Patent ID: 7018455

Claim:
An ink composition comprising a colorant, water, a compound A selected from the group consisting of a hydrazide compound, a tertiary amine compound and an inorganic salt, and a first compound expressed by the following general formula wherein W is a —SO 2 NH 2 group, —NHCOCH 3 group, —CONH 2 group, —C═NH(NH 2 ) group, —NHC═NH(NH 2 ) group, —SO 3 H group, sulfuric ester group, —P(O)(OH)(OR), —P(O)(OR) 2 , carbamoyl group ar salt thereof, salt of a carboxyl group, salt of an amino group, salt of a phenolic hydroxyl group, polyethylene glycol ether group, salt of —C═NH(NH 2 ), or salt of —NHC═NH(NH 2 ); R is an alkyl group or aryl group; X is a hydrogen, oxy radical, hydroxyl group, alkyl group, alkenyl group, alkynyl group, aryl group, acyl group, sulfonyl group, sulfinyl group, alkoxy group, aryloxy group, or acyloxy group; R 1 , R 2 , R 3 , and R 4 are each a hydrogen or alkyl group; Z is a group of nonmetal atoms necessary to complete a five- to seven-member ring; and any two groups out of R 1 to R 4 and Z may bond together to form a five- to seven-member ring, wherein the hydrazide compound is a compound expressed by (i) the general formula R 5 CXNHNR 6 R 7 , where R 5 is an alkyl group or aryl group; R 6 and R 7 are a hydrogen, alkyl group, or aryl group; and X is S or O, or (ii) the general formula R 5 SO 2 NHNR 6 R 7 , where R 5 is an alkyl group or aryl group; and R 6 and R 7 are a hydrogen, alkyl group, or aryl group or (iii) the general formula R 5 NHCXNHNR 6 R 7 , where R 5 is an alkyl group or aryl group; R 6 and R 7 are a hydrogen, alkyl group, or aryl group; and X is S or O; wherein the inorganic salt is selected from the group consisting of MS 2 O 4 , MSO 3 , MS 2 O 3 , MPH 2 O 2 , and MPHO 3 , where M is an alkali metal or alkaline earth metal, and wherein the first compound is selected from the group consisting of