Liquid crystal cells – elements and systems – Particular excitation of liquid crystal – Electrical excitation of liquid crystal
Reexamination Certificate
2001-12-17
2003-05-27
Kim, Robert H. (Department: 2871)
Liquid crystal cells, elements and systems
Particular excitation of liquid crystal
Electrical excitation of liquid crystal
C349S122000
Reexamination Certificate
active
06570631
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a liquid crystal display, and more particularly, to a black matrix in a liquid crystal display and a method of fabricating the same. Although the present invention is suitable for a wide scope of applications, it is particularly suitable for improving an aperture ratio.
2. Discussion of the Related Art
Until recently, a cathode-ray tube (CRT) has been mainly developed and used for display devices. However, flat panel displays draw attention because of their small depth dimensions, desirably low weight, and low voltage power supply requirements. Presently, thin film transistor-liquid crystal displays (TFT-LCDs) with high resolution and small depth dimension have been developed.
FIG. 1
shows a conventional liquid crystal display (LCD).
In
FIG. 1
, the LCD includes upper and lower substrates
5
and
22
. A black matrix
6
, a color filter
7
including sub-color filters (red, green, blue)
8
, and a transparent common electrode
18
disposed above the color filter
7
are formed on the upper substrate
5
. A pixel region “P”, a pixel electrode
17
disposed at the pixel region “P”, and an array line including a switching device “T” are formed on the lower substrate
22
. A liquid crystal layer
14
is interposed between the upper and lower substrates
5
and
22
. The black matrix
6
is formed by deposition and patterning of an opaque metallic material having a low reflectance or by coating and patterning an opaque photosensitive resin.
The lower substrate
22
may also be referred to as an array substrate where thin film transistors “T” are arranged in a matrix configuration, and gate and data lines
13
and
15
that cross the thin film transistors “T” are formed. The pixel region “P” is defined by the gate and data lines
13
and
15
, and a transparent conductive metal such as indium-tin-oxide (ITO) having a relatively high transmittance is used as the pixel electrode
17
on the pixel region “P”.
If a voltage is applied to the common electrode
18
of the upper substrate
5
and the pixel electrode
17
of the lower substrate
22
, a transmittance of the LCD is changed according to the alignment state of the liquid crystal layer
14
so that images can be displayed.
At the lower substrate
22
, the data line
15
and the pixel electrode
17
is spaced apart from each other, thereby eliminating an electric interference. Accordingly, the liquid crystal layer on a separated region
19
between the data line
15
and the pixel electrode
17
has a transmittance different from the liquid crystal layer on the pixel electrode
17
. Accordingly, a light leakage occurs at the separated region
19
. To prevent this phenomenon, the black matrix
6
is disposed at the corresponding region of the upper substrate
5
. In the conventional art, a black matrix is disposed on the upper substrate
5
. Thus, the black matrix is designed to include an alignment margin considering a misalignment in attachment.
However, in the conventional structure of the black matrix, an aperture ratio is reduced due to the alignment margin.
SUMMARY OF THE INVENTION
Accordingly, the present invention is directed to a black matrix in a liquid crystal display and a method of fabricating the same that substantially obviates one or more of problems due to limitations and disadvantages of the related art.
Another object of the present invention is to improve an aperture ratio of an LCD.
Another object of the present invention is to reduce a parasitic capacitance of an LCD.
Additional features and advantages of the invention will be set forth in the description which follows and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will 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 and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, a liquid crystal display includes a substrate, a gate line on the substrate, a gate insulating layer on the gate line, a data line on the gate insulating layer, a thin film transistor having a gate electrode, a source electrode, and a drain electrode, wherein the gate electrode is connected to the gate line and the source electrode is connected to the data line, a first passivation layer having a first contact hole exposing the drain electrode and covering the data line and the thin film transistor, the first passivation layer having a first resistance, an insulating layer having a second resistance lower than the first resistance and covering the data line and the thin film transistor, a second passivation layer having a second contact hole connected to the first contact hole and on the insulating layer and the first passivation layer, and a pixel electrode on the second passivation layer and contacting the drain electrode through the first and second contact holes.
In another aspect of the present invention, a method of fabricating a liquid crystal display includes forming a gate line on a substrate, forming a gate insulating layer on the gate line, forming a data line on the gate insulating layer, forming a thin film transistor having a gate electrode, a source electrode, and a drain electrode, forming a first passivation layer having a first resistance and covering the data line and the thin film transistor, forming an insulating layer having a second resistance lower than the first resistance and covering the data line and the thin film transistor, forming a second passivation layer on the insulating layer and the first passivation layer, forming first and second contact holes in the first and second passivation layers, respectively, the first contact hole exposing the drain electrode and the second contact hole connected to the first contact hole, and forming a pixel electrode contacting the drain electrode through the first and second contact holes.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.
REFERENCES:
patent: 6211928 (2001-04-01), Oh et al.
Duong Thoi V
Kim Robert H.
LG. Philps LCD Co., Ltd.
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