JPH08179314A - Liquid crystal display device - Google Patents

Abstract

PURPOSE: To make the luminance of an illuminator uniform and to enhance the uniformity of luminance in the effective display area of a liquid crystal panel by arranging a light reflection layer in the central area of the end face of a light transmission plate. CONSTITUTION: In this liquid crystal display device 10 on which the illuminator 11 is mounted, a rectangular light transmission plate 4 is disposed on the liquid crystal panel 3. A light reflector 7 is provided on one principal plane of the plate 11, and a light diffusing plate 6 is provided on another principal plane. A fluorescent lamp 5 is disposed along the end face of the plate 4. A light reflection layer 12, for example, the light reflection layer 12a of a dot pattern is arranged in the central area of the end face of the plate 4 being the incident surface of the lamp 5. The light reflection layer 12a is formed into such a shape that a light quantity made incident on the plate 4 may get larger from the central part to both ends thereof so that the light quantity made incident on the plate 4 from the central part of the lamp 5 may be small and that on the plate 4 from both ends of the lamp 5 may be large.

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 in response to the demands for thinning, weight reduction, and low power consumption (Japanese Patent Laid-Open No. H06-6).
-67025).

FIG. 5 shows an example of a liquid crystal display device 2 in which the above-mentioned one-lamp type edge light type thin lighting device 1 is mounted. A rectangular light guide plate 4 is arranged on a liquid crystal panel 3, and a light guide plate 4 is provided.
The fluorescent lamp 5 is arranged on the end face of the. Further, a diffusion plate 6 is provided on one main surface of the light guide plate 4, and a light reflection plate 7 and a light source reflection plate 8 are provided on the main surface of the light guide plate 4 so as to cover the other main surface and the fluorescent lamp 5, respectively. In addition, a reflection pattern 9 of white ink is printed in dots on the other main surface of the light guide plate 4.

FIG. 6 shows the pattern shape of the dot-shaped reflection pattern 9 in the lighting device 1. The size of each dot is increased as the distance from the fluorescent lamp 5 increases, and the reflectivity thereof is increased. It complements the distance 5 optical attenuation.

According to the above 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 illuminates the liquid crystal panel 3 through the diffusion plate 6 while being reflected by the dot-shaped reflection pattern 9 and the light reflection plate 7. .

[0006]

However, the liquid crystal display device 2 having the above-mentioned configuration 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, which is a problem. This will be described with reference to FIG.

This figure shows the longitudinal direction of the fluorescent lamp 5 (part A-
(Between the parts B), and the illuminance at the ends is smaller than that at the center. Therefore, the lighting device 1
The luminance tends to be low in the vicinity of the end portion of the fluorescent lamp 5 in the effective light emitting area of 1., which makes the luminance of the lighting device 1 non-uniform, and as a result, the luminance of the effective display area of the liquid crystal panel 3. Also, there is a problem that the uniformity cannot be obtained as required.

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.

[0009]

In the liquid crystal display device of the present invention, a light reflecting plate is provided on one main surface of the light guide plate, and a liquid crystal panel is provided on the other main surface side via a light diffusing plate, A long light source is provided on an end surface of the light guide plate, a reflecting member is provided along the longitudinal direction of the long light source, and a light reflecting layer is further arranged in a central region of the end surface of the light guide plate. To do.

[0010]

In the liquid crystal display device of the present invention, since the end portion of the elongated light source has a lower brightness than the center portion thereof, the light reflecting layer is arranged in the center area of the end surface of the light guide plate, and the pattern of the light reflecting layer is formed. By adjusting the shape, the amount of light incident on the center of the light guide plate can be adjusted, which can correct the uneven luminance distribution in the longitudinal direction of the elongated light source, and the luminance of the illuminating device becomes uniform over the surface, resulting in a liquid crystal display. The brightness of the effective display area of the panel becomes the desired uniformity.

[0011]

1 is a sectional view of a liquid crystal display device 10 of this embodiment, and FIGS. 2 and 3 show a light reflection layer on the end face of a light guide plate.
The same parts as those of the liquid crystal display device 2 of FIG. 5 are designated by the same reference numerals.

Reference numeral 11 denotes a one-lamp type edge light type illuminating device. According to the illuminating device 11, one main surface of a rectangular light guide plate 4 made of polymethylmethacrylate (PMMA) having a thickness of 4 mm is provided on the Toray Corporation. ) Is provided with a light-reflecting plate 7 of a low-foaming film made of white polyester and PE on the other main surface.
A sheet-like light diffusing plate 6 made of T or polycarbonate (PC) is provided, and a fluorescent lamp 5 (cold cathode type with a tube diameter of 3.8 mm or as a long-sized light source) is provided along one end face of the minor axis of the light guide plate 4. (A hot cathode fluorescent lamp) is provided, and the reflector 8 which is the above-mentioned reflecting member has a reflective surface of silver vapor deposition on the outer periphery of the fluorescent lamp 5 whose cross-sectional shape is curved along the longitudinal direction of the fluorescent lamp 5. It is provided.

Further, as shown in FIG. 6, a reflection pattern 9 containing glass beads formed by adding titanium oxide is formed by printing on one main surface of the light guide plate 4 and distributed in a high density. By doing so, the brightness was adjusted so as to increase the surface condition.

In this embodiment, a prism sheet (not shown) having a trade name of BEF100 manufactured by Sumitomo 3M Ltd. is interposed between the light diffusing plate 6 and the liquid crystal panel 3 to further increase the brightness. .

Further, a light reflecting layer 12 is arranged in the central region of the end surface of the light guide plate 4 which becomes the entrance surface of the fluorescent lamp 5. FIG. 2 shows the light-reflecting layer 12a having a dot pattern as shown in FIG.
Indicates the light reflection layer 12b having a linear pattern. Each of the light reflection layers 12a and 12b further reduces the amount of light that enters the light guide plate 4 from the central portion of the fluorescent lamp 5 and further increases the amount of light that enters the light guide plate 4 from both ends of the fluorescent lamp 5 toward the both ends. The shape is such that the amount of light incident on the light guide plate 4 gradually increases.

Thus, according to the illuminating device 11 having the above-mentioned structure, since the illustrated light reflecting layers 12a and 12b are arranged, the brightness in the vicinity of the end of the fluorescent lamp 5 in the light guide plate 4 is enhanced, and thereby the fluorescent lamp. It is possible to correct the unevenness of the luminance distribution in the longitudinal direction of No. 5, and the luminance of the lighting device 11 becomes uniform over the surface.

When measuring the brightness of the lighting device 11 having the above-described structure, the present inventor designates nine parts on the surface as shown in the plan view of the lighting device 11 of FIG. When the brightness of each site was measured, the results shown in Table 1 were obtained. In the table, Example (1) and Example (2) are cases where the light reflecting layer 12a and the light reflecting layer 12b are provided, respectively. In addition, the luminance was similarly measured for the conventional lighting device 1 shown in FIG. Then, the ratio between the minimum luminance and the maximum luminance in each example was obtained. The unit of the numerical value of each luminance is cd / m ² .

[0018]

[Table 1]

As is clear from the results in Table 1, the uniformity of Example (1) was 93.6%, and the uniformity of Example (2) was 93.2%. The degree was 87.2%.

The present invention is not limited to the above embodiments, and various modifications and improvements may be made without departing from the scope of the present invention. For example, in the above embodiment, the light source is arranged along the one end face of the minor axis of the light guide plate, but the light source may be arranged along one end face of the major axis of the light guide plate. Further, in the above-described embodiment, the one-lamp type edge light type lighting device is used, but a similar effect can be obtained by the two-lamp type edge light type lighting device.

[0021]

As described above, according to the present invention, the light reflection layer is arranged in the central area of the end face of the light guide plate so as to correct the unevenness of the luminance distribution in the longitudinal direction of the elongated light source, and the It is possible to provide a liquid crystal display device in which the brightness can be made uniform over the surface and thus the brightness of the effective display area of the liquid crystal panel has a desired degree of uniformity.

[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 perspective view of a main part of a light guide plate that constitutes the liquid crystal display device of the embodiment.

FIG. 3 is a perspective view of a main part of a light guide plate included in the liquid crystal display device according to the embodiment.

FIG. 4 is an explanatory diagram showing a luminance measurement portion of the illumination device.

FIG. 5 is a schematic cross-sectional view of a conventional liquid crystal display device.

FIG. 6 is a state diagram of a dot-shaped reflection pattern in a conventional liquid crystal display device.

FIG. 7 is an illuminance distribution chart of a fluorescent lamp.

[Explanation of symbols]

 3 Liquid Crystal Panel 4 Light Guide Plate 5 Fluorescent Lamp 6 Light Diffusing Plate 7 Light Reflecting Plate 8 Reflecting Plate 12, 12a, 12b Light Reflecting Layer 11 Lighting Device

Claims (1)

[Claims] 1. A light reflecting plate is provided on one main surface of the light guide plate, a liquid crystal panel is provided on the other main surface side through a light diffusing plate, and a long light source is provided on an end face of the light guide plate. A liquid crystal display device in which a reflection member is provided along the longitudinal direction of the elongated light source, wherein a light reflection layer is arranged in a central region of an end face of the light guide plate.