Liquid crystal cells – elements and systems – Nominal manufacturing methods or post manufacturing... – Sealing of liquid crystal
Reexamination Certificate
2000-12-14
2003-06-03
Sikes, William L. (Department: 2871)
Liquid crystal cells, elements and systems
Nominal manufacturing methods or post manufacturing...
Sealing of liquid crystal
C349S153000, C349S154000
Reexamination Certificate
active
06573972
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a Liquid-Crystal Display (LCD) panel and a method of fabricating the same and more particularly, to a LCD panel that provides a substantially uniform cell gap between opposing substrates and that displays images with excellent quality over the whole display area, and a method of fabricating the panel.
2. Description of the Prior Art
A LCD panel generally has a configuration including a pair of transparent, opposed substrates (e.g., glass substrates) fixed at a specific gap, a frame-shaped sealing member located between the substrates to couple the substrates with each other so as to form an inner space therebetween, spacer particles dispersed in the space to keep the gap, and a liquid crystal filled in the space.
With the LCD panels of the active-matrix addressing type, typically, Thin-Film Transistors (TFTs) are formed on one of the pair of substrates and a color filter is formed on the other. Usually, the substrate with TFTS is termed the “TFT array substrate” while the substrate with a color filter is termed the “color filter substrate”.
Conventionally, to fill the inner space between the substrates with liquid crystal, the “substrate dipping process” and the “liquid crystal dispensing process” have been developed and used practically. The substrate dipping process was developed in early days and has ever been used in practice and thus, the technique for performing the substrate dipping process has been diversified On the other hand, the liquid crystal dispensing process was developed in recent years and has been getting popular. However, the technique for performing the liquid crystal dispensing process has not been diversified compared with the substrate dipping process. Thus, there is the demand to grow or expand this technique.
With both the first and second methods of fabricating the LCD panel using the substrate dipping process and the liquid crystal dispensing process, the same process steps are carried out in their early stages. For example, in the patterning process, necessary parts or elements (e.g., dielectric layers, transparent electrodes, switching elements or devices, and color filter layers) are formed on the respective substrates. In the rubbing process subsequent to the patterning process, alignment layers (e.g., polyimide layers) are formed by printing on the inner surfaces of the substrates and then, the layers are rubbed to form grooves extending in the same direction or different directions for orientating the liquid crystal molecules toward a specific direction or directions. The following process steps are different in the fabrication methods using the dipping and dispensing methods.
FIGS.
1
and
FIGS. 2A
to
2
C show the LCD panel fabrication method using the substrate dipping process, which may be termed the first prior-art method later.
After the rubbing process C
1
as explained above, the sealing member formation process C
2
is carried out. In this process C
2
, as shown in
FIG. 2A
, two frame-shaped sealing members
132
are formed on the inner surface of a lower transparent substrate
131
at a specific distance. Each of the members
132
is used for the LCD panel. The member
132
is continuously written to draw a rectangular frame on the substrate
131
by dispensing a material for the sealing member
132
from the nozzle of a known dispenser. A proper epoxy-system thermosetting resin is used for the member
132
. Needless to say, the member
132
may be formed by the known screen printing method.
As shown in
FIG. 2A
, the frame-shaped sealing member
132
has a pattern of an approximately rectangular closed curve with an opening
133
. The member
132
is formed to surround the display area
114
, in other words, the member
132
extends around the periphery of the area
114
. The opening
133
is used as an inlet through which liquid crystal is injected into the inside of the member
132
.
After the sealing member formation process C
2
, the substrate coupling process C
3
is carried out In this process, another transparent substrate (not shown, an upper transparent substrate), is overlaid the lower substrate
131
so as to overlap entirely with each other, forming a substrate assembly. At this time, each cell on the lower substrate
131
is opposed to the corresponding cell on the upper substrate.
Thereafter, a pressure is applied to the substrate assembly with a pressing plate, setting the gap between the lower and upper substrates at a desired value.
If spacer particles are used for keeping the gap between the substrates, they are spayed or arranged on the inner surface of the lower substrate
131
in the display area
114
surrounded by the sealing member
132
prior to the substrate coupling process C
3
.
Subsequent to the substrate coupling process C
3
, the sealing member curing process C
4
is carried out. In this process, the sealing member
132
is cured with the heater provided on the pressing plate. This process C
4
may be carried out by placing the substrate pair in an oven and by heating the atmosphere in the oven up to a specific temperature.
Thereafter, the substrate cutting process C
5
is carried out. In this process, the substrate pair or substrate assembly is cut to divide it into LCD panel assemblies
100
. The cutting operation of the substrate pair is performed along the cutting line that surrounds each sealing member
132
, forming a rectangular-ring-shaped specific area outside the display area
114
in each panel assembly
100
. The assembly
100
thus divided is shown in FIG.
2
B.
In the method explained here, two panel assemblies
100
are produced from the substrate pair. The way to form a plurality of panel areas in the same substrate pair like this has been extensively performed in practice, because it is advantageous to raising the productivity.
Typically, the position of the cutting line is set in such a way that the cutting line involves a necessary module or unit including the driver circuit which will be provided on the lower substrate
131
outside the sealing member
132
in a subsequent process.
After the substrate cutting process C
5
, the liquid crystal injecting process C
6
is performed, which utilizes typically a vacuum atmosphere. In this case, the panel assembly
100
is placed in a vacuum chamber of a specific vacuum apparatus at an atmospheric pressure. Next, the air in the chamber is evacuated and then, the assembly
100
is dipped into a liquid crystal stored in the container so that the inlet
133
of the assembly
100
is immersed in the crystal. Thereafter, the pressure in the chamber is raised gradually toward the atmospheric pressure, thereby injecting the crystal into the inner space of the assembly
100
due to the pressure difference between the inner space and the outside.
In the process C
6
utilizing a vacuum atmosphere, the liquid crystal can be injected into the space of the panel assembly
100
until the pressure difference between the inner space and the outside is equal to zero. Typically, it takes about 10 hours to fill the inner space of the assembly
10
with the liquid crystal.
Subsequent to the liquid crystal injecting process C
6
, the inlet closing or blocking process C
7
is performed. In this process, as shown in
FIG. 2C
, a thermosetting blocking material
134
(e.g., thermosetting epoxy resin) is attached to the inlet
133
ant then, the material
134
is heated to be cured. Thus, the inlet
133
is blocked by the material
134
. At this time, a proper pressure may be applied to the panel assembly
100
under control to generate a force drawing the material
134
into the space. This is to ensure the blocking of the inlet
133
by the material
134
.
The liquid crystal thus injected into the inner space and filling the same forms a liquid crystal layer
115
between the two substrates.
In the polarizer plate attaching process C
8
, a polarizer plate (not shown) is attached to the outer surface of each of the lower and upper substrate. The polarizer plate is provided to
Akkapeddi P. R.
McGinn & Gibb PLLC
NEC Corporation
Sikes William L.
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