JPH07270788A - Illumination device for liquid crystal display device - Google Patents

Abstract

PURPOSE:To obviate generation of unequal display and to obtain a high quality and high reliability display by successively laminating a light reflection material and a heat insulating material on the outer peripheral surface of a long-sized light source disposed at the end face of a light transmission plate to coat this outer peripheral surface. CONSTITUTION:The one main surface of the light transmission plate 11 is provided with a light reflection means 12 and the other main surface is provided with a light diffusion plate 13 made of a PET or polycarbonate. The long-sized cylindrical light source 14 is disposed along the end face of the light transmission plate 11. The outer periphery of the light source 14 is provided with the light reflection material 15 formed by depositing silver by evaporation on a PET sheet. Further, the outer peripheral surface side of the light reflection material 15 is covered with the heat insulating material 16. In such a case, the light source 14 heats the light reflection material 15 very close to the light source but the light reflection material is covered with the heat insulating material 16 and, therefore, the heated up light reflection material 15 has an effect of immediately heighten the temp. of a liquid crystal panel 9 and the temp. rise of the liquid crystal near the light reflection material 15 decreases. The unequal temp. is thus lessened and the unequal display is obviated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a lighting device for a 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. FIG. 3 shows a liquid crystal display device 1 of that system. .

The liquid crystal display device 1 is a two-light type edge light system in which a rectangular light guide plate 3 is arranged on a liquid crystal panel 2 and a long cylindrical fluorescent lamp 4 is placed on an end face of the light guide plate 3. The diffusion plate 5 is provided on one main surface of the light guide plate 3, the elongated cylindrical fluorescent lamps 4 are arranged along a pair of opposite sides of the light guide plate 3, and the other main surface and the fluorescent lamp 4 are provided.
A reflector plate 6 and a reflector plate 7 made of Al or the like are provided so as to cover the respective parts (JP-A-51-88042, JP-A-64-57240, JP-A-2-17, and JP-A-4-1).
0913).

[0004]

However, the fluorescent lamp 4 of the liquid crystal display device 1 having the above-mentioned configuration generates heat due to the discharge current generated when the lamp is turned on, and accordingly, the heat generation is the most recent reflection plate. The temperature of the liquid crystal panel 2 is further increased by increasing the temperature of the liquid crystal panel 2 by the temperature rise of the liquid crystal panel 2, and the fluorescent lamp 4 as the heat source is arranged at the end of the device 1 in this temperature transmission path. So LCD panel 2
There is a problem that a part of the temperature rises remarkably, and as a result, temperature unevenness occurs in the plane of the liquid crystal panel 2.

That is, the temperature of the portion of the liquid crystal panel 2 close to the fluorescent lamp 4 tends to be higher than that of the central portion of the liquid crystal panel 2, whereby the optimum driving voltage between the two portions is
Since there are differences in Δn (refractive index anisotropy) and the like of liquid crystal materials, there is a problem in that display unevenness can occur.

To solve this problem, a transparent silicon rubber material may be arranged between the fluorescent lamp 4 and the reflection plate 7 to block the heat radiation of the fluorescent lamp 4. With this configuration, the irradiation light of the fluorescent lamp 4 reaches the reflector 7 via the silicone rubber material, and the reflected light passes through the silicone rubber material again, and the silicone rubber material is transparent. However, some light absorption is unavoidable, and therefore, there is a problem that the irradiation light is partly absorbed by the silicon rubber material and the amount of light incident on the end surface of the light guide plate 3 is significantly reduced.

[0007]

According to another aspect of the present invention, there is provided a lighting device for a liquid crystal display device, wherein an end face of a light guide plate having a liquid crystal panel on one main surface and a light reflecting means on the other main surface. The long light source is provided, and the long light source is covered with a cover member formed by sequentially stacking a light reflecting material and a heat insulating material.

[0008]

According to the illumination device for a liquid crystal display device of claim 1,
The temperature of the light-reflecting material that covers it is raised by the heat-generating long light source, but this is a cover member that is further covered with a heat insulating material. Since the material does not directly affect the liquid crystal panel directly, the temperature rise in the part of the liquid crystal panel close to the light reflecting material becomes small or almost nonexistent, and as a result, each part in the plane of the liquid crystal panel The temperature unevenness between the two becomes small and the display unevenness disappears.

Moreover, with the above structure, the irradiation light of the elongated light source is not absorbed by the heat insulating material, so that the light is efficiently incident on the end face of the light guide plate, and as a result, the illumination of high brightness is achieved. A device can be provided.

[0010]

EXAMPLE FIG. 1 shows a lighting device 8 for a liquid crystal display device of this example.
Will be described with reference to FIG. 2 is a schematic configuration diagram of a liquid crystal display device 10 in which the lighting device 8 is mounted on a liquid crystal panel 9, and FIG. 1 is a broken sectional view of the lighting device 8.

According to FIG. 2, a light-reflecting means 1 of a low-foaming film of white polyester is formed on one main surface of a rectangular light guide plate 11 made of polymethylmethacrylate (PMMA) having a thickness of 4 mm.
2 is provided, and a light diffusing plate 13 made of PET or polycarbonate (PC) is provided on the other main surface, and a long cylindrical light source 14 (cooling with a tube diameter of 3.8 mm is provided along the end face of the light guide plate 11. Cathode tube or hot cathode tube)
A light reflecting material 15 formed by depositing silver on a PET sheet is provided on the outer periphery of the light source 14. Further, the outer peripheral surface side of the light reflecting material 15 is covered with a sheet-shaped heat insulating material 16 made of, for example, black silicon rubber or the like. A combination of the light reflecting material 15 and the sheet-shaped heat insulating material 16 covers the light source 14 as a cover member 17.

In this example, the sheet-shaped heat insulating material 16 is used.
Although it is made of silicone rubber, a sheet-shaped heat insulating material 16 made of resin such as polyurethane, polystyrene and polyethylene may be provided.

Further, on one main surface of the light guide plate 11, a large number of high density distributions are formed on almost the entire surface as an adjusting means for increasing the brightness in a planar manner, and the density is increased as the distance from the light source 14 increases. A printing pattern (not shown) containing glass beads exhibiting a white to milky white system is formed, and the light reflecting means 12 is further provided on the lower surface thereof, whereby the brightness of the lighting device 8 is increased, A larger amount of light reflected by the light reflecting means 12 can be applied to the liquid crystal panel side.

A prism plate (not shown) made of PC may be further formed on the light diffusion plate 13 in order to increase the brightness.

Thus, according to the illumination device 8 having the above structure,
The light source 14 heats the nearest light reflecting material 15, but since the light reflecting material 15 is covered with the sheet-shaped heat insulating material 16, the temperature of the light reflecting material 15 is directly increased with respect to the liquid crystal panel 9. The light reflecting material 1
The temperature rise in the portion of the liquid crystal panel 9 close to 5 was extremely small, and as a result, the temperature unevenness between the in-plane portions of the liquid crystal panel 9 was small and the display unevenness was eliminated.

Further, in the lighting device 8 having the above-mentioned structure,
Since the irradiation light of the light source 14 is not absorbed by the sheet-shaped heat insulating material 16, the light efficiently enters the end surface of the light guide plate 11, and as a result, the illumination device 8 with high brightness can be provided.

Furthermore, in the present embodiment, the light reflecting material 15 has a structure in which silver is vapor-deposited on a PET sheet, and the vapor-deposited layer is very thin, so that partial defects are likely to occur, which causes Then, light leakage may occur, and the display area in the vicinity of the light source 14 in the liquid crystal panel 9 may deteriorate in quality. However, since the sheet-shaped heat insulating material 16 is made of black silicon rubber or the like, the sheet-shaped heat insulating material 16 is formed. There is also an advantage that light is absorbed by the heat insulating material 16 and, as a result, a liquid crystal panel 9 of high display quality can be obtained.

The inventor of the present invention has found that the liquid crystal display device 10 of the present embodiment.
In order to compare the conventional liquid crystal display device 1 with the conventional liquid crystal display device 1, except that the sheet-shaped heat insulating material 16 is not provided, the lighting time is set to 3 times.
When the in-plane temperature difference (difference between the maximum temperature and the minimum temperature) of the liquid crystal panel 9 was measured at 0 minutes or 60 minutes, the results shown in Table 1 were obtained.

[0019]

[Table 1]

As is clear from the results in the table, it can be seen that the temperature difference is remarkably reduced when the lighting device 8 of the present invention is mounted.

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, although the two light sources 14 are used in the above-described embodiment, the same operation and effect can be obtained even with the one-lamp type in which only one light source is arranged with respect to the light guide plate 11.

[0022]

As described above, the illumination device for a liquid crystal display device according to the present invention is provided on the outer peripheral surface of the elongated light source disposed on the end surface of the light guide plate used in the edge light system. It is a structure in which the light reflecting material and the heat insulating material are coated so as to be stacked in order, and by the long light source that has generated heat by this structure,
Although the temperature of the light-reflecting material is increased, the temperature rise of the light-reflecting material does not directly affect the liquid crystal panel. Therefore, the temperature rise in the part of the liquid crystal panel near the light-reflecting material is small or almost none. As a result, temperature unevenness between the respective in-plane portions of the liquid crystal panel is reduced, display unevenness is eliminated, and a high quality and highly reliable liquid crystal display device can be provided.

Further, according to the present invention, since the irradiation light of the elongated light source is not absorbed by the heat insulating material, the light is efficiently incident on the end surface of the light guide plate, and as a result, the high brightness liquid crystal display device. Illuminators could be provided.

Further, in the present invention, even if a silver sheet is vapor-deposited on the PET sheet as the light reflecting material, the heat insulating material is formed of a light absorbing material and By preventing light leakage, a lighting device for a liquid crystal display device having a high display quality can be provided.

[Brief description of drawings]

FIG. 1 is a sectional view of a lighting device of an embodiment.

FIG. 2 is a schematic configuration diagram of a liquid crystal display device of an embodiment.

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

[Explanation of symbols]

 8 Lighting device 2, 9 Liquid crystal panel 3, 11 Light guide plate 5, 13 Light diffusing plate 12 Light reflecting means 14 Light source 15 Light reflecting material 16 Sheet-like heat insulating material 17 Cover member

Claims (1)

[Claims] 1. A long light source is provided on an end surface of a light guide plate having a liquid crystal panel on one main surface side and a light reflecting means on the other main surface, and a light reflecting material and a heat insulating material. An illumination device for a liquid crystal display device, characterized in that the elongated light source is covered with a cover member formed by sequentially stacking.