Patent ID: 8791288

Claim:
An acid-labile ester monomer having a spirocyclic structure, represented by the general formula (2): wherein X is a divalent group which forms a substituted or unsubstituted cyclopentane, cyclohexane or norbornane ring with the carbon atom to which it is attached, R 1 is hydrogen, fluorine, methyl or trifluoromethyl, R 2 is a straight, branched or cyclic C 1 -C 10 monovalent hydrocarbon group, R 3 and R 4 are each independently hydrogen or a straight, branched or cyclic C 1 -C 10 monovalent hydrocarbon group, or R 3 and R 4 , taken together, stand for a divalent group which forms a substituted or unsubstituted cyclopentane or cyclohexane ring with the carbon atom to which they are attached, and n is 1 or 2.