Toray Industries, Inc.

Masanori Mizouchi

Hiroaki Kobayashi

Toshiyuki Asakura

Nobuaki Itoh

Image transfer material for thermal recording

The present invention relates to a process for producing an of aromatic polyimide film comprising (A) casting on a support a dope containing an amide-type polar solvent and 10-45 weight percent of a polyamic acid having more than 0.4 dl/g an inherent viscosity of more than 0.4 dl/g, (B) concentrating the polymer content to be at least higher than that of the initial dope while simultaneously raising the ring closure ratio above 30%, (C) removing the solvent from the film by extraction in an aqueous medium so as to lower the solvent content of the film below 10% and (D) then heating the film to a temperature of more than 200.degree. C. The process of the present invention is useful for the production of aromatic polyimide film having a reduced rate of solvent decomposition and improved productivity. The aromatic polyimide film produced by the process of the present invention is superior in thermal as well as mechanical properties and is highly useful as an electric insulation material and also as a base for flexible printed circuits, magnetic tape, etc.

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Ohtsu, Japan

Masanori Mizouchi