JPH09152600A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the liquid crystal display device which is increased in luminance. SOLUTION: This device 9 is provided with a light reflecting plate 7 on one principal surface of a light guide plate 11 where a fluorescent lamp 12 is arranged and a liquid crystal panel 3 is arranged on the other principal surface side across a light diffusing plate 6; and the irradiation light from the fluorescent lamp 12 is guided in the light guide plate 11 and projected on the liquid crystal panel 3 from the other principal surface. In this case, the the fluorescent lamp 12 which is provided with a light reflecting layer 13 on the inner peripheral surface of its semicylindrical part has the other semicylindrical part inserted into a recessed part A formed by curving an end surface of the light guide plate 11 inwardly.

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 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, JP-A-6-67025).

FIG. 4 shows an example of a liquid crystal display device 2 equipped with this one-lamp type edge light type illuminating device 1. A rectangular light guide plate 4 is disposed on a liquid crystal panel 3, and the light guide plate 4 is provided. A cylindrical fluorescent lamp 5 is arranged on one end surface.
Further, the light diffusion plate 6 is provided on one main surface of the light guide plate 4, the light reflection plate 7 is provided so as to cover the other main surface and the other end surface, and the 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 the effective light emitting area has substantially the same dimension as the effective display area.

[0005]

However, in the liquid crystal display device 2 having the above structure, some of the irradiation light amount of the fluorescent lamp 5 is absorbed or dissipated by itself, so that the irradiation light amount thereof is increased. However, the luminance of the effective light emitting region of the lighting device 1 is not sufficient, so that the amount of light emitted from the fluorescent lamp 5 is increased in order to achieve a desired luminance, and as a result, the power consumption of the fluorescent lamp 5 is increased. was there.

[0006] Further, with the market needs for portable devices,
In recent years, there has been a demand for size reduction and weight reduction of the liquid crystal display device, but the liquid crystal display device 2 has not yet been achieved to a satisfactory degree, and further size reduction and weight reduction are required. It has been demanded.

[0007] Therefore, as a result of diligent research in view of the above circumstances, the present inventor has found that the light irradiation of the fluorescent lamp 5
In order to efficiently introduce light into the light guide plate 4, the end surface of the light guide plate is curved so that one semi-cylindrical portion of the fluorescent lamp is almost inserted, and further, the other semi-cylindrical portion of the fluorescent lamp is formed. It has been found that the above problem can be solved by providing a light reflecting layer on almost the entire inner peripheral surface of the.

The present invention has been completed based on the above findings, and an object of the present invention is to provide a liquid crystal display device in which the brightness of a backlight type illumination device is increased and the size and weight of the device are reduced.

[0009]

A liquid crystal display device of the present invention is provided with a light reflecting means on one main surface of a light guide plate having a cylindrical elongated light source on its end surface, and a light reflecting means on the other main surface side. A liquid crystal panel is arranged through a diffusion plate, the irradiation light of the elongated light source is introduced into the light guide plate, and light is emitted from the other main surface,
The other semi-cylindrical portion of the elongated light source in which a light reflecting layer is provided on the inner peripheral surface of the semi-cylindrical portion in a concave portion in which the end surface of the light guide plate is curved inwardly, which is configured to project on a liquid crystal panel Is inserted.

[0010]

1 is a sectional view of a liquid crystal display device 9 of the present invention, and FIG. 2 is a sectional view of another liquid crystal display device 9a of the present invention. The same parts as those of the liquid crystal display device 2 shown in FIG.

According to the liquid crystal display device 9 of FIG. 1, 10 is 1
The lighting device 10 is a lighting type edge-light type lighting device, and according to the lighting device 10, one main surface of a rectangular light guide plate 11 made of polymethylmethacrylate (PMMA) having a thickness of 4 mm is a light reflection means and is provided by Toray Industries, Inc. A light reflecting plate 7 made of a low-foaming film made of white polyester is provided, and a sheet-like light diffusing plate 6 made of PET or polycarbonate (PC) is provided on the other main surface, and further along the minor axis one end surface of the light guide plate 11. A fluorescent lamp 12 (cold cathode type or hot cathode type fluorescent lamp having a tube diameter of 3.8 mm) is provided.

The fluorescent lamp 12 is provided with a light reflecting layer 13 over substantially the entire inner peripheral surface of the semi-cylindrical portion.
The light reflection layer 13 is a metal layer of Ag, Al, etc. formed on the inner peripheral surface of the glass cylindrical tube, and can be provided when manufacturing the glass cylindrical tube. Further, an inwardly curved concave portion A is provided on the end face of the light guide plate 11, and the other semi-cylindrical portion of the fluorescent lamp 12 is almost inserted into the concave portion A.

On one main surface of the light guide plate 11, a printing pattern (not shown) containing glass beads formed by adding titanium oxide exhibiting a white or milky white color as an adjusting means for planarly increasing the brightness. ) Are formed on almost the entire surface so as to be distributed in high density. In this printed pattern, the density of the dot pattern is increased as the distance from the fluorescent lamp 12 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, the light diffusion plate 6 and the liquid crystal panel 3
A prism sheet (not shown) having a trade name of BEF100 manufactured by Sumitomo 3M Co., Ltd. is interposed therebetween to further increase the brightness.

Thus, according to the liquid crystal display device 9 having the above-mentioned structure, the light reflecting layer 13 is provided over substantially the entire inner peripheral surface of the one semi-cylindrical portion of the fluorescent lamp 12, and the fluorescent lamp 1
The light guide plate 11 so that the other semi-cylindrical part of 2 is almost inserted.
Since the concave portion A is provided on the end surface of the fluorescent lamp 12, the ratio of the irradiation light amount of the fluorescent lamp 12 absorbed by the glass cylindrical tube of the fluorescent lamp 12 is significantly reduced, and therefore the light is efficiently introduced into the light guide plate 11. As a result, the luminance of the effective light emitting area of the lighting device 10 increases. In addition, since the semi-cylindrical portion of the fluorescent lamp 12 is almost inserted into the concave portion A of the light guide plate 11, the size of the lighting device 10 is small.

The liquid crystal display device 9 is provided with a light reflecting means such as a light source reflection plate 8 for covering the fluorescent lamp 5 provided in the conventional liquid crystal display device 2 to prevent light leakage and further to illuminate. The brightness of the device 10 can be increased.

Next, the liquid crystal display device 9a of FIG. 2 will be described. In the lighting device 10a, the diameter of the fluorescent lamp 12a is adjusted by appropriately adjusting the curved state of the end face of the light guide plate 11a and the size of the fluorescent lamp 12a. By making the thickness of the light guide plate 11a substantially equal to that of the light guide plate 11a, light leakage of the lighting device 10a can be prevented.

[0017]

EXAMPLES The present inventor measured the luminance as follows using the illumination device 10a having the above-mentioned configuration. That is, as shown in the plan view of the illuminating device 10a of FIG. 3, when nine parts were designated on the surface and the brightness of each part was measured, the results shown in Table 1 were obtained. In the table, the luminance was similarly measured for the conventional lighting device 1 shown in FIG. The unit of the numerical value of each luminance is cd / m ² .

[0018]

[Table 1]

As is clear from the results shown in Table 1, it can be seen that the brightness is improved for all the parts. Also,
Compared to the conventional liquid crystal display device 2, the liquid crystal display devices 9 and 9a of the present invention are at least fluorescent lamps 12 and 12.
It became smaller by the size of the radius of a. Then, the light guide plate 11,
Since 11a is also small, the weight can be reduced accordingly.

The present invention is not limited to the above embodiments and examples, and various modifications and improvements may be made without departing from the scope of the present invention. For example, a similar effect can be obtained with a two-lamp type edge light type lighting device instead of the one-lamp type edge light type lighting device.

[0021]

As described above, according to the liquid crystal display device of the present invention, the end surface of the light guide plate is provided in the concave portion which is curved inward.
Since the other semi-cylindrical part of the long light source with a light reflection layer provided on the inner peripheral surface of the semi-cylindrical part is inserted, the proportion absorbed by the long light source is greatly reduced, and further light leakage The brightness of the backlight type lighting device was increased, and the size and weight of the lighting device were reduced.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a liquid crystal display device of the present invention.

FIG. 2 is a schematic cross-sectional view of a liquid crystal display device of the present invention.

FIG. 3 is an explanatory diagram showing a luminance measurement portion of the illumination device.

FIG. 4 is a schematic cross-sectional view of a conventional liquid crystal display device.

[Explanation of symbols]

 3 liquid crystal panel 6 light diffusing plate 7 light reflecting plate 9, 9a liquid crystal display device 10, 10a lighting device 11, 11a light guide plate 12, 12a fluorescent lamp 13 light reflecting layer A concave portion

Claims (1)

[Claims] 1. A light reflecting means is provided on one main surface of a light guide plate having an end face provided with a cylindrical elongated light source, and a liquid crystal panel is provided on the other main surface side via a light diffusing plate, Introducing the irradiation light of the elongated light source into the light guide plate, in the liquid crystal display device that emits light from the other main surface and projects it on the liquid crystal panel, in the concave portion in which the end surface of the light guide plate is curved inward, A liquid crystal display device, wherein the other semi-cylindrical portion of the elongated light source having a light reflection layer provided on the inner peripheral surface of the cylindrical portion is inserted.