Patent ID: 8449978

Claim:
An insulated wire, comprising: a conductor; and an insulating film formed by coating and baking an insulating varnish on the conductor directly or via an other insulation layer, wherein the insulating varnish is a phenolic hydroxyl group-containing polyimide resin represented by a chemical formula (I): where X is a tetravalent aromatic group composing an aromatic tetracarboxylic dianhydride residue, Y 1 is a residue of a phenolic hydroxyl group-containing diamine that is selected from the group consisting of 1,3-diamino-4-hydroxybenzene, 3,3′-diamino-4,4′-dihydroxybiphenyl, 4,4′-diamino-3,3′-dihydroxybiphenyl, bis(3-amino-4-hydroxyphenyl)sulfone, bis(4-amino-3-hydroxyphenyl)sulfone, bis(3-amino-4-hydroxphenyl)hexafluoropropane, bis(4-amino-3-hydroxyphenyl)hexafluoropropane, bis(3-amino-4-hydroxyphenyl)propane, bis(4-amino-3-hydroxyphenyl)propane, 4,6-diaminoresorcinol and 4,5-diaminoresorcinol, and Y 2 is a residue of a diamine not including a phenolic hydroxyl group that is selected from the group consisting of 1,4diaminobenzene, 1,3-diaminobenzene, 4,4′-diaminodiphenyl methane, 4,4′-diaminodiphenyl ether, 3,4′-diaminodiphenyl ether, 4,4′-diaminobenzophenone, 3,3′-diaminobenzophenone, 4,4′-bis(4-aminophenyl)sulfide, 4,4′-diaminodiphenyl sulfone, 4,4′-diamino benzanilide, 1,4-bis(4-aminophenoxy)benzene, 1,3-bis(4-aminophenoxy)benzene and 1,3-bis(3-aminophenoxy)benzene, and a ratio of the number Z1 of phenolic hydroxyl groups included in Y 1 of the chemical formula (1) to the number Z2 of an imide group included in the chemical formula (1) is 0.15≦Z1/Z2≦0.85.