JPH06342159A - Surface light source body and production of surface light source body - Google Patents

Abstract

PURPOSE:To prevent the unequal brightness on the surface of a light transmission plate which is an exit surface of reflected light. CONSTITUTION:The reflection surface of the light transmission plate 50 is formed by forming many grooves 1 of an approximately V shape in section in parallel on the rear surface 50b of the light transmission plate 50. A fine rugged surface 2 having fine ruggedness to the extent of not impairing the shape over the entire part of these grooves 1 is formed on the rear surface 50b. As a result, the light rays L1, L2 from a light source are made into scattered light by this fine rugged surface 2 at the time of reflection on the groove slopes 1a, 1b, by which the reflected light quantity in the respective parts of the slopes is uniformalized. The scattered light over the entire part of the slopes is the reflected light L3 having directivity provided with a prescribed angle to the slopes and, therefore, the luminance of the surface of the light transmission plate is uniformalized when the reflected light is emitted on the surface of the light transmission plate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light source body, and more particularly to a planar light source body having a uniform brightness and a method for manufacturing the light source body.

[0002]

2. Description of the Related Art For example, as a back lighting means of a liquid crystal display device, that is, as a backlight, it is necessary to diffuse light as uniformly as possible to make the display easy to see. Recently, as one of the light diffusing methods, a method of using a transparent plate itself which transmits light as a light diffusing means has been proposed and put into practical use.

5 and 6 are shown in Japanese Patent Laid-Open No. 165504/1990.
No. 1 and JP-A-2-176692, etc., the concrete structure of the illuminating means is shown. Reference numeral 50 denotes a plate material (hereinafter referred to as a “light guide plate”) formed of a transparent material such as plastic such as acrylic resin or glass, and one surface (back surface) 50b thereof has a groove 51 having a substantially V-shaped cross section. A plurality of light guide plates 50 are formed so as to be parallel to each other in the width direction to form a reflection surface (FIG. 6).
reference). Light sources 52 and 53 such as fluorescent lamps are arranged on both sides of the light guide plate 50, and reflectors 54 are arranged close to the surface on the side where the groove 51 is formed. The light emitted from the light sources 52 and 53 by the groove 51 of the light guide plate 50 and the reflecting plate 54 on the back surface is emitted through the light guide plate surface 50a to illuminate the object. This illuminating means has relatively good performance as an illuminating means because the reflection of light in each groove is relatively uniform and the attenuation of light from the light source is small.

[0004]

FIG. 7 shows the light guide plate 5 described above.
The light reflection state at 0 is shown. Lights L1 and L2 emitted from the left and right light sources 52 and 3 are inclined surfaces 51A and 51 of the groove 51.
The light is reflected by B and goes upward, and the light is emitted from the light guide plate surface 50a. In this case, for example, the bottom portion 5 of each groove 51 is used.
In 1c, the light is not sufficiently reflected, which may cause uneven brightness on the surface of the light guide plate. In addition, the light itself emitted from the light sources 52 and 53 may not be perfectly parallel light, and the unevenness in brightness may occur depending on the processing accuracy of the groove 51.

FIG. 8 shows a means for preventing the uneven brightness as described above. A diffuser plate 52 is disposed in close contact with the surface 50a of the light guide plate 50, which is the light exit surface. The diffusion plate 52 is formed of, for example, a transparent plate material made of an acrylic resin or the like, which is the same as the light guide plate 50, or a thinner film, and the contact surface with the light guide plate surface 50a is formed flat, but the other surface is fine. It is the uneven surface 52a. Thereby, the light emitted from the surface 50a of the light guide plate 50 is scattered by passing through the uneven surface 52a of the diffusion plate 52, and the uneven brightness is eliminated. Although the diffuser plate 52 is quite effective in preventing uneven brightness, the following drawbacks have been pointed out.

First, moisture may enter the boundary surface between the diffusion plate 52 and the surface 50a of the light guide plate, which causes a considerable unevenness in brightness.
Further, even if the diffuser plate is formed of a transparent body, provision of the diffuser plate itself causes attenuation of light, and the light guide plate 5 is also provided.
Even if the diffuser plate 52 has the same refractive index as that of the light guide plate 50 by being formed of the same material as 0, it is avoided that a slight air layer is formed between the light guide plate surface 50a and the diffuser plate 52. Therefore, a part of the light emitted from the light guide plate surface 52 is reflected at this boundary surface.

On the other hand, regarding the back surface 50b which is the reflection surface of the light guide plate, at present, the technical interest is to form the groove slopes 51a and 51b of the groove forming portion as flat as possible, thereby improving the light reflectance. It is aimed at improving.
If this is done, the light reflectance will certainly improve, but since the directivity of the reflected light on each slope will also increase, the angle of the slope of the groove will be uneven, and the slope will be scratched. When the forming accuracy is low, the low forming accuracy immediately appears as uneven brightness on the surface of the light guide plate. Therefore, in forming the groove, a means such as cutting that can obtain high forming accuracy is used, resulting in an increase in the price of the light guide plate. In addition, it is necessary to pay close attention not to scratch the reflective surface even after forming the light guide plate.

[0008]

SUMMARY OF THE INVENTION The present invention is configured to solve the above-mentioned problems of the prior art, wherein at least one of the six surfaces of the light guide plate is provided. The present invention is characterized by a planar light source body in which a fine uneven surface is directly formed, and a method of integrally molding the planar light source body by molding.

[0009]

When the uneven surface is directly formed on the light exit surface of the light guide plate, light is scattered on the uneven surface to prevent uneven brightness, and in addition to or instead of this, on the groove forming surface side. When an uneven surface is formed on all or part of the slope of the groove, uneven brightness is prevented by making at least a part of the light reflected by the slope of the groove omnidirectional light.

[0010]

Embodiments of the present invention will be specifically described below with reference to the drawings.

In FIG. 1, an arrow 1 indicates a groove formed on the back surface 50b of the light guide plate 50, which is formed in parallel with the width direction of the back surface of the light guide plate as in the conventional example. By forming the
Is a reflective surface. The back surface 50b body of the light guide plate 50 including the slopes 1a and 1b of the groove 1 has an uneven surface (hereinafter, referred to as "the following" hereinafter, referred to as "an uneven surface" that is sufficiently fine with respect to the formation depth of the groove 1 so as not to impair the overall shape of the groove 1. 2). Incidentally, since the formation depth of the groove is generally 1 mm or less, the unevenness of the fine uneven surface 2 is fine in the unit of micron.

As a method of forming the fine uneven surface 2, first, the light guide plate 50 having the groove 1 is formed in advance.
There is a method of sandblasting the back surface 50b of the light guide plate having the groove 1.

The second method is a method in which the light guide plate forming material is poured into a molding die to mold the light guide plate at a stretch. With respect to the molding die, a fine concavo-convex surface is formed in advance on the portion of the molding die corresponding to the portion where the fine concavo-convex surface 2 of the light guide plate is to be formed. The most effective method for forming a fine uneven surface in the molding die is etching, which allows a uniform uneven surface to be formed relatively easily.

In the above structure, the lights L1 and L2 incident from the side surface of the light guide plate 50 reach the slopes 1a and 1b of the groove 1. Here, the lights L1 and L2 become non-directional scattered lights L1 ′ and L2 ′ on the individual fine uneven surfaces 2,
Since the entire fine uneven surface 2 is the slopes 1a and 1b,
The total of these scattered lights L1 ′ and L2 ′ is emitted from the surface of the light guide plate 50 as reflected light L3 having directivity as a whole. With this structure, the attenuation of light on the slopes 1a and 1b of the groove 1 which is the reflection surface is slightly larger than that when these slopes are formed flat, but on the other hand, on the other hand, in each reflection surface. Since the directivity of the reflected light becomes low, the unevenness in brightness on the surface of the light guide plate is significantly reduced even if the accuracy of forming the groove is somewhat low. Therefore, also in the first light guide plate forming method by sandblasting, the light guide plate previously formed before sandblasting may be formed by molding in which the groove 1 is simultaneously formed. By the way, conventionally, it was not practical to obtain the light guide plate as an integral mold at a low cost because the performance was drastically reduced because it was necessary to increase the accuracy of forming the groove.

FIG. 2 shows a second embodiment.

In this embodiment, the fine concavo-convex surface 2 is formed only on a part of each inclined surface 1a, 1b with the bottom 1c of each groove 1 as the center. Although the light is reflected uniformly on the sloped surface of each groove 1, the groove bottom 1c where the sloped surfaces 1a and 1b intersect is not formed as a sloped surface. Therefore, the reflectance of both the light L1 and L2 is lowered, and the light output portion On the surface of the light guide plate, the low-luminance portion tends to linearly form along the groove bottom portion 1c. If the fine concave-convex surface 2 is formed around the groove 1c as in this embodiment, the reflected light becomes scattered light at this portion and the directivity is lowered, and as a result, the low-luminance portion is clearly generated. It can be prevented. That is, in this embodiment, the fine uneven surface 2 is formed only on a portion where luminance unevenness is likely to occur, so that it is possible to prevent the occurrence of luminance unevenness while further suppressing the decrease in luminance as the light guide plate.

FIG. 3 shows a third embodiment.

In the illustrated structure, the fine uneven surface 2 is formed not only on the back surface 50b of the light guide plate shown in FIG. 1 but also on the front surface 50a of the light guide plate which is a light emitting portion of reflected light. As a result, the reflected light L3 is further scattered on the light guide plate surface 50a, which is the light emitting surface, to become diffused light, and the brightness on the light guide plate surface 50a becomes more uniform. In the illustrated configuration, the fine uneven surface 2 is formed on both the light guide plate front surface 50a and the light guide plate back surface 50b. However, the formation of the fine uneven surface 2 on the back surface 50b is omitted and the light guide plate surface 50a is formed. The fine uneven surface 2 may be formed only on the opposite side. If the surface of the fine uneven surface 2 is coated with a transparent resin and the refractive index of the transparent resin is different from that of the material forming the light guide plate 50, the effect of the fine uneven surface 2 on the light guide plate surface 50a will be obtained. The surface can be smoothed without damage.

FIG. 4 shows a fourth embodiment. In this embodiment, the fine concavo-convex surface 2 is formed on the light guide plate side surface 50c which is the light entrance surface of the light guide plate 1. In this configuration, when the light from the light source enters the light guide plate 50, the fine uneven surface 2
Thereby, the incident light is scattered, and the brightness of the incident light can be made uniform in the thickness direction and the width direction of the light guide plate. For example, even if dust adheres to the light source or the luminance of the entire light source becomes non-uniform due to deterioration over time, if the light guide plate side surface 50c, which is the incident surface, is set as the fine uneven surface 2, the incident light itself can be obtained. Can be made uniform. Note that it is also possible to form the surface on which the fine concavo-convex surface 2 is formed on the side surface of the light guide plate other than the light incident surface so that the light is uniformly reflected on this surface.

As is clear from the first to fourth embodiments, an appropriate light guide plate can be obtained by appropriately selecting and combining the surfaces on which the fine concavo-convex surface 2 is formed in consideration of the type of illumination target, the light amount of the light source, and the like. Is possible. Further, although the groove shape on the back surface of the light guide plate is shown to have a substantially V-shaped cross section, it goes without saying that the object of the present invention is not limited to the light guide plate having the groove of this cross section shape. In some cases, there is no need for such a groove having a continuous shape. In short, a continuous or discontinuous concave-convex surface is formed on one surface of the light guide plate, so that all of the light guide plate to be a reflection surface is formed. It is feasible, and the illumination target of the light guide plate is not limited to the liquid crystal display device.

[0021]

INDUSTRIAL APPLICABILITY As described in detail in each of the embodiments of the present invention, at least one of the constituent surfaces of the light guide plate having the groove or the unevenness for light reflection on the back surface has the fine uneven surface. By being formed, it is possible to eliminate the directivity of the reflected light on the fine uneven surface, thereby preventing the occurrence of uneven brightness on the surface of the light guide plate.

In the past, in order to reduce or prevent uneven brightness, it was required that the accuracy of forming the groove or the unevenness having the inclined surface for reflection was extremely high. However, by forming the minute uneven surface, the groove or the unevenness was formed. It becomes possible to make the reflection of light on the surface more uniform, and therefore, the allowable value of the formation accuracy of these grooves or the uneven surface itself may be gentler than before, and as a result, the cost and time required for manufacturing the light guide plate can be reduced. It becomes possible to reduce.

[Brief description of drawings]

FIG. 1 is an enlarged partial side view of a light guide plate showing a first embodiment of the present invention.

FIG. 2 is an enlarged partial side view of a light guide plate showing a second embodiment of the present invention.

FIG. 3 is an enlarged partial side view of a light guide plate showing a third embodiment of the present invention.

FIG. 4 is an enlarged partial side view of a light guide plate showing a fourth embodiment of the present invention.

FIG. 5 is a side view of a lighting device having a conventional light guide plate.

FIG. 6 is a rear view of the lighting device shown in FIG.

FIG. 7 is an enlarged partial side view of a light guide plate showing a light reflection state in a conventional lighting device.

FIG. 8 is an enlarged partial side view of a light guide plate of a conventional illumination device provided with a diffusion plate.

[Explanation of symbols]

 1 groove 1a, 1b (groove) slope 1c (groove) bottom 2 fine uneven surface 50 light guide plate 50a light guide plate surface (light emitting surface) 50b light guide plate back surface (reflection surface) 50c light guide plate side surface 52, 53 light source L1, L2 Light from light source L1 ', L2' Scattered light L3 Reflected light

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Makoto Tokunaga 3-14-12 Kamiosaki, Shinagawa-ku, Tokyo Inoue Electric Co., Ltd.

Claims (5)

[Claims] 1. A light guide plate in which a large number of grooves or uneven surfaces are formed on one surface of a transparent plate to serve as a light reflecting surface, and the unevenness is sufficiently fine with respect to the formation depth of the grooves or uneven surfaces. A planar light source body, characterized in that a fine uneven surface having is formed on at least one of the surfaces forming the light guide plate. 2. The planar light source body according to claim 1, wherein the fine concavo-convex surface is formed on the entire reflecting surface of the light guide plate. 3. The planar light source body according to claim 1, wherein the fine uneven surface is formed on the surface of the light guide plate. 4. The planar light source body according to claim 1, wherein a front fine concavo-convex surface is formed on a side surface of the light guide plate. 5. The planar light source body should be integrally molded by a molding die, and the molding die should be formed with fine irregularities in addition to grooves or irregularities forming the reflection surface of the light guide plate. A method for manufacturing a planar light source body, characterized in that the light guide plate is formed by a single molding without performing other processing by performing fine unevenness processing on the portion in advance.