Patent ID: 7066590

Claim:
An ink-jet printing apparatus, comprising: a printhead portion including an underprinting fixer fluid comprising a cationic polymer and a printhead portion including an ink composition comprising an anionic component, the anionic component comprising a water-soluble anionic binder and a water-soluble dye, the anionic binder comprising polymers having a complexing group, the complexing group being selected from the group consisting of Ethylene Diamine Tetraacetic Acid, Acetyl Acetonate Maleic Anhydride, an Acrylate and combinations thereof; wherein the cationic polymer is a polyelectrolyte selected from the group consisting of R 1 R 2 R 3 R 4 N + ; R 1 R 2 R 3 R 4 P + and R 1 R 2 R 3 R 4 As + , and where R is H, alkyl or other organic substituent, and where the weight average molecular weight of the polyelectrolyte is from 2000 up to 10,000 and wherein the cationic polymer is in solution with non-polymeric cations selected from the group consisting of calcium ions, aluminum ions, barium ions, strontium ions, zinc ions, magnesium ions and titanium ions; and wherein, when the ink composition is printed on a medium over the fixer fluid printed on the medium, the ink composition and fixer fluid together form an amorphous viscous fluid, the viscous fluid having a viscosity greater than the ink composition.