JP2723773B2 - Backlight - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a backlight, and more particularly to a backlight of a liquid crystal display device in which fluorescent tubes are arranged at upper and lower ends or left and right ends of a liquid crystal display surface.

[0002]

2. Description of the Related Art One of the backlights of a conventional liquid crystal display device.
In the example , as shown in FIGS. 4A and 4B, a method is employed in which a plurality of fluorescent tubes 10 are arranged immediately below the liquid crystal display surface in the vertical direction or the horizontal direction of the display surface. In this method, a plurality of inverter circuits are required to turn on the fluorescent tube 10, and the fluorescent tube 10 is disposed immediately below the display surface. Had become. However, in this method, since the leading lines from the transformer high-voltage output unit 11 to the fluorescent tubes 10 were at the same distance, the luminance of each fluorescent tube 10 did not vary.

[0003] Other backlights of conventional liquid crystal display devices
As an example , a fluorescent tube is arranged at the upper and lower ends or left and right ends of a liquid crystal display surface in order to realize a thinner and smaller size with respect to the direct-type backlight of the above-mentioned conventional example 1, and the light of this fluorescent tube is Side-type backlights have been devised that include light guide plates that reflect vertically. In this method, the required brightness is usually obtained by using one or two fluorescent tubes, but two fluorescent tubes are lit by one transformer depending on the length of the fluorescent tube to be used. At this time, the transformer tends to be biased toward one of the fluorescent tubes because the high-pressure parts are grouped together as much as possible from the viewpoint of safety and the like.

[0004] Still another conventional backlight for a liquid crystal display device is the side type backlight of the second conventional example, in which the transformer on the inverter board is shifted toward one of the upper, lower, left and right fluorescent tubes. Therefore, a high-voltage jumper wire is fitted on the inverter board. Further, since the high voltage section and the low voltage section are separated from the safety aspect on the inverter board, the low voltage side wiring of the fluorescent tube is adjacent to the high voltage jumper wire on the inverter board.

[0005]

In the above-mentioned conventional backlight, since the transformer on the inverter board is biased to one of the fluorescent tubes, if a high-voltage jumper wire is used to apply a voltage to the fluorescent tubes, Current leaks from this jumper line to the ground pattern on the inverter board. In addition, since the low-voltage side wiring of the fluorescent tube is wired near or adjacent to the high-voltage jumper line, current leaks from the high-voltage jumper line side to the low-voltage wiring side, and sufficient voltage is not applied to the fluorescent tube. However, there is a problem that the brightness of each of the fluorescent tubes changes, resulting in uneven brightness on the liquid crystal display surface.

SUMMARY OF THE INVENTION An object of the present invention is to provide a backlight which does not cause uneven brightness on a liquid crystal display surface and can provide an image having excellent display quality.

[0007]

SUMMARY OF THE INVENTION The present invention provides a liquid crystal display surface.
Fluorescent tubes are placed at the top and bottom or left and right ends, respectively,
Light from the fluorescent tube is incident from the end face and is directed toward the liquid crystal display surface.
A light guide plate disposed below the liquid crystal display surface to reflect light
And a transformer including a transformer for lighting the fluorescent tube.
In a backlight of a liquid crystal display device having a voltage generation circuit , two capacitors connected to each of the fluorescent tubes are arranged at a high voltage output portion of the transformer, and the capacitances of the capacitors are made different from each other. firefly
The brightness of the light tubes is adjusted to suppress uneven brightness between the fluorescent tubes, and each of the fluorescent lamps is output from the high voltage output section of the transformer.
Fluorescent tube high-voltage line that is a wiring to one end of a light tube and each of the fluorescent tubes
And the fluorescent tube low voltage line which is the wiring to the other end of the transformer
Wiring is performed on different surfaces of the board to be mounted, and a predetermined interval is provided .

[0008]

Next, embodiments of the present invention will be described with reference to the drawings.

1 (a) and 1 (b) are a perspective view of an embodiment according to the present invention and a plan view showing a configuration of an inverter unit thereof. In the first embodiment, as shown in FIGS. 1 (a) and 1 (b),
A fluorescent tube 10, a lamp holder 2 holding the fluorescent tube 10, and an inverter board 5 are fixed to the backlight chassis 1.

Further, a transformer 6 is mounted on the inverter board 5, and is connected to one end of one of the fluorescent tubes 10 from the transformer high voltage output section 11 of the transformer 6 via the high voltage capacitor 7 and the fluorescent tube high voltage line 4. 8, a high-voltage jumper wire 9 and a fluorescent tube high-voltage line 4 are connected to one end of the other fluorescent tube 10, and the other end of each fluorescent tube 10 is connected to the fluorescent tube low-voltage line 3 to apply a voltage. It has become.

By employing such a structure of the backlight, a sufficient brightness can be obtained by arranging two fluorescent tubes 10 up to a screen size of about 10 inches, and it can be turned on by one transformer 6. Becomes

When one transformer 6 is mounted and the high-voltage capacitors 7, 8 are arranged at one place, the transformer 6
The high-voltage output of the high-voltage capacitor 8 on the side of the transformer high-voltage output unit 11 is applied to the fluorescent tube 10 via the high-voltage jumper line 9 and the fluorescent tube high-voltage line 4. In order to eliminate the difference in luminance between the two fluorescent tubes 10 due to the current leakage to the ground pattern of, the respective capacitance values of the high-voltage capacitors 7 and 8 are set to one rank or two, such as 15 pF and 18 pF. Set different ranks. That is,
Of the fluorescent tube on the side to which a high voltage is applied via the jumper line 9
In order to compensate for the drop, the fireflies without the high voltage jumper wire
The capacity of the high-voltage capacitor 7 to reduce the brightness of the light tube
The value is set lower than that of the high voltage condenser 8. Thereby, it is possible to eliminate luminance unevenness due to a luminance difference of about 10% of the upper and lower or left and right fluorescent tubes 10.

FIG. 2 is a plan view showing a configuration of an inverter section according to a reference example of the present invention. As shown in FIG. 2, the basic configuration of this reference example is the same as that of FIG. 1 except that the distance between the high-voltage output unit 11 and the high-voltage capacitors 7 and 8 is reduced by changing the transformer 6 mounted on the inverter board 5. They are arranged so as to be almost the same and connected to a high-voltage capacitor via a high-voltage jumper wire 9.

By employing such a structure of the backlight, the amount of voltage drop by the high-voltage jumper wire 9 is equalized, and the voltage applied to the high-voltage capacitors 7 and 8 is made uniform.
It is possible to eliminate luminance unevenness in the vertical and horizontal directions due to the difference in luminance between the fluorescent tubes 10.

FIG. 3 is a plan view showing the configuration of the inverter section according to the preferred embodiment of the present invention. In this example , as shown in FIG. 3, the basic configuration is the same as that of FIG. 1 , but either one of the high-voltage jumper wire 9 and the fluorescent tube low-voltage wire 3 is placed on the back side of the inverter board 5 so as not to be adjacent to each other. It is configured to pass through.

By employing such a structure of the backlight, leakage from the high-voltage jumper line 9 to the fluorescent tube low-voltage line 3 can be prevented, and the brightness unevenness in the vertical and horizontal directions due to the difference in brightness between the two fluorescent tubes 10 can be prevented. Can be eliminated.

[0017]

As described above, according to the present invention, the high voltage capacitors 7 and 8 having different capacitance values are arranged, and the high voltage jumper line 9 and the fluorescent tube low voltage line 3 are arranged on different surfaces of the inverter board 5. There is an effect that luminance unevenness in the vertical and horizontal directions of the fluorescent tube is eliminated and image quality with excellent display quality is obtained.

[Brief description of the drawings]

FIGS. 1A and 1B are a perspective view of an embodiment of the present invention and a plan view showing a configuration of an inverter unit thereof.

FIG. 2 is a plan view illustrating a configuration of an inverter unit according to a reference example of the present invention.

FIG. 3 is a plan view showing a configuration of an inverter unit according to a preferred embodiment of the present invention.

FIGS. 4A and 4B are a perspective view of an example of a conventional backlight and a plan view showing a configuration of an inverter unit thereof.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Back light chassis 2 Lamp holder 3 Fluorescent tube low voltage line 4 Fluorescent tube high voltage line 5 Inverter board 6 Transformer 7,8 High voltage capacitor 9 High voltage jumper line 10 Fluorescent tube 11 Transformer high voltage output part 12 Illumination surface 13 Reflector 14 Lamp mounting board

Claims (1)

(57) [Claims] 1. Fluorescent light is applied to the upper and lower or left and right ends of a liquid crystal display surface.
Each tube is arranged, and the light of each fluorescent tube is incident from the end face
The liquid crystal display so as to reflect in the direction of the liquid crystal display surface.
A light guide plate portion arranged below the display surface and the fluorescent tube are turned on.
In a backlight of a liquid crystal display device having a high-voltage generating circuit including a transformer for causing the two fluorescent lamps to be connected to each of the fluorescent tubes, a high-voltage output portion of the transformer has two capacitors connected to each other. The value
By varying the brightness , the brightness of the fluorescent tubes is adjusted to suppress brightness unevenness between the fluorescent tubes, and wiring is provided from a high-voltage output portion of the transformer to one end of each of the fluorescent tubes.
Fluorescent light, which is the wiring between the fluorescent tube high-voltage line and the other end of each fluorescent tube
Tube low-voltage line to a different surface of the board on which the transformer is mounted
A backlight which is wired and has a predetermined interval .