Patent ID: 6319309
Filing Date: 2001-11-20
Classification: C09B,C09D

Abstract:
An aqueous ink composition having a pH in the range of from 4 to 12 comprising:(a) an organic polybasic acid and a volatile base, or a salt formed by the said acid and base;(b) a water-soluble dye; and(c) an aqueous medium;wherein the volatile base, has a boiling point of less than 80.degree. C.; and the organic polybasic acid is an aliphatic acid including 2 to 8 acid groups or an aromatic acid of Formula (1):Z--X.sub.n (1)whereinZ is an aromatic group;each X independently is an acidic group;n is 1, 2, 3, or 4; andprovided that:(i) the aqueous ink composition does not contain a polyamine or a phosphate;(ii) when the organic polybasic acid is oxalic acid, citric acid or phthalic acid the water-soluble dye has at least as many carboxy as sulpho groups; and(iii) when the volatile base is ammonia the organic polybasic acid has acid groups selected from carboxy, sulpho, phosphono, --SH and --COSH.