Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
1999-07-02
2002-12-10
Ton, Toan (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
C349S155000
Reexamination Certificate
active
06493057
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a liquid crystal device and a method for manufacturing same.
A prior art photoelectric device with liquid crystal is illustrated in FIG.
1
. The device, such as a liquid crystal display, comprises a pair of substrates
1
and
1
′ joined to each other with a suitable distance inbetween, a liquid crystal layer
5
disposed between the pair of substrates
1
and
1
′, opposed electrodes
2
and
2
′ formed on the opposed inside surfaces of the substrates
1
and
1
′ in the form of a matrix, and oriented coating
3
and
3
′ on the opposed insides contiguous to the liquid crystal layer
5
. By virtue of application of a voltage to the electrodes
2
and
2
′, the optical characteristics of the liquid crystal
5
is changed under the electric field induced by the applied voltage. Namely, the device can be controlled by applying a voltage selectively to each pixel of the matrix to display an image or picture or storing information in terms of encoded signals.
The distance between the opposed substrates
1
and
1
′ is about 10 microns, while devices with the distance of 5 microns are now being developed. Although devices having twisted nematic liquid crystal can be constructed with the distances of this scale, the distance is demanded to be decreased to less than 3 microns, generally 2±0.5 microns, when making use of a ferroelectric liquid crystal for the device in place of a nematic liquid crystal.
Conventionally, the distance has been kept by disposing spacers
7
and
4
between the pair of substrates
1
and
1
′. In the figure, two kinds of spacers are illustrated; one being mixed with a sealing member
6
and the other being disposed between the opposed electrodes
2
and
2
′. For example, the spacers
4
are a plurality of spherical particles made of an organic resin such as Micro Pearl SP-210 having the average diameter of 10.0±0.5 microns made of a bridged polymer of divinyl benzene. The spacers of Micro Pearl SP-210 are perfect spheres. The spacers
4
prevent the substrates
1
and
1
′ from contact due to unevenness of the substrates or due to external stress.
However, the spacers
4
and the electrodes
2
and
2
′ are in point contact so that the electrodes
2
and
2
′ are subjected to concentrated stress. In cases where active devices are provided near the electrode
2
and
2
′, the concentrated stress may destroy the active devices or disconnect electrode circuits, and therefore make the liquid device defective. Further, even with the spacers
7
and
4
, it is very difficult to obtain a constant distance between the substrates because the spacers, when distributed between the substrates, tend to aggregate to local positions on the substrates and because the diameters of spacers are not constant. Even if uniform distribution of the spacers is obtained between the substrates, the distribution is disturbed during filling process of liquid crystal. Especially, when a ferroelectric liquid crystal is disposed between the substrates with 3 microns or less in distance, the liquid crystal is charged into the distance by virtue of capillary action from an opening provided on a portion of sealed-off perimeter of the substrates in the manner that the entrance is dipped in an amount of liquid crystal in a vacuum condition and then the pressure is increased so that the liquid crystal is caused to enter the device through the opening by the differential pressure. So, the stream of the liquid crystal tends to move the distributed spacers. Because of this unevenness of the distance, color shade appears on a display with a ferroelectric liquid crystal which utilizes birefringence. The defect can appear only due to external stress, such as pushing with a finger.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a liquid crystal device with no color shade.
It is another object of the present invention to provide a method for manufacturing a liquid crystal device at high yield.
It is further object of the present invention to provide a liquid crystal device having resistance against external impact.
It is still further object of the present invention to provide a method for manufacturing a liquid crystal device at a low cost.
It is yet still further object of the present invention to provide a facilitated method for manufacturing a liquid crystal device.
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Aoyagi Osamu
Isigaki Chizuru
Kobayashi Ippei
Konuma Toshimitsu
Mase Akira
Robinson Eric J.
Robinson Intellectual Property Law Office P.C.
Semiconductor Energy Laboratory Co,. Ltd.
Ton Toan
LandOfFree
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