| 摘要 |
PROBLEM TO BE SOLVED: To make a polyimide film to have such water absorption, a coefficient of hygroscopic swelling, and a coefficient of thermal expansion that meet specific conditions by dehydrating and ring-closing a polyamic acid copolymer which is a precursor obtained by performing polymerization in an organic polar solvent by using an acid anhydrite and a diamine component under a substantially equimolar condition. SOLUTION: A polyamic acid film having a self-supporting property is obtained by making to flow and spread or applying a polyamic acid copolymer or its solution on or to the surface of a supporting plate, such an organic film as the PET, etc., or such a support as the drum, endless belt, etc., in a film-like state after a stoichiometric quantity of or more dehydrating agent and a catalytic amount of tertiary amine is added to the copolymer or its solution and evaporating an organic solvent. Then the stripping-off end section of the film from the supporting film is fixed. After fixing the stripping-off end, the polyamidic acid is imidized by gradually heating the film to about 100-500 deg.C and, after cooling the film, the film is stripped off from the supporting plate. Therefore, a polyimide film having water absorption of <=1.6%, a coefficient of hygroscopic swelling of <=15ppm, and a coefficient of expansion of >=1.0×10<-5> deg.C and <=2.5×10<-5> deg.C can be obtained. |
