JP2581308Y2 - 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.

[0002]

2. Description of the Related Art A conventional surface light source device using a light guide has, for example, a configuration as shown in FIG. That is, the light guide 12 is arranged so that the light incident surface 12a is close to the light source 11, and the light guide 12 is provided with the diffusion plate 13 and the light guide 12 on the light emitting surface side.
The reflective surface 14 is provided on the side facing the light emitting surface. According to such a device, the light from the light source 11 enters the light guide 12 from the incident end face 12a, and is emitted from the light emitting surface of the light guide 12 while transmitting through the inside. Becomes diffused light through the diffusion plate 13. This constitutes a surface light source.

[0003] Such a surface light source device has a light emitting surface of the light guide 12 so that light incident on the light guide 12 is efficiently emitted and becomes diffused light having a uniform luminance distribution on the surface of the diffuser plate. In general, a minute diffusion portion having a predetermined pattern is formed on the surface on the side opposite to the above by means such as printing with a diffusible paint.

[0004]

Since such a surface light source device is used for, for example, a backlight of a liquid crystal display device, a bright surface light source is required. However, the conventional surface light source device having the above configuration cannot obtain sufficient brightness.

[0005] Therefore, in this type of surface light source device, various devices have been devised to increase the brightness.

For example, there are surface light source devices described in Japanese Patent Application Laid-Open No. 3-189679 and Japanese Utility Model Application Laid-Open No. 3-31782. This surface light source device increases the luminance by forming a large number of pyramid-shaped convex portions or concave portions on the surface of the light guide opposite to the light-emitting surface side, and measures the area of the pyramid-shaped convex portions or concave portions. Is varied depending on the location to achieve uniform brightness.

However, in such a method, the brightness can be increased because the area of the surface of the pyramid is relatively large, but it is difficult to make the luminance distribution sufficiently uniform even if the area is changed. Further, since the convex portion or the concave portion has a pyramid shape, there is a disadvantage that a corner portion (a sharp corner portion or the like) is particularly shiny.

An object of the present invention is to provide a surface light source device using a light guide that is bright and has a sufficiently uniform luminance distribution.

[0009]

The surface light source device of the present invention comprises:
A linear light source, and the incident end face is arranged close to the light source.
A surface light source device comprising at least a light guide
The light source side is small on the surface facing the light emitting surface of the light guide.
Spherical concave or convex portion that increases as the distance from the light source increases
And a large number of the inner surface of the concave portion or the
All the outer surfaces of the projections are roughened .

[0010] The surface light source device of the present invention is formed on the back surface of the light guide.
By the concave or convex portion to be formed, a bright surface light source device
At the same time, change the size of the concave portion or the convex portion
This makes it possible to make the luminance distribution more uniform.
Wear.

Further , in the present invention, all of the recesses are provided.
The inner surface of the projection or all the outer surfaces of the projections are roughened to enlarge.
Scattering effect, making the luminance distribution even more uniform.
it can.

In the surface light source device of the present invention, the light guide
The shape of the concave or convex portion formed on the surface opposite to the optical surface
The following can be considered.

(A) When the light source side is small and away from the light source
A cylindrical or prismatic concave or convex part
In this case, the deepest portion of the concave portion or the tip end surface of the convex portion has a curved surface.
What you are doing. (B) Spherical concaves with the same radius of curvature and different depths
Part, the depth of the concave portion is shallower on the light source side and separated from the light source.
Things that get deeper as they get. Or the radii of curvature are equal and
Spherical convex portions having different heights, and the height of the convex portions is
The lower the light source side, the higher it gets away from the light source. (C) A spherical concave portion having the same radius of curvature and / or depth.
Or spherical convex portions having the same radius of curvature and / or height.
Thus, the inner surface of the concave portion or the outer surface of the convex portion
It has a rough surface that becomes finer as the distance from the light source increases.
of. (D) Cylinder or prism with the same cross-sectional area and / or depth
Cylinders or prisms having the same recess or cross-sectional area and / or height
Convex portion, and the inner surface of the concave portion or the outer surface of the convex portion is roughened.
Coarser as the light source side becomes finer and further away from the light source
What was a face.

In the above cases (a) and (b), all of the concave portions
All inner surfaces or all outer surfaces of the convex portions may be rough surfaces.
it can. In this case, the inner surface of the concave portion is
The roughness of the outer surface of the projection is finer on the light source side and away from the light source
It can also be a rough surface that becomes rougher as it is formed.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of the surface light source device of the present invention will be described.

FIG. 1 is a view showing a first embodiment of the present invention, wherein 1 is a light source, 2 is a light guide, 3 is a diffusion plate, and 4 is a reflection surface. FIG. 2 is a view showing the light guide 2 according to the first embodiment of the present invention, and a hemispherical concave portion 5 is provided on a surface opposite to the light emitting surface.
Are formed, and the radius of curvature of the hemisphere is changed depending on the location. The radius of curvature of the hemisphere close to the light source 1 is small, and the radius of curvature of the hemisphere increases as the distance from the light source 1 increases. As a result, whether the diffusion plate 3
Brightness et diffused light becomes large, it can be evenly brightness distribution. Further, since the concave portion has no curved portion and no corner, there is no local light. Furthermore, in the present invention,
In order to make the surface rough, the reflected light from this concave portion becomes diffused light.
This increases the amount of light exiting the light emitting surface of the light guide.
It is made uniform and the luminance distribution of the diffusion plate 3 becomes more uniform.

The recesses in the above embodiment may not necessarily hemisphere, and in curvature equal to the radius of the spherical surface, the depth is close to the light source is small, it may be composed to a large as the distance from the light source.

Further, the concave portion may be an elliptical surface, a parabolic surface, or the like, and may be a curved surface having a small size on the light source side and increasing with distance from the light source.

[0019]

FIG. 3 shows a cross-sectional shape of a light guide 2 of a second embodiment of the surface light source device according to the present invention, and the other configuration is the same as that of FIG. That is, the concave portions are formed in a columnar shape, and a large number of the columnar concave portions 6 are arranged at the same pitch. The cylindrical shape on the light source side is small, and is arranged so as to increase as the distance from the light source increases. This makes it possible to increase the amount of light emitted from the light guide 2 as a whole to increase the brightness on the plate surface of the diffusion plate 3 and to make the luminance distribution uniform.

In the light guide shown in FIG. 3, the size of the cylinder is changed by changing the bottom area from small to large while keeping the height of the cylinder constant, or by reducing the height by keeping the bottom area constant. A similar effect can be obtained by increasing the value from.

Further, as in the third embodiment shown in FIG. 4, the deepest end face of the cylinder may be a curved surface 7 such as a spherical surface.
This is preferable because the corner portions are eliminated and the light does not shine like an edge light.

In the second embodiment, the concave portion may have a prismatic shape. However, a column is preferred because it is almost a curved surface.

In place of the cylinder, a cylinder having a cross section of an elliptical shape or the like may be modified.

Also in this embodiment, it is preferable to make the inner surface of the concave part rough to have a diffusion effect, since the luminance distribution can be made more uniform. Further, the luminance distribution may be made uniform only by the surface roughness. In other words, by forming all the concave parts having the same cross-sectional size and the same depth, such as a spherical surface, a cylinder, and a prism, by making the roughness of the rough surface smaller on the light source side and gradually increasing as the distance from the light source increases. The luminance distribution can be made uniform.

FIG. 5 shows a fourth embodiment of the surface light source device according to the present invention, in which the hemispherical concave portion shown in FIG. 1 is changed to a convex shape.

As shown in FIG. 5, the same effect as in FIG. 1 can be obtained even if the concave portion is changed to a convex shape. The same applies to FIGS. 2 and 3, and the same effects as in FIGS. 2 and 3 can be obtained even if the concave portion is changed to a convex shape.

In the above description, the so-called one-lamp type in which the light source is arranged only on one end face of the light guide, but the so-called two-lamp type in which the light source is arranged on both end faces may be used.
In the case of a two-lamp type, the light source side in the description means both end faces,
From there, the size of the sphere, cylinder, etc. becomes larger toward the center, and the center becomes the largest. Similarly, when the roughness is changed, it is changed from both end faces toward the center.

Further, a so-called four-lamp surface light source device in which light sources are arranged on all four sides of a light guide, and a three-lamp surface light source device in which light sources are arranged on three sides of a light guide are also used. The size of a spherical surface, a column, or the like may be increased in a portion where light from a light source does not easily reach, and the roughness may be increased in a portion where light does not easily reach.

In the case of a prism or the like in the above-described embodiment, it is preferable that each ridge and corner have an appropriate curve so as not to be a sharp corner. Thus, it is possible to prevent the corners from shining due to the edge light effect.

The following method may be used to form a light guide in which the inner surface of the concave portion and the outer surface of the convex portion are roughened. That is, first, a mold having a convex portion or a concave portion is formed, a mold is formed by a method using sand blasting, etching, or electric discharge machining with a mask formed on the mold, and the mold is formed by molding means such as injection molding using the mold. I can do it. In this case, the method of electric discharge machining is preferable because the operation is simple and a desired rough surface can be accurately obtained.

In the drawings, each concave portion or convex portion is drawn so as to be separated from each other. However, for example, a large concave portion or convex portion may be in contact with each other at a part. Further, the configuration may be such that the adjacent concave portions or convex portions are partially in contact with each other and all the concave portions or convex portions are continuous.

The concave portions or convex portions need not be arranged at an equal pitch. Further, the same light guide may have both a concave portion and a convex portion. For example, the same light guide may have a concave portion and a convex portion arranged alternately, or may have both arranged appropriately. Also in this case, the concave portion and the concave portion, the convex portion and the convex portion, and the concave portion and the convex portion may be connected to each other.

It is clear that a rough surface as in the above-described embodiment may be provided also in these shapes.

[0035]

According to the surface light source device of the present invention, a large number of concave portions or convex portions formed on the back surface of the light guide makes the surface brighter, and at the same time, the luminance distribution can be made more uniform by changing the size and the like. In particular, the above-mentioned effect is remarkable by making the shape of the concave portion spherical, cylindrical, or prismatic. Further, by adding a diffusion effect by making the surface of the concave portion or the convex portion rough, a very uniform luminance distribution can be obtained, and if a light source having the same brightness is used, higher luminance can be obtained than in the past.

[Brief description of the drawings]

FIG. 1 is a sectional view of an embodiment of the present invention.

FIG. 2 is a cross-sectional view of the light guide used in the first embodiment of the present invention.

FIG. 3 is a cross-sectional view of a light guide used in a second embodiment of the present invention.

FIG. 4 is a sectional view of a light guide used in a third embodiment of the present invention.

FIG. 5 is a sectional view of a light guide used in a fourth embodiment of the present invention.

FIG. 6 is a cross-sectional view of a conventional surface light source device using a light guide.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Light source 2 Light guide 3 Diffusion plate 4 Reflection surface 5 Depression

Claims (7)

(57) [Scope of request for utility model registration] And 1. A linear light source, in at least comprises a surface light source device and a light guide arranged in proximity of the entrance end surface to the light source, the light emitting surface and the surface of the opposing sides of the light guide,
Provided many spherical concave or convex portion becomes large as the light source side away from the small light source Rutotomoni, all of the recesses
A surface light source device characterized in that the inner surface of the above or all the outer surfaces of the convex portions are roughened . 2. A surface light source device comprising at least a linear light source and a light guide whose entrance end face is arranged close to the light source, wherein a surface of the light guide facing the light emitting surface includes :
Provided a number of cylindrical or prismatic recesses or protrusions becomes larger as the light source side away from the small light source Rutotomoni, the concave
The surface light source device characterized in that the deepest portion of the portion or the tip surface of the convex portion has a curved surface . 3. A linear light source, and an incident end face of the light source.
A surface light source device comprising at least a light guide arranged close to
In the arrangement, on the surface on the side facing the light emitting surface of the light guide,
Many spherical recesses with the same radius of curvature and different depths
In addition to the light source, the depth of the concave portion is shallower on the light source side.
Or the radius of curvature
If there are many spherical convex parts with the same height and different height
In both cases, the height of the convex portion is lower on the light source side and separated from the light source.
A surface light source device characterized in that the height of the surface light source device is increased with increasing distance . 4. A surface light source device comprising at least a linear light source and a light guide whose entrance end face is arranged close to the light source, wherein a surface of the light guide facing the light-emitting surface includes :
Spherical recess or semi-curvature with the same radius of curvature and / or depth
Forming a large number of spherical convex portions having the same diameter and / or height ,
A surface light source device, wherein the inner surface of the concave portion or the outer surface of the convex portion is a rough surface whose roughness is finer on the light source side and becomes rougher as the distance from the light source increases. 5. A linear light source, in at least comprises a surface light source device and a light guide arranged in proximity of the entrance end surface to the light source, the light emitting surface and the surface of the opposing sides of the light guide,
It recesses also the cross-sectional area and / or depth of the same cylindrical or prismatic shape
The cross-sectional area and / or height to form a large number of identical cylindrical or prismatic protrusions, roughness of the concave inner surface or the convex portion outer surface was roughened rough as the light source side away from the fine light source A surface light source device characterized by the above-mentioned. 6. A surface light source device of any inner or according to claim 2 or 3 all of the outer surface of the convex portion was used as a crude surface of the recess. 7. A surface light source device according to claim 1 or 6 inner or outer surface roughness of the convex portion has a roughened rough as the light source side is separated from the finer light source of the recess.