Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
2000-09-19
2002-01-01
Sikes, William L. (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
C349S153000, C349S156000, C349S106000, C349S109000, C349S187000
Reexamination Certificate
active
06335779
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an in-plane switching type liquid crystal display apparatus. More particularly, the present invention relates to an in-plane response type liquid crystal display apparatus which is obtained by adhering two substrates of which at least electrodes on one side thereof are of a comb-like shape on at least one side thereof and enclosing liquid crystal therein, wherein it is arranged such that irregularities in colors can be eliminated and display property improved.
In contrast to twisted nematic display methods wherein an electric field is applied on liquid crystal in a direction vertical with respect to a substrate, developments are being made in these years employing display methods in which an electric field is applied in a direction substantially parallel with respect to a substrate. For instance, Japanese Unexamined Patent Publication No. 225388/1995 discloses an example of a liquid crystal display apparatus employing such a display method in which an electric field is applied in a direction substantially parallel with respect to a substrate, in which it is referred to that the gap between substrates is set to be not more than 6 &mgr;m or that the retardation, which will be described below in details, to be not less than 0.21 &mgr;m and not more than 0.36 &mgr;m in order to improve the response speed.
The inventors of the present invention have defined the above described liquid crystal display apparatus employing a display method in which an electric field is impressed in a direction substantially parallel with respect to a substrate as an in-plane switching liquid crystal display apparatus (hereinafter referred to as “IPS panel”).
FIG. 11
is a partial sectional explanatory view of a conventional in-plane switching type liquid crystal display apparatus. In the drawings, only two pixels have been partially shown for ease of explanation (and this also applies to all drawings hereafter).
FIG. 12
is a plan explanatory view of one pixel in a conventional IPS panel.
FIG. 13
is a sectional explanatory view taken along line X-Y of FIG.
11
. In
FIG. 11
,
FIG. 12
, and
FIG. 13
, numeral
1
denotes a TFT array substrate, numeral
2
pixel electrodes, numeral
3
TFT portions, and numeral
4
a counter substrate. The surface of the TFT array substrate
1
is provided with electrodes which are of comb-like shape. Each of the pixel electrodes
2
is comprised of a comb-like liquid crystal driving electrode
21
and a comb-like common electrode
22
at least a part of which is formed to oppose the liquid crystal driving electrode. TFT portion
3
is a generic term for thin film transistors (hereinafter referred to as “TFT”)
14
for writing image signals to the liquid crystal driving electrodes
21
, and signal cables for supplying image signal cables
12
, scanning signal cables
11
, or common electrodes
22
with signals. The counter substrate
4
is arranged to oppose the TFT array substrate
1
. Materials for forming the pixel electrodes
2
may be any one selected from among chrome, aluminum, indium tin oxide (hereinafter referred to as “ITO”). Numeral
25
denotes an insulating film. The counter substrate
4
is not required to be provided to be with electrodes on the surface thereof in case of IPS panels performing colored display, and is generally provided with a flag portion (not shown) formed of metal or resin and a color filter substrate with coloring layers
18
of red, green and blue. In order to prevent the coloring layers
18
from melting to the exterior, a protecting film
24
is formed on the counter substrate
4
. Numeral
17
denotes electrodes for writing in image signals, scanning signals or common signals from the substrate exterior. Numeral
7
denotes liquid crystal, and the thickness thereof is represented as d. Further, numeral
15
in
FIG. 13
denotes one molecule within the liquid crystal layer. Numeral
9
is a seal member for connecting the TFT array substrate
1
to the opposing substrate
4
, numeral
10
secondary spacers contained in the seal member, and numerals
5
and
6
polarizer. Numeral
23
denotes an alignment layer for aligning the liquid crystal
7
. Further, in
FIG. 13
, I
0
denotes incident light, I outgoing transmitted light, T transmittance axis, D aligning direction, and E electric field.
The basic arrangement of the IPS panel will be explained with reference to FIG.
11
. In the basic arrangement of the IPS panel, the TFT array substrate
1
and counter substrate
4
are opposed in a parallel manner, connected by seal member
9
, and liquid crystal
7
is interposed between the TFT array substrate
1
and the counter substrate
4
. Alignment treatments have been performed for the orientation film
23
(detailed descriptions thereof will be described later). Primary spacers
8
are dispersed within the seal surface for maintaining the gap d between the TFT array substrate
1
and the counter substrate
4
constant, and secondary spacers
10
are disposed by mixing them into the seal member
9
.
While it has been defined in the prior art as disclosed in the above mentioned Japanese Unexamined Patent Publication No. 225388/1995 that the gap between the substrates shall not be more than 6 &mgr;m, there is made neither any reference to secondary spacers
10
as shown in
FIG. 11
which are known in the art by the inventors of the present invention nor to making the gap between the substrates constant. This is considered to be due to the fact that it had not been recognized of the connection of these with improving irregularities in colors of display which is a subject of the present invention as it will be described in details hereafter.
The operational theory of the IPS panel will now be explained with reference to FIG.
13
. As noted in the above explanation of the basic arrangement, the TFT array substrate
1
and counter substrate
4
are opposed in a parallel manner. In case the liquid crystal
7
is liquid crystal of positive anisotropy of dielectric constant, liquid crystal molecules
15
are disposed such that the longitudinal axes thereof are parallel with respect to the substrate surface and such that they are also substantially parallel with respect to the electrodes. For this disposing method, known rubbing methods are generally used, and in case rubbing is performed for the alignment layer
23
in a direction substantially parallel to the electrodes, the liquid crystal molecules
15
assume the above described alignment. In this manner, the polarizer
5
is disposed such that the transmission axis thereof is parallel with respect to the aligning direction, and the polarizer
6
as to be orthogonal to the transmission axis of the polarizer
5
.
In case the electric field is OFF, light that has passed through the polarizer
5
reaches the second polarizer
6
along the alignment of the liquid crystal molecules
15
. Light can not path through since, as noted above, the transmission axis of the polarizer
6
is orthogonal to the transmission axis of the polarizer
5
. In case the electric field is ON, that is, an electric field has been generated in a horizontal direction with respect to the substrate between the liquid crystal driving electrodes
21
and common electrodes
22
which have been formed to as to oppose the former, the longitudinal axis of the liquid crystal molecules rotates in a parallel manner with respect to the substrates along a direction of the electric field which is due to the anisotropy of dielectric constant of the liquid crystal. At this time, the transmitted light changes from a linear polarized light to an elliptical polarization (the elliptical polarization is schematically shown on the counter substrate
4
in
FIG. 13
on the right-hand side thereof due to birefringence effects, and passes through the polarizer
6
.
In this manner, the IPS panel employs the birefringence effect. The birefringence effect is generally called an ECB (electrically controlled birefringence) effect (hereinafter referred to as “IPS mode”). Since the liqu
Fujii Masayuki
Fujita Yasuo
Matsukawa Fumio
Mizunuma Masaya
Morii Yasuhiro
Chowdhury Tarifur R.
Mistubishi Denki Kaubshiki Kaisha
Sikes William L.
LandOfFree
Liquid crystal display apparatus and method for producing... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Liquid crystal display apparatus and method for producing..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Liquid crystal display apparatus and method for producing... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2848403