Abstract: An ink set includes a combination of a first ink and a second ink, the first ink containing 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, the second ink containing a pigment, a polymer having an acid value of 160 mg KOH/g or less, and alkali metal ions, wherein the first ink further contains a compound (A) selected from nonionic surfactants and/or a compound (B) selected from the group consisting of polyethylene glycol with an average molecular weight of 600 to 2,000, ?,?-alkanediol having six carbon atoms, and an imidazolidinone derivative.

Abstract: An ink jet recording apparatus is provided with a plurality of inks and includes a unit configured to perform a recovery operation by suction of inks from a plurality of ink ejection portions using a suction cap, wherein the plurality of inks include an ink set including a combination of at least a first ink and a second ink, the first ink containing (i) a self-dispersion pigment having at least one hydrophilic group directly or through another atomic group bonded to the surface of the pigment, and (ii) ammonium ions, the second ink containing a pigment, a polymer having an acid value of 160 mg KOH/g or less, and alkali metal ions, and the suction cap used in the recovery operation is individually provided for each of the first ink and the second ink.

Abstract: Provided is an aqueous ink with high storage stability and scratch resistance at such a high level that the coloring material of an image is not scraped off even when lightly touched with a sharp product. The aqueous ink includes a water-insoluble coloring material and plural polymers. The plural polymers include a polymer A which relatively contributes to dispersion of the water-insoluble coloring material and a polymer B which does not relatively contribute to the dispersion of the water-insoluble coloring material compared to the polymer A. The polymer A includes a block copolymer having an acid value of 120 mgKOH/g to 180 mgKOH/g and having an ethylene oxide group as a nonionic group. The polymer B has an acid value of 150 mgKOH/g or less and a hydrogen bond parameter (?h) of the polymer obtained by solubility parameters of monomers constituting the polymer of 1.0 cal0.5/cm1.5 or more and 3.2 cal0.5/cm1.5 or less.

Abstract: An ink jet recording apparatus is provided with a plurality of inks and includes a unit configured to perform a recovery operation by suction of inks from a plurality of ink ejection portions using a suction cap, wherein the plurality of inks include an ink set including a combination of at least a first ink and a second ink, the first ink containing (i) a self-dispersion pigment having at least one hydrophilic group directly or through another atomic group bonded to the surface of the pigment, and (ii) ammonium ions, the second ink containing a pigment, a polymer having an acid value of 160 mg KOH/g or less, and alkali metal ions, and the suction cap used in the recovery operation is individually provided for each of the first ink and the second ink.

Abstract: An ink set includes a combination of a first ink and a second ink, the first ink containing 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, the second ink containing a pigment, a polymer having an acid value of 160 mg KOH/g or less, and alkali metal ions, wherein the first ink further contains a compound (A) selected from nonionic surfactants and/or a compound (B) selected from the group consisting of polyethylene glycol with an average molecular weight of 600 to 2,000, a,w-alkanediol having six carbon atoms, and an imidazolidinone derivative.

Abstract: Provided is an aqueous ink with high storage stability and scratch resistance at such a high level that the coloring material of an image is not scraped off even when lightly touched with a sharp product. The aqueous ink includes a water-insoluble coloring material and plural polymers. The plural polymers include a polymer A which relatively contributes to dispersion of the water-insoluble coloring material and a polymer B which does not relatively contribute to the dispersion of the water-insoluble coloring material compared to the polymer A. The polymer A includes a block copolymer having an acid value of 120 mgKOH/g to 180 mgKOH/g and having an ethylene oxide group as a nonionic group. The polymer B has an acid value of 150 mgKOH/g or less and a hydrogen bond parameter (?h) of the polymer obtained by solubility parameters of monomers constituting the polymer of 1.0 cal0.5/cm1.5 or more and 3.2 cal0.5/cm1.5 or less.