Patent ID: 8759462

Claim:
A method for producing a resist copolymer having a weight-average molecular weight of not less than 3000 and not more than 6000, said method comprising the step of continuously supplying a solution containing a monomer and a solution containing a polymerization initiator to a heated solvent in a polymerization tank to carry out a radical polymerization; wherein 1 to 10% by weight of a total amount of supplied polymerization initiator is supplied to the polymerization tank prior to the supply of the monomer solution; and wherein the variation range of the concentration of the polymerization initiator in polymerization solution is within ±25% of the median value between the maximum concentration and the minimum concentration during the time from the point where the amount of the supplied monomer reaches to 10% by mole of the total amount of the monomer to supply to the point where the supply of monomer solution is completed; and the variation range of the concentration of an unreacted monomer in the polymerization solution is within ±35% of the median value between the maximum concentration and the minimum concentration during the time from the point where the amount of the supplied monomer reaches to 10% by mole of the total amount of the monomer to supply to the point where the supply of monomer solution is completed.