| 摘要 |
PURPOSE:To obtain a low-thermal expansion resin excellent in mechanical properties such as bending resistance, and adhesiveness, etc., improved in water absorptivity, and useful for coating agents for flexible printed substrates, IC and LSI, comprising a polyamide-imide resin of a specified formula. CONSTITUTION:A polyamide-imide resin having structural units of formula I (wherein Ar is a tetravalent aromatic group, A is -NHCO-, R1, R2 and R3 are each an alkyl, alkoxy or a halogen, l, m and n are each 0-4, x is 0 or 1, and there is at least one alkoxy group). This resin is lowly thermally expandable, has excellent performances in mechanical properties such as bending resistance, adhesiveness, etc., is improved in water absorptivity, and is useful as a resin for producing a coating agents for IC and LSI, coating agents, etc. Said low-thermal expansion resin having structural units of formula I can be obtained by curing a polyamide precursor of formula II (wherein Ar, A, R1-R3, l-n and x are as defined above).
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