A quaternary ammonium compound of the present invention is a quaternary ammonium type compound having s a general formula (I) or (I):(in the formulae, A represents a straight-chain alkyl group with 1 to 4 carbon atoms, a branched alkyl group with 2 to 4 carbon atoms, a straight chain alkyl group with 1 to 4 carbon atoms having a hydroxyl group, or a branched alkyl group with 2 to 4 carbon atoms having a hydroxyl groupR1to R3represents the same of different straight-chain or a branched alkyl group with 1-12 carbon atomsone of R4to R8represents CO2-or SO3-, at most three of the remaining R4to R8represents one selected from the group consisting of hydroxyl group and an alkoxy group with 1 to 4 carbon atoms, the other R4to R8represents hydrogen atomone of R’4to R’8represents CO2H or SO3H, at most three of R’4to R’8represents one selected from the group consisting of a protected hydroxyl group and an alkoxy group with 1 to 4 carbon atoms, the other R’4to R’8represents hydrogen atomand X-represents an anion which can form a salt with a quaternary ammonium group.).
