Patent ID: 8011777
Filing Date: 2011-09-06
Classification: C09D

Abstract:
1. An ink set comprising: a first ink comprising a self-dispersion pigment having at least one hydrophilic group directly or through another atomic group bonded to the surface of the pigment particle, and ammonium ions; and a second ink comprising a pigment, a polymer having an acid value of 160 mg KOH/g or less, and alkali metal ions, wherein the first ink further comprises (A) a nonionic surfactant selected from the group consisting of a polyoxyethylene cetyl ether and a block copolymer of polyoxyethylene and polyoxypropylene and (B) a compound selected from the group consisting of polyethylene glycol with an average molecular weight of 600 to 2,000, α,ω-alkanediol having six carbon atoms, and an imidazolidinone derivative, and wherein, in the first ink, the ratio of the mass percentage of the nonionic surfactant (A) to the mass percentage of the compound (B), on the basis of the total mass of the ink, is 0.005 or more to 0.5 or less, and wherein the ratio of the ammonium ion concentration (mol/L) in the first ink to the alkali metal ion concentration (mol/L) in the second ink is greater than or equal to 0.33.