Disclosed is a method for producing a thermosetting resin which has excellent heat resistance and good electrical characteristics, while being improved in brittleness. Also disclosed is a thermosetting resin obtained by such a method. Specifically disclosed is a method for producing a thermosetting resin having a dihydrobenzoxazine ring structure, wherein (a) a polyfunctional phenol compound represented by the general formula (I) below, (b) a diamine compound represented by the general formula (II) below, and (c) an aldehyde compound are heated and reacted with each other. [Chemical formula 1] (I) (II) (In the formulae, X represents an organic group containing an aromatic ring and having 6 or more carbon atoms; and Y represents an organic group having 5 or more carbon atoms. Both X and Y may have N, O or F as a heteroatom. The benzene rings on both sides of X and Y are respectively bonded to different atoms in X and Y.)
展开▼
