Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From phenol – phenol ether – or inorganic phenolate
Patent
1997-06-20
1998-09-15
Hampton-Hightower, P.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From phenol, phenol ether, or inorganic phenolate
528 25, 528 26, 528 28, 528125, 528128, 528172, 528173, 528174, 528176, 528183, 528185, 528188, 528220, 528229, 528350, 528353, 4284735, 359173, C08G 7310, C09K 1930, G02F 11337
Patent
active
058079610
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention is directed to a polyimide film useful as use applications for electronic materials; a liquid crystal aligning film using the same; a liquid crystal display element provided with the liquid crystal aligning film; and a polyamic acid used as a raw material of the polyimide constituting the polyimide film.
BACKGROUND ART
For liquid crystal display elements used for watches, electronic calculator, etc., a twist.nematic (hereinafter abbreviated to TN) mode having a structure wherein the aligning direction of nematic liquid crystals is twisted by 90.degree. between a pair of upper and lower electrode substrates, has been mainly employed. Further, super twisted nematic (hereinafter abbreviated to STN) mode wherein the twist.angle has been increased to 180.degree. to 300.degree. has been developed; thus even in the case of a large picture surface, a liquid crystal display element having a superior display grade has been obtained.
Further, in recent years, since matrix display, color display, etc. have been carried out, MIM (metal-insulating phase-metal) element having employed an active type twist.nematic mode wherein a large number of picture element electrodes are provided and ON-OFF thereof can be carried out, and TFT (electric field effect type thin film transistor) element have been vigorously developed.
A problem common in all of these modes consists in that the following phenomenon occurs: is then shifted to another picture surface, the prior picture remains as a remaining one (image sticking). Particularly, in order to obtain a high grade, liquid crystal display element, improvement in the above image sticking is a very important problem.
The cause of the above image sticking is considered as follows: electric double layer is formed by the ion component of impurities contained in the liquid crystals present on the surface of the aligning film, and as a result, an electric charge deviation occurs between the upper and lower substrates and since the deviation is kept stable, a potential difference occurs, resulting in the above image sticking. Particularly, in the case of TFT element, since it is impossible to remove the DC component, in view of the characteristic of the element, the image sticking is more conspicuous as compared with the cases of TN and STN elements; hence this fact is serious.
Further, in the case of TFT mode, in order to prevent the picture surface from flicker, there has been required an aligning film holding a high voltage holding ratio even in the case of 60.degree. C. to 90.degree. C. at which the voltage holding ratio is notably lowered.
As aligning films used for such liquid crystal display elements, organic films such as those of polyimide, polyamide, etc. have been mainly used. For example, Japanese patent application laid-open No. Sho 51-65960 discloses a liquid crystal display element provided with a liquid crystal-aligning film using a polyimide resin having repetition units expressed by the following formula: ##STR1##
However, in the case of such an element using a polyimide aligning film obtained by using a compound having such an ether bond, image sticking or Vth unevenness is liable to occur.
The object of the present invention is to solve the above problems, and to provide a polyimide film which has no image sticking, has a high voltage holding ratio over low temperatures to high temperatures, and further does not generate any Vth unevenness at the peripheral part of liquid crystal panel even in an atmosphere of high temperature and high humidity; a liquid crystal aligning film and a liquid crystal display element using the same; and a polyamic acid as a raw material of the polyimide.
DISCLOSURE OF INVENTION
The present inventors have made extensive research and development of the art, and as a result, have found that the above image sticking, voltage holding ratio and Vth unevenness have a correlation to the polarity of the surface of aligning film, and when a diamino compound having a specified structure capable of reducing the pola
REFERENCES:
patent: 5122295 (1992-06-01), Weber et al.
patent: 5378395 (1995-01-01), Weber et al.
patent: 5449705 (1995-09-01), Wanatabe et al.
patent: 5519525 (1996-05-01), Weber et al.
Hayakawa Masaharu
Murata Shizuo
Nakagawa Etsuo
Oikawa Seiji
Sawai Toshiya
Chisso Corporation
Hampton-Hightower P.
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