JP2011046870A - Ink composition, ink set, image formation method, and pigment dispersion - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ink composition which has good dispersion stability and satisfies both ink delivery and rubbing resistance of a color image, to provide an ink set, and to provide an image formation method using the same. <P>SOLUTION: There is provided an ink composition comprising a pigment coated with a first resin dispersion agent containing structural units represented by general formula (I) and a second resin dispersion agent containing structural units represented by general formula (II), an organic solvent, a neutralizing agent, and water. In general formulas (I) and (II), R<SP>1</SP>is hydrogen or methyl; Ar<SP>1</SP>is an unsubstituted or substituted aromatic ring; n is an average repetition number and is 1-6; R<SP>2</SP>is hydrogen or methyl; L<SP>1</SP>is substituted or unsubstituted phenylene; L<SP>2</SP>is a single bond or a divalent bonding group; and Ar<SP>2</SP>is a monovalent group derived from an 8C or higher fused-ring-type aromatic ring, a heterocyclic ring fused with an aromatic ring, or a compound composed of two or more connected benzene rings. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an ink composition, an ink set, an image forming method, and a pigment dispersion.

  Various recording media have been studied as recording media for inkjet recording, and a technique capable of forming high-quality images is required. Also in inks, color materials such as pigments have been studied as ink materials that provide water resistance and light resistance.

  However, when recording on plain paper, sufficient performance may not be obtained in terms of color density, fixability, resolution, and the like. In particular, there is a case where the speed of ink-jet recording is increased, and there is a demand for recording suitability in the case of performing high-speed recording by a single pass method capable of recording by one head operation instead of the shuttle scan method.

When images are formed on a variety of recording media, uniform images can be obtained with high resolution and high density, with no bleeding and fogging, and there is no clogging due to ink drying at the nozzle tip. As a method for providing ink for ink jet recording having good ejection stability, a method of using two or more kinds of dispersants having different HLB values has been proposed. (For example, refer to Patent Document 1). In this method, it is said that the ink satisfying an appropriate HLB value can ensure dispersion stability and eliminate clogging due to ink drying at the nozzle tip.
Further, a method has been proposed in which two or more types of anionic group-containing organic polymer compounds having different weight average molecular weights are used as the aqueous pigment dispersion. (For example, refer to Patent Document 2). In this method, an aqueous pigment dispersion excellent in dispersibility and dispersion stability can be provided, and an aqueous recording liquid excellent in storage stability, sharpness and transparency using the aqueous pigment dispersion can be provided. It is supposed to be possible.

Japanese Patent No. 311893 JP 2000-160093 A

  However, in the above method, the formed image is not sufficiently resistant to rubbing, and in the case of high-speed recording, the ink dispersion stability is not sufficient, resulting in ejection direction failure and failure such as white spots. There is a problem that occurs.

The present invention has been made in view of the above, and by using two or more types of resin dispersants having a specific structure, the ink has good dispersion stability and can achieve both ink ejection properties and color image rub resistance. It is an object to provide a composition, an ink set, and an image forming method using the same.
Another object of the present invention is to provide a pigment dispersion excellent in dispersion stability.

<1> At least coated with a first resin dispersant containing a structural unit represented by the following general formula (I) and a second resin dispersant containing a structural unit represented by the following general formula (II) An ink composition comprising a pigment, an organic solvent, and water.

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

In the formula, R ² represents a hydrogen atom or a methyl group, and L ¹ represents a substituted or unsubstituted phenylene group. L ² represents a single bond or a divalent linking group. Ar ² represents a monovalent group derived from a condensed aromatic ring having 8 or more carbon atoms, a hetero ring in which an aromatic ring is condensed, or a benzene ring in which two or more are connected.

<2> The ink composition according to <1>, wherein the aromatic ring represented by Ar ¹ in the general formula (I) is an unsubstituted or substituted benzene ring.
<3> The ink composition according to <1> or <2>, wherein Ar ² in the general formula (II) is a monovalent group derived from acridone or phthalimide.
<4> At least one of the first resin dispersant and the second resin dispersant includes a hydrophilic structural unit (A) and a hydrophobic structural unit (B), and a content ratio of an aromatic ring is a resin. It is 20 mass% or less of the total mass of the dispersant, the ratio of the hydrophilic structural unit (A) is 15 mass% or less of the total mass of the resin dispersant, and the hydrophilic structural unit (A) is at least ( The ink composition according to any one of <1> to <3>, comprising a structural unit derived from (meth) acrylic acid.

<5> The ink composition according to any one of <1> to <4>, wherein the weight average molecular weight of at least one of the first resin dispersant and the second resin dispersant is 30,000 or more.
<6> The pigment according to any one of <1> to <5>, wherein the pigment is a pigment coated with at least one of the first resin dispersant and the second resin dispersant by a phase inversion emulsification method. Ink composition.
<7> The ink composition according to any one of <1> to <6>, further including a surfactant.

<8> The ink composition according to any one of <1> to <7>, further including resin particles.
<9> A treatment liquid containing the ink composition according to any one of <1> to <8>, and a flocculant that aggregates the components in the ink composition when mixed with the ink composition; Ink set containing.

<10> The ink set according to <9>, wherein the pH of the ink composition at 25 ° C. is 7.5 or more, and the pH of the treatment liquid at 25 ° C. is 4 or less.
<11> The ink set according to <9> or <10>, wherein the flocculant is an organic carboxylic acid.
<12> An ink application step in which the ink composition according to any one of <1> to <8> is applied onto a recording medium by an inkjet method, and the ink composition when mixed with the ink composition And a treatment liquid application step of applying a treatment liquid containing an aggregating agent that agglomerates the components to a recording medium, and forming an image by bringing the ink composition and the treatment liquid into contact with each other.

<13> After applying the treatment liquid on the recording medium by the treatment liquid application step, an ink composition is applied, and the image is obtained by bringing the ink composition applied by the ink application step into contact with the applied treatment liquid. <12> The image forming method according to <12>.
<14> At least a pigment, a first resin dispersant containing a structural unit represented by the following general formula (I), and a second resin dispersant containing a structural unit represented by the following general formula (II) And a pigment dispersion.

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

In the formula, R ² represents a hydrogen atom or a methyl group, and L ¹ represents a substituted or unsubstituted phenylene group. L ² represents a single bond or a divalent linking group. Ar ² represents a monovalent group derived from a condensed aromatic ring having 8 or more carbon atoms, a hetero ring in which an aromatic ring is condensed, or a benzene ring in which two or more are connected.

<15> The pigment dispersion according to <14>, wherein the aromatic ring represented by Ar ¹ in the general formula (I) is an unsubstituted or substituted benzene ring.
<16> The pigment dispersion according to <14> or <15>, wherein Ar ² in the general formula (II) is a monovalent group derived from acridone or phthalimide.
<17> At least one of the first resin dispersant and the second resin dispersant includes a hydrophilic structural unit (A) and a hydrophobic structural unit (B), and a content ratio of an aromatic ring is a resin. It is 20 mass% or less of the total mass of the dispersant, the ratio of the hydrophilic structural unit (A) is 15 mass% or less of the total mass of the resin dispersant, and the hydrophilic structural unit (A) is at least ( The pigment dispersion according to any one of <14> to <16>, comprising a structural unit derived from (meth) acrylic acid.

<18> The pigment dispersion according to any one of <14> to <17>, wherein the weight average molecular weight of at least one of the first resin dispersant and the second resin dispersant is 30,000 or more.
<19> The pigment according to any one of <14> to <18>, wherein the pigment is coated by at least one of the first resin dispersant and the second resin dispersant by a phase inversion emulsification method. Dispersion.

According to the present invention, by using two or more types of resin dispersants having a specific structure, an ink composition, an ink set, and an ink composition that have good dispersion stability and can achieve both ink ejection properties and color image abrasion resistance. An image forming method using can be provided.
Further, according to the present invention, a pigment dispersion excellent in dispersion stability can be provided.

  Hereinafter, the ink composition, the ink set, the image forming method, and the pigment dispersion suitable for them will be described in detail.

[Ink composition]
The ink composition according to the present invention includes at least a first resin dispersant containing a structural unit represented by the following general formula (I) and a second resin dispersion containing a structural unit represented by the following general formula (II): It contains at least a pigment coated with an agent (hereinafter sometimes referred to as “resin-coated pigment”), an organic solvent, and water, and preferably contains a neutralizing agent.
In the present invention, a first resin dispersant containing a structural unit represented by the following general formula (I) and a second resin dispersant containing a structural unit represented by the following general formula (II) will be described later. It functions as a dispersant for uniformly dispersing the pigment in the pigment dispersion.

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

In the formula, R ² represents a hydrogen atom or a methyl group, and L ¹ represents a substituted or unsubstituted phenylene group. L ² represents a single bond or a divalent linking group. Ar ² represents a monovalent group derived from a condensed aromatic ring having 8 or more carbon atoms, a hetero ring in which an aromatic ring is condensed, or a benzene ring in which two or more are connected.

The resin-coated pigment in the present invention does not necessarily need to be entirely coated with the first resin dispersant or the second resin dispersant in the present invention, and in some cases, at least a part of the pigment surface is coated. It may be in the state.
Hereinafter, in the present specification, the first resin dispersant and the second resin dispersant may be simply referred to as a resin dispersant.

<First resin dispersant: structural unit represented by general formula (I)>

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

Ar ¹ represents an unsubstituted or substituted aromatic ring. Examples of the substituent when the aromatic ring is substituted include a halogen atom, an alkyl group, an alkoxy group, a hydroxyl group, or a cyano group, and may form a condensed ring. In the case where a condensed ring is formed, for example, a condensed aromatic ring having 8 or more carbon atoms, an aromatic ring in which a hetero ring is condensed, or an aromatic ring in which two or more are connected are exemplified.

The “condensed aromatic ring having 8 or more carbon atoms” includes an aromatic ring in which at least two benzene rings are condensed, at least one aromatic ring and a condensed alicyclic hydrocarbon ring. Is an aromatic compound having 8 or more carbon atoms. Specific examples include naphthalene, anthracene, fluorene, phenanthrene, acenaphthene and the like.
The “aromatic ring condensed with a heterocycle” is a compound in which an aromatic compound not containing a heteroatom (preferably a benzene ring) and a cyclic compound having a heteroatom are condensed. Here, the cyclic compound having a hetero atom is preferably a 5-membered ring or a 6-membered ring. As a hetero atom, a nitrogen atom, an oxygen atom, or a sulfur atom is preferable. The cyclic compound having a hetero atom may have a plurality of hetero atoms. In this case, the heteroatoms may be the same or different from each other. Specific examples of the aromatic ring condensed with a heterocycle include phthalimide, acridone, carbazole, benzoxazole, and benzothiazole.

The aromatic ring represented by Ar ¹ is bonded to the main chain of the resin dispersant via the ester group and the ethylene oxide chain, and the aromatic ring is not directly bonded to the main chain. An appropriate distance is maintained between the resin structural unit and the resin dispersant easily interacts with the pigment, and is strongly adsorbed to enhance dispersibility.
Among these, as Ar ¹ , an unsubstituted or substituted benzene ring and an unsubstituted naphthalene ring are preferable, and an unsubstituted benzene ring is particularly preferable.

  n represents the repetition number which averaged the ethyleneoxy chain in the resin dispersing agent of the resin coating pigment contained in a water-based ink composition. The range of n is 1-6, preferably 1-2.

  Specific examples of the monomer forming the structural unit represented by the general formula (I) include phenoxyethyl (meth) acrylate and the following monomers.

Among the structural units represented by the general formula (I), from the viewpoint of dispersion stability, R ¹ is a methyl group, Ar ¹ is an unsubstituted benzene ring, and n is 1 to 2. The case is particularly preferred.

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

  Hereinafter, specific examples of the resin dispersant containing the structural unit represented by the general formula (I) in the present invention are shown. However, the present invention is not limited to the following.

<Second resin dispersant: structural unit represented by general formula (II)>

In general formula (II), R ² represents a hydrogen atom or a methyl group, and L ¹ represents a substituted or unsubstituted phenylene group. L ² represents a single bond or a divalent linking group. Ar ² represents a monovalent group derived from a condensed aromatic ring having 8 or more carbon atoms, a hetero ring in which an aromatic ring is condensed, or a benzene ring in which two or more are connected.

In the general formula (II), R ² represents a hydrogen atom or a methyl group, preferably a methyl group.

L ¹ represents a substituted or unsubstituted phenylene group. L ¹ is preferably an unsubstituted phenylene group.
L ² represents a single bond or a divalent linking group. The divalent linking group is preferably a linking group having 1 to 30 carbon atoms, more preferably a linking group having 1 to 25 carbon atoms, still more preferably a linking group having 1 to 20 carbon atoms, Particularly preferred is a linking group having 1 to 15 carbon atoms.
Among them, most preferably, an alkyleneoxy group having 1 to 25 carbon atoms (more preferably 1 to 10), an imino group (—NH—), a sulfamoyl group, and 1 to 20 carbon atoms (more preferably 1 to 15). A divalent linking group containing an alkylene group such as an alkylene group or an ethylene oxide group [— (CH ₂ CH ₂ O) _n —, n = 1 to 6], etc., and a group in which two or more of these are combined is there.

Ar ² represents a monovalent group derived from a condensed aromatic ring having 8 or more carbon atoms, a hetero ring in which an aromatic ring is condensed, or a benzene ring in which two or more are connected.

The “condensed aromatic ring having 8 or more carbon atoms” includes an aromatic ring in which at least two benzene rings are condensed, at least one aromatic ring and a condensed alicyclic hydrocarbon ring. Is an aromatic compound having 8 or more carbon atoms.
Specific examples include naphthalene, anthracene, fluorene, phenanthrene, acenaphthene and the like.

The “heterocycle having an aromatic ring condensed” is a compound in which an aromatic compound containing no hetero atom (preferably a benzene ring) and a cyclic compound having a hetero atom are condensed. Here, the cyclic compound having a hetero atom is preferably a 5-membered ring or a 6-membered ring. As a hetero atom, a nitrogen atom, an oxygen atom, or a sulfur atom is preferable. The cyclic compound having a hetero atom may have a plurality of hetero atoms. In this case, the heteroatoms may be the same or different from each other.
Specific examples of the heterocyclic ring condensed with an aromatic ring include phthalimide, acridone, carbazole, benzoxazole, and benzothiazole.

  Specific examples of the monomer forming the structural unit represented by the general formula (II) include the following monomers, but are not limited thereto.

Ar ² in the structural unit represented by the general formula (II) is preferably a monovalent group derived from acridone or phthalimide, from the viewpoint of the stability of the coated pigment. A monovalent group derived from is preferable.
Among the structural units represented by the general formula (II), R ² is a methyl group, L ¹ is an unsubstituted phenylene group, and L ² is divalent in terms of dispersion stability of the pigment. And Ar ² is preferably a monovalent group derived from acridone.

The content ratio of the structural unit represented by the general formula (II) in the total mass of the second resin dispersant is preferably 5 to 25% by mass, more preferably 10 to 18% by mass.
If the content is 5% by mass or more, the occurrence of image failure such as white spots tends to be remarkably suppressed. If the content is 25% by mass or less, the copolymerization reaction solution (for example, methyl ethyl ketone) is used. This is preferable because a problem in production suitability due to a decrease in solubility is not likely to occur.

  Hereinafter, specific examples of the resin dispersant containing the structural unit represented by the general formula (II) in the present invention will be shown. However, the present invention is not limited to the following.

At least one of the first resin dispersant and the second resin dispersant in the present invention can be stably present in the ink composition, and mitigates adhesion or accumulation of aggregates, From the viewpoint of easy removal, the resin contains a hydrophilic structural unit (A) and a hydrophobic structural unit (B), and the aromatic ring content is 20% by mass or less based on the total mass of the resin dispersant. It is preferable.
Here, the hydrophobic structural unit (B) includes at least one structural unit selected from the structural unit represented by the general formula (I) and the structural unit represented by the general formula (II). It is.

<Hydrophobic structural unit (B)>
At least one of the first resin dispersant and the second resin dispersant in the present invention is selected from the structural unit represented by the general formula (I) and the structural unit represented by the general formula (II). It may further have at least one structural unit and other hydrophobic structural units (B) other than the structural units represented by the general formula (I) and the general formula (II).
The hydrophobic structural unit (B) does not belong to the hydrophilic structural unit (A) (for example, has no hydrophilic functional group), such as (meth) acrylates, (meth) acrylamides, styrenes, and Structural units derived from vinyl monomers such as vinyl esters, hydrophobic structural units having an aromatic ring via a linking group at the atom forming the main chain, and the like can be mentioned. These structural units can be used individually by 1 type or in mixture of 2 or more types.

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

The above-mentioned “hydrophobic structural unit having an aromatic ring via a linking group to an atom forming a main chain” is a copolymer of an aromatic ring linking to an atom forming the main chain of the copolymer via a linking group The structural unit whose ratio in the inside is 15-27 mass% is preferable, the structural unit which is 15-25 mass% is more preferable, and the structural unit which is 15-20 mass% is still more preferable.
Since the aromatic ring has a structure in which it is bonded to an atom forming the main chain of the copolymer via a linking group and is not directly bonded to an atom forming the main chain of the copolymer, the hydrophobic aromatic ring and the hydrophilic structural unit Since an appropriate distance is maintained between the copolymer and the pigment, interaction between the copolymer and the pigment is likely to occur, and it is strongly adsorbed to further improve dispersibility.

  Examples of the “hydrophobic structural unit having an aromatic ring via a linking group in the main chain atom” include structural units represented by the following general formula (III) (the general formula (I) or the general formula (II) (Excluding the structural unit represented by)).

In the general formula (III), R ¹¹ represents a hydrogen atom, a methyl group, or a halogen atom.
L ¹¹ represents ^* —COO—, ^* —OCO—, ^* —CONR ¹² — or ^* —O—, and R ¹² represents a hydrogen atom or an alkyl group having 1 to 10 carbon atoms. Incidentally, * mark in group represented by L ¹¹ represents a connecting point with the main chain.

L ¹² represents a single bond or a divalent linking group having 1 to 30 carbon atoms, and when it is a divalent linking group, it is preferably a linking group having 1 to 25 carbon atoms, more preferably a carbon number. It is a 1-20 linking group, More preferably, it is a C1-C15 linking group.
Among them, particularly preferably, an imino group (—NH—), a sulfamoyl group, an alkylene group having 1 to 20 carbon atoms (more preferably 1 to 15) or an ethylene oxide group [— (CH ₂ CH ₂ O) _n —, a bivalent linking group containing an alkylene group, such as n = 1 to 6], and a combination of these two or more.

In the general formula (III), Ar ¹¹ represents a monovalent group derived from an aromatic ring.
The aromatic ring represented by Ar ¹¹ is not particularly limited, and examples thereof include a benzene ring, a condensed aromatic ring having 8 or more carbon atoms, an aromatic ring condensed with a heterocycle, or a benzene ring in which two or more are connected. . Details of the condensed aromatic ring having 8 or more carbon atoms and the aromatic ring condensed with the hetero ring are as described above.

  Specific examples of monomers that can form other hydrophobic structural units are listed below. However, the present invention is not limited to the following specific examples.

<Hydrophilic structural unit (A)>
As the hydrophilic structural unit (A), for example, a structural unit derived from acrylic acid or methacrylic acid is preferable. In the resin dispersant, either a structural unit derived from acrylic acid or a structural unit derived from methacrylic acid or It is preferable to include both. Examples of other hydrophilic structural units (A) include structural units derived from monomers having nonionic hydrophilic groups. For example, (meth) acrylates having hydrophilic functional groups, (meth) Mention may be made of vinyl monomers having a hydrophilic functional group, such as acrylamides and vinyl esters.

  Examples of the “hydrophilic functional group” include a hydroxyl group, an amino group, an amide group (unsubstituted with a nitrogen atom), and alkylene oxides such as polyethylene oxide and polypropylene oxide described later.

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

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

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

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

  In the above, for example, the content ratio of the hydrophilic structural unit differs depending on the ratio of the hydrophobic structural unit (B) described above. For example, when the resin dispersant is composed only of acrylic acid and / or methacrylic acid [hydrophilic structural unit (A)] and the aforementioned hydrophobic structural unit (B), the content ratio of acrylic acid and / or methacrylic acid Is determined by “100- (mass% of hydrophobic structural unit)”.

The resin dispersant in the present invention includes a hydrophilic structural unit (A) and a hydrophobic structural unit (B) (the structural unit represented by the general formula (I), the structural unit represented by the general formula (II)). The composition with the other hydrophobic structural unit (B) affects the degree of hydrophilicity and hydrophobicity of each, but the ratio of the hydrophilic structural unit (A) is 15% by mass or less. Is preferred. At this time, the proportion of the hydrophobic structural unit (B) is preferably more than 80% by mass and more preferably 85% by mass or more with respect to the total mass of the resin dispersant.
When the content of the hydrophilic structural unit (A) is 15% by mass or less, the amount of the component dissolved alone in the aqueous medium is suppressed, and various properties such as pigment dispersion are improved, which is favorable during ink jet recording. Ink discharge performance is obtained.

  A preferred content ratio of the hydrophilic structural unit (A) is in the range of more than 0% by mass and 15% by mass or less, more preferably in the range of 2 to 15% by mass with respect to the total mass of the resin dispersant. More preferably, it is the range of 5-15 mass%, Most preferably, it is the range of 8-12 mass%.

  A hydrophilic structural unit (A) can be used individually by 1 type or in mixture of 2 or more types.

In the resin dispersant in the present invention, among the above, the hydrophilic structural unit (A) is a group derived from (meth) acrylic acid, and the hydrophobic structural unit (B) is represented by (i) the general formula (II). Structural units (preferably structural units derived from the aforementioned M-25 / M-27, M-28 / M-29) and (ii) structural units represented by the general formula (I) (preferably phenoxyethyl ( It is preferable to include at least one of structural units derived from (meth) acrylate.
In particular, in the resin dispersant in the present invention, the hydrophilic structural unit (A) is a group derived from (meth) acrylic acid, and the hydrophobic structural unit (B) is at least one of the above (i) and (ii). And (iii) a hydrophobic structural unit (B) other than the above (preferably a structural unit derived from methyl (meth) acrylate, ethyl (meth) acrylate, or benzyl methacrylate).

The acid value of the resin dispersant in the present invention is preferably from 30 mgKOH / g to 100 mgKOH / g and more preferably from 30 mgKOH / g to 85 mgKOH / g from the viewpoint of pigment dispersibility and storage stability. It is preferably 50 mgKOH / g or more and 85 mgKOH / g or less.
The acid value is defined by the mass (mg) of KOH required to completely neutralize 1 g of the resin dispersant, and is measured by the method described in JIS standards (JIS K0070, 1992).

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

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

  The number average molecular weight and the weight average molecular weight are detected by a differential refractometer with a solvent THF using a GPC analyzer using columns of TSKgel GMHxL, TSKgel G4000HxL, and TSKgel G2000HxL (both manufactured by Tosoh Corporation) as a standard substance. It is the molecular weight expressed by converting using polystyrene.

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

<Pigment>
There is no restriction | limiting in particular as a pigment in this invention, According to the objective, it can select suitably, An organic pigment and an inorganic pigment are contained.

Examples of organic pigments include azo pigments, polycyclic pigments, dye chelates, nitro pigments, nitroso pigments, and aniline black. Among these, azo pigments and polycyclic pigments are more preferable.
Examples of the azo pigments include azo lakes, insoluble azo pigments, condensed azo pigments, and chelate azo pigments.
Examples of the polycyclic pigment include phthalocyanine pigments, perylene pigments, perinone pigments, anthraquinone pigments, quinacridone pigments, dioxazine pigments, indigo pigments, thioindigo pigments, isoindolinone pigments, and quinofullerone pigments.
Examples of the dye chelate include basic dye chelate and acid dye chelate.

  Examples of inorganic pigments include titanium oxide, iron oxide, calcium carbonate, barium sulfate, aluminum hydroxide, barium yellow, cadmium red, chrome yellow, and carbon black. Among these, carbon black is particularly preferable. In addition, as carbon black, what was manufactured by well-known methods, such as a contact method, a furnace method, a thermal method, is mentioned, for example.

  In the present invention, the pigments may be used alone, or a plurality of pigments may be selected from within each group or between each group and used in combination.

  The ratio (p: r) between the pigment (p) and the resin dispersant (r) in the present invention is preferably 100: 15 to 100: 140, more preferably 100: 15 to 100: 50, by weight. The ratio (p: r) tends to improve the dispersion stability and rub resistance when the resin dispersant is 100: 15 or more, and the ratio (p: r) is dispersed when the resin dispersant is 100: 140 or less. There is a tendency for stability to improve.

  The resin-coated pigment (encapsulated pigment) in the present invention can be produced by a conventional physical and chemical method using a resin dispersant and a pigment. For example, as described in JP-A-9-151342, JP-A-10-140065, JP-A-11-209672, JP-A-11-172180, JP-A-10-25440, or JP-A-11-43636. It can be manufactured by a method. Specific examples include the phase inversion method and acid precipitation method described in JP-A-9-151342 and JP-A-10-140065. Among them, the phase inversion method is preferable from the viewpoint of dispersion stability.

  The phase inversion method is basically a self-dispersion (phase inversion emulsification) method in which a mixed melt of a resin and a pigment having self-dispersibility or solubility is dispersed in water. The mixed melt may contain the above curing agent or polymer compound. Here, the mixed molten material refers to a mixed state that is not dissolved, a state that is dissolved and mixed, or a state that includes both of these states. A more specific production method of the “phase inversion method” includes the method described in JP-A-10-140065.

In the ink composition of the present invention, the resin-coated pigment in the present invention uses a resin dispersant, and for example, a preparation step of preparing a dispersion of the resin-coated pigment by a method including the following steps (1) and (2) Can be obtained. The ink composition of the present invention can be prepared by a method of providing this preparation step and using the resulting dispersion of the resin-coated pigment together with water and an organic solvent to form an aqueous ink.
Step (1): a resin dispersant containing a structural unit represented by the general formula (I), a resin dispersant containing a structural unit represented by the general formula (II), an organic solvent, a neutralizing agent, a pigment, And a step of dispersing the mixture containing water by stirring or the like to obtain a dispersion Step (2): Step of removing the organic solvent from the dispersion

  The stirring method is not particularly limited, and a commonly used mixing and stirring device, and a dispersing device such as an ultrasonic dispersing device, a high-pressure homogenizer, and a bead mill can be used as necessary.

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

  The neutralizing agent is preferably used in the step (1), and part or all of the acidic groups of the resin dispersant are neutralized to form a stable emulsified or dispersed state in water. Used to do. Details of the neutralizing agent will be described later.

  In the step (2), the organic solvent is distilled off from the dispersion obtained in the step (1) by a conventional method such as vacuum distillation, and the phase is changed to an aqueous system, whereby the pigment particle surface is resin-dispersed. A dispersion of resin-coated pigment particles coated with an agent can be obtained. The organic solvent in the obtained dispersion is substantially removed, and the amount of the organic solvent here is preferably 0.2% by mass or less, more preferably 0.1% by mass or less.

More specifically, for example, (1) a step of neutralizing a resin dispersant having an acidic group or a solution obtained by dissolving it in an organic solvent and a basic compound (neutralizing agent); A step of mixing a pigment with the obtained mixed liquid to form a suspension, and then dispersing the pigment with a disperser or the like to obtain a pigment dispersion; and (3) removing the organic solvent by distillation, for example, Is coated with a specific resin dispersant having an acidic group and dispersed in an aqueous medium to form an aqueous dispersion.
More specifically, the descriptions in JP-A-11-209672 and JP-A-11-172180 can be referred to.

  In the present invention, the dispersion treatment can be performed using, for example, a ball mill, a roll mill, a bead mill, a high-pressure homogenizer, a high-speed stirring type disperser, an ultrasonic homogenizer, or the like.

  The content of the pigment coated with the resin dispersant in the present invention is preferably 1 to 10% by mass, more preferably 2 to 8% by mass, from the viewpoint of dispersion stability and concentration of the aqueous ink composition. 6% by mass is particularly preferred.

<Organic solvent>
The ink composition in the invention contains at least one organic solvent. The organic solvent is used for the purpose of an anti-drying agent, a wetting agent or a penetration enhancer. The anti-drying agent is used for the purpose of preventing the ink from adhering and drying to form aggregates and clogging at the ink discharge port of the ejection nozzle, and the anti-drying agent and wetting agent have a vapor pressure lower than that of water. Low water-soluble organic solvents are preferred. Moreover, as a penetration accelerator, it is used for the purpose of improving the ink permeability to paper.

The organic solvent contained in the ink composition of the present invention can be appropriately selected from known organic solvents in consideration of the function as a drying inhibitor, wetting agent, or penetration enhancer. From the viewpoint of solubility, a water-soluble organic solvent is preferable.
Examples of water-soluble organic solvents include glycerin, 1,2,6-hexanetriol, trimethylolpropane, ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, pentaethylene glycol, dipropylene glycol, 2- Butene-1,4-diol, 2-ethyl-1,3-hexanediol, 2-methyl-2,4-pentanediol, 1,2-octanediol, 1,2-hexanediol, 1,2-pentanediol Alkanediols (polyhydric alcohols) such as 4-methyl-1,2-pentanediol; C1-C4 alkyl alcohols such as ethanol, methanol, butanol, propanol, isopropanol; ethylene glycol monomethyl ether Ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol monomethyl ether acetate, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol mono-n-propyl ether, ethylene glycol mono-iso-propyl ether, diethylene glycol mono-iso-propyl ether , Ethylene glycol mono-n-butyl ether, ethylene glycol mono-t-butyl ether, diethylene glycol mono-t-butyl ether, 1-methyl-1-methoxybutanol, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol mono-t- Butyl ether, propylene glycol Mono-n-propyl ether, propylene glycol mono-iso-propyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol mono-n-propyl ether, dipropylene glycol mono-iso-propyl ether, etc. Glycol ethers; 2-pyrrolidone, N-methyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, formamide, acetamide, dimethyl sulfoxide, sorbit, sorbitan, acetin, diacetin, triacetin, sulfolane, etc. These 1 type (s) or 2 or more types can be used.
Also, sugars such as glucose, mannose, fructose, ribose, xylose, arabinose, galactose, aldonic acid, glucitol, maltose, cellobiose, lactose, sucrose, trehalose, maltotriose; sugar alcohols; hyaluronic acids; ureas, etc. It is also preferable to use a solid wetting agent in combination.

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

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

The said organic solvent can be used individually by 1 type or in mixture of 2 or more types.
The content of the organic solvent in the ink composition is preferably 1 to 60% by mass, more preferably 5 to 40% by mass, and particularly preferably from the viewpoint of ensuring stability and ejection reliability. Is 10-30 mass%.

<Neutralizing agent>
The ink composition in the invention preferably contains at least one neutralizing agent. The neutralizing agent is used to neutralize acidic groups contained in the resin dispersant when producing pigment particles coated with the resin dispersant, and is 0.5 to It is preferable to use an amount of 1.5 equivalents, and it is preferable to be in the range of 0.5 to 1 equivalents.

  Examples of the neutralizing agent include alcohol amines (eg, diethanolamine, triethanolamine, 2-amino-2-ethyl-1,3-propanediol), alkali metal hydroxides (eg, lithium hydroxide, hydroxide) Sodium, potassium hydroxide, etc.), ammonium hydroxide (eg, ammonium hydroxide, quaternary ammonium hydroxide), phosphonium hydroxide, alkali metal carbonate, etc. Preferably used.

<Water>
The ink composition in the present invention contains water, but the amount of water is not particularly limited. Especially, the preferable content of water is 10 to 99% by mass, more preferably 30 to 80% by mass, and still more preferably 50 to 70% by mass.

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

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

  There is no restriction | limiting in particular in content in the ink composition of surfactant, 1 mass% or more is preferable, More preferably, it is 1-10 mass%, More preferably, it is 1-3 mass%.

<Resin particles>
The ink composition of the present invention preferably contains at least one kind of resin particles from the viewpoint of providing fixability, rubbing resistance and cohesiveness for avoiding droplet ejection interference.
The resin particles are contained separately from the resin dispersant containing the structural unit represented by the general formula (I) or the general formula (II).
The resin particles have a function of fixing the ink, that is, the image by aggregating or destabilizing the ink to increase the viscosity of the ink when the resin particles come into contact with a treatment liquid described later or a paper region where the resin liquid is dried. Such resin particles are preferably dispersed in water and an organic solvent.

  Examples of the resin particles include acrylic resins, vinyl acetate resins, styrene-butadiene resins, vinyl chloride resins, acrylic-styrene resins, butadiene resins, styrene resins, crosslinked acrylic resins, crosslinked styrene resins, A benzoguanamine resin, a phenol resin, a silicone resin, an epoxy resin, a urethane resin, a paraffin resin, a fluorine resin, or the like can be used. Various resin particles such as an acrylic resin, an acrylic-styrene resin, a styrene resin, a crosslinked acrylic resin, and a crosslinked styrene resin can be used. In particular, acrylic resin particles are preferable.

  The acrylic resin is obtained, for example, by polymerizing an acrylic monomer having an anionic group (anionic group-containing acrylic monomer) and, if necessary, another monomer copolymerizable with the anionic group-containing acrylic monomer in a solvent. It is done. Examples of the anionic group-containing acrylic monomer include an acrylic monomer having one or more selected from the group consisting of a carboxyl group, a sulfonic acid group, and a phosphonic group. Among them, an acrylic monomer having a carboxyl group (for example, acrylic acid) Methacrylic acid, crotonic acid, ethacrylic acid, propylacrylic acid, isopropylacrylic acid, itaconic acid, fumaric acid and the like), and acrylic acid or methacrylic acid is particularly preferred.

  Specifically, latex can be preferably used as the resin particles. For example, various latexes such as acrylic latex, vinyl acetate latex, styrene latex, and polyester latex can be preferably used. In particular, acrylic latex is preferable.

  As the resin particles in the present invention, self-dispersing polymer particles are preferable from the viewpoint of ejection stability and liquid stability (particularly dispersion stability) when a coloring material (particularly a pigment) is used, and self-dispersion having a carboxyl group. The polymer particles are more preferable. Self-dispersing polymer particles are water-insoluble polymers that can be dispersed in an aqueous medium by the functional groups (particularly acidic groups or salts thereof) of the polymer itself in the absence of other surfactants, By means of water-insoluble polymer particles containing no free emulsifier.

Here, the dispersed state means both an emulsified state (emulsion) in which a water-insoluble polymer is dispersed in an aqueous medium and a dispersed state (suspension) in which a water-insoluble polymer is dispersed in an aqueous medium. It includes the state of.
The water-insoluble polymer in the present invention is preferably a water-insoluble polymer that can be in a dispersed state in which the water-insoluble polymer is dispersed in a solid state from the viewpoint of aggregation rate and fixing property when a liquid composition is used.

  The dispersion state of the self-dispersing polymer particles refers to 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), a neutralizing agent that can neutralize the salt-forming group of the water-insoluble polymer 100% If the group is anionic, sodium hydroxide, acetic acid if it is cationic) and 200 g of water are mixed and stirred (apparatus: stirring apparatus with stirring blades, rotation speed 200 rpm, 30 minutes, 25 ° C.), and then mixed. It means a state in which even after removing the organic solvent from the liquid, it can be visually confirmed that the dispersed state exists stably at 25 ° C. for at least one week.

  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 aqueous medium includes water, and may include a hydrophilic organic solvent as necessary. In the present invention, it is preferably composed of water and 0.2% by mass or less of a hydrophilic organic solvent, more preferably composed of water.

  The main chain skeleton of the water-insoluble polymer is not particularly limited. For example, a vinyl polymer or a condensation polymer (epoxy resin, polyester, polyurethane, polyamide, cellulose, polyether, polyurea, polyimide, polycarbonate, etc.) is used. it can. Of these, vinyl polymers are particularly preferred.

Preferable examples of the vinyl polymer and the monomer constituting the vinyl polymer include those described in JP-A Nos. 2001-181549 and 2002-88294. In addition, radical transfer of vinyl monomers using dissociable groups (or substituents that can be induced to dissociable groups), polymerization initiators, and iniferters, or dissociable groups on either initiators or terminators A vinyl polymer in which a dissociable group is introduced at the end of a polymer chain by ionic polymerization using a compound having (or a substituent that can be derived from a dissociable group) can also be used.
Moreover, as a suitable example of the monomer which comprises a condensation system polymer and a condensation system polymer, what is described in Unexamined-Japanese-Patent No. 2001-247787 can be mentioned.

  The self-dispersing polymer particles preferably include a water-insoluble polymer including a hydrophilic structural unit and a structural unit derived from an aromatic group-containing monomer from the viewpoint of self-dispersibility.

The hydrophilic structural unit is not particularly limited as long as it is derived from a hydrophilic group-containing monomer, and even if it is derived from one kind of hydrophilic group-containing monomer, it contains two or more hydrophilic groups. It may be derived from a monomer. The hydrophilic group is not particularly limited, and may be a dissociable group or a nonionic hydrophilic group.
In the present invention, the hydrophilic group is preferably a dissociable group and more preferably an anionic dissociable group from the viewpoint of promoting self-dispersion and the stability of the formed emulsified or dispersed state. Examples of the dissociable group include a carboxyl group, a phosphoric acid group, and a sulfonic acid group. Among them, a carboxyl group is preferable from the viewpoint of fixability when an ink composition is configured.

The hydrophilic group-containing monomer in the present invention is preferably a dissociable group-containing monomer from the viewpoints of self-dispersibility and aggregation, and is a dissociable group-containing monomer having a dissociable group and an ethylenically unsaturated bond. It is preferable.
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, unsaturated carboxylic acid monomers are preferable, and acrylic acid and methacrylic acid are more preferable from the viewpoints of dispersion stability and ejection stability.

The self-dispersing polymer particles in the present invention preferably contain a polymer having a carboxyl group from the viewpoint of self-dispersibility and agglomeration speed when contacted with the treatment liquid, and have a carboxyl group and an acid value (mgKOH / g It is more preferable that the polymer contains 25-100. Furthermore, the acid value is more preferably from 25 to 80, and particularly preferably from 30 to 65, from the viewpoints of self-dispersibility and the aggregation rate when contacted with the treatment liquid.
In particular, when the acid value is 25 or more, the stability of self-dispersibility is good, and when it is 100 or less, the cohesiveness is improved.

The aromatic group-containing monomer is not particularly limited as long as it is a compound containing an aromatic group and a polymerizable group. The aromatic group may be a group derived from an aromatic hydrocarbon or a group derived from an aromatic heterocycle. In the present invention, an aromatic group derived from an aromatic hydrocarbon is preferable from the viewpoint of particle shape stability in an aqueous medium.
The polymerizable group may be a condensation polymerizable polymerizable group or an addition polymerizable polymerizable group. In the present invention, from the viewpoint of particle shape stability in an aqueous medium, an addition polymerizable polymerizable group is preferable, and a group containing an ethylenically unsaturated bond is more preferable.

  The aromatic group-containing monomer in the present invention is preferably a monomer having an aromatic group derived from an aromatic hydrocarbon and an ethylenically unsaturated bond. The aromatic group-containing monomer may be used alone or in combination of two or more.

Examples of the aromatic group-containing monomer include phenoxyethyl (meth) acrylate, benzyl (meth) acrylate, phenyl (meth) acrylate, and a styrene monomer. Of these, aromatic group-containing (meth) acrylate monomers are preferred from the viewpoint of the balance between the hydrophilicity and hydrophobicity of the polymer chain and the ink fixing property, and phenoxyethyl (meth) acrylate, benzyl (meth) acrylate, and phenyl (meth) are preferred. At least one selected from acrylates is more preferable, and phenoxyethyl (meth) acrylate and benzyl (meth) acrylate are more preferable.
“(Meth) acrylate” means acrylate or methacrylate.

The self-dispersing polymer particles in the present invention include a structural unit derived from an aromatic group-containing (meth) acrylate monomer, and the content is preferably 10% by mass to 95% by mass. When the content of the aromatic group-containing (meth) acrylate monomer is 10% by mass to 95% by mass, the stability of the self-emulsification or dispersion state can be improved, and further the increase in ink viscosity can be suppressed.
In the present invention, from the viewpoints of stability in a self-dispersing state, stabilization of particle shape in an aqueous medium due to hydrophobic interaction between aromatic rings, and reduction in the amount of water-soluble components due to appropriate hydrophobicization of particles. More preferably, the content is from mass% to 90 mass%, more preferably from 15 mass% to 80 mass%, and particularly preferably from 25 mass% to 70 mass%.

  The self-dispersing polymer particles in the present invention can be constituted using, for example, a structural unit derived from an aromatic group-containing monomer and a structural unit derived from a dissociable group-containing monomer. Furthermore, other structural units may be further included as necessary.

The monomer that forms the other structural unit is not particularly limited as long as it is a monomer copolymerizable with the aromatic group-containing monomer and the dissociable group-containing monomer. Among these, an alkyl group-containing monomer is preferable from the viewpoint of flexibility of the polymer skeleton and ease of control of the glass transition temperature (Tg).
Examples of the alkyl group-containing monomer include methyl (meth) acrylate, ethyl (meth) acrylate, isopropyl (meth) acrylate, n-propyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, alkyl (meth) acrylates such as t-butyl (meth) acrylate, hexyl (meth) acrylate, ethylhexyl (meth) acrylate; hydroxymethyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) Ethylenically unsaturated monomers having a hydroxyl group such as acrylate, 4-hydroxybutyl (meth) acrylate, hydroxypentyl (meth) acrylate, hydroxyhexyl (meth) acrylate; Dialkylaminoalkyl (meth) acrylates such as ru (meth) acrylate; N-hydroxyalkyl (meth) such as N-hydroxymethyl (meth) acrylamide, N-hydroxyethyl (meth) acrylamide, N-hydroxybutyl (meth) acrylamide Acrylamide; N-methoxymethyl (meth) acrylamide, N-ethoxymethyl (meth) acrylamide, N- (n-, iso) butoxymethyl (meth) acrylamide, N-methoxyethyl (meth) acrylamide, N-ethoxyethyl (meta And (meth) acrylamides such as N-alkoxyalkyl (meth) acrylamides such as acrylamide and N- (n-, iso) butoxyethyl (meth) acrylamide.

  The molecular weight range of the water-insoluble polymer constituting the self-dispersing polymer particles in the present invention is preferably 3000 to 200,000, more preferably 5000 to 150,000, and more preferably 10,000 to 100,000 in terms of weight average molecular weight. More preferably it is. 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 is measured by gel permeation chromatography (GPC). For GPC, HLC-8020GPC (manufactured by Tosoh Corporation) is used, and TSKgel SuperHZM-H, TSKgel SuperHZ4000, TSKgel SuperHZ200 (4.6 mm ID × 15 cm) manufactured by Tosoh Corporation are used as eluents as columns. Use THF (tetrahydrofuran). As conditions, the sample concentration is 0.45% by mass, the flow rate is 0.35 ml / min, the sample injection amount is 10 μl, the measurement temperature is 40 ° C., and an IR detector is 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 is prepared from 8 samples of “A-2500”, “A-1000”, “n-propylbenzene”.

The water-insoluble polymer constituting the self-dispersing polymer particle in the present invention is a structural unit derived from an aromatic group-containing (meth) acrylate monomer (preferably phenoxyethyl (meth) acrylate) from the viewpoint of controlling the hydrophilicity / hydrophobicity of the polymer. It is preferable that 15-80 mass% of the total mass of a self-dispersing polymer particle is included as a copolymerization ratio for the structural unit derived from and / or the structural unit derived from benzyl (meth) acrylate.
In addition, the water-insoluble polymer has a constitution derived from a carboxyl group-containing monomer having a copolymerization ratio of 15 to 80% by mass of a constitutional unit derived from an aromatic group-containing (meth) acrylate monomer from the viewpoint of controlling the hydrophilicity / hydrophobicity of the polymer. And a structural unit derived from an alkyl group-containing monomer (preferably a structural unit derived from an alkyl ester of (meth) acrylic acid), and a structural unit derived from phenoxyethyl (meth) acrylate and / or Alternatively, a structural unit derived from benzyl (meth) acrylate as a copolymerization ratio of 15 to 80% by mass, a structural unit derived from a carboxyl group-containing monomer, and a structural unit derived from an alkyl group-containing monomer (preferably (meth) A structural unit derived from an alkyl ester having 1 to 4 carbon atoms of acrylic acid) More preferably, the acid value is 25 to 100 and the weight average molecular weight is preferably 3000 to 200,000, the acid value is 25 to 95, and the weight average molecular weight is 5000 to 150,000. It is more preferable that

  Specific examples of the water-insoluble polymer constituting the self-dispersing polymer particles are listed below as exemplary compounds C-01 to C-19, but the present invention is not limited thereto. The values in parentheses represent the mass ratio of the copolymer component.

C-01: Phenoxyethyl acrylate / methyl methacrylate / acrylic acid copolymer (50/45/5)
C-02: Phenoxyethyl acrylate / benzyl methacrylate / isobutyl methacrylate / methacrylic acid copolymer (30/35/29/6)
C-03: Phenoxyethyl methacrylate / isobutyl methacrylate / methacrylic acid copolymer (50/44/6)
C-04: Phenoxyethyl acrylate / methyl methacrylate / ethyl acrylate / acrylic acid copolymer (30/55/10/5)
C-05: benzyl methacrylate / isobutyl methacrylate / methacrylic acid copolymer (35/59/6)
C-06: Styrene / phenoxyethyl acrylate / methyl methacrylate / acrylic acid copolymer (10/50/35/5)
C-07: benzyl acrylate / methyl methacrylate / acrylic acid copolymer (55/40/5)
C-08: Phenoxyethyl methacrylate / benzyl acrylate / methacrylic acid copolymer (45/47/8)
C-09: Styrene / phenoxyethyl acrylate / butyl methacrylate / acrylic acid copolymer (5/48/40/7)
C-10: benzyl methacrylate / isobutyl methacrylate / cyclohexyl methacrylate / methacrylic acid copolymer (35/30/30/5)
C-11: Phenoxyethyl acrylate / methyl methacrylate / butyl acrylate / methacrylic acid copolymer (12/50/30/8)
C-12: benzyl acrylate / isobutyl methacrylate / acrylic acid copolymer (93/2/5)
C-13: Styrene / phenoxyethyl methacrylate / butyl acrylate / acrylic acid copolymer (50/5/20/25)
C-14: Styrene / butyl acrylate / acrylic acid copolymer (62/35/3)
C-15: Methyl methacrylate / phenoxyethyl acrylate / acrylic acid copolymer (45/51/4)
C-16: Methyl methacrylate / phenoxyethyl acrylate / acrylic acid copolymer (45/49/6)
C-17: Methyl methacrylate / phenoxyethyl acrylate / acrylic acid copolymer (45/48/7)
C-18: Methyl methacrylate / phenoxyethyl acrylate / acrylic acid copolymer (45/47/8)
C-19: Methyl methacrylate / phenoxyethyl acrylate / acrylic acid copolymer (45/45/10)

  The method for producing the water-insoluble polymer constituting the self-dispersing polymer particles in the present invention is not particularly limited. For example, emulsion polymerization is carried out in the presence of a polymerizable surfactant to obtain a surfactant and a water-insoluble polymer. Examples include a method of covalent bonding, and a method of copolymerizing a monomer mixture containing the hydrophilic group-containing monomer and the aromatic group-containing monomer by a known polymerization method such as a solution polymerization method or a bulk polymerization method. Among the polymerization methods, a solution polymerization method is preferable and a solution polymerization method using an organic solvent is more preferable from the viewpoint of aggregation rate and droplet ejection stability when an ink composition is used.

  The self-dispersing polymer particles in the present invention include a polymer synthesized in an organic solvent from the viewpoint of aggregation rate, and the polymer has a carboxyl group (preferably having an acid value of 20 to 100). Part or all of the carboxyl groups of the polymer are preferably neutralized and prepared as a polymer dispersion having water as a continuous phase. That is, the production of the self-dispersing polymer particles in the present invention includes a step of synthesizing a polymer in an organic solvent, and a dispersion step of preparing an aqueous dispersion in which at least a part of the carboxyl groups of the polymer is neutralized. It is preferable to do so.

The dispersion step preferably includes the following step (1) and step (2).
Step (1): Step of stirring a mixture containing a polymer (water-insoluble polymer), an organic solvent, a neutralizing agent, and an aqueous medium Step (2): Step of removing the organic solvent from the mixture

The step (1) is preferably a treatment in which a polymer (water-insoluble polymer) is first dissolved in an organic solvent, then a neutralizing agent and an aqueous medium are gradually added, mixed and stirred to obtain a dispersion. In this way, 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, Dispersers, 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 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 for the purpose of moderating the polarity change during the phase inversion from oil to water. 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.

  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 of the present invention has an anionic dissociative group (for example, a carboxyl group) as a dissociable group, the neutralizing agent used is basic such as an organic amine compound, ammonia, or an alkali metal hydroxide. Compounds. Examples of organic amine compounds include monomethylamine, dimethylamine, trimethylamine, monoethylamine, diethylamine, triethylamine, monopropylamine, dipropylamine, monoethanolamine, diethanolamine, triethanolamine, N, N-dimethyl-ethanolamine, N, N-diethyl-ethanolamine, 2-dimethylamino-2-methyl-1-propanol, 2-amino-2-methyl-1-propanol, N-methyldiethanolamine, N-ethyldiethanolamine, monoisopropanolamine, diisopropanol Examples include amines and triisopropanolamine. Examples of the alkali metal hydroxide include lithium hydroxide, sodium hydroxide, and potassium hydroxide. Among these, sodium hydroxide, potassium hydroxide, triethylamine, and triethanolamine are preferable from the viewpoint of stabilizing the dispersion of the self-dispersing polymer particles of the present invention in water.

  These basic compounds are preferably used in an amount of 5 to 120 mol%, more preferably 10 to 110 mol%, still more preferably 15 to 100 mol%, based on 100 mol% of the dissociable group. . By setting it as 15 mol% or more, the effect which stabilizes dispersion | distribution of the particle | grains in water expresses, and there exists an effect which reduces a water-soluble component by setting it as 100 mol% or less.

  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 phase-inversion into an aqueous system. A dispersion can be obtained. The organic solvent in the obtained aqueous dispersion has been substantially removed, and the amount of the organic solvent is preferably 0.2% by mass or less, more preferably 0.1% by mass or less.

The weight average molecular weight of the resin particles is preferably 10,000 or more and 200,000 or less, more preferably 100,000 or more and 200,000 or less.
The average particle diameter of the resin particles is preferably in the range of 10 nm to 1 μm, more preferably in the range of 10 to 200 nm, still more preferably in the range of 20 to 100 nm, and particularly preferably in the range of 20 to 50 nm.

The content of the resin particles is preferably 0.5 to 20% by mass, more preferably 3 to 20% by mass, and still more preferably 5 to 15% by mass with respect to the total mass of the ink composition.
The glass transition temperature Tg of the resin is preferably 30 ° C. or higher, more preferably 40 ° C. or higher, and further preferably 50 ° C. or higher.
Moreover, there is no restriction | limiting in particular regarding the particle size distribution of a resin particle, What has a wide particle size distribution or a thing with a monodispersed particle size distribution may be sufficient. Two or more kinds of resin particles having a monodispersed particle size distribution may be mixed and used.

<Others>
In addition to the above components, the ink composition according to the present invention includes, for example, an ultraviolet absorber, an antifading agent, an antifungal agent, an antirust agent, an antioxidant, an emulsion stabilizer, an antiseptic, and an antifoam, as necessary. You may contain other components, such as an agent, a viscosity modifier, a dispersion stabilizer, and a chelating agent.

[Physical properties of ink composition]
The surface tension (25 ° C.) of the ink composition in the invention is preferably from 20 mN / m to 60 mN / m. More preferably, it is 20 mN or more and 45 mN / m or less, More preferably, it is 25 mN / m or more and 40 mN / m or less.
The surface tension is measured using an automatic surface tensiometer CBVP-Z (manufactured by Kyowa Interface Science Co., Ltd.) and a water-based ink at 25 ° C.

Further, the viscosity at 20 ° C. of the ink composition in the present invention is preferably 1.2 mPa · s or more and 15.0 mPa · s or less, more preferably 2 mPa · s or more and less than 13 mPa · s, and still more preferably. Is 2.5 mPa · s or more and less than 10 mPa · s.
The viscosity is measured using a VISCOMETER TV-22 (manufactured by TOKI SANGYO CO. LTD) under conditions of 25 ° C. of the ink composition.

The ink composition in the present invention can be used for forming a multicolor image (for example, a full color image). For the formation of a full color image, a magenta tone ink composition, a cyan tone ink composition, and a yellow tone ink composition can be used, and a black tone ink composition is used to further adjust the tone. Can do.
In addition, ink compositions having red (R), green (G), blue (B), and white (W) tones other than yellow (Y), magenta (M), and cyan (C), and so-called printing fields. Ink-colored ink compositions and the like can be used.
The ink composition of each color tone can be prepared by changing the hue of the pigment used as the colorant as desired.

[Ink set]
Next, the ink set according to the present invention will be described.
The ink set of the present invention includes at least a first resin dispersant containing a structural unit represented by the general formula (I) and a second resin dispersant containing a structural unit represented by the general formula (II). An ink composition of the present invention comprising a pigment coated with, an organic solvent, and water, and a treatment liquid comprising a flocculant that aggregates the components in the ink composition when mixed with the ink composition; including.
The ink set of the present invention forms an image by causing aggregation when contacting the above-described ink composition of the present invention and a treatment liquid described later, and includes one type each of the ink composition and the treatment liquid. It may be a form including a plurality of at least one.

  In the present invention, the pigment contained as the colorant includes the first resin dispersant containing the structural unit represented by the general formula (I) and the structural unit represented by the general formula (II). By adhering to the second resin dispersant in the ink liquid, the agglomerate formed by contact and aggregation of the two liquids of the ink composition and the processing liquid during recording adheres to the liquid discharge portion. Alternatively, the accumulation can be reduced, and the removal of the aggregates when the aggregates adhere to the liquid discharge portion can be facilitated. As a result, the maintenance frequency on the ejection device side can be reduced and the maintainability can be improved. Ink ejection direction failure during ink ejection can be suppressed, and image failure such as white spots can be prevented, resulting in higher resolution of the image. Can be realized. In addition, the formed image is excellent in abrasion resistance.

<Processing liquid>
The treatment liquid in the ink set of the present invention comprises an aggregating agent that aggregates the components in the ink composition when mixed with the ink composition of the present invention, and is configured using other components as necessary. can do.

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

(Flocculant)
The treatment liquid in the present invention contains at least one acid as an aggregating agent for aggregating components in the ink composition. When the treatment liquid is mixed with the ink composition ejected by the ink jet method, the components in the ink composition are aggregated, and in particular, the aggregation of the pigment stably dispersed in the ink composition is promoted.

As an aggregating agent for aggregating the components in the ink composition, it is necessary to contain an acid in the treatment liquid. Other examples include polyvalent metal salts, polyallylamine and derivatives thereof.
Examples of the acid include polyacrylic acid, acetic acid, glycolic acid, malonic acid, malic acid, maleic acid, ascorbic acid, succinic acid, glutaric acid, fumaric acid, citric acid, tartaric acid, lactic acid, sulfonic acid, orthophosphoric acid, pyrrolidone. It can be suitably selected from 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. it can.

  Examples of the polyvalent metal salt include alkaline earth metals belonging to Group 2 of the periodic table (eg, magnesium, calcium), transition metals belonging to Group 3 of the periodic table (eg, lanthanum), and Group 13 of the periodic table. Mention may be made of salts of cations (for example, aluminum) and lanthanides (for example, neodymium). These metal salts include nitrates, chlorides, and thiocyanates.

  Among the above, the acid is preferably an organic carboxylic acid, more preferably a divalent or trivalent organic carboxylic acid, and more preferably citric acid or malonic acid, from the viewpoint of improving the aggregation rate of components in the ink composition. Malic acid and maleic acid are particularly preferred.

The flocculants can be used alone or in combination of two or more.
The content of the acid as an aggregating agent for aggregating the components in the ink composition in the treatment liquid is preferably 10 to 35% by mass, more preferably 15 to 35% by mass, and still more preferably 20 to 35% by mass. % Range.

[Pigment dispersion]
Next, the pigment dispersion according to the present invention will be described.
The pigment dispersion of the present invention includes at least the above-described pigment, the first resin dispersant containing the structural unit represented by the general formula (I), and the structural unit represented by the general formula (II). A second resin dispersant containing.
The pigment dispersion liquid of the present invention uses at least two kinds of dispersants having different structures, which are the first resin dispersant and the second resin dispersant described in the ink composition of the present invention, so that particles over time can be obtained. The pigment dispersion is improved with improved dispersion stability.
Details of the pigment, the first resin dispersant containing the structural unit represented by the general formula (I), the second resin dispersant containing the structural unit represented by the general formula (II), and the like are described above. The preferred embodiments are also the same.

[Image forming method]
Next, the image forming method according to the present invention will be described.
The image forming method of the present invention includes an ink application step of applying the above-described ink composition onto a recording medium by an inkjet method, and an aggregating agent that aggregates the components in the ink composition when mixed with the ink composition. And a treatment liquid application step of applying a treatment liquid containing a liquid onto a recording medium, and the ink composition and the treatment liquid are brought into contact with each other to form an image.

  In the image forming method of the present invention, the pigment coated with the resin dispersant is used as a colorant in the case of recording an image by causing aggregation when the two liquids of the ink composition and the treatment liquid are brought into contact during recording. By using the ink composition described above, the adhesion or deposition of the agglomerates that can be contacted with two liquids on the liquid ejection part is alleviated and the adhered agglomerates can be easily removed. Therefore, it is possible to prevent the occurrence of image failure such as white spots by suppressing the ink ejection direction defect, and to record a high-resolution image having excellent abrasion resistance. In addition, the maintenance frequency on the discharge device side can be reduced and the maintainability can be improved.

  In the ink application process, the ink composition is applied by an inkjet method. Specifically, a desired recording medium, that is, plain paper, resin-coated paper, for example, JP-A-8-169172, 8-27693, 2-276670, 7-276789, 9 -323475, JP-A-62-238783, JP-A-10-153899, JP-A-10-217473, JP-A-10-235995, JP-A-10-337947, and JP-A-10-217597, The ink composition is ejected by applying energy to dedicated inkjet paper, film, electrophotographic co-paper, fabric, glass, metal, ceramics, etc. described in JP-A-10-337947, etc., and forms a colored image. As a preferable inkjet method for the present invention, the method described in paragraphs 0093 to 0105 of JP-A No. 2003-306623 can be applied.

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

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.

  In the treatment liquid application step, the treatment liquid is applied onto the recording medium before or after application of the ink composition. 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 a coating method, a known coating method using a bar coater, an extrusion die coater, an air doctor coater, a bread coater, a rod coater, a knife coater, a squeeze coater, a reverse roll coater, a bar coater or the like can be used. The details of the inkjet method are as described above.

  In the 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 ink composition to the recording medium, a processing liquid for aggregating the components in the ink composition is applied in advance, and the recording liquid is brought into contact with the processing liquid applied on the recording medium. An embodiment in which an ink composition is applied 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.

During image recording, a polymer or a polymer latex thereof may be used in combination for the purpose of imparting glossiness or water resistance or improving weather resistance. The timing of applying the polymer or polymer latex may be before or after applying the aqueous ink composition, or may be applied simultaneously. Therefore, the polymer or polymer latex may be used in a mode of being applied to the recording medium, or may be used in a mode of making it a separate liquid material.
Specifically, the methods described in JP-A No. 2002-166638, JP-A No. 2002-121440, JP-A No. 2002-154201, JP-A No. 2002-144696, and JP-A No. 2002-080759 are preferable. Can be used.

  The image forming method of the present invention may further include other steps in addition to the ink application step of applying the ink composition and the treatment liquid application step of applying the treatment liquid. There is no restriction | limiting in particular as another process, According to the objective, it can select suitably. For example, a drying and removing step of drying and removing an organic solvent in the ink composition applied to the recording medium, a heat fixing step of melting and fixing resin particles that can be included in the ink composition, and the like can be mentioned.

As another example of the image forming method of the present invention, the above-described ink composition using an intermediate transfer member as a recording medium for first image formation and containing the resin dispersant, the pigment, the organic solvent and water in the present invention. An ink application step for applying an ink onto the intermediate transfer member by an ink jet method, and a treatment liquid application step for applying a treatment liquid containing an acid as an aggregating agent for aggregating the components in the ink composition onto the intermediate transfer member. Examples thereof include a method in which an image is formed on an intermediate transfer member by bringing the composition into contact with the treatment liquid, and then a transfer step is provided for transferring the image formed on the intermediate transfer member to a desired final recording medium.
In this case as well, other processes such as a drying removal process and a heat fixing process can be further provided in the same manner as described above.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples unless it exceeds the gist thereof. Unless otherwise specified, “part” is based on mass.

  The weight average molecular weight was measured by gel permeation chromatography (GPC) by the method described in the above-mentioned section of resin particles.

(Synthesis Example 1)
-Synthesis of resin dispersant P-1-
To a 1000 ml three-necked flask equipped with a stirrer and a condenser tube, 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 prepared by dissolving 0.42 g of dimethyl-2,2′-azobisisobutyrate in 2 g of methyl ethyl ketone was added, heated to 78 ° C. and heated for 4 hours. The obtained reaction solution was reprecipitated twice in an excess amount of hexane, and the precipitated resin was dried to obtain 96.5 g of a phenoxyethyl methacrylate / methyl methacrylate / methacrylic acid copolymer (resin dispersant P-1). It was.
The composition of the obtained resin dispersant P-1 was confirmed by 1H-NMR, and the weight average molecular weight (Mw) determined by GPC was 37900. Furthermore, when the acid value of this resin dispersant was calculated | required by the method of JIS specification (JISK0070: 1992), it was 71.7 mgKOH / g.

(Synthesis Example 2)
-Synthesis of resin dispersants P-2 to P-5 and P-9 to P-11-
In the synthesis of the resin dispersant P-1, the resin dispersant P- was changed except that the phenoxyethyl methacrylate, methacrylic acid, and methyl methacrylate were changed to have the monomer types and ratios shown in Table 4 below. Resin dispersants P-2 to P-5 and P-9 to P-11 were synthesized in the same manner as in the synthesis of 1.
Table 4 below shows the weight average molecular weight and acid value measured by the same method as in the resin dispersant P-1.

(Synthesis Example 3)
<Monomer Synthesis Example A (M-27, Synthesis of Para-Substituted Product)>
A 5 L three-necked flask equipped with a stirrer and a condenser tube was charged with 375 g of acridone and 1800 mL of dimethyl sulfoxide in which 84.8 g of sodium hydroxide was dissolved, and stirred at room temperature for 10 minutes. 440 g of p-chloromethylstyrene was added dropwise over 10 minutes, and co-washed with 300 mL of dimethyl sulfoxide. The mixture was heated to 55 ° C. and reacted for 7 hours. After completion of the reaction, a mixed solution of 750 mL of methanol and 750 mL of water was added dropwise at 55 ° C. over 10 minutes, stirred at 40 ° C. for 30 minutes, and further stirred at 30 ° C. or lower for 1 hour. The resulting slurry was removed by vacuum filtration, placed in a 5 L three-necked flask, and 3 L of methanol was added. The mixture was stirred at 50 ° C. for 30 minutes, at 45 ° C. or lower for 30 minutes, at 30 ° C. or lower for 1 hour, and subjected to vacuum filtration to obtain 484 g of M-27.

<Monomer Synthesis Example B (M-25, synthesis of meta-substituted product)>
In the monomer synthesis example A, M-25 was obtained in the same manner as the monomer synthesis example A except that m-chloromethylstyrene was used instead of p-chloromethylstyrene.

  Monomers M-25 and M-27 obtained above were mixed at a ratio of 1: 1 to prepare a mixture of the monomer meta-substituted product and para-substituted product, and used for the synthesis of the following dispersant.

(Synthesis Example 4)
-Synthesis of resin dispersants P-6 to P-8-
To a 300 ml three-necked flask equipped with a stirrer and a condenser tube, 90 g of a monomer mixture having the monomer composition shown in Table 4 and 126 g of methyl ethyl ketone were added and heated to 75 ° C. in a nitrogen atmosphere. 1.20 g of dimethyl 2,2′-azobisisobutyrate dissolved in 8 g of methyl ethyl ketone was added to a three-necked flask and reacted for 2 hours, and dimethyl 2,2′-azobisisobutyrate dissolved in 0.6 g of methyl ethyl ketone was added. .50 g was added and reacted for another 2 hours. 0.50 g of dimethyl 2,2′-azobisisobutyrate dissolved in 0.6 g of methyl ethyl ketone was added, the temperature was raised to 80 ° C., and the mixture was heated and stirred for 4 hours to react all unreacted monomers. After completion of the reaction, 33 g of methyl ethyl ketone was added to the obtained polymer solution for dilution.
The composition of the obtained resin dispersant was confirmed by ¹ H-NMR. The weight average molecular weight (Mw) was detected with a solvent THF and a differential refractometer using a GPC analyzer in which columns of TSKgel GMHxL, TSKgel G4000HxL, and TSKgel G2000HxL (all manufactured by Tosoh Corporation) were connected in series. As polystyrene. Furthermore, the acid values of these resin dispersants were determined by the method described in JIS standards (JIS K 0070: 1992). The results are shown in Table 4.

Example 1
-Preparation of resin-coated pigment dispersion-
C. I. Pigment Red 122 (chromophthaljet magenta DMQ, manufactured by Ciba Specialty Chemicals; magenta pigment), 3 parts of the above resin dispersant P-1 and 1.5 parts of resin dispersant P-6 Then, 17 parts of methyl ethyl ketone, 7.3 parts of 1N NaOH aqueous solution, and 61.2 parts of ion-exchanged water were disperse-mixed and further subjected to 10-pass treatment with a disperser (Microfluidizer M-140K, 150 MPa). Subsequently, methyl ethyl ketone was removed from the obtained dispersion at 55 ° C. under reduced pressure, and a part of water was further removed to obtain a dispersion of resin-coated pigment particles having a pigment concentration of 12.5% by mass. .

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

-Preparation of self-dispersing polymer particles-
360.0 g of methyl ethyl ketone was charged into a 2-liter three-necked flask equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen gas inlet tube, and the temperature was raised to 75 ° C. While maintaining the temperature in the reaction vessel at 75 ° C., 180.0 g of phenoxyethyl acrylate, 162.0 g of methyl methacrylate, 18.0 g of acrylic acid, 72 g of methyl ethyl ketone, and “V-601” (manufactured by Wako Pure Chemical Industries, Ltd.) 1 .44 g of the mixed solution was added dropwise at a constant speed so that the addition was completed in 2 hours. After completion of the dropwise addition, a solution consisting of 0.72 g of “V-601” and 36.0 g of methyl ethyl ketone was added, stirred for 2 hours at 75 ° C., and then a solution consisting of 0.72 g of “V-601” and 36.0 g of isopropanol was added. After stirring at 75 ° C. for 2 hours, the temperature was raised to 85 ° C., and stirring was further continued for 2 hours. The weight average molecular weight (Mw) of the obtained copolymer was 64000 (calculated in terms of polystyrene by gel permeation chromatography (GPC), columns used: TSKgel SuperHZM-H, TSKgel SuperHZ4000, TSKgel SuperHZ200 (manufactured by Tosoh Corporation)), The acid value was 38.9 (mgKOH / g).

Next, 668.3 g of the polymerization solution was weighed, and 388.3 g of isopropanol, 1 mol / L.
145.7 ml of NaOH aqueous solution was added, and the temperature inside the reaction vessel was raised to 80 ° C. Next, 720.1 g of distilled water was added dropwise at a rate of 20 ml / min to disperse in water. Thereafter, the temperature in the reaction vessel was maintained at 80 ° C. for 2 hours, 85 ° C. for 2 hours, and 90 ° C. for 2 hours under atmospheric pressure, and then the reaction vessel was depressurized, and isopropanol, methyl ethyl ketone, and distilled water totaled 913. 7 g was distilled off to obtain an aqueous dispersion (emulsion) of self-dispersing polymer fine particles (C-01) having a solid content concentration of 28.0%.

-Preparation of ink composition-
Next, an ink composition having the following composition was prepared using the obtained dispersion of resin-coated pigment particles. The pH of this ink composition at 25 ° C. was 8.9.
<Composition>
-Dispersion of the resin-coated pigment particles-40 parts-Self-dispersing polymer fine particles (C-01)-7 parts-Sannix GP250-9.5 parts-Diethylene glycol monoethyl ether ... 8・ Orphine E1010 (manufactured by Nissin Chemical Industry Co., Ltd.) ・ ・ ・ 1 part ・ Ion-exchanged water ・ ・ ・ 34.5 parts

-Preparation of treatment solution-
The processing liquid was prepared by mixing the components having the following composition. When the physical properties of the obtained reaction liquid were measured, the viscosity was 4.9 mPa · s, the surface tension was 24.3 mN / m, and the pH was 1.5.
<Composition>
・ Citric acid: 16.7g
・ Zonyl FSN-100 (manufactured by DU PONT; surfactant) 1 g
・ Diethylene glycol monoethyl ether 20g
・ Ion-exchanged water: added to a total of 100 g

(Evaluation)
As described above, an ink set comprising a magenta color ink composition and a treatment liquid was produced.

-Evaluation of ink composition-
-Dispersion stability-
The particle diameter a ¹ immediately after the preparation of the ink composition obtained above was measured by the same method as the above volume average particle diameter, and the viscosity b ¹ and the number of coarse particles were measured by the following method. The ink composition was stored in a constant temperature bath at 60 ° C. for 14 days, and the particle diameter a ² and viscosity b ² after storage were measured by the same method. Further, the number of coarse particles of 0.5 to 5 μm contained in the ink composition after storage was counted. Then, from the obtained particle size and viscosity, a change in particle size (| a ² −a ¹ |; nm) and a change in viscosity (| b ² −b ¹ | / b ¹ × 100;%) before and after storage are obtained. Evaluation was made according to the following evaluation criteria. “||” represents an absolute value. The results are shown in the table below.

-Viscosity-
The obtained ink composition was measured using a VISCOMETER TV-22 (manufactured by TOKI SANGYO CO. LTD) at 25 ° C.

-Coarse particle count-
Using a flow type particle image analyzer FPIA 3000 (manufactured by Sysmex Corporation), the number of coarse particles of 0.8 to 5 μm or more in the ink composition was measured. At this time, a measurement sample was prepared by adding 1.8 ml of ion-exchanged water to 0.2 ml of the ink composition and measured at 25 ° C. From the obtained results, the number of coarse particles in 1 μl of ink was calculated.
<Evaluation criteria>
A: The particle size change is within 10 nm, the viscosity change is within 10%, and the number of coarse particles of 0.8 to 5 μm is 5000 or less.
B: Any one of the points where the particle diameter change exceeds 10 nm, the viscosity change exceeds 10%, and the number of coarse particles of 0.8 to 5 μm is 5000 or more is satisfied.
C: B satisfies at least two conditions.

~ Evaluation of ink set ~
-White-
As an ink jet recording apparatus, an ink jet apparatus provided with a trial print head of 600 dpi and 256 nozzles was prepared, and the ink set obtained above was loaded therein, and the occurrence of white spots was evaluated by the following method. As a recording medium, Tokuhishi Art Double Sided N (Mitsubishi Paper Co., Ltd.) was used.

Tokishi Art Double Sided N (Mitsubishi Paper Co., Ltd.) as a recording medium is fixed on a stage that can be moved in a predetermined linear direction at 500 mm / second, and the treatment liquid obtained above is fixed to this with a wire bar coater. It apply | coated so that it might become a thickness of 5 micrometers (0.84 g / m < ² > of citric acid), and it was made to dry at 50 degreeC for 2 second immediately after application | coating. Thereafter, a solid image was printed with the prototype head. 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. The fixing roller is composed of a heating roll in which the surface of the core of a SUS cylindrical body with a halogen lamp inside is coated with a silicone resin, and an opposing roll that is in pressure contact with the heating roller. is there. The recorded image (5 cm × 5 cm) was observed. And the observed image was visually evaluated according to the following evaluation criteria.
<Evaluation criteria>
A: No white spots were observed.
B: Occurrence of white spots was 2 or less.
C: There were 3 to 10 white spots.
D: The occurrence of white spots exceeded 10 locations.

-Evaluation of abrasion resistance-
The solid image obtained above was wound around a paperweight (weight 470 g, size 15 mm × 30 mm × 120 mm) with the printing surface facing outward, and the evaluation sample was rubbed 3 times on the unprinted special diamond art (load 260 kg / equivalent to m ² ). The printed surface after rubbing was visually observed and evaluated according to the following evaluation criteria.
<Evaluation criteria>
A: Not scratched.
B: Slightly scratched.
C: Scratches but not practically problematic.

(Example 2)
C. I. Pigment Red 122 (chromophthaljet magenta DMQ, manufactured by Ciba Specialty Chemicals; magenta pigment), 3 parts of the above-described resin dispersant P-2, and 1.5 parts of resin dispersant P-6 Then, 17 parts of methyl ethyl ketone, 6.9 parts of 1N NaOH aqueous solution, and 61.6 parts of ion-exchanged water were disperse-mixed and further subjected to 10-pass treatment with a disperser (Microfluidizer M-140K, 150 MPa). Subsequently, methyl ethyl ketone was removed from the obtained dispersion at 55 ° C. under reduced pressure, and a part of water was further removed to obtain a dispersion of resin-coated pigment particles having a pigment concentration of 12.5% by mass. .
Other than that was carried out similarly to Example 1, and produced the ink set which consists of a magenta color ink composition and a process liquid.

(Example 3)
C. I. Pigment Red 122 (chromophthaljet magenta DMQ, manufactured by Ciba Specialty Chemicals; magenta pigment), 3 parts of the above resin dispersant P-2, and 1.5 parts of resin dispersant P-7 Then, 17 parts of methyl ethyl ketone, 7.1 parts of 1N NaOH aqueous solution, and 61.4 parts of ion-exchanged water were disperse-mixed and further subjected to a 10-pass treatment with a disperser (Microfluidizer M-140K, 150 MPa). Subsequently, methyl ethyl ketone was removed from the obtained dispersion at 55 ° C. under reduced pressure, and a part of water was further removed to obtain a dispersion of resin-coated pigment particles having a pigment concentration of 12.5% by mass. .
Other than that was carried out similarly to Example 1, and produced the ink set which consists of a magenta color ink composition and a process liquid.

Example 4
C. I. Pigment Red 122 (chromophthaljet magenta DMQ, manufactured by Ciba Specialty Chemicals; magenta pigment), 3 parts of the above-described resin dispersant P-3, and 1.5 parts of resin dispersant P-6 Then, 17 parts of methyl ethyl ketone, 8.8 parts of 1N NaOH aqueous solution, and 59.7 parts of ion-exchanged water were disperse-mixed and further subjected to 10-pass treatment with a disperser (Microfluidizer M-140K, 150 MPa). Subsequently, methyl ethyl ketone was removed from the obtained dispersion at 55 ° C. under reduced pressure, and a part of water was further removed to obtain a dispersion of resin-coated pigment particles having a pigment concentration of 12.5% by mass. .
Other than that was carried out similarly to Example 1, and produced the ink set which consists of a magenta color ink composition and a process liquid.

(Example 5)
C. I. Pigment Red 122 (chromophthaljet magenta DMQ, manufactured by Ciba Specialty Chemicals; magenta pigment), 3 parts of the above-described resin dispersant P-4, and 1.5 parts of resin dispersant P-6 Then, 17 parts of methyl ethyl ketone, 9.2 parts of 1N NaOH aqueous solution, and 59.3 parts of ion-exchanged water were disperse-mixed and further subjected to 10-pass treatment with a disperser (Microfluidizer M-140K, 150 MPa). Subsequently, methyl ethyl ketone was removed from the obtained dispersion at 55 ° C. under reduced pressure, and a part of water was further removed to obtain a dispersion of resin-coated pigment particles having a pigment concentration of 12.5% by mass. .
Other than that was carried out similarly to Example 1, and produced the ink set which consists of a magenta color ink composition and a process liquid.

(Example 6)
C. I. Pigment Red 122 (chromophthaljet magenta DMQ, manufactured by Ciba Specialty Chemicals; magenta pigment), 3 parts of the above-described resin dispersant P-1 and 1.5 parts of resin dispersant P-8 Then, 17 parts of methyl ethyl ketone, 7.8 parts of 1N NaOH aqueous solution, and 60.7 parts of ion-exchanged water were disperse-mixed and further subjected to 10-pass treatment with a disperser (Microfluidizer M-140K, 150 MPa). Subsequently, methyl ethyl ketone was removed from the obtained dispersion at 55 ° C. under reduced pressure, and a part of water was further removed to obtain a dispersion of resin-coated pigment particles having a pigment concentration of 12.5% by mass. .
Other than that was carried out similarly to Example 1, and produced the ink set which consists of a magenta color ink composition and a process liquid.

(Example 7)
C. I. Pigment Red 122 (chromophthaljet magenta DMQ, manufactured by Ciba Specialty Chemicals; magenta pigment), 4 parts of the above resin dispersant P-1 and 0.5 part of resin dispersant P-6 Then, 17 parts of methyl ethyl ketone, 7.5 parts of 1N NaOH aqueous solution, and 61 parts of ion-exchanged water were dispersed in a dispersion and further subjected to 10-pass treatment with a disperser (Microfluidizer M-140K, 150 MPa). Subsequently, methyl ethyl ketone was removed from the obtained dispersion at 55 ° C. under reduced pressure, and a part of water was further removed to obtain a dispersion of resin-coated pigment particles having a pigment concentration of 12.5% by mass. .
Other than that was carried out similarly to Example 1, and produced the ink set which consists of a magenta color ink composition and a process liquid.

(Example 8)
C. I. Pigment Red 122 (chromophthaljet magenta DMQ, manufactured by Ciba Specialty Chemicals; magenta pigment), 3.5 parts of the above-described resin dispersant P-1 and 1 part of resin dispersant P-6 Then, 17 parts of methyl ethyl ketone, 7.5 parts of 1N NaOH aqueous solution, and 61 parts of ion-exchanged water were dispersed in a dispersion and further subjected to 10-pass treatment with a disperser (Microfluidizer M-140K, 150 MPa). Subsequently, methyl ethyl ketone was removed from the obtained dispersion at 55 ° C. under reduced pressure, and a part of water was further removed to obtain a dispersion of resin-coated pigment particles having a pigment concentration of 12.5% by mass. .
Other than that was carried out similarly to Example 1, and produced the ink set which consists of a magenta color ink composition and a process liquid.

(Comparative Example 1)
C. I. Pigment Red 122 (chromophthaljet magenta DMQ, manufactured by Ciba Specialty Chemicals; magenta pigment), 4.5 parts of the above resin dispersant P-1, 17 parts of methyl ethyl ketone, and 1 N aqueous NaOH solution 7.6 parts and 60.9 parts of ion-exchanged water were mixed, disperse mixed, and further subjected to 10 passes with a disperser (Microfluidizer M-140K, 150 MPa). Subsequently, methyl ethyl ketone was removed from the obtained dispersion at 55 ° C. under reduced pressure, and a part of water was further removed to obtain a dispersion of resin-coated pigment particles having a pigment concentration of 12.5% by mass. .
Other than that was carried out similarly to Example 1, and produced the ink set which consists of a magenta color ink composition and a process liquid.

(Comparative Example 2)
C. I. Pigment Red 122 (chromophthaljet magenta DMQ, manufactured by Ciba Specialty Chemicals; magenta pigment), 4.5 parts of the above resin dispersant P-6, 17 parts of methyl ethyl ketone, and 1 N aqueous NaOH solution 6.9 parts and 61.6 parts of ion-exchanged water were mixed, disperse mixed, and further processed for 10 passes with a disperser (Microfluidizer M-140K, 150 MPa). Subsequently, methyl ethyl ketone was removed from the obtained dispersion under reduced pressure at 55 ° C., and a part of water was further removed to obtain a dispersion of resin-coated pigment particles having a pigment concentration of 12.5% by mass. .
Other than that was carried out similarly to Example 1, and produced the ink set which consists of a magenta color ink composition and a process liquid.

(Comparative Example 3)
C. I. CI Pigment Red 122 (chromophthaljet magenta DMQ, manufactured by Ciba Specialty Chemicals; magenta pigment), 4.5 parts of the above resin dispersant P-2, 17 parts of methyl ethyl ketone, and 1 N aqueous NaOH solution 6.9 parts and 61.6 parts of ion-exchanged water were mixed, disperse mixed, and further processed for 10 passes with a disperser (Microfluidizer M-140K, 150 MPa). Subsequently, methyl ethyl ketone was removed from the obtained dispersion under reduced pressure at 55 ° C., and a part of water was further removed to obtain a dispersion of resin-coated pigment particles having a pigment concentration of 12.5% by mass. .
Other than that was carried out similarly to Example 1, and produced the ink set which consists of a magenta color ink composition and a process liquid.

(Comparative Example 4)
C. I. Pigment Red 122 (chromophthaljet magenta DMQ, manufactured by Ciba Specialty Chemicals; magenta pigment), 4.5 parts of the above resin dispersant P-7, 17 parts of methyl ethyl ketone, and 1 N aqueous NaOH solution 7.6 parts and 60.9 parts of ion-exchanged water were mixed, disperse mixed, and further subjected to 10 passes with a disperser (Microfluidizer M-140K, 150 MPa). Subsequently, methyl ethyl ketone was removed from the obtained dispersion at 55 ° C. under reduced pressure, and a part of water was further removed to obtain a dispersion of resin-coated pigment particles having a pigment concentration of 12.5% by mass. .
Other than that was carried out similarly to Example 1, and produced the ink set which consists of a magenta color ink composition and a process liquid.

(Comparative Example 5)
C. I. Pigment Red 122 (chromophthaljet magenta DMQ, manufactured by Ciba Specialty Chemicals, Inc .; magenta pigment), 4.5 parts of the above resin dispersant P-5, 17 parts of methyl ethyl ketone, and 1 N aqueous NaOH solution 5.5 parts and 63 parts of ion-exchanged water were mixed, disperse mixed, and further subjected to 10-pass treatment with a disperser (Microfluidizer M-140K, 150 MPa). Subsequently, methyl ethyl ketone was removed from the obtained dispersion at 55 ° C. under reduced pressure, and a part of water was further removed to obtain a dispersion of resin-coated pigment particles having a pigment concentration of 12.5% by mass. .
Other than that was carried out similarly to Example 1, and produced the ink set which consists of a magenta color ink composition and a process liquid.

(Comparative Example 6)
C. I. Pigment Red 122 (chromophthaljet magenta DMQ, manufactured by Ciba Specialty Chemicals; magenta pigment), 4.5 parts of the above-described resin dispersant P-8, 17 parts of methyl ethyl ketone, and 1N aqueous NaOH solution 8.3 parts and 60.2 parts of ion-exchanged water were mixed, disperse mixed, and further subjected to 10-pass treatment with a disperser (Microfluidizer M-140K, 150 MPa). Subsequently, methyl ethyl ketone was removed from the obtained dispersion at 55 ° C. under reduced pressure, and a part of water was further removed to obtain a dispersion of resin-coated pigment particles having a pigment concentration of 12.5% by mass. .
Other than that was carried out similarly to Example 1, and produced the ink set which consists of a magenta color ink composition and a process liquid.

(Comparative Example 7)
C. I. Pigment Red 122 (chromophthaljet magenta DMQ, manufactured by Ciba Specialty Chemicals, Inc .; magenta pigment), 4.5 parts of the above resin dispersant P-9, 17 parts of methyl ethyl ketone, and 1N aqueous NaOH solution 6.9 parts and 61.6 parts of ion-exchanged water were mixed, disperse mixed, and further subjected to 10 passes with a disperser (Microfluidizer M-140K, 150 MPa). Subsequently, methyl ethyl ketone was removed from the obtained dispersion at 55 ° C. under reduced pressure, and a part of water was further removed to obtain a dispersion of resin-coated pigment particles having a pigment concentration of 12.5% by mass. .
Other than that was carried out similarly to Example 1, and produced the ink set which consists of a magenta color ink composition and a process liquid.

(Comparative Example 8)
C. I. Pigment Red 122 (chromophthaljet magenta DMQ, manufactured by Ciba Specialty Chemicals; magenta pigment), 4.5 parts of the above resin dispersant P-10, 17 parts of methyl ethyl ketone, and 1 N aqueous NaOH solution 10.4 parts and 58.1 parts of ion-exchanged water were mixed, disperse mixed, and further subjected to 10 passes with a disperser (Microfluidizer M-140K, 150 MPa). Subsequently, methyl ethyl ketone was removed from the obtained dispersion at 55 ° C. under reduced pressure, and a part of water was further removed to obtain a dispersion of resin-coated pigment particles having a pigment concentration of 12.5% by mass. .
Other than that was carried out similarly to Example 1, and produced the ink set which consists of a magenta color ink composition and a process liquid.

(Comparative Example 9)
C. I. Pigment Red 122 (chromophthaljet magenta DMQ, manufactured by Ciba Specialty Chemicals, Inc .; magenta pigment), 4.5 parts of the above resin dispersant P-11, 17 parts of methyl ethyl ketone, and 1 N aqueous NaOH solution 13.8 parts and 54.7 parts of ion-exchanged water were mixed, disperse mixed, and further subjected to 10-pass treatment with a disperser (Microfluidizer M-140K, 150 MPa). Subsequently, methyl ethyl ketone was removed from the obtained dispersion at 55 ° C. under reduced pressure, and a part of water was further removed to obtain a dispersion of resin-coated pigment particles having a pigment concentration of 12.5% by mass. .
Other than that was carried out similarly to Example 1, and produced the ink set which consists of a magenta color ink composition and a process liquid.

The resin dispersant used in Examples 1-8 and Comparative Examples 1-9 is shown below. The brackets in the resin dispersants P-1 to P-8 represent the compounds described above as specific examples of the resin dispersant containing the structural unit represented by the general formula (I) and the general formula (II).
In the table, P-1 to P-5 are resin dispersants containing a structural unit represented by the general formula (I), and P-6 to P-8 are structural units represented by the general formula (II). It is a resin dispersant containing.
In the table, M-1 is a monomer (M-25 / M-27) mixture.

  For Examples 2 to 8 and Comparative Examples 1 to 9, the same evaluation method as in Example 1 was used to evaluate dispersion stability, white spots and abrasion resistance. The results are shown in the table below.

  In the table, dispersant 1 is a resin dispersant containing a structural unit represented by general formula (I), and dispersant 2 is a resin dispersant containing a structural unit represented by general formula (II). .

  It can be seen that in Examples using two types of resin dispersants having a specific structure, the dispersion stability, white spot evaluation and abrasion resistance evaluation are all good.

  In the above-described embodiments, the case where an ink composition having a magenta color tone is prepared as an ink composition has been mainly described. However, by changing the type (hue) of the pigment used in the magenta color tone ink composition, In the same manner as described above, ink compositions of various hues such as a black ink composition, a cyan ink composition, and a yellow ink composition can be obtained, and two or more ink compositions are loaded into an ink jet apparatus. As a result, a multicolor image can be recorded in the same manner as described above, and the same results and effects as in the above-described embodiment can be obtained.

Claims (19)

A pigment coated with at least a first resin dispersant containing a structural unit represented by the following general formula (I) and a second resin dispersant containing a structural unit represented by the following general formula (II), organic An ink composition comprising a solvent and water.

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

[Wherein, R ² represents a hydrogen atom or a methyl group, and L ¹ represents a substituted or unsubstituted phenylene group. L ² represents a single bond or a divalent linking group. Ar ² represents a monovalent group derived from a condensed aromatic ring having 8 or more carbon atoms, a hetero ring in which an aromatic ring is condensed, or a benzene ring in which two or more are connected. ] The ink composition according to claim 1, wherein the aromatic ring represented by Ar ¹ in the general formula (I) is an unsubstituted or substituted benzene ring. The ink composition according to claim 1 or 2, wherein Ar ² in the general formula (II) is a monovalent group derived from acridone or phthalimide. At least one of the first resin dispersant and the second resin dispersant includes a hydrophilic structural unit (A) and a hydrophobic structural unit (B), and the content ratio of the aromatic ring is that of the resin dispersant. 20% by mass or less of the total mass,
The ratio of the hydrophilic structural unit (A) is 15% by mass or less of the total mass of the resin dispersant, and the hydrophilic structural unit (A) includes at least a structural unit derived from (meth) acrylic acid. The ink composition according to claim 3.   The ink composition according to any one of claims 1 to 4, wherein the weight average molecular weight of at least one of the first resin dispersant and the second resin dispersant is 30,000 or more.   The ink according to any one of claims 1 to 5, wherein the pigment is a pigment coated with at least one of the first resin dispersant and the second resin dispersant by a phase inversion emulsification method. Composition.   The ink composition according to any one of claims 1 to 6, further comprising a surfactant.   The ink composition according to any one of claims 1 to 7, further comprising resin particles. The ink composition according to any one of claims 1 to 8,
A treatment liquid containing an aggregating agent that aggregates the components in the ink composition when mixed with the ink composition;
Ink set containing.   The ink set according to claim 9, wherein the pH of the ink composition at 25 ° C is 7.5 or more, and the pH of the treatment liquid at 25 ° C is 4 or less.   The ink set according to claim 9 or 10, wherein the flocculant is an organic carboxylic acid.   An ink application step of applying the ink composition according to any one of claims 1 to 8 onto a recording medium by an inkjet method, and a component in the ink composition when mixed with the ink composition And a treatment liquid application step of applying a treatment liquid containing an aggregating agent to a recording medium, and forming an image by bringing the ink composition and the treatment liquid into contact with each other.   After applying the treatment liquid onto the recording medium by the treatment liquid application step, an ink composition is applied, and an image is formed by bringing the ink composition applied by the ink application step into contact with the applied treatment liquid. The image forming method according to claim 12. At least a pigment, a first resin dispersant containing a structural unit represented by the following general formula (I), and a second resin dispersant containing a structural unit represented by the following general formula (II): Pigment dispersion containing.

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

[Wherein, R ² represents a hydrogen atom or a methyl group, and L ¹ represents a substituted or unsubstituted phenylene group. L ² represents a single bond or a divalent linking group. Ar ² represents a monovalent group derived from a condensed aromatic ring having 8 or more carbon atoms, a hetero ring in which an aromatic ring is condensed, or a benzene ring in which two or more are connected. ] The pigment dispersion according to claim 14, wherein the aromatic ring represented by Ar ¹ in the general formula (I) is an unsubstituted or substituted benzene ring. The pigment dispersion according to claim 14 or 15, wherein Ar ² in the general formula (II) is a monovalent group derived from acridone or phthalimide. At least one of the first resin dispersant and the second resin dispersant includes a hydrophilic structural unit (A) and a hydrophobic structural unit (B), and the content ratio of the aromatic ring is that of the resin dispersant. 20% by mass or less of the total mass,
The ratio of the said hydrophilic structural unit (A) is 15 mass% or less of the total mass of a resin dispersing agent, The said hydrophilic structural unit (A) contains the structural unit derived from at least (meth) acrylic acid. The pigment dispersion liquid according to any one of claims 16 to 16.   The pigment dispersion liquid according to any one of claims 14 to 17, wherein the weight average molecular weight of at least one of the first resin dispersant and the second resin dispersant is 30,000 or more.   The pigment dispersion according to any one of claims 14 to 18, wherein the pigment is coated with at least one of the first resin dispersant and the second resin dispersant by a phase inversion emulsification method. .