Patent ID: 6451501
Filing Date: 2002-09-17
Classification: G03F

Abstract:
An acid sensitive copolymer which is formed by copolymerization of two or more different monomers, the polymer being characterized in that(1) it is insoluble itself in basic aqueous solutions, but is rendered soluble in basic aqueous solutions when the protecting group of the protected carboxyl group bonded to the side chain of the first monomer unit of the copolymer is removed by the action of the acid, (2) the protecting group of the carboxyl group comprises an acid anhydride portion represented by the following formula (I): whereR1 represents a hydrogen atom or represents one or more substituents selected from the group consisting of alkyl, alkoxy and alkoxycarbonyl groups, and when more than one R1 substituent is present the substituents may be the same or different, L is either absent or represents a linking group comprising a linear or branched hydrocarbon group with 1 to 6 carbon atoms, and n is an integer of 1 to 4; (3) the second monomer unit of the copolymer further contains, bonded to its side chain, an acidic functional group protected with an acid-unstable protecting group; and (4) it has a weight average molecular weight of 2,000 to 1,000,000.