JP2018053010A - Aqueous pigment dispersion liquid, inkjet ink, image recording method, and method for producing aqueous pigment dispersion liquid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aqueous pigment dispersion liquid characterized by a high discharge rate in an inkjet printer of thermal system and less foreign matter, and an inkjet ink, an image recording method using an inkjet ink, and a method for producing the aqueous pigment dispersion liquid.SOLUTION: An aqueous pigment dispersion liquid contains a specific azo pigment, a water-soluble dye having an azo group, a specific polymer dispersant, and water. There are also provided an inkjet ink, an image recording method using an inkjet ink, and a method for producing the aqueous pigment dispersion liquid.SELECTED DRAWING: None

Description

  The present invention relates to an aqueous pigment dispersion, an inkjet ink, an image recording method, and a method for producing an aqueous pigment dispersion.

Azo pigments are widely used in various fields because they are excellent in hue and coloring power, which are color characteristics. For example, a pigment dispersion in which an azo pigment is dispersed in water is used for an ink jet ink.
For example, Patent Document 1 describes an inkjet ink containing an azo pigment having a specific structure and a copolymer (dispersant) of benzyl (meth) acrylate and methacrylic acid. Patent Document 2 describes an inkjet ink containing an azo pigment having a specific structure and a water-soluble dye having an azo group.

JP 2014-162875 A JP 2012-077190 A

The ink-jet inks of Patent Documents 1 and 2 exhibit excellent performance as described in each document. However, thermal inks that eject ink from a recording head by the action of ink ejection speed, particularly thermal energy, are disclosed. It has been found that there is room for further study regarding the ink ejection speed when ink is ejected by an ink jet printer. Furthermore, there is room for study on the suppression of foreign matter generation.
The problems to be solved by the present invention are an aqueous pigment dispersion, an ink jet ink, an image recording method using the ink jet ink, and an aqueous pigment dispersion excellent in the discharge rate in a thermal ink jet printer and having less foreign matter It is to provide a manufacturing method.

  As a result of intensive studies by the present inventors, it is a copolymer of a specific azo pigment, a water-soluble dye having an azo group, (meth) acrylic acid and (meth) acrylic ester, and has a specific structure. The present inventors have found that the above problems can be solved by dispersing an aqueous pigment containing a polymer dispersant having water and water, and have completed the present invention.

  That is, the said subject of this invention was solved by the following means.

<1>
An aqueous pigment dispersion containing a pigment, a water-soluble dye having an azo group, a polymer dispersant, and water,
The pigment is a pigment containing a compound represented by the following general formula (1) or a tautomer thereof, or a salt thereof.
The polymer dispersant is an aqueous pigment dispersion, which is a polymer compound having a repeating unit represented by the following general formula (2-1) and a repeating unit represented by the following general formula (2-2).

In general formula (1),
Z represents a substituted or unsubstituted 5-membered heterocycle or 6-membered heterocycle.
Y ₁ , Y ₂ , R ₁₁ and R ₁₂ each independently represents a hydrogen atom or a substituent.
G ₁ and G ₂ are each independently a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted aralkyl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted alkynyl group, substituted or unsubstituted An aryl group or a substituted or unsubstituted heterocyclic group is represented.
W ₁ and W ₂ each independently represent a substituted or unsubstituted alkoxy group, a substituted or unsubstituted amino group, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted aryl group.

In General Formula (2-1), R ₁ represents a hydrogen atom, a methyl group or a substituted methyl group, and R ₂ represents an alkyl group substituted with a substituent containing an aryl group or an aromatic heterocyclic group, substituted or unsubstituted It represents a substituted aralkyl group or a substituted or unsubstituted aryl group.
In General Formula (2-2), R ₃ represents a hydrogen atom, a methyl group, or a substituted methyl group. M represents a hydrogen atom or a counter cation.
<2>
The aqueous pigment dispersion according to <1>, wherein the water-soluble dye having an azo group is a compound represented by the following general formula (3).
(A−N = N−B) n−L (3)
In General Formula (3), A and B each independently represent a substituted or unsubstituted heterocyclic group. L represents a hydrogen atom, a single bond, or a divalent linking group. n represents 1 or 2. However, when n is 1, L represents a hydrogen atom, and both A and B are monovalent substituted or unsubstituted heterocyclic groups. When n is 2, L represents a single bond or a divalent linking group, one of A and B is a monovalent substituted or unsubstituted heterocyclic group, and the other is a divalent substituted or unsubstituted group. It is a heterocyclic group. When n is 2, A may be the same or different, and B may be the same or different.
<3>
The aqueous pigment dispersion according to <1> or <2>, wherein the water-soluble dye having an azo group is a compound represented by the following general formula (4) or (5).

In the general formula (4), R ₄₁ and R ₄₂ each independently represent a monovalent substituent, R ₅₁ and R ₅₂ each independently represent —OR ₆ or —NHR ₇ , and R ₆ and R ₇ each represent Independently represents a hydrogen atom or a monovalent substituent, X ₃ represents a single bond or a divalent linking group, Ar ₃₁ and Ar ₃₂ each independently represent a divalent substituted or unsubstituted heterocyclic group, Ar ₄₁ and Ar ₄₂ each independently represent a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, or a substituted or unsubstituted monovalent triazine ring group.

In General Formula (5), R ₆₁ , R ₆₂ , X ₅₁ , X ₅₂ , Y ₅₁ , Y ₅₂ , G ₅₁ and G ₅₂ each independently represent a hydrogen atom or a monovalent substituent, and Z ₅ is 5 An atomic group constituting an ˜8-membered nitrogen-containing heterocycle, and M ₁ represents a hydrogen atom or a cation. m ₁ represents an integer of 0 to 3.
<4>
<1> to <1>, wherein the pigment is a pigment containing at least one of a compound represented by the following formula (d1), formula (d2), or formula (d3) or a tautomer thereof, or a salt thereof. 3> The aqueous pigment dispersion according to any one of 3>.

<5>
The aqueous pigment dispersion according to any one of <1> to <4>, wherein R ₁ in the general formula (2-1) represents a methyl group and R ₂ represents a benzyl group.
<6>
The aqueous pigment dispersion according to any one of <1> to <5>, wherein the mass ratio of the pigment to the water-soluble dye having an azo group is 1/1 to 20/1.
<7>
<1>-<6> The inkjet ink containing the aqueous pigment dispersion liquid of any one of <6>.
<8>
The inkjet ink according to <7>, which is used in an inkjet recording method in which ink is ejected from a recording head by the action of thermal energy.
<9>
<7> or the image recording method using the inkjet ink as described in <8>.
<10>
Step (A): obtaining a composition containing a pigment, a polymer dispersant, and water,
Step (B): a step of dispersing the pigment in the composition,
Step (C): adding a water-soluble dye having an azo group to the composition,
The pigment is a pigment containing a compound represented by the following general formula (1) or a tautomer thereof, or a salt thereof.
The polymer dispersant is a polymer compound having a repeating unit represented by the following general formula (2-1) and a repeating unit represented by the following general formula (2-2). Method.

In general formula (1),
Z represents a substituted or unsubstituted 5-membered heterocycle or 6-membered heterocycle.
Y ₁ , Y ₂ , R ₁₁ and R ₁₂ each independently represents a hydrogen atom or a substituent.
G ₁ and G ₂ are each independently a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted aralkyl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted alkynyl group, substituted or unsubstituted An aryl group or a substituted or unsubstituted heterocyclic group is represented.
W ₁ and W ₂ each independently represent a substituted or unsubstituted alkoxy group, a substituted or unsubstituted amino group, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted aryl group.

In General Formula (2-1), R ₁ represents a hydrogen atom, a methyl group or a substituted methyl group, and R ₂ represents an alkyl group substituted with a substituent containing an aryl group or an aromatic heterocyclic group, substituted or unsubstituted It represents a substituted aralkyl group or a substituted or unsubstituted aryl group.
In General Formula (2-2), R ₃ represents a hydrogen atom, a methyl group, or a substituted methyl group. M represents a hydrogen atom or a counter cation.
<11>
The method for producing an aqueous pigment dispersion according to <10>, wherein the step (C) is performed before the step (B).
<12>
Furthermore, the manufacturing method of the aqueous pigment dispersion as described in <10> or <11> including the process (D) of heating the obtained aqueous pigment dispersion.
<13>
The method for producing an aqueous pigment dispersion according to <12>, wherein in the step (D), the aqueous pigment dispersion is heated at 40 to 95 ° C.

  According to the present invention, there are provided a water-based pigment dispersion, an ink-jet ink, an image recording method using the ink-jet ink, and a method for producing the water-based pigment dispersion that are excellent in ejection speed in a thermal ink jet printer and have few foreign matters. Can be provided.

  In the present specification, “(meth) acrylate” represents at least one of acrylate and methacrylate, “(meth) acryl” represents at least one of acryl and methacryl, and “(meth) acryloyl” represents at least acryloyl and methacryloyl. Represents a kind.

  In the present specification, “water-soluble” means that the solubility in water at 25 ° C. is 1% by mass or more.

The aqueous pigment dispersion of the present invention is
An aqueous pigment dispersion containing a pigment, a water-soluble dye having an azo group, a polymer dispersant, and water,
The pigment is a pigment containing a compound represented by the following general formula (1) or a tautomer thereof, or a salt thereof.
The polymer dispersant is an aqueous pigment dispersion, which is a polymer compound having a repeating unit represented by the following general formula (2-1) and a repeating unit represented by the following general formula (2-2).

In general formula (1),
Z represents a substituted or unsubstituted 5-membered heterocycle or 6-membered heterocycle.
Y ₁ , Y ₂ , R ₁₁ and R ₁₂ each independently represents a hydrogen atom or a substituent.
G ₁ and G ₂ are each independently a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted aralkyl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted alkynyl group, substituted or unsubstituted An aryl group or a substituted or unsubstituted heterocyclic group is represented.
W ₁ and W ₂ each independently represent a substituted or unsubstituted alkoxy group, a substituted or unsubstituted amino group, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted aryl group.

In General Formula (2-1), R ₁ represents a hydrogen atom, a methyl group or a substituted methyl group, and R ₂ represents an alkyl group substituted with a substituent containing an aryl group or an aromatic heterocyclic group, substituted or unsubstituted It represents a substituted aralkyl group or a substituted or unsubstituted aryl group.
In General Formula (2-2), R ₃ represents a hydrogen atom, a methyl group, or a substituted methyl group. M represents a hydrogen atom or a counter cation.

The reason why the inkjet ink containing the aqueous pigment dispersion of the present invention has excellent stability over time, few foreign substances, and excellent discharge speed in a thermal inkjet printer is not clear in detail. It is estimated as follows.
In a thermal ink jet printer, one of the causes of a drop in discharge performance (discharge speed) is that the dispersion state of the pigment contained in the ink becomes unstable due to the heat generated when droplets are ejected by the thermal head, and then the ink It is conceivable that the pigments that can no longer maintain the dispersed state are aggregated when cooled.
Since the specific polymer dispersant used in the present invention has an aryl group or an aromatic heterocyclic group having a high affinity with the specific pigment used in the present invention in the side chain, the pigment and the polymer dispersant It is considered that the above interaction becomes stronger, and the dispersion state of the pigment is not easily destabilized by heat when droplets are ejected by the thermal head. Furthermore, since the specific dye used in combination with the present invention has a chemical structure similar to that of the specific pigment used in the present invention, it is a dye that is easily adsorbed to the pigment. It is considered that the aggregation of the pigment that occurs when the is cooled is less likely to occur. As a result, the aqueous pigment dispersion of the present invention can suppress the generation of foreign matters such as secondary aggregates of pigments, and can provide a pigment dispersion with high dispersion stability. It is thought that the speed will be good.
Further, it is considered that the print density and the light resistance are improved due to the specific structure of the specific azo pigment used in the present invention.

  Below, each component used for the aqueous pigment dispersion of this invention is demonstrated.

(Pigment)
The pigment is a pigment containing a compound represented by the following general formula (1) or a tautomer thereof, or a salt thereof.
A pigment may be used individually by 1 type, or may be used in combination of 2 or more type.

In general formula (1),
Z represents a substituted or unsubstituted 5-membered heterocycle or 6-membered heterocycle.
Y ₁ , Y ₂ , R ₁₁ and R ₁₂ each independently represents a hydrogen atom or a substituent.
G ₁ and G ₂ are each independently a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted aralkyl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted alkynyl group, substituted or unsubstituted An aryl group or a substituted or unsubstituted heterocyclic group is represented.
W ₁ and W ₂ each independently represent a substituted or unsubstituted alkoxy group, a substituted or unsubstituted amino group, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted aryl group.

  The compound represented by the general formula (1) is easy to form intramolecular and intermolecular interactions (hydrogen bonds and π-π stacking) due to its specific structure, has excellent light resistance, and is soluble in water or organic solvents. Therefore, it is possible to obtain an azo pigment having a preferable form. The pigment is used as dispersed in the medium as particles such as molecular aggregates.

In General Formula (1), each of W ₁ and W ₂ independently represents a substituted or unsubstituted alkoxy group, a substituted or unsubstituted amino group, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted aryl group. Represent.

Examples of the alkyl group in the case where W ₁ and W ₂ represent a substituted or unsubstituted alkyl group include linear, branched, and cyclic substituted or unsubstituted alkyl groups, such as a cycloalkyl group, a bicycloalkyl group, and a tricyclo structure. Etc. are also included. An alkyl group (for example, an alkyl group of an alkoxy group or an alkylthio group) in a substituent described below also represents such an alkyl group. The linear or branched substituted or unsubstituted alkyl group is preferably a substituted or unsubstituted alkyl group having 1 to 30 carbon atoms, such as a methyl group, an ethyl group, an n-propyl group, i- A propyl group, n-butyl group, i-butyl group, s-butyl group, t-butyl group, n-octyl group, eicosyl group, 2-chloroethyl group, 2-cyanoethyl group, 2-ethylhexyl group and the like can be mentioned. The substituted or unsubstituted cycloalkyl group is preferably a substituted or unsubstituted cycloalkyl group having 3 to 30 carbon atoms, and examples thereof include a cyclohexyl group, a cyclopentyl group, and a 4-n-dodecylcyclohexyl group. . The substituted or unsubstituted bicycloalkyl group is preferably a substituted or unsubstituted bicycloalkyl group having 5 to 30 carbon atoms, that is, a hydrogen atom from a substituted or unsubstituted bicycloalkane having 5 to 30 carbon atoms. One monovalent group removed, for example, a bicyclo [1,2,2] heptan-2-yl group, a bicyclo [2,2,2] octane-3-yl group, and the like. The substituent that the alkyl group may have will be described in detail later.

The alkoxy group in the case where W ₁ and W ₂ represent a substituted or unsubstituted alkoxy group is preferably an alkoxy group having 1 to 30 carbon atoms, more preferably an alkoxy group having 1 to 8 carbon atoms, and 1 carbon atom. 4 to 4 alkoxy groups are more preferred. Examples of the alkoxy group include methoxy group, ethoxy group, n-propoxy group, i-propoxy group, n-butoxy group, i-butoxy group, s-butoxy group, t-butoxy group, n-octyloxy group, 2 -A methoxyethoxy group etc. are mentioned, Especially preferably, it is a methoxy group. The alkoxy group may have a substituent. The substituent will be described later.

When W ₁ and W ₂ represent a substituted or unsubstituted amino group, the substituted or unsubstituted amino group is preferably an amino group, an alkylamino group, an arylamino group, or a heterocyclic amino group, more preferably an amino group. Group, an alkylamino group having 1 to 30 carbon atoms, and an anilino group having 6 to 30 carbon atoms, and more preferably an amino group, an alkylamino group having 1 to 8 carbon atoms, and an anilino group having 6 to 18 carbon atoms. Particularly preferred are an amino group, an alkylamino group having 1 to 4 carbon atoms, and an anilino group having 6 to 12 carbon atoms. Examples of the substituted or unsubstituted amino group include an amino group (—NH ₂ ), a methylamino group (—NHCH ₃ ), a dimethylamino group {—N (CH ₃ ) ₂ }, an anilino group (—NHPh), N - methyl - anilino group _{{-N (CH 3) Ph}} , diphenylamino group {-N _{(Ph) 2},} and the like, particularly preferably an amino group. Ph represents a phenyl group. The substituent that the amino group may have will be described in detail later.

In the case where W ₁ and W ₂ represent a substituted or unsubstituted aryl group, the aryl group is preferably an aryl group having 6 to 30 carbon atoms, more preferably an aryl group having 6 to 18 carbon atoms, More preferred are 6 to 12 aryl groups. Examples of the substituted or unsubstituted aryl group include a phenyl group, a p-tolyl group, a naphthyl group, an m-chlorophenyl group, an o-hexadecanoylaminophenyl group, and the like. The substituent which the aryl group may have will be described in detail later.

W ₁ and W ₂ each independently preferably represent a substituted or unsubstituted alkoxy group, a substituted or unsubstituted amino group, or a substituted or unsubstituted alkyl group, and are preferably a substituted or unsubstituted alkoxy group or a substituted or unsubstituted group. More preferably, it represents a substituted amino group, more preferably an alkoxy group having a total carbon number of 5 or less, an amino group (—NH ₂ group), or an alkylamino group having a total carbon number of 5 or less, and a total carbon number of 3 It is particularly preferable to represent the following alkoxy group or an alkylamino group having 3 or less total carbon atoms, and most preferable to represent a methoxy group.

In General formula (1), R <_11> , R < ₁₂ > represents a hydrogen atom or a substituent each independently.
Examples of the substituent when R ₁₁ and R ₁₂ represent a substituent include a substituent selected from the following substituent group A.

(Substituent A)
A substituted or unsubstituted alkyl group (for example, a substituted or unsubstituted linear or branched alkyl group having 1 to 12 carbon atoms (for example, methyl, ethyl, n-propyl, i-propyl, n-butyl, i- Butyl, sec-butyl, t-butyl, 2-ethylhexyl, 2-methylsulfonylethyl, 3-phenoxypropyl, trifluoromethyl), substituted or unsubstituted aralkyl group having 7 to 18 carbon atoms, substituted or unsubstituted carbon A linear or branched alkenyl group having 2 to 12 carbon atoms, a substituted or unsubstituted linear or branched alkynyl group having 2 to 12 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 12 carbon atoms (for example, Cyclopentyl), a substituted or unsubstituted cycloalkenyl group having 3 to 12 carbon atoms, a halogen atom (for example, chlorine atom, bromine atom), Or an unsubstituted aryl group (for example, phenyl, 4-t-butylphenyl, 2,4-di-t-amylphenyl), a substituted or unsubstituted heterocyclic group (for example, imidazolyl, pyrazolyl, triazolyl, 2-furyl) 2-thienyl, 2-pyrimidinyl, 2-benzothiazolyl), cyano group, hydroxyl group, nitro group, carboxy group, substituted or unsubstituted amino group, substituted or unsubstituted alkyloxy group (for example, methoxy, ethoxy, 2 -Methoxyethoxy, 2-methylsulfonylethoxy), a substituted or unsubstituted aryloxy group (for example, phenoxy, 2-methylphenoxy, 4-t-butylphenoxy, 3-nitrophenoxy, 3-t-butyloxycarbonylphenoxy, 3-methoxycarbonylphenyloxy), Or an unsubstituted acylamino group (eg, acetamide, benzamide, 4- (3-tert-butyl-4-hydroxyphenoxy) butanamide), a substituted or unsubstituted alkylamino group (eg, methylamino, butylamino, diethylamino, methyl Butylamino), substituted or unsubstituted arylamino groups (eg, phenylamino, 2-chloroanilino), substituted or unsubstituted ureido groups (eg, phenylureido, methylureido, N, N-dibutylureido), substituted or unsubstituted A substituted sulfamoylamino group (for example, N, N-dipropylsulfamoylamino), a substituted or unsubstituted alkylthio group (for example, methylthio, octylthio, 2-phenoxyethylthio), a substituted or unsubstituted arylthio group ( For example, Phenylthio, 2-butoxy-5-t-octylphenylthio, 2-carboxyphenylthio), substituted or unsubstituted alkyloxycarbonylamino groups (eg, methoxycarbonylamino), substituted or unsubstituted alkylsulfonylamino groups and aryl Sulfonylamino group (eg, methylsulfonylamino, phenylsulfonylamino, p-toluenesulfonylamino), substituted or unsubstituted carbamoyl group (eg, N-ethylcarbamoyl, N, N-dibutylcarbamoyl), substituted or unsubstituted sulfamoyl A group (for example, N-ethylsulfamoyl, N, N-dipropylsulfamoyl, N-phenylsulfamoyl), a substituted sulfonyl group (for example, methylsulfonyl, octylsulfonyl, phenylsulfonyl, -Toluenesulfonyl), substituted or unsubstituted alkyloxycarbonyl group (for example, methoxycarbonyl, butyloxycarbonyl), substituted or unsubstituted heterocyclic oxy group (for example, 1-phenyltetrazol-5-oxy, 2-tetrahydropyrani) Oxy), substituted azo groups (eg phenylazo, 4-methoxyphenylazo, 4-pivaloylaminophenylazo, 2-hydroxy-4-propanoylphenylazo), substituted or unsubstituted acyloxy groups (eg acetoxy) ), Substituted or unsubstituted carbamoyloxy groups (eg, N-methylcarbamoyloxy, N-phenylcarbamoyloxy), substituted or unsubstituted silyloxy groups (eg, trimethylsilyloxy, dibutylmethylsilyloxy), substituted or unsubstituted Is an unsubstituted aryloxycarbonylamino group (for example, phenoxycarbonylamino), a substituted imide group (for example, N-succinimide, N-phthalimide), a substituted or unsubstituted heterocyclic thio group (for example, 2-benzothiazolylthio) 2,4-di-phenoxy-1,3,5-triazole-6-thio, 2-pyridylthio), substituted or unsubstituted sulfinyl group (for example, 3-phenoxypropylsulfinyl), substituted or unsubstituted phosphonyl group (Eg, phenoxyphosphonyl, octyloxyphosphonyl, phenylphosphonyl), substituted or unsubstituted aryloxycarbonyl groups (eg, phenoxycarbonyl), substituted or unsubstituted acyl groups (eg, acetyl, 3-phenylpropanoyl) , Benzoyl), ionic parent Aqueous group (for example, carboxyl group, sulfo group, phosphono group and quaternary ammonium group), phosphino group (preferably substituted or unsubstituted phosphino group having 0 to 30 carbon atoms, such as dimethylphosphino group, diphenylphosphino group) Group, methylphenoxyphosphino group), phosphinyl group (preferably a substituted or unsubstituted phosphinyl group having 0 to 30 carbon atoms, such as phosphinyl group, dioctyloxyphosphinyl group, diethoxyphosphinyl group), phosphinyl group A finyloxy group (preferably a substituted or unsubstituted phosphinyloxy group having 0 to 30 carbon atoms, such as a diphenoxyphosphinyloxy group, a dioctyloxyphosphinyloxy group), a phosphinylamino group ( Preferably, the substituted or unsubstituted phosphine having 0 to 30 carbon atoms. Substituents composed of amino groups such as dimethoxyphosphinylamino group, dimethylaminophosphinylamino group, mercapto groups, and combinations thereof (that is, among the above substituents, those having a hydrogen atom are The hydrogen atom may be further substituted with the above substituent).

R ₁₁ and R ₁₂ are each independently a substituted or unsubstituted acylamino group having 1 to 8 carbon atoms, a substituted or unsubstituted alkyl group having 1 to 12 carbon atoms, a substituted or unsubstituted total carbon number of 6 to It preferably represents an aryl group of 18 or a substituted or unsubstituted heterocyclic group having 4 to 12 carbon atoms in total, a linear or branched alkyl group having 1 to 8 carbon atoms in total, or a substituted or unsubstituted total group. It is more preferable to represent an aryl group having 6 to 18 carbon atoms, and a linear or branched alkyl group having 1 to 8 carbon atoms is preferable. Specifically, a methyl group, i-propyl group or t-butyl group is preferable, i-propyl group or t-butyl group is particularly preferable, and t-butyl group is most preferable.

  In the general formula (1), Z represents a substituted or unsubstituted 5-membered heterocyclic ring or a 6-membered heterocyclic ring, and preferably a substituted or unsubstituted 6-membered nitrogen-containing heterocyclic ring having 3 to 10 carbon atoms. Two substituents may be bonded to each other to form a condensed ring. The substituent will be described later.

  The 5-membered or 6-membered heterocycle represented by Z includes a pyridine ring, a pyrazine ring, a pyridazine ring, a pyrimidine ring, a triazine ring, a pyrroline ring, a furan ring, a thiophene ring, a pyrazole ring, an imidazole ring, a triazole ring, and an oxazole ring. , Thiazole ring, isothiazole ring, thiadiazole ring, isoxazole ring, pyrrolidine ring, piperidine ring, piperazine ring, imidazolidine ring, thiazoline ring and the like. The condensed ring formed by bonding two substituents of a 5-membered heterocyclic ring or a 6-membered heterocyclic ring to each other includes quinoline ring, isoquinoline ring, cinnoline ring, phthalazine ring, quinoxaline ring, indole ring, benzofuran ring, benzothiophene A ring, a benzimidazole ring, a benzoxazole ring, a benzothiazole ring, a benzoisothiazole ring, a benzoisoxazole ring, and the like.

  Z is preferably a pyridine ring, pyrimidine ring, S-triazine ring, pyridazine ring, pyrazine ring, 1,2,4-thiadiazole ring, 1,3,4-thiadiazole ring, imidazole ring, more preferably pyridine ring. Ring, pyrimidine ring, S-triazine ring, pyridazine ring, pyrazine ring, and particularly preferred are pyrimidine ring and S-triazine ring from the viewpoint of hue, tinting strength and image fastness, and further the formula ( The pyrimidine ring connected to the nitrogen atom of 1) and the S-triazine ring having an alkoxy group having 1 to 4 carbon atoms at the 2-position are preferred from the viewpoint of hue and image fastness, and especially the alkoxy having 1 to 4 carbon atoms at the 2-position. The S-triazine ring having a group is most preferable from the viewpoint of improving the light fastness of a good image.

In General Formula (1), G ₁ and G ₂ are each independently a hydrogen atom, a substituted or unsubstituted alkyl group (preferably having 1 to 20 carbon atoms), a substituted or unsubstituted aralkyl group (preferably having 7 carbon atoms). -20), a substituted or unsubstituted alkenyl group (preferably having 2 to 20 carbon atoms), a substituted or unsubstituted alkynyl group (preferably having 2 to 20 carbon atoms), a substituted or unsubstituted aryl group (preferably having a carbon number) 2-20), or a substituted or unsubstituted heterocyclic group (preferably having 1 to 20 carbon atoms).
G ₁ and G ₂ are a hydrogen atom, methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, i-butyl group, sec-butyl group, t-butyl group, cyclopropyl group, It preferably represents a benzyl group, 2-phenethyl group, vinyl group, allyl group, ethynyl group, propargyl group, phenyl group, p-tolyl group, naphthyl group, pyridyl group, pyrimidinyl group or pyrazinyl group, a hydrogen atom, methyl More preferably represents a group, a phenyl group, a pyridyl group, a pyrimidinyl group, or a pyrazinyl group, a linear or branched alkyl group having 1 to 8 carbon atoms, a 2-pyridyl group, a 2,6-pyrimidinyl group, 2 , 5-pyrazinyl group or phenyl group is more preferable, and an alkyl group having 3 or less carbon atoms is more preferable. Further, from the viewpoint of hue and image fastness, a hydrogen atom, a methyl group, and a phenyl group are preferable, and among them, a methyl group is particularly preferable from the viewpoint of improving the hue and light fastness.

In the general formula (1), Y ₁ and Y ₂ each independently represent a hydrogen atom or a substituent.
Examples of the substituent in the case where Y ₁ and Y ₂ represent a substituent include a substituent selected from the aforementioned substituent group A.
Y ₁ and Y ₂ are particularly preferably a hydrogen atom, an alkyl group (eg, a methyl group), an aryl group (eg, a phenyl group), a heterocyclic group (eg, a 2-pyridyl group), or an alkylthio group (eg, a methylthio group). In addition, a hydrogen atom, a linear or branched alkyl group having 1 to 4 carbon atoms, a phenyl group, and a methylthio group are preferable. Further, from the viewpoint of hue and image fastness, a hydrogen atom and a methyl group are preferable, and among them, a hydrogen atom is particularly preferable from the viewpoint of improving hue and light fastness.

In the general formula (1), the substituents in the case where G ₁ , G ₂ , Y ₁ , Y ₂ , W ₁ , W ₂ , R ₁₁ , R ₁₂ , Z further have a substituent include the above-described substituents. The substituents selected from group A can be mentioned.

As specific examples of the compound represented by the general formula (1), compounds described in [0124] to [0139] of JP 2011-74376 A can be referred to.
The pigment in the present invention is preferably a pigment containing at least one of a compound represented by the following formula (d1), formula (d2), or formula (d3) or a tautomer thereof, or a salt thereof. More preferably, the pigment contains at least one of a compound represented by the following formula (d1) or a tautomer thereof, or a salt thereof.

  When the crystalline polymorph is present in the pigment used in the present invention, any polymorph may be used, and a mixture of two or more polymorphs may be used. It is preferable to do. That is, it is preferable that the crystalline polymorph is not mixed, and the content of the pigment having a single crystal type is 70% to 100%, preferably 80% to 100%, more preferably 90% to 100% with respect to the whole pigment. %, More preferably 95% to 100%, particularly preferably 100%.

The pigment used in the present invention may contain a tautomer of the compound represented by the general formula (1).
The general formula (1) is shown in the form of an extreme structural formula among several tautomers that can be taken in terms of chemical structure, but may be a tautomer other than the structure described, You may use as a mixture containing these tautomers.
For example, the compound represented by the general formula (1) may be an azo-hydrazone tautomer represented by the following general formula (1 ′).

In general formula (1 ′), R ₁₁ , R ₁₂ , W ₁ , W ₂ , Y ₁ , Y ₂ , G ₁ , G ₂ and Z are R ₁₁ , R ₁₂ , W ₁ , and Z in general formula (1). W _2, a _{Y 1, Y 2,} synonymous with G 1, _{G 2} and Z.

  In the case where the compound represented by the general formula (1) has an acid group, a part or all of the acid group may be a salt type, and a salt type compound and a free acid type compound are mixed. You may do it. Examples of salt types include alkali metal salts such as Na, Li and K, alkaline earth metal salts such as Mg, Ca and Ba, ammonium salts optionally substituted with alkyl groups or hydroxyalkyl groups, or organic Examples include salts of amines. Examples of organic amines include lower alkyl amines, hydroxy-substituted lower alkyl amines, carboxy-substituted lower alkyl amines, and polyamines having 2 to 10 alkyleneimine units having 2 to 4 carbon atoms. In the case of these salt types, the type is not limited to one type, and a plurality of types may be mixed.

  In the compound represented by the general formula (1), when a plurality of acid groups are contained in one molecule, the plurality of acid groups may be salt type or free acid type and may be different from each other.

  The pigment used in the present invention may be a hydrate containing water molecules in the crystal.

The pigment used in the present invention is a pigment containing a compound represented by the general formula (1) or a tautomer thereof, or a salt thereof, and a compound represented by the general formula (1) or a tautomer thereof. Or an aggregate of molecules of their salts in the form of fine particles. The content of the compound represented by the general formula (1) in the pigment or a tautomer thereof, or a salt thereof is preferably 80% by mass or more.
As a method for synthesizing the compound represented by the general formula (1) used in the present invention and a method for producing a pigment (including post-treatment such as solvent sol trimming), JP-A-2011-74376 [0153] to Reference can be made to the description of [0159].

  The content of the pigment in the aqueous pigment dispersion of the present invention is preferably 0.1 to 50% by mass and more preferably 1 to 30% by mass with respect to the total amount of the aqueous pigment dispersion.

(Water-soluble dye having an azo group)
The aqueous pigment dispersion of the present invention contains a water-soluble dye having an azo group.
The water-soluble dye having an azo group may be used alone or in combination of two or more.
The water-soluble dye having an azo group is preferably a yellow dye, and is preferably a compound represented by the following general formula (3).
(A−N = N−B) n−L (3)
In General Formula (3), A and B each independently represent a substituted or unsubstituted heterocyclic group. L represents a hydrogen atom, a single bond, or a divalent linking group. n represents 1 or 2. However, when n is 1, L represents a hydrogen atom, and both A and B are monovalent substituted or unsubstituted heterocyclic groups. When n is 2, L represents a single bond or a divalent linking group, one of A and B is a monovalent substituted or unsubstituted heterocyclic group, and the other is a divalent substituted or unsubstituted group. It is a heterocyclic group. When n is 2, A may be the same or different, and B may be the same or different.

In general formula (3), A and B each independently represent a substituted or unsubstituted heterocyclic group. The heterocycle is preferably a 5-membered or 6-membered heterocycle, which may be a monocyclic structure or a polycyclic structure in which two or more rings are fused. It may be a ring or a non-aromatic heterocycle. As a hetero atom which comprises the said heterocyclic ring, a nitrogen atom, an oxygen atom, or a sulfur atom is preferable.
L represents a hydrogen atom, a single bond, or a divalent linking group.
n represents 1 or 2. However, when n is 1, L represents a hydrogen atom, and both A and B are monovalent substituted or unsubstituted heterocyclic groups. When n is 2, L represents a single bond or a divalent linking group, one of A and B is a monovalent substituted or unsubstituted heterocyclic group, and the other is a divalent substituted or unsubstituted group. It is a heterocyclic group. When n is 2, A may be the same or different, and B may be the same or different.

  In the above general formula (3), the heterocyclic ring represented by A includes 5-pyrazolone, pyrazole, triazole, oxazolone, isoxazolone, barbituric acid, pyridone, pyridine, rhodanine, pyrazolidinedione, pyrazolopyridone, meldrum acid In addition, a condensed heterocyclic ring obtained by further condensing a hydrocarbon aromatic ring or a heterocyclic ring to these heterocyclic rings is preferable. Among them, 5-pyrazolone, 5-aminopyrazole, pyridone, 2,6-diaminopyridine, and pyrazoloazoles are preferable, and 5-aminopyrazole, 2-hydroxy-6-pyridone, and pyrazolotriazole are particularly preferable.

  Examples of the heterocycle represented by B include pyridine, pyrazine, pyrimidine, pyridazine, triazine, quinoline, isoquinoline, quinazoline, cinnoline, phthalazine, quinoxaline, pyrrole, indole, furan, benzofuran, thiophene, benzothiophene, pyrazole, imidazole, benzo Examples include imidazole, triazole, oxazole, isoxazole, benzoxazole, thiazole, benzothiazole, isothiazole, benzoisothiazole, thiadiazole, benzisoxazole, pyrrolidine, piperidine, piperazine, imidazolidine, thiazoline and the like. Of these, pyridine, quinoline, thiophene, benzothiophene, pyrazole, imidazole, benzimidazole, triazole, oxazole, isoxazole, benzoxazole, thiazole, benzothiazole, isothiazole, benzoisothiazole, thiadiazole, and benzoisoxazole are preferable. Quinoline, thiophene , Pyrazole, thiazole, benzoxazole, benzisoxazole, isothiazole, imidazole, benzothiazole, thiadiazole are more preferable, and pyrazole, benzothiazole, benzoxazole, imidazole, 1,2,4-thiadiazole, 1,3,4-thiadiazole Is particularly preferred.

  Examples of the substituent that may be substituted with A and B include a substituent selected from the aforementioned substituent group A.

Examples of the divalent linking group represented by L include an alkylene group, an alkenylene group, an alkynylene group, an arylene group, a heterocyclic residue, —CO—, —SO _m2 — (m2 represents 0, 1, or 2), — NR- (R represents a hydrogen atom, an alkyl group, an aryl group), -O-, and a divalent group obtained by combining these linking groups, and further, they may be substituted with A and B. May have the substituents mentioned above.

  The water-soluble dye having an azo group preferably has at least one ionic hydrophilic group in the molecule. The ionic hydrophilic group includes a carboxyl group, a hydroxyl group on an aromatic ring including an aromatic heterocycle, a sulfo group, a phosphono group, a sulfonamide group, a quaternary ammonium group, and the like. As the ionic hydrophilic group, a carboxyl group, a hydroxyl group on an aromatic ring containing an aromatic heterocycle, a sulfo group, and a phosphono group are preferable, and among them, a hydroxyl group on an aromatic ring containing a carboxyl group and an aromatic heterocycle, sulfo Groups are preferred. In particular, at least one is most preferably a carboxyl group. In addition, a hydroxyl group or a sulfonamide group on an aromatic ring containing an aromatic heterocycle is preferable because it tends to increase the storage stability of the dye in the ink. A carboxyl group, a hydroxyl group on an aromatic ring including an aromatic heterocycle, a phosphono group, a sulfonamide group, and a sulfo group may be in a salt state. Examples of counter ions that form a salt include ammonium ions and alkali metals. Ions (eg, lithium ions, sodium ions, potassium ions) and organic cations (eg, tetramethylammonium ions, tetramethylguanidinium ions, tetramethylphosphonium) are included. Among the counter ions, alkali metal salts are preferable.

  The compound represented by the general formula (3) is preferably a compound represented by the following general formula (4) or (5).

In the general formula (4), R ₄₁ and R ₄₂ each independently represent a monovalent substituent, R ₅₁ and R ₅₂ each independently represent —OR ₆ or —NHR ₇ , and R ₆ and R ₇ each represent Independently represents a hydrogen atom or a monovalent substituent, X ₃ represents a single bond or a divalent linking group, Ar ₃₁ and Ar ₃₂ each independently represent a divalent substituted or unsubstituted heterocyclic group, Ar ₄₁ and Ar ₄₂ each independently represent a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, or a substituted or unsubstituted monovalent triazine ring group.

In the general formula (4), the monovalent substituent represented by R ₄₁ and R ₄₂ is preferably a substituent selected from the aforementioned substituent group A. More preferably, it is a substituted or unsubstituted alkyl group, a substituted or unsubstituted cycloalkyl group, a substituted or unsubstituted aralkyl group, a substituted or unsubstituted alkoxy group, a substituted or unsubstituted aryl group, a substituted or unsubstituted An amino group, a carboxyl group (which may be a salt), a substituted or unsubstituted carbamoyl group is preferable, and a substituted or unsubstituted alkyl group (preferably a lower alkyl group having 1 to 5 carbon atoms such as methyl, ethyl, butyl, t -Butyl) is most preferred.

R ₅₁ and R ₅₂ represent —OR ₆ or —NHR ₇ , and R ₆ and R ₇ represent a hydrogen atom or a monovalent substituent. The monovalent substituent represented by R ₆ and R ₇ has the same meaning as the substituent group A described above.
X ₃ represents a single bond or a divalent linking group. X ₃ is preferably a divalent linking group. Divalent linking groups include alkylene groups (eg, methylene, ethylene, propylene, butylene, pentylene), alkenylene groups (eg, ethenylene, propenylene), alkynylene groups (eg, ethynylene, propynylene), arylene groups (eg, phenylene) , Naphthylene), divalent heterocyclic group (eg, 6-chloro-1,3,5-triazine-2,4-diyl group, pyrimidine-2,4-diyl group, quinoxaline-2,3-diyl group) , —O—, —CO—, —NR— (wherein R is a hydrogen atom, an alkyl group or an aryl group), —S—, —SO ₂ —, —SO— or a combination thereof is preferable.
The alkylene group, alkenylene group, alkynylene group, arylene group, divalent heterocyclic group, alkyl group represented by R or aryl group may have a substituent. Examples of the substituent include the group of the substituent group A described above. Moreover, the alkyl group and aryl group represented by R are synonymous with the alkyl group and aryl group of the above-mentioned substituent group A.
Examples of the divalent linking group represented by X ₃ include an alkylene group having 10 or less carbon atoms, an alkenylene group having 10 or less carbon atoms, an alkynylene group having 10 or less carbon atoms, an arylene group having 6 to 10 carbon atoms, and a divalent complex. More preferably, it is a cyclic group, —O—, —S—, or a combination thereof.
The total number of carbon atoms in the divalent linking group is preferably 0 to 50, more preferably 0 to 30, and most preferably 0 to 10.

Examples of the divalent substituted or unsubstituted heterocyclic group represented by Ar ₃₁ and Ar ₃₂ include pyridine, pyrazine, pyrimidine, pyrazole, thiazole, benzothiazole, and thiadiazole, preferably thiadiazole. These groups may further have a substituent, and as the substituent, those mentioned in the above-mentioned substituent group A are preferable.

The substituted or unsubstituted alkyl group represented by Ar ₄₁ and Ar ₄₂ is preferably a linear or branched alkyl group having 1 to 12 carbon atoms, such as methyl, ethyl, propyl, isopropyl, sec-butyl, t-butyl. 2-ethylhexyl, 2-methylsulfonylethyl, 3-phenoxypropyl, trifluoromethyl.
As the substituted or unsubstituted aryl group represented by Ar ₄₁ and Ar ₄₂ , preferred examples of the substituted or unsubstituted aryl group include phenyl, 4-t-butylphenyl, and 2,4-di-t-amylphenyl. Can be mentioned.
As the substituent when Ar ₄₁ and Ar ₄₂ have a substituent, those mentioned in the above-mentioned substituent group A are preferable, and a carboxyl group, an alkoxy group, a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl More preferably, it is a group.
Ar ₄₁ and Ar ₄₂ are most preferably a substituted aryl group.

  Specific examples of the dye represented by the general formula (4) are shown below, but are not limited to the following examples.

  The synthesis of the dye represented by the general formula (4) can be performed by a known method. For example, it can be synthesized by the method described in JP-A Nos. 2003-277661 and 2003-277661.

  Next, the general formula (5) will be described in detail.

In General Formula (5), R ₆₁ , R ₆₂ , X ₅₁ , X ₅₂ , Y ₅₁ , Y ₅₂ , G ₅₁ and G ₅₂ each independently represent a hydrogen atom or a monovalent substituent, and Z ₅ is 5 An atomic group constituting an ˜8-membered nitrogen-containing heterocycle, and M ₁ represents a hydrogen atom or a cation. m ₁ represents an integer of 0 to 3.

R ₆₁ , R ₆₂ , X ₅₁ , X ₅₂ , Y ₅₁ , Y ₅₂ , G ₅₁ and G ₅₂ represent a hydrogen atom or a monovalent substituent. Examples of the monovalent substituent include a substituent selected from the aforementioned substituent group A.
Among them, particularly preferred are hydrogen atom, halogen atom, alkyl group, aryl group, heterocyclic group, cyano group, alkoxy group, amide group, ureido group, alkylsulfonylamino group, arylsulfonylamino group, sulfamoyl group, alkylsulfonyl group. An arylsulfonyl group, a carbamoyl group, or an alkoxycarbonyl group, particularly preferably a hydrogen atom, a halogen atom, an alkyl group, an aryl group, a cyano group, an alkylsulfonyl group, an arylsulfonyl group, or a heterocyclic group, and a hydrogen atom, an alkyl group Most preferred are groups, aryl groups, cyano groups, or alkylsulfonyl groups.

In the general formula (5), X ₅₁ and X ₅₂ are preferably electron withdrawing groups. In particular, it is an electron-withdrawing group having a Hammett's substituent constant σp value of 0.20 or more, and more preferably an electron-withdrawing group having a σp value of 0.30 or more. The upper limit is 1.0 or less electron withdrawing group.
Specific examples of X ₅₁ and X ₅₂ which are electron withdrawing groups having a σp value of 0.20 or more include acyl group, acyloxy group, carbamoyl group, alkyloxycarbonyl group, aryloxycarbonyl group, cyano group, nitro group Dialkylphosphono group, diarylphosphono group, diarylphosphinyl group, alkylsulfinyl group, arylsulfinyl group, alkylsulfonyl group, arylsulfonyl group, sulfonyloxy group, acylthio group, sulfamoyl group, thiocyanate group, thiocarbonyl group, A halogenated alkyl group, a halogenated alkoxy group, a halogenated aryloxy group, a halogenated alkylamino group, a halogenated alkylthio group, an aryl group substituted with another electron-withdrawing group having a σp value of 0.20 or more, hetero Ring group, halogen atom, azo group, Includes a selenocyanate group.

As preferred examples of X ₅₁ and X ₅₂ , an acyl group having 2 to 12 carbon atoms, an acyloxy group having 2 to 12 carbon atoms, a carbamoyl group having 1 to 12 carbon atoms, an alkyloxycarbonyl group having 2 to 12 carbon atoms, carbon 7-18 aryloxycarbonyl group, cyano group, nitro group, C1-C12 alkylsulfinyl group, C6-C18 arylsulfinyl group, C1-C12 alkylsulfonyl group, C6-C6 18 arylsulfonyl groups, C 0-12 sulfamoyl groups, C 1-12 halogenated alkyl groups, C 1-12 halogenated alkyloxy groups, C 1-12 halogenated alkylthio groups, carbon A halogenated aryloxy group of 7 to 18 carbon atoms, a carbon number of 7 to 18 substituted with two or more other electron-withdrawing groups of σp 0.20 or more Aryl group, and a nitrogen atom, an oxygen atom or 5-8 membered ring having sulfur atom include a heterocyclic group having 1 to 18 carbon atoms.
More preferably, they are a cyano group, an alkylsulfonyl group having 1 to 12 carbon atoms, an arylsulfonyl group having 6 to 18 carbon atoms, or a sulfamoyl group having 0 to 12 carbon atoms.

Particularly preferred as X ₅₁ and X ₅₂ are a cyano group, an alkylsulfonyl group having 1 to 12 carbon atoms, or a sulfamoyl group having 0 to 12 carbon atoms, and most preferred is a cyano group or 1 to 12 carbon atoms. Of the alkylsulfonyl group.

In the general formula (5), preferred examples of the substituent for G ₅₁ and G ₅₂ are a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted cycloalkyl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted group. A substituted alkynyl group, a substituted or unsubstituted aralkyl group, a substituted or unsubstituted aryl group, or a substituted or unsubstituted heterocyclic group;

The substituted or unsubstituted alkyl group is preferably a linear or branched alkyl group having 1 to 12 carbon atoms, such as methyl, ethyl, propyl, isopropyl, sec-butyl, t-butyl, 2-ethylhexyl, 2- Examples include methylsulfonylethyl, 3-phenoxypropyl, and trifluoromethyl.
The substituted or unsubstituted cycloalkyl group is preferably a linear or branched cycloalkyl group having 3 to 12 carbon atoms, and examples thereof include cyclopentyl.
As the substituted or unsubstituted alkenyl group, a linear or branched alkenyl group having 2 to 12 carbon atoms is preferable.
As the substituted or unsubstituted alkynyl group, a linear or branched alkynyl group having 2 to 12 carbon atoms is preferable.
As the substituted or unsubstituted aralkyl group, a linear or branched aralkyl group having 7 to 18 carbon atoms is preferable.
Preferred examples of the substituted or unsubstituted aryl group include phenyl, 4-t-butylphenyl, and 2,4-di-t-amylphenyl.
Preferred examples of the substituted or unsubstituted heterocyclic group include imidazolyl, pyrazolyl, triazolyl, 2-furyl, 2-thienyl, 2-pyrimidinyl, and 2-benzothiazolyl.

Particularly preferred substituents represented by G ₅₁ and G ₅₂ are a substituted aryl group or a substituted heterocyclic group, and among them, a substituted aryl group is particularly preferred.

In General Formula (5), R ₆₁ and R ₆₂ are a substituted or unsubstituted alkyl group having 1 to 12 carbon atoms, a substituted or unsubstituted aryl group having 6 to 18 carbon atoms, or a substituted or unsubstituted total group. A heterocyclic group having 4 to 12 carbon atoms is preferable, among which a linear alkyl group having 1 to 8 carbon atoms or a branched alkyl group is preferable, particularly a secondary or tertiary alkyl group is preferable, and a t-butyl group is preferable. Most preferred.

In General Formula (5), Y ₅₁ and Y ₅₂ are a hydrogen atom, a substituted or unsubstituted alkyl group having 1 to 12 carbon atoms, a substituted or unsubstituted aryl group having 6 to 18 carbon atoms, or a substituted or unsubstituted group. Preferred is a heterocyclic group having 4 to 12 carbon atoms in total, among which a hydrogen atom, a linear alkyl group having 1 to 8 carbon atoms and / or a branched alkyl group is preferable, and particularly a hydrogen atom or 1 to 8 carbon atoms. An alkyl group is preferred, and a hydrogen atom is most preferred.

Z ₅ represents an atomic group constituting a 5- to 8-membered nitrogen-containing heterocycle.
Preferred examples of the 5- to 8-membered nitrogen-containing heterocycle represented by Z ₅ are S-triazine ring, pyrimidine ring, pyridazine ring, pyrazine ring, pyridine ring, imidazole ring, pyrazole ring, or pyrrole ring, and among them, S- A triazine ring, a pyrimidine ring, a pyridazine ring or a pyrazine ring is more preferred, and an S-triazine ring is most preferred.

m ₁ represents an integer of 0 to 3, and in the case of a preferred example structure of a 5- to 8-membered nitrogen-containing heterocycle represented by Z ₅ , when -OM ₁ group can be substituted, 0 to 2 are preferable. 0 or 1 is preferable, and m ₁ = 1 is particularly preferable.

M ₁ represents a hydrogen atom or a cation.
The cation represented by M ₁ is an alkali metal ion, ammonium or quaternary ammonium cation, and preferably Li, Na, K, NH ₄ , or NR ₄ . However, R ₄ is an alkyl group and an aryl group, and is the same as the examples of the alkyl group and aryl group represented by R ₆₁ , R ₆₂ , Y ₅₁ , and Y ₅₂ described above. Among them, preferable examples of the cation of M ₁ are lithium ion, sodium ion, potassium ion, or ammonium ion, and lithium ion, sodium ion, and potassium ion are particularly preferable.

  Although the specific example of a compound represented by the said General formula (5) below is shown, it is not limited to the following example.

  The synthesis of the dye represented by the general formula (5) can be performed by a known method. For example, it can be synthesized by the method described in Japanese Patent Application Laid-Open No. 2007-063520.

  The content of the water-soluble dye having an azo group in the aqueous pigment dispersion of the present invention is preferably 0.01 to 25% by mass, and preferably 0.1 to 15% by mass with respect to the total amount of the aqueous pigment dispersion. It is more preferable that

  The mass ratio of the pigment and the water-soluble dye having an azo group (the mass of the pigment / the mass of the water-soluble dye having an azo group) in the aqueous pigment dispersion of the present invention is preferably 1/1 to 20/1. 2/1 to 20/1 is more preferable, and 3/1 to 20/1 is still more preferable. When (mass of pigment / mass of water-soluble dye having an azo group) is 1/1 or more, it is preferable from the viewpoint of water resistance of the printed material, and 20/1 or less is preferable from the viewpoint of suppressing foreign matter.

(Polymer dispersant)
The polymer dispersant used in the present invention is a polymer compound having a repeating unit represented by the following general formula (2-1) and a repeating unit represented by the following general formula (2-2).

In General Formula (2-1), R ₁ represents a hydrogen atom, a methyl group or a substituted methyl group, and R ₂ represents an alkyl group substituted with a substituent containing an aryl group or an aromatic heterocyclic group, substituted or unsubstituted It represents a substituted aralkyl group or a substituted or unsubstituted aryl group.
In General Formula (2-2), R ₃ represents a hydrogen atom, a methyl group, or a substituted methyl group. M represents a hydrogen atom or a counter cation.

In the general formula (2-1), R ₁ represents a hydrogen atom, a methyl group or a substituted methyl group. R ₁ is preferably a hydrogen atom or a methyl group, and more preferably a methyl group. Examples of the substituent that the substituted methyl group has include a substituent selected from the aforementioned substituent group A.

In the general formula (2-1), R ₂ represents an alkyl group substituted with a substituent containing an aryl group or an aromatic heterocyclic group, a substituted or unsubstituted aralkyl group, or a substituted or unsubstituted aryl group. .

The alkyl group substituted with a substituent containing an aryl group or an aromatic heterocyclic group is preferably an alkyl group having 1 to 30 carbon atoms substituted with a substituent containing an aryl group or an aromatic heterocyclic group, and an aryl group Or the C1-C20 alkyl group substituted by the substituent containing an aromatic heterocyclic group is more preferable.
Examples of the substituent containing an aryl group or an aromatic heterocyclic group include an aryl group, an aromatic heterocyclic group, an aryloxy group, a heterocyclic oxy group, an arylcarbonyloxy group, a heterocyclic carbonyloxy group, an arylcarbonylamino group, a hetero group Examples thereof include a ring carbonylamino group, an arylaminocarbonylamino group, a heterocyclic aminocarbonylamino group, and the like, and an aryl group, a heterocyclic group, an aryloxy group, an arylcarbonyloxy group, and a heterocyclic carbonyloxy group are preferable.
As the alkyl group substituted with a substituent containing an aryl group or an aromatic heterocyclic group, specifically, 2-phthalimidoethyl group, 2-naphthoyloxyethyl group, 2-thenoyloxyethyl group, or 2-phenoxy An ethyl group is preferred. In addition, about the alkyl group substituted by the aryl group, it describes in the following aralkyl group.

The substituted or unsubstituted aralkyl group is preferably a substituted or unsubstituted aralkyl group having 7 to 30 carbon atoms, more preferably a substituted or unsubstituted aralkyl group having 7 to 20 carbon atoms, specifically a benzyl group or A 2-phenethyl group is preferred.
The substituted or unsubstituted aryl group is preferably a substituted or unsubstituted aryl group having 6 to 30 carbon atoms, more preferably a substituted or unsubstituted aryl group having 6 to 20 carbon atoms, specifically a phenyl group, It is preferably a p-tolyl group or a naphthyl group.

  When the alkyl group, aralkyl group, and aryl group substituted with a substituent containing the aryl group or aromatic heterocyclic group have a substituent, the substituent selected from the aforementioned substituent group A Is mentioned.

R ₂ is preferably a benzyl group or a 2-phenoxyethyl group, more preferably a benzyl group.

In General Formula (2-2), R ₃ represents a hydrogen atom, a methyl group, or a substituted methyl group. R ₃ is preferably a hydrogen atom or a methyl group, and more preferably a methyl group. Examples of the substituent that the substituted methyl group has include a substituent selected from the aforementioned substituent group A.

In general formula (2-2), M represents a hydrogen atom or a counter cation. When M represents a counter cation, examples of the counter cation include alkali metal ions such as sodium ion, lithium ion, and potassium ion, ammonium ion, and organic cation. Examples of the organic cation include a lower alkyl ammonium cation, a hydroxy-substituted lower alkyl ammonium cation, a carboxy-substituted lower alkyl ammonium cation, and an organic cation having 2 to 10 alkyleneimine units having 2 to 4 carbon atoms.
M in the general formula (2-2) may be all hydrogen atoms, all may be counter cations, or some may be hydrogen atoms and some may be counter cations. . Moreover, 1 type may be sufficient as a counter cation, and 2 or more types may be mixed. The ratio of hydrogen atom to counter cation (molar ratio of hydrogen atom / counter cation) is preferably 50/50 to 0/100, and more preferably 30/70 to 0/100.

The polymer dispersant has a repeating unit represented by the general formula (2-1) and a repeating unit represented by the general formula (2-2). The content ratio (molar ratio) of each monomer unit contained in one molecule of the polymer dispersant, expressed as: a repeating unit represented by: / a repeating unit represented by the above general formula (2-2): The ratio is preferably 50/50 to 90/10 from the viewpoint of suppressing foreign matter, and more preferably 60/40 to 80/20.
The repeating unit represented by the general formula (2-1) and the repeating unit represented by the general formula (2-2) contained in the polymer dispersant may each be one kind. There may be more than species.

  The polymer dispersant may further contain other repeating units. Examples of other repeating units include styrene and (meth) acrylamide. When the polymer dispersant contains other repeating units, the content of the other repeating units is preferably 0.1 to 20 mol% with respect to all the repeating units of the polymer dispersant.

  The polymer dispersant used in the present invention may be produced by any appropriate means, and is represented by the monomer represented by the general formula (2-1) and the general formula (2-2). It is preferable to copolymerize the monomer to be produced by free radical polymerization. Suitable free radical polymerization is not particularly limited, such as suspension polymerization, solution polymerization, dispersion polymerization, and emulsion polymerization, but is preferably solution polymerization.

In the polymerization of the polymer dispersant, usually, the polymerization temperature is preferably 50 to 150 ° C., more preferably 60 to 120 ° C., and the polymerization time is preferably 1 to 24 hours. The polymerization atmosphere is preferably an inert gas atmosphere such as nitrogen gas or argon.
The polymerization reaction is carried out by adding an initiator solution prepared by adding a polymerization initiator to a polymerization solvent and a monomer solution prepared by adding a monomer and a chain transfer agent as raw materials to the polymerization solvent. It is preferable to carry out by dropping and mixing each inside.
After completion of the polymerization reaction, the purified polymer dispersant can be isolated from the reaction solution by a known method such as reprecipitation or solvent distillation. Further, the obtained polymer dispersant can be purified by removing unreacted monomers and the like by membrane separation, chromatographic method, extraction method or the like by repeated reprecipitation.

The weight average molecular weight (Mw) of the polymer dispersant is preferably 5,000 to 50,000, more preferably 7,000 to 20,000, and 7,000 to 17,000. Further preferred. When the weight average molecular weight of the polymer dispersant is 5,000 or more, the image quality of the printed matter is excellent and preferable. When the weight average molecular weight of the polymer dispersant is 50,000 or less, it is possible to suppress an increase in the viscosity of the pigment dispersion and the inkjet ink, and it is possible to increase the ink discharge speed. Moreover, it is possible to prevent a decrease in the storage stability of the ink, which is preferable.
In the present specification, the weight average molecular weight of the polymer dispersant is a polystyrene equivalent value measured by a GPC (gel permeation chromatography) method. For GPC, HLC-8220 (manufactured by Tosoh Corporation) was used, and TSK gel GMHXL, TSK gel G4000HXL, and TSK gel G2000HXL (manufactured by Tosoh Corporation, 7.8 mm ID × 30.0 cm) were used as eluents as columns. Measurement was performed using THF (tetrahydrofuran).

The amount of the polymer dispersant used in the present invention is preferably 10 to 100 parts by mass, more preferably 20 to 80 parts by mass, and 30 to 60 parts by mass with respect to 100 parts by mass of the pigment. More preferably. It is preferable that the amount of the polymer dispersant is 10 parts by mass or more with respect to 100 parts by mass of the pigment because the pigment can be efficiently dispersed. Further, it is preferable that the amount of the polymer dispersant is 100 parts by mass or less with respect to 100 parts by mass of the pigment because productivity is increased and economical.
Moreover, a polymer dispersing agent may be used individually by 1 type, or may be used in combination of 2 or more type.

(water)
The aqueous pigment dispersion of the present invention contains water as a dispersion medium.
The water used in the present invention may be tap water or well water, and is not particularly limited. For example, pure water or ultrapure water such as ion exchange water, ultrafiltration water, reverse osmosis water, and distilled water. Water is preferred. Furthermore, for the purpose of preventing the generation of mold, bacteria, etc., it is also preferable to use water sterilized by ultraviolet treatment, hydrogen peroxide treatment or the like.
The amount of water used in the present invention is preferably 20 to 98% by mass and more preferably 30 to 90% by mass with respect to the total amount of the aqueous pigment dispersion.

(Other ingredients)
The aqueous pigment dispersion of the present invention may contain other components in addition to the pigment, the water-soluble dye having an azo group, the polymer dispersant, and water. Examples of other components include organic solvents and preservatives.

(Organic solvent)
In the present invention, the aqueous pigment dispersion may contain an organic solvent in addition to the above water. In addition, it is preferable that the amount of the organic solvent to be contained is smaller than the content of water, and the content of the organic solvent is less than 100 parts by mass with respect to 100 parts by mass of water contained in the aqueous pigment dispersion. Preferably, it is 50 parts by mass or less, more preferably 30 parts by mass or less, and particularly preferably 10 parts by mass or less.
The organic solvent used in combination is preferably a water-soluble organic solvent, such as glycerin, diglycerol, 1,2,6-hexanetriol, trimethylolpropane, ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, Pentaethylene glycol, dipropylene glycol, polyoxyethylene glyceryl ether, polyoxypropylene glyceryl ether, 2-butene-1,4-diol, 2-ethyl-1,3-hexanediol, 2-methyl-2,4-pentane Alkanediols (polyhydric alcohols) such as diol, 1,2-octanediol, 1,2-hexanediol, 1,2-pentanediol, 4-methyl-1,2-pentanediol; vulcose, mannose Sugars such as fructose, ribose, xylose, arabinose, galactose, aldonic acid, glucitol, (sorbitol), maltose, cellobiose, lactose, sucrose, trehalose, maltotriose; sugar alcohols; Agents: C1-C4 alkyl alcohols such as ethanol, methanol, butanol, propanol, isopropanol; ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol monomethyl ether acetate, diethylene glycol monomethyl ether, diethylene glycol Monoethyl ether, diethylene glycol mono-n-propyl ether, ethylene Recall mono-iso-propyl ether, diethylene glycol mono-iso-propyl ether, ethylene glycol mono-n-butyl ether, ethylene glycol mono-t-butyl ether, diethylene glycol mono-t-butyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, Propylene glycol mono-t-butyl ether, propylene glycol mono-n-propyl ether, propylene glycol mono-iso-propyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol mono-n-propyl ether, di Glycol ethers such as propylene glycol mono-iso-propyl ether; 2-pyrrolidone, N-methyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, formamide, acetamide, dimethyl sulfoxide, sorbitol, sorbitan, acetin, diacetin, triacetin, sulfolane and the like. Species or two or more can be used.

(Preservative)
The aqueous pigment dispersion of the present invention may contain a preservative. An antiseptic means a substance having a function of preventing the generation and development of microorganisms, particularly bacteria and fungi.
Examples of the preservative include inorganic preservatives (such as silver ion-containing substances) and salts containing heavy metal ions. Organic preservatives include quaternary ammonium salts (tetrabutylammonium chloride, cetylpyridinium chloride, benzyltrimethylammonium chloride, etc.), phenol derivatives (phenol, cresol, butylphenol, xylenol, bisphenol, etc.), phenoxyether derivatives (Phenoxyethanol etc.), heterocyclic compounds (benzotriazole, proxel (PROXEL), 1,2-benzisothiazolin-3-one etc.), acid amides, carbamic acid, carbamates, amidine / guanidine, pyridines (sodium pyridine) Thione-1-oxide, etc.), diazines, triazines, pyrrole / imidazoles, oxazole / oxazines, thiazole / thiadiazines, thioureas, thiosemicarls Zides, dithiocarbamates, sulfides, sulfoxides, sulfones, sulfamides, antibiotics (penicillin, tetracycline, etc.), sodium dehydroacetate, sodium benzoate, ethyl p-hydroxybenzoate, and salts thereof Various things can be used.
In addition, as preservatives, those described in the antibacterial and microscopic handbook (Gihodo Publishing Co., Ltd .: 1986), the antibacterial and antifungal encyclopedia (edited by the Japanese Society for Antibacterial and Fungal Sciences) Can do.

As these compounds, various compounds such as oil-soluble structures and water-soluble structures can be used, but water-soluble compounds are preferred.
As the preservative, a phenol derivative or a heterocyclic compound is preferable, and a heterocyclic compound is more preferable.
The heterocyclic compound is preferably a thiazole compound or a benzotriazole compound. Among the antiseptics, thiazole compounds particularly function as antifungal agents. Examples of thiazole compounds include benzisothiazoline, isothiazoline, 1,2-benzisothiazolin-3-one, 5-chloro-2-methyl-4-isothiazolin-3-one, 2- (thiocyanomethylthio) benzthiazole, 2- Examples include mercaptobenzthiazole and 3-allyloxy-1,2-benzisothiazole-1,1-oxide. Moreover, as a thiazole antifungal agent, PROXEL (trademark) series (BDN, BD20, GXL, LV, XL2, Ultra10, etc.) manufactured and sold by Arch Chemicals Co., Ltd. can also be used.

  A benzotriazole-based compound functions as a rust preventive agent, among other antiseptics. For example, a metal material (particularly 42 alloy (a nickel-iron alloy containing 42% nickel)) constituting an ink jet head is in contact with ink. Rust generation, one of the causes, can be prevented. Examples of the benzotriazole compounds include 1H-benzotriazole, 4-methyl-1H-benzotriazole, 5-methyl-1H-benzotriazole, and sodium salts or potassium salts thereof.

One or more preservatives can be added to the aqueous solution in combination.
The preservative is preferably at least one selected from the group consisting of heterocyclic compounds, phenol derivatives, phenoxy ether derivatives, and alkanediols, and at least one preservative is a heterocyclic compound. Is more preferable.
More preferably, the preservative is a heterocyclic compound, and the heterocyclic compound is a thiazole compound or a benzotriazole compound.

  The content of the preservative can be used in a wide range, but is preferably 0.01 to 20% by mass, more preferably 0.1 to 10% by mass, and 0.5 to 5% by mass with respect to the pigment. Further preferred.

[Method for producing aqueous pigment dispersion]
The present invention also relates to a method for producing the aqueous pigment dispersion. The method for producing the aqueous pigment dispersion of the present invention comprises:
Step (A): obtaining a composition containing the pigment, the polymer dispersant, and water,
Step (B): a step of dispersing the pigment in the composition,
Step (C): A step of adding a water-soluble dye having an azo group to the composition.
Each step will be described below.

<Process (A)>
Step (A) is a step of obtaining a composition containing the pigment, the polymer dispersant, and water. In the step (A), each component is preferably mixed with the following composition. In addition, it describes together about the preferable addition amount of the water-soluble dye which has an azo group added in the below-mentioned process (C).
(A) 20-98 parts by weight, preferably 30-90 parts by weight of water (b) 0.1-50 parts by weight, preferably 1-30 parts by weight of pigment (c) 0.1-40 parts by weight, preferably 1 to 30 parts by mass of a polymeric dispersant (d) 0.01 to 25 parts by mass, preferably 0.1 to 15 parts by mass of a water-soluble dye having an azo group However, the total mass of the resulting composition is 100 The sum of (a) + (b) + (c) + (d) is 100 parts by mass or less when the parts are mass parts.
The mass ratio of the amount of pigment used / the amount of polymer dispersant is preferably 10/1 to 10/10, more preferably 10/2 to 10/8, and even more preferably 10/3 to 10/6.
The mass ratio of the amount of pigment used / the amount of the water-soluble dye having an azo group is preferably 1/1 to 20/1, more preferably 2/1 to 20/1, still more preferably 3/1 to 20/1.

In the step (A), each component is preferably mixed by a known mixing method. The mixing method is not particularly limited.
Moreover, the mixing temperature and mixing time in the step (A) are not particularly limited, and may be appropriately selected according to the desired progress of mixing.
In step (A), the components may be mixed in any order.
In the step (A), other components such as the above-mentioned organic solvent and preservative may be added as necessary.

<Process (B)>
Step (B) is a step of dispersing the pigment in a composition containing at least the pigment, the polymer dispersant, and water.
In the step (B), the composition containing at least the pigment, the polymer dispersant, and water is stirred by a disperser to disperse the pigment in the composition.
In step (B), a composition containing at least the pigment, the polymer dispersant, and water is used, but step (A) and step (B) may be performed simultaneously. As an example in the case where the step (A) and the step (B) are simultaneously performed, the pigment, the polymer dispersant, and water used in the step (A) are charged into the disperser, and the composition of the step (A) is used. In the case of obtaining and dispersing with a disperser at the same time.

  In the step (B), it is preferable to disperse so that the volume average particle diameter of the pigment is in a desired range, and it is more preferable to disperse so that the volume average particle diameter of the pigment is 100 nm or less.

The method for dispersing the pigment in the step (B) can be performed using a known disperser, and is not particularly limited. In the step (B), for example, a mill method (for example, colloid mill, ball mill, sand mill, bead mill, attritor, roll mill, jet mill, paint shaker, agitator mill, etc.), ultrasonic method (ultrasonic homogenizer), high pressure emulsification A dispersion system (high-pressure homogenizer; specific examples of commercially available devices include a gourin homogenizer, a microfluidizer, DeBEE2000, etc.), a high-speed stirring type disperser, and the like can be used.
Among these, a mill method is preferable, a medium dispersion method, that is, a disperser using a dispersion medium (a colloid mill, a ball mill, a sand mill, a bead mill, or the like) is more preferable, and a bead mill is still more preferable.

<Process (C)>
Step (C) is a step of adding a water-soluble dye having an azo group to the composition.
In the step (C), the above dye is preferably mixed by a known mixing method. The mixing method is not particularly limited.
Moreover, the mixing temperature and mixing time in the step (C) are not particularly limited, and may be appropriately selected according to a desired progress of mixing.

  The step (C) may be performed before the step (B) or after the step (B). However, the step (C) may be performed before the step (B) from the viewpoint of reducing the generation of foreign matter. preferable. After the step (C) is performed, the step (B) is performed in the presence of the dye, and the pigment is dispersed in the composition, so that the dye and the pigment are intimately mixed. It is considered that the dye is strongly adsorbed to the pigment and the generation of foreign matters can be suppressed.

<Process (D)>
The method for producing an aqueous pigment dispersion of the present invention comprises a step of performing a heat treatment on the obtained aqueous pigment dispersion as the step (D) after completion of the steps (A) to (C) (hereinafter simply referred to as “heat treatment”). It is preferable to further include a step. By having the heat treatment step, the relationship between the pigment in the aqueous pigment dispersion and the polymer dispersant becomes more stable, and the generation of foreign matters in the pigment dispersion is further suppressed.
The heating temperature in the heat treatment step is preferably 40 ° C. or higher and 95 ° C. or lower, more preferably 50 ° C. or higher and 95 ° C. or lower, and still more preferably 60 ° C. or higher and 95 ° C. or lower.
The heating time in the heat treatment step is preferably 5 minutes or longer, more preferably 5 minutes to 24 hours, and further preferably 30 minutes to 12 hours.
In the heat treatment step, the heat treatment may be performed while stirring.

  The method for producing an aqueous pigment dispersion of the present invention may include other steps in addition to the steps (A) to (D).

<PH adjustment step>
The method for producing an aqueous pigment dispersion of the present invention may have a pH adjustment step. By adjusting the pH to a specific value, a pigment dispersion having excellent storage stability can be obtained.
The pH adjustment step may be performed at a desired timing as long as the steps (A) to (C) are completed, but is more preferably performed after the step (D).

<Sterilization process>
The sterilization referred to in the present invention means an operation having a sterilizing action, and examples thereof include addition of an additive having a sterilizing effect such as irradiation with light such as ultraviolet rays (UV) and alcohol. Of these, light irradiation is preferred.
By having a sterilization step, a pigment dispersion superior in storage stability can be obtained.
As the light irradiation means, those capable of irradiating near-ultraviolet light or ultraviolet light of 400 nm or less are preferable, and specifically, a xenon lamp, a high-pressure mercury lamp, a black light, a sterilizing lamp, or the like is preferably used.
There is no restriction | limiting in particular in light irradiation time and light irradiation amount, It can select suitably.

<Solvent removal step>
The method for producing an aqueous pigment dispersion of the present invention may have a solvent removal step when an organic solvent is used in steps (A) to (C). When producing the desired ink, when the organic solvent used in the steps (A) to (C) is unnecessary, the organic solvent may be removed after the steps (A) to (C) are completed.
Examples of the method for removing the organic solvent include membrane separation methods such as ultrafiltration and nanofiltration.

<Deionization process>
The method for producing an aqueous pigment dispersion of the present invention may have a deionization step. By removing an ionic component that may be contained as an impurity in the specific pigment or dispersant, a pigment dispersion having excellent storage stability can be obtained.
The deionization step may be performed at a desired timing, but is preferably performed after the steps (A) to (C) are completed and before the step (D) or after the step (D). More preferably after this.
Examples of the method for removing the ionic component include a method using a membrane separation method such as ultrafiltration and nanofiltration, a method of adding an ion exchange resin, and the like.

<Centrifuge separation>
The method for producing an aqueous pigment dispersion of the present invention may include a step of centrifuging the obtained aqueous pigment dispersion after completion of steps (A) to (C) or after step (D). Coarse particles can be removed by centrifugation.
The centrifugal separation step is preferably performed before the filtration step described later. By having the centrifugal separation step before the filtration step, it is possible to suppress the coarse particles from being clogged and reducing the filterability.
As centrifugal force at the time of centrifugal separation, 500G to 50,000G is preferable, 700G to 20,000G is more preferable, and 1,000G to 15,000G is still more preferable. When it is 500 G or more, coarse particles can be sufficiently settled and removed, and when it is 50,000 G or less, sedimentation of the dispersed pigment is suppressed.

<Filtration process>
The method for producing an aqueous pigment dispersion of the present invention may have a step of filtering the pigment dispersion after completion of steps (A) to (C) and / or after step (D).
Coarse particles can be removed by filtration. The filtration step is not particularly limited as long as it is after the pigment is dispersed, but it is preferably performed after the addition of the preservative or as the last step of completing the pigment dispersion.
In particular, in the case of having the heat treatment step, a part of the dispersed pigment and dispersant may be dried or aged to become coarse particles and settle.
The filter that can be used is not particularly limited as long as filtration can be performed, but filter cloth, filter paper, and membrane filter are preferable. The pore size of the filter is preferably 0.1 mm or less, more preferably 10 μm or less, still more preferably 5 μm or less, and particularly preferably 1 μm or less.

[Inkjet ink]
The present invention also relates to an inkjet ink containing the aqueous pigment dispersion. The ink-jet ink contains the aqueous pigment dispersion and may contain various components in addition to the aqueous pigment dispersion. For example, a solvent (water or an organic solvent), a drying inhibitor (wetting agent), an amber color, and the like. Inhibitors, emulsion stabilizers, penetration enhancers, ultraviolet absorbers, antifungal agents, pH adjusters, surface tension adjusters, antifoaming agents, viscosity modifiers, dispersants, dispersion stabilizers, rust inhibitors, chelating agents, etc. And known additives (described in JP-A No. 2003-306623). These various additives are directly added to the ink liquid in the case of water-soluble ink. In the case of oil-soluble inks, it is common to add the pigment dispersion to the dispersion after preparation, but it may be added to the oil phase or water phase at the time of preparation.
The pigment content in the inkjet ink is preferably 2 to 15% by mass with respect to the total mass of the inkjet ink. Moreover, it is preferable that the content rate of the water-soluble dye which has an azo group in the inkjet ink is 0.1-10 mass% with respect to the total mass of the inkjet ink. A preferable range of the mass ratio of the pigment in the inkjet ink to the water-soluble dye having an azo group is the same as that in the aqueous pigment dispersion described above.

  The ink-jet ink according to the present invention contains a water-based pigment dispersion containing a specific pigment, a specific polymer dispersant, and a specific dye, so that the heat-induced pigment is ejected by a thermal head as described above. It is considered that the dispersion state of the ink and the aggregation of the pigment that occurs when the ink is cooled are suppressed. Therefore, the inkjet ink of the present invention can be preferably used as an inkjet ink used in a thermal inkjet printer.

[Image recording method]
The present invention also relates to an image recording method using the ink jet ink of the present invention.
The image recording method of the present invention can use any method in which ink is ejected as droplets from a fine nozzle and the droplets are attached to a recording medium.

  Some of them will be explained. First, there is an electrostatic suction method. In this method, a strong electric field is applied between the nozzle and the acceleration electrode placed in front of the nozzle, ink is continuously ejected from the nozzle in the form of droplets, and a print information signal is output while the ink droplets fly between the deflection electrodes. There is a method of recording by applying to the deflection electrode, or a method of ejecting ink droplets corresponding to the print information signal without deflecting the ink droplets.

  The second method is a method in which ink droplets are forcibly ejected by applying pressure to the ink liquid with a small pump and mechanically vibrating the nozzle with a crystal resonator or the like. The ejected ink droplet is charged simultaneously with the ejection, and a printing information signal is given to the deflection electrode and recorded while the ink droplet flies between the deflection electrodes.

  The third method is a method using a piezoelectric element, in which pressure and a print information signal are simultaneously applied to ink with a piezoelectric element, and ink droplets are ejected and recorded.

  The fourth method is a method in which the volume of ink is rapidly expanded by the action of thermal energy, and is a method in which ink is heated and foamed with a microelectrode in accordance with a print information signal, and ink droplets are ejected and recorded.

Any of the above methods can be used in the image recording method using the inkjet ink of the present invention.
The ink-jet ink of the present invention can be suitably used particularly when the fourth method, that is, the thermal method is adopted.

  The present invention will be described more specifically with reference to the following examples. The materials, amounts used, ratios, processing details, processing procedures, and the like shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention is not limited to the specific examples shown below. Unless otherwise specified, “part” and “%” are based on mass.

(Synthesis of dispersant (X11))
Under a nitrogen atmosphere, 101.4 g of triethylene glycol was heated to an internal temperature of 80 ° C., and the monomer solution (M) and initiator solution (I) having the composition shown in Table 1 were simultaneously added dropwise. The monomer solution was added dropwise over 4 hours and the initiator solution over 5 hours. After completion of the dropwise addition, the mixture was further stirred at 80 ° C. for 1 hour, and then the internal temperature was raised to 90 ° C. and further stirred for 2 hours. After completion of the heating and stirring, the mixture was cooled to 70 ° C., 25.4 g of 50% potassium hydroxide aqueous solution, 17.9 g of ultrapure water and 10.8 g of triethylene glycol were added in this order, and the mixture was stirred at 70 ° C. for 2 hours. After cooling to 25 ° C., 340.7 g of ultrapure water was added to obtain a triethylene glycol solution of the dispersant (X11). The solid content was 19.8% and the weight average molecular weight was 9000.

  The dispersant (X11) is a polymer compound having the following structure. The ratio of repeating units is a molar ratio.

(Synthesis of dispersant (X12))
In the synthesis of the dispersant (X11), the triethylene glycol of the dispersant (X12) was the same as the dispersant (X11) except that the composition of the monomer solution and the initiator solution was changed as shown in Table 2 below. A solution was obtained. The solid content was 19.4% and the weight average molecular weight was 9000.

  The dispersant (X12) is a polymer compound having the following structure. The ratio of repeating units is a molar ratio.

In addition, the dispersing agent (X20) used in the comparative example is a copolymer of benzyl methacrylate and methacrylic acid (Mw 83000) synthesized according to Synthesis Example (1) -4 described in JP 2014-162875 A, and a solvent. Is dipropylene glycol.
As the polymer dispersant (X21), a methacrylic acid-methacrylic acid ester copolymer described in [0346] of JP2012-077190A was used.
Dispersant (X21): a copolymer of methacrylic acid / methyl methacrylate / 2-ethylhexyl methacrylate (236.5 / 413.5 / 350, mass ratio) (Dispersant solution 10 described in International Publication No. 2006/064193) , Mw = 30105).

Example 1
<Process (A)>
The following components were mixed to obtain a composition containing a pigment, a polymer dispersant, triethylene glycol, and water.
Pigment (d1) 24.2 g
Dispersant (X11) in triethylene glycol solution 61.1g
24.5g of ultrapure water

<Process (B)>
Using a sand grinder mill (manufactured by Imex Co., Ltd.) as a disperser, the composition is placed in a pulverization container in a disperser together with zirconia beads having a diameter of 0.1 mm, and stirred for 5 hours so that the volume average particle size MV is 100 nm or less. Then, the pigment in the composition was dispersed. After dispersion, the beads were separated using a filter cloth.

<Process (C)>
After the step (B) (after pigment dispersion), 8.1 g of the dye (5-1) was added to the obtained dispersion and mixed. Furthermore, the aqueous pigment dispersion liquid (1) was obtained by diluting with the ultrapure water so that the content rate of the pigment in the dispersion liquid, dye, and a dispersing agent might become the value shown in Table 3 below.

  The structure of the pigment used is shown below.

  The structure of the water-soluble dye having an azo group used is shown below. tBu and t-Bu represent a t-butyl group.

<Centrifuge separation>
Coarse particles in the pigment dispersion (1) were precipitated using a centrifuge. The precipitated coarse particles were removed through a filter having a pore size of 0.3 μm, and then the dispersion was heated at 70 ° C. for 1 hour. Thereafter, the mixture was cooled to 25 ° C., and coarse particles were removed again through a filter having a pore size of 1.0 μm to obtain an aqueous pigment dispersion (1S).

<Preparation of inkjet ink>
The following components were mixed and sufficiently stirred, and an inkjet ink (1) was produced through a filter having a pore size of 0.8 μm.
Water-based pigment dispersion (1S) 40.0g
32.5g of ultrapure water
2-pyrrolidone 3.0 g
Glycerol 15.0g
1,2-hexanediol 4.0g
Ethylene glycol 5.0g
Surfynol 465 0.5g

Surfynol 465 is a surfactant manufactured by Nissin Chemical Industry Co., Ltd.
About the content rate of the pigment in the obtained inkjet ink, dye, and a dispersing agent, it described in following Table 4.

(Examples 2 to 11)
Except for changing the types of pigments, dyes and dispersants used as shown in Tables 3 and 4 and changing their contents as shown in Tables 3 and 4, in the same manner as in Example 1, Pigment dispersions (2) to (11), pigment dispersions (2S) to (11S), and inkjet inks (2) to (11) were prepared.

(Example 12)
<Process (A)>
In the same manner as in Example 1, a composition containing a pigment, a polymer dispersant, triethylene glycol, and water was obtained.

<Process (C)>
8.1 g of water-soluble dye (5-1) was added to the composition and mixed. That is, the step (C) was performed before the step (B).

<Process (B)>
Using a sand grinder mill (manufactured by Imex Co., Ltd.) as a disperser, the composition to which the above water-soluble dye was added was placed in a pulverization container in a disperser together with zirconia beads having a diameter of 0.1 mm, and stirred for 5 hours. Of pigment was dispersed. After the dispersion is completed, the beads are separated using a filter cloth, and the aqueous pigment dispersion is obtained by diluting with ultrapure water so that the content of the pigment, dye, and dispersant in the dispersion becomes the values shown in Table 3. A liquid (12) was obtained.

  A pigment dispersion (12S) and an inkjet ink (12) were prepared in the same manner as in Example 1, except that the aqueous pigment dispersion (1) was changed to the aqueous pigment dispersion (12).

(Example 13)
In Example 1, a pigment dispersion (13) was prepared in the same manner as in Example 1 except that the pigment dispersion was heated at 90 ° C. for 12 hours as a step (D) between the step (C) and the centrifugation step. ), A pigment dispersion (13S), and an inkjet ink (13).

(Comparative Example 1)
In Example 1, the triethylene glycol solution of the dispersant (X11) was changed to the dipropylene glycol solution of the dispersant (X20), and no dye was added, and the contents of the pigment and dispersant are shown in Tables 3 and 4 A pigment dispersion (R1), a pigment dispersion (R1S), and an inkjet ink (R1) were prepared in the same manner as in Example 1 except that the above changes were made.

(Comparative Example 2)
In Example 1, the triethylene glycol solution of the dispersant (X11) was changed to an aqueous solution of the dispersant (X21), and the contents of pigment, dye, and dispersant were changed as shown in Tables 3 and 4 Prepared a pigment dispersion (R2), a pigment dispersion (R2S), and an inkjet ink (R2) in the same manner as in Example 1.

(Evaluation)
-Stability of pigment dispersion over time-
The pigment dispersions (1S) to (13S) of Examples 1 to 13 and the pigment dispersions (R1S) to (R2S) of Comparative Examples 1 to 2 were allowed to stand at 60 ° C. for 14 days. The volume average particle size of the pigment particles in the pigment dispersion before standing at 60 ° C. for 14 days (also referred to as “before heating”) and after standing at 60 ° C. for 14 days (also referred to as “after heating”). The diameter and the viscosity of the pigment dispersion were measured. The particle diameter change rate and viscosity change rate were calculated based on the following equations.
Change rate of particle diameter (%) = (volume average particle diameter after heating / volume average particle diameter before heating) × 100
Viscosity change rate (%) = (viscosity after heating / viscosity before heating) × 100
The evaluation criteria were as follows.
A: Both the particle size change rate and the viscosity change rate fall within the range of 90 to 110%. B: Only one of the particle size change rate or the viscosity change rate is less than 90% or more than 110%. C: Particle size Both the rate of change and the rate of change in viscosity are less than 90% or more than 110%. The volume average particle diameter is Nanotrac150 (UPA-EX150) manufactured by Nikkiso Co., Ltd., and the viscosity is TV-22 manufactured by Toki Sangyo. And measured.

−Discharge rate−
Ink-jet inks (1) to (13) of Examples 1 to 13 and Ink-jet inks of Comparative Examples 1 and 2 were prepared in BCI-340 (manufactured by Canon Inc.), which is an ink cartridge incorporating a thermal-type inkjet head. (R1) to (R2) were refilled and ink was discharged. The ejection speed was calculated by taking an image of the ejected droplets with a camera. The ink jet ink (R1) of Comparative Example 1 was relatively compared with a discharge speed of 100, and evaluation was performed according to the following criteria.
A: Discharge speed is 150 or more B: Discharge speed exceeds 100 and less than 150 C: Discharge speed is 100 or less D: Not discharged

-Foreign matter-
In the same manner as the evaluation of the ejection speed, the inkjet inks (1) to (13) of Examples 1 to 13 and the inkjet inks (R1) to (R2) of Comparative Examples 1 to 2 were ejected. After discharging 60 million times, the ink in the cartridge was replaced with ultrapure water, and the head was visually observed with an optical microscope (Nikon Corporation: ECLIPSE LV150), and evaluated according to the following criteria.
AA: No foreign matter is seen in the head A: A little foreign matter is seen in the head B: Foreign matter is seen in the head, but the adhesion area of the foreign matter is less than half of the head C: More than half of the head D: Foreign matter is observed on the entire surface of the head.

-Print density-
The ink-jet inks (1) to (13) of Examples 1 to 13 and the ink-jet inks (R1) to (R2) of Comparative Examples 1 and 2 were used as ink jet recording apparatuses, using PIXUS MG3130 manufactured by Canon Inc. Printed a stepped yellow single color image. As a recording medium, Fuji Photo Film Co., Ltd. picture-finishing photo finishing Pro was used. Measurement was made with a reflection densitometer (GRETAG MACBETH Spectrolino) to evaluate OD (Opticai Density) at a printing density of 100%.
A: 2.0 or more B: 1.8 or more and less than 2.0 C: 1.6 or more and less than 1.8 D: Less than 1.6

-Light resistance-
In the same manner as in the evaluation of the print density, prints of the inkjet inks (1) to (13) of Examples 1 to 13 and the inkjet inks (R1) to (R2) of Comparative Examples 1 to 2 were produced. The image area before irradiation with an OD of 1.0 ± 0.2 was irradiated with a xenon weather meter (manufactured by Suga Test Instruments Co., Ltd.) for 14 days under 9.9 kW, # 320 filter conditions, and the dye residual ratio [( After irradiation / concentration before irradiation) × 100%], the light fastness was evaluated.
A: Dye remaining ratio is 95% or more B: Dye remaining ratio is less than 95% 85% or more C: Dye remaining ratio is less than 85% 70% or more D: Dye remaining ratio is less than 70%

From the results shown in Table 5, it was found that the pigment dispersions and ink-jet inks of the examples of the present invention were excellent in ejection speed in a thermal-type ink-jet printer and produced less foreign matter.
In addition, it was found that the pigment dispersions and ink-jet inks of the examples were excellent in stability over time, and excellent in print density and light resistance.

Claims (13)

An aqueous pigment dispersion containing a pigment, a water-soluble dye having an azo group, a polymer dispersant, and water,
The pigment is a pigment containing a compound represented by the following general formula (1) or a tautomer thereof, or a salt thereof.
The polymer dispersant is an aqueous pigment dispersion, which is a polymer compound having a repeating unit represented by the following general formula (2-1) and a repeating unit represented by the following general formula (2-2).

In general formula (1),
Z represents a substituted or unsubstituted 5-membered heterocycle or 6-membered heterocycle.
Y ₁ , Y ₂ , R ₁₁ and R ₁₂ each independently represents a hydrogen atom or a substituent.
G ₁ and G ₂ are each independently a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted aralkyl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted alkynyl group, substituted or unsubstituted An aryl group or a substituted or unsubstituted heterocyclic group is represented.
W ₁ and W ₂ each independently represent a substituted or unsubstituted alkoxy group, a substituted or unsubstituted amino group, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted aryl group.

In General Formula (2-1), R ₁ represents a hydrogen atom, a methyl group or a substituted methyl group, and R ₂ represents an alkyl group substituted with a substituent containing an aryl group or an aromatic heterocyclic group, substituted or unsubstituted It represents a substituted aralkyl group or a substituted or unsubstituted aryl group.
In General Formula (2-2), R ₃ represents a hydrogen atom, a methyl group, or a substituted methyl group. M represents a hydrogen atom or a counter cation. The aqueous pigment dispersion according to claim 1, wherein the water-soluble dye having an azo group is a compound represented by the following general formula (3).
(A−N = N−B) n−L (3)
In General Formula (3), A and B each independently represent a substituted or unsubstituted heterocyclic group. L represents a hydrogen atom, a single bond, or a divalent linking group. n represents 1 or 2. However, when n is 1, L represents a hydrogen atom, and both A and B are monovalent substituted or unsubstituted heterocyclic groups. When n is 2, L represents a single bond or a divalent linking group, one of A and B is a monovalent substituted or unsubstituted heterocyclic group, and the other is a divalent substituted or unsubstituted group. It is a heterocyclic group. When n is 2, A may be the same or different, and B may be the same or different. The water-based pigment dispersion according to claim 1 or 2, wherein the water-soluble dye having an azo group is a compound represented by the following general formula (4) or (5).

In the general formula (4), R ₄₁ and R ₄₂ each independently represent a monovalent substituent, R ₅₁ and R ₅₂ each independently represent —OR ₆ or —NHR ₇ , and R ₆ and R ₇ each represent Independently represents a hydrogen atom or a monovalent substituent, X ₃ represents a single bond or a divalent linking group, Ar ₃₁ and Ar ₃₂ each independently represent a divalent substituted or unsubstituted heterocyclic group, Ar ₄₁ and Ar ₄₂ each independently represent a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, or a substituted or unsubstituted monovalent triazine ring group.

In General Formula (5), R ₆₁ , R ₆₂ , X ₅₁ , X ₅₂ , Y ₅₁ , Y ₅₂ , G ₅₁ and G ₅₂ each independently represent a hydrogen atom or a monovalent substituent, and Z ₅ is 5 An atomic group constituting an ˜8-membered nitrogen-containing heterocycle, and M ₁ represents a hydrogen atom or a cation. m ₁ represents an integer of 0 to 3. The pigment is a pigment containing at least one of a compound represented by the following formula (d1), formula (d2), or formula (d3) or a tautomer thereof, or a salt thereof. The aqueous pigment dispersion according to any one of the above.

5. The aqueous pigment dispersion according to claim 1, wherein R ₁ in the general formula (2-1) represents a methyl group and R ₂ represents a benzyl group.   The water-based pigment dispersion according to any one of claims 1 to 5, wherein a mass ratio of the pigment and the water-soluble dye having an azo group is 1/1 to 20/1.   An ink-jet ink comprising the aqueous pigment dispersion according to any one of claims 1 to 6.   The inkjet ink according to claim 7, which is used in an inkjet recording method in which ink is ejected from a recording head by the action of thermal energy.   An image recording method using the inkjet ink according to claim 7. Step (A): obtaining a composition containing a pigment, a polymer dispersant, and water,
Step (B): a step of dispersing the pigment in the composition,
Step (C): adding a water-soluble dye having an azo group to the composition,
The pigment is a pigment containing a compound represented by the following general formula (1) or a tautomer thereof, or a salt thereof.
The polymer dispersant is a polymer compound having a repeating unit represented by the following general formula (2-1) and a repeating unit represented by the following general formula (2-2). Method.

In general formula (1),
Z represents a substituted or unsubstituted 5-membered heterocycle or 6-membered heterocycle.
Y ₁ , Y ₂ , R ₁₁ and R ₁₂ each independently represents a hydrogen atom or a substituent.
G ₁ and G ₂ are each independently a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted aralkyl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted alkynyl group, substituted or unsubstituted An aryl group or a substituted or unsubstituted heterocyclic group is represented.
W ₁ and W ₂ each independently represent a substituted or unsubstituted alkoxy group, a substituted or unsubstituted amino group, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted aryl group.

In General Formula (2-1), R ₁ represents a hydrogen atom, a methyl group or a substituted methyl group, and R ₂ represents an alkyl group substituted with a substituent containing an aryl group or an aromatic heterocyclic group, substituted or unsubstituted It represents a substituted aralkyl group or a substituted or unsubstituted aryl group.
In General Formula (2-2), R ₃ represents a hydrogen atom, a methyl group, or a substituted methyl group. M represents a hydrogen atom or a counter cation.   The method for producing an aqueous pigment dispersion according to claim 10, wherein the step (C) is performed before the step (B).   Furthermore, the manufacturing method of the aqueous pigment dispersion of Claim 10 or 11 including the process (D) of heating the obtained aqueous pigment dispersion.   The method for producing an aqueous pigment dispersion according to claim 12, wherein in the step (D), the aqueous pigment dispersion is heated at 40 to 95 ° C.