JP2010065131A - Manufacturing method for pigment dispersion, water-based ink for inkjet recording, and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method for a pigment dispersion with sufficient dispersion stability and a water-based ink for inkjet recording being excellent in delivery stability. <P>SOLUTION: The pigment dispersion is manufactured by the manufacturing method including a step of obtaining a water-based dispersion by mixing a water-insoluble resin, carbon black, a neutralizing agent, an organic solvent, an anionic polymer surfactant and a water-based medium and a step of removing at least a part of the organic solvent from the water-based dispersion. Further, the water-based ink for inkjet recording contains the pigment dispersion manufactured by the manufacturing method. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

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

Various techniques for obtaining high-quality recorded matter such as color density, fixability, and resolution have been studied for recording media for inkjet recording and inks used therefor.
Pigments are widely used as colorants used in ink for ink jet recording from the viewpoint of light resistance and water resistance. Carbon black is generally used as a black ink pigment in recording liquids for ink jet printers.

  When carbon black is used as a pigment for black ink, high definition and high color rendering properties cannot be obtained unless the particles are made fine and dispersed and stabilized. In particular, in the case of a recording liquid for an ink jet printer, when pigment particles that are insufficiently dispersed exist, it directly leads to the problem of clogging of the nozzles of the ejection head. However, since carbon black generally has a small primary particle size and strong secondary agglomeration properties, various devices have been required for fine dispersion and to keep the dispersed particle size stable.

In relation to such a situation, an aqueous dispersion for inkjet recording in which a carbon black pigment is coated with a water-insoluble polymer has been proposed as a carbon black pigment used in an aqueous ink for inkjet recording (see, for example, Patent Document 1). ), Excellent image density, image uniformity, and the like.
JP 2007-169506 A

  However, the aqueous dispersion for ink jet recording described in Patent Document 1 is not only insufficient in terms of black density, but it is difficult to keep the dispersed particle size stable after fine dispersion, for example, when trying to make it finer. There was a case.

In recent years, as black ink, ink with higher print density than ever has been demanded, but it is possible to stably disperse carbon black having a large specific surface area, that is, smaller particle diameter, and to ensure ejection stability. It is difficult, and the fact is that the conventional technology alone has not yet solved these problems.
Further, when recording an image, there may be a case where a discharge directionality defect is caused due to the fact that aggregates adhere and dry near the head due to the generation of mist during droplet ejection. This agglomerate is difficult to remove depending on the newly ejected liquid, and the removability (that is, maintainability) of the adhered agglomerates is not sufficient, so that problems such as white spots occur in the recorded image. There is.

  The present invention has been made in view of the above, and an object of the present invention is to provide a method for producing a pigment dispersion having good dispersion stability, an aqueous ink for inkjet recording having excellent ejection stability, and a method for producing the same. .

Specific means for solving the above problems are as follows.
<1> a step of obtaining an aqueous dispersion by mixing a water-insoluble resin, carbon black, a neutralizing agent, an organic solvent, an anionic polymer surfactant, and an aqueous medium, and at least the organic solvent from the aqueous dispersion And a step of removing a part of the pigment dispersion.
<2> The method for producing a pigment dispersion according to <1>, wherein the water-insoluble resin includes a structural unit represented by the following general formula (I).

[Wherein, R ¹ represents a hydrogen atom or a methyl group, and Ar represents an unsubstituted or substituted aromatic ring. n represents the average number of repetitions and is 1-6. ]

<3> The method for producing a pigment dispersion according to <1> or <2>, wherein Ar in the general formula (I) is an unsubstituted or substituted benzene ring.
<4> The water-insoluble resin includes a hydrophilic structural unit derived from (meth) acrylic acid and a hydrophobic structural unit represented by the general formula (I), and the content of the aromatic ring is a water-insoluble resin. <1> to <3>, wherein the content of the total hydrophilic structural unit is 15% by mass or less of the total mass of the water-insoluble resin. A method for producing a pigment dispersion.
<5> The method for producing a pigment dispersion according to any one of <1> to <4>, wherein the water-insoluble resin has an acid value of 30 mgKOH / g or more and 100 mgKOH / g or less.
<6> The aqueous dispersion according to any one of <1> to <5>, wherein the content of the anionic polymer surfactant with respect to the carbon black is 0.01% by mass to 10% by mass. The manufacturing method of the pigment dispersion of description.
<7> The pigment according to any one of <1> to <6>, wherein the anionic polymer surfactant is at least one selected from a naphthalenesulfonic acid formalin condensate and a polycarboxylic acid derivative. A method for producing a dispersion.

<8> A water-based ink for inkjet recording, comprising the pigment dispersion produced by the method for producing a pigment dispersion described in any one of <1> to <7>.
<9> a step of mixing a water-insoluble resin, carbon black, a neutralizing agent, an organic solvent, an anionic polymer surfactant, and an aqueous medium to obtain an aqueous dispersion, and at least the organic solvent from the aqueous dispersion A method for producing a water-based ink for ink-jet recording, comprising: a step of removing a part to obtain a pigment dispersion; and a step of preparing a water-based ink for ink-jet recording using the pigment dispersion.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of a pigment dispersion with favorable dispersion stability, the water-based ink for inkjet recordings which is excellent in discharge stability, and its manufacturing method can be provided.

[Method for producing pigment dispersion]
The method for producing a pigment dispersion of the present invention comprises at least one water-insoluble resin, at least one carbon black, at least one neutralizing agent, at least one organic solvent, and at least one anionic polymer surfactant. A step of mixing one type and an aqueous medium to obtain an aqueous dispersion, and a step of removing at least a part of the organic solvent from the aqueous dispersion.
The pigment dispersion in the present invention is obtained by dispersing carbon black coated with a water-insoluble resin in an aqueous medium. In the method for producing a pigment dispersion of the present invention, by using an anionic polymer surfactant as a dispersion aid in combination, a dispersion having good dispersion stability and particularly excellent stability over time at high temperature storage is obtained. It can be manufactured efficiently. Further, the dispersion stability is further improved by removing at least a part of the organic solvent from the aqueous dispersion.

  In addition, in the step of obtaining an aqueous dispersion, by using an anionic polymer surfactant having a high adsorption rate in the aqueous phase, for example, by suppressing aggregation of fine particles generated by surface grinding of carbon black caused by frictional force, It can be considered that a pigment dispersion excellent in dispersion stability (particularly stability over time at high temperature storage) can be obtained.

<Anionic polymer surfactant>
The anionic polymer surfactant in the present invention is a surfactant having a weight average molecular weight of 2,000 or more. The weight average molecular weight is preferably 2,000 to 50,000, more preferably 3,000 to 20,000, from the viewpoint of dispersion stability.

The anionic polymer surfactant in the present invention is not particularly limited as long as it has a weight average molecular weight of 2000 or more and contains at least one anionic group as a hydrophilic group.
The anionic group is not particularly limited as long as it has a negative charge. In the present invention, from the viewpoint of dispersion stability, a phosphoric acid group, a phosphonic acid group, a phosphinic acid group, a sulfuric acid group, a sulfonic acid group, a sulfinic acid group or a carboxylic acid group is preferable. It is more preferably a group or a carboxylic acid group, and further preferably a sulfonic acid group or a carboxylic acid group.
These anionic groups may constitute a salt. Further, the salt may be a salt with an organic cation or a salt with an inorganic cation.

  Moreover, in addition to an anionic group as a hydrophilic group, you may contain the nonionic group. Examples of the nonionic group include polyethylene oxide, polyglycerin, a part of sugar unit, and the like.

  Examples of the anionic polymer surfactant in the present invention include a formalin condensate (particularly naphthalene sulfonic acid formalin condensate) of a sulfonated aromatic compound containing a polynuclear aromatic compound, a polycarboxylic acid derivative and the like. it can.

The formalin condensate of a sulfonated aromatic compound containing a polynuclear aromatic compound is a compound obtained by formalin condensation of a sulfonated aromatic compound containing a polynuclear aromatic compound or a salt thereof.
The polynuclear aromatic compound is a compound in which two or more aromatic rings (including heterocycles) share two or more carbon atoms to form a condensed ring and derivatives thereof, and two or more aromatics A compound and a derivative thereof in which a ring (including a heterocyclic ring) is bonded directly or via an alkylene group.

Examples of the polynuclear aromatic compound include naphthalene, anthracene, phenanthrene, pyrene, acenaphthene, indene, fluoranthene, chrysene, benzofluorene, benzopyrene, perylene, benzoperylene, fluorene, diphenyl, dibenzofuran, and the like.
Preferably, it is at least one selected from naphthalene, anthracene, phenanthrene, pyrene, acenaphthene and fluorene, more preferably naphthalene.

  The sulfonated aromatic compound may be composed only of the polynuclear aromatic compound or may be composed of a polynuclear aromatic compound and a mononuclear aromatic compound. In the latter case, the mononuclear aromatic compound is preferably used in an amount of 20 to 40% by mass based on the total amount of the sulfonated aromatic compound. Examples of mononuclear aromatic compounds include lower monoalkylphenols such as benzene, toluene, xylene, phenol and cresol, lower dialkylphenols such as xylenol, and tetralin.

  The formalin condensate of a sulfonated aromatic compound containing a polynuclear aromatic compound in the present invention is preferably a formalin condensate of naphthalenesulfonic acid, and more preferably a compound containing at least one of the following structural units.

  In addition, the naphthalene sulfonic acid formalin condensate may contain other structural units as long as the function as a dispersant is not impaired. Examples of other structural units include structural units formed from a copolymerizable monomer such as alkyl naphthalene sulfonic acid, alkyl alcohol naphthalene sulfonic acid, alkyl maleic anhydride, and polycarboxylic acid. In this case, it is preferable to contain other structural units at 30 mass% or less.

  The naphthalenesulfonic acid formalin condensate has a weight average molecular weight of 2,000 or more, and preferably has a weight average molecular weight of 2,000 to 50,000 in terms of adsorptivity and dispersibility. More preferably, it is from 20,000 to 20,000.

The naphthalenesulfonic acid formalin condensate can be produced by polycondensation using a generally known method, for example, β-naphthalenesulfonic acid (salt), an equivalent amount of formalin, and other components as necessary. . Examples of other components include sulfonic acids (salts) such as β-methylnaphthalene, α-methylnaphthalene, acenaphthene, dibenzofuran, fluorene, phenanthrene, anthracene, fluoranthene, and pyrene.
As the naphthalene sulfonic acid formalin condensate, commercially available products such as DEMAL NL, DEMAL SS-L, DEMAL N, DEMAL MS, DEMAL C (all of which are trade names) manufactured by Kao Corporation can be used.

The polycarboxylic acid derivative is a polymer compound having a carboxyl group and / or a salt thereof in a polymer constituent unit and a weight average molecular weight of 2,000 to 100,000, and at least 1 in 1 kg of the polymer compound. It contains a mol carboxyl group and / or a salt thereof. The weight average molecular weight can be measured by a gel permeation chromatography method (GPC method) using a polyethylene glycol standard substance.
The polycarboxylic acid derivative is a polymer compound represented by the following general formula.

R _{1 to} R ₆ in the formula are any _one of a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, an alkoxyl group having 1 to 5 carbon atoms, COOM, and OH, and they may all be the same or different. Although both ends are not particularly limited, examples thereof include a hydrogen atom, OH, an alkyl group having 1 to 5 carbon atoms, an alkoxyl group having 1 to 5 carbon atoms, SO ₃ M, and the like, which may be the same or different. M is any one of a hydrogen atom, an alkali metal, an alkylamine having 1 to 4 carbon atoms, and an alkanolamine having 1 to 6 carbon atoms. m and n each represent the number of moles of the structural unit in parentheses, and m may be 0. When m is 0, it is a homopolymer composed of structural units whose number of moles is represented by n. The copolymer molar ratio m / n of m and n is 0/10 to 10/1. The polymerization form may be block copolymerization or random copolymerization.

  Examples of polycarboxylic acid derivatives in the present invention include acrylic acid homopolymer, acrylic acid-maleic acid copolymer, α-hydroxyacrylic acid homopolymer, C5 olefin-maleic acid copolymer, isobutylene-maleic acid copolymer, and the like. And alkali metal salts or amine salts thereof. Acrylic acid homopolymer, acrylic acid-maleic acid copolymer, and isobutylene-maleic acid copolymer are preferred.

  The polycarboxylic acid derivative has a weight average molecular weight of 2,000 to 100,000, but from the viewpoint of adsorptivity and dispersibility, the weight average molecular weight is preferably 2,000 to 50,000. More preferably, it is 000-20,000.

  Examples of the polycarboxylic acid derivative include commercially available products such as Poise 540, Poise 530, Poise 521, Poise 520, Demol P, Demol EP, Demol ST, Selesche 100, Seleshe 200 (all trade names) manufactured by Kao Corporation. And two or more water-soluble polymer carboxylic acids may be combined.

In the present invention, the anionic polymer dispersant is at least one selected from a formalin condensate of a sulfonated aromatic compound containing a polynuclear aromatic compound and a polycarboxylic acid derivative from the viewpoint of stability over time at high temperature storage. Preferably, it is at least one selected from a naphthalenesulfonic acid formalin condensate and a polycarboxylic acid derivative.
By using these specific anionic polymer surfactants, the rub resistance and ejection stability are improved when a water-based ink for inkjet recording is constituted.
Moreover, these can be used individually by 1 type or in combination of 2 or more types.

  In the present invention, the addition amount of the anionic polymer surfactant is preferably 0.01 to 10% by mass, more preferably 0.1 to 1% by mass with respect to the carbon black. By setting the content ratio of the anionic polymer surfactant (anionic polymer surfactant / carbon black) to 0.01 to 10% by mass, better dispersion stability (particularly filterability) can be obtained. it can.

  In the method for producing a pigment dispersion of the present invention, from the viewpoint of dispersion stability, an anionic surfactant having a weight average molecular weight of 2,000 to 50,000 is 0.01 to 10% by mass with respect to carbon black. It is preferable to use an anionic surfactant selected from naphthalene sulfonic acid formalin condensate and polycarboxylic acid derivative and having a weight average molecular weight of 3,000 to 20,000 relative to carbon black of 0.1 to 1. It is more preferable to use mass%.

<Water-insoluble resin>
In the method for producing a pigment dispersion of the present invention, at least one water-insoluble resin is used. The water-insoluble resin used in the present invention is not particularly limited as long as it is a resin that dissolves in an organic solvent, covers at least part of carbon black, and can be dispersed in an aqueous medium. Examples thereof include nonionic polymer compounds, anionic polymer compounds, cationic polymer compounds, and amphoteric polymer compounds that are copolymers of monomers having an ethylenically unsaturated group.

The water-insoluble resin in the present invention can exist stably in an aqueous medium, eases the adhesion or deposition of aggregates, and facilitates the removal of the adhered aggregates. It is preferable that the resin is composed of a structural unit.
In the present invention, the water-insoluble resin preferably contains at least one structural unit represented by the following general formula (I) as the hydrophobic structural unit.

In the general formula (I), R ¹ represents a hydrogen atom or a methyl group, preferably a methyl group.

  Ar represents an unsubstituted or substituted aromatic ring. Examples of the substituent when the aromatic ring is substituted include a halogen atom, an alkyl group, an alkoxy group, a hydroxyl group, and a cyano group, and may form a condensed ring. In the case where a condensed ring is formed, for example, a condensed aromatic ring having 8 or more carbon atoms, an aromatic ring in which a hetero ring is condensed, or an aromatic ring in which two or more are connected are exemplified.

The “condensed aromatic ring having 8 or more carbon atoms” includes an aromatic ring in which at least two benzene rings are condensed, at least one aromatic ring and a condensed alicyclic hydrocarbon ring. Is an aromatic compound having 8 or more carbon atoms. Specific examples include naphthalene, anthracene, fluorene, phenanthrene, acenaphthene and the like.
The “aromatic ring condensed with a heterocycle” is a compound in which an aromatic compound containing no hetero atom (preferably a benzene ring) and a cyclic compound having a hetero atom are condensed. Here, the cyclic compound having a hetero atom is preferably a 5-membered ring or a 6-membered ring. As a hetero atom, a nitrogen atom, an oxygen atom, or a sulfur atom is preferable. The cyclic compound having a hetero atom may have a plurality of hetero atoms. In this case, the heteroatoms may be the same or different from each other. Specific examples of the aromatic ring condensed with a heterocycle include phthalimide, acridone, carbazole, benzoxazole, and benzothiazole.

The aromatic ring represented by Ar is bonded to the main chain of the water-insoluble resin through the ester group and the ethylene oxide chain, and the aromatic ring is not directly bonded to the main chain. An appropriate distance is maintained between the hydrophilic structural units. Therefore, the water-insoluble resin is likely to interact with the pigment, and is strongly adsorbed on the pigment to enhance dispersibility.
Among these, as Ar, an unsubstituted benzene ring and an unsubstituted naphthalene ring are preferable, and an unsubstituted benzene ring is particularly preferable.

  n represents the number of repetitions obtained by averaging the ethyleneoxy chains in the water-insoluble resin. The range of n is 1-6, preferably 1-2.

  Specific examples of the monomer forming the structural unit represented by the general formula (I) include the following monomers including phenoxyethyl (meth) acrylate. In addition, this invention is not limited to these.

Of the structural units represented by the general formula (I), when R ¹ is a methyl group, Ar is an unsubstituted benzene ring, and n is 1 to 2 in terms of dispersion stability Is particularly preferred.

  The content ratio of the structural unit represented by the general formula (I) in the water-insoluble resin is preferably in the range of 30 to 70% by mass, more preferably 40 to 50% by mass with respect to the total mass of the water-insoluble resin. Range. When the content is 30% by mass or more, the dispersibility is excellent. When the content is 70% by mass or less, the adhesion / deposition of the aggregates is suppressed, and the attached aggregates are easily removed (maintenance). The occurrence of image failure can be suppressed.

The water-insoluble resin may further contain at least one hydrophobic structural unit other than the hydrophobic structural unit represented by the general formula (I).
As other hydrophobic structural units, for example, they do not belong to hydrophilic structural units (for example, have no hydrophilic functional group), for example, (meth) acrylates, (meth) acrylamides, styrenes, vinyl esters, etc. And a structural unit derived from vinyl monomers and the like, as well as a hydrophobic structural unit having an aromatic ring via a linking group at the atom forming the main chain. These structural units can be used individually by 1 type or in mixture of 2 or more types.

Examples of the (meth) acrylates include methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, isobutyl (meth) acrylate, hexyl (meth) acrylate, and the like. ) Acrylate, ethyl (meth) acrylate, and butyl (meth) acrylate are preferable, and methyl (meth) acrylate and ethyl (meth) acrylate are particularly preferable.
Examples of the (meth) acrylamides include N-cyclohexyl (meth) acrylamide, N- (2-methoxyethyl) (meth) acrylamide, N, N-diallyl (meth) acrylamide, N-allyl (meth) acrylamide, and the like. (Meth) acrylamides.
Examples of the styrenes include styrene, methyl styrene, dimethyl styrene, trimethyl styrene, ethyl styrene, isopropyl styrene, n-butyl styrene, tert-butyl styrene, methoxy styrene, butoxy styrene, acetoxy styrene, chlorostyrene, dichlorostyrene, Examples thereof include bromostyrene, chloromethylstyrene, hydroxystyrene protected with a group that can be deprotected by an acidic substance (for example, t-Boc), methyl vinylbenzoate, α-methylstyrene, vinylnaphthalene, and the like. Styrene and α-methylstyrene are preferred.
Examples of the vinyl esters include vinyl esters such as vinyl acetate, vinyl chloroacetate, vinyl propionate, vinyl butyrate, vinyl methoxyacetate, and vinyl benzoate. Of these, vinyl acetate is preferable.

  In the “hydrophobic structural unit having an aromatic ring via a linking group on an atom constituting the main chain”, the aromatic ring is bonded to the atom constituting the main chain of the water-insoluble resin via the linking group, and the main chain of the water-insoluble resin is obtained. Since a suitable distance is maintained between the hydrophobic aromatic ring and the hydrophilic structural unit, the water-insoluble resin and the pigment are likely to interact with each other. Adsorbs firmly and dispersibility is further improved.

  The “hydrophobic structural unit having an aromatic ring via a linking group on the atom constituting the main chain” is a structural unit represented by the following general formula (II) (the structural unit represented by the general formula (I) Except).

In the general formula (II), R ¹ represents a hydrogen atom, a methyl group, or a halogen atom.
L ¹ represents ^* —COO—, ^* —OCO—, ^* —CONR ² —, ^* —O—, or a substituted or unsubstituted phenylene group, and R ² represents a hydrogen atom having 1 to 10 carbon atoms. Represents an alkyl group. Incidentally, symbol * in the group represented by L ¹ represents a connecting point with the main chain. The substituent when the phenylene group is substituted is not particularly limited, and examples thereof include a halogen atom, an alkyl group, an alkoxy group, a hydroxyl group, and a cyano group.

L ² represents a single bond or a divalent linking group having 1 to 30 carbon atoms, and when it is a divalent linking group, it is preferably a linking group having 1 to 25 carbon atoms, more preferably a carbon number. It is a 1-20 linking group, More preferably, it is a C1-C15 linking group.
Among them, particularly preferably, an alkyleneoxy group having 1 to 25 carbon atoms (more preferably 1 to 10), an imino group (—NH—), a sulfamoyl group, and 1 to 20 carbon atoms (more preferably 1 to 15). A divalent linking group containing an alkylene group, such as an alkylene group or an ethylene oxide group [— (CH 2 CH 2 O) _n —, n = 1 to 6], and a group obtained by combining two or more of these.

In the general formula (II), Ar ¹ represents a monovalent group derived from an aromatic ring.
The aromatic ring represented by Ar ¹ is not particularly limited, and examples thereof include a benzene ring, a condensed aromatic ring having 8 or more carbon atoms, an aromatic ring condensed with a heterocycle, or a benzene ring in which two or more are connected. . Details of the condensed aromatic ring having 8 or more carbon atoms and the aromatic ring condensed with the hetero ring are as described above.

  Hereinafter, specific examples of monomers capable of forming a hydrophobic structural unit having an aromatic ring via a linking group at the atom forming the main chain will be given. However, the present invention is not limited to the following specific examples.

  The hydrophilic structural unit in the water-insoluble resin is not particularly limited as long as it is a structural unit derived from a monomer containing a hydrophilic group. The hydrophilic group may be any of anionic, cationic and nonionic. In the present invention, from the viewpoint of dispersibility, the hydrophilic structural unit preferably includes at least one structural unit including an anionic hydrophilic group, and includes a structural unit derived from at least one of acrylic acid and methacrylic acid. It is preferable.

The water-insoluble resin in the present invention preferably contains a structural unit derived from at least one of acrylic acid and methacrylic acid, but may contain other hydrophilic structural unit. Examples of other hydrophilic structural units include structural units derived from monomers having a nonionic hydrophilic group or a cationic hydrophilic group.
Examples of the nonionic or cationic “hydrophilic functional group” include a hydroxyl group, an amino group, an amide group (the nitrogen atom is unsubstituted), and alkylene oxides such as polyethylene oxide and polypropylene oxide described later.

  Examples of the monomer having a nonionic or cationic hydrophilic group include (meth) acrylates, (meth) acrylamides, and vinyl esters having a nonionic or cationic hydrophilic functional group. Mention may be made of structural units derived from vinyl monomers.

  Monomers that form a hydrophilic structural unit having a nonionic or cationic hydrophilic group include a functional group capable of forming a polymer such as an ethylenically unsaturated bond and a nonionic or cationic hydrophilic function. If it has a group, there will be no restriction | limiting in particular, It can select from a well-known monomer. Specific examples include hydroxyethyl (meth) acrylate, hydroxybutyl (meth) acrylate, (meth) acrylamide, aminoethyl acrylate, aminopropyl acrylate, and (meth) acrylate containing an alkylene oxide polymer. Can do.

  The hydrophilic structural unit having a nonionic or cationic hydrophilic group can be formed by polymerization of a corresponding monomer, but a hydrophilic functional group may be introduced into the polymer chain after polymerization.

  The hydrophilic structural unit having a nonionic hydrophilic group is more preferably a hydrophilic structural unit having an alkylene oxide structure. The alkylene moiety of the alkylene oxide structure is preferably an alkylene moiety having 1 to 6 carbon atoms, more preferably an alkylene moiety having 2 to 6 carbon atoms, and particularly preferably an alkylene moiety having 2 to 4 carbon atoms from the viewpoint of hydrophilicity. Moreover, as a polymerization degree of an alkylene oxide structure, 1-120 are preferable, 1-60 are more preferable, and 1-30 are especially preferable.

  Moreover, it is also a preferable aspect that the hydrophilic structural unit having a nonionic hydrophilic group is a hydrophilic structural unit containing a hydroxyl group. The number of hydroxyl groups in the structural unit is not particularly limited, and is preferably 1 to 4, more preferably 1 to 3, from the viewpoint of hydrophilicity of the water-insoluble resin and compatibility with the solvent and other monomers during polymerization. 1-2 is particularly preferred.

The content ratio of the hydrophilic structural unit in the water-insoluble resin in the present invention differs depending on the ratio of the hydrophobic structural unit. For example, when the water-insoluble resin is composed only of acrylic acid and / or methacrylic acid [hydrophilic structural unit] and a hydrophobic structural unit, the content ratio of acrylic acid and / or methacrylic acid is “100- (hydrophobic (Mass% of structural unit) ”.
A hydrophilic structural unit can be used individually by 1 type or in mixture of 2 or more types.

As the water-insoluble resin in the present invention, the composition of the hydrophilic structural unit and the hydrophobic structural unit (including the structural unit represented by the general formula (I)) also affects the degree of hydrophilicity and hydrophobicity of each. However, the ratio of the hydrophilic structural unit is preferably 15% by mass or less. At this time, the proportion of the hydrophobic structural unit is preferably more than 80% by mass and more preferably 85% by mass or more with respect to the total mass of the water-insoluble resin.
When the content of the hydrophilic structural unit is 15% by mass or less, the amount of the component dissolved alone in the aqueous medium is suppressed, and various properties such as pigment dispersion are improved. Is obtained.

  A preferable content ratio of the hydrophilic structural unit is in the range of more than 0% by mass and 15% by mass or less, more preferably in the range of 2 to 15% by mass, and still more preferably, with respect to the total mass of the water-insoluble resin. It is in the range of 5 to 15% by mass, particularly preferably in the range of 8 to 12% by mass.

  The content of the aromatic ring contained in the water-insoluble resin is preferably 27% by mass or less, more preferably 25% by mass or less, and more preferably 20% by mass or less with respect to the total mass of the water-insoluble resin. More preferably it is. Especially, it is preferable that it is 15-20 mass%, and the range of 17-20 mass% is more preferable. When the content ratio of the aromatic ring is within the above range, the scratch resistance is improved.

The acid value of the water-insoluble resin in the present invention is preferably from 30 mgKOH / g to 100 mgKOH / g and more preferably from 30 mgKOH / g to 85 mgKOH / g from the viewpoint of pigment dispersibility and storage stability. It is preferably 50 mgKOH / g or more and 85 mgKOH / g or less.
The acid value is defined by the mass (mg) of KOH required to completely neutralize 1 g of the water-insoluble resin, and is measured by the method described in JIS standards (JISK0070, 1992).

The molecular weight of the water-insoluble resin in the present invention is preferably 30,000 or more in terms of weight average molecular weight (Mw), more preferably 30,000 to 150,000, still more preferably 30,000 to 100,000, particularly preferably 30,000 to 80,000. When the molecular weight is 30,000 or more, the steric repulsion effect as a dispersant tends to be good, and the steric effect makes it easy to adsorb to the pigment.
Further, the number average molecular weight (Mn) is preferably in the range of 1,000 to 100,000, particularly preferably in the range of 3,000 to 50,000. When the number average molecular weight is within the above range, a function as a coating film in the pigment or a function as a coating film of the ink composition can be exhibited. The water-insoluble resin in the present invention is preferably used in the form of an alkali metal or organic amine salt.

  The molecular weight distribution (weight average molecular weight / number average molecular weight) of the water-insoluble resin in the present invention is preferably in the range of 1 to 6, and more preferably in the range of 1 to 4. When the molecular weight distribution is within the above range, the dispersion stability and ejection stability of the ink can be improved.

  The number average molecular weight and the weight average molecular weight are measured by gel permeation chromatography (GPC). GPC uses HLC-8020GPC (manufactured by Tosoh Corporation), TSKgel, Super Multipore HZ-H (manufactured by Tosoh Corporation, 4.6 mm ID × 15 cm) as columns, and THF (tetrahydrofuran) as an eluent. The molecular weight is obtained by conversion with polystyrene as a standard substance. The conditions are a sample concentration of 0.35 / min, a flow rate of 0.35 ml / min, a sample injection amount of 10 μl, a measurement temperature of 40 ° C., and an IR detector. In addition, the calibration curve is “standard sample TSK standard, polystyrene” manufactured by Tosoh Corporation: “F-40”, “F-20”, “F-4”, “F-1”, “A-5000”, It is prepared from 8 samples of “A-2500”, “A-1000”, “n-propylbenzene”.

The water-insoluble resin in the present invention can be synthesized by various polymerization methods such as solution polymerization, precipitation polymerization, suspension polymerization, precipitation polymerization, bulk polymerization, and emulsion polymerization. The polymerization reaction can be performed by a known operation such as a batch system, a semi-continuous system, or a continuous system. The polymerization initiation method includes a method using a radical initiator, a method of irradiating light or radiation, and the like. These polymerization methods and polymerization initiation methods are described in, for example, the revised version of Tsuruta Junji “Polymer Synthesis Method” (published by Nikkan Kogyo Shimbun, 1971), Takatsu Otsu and Masato Kinoshita, “Experimental Methods for Polymer Synthesis” , Published in 1972, pages 124-154.
Among the polymerization methods, a solution polymerization method using a radical initiator is particularly preferable. Solvents used in the solution polymerization method are, for example, ethyl acetate, butyl acetate, acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, tetrahydrofuran, dioxane, N, N-dimethylformamide, N, N-dimethylacetamide, benzene, toluene, acetonitrile And various organic solvents such as methylene chloride, chloroform, dichloroethane, methanol, ethanol, 1-propanol, 2-propanol, 1-butanol and the like. A solvent may be used individually by 1 type or in combination of 2 or more types. Moreover, you may use as a mixed solvent with water. The polymerization temperature needs to be set in relation to the molecular weight of the polymer to be produced, the type of initiator, etc., and is usually about 0 ° C. to 100 ° C., but the polymerization is preferably performed in the range of 50 to 100 ° C. . Although reaction pressure can be selected suitably, it is 1-100 kg / cm < ² > normally, and about 1-30 kg / cm < ² > is especially preferable. The reaction time is about 5 to 30 hours. The obtained resin may be subjected to purification such as reprecipitation.

  Hereinafter, preferred specific examples of the water-insoluble resin in the present invention will be shown. However, the present invention is not limited to the following. In addition, the numerical value of the lower right parenthesis of B-11-B-13 represents the mass%.

<Carbon black>
There are no particular limitations on the carbon black in the present invention, it is preferable that the BET specific surface area contains a large carbon black surface area of relatively particles surface of less than 180 m 2 / ^g or more 400m 2 / ^g. Carbon black having a specific surface area in the above range has a relatively small particle size, and when a pigment dispersion produced by the production method of the present invention is applied to, for example, a water-based ink, a high print density is obtained. Furthermore, by being coated and contained with the water-insoluble resin in the present invention described above, a black ink having stable dispersibility and dispersion stability after dispersion can be maintained, and stable ink ejection properties can be obtained. .

The specific surface area of the carbon black, printing density, in terms of ink ejection property, 180 m ² / g or more 300m is more preferably in the range of less than ² / g, further 200 meters ² / g or more from the viewpoint of dispersibility 280 meters ² / g or less The range of is more preferable.

  The specific surface area in the present invention is a specific surface area determined by the BET method. The BET method is one of the powder surface area measurement methods by the vapor phase adsorption method, and is a method for obtaining the total surface area, that is, the specific surface area of a 1 g sample from the adsorption isotherm. Usually, nitrogen gas is often used as the adsorbed gas, and the most frequently used method is to measure the amount of adsorption from the change in pressure or volume of the gas to be adsorbed. The most prominent expression for representing the isotherm of multimolecular adsorption is the Brunauer Emmett Teller equation, called the BET equation, which is widely used for determining the surface area. The adsorption amount is obtained based on the BET equation, and the surface area is obtained by multiplying the area occupied by one adsorbed molecule on the surface.

  Examples of carbon black include those produced by known methods such as a contact method, a furnace method, and a thermal method.

  Specific examples of carbon black in the present invention include Raven7000, Raven5750, Raven5250, Raven5000 ULTRAII, Raven3500, Raven2000, Raven1500, Raven1250, Raven1200, Raven1190 ULTRAII, Raven10, Raven10, Raven10, Raven10. Manufactured), Regal 400R, Regal 330R, Regal 660R, Mogu L, Black Pearls L, Monarch 700, Monarch 800, Monarch 880, Monarch 900, Monarch 1000, Monarch 1100, Monarch 1300, Monarch 1400 (above, manufactured by Cabot Corporation), Color Black FW1, Color Black FW2, Color Black FW2V, Color Black 18, Color Black FW200, Color Black S150, Color Black S150, Color Black S150, Color Black SFW, Color Black FW200, Color Black FW2 V, Printex 140U, Printex 140V, Special Black 6, Special Black 5, Special Black 4A, Special Black 4, NIPEX 180-IQ, NIPEX 170-IQ (above, Evonik Dessa) 25, no. 33, no. 40, no. 45, no. 47, no. 52, no. 900, no. 2200B, no. 2300, no. 990, no. 980, no. 970, no. 960, no. 950, no. 850, MCF-88, MA600, MA7, MA8, MA100 (above, manufactured by Mitsubishi Chemical Corporation). However, it is not limited to these.

  Carbon black may be used alone or in combination of two or more.

  The ratio (cb: r) between the carbon black (cb) and the water-insoluble resin (r) in the present invention is preferably 100: 25 to 100: 140, more preferably 100: 25 to 100: 50 by weight. . The ratio (cb: r) tends to improve dispersion stability and abrasion resistance when the water-insoluble resin is 100: 25 or more, and the ratio (cb: r) is dispersed when the water-insoluble resin is 100: 140 or less. There is a tendency for stability to improve.

<Neutralizing agent>
The neutralizing agent is used so that a part or all of the dissociable groups are neutralized and the water-insoluble resin forms a stable emulsified or dispersed state in water.
Examples of the neutralizing agent include alcohol amines (eg, diethanolamine, triethanolamine, 2-amino-2-ethyl-1,3-propanediol), alkali metal hydroxides (eg, lithium hydroxide, hydroxide) Sodium, potassium hydroxide, etc.), ammonium hydroxide (eg, ammonium hydroxide, quaternary ammonium hydroxide), phosphonium hydroxide, alkali metal carbonate, etc. Preferably used.

<Organic solvent>
Preferable examples of the organic solvent used in the present invention include alcohol solvents, ketone solvents, and ether solvents. Examples of the alcohol solvent include isopropyl alcohol, n-butanol, t-butanol, ethanol and the like. Examples of the ketone solvent include acetone, methyl ethyl ketone, diethyl ketone, and methyl isobutyl ketone. Examples of the ether solvent include dibutyl ether and dioxane. Among these solvents, ketone solvents such as methyl ethyl ketone and alcohol solvents such as isopropyl alcohol are preferable, and methyl ethyl ketone is more preferable.

  The method for producing a pigment dispersion of the present invention comprises a step of mixing a water-insoluble resin, carbon black, a neutralizing agent, an organic solvent, an anionic polymer surfactant, and an aqueous medium to obtain an aqueous dispersion, A step of removing at least a part of the organic solvent from the dispersion liquid, and may include other steps as necessary.

The method for producing a pigment dispersion of the present invention is basically a method called a phase inversion emulsification method. The phase inversion emulsification method is a self-dispersion (phase inversion emulsification) method in which a mixed melt of a resin and a pigment having self-dispersibility or solubility is dispersed in water. The mixed melt may contain a curing agent or a polymer compound. Here, the mixed molten material refers to a mixed state that is not dissolved, a state that is dissolved and mixed, or a state that includes both of these states. The specific method by the “phase inversion emulsification method” can refer to the method described in JP-A-10-140065.
Generally, in the phase inversion emulsification method, since the resin acts as a dispersant, it is not necessary to use a dispersant other than the resin, but in the present invention, the dispersion stability can be increased by using an anionic polymer surfactant in combination. A pigment dispersion having excellent filterability can be obtained.

More specifically, the method for producing a pigment dispersion of the present invention includes, for example, (1) a water-insoluble resin having an anionic group or a solution obtained by dissolving it in an organic solvent and a basic compound (neutralizing agent). (2) a step of mixing and neutralizing the mixture, (2) a step of mixing the obtained mixture with a pigment to form a suspension, and then dispersing the pigment with a disperser or the like to obtain an aqueous dispersion; The method preferably includes a step of coating the pigment with a water-insoluble resin having an anionic group by removing the organic solvent by distillation, for example, and dispersing the pigment in an aqueous medium to obtain an aqueous dispersion.
More specifically, the descriptions in JP-A-11-209672 and JP-A-11-172180 can be referred to.

  The mixing method and the dispersion method are not particularly limited, and a commonly used mixing and stirring device or a dispersing device such as an ultrasonic dispersing device, a high-pressure homogenizer, a ball mill, a roll mill, a bead mill, or a high-speed stirring type dispersing device is used as necessary. be able to

Moreover, there is no restriction | limiting in particular in the process of removing at least one part of the organic solvent from the obtained aqueous dispersion, The method etc. which distill off an organic solvent by conventional methods, such as vacuum distillation, can be applied. At this time, in addition to at least a part of the organic solvent, a part of the water may be removed.
By removing the organic solvent and performing phase inversion to an aqueous system, a dispersion of resin-coated carbon black particles in which the surface of the carbon black particles is coated with a water-insoluble resin can be obtained. It is preferable that the organic solvent in the obtained dispersion is substantially removed. The amount of the organic solvent here is preferably 0.2% by mass or less, and more preferably 0.1% by mass or less.

[Water-based ink for inkjet recording]
The water-based ink for ink-jet recording of the present invention (hereinafter sometimes simply referred to as “water-based ink”) contains at least one of the pigment dispersions, and if necessary, a water-soluble organic solvent, a surfactant, and an antiseptic Other components such as an agent and an antifungal agent can be included.
With such a configuration, an aqueous ink for inkjet recording having excellent dispersion stability, filterability, and dischargeability can be obtained.

  The content of the pigment dispersion in the water-based ink for ink-jet recording of the present invention is 1 to 10 mass from the viewpoint of the dispersion stability of the water-based ink and the image recording density as the content of the carbon black coated with the water-insoluble resin. % Is preferable, 2 to 8% by mass is more preferable, and 2 to 6% by mass is particularly preferable.

<Water-soluble organic solvent>
The water-based ink for inkjet recording in the present invention preferably contains at least one water-soluble organic solvent. By containing the water-soluble organic solvent, the effect of preventing drying, wetting or promoting penetration can be obtained. Here, the drying prevention effect and the wetting effect mean an effect of preventing clogging due to the water-based ink adhering and drying at the ink ejection port of the nozzle. As the drying inhibitor and wetting agent, a water-soluble organic solvent having a vapor pressure lower than that of water is preferable.
Further, the penetration promoting effect means an effect of allowing water-based ink to penetrate into paper better.

The water-soluble organic solvent contained in the water-based ink for ink-jet recording in the present invention can be appropriately selected from known water-soluble organic solvents in consideration of the function as a drying inhibitor, a wetting agent or a penetration accelerator. .
Examples of water-soluble organic solvents include glycerin, 1,2,6-hexanetriol, trimethylolpropane, ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, pentaethylene glycol, dipropylene glycol, 2- Butene-1,4-diol, 2-ethyl-1,3-hexanediol, 2-methyl-2,4-pentanediol, 1,2-octanediol, 1,2-hexanediol, 1,2-pentanediol Alkanediols (polyhydric alcohols) such as 4-methyl-1,2-pentanediol; glucose, mannose, fructose, ribose, xylose, arabinose, galactose, aldonic acid, glucitol, maltose, cellobiose, lact Sugars such as sucrose, trehalose and maltotriose; sugar alcohols; hyaluronic acids; so-called solid wetting agents such as ureas; alkyl alcohols having 1 to 4 carbon atoms such as ethanol, methanol, butanol, propanol and 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 glycol mono-iso-propyl ether, diethylene glycol Mono-iso-propyl ether, ethylene glycol mono-n-butyl ether, Tylene glycol mono-t-butyl ether, diethylene glycol mono-t-butyl ether, 1-methyl-1-methoxybutanol, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol mono-t-butyl ether, propylene glycol mono-n-propyl Glycol ethers such as ether, propylene glycol mono-iso-propyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol mono-n-propyl ether, dipropylene glycol mono-iso-propyl ether; 2 -Pyrrolidone, N-methyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, formamide, aceto Toamide, dimethyl sulfoxide, sorbit, sorbitan, acetin, diacetin, triacetin, sulfolane and the like can be mentioned, and one or more of these can be used.

  For the purpose of drying inhibitors and wetting agents, polyhydric alcohols are useful, such as glycerin, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, 1,3-butanediol. 2,3-butanediol, 1,4-butanediol, 3-methyl-1,3-butanediol, 1,5-pentanediol, tetraethylene glycol, 1,6-hexanediol, 2-methyl-2, Examples include 4-pentanediol, polyethylene glycol, 1,2,4-butanetriol, 1,2,6-hexanetriol, and the like. These may be used individually by 1 type and may use 2 or more types together.

  For the purpose of the penetrant, a polyol compound is preferable, and examples of the aliphatic diol include 2-ethyl-2-methyl-1,3-propanediol, 3,3-dimethyl-1,2-butanediol, 2,2- Diethyl-1,3-propanediol, 2-methyl-2-propyl-1,3-propanediol, 2,4-dimethyl-2,4-pentanediol, 2,5-dimethyl-2,5-hexanediol, Examples include 5-hexene-1,2-diol and 2-ethyl-1,3-hexanediol. Among these, preferred examples include 2-ethyl-1,3-hexanediol and 2,2,4-trimethyl-1,3-pentanediol.

The said organic solvent can be used individually by 1 type or in mixture of 2 or more types.
As content in the aqueous ink of an organic solvent, 1-60 mass% is preferable, More preferably, it is 5-40 mass%.

  The water-based ink for ink jet recording in the present invention contains water, but the amount of water is not particularly limited. Especially, the preferable content of water is 10 to 99% by mass, more preferably 30 to 80% by mass, and still more preferably 50 to 70% by mass.

<Surfactant>
The aqueous ink for inkjet recording in the present invention preferably contains at least one surfactant. The surfactant is used as a surface tension adjusting agent, and examples thereof include nonionic surfactants, cationic surfactants, anionic surfactants, and betaine surfactants.
The surfactant preferably contains an amount capable of adjusting the surface tension of the water-based ink to 20 to 60 mN / m in order to eject droplets well by the ink jet method. Especially, content of surfactant is the quantity which can adjust surface tension to 20-45 mN / m, More preferably, it is quantity which can be adjusted to 25-40 mN / m.

  As the surfactant, a compound having a structure having both a hydrophilic part and a hydrophobic part in the molecule can be used effectively. Anionic surfactant, cationic surfactant, amphoteric surfactant, nonionic surfactant Any of the surfactants can be used.

  Specific examples of the anionic surfactant include, for example, sodium dodecylbenzenesulfonate, sodium lauryl sulfate, sodium alkyldiphenyl ether disulfonate, sodium alkylnaphthalenesulfonate, sodium dialkylsulfosuccinate, sodium stearate, potassium oleate, Sodium dioctylsulfosuccinate, sodium polyoxyethylene alkyl ether sulfate, sodium polyoxyethylene alkyl ether sulfate, sodium polyoxyethylene alkyl phenyl ether sulfate, sodium dialkylsulfosuccinate, sodium stearate, sodium oleate, t-octylphenoxy Examples include sodium ethoxypolyethoxyethyl sulfate, and one or more of these are selected. Rukoto can.

Examples of the cationic surfactant include tetraalkylammonium salts, alkylamine salts, benzalkonium salts, alkylpyridium salts, imidazolium salts, and the like. Specific examples thereof include dihydroxyethyl stearylamine and 2-heptadecenyl. -Hydroxyethyl imidazoline, lauryl dimethyl benzyl ammonium chloride, cetyl pyridinium chloride, stearamide methyl pyridium chloride and the like.
Amphoteric surfactants include lauryldimethylaminoacetic acid betaine, 2-alkyl-N-carboxymethyl-N-hydroxyethylimidazolinium betaine, coconut oil fatty acid amidopropyldimethylaminoacetic acid betaine, polyoctylpolyaminoethylglycine and other imidazoline derivatives. There is.

  Specific examples of the nonionic surfactant include acetylene glycol surfactants, acetylene alcohol surfactants, polyoxyethylene alkyl ethers, polyoxyethylene phenyl ethers, and the like. In the present invention, from the viewpoint of suppressing the foaming of the water-based ink, it is preferable to use a nonionic surfactant, and an acetylene glycol surfactant is more preferable.

  Examples of the acetylene glycol surfactant include 2,4,7,9-tetramethyl-5-decyne-4,7-diol, 3,6-dimethyl-4-octyne-3,6-diol, 3, Examples include 5-dimethyl-1-hexyn-3-ol, or a substance obtained by adding an average of 1 to 30 ethyleneoxy groups or propyleneoxy groups to each of a plurality of hydroxyl groups in each of these substances. Moreover, as an acetylene glycol type surfactant, a commercial item can also be used, for example, "Orphine E1010" and "Orphine STG" (above, Nissin Chemical Industry Co., Ltd. product) etc. are mentioned.

  Examples of polyoxyethylene alkyl ether and polyoxyethylene phenyl ether include polyoxyethylene lauryl ether, polyoxyethylene octyl phenyl ether, polyoxyethylene oleyl phenyl ether, polyoxyethylene nonyl phenyl ether, and oxyethylene / oxypropylene block. Examples thereof include copolymers, t-octylphenoxyethyl polyethoxyethanol, and nonylphenoxyethyl polyethoxyethanol.

In this invention, surfactant can be used individually by 1 type or in combination of 2 or more types.
The content of the surfactant in the water-based ink for inkjet recording is not particularly limited and is preferably 0.1% by mass or more, more preferably 0.1 to 2.0% by mass, and still more preferably. It is 0.5 to 1.5% by mass.
Among them, it is preferable that 0.1 to 2.0% by mass of an acetylene glycol surfactant as a surfactant is contained in the aqueous ink, and more preferably 0.5 to 1.5% by mass.

<Other ingredients>
In addition to the above components, the water-based ink for inkjet recording in the present invention, if necessary, for example, resin fine particles or polymer latex, ultraviolet absorber, anti-fading agent, anti-mold agent, anti-rust agent, antioxidant, emulsification You may contain other components, such as a stabilizer, antiseptic | preservative, an antifoamer, a viscosity modifier, a dispersion stabilizer, and a chelating agent.

Examples of the resin fine particles include acrylic resins, vinyl acetate resins, styrene-butadiene resins, vinyl chloride resins, acrylic-styrene resins, butadiene resins, styrene resins, crosslinked acrylic resins, and crosslinked styrene resins. , Benzoguanamine resin, phenol resin, silicone resin, epoxy resin, urethane resin, paraffin resin, fluorine resin, or polymer latex containing these.
Preferred examples include acrylic resins, acrylic-styrene resins, styrene resins, cross-linked acrylic resins, and cross-linked styrene resins.

The weight average molecular weight of the resin fine particles is preferably 10,000 or more and 200,000 or less, more preferably 100,000 or more and 200,000 or less.
The average particle size of the resin fine particles is preferably in the range of 10 nm to 1 μm, more preferably in the range of 10 to 200 nm, still more preferably in the range of 20 to 100 nm, and particularly preferably in the range of 20 to 50 nm.
The addition amount of the resin fine particles is preferably 0.5 to 20% by mass, more preferably 3 to 20% by mass, and further preferably 5 to 15% by mass with respect to the ink.
The glass transition temperature (Tg) of the resin fine particles is preferably 30 ° C. or higher, more preferably 40 ° C. or higher, and further preferably 50 ° C. or higher.
Moreover, there is no restriction | limiting in particular regarding the particle size distribution of a polymer particle, Any of what has a wide particle size distribution or a monodispersed particle size distribution may be sufficient. Further, two or more kinds of polymer fine particles having a monodispersed particle size distribution may be mixed and used.

  Examples of the ultraviolet absorber include benzophenone ultraviolet absorbers, benzotriazole ultraviolet absorbers, salicylate ultraviolet absorbers, cyanoacrylate ultraviolet absorbers, and nickel complex salt ultraviolet absorbers.

  As the anti-fading agent, various organic and metal complex anti-fading agents can be used. Organic anti-fading agents include hydroquinones, alkoxyphenols, dialkoxyphenols, phenols, anilines, amines, indanes, chromans, alkoxyanilines, heterocycles, etc. Complex, zinc complex and the like.

  Examples of the antioxidant include phenol-based antioxidants (including hindered phenol-based antioxidants), amine-based antioxidants, sulfur-based antioxidants, and phosphorus-based antioxidants.

  Examples of the antifungal agent include sodium dehydroacetate, sodium benzoate, sodium pyridinethione-1-oxide, ethyl p-hydroxybenzoate, 1,2-benzisothiazolin-3-one, sodium sorbate, sodium pentachlorophenol Etc. These are preferably used in the ink in an amount of 0.02 to 1.00% by mass.

  Examples of the preservative include benzisothiazolone as an active ingredient (for example, Proxel XL-2, Proxel BDN, Proxel BD20, Proxel GXL, Proxel LV, Proxel TN: Arch Chemicals Japan, Inc .; Denside BIT, Denside NIPA: Nagase Kasei Kogyo Co., Ltd.), octylisothiazolone as an active ingredient as alkylisothiazolone (for example, NS-800H, NS800G, NS-800P: Nagase Kasei Kogyo Co., Ltd.), chloroalkylisothiazolone as chloroalkylisothiazolone (For example, NS-500W, NS-80D, NS-CG, NS-TM, NS-RS: Nagase Kasei Kogyo Co., Ltd.), bromonitroalcohol as an active ingredient (For example, bronopol, Miaside BT, Miaside AS: Nagase Kasei Kogyo Co., Ltd.), chlorxylenol as an active ingredient (for example, PCMX: Nagase Kasei Kogyo Co., Ltd.), oxazolidine compounds, mixtures of these components, Those containing a modified product as an active ingredient (for example, NS-BP, Denisec BIT-20N, Denisec SPB, Saniset HP, Microstat S520, Saniset SK2, Deniside NS-100, Deniside BF-1, Deniside C3H, Saniset 161, Deniside CSA Denise CST, Denise C3, Denide OMP, Denide XR-6, Denise NM, Mordenize N760, Denisat P4, Denisat P-8, Denisat CHR: Nagase Chemical Industries, Ltd.) It can be mentioned. Among these, those having an oxazolidine-based compound as an active ingredient, those having chloroisomethylthiazolone as an active ingredient, and those having benzisothiazolone as an active ingredient have high effects and are preferable. In addition, these preservatives are not single components, but composite components using two or more types that are not very similar in structure are preferred in terms of suppression of resistant bacteria.

  Examples of the chelating agent (metal ion scavenger) include ethylenediaminetetraacetic acid sodium, nitrilotriacetic acid sodium, hydroxyethylethylenediaminesodium acetate, diethylenetriaminepentaacetic acid sodium, uramil sodium diacetate, and the like.

  Examples of the rust inhibitor include acidic sulfite, sodium thiosulfate, ammonium thiodiglycolate, diisopropylammonium nitrite, pentaerythritol tetranitrate, dicyclohexylammonium nitrite, and benzotriazole. Of these, dicyclohexylammonium nitrite and benzotriazole are effective. These rust preventives are for preventing the metal head from rusting, and are effective for a rusted plated surface.

  Moreover, the addition amount (A) of the preservative is 0.01% by mass to 0.1% by mass, and the addition amount (B) of the metal ion scavenger is 0.01% by mass to 0.5% by mass. The addition amount (C) of the rust preventive agent is preferably 0.01% by mass to 0.2% by mass, and A + B + C is preferably 0.03% by mass to 0.8% by mass.

By making the addition amount (A) of the preservative 0.01% by mass or more, the antiseptic effect of the ink can be sufficiently obtained. By setting it to 0.1% by mass or less, the stability of long-term storage of the ink becomes better.
Furthermore, by making the addition amount (C) of the rust inhibitor 0.01% by mass or more, when the ink jet recording apparatus is used over a long period of time, the occurrence of rusting in the metal portion of the head, particularly in the vicinity of the nozzle tip, is further increased. It can be effectively suppressed. Moreover, by setting it as 0.2 mass% or less, the stability of the colorant in an ink becomes more favorable and long-term storage property improves more.
Further, by setting the addition amount (B) of the metal ion scavenger to 0.01% by mass or more, the ink cartridge having the urethane foam that may contain a trace amount of metal ions in the ink chamber is used in the aqueous solution of the present invention. When the ink is filled and used, the generation of foreign matters can be effectively suppressed. Moreover, by setting it as 0.5 mass% or less, the stability of the coloring agent in an ink becomes more favorable, and long-term storage property improves more.

~ Physical properties of water-based ink for inkjet recording ~
The surface tension (25 ° C.) of the aqueous inkjet recording ink in the present invention 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 40 mN / m or less.
The surface tension is measured using an automatic surface tensiometer CBVP-Z (manufactured by Kyowa Interface Science Co., Ltd.) and a water-based ink at 25 ° C.

Further, the viscosity at 20 ° C. of the aqueous inkjet recording ink of the present invention is preferably 1.2 mPa · s or more and 15.0 mPa · s or less, more preferably 2 mPa · s or more and less than 13 mPa · s, More preferably, it is 2.5 mPa · s or more and less than 10 mPa · s.
The viscosity is measured using a VISCOMETER TV-22 (manufactured by TOKI SANGYO CO. LTD) under the condition of 20 ° C. of a water-based ink.

  The water-based ink for inkjet recording in the present invention can be used for forming a multicolor image (for example, a full color image). For the formation of a full-color image, a magenta ink composition, a cyan ink composition, and a yellow ink composition, and red (R), green (G), blue (B), and white (W) It can be used together with a color tone ink composition, a so-called special color ink composition in the printing field, and the like.

[Method for producing water-based ink for inkjet recording]
The method for producing a water-based ink for inkjet recording of the present invention comprises a step of mixing a water-insoluble resin, carbon black, a neutralizing agent, an organic solvent, an anionic polymer surfactant, and an aqueous medium to obtain an aqueous dispersion, A step of obtaining a pigment dispersion by removing at least a part of the organic solvent from the aqueous dispersion, and a step of preparing a water-based ink for inkjet recording using the pigment dispersion. It can comprise and comprise a process.

The step of obtaining the aqueous dispersion and the step of obtaining the pigment dispersion are the same as the respective steps in the method for producing the pigment dispersion.
In the present invention, the pigment dispersion obtained as described above is mixed with a water-soluble organic solvent selected as necessary, a surfactant, and other components such as a preservative and a fungicide. By doing so, a water-based ink for inkjet recording can be produced.
With such a configuration, it is possible to efficiently produce a water-based ink for inkjet recording that is excellent in stability, filterability, and dischargeability.

~ Recording form ~
The water-based ink for ink-jet recording of the present invention can be used in a recording form (first recording form) in which an image is recorded on a desired recording medium by ejecting the ink-jet method according to image information to be recorded.
In addition to this first recording form, the aqueous ink of the present invention is used together with an aqueous liquid composition (aggregated liquid) containing a component that aggregates particles such as pigments such as carbon black in the aqueous ink when mixed with the aqueous ink. Also, it can be used in a recording form (second recording form) in which an image is recorded by bringing an aqueous ink and an aqueous liquid composition into contact.

~ Aqueous liquid composition ~
Hereinafter, the aqueous liquid composition used in the second recording form will be described.
The aqueous liquid composition comprises at least an aggregating component that aggregates the pigment in the aqueous ink when mixed with the above-described aqueous ink, and can be constituted using other components as necessary.

-Aggregation component-
The aqueous liquid composition contains at least one aggregation component that aggregates particles such as pigments such as carbon black in the aqueous ink. By mixing the water-based ink ejected by the inkjet method and the water-based liquid composition, aggregation of pigments and the like stably dispersed in the water-based ink is promoted.

Examples of the aqueous liquid composition include a liquid composition capable of generating an aggregate by changing the pH of the aqueous ink. At this time, the pH (25 ° C.) of the aqueous liquid composition is preferably 6 or less, more preferably 4 or less. Especially, pH (25 degreeC) has the preferable range of 1-4, Especially preferably, pH is 1-3. In this case, the pH (25 ° C.) of the water-based ink is preferably 7.5 or more (more preferably 8 or more).
Among these, in the present invention, from the viewpoint of image density, resolution, and speedup of ink jet recording, the pH (25 ° C.) of the aqueous ink is 7.5 or more, and the pH (25 ° C.) of the aqueous liquid composition. Is preferably 4 or less.

Examples of the aggregating component for aggregating particles such as carbon black pigments include polyvalent metal salts, organic acids, polyallylamine and derivatives thereof.
Examples of the polyvalent metal salt include alkaline earth metals belonging to Group 2 of the periodic table (eg, magnesium, calcium), transition metals belonging to Group 3 of the periodic table (eg, lanthanum), and Group 13 of the periodic table. Mention may be made of salts of cations (for example, aluminum) and lanthanides (for example, neodymium). As these metal salts, carboxylate (formic acid, acetic acid, benzoate, etc.), nitrate, chloride, and thiocyanate are suitable. Among them, preferred are calcium salts or magnesium salts of carboxylic acids (formic acid, acetic acid, benzoates, etc.), calcium salts or magnesium salts of nitric acid, calcium chloride, magnesium chloride, and calcium salts or magnesium salts of thiocyanic acid.

  Examples of the organic acid include polyacrylic acid, acetic acid, glycolic acid, malonic acid, malic acid, maleic acid, ascorbic acid, succinic acid, glutaric acid, fumaric acid, citric acid, tartaric acid, lactic acid, sulfonic acid, and orthophosphoric acid. , Pyrrolidone carboxylic acid, pyrone carboxylic acid, pyrrole carboxylic acid, furan carboxylic acid, pyridine carboxylic acid, coumaric acid, thiophene carboxylic acid, nicotinic acid, derivatives of these compounds, or salts thereof are preferably selected. be able to.

The aggregating components can be used alone or in combination of two or more.
As content in the aqueous liquid composition of the aggregation component which aggregates a pigment etc., 1-20 mass% is preferable, More preferably, it is 5-20 mass%, More preferably, it is the range of 10-20 mass%. .

-Image recording method-
The water-based ink for ink jet recording of the present invention can be used for both the first recording form and the second recording form.
In the first recording form, recording is performed on a desired recording medium by providing an ink application step of applying the above-described black-colored aqueous ink of the present invention by the inkjet method.
In the second recording mode, an ink application step of applying the black-colored aqueous ink of the present invention on the desired recording medium by the inkjet method, and carbon black in the aqueous ink on the recording medium and In some cases, an aggregating component applying step for applying an aqueous liquid composition containing a component for aggregating particles such as other pigments is provided, and the aqueous ink and the aqueous liquid composition are contacted to form an image.

  In both the first recording form and the second recording form, the water-based ink is constituted by using the pigment dispersion produced by the method for producing a pigment dispersion of the present invention as a colorant, thereby achieving good dispersion stability. In addition, a black image with high density can be obtained, and the adhesion or accumulation of aggregates on the head nozzle part is alleviated and the adhered aggregates can be easily removed. Defects are suppressed, image failures such as white spots are prevented, and high-resolution images can be obtained. Further, the maintenance frequency on the discharge device side can be reduced and the maintainability can be improved.

  In the ink application step, the aqueous ink is applied by an ink jet method. Specifically, by supplying energy, a desired recording medium, that is, plain paper, resin-coated paper, for example, JP-A-8-169172, JP-A-8-27693, JP-A-2-276670, JP-A-7-276789, JP-A-9-323475, JP-A-62-238783, JP-A-10-153899, JP-A-10-217473, JP-A-10-235995, and JP-A-10-337947. Ink jet paper, film, electrophotographic co-paper, cloth, glass, metal, ceramics, etc. described in JP-A-10-217597, JP-A-10-337947, etc., discharge water-based ink to form a colored image. As a preferable ink jet recording method for the present invention, the method described in paragraph Nos. 0093 to 0105 of JP-A No. 2003-306623 can be applied.

The inkjet method is not particularly limited, and is a known method, for example, a charge control method that ejects ink using electrostatic attraction, a drop-on-demand method (pressure pulse method) that uses vibration pressure of a piezoelectric element, Either an acoustic ink jet method that converts an electrical signal into an acoustic beam, irradiates the ink and ejects the ink by using radiation pressure, or a thermal ink jet method that heats the ink to form bubbles and uses the generated pressure. There may be. As an ink jet method, in particular, the method described in Japanese Patent Application Laid-Open No. Sho 54-59936 causes an abrupt volume change of the ink subjected to the action of thermal energy, and the ink is ejected from the nozzle by the action force due to this state change. Ink jet method can be used effectively.
The ink jet method includes a method of ejecting many low-density inks called photo inks in a small volume, a method of improving image quality using a plurality of inks having substantially the same hue and different concentrations, and colorless and transparent inks. The method using is included.

Further, the ink jet head used in the ink jet method may be an on-demand method or a continuous method. In addition, as a discharge method, an electro-mechanical conversion method (for example, a single cavity type, a double cavity type, a bender type, a piston type, a shear mode type, a shared wall type, etc.), an electro-thermal conversion method (for example, a thermal type) Specific examples include an ink jet type, an electrostatic suction method (for example, an electric field control type, a slit jet type, etc.), and a discharge method (for example, a spark jet type). You may use.
There are no particular restrictions on the ink nozzles used when recording by the ink jet method, and they can be appropriately selected according to the purpose.

  In the second recording form aggregation component application step, the aqueous liquid composition is applied onto the recording medium before or after application of the aqueous ink. The application of the aqueous liquid composition can be performed by applying a known method such as a coating method, an ink jet method, or an immersion method. As a coating method, a known coating method using a bar coater, an extrusion die coater, an air doctor coater, a bread coater, a rod coater, a knife coater, a squeeze coater, a reverse roll coater, a bar coater or the like can be used. The details of the inkjet method are as described above.

In the 2nd recording form, the aspect which provides an ink provision process after providing an aqueous liquid composition at an aggregation component provision process is preferable. That is, an aqueous liquid composition for aggregating pigments and the like in the aqueous ink is applied in advance to the recording medium before applying the aqueous ink, and the aqueous liquid composition applied on the recording medium. A mode in which an image is formed by applying water-based ink so as to come into contact with is preferable. Thereby, inkjet recording can be speeded up, and an image with high density and resolution can be obtained even at high speed recording.
Furthermore, it is preferable that the aggregation component application step includes a step of removing at least a part of the solvent of the aqueous liquid composition applied on the recording medium.

During image recording, a polymer latex compound may be used in combination for the purpose of imparting glossiness or water resistance or improving weather resistance. The timing for applying the latex compound may be before or after applying the water-based ink, or may be applied simultaneously. Accordingly, the latex compound may be used in a form applied to a recording medium, may be used in a form added to a water-based ink, or may be used in a form in which a polymer latex is used as another liquid material.
Specifically, Japanese Patent Application Laid-Open No. 2002-166638 (Japanese Patent Application No. 2000-363090), Japanese Patent Application Laid-Open No. 2002-121440 (Japanese Patent Application No. 2000-315231), Japanese Patent Application Laid-Open No. 2002-154201 (Japanese Patent Application No. 2000-354380), The methods described in JP-A No. 2002-144696 (Japanese Patent Application No. 2000-343944) and JP-A No. 2002-080759 (Japanese Patent Application No. 2000-268952) can be preferably used.

  In addition, when recording an image, in addition to the ink application process and the aggregation component application process, another process may be provided. There are no particular limitations on the other steps, for example, a dry removal step for drying and removing the organic solvent in the aqueous ink applied to the recording medium, and heating for melting and fixing the resin fine particles or polymer latex contained in the aqueous ink. The fixing process can be selected as appropriate according to the purpose.

Further, as another example of the image recording method, an intermediate transfer member is used as a recording medium on which an image is first formed. After an image is recorded on the intermediate transfer member, the image on the intermediate transfer member is placed on a desired recording medium. There is a method of transferring.
For example, in the case of the second recording form, an intermediate transfer member is used as a recording medium on which an image is first formed, and the above-described aqueous ink of the present invention is applied onto the intermediate transfer member by an ink jet method, and an intermediate transfer An aggregating component applying step for applying an aqueous liquid composition containing a component for aggregating the pigment in the aqueous ink on the body, and contacting the aqueous ink with the aqueous liquid composition to form an image on the intermediate transfer member Then, a method of providing a transfer step of transferring the image formed on the intermediate transfer body to a desired final recording medium can be mentioned.
In this case as well, for example, other steps such as a drying removal step and a heat fixing step can be further provided, and the ink application step is provided after the aqueous liquid composition is applied in the aggregation component application step. Embodiments are preferred.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. Unless otherwise specified, “part” and “%” are based on mass.

  The weight average molecular weight was measured by gel permeation chromatography (GPC). GPC uses HLC-8020GPC (manufactured by Tosoh Corporation), TSKgel, Super Multipore HZ-H (manufactured by Tosoh Corporation, 4.6 mm ID × 15 cm) as columns, and THF (tetrahydrofuran) as an eluent. ) Was used. The conditions were as follows: the sample concentration was 0.35 / min, the flow rate was 0.35 ml / min, the sample injection amount was 10 μl, the measurement temperature was 40 ° C., and an IR detector was used. In addition, the calibration curve is “standard sample TSK standard, polystyrene” manufactured by Tosoh Corporation: “F-40”, “F-20”, “F-4”, “F-1”, “A-5000”, It produced from eight samples of "A-2500", "A-1000", and "n-propylbenzene".

(Synthesis Example 1)
-Synthesis of resin dispersant P-1 (water-insoluble resin)-
To a 1000 ml three-necked flask equipped with a stirrer and a condenser, 88 g of methyl ethyl ketone was added and heated to 72 ° C. under a nitrogen atmosphere. To this, 50 g of methyl ethyl ketone was added with 0.85 g of dimethyl-2,2′-azobisisobutyrate and phenoxy. A solution in which 70 g of ethyl methacrylate, 10 g of methacrylic acid and 20 g of methyl methacrylate were dissolved was dropped over 3 hours. After completion of the dropwise addition, the reaction was further continued for 1 hour, and then a solution prepared by dissolving 0.42 g of dimethyl-2,2′-azobisisobutyrate in 2 g of methyl ethyl ketone was added, heated to 78 ° C. and heated for 4 hours. The obtained reaction solution was reprecipitated twice in an excess amount of hexane, the precipitated resin was dried, and phenoxyethyl methacrylate / methyl methacrylate / methacrylic acid (copolymerization ratio [mass ratio] = 70/20/10) 96.5 g of a polymer (resin dispersant P-1, water-insoluble resin) was obtained.
The composition of the obtained resin dispersant P-1 was confirmed by ¹ H-NMR, and the weight average molecular weight (Mw) determined by GPC was 43500. Furthermore, when the acid value of this polymer was determined by the method described in JIS standard (JIS K 0070: 1992), it was 65.2 mgKOH / g.

~ Synthesis of resin dispersants P-2 and P-3 ~
In the synthesis of the resin dispersant P-1, 70 g of phenoxyethyl methacrylate, 10 g of methacrylic acid, and 20 g of methyl methacrylate were used as the corresponding monomer types and ratios as shown in Table 1 below, and the corresponding weight average molecular weight (Mw Resin dispersants P-2 and P-3, which are water-insoluble resins, were synthesized in substantially the same manner as the synthesis of the resin dispersant P-1, except that the conditions were changed so that

<Example 1>
-Preparation of dispersion C1 (pigment dispersion) of resin-coated carbon black particles-
The mixture was mixed with the following composition, and dispersed with a bead mill using 0.1 mmφ zirconia beads for 3 to 6 hours. Subsequently, the dispersion obtained was subjected to dispersion of resin-coated carbon black particles so that the carbon black concentration was 10.0% by removing methyl ethyl ketone at 55 ° C. under reduced pressure and further removing some water. The body was prepared.

(Composition of dispersion C1 of resin-coated carbon black particles)
Carbon black: 10.0 parts (NIPEX 180-IQ, manufactured by degussa, specific surface area by BET method: 260 m ² / g)
-Resin dispersant P-1 (water-insoluble resin)-4.5 parts-Methyl ethyl ketone (organic solvent)-30.5 parts-1 mol / l NaOH aqueous solution (neutralizing agent)-6.3 parts- 0.24 parts of Demol NL (anionic polymer surfactant, manufactured by Kao Corporation, 41% aqueous sodium salt solution of β-naphthalenesulfonic acid formalin condensate)
・ Ion exchange water: 98.46 parts

-Preparation of water-based ink for inkjet recording-
Next, a water-based ink was prepared with the following composition using the obtained dispersion of resin-coated carbon black particles. The pH of the water-based ink at 25 ° C. was 8.9.
<Composition of water-based ink C1>
Dispersion C1 of the resin-coated carbon black particles 40.0 parts Glycerin 15.0 parts Diethylene glycol monoethyl ether 10.0 parts Proxel XL-2 0.05 (Preservative, manufactured by Arch Chemicals Japan Co., Ltd.)
・ Benzotriazole: 0.05 part ・ Orphine E1010 (manufactured by Nissin Chemical Industry Co., Ltd.): 1.0 part ・ Ion-exchanged water: 33.9 parts

[Evaluation]
The dispersion and resin-coated carbon black particle dispersion and aqueous ink were measured and evaluated as follows. The results of measurement and evaluation are shown in Table 1 below.

(Measurement of particle diameter of resin-coated carbon black particles)
The obtained resin-coated carbon black particle dispersion (pigment dispersion) was measured for volume average particle size by a dynamic light scattering method using a nanotrack particle size distribution analyzer UPA-EX150 (manufactured by Nikkiso Co., Ltd.). . The measurement was performed by adding 10 ml of ion exchange water to 30 μl of the dispersion of resin-coated carbon black particles to prepare a sample solution for measurement, and adjusting the temperature to 25 ° C. The measurement results are shown in Table 1 below.

(Dispersion stability)
The obtained aqueous ink for inkjet recording using the obtained dispersion of resin-coated carbon black particles was stored in a thermostat at 60 ° C. for 7 days. Before and after storage, the particle size and viscosity were measured and evaluated according to the following evaluation criteria. The evaluation results are shown in Table 1.
The particle diameter was measured by measuring the volume average particle diameter of the pigment dispersion obtained by the dynamic light scattering method using a nanotrack particle size distribution analyzer UPA-EX150 (manufactured by Nikkiso Co., Ltd.). Measurement conditions: 10 cc of ion-exchanged water was added to 10 μl of water-based ink to prepare a measurement solution, and measurement was performed at 25 ° C. The viscosity was measured by using VISCOMETER TV-22 (manufactured by TOKI SANGYO CO. LTD) under the condition of aqueous ink at 25 ° C.

~Evaluation criteria~
A: Change in volume average particle size within 10 mm, cumulative 95% (d95) particle size change within 30 mm and viscosity change within 10% after 7 days at 60 ° C. A stable state was maintained.
B: A water-based ink satisfying the condition A could not be obtained.

(Abrasion resistance)
As an ink jet recording apparatus, an ink jet apparatus provided with a trial print head of 600 dpi and 256 nozzles was prepared. Aqueous ink obtained by further storing the aqueous ink for inkjet recording prepared using the obtained dispersion of resin-coated carbon black particles in a constant temperature bath at 60 ° C. for 14 days was loaded therein.
Press a separate blank FX-L paper with a load of 4.9 × 10 ⁴ N / m ² on the printed matter printed on FX-L paper (Fuji Xerox Co., Ltd.) with 100% coverage pattern. The ink transferred to the FX-L paper was subjected to visual sensory evaluation against a predetermined limit sample. The evaluation results are shown in Table 1.

~Evaluation criteria~
AA ... not transferred.
A: Slightly transferred.
B: Transferred to a level that does not pose a practical problem.
C: Transfer was conspicuous and there was a problem in practical use.

(Discharge stability)
During printing using the ink jet recording apparatus in the above-described evaluation of abrasion resistance, the flying curve of ink from the start of printing to the end of printing and the occurrence of mist were evaluated by observing the printed matter, and judged based on the following criteria.

~Evaluation criteria~
A: Ink was bent and mist was not generated.
B: The flying curve of ink and mist occurred, but the frequency was low enough to cause no practical problems.
C: Ink flight bending, mist frequently occurred, and there was a problem in practical use.

<Example 2>
In Example 1, water-based ink for ink jet recording was used in the same manner as in Example 1 except that the pigment dispersion was prepared using the resin dispersant P-2 instead of the resin dispersant P-1 (water-insoluble resin). Were prepared and evaluated.

<Example 3>
In Example 1, water-based ink for ink jet recording was used in the same manner as in Example 1 except that the pigment dispersion was prepared using the resin dispersant P-3 instead of the resin dispersant P-1 (water-insoluble resin). Were prepared and evaluated.

<Example 4>
In the preparation of resin-coated carbon black particle dispersion C1 (pigment dispersion) in Example 1, the composition of the resin-coated carbon black particle dispersion was changed as follows, and the same procedure as in Example 1 was carried out. A water-based ink for recording was prepared and evaluated.

(Composition of dispersion C4 of resin-coated carbon black particles)
・ Carbon black: 10.0 parts (NIPEX180-IQ, manufactured by Degussa)
-Resin dispersant P-1 (water-insoluble resin) ... 2.0 parts-Methyl ethyl ketone ... 24.0 parts-1 mol / l NaOH aqueous solution ... 2.8 parts-Demol NL ... 0.24 parts (Anionic polymer surfactant, manufactured by Kao Corporation, 41% aqueous solution of sodium salt of β-naphthalenesulfonic acid formalin condensate)
・ Ion-exchanged water ... 80.96 parts

<Example 5>
In the preparation of resin-coated carbon black particle dispersion C1 (pigment dispersion) in Example 1, the composition of the resin-coated carbon black particle dispersion was changed as follows, and the same procedure as in Example 1 was carried out. A water-based ink for recording was prepared and evaluated.

(Composition of dispersion C5 of resin-coated carbon black particles)
Carbon black: 10.0 parts (NIPEX180-IQ, manufactured by Degussa)
-Resin dispersant P-1 (water-insoluble resin)-6.0 parts-Methyl ethyl ketone-29.0 parts-1 mol / l NaOH aqueous solution-8.4 parts-Demoll NL-0.24 parts (Anionic polymer surfactant, manufactured by Kao Corporation, 41% aqueous solution of sodium salt of β-naphthalenesulfonic acid formalin condensate)
・ Ion-exchanged water: 96.36 parts

<Example 6>
In the preparation of resin-coated carbon black particle dispersion C1 (pigment dispersion) in Example 1, the composition of the resin-coated carbon black particle dispersion was changed as follows, and the same procedure as in Example 1 was carried out. A water-based ink for recording was prepared and evaluated.

(Composition of dispersion C6 of resin-coated carbon black particles)
・ Carbon black: 10.0 parts (NIPEX180-IQ, manufactured by Degussa)
-Resin dispersant P-1 (water-insoluble resin)-4.5 parts-Methyl ethyl ketone-30.5 parts-1 mol / l NaOH aqueous solution-6.3 parts-Demol NL-0.02 parts (Anionic polymer surfactant, manufactured by Kao Corporation, 41% aqueous solution of sodium salt of β-naphthalenesulfonic acid formalin condensate)
・ Ion-exchanged water: 98.68 parts

<Example 7>
An ink composition was prepared in the same manner as in Example 1 except that the composition of the resin-coated carbon black particle dispersion C1 in Example 1 was changed as follows. And evaluated.
<Composition of dispersion C7 of resin-coated carbon black particles>
Carbon black: 10.0 parts (NIPEX180-IQ, manufactured by Degussa)
-Resin dispersant P-1 (water-insoluble resin)-4.5 parts-Methyl ethyl ketone-30.5 parts-1 mol / l NaOH aqueous solution-6.3 parts-Demol NL-2.44 parts (Anionic polymer surfactant, manufactured by Kao Corporation, 41% aqueous solution of sodium salt of β-naphthalenesulfonic acid formalin condensate)
・ Ion-exchanged water: 96.26 parts

<Example 8>
An ink composition was prepared in the same manner as in Example 1 except that the composition of the resin-coated carbon black particle dispersion C1 in Example 1 was changed as follows. And evaluated.
<Composition of dispersion C8 of resin-coated carbon black particles>
Carbon black: 10.0 parts (NIPEX180-IQ, manufactured by Degussa)
Resin dispersant P-2 (water-insoluble resin) 4.5 parts Methyl ethyl ketone 30.5 parts 1 mol / l NaOH aqueous solution 6.9 parts DEMAL SS-L 0. 03 parts (anionic polymer surfactant, manufactured by Kao Corporation, 30% aqueous sodium salt solution of aromatic sulfonic acid formalin condensate)
・ Ion-exchanged water: 98.07 parts

<Example 9>
In the preparation of resin-coated carbon black particle dispersion C1 (pigment dispersion) in Example 1, the composition of the resin-coated carbon black particle dispersion was changed as follows, and the same procedure as in Example 1 was carried out. A water-based ink for recording was prepared and evaluated.

(Composition of dispersion C9 of resin-coated carbon black particles)
Carbon black: 10.0 parts (NIPEX180-IQ, manufactured by Degussa)
-Resin dispersant P-2 (water-insoluble resin)-4.5 parts-Methyl ethyl ketone-30.5 parts-1 mol / l NaOH aqueous solution-6.9 parts-Demol EP-0.04 parts (Anionic polymer surfactant, manufactured by Kao Corporation, 25% aqueous solution of polycarboxylic acid derivative)
・ Ion-exchanged water: 98.06 parts

<Example 10>
In the preparation of resin-coated carbon black particle dispersion C1 (pigment dispersion) in Example 1, the composition of the resin-coated carbon black particle dispersion was changed as follows, and the same procedure as in Example 1 was carried out. A water-based ink for recording was prepared and evaluated.

(Composition of dispersion C10 of resin-coated carbon black particles)
Carbon black: 10.0 parts (NIPEX180-IQ, manufactured by Degussa)
-Resin dispersant P-2 (water-insoluble resin)-4.5 parts-Methyl ethyl ketone-30.5 parts-1 mol / l NaOH aqueous solution-6.9 parts-Poise 520-0.03 parts (Anionic polymer surfactant, manufactured by Kao Corporation, polycarboxylic acid derivative 40% aqueous solution)
・ Ion-exchanged water: 98.07 parts

<Comparative Example 1>
A water-based ink for inkjet recording was prepared in the same manner as in Example 1 except that the composition of the dispersion C1 of resin-coated carbon black particles in Example 1 was changed as follows. Prepared and evaluated.

(Composition of dispersion H1 of resin-coated carbon black particles)
・ Carbon black: 10.0 parts (NIPEX180-IQ, manufactured by Degussa)
-Resin dispersant P-1 (water-insoluble resin)-4.5 parts-Methyl ethyl ketone-30.5 parts-1 mol / l NaOH aqueous solution-6.3 parts-Ion-exchanged water-98.7 Part

(Comparative Example 2)
In Comparative Example 1, an aqueous ink for inkjet recording was prepared in the same manner as in Comparative Example 1 except that the resin dispersant P-2 (water-insoluble resin) was used instead of the resin dispersant P-1 (water-insoluble resin). Prepared and evaluated.
(Comparative Example 3)
In Comparative Example 1, an aqueous ink for inkjet recording was prepared in the same manner as in Comparative Example 1 except that the resin dispersant P-3 (water-insoluble resin) was used instead of the resin dispersant P-1 (water-insoluble resin). Prepared and evaluated.

(Comparative Example 4)
In the preparation of the resin-coated carbon black particle dispersion C1 (pigment dispersion) of Example 1, the same procedure as in Example 1 was carried out except that a water-insoluble resin was not used and the following changes were made. Then, an aqueous ink for inkjet recording was prepared and evaluated.

-Preparation of carbon black particle dispersion H4 (pigment dispersion)-
The mixture was mixed with the following composition and dispersed with a bead mill using 0.1 mmφ zirconia beads for 3 to 6 hours to prepare a dispersion of carbon black particles so that the carbon black concentration was 10.0% by mass.

(Composition of carbon black particle dispersion H4)
Carbon black: 10.0 parts (NIPEX180-IQ, manufactured by Degussa)
・ Demol NL ... 2.44 parts (anionic polymer surfactant, manufactured by Kao Corporation, sodium naphthalenesulfonic acid formalin condensate 41% aqueous solution)
・ Ion-exchanged water: 87.56 parts

  From Table 1, it can be seen that the pigment dispersion produced by the method for producing a pigment dispersion of the present invention has good dispersion stability. Moreover, it turns out that the water-based ink for inkjet recording of this invention has favorable discharge stability.

Claims (9)

Mixing a water-insoluble resin, carbon black, a neutralizing agent, an organic solvent, an anionic polymer surfactant, and an aqueous medium to obtain an aqueous dispersion;
Removing at least a portion of the organic solvent from the aqueous dispersion;
A method for producing a pigment dispersion comprising: The said water-insoluble resin is a manufacturing method of the pigment dispersion of Claim 1 containing the structural unit represented by the following general formula (I).

[Wherein, R ¹ represents a hydrogen atom or a methyl group, and Ar represents an unsubstituted or substituted aromatic ring. n represents the average number of repetitions and is 1-6. ]   The method for producing a pigment dispersion according to claim 1 or 2, wherein Ar in the general formula (I) is an unsubstituted or substituted benzene ring. The water-insoluble resin includes a hydrophilic structural unit derived from (meth) acrylic acid and a hydrophobic structural unit represented by the general formula (I),
The aromatic ring content is 20% by mass or less of the total mass of the water-insoluble resin,
The manufacturing method of the pigment dispersion of any one of Claims 1-3 whose content rate of a total hydrophilic structural unit is 15 mass% or less of the total mass of water-insoluble resin.   The method for producing a pigment dispersion according to any one of claims 1 to 4, wherein the water-insoluble resin has an acid value of 30 mgKOH / g or more and 100 mgKOH / g or less.   The pigment dispersion according to any one of claims 1 to 5, wherein the aqueous dispersion has a content of the anionic polymer surfactant with respect to the carbon black of 0.01% by mass to 10% by mass. Body manufacturing method.   The said anionic polymer surfactant is at least 1 sort (s) chosen from a naphthalenesulfonic acid formalin condensate and a polycarboxylic acid derivative, The manufacture of the pigment dispersion of any one of Claims 1-6. Method. Mixing a water-insoluble resin, carbon black, a neutralizing agent, an organic solvent, an anionic polymer surfactant, and an aqueous medium to obtain an aqueous dispersion;
Removing at least a portion of the organic solvent from the aqueous dispersion to obtain a pigment dispersion;
A step of preparing a water-based ink for inkjet recording using the pigment dispersion;
A method for producing a water-based ink for ink-jet recording.   A water-based ink for ink-jet recording, comprising the pigment dispersion produced by the method for producing a pigment dispersion according to any one of claims 1 to 7.