Pigment composition and method for producing pigment composition

Abstract

To provide a pigment composition comprising a yellow monoazo pigment and a pigment derivative and having excellent ink ejection stability when used as an ink for inkjet printing.SOLUTION: There is provided a pigment composition comprising a yellow monoazo pigment (P1) and a yellow monoazo pigment (P2) different from the yellow monoazo pigment (P1). The mass ratio of the content (mass%) of the yellow monoazo pigment (P1) to the content (mass%) of the yellow monoazo pigment (P2) is 10 times or more and 1000 times or less. The solubility of the yellow monoazo pigment (P1) in 1,2-hexanediol at 25°C is 10.0 mg / L or less and the solubility of the yellow monoazo pigment (P2) in 1,2-hexanediol at 25°C is 20.0 mg / L or more and 600.0 mg / L or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a pigment composition and a method for producing a pigment composition. [Background technology]

[0002] Pigments have been widely used as coloring materials for image recording, such as inkjet recording, electrophotography, and thermal transfer recording, from the viewpoint of fastness. Among these, yellow monoazo pigments are widely used as yellow pigments. It is known that when yellow monoazo pigments are micronized by a method such as solvent salt milling, they exhibit excellent physical properties such as color development, color tone, tinting strength, and transparency, and also have improved heat resistance and light resistance. The effect of micronizing the pigment to improve properties is particularly pronounced in inkjet inks.

[0003] When a yellow monoazo pigment is micronized as described above, a pigment derivative (synergist) with a chemical structure similar to that of the pigment molecules is sometimes used in combination with the pigment to suppress the crystal growth of the pigment. For example, it has been proposed to use a monoazo compound having a soluble substituent such as a carboxylic acid group or a sulfonic acid group as the pigment derivative (see Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-165920 Summary of the Invention [Problem to be solved by the invention]

[0005] As a result of investigations by the present inventors, it was found that although the pigment particles of a pigment composition comprising a yellow monoazo pigment and a pigment derivative were sufficiently fine, the ejection stability of the ink was likely to decrease, particularly when the composition was used as an inkjet ink.

[0006] Therefore, an object of the present invention is to provide a pigment composition that contains a yellow monoazo pigment and a pigment derivative, and that exhibits excellent ink ejection stability when used as an inkjet ink. Another object of the present invention is to provide a method for producing the pigment composition, which is capable of obtaining the above-mentioned pigment composition. [Means for solving the problem]

[0007] That is, according to the present invention, there is provided a pigment composition containing a yellow monoazo pigment (P1) and a yellow monoazo pigment (P2) different from the yellow monoazo pigment (P1), wherein the content (mass%) of the yellow monoazo pigment (P1) is from 10 to 1,000 times the content (mass%) of the yellow monoazo pigment (P2) in terms of a mass ratio, and the solubility of the yellow monoazo pigment (P1) in 1,2-hexanediol at 25°C is 10.0 mg / L or less, and the solubility of the yellow monoazo pigment (P2) in 1,2-hexanediol at 25°C is from 20.0 mg / L to 600.0 mg / L.

[0008] The present invention also provides a method for producing a pigment composition containing a yellow monoazo pigment (P1) and a yellow monoazo pigment (P2) different from the yellow monoazo pigment (P1), wherein the content (mass%) of the yellow monoazo pigment (P1) is from 10 to 1,000 times the content (mass%) of the yellow monoazo pigment (P2) in terms of mass ratio, the solubility of the yellow monoazo pigment (P1) in 1,2-hexanediol at 25°C is 10.0 mg / L or less, and the solubility of the yellow monoazo pigment (P2) in 1,2-hexanediol at 25°C is from 20.0 mg / L to 600.0 mg / L, and the method comprises the step of subjecting a crude yellow monoazo pigment (P1) to solvent salt milling in the presence of a crude yellow monoazo pigment (P2) to obtain the pigment composition.

[0009] Further, according to the present invention, there is provided a method for producing a pigment composition containing a yellow monoazo pigment (P1) and a yellow monoazo pigment (P2) different from the yellow monoazo pigment (P1), wherein the content (mass%) of the yellow monoazo pigment (P1) is 10 times or more and 1,000 times or less the content (mass%) of the yellow monoazo pigment (P2), in terms of a mass ratio, of the yellow monoazo pigment (P1), the solubility of the yellow monoazo pigment (P1) in 1,2-hexanediol at 25°C is 10.0 mg / L or less, and the solubility of the yellow monoazo pigment (P2) in 1,2-hexanediol at 25°C is 10.0 mg / L or less. a diazo component mixture (a3) ​​containing diazo components (a1) and (a2) obtained by converting an aniline derivative into a diazonium salt, the diazo component mixture (a3) ​​having a solubility in xanediol at 25°C of 20.0 mg / L or more and 600.0 mg / L or less, and a coupler component (b3) which is an acetoacetanilide derivative, to simultaneously synthesize the yellow monoazo pigment (P1) and the yellow monoazo pigment (P2), thereby obtaining a crude pigment composition. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a pigment composition that contains a yellow monoazo pigment and a pigment derivative, and that exhibits excellent ink ejection stability when used as an inkjet ink. Furthermore, according to the present invention, it is possible to provide a method for producing the pigment composition, which is capable of obtaining the above-mentioned pigment composition. DETAILED DESCRIPTION OF THE INVENTION

[0011] The present invention will be described in further detail below with reference to preferred embodiments. In the present invention, inkjet ink may be simply referred to as "ink." A "unit" of a resin refers to the smallest repeating unit constituting the resin, and refers to a structure formed by (co)polymerization of one monomer. In this specification, "(meth)acrylic acid" and "(meth)acrylate" represent "acrylic acid, methacrylic acid" and "acrylate, methacrylate," respectively. Unless otherwise specified, physical property values ​​are values ​​at room temperature (25°C).

[0012] The present inventors have investigated the causes of the deterioration of ink ejection stability, such as in the pigment composition described in Patent Document 1. As a result, they have found that when the pigment dissolved in the liquid medium contained in the ink becomes supersaturated in the ink liquid chamber and ink flow path in the recording head, and foreign matter is generated due to the precipitation of the pigment, the ink ejection speed decreases and the ejection stability decreases. Therefore, the present inventors have focused on the solubility of the pigment and pigment derivative in the ink.

[0013] Generally, yellow monoazo pigments are insoluble or slightly soluble in water unless they contain solubilizing groups, especially carboxylic acid or sulfonic acid groups. However, aqueous inks typically contain water-soluble polar organic solvents such as 1,2-hexanediol, and pigments dissolve in trace amounts in the aqueous ink medium due to their solubility in these polar organic solvents. However, their solubility is so low that it is difficult to directly measure their solubility in the aqueous ink medium. On the other hand, the solubility of pigments in water-soluble polar organic solvents such as 1,2-hexanediol is relatively large and therefore measurable, and their solubility in the aqueous ink medium is thought to be proportional to this. Therefore, it is possible to compare the solubility of aqueous inks in the aqueous ink medium using their solubility in water-soluble polar organic solvents.

[0014] Therefore, the inventors selected 1,2-hexanediol, which is believed to have the highest solubility for yellow monoazo pigments, from among the water-soluble polar organic solvents contained in inks. They measured the solubility of the yellow monoazo pigment in 1,2-hexanediol at 25°C and used this as an index of solubility in the ink medium. As a result, they found that it is effective to use a pigment composition that combines a yellow monoazo pigment with a low solubility as a main pigment and a different yellow monoazo pigment with a moderately high solubility as a pigment derivative. Specifically, they found that using this pigment composition in inks suppresses the deposition of foreign matter in the ink chambers and ink flow paths within the recording head, thereby preventing a decrease in ink ejection speed and improving ejection stability.

[0015] Specifically, a yellow monoazo pigment (P1) having a solubility of 10.0 mg / L or less in 1,2-hexanediol at 25°C is used as the main pigment, and a yellow monoazo pigment (P2) having the same solubility of 20.0 mg / L or more and 600.0 mg / L or less is used as the pigment derivative. The inventors have found that a pigment composition combining these pigments in a mass ratio of the content of the yellow monoazo pigment (P1) to the content of the yellow monoazo pigment (P2) of 10 to 1000 times improves the ejection stability of the ink.

[0016] The mechanism by which foreign matter deposition in the ink chambers and ink flow paths within the recording head is suppressed is believed to be as follows. Generally, in a solution, a solute containing trace amounts of impurities has a lower chemical potential than a pure solute containing no impurities, resulting in a higher saturated concentration of the solute. Therefore, a solute containing trace amounts of impurities is thought to have a greater margin for supersaturation and is therefore less likely to deposit. In the present invention, the yellow monoazo pigment (P2) as a pigment derivative is thought to act as a trace impurity in the yellow monoazo pigment (P1) as the main pigment. This action is thought to increase the saturated concentration of the yellow monoazo pigment (P1) in the ink liquid medium, thereby suppressing the deposition of the yellow monoazo pigment (P1). In this case, the precipitation suppression effect is greatest when the solubility of the yellow monoazo pigment (P2) acting as a trace impurity is sufficiently higher than that of the yellow monoazo pigment (P1) as the main pigment. However, if the solubility of the yellow monoazo pigment (P2) as a trace impurity is too high, i.e., if the difference in solubility with respect to the main pigment yellow monoazo pigment (P1) is too large, the similarity between the yellow monoazo pigment (P1) and the yellow monoazo pigment (P2) will decrease, and in that case, the effect of the yellow monoazo pigment (P2) as a pigment derivative will be lost, and the effect of improving the solubility described above will also be reduced.

[0017] <Pigment composition> The pigment composition of the present invention contains a yellow monoazo pigment (P1) as a main pigment and a yellow monoazo pigment (P2) as a pigment derivative different from the yellow monoazo pigment (P1). This pigment composition is an image recording material that can be used for image recording such as inkjet recording, electrophotography, and thermal transfer recording. Specifically, it is an image recording material such as an inkjet ink or an electrophotographic toner, and is obtained by adding components necessary for the image recording material to the pigment composition. Examples of components necessary for the image recording material include a resin, an additive, a liquid medium, and a solvent. The components constituting the pigment composition will be described in detail below.

[0018] (Yellow monoazo pigment (P1)) The pigment composition contains a yellow monoazo pigment (P1) as a primary pigment. The content (mass%) of the yellow monoazo pigment (P1) in the pigment composition is 10 to 1000 times the content (mass%) of the yellow monoazo pigment (P2) in the pigment composition. If this mass ratio is less than 10, the color of the pigment composition may deviate significantly from the color of the primary pigment, yellow monoazo pigment (P1), due to the influence of the color of the secondary pigment, yellow monoazo pigment (P2). On the other hand, if the mass ratio is more than 1000, the effect of suppressing the precipitation of foreign matter may not be obtained. Here, the primary pigment refers to a pigment that occupies a large mass proportion of the pigments contained in the pigment composition, and similarly, the secondary pigment refers to a pigment that occupies a small mass proportion.

[0019] The yellow monoazo pigment (P1) is a monoazo pigment that exhibits a yellow hue and has one azo group or hydrazone group in the molecule, and is a low-solubility yellow monoazo pigment with a solubility of 10.0 mg / L or less in 1,2-hexanediol at 25°C. Specific examples of the yellow monoazo pigment (P1) include CI Pigment Yellow 3, CI Pigment Yellow 65, CI Pigment Yellow 73, CI Pigment Yellow 74, CI Pigment Yellow 120, and CI Pigment Yellow 151. The yellow monoazo pigment (P1) can be used alone or in combination of two or more.

[0020] As the yellow monoazo pigment (P1), an acetoacetanilide-based monoazo pigment is preferred, and CI Pigment Yellow 74 (hereinafter also referred to as "PY74") is more preferred because of its excellent hue and vividness. In this specification, an acetoacetanilide-based monoazo pigment is a monoazo pigment having an acetoacetanilide moiety in the molecular structure of the pigment, and acetoacetanilide-based monoazo pigments also include benzimidazolone-based monoazo pigments.

[0021] More preferably, the yellow monoazo pigment (P1) has a solubility of 2.0 mg / L or less in 1,2-hexanediol at 25° C. The lower the solubility of the yellow monoazo pigment (P1) that is the main pigment, the greater the effect of suppressing the deposition of foreign matter in the ink liquid chamber and ink flow path in the recording head, and the higher the thermal stability of the pigment and the higher its storage stability in the ink.

[0022] Generally, yellow monoazo pigments are synthesized by coupling a diazo component (a1) obtained by converting an aniline derivative into a diazonium salt with a coupler component (b1) such as an acetoacetanilide derivative. Specifically, in the case of CI Pigment Yellow 74, for example, CI Pigment Yellow 74 is synthesized by coupling a diazonium salt of 2-methoxy-4-nitroaniline as the diazo component (a1) with o-acetoacetanisidide as the coupler component (b1).

[0023] (Yellow monoazo pigment (P2)) The pigment composition contains a yellow monoazo pigment (P2) as a pigment derivative. The content (mass%) of the yellow monoazo pigment (P2) in the pigment composition is 0.001 to 0.100 times the content (mass%) of the yellow monoazo pigment (P1) in the pigment composition. If this mass ratio is an extremely small amount less than 0.001, the effect of suppressing the deposition of foreign matter may not be sufficient. On the other hand, if the mass ratio exceeds 0.100, the color of the pigment composition may deviate significantly from the color of the yellow monoazo pigment (P1) as the primary pigment due to the influence of the color of the yellow monoazo pigment (P2) itself as the secondary pigment. The range of the mass ratio "0.001 to 0.100" is equivalent to the reciprocal of the mass ratio, i.e., the content (mass%) of the yellow monoazo pigment (P1) is 10 to 1000 times the content (mass%) of the yellow monoazo pigment (P2).

[0024] The yellow monoazo pigment (P2) is a monoazo pigment that exhibits a yellow hue and has one azo group or hydrazone group in the molecule. It is a monoazo pigment with moderate solubility in 1,2-hexanediol at 25°C of 20.0 mg / L to 600.0 mg / L. Specific examples of the yellow monoazo pigment (P2) include CI Pigment Yellow 1, CI Pigment Yellow 191, and compounds represented by the following chemical formulas (1) to (7). The yellow monoazo pigment (P2) is not limited to the above specific examples, as long as its solubility in 1,2-hexanediol at 25°C is within the range of 20.0 mg / L to 600.0 mg / L. The yellow monoazo pigment (P2) can be used alone or in combination of two or more. In particular, the yellow monoazo pigment (P2) is preferably at least one selected from the group consisting of compounds represented by the following chemical formulas (1) to (7) (hereinafter, sometimes referred to as compounds 1 to 7, respectively).

[0025] TIFF2025180164000001.tif163170

[0026] The yellow monoazo pigment (P2) is preferably an acetoacetanilide-based monoazo pigment, and even more preferably a yellow monoazo pigment (P2) having a solubility in 1,2-hexanediol at 25°C of 30.0 mg / L or more but 300.0 mg / L or less. When the solubility of the yellow monoazo pigment (P2) is within the above range, the difference in solubility with respect to the main pigment, the yellow monoazo pigment (P1), is relatively small, and the yellow monoazo pigment (P1) and the yellow monoazo pigment (P2) are highly similar. This makes the yellow monoazo pigment (P2) more effective as a pigment derivative and also more effective in suppressing the deposition of foreign matter in the ink chambers and ink flow paths within the recording head.

[0027] The yellow monoazo pigment (P2), like the aforementioned yellow monoazo pigment (P1), is synthesized by coupling a diazo component (a2) obtained by converting an aniline derivative into a diazonium salt with a coupler component (b2) such as an acetoacetanilide derivative.

[0028] Specific examples of the aniline derivative used to obtain the diazo component (a2) include 3-aminobiphenyl, 3-amino-4-methoxybiphenyl, 3-amino-4-ethoxybiphenyl, 3-amino-4-isopropoxybiphenyl, 3-amino-4-methylbiphenyl, 3-amino-4-ethylbiphenyl, 3-amino-4-fluorobiphenyl, 3-amino-4-chlorobiphenyl, 3-amino-4-(trifluoromethyl)biphenyl, 3-amino-4-nitrobiphenyl, 4-acetyl-3-aminobiphenyl, 2-amino-4-phenylbenzoate, 4-amino-4-methylbiphenyl, 4-amino-4-methylbenzoate ... Methyl benzoate, ethyl 2-amino-4-phenylbenzoate, 5-amino-2-chlorobiphenyl, 5-amino-2-methoxybiphenyl, 4-aminobiphenyl, 4-amino-3-methoxybiphenyl, 4-amino-3-ethoxybiphenyl, 4-amino-3-methylbiphenyl, 4-amino-3-ethylbiphenyl, 4-amino-3-fluorobiphenyl, 4-amino-3-chlorobiphenyl, 4-amino-3-(trifluoromethyl)biphenyl, 4-amino-3-nitrobiphenyl, 3-acetyl-4-aminobiphenyl, 2-amino-5-phenyl Methyl 2-amino-5-phenylbenzoate, Ethyl 2-amino-5-phenylbenzoate, 4-amino-2'-methoxybiphenyl, 4-amino-4'-nitrobiphenyl, 4-amino-4'-chlorobiphenyl, 4-phenoxyaniline, 4-amino-4'-methyldiphenyl ether, 4-amino-4'-chlorodiphenyl ether, 4-amino-4'-nitrodiphenyl ether, 4-amino-3-methyldiphenyl ether, 4-amino-3-(trifluoromethyl)diphenyl ether, 3-phenoxyaniline, 3-amino-4-methoxydiphenyl ether, 4- Aminobenzophenone, 4-amino-4'-chlorobenzophenone, 4-amino-4'-fluorobenzophenone, 4'-amino-3,4-dimethylbenzophenone, 4-amino-3-nitrobenzophenone, 3-aminobenzophenone, 3'-amino-3,4-dimethylbenzophenone, phenyl 3-aminobenzoate, phenyl 4-aminobenzoate, 3-aminophenyl benzoate, 4-aminophenyl benzoate, 4-chloro-2,5-dimethoxyaniline, 5-chloro-2,4-dimethoxyaniline, 2-chloro-4,5-dimethoxyaniline, 4,Examples of the aniline include 5-dichloro-2-methoxyaniline, 2,4,5-trichloroaniline, 2,4,5-trimethoxyaniline, 2,4-dimethoxyaniline, 2,5-dimethoxyaniline, 3,4-dimethoxyaniline, 2,4-dichloroaniline, 2,5-dichloroaniline, 3,4-dichloroaniline, 4-chloro-2-methoxyaniline, 4-bromo-2-methoxyaniline, 5-chloro-2-methoxyaniline, 2-chloro-4-methoxyaniline, 2-chloro-5-methoxyaniline, 2-fluoro-5-methoxyaniline, 2,5-diethoxyaniline, 2-methoxy-4-isopropoxyaniline, and 2-methoxy-4-isobutoxyaniline.

[0029] Specific examples of the coupler component (b2) include acetanilide, o-acetoacetanisidide, m-acetoacetanisidide, p-acetoacetanisidide, 2'-ethoxyacetoacetanilide, 4'-ethoxyacetoacetanilide, 2'-isopropoxyacetoacetanilide, 2'-tert-butoxyacetoacetanilide, 2',4'-dimethoxyacetoacetanilide, 2',5'-dimethoxyacetoacetanilide, 2'-methylacetoacetanilide, 4'-methylacetoacetanilide, 2',4'-dimethylacetoacetanilide, 2'-ethylacetoacetanilide, 2'-isopropylacetoacetanilide, 2'-n-butylacetoacetanilide, 4'-tert-butylacetoacetanilide, 5'-methylacetoacetanilide, 2'-chloroacetoacetanilide, 5'-chloro-2'-methoxyacetoacetanilide, 4'-chloro-2',5'-dimethoxyacetoacetanilide, 5'-chloro-2',4'-dimethoxyacetoacetanilide, 2'-chloro-4'-methylacetoacetanilide, 2'-chloro-5'-methylacetoacetanilide, 4'-tert-butyl-2'-chloroacetoacetanilide, 4'-chloro-2'-methylacetoacetanilide, 2'-(trifluoromethyl)acetoacetanilide, 4'-(trifluoromethyl)acetoacetanilide, 2'-chloroacetoacetanilide, 3'-chloroacetoacetanilide, 4'-chloroacetoacetanilide, 2',5'-dichloroacetoacetanilide, 2',4',5'-Trichloroacetoacetanilide, 2'-Nitroacetoacetanilide, 4'-Nitroacetoacetanilide, 4'-Chloro-2'-nitroacetoacetanilide, 4'-Methoxy-2'-nitroacetoacetanilide, 2'-Methoxy-4'-nitroacetoacetanilide, 3'-Acetoxyacetoacetanilide, 4'-Acetoxyacetoacetanilide, 4'-Valeryloxyacetoacetanilide, 5'-Acetoxy-2'-methoxyacetoacetanilide, 2'-Acetylacetoacetanilide, 4'-Acetylacetoacetanilide, 2'-Propionylacetoacetanilide, 4'-Acetyl-2'-methoxyacetoacetanilide, Methyl 2-(acetoacetylamino)benzoate, Methyl 3-(acetoacetylamino)benzoate, 4-(acetamido)acetoacetanilide Examples of the acetoacetylaminobenzoic acid include methyl acetoacetylaminobenzoate, ethyl 2-acetoacetylaminobenzoate, butyl 2-acetoacetylaminobenzoate, methyl 3-acetoacetylamino-4-methoxybenzoate, 3-methyl-1-phenyl-5-pyrazolone, 3-methyl-1-p-tolyl-5-pyrazolone, 1-(4-chlorophenyl)-3-methyl-5-pyrazolone, 1-(2-chlorophenyl)-3-methyl-5-pyrazolone, 3-methyl-1-(4-nitrophenyl)-5-pyrazolone, 3-methyl-1-(3'-sulfamidophenyl)-5-pyrazolone, 1-(4'-sulfophenyl)-3-methyl-5-pyrazolone, 1-(3'-sulfophenyl)-3-methyl-5-pyrazolone, and 5-(acetoacetamido)-2-benzimidazolinone.

[0030] (Other additives) In the pigment composition, the surfaces of pigment particles of the pigment composition may be treated with an additive such as a resin, a surfactant, etc. These additives may be used at any stage in preparing the pigment composition, for example, they may be used together with raw materials in the stage of synthesizing the pigment composition, or they may be used during acid pasting, solvent salt milling, dry milling, etc.

[0031] Examples of resins that can be used as additives include rosin-based resins, acrylic resins, styrene-acrylic resins, polyester-based resins, polyamide-based resins, polyurethane-based resins, fluorine-based resins, vinylnaphthalene-acrylic acid-based resins, and styrene-maleic acid-based resins. These resins can be used alone or in combination of two or more. When a resin is used, the content (mass %) of the resin in the pigment composition is preferably 0.1% by mass or more and 40.0% by mass or less, and more preferably 5.0% by mass or more and 30.0% by mass or less, based on the total mass of the pigment.

[0032] Examples of surfactants that can be used as additives include fatty acid salts, alkyl sulfate salts, alkylaryl sulfonates, alkylnaphthalenesulfonates, dialkylsulfonates, dialkylsulfosuccinates, alkyldiaryletherdisulfonates, alkylphosphate salts, polyoxyethylene alkylether sulfates, polyoxyethylene alkylarylether sulfates, naphthalenesulfonic acid formalin condensates, polyoxyethylene alkylphosphate salts, glycerol borate fatty acid esters, polyoxyethyleneglycerol fatty acid esters, polyoxyethylene alkyl ethers, polyoxyethylene alkylaryl ethers, polyoxyethyleneoxypropylene block copolymers, sorbitan fatty acid esters, polyoxyethylenesorbitan fatty acid esters, polyoxyethylenesorbitol fatty acid esters, glycerin fatty acid esters, polyoxyethylene alkylamines, fluorine-based nonionic surfactants, silicone-based nonionic surfactants, alkylamine salts, quaternary amine salts, alkylpyridinium salts, and alkylimidazolium salts. These surfactants can be used alone or in combination of two or more. When a surfactant is used, the content (mass %) of the surfactant in the pigment composition is preferably 0.1 mass % or more and 30.0 mass % or less, and more preferably 1.0 mass % or more and 15.0 mass % or less, based on the total mass of the pigment.

[0033] In one embodiment of the pigment composition, the pigment particles in the pigment composition may be treated with a rosin as an additive. Examples of rosins include rosin, rosin ester, hydrogenated rosin, hydrogenated rosin ester, disproportionated rosin, disproportionated rosin ester, and rosin amine. One of these rosins can be used alone, or two or more can be used in combination. Among rosins, rosin amine is preferred. When rosins are used, the content (mass %) of the rosins in the pigment composition is preferably 0.1% by mass or more and 10.0% by mass or less, and more preferably 0.5% by mass or more and 5.0% by mass or less, based on the total mass of the pigment.

[0034] <Ink> Next, among the pigment compositions described above, inkjet ink will be described in detail. When the pigment composition is used as ink, the ink contains the yellow monoazo pigment (P1) and the yellow monoazo pigment (P2) described in the description of the pigment composition, a liquid medium, and other components used as needed. Each component of the ink will be described below.

[0035] (colorant) The ink contains, as colorants, a yellow monoazo pigment (P1) having a solubility in 1,2-hexanediol of 10.0 mg / L or less at 25°C, and a yellow monoazo pigment (P2) having the same solubility of 20.0 mg / L to 600.0 mg / L. The ink may contain either one type of yellow monoazo pigment (P1) or one type of yellow monoazo pigment (P2) alone, or a combination of two or more types. The total content (mass %) of the yellow monoazo pigment (P1) and the yellow monoazo pigment (P2) in the ink is preferably 0.1% to 15.0% by mass, and more preferably 1.0% to 10.0% by mass, based on the total mass of the ink.

[0036] Examples of pigment dispersion methods include resin-dispersed pigments that use a resin (resin dispersant) as a dispersant, and self-dispersed pigments in which hydrophilic groups are bonded to the pigment particle surface. Other examples include resin-bonded pigments in which organic groups containing a resin are chemically bonded to the pigment particle surface, and microencapsulated pigments in which the pigment particle surface is coated with a resin or the like. Among these, it is preferable to use resin-dispersed pigments in which a resin as a dispersant is physically adsorbed onto the pigment particle surface, rather than resin-bonded pigments or microencapsulated pigments.

[0037] Furthermore, the ink may contain pigments other than the aforementioned pigment compositions (yellow monoazo pigments (P1) and (P2)) as long as the effects of the present invention are not impaired. In particular, it is preferable to contain an azo pigment having a yellow hue. The content (mass %) of the other pigments in the ink is preferably 0.1% by mass or more and 5.0% by mass or less, and more preferably 0.1% by mass or more and 1.0% by mass or less, based on the total mass of the ink.

[0038] (resin) The ink may contain a resin. The resin content (mass %) in the ink is preferably 0.1% to 5.0% by mass, and more preferably 0.3% to 2.0% by mass, based on the total mass of the ink. Of these, the resin content (mass %) in the ink is even more preferably 0.5% to 1.5% by mass, based on the total mass of the ink.

[0039] Resins can be added to inks (i) to stabilize the dispersion state of pigments, i.e., as resin dispersants or their auxiliary agents. Resins can also be added to inks (ii) to improve various properties of the printed image. Since inks preferably contain resin-dispersed pigments, the resin is preferably a resin dispersant. In other words, it is preferable for inks to contain a resin dispersant in addition to the pigment derivatives.

[0040] The resin may be in the form of a block copolymer, a random copolymer, a graft copolymer, or a combination thereof. The resin may be a soluble resin that can be dissolved in a liquid medium, or may be resin particles that are dispersed in a liquid medium. The resin particles do not necessarily contain a colorant.

[0041] As used herein, "a resin is soluble" means that when the resin is neutralized with an alkali equivalent to its acid value, it exists in a liquid medium in a state in which it does not form particles whose particle size can be measured by dynamic light scattering. Whether a resin is soluble or not can be determined according to the following method. First, a liquid (resin solids content: 10% by mass) containing a resin neutralized with an alkali (sodium hydroxide, potassium hydroxide, etc.) equivalent to the acid value is prepared. Next, the prepared liquid is diluted 10 times (by volume) with pure water to prepare a sample solution. When the particle size of the resin in the sample solution is measured by dynamic light scattering, if no particles having the particle size are measured, the resin can be determined to be soluble. The measurement conditions can be, for example, Set Zero: 30 seconds, measurement count: 3, and measurement time: 180 seconds. A particle size distribution measurement device such as a particle size analyzer using dynamic light scattering (e.g., "UPA-EX150" manufactured by Nikkiso) can be used. Of course, the particle size distribution measuring device and measuring conditions to be used are not limited to those described above.

[0042] Examples of resins include acrylic resins, urethane resins, and urea resins. These resins can be used alone or in combination. Among these, acrylic resins are preferred, and acrylic resins having a hydrophilic unit and a hydrophobic unit are more preferred. When using a resin as a resin dispersant for aqueous inks, acrylic resins having a hydrophilic unit derived from (meth)acrylic acid and a hydrophobic unit derived from a monomer having an aliphatic group or an aromatic ring are preferred. It is more preferred to use an acrylic resin having a hydrophilic unit derived from (meth)acrylic acid and a hydrophobic unit derived from at least one monomer of styrene and α-methylstyrene as a resin dispersant. These resin dispersants are suitable because they are particularly prone to interact with pigments.

[0043] The hydrophilic unit is a unit having a hydrophilic group such as an anionic group. The hydrophilic unit can be formed, for example, by polymerizing a hydrophilic monomer having a hydrophilic group. Examples of the hydrophilic group include anionic groups such as a carboxylic acid group, a hydroxy group, and an ethylene oxide group. Examples of the hydrophilic monomer include acidic monomers having a carboxylic acid group such as (meth)acrylic acid, itaconic acid, maleic acid, and fumaric acid, anionic monomers such as anhydrides and salts of these acidic monomers, 2-hydroxyethyl (meth)acrylate, and (poly)ethylene glycol (meth)acrylate. Examples of cations constituting the salts of acidic monomers include ions of lithium, sodium, potassium, ammonium, and organic ammonium. The hydrophobic unit is a unit not having a hydrophilic group such as an anionic group, a hydroxy group, or an ethylene oxide group. The hydrophobic unit can be formed, for example, by polymerizing a hydrophobic monomer not having a hydrophilic group such as an anionic group. Specific examples of hydrophobic monomers include monomers having an aromatic ring, such as styrene, α-methylstyrene, and benzyl (meth)acrylate; and (meth)acrylic acid ester monomers, such as methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate.

[0044] When a resin is used as a resin dispersant for an oil-based ink, examples of the resin include hydroxy group-containing carboxylic acid esters, salts of polyaminoamides and polymeric acid esters, salts of polycarboxylic acids, salts of polar acid esters such as polyaminoamides and sulfuric acid esters, unsaturated acid esters, copolymers of vinylpyrrolidone and alkenes, modified polyurethanes, modified polyacrylates, polyether ester-type anionic surfactants, polyoxyethylene alkyl phosphate esters, and polyester polyamines. Modified polyurethanes and modified polyacrylates include those that are epoxy-modified or acrylic-modified.

[0045] The weight-average molecular weight of the resin is preferably 1,000 to 30,000, more preferably 5,000 to 15,000. In this specification, the weight-average molecular weight of the resin is a polystyrene-equivalent value measured by gel permeation chromatography (GPC). The acid value of the resin is preferably 80 to 250 mgKOH / g, more preferably 100 to 200 mgKOH / g. In this specification, the acid value of the resin can be a value measured by a potentiometric titrator using a potassium hydroxide-ethanol titrant.

[0046] (liquid medium) The ink contains a liquid medium. A water-insoluble organic solvent is preferably used as the liquid medium for the oil-based ink. Examples of water-insoluble organic solvents include hydrocarbon compounds, ketones, ethers, acetate esters, and aromatic compounds. Alternatively, a water-soluble organic solvent, as described below, may be used. One of these organic solvents may be used alone, or two or more may be used in combination as long as they form a single phase. The content (mass %) of the organic solvent in the oil-based ink is preferably 60.0% to 95.0% by mass, and more preferably 80.0% to 95.0% by mass, based on the total mass of the ink.

[0047] The liquid medium for the aqueous ink is preferably water or a mixed solvent of water and a water-soluble organic solvent. Deionized water (ion-exchanged water) is preferably used as the water. The water content (mass %) in the aqueous ink is preferably 50.0% to 95.0% by mass, and more preferably 50.0% to 85.0% by mass, based on the total mass of the ink. The water-soluble organic solvent that can be used to prepare the aqueous ink is not particularly limited as long as it is water-soluble (preferably, one that dissolves in water at any ratio at 25°C). Specific examples include monohydric or polyhydric alcohols, alkylene glycols, glycol ethers, nitrogen-containing polar compounds, and sulfur-containing polar compounds. One of these water-soluble organic solvents can be used alone, or two or more can be used in combination. Among the water-soluble organic solvents, 1,2-hexanediol, which has relatively high pigment solubility, is preferred. The content (mass %) of the water-soluble organic solvent in the aqueous ink is preferably 3.0 mass % or more and 48.0 mass % or less, and more preferably 10.0 mass % or more and 45.0 mass % or less, based on the total mass of the ink.

[0048] (Other additives) In addition to the above components, the ink may contain various additives, such as surfactants, pH adjusters, preservatives, antifungals, antioxidants, reduction inhibitors, evaporation promoters, and chelating agents, as needed. Among these, it is preferable for the ink to contain a surfactant. The content (mass %) of the surfactant in the ink is preferably 0.1% by mass or more and 5.0% by mass or less, and more preferably 0.1% by mass or more and 2.0% by mass or less, based on the total mass of the ink. Examples of surfactants include anionic surfactants, cationic surfactants, and nonionic surfactants.

[0049] (Ink properties) The ink is used in inkjet printing. Therefore, from the viewpoint of reliability, it is preferable to appropriately control its physical properties. Specifically, the surface tension of the ink at 25°C is preferably 10 mN / m or more and 60 mN / m or less, and more preferably 20 mN / m or more and 40 mN / m or less. The surface tension of the ink can be adjusted by appropriately determining the type and content of surfactant in the ink. Furthermore, the viscosity of the ink at 25°C is preferably 1.0 mPa·s or more and 10.0 mPa·s or less. If the ink is aqueous, the pH of the ink at 25°C is preferably 5.0 or more and 10.0 or less.

[0050] <Method of producing pigment composition> The method for producing a pigment composition of the present invention is a method for producing a pigment composition containing a yellow monoazo pigment (P1) and a yellow monoazo pigment (P2) different from the yellow monoazo pigment (P1). As described above, the content (mass %) of the yellow monoazo pigment (P1) in the pigment composition is 10 to 1,000 times the content (mass %) of the yellow monoazo pigment (P2) in terms of mass ratio. Furthermore, the solubility of the yellow monoazo pigment (P1) in 1,2-hexanediol at 25°C is 10.0 mg / L or less, and the solubility of the yellow monoazo pigment (P2) in 1,2-hexanediol at 25°C is 20.0 to 600.0 mg / L.

[0051] The method for producing a pigment composition of the present invention includes the following first step of obtaining a pigment mixture as a pigment composition. Furthermore, the method for producing a pigment composition may, in addition to the first step, optionally include the following second step. Furthermore, the method for producing a pigment composition may, in addition to the first and second steps, optionally include the following third step. [1] A first step of producing a pigment mixture containing a yellow monoazo pigment (P1) and a yellow monoazo pigment (P2). [2] A second step in which the pigment mixture is subjected to a treatment suited to each image recording material. [3] A third step in which the pigment mixture treated in the second step is mixed with other components required for each image recording material.

[0052] <Ink manufacturing method> Among the methods for producing the pigment composition of the present invention, the method for producing an inkjet ink of the present invention will be described in detail below. The method for producing an inkjet ink of the present invention includes the following steps. Each step will be described in detail below. [1] A first step of producing a pigment mixture containing a yellow monoazo pigment (P1) and a yellow monoazo pigment (P2). [2] A second step of producing a pigment dispersion from the pigment mixture obtained in the first step. [3] A third step of preparing ink by mixing the pigment dispersion obtained in the second step with other components necessary for inkjet ink.

[0053] (Step 1: Preparation of pigment mixture) The method for producing a pigment composition includes a first step of producing a pigment mixture containing a yellow monoazo pigment (P1) and a yellow monoazo pigment (P2). In the first step, it is preferable to produce a pigment mixture whose pigment components consist of the yellow monoazo pigment (P1) and the yellow monoazo pigment (P2). From the viewpoint of producing a pigment dispersion, it is preferable that the pigments are finely divided.

[0054] (i) Mixed Coupling Reaction In the first step, the pigment composition (pigment mixture) can be produced, for example, by a so-called "mixed coupling reaction" in which a yellow monoazo pigment (P1) and a yellow monoazo pigment (P2) are simultaneously synthesized in the same system. Specifically, a coupling reaction is carried out using a diazo component mixture (a3) ​​containing diazo components (a1) and (a2) obtained by converting an aniline derivative into a diazonium salt, and a coupler component (b3) that is an acetoacetanilide derivative. Here, the coupler component (b3) refers to a common coupler component when the coupler component (b1) for the yellow monoazo pigment (P1) and the coupler component (b2) for the yellow monoazo pigment (P2) are the same component.

[0055] In this way, by performing a "mixed coupling reaction" using the diazo component mixture (a3) ​​and the common coupler component (b3), a crude pigment composition can be obtained by simultaneously synthesizing the yellow monoazo pigment (P1) and the yellow monoazo pigment (P2). In the step of obtaining the crude pigment composition, a crude pigment composition containing the yellow monoazo pigment (P1) and the yellow monoazo pigment (P2) can be obtained. Preferably, a crude pigment composition consisting of the yellow monoazo pigment (P1) and the yellow monoazo pigment (P2) can be obtained. Furthermore, by coupling the common coupler component (b3), the yellow monoazo pigment (P1) and the yellow monoazo pigment (P2) can be simultaneously synthesized, each having the same molecular structure derived from the coupler. In this case, the resulting yellow monoazo pigment (P1) and the yellow monoazo pigment (P2) have similar molecular structures, and the molecules of both pigments easily interact on the pigment particle surface. This allows for a greater precipitation suppression effect due to solubility control, resulting in a pigment composition with superior ink ejection stability.

[0056] (ii) Solvent salt milling method In the first step, the pigment composition (pigment mixture) can also be produced by wet kneading and grinding a crude mixture of crude yellow monoazo pigment (P1) and crude yellow monoazo pigment (P2) using a solvent salt milling method. In this case, the crude mixture may be a mixture produced by the above-mentioned (i) mixing and coupling reaction, or a mixture of the yellow monoazo pigment (P1) alone and the yellow monoazo pigment (P2) alone, which have been produced separately. However, a crude mixture produced by a mixing and coupling reaction is preferred because it allows for a more uniform pigment composition containing the yellow monoazo pigment (P1) and the yellow monoazo pigment (P2) alone to be obtained. When a mixture of the yellow monoazo pigment (P1) alone and the yellow monoazo pigment (P2) alone is used, in the first step, the crude yellow monoazo pigment (P1) is subjected to solvent salt milling in the presence of crude yellow monoazo pigment (P2). This allows the step of obtaining the pigment composition (pigment mixture) to be carried out.

[0057] In addition, as a method for treating the particle surfaces of the pigment composition with a rosin, a rosin can be added during the synthesis of the yellow monoazo pigment (P1) alone to obtain a yellow monoazo pigment (P1) whose particle surfaces have been treated with the rosin. The rosin-treated yellow monoazo pigment (P1) and the yellow monoazo pigment (P2) can then be kneaded together by a solvent salt milling method. Alternatively, a rosin can be added during the above (i) mixing and coupling reaction to obtain a pigment mixture of the yellow monoazo pigment (P1) whose particle surfaces have been treated with the rosin and the yellow monoazo pigment (P2).

[0058] (Solvent salt milling method) As a method for converting coarse pigment particles into fine pigment particles, wet kneading pulverization methods such as solvent salt milling and dry pulverization methods are known. Among these, wet kneading pulverization by the solvent salt milling method is preferred as a method for producing a pigment composition.

[0059] The solvent salt milling method is a method of mechanically grinding pigment particles using a kneader or the like in the presence of an inorganic salt (salt) and an organic solvent (solvent), and is a method that can efficiently reduce the size of pigment particles. The solvent salt milling method includes a kneading step in which a kneaded product of pigment and the like is produced in the presence of an inorganic salt and an organic solvent, and a post-step in which the inorganic salt and the organic solvent are removed.

[0060] [Inorganic salts] The inorganic salt is used to pulverize the pigment during the kneading process by utilizing its high hardness, thereby reducing the size of the pigment. Taking into consideration the handling during removal, it is preferable to use an inorganic salt that is water-soluble (a water-soluble inorganic salt). The water-soluble inorganic salt is not particularly limited as long as it dissolves in water. Specific examples include chlorides of alkali metals such as sodium chloride and potassium chloride, and chlorides of polyvalent metals such as zinc chloride and magnesium chloride. One type of water-soluble inorganic salt may be used alone, or two or more types may be used in combination.

[0061] The volume-based cumulative 50% particle size (D 50 ) is preferably 1 μm or more and 50 μm or less. 95 ) is preferably 80 μm or less. 50 and D 95 are the diameters of particles that are 50% and 95% of the total volume of the measured particles when integrated from the small particle size side in the particle size integration curve. 50 and D 95 can be measured, for example, using a particle size analyzer using dynamic light scattering.

[0062] The amount of inorganic salt used is preferably 3 parts by mass or more and 20 parts by mass or less, and more preferably 4 parts by mass or more and 10 parts by mass or less, per 1 part by mass of the total of the crude yellow monoazo pigment (P1) and the crude yellow monoazo pigment (P2).

[0063] [Organic solvents] The organic solvent is used in the kneading step to wet the pigment particles, pigment derivative, and inorganic salt, thereby increasing the grinding effect and promoting the pulverization of the pigment. The organic solvent is not particularly limited as long as it can achieve the above, but water-soluble organic solvents such as alcohols, glycols, and ethers are preferred. Among these, highly viscous water-soluble organic solvents such as ethylene glycol, diethylene glycol, and polyethylene glycol are more preferred from the viewpoint of improving the grinding effect.

[0064] The amount of the organic solvent used is preferably 0.1 parts by mass or more and 5 parts by mass or less, and more preferably 0.5 parts by mass or more and 2.5 parts by mass or less, per 1 part by mass of the total of the crude yellow monoazo pigment (P1) and the crude yellow monoazo pigment (P2).

[0065] [Mixing process] The kneading step is a step in which a mixture of a pigment and a pigment derivative is kneaded while being compressed by applying a load in the presence of the inorganic salt and the organic solvent. Examples of the apparatus used in the kneading step include a kneader, a roll mill, a ball mill, an attritor, a sand mill, and a planetary mixer. Among these, it is preferable to use a kneader.

[0066] The amount (mass %) of the yellow monoazo pigment (P2) used in the kneading step is preferably 0.001 to 0.100 times the amount (mass %) of the yellow monoazo pigment (P1). In particular, the amount is more preferably 0.01 to 0.07 times. A very small amount less than 0.001 times may not be effective in suppressing the deposition of foreign matter. On the other hand, a mass ratio exceeding 0.100 times may result in the color of the pigment composition significantly differing from that of the primary pigment, the yellow monoazo pigment (P1), due to the influence of the color of the secondary pigment, the yellow monoazo pigment (P2). The mass ratio range of "0.001 to 0.100 times" is equivalent to the reciprocal of the mass ratio, i.e., the amount (mass %) of the yellow monoazo pigment (P1) used relative to the amount (mass %) of the yellow monoazo pigment (P2) used, being 10 to 1000 times.

[0067] The temperature during the kneading step is preferably 25°C or higher and 90°C or lower. When the temperature during the kneading step is 25°C or higher, the pigment particles are easily micronized to an appropriate degree, and sufficient lightfastness of the image is easily obtained. On the other hand, when the temperature during the kneading step is 90°C or lower, the rate of pigment crystal growth becomes appropriate, and the pigment particles are easily micronized to an appropriate degree. As a result, sufficient color development is easily obtained.

[0068] [Post-process] The post-process is a process for removing water-soluble inorganic salts and organic solvents from the kneaded product obtained in the kneading process. Specifically, a method can be used in which water is added to the kneaded product in a predetermined ratio, and then the resulting slurry is filtered and washed. Ion-exchanged water or pure water is preferably used as the water. Examples of the filtration method include a method in which a suspension obtained by adding water to the kneaded product is passed through an ultrafiltration membrane or a dialysis membrane for separation, and a method in which separation is performed using a high-pressure filter press. By performing this process, a wet cake of the pigment composition can be obtained in which the content of organic solvents and inorganic salts has been reduced or removed.

[0069] The obtained wet cake is preferably dried to a water content (moisture content) of about 5% or less to inhibit bacterial growth. In particular, to prepare a pigment dispersion for oil-based ink, it is preferable to remove water so that the water content is 0%. Examples of methods for removing water include batch or continuous drying, in which dehydration is performed by heating at 80°C to 120°C using a heat source installed in a dryer, and drying under reduced pressure. Specific examples of dryers include box dryers, band dryers, and spray dryers.

[0070] (Second step: production of pigment dispersion) The second step in the ink production method is the preparation of a pigment dispersion for use in the production of inkjet inks, in which the pigment mixture obtained in the first step is dispersed in a liquid medium. In this step, additives such as a pH adjuster may be used as needed. In the second step, the pigment mixture is further dispersed in the liquid medium by applying a shear force necessary to achieve the desired particle size distribution.

[0071] Examples of pigment dispersion methods include resin-dispersed pigments, self-dispersed pigments, resin-bonded pigments, and microencapsulated pigments. Of these, resin-dispersed pigments are preferred. In the second step, known dispersion methods such as media dispersion and medialess dispersion can be used. Examples of dispersers using media dispersion include paint shakers, bead mills, sand mills, ball mills, and roll mills. Examples of dispersers using medialess dispersion include ultrasonic homogenizers and high-pressure homogenizers. The second step may be performed using one of the above dispersers alone, or two or more types of dispersers in combination.

[0072] The temperature of the second step can be set as desired. Because the second step is carried out in an aqueous liquid medium, the temperature is preferably from 0°C to 100°C, and more preferably from 10°C to 40°C from the viewpoints of heat generation during the process and, when a media dispersion method is used, the reliability of the media. The time for the second step can be adjusted depending on the apparatus used, the concentration of the dispersion liquid, and the like, and can be set as desired as long as the pigment composition does not become over-dispersed.

[0073] A pre-dispersion step may be performed to mix the components containing the pigment mixture, wet them in a liquid medium, and facilitate dispersion. The pre-dispersion step may utilize the dispersion methods and devices described above as being usable in the second step.

[0074] [Liquid medium] The second step is carried out in a liquid medium. When preparing a pigment dispersion for aqueous ink, the second step is carried out in an aqueous liquid medium. The aqueous liquid medium can be water alone, or an aqueous medium in which water is the main solvent and a protic or aprotic organic solvent is used in combination. The organic solvent is preferably one that is miscible or soluble with water in any ratio. In particular, it is preferable to use a homogeneous mixed solvent containing 50% by mass or more of water as the aqueous medium. The water used is preferably ion-exchanged water or pure water.

[0075] Protic organic solvents are organic solvents that have a hydrogen atom (acidic hydrogen atom) bonded to oxygen or nitrogen. Furthermore, aprotic organic solvents are organic solvents that do not have an acidic hydrogen atom. Examples of organic solvents include alcohols, alkylene glycols, polyalkylene glycols, glycol ethers, glycol ether esters, carboxylic acid amides, ketones, ketoalcohols, cyclic ethers, nitrogen-containing compounds, and sulfur-containing compounds.

[0076] Post-processing The produced pigment dispersion is preferably subjected to a general post-treatment method such as purification before being used to produce an inkjet ink. When only water is used as the liquid medium without using an organic solvent, the obtained dispersion can be used directly to prepare an ink, or it can be used as the final pigment dispersion after washing and adjusting the pigment content. When a liquid medium containing an organic solvent is used, the organic solvent may be removed. Examples of methods for removing the organic solvent include a method in which water is added while removing the organic solvent by reducing pressure or heating using an evaporator or the like to obtain an aqueous pigment dispersion. Another example is a method in which the organic solvent is removed by ultrafiltration or the like, and then the operation of adding water is repeated.

[0077] (Step 3: Ink production) The third step in the ink production method is to prepare the ink by mixing the pigment dispersion obtained in the second step with other components necessary for inkjet ink. Examples of other components include water, water-soluble organic solvents, water-insoluble organic solvents, resins, and the "other additives" mentioned above. The ink production method can be carried out, for example, by adding the pigment dispersion and other components to a suitable container and stirring them. Conditions such as stirring speed, temperature, and time can be appropriately set according to the desired conditions. Other known production processes may also be combined. [Example]

[0078] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples as long as the gist of the invention is not exceeded. The terms "parts" and "%" used to describe the amounts of components are based on mass unless otherwise specified.

[0079] <Analysis of pigments> (High-Performance Liquid Chromatography Mass Spectrometry) High performance liquid chromatography mass spectrometry (HPLC / MS) was carried out under the following conditions. [HPLC analysis conditions] Column: Silica gel column (trade name "SunFire C18 Column", 2.1 mm x 150 mm, manufactured by Waters) Column temperature: 40℃ ·Flow rate: 0.2mL / min Detector: Diode array (PDA) detector Detection range: 200nm~700nm ·Analysis time: 45 minutes Mobile phase gradient conditions: See Table 1 below Sample solution: Dimethyl sulfoxide (DMSO) solution with a pigment concentration of 30 ppm Sample solution injection volume: 2 μL

[0080] TIFF2025180164000002.tif33170

[0081] [Mass spectrometry conditions] Mass spectra of the peaks obtained in the HPLC analysis performed under the above conditions were measured under the following conditions: The most strongly detected m / z was measured for both the positive (ES+) and negative (ES-) peaks. Ionization method: Electrospray ionization (ESI) Capillary voltage: 3.5kV Desolvation gas: 350℃ Ion source temperature: 120℃ Detector: posi(ES+); 40V, 100~2000amu / 1.0sec nega(ES-);40V, 100~2000amu / 1.0sec

[0082] [Measurement of the mass ratio of each pigment component in a pigment mixture] The mixed pigment sample was analyzed using HPLC analysis under the above conditions, and the peak area of ​​each pigment component in the mixed pigment obtained on the chromatogram at a detection wavelength of 254 nm was measured. At the same time, a standard DMSO solution of each pigment component at a pigment concentration of 30 ppm was also analyzed to create a concentration calibration curve for each pigment component at a detection wavelength of 254 nm. The pigment concentration of each pigment component in the mixed pigment sample was then calculated from the created concentration calibration curve, and the mass ratio of each pigment component in the mixed pigment was determined.

[0083] (Method for measuring solubility) The solubility (mg / L) of pigments in 1,2-hexanediol at 25°C was measured as follows. Approximately 50 mg of pigment was added to 8.00 mL of 1,2-hexanediol and stirred at 70°C for 10 minutes to obtain a partially dissolved suspension / dispersion. However, if the pigment completely dissolved to form a uniform, transparent solution, additional pigment was added to obtain a suspension / dispersion. This suspension / dispersion was cooled to 25°C and stirred at the same temperature for 30 minutes to obtain a suspension / dispersion in which the pigment had dissolved to its saturated concentration at 25°C. This suspension / dispersion was centrifuged (12 krpm, 10 minutes). The supernatant obtained from the centrifugation was passed through a 0.45 μm syringe filter to prepare a 1,2-hexanediol solution of each pigment at its saturated concentration at 25°C. This was used as the sample solution for solubility measurement. Separately, standard DMSO solutions with pigment concentrations of 20 to 100 ppm were prepared for each pigment for calibration curve analysis.

[0084] The resulting sample solution was then subjected to HPLC analysis under the aforementioned conditions, and the peak areas of the pigment peaks detected on the chromatogram at a detection wavelength of 254 nm were measured. At the same time, standard DMSO solutions for calibration curves of each pigment were also analyzed, and concentration calibration curves for each pigment component at a detection wavelength of 254 nm were created. The pigment concentration (mg / L) of the sample solution for solubility measurement was then calculated from the resulting concentration calibration curve, and this pigment concentration was used as the solubility (mg / L) in 1,2-hexanediol at 25°C.

[0085] <Synthesis example> (Compound 1 represented by chemical formula (1)) A suspension was prepared by adding 9.26 parts of 4-phenoxyaniline to 63.0 parts of ion-exchanged water and stirring. After adding 13.0 parts of 35% hydrochloric acid, the mixture was stirred for 1 hour and then cooled to an internal temperature of 0°C or below in an ice-salt bath. An aqueous solution of sodium nitrite prepared by adding 8.96 parts of ion-exchanged water to 3.49 parts of sodium nitrite was then added, and the mixture was stirred for 1 hour while maintaining the internal temperature below 0°C in an ice-salt bath to form a diazonium salt. To the resulting diazonium salt solution, 0.049 parts of sulfamic acid was added to remove excess nitrous acid, preparing a diazo component solution.

[0086] 10.2 parts of o-acetoacetanisidide, 5.12 parts of sodium hydroxide, and 80.6 parts of ion-exchanged water were mixed and stirred to completely dissolve the mixture. The liquid obtained above was added to an aqueous solution prepared by mixing 8.20 parts of acetic acid and 54.5 parts of ion-exchanged water, and the mixture was stirred to prepare a coupler component slurry.

[0087] The coupler component slurry was heated to 40°C using a hot stirrer, and the diazo component solution was added dropwise over 30 minutes while maintaining the internal temperature at 40°C. After stirring at 40°C for 30 minutes, the internal temperature was raised to 70°C and stirred for 20 minutes to complete the reaction. The reaction solution was then filtered to remove the reaction precipitate. The reaction precipitate was washed three times with an appropriate amount of ion-exchanged water to obtain a crude cake of the reaction product. Ethanol was added to the obtained crude cake to form a suspension, which was stirred and washed for 1 hour, and the resulting filter cake was dried to obtain 18.9 parts of compound 1 (yield 95%).

[0088] The results of identifying Compound 1 by HPLC / MS under the above conditions are shown below. [HPLC / MS] Measured value: MS (ES+) m / z 404.32 (M+H) + MS(ES-)m / z 402.32(MH) - Calculated value: C 23 H 21 N3O4=403.15

[0089] (Compound 2 represented by chemical formula (2)) Except for changing 9.26 parts of 4-phenoxyaniline to 10.0 parts of 3-amino-4-methoxybiphenyl, 19.5 parts of compound 2 were obtained (yield 95%) in the same manner as in the production of compound 1. The results of identifying compound 2 by HPLC / MS under the above conditions are shown below. [HPLC / MS] Measured value: MS (ES+) m / z 418.33 (M+H) + MS(ES-)m / z 416.32(MH) - Calculated value: C 24 H 23 N3O4=417.17

[0090] (Compound 3 represented by chemical formula (3)) Except for changing 9.26 parts of 4-phenoxyaniline to 10.6 parts of 4'-aminobenzanilide, 19.0 parts of compound 3 were obtained (yield 94%) in the same manner as in the production of compound 1. The results of identifying compound 3 by HPLC / MS under the above conditions are shown below. [HPLC / MS] Measured value: MS (ES+) m / z 431.32 (M+H) + MS(ES-)m / z 429.31(MH) - Calculated value: C 24 H 22 N4O4=430.16

[0091] (Compound 4 represented by chemical formula (4)) 11.3 parts of 4-chloro-2,5-dimethoxyaniline were added to 109 parts of ion-exchanged water and stirred to prepare a suspension. 15.6 parts of 35% hydrochloric acid were added and stirred for 1 hour, and then the mixture was cooled in an ice-salt bath until the internal temperature reached 0°C or below. An aqueous sodium nitrite solution prepared by adding 10.8 parts of ion-exchanged water to 4.18 parts of sodium nitrite was added, and the mixture was stirred for 1 hour while maintaining the internal temperature at 0°C or below in the ice-salt bath to convert the diazonium salt to a diazonium salt solution. 0.059 parts of sulfamic acid were added to the resulting diazonium salt solution to remove excess nitrous acid, preparing a diazo component solution.

[0092] 12.2 parts of o-acetoacetanisidide, 6.14 parts of sodium hydroxide, and 96.7 parts of ion-exchanged water were mixed and stirred to completely dissolve the components, obtaining a liquid. The liquid was added to an aqueous solution of 9.84 parts of acetic acid and 65.4 parts of ion-exchanged water, and the mixture was stirred to prepare a coupler component slurry.

[0093] The coupler component slurry was heated to 40°C using a hot stirrer, and the diazo component solution was added dropwise over 30 minutes while maintaining the internal temperature at 40°C. After stirring at 40°C for 30 minutes, the internal temperature was raised to 70°C and stirred for 20 minutes to complete the reaction. The reaction solution was filtered and the reaction precipitate was washed three times with an appropriate amount of ion-exchanged water to obtain a crude cake of the reaction product. Ethanol was added to the obtained crude cake, and the mixture was stirred for 1 hour for washing. The filtered cake was dried to obtain 23.0 parts of compound 4 (yield 97%).

[0094] The results of identifying Compound 4 by HPLC / MS under the above conditions are shown below. [HPLC / MS] Measured value: MS (ES+) m / z 406.32, 408.30 (M+H) + MS(ES-)m / z 404.35, 406.44(MH) - Calculated value: C 19 H20 ClN3O5 = 405.11

[0095] (Compound 5 represented by chemical formula (5)) Except for changing 11.3 parts of 4-chloro-2,5-dimethoxyaniline to 11.3 parts of 5-chloro-2,4-dimethoxyaniline, 22.8 parts of compound 5 were obtained (yield 95%) in the same manner as in the production of compound 4. The results of identifying compound 5 by HPLC / MS under the above conditions are shown below. [HPLC / MS] Measured value: MS (ES+) m / z 406.30, 408.32 (M+H) + MS(ES-) m / z 404.29, 406.33(MH) - Calculated value: C 19 H 20 ClN3O5 = 405.11

[0096] (Compound 6 represented by chemical formula (6)) Except for changing 11.3 parts of 4-chloro-2,5-dimethoxyaniline to 9.20 parts of 2,4-dimethoxyaniline, 20.1 parts of compound 6 were obtained (yield 92%) in the same manner as in the production of compound 4. The results of identifying compound 6 by HPLC / MS under the above conditions are shown below. [HPLC / MS] Measured value: MS (ES+) m / z 372.32 (M+H) + MS(ES-)m / z 370.35(MH) - Calculated value: C 19 H 21 N3O5=371.15

[0097] (Compound 7 represented by chemical formula (7)) Except for changing 11.3 parts of 4-chloro-2,5-dimethoxyaniline to 9.70 parts of 2,5-dichloroaniline, 21.0 parts of compound 7 were obtained (yield 94%) in the same manner as in the production of compound 4. The results of identifying compound 7 by HPLC / MS under the above conditions are shown below. [HPLC / MS] Measured value: MS (ES+) m / z 380.32, 382.33 (M+H) + MS(ES-)m / z 378.33,380.32(MH) - Calculated value: C 17 H 15 Cl2N3O3 = 379.05

[0098] (Comparative Compound 1) The 9.26 parts of 4-phenoxyaniline used in the production of Compound 1 were changed to 8.40 parts of 2-methoxy-4-nitroaniline, and the 10.2 parts of o-acetoacetanisidide were changed to 10.2 parts of p-acetoacetanisidide. Except for these changes, the same procedure as in the production of Compound 1 was used to obtain 17.7 parts of Comparative Compound 1 (a compound represented by the following chemical formula (8)) (yield 93%). The results of identifying Comparative Compound 1 by HPLC / MS under the above conditions are shown below. [HPLC / MS] Measured value: MS (ES+) m / z 387.40 (M+H) + MS(ES-)m / z 385.39(MH) - Calculated value: C 18 H 18 N4O6=386.12

[0099] TIFF2025180164000003.tif36170

[0100] (Mixed coupling product 1) 42.3 parts of 2-methoxy-4-nitroaniline and 2.64 parts of 3-amino-4-methoxybiphenyl were added to 337 parts of ion-exchanged water and stirred to prepare a suspension. 69.0 parts of 35% hydrochloric acid were added and stirred for 1 hour, followed by cooling in an ice-salt bath until the internal temperature reached 0°C or below. An aqueous solution of sodium nitrite prepared by adding 44.0 parts of ion-exchanged water to 18.5 parts of sodium nitrite was added, and the mixture was stirred for 1 hour while maintaining the internal temperature below 0°C in an ice-salt bath to convert the diazonium salt to a diazonium salt solution. 0.258 parts of sulfamic acid was added to the resulting diazonium salt solution to remove excess nitrous acid, preparing a mixed diazo component solution.

[0101] 53.8 parts of o-acetoacetanisidide, 27.1 parts of sodium hydroxide, and 427 parts of ion-exchanged water were mixed and stirred to completely dissolve the mixture, obtaining a liquid. The liquid was added to an aqueous solution prepared by mixing 43.4 parts of acetic acid and 289 parts of ion-exchanged water, and the mixture was stirred to prepare a coupler component slurry.

[0102] The coupler component slurry was heated to 40°C using an oil bath, and the mixed diazo component solution was added dropwise over 45 minutes while maintaining the internal temperature at 40°C. After stirring at 40°C for 30 minutes, the internal temperature was raised to 70°C and stirred for 20 minutes to complete the reaction. The reaction solution was allowed to cool to room temperature, and the reaction precipitate collected by filtration was washed three times with 1,500 parts of ion-exchanged water to obtain a cake-like crude reaction product. 5,000 parts of ion-exchanged water was added to the crude reaction product, and the resulting slurry was stirred for 1 hour, washed, and filtered. 2,500 parts of ethanol was added to the filter cake and washed in the same manner. The resulting filter cake was then dried to obtain 97.6 parts of mixed coupling product 1 containing PY74 and compound 2 (yield 97%).

[0103] The results of identifying the mixed coupling product 1 by HPLC / MS under the above conditions are shown below. [HPLC / MS] (i) Peak (a): PY74 Measured value: MS (ES+) m / z 387.34 (M+H) + MS(ES-)m / z 385.35(MH)- Calculated value: C 18 H 18 N4O6=386.12 (ii) Peak (b): Compound 2 Measured value: MS (ES+) m / z 418.34 (M+H) + MS(ES-)m / z 416.33(MH) - Calculated value: C 24 H 23 N3O4=417.17 (iii) Mass ratio PY74: 95.16% ·Compound 2:4.84% Mass ratio of PY74 to compound 2 (PY74 / compound 2): 19.7

[0104] (Mixed coupling product 2) 47.9 parts of 2-methoxy-4-nitroaniline and 2.80 parts of 4-chloro-2,5-dimethoxyaniline were added to 360 parts of ion-exchanged water and stirred to prepare a suspension. 78.1 parts of 35% hydrochloric acid was added and stirred for 1 hour, and then the mixture was cooled in an ice-salt bath until the internal temperature reached 0°C or below. An aqueous sodium nitrite solution prepared by adding 53.7 parts of ion-exchanged water to 20.9 parts of sodium nitrite was added, and the mixture was stirred for 1 hour while maintaining the internal temperature below 0°C in an ice-salt bath to convert the diazonium salt to a diazonium salt solution. 0.29 parts of sulfamic acid was added to the resulting diazonium salt solution to remove excess nitrous acid, preparing a mixed diazo component solution.

[0105] 60.9 parts of o-acetoacetanisidide, 30.7 parts of sodium hydroxide, and 400 parts of ion-exchanged water were mixed and stirred to completely dissolve the mixture, obtaining a liquid. The liquid was added to an aqueous solution prepared by mixing 49.2 parts of acetic acid and 327 parts of ion-exchanged water, and the mixture was stirred to prepare a coupler component slurry.

[0106] The coupler component slurry was heated to 40°C using an oil bath, and the mixed diazo component solution was added dropwise over 45 minutes while maintaining the internal temperature at 40°C. After stirring at 40°C for 30 minutes, the internal temperature was raised to 70°C and stirred for 20 minutes to complete the reaction. The reaction solution was allowed to cool to room temperature, and the reaction precipitate collected by filtration was washed three times with 1,500 parts of ion-exchanged water to obtain a cake-like crude reaction product. 5,000 parts of ion-exchanged water was added to the crude reaction product, and the resulting slurry was stirred for 1 hour, washed, and filtered. 2,500 parts of ethanol was added to the filter cake and washed in the same manner. The resulting filter cake was then dried to obtain 108 parts of a mixed coupling product 2 containing PY74 and compound 4 (yield 95%).

[0107] The results of identifying the mixed coupling product 2 by HPLC / MS under the above conditions are shown below. [HPLC / MS] (i) Peak (a): PY74 Measured value: MS (ES+) m / z 387.32 (M+H) + MS(ES-)m / z 385.33(MH) - Calculated value: C 18 H 18 N4O6=386.12 (ii) Peak (b): Compound 4 Measured value: MS (ES+) m / z 406.31, 408.32 (M+H) + MS(ES-)m / z 404.33, 406.36(MH) - Calculated value: C 19 H 20 ClN3O5 = 405.11 (iii) Mass ratio PY74: 95.87% ·Compound 4:4.13% Mass ratio of PY74 to compound 4 (PY74 / compound 4): 23.2

[0108] <Solubility measurement> The solubility (mg / L) of various pigments in 1,2-hexanediol at 25°C was measured using the solubility measurement method described above, and the results are shown in Table 2. The meanings of the abbreviations in Table 2 are as follows: PY1: CI Pigment Yellow 1 PY3: CI Pigment Yellow 3 PY65: CI Pigment Yellow 65 PY73: CI Pigment Yellow 73 PY74: CI Pigment Yellow 74 PY120: CI Pigment Yellow 120 PY151: CI Pigment Yellow 151 PY191: CI Pigment Yellow 191

[0109] TIFF2025180164000004.tif60170

[0110] <Preparation of Pigment Composition> (Pigment composition 1) 98.48 parts of PY74, 1.52 parts of Compound 1, 500 parts of sodium chloride (trade name "Naclfour 1", manufactured by Naikai Salt Industry Co., Ltd.), and 85 parts of diethylene glycol were mixed. The pigment was then kneaded and pulverized by a solvent salt milling method using a kneader (trade name "TX-2L", manufactured by Inoue Seisakusho Co., Ltd.) at 30°C for 4 hours to obtain a kneaded product. The resulting kneaded product was thoroughly washed with ion-exchanged water, filtered, and dried to obtain Pigment Composition 1.

[0111] (Pigment compositions 2 to 19 and 24 to 30) Pigment compositions 2 to 19 and 24 to 30 were obtained by the same solvent salt milling method as in the case of pigment composition 1, using the raw materials (yellow monoazo pigment (P1), yellow monoazo pigment (P2), and other compounds) of the types and amounts shown in Table 3. Note that for pigment composition 24, only PY74, the yellow monoazo pigment (P1), was used as the pigment raw material, without using the yellow monoazo pigment (P2).

[0112] (Pigment Compositions 20 and 21) To 100 parts of the mixed coupling product shown in Table 3, 500 parts of sodium chloride (trade name "Naclefour 1", manufactured by Naikai Salt Industry Co., Ltd.) and 85 parts of diethylene glycol were added. The pigment was then kneaded and pulverized by a solvent salt milling method using a kneader (trade name "TX-2L", manufactured by Inoue Seisakusho Co., Ltd.) at 30°C for 4 hours to obtain a kneaded product. The obtained kneaded product was thoroughly washed with ion-exchanged water, filtered, and dried to obtain pigment compositions 20 and 21.

[0113] (Pigment Compositions 22 and 23) The raw materials shown in Table 3 in the types and amounts used were placed in a mortar and mixed thoroughly to obtain pigment compositions 22 and 23. That is, the pigments were subjected to a dry grinding method to reduce the size of the pigments, thereby preparing pigment compositions 22 and 23. The properties of the pigment compositions obtained above are summarized in Table 3.

[0114] TIFF2025180164000005.tif207170

[0115] <Resin synthesis> (Resin 1) A flask equipped with a stirrer, nitrogen inlet tube, reflux condenser, and thermometer was charged with 200.0 parts of isopropanol and heated to 85°C under a nitrogen atmosphere while stirring. A mixture of 60.0 parts of styrene, 20.0 parts of n-butyl acrylate, 20.0 parts of acrylic acid, and 5.0 parts of a polymerization initiator was added dropwise to the flask over two hours while maintaining the system at 85°C. The polymerization initiator used was a solution of 5.0 parts of "Perkadox L-W75 (LS)" (dibenzoyl peroxide, manufactured by Kayaku Akzo, purity 75%) dissolved in 10.0 parts of isopropanol. The system was maintained at 85°C and stirred for four hours to synthesize Resin 1. Potassium hydroxide (0.9 times the acid value of the resin on a molar basis) and an appropriate amount of ion-exchanged water were added, and the isopropanol was removed under reduced pressure to obtain a liquid containing Resin 1 with a resin content of 17.8%.

[0116] (Resin 2) A commercially available polymer dispersant (product name "Solsperse 17000", manufactured by Lubrizol Japan) was used as resin 2. The resin content in resin 2 was 100.0%.

[0117] <Preparation of pigment dispersion> (Pigment dispersion 1-30) The pigment composition, resin (liquid containing resin), and liquid medium were mixed in the types and amounts shown in Table 4, and dispersed using a homogenizer (trade name "Starburst", manufactured by Sugino Machine) at a processing pressure of 200 MPa. An appropriate amount of ion-exchanged water was then added to obtain pigment dispersions 1 to 30, each with a pigment content (total of the main pigment, such as yellow monoazo pigment (P1), and the secondary pigment, such as yellow monoazo pigment (P2)) of 15.0%.

[0118] (Pigment Dispersion 31) Pigment dispersion 31 was obtained in the same manner as in the above-described pigment dispersions 1 to 30, except that after the dispersion treatment, an appropriate amount of isopropyl palmitate was added instead of the appropriate amount of ion-exchanged water. The pigment content in pigment dispersion 31 (total of yellow monoazo pigment (P1) and yellow monoazo pigment (P2)) was 15.0%. In Table 4, "IPP" means isopropyl palmitate.

[0119] TIFF2025180164000006.tif207170

[0120] <Ink Preparation> Each ink was prepared by mixing the components (unit: parts) shown in Table 5-1, thoroughly stirring, and then pressure filtering through a 2.5 μm pore size microfilter (manufactured by Fujifilm). In Table 5-1, "Acetylenol E100," abbreviated as "AE100," is the trade name of a nonionic surfactant manufactured by Kawaken Fine Chemicals. Similarly, "AF Solvent No. 4," abbreviated as "AF4," is the trade name of a nonpolar organic solvent manufactured by ENEOS. The meanings of the abbreviations in Table 5-1 are as follows: Gly: Glycerin 12HD: 1,2-hexanediol TEG: Triethylene glycol PEG1K: Polyethylene glycol (number average molecular weight 1000) AE100: Acetylenol E100 IPP: Isopropyl palmitate OD: 1-octadecanol AF4: AF Solvent No. 4

[0121] TIFF2025180164000007.tif202170

[0122] The properties of each ink prepared are shown in Table 5-2. The "solubility (mg / L)" of the primary pigment, such as yellow monoazo pigment (P1), and the secondary pigment, such as yellow monoazo pigment (P2), shown in Table 5-2, represents the solubility (mg / L) of the pigment in 1,2-hexanediol at 25°C. Table 5-2 also shows the content A (%) of the primary pigment, such as yellow monoazo pigment (P1), and the content B (%) of the secondary pigment, such as yellow monoazo pigment (P2), based on the total mass of the ink, as well as the A / B value (times).

[0123] TIFF2025180164000008.tif202170

[0124] <Evaluation> The ejection stability of each ink obtained above was evaluated. In the present invention, "A," "B," and "C" were defined as acceptable levels, and "D" was defined as unacceptable level, based on the following evaluation criteria. The evaluation results are shown in Table 6.

[0125] (Discharge stability) Each ink obtained above was filled into an ink cartridge and inserted into an inkjet recording device (product name: "PIXUS PRO-10S," manufactured by Canon) equipped with a recording head that ejects ink using thermal energy. Five nozzles were randomly selected from the recording head, and ink was continuously ejected at a rate of 50,000 shots per second. The ejected ink droplets were photographed from the side and image processed to calculate the ink droplet ejection velocity. The ink droplet ejection velocity was calculated at predetermined times (1 minute and 3 hours) after the start of continuous ejection. The "ejection velocity change" was calculated for each nozzle using the formula ("ink droplet ejection velocity after 1 minute" - "ink droplet ejection velocity after 3 hours") / ("ink droplet ejection velocity after 1 minute"). The "ejection velocity change" for the five nozzles was averaged to calculate the rate of change in the ejection velocity. The ink ejection stability was evaluated according to the following evaluation criteria. A smaller rate of change in the ejection velocity indicates better ink ejection stability. Conversely, for example, if foreign matter occurs on the surface of the heating section in the ink liquid chamber or on the surface of the ink flow path due to the precipitation of pigment, the ink ejection speed decreases and the rate of change in the ejection speed increases. A: The rate of change in discharge speed was 0.05 or less. B: The rate of change in discharge velocity was greater than 0.05 and 0.10 or less. C: The rate of change in discharge velocity was greater than 0.10 and not more than 0.20. D: The rate of change of the discharge velocity exceeded 0.20.

[0126] TIFF2025180164000009.tif107170

[0127] The disclosure of this embodiment includes the following configurations and methods. (Configuration 1) A pigment composition containing a yellow monoazo pigment (P1) and a yellow monoazo pigment (P2) different from the yellow monoazo pigment (P1), the content (mass%) of the yellow monoazo pigment (P1) is 10 times or more and 1000 times or less in mass ratio to the content (mass%) of the yellow monoazo pigment (P2), A pigment composition, characterized in that the solubility of the yellow monoazo pigment (P1) in 1,2-hexanediol at 25°C is 10.0 mg / L or less, and the solubility of the yellow monoazo pigment (P2) in 1,2-hexanediol at 25°C is 20.0 mg / L or more and 600.0 mg / L or less. (Configuration 2) The pigment composition according to Configuration 1, wherein the yellow monoazo pigment (P1) and the yellow monoazo pigment (P2) are both acetoacetanilide-based monoazo pigments. (Configuration 3) The pigment composition according to Configuration 1 or 2, wherein the solubility of the yellow monoazo pigment (P1) in 1,2-hexanediol at 25°C is 2.0 mg / L or less, and the solubility of the yellow monoazo pigment (P2) in 1,2-hexanediol at 25°C is 30.0 mg / L or more and 300.0 mg / L or less. (Configuration 4) The pigment composition according to any one of Configurations 1 to 3, wherein the yellow monoazo pigment (P1) is CI Pigment Yellow 74. (Configuration 5) The pigment composition according to any one of Configurations 1 to 4, wherein the yellow monoazo pigment (P2) is at least one selected from the group consisting of compounds represented by each of the following chemical formulas (1) to (7):

[0128] TIFF2025180164000010.tif163170

[0129] (Configuration 6) The pigment composition according to any one of Configurations 1 to 5, wherein the pigment composition is a water-based inkjet ink. (Method 1) A method for producing a pigment composition containing a yellow monoazo pigment (P1) and a yellow monoazo pigment (P2) different from the yellow monoazo pigment (P1), comprising the steps of: the content (mass%) of the yellow monoazo pigment (P1) is 10 times or more and 1000 times or less in mass ratio to the content (mass%) of the yellow monoazo pigment (P2), the solubility of the yellow monoazo pigment (P1) in 1,2-hexanediol at 25°C is 10.0 mg / L or less, and the solubility of the yellow monoazo pigment (P2) in 1,2-hexanediol at 25°C is 20.0 mg / L or more and 600.0 mg / L or less; A method for producing a pigment composition, comprising a step of subjecting a crude yellow monoazo pigment (P1) to solvent salt milling in the presence of a crude yellow monoazo pigment (P2) to obtain the pigment composition. (Method 2) A method for producing a pigment composition containing a yellow monoazo pigment (P1) and a yellow monoazo pigment (P2) different from the yellow monoazo pigment (P1), comprising the steps of: the content (mass%) of the yellow monoazo pigment (P1) is 10 times or more and 1000 times or less in mass ratio to the content (mass%) of the yellow monoazo pigment (P2), the solubility of the yellow monoazo pigment (P1) in 1,2-hexanediol at 25°C is 10.0 mg / L or less, and the solubility of the yellow monoazo pigment (P2) in 1,2-hexanediol at 25°C is 20.0 mg / L or more and 600.0 mg / L or less; A method for producing a pigment composition, comprising the step of: conducting a coupling reaction using a diazo component mixture (a3) ​​containing diazo components (a1) and (a2) obtained by converting an aniline derivative into a diazonium salt, and a coupler component (b3) which is an acetoacetanilide derivative, to simultaneously synthesize the yellow monoazo pigment (P1) and the yellow monoazo pigment (P2), thereby obtaining a crude pigment composition. (Method 3) A method for producing a pigment composition according to Method 2, further comprising a step of subjecting the crude pigment composition to solvent salt milling to obtain the pigment composition.

Claims

1. A pigment composition containing a yellow monoazo pigment (P1) and a yellow monoazo pigment (P2) different from the yellow monoazo pigment (P1), the content (mass%) of the yellow monoazo pigment (P1) is 10 times or more and 1,000 times or less in mass ratio to the content (mass%) of the yellow monoazo pigment (P2); a pigment composition, wherein the solubility of the yellow monoazo pigment (P1) in 1,2-hexanediol at 25°C is 10.0 mg / L or less, and the solubility of the yellow monoazo pigment (P2) in 1,2-hexanediol at 25°C is 20.0 mg / L or more and 600.0 mg / L or less.

2. 2. The pigment composition according to claim 1, wherein the yellow monoazo pigment (P1) and the yellow monoazo pigment (P2) are both acetoacetanilide-based monoazo pigments.

3. 2. The pigment composition according to claim 1, wherein the solubility of the yellow monoazo pigment (P1) in 1,2-hexanediol at 25°C is 2.0 mg / L or less, and the solubility of the yellow monoazo pigment (P2) in 1,2-hexanediol at 25°C is 30.0 mg / L or more and 300.0 mg / L or less.

4. 2. The pigment composition according to claim 1, wherein the yellow monoazo pigment (P1) is C.I. Pigment Yellow 74.

5. 2. The pigment composition according to claim 1, wherein the yellow monoazo pigment (P2) is at least one selected from the group consisting of compounds represented by the following chemical formulas (1) to (7):

6. The pigment composition according to claim 1 , which is an aqueous inkjet ink.

7. A method for producing a pigment composition containing a yellow monoazo pigment (P1) and a yellow monoazo pigment (P2) different from the yellow monoazo pigment (P1), comprising the steps of: the content (mass%) of the yellow monoazo pigment (P1) is 10 times or more and 1,000 times or less in mass ratio to the content (mass%) of the yellow monoazo pigment (P2); the solubility of the yellow monoazo pigment (P1) in 1,2-hexanediol at 25°C is 10.0 mg / L or less, and the solubility of the yellow monoazo pigment (P2) in 1,2-hexanediol at 25°C is 20.0 mg / L or more and 600.0 mg / L or less; a step of subjecting a crude yellow monoazo pigment (P1) to solvent salt milling in the presence of a crude yellow monoazo pigment (P2) to obtain the pigment composition.

8. A method for producing a pigment composition containing a yellow monoazo pigment (P1) and a yellow monoazo pigment (P2) different from the yellow monoazo pigment (P1), comprising the steps of: the content (mass%) of the yellow monoazo pigment (P1) is 10 times or more and 1,000 times or less in mass ratio to the content (mass%) of the yellow monoazo pigment (P2); the solubility of the yellow monoazo pigment (P1) in 1,2-hexanediol at 25°C is 10.0 mg / L or less, and the solubility of the yellow monoazo pigment (P2) in 1,2-hexanediol at 25°C is 20.0 mg / L or more and 600.0 mg / L or less; a coupling reaction of a diazo component mixture (a3) ​​containing diazo components (a1) and (a2) obtained by converting an aniline derivative into a diazonium salt, and a coupler component (b3) that is an acetoacetanilide derivative, thereby simultaneously synthesizing the yellow monoazo pigment (P1) and the yellow monoazo pigment (P2), and thereby obtaining a crude pigment composition.

9. The method for producing a pigment composition according to claim 8, further comprising a step of subjecting the crude pigment composition to solvent salt milling to obtain the pigment composition.

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