Silicon-containing soluble polyimide precursor, its cured material, and

Abstract

The present invention intends to provide a cured material of a silicon-containing polyimide having high heat resistance, low coefficient of thermal expansion, no brittleness and high hardness. In order to enable liquid coating and impregnation, a silicon-containing soluble polyimide precursor is first prepared. The precursor may be prepared by mixing five compounds of ##STR1## (R.sup.1 is a tetravalent carbon cyclic aromatic group), NH.sub.2 --R.sup.2 --NH.sub.2 (R.sup.2 is an aliphatic group, an alicyclic group, an aromatic aliphatic group or a carbon cyclic aromatic group, a polysiloxane group or 1,3,5-triazine group having a substituent), NH.sub.2 --R.sup.3 --SiR.sup.4.sub.3-k X.sup.1.sub.k and NH.sub.2 --R.sup.3 --SiR.sub.3-m.sup.4 X.sup.1.sub.m (R.sup.3 is --(CH.sub.2).sub.s --, ##STR2## wherein s is an integer of 1 to 4, and R.sup.4 is an alkyl group, a phenyl group or an alkyl-substituted phenyl group and SiX.sub.4.sup.2, X.sup.1 and X.sup.2 are independently an alkoxy group, an acetoxy group, a halogen or a hydroxyl group), and then heating the mixture. Coating or impregnation of this precursor is then given and afterward heated at a temperature of 50.degree. to 500.degree. C., thereby obtaining the cured material of the silicon-containing polyimide.