Electric lamp or space discharge component or device manufacturi – Process – With assembly or disassembly
Reexamination Certificate
2002-05-09
2004-11-02
Patel, Vip (Department: 2879)
Electric lamp or space discharge component or device manufacturi
Process
With assembly or disassembly
C445S025000, C349S189000, C349S190000
Reexamination Certificate
active
06811458
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for manufacturing a Liquid Crystal Display (LCD) and, more particularly to, a method for manufacturing the LCD in which a columnar spacer is provided to maintain a gap to be filled with liquid crystal between a driver element substrate and a facing substrate.
The present application claims priority of Japanese Patent Application No. 2001-140776 filed on May 10, 2001, which is hereby incorporated by reference.
2. Description of the Related Art
A Liquid Crystal Display (LCD) is widely used as a display for use in a variety of information apparatuses or a like The LCD has a basic configuration in that a gap is filled with liquid crystal between a TFT (Thin Film Transistor) substrate (driver element substrate) on which a Thin Film Transistor (TFT) operating as a driver element (switching element) is formed and a CF (Color Filter) substrate (facing substrate) on which a Color Filter (CF) is formed. In this configuration, conventionally, to maintain the gap between the TFT substrate and the CF substrate, a spherical spacers are disposed between these two substrates.
First, as shown in
FIG. 9A
, on either one of the two substrates, shown as an example, a TFT substrate
101
are distributed spherical spacers
102
prepared beforehand that are made of resin or a like and that have a diameter of 4-8 &mgr;m Then, as shown in
FIG. 9B
, a CF substrate
103
is superposed over the TFT substrate
101
in such a manner as to come in contact with the spherical spacers
102
, so that these two substrates are adhered to each other to thereby form a liquid crystal cell. In this case, the TFT substrate
101
and the CF substrate
103
are supposed to have been mounted with necessary components (elements) such as TFTs and CFs (they are not shown in the drawing for simplification) formed thereon already. Then, liquid crystal (not shown) is injected between the TFT substrate
101
and the CF substrate
103
of the liquid crystal cell, to which is then connected a peripheral driver circuit (not shown), thus completing the LCD.
Thus, according to the method for manufacturing the LCD using spherical spacers
102
, as mentioned above, the spherical spacers
102
only need to be distributed on said either one of the two substrates, that is the TET substrate
101
, thus giving a merit of a simplified step of providing the spherical spacers
102
. Oppositely, however, by this method, the spherical spacers
102
are distributed randomly on the TFT substrate
101
, so that they are not uniform in dispersion density (disposition density) and, because of their spherical shape, are liable to roll (move) on the TFT substrate
101
during manufacture, thus giving a problem that they may readily move around to thereby deteriorate a so-called an “on-the-surface uniformity” Also, the spherical spacers
102
are present in some display picture elements, thus inevitably deteriorating contrast of the LCD.
To solve these problems, a recent LCD has, in place of the spherical spacers
102
, columnar spacers disposed between the TFT substrate
101
and the CF substrate
103
. For example, Japanese Patent Application Laid-open No. Hei 11-305239 discloses an LCD (shown in
FIGS. 11A
to
11
B) having such a configuration that columnar spacers
105
are disposed between the TFT substrate
101
and the CF substrate
103
. These columnar spacers
105
are typically formed on the CF substrate
103
by using the same material as the color filter and at the same time as, for example, this color filter is formed
The following will roughly describe a method for manufacturing a conventional LCD employing the columnar spacer
105
with reference to
FIGS. 10A
to
10
D First, as shown in
FIG. 10A
, a photo-resist film
104
mainly made up of an acrylic resin is coated on such a surface of, for example, the CF substrate
103
on which necessary components are formed beforehand as to face the TFT substrate
101
and then exposed, developed, and patterned to form the columnar spacers
105
. The columnar spacers
105
are thus formed as fixed on the CF substrate
103
. The columnar spacers
105
, therefore, do not vary in disposition density like the spherical spacers
102
nor move around on the CF substrate
103
when manufactured, thus avoiding deteriorating the on-the-surface uniformity. Moreover, the columnar spacers
105
can be disposed at an arbitrary position and
50
be adjusted not to be present in a display picture element, thus giving a merit of avoiding deteriorating the contrast.
Next, as shown in
FIG. 10B
, an oriented film
106
made up of, for example, polyimide with a solvent added is formed throughout on the CF substrate
103
by printing. Then, to remove the solvent from the inside of the oriented film
106
, orientation baking processing is performed on the CF substrate
103
Then, a seal
107
made up of, for example, epoxy-resin is formed by printing at a predetermined position of the oriented film
106
. In the side surface of the seal
107
is formed an injection hole
109
for injecting liquid crystal therethrough.,
On the other hand, as shown in
FIG. 10C
, the TFT substrate
101
on which necessary components including TFTs are formed beforehand is superposed over the CF substrate
103
in such a manner as to be in contact with the columnar spacers
105
. In this superposition, the TFT substrate
101
is aligned by, specifically, shifting the TFT substrate
101
laterally with respect to the columnar spacers
105
so as to give a predetermined positional relationship between the TFT substrate
101
and the CF substrate
103
by applying a predetermined superposing load W
1
on the TFT substrate
101
and the CF substrate
103
. Conventional superposition values are roughly the same as those when the spherical spacer
102
is employed, where they are aligned with each other by crushing the seal
107
when applying the superposing load W
1
of 0.3-0.6 kg/cm
2
. Then, seal baking processing is performed by heating the seal
107
to harden the columnar spacers
105
while applying seal baking load W
2
(not shown) or about 0.5 kg/cm
2
, which is roughly the same value as that by use of spherical spacers
102
, across these the TFT substrate
101
and the CF substrate
103
thus superposed one over the other. By doing so, a gap
108
is maintained between the TFT substrate
101
and the CF substrate
103
due to the columnar spacers
105
, thus forming a liquid crystal cell.
Next, as shown in
FIG. 10D
, liquid crystal
110
is injected through the injection hole
109
in the seal
107
to then perform under-pressure hole sealing processing for determining the gap
108
finally. This under-pressure hole sealing is carried out specifically by expelling extra liquid crystal from the inside of the liquid crystal cell and also as applying an under-pressure hole sealing load W
3
of at least about 0.6 kg/cm
2
to make the gap
108
uniform. Subsequently, a peripheral driver circuit (not shown) is connected to the liquid crystal cell, thus completing the LCD.
This conventional method for manufacturing the LCD, however, has a problem that it is difficult to form a stable gap
108
using columnar spacers
105
because these columnar spacers
105
are affected by the heat or the load from the manufacturing process after they are formed.
First, after being formed, the columnar spacers
105
shrink owing to the heat produced by the processing of an orientation baking process, thus being decreased in height. As shown in
FIG. 11A
, when the columnar spacers
105
are formed on the CF substrate
103
and the oriented film
106
is printed throughout the surface and then the orientation baking processing is performed, the resultant heat affects the columnar spacers
105
so that they would be fixed as shrunk as shown in
FIG. 11B
, thus the gap
108
formed between them and the TFT substrate
101
narrowing.
Also, although in the under-pressure hole sealing process to determine the gap
108
finally, in order to make the gap
108
Choate Hall & Stewart
NEC LCD Technologies Ltd.
Patel Vip
Santiago Mariceli
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