Patent ID: 7311391

Claim:
An ink composition comprising: at least one dye having an oxidation potential of more positive than 1.0 V dissolved or dispersed in an aqueous medium; and a surface active agent in an amount of from 0.05 to 50 g/l wherein the surface active agent is a compound represented by the following general formula (I), (II) or (III): wherein R 21 represents a C 5 -C 40 alkyl group; and m 1 is from 2 to 40; wherein R 24 represents a C 5 -C 40 alkyl group; and m 2 is from 2 to 40; wherein R 31 and R 32 each independently represent a C 1 -C 18 alkyl group; R 33 represents a hydrogen atom, C 1 -C 6 alkyl group, or phenyl group; and X represents a hydrogen atom or in which R 34 and R 35 each independently represent a C 1 -C 18 alkyl group; represents a hydrogen atom, C 1 -C 6 alkyl group or phenyl group; m 3 and m 4 each independently are 0 to 100, and the sum of m 3 and m 4 is from 0 to 100, and when m 3 is 0, R 33 represents a hydrogen atom, and when m 4 is 0, R 36 represents a hydrogen atom, and when X is a hydrogen atom, m 3 is from 1 to 100.