JPH0894848A - 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 forming a light reflection layer at a peripheral part along the liquid crystal panel out of the end face of a light transmission plate where a long light source should be disposed. CONSTITUTION: The light reflection layer 11 is formed at the peripheral part along the liquid crystal panel 3 out of the end face of the light transmission plate 4 where a fluorescent lamp 5 should be disposed. The layer 11 is formed by a printing pattern containing glass beads constituted by adding titanium oxide which is white or milky white. Since the layer 11 is formed, the large projection of the light from the vicinity of the end of the conventional diffusing plate 6 is restrained by the layer 11 even when a distance between the end face of the plate 4 and a diffusing plate 6 becomes short and irradiating light from the lamp 5 is made incident on the end face of the plate 4. Thus, the luminace of the illuminator 10 is made uniform and consequently the uniformity of the luminance of the effective display area of the panel 3 is obtained as required.

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 on each of the other main surfaces so as to cover the other main surface and the fluorescent lamp 5.

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 via the diffusion plate 6.

[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 FIG. 6, which is an enlarged view of a main part of the liquid crystal display device 2.

According to the figure, an effective light emitting area for illuminating the effective display area of the illuminating device 1 is defined corresponding to the actual image display area of the liquid crystal panel 3, that is, the effective display area. However, in order to meet the demand for thinning and lightening of the liquid crystal display device 2, the liquid crystal panel 3 is reduced in size other than the effective display region, and the lighting device 1 is reduced in size except the effective light emission region. There is. Along with this, the distance between the end surface of the light guide plate 4 and the diffusion plate 6 becomes shorter, and the irradiation light of the fluorescent lamp 5 directly enters the end surface of the light guide plate 4, so that the light is emitted from the vicinity of the end portion of the diffusion plate 6. That is, the light emission from the end portion of the effective light emitting region increases, and the luminance of the lighting device 1 becomes non-uniform, and as a result, the luminance of the effective display region of the liquid crystal panel 3 also has a uniform degree as required. There was a problem that I could not get it.

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 long light source is arranged on an end surface of a light guide plate having a light reflecting means provided on one principal surface, and the long light source is provided along the longitudinal direction of the light source. In a liquid crystal display device in which a reflection member having a light reflection surface with a curved cross-sectional shape is provided, and a liquid crystal panel is arranged on the other main surface side of the light guide plate via a light diffusion plate, the elongated light source is arranged. It is characterized in that a light reflection layer is formed on the edge portion along the liquid crystal panel of the end surface of the light guide plate to be provided.

[0009]

In the liquid crystal display device according to the first aspect, since the light reflecting layer is formed on the edge portion along the liquid crystal panel of the end surface of the light guide plate on which the elongated light source is to be disposed, the light guide plate and the end surface are diffused. Even if the light emitted from the elongated light source is directly incident on the end face of the light guide plate due to the short distance from the plate, the light reflection layer tends to reduce the light emission from the vicinity of the end part of the diffusion plate. , The amount of light emitted from the end of the effective light emitting area is smaller than that of the conventional one, and as a result, the luminance of the lighting device is uniform, and the luminance of the effective display area of the liquid crystal panel is also uniform as required. .

[0010]

1 is a sectional view of a liquid crystal display device 9 of the present embodiment, and FIG. 2 is an enlarged sectional view of a main part of the liquid crystal display device 9. The same parts as those of the liquid crystal display device 2 shown in FIGS. 3 and 4 are designated by the same reference numerals.

Reference numeral 10 denotes a one-lamp type edge light type lighting device. According to this lighting device 10, the thickness is 4 m.
m of polymethylmethacrylate (PMMA) rectangular light guide plate 4 is provided on one main surface thereof with a light-reflecting plate 7 of a low-foaming film of white polyester manufactured by Toray Industries, Inc., which is a light reflection means, and PET or the other main surface is provided. Polycarbonate (P
The sheet-like light diffusing plate 6 made of C) is provided, and the fluorescent lamp 5 (tube diameter 3.8 mm) is arranged along the minor axis one end surface of the light guide plate 4.
Cold cathode type or hot cathode type fluorescent lamp), and a reflector 8 having a silver vapor-deposited reflecting surface whose cross-sectional shape is curved along the longitudinal direction of the fluorescent lamp 5 is provided on the outer periphery of the fluorescent lamp 5. It is provided.

A printing 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 reflector 7 is provided on the lower side thereof, and the illumination device 1 is configured by combining such a dot-shaped print pattern and the reflector 7.
The brightness of 0 is increased and the uniformity of the brightness is increased.

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.

In the present embodiment, the light reflection layer 11 is formed on the edge of the end surface of the light guide plate 4 on which the fluorescent lamp 5 is to be arranged, along the liquid crystal panel 3. This light reflecting layer 11 was formed by a printing pattern containing glass beads formed by adding titanium oxide exhibiting a white or milky white color. This print pattern may be the same as the print pattern on the one main surface of the light guide plate 4. An example of the shape of the light reflection layer 11 is shown in FIG. 3 or 4. FIG. 3 shows a dot-shaped light reflection layer 11a provided on the end surface of the light guide plate 4,
FIG. 4 shows two rows of light reflecting layers 11b.

Thus, according to the illumination device 10 having the above structure, since the light reflection layer 11 is formed, the distance between the end face of the light guide plate 4 and the diffusion plate 6 is shortened, and the light emitted from the fluorescent lamp 5 is guided by the light guide plate. Even when the light is incident on the end face of the light diffusing plate 4, the light reflecting layer 11 suppresses a large light emission from the vicinity of the end of the conventional diffusion plate 6, whereby the brightness of the lighting device 10 becomes uniform, and as a result, the liquid crystal panel 3 As for the brightness of the effective display area, the uniformity was obtained as required.

The inventor of the present invention uses the illumination device 10 to
In measuring the brightness, as shown in the plan view of the illumination device 10 in FIG. 7, nine parts were designated on the surface, and the brightness of each part was measured, and the result as shown in FIG. 7 was obtained. Was obtained. The unit of each luminance value is cd / m ²
Is. In addition, the luminance was similarly measured for the conventional lighting device 1 having the same structure except for the light reflecting layer 11.

Then, when the ratio between the minimum luminance and the maximum luminance in each example was obtained, the results shown in Table 1 were obtained.

[0018]

[Table 1]

As is clear from this result, the uniformity of this example was 93.0%, and the conventional one was 85.9%.

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 liquid crystal display device of the present invention, since the light reflecting layer is formed on the edge portion of the end face of the light guide plate along the liquid crystal panel, the irradiation light from the elongated light source is used. Even when incident on the end surface of the light guide plate, the light reflection layer suppresses large light emission from the vicinity of the end portion of the conventional diffusion plate, thereby reducing the amount of light emission from the end portion of the effective light emitting region, As a result, the brightness of the illuminating device became uniform, and good uniformity of the brightness of the effective display area of the liquid crystal panel was obtained.

[Brief description of drawings]

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

FIG. 2 is an enlarged cross-sectional view of a main part of a liquid crystal display device according to an example.

FIG. 3 is a schematic view showing a light reflection layer on an end surface of a light guide plate.

FIG. 4 is a schematic view showing a light reflection layer on an end surface of a light guide plate.

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

FIG. 6 is an enlarged cross-sectional view of a main part of a conventional liquid crystal display device.

FIG. 7 is an explanatory diagram showing a luminance measurement portion of the illumination device.

[Explanation of Codes] 3 Liquid crystal panel 4 Light guide plate 5 Fluorescent lamp 6 Light diffusing plate 7 Reflecting plate 8 Reflecting plate 9 Liquid crystal display device 10 Illuminating device 11, 11a, 11b Light reflecting layer

Claims (1)

[Claims] 1. A long light source is disposed on an end surface of a light guide plate having a light reflecting means provided on one main surface, and a light reflecting surface having a cross-sectional shape curved along the longitudinal direction of the long light source. In a liquid crystal display device in which a reflective member having a light guide plate is provided, and a liquid crystal panel is provided on the other main surface side of the light guide plate via a light diffusing plate, the liquid crystal panel among the end faces of the light guide plate on which the elongated light source is to be provided. A liquid crystal display device, characterized in that a light reflection layer is formed at a peripheral portion along the edge.