Patent ID: 7417079

Claim:
An inkjet ink set, comprising: a pigment-based black ink including a self-dispersed black pigment, at least one cosolvent, water, optionally at least one water-soluble surfactant/amphiphile, and a hydrolyzed styrene-maleic anhydride copolymer; and at least one dye-based color ink including, a water-soluble dye, at least one cosolvent, water, and at least one of multivalent salts or organic acids; wherein said hydrolyzed styrene-maleic anhydride copolymer interacts with said multivalent salts or with said organic acids by rendering said copolymer in said pigment-based black ink insoluble by transforming said copolymer into a water-insoluble protonated form and thereby improving black-to-color bleed; wherein said organic acids are selected from the group consisting of: polyacrylic, acetic, glycolic, malonic, malic, maleic, ascorbic, succinic, glutaric, fumaric, citric, tartaric, lactic, sulfonic, ortho-phosphoric acids and mixtures thereof; wherein no bleed-controlling polymer besides the hydrolyzed styrene-maleic anhydride copolymer is present in the pigment-based black ink; and wherein no dispersible black pigment is present in said pigment-based black ink.