Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
2000-12-26
2004-05-18
Nguyen, Dung (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
C349S155000, C349S158000, C349S187000
Reexamination Certificate
active
06738125
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a liquid crystal display apparatus, and also to a method for manufacturing the same.
2. Description of the Related Art
A liquid crystal display apparatus has a pair of substrates which are opposed to each other. A cell gap is maintained to a constant value by spacers, and a liquid crystal is filled between the substrates.
FIG. 7
is a section view showing the configuration of a liquid crystal display apparatus
220
of the conventional art. The liquid crystal display apparatus
220
has a color filter side substrate
225
and a TFT (Thin Film Transistor) side substrate
226
.
In the color filter side substrate
225
, a color filter
202
, black masks
204
, an counter electrode which is not shown, and the like are arranged on a transparent substrate
208
which is made of glass or the like, and the surface is covered with an orientation film
215
. In the TFT side substrate
226
, liquid crystal driving elements such as TFT elements, wiring portions
203
, an insulating film
207
, pixel electrodes which are not shown, and the like are arranged on a transparent substrate
209
, and the surface is covered with an orientation film
216
.
The liquid crystal display apparatus
220
is produced in the following manner. For example, the color filter side substrate
225
and the TFT side substrate
226
are bonded together to form an empty cell, via dispersed spacers
201
for maintaining the cell gap, and a liquid crystal sealing material
214
into which a spacer
213
for maintaining the cell gap in the periphery of the liquid crystal display apparatus
220
is mixed. A liquid crystal
217
is filled into the empty cell. Then, the filling port is sealed by a sealing agent such as a resin.
The cell gap means the gap G between the color filter side substrate
225
and the TFT side substrate
226
in a pixel region where the pixel electrodes are opposed to the counter electrode, and is determined mainly depending on the diameters of the dispersed spacers
201
, and the spacer
213
in the sealing material
214
, and the filling and sealing conditions of the liquid crystal
217
. The uniformity of the cell gap is closely related to the display quality of the liquid crystal display apparatus
220
. When the uniformity of the cell gap is low, there arises problems such as that display unevenness such as brightness unevenness or color unevenness is caused in the display screen.
In a rectangular display region
240
of the liquid crystal display apparatus
220
, a large number of pixels in which the respective pixel electrodes are opposed to the counter electrode, and the color filters
202
are formed correspondingly with the pixels. In the display region, in order to prevent light from leaking from adjacent pixels, the black mask
204
which surrounds the color filters
202
of the pixels is formed as required into a lattice-like shape extending over the whole of the display region
240
. In a picture frame region
241
surrounding the display region, a frame-like black mask
210
is formed.
The black mask
204
,
210
is made of a resin in the same manner as the color filters
202
. In order to attain sufficient light shielding properties, therefore, the black masks must be formed so as to be thick. Consequently, a film thickness of the black mask
204
,
210
is thicker than that of the color filters
202
. As a result, protrusions
205
and
212
are formed in the surface of the orientation film
215
of the color filter side substrate
225
.
In the liquid crystal display apparatus
220
, the protrusions
205
and
212
are formed by the black masks
204
and
210
in the surface of the color filter side substrate
225
which faces the liquid crystal
217
. For example, protrusions caused by the wiring portions
203
, the liquid crystal driving elements, and the like may be sometimes formed in the surface of the TFT side substrate
226
, so that convex and concave portions are formed in the surfaces of the substrates
225
and
226
which face the liquid crystal.
FIG. 7
shows a state in which a uniform cell gap is formed while the dispersed spacers
201
are not placed on the protrusions
205
and
212
formed by the black masks
204
and
210
. However, the dispersed spacers
201
are indefinitely placed because the dispersed spacers are randomly dispersed on the color filter side substrate
225
or the TFT side substrate
226
.
FIG. 8
is a section view schematically showing a state where a dispersed spacer
206
is placed on a protrusion
205
of the display region. Since the dispersed spacer
206
is placed on the protrusion
205
formed by the black mask
204
of the color filter side substrate
225
, the cell gap which is defined by the dispersed spacer
206
placed on the protrusion
205
is larger than that which is defined by the other dispersed spacers
201
placed on the flat portion, by the dimension equal to the height of the protrusion
205
. This difference in the substrate gap causes an uneven cell gap, whereby display unevenness such as brightness unevenness or color unevenness is caused in the display screen.
FIG. 9
is a section view schematically showing a state where a dispersed spacer
211
is placed on the protrusion
212
of the picture frame region
241
. In the display region
240
, most of area excluding the liquid crystal driving elements and the wiring portions
203
is formed by transparent thin films through which pixel electrode light can be transmitted. By contrast, in the picture frame region
241
surrounding the display region
240
, the frame-like black mask
210
is formed in order to prevent light from leaking from the region. In this way, the display region
240
and the picture frame region
241
are different from each other in film structure.
The film thickness of the black mask
210
is thicker than that of the color filters
202
. This causes a step to be formed between the display region
240
and the picture frame region
241
, and the protrusion
212
to be formed on the face of the orientation film
215
of the color filter side substrate
225
in the picture frame region
241
. Therefore, the cell gap which is defined by the dispersed spacers
211
placed on the protrusion
212
of the picture frame region is larger than that which is defined by the spacer
213
in the sealing material
214
, and the dispersed spacers
211
push up the cell gap in the periphery of the display region. As a result, an uneven cell gap is formed, and display unevenness such as brightness unevenness or color unevenness is caused in the display screen in the vicinities of the dispersed spacers
211
.
In some of conventional art techniques for spacers of a liquid crystal display apparatus, the cell gap in the peripheral portion is adjusted by changing the diameter of the spacer
213
in the sealing material
214
. In the case where the dispersed spacers
211
are placed on the protrusion
212
due to, for example, the black mask
210
in the picture frame region
241
, however, the dispersed spacers
211
affect the value of the cell gap more dominantly than the spacer
213
in the sealing material
214
as shown in FIG.
9
. Even when the diameter of the spacer
213
in the sealing material
214
is changed, therefore, unevenness of the cell gap caused by the dispersed spacers
211
placed in the picture frame region
241
cannot be prevented.
By contrast, in another conventional art technique, it is intended to overcome the problem of an uneven cell gap by reducing the thickness of a film forming protrusions, such as a black mask. However, such a technique has a problem in that the thickness of a film forming protrusions cannot be reduced because of a technical reason such as a method for manufacturing the film forming protrusions, or a reason in display quality such as that sufficient light shielding properties cannot be obtained in the case of a reduced film thickness.
In a further conventional art technique, a method is employed in which a liquid acrylic resin or t
Araki Hiroyuki
Nakagawa Okifumi
Nakamura Ichiro
Nishimura Eiichiro
Toriumi Kohichi
Nguyen Dung
Nixon & Vanderhye P.C.
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