JPH0368923A - Illuminating device - Google Patents

Abstract

PURPOSE:To obtain an illuminating device with high efficiency and with high brightness which is excellent in brightness distribution by forming a dotted reflection part on the irregular reflection surface of a transparent plate. CONSTITUTION:A light source 2 is arranged adjacently to the light inducting end face 8 of the transparent plate 1 and light is emitted in one way from the transparent plate 1 through a reflector 3 and a diffusion plate 4. The irregular reflection surface 7 of the transparent plate 1 is constituted of the dotted reflection part 6 and an irregular reflection part 5. A luminous flux from the light source 2 enters the light transmissive plate 1 and conducted by a reflection surface 9 and the reflection part 6. The reflection surface 9 which is obtained by performing specular finishing to the transparent plate 1 reflects the luminous flux having an angle equal to or above a critical angle. The luminous flux is irregularly reflected by the irregular reflection part 5 and a part of the luminous flux comes to have an angle equal to or below the critical angle of the reflection surface 9 to be emitted. The reflector 3 is provided so as to emit the light only in an A direction and the diffusion plate 4 is provided so as to identically emit the light. The transparent plate 1 is a PMMA resin plate and is formed by printing by setting the spacing between dots is about 0.31mm.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a thin backlight installed in computers, word processors, liquid crystal televisions, and the like.

[Prior art 1] Conventionally, there has been a method of forming a diffused reflection part by roughening a transparent plate on a transparent plate, as described in JP-A-63-168604, or a method as described in JP-A-63-62105. A method is known in which a diffused reflection area is formed using milky-white halftone dots on a transparent plate.

[Problem to be solved by the invention] However, such a conventional lighting device is
In the method of Patent No. 04, in which a diffused reflection part is formed by roughening the surface, it is difficult to produce a rough surface with a uniform distribution in an industrially stable manner, resulting in high costs, or the uneven distribution cannot be obtained. There is a problem that brightness unevenness occurs, and when processing a rough surface uniformly, the brightness difference within the lighting device is reduced, so there is a problem that the overall efficiency is significantly reduced.

On the other hand, in the method disclosed in Japanese Patent Application Laid-open No. 63-62105, which uses halftone dots to form a diffusely reflective area, when the area of halftone dots is increased to increase efficiency, a very fine reflective surface remains, resulting in industrially stable processing. There are problems that make it difficult to do so.

Therefore, the present invention aims to solve the above-mentioned problems in the prior art6, and its purpose is to provide a means for industrially stable manufacturing of thin lighting devices.

[Means for Solving the Problems] In order to solve the above problems, a lighting device of the present invention is a surface lighting device in which a light source is arranged adjacent to the light introduction end face of a transparent plate provided with a diffused reflection surface on at least one surface, It is characterized by having dot-shaped reflective parts on the diffused reflection surface of the plate.

[Example] Examples of the present invention will be described below based on the drawings. 1st
The figure is a perspective view showing one embodiment of the present invention. It is composed of a light source 2 disposed adjacent to the light introduction end surface 8 of the transparent plate 1, a reflecting plate 3 for emitting light from the transparent plate in one direction, and a diffusing plate 4. The diffused reflection surface 7 of the transparent plate 1 is composed of a dot-shaped reflection section 6 and a diffused reflection section 5. The light beam emitted from the light source 2 enters the transparent plate 1 and is guided by the reflecting surface 9 and the reflecting section 6. The reflecting surface 9 mirror-finishes the transparent plate 1 and reflects the light beam at a critical angle or more. The guided light flux hits the diffuse reflection section 5 and is diffusely reflected, so that a part of the light beam is further repeated, and a part of the light beam becomes less than the critical angle of the reflection surface 9 and is emitted. At this time, a reflecting plate 3 is provided so that the light is emitted only in the angular direction, and a diffusing plate 4 is provided so that the light is emitted uniformly.

In this case, a PMMAtH resin plate was used as the transparent plate 1, but any transparent material such as polycarbonate, polystyrene, glass, etc. can be used. Furthermore, although a fluorescent discharge tube is used as the light source 2, any direct linear source such as an LED may be used.

FIG. 2(a) is an enlarged plan view of the diffusion surface of the present invention, and FIG. 2(b) is an enlarged sectional view of the diffusion surface of the present invention.

The diffuse reflection section 5 is uniformly formed on the diffuse reflection surface of the transparent plate, and the reflection section 6 is formed directly on the diffuse reflection surface. In this case, the diffused reflection surface is formed by knitting, but it may also be transferred by etching the roll during sandblasting or extrusion molding. Further, although the reflecting portion 6 is sputtered with AI2, it may be formed by plating or the like.

FIG. 3(a) shows the luminance distribution of the lighting device in which a reflective part is formed on the diffused reflection surface, FIG. 3(b) shows the luminance distribution of the lighting device in which a uniform weak diffused reflection surface is formed, and Diagram (C)
Figure 3 shows the luminance distribution of a lighting device with a uniform, strong diffused reflection surface.

The illumination device has the structure shown in FIG. 1, and has a diffuser plate 4 installed on the diffused reflection surface 7 side and a reflection plate 3 installed on the reflection surface 9 side. The surface brightness of the discharge fluorescent tube is 8,000 cd/m2, and the opposing discharge fluorescent tube line is 11,130 mm.

It can be seen that the efficiency is low in FIG. 3(b) and the luminance difference is large in FIG. 3(c). In FIG. 3(a) according to the present invention, the efficiency is high and the luminance difference is small.

FIG. 4(a) is another embodiment of an enlarged plan view of the diffusion surface of the present invention, and FIG. 4(b) is a sectional view thereof.

The diffuse reflection surface of the transparent plate is a uniform reflection surface by mirror processing, and the diffuse reflection portion 5 is formed by printing.

FIG. 5(a) is an enlarged plan view of the diffusion surface according to the prior art;
Figure (b) is a sectional view of the same.

It is obvious that by increasing the area of the diffused reflection section 5, the efficiency of the illumination device is improved and high brightness surface illumination is achieved.

The area of the diffused reflection part with a dot interval of 1 mm is 70% of the total area.
%, the minimum spacing lO between prints is 0.055 mm according to the prior art, and 0.31 mm according to the present invention.
becomes. In printing, if the minimum interval is 0.1 mm or less, there is a problem that ink collapses on the printing surface, and conventional techniques cannot cope with high brightness.

[Effects of the Invention] As detailed above, the illumination device of the present invention has higher efficiency and brightness and has a uniform brightness distribution compared to the conventional technology by forming dot-shaped reflective parts on the diffused reflection surface of the transparent plate. This has the great effect of providing an excellent lighting device. Furthermore, it has an excellent effect in that it can provide easier and more stable manufacturing than conventional techniques.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing an embodiment of the illumination device of the present invention. FIG. 2(a) is an example of an enlarged plan view of the diffusion surface of the present invention. FIG. 2(b) is a sectional view of FIG. 1(a). FIG. 3(a) is a luminance distribution diagram of the lighting device according to the present invention. FIG. 3(b) is a brightness distribution diagram of a uniform weak diffuse reflection surface according to a conventional embodiment, and FIG. 3(c) is a brightness distribution diagram of the same strong diffuse reflection surface. FIG. 4(a) is an enlarged plan view of a diffusion surface showing another embodiment of the lighting device of the present invention, and FIG. 4(b) is a sectional view of FIG. 4(a). FIG. 5(a) is an enlarged plan view of the diffusion surface according to the prior art;
FIG. 5(b) is a sectional view of FIG. 5(a).・Minimum printing interval

Claims (1)

[Claims] 1. A surface illumination device in which a light source is disposed adjacent to a light introduction end surface of a transparent plate having a diffused reflection surface on at least one surface, the illumination device comprising a dot-shaped reflective portion on the diffused reflection surface of the transparent plate.