Compositions – Liquid crystal compositions – Containing nonchiral aligning agents
Patent
1999-01-11
2000-09-19
Wu, Shean C.
Compositions
Liquid crystal compositions
Containing nonchiral aligning agents
428 125, 428 126, 528353, C09K 1956, C08G 6926, C08G 7310
Patent
active
061207020
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to an alignment treating agent for a liquid crystal cell. More particularly, it relates to an alignment treating agent for a liquid crystal cell wherein nematic liquid crystal molecules have a low tilt angle to a substrate, an excellent alignment stability can be obtained with no change in the tilt angle during heat treatment after injection of liquid crystal, and an excellent uniformity in alignment of ferroelectric liquid crystal or antiferroelectric liquid crystal can be obtained.
BACKGROUND ART
A liquid crystal display device is a display device utilizing electro-optic changes of liquid crystal. Attention has been drawn to its characteristic such as small lightweight of the device or small consumption of electric power, and it has been developed significantly as a display device for various kinds of displays. Among these, a field effect type liquid crystal display device of twisted nematic type (TN type) is a typical example, wherein nematic liquid crystal having positive dielectric anisotropy is used, liquid crystal molecules are aligned in parallel to a substrate at the interface of each of a pair of electrode substrates facing each other, and the substrates are arranged so that the alignment directions of liquid crystal molecules are perpendicular to each other.
With regard to such a liquid crystal display device of TN type, it is important to align liquid crystal molecules so that the major axis direction of liquid crystal molecules is uniformly parallel to the substrate surface, and further liquid crystal molecules have a certain tilt angle to the substrate.
As typical methods to align liquid crystal molecules, two methods have been known. One method is to form an inorganic film on a substrate by vapor-depositing an inorganic substance such as silicon dioxide obliquely to the substrate, and to align liquid crystal molecule in the direction of vapor deposition. By this method, a stable alignment having a certain tilt angle can be obtained, but it is not industrially effective. The other method is to form an organic coating film on a substrate surface, to rub the surface with a cloth such as cotton, nylon or polyester in a predetermined direction, and to align liquid crystal molecules in the rubbing direction. By this method, stable alignment can be obtained relatively easily, and thus this method is mainly employed industrially. As the organic film, a polyvinyl alcohol, a polyoxyethylene, a polyamide or a polyimide may, for example, be mentioned. However, in view of chemical stability and thermal stability, a polyimide is most commonly used. A typical example of the polyimide used for a liquid crystal alignment film is disclosed in JP-A-61-47932.
On the other hand, with regard to a ferroelectric liquid crystal display device or an antiferroelectric liquid crystal display device, wherein ferroelectric liquid crystal or antiferroelectric liquid crystal having chiral smectic phase is used, and liquid crystal molecules are aligned at the interface of each of a pair of electrode substrates facing each other so that the layer direction is oriented in one direction to the substrate, it has been known to have more excellent high speed response and high angle of visibility as compared with a nematic liquid crystal display device, due to direct interaction between the field and a spontaneous polarization of liquid crystal molecules. Further, with regard to a surface-stabilized ferroelectric liquid crystal device or a surface-stabilized antiferroelectric liquid crystal device wherein the cell gap is made thinner than a helical pitch of ferroelectric liquid crystal or antiferroelectric liquid crystal, it has been known that a display device having bi-stability or tri-stability which can not be attained in a nematic liquid crystal display device and being highly precise even in a simple matrix electrode structure, can be prepared.
It is particularly important to align liquid crystal molecules uniformly in a predetermined direction in the ferroelectric liquid cry
REFERENCES:
patent: 5607732 (1997-03-01), Miyamoto et al.
patent: 5608033 (1997-03-01), Nihira et al.
patent: 5665856 (1997-09-01), Nihira et al.
patent: 5861534 (1999-01-01), Nihira et al.
Patent Abstracts of Japan, vol. 16, No. 180 (C-0935), Apr. 30. 1992, JP 04 023832, Jan. 28, 1992.
Fukuro Hiroyoshi
Mishina Makoto
Miyamoto Yoshio
Sano Syunichi
Nissan Chemical Industries Ltd.
Wu Shean C.
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