Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
2000-09-28
2004-12-14
Chowdhury, Tarifur R. (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
C349S143000
Reexamination Certificate
active
06831723
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
The present invention relates to a liquid-crystal device and electronic equipment incorporating the liquid-crystal device. More particularly, the present invention relates to a liquid-crystal device which prevents scanning electrodes from shorting with each other when the electrodes are produced by partly arranging a narrow portion in the electrode width of an electrode strip serving as a scanning electrode or a data electrode.
2. Description of Related Art
Conventionally, a liquid-crystal device that employs a TFD (Thin Film Diode) device, for example, includes a transparent substrate, namely a so-called array substrate, on which a TFD device and a pixel electrode are formed, and an opposing substrate opposing the transparent substrate.
Polarizers are respectively glued onto the surfaces of the transparent substrate and the opposing substrate, the surfaces being opposite to the opposing surfaces. Alignment layers are formed on the opposing surfaces of the transparent substrate and the opposing substrate. A liquid crystal layer and spacers are arranged between these opposing alignment layers.
FIG. 17
is a plan view showing a major portion of the opposing substrate of the above-referenced liquid-crystal device, and
FIG. 18
is a cross-sectional view of the major portion of the opposing substrate, taken along line XVIII-XVIII′ in FIG.
17
. These figures are intended to explain the construction of the opposing substrate, and dimensions, sizes, and thicknesses of components shown here are different from the dimensional relationship of the actual opposing substrate.
Referring to FIG.
17
and
FIG. 18
, a plurality of color material layers
21
are formed on the opposing substrate
20
, and a matrix of a light-shielding layer
22
, constructed of chromium or the like, is arranged between the color material layers
21
.
Further arranged on the opposing substrate
20
is a protective layer
23
which covers the color material layers
21
and the light-shielding layer
22
, as shown in FIG.
17
and FIG.
18
. The color material layers
21
, the light-shielding layer
22
and the protective layer
23
form a so-called color filter. Referring to
FIG. 18
, the protective layer
23
has a step portion
23
b formed by the color material layer
21
on the outermost outline of an effective region and a light-shielding layer outline portion
22
a
that forms the outermost configuration of the light-shielding layer
22
. The protective layer
23
also has a step portion
23
c
formed by the thickness of the protective layer
23
at a protective layer peripheral portion
23
a
external to the light-shielding layer outline portion
22
a
. The total thickness of the step portion
23
b
and the step portion
23
c
, i.e., the height from the top surface (an unformed region
26
of the protective layer) of the opposing substrate
20
to the top surface of the protective layer
23
in the effective region
27
, is approximately 5 &mgr;m in the typical liquid-crystal devices.
The protective layer
23
has a plurality of elongated rectangular electrode strips
24
formed thereon which function as scanning electrodes or data electrodes.
The electrode strips
24
are formed of a transparent conductive film such as an ITO (Indium Tin Oxide) film, and are formed on the protective layer
23
(a formation region
25
of the protective layer) as shown in FIG.
17
and
FIG. 18
, extending over to the unformed region
26
of the protective layer
23
beyond the protective layer peripheral portion
23
a.
The unformed region
26
of the protective layer represents an area where no protective layer
23
is formed, and specifically indicates a region surrounding the protective layer
23
, where the top surface of the opposing substrate
20
is exposed.
The electrode width of the electrode strip
24
in typically available high-definition liquid-crystal devices is 100 &mgr;m or so, and the spacing between the electrode strips
24
(hereinafter referred to as a wiring gap G) is typically equal to or narrower than 20 &mgr;m. Particularly, high-definition liquid-crystal devices have a wiring gap G of 12 &mgr;m or smaller.
The elongated rectangular electrode strips
24
, constructed of ITO, are manufactured through a so-called photolithographic process. Specifically, the electrode strips are produced through the following manufacturing steps, including the formation of an ITO layer on the protective layer
23
and the opposing substrate
20
through sputtering or the like, the formation of a positive resist layer on the ITO layer, the patterning of the positive resist through exposure and development, and the etching of the ITO using the patterned resist as a mask.
SUMMARY OF THE INVENTION
Since the wiring gap G is extremely narrow, compared to the electrode width of the electrode strip
24
, and is subject to variations, the wiring gap G is visually checked using a microscope or the like after the formation of the electrode strips
24
.
Since the variations in the wiring gap G become a cause of the position shift of the electrode strips
24
relative to a pixel electrode arranged on the transparent substrate, it is considered the most preferable to inspect the wiring gap G in the formation region
25
of the protective layer
23
.
Since a high-reflectance light-shielding layer
22
is present beneath the transparent electrode strip
24
in the formation region
25
of the protective layer
23
, particularly in the effective region
27
, light rays reflected from the light-shielding layer
22
make it difficult to visually recognize the electrode strip
24
and inspect the wiring gap G in the formation region
25
of the protective layer
23
. The inspection of the wiring gap G is normally performed outside the effective region
27
, based on the fact that the electrode strips
24
have a constant electrode width in the longitudinal direction thereof.
In the formation step of the above-referenced electrode strips
24
, the thickness of a positive resist stacked onto the ITO layer becomes occasionally thicker than a rated thickness in the area of the step portions
23
b
and
23
c
. Exposure tends to be insufficient in an area where the thickness of the positive resist is thicker than the rated value, and part of the positive resist is left in the area of the step portions
23
b
and
23
c
after development. As shown in
FIG. 17
, the presence of a resist residue is a cause of the generation of a burr
24
x
of the electrode strip
24
and the generation of a bridge
24
y
that causes a shorting between adjacent electrode strips
24
, thereby becoming a remote cause of a drop in the yield of the liquid-crystal device.
The generation of the burr
24
x
and the bridge
24
y
makes the electrode width of the electrode strips
24
inconstant in the longitudinal direction thereof, the inspection of the wiring gap G outside the effective region
27
becomes meaningless, and an increase in the yield of the liquid-crystal device is difficult.
Short-circuiting between adjacent electrode strips
24
frequently occurs in a high-definition liquid-crystal device having a smaller wiring gap, thereby lowering the yield of the high-definition liquid-crystal device.
The present invention has been developed in view of at least the above problem, and it is an object of the present invention to provide a liquid-crystal device which at least is free from short-circuiting between adjacent electrodes, presents a high yield in manufacturing process, and facilitates the measurement of a wiring gap.
A liquid-crystal device of one exemplary embodiment of the present invention includes a plurality of color material layers arranged on a substrate, a light-shielding layer surrounding each color material layer, a protective layer covering the color material layers and the light-shielding layer, and a plurality of electrode strips arranged on the protective layer and extending from a formation region of the protective layer to an unformed region of the protective layer. The electrode widt
Chowdhury Tarifur R.
Di Grazio Jeanne Andrea
Oliff & Berridg,e PLC
Seiko Epson Corporation
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