Patent ID: 7491483

Claim:
A polymer comprising recurring units of the general formulae (1a) and (1b): wherein R 1 is each independently hydrogen or methyl, R 2 is a hydrogen atom, C 1 -C 10 acyl group or acid labile group, R 3 is hydrogen, methyl or —CO 2 R 8 , R 4 is hydrogen, methyl or —CH 2 CO 2 R 8 , each of R 5 to R 7 is hydrogen, methyl, trifluoromethyl or —CO 2 R 9 , R 8 is hydrogen or a straight, branched or cyclic C 1 -C 15 alkyl group, R 9 is a hydrogen atom, straight, branched or cyclic C 1 -C 10 alkyl or fluoroalkyl group or acid labile group, X is —CH 2 —, —O— or —S—, with the proviso that —CH 2 — is excluded from X when all of R 5 to R 7 are hydrogen, n is an integer of 1 to 3, a1 and b1 are numbers in the range: 0<a1<1.0 and 0<b1≦0.8.