The invention relates to the use of pigment mixtures which contain at least one pigment of formulas (la) and (lb), wherein variables X.sup.1, X.sup.2, X.sup.3, X.sup.4, Y.sup.1, Y.sup.2, Z.sup.1 and Z.sup.2 are as ##STR00001##
defined and wherein the pigment mixtures are useful as dyes in printing methods.

The invention relates to the use of pigment mixtures which contain at least one pigment of formulas (la) and (lb), wherein variables X.sup.1, X.sup.2, X.sup.3, X.sup.4, Y.sup.1, Y.sup.2, Z.sup.1 and Z.sup.2 are as ##STR00001##
defined and wherein the pigment mixtures are useful as dyes in printing methods.

Naphthol AS-pigments of formula (I), wherein R1 represents methyl or C3-C8-alkyl; R2 represents hydrogen or C1-C4-alkyl; Y represents C1-C4-alkyl or C1-C4-alkoxy; and Z represents hydrogen, phenyl, naphthyl, or substituted phenyl or substituted naphthyl, wherein the number of substituents can be 1, 2, 3 or 4 and are selected from the group consisting of halogen, nitro, cyano, C1-C4-alkoxycarbonyl, carbamoyl, C1-C4-alkylcarbamoyl, di(C1-C4)-alkylcarbamoyl, phenylcarbamoyl, sulfamoyl, phenylsulfannoyl, C1-C4-alkylsulfamoyl, di(C1-C4)-alkylsulfamoyl, C1-C4-acylamino, C1-C4-alkyl and C1-C4-alkoxy.

Naphthol AS-pigments of formula (I), wherein R1 represents methyl or C3-C8-alkyl; R2 represents hydrogen or C1-C4-alkyl; Y represents C1-C4-alkyl or C1-C4-alkoxy; and Z represents hydrogen, phenyl, naphthyl, or substituted phenyl or substituted naphthyl, wherein the number of substituents can be 1, 2, 3 or 4 and are selected from the group consisting of halogen, nitro, cyano, C1-C4-alkoxycarbonyl, carbamoyl, C1-C4-alkylcarbamoyl, di(C1-C4)-alkylcarbamoyl, phenylcarbamoyl, sulfamoyl, phenylsulfannoyl, C1-C4-alkylsulfamoyl, di(C1-C4)-alkylsulfamoyl, C1-C4-acylamino, C1-C4-alkyl and C1-C4-alkoxy.

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.

The invention relates to the use of pigment mixtures which contain at least one pigment of formulas (Ia) and (Ib), wherein, independent from each other, X1, X3 represent carbamoyl, C1-C4-alkylcarbamoyl, di(C1-C4)-alkylcarbamoyl, sulfamoyl, phenylsulfamoyl, C1-C4-alkylsulfamoyl or di(C1-C4)-alkylsulfamoyl; X2, X4 represents hydrogen, C1-C4-alkyl, C1-C4-alkoxy, halogen or nitro; Y1, Y2 represents hydrogen, halogen or C1-C4-alkyl, C1-C4-alkoxy or C1-C4-alkoxycarbonyl; and Z1, Z2 represents hydrogen, phenyl, naphthyl, benzimidazolonyl, substituted phenyl or substituted naphthyl, wherein the substituents can be 1, 2, 3 or 4 and selected from the groups halogen, nitro, cyano, C1-C4-alkoxycarbonyl, carbamoyl, C1-C4-alkylcarbamoyl, di(C1-C4)-alkylcarbamoyl, phenylcarbamoyl, sulfamoyl, phenylsulfamoyl, C1-C4-alkylsulfamoyl, di(C1-C4)-alkylsulfamoyl, C1-C4-acylamino, C1-C4-alkyl and C1-C4-alkoxy, and the pigments of formulas (Ia) and (Ib) are different. Said pigment mixtures are used as a dye in printing methods.

Naphthol AS-pigments of formula (I), wherein R1 represents methyl or C3-C8-alkyl; R2 represents hydrogen or C1-C4-alkyl; Y represents C1-C4-alkyl or C1-C4-alkoxy; and Z represents hydrogen, phenyl, naphthyl, or substituted phenyl or substituted naphthyl, wherein the number of substituents can be 1, 2, 3 or 4 and are selected from the group consisting of halogen, nitro, cyano, C1-C4-alkoxycarbonyl, carbamoyl, C1-C4-alkylcarbamoyl, di(C1-C4)-alkylcarbamoyl, phenylcarbamoyl, sulfamoyl, phenylsulfannoyl, C1-C4-alkylsulfamoyl, di(C1-C4)-alkylsulfamoyl, C1-C4-acylamino, C1-C4-alkyl and C1-C4-alkoxy.