Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
2002-11-12
2003-07-15
Ton, Toan (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
C349S122000, C349S043000
Reexamination Certificate
active
06593992
ABSTRACT:
The present invention claims the benefit of Korean Patent Application No. P2001-81871 filed in Korea on Dec. 20, 2001, which is hereby incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a liquid crystal display (LCD) device, and more particularly, and to an LCD device and a method for fabricating the same, in which an adhesive power of upper and lower substrates is improved and a cell gap is uniformly maintained.
2. Discussion of the Prior Art
Generally, an LCD device is commonly used as a substitute for a cathode ray tube (CRT) because of its highs contrast ratio, suitability for displaying gray scales or moving pictures, and low power consumption. The liquid crystal display device for displaying images by external signals includes a thin film transistor (TFT) substrate, a color filter substrate, and a liquid crystal material layer. The TFT substrate has a TFT and a pixel electrode formed in each pixel region defined by gate and data lines. On the color filter substrate, a color filter layer and a common electrode are formed and the liquid crystal material layer is interposed between the two substrates. Presently, a spacer is inserted between the two substrates to leave a uniform space between them, and a sealant is formed along edges of the substrates to completely bond the two substrates together. The sealant prevents the liquid crystal material from flowing outside, and maintains a constant interval between the two substrates along a periphery of an active region.
A method for fabricating an LCD device according to the related art will be described below with reference to the accompanying drawings.
FIG. 1
is a cross sectional view of an LCD device according to the related art.
In
FIG. 1
, an LCD device includes upper and lower substrates
18
and
19
and a liquid crystal material layer
20
formed there between. A black matrix
11
for preventing a light leakage, a color filter
12
for displaying colors, and a common electrode
13
for applying a voltage to the liquid crystal layer
20
are formed on the upper substrate
18
. Gate and data lines (not show) are formed on the lower substrate
19
and cross each other to define a pixel, a TFT
21
is formed at the crossings of the gate and data lines for switching a signal, and a pixel electrode
22
is formed on the liquid crystal material layer
20
forming an electric field by being provided with the signal from the TFT
21
. In addition, an insulating film
27
is formed between the gate and data lines for insulating the gate and data lines from each other and a passivation film
28
is formed between the TFT
21
and the pixel electrode
22
.
At this time, the gate insulting film
27
is deposited by a plasma enhanced chemical vapor deposition (PECVD) method using an inorganic material that closely adheres to the metal, and has an excellent insulating property, such as SiNx or SiOx, BCB or an acryl resin having a low dielectric constant property is used for a material of the passivation film
28
. Additionally, a ball spacer
16
is inserted between the upper and lower substrates
18
and
19
and a seal pattern is formed on along the edges of the substrates for maintaining the interval of the two substrates.
In
FIG. 2
, the seal pattern is divided into an active seal pattern
14
and a dummy seal pattern
15
. The active seal pattern
14
is formed along a circumference of an effective display area
13
, thereby forming a cell gap and preventing a leakage of the liquid crystal material. The dummy seal pattern
15
is formed outside the active seal pattern
14
, thereby absorbing vibrational shock generated during scribing and breaking process. The active and dummy seal patterns
14
and
15
are formed with an equal amount of a spray material, without being formed on an inlet
30
for the liquid crystal material. The active and dummy seal patterns
14
and
15
are formed by a screen printing method or a dispensing method using a thermosetting adhesive with a micro pearl material.
In FIG.
3
. during the screen printing method, a screen mask
51
with a predetermined pattern is placed on the substrate
52
, and a thermosetting adhesive
53
is dropped on the screen mask
51
. Then, the thermosetting adhesive
53
is printed on the substrate
52
by a rubber squeezer. Accordingly, a seal pattern is formed on the substrate
52
as the thermosetting adhesive passes through the inlet of the screen mask
51
.
During the dispensing method, the adhesive material is sprayed by compression of a sprayer filled with a thermosetting adhesive. Accordingly, a predetermined pattern is formed on the substrate to form a seal pattern.
In both methods, it is problematic to control the amount of spray material for forming the seal pattern. In addition, when the liquid crystal material is injected between the substrates, the liquid crystal material may leak through the space between the seal pattern and the passivation film
28
due to a lower adhesive strength of the sealant and organic insulating film.
In
FIGS. 4A and 4B
, a contact hole
29
is formed on the lower part of the active seal pattern
14
. Accordingly, the active seal pattern
14
contacts the gate insulating film
12
, thereby improving the adhesive strength of the sealant and organic irritating film.
In
FIG. 4B
, a step difference (b−a) is generated between the active and dummy seal patterns
14
and
15
. Because of the step difference, intervals between the upper and lower substrates become uneven, and the liquid crystal material may flow outside the substrates since the active seal pattern
14
does not adhere to the upper substrate. Controlling the amount of spraying material can be one way to reduce the step difference between the active and dummy seal patterns
14
and
15
. However, controlling the amount of spray material remains difficult.
SUMMARY OF THE INVENTION
Accordingly, the present invention is directed to a liquid crystal display device and a method for fabricating the same that substantially obviates one or more problems due to limitations and disadvantages of the prior art.
An object of the present invention is to provide an LCD device and a method for fabricating the same, in which a uniform cell gap is maintained and an adhesive strength between upper and lower substrates is improved.
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, a liquid crystal display device, includes a substrate having an active region and a periphery region; an insulating film formed on the substrate; a passivation film formed on the insulating film and having a plurality of first and second contact holes formed along a circumference of the active region; a first seal pattern formed on the passivation film along a direction of the first contact holes; and a second seal pattern formed on the passivation film along a direction of the second contact holes.
In another aspect of the invention, a liquid crystal display device, includes a first substrate having an active region, a gate insulating film, and a plurality of thin film transistors; a second substrate having a color filter layer; a passivation film formed on the gate insulating film and having a plurality of first and second contact holes formed along a circumference of the active region, in which the first contact holes are located to the active region than the second contact holes; an active seal pattern formed on the gate insulating film within the first contact holes and on a prede
Chin Gyo Won
Ryu Ho Jin
Duong Tai
LG.Philips LCD Co. , Ltd.
Morgan & Lewis & Bockius, LLP
Ton Toan
LandOfFree
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