Patent ID: 8075824

Claim:
A process of producing a polyimide film of a multicomponent polyimide comprising the steps of: (1) mixing a polyimide component A and a polyimide component B to prepare a multicomponent polyimide blend solution, the polyimide component A being raw materials of a polyimide A and/or a polyimidation product of the raw materials, and the polyimide component B being raw materials of a polyimide B and/or a polyimidation product of the raw materials, the polyimide components A and B being combined to satisfy the relation: 2.35×N A −2.09 <N B <450×N A −1.12 , wherein, the absolute difference between solubility parameter SP A of the polyimide A and solubility parameter SP B of the polyimide B, |SP B -SP A |, is 0.5 MPa 1/2 or greater, N A is the number average polymerization degree of the polyimide component A and N B is the number average polymerization degree of the polyimide component B, provided that the degree of polymerization of each of unreacted polyimide raw materials, a tetracarboxylic acid component and a diamine component, is taken as 0.5; (2) subjecting the multicomponent polyimide blend solution to further polyimidation reaction; and (3) removing a solvent from a film of the multicomponent polyimide obtained in step (2).