Patent ID: 7641722

Claim:
An ink composition comprising: a self-dispersible coloring agent that includes an ionic group (A) and a non-ionic linear or cyclic ester, or a non-ionic cyclic amide moiety (B) on a surface of the coloring agent at a mole ratio of about 1:10 to about 10:1; an organic solvent; and water, wherein the ionic group (A) is at least one compound selected from the group consisting of a tertiary ammonium group (—NR 3+ ), a tertiary phosphonium group (—PR 3+ ), a tertiary sulfonium group (—SR 2 + ) where R is a C1-C10 alkyl group or a hydrogen atom, —COOH, —SO 3 H, —PO 3 H 2 , —SO 2 NH 2 , —COOM, —SO 3 M, —PO 3 HM, and —PO 3 M 2 where M is a hydrogen atom, an alkali metal, ammonium, or an organic ammonium, and wherein the non-ionic moiety (B) comprises non-ionic linear or cyclic ester, or a non-ionic cyclic amide moiety selected from the group consisting of C3-C10 lactone, C3-C10 lactam, and —C(═O)OR where R is a C1-C10 alkyl group or a C6-C20 aryl group.