Liquid crystal cells – elements and systems – Nominal manufacturing methods or post manufacturing... – Defect correction or compensation
Reexamination Certificate
2000-09-27
2002-08-27
Dudek, James (Department: 2871)
Liquid crystal cells, elements and systems
Nominal manufacturing methods or post manufacturing...
Defect correction or compensation
C349S153000, C349S155000
Reexamination Certificate
active
06441882
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method for correcting a conduction defect in a liquid crystal display device and a manufacturing method of the liquid crystal display device using the method, particularly to a method of correcting a conduction defect on a conducting part, which is provided between substrates in a liquid crystal panel.
BACKGROUND OF THE INVENTION
A liquid crystal display device according to a direct matrix method (direct matrix liquid crystal display) is provided with a pair of substrates. An electrode pattern composed of transparent electrodes such as an ITO is formed on each of the substrates, and an alignment film made of a material such as polyimide is formed thereon so as to cover the electrode pattern. A pair of the substrates are fixed to each other at the circumference with a sealing material, which is made of a material such as an epoxy resin, while surfaces of the substrates, that have the electrode patterns, are opposed to each other and spacers maintain a predetermined gap therebetween. Further, a liquid crystal material is filled into a gap surrounded by a sealing member at the circumference between the substrates.
In the direct matrix liquid crystal display device with such a construction, voltage is applied between the electrode patterns formed on the substrates so as to generate an electric field in a liquid crystal material at a position (cell) where the electrode patterns are opposed to each other. With this arrangement, a polarizing property of the liquid crystal material is controlled so as to display an image.
In the above direct matrix liquid crystal display device, the ends of the electrode pattern are drawn to the ends of the substrates to connect a driver for applying voltage between the electrode patterns, so as to form a terminal part. In some direct matrix liquid crystal display devices, a terminal part is disposed only on one of the substrates to connect terminals together to the driver. In such a direct matrix liquid crystal display device, conducting members made of carbon paste and silver paste are disposed between the substrates so as to form a conducting part, in order to connect the terminal part and the electrode pattern on the substrate having no terminal part thereon.
Referring to FIGS.
8
(
a
) and
8
(
b
), the following explanation describes the construction of a conducting part according to a conventional art. FIG.
8
(
a
) is a plan view showing the construction of the conducting part in accordance with the conventional direct matrix liquid crystal display device. FIG.
8
(
b
) is a sectional view taken along A—A line shown in FIG.
8
(
a
).
The direct matrix liquid crystal display device has a construction in which a scanning electrode terminal
104
and a scanning electrode
110
are brought into electrical conduction via conducting members
106
. The scanning electrode terminal
104
is formed on a lower substrate
102
and the scanning electrodes
110
are formed on an upper substrate
108
. Further, a large number of the scanning electrodes
110
form an electrode pattern of the upper substrate
108
. Here, the conducting members
106
are patterned and formed according to printing method and so on, and conduction is made between the scanning electrode terminal
104
and the scanning electrodes
110
with a one-to-one correspondence.
Moreover, a sealing member
112
is disposed at the circumference of the upper substrate
108
so as to surround the electrode pattern composed of the scanning electrodes
110
. Besides, liquid crystal material (not shown) is sealed into an area surrounded by the upper substrate
108
, the lower substrate
102
, and the sealing member
112
. Here, an alignment film, data electrodes forming the lower substrate
102
, and a data electrode terminal connected to a data electrode are omitted in FIGS.
8
(
a
) and
8
(
b
).
In the conducting part with such a construction, a conduction defect or a broken wire has hardly occurred between the scanning electrode terminal
104
and the scanning electrodes
110
.
However, in the case of the construction in which the conducting part is formed according to the printing method and so on, it has been difficult to meet the needs for a larger display capacity of a liquid crystal display device and a fine pitch of an electrode pattern.
Thus, a construction has been adopted in which fine conducting members are dispersed into a sealing member so as to form a conducting part. Referring to FIGS.
9
(
a
) and
9
(
b
), the following discusses the above construction. FIG.
9
(
a
) is a plan view showing another construction of the conducting part according to a conventional direct matrix liquid crystal display device. FIG.
9
(
b
) is a sectional view taken along line B—B shown in FIG.
9
(
a
). Those members that have the same functions and are described referring to FIGS.
8
(
a
) and
8
(
b
) are indicated by the same reference numerals and the description thereof is omitted.
In this construction, conducting members
114
are used in place of the conducting members
106
of FIGS.
8
(
a
) and
8
(
b
). Further, the conducting m embers
114
are disposed in the sealing member
112
so as to form a conducting part.
The conducting part is formed as follows: particles serving as the conducting members
114
with conductivity are dispersed into the sealing member
112
, and an upper substrate
108
and a lower substrate
102
are bonded to each other via the sealing member
112
. Here, when bonding the upper substrate
108
and the lower substrate
102
together, a suitable pressure is applied. This arrangement makes it possible to squeeze and remove a material of the sealing member
112
, which is disposed between the conducting members
114
, a scanning electrode terminal
104
, and a scanning electrode
110
. Thus, the conducting members
114
, the scanning electrode terminal
104
, and the scanning electrode
110
directly come into contact with one another so as to secure conduction.
However, when the conducting part of FIGS.
9
(
a
) and
9
(
b
) is formed according to the above method, a material of the sealing member
112
(hereinafter, referred to as an intermediate sealing member) cannot be sufficiently removed in some of a large number of the conducting parts, so that sufficient conduction may not be achieved.
In this case, the conducting part is formed between the scanning electrode terminal
104
and the scanning electrodes
110
. Thus, when a voltage is applied to the scanning electrode terminal
104
, the conducting part with insufficient conduction, i.e., the conducting part with a high electrical resistance (hereinafter, referred to as a defective conducting part) may cause a drop in voltage. Hence, on a liquid crystal display composed of the scanning electrodes
110
connected to the defective conducting part, a displayed image becomes less sharp or a display itself becomes unavailable. Hence, irregularity or a defect occurs on a displayed image, causing deterioration in display quality.
The defective conducting part is formed under the influence of smoothness and flexibility on the upper and lower substrates
108
and
102
(hereinafter, simply referred to as substrates), and irregular pressures for bonding the substrates.
Also, particularly when a polymeric material such as plastic and resin is used for the substrates, the foregoing problem is more likely to occur. The polymeric material is generally smaller than a material such as glass in hardness on a surface (surface hardness), and the polymeric material is inferior in smoothness as well.
When glass, is used for the substrates, a pressure applied for bonding the substrates causes deformation, but the pressure is small on a part of the substrates that opposes the conducting member
114
. Therefore, a pressure is sufficiently applied to the intermediate sealing member so as to completely remove the intermediate sealing member.
Meanwhile, when plastic is used for the substrates, a pressure applied for bonding the substrates results in large deformation on a part of
Conlin David G.
Dike, Bronstein, et al.
Dudek James
IP Practice Group of Edwards & Angell
Sharp Kabushiki Kaisha
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