TWI464459B - A light control board, a surface light source device, and a transmission type image display device - Google Patents

Description

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

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

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 a light source for outputting backlight of a liquid crystal display unit. As a typical surface light source device, a plurality of light sources are arranged on the back side of a light control panel called a light diffusing plate. In such a surface light source device, it is possible to easily increase the luminance of the light-emitting surface by increasing the number of light sources arranged, and conversely, there is a problem that luminance uniformity is low. In particular, in the vicinity of the light source, the brightness becomes high, so there is a problem of periodic unevenness in light emission, and the front surface periodic light is emitted as the surface light source device is thinned or the number of light sources with low power consumption is reduced. The problem of inhomogeneity has become more serious.

In order to ensure the brightness uniformity, a light amount correction pattern is formed on the light diffusing plate which is an example of the light control plate in accordance with the distance from the light source, for example, in Japanese Laid-Open Patent Publication No. Hei 6-273760 (Patent Document 1). In the same manner, in the vicinity of the light source side surface of the light diffusing plate, a portion having a zigzag cross section is provided in a portion near the light source side of the light diffusing plate, and the light source having a large amount of scattered light is directly above. Light near.

However, as in the light amount correction pattern of Patent Document 1, and the cross-sectional jagged shape of Patent Document 2, the backlight configuration having a dependency relationship with the position of the light source is shifted in accordance with the position of the light control plate called the light diffusion plate. Or heat-induced deformation or the like, which deteriorates brightness uniformity.

Accordingly, 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, which are more stable and can suppress unevenness in light emission.

In the light control panel according to the present invention, the light incident on the first surface can be emitted from the second surface positioned on the opposite side of the first surface, and is characterized in that it extends in the first direction and is positive. The plurality of convex portions arranged in parallel in the second direction in the first direction are formed on the second surface, and the ends of the convex portions orthogonal to the first direction pass through the two ends of the cross section in the second direction The axis is the x-axis, and when the axis orthogonal to the x-axis at the center of the both ends is the z-axis on the x-axis, the contour shape of the convex portion in the cross section satisfies the z(x) of the following formula (1) Light control panel,

0.95×z ₀ (x)≦z(x)≦1.05×z ₀ (x)‧‧‧(1)

Wherein, in the above formula (1),

(In the formula (2), w _a is the length of the convex portion in the x-axis direction, h _a = 0.525w _a , k _a = -0.4).

According to this configuration, since the convex portion has the cross-sectional shape indicated by z(x), it is possible to more stably reduce the unevenness of the light emitted by the light control panel of the present invention.

A surface light source device according to the present invention includes a light control panel according to the present invention, and a plurality of light sources that are disposed apart from each other and that supply light to the first surface of the light control panel.

Since the surface light source device includes the light control panel according to the present invention, it is possible to more stably reduce the unevenness of light emitted from the light control panel.

A transmissive image display device according to the present invention includes: a light control panel according to the present invention; and a plurality of light sources that are disposed apart from each other, and that supply light to the first surface of the light control panel, and from the plurality of light sources A transmissive image display unit that outputs an image and illuminates the light of the light diffusing plate to display an image.

Since the transmissive image display device includes the light control panel according to the present invention, it is possible to illuminate the transmissive image display unit with light that is suppressed in light emission unevenness. Therefore, an image excellent in unevenness in light emission can be displayed in a stable manner.

According to the present invention, it is possible to provide a light control panel which can be more stable and suppresses unevenness in light emission, and a surface light source device and a transmissive image display device including the light control panel.

Hereinafter, embodiments of the light control panel, the surface light source device, and the transmissive image display device of the present invention will be described with reference to the drawings. In the description of the drawings, the same components are denoted by the same reference numerals, and the description thereof will not be repeated. Moreover, the dimensional ratio of the drawings is not necessarily consistent with the description.

Fig. 1 is a cross-sectional view showing a configuration of an embodiment of a transmissive image display device according to the present invention. Fig. 1 shows an exploded display transmissive image display device. FIG. 2 is an enlarged view of a light diffusing 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 the linear polarizing plates 12 and 13 are disposed on both surfaces of the liquid crystal cell 11 can be cited. In this case, the transmissive image display device 1 is a liquid crystal display device (or a liquid crystal television). As the liquid crystal cell 11 and the polarizing plates 12 and 13, a user of a transmissive image display device such as a liquid crystal display device of the prior art can be used. As the liquid crystal cell 11, for example, a known liquid crystal cell such as a TFT type or an STN type can be exemplified.

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 of the light sources 31 is a linear light source extending in a direction orthogonal to the direction in which the plurality of light sources 31 are arranged, and is, for example, a straight tubular light source such as a fluorescent lamp (cold cathode line lamp). The plurality of light sources 31 are arranged at intervals such that the central axes of the respective light sources 31 are located on the same plane P1. When the distance between the central axes of the adjacent two light sources 31, 31 is L, the distance L is, for example, 10mm ~ 150mm. Here, the light source 31 is linear, and a point light source such as an LED is also possible. Further, the plane P1 shown in Fig. 1 is a plane assumed for convenience of explanation.

The plurality of light sources 31, as shown in Fig. 1, are preferably disposed in the light box 32, and the inner surface 32a of the light box 32 is preferably formed as a light reflecting surface. Thereby, the light output from each light source 31 is surely outputted to the transmissive image display unit 10 side, so that the light from each light source 31 can be utilized efficiently. In the present embodiment, the light source unit 30 will be described with reference to the light box 32 having the above-described preferred configuration.

The surface light source device 20 is provided on the front surface side (upper side in FIG. 1) of the light source unit 30, that is, on the side of the transmissive image display unit 10, a light diffusing plate 40 as a light control plate which is disposed apart from the light source 31. As will be described later, when the distance between the light diffusing plate 40 and the complex light source 31 is D, the distance D is, for example, 3 mm to 50 mm. In order to reduce the thickness of the surface light source device 20, L/D is 2 or more, and L/D is preferably 2.5 or more, and the distance L between the adjacent two light sources 31 and 31 and the distance D are selected.

The light diffusing plate 40 is configured such that the light from the light source unit 30, that is, the direct light from each of the light sources 31, and the inside of the light box 32 are not projected so as to project the image of each of the light sources 31 to the transmissive image display unit 10. The reflected light reflected by the surface 32a is diffused and irradiated toward the transmissive image display unit 10. The thickness d ₁ of the light diffusing plate 40 is exemplified by about 2 mm.

The light diffusing plate 40 is made of a transparent material. The refractive index of the transparent material is usually from 1.56 to 1.62, and a transparent resin material or a transparent glass material can be exemplified as the transparent material. Further, as the transparent resin material, a polycarbonate resin (refractive index: 1.59), an MS resin (methyl methacrylate-styrene copolymer resin) (refractive index: 1.56 to 1.59), and a polystyrene resin (refraction) are exemplified. Rate: 1.59), etc., from the viewpoint of cost and low moisture absorption rate, polystyrene resin is preferred.

When a transparent resin material is used as the transparent material, an additive such as an ultraviolet absorber, a charge preventive agent, an oxidation preventive agent, a processing stabilizer, a flame retardant, or a slip agent may be added to the transparent resin material. These additives may be used alone or in combination of two or more.

Examples of the ultraviolet absorber include a benzotriazole-based ultraviolet absorber, a benzophenone-based ultraviolet absorber, a cyanoacrylate-based ultraviolet absorber, and a malonate-based ultraviolet absorber. The absorbent, the herbicide diphenylamine-based ultraviolet absorber, and the triazine-based ultraviolet absorber are preferably a benzotriazole-based ultraviolet absorber or a triazine-based ultraviolet absorber.

The transparent resin material usually does not contain a light diffusing agent as an additive, but in the present invention, a light diffusing agent may be added as long as it is not significantly detrimental to the effect.

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

As shown in FIG. 2, each convex portion 41 is a linear optical element extending in one direction. The plurality of convex portions 41 are arranged side by side in a direction approximately orthogonal to the extending direction thereof. The plurality of convex portions 41 are formed to be denser from the one side (40c) to the other side (40d) of the light diffusing plate 40 (see FIG. 1).

The cross-sectional shape orthogonal to the extending direction of each convex portion 41 is approximately the same between the plurality of convex portions 41. Further, the distance D and the distance L are selected such that the distance L between the distance D and the distance L between the adjacent two light sources 31 and 31 is 2 or more, and preferably 2.5 or more. As mentioned above.

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

On the xz plane of the xz coordinate system, the 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 contour symmetrical with respect to the z-axis.

This outline is expressed by satisfying z(x) of the following formula (3).

0.95×z ₀ (x)≦z(x)≦1.05×z ₀ (x)‧‧‧(3)

Wherein, in the above formula (3),

Formula (4), w _a is the length of the x-axis direction of the convex portion _{41, h a = 0.525w a, k} a = -0.4. h _a corresponds to the maximum height in the z-axis direction between the both ends 41a, 41a of the convex portion 41 when the shape of the convex portion 41 is represented by z ₀ (x). In FIG. 3, a shape in which z ₀ (x) is stretched by a specific multiple (for example, 1 time) in the z direction within a range satisfying the formula (3) is exemplified.

In equation (3), z(x) is as shown in FIG. 4, and when z ₀ (x) is determined for a certain width w _a , as long as it passes through the contour line represented by 0.95z ₀ (x) and 1.05 The contour of the area between the contour lines represented by z ₀ (x) is sufficient.

The width w _a of the convex portion 41 is easily formed by the convex portion 41, and is usually 40 μm or more, preferably 250 μm or more. When incorporated into the surface light source device 20 or the transmissive image display device 1, the convex portion is convex. Since the shape of the shape 41 is not easily confirmed by the naked eye, it is usually 800 μm or less, preferably 450 μm or less. As the broad width w _a , w _a = 410 μm, w _a = 400 μm, and w _a = 325 μm can be specifically exemplified, but the value of w _a is not limited thereto.

The light diffusing plate 40 may be a single-layered plate made of a single transparent material, or a laminated plate of a structure in which layers of mutually different transparent materials are laminated. When the light diffusing plate 40 is a multilayer plate, the light diffusing plate 40 is usually formed of a skin layer having a thickness of 10 μm to 200 μm, preferably 20 μm to 100 μm, as a transparent resin material constituting the skin layer. It is best to use those who are added with UV absorbers. According to the configuration, it is possible to prevent deterioration of the light diffusing plate 40 due to ultraviolet rays contained in the light source or light from the outside, and in particular, when a fluorescent tube or the like is used as the light source, deterioration due to ultraviolet rays from the fluorescent tube can be prevented. Therefore, it is preferable to form the skin layer on the first surface 40a, and it is more preferable from the viewpoint of cost in the case where the skin layer is not formed on the second surface. When the ultraviolet absorber is used as the transparent resin material constituting the skin layer, the content thereof is usually 0.5% by mass to 5% by mass, preferably 1% by mass to 2.5% by mass based on the transparent resin material.

The light diffusing plate 40 can be manufactured, for example, by a method of cutting out from a transparent material. Further, when a transparent resin material is used as the transparent material, it can be produced, for example, by a method such as an injection molding method, an extrusion molding method, or a press molding method.

The light diffusing plate 40 may be coated with an antistatic agent on one side or both sides. By applying an antistatic agent, it is possible to prevent dust from adhering due to static electricity, and to prevent a decrease in light transmittance due to adhesion of dust.

In the surface light source device 20 and the transmissive image display device 1 including the light diffusing plate 40, the light output from each of the light sources 31 of the light source unit 30 is directly reflected on the inner surface 32a of the light box 32 and enters the light diffusing plate 40. The light incident on the light diffusing plate 40 is irradiated toward the transmissive image display unit 10 by the second surface 40b. At this time, since the plurality of convex portions 41 are formed on the second surface 40b of the light diffusion plate 40, the light is emitted through the convex portion 41. Since the convex portion 41 has a cross-sectional shape indicated by z(x) described above, light is refracted in various directions in response to the light passing position (ejection position). By 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 the light diffusing plate 40, it is possible to output light in which unevenness in light emission is suppressed. Further, in the surface light source device 20, the change in luminance uniformity is also suppressed for the change in L/D.

Then, in the transmissive image display device 1 including the optical diffusing plate 40, light having suppressed light emission unevenness can illuminate the transmissive image display unit 10, so that display quality can be improved.

Although the embodiments of the present invention have been described above, the present invention is not limited to these embodiments. For example, the light control plate 40 is used to describe the light control plate, but the invention is not limited thereto, as long as the light output by the plurality of light sources is adjusted parallel to the brightness uniformity of the plane in which the plane of the complex light source is arranged. Just fine. For example, the light control plate may be a light-adjusting plate of an optical sheet such as a cymbal or a lens sheet or an optical film, which has a plurality of convex portions on the light-emitting side of the plate made of a transparent material. Further, the end 41a of the cross-sectional shape of the adjacent convex portion 41 is overlapped in the direction in which the convex portions 41 are arranged, but a flat portion may be formed in the cross-sectional shape of the light diffusing plate 40 (for example, due to manufacturing errors) .

Further, as described so far, the plurality of light sources 31 having the light source unit 30 are arranged at substantially equal intervals with an interval L therebetween, but the distance between the adjacent two light sources 31 and 31 may be different. In this case, the distance L _m may average interval between adjacent second light sources 31, 31, to define the distance between the ratio of the distance between the light sources 31 and light source 31 and the light control plate.

In the above description, the light diffusing plate 40 is exemplified as one example. However, the surface light source device 20 may be used in two or more, and preferably three or four light diffusing plates 40 are overlapped. The two or more light diffusion plates 40 are superposed so that the first surface 40a becomes the light source 30 side. Further, at least two of the light diffusing plates 40 are preferably orthogonal to each other in the extending direction (first direction) of the convex portion 41 of the light diffusing plate 40.

[Industry use possibility]

According to the present invention, it is possible to provide a light control panel which can be more stable and suppresses unevenness in light emission, and a surface light source device and a transmissive image display device including the light control panel.

1. . . Transmissive image display device

10. . . Transmissive image display unit

20. . . Surface light source device

30. . . Light source department

31. . . light source

40. . . Light diffusing plate (light control board)

40a. . . First side

40b. . . Second side

41c, 41d. . . Side of a pair

41. . . Convex

41a. . . End of the convex part

41b. . . Top of the convex part

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

Fig. 2 is a cross-sectional view showing a light diffusing plate (light control plate) used in the transmissive image display device shown in Fig. 1.

Fig. 3 is a view showing a sectional shape of a convex portion of a light diffusing plate (light diffusing plate).

Fig. 4 is a view showing conditions under which the outline of the cross-sectional shape of the convex portion is satisfied.

31. . . light source

40. . . Light diffusing plate (light control board)

40a. . . First side

41. . . Convex

41a. . . End of the convex part

w _a . . . Length of the convex portion 41 in the x-axis direction

D. . . Separation distance between complex light sources 31

L. . . Distance between the central axes

Claims (3)

A light control panel is characterized in that light incident on the first surface is emitted from a second surface opposite to the first surface, and is characterized by extending in the first direction and orthogonal to the first direction a plurality of convex portions arranged in parallel in the second direction are formed on the second surface, and a cross section orthogonal to the first direction of the convex portion passes through both end axes of the cross section passing through the second direction As the x-axis, when the axis passing through the center of the both ends on the x-axis and orthogonal to the x-axis is the z-axis, the outline shape of the convex portion in the cross section satisfies the following formula (1). (x) The light control panel represented by 0.95 × z ₀ (x) ≦ z (x) ≦ 1.05 × z ₀ (x) ‧ ‧ (1) wherein, in the above formula (1), In the formula (2), w _a is the length of the convex portion in the x-axis direction, and h _a = 0.525 w _a and k _a = -0.4. A surface light source device comprising: the light control panel according to claim 1; and a plurality of light sources that are disposed apart from each other and that supply light to the first surface of the light control panel. A transmissive image display device comprising: the light control panel according to claim 1; and a plurality of light sources arranged to be spaced apart from each other to supply light to the first surface of the light control panel; A transmissive image display unit that displays an image by illuminating light from the plurality of light sources and passing through the light of the light control plate.