Plane switching mode liquid crystal display device

Details Plane switching mode liquid crystal display device Plane switching mode liquid crystal display device

2001-08-27

2004-06-29

Thomas, Tom (Department: 2815)

Liquid crystal cells, elements and systems

Particular structure

Having significant detail of cell structure only

C349S139000, C349S141000

Reexamination Certificate

active

06757042

ABSTRACT:

This application claims the benefit of Korean Patent Application No. 2000-50430 filed on Aug. 29, 2000, which is hereby incorporated by reference as if fully set forth herein.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a liquid crystal display (LCD) device, and more particularly, to an in-plane switching mode LCD device that has a substantially zigzag pattern electrode structure in which high response time is obtained and residual images are prevented from occurring.
2. Discussion of the Related Art
Recently, research into in-plane switching mode LCD devices is being performed to solve the problems of a twisted nematic (TN) mode LCD device having a narrow viewing angle.
Furthermore, research for improving viewing angle and color shift characteristics is being performed by forming an electrode of the in-plane switching mode LCD in a substantially zigzag pattern.
A related art in-plane switching mode LCD device will be described with reference to the accompanying drawings.
FIG. 1
shows a layout of the related art in-plane switching mode LCD device.
FIG. 2
shows an enlarged view of a disclination region in the related art.
FIG. 3
shows an enlarged view of a region where electric field is uneven in the related art.
The related art in-plane switching mode LCD device includes a gate line
1
, a data line
2
, a common line
3
, a thin film transistor (TFT)
6
, a plurality of common electrodes
4
, and a pixel electrode
5
.
The gate and data lines
1
and
2
are arranged on a substrate to define a pixel region. The common line
3
is formed within the pixel region in parallel with the gate line
1
. The TFT
6
is formed in a portion where the gate line
1
crosses the data line
2
. The TFT
6
has a gate electrode (not shown) connected with the gate line
1
and a source electrode connected with the data line
2
. The common electrodes
4
are arranged within the pixel region in a zigzag pattern in parallel with the data line
2
. The pixel electrode
5
is formed between the common electrodes
4
in a zigzag pattern within the pixel region. Also, the pixel electrode
5
is connected with a drain electrode of the TFT
6
and overlaps the common line
3
.
In the related art in-plane switching mode LCD device, if a voltage is applied from an external driving circuit, an electric field parallel to the substrate occurs between the pixel electrode
5
and the common electrode
4
, so that liquid crystal molecules are rotated along the electric field, thereby displaying a picture image.
The related art in-plane switching mode LCD device having a zigzag pattern electrode structure has the following characteristics due to its electrode structure.
FIG. 2
is an enlarged view of a portion “K” of FIG.
1
. In this portion “K”, disclination occurs in which the liquid crystal molecules do not rotate. This is because the electrode structure has a zigzag pattern. As a result, dynamic residual images occur and response time increases.
In portions “A” and “B” of
FIG. 2
, the liquid crystal
7
moves depending on a pretwist angle and a direction of electric field. However, in a portion “C”, where the pixel electrode
5
and the common electrode
4
are bent, the liquid crystal
7
does not move as no pretwist angle exists.
As described above, in case where the electrode structure has a zigzag pattern, the portion of the liquid crystal moves not because of the electric field but in accordance with adjacent liquid crystals.
Particularly, since the liquid crystal
7
in the portions “A” and “B” has a driving direction opposite to that of its adjacent liquid crystal
7
in the portion “C”, the liquid crystal in the portion “C” may not be driven.
Furthermore, as shown in
FIG. 3
, in the in-plane switching mode LCD device having two domains, uneven electric field occurs in a region
8
outside the bend of the common electrode
4
and inside the bend of the pixel electrode
5
.
In other words, the electric field generated to be perpendicular to the common electrode
4
and the pixel electrode
5
has an uneven arrangement in the region
8
and thus is not perpendicular to the common electrode
4
and the pixel electrode
5
. In such case, response time of the liquid crystal molecules is reduced and dynamic residual images occur.
The related art in-plane switching mode LCD device has several problems.
In case where the electrode has a zigzag pattern to improve viewing angle and color shift characteristics, the liquid crystal may be operated not by the electric field but by adjacent liquid crystal molecules. In this case, the electric field may unevenly be arranged. As a result, the response time becomes slower and the dynamic residual images occur, thereby deteriorating characteristic of the liquid crystal panel.
SUMMARY OF THE INVENTION
Accordingly, the present invention is directed to an in-plane switching mode LCD device that substantially obviates one or more problems due to limitations and disadvantages of the related art.
An object of the present invention is to provide an in-plane switching mode LCD device in which a dielectric frame having a smaller dielectric anisotropy than that of a liquid crystal or an electrode frame is formed in a portion where an electrode is bent, so that the liquid crystal is exactly operated, thereby obtaining high response time and preventing residual images from occurring.
Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objectives and other advantages of the invention may be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
To achieve these objects and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, an in-plane switching mode LCD device according to the present invention includes: first and second substrates; common electrodes arranged on one of the first and second substrates in a substantially zigzag pattern wherein each common electrode has at least one bent portion; pixel electrodes arranged with a substantially zigzag pattern corresponding to the common electrodes roughly in parallel with the common electrodes; common electrode frames extending from the bent portion; and a liquid crystal between the first and second substrates.
In another aspect of the present invention, an in-plane switching mode LCD device includes: first and second substrates; common electrodes arranged on one of the first and second substrates in a substantially zigzag pattern; pixel electrodes arranged with a substantially zigzag pattern corresponding to the common electrodes roughly in parallel with the common electrodes wherein each pixel electrode has at least one bent portion; a dielectric frame partially overlapping the bent portion of the pixel electrode and extending from the bent portion, having a gradually decreasing width toward the common electrodes; and a liquid crystal between the first and second substrates.
It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.


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R. Kieler et al.; “In-Plane Switching of Nematic Liquid Crystals”; Japan Di

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