Patent ID: 7923142

Claim:
An onium salt illustrated by the general formula (V); wherein R 1 is selected from the group consisting of a perfluoroalkyl group having 1 to 6 carbon atoms, a perfluoroalkyl group and a perfluoroaralkyl group having 7 to 9 carbon atoms, R 2 is selected from the group consisting of a formyl group, a acetyl group, a propionyl group, a butyryl group, a isobutyryl group, a valeryl group, a isovaleryl group, a pivaloyl group, a lauroyl group, a trifluoroacetyl group, a 2,2-difuluoropropionyl group, a perfuluoropropionyl group, a perfluorobutyryl group, a perfluoroisobutyryl group, a perfuluorovaleryl group, a methoxycarbonyl group, a ethoxycarbonyl group, a tert-butoxycarbonyl group, a trifuluoromethoxycabonyl group, a perfluoroethylcarbonyl group, a perfluoro-tert-butoxycarbonyl group, a methanesulfonyl group, a ethanesulfonyl group, a propanesulfonyl group, a tert-butanesulfonyl group, a trifluoromethanesulfonyl group, a pentafluoroethanesulfonyl group, a heptafluoropropanesulfonyl group, a nonafluorobutanesulfonyl group, a heptafluoroisopropanesulfonyl group, a nonafluoroisobutanesulfonyl group, a 2,2,2-trifluoroethanesulfonyl group, a 1,1-difuluoroethanesulfonyl group, a pentafuluorobenzenesulfonyl and a 2,4,6-trifuluorobenzenesulfonyl group, R 4 is a hydrogen atom, and R 3 and R 5 are, independently, selected from the group consisting of a methyl group, a ethyl group, a propyl group, a isopropyl group and a tert-butyl group.