JP2009079209A - Aqueous pigment dispersion, ink composition, and inkjet recording method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pigment dispersion type recording liquid which gives printed matter excellent in glossiness and good in printing quality and abrasion-resistance, and which has a satisfactory ejection property. <P>SOLUTION: An aqueous pigment dispersion contains an aqueous medium (a), a pigment (b) and a dispersant (c). The dispersant (c) contains a polymer (I) which is obtained by copolymerizing a hydrophobic monomer, an anionic monomer and an oxyalkylene chain-containing monomer represented by formula (1) and in which the weight ratio of the hydrophobic monomer unit to the oxyalkylene chain-containing monomer unit is 0.1-10 and the content of the anionic monomer unit is ≤10 wt.%. In the formula (1), R<SP>1</SP>represents a (meth)acryloyloxy group or the like; R<SP>2</SP>represents a 1-20C alkyl group or the like; h and j are each 1-5; i is 1-100; and k is 0-50. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an aqueous pigment dispersion using a polymer obtained by copolymerizing a hydrophobic group monomer, an anionic monomer and a specific oxyalkylene chain monomer as a dispersant. More specifically, the present invention relates to a pigment dispersion type recording liquid suitable as a recording liquid for an ink jet printer, an ink composition containing the aqueous pigment dispersion, and an ink jet recording method using the ink composition.

  Inkjet printers are rapidly becoming popular for both personal use and business use due to the ease of full color, low noise, high-resolution images at low cost, and high-speed printing. I am doing. At present, aqueous recording liquids are mainly used as recording liquids for ink jet printers, and printed materials with high resolution are being obtained.

  Conventionally, the aqueous recording liquid mainly contains a water-soluble dye and a liquid medium. However, the printed matter obtained with this aqueous recording liquid has insufficient water resistance, light resistance, ozone resistance and the like because the aqueous recording liquid contains a water-soluble dye. Therefore, in recent years, a pigment dispersion type aqueous recording liquid (hereinafter sometimes simply referred to as “ink”) in which a pigment is dispersed in an aqueous medium has been developed instead of such a dye.

  In recent years, with the improvement of the resolution of printed matter, the amount of ink discharged from the ink discharge nozzle has decreased significantly. And since the request | requirement with respect to the printing speed improvement of an inkjet printer is increasing, higher pigment dispersion stability and low viscosity have been calculated | required with respect to the pigment dispersion-type aqueous recording liquid. On the other hand, a method has been proposed in which various water-soluble polymers, water-dispersible polymers, and the like are used as pigment dispersants in pigment-dispersed aqueous recording liquids.

  As this water-soluble or water-dispersible polymer, for example, a polymer containing an oxyalkylene chain is generally known. With the aim of improving performance in inkjet applications, an oxyalkylene chain-containing monomer, a hydrophobic monomer, and a hydrophilic monomer are known. It has been proposed to use a copolymer obtained by copolymerizing a functional monomer as a polymer dispersant for a pigment.

  For example, in Patent Document 1, a polymer containing 3 to 25 mol% of a monomer structural unit specifically containing an oxyalkylene chain and 5 to 60 mol% of an α, β-ethylenically unsaturated carboxylic acid component was used. An aqueous pigment ink has been proposed, and is said to be effective in printing density on plain paper, ejection stability, and long-term storage stability.

  In Patent Document 2, a monomer mixture comprising specifically 5 to 70% by weight of a monomer having an ether structure, 10 to 45% by weight of a monomer having an acidic group, and 5 to 50% by weight of a monomer having affinity for a pigment. Ink jet printer inks using copolymers have been proposed, and are said to be effective in reducing the viscosity and redispersibility of dispersions.

  In Patent Document 3, a polyalkylene glycol mono (meth) acrylic acid ester monomer is 10 to 50% by weight, a (meth) acrylic acid monomer is 50 to 89% by weight, and a monomer copolymerizable with these is 1 to 50% by weight. A water-based pigment ink using a copolymer obtained by using the polymer or a polymer obtained by neutralizing the copolymer with an alkaline substance has been proposed, and is said to be effective for storage stability of the ink and prevention of clogging of the printer head. .

  Patent Document 4 proposes a recording liquid using a copolymer having an aromatic ring, a carboxylic acid group, and a carboxylic acid oxyalkylene ester group. The recording liquid has a pigment dispersibility, storage stability, water resistance and ejection. And effective in preventing clogging.

  In Patent Document 5, it is proposed that a recording liquid using a polymer containing an alkylene oxide portion, an aromatic ring portion, and a carboxyl portion has an effect in preventing kogation, ejection stability, and prevention of solidification of the head tip. .

In Patent Document 6, the pigment includes fine particles coated with a resin having a polyether structure with an acid value of 5 to 70 KOH mg / g, and the coating amount by the resin is 15 to 1,000 weights with respect to 100 parts by weight of the pigment. An aqueous dispersion characterized by being part thereof has been proposed as having an effect on dispersion stability and long-term storage stability.
JP-A-6-306317 JP 2003-238849 A Japanese Patent Laid-Open No. 10-60345 JP-A-8-3500 JP 2004-10733 A Japanese Patent Laid-Open No. 2003-238883

  In recent years, in inkjet printers, the demand for pigment inks in the large-format and high-end photo fields has increased due to the high robustness of the printed matter. There is an increasing demand for high gloss and high scratch resistance of printed matter on paper.

  However, according to the study by the present inventors, in the recording liquid prepared with the pigment dispersion using the dispersant exemplified in the above-mentioned patent document, the printed matter on the photographic paper has a low gloss value and a high haze value. However, a product satisfying a sufficient photographic high print quality could not be obtained. Among them, in the text of Patent Document 2, there is a description that the redispersibility deteriorates unless the monomer having an acidic group is 10% by weight or more. When the polymer was used in an amount of not less than%, the gloss of the printed matter tended to be remarkably lowered.

  In addition, Patent Document 6 describes that a resin containing a polyether structure having an acid value of 5 to 70 KOHmg / g is used as a dispersant, but the hydrophobic monomer structure constituting the polymer that the present inventors have paid attention to. There is no description about the weight ratio of the unit / oxyalkylene chain monomer structural unit, and there is no description of the preferred composition ratio of the hydrophobic monomer structural unit. Furthermore, as a result of examining the range of the weight ratio of the hydrophobic monomer structural unit / oxyalkylene chain monomer structural unit described in the Examples of Patent Document 6, the present inventors were unable to print.

  For this reason, it is possible to provide an aqueous pigment dispersion that can provide an ink jet recording liquid that is excellent not only in printing characteristics and storage stability but also in high gloss and high scratch resistance of printed matter on photographic paper. Development was desired.

  In order to solve such problems, the present inventors have intensively studied a pigment-dispersed aqueous recording liquid. As a result, the polymer dispersant used in the pigment-dispersed recording liquid is a copolymer of an oxyalkylene chain monomer, a hydrophobic monomer, and an anionic monomer, which is a hydrophobic monomer structural unit / oxyalkylene chain monomer structural unit. (Weight ratio) is in a specific range, and by using a limited range in which the ratio of anionic monomer structural units is limited, printed matter excellent in gloss and scratch resistance can be obtained. The headline and the present invention were completed.

（式（１）中、Ｒ^１はビニル基、アクリロイルオキシ基、アクリロイルアミノ基、メタクリロイルオキシ基、メタクリロイルアミノ基、アクリルアミノ基、スチリル基、ビニルエーテル基、ビニルシリル基、シアノビニル基、又は２−シアノアクリロイル基を表し、Ｒ^２は水素原子、炭素１〜２０のアルキル基又はアルキル基で置換されていても良いフェニル基を表し、ｈ、ｊはそれぞれ独立に１〜５の整数であり、ｉは１〜１００の整数であり、ｋは０〜５０の整数である。） That is, the gist of the present invention is that, in an aqueous pigment dispersion containing (a) an aqueous medium, (b) a pigment, and (c) a dispersant, the (c) dispersant contains at least one or more types of hydrophobic monomers. A polymer obtained by copolymerizing one or more types of anionic monomers and one or more types of oxyalkylene chain monomers represented by the following general formula (1), wherein the hydrophobic monomer structural unit constituting the polymer To oxyalkylene chain monomer structural unit (hydrophobic monomer structural unit / oxyalkylene chain monomer structural unit (weight ratio)) is 0.1 to 1.0, and anionic monomer structural unit is contained An aqueous pigment dispersion characterized in that it contains a polymer (I) whose amount is not more than 10% by weight of the total polymer.

(In the formula (1), R ¹ is vinyl group, acryloyloxy group, acryloylamino group, methacryloyloxy group, methacryloylamino group, acrylamino group, styryl group, vinyl ether group, vinylsilyl group, cyanovinyl group, or 2-cyanoacryloyl. R ² represents a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, or an optionally substituted phenyl group, h and j are each independently an integer of 1 to 5, and i is 1 (It is an integer of ~ 100, and k is an integer of 0-50.)

  Another gist of the present invention resides in an ink composition (Claim 7) containing the aqueous pigment dispersion.

  Still another subject matter of the present invention lies in an ink jet recording method (claim 8), wherein the ink composition droplets are ejected from an ink jet head, and the droplets are adhered to a recording medium.

According to the aqueous pigment dispersion of the present invention, it is possible to provide a pigment-dispersed recording liquid that has excellent gloss, good print quality, good printed matter, and good ejection properties, as well as good ejection properties.
In particular, the aqueous pigment dispersion of the present invention can be suitably used as a recording liquid for an inkjet printer or the like, and an ink composition containing the aqueous pigment dispersion of the present invention is used to perform high-quality and high-durability inkjet recording. You can get things.

Hereinafter, embodiments of the present invention will be described in detail. However, the description of the constituent elements described below is an example (representative example) of the embodiments of the present invention, and the present invention does not exceed the gist thereof. These contents are not specified.
In the following, “(meth) acrylate” means “acrylate and / or methacrylate”, and “(meth) acryl” means “acryl and / or methacryl”.

  Here, the “monomer structural unit” is a constituent unit of the basic structure of the polymer. In the case of a synthetic polymer, the basic structure of a polymer is a structure derived from a monomer molecule used for production of the polymer by polymerization or copolymerization, or a structure in which they are modified by modification. In the case of a natural polymer, it is a repeating structure or a structure modified by modification or the like.

  In the present invention, the monomer structural unit is not limited to a structural unit introduced into a polymer by synthesizing a polymer using the monomer (for example, “monomer x”), but is different from the monomer x (for example, “Monomer y”) is used to synthesize a polymer, and then the structural unit introduced by the monomer y is modified or modified to form the same structural unit as the structural unit introduced by the monomer x. Even in this case, the monomer structural unit is not called “monomer y structural unit”, but “monomer x structural unit”.

[Aqueous pigment dispersion]
The aqueous pigment dispersion of the present invention is an aqueous pigment dispersion containing (a) an aqueous medium, (b) a pigment, and (c) a dispersant, wherein (c) the dispersant is at least one or more types of hydrophobic monomers. And the one or more kinds of anionic monomers and one or more kinds of oxyalkylene chain monomers represented by the following general formula (1), the hydrophobic monomer structure constituting the polymer The weight ratio of the unit to the oxyalkylene chain monomer structural unit (hydrophobic monomer structural unit / oxyalkylene chain monomer structural unit (weight ratio)) is 0.1 to 1.0, and the anionic monomer structural unit It contains the polymer (I) whose content is 10% by weight or less of the whole polymer.

（式（１）中、Ｒ^１はビニル基、アクリロイルオキシ基、アクリロイルアミノ基、メタクリロイルオキシ基、メタクリロイルアミノ基、アクリルアミノ基、スチリル基、ビニルエーテル基、ビニルシリル基、シアノビニル基、又は２−シアノアクリロイル基を表し、Ｒ^２は水素原子、炭素１〜２０のアルキル基又はアルキル基で置換されていても良いフェニル基を表し、ｈ、ｊはそれぞれ独立に１〜５の整数であり、ｉは１〜１００の整数であり、ｋは０〜５０の整数である。）

(In the formula (1), R ¹ is vinyl group, acryloyloxy group, acryloylamino group, methacryloyloxy group, methacryloylamino group, acrylamino group, styryl group, vinyl ether group, vinylsilyl group, cyanovinyl group, or 2-cyanoacryloyl. R ² represents a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, or an optionally substituted phenyl group, h and j are each independently an integer of 1 to 5, and i is 1 (It is an integer of ~ 100, and k is an integer of 0-50.)

  Details of the reason why the gloss and scratch resistance of the printed matter are increased while having fixability by using the aqueous pigment dispersion of the present invention using the polymer (I) as a dispersant are not clear. However, it is considered as follows.

That is, on the paper, hydrophilic alkylene oxide chains interact with each other in a state of retaining water, forming a loose and large network, and forming a highly smooth film on the surface of the printed material. Improve sexiness. However, since only the alkylene oxide chain does not have sufficient fixability on photographic paper, it is necessary to introduce an anionic monomer structural unit having high fixability on photographic paper into the polymer. However, if a large amount of anionic monomer structural units are present in the polymer (I) as a dispersant, the anionic monomer inhibits uniform film formation of the alkylene oxide chain, resulting in a decrease in surface smoothness of the printed matter and gloss. It becomes low.
On the other hand, if the value of the hydrophobic monomer structural unit / oxyalkylene chain monomer structural unit (weight ratio) is too small, the adsorptivity of the polymer (I) to the pigment is lowered and the dispersion stability is deteriorated. Is too large, the above-mentioned loosely widened network is not formed due to the small number of oxyalkylene chain monomer structural units, and the gloss of the printed matter is lowered.

  Therefore, in the present invention, the value of the hydrophobic monomer structural unit / oxyalkylene chain monomer structural unit (weight ratio) in the polymer (I) is in a specific range, and the anionic monomer structural unit is converted into the above effect by the alkylene oxide chain. By introducing it into the polymer (I) in such an amount that does not impair the appearance, it is considered that a printed matter with high gloss and high scratch resistance can be obtained.

{Polymer (I)}
<Hydrophobic monomer>
The hydrophobic monomer constituting the polymer (I) as the dispersant (c) according to the present invention is not particularly limited, and a conventionally known hydrophobic monomer can be used, and in particular, as described below. Aromatic ring-containing monomers and / or aliphatic hydrocarbon group-containing monomers are preferably used.

  The aromatic ring-containing monomer is an aromatic heterocyclic ring-containing monomer or an aromatic hydrocarbon ring-containing monomer. For example, benzyl (meth) acrylate, phenyl (meth) acrylate, phenoxyethyl (meth) acrylate, phenoxyethylene glycol (meta ) Acrylate, phenoxyethylene glycol (meth) acrylate, phenoxydiethylene glycol (meth) acrylate, phenoxydiethylene glycol (meth) acrylate, 2-naphthyl (meth) acrylate, 9-anthracenyl (meth) acrylate, 1-pyrenylmethyl (meth) acrylate , Styrene, vinyl naphthalene, α-methyl styrene, t-butyl styrene, p-methyl styrene, o-methoxy styrene, m-methoxy styrene, p-methoxy styrene, o t-butoxystyrene, mt-butoxystyrene, pt-butoxystyrene, o-chloromethylstyrene, m-chloromethylstyrene, p-chloromethylstyrene, vinyltoluene, ethylvinylbenzene, 4-vinylbiphenyl, 1 , 1-diphenylethylene, vinylphenol, vinyl benzoate, vinylnaphthalene, benzyl vinyl ether and the like.

  Among these, from the viewpoint of pigment affinity, benzyl (meth) acrylate, phenyl (meth) acrylate, phenoxyethyl (meth) acrylate, phenoxyethylene glycol (meth) acrylate, phenoxyethylene glycol (meth) acrylate, phenoxydiethylene glycol A monomer structure having an unsubstituted phenyl group such as coal (meth) acrylate, phenoxydiethylene glycol (meth) acrylate, styrene, and α-methylstyrene is preferable, and styrene and benzyl methacrylate are more preferable.

  The aliphatic hydrocarbon group contained in the aliphatic hydrocarbon group-containing monomer may be linear, cyclic, or branched.

As a monomer having a linear or branched aliphatic hydrocarbon group, for example,
Olefins such as ethylene, propylene, 1-butene and isobutene;
Methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, i-propyl (meth) acrylate, butyl (meth) acrylate, i-butyl (meth) acrylate, t-butyl (meth) acrylate, amyl ( (Meth) acrylate, i-amyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, octyl (meth) acrylate, i-octyl (meth) acrylate, decyl (meth) acrylate, i-decyl (meth) acrylate, dodecyl ( (Meth) acrylate, i-dodecyl (meth) acrylate, stearyl (meth) acrylate, i-stearyl (meth) acrylate, (meth) acrylate esters of behenyl (meth) acrylate;
Vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, i-propyl vinyl ether, i-butyl vinyl ether, t-butyl vinyl ether, dodecyl vinyl ether, stearyl vinyl ether;
Nitriles such as acrylonitrile and methacrylonitrile;
Vinyl halides such as vinyl chloride, vinylidene chloride, vinyl fluoride, vinylidene fluoride;
Allyl compounds such as allyl acetate and allyl chloride;
Dicarboxylic acid ester derivatives such as maleic acid ester and itaconic acid ester;
Vinylsilyl compounds such as vinyltrimethoxysilane;
And vinyl esters such as vinyl acetate and isopropenyl acetate.

  Examples of the monomer having a cyclic aliphatic hydrocarbon group include cyclopropyl (meth) acrylate, cyclobutyl (meth) acrylate, cyclopentyl (meth) acrylate, cyclohexyl (meth) acrylate, cycloheptyl (meth) acrylate, cyclooctyl (meth) ) Acrylate, cyclononyl (meth) acrylate, cyclodecyl (meth) acrylate, etc., isobornyl (meth) acrylate, norbornyl (meth) acrylate, etc., (meth) acrylate esters such as adamantyl (meth) acrylate, etc., cyclopentene, cycloheptene, cyclooctene , Cyclododecene, 1,5-cyclooctadiene, cyclopentadiene, 1,5,9-cyclododecatriene, 1-chloro-1,5-cyclooctadiene, di Black dicyclopentadiene, ethylidene norbornene, 5-norbornene-2-carboxylate, and 5-norbornene 2,3-dicarboxylic acid dimethyl, etc. cyclic olefins and the like.

  Among these, a monomer having a linear alkyl structure and a monomer containing an aliphatic hydrocarbon group having a cyclic structure are preferable from the viewpoint of affinity with the pigment.

  These hydrophobic monomers may be used alone or in combination of two or more.

<Anionic monomer>
As the anionic monomer, those exemplified below can be used, but the anionic monomer is not limited thereto, and conventionally known monomers can be used.
Carboxylic acid monomers such as acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, or salts thereof;
Vinyl sulfonic acid, allyl sulfonic acid, methacryl sulfonic acid, styrene sulfonic acid, 2-acrylamide ethane sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid, 2-methacrylamide ethane sulfonic acid, 2-methacrylamide-2-methyl Propanesulfonic acid, 2-acryloyloxyethanesulfonic acid, 3-acryloyloxypropanesulfonic acid, 4-acryloyloxybutanesulfonic acid, 2-methacryloyloxyethanesulfonic acid, 3-methacryloyloxypropanesulfonic acid, 4-methacryloyloxybutanesulfone Sulfonic acid monomers such as acids or salts thereof;
Vinylphosphonic acid, methacryloxyethyl phosphate, diphenyl-2-acryloyloxyethyl phosphate, diphenyl-2-methacryloyloxyethyl phosphate, dibutyl-2-acryloyloxyethyl phosphate, dibutyl-2-methacryloyloxyethyl phosphate, Phosphoric monomers such as dioctyl-2- (meth) acryloyloxyethyl phosphate or salts thereof.

The anionic monomer is preferably a monomer having a carboxyl group or a salt thereof, and more preferably acrylic acid or a salt thereof, from the viewpoint of print quality such as low print density or bleeding.
The anionic monomer is preferably a salt. Of these, alkali metal salts and alkaline earth metal salts are particularly preferable. Particularly preferred is a sodium salt.

  These anionic monomers may be used individually by 1 type, and 2 or more types may be mixed and used for them.

<Oxy-containing alkylene chain monomer>
The oxyalkylene-containing monomer has an oxyalkylene chain structure in the molecule, and is represented by the following general formula (1). In the following general formula (1), the total of i and k is preferably 2 to 50, and more preferably 2 to 30. This is because if the sum of i and k is 1 or less, the gloss of the printed matter on the photographic paper is lowered, and if it exceeds 50, the fixability to the paper is lowered. The alkyl groups of the phenyl group R ^2, include alkyl groups having 1 to 20 carbon atoms.

（式（１）中、Ｒ^１はビニル基、アクリロイルオキシ基、アクリロイルアミノ基、メタクリロイルオキシ基、メタクリロイルアミノ基、アクリルアミノ基、スチリル基、ビニルエーテル基、ビニルシリル基、シアノビニル基、又は２−シアノアクリロイル基を表し、Ｒ^２は水素原子、炭素１〜２０のアルキル基又はアルキル基で置換されていても良いフェニル基を表し、ｈ、ｊはそれぞれ独立に１〜５の整数であり、ｉは１〜１００の整数であり、ｋは０〜５０の整数である。）

(In the formula (1), R ¹ is vinyl group, acryloyloxy group, acryloylamino group, methacryloyloxy group, methacryloylamino group, acrylamino group, styryl group, vinyl ether group, vinylsilyl group, cyanovinyl group, or 2-cyanoacryloyl. R ² represents a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, or an optionally substituted phenyl group, h and j are each independently an integer of 1 to 5, and i is 1 (It is an integer of ~ 100, and k is an integer of 0-50.)

  Specific examples of the oxyalkylene chain monomer represented by the general formula (1) include polyethylene glycol (meth) acrylate, methoxypolyethylene glycol (meth) acrylate, ethoxypolyethylene glycol (meth) acrylate, and ethoxydiethylene glycol (meth) acrylate. , Lauroxy polyethylene glycol (meth) acrylate, stearoxy polyethylene glycol (meth) acrylate, nonylphenoxy polyethylene glycol (meth) acrylate, phenoxy polyethylene glycol (meth) acrylate, polypropylene glycol (meth) acrylate, poly (ethylene glycol-propylene glycol) ) (Meth) acrylate, polyethylene glycol-polypropylene glycol (meth) Acrylate, poly (ethylene glycol-tetramethylene glycol) (meth) acrylate, poly (propylene glycol-tetramethylene glycol) (meth) acrylate, propylene glycol polybutylene glycol (meth) acrylate, octoxypolyethylene glycol polypropylene glycol (meth) acrylate , Stearoxy polyethylene glycol-polypropylene glycol (meth) acrylate, allyloxy polyethylene glycol-polypropylene glycol (meth) acrylate, nonylphenoxy poly (ethylene glycol-propylene glycol) (meth) acrylate, and the like.

Among the oxyalkylene chain monomers represented by the general formula (1), R ¹ is preferably an acryloyloxy group or a methacryloyloxy group. R ² is more preferably an alkyl group having 1 to 20 carbon atoms or an optionally substituted phenyl group, particularly preferably an alkyl group having 1 to 20 carbon atoms, and among them, an alkyl group having 1 to 10 carbon atoms. The group is most preferred. In particular, the oxyalkylene chain monomer is preferably an oxyethylene chain monomer in which the oxyalkylene chain is an oxyethylene chain.

  As the oxyalkylene chain monomer used in the present invention, those represented by the following general formula (2) are particularly preferred from the viewpoint of improving the dispersion stability due to their high hydrophilicity. Specific examples of the monomer include, for example, polyethylene glycol (meth) acrylate, methoxypolyethylene glycol (meth) acrylate, ethoxypolyethylene glycol (meth) acrylate, ethoxydiethylene glycol (meth) acrylate, lauroxy polyethylene glycol (meth) acrylate, stearoxy polyethylene Examples include glycol (meth) acrylate, nonylphenoxypolyethylene glycol (meth) acrylate, and phenoxypolyethylene glycol (meth) acrylate.

（式（２）中、Ｒ^１，Ｒ^２は式（１）におけると同義であり、ｍは１〜５０の整数である。）

(In formula (2), R ¹ and R ² have the same meaning as in formula (1), and m is an integer of 1 to 50.)

In particular, among the above general formula (2), those in which R ¹ is a (meth) acryloyloxy group and R ² is an alkyl group having 1 to 20 carbon atoms are more preferred, and specific examples thereof include methoxypolyethylene glycol (meth). Examples include acrylate, ethoxypolyethylene glycol (meth) acrylate, ethoxydiethylene glycol (meth) acrylate, lauroxypolyethyleneglycol (meth) acrylate, stearoxypolyethyleneglycol (meth) acrylate, and the like.
Among them, R ² is particularly preferably an alkyl group having 1 to 10 carbon atoms, and specific examples thereof include methoxypolyethylene glycol (meth) acrylate and ethoxypolyethylene glycol (meth) acrylate.
Moreover, m is preferably 2 to 50, and more preferably 2 to 30.

  These oxyalkylene chain monomers may be used alone or in a combination of two or more.

<Other monomers>
The polymer (I) as a dispersant according to the present invention comprises one or more types of hydrophobic monomer structural units, one or more types of anionic monomer structural units, and an oxyalkylene chain monomer represented by the general formula (1). What is necessary is just to be comprised including 1 or more types of a structural unit, and the other polymerizable monomer structural unit may be included. Other polymerizable monomers that can be used in the polymer (I) according to the present invention are not particularly limited, and conventionally known monomers can be used.

Specifically, as other polymerizable monomer, for example,
(Meth) acrylamide, C1-C6 N-alkyl (meth) acrylamide, C1-C3 N, N-dialkyl (meth) acrylamide, diacetone (meth) acrylamide, N-methylol (meth) acrylamide, N 2-hydroxyethyl (meth) acrylamide, N, N-diethanol (meth) acrylamide, N-vinylacetamide, N-methyl-N-vinylacetamide, N-vinylformamide, N-methyl-N-vinylformamide, N- Amide group-containing monomers such as (2- (polyethylene glycol) ethyl) (meth) acrylamide, N, N- (2,2 ′-(polyethylene glycol) diethyl) (meth) acrylamide;
Monomers having primary amino groups such as aminoethyl (meth) acrylate and aminopropyl (meth) acrylate;
Secondary such as methylaminoethyl (meth) acrylate, methylaminopropyl (meth) acrylate, ethylaminoethyl (meth) acrylate, ethylaminopropyl (meth) acrylate, 2-vinylpyridine, 4-vinylpyridine A monomer having an amino group;
Monomers having a tertiary amino group such as dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, dimethylaminopropyl (meth) acrylate, diethylaminopropyl (meth) acrylate;
2-vinylpyridine, 4-vinylpyridine, 1-vinylimidazole, N-vinylpyrrolidone, 2-vinyl-2-oxazoline, 5-methyl-2-vinyl-2-oxazoline, N-vinyloxazolidone, 2-N-pyrrolidoneethyl Monomers having a heterocyclic ring such as (meth) acrylate, N-vinylcaprolactam, 9-vinylcarbazole, N-vinylphthalimide;
Monomers containing a hydroxyl group such as 2-hydroxyethyl (meth) acrylic acid ester, 2-hydroxypropyl (meth) acrylic acid ester, 2,3-dihydroxypropyl (meth) acrylate, 2-hydroxyethyl vinyl ether;
Glucose, mannose, galactose, glucosamine, mannosamine, galactosamine, etc., hexoses, arabinose, xylose, ribose, etc. Disaccharides such as mannobiose and sophorose, other oligosaccharides such as maltotriose, isomaltotriose, maltotetraose, maltopentaose, mannotriose and manninotriose, polysaccharides such as cellulose and modified cellulose A monomer having a structure as derived and having a glycosyl group, such as a monomer such as glucosylethyl methacrylate;
A macromonomer having a polyvinyl alcohol structure in the side chain;
And other hydrophilic nonionic monomers.

  Among these, an amide group-containing monomer, a monomer having a heterocyclic ring, a monomer containing a hydroxyl group, and a macromonomer having a polyvinyl alcohol structure in the side chain are preferable because of high dispersion stability when used as a dispersant. In particular, N-alkyl (meth) acrylamide having 1 to 6 carbon atoms, N-2-hydroxyethyl (meth) acrylamide, N-vinylpyrrolidone, 2-hydroxyethyl (meth) acrylic acid ester, polyvinyl alcohol structure in the side chain The macromonomer having is particularly preferable, and N-2-hydroxyethyl (meth) acrylamide is most preferable.

  These other monomers may be used alone or in combination of two or more.

  The polymer (I) as a dispersant according to the present invention is produced by performing radical polymerization described below, for example, using each monomer at a predetermined ratio. As for the monomer, it is copolymerized with one or more hydrophobic monomers, one or more anionic monomers and one or more oxyalkylene chain monomers as described above in the form of vinyl acetate, and then saponified to produce polyacetic acid. The vinyl moiety can also be introduced as polyvinyl alcohol.

<Monomer composition>
The polymer (I) as a dispersant according to the present invention comprises at least one hydrophobic monomer, at least one anionic monomer, and at least one oxyalkylene chain monomer represented by the general formula (1). As a composition, the value of hydrophobic monomer structural unit / oxyalkylene chain monomer structural unit (weight ratio) is 0.1 to 1.0, and the anionic monomer structural unit is polymer ( I) It is characterized by being 10% by weight or less of the whole.
Here, regarding the composition ratio (% by weight) of the anionic monomer structural unit, the anion component is preferably neutralized as described above to form a salt. It is calculated using the molecular weight of the product in the state of

  If the value of the hydrophobic monomer structural unit / oxyalkylene chain monomer structural unit (weight ratio) is less than 0.1, the adsorption of the polymer (I) to the pigment is weak, the viscosity increases, and the ejection properties deteriorate. On the other hand, if the hydrophobic monomer structural unit / oxygen-containing alkylene chain monomer structural unit (weight ratio) is larger than 1.0, the gloss of the printed matter is lowered. The hydrophobic monomer structural unit / oxyalkylene chain monomer structural unit (weight ratio) is preferably 0.2 to 0.9, and particularly preferably 0.3 to 0.8.

  The anionic monomer structural unit is more preferably 0.001% by weight or more and 10% by weight or less, and particularly preferably 0.01% by weight or more and 10% by weight or less of the entire polymer (I). . If the content of the anionic monomer structural unit exceeds 10% by weight of the total polymer (I), the gloss of the printed matter on the photographic paper decreases, and if the content of the anionic monomer structural unit is too small, the dispersion stability and the paper The fixability of the ink will deteriorate.

  The content of the hydrophobic monomer structural unit and the oxyalkylene chain monomer structural unit contained in the polymer (I) according to the present invention is as follows: hydrophobic monomer structural unit / oxyalkylene chain monomer structural unit (weight ratio). Although there will be no restriction | limiting in particular if the said range is satisfy | filled, It is preferable that it is the following quantity.

  The hydrophobic monomer structural unit is preferably 10% by weight or more, particularly preferably 20% by weight or more, based on the entire polymer (I). Moreover, 45 weight% or less is preferable and 40 weight% or less is especially preferable. If the proportion of the hydrophobic monomer structural unit is too small, the polymer (I) is difficult to adsorb on the pigment, the free polymer (I) increases and the viscosity increases, and if it is too large, the water solubility of the polymer (I) decreases. The pigment dispersibility becomes worse.

  The oxyalkylene chain monomer structural unit is preferably 50% by weight or more, preferably 80% by weight or less, particularly preferably 75% by weight or less, based on the entire polymer (I). If the proportion of the oxyalkylene chain monomer structural unit is too small, the gloss of the printed matter on the photographic paper is lowered, and if it exceeds this upper limit, the fixability to the paper is lowered.

  Moreover, it is preferable that the other monomer structural unit used as needed is 30 weight% or less of the whole polymer (I). By using other monomer structural units, effects such as improvement in dispersion stability and dischargeability may be obtained. However, if the amount exceeds this upper limit, the effect of the present invention is lowered. When other monomer structural units are used, the more preferable content is 0.1% by weight or more and 20% by weight or less of the whole polymer (I).

<Polymer structure>
The polymer structure of the polymer (I) according to the present invention may be any of a random copolymer, a diblock copolymer, a triblock or more multiblock copolymer, a gradient copolymer, a graft copolymer, a star copolymer, etc. Among them, a random copolymer is preferable. .

<Molecular weight>
The number average molecular weight of the polymer (I) used in the present invention is preferably 150,000 or less, more preferably 100,000 or less, and particularly preferably 1,000 or more and 50,000 or less. If the molecular weight is larger than this range, the viscosity of the dispersion liquid and the ink is high and the dischargeability is lowered. If the molecular weight is smaller, the polymer is peeled off from the pigment when the recording liquid is prepared. The weight average molecular weight of the polymer (I) is preferably 300,000 or less, more preferably 200,000 or less, particularly preferably 2000 or more and 100,000 or less.

<Water-soluble and water-dispersible>
As the polymer (I) used in the present invention, a polymer whose solubility in water at 25 ° C. is 2% by weight or more in a state where 90 mol% of ionic groups present in the polymer is neutralized. preferable. In addition, in the state where 90 mol% of the ionic groups present in the polymer is neutralized, it is also preferable that no precipitation occurs in an aqueous dispersion having a concentration of 2% by weight of the polymer. In the aqueous dispersion having a concentration of not more than% by weight, one that does not cause precipitation is used. Whether or not precipitation occurs is visually confirmed immediately after the polymer aqueous dispersion is prepared.

The above-mentioned “ionic group” refers to a group that can dissociate into ions in water, and examples thereof include an amino group, a carboxyl group, a sulfonic acid group, and salts thereof. The above-mentioned "in a state where 90 mol% of the ionic groups present in the polymer are neutralized" means that 90 mol% of the ionic groups contained in the polymer is converted into a salt by the neutralizing agent. Point to. As a procedure for confirming that the polymer is contained in the above definition range, for example, the ratio of the ionic groups in the polymer that are neutralized to form a salt (degree of neutralization of the ionic groups) is measured. The degree of neutralization of the ionic group is adjusted to 90 mol%, and this is dissolved or dispersed in water at 25 ° C. and 2 wt% concentration, and the appearance is visually observed. The degree of neutralization of the ionic group is determined by measuring the composition ratio of the ionic group with respect to the whole polymer by, for example, ¹ H-NMR, and the counter ion of the polymer forming the salt, for example, the carboxyl group forms a salt with Na. , Measure Na ⁺ charge, and divide the amount that is actually Na ⁺ salt by the amount of charge that is calculated from the composition ratio assuming that it is all Na ⁺ salt. Can be sought. As a result of the measurement, when the degree of neutralization is less than 90%, the degree of neutralization is adjusted by adding an alkali. As another method, from the synthesis of the polymer to the preparation of the ink, it is assumed that the addition of alkali neutralizes the ionic groups of the remaining monomers without polymerizing with the ionic groups in the polymer at the same rate. The degree of neutralization of the ionic groups in the polymer can also be estimated by dividing the number of moles of alkali added in the series of steps by the number of moles of the entire ionic groups of the charged monomer at the time of polymer synthesis.

  As the polymer (I), among the above-mentioned polymers, even when 50 mol% of the ionic groups present in the polymer is neutralized, the solubility of the polymer in water at 25 ° C. is 2% by weight or more. Some are more preferred. Further, even in a state where 50 mol% of the ionic groups present in the polymer are neutralized, it is more preferable that the polymer does not cause precipitation in an aqueous dispersion of 2 wt% concentration at 25 ° C.

  The polymer (I) is particularly preferably a water-soluble polymer or a water-dispersible polymer. As used herein, “water-soluble polymer” refers to a polymer whose solubility in water at 25 ° C. is 2% by weight or more, and “water-dispersible polymer” refers to 2% by weight of the polymer at 25 ° C. % Aqueous dispersion that does not cause precipitation immediately after preparation of the aqueous dispersion.

  When such a water-soluble or water-dispersible polymer, preferably a water-soluble polymer, is used as the polymer dispersant of the aqueous pigment dispersion, excellent pigment dispersibility is exhibited in this aqueous liquid. In addition, by using this aqueous pigment dispersion as a recording liquid, particularly an inkjet recording liquid, not only the dispersion stability of the pigment, but also the dischargeability of the recording liquid from the discharge nozzle, scratch resistance, print density, The effect that a printed matter having excellent gloss can be obtained is also obtained.

<Method for synthesizing polymer (I)>
The method for synthesizing the polymer (I) is not particularly limited. For example, a known polymerization method such as radical polymerization, ionic polymerization, polyaddition or polycondensation can be selected, and the polymer (I) can be synthesized by these known methods. It may be a derivative or modified product of the polymer. Among these, a polymer synthesized using a radical polymerization method is preferable because the synthesis method is simple.

(Polymerization reaction solvent)
The radical polymerization reaction can be performed without a solvent or in the presence of a solvent, but the polymerization reaction is preferably performed in the presence of a solvent.

  Examples of the polymerization reaction solvent include ethers such as diethyl ether, tetrahydrofuran, diphenyl ether, anisole and dimethoxybenzene, amides such as N, N-dimethylformamide and N, N-dimethylacetamide, acetonitrile, propionitrile and benzonitrile. Nitriles, acetone, methyl ethyl ketone, methyl isobutyl ketone, carbonyl compounds such as ethyl acetate, butyl acetate, ethylene carbonate, propylene carbonate, alcohols such as methanol, ethanol, propanol, isopropanol, n-butyl alcohol, t-butyl alcohol, isoamyl alcohol , Aromatic hydrocarbons such as benzene, toluene, xylene, chlorobenzene, methylene chloride, chloroform, chlorobenzene, carbon tetrachloride And halogenated hydrocarbons. Among these, preferred aqueous solvents as a polymerization reaction solvent.

  The aqueous solvent refers to a solvent obtained by mixing 100% water or water and a polar organic solvent at an arbitrary ratio. The polar organic solvent used here is not particularly limited as long as it can be mixed with water at an arbitrary ratio, and specifically, methanol, ethanol, isopropanolacetonitrile, acetone, dimethylformamide, dityl sulfoxide, tetrahydrofuran and the like are exemplified. Of these, methyl alcohol, ethyl alcohol, and isopropyl alcohol are particularly preferable.

  These solvents may be a single solvent composed of only one kind or a mixed solvent composed of two or more kinds.

(Polymerization initiator)
A known radical polymerization initiator can be used for the radical polymerization reaction in the synthesis of the polymer. As the polymerization initiator, either a water-soluble polymerization initiator or an oil-soluble polymerization initiator can be used.

<Water-soluble polymerization initiator>
Examples of the water-soluble polymerization initiator include 2,2′-azobis (2-amidinopropane) dihydrochloride, 4,4′-azobis (4-cyanovaleric acid), 2,2′-azobis [2- (2-Imidazolin-2-yl) propane] dihydrochloride, 2,2′-azobis [2- (2-imidazolin-2-yl) propane] disulfate dihydrate, 2,2′-azobis [ N- (2-carboxyethyl) -2-methylpropionamide], 2,2′-azobis {2- [1- (2-hydroxyethyl) -2-imidazolin-2-yl) propane} dihydrochloride, 2, 2′-azobis (1-imino-1-pyrrolidino-2-methylpropane) dihydrochloride, 2,2′-azobis {2-methyl-N- [2- (1-hydroxybutyl)] propionamide}, 2 , 2′-azobis [2- (5-methyl) -Izozolin-2-yl) propane] dihydrochloride, 2,2′-azobis [2- (3,4,5,6, -tetrahydropyrimidin-2-yl) propane] dihydrochloride, etc. Oxidizing agents such as potassium persulfate, sodium persulfate, ammonium persulfate, and hydrogen peroxide alone, or sodium sulfite, sodium hyposulfite, ferrous sulfate, ferrous nitrate, sodium formaldehyde sulfoxylate, thiourea, etc. A redox initiator combined with a water-soluble reducing agent may be mentioned.
These may be used alone or in combination of two or more.

<Oil-soluble polymerization initiator>
Examples of oil-soluble polymerization initiators include 2,2′-azobisisobutyronitrile, 2,2′-azobis (2-methylbutyronitrile), 1,1′-azobiscyclohexane 1-carbonitrile, , 2′-azobis-4-methoxy-2,4-dimethylvaleronitrile, 2,2′-azobis-2,4-dimethylvaleronitrile, dimethyl-2,2′-azobis (2-methylpropionate), Azo compound initiators such as 1,1′-azobis (1-acetoxy-1-phenylethane), 2,2′-azobis (4-methoxy-2,4-dimethylvaleronitrile), acetylcyclohexylsulfonyl peroxide, Isobutyryl peroxide, diisopropyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, 2,4-dichlorobenzo Ruperoxide, t-butylperoxypivalate, 3,5,5-trimethylhexanonyl peroxide, octanoyl peroxide, decanoyl peroxide, lauroyl peroxide, stearoyl peroxide, propionitrile peroxide, succinic acid Peroxide, acetyl peroxide, t-butylperoxy-2-ethylhexanoate, benzoyl peroxide, parachlorobenzoyl peroxide, t-butylperoxyisobutyrate, t-butylperoxymaleic acid, t- Butyl peroxylaurate, cyclohexanone peroxide, t-butyl peroxyisopropyl carbonate, 2,5-dimethyl-2,5-dibenzoyl peroxyhexane, t-butyl peroxyhexane -Oxyacetate, t-butylperoxybenzoate, diisobutyldiperoxyphthalate, methyl ethyl ketone peroxide, dicumyl peroxide, 2,5-dimethyl-2,5-di-t-butylperoxyhexane, t-butylcumyl peroxide , T-butyl hydroperoxide, di-t-butyl peroxide, diisopropylbenzene hydroperoxide, paramentane hydroperoxide, pinane hydroperoxide, 2,5-dimethylhexane-2,5-dihydroperoxide and cumene peroxide Peroxide polymerization initiators such as hydroperoxide (tret-butylhydroxyperoxide, cumenehydroxyperoxide, etc.), dialkyl peroxides (lauroyl peroxide, etc.) and peracids Oil-soluble peroxides such as diacyl (benzoyl peroxide, etc.), tertiary amines (triethylamine, tributylamine, etc.), naphthenates, mercaptans (mercaptoethanol, lauryl mercaptan, etc.), organometallic compounds (triethylaluminum, triethylboron) And an oil-soluble redox polymerization initiator used in combination with an oil-soluble reducing agent such as diethyl zinc).
These may be used alone or in combination of two or more.

(Additives such as chain transfer agents)
In the radical polymerization reaction, in addition to the above polymerization initiator, known materials such as a chain transfer agent, a chain terminator, and a polymerization accelerator can be added and used in order to adjust the resulting polymer to a preferred molecular weight.

(Polymerization conditions)
When conducting the polymerization reaction, the order of addition of the monomer, polymerization reaction solvent, radical initiator, etc. is arbitrary. And performing a polymerization reaction. In this case, the monomer or radical polymerization initiator may be added as it is or in a solution. As another method, a polymerizable monomer and a polymerization reaction solvent are charged into a reaction vessel and the temperature is raised, and then a monomer solution containing a radical polymerization initiator, a polymerization reaction solvent, or a mixture thereof is continuously added. Or a method in which the polymerization reaction is carried out by adding in portions.
Among these, from the viewpoint of simplicity of operation, a method in which the polymerization reaction is performed by raising the temperature after charging the raw materials all at once is preferable.

  Although the usage-amount of a polymerization reaction solvent is not specifically limited, It is 1 weight part or more normally with respect to 100 weight part of monomers, Usually 2000 weight part or less, Preferably it is 1000 weight part or less.

  The amount of the polymerization initiator used varies depending on the type of the polymerization initiator used and is not particularly limited, but is usually 0.5 parts by weight or more and 15 parts by weight or less with respect to 100 parts by weight of the monomer.

  The polymerization temperature is not particularly limited, but is usually 0 ° C or higher, preferably 20 ° C or higher, and the upper limit is usually 200 ° C or lower, preferably 150 ° C or lower.

(Purification)
Although there is no particular problem even if the polymer obtained by polymerization is used as it is, it is preferably purified according to a conventional method and subjected to the subsequent pigment dispersion step. Purification methods include dropping the polymer solution into a solvent in which the polymer is insoluble and the monomer and polymerization initiator are soluble, reprecipitation purification by repeating the precipitation and filtration of the polymer, and the polymer and the polymer insoluble in the polymer solution and the polymerization initiator. Add a solvent that is soluble in water, remove the unreacted monomer and reaction solvent by fractional precipitation purification, heating distillation, vacuum distillation, etc. that repeat polymer precipitation and filtration, and then replace the solvent with water and / or aqueous solvent And a method of removing low molecular impurities and low molecular weight oligomer components using an ultrafiltration membrane or a dialysis membrane.

{About pigment}
The pigment used in the present invention may be appropriately selected from those commonly used in each application, and is not particularly limited. Examples of typical pigments include calcium carbonate, kaolin clay, talc, bentonite, and mica. Extender pigments; metal oxide pigments such as titanium oxide, zinc oxide, goethite, magnetite, chromium oxide; titanium yellow, titanium buff, antimony yellow, vanadium tin yellow, cobalt green, cobalt chromium green, manganese green Composite oxide pigments such as cobalt blue, cerulean blue, manganese blue, tungsten blue, Egyptian blue and cobalt black; sulfide pigments such as lithobon, cadmium red yellow and cadmium red; Phosphate pigments such as violet, cobalt violet, lithium cobalt phosphate, sodium cobalt phosphate, potassium potassium phosphate, cobalt ammonium phosphate, nickel phosphate, copper phosphate; yellow lead, molybdate orange Chromate-based pigments; Metal complex salt pigments typified by ultramarine and Prussian blue; Metal powder-based pigments typified by aluminum paste, bronze powder, zinc dust, stainless steel flakes, and nickel flakes; Carbon black, bismuth oxychloride , Basic carbonates, titanium dioxide, coated mica, ITO, inorganic pigments such as pearlescent pigments and pearlescent conductive pigments such as ATO; and quinacridone pigments, quinacridone quinone pigments, dioxazine pigments, phthalocyanine pigments , Anthrapyrimidine pigment, answer Throne pigment, Indanthrone pigment, Flavanthrone pigment, Perylene pigment, Diketopyrrolopyrrole pigment, Perinone pigment, Quinophthalone pigment, Anthraquinone pigment, Thioindigo pigment, Metal complex pigment, Azomethine pigment Or organic pigments, such as an azo pigment, are mentioned.

  Specific examples of the pigment include pigments having the following pigment numbers and known carbon blacks generally used in the color material field. Note that terms such as “CI Pigment Red 2” mentioned below mean a color index (CI).

  Red colorant: C.I. I. Pigment Red 1, 2, 3, 4, 5, 6, 7, 8, 9, 12, 14, 15, 16, 17, 21, 22, 23, 31, 32, 37, 38, 41, 47, 48, 48: 1, 48: 2, 48: 3, 48: 4, 49, 49: 1, 49: 2, 50: 1, 52: 1, 52: 2, 53, 53: 1, 53: 2, 53: 3, 54, 57, 57: 1, 57: 2, 58, 58: 4, 60, 63, 63: 1, 63: 2, 64, 64: 1, 68, 69, 81, 81: 1, 81: 2, 81: 3, 81: 4, 83, 88, 90: 1, 101, 101: 1, 104, 108, 108: 1, 109, 112, 113, 114, 122, 123, 144, 146, 147, 149, 151, 166, 168, 169, 170, 172, 173, 174, 175, 176, 177, 78, 179, 181, 184, 185, 187, 188, 190, 193, 194, 200, 202, 206, 207, 208, 209, 210, 214, 216, 220, 221, 224, 230, 231, 232, 233, 235, 236, 237, 238, 239, 242, 243, 245, 247, 249, 250, 251, 253, 254, 255, 256, 257, 258, 259, 260, 262, 263, 264, 265, 266, 267, 268, 269, 270, 271, 272, 273, 274, 275, 276;

  Blue colorant: C.I. I. Pigment Blue 1, 1: 2, 9, 14, 15, 15: 1, 15: 2, 15: 3, 15: 4, 15: 6, 16, 17, 19, 25, 27, 28, 29, 33, 35, 36, 56, 56: 1, 60, 61, 61: 1, 62, 63, 66, 67, 68, 71, 72, 73, 74, 75, 76, 78, 79;

  Green colorant: C.I. I. Pigment Green 1, 2, 4, 7, 8, 10, 13, 14, 15, 17, 18, 19, 26, 36, 45, 48, 50, 51, 54, 55;

  Yellow colorant: C.I. I. Pigment Yellow 1, 1: 1, 2, 3, 4, 5, 6, 9, 10, 12, 13, 14, 16, 17, 23, 24, 31, 32, 34, 35, 35: 1, 36, 36: 1, 37, 37: 1, 40, 41, 42, 43, 48, 53, 55, 61, 62, 62: 1, 63, 65, 73, 74, 75, 81, 83, 87, 93, 94, 95, 97, 100, 101, 104, 105, 108, 109, 110, 111, 116, 119, 120, 126, 127, 127: 1, 128, 129, 133, 134, 136, 138, 139, 142, 147, 148, 150, 151, 153, 154, 155, 157, 158, 159, 160, 161, 162, 163, 164, 165, 166, 167, 168, 169, 170, 172, 173 174, 175, 176, 180, 181, 182, 183, 184, 185, 188, 189, 190, 191, 191: 1, 192, 193, 194, 195, 196, 197, 198, 199, 200, 202, 203, 204, 205, 206, 207, 208;

  Orange colorant: C.I. I. Pigment Orange 1, 2, 5, 13, 16, 17, 19, 20, 21, 22, 23, 24, 34, 36, 38, 39, 43, 46, 48, 49, 61, 62, 64, 65, 67, 68, 69, 70, 71, 72, 73, 74, 75, 77, 78, 79;

  Violet colorant: C.I. I. Pigment Violet 1, 1: 1, 2, 2: 2, 3, 3: 1, 3: 3, 5, 5: 1, 14, 15, 16, 19, 23, 25, 27, 29, 31, 32, 37, 39, 42, 44, 47, 49, 50

  Brown colorant: C.I. I. Pigment Brown 1, 6, 11, 22, 23, 24, 25, 27, 29, 30, 31, 33, 34, 35, 37, 39, 40, 41, 42, 43, 44, 45

  Black colorant: C.I. I. Pigment Black 1, 31, 32

  Among the above pigments, the red pigment is preferably a quinacridone pigment, a xanthene pigment, a perylene pigment, an anthanthrone pigment and a monoazo pigment, and specific examples thereof include CI Pigment Red-5, -7, -12, -112, -81, -122, -123, 146, -147, -168, -173, -202, -206, -207, -209, C.I. I. And CI Pigment Violet-19. Among these, the solid solution which consists of a quinacridone-type pigment and two or more types of quinacridone-type pigments is more preferable from the surface of a pigment's stability and hue.

  Of the above-mentioned pigments, monoazo pigments and disazo pigments are preferable as yellow pigments because color development as printed matter is better than other pigments. Among them, C.I. I. Pigment Yellow-1, -3, -16, -17, -74, -120, -128, -151, -175, and -215 are particularly preferred from the viewpoint of their hues. I. CI Pigment Yellow-74 and -155 are non-halogen compounds, and are particularly preferable from the viewpoint of little influence on the environment and hue.

  Of the above-mentioned pigments, a blue pigment is preferable, and a copper phthalocyanine pigment is preferable because color development as a printed matter is better than other pigments. Among them, C.I. I. Pigment Blue-15: 3 is preferable from the viewpoints of stability and hue.

  Further, as the carbon black used in the present invention, various carbon blacks such as acetylene black, channel black and furnace black can be used. Among these, channel black or furnace black is preferable, and furnace black is particularly preferable.

The DBP oil absorption amount of the carbon black is preferably 40 ml / 100 g or more, more preferably 50 ml / 100 g or more, and particularly preferably 60 ml / 100 g or more from the viewpoint of printing density. The upper limit is preferably 250 ml / 100 g or less, particularly preferably 200 ml / 100 g or less.
However, from the viewpoint of glossiness with photographic paper, a range of 30 to 100 ml / 100 g is preferable, and a range of 30 to 70 ml / 100 g is particularly preferable.
The volatile content is preferably 8% by weight or less, particularly preferably 4% by weight or less.
From the viewpoint of storage stability of the recording liquid, the pH is preferably 3 or more, more preferably 6 or more, and the upper limit is preferably 11 or less, particularly preferably 9 or less.
The BET specific surface area is usually 100 m ² / g or more, preferably 150 m ² / g or more, and the upper limit is preferably 700 m ² / g or less, particularly preferably 600 m ² / g or less.

  Here, the DBP oil absorption is a value measured by the method of JISK6221A, the volatile content is a value measured by the method of JISK6221, pH is a value measured by a glass electrode meter with a mixture of carbon black and distilled water, and the BET specific surface area is that of JISK6217. It is the value measured by the method.

  From the viewpoint of safety, it is preferable to use carbon black in which the polycyclic aromatic component is reduced by baking at 600 to 1500 ° C. or washing with water, warm water, a solvent, or the like. In particular, baking at a high temperature is more preferable because the functional group on the surface of the carbon black is removed, whereby the dispersant is more efficiently adsorbed more firmly on the surface of the carbon black.

  Specific examples of the carbon black include products shown in the following (1) to (4).

(1) # 2700B, # 2650, # 2650B, # 2600, # 2600B, 2450B, 2400B, # 2350, # 2300, # 2300B, # 2200B, # 1000, # 1000B, # 990, # 990B, # 980, # 980B, # 970, # 960, # 960B, # 950, # 950B, # 900, # 900B, # 850, # 850B, MCF88, MCF88B, MA600, MA600B, # 750B, # 650B, # 52, # 52B, # 50, # 47, # 47B, # 45, # 45B, # 45L, # 44, # 44B, # 40, # 40B, # 33, # 33B, # 32, # 32B, # 30, # 30B, # 25, # 25B, # 20, # 20B, # 10, # 10B, # 5, # 5B, CF9, CF9B, # 95, # 260, MA77 MA77B, MA7, MA7B, MA8, MA8B, MA11, MA11B, MA100, MA100B, MA100R, MA100RB, MA100S, MA230, MA220, MA200RB, MA14, # 3030B, # 3040B, # 3050B, # 3230B, # 3350B (and above, Mitsubishi Chemical company product).

(2) Monarch 1400, Black Pearls 1400, Monarch 1300, Black Pearls 1300, Monarch 1100, Black Pearls 1100, Monarch 1000, Black Pearls 1000, Monarch 900, Black Pearl 900 800, Monarch 700, Black Pearls 700, Black Pearls 2000, Vulcan XC72R, Vulcan XC72, Vulcan PA90, Vulcan 9A32, Mogul L, Black Pearls L, Regal 660R, R gal 660, Black Pearls 570, Black Pearls 520, Regal 400R, Regal 400, Regal 330R, Regal 330, Regal 300R, Black Pearls 490, Black Pearls 480, Black Pearls 480, Black Pearls 480, Black Pearls 480, Black Pearls 480, Black Pearls 480 Black Pearls 420, Black Pearls 410, Regal 350R, Regal 350, Regal 250R, Regal 250, Regal 99R, Regal 99I, Elftex Pellets 115, Elftex 8, Elftex 5, Elftex 12, Mftex 12 ch 280, Black Pearls 280, Black Pearls 170, Black Pearls 160, Black Pearls 130, Monarch 120, Black Pearls 120 (above, products of Cabot Corporation).

(3) Color Black FW1, Color Black FW2, Color Black FW2V, Color Black FW18, Color Black FW200, Special Black 4, Special Black 4A, Special Black 4A, Special Black 4W, Color Black FW2V, Color Black FW2V, Color Black FW2 V, Printex 150T, Printex 140U, Printex 140V, Printex 95, Printex 90, Printex 85, Printex 80, Printex 75, Printex 55, Printex 45, Printex 40, Printex 40, Princex ntex 60, Printex XE, Printex L6, Printex L, Printex 300, Printex 30, Printex 3, Printex 35, Printex 25, Printex 200, Printex A, Printex G, Stex 100 (above, Degussa product).

(4) Raven 7000, Raven 5750, Raven 5250, Raven 5000 ULTRA, Raven 3500, Raven 2000, Raven 1500, Raven 1250, Raven 1250, Raven 10R, Raven 1170, Raven 1170, Raven 1170, Raven 1170, Raven 1170, Raven 1170, Raven 1170, Raven 1170, Raven 1170, Raven 1170 Raven 1000, Raven 890H, Raven 890, Raven 850, Raven 790 ULTRA, Raven 760 ULTRA, Raven 520, Raven 500, Raven 450, Raven 430, Raven 420, Raven 420, Raven 420, Raven 420, Raven 420 ULTRA, Raven H2O, Raven C ULTRA (or more, Columbia's products).

As the pigment according to the present invention, one of the above pigments may be used alone, or two or more of them may be used in combination. It can also be used in combination with other color materials.
The shape of the pigment may be any form such as paste, powder, solid solution and the like.

The size of the primary particles of these pigments may be arbitrarily set according to the purpose, but is usually 10 nm or more and 800 nm or less, preferably 500 nm or less, more preferably 300 nm or less, and further preferably 200 nm. Hereinafter, it is particularly preferably 100 nm or less.
Here, the primary particle diameter of the pigment is an arithmetic average diameter (number average) measured by an electron microscope.

Further, the average dispersed particle size of the pigment in the dispersion is usually 500 nm or less, preferably 200 nm or less. Moreover, as a minimum, it is 20 nm or more normally.
As a measuring method of the said average particle diameter, it can measure using electron microscopes, such as SEM and TEM, or can be measured using a commercially available dynamic light-scattering measuring apparatus.

  The pigment is not chemically modified, and a pigment that does not contain impurities other than the pigment, such as a crystallization inhibitor for promoting the reduction in the particle size of the pigment, It is preferable because it does not inhibit the adsorption. However, in order to give the pigment self-dispersibility, a pigment having self-dispersibility which has been subjected to known chemical modification in advance can also be used. That is, the pigment used in the aqueous pigment dispersion of the present invention can be any pigment, whether it is an untreated pigment or a pigment whose surface is chemically modified, as described above.

{About aqueous media}
Examples of the aqueous medium used in the aqueous pigment dispersion of the present invention include water and / or a water-soluble organic solvent. The water-soluble organic solvent is not particularly limited as long as it is generally used for this application. Specifically, the water-soluble organic solvent has a vapor pressure lower than that of water, such as ethylene glycol, diethylene glycol, triethylene glycol, Tetraethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, 1,3-propylene glycol, isopropylene glycol, polypropylene glycol, pentamethylene glycol, trimethylene glycol, butylene glycol, isobutylene glycol, thiodiglycol, 1,2-hexanediol, 1,6-hexanediol, 2-ethyl-1,3-hexanediol, 1,2-pentanediol, 1,5-pentanediol, 2-methyl Multivalents such as 2,4-pentanediol, 1,3-propanediol, 1,4-butanediol, 1,7-heptanediol, 1,8-octanediol, 2-butene-1,4-diol, glycerin, etc. Alcohols;
Ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol mono-t-butyl ether, ethylene glycol monopropyl ether, ethylene glycol monoisopropyl ether, ethylene glycol monophenyl ether, ethylene glycol monomethyl ether acetate, diethylene glycol monomethyl Ether, diethylene glycol monoethyl ether, diethylene glycol monoisopropyl ether, diethylene glycol monobutyl ether, diethylene glycol mono-t-butyl ether, triethylene glycol monoethyl ether, triethylene glycol monobutyl ether, propylene glycol monomethyl ether, Lopylene glycol monoethyl ether, propylene glycol monobutyl ether, propylene glycol-t-butyl ether, propylene glycol monopropyl ether, propylene glycol isopropylene ether, propylene glycol monophenyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, di Polyhydric alcohol ethers such as propylene glycol monobutyl ether, dipropylene glycol monopropyl ether, dipropylene glycol monoisopropyl ether;
Ketones such as acetonylacetone;
Esters such as γ-butyrolactone, diacetin, triethyl phosphate;
Lower alkoxy alcohols such as 2-methoxyethanol and 2-ethoxyethanol;
Amines such as ethanolamine, diethanolamine, triethanolamine, N-methyldiethanolamine, N-ethyldiethanolamine, triethylenetetramine, tetraethylenepentamine, pentamethyldiethylenetriamine;
Amides such as formamide, N, N-dimethylformamide, N-methylformamide, N, N-dimethylacetamide;
2-pyrrolidone, N-ethylpyrrolidone, N-methyl-2-pyrrolidone, cyclohexylpyrrolidone, morpholine, N-ethylmorpholine, 2-oxazolidone, 1,3-dimethyl-2-imidazolidinone, imidazole, methylimidazole, hydroxyimidazole , Heterocycles such as dimethylaminopyridine, 1,3-propane sultone, hydroxyethylpiperazine, piperazine;
Sulfoxides such as dimethyl sulfoxide;
Examples include sulfones such as sulfolane.
These may be used alone or in combination of two or more.

  The aqueous medium used in the present invention is preferably water or a mixture of water and a water-soluble organic solvent as described above.

{Aqueous pigment dispersion composition}
The aqueous pigment dispersion of the present invention comprises the above-mentioned aqueous medium, the pigment, and the polymer (I) as a dispersant.
In the aqueous pigment dispersion of the present invention, one type of polymer (I) may be contained alone, or two or more types may be contained.

  The pigment concentration in the aqueous pigment dispersion of the present invention is usually 30% by weight or less, preferably 20% by weight or less. Here, if the pigment concentration is too high, the pigment becomes poorly dispersed, the viscosity of the dispersion increases, the dispersion becomes gelled, and the dispersion cannot be used due to dispersion failure. If the concentration is too low, there is a problem that it takes a lot of time and effort to concentrate the ink, so that the concentration is usually 0.1% by weight or more, preferably 0.5% by weight or more, more preferably 1% by weight or more.

  The weight ratio of the pigment in the aqueous pigment dispersion of the present invention to the polymer (I) as the dispersant according to the present invention may be appropriately selected and determined. Generally, 1 part by weight of the pigment is used. The polymer (I) (the total when two or more polymers (I) are included) is 0.01 parts by weight or more, especially 0.05 parts by weight or more, particularly 0.1 parts by weight or more. The upper limit is preferably 2 parts by weight or less, and particularly preferably 1.5 parts by weight or less. If the amount of the polymer (I) is less than this range, the dispersion stability is lowered, and if it is too much, the viscosity of the dispersion liquid and ink is increased and the dischargeability is lowered.

  The aqueous pigment dispersion of the present invention may contain components other than the above-mentioned aqueous medium, pigment, and polymer (I) as a dispersant, and in particular, the ink composition of the present invention as described later. Polymers other than the polymer (I) exemplified as other additives that can be contained in the product, and other components may be contained.

[Ink composition (recording liquid)]
The ink composition of the present invention containing the aqueous pigment dispersion of the present invention characterized by containing the above-mentioned polymer (I) as a dispersant exhibits particularly excellent effects as a recording liquid, particularly an inkjet recording liquid.
The ink composition of the present invention used as a recording liquid (hereinafter referred to as “recording liquid of the present invention”) adjusts the colorant concentration of the above-described aqueous pigment dispersion of the present invention as necessary, and further uses Depending on the conditions, various additives are added.

  As the colorant, in addition to the pigment in the aqueous pigment dispersion of the present invention described above, it is further dispersed with a self-dispersing pigment surface-treated for purposes such as toning, a dye, a surfactant, a polymer dispersant, etc. It may also contain added pigments or dyes.

  The concentration of the total colorant in the recording liquid of the present invention is preferably 0.1% by weight or more, more preferably 0.5% by weight or more, and the upper limit is 20% by weight, based on the total amount of the recording liquid. Hereinafter, it is preferably 15% by weight or less, particularly preferably 10% by weight or less. If the colorant concentration is too high, the viscosity is increased and the discharge property is deteriorated. If the colorant concentration is too low, the print density is too low. On the other hand, the amount of the colorant added to the aqueous pigment dispersion is usually 100 parts by weight or less, preferably 75 parts by weight or less, more preferably 50 parts by weight or less with respect to 100 parts by weight of the pigment in the aqueous pigment dispersion. The amount is particularly preferably 25 parts by weight or less. If the additional amount of the colorant is too large, the effect of the present invention is reduced.

  The solvent used in the recording liquid of the present invention preferably contains water and a water-soluble organic solvent, and can further contain other components as desired.

The concentration of the water-soluble organic solvent in the recording liquid of the present invention may be appropriately selected and determined. Usually, it is preferably 1% by weight or more and 45% by weight or less, more preferably 40% by weight or less with respect to the recording liquid. In addition, the content of water in the recording liquid may be an amount that can appropriately set the concentration of the above-described colorant, water-soluble organic solvent, and optional additive components described below.
As the water-soluble organic solvent, those exemplified as the aqueous medium of the aqueous pigment dispersion of the present invention described above can be used.

The recording liquid of the present invention may contain various additives as necessary within the range not impairing the effects of the present invention.
Examples of such additives include recording liquids such as penetration accelerators, surface tension modifiers, hydrotropic agents, pH adjusters, chelating agents, preservatives, viscosity modifiers, moisturizers, antifungal agents, and rust inhibitors. Known additives can be used.
The content of these additives in the recording liquid of the present invention is usually 30% by weight or less, and particularly preferably 15% by weight or less, based on the total amount of the recording liquid.

  Examples of penetration enhancers include lower alcohols such as methanol, ethanol, propanol, isopropanol, butanol, isobutanol and pentanol, carbitols such as ethylene glycol monobutyl ether and triethylene glycol monobutyl ether glycol ether, and surfactants 1 A seed | species or 2 or more types is mentioned.

  As the surfactant, any one or more of nonionic surfactants, anionic surfactants, cationic surfactants, amphoteric surfactants, polymer surfactants and the like can be used. Can be used. Of these, nonionic surfactants, anionic surfactants and polymer surfactants are preferred.

  Nonionic surfactants include, for example, polyoxyethylene alkyl ethers, polyoxyethylene alkyl aryl ethers, polyoxyethylene derivatives, oxyethylene / oxypropylene block copolymers, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid Examples thereof include esters, polyoxyethylene sorbitol fatty acid esters, glycerin fatty acid esters, polyoxyethylene fatty acid esters, polyoxyethylene alkylamines, acetylene glycols, and acetylene alcohols.

  Examples of the anionic surfactant include fatty acid salts, alkyl sulfate esters, alkyl benzene sulfonates, alkyl naphthalene sulfonates, alkyl sulfosuccinates, alkyl diphenyl ether sulfonates, alkyl phosphates, polyoxyethylene alkyl sulfates. Examples include ester salts, polyoxyethylene alkylaryl sulfate esters, alkane sulfonates, naphthalene sulfonate formalin condensates, polyoxyethylene alkyl phosphates, α-olefin sulfonates, and the like.

  Polymeric surfactants include polyacrylic acid, styrene / acrylic acid copolymer, styrene / acrylic acid / acrylic acid ester copolymer, styrene / maleic acid copolymer, styrene / maleic acid / acrylic acid ester copolymer, styrene / methacrylic acid. Examples thereof include acid copolymers, styrene / methacrylic acid / acrylic acid ester copolymers, styrene / maleic acid half ester copolymers, styrene / styrene sulfonic acid copolymers, vinyl naphthalene / maleic acid copolymers, vinyl naphthalene / acrylic acid copolymers, and salts thereof.

  Examples of the cationic surfactant include, but are not limited to, tetraalkylammonium salts, alkylamine salts, benzalkonium salts, alkylpyridium salts, imidazolium salts, and the like.

  In addition, silicone surfactants such as polysiloxane oxyethylene adducts, fluorine surfactants such as perfluoroalkyl carboxylates, perfluoroalkyl sulfonates, oxyethylene perfluoroalkyl ethers, rhamnolipids, lysolecithins, etc. Surfactants such as biosurfactants can also be used.

  The content of these surfactants may be selected and determined as appropriate. Usually, by adding in the range of 0.001 wt% or more and 5 wt% or less with respect to the recording liquid, the quick drying property and the print quality of the printed matter can be further improved.

  Examples of the surface tension adjusting agent include alcohols such as diethanolamine, triethanolamine, glycerin, and diethylene glycol, nonions, cations, anions, and amphoteric surfactants.

  As the hydrotropic agent, one or more of urea, alkylurea, ethyleneurea, propyleneurea, thiourea, guanidate, tetraalkylammonium halide and the like are preferable.

  As a humectant, 1 type (s) or 2 or more types, such as glycerol and diethylene glycol, can also be added as what also serves as a water-soluble organic solvent.

  Furthermore, a solid moisturizing agent (a water-soluble substance having a water retaining function and solid at 25 ° C.) can also be added. Preferred solid humectants include saccharides, sugar alcohols, hyaluronate, trimethylolpropane, 1,2,6-triol and the like. Examples of the saccharide include monosaccharides, disaccharides, oligosaccharides (including trisaccharides and tetrasaccharides), and polysaccharides. Specifically, glucose, fructose, ribose, xylose, arabinose, galactose, sorbit, maltose, and lactose. , Sucrose, trehalose and the like. Examples of sugar alcohols include maltitol, sorbitol, xylitol, and the like, and one or more of these solid humectants can be added.

  Although it does not specifically limit as a chelating agent, 1 type (s) or 2 or more types, such as a sodium salt of ethylenediaminetetraacetic acid, a diammonium salt of ethylenediaminetetraacetic acid, are used. These are preferably used in the range of 0.005 wt% to 0.5 wt% with respect to the recording liquid.

  The antifungal agent is not particularly limited, but sodium dehydroacetate, dichlorophen, sorbic acid, sodium benzoate, p-hydroxybenzoate, 1,2-Benzisothiazoline-3-one (product name: Proxel) GXL (manufactured by Arch Chemicals)) or the like is used. These are preferably contained in the range of 0.05 wt% to 1 wt% with respect to the recording liquid.

Further, in order to adjust the pH of the recording liquid and obtain the stability of the recording liquid, it is not particularly limited, but sodium hydroxide, potassium hydroxide, lithium hydroxide, nitric acid, ammonia, diethanolamine, triethanolamine, etc. PH adjusters and buffer solutions such as phosphoric acid can be used.
The pH of the recording liquid is usually in the neutral to alkaline range, and is preferably adjusted to about pH 6 to 11.

  Further, the recording liquid of the present invention preferably contains a resin other than the aforementioned polymer (I) within a range not impairing the effects of the present invention. Specific examples of such resins include vinyl resins such as acrylic resins, styrene-acrylic resins, polyvinyl alcohol resins, vinyl acetate resins, and polyester resins, polyamide resins, polyurethane resins, and epoxy resins. And known resins such as butadiene-based resins, petroleum-based resins, and fluorine-based resins. Among these, water-soluble or water-dispersible resins are preferable. Of these, polyvinyl alcohol resins and acrylic resins are more preferable, and polyvinyl alcohol resins are particularly preferable. Among the polyvinyl alcohol resins, the following resins are more preferable.

  Preferable polyvinyl alcohol resins include those containing a vinyl alcohol structural unit represented by the following general formula (3) and a hydrophobic group in the polymer (hereinafter referred to as “polymer (II)”). In the polymer (II), only one kind of vinyl alcohol structural unit represented by the following general formula (3) may be contained, or two or more kinds may be contained. Moreover, only 1 type of hydrophobic groups may be contained and 2 or more types may be contained.

（式（３）中、Ｒ^３は水素原子又は炭素数１〜６の炭化水素基を表す）

(In formula (3), R ³ represents a hydrogen atom or a hydrocarbon group having 1 to 6 carbon atoms)

Specific examples of R ³ in the general formula (3) include methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, t-butyl group, sec-butyl group, pentyl group, isopentyl group, neopentyl group. And alkyl groups such as a group, t-pentyl group, and hexyl group. Among these, a hydrogen atom or an alkyl group having a small number of carbon atoms is preferable, specifically, an alkyl group having 1 to 3 carbon atoms is preferable, and a hydrogen atom or a methyl group is particularly preferable.

  Examples of the vinyl alcohol structural unit represented by the general formula (3) include vinyl alcohol, α-methyl vinyl alcohol, α-ethyl vinyl alcohol, α-propyl vinyl alcohol, α-butyl vinyl alcohol, and α-hexyl vinyl. Examples include structural units derived from alcohols and the like.

  On the other hand, examples of hydrophobic groups include aliphatic hydrophobic groups such as alkyl groups, alkenyl groups, and alkynyl groups, alicyclic hydrophobic groups such as cyclohexyl groups and isobornyl groups, and aromatic groups such as phenyl groups and naphthyl groups. System hydrophobic groups. These groups may be unsubstituted or may further have a substituent.

  In order to introduce the vinyl alcohol structural unit represented by the general formula (3) and the hydrophobic group into the polymer structure, a polymerizable monomer that induces a vinyl alcohol structural unit such as a vinyl ether monomer or a vinyl ester monomer and a hydrophobic group are introduced. After polymerizing with a polymerizable monomer having a functional group and introducing them into the polymer structure, the side chain portion of the vinyl ether monomer or vinyl ester monomer is modified by the above general formula (3 It may be converted into a vinyl alcohol structural unit represented by

  Examples of vinyl ether monomers that derive the vinyl alcohol structural unit represented by the general formula (3) include methyl vinyl ether, ethyl vinyl ether, isopropyl vinyl ether, n-butyl vinyl ether, t-butyl vinyl ether, isobutyl vinyl ether, cyclohexyl vinyl ether, Examples thereof include n-hexadecyl vinyl ether, 2-chloroethyl vinyl ether, phenyl vinyl ether, benzyl vinyl ether, and trimethylsilyl vinyl ether.

  Examples of the vinyl ester monomer for deriving the vinyl alcohol structural unit include vinyl acetate, vinyl propionate, vinyl laurate, vinyl stearate, vinyl pivalate, vinyl formate, vinyl caproate, vinyl caprate, myristine. Vinyl acetate, vinyl palmitate, vinyl 2-ethylhexanoate, vinyl cyclohexanecarboxylate, vinyl monochloroacetate, vinyl adipate, vinyl methacrylate, vinyl crotonate, vinyl sorbate, vinyl benzoate, vinyl cinnamate, these α -Substituent etc. are mentioned.

  In addition, the vinyl alcohol structural unit and the hydrophobic group represented by the general formula (3) contained in the vinyl alcohol-based polymer are a main chain and / or side chain portion in the polymer structure by a modification reaction or a modification reaction. May be introduced.

  The polymer (II) only needs to contain a vinyl alcohol structural unit represented by the general formula (3) and a hydrophobic group, and other oxyalkylene groups, hydroxyl groups, amide groups, pyrrolidone groups, oxazoline groups, etc. Representative hydrophilic groups, carboxylic acid groups, sulfonic acid groups, acidic groups typified by phosphoric acid groups, basic groups typified by amino groups, pyridinium groups, imidazolium groups, and even acidic groups and basic groups And an ionic dissociation group which is a salt thereof. Among these, an ionic dissociation group structure that is an acidic group, a basic group, or a salt thereof is preferably included.

  The hydrophobic group and the ionic dissociation group contained in the polymer (II) are preferably contained in the polymer structure as monomer structural units. That is, the polymer (II) is particularly preferably a polymer including the vinyl alcohol structural unit represented by the general formula (3), the monomer structural unit having a hydrophobic group, and the monomer structural unit having an ionic dissociation group.

  The form of the polymer (II) is not particularly limited, such as a random copolymer, a diblock copolymer, a triblock or more multiblock copolymer, a gradient copolymer, a graft copolymer, a star copolymer, etc. Among them, a block copolymer is preferable.

In the recording liquid of the present invention, the content of all the resins including the above-mentioned polymer (I) and other resins such as the polymer (II) is usually 0.05% by weight or more, preferably 0.25% by weight. Above, more preferably 0.5% by weight or more, and the upper limit is usually 20% by weight or less, and preferably 10% by weight or less. In addition, as a use ratio of the polymer (I) and other resins, the weight ratio of the polymer (I) and the other resin may be appropriately selected and determined in the range of 99: 1 to 1:99. In order to effectively exhibit the above-described improvement effect by the polymer (I), specifically, the other resin is 10 parts by weight or less, particularly 5 parts by weight or less with respect to 1 part by weight of the total amount of the polymer (I). In particular, the amount is preferably 3 parts by weight or less.
In particular, when the polymer (I) and the polymer (II) are used in combination, the use ratio thereof is specifically the total amount of the polymer (I) in order to effectively exhibit the above-described improvement effect by the polymer (I). The amount of the polymer (II) is preferably 10 parts by weight or less, more preferably 5 parts by weight or less, and particularly preferably 3 parts by weight or less.

In addition, polymer fine particles may be added to the recording liquid of the present invention in order to further improve the fixability of images on a recording medium and the abrasion resistance. The polymer fine particles are not particularly limited, but those having an ionic group on the surface and a particle diameter of 10 to 150 nm are preferable.
The amount of the polymer fine particles used may be appropriately selected and determined within a range not impairing the effects of the present invention. Specifically, it is 1 to 100% by weight, preferably 10 to 80%, based on the pigment in the recording liquid. % By weight, more preferably 10 to 50%.

[Method for producing aqueous pigment dispersion and ink composition]
In the method for producing the aqueous pigment dispersion of the present invention containing the polymer (I) described above as the dispersant, the mixing method and the order of addition of the pigment, the aqueous medium, the dispersant and the like are arbitrary. For example, (a) What is necessary is just to disperse | distribute the thing which mixed the aqueous medium, the (b) pigment, and the mixture which has (c) a dispersing agent as a main component at once using a common disperser.

  As the disperser used for the dispersion treatment, various dispersers that are generally used for pigment dispersion can be used.

  The disperser is not particularly limited, and a paint shaker, ball mill, sand mill, attritor, pearl mill, coball mill, homomixer, homogenizer, wet jet mill, high pressure homogenizer, ultrasonic homogenizer, and the like can be used. Glass beads, zirconia beads, alumina beads, magnetic beads, and styrene beads can be used for those using media as a disperser. Among these, a particularly preferable dispersion treatment method is a method in which beads are dispersed with a mill using a medium and then dispersed with an ultrasonic homogenizer.

  A method for obtaining a pigment dispersion having a preferable particle size is not particularly limited, but the size of the dispersion medium of the disperser is reduced, the filling rate of the grinding media is increased, and the pigment concentration in the dispersion is increased. Methods such as increasing the length, increasing the processing time, and classifying with a filter or a centrifuge after pulverization are used. Or the combination of those methods is mentioned. Although not particularly defined, when the dispersion becomes thick due to heat generation during dispersion, it is desirable to perform the dispersion treatment while cooling.

  As described above, the ink composition of the present invention is prepared by adding a colorant and various additives as necessary to the aqueous pigment dispersion thus produced, and mixing and dispersing the mixture in the same manner. .

  Hereinafter, the present invention will be described more specifically with reference to synthesis examples, examples, and comparative examples. However, the present invention is not limited to the following examples unless it exceeds the gist.

  In the following examples, the weight average molecular weight (Mw) is measured with a polystyrene standard sample for polymer (I) (random copolymers A to H) and with polyethylene glycol for polymer (II) (block copolymer X). Using standard calibrated gel permeation chromatography (GPC), the following conditions were used.

<GPC measurement conditions for polymer (I)>
Column packing: Styrene-divinylbenzene copolymer Solvent: Tetrahydrofuran Flow rate: 0.7ml / min
Temperature: 40 ° C
Calibration was performed using polystyrene.
In addition, this time, it measured using the following apparatuses, detectors, and columns.
Apparatus: Waters 2690 manufactured by Nippon Waters Co., Ltd.
Detector: Waters 2410 manufactured by Nippon Waters Co., Ltd.
Column: Shodex KF-604 / KF-603 / KF-602.5 manufactured by Showa Denko KK

<GPC measurement conditions for polymer (II)>
Column packing material: Polyhydroxymethacrylate Solvent: Water / acetonitrile
(70/30 (v / v), 0.2M Tris-HCl buffer, 0.1M KCl included)
Flow rate: 0.7mL / min
Temperature: 40 ° C
Calibration was performed using polyethylene glycol.
In addition, this time, it measured using the following apparatuses, detectors, and columns.
Apparatus: Waters 2695 made by Nippon Waters Co., Ltd.
Detector: Waters 2410 manufactured by Nippon Waters Co., Ltd.
Column used: Shodex OHpak manufactured by Showa Denko KK
SB-G / SB-804HQ / SB-803HQ / SB-802.5HQ

In the following notation, “b” means block polymer, and “co” means copolymer.
Hereinafter, the “structural unit” may be simply referred to as “unit”.

[Polymer synthesis]
<Synthesis Example 1>
Synthesis of poly (styrene-co-methoxypolyethyleneglycol acrylate-co-sodium acrylate) (Random Copolymer A) Into a flask with a nitrogen-substituted interior, a nitrogen introduction tube, a stirrer and a thermometer, 2 , 2′-azobis (2,4-dimethylvaleronitrile) 16.8 g, methanol 1817.3 g as a solvent, styrene 455.2 g as a monomer, methoxypolyethylene glycol acrylate (light acrylate 130A, manufactured by Kyoeisha Chemical Co., Ltd.) In the general formula (2), m = 9) 805.2 g and 49.0 g of acrylic acid were charged. The bath temperature was raised from room temperature to 70 ° C. over 30 minutes, and a polymerization reaction was carried out at 70 ° C. for 4 hours. Thereafter, a solution obtained by dissolving 7.0 g of 2,2′-azobis (2,4-dimethylvaleronitrile) as a polymerization initiator in 70 g of methanol was added to the reaction system, and a polymerization reaction was further performed for 6 hours.

  After completion of the reaction, the reaction solution was cooled to room temperature, 95.2 g of 5N sodium hydroxide aqueous solution was added with stirring, and then distilled water was added while removing methanol with an evaporator to obtain a crude polymer aqueous solution. . After removing impurities from the crude polymer aqueous solution by ultrafiltration, the polymer aqueous solution is concentrated and dried to obtain water-soluble poly (styrene-co-methoxypolyethylene glycol acrylate-co-sodium acrylate): random copolymer A. It was. The number average molecular weight (Mn) of this random copolymer A determined by gel permeation chromatography (GPC) was 10,000, the weight average molecular weight (Mw) was 19000, and the molecular weight distribution (Mw / Mn) was 1.9.

The structure of the random copolymer A was confirmed by ¹ H-NMR using d-DMSO (dimethyl sulfoxide) as a solvent. As a result, the styrene unit, methoxypolyethylene glycol acrylate unit, and sodium acrylate in the random copolymer A (in terms of acrylic acid) ) Unit composition ratio was 61/20/19 (molar ratio) = 37/55/8 (weight ratio). (Hydrophobic monomer structural unit / oxyalkylene-containing monomer structural unit (weight ratio) = 0.67)
Polymer A is in a state in which 70 mol% of carboxyl groups which are ionic groups are neutralized by the above-described steps, and an aqueous solution having a concentration of 15.3% by weight and 10.5% by weight is prepared at 25 ° C. It was colorless and transparent.

<Synthesis Example 2>
Synthesis of poly (styrene-co-methoxypolyethyleneglycol acrylate-co-sodium acrylate) (Random Copolymer B) Into a flask with a nitrogen-substituted interior, a nitrogen introduction tube, a stirrer and a thermometer, 2 , 2′-azobis (2,4-dimethylvaleronitrile) 5.6 g, 700 g of methanol as a solvent, 349.9 g of styrene as a monomer, methoxypolyethylene glycol acrylate (Light Acrylate 130A, manufactured by Kyoeisha Chemical Co., Ltd.) 809. 8 g and 121.0 g of acrylic acid were charged. The bath temperature was raised from room temperature to 70 ° C. over 30 minutes, and a polymerization reaction was carried out at 70 ° C. for 4 hours. Thereafter, a solution prepared by dissolving 5.6 g of 2,2′-azobis (2,4-dimethylvaleronitrile) as a polymerization initiator in 56 g of methanol was added to the reaction system, and the polymerization reaction was further performed for 6 hours.

  After completion of the reaction, the reaction solution was cooled to room temperature, 235.3 g of 5N sodium hydroxide aqueous solution was added with stirring, and then distilled water was added while removing methanol with an evaporator to obtain a crude polymer aqueous solution. . After removing impurities from the crude polymer aqueous solution by ultrafiltration, the polymer aqueous solution is concentrated and dried to obtain water-soluble poly (styrene-co-methoxypolyethylene glycol acrylate-co-sodium acrylate): random copolymer B. It was. The random polymer B obtained by gel permeation chromatography (GPC) had a number average molecular weight (Mn) of 15000, a weight average molecular weight (Mw) of 31500, and a molecular weight distribution of (Mw / Mn) of 2.1. .

The structure of the random copolymer B was confirmed by ¹ H-NMR using d-DMSO as a solvent. The composition of the styrene unit, the methoxypolyethylene glycol acrylate unit, and the sodium acrylate (acrylic acid equivalent) unit in the random copolymer B. The ratio was 56/21/23 (molar ratio) = 33/58/9 (weight ratio). (Hydrophobic monomer structural unit / oxyalkylene-containing monomer structural unit (weight ratio) = 0.57)
Polymer B was in a state in which 70 mol% of carboxyl groups which are ionic groups were neutralized by the above-described process, and when an aqueous solution having a concentration of 10.1 wt% was prepared, it was colorless and transparent at 25 ° C.

<Synthesis Example 3>
Synthesis of poly (styrene-co-2-hydroxyethylacrylamide-co-methoxypolyethylene glycol acrylate-co-sodium acrylate) (random copolymer C) with condenser, nitrogen inlet tube, stirrer and thermometer inside Was charged with 3.9 g of 2,2′-azobis (2,4-dimethylvaleronitrile) as a polymerization initiator, 416.0 g of methanol as a solvent, 63.0 g of styrene as a monomer, and 43. 2-hydroxyethylacrylamide. The flask was charged with 5 g, 182.6 g of methoxypolyethylene glycol acrylate (Light Acrylate 130A, manufactured by Kyoeisha Chemical Co., Ltd.), and 10.9 g of acrylic acid. The bath temperature was raised from room temperature to 70 ° C. over 30 minutes, and a polymerization reaction was carried out at 70 ° C. for 5 hours. Thereafter, a solution prepared by dissolving 1.6 g of 2,2′-azobis (2,4-dimethylvaleronitrile) as a polymerization initiator in 14.0 g of methanol was added to the reaction system, and the polymerization reaction was further performed for 3 hours. .

  After completion of the reaction, the reaction solution was cooled to room temperature, 28.70 g of 5N sodium hydroxide aqueous solution was added with stirring, and then distilled water was added while removing methanol with an evaporator to obtain a crude polymer aqueous solution. . After removing impurities from the crude aqueous polymer solution by ultrafiltration, the aqueous polymer solution is concentrated and dried to poly (styrene-co-2-hydroxyethylacrylamide-co-methoxypolyethylene glycol acrylate-co-sodium acrylate): Random copolymer C was obtained. The random copolymer C obtained by gel permeation chromatography (GPC) had a number average molecular weight (Mn) of 10,200, a weight average molecular weight (Mw) of 19,500, and a molecular weight distribution (Mw / Mn) of 1.9.

The structure of this random copolymer C was confirmed by ¹ H-NMR using D ₂ O as a solvent. The composition ratio of the styrene unit, 2-hydroxyethylacrylamide unit, methoxypolyethylene glycol acrylate unit, and sodium acrylate (acrylic acid equivalent) unit in the random copolymer C determined by ¹ H-NMR was 50/13/24. / 13 (molar ratio) = 27/8/60/5 (weight% ratio). (Hydrophobic monomer structural unit / oxyalkylene-containing monomer structural unit (weight ratio) = 0.45)
Polymer C was in a state in which 95 mol% of carboxyl groups, which are ionic groups, were neutralized by the above-mentioned process. When an aqueous solution having a concentration of 26.4% by weight was prepared, it was colorless and transparent at 25 ° C.

<Synthesis Example 4>
Synthesis of poly (styrene-co-methoxypolyethyleneglycol acrylate-co-sodium acrylate) (Random Copolymer D) Into a flask with a nitrogen-substituted interior, a nitrogen introduction tube, a stirrer and a thermometer, 2 , 2′-azobis (2,4-dimethylvaleronitrile) 16.9 g, 1834.8 g of methanol as a solvent, 272.4 g of styrene as a monomer, methoxypolyethylene glycol acrylate (Light Acrylate 130A, manufactured by Kyoeisha Chemical Co., Ltd.) 1009.9 g and 37.7 g of acrylic acid were charged. The bath temperature was raised from room temperature to 70 ° C. over 30 minutes, and a polymerization reaction was carried out at 70 ° C. for 4 hours. Thereafter, a solution prepared by dissolving 7.0 g of 2,2′-azobis (2,4-dimethylvaleronitrile) as a polymerization initiator in 70.0 g of methanol was added to the reaction system, and the polymerization reaction was further performed for 6 hours. .

  After completion of the reaction, the reaction solution was cooled to room temperature, 86.8 g of 5N sodium hydroxide aqueous solution was added with stirring, and then distilled water was added while removing methanol with an evaporator to obtain a crude polymer aqueous solution. . After removing impurities from the crude polymer aqueous solution by ultrafiltration, the polymer aqueous solution is concentrated and dried to obtain water-soluble poly (styrene-co-methoxypolyethylene glycol acrylate-co-sodium acrylate): random copolymer D. It was. The random polymer D obtained by gel permeation chromatography (GPC) had a number average molecular weight (Mn) of 11000, a weight average molecular weight (Mw) of 20700, and a molecular weight distribution (Mw / Mn) of 1.9.

The structure of the random copolymer D was confirmed by ¹ H-NMR using d-DMSO as a solvent. The composition ratio of the styrene unit, methoxypolyethylene glycol acrylate unit, and sodium acrylate (acrylic acid equivalent) unit in the random copolymer. Was 57/33/10 (molar ratio) = 26/71/3 (weight ratio). (Hydrophobic monomer structural unit / oxyalkylene chain monomer structural unit (weight ratio) = 0.37)
Polymer D was in a state where 83 mol% of the carboxyl groups which are ionic groups were neutralized by the above-mentioned process, and when an aqueous solution having a concentration of 13.1 wt% was prepared, it was colorless and transparent at 25 ° C.

<Synthesis Example 5>
Synthesis of poly (sodium acrylate-co-n-butyl acrylate-co-styrene) (Random Copolymer E) In a flask equipped with a nitrogen-substituted condenser, a nitrogen introducing tube, a stirrer and a thermometer, 2 was added as a polymerization initiator. , 2′-azobis (2,4-dimethylvaleronitrile) 30 g, tetrahydrofuran 3500.0 g as a solvent, acrylic acid 600.0 g, n-butyl acrylate 600.0 g, and styrene 400.0 g as the above flask. Prepared inside. The bath temperature was raised from room temperature to 70 ° C. over 1 hour, and the polymerization reaction was carried out at 70 ° C. for 8 hours.

  After completion of the reaction, the reaction solution was cooled to room temperature, neutralized with a sodium hydroxide / methanol solution, and precipitated in isopropyl alcohol. The precipitate was filtered and dried under vacuum to obtain a mixture of poly (sodium acrylate-co-n-butyl acrylate-co-styrene) and sodium acrylate. The number average molecular weight (Mn) of this polymer was 11000, the weight average molecular weight (Mw) was 17600, and the molecular weight distribution (Mw / Mn) was 1.6.

30.0 g of the mixture of the random copolymer and sodium acrylate was dissolved in 970.0 g of water, and then sodium acrylate was removed by ultrafiltration. After removing sodium acrylate, the aqueous polymer solution was concentrated and dried to obtain the random copolymer E.
The structure of this random copolymer E was confirmed by ¹ H-NMR using D ₂ O as a solvent. The composition ratio of the styrene unit, n-butyl acrylate unit, and sodium acrylate (acrylic acid equivalent) unit in the random copolymer E determined by ¹ H-NMR is 32/21/47 (molar ratio) = 35 / It was 29/36 (weight% ratio).

<Synthesis Example 6>
Synthesis of poly (styrene-co-methoxypolyethyleneglycol acrylate-co-sodium acrylate) (Random Copolymer F) Into a flask equipped with a nitrogen-substituted interior, a nitrogen introduction tube, a stirrer and a thermometer, 2 , 2'-azobis (2,4-dimethylvaleronitrile) 15.6 g, 1722.5 g of methanol as a solvent, 324.9 g of styrene as a monomer, methoxypolyethylene glycol acrylate (Light Acrylate 130A, manufactured by Kyoeisha Chemical Co., Ltd.) 751.9 g and 112.3 g of acrylic acid were charged into the flask. The bath temperature was raised from room temperature to 70 ° C. over 30 minutes, and a polymerization reaction was carried out at 70 ° C. for 4 hours. Thereafter, a solution prepared by dissolving 6.5 g of 2,2′-azobis (2,4-dimethylvaleronitrile) as a polymerization initiator in 65 g of methanol was added to the reaction system, and a polymerization reaction was further performed for 6 hours.

  After completion of the reaction, the reaction solution was cooled to room temperature, 312.3 g of 5N sodium hydroxide aqueous solution was added with stirring, and then distilled water was added while removing methanol with an evaporator to obtain a crude polymer aqueous solution. . After removing impurities from the crude polymer aqueous solution by ultrafiltration, the polymer aqueous solution was concentrated and dried to obtain poly (styrene-co-methoxypolyethylene glycol acrylate-co-sodium acrylate): random copolymer F. The random copolymer F obtained by gel permeation chromatography (GPC) had a number average molecular weight (Mn) of 8000, a weight average molecular weight (Mw) of 17,600, and a molecular weight distribution (Mw / Mn) of 2.2.

The structure of this random copolymer F was confirmed by ¹ H-NMR using d-DMSO as a solvent. The composition ratio of the styrene unit, methoxypolyethylene glycol acrylate unit, and sodium acrylate (acrylic acid equivalent) unit in the random copolymer F determined by ¹ H-NMR is 52/19/29 (molar ratio) = 32 / 55/13 (% by weight). (Hydrophobic monomer structural unit / oxyalkylene-containing monomer structural unit (weight ratio) = 0.58)
Polymer F was in a state in which almost all of the carboxyl groups, which are ionic groups, were neutralized by the above-described process. When an aqueous solution having a concentration of 17.6% by weight was prepared, it was colorless and transparent at 25 ° C.

<Synthesis Example 7>
Synthesis of poly (styrene-co-methoxypolyethyleneglycol methacrylate) (Random Copolymer G) 2,2′-Azobis (as a polymerization initiator) was placed in a condenser equipped with nitrogen, a nitrogen inlet tube, a stirrer and a thermometer. 2,4-dimethylvaleronitrile) 2.2 g, methanol 210.7 g as solvent, styrene 60.3 g as monomer, methoxypolyethylene glycol methacrylate (Light Acrylate 130A, manufactured by Kyoeisha Chemical Co., Ltd.) 140.1 g as above The flask was charged. The bath temperature was raised from room temperature to 70 ° C. over 30 minutes, and a polymerization reaction was carried out at 70 ° C. for 4 hours. Thereafter, a solution prepared by dissolving 0.9 g of 2,2′-azobis (2,4-dimethylvaleronitrile) as a polymerization initiator in 9.2 g of methanol was added to the reaction system, and the polymerization reaction was further performed for 4 hours. .

  After completion of the reaction, the reaction solution was cooled to room temperature, and distilled water was added while removing methanol with an evaporator to obtain a crude polymer aqueous solution. After removing impurities from the crude polymer aqueous solution by ultrafiltration, the polymer aqueous solution was concentrated and dried to obtain poly (styrene-co-methoxypolyethyleneglycol methacrylate): random copolymer G. The random copolymer G obtained by gel permeation chromatography (GPC) had a number average molecular weight (Mn) of 12000, a weight average molecular weight (Mw) of 21600, and a molecular weight distribution (Mw / Mn) of 1.8.

The structure of this random copolymer G was confirmed by ¹ H-NMR using d-DMSO as a solvent. The composition ratio of the styrene unit and the methoxypolyethylene glycol methacrylate unit in the random copolymer G determined by ¹ H-NMR was 70/30 (molar ratio) = 33/67 (% by weight). (Hydrophobic monomer structural unit / oxyalkylene chain monomer structural unit (weight ratio) = 0.49)
Polymer G was colorless and transparent at 25 ° C. when an aqueous solution having a concentration of 14.0% by weight was prepared.

<Synthesis Example 8>
Synthesis of poly (styrene-co-methoxypolyethyleneglycol acrylate-co-sodium acrylate) (Random Copolymer H) Into a flask equipped with a nitrogen-substituted interior, a nitrogen introduction tube, a stirrer and a thermometer, 2 , 2'-azobis (2,4-dimethylvaleronitrile) 2.8 g, 318.5 g of methanol as a solvent, 87.8 g of styrene as a monomer, methoxypolyethylene glycol acrylate (Light Acrylate 130A, manufactured by Kyoeisha Chemical Co., Ltd.) 108.2 g and 4.1 g of acrylic acid were charged. The bath temperature was raised from room temperature to 70 ° C. over 30 minutes, and a polymerization reaction was carried out at 70 ° C. for 4 hours. Thereafter, a solution obtained by dissolving 1.2 g of 2,2′-azobis (2,4-dimethylvaleronitrile) as a polymerization initiator in 12.0 g of methanol was added to the reaction system, and the polymerization reaction was further performed for 6 hours. .

  After completion of the reaction, the reaction solution was cooled to room temperature, 22.2 g of a 10 wt% sodium hydroxide methanol solution was added with stirring, and then distilled water was added while removing the methanol with an evaporator to obtain a crude polymer aqueous solution. Got. After removing impurities from the crude polymer aqueous solution by ultrafiltration, the polymer aqueous solution is concentrated and dried to obtain water-soluble poly (styrene-co-methoxypolyethylene glycol acrylate-co-sodium acrylate): random copolymer H. It was. The random polymer H obtained by gel permeation chromatography (GPC) had a number average molecular weight (Mn) of 10,000, a weight average molecular weight (Mw) of 20000, and a molecular weight distribution of (Mw / Mn) of 2.0. .

The structure of the random copolymer H was confirmed by ¹ H-NMR using d-DMSO as a solvent, and the composition of styrene units, methoxypolyethylene glycol acrylate units, and sodium acrylate (in terms of acrylic acid) in the random copolymer H. The ratio was 74/14/12 (molar ratio) = 50/44/6 (weight ratio). (Hydrophobic monomer structural unit / oxyalkylene-containing monomer structural unit (weight ratio) = 1.14)
The polymer H was in a state in which almost all of the carboxyl groups which are ionic groups were neutralized by the above-described process. When an aqueous solution having a concentration of 14.0% by weight was prepared, the polymer H was colorless and transparent at 25 ° C.

<Synthesis Example 9>
Synthesis of polyvinyl alcohol-b-poly (sodium acrylate-co-methyl acrylate-co-sodium methacrylate-co-benzyl methacrylate-co-styrene) (block copolymer X) Capacitor with nitrogen substitution inside, nitrogen introduction tube Into a flask equipped with a stirrer and a thermometer, 3587 g of vinyl acetate, 1907 g of chloroform as a chain transfer agent and a solvent were charged, and the temperature was raised to 70 ° C. over 1 hour. Next, a polymerization initiator solution in which 0.3 g of azobis (2-methylbutyronitrile) as a polymerization initiator was dissolved in 534 g of chloroform was dropped over 6 hours. Thereafter, a polymerization initiator solution in which 0.5 g of azobis (2-methylbutyronitrile) as a polymerization initiator was dissolved in 444.5 g of chloroform was dropped over 5 hours. After dropwise addition of the polymerization initiator solution, the mixture was heated and polymerized for 10 hours under reflux conditions. After completion of the reaction, 0.01 N sodium hydroxide / methanol solution was continuously added dropwise to the reaction solution, and unreacted vinyl acetate and chloroform were distilled off under reduced pressure at an internal temperature of 40 ° C. to obtain a polyvinyl acetate methanol solution (polymer concentration). 74% by weight). This polyvinyl acetate had a number average molecular weight (Mn) of 3500 and a molecular weight distribution (Mw / Mn) of 2.4.

The terminal structure of the polyvinyl acetate was —CCl ₃ . This is because, in ¹ H-NMR (solvent CDCl ₃ ), a peak of a methylene group (peak of chemical shift δ = 2.8 to 3.2) was observed adjacent to the end of the polyvinyl acetate, Based on the fact that the number average molecular weight (3500) calculated by using -CCl ₃ as the terminal structure and the number average molecular weight determined from GPC coincide with each other, a group in which one end is quantitatively halogen-substituted (-CCl ₃ ) It was confirmed that the polyvinyl acetate having the above could be synthesized.

  Next, a condenser with a nitrogen-substituted interior, a nitrogen inlet tube, a stirrer and a thermometer-equipped flask, 17 g of methanol as a solvent and 1048.5 g of isopropyl alcohol, 2623 g of methyl acrylate, 2142 g of benzyl methacrylate, and styrene as monomers 63.5 g and the above polyvinyl acetate methanol solution 1353 g as a macroinitiator were charged, and the temperature was raised from room temperature to 60 ° C. over 1 hour. When the internal temperature reached 60 ° C., a catalyst solution in which 0.6 g of cuprous bromide as a catalyst and 12.0 g of tris (2-dimethylamino) ethylamine as a ligand were dissolved in 30 g of methanol was added. After addition of the catalyst solution, the mixture was heated and polymerized for 30 hours under reflux conditions.

  The number average molecular weight (Mn) of the obtained polymer increased with the lapse of the polymerization reaction time.

  Table 1 shows the molar ratio of each monomer of methyl acrylate (MA), benzyl methacrylate (BzMA), and styrene (St) in the polymer calculated from the amount of monomer consumption in the polymerization solution, obtained from gas chromatography. .

  As is clear from Table 1, the composition of the block copolymer linked with polyvinyl acetate changes as the number average molecular weight increases, and the monomer composition in the block copolymer changes toward the end (gradient). ) Polyvinyl acetate-b-poly (methyl acrylate-co-benzyl methacrylate-co-styrene) was confirmed. The polymer had a number average molecular weight of 16,300 and a molecular weight distribution (Mw / Mn) of 1.63. In this polyvinyl acetate block copolymer, the linking group connecting the polyvinyl acetate block and the other block is a dichloromethylene group.

  Next, in a reaction vessel equipped with a condenser, a stirrer and a thermometer, the above polymerized solution 502 g was dissolved in a mixed solvent of 276 g of methanol, 552 g of tetrahydrofuran and 138 g of water, and then the temperature was raised to 60 ° C. and 728 g of 5N sodium hydroxide aqueous solution. In addition, the reaction was carried out at 65 ° C. for 7 hours. After completion of the reaction, 550 g of tetrahydrofuran (THF) and 140 g of water were added to the polymer mass obtained by removing the supernatant and suspended, and then 280 g of methanol was added to precipitate the polymer. The supernatant was removed again, 300 g of water was added, neutralized with acetic acid, the solution was heated to 90 ° C., and the remaining THF and methanol were distilled off to obtain an aqueous polymer solution. Thereafter, impurities were removed from the aqueous polymer solution using an ultrafiltration membrane (ACP-1050, manufactured by Asahi Kasei Corporation). Polyvinyl alcohol-b-poly (sodium acrylate-co-methyl acrylate-co-methacrylic acid) in which the copolymer linked to the polyvinyl alcohol block is a gradient copolymer by concentrating and drying the polymer aqueous solution after ultrafiltration Sodium-co-benzyl methacrylate-co-styrene) (block copolymer X) was obtained.

  In this polyvinyl alcohol block copolymer X, the linking group linking the polyvinyl alcohol block and the other block is one in which some or all of the chlorine atoms in the linking group (dichloromethylene group) are replaced with hydrogen atoms. It is.

The structure of the block copolymer X was confirmed by ¹ H-NMR using D ₂ O as a solvent. The composition ratio of vinyl alcohol units, sodium acrylate units, methyl acrylate units, sodium methacrylate units, benzyl methacrylate units, and styrene units in the block polymer X determined by ¹ H-NMR was 25:26:21. : 2: 21: 5 (molar ratio). The number average molecular weight (Mn) of the polymer was 14,000, the weight average molecular weight (Mw) was 22200, and the molecular weight distribution (Mw / Mn) was 1.59.

[Examples and Comparative Examples]
Hereinafter, random copolymers A to D, which are the polymers (I) according to the present invention obtained in Synthesis Examples 1 to 4, and random copolymers E to H other than the polymer (I) obtained in Synthesis Examples 5 to 8, Furthermore, the manufacture example of an aqueous pigment dispersion using the block copolymer X which is the polymer (II) obtained in Synthesis Example 9 and the evaluation results of the ink using the same are shown.

<Example 1>
Carbon black (Mitsubishi Chemical Corporation: # 960) 28.0 g, random copolymer A aqueous solution (random copolymer A concentration 15.3% by weight) 110.0 g, and distilled water 142.1 g were mixed, and 0.5 mmφ zirconia The beads were dispersed using a self-made bead mill as a medium at 25 ° C. for 8 hours. After removing the beads, the pigment concentration was adjusted to 8% by weight to obtain dispersion a.
This dispersion a was placed in a 500 ml tall beaker, the beaker was immersed in ice water, and dispersed for 30 minutes with an ultrasonic homogenizer (Nippon Seiki Seisakusho; US-600T; used chip 36 mmφ) to obtain pigment dispersion A. .

The dispersion A was used to make an ink according to the following formulation.
Dispersion A 7.50 g
Distilled water 3.83g
1,5-hexanediol 0.45g
2-pyrrolidone 0.38g
Triethylene glycol monobutyl ether 0.15 g
Glycerin 2.10g
Triethylene glycol 0.30g
Triisopropanolamine 0.15g
Olfin E1010 (Surfactant manufactured by Air Products) 0.15 g

  The above components were mixed, stirred for 15 minutes, and subjected to ultrasonic treatment for 30 minutes to obtain an ink composition of Example 1.

  With respect to the obtained ink composition of Example 1, the following characteristics (1) and (2) were evaluated by the following test methods.

  As the printer, an inkjet recording system printer (Seiko Epson EM930C printer) was used, and commercially available glossy paper (PR-101 manufactured by Canon Inc.) was used as the printing paper.

(1) Image scratching The ink composition of Example 1 was printed with a printer. Immediately thereafter, the printed material was rubbed with a finger, and the ink was visually observed to see if it was peeled off. .
○: No peeling off △: Some peeling off ×: Almost all peeling off and the surface of glossy paper is visible

(2) Gloss / Haze measurement of image Gloss / Haze of glossy paper (PR-101 manufactured by Canon Inc.) on which the ink composition of Example 1 was printed was dried at room temperature for 1 day, and measured. The Gloss / Haze measurement was performed using a Haze-Gloss meter (Cat. No. 4601 manufactured by BYK Gardner), and the Gloss / Haze value was measured at 20 °. The measured Haze value and the linear Haze value have the following relationship.
Measurement Haze = 1285.1 × log (linear Haze / 20 + 1)
In general, when Gloss is high, Haze tends to be high. Therefore, it is difficult to obtain superiority or inferiority of glossiness only by comparing each value. Therefore, Haze / Gloss values are compared. It shows that glossiness is so high that a numerical value is small.
The results are shown in Table 2.

<Example 2>
Baked product carbon black (# 2300B (manufactured by Mitsubishi Chemical Corporation) at 1200 ° C. for 1 month in a nitrogen atmosphere; powder; solid content: 100 wt%) 28.0 g, random copolymer A aqueous solution (random copolymer A concentration 10) 0.5 wt.%) 120.1 g and deionized water 131.9 g were mixed, and after pre-dispersion for 1 hour with CLEARMIX (MTECHNIQUE; CLM-0.8S), which is a rotary disperser, 0.3 mmφ Using a self-made bead mill with zirconia beads as a medium, dispersion was performed at 60 ° C. for 8 hours, and after removing the beads, a pigment concentration was adjusted to 8% by weight to obtain dispersion liquid b.

The dispersion b was put in a 500 ml tall beaker, the beaker was immersed in ice water, and dispersed for 90 minutes with an ultrasonic homogenizer (Nippon Seiki Seisakusho; US-600T; used chip 36 mmφ) to obtain a pigment dispersion B. . Using this pigment dispersion B, an ink was prepared and evaluated in the same manner as in Example 1.
The results are shown in Table 2.

<Example 3>
Carbon black (Mitsubishi Chemical Corporation: # 990) 28.0 g, random copolymer B aqueous solution (random copolymer B concentration 10.1 wt%) 110.7 g, and distilled water 141.3 g were mixed, and 0.5 mmφ zirconia The beads were dispersed using a self-made bead mill as a medium at 25 ° C. for 8 hours. After removing the beads, the pigment concentration was adjusted to 8% by weight to obtain dispersion c.

The dispersion c was placed in a 500 ml tall beaker, the beaker was immersed in ice water, and dispersed for 90 minutes with an ultrasonic homogenizer (Nippon Seiki Seisakusho; US-600T; used chip 36 mmφ) to obtain a pigment dispersion C. . Using this pigment dispersion C, an ink was prepared and evaluated in the same manner as in Example 1.
The results are shown in Table 2.

<Example 4>
Pigment Blue-15: 3 (manufactured by Dainichi Seika Kogyo Co., Ltd .; powder; solid content: 100 wt%) 28.0 g, random copolymer C aqueous solution (random copolymer C concentration: 26.4 wt%), 42.4 g, and deionized Mix 209.6 g of water, pre-disperse for 1 hour with Claremix (MTECHNIQUE; CLM-0.8S), then disperse for 8 hours at 25 ° C. using a self-made bead mill with 0.3 mmφ zirconia beads as media. After removing the beads, the pigment concentration was adjusted to 8% by weight to obtain dispersion d.

The dispersion d was placed in a 500 ml tall beaker, the beaker was immersed in ice water, and dispersed with an ultrasonic homogenizer (Nippon Seiki Seisakusho; US-600T; used chip 36 mmφ) for 120 minutes to obtain a pigment dispersion D. . Using this pigment dispersion D, an ink was prepared and evaluated in the same manner as in Example 1.
The results are shown in Table 2.

<Example 5>
Carbon Black (Mitsubishi Chemical Corporation: # 960) 28.0 g, Random Copolymer D aqueous solution (Random Copolymer D concentration 13.1 wt%) 128.3 g, and 123.7 g of deionized water were mixed, and CTECHMIX (MTECHNIQUE) was mixed. After pre-dispersing for 1 hour using CLM-0.8S), using a self-made bead mill with 0.3 mmφ zirconia beads as a medium, dispersing for 8 hours at 60 ° C. After removing the beads, the pigment concentration was 8% by weight. To obtain a dispersion e.

The dispersion e was put into a 500 ml tall beaker, the beaker was immersed in ice water, and dispersed for 30 minutes with an ultrasonic homogenizer (Nippon Seiki Seisakusho; US-600T; used chip 36 mmφ) to obtain a pigment dispersion E. Using this pigment dispersion E, inks were prepared and evaluated in the same manner as in Example 1.
The results are shown in Table 2.

<Example 6>
Baked product carbon black (# 2300B (manufactured by Mitsubishi Chemical Corporation) at 1200 ° C. for 1 month in a nitrogen atmosphere; powder; solid content: 100 wt%) 28.0 g, random copolymer A aqueous solution (random copolymer A concentration 10) .5 wt%) 106.8 g, 14 g of block copolymer X aqueous solution (block copolymer X concentration 10 wt%) and 131.2 g of deionized water are mixed and pre-dispersed for 10 minutes with an omni homogenizer (Omni Corp .; GLH type). Thereafter, 0.3 mmφ zirconia beads were used as a medium and dispersed at 60 ° C. for 8 hours using a self-made bead mill. After removing the beads, the pigment concentration was adjusted to 8% by weight to obtain dispersion f.

The dispersion f was placed in a 500 ml tall beaker, the beaker was immersed in ice water, and dispersed for 90 minutes with an ultrasonic homogenizer (Nippon Seiki Seisakusho; US-600T; used chip 36 mmφ) to obtain a pigment dispersion F. Using this pigment dispersion F, an ink was prepared and evaluated in the same manner as in Example 1.
The results are shown in Table 2.

<Comparative Example 1>
Carbon black (Mitsubishi Chemical Corporation: # 960) 28.0 g, random copolymer E aqueous solution (random copolymer E concentration 13.14 wt%) 127.9 g, and distilled water 124.2 g were mixed, and 0.5 mmφ zirconia The beads were dispersed using a self-made bead mill as a medium at 25 ° C. for 8 hours. After removing the beads, the pigment concentration was adjusted to 8% by weight to obtain dispersion g.

The dispersion g was put into a 500 ml tall beaker, the beaker was immersed in ice water, and dispersed for 45 minutes with an ultrasonic homogenizer (Nippon Seiki Seisakusho; US-600T; chip used 36 mmφ) to obtain a pigment dispersion G. . Using this pigment dispersion G, an ink was prepared and evaluated in the same manner as in Example 1.
The results are shown in Table 2.

<Comparative example 2>
Carbon black (Mitsubishi Chemical Corporation: # 960) 28.0 g, random copolymer F aqueous solution (random copolymer F concentration 17.6 wt%) 95.5 g, and distilled water 156.5 g were mixed, and 0.5 mmφ zirconia The beads were dispersed using a self-made bead mill as a medium at 25 ° C. for 8 hours. After removing the beads, the pigment concentration was adjusted to 8% by weight to obtain a dispersion liquid h.

The dispersion h was placed in a 500 ml tall beaker, the beaker was immersed in ice water, and dispersed for 30 minutes with an ultrasonic homogenizer (Nippon Seiki Seisakusho; US-600T; used chip 36 mmφ) to obtain a pigment dispersion H. . Using this pigment dispersion H, an ink was prepared and evaluated in the same manner as in Example 1.
The results are shown in Table 2.

<Comparative Example 3>
Carbon black (Mitsubishi Chemical Corporation: # 960) 28.0 g, random copolymer G aqueous solution (random copolymer G concentration 14.0 wt%) 119.8 g, and distilled water 132.2 g were mixed, and 0.5 mmφ zirconia The beads were dispersed for 8 hours at 25 ° C. using a self-made bead mill as a medium. After removing the beads, the pigment concentration was adjusted to 8% by weight to obtain dispersion i.

The dispersion i was placed in a 500 ml tall beaker, the beaker was immersed in ice water, and dispersed with an ultrasonic homogenizer (Nippon Seiki Seisakusho; US-600T; chip used 36 mmφ) for 30 minutes to obtain a pigment dispersion I. . Using this pigment dispersion I, an ink was prepared and evaluated in the same manner as in Example 1.
The results are shown in Table 2.

<Comparative example 4>
Carbon black (Mitsubishi Chemical Corporation: # 960) 28.0 g, random copolymer H aqueous solution (random copolymer H concentration 14.0 wt%) 119.8 g, and distilled water 132.2 g were mixed, and 0.5 mmφ zirconia was mixed. The beads were dispersed using a self-made bead mill as a medium at 25 ° C. for 8 hours. After removing the beads, the pigment concentration was adjusted to 8% by weight to obtain a dispersion j.

Dispersion liquid j was placed in a 500 ml tall beaker, the beaker was immersed in ice water, and dispersed with an ultrasonic homogenizer (Nippon Seiki Seisakusho; US-600T; used chip 36 mmφ) for 30 minutes to obtain pigment dispersion liquid J. Using this pigment dispersion J, an ink was prepared and evaluated in the same manner as in Example 1.
The results are shown in Table 2.

From Table 2, the following is clear.
Comparative Example 1 uses a random copolymer E that does not contain an oxyalkylene chain monomer structural unit. However, the ejectability is very poor, and an evaluation print cannot be obtained.
Comparative Example 2 uses a random copolymer F having an oxyalkylene chain monomer, but contains 13% by weight of an anionic monomer structural unit, so there is no problem with scratch resistance, but the gloss value is low. Therefore, since the value of Haze / Gloss is also high, both glossiness and sharpness are insufficient.
On the other hand, Comparative Example 3 uses a random copolymer G consisting only of a hydrophobic monomer structural unit and an oxyalkylene chain monomer structural unit. Although the gloss shows a high value, an anionic monomer structural unit is used. Since it is not contained, the scratch resistance is insufficient.
Comparative Example 4 uses a random copolymer H containing a hydrophobic monomer structural unit, an oxyalkylene chain monomer structural unit, and an anionic monomer structural unit. However, the hydrophobic monomer structural unit / oxyalkylene chain monomer structural unit ( Since the value of (weight ratio) exceeds 1.0, the dischargeability is very poor, and a printable product that cannot be evaluated cannot be obtained.

  On the other hand, in Examples 1 to 6 using the polymer (I) of the present invention, compared to these comparative examples, the ejection properties are good and the scratch resistance is good, but the glossiness and the sharpness are high. Both show excellent values, and it is clear that the printing characteristics, particularly the glossiness of photographic paper, is excellent.

  From the above results, the hydrophobic monomer structural unit comprising one or more types of hydrophobic monomer structural units, one or more types of anionic monomer structural units, and one or more types of oxyalkylene chain monomer structural units, constituting a random copolymer / Disperse polymer (I) having an oxyalkylene chain monomer structural unit (weight ratio) value of 0.1 to 1.0 and an anionic monomer structural unit content of 10% by weight or less of the total polymer The printed matter obtained from the recording liquid using the aqueous pigment dispersion of the present invention used as a dispersant uses a pigment dispersion prepared with a conventional styrene-acrylic dispersant or a dispersant using an oxyalkylene chain monomer. Compared with the printed matter obtained with the recorded liquid, it is clear that the gloss is excellent, the printing quality is good, and the scratch resistance is also good. That.

Claims (8)

In an aqueous pigment dispersion containing (a) an aqueous medium, (b) a pigment, and (c) a dispersant, the (c) dispersant comprises at least one or more types of hydrophobic monomers and one or more types of anionic monomers. A polymer obtained by copolymerizing at least one oxyalkylene chain monomer represented by the following general formula (1), wherein the hydrophobic monomer structural unit and the oxyalkylene chain monomer structural unit constituting the polymer The weight ratio of (hydrophobic monomer structural unit / oxyalkylene chain monomer structural unit (weight ratio)) is 0.1 to 1.0, and the content of the anionic monomer structural unit is 10% by weight of the whole polymer. An aqueous pigment dispersion characterized by containing the following polymer (I):

(In the formula (1), R ¹ is vinyl group, acryloyloxy group, acryloylamino group, methacryloyloxy group, methacryloylamino group, acrylamino group, styryl group, vinyl ether group, vinylsilyl group, cyanovinyl group, or 2-cyanoacryloyl. R ² represents a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, or an optionally substituted phenyl group, h and j are each independently an integer of 1 to 5, and i is 1 (It is an integer of ~ 100, and k is an integer of 0-50.)   The aqueous pigment dispersion according to claim 1, wherein the anionic monomer is a carboxylic acid and / or a salt thereof.   The aqueous pigment dispersion according to claim 1 or 2, wherein the oxyalkylene chain of the oxyalkylene-containing monomer is an oxyethylene chain.   The aqueous pigment dispersion according to any one of claims 1 to 3, wherein at least one of the hydrophobic monomers is an aromatic-containing monomer and / or an aliphatic hydrocarbon group-containing monomer.   The aqueous pigment dispersion according to any one of claims 1 to 4, wherein in the general formula (1), the sum of i and k is 2 to 50.   6. The aqueous pigment dispersion according to claim 1, wherein the polymer (I) has a number average molecular weight of 1,000 to 50,000.   An ink composition comprising the aqueous pigment dispersion according to any one of claims 1 to 6.   8. An ink jet recording method comprising ejecting droplets of the ink composition according to claim 7 from an ink jet head and attaching the droplets to a recording medium.