Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
2001-01-30
2003-02-25
Parker, Kenneth (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
C349S141000
Reexamination Certificate
active
06525793
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a liquid crystal display apparatus and, more particularly, to a TFT liquid crystal display apparatus which prevents display non-uniformity caused by a non-uniform distribution of static electricity on the surface of the liquid crystal display apparatus.
2. Description of the Prior Art
FIG. 1
shows the section of a usual, conventional liquid crystal display apparatus. As shown in
FIG. 1
, a liquid crystal display apparatus
20
is constituted by a TFT substrate
22
a
which is made of, e.g., a transparent glass having an electrode on its inner surface, an opposite substrate
22
b
which is also made of, e.g., a transparent glass having an electrode on its inner surface and arranged in parallel to the TFT substrate
22
a
via a spacer/sealing member
24
, a liquid crystal
26
liquid-tightly sealed among the pair of substrates
22
a
,
22
b
and the spacer/sealing member
24
, a color filter
27
adhered to the inner surface of the opposite substrate
22
b
, a pair of polarizing plates
28
and
29
respectively adhered to the outer surfaces of the TFT substrate
22
a
and the opposite substrate
22
b
, and protective films
23
and
25
respectively adhered to the outer surfaces of the polarizing plates
28
and
29
. The polarizing plates
28
and
29
are readily chargeable, and therefore when the protective films
23
and
25
respectively adhered to the outer surfaces of the pair of polarizing plates
28
,
29
are peeled off during manufacturing processes of the liquid crystal display apparatus or just before use after the liquid crystal display apparatus has been forwarded to the user, static electricity is generated on the outer surfaces of the polarizing plates
28
and
29
.
Since the polarizing plate
28
is formed of an insulating film, static electricity generated by peeling of the protective film
23
is locally electrified at a part of the outer surface of the polarizing plate
28
, and this nonuniform static electricity causes display non-uniformity. An IPS (In-Plane Switching) liquid crystal panel uses the same polarizing plate as a TN (Twisted Nematic) liquid crystal panel. In the conventional panel, when the protective films
23
and
25
are peeled off, the removal of electrification of the static electricity is done for a long time to suppress display non-uniformity.
FIG. 2
is a plan view showing a conventional polarizing plate
40
when the surface is not coated with any high-resistance conductive agent, and the protective film is peeled off. When the protective film is peeled off, static electricity is generated on the surface of the polarizing plate
40
. At this time, since the conventional polarizing plate
40
has a high surface resistance (1×10
16
ohm or more), the generated static electricity is not uniformly distributed, and the potential locally increases, as shown in FIG.
2
. These high-potential portions result in display non-uniformity, which requires the removal of electrification of the static electricity for a long time (about 1 min).
However, the long-time removal of electrification of the static electricity for suppressing display non-uniformity of the display apparatus decreases productivity, so the removal time of the electrification must be shortened. In the IPS panel, even if display non-uniformity is suppressed by the long-time removal of the electrification, static electricity may still be generated on the outer surface of the polarizing plate when the polarizing plate rubs against the backlight.
That is, if the polarizing plate contacts the diffusion sheet of the backlight due to vibration, shock, or the like after assembling the backlight, static electricity is generated on the outer surface of the polarizing plate. For the same reason as described above, the potential locally increases to generate electrified portions, resulting in display non-uniformity.
Another conventional liquid crystal display apparatus in which, in order to prevent the surface of the polarizing plate from generating a locally electrified portion due to the static electricity, an organic conductive film is formed on a polarizing plate is disclosed in Japanese Unexamined Patent Publication No. 10-96953. The organic conductive film used in this conventional liquid crystal display unit has a surface resistance of 1×10
5
ohm. However, in order to secure such a low surface resistance, the organic conductive film must be so formed as to have a remarkably high thickness even if the most suitable material for the organic conductive film, which is available at present, is used. As a result, it causes the organic conductive film to decrease its transparency, resulting in having a bad effect upon the liquid crystal display apparatus.
SUMMARY OF THE INVENTION
The present invention has been made in consideration of the conventional situation, and has as its object to provide a liquid crystal display apparatus in which static electricity is uniformly distributed on the surface of an IPS panel so as to prevent any display non-uniformity even when a protective film is peeled off.
In order to achieve the above object, according to the first aspect of the present invention, there is provided a liquid crystal display apparatus in which a backlight unit is mounted on one surface side thereof, and in which a liquid crystal is sealed between a pair of transparent substrates, comprising a conductive film made of a high-resistance conductive agent and formed on an outer surface of a polarizing plate adhered to an outer surface of one transparent substrate mounted on the side of said backlight unit so as to secure a surface resistance of from 1×10
9
ohm to 1×10
12
ohm for the polarizing plate.
According to the second aspect of the present invention, there is provided a liquid crystal display apparatus in which a backlight unit is mounted on one surface side thereof, in which a liquid crystal is sealed between a pair of transparent substrates, in which a color filter is adhered to an inner surface of one of said pair of transparent substrates, which is mounted on the side opposite to the side of said backlight unit, and in which polarizing plates are respectively adhered to outer surfaces of said pair of transparent substrates, comprising a conductive film made of a high-resistance conductive agent and formed on an outer surface of the polarizing plate adhered to an outer surface of one of said pair of transparent substrate mounted on the side of said backlight unit so as to secure a surface resistance of from 1×10
9
ohm to 1×10
12
ohm for the polarizing plate.
The high-resistance conductive agent in the first and second aspects has a composition of not more than 1% of a trialkyl-(2-hydroxyethyl) ammonium salt, not more than 10% of pentaerythritol, and not less than 90% of ethanol, or a composition of 5% of tin oxide, 2 to 5% of tetraethoxysilane, 1 to 2% of a polyester resin, and 87 to 90% of water.
The liquid crystal display apparatus in the first and second aspects may be an IPS panel.
According to the present invention having these aspects, the high-resistance conductive film is formed on the surface of the polarizing plate. Even if the protective film is peeled off from the polarizing plate, static electricity is not locally electrified on the polarizing plate, but is uniformly distributed, and no working time for removing static electricity is required.
Even if static electricity is generated between the liquid crystal display apparatus and backlight upon assembling the backlight, no display non-uniformity by the generated static electricity occurs.
The above and many other objects, features and advantages of the present invention will become manifest to those skilled in the art upon making reference to the following detailed description and accompanying drawings in which preferred embodiments incorporating the principle of the present invention are shown by way of illustrative examples.
REFERENCES:
patent: 5281365 (1994-01-01), Sohn et al.
patent: 5318
Parker Kenneth
Scully Scott Murphy & Presser
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