JPH0593910A - LCD lighting device - Google Patents

Abstract

(57) [Summary] [Purpose] To prevent the phenomenon of white spots on the LCD panel. [Structure] A first heat dissipation plate 21 having a high heat conductivity is brought into close contact with the rear surface of the light guide body 11, and heat near the light source 12 is evenly conducted to the rear surface of the light guide body 11. The second heat dissipation plate 22 having a high heat dissipation property is brought into close contact with the rear surface of the first heat dissipation plate 21 to dissipate heat rearward.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light guide type lighting device used for back lighting of a light receiving type liquid crystal display device.

[0002]

2. Description of the Related Art Conventionally, as a backlight for a liquid crystal display device, as shown in FIG. 3, a light guide type one using a light guide is becoming mainstream as the liquid crystal display device becomes thinner. The liquid crystal lighting device used here is
A lamp such as a cold cathode tube or a hot cathode tube is used as the light source 1,
This is arranged on both sides of the light guide 2 made of a translucent material, and the reflection sheet 3 for reflecting the light emitted from the light source 1 toward the back surface and guiding it to the front surface, and the light emitted from the light source 1 are effectively guided. A reflector 4 for reflecting the light on the light incident surface of the light body 2, a diffusion sheet 5 on the upper surface of the light guide 2 for uniformizing the brightness of the illumination surface over the entire surface, and front and rear surfaces of the light guide 2. And a dot pattern 6 of white ink having a light scattering effect. The light guide 2 is generally made of polymethylmethacrylate (PMMA) resin in consideration of light transmission.

In FIG. 3, 7 is a liquid crystal display panel.

[0004]

However, in the light guide type liquid crystal lighting device having the light source 1 and the light guide 2, the portion near the electrode of the light source 1 becomes the most as it becomes thinner and higher in brightness. The temperature rises, causing uneven temperature distribution in the tube axis direction of the light source 1. In particular, as the LCD unit becomes thinner and has higher brightness, the heat radiation of the light source 1 affects the display quality of the liquid crystal display panel due to the fact that the heat radiation effect due to natural convection of air becomes more and less due to the mechanical design. Becomes noticeable.

As a result, uneven temperature distribution occurs in the effective display area of the liquid crystal display panel 10, and in particular, at the end of the effective display area of the liquid crystal display panel on the side where the light source 1 is arranged, so-called white spots are caused by the influence of heat. There was a serious problem that the phenomenon occurred and the display quality of this part was deteriorated.

In view of the above problems, it is an object of the present invention to provide a liquid crystal lighting device capable of improving display quality.

[0007]

The means for solving the problems according to the first aspect of the present invention is to illuminate the liquid crystal display panel 10 from the rear side as shown in FIG. 1, and the liquid crystal display panel 10 is provided behind the liquid crystal display panel 10. A light guide 11 arranged in parallel with the light guide 11, and the light guide 11
A light source 12 arranged at the end of the light source, and a light source reflector 13 for reflecting light from the light source 12 to the light guide 11 side. A heat radiating body 14 for uniformly radiating the heat locally raised in the vicinity of the light source 12 rearward is formed on the heat radiating body 14
Is composed of a first heat dissipation plate 21 that is in close contact with the rear surface of the light guide 11 and has high heat conductivity, and a second heat dissipation plate 22 that is in close contact with the rear surface of the first heat dissipation plate 21 and has high heat dissipation. is there.

According to a second aspect of the present invention, the means for solving the problem is the liquid crystal display device according to the first aspect, wherein the first heat dissipation plate 21 is provided.
Is closely contacted with the entire area of the rear surface of the light guide 11, and the contact surface with the light guide 11 is a mirror surface.

[0009]

In the means for solving the problems according to the first and second aspects, the light from the light source 12 enters the inside of the light guide 11 from the end face thereof. The light traveling backward in the light guide 11 is reflected forward by the mirror surface of the first heat dissipation plate 21. Then, the liquid crystal display panel 10 is irradiated with light from the front surface of the light guide 11.

At this time, the heat generated near the light source 12 is uniformly conducted to the rear surface of the light guide body 11 by the first heat dissipation plate 21 provided on the back surface of the light guide body 11, and rearward by the second heat dissipation plate 22. Is radiated to. As a result, unevenness in the temperature distribution of the light guide 11 is reduced and the light guide 11 is cooled efficiently.

[0011]

1 is a plan view of a liquid crystal lighting device showing an embodiment of the present invention.

As shown in the figure, the liquid crystal illuminating device (LCD unit) of this embodiment illuminates the liquid crystal display panel 10 from the rear by the edge light method.
0 (LCD panel), a light guide 11 arranged in parallel with the liquid crystal display panel 10, light sources 12 arranged at both ends of the light guide 11, and an outside of the light source 12, that is, a light guide. Body 1
1 and a light source reflector 13 (reflector) that reflects the light to the opposite side to the light guide 11 side, and the heat locally raised in the vicinity of the light source 12 is directed backward on the rear surface of the light guide 11. The radiator 14 is formed so as to dissipate the heat evenly.

As shown in FIG. 1, the light guide 11 is made of a translucent polymethylmethacrylate (PMMA) resin and formed into a flat plate having a length of 205 mm, a width of 155 mm and a thickness of 6.0 mm. Has been formed. Both end surfaces of the light guide 11 are light incident end surfaces 11a. The light guide 11
A diffusion sheet 16 similar to the conventional one, which uniformizes the brightness over the front surface of the body, is closely attached to the front surface of the.

For each of the light sources 12, for example, a straight tube type cold cathode tube with a tube current of 5 mA is used, and the diameter thereof is 4.1 mm, the tube surface brightness is 15000 nt, and the power consumption is 5 W. There is.

The light source reflector 13 is formed by sticking a polyethylene terephthalate (PET) film on a silver film having a high thermal conductivity, and is arranged with its central portion curved in an arc shape.

The heat radiating body 14 is composed of a first heat radiating plate 21 which is in close contact with the rear surface of the light guide 11 and a second heat radiating plate 22 which is in close contact with the rear surface of the first heat radiating plate 22.

The first heat dissipation plate 21 has a heat conductivity (thermal conductivity: Thermal conductivity) of 0.1 mm.
A high n) aluminum sheet is used. The first heat dissipation plate 21 is laid over the entire area of the rear surface of the light guide body 11, and is in mechanical contact with the light source reflector 13 so as to dissipate the heat of the light source reflector 13. In addition,
The close contact surface of the first heat dissipation plate 21 with the light guide 11 is made into a mirror surface, whereby a reflection mirror for reflecting the light directed to the back side in the light guide 11 forward is formed.

The second heat dissipation plate 22 is made of a copper sheet having a thickness of 0.1 mm and a high heat dissipation property (Thermal diffusion) as a coating material of the first heat dissipation plate 21. It is laid in the whole area of the rear surface of 21.

The operation of the illuminating device having the above-described structure when it is used will be described. The light from the light source 12 is the light incident end face 1 of the light guide 11.
Enter the inside from 1a. Here, the light traveling backward in the light guide 11 is reflected forward by the mirror surface of the first heat dissipation plate 21. After that, the incoming light is transmitted from the front surface to the diffusion sheet 16
The substantially evenly distributed light is applied to the back surface of the liquid crystal display panel 10 via the.

At this time, heat is radiated from the light source 12, especially the electrode portion thereof, and the heat is retained in the space enclosed by the light source 12, the light guide 11 and the light source reflector 13. Then, the temperature locally rises around this, and a whitening phenomenon may occur in the liquid crystal display panel 10.

However, in this embodiment, since the first heat dissipation plate 21 having excellent heat conductivity is in close contact with the rear surface of the light guide 11, the heat locally raised near the light source 12 is not The heat radiating plate 21 uniformly conducts the light to the entire area of the rear surface of the light guide 11, so that the uneven temperature distribution on the illumination surface of the liquid crystal display plate 10 can be reduced.

Further, since the second heat dissipation plate 22 having excellent heat dissipation is in close contact with the rear surface of the first heat dissipation plate 21, the light guide 11
It is possible to efficiently dissipate the heat from the rear surface and cool the light guide 11.

From the above, it is possible to stabilize the temperature distribution of the liquid crystal lighting device and increase the cooling power. As a result, it is possible to alleviate the white spot phenomenon that occurs at the end of the effective display area of the liquid crystal display panel 10 and to reduce the deterioration of the display quality of the liquid crystal display panel 10.

Specifically, the difference between the temperature in the vicinity of the light source 12 in the effective display area of the liquid crystal display panel 10 and the temperature in the central portion separated from the light source 12 is 4.7 ° C. in the conventional case.
However, in the above embodiment, it was possible to reduce the temperature to 2.5 ° C. and prevent the whitening phenomenon.

The present invention is not limited to the above embodiments, and it goes without saying that many modifications and changes can be made to the above embodiments within the scope of the present invention.

For example, although copper and aluminum are used as the first and second heat dissipation plates 21 and 22 in the above embodiment,
Other materials may be used as long as they are made of a material having good heat conductivity or heat dissipation.

Further, in the above embodiment, the second heat radiating plate 22 is arranged in the entire area of the rear surface of the first heat radiating plate 21, but it may be limited to a particularly high temperature portion as shown in FIG. Further, conversely, the second heat dissipation plate 22 may be arranged not only on the rear surface of the first heat dissipation plate 21 but also in an area having a low heat conductivity such as other resin substances.

Further, the first heat dissipation plate 21 and the light source reflector 13
And may be continuously formed from the same metal sheet.

Furthermore, in the above embodiment, the light guide 11
Although the light sources 12 are arranged at both ends of the above, they may be arranged only at one end.

[0030]

According to the first aspect of the present invention, the heat dissipating member including the first heat dissipating plate having excellent heat transfer property and the second heat dissipating plate having excellent heat dissipation property is closely attached to the rear surface of the light guide member. Therefore, the temperature distribution of the light guide can be made uniform, and efficient cooling can be performed.
Particularly in the field of color LCD units, it is possible to alleviate the occurrence of a whitening phenomenon in the liquid crystal display plate due to non-uniform temperature distribution, and improve the display quality of the liquid crystal display plate. As a result, the yield in mass production can be improved and the cost can be reduced.

According to claim 2 of the present invention, the first heat dissipation plate 21
Since the close contact surface with the light guide body 11 is a mirror surface and this is also used as a reflection sheet, it is possible to prevent the whitening phenomenon of the liquid crystal display panel by a slight increase in the number of parts compared with the conventional one. Have an effect.

[Brief description of drawings]

FIG. 1 is a sectional view of a liquid crystal lighting device showing an embodiment of the present invention.

FIG. 2 is a sectional view of a liquid crystal lighting device showing another embodiment of the present invention.

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

[Explanation of symbols]

 10 Liquid Crystal Display Board 11 Light Guide 12 Light Source 13 Light Source Reflector 14 Heat Sink 21 First Heat Sink 22 Second Heat Sink

Claims (2)

[Claims] 1. A light source for illuminating a liquid crystal display plate from the rear side, the light guide body being arranged in parallel with the liquid crystal display plate behind the liquid crystal display plate, and a light source arranged at an end of the light guide body. And a light source reflector that reflects light from the light source to the outside toward the light guide body, in a rear surface of the light guide body,
A heat radiator is formed to dissipate the locally raised heat near the light source to the rear, and the heat radiator is closely attached to the rear surface of the light guide and has a high heat conductivity, and the first heat radiator. A lighting device for a liquid crystal, comprising a second heat dissipation plate which is closely attached to the rear surface of the plate and has a high heat dissipation property. 2. The liquid crystal display device according to claim 1, wherein the first heat dissipation plate is in close contact with the entire area of the rear surface of the light guide,
An illuminating device for liquid crystal, characterized in that the contact surface with the light guide is a mirror surface.