The polyimide alignment layer containing trifluoro methyl moiety was synthesized. It is found that the imidization percentage reached 97.2% after one hour heating at 250 C and the thermal decomposition temperature was 420 C. The high pretilt angles from 6.7～7.8° were acquired by changing the rubbing strength. STN liquid crystal cells with 240° twist angle were fabricated by using this kind of polyimide alignment material. After a series of reliability experiment at certain temperature and humidity, high temperature, low temperature and thermal impact, the power consumption currents of the cells changed little. All the results show that this kind of material is a good alignment material and can be used for STN liquid crystal display.
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