Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
2003-01-09
2004-05-11
Chowdhury, Tarifur R. (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
C349S156000, C349S157000, C349S189000, C349S190000
Reexamination Certificate
active
06734943
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a liquid crystal display (LCD) panel and a manufacturing method thereof, and more particularly, to sealing structures suited for a process of liquid crystal dispenser method.
2. Description of the Related Art
A typical liquid crystal display (LCD) panel has a front substrate and a rear substrate with a liquid crystal interposed therebetween. More specifically, the front substrate is provided with a common electrode and a color filter, while the rear substrate is provided with an array of pixel electrodes connected to switching elements such as thin film transistors (TFTs).
FIG. 1
shows a first structural example of a liquid crystal display (LCD) panel according to the prior art. The LCD panel includes a rear substrate
101
with an array of pixel electrodes
11
, a front substrate
201
with a color filter
12
, a pair of alignment layers
4
, a liquid crystal material
5
, a spacer
6
, and a sealing material
7
.
The rear substrate
101
is a glass substrate provided with transparent pixel electrodes and an alignment layer
4
. The front substrate
201
is a glass substrate provided with color filters
12
(R,G,B) and an alignment layer
4
. The alignment layers
4
are provided for aligning molecules of the liquid crystal material
5
in a predetermined direction when an electric field is not applied to the molecules of the liquid crystal material
5
.
The liquid crystal material
5
can be modulated by applying an electric field thereto when the driving voltage is applied between the pixel electrodes and a common electrode (not shown). The spacer
6
is arranged for keeping a cell gap between the rear substrate
101
and the front substrate
201
at a predetermined distance. The sealing material
7
is a material for sealing the liquid crystal material
5
within a display region (in this case, the display region is defined as a region covering all the pixel electrodes).
FIG. 2A
is a plan view showing a bonding surface of the rear substrate at which surface the rear substrate and the front substrate, those substrates constituting the LCD panel of the first structure in the prior art, are bonded to each other.
FIG. 2B
is a cross-sectional view taken along a line X-X′ shown in FIG.
2
A. Furthermore,
FIG. 3A
is a plan view showing a bonding surface of the front substrate at which surface the rear substrate and the front substrate, those substrates constituting the LCD panel of the first structure in the prior art, are bonded to each other.
FIG. 3B
is a cross-sectional view taken along a line X-X′ shown in FIG.
3
A.
As shown in
FIGS. 2A
,
2
B and
FIGS. 3A
,
3
B, the LCD panel is formed in the following order.
(1) On the rear substrate
101
, the array of pixel electrodes
11
and the alignment layer
4
are formed to provide a display region, and the sealing material
7
is provided on the outer circumference of the display region. Then, the liquid crystal material
5
is dropped on the alignment layer
4
.
(2) In the front substrate
201
, the color filter and the alignment layer
4
are formed to provide the display region, and the spacers
6
are distributed over the alignment layer
4
.
(3) The rear substrate
101
and the front substrate
201
are overlapped with each other in a vacuum room, and then, the sealing material
7
is cured.
Note that in some cases, the sealing material
7
may be provided on the front substrate
201
.
Furthermore,
FIG. 4
shows a second structural example of the LCD panel in accordance with the prior art. The LCD panel includes the rear substrate
101
, the front substrate
201
, the alignment layer
4
, the liquid crystal material
5
, the spacer
6
, the sealing material
7
, and a sealant
8
. The sealant
8
is a material for sealing an outlet
3
for surplus liquid crystal as shown in
FIG. 5A
, and is realized by employing UV-curing resin or the like.
FIG. 5A
is a plan view showing a bonding surface of the rear substrate at which surface the rear substrate and the front substrate, those substrates constituting the LCD panel of the second structure in the prior art, are bonded to each other.
FIG. 5B
is a cross-sectional view taken along a line X-X′ of FIG.
5
A. Furthermore,
FIG. 6A
is a plan view showing a bonding surface of the front substrate at which surface the rear substrate and the front substrate, those substrates constituting the LCD panel of the second structure in the prior art, are bonded to each other.
FIG. 6B
is a cross-sectional view taken along a line X-X′ of FIG.
6
A.
As shown in
FIGS. 5A
,
5
B and
FIGS. 6A
,
6
B, and
FIG. 7
, the LCD panel is formed in accordance with the following procedure.
(1) In the rear substrate
101
, the sealing material
7
is applied to the outer circumference of the display region such that the liquid crystal outlet
3
is formed, the alignment layer
4
is arranged in the display region, and the liquid crystal material
5
is dropped in the inside thereof.
(2) In the front substrate
201
, the alignment layer
4
is arranged in the display region, and the spacer
6
is dispersed.
(3) The rear substrate
101
and the front substrate
201
are bonded to each other while being pressurized in the atmosphere, the excess liquid crystal material
5
is discharged from the liquid crystal outlet
3
, and the sealing material
7
is hardened.
(4) A sealing operation is performed by applying the sealant
8
made of UV-curing resin or the like to the liquid crystal outlet
3
and hardening the sealant
8
.
In the second structure, both the substrates can be bonded to each other in the atmosphere. Note that the sealing material
7
is applied to the front substrate
201
in some cases.
The LCD panel according to the prior art is formed in accordance with the above first or second structural example.
However, in the above LCD panel of the first structure according to the prior art, decompression (vacuuming) needs to be conducted in order to bond the rear substrate
101
and the front substrate
201
in a vacuum, and this operation is time-consuming. Furthermore, the liquid crystal material
5
dropped on the rear substrate
101
is not discharged but sandwiched by both the substrates in the structure, and thus, precision in the drop amount of the liquid crystal is required.
Furthermore, in the above LCD panel of the second structure according to the prior art, the operation for sealing the liquid crystal outlet
3
needs to be conducted.
Moreover, as to the LCD panel according to the prior art, both the first and second structures make the sealing material
7
thereof directly contact the liquid crystal material
5
, and thus, deterioration and contamination of the liquid crystal material
5
occur owing to the sealing material
7
. Furthermore, since the rear substrate
101
and the front substrate
201
are bonded to each other by the sealing material
7
, the amount of the sealing material for the height corresponding to the diameter of the spacer
6
is required, which disadvantageously makes the amount of the sealing material
7
to be consumed large.
That is, there have been the following problems of the LCD panel according to the prior art.
(1) The decompression process makes the whole manufacturing process long in the manufacture of the LCD panel because decompression is time-consuming.
(2) Since high precision in the drop amount of the liquid crystal is required, the process of dropping the liquid crystal is long in the manufacture of the LCD panel.
(3) The sealing process needs to be performed.
(4) The usage amount of the sealing material is large.
(5) Since the liquid crystal material and the sealing material contact each other, the liquid crystal material is contaminated/deteriorated.
SUMMARY OF THE INVENTION
The present invention has been conceived in view of the above-mentioned problems, and therefore has an object to provide a LCD panel which can be formed without necessity for a sealing operation in the atmospheric pressure and with less amount of a sea
Chowdhury Tarifur R.
McGinn & Gibb PLLC
NEC LCD Technologies Ltd.
Schechter Andrew
LandOfFree
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