JP5538733B2 - Aqueous ink composition, ink set and image forming method - Google Patents

Description

  The present invention relates to an aqueous ink composition, an ink set, and an image forming method.

    In recent years, paints and inks (hereinafter also referred to as “inks”) are becoming water-based due to increasing needs such as resource protection, environmental protection, and improvement of work stability. The quality required for water-based paints and water-based inks is fluidity, storage stability, gloss of film, vividness, coloring power and the like, similar to oil-based paints and oil-based inks. However, since most pigments are remarkably inferior in suitability for pigment dispersibility and the like as compared with an oily vehicle with respect to an aqueous vehicle, satisfactory quality cannot be obtained by a normal dispersion method. Until now, the use of various additives such as aqueous pigment dispersion resins and surfactants has been studied, but all the above-mentioned suitability is satisfied, and it is comparable to existing high-quality oil-based paints or oil-based inks. No water-based paint or water-based ink has been obtained.

In order to solve such a problem, for example, water, a pigment dispersed using a polymer having a specific configuration, 50% by mass or more of benzyl acrylate, and 15% by weight or less of (meth) acrylic acid An ink containing an emulsion of polymerized resin fine particles is disclosed (for example, see Patent Document 1), and it is said that storage stability, ejection stability, and color developability are good.
Also disclosed is an aqueous ink for inkjet recording comprising a self-dispersing pigment, and polymer particles having a structural unit derived from a salt-forming group-containing monomer and a structural unit derived from an alicyclic (meth) acrylate (for example, Patent Document 2), it is said that the marker resistance and the ink ejection properties are good.

JP 2007-99913 A JP 2007-77371 A

However, with the ink described in Patent Document 1, although glossiness and scratch resistance are improved to some extent, they are insufficient in terms of blocking resistance and ejection properties. Further, the water-based ink for inkjet recording described in Patent Document 2 is insufficient in terms of blocking resistance and ejection stability.
The present invention has been made in view of the above, and an object of the present invention is to provide a water-based ink composition excellent in ink ejection properties and anti-blocking properties of images formed.

Specific means for solving the above problems are as follows.
<1> has a water-based medium, a pigment, and a colored particle containing a water-insoluble polymer dispersant having a hydrophobic structural unit represented by the structural units and the following general formula having a carboxyl group (1), a carboxyl group A water-based ink composition comprising: a structural unit; and self-dispersing polymer particles having a hydrophobic structural unit derived from an alicyclic (meth) acrylate.

(In the formula, R ¹ represents a hydrogen atom or a methyl group. L ¹ represents —COO—, —OCO—, —CONR ² —, or a phenylene group which may have a substituent, and R ^2. Represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, L ² represents a single bond, an alkylene group having 1 to 12 carbon atoms, an alkenylene group having 2 to 12 carbon atoms, —CO—, or —NR ³ —. , —O—, —S—, —SO—, and —SO ₂ — represents a divalent linking group selected from the group consisting of linking groups, and R ³ represents a hydrogen atom or a carbon number of 1 to 6 the .Ar representing the alkyl group, a phenyl group or a condensed cyclic aromatic ring compound, the heterocyclic compound condensed with (an) aromatic ring, a compound in which two or more benzene are linked by a single bond, triphenylmethane, diphenylmethane, diphenyl ether And gif A monovalent group derived from a compound selected from vinyl sulfonic)

<2> The aqueous ink composition according to <1>, wherein the self-dispersing polymer particles further include a structural unit derived from a (meth) acrylate having a linear alkyl group having 1 to 8 carbon atoms.
<3> The water-based ink according to <1> or <2>, wherein the water-insoluble polymer dispersant further includes a structural unit derived from a (meth) acrylate having a chain alkyl group having 1 to 8 carbon atoms. Composition.
<4> The water-based ink composition according to any one of <1> to <3>, wherein the self-dispersing polymer particle has a content of a structural unit derived from a styrene monomer of 20% by mass or less .
<5 > The water-based ink composition according to any one of <1> to < 4 >, which is an inkjet recording ink.

< 6 > An ink set comprising at least one water-based ink composition according to any one of <1> to < 5 >.
< 7 > Using the aqueous ink composition according to any one of <1> to < 5 > or the ink set according to < 6 >, the aqueous ink composition is placed on a recording medium. An image forming method including an ink application step of applying and forming an image.

  ADVANTAGE OF THE INVENTION According to this invention, the water-based ink composition excellent in the discharge property of an ink and the blocking resistance of the image formed can be provided.

The water-based ink composition of the present invention includes at least colored particles including an aqueous medium, a pigment , a structural unit having a carboxyl group, and a water-insoluble polymer dispersant having a hydrophobic structural unit represented by the following general formula (1). 1 type and at least 1 type of the self-dispersion polymer particle | grains which have the structural unit which has a carboxyl group, and the hydrophobic structural unit derived from an alicyclic (meth) acrylate.
With such a configuration, it is possible to obtain a water-based ink composition having good blocking resistance of an image formed and excellent offset resistance at the time of fixing. In addition, when the aqueous ink composition of the present invention is applied to, for example, an ink jet recording method, the ink ejection property is also excellent.

In general formula (1), R ¹ represents a hydrogen atom or a methyl group. L ¹ represents —COO—, —OCO—, —CONR ² —, or an optionally substituted phenylene group, and R ² represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms. L ² represents a single bond or an alkylene group having 1 to 12 carbon atoms, an alkenylene group having 2 to 12 carbon atoms, —CO—, —NR ³ —, —O—, —S—, —SO—, and —. It represents a divalent linking group consisting of at least one selected from the group of linking groups consisting of SO ₂ —, and R ³ represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms. Ar is a phenyl group or a condensed cyclic aromatic ring compound, the heterocyclic compound condensed with (an) aromatic ring, a compound in which two or more benzene are linked by a single bond, selected triphenylmethane, diphenylmethane, from diphenyl ether and diphenyl sulfone Represents a monovalent group derived from the compound .

[Colored particles]
The aqueous ink composition of the present invention includes at least one pigment, and at least one water-insoluble polymer dispersant having a structural unit having a carboxyl group and a hydrophobic structural unit represented by the general formula (1). Containing colored particles.

(Pigment)
There is no restriction | limiting in particular as a pigment in this invention, A conventionally well-known organic and inorganic pigment can be used. For example, polycyclic pigments such as azo lakes, azo pigments, phthalocyanine pigments, perylene and perinone pigments, anthraquinone pigments, quinacridone pigments, dioxazine pigments, diketopyrrolopyrrole pigments, thioindigo pigments, isoindolinone pigments, quinophthalone pigments, basic Examples include dye lakes such as dye-type lakes and acid dye-type lakes, organic pigments such as nitro pigments, nitroso pigments, aniline black, and daylight fluorescent pigments, and inorganic pigments such as titanium oxide, iron oxide, and carbon black. Any pigment that is not described in the color index can be used as long as it can be dispersed in an aqueous medium. Further, it is of course possible to use a pigment obtained by surface-treating the above pigment with a surfactant, a polymer dispersing agent or the like, or graft carbon.

Of the above pigments, organic pigments and carbon black pigments are particularly preferred from the viewpoints of ink colorability, light resistance, weather resistance, and water resistance. Azo pigments, phthalocyanine pigments, anthraquinone pigments, quinacridone pigments, carbon black It is more preferable to use a pigment.
Specific examples of the pigment that can be used in the present invention include pigments described in paragraph numbers [0142] to [0145] of JP-A-2007-100071.
The pigments may be used alone or in combination.

(Water-insoluble polymer dispersant)
The water-insoluble polymer dispersant in the present invention (hereinafter sometimes simply referred to as “dispersant” or “polymer dispersant”) is represented by at least one structural unit having a carboxyl group and the following general formula (1). And at least one kind of hydrophobic structural unit. By using the polymer dispersant having such a configuration, it is possible to form an aqueous ink composition in which pigments are finely dispersed and excellent in stability over time.

In general formula (1), R ¹ represents a hydrogen atom or a methyl group.
L ¹ represents —COO—, —OCO—, —CONR ² —, or an optionally substituted phenylene group, and R ² represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms. Among these, L ¹ is preferably —COO—, —CONH—, or —CONCH ₃ —, more preferably —COO—, from the viewpoint of dispersion stability of the pigment.

In General Formula (1), L ² represents a single bond or a divalent linking group composed of at least one selected from the following linking group group. In addition, when there are two or more linking groups selected from the following linking group group, they may be the same or different from each other.

-Linking group group-
Alkylene group having 1 to 12 carbon atoms, an alkenylene group having 2 to 12 carbon ^{atoms, -CO -, - NR 3 -} , - O -, - S -, - SO -, - SO 2 -
Here, R ³ represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms.

The alkylene group has 1 to 12 carbon atoms, and more preferably 2 to 6 carbon atoms. The alkenylene group has 2 to 12 carbon atoms, and more preferably 2 to 4 carbon atoms.
The alkylene group or alkenylene group is independently substituted with a substituent (for example, an alkyl group having 1 to 6 carbon atoms, a halogen atom, a cyano group, an alkoxy group having 1 to 6 carbon atoms, or the like). Also good.

In the present invention, L ² is a single bond or an alkylene group having 1 to 12 carbon atoms, —O—, —CO—, and —NR ³ — (R ³ is a hydrogen atom or an alkyl having 1 to 6 carbon atoms. And a divalent linking group consisting of at least one selected from alkylene groups having 1 to 12 carbon atoms, —O—, and —CO—. More preferably, it is a group.

In the general formula (1), Ar, a phenyl group or a condensed cyclic aromatic ring compound, the heterocyclic compound condensed with (an) aromatic ring, a compound in which two or more benzene are linked by a single bond, triphenylmethane, diphenylmethane, It represents a monovalent group derived from a compound selected from diphenyl ether and diphenyl sulfone .
In the present invention, from the viewpoint of dispersion stability, Ar is a phenyl group or a condensed aromatic ring compound having 8 or more carbon atoms, a heterocyclic compound having a condensed aromatic ring , or two or more benzenes by a single bond. It is preferably a monovalent group derived from a compound selected from a linked compound , triphenylmethane, diphenylmethane, diphenyl ether and diphenylsulfone, a condensed aromatic compound having 8 or more carbon atoms, and an aromatic ring condensed. It is more preferably a monovalent group derived from a heterocyclic compound, a compound in which two or more benzenes are linked by a single bond , a compound selected from triphenylmethane, diphenylmethane, diphenyl ether and diphenylsulfone .

  The condensed aromatic ring compound having 8 or more carbon atoms is an aromatic ring compound in which two or more benzene rings are condensed and / or an alicyclic carbonization in which at least one aromatic ring is condensed with the aromatic ring. It is an aromatic compound composed of hydrogen and having 8 or more carbon atoms. Specific examples include naphthalene, anthracene, fluorene, phenanthrene, acenaphthene and the like.

The heterocyclic compound in which the aromatic ring is condensed is a compound in which an aromatic compound not containing a hetero atom (preferably a benzene ring) and at least one kind of a cyclic compound having a hetero atom are condensed. The cyclic compound having a hetero atom is preferably a 5-membered ring or a 6-membered ring. As the hetero atom, a nitrogen atom, an oxygen atom, or a sulfur atom is preferable. The cyclic compound having a hetero atom may have a plurality of hetero atoms, and in this case, each hetero atom may be the same as or different from each other.
Specific examples of the heterocyclic compound having a condensed aromatic ring include phthalimide, naphthalimide, acridone, carbazole, benzoxazole, and benzothiazole.

Wherein a compound in which two or more benzene rings are linked, a compound composed of two or more benzene rings are engaged forming a single binding will have triphenylmethane, diphenylmethane, a compound selected from diphenyl ether and diphenyl sulfone . The number of benzene rings is preferably 2 to 6, 2-3 is more preferable.
Specific examples of the compound in which two or more benzene rings are linked include biphenyl, triphenylmethane, diphenylmethane, diphenyl ether, diphenyl sulfone and the like .

  Ar in the general formula (1) in the present invention is derived from benzene, naphthalene, biphenyl, triphenylmethane, phthalimide, naphthalimide, acridone, fluorene, anthracene, phenanthrene, diphenylmethane, or carbazole from the viewpoint of dispersion stability. And monovalent groups derived from naphthalene, biphenyl, phthalimide, naphthalimide, or acridone are more preferred.

Ar in the general formula (1) may have a substituent. Examples of the substituent include an alkyl group, an alkoxyl group, an alkylcarbonyl group, an alkylcarbonyloxy group, an alkyloxycarbonyloxy group, a halogen group, and a cyano group. More preferable substituents have 1 to 10 carbon atoms. Examples thereof include an alkyl group, an alkoxyl group having 1 to 10 carbon atoms, an alkylcarbonyl group having 1 to 10 carbon atoms, an alkylcarbonyloxy group having 1 to 10 carbon atoms, a chloro group, and a cyano group.
These substituents may be substituted with other substituents, and preferred substituents in this case are also as defined above. Moreover, when it has two or more substituents, each substituent may be the same or different. If possible, the substituents may be bonded to each other to form a ring.

  The water-insoluble polymer dispersant having a hydrophobic structural unit represented by the general formula (1) may be formed by introducing a corresponding functional group by a polymer reaction after obtaining a polymer. It is preferably formed by copolymerizing a monomer mixture containing a monomer represented by the following general formula (2).

In the general formula ^{(2), R 1, L} 1, L 2, Ar is each the same meaning as ^{R 1,} L ^1, L 2, Ar in the corresponding general formula (1), and preferred examples are also the same . The monomers represented by the general formula (2) may be used alone or in admixture of two or more.
Specific examples of the monomer represented by the general formula (2) are given below, but the present invention is not limited to the following specific examples.

The water-insoluble polymer dispersant in the present invention contains at least one structural unit having a carboxyl group . Below, it demonstrates including a hydrophilic structural unit other than the structural unit which has a carboxyl group. The hydrophilic structural unit may be a hydrophilic structural unit containing a nonionic group or a hydrophilic structural unit containing an ionic group. In the present invention, a hydrophilic structural unit containing an ionic group is preferable from the viewpoint of dispersibility.

The hydrophilic structural unit containing an ionic group may contain an anionic group or a cationic group. In the present invention, a hydrophilic structural unit containing an anionic group is preferable.
Examples of the anionic group include a carboxyl group, a sulfonic acid group, and a phosphoric acid group. In the present invention, a carboxyl group is preferable from the viewpoint of stability over time.
Examples of the cationic group include an amino group and an ammonium group.

  The hydrophilic structural unit containing an ionic group may be introduced into the dispersant in the present invention by copolymerizing a monomer mixture containing a monomer having an ionic group, and the hydrophilic unit containing no ionic group. After preparing the union, an ionic group may be introduced by a polymer reaction.

  Examples of monomers having an ionic group that can be used in the present invention include monomers having an anionic group and monomers having a cationic group, but the present invention is not limited thereto. Moreover, the monomer which has an ionic group in this invention can be used individually by 1 type or in combination of 2 or more types.

  Among monomers having an anionic group, those containing a carboxyl group include, for example, unsaturated carboxylic acid monomers such as acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid, citraconic acid, and β -Carboxyethyl acrylic acid, 2-methacryloyloxymethyl succinic acid, etc. are mentioned. Examples of the sulfonic acid group-containing monomer include styrene sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid, 3-sulfopropyl (meth) acrylic acid ester, bis- (3-sulfopropyl) -itaconic acid ester, and the like. Can be mentioned. Examples of the phosphoric acid group-containing monomer include vinyl phosphonic acid, vinyl phosphate, bis (methacryloxyethyl) phosphate, diphenyl-2-acryloyloxyethyl phosphate, diphenyl-2-methacryloyloxyethyl phosphate, dibutyl-2-acryloyloxyethyl. A phosphate etc. are mentioned.

Examples of the cationic group-containing monomer include one or more selected from the group consisting of tertiary amine-containing vinyl monomers and ammonium salt-containing vinyl monomers.
Examples of the tertiary amine-containing vinyl monomer include N, N-dimethylaminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylate, N, N-diethylaminoethyl (meth) acrylate, N, N- Examples include dimethylaminopropyl (meth) acrylamide, vinylpyrrolidone, 2-vinylpyridine, 4-vinylpyridine, 2-methyl-6-vinylpyridine, 5-ethyl-2-vinylpyridine, and the like.
Examples of the ammonium salt-containing monomer include N, N-dimethylaminoethyl (meth) acrylate quaternized product, N, N-diethylaminoethyl (meth) acrylate quaternized product, and N, N-dimethylaminopropyl (meth) acrylate quaternized product. And the like.

  Among these, anionic monomers are preferable, and unsaturated carboxylic acid monomers are preferable, and acrylic acid and methacrylic acid are particularly preferable from the viewpoints of ink viscosity and dischargeability.

  Examples of the nonionic group include a hydroxyl group, an unsubstituted amide group, a polyalkylene oxide group such as polyethylene oxide and polypropylene oxide, and the like.

  The hydrophilic structural unit containing a nonionic group may be introduced into the dispersant in the present invention by copolymerizing a monomer mixture containing a monomer having a nonionic group. A nonionic group may be introduced by a polymer reaction after preparing a polymer not containing the polymer.

  The monomer having a nonionic group is not particularly limited as long as it has a functional group capable of forming a polymer and a nonionic hydrophilic functional group, and any known monomer may be used. However, vinyl monomers are preferred from the viewpoints of availability, handleability, and versatility.

Examples of these vinyl monomers include (meth) acrylates, (meth) acrylamides, and vinyl esters having a hydrophilic functional group. Specific examples include hydroxyethyl (meth) acrylate, hydroxybutyl (meth) acrylate, (meth) acrylamide, and (meth) acrylate containing a polyalkylene oxide group.
In the present invention, these monomers having a nonionic group can be used singly or in combination of two or more.

In the present invention, when the hydrophilic structural unit has a nonionic group, it is preferably a hydrophilic structural unit containing a polyalkylene oxide group (alkylene oxide polymer).
The alkylene of the alkylene oxide polymer preferably has 1 to 6 carbon atoms, more preferably 2 to 6 carbon atoms, and particularly preferably 2 to 4 carbon atoms from the viewpoint of hydrophilicity / hydrophobicity.
Moreover, as a polymerization degree of the said alkylene oxide polymer, 1-120 are preferable, 1-60 are more preferable, and 1-30 are especially preferable.

In a preferred embodiment, the hydrophilic structural unit containing a nonionic group is a hydrophilic structural unit containing a hydroxyl group.
The number of hydroxyl groups in the hydrophilic structural unit is not particularly limited, but from the viewpoint of hydrophilicity / hydrophobicity of the dispersant and compatibility with the solvent and other monomers during polymerization, 1 to 4 is preferable, and 1 to 3 is more preferable. Preferably, 1-2 is especially preferable.

  In the present invention, the hydrophilic structural unit may be contained in an amount of, for example, 2% by mass to 20% by mass with respect to the total mass of the polymer dispersant, and preferably 2% by mass to 15% by mass. More preferably, it is at least 12% by mass.

When the water-insoluble polymer dispersant in the present invention contains an anionic group such as a carboxyl group, the acid value of the polymer dispersant is preferably 10 mgKOH / g or more and less than 85 mgKOH / g, 15 mgKOH / g or more, 85 mgKOH Is more preferably less than 15 mgKOH / g, and particularly preferably less than 80 mgKOH / g.
By setting the acid value of the polymer dispersant to 10 mgKOH / g or more, dispersibility is further improved due to charge repulsion of the dispersion due to dissociated carboxyl groups or the like. Moreover, by setting it as 85 mgKOH / g or less, it can suppress that a polymer dispersing agent becomes easy to adsorb | suck to a pigment and it elutes in an aqueous medium.
The acid value here is defined by the mass (mg) of KOH required to completely neutralize 1 g of the dispersant, and is calculated according to the method described in the JIS standard (JIS K0070: 1992). .

  In the present invention, the hydrophilic structural unit contains an ionic group, and the content in the total mass of the dispersant is preferably 2 to 20% by mass, contains an anionic group, and the content is 3 to 15%. It is more preferable that it is mass%, and it is further more preferable that it is 5-15 mass% including a carboxyl group and containing.

  The water-insoluble polymer dispersant in the present invention includes, in addition to the hydrophilic structural unit and the hydrophobic structural unit represented by the general formula (1), a hydrophobic structural unit represented by the general formula (1) Preferably further has a hydrophobic structural unit having a different structure (hereinafter sometimes referred to as “other structural unit”). In addition to the hydrophobic structural unit and the hydrophilic structural unit represented by the general formula (1), dispersibility is further improved by further including other structural units.

The other structural unit in the present invention is not particularly limited as long as it has a hydrophobic group having a structure different from the hydrophobic group of the hydrophobic structural unit represented by the general formula (1).
Other structural units can be formed by copolymerizing a monomer mixture containing the corresponding monomer. Further, after the polymer is prepared, it may be formed by introducing a hydrophobic functional group.

The other monomer that forms the structural unit is not particularly limited as long as it has a functional group capable of forming a polymer and a hydrophobic functional group, and any known monomer can be used.
Examples of the monomer that can form the other structural unit include vinyl monomers ((meth) acrylates, (meth) acrylamides, styrenes, vinyl esters, etc.) from the viewpoints of availability, handleability, and versatility. preferable.

Examples of these include (meth) acrylates such as methyl (meth) acrylate, ethyl (meth) acrylate, (iso) propyl (meth) acrylate, (iso or tertiary) butyl (meth) acrylate, 2-ethylhexyl ( Examples include alkyl (meth) acrylates such as (meth) acrylate, (iso) octyl (meth) acrylate, (iso) decyl (meth) acrylate, and (iso) stearyl (meth) acrylate. Among these, from the viewpoint of dispersion stability, a (meth) acrylate having a chain alkyl group having 1 to 8 carbon atoms is preferable, and a (meth) acrylate having a chain alkyl group having 1 to 6 carbon atoms is more preferable.
The chain alkyl group may be a linear alkyl group or a branched alkyl group.

  Examples of the unsaturated polycarboxylic acid diesters include dimethyl maleate, dibutyl maleate, dimethyl itaconate, dibutyl itaconate, dibutyl crotonate, dihexyl crotonate, diethyl fumarate, and dimethyl fumarate.

  As amides of α, β-unsaturated carboxylic acids, N, N-dimethylacrylamide, N, N-diethylacrylamide, Nn-propylacrylamide, N-tertbutylacrylamide, N-tertoctylmethacrylamide, N- Examples include cyclohexylacrylamide, N-phenylacrylamide, N- (2-acetoacetoxyethyl) acrylamide, N-benzylacrylamide, N-acryloylmorpholine, diacetoneacrylamide, N-methylmaleimide, and the like. N, N-dimethyl (meth) acrylamide is preferred.

Examples of unsaturated nitriles include acrylonitrile and methacrylonitrile.
Examples of styrene and derivatives thereof include styrene, vinyl toluene, ethyl styrene, p-tert butyl styrene, methyl p-vinyl benzoate, α-methyl styrene, p-chloromethyl styrene, vinyl naphthalene, p-methoxy styrene, p-hydroxy. Examples thereof include methyl styrene and p-acetoxy styrene, and styrene and α-methyl styrene are preferable.
Examples of vinyl esters include vinyl acetate, vinyl propionate, vinyl butyrate, vinyl isobutyrate, vinyl benzoate, vinyl salicylate, vinyl chloroacetate, vinyl methoxyacetate, and vinyl vinyl acetate. Of these, vinyl acetate is preferred.

Examples of vinyl ethers include methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, isopropyl vinyl ether, n-butyl vinyl ether, isobutyl vinyl ether, tert-butyl vinyl ether, n-pentyl vinyl ether, n-hexyl vinyl ether, n-octyl vinyl ether, n-dodecyl. Examples include vinyl ether, n-eicosyl vinyl ether, 2-ethylhexyl vinyl ether, cyclohexyl vinyl ether, fluorobutyl vinyl ether, and fluorobutoxyethyl vinyl ether.
Other monomers include N-vinyl pyrrolidone, methyl vinyl ketone, phenyl vinyl ketone, methoxyethyl vinyl ketone, 2-vinyl oxazoline, 2-isopropenyl oxazoline and the like.
These monomers can be used alone or in combination of two or more.

In the present invention, the other structural unit may be contained, for example, in an amount of 10 to 60% by mass, preferably 10 to 50% by mass, and more preferably 20 to 40% by mass with respect to the total mass of the dispersant.
Moreover, at least 1 type of the monomer which forms the said other structural unit is a (meth) acrylate which has a C1-C8 linear alkyl group, Comprising: The content rate in the total mass of a dispersing agent is 10-50. It is preferable that it is mass%, It is (meth) acrylate which has a C1-C6 linear alkyl, Comprising: It is more preferable that a content rate is 20-40 mass%.

  The polymer dispersant in the present invention may be a random copolymer in which each structural unit is irregularly introduced, or may be a block copolymer that is regularly introduced, or a block copolymer. Each structural unit in this case may be synthesized in any order of introduction, and the same structural component may be used twice or more, but a random copolymer is a point of versatility and manufacturability Is preferable.

Furthermore, the molecular weight range of the polymer dispersant used in the present invention is a weight average molecular weight (Mw), preferably 1000 to 1 million, more preferably 2000 to 200,000, and further preferably 3000 to 100,000. .
By setting the molecular weight within the above range, the steric repulsion effect as a dispersing agent tends to be good, and it is preferable from the viewpoint of the tendency that adsorption to the pigment does not take time due to the steric effect.
Further, the molecular weight distribution (expressed by weight average molecular weight (Mw) / number average molecular weight (Mn)) of the polymer dispersant used in the present invention is preferably 1 to 6, and more preferably 1 to 4. preferable.
By setting the molecular weight distribution (Mw / Mn) within the above range, it is preferable from the viewpoint of shortening the dispersion time of the pigment and stability with time of the dispersion. Here, the number average molecular weight and the weight average molecular weight were measured using a TPCgel SuperHZM-H, TSKgel SuperHZ4000, and TSKgel SuperHZ200 (both trade names manufactured by Tosoh Corporation) using a solvent THF and a differential refractometer. The molecular weight is expressed by conversion using polystyrene as a standard substance.

  In the water-insoluble polymer dispersant in the present invention, the hydrophobic constituent unit represented by the general formula (1) is 10 to 70% by mass as a copolymerization ratio, and the hydrophilic constituent unit is derived from an anionic group-containing monomer. A structural unit derived from an alkyl (meth) acrylate, an acid value of 10 to 85, a weight average molecular weight of preferably 1,000 to 1,000,000, and a hydrophobic structure represented by the general formula (1) A unit is 40-70 mass% as a copolymerization ratio, Comprising: The hydrophilic structural unit derived from a carboxyl group-containing monomer, and the structural unit derived from the (meth) acrylate which has a C1-C8 alkyl group. More preferably, the acid value is 15 to 80 and the weight average molecular weight is 3000 to 100,000.

The polymer dispersant used in the present invention can be synthesized by various polymerization methods such as solution polymerization, precipitation polymerization, suspension polymerization, precipitation polymerization, bulk polymerization, and emulsion polymerization. The polymerization reaction can be performed by a known operation such as a batch system, a semi-continuous system, or a continuous system.
The polymerization initiation method includes a method using a radical initiator, a method of irradiating light or radiation, and the like. These polymerization methods and polymerization initiation methods are, for example, the revised version of Tsuruta Junji “Polymer Synthesis Method” (published by Nikkan Kogyo Shimbun, 1971), Takatsu Otsu, Masato Kinoshita, “Experimental Methods for Polymer Synthesis” It is described in pp. 47-154 published in 1972.
Among the above polymerization methods, a solution polymerization method using a radical initiator is particularly preferable. Solvents used in the solution polymerization method include, for example, ethyl acetate, butyl acetate, acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, tetrahydrofuran, dioxane, N, N-dimethylformamide, N, N-dimethylacetamide, benzene, toluene, acetonitrile, A single organic solvent such as methylene chloride, chloroform, dichloroethane, methanol, ethanol, 1-propanol, 2-propanol, and 1-butanol, or a mixture of two or more thereof may be used, or a mixed solvent with water may be used.
The polymerization temperature needs to be set in relation to the molecular weight of the polymer dispersant to be produced, the type of initiator, etc., and is usually about 0 ° C. to 100 ° C., but the polymerization can be carried out in the range of 50 to 100 ° C. preferable.
The reaction pressure can be appropriately selected, but is usually preferably 1 to 100 kg / cm ² , particularly preferably about 1 to 30 kg / cm ² . The reaction time is about 5 to 30 hours. The obtained polymer dispersant may be subjected to purification such as reprecipitation.

  Specific examples of preferred water-insoluble polymer dispersants in the present invention are shown below, but the present invention is not limited thereto. In addition, a numerical value represents the mass ratio of each copolymerization component.

The content of the water-insoluble polymer dispersant in the aqueous ink composition of the present invention is preferably 5 to 200% by mass with respect to the pigment from the viewpoint of pigment dispersibility, ink colorability, and dispersion stability. -100 mass% is more preferable, and 20-80 mass% is especially preferable.
When the content of the water-insoluble polymer dispersant is within the above range, the pigment is preferably coated with an appropriate amount of the polymer dispersant, and a water-based ink composition having a small particle size and excellent stability over time is likely to be obtained.
In the present invention, a pigment dispersant other than the water-insoluble polymer dispersant may be contained within a range not impairing the effects of the present invention. The content of other pigment dispersants can be used within the range of the content of the water-insoluble polymer dispersant in the present invention.
As other dispersants other than the pigment dispersant, conventionally known water-soluble low-molecular dispersants, water-soluble polymers, and the like can be used.

(Other additives)
In addition to the pigment and the water-insoluble polymer dispersant, other additives such as a neutralizing agent and a surfactant can be added to the colored particles in the present invention, if necessary.
When the water-insoluble polymer dispersant contains a hydrophilic constituent unit having an anionic group, a basic substance is used as the neutralizing agent.

(Basic substance)
As the basic substance, a commonly used organic base or inorganic alkali can be used. For the purpose of neutralizing the dispersant, the basic substance is preferably added so that the composition containing the dispersant has a pH of 7 to 11, more preferably 8 to 10.
As content of a basic substance, it is preferable that it is 50-150 mol% with respect to 100 mol% of ionic groups (anionic group) of a dispersing agent, and it is more preferable that it is 70-120 mol%. It is especially preferable that it is -100 mol%.
In addition, the specific example of a basic substance is the same as that of the neutralizing agent in the below-mentioned self-dispersion polymer.

(Method for producing colored particle dispersion)
The colored particles in the present invention are, for example, colored particles by dispersing, using a disperser, a mixture containing a pigment as a colorant, a water-insoluble polymer dispersant, and a solvent (preferably a solvent containing an organic solvent) as necessary. It can be obtained as a dispersion.

The method for producing a colored particle dispersion according to the present invention comprises mixing a solution containing a pigment, a water-insoluble polymer dispersant, an organic solvent for dissolving or dispersing the polymer dispersant, and a basic substance, and containing water as a main component. (Mixing / hydration step), preferably a production method including removing at least part of the organic solvent (solvent removal step).
According to this method for producing a colored particle dispersion, a colored particle dispersion in which colored particles are finely dispersed and excellent in storage stability can be produced.

  The organic solvent in the present invention is not particularly limited as long as it can dissolve or disperse the water-insoluble polymer dispersant, but in addition, it preferably has a certain degree of affinity for water. Specifically, the solubility in water at 20 ° C. is preferably 10% by mass or more and 50% by mass or less.

  The colored particle dispersion in the present invention can be produced in more detail by the production method comprising the following steps (1) and (2), but is not limited thereto.

Step (1): A step of dispersing a mixture containing a pigment, a water-insoluble polymer dispersant, an organic solvent for dissolving and dispersing the water-insoluble polymer dispersant, and a basic substance, and water. (2): Step of removing at least a part of the organic solvent from the mixture

In the step (1), first, the water-insoluble polymer dispersant is dissolved or dispersed in an organic solvent to obtain a mixture thereof (mixing step). Next, a pigment, a solution containing a basic substance and containing water as a main component, water and, if necessary, a surfactant or the like are added to the mixture and mixed and dispersed to give an oil-in-water coloring. A particle dispersion is obtained.
There is no limitation in the addition amount (degree of neutralization) of the basic substance. Usually, it is preferable that the liquid property of the finally obtained colored particle dispersion is neutral, for example, pH is 4.5 to 10. The pH can also be determined by the degree of neutralization according to the dispersant.

  The pigment, water-insoluble polymer dispersant, and other additives used in the method for producing the colored particle dispersion have the same meanings as those described in the section of the colored particles, and preferred examples are also the same.

Preferable examples of the organic solvent used in the present invention include alcohol solvents, ketone solvents, and ether solvents. Among these, examples of alcohol solvents include ethanol, isopropanol, n-butanol, tertiary butanol, isobutanol, and diacetone alcohol. Examples of the ketone solvent include acetone, methyl ethyl ketone, diethyl ketone, and methyl isobutyl ketone. Examples of the ether solvent include dibutyl ether, tetrahydrofuran, dioxane and the like. Among these organic solvents, isopropanol, acetone and methyl ethyl ketone are preferable, and methyl ethyl ketone is particularly preferable.
These organic solvents may be used alone or in combination.

In the production of the colored particle dispersion, a strong shearing force is applied using a two-roll, three-roll, ball mill, tron mill, disper, kneader, kneader, homogenizer, blender, single-screw or twin-screw extruder, etc. The kneading and dispersing process can be carried out.
For details on kneading and dispersing, see T.W. C. “Paint Flow and Pigment Dispersion” by Patton (published by John Wiley and Sons, 1964) and the like.
If necessary, use a vertical or horizontal sand grinder, pin mill, slit mill, ultrasonic disperser, etc. to finely disperse with beads made of glass with a particle diameter of 0.01 to 1 mm, zirconia, etc. Can be obtained.

  In the method for producing a colored particle dispersion in the present invention, the removal of the organic solvent is not particularly limited, and can be removed by a known method such as vacuum distillation.

The volume average particle size of the colored particles in the present invention is preferably in the range of 10 to 200 nm, more preferably 10 to 100 nm, from the viewpoint of color reproducibility and light resistance.
Further, the particle size distribution of the colored particles is not particularly limited, and may be any having a wide particle size distribution or a monodispersed particle size distribution. In addition, two or more kinds of colored particles may be mixed and used.
The volume average particle size and particle size distribution of the colored particles can be measured using a normal light scattering method.

In the water-based ink composition of the present invention, the content of the colored particles is preferably in the range of 0.1 to 20% by mass, and 0.5 to 10% by mass from the viewpoints of ink colorability, storage stability, and dischargeability. % Range is more preferred.
The colored particles can be contained alone or in combination of two or more in the aqueous ink composition of the invention.

  The colored particles in the colored particle dispersion obtained as described above maintain a good dispersion state, and the obtained colored particle dispersion has excellent temporal stability.

[Self-dispersing polymer particles]
The self-dispersing polymer particle according to the invention includes a structural unit having a carboxyl group and a hydrophobic structural unit, and the hydrophobic structural unit has a structure derived from at least an alicyclic (meth) acrylate. And By having a structure derived from an alicyclic (meth) acrylate, it is possible to obtain an aqueous ink composition having good fixability and anti-blocking property of the formed image. Further, when applied to ink jet recording, good ejection properties can be obtained.

In the present invention, the self-dispersing polymer is a dispersion state in an aqueous medium due to a functional group (particularly an acidic group or a salt thereof) of the polymer itself when it is dispersed by a phase inversion emulsification method in the absence of a surfactant. A water-insoluble polymer.
Here, the dispersed state means both an emulsified state (emulsion) in which a water-insoluble polymer is dispersed in an aqueous medium and a dispersed state (suspension) in which a water-insoluble polymer is dispersed in an aqueous medium. It includes the state of.
The self-dispersing polymer in the present invention is preferably a self-dispersing polymer that can be in a dispersed state in which a water-insoluble polymer is dispersed in a solid state from the viewpoint of ink fixing properties when contained in an aqueous ink composition.

  Examples of a method for preparing an emulsified or dispersed state of the self-dispersing polymer, that is, an aqueous dispersion of the self-dispersing polymer include a phase inversion emulsification method. As the phase inversion emulsification method, for example, a self-dispersing polymer is dissolved or dispersed in a solvent (for example, a water-soluble organic solvent) and then poured into water as it is without adding a surfactant. A method of obtaining an aqueous dispersion in an emulsified or dispersed state after stirring and mixing in a state in which a salt-forming group (for example, an acidic group) is neutralized and mixing to remove the solvent.

  The stable emulsified or dispersed state in the self-dispersing polymer of the present invention is a solution in which 30 g of water-insoluble polymer is dissolved in 70 g of an organic solvent (for example, methyl ethyl ketone), and the salt-forming group of the water-insoluble polymer can be neutralized 100%. Neutralizing agent (sodium hydroxide if anionic salt formation group, acetic acid if cationic) and 200 g of water are mixed and stirred (apparatus: stirring device with stirring blades, rotation speed 200 rpm, 30 minutes, 25 ° C. After the removal of the organic solvent from the mixed solution, the emulsified or dispersed state exists stably at 25 ° C. for at least one week, and the occurrence of precipitation cannot be visually confirmed.

The stability of the emulsified or dispersed state in the self-dispersing polymer can also be confirmed by an accelerated sedimentation test by centrifugation. The stability by the accelerated sedimentation test by centrifugation is, for example, adjusted to an aqueous dispersion of polymer particles obtained by the above method to a solid content concentration of 25% by mass, then centrifuged at 12000 rpm for 1 hour, and centrifuged. It can be evaluated by measuring the solid content concentration of the supernatant after separation.
If the ratio of the solid content concentration after centrifugation to the solid content concentration before centrifugation is large (a value close to 1), the sedimentation of the polymer particles by centrifugation does not occur, that is, the aqueous dispersion of polymer particles Means more stable. In the present invention, the ratio of the solid content concentration before and after centrifugation is preferably 0.8 or more, more preferably 0.9 or more, and particularly preferably 0.95 or more.

  The water-insoluble polymer means a polymer having a dissolution amount of 10 g or less when the polymer is dried at 105 ° C. for 2 hours and then dissolved in 100 g of water at 25 ° C., and the dissolution amount is preferable. Is 5 g or less, more preferably 1 g or less. The dissolution amount is the dissolution amount when neutralized with sodium hydroxide or acetic acid according to the kind of the salt-forming group of the water-insoluble polymer.

In the self-dispersing polymer in the present invention, the content of a water-soluble component exhibiting water solubility in a dispersed state is preferably 10% by mass or less, more preferably 8% by mass or less, and 6% by mass or less. More preferably. When the water-soluble component is 10% by mass or less, swelling of the polymer particles and fusion between the polymer particles can be effectively suppressed, and a more stable dispersion state can be maintained. In addition, an increase in the viscosity of the aqueous ink composition can be suppressed. For example, when the aqueous ink composition is applied to an ink jet method, the ejection stability becomes better.
Here, the water-soluble component is a compound contained in the self-dispersing polymer, and is a compound that dissolves in water when the self-dispersing polymer is in a dispersed state. The water-soluble component is a water-soluble compound that is by-produced or mixed when the self-dispersing polymer is produced.

(Hydrophobic structural unit)
The self-dispersing polymer particle in the present invention contains at least one kind of structure derived from alicyclic (meth) acrylate as a hydrophobic constituent unit.
Although there is no restriction | limiting in particular about the principal chain skeleton of the polymer which comprises the self-dispersing polymer particle in this invention, From a viewpoint of the dispersion stability of a polymer particle, it is preferable that it is a vinyl polymer.

-Alicyclic (meth) acrylate-
In the present invention, the alicyclic (meth) acrylate includes a structural part derived from (meth) acrylic acid and a structural part derived from alcohol, and the structural part derived from alcohol is unsubstituted or substituted. It has a structure containing at least one cyclic hydrocarbon group. The alicyclic hydrocarbon group may be a structural part derived from alcohol itself or may be bonded to a structural part derived from alcohol via a linking group.
The “alicyclic (meth) acrylate” means methacrylate or acrylate having an alicyclic hydrocarbon group.

The alicyclic hydrocarbon group is not particularly limited as long as it contains a cyclic non-aromatic hydrocarbon group, and is a monocyclic hydrocarbon group, a bicyclic hydrocarbon group, a tricyclic or more polycyclic group. A hydrocarbon group is mentioned.
Examples of the alicyclic hydrocarbon group include a cycloalkyl group such as a cyclopentyl group and a cyclohexyl group, a cycloalkenyl group, a bicyclohexyl group, a norbornyl group, an isobornyl group, a dicyclopentanyl group, a dicyclopentenyl group, and an adamantyl group. , Decahydronaphthalenyl group, perhydrofluorenyl group, tricyclo [5.2.1.0 ^2,6 ] decanyl group, and bicyclo [4.3.0] nonane.

The alicyclic hydrocarbon group may further have a substituent. Examples of the substituent include alkyl groups, alkenyl groups, aryl groups, aralkyl groups, alkoxy groups, hydroxyl groups, primary amino groups, secondary amino groups, tertiary amino groups, alkyl or arylcarbonyl groups, and cyano groups. Is mentioned.
The alicyclic hydrocarbon group may further form a condensed ring.
As an alicyclic hydrocarbon group in this invention, it is preferable that carbon number of an alicyclic hydrocarbon group part is 5-20 from a viscosity or a soluble viewpoint.

  Examples of the linking group that connects the alicyclic hydrocarbon group and the structural portion derived from alcohol include alkyl groups, alkenyl groups, alkylene groups, aralkyl groups, alkoxy groups, mono- or oligoethylene groups having 1 to 20 carbon atoms. Preferable examples include a cholic group, a mono- or oligopropylene glycol group, and the like.

Specific examples of the alicyclic (meth) acrylate in the present invention are shown below, but the present invention is not limited thereto.
Monocyclic (meth) acrylates include cyclopropyl (meth) acrylate, cyclobutyl (meth) acrylate, cyclopentyl (meth) acrylate, cyclohexyl (meth) acrylate, cycloheptyl (meth) acrylate, cyclooctyl (meth) acrylate, and cyclononyl. Examples thereof include cycloalkyl (meth) acrylates having 3 to 10 carbon atoms in the cycloalkyl group such as (meth) acrylate and cyclodecyl (meth) acrylate.
Examples of the bicyclic (meth) acrylate include isobornyl (meth) acrylate and norbornyl (meth) acrylate.
Examples of the tricyclic (meth) acrylate include adamantyl (meth) acrylate, dicyclopentanyl (meth) acrylate, and dicyclopentenyloxyethyl (meth) acrylate.
These can be used alone or in admixture of two or more.

  Among these, at least one kind of bicyclic (meth) acrylate or tricyclic or higher polycyclic (meth) acrylate is used from the viewpoints of dispersion stability, fixing property, and blocking resistance of the self-dispersing polymer particles. It is preferable that it is at least one selected from isobornyl (meth) acrylate, adamantyl (meth) acrylate, and dicyclopentanyl (meth) acrylate.

In the present invention, the content of the structural unit derived from the alicyclic (meth) acrylate contained in the self-dispersing polymer particles is as follows: the stability of the self-dispersing state, the aqueousity due to the hydrophobic interaction between the alicyclic hydrocarbon groups. From the viewpoint of stabilizing the particle shape in the medium and reducing the amount of the water-soluble component due to appropriate hydrophobicization of the particles, it is preferably 20% by mass or more and 90% by mass or less, and 40% by mass or more and 90% by mass or less More preferably. Particularly preferred is 50 mass% or more and 80 mass% or less.
By making the structural unit derived from the alicyclic (meth) acrylate 20% by mass or more, the fixing property and the blocking property can be further improved. On the other hand, when the structural unit derived from the alicyclic (meth) acrylate is 90% by mass or less, the stability of the polymer particles is further improved.

  In the present invention, the self-dispersing polymer can be configured to further include other structural units as necessary in addition to the structural unit derived from the alicyclic (meth) acrylate as a hydrophobic structural unit. The monomer that forms the other structural unit is not particularly limited as long as it is a monomer copolymerizable with the alicyclic (meth) acrylate and a hydrophilic group-containing monomer described later, and a known monomer can be used. .

  Specific examples of the monomer that forms the other structural unit (hereinafter sometimes referred to as “other copolymerizable monomer”) include, for example, methyl (meth) acrylate, ethyl (meth) acrylate, and isopropyl (meth) acrylate. Alkyl (meth) acrylates such as n-propyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, t-butyl (meth) acrylate, hexyl (meth) acrylate, ethylhexyl (meth) acrylate; Aromatic ring-containing (meth) acrylates such as benzyl (meth) acrylate and phenoxyethyl (meth) acrylate; styrenes such as styrene, α-methylstyrene and chlorostyrene; dialkylaminoalkyl such as dimethylaminoethyl (meth) acrylate (Meth) acrylate; N-hydroxymethyl (meth) acrylamide, N-hydroxyethyl (meth) acrylamide, N-hydroxyalkyl (meth) acrylamide such as N-hydroxybutyl (meth) acrylamide; N-methoxymethyl (meth) acrylamide, N-ethoxymethyl (meth) acrylamide, N- (n-, iso) butoxymethyl (meth) acrylamide, N-methoxyethyl (meth) acrylamide, N-ethoxyethyl (meth) acrylamide, N- (n-, iso) Examples include (meth) acrylamides such as N-alkoxyalkyl (meth) acrylamides such as butoxyethyl (meth) acrylamide.

  Among these, (meth) acrylates containing a chain alkyl group having 1 to 8 carbon atoms from the viewpoint of flexibility of the polymer skeleton and ease of control of the glass transition temperature (Tg) and from the viewpoint of dispersion stability of the self-dispersing polymer. Preferably, it is a (meth) acrylate having a chain alkyl group having 1 to 4 carbon atoms, and particularly preferably methyl (meth) acrylate or ethyl (meth) acrylate. Here, the chain alkyl group refers to an alkyl group having a straight chain or a branched chain.

In the present invention, (meth) acrylates containing an aromatic group can also be preferably used.
When aromatic-containing (meth) acrylate is included as another copolymerizable monomer, the structural unit derived from aromatic-containing (meth) acrylate is 40% by weight or less from the viewpoint of dispersion stability of the self-dispersing polymer particles. Is more preferable, 30% by weight or less is more preferable, and 20% by weight or less is particularly preferable.

In addition, when using a styrenic monomer as another copolymerizable monomer, from the viewpoint of stability when the self-dispersing polymer particles are used, the structural unit derived from the styrenic monomer is preferably 20% by mass or less, The content is more preferably 10% by mass or less, still more preferably 5% by mass or less, and an embodiment that does not include a structural unit derived from a styrene monomer is particularly preferable.
Here, the styrene monomer refers to styrene, substituted styrene (α-methylstyrene, chlorostyrene, etc.), and a styrene macromer having a polystyrene structural unit.

In the present invention, other copolymerizable monomers may be used singly or in combination of two or more.
When the self-dispersing polymer particles contain other structural units, the content is preferably 10 to 80% by mass, more preferably 15 to 75% by mass, and particularly preferably 20 to 70% by mass. %. When using the monomer which forms another structural unit in combination of 2 or more types, it is preferable that the total content is the said range.

(Constitutional unit having a carboxyl group )
The self-dispersing polymer in the present invention contains at least one structural unit having a carboxyl group . Below, it demonstrates including a hydrophilic structural unit other than the structural unit which has a carboxyl group. The hydrophilic structural unit is not particularly limited as long as it is derived from a hydrophilic group-containing monomer, and even if it is derived from one kind of hydrophilic group-containing monomer, it contains two or more hydrophilic groups. It may be derived from a monomer. The hydrophilic group is not particularly limited, and may be a dissociable group or a nonionic hydrophilic group.
In the present invention, at least one of the hydrophilic groups is preferably a dissociable group from the viewpoint of promoting self-dispersion and the stability of the formed emulsified or dispersed state, and is an anionic dissociable group. More preferably. Examples of the anionic dissociable group include a carboxyl group, a phosphoric acid group, and a sulfonic acid group. Among these, a carboxyl group is particularly preferable from the viewpoint of fixability when an aqueous ink composition is formed.

The hydrophilic group-containing monomer in the present invention is preferably a dissociable group-containing monomer from the viewpoint of self-dispersibility, and is preferably a dissociable group-containing monomer having a dissociable group and an ethylenically unsaturated bond. .
Examples of the dissociable group-containing monomer include an unsaturated carboxylic acid monomer, an unsaturated sulfonic acid monomer, and an unsaturated phosphoric acid monomer.

Specific examples of the unsaturated carboxylic acid monomer include acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid, citraconic acid, and 2-methacryloyloxymethyl succinic acid. Specific examples of the unsaturated sulfonic acid monomer include styrene sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid, 3-sulfopropyl (meth) acrylate, and bis- (3-sulfopropyl) -itaconate. It is done. Specific examples of unsaturated phosphoric acid monomers include vinylphosphonic acid, vinyl phosphate, bis (methacryloxyethyl) phosphate, diphenyl-2-acryloyloxyethyl phosphate, diphenyl-2-methacryloyloxyethyl phosphate, dibutyl-2- Examples include acryloyloxyethyl phosphate.
Among the dissociable group-containing monomers, from the viewpoints of dispersion stability and ejection stability, unsaturated carboxylic acid monomers are preferable, and at least one of acrylic acid and methacrylic acid is more preferable.

Examples of the monomer having a nonionic hydrophilic group include 2-methoxyethyl acrylate, 2- (2-methoxyethoxy) ethyl acrylate, 2- (2-methoxyethoxy) ethyl methacrylate, ethoxytriethylene glycol methacrylate, and methoxypolyethylene. Ethylenically unsaturated monomers containing (poly) ethyleneoxy groups or polypropyleneoxy groups such as glycol (molecular weight 200 to 1000) monomethacrylate, polyethylene glycol (molecular weight 200 to 1000) monomethacrylate, hydroxymethyl (meth) acrylate, 2 -Hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, hydroxypentyl (meth) acrylate Rate, ethylenically unsaturated monomer having a hydroxyl group such as hydroxymethyl (meth) acrylate.
In addition, as a monomer having a nonionic hydrophilic group, an ethylenically unsaturated monomer having a terminal alkyl ether is more stable in terms of particle stability and content of water-soluble components than an ethylenically unsaturated monomer having a terminal hydroxyl group. It is preferable from the viewpoint.

As the hydrophilic structural unit in the present invention, an embodiment containing only a hydrophilic unit having an anionic dissociable group, a hydrophilic structural unit having an anionic dissociative group, and a nonionic hydrophilic group It is preferable that it is either of the aspects containing both the hydrophilic structural unit which has.
Also, an embodiment containing two or more hydrophilic units having an anionic dissociable group, a hydrophilic structural unit having an anionic dissociative group, and a hydrophilic structural unit having a nonionic hydrophilic group It is also preferable that two or more are used in combination.

The content of the hydrophilic constituent unit in the self-dispersing polymer is preferably 25% by mass or less, more preferably 1 to 25% by mass, and more preferably 2 to 23% by mass from the viewpoints of viscosity and stability over time. It is further more preferable that it is 4-20 mass%.
Moreover, when it has 2 or more types of hydrophilic structural units, it is preferable that the total content rate of a hydrophilic structural unit exists in the said range.

The content of the structural unit having an anionic dissociative group in the self-dispersing polymer is preferably in a range where the acid value is in a suitable range described later.
In addition, the content of the structural unit having a nonionic hydrophilic group is preferably 0 to 25% by mass, more preferably 0 to 20% by mass, from the viewpoint of ejection stability and temporal stability. Particularly preferred is 0 to 15% by mass.

  When the self-dispersing polymer has an anionic dissociative group, the acid value (mgKOH / g) is determined from the viewpoint of self-dispersibility, the content of water-soluble components, and the fixing property when an aqueous ink composition is formed. Therefore, it is preferably 20 or more and 200 or less, more preferably 22 or more and 120 or less, and particularly preferably 25 or more and 100 or less. Particularly preferred is 30 or more and 80 or less. When the acid value is 20 or more, the particles can be more stably dispersed, and when the acid value is 200 or less, water-soluble components can be reduced.

The self-dispersing polymer in the present invention is a polymer obtained by polymerizing at least three kinds of alicyclic (meth) acrylate, other copolymerizable monomer, and hydrophilic group-containing monomer from the viewpoint of dispersion stability. A polymer obtained by polymerizing at least three types of alicyclic (meth) acrylate, linear or branched alkyl group-containing (meth) acrylate having 1 to 8 carbon atoms, and hydrophilic group-containing monomer It is more preferable that
In the present invention, from the viewpoint of dispersion stability, substitution with a large hydrophobicity derived from a (meth) acrylate having a linear or branched alkyl group having 9 or more carbon atoms, an aromatic group-containing macromonomer, or the like The content of the structural unit having a group is preferably substantially not contained, and more preferably not contained at all.

  The self-dispersing polymer in the present invention may be a random copolymer in which each constitutional unit is irregularly introduced, or may be a block copolymer that is regularly introduced, and is a block copolymer. Each structural unit in this case may be synthesized in any order of introduction, and the same structural component may be used twice or more, but a random copolymer is a point of versatility and manufacturability Is preferable.

The molecular weight range of the self-dispersing polymer in the present invention is preferably 3000 to 200,000, more preferably 10,000 to 200,000, and still more preferably 30000 to 150,000 in terms of weight average molecular weight. By setting the weight average molecular weight to 3000 or more, the amount of water-soluble components can be effectively suppressed. Moreover, self-dispersion stability can be improved by making a weight average molecular weight into 200,000 or less.
The weight average molecular weight can be measured by gel permeation chromatography (GPC) as in the case of the water-insoluble polymer dispersant.

  Moreover, 40-180 degreeC is preferable, as for the glass transition temperature (Tg) of the self-dispersing polymer in this invention, 60-170 degreeC is more preferable, and 70-150 degreeC is especially preferable. When the glass transition temperature is 40 ° C. or higher, the scratch resistance and blocking property of an image formed using the aqueous ink composition are further improved. Further, when the glass transition temperature is 180 ° C. or lower, the abrasion resistance of the image becomes better.

From the viewpoint of controlling the hydrophilicity / hydrophobicity of the polymer, the self-dispersing polymer of the present invention is derived from a dissociable group-containing monomer having a structure derived from an alicyclic (meth) acrylate as a copolymerization ratio of 20% by mass to 90% by mass. And a structure derived from (meth) acrylate containing a chain alkyl group having 1 to 8 carbon atoms, an acid value of 20 to 120, and a total content of hydrophilic structural units A vinyl polymer having a rate of 25% by mass or less and a weight average molecular weight of 3000 to 200,000 is preferable.
In addition, a structure derived from a bicyclic or tricyclic or higher polycyclic (meth) acrylate having a copolymerization ratio of 30% by mass or more and less than 90% by mass and a chain alkyl group having 1 to 4 carbon atoms is contained. A structure derived from (meth) acrylate as a copolymerization ratio is 10% by mass or more and less than 70% by mass, and a structure derived from a carboxyl group-containing monomer has an acid value in the range of 25 to 100, and the total content of hydrophilic structural units A vinyl polymer having a rate of 25% by mass or less and a weight average molecular weight of 10,000 to 200,000 is more preferable.
Furthermore, a structure derived from a bicyclic or tricyclic or higher polycyclic (meth) acrylate having a copolymerization ratio of 40% by mass or more and less than 80% by mass, at least methyl (meth) acrylate or ethyl (meth) acrylate Containing the derived structure as a copolymerization ratio of 20% by mass or more and less than 60% by mass, including the structure derived from acrylic acid or methacrylic acid in an acid value range of 30 to 80, and the total content of hydrophilic structural units being 25% by mass %, And a vinyl polymer having a weight average molecular weight of 30,000 to 150,000 is particularly preferable.

  Specific examples of the self-dispersing polymer are listed below as exemplary compounds C-01 to C-13, but the present invention is not limited thereto. In addition, the parenthesis represents the mass ratio of the copolymerization component.

C-01: Methyl methacrylate / isobornyl methacrylate / methacrylic acid copolymer (40/52/8)
C-02: Methyl methacrylate / isobornyl methacrylate / benzyl methacrylate / methacrylic acid copolymer (30/50/14/6)
C-03: Methyl methacrylate / dicyclopentanyl methacrylate / methacrylic acid copolymer (40/50/10)
C-04: Methyl methacrylate / dicyclopentanyl methacrylate / phenoxyethyl methacrylate / methacrylic acid copolymer (30/50/14/6)
C-05: Methyl methacrylate / isobornyl methacrylate / methoxypolyethylene glycol methacrylate (n = 2) / methacrylic acid copolymer (30/54/10/6)
C-06: Methyl methacrylate / dicyclopentanyl methacrylate / methoxy polyethylene glycol methacrylate (n = 2) / methacrylic acid copolymer (54/35/5/6)
C-07: Methyl methacrylate / adamantyl methacrylate / methoxy polyethylene glycol methacrylate (n = 23) / methacrylic acid copolymer (30/50/15/5)
C-08: Methyl methacrylate / isobornyl methacrylate / dicyclopentanyl methacrylate / methacrylic acid copolymer (20/50/22/8)
C-09: Ethyl methacrylate / cyclohexyl methacrylate / acrylic acid copolymer (50/45/5)
C-10: Isobutyl methacrylate / cyclohexyl methacrylate / acrylic acid copolymer (40/50/10)
C-11: n-butyl methacrylate / cyclohexyl methacrylate / styrene / acrylic acid copolymer (30/55/10/5)
C-12: Methyl methacrylate / dicyclopentenyloxyethyl methacrylate / methacrylic acid copolymer (40/52/8)
C-13: lauryl methacrylate / dicyclopentenyloxyethyl methacrylate / methacrylic acid copolymer (25/65/10)

There is no restriction | limiting in particular as a manufacturing method of the self-dispersing polymer in this invention, It can manufacture by copolymerizing a monomer mixture by a well-known polymerization method. Among these polymerization methods, polymerization from an organic medium is more preferable, and solution polymerization is particularly preferable from the viewpoint of droplet ejection stability when an aqueous ink composition is obtained.
In the method for producing a self-dispersing polymer of the present invention, the water-insoluble polymer is obtained by copolymerizing a monomer mixture and, if necessary, a mixture containing an organic solvent and a radical polymerization initiator in an inert gas atmosphere. Can be manufactured.

The method for producing an aqueous dispersion of self-dispersing polymer particles in the present invention is not particularly limited, and an aqueous dispersion of self-dispersing polymer particles can be obtained by a known method. The step of obtaining the self-dispersing polymer as an aqueous dispersion is preferably a phase inversion emulsification method including the following step (1) and step (2).
Step (1): A step of obtaining a dispersion by stirring a mixture containing a water-insoluble polymer, an organic solvent, a neutralizing agent, and an aqueous medium.
Step (2): A step of removing at least a part of the organic solvent from the dispersion.

The step (1) is preferably a treatment in which the water-insoluble polymer is first dissolved in an organic solvent, and then a neutralizer and an aqueous medium are gradually added, mixed and stirred to obtain a dispersion. Thus, by adding a neutralizing agent and an aqueous medium to a water-insoluble polymer solution dissolved in an organic solvent, a self-dispersing polymer particle having a particle size with higher storage stability without requiring strong shearing force. Can be obtained.
There is no restriction | limiting in particular in the stirring method of this mixture, Dispersing machines, such as a generally used mixing stirring apparatus and an ultrasonic disperser, a high-pressure homogenizer, can be used as needed.

Preferred examples of the organic solvent include alcohol solvents, ketone solvents, and ether solvents.
Examples of the alcohol solvent include isopropyl alcohol, n-butanol, t-butanol, ethanol and the like. Examples of the ketone solvent include acetone, methyl ethyl ketone, diethyl ketone, and methyl isobutyl ketone. Examples of the ether solvent include dibutyl ether and dioxane. Among these organic solvents, ketone solvents such as methyl ethyl ketone and alcohol solvents such as isopropyl alcohol are preferable.
It is also preferable to use isopropyl alcohol and methyl ethyl ketone in combination. By using the solvent in combination, it is possible to obtain self-dispersing polymer particles having a fine particle size with high dispersion stability without agglomeration and sedimentation or fusion between particles. This can be considered, for example, because the polarity change during the phase inversion from the oil system to the water system becomes mild.

  The neutralizing agent is used so that a part or all of the dissociable groups are neutralized and the self-dispersing polymer forms a stable emulsified or dispersed state in water. When the self-dispersing polymer has an anionic dissociative group as a dissociable group, examples of the neutralizing agent used include basic compounds such as organic amine compounds, ammonia, and alkali metal hydroxides. Examples of organic amine compounds include monomethylamine, dimethylamine, trimethylamine, monoethylamine, diethylamine, triethylamine, monopropylamine, dipropylamine, monoethanolamine, diethanolamine, triethanolamine, N, N-dimethyl-ethanolamine, N, N-diethyl-ethanolamine, 2-dimethylamino-2-methyl-1-propanol, 2-amino-2-methyl-1-propanol, N-methyldiethanolamine, N-ethyldiethanolamine, monoisopropanolamine, diisopropanol Examples include amines and triisopropanolamine. Examples of the alkali metal hydroxide include lithium hydroxide, sodium hydroxide, and potassium hydroxide. Among these, sodium hydroxide, potassium hydroxide, triethylamine, and triethanolamine are preferable from the viewpoint of stabilizing the dispersion of the self-dispersing polymer particles of the present invention in water.

  These basic compounds are preferably used in an amount of 5 to 120 mol%, more preferably 20 to 100 mol%, still more preferably 30 to 80 mol%, based on 100 mol% of the dissociable group. By setting it as 15 mol% or more, the effect which stabilizes dispersion | distribution of the particle | grains in water expresses, and there exists an effect which reduces a water-soluble component by setting it as 80 mol% or less.

  In the step (2), an aqueous dispersion of self-dispersing polymer particles is obtained by distilling off the organic solvent from the dispersion obtained in the step (1) by a conventional method such as vacuum distillation and phase-inversion into an aqueous system. Can be obtained. The organic solvent in the obtained aqueous dispersion has been substantially removed, and the amount of the organic solvent is preferably 0.2% by mass or less, more preferably 0.1% by mass or less.

The average particle size of the self-dispersing polymer particles in the present invention is preferably in the range of 1 to 100 nm, more preferably 3 to 80 nm, and further preferably 5 to 60 nm. Most preferably, it is 5-40 nm. Manufacturability is improved when the average particle diameter is 1 nm or more. Moreover, storage stability improves by setting it as an average particle diameter of 100 nm or less.
Further, the particle size distribution of the self-dispersing polymer particles is not particularly limited, and may be either a wide particle size distribution or a monodispersed particle size distribution. Further, two or more kinds of water-insoluble particles may be mixed and used.
The average particle size and particle size distribution of the self-dispersing polymer particles can be measured using, for example, a light scattering method.

In the aqueous ink composition of the invention, the self-dispersing polymer particles are preferably present in a form that does not substantially contain a colorant.
The self-dispersing polymer particles of the present invention are excellent in self-dispersibility, and the stability when dispersed alone is very high. However, for example, since the function as a so-called dispersant for stably dispersing the pigment is not high, if the self-dispersing polymer in the present invention is present in the aqueous ink composition in a form containing the pigment, the aqueous ink composition is consequently obtained. The overall stability may be greatly reduced.

In the water-based ink composition of the present invention, the self-dispersing polymer particles may be contained singly or in combination of two or more.
In addition, the content of the self-dispersing polymer particles in the aqueous ink composition of the present invention is preferably 1 to 30% by mass with respect to the aqueous ink composition from the viewpoint of image glossiness and the like. The content is more preferably mass%, and particularly preferably 2 to 10 mass%.
The content ratio of the colored particles to the self-dispersing polymer particles (colored particles / self-dispersing polymer particles) in the aqueous ink composition of the present invention is 1 / 0.5 to 1 / from the viewpoint of image scratch resistance. 10 is preferable, and 1/1 to 1/4 is more preferable.

[Aqueous medium]
(Water-soluble solvent)
The aqueous ink composition of the present invention contains an aqueous medium. The aqueous medium contains at least water as a solvent, but preferably contains water and a water-soluble solvent. The water-soluble solvent is used for the purpose of an anti-drying agent, a wetting agent or a penetration accelerator.
Anti-drying agents and wetting agents are used for the purpose of preventing clogging due to drying of the ink-jet ink at the nozzles, and the anti-drying agents and wetting agents are water-soluble organic compounds having a vapor pressure lower than that of water. Solvents are preferred.
In addition, a water-soluble organic solvent is preferably used as a penetration accelerator for the purpose of allowing a water-based ink composition (particularly, an ink-jet ink composition) to penetrate into paper better.

There are no particular restrictions on the anti-drying agent or wetting agent used in the present invention, and any known anti-drying agent or wetting agent can be used. In the present invention, the water-soluble solvent contains 90% by mass or more of a water-soluble solvent having an SP value of 27.5 or less based on the total water-soluble solvent from the viewpoint of suppressing the occurrence of curling in the recording medium, and has the following structure It is preferable to contain at least one compound represented by the formula (1).
The “water-soluble solvent having an SP value of 27.5 or less” and the “compound represented by the structural formula (1)” may be the same or different.

  The solubility parameter (SP value) of the water-soluble solvent referred to in the present invention is a value represented by the square root of the molecular cohesive energy. F. It can be calculated by the method described in Fedors, Polymer Engineering Science, 14, p147-154 (1974), and this numerical value is adopted in the present invention.

In the structural formula (1), l, m, and n are each independently an integer of 1 or more and l + m + n = 3-15, but l + m + n is preferably 3-12, more preferably 3-10. .
When l + m + n is 3 or more, a good curl suppressing force can be exhibited. Moreover, favorable dischargeability is acquired because it is 15 or less.
In the structural formula (1), AO represents ethyleneoxy (EO) and / or propyleneoxy (PO), and among them, a propyleneoxy group is preferable. In addition, each AO in (AO) l, (AO) m, and (AO) n may be the same or different.

  Examples of the water-soluble solvent having an SP value of 27.5 or less and the compound represented by the structural formula (1) are shown below together with the SP value (in parentheses). However, the present invention is not limited to this.

Diethylene glycol monoethyl ether (SP value 22.4)
Diethylene glycol monobutyl ether (SP value 21.5)
Triethylene glycol monobutyl ether (SP value 21.1)
Dipropylene glycol monomethyl ether (SP value 21.3)
Dipropylene glycol (SP value 27.2)

_{nC 4 H 9 O (AO)} 4 -H ( in AO = EO or PO, the ratio of EO: PO = 1: 1) (SP value 20.1)
_{nC 4 H 9 O (AO)} 10 -H ( in AO = EO or PO, the ratio of EO: PO = 1: 1) (SP value 18.8)
HO (A′O) ₄₀ −H (A′O = EO or PO, the ratio is EO: PO = 1: 3) (SP value 18.7)
HO (A ″ O) ₅₅ −H (A ″ O = EO or PO, the ratio is EO: PO = 5: 6) (SP value 18.8)
HO (PO) ₃ -H (SP value 24.7)
HO (PO) ₇ -H (SP value 21.2)
1,2-hexanediol (SP value 27.4)
In the present invention, EO and PO represent an ethyleneoxy group and a propyleneoxy group, respectively.

  The proportion (content) of the compound of the structural formula (1) in the total water-soluble solvent is preferably 10% or more, more preferably 30% or more, and further preferably 50% or more. By setting it in the above range, curling can be suppressed without deteriorating the stability and ejection properties of the ink, which is preferable.

In the present invention, other solvents may be used in combination as long as the ratio of the water-soluble solvent having an SP value of 27.5 or less to the total water-soluble solvent is not less than 90%.
Examples of water-soluble organic solvents that can be used in combination include glycerin, 1,2,6-hexanetriol, trimethylolpropane, ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, pentaethylene glycol, dipropylene glycol, 2 -Butene-1,4-diol, 2-ethyl-1,3-hexanediol, 2-methyl-2,4-pentanediol, 1,2-octanediol, 1,2-hexanediol, 1,2-pentane Alkanediols (polyhydric alcohols) such as diol and 4-methyl-1,2-pentanediol; C1-C4 alkyl alcohols such as ethanol, methanol, butanol, propanol and isopropanol;

Ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol monomethyl ether acetate, ethylene glycol mono-iso-propyl ether, ethylene glycol mono-n-butyl ether, ethylene glycol mono-t-butyl ether, diethylene glycol mono- glycol ethers such as t-butyl ether and 1-methyl-1-methoxybutanol; 2-pyrrolidone, N-methyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, formamide, acetamide, dimethyl sulfoxide, sorbit Sorbitan, acetin, diacetin, triacetin, sulfolane and the like, and one or more of these can be used. That.

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

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

The water-soluble solvent used in the present invention may be used alone or in combination of two or more.
The content of the water-soluble solvent is preferably 1% by mass or more and 60% by mass or less, more preferably 5% by mass or more and 40% by mass or less, from the viewpoint of ensuring stability and ejection reliability in the entire ink composition. 10 mass% or more and 30 mass% or less are used especially preferably.

  The amount of water used in the present invention is not particularly limited, but is preferably 10% by mass or more and 99% by mass or less, more preferably from the viewpoint of securing stability and ejection reliability in the aqueous ink composition. They are 30 mass% or more and 80 mass% or less, More preferably, they are 50 mass% or more and 70 mass% or less.

(Other additives)
Examples of other additives in the present invention include, for example, antifading agents, emulsion stabilizers, penetration enhancers, ultraviolet absorbers, preservatives, antifungal agents, pH adjusters, surface tension adjusters, antifoaming agents, and viscosity adjusters. Known additives such as an agent, a dispersant, a dispersion stabilizer, a rust inhibitor, a chelating agent, and a solid wetting agent are included. These various additives may be added directly after the aqueous ink composition is prepared, or may be added when the aqueous ink composition is prepared.

  The ultraviolet absorber is used for the purpose of improving image storability. Examples of ultraviolet absorbers include benzotriazoles described in JP-A Nos. 58-185677, 61-190537, JP-A-2-782, JP-A-5-97075, JP-A-9-34057, and the like. Compounds, benzophenone compounds described in JP-A No. 46-2784, JP-A No. 5-194433, US Pat. No. 3,214,463, etc., JP-B Nos. 48-30492, 56-211141, Cinnamic acid compounds described in, for example, Kaihei 10-88106, JP-A-4-298503, 8-53427, 8-239368, 10-182621, JP-A-8- No. 501291, etc., triazine compounds, Research Disclosure No. Compounds described in No. 24239, compounds that emit fluorescence by absorbing ultraviolet rays typified by stilbene-based and benzoxazole-based compounds, so-called fluorescent brighteners, can also be used.

  The anti-fading agent is used for the purpose of improving image storage stability. As the antifading agent, various organic and metal complex antifading agents can be used. Organic anti-fading agents include hydroquinones, alkoxyphenols, dialkoxyphenols, phenols, anilines, amines, indanes, chromans, alkoxyanilines, heterocycles, etc. Complex, zinc complex and the like. More specifically, Research Disclosure No. No. 17643, Nos. VII to I, J; 15162, ibid. No. 18716, page 650, left column, ibid. No. 36544, page 527, ibid. No. 307105, page 872, ibid. The compounds described in the patent cited in Japanese Patent No. 15162 and the compounds included in the general formulas and compound examples of typical compounds described on pages 127 to 137 of JP-A-62-215272 can be used.

Examples of the antifungal agent include sodium dehydroacetate, sodium benzoate, sodium pyridinethione-1-oxide, p-hydroxybenzoic acid ethyl ester, 1,2-benzisothiazolin-3-one and salts thereof. These are preferably used in the water-based ink composition in an amount of 0.02 to 1.00% by mass.
As the pH adjuster, a neutralizer (organic base, inorganic alkali) can be used. For the purpose of improving the storage stability of the aqueous ink composition, the pH adjuster is preferably added so that the aqueous ink composition has a pH of 6 to 10, and more preferably added to have a pH of 7 to 10. .

Examples of the surface tension adjusting agent include nonionic surfactants, cationic surfactants, anionic surfactants, betaine surfactants, and the like.
The addition amount of the surface tension adjusting agent is preferably an addition amount for adjusting the surface tension (25 ° C.) of the water-based ink composition to 20 to 60 mN / m, in order to achieve good droplet ejection by the ink jet method. The addition amount adjusted to / m is more preferable, and the addition amount adjusted to 25 to 40 mN / m is more preferable. On the other hand, when ink is applied by a method other than the inkjet method, a range of 20 to 60 mN / m is preferable, and a range of 30 to 50 mN / m is more preferable.
The surface tension of the water-based ink composition can be measured using, for example, a plate method.

Specific examples of surfactants include fatty acid salts, alkyl sulfate esters, alkylbenzene sulfonates, alkyl naphthalene sulfonates, dialkyl sulfosuccinates, alkyl phosphate esters, naphthalene sulfonate formalin condensation in hydrocarbons Products, anionic surfactants such as polyoxyethylene alkyl sulfates, polyoxyethylene alkyl ethers, polyoxyethylene alkyl allyl ethers, polyoxyethylene fatty acid esters, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, polyoxy Nonionic surfactants such as ethylene alkylamine, glycerin fatty acid ester and oxyethyleneoxypropylene block copolymer are preferred. Further, SURFYNOLS (Air Products & Chemicals), which is an acetylene-based polyoxyethylene oxide surfactant, is also preferably used. An amine oxide type amphoteric surfactant such as N, N-dimethyl-N-alkylamine oxide is also preferred.
Furthermore, pages (37) to (38) of JP-A-59-157636, Research Disclosure No. The surfactants described in 308119 (1989) can also be used.
Further, fluorine (fluorinated alkyl type) surfactants, silicone type surfactants and the like described in JP-A Nos. 2003-322926, 2004-325707, and 2004-309806 are disclosed. By using, the abrasion resistance can be improved.
These surface tension modifiers can also be used as antifoaming agents, and fluorine compounds, silicone compounds, chelating agents represented by EDTA, and the like can also be used.

The viscosity (25 ° C.) of the water-based ink composition of the present invention is preferably in the range of 1 to 30 mPa · s from the viewpoint of droplet ejection stability and agglomeration speed when ink is applied by an inkjet method, and 1 to 20 mPa. -The range of s is more preferable, the range of 2-15 mPa * s is further more preferable, and the range of 2-10 mPa * s is especially preferable.
In addition, when ink is applied by a method other than the inkjet method, a range of 1 to 40 mPa · s is preferable, and a range of 5 to 20 mPa · s is more preferable.
The viscosity of the water-based ink composition can be measured using, for example, a Brookfield viscometer.

  Examples of solid wetting agents include glucose, mannose, fructose, ribose, xylose, arabinose, galactose, aldonic acid, glucitol, maltose, cellobiose, lactose, sucrose, trehalose, maltotriose and other sugars; sugar alcohols; hyaluronic acids; urea And the like.

<Ink set>
The ink set of the present invention includes at least one water-based ink composition. By including the water-based ink composition as the ink constituting the ink set, fixability and blocking of an image formed using the ink set of the present invention are improved. The ink set of the present invention is used in a recording method using the water-based ink composition, and is particularly preferable as an ink set used in an inkjet recording method described later.
The ink set of the present invention can be used as an ink cartridge that accommodates them integrally or independently, and is preferable from the viewpoint of easy handling. An ink cartridge including an ink set is known in the art, and can be formed into an ink cartridge by appropriately using a known method.
Further, the ink set of the present invention can contain a treatment liquid composition for improving printability in addition to at least one of the recording liquids.

(Treatment liquid composition for improving printability)
In the present invention, prior to the application of the water-based ink composition, a treatment liquid composition that improves printability can be applied onto a recording medium.
The treatment liquid in the present invention is an aqueous composition capable of forming an aggregate when it comes into contact with the aqueous ink composition. Specifically, when mixed with the ink composition, the colored particles in the ink composition It contains at least an aggregating component capable of aggregating dispersed particles such as (pigment etc.) to form an agglomerate, and may be constituted using other components as necessary. By using the treatment liquid together with the ink composition, it is possible to increase the speed of inkjet recording, and an image with high density and resolution can be obtained even when recording at high speed.

(Aggregating component)
The treatment liquid contains at least one aggregation component capable of forming an aggregate upon contact with the ink composition. For example, when the treatment liquid is mixed with the ink composition ejected by the ink jet method, aggregation of pigments and the like stably dispersed in the ink composition is promoted.

Examples of the treatment liquid include a liquid capable of generating an aggregate by changing the pH of the ink composition. At this time, the pH (25 ° C. ± 1 ° C.) of the first treatment liquid is preferably 1 to 6, more preferably 1.2 to 5, from the viewpoint of the aggregation rate of the ink composition. More preferably, it is 5-4. In this case, the pH (25 ± 1 ° C.) of the ink composition used in the ejection process is preferably 7.5 to 9.5 (more preferably 8.0 to 9.0).
Among these, in the present invention, from the viewpoint of image density, resolution, and speedup of inkjet recording, the pH (25 ° C.) of the ink composition is 7.5 or more, and the pH (25 ° C.) of the treatment liquid is. The case of 3-5 is preferable.
The aggregating components can be used alone or in combination of two or more.

  The treatment liquid can be configured using at least one acidic compound as an aggregation component. As the acidic compound, a compound having a phosphoric acid group, a phosphonic acid group, a phosphinic acid group, a sulfuric acid group, a sulfonic acid group, a sulfinic acid group, or a carboxyl group, or a salt thereof (for example, a polyvalent metal salt) may be used. it can. Among these, from the viewpoint of the aggregation rate of the ink composition, a compound having a phosphate group or a carboxyl group is more preferable, and a compound having a carboxyl group is still more preferable.

  Compounds having a carboxyl group include polyacrylic acid, acetic acid, glycolic acid, malonic acid, malic acid, maleic acid, ascorbic acid, succinic acid, glutaric acid, fumaric acid, citric acid, tartaric acid, lactic acid, sulfonic acid, orthophosphoric acid , Pyrrolidone carboxylic acid, pyrone carboxylic acid, pyrrole carboxylic acid, furan carboxylic acid, pyridine carboxylic acid, coumaric acid, thiophene carboxylic acid, nicotinic acid, derivatives of these compounds, or salts thereof (for example, polyvalent metal salts), etc. It is preferable to be selected from among These compounds may be used alone or in combination of two or more.

The treatment liquid in the present invention can be configured to further contain an aqueous solvent (for example, water) in addition to the acidic compound.
As content of the acidic compound of a processing liquid, it is preferable that it is 5-95 mass% with respect to the total mass of a processing liquid from a viewpoint of the aggregation effect, and it is more preferable that it is 10-80 mass%.

  Further, as a preferred example of the treatment liquid for improving the high-speed aggregation property, a treatment liquid to which a polyvalent metal salt or polyallylamine is added can be mentioned. Examples of the polyvalent metal salt include alkaline earth metals belonging to Group 2 of the periodic table (eg, magnesium, calcium), transition metals belonging to Group 3 of the periodic table (eg, lanthanum), and cations from Group 13 of the periodic table. (For example, aluminum), salts of lanthanides (for example, neodymium), polyallylamine, and polyallylamine derivatives. As the metal salt, carboxylate (formic acid, acetic acid, benzoate, etc.), nitrate, chloride, and thiocyanate are suitable. Among them, preferred are calcium salts or magnesium salts of carboxylic acids (formic acid, acetic acid, benzoates, etc.), calcium salts or magnesium salts of nitric acid, calcium chloride, magnesium chloride, and calcium salts or magnesium salts of thiocyanic acid.

  As content in the process liquid of a metal salt, 1-10 mass% is preferable, More preferably, it is 1.5-7 mass%, More preferably, it is the range of 2-6 mass%.

The viscosity of the treatment liquid is preferably in the range of 1 to 30 mPa · s, more preferably in the range of 1 to 20 mPa · s, still more preferably in the range of 2 to 15 mPa · s, from the viewpoint of the aggregation rate of the ink composition. The range of 10 mPa · s is particularly preferable. The viscosity is measured under a condition of 20 ° C. using VISCOMETER TV-22 (manufactured by TOKI SANGYO CO. LTD).
The surface tension of the treatment liquid is preferably 20 to 60 mN / m, more preferably 20 to 45 mN / m, and more preferably 25 to 40 mN / m from the viewpoint of the aggregation rate of the ink composition. More preferably. The surface tension is measured under conditions of 25 ° C. using an Automatic Surface Tensiometer CBVP-Z (manufactured by Kyowa Interface Science Co., Ltd.).

<Image forming method>
The image forming method of the present invention includes an ink application step of forming an image by applying the aqueous ink composition on a recording medium using the aqueous ink composition of the present invention or the ink set, and if necessary, In addition, a drying process, a fixing process, and the like can be further included. By using the water-based ink composition, the formed image has good abrasion resistance and blocking property. Further, when the image forming method includes a fixing step, the offset resistance is improved.

  The water-based ink composition and ink set of the present invention can be used for general writing instruments, recorders, pen plotters, and the like, but are particularly preferably used for inkjet recording methods. The ink jet recording method in which the ink set or the ink cartridge of the present invention can be used includes any recording method in which the ink composition is ejected as droplets from a thin nozzle and the droplets are attached to a recording medium. The recording medium in the present invention is not particularly limited, and examples thereof include plain paper, high-quality paper, and coated paper. In addition, the description of paragraph numbers 0093 to 0105 in JP-A No. 2003-306623 can be applied as an ink jet recording method preferable for the present invention.

An example of an image forming method preferable for the present invention is an image forming method including the following steps.
1st process: The process of providing the liquid composition which improves printability to a recording medium.
Second step: a step of applying a water-based ink composition to the recording medium to which the liquid composition has been applied.
Other steps: Other steps are not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include a drying removal step and a heat fixing step.

  The drying and removing step is not particularly limited as long as at least a part of the ink solvent in the ink composition applied to the recording medium can be dried and removed, and can be appropriately selected according to the purpose. The heat fixing step is not particularly limited as long as latex particles contained in the ink composition can be melt-fixed, and can be appropriately selected according to the purpose.

Another example of the image forming method preferable for the present invention is an image forming method including the following steps.
1st process: The process of providing the liquid composition which improves printability to an intermediate transfer body.
Second step: a step of applying ink of an ink set to the intermediate transfer body to which the liquid composition has been applied.
Third step: a step of transferring an ink image formed on the intermediate transfer member to a recording medium.
Other steps: Other steps are not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include the drying removal step and the heat fixing step.

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

[Preparation of water-insoluble polymer dispersant]
Monomer synthesis example (Synthesis of M-3)
130 g of 2-hydroxyethyl methacrylate and 167 ml of triethylamine were added to 1000 ml of ethyl acetate and stirred at 0 ° C. for 30 minutes. To this solution, 120 g of methanesulfonyl chloride was slowly added dropwise, and stirring was further continued at 0 ° C. for 3 hours. After the reaction, 500 ml of pure water was added to the resulting solution and stirred. The ethyl acetate layer was separated using a separatory funnel, washed with a saturated saline solution, and dried over anhydrous magnesium sulfate. Magnesium sulfate was filtered off and the solution was concentrated to obtain 207 g of 2-methanesulfonyloxyethyl methacrylate.
Synthesized 2-methanesulfonyloxyethyl methacrylate 48 g, 2-naphthol 30 g, and potassium carbonate 43 g were added to 200 ml of N-methylpyrrolidone (NMP) and stirred at room temperature for 1 hour. Furthermore, it stirred at 80 degreeC for 10 hours. After the reaction, the precipitated insoluble matter was removed by filtration, and then 500 ml of ethyl acetate and 200 ml of pure water were added to the resulting solution and stirred. The ethyl acetate layer was separated, washed with a saturated saline solution, and dried over anhydrous magnesium sulfate. Magnesium sulfate was filtered off, the solution was concentrated, and this was purified by silica chromatography to obtain 48 g of M-3.

Monomer Synthesis Example 2 (Synthesis of M-4)
65 g of 2-hydroxyethyl methacrylate, 104 ml of triethylamine and 3 g of dimethylaminopyridine were added to 500 ml of tetrahydrofuran (THF) and stirred at room temperature for 30 minutes. To this solution, 167 g of triphenylmethyl chloride was added, and stirring was continued at room temperature for 10 hours. After the reaction, 500 ml of ethyl acetate and 200 ml of pure water were added to the resulting solution and stirred. The ethyl acetate layer was separated, washed with a saturated saline solution, and dried over anhydrous magnesium sulfate. Magnesium sulfate was filtered off, the solution was concentrated, and this was purified by silica chromatography to obtain 115 g of M-4.

Monomer Synthesis Example 3 (Synthesis of M-5)
30 g of 2-hydroxyethyl methacrylate and 40 ml of triethylamine were added to 500 ml of THF, and the mixture was stirred at 0 ° C. for 30 minutes. To this solution, 50 g of biphenyl-4-carbonyl chloride was added, and stirring was further continued at 0 ° C. for 3 hours. After the reaction, 500 ml of ethyl acetate and 200 ml of pure water were added to the resulting solution and stirred. The ethyl acetate layer was separated using a separatory funnel, washed with a saturated saline solution, and dried over anhydrous magnesium sulfate. Magnesium sulfate was filtered off, the solution was concentrated and purified by silica chromatography to obtain 70 g of M-5.

Monomer Synthesis Example 4 (Synthesis of M-8)
144 g of 2-naphthol, 250 g of ethylene glycol mono-2-chloroethyl ether and 205 g of potassium carbonate were added to 1000 ml of N-methylpyrrolidone (NMP) and stirred at room temperature for 1 hour. Furthermore, it stirred at 110 degreeC for 10 hours. After the reaction, the solution was cooled until it returned to room temperature, 5000 ml of pure water was added to the resulting solution, and the mixture was stirred at room temperature for 1 hour. The precipitated solid was collected by filtration and dried under reduced pressure conditions. 139 g of the solid obtained in the above reaction and 125 ml of triethylamine were added to 500 ml of THF, and the mixture was stirred at 0 ° C. for 30 minutes. To this solution, 75 g of methacrylic acid chloride was slowly added dropwise, and stirring was further continued at 0 ° C. for 3 hours. After the reaction, 500 ml of ethyl acetate and 200 ml of pure water were added to the resulting solution and stirred. The ethyl acetate layer was separated using a separatory funnel, washed with a saturated saline solution, and dried over anhydrous magnesium sulfate. Magnesium sulfate was filtered off, the solution was concentrated, and purified by silica chromatography to obtain 174 g of M-8.

Monomer Synthesis Example 5 (Synthesis of M-9)
N- (2-hydroxyethyl) phthalimide (100 g) and triethylamine (93 ml) were added to 1500 ml of THF, and the mixture was stirred at 0 ° C. for 30 minutes. To this solution, 60 g of methacrylic acid chloride was slowly added dropwise, and stirring was further continued at 0 ° C. for 3 hours. After the reaction, 1000 ml of ethyl acetate and 200 ml of pure water were added to the resulting solution and stirred. The ethyl acetate layer was separated using a separatory funnel, washed with a saturated saline solution, and dried over anhydrous magnesium sulfate. Magnesium sulfate was filtered off, the solution was concentrated, and this was purified by silica chromatography to obtain 113 g of M-9.

Monomer Synthesis Example 6 (Synthesis of M-25 / M-27 mixture)
9.76 parts of 9 (10H) -acridone and 5.61 parts of potassium t-butoxy were dissolved in 30 parts of dimethyl sulfoxide and heated to 45 ° C. To this, 15.26 parts of chloromethylstyrene (CMS-P manufactured by Seimi Chemical Co., Ltd., a mixture of meta-form / para-form = 50/50 (mol / mol)) was added dropwise, and the mixture was further stirred at 50 ° C. for 5 hours. went. The reaction solution was poured into 200 parts of distilled water with stirring, and the resulting precipitate was filtered and washed to obtain 11.9 parts of a M-25 / M-27 mixture.

Monomer Synthesis Example 7 (Synthesis of M-28 / M-29 mixture)
355.0 g of 1,8-naphthalimide was dissolved in 1500 mL of N-methylpyrrolidone, 0.57 g of nitrobenzene was added at 25 ° C., and 301.4 g of DBU (diazabicycloundecene) was added dropwise thereto. After stirring for 30 minutes, 412.1 g of chloromethylstyrene (CMS-P manufactured by Seimi Chemical Co., Ltd., a mixture of meta-form / para-form = 50/50 (mol / mol)) was added dropwise, and further at 60 ° C. for 4 hours. Heating and stirring were performed. To this reaction solution, 2.7 L of isopropanol and 0.9 L of distilled water were added and stirred while cooling to 5 ° C. The obtained precipitate was separated by filtration and washed with 1.2 L of isopropanol to obtain 544.0 g of a M-28 / M-29 mixture.

(Synthesis Example 1) [Synthesis of Polymer Dispersant B-06]
To a 500 ml three-necked flask equipped with a stirrer and a condenser, 60 g of methyl ethyl ketone was added and heated to 72 ° C. in a nitrogen atmosphere. A solution obtained by dissolving the monomer mixture shown in Table 1 and 0.64 g of dimethyl 2,2′-azobisisobutyrate in 30 g of methyl ethyl ketone was dropped into a three-necked flask over 3 hours. After completion of the dropwise addition, the reaction was further continued for 1 hour, and then a solution of 0.3 g of dimethyl 2,2′-azobisisobutyrate dissolved in 10 g of methyl ethyl ketone was added, heated to 78 ° C., heated and stirred for 4 hours, and unreacted. All monomers were reacted. The disappearance of the monomer was confirmed by 1H-NMR. The obtained reaction solution was reprecipitated twice using a large excess of hexane, and the precipitated polymer was dried to obtain 59 g of a water-insoluble polymer dispersant B-06.
The composition of the obtained polymer was confirmed by ¹ H-NMR, and the weight average molecular weight (Mw) and molecular weight distribution (Mw / Mn) were determined by GPC. The GPC conditions are the same as the GPC conditions for the self-dispersing polymer described below.

(Synthesis Examples 2-7)
In Synthesis Example 1, the monomers used for the reaction were changed to those shown in Table 1, and the amount of initiator (dimethyl 2,2′-azobisisobutyrate) was adjusted for the purpose of adjusting the molecular weight. Reaction was carried out in the same manner as in Synthesis Example 1 to obtain the corresponding polymer dispersants (B-13, B-11, B-28, B-23, B-31, B-35).
The composition of the obtained polymer was confirmed by ¹ H-NMR, and the weight average molecular weight (Mw) and molecular weight distribution (Mw / Mn) were determined by GPC.

(Synthesis Example 8) [Synthesis of Polymer Dispersant B-42]
To a 500 ml three-necked flask equipped with a stirrer and a condenser, 90.9 g of methyl ethyl ketone and the monomer mixture shown in Table 1 were added and heated to 75 ° C. under a nitrogen atmosphere. A solution obtained by dissolving 2.0 g of dimethyl 2,2′-azobisisobutyrate in 8.0 g of methyl ethyl ketone was added thereto and reacted for 2 hours while maintaining at 75 ° C. A solution prepared by dissolving 0.5 g of dimethyl 2,2′-azobisisobutyrate in 1.0 g of methyl ethyl ketone was added thereto, and further reacted for 2 hours. Further, a solution in which 0.5 g of dimethyl 2,2′-azobisisobutyrate was dissolved in 1.0 g of methyl ethyl ketone was added, and the temperature was raised to 78 ° C., followed by heating and stirring for 4 hours to react all unreacted monomers. The disappearance of the monomer was confirmed by 1H-NMR. The obtained reaction solution was reprecipitated twice using a large excess of hexane, and the precipitated polymer was dried to obtain 97 g of water-insoluble polymer dispersant B-42.
The composition of the obtained polymer was confirmed by ¹ H-NMR, and the weight average molecular weight (Mw) and molecular weight distribution (Mw / Mn) were determined by GPC.

(Synthesis Examples 9 to 13)
In Synthesis Example 8, the monomers used for the reaction were changed to those shown in Table 1, and the amount of initiator (dimethyl 2,2′-azobisisobutyrate) was adjusted for the purpose of adjusting the molecular weight. Reaction was performed in the same manner as in Synthesis Example 1 to obtain the corresponding polymers (B-43, B-46, B-47, B-49, B-53).
The composition of the obtained polymer was confirmed by ¹ H-NMR, and the weight average molecular weight (Mw) and molecular weight distribution (Mw / Mn) were determined by GPC.

(Synthesis Example 14) [Synthesis of Polymer Dispersant BH-01]
According to Production Example A of the resin composition solution described in paragraphs [0046] to [0059] of JP-A-2007-99913, the following polymer dispersant BH-01 was obtained.
-BH-01: benzyl acrylate / acrylic acid = 90/10 (mass ratio)

[Preparation of self-dispersing polymer]
Synthesis Example 15 Preparation of Self-Dispersing Polymer (C-01)
In a 2 liter three-necked flask equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen gas introduction tube, 540.0 g of methyl ethyl ketone was charged and heated to 75 ° C. While maintaining the reaction vessel temperature at 75 ° C., 216 g of methyl methacrylate, 280.8 g of isobornyl methacrylate, 43.2 g of methacrylic acid, 108 g of methyl ethyl ketone, and 2.16 g of “V-601” (manufactured by Wako Pure Chemical Industries, Ltd.) The mixed solution consisting of was dropped at a constant speed so that the dropping was completed in 2 hours. After completion of the dropwise addition, a solution consisting of 1.08 g of “V-601” and 15.0 g of methyl ethyl ketone was added, stirred for 2 hours at 75 ° C., and then a solution consisting of 0.54 g of “V-601” and 15.0 g of methyl ethyl ketone was added. After stirring at 75 ° C. for 2 hours, the temperature was raised to 85 ° C., and stirring was further continued for 2 hours.
The weight average molecular weight (Mw) of the obtained copolymer was 61000 (calculated in terms of polystyrene by gel permeation chromatography (GPC), the columns used were TSKgel SuperHZM-H, TSKgel SuperHZ4000, TSKgel SuperHZ200 (manufactured by Tosoh Corporation)), The acid value was 52.1 (mgKOH / g).

Next, 588.2 g of the polymerization solution was weighed, 165 g of isopropanol and 120.8 ml of 1 mol / L NaOH aqueous solution were added, and the temperature in the reaction vessel was raised to 80 ° C. Next, 718 g of distilled water was added dropwise at a rate of 20 ml / min to disperse in water. Then, the solvent was distilled off by keeping the temperature in the reaction vessel at 80 ° C. for 2 hours, 85 ° C. for 2 hours, and 90 ° C. for 2 hours under atmospheric pressure. Furthermore, the pressure in the reaction vessel was reduced, and isopropanol, methyl ethyl ketone, and distilled water were distilled off to obtain an aqueous dispersion of a self-dispersing polymer (C-01) having a solid content concentration of 26.0%.
In addition, the number of each structural unit of the following compound example (C-01) represents mass ratio. Hereinafter, the same applies to each structural formula.
C-01: Methyl methacrylate / isobornyl methacrylate / methacrylic acid copolymer (40/52/8), Mw: 62000, Mw / Mn: 2.16

Synthesis Example 16 Preparation of Self-Dispersing Polymers (C-02) to (C-13)
In Synthesis Example 14, Example 1 except that the mixing ratio of each monomer was changed so as to be the mass ratio of the following exemplary compounds instead of 108 g of methyl methacrylate, 388.8 g of isobornyl methacrylate, and 43.2 g of methacrylic acid. In the same manner as described above, the following exemplified self-dispersing polymers (C-02) to (C-13) were obtained. In all cases, the amount of NaOH aqueous solution (1 mol / L) was adjusted so that the degree of neutralization of the self-dispersing polymer was 65 mol% with respect to 1 mol of the dissociable group.

C-02: Methyl methacrylate / isobornyl methacrylate / benzyl methacrylate / methacrylic acid copolymer (30/50/14/6), Mw: 54000, Mw / Mn: 2.86
C-03: Methyl methacrylate / dicyclopentanyl methacrylate / methacrylic acid copolymer (40/50/10), Mw: 92000, Mw / Mn: 1.92
C-04: Methyl methacrylate / dicyclopentanyl methacrylate / phenoxyethyl methacrylate / methacrylic acid copolymer (30/50/14/6), Mw: 72000, Mw / Mn: 2.45
C-05: Methyl methacrylate / isobornyl methacrylate / methoxypolyethylene glycol methacrylate (n = 2) / methacrylic acid copolymer (30/54/10/6), Mw: 48000, Mw / Mn: 2.97
C-06: Methyl methacrylate / dicyclopentanyl methacrylate / methoxy polyethylene glycol methacrylate (n = 2) / methacrylic acid copolymer (54/35/5/6), Mw: 32000, Mw / Mn: 1.82
C-07: Methyl methacrylate / adamantyl methacrylate / methoxy polyethylene glycol methacrylate (n = 23) / methacrylic acid copolymer (30/50/15/5), Mw: 68000, Mw / Mn: 2.89
-C-08: Methyl methacrylate / isobornyl methacrylate / dicyclopentanyl methacrylate / methacrylic acid copolymer (20/50/22/8), Mw: 126000, Mw / Mn: 3.45
C-09: Ethyl methacrylate / cyclohexyl methacrylate / acrylic acid copolymer (50/45/5), Mw: 26000, Mw / Mn: 2.26
C-10: isobutyl methacrylate / cyclohexyl methacrylate / acrylic acid copolymer (40/50/10), Mw: 24000, Mw / Mn: 2.08
C-11: n-butyl methacrylate / cyclohexyl methacrylate / styrene / acrylic acid copolymer (30/55/10/5), Mw: 157000, Mw / Mn: 4.69
C-12: Methyl methacrylate / dicyclopentenyloxyethyl methacrylate / methacrylic acid copolymer (40/52/8), Mw: 108000, Mw / Mn: 3.24
C-13: lauryl methacrylate / dicyclopentenyloxyethyl methacrylate / methacrylic acid copolymer (25/63/12), Mw: 185000, Mw / Mn: 4.25

Synthesis Example 17 Preparation of Polymer Dispersions CH-01 and CH-02
According to Resin Emulsion Production Example A described in paragraphs [0046] to [0059] of JP-A-2007-99913, the following exemplified compound CH-01 (polymer dispersion CH-01) was obtained.
Moreover, according to the manufacture example 1 of the resin emulsion as described in Unexamined-Japanese-Patent No. 2007-77371, paragraph number [0051] to [0054], the following exemplary compound CH-02 (polymer dispersion CH-02) was obtained.
CH-01: benzyl acrylate / acrylic acid = 90/10 (mass ratio), Mw: 34000, Mw / Mn: 2.58
CH-02: methacrylic acid / styrene macromer (trade name: As-6: manufactured by Toa Gosei Co., Ltd.) / Isobornyl methacrylate / NK ester EH-4E (octaethylene glycol monomethacrylate manufactured by Shin-Nakamura Chemical Co., Ltd., ethylene Average addition mole number of oxide = 4) = 15/30/50/5 (mass ratio), Mw: 21000, Mw / Mn: 2.32

<Example 1>
[Preparation of water-based ink composition]
(Preparation of colored particle dispersion) -Preparation of cyan dispersion-
The water-insoluble polymer dispersant (polymer dispersant B-42) obtained in the above synthesis example was 5.0 g in terms of solid content, cyan pigment C.I. I. Pigment Blue 15: 3 powder (manufactured by Dainichi Seika, Phthalocyanine Blue A220) 10.0 g, methyl ethyl ketone 40.0 g, 1 mol / L sodium hydroxide 8.0 g, ion-exchanged water 82.0 g, 0.1 mm zirconia beads 300 g And dispersed at 1000 rpm for 6 hours with a ready mill disperser (manufactured by IMEX). The obtained dispersion was concentrated under reduced pressure using an evaporator until methyl ethyl ketone was sufficiently distilled off, and a cyan dispersion was prepared as a dispersion containing colored particles so that the pigment concentration was 10%. The obtained cyan dispersion liquid had a volume average particle diameter of 77 nm.

  And, using the polymer dispersion C-01 obtained above as a dispersion of resin particles containing the cyan dispersion and a self-dispersing polymer, water, Sanix GP250 (manufactured by Sanyo Chemical Industries, Ltd.) as an aqueous medium ) And diethylene glycol monoethyl ether (Wako Pure Chemical Industries, Ltd.) were used to prepare the following ink composition. After the preparation, coarse particles were removed with a 5 μm filter to prepare an aqueous ink composition D-01.

<Ink composition of water-based ink composition D-01>
Cyan pigment (C.I.P.B.15: 3, manufactured by Dainichi Seika) 4%
-Water-insoluble polymer dispersant (B-42) (solid content) 2%
・ Self-dispersing polymer (B-01) (solid content) 8%
・ Sanix GP250: 10%
・ Diethylene glycol monoethyl ether 5%
・ Orphine E1010 (manufactured by Nissin Chemical)… 1%
・ Ion-exchanged water: added so that the total is 100%

<Examples 2 to 4>
In the preparation of the water-based ink composition D-01, the dispersant shown in Table 2 below was used in place of the polymer dispersant B-42, respectively, and in Table 2 below instead of the self-dispersing polymer particles C-01. Aqueous ink compositions D-02 to 04 were prepared in the same manner as in the preparation of cyan ink D-01 in Example 1, except that each of the self-dispersing polymers was used.

<Examples 5 to 13>
In the preparation of the colored particle dispersion of Example 1, instead of Pigment Blue 15: 3 (Phthalocyanine Blue A220 manufactured by Dainichi Seika) as a pigment, the pigment (CI Pigment Red 122) (Ciba Specialty) shown in Table 2 was used.・ Chemicals Co., Ltd. trade name: CROMOPHTAL Jet Magenta DMQ), CI Pigment Yellow 74 (Ciba Specialty Chemicals Co., Ltd.) and carbon black (DEGUSSA brand name: NIPEX 160-IQ)) In place of the polymer dispersant B-42, the polymer dispersant shown in the following Table 2 was used, respectively. In place of the self-dispersing polymer dispersion C-01, the self-dispersing polymer dispersion shown in the following Table 2 was used. The water-based ink set of Example 1 except that each was used In the same manner as the preparation of the object D-01, to prepare an aqueous ink composition D-05~D-13, respectively.

<Comparative Example 1>
According to the ink preparation method described in paragraphs [0060] to [0064] of JP-A-2007-99913, the polymer dispersant BH-01 produced in the synthesis example was used instead of the polymer dispersant B-42 in Example 1. A comparative aqueous ink composition DH-01 was prepared in the same manner as in Example 1 except that the polymer dispersion CH-01 was used instead of the self-dispersing polymer dispersion C-01.

<Comparative example 2>
According to the ink preparation method described in paragraph No. [0055] of JP-A-2007-77371, self-dispersing carbon black is used as a pigment, and CH-02 produced in the above synthesis example is used as a polymer particle dispersion. Ink composition DH-02 was prepared.

<Evaluation>
[Image formation]
(Preparation of treatment solution)
The processing liquid was prepared by mixing each component so that it might become the following composition.
-Composition of treatment liquid-
・ Malonic acid (made by Wako Pure Chemical Industries) ... 15.0%
・ Diethylene glycol monomethyl ether 20.0%
(Wako Pure Chemical Industries, Ltd.)
・ N-oleoyl-N-methyltaurine sodium: 1.0%
(Surfactant)
Ion-exchanged water ... 64.0%

  The physical properties of the obtained treatment liquid were measured under the same conditions as those for the water-based ink composition. As a result, the viscosity was 2.6 mPa · s, the surface tension was 37.3 mN / m, and the pH was 1.6 (25 ° C.).

(Dischargeability)
The obtained water-based ink composition was refilled with a cartridge of GELJETG717 manufactured by Ricoh Co., Ltd., and a resolution of 1200 × 600 dpi, ink using a GELJETG717 printer head manufactured by Ricoh Co., Ltd. Ink was ejected so that the droplet ejection amount was 12 pL. The discharge stability was evaluated according to the following evaluation criteria by observing the state after 5 hours of continuous droplet ejection.

~Evaluation criteria~
◎… There was no discharge failure.
○: There was almost no ejection failure, and there was no problem in practical use.
Δ: Discharge failure was observed, and it was at a level causing a problem in practical use.
X: There were many ejection defects and the level of practicality was extremely low.

(Blocking property)
Tokishi Art Double Sided N (recording medium, manufactured by Mitsubishi Paper Industries Co., Ltd.) was fixed on a stage operating at 500 mm / second, and the treatment liquid was applied with a wire bar coater to a thickness of about 2.5 μm. Immediately after that, it was dried at 50 ° C. for 2 seconds. Thereafter, a solid image was printed (image formation) with a resolution of 1200 × 600 dpi, a droplet ejection amount of 3.5 pL, and a line method with a GELJET GX5000 printer head manufactured by Ricoh Co., Ltd. arranged and fixed obliquely with respect to the scanning direction.
Immediately after printing, the sample was dried at 60 ° C. for 3 seconds, passed between a pair of fixing rollers heated to 60 ° C., and fixed at a nip pressure of 0.25 MPa and a nip width of 4 mm to prepare a print sample.
A print sample was cut into 3.5 cm × 4 cm. A printing sample is placed on a 10 cm × 10 cm acrylic plate, and 10 sheets of Tokuhishi art double-sided N (Mitsubishi Paper Co., Ltd.) cut to the same size are placed on the sample, and then a 10 cm × 10 cm acrylic plate Was placed under conditions of a temperature of 50 ° C. and a relative humidity of 60% for 12 hours, and then a 1 kg weight was placed on the acrylic plate and left for 24 hours (corresponding to a load of 700 kg / m ² ). Furthermore, after storing for 2 hours in an environment of 25 ° C. and 50% RH, Tokuhishi art was peeled off from the print sample, and blocking was evaluated according to the following evaluation criteria.

~Evaluation criteria~
◎… Naturally peeled off.
○: There was resistance when peeling, but there was no color transfer of the sample.
Δ: There was some color transfer, which was a practical limit level.
X: About 50% of the printed part was transferred, and it was a level that would cause a problem in practice.

(Offset property)
Tokishi Art Double Sided N (recording medium, manufactured by Mitsubishi Paper Industries Co., Ltd.) was fixed on a stage operating at 500 mm / second, and the treatment liquid was applied with a wire bar coater to a thickness of about 2.5 μm. Immediately after that, it was dried at 50 ° C. for 2 seconds. Thereafter, a solid image was printed (image formation) with a resolution of 1200 × 600 dpi, a droplet ejection amount of 3.5 pL, and a line method with a GELJET GX5000 printer head manufactured by Ricoh Co., Ltd. arranged and fixed obliquely with respect to the scanning direction.
Immediately after printing, the sample is dried at 60 ° C. for 3 seconds, passed through a pair of fixing rollers heated to 60 ° C., and fixed (thermocompression bonding) with a nip pressure of 0.25 MPa and a nip width of 4 mm to produce a print sample. did.
The image portion of the obtained print sample was visually observed for the degree of offset after thermocompression bonding, and evaluated according to the following evaluation criteria using the degree of density unevenness as an index.

~Evaluation criteria~
◎… There was no offset.
A: Some offset was observed in some areas, but it was at a level where there was no practical problem.
Δ: An offset was generated, which was a practically problematic level.
X: The occurrence of offset was remarkable and the level of practicality was extremely low.

As can be seen from Table 3, the water-based ink composition of the present invention was not only excellent in ink ejection properties, but also had good blocking properties for images formed and excellent offset properties during fixing.
On the other hand, when a conventionally known polymer dispersant and polymer dispersion were used (DH-01), the blocking property was inferior and the offset property at the time of fixing was also inferior. Further, when a self-dispersing pigment and a conventionally known polymer dispersion were used (DH-02), there was a practical problem in ejection properties, and the offset property during fixing was greatly inferior.
From the above, it can be seen that according to the present invention, it is possible to provide a water-based ink composition that is excellent in unprecedented ejection properties, blocking properties, and fixing offset properties.

Claims (7)

An aqueous medium;
Pigments, and colored particles containing a water-insoluble polymer dispersant having a structural unit having a carboxyl group and a hydrophobic structural unit represented by the following general formula (1);
A water-based ink composition comprising: a structural unit having a carboxyl group; and a self-dispersing polymer particle having a hydrophobic structural unit derived from an alicyclic (meth) acrylate.


(In the formula, R ¹ represents a hydrogen atom or a methyl group. L ¹ represents —COO—, —OCO—, —CONR ² —, or a phenylene group which may have a substituent, and R ^2. Represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, L ² represents a single bond, an alkylene group having 1 to 12 carbon atoms, an alkenylene group having 2 to 12 carbon atoms, —CO—, or —NR ³ —. , —O—, —S—, —SO—, and —SO ₂ — represents a divalent linking group selected from the group consisting of linking groups, and R ³ represents a hydrogen atom or a carbon number of 1 to 6 the .Ar representing the alkyl group, a phenyl group or a condensed cyclic aromatic ring compound, the heterocyclic compound condensed with (an) aromatic ring, a compound in which two or more benzene are linked by a single bond, triphenylmethane, diphenylmethane, diphenyl ether And gif A monovalent group derived from a compound selected from vinyl sulfonic)   The water-based ink composition according to claim 1, wherein the self-dispersing polymer particles further include a structural unit derived from (meth) acrylate having a chain alkyl group having 1 to 8 carbon atoms.   The water-based ink composition according to claim 1, wherein the water-insoluble polymer dispersant further includes a structural unit derived from (meth) acrylate having a linear alkyl group having 1 to 8 carbon atoms.   The water-based ink composition according to any one of claims 1 to 3, wherein the self-dispersing polymer particles have a content of a constituent unit derived from a styrene monomer of 20% by mass or less. The aqueous ink composition according to any one of claims 1 to 4 , which is an ink for inkjet recording. An ink set comprising at least one water-based ink composition according to any one of claims 1 to 5 . An image is formed by applying the water-based ink composition according to any one of claims 1 to 5 or the ink set according to claim 6 and applying the water-based ink composition onto a recording medium. An image forming method including an ink application step of forming.