JP3274930B2 - Lighting device for liquid crystal display - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

This liquid crystal display device 1 is of a two-light type edge light type in which a rectangular light guide plate 3 is disposed 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. A light diffusing plate 5 is provided on one main surface of the light guide plate 3, and a long cylindrical fluorescent lamp 4 is arranged along a pair of opposite sides of the light guide plate 3.
A reflection plate 6 and a reflection plate 7 each made of Al or the like are provided so as to cover
No. 0913).

[0004]

However, the fluorescent lamp 4 of the liquid crystal display device 1 having the above-described structure generates heat due to a discharge current generated when the fluorescent lamp is turned on. 7, the temperature of the liquid crystal panel 2 is further increased by the increased temperature of the reflecting plate 7. In this temperature transmission path, the fluorescent lamp 4, which is a heat source, is disposed at the end of the device 1. So the liquid crystal panel 2
Of the liquid crystal panel 2 has a problem that temperature unevenness occurs over the surface of the liquid crystal panel 2 as a result.

That is, the temperature of the portion of the liquid crystal panel 2 near the fluorescent lamp 4 tends to be higher than that of the central portion of the liquid crystal panel 2, so that the optimum driving voltage and
Since there is a difference in Δn (refractive index anisotropy) and the like of the liquid crystal material, there is a problem that display unevenness occurs.

In order to solve this problem, a configuration in which a transparent silicon rubber material is disposed between the fluorescent lamp 4 and the reflecting plate 7 so as to block heat radiation of the fluorescent lamp 4 can be considered. In this configuration, the light emitted from the fluorescent lamp 4 reaches the reflection plate 7 via the silicon rubber material, and the reflected light passes through the silicon rubber material again, and the silicon rubber material is transparent. Even so, slight light absorption is unavoidable, and therefore, there is a problem that the irradiation light is partially absorbed by the silicon rubber material, and the amount of light incident on the end face of the light guide plate 3 is significantly reduced.

[0007]

According to a first aspect of the present invention, there is provided an illuminating device for a liquid crystal display device, wherein a liquid crystal panel is disposed on one main surface side and a light reflecting plate is provided on the other main surface. A long light source is provided, and the long light source is covered with a cover member formed by sequentially stacking a light reflecting material obtained by evaporating silver on a PET sheet and a black heat insulating material.

[0008]

According to the illumination device for a liquid crystal display device of the first aspect,
The temperature of the light-reflecting material that covers it is raised by the heated long light source, but the light-reflecting material is further covered with a heat insulating material. Since the material does not directly affect the liquid crystal panel thermally, the temperature rise at the portion of the liquid crystal panel close to the light reflecting material is small or almost nil, and as a result, each portion within the plane of the liquid crystal panel is reduced. The temperature unevenness between them becomes small, and the display unevenness disappears.

In addition, according to the above configuration, since the irradiation light of the long light source is not absorbed by the heat insulating material, the light is efficiently incident on the end face of the light guide plate. Equipment can be provided.

[0010]

FIG. 1 shows a lighting device 8 for a liquid crystal display device according to this embodiment.
FIG. 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 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 provided on one main surface of a rectangular light guide plate 11 made of polymethyl methacrylate (PMMA) having a thickness of 4 mm.
2 and a light diffusion plate 13 made of PET or polycarbonate (PC) is provided on the other main surface, and a long cylindrical light source 14 (a cold tube having a diameter of 3.8 mm) is provided along the end surface of the light guide plate 11. Cathode tube or hot cathode tube)
On the outer periphery of the light source 14, a light reflecting material 15 obtained by depositing silver on a PET sheet is provided. Further, a sheet-like heat insulating material 16 made of, for example, black silicon rubber or the like is coated on the outer peripheral surface side of the light reflecting material 15. The combination of the light reflecting material 15 and the sheet-like heat insulating material 16 covers the light source 14 as a cover member 17.

In this embodiment, the sheet-like heat insulating material 16
Is formed of silicone rubber, but a sheet-like heat insulating material 16 made of a resin such as polyurethane, polystyrene, or polyethylene may be provided.

On one main surface of the light guide plate 11, a large number of high-density distributions are provided over substantially the entire surface as 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 or milky white color is formed, and the light reflecting means 12 is provided on the lower surface thereof, whereby the brightness of the lighting device 8 is increased. The light reflected by the light reflecting means 12 can be applied to the liquid crystal panel more.

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

Thus, according to the illumination device 8 having the above configuration,
The light source 14 heats the nearest light reflecting material 15, but the light reflecting material 15 is covered with the sheet-like heat insulating material 16. The effect of increasing the light reflection 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 portions in the plane of the liquid crystal panel 9 was reduced, and the display unevenness was eliminated.

Further, in the lighting device 8 having the above configuration,
Since the irradiation light of the light source 14 is not absorbed by the sheet-like heat insulating material 16, the light is efficiently incident on the end face of the light guide plate 11, and as a result, the illumination device 8 with high luminance can be provided.

Furthermore, in the present embodiment, the light reflecting material 15 has a structure in which silver is deposited on a PET sheet, and since the deposited layer is very thin, defects are liable to occur partially. As a result, the display area near the light source 14 on the liquid crystal panel 9 may be degraded in quality. However, since the sheet-like heat insulating material 16 is made of black silicon rubber or the like, the sheet-like heat insulating material 16 has a sheet-like shape. There is also an advantage that the light is absorbed by the heat insulating material 16 and as a result, the liquid crystal panel 9 having high display quality can be obtained.

The present inventor has proposed a liquid crystal display device 10 of the present embodiment.
In order to compare the conventional liquid crystal display device 1 with that of the conventional liquid crystal display device 1, the lighting configuration is the same except for the presence or absence of the sheet-shaped heat insulating material 16, and the lighting time is
When the in-plane temperature difference (difference between the maximum temperature and the minimum temperature) of the liquid crystal panel 9 at 0 minute or 60 minutes was measured, the results as shown in Table 1 were obtained.

[0019]

[Table 1]

As is clear from the results shown in the table, it is understood that the above-mentioned temperature difference was significantly reduced when the lighting device 8 of the present invention was mounted.

It should be noted that the present invention is not limited to the above-described embodiment, and various changes and improvements may be made without departing from the scope of the present invention. For example, in the above embodiment, two light sources 14 are used. However, the same operation and effect can be obtained by a single light type in which only one light source is arranged for the light guide plate 11.

[0022]

As described above, the illuminating device for a liquid crystal display device of the present invention has a long light source disposed on an end face of a light guide plate employed in an edge light system, and is provided on an outer peripheral surface thereof. It is a configuration in which the light reflecting material and the heat insulating material are coated so as to be sequentially stacked.
Although the temperature of the light-reflecting material is raised, the temperature rise of the portion of the liquid-crystal panel near the light-reflecting material is small or almost non-existent because the light-reflecting material whose temperature has risen does not directly affect the liquid crystal panel. As a result, the temperature non-uniformity between each part in the plane of the liquid crystal panel was reduced, and the display non-uniformity was eliminated, so that a high quality and high reliability liquid crystal display device could be provided.

Further, according to the present invention, since the irradiation light of the long light source is not absorbed by the heat insulating material, the light is efficiently incident on the end face of the light guide plate, and as a result, a high brightness liquid crystal display device is obtained. Lighting equipment was provided.

Further, in the present invention, even if a structure in which silver is deposited on a PET sheet as the light reflecting material is adopted, the heat insulating material is formed of a light absorbing material, and the light reflecting material is Light leakage was prevented, thereby providing a lighting device for a liquid crystal display device having high display quality.

[Brief description of the drawings]

FIG. 1 is a cutaway view of a lighting device according to an embodiment.

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

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

[Explanation of symbols]

 Reference Signs List 8 lighting device 2, 9 liquid crystal panel 3, 11 light guide plate 5, 13 light diffusion plate 12 light reflection means 14 light source 15 light reflection material 16 sheet heat insulation material 17 cover member

Claims (1)

(57) [Claims] 1. A long light source is disposed on an end surface of a light guide plate having a liquid crystal panel disposed on one main surface and light reflecting means on the other main surface, and silver is vapor-deposited on a PET sheet. A lighting device for a liquid crystal display device, wherein the elongated light source is covered by a cover member formed by sequentially stacking a light reflecting material and a black heat insulating material.