Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
1998-05-20
2001-08-28
Malinowski, Walter J. (Department: 2164)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
Reexamination Certificate
active
06281955
ABSTRACT:
BACKGROUND OF THE INVENTION
FIELD OF THE INVENTION
This invention relates to a liquid crystal display device and a method of making the same and, more particularly, to a liquid crystal display device with excellent quality pictures in which color filters are provided on a switching element array substrate and a method of making the same with high productivity.
FIG. 5
is a cross sectional view of a conventional active-matrix type liquid crystal display device. The liquid crystal display device
100
consists primarily of an array substrate
110
on which switching elements, such as thin film transistors (TFTs) are disposed in a matrix form, a counter substrate
150
provided opposite to the array substrate
110
and a liquid crystal layer
170
held between the substrates
110
and
150
.
Gate electrodes
116
of the TFTs are disposed on a glass plate substrate
111
and a gate isolation layer
112
is coated on the gate electrodes
116
. The TFT
114
includes the gate electrode
116
, an insulation layer
112
, a semiconductor layer
115
made of amorphous silicon, for instance, and source and drain electrodes
120
and
118
. The drain electrode
118
is connected to a signal line. The source electrode
120
is also connected to a transparent pixel electrode
130
covering an organic isolation film
124
and extending along an aperture
126
defined in the isolation film
124
.
The counter substrate
150
includes a transparent substrate
152
, a color filter layer consisting of a light blocking layer
154
and filter elements
156
disposed on the substrate
152
, and a transparent common electrode
158
covering the color filter layer. The common electrode
158
may be made of Indium Tin Oxide (ITO), for instance. Further, an alignment layer (not shown in
FIG. 5
) is coated on the inner surface of the common electrode
158
.
The liquid crystal display device shown in
FIG. 5
is apt to be faced with such technical problems that electrical coupling between the pixel electrode
130
and the signal and gate lines
118
and
116
increases coupling capacitance and brings about crosstalk between pixels. In addition, since an exact position alignment must be made between each filter element
156
of the counter substrate
150
and every pixel aperture of the array substrate
110
, assembling processes therefor are complicated.
In order to solve them, the structure may be modified to form the color filters on the array substrate. The organic isolation layer
124
, for instance, is also used for the color filters.
In the case of the modified structure, however, the isolation layer
124
necessarily contains three-color (red, green and blue) filter elements. Thus, stripe-like patterning, for instance, is applied to make the color filters so that each pixel electrode may correspond to a filter element. The color filters are formed by processing one filter element to another in the following way, i.e., coating a filter layer material on the array substrate, and exposing and patterning it.
Where apertures are further made to connect the switching elements to the pixel electrodes at the same time of such patterning process for each filter element, the second and third filter layers are quite easy to peel off the array substrate at the end thereof.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a liquid crystal display device which structure can effectively prevent filter elements from peeling of f a switching element array substrate, display excellent quality images, and have a high production yield, and a method of making the same.
A liquid crystal display device of the present invention includes an array substrate made of a substrate and switching elements disposed on the substrate in a matrix form, a transparent counter substrate provided opposite to the array substrate with a transparent counter electrode, and a liquid crystal layer held between the array and counter substrates. The array substrate is composed of a plurality of filter elements disposed on the substrate with a predetermined pattern. The filter elements form color filter layers, at the edges of which two adjacent layers are overlapped with each other. Each filter element is covered with a pixel electrode and is provided with an aperture to connect the pixel electrode to the switching element. The overlapping portions are designed to prevent the filter element from peeling off during the manufacturing processes of the liquid crystal display device.
The color filter layer consists of at least three kinds of filter elements which have different spectral characteristics from each other. The filter elements with the same spectral characteristics are concurrently formed through the same process. The overlapping portions are designed to be wider in width as the filter elements are formed later in order to prevent the later formed elements from peeling off.
The peeling-off of the filter elements is effectively avoided if the diameter TH (&mgr;m) of the aperture and the width (&mgr;m) of the overlapping portions are satisfied with the following:
TH<5 &mgr;m, OL≧1.5 &mgr;m
5 &mgr;m≦TH≦10 &mgr;m, OL≧1.0 &mgr;m, and
10 &mgr;m<TH, OL≧0.5 &mgr;m.
The overlapping portions are also effectively kept from peeling off if the thickness T(&mgr;m) of the filter element and the minimum distance L(&mgr;m) between the end of the filter element and the aperture are satisfied with the following:
L≧2×(T/1.5)
2 +
2
Further, where the filter elements are made of photosensitive materials, the forming processes are simplified.
Since the liquid crystal display device of the present invention is provided with the color filters formed on the array substrate and the overlapping portions at the boundary of the color filters, the electrical coupling with the pixel electrode is substantially reduced, the display device shows high quality color images, assembling troubles seldom occur, and high production yields can be obtained.
The inventors of this application have carried out experiments and eventually discovered conditions with respect to the overlapping layer width and other related configurations to gain remarkable effects.
The above-stated and other objects and technical features of the present invention will become apparent from the following description when taken with the accompanying drawings. It will be understood, however, that the drawings are for purposes of illustration and are not to be construed as defining the scope of the invention, reference being had for the latter purpose to the claims appended hereto.
REFERENCES:
patent: 5499128 (1996-03-01), Hasegawa et al.
patent: 5568293 (1996-10-01), Takao et al.
patent: 5994721 (1999-11-01), Zhong et al.
patent: 2-54217 (1990-02-01), None
Akiyoshi Muneharu
Hatoh Hitoshi
Kurosaki Minako
Manabe Masumi
Midorikawa Teruyuki
Kabushiki Kaisha Toshiba
Malinowski Walter J.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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