Abstract: To provide an ink jet ink that produces an image having high optical density, scratch resistance, and highlighter resistance, has excellent ink ejection stability, and can reduce image deflection caused by face wetting. The ink jet ink contains a polyurethane polymer and a self-dispersing pigment. The polyurethane polymer has units derived from a polyisocyanate, a polyol having no acid group, and a diol having an acid group. The molar ratio of the percentage of the urethane bond in the polyurethane polymer to the percentage of the urea bond in the polyurethane polymer is 85.0/15.0 or more and 100.0/0 or less.

Abstract: Provided is a set of a reaction liquid that has a buffering action against pH change and exhibits a pH of 3.5 or more and 5.5 or less, and an ink that has a higher pH than the reaction liquid. The ink comprises a pigment to a surface of a pigment particle of which a basic group that forms a cation form at the pH of the reaction liquid is bonded. The pigment does not have an acidic group having a pKa equal to or less than the pH of the reaction liquid. The pigment is dispersed by a water-soluble polymer that has an acidic group having a pKa equal to or more than the pH of the reaction liquid and equal to or less than the pH of the ink.

Abstract: The invention provides an aqueous ink comprising a polymer having hydroxyl groups and a pigment, which can provide images excellent in scratch resistance and highlighter resistance and can inhibit the seeping out phenomenon of the polymer and the deterioration of ejection characteristics even when it is stored for a long period of time. The aqueous ink comprises a polymer having hydroxyl groups, a pigment and a water-soluble organic solvent, wherein the water-soluble organic solvent comprises a polyhydric alcohol having a value of number of hydroxyl groups/number of carbon atoms in its molecule of 0.50 or less.

Abstract: An aqueous ink comprising a polymer having hydroxyl groups and a pigment, which can provide images excellent in scratch resistance and highlighter resistance and can inhibit the seeping out phenomenon of the polymer and the deterioration of ejection characteristics even when it is stored for a long period of time. The aqueous ink comprises a polymer having hydroxyl groups, a pigment and a water-soluble organic solvent, wherein the water-soluble organic solvent comprises a poor medium for a polymer that is not adsorbed on the pigment (out of the polymer having hydroxyl groups), and wherein when the segment constituting the polymer that is not adsorbed on the pigment (out of the polymer having hydroxyl groups) is comprised of a segment A having hydroxyl groups and a segment B having no hydroxyl group, at least one of the poor medium is a good medium for either one of the segment A and the Segment B.

Abstract: The present invention preferably provides an ink including an organic pigment, a water-soluble resin and a surfactant that allows images having high color developability to be obtained independently of the type of recording medium, even when a small amount of ink is applied. Preferably, the organic pigment is a phosphonic acid-type self-dispersible pigment, the acid value of the water-soluble resin is 100 mg KOH/g to 160 mg KOH/g, the surfactant is an ethylene oxide adduct of a higher alcohol selected from the group consisting of a linear primary alcohol, a linear secondary alcohol and an isoalkyl alcohol, the HLB value of the surfactant as determined by the Griffin method is 13.0 or more, and the mass ratio of the content (% by mass) of the surfactant in the ink to the content (% by mass) of the water-soluble resin in the ink is 0.07 to 0.70.

Abstract: A set of an ink containing a self-dispersible pigment and a water-soluble resin, which is a copolymer having a unit derived from (meth)acrylic acid, and a reaction liquid containing a surfactant, which is an ethylene oxide adduct of a higher alcohol of a linear primary or secondary alcohol or an isoalkyl alcohol and has a HLB value of 13.0 or more determined by the Griffin method, and having buffering ability in an acid region. Content of the surfactant in the reaction liquid is 0.20 times or more in terms of mass ratio as much as total content of the pigment and water-soluble resin.

Abstract: A set of an ink containing a pigment dispersed by a water-soluble resin and having the surface tension of 38 mN/m or less and a reaction liquid containing a polyvalent metal ion and a surfactant, which is an ethylene oxide adduct of a higher alcohol of a linear primary or secondary alcohol or an isoalkyl alcohol, and has a HLB value of 13.0 or more as determined by the Griffin method. The content of the polyvalent metal ion in the reaction liquid is 10.0 times or more in terms of molar ratio as much as an amount of an acidic group derived from the water-soluble resin in the ink and the content of the surfactant in the reaction liquid is 0.15 times or more in terms of mass ratio as much as the total content of the pigment and water-soluble resin in the ink.

Abstract: An ink jet ink contains a polyurethane polymer and a pigment. The polyurethane polymer has units derived from a polyisocyanate, a polyether polyol having no acid group, and a diol having an acid group. The pigment is dispersed using a polymer other than the polyurethane polymer. The molar ratio of the percentage of the urethane bond in the polyurethane polymer to the percentage of the urea bond in the polyurethane polymer is 85.0/15.0 or more and 100.0/0 or less.

Abstract: An ink jet ink contains a polyurethane polymer and a pigment. The polyurethane polymer has units derived from a polyisocyanate, a polyether polyol having no acid group, and a diol having an acid group. The pigment is dispersed using a polymer other than the polyurethane polymer. The ratio of the percentage of the urethane bond in the polyurethane polymer to the percentage of the urea bond in the polyurethane polymer is 85.0/15.0 or more and 98.5/1.5 or less.

Abstract: The invention provides an aqueous ink comprising a polymer having hydroxyl groups and a pigment, which can provide images excellent in scratch resistance and highlighter resistance and can inhibit the seeping out phenomenon of the polymer and the deterioration of storage stability and ejection characteristics even when it is stored for a long period of time. The aqueous ink comprises a polymer having hydroxyl groups and a pigment, wherein a proportion of a content of a polymer that is not adsorbed on the pigment out of the polymer having hydroxyl groups to the content of the pigment in the ink is 2.0 mass % or more, and a content (mass %) of the polymer that is not adsorbed on the pigment out of the polymer having hydroxyl groups is 0.20 mass % or less based on the total mass of the ink.

Abstract: An aqueous ink to be used together with a pigment ink containing a pigment and a polymer, wherein the aqueous ink contains a reactive component for destabilizing the dispersion state of the pigment, the dynamic surface tension of the aqueous ink at a lifetime of 30 milliseconds is 41 mN/m or more, and the dynamic surface tension of the aqueous ink at a lifetime of 500 milliseconds is from 28 mN/m or more to 38 mN/m or less as determined by a maximum bubble pressure method.

Abstract: An aqueous ink used together with a black ink containing a self-dispersion pigment, wherein the aqueous ink contains a reactive component for destabilizing the dispersion state of the self-dispersion pigment, the dynamic surface tension of the aqueous ink at a lifetime of 30 milliseconds is 41 mN/m or more, and the dynamic surface tension of the aqueous ink at a lifetime of 500 milliseconds is from 28 mN/m or more to 38 mN/m or less as determined by a maximum bubble pressure method.

Abstract: An ink set is provided which can suppress bleeding irrespective of the type of recording medium. The ink set includes a plurality of aqueous inks each containing a dye, and has at least a first aqueous ink containing a dye, wherein the difference between the dynamic surface tension of the first aqueous ink at a lifetime of 50 milliseconds and the dynamic surface tension of the first aqueous ink at a lifetime of 500 milliseconds is 7 mN/m or more; and, between the first aqueous ink and at least one type of aqueous ink except the first aqueous ink included in the ink set, dynamic surface tension ?a (mN/m) of an ink A having relatively higher lightness at a lifetime of 500 milliseconds and dynamic surface tension ?b (mN/m) of an ink B having relatively lower lightness at a lifetime of 500 milliseconds satisfy ?5?(?a??b)?3.

Abstract: The invention provides an aqueous ink comprising a polymer having hydroxyl groups and a pigment, which can provide images excellent in scratch resistance and highlighter resistance and can inhibit the seeping out phenomenon of the polymer and the deterioration of storage stability and ejection characteristics even when it is stored for a long period of time. The aqueous ink comprises a polymer having hydroxyl groups and a pigment, wherein a proportion of a content of a polymer that is not adsorbed on the pigment out of the polymer having hydroxyl groups to the content of the pigment in the ink is 2.0 mass % or more, and a content (mass %) of the polymer that is not adsorbed on the pigment out of the polymer having hydroxyl groups is 0.20 mass % or less based on the total mass of the ink.

Abstract: An ink jet recording ink tank includes: an ink retention member, which to hold ink exerts a negative pressure through capillary force; and ink, which is retained in the ink retention member, for which a dynamic surface tension in a lifetime of 50 msec, obtained by a maximum bubble pressure method, is higher than an interfacial tension of the ink retention member, a dynamic surface tension in a lifetime of 5000 msec is lower than the interfacial tension of the ink retention member, and a difference between the dynamic surface tension in the lifetime of 50 msec and the dynamic surface tension in the lifetime of 5000 msec is equal to or greater than 8 mN/m.

Abstract: Provided is a set of a reaction liquid that has a buffering action against pH change and exhibits a pH of 3.5 or more and 5.5 or less, and an ink that has a higher pH than the reaction liquid. The ink comprises a pigment to a surface of a pigment particle of which a basic group that forms a cation form at the pH of the reaction liquid is bonded. The pigment does not have an acidic group having a pKa equal to or less than the pH of the reaction liquid. The pigment is dispersed by a water-soluble polymer that has an acidic group having a pKa equal to or more than the pH of the reaction liquid and equal to or less than the pH of the ink.

Abstract: The invention provides an aqueous ink comprising a polymer having hydroxyl groups and a pigment, which can provide images excellent in scratch resistance and highlighter resistance and can inhibit the seeping out phenomenon of the polymer and the deterioration of storage stability and ejection characteristics even when it is stored for a long period of time. The aqueous ink comprises a polymer having hydroxyl groups and a pigment, wherein a proportion of a content of a polymer that is not adsorbed on the pigment out of the polymer having hydroxyl groups to the content of the pigment in the ink is 2.0 mass % or more, and a content (mass %) of the polymer that is not adsorbed on the pigment out of the polymer having hydroxyl groups is 0.20 mass % or less based on the total mass of the ink.

Abstract: An aqueous ink contains at least an aqueous medium, a surfactant, and a dye. The aqueous medium includes only water and at least one water-soluble organic compound(s) and the static surface tension of the aqueous medium is from 45 mN/m or more to 57 mN/m or less. The dynamic surface tension of the aqueous ink satisfies the following conditions: (1) The dynamic surface tension of the aqueous ink at a lifetime of 50 milliseconds is from 42 mN/m or more to less than 49 mN/m; (2) The dynamic surface tension of the aqueous ink at a lifetime of 500 milliseconds is from 28 mN/m or more to 38 mN/m or less; and (3) A difference between the dynamic surface tension of the aqueous ink at a lifetime of 50 milliseconds and the dynamic surface tension of the aqueous ink at a lifetime of 500 milliseconds is 7 mN/m or more.

Abstract: Novel conditions in the physical properties of an ink have been found out to provide an aqueous ink, which can give a high image density and achieve excellent fixing ability. The aqueous ink comprises at least water, a water-soluble organic solvent, a surfactant and a coloring material, wherein the dynamic surface tension at a lifetime of 50 milliseconds as determined by a maximum bubble pressure method is 49 mN/m or more, and the dynamic surface tension at a lifetime of 5,000 milliseconds as determined by the maximum bubble pressure method is 38 mN/m or less.

Abstract: An aqueous ink contains at least an aqueous medium, a surfactant, and a dye. The aqueous medium includes only water and at least one water-soluble organic compound(s) and the static surface tension of the aqueous medium is from 45 mN/m or more to 57 mN/m or less. The dynamic surface tension of the aqueous ink satisfies the following conditions: (1) The dynamic surface tension of the aqueous ink at a lifetime of 50 milliseconds is from 42 mN/m or more to less than 49 mN/m; (2) The dynamic surface tension of the aqueous ink at a lifetime of 500 milliseconds is from 28 mN/m or more to 38 mN/m or less; and (3) A difference between the dynamic surface tension of the aqueous ink at a lifetime of 50 milliseconds and the dynamic surface tension of the aqueous ink at a lifetime of 500 milliseconds is 7 mN/m or more.