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In formula (b-1), two ofR 1 " to R 3 " may be bonded to each other to form a ring with the sulfur atom. The ring may be saturated or unsaturated. Further, the ring may be monocyclic or polycyclic. For example, in the case where either one or both of the two ofR 1 " to R 3 represent a cyclic group (i.e., a cyclic alkyl group or an aryl group), when the two groups are bonded, a polycyclic ring (fused ring) is formed. 

As the ring to be formed, the ring containing the sulfur atom in the skeleton thereof is preferably a 3 to 10-membered ring, and most preferably a 5 to 7-membered ring. 

The ring may have a hetero atom as an atom constituting the ring skeleton other than the sulfur atom having R 1 " to R 3 " bonded thereto. Examples ofhetero atoms include an oxygen atom, a nitrogen atom, and a sulfur atom. 

Specific examples of the rings to be formed include a thiophene ring, a thiazole ring, a benzothiophene ring, a thi› anthrene ring, a benzothiophene ring, a dibenzothiophene ring, a 9H-thioxanthene ring, a thioxanthone ring, a thian› threne ring, a phenoxathiin ring, a tetrahydrothiophenium ring and tetrahydrothiopyranium ring. 

In the formula (b-1 ), preferable examples of the cation moiety represented by formula cs+(R $^{1}$")(R$^{2}$")(R 3 ")) in which two ofR 1 " to R 3 " are mutually bonded with the sulfur atom to form a ring include cation moieties represented by formula (ca-12) to (ca-15) shown below. 

[Chemical Formula 60] 

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