JPH06123885A - Surface light source device - Google Patents

Abstract

PURPOSE:To obtain the surface light source device which uses a photoconductor having a uniform luminance distribution by forming the back surface of the photoconductor, i.e., the opposite surface to a projection surface into wavy uneven surface so that the uneven surface is continuously formed with curved surfaces or curved surfaces and planes in any directions continuously, and roughly finishing the surface. CONSTITUTION:The surface light source device includes the photoconductor 2 having the reverse surface 2b in the wavy shape as shown in the figure. Further, the waveform is successive not only in section perpendicular to an incidence end surface 2a as shown in the figure, but also in different section of a plane perpendicular to the surface 2c, e.g. section parallel to the incidence end surface 2a or section slanting to the incidence end surface 2a. The back surface 2b of the photoconductor is therefore a continuous surface formed of curved surfaces or planes and curved surfaces in combination and includes none of a part like the apex angle of a cone, a linear part like a ridge, etc. Then, the curved surfaces of this waveform surface are roughly finished by forming what is called crimps.

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 a structure as shown in FIG. That is, the light guide 22 is arranged with the incident end face 22a thereof being close to the light source 21,
A diffuser plate 23 is provided on the emission surface side of the light guide 22.
A reflection surface 24 is provided on the side of the second surface facing the emission surface. According to such a device, the light from the light source 21 enters the light guide 22 through the incident end face 22a, is emitted from the emission face of the light guide 22 while being transmitted through the inside, and the emitted light is emitted. Becomes diffused light through the diffusion plate 23. This constitutes a surface light source.

In such a surface light source device, the light-incident surface of the light guide 22 is so arranged that the light incident on the light guide 22 is efficiently emitted and becomes diffused light having a uniform luminance distribution on the surface of the diffuser plate. It is general to form a minute diffusing portion having a constant pattern on the surface opposite to the surface by means of printing with a diffusing paint.

Since such a surface light source device is used, for example, as 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.

Therefore, in this type of surface light source device, various measures have been taken to increase the brightness.

For example, there are surface light source devices described in JP-A-3-189679 and JP-A-3-31782. This surface light source device increases brightness by forming a large number of pyramidal projections or recesses on the surface of the light guide opposite to the emission surface side, and increases the area of the pyramidal projections or recesses. The brightness is made uniform by changing the value depending on the place.

However, in such a method, although the area of the surface of the pyramid is relatively large, the brightness can be increased, but it is difficult to make the luminance distribution sufficiently uniform even if the area is changed. Further, since the projections or depressions are pyramidal, there is a defect that corners (parts with sharp corners) are particularly bright.

[0008] In order to solve the above drawbacks, the applicant of the present application filed a first application for a utility model registration application No. 24 in 1992.
There are surface light source devices of No. 601 and 1992 utility model registration application No. 24608. It has the configuration shown in FIGS. 12 to 15 and FIGS. 16 to 19, respectively.

First, in the surface light source device shown in FIGS. 12 to 15, a spherical concave portion 25 or a spherical convex portion 26 is provided on a surface 22a of the light guide 22 opposite to the emitting surface, or a cylindrical shape. It has a concave portion 25 'and a cylindrical convex portion, which can increase the brightness, and can make the luminance uniform by making the concave portion or the convex portion a rough surface.

The surface light source device shown in FIG. 16 also has a concave portion or a convex portion provided on the lower surface 22a of the light guide body 22 to increase the brightness and to form a rough surface on the concave portion or the convex portion. It is formed to change the roughness of this rough surface so that a more uniform luminance distribution can be obtained over the entire emission surface. Further, as shown in FIGS. 17 to 19, the pitch of the concave portions and the convex portions is changed, or the depth of the concave portions or the height of the convex portions is changed so that a more uniform luminance distribution can be obtained over the entire emission surface. It is a thing.

[0011]

In the light guide shown in FIGS. 12 to 19, the concave portion and the convex portion each include a corner portion in cross section, and such a corner portion is It is brighter than other parts and appears to be partially bright. Also, since the surface of the light guide having the protrusions or recesses has a shape in which a large number of protrusions or recesses are formed on a flat surface, when the light guide is thinned, the protrusions or recesses can be clearly seen from the diffusion plate side. Therefore, this is not visible because it is visible even through the diffusion plate.

[0012]

The surface light source device of the present invention comprises:
A light source, a light guide body whose incident end face is arranged close to the light source, a diffusion plate arranged on the front surface side (emission surface side) of the light guide body, and a back surface side of the light guide body (opposite to the diffusion plate side). Side) and a reflection surface disposed on the side), and the back surface of the light guide body (the surface opposite to the emission surface) has a large number of corrugated uneven surfaces. Is also characterized in that it is formed into a shape that does not have a point or linear portion that is continuously formed by a curved surface or a curved surface and a flat surface, and the back surface of this corrugation is a rough surface for forming a so-called grain. The brightness is made uniform along with the waveform.

As described above, in the surface light source device of the present invention, since the back surface of the light guide body has a continuous corrugation, it is possible to obtain a bright surface light source by reflecting and refracting light on the corrugated surface. , Because the changes in the direction (inclination of the tangential plane) at each part on this surface are continuous, the brightness distribution of the diffused light is uniform over the entire surface of the diffuser plate, and the brightness changes partly abruptly. It is possible to obtain a good brightness distribution in which there is no local glow. Further, since the light guide body is transparent and the back surface is a continuous surface, the corrugations cannot be seen from the front surface side even if it is not a flat surface.

Furthermore, when the corrugated surface on the back surface is roughened, it is easy to process the entire surface to a desired rough surface because the back surface is a continuous surface.

[0015]

Embodiments of the surface light source device of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view of the surface light source device of the present invention.
Is a light source, 2 is a light guide, 3 is a diffusion plate, and 4 is a reflecting surface.
In the surface light source device of this embodiment, the back surface 2b of the light guide 2 has a waveform as illustrated. Moreover, the surface of this waveform is
In the drawing, a vertical cross section is shown which is perpendicular to the incident end face, but the cross-sectional shape perpendicular to the surface 2c is different from that of the vertical face, for example, a cross section parallel to the incident end face 2a or a cross section inclined to the incident end face 2a are all continuous. Therefore, the back surface 2b of the light guide body is a continuous surface with a curved surface or a combination of flat surfaces and curved surfaces in all parts, for example, a portion such as a cone-shaped apex angle or a ridge line. The shape is such that there is no such part. Further, the curved surface of this waveform is rough.

In this embodiment, the light from the light source 1 is incident from the incident end face 2a of the light guide 2 and then the surface 2c.
Then, the light is totally reflected on the back surface 2b (a part of the light is emitted from the front surface and the light emitted from the back surface is reflected by the reflection surface) and is transmitted to the reflection side from the incident end surface 2a. Here, a part of the light is emitted from the surface 2c, passes through the diffuser plate 3, and becomes diffused light, which serves as a surface light source.

In this embodiment, since the back surface is a corrugated surface, the light totally reflected here is reflected in different directions depending on the reflection points, and the light that passes through the back surface and is reflected by the reflecting surface 4 and is incident again is different. , It is refracted on the corrugated surface and goes in different directions depending on the place. Due to the action of the corrugated surface of the back surface 2b, the light emitted from the front surface 2c of the light guide is made uniform and becomes bright light. Further, by making the corrugated surface a rough surface, a diffusing action is added and uniform brightness is obtained.

Here, since the back surface is corrugated and continuous in all directions, the change is also continuous depending on the position of the direction of reflection of light by this surface or the direction of refraction toward the surface. The brightness does not become large, and no bright part is produced on the diffusion plate. Further, when the back surface is made rough, it is relatively easy to make all the surfaces uniform and to change the roughness depending on the location because all the parts of the back surface are continuous.

Although the waveforms are shown in the same shape in FIG. 1, the direction in which light is reflected or refracted at each portion differs depending on the shape and size of the waveform. Therefore, in the illumination device of the present invention, in order to obtain a brighter one with a more uniform luminance distribution, the shape and size of the wave are actually changed depending on the place. Further, the distribution of the size and shape of the waveform is made different depending on the application of the surface light source device.

FIG. 2 is a diagram showing an example of the cross-sectional shape of the corrugated surface. From the experimental results, in this figure, the greater the height h of the wave, the greater the brightness on the exit surface above the wave. Also, the smaller the f corresponding to the wavelength of the wave, the greater the brightness at the exit surface above the waveform. The shape of the wave is brightest when the inclination angle of the portion g is 45 ° to 60 ° and becomes darker as it becomes larger or smaller.

Generally, in a surface light source device using a light guide, the emitted light on the side closer to the light source of the light guide (the side closer to the incident end face) is relatively large, and becomes smaller as the distance from the light source increases. Therefore, as for the waveform on the back surface of the light guide, it is desirable that the height h on the side closer to the incident end face 2a is made smaller and becomes gradually larger as it goes away from this, as shown in FIG. This makes it possible to make the brightness on the diffusion plate 3 uniform.

FIG. 4 shows another specific example, in which the waveform on the back surface of the light guide 2 is shaped such that the wavelength f is large on the side close to the incident end face 2a and becomes smaller as it goes away from it. The brightness on the surface is uniform and the brightness distribution is uniform as a whole. In this case, the height h is almost constant.

In FIG. 5, the light sources 1 are arranged on both the left and right sides of the drawing to increase the overall brightness. In the case of this specific example, since the light is incident from both sides, the left and right incident ends 2
The height h of the waves closer to a and 2a 'is made smaller and h is gradually increased toward the center. This makes it possible to make the brightness on the emission surface uniform.

FIG. 6 shows still another example in which the shape of the waveform is continuously changed to obtain a surface light source having uniform brightness. That is, the inclination of the portion g in FIG. 2 (angle θ in FIG. 10) is made to differ sequentially, and the inclination angle on the incident end face side is small and gradually increases as it deviates from this, and the inclination angle near the end face on the opposite side to the incident end face is increased. Is 45
It is in the range of 60 °.

Contrary to FIG. 6, the inclination of the portion g in FIG. 2 is large on the incident end face side and becomes gradually smaller as it goes away, and the inclination angle is 45 ° to 60 ° near the end face opposite to the incident end face. It may be in the range of °.

In FIG. 7, a light reflection member 5 such as a reflection tape is arranged on the end face 2d side of the light guide 2 opposite to the incident end face 2a. When this surface 2d is a transparent surface, light is emitted from this surface, and therefore, there is one in which a light reflection member 5 such as a reflection tape is arranged on this surface side and returned in the opposite direction to increase the brightness. In this way, the light reflection member 5 such as a reflection tape is provided on the 2d side.
In addition, when considering a flat plate-shaped light guide in which the front surface and the back surface are flat, the brightness on the exit surface side is the brightest and gradually decreases at the incident end surface, and approaches the surface 2d on the opposite side to the incident end surface. It tends to increase again. Therefore, as shown in FIG. 7, the height h of the back surface 2b of the light guide 2 is the smallest on the incident end surface 2a side and is gradually increased, and then the surface 2 is formed.
It is preferable to reduce the value again as it approaches d.

In FIGS. 8 and 9, the basic shapes of the light guides 12 and 12 'themselves are large at the incident end face and are gradually thinned, and the back surfaces 12b and 12b' of these light guides have the above-mentioned waveforms. It was done.

The embodiment shown in FIGS. 3 to 9 described above is
In both cases, a general surface light source device using a light guide was made for the purpose of eliminating the point that the amount of light emitted from the light guide is larger when it is closer to the incident end face and is smaller as it is farther from this. It is a thing. Therefore, changes in the wave height h, the wavelength f, and the inclination angle of the wave shape g portion all occur in the direction perpendicular to the incident end face. Therefore, when viewed on the entire back surface of the light guide, the undulations due to the waveform are almost the same in the direction perpendicular to the incident end surface.
And, in all directions where the unevenness having such undulations is parallel to the incident end face or in the direction inclined with respect to the incident end face, it is not necessarily the same as the above-mentioned vertical direction, but they are curved surfaces or It has a shape in which it is continuously connected by a flat surface and a curved surface, and there is no point-shaped or linear portion.

In the above description, the so-called one-lamp type or two-lamp type in which the light source is arranged only on one end face of the light guide is described, but the light source is arranged on all four sides of the light guide. Of course, it may be applied to a so-called four-lamp type surface light source device or a three-lamp type surface light source device in which light sources are arranged on three sides of the light guide. In these cases, the more difficult it is for the light from the light source to reach the above h
The waveform may have a large value of or a small value of f, and the roughness of the rough surface may be increased in the portion where light is hard to reach. Further, the slope of g may be changed. Also, the above h
It is also possible to appropriately select and combine some terms from the values of and f, the roughness, and the inclination of g, and change them.

The following method may be used to form a light guide body in which the inner surface of the concave portion and the outer surface of the convex portion are roughened. That is, first, a metal mold having a corrugated shape is formed, and then a metal mold is formed by a method such as sandblasting, etching, or electric discharge machining, and this metal mold can be formed by a molding means such as injection molding. In this case, the method of electric discharge machining is preferable because the work is simple and a desired rough surface can be obtained accurately.

[0032]

According to the present invention, the reflecting surface of the light guide is formed into a curved surface in any direction, or a waveform having a continuous curved surface and a flat surface without any points or linear portions, and The surface is a rough surface, the height of the waveform, the slope of the wavelength waveform,
By appropriately changing the surface roughness, it is possible to provide a surface light source device having an extremely uniform luminance distribution.

[Brief description of drawings]

FIG. 1 is a sectional view of an embodiment of a surface light source device of the present invention.

FIG. 2 is a diagram showing an example of a waveform formed on the light guide according to the present invention.

FIG. 3 is a diagram showing an example in which the corrugated height is changed depending on the location in the light guide according to the embodiment of the present invention.

FIG. 4 is a diagram showing an example in which the length of the light guide according to the embodiment of the present invention is changed depending on the place.

FIG. 5 is a diagram showing an embodiment in which light sources are arranged at both ends of a light guide according to the present invention.

FIG. 6 is a diagram showing an example in which the wave inclination angle θ is changed depending on the location in the light guide according to the embodiment of the present invention.

FIG. 7 is a diagram showing an example in which a light guide body according to an embodiment of the present invention has an incident end and a reflection side end surface as reflection surfaces.

FIG. 8 is a diagram showing an example in which the back surface is inclined with the light guide according to the embodiment of the present invention.

FIG. 9 is a view showing an example in which the back surface is inclined so that the central thickness is small in the light guide according to the embodiment of the present invention.

FIG. 10 is an enlarged view showing the inclination θ of the wave formed on the light guide according to the embodiment of the invention.

FIG. 11 is a sectional view of a conventional surface light source device.

FIG. 12 is a view showing a conventional light guide body having a hemispherical recess.

FIG. 13 is a view showing a conventional light guide body having a cylindrical recess.

FIG. 14 is a view showing a conventional light guide body in which a curved surface is further formed in the concave portion of FIG.

FIG. 15 is a view showing a conventional light guide body having a hemispherical convex portion formed therein.

FIG. 16 is a view showing a conventional light guide body having a concave portion and a roughened inner surface.

FIG. 17 is a view showing a conventional light guide body in which a concave portion that changes depending on a place is formed and an inner surface of the concave portion is roughened.

FIG. 18 is a view showing a conventional light guide body in which the concave portion of FIG. 17 is modified.

FIG. 19 is a view showing a conventional light guide body in which a convex portion that changes depending on a place is formed and the surface thereof is roughened.

[Explanation of symbols]

 1 light source 2 light guide 2b corrugated uneven surface 3 diffuser plate 4 reflective surface

Claims (11)

[Claims] 1. A linear light source, a light guide body having an incident end face arranged close to the light source, a diffuser plate arranged on an emission surface side of the light guide body, and an emission surface side of the light guide body. In a surface light source device having a reflection surface provided on the side opposite to the surface, the surface of the light guide opposite to the emission surface side has a number of corrugated uneven surfaces, and A surface light source device characterized in that it is formed continuously with a curved surface or a curved surface and a flat surface in any direction, and that this surface is a rough surface. 2. The surface light source according to claim 1, wherein the wave shape of the corrugated surface has a small wave height on the incident end face side and increases as the distance from the incident end face increases. apparatus 3. The surface light source device according to claim 1, wherein the wave shape of the corrugated surface has a large wavelength on the incident end face side and becomes smaller as the distance from the incident end face increases. 4. The wave shape of the corrugated surface of the corrugated surface becomes larger or smaller as the angle of inclination between the wave bottom and the apex on the incident end face side increases away from the incident end face, and about 45 ° at the farthest position. ~
The surface light source device according to claim 1, wherein the surface light source device has an angle of 60 °. 5. The surface light source device according to claim 1, wherein the roughness of the rough surface formed on the corrugated uneven surface is small on the incident end face side and increases as the distance from the incident end face increases. 6. A plurality of requirements are appropriately selected and changed from among the height of the wave, the wavelength of the wave, the inclination between the bottom and the top of the wave, and the roughness of the wave surface of the wave. The surface light source device according to claim 1. 7. A linear light source, a light guide body having an incident end face arranged close to the light source, a light reflecting member arranged on a surface side of the light guide body facing the incident end face, and the light guide body. In a surface light source device including a diffuser plate disposed on the emission surface side of the body and a reflection surface provided on the side of the light guide body that faces the emission surface side, the surface light source device faces the emission surface side of the light guide body. The surface on the side to be formed is a corrugated concavo-convex surface, and the corrugated concavo-convex is continuously formed by a curved surface or a curved surface and a flat surface in any direction and is folded to form a rough surface. The shape of the wave on the surface is such that the height of the wave on the side of the incident end face is small, the height of the wave increases as the distance from the incident end face increases, and decreases again as it approaches the light reflecting member. Surface light source device. 8. A linear light source, a light guide body having an incident end face arranged close to the light source, a light reflecting member arranged on a surface side of the light guide body facing the incident end face, and the light guide body. In a surface light source device including a diffuser plate disposed on the emission surface side of the body and a reflection surface provided on the side of the light guide body that faces the emission surface side, the surface light source device faces the emission surface side of the light guide body. The light source side is a corrugated uneven surface on the surface of the side to be formed, and the corrugated unevenness is formed continuously by a curved surface or a curved surface and a flat surface in any direction, and this surface is a rough surface. The surface light source device is characterized in that the wave shape of the corrugated surface is such that the wavelength on the incident end face side is large, the wavelength becomes smaller as it goes away from the incident end face, and becomes larger again as it approaches the light reflecting member. 9. A linear light source, a light guide body having an incident end face arranged close to the light source, a light reflecting member arranged on a surface side of the light guide body facing the incident end face, and the light guide body. In a surface light source device including a diffuser plate disposed on the emission surface side of the body and a reflection surface provided on the side of the light guide body that faces the emission surface side, the surface light source device faces the emission surface side of the light guide body. The surface on the side of the corrugated surface is a corrugated surface, and the wave shape of the corrugated surface of the corrugated surface becomes larger or smaller as the tilt angle between the bottom and the apex of the wave on the incident end surface side increases from the incident end surface. 45 ° to 60 °
45 ° to 60 ° by approaching the angle of 45 ° to 60 ° and then increasing or decreasing again as approaching the reflecting member.
A surface light source device characterized in that it is arranged to be further away. 10. A linear light source, a light guide body having an incident end face arranged close to the light source, a light reflecting member arranged on a surface side of the light guide body facing the incident end face, and the light guide body. In a surface light source device including a diffuser plate disposed on the emission surface side of the body and a reflection surface provided on the side of the light guide body that faces the emission surface side, the surface light source device faces the emission surface side of the light guide body. The surface of the corrugated surface is a corrugated concave and convex surface, and the roughness of the rough surface formed on the corrugated corrugated surface is small on the incident end face side and increases as the distance from the incident end face increases, and again as it approaches the reflecting member. A surface light source device characterized by being made small. 11. A linear light source, a light guide body having an incident end face arranged close to the light source, a diffuser plate arranged on an emission surface side of the light guide body, and an emission surface side of the light guide body. In a surface light source device having a reflection surface provided on the side facing the side, the surface on the side facing the exit surface side of the light guide is a corrugated uneven surface, and the corrugated uneven surface, A surface light source device characterized in that a plurality of requirements are appropriately selected and changed from the height of the wave, the wavelength, the inclination between the bottom and the top of the wave, and the roughness of the surface of the wave.