Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
2000-12-05
2002-10-15
Sikes, William L. (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
C349S129000, C349S143000
Reexamination Certificate
active
06466291
ABSTRACT:
BACKGROUND OF THE INVENTION
A. Field of the Invention
The present invention relates to a liquid crystal display device, and more particularly to an in-plane switching (“IPS”) mode liquid crystal display device.
B. Description Of The Related Art
Recently, the thin film transistor liquid crystal display devices (TFT LCDs) have been used as display devices in such applications as portable televisions and notebook computers, but these TFT LCDs have small viewing angles.
In order to solve this problem, twisted nematic LCDs having, for example, optical compensation films and multi-domains, have been introduced. In these LCDs, however, the color of the image is largely shifted as the viewing angle direction increases.
For a wide viewing angle, the IPS mode LCD is disclosed, for example, in JAPAN DISPLAY 92 page 547, Japanese Patent Unexamined Publication No. 7-36058, Japanese Patent Unexamined Publication No. 7-225388, and ASIA DISPLAY 95 page 707.
FIG. 1
is a view showing the operation of liquid crystal (LC) molecules of the conventional IPS mode LCD.
FIG. 2
is a view showing the long axis of the LC molecules shown in FIG.
1
. As shown in the figures, a data electrode
8
and a common electrode
9
are aligned in Y axis direction at an angle &thgr;
EL
=90° relative to the X axis direction which is the extension direction of a gate bus line (not shown). &thgr;
E
=180° indicates an angle between the direction of electric field and X axis direction. &thgr;
R
indicates an angle between the alignment direction and the X axis direction, and angle &thgr;
R
is determined by a rubbing process in the range of 90° to 180°. &thgr;
rot
indicates a rotated angle of liquid crystal molecules
35
by the electric field applied between the two electrodes.
When a voltage is not applied, liquid crystal molecules
35
denoted by dotted line are aligned according to the alignment direction at angle &thgr;
R
. When the voltage is applied, liquid crystal molecules
35
rotate counterclockwise by angle &thgr;
rot
. In the figures, liquid crystal molecules
35
are denoted by solid line after the voltage is applied, and a positive type liquid crystal is used in which electric permittivity of liquid crystal molecules in the long axis direction is larger than in the short axis direction. On the other hand, when negative type liquid crystal is used, the liquid crystal molecules are aligned perpendicular to the electric field direction.
However, in the conventional IPS mode LCD, grey level inversion is caused by birefringence of the liquid crystal molecules as shown in
FIG. 3
a.
Further, as shown in
FIG. 3
b,
a white color is shifted to blue and yellow colors respectively in A and B viewing directions shown in FIG.
1
.
SUMMARY OF THE INVENTION
An object of the present invention is to prevent a color shift in an in-plane switching mode liquid crystal display device.
Another object of the present invention is to prevent a grey level inversion in an in-plane switching mode liquid crystal display device.
Additional objects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the appended claims.
To achieve the objects and in accordance with the purpose of the invention, as embodied and broadly described herein, the in-plane switching mode liquid crystal display of the present invention comprises: a first substrate having a plurality of pixels, data and common electrodes over the first substrate and substantially parallel with a reference direction, a first alignment layer over the data and common electrodes, wherein at least one of the plurality of pixels has a plurality of domains, and at least two adjacent domains of the plurality of domains have alignment directions opposite one another with respect to the reference direction.
In another aspect the in-plane switching mode liquid crystal display of the present invention comprises: a substrate having a plurality of pixels, data and common electrodes over the substrate and substantially parallel with a reference direction, an alignment layer over the data and common electrodes and having first and second domains adjacent one another, each of the first and second domains having at least one of the pluarity of pixels and an alignment direction opposite that of the other domain with respect to the reference direction.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed.
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Chowdhury Tarifur R.
LG.Philips LCD Co. , Ltd.
McKenna Long & Aldridge LLP
Sikes William L.
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