AROMATIC IMIDE POLYMER FILM FOR MAGNETIC RECORDING MATERIAL AND PROCESS FOR PRODUCING THE SAME

摘要

An aromatic polyimide film useful as a face for a magnetic recording material having a back face-side half stratum thereof containing principal filler fine particles which provide a low friction back face-side surface having a centerline average surface roughness of 2 to 10 m mu m, and a front face-side half stratum thereof free from the principal filler particles and optionally containing additional filler fine particles having a size of 0.05 to 0.7 time that of the principal filler particles in a concentration of 0.1 to 0.8 time that of the principal filler particles, which additional filler particles provide a high smoothness front face-side surface having a centerline average surface roughness (Ra) of 0.1 to 0.8 time that of the back face-side surface, is produced from a first aromatic polyamic acid solution containing the principal filler particles and a second aromatic polyamic acid solution free from the principal filler particles and optionally containing the additional filler particles, by forming a film-shaped composite solution stream consisting of a first film-shaped solution stream united with a second film shaped solution stream, solidifying the film-shaped composite solution stream, and heat treating the solidified film to convert the polyamic acid to a corresponding polyimide.