Abstract: A circuit substrate having an insulating layer comprising a polyimide resin on a metal foil substrate, wherein the polyimide resin is a polyimide resin obtained by the reaction of(A) aromatic diamines comprising(a) p-phenylene diamine and(b) 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl.(B) 3,4,3',4'-biphenyltetracarboxylic acid dianhydride.The circuit-formed substrate has a desired circuit comprising a conductive layer on the circuit substrate.The polyimide resin has a coefficient of thermal linear expansion close to that of the metal foil, and hence breakage does not occur on the resin layer, the resin layer does not separate, and warping does not occur.

Abstract: A circuit substrate having an insulating layer comprising a polyimide resin on a metal foil substrate, wherein the polyimide resin is a polyimide resin obtained by the reaction of(A) aromatic diamines comprising(a) 1,3-bis(4-aminophenoxy)benzene and(b) 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyland(B) aromatic tetracarboxylic acid dianhydrides comprising(a) 3,4,3',4'-biphenyltetracarboxylic acid dianhydrideand(b) 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride.The circuit-formed substrate has a desired circuit comprising a conductive layer on the circuit substrate.The polyimide resin has a low hygroscopic property and thus the substrate is excellent in the dimensional stability and does not cause warping even when the humidity in the environmental atmosphere is changed.

Abstract: A heat-resistant photoresist composition comprising a polyimide precursor having a structural unit represented by formula (I): ##STR1## wherein the arrows, R.sub.1, and R.sub.2 are the same as defined hereinbefore, and a compound which becomes basic upon irradiation with actinic rays, for example, represented by formula (II): ##STR2## wherein R.sub.3 to R.sub.6 and X.sub.1 to X.sub.4 are the same as defined hereinbefore,a photosensitive substrate obtained by coating a substrate with the heat-resistant composition, anda process for forming a pattern using the heat-resistant negative photoresist composition.

Abstract: A photoresist composition which can form a negative pattern with good heat resistance upon irradiation with actinic rays can be prepared by adding a 4-(2'-nitrophenyl)-1-alkyl (or alkoxyl)-4-dihydropyridine as a photosensitive compound which shows basicity by the irradiation with actinic rays to a resin component comprising a polyimide precursor having a specific structure.

Abstract: A positively photosensitive polyimide composition is disclosed, which composition comprises polyimide having repeating unit represented by formula (I): ##STR1## wherein Ar.sup.1 represents a tetravalent aromatic hydrocarbon group; Ar.sup.2 represents a divalent aromatic hydrocarbon group having an acyloxy group at the ortho-position and/or the meta-position of the aromatic ring; Ar.sup.3 represents a divalent aromatic hydrocarbon group; and the subunit having an amount ratio of m in the repeating unit is present in an amount of at least 20% by weight based on the polyimide. The composition exhibits high photosensitivity in reproduction of a fine pattern and excellent dimensional stability.