Compositions – Liquid crystal compositions – Containing nonchiral aligning agents
Patent
1997-08-13
1999-01-12
Wu, Shean C.
Compositions
Liquid crystal compositions
Containing nonchiral aligning agents
25229901, 428 1, 349132, 349135, 349136, C09K 1938, C09K 1956, G02F 11337
Patent
active
058582746
DESCRIPTION:
BRIEF SUMMARY
This application is a 371 of PCT/JP96/00283 filed Feb. 9, 1996.
TECHNICAL FIELD
The present invention relates to a treating agent for liquid crystal alignment useful for liquid crystal devices such as a liquid crystal display. More particularly, it relates to a treating agent for liquid crystal alignment for the production of a liquid crystal alignment film which has a high tilt angle to a substrate of liquid crystal molecules and is excellent in electrical properties of liquid crystal devices such as voltage holding ratio and charge-accumulation property.
BACKGROUND ART
In recent years, active matrix operation systems using, for example, a thin-layer transistor, have been actively developed by virtue of their excellent display performance. Among them, a so-called TFT (thin film transister) display system is the most representative system, and further progress of its display performance have been made. Together with such progress, it is required to improve various properties at the same time with respect to liquid crystal alignment films. As liquid crystal alignment film properties usually required for a so-called TFT display system, most basic necessary properties are, for example, the tilt angle of liquid crystal molecules, voltage holding ratio and charge-accumulation property by a direct current voltage. Alignment film materials which satisfy all of these properties have been desired. Namely, it is required to develop a treating agent for liquid crystal alignment by which a liquid crystal alignment film which is high in the tilt angle and voltage holding ratio and brings about sufficiently low charge-accumulation by a direct current voltage, is obtained.
In conventional treating agents for liquid crystal alignment, film properties are generally improved by employing one type of a polyimide or a polyimide precursor and selecting its structure from various ones.
It is known that all these properties are affected by the structure of the polyimide to be used, and it is the actual circumstance that all the properties of the alignment films are not adequately satisfied by only one polymer structure. Namely, with respect to the conventional alignment treating agents, for example, one agent can exhibit excellent properties of the voltage holding ratio, but is low in the tilt angle or large in the charge-accumulation property, and another one is excellent in the tilt angle and the voltage holding ratio, but large in the charge-accumulation property. Accordingly, no material has been found by which these free properties are satisfied adequately and at the same time.
Further, for the practical mass production of liquid crystal devices, not only the above basic properties but also various properties such as adhesive properties to a substrate, printing properties and rubbing resistance are required.
Namely, it is required to develop various properties including productivity as well as the above basic properties, and it is the actual circumstance that adequate performance can not necessarily be obtained only by a single polyimide resin.
Conventional treating agents for liquid crystal alignment are generally, for example, the one obtained by coating a varnish having a solvent-soluble polyimide dissolved in a solvent on a substrate, and baking it to form a polyimide film, and then rubbing treated it to form a liquid crystal alignment film, or the one obtained by coating a polyimide precursor solution on a substrate, and baking it generally at a temperature of at least 150.degree. C. for imide-modification to form a polyimide film, and then rubbing treated to prepare a liquid crystal alignment film.
Here, it is known that liquid crystal alignment films formed by a solvent-soluble polyimide are generally excellent in the voltage holding ratio, but such films have problems that the tilt angle is not adequate or its stability is not adequate, or the charge-accumulation property is not adequately low. Further, such films are known to be poor in the adhesive properties to a substrate and the printing properties.
On th
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Fukuro Hiroyoshi
Mishina Makoto
Sato Terumi
Sawahata Kiyoshi
Tanaka Atsuko
Nissan Chemical Industries Ltd.
Wu Shean C.
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