Liquid crystal cells – elements and systems – Nominal manufacturing methods or post manufacturing...
Reexamination Certificate
2000-08-22
2003-12-16
Kim, Robert H. (Department: 2871)
Liquid crystal cells, elements and systems
Nominal manufacturing methods or post manufacturing...
C349S190000
Reexamination Certificate
active
06665043
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a bonding method and bonding device of substrates and a manufacturing method of a liquid crystal display device, and more particularly to a bonding method and bonding device for bonding a pair of substrates together by placing the substrates one upon another and sandwiching the substrates between a pair of mutually facing surface plates, and a method of manufacturing a liquid crystal display device by introducing liquid crystals into the space between a pair of substrates after bonding the substrates.
BACKGROUND OF THE INVENTION
Conventionally, a substrate bonding method for bonding a pair of substrates together by placing the substrates one upon another and sandwiching the substrates between a pair of mutually facing surface plates has been used for the manufacture of various products.
For instance, according to a typical manufacturing method of a liquid crystal display device, a wiring layer, pixel electrodes, active elements and color filter are suitably formed on the inner surface of each of two pieces of glass substrates and coated with an alignment film or the like to provide two pieces of composite substrates. Next, these composite substrates are bonded together with a seal material therebetween by sandwiching them between a pair of mutually facing surface plates. Finally, liquid crystals are introduced between the two pieces of composite substrates to provide a liquid crystal display device.
For example, Tokukaihei No. 11-95181 (Japanese laid-open patent publication; published on Apr. 9, 1999) specifically explains a substrate bonding method for use in a manufacturing method of a liquid crystal display device. More specifically, as shown in
FIG. 10
(corresponding to
FIG. 1
of the above publication), in the step of bonding an element substrate
120
and a counter substrate
130
together, the counter substrate
130
is pressed from an upward direction by a bonding head
115
so as to stick to the element substrate
120
with a seal material (not shown) therebetween.
A rigid base plate
113
is positioned under the element substrate
120
, and provided with a recessed section
113
a
formed at the center part thereof. An outer edge of the recessed section
113
a
is located in the vicinity of an outer edge section of a liquid crystal display area A of the element substrate
120
and counter substrate
130
and on a slightly inner side of the formation area of the seal material (not shown) More precisely, the outer edge of the recessed section
113
a
is located slightly outside of the outer edge section of the liquid crystal display area A.
A buffer material
114
is placed on the rigid base plate
113
. The buffer material
114
is provided with a pierced section
114
b
having the same shape as the recessed section
113
a.
The recessed section
113
a
and pierced section
114
b
prevent a portion of the outer surface section of the element substrate
120
, which is slightly larger than the liquid crystal display area A, from coming into contact with the base plate
113
and buffer material
114
. Therefore, even if broken pieces and dusts are present between the element substrate
120
and the base plate
113
, it is possible to prevent the outer surface of the element substrate
120
in the liquid crystal display area A from been scratched.
Besides, there is a method in which a non-contact section is provided by forming a pierced section
117
b
(or recessed section) in the buffer material
117
as shown in
FIG. 11
(corresponding to FIG. 3 of Japanese laid-open patent publication (Tokukaihei) No. 11-95181) instead of forming the recessed section
113
a
in the base plate
113
.
There is another method in which a recessed section
116
b
is formed at the center part of a press section
116
a
of a bonding head
116
as shown in
FIG. 11
so as to prevent the outer surface of the counter substrate
130
in the liquid crystal display area A from being scratched. The outer edge of the recessed section
116
b
is located in the vicinity of the outer edge section of the liquid crystal display area A and on a slightly inner side of the formation area of the seal material (not shown).
However, the above-mentioned substrate bonding methods suffer from the following problems.
First, in either the method using the rigid base plate
113
provided with the recessed section
113
b
as shown in
FIG. 10
(or the base plate
113
provided with the non-contact section) or the method in which the non-contact section is produced by forming the pierced section
114
b
(or recessed section) in the buffer material
114
as shown in
FIG. 11
, since the buffer material
114
positioned between the rigid base plate
113
and the element substrate
120
is not secured to either the base plate
113
or the element substrate
120
, it tends to be displaced. For this reason, displacement often occurs between the base plate
113
and the buffer material
114
and between the buffer material
114
and the element substrate
120
, and thus making it difficult to accurately align the element substrate
120
on the base plate
113
. As a result, the distance (gap) between the substrates
120
and
130
is irregular and the alignment accuracy of the substrates
120
and
130
deteriorates. In actual fact, for such non-uniformity and instability of the distance between the substrates
120
and
130
and deterioration of the alignment accuracy, it is extremely difficult to mass-produce a liquid crystal display device while accurately keeping a slight and uniform distance (a cell gap of around a few &mgr;m) between the substrates
120
and
130
over the entire surface of the substrates
120
and
130
in a stable manner.
Moreover, since the buffer material
114
is formed of a pile of thick paper, it has a low strength and low reliability (durability) fore repeated use. For this reason, when such a buffer material
114
formed of such a pile of thick paper is used repeatedly to bond the substrates for the mass-production of a liquid crystal display device, a problem arises. In actual fact, it is impossible to use this buffer material
114
in this manner. Furthermore, since the buffer material
114
is formed of a pile of thick paper, even if it is made stick to the base plate
113
by vacuum suction, it is difficult to completely secure the buffer material
114
to the base plate
113
, and the buffer material
114
tends to be displaced. This causes non-uniformity of the gap between the substrates
120
and
130
and deterioration of the alignment accuracy of the substrates
120
and
130
.
Additionally, a method using the rigid base plate
113
provided with the recessed section
113
b
as shown in
FIG. 10
(or the base plate
113
provided with the non-contact section) suffers from the following problem. Specifically, whenever the dimensions of a liquid crystal display device to be manufactured are changed, it is necessary to replace not only the buffer material
114
with the one having a pierced section
114
b
corresponding to the changed dimensions of the liquid crystal display device, but also the base plate
113
with the one having a recessed section
113
b
corresponding to the changed dimensions of the liquid crystal display device. For this reason, this method can not readily meet liquid crystal display devices of a variety of dimensions.
Besides, the above-mentioned publication discloses a modified example of the structure shown in
FIG. 11
, in which a buffer material having a recessed section is made stick to a press surface
116
a
of a bonding head
116
having a recessed section
116
b.
However, this publication does not mention sticking the buffer material having a recessed section to a flat press surface
116
a.
Therefore, whenever the dimensions of a liquid crystal display device to be manufactured are changed, it is also necessary to replace the bonding head
116
with the one having a recessed section
116
b
corresponding to the dimensions of the liquid crystal display device. For this reason, this method can no
Fukushima Yuji
Hori Michio
Okuyama Motohiro
Tamura Kazuyuki
Tsuji Masayuki
Conlin David G.
Edwards & Angell LLP
Hazzard Lisa Swiszcz
Kim Robert H.
Nguyen Hoan
LandOfFree
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