Patent ID: 7576223

Claim:
A sulfonium salt of the formula (Ia) wherein Q 1 and Q 2 each independently represent alkyl having 1 to 6 carbon atoms or cycloalkyl having 3 to 10 carbon atoms, or Q 1 and Q 2 bond to form divalent acyclic hydrocarbon having 3 to 7 carbon atoms which form a ring together with the adjacent S + ; Q 3 , Q 6 and Q 7 each independently represent hydrogen or methyl; Q 4 represents a group of the formula (X) wherein T represents hydrogen, alkyl having 1 to 10 carbon atoms or cycloalkyl having 3 to 10 carbon atoms, Z represents hydrogen, alkyl having 1 to 10 carbon atoms or cycloalkyl having 3 to 10 carbon atoms, K represents a divalent group selected from the group consisting of the following formulae n denotes an integer of from 0 to 10, and p denotes an integer of from 0 to 3, when n or p is 2 or more, each T may be the same or different and when n is 2 or more, each K may be the same or different; n 1 denotes 0 or natural number; and Q 5 represents perfluoroalkyl having 1 to 8 carbon atoms, alkyl having 1 to 8 carbon atoms or aromatic group having 6 to 12 carbon atoms which may be substituted; or camphor group; with the proviso that when n 1 denotes 0, n denotes an integer of from 1 to 10, and when n 1 denotes 1 and n denotes 0, Z is not alkyl.