Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
1999-10-06
2002-08-27
Ton, Toan (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
C349S043000
Reexamination Certificate
active
06441877
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an active matrix type liquid crystal display device and a method of forming the same, and more particularly to the active matrix type liquid crystal display device in construction, and to its electrodes for controlling a liquid crystal of the active matrix type liquid crystal display device.
2. Description of the Related Art
Heretofore, liquid crystal display devices of a so-called “In-Plate Switching (i.e., IPS)” type have been proposed.
FIG. 12
shows a plan view of a conventional liquid crystal display device.
FIG. 13
shows a cross-sectional view of the conventional liquid crystal display device, taken along the line IV—IV of FIG.
12
.
In a conventional liquid crystal display device
100
of the above-mentioned IPS type shown in
FIGS. 12 and 13
, a liquid crystal layer
107
is sandwiched between a pair of transparent glass substrates, which comprise: an opposing-side glass substrate
105
; and, a thin-film-transistor-side (i.e., TFT-side) glass substrate
104
oppositely disposed from the opposing-side glass substrate
105
.
Formed on the TFT-side glass substrate
104
are: a lower layer wiring
101
; a lower layer comb-shaped electrode
110
, wherein both the lower layer wiring
101
and the lower layer comb-shaped electrode
110
are made of non-transparent metals such as Cr, Al, Mo, etc.; an interlayer insulation film
108
; and, a semiconductor layer, wherein both the interlayer insulation film
108
and the semiconductor layer are formed by a plasma enhanced CVD process (hereinafter referred to as the P-CVD process). After that, a semiconductor pattern
102
is formed by a photo resist process (hereinafter referred to as the PR process). Both an upper layer wiring
103
and an upper layer comb-shaped electrode
109
are made of the same material as that of the lower layer wiring
101
. After completion of a channel etching process, a transistor protection film
114
is formed. The transistor is hereinafter referred to as Tr.
On the other hand, in the side on the opposing-side glass substrate
105
, as is clear from
FIG. 13
, a color layer
106
is applied to the opposing-side substrate
105
. Then, acrylic resins are applied to the entire surface of the opposing-side glass substrate
105
to form an overcoat layer
111
, which prevents any substance issued from the color layer
106
from entering and affecting the liquid crystal layer
107
in characteristic. Then, an orientation film
112
is applied to each of the opposing-side substrates
105
and the TFT-side substrate
104
. The thus applied orientation film
112
is then subjected to an orientation treatment, which is followed by formation of the liquid crystal layer
107
of a liquid crystal filled in a panel gap between the TFT-side glass substrate
104
and the opposing-side glass substrate
105
.
In the so-called IPS type of liquid crystal display device having the above construction, an electric field is produced between the upper layer comb-shaped electrode
109
and the lower layer comb-shaped electrode
110
to form a lateral electric field therebetween, wherein: through the thus formed lateral electric field, the liquid crystal is controlled in operation.
In the conventional IPS type liquid crystal display device having the above construction, since its electrode for producing the lateral electric field is not transparent, the display device is poor in light transmission rate. Further, in an area of the conventional display device in which area the opposing-side electrode is brought into contact with the liquid crystal layer, it is not possible to form a transparent electrode made of a transparent metal such as ITO (i.e., Indium Tin Oxide), etc., because it is necessary to prevent the lateral electric field of the liquid crystal layer from being disturbed. Since the metal electrode excellent in barrier properties can't be used as described above, in order to prevent any substance issued from the color layer
106
from entering the liquid crystal layer
107
, it is necessary to apply the overcoat layer
111
to the entire surface of the opposing-side glass substrate
105
.
Further, in the conventional display device, since no conductive element for shielding the electric field (i.e., inner electric field) produced in the liquid crystal layer
107
is formed in the opposing-side glass substrate
105
, it is necessary to shield such inner electric field from any external electric field by means of a suitable shield means such as: a transparent conductive film formed in a rear surface of the substrate so as to prevent the conductive film from affecting the inner electric field; a conductive polarizing plate; or, like elements. As described above, the conventional display device suffers from various disadvantages.
SUMMARY OF THE INVENTION
In view of the above, it is an object of the present invention to provide an active matrix type liquid crystal display device and a method of forming the same, wherein:
electrodes in each of an opposing-side substrate and a TFT-side substrate are made of a transparent metal to improve the display device in light transmission rate; and, the display device may operate in substantially the same manner as that of the so-called IPS type liquid crystal display device.
According to a first aspect of the present invention, there is provided an active matrix type liquid crystal display device having:
a TFT-side substrate;
an opposing-side substrate oppositely disposed from the TFT-side substrate;
a liquid crystal sandwiched between the TFT-side substrate and the opposing-side substrate;
a transparent conductive electrode formed on an opposing surface of the opposing-side substrate, wherein the opposing surface of the opposing-side substrate faces the TFT-side substrate;
a pixel electrode provided with a plurality of pixel electrode portions formed on an opposing surface of the TFT-side substrate, wherein the opposing surface of the TFT-side substrate faces the opposing-side substrate; and
an interlayer insulation film provided with a plurality of slits each aligned in position with each of the pixel electrode portions,
wherein the liquid crystal has a negative dielectric anisotropy.
According to a second aspect of the present invention, there is provided an active matrix type liquid crystal display device having:
a TFT-side substrate;
an opposing-side substrate oppositely disposed from the TFT-side substrate;
a liquid crystal sandwiched between the TFT-side substrate and the opposing-side substrate;
a transparent conductive electrode formed on an opposing surface of the opposing-side substrate, wherein the opposing surface of the opposing-side substrate faces the TFT-side substrate;
a pixel electrode provided with a plurality of pixel electrode portions formed on an opposing surface of the TFT-side substrate, wherein the opposing surface of the TFT-side substrate faces the opposing-side substrate, and the pixel electrode portions each having an electrode width are spaced apart from each other at predetermined electrode spacings; and
an interlayer insulation film provided with a plurality of slits each aligned in position with each of the pixel electrode portions,
wherein the liquid crystal has a negative dielectric anisotropy.
In the active matrix type liquid crystal display device according to the second aspect of the present invention, preferably:
W<d
where W is an electrode width of each of the pixel electrode portions; and, d is a panel gap between the opposing-side substrate and the TFT-side substrate. Further, preferably:
d<S
<3
d
where S is each of the electrode spacings of the pixel electrode portions; and, d is the panel gap between the opposing-side substrate and the TFT-side substrate.
According to a third aspect of the present invention, there is provided an active matrix type liquid crystal display device having:
a TFT-side substrate;
an opposing-side substrate oppositely disposed from the TFT-side substrate;
a liquid crystal sandwiched between the TFT-side
McGinn & Gibb PLLC
Ton Toan
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