Patent ID: 6855195

Claim:
An ink composition comprising at least one of water-soluble dyes represented by the following formulae (1) to (3) and a surfactant: wherein R 1 , R 2 and R 3 each independently represents a hydrogen atom, a halogen atom, a cyano group, an alkyl group, a cycloalkyl group, an aralkyl group, an aryl group, an alkylthio group, an arylthio group or ionic hydrophilic group, and R 4 represents an optionally substituted heterocyclic group selected from the group consisting of the members of the following Group 1, provided that the water-soluble dye represented by the formula (1) has at least one ionic hydrophilic group within the molecule; Group 1: wherein * represents a linking position; wherein R 5 represents a hydrogen atom, a cyano group, an alkyl group, a cycloalkyl group, an aralkyl group, an aryl group, an alkylthio group, an arylthio group or an ionic hydrophilic group, Z a represents —N═, —NH— or —C(R 11 )═, and Z b and Z c each independently represents —N═ or —C(R 11 )═ wherein R 11 represents a hydrogen atom or a non-metallic substituent, and R 6 represents an optionally substituted heterocyclic group selected from the group consisting of the members of the following Group 2, provided that the water-soluble dye represented by the formula (2) has at least one ionic hydrophilic group within the molecule; Group 2: wherein * represents a linking position; and wherein R 7 and R 9 each independently represents a hydrogen atom, a cyano group, an alkyl group, a cycloalkyl group, an aralkyl group, an aryl group, an alkylthio group, an arylthio group or an ionic hydrophilic group, R 8 represents a hydrogen atom, a halogen atom, an alkyl group, an alkoxy group, an aryl group, an aryloxy group, a cyano group, an acylamino group, a sulfonylamino group, an alkoxycarbonylamino group, an ureido group, an alkylthio group, an arylthio group, an alkoxycarbonyl group, a carbamoyl group, a sulfamoyl group, a sulfonyl group, an acyl group, an alkylamino group, an arylamino group, a hydroxyl group or an ionic hydrophilic group, and R 10 represents an optionally substituted heterocyclic group selected from the group consisting of the members of the following Group 3, provided that the water-soluble dye represented by the formula (3) has at least one ionic hydrophilic group within the molecule; Group 3: wherein * represents a linking position.