JP2011042737A - Colorant dispersion resin, colorant dispersion, ink composition, ink set, and image forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a colorant dispersion resin that is excellent in dispersion control for change in liquid properties (especially pH change) of dispersed particles, and finely disperses a colorant, and is excellent in aging stability after dispersion. <P>SOLUTION: The colorant dispersion resin includes a structural unit (a) that has a plurality of ionic groups and also has the minimum number of the atoms of 7 or less between the ionic groups. The ionic group is preferably at least one of a carboxy group, a sulfonate group, and a phosphate group. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a colorant-dispersed resin that disperses a colorant, and a colorant dispersion, an ink composition, an ink set, and an image forming method using the same.

  In recent years, inks have become water-based due to increasing needs such as resource protection, environmental protection, and improved work stability. The quality required for the water-based ink is, like the oil-based ink, fluidity, storage stability, gloss of the film, sharpness, coloring power, and the like.

  However, since most pigments are significantly inferior in suitability for pigment dispersibility in aqueous vehicles as compared with oil-based vehicles, satisfactory quality cannot be obtained by ordinary dispersion methods. Until now, the use of various additives such as aqueous pigment dispersion resins and surfactants has been studied, but they satisfy the suitability of pigment dispersibility and are comparable to existing high-quality oil-based inks. A water-based ink has not been obtained.

  In connection with such a situation, for example, an aqueous pigment ink containing a pigment dispersion encapsulated with a polymer containing 20 to 70% by mass of an aromatic ring is disclosed (for example, see Patent Document 1).

  Also disclosed is an ink jet recording pigment ink comprising a pigment dispersion in which a random copolymer of a hydrophilic monomer and a hydrophobic monomer of 50 to 80% by weight based on the weight of the polymer is used as a dispersant (for example, , See Patent Document 2).

US Patent Application Publication No. 2005/0124726 US Patent Application Publication No. 2006/0014855

  However, in the above-mentioned aqueous pigment ink, the content of the aromatic ring contained in the polymer that encapsulates and disperses the pigment is too high, and the ink obtained by applying the technique disclosed herein has various performances of the water-based ink, In particular, the redispersibility after the solvent component was discharged to some extent was not satisfactory. In addition, in the ink jet recording pigment ink using a random copolymer as a dispersant, the hydrophilicity of the dispersant polymer becomes too high, so the ink obtained by applying the technique disclosed herein has a high viscosity, Further, the stability over time of the viscosity and the dispersed particle diameter was insufficient.

  Furthermore, inks obtained by applying any of the above-mentioned conventional prior arts do not satisfy the stability of ejection and the recovery of ejection after the completion of ejection when used for inkjet recording.

  The present invention has been made in view of the above, and is excellent in dispersibility control with respect to liquidity change (particularly pH change) of dispersed particles, finely disperse the colorant, and excellent in temporal stability after dispersion. The dispersion state of the colorant-dispersed resin and the dispersed particles is easily controlled by change in liquidity (particularly pH change), the colorant is finely dispersed, has excellent temporal stability, and has excellent water redispersibility. Ink composition with excellent colorant dispersion, ejection stability and recovery, low image bleeding, excellent response (aggregation) when liquidity changes (especially pH change), low image bleeding, stable ejection It is an object of the present invention to provide an ink set having excellent properties and recoverability, and an image forming method capable of forming an image having good bleeding resistance with little blurring while maintaining ejection stability and recoverability. The challenge is to achieve.

  The present invention relates to a structure having a predetermined number of atoms between ionic groups in a repeating structural unit containing a plurality of ionic groups such as acid groups and having a plurality of coordination sites (eg, ionic groups are acid groups). In this case, by giving the dispersion resin a structure having a chelate group, proton consumption is likely to proceed, and therefore the surface of the dispersed particles, that is, the pH environment around the dispersed resin covering the dispersed particles changes. Focusing on the molecular structure that increases the charge loss on the surface of the dispersed particles, that is, greatly reduces the zeta potential, water redispersibility is obtained after the solvent component is lost, especially the change in pH It has been achieved on the basis of the knowledge that the change of the dispersion state with respect to the above becomes sensitive and that the dispersion state can be greatly changed.

Specific means for achieving the above object are as follows.
<1> A colorant-dispersed resin having a structural unit (a) having a plurality of ionic groups and having a minimum number of atoms of 7 or less between the ionic groups.
<2> The colorant-dispersed resin according to <1>, further comprising a hydrophobic structural unit (b) having an aromatic ring via a linking group in an atom forming the main chain.
<3> The colorant-dispersed resin according to <2>, wherein at least one of the structural units (b) is a structural unit represented by the following general formula (1).

In General Formula (1), R ₁ represents a hydrogen atom or a methyl group, and L ₁ represents ^* —COO—, ^* —OCO—, ^* —CONH—, ^* —CONR ₃ —, or substituted or unsubstituted. Represents a phenylene group. R ₃ represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and the * mark in the group represented by L ₁ represents a bond connected to the main chain. L ₂ represents a single bond or a divalent linking group formed by combining one or more selected from the following linking group group. Ar 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.
Linking Group: alkylene group having 1 to 12 carbon atoms, an alkenylene group having 2 to 12 carbon _{atoms, -CO -, - NR 7 -} ( alkyl group _{R 7} is a hydrogen atom or a carbon atoms 1 to 6), - O -, - S -, - SO -, - SO 2 - ]

<4> The colorant-dispersed resin according to <2>, wherein the structural unit (b) has a structure represented by the following general formula (2).
In the following general formula (2), * represents a connection point with the main chain, and L represents a divalent linking group having 1 to 30 carbon atoms.

<5> The L ₁ is ^* —COO—, ^* —CONH—, or ^* —CONR ₃ — (R ₃ represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms). The colorant-dispersed resin according to <3>.
<6> The coloring according to any one of <1> to <5>, wherein the ionic group is at least one of a carboxyxyl group, a sulfonic acid group, and a phosphoric acid group. Agent-dispersed resin.
<7> The colorant-dispersed resin according to any one of <1> to <6>, wherein the structural unit (a) has an amino group structure.
<8> A colorant dispersion comprising a colorant and the colorant-dispersed resin according to any one of <1> to <7>.
<9> An ink composition comprising a colorant and the colorant-dispersed resin according to any one of <1> to <7>.
<10> An ink set comprising the ink composition according to <9> and a treatment liquid containing an aggregating component for aggregating the components in the ink composition.
<11> An ink application step of applying the ink composition according to <9> onto a recording medium, and a process of applying a treatment liquid containing an aggregating component that aggregates the components in the ink composition onto the recording medium. And a liquid application step.

According to the present invention, there is provided a colorant-dispersed resin that is excellent in dispersibility control with respect to liquid property change (particularly pH change) of dispersed particles, finely disperses a colorant, and has excellent temporal stability after dispersion. be able to.
According to the present invention, it is easy to control the dispersion state of the dispersed particles dispersed by change in liquidity (particularly pH change), the colorant is finely dispersed, excellent in temporal stability, and excellent in water redispersibility. An agent dispersion can be provided.
According to the present invention, an ink composition having excellent ejection stability and recoverability, less image bleeding, and excellent response (aggregation) when liquidity changes (particularly pH change), less image bleeding, and ejection It is possible to provide an ink set having excellent stability and recoverability.
According to the present invention, it is possible to provide an image forming method capable of forming an image having excellent rub resistance with little bleeding while maintaining ejection stability and recoverability.

  Hereinafter, the colorant-dispersed resin of the present invention, and the colorant dispersion, ink composition, ink set, and image forming method using the same will be described in detail.

<Colorant dispersed resin>
The colorant-dispersed resin of the present invention comprises a plurality of structural units (a) having the same or different ionic groups and having a minimum number of atoms of 7 or less between the ionic groups. It is a thing. That is, when the structural unit (a) has a plurality of ionic groups, the number of atoms is set to 7 or less when counted so that the number of atoms existing between any two ionic groups is minimized.

In the present invention, the structural unit in the dispersion resin has a plurality of ionic groups, and the number of atoms between the ionic groups having the smallest number of atoms between any two ionic groups is 7 or less. By having the structure, the charge repulsion between the colorants is likely to occur, so that dispersibility is improved. Thereby, a coloring agent is disperse | distributed finely and the dispersion excellent in temporal stability is obtained.
In addition, when the environment around the dispersed polymer changes, the structure part having a plurality of coordination sites in the polymer on the surface of the dispersed particle (eg, chelate group when the ionic group is an acid group) acts on the pH. Rises rapidly, and charge disappearance (that is, a decrease in zeta potential) increases on the surface of the dispersed particles. That is, the change in the dispersion state due to the pH change becomes sensitive, and the dispersion / aggregation state of the dispersed colorant (pigment or the like) becomes easy. When the dispersed particles are agglomerated, the aggregability is improved.

-Structural unit (a)-
The structural unit (a) in the present invention has a plurality of ionic groups (anionic groups or cationic groups), and the atoms between the ionic groups having the smallest number of atoms between any two ionic groups. It can be formed by polymerizing monomers having a number of 7 or less. Alternatively, it may be formed by polymerizing a polymer having no ionic group and then introducing an ionic group (anionic group or cationic group) into the polymer chain.

  Examples of the ionic group include an anionic group such as a carboxyl group, a sulfonic acid group, and a phosphoric acid group, and a cationic group such as an amino group and an ammonium group. Among them, the ionic group tends to cause charge repulsion between the colorants, improves dispersibility, has a large pH change at the time of aggregation, and improves the aggregation property, so that the carboxyl group, sulfonic acid group, and phosphoric acid are improved. One or more anionic groups selected from groups are preferred.

  In the structural unit (a), the minimum number of atoms between the ionic groups is 7 or less, more preferably 6 or less, and even more preferably 5 or less from the viewpoint that charge repulsion between the colorants easily occurs and dispersibility is improved. . The lower limit is preferably 1 or more, and more preferably 2 or more.

  The structural unit (a) preferably has an amino group structure in its repeating structure. Having an amino group structure is advantageous for improving cohesion.

  When the colorant-dispersed resin in the present invention is a branched polymer such as a graft polymer, a comb polymer, or a star polymer, the atoms that form the so-called “side chain” or “branch polymer” of the graft polymer or comb polymer are also “main chain”. Are similarly regarded as atoms forming the “main chain”.

  The preferred amount of the ionic group contained in the structural unit (a) varies depending on the type of the ionic group, but is 1% by mass or more and less than 80% by mass with respect to the total mass of the colorant-dispersed resin. Is more preferably 2% by mass or more and less than 70% by mass, and particularly preferably 3% by mass or more and less than 60% by mass. When the proportion of the ionic group in the structural unit (a) is 1% by mass or more, the charge repulsion when used as an aqueous dispersion is good, and the pigment is miniaturized and excellent in dispersion stability. Further, when the ratio of the ionic group is less than 80% by mass with respect to the total mass of the colorant-dispersed resin, the water-solubility of the dispersant does not become too high, and the desorption of the dispersant from the pigment surface is suppressed, which is good. Dispersion stability is obtained.

When the colorant-dispersed resin of the present invention has an acidic group such as a carboxyl group, the acid value of the colorant-dispersed resin is preferably 5 mgKOH / g or more and less than 500 mgKOH / g, and preferably 10 mgKOH / g or more and less than 450 mgKOH / g. More preferably, it is particularly preferably 15 mgKOH / g or more and less than 400 mgKOH / g. The acid value here is defined as the mass (mg) of KOH required to completely neutralize 1 g of the colorant-dispersing resin, and is a method described in JIS standard (JIS K 0070: 1992). It is to be measured.
When the acid value of the colorant-dispersed resin containing an acidic group such as carboxylic acid is 5 mgKOH / g or more, charge repulsion of the dispersion due to the dissociated carboxyl group is likely to occur, resulting in improved dispersibility. When the amount is 500 mgKOH / g or less, the hydrophilicity of the polymer does not become too high, so that it is adsorbed by the colorant and elution into the aqueous medium is suppressed.

  Hereinafter, preferred specific examples (exemplary compounds MM-1 to MM-22) of monomers for forming the structural unit (a) are shown below. However, the present invention is not limited to the following.

  The colorant-dispersed resin having the structural unit (a) may be a random copolymer in which each structural unit is irregularly introduced or a block copolymer in which the structural units are regularly introduced. In the case of a block copolymer, each structural unit may be synthesized in any order of introduction, and the same component may be used twice or more. Among these, a random copolymer is preferable in terms of versatility and manufacturability.

  The colorant-dispersed resin of the present invention preferably further has the following structure (such as a hydrophobic / hydrophilic structural unit) from the viewpoint of improving dispersibility.

-Hydrophobic structural unit (b)-
The colorant-dispersed resin in the present invention has a hydrophobic structural unit (b) containing an aromatic ring via a linking group at an atom forming a polymer main chain as a hydrophobic structural unit (hereinafter simply referred to as “hydrophobic structure”). It is preferable that at least the unit (b) "is included.
Here, “through a linking group” means that the aromatic ring and the atom forming the main chain structure of the polymer have a structure bonded through the linking group. By having such a form, since an appropriate distance between the hydrophilic structural unit and the hydrophobic aromatic ring in the colorant-dispersed resin is maintained, there is an interaction between the colorant-dispersed resin and the colorant. It becomes easy to occur, it adsorbs firmly, and the result dispersibility improves.

  The content ratio of the hydrophobic structural unit (b) having an aromatic ring via a linking group to the atom forming the main chain varies depending on the type of the aromatic ring, but within the range in which the aromatic ring content is determined. , Preferably from 10% by weight to less than 90% by weight, more preferably from 20% by weight to less than 85% by weight, and from 30% by weight to less than 80% by weight, based on the total weight of the colorant-dispersed resin. It is particularly preferred. When the content ratio of the hydrophobic structural unit (b) is 10% by mass or more, the adsorptivity of the dispersant to the pigment is good, and the finer pigment and dispersion stability are excellent. On the other hand, when the content ratio of the hydrophobic structural unit (b) is 90% by mass or less, the dispersing agent does not become hydrophobic and the cohesiveness is kept low, so that the dispersion stability is excellent.

  In the present invention, the aromatic ring in the hydrophobic structural unit (b) is preferably a substituted or unsubstituted benzene ring or a substituted or unsubstituted naphthalene ring. Preferred substituents when substituted include an alkyl group, an alkyloxy group, a halogen atom, a cyano group, a nitro group, etc. From the viewpoint of dispersibility, availability, and versatility of the colorant, an aromatic ring Is preferably an unsubstituted benzene ring.

  The benzene ring in the hydrophobic structural unit (b) preferably has a structure represented by the following general formula (2) and is introduced into the colorant-dispersed resin.

  In General formula (2), L represents a C1-C30 bivalent coupling group, More preferably, it is a C1-C25 bivalent coupling group, Most preferably, it is C1-C20. It is a divalent linking group. The divalent linking group may be a saturated group or an unsaturated group, may have a linear structure, or may have a branched structure or a ring structure. The divalent linking group may contain a heteroatom selected from O, N, and S. “*” Represents a connection point with the main chain of the colorant-dispersed resin.

  As the hydrophobic structural unit (b) having a benzene ring via a linking group at the atom forming the main chain of the colorant-dispersed resin, among the forms in which the structure represented by the general formula (2) is introduced, In particular, a structure represented by the following general formula (3) is preferable.

In General Formula (3), R ₁ represents a hydrogen atom, a methyl group, or a halogen atom (for example, a chlorine atom, a bromine atom, or an iodine atom), and L ₁ represents ^* —COO—, ^* —OCO—, ^* — CONR _2- , ^* -O-, or a substituted or unsubstituted phenylene group, R ₂ represents a hydrogen atom or an alkyl group having 1 to 10 carbon atoms (for example, a methyl group, an ethyl group, (n-, i- ) Propyl group, n-butyl group and the like. Incidentally, symbol * in the group represented by L ₁ represents a connecting point with the main chain. L ₂ represents a single bond or a divalent linking group having 1 to 30 carbon atoms, and a preferred range thereof is the same as L.
Here, there is no restriction | limiting as a substituent in the case of the said substitution, For example, cyano groups etc. are mentioned, such as a halogen atom, an alkyl group, an alkoxy group, a hydroxyl group.

Among the general formula (3), there is a structural unit in which R ₁ is a hydrogen atom or a methyl group, L ₁ is ^* —COO—, and L ₂ is a divalent linking group having 1 to 15 carbon atoms. More preferably, R ₁ is a hydrogen atom or a methyl group, L ₁ is ^* —COO—, and L ₂ is a divalent linking group containing an alkylene group or oxyalkylene group having 1 to 12 carbon atoms. A structural unit, R ₁ is a hydrogen atom or a methyl group, L ₁ is —COO—, and L ₂ is a structural unit having 1 to 4 carbon atoms, particularly preferably R _1. Is a hydrogen atom or a methyl group, L ₁ is —COO—, and L ₂ is a structural unit having a C 1 divalent linking group.
Corresponding monomers include at least one selected from benzyl acrylate, benzyl methacrylate, phenoxyethyl acrylate, phenoxyethyl methacrylate, and oligo (with about 2 to 6 repeating units) ethylene glycol monophenyl ether acrylates and methacrylates. Can be mentioned. Of these, 2-phenoxyethyl acrylate or 2-phenoxyethyl methacrylate is most preferred.

  When the structural unit represented by the general formula (3) is a structural unit derived from phenoxyethyl acrylate or phenoxyethyl methacrylate, the total of the structural unit derived from the phenoxyethyl acrylate and the structural unit derived from phenoxyethyl methacrylate The content of the colorant-dispersed resin is preferably 40% by mass to 53% by mass, more preferably 42% by mass to 53% by mass, and 45% by mass to 53% by mass. Is particularly preferred.

  Moreover, it is preferable that the structural unit represented by the following general formula (1) is included as a copolymer unit as the structural unit (b).

In the general formula (1), R ₁ represents a hydrogen atom or a methyl group. L ₁ represents ^* —COO—, ^* —OCO—, ^* —CONH—, ^* —CONR ₃ —, or a substituted or unsubstituted phenylene group. R ₃ represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms (for example, a methyl group, an ethyl group, a (n-, i-) propyl group, an n-butyl group, etc.). Incidentally, symbol * in the group represented by L ₁ represents a connecting point with the main chain. L ₁ is preferably ^* —COO—, ^* —CONH—, ^* —CONCH ₃ —, and more preferably ^* —COO—.

L ₂ represents a single bond or a divalent linking group formed by combining one or more selected from the following linking group group. When L ₂ selected from the group of linking groups is a combination of two or more divalent linking groups, they may be the same or different.
(Linked group group)
Alkylene group having 1 to 12 carbon atoms, an alkenylene group having 2 to 12 carbon _{atoms, -CO -, - NR 7 -} ( alkyl group _{R 7} is a hydrogen atom or a carbon atoms 1~6), - O -, - S -, - SO -, - SO 2 -

The alkylene group preferably has 1 to 12 carbon atoms, and more preferably 2 to 6 carbon atoms.
The alkenylene group preferably has 2 to 12 carbon atoms, and more preferably 2 to 4 carbon atoms.
The alkylene group and the alkenylene group may each independently be substituted with a substituent (such as an alkyl group having 1 to 6 carbon atoms, a halogen atom, a cyano group, or an alkoxy group having 1 to 6 carbon atoms).

L ₂ is a single bond or a divalent linking group containing an alkylene group, —O—, —CO—, or —NR ₇ — (R ₇ is a hydrogen atom or an alkyl group having 1 to 6 carbon atoms). It is preferably a divalent linking group containing an alkylene group, —O—, or —CO—.

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

  The heterocyclic ring condensed with the aromatic ring is a compound in which an aromatic compound not containing a hetero atom (preferably a benzene ring) and a cyclic compound having a hetero atom are condensed at least. 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, and in this case, the hetero atoms may be the same as or different from each other. Specific examples of the heterocyclic ring condensed with an aromatic ring include phthalimide, naphthalimide, acridone, carbazole, benzoxazole, and benzothiazole.

The term “two or more linked benzene rings” means that two or more benzene rings are bonded by a single bond, a divalent linking group, or a trivalent linking group. The divalent linking group is a divalent group selected from the group consisting of an alkylene group having 1 to 4 carbon atoms, —CO—, —O—, —S—, —SO—, —SO ₂ — and combinations thereof. A linking group is preferred. Examples of the trivalent linking group include a methine group. Here, the benzene rings may be bonded to each other by a plurality of linking groups, and the plurality of linking groups may be the same or different. The number of benzene rings is preferably 2 to 6, and more preferably 2 to 3. Specific examples of two or more linked benzene rings include biphenyl, triphenylmethane, diphenylmethane, diphenyl ether, diphenylsulfone, and the like.

Ar is preferably a monovalent group derived from naphthalene, biphenyl, triphenylmethane, phthalimide, naphthalimide, acridone, fluorene, anthracene, phenanthrene, diphenylmethane, or carbazole. Naphthalene, biphenyl, phthalimide, naphthalimide, acridone A monovalent group derived from is more preferable. Each Ar may have a substituent. Examples of the substituent when Ar is substituted include an alkyl group, an alkoxyl group, an alkylcarbonyl group, an alkylcarbonyloxy group, an alkyloxycarbonyloxy group, a halogen group, and a cyano group, and more preferable substituents. Examples thereof include an alkyl group having 1 to 10 carbon atoms, an alkoxyl group having 1 to 10 carbon atoms, an alkylcarbonyl group having 1 to 10 carbon atoms, an alkylcarbonyloxy group having 1 to 10 carbon atoms, a chloro group, and a cyano group. Can do.
These substituents may be substituted with other substituents, and preferred substituents in this case are also as defined above. Moreover, when it has two or more substituents, each substituent may be the same or different. If possible, the substituents may be bonded to each other to form a ring.

  The copolymer having the structural unit represented by the general formula (1) may be introduced with a corresponding functional group by polymer reaction after obtaining the copolymer, but is represented by the following general formula (4). It is preferably formed by polymerizing the monomer.

In the general formula _{(4), R 1, L} 1, L 2, Ar is the same meaning as _{R 1,} L _1, L 2, Ar corresponding general formula (1), and preferred examples are also the same. Monomers represented by the general formula (4) may be used alone or in admixture of two or more.

  Hereinafter, specific examples (exemplary monomers M-1 to M-30) of the monomer represented by the general formula (4) will be given. However, the present invention is not limited to these specific examples.

  The colorant-dispersed resin of the present invention may be copolymerized with a monomer having an ionic group other than the structural unit (a), which is conventionally known in a polymer handbook or the like.

-Hydrophilic structural unit (c)-
The colorant-dispersed resin in the present invention can further include other hydrophilic structural unit different from the structural unit (a) as the hydrophilic structural unit (c). The hydrophilic structural unit may be a hydrophilic structural unit containing an ionic group.

  A hydrophilic structural unit containing an ionic group can be obtained by polymerizing an ionic group-containing monomer. After polymerizing a polymer having no ionic group, an ionic group (anionic property) is added to the polymer chain. Group or cationic group) may be introduced. Examples of the ionic group include an anionic group such as a carboxyl group, a sulfonic acid group, and a phosphoric acid group, and a cationic group such as an amino group and an ammonium group, and among them, a carboxyl group, a sulfonic acid group, and a phosphoric acid group. One or more anionic groups selected from groups are preferred.

Examples of the anionic group-containing monomer and the cationic group-containing monomer are listed below. However, the present invention is not limited to these.
Among the anionic group-containing monomers, those containing a carboxyl group include, for example, unsaturated carboxylic acid monomers such as acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid, citraconic acid, and β -Carboxyethyl acrylic acid, 2-methacryloyloxymethyl succinic acid, etc. are mentioned.
Examples of the sulfonic acid group-containing monomer include styrene sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid, 3-sulfopropyl (meth) acrylic acid ester, bis- (3-sulfopropyl) -itaconic acid ester, and the like. Can be mentioned.
Examples of the phosphoric acid group-containing monomer include vinyl phosphonic acid, vinyl phosphate, bis (methacryloxyethyl) phosphate, diphenyl-2-acryloyloxyethyl phosphate, diphenyl-2-methacryloyloxyethyl phosphate, dibutyl-2-acryloyloxyethyl. A phosphate etc. are mentioned.

Examples of the cationic group-containing monomer include tertiary amine-containing vinyl monomers and ammonium salt-containing vinyl monomers. A cationic group containing monomer can be included individually by 1 type or in combination of 2 or more types.
Examples of the tertiary amine-containing vinyl monomer include N, N-dimethylaminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylate, N, N-diethylaminoethyl (meth) acrylate, N, N- Examples include dimethylaminopropyl (meth) acrylamide, vinylpyrrolidone, 2-vinylpyridine, 4-vinylpyridine, 2-methyl-6-vinylpyridine, 5-ethyl-2-vinylpyridine, and the like.
Examples of the ammonium salt-containing monomer include N, N-dimethylaminoethyl (meth) acrylate quaternized product, N, N-diethylaminoethyl (meth) acrylate quaternized product, and N, N-dimethylaminopropyl (meth) acrylate quaternized product. And the like.

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

  Further, the colorant-dispersed resin of the present invention may be copolymerized with conventionally known monomer units in a polymer handbook or the like.

<Other structural unit (d)>
The colorant-dispersed resin of the present invention preferably contains a hydrophobic or hydrophilic structural unit (d) different from the above structural units (a) to (c). The content ratio of the structural unit (d) is more preferably 15% by mass, more than 15% by mass, and more preferably 15% by mass with respect to the total mass of the colorant-dispersed resin. And more preferably 40% by mass or less, particularly preferably 20% by mass or more and 30% by mass or less.

When the colorant-dispersed resin has the structural unit (d), the colorant dispersion of the present invention exhibits good dispersibility. The mechanism is unknown in detail, but is presumed as follows. That is,
The colorant-dispersed resin is composed of a hydrophobic structural unit (b) mainly showing affinity with the colorant, a structural unit (a) showing mainly affinity with an aqueous medium, and a hydrophilic structural unit (c). Including structural units of the property If the colorant-dispersed resin is composed solely of these, each of the hydrophobic structural unit (b), the structural unit (a), and the hydrophilic structural unit (c) inhibits the function of each other, resulting in dispersion. May be insufficient. It is considered that good dispersibility is exhibited when the colorant-dispersed resin contains a structural unit (d) that exhibits intermediate properties between a hydrophobic structural unit and a hydrophilic structural unit.

When the structural unit (d) is a hydrophobic structural unit, the structural unit (d) can be formed by polymerizing a monomer corresponding to the structural unit (d). Moreover, you may introduce | transduce a hydrophobic functional group into a polymer chain after superposition | polymerization of a polymer.
The monomer in the case where the structural unit (d) is a hydrophobic structural unit is not particularly limited as long as it has a functional group capable of forming a polymer and a hydrophobic functional group, and any known monomers Can also be used. As the monomer in this case, vinyl monomers ((meth) acrylates, (meth) acrylamides, styrenes, vinyl esters, etc.) are preferable from the viewpoints of availability, handleability, and versatility.
Specific examples include (meth) acrylates such as methyl (meth) acrylate, ethyl (meth) acrylate, (iso) propyl (meth) acrylate, (iso or tertiary) butyl (meth) acrylate, 2-ethylhexyl. Examples thereof include alkyl (meth) acrylates such as (meth) acrylate, (iso) octyl (meth) acrylate, (iso) decyl (meth) acrylate, and (iso) stearyl (meth) acrylate. (Meth) acrylate is preferred. As (meth) acrylamides, N-methyl (meth) acrylamide, N-ethyl (meth) acrylamide, N-propyl (meth) acrylamide, N-isopropyl (meth) acrylamide, Nn-butylacryl (meth) amide, N-t-butyl (meth) acrylamide, N-cyclohexyl (meth) acrylamide, N- (2-methoxyethyl) (meth) acrylamide, N, N-dimethyl (meth) acrylamide, N, N-diethyl (meth) acrylamide , (Meth) acrylamides such as vinyl (meth) acrylamide, N, N-diallyl (meth) acrylamide, N-allyl (meth) acrylamide, etc., (meth) acrylamide, N, N-dimethyl (meth) acrylamide preferable. As styrenes, 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, bromostyrene, chloro Examples include methylstyrene, hydroxystyrene protected with a group that can be deprotected by an acidic substance (for example, t-Boc, etc.), methyl vinylbenzoate, α-methylstyrene, vinylnaphthalene, and the like. Styrene, α-methylstyrene Is preferred. Examples of 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 preferred.
These can be used alone or in admixture of two or more.

When the structural unit (d) is a hydrophilic structural unit, the structural unit (d) preferably has a nonionic hydrophilic group. The structural unit (d) can be formed by polymerizing a monomer corresponding to the structural unit (d), but a hydrophilic functional group may be introduced into the polymer chain after the polymerization of the polymer.
The monomer forming the structural unit (d) is not particularly limited as long as it has a functional group capable of forming a polymer and a nonionic hydrophilic functional group, and any known monomer is used. However, vinyl monomers are preferred from the viewpoints of availability, handleability, and versatility.
Examples of vinyl monomers include (meth) acrylates, (meth) acrylamides, and vinyl esters having a hydrophilic functional group. Examples of the hydrophilic functional group include a hydroxyl group, an amide group (the nitrogen atom is unsubstituted), and alkylene oxide polymers such as polyethylene oxide and polypropylene oxide as described later. Of these, hydroxyethyl (meth) acrylate, hydroxybutyl (meth) acrylate, (meth) acrylamide, and (meth) acrylate containing an alkylene oxide polymer are particularly preferable.

  The structural unit (d) preferably includes a hydrophilic structural unit having an alkylene oxide polymer structure. The alkylene moiety of the alkylene oxide polymer preferably has 1 to 6 carbon atoms, more preferably 2 to 6 carbon atoms, and particularly preferably 2 to 4 carbon atoms from the viewpoint of hydrophilicity / hydrophobicity. Moreover, as a polymerization degree of an alkylene oxide polymer, 1-120 are preferable, 1-60 are more preferable, and 1-30 are especially preferable.

  It is also a preferred embodiment that the structural unit (d) is a hydrophilic structural unit containing a hydroxyl group. The number of hydroxyl groups in the structural unit (d) is not particularly limited, and is preferably 1 to 4 from the viewpoint of hydrophilicity / hydrophobicity of the colorant-dispersed resin and compatibility with the solvent and other monomers during polymerization. Is more preferable, and 1-2 is particularly preferable.

  In the present invention, the structural unit (a) having a plurality of ionic groups and having a minimum number of atoms of 7 or less between the ionic groups, and the hydrophobic structural unit, the general formula (1) or the general formula (3 And a structural unit represented by the general formula (1) as a hydrophobic structural unit together with the structural unit (a). ) Is more preferably a dispersion resin in which Ar is a monovalent group derived from naphthalene, biphenyl, phthalimide, naphthalimide, or acridone. In particular, together with the structural unit (a), a hydrophobic structural unit represented by the general formula (1) (Ar: a monovalent group derived from naphthalene, biphenyl, phthalimide, naphthalimide, and acridone), an alkyl A dispersion resin having a structural unit derived from (meth) acrylate or (meth) acrylamide is more preferable.

Furthermore, the molecular weight range of the colorant-dispersed resin is a weight average molecular weight (Mw), preferably 1000 to 1,000,000, more preferably 2000 to 500,000, and still more preferably 3000 to 150,000. By setting the molecular weight within the above range, the steric repulsion effect as a dispersant tends to be good, and the steric effect is preferable from the viewpoint that adsorption to the colorant does not take time.
In addition, the molecular weight distribution (weight average molecular weight value / number average molecular weight value) of the colorant-dispersed resin is preferably 1 to 6, and more preferably 1 to 4. By setting the molecular weight distribution within the above range, it is preferable from the viewpoint of shortening the dispersion time of the pigment and stability with time of the dispersion.
Here, the number average molecular weight and the weight average molecular weight are detected by a solvent THF and a differential refractometer using a GPC analyzer using columns of TSKgel GMHxL, TSKgel G4000HxL, and TSKgel G2000HxL (both are trade names manufactured by Tosoh Corporation). The molecular weight is expressed using polystyrene as a standard substance.

The colorant-dispersed resin 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.
Examples of the polymerization initiation method include a method using a radical initiator, a method of irradiating light or radiation, and the like. These polymerization methods and polymerization initiation methods are, for example, the revised version of Tsuruta Junji “Polymer Synthesis Method” (published by Nikkan Kogyo Shimbun, 1971), Takatsu Otsu, Masato Kinoshita, “Experimental Methods for Polymer Synthesis” It is described in pp. 47-154 published in 1972. Among the 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 , Methylene chloride, chloroform, dichloroethane, methanol, ethanol, 1-propanol, 2-propanol, 1-butanol and the like, or a mixture of two or more organic solvents such as water may be used.
The polymerization temperature needs to be set in relation to the molecular weight of the polymer to be produced, the type of initiator, and the like, and is usually about 0 ° C. to 100 ° C., but the polymerization is preferably performed in the range of 50 to 100 ° C.
The reaction pressure can be appropriately selected, but it is usually preferably 1 to 100 kg / cm ² , particularly preferably about 1 to 30 kg / cm ² . The reaction time is about 5 to 30 hours. The obtained polymer may be subjected to purification such as reprecipitation.

  As specific examples of the colorant-dispersed resin of the present invention, preferred compounds (Exemplary Compounds P-1 to P-15) are listed below. However, the present invention is not limited to the following.

<Colorant dispersion>
The colorant dispersion of the present invention contains a colorant and the colorant-dispersed resin of the present invention described above, and can be constituted using other components as necessary. Details of the colorant-dispersed resin are as described above.

The colorant dispersion of the present invention includes the above-described colorant-dispersed resin, so that charge repulsion between the colorants easily occurs. Therefore, when the colorant is dispersed, the colorant is finely dispersed, A dispersion having excellent stability over time is obtained.
In addition, when the pH environment around the dispersion resin changes, a structure portion having a plurality of coordination sites in the polymer on the surface of the dispersion particle (eg, chelate group when the ionic group is an acid group) acts. Since the pH is likely to increase rapidly, the charge disappearance (that is, the decrease in zeta potential) increases on the surface of the dispersed particles. That is, the change in the dispersion state due to pH is sensitive, and the dispersion / aggregation state of the dispersed colorant (pigment or the like) can be easily controlled. When the dispersed particles are agglomerated, the aggregability is improved.

-Colorant-
The colorant dispersion of the present invention contains at least one colorant.
As the colorant, known dyes, pigments and the like can be used without particular limitation. Among these, from the viewpoint of ink colorability, a colorant that is almost insoluble or hardly soluble in water is preferable. Specific examples include various pigments, disperse dyes, oil-soluble dyes, dyes forming J-aggregates, and the like, and more preferably pigments from the viewpoint of light resistance.

There is no restriction | limiting in particular as said pigment, According to the objective, it can select suitably, For example, any of an organic pigment and an inorganic pigment may be sufficient.
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 quinophthalone pigments. Examples of dye chelates include basic dye chelates and acid dye chelates.

  Examples of the inorganic pigment 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 said carbon black, what was manufactured by well-known methods, such as a contact method, a furnace method, and a thermal method, is mentioned, for example.

  Specific examples of carbon black include Raven7000, Raven5750, Raven5250, Raven5000 ULTRAII, Raven 3500, Raven2000, Raven1500, Raven1250, Raven1200, Raven1190 ULTRAII, Raven1170, Raven1255, Raven1080, Raven1060, Raven700 (above Colombian Carbon) , Regal400R, Regal330R, Regal660R, Mogul L, Black Pearls L, Monarch 700, Monarch 800, Monarch 880, Monarch 900, Monarch 1000, Monarch 1100, Monarch 1300, Monarch 1400 (above, manufactured by Cabot), Color Black FW1, Color Black FW2, Color Black FW2V, Color Black 18, Color Black FW200, Color Black S150, Color Black S160, Color Black S170, Printex U, Printex V, Printex140U, Printex140V, Special Black 6, Special Black 5, Special Black 4A , Special Black4 (Degussa), No.25, No.33, No.40, No.45, No.47, No.52, No.900, No.2200B, No.2300, MCF-88 , MA600, MA7, MA8, MA100 (Mitsubishi Chemical Co., Ltd.). However, it is not limited to these.

Specific examples of organic pigments include C.I. pigments for yellow ink. I. Pigment Yellow 1, 2, 3, 4, 5, 6, 7, 10, 11, 12, 13, 14, 14C, 16, 17, 24, 34, 35, 37, 42, 53, 55, 65, 73 , 74, 75, 81, 83, 93, 95, 97, 98, 100, 101, 104, 108, 109, 110, 114, 117, 120, 128, 129, 138, 150, 151, 153, 154, 155 , 180, and the like, and C.I. I. Pigment Red 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 21, 22, 23, 30, 31 , 32, 37, 38, 39, 40, 48 (Ca), 48 (Mn), 48: 2, 48: 3, 48: 4, 49, 49: 1, 50, 51, 52, 52: 2, 53 : 1, 53, 55, 57 (Ca), 57: 1, 60, 60: 1, 63: 1, 63: 2, 64, 64: 1, 81, 83, 87, 88, 89, 90, 101 ( Bengal), 104, 105, 106, 108 (Cadmium Red), 112, 114, 122 (Quinacridone Magenta), 123, 146, 149, 163, 166, 168, 170, 172, 177, 178, 179, 184, 185 , 190, 193, 202, 209, 219, 269, etc., and C.I. I. And CI Pigment Violet 19. Pigments for magenta inks are especially C.I. I. Pigment Red 122 is preferred. Examples of the pigment for cyan ink include C.I. I. Pigment Blue 1, 2, 3, 15, 15: 1, 15: 2, 15: 3, 15:34, 16, 17: 1, 22, 25, 56, 60, C.I. I. Bat blue 4, 60, 63 and the like. I. Pigment Blue 15: 3 is preferred.
The above pigments may be used alone or in combination of a plurality selected from the above-mentioned groups or between the groups.

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

-Aqueous liquid medium-
The colorant dispersion of the present invention contains at least water as an aqueous liquid medium, but can further contain a water-soluble organic solvent. By containing a water-soluble organic solvent, it is possible to prevent drying, impart wettability, or promote penetration. Specifically, by containing a water-soluble organic solvent as an anti-drying agent, for example, clogging due to drying of the ink using the colorant dispersion at the ink ejection port of the nozzle can be prevented. When contained as a drying inhibitor or wetting agent, a water-soluble organic solvent having a vapor pressure lower than that of water is preferred. Further, by containing a water-soluble organic solvent as a penetration accelerator, the ink ejected by the ink jet method can be better penetrated into the paper.

  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; glucose, mannose, fructose, ribose, xylose, arabinose, galactose, aldonic acid, glucitol, maltose, cellobiose, lacto Sugars such as sucrose, trehalose, maltotriose; sugar alcohols; hyaluronic acids; so-called solid wetting agents such as ureas; alkyl alcohols having 1 to 4 carbon atoms 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, Lenglycol 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 Glycol ethers such as 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; 2 -Pyrrolidone, N-methyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, formamide, aceto Examples include amide, dimethyl sulfoxide, sorbit, sorbitan, acetin, diacetin, triacetin, sulfolane and the like. These can be used alone or in combination of two or more.

  For the purpose of preventing drying and wetting, 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-2,4- Examples include 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 promoting penetration, polyol compounds are preferred, and aliphatic diols are preferred. 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, -Methyl-2-propyl-1,3-propanediol, 2,4-dimethyl-2,4-pentanediol, 2,5-dimethyl-2,5-hexanediol, 5-hexene-1,2-diol, Examples include 2-ethyl-1,3-hexanediol and 2,2,4-trimethyl-1,3-pentanediol. Among these, preferred examples include 2-ethyl-1,3-hexanediol and 2,2,4-trimethyl-1,3-pentanediol.

The water-soluble organic solvents may be used alone or in combination of two or more. The content of the water-soluble organic solvent is 1% by mass to 60% by mass, preferably 5% by mass to 40% by mass with respect to the total mass of the colorant dispersion.
The amount of water contained in the colorant dispersion is not particularly limited, but is preferably 10% by mass to 99% by mass, more preferably 30% by mass to 80% by mass, Preferably they are 50 mass% or more and 70 mass% or less.
The content of the aqueous liquid medium in the colorant dispersion of the present invention is preferably 1 to 70% by mass from the viewpoint of liquid properties such as drying prevention, permeability to an adherend, and viscosity. 60 mass% is more preferable, and 5-50 mass% is especially preferable. By setting the content of the aqueous liquid medium in the above range, the liquid properties such as the drying speed of the colorant dispersion, the permeability to the adherend, and the viscosity can be adjusted to an appropriate state.

-Method for producing colorant dispersion-
The colorant dispersion of the present invention is a method for producing the colorant dispersion of the present invention described above. Specifically, the colorant, the colorant-dispersed resin, and the colorant-dispersed resin are dissolved or dispersed. After the step of adding the aqueous solution (III) containing the basic substance (mixing / hydration step) to the mixture (II) with the organic solvent, the step of removing the organic solvent (solvent removal step) is provided. Obtainable.

  In the present invention, a colorant dispersion in which the colorant is finely dispersed and excellent in storage stability can be produced.

  The organic solvent needs to be able to dissolve or disperse the colorant-dispersed resin, but in addition to this, it preferably has a certain affinity for water. Specifically, the solubility in water at 20 ° C. is preferably 10% by mass or more and 50% by mass or less.

More specifically, the colorant dispersion of the present invention can be produced by a production method comprising the following steps (1) and (2), but is not limited thereto.
Step (1): Dispersing a mixture containing a colorant, a colorant-dispersed resin, and an organic solvent that dissolves or disperses the colorant-dispersed resin and a solution (III) containing a basic substance and containing water as a main component Step (2): Step of removing the organic solvent

  In the step (1), first, a colorant-dispersed resin is dissolved or dispersed in an organic solvent to obtain a mixture (II) (mixing step). Next, a solution containing a colorant, a basic substance and containing water as a main component (III), water and, if necessary, a surfactant, etc. are added to the mixture (II) and mixed and dispersed, An oil-type colorant dispersion is obtained.

  There is no particular limitation on the degree of neutralization. Usually, the liquid property of the finally obtained colorant dispersion is preferably such that the pH is, for example, 4.5 to 10. The pH can also be determined by the desired degree of neutralization of the water-insoluble vinyl polymer.

  The colorant, the colorant-dispersed resin, and other additives used in the method for producing the colorant dispersion are the same as those described in the section of the colorant dispersion described above, and preferred examples are also the same.

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

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

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

  The average particle diameter of the colorant in the colorant dispersion and the production method thereof of the present invention is preferably 10 nm or more and less than 200 nm, more preferably 50 nm or more and less than 130 nm, and further preferably 60 nm or more and less than 100 nm. When the average particle size is within the above range, color developability, dispersion stability, and ejection stability during jetting are improved. The average particle diameter of the dispersed particles of the colorant is a value measured using a dynamic light scattering method.

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

<Ink composition>
The ink composition of the present invention includes a colorant and the above-described colorant-dispersed resin of the present invention, and is generally configured using an aqueous liquid medium. The ink composition preferably contains a polymerization initiator and a polymerizable compound, and can be constituted by using other components such as resin particles as necessary.

  The ink composition of the present invention may be prepared by any method as long as it can be prepared so as to include at least a colorant and a colorant-dispersed resin. The ink composition of the present invention can be diluted with an aqueous liquid medium, for example, with the aqueous colorant dispersion of the present invention described above as it is or with further addition of a drying inhibitor or other additives as necessary. Can be prepared.

Details and preferred embodiments of the colorant and the colorant-dispersed resin are the same as in the case of the aqueous colorant dispersion described above.
The content of the colorant in the ink composition is preferably in the range of 0.1 to 20% by mass, and in the range of 0.5 to 10% by mass from the viewpoints of ink colorability, storage stability, and dischargeability. More preferred.
The content of the colorant-dispersed resin in the ink composition is preferably in the range of 1 to 150% by mass with respect to the colorant from the viewpoints of dispersibility, storage stability, and dischargeability of the ink composition. The range of 100% by mass is more preferable.

-Resin particles-
The ink composition of the present invention may contain at least one kind of resin particles. By containing the resin particles, image fixability and abrasion resistance can be improved.

  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, benzoguanamines. Examples thereof include particles of resin, phenol resin, silicone resin, epoxy resin, urethane resin, paraffin resin, fluorine resin, and the like. The resin particles can be contained in the ink composition using these latexes. Among them, preferable examples of the resin particles include acrylic resins, acrylic-styrene resins, styrene resins, crosslinked acrylic resins, and crosslinked styrene resins.

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.
Moreover, there is no restriction | limiting in particular regarding the particle size distribution of a resin particle, Any of what has a wide particle size distribution or a monodispersed particle size distribution may be sufficient. Further, two or more kinds of resin particles having a monodispersed particle size distribution may be mixed and used.

  The glass transition temperature (Tg) of the resin particles is preferably 30 ° C. or higher, more preferably 40 ° C. or higher, and further preferably 50 ° C. or higher.

  The content of the resin particles in the ink composition is preferably 20% by mass or less, and more preferably 15% by mass or less with respect to the total mass of the ink composition.

-Aqueous UV curable material-
In addition to the above components, the ink composition of the present invention may further contain a water-soluble polymerizable compound having an ethylenically unsaturated bond and a polymerization initiator as an aqueous UV curable material. By containing the polymerizable compound and the polymerization initiator, the ink composition can be configured in a UV (ultraviolet) curable type, and the fixability and abrasion resistance of the formed image can be further improved.
Any of the polymerizable compound and the polymerization initiator may be used alone or in combination of two or more.

(Polymerizable compound)
Examples of the polymerizable compound include a water-soluble compound having an ethylenically unsaturated double bond (hereinafter sometimes referred to as “specific polymerizable compound”), and an ethylenically unsaturated bond capable of radical polymerization in the molecule. A water-soluble compound having at least one (for example, any of chemical forms such as a monomer, an oligomer, and a polymer may be included). Only one kind of the specific polymerizable compound may be used in the ink composition, or two or more kinds thereof may be used in combination at an arbitrary ratio in order to improve the target characteristics. Preferably, two or more kinds of polymerizable compounds are used in combination for controlling performance such as reactivity and physical properties.

  The specific polymerizable compound is preferably dissolved in distilled water at 2% by mass or more at room temperature, more preferably dissolved in 15% by mass or more, and particularly preferably mixed uniformly with water at an arbitrary ratio.

  Examples of specific polymerizable compounds include esters of unsaturated carboxylic acids such as acrylic acid, methacrylic acid, itaconic acid, crotonic acid, isocrotonic acid, maleic acid, amides, anhydrides having an ethylenically unsaturated group, acrylonitrile , Styrene, various unsaturated polyesters, unsaturated polyethers, unsaturated polyamides, unsaturated urethanes, vinyl ethers, allyl ethers, and the like. Acrylic acid, methacrylic acid esters and amides are preferred.

  The specific polymerizable compound preferably has a poly (ethyleneoxy) chain, a poly (propyleneoxy) chain, or an ionic group (for example, a carboxyl group or a sulfo group) in order to impart water solubility. When it has a poly (ethyleneoxy) chain and a poly (propyleneoxy) chain, the number of units of ethyleneoxy and propyleneoxy is preferably in the range of 1 to 10, more preferably in the range of 1 to 5. When the chain length is within the above range, the hardness of the film when cured and the adhesion to the recording medium can be secured while obtaining water solubility.

  The specific polymerizable compound is a polyfunctional acrylate monomer or polyfunctional acrylate having a monoacrylate and a molecular weight of 400 or more, preferably 500 or more, as a radical polymerizable compound in order to further improve sensitivity, bleeding, and adhesion to a recording medium. A mode in which an oligomer is used in combination is preferred. In particular, in an ink composition used for recording on a flexible recording medium such as a PET film or a PP film, a combination of a monoacrylate selected from the above compound group and a polyfunctional acrylate monomer or polyfunctional acrylate oligomer, This is preferable in that the film strength can be increased while the film is flexible to improve adhesion. In addition, the aspect in which at least three polymerizable compounds of monofunctional, bifunctional, and trifunctional or higher polyfunctional monomers are used in combination further improves sensitivity, bleeding, and adhesion to the recording medium while maintaining safety. It is preferable from the viewpoint of improvement.

  Particularly preferred specific examples of the specific polymerizable compound include compounds having the structures shown below (Exemplary Compounds 2-1 to 2-4). However, the present invention is not limited to these.

-Exemplary compound 2-1

Exemplified compound 2-2

Exemplified compound 2-3

Exemplified compound 2-4

-Polymerization initiator-
The polymerization initiator is not particularly limited as long as it has a good polymerization initiating ability in combination with a specific sensitizing dye, and can be selected from known polymerization initiators. Among the polymerization initiators, those that are water-soluble are preferred. The degree of “water solubility” is preferably 0.5% by mass or more, preferably 1% by mass or more, and particularly preferably 3% by mass or more in distilled water at 25 ° C.

  Of the polymerization initiators, polymerization initiators selected from the group consisting of α-aminoketone compounds and acylphosphine oxide compounds are preferred.

  As the α-aminoketone compound, a compound having a structure represented by the following general formula (1) is preferably used.

In the general formula (1), Ar represents a phenyl group substituted with —SR ¹³ or —N (R ^7E ) (R ^8E ), and R ¹³ represents a hydrogen atom or an alkyl group. R ^7E and R ^8E are each independently a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 2 to 4 carbon atoms substituted by an alkoxy group having 1 to 4 carbon atoms, or an alkenyl group having 3 to 5 carbon atoms. Represents a group. R ^7E and R ^8E may combine with each other to form an alkylene group having 3 to 7 carbon atoms, and the alkylene group contains —O— or —N (R ¹² ) — in the alkylene chain. There may be. R ¹² represents an alkyl group having 1 to 4 carbon atoms.

R ^1D and R ^2D each independently represent an alkyl group having 1 to 8 carbon atoms. R ^1D and R ^2D may be bonded to each other to form an alkylene group having 2 to 9 carbon atoms. R ^3D and R ^4D are each independently a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, an alkoxy-substituted alkyl group having 2 to 4 carbon atoms, or an alkenyl group having 3 to 5 carbon atoms. Represents. Here, R ^3D and R ^4D may be bonded to each other to form an alkylene group having 3 to 7 carbon atoms, and the alkylene group has —O— or —N (R ¹² ) — in the alkylene chain. It may be included. R ¹² represents an alkyl group having 1 to 4 carbon atoms.

  Examples of the compound contained in the α-aminoketone compound include 2-methyl-1-phenyl-2-morpholinopropan-1-one, 2-methyl-1- [4- (hexyl) phenyl] -2- And morpholinopropan-1-one, 2-ethyl-2-dimethylamino-1- (4-morpholinophenyl) -butanone-1, and the like. In addition, Irgacure series manufactured by Ciba Geigy, for example, Irgacure 907, Irgacure 369, Irgacure 379 and the like are also available as commercial products, and these are compounds included in α-aminoketone compounds.

  As the acylphosphine oxide compound, a compound represented by the following general formula (2) or general formula (3) is preferable.

In the general formula (2), R ^5D and R ^6D each independently represent an aliphatic group, an aromatic group, an aliphatic oxy group, an aromatic oxy group, or a heterocyclic group, and R ^7D represents an aliphatic group. Represents an aromatic group or a heterocyclic group.

Examples of the aliphatic group represented by R ^5D , R ^6D , or R ^7D include an alkyl group, a substituted alkyl group, an alkenyl group, a substituted alkenyl group, an alkynyl group, a substituted alkynyl group, an aralkyl group, and a substituted aralkyl group. Among them, an alkyl group, a substituted alkyl group, an alkenyl group, a substituted alkenyl group, an aralkyl group, or a substituted aralkyl group is preferable, and an alkyl group and a substituted alkyl group are particularly preferable. The aliphatic group may be a cyclic aliphatic group or a chain aliphatic group. The chain aliphatic group may have a branch.

  Examples of the alkyl group include linear, branched and cyclic alkyl groups, and the number of carbon atoms of the alkyl group is preferably 1 to 30, and more preferably 1 to 20. The preferred range of the number of carbon atoms in the alkyl part of the substituted alkyl group is the same as in the case of the alkyl group. Further, the alkyl group may be either a substituted alkyl group or an unsubstituted alkyl group. Examples of the alkyl group include methyl group, ethyl group, propyl group, butyl group, pentyl group, hexyl group, octyl group, 2-ethylhexyl group, decyl group, dodecyl group, octadecyl group, cyclohexyl group, cyclopentyl group, neopentyl group, An isopropyl group, an isobutyl group, etc. are mentioned.

Examples of the substituent of the substituted alkyl group include a carboxyl group, a sulfo group, a cyano group, a halogen atom (for example, a fluorine atom, a chlorine atom, a bromine atom), a hydroxy group, and an alkoxycarbonyl group having 30 or less carbon atoms (for example, methoxycarbonyl). Group, ethoxycarbonyl group, benzyloxycarbonyl group), alkylsulfonylaminocarbonyl group having 30 or less carbon atoms, arylsulfonylaminocarbonyl group, alkylsulfonyl group, arylsulfonyl group, acylaminosulfonyl group having 30 or less carbon atoms, carbon number 30 The following alkoxy groups (for example, methoxy group, ethoxy group, benzyloxy group, phenoxyethoxy group, phenethyloxy group, etc.), alkylthio groups having 30 or less carbon atoms (for example, methylthio group, ethylthio group, methylthioethylthioethyl group, etc.) An aryloxy group having 30 or less carbon atoms (eg, phenoxy group, p-tolyloxy group, 1-naphthoxy group, 2-naphthoxy group, etc.), nitro group, alkyl group having 30 or less carbon atoms, alkoxycarbonyloxy group, aryloxy A carbonyloxy group, an acyloxy group having 30 or less carbon atoms (for example, acetyloxy group, propionyloxy group, etc.), an acyl group having 30 or less carbon atoms (for example, acetyl group, propionyl group, benzoyl group, etc.), carbamoyl group (for example, Carbamoyl group, N, N-dimethylcarbamoyl group, morpholinocarbonyl group, piperidinocarbonyl group, etc.), sulfamoyl group (for example, sulfamoyl group, N, N-dimethylsulfamoyl group, morpholinosulfonyl group, piperidinosulfonyl group) Etc.), an aryl group having 30 or less carbon atoms For example, phenyl group, 4-chlorophenyl group, 4-methylphenyl group, α-naphthyl group, etc.), substituted amino group (for example, amino group, alkylamino group, dialkylamino group, arylamino group, diarylamino group, acylamino group) Etc.), substituted ureido groups, substituted phosphono groups, heterocyclic groups and the like. Here, the carboxyl group, the sulfo group, the hydroxy group, and the phosphono group may be in a salt state. At that time, examples of the cation forming the salt include M ⁺ described later.

  Examples of the alkenyl group include linear, branched, and cyclic alkenyl groups. The number of carbon atoms of the alkenyl group is preferably 2 to 30, and more preferably 2 to 20. The alkenyl group may be a substituted alkenyl group having a substituent or an unsubstituted alkenyl group, and the preferred range of the number of carbon atoms in the alkenyl part of the substituted alkenyl group is the same as that of the alkenyl group. . Examples of the substituent of the substituted alkenyl group include the same substituents as those of the substituted alkyl group.

  Examples of the alkynyl group include linear, branched, and cyclic alkynyl groups, and the number of carbon atoms of the alkynyl group is preferably 2 to 30, and more preferably 2 to 20. The alkynyl group may be a substituted alkynyl group having a substituent or an unsubstituted alkynyl group, and the preferred range of the number of carbon atoms in the alkynyl part of the substituted alkynyl group is the same as in the case of the alkynyl group. . Examples of the substituent for the substituted alkynyl group include the same substituents as those for the substituted alkyl group.

  Examples of the aralkyl group include linear, branched, and cyclic aralkyl groups. The number of carbon atoms in the aralkyl group is preferably 7 to 35, and more preferably 7 to 25. The aralkyl group may be a substituted aralkyl group having a substituent or an unsubstituted aralkyl group, and the preferred range of the number of carbon atoms in the aralkyl part of the substituted aralkyl group is the same as in the case of the aralkyl group. . Examples of the substituent for the substituted aralkyl group include the same substituents as those for the substituted alkyl group.

Examples of the aromatic group represented by R ^5D , R ^6D , or R ^7D include an aryl group and a substituted aryl group. As a carbon atom number of an aryl group, 6-30 are preferable and 6-20 are more preferable. The preferable range of the number of carbon atoms in the aryl part of the substituted aryl group is the same as that of the aryl group. Examples of the aryl group include a phenyl group, an α-naphthyl group, a β-naphthyl group, and the like. Examples of the substituent for the substituted aryl group include the same substituents as those for the substituted alkyl group.

The aliphatic oxy group represented by R ^5D or R ^6D is preferably an alkoxy group having 1 to 30 carbon atoms, and examples thereof include a methoxy group, an ethoxy group, a butoxy group, an octyloxy group, and a phenoxyethoxy group. It is done. However, it is not limited to these.

The aromatic oxy group represented by R ^5D or R ^6D is preferably an aryloxy group having 6 to 30 carbon atoms, such as a phenoxy group, a methylphenyloxy group, a chlorophenyloxy group, a methoxyphenyloxy group, and an octyl group. An oxyphenyloxy group etc. are mentioned. However, it is not limited to these.

The heterocyclic group represented by R ^5D , R ^6D , or R ^7D is preferably a heterocyclic group containing an N, O, or S atom, such as a pyridyl group, a furyl group, a thienyl group, an imidazolyl group, or a pyrrolyl group. Etc.

In the general formula (3), R ^8D and R ^10D each independently represent an alkyl group, an aryl group, or a heterocyclic group, and R ^9D represents an alkyl group, an aryl group, an alkoxy group, an aryloxy group, or a heterocyclic ring. Represents a group. The alkyl group, aryl group, heterocyclic group, alkoxy group and aryloxy group represented by R ^8D , R ^9D or R ^10D may be unsubstituted or have a substituent. In the case of having a substituent, examples of the substituent include the same substituents as those in the general formula (2).

  The alkyl group, aryl group, heterocyclic group, alkoxy group and aryloxy group in the general formula (3) have the same meaning as in the general formula (2).

  Of the above, for example, [2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide] is available under the trade name Darocur TPO (manufactured by Ciba Specialty Chemicals) and [bis (2, 4,6-trimethylbenzoyl) -phenylphosphine oxide] is available under the trade name Irgacure 819 (manufactured by Ciba Specialty Chemicals).

  Furthermore, as a polymerization initiator, a water-soluble acyl phosphine oxide compound is preferably exemplified. The acylphosphine oxide compound is preferably dissolved in distilled water at 25 ° C. in an amount of 0.5% by mass or more, more preferably 1% by mass or more, and particularly preferably 3% by mass or more.

  Specific examples of the water-soluble acylphosphine oxide compound include compounds described in JP-A-2005-307199 (for example, Exemplified Compounds 5, 6, and 7). Preferred specific examples (exemplary compounds 1-1 to 1-3) of water-soluble acylphosphine oxide compounds are listed below. However, the present invention is not limited to these.

Exemplified compound 1-1

Exemplified compound 1-2

Exemplified compound 1-3

Among the above, acylphosphine oxide compounds are preferably used as polymerization initiators.
In addition to the above polymerization initiator, other polymerizable initiators may be used as long as the effects of the present invention are not impaired. Moreover, combined use with an acyl phosphine oxide type compound is also possible. In this case, it is preferable to use a water-soluble polymerization initiator. The “water solubility” is the same as described above.

  Examples of the other polymerization initiators include camphorquinone, benzophenone, benzophenone derivatives, acetophenone, acetophenone derivatives, such as α-hydroxycycloalkylphenyl ketones or 2-hydroxy-2-methyl-1-phenyl-propanone, Alkoxyacetophenones, α-hydroxy- or 4-aroyl-1,3-dioxolanes, benzoin alkyl ethers, and benzyl ketals, such as benzyl dimethyl ketal, phenyl glyoxalate and its derivatives, dimeric phenyl glyoxalate, Peresters such as benzophenone tetracarboxylic acid peresters (e.g. those described in EP1126541), halomethyltriazines such as 2- [2- (4-methoxy-phenyl) -bi Nyl] -4,6-bis-trichloromethyl [1,3,5] triazine, 2- (4-methoxy-phenyl) -4,6-bis-trichloromethyl [1,3,5] triazine, 2- ( 3,4-dimethoxy-phenyl) -4,6-bis-trichloromethyl [1,3,5] triazine, 2-methyl-4,6-bis-trichloromethyl [1,3,5] triazine, hexaarylbis Imidazole / co-initiator systems such as ortho-chlorohexaphenyl-bisimidazole in combination with 2-mercaptobenzothiazole; ferrocenium compounds or titanocenes such as dicyclopentadienyl-bis (2,6-difluoro -3-pyrrolo-phenyl) titanium; for example, an O-acyloxime described in GB 2,339,571 It is also possible to use mixtures of ether compound. A boric acid compound can also be used as a co-initiator.

  The content of the polymerization initiator in the ink composition is preferably 0.01 to 35 parts by mass, more preferably 0.1 to 30 parts by mass, and still more preferably 0 with respect to 100 parts by mass of the polymerizable compound. It is contained in the range of 5 to 30 parts by mass. In addition, content of a polymerization initiator means the total amount which the polymerization initiator used.

-Other additives-
The ink composition of the present invention may contain other additives as necessary in addition to the above components. Other additives include, for example, ultraviolet absorbers, anti-fading agents, anti-mold agents, pH adjusters, rust inhibitors, antioxidants, emulsion stabilizers, preservatives, antifoaming agents, viscosity modifiers, and dispersion stabilizers. Known additives such as known additives such as an agent, a chelating agent, and a surface tension modifier.

As the antifading agent, various organic and metal complex antifading agents can be used. Organic anti-fading agents include hydroquinones, alkoxyphenols, dialkoxyphenols, phenols, anilines, amines, indanes, chromans, alkoxyanilines, heterocycles, etc. Complex, zinc complex and the like. Examples of the antioxidant include phenol-based antioxidants (including hindered phenol-based antioxidants), amine-based antioxidants, sulfur-based antioxidants, and phosphorus-based antioxidants. Examples of the surface tension adjusting agent include nonionic surfactants, cationic surfactants, anionic surfactants, betaine surfactants, and the like. The addition amount of the surface tension adjusting agent is preferably an addition amount for adjusting the surface tension of the ink composition to 20 to 60 mN / m, in order to achieve good droplet ejection by the ink jet method, and the addition amount for adjusting to 20 to 45 mN / m. Is more preferable, and the addition amount adjusted to 25 to 40 mN / m is more preferable.
Specific examples include other additives described in paragraphs [0153] to [0162] of JP-A-2007-100071.
Various additives may be added directly after the ink composition is prepared, or may be added when the ink composition is prepared.

In addition to the above, the ink composition of the present invention may contain a surfactant.
As the surfactant, a compound having a structure having both a hydrophilic part and a hydrophobic part in the molecule is preferable, and any of anionic surfactants, cationic surfactants, amphoteric surfactants and nonionic surfactants is preferable. It can be used. Furthermore, a polymer substance (polymer dispersant) can also be used as a surfactant.
Specific examples of the anionic surfactant include sodium dodecylbenzenesulfonate, sodium lauryl sulfate, sodium alkyldiphenyl ether disulfonate, sodium alkylnaphthalenesulfonate, sodium dialkylsulfosuccinate, sodium stearate, potassium oleate, sodium dioctylsulfosuccinate. Nate, sodium polyoxyethylene alkyl ether sulfate, sodium polyoxyethylene alkyl ether sulfate, sodium polyoxyethylene alkyl phenyl ether sulfate, sodium dialkylsulfosuccinate, sodium stearate, sodium oleate, sodium t-octylphenoxyethoxypolyethoxyethyl sulfate Salt, etc., and specific examples of nonionic surfactants , Polyoxyethylene lauryl ether, polyoxyethylene octyl phenyl ether, polyoxyethylene oleyl phenyl ether, polyoxyethylene nonyl phenyl ether, oxyethylene oxypropylene block copolymer, t-octylphenoxyethyl polyethoxyethanol, nonylphenoxyethyl polyethoxy Examples include ethanol. Specific examples of the cationic surfactant include a tetraalkylammonium salt, an alkylamine salt, a benzalkonium salt, an alkylpyridium salt, an imidazolium salt, and the like. Specifically, for example, dihydroxyethyl stearylamine 2-heptadecenyl-hydroxyethylimidazoline, lauryldimethylbenzylammonium chloride, cetylpyridinium chloride, stearamide methylpyridium chloride, and the like.
Surfactant can be used individually by 1 type or in combination of 2 or more types. 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%.

  Of the above water-soluble organic solvents, it is preferable to add a low-volatile or non-volatile solvent to the ink composition, and the ink jet nozzle can be prevented from being clogged by drying. Further, by adding a volatile solvent, the permeability to the recording medium can be enhanced. It is also preferable to add a surfactant, and the ink can have an appropriate surface tension.

  The viscosity of the ink composition is preferably in the range of 1 to 30 mPa · s, more preferably in the range of 1 to 20 mPa · s, from the viewpoint of droplet ejection stability and aggregation rate when ink is applied by an inkjet method. A range of 2.5 to 15 mPa · s is more preferable, and a range of 2 to 10 mPa · s is particularly preferable. The viscosity of the ink composition can be measured at 20 ° C. using an E-type viscometer, for example.

The pH of the ink composition is preferably pH 7 to 10, more preferably pH 7 to 9, from the viewpoint of ink stability and aggregation rate. By setting the pH within this range, storage stability is improved, and corrosion of members of an apparatus (ink jet recording apparatus) to which the ink composition is applied is suppressed. The pH of the ink composition is measured by a pH measuring device (for example, pH meter D-50, manufactured by HORIBA) usually used at 25 ° C.
The pH of the ink composition can be appropriately adjusted using an acidic compound or a basic compound. As an acidic compound or a basic compound, a compound that is usually used can be used without particular limitation.

<Ink set>
The ink set of the present invention is configured by providing the ink composition of the present invention described above and a treatment liquid containing an aggregating component for aggregating the components in the ink composition. This ink set is composed of the ink composition of the present invention described above, has water redispersibility, and changes in pH due to pH change that occurs when the ink composition comes into contact with the treatment liquid. Aggregation of dispersed particles such as a colorant dispersed in the particle progresses sensitively (aggregation is improved), and a large amount of aggregation can be obtained. An image with less blur is obtained.

Details of the ink composition are as described above. Hereinafter, the treatment liquid will be described in detail.
The treatment liquid in the present invention is an aqueous composition capable of forming an aggregate when it comes into contact with the ink composition. Specifically, when mixed with the ink composition, a colored particle ( Aggregating components capable of aggregating dispersed particles such as pigments) to form aggregates. The treatment liquid can be configured to include other components as necessary. By using the treatment liquid together with the ink composition, it is possible to increase the speed of inkjet recording, and an image with high density and resolution can be obtained even when recording at high speed.

-Treatment liquid-
The treatment liquid contains at least one aggregating component (hereinafter also referred to as an aggregating agent) capable of forming an aggregate upon contact with the ink composition. By mixing the treatment liquid with the ink composition ejected by the ink jet method, aggregation of pigments and the like stably dispersed in the ink composition is promoted.

  Examples of the aggregating agent include compounds capable of changing the pH of the ink composition, polyvalent metal salts, and cationic compounds. In the present invention, from the viewpoint of cohesiveness of the ink composition, a compound capable of changing the pH of the ink composition is preferable, and a compound capable of lowering the pH of the ink composition is more preferable.

Examples of the compound that can lower the pH of the ink composition include acidic compounds.
Examples of acidic compounds include sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, polyacrylic acid, acetic acid, glycolic acid, malonic acid, malic acid, maleic acid, ascorbic acid, succinic acid, glutaric acid, fumaric acid, citric acid, and tartaric acid. , Lactic acid, sulfonic acid, orthophosphoric acid, metaphosphoric acid, pyrrolidone carboxylic acid, pyrone carboxylic acid, pyrrole carboxylic acid, furan carboxylic acid, pyridine carboxylic acid, coumaric acid, thiophene carboxylic acid, nicotinic acid, and derivatives of these compounds, and These salts etc. are mentioned suitably.

Of these, acidic compounds having high water solubility are preferable. Further, from the viewpoint of fixing the whole ink by reacting with the ink composition, an acidic compound having a valence of 3 or less is preferable, and an acidic compound having a valence of 2 to 3 is particularly preferable.
An acidic compound may be used individually by 1 type, and may use 2 or more types together.

  When the treatment liquid in the present invention contains an acidic compound, the pH (25 ° C.) of the treatment liquid is preferably 0.1 to 6.0, more preferably 0.5 to 5.0, and 0 It is more preferable that it is .8 to 4.0.

  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. Cation (for example, aluminum) and the salt of lanthanides (for example, neodymium) can be mentioned. As these metal salts, carboxylate (formic acid, acetic acid, benzoate, etc.), nitrate, chloride, and thiocyanate are suitable. Among them, preferred are calcium salts or magnesium salts of carboxylic acids (formic acid, acetic acid, benzoates, etc.), calcium salts or magnesium salts of nitric acid, calcium chloride, magnesium chloride, and calcium salts or magnesium salts of thiocyanic acid.

Preferred examples of the cationic compound include cationic surfactants. As the cationic surfactant, for example, a primary, secondary, or tertiary amine salt type compound is preferable. Examples of the amine salt type compounds include compounds such as hydrochloride or acetate (for example, laurylamine, cocoamine, stearylamine, rosinamine), quaternary ammonium salt type compounds (for example, lauryltrimethylammonium chloride, cetyltrimethyl). Ammonium chloride, lauryldimethylbenzylammonium chloride, benzyltributylammonium chloride, benzalkonium chloride, etc.), pyridinium salt type compounds (eg, cetylpyridinium chloride, cetylpyridinium bromide, etc.), imidazoline type cationic compounds (eg, 2-heptadecenyl- Hydroxyethyl imidazoline), ethylene oxide adducts of higher alkylamines (eg dihydroxyethyl stearylamine) It can gel. Polyallylamines may also be used. In addition to these, amphoteric surfactants that are cationic in a desired pH range can also be used. For example, amino acid type amphoteric surfactants, R-NH-CH ₂ CH ₂ -COOH type compounds (R is an alkyl group) Group), carboxylate type amphoteric surfactants (eg, stearyl dimethyl betaine, lauryl dihydroxyethyl betaine, etc.), amphoteric surfactants such as sulfate ester type, sulfonic acid type, or phosphate ester type, etc. Can be mentioned.

A flocculant can be used individually by 1 type or in mixture of 2 or more types.
The content of the flocculant for aggregating the ink composition in the treatment liquid is preferably 1 to 50% by mass, more preferably 3 to 45% by mass, and still more preferably 5 to 40% by mass.
When at least one of an acidic compound and a cationic compound is used in combination with the polyvalent metal compound, the content of the acidic compound and the cationic compound in the treatment liquid (the total content of the acidic compound and the cationic compound) is 5 mass%-95 mass% are preferable with respect to the total content of a valent metal compound, and 20 mass%-80 mass% are more preferable.

  The treatment liquid in the present invention can generally contain a water-soluble organic solvent in addition to the aggregating agent, and can be constituted using other various additives. The details of the water-soluble organic solvent and other various additives are the same as those in the ink composition described above.

  The surface tension (25 ° C.) of the treatment liquid is preferably 20 mN / m or more and 60 mN / m or less. More preferably, it is 25 mN / m or less and 50 mN / m or less, More preferably, it is 25 mN / m or more and 45 mN / m or less. The surface tension is measured with an ink composition at 25 ° C. using an Automatic Surface Tensiometer CBVP-Z (manufactured by Kyowa Interface Science Co., Ltd.).

  For applying the treatment liquid onto the coated paper, a known liquid application method can be used without particular limitation, and any method such as spray application, application using an application roller, application by an inkjet method, immersion, etc. can be selected. it can.

  The region to which the treatment liquid is applied may be the entire surface application to be applied to the entire recording medium (coated paper) or the partial application to be partially applied to the region where ink jet recording is performed in the subsequent ink application process. Good. In the present invention, the application amount of the treatment liquid is uniformly adjusted, and fine lines and fine image portions are uniformly recorded, and from the viewpoint of suppressing density unevenness such as image unevenness, coating is performed by application using an application roller or the like. It is preferable to apply the entire surface to the entire paper. Examples of the method for applying the flocculant by controlling the amount of the flocculant within the above range include a method using an anilox roller. An anilox roller is a roller with a ceramic-sprayed roller surface processed with a laser to give it a pyramid shape, a diagonal line, a turtle shell shape, or the like. The treatment liquid enters the dent portion formed on the roller surface, is transferred when it comes into contact with the paper surface, and is applied in an application amount controlled by the dent of the anilox roller.

<Image forming method>
The image forming method of the present invention comprises an ink application process for applying the ink composition of the present invention described above onto a recording medium, and a treatment liquid containing an aggregating component for aggregating the components in the ink composition on the recording medium. The process liquid provision process to provide is comprised.

-Ink application process-
In the ink application step, the ink composition of the present invention described above is applied onto a recording medium to record an image. Application of the ink composition can be performed by ejection by an inkjet method.

  In image recording by the ink jet method, an ink composition is ejected onto a recording medium by applying energy to form a colored image. As a preferable ink jet recording method for the present invention, the method described in paragraph Nos. 0093 to 0105 of JP-A No. 2003-306623 can be applied.

The inkjet method is not particularly limited, and is a known method, for example, a charge control method that ejects ink using electrostatic attraction, a drop-on-demand method (pressure pulse method) that uses vibration pressure of a piezoelectric element, Either an acoustic ink jet method that converts an electrical signal into an acoustic beam, irradiates the ink and ejects the ink by using radiation pressure, or a thermal ink jet method that heats the ink to form bubbles and uses the generated pressure. There may be. 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 the ink application process, for example, an image can be recorded by changing the conveyance speed of the recording medium. The conveying speed is not particularly limited as long as the image quality is not impaired, and is preferably 100 to 3000 mm / s, more preferably 150 to 2700 mm / s, and further preferably 250 to 2500 mm / s. .

  The recording medium is not particularly limited, and for example, so-called coated paper used for general offset printing can be used. The coated paper is obtained by applying a coating material to the surface of high-quality paper, neutral paper, or the like that is mainly surface-treated with cellulose as a main component and is not generally surface-treated. In general, image formation by normal aqueous ink jet using coated paper as a recording medium tends to cause quality problems such as image bleeding and abrasion resistance. However, the ink jet recording method of the present invention suppresses image bleeding. As a result, uniform and density unevenness is prevented, and an image having good blocking resistance, offset resistance, and abrasion resistance can be recorded.

  The coated paper can be obtained and used on the market. For example, coated paper for general printing can be used. Specifically, coated paper such as “OK Top Coat +” manufactured by Oji Paper Co., “Aurora Coat” manufactured by Nippon Paper Industries Co., Ltd., “Ulite”, etc. (A2 B2), and art paper (A1) such as “Tokuhishi Art” manufactured by Mitsubishi Paper Industries.

-Treatment liquid application process-
In the treatment liquid application step, a treatment liquid containing an aggregating agent for aggregating the components in the ink composition described above is applied to a recording medium (preferably coated paper). By configuring the image recording using the ink composition in the presence of the treatment liquid, it is possible to record an image having good blocking resistance, offset resistance and scratch resistance, and curl and cockle after recording, In addition, the effect of suppressing the occurrence of ink repellency is also obtained.

  Either the ink application step or the treatment liquid application step may be performed first, but from the viewpoint of forming a higher quality image, the ink application step is performed after applying the treatment liquid on the recording medium in the treatment liquid application step. An embodiment in which an image is formed by providing is more preferable.

-Heat fixing process-
The image forming method of the present invention may further include a heat fixing step of fixing the image recorded in the ink application step by heat fixing. The image can be fixed by press-contacting the pressure-bonding member to the ink on the recording medium forming the image portion. In the present invention, an offset phenomenon that an image (ink composition) is transferred to the pressure-bonding member when the pressure-bonding member comes into contact with the image and damages the image is prevented, and the image can be fixed quickly while maintaining the image quality. As a result, an image having a good texture such as glossiness of the image, scratch resistance (for example, adhesion to paper) and excellent image quality is recorded at high speed.

  The fixing of the image portion is performed by, for example, using at least a pressure applying unit that applies pressure to the image after the ink applying step, and pressing the image portion while pressing the pressure applying unit against the image portion. You may carry out by providing the pressurizing process to process. In addition, a heating means for fixing (fixing process) may be provided by combining the pressure applying means with a heating means for heating the image portion and heat-pressing the image portion. Examples of the pressure applying unit include a pair of rolls and a pressure plate that are in pressure contact with each other, and examples of the heating unit include a heating roll and a hot plate. Specifically, for example, after the ink application process, the surface of the recording medium can be pressure-bonded with a heated roll or hot plate. In this case, the resin particles contained in the ink can be melted. At this time, the heating temperature is preferably higher than the Tg of the resin particles in the ink composition.

  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.

Example 1
Synthesis Example 1 Synthesis of Monomer MM-22 Malic acid (0.2 mol) and methacrylic anhydride (0.4 mol) were added to a 500 ml three-necked flask equipped with a stirrer and a condenser tube at 50 ° C. under a nitrogen stream. For 2 hours. From this reaction solution, methacrylic acid and methacrylic anhydride were removed under reduced pressure to precipitate a solid. The precipitated solid was collected by filtration, washed with hexane, and dried to obtain monomer MM-22 (the above-mentioned exemplified compound forming the structural unit (a)) (yield 65%). The structure of the obtained compound was confirmed by ¹ H-NMR.

-Synthesis Example 2-: Synthesis of monomer MM-10 3-Aminophthalic acid hydrochloride (0.2 mol) and N-methylpyrrolidone 150 mL were weighed in a 500 ml three-necked flask equipped with a stirrer and a condenser, and under a nitrogen stream, Stir. To this solution, 0.2 mol of Karenz MOI (manufactured by Showa Denko KK) was dropped and reacted at 50 ° C. for 2 hours. This reaction solution was added to 500 mL of water, and the precipitated solid was collected by filtration, washed with hexane, and dried to obtain monomer MM-10 (the above-mentioned exemplified compound forming the structural unit (a)). (Yield 61%). The structure of the obtained compound was confirmed by ¹ H-NMR.

-Synthesis Example 3-: Synthesis of Monomer MM-1 To a 1 L (liter) three-necked flask equipped with a stirrer and a cooling tube, 0.35 mol of iminodiacetic acid, 350 ml of methanol and 350 ml of water were added and mixed, and stirred at 60 ° C. While adding 0.6 mol of NaOH little by little. Thereafter, 0.35 mol of chloromethylstyrene was added dropwise over 30 minutes, 0.6 mol of NaOH was further added, and the remaining half of chloromethylstyrene was added dropwise. After further reaction at 60 ° C. for 3 hours, the reaction solution was removed to 1/3 volume, and then extracted with methyl ethyl ketone. Concentrated hydrochloric acid was added to the aqueous phase to adjust to pH 2-3. The precipitated white solid was filtered, washed with water, and dried to obtain monomer MM-1 (the above-mentioned exemplified compound forming the structural unit (a)) (yield 40%).

-Synthesis Example 4-: Synthesis of dispersion polymer P-1 To a 500 ml three-necked flask equipped with a stirrer and a condenser tube, 88 g of methyl ethyl ketone was added and heated to 75 ° C. in a nitrogen atmosphere, and 50 g of methyl ethyl ketone was mixed with dimethyl 2,2 A solution in which 1.2 g of '-azobisisobutyrate, 10 g of the monomer MM-22, and 90 g of 2-ethylhexyl methacrylate were dissolved was added dropwise over 3 hours. After completion of the dropwise addition, the reaction was further continued for 1 hour, and then a solution prepared by dissolving 0.36 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 a large excess of hexane, and the precipitated polymer was dried to obtain 93 g of dispersed polymer P-1 (colorant-dispersed resin of the present invention).
It was 62000 when the composition of the obtained dispersion polymer was confirmed by ¹ H-NMR and the weight average molecular weight (Mw) was calculated | required from GPC.

Synthesis Example 5: Synthesis of Dispersed Polymer P-7 To a 500 ml three-necked flask equipped with a stirrer and a condenser tube, 88 g of methyl ethyl ketone was added and heated to 75 ° C. in a nitrogen atmosphere, and 50 g of methyl ethyl ketone was added with dimethyl 2,2 A solution prepared by dissolving 1.2 g of '-azobisisobutyrate, 15 g of the monomer MM-1, 65 g of phenoxyethyl methacrylate, and 20 g of methyl methacrylate was added dropwise over 3 hours. After completion of the dropwise addition, the reaction was further continued for 1 hour, and then a solution prepared by dissolving 0.36 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 a large excess amount of hexane, and the precipitated polymer was dried to obtain 93 g of dispersed polymer P-7 (colorant-dispersed resin of the present invention).
The composition of the obtained dispersion polymer was confirmed by ¹ H-NMR, and the weight average molecular weight (Mw) was determined by GPC.

-Synthesis of other dispersion polymers-
Further, in the same manner as in Synthesis Examples 4 to 5, the dispersion polymers P-2 to P-6, P-8 to P-15 (the colorant-dispersed resin of the present invention), and the polymer A-1 for comparison were used. , A-2 was synthesized. The molecular weight was adjusted by adjusting the amount of addition of dimethyl 2,2′-azobisisobutyrate as an initiator.

Example 2 Preparation of Pigment-Containing Resin Particle Dispersion (Pigment Dispersion D-7) 10 parts of Pigment Blue 15: 3 (PB15: 3, manufactured by Dainichi Seika Kogyo Co., Ltd., Phthalocyanine A220) And 5 parts of the dispersion polymer P-7, 42 parts of methyl ethyl ketone, 5.5 parts of 1N NaOH aqueous solution, and 87.2 parts of ion-exchanged water were mixed using a φ0.1 mm zirconia bead with a bead mill. Dispersed for 2-6 hours.

  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 pigment-containing resin particles having a pigment concentration of 10.2% by mass. Further, after centrifuging with a centrifuge (05P-21, manufactured by Hitachi, Ltd.) for 30 minutes at 5000 rpm, ion-exchanged water was added to adjust the pigment dispersion so that the pigment concentration was 15% by mass. The solution was filtered under pressure using a 2.5 μm membrane filter (manufactured by Advantech). Thereafter, ion-exchanged water was added so that the pigment concentration was 4% by mass to obtain a pigment dispersion D-7.

(Example 3): Preparation of pigment dispersions D-1 to D-6, D-8 to D-42 In Example 2, instead of the dispersion polymer P-7 and Pigment Blue 15: 3, the following Table 1 was prepared. Pigment dispersions D-1 to D-6 and D-8 to D-42 were prepared in the same manner as in the preparation of pigment dispersion D-1 of Example 2, except that the dispersion polymer and the colorant shown in FIG. Each was prepared.

Details of the pigments in Table 1 below are as follows.
・ C. I. Pigment Red 122 (PR122, manufactured by Ciba Specialty Chemicals Co., Ltd., trade name: CROMOPHTAL Jet Magenta DMQ)
・ C. I. Pigment Yellow 74 (PY74, manufactured by Ciba Specialty Chemicals, Inc., trade name: Irgalite Yellow GS)
・ Carbon black (CB, manufactured by degussa, trade name: NIPEX180-IQ)

(Example 4): Preparation of water-based ink Using the pigment dispersion D-1 obtained above, a pigment dispersion-containing composition having the following composition was prepared, and the composition was centrifuged (at 10,000 to 20000 rpm). 30 minutes to 2 hours), and an aqueous inkjet recording ink J-1 was obtained.
<Composition of water-based ink>
-Pigment dispersion D-1 ... 40 parts-Glycerin ... 7 parts-Diethylene glycol ... 9 parts-Triethanolamine ... 1 part-Olphine E1010 (manufactured by Nissin Chemical Industry Co., Ltd.)・ ・ 1 part ・ Triethylene glycol monobutyl ether ・ ・ ・ 9 parts ・ Ion-exchanged water ・ ・ ・ 34 parts

  The pH of the aqueous ink J-1 measured with a pH meter WM-50EG manufactured by Toa DKK was 8.6.

  Further, the water-based inks J-2 to J-42 (pigment dispersions D-2 to D-2) were replaced with the pigment dispersions D-1 in place of the pigment dispersions D-2 to D-42 in the same manner as the water-based ink J-1. Corresponding to D-42).

(Comparative Example 1): Preparation of Pigment Dispersions D-43 to D-50 In the preparation of P-1 of Example 2, the dispersion polymer P-1 was dispersed polymers A-1 to A as shown in Table 1 below. Pigment dispersions D-43 to D-50 were prepared in the same manner as in the preparation of pigment dispersion D-1 of Example 2, except that it was replaced with any of -2.

(Comparative example 2): Preparation of comparative water-based inks J-43 to J-50 In Example 3, the pigment dispersion D-1 was replaced with the pigment dispersions D-43 to D-50, and the water-based ink J- In the same manner as in Example 1, water-based inks D-43 to D-50 (corresponding to pigment dispersions D-43 to D-50, respectively) were prepared.

(Evaluation 1)
The pigment dispersion (aqueous colorant dispersion) obtained above was subjected to the following measurements and evaluations. The results are shown in Table 1 below.

-1. Measurement of average particle size
The volume average particle diameter of the pigment dispersion was measured by a dynamic light scattering method using a nanotrack particle size distribution analyzer UPA-EX150 (manufactured by Nikkiso Co., Ltd.).
Measurement conditions: 10 cc of ion exchange water was added to 10 μl of the dispersion to prepare a measurement solution, measured at 25 ° C., and evaluated according to the following evaluation criteria.
<Evaluation criteria>
A: The average particle size was 70 nm or more and less than 100 nm.
A: The average particle size was 100 nm or more and less than 130 nm.
Δ: The average particle size was 130 nm or more and less than 200 nm.
X: The average particle diameter was 200 nm or more.

-2. Stability of pigment dispersion over time
The stability over time was evaluated under the following two test conditions.
The average particle diameter and viscosity were measured before and after leaving the pigment dispersion in a sealed state at 50 ° C. for 2 days, and the aggregation and thickening of the pigment particles were evaluated according to the following evaluation criteria.
<Evaluation criteria>
(Double-circle): The change of the average particle diameter and viscosity of a pigment particle was not recognized at all.
○: Almost no change in the average particle diameter and viscosity of the pigment particles was observed within ± 5%.
Δ: Changes in the average particle diameter and viscosity of the pigment particles were slightly recognized within ± 15%, but were practically acceptable.
X: About ± 30% change in the average particle diameter and viscosity of the pigment particles was recognized, which was a problem in practical use.

Here, the measurement of the average particle size is as described in 1. above. The measurement was performed in the same manner as the measurement of the average particle diameter. The viscosity was measured according to the following procedure.
<Measurement of viscosity>
Using a TV-22 viscometer (manufactured by Toki Sangyo Co., Ltd.), the viscosity of the pigment dispersion was measured at 25 ° C.

(Evaluation 2)
For the water-based ink obtained above, an ink jet printer equipped with a 600 dpi, 256 nozzle prototype print head was prepared as an ink jet recording apparatus, and the following measurements and evaluations were performed. The results are shown in Table 1 below.

-3. Discharge stability
At the time of recording using an ink jet recording apparatus, the printed matter was observed for the occurrence of ink flight bending and mist generation from the start of recording to the end of recording, and evaluated according to the following evaluation criteria.
<Evaluation criteria>
A: Ink was bent, and mist was hardly generated.
○: Ink flight bending and mist were observed, but the frequency was low enough that there was no practical problem.
△: Ink flight bending and mist are not frequently generated, but are more frequently generated than those given the standard “◯”, and may cause a practical problem when high quality image quality is required. There was sex.
X: Ink flight bending and mist frequently occurred, and there was a practical problem.

-4. Discharge recovery-
After recording using an ink jet recording apparatus, the head part is not exposed to the cover, and is left in the air at a temperature of 25 ° C. and 65% RH for 2 days. Sexual state was observed and evaluated according to the following evaluation criteria.
<Evaluation criteria>
A: Discharge was possible without maintenance.
○: It was possible to discharge again by applying predetermined maintenance.
(Triangle | delta): It was possible to discharge again by performing predetermined maintenance twice.
X: As long as predetermined maintenance was performed three times, ejection could not be performed.
Here, the predetermined maintenance refers to an operation for eliminating the clogging of the head by ejecting ink by applying a pressure of 15 Pa.

-5. Image quality
Immediately after OK top coat + (recording medium) manufactured by Oji Paper Co., Ltd. was fixed on a stage operating at 500 mm / second and the following treatment liquid was applied to a thickness of about 1.2 μm with a wire bar coater. And dried at 50 ° C. for 2 seconds. After that, with a GELJET GX5000 printer head (manufactured by Ricoh Co., Ltd.) that is arranged obliquely (75.5 degrees) with respect to the scanning direction, the resolution is 1200 × 1200 dpi, the droplet ejection amount is 2.4 pL, and the cyan ink is in a line system. Was printed solid. Immediately after printing, the film was dried at 60 ° C. for 3 seconds, passed between a pair of fixing rollers heated to 60 ° C., and subjected to heat fixing treatment with a nip pressure of 0.25 MPa and a nip width of 4 mm to obtain a print sample. About the obtained printing sample, the printing state was observed visually or with a magnifying glass and evaluated according to the following evaluation criteria.
<Evaluation criteria>
A: It was difficult to find a white portion with a loupe.
○: Although it was difficult to visually check the white spots, the white spots were found with a loupe.
(Triangle | delta): The white spot part was looked for visually (without a magnifying glass).
X: A white spot was easily confirmed visually (without a magnifying glass).

-6. Abrasion resistance
Immediately after the Oji Paper Co., Ltd. OK top coat + (recording medium) was fixed on a stage operating at 500 mm / second, and the following treatment liquid was applied to a thickness of about 1.2 μm with a wire bar coater, Dry at 50 ° C. for 2 seconds. After that, with a GELJET GX5000 printer head (manufactured by Ricoh Co., Ltd.) that is fixed obliquely (75.5 degrees) with respect to the scanning direction, the resolution is 1200 × 1200 dpi, the droplet ejection amount is 2.4 pL, and the cyan ink is applied by the line method. I made a solid print. Immediately after printing, the film was dried at 60 ° C. for 3 seconds, passed between a pair of fixing rollers heated to 60 ° C., and subjected to heat fixing treatment with a nip pressure of 0.25 MPa and a nip width of 4 mm to obtain a print sample. About the obtained printing sample, an Oji Paper Co., Ltd. OK top coat + was wound around a paperweight (weight 470 g, size 15 mm × 30 mm × 120 mm, load 260 kg / m ² ), and the image forming surface of the printing sample These were rubbed 3 times and visually observed for the presence or absence of image peeling, and evaluated according to the following evaluation criteria.
In addition, when image peeling was not confirmed in 3 reciprocations, it rubbed to 6 reciprocations.
<Evaluation criteria>
A: Image peeling was not visible even after 6 reciprocations.
○: Image peeling was not visible on the image forming surface after rubbing 4 times, but was confirmed after rubbing 6 times.
Δ: Image peeling was not visible on the image forming surface after 2 reciprocations, but was confirmed after 4 reciprocations.
X: Image peeling was visible on the image forming surface after rubbing twice.

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

(Example 5): Preparation of aqueous UV curable inks J-51 to J-77 Using the pigment dispersion D-1 obtained above, a pigment dispersion-containing composition having the following composition was prepared, and the composition The product was centrifuged (at 10000 to 20000 rpm for 30 minutes to 2 hours) to obtain an aqueous inkjet recording ink J-51.
<Ink composition>
-Pigment dispersion (D-1)-40 parts-Exemplified compound 1-1 (polymerization initiator)-3 parts-Exemplified compound 2-1 (polymerizable compound)-20 parts-Glycerin・ ・ ・ 7 parts ・ Diethylene glycol ・ ・ ・ 9 parts ・ Triethanolamine ・ ・ ・ 1 part ・ Orphine E1010 (manufactured by Nissin Chemical Industry Co., Ltd.) ・ ・ ・ 1 part ・ Triethylene glycol monobutyl ether ・ ・ ・ 9 parts・ Ion-exchanged water: 10 parts

  When the pH of the water-based ink was measured with a pH meter-WM-50EG manufactured by Toa DKK, the pH was 8.6.

  Also, water-based inks J-52 to J-77 (pigment dispersions shown in Table 2 below) were replaced with the pigment dispersions D-1 shown in Table 2 below in the same manner as in the water-based ink J-51. D-2 to D-42, respectively) were prepared.

The obtained water-based UV curable inks J-51 to J-77 were used and the same evaluations as in the evaluations 1 to 2 were performed. The evaluation results are shown in Table 2 below. In the evaluation of evaluation 2 for image quality and abrasion resistance, image fixing was performed by the following method to obtain a print sample.
* Water-based UV image fixing method *
Immediately after Oji Paper Co., Ltd. OK Top Coat + (recording medium) was fixed on a stage operating at 500 mm / second and the treatment liquid (1) was applied to a thickness of about 1.2 μm with a wire bar coater. And dried at 50 ° C. for 2 seconds. After that, with a GELJET GX5000 printer head (manufactured by Ricoh Co., Ltd.) that is fixed obliquely (75.5 degrees) with respect to the scanning direction, the resolution is 1200 × 1200 dpi, the droplet ejection amount is 2.4 pL, and the cyan ink is applied by the line method. I made a solid print. Immediately after printing, the film was dried at 60 ° C. for 3 seconds, and further exposed to an exposure amount of 2.5 J / cm ² using a UV lamp, and subjected to fixing treatment to obtain a printed sample.

(Comparative Example 3): Preparation of water-based inks J-78 to J-81 The water-based ink J described above except that the pigment dispersion D-1 in Example 5 was replaced with the pigment dispersions D-43 to D-46. In the same manner as -51, aqueous UV curable inks J-78 to J-81 (corresponding to pigment dispersions D-43 to D-46, respectively) were prepared.
The obtained water-based UV curable inks J-78 to J-81 were used for the same evaluations as in the evaluations 1 to 2. The evaluation results are shown in Table 2 below. In evaluation 2, the image quality and abrasion resistance were evaluated, and an image was fixed by the aqueous UV image fixing method to obtain a print sample.

  As shown in Tables 1 and 2, in the pigment dispersion of the present invention, the colorant was finely dispersed as compared with the comparative one, and the stability over time and water redispersibility were excellent. In addition, the formed image formed using the water-based ink and the water-based UV curable ink of the present invention had better image quality and excellent abrasion resistance than those for comparison.

Claims (11)

  A colorant-dispersed resin comprising a structural unit (a) having a plurality of ionic groups and having a minimum number of atoms of 7 or less between the ionic groups.   The colorant-dispersed resin according to claim 1, further comprising a hydrophobic structural unit (b) having an aromatic ring via a linking group at an atom forming the main chain. The colorant-dispersed resin according to claim 2, wherein at least one of the structural units (b) is a structural unit represented by the following general formula (1).

[In General Formula (1), R ₁ represents a hydrogen atom or a methyl group, and L ₁ represents ^* —COO—, ^* —OCO—, ^* —CONH—, ^* —CONR ₃ —, or substituted or unsubstituted. Represents a phenylene group. R ₃ represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and the * mark in the group represented by L ₁ represents a bond connected to the main chain. L ₂ represents a single bond or a divalent linking group formed by combining one or more selected from the following linking group group. Ar 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.
Linking Group: alkylene group having 1 to 12 carbon atoms, an alkenylene group having 2 to 12 carbon _{atoms, -CO -, - NR 7 -} ( alkyl group _{R 7} is a hydrogen atom or a carbon atoms 1 to 6), - O -, - S -, - SO -, - SO 2 - ] The colorant-dispersed resin according to claim 2, wherein the structural unit (b) has a structure represented by the following general formula (2).

[In General Formula (2), * represents a connection point with the main chain, and L represents a divalent linking group having 1 to 30 carbon atoms. ] The L ₁ is ^* -COO-, ^* -CONH-, or ^* -CONR _3- (R ₃ represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms). The colorant-dispersed resin described in 1.   The colorant-dispersed resin according to any one of claims 1 to 5, wherein the ionic group is at least one of a carboxyxyl group, a sulfonic acid group, and a phosphoric acid group.   The colorant-dispersed resin according to any one of claims 1 to 6, wherein the structural unit (a) has an amino group structure.   The coloring agent dispersion containing a coloring agent and the coloring agent dispersion resin of any one of Claims 1-7.   An ink composition comprising a colorant and the colorant-dispersed resin according to any one of claims 1 to 7. An ink composition according to claim 9;
A treatment liquid containing an aggregating component for aggregating the components in the ink composition;
An ink set. An ink application step of applying the ink composition according to claim 9 onto a recording medium;
A treatment liquid application step of applying a treatment liquid containing an aggregating component for aggregating the components in the ink composition onto a recording medium;
An image forming method comprising: