JP2005017414A - Liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make the size of a liquid crystal display device equipped with a direct backlight device larger by improving the heat discharge power of the liquid crystal display device without installing a fan. <P>SOLUTION: In the liquid crystal display device equipped with the direct backlight device, a reflection plate 10 is disposed on the rear side of fluorescent lamps 9 which irradiate a liquid crystal panel 5 via a diffusion plate 3 and an optical sheet 4 disposed on the front side, and the backlight device is contained in a cabinet 6. Discharge of the backlight heat to the rear side is increased by coating both sides of the cabinet 6 and both sides of the reflection plate 10 with a material having large heat radiation capability and by coating the front surface of the optical sheet 4 with a material having small heat radiation capability. Furthermore, lowering of luminance due to dust and dirt is prevented by coating the front surface of the reflection plate 10 with a photocatalyst which decomposes dust and dirt. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a liquid crystal display device having a backlight device such as a liquid crystal television, and more specifically, a liquid crystal display capable of meeting the demand for an increase in size by efficiently discharging heat generated by the backlight device and suppressing a temperature rise. Relates to the device.
[0002]
[Prior art]
Conventionally, a liquid crystal display device using a liquid crystal panel as a display unit includes a backlight device as a light source on the back surface of the liquid crystal panel. There are two types of backlight devices, an edge light type and a direct type. In the case of a large liquid crystal display device, a direct type backlight device is used. FIG. 2 is a longitudinal sectional view showing a specific configuration of a liquid crystal display device using the direct type backlight device. As shown in the figure, a backlight reflector 10 is arranged in parallel on the back surface of the liquid crystal panel 5, fluorescent tubes 9 are arranged on the surface thereof at equal intervals, and further a diffusion plate 3 and an optical sheet (prism sheet, Polarized reflection film) 4 is disposed. Circuit boards 71 and 72 are attached to the back surface of the backlight reflector 10.
[0003]
These parts are housed in the cabinet 6, and heat radiating holes 61 and 62 are formed in the upper and lower parts of the cabinet 6, respectively. A front protective plate 8 for protecting the liquid crystal panel 5 has been attached to the front opening of the cabinet 6 in accordance with the recent increase in the size of liquid crystal display devices. While the liquid crystal display device is in operation, the fluorescent tube 9 is turned on to irradiate the liquid crystal panel 5 and at the same time, the fluorescent tube 9 generates heat, and a part of the generated heat is discharged from the front of the liquid crystal panel 5 by radiation. The heat generated in the portion was discharged to the outside by convection passing through the heat radiation holes 61 and 62.
[0004]
However, when the amount of heat generation increases due to the increase in the size of the liquid crystal display device, or when the front protective plate 8 is attached and the heat dissipation from the front surface is interrupted due to the increase in size, the natural convection only by the conventional heat dissipation holes 61 and 62 is discharged. The heat method cannot exhaust heat sufficiently, and the temperature of the liquid crystal display device itself rises. As a countermeasure, conventionally, a method of forcibly ventilating by providing a fan in the cabinet 6 has been used. As another countermeasure, it has been proposed to use a reflective sheet in which the reflective plate 10 is coated with a reflective paint having excellent heat radiation characteristics so that the temperature of the reflective plate 10 does not rise excessively due to heat radiation from the fluorescent tube 9. (Patent Document 1).
[0005]
[Patent Document 1]
Japanese Patent Laid-Open No. 2002-258020 [0006]
[Problems to be solved by the invention]
However, if a fan is provided to cope with the increase in size of the liquid crystal display device as described above, there is a problem that wind noise is generated in the fan and countermeasures are required, although the necessary heat discharge capability can be obtained. It was. In addition, when the fan is forcibly ventilated, dust begins to accumulate inside over a long period of time, and the white reflector 10 becomes dirty and the reflectivity decreases, resulting in a decrease in luminance. In addition, when a reflective sheet having a reflective surface coated with a reflective paint having excellent heat dissipation characteristics is used, there is a problem that dust adheres to the reflective surface and becomes dirty, resulting in a decrease in heat dissipation capability. SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a liquid crystal display device that can sufficiently eliminate heat generation of a backlight device without using a fan and can cope with an increase in size without reducing the reflectance of a reflector.
[0007]
[Means for Solving the Problems]
In order to solve the above-described problems, the present invention is characterized in that in a liquid crystal display device provided with a backlight device, a material having high heat radiation is coated on the backlight device and a temperature rising portion behind the backlight device. Specifically, in a liquid crystal display device in which a direct-type backlight device is disposed in the cabinet, which is provided with a reflector on the back surface of the fluorescent tube and irradiates a liquid crystal panel through a diffuser plate and an optical sheet in front of the fluorescent tube. A material having high heat radiation is coated on both surfaces and both the front and back surfaces of the reflector. Further, the invention is characterized in that a material having a low thermal radiation property is coated on the front surface of the optical sheet. Furthermore, the front surface of the reflector is coated with dust or / and a photocatalytic substance that decomposes dust. Here, a white or black lacquer-based paint or enamel-based paint is used as a material having high heat radiation. Also, a silver or aluminum thin film is used as a material having low thermal radiation. Further, white titanium oxide is used as a photocatalytic substance.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a longitudinal sectional view of a liquid crystal display device using a direct type backlight device according to the present invention. As shown in the figure, a backlight reflector 10 is arranged in parallel on the back surface of the liquid crystal panel 5, fluorescent tubes 9 are arranged on the surface thereof at equal intervals, and further a diffusion plate 3 and an optical sheet (prism sheet, Polarized reflection film) 4 is disposed. Circuit boards 71 and 72 are attached to the back surface of the backlight reflector 10. These parts are housed in the cabinet 6, and heat radiating holes 61 and 62 are formed in the upper and lower parts of the cabinet 6, respectively. Part of the heat generated in the fluorescent tube 9 is discharged to the outside by natural convection through the heat radiation holes 61 and 62. The configuration so far is the configuration of a conventional liquid crystal display device.
[0009]
In the present invention, high heat radiation films 11 to 14 having high heat radiation are formed on both the front and back surfaces of the backlight reflector 10 and the cabinet 6, and at the same time, a low heat radiation film 2 having low heat radiation is formed on the front surface of the optical sheet 4. Formed. Specifically, white enamel is applied as the high thermal radiation film 11 on the surface of the backlight reflector 10, and white or black lacquer or enamel is applied as the high thermal radiation film 12 on the back surface of the backlight reflector 10. Similarly, white or black lacquer or enamel is applied as the high heat radiation films 13 and 14 on both sides of the cabinet 6.
[0010]
In general, the cabinet 6 and the backlight reflector 10 are formed of an iron plate or an aluminum plate, and the thermal emissivity when a white enamel is applied on the iron plate is 0.90. The thermal emissivity when black lacquer is applied is 0.88. These values are sufficiently larger than the thermal emissivity of the polished steel sheet, such as 0.07. The optical sheet 4 is made of PET, PC, PMMA, or the like, and the low thermal radiation film 2 having low thermal radiation formed on the front surface thereof is coated with silver or aluminum by sputtering, vapor deposition, or the like. The thermal emissivity in this case is 0.05 for aluminum and 0.03 for silver, which is a sufficiently small value.
[0011]
By being configured in this way, the heat generation of the fluorescent tube 9 is less likely to be radiated to the front liquid crystal panel 5 side because the front surface of the optical sheet 4 is covered with the low thermal radiation film 2 having low thermal radiation. On the other hand, since the back backlight reflector 10 and the front and back surfaces of the cabinet 6 are covered with high heat radiation films 11 to 14 having high heat radiation, the heat radiation to the rear increases. As a result, even if the liquid crystal display device is enlarged and the calorific value of the fluorescent tube 9 is increased, the heat is wasted by natural convection by the conventional heat radiation holes 61 and 62 and the heat radiation to the front of the backlight is suppressed. Since a large amount of heat is exhausted to the rear of the light by heat radiation, it is possible to suppress an excessive temperature rise of the liquid crystal display device itself.
[0012]
In the present invention, the surface of the backlight reflector 10 is further coated with a photocatalytic substance that decomposes dust and dust, specifically, white titanium oxide. As a result, even if dust or dust enters the backlight portion and dust or dust adheres to the surface of the backlight reflector 10, it is decomposed into titanium oxide, and the surface of the backlight reflector 10 becomes dust or dust. Thus, the reflectance of the surface is always kept at the maximum level, and the brightness of the backlight is not reduced by dirt.
[0013]
【The invention's effect】
As described above, according to the liquid crystal display device of the present invention, a large amount of heat radiation is coated on the backlight device and the temperature rising portion behind the backlight device. As a result, the liquid crystal display device can be increased in size. In addition, since the front surface of the optical sheet is coated with a material having low heat radiation, the amount of heat radiation to the liquid crystal panel is reduced even if heat generation of the backlight device is increased, and the temperature rise of the liquid crystal panel is suppressed. Furthermore, since the front surface of the reflecting plate is coated with dust and a photocatalytic substance that decomposes dust, the dust and dust are prevented from adhering to the reflecting plate, and the luminance reduction of the backlight due to dirt is eliminated.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view of a liquid crystal display device according to the present invention.
FIG. 2 is a longitudinal sectional view of a conventional liquid crystal display device.
[Explanation of symbols]
2 Low thermal radiation film 3 Diffusion plate 4 Optical sheet (prism sheet, polarized reflection film)
DESCRIPTION OF SYMBOLS 5 Liquid crystal panel 6 Cabinet 9 Fluorescent tube 10 Backlight reflectors 11-14 High heat radiation film | membranes 61 and 62 Heat radiation holes 71 and 72 Circuit board

Claims (7)

In a liquid crystal display device provided with a backlight device,
A liquid crystal display device, characterized in that a backlight device and a temperature rising portion behind the backlight device are coated with a material having high thermal radiation. In a liquid crystal display device in which a direct-type backlight device that irradiates a liquid crystal panel through a diffuser plate and an optical sheet in a cabinet is provided in the cabinet, with a reflector disposed on the back of the fluorescent tube,
A liquid crystal display device, wherein both the front and back surfaces of the cabinet and the front and back surfaces of the reflector are coated with a material having high heat radiation. The liquid crystal display device according to claim 2,
A liquid crystal display device, wherein a front surface of the optical sheet is coated with a material having low thermal radiation. The liquid crystal display device according to claim 2 or 3,
A liquid crystal display device characterized in that dust or / and a photocatalytic substance for decomposing dust are coated on the front surface of the reflector. The liquid crystal display device according to claim 1,
A liquid crystal display device characterized by using a white or black lacquer or enamel paint as a material having high heat radiation. The liquid crystal display device according to claim 2,
A liquid crystal display device characterized by using a thin film of silver or aluminum as a material having low thermal radiation. The liquid crystal display device according to any one of claims 4 to 6,
A liquid crystal display device characterized by using white titanium oxide as a photocatalytic substance.

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