PURPOSE: To obtain a polymer film having distribution in the coefficient of thermal expansion, by applying precursor varnishes which can give polyamides of different coefficients of thermal expansion to a substrate in a state in contact with one another and imidating the precursor varnishes.
CONSTITUTION: An aromatic diamine (A) (e.g., p-phenylene-diamine) or an aromatic isocyanate is reacted with a tetracarboxylic acid derivative (B) (e.g., 3,3',4,4'-biphenyltetracarboxylic dianhydride) at -20W200°C in a solvent (e.g., N-methylpyrrolidone) to obtain a precursor varnish which can give a polyimide. Precursor varnishes of different coefficients of thermal expansion are applied to a substrate in a state in contact with one another and are imidated thermally or chemically to obtain the title film composed of the polymers of different coefficients of thermal expansion successively arranged in the direction of the face. This film is useful for bonding a material of a larger coefficient of thermal expansion to one of a smaller coefficient of thermal expansion.
FUJISAKI KOJI
IKEDA TAKAE
MIWA TAKAO
OGIWARA SATORU
MIYAZAKI KUNIO
HITACHI CHEMICAL CO LTD
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