Liquid crystal cells – elements and systems – Particular excitation of liquid crystal – Electrical excitation of liquid crystal
Reexamination Certificate
2002-06-28
2004-08-10
Ton, Toan (Department: 2871)
Liquid crystal cells, elements and systems
Particular excitation of liquid crystal
Electrical excitation of liquid crystal
C349S139000, C349S149000
Reexamination Certificate
active
06774958
ABSTRACT:
This application claims the benefit of Korean Patent Applications P2002-10197 and P2002-13527, which were respectively filed on Feb. 26, 2002 and Mar. 13, 2002, and which are hereby incorporated by reference.
This application incorporates by reference two co-pending applications, Ser. No. 10/184,096, filed on Jun. 28, 2002, entitled “SYSTEM AND METHOD FOR MANUFACTURING LIQUID CRYSTAL DISPLAY DEVICES” and Ser. No. 10,184,088, filed on Jun. 28, 2002, entitled “SYSTEM FOR FABRICATING LIQUID CRYSTAL DISPLAY AND METHOD OF FABRICATING LIQUID CRYSTAL DISPLAY USING THE SAME”, as if fully set forth herein.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to liquid crystal display panels. In particular, the present invention relates methods of fabricating and inspecting such panels.
2. Discussion of the Related Art
Following the expansion of the information society, a need has arisen for displays that produce high quality images in thin, lightweight packages that consume little power. To meet such needs, research has produced a variety of flat panel display devices, including liquid crystal displays (LCD), plasma displays (PDP), electro luminescent displays (ELD), and vacuum fluorescent displays (VFD). Some of these display technologies have already been applied in information displays.
Of the various types of flat panel display devices, the LCD is probably the most widely used. In fact, in portable devices, such as notebook PC computers, LCD technology has already replaced cathode ray tubes (CRT) as the display of choice. Moreover, even in desktop PCs and in TV monitors, LCDs devices are becoming more common.
The basic LCD is comprised of opposing substrates and a liquid crystal material that is disposed between the substrates.
Liquid crystal is a material phase that has properties between liquid and solid. Liquid crystal has the fluidity of a liquid, but has the long-range crystal ordering of a solid. Liquid crystal has optical anisotropy due to its long-range crystal ordering and fluidity.
An LCD is manufactured using a number of processes, including array formation, color filter (CF) formation, liquid crystal filling (disposing), and module forming (described subsequently).
Array formation involves depositions, photolithography, and etching to form a thin film transistor (TFT) array on a first substrate (the TFT substrate). Color filter (CF) formation includes forming red, green, and blue color filters in a black matrix, and forming an ITO (Indium Tin Oxide) film that acts as a common electrode on a CF substrate.
The liquid crystal filling (disposing) process involves assembling the TFT substrate and the CF substrate together. Generally, the TFT and color filter substrates are mated to produce a thin gap between substrates. Then, liquid crystal is filled through a gap opening to form a liquid crystal panel.
In module forming a driving circuit for processing input and output signals is connected to the liquid crystal panel. Additionally, frames are added to complete the liquid crystal module.
LCDs are typically assembled on a production line. In the prior art, cassettes, each having a plurality of TFT substrates or a plurality of color filter substrates, are input to a loader. Each TFT substrate includes a plurality of gate lines that extend in one direction, and a plurality of perpendicularly crossing data lines. Thin film transistors and pixel electrodes are arranged in a matrix at areas between the gate and data lines. The CF substrates each have a black matrix layer, a color filter, and a common electrode. Hence, the black matrix layer shields light leakage except for that desired from the pixel region.
Each TFT substrate or color filter substrate is individually removed from the cassette by the loader and transferred to the input of an alignment layer production line. That line, which includes a hand-programmed robot, forms an alignment layer on the individual substrates, reference alignment process step
1
S of FIG.
1
.
Step
1
S includes cleaning individual substrates to enable formation of a uniform alignment layer coating. Then, an alignment material is coated on the substrate. Then, the alignment material is cured by drying off a solvent in the alignment material, and/or by inducing thermal polymerization of the alignment material. After curing, the alignment material is mechanically rubbed to induce a surface that anchors the liquid crystal in a uniformly align fashion. Finally, a cleaning process is carried out again, resulting in an alignment layer.
After the alignment layer
1
S is completed, several processes are performed to produce a gap. Those processes can be carried out in serial or in parallel. The gap forming processes include a cleaning process (step
2
S) in which a substrate (TFT or color filter substrate) is cleaned and a spacer scattering process (step
3
S) in which spacers are scattered onto that substrate. The spacers are used to maintain the gap thickness constant and uniform.
Instead of forming a gap, a sealant coating process (step
4
S) can be performed on the substrate (one type of substrate [TFT or CF] undergoes gap forming, the other undergoes sealant coating). After a cleaning step
2
S, a sealing material is disposed on a peripheral part of the substrate. The sealing material is subsequently used to attach the TFT substrate to the CF substrate to form an assembled panel. It should be understood that the sealant coating process (
4
S) is performed on one type of substrate (TFT or CF), while spacer scattering is performed on the other type. Thus, as shown in
FIG. 1
, the production line has two sub-portions. One sub-portion cleans (step
2
S) and scatters spacers (step
3
S). The other cleans (step
2
S) and produces a seal (step
4
S).
After the spacer scattering process
3
S and the sealant coating process
4
S, an assembling process (
5
S) that aligns, heats, and presses the TFT substrate and the color filter substrate together to produce an LCD panel is performed. In the assembly process, the TFT substrate and the color filter substrate are arranged in an opposing fashion and then joined to form an LCD panel.
After the assembly process (step
5
S), a cutting process (step
6
S) cuts the assembled empty LCD panel into a plurality of unit panels by scribing and breaking the assembled empty panel.
After the cutting process (step
6
S) is complete, liquid crystal is filled into the unit panels through a liquid crystal filling hole in the sealing material and the filling hole is then sealed (step
7
S).
Finally, after step
7
S, the individual liquid crystal unit panels are ground (to removed cutting burrs), and inspected, reference step
8
S. The liquid crystal cell is then complete.
A typical prior art liquid crystal injection process per step
7
S is schematically illustrated in FIG.
2
. As shown, liquid crystal
25
is put into a vessel
30
. The vessel
30
is inserted in a vacuum chamber
20
. The vacuum chamber
20
is evacuated for a period of time to remove water adhering to an inner wall of the vessel
30
, water in the liquid crystal
25
, and micro bubbles in the liquid crystal
25
.
Still referring to
FIG. 2
, the seal opening of several unit panels
40
are then dipped into the liquid crystal. Inflowing N
2
gas produces atmospheric pressure in the chamber
20
. The pressure difference between the vacuum in the unit panels
40
and the chamber
20
forces liquid crystal into the unit panels.
After the respective unit panels
40
have been charged with liquid crystal
20
, the liquid crystal inlet is sealed. The unit liquid crystal panels are then cleaned. This completes step
7
S.
While beneficial, liquid crystal injection using the foregoing procedures has problems. For example, liquid crystal injection method requires a long time, such as over 10 hours to fill a ten-inch panel. The injection time is so long because the gap thickness between the substrates is very small and the area to be filled is relatively large. This problem is particularly acute when fabricating a large area LCD.
Kim Wan Soo
Kweon Hyug Jin
Son Hae Joon
Duong Tai
LG.Philips LCD Co. , Ltd.
McKenna Long & Aldridge LLP
Ton Toan
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