JP5322861B2 - Ink set, image forming method, and recorded matter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ink set capable of forming images excellent in light stability. <P>SOLUTION: The ink set includes an ink containing at least one kind of coloring material selected from an azo pigment represented by a formula (1), a tautomer thereof, and salts and hydrates thereof, a treatment liquid coagulating the components in the ink. Here, Z is a divalent group derived from five to eight members nitrogen containing heterocycles, Y<SP>1</SP>, Y<SP>2</SP>, R<SP>11</SP>, R<SP>12</SP>are hydrogen atoms, substituents, G<SP>1</SP>and G<SP>2</SP>are hydrogen atoms, alkyl groups, aralkyl groups, alkenyl groups, alkynyl groups, aryl groups, or heterocyclic groups, W<SP>1</SP>and W<SP>2</SP>are alkoxy groups, amino groups, alkyl groups, aryl groups. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to an ink set, an image forming method, and a recorded matter.

The ink jet recording method is a method of forming an image by applying small droplets of an ink composition (ink) to a recording medium such as paper. This method has a feature that a high-resolution and high-quality image can be printed at a high speed with a relatively inexpensive apparatus.
In recent years, with respect to inkjet recording methods, from the viewpoint of improving color density, suppressing bleeding and unevenness, and the like, a reaction liquid and an ink composition that form an image by contacting the reaction liquid (treatment liquid) and the ink composition. Studies have been conducted on an ink jet recording method using two liquids.
For example, an inkjet recording method for printing by attaching a reaction liquid containing a reactive agent and an ink composition to a recording medium, the step of attaching the reaction liquid onto the recording medium, and the reaction liquid attaching There is known a method comprising a step of pressurizing the recording medium, and a step of recording an image by discharging droplets of the ink composition onto the recording medium (see, for example, Patent Document 1).
On the other hand, as a pigment contained in ink, Pigment Yellow 74 (P.Y.74) is generally used as a yellow pigment excellent in hue (see, for example, Patent Document 2).

JP 2000-37942 A JP 2000-239594 A

However, in the ink jet recording method using the two liquids, when the ink containing Pigment Yellow 74 (PY 74) is used, the light resistance of the formed image tends to decrease.
This invention is made | formed in view of the above, and makes it a subject to achieve the following objectives.
That is, an object of the present invention is to provide an ink set capable of forming an image excellent in light resistance.
Another object of the present invention is to provide an image recording method capable of forming an image excellent in light resistance.
Another object of the present invention is to provide a recorded matter with excellent light resistance.

Specific means for solving the above problems are as follows.
<1> An ink containing at least one colorant selected from the azo pigments represented by the following general formula (1), tautomers thereof, and salts and hydrates thereof, An ink set comprising a treatment liquid for aggregating the components.

(In general formula (1), Z represents a divalent group derived from a 5- to 8-membered nitrogen-containing heterocycle, and Y ¹ , Y ² , R ¹¹ , and R ¹² are each independently a hydrogen atom or a substituent. G ¹ and G ² each independently represent a hydrogen atom, an alkyl group, an aralkyl group, an alkenyl group, an alkynyl group, an aryl group, or a heterocyclic group, and W ¹ and W ² each independently represent an alkoxy group Represents an amino group, an alkyl group or an aryl group.)

<2> W ¹ and W ² in the general formula (1) are described independently having 3 or less carbon atoms of an alkoxy group, an amino group or a total carbon number of 3 or less alkyl amino group, <1> Ink set.
<3> The ink set according to <1> or <2>, wherein G ¹ and G ² in the general formula (1) are each independently an alkyl group having a total carbon number of 3 or less.
<4> The ink set according to any one of <1> to <3>, wherein Z in the general formula (1) is a divalent group derived from a 6-membered nitrogen-containing heterocycle.

<5> The ink set according to any one of <1> to <4>, wherein the color material is coated with a polymer dispersant.
<6> The ink set according to any one of <1> to <5>, wherein the ink further contains a hydrophilic organic solvent, a surfactant, and water.
<7> The ink set according to any one of <1> to <6>, wherein the ink further contains polymer particles.
<8> The ink set according to any one of <1> to <7>, wherein the ink further contains a solid wetting agent.

<9> Using the ink set according to any one of <1> to <8>, a treatment liquid application step for applying the treatment liquid to a recording medium, and an ink application step for applying the ink to the recording medium. And an image forming method.
<10> The image forming method according to <9>, wherein the treatment liquid application step applies the treatment liquid to a recording medium.
<11> The image forming method according to <9> or <10>, wherein the ink application step deposits the ink on a recording medium by a single-pass inkjet method.
<12> The image forming method according to any one of <9> to <11>, further comprising a fixing step of fixing the image by applying at least one of heating and pressurization to the recording medium to which the ink has been applied. .
<13> A recorded matter recorded on a recording medium by the image forming method according to any one of <9> to <12>.

ADVANTAGE OF THE INVENTION According to this invention, the ink set which can form the image excellent in light resistance can be provided.
In addition, the present invention can provide an image recording method capable of forming an image having excellent light resistance.
In addition, the present invention can provide a recorded matter excellent in light resistance.

≪Ink set≫
The ink set of the present invention includes an ink containing at least one colorant selected from azo pigments represented by the general formula (1) described below and tautomers thereof, and salts and hydrates thereof ( (Hereinafter also referred to as “specific ink”) and a treatment liquid for aggregating components in the ink.
By setting the ink set to the configuration of the present invention, the light fastness of the recorded image is improved.
The ink set of the present invention is not particularly limited as long as it contains the specific ink and the treatment liquid, and may contain ink other than the specific ink as necessary.
For example, the ink set of the present invention includes a set (preferably yellow) of the specific ink as a yellow ink, at least one selected from the group consisting of cyan ink, magenta ink, and black ink, and a treatment liquid. A form including the specific ink, the cyan ink, the magenta ink, the black ink, and the treatment liquid as the ink is also preferable.
When the ink set of the present invention contains an ink other than the specific ink (hereinafter also referred to as “other ink”), a known ink can be used as the other ink. In addition, as an example of other ink forms, there are preferable forms of specific inks described later, except for the difference in the types of color materials.
Hereinafter, the specific ink and the treatment liquid that are components of the ink set of the present invention will be described, and then the image forming method and recorded matter of the present invention will be described.

≪Ink≫
<Color material>
The ink (specific ink) that is a constituent element of the ink set of the present invention is at least one selected from the azo pigments represented by the following general formula (1), tautomers thereof, and salts and hydrates thereof. A color material (hereinafter also referred to as “specific color material”).
The specific color material exhibits a good hue equivalent to that of Pigment Yellow 74 (P.Y.74) as a yellow hue, and is excellent in light resistance.
Furthermore, the light resistance of the formed image can be further improved by using the specific ink containing the specific color material in combination with a treatment liquid described later.
In addition, by including a specific color material, it is possible to improve the ejection stability (particularly, ejection recoverability) of the ink.
The specific color material is typically represented by the general formula (1). The azo pigment may be a structure represented by the general formula (1) or a tautomer thereof.
Hereinafter, the azo pigment represented by the following general formula (1) will be described.
The compound represented by the general formula (1) easily forms an intermolecular interaction due to its specific structure, has low solubility in water or an organic solvent, and can be an azo pigment.
A pigment is used by being finely dispersed as solid particles such as molecular aggregates in a solvent, unlike a dye used by being dissolved in water or an organic solvent in a molecular dispersion state.

In General Formula (1), Z represents a divalent group derived from a 5- to 8-membered nitrogen-containing heterocycle, and Y ¹ , Y ² , R ¹¹ , and R ¹² are each independently a hydrogen atom or a substituent. G ¹ and G ² each independently represent a hydrogen atom, an alkyl group, a cycloalkyl group, an aralkyl group, an alkenyl group, an alkynyl group, an aryl group or a heterocyclic group, and W ¹ and W ² each independently represent Represents an alkoxy group, an amino group, an alkyl group or an aryl group;

In the general formula (1), Z represents a divalent group derived from a 5- to 8-membered nitrogen-containing heterocycle. Examples of preferred nitrogen-containing heterocycles without limiting the substitution position include pyrrole ring, pyrazole ring, triazole ring, imidazole ring, thiazole ring, isothiazole ring, oxazole ring, isoxazole ring, thiadiazole ring, thiophene ring, furan A ring, a pyridine ring, a pyrimidine ring, a triazine ring, and a pyridazine ring. More preferably, it is a 6-membered nitrogen-containing heterocycle, and examples thereof include a pyridine ring, a pyrimidine ring, and an s-triazine ring. Z is particularly preferably a divalent group derived from a pyrimidine ring.
When Z is a 6-membered nitrogen-containing heterocycle, the intramolecular and intermolecular action of the dye molecule is preferable in terms of easy improvement from the viewpoint of hydrogen bondability and molecular planarity.
The divalent group derived from a 5- to 8-membered nitrogen-containing heterocycle represented by Z may be further condensed.

Examples of the case where Y ¹ and Y ² represent a substituent include a halogen atom, an alkyl group (a linear, branched, cyclic substituted or unsubstituted alkyl group, a cycloalkyl group, a bicycloalkyl group, and a ring structure. In addition, the alkyl group in the substituents described below (for example, an alkyl group such as an alkoxy group, an alkylcarbonyl group, and an alkylsulfonyl group) also includes an alkyl group having such a concept. Aralkyl group, alkenyl group, alkynyl group, aryl group, heterocyclic group, cyano group, hydroxyl group, nitro group, alkoxy group, aryloxy group, silyloxy group, heterocyclic oxy group, acyloxy group, carbamoyloxy group, Alkoxycarbonyloxy group, aryloxycarbonyloxy group, amino group, acyl Mino group, aminocarbonylamino group, alkoxycarbonylamino group, aryloxycarbonylamino group, sulfamoylamino group, alkyl or arylsulfonylamino group, mercapto group, alkylthio group, arylthio group, heterocyclic thio group, sulfamoyl group, alkyl Or arylsulfinyl group, alkyl or arylsulfonyl group, acyl group, aryloxycarbonyl group, alkoxycarbonyl group, carbamoyl group, aryl or heterocyclic azo group, imide group, phosphino group, phosphinyl group, phosphinyloxy group, phosphini Examples include a ruamino group and a silyl group.
Y ¹ and Y ² are particularly preferably a hydrogen atom, an alkyl group (eg, a methyl group), an aryl group (eg, a phenyl group), a heterocyclic group (eg, a 2-pyridyl group), or an alkylthio group (eg, a methylthio group). And more preferably a hydrogen atom, a methyl group, a phenyl group, or a methylthio group, and among them, a hydrogen atom is most preferable. Y ¹ and Y ² may be the same or different.

In formula ^{(1), R 11} and ^{R 12} represents a hydrogen atom or a substituent. When R ¹¹ and R ¹² represent a substituent, examples of the substituent include a linear or branched alkyl group having 1 to 12 carbon atoms (for example, methyl, ethyl, n-propyl, i-propyl, n-butyl, i- Butyl, sec-butyl, t-butyl, 2-ethylhexyl, 2-methylsulfonylethyl, 3-phenoxypropyl, trifluoromethyl), a linear or branched aralkyl group having 7 to 18 carbon atoms (for example, benzyl), carbon C2-C12 linear or branched alkenyl group (for example, vinyl), C2-C12 linear or branched alkynyl group (for example, ethynyl), C3-C12 linear or branched cycloalkyl A group (for example, cyclopentyl), a linear or branched cycloalkenyl group having 3 to 12 carbon atoms (for example, cyclopentenyl), a halogen atom (for example, , Chlorine atom, bromine atom), aryl group (eg, phenyl, 4-t-butylphenyl, 2,4-di-t-amylphenyl), heterocyclic group (eg, imidazolyl, pyrazolyl, triazolyl, 2-furyl, 2-thienyl, 2-pyrimidinyl, 2-benzothiazolyl), cyano group, hydroxy group, nitro group, carboxy group, amino group, alkyloxy group (for example, methoxy, ethoxy, 2-methoxyethoxy, 2-methylsulfonylethoxy), Aryloxy groups (for example, phenoxy, 2-methylphenoxy, 4-t-butylphenoxy, 3-nitrophenoxy, 3-t-butyloxycarbonylphenoxy, 3-methoxycarbonylphenyloxy, acylamino groups (for example, acetamide, benzamide, 4- (3-tert-butyl-4-butyl Droxyphenoxy) butanamide), alkylamino groups (eg methylamino, butylamino, diethylamino, methylbutylamino), arylamino groups (eg phenylamino, 2-chloroanilino), ureido groups (eg phenylureido, methylureido) , N, N-dibutylureido), sulfamoylamino group (eg, N, N-dipropylsulfamoylamino), alkylthio group (eg, methylthio, octylthio, 2-phenoxyethylthio), arylthio group (eg, phenylthio) 2-butoxy-5-t-octylphenylthio, 2-carboxyphenylthio), alkyloxycarbonylamino group (for example, methoxycarbonylamino), alkylsulfonylamino group and arylsulfonylamino group For example, methylsulfonylamino, phenylsulfonylamino, p-toluenesulfonylamino), carbamoyl group (for example, N-ethylcarbamoyl, N, N-dibutylcarbamoyl), sulfamoyl group (for example, N-ethylsulfamoyl, N, N -Dipropylsulfamoyl, N-phenylsulfamoyl), sulfonyl groups (eg methylsulfonyl, octylsulfonyl, phenylsulfonyl, p-toluenesulfonyl), alkyloxycarbonyl groups (eg methoxycarbonyl, butyloxycarbonyl), hetero A ring oxy group (for example, 1-phenyltetrazol-5-oxy, 2-tetrahydropyranyloxy), an azo group (for example, phenylazo, 4-methoxyphenylazo, 4-pivaloylaminophenylazo, 2 Hydroxy-4-propanoylphenylazo), acyloxy group (for example, acetoxy), carbamoyloxy group (for example, N-methylcarbamoyloxy, N-phenylcarbamoyloxy), silyloxy group (for example, trimethylsilyloxy, dibutylmethylsilyloxy) , Aryloxycarbonylamino group (for example, phenoxycarbonylamino), imide group (for example, N-succinimide, N-phthalimide), heterocyclic thio group (for example, 2-benzothiazolylthio, 2,4-di-phenoxy- 1,3,5-triazole-6-thio, 2-pyridylthio), sulfinyl group (for example, 3-phenoxypropylsulfinyl), phosphonyl group (for example, phenoxyphosphonyl, octyloxyphosphonyl, phenylphosphonyl) , Aryloxycarbonyl group (for example, phenoxycarbonyl), acyl group (for example, acetyl, 3-phenylpropanoyl, benzoyl), ionic hydrophilic group (for example, carboxyl group, sulfo group, phosphono group and quaternary ammonium group) Is mentioned.

In general formula (1), preferred R ¹¹ and R ¹² are substituted or unsubstituted acylamino groups having 1 to 8 carbon atoms in total, substituted or unsubstituted alkyl groups having 1 to 12 carbon atoms in total, substituted or unsubstituted An aryl group having 6 to 18 carbon atoms, or a substituted or unsubstituted heterocyclic group having 4 to 12 carbon atoms, and more preferably a linear or branched alkyl group having 1 to 8 carbon atoms. Furthermore, a methyl group or a t-butyl group is preferable, and among them, a t-butyl group is particularly preferable.
By making R ¹¹ and R ^{12 a} linear alkyl group or a branched alkyl group having a small total number of carbon atoms (for example, having 1 to 4 carbon atoms), it is possible to achieve better hue, tinting strength and image fastness.
R ¹¹ and R ¹² may be the same or different.

G ¹ and G ^{2 each} represents a hydrogen atom, an alkyl group, a cycloalkyl group, an aralkyl group, an alkenyl group, an alkynyl group, an aryl group or a heterocyclic group, and particularly preferably a hydrogen atom, a methyl group, an ethyl group, n- Propyl group, i-propyl group, t-butyl group, cyclopropyl group, benzyl group, 2-phenethyl group, vinyl group, allyl group, ethynyl group, propargyl group, phenyl group, p-tolyl group, naphthyl group, pyridyl group , A pyrimidinyl group and a pyrazinyl group are preferable, and a hydrogen atom, a methyl group, a phenyl group, a pyridyl group, a pyrimidinyl group and a pyrazinyl group are preferable. Among them, a methyl group, a 2-pyridyl group, a 2,6-pyrimidinyl group, -A pyrazinyl group is preferred.
When G ¹ and G ² represent an alkyl group, it is preferably an alkyl group having 5 or less carbon atoms, more preferably an alkyl group having 3 or less carbon atoms, and most preferably a methyl group. G ¹ and G ² may be the same or different.

In the general formula (1), ^{W 1} and ^{W 2} represents an alkoxy group, an amino group, an alkyl group or an aryl group.
The alkoxy group represented by W ¹ and W ² is preferably a substituted or unsubstituted alkoxy group having 1 to 30 carbon atoms, and particularly preferably a substituted or unsubstituted alkoxy group having 1 to 5 carbon atoms. For example, methoxy group, ethoxy group, i-propoxy group, t-butoxy group, n-octyloxy group, 2-methoxyethoxy group and the like can be mentioned.

The amino group represented by W ¹ and W ² includes an alkylamino group, an arylamino group, and a heterocyclic amino group, preferably an amino group, a substituted or unsubstituted alkylamino group having 1 to 30 carbon atoms, Examples thereof include substituted or unsubstituted anilino groups having 6 to 30 carbon atoms, including amino groups, substituted or unsubstituted alkylamino groups having 1 to 8 carbon atoms, and substituted or unsubstituted anilino groups having 6 to 18 carbon atoms. Further, an amino group, a substituted or unsubstituted alkylamino group having 1 to 4 carbon atoms, and a substituted or unsubstituted anilino group having 6 to 12 carbon atoms are preferable. For example, an amino group (—NH ₂ ), methylamino Group (—NHCH ₃ ), dimethylamino group {—N (CH ₃ ) ₂ }, anilino group (—NHPh), N-methyl-anilino group {—N (C H ₃ ) Ph}, diphenylamino group {—N (Ph) ₂ } and the like.

Examples of the alkyl group represented by W ¹ and W ² include, independently, a linear, branched, or cyclic substituted or unsubstituted alkyl group. A cycloalkyl group, a bicycloalkyl group, and a tricyclo structure having many ring structures. Etc. are also included.
Specifically, the alkyl group is preferably an alkyl group having 1 to 30 carbon atoms, such as a methyl group, an ethyl group, an n-propyl group, an i-propyl group, a t-butyl group, an n-octyl group, Examples include an eicosyl group, 2-chloroethyl group, 2-cyanoethyl group, 2-ethylhexyl group, and the like. Preferred examples of the cycloalkyl group include substituted or unsubstituted cycloalkyl groups having 3 to 30 carbon atoms, such as a cyclohexyl group, a cyclopentyl group, and a 4-n-dodecylcyclohexyl group. The bicycloalkyl group is preferably a substituted or unsubstituted bicycloalkyl group having 5 to 30 carbon atoms, that is, a monovalent group obtained by removing one hydrogen atom from a bicycloalkane having 5 to 30 carbon atoms, for example, bicyclo [ 1.2.2] heptan-2-yl group, bicyclo [2.2.2] octane-3-yl group and the like.

The aryl group represented by W ¹ and W ² is preferably a substituted or unsubstituted aryl group having 6 to 30 carbon atoms, and among them, a substituted or unsubstituted aryl group having 6 to 18 carbon atoms. Further, a substituted or unsubstituted aryl group having 6 to 12 carbon atoms is preferable, and examples thereof include a phenyl group, a p-tolyl group, a naphthyl group, an m-chlorophenyl group, and an o-hexadecanoylaminophenyl group. .

Among them, preferred W ¹ and W ² are alkoxy groups (for example, methoxy group, ethoxy group, i-propoxy group, t-butoxy group), amino groups (for example, —NH ₂ group, methylamino group, dimethylamino group, Anilino group), alkyl group (for example, methyl group, ethyl group, n-propyl group, i-propyl group, t-butyl group, cyclopropyl group) or aryl group (for example, phenyl group, p-tolyl group, naphthyl group) Among them, an alkoxy group, an amino group, a phenyl group or an alkyl group is preferable, and an alkoxy group or an amino group is more preferable.
More preferably, it is an alkoxy group having a total carbon number of 5 or less, an amino group (—NH ₂ group), an alkylamino group having a total carbon number of 5 or less, and W ₁ and W ₂ are alkoxy groups having a total carbon number of 5 or less, amino In the case of an alkylamino group having a total carbon number of 5 or less, the dye molecule tends to form a hydrogen bond firmly at least in the molecule and between molecules, and has a good hue and high fastness (for example, light resistance, gas resistance) , Heat resistance, water resistance, chemical resistance, etc.).
Particularly preferred from the viewpoint of hue, light fastness and solvent resistance are an alkoxy group having 3 or less carbon atoms, an amino group (—NH ₂ group), and an alkylamino group having 3 or less carbon atoms, among which methoxy A group (—OCH ₃ group) or an ethoxy group (—OC ₂ H ₅ group) is preferred, and a methoxy group is particularly preferred from the viewpoint of good hue and improved light fastness.
W ₁ and W ₂ may be the same or different.

In the present invention, examples of the substituent in the case where Z, Y ¹ , Y ² , R ¹¹ , R ¹² , G ¹ , G ² , W ¹ , and W ² further have a substituent include the following substituents. be able to.
For example, halogen atom, alkyl group, aralkyl group, alkenyl group, alkynyl group, aryl group, heterocyclic group, cyano group, hydroxy group, nitro group, alkoxy group, aryloxy group, silyloxy group, heterocyclic oxy group, acyloxy group , Carbamoyloxy group, alkoxycarbonyloxy group, aryloxycarbonyloxy group, amino group, acylamino group, aminocarbonylamino group, alkoxycarbonylamino group, aryloxycarbonylamino group, sulfamoylamino group, alkyl or arylsulfonylamino group , Mercapto group, alkylthio group, arylthio group, heterocyclic thio group, sulfamoyl group, alkyl or arylsulfinyl group, alkyl or arylsulfonyl group, acyl group, aryloxycal Group, an alkoxycarbonyl group, a carbamoyl group, an aryl or heterocyclic azo group, an imido group, a phosphino group, phosphinyl group, phosphinyloxy group, phosphinylamino group, a silyl group.

The azo pigment in the present invention includes a tautomer of the azo pigment represented by the general formula (1) within the range. The general formula (1) is shown in the form of an extreme structural formula among several tautomers that can be taken in terms of chemical structure, but may be a tautomer other than the structure described, You may use as a mixture containing these tautomers.
For example, the azo pigment represented by the general formula (1) may be an azo-hydrazone tautomer represented by the following general formula (1 ′).
The present invention includes in its scope a compound represented by the following general formula (1 ′), which is a tautomer of the azo pigment represented by the general formula (1).

In General Formula (1 ′), R ¹¹ , R ¹² , W ¹ , W ² , Y ¹ , Y ² , G ¹ , G ² and Z are R ¹¹ , R ¹² , W ^{1 in} General Formula (1). , W ² , Y ¹ , Y ² , G ¹ , G ² and Z have the same meanings.

  In addition, about the preferable combination of a substituent of the compound represented by the said General formula (1), the compound whose at least 1 of a various substituent is the said preferable group is preferable, and many more various substituents are the said preferable. More preferred are compounds that are groups, and most preferred are compounds in which all substituents are the preferred groups.

  A particularly preferred combination as the azo pigment represented by the general formula (1) of the present invention includes at least one of the following (A) to (E).

(A) W ¹ and W ² are each independently an alkoxy group (for example, methoxy group, ethoxy group, i-propoxy group, t-butoxy group), amino group (for example, —NH ₂ group, methylamino group, dimethyl group). Amino group, anilino group), alkyl group (for example, methyl group, ethyl group, n-propyl group, i-propyl group, t-butyl group, cyclopropyl group) or aryl group (for example, phenyl group, p-tolyl group) , A naphthyl group) is preferable, among which an alkoxy group, an amino group or an alkyl group is preferable, an alkoxy group or an amino group is more preferable, and an alkoxy group having 5 or less total carbon atoms or an amino group (-NH ₂ group) is more preferable. , total carbon is 5 or less alkylamino group, particularly preferably having 3 or less carbon atoms an alkoxy group, an amino group (-NH ₂ group), total carbon Number 3 is an alkyl amino group, especially a methoxy group among them (-OCH ₃ group) being most preferred.

(B) R ¹¹ and R ¹² are each independently a hydrogen atom or a substituent (for example, a substituted or unsubstituted acylamino group having 1 to 8 carbon atoms, a substituted or unsubstituted alkyl group having 1 to 12 carbon atoms). Group, a substituted or unsubstituted aryl group having 6 to 18 carbon atoms in total, or a substituted or unsubstituted heterocyclic group having 4 to 12 carbon atoms in total, and more preferably a straight chain having 1 to 8 carbon atoms in total. It is an alkyl group or a branched alkyl group, more preferably a methyl group, an i-propyl group or a tert-butyl group, and most preferably a tert-butyl group.

  (C) Z represents a divalent group derived from a 5- to 8-membered nitrogen-containing heterocyclic group, and they may be further condensed. The nitrogen-containing heterocycle in Z is a 5- or 6-membered substituted or unsubstituted nitrogen-containing heterocycle, such as a pyrrole ring, pyrazole ring, triazole ring, imidazole ring, thiazole ring, isothiazole ring, oxazole ring, isoxazole A ring, a thiadiazole ring, a thiophene ring, a furan ring, a pyridine ring, a pyrimidine ring, a triazine ring, and a pyridazine ring are preferable, and a 6-membered nitrogen-containing heterocyclic group having 3 to 10 carbon atoms is particularly preferable. Further preferred examples of the heterocyclic ring are a pyridine ring, a pyrimidine ring, an S-triazine ring, a pyridazine ring and a pyrazine ring, and more preferably a pyridine ring, a pyrimidine ring, an S-triazine ring, a pyridazine ring and a pyrazine ring. More preferred are a pyrimidine ring and an S-triazine ring, and among them, a pyrimidine ring is most preferred.

(D) G ¹ and G ² each independently represent a hydrogen atom, an alkyl group, a cycloalkyl group, an aralkyl group, an alkenyl group, an alkynyl group, an aryl group or a heterocyclic group, and particularly preferably a hydrogen atom or a methyl group , Ethyl group, n-propyl group, i-propyl group, t-butyl group, cyclopropyl group, benzyl group, 2-phenethyl group, vinyl group, allyl group, ethynyl group, propargyl group, phenyl group, p-tolyl group , A naphthyl group, a pyridyl group, a pyrimidinyl group, and a pyrazinyl group are preferable, and a hydrogen atom, a methyl group, a phenyl group, a pyridyl group, a pyrimidinyl group, and a pyrazinyl group are preferable, and among them, a methyl group, a 2-pyridyl group, 2,6- A pyrimidinyl group and a 2,5-pyrazinyl group are preferable.
Further, the alkyl group represented by G ¹ and G ² is more preferably an alkyl group having a total carbon number of 5 or less, more preferably an alkyl group having a total carbon number of 3 or less, and most preferably a methyl group.

(E) Y ¹ and Y ² are each independently a hydrogen atom, an alkyl group (for example, a methyl group), an aryl group (for example, a phenyl group), a heterocyclic group (for example, a 2-pyridyl group), an alkylthio group (for example, Methylthio group), preferably a hydrogen atom, a methyl group, a phenyl group, or a methylthio group, and among them, a hydrogen atom is particularly preferable.

  Among the azo pigments represented by the above general formula (1) in the present invention, an azo pigment represented by the following general formula (2) is preferable.

G ¹ , G ² , R ¹¹ , R ¹² , W ¹ , W ² , Y ¹ and Y ² in the general formula (2) are the same as G ¹ , G ² , R ¹¹ , R ¹² , W ¹ , W ² , Y ¹ and Y ² have the same meanings.
X ¹¹ and X ¹² each independently represent a hetero atom in a divalent group (Het.) Derived from the nitrogen-containing heterocyclic compound represented by Z in the general formula (1).

In the present invention, a large number of tautomers can be considered in the azo pigment represented by the general formula (1).
In the present invention, the azo pigment represented by the general formula (1) preferably has a substituent that forms an intramolecular hydrogen bond or an intramolecular cross-hydrogen bond. The azo pigment represented by the general formula (1) in the present invention preferably has at least one substituent that forms an intramolecular cross-hydrogen bond, and at least three substituents that form an intramolecular hydrogen bond. More preferably, it has at least three substituents that form an intramolecular hydrogen bond, and at least two of these hydrogen bonds have a substituent that forms an intramolecular cross-hydrogen bond Is particularly preferred.

Among the azo pigments represented by the general formula (1), examples of the particularly preferred azo pigments represented by the general formula (1) include azo pigments represented by the above general formula (2).
The reason why this structure is preferable is that, as shown in the general formula (2), a nitrogen atom, a hydrogen atom, and a hetero atom (a hydrazone group that is an azo group or a tautomer thereof) constituting a heterocycle contained in the azo pigment structure. The nitrogen atom and the oxygen atom of the carbonyl group or the nitrogen atom of the amino group) can easily form at least one intramolecular hydrogen bond (intramolecular hydrogen bond).
The reason why these structures are preferable is that, as shown in the general formula (2), a nitrogen atom, a hydrogen atom of an amino group, and a hetero atom (for example, an azo group or a combination thereof) constituting a heterocyclic group contained in an azo pigment. The nitrogen atom of the hydrazone group, the oxygen atom of the carbonyl group or the nitrogen atom of the amino group, which is a mutant, easily forms at least 4 intramolecular hydrogen bonds, and has at least 2 intramolecular hydrogen bonds. It is easy to form a cross hydrogen bond easily.
As a result, the planarity of the molecule is improved, the intramolecular / intermolecular interaction is further improved, and for example, the crystallinity of the azo pigment represented by the general formula (2) is increased (higher order structure is easily formed). This is the most preferable example because the required performance as a pigment, which is light fastness, thermal stability, wet heat stability, water resistance, gas resistance and / or solvent resistance, is greatly improved.

Moreover, in the azo pigment in this invention, the compound represented by General formula (1) may contain isotopes (for example, ² H, ³ H, ¹³ C, ¹⁵ N).

  As specific examples of the azo pigment represented by the general formula (1), Pig. -1 to Pig. Although -48 is shown, the azo pigment used in the present invention is not limited to the following examples. In addition, the structures of the following specific examples are shown in the form of an extreme structural formula among several tautomers that can be taken from the chemical structure. Needless to say, it may be.

  The azo pigment represented by the general formula (1) in the present invention may have a chemical structural formula of the general formula (1) or a tautomer thereof, and the crystal form is not particularly limited. For example, it may be an azo pigment having any crystal form also called polymorph (crystal polymorph).

Crystal polymorphs refer to crystals that have the same chemical composition but differ in the arrangement of building blocks (molecules or ions) in the crystal. In crystal polymorphs, the crystal structure determines chemical and physical properties, and each crystal polymorph can be distinguished by rheology, hue, and other color characteristics. Different crystal polymorphs can also be confirmed by X-Ray Diffraction (powder X-ray diffraction measurement result) and X-Ray Analysis (X-ray crystal structure analysis result).
When the azo pigment represented by the general formula (1) in the present invention has a crystal polymorph, the crystal form may be any polymorph, and may be a mixture of two or more polymorphs. However, it is preferable that the main component is a crystal type. That is, it is preferable that the polymorph is less mixed, and the content of the azo pigment having a single crystal type is 70% to 100%, preferably 80% to 100%, more preferably 90% to the entire azo pigment. 100%, more preferably 95% to 100, and particularly preferably 100%.

By using an azo pigment having a single crystal form as a main component, the regularity of the dye molecule arrangement is improved, the intramolecular / intermolecular interaction is strengthened, and a higher-order three-dimensional network is easily formed. . As a result, it is preferable in terms of performance required for the pigment, such as improvement of hue, light fastness, heat fastness, humidity fastness, oxidizing gas fastness and solvent resistance.
The mixing ratio of crystal polymorphs in azo pigments is based on solid physicochemical measurements such as single crystal X-ray crystal structure analysis, powder X-ray diffraction (XRD), crystal micrograph (TEM), IR (KBr method), etc. I can confirm.

  In the present invention, when the azo pigment represented by the general formula (1) has an acid group, a part or all of the acid group may be a salt type, and a salt type pigment and a free acid type The pigment may be mixed. Examples of the salt type include salts of alkali metals such as Na, Li, and K, ammonium salts optionally substituted with an alkyl group or hydroxyalkyl group, and organic amine salts. Examples of organic amines include lower alkyl amines, hydroxy substituted lower alkyl amines, carboxy substituted lower alkyl amines, and polyamines having 2 to 10 alkyleneimine units having 2 to 4 carbon atoms. In the case of these salt types, the type is not limited to one type, and a plurality of types may be mixed.

  Further, in the structure of the azo pigment used in the present invention, when a plurality of acid groups are contained in one molecule, the plurality of acid groups are each independently a salt type or an acid type and are different from each other. May be.

  In the present invention, the azo pigment represented by the general formula (1) may be a hydrate containing water molecules in the crystal, and the number of water molecules contained in the crystal is not particularly limited. .

Next, an example of a method for producing the azo pigment represented by the general formula (1) will be described. For example, the heterocyclic amine represented by the following general formula (A) is diazonium under acidic conditions, subjected to a coupling reaction with a compound represented by the following general formula (B), followed by post-treatment by a conventional method, An azo pigment represented by the formula (1) can be produced.

In the general formulas (A) and (B), W has the same meaning as W ¹ and W ² in the general formula (1), G has the same meaning as G ¹ and G ² in the general formula (1), R ¹¹ , R ¹² and Z have the same meanings as R ¹¹ , R ¹² and Z in the general formula (1), respectively.

The heterocyclic amines represented by the above general formula (A) are generally known and commonly used methods such as those described in Helv. Chim. Acta, 41, 1958, 1052 to 1056 and Helv. Chim. Acta, 42, 1959, 349 to 352 and the like, and methods similar thereto can be used.
Moreover, the compound represented by the said general formula (B) can be manufactured by the method as described in international publication 06/082669, Unexamined-Japanese-Patent No. 2006-57076, and the method according to it.

The diazoniumation reaction of the heterocyclic amine represented by the general formula (A) is, for example, in an acidic solvent such as sulfuric acid, phosphoric acid, acetic acid, hydrochloric acid, methanesulfonic acid, sodium nitrite, nitrosylsulfuric acid, isoamyl nitrite, etc. This reagent can be reacted at a temperature of 15 ° C. or lower for about 10 minutes to 6 hours.
The coupling reaction is performed by reacting the diazonium salt obtained by the above-described method with the compound represented by the general formula (B) at 40 ° C. or lower, preferably at 25 ° C. or lower for about 10 minutes to 12 hours. be able to.

  Crystals may be precipitated in the case of reaction in this way, but in general, water or an alcohol solvent is added to the reaction solution to precipitate crystals, and the crystals are collected by filtration. Can do. In addition, an alcohol solvent, water or the like can be added to the reaction solution to precipitate crystals, and the precipitated crystals can be collected by filtration. The crystals collected by filtration can be washed and dried as necessary to obtain an azo pigment represented by the general formula (1).

  Although the azo pigment represented by the general formula (1) is obtained as a crude azo pigment (crude) by the above production method, when used as a specific color material in the present invention, it is desirable to perform post-treatment. Examples of post-treatment methods include solvent salt milling, salt milling, dry milling, solvent milling, pigment particle control step by grinding treatment such as acid pasting, solvent heating treatment, resin, surfactant and dispersant. The surface treatment process by etc. is mentioned.

The azo pigment represented by the general formula (1) of the present invention is preferably subjected to solvent heat treatment and / or solvent salt milling as post-treatment.
Examples of the solvent used in the solvent heat treatment include water, aromatic hydrocarbon solvents such as toluene and xylene, halogenated hydrocarbon solvents such as chlorobenzene and o-dichlorobenzene, and alcohols such as isopropanol and isobutanol. Examples thereof include solvents, polar aprotic organic solvents such as N, N-dimethylformamide, N, N-dimethylacetamide, and N-methyl-2-pyrrolidone, glacial acetic acid, pyridine, and mixtures thereof. An inorganic or organic acid or base may be further added to the solvents mentioned above. The temperature of the solvent heat treatment varies depending on the desired primary particle size of the pigment, but is preferably 40 to 150 ° C, more preferably 60 to 100 ° C. The treatment time is preferably 30 minutes to 24 hours.

  As solvent salt milling, for example, a crude azo pigment, an inorganic salt, and an organic solvent that does not dissolve the crude azo pigment are charged into a kneader and kneaded and ground therein. As the inorganic salt, a water-soluble inorganic salt can be preferably used. For example, an inorganic salt such as sodium chloride, potassium chloride, sodium sulfate is preferably used. Moreover, it is more preferable to use an inorganic salt having an average particle size of 0.5 to 50 μm. The amount of the inorganic salt used is preferably 3 to 20 times by mass, more preferably 5 to 15 times by mass with respect to the crude azo pigment. As the organic solvent, a water-soluble organic solvent can be suitably used, but a high boiling point solvent is preferable from the viewpoint of safety because the solvent easily evaporates due to a temperature rise during kneading.

  Examples of such water-soluble organic solvents include diethylene glycol, glycerin, ethylene glycol, propylene glycol, liquid polyethylene glycol, liquid polypropylene glycol, 2- (methoxymethoxy) ethanol, 2-butoxyethanol, 2- (isopentyloxy). Ethanol, 2- (hexyloxy) ethanol, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, triethylene glycol, triethylene glycol monomethyl ether, 1-methoxy-2-propanol, 1-ethoxy-2-propanol , Dipropylene glycol, dipropylene glycol monomethyl ether, dipropylene glycol monomethyl ether, di B propylene glycol or mixtures thereof. The amount of the water-soluble organic solvent used is preferably 0.1 to 5 times by mass with respect to the crude azo pigment. The kneading temperature is preferably 20 to 130 ° C, particularly preferably 40 to 110 ° C. As a kneader, for example, a kneader or a mix muller can be used.

  The content of the azo pigment (coloring material) used in the present invention is preferably 0.1 to 15% by mass, more preferably 1 to 8% by mass in the specific ink. The blending amount of the pigment used in the present invention is appropriately adjusted according to the type of ink such as dark and light ink.

The volume average particle diameter of the azo pigment (coloring material) used in the present invention is 250 nm or less, more preferably 150 nm or less, from the viewpoint of ink stability. Furthermore, it is more preferable to use an azo pigment having a volume average particle diameter of 120 nm or less because the effects of the present invention can be further improved.
The volume average particle diameter is measured under normal conditions using a dynamic light scattering method.

(Other color materials)
The specific ink in the present invention may contain a color material other than the above.
When the ink set of the present invention contains other inks other than the specific ink, the other inks contain other color materials other than those described above.
As the “other colorant” here, for example, known dyes, pigments and the like can be used without particular limitation. Among these, from the viewpoint of ink colorability, a color material that is almost insoluble or hardly soluble in water is preferable. Specific examples include various pigments, disperse dyes, oil-soluble dyes, dyes forming J aggregates, and the like, and pigments are more preferable.
The water-insoluble pigment itself or the pigment itself surface-treated with a dispersant can be used as the colorant.

-Pigment-
The pigment as the “other colorant” is not particularly limited in kind, and conventionally known organic and inorganic pigments can be used. For example, azo lakes, azo pigments other than specific color materials, phthalocyanine pigments, perylene and perinone pigments, anthraquinone pigments, quinacridone pigments, dioxazine pigments, diketopyrrolopyrrole pigments, thioindigo pigments, isoindolinone pigments, quinophthalone pigments, etc. Pigments, dye lakes such as basic dye type lakes, acid dye type lakes, organic pigments such as nitro pigments, nitroso pigments, aniline black, daylight fluorescent pigments, inorganics such as titanium oxides, iron oxides, and carbon blacks Pigments. 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 whose surface is treated with a surfactant, a polymer dispersing agent or the like, or graft carbon. Among the pigments, it is particularly preferable to use an azo pigment other than the specific color material, a phthalocyanine pigment, an anthraquinone pigment, a quinacridone pigment, or a carbon black pigment. Specific examples include pigments described in JP2007-100071A.

<Polymer dispersant>
The specific ink in the invention preferably includes a polymer dispersant.
In this case, a particularly preferable form is a form in which at least the specific color material which is an essential component of the specific ink is coated with a polymer dispersant.
A more preferable form is a form in which the specific color material coated with the polymer dispersant is dispersed in an aqueous solvent as color material particles.
The dispersant may be a polymer dispersant or a low molecular surfactant type dispersant, but is preferably a polymer dispersant.

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

The water-insoluble polymer dispersant is not particularly limited as long as the specific color material can be dispersed, and a conventionally known one can be used.
The water-insoluble polymer dispersant can be configured to include both a hydrophobic structural unit and a hydrophilic structural unit, for example.

Examples of the monomer constituting the hydrophobic structural unit include styrene monomers, alkyl (meth) acrylates, aromatic group-containing (meth) acrylates, and the like.
The monomer constituting the hydrophilic structural unit is not particularly limited as long as it is a monomer containing a hydrophilic group. Examples of the hydrophilic group include a nonionic group, a carboxyl group, a sulfonic acid group, and a phosphoric acid group. In addition, a nonionic group is synonymous with the nonionic group in the below-mentioned self-dispersing polymer.
From the viewpoint of dispersion stability, the hydrophilic structural unit preferably includes at least a carboxyl group, and preferably includes a nonionic group and a carboxyl group.

Specifically, as the polymer dispersant in the present invention, a styrene- (meth) acrylic acid copolymer, a styrene- (meth) acrylic acid- (meth) acrylic acid ester copolymer, a (meth) acrylic acid ester- ( Examples thereof include a meth) acrylic acid copolymer, a polyethylene glycol (meth) acrylate- (meth) acrylic acid copolymer, and a styrene-maleic acid copolymer.
Here, “(meth) acrylic acid” means acrylic acid or methacrylic acid.

  The water-insoluble polymer dispersant is preferably a vinyl polymer containing a carboxyl group from the viewpoint of pigment dispersion stability, and has at least a structural unit derived from an aromatic group-containing monomer as a hydrophobic structural unit. A vinyl polymer having a structural unit containing a carboxyl group as a hydrophilic structural unit is more preferable.

  The weight average molecular weight of the polymer dispersant is preferably 3,000 to 200,000, more preferably 5,000 to 100,000, and still more preferably 5,000 to 80, from the viewpoint of dispersion stability of the pigment. 1,000, particularly preferably 10,000 to 60,000.

  The content of the polymer dispersant in the color material particles (specific color material coated with the polymer dispersant) is such that the dispersant is compared with the color material from the viewpoints of dispersibility of the color material, ink colorability, and dispersion stability. Is preferably 5 to 200% by mass, more preferably 10 to 100% by mass, and particularly preferably 20 to 80% by mass.

  The colorant particles may contain other dispersant in addition to the water-insoluble polymer dispersant. For example, a conventionally known water-soluble low-molecular dispersant, water-soluble polymer, or the like can be used. The content of the dispersant other than the water-insoluble polymer dispersant can be used within the range of the content of the polymer dispersant.

<Hydrophilic organic solvent>
The specific ink in the invention preferably contains a hydrophilic organic solvent.
The hydrophilic organic solvent is not particularly limited, and a known hydrophilic organic solvent can be used. For example, the following first hydrophilic organic solvent, the following second hydrophilic organic solvent, and the following other hydrophilic organic solvents can be used. It is preferable to use at least one selected from solvents.
In particular, the specific ink in the invention includes two or more hydrophilic organic solvents including at least one of the following first hydrophilic organic solvents and at least one of the following second hydrophilic organic solvents. It is more preferable.

The first hydrophilic organic solvent is a hydrophilic organic solvent having an I / O value of 0.70 or more and less than 1.00.
When the I / O value of the first hydrophilic organic solvent is less than 1.00, compatibility with the self-dispersing polymer particles described later is improved, and the fixability of the formed image is more effectively improved. In addition, the abrasion resistance of the image is further improved. In addition, since the I / O value of the first hydrophilic organic solvent is 0.70 or more, the stability of the ink is improved.
The I / O value of the hydrophilic organic solvent is calculated in the same manner as the calculation of the I / O value in the self-dispersing polymer described later.

The second hydrophilic organic solvent is a hydrophilic organic solvent having an I / O value of 1.00 or more and 1.50 or less.
When the I / O value of the second hydrophilic organic solvent is 1.00 or more, the stability of the ink is more effectively improved. Moreover, it can suppress that the fixability of the image formed by the I / O value of the 2nd hydrophilic organic solvent being 1.50 or less falls.

Specific examples of the first hydrophilic organic solvent having an I / O value of 0.70 or more and less than 1.00 include glycol ethers, and propylene glycol ethers or ethylene glycol ethers are preferable, and more preferable. Is propylene glycol ether, specifically, triprolene glycol monomethyl ether (I / O value: 0.80), triprolene glycol monoethyl ether (I / O value: 0.73), triprolene glycol monobutyl ether ( I / O value: 0.61), diprolene glycol monoethyl ether (I / O value: 0.78), diprolene glycol monobutyl ether (I / O value: 0.70), prolene glycol monobutyl ether (I / O value: 0.88).
Among these, from the viewpoints of image fixability and ink stability, triprolene glycol monomethyl ether (I / O value: 0.80) is preferable.

  Specific examples of the second hydrophilic organic solvent having an I / O value of 1.0 or more and 1.5 or less include propylene glycol monomethyl ether (I / O value: 1.50), propylene glycol monoethyl ether (I / O value: 1.20), diethylene glycol monobutyl ether (I / O value: 1.40), triethylene glycol monobutyl ether (I / O value: 1.20), 2,2-diethyl-1,3 -Propanediol (I / O value: 1.43), 2-methyl-2-propyl-1,3-propanediol (I / O value: 1.43), 2,4-dimethyl-2,4-pentane Diol (I / O value: 1.43), 2,5-dimethyl-2,5-hexanediol (I / O value: 1.25), tripropylene glycol (I / O value: 1.33), Sun Knicks GP 50 (I / O value: 1.30, manufactured by Sanyo Chemical Industries, Ltd.), and the like. Of these, SANNIX GP250 is preferable from the viewpoint of image fixability and ink stability.

The content of the first hydrophilic organic solvent in the specific ink in the invention is preferably 0.1 to 20% by mass, and 1 to 16% by mass from the viewpoints of image fixability and ink stability. More preferably, it is more preferably 2 to 12% by mass.
Further, the first hydrophilic organic solvent preferably contains 1 to 16% by mass of a hydrophilic organic solvent selected from an I / O value of 0.70 or more and less than 1.00, and an I / O value of 0.70 or more. It is more preferable that 2-12 mass% of hydrophilic organic solvents chosen from less than 0.90 are included.

In the present invention, the content ratio of the second hydrophilic organic solvent in the specific ink is preferably 0.1 to 20% by mass, and 1 to 16% by mass from the viewpoint of image fixability and ink stability. It is more preferable that it is 2-12 mass%.
Further, the second hydrophilic organic solvent preferably contains 1 to 16% by weight of a hydrophilic organic solvent selected from an I / O value of 1.00 to 1.50, and an I / O value of 1.20 or more. It is more preferable that 2-12 mass% of hydrophilic organic solvents chosen from 1.40 or less are included.

  Furthermore, the content ratio of the second hydrophilic organic solvent to the first hydrophilic organic solvent in the specific ink in the present invention (second hydrophilic organic solvent: first hydrophilic organic solvent) is the image fixing property. From the viewpoint of ink stability, it is preferably 1:10 to 10: 1, more preferably 1: 4 to 4: 1, and more preferably 1: 2 to 2: 1.

The specific ink in the invention may further contain other hydrophilic organic solvent other than the first hydrophilic organic solvent and the second hydrophilic organic solvent.
As other hydrophilic organic solvents, polyhydric alcohols are useful for the purpose of drying inhibitors and wetting agents. For example, glycerin (I / O value: 5.00), ethylene glycol (I / O value: 2.00), diethylene glycol (I / O value: 5.00), triethylene glycol (I / O value: 3.43), propylene glycol (I / O value: 2.50), dipropylene glycol (I / O) O value: 2.00), 1,3-butanediol (I / O value: 2.50), 2,3-butanediol (I / O value: 2.50), 1,4-butanediol (I / O value: 2.50), 3-methyl-1,3-butanediol (I / O value: 2.00), 1,5-pentanediol (I / O value: 2.00), tetraethylene glycol (I / O value: 2.91), 1,6-hexane All (I / O value: 1.67), 2-methyl-2,4-pentanediol (I / O value: 1.67), polyethylene glycol (I / O value depends on the number of ethylene chain repeats), 1 2,4-butanetriol (I / O value: 3.75), 1,2,6-hexanetriol (I / O value: 2.50), 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 (I / O value: 1.67), 3,3- Dimethyl-1,2-butanediol (I / O value: 1.67), 5-hexene-1,2-diol, 2-ethyl-1,3-hexanediol (I / O value: 2.00), 2,2,4-trimethyl-1,3-pentanediol (I / O value: 1.88) can be mentioned as a preferred example.

  As content rate of another hydrophilic organic solvent, it can be 16 mass% or less, for example, it is preferable that it is 12 mass% or less, and it is more preferable that it is 8% or less.

  The specific ink in the invention may contain two or more hydrophilic organic solvents, and the content is preferably 1% by mass or more and 60% by mass or less, from the viewpoint of stability and dischargeability, and 5% by mass. The content is more preferably 40% by mass or less, and particularly preferably 10% by mass or more and 30% by mass or less.

As mentioned above, although the said specific ink of this invention demonstrated centering on the form containing 2 or more types of hydrophilic organic solvents, this invention is not limited to this form, It is 1 type of the hydrophilic organic solvent illustrated above. The form containing only may be sufficient.
In the case of only one kind, the content of the hydrophilic organic solvent is also 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 stability and dischargeability, and 10% by mass. % To 30% by mass is particularly preferable.

In addition, the specific ink of the present invention preferably contains water in addition to the hydrophilic organic solvent.
The amount of water is not particularly limited, but is preferably 10% by mass or more and 99% by mass or less, more preferably 30% by mass or more and 80% by mass or less, from the viewpoint of ensuring stability and ejection reliability in the specific ink. Yes, and more preferably 50 mass% or more and 70 mass% or less.

<Surfactant>
The specific ink in the invention preferably contains a surfactant.
Examples of the surfactant include nonionic surfactants, cationic surfactants, anionic surfactants, and betaine surfactants.
In addition, the addition amount of the surfactant is preferably an addition amount for adjusting the surface tension of the specific ink to 20 to 60 mN / m, and preferably an addition amount for adjusting to 20 to 45 mN / m, in order to perform droplet ejection well by the ink jet method. 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.
In the present invention, the surface tension of the specific ink is measured at 25 ° C. using 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. 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 surfactants can also be used as antifoaming agents, and fluorine compounds, silicone compounds, chelating agents represented by EDTA, and the like can also be used.

  Specific examples of the nonionic surfactant include, for example, polyoxyethylene lauryl ether, polyoxyethylene octyl phenyl ether, polyoxyethylene oleyl phenyl ether, polyoxyethylene nonyl phenyl ether, oxyethylene / oxypropylene block copolymer, t -Octylphenoxyethyl polyethoxyethanol, nonylphenoxyethyl polyethoxyethanol, SURFYNOLS (Air Products & Chemicals), which is an acetylene-based polyoxyethylene oxide surfactant, Orphine E1010 (manufactured by Nissin Chemical Industry Co., Ltd.), etc. One type or two or more types can be selected. Preferably, it is an acetylene-based polyoxyethylene oxide surfactant

  The amount of the surfactant added to the specific ink in the invention is not particularly limited, but is preferably 1% by mass or more, more preferably 1 to 10% by mass, and further preferably 1 to 3% by mass. %.

<Basic substance>
The specific ink in the invention may contain a basic substance.
As the basic substance, a neutralizing agent (organic base, inorganic alkali) can be used. For the purpose of neutralizing the polymer 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 of a polymer dispersing agent, It is more preferable that it is 70-120 mol%, 80-100 mol% It is particularly preferred that
Specific examples of the basic substance are the same as those in the self-dispersing polymer particles described later.

<Method for producing colorant particle dispersion>
Here, the manufacturing method of the color material particle dispersion containing the above-mentioned color material particles (the specific color material coated with the polymer dispersant) will be described.
The colorant particle dispersion can be produced, for example, by dispersing a mixture containing a specific colorant, a polymer dispersant, and, if necessary, a solvent (preferably an organic solvent) with a disperser.
In particular, the colorant particle dispersion includes a specific colorant, a dispersant, an organic solvent that dissolves or disperses the dispersant, and a basic substance, and after mixing a solution containing water as a main component (mixing / water It is preferable that the organic solvent is produced by removing the organic solvent (solvent removing step).
According to this method for producing a color material particle dispersion, the color material particle dispersion in which the color material particles are finely dispersed and excellent in storage stability can be produced.

  The organic solvent in the method for producing the colorant particle dispersion is preferably capable of dissolving or dispersing the polymer dispersant, but more 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.

  More specifically, the colorant particle dispersion can be produced by a production method including the following steps (1) and (2), but is not limited thereto.

Step (1): A step of dispersing a mixture containing a specific color material, a polymer dispersant, an organic solvent for dissolving and dispersing the polymer dispersant, a basic substance, and water. Step (2): Removing at least a portion of the organic solvent from the mixture after the dispersion treatment;

In the step (1), first, the polymer dispersant is dissolved or dispersed in an organic solvent to obtain a mixture thereof (mixing step). Next, a specific colorant, 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 obtain an oil-in-water type. To obtain a colorant particle dispersion.
There is no limitation in the addition amount (degree of neutralization) of the basic substance. Usually, it is preferable that the finally obtained colorant particle dispersion has a liquidity close to neutrality, for example, pH (25 ° C.) of 4.5 to 10. The pH can also be determined by the degree of neutralization according to the dispersant.

Preferable examples of the organic solvent 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 may be used alone or in combination.

In the production of the colorant particle 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 screw or a twin screw extruder. 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 colorant particle dispersion, the removal of the organic solvent is not particularly limited, and can be removed by a known method such as vacuum distillation.

  The color material particles in the color material particle dispersion obtained in this way maintain a good dispersion state, and the obtained color material particle dispersion has excellent stability over time.

In the present invention, the average particle diameter of the color material particles is preferably 10 to 200 nm, more preferably 10 to 150 nm, and still more preferably 10 to 100 nm. When the average particle size is 200 nm or less, the color reproducibility is good, and in the case of the ink jet method, the droplet ejection characteristics are good. Moreover, light resistance becomes favorable because an average particle diameter is 10 nm or more.
The particle size distribution of the color material particles is not particularly limited, and may be either a wide particle size distribution or a monodispersed particle size distribution. Further, two or more colorant particles having a monodispersed particle size distribution may be mixed and used.
The average particle size and particle size distribution of the color material particles can be measured using, for example, a dynamic light scattering method.

In the specific ink of the present invention, the color material particles may be used alone or in combination of two or more.
The content of the colorant particles is preferably 0.1 to 25% by mass, more preferably 1 to 20% by mass, and more preferably 1.5 to 15% with respect to the specific ink from the viewpoint of image density. % By mass is more preferable, and 1.5 to 10% by mass is particularly preferable.

<Polymer particles>
The specific ink in the invention preferably includes at least one kind of polymer particles (polymer particles other than the polymer dispersant).
As the polymer particles, polymer particles containing a structural unit derived from a hydrophilic monomer and a structural unit derived from a hydrophobic monomer and having a volume average particle diameter of 0.1 to 10 nm (hereinafter referred to as “self-dispersing polymer” or Also referred to as “self-dispersing polymer particles”).
Among these, polymer particles having a glass transition temperature of 150 ° C. or higher and an I / O value of 0.2 to 0.55 are more preferable.
As the glass transition temperature (Tg), a measured Tg obtained by actual measurement is applied. Specifically, the measurement Tg means a value measured under normal measurement conditions using a differential scanning calorimeter (DSC) EXSTAR 6220 manufactured by SII Nanotechnology.

However, when measurement is difficult due to polymer decomposition or the like, calculation Tg calculated by the following calculation formula is applied.
Calculation Tg is calculated by the following formula (1).
1 / Tg = Σ (X _i / Tg _i ) (1)
Here, it is assumed that n types of monomer components from i = 1 to n are copolymerized in the polymer to be calculated. X _i is the weight fraction of the i-th monomer (ΣX _i = 1), and Tg _i is the glass transition temperature (absolute temperature) of the homopolymer of the i-th monomer. However, Σ is the sum from i = 1 to n. The homopolymer glass transition temperature value (Tg _i ) of each monomer is the value of Polymer Handbook (3rd Edition) (by J. Brandrup, EH Immergut (Wiley-Interscience, 1989)).

The I / O value of the self-dispersing polymer is preferably 0.20 or more and 0.55 or less, but from the viewpoint of blocking resistance and ink stability, it is preferably 0.30 or more and 0.54 or less. More preferably, it is 0.40 or more and 0.50 or less.
If the I / O value of the self-dispersing polymer is 0.20 or more, the stability of the ink can be further suppressed. Moreover, if I / O value is 0.55 or less, the fall of blocking resistance (especially high temperature high humidity conditions) can be suppressed more.
The I / O value is a value that treats the polarity of various organic compounds, also called inorganic values / organic values, in an organic concept, and is one of functional group contribution methods for setting parameters for each functional group. It is.

  The I / O value is described in detail in an organic conceptual diagram (written by Yoshio Koda, Sankyo Publishing (1984)). The concept of the I / O value is that the properties of a compound are divided into an organic group that represents covalent bonding and an inorganic group that represents ionic bonding, and all organic compounds are orthogonal coordinates named organic axes and inorganic axes. Each of the above points is shown.

The inorganic value is obtained by quantifying the magnitude of the influence on the boiling point of various substituents and bonds of an organic compound with reference to a hydroxyl group. Specifically, when the distance between the boiling point curve of a straight chain alcohol and the boiling point curve of a straight chain paraffin is about 100 ° C., the influence of one hydroxyl group is set to 100 as a numerical value. A value obtained by quantifying the influence of various substituents or various bonds on the boiling point based on this numerical value is the inorganic value of the substituent that the organic compound has. For example, the inorganic value of the —COOH group is 150, and the inorganic value of the double bond is 2. Therefore, the inorganic value of a certain kind of organic compound means the sum of inorganic values such as various substituents and bonds of the compound.
The organic value is determined based on the influence of the methylene group in the molecule as a unit and the boiling point of the carbon atom representing the methylene group. That is, since the average value of the boiling point increase due to the addition of one carbon in the vicinity of 5 to 10 carbon atoms of the linear saturated hydrocarbon compound is 20 ° C., the organic value of one carbon atom is set to 20 on the basis of this. A value obtained by quantifying the influence on the boiling point of various substituents and bonds based on this is the organic value. For example, the organic value of a nitro group (—NO ₂ ) is 70.
An I / O value closer to 0 indicates a non-polar (hydrophobic or organic) organic compound, and a larger value indicates a polar (hydrophilic or inorganic) organic compound. Indicate

In the present invention, the I / O value of the self-dispersing polymer means that obtained by the following method. Based on the organicity (O value) and inorganicity (I value) described in Yoshida Koda, Organic Conceptual Diagram-Basics and Applications (1984), p.13, etc. An I / O value (= I value / O value) is calculated. For each monomer constituting the polymer, calculate the product of its (I / O value) and (mol% in the polymer), add these up, and round off the third decimal place. I / O value.
However, as a method for calculating the inorganic value of each monomer, a double bond is generally added as an inorganic value of 2, but when polymerized, the double bond disappears. The I / O value of the self-dispersing polymer was calculated using a numerical value not added to the bond.

  In this invention, the polymer which has a desired I / O value can be comprised by adjusting suitably the structure and content rate of the monomer which comprise a self-dispersing polymer.

When the self-dispersing polymer in the present invention is dispersed by the phase inversion emulsification method in the absence of a surfactant, the polymer becomes a dispersed state in an aqueous medium due to the functional group of the polymer itself (particularly an acidic group or a salt thereof). Preferred are water insoluble polymers.
Here, the dispersed state means both an emulsified state (emulsion) in which a water-insoluble polymer is dispersed in a liquid state in an aqueous medium, and a dispersed state (suspension) in which a water-insoluble polymer is dispersed in a solid state in an aqueous medium. It includes the state of.
The self-dispersing polymer 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 the ink.

  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 hydrophilic organic solvent) and then poured into water as it is without adding a surfactant. Examples include 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) of the polymer is neutralized and removing the solvent.

  Further, the stable emulsified or dispersed state in the self-dispersing polymer is a solution in which 30 g of a 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% Mixing agent (sodium hydroxide if the salt-forming group is anionic, acetic acid if it is cationic) and water 200g, stirring (device: stirring device with stirring blades, rotation speed 200rpm, 30 minutes, 25 ° C) Then, even after removing the organic solvent from the mixed solution, it means that the emulsified or dispersed state is stably present 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 of the sedimentation acceleration test by centrifugation is, for example, adjusted by adjusting the aqueous dispersion of polymer particles obtained by the above method to a solid concentration of 25% by mass, and then centrifuging at 12,000 rpm for 1 hour. 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.

The self-dispersing polymer preferably has a water-soluble component content that exhibits water solubility in a dispersed state of 10% by mass or less, more preferably 8% by mass or less, and 6% by mass or less. More preferably it is. 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 specific ink can be suppressed. For example, when the specific ink 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.

  The self-dispersing polymer includes at least one hydrophilic constituent unit derived from a hydrophilic monomer and at least one hydrophobic constituent unit derived from a hydrophobic monomer. The main chain skeleton of the self-dispersing polymer is not particularly limited, but from the viewpoint of dispersion stability of polymer particles, a vinyl polymer is preferable, and a (meth) acrylic polymer is preferable. Here, the (meth) acrylic polymer means a polymer containing at least one of a structural unit derived from a methacrylic acid derivative and a structural unit derived from an acrylic acid derivative.

(Hydrophilic structural unit)
The hydrophilic structural unit is not particularly limited as long as it is derived from a hydrophilic group-containing monomer (hydrophilic monomer). Even if it is derived from one kind of hydrophilic group-containing monomer, two or more types of hydrophilic structural units are used. It may be derived from a hydrophilic group-containing monomer. The hydrophilic group is not particularly limited, and may be a dissociable group or a nonionic hydrophilic group.
From the viewpoint of promoting self-dispersion and the stability of the formed emulsified or dispersed state, at least one of the hydrophilic groups is preferably a dissociable group, and preferably an anionic dissociable group. More preferred. Examples of the anionic dissociable group include a carboxyl group, a phosphoric acid group, and a sulfonic acid group, and among them, a carboxyl group is particularly preferable from the viewpoint of fixability when a specific ink is configured.

The hydrophilic group-containing monomer 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 viewpoint 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, an embodiment containing only a hydrophilic structural unit having an anionic dissociable group, a hydrophilic structural unit having an anionic dissociative group, and a hydrophilic having a nonionic hydrophilic group It is preferable that it is either of the aspects containing both sex structural units.
In addition, an embodiment containing two or more hydrophilic structural units having an anionic dissociative group, a hydrophilic structural unit having an anionic dissociative group, and two hydrophilic structural units having a nonionic hydrophilic group are provided. It is also preferable that more than one species be used in combination.

The content of the hydrophilic structural 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. % Is more preferable, and 4 to 20% by mass is particularly preferable.
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 hydrophilic 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 from the viewpoint of self-dispersibility, the content of water-soluble components, and fixability when a specific ink is formed. 50 mgKOH / g or more and 75 mgKOH / g or less is preferable, 52 mgKOH / g or more and 75 mgKOH / g or less is more preferable, and 55 mgKOH / g or more and 72 mgKOH / g or less is still more preferable. Particularly preferred is 60 mg KOH / g or more and 70 mg KOH / g or less.
When the acid value is 50 mgKOH / g or more, the ejection response and ejection recovery property of the ink using the polymer are improved, and when the acid value is 75 mgKOH / g or less, the viscosity is increased and the blocking resistance is improved. It becomes a trend.

(Hydrophobic building block)
The hydrophobic structural unit is not particularly limited as long as it is derived from a hydrophobic group-containing monomer (hydrophobic monomer). It may be derived from a hydrophobic group-containing monomer. The hydrophobic group is not particularly limited and may be any of a chain aliphatic group, a cyclic aliphatic group, and an aromatic group.
From the viewpoint of blocking resistance, abrasion resistance, and dispersion stability, at least one of the hydrophobic monomers is preferably a cyclic aliphatic group-containing monomer, and a cyclic aliphatic group-containing (meth) acrylate (hereinafter, “ More preferably, it may be referred to as “alicyclic (meth) acrylate”.

-Alicyclic (meth) acrylate-
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 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 an alkyl group, an alkenyl group, an aryl group, an aralkyl group, an alkoxy group, a hydroxyl group, a primary amino group, a secondary amino group, a tertiary amino group, an alkyl or arylcarbonyl group, and a cyano group. Is mentioned.
The alicyclic hydrocarbon group may further form a condensed ring.
As said alicyclic hydrocarbon group, 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 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. Preferably, it is at least one selected from isobornyl (meth) acrylate, adamantyl (meth) acrylate, and dicyclopentanyl (meth) acrylate.

The content of the structural unit derived from the alicyclic (meth) acrylate contained in the self-dispersing polymer particles is as follows: in the aqueous medium due to the stability of the self-dispersing state and the hydrophobic interaction between the alicyclic hydrocarbon groups From the viewpoint of stabilization of the particle shape in the particle and reduction in the amount of the water-soluble component due to appropriate hydrophobization 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. Is more preferable. Particularly preferred is 50 mass% or more and 80 mass% or less.
Fixing property and blocking can be improved by making the structural unit derived from the alicyclic (meth) acrylate 20% by mass or more. On the other hand, the stability of the polymer particles is improved when the structural unit derived from the alicyclic (meth) acrylate is 90% by mass or less.

  The self-dispersing polymer may be configured to further include other structural units as necessary in addition to the structural units derived from the alicyclic (meth) acrylate as hydrophobic structural units. 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 the above-described hydrophilic group-containing monomer, and a known monomer may be used. it can.

  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; dialkylaminoalkyls 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 ) (Meth) acrylamide such as N-alkoxyalkyl (meth) acrylamide such as butoxyethyl (meth) acrylamide.

  Among these, from the viewpoint of the flexibility of the polymer skeleton and the ease of controlling the glass transition temperature (Tg) and the viewpoint of the dispersion stability of the self-dispersing polymer, it contains a chain alkyl group having 1 to 8 carbon atoms (meth). It is preferably at least one acrylate, more preferably 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.

As other copolymerizable monomers, (meth) acrylates containing an aromatic group can also be preferably used.
In the case of containing an aromatic-containing (meth) acrylate as another copolymerizable monomer, the structural unit derived from the aromatic-containing (meth) acrylate is 40% by mass or less from the viewpoint of dispersion stability of the self-dispersing polymer particles. It is preferably 30% by mass or less, and particularly preferably 20% by mass or less.

In addition, when a styrene monomer is used as another copolymerizable monomer, the structural unit derived from the styrene monomer is preferably 20% by mass or less from the viewpoint of stability when the self-dispersing polymer particles are obtained. More preferably, it is 10 mass% or less, More preferably, it is 5 mass% or less, The aspect which does not contain the structural unit derived from a styrene-type monomer is especially preferable.
Here, the styrene monomer refers to styrene, substituted styrene (α-methylstyrene, chlorostyrene, etc.), and a styrene macromer having a polystyrene structural unit.

The other copolymerizable monomers may be used singly or in combination of two or more.
When other structural units are contained, 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.

From the viewpoint of dispersion stability, the self-dispersing polymer may be a polymer obtained by polymerizing at least three types of alicyclic (meth) acrylate, other copolymerizable monomers, and hydrophilic group-containing monomers. Preferably, it is a polymer obtained by polymerizing at least three kinds of alicyclic (meth) acrylate, alkyl group-containing (meth) acrylate having 1 to 8 carbon atoms having a linear or branched chain, and hydrophilic group-containing monomer. More preferably.
From the viewpoint of dispersion stability, the self-dispersing polymer has 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 constitutional unit having a large substituent is preferably substantially free, and more preferably has no aspect at all.

  The self-dispersing polymer may be a random copolymer in which each constituent unit is irregularly introduced, or may be a block copolymer that is regularly introduced, or a block copolymer Each structural unit may be synthesized in any order of introduction, and the same structural component may be used twice or more. However, a random copolymer is used in terms of versatility and manufacturability. preferable.

The molecular weight range of the self-dispersing polymer 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).

The self-dispersing polymer preferably has an acid value of 50 to 75 mgKOH / g, more preferably 52 to 75 mgKOH / g, from the viewpoints of ink viscosity adjustment, ejection response, and ejection recovery. More preferably, it is -72 mgKOH / g, and it is especially preferable that it is 60-70 mgKOH / g.
When the acid value is 50 mgKOH / g or more, the ejection responsiveness and ejection recovery property of the ink using the polymer are improved, and when the acid value is 75 mgKOH / g or less, the viscosity tends to increase.
In the present invention, the acid value is determined by the method described in JIS standard (JIS K 0070: 1992).

The self-dispersing polymer preferably has a degree of neutralization of 40 to 60%, more preferably 45 to 55%, and more preferably 47 to 53% from the viewpoints of viscosity adjustment, discharge response, and discharge recovery. It is particularly preferred that
When the degree of neutralization is 40% or more, the effect of increasing the viscosity and the effect of improving the discharge response are obtained, and when it is 60% or less, the discharge recovery property is improved.
Further, when the degree of neutralization is 40% or less, or 60% or more, there is a problem that the self-dispersing polymer cannot be stably produced.
Here, the degree of neutralization refers to the mol% of the added alkali when the dissociable group contained in the self-dispersing polymer chain is 100 mol% during the production of the self-dispersing polymer.

  The self-dispersing polymer is preferably a combination of the acid value and the neutralization degree when the acid value is 52 to 75 mgKOH / g and the neutralization degree is 45 to 55%, and the acid value is 55 to 72 mgKOH / g. More preferable when the sum is 45 to 55%, more preferable when the acid value is 55 to 65 mgKOH / g and the degree of neutralization is 47 to 53%.

From the viewpoint of controlling the hydrophilicity / hydrophobicity of the polymer, the self-dispersing polymer 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. Including the structure and at least one structure derived from a (meth) acrylate containing a linear alkyl group having 1 to 8 carbon atoms, the acid value is 20 to 120, and the total content of hydrophilic structural units Is a vinyl polymer having a weight average molecular weight of 3000 to 200,000.
Moreover, it contains a chain alkyl group having 1 to 4 carbon atoms and a structure derived from a bicyclic or tricyclic or higher polycyclic (meth) acrylate as a copolymerization ratio of 20% by mass or more and less than 90% by mass. A structure derived from (meth) acrylate as a copolymerization ratio of 10% by mass to less than 80% by mass, and a structure derived from a carboxyl group-containing monomer in an acid value of 50 to 75 mgKOH / g, A vinyl polymer having a total content 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 A structure derived from a copolymerization ratio of 20% by mass to less than 60% by mass, a structure derived from acrylic acid or methacrylic acid in an acid value of 50 to 75 mgKOH / g, and a total content of hydrophilic structural units. The vinyl polymer is particularly preferably 25% by mass or less and having a weight average molecular weight of 30,000 to 150,000.

  Hereinafter, as specific examples of the self-dispersing polymer, exemplary compounds are listed, but the present invention is not limited thereto. In addition, the parenthesis represents the mass ratio of the copolymerization component.

Methyl methacrylate / isobornyl methacrylate / methacrylic acid copolymer (20/72/8), glass transition temperature: 180 ° C., I / O value: 0.44, acid value: 52.1
Methyl methacrylate / isobornyl methacrylate / methacrylic acid copolymer (40/52/8), glass transition temperature: 160 ° C., I / O value: 0.50, acid value: 52.1
Methyl methacrylate / isobornyl methacrylate / methacrylic acid copolymer (38/52/10), glass transition temperature: 160 ° C., I / O value: 0.523, acid value: 65.1
Methyl methacrylate / isobornyl methacrylate / methacrylic acid copolymer (42/52/6), glass transition temperature: 161 ° C., I / O value: 0.469, acid value: 39.1
Methyl methacrylate / isobornyl methacrylate / methacrylic acid copolymer (36.5 / 52 / 11.5), glass transition temperature: 160 ° C., I / O value: 0.538, acid value: 74.8
Methyl methacrylate / isobornyl methacrylate / methacrylic acid copolymer (36/52/12), glass transition temperature: 160 ° C., I / O value: 0.543, acid value: 78.1
Methyl methacrylate / isobornyl methacrylate / dicyclopentanyl methacrylate / methacrylic acid copolymer (20/62/10/8), glass transition temperature: 170 ° C., I / O value: 0.44, acid value: 52 .1
Methyl methacrylate / dicyclopentanyl methacrylate / methacrylic acid copolymer (20/72/8), glass transition temperature: 160 ° C., I / O value: 0.47, acid value: 52.1
Methyl methacrylate / dicyclopentanyl methacrylate / methacrylic acid copolymer (18/72/10), glass transition temperature: 161 ° C., I / O value: 0.47, acid value: 65.1

In the calculation of the I / O value, the following numerical values were used as the I / O values of the monomers constituting each polymer.
Methyl methacrylate: 0.60, isobornyl methacrylate: 0.29, dicyclopentanyl methacrylate: 0.32, methacrylic acid: 0.47

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

There is no restriction | limiting in particular as a manufacturing method of the aqueous dispersion of the said self-dispersing polymer particle, It can be set as the aqueous dispersion of a self-dispersing polymer particle by a well-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 stirring a mixture containing a water-insoluble polymer, an organic solvent, a neutralizing agent, and an aqueous medium to obtain a dispersion.
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 having a particle size with higher storage stability without requiring strong shearing force. Particles 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 this solvent in combination, it is possible to obtain self-dispersing polymer particles having a fine particle size with high dispersion stability without aggregation and sedimentation and 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 group is 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 in water.

  In the step (2), the aqueous dispersion of the 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 distillation under reduced pressure and inversion into an aqueous system. You can get things. 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 self-dispersing polymer particles preferably have a volume average particle diameter (hereinafter also simply referred to as “average particle diameter”) of 0.1 to 10 nm.
Among the above average particle diameter ranges, 0.5 to 8 nm is preferable, 1 to 7 nm is more preferable, and 1 to 5 nm is even more preferable in terms of thickening and discharge properties (discharge response and discharge recovery properties). . Especially preferably, it is 1-4 nm.
An average particle size of 0.1 nm or more is preferable in terms of further improving the production suitability and ejection recovery property, and an average particle size of 10 nm or less improves storage stability and the ink thickening effect. Further, by giving the self-dispersing polymer particles a thickening effect, it is possible to improve the discharge response by reducing the amount of the thickener added as a result.
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 specific ink of the present invention, the self-dispersing polymer particles are preferably present in a form that does not substantially contain a coloring material.
The self-dispersing polymer particles 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 is present in the ink in a form containing the pigment, the stability of the entire ink is greatly reduced as a result. There is a case.

In the specific ink of the present invention, the self-dispersing polymer particles may be contained singly or in combination of two or more.
Further, the content of the self-dispersing polymer particles in the specific ink of the present invention is preferably 1 to 30% by mass, and 2 to 20% by mass with respect to the specific ink from the viewpoint of glossiness of the image. More preferably, it is particularly preferably 2 to 10% by mass.
Further, the content ratio of the colorant particles and the self-dispersing polymer particles (coloring material particles / self-dispersing polymer particles) in the specific ink of the present invention is 1 / 0.5 to from the viewpoint of scratch resistance of the image. 1/10 is preferable, and 1/1 to 1/4 is more preferable.

<Solid wetting agent>
The specific ink in the invention preferably contains at least one solid wetting agent.
When the specific ink contains a solid wetting agent, the wiping property is further improved.
Here, the solid wetting agent in the present invention means a water-soluble compound having a water retention function and solid at 25 ° C.

  As the solid wetting agent, those generally used in aqueous ink compositions can be used as they are. More specifically, sugars, sugar alcohols, hyaluronic acids, trimethylolpropane, 1, 2, Polyhydric alcohols such as 6-hexanetriol, urea and urea derivatives.

  Examples of the urea derivative include a compound in which hydrogen on nitrogen of urea is substituted with an alkyl group or alkanol, thiourea, a compound in which hydrogen on nitrogen of thiourea is substituted with an alkyl group or alkanol, and the like. Specific examples include N, N-dimethylurea, thiourea, ethyleneurea, hydroxyethylurea, hydroxybutylurea, ethylenethiourea, and diethylthiourea.

Examples of the saccharide include monosaccharides, disaccharides, oligosaccharides (including trisaccharides and tetrasaccharides), and polysaccharides. Specifically, glucose, mannose, fructose, ribose, xylose, arabinose, galactose, Examples thereof include aldonic acid, glucitol, (sorbit), maltose, cellobiose, lactose, sucrose, trehalose, maltotriose, and the like. Here, the polysaccharide means a saccharide in a broad sense, and is used to include a substance that exists widely in nature, such as alginic acid, α-cyclodextrin, and cellulose. Examples of derivatives of these saccharides include the reducing sugars (eg, sugar alcohols) and oxidized sugars (eg, aldonic acid, uronic acid, amino acids, thio sugars, etc.) of the aforementioned saccharides. Particularly preferred are sugar alcohols, and specific examples include maltitol, sorbitol, xylitol and the like. As the hyaluronate, a commercially available sodium hyaluronate 1% aqueous solution (molecular weight 350,000) can be used.
Among these, urea and urea derivatives have a high moisturizing function and can be more suitably used as a solid wetting agent.

  The content of the solid wetting agent in the specific ink is preferably 5% by mass or more, more preferably 5 to 30% by mass, and further preferably 5 to 20% by mass from the viewpoint of improving wiping properties.

The combination of the content of the solid wetting agent in the specific ink and the content of the polymer particles in the specific ink is not particularly limited, but it is possible to more effectively achieve both wiping properties and image fixing properties. From the viewpoint, the following combinations are preferable.
That is, a combination in which the content of the solid wetting agent is 5% by mass or more and the content of the polymer particles is 5% by mass or more is preferable, and the content of the solid wetting agent is 5 to 20% by mass, A combination in which the content of the polymer particles is 5 to 20% by mass is more preferable, the content of the solid wetting agent is 5 to 10% by mass, and the content of the polymer particles is 5 to 10% by mass. Particularly preferred.
Further, the ratio of the content of the solid wetting agent to the total solid content in the specific ink (the mass of the solid wetting agent / the mass of the total solid content) is preferably 0.3 or more, and is preferably 0.4 to 2.0. More preferably, it is most preferable that it is 0.5-1.5.

<Other ingredients>
The specific ink in the present invention may contain other components other than those described above.
Examples of other components include a thickener and a water-soluble acidic compound.

(Thickener)
The specific ink in the invention may contain at least one thickener.
The thickener is preferably a water-soluble polymer thickener, and can be used without particular limitation as long as it is a compound in which the viscosity of the aqueous solution is higher than that of water in the aqueous solution in which it is dissolved. .

The thickener preferably has a solubility (25 ° C.) in 100 g of water of 1 g or more. Moreover, as the molecular weight, it is preferable that it is 3000-100000 as a weight average molecular weight, It is more preferable that it is 4000-50000, It is still more preferable that it is 1500-40000.
Examples of the thickener may include vinyl polymers, polyether polymers, polysaccharide polymers, polyacrylic polymers, pyrrolidone polymers, and cellulose polymers.

  Specific examples of the thickener include gelatins, polyvinyl alcohols, various modified polyvinyl alcohols, polyvinylpyrrolidones, vinyl formals and derivatives thereof, polyoxyalkylene glycols, polyacrylamide, polydimethylacrylamide, poly Dimethylamino acrylate, polyacrylic acid soda, acrylic acid methacrylic acid copolymer salt, polymethacrylic acid soda, acrylic acid vinyl alcohol copolymer salt-containing polymer, starch, oxidized starch, carboxyl starch, dialdehyde starch, Dextrin, sodium alginate, gum arabic, casein, pullulan, dextran, cellulose or derivatives thereof (for example, methylcellulose, ethylcellulose, carboxymethylcellulose, hydroxypropyl Natural polymers such as cellulose) or derivatives thereof, polyethylene glycol, polypropylene glycol, polyvinyl ether, polyglycerin, maleic acid alkyl vinyl ether copolymer, maleic acid N-vinyl pyrrole copolymer, styrene maleic anhydride copolymer, polyethylene Examples include synthetic polymers such as imines.

  Among them, from the viewpoint of ejection stability, polyvinyl alcohol, polyvinyl pyrrolidone, polyoxyalkylene glycols, gelatins, vinyl formals and derivatives thereof, polymers containing an acrylic group of vinyl acrylate copolymer salt, starch, dextrin, Natural polymers such as gum arabic, casein, pullulan, dextran, cellulose or derivatives thereof (for example, methylcellulose, ethylcellulose, carboxymethylcellulose, hydroxypropylcellulose, etc.) or derivatives thereof are preferred. Furthermore, polyvinyl alcohol, polyvinyl pyrrolidone, and polyoxyalkylene glycols are more preferable.

The polyoxyalkylene glycols may contain a single oxyalkylene group or may contain two or more oxyalkylene groups. When the polyoxyalkylene glycol contains two or more oxyalkylene groups, it may be a random polymer or a block polymer.
In the present invention, from the viewpoint of ejection stability, it is preferably at least one of polyoxyethylene glycol and polyoxyethylene polyoxypropylene block polymer.

  The average degree of polymerization of the polyvinyl alcohol is preferably from 100 to 3500, more preferably from 120 to 2000, from the viewpoints of curling suppression and ejection stability. The degree of saponification is preferably 50 mol% or more, more preferably 70 mol% or more, from the viewpoint of ink dispersion stability.

  The thickener preferably has a weight average molecular weight of 3000 to 100,000, and is preferably at least one selected from polyvinyl alcohol, polyvinyl pyrrolidone, polyoxyethylene glycol, and polyoxyethylene polyoxypropylene block polymer. The average molecular weight is 4000 to 50000, and it is more preferably at least one selected from polyvinyl alcohol, polyvinyl pyrrolidone, polyoxyethylene glycol, and polyoxyethylene polyoxypropylene block polymer.

Moreover, it is also preferable that the said thickener contains a basic group or an acidic group.
Examples of the basic group include an amino group and a quaternary ammonium group which may have a substituent. Of these, amino groups are preferred from the viewpoint of ink dispersion stability.
Examples of the acidic group include a carboxyl group, a phosphoric acid group, a phosphonic acid group, a sulfonic acid group, and a sulfonamide group. Of these, a carboxyl group and a sulfonic acid group are preferable from the viewpoint of ink dispersion stability.

The thickener having the basic group has at least one basic functional group. Among them, the amine value is preferably 10 mgKOH / g or more, more preferably 20 mgKOH / g or more, and further preferably 40 mgKOH / g or more.
The thickener having an acidic group has at least one acidic functional group. Especially, it is preferable that an acid value is 10 mgKOH / g or more, It is more preferable that it is 20 mgKOH / g or more, It is still more preferable that it is 40 mgKOH / g or more.
Here, the amine value indicates the total amount of 1, 2, and tertiary amines that are basic groups, and mg of KOH equivalent to hydrochloric acid required to neutralize all basic groups in 1 g of a sample. It is expressed in numbers. The acid value is the number of mg of KOH required to neutralize all the acidic groups contained in 1 g of the sample.

When the thickener contains a basic group, the pH of the specific ink is preferably 7.5 or more, more preferably 8.0 to 9.0, from the viewpoint of ink dispersion stability.
Moreover, when the said thickener contains an acidic group, it is preferable that pH of a specific ink is 6.5 or less from a viewpoint of ink dispersion stability, and it is more preferable that it is 5.0-6.0. .

The said thickener may be used individually by 1 type, and may use 2 or more types together.
When the specific ink in the present invention contains a thickener, the content of the thickener in the specific ink can be appropriately selected according to the type of the thickener. For example, it can be 0.01-20 mass%. Among these, from the viewpoint of ejection stability, it is preferably 0.01 to 5% by mass, more preferably 0.1 to 3% by mass, and still more preferably 0.1 to 2% by mass.

(Water-soluble acidic compound)
The specific ink in the invention may contain at least one water-soluble acidic compound.
The water-soluble acidic compound is not particularly limited as long as it has a dissociable functional group that dissolves in water and exhibits acidity, and has a molecular weight of 200 or less. Even if it is an organic compound, it is an inorganic compound. May be. The term “water-soluble” as used herein means that 5 g or more is dissolved in 100 g of water at 25 ° C.

Examples of the water-soluble acidic compounds and salts thereof in the present invention include acidic compounds such as carboxylic acid derivatives, sulfonic acid derivatives, phosphoric acid derivatives, inorganic acids, and compounds in which these acidic functional groups form salts. Can do. Among these, the water-soluble acidic compound is preferably an organic compound selected from a carboxylic acid derivative, a sulfonic acid derivative, and a phosphoric acid derivative from the viewpoint of ejection stability, and is a carboxylic acid derivative or a sulfonic acid derivative. Is more preferable, and a carboxylic acid derivative is more preferable.
The molecular weight of the water-soluble acidic compound is 200 or less, but from the viewpoint of ejection response, it is preferably 30 or more and 200 or less, more preferably 45 or more and 150 or less, and still more preferably 50 or more and 140 or less. .
If the molecular weight of the water-soluble acidic compound exceeds 200, the ejection stability may decrease.

Examples of cations that form salts with water-soluble acidic compounds include alkali metal ions such as sodium ion, lithium ion or potassium ion, ammonium ion (NH ₄ ⁺ ), and monoethanolammonium ion (HOCH ₂ CH ₂ NH ₃ ⁺ An amino alcohol ion such as The cation forming the salt may be one kind or a combination of two or more kinds.

Specific examples of water-soluble acidic compounds and salts thereof include acids containing carboxyl groups such as acrylic acid, methacrylic acid, maleic acid, malic acid, tartaric acid, fumaric acid, lactic acid, succinic acid, glutaric acid, butanoic acid, and acetic acid. Examples thereof include compounds and salts thereof, acidic compounds containing a sulfonyl group such as methanesulfonic acid and p-toluenesulfonic acid, and salts thereof.
Among these, from the viewpoint of discharge recovery and ease of viscosity adjustment, it is preferably at least one selected from an acidic compound containing a carboxyl group and a salt thereof, and an inorganic acid salt, and a carboxyl having a molecular weight of 30 to 200 More preferably, it is at least one selected from acidic compounds containing a group and salts thereof, and inorganic acid salts, and maleic acid, malic acid, tartaric acid, succinic acid, glutaric acid, acetic acid, butanoic acid and alkali metals thereof More preferably, it is at least one selected from salts.

When the specific ink in the invention contains a water-soluble acidic compound, the content of the water-soluble acidic compound and the salt thereof is 0.1 to 0.5% by mass with respect to the total mass of the polymer particles described above. Is more preferable, and 0.2 to 0.4 mass% is more preferable.
When the content is 0.1% by mass or more and 0.5% by mass or less, the volume average particle diameter of the polymer particles can be easily adjusted, and the viscosity becomes high and the discharge recoverability is good.

When the specific ink in the present invention contains a water-soluble acidic compound, it is preferable that 0.1 to 0.5% by mass of at least one selected from a water-soluble acidic compound and a salt thereof is included from the viewpoints of viscosity and ejection recoverability. More preferably, it contains 0.1 to 0.5% by mass of at least one selected from acidic compounds containing carboxyl groups and salts thereof, and inorganic acid salts, and water-soluble acidic containing carboxyl groups having a molecular weight of 30 to 200 More preferably, it contains 0.1 to 0.5% by mass of at least one selected from compounds and salts thereof, and maleic acid, malic acid, tartaric acid, succinic acid, glutaric acid, acetic acid, butanoic acid and alkali metals thereof It is particularly preferable to contain 0.1 to 0.5% by mass of at least one selected from salts.

(Other additives)
The specific ink of the present invention may contain other additives as necessary in addition to the above components.
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. Well-known additives, such as an agent, a dispersing agent, a dispersion stabilizer, a rust preventive agent, and a chelating agent, are mentioned. These various additives may be added directly after preparation of the specific ink, or may be added at the time of preparation of the specific ink. Specific examples include other additives described in paragraph numbers [0153] to [0162] of JP-A-2007-100071.

≪Processing liquid≫
The ink set of the present invention includes a treatment liquid that aggregates the components in the specific ink described above.
The treatment liquid is configured such that an aggregate can be formed by contact with the specific ink described above.
Specifically, the treatment liquid preferably includes at least an aggregating component capable of aggregating dispersed particles such as colorant particles in the specific ink to form an aggregate, and using other components as necessary. Can be configured. By using the treatment liquid together with the specific ink, it is possible to increase the speed of ink jet recording, and an image with excellent density and resolution (for example, reproducibility of fine lines and fine portions) can be obtained even at high speed recording.

<Aggregating component>
The treatment liquid may contain at least one aggregation component capable of forming an aggregate upon contact with the specific ink. By mixing the treatment liquid and the specific ink ejected by the ink jet method, aggregation of a specific color material or the like stably dispersed in the specific ink is promoted.

Examples of the treatment liquid include a liquid that can generate an aggregate by changing the pH of the ink. At this time, the pH (25 ° C. ± 1 ° C.) of the treatment liquid is preferably 1 to 6, more preferably 1.2 to 5, and more preferably 1.5 to 5 from the viewpoint of the aggregation rate of the specific ink. 4 is more preferable, and 1.5 to 3 is particularly preferable. In this case, the pH (25 ± 1 ° C.) of the specific ink used in the ejection step is preferably 7.5 or more, more preferably 7.5 to 9.5, and 8.0 to 9. Particularly preferred is 0.
As the ink set of the present invention, a combination of a treatment liquid having a pH in the above range and a specific ink in the above range is preferable. Among these, from the viewpoint of image density, resolution, and speedup of inkjet recording, the specific A combination ink set in which the pH (25 ± 1 ° C.) of the ink is 7.5 or more and the pH (25 ± 1 ° C.) of the treatment liquid is 1.5 to 3 is particularly preferable.
The aggregating components can be used alone or in combination of two or more.

Examples of the treatment liquid include a treatment liquid containing at least one acidic compound as an aggregating 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) is used. Can do. Among these, from the viewpoint of the aggregation rate of the specific ink, a compound having a phosphate group or a carboxyl group is more preferable, and a compound having a carboxyl group is more preferable.

  The compound having a carboxyl group includes 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.

Examples of the treatment liquid include a treatment liquid containing at least one selected from polyvalent metal salts and polyallylamine as an aggregating component.
By using such a treatment liquid, high-speed cohesion can be improved.
Examples of the polyvalent metal salt or polyallylamine include alkaline earth metals belonging to Group 2 of the periodic table (for example, magnesium and calcium), transition metals belonging to Group 3 of the periodic table (for example, lanthanum), and group 13 of the periodic table. Mention may be made of cations from the genus (for example aluminum), salts of lanthanides (for example neodymium), and polyallylamine, 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.

  The content of the metal salt in the treatment liquid is preferably 1 to 10% by mass, more preferably 1.5 to 7% by mass, and still more preferably 2 to 6% by mass from the viewpoint of the aggregation effect. It is.

Examples of the treatment liquid include a treatment liquid containing at least one cationic organic compound as an aggregating component.
Examples of the cationic organic compound include poly (vinyl pyridine) salt, polyalkylaminoethyl acrylate, polyalkylaminoethyl methacrylate, poly (vinyl imidazole), polyethyleneimine, polybiguanide, polyguanide, and polyallylamine and derivatives thereof. Can be mentioned.

  The weight average molecular weight of the cationic polymer is preferably smaller in terms of the viscosity of the treatment liquid. When the treatment liquid is applied to the recording medium by an ink jet method, a range of 1,000 to 500,000 is preferable, a range of 1,500 to 200,000 is more preferable, and a range of 2,000 to 100,000 is more preferable. Range. When the weight average molecular weight is 1000 or more, it is advantageous from the viewpoint of the aggregation rate, and when it is 500,000 or less, it is advantageous from the viewpoint of ejection reliability. However, this is not the case when the treatment liquid is applied to the recording medium by a method other than inkjet.

Furthermore, as the cationic organic compound, for example, a primary, secondary, or tertiary amine salt type compound is preferable. Examples of the amine salt type compounds include compounds such as hydrochloride or acetate (for example, laurylamine, cocoamine, stearylamine, rosinamine), quaternary ammonium salt type compounds (for example, lauryltrimethylammonium chloride, cetyltrimethyl). Ammonium chloride, lauryldimethylbenzylammonium chloride, benzyltributylammonium chloride, benzalkonium chloride, etc.), pyridinium salt type compounds (eg, cetylpyridinium chloride, cetylpyridinium bromide, etc.), imidazoline type cationic compounds (eg, 2-heptadecenyl- Hydroxyethyl imidazoline etc.), ethylene oxide adducts of higher alkylamines (eg dihydroxyethyl stearylamine etc.), etc. And cationic compounds, for example, amino acid type amphoteric _{surfactants, R-NH-CH 2 CH} 2 -COOH type compounds (R represents an alkyl group), carboxylic acid salt type amphoteric surfactants (e.g., Stearyl dimethyl betaine, lauryl dihydroxyethyl betaine, etc.), amphoteric surfactants exhibiting a cationic property in a desired pH region, such as amphoteric surfactants such as sulfate ester type, sulfonic acid type, and phosphate ester type.
Of these, divalent or higher cationic organic compounds are preferred.

  As content in the processing liquid of a cationic organic compound, 1-50 mass% is preferable from a viewpoint of the aggregation effect, More preferably, it is 2-30 mass%.

  Among the above, the aggregating component is preferably a divalent or higher carboxylic acid or a divalent or higher cationic organic compound from the viewpoint of aggregability and image scratch resistance.

  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 specific ink. A range of 10 mPa · s is particularly preferred. 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 speed of the specific ink. Is more preferable. The surface tension is measured under conditions of 25 ° C. using an Automatic Surface Tensiometer CBVP-Z (manufactured by Kyowa Interface Science Co., Ltd.).

<Other ingredients>
The treatment liquid in the present invention can generally contain a water-soluble organic solvent in addition to the aggregating component, and can be constituted using other various additives within a range not impairing the effects of the present invention. The details of the water-soluble organic solvent are the same as those in the specific ink described above.

  Examples of the other additives include a drying inhibitor (wetting agent), an antifading agent, an emulsion stabilizer, a penetration accelerator, an ultraviolet absorber, an antiseptic, an antifungal agent, a pH adjuster, a surface tension adjuster, Known additives such as antifoaming agents, viscosity modifiers, dispersants, dispersion stabilizers, rust preventives, chelating agents are listed, and specific examples of other additives included in the specific ink described above Can be applied.

<< Image forming method and recorded matter >>
The image forming method of the present invention comprises the treatment liquid application step of applying the treatment liquid to a recording medium, and the ink application step of applying the ink to the recording medium, using the ink set of the present invention. Is done.
That is, the image forming method of the present invention includes a treatment liquid application step for applying a treatment liquid that can form an aggregate upon contact with the specific ink, and an image obtained by applying the specific ink on the recording medium. And an ink applying step for forming the other, and other steps as necessary.
According to the image forming method of the present invention, since the ink set of the present invention is used, an image having excellent light resistance can be formed.

Hereafter, each process which comprises the image forming method of this invention is demonstrated.
<Ink application process>
In the ink application process, the above-described specific ink is applied to the recording medium by, for example, an ink jet method.
In this step, specific ink can be selectively applied on the recording medium, and a desired visible image can be formed. Details of each component in the specific ink and details such as preferred embodiments are as described above.

  Specifically, the image formation using the ink jet method is performed by supplying energy to a desired recording medium, that is, plain paper, resin-coated paper, such as JP-A-8-169172 and JP-A-8-27693. JP-A-2-276670, JP-A-7-276789, JP-A-9-323475, JP-A-62-238783, JP-A-10-153789, JP-A-10-217473, JP-A-10-235995. No. 10-337947, No. 10-217597, No. 10-337947, etc. Inkjet exclusive paper, film, electrophotographic co-paper, fabric, glass, metal, ceramics, etc. This can be done by discharging. As a preferred image forming method of the present invention, the method described in paragraph Nos. 0093 to 0105 of JP-A No. 2003-306623 can be applied.

The inkjet method is not particularly limited, and is a known method, for example, a charge control method that discharges ink using electrostatic attraction, a drop-on-demand method (pressure pulse method) that uses vibration pressure of a piezoelectric element, an electric method An acoustic ink jet system that converts a signal into an acoustic beam, irradiates the ink with ink and ejects the ink using radiation pressure, and a thermal ink jet (bubble jet (registered trademark)) that heats the ink to form bubbles and uses the generated pressure. )) Any method may be used.
The ink jet method includes a method of ejecting many low-density inks called photo inks in a small volume, a method of improving image quality using a plurality of inks having substantially the same hue and different concentrations, and colorless and transparent inks. The method using is included.

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

As an inkjet head, a short serial head is used, and a shuttle system that performs recording while scanning the head in the width direction of the recording medium, and a line head in which recording elements are arranged corresponding to the entire area of one side of the recording medium There is a line system (also referred to as “single-pass system”) using the above.
In the line method (single-pass method), an image can be recorded on the entire surface of the recording medium by scanning the recording medium in a direction orthogonal to the arrangement direction of the recording elements, and a carriage system such as a carriage for scanning a short head is provided. It becomes unnecessary. Further, since complicated scanning control of the carriage movement and the recording medium is not required, and only the recording medium is moved, the recording speed can be increased as compared with the shuttle system. The image forming method of the present invention can be applied to any of these, but generally, when applied to a line system that does not use a dummy jet, the effect of improving ejection accuracy and image scratch resistance is great.

Furthermore, in the ink application process according to the present invention, in the case of the line method, not only one type of ink is used but also two or more types of ink are used, and the ink ejected first (the nth color (n ≧ 1), for example, Recording can be suitably performed by setting the ejection (droplet ejection) interval between the second color) and the ink (n + 1th color, eg, the third color) ejected subsequently to 1 second or less.
In this case, the specific ink described above is used as the n-th color ink or the (n + 1) th color ink.
In the present invention, an ejection interval of 1 second or less in the line method prevents bleeding and color mixing between ink droplets, and has excellent scratch resistance under high-speed recording higher than that of the prior art, and occurrence of blocking. A suppressed image can be obtained. In addition, an image having excellent hue and drawability (reproducibility of fine lines and fine portions in the image) can be obtained.

  The amount of ink droplets ejected from the inkjet head is preferably 0.5 to 6 pl (picoliter), more preferably 1 to 5 pl, and still more preferably 2 to 4 pl from the viewpoint of obtaining a high-definition image. .

<Processing liquid application process>
In the treatment liquid application step, a treatment liquid capable of forming an aggregate by contact with the specific ink is applied to the recording medium, and the treatment liquid is brought into contact with the specific ink to form an image. In this case, dispersed particles such as polymer particles and coloring material (for example, pigment) in the specific ink aggregate to fix the image on the recording medium. The details and preferred embodiments of each component in the treatment liquid are as described above.

The treatment liquid can be applied by applying a known method such as a coating method, an ink jet method, or an immersion method.
As the coating method, a known coating method using a bar coater, an extrusion die coater, an air doctor coater, a bread coater, a rod coater, a knife coater, a squeeze coater, a reverse roll coater, a bar coater or the like can be used. The details of the inkjet method are as described above.

  The treatment liquid application step may be provided either before or after the ink application step using the specific ink.

In the present invention, an embodiment in which the ink application step is provided after the treatment liquid is applied in the treatment liquid application step is preferable.
That is, before applying the specific ink on the recording medium, a processing liquid for aggregating the color material (preferably pigment) in the specific ink is applied in advance, and the processing liquid applied on the recording medium is applied. An embodiment in which a specific ink is applied so as to come into contact with each other to form an image is preferable. Thereby, inkjet recording can be speeded up, and an image with high density and resolution can be obtained even at high speed recording.

The application amount of the treatment liquid is not particularly limited as long as the specific ink can be aggregated. Preferably, the application amount of the aggregation component (for example, divalent or higher carboxylic acid or cationic organic compound) is 0.1 g / The amount can be m ² or more. Especially, the quantity from which the provision amount of an aggregation component will be 0.1-1.0 g / m < ² > is preferable, More preferably, it is 0.2-0.8 g / m < ² >. When the amount of the aggregating component is 0.1 g / m ² or more, the agglomeration reaction proceeds favorably, and when it is 1.0 g / m ² or less, the glossiness is not excessively increased.

  In the present invention, an ink application step is provided after the treatment liquid application step, and after the treatment liquid is applied onto the recording medium, the treatment liquid on the recording medium is heated and dried until the specific ink is applied. It is preferable to further provide a heat drying step. By heating and drying the treatment liquid in advance before the ink application step, ink colorability such as bleeding prevention is improved, and a visible image with good color density and hue can be recorded.

  Heating and drying can be performed by known heating means such as a heater, air blowing means using air blowing such as a dryer, or a combination of these. As the heating method, for example, a method of applying heat with a heater or the like from the side opposite to the treatment liquid application surface of the recording medium, a method of applying warm air or hot air to the treatment liquid application surface of the recording medium, or an infrared heater was used. The heating method etc. are mentioned, You may heat combining these two or more.

<Fixing process>
The image recording method of the present invention preferably has a fixing step of fixing the image by applying at least one of heating and pressurization to the recording medium to which the ink has been applied, at least after the ink application step.
By performing the fixing process, it is possible to further improve the resistance to image abrasion.
In the fixing step, it is preferable to fix the image by at least heating, and it is more preferable to fix the image by heating and pressing (hereinafter, also referred to as “heating and pressing”).
The fixing of the image by heating can be performed, for example, by bringing the heating surface into contact with the image formed on the recording medium.

The heating is preferably performed at a temperature equal to or higher than the minimum film-forming temperature (MFT) of the polymer particles in the image. By heating to MFT or higher, the polymer particles become a film and the image is enhanced. The heating temperature is preferably in the temperature range of MFT or higher. Specifically, the heating temperature is preferably in the range of 40 to 80 ° C, more preferably in the range of 50 ° C to 75 ° C, and still more preferably in the range of 55 ° C to 70 ° C.
The minimum film forming temperature (MFT) of the polymer particles is controlled by the Tg of the polymer and the type and amount of the ink solvent. Generally, the lower the Tg, the lower the I / O value of the ink solvent, the lower the amount of the ink solvent. The greater the number, the lower the MFT.

  The pressure at the time of pressurizing with heating is preferably in the range of 0.1 to 3.0 MPa, more preferably in the range of 0.1 to 1.0 MPa, and still more preferably 0.1 in terms of surface smoothing. It is the range of -0.5MPa.

The method of heating is not particularly limited, but a non-contact drying method such as a method of heating with a heating element such as a nichrome wire heater, a method of supplying warm air or hot air, a method of heating with a halogen lamp, an infrared lamp, etc. Preferably, it can be mentioned.
The heating and pressing method is not particularly limited. For example, a method of pressing a hot plate against the image forming surface of a recording medium, a pair of heating and pressing rollers, a pair of heating and pressing belts, or a recording medium Using a heating and pressing device equipped with a heating and pressing belt arranged on the image recording surface side and a holding roller arranged on the opposite side, heat fixing by bringing them into contact, such as a method of passing a pair of rollers, etc. The method of performing is mentioned suitably.

  In the case of heating and pressing, a preferable nip time is 1 to 10 seconds, more preferably 2 to 1 second, and further preferably 4 to 100 milliseconds. Moreover, a preferable nip width is 0.1 mm to 100 mm, more preferably 0.5 mm to 50 mm, and still more preferably 1 to 10 mm.

  The heat and pressure roller may be a metal metal roller, or a metal core bar provided with a coating layer made of an elastic body and, if necessary, a surface layer (also referred to as a release layer). Good. The latter metal core can be formed of, for example, a cylindrical body made of iron, aluminum, SUS, or the like, and the surface of the metal core is preferably at least partially covered with a coating layer. The coating layer is particularly preferably formed of a silicone resin or fluororesin having releasability. Further, it is preferable that a heating element is built in one core metal of the heat and pressure roller, and heat treatment and pressure treatment are performed simultaneously or necessary by passing a recording medium between the rollers. Accordingly, the recording medium may be sandwiched and heated using two heating rollers. As the heating element, for example, a halogen lamp heater, a ceramic heater, a nichrome wire or the like is preferable.

  As a belt base material constituting the heat and pressure belt used in the heat and pressure apparatus, seamless nickel brass is preferable, and the thickness of the base material is preferably 10 to 100 μm. Further, as the material of the belt base material, aluminum, iron, polyethylene or the like can be used in addition to nickel. When silicone resin or fluororesin is provided, the thickness of the layer formed using these resins is preferably 1 to 50 μm, more preferably 10 to 30 μm.

  Further, in order to realize the pressure (nip pressure), for example, an elastic member such as a spring having tension so that a desired nip pressure can be obtained in consideration of the nip gap at both ends of a roller such as a heat and pressure roller. Select and install.

  The conveyance speed of the recording medium when using a heat and pressure roller or a heat and pressure belt is preferably in the range of 200 to 700 mm / second, more preferably 300 to 650 mm / second, and still more preferably 400 to 600 mm / second. It is.

<Recording medium>
The image forming method of the present invention records an image on a recording medium.
The recording medium is not particularly limited, and general printing paper mainly composed of cellulose, such as so-called high-quality paper, coated paper, and art paper, used for general offset printing and the like can be used. General printing paper mainly composed of cellulose is relatively slow in ink absorption and drying in image recording by a general ink jet method using water-based ink, and color material movement is likely to occur after droplet ejection, and image quality is likely to deteriorate. However, according to the image forming method of the present invention, it is possible to record a high quality image excellent in color density and hue by suppressing the movement of the color material.

  As the recording medium, commercially available media can be used. For example, “OK Prince fine quality” manufactured by Oji Paper Co., Ltd., “Shiorai” manufactured by Nippon Paper Industries Co., Ltd., and Nippon Paper Industries ( Fine coated paper such as “New NPI fine quality” manufactured by Co., Ltd., “OK Everlight Coat” manufactured by Oji Paper Co., Ltd., and “Aurora S” manufactured by Nippon Paper Industries Co., Ltd., Oji Lightweight coated paper (A3) such as “OK Coat L” manufactured by Paper Industries Co., Ltd. and “Aurora L” manufactured by Nippon Paper Industries Co., Ltd. “OK Top Coat +” manufactured by Oji Paper Co., Ltd. and Nippon Paper Industries Co., Ltd. ) Coated paper (A2, B2) such as “Aurora Coat” manufactured by Oji Paper Co., Ltd. Art paper (A1) such as “OK Kanfuji +” manufactured by Oji Paper Co., Ltd. and “Tokuhishi Art” manufactured by Mitsubishi Paper Industries Co., Ltd. Is mentioned. It is also possible to use various photographic papers for ink jet recording.

Among these, from the viewpoint of obtaining a high-quality image having a large color material movement suppression effect and better color density and hue than before, the water absorption coefficient Ka is preferably 0.05 to 0.5. a recording medium mL ^/ m 2 ^{· ms 1/2,} more preferably recording medium 0.1~0.4mL ^/ m 2 ^{· ms 1/2,} more preferably 0.2-0.3 ml / It is a recording medium of m ² · ms ^1/2 .

  The water absorption coefficient Ka is synonymous with that described in JAPAN TAPPI paper pulp test method No. 51: 2000 (issued by Japan Paper Pulp Technology Association). Specifically, the absorption coefficient Ka is an automatic scanning absorption meter. It is calculated from the difference in the amount of water transferred between the contact time of 100 ms and the contact time of 900 ms using KM500Win (manufactured by Kumagai Riki Co., Ltd.).

  Among the recording media, so-called coated paper used for general offset printing is preferable. The coated paper is obtained by applying a coating material to the surface of high-quality paper, neutral paper, or the like that is mainly surface-treated with cellulose as a main component and is not surface-treated. The coated paper tends to cause quality problems such as image gloss and scratch resistance in image formation by ordinary aqueous inkjet, but in the inkjet recording method of the present invention, gloss unevenness is suppressed and gloss and resistance are reduced. An image having good rubbing properties can be obtained. In particular, it is preferable to use a coated paper having a base paper and a coat layer containing kaolin and / or calcium bicarbonate. More specifically, art paper, coated paper, lightweight coated paper, or finely coated paper is more preferable.

<Recorded material>
Since the recorded matter of the present invention is recorded on a recording medium by the image forming method of the present invention, it has excellent light resistance. In addition, even when high-speed recording is performed, it has high definition and excellent blocking resistance and abrasion resistance.

  Hereinafter, the present invention will be described more specifically with reference to examples. The scope of the present invention is not limited to the following examples. Unless otherwise specified, “part” and “%” are based on mass.

  The weight average molecular weight was measured by gel permeation chromatography (GPC). GPC uses HLC-8220GPC (manufactured by Tosoh Corporation), and three columns are connected in series using TSKgeL SuperHZM-H, TSKgeL SuperHZ4000, and TSKgeL SuperHZ2000 (all are trade names of Tosoh Corporation). , THF (tetrahydrofuran) was used as an eluent. The conditions were as follows: the sample concentration was 0.35% by mass, the flow rate was 0.35 ml / min, the sample injection amount was 10 μl, the measurement temperature was 40 ° C., and an IR detector was used. In addition, the calibration curve is “standard sample TSK standard, polystyrene” manufactured by Tosoh Corporation: “F-40”, “F-20”, “F-4”, “F-1”, “A-5000”, It produced from eight samples of "A-2500", "A-1000", and "n-propylbenzene".

≪Synthesis of coloring materials≫
<Synthesis of Exemplary Compound (Pig.-1)>
A synthesis scheme of the exemplary compound (Pig.-1) is shown below.

(1) Synthesis of intermediate (a) 29.7 g (0.3 mol) of methyl cyanoacetate, 42.4 g (0.4 mol) of trimethyl orthoformate, 20.4 g (0.2 mol) of acetic anhydride, p- Toluenesulfonic acid 0.5 g was added and heated to 110 ° C. (external temperature), and the mixture was stirred for 20 hours while distilling off low-boiling components generated from the reaction system. The reaction solution was concentrated under reduced pressure, and then purified on a silica gel column to obtain 14.1 g of the intermediate (a) (yellow powder, yield 30%). The NMR measurement result of the obtained intermediate (a) is as follows.
¹ H-NMR (300 MHz, CDCl ₃ ) 7.96 (s, 1H), 4.15 (s, 3H), 3.81 (s, 3H)

(2) Synthesis of Intermediate (b) 150 mL of isopropanol was added to 7.4 mL (141 mmol) of methyl hydrazine and cooled to 15 ° C. (internal temperature), and 7.0 g (49. 6 mmol) was gradually added, and the mixture was heated to 50 ° C. and stirred for 1 hour and 40 minutes. After concentrating this reaction liquid under reduced pressure, silica gel column purification was performed to obtain 10.5 g of the intermediate (b) (white powder, yield 50%). The NMR measurement result of the obtained intermediate (b) is as follows.
¹ H-NMR (300 MHz, CDCl ₃ ) 7.60 (s, 1H), 4.95 (brs, 2H), 3.80 (s, 3H), 3.60 (s, 3H)

(3) Synthesis of Intermediate (c) 100 mL of methanol was added to 130 mL of hydrazine monohydrate and cooled to 10 ° C. (internal temperature), and 50.0 g (336 mmol) of 4,6-dichloropyrimidine was added to this mixture. After gradually adding (internal temperature 20 ° C. or less), the mixture was heated to 50 ° C. and stirred for 4 hours 30 minutes. Crystals precipitated from the reaction solution were collected by filtration, washed with isopropanol, and dried to obtain 43.1 g of the intermediate (c) (white powder, yield 92%). The NMR measurement result of the obtained intermediate (c) is as follows.
¹ H-NMR (300 MHz, d ₆ -DMSO) 7.82 (s, 1H), 7.55 (s, 2H), 5.96 (s, 1H), 4.12 (s, 4H)

(4) Synthesis of intermediate (d) 900 mL of water was added to 35.0 g (0.25 mol) of intermediate (c) and 68.8 g (0.55 mol) of pivaloyl acetonitrile, and the mixture was stirred at room temperature. To this suspension, 1M aqueous hydrochloric acid was added dropwise so as to have a pH of 3, and the mixture was heated to 50 ° C. and stirred for 8 hours. To this reaction solution, 8M aqueous potassium hydroxide solution is added dropwise to adjust the pH to 8. Further, 1M hydrochloric acid solution is added dropwise to adjust to pH 6, and the precipitated crystals are collected by filtration, washed with isopropanol, dried, and dried. 83.0 g (white powder, 94% yield) of (d) was obtained. The NMR measurement result of the obtained intermediate (d) is as follows.
¹ H-NMR (300 MHz, d ₆ -DMSO) 8.73 (s, 1H), 7.97 (s, 1H), 6.88 (s, 4H), 5.35 (s, 2H), 1.22 (s, 18H)

(5) Synthesis of Exemplary Compound (Pig.-1) Acetic acid (18.5 mL) was added to concentrated sulfuric acid (4.1 mL), and the mixture was stirred with ice cooling, and 40% nitrosylsulfuric acid (3.85 g, 12.1 mmol) was added dropwise. Intermediate (b) 1.71 g (11.0 mmol) was gradually added to this mixture (internal temperature of 0 ° C. or lower), and the mixture was stirred at 0 ° C. for 2 hours. 150 mg of urea was added to this reaction liquid, and further stirred at 0 ° C. for 15 minutes to prepare diazo liquid A.
50 mL of methanol was added to the intermediate (d) and dissolved by heating, and then the diazo solution A was slowly added dropwise to an ice-cooled mixture (internal temperature of 10 ° C. or lower). After the reaction solution was stirred at room temperature for 2 hours, the precipitated crystals were collected by filtration and washed with methanol to obtain crude crystals of the exemplified compound (Pig.-1). Further, after adding water to the crude crystals and stirring, the suspension was adjusted to pH 7 with an aqueous sodium hydroxide solution, and further 20 mL of dimethylacetamide was added and stirred at 80 ° C. for 2 hours. The precipitated crystals were collected by filtration and suspended and washed with methanol. The obtained crystals were collected by filtration and dried to obtain 2.0 g (yellow powder, yield 79%) of the exemplified compound (Pig.-1).

  In the same manner as in the above synthesis scheme, exemplary compounds (Pig.-2) to (Pig.-4), (Pig.-6), (Pig.-9) to (Pig.-12), (Pig.-12) -15), (Pig.-18), (Pig.-19), (Pig.-21), (Pig.-24), (Pig.-25), (Pig.-34) to (Pig.-34) 37) were synthesized respectively.

[Example 1]
≪Preparation of yellow ink≫
<Preparation of self-dispersing polymer particles B-01>
In a 2-liter three-necked flask equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen gas inlet tube, 560.0 g of methyl ethyl ketone was charged and the temperature was raised to 87 ° C. While maintaining the reflux state in the reaction vessel (hereinafter referred to as reflux until the end of the reaction), 220.4 g of methyl methacrylate, 301.6 g of isobornyl methacrylate, 58.0 g of methacrylic acid, 108 g of methyl ethyl ketone, and “V-601” (Wako Pure) A mixed solution consisting of 2.32 g (manufactured by Yakuhin Co., Ltd.) was added dropwise at a constant speed so that the addition was completed in 2 hours. After completion of the dropwise addition, the mixture was stirred for 1 hour, (1) a solution consisting of 1.16 g of “V-601” and 6.4 g of methyl ethyl ketone was added, and the mixture was stirred for 2 hours. Subsequently, the step (1) was repeated four times, and a solution consisting of 1.16 g of “V-601” and 6.4 g of methyl ethyl ketone was added, and stirring was continued for 3 hours. After completion of the polymerization reaction, the temperature of the solution was lowered to 65 ° C., and 163.0 g of isopropanol was added and allowed to cool. The weight average molecular weight (Mw) of the obtained copolymer was 63000, and the acid value was 65.1 (mgKOH / g).

Next, 317.3 g of the obtained polymerization solution (solid content concentration 41.0%) was weighed, 46.4 g of isopropanol, 1.65 g of a 20% maleic anhydride aqueous solution (based on the water-soluble acidic compound and copolymer). 40.77 g of 2 mol / L NaOH aqueous solution was added, and the temperature in the reaction vessel was raised to 70 ° C. Next, 380 g of distilled water was added dropwise at a rate of 10 ml / min to disperse in water (dispersing step).
Thereafter, under reduced pressure, the reaction vessel was kept at a temperature of 70 ° C. for 1.5 hours, and 287.0 g of isopropanol, methyl ethyl ketone and distilled water were distilled off (solvent removal step), and the self-dispersion with a solid content concentration of 26.5% An aqueous dispersion of conductive polymer particles B-01 was obtained.

~ Measurement of glass transition temperature Tg ~
It was 160 degreeC when the glass transition temperature of the obtained self-dispersing polymer particle (B-01) was measured with the following method.
The polymer solution after the polymerization was dried under reduced pressure at 50 ° C. for 4 hours, in particular, to obtain a solid content of 0.5 g. Using the obtained polymer solid content, Tg was measured with a differential scanning calorimeter (DSC) EXSTAR 6220 manufactured by SII Nanotechnology. The measurement condition was that a sample amount of 5 mg was sealed in an aluminum pan, and the DSC peak top value of the measurement data at the second temperature increase was defined as Tg under the following temperature profile in a nitrogen atmosphere.
30 ° C to -50 ° C (cooled at 50 ° C / min)
−50 ° C. → 120 ° C. (temperature rising at 20 ° C./min)
120 ° C to -50 ° C (cooling at 50 ° C / min)
−50 ° C. → 120 ° C.

~ Measurement of volume average particle diameter Mv ~
The obtained aqueous dispersion of self-dispersing polymer particles (B-01) is appropriately diluted to a concentration suitable for measurement (with a loading index in the range of 0.1 to 10), and an ultrafine particle size distribution analyzer Nanotrac UPA- Using EX150 (Nikkiso Co., Ltd.), the volume average particle diameter of each aqueous dispersion was measured under the same measurement conditions by the dynamic light scattering method. That is, the measurement was performed under the conditions of particle permeability: transmission, particle refractive index: 1.51, particle shape: non-spherical, density: 1.2 g / cm ³ , solvent: water, cell temperature: 18-25 ° C.

<Synthesis of Resin Dispersant P-1>
To a 1000 ml three-necked flask equipped with a stirrer and a condenser, 88 g of methyl ethyl ketone was added and heated to 72 ° C. under a nitrogen atmosphere. To this, 50 g of methyl ethyl ketone was added with 0.85 g of dimethyl-2,2′-azobisisobutyrate and phenoxy. A solution in which 50 g of ethyl methacrylate, 11 g of methacrylic acid, and 39 g of methyl methacrylate were dissolved was dropped over 3 hours. After completion of the dropwise addition, the reaction was further continued for 1 hour, and then a solution of 0.42 g of dimethyl 2,2′-azobisisobutyrate in 2 g of methyl ethyl ketone was added, and the temperature was raised to 78 ° C. and heated for 4 hours. The obtained reaction solution was reprecipitated twice in an excess amount of hexane, the precipitated resin was dried, and phenoxyethyl methacrylate / methyl methacrylate / methacrylic acid (copolymerization ratio [mass% ratio] = 50/39/11) 96.5 g of a copolymer (resin dispersant P-1) was obtained.
The composition of the obtained resin dispersant P-1 was confirmed by ¹ H-NMR, and the weight average molecular weight (Mw) determined by GPC was 49400. Furthermore, when the acid value of this polymer was determined by the method described in JIS standard (JIS K 0070: 1992), it was 71.7 mgKOH / g.

<Preparation of yellow pigment dispersion>
10 g of the exemplified compound (Pig.-1) as a yellow pigment, 4.2 parts of the pigment dispersant P-1), 42 parts of methyl ethyl ketone, and 4.72 parts of 1 mol / L sodium hydroxide (methacrylic acid) as a pH adjuster The acid neutralization degree of 88 mol%) and 87.2 parts of ion-exchanged water were mixed with a disperser, and further treated for 8 passes with a disperser (Microfluidizer M-140K, 150 MPa, manufactured by Mizuho Industry Co., Ltd.). .
Subsequently, methyl ethyl ketone was removed from the obtained dispersion at 56 ° C. under reduced pressure, and Proxel GXL (S) (manufactured by Arch Chemicals Japan Co., Ltd.) was added to 1,2-benzoisothiazoline- It added so that it might become 16.5 ppm as 3-one. After removing 1 part of water, further, using a high-speed centrifugal cooler 7550 (manufactured by Kubota Seisakusho), centrifuge at 8000 rpm for 30 minutes using a 50 mL centrifuge, and collect the supernatant other than the precipitate. did. Thereafter, the pigment concentration was determined from the absorbance spectrum, and a dispersion (yellow pigment dispersion) of resin-coated yellow pigment particles having a pigment concentration of 15% was obtained.

<Preparation of yellow ink (Y-1)>
Each component was mixed so that it might become the following ink composition using the yellow pigment dispersion obtained above and self-dispersing polymer particle B-01. This was packed in a plastic disposable syringe and filtered through a PVDF 5 μm filter (Millex-SV, diameter 25 mm, manufactured by Millipore) to prepare a yellow ink (Y-1).

-Composition of yellow ink (Y-1)-
Yellow pigment (Exemplary compound (Pig.-1): 4.0%
-Resin dispersant P-1 (solid content) 1.7%
・ Self-dispersing polymer particles B-01 (solid content) 7%
・ Sanix GP250 ... 8%
(Sanyo Chemical Industries, Ltd., hydrophilic organic solvent, I / O value 1.30)
・ Tripropylene glycol monomethyl ether (TPGmME) 8%
(Wako Pure Chemical Industries, Ltd., hydrophilic organic solvent, I / O value 0.80)
・ Urea: 5%
(Wako Pure Chemical Industries, Ltd., solid wetting agent)
・ New Pole PE-108 ... 0.15%
(Thickener made by Sanyo Chemical Industries, Ltd.)
・ Orphine E1010: 1%
(Surfactant manufactured by Nissin Chemical Industry Co., Ltd.)
・ Ion-exchanged water… the balance

<Preparation of yellow ink (Y-2), etc.>
In the preparation of the yellow ink (Y-1), the exemplified compound (Pig.-1) used as a yellow pigment was changed to exemplified compounds (Pig.-2) to (Pig.-4), (Pig.-6), (Pig.-9) to (Pig.-12), (Pig.-15), (Pig.-18), (Pig.-19), (Pig.-21), (Pig.-24), ( Pig.-25) and (Pig.-34) to (Pig.-37), respectively, except that the yellow inks (Y-2) to (Y-) were prepared in the same manner as the yellow ink (Y-1). 4), (Y-6), (Y-9) to (Y-12), (Y-15), (Y-18), (Y-19), (Y-21), (Y-24) , (Y-25), (Y-34) to (Y-37) were prepared.

<Preparation of Comparative Ink 1>
In the preparation of the yellow ink (Y-1), the example compound (Pig.-1) used as the yellow pigment was changed to Pigment Yellow 74 (P.Y.74). Comparative ink 1 was prepared in the same manner as the preparation.

≪Preparation of treatment liquid≫
<Preparation of treatment liquid 1>
The following composition was mixed to prepare treatment liquid 1 as a polyvalent metal treatment liquid.
-Composition-
・ Magnesium nitrate hexahydrate: 25% by mass
・ Glycerin: 5% by mass
・ Ethanol: 3% by mass
・ Proxel-XLII (manufactured by ICI-preservative): 0.3% by mass
・ Pure water… remaining amount ・ surface tension… 49mN / m

<Preparation of treatment liquid 2>
The following composition was mixed and the processing liquid 2 was prepared as a cationic polymer processing liquid.
-Composition-
・ Polyallylamine PAA-HCl-3L 20% by mass
(Resin component 50%, manufactured by Nitto Boseki Co., Ltd.)
・ Diethylene glycol: 15% by mass
・ Proxel-XLII (manufactured by ICI-preservative): 0.3% by mass
・ Pure water: remaining amount, surface tension: 55 mN / m

<Preparation of treatment liquid 3>
The following composition was mixed and the processing liquid 3 was prepared as a cationic polymer processing liquid.
・ Propylene glycol n-propyl ether: 1.0% by mass
・ Ethylene glycol: 5.0% by mass
・ Zonyl FSN100 (manufactured by Dupont): 0.3% by mass
・ Diethylene glycol monobutyl ether: 0.4% by mass
・ 2-Pyrrolidone: 1.0% by mass
・ EDTA · 2Na (ethylenediaminetetraacetic acid disodium salt) 0.1% by mass
・ Polybiguanide: 4% by mass
・ Pure water… remaining amount

<Preparation of treatment liquid 4>
The following composition was mixed and the processing liquid 4 was prepared as an acidic processing liquid.
The physical properties of the treatment liquid 4 were a viscosity of 2.6 mPa · s, a surface tension of 37.3 mN / m, and a pH of 1.6 (25 ° C.).
-Composition-
-Malonic acid: 15.0% by mass
(Divalent carboxylic acid, manufactured by Wako Pure Chemical Industries, Ltd.)
・ Diethylene glycol monomethyl ether 20.0 mass%
(Wako Pure Chemical Industries, Ltd.)
・ N-oleoyl-N-methyltaurine sodium: 1.0% by mass
(Surfactant)
・ Ion-exchanged water: 64.0% by mass

≪Image formation≫
Hereinafter, an example of image formation shown in “Example 6” in Table 1 will be mainly described.
A GELJET GX5000 printer head manufactured by Ricoh Co., Ltd. was prepared, and the yellow ink in the storage tank connected thereto was refilled with the yellow ink (Y-1) obtained above.
Next, Tokuhishi Art Double Side N (Mitsubishi Paper Co., Ltd.) as a recording medium is fixed on a stage movable in a predetermined linear direction at 500 mm / second, and the stage temperature is kept at 30 ° C. The treatment liquid 1 obtained above was applied with a bar coater to a thickness of about 1.2 μm, and was dried at 50 ° C. for 2 seconds immediately after the application.
Thereafter, the GELJET GX5000 printer head is fixedly arranged so that the direction of the line head in which the nozzles are arranged (main scanning direction) is inclined by 75.7 degrees with respect to the direction orthogonal to the moving direction of the stage (sub-scanning direction). , While the recording medium is moved at a constant speed in the sub-scanning direction, the ink droplet amount is 2.4 pL, the discharge frequency is 24 kHz, the discharge condition is 1200 dpi × 1200 dpi, and the line method (single pass method) is used to discharge a yellow solid image. Printed.
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 subjected to a fixing process at a nip pressure of 0.25 MPa and a nip width of 4 mm to obtain an evaluation sample.
An example of the above image formation is shown as “Example 6” in Table 1.

<Light resistance>
The above printed matter (image) is irradiated for 25 days using a xenon weather meter (manufactured by Suga Test Instruments Co., Ltd.) under outdoor direct exposure equivalent conditions (9.9 klux), and the density (OD) before irradiation is about 1. The dye residual ratio [(concentration after irradiation / concentration before irradiation) × 100%] was determined to evaluate the light resistance.
The results are shown in Table 1.
-Evaluation criteria-
A: Dye remaining ratio is 95% or more B ... Dye remaining ratio is 95% or less 90% or more C ... Dye remaining ratio is 90% or less 85% or more D ... Dye remaining ratio is 85% or less 50% or more E: Dye remaining ratio is 50% or less

Next, in the same manner as in the image formation of Example 6 except that the combination (ink set) of the yellow ink and the treatment liquid was changed as shown in Table 1 below, Examples 1 to 5 and Examples 7 to 27 were used. Each image was formed, and light resistance was evaluated in the same manner as in Example 6 above.
The evaluation results are shown in Table 1 below.
In Table 1 below, “None” in the processing liquid column indicates that no processing liquid was used in image formation.

  As shown in Table 1, the yellow image formed using the ink set of the present invention was excellent in light resistance.

Claims (13)

An ink containing at least one colorant selected from the azo pigments represented by the following general formula (1), tautomers thereof, salts and hydrates thereof, and the components in the ink are aggregated An ink set containing a treatment liquid.

(In general formula (1), Z represents a divalent group derived from a 5- to 8-membered nitrogen-containing heterocycle, and Y ¹ , Y ² , R ¹¹ , and R ¹² are each independently a hydrogen atom or a substituent. G ¹ and G ² each independently represent a hydrogen atom, an alkyl group, an aralkyl group, an alkenyl group, an alkynyl group, an aryl group, or a heterocyclic group, and W ¹ and W ² each independently represent an alkoxy group Represents an amino group, an alkyl group or an aryl group.) ^2. The ink set according to claim 1, wherein W ¹ and W ² in the general formula (1) are each independently an alkoxy group having 3 or less carbon atoms, an amino group, or an alkylamino group having 3 or less carbon atoms. . The ink set according to claim 1, wherein G ¹ and G ² in the general formula (1) are each independently an alkyl group having a total carbon number of 3 or less.   The ink set according to any one of claims 1 to 3, wherein Z in the general formula (1) is a divalent group derived from a 6-membered nitrogen-containing heterocycle.   The ink set according to claim 1, wherein the color material is coated with a polymer dispersant.   The ink set according to any one of claims 1 to 5, wherein the ink further contains a hydrophilic organic solvent, a surfactant, and water.   The ink set according to any one of claims 1 to 6, wherein the ink further contains polymer particles.   The ink set according to any one of claims 1 to 7, wherein the ink further contains a solid wetting agent. Using the ink set according to any one of claims 1 to 8,
A treatment liquid application step of applying the treatment liquid to a recording medium;
An ink application step of applying the ink to a recording medium;
An image forming method comprising:   The image forming method according to claim 9, wherein in the treatment liquid application step, the treatment liquid is applied to a recording medium.   11. The image forming method according to claim 9, wherein in the ink application step, the ink is ejected onto a recording medium by a single-pass inkjet method.   The image forming method according to claim 9, further comprising a fixing step of fixing the image by applying at least one of heating and pressurization to the recording medium to which the ink has been applied.   A recorded matter recorded on a recording medium by the image forming method according to claim 9.