Liquid crystal display device

Details Liquid crystal display device Liquid crystal display device

2002-08-27

2004-03-16

Nguyen, Dung (Department: 2871)

Liquid crystal cells, elements and systems

Particular structure

Having significant detail of cell structure only

C349S141000

Reexamination Certificate

active

06707522

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a liquid crystal display device, and more particularly to a liquid crystal display device realizing a high screen quality by preventing light leakage due to ion adsorption in a signal applying unit.
2. Description of the Prior Art
A liquid crystal display (hereinafter, referred to as LCD) has advantages of light weight, thin thickness and low power consumption, thereby advantageously applied to terminals of information apparatus and video apparatus instead of CRT (Cathode Ray Tube). Especially, TFT-LCD having thin film transistor (hereinafter, referred to as TFT) can realize the high screen quality and can be the large display device, because it has improved response features and is suitable for high number of pixels.
The LCD can be classified into Storage On Gate mode as illustrated in FIG.
1
A and Storage On Common mode as illustrated in
FIG. 1B
by the line design.
As shown in
FIG. 1A
, the storage on gate mode LCD comprises a gate line
12
and a common line
14
in a signal applying unit
11
out of a display unit
10
realizing image on a substrate
19
, applying signals into the display unit
10
.
In the storage on gate mode LCD, all the pixels in the display unit
10
have the same structures and they are adjacent to a plurality of pixels comprising a gate line
12
, a data line
13
, a common line
14
, a counter electrode
15
, a pixel electrode
16
and a TFT LCD in the same manner.
However, the outmost pixel that is the most adjacent to the signal applying unit
11
has the structure different from other pixels in the display unit
10
. Or, a data line is not formed in the direction of the signal applying unit
11
in the outmost pixel.
When a scanning signal is applied to one of gate lines
12
and a display signal is applied to the data line, a TFT
17
disposed at the intersection of the gate line and the data line is turned on. Then, the display signal of data line
13
is transmitted to the pixel electrode
16
through the TFT
17
and the common signal is continuously applied to the counter electrode
15
, thereby generating electric field between the electrodes
15
,
16
.
Therefore, liquid crystal molecules (not shown) are arranged to be parallel to the electric field (positive dielectric anisotropy) or to be perpendicular thereto (negative dielectric anisotropy), thereby light leakage is generated and a predetermined image is realized.
Referring to
FIG. 1B
, the storage on common mode LCD is the same manner.
There are, however, several problems in the conventional LCD.
For gate line and common line, difference between DC (direct current) component signal of gate line and that of common line causes voltage difference. The data line is swung into positive and negative voltage to common voltage in each frame, thereby preventing maintenance of a predetermined DC voltage.
As describe above, the conventional pixel the most adjacent to the signal applying unit has no data line formed in the direction of the signal applying unit. Therefore, ion adsorption is generated due to voltage difference between gate line and common line, and pixels are influenced by the resulting electric field.
In a normally black mode, outmost pixels, which are switched by the electric field generated due to ion adsorption, has a problem of light leakage in a low gray, thereby lowering screen quality.
SUMMARY OF THE INVENTION
The present invention has made to solve the above-mentioned problems and the primary objective of the present invention is to provide a LCD preventing light leakage due to ion adsorption in a signal applying unit by extending pixel electrode of outmost pixel to the signal applying unit.
In order to accomplish the objective, the present invention comprises: a substrate; a signal applying unit having a gate line and a common line on the substrate; and a display unit having a plurality of pixels with a data line, a counter electrode, a pixel electrode, a TFT and the gate line and the common line extended from the signal applying unit, wherein the pixel electrode comprises a body unit and a branch unit, the body unit being parallel to the gate line and the branch unit comprising a plurality of branches being parallel to the data line, and pixel electrode of the pixel the most adjacent to the signal applying unit has some of branches formed on the signal applying unit.


REFERENCES:
patent: 5933202 (1999-08-01), Watanabe et al.
patent: 6078368 (2000-06-01), Ichikawa et al.
patent: 6223034 (2001-04-01), Yamashita
patent: 6344842 (2002-02-01), Hebiguchi
patent: 2003/0035080 (2003-02-01), Battersby

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