JPH0815529A - Surface light source element and liquid crystal display device - Google Patents

Abstract

(57) [Summary] [Purpose] To achieve high brightness. [Structure] Light-diffusing pattern 11 including grooves in light guide plate 10
Are integrally provided, the light reflecting material 14b is formed on the light diffusion pattern 11, and the light source 1 is provided on the end surface of the light guide plate 10.
3 is provided so that the light guide plate 10 emits light from the other main surface side.

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 element which is mounted on a liquid crystal display device or the like and irradiates light in a plane shape, and a liquid crystal display device having the surface light source element.

[0002]

2. Description of the Related Art A liquid crystal display device of a time division system or an active matrix system employs a backlight system in order to improve its visibility. Especially in color liquid crystal display devices, compared to monochrome liquid crystal display devices,
Since the panel transmittance is extremely low, a high-luminance thin lighting device is required.

FIG. 4 shows a liquid crystal display device 1 of this backlight system. The liquid crystal display device 1 is a two-light type edge light system in which a rectangular light guide plate 3 is arranged on a liquid crystal panel 2, and a long cylindrical fluorescent lamp 4 is placed on an end surface of the light guide plate 3. A diffuser plate 5 is provided on one main surface of the light guide plate 3, a long cylindrical fluorescent lamp 4 is arranged along a pair of opposite sides of the light guide plate 3, and the other main surface and the fluorescent lamp 4 are provided.
A reflector 6 made of Al or the like so as to cover
A reflector 7 is provided. Further, on the other main surface of the light guide plate 3, a printing pattern 8 containing glass beads exhibiting a white or milky white color is formed over a substantially entire surface so as to be distributed in high density, and an adjusting means for increasing the brightness in a planar manner. (JP-A-51
-88042, JP-A-64-57240, JP-A-2
-17, JP-A-4-10913, etc.).

[0004]

However, in the liquid crystal display device 1 having the above-mentioned configuration, the print pattern 8 and the reflection plate 6 are separately provided on the light guide plate 3, so that the print pattern 8 and the reflection plate 6 are combined. In addition, an air layer is generated between the light guide plate 3 and the reflection plate 6, which causes a part of the light emitted from the light guide plate 3 to be reflected by the reflection plate 6 and emit light. There is a problem that the emitted light is attenuated due to reflection at the interface with the air layer.

Therefore, an object of the present invention is to provide a high-luminance surface light source element by reducing the attenuation of the amount of light emitted from the elongated light source.

Another object of the present invention is to provide a high performance liquid crystal display device equipped with this high brightness surface light source element.

[0007]

According to another aspect of the surface light source element of the present invention, a light diffusion pattern made of a groove is provided on one main surface of a light guide plate made of resin, and a reflection layer is formed on the light diffusion pattern. A long light source is disposed on the end surface of the light guide plate, and light is emitted from the other main surface side of the light guide plate.

A liquid crystal display device according to a second aspect is characterized in that a liquid crystal panel is provided on the other main surface side of the surface light source element according to the first aspect through a light diffusing means.

[0009]

In the surface light source element according to claim 1, a groove is formed on one main surface to form a light diffusion pattern, and this is replaced with a conventional printing pattern containing glass beads exhibiting a white or milky white system. Eliminates the air layer between the light guide plate and the reflective layer, which eliminates the reflection at the interface with the air layer when the light is emitted after being reflected by the reflective layer. The light is no longer attenuated.

In the second aspect, since the surface light source element is mounted, a high-performance liquid crystal display device can be obtained due to its high brightness.

[0011]

1 is a sectional view of an illumination device for a liquid crystal display device which is a surface light source element of the present invention, and FIGS. 2 and 3 are explanatory views showing a method of forming a light diffusion pattern.

According to the illumination device 9 for a liquid crystal display device of FIG. 1, a polymethylmethacrylate (PMM) having a thickness of 4 mm is used.
A) A large number of grooves are provided on one main surface of the rectangular light guide plate 10 made by the method described below, and the grooves form a light diffusion pattern 11 having a light diffusion function. A light diffusing plate 12 made of PET or polycarbonate (PC) is provided on the other main surface, and a long cylindrical light source 13 (cold cathode with a tube diameter of 3.8 mm) is provided along the end surface of the light guide plate 10. Tube or hot cathode tube), and a light reflecting material 14a made of Al, which is formed by vapor-depositing silver on a PET sheet or whose inner surface is mirror-finished, is provided on the outer periphery of the light source 13. Further, a similar light reflecting material 14b (a low foaming film of white polyester manufactured by Toray Industries, Inc.) is provided on the surface on which the light diffusion pattern 11 is formed. In addition, in order to increase the brightness
Prism plate made by Sumitomo 3M (trade name: BEF1)
00 prism sheet) may be formed on the light diffusion plate 12.

Next, a method of manufacturing the light guide plate 10 integrally provided with the light diffusion pattern 11 will be described. FIG. 2 shows a method of manufacturing the light guide plate 10 by an injection molding method. According to the figure, in the die 16 having the recess 15 and the lid 17 for the die 16, a large number of grooves are formed on the bottom surface 15a of the recess 15 of the die 16. ing. Then, for example, melted PMMA is injected into the concave portion 15, and after the injection, pressure is applied to the mold 17 to perform molding while cooling. According to this manufacturing method, since the light diffusion pattern 11 is formed corresponding to a large number of grooves formed on the bottom surface 15a, the light guide plate 10 integrally provided with the light diffusion pattern 11 is obtained.

FIG. 3 shows a method of manufacturing the light guide plate 10 by a surface grinding method. According to the figure, a light guide plate 18 having a smooth surface is prepared in advance, and linear grooves 20 are sequentially arranged on the light guide plate 18 with needles 19. The light guide plate 10 is provided in which the linear grooves 20 are provided over the entire surface and the light diffusing patterns 11 are formed, and which are integrally provided.

Thus, according to the lighting device 9 having the above structure,
Since the light diffusion pattern 11 is integrally provided on the light guide plate 10, the air layer between the light guide plate 10 and the light reflection material 14b is eliminated, whereby the light reflection material 14b reflects and emits light. At this time, there was no reflection at the interface with the air layer, and the emitted light of this illumination device 9 was no longer attenuated. Therefore, the liquid crystal display device equipped with the illumination device 9 is suitable for a color liquid crystal display device due to its high brightness.

The present inventor has the same configuration except that the light diffusing pattern 11 or the printing pattern 8 is provided in order to compare the illuminating device 9 of this embodiment with the illuminating device of the conventional liquid crystal display device 1. , Light diffusion plate 12 (diffusion plate 5)
The brightness (in-plane average brightness) of the light emitted from the device was measured using a SR-1 instrument manufactured by Topcon, and the results were obtained as follows.

Illumination device 9 of the embodiment (adopts the light guide plate 10 manufactured by the injection molding method of FIG. 2) Luminance 2300 cd Illumination device 9 of the embodiment (adopts the light guide plate 10 manufactured by the surface grinding method of FIG. 3) ) Luminance 2260 cd-Illumination device of conventional liquid crystal display device 1 Luminance 2035 cd As is clear from the above results, it is understood that when the illumination device 9 of the present invention is mounted, the luminance is significantly reduced.

The present invention is not limited to the above embodiments, and various changes and improvements may be made without departing from the scope of the present invention. For example, in the above-described embodiment, the case where the surface light source element of the present invention is mounted on the liquid crystal display device is illustrated, but the surface light source element can also be mounted on other devices requiring surface irradiation. For example, it can also be mounted on devices such as EL displays and plasma displays.

[0019]

As described above, according to the surface light source element of claim 1, a groove is formed in the light guide plate made of resin to form a light diffusion pattern, and the air between the light guide plate and the reflection layer is formed. By eliminating the layer, reflection at the interface with the air layer was eliminated, and as a result, a surface light source element with high brightness could be provided.

Since the liquid crystal display device of the present invention is equipped with the above-mentioned surface light source element, a high-performance liquid crystal display device can be obtained due to its high brightness, and a color liquid crystal display device having an extremely low panel transmittance can be obtained. It became suitable.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a lighting device of an embodiment.

FIG. 2 is an explanatory diagram showing a method for manufacturing a light guide plate.

FIG. 3 is an explanatory view showing a method for manufacturing a light guide plate.

FIG. 4 is a schematic cross-sectional view of a conventional liquid crystal display device.

[Explanation of symbols]

 9 Illumination device for liquid crystal display device 10 Light guide plate 11 Light diffusion pattern 12 Light diffusion plate 13 Light source 16, 17 Mold

Claims (2)

[Claims] 1. A light diffusion pattern made of a groove is provided on one main surface of a light guide plate made of resin, a reflection layer is formed on the light diffusion pattern, and a long light source is arranged at an end face of the light guide plate. The surface light source element is configured to emit light from the other main surface side of the light guide plate. 2. A liquid crystal display device in which a liquid crystal panel is arranged on the other main surface side of the surface light source element of claim 1 through a light diffusing means.