Patent ID: 7704575

Claim:
An ink-jet printing system, comprising: a) a print medium having an ink-receiving layer, the ink receiving layer being selected from the group consisting of a metal oxide particulate-based coating, a semi-metal oxide particulate-based coating, and a polymeric swellable coating; and b) an ink-jet ink configured for printing on the ink-receiving layer, said ink-jet ink comprising: i) a liquid vehicle, ii) a water soluble dye, and iii) an amine anti-bronzing agent that is at least partially protonated when the ink-jet ink is printed on the ink-receiving layer, said anti-bronzing agent being present at from about 0.2 wt % to 30 wt % and in an effective concentration to at least reduce bronzing of the ink-jet ink printed on the ink-receiving layer, wherein the amine anti-bronzing agent is selected from the group consisting of ethylamines, ammonia, pyridines, naphthalenes, morpholines, amino acids, and mixtures thereof, and wherein (a) the amine anti-bronzing agent has a pKa value no more than 1 pH unit less than the pH value of the ink-jet ink printed on the ink-receiving layer, or (b) the amine anti-bronzing agent has a pKa value that is greater than a pH value of the ink-receiving layer.