Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
2000-12-15
2004-10-12
Dudek, James A. (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
C349S190000
Reexamination Certificate
active
06803983
ABSTRACT:
This application claims the benefit of Korean Patent Application No. 1999-58746, filed on Dec. 17, 1999, which is hereby incorporated by reference for all purposes as if fully set forth herein.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to liquid crystal displays. More particularly it relates to liquid crystal displays, and its fabricating method, having improved bonding of an upper plate to a lower plate.
2. Discussion of the Related Art
Generally, a liquid crystal display (LCD) controls the light transmissivity of liquid crystal cells arranged in a matrix pattern in response to video signals so as to display a picture that corresponds to the video signals. To this end, the LCD includes a liquid crystal display panel having active matrix liquid crystal cells and driving integrated circuits (IC's) for driving the liquid crystal cells.
The driving IC's are usually manufactured in chip form. They are then mounted on a tape carrier package (TCP) film that is attached to the outer periphery of the liquid crystal panel. The driving chips are then connected to the liquid crystal display by a tape automated bonding (TAB) system of a chips on glass (COG) system. The driving IC's electrically connect to pads along edges of the liquid crystal panel. The pads electrically connect to electrode lines that connect to the liquid crystal cells. Thus, driving signals from the driving IC's are applied to the liquid crystal cells.
FIG. 1
is a plan view showing a conventional liquid crystal display panel. As shown, the liquid crystal panel
2
has a lower plate
4
and an upper plate
6
. Those plates are bonded together in parallel. The liquid crystal panel
2
includes a picture display part
8
having liquid crystal cells that are arranged in a matrix pattern, and gate pads
12
and data pads
14
that connect to the driving IC's (which are not shown). Gate links
34
and data links
16
, respectively, connect the gate pads
12
and the data pads
14
to the picture display part
8
. A seal
10
is provided at the outer circumference of the picture display part
8
. The seal assists the bonding of the lower plate
4
to the upper plate
6
.
In the picture display part
8
, a plurality of data lines
13
receive video signals applied via the data pads
14
and the data links
16
. The data lines are arranged in such a manner as to intersect with a plurality of gate lines
11
. The gate lines
11
receive scanning signals that are input via the gate pads
12
and the gate links
34
. At the intersections are thin film transistors (TFTs) that switch data signals to pixel electrodes so as to drive the liquid crystal cells. The upper plate
6
has red, green and blue color filters formed separately using a black matrix, and a common transparent electrode that is formed on the color filters. The lower plate
4
and the upper plate
6
are separated by a uniform distance using a spacer to provide a cell gap.
The lower plate
4
and the upper plate
6
are bonded together using a sealant that is coated on the seal
10
. The gap between the upper plate
6
and the lower plate
4
is injected-filled with a liquid crystal material and then sealed. The gate pads
12
and the data pads
14
are located along edges of the lower plate
4
that are not overlapped by the upper plate
6
. Each gate pad
12
applies a scanning signal, via a wire within the TCP film, from a gate driving IC, via a gate link
34
, to a gate line
11
of the picture display part
8
. Each of the data pads
14
applies video data signals from a data driving IC, via a data link
16
, to a data line
13
of the picture display part
8
.
In the liquid crystal panel
2
, a protective film that protects the metal electrode lines and the thin film transistors is coated over the lower plate
4
. The pixel electrodes connect, via contact holes, to the thin film transistors. Each pixel electrode is a transparent electrode, beneficially made from indium tin oxide (ITO), which has a relatively strong affinity to the liquid crystal material. Generally, the protective film is an inorganic material, such as SiN
x
or SiO
x
. Since inorganic films usually have high dielectric constants, conventional liquid crystal panels with inorganic protective films have a problem in that coupling between pixel electrodes and data lines
13
caused by a parasitic capacitor is high. To minimize that coupling it is often necessary to widely space the electrodes, for example, by 3 to 5 &mgr;m, such that the pixel electrodes do not overlap the data line
13
. Accordingly, in conventional liquid crystal display panels it is necessary to form narrow pixel electrodes. Thus, an aperture ratio of the liquid crystal cell that depends on the area of the pixel electrode is inevitably lowered. To address this problem, an organic material, such as benzocyclobutene (BCB), spin on glass (SOG) or Acryl, etc., having a relatively low dielectric constant (about 2.7) has been used as the protective film. Such organic protective films can enable an enlarged aperture ratio.
In a high aperture ratio LCD having an organic protective film, the sealant on the seal contacts the organic protective film during the bonding of the upper plate
6
to the lower plate
4
. However, many sealants, such as epoxy resins, have strong adhesion with glass but weak adhesion with respect to organic protective films. For this reason, a high aperture ratio LCD employing an organic protective film has a problem in that an impact can cause a crack between the sealant and the organic protective film that the liquid crystal material can leaked through. Additionally, an organic protective film generally has poor adhesion with the gate insulating film. Such problems are described in more detail with reference to the accompanying drawings.
FIG. 2
is an enlarged plan view of data links
16
crossing the seal
10
in FIG.
1
.
FIG. 2
also shows data pads
14
. A semiconductor layer
18
extends from each data line into a data pad
14
that is located at an end of the data link
16
. As previously discussed the seal
10
is coated with a sealant. That seal is on an organic protective film
24
(see
FIG. 3A
) and crosses the data links
16
. Each data pad
14
contacts a transparent electrode
17
through a contact hole
19
.
FIG. 3A
shows a vertical section of the liquid crystal display panel taken along the A—A′ line in
FIG. 2
, while
FIG. 3B
shows a vertical section of the liquid crystal display panel taken along the B—B′ line in FIG.
2
. In
FIGS. 3A and 3B
, the lower plate
4
has an inorganic gate insulating layer
22
, semiconductor layers
18
, and data links
16
on a lower glass substrate
20
, and an organic protective film
24
that entirely coats the lower plate
4
. The upper plate
6
has a color filter and black matrix
28
on one side of an upper glass substrate
30
and a common transparent electrode
26
. The lower plate
4
and the upper plate
6
are bonded to each other using a sealant coated on the seal
10
. The sealant has poor adhesion to the organic protective film
24
. Also, the organic protective film
24
has poor adhesion with the gate insulating film
22
. Floating of the organic protective film
24
, or leakage of a liquid crystal material
32
, may result from a crack generated from an exterior impact.
FIG. 3B
shows a picture display part
8
that holds the liquid crystal material
32
.
FIG. 4
is an enlarged plan view of
FIG. 1
showing the seal
10
crossing gate links
34
.
FIG. 4
also shows gate pads
12
. The gate pads
12
contact transparent electrodes
17
through contact holes
19
. As previously mentioned the seal
10
coated with a sealant.
FIG. 5A
shows a vertical section of the liquid crystal display panel taken along the A—A′ line in
FIG. 4
, while
FIG. 5B
shows a vertical section of the liquid crystal display panel taken along the B—B′ line in FIG.
4
. In
FIGS. 5A and 5B
, the lower plate
4
has gate links
34
and a gate insulating layer
22
, disposed o
Kwak Dong Yeung
Park Kwang Seop
Dudek James A.
LG.Philips LCD Co. , Ltd.
McKenna Long & Aldridge LLP
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