JPH0915593A - Liquid crystal display device - Google Patents

Abstract

PURPOSE: To improve the luminance of a light transmission plate by disposing a liquid crystal panel on the maximum main surface side of a triangular light transmission plate through a light diffusing plate and disposing a light reflector on either main surface between other main surfaces and a long-length light source along the other. CONSTITUTION: In a one-lamp type edge light system illuminator 12, the liquid crystal panel 3 is disposed on the maximum main surface side having the maximum area of the triangular light transmission plate 4b made of polymethyl methacrylate through the light diffusing plate 6. The light reflector 7 consisting of a low ratio expansion film made of polyester is provided on either main surface between other main surfaces and a fluorescent lamp 5 is disposed along the other main surface (inclined surface (b)) between them, and a reflector 8a is provided in the longitudinal direction of the lamp 5 on the outer periphery of the lamp 5. Irradiating light from the lamp 5 enters the inclined surface (b) of the plate 4b, and a part of the irradiating light is reflected by the reflector 8a and enters the surface (b) of the plate 4b, then they are reflected by the light reflector 7 together so as to form the effective light emitting area of the illuminator 12.

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 In a time-division or active matrix liquid crystal display device, a backlight system is employed to improve the visibility. As an example of this method, a one-light type edge light method has been proposed in response to demands for thinner, lighter, and lower power consumption (see, for example, JP-A-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 diffusion plate 6 is provided on one main surface of the light guide plate 4, a light reflection plate 7 is provided so as to cover the other main surface and the other end surface, and a light source reflection plate 8 is provided so as to cover the fluorescent lamp 5. It is provided.

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 while irradiating 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.

However, the liquid crystal display device 2 having the above structure
In the case where the irradiation light of the fluorescent lamp 5 is incident from the end surface of the light guide plate 4, the amount of incident light is not sufficient, and accordingly, the emitted light of the effective light emitting region of the illumination device 1 is not sufficient, and as a result, However, there is a problem that it is not suitable for a transmissive / semi-transmissive high-brightness edge light illumination device for color liquid crystal display or monochrome liquid crystal display.

Therefore, as a result of intensive research conducted by the present inventors in view of the above circumstances, a liquid crystal display device 9 as shown in FIG. 3 was proposed. The same parts as those of the liquid crystal display device 2 shown in FIG. 2 are designated by the same reference numerals.

That is, according to the illuminating device 10 of the liquid crystal display device 9, one end face of the rectangular axis of the rectangular light guide plate 4a is inclined, the fluorescent lamp 5 is arranged along the inclined face b, and the fluorescent light is emitted. On the outer circumference of the lamp 5, there is provided a reflector 8a having a reflective surface of silver vapor deposition along the longitudinal direction of the fluorescent lamp 5.

According to the liquid crystal display device 9 having the above structure, the irradiation light of the fluorescent lamp 5 enters the inclined surface b of the light guide plate 4a, or a part of the irradiation light is reflected by the light source reflection plate 8a, and the reflected light thereof is reflected. Is also guided to the inclined surface b of the light guide plate 4a, and the light introduced into the light guide plate 4a forms an effective light emitting region of the illumination device 1 while being reflected by the light reflection plate 7.

According to the illuminating device 10 having the above-mentioned structure, the one end face of the minor axis of the light guide plate 4a is inclined, and the fluorescent lamp 5 is arranged along the inclined face b, so that the fluorescent lamp 5 is guided to the light guide plate. The light introduced into the light guide plate 4a is increased, so that the light emitted from the light guide plate 4a is further increased.

[0010]

However, in any of the liquid crystal display devices 2 and 9, the light incident end faces of the light guide plates 4 and 4a have a small area, so that the irradiation light of the fluorescent lamp 5 is not effectively introduced. There is a problem.

Moreover, since the light guide plate 4a is a plate body having two parallel main surfaces, for most of the light introduced from the fluorescent lamp 5 to the light guide plate 4a, the light projection path in the light guide plate 4a becomes long. However, there is a problem that the amount of light emitted from the light guide plate 4a cannot be increased to a satisfactory level due to the light attenuation.

Therefore, an object of the present invention is to provide a liquid crystal display device in which the brightness of the light guide plate is further increased.

[0013]

In the liquid crystal display device of the present invention, a liquid crystal panel is disposed on the side of the largest principal surface having the largest area of the triangular prism-shaped light guide plate via a light diffusion plate, and other Of the main surfaces, while providing a light reflecting means on one main surface,
On the other hand, a long light source is arranged along the main surface, and the light introduced from the long light source into the light guide plate is emitted from the largest main surface and projected onto the liquid crystal panel.

[0014]

In the liquid crystal display device having the above structure, the liquid crystal panel is disposed on the side of the largest principal surface having the largest area of the triangular prism-shaped light guide plate through the light diffusion plate, and one of the other principal surfaces is arranged. The surface is provided with the light reflecting means, and the elongated light source is arranged along the other principal surface. With such a structure, the other principal surface (the light incident end surface) on which the elongated light source is arranged is arranged. ) Area can be made larger than the conventional one, which increases the amount of light introduced from the long light source to the light guide plate, and further shortens the light projection path in the light guide plate to reduce light attenuation. As a result, the light emitted from the light guide plate is further increased.

[0015]

1 is a cross-sectional view of a liquid crystal display device 11 of this embodiment, in which the same parts as those of the liquid crystal display devices 2 and 9 shown in FIGS. 2 and 3 are designated by the same reference numerals. Reference numeral 12 denotes a single-lamp type edge light type lighting device. According to the lighting device 12, triangular prism-shaped polymethylmethacrylate (PMM) is used.
A) A sheet-like light diffusing plate 6 made of PET or polycarbonate (PC) is provided on the side of the largest main surface having the largest area of the light guide plate 4b made of A, and the light reflecting means is provided on one of the other main surfaces. A light reflection plate 7 made of a low-foamed film of white polyester manufactured by Toray Industries, Inc. is provided, and a fluorescent lamp 5 (cold-cathode type or hot-cathode type with a tube diameter of 3.8 mm) is provided along the other main surface (inclined surface b). A fluorescent lamp) is provided, and a reflector plate 8a having a reflective surface of silver vapor deposition is provided on the outer periphery of the fluorescent lamp 5 along the longitudinal direction of the fluorescent lamp 5.

On one main surface of the light guide plate 4a, a print pattern (not shown) containing glass beads formed by adding titanium oxide exhibiting a white or milky white color is provided as a means for adjusting the brightness in a planar manner. 2) are formed on almost the entire surface so as to be distributed in high density. In this print pattern, as the distance from the fluorescent lamp 5 increases, the density of the dot pattern increases. The light reflection plate 7 is provided on the lower side of the lighting device 12, and the combination of the dot-shaped print pattern and the light reflection plate 7 enhances the brightness of the lighting device 12 and improves the uniformity of the brightness. It is increasing.

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

According to the liquid crystal display device 11 having the above structure, in the illumination device 12, the light emitted from the fluorescent lamp 5 is guided by the light guide plate 4.
The light entering the inclined surface b of b or a part of the irradiation light is reflected by the light source reflection plate 8a, the reflected light is also guided to the inclined surface b of the light guide plate 4b, and the light introduced into the light guide plate 4b is The light is reflected by the light reflection plate 7 to form an effective light emitting region of the lighting device 1. The effective light emitting area has substantially the same shape dimensionally corresponding to the effective display area of the liquid crystal panel 3.

Thus, according to the illuminating device 12 having the above-described structure, the one end surface of the light guide plate 4b on the minor axis is inclined and the fluorescent lamp 5 is arranged along the inclined surface b. Since more light can be introduced from the fluorescent lamp 5 to the surface b, and these introduced lights are emitted by the combined structure of the dot-shaped print pattern and the light reflecting plate 7, The light projection path is shortened and the light attenuation is reduced, whereby the light emitted from the light guide plate 4b is further increased.

Next, the present inventor has found that the liquid crystal display device 1 having the above-described configuration is used.
When the luminance of the effective light emitting area of the light emitted from the light diffusing plate 6 of the illuminating device 12 is measured for No. 1, 28
It became 90 cd / m ² . Therefore, regarding the conventional liquid crystal display device 2 and liquid crystal display device 9, the illumination device 1,
Measurement of the luminance of the effective light emitting area in the light emitted from the light diffusion plate 6 of 10, respectively 2150 cd / m ² and 2790cd / m ^2, and the according to the liquid crystal display device 11 of the present invention, high luminance in the effective light emitting area was gotten.

The present invention is not limited to the above embodiments, and various modifications and improvements can be made without departing from the scope of the present invention. For example, in the above embodiment, the inclined surface b with respect to the one end face of the minor axis of the light guide plate 4b.
However, a similar inclined surface b may be provided on one end surface of the major axis.

[0022]

As described above, according to the liquid crystal display device of the present invention, the liquid crystal panel is disposed on the side of the largest principal surface having the largest area of the triangular prism-shaped light guide plate through the light diffusion plate, Of the other main surfaces, the light reflecting means is provided on one main surface, and the elongated light source is arranged along the other main surface. With such a configuration, it is longer than the conventional one. The more light that is introduced from the circular light source to the light guide plate, the shorter the light projection path inside the light guide plate, and the smaller the light attenuation.
It is possible to provide a liquid crystal display device for a color liquid crystal display or a monochrome liquid crystal display, which includes a semi-transmissive edge-light type illumination device of a higher brightness type.

[Brief description of the 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.

FIG. 3 is a schematic cross-sectional view of a conventional liquid crystal display device.

[Explanation of symbols]

 1, 10, 12 Lighting device 3 Liquid crystal panel 4, 4a, 4b Light guide plate b Inclined surface 5 Fluorescent lamp 6 Light diffusing plate 7 Light reflecting plate 8, 8a Reflecting plate 2, 9, 11 Liquid crystal display device

Claims (1)

[Claims] 1. A liquid crystal panel is disposed on the side of the largest principal surface having the largest area of a triangular prism-shaped light guide plate through a light diffusing plate, and a light reflecting means is provided on one principal surface of the other principal surfaces. A liquid crystal display device in which a long light source is provided along the other main surface, and light introduced from the long light source into the light guide plate is emitted from the largest main surface and projected onto a liquid crystal panel. .