Polyimide film made of multicomponent polyimide and process of producing the same

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×NA−2.09<NB<450×NA−1.12,
• wherein,
• the absolute difference between solubility parameter SPA of the polyimide A and solubility parameter SPB of the polyimide B, |SPB-SPA|, is 0.5 MPa1/2 or greater,
• NA is the number average polymerization degree of the polyimide component A and NB 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,
• the ratio of elastic modulus EB of a film of the polyimide B to elastic modulus EA of a film of the polyimide A, EB/EA, is 1.05 or higher,
• glass transition temperature TgA of the polyimide A is lower than glass transition temperature TgB of the polyimide B by 20° C. or more, and
• the polyimide A contains at least one of a fluorine atom and a silicon atom in its chemical structure;
• (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).