WO2012011500A1 - Azo pigment dispersion, ink composition using same, ink for inkjet recording, recording method, recorded material, and method for stabilizing ink for inkjet recording during storage - Google Patents

Abstract

Provided is a pigment dispersion, in which increases in particle diameter and viscosity are suppressed even after being exposed to a high temperature over time, and which has excellent light resistance. The pigment dispersion contains an azo pigment represented by formula (1) or a tautomer thereof and a polymer having an acid value and an amine value. The polymer has an acid value of 10 to 120 mgKOH/g and an amine value of 10 to 120 mgKOH/g. Further, the polymer is contained in an amount of 10 to 80% by mass of the total amount of the azo pigment and the like.

Description

Azo pigment dispersion and ink composition using the same, ink for ink jet recording, recording method, recorded matter, and method for stabilizing storage of ink for ink jet recording

The present invention relates to a pigment dispersion and an ink composition using the same, an ink for ink jet recording, a recording method, a recorded material, and a storage stabilization method for ink for ink jet recording, and more specifically, an azo pigment having a specific structure. The present invention relates to a pigment dispersion, an ink composition using the pigment dispersion, and a storage stabilization method of an ink for inkjet recording containing the azo pigment.

In recent years, a material for forming a color image has been mainly used as an image recording material, and specifically, an ink jet recording material, a thermal transfer recording material, an electrophotographic recording material, a transfer halogen. Silver halide photosensitive materials, printing inks, recording pens, and the like are actively used. Further, a color filter is used for recording and reproducing a color image on an image pickup device such as a CCD in a photographing apparatus and on an LCD or PDP in a display. In these color image recording materials and color filters, three primary colors (dyes and pigments) of the so-called additive color mixing method and subtractive color mixing method are used to display or record full color images. The fact is that there are no fast-acting dyes that have absorption characteristics that can satisfy the above conditions and that can withstand various use conditions and environmental conditions, and improvements are strongly desired.

The dyes and pigments used in each of the above applications must have the following properties in common. That is, it has preferable absorption characteristics in terms of color reproducibility, fastness under environmental conditions to be used, for example, light resistance, heat resistance, good resistance to oxidizing gases such as ozone, and the like. In addition, when the pigment is a pigment, it is further substantially insoluble in water and organic solvents and has good chemical fastness, and even when used as particles, the preferred absorption characteristics in the molecular dispersion state are impaired. It is also necessary to have properties such as absence. The required characteristics can be controlled by the strength of intermolecular interaction, but it is difficult to achieve both because they are in a trade-off relationship.
In addition, when using the pigment, in addition to having a particle size and a particle shape necessary for expressing the desired transparency, fastness under the environmental conditions used, such as light resistance, heat resistance, Good resistance to oxidative gases such as ozone, and other chemical fastness to organic solvents and sulfurous acid gas. Disperse even fine particles in the medium used, and stable dispersion. , Etc. are also required.

In other words, the required performance for pigments is more diverse than dyes that require performance as pigment molecules, and not only the performance as pigment molecules, but also the above requirements as solids (fine particle dispersions) as aggregates of pigment molecules All performance needs to be satisfied. As a result, the group of compounds that can be used as pigments is extremely limited compared to dyes, and even if high-performance dyes are derived into pigments, there are only a few that can satisfy the required performance as fine particle dispersions. It cannot be developed. This is confirmed by the fact that the number of pigments registered in the color index is less than 1/10 of the number of dyes.

In particular, azo pigments are widely used as printing inks, inkjet inks, electrophotographic materials, and color filter pigments because of their high lightness and excellent light resistance and heat resistance. With the expansion of applications, pigments are required to have better dispersibility in the medium used than printing inks, gravure inks and colorants, and stability and light resistance of the dispersion over time. ing.
Among them, azo pigments (for example, CI Pigment Yellow 74) are preferably used as yellow pigments used in inkjet recording pigment inks. For example, Patent Document 1 discloses C.I. I. An inkjet recording ink is disclosed that includes Pigment Yellow 74 and a pigment dispersion containing an anionic group-containing organic polymer compound.
Patent Document 2 discloses an aqueous inkjet recording ink containing a structural unit derived from a styrenic monomer and a structural unit derived from at least one of acrylic acid and methacrylic acid and containing an azo pigment represented by the formula (1). Is disclosed.

Japanese Unexamined Patent Publication No. 2000-239594 Japanese Unexamined Patent Publication No. 2010-65212

However, in the ink for ink jet recording constituted using the pigment dispersion described in Patent Document 1, when used after aging at a high temperature, the ink is not ejected due to clogging caused by aggregation of the pigment, and the pigment itself used It was found that it was not a satisfactory level in terms of low light resistance.
Further, it has been found that the water-based ink for inkjet recording described in Patent Document 2 is not at a satisfactory level in terms of suppressing the increase in particle diameter and viscosity after being subjected to more severe conditions, for example, after aging at a high temperature.

The present invention has been made paying attention to the above-mentioned problems in pigment dispersions using azo pigments, ink compositions using the same, and inks for inkjet recording, and the purpose thereof is excellent in light resistance and at high temperatures. An object is to provide an azo pigment dispersion in which an increase in particle diameter and viscosity is suppressed even after aging, an ink composition using the same, an ink for ink jet recording, a recording method, and a recorded matter. Another object of the present invention is to provide a method for stabilizing the storage of ink for inkjet recording using an azo pigment having a specific structure.

As a result of intensive investigations to achieve the above object, the present inventors have solved the above problems with a pigment dispersion containing an azo pigment having a specific structure and a polymer having an acid value and an amine value. The present invention has been found and the present invention has been completed.
The acid value here is defined by the mass (mg) of KOH required to completely neutralize 1 g of the polymer, and can be measured by the method described in JIS standard (JIS K0070: 1992). This will be adopted. The amine value indicates the total amount of basic amines 1, 2, and tertiary amines. The number of mg of KOH equivalent to hydrochloric acid required to neutralize all basic groups in 1 g of a sample. It is represented by. The acid value is the number of mg of KOH required to neutralize all the acidic groups contained in 1 g of the sample.
That is, the said subject can be achieved by the following means.

[1]
A pigment dispersion comprising an azo pigment represented by the following formula (1) or a tautomer thereof, and a polymer having an acid value and an amine value.

[2]
Bragg angles (2θ ± 0.2 °) in CuKα characteristic X-ray diffraction of the azo pigment or its tautomer are 7.6 °, 25.6 °, 7.0 °, 26.4 ° and 27.3. The pigment dispersion according to [1], which has characteristic X-ray diffraction peaks at °, or 6.4 °, 26.4 °, and 27.2 °.
[3]
The azo pigment or its tautomer has characteristic X-ray diffraction peaks at Bragg angles (2θ ± 0.2 °) in CuKα characteristic X-ray diffraction of 7.6 ° and 25.6 °. The pigment dispersion according to [1] or [2].
[4]
The pigment dispersion according to any one of [1] to [3], wherein the polymer has an acid value of 10 to 120 mgKOH / g and an amine value of 10 to 120 mgKOH / g.
[5]
The polymer having an acid value and an amine value is contained in an amount of 10 to 80% by mass based on the total content of the azo pigment represented by the formula (1) and tautomers thereof [1] to [4] The pigment dispersion according to any one of [4].
[6]
An ink composition comprising the pigment dispersion according to any one of [1] to [5].
[7]
An ink for ink-jet recording, comprising the pigment dispersion according to any one of [1] to [5] or the ink composition according to [6].
[8]
A recording method comprising using the ink composition according to [6] or the inkjet recording ink according to [7].
[9]
A recorded matter obtained by using the ink composition according to [6] or the inkjet recording ink according to [7].
[10]
A method for storage stabilization of an ink for ink jet recording, comprising using a pigment dispersion containing an azo pigment represented by the following formula (1) or a tautomer thereof and a polymer having an acid value and an amine value.

Since the pigment dispersion of the present invention contains an azo pigment having a specific structure and a polymer having an acid value and an amine value, it is excellent in light resistance and has a particle diameter and viscosity even after aging at high temperatures. An azo pigment dispersion in which an increase in the amount of the azo pigment is suppressed, an ink composition using the same, an ink for inkjet recording, a recording method, and a recorded matter can be provided. Further, it is possible to provide a storage stabilization method for ink for inkjet recording using an azo pigment having a specific structure.

<Pigment dispersion>
The pigment dispersion of the present invention has an azo pigment of the following formula (1) or a tautomer thereof (hereinafter sometimes referred to as “azo pigment of the formula (1)”), an acid value and an amine value. Preferably, it contains an acid group and a basic group in the side chain, or a polymer having an acid group in the side chain and neutralized with a base. Thereby, it can be set as the pigment dispersion excellent in light resistance, dispersion stability, and dispersion stability over time.
The total amount of the azo pigment and its tautomer contained in the pigment dispersion is preferably 1 to 40% by mass, more preferably 2 to 30% by mass, based on the mass of the pigment dispersion. The content is preferably 3 to 15% by mass. This is because if it is 1% by mass or more, the pigment concentration is sufficient and the concentration tends to be obtained. On the other hand, if it is 40% by mass or less, the viscosity does not become too high, and it tends to aggregate, which may cause a problem in storage stability over time.

In the present specification, the Bragg angle (2θ ± 0.2 °) in CuKα characteristic X-ray diffraction is expressed by the following formula (1) having characteristic X-ray diffraction peaks at 7.6 ° and 25.6 °. This azo pigment is referred to as an α-type crystal form azo pigment.
An azo pigment represented by the formula (1) having characteristic X-ray diffraction peaks at Bragg angles (2θ ± 0.2 °) of 7.0 °, 26.4 ° and 27.3 ° in CuKα characteristic X-ray diffraction Is referred to as a β-type crystal form azo pigment.
An azo pigment represented by formula (1) having characteristic X-ray diffraction peaks at a Bragg angle (2θ ± 0.2 °) in CuKα characteristic X-ray diffraction of 6.4 °, 26.4 ° and 27.2 °. Is referred to as a γ-type crystal form azo pigment.

In the present invention, the X-ray diffraction measurement of the α-type, β-type, and γ-type crystal form azo pigments represented by the above formula (1) is performed according to Japanese Industrial Standard JISK0131 (general rules for X-ray diffraction analysis). It can be performed with a powder X-ray diffraction measurement apparatus RINT2500 (manufactured by Rigaku Corporation).

The crystal form of the azo pigment represented by the formula (1) or a tautomer thereof that can be used is not particularly limited, but the Bragg angle (2θ in CuKα characteristic X-ray diffraction of the azo pigment or the tautomer thereof is not limited. ± 0.2 °) is characteristic of 7.6 ° and 25.6 °, 7.0 °, 26.4 ° and 27.3 °, or 6.4 °, 26.4 ° and 27.2 ° It is preferable to have an X-ray diffraction peak, that is, an α-type crystal form azo pigment, a β-type crystal form azo pigment, or a γ-type crystal form azo pigment is preferable from the viewpoint of light fastness and hue. Among them, α-type crystal form azo pigments and β-type crystal form azo pigments are more preferable, and it is preferable to have characteristic X-ray diffraction peaks at 7.6 ° and 25.6 °. Particularly preferred. This is because α-type crystal form azo pigments are particularly preferable from the viewpoint of light fastness.

The volume average particle diameter of the particles in the pigment dispersion is preferably 10 nm or more and 200 nm or less, more preferably 15 nm or more and 200 nm or less, further preferably 20 nm or more and 150 nm or less, and 25 nm or more and 130 nm or less. Most preferred. When the volume average particle diameter of the particles in the pigment dispersion is 10 nm or more, it is preferable because the stability of the dispersion with time increases and aggregation hardly occurs. Further, when the volume average particle diameter of the particles is 200 nm or less, the optical density becomes high and the density of the printed matter becomes high, and it is preferable that the nozzle is not clogged when printing by ink jet or the like.

In addition, the volume average particle diameter of the pigment particles refers to the particle diameter of the pigment itself, or, in the case where an additive such as a dispersant is attached to the pigment, the particle diameter to which the additive is attached. In the present invention, a nanotrac UPA particle size analyzer (UPA-EX150; manufactured by Nikkiso Co., Ltd.) can be used as a volume average particle diameter measuring apparatus for pigments. The measurement can be performed according to a predetermined measurement method by placing 3 ml of the pigment dispersion in a measurement cell. As parameters input at the time of measurement, the pigment dispersion viscosity is used as the viscosity, and the pigment density is used as the density of the dispersed particles.

The viscosity of the pigment dispersion is preferably 1.2 mPa · s or more and 8.0 mPa · s or less, more preferably 1.5 mPa · s or more and 6.0 mPa · s or less, and still more preferably 1.8 mPa · s or more. 4.5 mPa · s or less. If the viscosity is 1.2 mPa · s or more, long-term jetting property can be maintained, which is preferable. On the other hand, the case of 8.0 mPa · s or less is preferable because the discharge property is stabilized.
The viscosity (including those described later) was measured using a RE80L viscometer manufactured by Toki Sangyo Co., Ltd. under the conditions of 25 ° C. and 100 rpm.

1. Polymer The polymer used in the present invention has an acid value and an amine value, and preferably contains at least one of a monomer having an acidic group and a monomer having a basic group as a constituent unit. It may be converted. If the polymer has an acid value and an amine value, there is no particular limitation on the polymer structure, and a homopolymer of a monomer having an acidic group and a basic group or a monomer having an acidic group and a monomer having a basic group A copolymer, a salt of a polymer of a monomer having an acidic group and a base, and a salt of a polymer of a monomer having a basic group and an acid can be used. Moreover, it can comprise including the structural unit derived from the other monomer polymerizable with these monomers.

The monomer having an acidic group constituting the polymer includes a monomer having a carboxylic acid group (for example, acrylic acid, methacrylic acid, crotonic acid, ethacrylic acid, propylacrylic acid, isopropylacrylic acid, itaconic acid, fumaric acid, acroyloxy). Ethyl phthalate, acroyloxy succinate and the like), monomers having a sulfonic acid group (for example, 2-ethyl acrylate, 2-methacrylic acid 2-ethyl acrylate, butylacrylamide sulfonate, etc.), phosphones Monomers having an acid group (eg, 2-ethyl phosphonate methacrylate, 2-ethyl acrylate acrylate, etc.), monomers having a hydroxyl group (eg 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, A Acrylic acid hydroxypropyl, include hydroxypropyl methacrylate, and the like), among others, carboxyl group, a monomer having a phosphonic acid group.

As the monomer having a basic group constituting the polymer, a monomer having a primary amino group (for example, acrylic acid amide, aminoethyl acrylate, aminopropyl acrylate, methacrylamide, aminoethyl methacrylate, aminomethacrylate) Propyl, polyoxyalkyleneamine, etc.), monomers having secondary amino groups (for example, methylaminoethyl acrylate, methylaminopropyl acrylate, ethylaminoethyl acrylate, ethylaminopropyl acrylate, methyl methacrylate) Aminoethyl, methylaminopropyl methacrylate, ethylaminoethyl methacrylate, ethylaminopropyl methacrylate, etc.), monomers having a tertiary amino group (for example, dimethylaminoethyl acrylate, And diethylaminoethyl acrylate, dimethylaminopropyl acrylate, diethylaminopropyl acrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, dimethylaminopropyl methacrylate, diethylaminopropyl methacrylate, etc.), and having a quaternary amino group Monomers (for example, dimethylaminoethyl methyl chloride acrylate, dimethylaminoethyl methyl methacrylate, dimethylaminoethyl benzyl acrylate, dimethylaminoethyl benzyl methacrylate, etc.) are preferred.

Other preferable polymerizable monomers include (meth) acrylic acid esters (for example, methyl acrylate, ethyl acrylate, isopropyl acrylate, acrylic acid-n-propyl, acrylic acid-n-butyl, acrylic acid-t- Butyl, benzyl acrylate, methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, methacrylate-n-propyl, methacrylate-n-butyl, isobutyl methacrylate, tert-butyl methacrylate, tridecyl methacrylate, benzyl methacrylate , 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, octyl acrylate, octyl methacrylate, lauryl acrylate, lauryl methacrylate, cetyl acrylate, cetyl methacrylate, stearyl acrylate, stearyl Methacrylate, behenyl acrylate, behenyl methacrylate, etc.), styrene monomers (for example, styrene, α-methyl styrene, o-methyl styrene, m-methyl styrene, p-methyl styrene, p-tert-butyl styrene, etc.) ), Itaconic anhydride, itaconic ester (for example, benzyl itaconate, etc.), maleic anhydride, maleic ester (for example, dimethyl maleate, etc.), fumaric anhydride, fumarate ( Examples thereof include dimethyl fumarate), acrylonitrile, methacrylonitrile, vinyl acetate, hydroxyl group-containing monomers (for example, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, hydroxypropyl acrylate, methacrylic acid) Hydroxypropyl, etc.), amino group-containing monomers (for example, aminoethyl ethyl acrylate, aminopropyl acrylate, methacrylamide, aminoethyl methacrylate, aminopropyl methacrylate, dimethylaminoethyl acrylate, dimethylamino methacrylate) Ethyl, etc.), α-olefin (eg, ethylene etc.), epoxide (eg, ethylene oxide, propylene oxide, butylene oxide, styrene oxide, bisphenol A epoxide, novolac etc.) allyl alcohol, allyl poly Ethers (eg, polyoxyethylene allyl methyl ether, polyoxypropylene monoallyl methyl ether, polyoxypropylene monoallyl ether monoacetate) , Polyoxyethylene - polyoxypropylene allyl methyl ether, and the like) and the like.

In order to neutralize acidic groups in the polymer, an alkali metal hydroxide (for example, lithium hydroxide, sodium hydroxide, potassium hydroxide, etc.), an alkaline earth metal hydroxide (for example, magnesium hydroxide, calcium hydroxide, etc.) And ammonia, primary, secondary or tertiary amines and amino alcohols can be used. Examples of amines and amino alcohols include butylamine, dibutylamine, triethylamine, N-oleyl-1,3-propanediamine, dimethylaminoethanol, diethylaminoethanol, aminomethylpropanol, 2-dibutylaminoethanol, monoamine, diamine or polyamine alkoxylate , Monoethanolamine, diethanolamine or triethanolamine, N, N-bis [poly (oxyethylene)]-N-oleylamine, among which primary, secondary, tertiary amines and amino alcohols are preferred, Diethanolamine, monoethanolamine, and polyamine alkoxylate are preferred.

The degree of neutralization will be guided by the hydrophilic nature of the polymer and the intended use. Accordingly, neutralization of the hydrophilically adjusted polymer requires far less neutralization than that of the hydrophobically adjusted polymer. When used in systems that require strong basicity, it may be advantageous to use an excess of base. Further, since the degree of neutralization depends on the type of neutralizing agent, the degree of neutralization must be increased when triethyleneamine is used compared to when potassium hydroxide is used. The solubility, dispersion characteristics and stability of the final product are amongst others due to the degree of neutralization. The degree of neutralization of the acidic groups remaining in the polymer is preferably 0 to 100%, particularly 50 to 100%.

The number average molecular weight of the polymer is preferably 1,000 to 30,000, more preferably 2,000 to 25,000, and particularly preferably 3,000 to 20,000. As a result, the steric repulsion effect is excellent, and high dispersibility, fluidity, and storage stability can be obtained. When the molecular weight is 1,000 or more, a steric repulsion effect due to the solvent affinity block is generated, which makes aggregation difficult. Moreover, if it is 30,000 or less, the viscosity of a dispersion does not become high too much and it is preferable.

The acid value of the polymer can be determined by a method based on, for example, DIN EN ISO 2114.
The amine value for the polymer can be determined, for example, by a method according to DIN 16945.

The acid value of the polymer is preferably 10 to 120 mgKOH / g, more preferably 10 to 80 mgKOH / g, and particularly preferably 15 to 50 mgKOH / g.
The amine value of the polymer is preferably 10 to 120 mg KOH / g, more preferably 10 to 80 mg KOH / g, and particularly preferably 15 to 50 mg KOH / g.
An acid value and an amine value of 10 mgKOH / g or more are preferred because of high affinity with the pigment and high stability over time. Moreover, if an acid value and an amine value are 120 mgKOH / g or less, the affinity with a pigment will become low and the dispersibility of a pigment will become high, and it is preferable.

The addition amount of the polymer (solid content) is preferably 10 to 80% by mass, and 15 to 60% by mass with respect to the total content of the azo pigment represented by the formula (1) and its tautomer. % Is more preferable, and 20 to 50% by mass is particularly preferable. When the content is 10% by mass to 80% by mass, the polymer can sufficiently act on the pigment, and the aggregation of particles hardly occurs during the dispersion, so that the dispersibility is improved and the dispersion stability over time is excellent.

The polymer may be water-soluble or water-insoluble. In the case of being water-soluble, it is easy to cause a strong interaction between the pigment and the polymer, which is advantageous when dispersed in an aqueous system. On the other hand, it is advantageous in the case of water-insoluble, in the case of dispersing in an organic solvent system, or in the case of making an aqueous system after dispersing in an organic solvent system, for example, in the case of a phase inversion emulsification method or the like.

Commercially available products can be used as the polymer having an acidic group and a basic group. For example, DISPERBYK, DISPERBYK-101, DISPERBYK-106, DISPERBYK-140, DISPERBYK-142, DISPERBYK-145, DISPERBYK-187, DISPERBYK-181, DISPERBYK180, DISPERBYK180, DISPERBYK180, DISPERBYK180, DISPERBYK180, DISPERBYK180, DISPERBYK-180 2020, EFKA-4008, EFKA-4009, EFKA-4010, EFKA-4406, EFKA-4510, EFKA-4520, EFKA-4530, EFKA-5044, EFKA-5054, EFKA-5055, manufactured by Ciba Co., Ltd. EFKA-5063, EFKA-5064, EFKA-5071, EFKA-6220, EF And the like can be given A-6225.

2. Medium The pigment dispersion of the present invention may be aqueous or non-aqueous, but is preferably an aqueous pigment dispersion. As the aqueous liquid in which the pigment is dispersed in the aqueous pigment dispersion of the present invention, a mixture containing water as a main component and optionally adding a hydrophilic organic solvent can be used. Examples of the hydrophilic organic solvent include methanol, ethanol, propanol, isopropanol, butanol, isobutanol, sec-butanol, t-butanol, pentanol, hexanol, cyclohexanol, benzyl alcohol and other alcohols, ethylene glycol, diethylene glycol Polyhydric alcohols such as triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, butylene glycol, hexanediol, pentanediol, glycerin, hexanetriol, thiodiglycol, ethylene glycol monomethyl ether, ethylene glycol mono Ethyl ether, ethylene glycol monobutyl ether, diethylene glycol mono Chill ether, diethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monobutyl ether, dipropylene glycol monomethyl ether, triethylene glycol monomethyl ether, ethylene glycol diacetate, ethylene glycol monomethyl ether acetate, triethylene glycol monoethyl ether, ethylene glycol monophenyl Glycol derivatives such as ether, ethanolamine, diethanolamine, triethanolamine, N-methyldiethanolamine, N-ethyldiethanolamine, morpholine, N-ethylmorpholine, ethylenediamine, diethylenetriamine, triethylenetetramine, polyethyleneimine, tetramethylpropylenedia Amines such as amine, formamide, N, N-dimethylformamide, N, N-dimethylacetamide, dimethyl sulfoxide, sulfolane, 2-pyrrolidone, N-methyl-2-pyrrolidone, N-vinyl-2-pyrrolidone, 2-oxazolidone, Examples include 1,3-dimethyl-2-imidazolidinone, acetonitrile, acetone and the like.

The aqueous pigment dispersion of the present invention may contain an aqueous resin. Examples of the aqueous resin include water-soluble resins that dissolve in water, water-dispersible resins that disperse in water, colloidal dispersion resins, and mixtures thereof. Specific examples of the aqueous resin include acrylic, styrene-acrylic, polyester, polyamide, polyurethane, and fluorine resins.

The non-aqueous pigment dispersion is obtained by dispersing the pigment represented by the formula (1) in a non-aqueous vehicle. Resins used in non-aqueous vehicles are, for example, petroleum resins, casein, shellac, rosin modified maleic resin, rosin modified phenolic resin, nitrocellulose, cellulose acetate butyrate, cyclized rubber, chlorinated rubber, oxidized rubber, hydrochloric acid rubber , Phenolic resin, alkyd resin, polyester resin, unsaturated polyester resin, amino resin, epoxy resin, vinyl resin, vinyl chloride, vinyl chloride-vinyl acetate copolymer, acrylic resin, methacrylic resin, polyurethane resin, silicone resin, fluorine resin , Drying oil, synthetic drying oil, styrene / maleic acid resin, styrene / acrylic resin, polyamide resin, polyimide resin, benzoguanamine resin, melamine resin, urea resin chlorinated polypropylene, butyral resin, vinylidene chloride resin and the like. A photocurable resin may be used as the non-aqueous vehicle.

Examples of the solvent used in the non-aqueous vehicle include aromatic solvents such as toluene, xylene, and methoxybenzene, and acetates such as ethyl acetate, butyl acetate, propylene glycol monomethyl ether acetate, and propylene glycol monoethyl ether acetate. Solvents, propionate solvents such as ethoxyethyl propionate, alcohol solvents such as methanol and ethanol, ether solvents such as butyl cellosolve, propylene glycol monomethyl ether, diethylene glycol ethyl ether, diethylene glycol dimethyl ether, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, etc. Ketone solvents, aliphatic hydrocarbon solvents such as hexane, N, N-dimethylformamide, γ-butyrolactam, - methyl-2-pyrrolidone, aniline, nitrogen compound-based solvent such as pyridine, a lactone-based solvents such as γ- butyrolactone, carbamic acid esters such as a mixture of 48:52 of methyl carbamate and ethyl carbamate acid.

In the pigment dispersion of the present invention, a surfactant may be used in order to improve pigment dispersion and image quality. Examples of the surfactant include anionic, nonionic, cationic and amphoteric surfactants. Any surfactant may be used, but anionic or nonionic surfactants may be used. It is preferable to use it. Examples of anionic surfactants include fatty acid salts, alkyl sulfate esters, alkylbenzene sulfonates, alkyl naphthalene sulfonates, dialkyl sulfosuccinates, alkyl diaryl ether disulfonates, alkyl phosphates, and polyoxyethylene alkyls. Examples thereof include ether sulfate, polyoxyethylene alkylaryl ether sulfate, naphthalene sulfonic acid formalin condensate, polyoxyethylene alkyl phosphate ester salt, glycerol borate fatty acid ester, polyoxyethylene glycerol fatty acid ester and the like.

Nonionic surfactants include, for example, polyoxyethylene alkyl ether, polyoxyethylene alkyl aryl ether, polyoxyethylene oxypropylene block copolymer, sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene sorbitol fatty acid ester, glycerin Examples include fatty acid esters, polyoxyethylene fatty acid esters, polyoxyethylene alkylamines, fluorine-based resins, and silicone-based resins.

3. Production Method The pigment dispersion of the present invention is obtained by dispersing the azo pigment of the formula (1) and the like and an aqueous or non-aqueous medium using a dispersing device. Dispersing devices include simple stirrer, impeller stirring method, in-line stirring method, mill method (for example, colloid mill, ball mill, sand mill, bead mill, attritor, roll mill, jet mill, paint shaker, agitator mill, etc.), ultrasonic method Further, a high-pressure emulsification dispersion system (high-pressure homogenizer; specific commercially available devices such as gorin homogenizer, microfluidizer, DeBEE2000, etc.) can be used.

In addition, it is preferable that the azo pigment of the formula (1) used for the production of the pigment dispersion of the present invention has been subjected to post-treatment (finishing). Finishing in the present invention represents processing for adjusting the crystal form, the size and shape of the particles, and the like. As a method of this post-treatment step, for example, solvent particle milling process such as solvent salt milling, salt milling, dry milling, solvent milling, acid pasting, pigment heat control process, solvent heating treatment, etc., resin, surfactant and dispersion A surface treatment step with an agent or the like can be mentioned, but for the azo pigment of formula (1) and the like, it is preferable to perform at least one of solvent heating treatment and solvent salt milling.

Examples of the solvent used in the solvent heat treatment include water, aromatic hydrocarbon solvents such as toluene and xylene, halogenated hydrocarbon solvents such as chlorobenzene and o-dichlorobenzene, and alcohols such as isopropanol and isobutanol. Examples include solvents, polar aprotic organic solvents such as N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, acetone, methyl ethyl ketone, and acetonitrile, glacial acetic acid, pyridine, or a mixture thereof. It is done. An inorganic or organic acid or base may be further added to the solvents mentioned above.
The temperature of the solvent heat treatment varies depending on the desired primary particle diameter of the pigment, but is preferably 40 to 150 ° C, more preferably 60 to 100 ° C. The treatment time is preferably 30 minutes to 24 hours.

Solvent salt milling includes, for example, charging a crude azo pigment, an inorganic salt, and an organic solvent that does not dissolve it into a kneader, and kneading and grinding therein. As the inorganic salt, a water-soluble inorganic salt can be preferably used. For example, an inorganic salt such as sodium chloride, potassium chloride, sodium sulfate is preferably used. It is more preferable to use an inorganic salt having an average particle size of 0.5 to 50 μm. The amount of the inorganic salt used is preferably 3 to 20 times by mass, more preferably 5 to 15 times by mass with respect to the crude azo pigment. As the organic solvent, a water-soluble organic solvent can be suitably used, and the solvent easily evaporates due to a temperature rise during kneading, so that a high boiling point solvent is preferable from the viewpoint of safety. Examples of such organic solvents include diethylene glycol, glycerin, ethylene glycol, propylene glycol, liquid polyethylene glycol, liquid polypropylene glycol, 2- (methoxymethoxy) ethanol, 2-butoxyethanol, 2- (isopentyloxy) ethanol, 2- (hexyloxy) ethanol, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, triethylene glycol, triethylene glycol monomethyl ether, 1-methoxy-2-propanol, 1-ethoxy-2-propanol, di Propylene glycol, dipropylene glycol monomethyl ether, dipropylene glycol monomethyl ether, dipropylene Glycol or mixtures thereof. The amount of the water-soluble organic solvent used is preferably 0.1 to 5 times by mass with respect to the crude azo pigment. The kneading temperature is preferably 20 to 130 ° C, particularly preferably 40 to 110 ° C. As a kneader, for example, a kneader or a mix muller can be used.

4). Applications Applications of the pigment dispersion of the present invention include image recording materials for forming images, particularly color images, and specifically, thermal recording materials including ink jet recording materials described in detail below. , Pressure-sensitive recording materials, recording materials using electrophotography, transfer-type silver halide photosensitive materials, printing inks, recording pens, etc., preferably ink-jet recording materials, thermal recording materials, recording materials using electrophotography Yes, more preferably an ink jet recording material.

Also, it can be applied to a solid-state image pickup device such as a CCD, a color filter for recording / reproducing a color image used in a display such as an LCD or a PDP, and a dyeing solution for dyeing various fibers.

<Ink composition>
The ink composition of the present invention contains the pigment dispersion of the present invention described above. Although the pigment dispersion of the present invention may be used as an ink composition as it is, it is preferably prepared by mixing the pigment dispersion of the present invention with a water-soluble solvent, water or the like.

<Ink for inkjet recording>
The ink for inkjet recording of the present invention (hereinafter sometimes referred to as “ink”) contains the pigment dispersion or ink composition of the present invention described above. Although the pigment dispersion or ink composition of the present invention may be used as an ink composition as it is, it is preferably prepared by mixing the pigment dispersion of the present invention with a water-soluble solvent, water or the like.

The content ratio of the pigment dispersion in the ink is preferably in the range of 1 to 100% by mass, considering the hue, color density, saturation, transparency, etc. of the image formed on the recording medium, and is preferably 3 to 50% by mass. The range is particularly preferable, and the range of 3 to 40% by mass is most preferable.

It is preferable to contain 0.1 to 20 parts by mass of the azo pigment of formula (1) in 100 parts by mass of the ink, more preferably 0.2 to 10 parts by mass. More preferably, it is contained in an amount of 10 to 10 parts by mass. In the ink of the present invention, other pigments may be used in combination with the azo pigment of the formula (1). When two or more types of pigments are used in combination, the total content of the pigments is preferably within the above range.

The ink can be used not only for forming a single color image but also for forming a full color image. In order to form a full color image, a magenta color ink, a cyan color ink, and a yellow color ink can be used, and a black color ink may be further used to adjust the color tone.

Furthermore, in the ink according to the present invention, other pigments can be used simultaneously in addition to the azo pigment according to the present invention. Examples of yellow pigments that can be applied include C.I. I. P. Y. -74, C.I. I. P. Y. -128, C.I. I. P. Y. -155, C.I. I. P. Y. -213, and applicable magenta pigments include C.I. I. P. V. -19, C.I. I. P. R. -122, and examples of applicable cyan pigments include C.I. I. P. B. -15: 3, C.I. I. P. B. -15: 4, and any of these can be used separately. Applicable black materials include disazo, trisazo, and tetraazo pigments, as well as carbon black dispersions.

As the water-soluble solvent used in the ink, polyhydric alcohols, polyhydric alcohol derivatives, nitrogen-containing solvents, alcohols, sulfur-containing solvents and the like are used.
Specific examples of polyhydric alcohols include ethylene glycol, diethylene glycol, propylene glycol, butylene glycol, triethylene glycol, 1,5-pentanediol, 1,2-hexanediol, 1,2,6-hexanetriol, and glycerin. Etc.

Examples of the polyhydric alcohol derivative include ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, propylene glycol monobutyl ether, dipropylene glycol monobutyl ether, and triethylene. Examples include glycol monobutyl ether and diglycerin ethylene oxide adducts.

Examples of the nitrogen-containing solvent include 2-pyrrolidone, N-methyl-2-pyrrolidone, cyclohexyl pyrrolidone, and triethanolamine. Examples of alcohols include alcohols such as ethanol, isopropyl alcohol, butyl alcohol, and benzyl alcohol. Examples of the sulfur-containing solvent include thiodiethanol, thiodiglycerol, sulfolane, dimethyl sulfoxide and the like. In addition, propylene carbonate, ethylene carbonate, or the like can be used.

The water-soluble solvent used in the present invention may be used alone or in combination of two or more. The content of the water-soluble solvent is preferably 1% by mass or more and 60% by mass or less, more preferably 5% by mass or more and 40% by mass or less of the whole ink. If the amount of the water-soluble solvent in the ink is 1% by mass or more, a sufficient optical density can be obtained. If the amount is 60% by mass or less, the viscosity of the liquid does not increase too much, and the ejection characteristics of the ink liquid are stabilized. preferable.

In addition to the above-described components, water may be added to the ink in a range that provides preferable surface tension and viscosity described below. The amount of water added is not particularly limited, but is preferably 10% by mass to 99% by mass, and more preferably 30% by mass to 80% by mass with respect to the entire ink.

Furthermore, if necessary, for the purpose of controlling properties such as improvement in ejection properties, cellulose derivatives such as polyethyleneimine, polyamines, polyvinylpyrrolidone, polyethylene glycol, ethylcellulose, carboxymethylcellulose, polysaccharides and derivatives thereof, other water-soluble polymers, acrylics Polymer emulsion, polyurethane emulsion, polymer emulsion such as hydrophilic latex, hydrophilic polymer gel, cyclodextrin, macrocyclic amines, dendrimers, crown ethers, urea and its derivatives, acetamide, silicone surfactant, fluorine-based A surfactant or the like can be used.

In order to adjust conductivity and pH, compounds of alkali metals such as potassium hydroxide, sodium hydroxide, lithium hydroxide, ammonium hydroxide, triethanolamine, diethanolamine, ethanolamine, 2-amino-2-methyl Nitrogen-containing compounds such as 1-propanol, alkaline earth metal compounds such as calcium hydroxide, acids such as sulfuric acid, hydrochloric acid and nitric acid, strong acid and weak alkali salts such as ammonium sulfate, and the like can be used.

Other pH buffering agents, antioxidants, fungicides, viscosity modifiers, conductive agents, ultraviolet absorbers, etc. can be added as necessary.

Preferred physical properties of the ink for ink jet recording of the present invention are as follows. The surface tension of the ink is preferably 20 mN / m or more and 60 mN / m or less. More preferably, it is 20 mN or more and 45 mN / m or less, More preferably, it is 25 mN / m or more and 35 mN / m or less. If the surface tension is 20 mN / m or more, liquid can be prevented from overflowing to the nozzle surface of the recording head, and printing can be performed normally. On the other hand, if it is 60 mN / m or less, the permeability to the recording medium after printing is good and drying time is not required, which is preferable. The surface tension was measured under the environment of 23 ° C. and 55% RH using a Wilhelmy surface tension meter as described above.

The volume average particle diameter of the pigment particles in the ink is preferably 10 nm or more and 250 nm or less, more preferably 20 nm or more and 250 nm or less, still more preferably 30 nm or more and 200 nm or less, and 50 nm or more and 150 nm or less. Is most preferred. When the volume average particle diameter of the particles in the ink is 10 nm or more, it is preferable because the aging stability of the dispersion is increased and aggregation is difficult. Further, when the volume average particle diameter of the pigment particles is 250 nm or less, the optical density becomes high and the density of the printed matter becomes high, and it is preferable that the nozzle is not clogged when printing with an inkjet or the like.

In addition, the volume average particle diameter of the pigment particles refers to the particle diameter of the pigment itself, or, in the case where an additive such as a dispersant is attached to the pigment, the particle diameter to which the additive is attached. In the present invention, a nanotrac UPA particle size analyzer (UPA-EX150; manufactured by Nikkiso Co., Ltd.) can be used as a volume average particle diameter measuring apparatus for pigments. The measurement can be performed according to a predetermined measurement method by placing 3 ml of the pigment dispersion in a measurement cell. As parameters input at the time of measurement, the ink viscosity is used as the viscosity, and the pigment density is used as the density of the dispersed particles.

The viscosity of the ink is preferably from 1.2 mPa · s to 8.0 mPa · s, more preferably from 1.5 mPa · s to less than 6.0 mPa · s, still more preferably from 1.6 mPa · s to 4. It is less than 5 mPa · s. If the viscosity is 8.0 mPa · s or less, it is possible to prevent the discharge property from being lowered. On the other hand, if it is 1.2 mPa · s or more, it is possible to prevent the long-term jetability from deteriorating.
The viscosity (including those described later) was measured using a RE80L viscometer manufactured by Toki Sangyo Co., Ltd. under the conditions of 25 ° C. and 100 rpm.

<Recording method>
The recording method of the present invention is a method using the ink composition of the present invention or ink for ink jet recording (hereinafter sometimes referred to as “inks”) described above. In addition, an ink jet recording apparatus and an ink tank for ink jet recording can be used as needed.

For example, one embodiment of the recording method of the present invention is a method for forming an image on the surface of a recording medium by using the ink for inkjet recording of the present invention and ejecting ink from the recording head to the surface of the recording medium in accordance with a recording signal It is.
The ink jet recording apparatus includes a recording head that uses ink jet recording ink and ejects ink (if necessary, treatment liquid) onto the surface of the recording medium, and forms an image by ejecting the ink from the recording head onto the surface of the recording medium. It can be set as a device. The ink jet recording apparatus supplies an ink tank for ink jet recording (hereinafter sometimes referred to as “ink tank”) that can supply ink to the recording head and is detachable from the main body of the ink jet recording apparatus. You may have. In this case, ink is stored in the ink tank for ink jet recording.

As the ink jet recording apparatus, a normal ink jet recording apparatus having a printing method capable of using ink can be used. In addition, a heater for controlling the ink drying is mounted as necessary. Alternatively, an intermediate transfer mechanism may be mounted, and a mechanism for discharging (printing) ink and processing liquid onto the intermediate and then transferring it to a recording medium such as paper may be provided.
Further, an ink tank for ink jet recording is detachable from an ink jet recording apparatus equipped with a recording head, and can be used as long as it has a configuration capable of supplying ink to the recording head while attached to the ink jet recording apparatus. A known ink tank can be used.

The recording method (and apparatus) using the ink for ink jet recording preferably employs a thermal ink jet recording method or a piezo ink jet recording method from the viewpoint of an effect of improving bleeding and intercolor bleeding. In the case of the thermal ink jet recording method, the ink is heated at the time of ejection and has a low viscosity, but the viscosity rapidly increases because the temperature of the ink is lowered on the recording medium. For this reason, there is an effect of improving bleeding and intercolor bleeding. On the other hand, in the case of the piezo ink jet method, it is possible to discharge a high-viscosity liquid, and the high-viscosity liquid can suppress spreading in the paper surface direction on the recording medium. There is an improvement effect on intercolor bleeding.

In a recording method (and apparatus) using ink for ink jet recording, replenishment (supply) of ink to a recording head may be performed from an ink tank (including a treatment liquid tank if necessary) filled with ink liquid. Good. The ink tank is preferably of a cartridge type that can be attached to and detached from the apparatus main body, and ink can be easily replenished by exchanging the cartridge type ink tank.

<Recorded material>
The recorded matter of the present invention can be obtained by using the ink composition or the ink for ink jet recording described above. The recording method is not particularly limited, but the recording method according to the present invention described above is preferable.

<Storage stabilization method of ink for inkjet recording>
The ink jet recording ink storage stabilization method of the present invention is an ink jet recording ink containing an azo pigment of formula (1) and the like, and has an acid value and an amine value, preferably on the side. A pigment dispersion containing a polymer having an acidic group and a basic group in a chain or an acidic group in a side chain and neutralized with a base is used.
An azo pigment having the structure of the formula (1) becomes a pigment dispersion having excellent dispersion stability over time by dispersing a polymer having an acidic group and a basic group in the side chain as a dispersant. The “polymer having an acidic group and a basic group in the side chain” and the “polymer having an acidic group in the side chain and neutralized with a base” are described in the polymer section of the “pigment dispersant” above. Synonymous with

Hereinafter, the present invention will be specifically described with reference to examples and comparative examples, but the scope of the present invention is not limited to the examples shown below.

1. Preparation of pigment dispersion <Synthesis of azo pigment>
The azo pigment (1) was synthesized by the method described in JP-A 2010-31215 (paragraphs [0125] to [0134]). The obtained azo pigment (1) was visually observed with a transmission microscope (manufactured by JEOL Ltd .: JEM-1010 electron microscope). The length of the primary particles in the major axis direction was about 15 μm. It was. The obtained crystal has an α-type crystal form having characteristic X-ray diffraction peaks at Bragg angles (2θ ± 0.2 °) in CuKα characteristic X-ray diffraction of 7.6 °, 25.6 °, and 27.7 °. It was an azo pigment (1) -a.
Further, the azo pigment (1) was synthesized by the method described in JP-A 2010-31215 (paragraph [0135]). The obtained azo pigment (1) was visually observed with a transmission microscope (JEM-1010 electron microscope manufactured by JEOL Ltd.). As a result, the length of the primary particles in the major axis direction was about 150 nm. The obtained crystal has a β-type crystal form having characteristic X-ray diffraction peaks at Bragg angles (2θ ± 0.2 °) of 7.0 °, 26.4 °, and 27.3 ° in CuKα characteristic X-ray diffraction. It was an azo pigment (1) -b.

<Synthesis of γ-type crystal form azo pigment (1) -c>

In a mixed solution of 55 mL of acetic acid and 37 mL of propionic acid, 9.2 g of compound (a) was dissolved at room temperature. The inner temperature was cooled to −3 ° C. with ice cooling, and a 40 mass% sulfuric acid solution of nitrosylsulfuric acid was added dropwise over 10 minutes at an inner temperature of −3 ° C. to 4 ° C. After stirring for 1 hour at an internal temperature of 4 ° C., 0.2 g of urea was added, and then the internal temperature was cooled to −3 ° C. and further stirred for 10 minutes to obtain a diazonium salt solution. Separately, 11.1 g of compound (b) was completely dissolved in 160 mL of acetone, then the internal temperature was cooled to 17 ° C., and added to the above diazonium salt solution within the range of −3 ° C. to 3 ° C. over 25 minutes. did. After completion of the addition, the mixture was stirred at 3 ° C. for 30 minutes, then the ice bath was removed and the temperature was raised to room temperature over 30 minutes. After stirring at room temperature for 30 minutes, the obtained crystals were filtered off, washed with 150 mL of acetone, and further washed with 100 mL of water. The obtained crystals were suspended in 400 mL of water without drying, and an 8N aqueous potassium hydroxide solution was added to adjust the pH to 6.7. After stirring at room temperature for 25 minutes, the obtained crystals were separated by filtration, thoroughly washed with water, and then washed with 80 mL of acetone. The obtained crystals were dried at room temperature for 12 hours. The obtained crystal was suspended in 500 mL of acetone and then stirred for 30 minutes under reflux. Then, it cooled to room temperature over 1 hour, the obtained crystal | crystallization was separated by filtration, and it dried at room temperature for 5 hours, and obtained 17.4g of azo pigments (1). Yield 81.0%
The obtained azo pigment (1) was visually observed with a transmission microscope (manufactured by JEOL Ltd .: JEM-1010 electron microscope). The length of the primary particles in the major axis direction was about 300 nm. It was. The obtained crystal has a γ-type crystal form having characteristic X-ray diffraction peaks at CuKα characteristic X-ray diffraction with Bragg angles (2θ ± 0.2 °) of 6.4 °, 26.4 ° and 27.2 °. It was an azo pigment (1) -c.

<Example 1> Preparation of pigment dispersion 1 2.5 g of azo pigment (1) -a, 0.71 g of DISPERBYK-187 (manufactured by Big Chemie Co., Ltd., 70% by mass), 5 g of glycerin, 41.79 g of water Were mixed together with 100 g of zirconia beads having a diameter of 0.1 mm using a planetary ball mill at 300 rpm for 7 hours. After dispersion, the zirconia beads were separated, and further filtered through a syringe with a volume of 50 mL equipped with a 5 μm pore size filter (Mirex-SV manufactured by Millipore Corporation, polyvinylidene fluoride membrane, outer diameter: 25 mm), and a yellow pigment Dispersion 1 (volume average particle diameter; 61.0 nm: measured using Nanotrac 150 (UPA-EX150) manufactured by Nikkiso Co., Ltd.) was obtained. The viscosity of the resulting pigment dispersion 1 was 1.842 mPa · s (measured using a RE80L viscometer manufactured by Toki Sangyo Co., Ltd. under the conditions of 25 ° C. and 100 rpm).

Example 2 Preparation of Pigment Dispersion 2 2.5 g of azo pigment (1) -a, 0.79 g of DISPERBYK-181 (manufactured by Big Chemie Co., Ltd., 63% by mass), 5 g of glycerin, 41.71 g of water Were mixed together with 100 g of zirconia beads having a diameter of 0.1 mm using a planetary ball mill for 300 rotations per minute for 4 hours. After dispersion, the zirconia beads were separated, and further filtered through a syringe with a volume of 50 mL equipped with a 5 μm pore size filter (Mirex-SV manufactured by Millipore Corporation, polyvinylidene fluoride membrane, outer diameter: 25 mm), and a yellow pigment Dispersion 2 (volume average particle size; 79.5 nm: measured using Nanotrac 150 (UPA-EX150) manufactured by Nikkiso Co., Ltd.) was obtained. The viscosity of the resulting pigment dispersion 2 was 1.752 mPa · s (measured using a RE80L viscometer manufactured by Toki Sangyo Co., Ltd. under the conditions of 25 ° C. and 100 rpm).

<Example 3> Preparation of pigment dispersion 3 2.5 g of azo pigment (1) -a, 0.35 g of DISPERBYK-187 (manufactured by Big Chemie Co., Ltd., 70% by mass), 5 g of glycerin, 42.15 g of water Were mixed together with 100 g of zirconia beads having a diameter of 0.1 mm using a planetary ball mill at 300 rpm for 7 hours. After dispersion, the zirconia beads were separated, and further filtered through a syringe with a volume of 50 mL equipped with a 5 μm pore size filter (Mirex-SV manufactured by Millipore Corporation, polyvinylidene fluoride membrane, outer diameter: 25 mm), and a yellow pigment Dispersion 3 (volume average particle diameter; 128.1 nm: measured using Nanotrac 150 (UPA-EX150) manufactured by Nikkiso Co., Ltd.) was obtained. The viscosity of the obtained pigment dispersion 3 was 1.585 mPa · s (measured using a RE80L viscometer manufactured by Toki Sangyo Co., Ltd. under the conditions of 25 ° C. and 100 rpm).

<Example 4> Preparation of pigment dispersion 4 2.5 g of azo pigment (1) -a, 1.42 g of DISPERBYK-187 (manufactured by Big Chemie Co., Ltd., 70% by mass), 5 g of glycerin, and 41.08 g of water Were mixed together with 100 g of zirconia beads having a diameter of 0.1 mm using a planetary ball mill at 300 rpm for 7 hours. After dispersion, the zirconia beads were separated, and further filtered through a syringe with a volume of 50 mL equipped with a 5 μm pore size filter (Mirex-SV manufactured by Millipore Corporation, polyvinylidene fluoride membrane, outer diameter: 25 mm), and a yellow pigment Dispersion 4 (volume average particle size; 70.2 nm: measured using Nanotrac 150 (UPA-EX150) manufactured by Nikkiso Co., Ltd.) was obtained. The viscosity of the obtained pigment dispersion 4 was 1.981 mPa · s (measured using a RE80L viscometer manufactured by Toki Sangyo Co., Ltd. under the conditions of 25 ° C. and 100 rpm).

<Example 5> Preparation of pigment dispersion 5 2.5 g of azo pigment (1) -a, 2.50 g of DISPERBYK-187 (manufactured by Big Chemie Co., Ltd., 70% by mass), 5 g of glycerin, 40.05 g of water Were mixed together with 100 g of zirconia beads having a diameter of 0.1 mm using a planetary ball mill at 300 rpm for 7 hours. After dispersion, the zirconia beads were separated, and further filtered through a syringe with a volume of 50 mL equipped with a 5 μm pore size filter (Mirex-SV manufactured by Millipore Corporation, polyvinylidene fluoride membrane, outer diameter: 25 mm), and a yellow pigment Dispersion 5 (volume average particle diameter; 97.9 nm: measured using Nanotrac 150 (UPA-EX150) manufactured by Nikkiso Co., Ltd.) was obtained. The viscosity of the obtained pigment dispersion 5 was 1.978 mPa · s (measured using a RE80L viscometer manufactured by Toki Sangyo Co., Ltd. under the conditions of 25 ° C. and 100 rpm).

Example 6 Preparation of Pigment Dispersion 6 Azo Pigment (1) -a 2.5 g, EFKA-5071 (Ciba Co., Ltd., 53 mass%) 0.94 g, glycerin 5 g, water 41.56 g Were mixed together with 100 g of zirconia beads having a diameter of 0.1 mm using a planetary ball mill at 300 rpm for 7 hours. After dispersion, the zirconia beads were separated, and further filtered through a syringe with a volume of 50 mL equipped with a 5 μm pore size filter (Mirex-SV manufactured by Millipore Corporation, polyvinylidene fluoride membrane, outer diameter: 25 mm), and a yellow pigment Dispersion 6 (volume average particle diameter; 196.6 nm: measured using Nanotrac 150 (UPA-EX150) manufactured by Nikkiso Co., Ltd.) was obtained. The viscosity of the obtained pigment dispersion 6 was 1.616 mPa · s (measured using a RE80L viscometer manufactured by Toki Sangyo Co., Ltd. under the conditions of 25 ° C. and 100 rpm).

<Example 7> Preparation of pigment dispersion 7 A mixture of 2.5 g of azo pigment (1) -a, 1.00 g of DISPERBYK (manufactured by Big Chemie Co., Ltd., 50% by mass), 5 g of glycerin and 41.50 g of water. Then, 100 g of zirconia beads having a diameter of 0.1 mm and a planetary ball mill were used for dispersion at 300 rpm for 7 hours. After dispersion, the zirconia beads were separated, and further filtered through a syringe with a volume of 50 mL equipped with a 5 μm pore size filter (Mirex-SV manufactured by Millipore Corporation, polyvinylidene fluoride membrane, outer diameter: 25 mm), and a yellow pigment Dispersion 7 (volume average particle size; 132.9 nm: measured using Nanotrac 150 (UPA-EX150) manufactured by Nikkiso Co., Ltd.) was obtained. The viscosity of the obtained pigment dispersion 7 was 1.732 mPa · s (measured using a RE80L viscometer manufactured by Toki Sangyo Co., Ltd. under the conditions of 25 ° C. and 100 rpm).

<Example 8> Preparation of pigment dispersion 8 2.5 g of azo pigment (1) -a, 0.63 g of DISPERBYK-180 (manufactured by Big Chemie Co., Ltd., 79% by mass), 5 g of glycerin, and 41.87 g of water Were mixed together with 100 g of zirconia beads having a diameter of 0.1 mm using a planetary ball mill at 300 rpm for 7 hours. After dispersion, the zirconia beads were separated, and further filtered through a syringe with a volume of 50 mL equipped with a 5 μm pore size filter (Mirex-SV manufactured by Millipore Corporation, polyvinylidene fluoride membrane, outer diameter: 25 mm), and a yellow pigment Dispersion 8 (volume average particle diameter; 145.9 nm: measured using Nanotrac 150 (UPA-EX150) manufactured by Nikkiso Co., Ltd.) was obtained. The viscosity of the obtained pigment dispersion 8 was 1.755 mPa · s (measured using a RE80L viscometer manufactured by Toki Sangyo Co., Ltd. under the conditions of 25 ° C. and 100 rpm).

<Example 9> Preparation of pigment dispersion 9 2.5 g of azo pigment (1) -a, 1.51 g of EFKA-4520 (Ciba Co., Ltd., 33% by mass), 5 g of glycerin, 40.98 g of water The mixture was mixed with 100 g of zirconia beads having a diameter of 0.1 mm and dispersed at 300 rpm for 5 hours using a planetary ball mill. After dispersion, the zirconia beads were separated, and further filtered through a syringe with a volume of 50 mL equipped with a 5 μm pore size filter (Mirex-SV manufactured by Millipore Corporation, polyvinylidene fluoride membrane, outer diameter: 25 mm), and a yellow pigment Dispersion 9 (volume average particle diameter; 72.8 nm: measured using Nanotrac 150 (UPA-EX150) manufactured by Nikkiso Co., Ltd.) was obtained. The viscosity of the obtained pigment dispersion 9 was 1.682 mPa · s (measured using a RE80L viscometer manufactured by Toki Sangyo Co., Ltd. under the conditions of 25 ° C. and 100 rpm).

<Example 10> Preparation of pigment dispersion 10 2.5 g of azo pigment (1) -a, 1.00 g of EFKA-4510 (manufactured by Ciba), 5 g of glycerin, 41.50 g of water Were mixed together with 100 g of zirconia beads having a diameter of 0.1 mm using a planetary ball mill for 300 rotations per minute for 6 hours. After dispersion, the zirconia beads were separated, and further filtered through a syringe with a volume of 50 mL equipped with a 5 μm pore size filter (Mirex-SV manufactured by Millipore Corporation, polyvinylidene fluoride membrane, outer diameter: 25 mm), and a yellow pigment Dispersion 10 (volume average particle size; 68.5 nm: measured using Nanotrac 150 (UPA-EX150) manufactured by Nikkiso Co., Ltd.) was obtained. The obtained pigment dispersion 10 had a viscosity of 1.539 mPa · s (measured using a RE80L viscometer manufactured by Toki Sangyo Co., Ltd. under the conditions of 25 ° C. and 100 rpm).

<Example 11> Preparation of pigment dispersion 11 2.5 g of azo pigment (1) -a, 1.00 g of EFKA-4530 (Ciba Co., Ltd., 50% by mass), 5 g of glycerin, 41.50 g of water Were mixed together with 100 g of zirconia beads having a diameter of 0.1 mm using a planetary ball mill for 300 rotations per minute for 6 hours. After dispersion, the zirconia beads were separated, and further filtered through a syringe with a volume of 50 mL equipped with a 5 μm pore size filter (Mirex-SV manufactured by Millipore Corporation, polyvinylidene fluoride membrane, outer diameter: 25 mm), and a yellow pigment Dispersion 11 (volume average particle diameter; 71.2 nm: measured using Nanotrac 150 (UPA-EX150) manufactured by Nikkiso Co., Ltd.) was obtained. The viscosity of the obtained pigment dispersion 11 was 1.691 mPa · s (measured using a RE80L viscometer manufactured by Toki Sangyo Co., Ltd. under the conditions of 25 ° C. and 100 rpm).

<Example 12> Preparation of pigment dispersion 12 2.5 g of azo pigment (1) -a, 3.55 g of DISPERBYK-187 (manufactured by Big Chemie Co., Ltd., 70% by mass), 5 g of glycerin, 38.95 g of water Were mixed together with 100 g of zirconia beads having a diameter of 0.1 mm using a planetary ball mill at 300 rpm for 7 hours. After dispersion, the zirconia beads were separated, and further filtered through a syringe with a volume of 50 mL equipped with a 5 μm pore size filter (Mirex-SV manufactured by Millipore Corporation, polyvinylidene fluoride membrane, outer diameter: 25 mm), and a yellow pigment Dispersion 12 (volume average particle diameter; 130.8 nm: measured using Nanotrac 150 (UPA-EX150) manufactured by Nikkiso Co., Ltd.) was obtained. The viscosity of the resulting pigment dispersion 12 was 1.932 mPa · s (measured using a RE80L viscometer manufactured by Toki Sangyo Co., Ltd. under the conditions of 25 ° C. and 100 rpm).

<Example 13> Preparation of pigment dispersion 13 2.5 g of azo pigment (1) -a, 0.18 g of DISPERBYK-187 (manufactured by Big Chemie Co., Ltd., 70% by mass), 5 g of glycerin, 42.32 g of water The mixture was mixed with 100 g of zirconia beads having a diameter of 0.1 mm and dispersed at 300 rpm for 5 hours using a planetary ball mill. After dispersion, the zirconia beads were separated, and further filtered through a syringe with a volume of 50 mL equipped with a 5 μm pore size filter (Mirex-SV manufactured by Millipore Corporation, polyvinylidene fluoride membrane, outer diameter: 25 mm), and a yellow pigment Dispersion 13 (volume average particle size; 69.0 nm: measured using Nanotrac 150 (UPA-EX150) manufactured by Nikkiso Co., Ltd.) was obtained. The viscosity of the obtained pigment dispersion 13 was 1.691 mPa · s (measured using a RE80L viscometer manufactured by Toki Sangyo Co., Ltd. under the conditions of 25 ° C. and 100 rpm).

<Example 14> Preparation of pigment dispersion 14 2.5 g of azo pigment (1) -b, 0.71 g of DISPERBYK-187 (manufactured by Big Chemie Co., Ltd., 70% by mass), 5 g of glycerin, 41.79 g of water The mixture was mixed with 100 g of zirconia beads having a diameter of 0.1 mm and dispersed at 300 rpm for 5 hours using a planetary ball mill. After dispersion, the zirconia beads were separated, and further filtered through a syringe with a volume of 50 mL equipped with a 5 μm pore size filter (Mirex-SV manufactured by Millipore Corporation, polyvinylidene fluoride membrane, outer diameter: 25 mm), and a yellow pigment Dispersion 1 (volume average particle diameter; 62.2 nm: measured using Nanotrac 150 (UPA-EX150) manufactured by Nikkiso Co., Ltd.) was obtained. The viscosity of the obtained pigment dispersion 14 was 1.752 mPa · s (measured using a RE80L viscometer manufactured by Toki Sangyo Co., Ltd. under the conditions of 25 ° C. and 100 rpm).

<Example 15> Preparation of pigment dispersion 15 2.5 g of azo pigment (1) -c, 0.71 g of DISPERBYK-187 (manufactured by Big Chemie Co., Ltd., 70% by mass), 5 g of glycerin, 41.79 g of water Were mixed together with 100 g of zirconia beads having a diameter of 0.1 mm using a planetary ball mill for 300 rotations per minute for 6 hours. After dispersion, the zirconia beads were separated, and further filtered through a syringe with a volume of 50 mL equipped with a 5 μm pore size filter (Mirex-SV manufactured by Millipore Corporation, polyvinylidene fluoride membrane, outer diameter: 25 mm), and a yellow pigment Dispersion 1 (volume average particle diameter; 67.5 nm: measured using Nanotrac 150 (UPA-EX150) manufactured by Nikkiso Co., Ltd.) was obtained. The viscosity of the obtained pigment dispersion 15 was 1.788 mPa · s (measured using a RE80L viscometer manufactured by Toki Sangyo Co., Ltd. under the conditions of 25 ° C. and 100 rpm).

<Comparative Example 1> Preparation of Comparative Pigment Dispersion 1 Pigment Yellow-74 (Irgalite Yellow GO manufactured by Ciba) 2.5 g, DISPERBYK-187 (Bic Chemie Co., Ltd., 70% by mass) 0.71 g, glycerin 5 g and 41.8 g of water were mixed, and dispersion was performed at 300 rpm for 7 hours using a planetary ball mill together with 100 g of zirconia beads having a diameter of 0.1 mm. After dispersion, the zirconia beads were separated, and further filtered through a syringe with a volume of 50 mL equipped with a 5 μm pore size filter (Mirex-SV manufactured by Millipore Corporation, polyvinylidene fluoride membrane, outer diameter: 25 mm), and a yellow pigment Dispersion 1 (volume average particle size; 204.7 nm: measured using Nanotrac 150 (UPA-EX150) manufactured by Nikkiso Co., Ltd.) was obtained. The viscosity of the obtained comparative pigment dispersion 1 was 1.826 mPa · s (measured using a RE80L viscometer manufactured by Toki Sangyo Co., Ltd. under the conditions of 25 ° C. and 100 rpm).

<Comparative Example 2> Preparation of Comparative Pigment Dispersion 2 2.5 g of azo pigment (1) -a, 0.5 g of DISPERBYK-192 (by Big Chemie Co., Ltd., 98% by mass), 5 g of glycerin, and 42 g of water The resultant mixture was mixed with 100 g of zirconia beads having a diameter of 0.1 mm and dispersed at 300 rpm for 2 hours using a planetary ball mill. After dispersion, the zirconia beads were separated, and further filtered through a 50 mL syringe equipped with a 5 μm pore size filter (Millex-SV, manufactured by Millipore Corp., polyvinylidene fluoride membrane, outer diameter: 25 mm). Pigment dispersion 2 (volume average particle diameter; 58.4 nm: measured using Nanotrac 150 (UPA-EX150) manufactured by Nikkiso Co., Ltd.) was obtained. The viscosity of the obtained comparative pigment dispersion 2 was 1.590 mPa · s (measured using a RE80L viscometer manufactured by Toki Sangyo Co., Ltd. under the conditions of 25 ° C. and 100 rpm).

Comparative Example 3 Preparation of Comparative Pigment Dispersion 3 2.5 g of azo pigment (1) -a, 1.25 g of DISPERBYK-193 (manufactured by Big Chemie Co., Ltd., 40% by mass), 5 g of glycerin, 41. When 25 g was mixed and dispersed with 100 g of zirconia beads having a diameter of 0.1 mm using a planetary ball mill at 300 rpm for 7 hours, the solution was gelled.

<Comparative Example 4> Preparation of Comparative Pigment Dispersion 4 Using azo pigment (1) -a, a polymer was synthesized according to the synthesis examples described in paragraphs [0300] to [0304] of JP 2010-65212 A. A dispersion of polymer particles including the pigment was prepared. Pure water was added so that the pigment content was 5% by mass to obtain a comparative pigment dispersion 4. Volume average particle diameter of the obtained comparative pigment dispersion 4; 64.4 nm: measured using Nanotrac 150 (UPA-EX150) manufactured by Nikkiso Co., Ltd. The viscosity was 1.680 mPa · s (measured under the conditions of 25 ° C. and 100 rpm using a RE80L viscometer manufactured by Toki Sangyo Co., Ltd.).

The polymers used in the above examples and comparative examples are described below.
DISPERBYK-187: alkylol ammonium salt of polyfunctional polymer, acid value 35 mgKOH / g, amine value 35 mgKOH / g
DISPERBYK-181: an alkylolamine salt of an anionic and nonionic polyfunctional polymer, acid value 33 mgKOH / g, amine value 33 mgKOH / g
DISPERBYK: alkylamine salt of polycarboxylic acid, acid value 85 mgKOH / g, amine value 85 mgKOH / g
DISPERBYK-180: an alkylolamine salt of a copolymer containing an acid group, an acid value of 95 mgKOH / g, an amine value of 95 mgKOH / g
EFKA-5071: alkylol ammonium salt of high molecular weight polycarboxylic acid, acid value 100 mgKOH / g, amine value 105 mgKOH / g
EFKA-4520: Modified polyurethane, acid value 6 mgKOH / g, amine value 6 mgKOH / g
EFKA-4510: Modified polyacrylate, acid value 17 mgKOH / g, amine value 40 mgKOH / g
EFKA-4530: Modified polyacrylate, acid value 24 mgKOH / g, amine value 32 mgKOH / g
DISPERBYK-192: Pigment affinity copolymer, no acid value and amine value DISPERBYK-193: Pigment affinity copolymer, no acid value and amine value Polymer used in Comparative Example 4: Styrene-acrylic acid system Copolymer, acid value 143 mgKOH / g, no amine value

2. Evaluation of Pigment Dispersion The following items were evaluated for the pigment dispersions obtained in the above Examples and Comparative Examples.
<Dispersibility>
In the process of preparing the pigment dispersion, after dispersion, the particles having an average volume particle diameter of less than 80 nm were A, the particles having an average particle size of 80 nm to less than 200 nm were B, the particles having a particle size of 200 nm or more were C, and could not be dispersed. The thing was set to D. The results are shown in Table 1. Comparative Example 4 was not evaluated because the dispersion method was different.

<Dispersion stability (average volume particle diameter)>
When the obtained pigment dispersion is allowed to stand at 70 ° C. for 2 weeks, the average volume particle diameter change is less than 20 nm A, the change is 20 nm or more to less than 50 nm B, the change is 50 nm or more C was defined as less than 200 nm, and D was defined as a change of 200 nm or more, or a particle that could be visually confirmed as precipitated. The results are shown in Table 1. Since Comparative Example 3 was gelled, no evaluation was performed.

<Dispersion stability (viscosity)>
When the obtained pigment dispersion is allowed to stand at 70 ° C. for 4 weeks, the viscosity change is less than 0.1 mPa · s A, and 0.1 to less than 0.2 mPa · s. B, the change was 0.2 mPa · s or more to less than 0.5 mPa · s, C was changed, and the change was 0.5 mPa · s or more, or D could be confirmed by particle precipitation. Since Comparative Example 3 was gelled, no evaluation was performed. The results are shown in Table 1.

<Light resistance evaluation>
Mix 3.5g of ion-exchanged water, 1.1g of 1,2-hexanediol, 5.6g of glycerin, 1.7g of 2-pyrrolidone, 1.1g of triethylene glycol monobutyl ether, and 0.3g of propylene glycol. Obtained. The obtained pigment dispersion (30 g) was added thereto, and the obtained mixed solution was attached with a filter having a pore size of 5 μm (Mirex-SV, manufactured by Millipore Corporation, polyvinylidene fluoride membrane, outer diameter: 25 mm). The pigment ink liquid was obtained by filtering with a syringe and removing coarse particles.
The ink liquid was loaded into a cartridge of an ink jet printer PM-G800 manufactured by EPSON, and printed on an image receiving sheet EPSON photographic paper Krispia <high gloss>. The image density of the obtained printed matter was measured using a reflection densitometer (X-Rite 938 manufactured by X-Rite) to prepare a coated product having an image density of 1.0. Xenon light (130000lux; in the presence of a TAC filter) was irradiated for 10 days using a fade meter, and the image density before and after the xenon irradiation was measured using a reflection densitometer, and the dye residual ratio [(density after irradiation / density before irradiation) × 100%] is 90% or more, A is 80% or more to less than 90%, B is 60% or more to less than 80%, C is less than 60%, and D is a pigment dispersion. evaluated. Since Comparative Example 3 was gelled, no evaluation was performed. The results are shown in Table 1.

From the above results, the pigment dispersion containing the azo pigment of the formula (1) and the like and the polymer having an acid value and an amine value is excellent in light resistance and has a particle diameter and a viscosity even after aging at a high temperature. It was confirmed that the increase in the number was suppressed (Examples 1 to 15). On the other hand, a pigment dispersion (Comparative Example 1) using an azo pigment containing a polymer having an acid value and an amine value but not having the structure of Formula (1), or an azo pigment of Formula (1) is used. However, it was confirmed that the pigment dispersions (Comparative Examples 2 to 4) in which both the acid value and the amine value were not contained in the contained polymer were inferior in light resistance.

3. Preparation of Pigment Ink Solution <Example 16> Preparation of Pigment Ink Solution 1 3.5 g of ion exchange water, 1.1 g of 1,2-hexanediol, 5.6 g of glycerin, 1.7 g of 2-pyrrolidone, triethylene glycol monobutyl ether 1.1 g and propylene glycol 0.3 g were mixed to obtain a uniform solution. 30 g of Pigment Dispersion 1 was added thereto, and the resulting mixture was mixed with a 50 mL syringe equipped with a pore size 5 μm filter (Milex-SV, manufactured by Millipore Corp., polyvinylidene fluoride membrane, outer diameter: 25 mm). The pigment ink liquid 1 was obtained by filtering and removing coarse particles.

<Comparative Example 5> Preparation of Comparative Pigment Ink Liquid 1 Comparative Pigment Ink 1 was obtained in the same manner as in Example 16 except that Comparative Pigment Dispersion 1 was used instead of Pigment Dispersion 1.

<Comparative Example 6> Preparation of Comparative Pigment Ink Liquid 2 Comparative Pigment Ink 2 was obtained in the same manner as in Example 16 except that Comparative Pigment Dispersion 2 was used instead of Pigment Dispersion 1.

4). Evaluation of pigment ink liquid <Ink storage stability (average volume particle diameter)>
When the obtained ink liquid is allowed to stand at 70 ° C. for 2 weeks, the average volume particle diameter change is less than 20 nm A, the change is 20 nm to less than 50 nm B, and the change is 50 nm to 200 nm. Less than C, the change is 200 nm or more, or D can be confirmed by particle precipitation. The results are shown in Table 1.

<Ink storage stability (viscosity)>
When the obtained ink liquid is allowed to stand at 70 ° C. for 4 weeks, the viscosity change is less than 0.1 mPa · s A, and the viscosity change is 0.1 mPa · s or more to less than 0.2 mPa · s B. The change was 0.2 mPa · s or more to less than 0.5 mPa · s, C, the change was 0.5 mPa · s or more, or the particle precipitation was visually confirmed as D. The results are shown in Table 2.

From the above results, the ink for ink jet recording using the pigment dispersion containing the azo pigment of formula (1) and the like and the polymer having an acid value and an amine value has a particle size even after aging at a high temperature. And it was confirmed that the increase in viscosity was suppressed (Example 16). On the other hand, using a pigment ink (Comparative Example 5) using an azo pigment containing a polymer having an acid value and an amine value but not having the structure of formula (1), or using an azo pigment of formula (1) In the case of the pigment ink (Comparative Example 6) in which both the acid value and the amine value are not contained in the contained polymer, an increase in the particle size and viscosity was confirmed after aging at a high temperature.

Since the pigment dispersion of the present invention contains an azo pigment having a specific structure and a polymer having an acid value and an amine value, it is excellent in light resistance and has a particle diameter and viscosity even after aging at high temperatures. An azo pigment dispersion in which an increase in the amount of the azo pigment is suppressed, an ink composition using the same, an ink for inkjet recording, a recording method, and a recorded matter can be provided. Further, it is possible to provide a storage stabilization method for ink for inkjet recording using an azo pigment having a specific structure.

Although the present invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention.
This application is based on a Japanese patent application filed on July 23, 2010 (Japanese Patent Application No. 2010-166557), the contents of which are incorporated herein by reference.

Claims (10)

1. A pigment dispersion comprising an azo pigment represented by the following formula (1) or a tautomer thereof, and a polymer having an acid value and an amine value.
   

   
2. Bragg angles (2θ ± 0.2 °) in CuKα characteristic X-ray diffraction of the azo pigment or its tautomer are 7.6 °, 25.6 °, 7.0 °, 26.4 ° and 27.3. The pigment dispersion according to claim 1, characterized by having characteristic X-ray diffraction peaks at °, or 6.4 °, 26.4 ° and 27.2 °.
3. The azo pigment or its tautomer has characteristic X-ray diffraction peaks at Bragg angles (2θ ± 0.2 °) in CuKα characteristic X-ray diffraction of 7.6 ° and 25.6 °. The pigment dispersion according to claim 1 or 2.
4. The pigment dispersion according to any one of claims 1 to 3, wherein the acid value of the polymer is 10 to 120 mgKOH / g and the amine value is 10 to 120 mgKOH / g.
5. The polymer having an acid value and an amine value is contained in an amount of 10 to 80% by mass based on the total content of the azo pigment represented by the formula (1) and tautomers thereof. 5. The pigment dispersion according to any one of 4 above.
6. An ink composition comprising the pigment dispersion according to any one of claims 1 to 5.
7. An ink for inkjet recording, comprising the pigment dispersion according to any one of claims 1 to 5 or the ink composition according to claim 6.
8. A recording method comprising using the ink composition according to claim 6 or the ink-jet recording ink according to claim 7.
9. A recorded matter obtained by using the ink composition according to claim 6 or the inkjet recording ink according to claim 7.
10. A method for storage stabilization of an ink for ink jet recording, comprising using a pigment dispersion containing an azo pigment represented by the following formula (1) or a tautomer thereof and a polymer having an acid value and an amine value.