two or more.

Examples of the ultraviolet absorber include: benzotriazole-based ultraviolet absorbers, benzophenone-based ultraviolet absorbers, cyanoacrylate-based ultraviolet absorbers, malonate-based ultraviolet absorbers, oxalanilide-based The ultraviolet absorber, triazine ultraviolet absorber, etc. are preferably benzotriazole ultraviolet absorbers and triazine ultraviolet absorbers.

A transparent resin material is usually used as an additive without adding a light-diffusing agent, but it can be used by adding a light-diffusing agent as long as the amount does not significantly impair the effect of the present invention.

As shown in FIGS. 1 and 2 , the light diffusion plate 40 has a substantially flat first surface 40 a on the light source unit 30 side, and has a second surface 40 b on the transmissive image display unit 10 side. A plurality of convex portions 41 are formed on the second surface 40b. In the light-diffusing plate 40 in which such a convex portion 41 is formed, the thickness d ₁ is the distance between the top of the convex portion 41 and the first surface 40 a.

As shown in FIG. 2 , each convex portion 41 is a linear optical element extending in one direction. A plurality of convex portions 41 are arranged in parallel in a direction substantially perpendicular to the extending direction thereof. The several convex-shaped part 41 is densely formed over the whole surface (refer FIG. 1) from one side (40c) of the light-diffusion plate 40 to the other side (40d).

The cross-sectional shape perpendicular to the extending direction of each convex portion 41 is substantially the same among the plurality of convex portions 41 . Here, the distance D and the distance L are selected so that the ratio of the distance D to the distance L between the adjacent two light sources 31, 31, that is, L/D, is 2 or more, preferably 2.5 or more, as described above. stated.

FIG. 3 is a diagram showing an example of a cross-sectional shape perpendicular to the extending direction of the convex portion, and is an enlarged view showing one convex portion. The cross-sectional shape of the convex portion 41 will be described using a local xz coordinate system set as shown in FIG. 3 . The x-axis constituting the xz coordinate system is an axis parallel to the arrangement direction (second direction) of the plurality of convex portions 41, and the z-axis is an axis parallel to the plate thickness direction (direction orthogonal to the first and second directions). .

In the xz plane of the xz coordinate system, both ends 41a, 41a are located on the x-axis, the top 41b is located on the z-axis, and the cross-sectional shape of the convex portion 41 has a symmetrical contour with respect to the z-axis.

This contour line is represented by z(x) satisfying the following formula (3).

0.95×z ₀ (x)≤z(x)≤1.05×z ₀ (x)···(3)

And, in the above formula (3),

${\mathrm{<span\; class="notranslate">\; z</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; -</span>\frac{{\mathrm{<span\; class="notranslate">\; 8</span>}\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}{<span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; x</span>}}{{\mathrm{<span\; class="notranslate">\; w</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; k</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; +</span>\sqrt{{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; k</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 16</span>}{\mathrm{<span\; class="notranslate">\; k</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}{<span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; x</span>}}{{\mathrm{<span\; class="notranslate">\; w</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}}<span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; )</span>$

In Equation (4), w _a is the length of the convex portion 41 in the x-axis direction, h _a = _0.525wa , k _a =-0.4. h _a corresponds to the maximum height in the z-axis direction between both ends 41 a of the convex portion 41 when z ₀ (x) represents the shape of the convex portion 41 . FIG. 3 exemplifies a shape in which z ₀ (x) is expanded and contracted by a predetermined multiple (for example, 1 time) in the z direction within the range satisfying the formula (3).

In formula (3), z(x) is shown in Fig. 4, when z ₀ (x) is determined for a certain width w _a , it can pass through the contour line represented by 0.95z ₀ (x) and use 1.05z ₀ (x) represents the contours of the area between the contours.

The width w _a of the convex portion 41 is usually 40 μm or more, preferably 250 μm or more from the viewpoint of the ease of molding of the convex portion 41 . Due to the pattern of the convex portion 41, it is usually 800 μm or less, preferably 450 μm or less. As the width w _a , specifically, w _a =410 μm, w _a =400 μm, and w _a =325 μm can be exemplified, but the value of w _a is not limited thereto.

The light-diffusing plate 40 may be a single-layer plate made of a single transparent material, or may be a multi-layer plate having a structure in which layers made of different transparent materials are laminated. When the light-diffusing plate 40 is a multi-layer plate, one or both sides of the light-diffusing plate 40 are usually formed with a surface layer with a thickness of 10 μm to 200 μm, preferably 20 μm to 100 μm, and the transparent resin material constituting the surface layer is preferably Make sure to use materials with UV absorbers added. With this structure, it is possible to prevent the deterioration of the light diffusion plate 40 caused by certain ultraviolet rays contained in the light from the light source or outside. , so it is preferable to form a surface layer on the first surface 40a. In this case, although no surface layer is formed on the second surface, it is more preferable from the viewpoint of cost. When a UV absorber is added as the transparent resin material constituting the surface layer, the content thereof is usually 0.5 to 5% by mass, preferably 1 to 2.5% by mass, based on the transparent resin material.

The light diffusion plate 40 can be manufactured, for example, by cutting out a transparent material. Moreover, when using a transparent resin material as a transparent material, it can manufacture by methods, such as injection molding, extrusion molding, and press molding, for example.

The light diffusion plate 40 can also be coated with an antistatic agent on one side or both sides. By applying the antistatic agent, it is possible to prevent the adhesion of dust due to static electricity, and thus prevent the decrease in light transmittance due to the adhesion of dust.

In the surface light source device 20 including the light diffusing plate 40 and the transmissive image display device 1 , the light output from each light source 31 of the light source unit 30 enters the light diffusing plate 40 directly or reflected by the inner surface 32 a of the light box 32 . The light incident on the light diffusing plate 40 is irradiated toward the transmissive image display unit 10 from the second surface 40 b. At this time, since the plurality of convex portions 41 are formed on the second surface 40 b of the light diffusion plate 40 , light is emitted through the convex portions 41 . Since the convex portion 41 has a cross-sectional shape represented by z(x) above, the light is refracted in various directions according to the passing position (emission position) of the light. Through such a diffusion action, the light from the light source 31 is diffused to generate planar light, and the image of the light source 31 is not projected onto the transmissive image display unit 10 .

In the surface light source device 20 including this light diffusion plate 40 , it is possible to output light with suppressed luminance non-uniformity. Furthermore, in the surface light source device 20, variations in luminance uniformity are suppressed for variations in L/D.

Furthermore, in the transmissive image display device 1 including the light diffusion plate 40 , since the light with suppressed luminance non-uniformity can illuminate the transmissive image display portion 10 , it is possible to achieve an improvement in display quality.

As mentioned above, although embodiment of this invention was described, this invention is not limited to the said embodiment. For example, although the light control plate has been described by taking the light diffusion plate 40 as an example, the present invention is not limited thereto, as long as the light output from a plurality of light sources can be controlled on a plane parallel to a plane on which a plurality of light sources are arranged. The uniformity of brightness within the light element can be adjusted. For example, the light control plate may be a brightness adjustment plate such as an optical sheet such as a prism sheet or a lens sheet having a plurality of the above-mentioned convex portions on the light emitting side of a plate made of a transparent material, or an optical film. In addition, the end portions 41a of the cross-sectional shapes of adjacent convex portions 41 overlap in the alignment direction of the convex portions 41, but it is also possible to make flat portions appear in the cross-sectional shape of the light diffusing plate 40 (for example, due to manufacturing errors). The shape of the degree produced) etc.

In addition, in the description so far, the plurality of light sources 31 included in the light source unit 30 are arranged at substantially equal intervals at the interval L, but the distance between two adjacent light sources 31 , 31 may be different. In this case, the average distance L _a between adjacent two light sources 31 , 31 can be used to define the distance between the light sources 31 and the distance ratio between the light source 31 and the light control board.

In the above description, an example using one light-diffusing plate 40 was shown, but the surface light source device 20 may include two or more, and it is preferable to adopt a state in which three to four light-diffusing plates are superimposed. Two or more light-diffusing plates 40 are superimposed so that the first surface 40 a is on the light source 30 side. Moreover, it is preferable that the extension direction (1st direction) of the convex-shaped part 41 of the light-diffusion plate 40 mutually orthogonally crosses at least two sheets among the light-diffusion plates 40.

Industrial availability

According to the present invention, it is possible to provide a light control panel that suppresses unevenness in luminance more stably, and a surface light source device and a transmissive image display device including the light control panel.

Claims (3)

1. A light control panel capable of emitting light incident from a first surface from a second surface opposite to the first surface, wherein: A plurality of convex portions are formed on the second surface, the plurality of convex portions extend in a first direction and are arranged side by side in a second direction perpendicular to the first direction, In a cross section perpendicular to the first direction of the convex portion, the axis passing through the two ends of the cross section in the second direction is taken as the x-axis, and the x-axis passes through the centers of the two ends and In the case of an axis orthogonal to the x-axis as the z-axis, The outline shape of the convex portion in the cross section is represented by z(x) satisfying the following formula (1), 0.95×z ₀ (x)≤z(x)≤1.05×z ₀ (x)···(1) Among them, in the above formula (1), ${\mathrm{<span\; class="notranslate">\; z</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; -</span>\frac{{\mathrm{<span\; class="notranslate">\; 8</span>}\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}{<span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; x</span>}}{{\mathrm{<span\; class="notranslate">\; w</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; k</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; +</span>\sqrt{{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; k</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 16</span>}{\mathrm{<span\; class="notranslate">\; k</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}{<span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; x</span>}}{{\mathrm{<span\; class="notranslate">\; w</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}}<span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$ In Equation (2), w _a is the length of the convex portion in the x-axis direction, h _a =0.525wa _, k _a =-0.4. 2. A surface light source device, characterized in that it has: The light control panel of claim 1; a plurality of light sources arranged at intervals from each other and supplying light to the first face of the light control panel. 3. A transmissive image display device, characterized in that it has: The light control panel of claim 1; a plurality of light sources arranged at intervals from each other and supplying light to the first face of the light control panel; A transmissive image display section is illuminated by light output from the plurality of light sources and passed through the light control panel and displays an image.

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