Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
2002-04-18
2004-05-18
Chowdhury, Tarifur R. (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
Reexamination Certificate
active
06738124
ABSTRACT:
This application claims the benefit of the Korean Application No. P2002-12056 filed on Mar. 7, 2002, which are hereby incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a liquid crystal display, and more particularly, to a method for fabricating a liquid crystal display (LCD) panel by a liquid crystal dropping method.
2. Discussion of the Related Art
A thin flat panel display tends to have a thickness of no more than a few centimeters. Particularly, a liquid crystal display (LCD) has a wide scope of applications, such as notebook computers, computer monitors, gauge monitors for space crafts, and air crafts, and the like.
In general, the LCD is provided with a lower substrate having thin film transistors and pixel electrodes formed thereon, an upper substrate opposite to the lower substrate having a black matrix (BM), a color filter layer, and a common electrode, which are formed thereon, and a liquid crystal layer between the two substrates, for driving the liquid crystal by the electric field generated by the power supply applied to the pixel electrode and the common electrode between the substrates, to regulate the transmittivity of the liquid crystal, thereby displaying a picture on the display screen.
In the foregoing LCD, a vacuum injection method has been used for forming the liquid crystal layer between the lower substrate and the upper substrate. In such a method, after the lower substrate and the upper substrate are bonded together, a liquid crystal is injected between the two substrates by using capillary phenomenon and a pressure difference. However, the vacuum injection method takes much time to inject the liquid crystal between the substrates. As a result, productivity is much reduced as the substrate becomes large.
Consequently, a method called a liquid crystal dropping method is suggested for solving such a problem. A method for fabricating an LCD panel by using a related art liquid crystal dropping method will be explained with reference to the attached drawings.
FIGS. 1A
to
1
E illustrate expanded perspective views showing a method for fabricating an LCD panel by using a related art liquid crystal dropping method. For convenience, only four unit cells are illustrated in the drawings.
Referring to
FIG. 1A
, a lower substrate
1
and an upper substrate
3
are prepared for the process. A plurality of gate lines and data lines (both not shown) are formed on the lower substrate
1
to cross each other defining pixel regions. A thin film transistor is formed at every crossing point of the gate lines and the data lines. A pixel electrode is formed at every pixel region connected to the thin film transistor.
A black matrix is formed on the upper substrate
3
for shielding a light leakage from the gate lines, the data lines, and the thin film transistor regions. A color filter layer of red, green, and blue is formed thereon. A common electrode is formed thereon in this order. An orientation film is formed on both of the lower substrate
1
and the upper substrate
3
for an initial orientation of the liquid crystal.
In
FIG. 1B
, a main sealant
7
and a dummy sealant
8
are coated on the lower substrate
1
, and a plurality of liquid crystal droplets
5
are positioned thereon to form a liquid crystal layer. Then, spacers (not shown) are spread on the upper substrate
3
for maintaining a cell gap.
The main sealant
7
prevents the liquid crystal from leaking, and bonds the upper and lower substrates. The dummy sealant
8
is formed at the dummy region on the outside of the main sealant
7
. The dummy sealant is to protect the main sealant
7
.
In the liquid crystal dropping method, the liquid crystal layer is placed between the attached substrates before hardening a sealant. Accordingly, if a thermo-hardening sealant is used to bond the substrates, it may flow and contaminate the liquid crystal during the heating process. Thus, a UV sealant has to be used as a sealant to avoid such a problem.
Referring to
FIG. 1C
, the lower substrate
1
and the upper substrate
3
are attached to each other. As shown in
FIG. 1D
, a UV ray is irradiated by using a UV irradiating device
9
, to harden the sealant
7
(shown in FIG.
1
B), thereby bonding the lower substrate
1
and the upper substrate
3
.
FIG. 1E
illustrates the bonded substrates
1
and
3
are cut into a plurality of unit cells.
FIG. 2
illustrates a process for cutting the substrates into the unit cells. In
FIG. 2
, a scribing line is formed on the surface of the bonded substrates
1
and
3
using a scriber, such as a diamond pen having a hardness greater than glass, which is a material of the substrates (scribing process). Thereafter, a mechanical impact is given along the scribing line
10
(break process), to cut into a plurality of unit cells. Alternatively, a diamond pen or wheel may be used, to carry out the scribing process and the breaking process in one process, to obtain the unit cell one by one.
FIG. 2
is provided for illustrating the cell cutting process, and the scribing line is not shown in detail. More scribing lines may be formed to remove the dummy region at the outside of the cell in the actual cell cutting process.
FIG. 3
illustrates a plane view of the scribing lines in detail. Particularly, sealants
7
and
8
formed on the lower substrate
1
are illustrated with the scribing lines
10
.
Referring to
FIG. 3
, the scribing line
10
overlaps a portion of the dummy sealant
8
at the region (shown as circles) when the dummy sealant
8
is hardened by the V irradiating process before the cell cutting process.
Consequently, unit cells the hardened dummy sealant
8
does not cause a problem when the scribing and breaking are processed one by one to obtain unit cells. However, when unit cell one by one by the scribing and breaking are processed at the same time, it will be difficult to cut into the unit cell due to the hardened dummy sealant
8
.
SUMMARY OF THE INVENTION
Accordingly, the present invention is directed to a method for fabricating a liquid crystal display panel 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 provide a method for fabricating a liquid crystal display panel, which facilitates an easy cell cutting in the simultaneous scribing and breaking processes.
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 method for fabricating a liquid crystal display panel includes forming a main UV sealant to surround a plurality of unit cells on either one of first and second substrates, the dummy UV sealant being formed at an outside of the main UV sealant, dropping at least one droplet of liquid crystal onto either one of the first and second substrates, attaching the first and second substrates, irradiating a UV ray on the attached substrates with masking regions where the dummy UV sealant and at least one scribing line are crossed, thereby bonding the substrates, and cutting the bonded substrates into a plurality of unit cells.
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: 3978580 (1976-09-01), Leupp et al.
patent: 4094058 (1978-06-01), Yasutake et al.
patent: 4653864 (1987-03-01), Baron et al.
patent: 4691995 (1987-09-01), Yamazaki et al.
patent: 4775225 (1988-10-01), Tsuboyama et al.
patent: 5247377 (1993-09-01), Omeis et al.
patent:
Jung Sung Su
Park Moo Yeol
Chowdhury Tarifur R.
Kim Richard H.
LG. Philips LCD Co. Ltd.
Morgan & Lewis & Bockius, LLP
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