JPH05134231A - Backlight device and liquid crystal display device - Google Patents

Abstract

(57) [Abstract] [Purpose] It is possible to prevent leakage current and reduce chromaticity change in the backlight device, and the liquid crystal display device using this backlight makes it easy to replace the cathode tube and realize cost reduction. To do. A backlight device of the present invention is characterized in that a cathode tube reflection cover is provided with a high reflection plastic manufactured by extrusion molding. According to the present invention, the change in chromaticity of the backlight device can be reduced and the leakage current of the cathode tube can be prevented. Further, by adopting the extrusion molding method, the cost can be reduced and the cathode tube can be easily replaced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a backlight device for illuminating a liquid crystal display section and a liquid crystal display device using the same.

[0002]

2. Description of the Related Art In recent years, liquid crystal devices that display images using liquid crystals have been widely used.

In order to display images in these liquid crystal display devices even in a dark place, a so-called backlight device is required as an illuminating device, and a sidelight type backlight device which can be thinned is mainly used. Has become.

As shown in FIGS. 4 (a) and 4 (b), a conventional side-light type backlight device is provided with a cathode tube reflection sheet having silver vapor deposition around the cathode tube to emit light emitted from the cathode tube. The structure is such that it reflects and irradiates the light guide plate.

[0005]

However, in the conventional method, as shown in FIGS. 4 (a) and 4 (b), since a cathode tube reflection sheet having silver vapor deposition around the cathode tube is used, leakage from the cathode tube occurs. A current is generated and the amount of light emitted from the cathode tube is reduced, causing a decrease in the brightness of the light guide surface, and since silver deposition is performed, absorption and transmission in the low wavelength region are large, and the light guide from the light source There is a problem that the change in chromaticity becomes large at the stage where the light shifts.

Further, since the reflective sheet is used, the liquid crystal display device has a structure as shown in FIGS. 5A and 5B, so that it is difficult to replace the cathode tube.

Therefore, the present invention is intended to solve such a problem, and an object of the present invention is to prevent leakage current of a cathode tube used in a backlight device and to reduce light color shift. It is an object of the present invention to provide a backlight device using a cost-effective cathode-ray tube reflection cover and a liquid crystal display device that enables easy replacement of the cathode-ray tube using the backlight device.

[0008]

A backlight device of the present invention is a backlight device comprising a cathode tube and a reflection member for a cathode tube, wherein the reflection member for a cathode tube extrudes a plastic material having a high reflectance characteristic. It is characterized by being formed by molding.

The liquid crystal display device of the present invention is characterized in that the above-mentioned backlight device is arranged on the back surface of the liquid crystal display panel.

[0010]

The present invention will be described in detail with reference to Examples.

[Embodiment 1] FIGS. 1A and 1B show a backlight device using the present invention.

Here, 1 is a cathode tube reflection cover, 2 is a cathode tube, 4 is a light guide plate, 5 is a diffusion sheet, and 6 is a light guide plate lower reflection plate.

The cathode tube reflection cover 1 is manufactured by an extrusion molding method using a color plate ML-4351-88001, which is a highly reflective plastic manufactured by Japan GE Plastics Co., Ltd., which is commercially available. Comparing the current value flowing in the cathode tube reflection sheet and the cathode tube, the current value of the cathode tube alone is 5.00 mA, the current value when using the high reflection plastic made of the cathode tube reflection cover is 5.00 mA. The current value when a certain cathode ray tube reflection sheet having silver vapor deposition was used was 4.85 mA.

As a result, a backlight device capable of preventing leakage current was obtained with the cathode ray tube reflective cover using a highly reflective plastic.

[Embodiment 2] FIG. 2 shows reflectance curves 11 in the respective wavelength bands of highly reflective plastic and silver vapor deposition film.
12 is shown.

According to this, the silver vapor deposition film has a thickness of 430 nm.
It can be seen that there is a large absorption and transmission in the range from 450 nm to 450 nm, but a high reflection plastic has a small absorption and transmission in the range from 430 nm to 450 nm.

As in the first embodiment, the cathode chromaticity of the cathode tube is X = 0.33.
6. The chromaticity of the backlight surface was measured using a cathode tube with Y = 0.364, and X =
0.323, Y = 0.362, and X = 0.342, Y = 0.382 for the cathode ray tube reflection sheet having silver vapor deposited.

As a result, in the cathode ray tube reflective cover made of highly reflective plastic, the same effect as in Example 1 can be obtained, and further, the change in chromaticity can be suppressed as compared with the conventional method.

[Embodiment 3] FIGS. 3A and 3B show a liquid crystal display device using the backlight device of the present invention.

Here, 7 is a liquid crystal display panel, 8 is a holding frame, and 9 is a metal fitting for fixing the cathode tube reflection cover. Fixing of the cathode ray tube reflection cover is performed by a fixing member 9. The fixing metal fittings such as screws and industrial bushes can be selected according to the specifications of the liquid crystal display device.

The cathode tube 2 can be replaced by removing the fixing metal fitting 9 including the cathode tube reflection cover. As described above, the same effects as those of the first and second embodiments are obtained, and further, by exchanging the unit including the cathode ray tube reflection cover as a unit, it is possible to suppress the variation before and after the exchange.

[0022]

As described above, according to the present invention, a cathode tube reflection sheet made of a highly reflective plastic is formed by an extrusion molding method for a cathode tube reflection sheet used in a backlight device to prevent a cathode tube leakage current. It also has the effect of reducing changes in light color shift.

Further, by selecting a cathode tube reflection cover manufactured by an extrusion molding method, it is possible to realize a liquid crystal display device having a structure in which the cathode tube can be easily replaced.

[Brief description of drawings]

FIG. 1 is a diagram showing a first embodiment of the present invention.

FIG. 2 is a diagram showing a second embodiment of the present invention.

FIG. 3 is a diagram showing a structure of a liquid crystal display device using the present invention.

FIG. 4 is a diagram showing a conventional backlight device.

FIG. 5 is a diagram showing a structure of a liquid crystal display device using a conventional backlight device.

[Explanation of symbols]

 1. Cathode tube reflection cover 2. Cathode tube 3. Silver vapor deposition film 4. Light guide plate 5. Diffusing sheet 6. Light guide plate lower reflection plate 7. Liquid crystal display panel 8. Holding frame 9. Cathode tube reflection cover fixing bracket 10. Backlight case 11 ・ High reflectance plastic reflectance curve 12 ・ Silver evaporated film reflectance curve

Claims (2)

[Claims] 1. A backlight device comprising a cathode tube and a reflection member for the cathode tube, wherein the reflection member for the cathode tube is formed by extrusion molding a plastic material having a high reflectance characteristic. Light device. 2. A liquid crystal display device, wherein the backlight device according to claim 1 is arranged on the back surface of a liquid crystal display panel.