JPH0633131U - Liquid crystal display - Google Patents

Abstract

(57) [Abstract] [Purpose] In a liquid crystal display device, the heat dissipation efficiency is improved so that the liquid crystal panel can be illuminated with backlight uniformly and with sufficient illuminance. [Structure] Cold cathode tubes U1, U are provided behind the liquid crystal panel 12.
2 is arranged and is held by the holding member 14 in which the slot 22 is formed. A heat radiating plate 19 is attached to the holding member 14, and the heat generated from the cold cathode fluorescent lamps U1 and U2 passes through the elongated holes 22 and is absorbed by the heat radiating plate 19, so that the housing for holding the liquid crystal display device 11 having the above-described structure is provided. Part 20 is dissipated. This makes it possible to supply a sufficient tube current and perform bright and uniform backlight illumination.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a liquid crystal display device that is preferably implemented in a liquid crystal television receiver installed in an automobile.

[0002]

[Prior art]

 A video signal output from a television receiver, a microcomputer, etc. is converted by a drive circuit into a drive signal corresponding to each pixel electrode arranged in a matrix on a glass substrate and given to each of the pixel electrodes, thereby character Liquid crystal panels that can display images, figures, etc. can be displayed by incident light from the front, especially when they are embedded in a relatively dark place such as an instrument panel of an automobile for color display. It is not recognizable and therefore requires illumination from behind, the so-called backlight. A cold cathode tube has been widely used as a light emitting member for the backlight.

FIG. 6 is an exploded perspective view of a typical conventional liquid crystal display device 1. The liquid crystal display device 1 generally includes a liquid crystal panel 2, a drive circuit board 3, cold cathode tubes u1 and u2, a holding member 4, a diffuser plate 5, a holder 6, and a lid 7. It is composed of. A thin film transistor corresponding to each pixel is formed on the surface 2a of the liquid crystal panel 2, and these thin film transistors are connected to a flexible print (not shown) from terminals formed on the peripheral edge 2b of the liquid crystal panel 2. It is connected to the drive circuit board 3 via a board or the like. An integrated circuit 3a for converting the video signal into a drive signal for each pixel is mounted on the drive circuit board 3. Behind the liquid crystal panel 2, U-shaped cold cathode tubes u1 and u2 are arranged, and these cold cathode tubes u1 and u2 are held by a holding member 4. The surface 4a of the holding member 4 is concave and white so that the light emitted rearward from the cold cathode tubes u1 and u2 can be reflected forward. A diffuser plate 5 is interposed between the cold cathode fluorescent lamps u1 and u2 and the liquid crystal panel 2, and the light emitted from the cold cathode fluorescent lamps u1 and u2 and the surface of the holding member 4 are interposed by the diffuser plate 5. The light reflected by 4a is scattered to illuminate the entire surface of the liquid crystal panel 2 with a uniform illuminance without brightening only just above the cold cathode tubes u1 and u2.

In the cold cathode fluorescent lamps u1 and u2, the bent central portions u1a and u2a are locked by locking claws f1 and f2 formed at one end 4c of the holding member 4, respectively. Further, both ends u1b, u1c; u2b, u2c of the cold cathode tubes u1, u2 are soldered to the wiring boards k1, k2, respectively, with electrodes provided near the both ends u1b, u1c; u2b, u2c, respectively. The wiring boards k1 and k2 are held by being screwed on the other end 4d of the holding member 4 with screws 8, and thus the cold cathode tubes u1 and u2 are held without falling off from the holding member 4.

On the other hand, an opening window 6a is formed in the holder 6, and the liquid crystal panel 2 is attached so as to face the opening window 6a from the rear side of the holder 6. When the lid 7 is attached to the side walls 6b and 6c of the holder 6, the diffuser plate 5 is held immediately after the liquid crystal panel 2, and the drive circuit board 3 is spaced apart from the diffuser plate 5. Retained. The holding member 4 having the cold cathode tubes u1 and u2 assembled therein is inserted into the space 10 between the drive circuit board 3 and the light diffusing plate 5, and thus the cold cathode tubes u1 and u2 are connected to the liquid crystal panel 2. You can face behind.

[0006]

[Problems to be solved by the device]

 In the above-mentioned conventional technique, both ends u1b, u1c; u2b, u2c of the cold cathode tubes u1, u2, which are in the vicinity of the electrodes, become very hot due to the heat generated from the filaments of the electrodes, and the heat remains.

That is, for example, at the both ends u1b, u1c; u2b, u2c, the tube currents of the cold cathode tubes u1, u2 reach about 100 ° C. at 11 mA, and reach about 140 ° C. at 17 mA. On the other hand, the operating temperature limit of the liquid crystal panel 2 is, for example, 80 ° C. Therefore, when the environmental temperature is as high as about 60 ° C. in a summer automobile, for example, the display of the liquid crystal panel 2 is not displayed. In the region a1, the above limit may be exceeded in the vicinity of just above the high temperature portions u1b, u1c; u2b, u2c. If the limit is exceeded in this way, the display drive of the liquid crystal panel 2 cannot be performed, and the screen turns blackish or whitish.

In order to solve the above-mentioned problems, in other conventional techniques, the tube current is reduced to reduce the temperature rise. For example, by setting the tube current to 7 mA, the temperature of the high temperature portions u1b, u1c; u2b, u2c can be suppressed to about 80 ° C. However, such a configuration causes a decrease in illuminance. Further, if the holding member 4 is made of a metal having good heat dissipation, it is difficult to obtain the accuracy for fitting the holder 6 well.

In still another conventional technique, backlight illumination is performed by a so-called edge light system in which a light emitting member is arranged behind the peripheral edge portion 2b of the liquid crystal panel 2. With such a configuration, the illuminance is insufficient in the central portion of the liquid crystal panel 2, and the illumination efficiency is poor.

It is an object of the present invention to provide a liquid crystal display device capable of suppressing backlight temperature rise and performing backlight illumination with sufficient illuminance.

[0011]

[Means for Solving the Problems]

 The present invention provides a liquid crystal panel that displays characters, figures, etc. in response to a drive signal from a drive circuit, a light emitting member for a backlight arranged behind the liquid crystal panel, and a holding member for holding the light emitting member. A liquid crystal display device comprising: a holding member having a through hole formed in at least a portion immediately below a light emitting member; and a heat radiating plate facing the back of the holding member and connected to a housing.

[0012]

[Action]

 According to the invention, a light emitting member such as a cold cathode tube used for a backlight of a liquid crystal panel that displays characters and figures in response to a drive signal from a drive circuit is disposed behind the liquid crystal panel. It is held by the holding member in the opened state. A through hole is formed in at least a portion of the holding member immediately below the light emitting member, for example, at a portion of the electrode and its vicinity where the temperature is high. A heat radiation plate is provided behind the holding member, and the heat radiation plate is connected to the housing. With such a configuration, the heat generated from the light emitting member is absorbed by the heat radiating plate through the through hole formed in the holding member, and the absorbed heat is dissipated by the housing connected to the heat radiating plate.

Therefore, the temperature rise of the liquid crystal panel can be suppressed, and the backlight illumination can be performed with sufficient illuminance, so that the display quality of the liquid crystal panel can be improved.

[0014]

【Example】

 1 is an exploded perspective view of a liquid crystal display device 11 according to an embodiment of the present invention, and FIG. 2 is a front view thereof. The liquid crystal display device 11 generally includes a liquid crystal panel 12, a drive circuit board 13, cold cathode tubes U1 and U2, a holding member 14, a heat radiating plate 19, a light diffusing plate 15, a holder 16, and The lid 17 is included. Thin film transistors corresponding to the respective pixels are formed on the surface 12a of the liquid crystal panel 12, and these thin film transistors are connected to a flexible printed circuit board (not shown) from a terminal formed on the peripheral portion 12b of the liquid crystal panel 12. It is connected to the drive circuit board 13 via the. An integrated circuit 13a for converting a video signal into a drive signal for each pixel is mounted on the drive circuit board 13.

Behind the liquid crystal panel 12, U-shaped cold cathode tubes U1 and U2 are arranged, and these cold cathode tubes U1 and U2 are provided by a holding member 14 made of a material such as resin. Is held. Further, a heat radiating plate 19 is screwed and fixed to the holding member 14 with screws 18.

The holding member 14 has a surface 14a that is concave and white so that the light emitted rearward from the cold cathode tubes U1 and U2 can be reflected forward. Further, an elongated hole 22 which is a through hole is formed in a portion immediately below the cold cathode fluorescent lamps U1 and U2 so as to extend from one end portion 14d to the other end portion 14c. A diffuser plate 15 is interposed between the cold cathode tubes U1 and U2 and the liquid crystal panel 12, and the diffuser plate 15 allows the light emitted from the cold cathode tubes U1 and U2 and the surface 14a of the holding member 14. The entire surface of the liquid crystal panel 12 is illuminated with a uniform illuminance without scattering the light reflected by the above so that only the portions directly above the cold cathode fluorescent lamps U1 and U2 become bright.

FIG. 3 is a front view showing a state in which the cold cathode tubes U1 and U2 are assembled to the holding member 14, and FIG. 4 is a sectional view taken along the section line AA of FIG. FIG. 4 is a sectional view taken along the section line B-B of FIG. 3.

In the cold cathode tubes U1 and U2, the bent central portions U1a and U2a are locked by locking claws F1 and F2 formed on the other end 14c of the holding member 14, respectively. Further, both ends U1b, U1c; U2b, U2c of the cold cathode fluorescent lamps U1, U2 have wiring boards K1, K2 respectively provided with electrodes G1b, G1c; G2b, G2c provided near the both ends U1b, U1c; U2b, U2c. The wiring boards K1 and K2 are held by being screwed onto one end 14d of the holding member 14 with screws 28, and thus the cold cathode tubes U1 and U2 are removed from the holding member 14. It is retained without falling off.

A DC-DC converter 29 is connected to the wiring boards K1 and K2. The DC-DC converter 29 boosts a DC input voltage of 12V to a DC output voltage of 200V and outputs the boosted DC output voltage. Then, this high voltage is applied between the electrodes G1b and G1c of the cold cathode tubes U1 and U2 and between G2b and G2c via the wiring boards K1 and K2. As a result, the cold cathode fluorescent lamps U1 and U2 are turned on, and the illumination light for the backlight of the liquid crystal panel 12 can be generated.

On the other hand, an opening window 16a is formed in the holder 16, and the liquid crystal panel 12 is attached from the rear side of the holder 16 so as to face the opening window 16a. Further, when the lid 17 is attached to the side walls 16b and 16c of the holder 16, the diffusing plate 15 is held immediately after the liquid crystal panel 12, and the driving circuit board 13 is held at a distance from the diffusing plate 15. To be done. In the space 30 between the drive circuit board 13 and the diffuser plate 15, the cold cathode tubes U1 and U2 are assembled and then inserted into the holding member 14 to which the heat dissipation plate 19 is attached. , U2 can face the rear side of the liquid crystal panel 12.

The liquid crystal display device 11 configured as described above is attached by screwing or the like to a part 20 of a housing provided in an instrument panel or the like of an automobile. At this time, the screw 38 is inserted through the insertion holes 24 and 25 formed in the part 20 of the housing, and further inserted into the insertion holes 26 and 27 formed in the heat dissipation plate 19 to illustrate the holding member 14. The contact surface 21 of the part 20 of the housing is brought into close contact with the heat dissipation plate 19 by being screwed into the non-threaded hole. The contact surface 21 is provided so as to project upward from a part 20 of the housing, and this part fits into a groove 40 formed in the lid 17.

The heat generated by the tube current flowing through the cold cathode tubes U1 and U2, particularly the heat generated from the high temperature portions H1b, H1c; H2b and H2c near both ends U1b, U1c; U2b, U2c, is retained. After passing through the long hole 22 formed in the member 14 and absorbed by the heat dissipation plate 19, it is conducted to the part 20 of the housing through the contact surface 21, and is radiated from the part 20 of the housing.

Therefore, as described in the section of the prior art, the entire surface of the liquid crystal panel 12 can be illuminated brightly without suppressing the tube current. Further, the liquid crystal panel 12 can be illuminated uniformly and efficiently as compared with the edge light system in which the light emitting member is provided on the peripheral portion 12b of the liquid crystal panel 12.

[0024]

[Effect of device]

 As described above, according to the present invention, the heat generated from the light emitting member passes through at least a portion immediately below the light emitting member, for example, the through hole formed in the electrode and a portion having a high temperature near the electrode, and the heat is transmitted through the through hole. It is absorbed by the heat sink provided behind the hole, and the absorbed heat is dissipated by the housing connected to the heat sink. As a result, the temperature rise of the liquid crystal panel can be suppressed and the backlight illumination can be performed with sufficient illuminance, so that the display quality of the liquid crystal panel can be improved.

[Brief description of drawings]

FIG. 1 is an exploded perspective view of a liquid crystal display device 11 according to an embodiment of the present invention.

2 is a front view of the liquid crystal display device 11. FIG.

FIG. 3 is a front view showing a state in which cold cathode tubes U1 and U2 are assembled to a holding member 14.

4 is a cross-sectional view taken along the section line AA of FIG.

5 is a cross-sectional view taken along the section line BB in FIG.

FIG. 6 is an exploded perspective view of a typical conventional liquid crystal display device 1.

[Explanation of symbols]

 11 liquid crystal display device 12 liquid crystal panel 13 drive circuit board 14 holding member 15 diffuser plate 16 holder 19 heat dissipation plate 20 part of housing 22 long hole

Claims (1)

[Scope of utility model registration request] 1. A liquid crystal panel that displays characters, graphics, etc. in response to a drive signal from a drive circuit, a light emitting member for a backlight arranged behind the liquid crystal panel, and a holding member for holding the light emitting member. A liquid crystal display device comprising: a holding member having a through hole formed in at least a portion immediately below a light emitting member; and a heat radiating plate facing the back of the holding member and connected to a housing.