JPH07104132A - Surface light source body - Google Patents

Abstract

PURPOSE:To keep luminance on the light emitting face of a light transmission plate constant by making reflected light uniform on the light transmission plate. CONSTITUTION:Among plural grooves having nearly V-shaped section which are recessed parallel to each other on the rear of the light transmission plate, at least the groove base part 1c is formed to a curved surface so that the sectional shape of the groove base part 1c may be the curved one. Light L1 and L2 from the light source are reflected by inclined surfaces 1a and 1b, and the reflected light L1' and L2' are reflected so as to be separated each other. Light is omnidirectionally reflected by the curved groove base part 1c, so that reflected light L3 for filling up in between the reflected light L1' and L2' is emitted, then, the luminance is made uniform all over the light emitting surface of the light transmission plate 50.

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.

[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.

8 and 9 are shown in Japanese Patent Laid-Open No. 165504/1990.
No. 1 and Japanese Patent Laid-Open No. 2-176692. Reference numeral 50 is a plate material (hereinafter referred to as “light guide plate”) formed of a transparent material such as plastic such as acrylic resin or glass.
In addition, a large number of grooves 51 having a substantially V-shaped cross section are formed on one surface thereof so as to be parallel to each other in the width direction of the light guide plate 50 (see FIG. 9). Light sources 52 and 53 such as fluorescent lamps are arranged on both sides of the light guide plate 50, and a reflection plate 54 is provided on the surface on which the groove 51 is formed in the vicinity of the light guide plate.
Are arranged. Due to the groove 51 of the light guide plate 50 and the back reflector 54 used as an auxiliary, the light sources 52, 53
The light emitted from the light exits through the light guide plate surface 50a and illuminates the object. This type of illumination means has relatively good performance because the reflection of light in each groove is relatively uniform and the attenuation of light from the light source is small.

[0004]

10 to 12 specifically show the operation of the illuminating means. First, in FIG. 10, the light L1 from the light source 52 strikes the inclined surface 51a of the groove 51 as substantially parallel light, and most of it is reflected as shown by the arrow toward the thickness direction of the light guide plate 50, and the surface 50
Light will be emitted from a. On the other hand, the light L2 from the light source 53
Hits the opposite slopes 51b of the groove 51, and the light L1
Similarly to, the light is reflected in the thickness direction of the light guide plate 50. In this case, the angle α1 formed between the slopes 51a and 51b and the back surface 50b of the light guide plate
Is 45 ° or more, the reflected light is reflected so as to be separated on both sides centering on the groove bottom portion 51c. Therefore, the amount of light emitted from the portion corresponding to the groove bottom portion 51c on the light guide plate surface 50a is reduced, and as shown by the light guide plate surface brightness BR, the brightness of this portion is reduced, and the light guide plate surface 50 has the groove 51. A low-intensity part is generated in a streak pattern along the bottom part 51c. In reality, neither the light L1 nor the light L2 emitted from each of the light sources 52 and 53 is a perfect parallel light beam, so that an extremely low luminance portion does not occur as shown in the figure, but a visually recognizable low luminance portion does occur. I will end up.

FIG. 11 shows a case where a situation opposite to the above situation occurs. In this example, the slopes 51a and 5 of the groove 51 are
The angle α2 formed by 1b and the back surface 50b of the light guide plate is 45 ° or less, and in this case, the respective lights L1 and L2 are formed.
Will be reflected so as to converge toward the groove bottom portion 51c. As a result, contrary to the above case, the light guide plate surface brightness BR is higher in the portion along the bottom of the groove 51 than in the peripheral portion.

As described above, the unevenness of light basically occurs in the configurations of FIGS. 10 and 11. Therefore, on the premise of occurrence of the unevenness, the number of the grooves is increased so that the unevenness is hardly visually recognized. That is, as the number of grooves formed is increased, the width of the change in the brightness on the surface of the light guide plate becomes narrower, so that the low brightness part and the light brightness part are naturally integrated with each other, and the entire light guide plate is recognized as a relatively uniform brightness. However, on the other hand, fine processing is required.

From the above points, the slope 51 of the groove 51 is
The angle between a and 51b and the back surface 50b of the light guide plate is approximately 45 °.
If so, it is expected that good results will be obtained, but in reality, uneven illumination occurs due to the following reasons.

That is, in FIG. 12, the slope 51 of the groove 51 is
The angle α3 formed by a and 51b and the back surface 50b of the light guide plate is approximately 4
It is set at 5 °. As a result, the lights L1 and L2 that hit the slopes 51a and 51b are reflected substantially vertically, and both lights L1 and L2 are emitted to the light guide plate surface 50a as parallel lights. That is, the light emitted to the surface of the light guide plate tends to be divided into a light L1 region and a light L2 region with the groove bottom 51c as the center. In this case, for example, as shown in the figure, the light L1 transmitted through the light guide plate has a small amount of attenuation in the groove near the light source 52, and the light L2 traveling from a long distance has a large amount of attenuation. There is a difference in the amount of light between L1 and L2, and when two light regions are formed relatively clearly on the light guide plate surface 50b as described above, this difference in the amount of light is directly regarded as the difference in the light guide plate surface brightness BR. Will appear.

[0009]

The present invention is constructed to solve the above-mentioned problems, and as described above, the performance of the light guide plate formed by forming grooves in the transparent plate is basically good. In view of the above, the present invention is based on this grooved type light guide plate and solves the above-mentioned problems of the light guide plate of this type.

That is, in a light guide plate in which a groove is formed on one surface of a transparent plate, at least a part of each groove surface is configured so that its cross-sectional shape is curved, and preferably at least the groove bottom has a curved cross-sectional shape. The light guide plate is configured so that The term "transparent plate" broadly refers to a plate material capable of transmitting light, and includes not only a so-called non-colored so-called transparent body but also a colored one or an emulsified one if light can be transmitted. Shall be used below.

[0011]

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

FIG. 1 shows a first embodiment. This embodiment has a groove corresponding to the groove shape shown in FIG. In the figure, reference numeral 1 is the back surface 5 of the light guide plate 50, similar to the groove 51.
At 0b, the grooves are formed in parallel with each other in the width direction of the light guide plate. Opposing slopes 1a and 1b of the groove 1 are formed to be flat so that their cross-sectional shapes form a straight line, similarly to the conventional configuration shown in FIG. On the other hand, the bottom portion 1c with which the two inclined surfaces 1a and 1b come into contact is formed as a curved surface so that the cross-sectional shape thereof draws an arc.

With the above construction, the slope 1a,
In the plane portion of 1b, both parallel lights L1 and L2 are reflected in parallel,
In the illustrated configuration, the slopes 1a, 1 with respect to the back surface 50b of the light guide plate
Since the angle formed by b is 45 ° or more as α1, the reflected lights L1 ′ and L2 ′ tend to be reflected to the outside while being separated from each other. However, since the groove bottom portion 1c located at the central portion of the both slopes 1a and 1b is formed into a curved surface, both lights L1 and L2 are reflected as reflected light L3 without directivity at this portion. As a result, the reflected light L3 is emitted in the low brightness portion as shown in FIG. 10, so that the brightness of the entire surface of the light guide plate 50a becomes uniform. Note that reference numeral 1c ₁ ,
As shown in 1c _2, since a change in the reflection area of the reflection light L3 by changing the cross-sectional shape of the groove bottom, the whole by setting the arrangement intervals of the grooves in response to a change in the reflection area appropriately Make uniform brightness

FIG. 2 shows a second embodiment. This embodiment corresponds to the groove shape shown in FIG. The inclined surfaces 1a, 1b facing each other of the groove 1 are formed to be flat so that their cross-sectional shapes form a straight line, and the angle formed with the light guide plate back surface 50b is smaller than 45 ° as α2. . The bottom portion 1c with which the two inclined surfaces 1a and 1b come into contact is formed as a curved surface so that its cross-sectional shape draws an arc, but unlike the above embodiment, the curved surface is formed so as to bulge inside the light guide plate 50. There is.

In this structure, since the angle formed by the slopes 1a and 1b is α2 and is 45 ° or less, the reflected lights L1 'and L2' of the lights L1 and L2 are reflected inward so as to converge with each other. Show a trend. However, both slopes 1a, 1b
Since the groove bottom portion 1c located in the central portion of the is formed into a curved surface so as to bulge inside the light guide plate 50, both lights L1 and L2 are largely dispersed to the outside in this portion, and are reflected light L3. Reflects without directivity. As a result, of the lights L1 and L2, the light in the vicinity of the groove bottom portion 1c, which is the center of convergence, can be broadly omnidirectional reflected light L3,
The brightness can be made uniform.

FIG. 3 shows a third structure. In this structure, the entire surface forming the groove 1 is formed as a curved surface 1d so that almost all of the lights L1 and L2 are omnidirectional reflected light L3. Has been formed.

FIG. 4 shows a modification of the configuration shown in FIG.
The boundary between the groove forming surface and the back surface 50b of the light guide plate is clearly distinguished as an edge portion, whereas this boundary portion is also formed as a curved surface 1d 'in this embodiment. Light guide plate 5
The lights L1 and L2 radiated to 0 are not perfectly parallel rays, and therefore some of the lights L1 and L2 include the back surface 50b of the light guide plate.
Also included is a component that is irradiated at a certain angle with respect to. Therefore, if the boundary portion is formed as a curved surface, light is reflected even in this portion without directivity, and therefore there is no possibility that the boundary portion adversely affects the uniform brightness of the light guide plate surface 50a.

FIG. 5 shows another example of the groove shape.

First, in the configuration (A), the entire groove 1 is formed as a curved surface and the slope 1a which is a curved surface and the slope 1b which is also a curved surface are formed so that one is gentle and the other is strongly inclined. Thus, the amount of reflection is changed in accordance with the amount of light emitted from both sides of the sloped surface of the groove so that the brightness of the entire surface of the light guide plate is made uniform.

In (B), since the ridges 1e are formed at the center of the bottom of the groove 1, a pair of groove bottoms 1c are formed on both sides of the ridge 1e.
'Is formed.

(C) has a structure in which the grooves having the structure (A) and the grooves having the structure (B) are alternately arranged.

FIGS. 6 and 7 show a ridge formed on the surface of the plate material 3 so as to have the same sectional shape as the groove shown in FIGS. 1 and 2, and the ridge forming surface is referred to as a reflecting surface. It was done. That is, the slopes 2a and 2b of the ridge 2 are formed obliquely so as to converge toward the top 2c.
Is formed with a curved surface so that its cross-sectional shape is curved. Even in this configuration, the lights L1 and L2 traveling in the air
When the light is reflected by the ridges 2, the same effect as that of the groove is exhibited, and the reflected light on the reflecting surface, which is the ridge forming surface, can be made uniform.

[0023]

As described above in detail, according to the present invention, of the grooves or protrusions formed on the transparent plate, at least the portions in contact with the opposite slopes are curved, so that the reflection at this curved portion The light is made non-directional, and the non-directional light makes it possible to make the brightness on the light emitting surface uniform.

Further, since the amount of reflected light in each groove or ridge is uniform, it is possible to maintain the uniformity of brightness even if the number of grooves or ridges formed is reduced, and the light guide plate or the reflector plate is kept uniform. It can be expected to reduce the manufacturing cost.

[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 modification of the third embodiment.

5 (A), (B) and (C) are enlarged partial side views of a light guide plate showing another modification of the cross-sectional shape of the groove.

6 is an enlarged sectional partial view of a reflecting surface of a light guide plate having a ridge having the same sectional shape as the groove shown in FIG.

7 is an enlarged partial sectional view of a reflecting surface of a light guide plate having a ridge having the same sectional shape as the groove shown in FIG.

FIG. 8 is a side view of a lighting device having a conventional light guide plate.

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

FIG. 10 is a combination diagram with a partial enlarged side view of a light guide plate showing an example of a light reflection state in a conventional lighting device and a diagram showing the luminance on the light guide plate surface at a position corresponding to the back surface of the light guide plate. is there.

11 is a combination with a partial enlarged side view of a light guide plate showing another example of a light reflection state in a conventional lighting device and a diagram showing the luminance on the front surface of the light guide plate at a position corresponding to the back surface of the light guide plate. It is a figure.

FIG. 12 is a partially enlarged side view of a light guide plate showing still another example of a light reflection state in a conventional lighting device and a diagram showing the luminance on the light guide plate surface at a position corresponding to the back surface of the light guide plate. FIG.

[Explanation of symbols]

 1 groove 1a, 1b (groove) slope 1c (groove) bottom 2 ridge 2a (ridge) slope 2b (ridge) slope 2c (ridge) top 50 light guide plate 50a light guide plate surface (light emitting surface) ) 50b Back surface (reflection surface) of light guide plate 52, 53 Light source L1, L2 Light from light source

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

Claims (3)

[Claims] 1. A large number of grooves are formed on one surface of a transparent plate, and a pair of slopes are formed in the grooves so as to converge toward the bottom, and the light emitted from the side surface of the transparent plate is formed in the grooves. The reflected light is reflected by the inclined surface of the transparent plate, and the reflected light is emitted from the surface of the transparent plate that faces the groove forming portion. A planar light source body, which is formed by a curved surface having a curved cross-sectional shape and is configured to make the brightness of the light emitting portion uniform by making the reflected light of this curved portion omnidirectional. 2. The planar light source body according to claim 1, wherein the entire groove forming surface is a curved surface so that the groove has a curved sectional shape. 3. A large number of ridges are formed on one surface of the transparent plate, and a pair of slopes are formed on the ridges so as to converge toward the top. The converging part is formed by a curved surface so that its cross-sectional shape is a curve, and the reflected light on this curved part is made non-directional so that the brightness of the reflected light on the ridge-forming surface is made uniform. A planar light source body characterized by the above.