| 摘要 |
PROBLEM TO BE SOLVED: To obtain a display having high contrast and high quality without defects by using a polyamic acid having a specified structure which forms imide rings in a specified proportion to align liquid crystal molecules in the perpendicular direction as a liquid crystal alignment film material. SOLUTION: A polyamic acid is imidized by using acetic acid anhydride and pyridine as an imidizing agent in N-methyl-2-pyrrolidone and then purified to obtain a polyimide. By controlling the add amt. of the imidizing agent, the imidization degree can be controlled. The imidization degree is preferably 25 to 99%, and more preferably 50 to 95%. After the imidization reaction, the imidizing agent used is removed. The proportion of the add amt. (the amt. of functional groups) of the crosslinking agent calculated as the chemical equiv. to the amt. of functional groups when all polymers are regarded as a polyamic acid is preferably 1 to 50% and properly 5 to 20%. |
