Pigment particles containing a vinyl group are encapsulated by a cross-linked polymer, wherein the polymer has a dielectric constant of 2.8 or more. An inkjet ink containing the pigment particles is also described.

Pigment particles containing a vinyl group are encapsulated by a cross-linked polymer, wherein the polymer has a dielectric constant of 2.8 or more. An inkjet ink containing the pigment particles is also described.

An ink composition includes colorant, hydroxylated and non-hydroxylated co-solvents, and water. A weight percent ratio of hydroxylated to non-hydroxylated co-solvents ranges from 46:54 to about 62:38. The composition also includes an acid and a polyurethane copolymer binder. The acid is selected from the group consisting of oleic acid, linoleic acid, undecanoic acid, dodecanoic acid, tridecanoic acid, and combinations thereof. The binder is formed from the polymerization of a diisocyanate and at least three diols including a first diol containing a hydrophilic stabilizing group, and a second diol having less than 8 atoms in a backbone chain between two hydroxyl groups. A mole percentage of the second diol is at least 30% of a total mole percentage of diol monomers in the binder. An acid number of the binder ranges from 50 to 75. The composition also includes lithium present in an amount ranging from about 50 to about 400 ppm.

An ink-jet ink set includes a black ink containing carbon black; a cyan ink containing a first cyan dye; a magenta ink containing a first magenta dye; a yellow ink containing a first yellow dye; and a gray ink containing a second cyan dye, a second magenta dye, and a second yellow dye. The cyan ink, the magenta ink, the yellow ink, and the gray ink have a ROD of 65% or more, the ROD being defined by Equation (A). The gray ink has an OD value of 1.40 to less than 2.30, the OD value being defined by Equation (B).

An ink set includes a metallic ink composition containing a metal pigment and at least one curable ink composition selected from the group consisting of a chromatic ink composition, a black ink composition, and a white ink composition.

A process for printing on a water-soluble material using a self-dispersible pigment which comprises a carboxy-functional dispersant crosslinked around a pigment core by a crosslinking agent having at least two groups selected from oxetane, carbodiimide, hydrazide, oxazoline, aziridine, isocyanate, N-methylol, keteneimine, isocyanurate and epoxy groups. Also inks, ink-sets, printed material and ink-jet printers.

A process for printing on a water-soluble material using a self-dispersible pigment which comprises a carboxy-functional dispersant crosslinked around a pigment core by a crosslinking agent having at least two groups selected from oxetane, carbodiimide, hydrazide, oxazoline, aziridine, isocyanate, N-methylol, keteneimine, isocyanurate and epoxy groups. Also inks, ink-sets, printed material and ink-jet printers.

An ink composition includes a colorant, a co-solvent, a surfactant system, and water. The surfactant system consists of an acid, lithium, and a non-ionic surfactant. The acid is selected from the group consisting of oleic acid, linoleic acid, undecanoic acid, dodecanoic acid, tridecanoic acid, and combinations thereof. The non-ionic surfactant includes a hydrophilic head group to interact with the lithium and a hydrophobic tail to not sterically hinder formation of an anti-evaporative layer to be formed by the surfactant system. The non-ionic surfactant also excludes any ethyleneoxy groups.

An ink composition includes a colorant, a co-solvent, a surfactant system, and water. The surfactant system consists of an acid, lithium, and a non-ionic surfactant. The acid is selected from the group consisting of oleic acid, linoleic acid, undecanoic acid, dodecanoic acid, tridecanoic acid, and combinations thereof. The non-ionic surfactant includes a hydrophilic head group to interact with the lithium and a hydrophobic tail to not sterically hinder formation of an anti-evaporative layer to be formed by the surfactant system. The non-ionic surfactant also excludes any ethyleneoxy groups.

A problem to be solved by the present invention is to provide an ink jet printing ink which can produce a printed matter having a high optical density and excellent rub fastness even when printed on plain paper and which has excellent storage stability and resolubility. The inventors solved the problem by an ink jet printing ink including an aqueous medium, a dispersion (A), and a dispersion (B). The dispersion (A) contains a pigment (a) and a dispersing resin for pigment, and the volume-average particle diameter of the dispersion (A) is 70 nm or more and less than 90 nm. The dispersion (B) contains a self-dispersed pigment (b), and the volume-average particle diameter of the dispersion (B) is 160 nm or more and 210 nm or less. The mass ratio [dispersion (A)/dispersion (B)] between the dispersion (A) and the dispersion (B) is 1.5 to 9.