A compound represented by formula (I); and a compound represented by formula (b1-1): wherein X represents —O—, —S—, —O—R3— or —S—R4—, wherein each of R3 and R4 independently represents an alkylene group of 1 to 5 carbon atoms; R2 represents an alkyl group of 1 to 6 carbon atoms, an alkoxy group of 1 to 6 carbon atoms, a halogenated alkyl group of 1 to 6 carbon atoms, a halogen atom, a hydroxyalkyl group of 1 to 6 carbon atoms, a hydroxyl group or a cyano group; a represents an integer of 0 to 2; Q1 represents an alkylene group of 1 to 12 carbon atoms or a single bond; Y1 represents an alkylene group of 1 to 4 carbon atoms or a fluorinated alkylene group; M+ represents an alkali metal ion; and A+ represents an organic cation.