JPH04109287A - Illuminator - Google Patents

Abstract

PURPOSE:To eliminate the loss at the time of propagation of light at the boundary of a light transmission plate and to provide the panel light source which has high efficiency and excellent uniformity of brightness by laminating two sheets of diffusing materials varying in the content of the diffusing materials and limiting the content of one thereof, thereby forming the light transmission plate. CONSTITUTION:The light transmission plate 1 contg. the diffusing materials formed by dispersing the diffusing materials into a transparent acrylic resin so as to have 70 to 95% transmissivity and the diffusing plate 2 formed by incorporating the diffusing materials b into the transparent acrylic resin so as to have 40 to 70% transmissivity are stuck to each other. A white reflecting sheet 3 having a high reflectivity is stuck to the rear surface of the light transmission plate 1. A fluorescent lamp 4 and a reflector 5 for making the light of this fluorescent lamp 4 efficient incident on the light transmission plate 1 from the end face thereof are provided along the end face of the light transmission plate 1. Both the front and rear surfaces of the light transmission plate 1 contg. the diffusing materials are made into a specular mirror state in this way and the loss at the time of light propagation at the boundary of the light transmission plate 1 is eliminated. The rate of utilizing the light is thus enhanced and the light emitting surface having uniform brightness is obtd.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a surface light source illumination device used as a backlight for a liquid crystal display device.

[Conventional technology]

Conventionally, for example, a transparent acrylic plate 21 as shown in FIG.
Satin finish or blasting treatment 2 on the back (or front) of
After step 2 is applied, a white (or silver) mirror sheet 23 is attached or a transparent acrylic plate 2 is attached as shown in Figure 5.
The light guide plate has a structure in which a white (or silver) mirror sheet 23 is attached to the back surface of the light guide plate 1, and an acrylic plate 24 containing a white diffusion material is attached to the front surface of the light guide plate, and a fluorescent lamp 25 is attached along the end surface of the acrylic light guide plate. In the former case (FIG. 4), the light from the fluorescent lamp 25 enters from the end face of the transparent acrylic plate 21, propagates inside, diffuses through the processing section 22, and the component exceeding the critical angle exits from the surface. In the latter case (FIG. 5), the light from the fluorescent lamp 25 enters from the end face of the transparent acrylic plate 21, is diffused by the acrylic plate 24 containing a white diffusing material, and exits from the surface. In other words, it becomes a surface light source with the front surface serving as a light emitting surface.

[Problem to be solved by the invention]

However, when using an acrylic light guide plate with such a structure, one surface of the light guide plate is not flat and light propagation is poor, resulting in poor brightness such as brightness in the area near the fluorescent lamp 25. It becomes uniform. In addition, the means for emitting light that has entered the acrylic light guide plate to the surface is limited to diffusion or reflection treatment (surface treatment) of the surface portion, resulting in poor efficiency in emitting light to the surface. Furthermore, post-processing such as blasting, printing, coating, and vapor deposition is required after surface treatment, which increases costs. In addition, the uniformity of brightness can be improved by reducing the degree of satin finish and blasting, and by adjusting the gradation of printing according to the distance from the fluorescent lamp 25 to reduce the diffusion in the area near the fluorescent lamp 25. is improved, but adjustment is difficult and costs increase. SUMMARY OF THE INVENTION An object of the present invention is to provide a lighting device that has a high light utilization rate, has a uniform brightness on a light emitting surface, and can reduce costs.

[Means to solve the problem]

The present invention provides a light guide plate containing a diffusion material with a transmittance of 70 to 95%,
It is characterized by comprising a 40-70% diffusion plate provided on the surface of the light guide plate, a reflective layer provided on the back surface of the light guide plate, and a fluorescent lamp mounted along the end surface of the light guide plate. Both the front and back sides of the light guide plate containing a diffusing material become mirror-like, eliminating loss during light propagation at the interface of the light guide plate, increasing the light utilization rate and providing a light emitting surface with uniform brightness. It will be done.

【Example】

Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings. FIG. 1 shows an embodiment of the present invention. 1 shows a light guide plate containing a diffusion material (diffusing plate and guide light plate),
Reference numeral 2 denotes a diffusion plate made of a transparent acrylic resin containing a diffusion material so as to have a transmittance of 40 to 70Vo, and is attached to the surface of the light guide plate 1. Reference numeral 3 denotes a white reflective sheet with a high reflectance attached to the back surface of the light guide plate 1, 4 a fluorescent lamp attached along the end surface of the light guide plate 1, and 5 a reference numeral 5 directs the light from the fluorescent lamp 4 to the light guide plate 1. This is a glue shifter for efficient injection from the end face. Next, we will discuss the effect. The light incident on the light guide plate 1 is
Upon hitting the diffusing material a, the light is diffused while changing its traveling direction, and only light having a critical angle of 42° 10' or less of acrylic comes out from the front and back surfaces of the light guide plate 1. The light emitted from the surface passes through the diffuser plate 2 and is radiated to the outside. Further, the light emitted from the back surface is reflected by the reflective sheet 3, enters the light guide plate 1 again, and eventually exits from the front surface. Since the light is diffused throughout the light guide plate 1 containing a diffusing material in this way, the light is effectively utilized and is diffused when passing through the diffusing plate 2, making the brightness of the light emitting surface uniform. FIG. 2 is a light intensity distribution diagram without the diffuser plate 2 attached, in which the perpendicular direction to the light guide plate 1 surface is dark, and the larger the angle, the brighter it becomes. This is the diffusion material a of the light guide plate 1.
This is thought to be because the content of the light guide plate 1 is small and the light component in the direction along the light guide plate 1 is large. Here, the content of the diffusion material a of the light guide plate 1 can be increased to increase the light in the perpendicular direction. ,
In that case, the attenuation of light by the diffusing material becomes large, resulting in an uneven surface light source where only the area near the light source is bright and the further away from the light source, the darker it is. Therefore, the appropriate transmittance of the light guide plate 1 is 70 to 95% in the thickness direction.
It can be seen that the light emitted from the light guide plate 1 changes in the direction perpendicular to the light guide plate 1 and becomes a surface light source with a uniform luminous intensity distribution. In the above embodiment, the white reflective sheet 3 was attached to the back surface of the light guide plate 1 to form a reflective layer, but instead of attaching the reflective sheet 3, a metal with high reflectance may be deposited.

【Effect of the invention】

As described above, according to the present invention, two diffusion materials with different contents of diffusion materials are combined to form a light guide plate with the content of one being limited, so that the loss during light propagation at the interface of the light guide plates is reduced. A surface light source with high efficiency and excellent brightness uniformity can be obtained. Furthermore, since there is no need to perform surface treatment on the light guide plate, cost reduction and quality stabilization can be achieved. Furthermore, there is an advantage that brightness and uniformity can be easily controlled by adjusting the amount of diffusing material contained in the light guide plate.

[Brief explanation of drawings]

Fig. 1 is a sectional view showing an embodiment of the lighting device according to the present invention, Fig. 2 is a luminous intensity distribution diagram of the same embodiment without a diffuser plate attached, and Fig. 3 is a diagram showing the diffuser plate of the same embodiment. The luminous intensity distribution diagram in the attached state, FIG. 4, and FIG. 5 are sectional views showing conventional examples, respectively. DESCRIPTION OF SYMBOLS 1... Light guide plate containing a diffusing material, 2... Diffusion plate, 3... White reflective sheet, 4... Fluorescent lamp, 5... Reflector a, b... Diffusion material. 1 Figure 2 Figure 3 Patent Applicant Stanley Electric Co., Ltd. Agent Akira Akimoto Procedural Amendment April 30, 1991 1, Indication of Case 1990 Patent 2, Title of Invention Lighting Device No. 228907 No. Stanley Electric Co., Ltd. Figure 5, 1-1 Minami-Aoyama-chome, Minato-ku, Tokyo 107-8-3475-1501J, -. Contents of the 1995 amendment (1). ``Perpendicular direction'' on page 5, line 13 of the specification is corrected to ``r-normal direction''. ■. The drawings, Figures 2 and 3 will be amended as shown in the attached sheet. Above Figure 2 Figure 3

Claims (1)

[Claims] A light guide plate containing a diffusing material with a transmittance of 70 to 95%, a diffuser plate with a transmittance of 40 to 70% provided on the surface of the light guide plate, a reflective layer provided on the back surface of the light guide plate, and the light guide plate. A lighting device comprising: a fluorescent lamp mounted along an end surface of the lamp.