JP2009084493A - Aqueous colorant dispersion, method of producing aqueous colorant dispersion, and aqueous ink for inkjet recording - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an aqueous colorant dispersion in which a colorant is finely dispersed and which is excellent in temporal stability, a method of producing the aqueous colorant dispersion, and an aqueous ink for inkjet recording comprising the aqueous colorant dispersion. <P>SOLUTION: The aqueous colorant dispersion comprises the colorant (A), a polymer (B) and an aqueous liquid medium (I), wherein the polymer (B) is a copolymer containing a hydrophilic structural unit and >80 to <100 mass% of a hydrophobic structural unit. The polymer contains an acrylate or methacrylate (a) having a benzene ring as the above hydrophobic structural unit and a hydrophilic structural unit (b) having an acid group which is not directly bonded to an atom that forms a main chain of the polymer (B) as the above hydrophilic structural unit. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an aqueous colorant dispersion excellent in colorant dispersibility, a method for producing an aqueous colorant dispersion, and an aqueous ink for inkjet recording.

  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. Therefore, the use of various additives such as aqueous pigment dispersion resins and surfactants has been studied so far, but they satisfy all the above-mentioned suitability and are 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, a monomer unit containing a resin, a hydrophilic solvent, a conductivity-imparting agent, and a pigment, wherein the resin contains a carboxyl group from the main chain through a linking group in the molecule. An ink for inkjet recording, which is a copolymer containing ˜60% by weight, is disclosed (for example, see Patent Document 1).
Further, an aqueous pigment dispersion for preparing an aqueous pigment ink for ink-jet recording, which comprises an organic pigment, an acrylic copolymer (A), a basic substance, and water, and an acrylic copolymer that does not cover the organic pigment. In the aqueous pigment dispersion-containing composition for preparing an aqueous pigment ink for ink-jet recording containing the polymer (B), the acrylic copolymer (A) contains (meth) acrylic containing a benzene ring on a mass basis. The total of the acid ester monomer and the (meth) acrylic acid monomer is an acrylic copolymer having 85% or more of the total polymerization units, an acid value of 40 to 100 mgKOH / g, and a hydroxyl value of 10 mgKOH / g or less, The acrylic copolymer (B) has a (meth) acrylic acid ester monomer containing a benzene ring and a (meth) acrylic acid monomer as essential components, and has an acid value of 40 to 100 mgKO. / G acrylic copolymer aqueous pigment dispersion-containing composition for ink jet recording water-based pigment ink prepared is (B) has been disclosed (e.g., see Patent Document 2.).
Japanese Patent No. 3897646 JP 2007-511199 A

However, in Patent Document 1, the main purpose is to suppress a decrease in dispersibility when a conductivity-imparting agent (salts) is added, and the structure acts on the adsorption with the colorant in the resin as the dispersant. The description was insufficient, and the resulting dispersibility of the colorant was not satisfactory. Moreover, in patent document 2, the monomer unit containing the carboxylic acid in resin is limited to what originates in a (meth) acrylic acid monomer, and the dispersibility of the resulting colorant dispersion, The stability was not satisfactory.
An object of the present invention is to solve the above conventional problems and achieve the following objects.
That is, an object of the present invention is to provide a water-based colorant dispersion in which a colorant is finely dispersed and excellent in stability over time, and a method for producing the water-based colorant dispersion.
Another object of the present invention is to provide a water-based ink for ink jet recording comprising the water-based colorant dispersion.

  In the present invention, the means for achieving the above-described problems by using a specific copolymer containing a hydrophobic structural unit and a hydrophilic structural unit as a pigment dispersant is as follows.

<1> A water-based colorant dispersion containing a colorant (A), a polymer (B), and an aqueous liquid medium (I), wherein the polymer (B) exceeds 100% by mass with the hydrophilic structural unit. A copolymer having less than% hydrophobic structural units,
The hydrophobic structural unit includes a hydrophobic structural unit (a) derived from an acrylate or methacrylate having a benzene ring,
An aqueous colorant dispersion comprising a hydrophilic structural unit (b) having an acidic group that is not directly bonded to an atom forming the main chain of the polymer (B) as the hydrophilic structural unit.

<2> The aqueous colorant dispersion as described in <1> above, wherein the acidic group of the hydrophilic structural unit (b) is a carboxyl group.
<3> The aqueous colorant dispersion as described in <1> or <2> above, wherein the hydrophilic structural unit (b) includes a structure represented by the following general formula (1).

(In General Formula (1), * represents a connecting point with the main chain, and L represents a connecting group having 1 to 30 carbon atoms.)

<4> The aqueous colorant dispersion as described in <3> above, wherein the hydrophilic structural unit (b) is a structural unit represented by the following general formula (2).

(In General Formula (2), R ₁ represents a hydrogen atom, a methyl group, or a halogen atom, and L ₁ represents —COO—, —OCO—, —CONR ₂ —, —O—, or substituted or unsubstituted phenylene. R ₂ represents a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, L ₂ represents a single bond or a divalent linking group having 1 to 30 carbon atoms.)
<5> The aqueous system according to any one of <1> to <4>, wherein the acrylate or methacrylate having a benzene ring of the hydrophobic structural unit (a) is benzyl acrylate or benzyl methacrylate. Colorant dispersion.
<6> The water-based pigment dispersion according to any one of <1> to <5>, wherein the colorant (A) is a pigment.

<7> A solution (II) containing a basic substance in a mixture (II) of an organic solvent (C) capable of dissolving and dispersing the colorant (A), the polymer (B) and the polymer (B) ( After adding III), the said organic solvent (C) is remove | excluded, The manufacturing method of the aqueous colorant dispersion of any one of said <1>-<6> characterized by the above-mentioned.

<8> A water-based ink for ink-jet recording, comprising the water-based colorant dispersion described in any one of the above items <1> to <6>.

According to the present invention, it is possible to provide an aqueous colorant dispersion in which a colorant is finely dispersed and excellent in stability over time, and a method for producing the aqueous colorant dispersion.
Moreover, according to this invention, the aqueous ink for inkjet recording containing the said aqueous coloring agent dispersion can be provided.

Details of the present invention will be described below.
The aqueous colorant dispersion of the present invention is an aqueous colorant dispersion comprising a colorant (A), a polymer (B), and an aqueous liquid medium (I),
The polymer (B) is a copolymer having a hydrophilic structural unit and a hydrophobic structural unit of more than 80% by mass and less than 100% by mass, and the hydrophobic structural unit is derived from an acrylate or methacrylate having a benzene ring. A hydrophilic structural unit (b) having an acidic group that is not directly bonded to an atom forming the main chain of the polymer (B). It is characterized by that.
When the water-based colorant dispersion of the present invention has the above-described configuration, the colorant is finely dispersed and becomes a dispersion excellent in stability over time.

(Colorant (A))
The colorant (A) in the present invention will be described in detail.
As the colorant in the present invention, known dyes, pigments and the like can be used without particular limitation. Among these, from the viewpoint of ink colorability, a colorant that is almost insoluble or hardly soluble in water is preferable. Specific examples include various pigments, disperse dyes, oil-soluble dyes, dyes that form J aggregates, and more preferably pigments from the viewpoint of light resistance.

  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, quinophthaloni 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 not described in the color index can be used as long as it can be dispersed in the aqueous phase. 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 preferably used from the viewpoint of ink colorability.

Specific examples of the organic pigment used in the present invention are shown below.
Examples of organic pigments for orange or yellow include C.I. I. Pigment orange 31, C.I. I. Pigment orange 43, C.I. I. Pigment yellow 12, C.I. I. Pigment yellow 13, C.I. I. Pigment yellow 14, C.I. I. Pigment yellow 15, C.I. I. Pigment yellow 17, C.I. I. Pigment yellow 74, C.I. I. Pigment yellow 93, C.I. I. Pigment yellow 94, C.I. I. Pigment yellow 128, C.I. I. Pigment yellow 138, C.I. I. Pigment yellow 151, C.I. I. Pigment yellow 155, C.I. I. Pigment yellow 180, C.I. I. And CI Pigment Yellow 185.

  Examples of organic pigments for magenta or red include C.I. I. Pigment red 2, C.I. I. Pigment red 3, C.I. I. Pigment red 5, C.I. I. Pigment red 6, C.I. I. Pigment red 7, C.I. I. Pigment red 15, C.I. I. Pigment red 16, C.I. I. Pigment red 48: 1, C.I. I. Pigment red 53: 1, C.I. I. Pigment red 57: 1, C.I. I. Pigment red 122, C.I. I. Pigment red 123, C.I. I. Pigment red 139, C.I. I. Pigment red 144, C.I. I. Pigment red 149, C.I. I. Pigment red 166, C.I. I. Pigment red 177, C.I. I. Pigment red 178, C.I. I. Pigment red 222C. I. Pigment violet 19 and the like.

Examples of organic pigments for green or cyan include C.I. I. Pigment blue 15, C.I. I. Pigment blue 15: 2, C.I. I. Pigment blue 15: 3, C.I. I. Pigment blue 15: 4, C.I. I. Pigment blue 16, C.I. I. Pigment blue 60, C.I. I. Pigment Green 7 and siloxane-crosslinked aluminum phthalocyanine described in U.S. Pat. No. 4,311,775.
Examples of organic pigments for black include C.I. I. Pigment black 1, C.I. I. Pigment black 6, C.I. I. Pigment black 7 and the like.
The colorants may be used alone or in combination.

  The content of the colorant in the aqueous colorant dispersion is preferably 0.1 to 20% by mass with respect to the total solid mass of the dispersion, from the viewpoint of ink colorability, storage stability, and the like. 2 to 15% by mass is more preferable, and 0.5 to 10% by mass is particularly preferable.

The polymer (B) in the present invention will be described in detail.
The polymer (B) in the present invention is used as a dispersant for the colorant (A) in the aqueous liquid medium (I).
The structure of the polymer (B) is composed of a hydrophilic structural unit and a hydrophobic structural unit.
As the hydrophilic structural unit and the hydrophobic structural unit, although depending on the hydrophilicity and the degree of hydrophobicity of each hydrophilic structural unit and the hydrophobic structural unit, the hydrophobic structural unit is composed of the whole polymer (B). It is necessary to contain more than 80 mass% and less than 100 mass% with respect to mass. That is, the hydrophilic structural unit needs to be 20% by mass or less, and when there are more hydrophilic structural units than this, the component that does not contribute to the dispersion of the colorant and dissolves alone in the water-soluble medium (I). Increases and causes various performances such as dispersibility to deteriorate.

<Hydrophilic structural unit>
The hydrophilic structural unit constituting the polymer (B) in the present invention will be described.
The polymer (B) in the present invention is a hydrophilic structural unit (b) having an acidic group that is not directly bonded to an atom forming the main chain of the polymer (B) (hereinafter referred to as “hydrophilic structural unit”). Sex structural unit (b) ").
Here, “not directly bonded” represents that the acidic group and the atom forming the main chain structure of the polymer (B) have a structure bonded via a linking group. By having such a form, the distance between the benzene ring of the hydrophobic structural unit (a) in the polymer (B) and the acidic group of the hydrophilic structural unit (b) is appropriately maintained. It is presumed that the polymer (B), the colorant (A), and the aqueous liquid medium are likely to interact with each other, resulting in improved dispersibility.

(Hydrophilic structural unit (b) having an acidic group not directly bonded to the atom forming the main chain)
The hydrophilic structural unit (b) can be obtained by polymerizing a monomer containing a corresponding acidic group, but may be formed by introducing the acidic group into a polymer chain after polymerization of the polymer. .
Examples of the acidic group include a carboxyl group, a sulfonic acid group, and a phosphoric acid group, and a carboxyl group is particularly preferable. The acidic group may consist of a single type or a combination of two or more types.

The preferred range of the ratio of the hydrophilic structural unit (b) having an acidic group that is not directly bonded to the atoms forming the main chain of the polymer (B) in the present invention to the total mass of the polymer (B) is Although it varies depending on the structure of the hydrophilic structural unit (b), it is generally from 0.1% by mass to less than 20% by mass, more preferably from 1% by mass to 15% by mass, and more preferably from 2% by mass to 12% by mass. A range of less than mass% is particularly preferred.
The acidic group (particularly carboxyl group) contained in the polymer (B) in the present invention is preferably in a form introduced with a structure represented by the following general formula (1).

  In general formula (1), * represents a connection point with the main chain of the polymer (B), L represents a divalent linking group having 1 to 30 carbon atoms, more preferably a connection having 1 to 25 carbon atoms. And particularly preferably a linking group having 1 to 20 carbon atoms. The divalent linking group may be saturated or unsaturated, may have a linear structure, a branched structure, or a ring structure, and contains a heteroatom selected from O, N, and S. May be.

  As a structural unit containing an acidic group (particularly a carboxyl group) that is not directly bonded to an atom forming the main chain of the polymer (B), a particularly preferred example is a structure represented by the following general formula (2) Can be mentioned.

In General Formula (2), R ₁ represents a hydrogen atom, a methyl group, or a halogen atom, and L ₁ represents —COO—, —OCO—, —CONR ₂ —, —O—, or a substituted or unsubstituted phenylene group. R ₂ represents a hydrogen atom or an alkyl group having 1 to 10 carbon atoms. L ₂ represents a single bond or a divalent linking group having 1 to 30 carbon atoms, and the preferred range of the divalent linking group having 1 to 30 carbon atoms of L ₂ is the same as L in the general formula (1). . Here, examples of the substitution include a halogen atom, an alkyl group, an alkoxy group, a hydroxyl group, and a cyano group, but are not particularly limited.

  The acid value of the polymer (B) in the present invention is preferably from 10 mgKOH / g to 130 mgKOH / g, more preferably from 10 mgKOH / g to 85 mgKOH / g, from the viewpoints of dispersibility and storage stability. It is particularly preferably 15 mgKOH / g or more and 50 mgKOH / g or less.

  The structural unit represented by the general formula (2) can be introduced by polymerizing a monomer corresponding to the structural unit represented by the general formula (2).

Among the general formula (2), a combination of structural units in which R ₁ is a hydrogen atom or a methyl group, L ₁ is —COO— or —CONH—, and L ₂ has 1 to 10 carbon atoms is preferable. More preferably, it is a combination of structural units in which R ₁ is a hydrogen atom or a methyl group, L ₁ is —COO—, and L ₂ is a divalent linking group having 1 to 8 carbon atoms.

  Examples of the monomer capable of forming the hydrophilic structural unit represented by the general formula (2) include unsaturated carboxylic acid monomers such as a monomer that can be used in a suitable polymer (B) described later, and β-carboxyethyl. Acrylic acid, 2-methacryloyloxymethyl succinic acid, etc. are mentioned. Among these, the monomer used for the suitable polymer (B) mentioned later is preferable.

  In the polymer (B) in the present invention, the hydrophilic structural unit may include a hydrophilic structural unit having an acidic group directly bonded to an atom forming the main chain of the polymer (B). Examples of the monomer capable of forming such a structural unit include unsaturated carboxylic acid monomers such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid, and citraconic acid.

  Moreover, in the polymer (B) in this invention, you may use together the hydrophilic structural unit containing an acidic group other than the hydrophilic structural unit which has a carboxyl group represented by the said General formula (2). Examples of the acidic group include a sulfonic acid group, a phosphoric acid group, and a boric acid group. Examples of such structures include those in which the carboxyl group is replaced with an acidic group such as the sulfonic acid group.

The polymer (B) in the present invention may contain a hydrophilic structural unit other than the hydrophilic structural unit containing the acidic group.
Examples of the monomer capable of forming a hydrophilic structural unit other than the acidic group include nonionic hydrophilic monomers. Any known nonionic hydrophilic monomer can be used, but vinyl monomers are preferred from the viewpoints of availability, handleability, and versatility. Examples of such nonionic hydrophilic vinyl monomers include (meth) acrylates, (meth) acrylamides, and vinyl esters having a nonionic hydrophilic functional group. Examples of the hydrophilic functional group include a hydroxyl group, an amide group (the nitrogen atom is unsubstituted), and an alkylene oxide polymer such as polyethylene oxide and polypropylene oxide. Of these, hydroxyethyl (meth) acrylate, hydroxybutyl (meth) acrylate, (meth) acrylamide, and (meth) acrylate containing an alkylene oxide polymer are particularly preferable.

<Hydrophobic structural unit>
Next, the hydrophobic structural unit constituting the polymer (B) in the present invention will be described.
In order to strongly adsorb the colorant (A), the polymer (B) in the present invention contains a hydrophobic structural unit of more than 80% by mass and less than 100% by mass with respect to the total mass of the polymer (B). More preferably 85% by mass or more and less than 99% by mass, particularly preferably 90% by mass or more and less than 98% by mass. By setting the hydrophobic structural unit of the polymer (B) to 85% by mass or more and less than 99% by mass, the single dissolution of the polymer (B) in the water-soluble medium (I) can be suppressed, and the colorant (A) It is preferable in that various properties such as dispersibility can be improved.
The hydrophobic structural unit must contain at least a hydrophobic structural unit (a) derived from an acrylate or methacrylate having a benzene ring (hereinafter also simply referred to as “hydrophobic structural unit (a)”).

(Hydrophobic structural unit (a))
The hydrophobic structural unit has at least a hydrophobic structural unit (a) derived from an acrylate or methacrylate having a benzene ring.
Preferred examples of the acrylate or methacrylate having a benzene ring include benzyl (meth) acrylate, phenyl (meth) acrylate, phenylethyl (meth) acrylate, phenylpropyl (meth) acrylate, and phenoxy (meth) acrylate. Ethyl and the like can be mentioned. Among them, the technical effect of the present invention is that the adsorbability of the polymer (B) to the colorant (A) is excellent, and since it is inexpensive and easily available, benzyl (meth) acrylate Is particularly preferred.
The acrylate or methacrylate having a benzene ring may be used alone or in combination of two or more. The (meth) acrylic acid represents acrylic acid or methacrylic acid.

The structural unit derived from the (meth) acrylate having a benzene ring is preferably 40% by mass or more and 100% by mass or less of the hydrophobic structural unit contained in the polymer (B) in the present invention, and 50 More preferably, the content is from 100% by mass to 100% by mass, and particularly preferably from 60% by mass to 100% by mass.
The hydrophobic structural unit derived from the (meth) acrylate having a benzene ring has the above-mentioned range among the hydrophobic structural units, so that the adsorption with the colorant becomes strong, and the dispersibility and storage stability are improved. It is preferable in that it can be performed.

Furthermore, the polymer (B) in the present invention may contain a hydrophobic structural unit other than the hydrophobic structural unit (a).
The monomer capable of forming a structural unit other than the hydrophobic structural unit (a) derived from the (meth) acrylate containing a benzene ring has a functional group capable of forming a polymer and a hydrophobic functional group. If it does, there will be no restriction | limiting in particular, Any well-known monomers can be used. Of these, vinyl monomers ((meth) acrylates, (meth) acrylamides, styrenes, vinyl esters, etc.) are preferred from the viewpoints of availability, handleability, and versatility. 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. ) Acrylate is preferred.

  (Meth) acrylamides include (meth) acrylamide, N-methyl (meth) acrylamide, N-ethyl (meth) acrylamide, N-propyl (meth) acrylamide, N-isopropyl (meth) acrylamide, and Nn-butyl. Acrylic (meth) amide, Nt-butyl (meth) acrylamide, N-cyclohexyl (meth) acrylamide, N- (2-methoxyethyl) (meth) acrylamide, N, N-dimethyl (meth) acrylamide, N, N -Diethyl (meth) acrylamide, N-phenyl (meth) acrylamide, N-nitrophenyl acrylamide, N-ethyl-N-phenyl acrylamide, N-benzyl (meth) acrylamide, (meth) acryloylmorpholine, diacetone acrylamide, N- Methylo Examples include (meth) acrylamides such as acrylamide, N-hydroxyethyl acrylamide, vinyl (meth) acrylamide, N, N-diallyl (meth) acrylamide, and N-allyl (meth) acrylamide. Among them, (meth) acrylamide, N N-dimethyl (meth) acrylamide is preferred.

  Styrenes include styrene, methyl styrene, dimethyl styrene, trimethyl styrene, ethyl styrene, isopropyl styrene, n-butyl styrene, tert-butyl styrene, hydroxy styrene, methoxy styrene, butoxy styrene, acetoxy styrene, chloro styrene, dichloro styrene, Examples include bromostyrene, chloromethylstyrene, hydroxystyrene protected with a group that can be deprotected by an acidic substance (for example, t-Boc), methyl vinylbenzoate, and α-methylstyrene, vinylnaphthalene, and the like. α-methylstyrene is preferred.

Examples of the vinyl esters include vinyl esters such as vinyl acetate, vinyl chloroacetate, vinyl propionate, vinyl butyrate, vinyl methoxyacetate, and vinyl benzoate. Of these, vinyl acetate is preferable.
These can be used alone or in admixture of two or more.

  The polymer (B) in the present invention may be a random copolymer in which each structural unit is irregularly introduced, or a block copolymer in which the structural units are regularly introduced. In some cases, each structural unit may be synthesized in any order of introduction, and the same constituent component may be used twice or more, but a random copolymer improves dispersibility of the colorant. It is preferable in terms of versatility and manufacturability.

Furthermore, the molecular weight range of the polymer (B) used by this invention is a weight average molecular weight (Mw), Preferably it is 1000-1 million, More preferably, it is 2000-200,000, More preferably, it is 3000-100,000. is there.
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 colorant does not take time due to the steric effect.
In addition, the molecular weight distribution (expressed by weight average molecular weight value / number average molecular weight value) of the polymer used in the present invention is preferably 1 to 6, and more preferably 1 to 4. By setting the molecular weight distribution 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 are detected with a solvent THF and a differential refractometer using a GPC analyzer using columns of TSKgel GMHxL, TSKgel G4000HxL, and TSKgel G2000HxL (both are trade names manufactured by Tosoh Corporation). The molecular weight is expressed using polystyrene as a standard substance.

The polymer 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 to be produced, the type of initiator, etc., and is usually about 0 ° C. to 100 ° C., but the polymerization is preferably performed in the range of 50 to 100 ° C.
The reaction pressure can be selected as appropriate, 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 may be subjected to purification such as reprecipitation.

  Specific preferred examples of the polymer (B) in the present invention are shown below, but the present invention is not limited to the following.

(Aqueous liquid medium (I))
The aqueous liquid medium in the aqueous colorant dispersion of the present invention contains water, but can further contain a water-soluble organic solvent. The water-soluble organic solvent can be contained as a drying inhibitor and a penetration enhancer.
The anti-drying agent can effectively prevent nozzle clogging that may occur due to drying of ink at the ink ejection port, particularly when the aqueous ink composition of the present invention is applied to an image recording method using an ink jet method. .

  The drying inhibitor is preferably a water-soluble organic solvent having a vapor pressure lower than that of water. Specific examples of the drying inhibitor include ethylene glycol, propylene glycol, diethylene glycol, polyethylene glycol, thiodiglycol, dithiodiglycol, 2-methyl-1,3-propanediol, 1,2,6-hexanetriol, Polyhydric alcohols represented by acetylene glycol derivatives, glycerin, trimethylolpropane, etc., polyvalent alcohols such as ethylene glycol monomethyl (or ethyl) ether, diethylene glycol monomethyl (or ethyl) ether, triethylene glycol monoethyl (or butyl) ether Lower alkyl ethers of alcohols, 2-pyrrolidone, N-methyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, heterocyclic rings such as N-ethylmorpholine, sulfolane, dimethyls Sulfoxide, sulfur-containing compounds such as sulfolane, diacetone alcohol, polyfunctional compounds such as diethanolamine, and urea derivatives. Of these, polyhydric alcohols such as glycerin and diethylene glycol are preferred as the drying inhibitor. Moreover, said drying inhibitor may be used independently or may be used together 2 or more types. These drying inhibitors are preferably contained in the ink in an amount of 10 to 50% by mass.

  Further, the penetration accelerator is preferably used for the purpose of allowing the ink to penetrate better into the recording medium (printing paper). Specific examples of penetration enhancers include alcohols such as ethanol, isopropanol, butanol, di (tri) ethylene glycol monobutyl ether, 1,2-hexanediol, sodium lauryl sulfate, sodium oleate, and nonionic surfactants. Etc. can be used suitably. These penetration enhancers exhibit a sufficient effect when contained in the ink composition in an amount of 5 to 30% by mass. Further, it is preferable that the penetration enhancer is used within a range of an addition amount that does not cause printing bleeding and paper loss (print through).

In addition to the above, the water-soluble organic solvent can be used for adjusting the viscosity. Specific examples of water-soluble organic solvents that can be used to adjust the viscosity include alcohols (eg, methanol, ethanol, propanol, isopropanol, butanol, isobutanol, sec-butanol, t-butanol, pentanol, hexanol, Cyclohexanol, benzyl alcohol), polyhydric alcohols (for example, ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, butylene glycol, hexanediol, pentanediol, glycerin, hexanetriol, Thiodiglycol), glycol derivatives (eg, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether) Ter, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monobutyl ether, dipropylene glycol monomethyl ether, triethylene glycol monomethyl ether, ethylene glycol diacetate, ethylene glycol monomethyl ether acetate, Triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, ethylene glycol monophenyl ether), amine (eg, ethanolamine, diethanolamine, triethanolamine, N-methyldiethanolamine, N-ethyldiethanolamine, morpholine, N-ethylmorpholine, Tylenediamine, diethylenetriamine, triethylenetetramine, polyethyleneimine, tetramethylpropylenediamine) and other polar solvents (eg, formamide, N, N-dimethylformamide, N, N-dimethylacetamide, dimethylsulfoxide, sulfolane, 2-pyrrolidone, N-methyl-2-pyrrolidone, N-vinyl-2-pyrrolidone, 2-oxazolidone, 1,3-dimethyl-2-imidazolidinone, acetonitrile, acetone).
In addition, a water-soluble organic solvent may be used independently and may use 2 or more types together.
The content of the aqueous liquid medium in the aqueous colorant dispersion of the present invention is preferably 1% by mass to 70% by mass from the viewpoint of liquid properties such as drying prevention, permeability to an adherend, and viscosity. 2 mass%-60 mass% are more preferable, and 5 mass%-50 mass% are especially preferable.
By setting the content of the aqueous liquid medium in the above range, the liquid properties such as the drying speed of the colorant dispersion, the permeability to the adherend, and the viscosity can be adjusted to an appropriate state.

In the aqueous colorant dispersion of the present invention, other additives can be added as necessary in addition to the essential components. As other additives, known pigment dispersions and additives that can be used in water-based inks can be used.
For example, anti-fading agent, emulsion stabilizer, penetration enhancer, ultraviolet absorber, preservative, antifungal agent, pH adjuster, surface tension adjuster, antifoaming agent, viscosity adjuster, dispersant, dispersion stabilizer, Well-known additives, such as a rust agent and a chelating agent, are mentioned. These various additives may be added during or after the preparation of the aqueous colorant dispersion.

(Other additives)
The ultraviolet absorber is used for the purpose of improving image storability. Examples of the ultraviolet absorber 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. The compounds described in No. 24239, compounds that emit fluorescence by absorbing ultraviolet rays typified by stilbene-based compounds 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, No. VII, I to J, ibid. 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 aqueous colorant dispersion in an amount of 0.02 to 1.00% by mass.
As the pH adjuster, basic substances (neutralizing agents such as organic bases and inorganic alkalis) can be used. For the purpose of improving the storage stability of the aqueous colorant dispersion, the basic substance is preferably added so that the aqueous colorant dispersion has a pH of 6 to 10, and added so as to have a pH of 7 to 10. More preferred.
As the basic substance, inorganic alkali agents such as alkali metal hydroxides such as sodium hydroxide and potassium hydroxide, and organic amines such as diethanolamine and triethanolamine can be used. If necessary, organic acids such as citric acid and tartaric acid, mineral acids such as hydrochloric acid and phosphoric acid, and the like can be used. Among these, inorganic alkali agents such as alkali metal hydroxides such as sodium hydroxide and potassium hydroxide are preferable from the viewpoint of ease of use.

Examples of the surface tension adjusting agent include nonionic surfactants, cationic surfactants, anionic surfactants, betaine surfactants, and the like.
Further, the addition amount of the surface tension adjusting agent is preferably an addition amount for adjusting the surface tension of the aqueous ink composition to 20 to 60 mN / m in order to drop the aqueous colorant dispersion as it is by the ink jet method. The addition amount adjusted to 20 to 45 mN / m is more preferable, and the addition amount adjusted to 25 to 40 mN / m is more preferable.
The surface tension of the aqueous colorant dispersion was measured using, for example, the Wilhelmy 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.
Also, fluorine (fluorinated alkyl) surfactants, silicone 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 of the aqueous colorant dispersion is preferably in the range of 1 to 30 mPa · s, more preferably in the range of 1 to 20 mPa · s, from the viewpoint of droplet ejection stability and agglomeration speed when ink is applied by an inkjet method. More preferably, the range of 2-15 mPa * s is further more preferable, and the range of 2.5-15 mPa * s is especially preferable. In addition, the value of a viscosity here shall be a measured value in 25 degreeC.
The viscosity of the water-based ink composition can be measured using, for example, an E-type viscometer.

(Method for producing aqueous colorant dispersion)
The method for producing an aqueous colorant dispersion of the present invention comprises a colorant (A), a polymer (B), an organic solvent (C) in which the polymer (B) is dissolved or dispersed, and a basic substance and water as a main component. After the solution (III) is mixed (mixing / hydration step), the organic solvent (C) is removed (solvent removal step).
According to the method for producing an aqueous colorant dispersion of the present invention, an aqueous colorant dispersion in which the colorant is finely dispersed and excellent in storage stability can be produced.

  The organic solvent (C) of the present invention needs to be able to dissolve or disperse the polymer (B) of the present invention, but in addition to this, it preferably has a certain affinity for water. Specifically, the solubility in water at 20 ° C. is preferably 10% by mass or more and 50% by mass or less.

  In more detail, the aqueous colorant dispersion of the present invention can be produced by a production method comprising steps (1) and (2) shown below, but is not limited thereto.

Step (1): Colorant (A), polymer (B), organic solvent (C) for dissolving / dispersing polymer (B), solution (III) containing a basic substance and containing water as a main component, and Step (2) of dispersing the mixture containing water: Step of removing the organic solvent (C) In the step (1), first, the polymer (B) is dissolved in the organic solvent (C), or Disperse to obtain a mixture (II) (mixing step). Next, a colorant (A), a solution (III) containing a basic substance and containing water as a main component, water, and a surfactant as necessary are added to the mixture (II) and mixed and dispersed. An oil-in-water aqueous colorant dispersion is obtained. There is no particular limitation on the degree of neutralization. Usually, it is preferable that the finally obtained aqueous colorant dispersion has neutral liquidity, for example, pH of 4.5 to 10. The pH can also be determined by the desired degree of neutralization of the water-insoluble vinyl polymer.

  The colorant (A), polymer (B), and other additives used in the method for producing the aqueous colorant dispersion are the same as those described in the above-mentioned aqueous colorant dispersion, and preferred examples are also included. It is the same.

Preferable examples of the organic solvent (C) 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 solvents, isopropanol, acetone and methyl ethyl ketone are preferable, and methyl ethyl ketone is particularly preferable.
These organic solvents (C) may be used alone or in combination.

In the production of the aqueous colorant dispersion, a strong shearing force is applied using a two-roll, a three-roll, a ball mill, a tron mill, a disper, a kneader, a kneader, a homogenizer, a blender, a single or twin screw extruder, and the like. The kneading and dispersing process can be performed while feeding.
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 the aqueous colorant dispersion of 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 average particle size of the colorant obtained by the method for producing the aqueous colorant dispersion of the present invention is preferably 10 nm or more and less than 200 nm, more preferably 50 nm or more and less than 130 nm, and further preferably 60 nm or more and less than 100 nm. By setting it as such a range, it is preferable at the point from which the color development property, dispersion stability, and the discharge stability at the time of jetting become favorable.
The average particle diameter of the dispersed particles of the colorant is a value measured using a dynamic light scattering method.

  The aqueous colorant dispersion of the present invention can be used, for example, in an aqueous ink for ink jet recording described later, and an aqueous ink for writing instruments such as an aqueous ballpoint pen and a marker pen. In this case, in order to prevent the inkjet nozzle and the nib from being clogged by drying, a low-volatile or non-volatile solvent can be added among the above water-soluble organic solvents. In order to increase the permeability to the recording medium, a volatile solvent can be added.

(Water-based ink for inkjet recording)
The water-based ink for ink-jet recording of the present invention (hereinafter referred to as “water-based ink” as appropriate) comprises the water-based colored dispersion of the present invention.
The water-based ink for ink-jet recording of the present invention is obtained by adding the water-based colorant dispersion of the present invention as it is or, if necessary, further adding the anti-drying agent or the other additives to the aqueous liquid medium (I ) And can be prepared.

  The amount of the colorant contained in the water-based ink is preferably in the range of 0.1 to 20% by mass, and more preferably in the range of 0.5 to 10% by mass, from the viewpoints of ink colorability, storage stability, and dischargeability. .

  The amount of the polymer (B) contained in the water-based ink is in the range of 1 to 150% by weight with respect to the pigment (colorant) from the viewpoint of dispersibility, storage stability, and dischargeability of the water-based ink. It is preferable that the range be 5 to 100% by mass.

The pH of the water-based ink is preferably in the range of 4.5-10. By setting the pH within this range, storage stability can be improved, and corrosion of members of an ink jet recording apparatus, which is an apparatus to which aqueous ink is applied, can also be suppressed.
The pH adjustment in the water-based ink can be prepared using the basic substance described in the section of the aqueous colorant dispersion.

  In order to prevent the ink jet nozzle from being clogged by drying, the water-based ink of the present invention may be added with a low-volatile or non-volatile solvent among the above water-soluble organic solvents. In order to increase the permeability to the recording medium, a volatile solvent may be added. It is also preferable to add a surfactant in order to give the ink an appropriate surface tension.

  EXAMPLES The present invention will be described more specifically with reference to the following examples, but the present invention is not limited to the specific examples shown below.

[Synthesis Example 1] (Synthesis of B-7)
Synthesized according to the following scheme.

To a 1000 ml three-necked flask equipped with a stirrer and a condenser, 90 g of methyl ethyl ketone was added and heated to 72 ° C. under a nitrogen atmosphere. Here, 50 g of methyl ethyl ketone was mixed with 0.80 g of dimethyl 2,2′-azobisisobutyrate, 85 g of benzyl methacrylate, A solution in which 15 g of NK ester SA (trade name, 2-methacryloyloxyethyl succinic acid manufactured by Shin-Nakamura Chemical Co., Ltd.) was dissolved was dropped over 3 hours. After completion of the dropwise addition, the reaction was further continued for 1 hour, and then a solution of 0.8 g of dimethyl 2,2′-azobisisobutyrate dissolved in 10 g of methyl ethyl ketone was added, heated to 78 ° C. and heated for 4 hours. The obtained reaction solution was reprecipitated twice in a large excess amount of hexane, and the precipitated polymer was dried to obtain 98 g of B-7.
The composition of the obtained polymer was confirmed by ¹ H-NMR, and the weight average molecular weight (Mw) determined by GPC was 39900.

  Other polymers in the present invention can be synthesized in the same manner.

[Example 1] (Preparation of pigment dispersion (D-1))
A pigment dispersion was prepared by the following procedure using a Frichtux planetary ball mill model P-7 (manufactured by Fritsch).
B-7 obtained by Synthesis Example 1 was prepared as a MEK solution having a solid content of 40% by mass. In a 45 ml container made of zirconia, 1.0 g of phthalocyanine blue A220 powder (manufactured by Dainichi Seika), 1.25 g of prepared B-7 MEK solution, 3.75 g of MEK, 326 μL of 1 mol / L NaOH aqueous solution (included in the dispersant) Add 1 equivalent) to the amount of carboxylic acid, add ultrapure water so that the total mass of the carboxylic acid is 15 g, add 40 g of 0.1 mmΦ zirconia beads (TORAY Ray Treceram beads), and Mix gently.

  A 45 ml container made of zirconia was placed in an overpot special atmosphere control container, purged with nitrogen, and dispersed at a rotation speed of 300 rpm for 3 hours. After the dispersion, the beads were removed by filtration with a filter cloth to obtain a pigment dispersion.

  Further, MEK is removed from the pigment dispersion by distillation under reduced pressure, and centrifuged at 5000 rpm for 30 minutes with a centrifugal separator (05P-21, manufactured by Hitachi, Ltd.), and then ion-exchanged water is added so that the pigment concentration becomes 10% by mass. This was added to prepare a pigment dispersion. And after carrying out pressure filtration using a 2.5 micrometer membrane filter (made by Advantech), ion-exchange water is added so that it may become a pigment concentration of 4 mass%, and the pigment dispersion (D-1) of this invention Got.

[Example 2] (Preparation of pigment dispersions (D-2) to (D-9))
Except for changing B-7 in Example 1 to B-1, B-15, B-23, B-41, and B-43, respectively, all the same as the pigment dispersion (D-1) of Example 1 Thus, pigment dispersions (D-2) to (D-6) of the present invention were prepared. Further, in place of phthalocyanine blue A220 in Example 1, C.I. I. Pigment Red 122 (trade name: CROMOPHTAL Jet Magenta DMQ) manufactured by Ciba Specialty Chemicals, C.I. I. Pigment Yellow 74 (manufactured by Ciba Specialty Chemicals Co., Ltd.) and carbon black (trade name: NIPEX 160-IQ manufactured by DEGUSSA) were all used in the same manner as in the preparation of pigment dispersion (D-1) of Example 1. Thus, pigment dispersions (D-7), (D-8) and (D-9) of the present invention were prepared.

[Example 3] (Preparation of water-based ink for inkjet recording)
Using the pigment dispersion (D-1) obtained above, a pigment dispersion-containing composition having the following composition is prepared, and the composition is centrifuged (at 10,000 to 20000 rpm for 30 minutes to 2 hours). Ink jet recording ink (J-1) was obtained.
Pigment dispersion (D-1) 40 parts by mass Glycerin 8 parts by mass Diethylene glycol 10 parts by mass Triethanolamine 1 part by mass Olphine E1010 (manufactured by Nissin Chemical Industry Co., Ltd.) 1 part by mass Triethylene glycol monobutyl ether 8 parts by mass Ion exchange 34 parts by weight of water When the pH of the ink composition was measured with a pH meter-WM-50EG manufactured by Toa DKK Corporation, the pH was 8.5.
Similarly, (J-2) to (J-9) were prepared from the pigment dispersions (D-2) to (D-9), respectively.

[Comparative Example 1] (Preparation of pigment dispersions (D-10) and (D-11))
B-7 in Example 1 was replaced with the copolymer P-30 of Synthesis Example 1 described in [0065] in JP-A-2007-51199 and Synthesis Example 1 described in [0021] in Patent No. 3897646, respectively. Except for the change to copolymerization (hereinafter referred to as copolymer A), the same procedures as in the preparation of pigment dispersion (D-1) in Example 1 were followed, except for pigment dispersions (D-10) and (D-11). ) Were prepared respectively.

[Comparative Example 2] (Preparation of water-based ink for inkjet recording)
In Example 3, instead of using the pigment dispersion (D-1), the inkjet recording ink (J-) of Example 3 was used except that the pigment dispersions (D-10) and (D-11) were used. In the same manner as in 1), water-based inks for jet recording (J-10) and (J-11) were prepared.

[Evaluation of pigment dispersion]
(1) Measurement of average particle diameter The volume average particle diameter of the pigment dispersion obtained by the dynamic light scattering method was measured using Nanotrac particle size distribution analyzer UPA-EX150 (manufactured by Nikkiso Co., Ltd.). The results are shown in Table 1. Measurement conditions: 10 cc of ion-exchanged water was added to 10 μl of the dispersion to prepare a measurement solution and measured at 25 ° C. Evaluation is based on the following criteria.
A: Average particle size is 70 nm or more and less than 100 nm ○: Average particle size is 100 nm or more and less than 130 nm Δ: Average particle size is 130 nm or more and less than 200 nm ×: Average particle size is 200 nm or more

2. Stability over time of pigment dispersion After the obtained pigment dispersion was left in a sealed state at 60 ° C. for 14 days, the average particle diameter and viscosity were measured for aggregation and thickening of the pigment particles, and the following evaluation criteria were used. evaluated.
(Double-circle): The change of the average particle diameter and viscosity of a pigment particle was not recognized at all.
○: No change in the average particle diameter / viscosity of the pigment particles was observed.
Δ: Slight changes in the average particle diameter and viscosity of the pigment particles were observed, but there was no practical problem.
X: Changes in the average particle diameter and viscosity of the pigment particles were observed, which became a problem in practical use.
The average particle size was measured in the same manner as (1) above, and the viscosity was measured according to the following procedure.
(2) Measurement of viscosity The viscosity of the obtained pigment dispersion was measured at 25 ° C using a TV-22 viscometer (manufactured by Toki Sangyo Co., Ltd.).

[Evaluation of ink for inkjet recording]
As the ink jet recording apparatus, a commercially available ink jet recording printer PX-G930 (trade name: manufactured by Seiko Epson Corporation) was used, and ink jet recording inks (J-1) to (J-12) were filled and printed. .
Although any of the inks for ink jet recording of the present invention could be ejected satisfactorily, the ink jetting properties of the comparative ink jet recording inks (J-11) and (J-12) were poor. The results are shown in Table 2.

2. Measurement of average particle diameter The average particle diameter of the obtained ink for inkjet recording was measured by the same method as the measurement of the average particle diameter of the pigment dispersion, and the results are shown in Table 2.
A: Average particle diameter is 70 nm or more and less than 100 nm ○: Average particle diameter is 100 nm or more and less than 130 nm Δ: Average particle diameter is 130 nm or more and less than 200 nm x: Average particle diameter is 200 nm or more

3. Stability over time After the ink for inkjet recording thus obtained was allowed to stand at 30 ° C. for 14 days in a sealed state, the aggregation and thickening of pigment particles were observed by measuring the average particle diameter and viscosity, and evaluated according to the following evaluation criteria. did.
(Double-circle): The change of the average particle diameter and viscosity of a pigment particle was not recognized at all.
○: No change in the average particle diameter / viscosity of the pigment particles was observed.
Δ: Slight changes in the average particle diameter and viscosity of the pigment particles were observed, but there was no practical problem.
X: Changes in the average particle diameter and viscosity of the pigment particles were observed, which became a problem in practical use.

4). Inkjet droplet ejection evaluation The droplet ejection stability was evaluated by visually observing the droplet ejection state. The results are shown in Table 2. Evaluation is based on the following criteria.
◎ ... No discharge failure.
○: There is almost no ejection failure, and there is no practical problem.
Δ: Discharge failure is observed, which is a practically problematic level.
×: Many ejection failures.

As is clear from Tables 1 and 2, the pigment dispersion (aqueous colorant dispersion) of the present invention had a fine dispersed particle diameter of the pigment and good stability over time. On the other hand, it can be seen that the comparative pigment dispersion is inferior in any of the evaluation items.
In addition, it was shown that the water-based ink of the present invention obtained favorable results in any of the average particle diameter, stability over time, and droplet ejection properties, and can be suitably used as an ink for an ink jet recording apparatus. The water-based ink is inferior in any of the evaluation items, and it can be seen that the performance as an ink for an ink jet recording apparatus is not sufficient.

Claims (8)

An aqueous colorant dispersion comprising a colorant (A), a polymer (B), and an aqueous liquid medium (I),
The polymer (B) is a copolymer having a hydrophilic structural unit and a hydrophobic structural unit of more than 80% by mass and less than 100% by mass,
The hydrophobic structural unit includes a hydrophobic structural unit (a) derived from an acrylate or methacrylate having a benzene ring,
An aqueous colorant dispersion comprising a hydrophilic structural unit (b) having an acidic group that is not directly bonded to an atom forming the main chain of the polymer (B) as the hydrophilic structural unit. The aqueous colorant dispersion according to claim 1, wherein the acidic group of the hydrophilic structural unit (b) is a carboxyl group. The aqueous colorant dispersion according to claim 1, wherein the hydrophilic structural unit (b) includes a structure represented by the following general formula (1).

(In General Formula (1), * represents a connecting point with the main chain, and L represents a connecting group having 1 to 30 carbon atoms.) The aqueous colorant dispersion according to claim 3, wherein the hydrophilic structural unit (b) is a structural unit represented by the following general formula (2).

(In General Formula (2), R ₁ represents a hydrogen atom, a methyl group, or a halogen atom, and L ₁ represents —COO—, —OCO—, —CONR ₂ —, —O—, or substituted or unsubstituted phenylene. R ₂ represents a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, L ₂ represents a single bond or a divalent linking group having 1 to 30 carbon atoms.) The water-based colorant dispersion according to any one of claims 1 to 4, wherein the acrylate or methacrylate having a benzene ring of the hydrophobic structural unit (a) is benzyl acrylate or benzyl methacrylate. . The aqueous colorant dispersion according to any one of claims 1 to 5, wherein the colorant (A) is a pigment. A solution (III) containing a basic substance and containing water as a main component is added to a mixture (II) of a colorant (A), a polymer (B) and an organic solvent (C) capable of dissolving and dispersing the polymer (B). After adding, the said organic solvent (C) is remove | excluded, The manufacturing method of the water-based colorant dispersion of any one of Claims 1-6 characterized by the above-mentioned. A water-based ink for ink-jet recording, comprising the water-based colorant dispersion according to any one of claims 1 to 6.