| 摘要 |
PURPOSE:To facilitate the formation of a polyimide film excellent in strength, by producing the film from a solution of a polyamic acid in a mixture of an aprotic polar solvent with a specified solvent by cast molding. CONSTITUTION:A polyimide film is produced by cast molding from a solution of a polyamic acid which is a polycondensation product of an aromatic tetracarboxylic acid dianhydride with an aromatic diamine by the following way. A polyamic acid solution in which the solvent for the polyamic acid is a mixture of an aprotic polar solvent with a solvent having a solubility >=1.0wt.% in water at 140 deg.C, and the amount of said aprotic polar solvent is 70-97wt.% based on the total solvent is used. When said vapor pressure is below 550mmHg, the effect of solvent removal is not sufficient undesirably. When said water solubility is 1.0wt.% or above, the azeotropic temperature is too high to control hydrolysis, which is undesirable.
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