Patent ID: 7871554

Claim:
A process for producing polyimide film, comprising stretching at a stretch ratio of 1.2 to 4.0, an unstretched polyimide film which is formed of a polyimide having a repeating unit represented by formula (1): wherein R represents a tetravalent group derived from cyclohexane; and Φ represents a divalent aliphatic, alicyclic, or aromatic group, or a combination thereof that has a total number of carbon atoms of 2 to 39 and may have at least one connecting group selected from the group consisting of —O—, —SO 2 —, —CO—,—CH 2 —, —C(CH 3 ) 2 —, —OSi(CH 3 ) 2 —, —C 2 H 4 O—, and —S—, and wherein the unstretched polyimide film which has an organic solvent content of 0.5 wt. % or more and less than 10 wt. % is stretched at 220° C. to 380° C., and the process further includes reducing the stretch degree of the stretched film, maintaining the film at the reduced stretch degree, heating the film to a temperature higher than the stretch temperature by 1° C. to 50° C., and maintaining the heated film for 10 seconds to 10 minutes.