JPH08122778A - Liquid crystal display device - Google Patents

Abstract

PURPOSE: To obtain a liquid crystal display device enhanced in the uniformity ratio of illuminance by providing a reflecting member in the outside of an effective light emitting area. CONSTITUTION: In this liquid crystal display device 9, a dotted printing pattern and a light reflector 7 are provided on one principal plane of a light transmission plate 4 having an end face where a fluoresent lamp 5 is disposed, a liquid crystal panel 3 is disposed on the other principal plane side through a light diffusing plate 6, and light introduced from the lamp 5 to the light transmission plate 4 is emitted from the other principle plane and projected to the effective display area of the panel 3. Then, the reflecting members 11 and 12 are provided outside the effective light emitting area of the light transmission plate opposed to the effective display area of the panel 3 on the other principal plane of the light transmission plate 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a backlight type liquid crystal display device.

[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. As an example of this system, a one-lamp type edge light system has been proposed to meet the demands for thinning, lightening, and low power consumption (see, for example, Japanese Patent Laid-Open No. 6-67025).

FIG. 2 shows an example of a liquid crystal display device 2 in which the one-light type edge light type illumination device 1 is mounted. A rectangular light guide plate 4 is arranged on a liquid crystal panel 3, and the light guide plate 4 is provided. A fluorescent lamp 5 is arranged on one end surface. Further, a light diffusing plate 6 is provided on one main surface of the light guide plate 4, a light reflecting plate 7 is provided so as to cover the other main surface and the other end surface, and a light source reflecting plate 8 is provided so as to cover the fluorescent lamp 5. ing.

According to the liquid crystal display device 2, the irradiation light of the fluorescent lamp 5 directly projects the light guide plate 4, or a part of the irradiation light is reflected by the light source reflection plate 8, and the reflected light is also reflected. The light guided to the light guide plate 4 and introduced into the light guide plate 4 is reflected by the light reflection plate 7 and illuminates the liquid crystal panel 3 through the light diffusion plate 6. With the configuration, the effective light emitting area of the illuminating device 1 is defined corresponding to the effective display area of the liquid crystal panel 3, and normally, the effective light emitting area has substantially the same shape as the effective display area.

[0005]

However, the liquid crystal display device 2 having the above structure has a problem that the brightness of the illumination device 1 becomes non-uniform over the effective display area of the liquid crystal panel 3.

That is, in response to the recent demand for thinning and lightening, the distance A between the end of the light guide plate 4 and the end of the light diffusion plate 6 is shortened. Part of the light directly incident on the end face of 4 becomes light emission from the vicinity of the end of the diffuser plate 6, and the light emission from the vicinity of the end of the effective light emitting region increases. Therefore, the brightness of the lighting device 1 is increased. As a result, there is a problem in that the brightness of the effective display area of the liquid crystal panel 3 does not reach the required degree of uniformity and light leakage occurs as a result.

Further, according to the illuminating device 1 having the above-mentioned configuration, even at the other three side ends where the fluorescent lamp 5 is not disposed
Since a part of the light reflected by the light reflecting plate 7 and the like inside the light guide plate 4 is emitted from the vicinity of the end portion of the light guide plate 4, such light leakage was remarkable.

Therefore, an object of the present invention is to provide a high-performance liquid crystal display device in which the brightness of an edge-light type illuminating device is made uniform and the brightness uniformity of the effective display area of the liquid crystal panel is achieved. is there.

Another object of the present invention is to provide a liquid crystal display device which achieves high brightness by preventing light leakage from the lighting device.

[0010]

According to a first aspect of the present invention, a light reflecting means is provided on one main surface of a light guide plate having an elongated light source on its end surface, and a light diffusing plate is provided on the other main surface side. In a liquid crystal display device in which a liquid crystal panel is arranged and light introduced from a long light source into a light guide plate is emitted from the other main surface and projected onto an effective display area of the liquid crystal panel, the other main surface of the light guide plate Among them, a reflecting member is provided outside the light emitting area of the light guide plate facing the effective display area of the liquid crystal panel.

[0011]

In the liquid crystal display device according to the first aspect, the reflecting member is provided on the other main surface of the light guide plate, outside the light emitting region (effective light emitting region) of the light guide plate facing the effective display region of the liquid crystal panel. Therefore, a part of the light that is directly incident on the end surface of the light guide plate is blocked by the reflecting member and reflected to the inside of the light guide plate.
Then, since the reflected light is emitted from the effective light emitting area, light leakage does not occur, the brightness of the illuminating device becomes uniform, and the brightness of the effective display area of the liquid crystal panel can be obtained as required.

[0012] In addition, the other three that do not have a long light source
Even at the end of the side, the reflection member prevents light from being projected from the ineffective light emitting region to the effective display region, and light emission from the vicinity of the end of the light guide plate can be reduced or eliminated. It can be resolved.

[0013]

1 is a sectional view of a liquid crystal display device 9 of this embodiment, and the same parts as those of the liquid crystal display device 2 shown in FIG. Reference numeral 10 denotes a one-lamp type edge light type lighting device. According to this lighting device 10, the thickness is 4 mm.
On one main surface of the rectangular light guide plate 4 made of polymethylmethacrylate (PMMA), a light reflection plate 7 made of a low-foaming film of white polyester made by Toray Industries, Inc., which is a light reflection means, is provided, and at the other main surface, PET is provided. Alternatively, a sheet-like light diffusing plate 6 made of polycarbonate (PC) is provided, and the fluorescent lamp 5 (tube diameter 3.8) is provided along the minor axis one end face of the light guide plate 4.
mm cold-cathode type or hot-cathode type fluorescent lamp), and a reflector 8 having a silver vapor-deposited reflective surface on the outer periphery of the fluorescent lamp 5 whose cross-sectional shape is curved along the longitudinal direction of the fluorescent lamp 5. Is provided.

A print pattern (not shown) containing glass beads formed by adding titanium oxide exhibiting a white or milky white color on one main surface of the light guide plate 4 as a means for adjusting the brightness in a planar manner. ) Are distributed in high density,
It was formed on almost the entire surface. In this printed pattern, the density of the dot pattern is increased as the distance from the fluorescent lamp 5 increases. The light reflection plate 7 is provided below the light reflection plate 7. By combining such a dot-shaped print pattern and the light reflection plate 7, the brightness of the lighting device 10 is increased and the brightness uniformity is improved. It is increasing.

Further, a prism sheet (not shown) of Sumitomo 3M Co., Ltd. under the trade name of BEF100 is interposed between the light diffusion plate 6 and the liquid crystal panel 3 to further increase the brightness.

Further, on the other main surface of the light guide plate 4, a reflection member 11 is provided outside the effective light emitting area of the light guide plate 4 facing the effective display area of the liquid crystal panel 3. This reflective member 1
1 is formed by a printing pattern containing glass beads formed by adding titanium oxide exhibiting a white or milky white system, or a metal such as silver or aluminum is vapor-deposited. Similar reflective members 12 are provided outside the effective light emitting region of the light guide plate 4 near the ends of the other three sides where the fluorescent lamp 5 is not disposed.

Thus, according to the illuminating device 10 having the above structure, since the reflecting members 11 and 12 are provided outside the effective light emitting region, a part of the light directly incident on the end face of the light guide plate 4 is reflected by the reflecting member. The light guide plate 4 is blocked by 11 and 12.
Since the reflected light is reflected to the inside of the, and the reflected light is emitted from the effective light emitting region, light leakage does not occur. Furthermore,
The brightness of the illuminating device 10 became uniform, and the brightness of the effective display area of the liquid crystal panel 3 was obtained as required.

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 one-lamp type edge light type lighting device is used, but a similar effect can be obtained with a two-lamp type edge light type lighting device.

[0019]

As described above, according to the liquid crystal display device of the present invention, since the reflection member is provided outside the effective light emitting region, light leakage does not occur, and the brightness of the illuminating device becomes uniform, so that the liquid crystal As for the brightness of the effective display area of the panel, the uniformity was obtained as required, and as a result, a highly efficient and high-performance liquid crystal display device could be provided.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of a liquid crystal display device of an example.

FIG. 2 is a schematic cross-sectional view of a conventional liquid crystal display device.

[Explanation of symbols]

 3 Liquid crystal panel 4 Light guide plate 5 Fluorescent lamp 6 Light diffusing plate 7 Light reflecting plate 9 Liquid crystal display device 10 Lighting device 11, 12 Reflecting member

Claims (1)

[Claims] 1. A light reflecting means is provided on one main surface of a light guide plate having an elongated light source on its end surface, and a liquid crystal panel is provided on the other main surface side via a light diffusing plate, wherein In a liquid crystal display device that emits light introduced from a light source into a light guide plate from the other main surface and projects the light onto the effective display area of the liquid crystal panel, in the other main surface of the light guide plate, the effective display area of the liquid crystal panel. A liquid crystal display device, characterized in that a reflecting member is provided outside the light emitting region of the light guide plate facing the light guide plate.