An ink set includes a pigment ink, containing a pigment, and a dye ink containing the compound represented by formula (y-1) below or a salt thereof. ##STR00001##

An ink set includes a pigment ink, containing a pigment, and a dye ink containing the compound represented by formula (y-1) below or a salt thereof. ##STR00001##

An ink set includes a pigment ink, containing a pigment, and a dye ink containing the compound represented by formula (y-1) below or a salt thereof.

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An ink set includes a pigment ink, containing a pigment, and a dye ink containing the compound represented by formula (y-1) below or a salt thereof.

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An object that is to be achieved by the present invention is to provide an azo pigment having excellent transparency, suitable dispersibility, and a low viscosity, an ink, and the like. An azo pigment according to the present invention has a zeta potential of 80 to 30 mV in isopropanol (IPA). The content of a metal element in the azo pigment is preferably 0.05 to 2.00 parts by mass relative to 100 parts by mass of the azo pigment. The metal element is preferably an iron element. The ratio (Fe/C) of the concentration Fe (atomic %) of an iron element in the surfaces of particles of the azo pigment to the concentration C (atomic %) of a carbon element in the surfaces of the particles of the azo pigment which are determined by X-ray photoelectron spectroscopy is preferably 0.20 or less.

Provided are a pigment dispersion liquid including a pigment, a polymer dispersant, and water, in which the pigment is a pigment including a compound represented by General Formula (1) as described in the specification, a tautomer thereof, or a salt of the compound or the tautomer, and the polymer dispersant includes a polymer compound having a repeating unit represented by General Formula (2-1) and a repeating unit represented by General Formula (2-2) as described in the specification, and having a structure represented by General Formula (3) introduced into at least one terminal of the main chain; and an inkjet ink including this pigment dispersion liquid.

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In General Formula (3), L represents a linking group; R.sub.4 represents a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, or a substituted or unsubstituted heterocyclic group; and the symbol * represents a linking bond.

Provided are a pigment dispersion liquid including a pigment, a polymer dispersant, and water, in which the pigment is a pigment including a compound represented by General Formula (1) as described in the specification, a tautomer thereof, or a salt of the compound or the tautomer, and the polymer dispersant includes a polymer compound having a repeating unit represented by General Formula (2-1) and a repeating unit represented by General Formula (2-2) as described in the specification, and having a structure represented by General Formula (3) introduced into at least one terminal of the main chain; and an inkjet ink including this pigment dispersion liquid.

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In General Formula (3), L represents a linking group; R.sub.4 represents a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, or a substituted or unsubstituted heterocyclic group; and the symbol * represents a linking bond.