Liquid crystal display

Details Liquid crystal display Liquid crystal display

1999-07-27

2002-05-28

Parker, Kenneth (Department: 2871)

Liquid crystal cells, elements and systems

Particular structure

Having significant detail of cell structure only

Reexamination Certificate

active

06396556

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a liquid crystal display of a transverse electric field driving type, having an electrode structure for driving an in-plane switching mode cell (hereinafter referred to as “IPS cell”).
This application is based on Japanese Patent Application No. Hei 10-229142, the content of which is incorporated herein by reference.
2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 37 CFR 1.98
FIG.
4
.
FIG. 6
is a cross-sectional view of the electrode structure at section
6
—
6
of FIG.
4
. The term “IPS” or “in-plane switching mode” indicates a mode of driving an active
FIG. 4
is a plan view showing an electrode structure for driving a conventional IPS cell.
FIG. 5
is a cross-sectional view of the electrode structure at section
5
—
5
of matrix display, in which a parallel electrode structure controls an electric field which is parallel to the substrate so as to drive the display. The electrodes which drive the IPS cell are gate electrodes
101
, common electrodes
102
, and comb-tooth-like electrodes
103
, which are formed on a thin film transistor (TFT) glass substrate
100
by the same process. Then, an interlayer isolation film
104
and a semiconductor layer are sequentially formed, and island patterns
105
are formed by a photoresist process. Subsequently, drain lines
106
and upper comb-tooth-like electrodes
107
(which also serve as source electrodes) are formed. Then, a channel etching process and formation of a transistor protection film
108
are performed to complete an electrode substrate for driving an IPS cell.
The background art had the disadvantage in that transmitted light is uneven, since in the space between a lower comb-tooth-like electrode
103
and an upper comb-tooth-like electrode
107
when the display is viewed from the front, through the space light being transmitted, the molecules of the liquid crystal stand up in the vicinity of each comb-tooth-like electrode. That is, if the comb-tooth-like electrodes are disposed as shown in the cross-sectional view in
FIG. 6
, the electric field concentrates at the edges of the electrodes . The electric field is generated such that it is vertical to the substrate at the edges of the electrodes. If the liquid crystal used is of positive permittivity type, the molecules of the liquid crystal stand up at the edges of the electrodes. In this case, since the action of the molecules of the liquid crystal is similar to that in a TN (twisted nematic) mode, a dark image is formed in the vicinity of the edges of the electrodes. Thus, unevenness of transmitted light is caused in which portions in the vicinity of the edges of the electrodes are dark while the middle portions are bright.
Related art is also disclosed in Japanese Unexamined Patent Application, First Publication (Kokai) No. Hei 9-318972, published on Dec. 12, 1997; Japanese Unexamined Patent Application, First Publication (Kokai) No. Hei 9-179096, published on Jul. 11, 1997; Japanese Unexamined Patent Application, First Publication (Kokai) No. Hei 10-3092, published on Jan. 6, 1998; and Japanese Patent (Granted) No. 2701698, published on Oct. 3, 1997.
BRIEF SUMMARY OF THE INVENTION
The present invention was achieved in view of the above circumstances, and thus the object of the present invention is to provide a liquid crystal display with which unevenness of transmitted light can be diminished.
In order to achieve the above object, the present invention provides a liquid crystal display having a parallel electrode structure for driving the display by controlling an electric field which is parallel to a substrate, the liquid crystal display comprising pairs of electrodes, each pair consisting of a common electrode and a pixel electrode which at least partially overlap each other, wherein the pairs of electrodes are disposed at a predetermined interval.
In addition, in the above liquid crystal display, the common electrodes may include lower comb-tooth-ike electrodes, and the pixel electrodes may be upper comb-tooth-like electrodes provided on an interlayer insulation film formed over the lower comb-tooth-like electrodes.
According to this invention, since pairs of electrodes, each pair consists of a common electrode and a pixel electrode overlapping each other by several micrometers, are disposed at a certain interval, the electric fields in the spaces between the electrode pairs when the display is viewed from the front extends in a single direction within a liquid crystal cell, and thereby unevenness of the transmitted light is diminished.
That is, the above constitution provides advantages in that the transmitted light is uniform since no vertical electric field exists in the space between the electrode pairs when the display is viewed from the front, through the space the light being transmitted, and thus unevenness of the transmitted light is diminished.


REFERENCES:
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patent: 11-125836 (1999-05-01), None
patent: 11-153802 (1999-06-01), None

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