JP2580451Y2 - Surface light source device - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface light source device using a light guide, which is used for illuminating a liquid crystal display panel or the like.

[0002]

2. Description of the Related Art A surface light source device using a light guide has, for example, a configuration as shown in FIG. That is, a light guide 2 made of a transparent material in which the light source 1 and the incident end face 2 a are arranged close to the light source 1, a diffusion plate 3 arranged on the front surface side of the light guide 2, and a rear surface side of the light guide 2 And a reflecting plate 4. In such a device, the illumination light emitted from the light source 1 enters the light guide 2 from the incident end face 2a, and is transmitted to the other end 2b side while totally reflecting the inside of the light guide 2 on the front and back surfaces. In the meantime, light emitted from the light guide without being totally reflected by the surface passes through the diffusion plate 3 and becomes diffused light. Therefore, the diffused light is emitted from above the diffusion plate 3 to be a surface light source, which can be used to illuminate the liquid crystal display panel. Reflector 4
Is to prevent the light guide from going outside without being totally reflected on the back surface (the lower surface in the drawing) of the light guide, resulting in a loss of light quantity. Further, an end surface 2b of the light guide 2 opposite to the incident end surface 2a.
In some cases, a reflection surface 5 is provided to prevent light from leaking. As a result, light that enters the light guide 2 and enters the light guide 2 and reaches the end surface 2b without exiting the surface as illumination light is reflected back by the reflection surface 5 and the loss of light amount is reduced accordingly.

A surface light source device using such a light guide is
Since a part of the light incident on the light guide 2 sequentially goes out of the light guide from the surface, the amount of light gradually decreases in the light guide. Therefore, the light amount is large on the side close to the incident end face 2a of the light guide 2, and becomes smaller as it goes to the opposite end face 2b. As a result, the amount of light emitted from the surface of the light guide 2 is larger when it is closer to the incident end face 2a, and becomes smaller as it is closer to the end face 2b. Therefore, the diffused light, which is the illumination light emitted from the diffuser plate, has a large light amount on the left side and a small light amount on the right side in FIG.

[0004] In order to eliminate the luminance unevenness and obtain an illumination device having a uniform luminance distribution, it is necessary to decrease the luminance on the incident end face 2a side and increase the luminance on the opposite end face 2b side.

For this reason, the conventional surface light source device has a light guide 2
A large number of diffusion parts having a small area are formed on the back surface of the light-emitting element. For example, as shown in FIG. By making the area of the minute diffusion portion existing in the same area per unit area relatively small by means such as reducing the area to some extent, the emission light amount is reduced, and as the distance from the incident end surface increases, the per unit area becomes smaller. By increasing the total area of the minute diffusion portion to increase the light amount, the luminance distribution is made uniform over the entire diffusion plate 3.

Further, the entire back surface of the light guide is formed as a grained surface, and a change in the density is provided, for example, a change in the density is made such that the density on the incident end face side is small and the density increases as the distance from the end face increases. It is also known to measure the distance.

[0007]

Conventionally, as described above, a surface light source device using a light guide provided with a minute diffusion portion on the lower surface of the light guide as described above requires a transparent synthetic resin first. A method of printing a light guide 2 in the form of a plane-parallel plate made of a material and providing a large number of minute diffusion portions 10 formed of a large number of dots 11 as shown in FIG. Therefore, a printing process is required, and a loss of light amount occurs due to absorption by the printing ink.

On the other hand, in the conventional surface light source device in which the entire back surface of the light guide has a roughened surface, the entire surface of the diffusion plate is darkened by improving the uniformity as compared with the device having a large number of minute diffusion portions. There were disadvantages.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a surface light source device provided with a light guide capable of simultaneously forming a minute diffusion portion at the time of molding the light guide and capable of controlling the amount of light accurately and easily. Things.

[0010]

The surface light source device of the present invention comprises:
The light guide includes a light source, a light guide, a diffusion plate, and a reflection surface on the back side of the light guide. , Or the innermost end surface of the concave portion is formed as a grained surface or a matt-like surface. By selecting the length of the convex portion or the depth of the concave portion, the amount of light emitted from the periphery of the surface of the light guide corresponding to the convex portion or the concave portion is controlled.

In addition, the length of the convex portion or the depth of the concave portion is made constant, and the light exits from the light guide surface on the corresponding side by changing the area of the end surface having a rough surface (grain surface or satin surface). It is also possible to control the amount of light.

Further, it is possible to control the amount of light emitted from the surface of the light guide by combining a change in the length of the convex portion and the area of the end face or a change in the depth of the concave portion and the area of the end face.

[0013] The surface light source device of the present invention has the object of preventing the emitted light on the side close to the incident end face of the light guide from being large and preventing the emitted light from decreasing as the distance from the incident end face increases, as described above.
Obviously, it can also be used to eliminate local luminance unevenness.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the surface light source device of the present invention will be described with reference to the drawings.

FIG. 1 is a sectional view of a first embodiment of the present invention.
In FIG. 1, 1 is a linear light source such as a cold-cathode tube, 2 is a light guide, 3 is a diffusion plate, 4 is a reflection surface, and 5 is another reflection surface, except for the structure of the light guide. Is substantially the same as that shown in FIG. The light guide 2 in the embodiment of FIG. 1 is different from the light guide of the surface light source device shown in FIG.

FIG. 2 is an enlarged view of a part of the light guide 2 of the embodiment shown in FIG. Is formed. As shown in FIG. 1, the length t of the convex portion 6 is small on the incident end face 2a side of the light guide 2, and gradually increases as the distance from the incident end face 2a increases.

In this embodiment, the length t of the convex portion 6 is gradually reduced from the vicinity indicated by A in FIG. 1, but this is because a reflecting surface is provided on the end surface 2b of the light guide 2. With the provision, the end face 2b side is prevented from becoming bright again by the light reflected by the reflection surface 5, so that the brightness becomes uniform. Therefore, in the case of using a light guide of a type having no reflection surface on the end face 2b, if the length t of the convex portion 6 is formed so as to continuously increase from the incident end face 2a to the end face 2b on the opposite side, the length t may be increased. Good.

In the first embodiment of the present invention, as shown in FIG. 1, the amount of light incident on the light guide 2 from the light source 1 decreases as the light advances from the incident end face 2a to the other end face 2b. Light entering the convex portion 6 formed on the back surface of the light guide 2
Is diffused on the lower surface (end surface) 7 and the like, thereby
Are emitted from the surface of the light guide 2. As a result of the experiment
Therefore, if the length t of the concave portion 6 is small, the emitted light increases so much.
Absent. Therefore, as shown in FIG.
If the value of is small, the position of t
Light exits from the light guide 2 compared to the position where the value is large.
As a result, there is no uniform
A luminance distribution is obtained.

FIGS. 3 and 4 show a second embodiment of the present invention, in which a concave portion 8 is used instead of the convex portion 6 in the first embodiment.
Is formed.

In this embodiment, as shown in FIG. 3, the depth t of the concave portion 8 is made smaller and gradually larger near the incident end face 2a. Also in this embodiment, since the reflection surface 5 is provided on the opposite end surface 2b, the depth t of the concave portion 8 becomes smaller near the end surface 2b.
In the same manner, on the end faces of these recesses 8, crimps 7 are formed.

Also in the second embodiment, the smaller the depth t is, the smaller the amount of light emitted to the outside of the light guide 2 is. Therefore, if the configuration shown in FIG. 3 is used, a surface light source device having a uniform luminance distribution can be obtained. I can do it.

Although the length of the convex portion 6 in FIGS. 1 and 2 and the depth of the concave portion 8 in FIGS. 3 and 4 are emphasized to be larger than necessary, the actual length may be large. It is around 1 mm.

FIGS. 5 and 6 show a third embodiment of the present invention, in which the height or depth t is constant, a large number of convex portions or concave portions having different areas S are provided, and a region having a constant area is formed. The ratio of the amount of light emitted from the region on the surface of the light guide corresponding to the region is controlled by the ratio of the total area of the convex portions or concave portions existing in the region.

Among these figures, the one shown in FIG. 5 is one in which convex portions 6 are provided on the back surface of the light guide 2, and the area S of these convex portions 6 is small on the incident end face 2a side and opposite to the incident end face 2a. The amount of light emitted from the surface of the light guide 2 is made constant irrespective of the location so that the luminance distribution in the diffuser plate 3 is made uniform by increasing the size toward the side end face 2b.

FIG. 6 shows a configuration in which a concave portion 7 is provided on the back surface of the light guide 2 instead of the convex portion 6 so that the luminance distribution in the diffusion plate 3 becomes uniform by changing the area S. It was done.

The above-described embodiment is an example in which the surface light source device has a uniform luminance distribution by preventing the incident end face side of the light guide from becoming bright and gradually dark.

However, for example, it is possible to prevent the surface portion of the light guide near the electrode portions at both ends of the light source from being darkened. In other words, the length t of the convex portion provided on the lower surface of the darkened portion (the back surface portion corresponding to the darkened portion of the surface of the light guide) or the depth t of the concave portion is made larger than the other portions so that the whole is uniform. High brightness. Further, a screw hole or the like provided in the light guide for fixing the light guide with a screw or the like blocks direct light from the light source, and also in a portion where the surface of the light guide becomes dark, and the like. Luminance can be made uniform by making the length t of the convex portion or the depth t of the concave portion larger than other portions.

As described above, the light amount can be freely adjusted depending on the position on the surface of the diffuser plate of the surface light source device by adjusting the length of the convex portion or the concave portion.

Further, the combination of the embodiment shown in FIGS. 1 and 2 and the embodiment shown in FIG. 5 and the combination of the embodiment shown in FIGS. 3 and 4 and the embodiment shown in FIG. .

The shape of each minute diffusion portion is not limited to a circle, but may be any shape such as a regular polygon, a rectangle, an oval, and an ellipse.

[0031]

According to the present invention, since no printing means is used, there is no influence of absorption by the printing ink. Further, a light guide having a grained surface can be easily formed by molding. Further, when the amount of light is adjusted by adjusting the length of the convex portion or the depth of the concave portion, the adjustment is simple because the shape and cross-sectional area of all the convex portions or concave portions may be the same and their distributions may be the same. Further, if the adjustment of the length or the depth and the adjustment of the cross-sectional area of each convex or concave portion are combined, more accurate adjustment is possible.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a first embodiment of the present invention.

FIG. 2 is a partially enlarged view of the first embodiment.

FIG. 3 is a sectional view of a second embodiment of the present invention;

FIG. 4 is a partially enlarged view of the second embodiment.

FIG. 5 is a sectional view of a third embodiment of the present invention.

FIG. 6 is a sectional view of another example of the third embodiment of the present invention.

FIG. 7 is a cross-sectional view of a conventional surface light source device using a light guide.

FIG. 8 is a diagram showing an example of a putter formed on the back surface of a light guide in the conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Light source 2 Light guide 3 Diffusing plate 4 Convex part 5 Concave part

Claims (6)

(57) [Scope of request for utility model registration] 1. A light source, a light guide made of a transparent material having an incident end face arranged close to the light source, a diffusion plate arranged on a front side of the light guide, and a back side of the light guide. A surface light source device having a reflecting surface disposed on the light source so that light incident on the light guide from the light source is emitted from the surface of the light guide while being transmitted through the light guide and becomes diffused light through the diffusion plate. The light guide has a fine surface whose front end surface is a grained surface.
A small convex portion is provided, and the amount of light emitted from around the surface position of the light guide corresponding to the convex portion is controlled by changing the length of the convex portion so as to adjust the brightness on the diffusion plate. Surface light source device. 2. A light source, a light guide made of a transparent material having an incident end face arranged close to the light source, a diffusion plate arranged on a front side of the light guide, and a back side of the light guide. A surface light source device having a reflecting surface disposed on the light source so that light incident on the light guide from the light source is emitted from the surface of the light guide while being transmitted through the light guide and becomes diffused light through the diffusion plate. A minute surface whose end surface is a grained surface on the back surface of the light guide.
The provided a recess, a surface light source which is adapted to control performs brightness adjustment on the diffusion plate by causing the amount of light emitted from the surface location near the corresponding light guide in the recess to change the depth of the recess apparatus. 3. A light source, a light guide made of a transparent material disposed so that an incident end face is close to the light source, a diffusion plate disposed on a front side of the light guide, and a back side of the light guide. A surface light source device having a reflecting surface disposed on the light source so that light incident on the light guide from the light source is emitted from the surface of the light guide while being transmitted through the light guide and becomes diffused light through the diffusion plate. The light guide has a fine surface whose front end surface is a grained surface.
A small convex portion is provided, and the amount of light emitted from around the surface position of the light guide corresponding to the convex portion is controlled by changing the area of the convex portion so as to adjust the brightness on the diffusion plate. Surface light source device. 4. A light source, a light guide made of a transparent material having an incident end face arranged close to the light source, a diffusion plate arranged on a front side of the light guide, and a back side of the light guide. A surface light source device having a reflecting surface disposed on the light source so that light incident on the light guide from the light source is emitted from the surface of the light guide while being transmitted through the light guide and becomes diffused light through the diffusion plate. A minute surface whose end surface is a grained surface on the back surface of the light guide.
Surface light source device in which a concave portion is provided, and the amount of light emitted from around the surface position of the light guide corresponding to the concave portion is controlled by changing the area of the concave portion to adjust the brightness on the diffusion plate. . 5. The surface light source device according to claim 1, wherein the area of the projection is also changed. 6. The surface light source device according to claim 2, wherein the area of the concave portion is also changed.