An ink set includes an ink A including water, a first organic solvent, and a first pigment and an ink B including water, a second organic solvent, a second pigment, and a urethane resin particle. The first organic solvent includes at least one of N,N-dimethyl-β-buthoxy propionamide, N,N-dimethyl-β-methoxy propionamide, and 3-ethyl-3-hydroxymethyl oxetane and has a mixing solubility parameter A of 10.00 to less than 13.00 and the second organic solvent has a mixing solubility parameter B of 13.00 to 16.00.

A non-Newtonian photo-curable ink composition that comprises a structured network forming agent in an amount ranging from about 0.1 wt % to about 20 wt % by total weight of the ink composition; a salt in an amount ranging from about 0.05 wt % to about 20 wt % by total weight of the ink composition; an organic solvent; a photo-initiator; and a polymerizable material; wherein the ink composition has a first dynamic viscosity ranging from 25 cps to 10,000 cps at a first state and a second dynamic viscosity ranging from 1 cps to 50 cps at a second state. Also described herein is a method for making such non-Newtonian photo-curable ink composition and a method for producing printed images using such non-Newtonian photo-curable ink composition.

A non-Newtonian photo-curable ink composition that includes a metal oxide/alkoxysilane complex in an amount ranging from about 0.1 wt % to about 10 wt %, a salt in an amount ranging from about 0.05 wt % to about 20 wt %, a photo-initiator, an organic solvent, and water, wherein the ink composition has a first dynamic viscosity ranging from 25 cps to 10,000 cps at a first sate and a second dynamic viscosity ranging from 1 cps to 50 cps at a second state. Also described herein is a method for making such non-Newtonian photo-curable ink composition and a method for producing printed images using such non-Newtonian pho to-curable ink composition.

A non-Newtonian photo-curable ink composition that includes a metal oxide/alkoxysilane complex in an amount ranging from about 0.1 wt % to about 10 wt %, a salt in an amount ranging from about 0.05 wt % to about 20 wt %, a photo-initiator, an organic solvent, and water, wherein the ink composition has a first dynamic viscosity ranging from 25 cps to 10,000 cps at a first sate and a second dynamic viscosity ranging from 1 cps to 50 cps at a second state. Also described herein is a method for making such non-Newtonian photo-curable ink composition and a method for producing printed images using such non-Newtonian pho to-curable ink composition.

An object is to provide an aqueous inkjet ink composition offering excellent high-gap discharge stability, antifouling property, adhesion, drying property, abrasion resistance, discharge stability, and preservation stability, even when printed on nonabsorbent media. As a solution, an aqueous inkjet ink composition is provided that contains a pigment, an alkali-soluble resin, a polyolefin resin emulsion, a basic compound, an aqueous medium, and a surfactant, wherein the glass transition temperature of the alkali-soluble resin is 40 to 100° C., the average grain size of the polyolefin resin emulsion is 5 to 300 nm, the solids content of the polyolefin resin emulsion is 0.5 to 5.0 percent by mass in the aqueous inkjet ink composition, and the surfactant contains at least an acetylenediol-based surfactant.

An object is to provide an aqueous inkjet ink composition offering excellent high-gap discharge stability, antifouling property, adhesion, drying property, abrasion resistance, discharge stability, and preservation stability, even when printed on nonabsorbent media. As a solution, an aqueous inkjet ink composition is provided that contains a pigment, an alkali-soluble resin, a polyolefin resin emulsion, a basic compound, an aqueous medium, and a surfactant, wherein the glass transition temperature of the alkali-soluble resin is 40 to 100° C., the average grain size of the polyolefin resin emulsion is 5 to 300 nm, the solids content of the polyolefin resin emulsion is 0.5 to 5.0 percent by mass in the aqueous inkjet ink composition, and the surfactant contains at least an acetylenediol-based surfactant.

The present invention provides an aqueous pigment dispersion including at least a pigment, colloidal silica, bio-nanofibers having an average diameter of 1 nm to 100 nm and an aspect ratio of 100 or more, an anionic group-containing organic polymer compound, and also provides an aqueous ink. The bio-nanofibers are preferably cellulose nanofibers or chitosan nanofibers, and the ratio between the pigment, the colloidal silica, and the bio-nanofibers preferably satisfies (1) colloidal silica/pigment=1/100 to 20/100 or (2) colloidal silica/bio-nanofibers=1/2 to 10/1 and (3) bio-nanofibers/pigment=1/100 to 15/100.

The present invention provides an aqueous pigment dispersion including at least a pigment, colloidal silica, bio-nanofibers having an average diameter of 1 nm to 100 nm and an aspect ratio of 100 or more, an anionic group-containing organic polymer compound, and also provides an aqueous ink. The bio-nanofibers are preferably cellulose nanofibers or chitosan nanofibers, and the ratio between the pigment, the colloidal silica, and the bio-nanofibers preferably satisfies (1) colloidal silica/pigment=1/100 to 20/100 or (2) colloidal silica/bio-nanofibers=1/2 to 10/1 and (3) bio-nanofibers/pigment=1/100 to 15/100.

An ink set includes an inkjet ink and a recording head filling liquid. The inkjet ink contains a pigment, a pigment covering resin, and water. The recording head filling liquid contains polyethylene glycol, a nonionic surfactant, and water. The recording head filling liquid has a viscosity of at least 3 mPa.Math.s and no greater than 10 mPa.Math.s. The polyethylene glycol has a mass average molecular weight of at least 170 and no greater than 300. A percentage content of the polyethylene glycol in the recording head filling liquid is at least 7.0% by mass and no greater than 55.0% by mass. The pigment covering resin includes a styrene-acrylic resin.

An ink set includes an inkjet ink and a recording head filling liquid. The inkjet ink contains a pigment, a pigment covering resin, and water. The recording head filling liquid contains polyethylene glycol, a nonionic surfactant, and water. The recording head filling liquid has a viscosity of at least 3 mPa.Math.s and no greater than 10 mPa.Math.s. The polyethylene glycol has a mass average molecular weight of at least 170 and no greater than 300. A percentage content of the polyethylene glycol in the recording head filling liquid is at least 7.0% by mass and no greater than 55.0% by mass. The pigment covering resin includes a styrene-acrylic resin.