PURPOSE: To produce a polyimide which has excellent mechanical strengths, a high elastic modulus, a low coefficient of linear thermal expansion, and low water absorption properties and is suitable for a fine-patterned flexible printed circuit board by subjecting a specific polyamic acid to cyclodehydration.
CONSTITUTION: An arom. tetracarboxylic dianhydride of formula I (wherein Ar1 is a tetravalent arom. hydrocarbon group) is polymerized with an arom. diamine of formula II (wherein Ar2 is a divalent arom. hydrocarbon group) to give a polyamic acid mainly comprising repeating units of formula III (wherein Ar1 and Ar2 are each the same as described above), which is thermally or chemically subjected to cyclodehydration. Thus is easily obtd. a polyimide mainly comprising repeating units of formula IV (wherein Ar1 and Ar2 are each the same as described above), which, having excellent mechanical strengths, a high elastic modulus, a low coefficient of linear thermal expansion, low water absorption properties, and an excellent dimensional stability, is suitable for an electric insulating material, a film for a fine-patterned flexible printed circuit board, etc.
SUGITANI ATSUSHI
YUYAMA MASAHIRO
MOTOUMI KIYOSHI
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