Cationic modified self-dispersing pigment dispersions

1. An aqueous pigment dispersion comprising:

a self-dispersing pigment having at least one type of hydrophilic functional group bonded onto a surface of the self-dispersing pigment, said at least one type of hydrophilic functional group comprising a carboxyl group;

a multivalent cation selected from the group consisting of Mg 2+ , Ca 2+ , Cu 2+ , Al 3+ , Fe 3+ , and mixtures thereof, wherein said multivalent cation is adsorbed onto said self-dispersing pigment via ionic bonds between the multivalent cation and surface acid group on the self-dispersing pigment displacing monovalent cation(s) associating with the carboxyl group on the surface of the self-dispersing pigment, the displaced monovalent cation(s) are removed from the pigment dispersion; and

an anionic polymeric binder.

2. The pigment dispersion of claim 1 , wherein said multivalent cation is present at a level of at least 2 ppm.

3. The pigment dispersion of claim 1 , wherein said multivalent cation is Mg 2+ .

4. The pigment dispersion of claim 1 , wherein said multivalent cation is Cu 2+ .

5. The pigment dispersion of claim 1 , wherein said multivalent cation is Ca 2+ .

6. The pigment dispersion of claim 1 , wherein said multivalent cation is Al 3+ .

7. The pigment dispersion of claim 1 , wherein said anionic polymeric binder is selected from the group consisting of polyurethane, waterborne acrylic copolymer, waterborne polyester, and mixtures thereof.

8. The pigment dispersion of claim 7 , wherein said polyurethane is amphoteric.

9. The pigment dispersion of claim 7 , wherein said polyurethane is an amphoteric polyester.

10. The pigment dispersion of claim 7 , wherein said waterborne acrylic copolymer is a random polymer.

11. The pigment dispersion of claim 7 , wherein said waterborne acrylic copolymer is a block polymer.

12. The pigment dispersion of claim 7 , wherein said waterborne acrylic copolymer is a graft polymer.