Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
2003-02-24
2004-09-14
Dudek, James A. (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
C349S154000
Reexamination Certificate
active
06791654
ABSTRACT:
The present invention claims the benefit of Korean Patent Application No. 2002-29624, filed in Korea on May 28, 2002, 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, to a seal pattern for a liquid crystal display device and a method for manufacturing a liquid crystal display (LCD) device having an improved seal pattern.
2. Discussion of the Related Art
Liquid crystal display (LCD) devices are image display devices that make use of a property of liquid crystal molecules that align according to an applied voltage. The LCD devices are commonly used in notebook computers, desktop monitors, and digital TV due to their high resolution and ability to display colors and moving images. The LCD devices generally include an upper substrate upon which a color filter is formed, a lower substrate upon which a plurality of thin film transistors are formed, and a liquid crystal layer interposed between the upper and lower substrates. The LCD devices display images by controlling changing orientations of the liquid crystal molecules by applying voltage pulses to pixel and common electrodes.
A manufacturing process of the LCD devices includes a thin film transistor array process for forming the lower substrate, an upper substrate forming process, and a liquid crystal cell process. During the thin film transistor array process, a plurality of gate and data lines is formed on a substrate and a plurality of thin film transistors are formed at crossing portions of the gate and data lines. Then, a pixel electrode is formed in a pixel region of the lower substrate. During the upper substrate forming process, a color filter, a black matrix, and a common electrode are sequentially formed on a substrate. The liquid crystal cell process includes an alignment layer forming process, a rubbing process, a cleaning process subsequent to the rubbing process, an attachment process of the upper and lower substrates, and a liquid crystal material injection process. The aforementioned liquid crystal cell process will be described more in detail hereinafter with reference to FIG.
1
.
FIG. 1
is a flow chart of a process used in manufacturing an LCD device according to the related art. In
FIG. 1
, a first process step (ST
1
) includes forming an array substrate, i.e., a lower substrate. During the first process step ST
1
, a plurality of thin film transistors are formed on the lower substrate and each of the thin film transistors is electrically connected to a pixel electrode.
A second process step (ST
2
) includes forming an alignment layer by forming a thin polymer film on a substrate. Then, subsequent steps include hardening and rubbing the thin polymer film. During the subsequent steps, the thin polymer film must be uniformly formed and the rubbing process must also be performed uniformly on the thin polymer film.
A third process step (ST
3
) includes forming a seal pattern. The formation of the seal pattern includes forming a cell gap to allow for injection of liquid crystal material between the substrates. In addition, the seal pattern prevents the injected liquid crystal material from leaking outside of the seal pattern. The seal pattern is commonly fabricated using screen-printing processes, thermosetting resin, and glass fiber.
A fourth process step (ST
4
) includes dispensing a spacer. The spacer is commonly formed on the array substrate to uniformly maintain the cell gap between the two substrates.
A fifth process step (ST
5
) includes aligning the upper and lower substrates to each other. Then, the upper and lower substrates are attached to each other along the seal pattern.
A sixth process step (ST
6
) includes cutting the attached substrates into unit cells. A single glass substrate commonly includes a plurality of smaller arrays or color filter substrates in cell areas that need to be separated. During past manufacturing processes, liquid crystal material was simultaneously injected into a plurality of liquid crystal cells of a liquid crystal display panel, and the liquid crystal display panel was cut into individual liquid crystal cells. However, as sizes of LCD devices have increased, the liquid crystal display panel has been first cut into individual liquid crystal cells and the liquid crystal material has been injected into each of the individual liquid crystal cells.
A seventh process step (ST
7
) includes injection of liquid crystal material into the individual liquid crystal cells.
FIG. 2A
is a plan view of a seal pattern structure according to the related art. In
FIG. 2A
, a seal pattern
18
is formed between upper and lower substrates
20
and
10
, and liquid crystal material is injected into a liquid crystal cell
1
via an injection hole
16
. Then, the injection hole
16
is sealed with a sealing material
22
after the injection of the liquid crystal material.
FIG. 2B
is an expanded view of area “C” in FIG.
2
A and illustrates a hardening process of sealing material according to the related art. In
FIG. 2B
, the seal pattern
18
includes the injection hole
16
having a tapered width increasing from an exterior to an interior of the liquid crystal cell
1
. If the sealing material
22
is formed in the injection hole
16
and ultraviolet light is irradiated onto the sealing material
22
, a portion “A” of the sealing material
22
is not exposed to the ultraviolet light because of the tapered shape of the injection hole
16
. Thus, the ultraviolet light is diffracted while passing through the injection hole
16
. Accordingly, the portion “A” of the sealing material
22
does not receive adequate amounts of the ultraviolet light and fails to be properly hardened. Conversely, if the ultraviolet light is excessively irradiated in an attempt to harden the portion “A” of the sealing material, the liquid crystal material is adversely affected, thereby decreasing specific resistance of the liquid crystal material.
The effect of not adequately hardening the sealing material
22
is significant in in-plane switching (IPS) mode LCD devices, whereby application of direct current (DC) adversely affects device performance. Accordingly, inadequate hardening of the sealing material
22
decreases production yield and product integrity.
SUMMARY OF THE INVENTION
Accordingly, the present invention is directed to a seal pattern for a liquid crystal display device and method for manufacturing a liquid crystal display device having the same that substantially obviates one or more of problems due to limitations and disadvantages of the related art.
An object of the present invention is to provide a seal pattern structure for a liquid crystal display device to provide for adequate hardening of the seal pattern.
Another object of the present invention is to provide a method for manufacturing a liquid crystal display device having a seal pattern structure to provide for adequate hardening of the seal pattern.
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 device includes a first substrate having a plurality of thin film transistors and first electrodes connected to the thin film transistor, a second substrate having a plurality of color filters and second electrodes, and a seal pattern formed along edges of one of the first and second substrates, the seal pattern having at least one injection hole having a trapezoid shape, wherein a width of the injection hole decreases from a side exterior to the first and second substrates to a side interior to the fi
Dudek James A.
LG Philips LCD. Co., Ltd.
Morgan & Lewis & Bockius, LLP
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