To produce the subject film, capable of reducing surface defects and the oligomer content and manifesting a high elastic modulus and useful for a magnetic recording medium or a film, etc., for electrical insulation by adding a polysiloxane to a polyester.
This polyester film is produced by compounding (A) a polyester with (B) a polysiloxane [e.g. a straight polysiloxane having 20,000-300,000 molecular weight (concretely methylphenylpolysiloxane, etc.) or an organic modified polysiloxane], as necessary, further (C) a copolyester having (C1) mesogen groups in the main chain [e.g. the one having a structural unit of formulae I, II (R1 is 4,4'-biphenylylene, etc.) and formulae III and IV (R2 is 1,4-phenylene, etc.) and having the mesogen groups C1 in the main chain] and preferably contains 0.05-10wt.% component B and 0.1-10wt.% component C.
TSUNEKAWA TETSUYA
TSUNASHIMA KENJI
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