wherein Z represents an oxygen atom or sulfur atom; R₁ and R₂ each represent a substituted or unsubstituted alkyl group; V₁, V₂, V₃, V₄, V₅, V₆, V₇, and V₈ each represents a hydrogen atom, a halogen atom, an alkyl group, an acyl group, an acyloxy group, an alkoxycarbonyl group, a carbamoyl group, a sulfamoyl group, a carboxyl group, a cyano group, a hydroxyl group, an amino group, an acylamino group, an alkoxy group, an alkylthio group, an alkylsulfonyl group, a sulfonic acid group or an aryl group, with the proviso that two of V, to V₈ which are bonded to adjacent carbon atoms do not together form a condensed ring and that assuming Hammett's value ap of each of V₁ to Vs is σpi (i = 1 to 8) and Y= ap1 + ap2 + ap3 + ap4 +σp5 + σp⁶ + σp7 + σp8, then Y ≦ -0.08 if Z is an oxygen atom or Y ≦ -0.15 if Z is a sulfur atom; X' represents a charge balance paired ion; and n represents a value required to neutralize the electric charge:

wherein R represents an alkyl group, an alkenyl group or an aryl group; and X represents a hydrogen atom, an alkali metal atom, an ammonium group or a precursor:

wherein L represents a divalent connecting group; R⁴ represents a hydrogen atom. alkyl group, alkenyl group or aryl group; X is as defined for the formula (II); and m represents an integer 0 or 1:

wherein R and X are as defined for the formula (II); L and m are as defined for the formula (III); R³ has the same meaning as R, with the proviso that these groups may be the same or different; and m represents an integer 0 or 1.