Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
2003-01-24
2004-09-14
Ton, Toan (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
C349S096000
Reexamination Certificate
active
06791656
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to a liquid crystal display panel and a method of manufacturing the same, and more particularly to a method of manufacturing a liquid crystal display panel in which a warp in each of glass substrates of the liquid crystal display panel can be avoided to suppress display unevenness.
BACKGROUND OF THE INVENTION
With reference to the drawings, an explanation will be made on a conventional liquid crystal display panel or cell.
FIG. 8A
is a cross sectional view illustrating a schematic structure of a conventional liquid crystal display panel, and
FIG. 8B
is a cross sectional view illustrating a schematic structure of a polarizer film used in the conventional liquid crystal display panel.
As shown in
FIG. 8A
, the conventional liquid crystal display panel
120
comprises a liquid crystal substrate assembly
110
, and a pair of polarizer films
101
a
and
101
b
respectively stuck on both sides of the liquid crystal substrate assembly
110
. The liquid crystal assembly
110
has a pair of glass substrates
102
a
and
102
b
. The glass substrates
102
a
and
102
b
are opposed to each other, and mutually joined via a sealing material portion
103
a
. Between the glass substrates
102
a
and
102
b
, there are disposed gap material portions or spacers not shown in the drawing. Also, the space between the glass substrates
102
a
and
102
b
is filled with a liquid crystal material. In
FIG. 8A
, a portion between the glass substrates
102
a
and
102
b
into which the liquid crystal material is injected is schematically shown as a liquid crystal layer
103
.
Each of the polarizer films
101
a
and
101
b
comprises a film made of stretched polyvinyl alcohol into which iodine is doped or impregnated. Such film is hereafter called a PVA film or a PVA layer.
FIG. 8B
is a cross sectional view illustrating a schematic structure of a polarizer film which is used in a conventional liquid crystal display panel and which is in a condition before sticking on the liquid crystal substrate assembly.
As shown in
FIG. 8B
, the polarizer film
101
a
on the side of a display surface has a multilayer structure which comprises, from the side of the surface stuck on the liquid crystal substrate assembly
110
, a separator
104
, a glue or adhesive layer
105
, a triacetyle cellulose (TAC) layer
106
a
, a PVA layer
107
, a TAC layer
106
b
, an antiglare (AG) layer
108
, and a protective film
109
. Also, the polarizer film
101
b
on the side of a backlight source has a structure similar to that of the polarizer film
101
a
shown in
FIG. 8B
, except that the AG layer
108
is not provided. Therefore, a detailed description on the polarizer film
101
b
is omitted here.
In the polarizer film
107
a
shown in
FIG. 8B
, the TAC layers
106
a
and
106
b
are stuck on both surfaces of the PVA layer
107
as a polarizer, and function as protective layers of the PVA layer
107
. The protective layers of the PVA layer
107
, that is, the TAC layers
106
a
and
106
b
, are provided for preventing the PVA layer
107
which is water-soluble from absorbing moisture in the air and from becoming much deteriorated thereby. As a material for the protective films of the PVA layer, triacetyle cellulose (TAC) is often used. The TAC film has a high transparency, and has superior optical isotropy. Considering these points, in the polarizing film of a liquid crystal display panel, the TAC film is a preferred material for a protective film of the PVA layer.
On the surface of the TAC layer
106
a
, which surface is to be stuck on the glass substrate
102
a
or
102
b
, there is formed a glue or adhesive layer
105
. Further, a separator
104
is stuck on the adhesive layer
105
. The separator
104
is used for protecting the adhesive layer
105
and is peelable therefrom.
Also, on the surface of the TAC layer
106
b
, which surface is opposite to the PVA layer
107
, the AG layer
108
made of acrylic resin containing silicon particles is provided. Further, a protective film
109
for protecting the whole area of the polarizer film is stuck on the AG layer
108
.
In the above-mentioned structure, the polarizer films
101
a
and
101
b
easily deform, that is, contract, due to heat treatment and the like. If the polarizer films
101
a
and
101
b
deform, each of the glass substrates
102
a
and
102
b
warps, and a gap between the glass substrates
102
a
and
102
b
varies depending on the location thereof. Thereby, there is a possibility of occurrence of deterioration or unevenness of a contrast ratio and brightness, and/or coloring in the liquid crystal display portion, that is, there is a possibility of occurrence of display unevenness. In the conventional liquid crystal display, such display unevenness caused the deterioration of display quality, display performance and reliability.
Especially, recently, the size of the display panel of the liquid crystal display has become large, and accordingly an optical film having a large area is used as a polarizer film. When the optical film having a large area is used as the polarizer film, the polarizer film is deformed more easily than the polarizer film constituted of the optical film having a smaller area, and a warp in the glass substrate and display unevenness caused by the deformation of the polarizer film appear remarkably.
Therefore, the deterioration of display performance, display quality and reliability caused by the deformation of the polarizer film was a large obstacle to the realization of a liquid crystal display having a large size.
In Japanese patent laid-open publication No. 59-226324, there is disclosed a method of sticking a polarizer film of a liquid crystal display panel. In the method disclosed in Japanese patent laid-open publication No. 59-226324, after sticking the polarizer films on a liquid crystal display panel, the liquid crystal display panel is disposed in a pressure vessel. Then, the liquid crystal display panel is pressurized in the air while heating the liquid crystal display panel at a particular temperature.
In the method disclosed in Japanese patent laid-open publication No. 59-226324, it is possible to easily remove minute bubbles produced between the polarizer films and the liquid crystal display panel when the polarizer films are stuck on the liquid crystal display panel.
However, in the method disclosed in Japanese patent laid-open publication No. 59-226324, during a heating process after sticking the polarizer films, the polarizer films, especially the TAC layers, contract or deform, and thereby a stress is produced in each of the polarizer films. By this stress, glass substrates of a liquid crystal display panel warp and the liquid crystal display panel itself deforms. Thereby, display unevenness, deterioration of a manufacturing yield and an increase in manufacturing costs are caused.
Therefore, in the conventional structures and methods, disadvantages of display unevenness caused by the deformation of the polarizer films in the liquid crystal display portion, and of deterioration of display performance, display quality and reliability of display were not obviated.
SUMMARY OF THE INVENTION
Therefore, it is an object of the present invention to obviate the disadvantages of the conventional liquid crystal display panel and the conventional method of manufacturing the same.
It is another object of the present invention to provide a liquid crystal display panel and a method of manufacturing the same in which deformation or contraction of polarizer films in a liquid crystal display panel can be suppressed.
It is still another object of the present invention to provide a liquid crystal display panel and a method of manufacturing the same in which a warp of glass substrates in a liquid crystal display panel can be suppressed.
It is still another object of the present invention to provide a liquid crystal display panel and a method of manufacturing the same in which display unevenness in a liquid crystal display panel can be suppressed.
It is still another object
NEC LCD Technologies Ltd.
Ton Toan
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