JPH0894849A - Liquid crystal display device - Google Patents

Abstract

PURPOSE: To make the luminance of an edge light system illuminator uniform and to improve the uniformity of the luminance of the effective display area of a liquid crystal panel by arranging a reflection adjusting pattern on one main surface of a light transmission plate. CONSTITUTION: Many reflection adjusting patterns 12 containing glass beads constituted by adding titanium oxide which is white or milky white are pattern- printed to be distributed with high density nearly all over the surface of one main surface of the light transmission plate as an adjusting means improving the luminance in terms of surface. As for the pattern 12, the density of the dot pattern becomes higher as a distance from a fluorescent lamp 5 becomes longer. Since the reflection adjusting patterns 12a and 12b are arranged, the luminance near the end of the lamp 5 on the light transmission plate is improved, and irregular luminance distribution in the longitudinal direction of the lamp 5 is corrected, whereby the luminance of the illuminator 11 becomes uniform over the surface.

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. 5 shows an example of a liquid crystal display device 2 equipped with the edge-light type thin illuminating device 1 of this one-lamp type. A rectangular light guide plate 4 is arranged on a liquid crystal panel 3, and the light guide plate 4 is provided. The fluorescent lamp 5 is arranged on the end face. 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 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.

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 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. .

[0005]

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 FIGS. 6 and 7, which are enlarged views of the main part of the liquid crystal display device 2.

FIG. 6 shows a pattern shape of the dot-shaped reflection pattern 9 in the illumination device 1. The dot size is increased as the distance from the fluorescent lamp 5 increases so that the reflectivity is increased, whereby the fluorescence is increased. It complements the distance 5 light attenuation of the lamp 5. Further, FIG. 7 shows a light irradiation distribution in the longitudinal direction (between the portion A and the portion B) of the fluorescent lamp 5, and the illuminance at the end portion thereof is smaller than that at the central portion. Therefore, in the effective light emitting area of the illuminating device 1, the brightness tends to be low in the vicinity of the end portion of the fluorescent lamp 5, which causes the brightness of the illuminating device 1 to be non-uniform, and as a result, the liquid crystal panel 3 There is also a problem in that the luminance of the effective display area cannot be obtained as desired.

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 of the effective display area of the liquid crystal panel is evenly distributed. is there.

[0008]

According to a first aspect of the present invention, a light reflecting plate is provided on one main surface of a light guide plate, a liquid crystal panel is provided on the other main surface side through a light diffusing plate, and the light guide plate is provided. In a liquid crystal display device in which a long light source is provided on an end surface of a light plate, and a reflecting member is covered along the longitudinal direction of the long light source, it is possible to correct uneven brightness distribution in the longitudinal direction of the long light source. It is characterized in that a reflection adjusting pattern is arranged on one main surface of the light guide plate.

[0009]

In the liquid crystal display device according to the present invention, since the end of the elongated light source tends to have lower brightness than the central part, the brightness near the end of the elongated light source in the light guide plate is increased. The reflection adjustment pattern is arranged so that it can be seen. By setting the reflection adjustment pattern in this way, it is possible to correct the uneven brightness distribution in the longitudinal direction of the elongated light source, so that the brightness of the illuminating device becomes uniform over the surface, and thus the brightness of the effective display area of the liquid crystal panel is as required. It becomes equality of.

[0010]

FIG. 1 is a sectional view of a liquid crystal display device 10 of this embodiment, and FIGS. 2 and 3 show reflection adjusting pattern shapes on 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, the thickness is 4 m.
m of polymethylmethacrylate (PMMA) rectangular light guide plate 4 is provided with a light reflection plate 7 of a low-foaming film of white polyester manufactured by Toray Industries, Inc. on the other main surface, and PET or polycarbonate (PC) on the other main surface. And a fluorescent lamp 5 (cold-cathode type or hot-cathode fluorescent lamp with a tube diameter of 3.8 mm) is arranged along the minor axis one end surface of the light guide plate 4. Around the outer circumference of the fluorescent lamp 5, a reflector 8 is provided, which is a reflecting member having a silver vapor-deposited reflecting surface whose cross-sectional shape is curved along the longitudinal direction of the fluorescent lamp 5.

Further, on one main surface of the light guide plate 4, there are provided a large number of reflection adjusting patterns 12 containing glass beads formed by adding titanium oxide exhibiting a white or milky white color as an adjusting means for planarly increasing the brightness. A pattern was printed on almost the entire surface so as to be distributed at a high density. This reflection adjustment pattern 12
As shown in FIG. 3 or FIG. 4, the dot pattern density is increased as the distance from the fluorescent lamp 5 increases. The reflection adjustment pattern 12 shown in FIG. 2 is referred to as 12a, and the reflection adjustment pattern 12 shown in FIG.
Is displayed as 12b.

Further, in this embodiment, a product name BEF10 manufactured by Sumitomo 3M Co., Ltd. is provided between the light diffusion plate 6 and the liquid crystal panel 3.
A 0 prism sheet (not shown) is interposed to further increase the brightness.

Thus, according to the illumination device 11 having the above structure, the reflection adjustment patterns 12a, 1 having the shapes as shown in the drawings.
2b are arranged, so that the fluorescent lamp 5 in the light guide plate 4
Since the brightness near the end of the fluorescent lamp 5 is increased, and the uneven brightness distribution in the longitudinal direction of the fluorescent lamp 5 can be corrected,
The luminance of the lighting device 11 became uniform over the surface.

The present inventor uses the lighting device 11 to
In measuring the brightness, as shown in the plan view of the illumination device 11 in FIG. 4, nine parts were designated on the surface, and the brightness of each part was measured. The results shown in Table 1 were obtained. Was obtained. In the table, the reflection adjusting pattern 12a and the reflection adjusting pattern 1 are respectively shown in the embodiment (1) and the embodiment (2).
This is the case where 2b is provided. Further, the luminance was similarly measured for the conventional lighting device 1 provided with the reflection pattern 9 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
^{Is 2} .

[0016]

[Table 1]

As is clear from this result, the embodiment (1)
Was 93.6%, that of Example (2) was 94.0%, and that of the conventional one was 87.2%.

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 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.

[0019]

As described above, according to the present invention, by providing the reflection adjusting pattern so as to correct the unevenness of the luminance distribution in the longitudinal direction of the elongated light source, the luminance of the illuminating device is uniform over the surface. As a result, it was possible to provide a liquid crystal display device in which 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 state diagram of a reflection adjustment pattern in the liquid crystal display device of the example.

FIG. 3 is a state diagram of a reflection adjustment pattern in the liquid crystal display device of the example.

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 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 Reflection Adjustment Pattern 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. In a liquid crystal display device in which a reflecting member is provided along the longitudinal direction of the elongated light source, the reflection adjustment is performed on one main surface of the light guide plate so as to correct the uneven brightness distribution in the longitudinal direction of the elongated light source. A liquid crystal display device having a pattern.