Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
2003-05-28
2004-11-30
Dudek, James A. (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
Reexamination Certificate
active
06825908
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to apparatus and method of forming a spacer for use in a liquid crystal panel, wherein the spacer is disposed between two substrates that together form the liquid crystal panel and thereby secures a spacing between the substrates.
2. Description of the Related Art
FIG. 13
is a view showing a structure of a liquid crystal panel employed in a display device of a computer or the like.
The liquid crystal panel
201
is formed by placing a lower substrate
203
and an upper substrate
205
to oppose each other, and sealing a liquid crystal material
207
in a space between the substrates
203
and
205
.
The lower substrate
203
has a glass substrate
203
a
, on one surface of which is formed a circuit layer
203
b
including pixel electrodes, thin film transistors (TFTs), MIM forming elements, matrix wiring, etc., and on the other surface of which is formed a phase difference plate
203
c
, with the circuit layer
203
b
being faced toward the upper substrate
205
.
The upper substrate
205
has a glass substrate
205
a
, on one surface of which are formed electrodes, a color filter
205
b
, etc., and on the other surface of which is formed a phase difference plate
205
c
, with the color filter
205
b
being faced toward the lower substrate
203
.
The substrates
203
and
205
are placed to oppose each other with spacers
209
being sandwiched in between, and thereby secure a spacing between the substrates
203
and
205
, into which the liquid crystal material
207
is sealed.
The liquid crystal material
207
is sealed in a space between the substrates
203
and
205
as the periphery thereof is hermetically sealed with a seal
211
.
A polarizing plate
213
is further deposited on the main surface side of the upper substrate
205
.
Also, a polarizing plate
215
, an optical film
217
used to improve a light utilization factor, an optical film
219
functioning as a prism or a lens, and a diffusing plate
221
are sequentially deposited on the back surface side of the lower substrate
203
, and an optical waveguide
223
and a reflecting plate
225
are further deposited on the outside.
In addition, a lamp
227
is placed in close proximity to the optical waveguide
223
so that light is projected onto the optical waveguide
223
.
Incidentally, while the display performance, such as resolution, is being upgraded, a cost reduction of the liquid crystal panel has been pursued by reducing the number of components used, improving the manufacturing method, etc.
For example, in the case of the conventional liquid crystal panel
201
, transparent, cylindrical or granular beads are used as the spacers
209
, and a spacing between the substrates is secured by scattering the beads across the surface of either substrate (or occasionally the both substrates) before the upper and lower substrates
205
and
203
are coupled to each other, so that the beads are sandwiched by a pair of the substrates
203
and
205
.
According to this method, however, only a small number of spacers
209
, which are the beads scattered over protrusions (the pixel electrodes, TFTs, MIM forming elements, matrix wiring, etc, forming the circuit layer
203
b
) on the lower substrate
203
, are brought into contact with the upper substrate
205
. This causes a load to be concentrated on the contact portions of a small number of spacers
209
, which may possibly damage the elements and electrodes.
A countermeasure to avoid concentration of a load on part of the spacers
209
could have been taken by increasing a scattering density of the spacers
209
. However, such a countermeasure scatters a number of spacers
209
on the display portion as well, and raises a new problem that the contrast is deteriorated.
In order to eliminate the foregoing problems, a technique, disclosed in JP-A-3-89320, has been proposed.
According to this technique, spacers are formed by applying a resin material on the surface of a lower substrate
8
composed of, as shown in
FIG. 14A
, a glass substrate
1
on the surface of which gate electrodes
2
, an insulation film
5
, drain electrodes
6
, a passivation film
7
, etc. are formed sequentially from bottom to top.
A more concrete procedure is as follows. That is, as shown in
FIG. 14B
, UV cure resin
9
is applied first across the entire surface of the lower substrate
8
in a predetermined thickness, then UV rays are irradiated to the resin
9
at portions that are not positioned above the pixel electrodes, and resin
9
a
on the irradiated portions is thereby cured, after which resin
9
b
on an uncured portion is removed. The resin
9
a
left in the form of pillars as shown in
FIG. 14C
is thus obtained as spacers.
According to this method, because the spacers are positioned on the outside of the portions above the pixel electrodes, even when the number of spacers are increased, neither the elements nor the electrodes will be damaged by a load acting on the spacers, and deterioration of the contract can be prevented. It is thus possible to obtain a liquid crystal panel with a high display performance.
This method, however, takes a long time in the coating process and the drying process for resin to be made into spacers. Also, another process is generally needed to provide a protection layer on the surface of the applied UV cure resin
9
in preventing deterioration of writing reproducibility resulted from oxygen-induced desentization during the exposure with UV rays, which raises a problem that the productivity becomes poor.
Further, in a case where spacers are formed on the substrate including a black stripe that forms a color filter, there is a possibility that the alignment layer in contact with the UV cure resin is dissolved in a solvent contained in the resin.
In order to eliminate the foregoing problems, a method of forming a spacer for use in a liquid crystal panel, disclosed in JP-A-5-11256, has been proposed.
According to this method of forming a spacer for use in a liquid crystal panel, a photosensitive sheet subjected to development processing is used. The photosensitive sheet is formed by depositing an organic polymer layer used to block oxygen during exposure and a light-cure resin layer that can be developed in a water-based developer on a sheet-like flexible supporting body.
The procedure of forming a spacer is as follows.
Firstly, the oxygen-blocking organic polymer layer and the light-cure resin layer used for development provided on the photosensitive sheet are transferred onto at least one of two substrates that together form a liquid crystal panel.
Then, the light-cure resin layer transferred onto the substrate is subjected to pattern exposure at positions that do not overlap the pixel electrodes on the substrate or at local positions corresponding to the portion above the black stripe forming the color filter. Cured portions that will be used as the spacers are thus obtained.
Subsequently, an unexposed portion on the substrate is removed through development processing, and as a consequence, only the portions of the light-cure resin layer cured through exposure are left on the substrate as the spacers.
According to this method of forming a spacer for use in a liquid crystal panel, as shown in
FIG. 15
for example, in a pixel array on the surface
13
of the substrate used to form the liquid crystal panel, it is possible to form spacers
14
for the sets of pixel electrodes
11
r
,
11
g
, and
11
b
respectively provided with RGB color filters on a one-to-one basis exactly in a narrow region
15
between pixels
11
or at a position on the black stripe. Consequently, concentration of a load on the spacers can be reduced. Also, because exposure is performed while the surface of the substrate is covered with the oxygen-blocking organic polymer layer, oxygen-induced desentization will not occur, which makes it possible to prevent deterioration of writing reproducibility. Further, even in a case where spacers are formed on the substrate having the black stripe, a possibility th
Dudek James A.
Fuji Photo Film Co. , Ltd.
Young & Thompson
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