JP2014065876A - Ink set and inkjet recording method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink set and an inkjet recording method excellent in terms of ink cohesiveness, hue, and image drawing aptitude and enabling unprecedented high-speed recordings.SOLUTION: The provided ink set and inkjet recording method targets an ink set consisting of an active energy ray-curable ink composition and a processing liquid, in which the active energy ray-curable ink composition includes a coloring material, a polymerizable compound, and either of an oxidant and a reductant constituting a redox initiator, and in which the processing liquid includes the other remaining constituent member of the redox initiator.

Description

  The present invention relates to an ink set suitable for recording an image by ejecting ink by an ink jet method, and an ink jet recording method using the ink set.

  The ink jet recording method performs recording by ejecting ink from a large number of nozzles provided in an ink jet head in the form of liquid droplets. The noise during the recording operation is low, the running cost is low, and a wide variety of recording media. However, it is widely used because it can record high-quality images.

  As an ink jet recording method for suppressing printing bleeding and mixed color bleeding for the purpose of obtaining a high-quality image, an ink containing a high molecular compound that becomes insoluble when dried by ejecting ink containing a thermosensitive gelling agent. Ink has been proposed (see, for example, Patent Document 1).

  As the ink jet recording method, there is known a two-liquid reaction type recording method that promotes ink fixing by causing two liquids of an ink and a treatment liquid that aggregates the ink to react to cause the ink to aggregate. . For example, in order to suppress image bleeding and image unevenness, an ink jet recording method has been proposed in which an ink composition containing a pigment and a resin emulsion and a reaction liquid containing a polyvalent metal salt are attached to a recording medium (for example, , See Patent Document 2).

Japanese Patent Laid-Open No. 9-12947 JP-A-9-207424

  However, the conventional recording method as described above has an insufficient ink aggregation rate, and it has been difficult to apply to a higher speed ink jet recording method.

  The present invention has been made in view of the above, and has an ink set that is excellent in ink agglomeration, capable of high-speed recording as compared with the conventional ink set, and an image excellent in hue and image drawability. It is an object of the present invention to provide an ink set suitable for an ink jet recording method capable of recording, particularly an active energy ray curable ink set.

  As a result of various studies, the present inventors have found a clue to solve the above problems by using a redox initiator, and have further studied the present invention.

That is, the said subject of this invention was solved by the following means.
(1) An ink set comprising an active energy ray-curable ink composition and a treatment liquid, wherein the active energy ray-curable ink composition comprises a coloring material, a polymerizable compound, and a redox initiator. An ink set comprising an agent, wherein the treatment liquid comprises one of the remaining redox initiators.
(2) The oxidizing agent or reducing agent constituting the redox initiator in the active energy ray-curable ink composition is a reducing agent, and the other one of the redox initiators in the treatment liquid is an oxidizing agent. The ink set according to (1).
(3) The oxidizing agent is hydrogen peroxide or a salt thereof, persulfuric acid or a salt thereof, peroxodisulfuric acid or a salt thereof, cumene hydroperoxide, diacyl peroxide, a percarboxylic acid or a salt thereof (1) or (2 ) Ink set.
(4) The reducing agent is an iron (II) salt, sulfurous acid, hydrogen sulfite or a salt thereof, metabisulfite, metabisulfite or a salt thereof, an amine compound or an amidine compound (1) to (3) The ink set according to any one of the above.
(5) Any of (1) to (3), wherein the reducing agent is an iron (II) salt, sulfurous acid, hydrogen sulfite or a salt thereof, metabisulfite, metabisulfite or a salt thereof, or an amidine compound. The ink set according to item 1.
(6) The ink set according to any one of (1) to (5), wherein the color material is a pigment.
(7) The ink set according to any one of (1) to (6), wherein the active energy ray-curable ink composition further contains a photopolymerization initiator.
(8) The ink set according to (7), wherein the photopolymerization initiator is a radical polymerization initiator.
(9) The ink set according to any one of (1) to (8), wherein the polymerizable compound is a radical polymerizable monomer.
(10) The ink set according to any one of (1) to (9), wherein the polymerizable compound is a (meth) acrylamide compound.
(11) The ink set according to any one of (1) to (10), wherein the active energy ray-curable ink composition further contains water.
(12) The ink set according to any one of (1) to (11), wherein the processing liquid is an acidic processing liquid.
(13) The ink set according to any one of (1) to (12), wherein the ink set is an inkjet ink set.
(14) An active energy ray-curable ink composition comprising an ink application step of applying an active energy ray-curable ink composition to a recording medium by an inkjet method and a treatment liquid application step of applying a treatment liquid to the recording medium. And an ink jet recording method wherein the treatment liquid is the active energy ray-curable ink composition according to any one of (1) to (13) and a treatment liquid.

In the present invention, “(meth) acryloyl” has the same meaning as —C (═O) CH═CH ₂ and / or —C (═O) C (CH ₃ ) ═CH _2. “Acrylic” represents acrylic and / or methacrylic, “(meth) acrylamide” represents acrylamide and / or methacrylamide, and “(meth) acrylate” represents acrylate and / or methacrylate. Further, in the present invention, “to” is used in the sense of including numerical values described before and after it as a lower limit value and an upper limit value.
In addition, unless there is a particular notice, when there are a plurality of groups having the same symbol, they may be the same or different from each other. Similarly, when there are repetitions of a plurality of partial structures, these repetitions are the same. It means both the repetition of and the mixing of different repetitions within the specified range.
Furthermore, the geometrical isomer which is the substitution mode of the double bond in each general formula is not limited to the E-form or the Z-form unless otherwise specified, even if one of the isomers is described for convenience of display. Or a mixture thereof.

  According to the present invention, an ink set having excellent ink cohesiveness and capable of high-speed recording as compared with the prior art, and an inkjet recording method capable of maintaining such performance and performing image recording excellent in hue and image drawability, particularly An ink set suitable for the active energy ray-curable ink set can be provided.

It is a schematic diagram which shows the image formation process of an Example.

  The present invention uses an active energy ray-curable ink composition and a treatment liquid that are suitable for ink jet recording.

<< Ink set >>
The ink set of the present invention is an ink set comprising the active energy ray-curable ink composition and a treatment liquid.

<Active energy ray-curable ink composition>
The active energy ray-curable ink composition used in the present invention contains a coloring material, a polymerizable compound, and a redox initiator. Moreover, you may contain other additives according to the objective, such as a photoinitiator, a sensitizing dye, surfactant, antioxidant, a ultraviolet absorber, a color tone regulator.
The redox initiator will be described below.

[Redox initiator]
The redox initiator used in the present invention is a polymerization initiator that initiates polymerization by a redox function, for example, oxidation or reduction, and includes an oxidizing agent (hereinafter also referred to as an oxidized redox initiator) and a reducing agent (hereinafter referred to as “oxidized redox initiator”). It is also an initiator that generates a reactive active species by mixing them together.
The active energy ray curable ink composition and the treatment liquid contain either an oxidizing agent or a reducing agent in the active energy ray curable ink composition and the other in the treatment liquid, and these are mixed to produce a reactive active species. Preferably, a reactive radical is generated, and a polymerizable compound, preferably a radically polymerizable compound, can be efficiently polymerized even at a low temperature.

As the oxidized redox initiator, any redox initiator having oxidation ability may be used. It may be an inorganic oxidized redox initiator or an organic oxidized redox initiator.
As the inorganic oxidized redox initiator, a peroxide is preferable, for example, hydrogen peroxide or a salt thereof, persulfuric acid or a salt thereof, peroxodisulfuric acid or a salt thereof, perboric acid or a salt thereof, formic acid or Examples thereof include diformyl peroxide and its salt.
As these salts, sodium salts, potassium salts, and ammonium salts are preferable, and sodium salts and potassium salts are particularly preferable.

  Examples of organic oxidized redox initiators include alkyl or aryl peroxides such as cumene hydroperoxide, diacyl peroxides such as diacetyl peroxide, dibenzoyl peroxide, and diacyl peroxides such as dilauroyl peroxide, and percarboxylic acids such as peracetic acid. An acid or its salt is mentioned.

Specific examples of the organic oxidized redox initiator include, but are not limited to, the following.
Specific examples of peroxides include tert-butyl hydroperoxide, tert-amyl hydroperoxide, cumene hydroperoxide, toluyl hydroperoxide, p-bromobenzoyl hydroperoxide, pinane hydroperoxide, diisopropylbenzene hydroperoxide, 1-cyclohexanol-1- And hydroperoxide.
Specific examples of the percarboxylic acid or a salt thereof include peracetic acid, perbenzoic acid, monoperphthalic acid, meta-chloroperbenzoic acid, and the like.
Specific examples of other organic oxidized redox initiators include di-tert-butyl peroxide, di-cumyl peroxide, bis- (α, α-dimethylbenzyl) peroxide, dialkyl peroxides such as diethyl peroxide, and tert-butyl. Mixed acyl-alkyl peroxides such as perbenzoic acid ester, acetone peroxide, butanone peroxide, 1,1′-peroxy-bis-cyclohexanol, methyl ethyl ketone peroxide, ketoperoxides such as anisoyl peroxide, 1,2,4-trioxolane or 9 , 10-dihydro-9,10-epidioxide anthracene.
In addition, Polymer Handbook 4th ed. , 2005, Wiley & Sons, New York, can also be used.

  A preferred compound of the oxidized redox initiator can be represented by the following general formula (IO).

General formula (IO)
R ^IO1 -O-O-R ^IO2

In general formula (IO), ^RIO1 and ^RIO2 each independently represent a hydrogen atom, an alkali metal, an alkaline earth metal, an alkyl group, an aryl group, or an acyl group.

Examples of the alkali metal include lithium, sodium, and potassium, and examples of the alkaline earth metal include calcium.
The alkyl group is preferably a linear or branched alkyl group, and the alkyl group preferably has 1 to 18 carbon atoms, and more preferably 1 to 12 carbon atoms. The alkyl group may have a substituent, and examples of the substituent include an alkyl group, an aryl group, a halogen atom, and an alkoxy group. The alkyl group is preferably a tertiary alkyl group, more preferably a tertiary alkyl group substituted with an aryl group, and particularly preferably cumene hydroperoxide.
As the aryl group, an aryl group having 6 to 18 carbon atoms is preferable, and an aryl group having 6 to 12 carbon atoms is more preferable. The aryl group may have a substituent, and examples of the substituent include an alkyl group, a halogen atom, and an alkoxy group.

The acyl group is preferably an alkylcarbonyl group or an arylcarbonyl group, the alkylcarbonyl group preferably has 1 to 19 carbon atoms, and the arylcarbonyl group preferably has 7 to 20 carbon atoms.
Examples of the acyl group include formyl, acetyl, pivaloyl, lauroyl, and benzoyl.

  The oxidized redox initiator is preferably a peroxide as an inorganic oxidized redox initiator, especially hydrogen peroxide, persulfuric acid or a salt thereof, peroxodisulfuric acid or a salt thereof, and most preferably hydrogen peroxide. .

As the reduced redox initiator, any redox initiator having a reducing ability may be used. It may be an inorganic reduced redox or an organic reduced redox initiator.
Examples of inorganic reduced redox initiators include iron (II) salts, sulfurous acid, hydrogen sulfite or salts thereof, metabisulfite, metabisulfite or salts thereof. Here, examples of the iron (II) salt include iron (II) sulfate, iron (II) chloride, and potassium hexacyanoferrate (II).
Organic reduced redox initiators include amine compounds or amidine compounds. Examples of the amine compound include alkylamines and arylamines, and any of primary amines, secondary amines, and tertiary amines may be used. As specific examples of the amine compound, N, N-dimethyltoluidine, tetramethylethylenediamine, and compounds described in Polymer International, 46, 241-250 (1998) can be preferably used.
The amidine compound is preferably a compound represented by the following general formula (IR).

General formula (IR)
R ^IR1 -C (= N-R ^IR2 ) -N (R ^IR3 ) (R ^IR4 )

In general formula (IR), R ^{IR1 to} R ^IR4 each independently represents a hydrogen atom, an alkyl group or an aryl group.

  Examples of amidine compounds include diazabicycloundecene and diazabicyclononene, and amidine compounds described in JP-T-2011-514393 can also be used.

  The combination of an oxidized redox initiator and a reduced redox initiator includes a peroxide as an oxidizing agent, an iron (II) salt, hydrogen sulfite or a salt thereof as a reducing agent, metabisulfite, metabisulfite. Or a salt thereof, or an amidine compound, and an inorganic peroxide as an oxidizing agent and an iron (II) salt, hydrogen sulfite or a salt thereof as a reducing agent, metabisulfite, metabisulfite or their Particularly preferred are hydrogen peroxide, persulfuric acid or a salt thereof, peroxodisulfuric acid or a salt thereof as an oxidizing agent, and iron (II) salt, hydrogen sulfite or a salt thereof as a reducing agent, metabisulfite, metabisulfite. Most preferred is bisulfite or a salt thereof. Among these, a combination of hydrogen peroxide and iron (II) salt is preferable.

  The organic reduced redox initiator is preferably an iron (II) salt, hydrogen sulfite or a salt thereof, metabisulfite, metabisulfite or a salt thereof, an amine compound, an iron (II) salt, a hydrogen sulfite or a salt thereof. Of these, the metabisulfite is particularly preferred, and the iron (II) salt is most preferred.

  The solid content in the active energy ray-curable ink composition of the oxidized redox initiator or reduced redox initiator is 0.05 to 10 parts by mass with respect to 100 parts by mass of the total solids in the composition. Preferably, 0.2-5 mass parts is more preferable, and 0.5-3 mass parts is the most preferable.

  In the present invention, the active energy ray-curable ink composition preferably contains a reduced redox initiator, that is, a reducing agent.

[Color material]
The active energy ray-curable ink composition of the present invention contains at least one color material.
As the coloring material, ordinary dyes, pigments and the like can be used without particular limitation. Among these, from the viewpoint of ink colorability, it is preferable to use a color material that is almost insoluble or hardly soluble in water. Specific examples include various pigments, disperse dyes, oil-soluble dyes, and dyes that form J aggregates. Among these, pigments are preferable from the viewpoint of light resistance. As the pigment, either an organic pigment or an inorganic pigment can be used.

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 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, diketopyrrolopyrrole pigments, dioxazine pigments, indigo pigments, thioindigo pigments, isoindolinone pigments, and quinophthalone pigments. As the dye chelate, a basic dye chelate, an acid dye chelate, or the like can be used.
As the inorganic pigment, titanium oxide, iron oxide, calcium carbonate, barium sulfate, aluminum hydroxide, barium yellow, cadmium red, chrome yellow, and carbon black can be used. Among these, carbon black is particularly preferable, and carbon black produced by a known method such as a contact method, a furnace method, or a thermal method can be used.
More specifically, pigments described in paragraph numbers [0142] to [0145] of JP-A-2007-100071 can be mentioned, and these are preferably used in the active energy ray-curable ink composition of the present invention. .

One color material may be used alone, or a plurality of color materials may be selected and combined in each group or between groups.
The content of the coloring material in the active energy ray-curable ink composition is 0.5 to 20% by mass with respect to the ink composition from the viewpoints of color density, granularity, ink stability, and ejection reliability. Preferably, 1-15 mass% is more preferable, and 2-10 mass% is especially preferable.

(Pigment dispersion)
When the colorant contains a pigment, it is preferable to use a dispersion in which the pigment is dispersed in an aqueous medium with a dispersant (hereinafter also referred to as a colored particle dispersion). The pigments described above can be used. As the dispersant, a polymer dispersant, a low molecular surfactant type dispersant and the like can be used, and the polymer dispersant is preferable.
From the viewpoint of dispersion stability of pigment particles and dischargeability when applied to an ink jet method, the colored particle dispersion is obtained by dispersing a pigment in an aqueous medium with a polymer dispersant and then adding a crosslinking agent to the polymer dispersant. It is preferably a colored particle dispersion obtained by crosslinking each other and covering at least a part of the pigment surface with a crosslinked polymer.

  As the polymer dispersant, a water-soluble polymer dispersant and a water-insoluble polymer dispersant can be used, but a water-insoluble polymer dispersant is preferable from the viewpoint of dispersion stability of pigment particles and dischargeability when applied to an inkjet method. .

(Water-insoluble polymer dispersant)
The water-insoluble polymer dispersant that can be used in the present invention is not particularly limited as long as it can disperse the pigment, and a normal one can be used. For example, a polymer composed of a hydrophobic structural unit and a hydrophilic structural unit can be used as the water-insoluble polymer dispersant.
Examples of the monomer serving as the hydrophobic structural unit include styrene monomers, alkyl (meth) acrylates, aromatic group-containing (meth) acrylates, and the like.
The monomer serving as the hydrophilic structural unit is not particularly limited as long as it is a monomer containing a hydrophilic group, and examples of the hydrophilic group include nonionic groups, carboxyl groups, sulfonic acid groups, and phosphoric acid groups. Examples of the nonionic group include a hydroxyl group, an amide group (nitrogen atom is unsubstituted), a group derived from an alkylene oxide polymer (for example, polyethylene oxide, polypropylene oxide, etc.), a group derived from a sugar alcohol, and the like. . From the viewpoint of dispersion stability, the hydrophilic structural unit preferably contains at least a carboxyl group, and preferably contains both a nonionic group and a carboxyl group.

  Specific examples of the water-insoluble polymer dispersant include styrene- (meth) acrylic acid copolymer, styrene- (meth) acrylic acid- (meth) acrylic acid ester copolymer, (meth) acrylic acid ester- (meth). Examples include acrylic acid copolymers, polyethylene glycol (meth) acrylate- (meth) acrylic acid copolymers, and styrene-maleic acid copolymers.

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

The weight average molecular weight of the water-insoluble polymer dispersant is preferably 3,000 to 200,000, more preferably 5,000 to 100,000, and even more preferably 5,000 to 80,000, from the viewpoint of dispersion stability of the pigment. Preferably, 10,000 to 60,000 is particularly preferable.
The mass average molecular weight is measured by gel permeation chromatography (GPC). GPC uses HLC-8020GPC (manufactured by Tosoh Corporation), and TSKgel SuperHZM-H, TSKgel SuperHZ4000, TSKgel SuperHZ200 (4.6 mm ID × 15 cm, Tosoh Corporation) are used as eluents as columns. Use THF (tetrahydrofuran).

In the present invention, it is preferable that the coloring material includes the pigment and the water-insoluble polymer dispersant, and the coloring material is configured such that at least a part of the surface of the pigment is coated with the water-insoluble polymer dispersant. Particles are preferred.
Such colored particles can be obtained as a colored particle dispersion by dispersing, for example, a mixture containing a pigment, a dispersant, and optionally a solvent (preferably an organic solvent) with a disperser. Specifically, for example, after a step of adding an aqueous solution containing a basic substance (mixing / hydration step) to a mixture of the pigment, the water-insoluble polymer dispersant, and an organic solvent in which the dispersant is dissolved or dispersed A colored particle dispersion can be produced by providing a step (solvent removing step) for removing the organic solvent. According to this method, a colored particle dispersion in which the pigment is finely dispersed and excellent in storage stability can be obtained.

The volume average particle size of the colored particle dispersion is preferably 10 to 200 nm, more preferably 10 to 150 nm, and particularly preferably 10 to 100 nm. When the volume average particle size is 200 nm or less, the color reproducibility is good, and in the case of the ink jet method, the droplet ejection characteristics are good. Moreover, light resistance becomes favorable because a volume average particle diameter is 10 nm or more.
The particle size distribution of the colored particles (coloring material) is not particularly limited, and may be either a wide particle size distribution or a monodisperse particle size distribution. Two or more color materials having a monodisperse particle size distribution may be mixed and used. The volume average particle size and the particle size distribution can be measured using, for example, a light scattering method.
In the present invention, such colored particle dispersions may be used singly or in combination of two or more.

In the colored particle dispersion, the dispersant is preferably used in an amount of 10 to 100% by mass, more preferably 20 to 70% by mass, and particularly preferably 30 to 50% by mass with respect to the pigment. By setting the content of the dispersant to the pigment within the above range, the pigment particles are coated with an appropriate amount of the dispersant, and colored particles having excellent dispersibility, dispersion stability, and colorability can be obtained.
The colored particle dispersion may contain other dispersants in addition to the water-insoluble polymer dispersant. For example, a commonly used water-soluble low molecular dispersant, water-soluble polymer, or the like can be used. A dispersant other than the water-insoluble polymer dispersant can be used within the range of the content of the above-described dispersant.

(Polymerizable compound)
The active energy ray-curable ink composition of the present invention contains at least one polymerizable compound. The polymerizable compound is preferably a radical polymerizable compound, and more preferably a radical polymerizable monomer.
The radically polymerizable compound is preferably a compound having at least one ethylenically unsaturated group, and the ethylenically unsaturated group is preferably —C (R ^x ) ═CH ₂ . Here, R ^x represents a hydrogen atom or an alkyl group. R ^x is preferably a hydrogen atom or a methyl group.
Among the above, the ethylenically unsaturated group is —O—C (═O) —C (R ^x ) ═CH ₂ , —N (R ^y ) —C (═O) —C (R ^x ) ═CH _2. , —CH ₂ CH═CH ₂ , —Ar—C (R ^x ) ═CH ₂ are preferred, —O—C (═O) —C (R ^x ) ═CH ₂ , —N (R ^y ) —C ( ═O) —C (R ^x ) ═CH ₂ is more preferred, and —N (R ^y ) —C (═O) —C (R ^x ) ═CH ₂ is more preferred. That is, in the present invention, the radical polymerizable compound is particularly preferably a (meth) acrylamide compound. In addition, although ^Ry represents a hydrogen atom or an alkyl group, a hydrogen atom is preferable. -Ar- represents an arylene group. Examples of the arylene group include phenylene and naphthylene. The arylene group may have a substituent, and examples of the substituent include an alkyl group, a halogen atom, and an alkoxy group.

  The polymerizable compound may be either a monofunctional polymerizable compound having only one ethylenically unsaturated group or a polyfunctional polymerizable compound, and it is also preferable to use these in combination.

  Examples of the monofunctional polymerizable monomer having an ethylenically unsaturated group include (meth) acrylate compounds, (meth) acrylamide compounds, vinyl ether compounds, aromatics described in JP-A-2008-208190 and JP-A-2008-266561. Examples thereof include vinyl compounds and N-vinyl compounds (polymerizable monomers having an amide bond). Among these, from the viewpoint of improving storage stability, it is preferable to use a (meth) acrylamide compound, a vinyl ether compound, an aromatic vinyl compound, or an N-vinyl compound (a polymerizable monomer having an amide bond). It is particularly preferable to use it. Moreover, it is preferable to use a (meth) acrylamide compound from the viewpoint of curability.

  (Meth) acrylate compounds include, for example, methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, ( And isobornyl (meth) acrylate.

  The (meth) acrylic acid amide compound is preferably a compound represented by the following general formula (MA).

In general formula (MA), R ^b1 represents a hydrogen atom or a methyl group, R ^c1 represents a hydrogen atom, a methyl group or an ethyl group, and R ^c2 represents an alkyl group. Here, R ^c1 and R ^c2 may be bonded to each other to form a 5- to 8-membered ring.

R ^b1 is preferably a hydrogen atom. R ^c1 is preferably a hydrogen atom or a methyl group, more preferably a hydrogen atom.
R ^c2 is preferably a linear or branched alkyl group having 1 to 6 carbon atoms (for example, methyl (Me), ethyl, propyl, butyl, pentyl, hexyl), more preferably an alkyl group having 2 to 4 carbon atoms, A number 2 or 3 alkyl group is particularly preferred.
The alkyl group of R ^c2 may have a substituent, and examples of the substituent include an acyl group, a hydroxyl group, an amino group, an alkylamino group, an arylamino group, and a heterocyclic amino group (in particular, a tertiary amino group). Preferred), a quaternary ammonium group or a sulfo group. Among these, an acyl group, a hydroxyl group or a dialkylamino group is preferred, and a hydroxyl group is more preferred.

  In the following, the compound represented by the general formula (MA) is preferably the following exemplified compound.

  Polyfunctional polymerizable monomers having a plurality of ethylenically unsaturated groups include polyfunctional (meth) acrylates, polyfunctional (meth) acrylamide compounds, polyfunctional vinyl ether compounds, polyfunctional aromatic vinyl compounds, polyfunctional N-vinyl compounds. Is mentioned.

  Examples of the polyfunctional (meth) acrylate include ethylene glycol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, propylene glycol di (meth) acrylate, and dipropylene di (meth) acrylate. Glycol, tripropylene glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate, hexamethylene glycol di (meth) acrylate, bisphenol A di (meth) acrylate, 4,4′-bis [2- (Meth) acryloyloxyethoxy] diphenylpropane, trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate and pentaerythritol tetra (meth) acrylate, and mono- or polyalkoxy alcohols as ester raw materials. (Meth) acrylic esters such as glycerol ethoxylate tri (meth) acrylate, glycerol propoxylate tri (meth) acrylate, trimethylolpropane ethoxylate tri (meth) acrylate, trimethylolpropane propoxylate tri (meth) Acrylate, pentaerythritol ethoxylate tetra (meth) acrylate, pentaerythritol propoxylate tri (meth) acrylate, pentaerythritol propoxylate tetra (meth) acrylate, neopentyl glycol ethoxylate di (meth) acrylate or neopentyl glycol propoxylate di ( And (meth) acrylate.

  The polyfunctional (meth) acrylamide compound is preferably a polymerizable compound represented by the following general formula (1).

In general formula (1), R ¹ represents a hydrogen atom or a methyl group. na represents an integer of 2 to 6. Za represents ^a na-valent organic group. La represents ^a single bond or a divalent linking group.

Z ^a is preferably an aliphatic group optionally na value have an ether bond, ^{L a} is an alkylene group is preferred which may have an ether _bond, -CH 2 _CH 2 CH ₂ - is particularly preferred.
L ^a is, in the case of trimethylene group above, Z ^a is from na polyols, na number except polyol residue a hydrogen atom of the hydroxyl group is preferred.

The polyol is more preferably a trivalent to pentavalent polyol, and particularly preferably a trivalent to tetravalent polyol.
The polyol preferably has 3 to 12 carbon atoms, more preferably 4 to 10 carbon atoms, and particularly preferably 4 to 6 carbon atoms. The polyol may contain an ether bond in the molecule.
Specific examples of the polyol include glycerin, erythritol, xylitol, mannitol, sorbitol, trimethylolethane, trimethylolpropane, ditrimethylolpropane, pentaerythritol, dipentaerythritol, tris (2-hydroxyethyl) isocyanurate, and the like. In particular, glycerin, erythritol, xylitol, mannitol, sorbitol, pentaerythritol or dipentaerythritol is preferable.

  The polymerizable compound represented by the general formula (1) is preferably a polymerizable compound represented by the following general formula (2).

In general formula (2), R ¹ represents a hydrogen atom or a methyl group. L ¹ represents a linear or branched alkylene group having 2 to 4 carbon atoms. However, in L ^1, the oxygen atom and the nitrogen atom bonded to both ends of the L ¹ does not take a structure bound to the same carbon atom of L ^1. L ² represents a divalent linking group. k represents 2 or 3. x, y, and z each independently represent an integer of 0-6, and x + y + z satisfies 0-18.

  The polymerizable compound represented by the general formula (2) has four acrylamide groups or methacrylamide groups as polymerizable groups in the molecule, and has high polymerization performance and curing ability. For example, it is polymerized to exhibit curability by irradiation (giving) with energy such as active energy rays such as α rays, γ rays, X rays, ultraviolet rays, visible rays, infrared rays, electron beams, and heat. Moreover, the polymerizable compound represented by the general formula (1) is water-soluble and dissolves well in water-soluble organic solvents such as water and alcohol.

R ¹ represents a hydrogen atom or a methyl group. Several R < ¹ > may mutually be same or different. R ¹ is preferably a hydrogen atom.

L ¹ represents a linear or branched alkylene group having 2 to 4 carbon atoms. The plurality of L ¹ may be the same as or different from each other. The number of carbon atoms of the alkylene group represented by L ¹ is preferably 3 or 4, more preferably 3, and among these, a linear alkylene group having 3 carbon atoms is particularly preferable. The alkylene group of L ¹ may further have a substituent, and examples of the substituent include an aryl group and an alkoxy group.
However, in L ^1, the oxygen atom and the nitrogen atom bonded to both ends of the L ¹ does not take a structure bound to the same carbon atom of L ^1. L ¹ is a linear or branched alkylene group linking an oxygen atom and a nitrogen atom of a (meth) acrylamide group. When the alkylene group has a branched structure, oxygen atoms at both ends and the nitrogen of the (meth) acrylamide group It is also conceivable to take an —O—C—N— structure (hemaminal structure) in which an atom is bonded to the same carbon atom in an alkylene group. However, the polymerizable compound represented by the general formula (2) does not include a compound having such a structure. When the molecule has an —O—C—N— structure, decomposition is likely to occur at the position of the carbon atom. In particular, such a compound is easily decomposed during storage, and the decomposition is accelerated in the presence of water and moisture, thereby reducing the storage stability of the cured composition.

Examples of the divalent linking group in L ² include an alkylene group, an arylene group, a divalent heterocyclic group, or a group composed of a combination thereof, and an alkylene group is preferable. When the divalent linking group includes an alkylene group, the alkylene group may further include at least one group selected from -O-, -S-, and -N (Ra)-. . Here, Ra represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.
The term “-O— contained in the alkylene group” means that the alkylene group of the linking group of the linking group is linked via the heteroatom as in, for example, -alkylene-O-alkylene-.
Specific examples of the alkylene group containing —O— include —C ₂ H ₄ —O—C ₂ H ₄ —, —C ₃ H ₆ —O—C ₃ H ₆ — and the like.

When L ² contains an alkylene group, examples of the alkylene group include methylene, ethylene, propylene, butylene, pentylene, hexylene, heptylene, octyne, nonylene and the like. L number of carbon atoms in the alkylene group of ² to 6 is preferred, more preferably 1 to 3, 1 is particularly preferred. Further, this alkylene group may further have a substituent, and examples of the substituent include an aryl group and an alkoxy group.

When L ² contains an arylene group, examples of the arylene group include phenylene and naphthylene. 6-14 are preferable, as for carbon number of an arylene group, 6-10 are more preferable, and 6 is especially preferable. The arylene group may further have a substituent, and examples of the substituent include an alkyl group and an alkoxy group.

When L ² contains a divalent heterocyclic group, this heterocyclic ring is preferably a 5-membered or 6-membered ring and may be condensed. Further, it may be an aromatic heterocyclic ring or a non-aromatic heterocyclic ring. The heterocyclic ring of the divalent heterocyclic group includes pyridine, pyrazine, pyrimidine, pyridazine, triazine, quinoline, isoquinoline, quinazoline, cinnoline, phthalazine, quinoxaline, pyrrole, indole, furan, benzofuran, thiophene, benzothiophene, pyrazole, imidazole, Examples include benzimidazole, triazole, oxazole, benzoxazole, thiazole, benzothiazole, isothiazole, benzisothiazole, thiadiazole, isoxazole, benzisoxazole, pyrrolidine, piperidine, piperazine, imidazolidine, thiazoline and the like. Of these, aromatic heterocycles are preferable, and pyridine, pyrazine, pyrimidine, pyridazine, triazine, pyrazole, imidazole, benzimidazole, triazole, thiazole, benzothiazole, isothiazole, benzisothiazole, and thiadiazole are preferable.

The position of the two bonds of the heterocycle of the divalent heterocyclic group is not particularly limited. For example, in the case of pyridine, substitution at the 2-position, 3-position, and 4-position is possible. The bond may be in any position.
Moreover, the heterocyclic ring of a bivalent heterocyclic group may further have a substituent, and examples of the substituent include an alkyl group, an aryl group, and an alkoxy group.

k represents 2 or 3, and a plurality of k may be the same as or different from each other. C _k H _2k may have a linear structure or a branched structure.

  x, y, and z each independently represent an integer of 0 to 6, preferably an integer of 0 to 5, and more preferably an integer of 0 to 3. Although x + y + z satisfies 0-18, 0-15 are preferable and 0-9 are more preferable.

  Specific examples of the polymerizable compound represented by the general formula (2) are shown below, but the present invention is not limited thereto.

  The polymerizable compound represented by the general formula (2) can be produced, for example, according to the following scheme 1 or scheme 2.

Scheme 1
(First step) A step of obtaining a polycyano compound by a reaction of acrylonitrile and trishydroxymethylaminomethane. The reaction in this step is preferably performed at 3 to 60 ° C. for 2 to 8 hours.
(Second step) A step of reacting a polycyano compound with hydrogen in the presence of a catalyst to obtain a polyamine compound by a reduction reaction. The reaction in this step is preferably performed at 20 to 60 ° C. for 5 to 16 hours.
(Third step) A step of obtaining a polyfunctional acrylamide compound by an acylation reaction between a polyamine compound and acrylic acid chloride or methacrylic acid chloride. The reaction in this step is preferably performed at 3 to 25 ° C. for 1 to 5 hours. As the acylating agent, diacrylic anhydride or dimethacrylic anhydride may be used instead of acid chloride. In addition, by using both acrylic acid chloride and methacrylic acid chloride in the acylation step, a compound having an acrylamide group and a methacrylamide group in the same molecule can be obtained as the final product.

Scheme 2
(First step) A step of obtaining a nitrogen-protected aminoalcohol compound by a protective group introduction reaction with a benzyl group (Bz in the above scheme), a benzyloxycarbonyl group or the like on the nitrogen atom of the aminoalcohol. The reaction in this step is preferably performed at 3 to 25 ° C. for 3 to 5 hours.
(2nd process) The process of introduce | transducing leaving groups, such as a methanesulfonyl group and p-toluenesulfonyl group, into OH group of a nitrogen protection amino alcohol compound, and obtaining a sulfonyl compound. The reaction in this step is preferably performed at 3 to 25 ° C. for 2 to 5 hours.
(Third step) A step of obtaining an amino alcohol addition compound by S _N 2 reaction between a sulfonyl compound and trishydroxymethylnitromethane. The reaction in this step is preferably performed at 3 to 70 ° C. for 5 to 10 hours.
(Fourth step) A step of reacting an amino alcohol addition compound with hydrogen in the presence of a catalyst to obtain a polyamine compound by hydrogenation reaction. The reaction in this step is preferably performed at 20 to 60 ° C. for 5 to 16 hours.
(Fifth step) A step of obtaining a polyfunctional acrylamide compound by an acylation reaction between a polyamine compound and acrylic acid chloride or methacrylic acid chloride. The reaction in this step is preferably performed at 3 to 25 ° C. for 1 to 5 hours. The acylating agent may be diacrylic anhydride or dimethacrylic anhydride instead of acid chloride. In addition, by using both acrylic acid chloride and methacrylic acid chloride in the acylation step, a compound having an acrylamide group and a methacrylamide group in the same molecule can be obtained as the final product.

  The compound obtained by the above steps can be purified from the reaction product solution by a conventional method. For example, it can be purified by liquid separation extraction using an organic solvent, crystallization using a poor solvent, column chromatography using silica gel, and the like.

  In the present invention, two or more polymerizable compounds represented by the general formula (1) may be used in combination.

  Other polyfunctional polymerizable monomers having a plurality of ethylenically unsaturated groups other than the above include vinyl (meth) acrylate, divinylbenzene, divinyl succinate, diallyl phthalate, triallyl phosphate, triallyl isocyanurate, Examples include (meth) acrylic acid tris (hydroxyethyl) isocyanurate and tris [2- (meth) acryloylethyl] isocyanurate.

  Examples of the high molecular weight (oligomer) polymerizable compound having an ethylenically unsaturated group include (meth) acrylated epoxy resin, (meth) acrylated or vinyl-ether or epoxy group-containing polyester, polyurethane and polyether. . Further, ethylenically unsaturated polyester resins made from maleic acid, phthalic acid and one or more diols and having a weight average molecular weight of about 500 to 3000, as well as vinyl ether monomers and oligomers, and polyesters, polyurethanes, polyethers, Maleate-terminated oligomers having polyvinyl ether and epoxide backbones can also be used.

The content of the polymerizable compound in the active energy ray-curable ink composition of the present invention is preferably 0.1 to 99.9% by mass, more preferably 1 to 45% by mass, and still more preferably 2 to 35% by mass. 10 to 20% by mass is particularly preferable.
It is preferable that the content of the polymerizable compound is within the above range since both desired curability and flexibility can be provided.
Moreover, when using a polyfunctional polymerizable compound for a polymeric compound or using together with a monofunctional polymerizable compound, 0.1-99.9 mass% is preferable, and, as for content of a polyfunctional polymerizable compound, 0.0. 1-45 mass% is more preferable, 0.1-20 mass% is further more preferable, and 1-10 mass% is especially preferable. It is preferable for the content of the polymerizable compound to be in the above-mentioned range since the curability can be improved and the storage stability of the active energy ray-curable ink composition can also be improved.

(Polymerization initiator)
The active energy ray-curable ink composition of the present invention particularly preferably contains a polymerization initiator. The polymerization initiator is not particularly limited as long as the polymerizable compound can be polymerized. However, since the ink composition of the present invention is an active energy ray curable type, a photopolymerization initiator is preferable, and radical polymerization initiation is particularly preferable. Agents are preferred.
A radical polymerization initiator is a compound that absorbs external energy to generate radical polymerization initiating species. Radical polymerization initiators are broadly divided into those whose external energy for initiating polymerization is heat and those that are active energy rays. In the present invention, photopolymerization that generates radical polymerization initiating species by active energy rays. Initiators are preferably used.
Among these, a water-soluble photopolymerization initiator or an aqueous dispersion of a water-insoluble photopolymerization initiator is preferably used, and a water-soluble photopolymerization initiator is more preferable. In addition, the water solubility in a photoinitiator means melt | dissolving 0.5 mass% or more in distilled water at 25 degreeC. The water-soluble photopolymerization initiator is more preferably dissolved by 1% by mass or more in distilled water at 25 ° C., particularly preferably 3% by mass or more.

  Photopolymerization initiators include aromatic ketones, acylphosphine compounds, aromatic onium salt compounds, thio compounds, hexaarylbiimidazole compounds, ketoxime ester compounds, borate compounds, azinium compounds, metallocene compounds, active ester compounds, carbon Examples thereof include compounds having a halogen bond, and alkylamine compounds.

  Examples of aromatic ketones, acylphosphine oxide compounds and thio compounds include “RADIATION CURING IN POLYMER SCIENCE AND TECHNOLOGY”, J. Am. P. FOUASSIER, J.A. F. RABEK (1993), pp. And compounds having a benzophenone skeleton or a thioxanthone skeleton described in 77-117. For example, an α-thiobenzophenone compound described in JP-B-47-6416, a benzoin ether compound described in JP-B-47-3981, an α-substituted benzoin compound described in JP-B-47-22326, Benzoin derivatives described in JP-A-47-23664, aroylphosphonic acid esters described in JP-A-57-30704, dialkoxybenzophenones described in JP-B-60-26483, JP-B-60-26403, Benzoin ethers described in JP-A No. 62-81345, Japanese Patent Publication No. 1-33422, US Pat. No. 4,318,791, and European Patent Application Publication No. 0284561A1 Benzophenones, p-di (dimethylamino) described in JP-A-2-211452 Nzoyl) benzene, thio-substituted aromatic ketone described in JP-A-61-194062, acylphosphine sulfide described in JP-B-2-9597, acylphosphine described in JP-B-2-9596, Examples thereof include thioxanthones described in JP-A-63-61950 and coumarins described in JP-B-59-42864. Moreover, the polymerization initiators described in JP 2008-105379 A and JP 2009-114290 A are also preferable. Moreover, the polymerization initiator etc. which are described in 65th-148th pages of "An ultraviolet curing system" written by Kiyosuke Kato (the General Technology Center Co., Ltd. issue: 1989), etc. can be mentioned.

  Among these, aromatic ketones or acylphosphine oxide compounds. In particular, p-phenylbenzophenone (manufactured by Wako Pure Chemical Industries), bis (2,4,6-trimethylbenzoyl) phenylphosphine oxide (Irgacure 819, manufactured by BASF Japan), 2,4,6-trimethylbenzoyldiphenylphosphine Oxide (Darocur TPO, manufactured by BASF Japan), 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butanone-1 (Irgacure 369, manufactured by BASF Japan), 2-methyl-1 -(4-Methylthiophenyl) -2-morpholinopropan-1-one (Irgacure 907, manufactured by BASF Japan Ltd.), 1- [4- (2-hydroxyethoxy) -phenyl] -2-hydroxy-2-methyl -1-propan-1-one (Irgac re 2959, BASF · Japan Ltd.) are preferable, from the viewpoint of water solubility and hydrolysis resistance, Irgacure 2959 (manufactured by BASF · Japan) are most preferred.

In this invention, a polymerization initiator may be contained individually by 1 type and may contain 2 or more types.
The content of the polymerization initiator in the active energy ray-curable ink composition is preferably 0.1 to 20% by mass in terms of solid content, more preferably 0.5 to 10% by mass, and 1.0 to 5%. Mass% is particularly preferred.

〔solvent〕
The active energy ray-curable ink composition of the present invention preferably contains a solvent. Examples of the solvent include water, organic solvents, and mixtures thereof. Although only an organic solvent may be used as the solvent, from the viewpoint of reducing environmental burden and improving safety, the solvent preferably contains at least water, and particularly preferably water. By using water as the solvent, the above-described polymerizable compound (particularly the polymerizable compound represented by the general formula (1)) can be dissolved well. The water is more preferably water containing no ionic impurities such as ion-exchanged water or distilled water. The water content in the active energy ray-curable ink composition of the present invention is preferably 10 to 95% by mass, more preferably 30 to 90% by mass, and 50 to 80% by mass. Particularly preferred.

  The organic solvent may be expected to have an effect of preventing drying or promoting the penetration of ink into paper, and may be used in the present invention. In this case, it is preferably used in combination with water, and has characteristics such as safety. It is more preferable to use in the range which does not impair. In consideration of combined use with water, it is more preferable to use a water-soluble organic solvent. In order to prevent the ink composition adhering to the vicinity of the ink discharge port of the ejection nozzle from drying and solidifying and clogging the ink discharge port, it is preferable to use an organic solvent having a vapor pressure lower than that of water. .

  Examples of the organic solvent that can be used in the present invention include alkanediols (polyhydric alcohols) such as glycerin, 1,2,6-hexanetriol, trimethylolpropane, ethylene glycol, and propylene glycol; sugar alcohols; ethanol, methanol Alkyl alcohols having 1 to 4 carbon atoms, such as butanol, propanol and 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-isopropyl ether, diethylene glycol Mono-isopropyl ether, ethylene glycol mono-n-butyl ether, ethylene glycol mono-t-butyl ether, diethylene glycol mono-t-butyl ether, triethylene glycol monoethyl ether, 1-methyl-1-methoxybutanol, propylene glycol monomethyl ether, propylene Glycol monoethyl ether, propylene glycol mono-t-butyl ether, propylene glycol mono-n-propyl ether, propylene glycol mono-isopropyl ether, dipropylene glycol, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol mono -N-propyl ether, dipropylene glycol mono-isopropyl Ether, glycol ethers such as tripropylene glycol monomethyl ether, and the like.

  For the purpose of preventing drying, polyhydric alcohols are useful. Examples include glycerin, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, 1,3-butanediol, 2,3-butanediol, and the like.

  For the purpose of promoting penetration, aliphatic diols are suitable. 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, -Ethyl-1,3-hexanediol, 2,2,4-trimethyl-1,3-pentanediol and the like. Among these, preferred examples include 2-ethyl-1,3-hexanediol and 2,2,4-trimethyl-1,3-pentanediol.

  Moreover, it is preferable to contain at least 1 sort (s) of the compound represented by the following general formula (S) as an organic solvent from the point of curling generation | occurrence | production on a recording medium.

In the general formula (S), ^{L a} represents an alkylene group. l1, l2 and l3 each independently represents an integer of 1 or more and satisfies l + m + n = 3 to 15.

L ^a is ethylene, propylene is preferred, propylene is more preferred. Here, when l1, l2, and l3 are 2 or more, a plurality of —O—L ^a — may be the same or different.
l + m + n is preferably in the range of 3 to 12, and more preferably in the range of 3 to 10. When the value of l + m + n is 3 or more, a good curling suppression force is shown, and when it is 15 or less, a good discharge property is obtained.

  Specific examples of the compound represented by the general formula (S) are shown below. In the following exemplary compounds, the description “POP (3) glyceryl ether” means glyceryl ether in which a total of three propyleneoxy groups are bonded to glycerin, and the same applies to other descriptions.

Furthermore, it is also preferable to contain the compounds (a) to (g) exemplified below as organic solvents from the viewpoint of curling generation in the recording medium. AO represents at least one of ethyleneoxy (EO) [—CH ₂ CH ₂ O—] and propyleneoxy (PO) [—C ₃ H ₆ O—].

_{(A) n-C 4 H} 9 O (AO) 4 -H ( in AO = EO or PO, the ratio of EO: PO = 1: 1) ( manufactured by NOF Corporation)
_{(B) n-C 4 H} 9 O (AO) 10 -H ( in AO = EO or PO, the ratio of EO: PO = 1: 1) ( manufactured by NOF Corporation)
(C) HO (AO) ₄₀ -H (AO = EO or PO, the ratio is EO: PO = 1: 3) (manufactured by NOF Corporation)
(D) HO (AO) ₅₅ -H (AO = EO or PO, the ratio is EO: PO = 5: 6) (manufactured by NOF Corporation)
(E) HO (PO) _3- H (PP-200, manufactured by Sanyo Chemical Industries, Ltd.)
(F) HO (PO) ₇ -H (PP-400, manufactured by Sanyo Chemical Industries, Ltd.)
(G) 1,2-hexanediol (manufactured by Ube Industries)

In this invention, the organic solvent may be used individually by 1 type, or may be used in mixture of 2 or more types. The content of the organic solvent is preferably 0 to 40% by mass, more preferably 0 to 20% by mass, and particularly preferably 0 to 10% by mass with respect to the total amount of the ink composition.
In addition, the content of the compound represented by the general formula (S) and the exemplary compounds (a) to (g) in the total water-soluble organic solvent is preferably 3% by mass or more, and more preferably 4% by mass or more. Preferably, 5 mass% or more is more preferable. By setting it within this range, curling can be suppressed without deteriorating the stability and ejection properties of the ink.

[Sensitizer]
The active energy ray-curable ink composition of the present invention may contain a sensitizer such as a sensitizing dye in addition to the components described above, and is preferable in the present invention. A normal sensitizing dye can be used and is not particularly limited. However, considering the characteristics of the ink composition of the present invention, those having good solubility in water or a water-soluble organic solvent are preferable. Specifically, those that dissolve 0.5% by mass or more in distilled water at room temperature are preferable, those that dissolve 1% by mass or more are more preferable, and those that dissolve 3% by mass or more are particularly preferable. As the sensitizing dye, a polymerization initiator in which a water-insoluble polymerization initiator is dispersed in a water-soluble medium or the like can also be used.
Examples of sensitizing dyes include N- [2-hydroxy-3- (3,4-dimethyl-9-oxo-9H-thioxanthen-2-yloxy) propyl] -N, N, N-trimethylaluminum chloride, Benzophenone, thioxanthone, anthraquinone derivatives and 3-acylcoumarin derivatives, terphenyl, styryl ketone and 3- (aroylmethylene) thiazoline, camphorquinone, eosin, rhodamine and erythrosine, and their modified and dispersed forms that are water-soluble Is mentioned. In addition, a sensitizing dye described in JP 2010-24276 A and a sensitizing dye described in JP 6-107718 A can be preferably used in the present invention.

[Resin particles]
The active energy ray-curable ink composition of the present invention may contain resin particles as necessary. 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, and benzoguanamine resins. A phenol resin, a silicone resin, an epoxy resin, a urethane resin, a paraffin resin, a fluorine resin, or a latex thereof can be used. Of these, acrylic resins, acrylic-styrene resins, styrene resins, crosslinked acrylic resins, and crosslinked styrene resins are preferable.

The mass average molecular weight of the resin particles is preferably 10,000 to 200,000, more preferably 100,000 to 200,000. The mass average molecular weight can be measured in the same manner as in the case of the water-insoluble polymer dispersant described above.
The volume average particle size of the resin particles is preferably 10 nm to 1 μm, more preferably 15 to 200 nm, and particularly preferably 20 to 50 nm. The particle size distribution of the resin particles is not particularly limited, and may be either a wide particle size distribution or a monodispersed particle size distribution. Two or more kinds of resin particles having a monodispersed particle size distribution may be mixed and used. The volume average particle size and the particle size distribution can be measured in the same manner as in the case of the colored particle dispersion described above.
The glass transition temperature (Tg) of the resin particles is preferably 30 ° C. or higher, more preferably 40 ° C. or higher, and particularly preferably 50 ° C. or higher. In the present invention, the glass transition temperature is a measured Tg obtained by actual measurement. Specifically, the measurement Tg means a value measured under normal measurement conditions using a differential scanning calorimeter (DSC) EXSTAR 6220 manufactured by SII Nanotechnology.

  The content of the resin particles is preferably 0 to 20% by mass, more preferably 0 to 10% by mass, and particularly preferably 0 to 5% by mass with respect to the active energy ray-curable ink composition.

[Surfactant]
The active energy ray-curable ink composition of the present invention may contain a surfactant as a surface tension adjusting agent, if necessary. As the surfactant, any of an anionic surfactant, a cationic surfactant, an amphoteric surfactant, a nonionic surfactant, and a betaine surfactant can be used. Moreover, you may use the dispersing agent (polymer dispersing agent) mentioned above as surfactant. Among these, nonionic surfactants are preferably used, and acetylene glycol derivatives are particularly preferable.

The content of the surfactant in the active energy ray-curable ink composition is not particularly limited, but for example, when used as an ink composition, it is contained so that an appropriate surface tension can be obtained in consideration of the use of the ink and the like. It is preferable to adjust the amount appropriately.
When used as an ink for inkjet recording, from the viewpoint of satisfactorily discharging the active energy ray-curable ink composition, the surface tension of the active energy ray-curable ink composition is preferably 20 to 60 mN / m. It is more preferable to set it to -45 mN / m, and it is especially preferable to set it as 25-40 mN / m. In this case, it is preferable to adjust the content of the surfactant in the ink composition so that the surface tension is within the above range. Specifically, it is preferably 1% by mass or more, more preferably 1 to 10% by mass, and particularly preferably 1 to 3% by mass with respect to the ink composition.

[Other ingredients]
In addition to the above components, the active energy ray-curable ink composition of the present invention may contain other components. Other components include UV absorbers, antifading agents, antifungal agents, pH adjusters, rust inhibitors, antioxidants, emulsion stabilizers, preservatives, antifoaming agents, viscosity modifiers, dispersion stabilizers, chelates Well-known various additives, such as an agent and a solid wetting agent, are mentioned.

  Examples of the ultraviolet absorber include a benzophenone ultraviolet absorber, a benzotriazole ultraviolet absorber, a salicylate ultraviolet absorber, a cyanoacrylate ultraviolet absorber, and a nickel complex ultraviolet absorber.

  As the anti-fading agent, various organic and metal complex anti-fading agents can be used. Examples of the organic anti-fading agent include hydroquinones, alkoxyphenols, dialkoxyphenols, phenols, anilines, amines, indanes, chromans, alkoxyanilines, and heterocycles. Examples of the metal complex anti-fading agent include nickel complexes and zinc complexes.

  Antifungal agents include sodium dehydroacetate, sodium benzoate, sodium pyridinethione-1-oxide, p-hydroxybenzoic acid ethyl ester, 1,2-benzisothiazolin-3-one, sodium sorbate, sodium pentachlorophenol, etc. Is mentioned. The antifungal agent is preferably contained in the ink composition in the range of 0.02 to 1.00% by mass.

  The pH adjuster is not particularly limited as long as it is a compound that can adjust the pH to a desired value without adversely affecting the cured composition to be prepared. For example, alcohol amines (for example, diethanolamine, triethanolamine, 2-amino-2-ethyl-1,3-propanediol, etc.), alkali metal hydroxides (for example, lithium hydroxide, sodium hydroxide, potassium hydroxide) Etc.), ammonium hydroxide (for example, ammonium hydroxide, quaternary ammonium hydroxide, etc.), phosphonium hydroxide, alkali metal carbonate and the like.

  Examples of the antirust agent include acidic sulfite, sodium thiosulfate, ammonium thiodiglycolate, diisopropylammonium nitrite, pentaerythritol tetranitrate, and dicyclohexylammonium nitrite.

  Examples of the antioxidant include phenolic antioxidants (including hindered phenolic antioxidants), amine antioxidants, sulfur antioxidants, phosphorus antioxidants, and the like.

  Examples of the chelating agent include sodium ethylenediaminetetraacetate, sodium nitrilotriacetate, sodium hydroxyethylethylenediaminetriacetate, sodium diethylenetriaminepentaacetate, sodium uramil diacetate and the like.

[Physical properties of active energy ray-curable ink composition]
The viscosity and surface tension of the active energy ray-curable ink composition of the present invention can be appropriately selected and adjusted according to the use of the active energy ray-curable ink composition and the image forming method.
For example, when the active energy ray-curable ink composition of the present invention is used as an inkjet recording ink, the viscosity of the active energy ray-curable ink composition may be 1.2 mPa · s or more and 15.0 mPa · s or less. It is more preferably 2 mPa · s or more and less than 13 mPa · s, and particularly preferably 2.5 mPa · s or more and less than 10 mPa · s. The surface tension is preferably 20 to 60 mN / m, more preferably 20 to 45 mN / m, and particularly preferably 25 to 40 mN / m. These viscosities and surface tensions in this specification are both measured values at a temperature of 25 ° C.

<Processing liquid>
In the present invention, the treatment liquid contains at least one redox initiator. Moreover, it is comprised including other components, such as an acidic compound and a cationic polymer, as needed.

[Redox initiator]
The redox initiator used in the treatment liquid is a redox initiator having a different action from that of the active energy ray-curable ink composition.
Examples of the redox initiator include an active energy ray-curable ink composition, and an oxidizing agent that is an oxidized redox initiator is preferable for the treatment liquid.

  The content of the oxidized redox initiator or the reduced redox initiator is more preferably 0.05 to 10% by mass, further preferably 0.2 to 5% by mass with respect to the total mass of the treatment liquid, 0.5 -3 mass% is particularly preferred.

In addition to at least one redox initiator, the treatment liquid in the present invention preferably contains a pigment in the ink composition and a flocculant for aggregating other components. The flocculant in the present invention is capable of aggregating (fixing) the ink composition by contacting with the ink composition on the recording medium, and functions as a fixing agent.
Examples of the component for fixing the components in the ink composition include acidic compounds, polyvalent metal salts, and cationic polymers. These can be used alone or in combination of two or more. As the flocculant, an acidic compound is preferable.
The pH (25 ° C.) of the treatment liquid is preferably 0.1 to 6.8, more preferably 0.5 to 6.0, and even more preferably 0.8 to 5.0. .
In order to make the treatment liquid acidic, it may be made acidic by using an acidic redox initiator, or it can be made acidic by containing an acidic compound.

[Acid compound]
In order to make the treatment liquid acidic, it is also preferable to add an acidic compound to the treatment liquid.
The acidic compound preferably has a molecular weight of 50 or more and 200 or less, and preferably has a pKa (25 ° C.) in water of 1 or more and 5 or less.

Acidic compounds include, for example, 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, 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, oxalic acid, acetic acid, benzoic acid and these Preferred examples include derivatives of these compounds, and salts thereof.
The acidic compound preferably has a molecular weight of 50 or more, 1000 or less, more preferably a molecular weight of 50 or more, and 500 or less, and particularly preferably a molecular weight of 50 or more and 200 or less, from the viewpoint of achieving both suppression of volatilization and solubility in a solvent. pKa (in H ₂ O) is preferably an acid of −10 or more and 7 or less, more preferably an acid of 1 or more and 7 or less, and particularly preferably an acid of 1 or more and 5 or less, from the viewpoint of achieving both ink bleeding prevention and photocurability. preferable.

Among these, acidic compounds with high water solubility are preferable. Also, from the viewpoint of fixing the whole ink by reacting with the active energy ray-curable 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 contains an acidic compound, the pH (25 ° C.) of the treatment liquid is preferably 0.1 to 6.8, more preferably 0.5 to 6.0, and 0.8 to More preferably, it is 5.0.

  The content of the acidic compound is preferably 40% by mass or less, more preferably 15 to 40% by mass, further preferably 15% to 35% by mass, and 20% to 30% by mass with respect to the total mass of the treatment liquid. Particularly preferred. By setting the content of the acidic compound to 15 to 40% by mass, the components in the ink composition can be more efficiently fixed.

The amount of the acidic compound applied to the recording medium is not particularly limited as long as it is an amount sufficient to agglomerate the active energy ray-curable ink composition, but the viewpoint that the active energy ray-curable ink composition is easily fixed. from is ^{preferably 0.5g / m 2 ~4.0g / m 2} , more preferably ^{0.9g / m 2 ~3.75g / m 2} .

[Cationic polymer]
The cationic polymer is preferably at least one cationic polymer selected from poly (vinyl pyridine) salts, poly (vinyl imidazole), polybiguanide and polyguanide.
Among the cationic polymers, polyguanides (preferably poly (hexamethylene guanidine) acetate, polymonoguanide, polymeric biguanide) and poly (vinyl pyridine), which are advantageous from the viewpoint of aggregation rate, are preferable.
A cationic polymer may be used individually by 1 type, and may use 2 or more types together.

  The mass average molecular weight of the cationic polymer is preferably smaller in terms of the viscosity of the treatment liquid. When the treatment liquid is applied to the recording medium by an inkjet method, a range of 500 to 500,000 is preferable, a range of 700 to 200,000 is more preferable, and a range of 1,000 to 100,000 is more preferable. . When the mass average molecular weight is 500 or more, it is advantageous from the viewpoint of the aggregation rate, and when it is 500,000 or less, it is advantageous from the viewpoint of ejection reliability. However, this is not the case when the treatment liquid is applied to the recording medium by a method other than inkjet.

  The treatment liquid preferably contains a cationic polymer, and the pH (25 ° C.) of the treatment liquid is preferably from 1.0 to 10.0, more preferably from 2.0 to 9.0. More preferably, it is 0.0 to 7.0.

1-35 mass% is preferable with respect to the total mass of a processing liquid, and, as for content of a cationic polymer, 5-25 mass% is more preferable.
The amount of cationic polymer applied to the coated paper is not particularly limited as long as it is an amount sufficient to stabilize the active energy ray-curable ink composition, but from the viewpoint that the ink composition is easily fixed, preferably ^{0.5g / m 2 ~4.0g / m 2} , 0.9g / m 2 ~3.75g / m 2 is more preferable.

  The treatment liquid can further comprise an aqueous solvent (for example, water, a water-soluble organic solvent, etc.). Moreover, you may comprise suitably including various additives, such as surfactant.

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

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

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

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

The application amount of the treatment liquid is not particularly limited as long as the active energy ray-curable ink composition can be aggregated, but preferably, the application amount of the aggregating agent is 0.5 to 4.0 g / m ² or more. It can be an amount. Especially, the quantity from which the provision amount of an aggregating agent will be 0.9-3.75 g / m < ² > is preferable. When the application amount of the flocculant is 0.5 g / m ² or more, good high-speed flocculence can be maintained according to various usage forms of the ink composition. In addition, it is preferable that the amount of the flocculant applied is 4.0 g / m ² or less because the surface properties of the applied recording medium are not adversely affected (such as a change in gloss).

<< Image Forming Method >>
The image forming method of the present invention forms an image using the ink set described above.
It includes at least an ink application step of applying the active energy ray-curable ink composition to the recording medium by an inkjet method and a treatment liquid application step of applying the treatment liquid to the recording medium.
In addition to the above, an irradiation step of irradiating the applied active energy ray-curable ink composition with active energy rays is included.

<Recording medium>
The recording medium used in the image forming method of the present invention is not particularly limited, and is a general printing paper mainly composed of cellulose, used exclusively for offset printing, dedicated inkjet paper, dedicated photographic paper, electrophotographic paper, film (resin Film, etc.), fabric, glass, metal, ceramics and the like can be used.

  As the recording medium, so-called coated paper used for general offset printing or the like is preferable. The coated paper is obtained by applying a coating material to the surface of high-quality paper, neutral paper, or the like that is mainly surface-treated with cellulose as a main component and is not surface-treated. The coated paper is relatively slow in ink absorption and drying in ink jet recording using ordinary water-based inks, and tends to cause quality problems such as color density, image gloss, and scratch resistance. An image having good color density, glossiness, and scratch resistance can be obtained by the image forming method. In particular, a coated paper having a base paper and a coat layer containing an inorganic pigment is preferably used, and a coated paper having a base paper and a coat layer containing kaolin and / or calcium bicarbonate is more preferably used. Specifically, art paper, coated paper, lightweight coated paper or finely coated paper is more preferable.

  Commercially available paper can be used as the coated paper, for example, art paper (A1) such as “OK Kanfuji +” manufactured by Oji Paper Co., Ltd. and “Tokuhishi Art” manufactured by Mitsubishi Paper Industries Co., Ltd. ), Coated paper (A2, B2) such as “OK Top Coat +” manufactured by Oji Paper Co., Ltd. and “Aurora Coat” manufactured by Nippon Paper Industries Co., Ltd., and mat coated paper such as “Ulite” manufactured by Nippon Paper Industries Co., Ltd. Lightweight coated paper (A3) such as “OK Coat L” manufactured by Oji Paper Co., Ltd. and “Aurora L” manufactured by Nippon Paper Industries Co., Ltd. “OK Everlight Coat” manufactured by Oji Paper Co., Ltd. and Nippon Paper Industries Co., Ltd. Examples thereof include finely coated paper such as “Aurora S” manufactured by the Company.

<Ink application process>
The method for applying the active energy ray-curable ink composition of the present invention to a recording medium is not particularly limited as long as the ink composition can be applied in a desired image-like manner, and various commonly used ink application methods can be used. it can. Examples thereof include a relief printing method, a lithographic printing method, an intaglio printing method, a stencil printing method, and an ink jet method. Among these, the ink application process is an active energy ray curable type by an ink jet method from the viewpoint that the ink composition of the present invention is particularly suitable as an ink for ink jet recording and that the recording apparatus is compact and has high speed recording properties. It is preferable to carry out by applying the ink composition onto a recording medium.

(Inkjet method)
In the ink jet method, energy is supplied to the active energy ray-curable ink composition, whereby the ink composition is ejected from the head to form a colored image on the recording medium.

The ink jet method used in the image forming method of the present invention is not particularly limited, and is a known method, for example, a thermal ink jet (Bubble Jet (registered trademark)) method in which air is formed by heating ink to form bubbles. Charge control method that discharges ink using electrostatic attraction force, Drop-on-demand method (pressure pulse method) that uses vibration pressure of piezo element, Irradiation pressure by irradiating ink by changing electric signal to acoustic beam Any acoustic method that uses ink to eject ink can be applied.
The ink jet method may be either an on-demand method or a continuous method. Furthermore, there is no restriction | limiting in particular about the ink nozzle etc. to be used, According to the objective, it can select suitably.
The ink jet method includes a method of ejecting a large number of 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.

Also, as an ink jet method, a short type serial head is used, and a shuttle system that performs recording while scanning the head in the width direction of the recording medium, and a line head in which recording elements are arranged corresponding to the entire area of one side of the recording medium There is a line system using. In the line method, an image can be recorded on the entire surface of the recording medium by scanning the recording medium in a direction orthogonal to the arrangement direction of the recording elements, and a carriage system such as a carriage for scanning a short head is not necessary. Further, since complicated scanning control of the carriage movement and the recording medium is not required, and only the recording medium is moved, the recording speed can be increased as compared with the shuttle system.
More specifically, in the image forming method of the present invention, the ink jet method described in paragraph Nos. 0093 to 0105 of JP-A No. 2003-306623 can be preferably applied.

<Processing liquid application process>
The image forming method of the present invention includes a treatment liquid application step of applying the treatment liquid containing at least a redox initiator onto a recording medium. The treatment liquid application step may be provided either before or after the ink application step. In the image forming method of the present invention, an embodiment in which an ink application process is provided after the treatment liquid application process is preferable.
Specifically, before applying the active energy ray-curable ink composition, a treatment liquid for aggregating the color material (pigment, etc.) and / or polymer particles in the ink composition is applied on the recording medium in advance. A mode in which the active energy ray-curable ink composition is applied so as to come into contact with the treatment liquid applied on the recording medium is preferable. By performing this step, the image recording can be speeded up, and an image with high density and resolution can be obtained even at high speed recording.

<Heat drying process>
In the image forming method of the present invention, the ink application step is provided after the treatment liquid application step, and the treatment liquid on the recording medium is applied after the treatment liquid is applied on the recording medium and before the ink composition is applied. It is preferable to further provide a heat drying step for heat drying. By heating and drying the treatment liquid in advance before the ink application step, ink colorability such as bleeding prevention is improved, and a visible image with good color density and hue can be recorded.

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

<Active energy ray irradiation process>
After the ink application step, the ink composition applied on the recording medium is irradiated with active energy rays. By irradiation with active energy rays, the polymerizable compound in the ink composition is cured to form a cured film containing a color material, and the image can be fixed.

In the image forming method of the present invention, α-rays, γ-rays, electron beams, X-rays, ultraviolet rays, visible light, infrared light, etc. can be used as active energy rays. Of these active energy rays, ultraviolet rays, visible rays, and infrared rays are preferable from the viewpoint of safety and the like, and ultraviolet rays are more preferable. The wavelength of the active energy ray is, for example, preferably 200 to 600 nm, more preferably 250 to 450 nm, and particularly preferably 250 to 400 nm.
The output of the active energy ray is preferably at 5000 mJ / cm ² or less, more preferably ^{10~4000mJ / cm 2, 20~3000mJ / cm} 2 is particularly preferred.

Devices that can irradiate active energy rays include mercury lamps such as LED lamps, high-pressure mercury lamps, ultra-high pressure mercury lamps, deep UV lamps, and low-pressure UV lamps, halide lamps, xenon flash lamps, metal halide lamps, ArF excimer lamps, and KrF excimer lamps. There are exposure apparatuses that use an excimer lamp, an extreme ultraviolet lamp, an electron beam, or an X-ray lamp as a light source. The ultraviolet irradiation can be performed using a normal ultraviolet irradiation apparatus, for example, a commercially available ultraviolet irradiation apparatus for curing / adhesion / exposure (USHIO INC. SP9-250UB, etc.).
Moreover, a light emitting diode (LED) and a laser diode (LD) can also be used as an active energy ray source. LED (UV-LED) and LD (UV-LD) are small, have a long lifetime, high efficiency, and low cost, and are expected as light sources for photo-curable ink jets. In particular, when an ultraviolet light source is required, an ultraviolet LED and an ultraviolet LD can be used. For example, Nichia Corporation has introduced a purple LED whose main emission spectrum has a wavelength between 365 nm and 420 nm.
The active energy ray source used in the image forming method of the present invention is preferably a mercury lamp or a metal halide lamp.

<Ink drying process>
In the image forming method of the present invention, if necessary, an ink drying step of drying and removing an ink solvent (for example, water, an organic solvent, etc.) in the active energy ray-curable ink composition applied on the recording medium is performed. You may have.
The ink drying step may be performed after the ink application step and may be performed before or after the active energy ray irradiation step, but is preferably performed before the active energy ray irradiation step.
The ink drying method only needs to remove at least a part of the ink solvent, and a commonly used method can be applied. For example, heating by a heater or the like, blowing by a dryer or the like, or a combination of these can be performed.

  EXAMPLES Hereinafter, although this invention is demonstrated in detail based on an Example, this invention is not limited to these Examples. Unless otherwise specified, “part” and “%” are based on mass.

Example 1
After preparing the polymer dispersion P-1 as follows, a dispersion of a resin-coated pigment was prepared using the polymer dispersion P-1.

(Synthesis of polymer dispersant P-1)
To a 1000 ml three-necked flask equipped with a stirrer and a condenser tube, 88 g of methyl ethyl ketone was added and heated to 72 ° C. under a nitrogen atmosphere. Here, 50 g of methyl ethyl ketone was mixed with 0.85 g of dimethyl 2,2′-azobisisobutyrate and benzyl methacrylate. A solution in which 60 g, 10 g of methacrylic acid and 30 g of methyl methacrylate were dissolved was dropped over 3 hours. After completion of the dropwise addition, the reaction was further continued for 1 hour, and then a solution of 0.42 g of dimethyl 2,2′-azobisisobutyrate in 2 g of methyl ethyl ketone was added, 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 resin was dried to obtain 96 g of a polymer dispersant P-1.
The composition of the obtained resin was confirmed by ¹ H-NMR, and the mass average molecular weight (Mw) determined by GPC was 44,600. Furthermore, when the acid value was calculated | required by the method as described in JIS specification (JISK0070: 1992), it was 65.2 mgKOH / g.

(Preparation of dispersion of resin-coated pigment)
-Resin-coated cyan pigment dispersion-
Pigment Blue 15: 3 (phthalocyanine blue A220, manufactured by Dainichi Seika Co., Ltd.), 5 parts by mass of the polymer dispersant P-1, 42 parts by mass of methyl ethyl ketone, and 5.5 mol of 1 mol / L NaOH aqueous solution. Part by mass and 87.2 parts by mass of ion-exchanged water were mixed and dispersed with a bead mill for 2 to 6 hours using 0.1 mmφ zirconia beads.
Methyl ethyl ketone was removed from the obtained dispersion at 55 ° C. under reduced pressure, and a part of water was further removed to obtain a dispersion (colored particles) of a resin-coated cyan pigment having a pigment concentration of 10.2% by mass. It was.

-Resin-coated magenta pigment dispersion-
In the preparation of the resin-coated cyan pigment dispersion, Chromaphal Jet Magenta DMQ (Pigment Red 122, manufactured by Ciba Specialty Chemicals) was used instead of phthalocyanine blue A220 used as a pigment. A dispersion (colored particles) of a resin-coated magenta pigment was obtained.

-Resin-coated yellow pigment dispersion-
Resin-coated cyan pigment dispersion was prepared in the same manner as above except that Irgalite Yellow GS (Pigment Yellow 74, manufactured by Ciba Specialty Chemicals) was used instead of phthalocyanine blue A220 used as a pigment. A dispersion (colored particles) of a coated yellow pigment was obtained.

-Resin-coated black ink pigment dispersion-
In the preparation of the resin-coated cyan pigment dispersion, the same procedure as described above except that the pigment dispersion CAB-O-JETTM200 (carbon black dispersion, manufactured by CABOT) was used instead of the resin-coated cyan pigment dispersion. A resin-coated black ink pigment dispersion was prepared. The pH value was 8.5.

(Synthesis of polymerizable compounds)
The polymerizable compound to be used was synthesized as follows.
(Synthesis of polyfunctional polymerizable compounds)
-Synthesis of polymerizable compound 1-
The polymerizable compound 1 exemplified above was synthesized according to the following.

(First step)
In a 1 L three-necked flask equipped with a stirrer bar, 121 g (1 equivalent) of tris (hydroxymethyl) aminomethane (manufactured by Tokyo Chemical Industry Co., Ltd.), 84 ml of 50% aqueous potassium hydroxide solution and 423 ml of toluene were added and stirred. The reaction system was maintained at 20 to 25 ° C., and 397.5 g (7.5 equivalents) of acrylonitrile was added dropwise over 2 hours. After dripping, after stirring for 1.5 hours, 540 ml of toluene was added to the reaction system, the reaction mixture was transferred to a separatory funnel, and the aqueous layer was removed. The remaining organic layer was dried over magnesium sulfate, filtered through celite, and the solvent was distilled off under reduced pressure to obtain an acrylonitrile adduct. The results of analysis of the obtained substance by ¹ H NMR and MS showed a good agreement with the known substance, and thus it was used for the next reduction reaction without further purification.

(Second step)
In a 1 L autoclave, 24 g of the previously obtained acrylonitrile adduct, 48 g of Ni catalyst (Raney nickel 2400, manufactured by WR Grace & Co.), and 600 ml of 25% aqueous ammonia: methanol = 1: 1 solution were suspended and reacted. The container was sealed. 10 Mpa of hydrogen was introduced into the reaction vessel and reacted at a reaction temperature of 25 ° C. for 16 hours.
The disappearance of the raw materials was confirmed by ¹ H NMR, the reaction mixture was filtered through celite, and the celite was washed several times with methanol. The filtrate was evaporated under reduced pressure to obtain a polyamine compound. The obtained material was used in the next reaction without further purification.

(Third process)
To a 2 L three-necked flask equipped with a stirrer was added 30 g of the polyamine obtained above, 120 g of NaHCO ₃ (14 equivalents), 1 L of dichloromethane, and 50 ml of water, and 92.8 g (10 equivalents) of acrylic acid chloride in an ice bath. Was added dropwise over 3 hours and then stirred at room temperature for 3 hours. After confirming the disappearance of the raw materials by ¹ H NMR, the reaction mixture was evaporated under reduced pressure, the reaction mixture was dried over magnesium sulfate, filtered through celite, and the solvent was evaporated under reduced pressure. Finally, it was purified by column chromatography (ethyl acetate / methanol = 4: 1) to obtain a white solid (yield 40%) at room temperature. The yield of the above three steps was 40%.

The obtained white solid was identified by ¹ H-NMR under the following measurement conditions.

-Synthesis of polymerizable compound 2-
In the first step of the synthesis scheme of the polymerizable compound 1, the polymerizable compound 2 (colorless liquid) was prepared in the same manner as in the synthesis example of the polymerizable compound 1 except that 74.7 g of methacrylonitrile was added instead of acrylonitrile. Synthesized. The yield of 3 steps was 37%.
The colorless liquid obtained by synthesis was identified by ¹ H-NMR in the same manner as in the synthesis example of the polymerizable compound 1, and confirmed to have a structure represented by the polymerizable compound 2.

(Preparation of active energy ray-curable ink composition)
An active energy ray-curable ink composition C-1 was prepared according to the following formulation.

-Ink formula C-1-
-Resin-coated cyan pigment dispersion (solid content) 6% by mass
・ Polymerization initiator 3% by mass
Irgacure 2959 [Ciba Specialty Chemicals Co., Ltd.]
・ Polymerizable compound 20% by mass
Illustrative polymerizable compound 1
・ Redox initiator 0.5% by mass
Iron (II) sulfate [reducing agent]
・ Surfactant 1% by mass
Olphine E1010 [Nisshin Chemical Co., Ltd.]
・ Ion-exchanged water added to 100% by mass in total

  As shown in Table 1 below, ink formulations C-2 to C-7, M-1, Y-1, and K-1 are prepared from the ink formulation C-1, and the active energy ray-curable ink composition C is prepared. -2 to C-7, M-1, Y-1, and K-1 were prepared.

  Here, A-400 represents NK ester A-400 [poly (ethylene glycol) diacrylate, Mn400, manufactured by Shin-Nakamura Chemical Co., Ltd.].

(Preparation of treatment solution)
Treatment liquid 1 was prepared with the following formulation.

-Treatment solution composition-
-Redox initiator 1.7% by mass
Hydrogen peroxide solution (30% by mass) [Oxidizing agent] (Equivalent to 0.5% by mass of active ingredient)
・ Tripropylene glycol monomethyl ether 10.0% by mass
(Water-soluble organic solvent)
・ Ion-exchanged water 89.5% by mass

  Treatment liquids 2 to 6 were prepared from the treatment liquid formulation 1 as shown in Table 2 below.

  In addition, when pH (25 degreeC) of the processing liquid 2 was measured using pH meter WM-50EG (made by Toa DKK Co., Ltd.), it was 1.0.

  Images were formed as described below using a combination of these active energy ray-curable ink compositions and treatment liquid, and various evaluations were performed.

(Image formation)

For GELJET GX5000 printer head (Ricoh's full line head)
The storage tank connected to this was refilled with inks C-1 to C-7, ink M-1, ink Y-1, and ink K-1 obtained above. As the recording medium, “OK Top Coat N +” (basis weight 104.7 g / m ² ) manufactured by Nippon Paper Industries Co., Ltd. was used.

Then, “OK topcoat N +” is fixed on a stage that can move at a speed of 500 mm / second in a predetermined linear direction, which is the sub-scanning direction during recording, and the treatment liquid obtained above is fixed to this with a wire bar coater. It apply | coated so that it might become a thickness of 10 micrometers, and it was made to dry at 50 degreeC for 5 second immediately after application | coating. Then GELJET
The GX5000 printer head is fixedly arranged so that the direction of the line head in which the nozzles are aligned (main scanning direction) is inclined by 75.7 ° with respect to the direction orthogonal to the stage moving direction (sub-scanning direction). Then, while moving the recording medium at a constant speed in the sub-scanning direction, the ink droplet amount is 3.5 pL, the discharge frequency is 24 kHz, the resolution is 1200 dpi × 600 dpi, and the stage speed is 50 mm / s. Printed. Immediately after printing, the image is dried at 60 ° C. for 10 seconds, and after image drying, the image is cured by irradiating with ultraviolet rays (a metal halide lamp manufactured by Eye Graphics Co., Ltd., maximum irradiation wavelength 365 nm) so that the integrated irradiation amount is 1500 mJ / cm ^2. Then, an evaluation sample was obtained.

  Subsequently, the stage moving speed is changed to 50 mm / s, 150 mm / s, 260 mm / s, 340 mm / s, 420 mm / s, and 500 mm / s, and the ejection frequency is set so that the droplet ejection amount is the same as above. The sample was discharged under the changed conditions, and an evaluation sample was prepared for each.

[Evaluation of cohesiveness]
About the obtained evaluation sample, the degree of bleeding (interference between droplets) generated between the ink droplets due to the interference between the droplets by visually checking the uniformity of the image is visually observed, and high-speed cohesion is exhibited. The index to be evaluated. The agglomeration speed was evaluated at a stage speed at which no droplet ejection interference was observed.
The evaluation results are shown in Table 3 below.

<Evaluation criteria>
A +: No droplet ejection interference was observed at 500 mm / s.
A: No droplet ejection interference was observed at 420 mm / s.
A-: No droplet ejection interference was observed at 340 mm / s.
B: No droplet ejection interference was observed at 260 mm / s.
C: No droplet ejection interference was observed at 150 mm / s.
D: No droplet ejection interference was observed at 50 mm / s.

  The obtained results are shown in Table 3 below.

In any of the inks of the present invention, the aggregation speed was fast, and an image excellent in hue and drawing properties (reproducibility of fine lines and fine portions in the image) was obtained even at high speed recording.
On the other hand, in the ink C-7 and the treatment liquid 1 not containing a redox initiator, the aggregation rate when the treatment liquid contacted was inferior.

DESCRIPTION OF SYMBOLS 12 ... Treatment liquid application part 12S ... Treatment liquid discharge head 13 ... Treatment liquid drying zone 14 ... Ink discharge part 15 ... Ink drying zone 16 ... Ultraviolet irradiation part 16S ... UV irradiation lamps 30K, 30C, 30M, 30Y, 30A, 30B... Ink ejection head

Claims (14)

  An ink set comprising an active energy ray-curable ink composition and a treatment liquid, the active energy ray-curable ink composition comprising a coloring material, a polymerizable compound, and an oxidizing agent or a reducing agent constituting a redox initiator. The ink set includes the remaining one of the redox initiators.   The oxidizing agent or reducing agent constituting the redox initiator in the active energy ray-curable ink composition is a reducing agent, and the other one of the redox initiators in the treatment liquid is an oxidizing agent. Item 2. The ink set according to Item 1.   The ink according to claim 1 or 2, wherein the oxidizing agent is hydrogen peroxide or a salt thereof, persulfuric acid or a salt thereof, peroxodisulfuric acid or a salt thereof, cumene hydroperoxide, diacyl peroxide, a percarboxylic acid or a salt thereof. set.   The reducing agent is an iron (II) salt, sulfurous acid, hydrogen sulfite or a salt thereof, metabisulfite, metabisulfite or a salt thereof, an amine compound or an amidine compound. The ink set described in 1.   The reducing agent is an iron (II) salt, sulfurous acid, hydrogen sulfite or a salt thereof, metabisulfuric acid, metabisulfite or a salt thereof, or an amidine compound. Ink set.   The ink set according to claim 1, wherein the color material is a pigment.   The ink set according to any one of claims 1 to 6, wherein the active energy ray-curable ink composition further contains a photopolymerization initiator.   The ink set according to claim 7, wherein the photopolymerization initiator is a radical polymerization initiator.   The ink set according to claim 1, wherein the polymerizable compound is a radical polymerizable monomer.   The ink set according to claim 1, wherein the polymerizable compound is a (meth) acrylamide compound.   The ink set according to any one of claims 1 to 10, wherein the active energy ray-curable ink composition further contains water.   The ink set according to claim 1, wherein the treatment liquid is an acidic treatment liquid.   The ink set according to claim 1, wherein the ink set is an inkjet ink set.   An active energy ray-curable ink composition and an ink treatment step for applying an active energy ray-curable ink composition to a recording medium by an inkjet method and a treatment liquid application step for applying a treatment liquid to the recording medium. An inkjet recording method, wherein the liquid is the active energy ray-curable ink composition according to any one of claims 1 to 13 and a treatment liquid.

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