Liquid crystal cells – elements and systems – Particular excitation of liquid crystal – Electrical excitation of liquid crystal
Reexamination Certificate
2000-10-27
2003-09-02
Chowdhury, Tarifur R. (Department: 2871)
Liquid crystal cells, elements and systems
Particular excitation of liquid crystal
Electrical excitation of liquid crystal
C349S039000, C349S130000, C349S139000, C257S059000
Reexamination Certificate
active
06614492
ABSTRACT:
BACKGROUND OF THE INVENTION
(a) Field of the Invention
The present invention relates to a vertical alignment mode liquid crystal display and, more particularly, to a vertical alignment mode liquid crystal display having an electrode with opening patterns such that it can accomplish a wide viewing angle.
(b) Description of the Related Art
Generally, a liquid crystal display has a liquid crystal layer sandwiched between two substrates. Electric field is applied to the liquid crystal layer to control light transmission, thereby producing display images.
Among them, the vertical alignment mode liquid crystal displays have been the choice of consumers because they bear a high contrast ratio and a wide viewing angle. The vertical alignment mode liquid crystal display has the directors of the liquid crystal molecules aligned normal to the substrates when the electric field is not applied.
In order to realize a wide viewing angle with such a mode, it has been proposed that opening patterns or protrusions may be formed at electrodes. The opening patterns or protrusions form fringe fields to thereby make the liquid crystal molecules lean in all different directions and accomplish a wide viewing angle.
FIG. 1
is a cross sectional view of a vertical alignment mode liquid crystal display with electrode opening patterns according to a prior art.
The liquid crystal display includes a bottom insulating substrate
100
and a top insulating substrate
600
.
Gate lines (not shown) are formed on the bottom insulating substrate
100
with gate electrodes in the horizontal direction. Common electrode lines (not shown) are formed on the bottom substrate
100
while proceeding parallel to the gate lines, and storage capacitor electrodes
230
and
240
are connected to the common electrode lines perpendicularly. A gate insulating layer
310
is formed on the entire surface of the bottom substrate
100
with the gate lines and the common electrode lines. Data lines
400
are formed on the gate insulating layer
310
in the vertical direction, and a protective layer
320
covers the data lines
400
. Pixel electrodes
500
are formed on the protective layer
320
with opening patterns
510
.
The outlines of the pixel electrodes
500
are partially overlapped with the storage capacitor electrodes
230
and
240
such that the storage capacitor electrodes
230
and
240
are partially exposed along the periphery of the pixel electrodes
240
when viewed from the top side.
In contrast, the top insulating substrate
600
is sequentially overlaid with a black matrix
700
and a transparent common electrode
800
having opening patterns
810
.
The liquid crystal display further includes several components that are not shown in the drawing for simplification and convenience in description. For instance, thin film transistor components such as source and drain electrodes, and a semiconductor layer are formed on the bottom substrate
100
. Color filters are formed on the top substrate
600
.
However, in the above-structured liquid crystal display, an unintended reverse turn in orienting directions of the liquid crystal molecules may occur at the pixel area, causing T textures in screen images that harm the picture quality.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a liquid crystal display, which bears improved picture quality.
This and other objects may be achieved by a liquid crystal display with a bottom insulating substrate. Common electrode lines are formed on the bottom substrate with branched electrodes. Pixel electrodes are insulated from the common electrode lines with first opening patterns. The pixel electrodes completely cover the branched electrodes of the common electrode lines at particular regions when viewed from the top side.
A top insulating substrate faces the bottom substrate with a common electrode. The common electrode is provided with second opening patterns, and the second opening patterns are overlapped with sides of the pixel electrodes at the particular regions where the pixel electrodes completely cover the branched electrodes of the common electrode lines.
The branched electrodes may be provided at left and right sides of each pixel electrode one by one, and the common electrode lines may be two separate lines.
Each first opening pattern has a horizontal opening portion formed at the boundary of the pixel electrode bisecting it into upper and lower regions, and inclined opening portions are formed at the upper and lower regions of the pixel electrode while proceeding perpendicular to each other. Each second opening pattern has inclined opening portions externally proceeding parallel to the upper and lower inclined opening portions of the pixel electrode, and linear opening portions are bent from the inclined opening portions while being overlapped with the sides of the pixel electrode. The linear opening portions of the second opening pattern are overlapped with the vertical sides of the pixel electrode at the particular regions where the pixel electrode completely covers the branched electrodes of the common electrode lines.
REFERENCES:
patent: 5666179 (1997-09-01), Koma
patent: 6252643 (2001-06-01), Song
patent: 6285431 (2001-09-01), Lyu et al.
patent: 10-288794 (1998-10-01), None
Chowdhury Tarifur R.
McGuireWoods LLP
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