A
pyridinium compound represented by the following general formula (1), (2) or (3):wherein X11, X21 and X31 each represent a
halogen atom being bonded to a
carbon atom at position 2, 4 or 6 of the
pyridine ring; R11 is an alkylene group having 1 to 24 carbons and which may contain a
heteroatom; Z21 is a group selected from —COO—R22, —CONH—R23 and —CON(R24)(R25), Z21 being bonded to a
carbon atom of the
pyridine ring different from the
carbon atom to which X21 is bonded; R21 is an
alkyl group having 3 to 24 carbons and which may contain a
heteroatom; R22, R23, R24 and R25 each represent an
alkyl group with 3 or more carbons which may contain a
heteroatom; R31 is a branched
alkyl group having 10 to 24 carbons and which may contain a heteroatom; and A21− and A31− each represent an anion.