Patent ID: 8038780

Claim:
An ink composition comprising: a colorant represented by the following formula (I); water; a guanidine-based compound; and a colorless water-soluble planar compound having more than ten delocalized π-electrons within one molecule: wherein M represents a hydrogen atom, a metal atom, an oxide thereof, a hydroxide thereof or a halide thereof; each of X 1 , X 2 , X 3 and X 4 represents a substituent selected from the group consisting of —SO—R 1 , —SO 2 —R 1 , —SO 2 NR 2 R 3 , —CONR 2 R 3 , —CO 2 —R 1 , —CO—R 1 , a sulfo group and a salt thereof, a carboxyl group and a salt thereof, and a phosphono group and a salt thereof; R 1 represents a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, or a substituted or unsubstituted heterocyclic group; R 2 represents a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, or a substituted or unsubstituted heterocyclic group; R 3 represents a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, or a substituted or unsubstituted heterocyclic group; each of Y 1 , Y 2 , Y 3 and Y 4 represents a hydrogen atom or a monovalent substituent which may further have a substituent; and a 1 to a 4 and b 1 to b 4 represent the numbers of X 1 to X 4 and Y 1 to Y 4 , respectively, and each of a 1 to a 4 and b 1 to b 4 represents an integer of 0 to 4, provided that at least one of X 1 , X 2 , X 3 , X 4 , Y 1 , Y 2 , Y 3 and Y 4 is itself an ionic hydrophilic group or has an ionic hydrophilic group as a substituent; and at least one of a 1 to a 4 is not 0.