PURPOSE: To obtain a three-component polyimide resin compsn. having additional functions while keeping excellent intrinsic properties of the polyimide, by conducting the imidation in one step with a specified phenol mixture soln. and also by employing successive addition method.
CONSTITUTION: A three-component polyimide resin compsn. comprising repeating units of formula I, II or III (wherein R 1 is a group obtained by removing amino groups from a first aromatic diamine; R 2 is a group obtained by removing amino groups from a second aromatic diamine; X is a divalent group selected from among CO, O, S, SO 2 , CH 3 CCH 3 , a group of formula IV and CF 3 CCF 3 ; n is 1 to 4 and the amount of the segment in which n is 1 is at least 70%; m is 1 to 6; and q is 10 to 100) and having a mol. wt. of 50,000 to 200,000 (in terms of polystyrene).