JPH10208529A - Sheet type light source device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sheet type light source device of a low electric power consumption type which emits uniform light with a high brightness, while the angle of visibility of an outgoing ray is assured to some extent. SOLUTION: A light reflection pattern 27 formed out of a groove 28 in a triangle in cross section, and of a flat part 29, is made out of a resin substrate 26. The inclination angle α of an oblique surface 30 is determined in such a way that an emission beam out of a light source lamp is totally reflected, and furthermore, the inclined angle β of an oblique surface 31 is so determined in such a way that light passing through the oblique surface 30 can be incident. By this constitution, since no reflecting plate is required, a beam other than the emission beam of the light source can be made incident from the back face 7 and the side surface of a resin substrate 26. And, since the space or the size of the groove part 28 is changed, a beam is increased, which is reflected by the groove part 28 while being inversely proportional to a distance to the light source lamp, and the sheet type light source device can thereby be obtained, which is wide in the angle of visibility, and high and uniform in brightness.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin planar light source device used as a back lighting device for a signboard or various display devices, and more particularly to a planar light source device used as a back lighting device for a liquid crystal display device. It is related to the structure of.

[0002]

2. Description of the Related Art In recent years, a liquid crystal display device having a thin and easy-to-see back light source mechanism has been used as a display device for a computer or the like in order to meet the needs of light weight and compactness. As a means for realizing such a back light source mechanism, a side light type (light guide plate type) planar light source device shown in FIG. 15 will be described. 1 is a cold cathode fluorescent lamp (CCFL) or a hot cathode fluorescent lamp (HCFL) as a light source of the planar light source device.
It is a linear light source lamp using the same. The resin substrate 2 formed of a highly translucent material has a substantially rectangular cross section,
The light source lamp 1 is arranged at a predetermined distance along the one side end surface 3.

A peripheral surface of the light source lamp 1 which is not opposed to the one end surface 3 is a lamp reflector 4 on which silver or the like is deposited.
Covered with. By providing the lamp reflector 4, most of the light emitted from the light source lamp 1 can enter the resin substrate 2 from the one end surface 3. Then, on a side surface other than the one side end surface 3 of the resin substrate 2 (for example, the side end surface 5 opposite to the one side end surface 3 shown in FIGS. 15 and 16), a reflective material 6 made of a reflective tape or the like is added. ing.

A light scattering pattern 8 (details) for uniformly emitting the screen of the planar light source device regardless of the distance from the light source lamp 1 is provided on the back surface 7 (below FIG. 15) of the resin substrate 2. (To be described later), and a reflection plate 9 is disposed further below the reflection plate 9. By providing the reflection material 6 and the reflection plate 9, the side surface and the back surface 7 of the resin substrate 2 are provided.
The light rays traveling toward the inside are reflected so as to travel inside the resin substrate 2 to prevent the light rays from being emitted from surfaces other than the surface 10 (upper part in FIG. 15) of the resin substrate 2.

[0005] A diffusion plate 11 is provided on the front surface 10 of the resin substrate 2 so as to cover the entire surface. The diffusion plate 11 is provided to remove a phenomenon (usually referred to as a dot image) in which only the light scattering pattern 8 appears to shine due to light rays reflected and diffused by the light scattering pattern 8.

[0006] For example, Utility Model Registration Publication No. 250
One or a plurality of prism plates 12 disclosed in Japanese Patent No. 7092 are provided above the diffusion plate 11 (upper in FIG. 15) with the prism surface 13 on which the prisms are formed as the upper surface. By providing the prism plate 12, it is possible to improve the luminance in the front direction of the screen by converging the widened light beams transmitted through the diffusion plate 11 in the vertical direction (front direction) of the screen.

The light scattering pattern 8 is formed, for example, by forming a medium containing a light diffusion / reflection material into a dot shape as described in Japanese Patent Laid-Open No. 5-134251.
It is applied by a screen printing method over the entire surface.

[0008] As shown in FIG.
Is printed so that the diameter of the dot gradually increases from one side end surface 3 where the light source lamp 1 is disposed to the side end surface 5 which is the opposite surface, so that the dot is farther from the light source lamp 1. Accordingly, the ratio of the medium containing the light diffusion / reflection material to the unit area of the back surface 7 increases (hereinafter, the ratio of the predetermined material to the unit area is referred to as area density). In FIG. 16, the light scattering pattern 8 is not a cross section, but is hatched for easy understanding.

As described above, when the area density of the light scattering pattern 8 formed by applying the medium containing the light diffusion reflective material formed on the back surface 7 of the resin substrate 2 is changed, the surface 10 of the resin substrate 2 is changed.
Since the amount of light emitted from the light source can be changed, only a portion close to the light source lamp 1 does not emit light brightly.

Further, as described above, instead of the light scattering pattern 8 applied to the resin substrate 2 by the screen printing method,
For example, as shown in Japanese Patent Application No. 7-208461, a minute uneven surface is formed directly on the back surface 7 of the resin substrate 2 to form a light scattering pattern for diffusing and / or reflecting light by the uneven surface. Accordingly, it is also possible to exert the same function as the above-mentioned light scattering pattern 8.

In the planar light source device having the above-described structure, there is a problem that the loss caused by the light rays entering the light scattering pattern 8 and being absorbed is large, and the efficiency is reduced. Further, there is a problem that the member cost is increased because of being constituted by a large number of members, and the occurrence rate of defective products is high because of the large number of assembly steps.

In order to solve these problems, in order to reduce the number of components, the light scattering pattern 8 and the prism plate 1
A planar light source device provided with a resin substrate 14 having two functions is disclosed in JP-A-8-94444. As shown in FIG. 17, the configuration of this planar light source device is substantially the same as that of the planar light source device described with reference to FIG. 15, but the resin substrate 14 is different. On the back surface 7 of the resin substrate 14, a light reflection pattern 15 composed of a prism array P connected along the axial direction of the light source lamp 1 is formed.

As shown in FIG. 18, an imaginary plane S ′ parallel to the planar surface 10 of the resin substrate 14 is assumed to be at a position which is the base of the prism array P having a triangular cross section. And
In the prism array P, the inclination angle of the inclined surface 16 near the side end surface 5 (right side in FIGS. 17 and 18) is α ′, and the inclined surface 1 near the one end surface 3 (left side in FIGS. 17 and 18).
7 is denoted by β ′. Here, the arrow in FIG.
The traveling state of the light beams 18 and 19 traveling inside the resin substrate 14 (details will be described later) is shown.

In the planar light source device disclosed in Japanese Patent Application Laid-Open No. Hei 8-94844, the inclination angle α ′ is about 45 °, the inclination angle β ′ is 10 ° or less, and the inclination angle increases as the distance from the light source lamp 1 increases. By setting the angle β ′ to be gradually increased, it is possible to uniformly emit light on the screen of the planar light source device for observation from the front direction without providing the light scattering pattern 8 and the prism plate 12. .

The above-mentioned planar light source device is used particularly as a back-lighting means of a liquid crystal display device. The characteristics of the liquid crystal display device are thinness, light weight and low power consumption. And is often used as a portable device. For this reason, in order to maintain the portability of the planar light source device, low power consumption is particularly required.

Japanese Patent Application Laid-Open No. 60-123823 discloses a means for using the ambient light in addition to the light source lamp 1 as a light source for emitting a screen in order to realize the low power consumption.

As shown in FIG. 19, a planar light source device which also utilizes ambient light has a light source lamp 1 provided on a wide side surface 21 of a resin substrate 20 having a substantially wedge-shaped cross section. On the rear surface 7 of the light source 20, a light reflection pattern 22 formed by a prism array P connected along the axial direction of the light source lamp 1 is formed. A screen 23 is provided above the front surface 10 of the resin substrate 20, and the resin substrate 20, the light source lamp 1, and the like are housed in a box 24. A turning surface 25, which is a surface facing the back surface 7 of the resin substrate 20, is provided rotatably so that a portion close to the light source lamp 1 is opened.
Has been fixed.

The planar light source device having such a configuration is shown in FIG.
As shown in FIG. 9A, when the rotating surface 25 of the box body 24 is closed, the surface light emission is performed using the light source lamp 1 as a light source, as in a normal case, while FIG. When the turning surface 25 is open as shown in FIG. 7, it is possible to emit natural light from the outside in a planar manner as a light source.

[0019]

SUMMARY OF THE INVENTION The present applicants have found that FIG.
Or JP-A-8-94844 described with reference to FIG.
A planar light source device having a configuration disclosed in Japanese Patent Application Laid-Open Publication No. H10-26095 was prepared, and the light emission state of a screen was observed. As a result, it was found that when viewed from the front of the screen, high-luminance and uniform light emission was obtained. However, when the observation position was slightly shifted from the front and observed obliquely with respect to the screen, it was close to the light source lamp 1. It was found that the vicinity of the one side end face 3 was extremely bright, and the vicinity of the side end face 5 was extremely dark, non-uniform and poorly balanced surface light emission. This is due to the shape of the light reflection pattern 15.

As shown in FIG. 18, light rays 18 entering the prism array P at an angle nearly parallel to the virtual plane S '
Are mostly totally reflected by the inclined surface 16 and the resin substrate 1
4 and exits in a direction perpendicular to the screen (front direction). On the other hand, most of the light rays 19 entering the prism array P from the direction slightly inclined with respect to the virtual plane S ′ are emitted from the back surface 7 of the resin substrate 14 because the incident angle on the inclined surface 16 is smaller than the critical angle. I do. And ray 19
Is reflected by a reflecting plate 9 provided below the back surface 7,
It again enters the inside of the resin substrate 14 from the inclined surface 17 and proceeds to the front surface 10. Therefore, the light ray 19 is emitted while being shifted from the screen vertical direction.

Since the amount of light emitted to the screen along a traveling path similar to the light 19 is relatively large, the dispersion of the light emitted from the screen is not well balanced. For this reason, since the viewing angle of the screen is narrowed, the brightness of the screen becomes extremely non-uniform if slightly deviated from the front direction, causing a problem that the viewing angle is narrow.

On the other hand, Japanese Unexamined Patent Application Publication No.
In the case of the planar light source device disclosed in Japanese Patent Application Laid-Open No. 0-123823, as shown in FIG. 19B, when natural light is used as a light source to emit planar light, a reflector fixed to the rotating surface 25 is used. 9 reflects natural light into the resin substrate 20. At this time, since the light reflection pattern 22 is provided on the back surface 7 of the resin substrate 20, when natural light enters the resin substrate 20, Since the light is refracted by the prism array P, there is a problem that the light emitted from the screen is not focused in the front direction.

In the case of the configuration of the planar light source device shown in FIG. 19, the light source must be determined by using either the light source lamp 1 or natural light. As described above, if the light source must be determined in an alternative manner, the light source lamp 1 cannot be used in an auxiliary manner according to the brightness of ambient light (that is, natural light). For this reason, when using natural light as a light source, there is a problem that it can be practically used only in an extremely bright place, and there is a problem that a great limitation is imposed when actually used as a planar light source device.

Accordingly, the present invention provides a planar light source device which secures a certain viewing direction on a screen and has high luminance and uniform power consumption.

[0025]

According to a first aspect of the present invention, a light source lamp is brought into contact with at least one side end surface of a resin substrate made of a translucent material. In the side light type planar light source device, a light reflection pattern is formed on a surface of the resin substrate opposite to the light emitting surface, and the light reflection pattern has a cross-sectional shape continuously provided along the axial direction of the light source lamp. It is composed of a substantially triangular groove portion and a flat portion, and the ratio of the groove portion and the flat portion is constant, or the ratio of the groove portion increases as the distance from the light source lamp increases, or
The inclined surface having a triangular cross-sectional shape of the groove portion has an inclined angle of 40 ° to 55 ° on the side closer to the light source lamp 1 and an inclined angle of another inclined surface other than the inclined surface of 60 °. A planar light source device characterized by being formed at an angle of from 90 ° to 90 °.

According to a second aspect of the present invention, in the groove, the angle of the valley corresponding to the apex angle of the triangular cross-section is made constant, and the angle of the base angle is made constant or changed.

According to a third aspect of the present invention, in the light reflection pattern, the width of the groove is formed to be 1.5 times the width of the adjacent flat portion, and a light source different from a light source lamp is provided on the back surface of the resin substrate. Is provided.

According to a fourth aspect of the present invention, the light source is ambient light, and the light emission intensity of the light source lamp can be adjusted according to the intensity of the ambient light.

According to a fifth aspect of the present invention, a diffusion plate is provided to cover the back surface of the resin substrate.

According to the present invention, a prism plate composed of a series of prisms connected in a direction perpendicular to the axial direction of the light source lamp is provided integrally with the resin substrate on the surface of the resin substrate; A reflection plate is provided to cover the back surface of the resin substrate.

[0031]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A planar light source device according to the present invention will be described below with reference to the accompanying drawings. As a planar light source device according to the first embodiment of the present invention, a resin substrate 26 as a main part of the present invention shown in FIGS. 1 and 2 will be described below. Here, FIG.
Are regions A, B and C surrounded by a dashed line shown in FIG.
FIG.

The cross section of the resin substrate 26 is substantially rectangular.
A light reflection pattern 27 is formed on the back surface 7 (below FIG. 1). As shown in FIG. 2, the light reflection pattern 27 includes a groove 28 and a flat portion 29 having a substantially triangular cross section.
It is composed of The groove 28 has a constant cut width and depth, and is formed in a large number in parallel with the axial direction of the light source lamp 1.

At this time, the light reflecting pattern 27 is formed on the groove 28 and the flat surface so that the interval between the grooves 28 is constant in about one-third of the area of the resin substrate 26 from the side end face 3 (right side in FIG. 1). A part 29 is formed. In a region other than the one-third region, the flat portion 29 is provided so that the width of the flat portion 29 gradually decreases as the distance from the light source lamp 1 increases (that is, as it goes to the left side in FIG. 1).

As shown in FIG. 3, the light reflection pattern 27 is formed at regular intervals to form the groove 28, and the cut width and depth of the groove 28 increase as the distance from the light source lamp 1 increases. May be. Thus groove 2
In the case where the light reflection pattern 27 changes in size, there is almost no change in the optical characteristics (details will be described later) as compared with the light reflection pattern 27 formed on the resin substrate 26 shown in FIG. Any one of them can be appropriately selected in consideration of various conditions such as the workability and the like, and the light reflection pattern 27 can be selected by combining the above two types (changing the interval between the grooves 28 and changing the size of the grooves 28). May be formed.

The progress of the light beam entering the light reflection pattern 27 will be described with reference to FIG. Here, in order to limit the cross-sectional shape of the groove 28, a portion corresponding to the base of the cross-sectional triangle is assumed to be a virtual plane S, and the inclination angle of the inclined surface 30 on the side close to the light source lamp 1 (the right side in FIG. , Side end face 5
The inclination angle of the inclined surface 31 on the side closer to (left side in FIG. 4) is β.

The inclined surface 30 makes the light beam 32 traveling from the right side of FIG. 4 totally reflected by the inclined surface 30 to travel almost perpendicularly to the surface 10 of the resin substrate 26, and is emitted almost perpendicularly to the screen. Set to make it. Experiments have shown that in order to realize the traveling path of the light beam 32, the inclination angle α of the inclined surface 20 should be set in a range of approximately 40 ° to 55 °. At this time, since the optimum inclination angle α changes depending on the size of the resin substrate 26, it is appropriately selected according to the size of the resin substrate 26.

On the other hand, the inclination angle β of the inclined surface 31 is set in consideration of the light beam 33 incident on the inclined surface 30 at a critical angle or less. Since the light beam 33 is incident on the inclined surface 30 at a critical angle or less as described above, most of the light beam is transmitted without being reflected and exits from the back surface 7 (the lower part in FIG. 4) of the resin substrate 26. At this time, the inclination angle β is the light beam 3 emitted from the resin substrate 26.
The angle of incidence on the inclined surface 31 is set so that 3 enters the resin substrate 26 again and is incident on the inclined surface 30 of the adjacent groove 28. In order to realize the traveling path of the light ray 33, the inclination angle β is set to about 60 ° to 90 °.
Experiments have shown that it is sufficient to set the angle in the range of °.

At this time, as described above, the inclination angle α of the inclined surface 30 is set so as to totally reflect the light beam entering the inclined surface 30 in a direction substantially perpendicular to the screen. When the light enters the inside of the resin substrate 26 from the inclined surface 31 and reaches the inclined surface 30, the light is totally reflected by the inclined surface 30 and travels in the vertical direction of the screen.

As described above, the inclination angles α and β
Is determined, the light traveling to the light reflection pattern 27 is
Since it follows a traveling path similar to one of the light beam 32 and the light beam 33, it is possible to finally emit the light substantially perpendicular to the screen. Further, since almost no light beam exits from the back surface 7 of the resin substrate 26, there is no need to provide a reflection plate, which is essential as a component of the conventional planar light source device.

Here, the light beam emitted onto the screen follows a traveling path of being emitted from the surface 10 of the resin substrate 26 mainly by total reflection at the inclined surface 30 of the groove 28. For this reason, in the case of the resin substrate 26 in which the interval between the grooves 28 shown in FIG. 1 is changed, the width of the flat portion 29 is reduced and the number of the groove portions 28 is increased as the distance from the light source lamp 1 increases. The amount of light traveling to the groove 28 gradually increases. Therefore, it is possible to realize uniform light emission on the screen regardless of the attenuation of the light beam intensity during propagation.

In the case of the resin substrate 26 shown in FIG. 3 in which the size of the groove 28 is changed, the area of the inclined surface 30 and the inclined surface 31 increases as the distance from the light source lamp 1 increases. The amount of light traveling to 28 gradually increases. For this reason, it is possible to realize uniform light emission on the screen regardless of attenuation of the intensity of the light beam during propagation.

Next, as a second embodiment of the present invention, the resin substrate 26 'of the planar light source device shown in FIG. 5 has a substantially wedge-shaped cross section in order to reduce the weight. I do. By forming the light reflection pattern 27 on the resin substrate 26 'in the same manner as the light reflection pattern 27 shown in FIGS. 1 and 3, the light reflection pattern 27 functions in the same manner as described above, so that uniform light emission on the screen can be realized.

Further, as a third embodiment of the present invention, the resin substrate 26 of the planar light source device shown in FIG. 6 can incorporate a light beam 33 as a light source in addition to the light beam emitted from the light source lamp 1. is there. By providing a so-called direct type light source lamp (not shown) as a light source of the light beam 33, the luminance on the screen can be further improved.

As the light beam 33, ambient natural light (hereinafter referred to as ambient light) can be taken from the back surface 7 and the side surface of the resin substrate 26. When the ambient light is taken in this way, the light reflection pattern 27 is
8 is always set to 1.5 times or less of the width of the flat portion 29, so that the uniformity of screen light emission when the light source lamp 1 is turned off and the screen of the planar light source device is observed can be practically used. It turned out to be a degree.

As described above, it is possible to obtain the optimum light emission intensity by adjusting the light emission intensity of the light source lamp 1 according to the light intensity of the light beam 33. In particular, when the light beam 33 is the ambient light, By suppressing the light emission amount of the light source lamp 1 to a necessary minimum, a dramatic reduction in power consumption can be achieved.

However, when ambient light is directly incident on the resin substrate 26 from behind the lower surface 7 of the resin substrate 26 (below in FIG. 7), the rear scene is displayed on the screen of the planar light source device. When ambient light is introduced from behind the back surface 7, a diffusion plate 34 that covers the entire back surface 7 must be provided, as shown in FIG. When the diffusion plate 34 is provided, the diffusion plate 34 may be provided as a separate member as described above. For example, a diffusion layer may be formed on or inside a transparent back cover that houses the planar light source device,
Further, a light beam in which ambient light is reflected once by a reflecting material (not shown) may be made to enter the resin substrate 26. Further, in order to more effectively solve the problem that the scenery behind is displayed on the screen of the planar light source device, it is also possible to provide a diffusion plate on the surface 10 side of the resin substrate 26.

As a fourth embodiment of the present invention, a light reflecting pattern 27 is formed on a back surface 7 of a resin substrate 26 of the planar light source device shown in FIG. As shown in FIG. 8B as viewed from the side end face 5 of FIG. 8A, the prism plate 12 composed of the prism rows P connected in a direction orthogonal to the axial direction of the light source lamp 1 is attached to the resin substrate 26. And is provided integrally. The cross-sectional shape of the prism row P constituting the prism plate 12 is triangular.

In the case of a planar light source device provided with the resin substrate 26 having such a configuration, the light rays entering the prism plate 12 are further emitted on the screen by the retroreflection effect of the prism array P. Since the light is focused, a planar light source with higher luminance can be realized. At this time, the prism plate 12
Since about half of the amount of light rays entering the substrate 26 is reflected toward the inside of the resin substrate 26, the reflecting plate 9 must be arranged so as to cover the back surface 7 of the resin substrate 26.

In the surface light source device of the present invention described in detail above, the groove 28 of the light reflection pattern 27 can be processed by cutting with a diamond tool. At this time, in order to fix the machining tool, the angle of the valley (see FIG. 4) corresponding to the apex angle of the substantially triangular cross section of the groove 28 must be constant. For this reason, the sum of the inclination angle α and the inclination angle β is constant, but the inclination angle α and the inclination angle β are not constant as described in the present embodiment, and the inclination angle α and the inclination angle By appropriately changing and setting β, it is possible to realize more efficient planar light emission.

In practicing the present invention, an acrylic resin is most suitable as the material of the resin substrate 26 because of its transparency and workability. However, the present invention is not limited to this, and various thermoplastic transparent resins such as a vinyl chloride resin, a polycarbonate resin, an olefin resin, and a styrene resin can be used. In some cases, an inorganic transparent material such as a thermosetting transparent resin such as an epoxy resin or an allyl diglycol carbonate resin or various glass materials can be used.

The method of forming the resin substrate 26 is as follows.
Direct machining such as cutting and grinding, or various molding methods such as cast molding, extrusion molding, hot press molding, and injection molding are applicable, but from the viewpoint of productivity, the injection molding method is the best. I have.

In the planar light source device of the present invention described in detail with reference to FIGS. 1 to 7, what is shown is a resin substrate 26 and a light source lamp 1 which are main parts. When used, the lamp reflector 4 that allows most of the light emitted from the light source lamp 1 to enter the resin substrate 26 cannot be omitted. Further, the reflector 9, the diffusion plate 34, the prism plate 12, and the like can be used in combination with the surface light source device of the present invention, as in the related art.

[0053]

EXAMPLE As an example, a planar light source device of the present invention was prepared, and its luminance was measured. The configuration of the planar light source device of Embodiment 1 will be described below. The resin substrate 26 has a flat plate (size: 2) made of a transparent acrylic resin whose entire peripheral surface is polished smoothly.
A light reflection pattern 27 having a groove 28 is formed on the back surface 7 having a size of 40 mm × 160 mm and a thickness of 3 mm in parallel with the long side of the resin substrate 26.

As shown in FIG. 1, the groove 28 of the light reflection pattern 27 fixes the apex angle or valley of the triangular sectional shape of the groove 28 at 60 °, and the inclination angle α is 48 ° to 52 °.
It is formed so as to continuously change to 46 °, and the inclination angle β is changed accordingly. The cut width of the groove 28 is constant at 20 μm, and the ratio of the groove 28 to the flat portion 29 is constant at 0.1 from the one end face 3 on the light source lamp 1 side to one third of the area of the resin substrate 26. age,
Except for the region, the ratio gradually increases as the distance from the light source lamp 1 increases, and the ratio becomes 1.
2 was formed.

As the light source lamp 1, a cold cathode fluorescent tube having an outer diameter of 2.3φ is used. As the lamp reflector 4 covering the peripheral surface of the light source lamp 1, a PET film on which silver was deposited was used, and as the diffusion plate 34 provided on the back surface 7 of the resin substrate 26, a PET film coated with a diffusion material was used.

As Example-2, a resin substrate 26 ′ having a substantially wedge-shaped cross section shown in FIG. 5 (size: 240 mm × 160
mm, thickness on one side end face 3 side: 3 mm, thickness on one side end face 5 side: 1 mm). The second embodiment is different from the first embodiment only in the shape of the resin substrate 26 ', and the other configuration is the same.

Subsequently, as Example 3, a planar light source device including the resin substrate 26 described with reference to FIG. The prism plate 12 integrally provided on the surface 10 of the resin substrate 26 has a prism array having a cross-sectional shape of an isosceles triangle with a vertex angle of 90 °. The third embodiment is different from the first embodiment in that a prism plate 12 is provided on the surface 10 of a resin substrate 26, and other configurations are the same.

Further, as Comparative Example 1, a planar light source device including the resin substrate 14 of the planar light source device described with reference to FIGS. The light reflection pattern 15 formed on the back surface 7 of the resin substrate 14 has an inclination angle α ′ of 44 in the prism row P shown in FIG.
And the inclination angle β ′ is 8 °, and is formed at intervals of 0.1 mm. In addition, the components, size, and the like were all the same as those of the planar light source device of Example 1.

The luminance on the screen of each of the four types of planar light source devices created as described above is measured by the method described below, and the emission angle distribution of the light beam emitted on the screen is observed.
As shown in FIG. 9A, the center of the screen of the planar light source device is set as a reference point O, and the luminance measuring device K is separated from the reference point O by a predetermined distance (50 cm) in a direction perpendicular (front) to the screen. The located position is set to 0 degree. Then, as shown in FIG. 4B, the luminance measuring device K is moved up to 45 degrees in the direction of the one end surface 3 and the one end surface 5 around the reference point 0, and the luminance is measured at predetermined angles. Measurement (hereinafter referred to as measurement in the short side direction).

The measurement distance (the distance from the reference point O to the tip of the luminance measuring device K) is constant (50 cm) regardless of the movement of the luminance measuring device K. At this time, the movement of the luminance measuring device K in the direction of the one side end surface 3 is represented by plus, and the movement of the luminance measuring device K in the direction of the side end surface 5 is represented by minus. The luminance measurement device K is a luminance meter (BM-
7, the field of view 1 °), and the cold cathode tube used as the light source lamp 1 has a tube current of 3.5 mArms and a lighting frequency of 60.
It is lit with a KHz sine wave.

As described above, the observation at the position of the reference point O is defined as the measurement point A. Similarly, in FIG. 9, the vicinity of the light source lamp 1 on the center line of the long side of the resin substrate 26 is the measurement point B, The luminance is measured in the same manner as described above, with the symmetric position of the measurement point B as the measurement point C.

Further, the luminance measuring device K is set so as to move in the direction perpendicular to the movement from the one side end face 3 to the side end face 5 (hereinafter referred to as measurement in the long side direction). The luminance was measured similarly without changing the luminance.

The results of measuring the luminance of the above planar light source device are shown in the tables of FIGS. FIGS. 10 and 11 show the luminance measurement results of the planar light source device of Example-1.
The measurement result in the short side direction is shown in FIG. 10. When the viewing angle θ = 0, the brightness of the measurement points A, B, and C becomes the same. It can be seen that the light is emitted uniformly irrespective of the distance from the lamp 1. Further, since the measurement results of the measurement points A, B and C almost overlap each other, even when the screen is observed from an oblique direction with respect to the vertical direction of the screen, the screen emits extremely uneven light. I can't see it. Further, the measurement result in the long side direction is shown in FIG. 11, and it was found that a wide viewing angle was obtained.

In a bright room with an ambient light illuminance of 10001x, light rays (that is, ambient light) are introduced into the resin substrate 26 from behind the planar light source device and the screen of the planar light source device is observed. It was confirmed that the same luminance could be obtained even when the tube current was about one half of the case where only the light source lamp 1 was used as the light source.

The luminance measurement result of the planar light source device of Example-2 was almost the same as the luminance measurement result of the planar light source device of Example-1.

Next, FIGS. 12 and 13 show the results of measuring the luminance of the planar light source device of Example-3. Viewing angle θ = 0
13 is increased by about 1.3 times as compared with Example-1 (the same applies to Example-2), and becomes high. However, as is clear from FIG. 13, the visual field range is reduced to about half. .

FIG. 14 shows the results of luminance measurement in the short side direction of the planar light source device of Comparative Example-1. The brightness at the viewing angle θ = 0 is
Although the measurement points A, B, and C are almost equal, the measurement results at other viewing angles vary, so that it can be seen that the balance of the viewing range is poor.

[0068]

As described above in detail, the planar light source device of the present invention has a light reflection pattern formed of a triangular groove and a flat portion on the back surface of the resin substrate. For this reason, the light beam entering the groove portion is totally reflected on the inclined surface, or passes through the inclined surface and enters the resin substrate from the adjacent inclined surface, and most of the light is emitted on the screen of the planar light source device. It becomes a ray. Therefore, it is possible to realize high-luminance and uniform screen light emission with a wide viewing angle.

Further, since it is not necessary to provide a reflection plate on the back surface of the resin substrate, it is possible to cause light rays other than light emitted from the light source lamp to enter the screen from the back surface and side surfaces of the resin substrate and emit the light to the screen. In addition, since the light source lamp can be used auxiliary according to the ambient brightness, low power consumption can be realized.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating a configuration of a resin substrate which is a main part of a planar light source device according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view illustrating a configuration of a resin substrate as a main part of the present invention.

FIG. 3 is a schematic diagram for explaining a configuration of a resin substrate which is a main part of the planar light source device according to one embodiment of the present invention, which is different from FIG.

FIG. 4 is a schematic diagram for explaining a traveling state of a light beam to a light reflection pattern.

FIG. 5 is a schematic diagram for explaining a configuration of a resin substrate of the planar light source device according to the embodiment of the present invention which is different from FIG.

FIG. 6 is a schematic diagram for explaining a configuration of a resin substrate of the planar light source device according to the embodiment of the present invention, which is different from FIG.

FIG. 7 is a schematic diagram for explaining another configuration of the resin substrate of FIG. 6;

FIG. 8 is a schematic diagram for explaining a configuration of a resin substrate of the planar light source device according to the embodiment of the present invention, which is different from FIG.

FIG. 9 is a schematic diagram for explaining a luminance measuring method.

FIG. 10 is a table showing luminance measurement results of the planar light source device according to the example of the present invention.

FIG. 11 is a chart showing another luminance measurement result of the planar light source device according to the embodiment of the present invention, which is different from FIG.

12 is a table showing luminance measurement results of the planar light source device according to the embodiment of the present invention which is different from FIG.

FIG. 13 is a table showing another luminance measurement result of the planar light source device according to the embodiment of the present invention, which is different from FIG. 12;

FIG. 14 is a table showing luminance measurement results of the planar light source device of the comparative example.

FIG. 15 is a cross-sectional view illustrating a configuration of a conventional planar light source device.

FIG. 16 is a schematic view showing a light scattering pattern of a conventional planar light source device.

FIG. 17 is a cross-sectional view showing a configuration of another conventional planar light source device different from FIG.

FIG. 18 is a schematic view for explaining a traveling state of light rays in the planar light source device of FIG.

FIG. 19 is a cross-sectional view showing a configuration of another conventional planar light source device different from FIG.

[Explanation of symbols]

 Reference Signs 26 Resin substrate 27 Light reflection pattern 28 Groove 29 Flat part 30 Inclined surface 31 Inclined surface

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[Procedure amendment]

[Submission date] October 21, 1997

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claim 3

[Correction method] Change

[Correction contents]

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0027

[Correction method] Change

[Correction contents]

According to the third aspect of the present invention, the light reflection pattern is formed so that the width of the groove is 1.5 times or less the width of an adjacent flat portion, and a light source is provided on a back surface of the resin substrate. A light source different from a lamp is provided.

Claims (6)

[Claims] 1. A side light type planar light source device comprising a light source lamp in contact with at least one or more side end surfaces of a resin substrate made of a translucent material, wherein a light emitting surface of the resin substrate is opposed to the light emitting surface. A light reflection pattern is formed on the surface, and the light reflection pattern includes a substantially triangular cross-sectional groove and a flat portion that are continuously provided along the axial direction of the light source lamp. Or the ratio of the grooves increases as the distance from the light source lamp increases, or a combination thereof, and the inclined surface of the triangular cross section of the groove has an inclined surface closer to the light source lamp 1. Angle of inclination of 40 ° to 55 °,
The angle of inclination of another inclined surface other than the inclined surface is 60 ° to 9 °.
A planar light source device formed at 0 °. 2. The groove has a constant valley angle corresponding to the apex angle of the cross-sectional triangle and a constant base angle,
The planar light source device according to claim 1, wherein the surface light source device is changed. 3. The light reflection pattern according to claim 1, wherein a width of the groove is formed to be 1.5 times a width of an adjacent flat portion, and a light source different from a light source lamp is provided on a back surface of the resin substrate. The planar light source device according to claim 1 or 2, wherein: 4. The planar light source device according to claim 3, wherein the light source is ambient light, and the light emission intensity of the light source lamp can be adjusted according to the intensity of the ambient light. 5. The planar light source device according to claim 3, further comprising a diffusion plate that covers a back surface of the resin substrate. 6. A resin plate, comprising a prism plate formed of a series of prisms connected in a direction perpendicular to the axial direction of a light source lamp on a front surface of the resin substrate, and a back surface of the resin substrate. The planar light source device according to claim 1, further comprising a reflection plate that covers the light source.