JP2009235133A - Pigment dispersion and ink composition using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pigment dispersion excellent in dispersibility of a fine pigment and its stability and having a vivid color tone, and an ink composition excellent in dispersibility of a fine pigment and its stability, having a vivid color tone and high coloring power, and capable of forming a high-quality image. <P>SOLUTION: The pigment dispersion includes at least (a) a polymer including a repeating unit represented by general formula (1) and (b) a pigment. The ink composition includes the pigment dispersion. In the formula, R<SP>1</SP>represents a hydrogen atom or the like; R<SP>2</SP>-R<SP>4</SP>each independently represent an alkylene group or a phenylene group; V represents -O-, -CO- or the like; W and X each independently represent -O-, -C(=O)O- or the like; l, m, n, o and p each independently represent 0 or 1; Y represents a single bond or an alkylene group; and Z<SP>1</SP>-Z<SP>3</SP>each independently represent NH, O or the like. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a pigment dispersion having good pigment dispersibility and excellent color development, and an ink composition using the pigment dispersion. In particular, the present invention relates to an ink composition that can be cured by irradiation with actinic radiation to form a high-quality image, and is particularly suitable for inkjet recording applications.

As an image recording method for forming an image on a recording medium such as paper based on an image data signal, an electrophotographic method, a sublimation / melting thermal transfer method, an inkjet method, and the like are known. Among these, the ink jet method can be implemented with an inexpensive apparatus, and the ink can be efficiently used because the ink is ejected only to the required image portion to directly form the image on the recording medium. The running cost is low, the noise is low, and it is excellent as an image recording method.
In addition, according to the ink jet method, it is possible to print not only on plain paper but also on a non-water-absorbing recording medium such as a plastic sheet or metal plate. In addition, the time required for drying and curing of the droplets after printing has a property of greatly affecting the sharpness of the image.

  As one of the ink jet methods, there is a recording method using a curable ink composition for ink jet recording that can be cured by irradiation with actinic radiation. According to this method, a sharp image can be formed by irradiating actinic radiation immediately after printing a curable ink composition and curing ink droplets.

  A curable ink composition that can be applied to such a recording system is required to have high pigment dispersibility and stability over time in order to form a high-definition image excellent in color developability. Generally, in order to give a clear color tone and high coloring power to an ink composition, it is essential to make the pigment finer. In particular, in an ink composition for ink jet recording, the ejected ink droplets have a sharpness of the image. Therefore, it is essential to use particles that are smaller in volume than the thickness of the ink cured film formed by the ink composition. Thus, if the pigment particles are made finer in order to obtain a high coloring power, it becomes difficult to disperse the pigment, and pigment aggregates are likely to be formed. When a pigment dispersant is added, the viscosity of the ink composition is increased. The problem of rising will also arise. The occurrence of pigment aggregates and the increase in the viscosity of the ink composition both adversely affect the ink ejection properties and cause a significant decrease in the performance of the ink composition. The ink composition used in the ink jet system is stored in a cartridge, heated during ejection, and cooled during non-ejection and storage, and thus undergoes repeated heating-cooling temperature changes. There is a problem that the dispersibility of the pigment is deteriorated with time, and viscosity and aggregation are likely to occur.

Therefore, there is a need for an ink composition that has sufficient fluidity, stably disperses finely divided pigments, and has excellent temporal dispersion stability of the pigment dispersion. Various proposals have been made on dispersants for obtaining products.
For example, as a dispersant for a specific pigment such as an ink composition using a pigment derivative as a dispersant (see, for example, Patent Documents 1 and 2), phthalocyanine, or quinacridone to improve the affinity with the pigment. Dispersant such as ink composition using polymer having basic group (for example, refer to Patent Document 3), poly (ethyleneimine) -poly (12-hydroxystearic acid) graft polymer, and specific for dissolving the dispersant An ink composition containing no monomer and using no organic solvent (see, for example, Patent Document 4) has been proposed.
However, in the case of these ink compositions, although the pigment dispersion stability is improved by the function of the dispersant as compared with the conventional case, the fineness of the pigment used is insufficient, and the further fine pigment particles There is room for improvement in the dispersibility enhancement effect, and there is a problem that the dispersion stability after a long period of time or after repeated temperature changes is not sufficient.
JP 2003-119414 A JP 2004-18656 A JP 2003-321628 A JP 2004-131589 A

The problem to be solved by the present invention is to solve the conventional problems and achieve the following object.
That is, the first object of the present invention is to provide a pigment dispersion which is excellent in dispersibility and stability of fine pigments and has a clear color tone.
The second object of the present invention is to provide an ink composition that is excellent in dispersibility and stability of fine pigments, has a clear color tone and high coloring power, and can form a high-quality image. It is to provide.

In order to solve the above-mentioned problems, the present inventors have conducted intensive studies, and as a result, when a polymer having a specific heterocyclic skeleton is used as a pigment dispersant, the pigment dispersibility is excellent, and long-term storage, or The inventors have found that an ink composition in which a decrease in dispersion stability is effectively suppressed even after repeated temperature changes can be obtained.
That is, the present invention is as follows.

<1> A pigment dispersion comprising at least (a) a polymer containing a repeating unit represented by the following general formula (1), and (b) a pigment.

In the general formula (1), R ¹ represents a hydrogen atom or an alkyl group. R ² , R ³ , and R ⁴ each independently represent an alkylene group or a phenylene group. V represents any of —O—, —CO—, —C (═O) O—, —CONR ⁵ —, —OC (═O) —, and a phenylene group, and R ⁵ represents a hydrogen atom, alkyl Represents a group or an aryl group. W and X are each independently —O—, —C (═O) O—, —CONH—, —NHCO—, —NHC (═O) O—, —NHC (═O) NH—, — It represents either OC (= O)-or a phenylene group. l, m, n, o, and p each independently represent 0 or 1. Y represents a single bond or an alkylene group. Z ¹ , Z ² , and Z ³ each independently represent any of NH, NR ⁶ , O, and S, and R ⁶ represents an alkyl group or an aryl group.

<2> In the general formula (1), R ¹ represents a hydrogen atom or a methyl group, and R ² , R ³ , and R ⁴ are each independently an alkylene group having 1 to 12 carbon atoms or a phenylene group. W represents —C (═O) O—, —OC (═O) —, or a phenylene group, and X represents —O—, —NHC (═O) O—, —NHC (═O ) NH— or —C (═O) O—, wherein l, m, n, o, and p each independently represent 0 or 1, It is a dispersion.

<3> An ink composition comprising the pigment dispersion according to <1> or <2>.

<4> The ink composition according to <3>, further including (c) a polymerizable compound.

<5> The ink composition according to <3> or <4>, further including (d) a photopolymerization initiator.

According to the present invention, it is possible to provide a pigment dispersion which is excellent in dispersibility and stability of fine pigments and has a clear color tone.
The present invention also provides an ink composition that is excellent in dispersibility and stability of fine pigments, has a clear color tone and high coloring power, and can form a high-quality image. Can do.

Hereinafter, the present invention will be described in detail.
(Pigment dispersion)
The pigment dispersion of the present invention includes at least (a) a polymer containing a repeating unit represented by the following general formula (1), and (b) a pigment.
Hereinafter, the components (a) and (b) will be described.

<(A) Polymer containing repeating unit represented by general formula (1)>
The pigment dispersion of the present invention is characterized by using (a) a polymer containing a repeating unit represented by the following general formula (1) (hereinafter sometimes simply referred to as “specific polymer”). To do.
In the present invention, the specific polymer acts or functions as a dispersant for the pigment (b) used in combination. Therefore, the specific polymer (b) has a high affinity with the pigment, has a good adsorptivity to the (b) pigment, and is a polymer compound having a specific repeating unit. Due to the steric repulsion effect, the dispersion stability of the ink composition containing the specific polymer can be improved.

In the general formula (1), R ¹ represents a hydrogen atom or an alkyl group.
The alkyl group may be any of linear, branched, and cyclic embodiments, and may have a substituent such as a hydroxyl group or an alkoxy group.
Moreover, as carbon number of an alkyl group, 1-12 are preferable, 1-8 are more preferable, and 1-4 are especially preferable.
Specific examples of the alkyl group represented by R ¹ include methyl group, ethyl group, propyl group, n-butyl group, i-butyl group, t-butyl group, n-hexyl group, cyclohexyl group, 2-hydroxyethyl. Group, 3-hydroxypropyl group, 2-hydroxypropyl group, 2-methoxyethyl group and the like.
R ¹ is preferably a hydrogen atom or a methyl group from the viewpoint of polymerization reactivity.

In the general formula (1), R ² , R ³ , and R ⁴ each independently represent an alkylene group or a phenylene group.
As carbon number of an alkylene group, 1-12 are preferable, 1-8 are more preferable, and 1-6 are especially preferable. Moreover, this alkylene group may have substituents, such as an alkyl group, a hydroxyl group, and an alkoxy group, and may form ring structures, such as a cyclohexyl group, with these substituents.
Specific examples of the alkylene group represented by R ² , R ³ , and R ⁴ include a methylene group, an ethylene group, a propylene group, a trimethylene group, a tetramethylene group, a —CH ₂ CH (OH) CH ₂ — group, and the like. Can be mentioned.
Moreover, the connection mode of the phenylene group represented by R ² , R ³ , and R ⁴ includes any of ortho, meta, and para substitution. The phenylene group may also have a substituent such as an alkyl group, an alkoxy group, a chloro group, a bromo group, an ester group, an amide group.
Among these, as R ² , R ³ , and R ⁴ , an alkylene group and a phenylene group linked at an ortho position are preferable from the viewpoint of easy synthesis.

In the general formula (1), V represents any of —O—, —CO—, —C (═O) O—, —CONR ⁵ —, —OC (═O) —, and a phenylene group. R ⁵ represents a hydrogen atom, an alkyl group, or an aryl group.
The phenylene group represented by V may have a substituent such as an alkyl group, an alkoxy group, a chloro group, a bromo group, an amide group.
Here, specific examples of the alkyl group represented by R ⁵ include methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, i-butyl group, t-butyl group, n- Examples include hexyl group, cyclohexyl group, n-octyl group, 2-hydroxyethyl group, 3-hydroxypropyl group, 2-hydroxypropyl group, 2-methoxyethyl group, phenylmethyl group, and phenylethyl group. R ⁵ is preferably a hydrogen atom, a methyl group, or an ethyl group.
Specific examples of the aryl group represented by R ⁵ include a phenyl group.
Among these, V is preferably —O—, —C (═O) O—, —CONR ⁵ —, or a phenylene group from the viewpoint of polymerization reactivity.

In the general formula (1), W and X are each independently —O—, —C (═O) O—, —CONH—, —NHCO—, —NHC (═O) O—, —NHC. (═O) represents any of NH—, —OC (═O) —, and a phenylene group.
Among these, as W and X, from the viewpoint of easy synthesis, —O—, —C (═O) O—, —OC (═O) —, —NHC (═O) O—, or -NHC (= O) NH- is preferred.

In the said General formula (1), l, m, n, о, and p represent 0 or 1 each independently.
Among these, the following is preferable as a combination of l, m, n, о, and p.
That is, l, m, n, о, and p are all 0 combinations, l, m, and n are 1, о, and p are 0 combinations, or l, m, n, о, and p. A combination in which all are 1 is preferred.

In the general formula (1), Y represents a single bond or an alkylene group.
Specific examples of the alkylene group represented by Y include a methylene group, an ethylene group, and a propylene group.
Y is preferably a single bond or a methylene group from the viewpoint of easy synthesis.

In the general formula (1), Z ¹ , Z ² , and Z ³ each independently represent any of NH, NR ⁶ , O, and S, and R ⁶ represents an alkyl group or an aryl group. .
Among these, a combination in which Z ¹ , Z ² , and Z ³ are all O, a combination in which Z ¹ and Z ² are S, Z ³ is O, Z ¹ and Z ³ are NH, and Z ² A combination in which Z ¹ and Z ³ are NH, Z ² is S, a combination in which Z ¹ is N, and Z ² and Z ³ are O. From an easy point, it is preferable.

Specific examples of the alkyl group represented by R ⁶ include methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, i-butyl group, t-butyl group, n-hexyl group, Examples include cyclohexyl group, n-octyl group, 2-hydroxyethyl group, 3-hydroxypropyl group, 2-hydroxypropyl group, 2-methoxyethyl group, phenylmethyl group, phenylethyl group and the like. Among these, a methyl group or an ethyl group is preferable from the viewpoint of availability of raw materials and easy synthesis.

The aryl group represented by R ⁶ may have a substituent, and examples of the substituent include the alkyl group, aryl group, alkoxy group (methoxy, ethoxy, isopropoxy, etc.), aryloxy group (phenoxy, etc.). ), Halogen (fluorine, chlorine, bromine, etc.), cyano group, alkylthio group, arylthio group, amino group, hydroxyl group and the like.
Specific examples of the aryl group represented by R ⁶ include phenyl group, 2-methylphenyl group, 3-methylphenyl group, 4-methylphenyl group, 4-phenylphenoxy group, 3,5-dimethylphenyl group, 2 -Chlorophenyl group, 3-chlorophenyl group, 4-chlorophenyl group, 3-benzylphenyl group, 4-benzylphenyl group, 3-hydroxymethylphenyl group, 4-hydroxymethylphenyl group, 2-methoxyphenyl group, 3-ethoxyphenyl Group, 4-butoxyphenyl group, 4-t-butoxyphenyl group, 2,4-diethoxyphenyl group, 2,5-dibutoxyphenyl group, 4-phenoxyphenyl group, naphthyl group, 4-dibutylcarbamoylphenyl group, 4-dibutylsulfamoylphenyl group, 3-dodecyloxyphenyl group, 4-dodecyl Examples include oxyphenyl group, 3,4-bis (dodecyloxy) phenyl group, anthracenyl group, phenanthryl group, pyrenyl group, perylenyl group, 4-aminophenyl group, and 4-hydroxyphenyl group. Among these, a phenyl group and a phenyl group substituted with a halogen atom are preferable from the viewpoint of availability of raw materials and easy synthesis.

In the general formula (1), R ¹ represents a hydrogen atom or a methyl group because R ¹ , R ³ , and R ⁴ are Independently represents an alkylene group having 1 to 12 carbon atoms or a phenylene group, W represents —C (═O) O—, —OC (═O) —, or a phenylene group, and X represents —O—, -NHC (= O) O-, -NHC (= O) NH-, or -C (= O) O-, wherein l, m, n, o, and p are each independently 0 or 1 Preferably there is.

  Preferred specific examples [monomers M-1 to M-18] of monomers capable of forming the repeating unit represented by the general formula (1) are shown below. The present invention is not limited to these specific examples.

The specific polymer in the present invention is a graft copolymer containing a repeating unit derived from a polymerizable oligomer having an ethylenically unsaturated double bond at the terminal in addition to the repeating unit represented by the general formula (1) as described above. Particularly preferred is a polymer.
Such a polymerizable oligomer having an ethylenically unsaturated double bond at the terminal is also called a macromonomer because it is a compound having a predetermined molecular weight.
Hereinafter, this polymerizable oligomer will be described.

The polymerizable oligomer in the present invention comprises a polymer chain portion and a polymerizable functional group portion having an ethylenically unsaturated double bond. The polymerizable functional group having an ethylenically unsaturated double bond is preferably present only at one end of the polymer chain in the polymerizable oligomer from the viewpoint of obtaining a desired graft polymer. .
Preferred examples of the polymerizable functional group having an ethylenically unsaturated double bond constituting the polymerizable oligomer include a (meth) acryloyl group and a vinyl group, and a (meth) acryloyl group is particularly preferable.

  The polymer chain portion constituting the polymerizable oligomer is, for example, a single chain formed from at least one monomer selected from the group consisting of alkyl (meth) acrylate, styrene and derivatives thereof, acrylonitrile, vinyl acetate, and butadiene. Preferred examples include polymers or copolymers, polyethylene oxide, polypropylene oxide, polycaprolactone, and the like.

  Preferable examples of the polymerizable oligomer used in the present invention include oligomers represented by the following general formula (2).

In the general formula (2), R ⁷ and R ⁹ each independently represent a hydrogen atom or a methyl group.
R ⁸ is an alkylene group having 1 to 12 carbon atoms (preferably an alkylene group having 2 to 4 carbon atoms, which may have a substituent (for example, a hydroxyl group), and further an ester bond, an ether bond, or an amide bond. Etc.) may be connected through the like.
U is a phenyl group, a phenyl group having an alkyl group having 1 to 4 carbon atoms, or —COOR ^a (where R ^a is an alkyl group having 1 to 6 carbon atoms, a phenyl group, or an aryl having 7 to 10 carbon atoms) Represents an alkyl group), and is preferably ^a phenyl group or —COOR ^a (wherein R ^a represents an alkyl group having 1 to 12 carbon atoms).
q is an integer of 20-200.

Preferable examples of the oligomer (macromonomer) represented by the general formula (2) include polymethyl (meth) acrylate, poly-n-butyl (meth) acrylate, poly-i-butyl (meth) acrylate, and polystyrene molecules. Examples thereof include a polymer having a (meth) acryloyl group bonded to one terminal.
Commercially available products of such polymerizable oligomers include, for example, one-end methacryloylated polystyrene oligomer (Mn = 6000, trade name: AS-6, manufactured by Toa Gosei Chemical Co., Ltd.), one-end methacryloylated polymethyl methacrylate oligomer. (Mn = 6000, trade name: AA-6, manufactured by Toa Gosei Chemical Co., Ltd.) and one-terminal methacryloylated poly-n-butyl acrylate oligomer (Mn = 6000, trade name: AB-6, Toa Gosei Chemical Industry ( Etc.).

  As the polymerizable oligomer used in the present invention, an oligomer represented by the following general formula (3) is also preferred in addition to the polymerizable oligomer represented by the general formula (2).

In the general formula (3), R ¹⁰ represents a hydrogen atom or a methyl group.
R ¹¹ represents an alkylene group having 1 to 8 carbon atoms, preferably an alkylene group having 1 to 6 carbon atoms, and more preferably an alkylene group having 2 to 3 carbon atoms.
X ² represents —OR ¹² or OCOR ¹³ . R ¹² and R ¹³ are each independently a hydrogen atom, an alkyl group (preferably an alkyl group having 1 to 18 carbon atoms), or an aryl group (a phenyl group substituted with an alkyl group having 1 to 18 carbon atoms). ).
r represents an integer of 2 to 200, preferably an integer of 5 to 100, and more preferably an integer of 10 to 100.

  Examples of the oligomer represented by the general formula (3) include polyethylene glycol mono (meth) acrylate, polypropylene glycol mono (meth) acrylate, polyethylene glycol polypropylene glycol mono (meth) acrylate, and polytetramethylene glycol monomethacrylate. Preferably mentioned. These may be commercial products or may be appropriately synthesized.

  As a commercial item of the oligomer represented by the general formula (3), for example, methoxypolyethylene glycol methacrylate (trade names: NK ester M-40G, M-90G, M-230G (above, Toa Gosei Chemical Co., Ltd.) Product name: Blemmer PME-100, PME-200, PME-400, PME-1000, PME-2000, PME-4000 (manufactured by NOF Corporation)), polyethylene glycol monomethacrylate (trade name: BLEMMER PE-90, PE-200, PE-350, manufactured by NOF Corporation, polypropylene glycol monomethacrylate (trade names: BLEMMER PP-500, PP-800, PP-1000, manufactured by NOF Corporation), Polyethylene glycol polypropylene glycol monomethacrylate (trade name BLEMMER 70PEP-370B, manufactured by NOF Corporation, polyethylene glycol polytetramethylene glycol monomethacrylate (trade name: BLEMMER 55PET-800, manufactured by NOF Corporation), polypropylene glycol polytetramethylene glycol monomethacrylate (trade name: BLEMMER NHK-5050, manufactured by NOF Corporation) and the like.

  Here, as molecular weight of the polymerizable oligomer (macromonomer) used in this invention, 1000-10000 are preferable and 2000-9000 are more preferable by the number average molecular weight (Mn) of polystyrene conversion.

The specific polymer in the present invention is preferably a copolymer containing a repeating unit derived from a monomer having a nitrogen atom or a monomer having an acidic functional group as shown below.
That is, when a polymer having a basic group is applied to an acidic pigment, or when a polymer having an acidic group is applied to a basic pigment, an interaction due to an acid-base reaction is likely to occur. It is preferable that a basic group or an acidic group is introduced into the specific polymer in accordance with the type (b) pigment (acid pigment or basic pigment) used in combination.

  Examples of the monomer having a nitrogen atom include N, N-dimethylaminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylate, 1- (N, N-dimethylamino) -1, 1- Dimethylmethyl (meth) acrylate, N, N-dimethylaminohexyl (meth) acrylate, N, N-diethylaminoethyl (meth) acrylate, N, N-diisopropylaminoethyl (meth) acrylate, N, N-di-n- Butylaminoethyl (meth) acrylate, N, N-di-i-butylaminoethyl (meth) acrylate, morpholinoethyl (meth) acrylate, piperidinoethyl (meth) acrylate, 1-pyrrolidinoethyl (meth) acrylate, N, N -Methyl-2-pyrrolidylaminoethyl (meth) ac Rate and N, N- methylphenyl aminoethyl (meth) acrylate (or (meth) acrylates);

Dimethyl (meth) acrylamide, diethyl (meth) acrylamide, diisopropyl (meth) acrylamide, di-n-butyl (meth) acrylamide, di-i-butyl (meth) acrylamide, morpholino (meth) acrylamide, piperidino (meth) acrylamide, N-methyl-2-pyrrolidyl (meth) acrylamide and N, N-methylphenyl (meth) acrylamide (above (meth) acrylamides);
2- (N, N-dimethylamino) ethyl (meth) acrylamide, 2- (N, N-diethylamino) ethyl (meth) acrylamide, 3- (N, N-diethylamino) propyl (meth) acrylamide, 3- (N , N-dimethylamino) propyl (meth) acrylamide, 1- (N, N-dimethylamino) -1,1-dimethylmethyl (meth) acrylamide and 6- (N, N-diethylamino) hexyl (meth) acrylamide (above) Aminoalkyl (meth) acrylamides);
p-vinylbenzyl-N, N-dimethylamine, p-vinylbenzyl-N, N-diethylamine, p-vinylbenzyl-N, N-dihexylamine (above vinylbenzylamines);
2-vinylpyridine, 4-vinylpyridine, N-vinylimidazole;
Mention may be made of vinyl cyanide such as (meth) acrylonitrile and α-chloroacrylonitrile.
Among these, N, N-dimethylaminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylate, 3- (N, N-diethylamino) propyl (meth) acrylamide, 3- (N, N- Preferable examples include dimethylamino) propyl (meth) acrylamide, 2-vinylpyridine, 4-vinylpyridine, N-vinylimidazole, and the like.

Examples of the monomer having an acidic functional group include (meth) acrylic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid, mono-2-((meth) acryloxy) ethyl succinate (trade name: NK ester A-SA, NK ester SA (above, Shin-Nakamura Chemical), HOA-MS, light ester HO-MS (above, Kyoeisha Chemical)), mono-2-((meth) acryloxy) ethyl phthalate ( Product name: NK ester A-SA, NK ester CB-1 (manufactured by Shin-Nakamura Chemical), HOA-MPL (manufactured by Kyoeisha Chemical), Biscote # 2000 (manufactured by Osaka Organic Chemical Industry), Aronix M-5400 (Toagosei) Acrylic ester PA (manufactured by Mitsubishi Rayon)), mono-2-((meth) acryloxy) ethyl hexahydrophthalate (trade name: N) Ester ACB-3, NK ester CB-3 (above, Shin-Nakamura Chemical), HOA-HH, light ester HO-HH (above, Kyoeisha Chemical), acrylic ester HH (Mitsubishi Rayon))), 2-carboxy Ethyl (meth) acrylate (trade name: Aronix M-5600 (manufactured by Toagosei Co., Ltd.), Ebecryl β-CEA (manufactured by Daicel Cytec)), mono-2-((meth) acryloxy) ethylmaleic acid (trade name: SM- 001 (manufactured by degussa)), 2-((meth) acryloxy) ethyl acid phosphate (trade names: light acrylate P-1A, light acrylate P-1M (manufactured by Kyoeisha Chemical), Phosmer M (manufactured by Unichemical)), 2-((Meth) acryloxy) hexyl acid phosphate (trade name: SI POMER PZ (manufactured by Unichemical)) and the like.
Among these, mono-2-((meth) acryloxy) ethyl succinate, mono-2-((meth) acryloxy) ethyl phthalate, mono-2-((meth) acryloxy) ethyl hexahydrophthalate Preferably mentioned.

Moreover, the specific polymer in this invention may contain the repeating unit derived from the other monomer as shown below.
Examples of other monomers include aromatic vinyl compounds (eg, styrene, α-methylstyrene, vinyltoluene), (meth) acrylic acid alkyl esters (eg, methyl (meth) acrylate, ethyl (meth) acrylate, n -Butyl (meth) acrylate, i-butyl (meth) acrylate, etc.), (meth) acrylic acid alkyl aryl esters (eg, benzyl (meth) acrylate etc.), (meth) acrylic acid substituted alkyl esters (eg, glycidyl (meth) ) Acrylate, 2-hydroxyethyl (meth) acrylate, etc.), carboxylic acid vinyl esters (eg, vinyl acetate and vinyl propionate), aliphatic conjugated dienes (eg, 1,3-butadiene and isoprene), and the like. Among these, (meth) acrylic acid alkyl ester, (meth) acrylic acid alkyl aryl ester, carboxylic acid vinyl ester and the like are preferable.

  The specific polymer in the present invention is a copolymer comprising the repeating unit represented by the general formula (1) and the repeating unit derived from the polymerizable oligomer (macromonomer), or the general formula (1). ), A copolymer comprising a repeating unit derived from the polymerizable oligomer (macromonomer), and a repeating unit derived from the monomer having a nitrogen atom, or the general formula (1) And a repeating unit derived from the polymerizable oligomer (macromonomer) and a repeating unit derived from the monomer having an acidic functional group.

In the specific polymer in this invention, as a ratio of the repeating unit represented by the said General formula (1) which occupies for all the repeating units, 5 mass%-70 mass% are preferable, and 5 mass%-30 mass% are more. preferable.
Moreover, in the specific polymer in this invention, as a ratio of the repeating unit derived from the said polymerizable oligomer (macromonomer), 30 mass%-95 mass% are preferable, and 50 mass%-90 mass% are more preferable.
Furthermore, in the specific polymer in the present invention, the ratio of the repeating unit derived from the monomer having the nitrogen-containing group or acidic functional group is preferably 5% by mass to 80% by mass, and more preferably 5% by mass to 50% by mass. preferable.
In addition, in the specific polymer in the present invention, the ratio of the repeating unit derived from the other monomer is preferably 5% by mass to 30% by mass.

As a weight average molecular weight (Mw) of the specific polymer in this invention, 1000-200000 are preferable, for example, and 10,000-100000 are more preferable.
This weight average molecular weight (Mw) can be measured, for example, by gel permeation chromatography (carrier: tetrahydrofuran or dimethylformamide), and is calculated as a polystyrene equivalent weight average molecular weight.

Preferred specific examples [1) to 29)] of the specific polymer in the present invention are shown below. The present invention is not limited to these specific examples. In the following specific examples, the compounds displayed before and after “/” indicate monomers capable of forming a repeating unit constituting the specific polymer.
(1) 10/90 (mass ratio) copolymer of the monomer M-1 / terminal methacryloylated polymethyl methacrylate copolymer (Mn: 6000), weight average molecular weight: Mw = 23000
(2) 10/90 (mass ratio) copolymer of the monomer M-2 / terminal methacryloylated polymethyl methacrylate copolymer (Mn: 6000), weight average molecular weight: Mw = 22000
(3) 10/90 (mass ratio) copolymer of the monomer M-3 / terminal methacryloylated polymethyl methacrylate copolymer (Mn: 6000), weight average molecular weight: Mw = 22000
(4) 10/90 (mass ratio) copolymer of the monomer M-1 / polyethylene glycol mono (meth) acrylate copolymer (Mn: 439), weight average molecular weight: Mw = 15000
(5) 10/90 (mass ratio) copolymer of the monomer M-1 / terminal methacryloylated polycaprolactone copolymer (Mn: 3000), weight average molecular weight: Mw = 20000

(6) 10/90 (mass ratio) copolymer of the monomer M-7 / terminal methacryloylated polymethyl methacrylate copolymer (Mn: 6000), weight average molecular weight: 30000
(7) 10/90 (mass ratio) copolymer of the monomer M-7 / polyethylene glycol mono (meth) acrylate copolymer Mn: 439), weight average molecular weight: Mw = 17000
(8) 10/90 (mass ratio) copolymer of the monomer M-7 / terminal methacryloylated polycaprolactone copolymer (Mn: 3000), weight average molecular weight: 22000
(9) 10/90 (mass ratio) copolymer of the monomer M-7 / terminal methacryloylated polybutyl acrylate copolymer (Mn: 6000), weight average molecular weight: 32000
(10) 10/90 (mass ratio) copolymer of the monomer M-8 / terminal methacryloylated polymethyl methacrylate copolymer (Mn: 6000), weight average molecular weight: 28000

(11) 10/90 (mass ratio) copolymer of the monomer M-11 / terminal methacryloylated polymethyl methacrylate copolymer (Mn: 6000), weight average molecular weight: 30000
(12) 10/90 (mass ratio) copolymer of the monomer M-16 / terminal methacryloylated polymethyl methacrylate copolymer (Mn: 6000), weight average molecular weight: 33000
(13) 10/90 (mass ratio) copolymer of the monomer M-18 / terminal methacryloylated polymethyl methacrylate copolymer (Mn: 6000), weight average molecular weight: 33000
(14) 10/10/80 (mass ratio) copolymer of the monomer M-7 / 3- (N, N-dimethylamino) propylacrylamide / terminal methacryloylated polymethyl methacrylate copolymer (Mn: 6000), Weight average molecular weight: 29000
(15) 10/10/80 (mass ratio) copolymer of the monomer M-11 / 3- (N, N-dimethylamino) propylacrylamide / terminal methacryloylated polybutylacrylate copolymer (Mn: 6000), Weight average molecular weight: 32000

(16) 10/10/80 (mass ratio) copolymer of the monomer M-13 / 3- (N, N-dimethylamino) propylacrylamide / terminal methacryloylated polymethyl methacrylate copolymer (Mn: 6000), Weight average molecular weight: 30000
(17) Monomer M-15 / 2- (N, N-dimethylamino) ethyl (meth) acrylate / terminal methacryloylated polymethyl methacrylate (Mn: 6000) / polyethylene glycol mono (meth) acrylate copolymer (Mn: 439), 10/10/60/20 (mass ratio) copolymer, weight average molecular weight: 28000
(18) 10/10/80 (mass ratio) copolymer of the monomer M-7 / 2-vinylpyridine / terminal methacryloylated polymethyl methacrylate copolymer (Mn: 6000), weight average molecular weight: 26000
(19) 10/10/80 (mass ratio) copolymer of the monomer M-7 / p-vinylbenzyl-N, N-dimethylamine / polyethylene glycol mono (meth) acrylate copolymer (Mn: 439), Weight average molecular weight: 16000
(20) 10/10/80 (mass ratio) copolymerization of the monomer M-8 / 2- (N, N-dimethylamino) ethyl methacrylate / terminal methacryloylated poly n-butyl methacrylate copolymer (Mn: 6000) Combined, weight average molecular weight: 28000

(21) 10/10/80 (mass ratio) copolymer of the monomer M-8 / styrene / terminal methacryloylated polymethyl methacrylate copolymer (Mn: 6000), weight average molecular weight: 34000
(22) 10/10/80 (mass ratio) copolymer of the monomer M-1 / mono-2- (acryloxy) ethyl succinate / terminal methacryloylated polymethyl methacrylate copolymer (Mn: 6000), Weight average molecular weight: 33000
(23) 10/10/80 (mass ratio) copolymer of the monomer M-7 / mono-2- (acryloxy) ethyl succinate / terminal methacryloylated polybutyl acrylate copolymer (Mn: 6000), Weight average molecular weight: 33000
(24) 10/10/80 (mass ratio) copolymer of the monomer M-8 / mono-2- (methacryloxy) ethyl phthalate / polyethylene glycol mono (meth) acrylate copolymer (Mn: 439), Weight average molecular weight: 19000
(25) 10/10/80 (mass ratio) copolymer of the monomer M-10 / mono-2- (acryloxy) ethyl phthalate / terminal methacryloylated polymethyl methacrylate copolymer (Mn: 6000), weight average Molecular weight: 33000

(26) 10/10/80 (mass ratio) copolymer of the monomer M-11 / mono-2- (acryloxy) ethyl hexahydrophthalate / terminal methacryloylated polymethyl methacrylate copolymer (Mn: 6000), Weight average molecular weight: 33000
(27) 10/10/80 (mass ratio) copolymer of the monomer M-13 / mono-2- (methacryloxy) ethyl hexahydrophthalate / terminal methacryloylated polymethyl methacrylate copolymer (Mn: 6000) , Weight average molecular weight: 29000
(28) 10/5/85 (mass ratio) copolymer of the monomer M-16 / 2- (acryloxy) ethyl acid phosphate / polyethylene glycol mono (meth) acrylate copolymer (Mn: 6000), weight average Molecular weight: 23000
(29) 10/5/85 (mass ratio) copolymer of the monomer M-17 / 2- (methacryloxy) ethyl acid phosphate / terminal methacryloylated polymethyl methacrylate copolymer (Mn: 6000), weight average Molecular weight: 25000

Preferred specific examples of the specific polymer described above are all graft polymers. Such a graft polymer can be synthesized, for example, as follows. That is, a monomer that can form the repeating unit represented by the general formula (1), the polymerizable oligomer, and a monomer having a nitrogen atom-containing group, or a monomer having an acidic functional group, which are used in combination as desired. It can be obtained by radical polymerization of the other monomer in a solvent.
In the radical polymerization, a radical polymerization initiator is generally used. In addition to the radical polymerization initiator, a chain transfer agent (eg, 2-mercaptoethanol and dodecyl mercaptan) may be used.

In the present invention, the specific polymer may be used alone or in combination of two or more.
As content of the specific polymer in the pigment dispersion of this invention, 1 mass%-100 mass% are preferable with respect to the pigment mass in a dispersion, and 5 mass%-50 mass% are more preferable.
When the content of the specific polymer is in the above range, the dispersibility of the pigment becomes sufficient, aggregation of the pigment can be prevented, and an increase in viscosity can be suppressed.

In addition, in the pigment dispersion of the present invention, a known pigment dispersant can be used in combination with the specific polymer as long as the effects of the present invention are not impaired.
In this case, the content of the known pigment dispersant in the pigment dispersion is preferably 50% by mass or less with respect to the specific polymer.

<(B) Pigment>
There is no restriction | limiting in particular as (b) pigment used for the pigment dispersion of this invention, According to the objective, it can select suitably. Examples thereof include known organic pigments and inorganic pigments, resin particles dyed with dyes, commercially available pigment dispersions and surface-treated pigments (for example, dispersed in an insoluble resin or the like using a pigment as a dispersion medium). And those obtained by grafting a resin on the pigment surface).
Examples of pigments include, for example, “Spirit Dictionary” (2000), edited by Seijiro Ito. Herbst, K.M. Examples include those described in Hunger “Industrial Organic Pigments”, JP 2002-12607 A, JP 2002-188025 A, JP 2003-26978 A, and JP 2003-342503 A.

  Examples of organic pigments and inorganic pigments include yellow pigments, magenta pigments, blue, cyan pigments, green pigments, orange pigments, brown pigments, violet pigments, black pigments, and white pigments. Examples of the organic pigment include phthalocyanine, insoluble azo, azo lake, anthraquinone, quinacridone, dioxazine, diketopyrrolopyrrole, anthrapyrimidine, anthanthrone, indanthrone, flavanthrone. Generally, a perinone type, a perylene type, a thioindigo type, a quinophthalone type, etc. are mentioned.

  The yellow pigment is a pigment exhibiting a yellow color. I. Pigment Yellow 1 (Fast Yellow G etc.), C.I. I. Monoazo pigments such as CI Pigment Yellow 74; I. Pigment Yellow 12 (disaji yellow, etc.), C.I. I. Pigment yellow 17, C.I. I. Pigment yellow 97, C.I. I. Pigment yellow 3, C.I. I. Pigment yellow 16, C.I. I. Pigment yellow 83, C.I. I. Pigment yellow 155, C.I. I. Disazo pigments such as CI Pigment Yellow 219; I. Azo lake pigments such as C.I. Pigment Yellow 100 (eg Tartrazine Yellow Lake); I. Pigment yellow 95 (condensed azo yellow, etc.), C.I. I. Pigment yellow 93, C.I. I. Pigment yellow 94, C.I. I. Pigment yellow 128, C.I. I. Condensed azo pigments such as C.I. Pigment Yellow 166; I. Pigment Yellow 115 (quinoline yellow lake, etc.), etc., acidic dye lake pigments, C.I. I. Basic dye lake pigments such as C.I. Pigment Yellow 18 (such as thioflavine lake); I. Anthraquinone pigments such as C.I. Pigment Yellow 24 (Flavantron Yellow, etc.); I. Quinophthalone pigments such as C.I. Pigment Yellow 110 (e.g., Quinophthalone Yellow); I. Pigment yellow 139 (isoindoline yellow, etc.) and the like, isoindoline pigments such as C.I. I. Pyrazolone pigments such as C.I. Pigment Yellow 60 (Pyrazolone Yellow, etc.); I. Pigment yellow 120, C.I. I. Pigment yellow 154, C.I. I. Pigment yellow 167, C.I. I. Pigment yellow 151, C.I. I. Pigment yellow 175, C.I. I. Pigment yellow 180, C.I. I. Pigment yellow 181, C.I. I. An acetolone pigment such as C.I. Pigment Yellow 194; I. Pigment complex pigments such as CI Pigment Yellow 150, C.I. I. Nitroso pigments such as C.I. Pigment Yellow 153 (nickel nitroso yellow, etc.), C.I. I. And metal complex salt azomethine pigments such as CI Pigment Yellow 117 (copper azomethine yellow and the like).

  The magenta pigment is a pigment exhibiting a red or magenta color. I. Monoazo pigments such as CI Pigment Red 3 (Toluidine Red, etc.); I. Pigment red 1, C.I. I. Pigment red 4, C.I. I. Pigment Red 6 and other B-naphthol pigments, C.I. I. Disazo pigments such as CI Pigment Red 38 (Pyrazolone Red B, etc.); I. Pigment Red 53: 1 (Lake Red C, etc.) and C.I. I. Pigment Red 57: 1 (Brilliant Carmine 6B etc.), C.I. I. Pigment red 52: 1, C.I. I. Pigment Red 48 (B-oxynaphthoic acid lake, etc.) azo lake pigment, C.I. I. Pigment red 144, C.I. I. Pigment red 166, C.I. I. Pigment red 220, C.I. I. Pigment red 214, C.I. I. Pigment red 221, C.I. I. Condensed azo pigments such as C.I. Pigment Red 242 (condensed azo red and the like), C.I. I. Pigment Red 174 (Phloxine B lake, etc.), C.I. I. Pigment Red 172 (Erythrosin Lake, etc.) and other acidic dye lake pigments, C.I. I. Basic dye lake pigments such as C.I. Pigment Red 81 (Rhodamine 6G 'lake, etc.); I. Anthraquinone pigments such as C.I. Pigment Red 177 (eg, dianthraquinonyl red); I. Thioindigo pigments such as CI Pigment Red 88 (Thioindigo Bordeaux and the like), C.I. I. Perinone pigments such as CI Pigment Red 194 (perinone red, etc.); I. Pigment red 149, C.I. I. Pigment red 179, C.I. I. Pigment red 178, C.I. I. Pigment red 190, C.I. I. Pigment red 224, C.I. I. Pigment red 123, C.I. I. Perylene pigments such as CI Pigment Red 224; I. Pigment violet 19 (unsubstituted quinacridone), C.I. I. Pigment red 122, C.I. I. Pigment red 262, C.I. I. Pigment red 207, C.I. I. Quinacridone pigments such as CI Pigment Red 209; I. Pigment Red 180 (Isoindolinone Red 2BLT, etc.), etc., isoindolinone pigments, C.I. I. Alizarin lake pigments such as C.I. Pigment Red 83 (Mada Lake, etc.); I. Pigment red 171, C.I. I. Pigment red 175, C.I. I. Pigment red 176, C.I. I. Pigment red 185, C.I. I. Naphtholone pigments such as CI Pigment Red 208; I. Naphthol AS-based lake pigments such as CI Pigment Red 247; I. Pigment red 2, C.I. I. Pigment red 5, C.I. I. Pigment red 21, C.I. I. Pigment red 170, C.I. I. Pigment red 187, C.I. I. Pigment red 256, C.I. I. Pigment red 268, C.I. I. Naphthol AS pigments such as C.I. Pigment Red 269; I. Pigment red 254, C.I. I. Pigment red 255, C.I. I. Pigment red 264, C.I. I. And diketopyrrolopyrrole pigments such as CI Pigment Red 272.

  The cyan pigment is a pigment exhibiting a blue or cyan color. I. Disazo pigments such as C.I. Pigment Blue 25 (dianisidine blue, etc.); I. Pigment blue 15, C.I. I. Pigment blue 15: 1, C.I. I. Pigment blue 15: 2, C.I. I. Pigment blue 15: 3, C.I. I. Pigment blue 15: 4, C.I. I. Pigment blue 15: 6, C.I. I. Phthalocyanine pigments such as C.I. Pigment Blue 16 (phthalocyanine blue, etc.); I. Acidic dye lake pigments such as C.I. Pigment Blue 24 (peacock blue lake, etc.); I. Basic dye lake pigments such as C.I. Pigment Blue 1 (such as Biclothia Pure Blue BO Lake); I. Anthraquinone pigments such as C.I. Pigment Blue 60 (Indantron Blue, etc.); I. And alkaline blue pigments such as CI Pigment Blue 18 (Alkali Blue V-5: 1).

The green pigment is a pigment exhibiting a green color. I. Pigment green 7 (phthalocyanine green), C.I. I. Phthalocyanine pigments such as C.I. Pigment Green 36 (phthalocyanine green); I. Pigment green 8, C.I. I. And azo metal complex pigments such as CI Pigment Green 10.
The orange pigment is a pigment exhibiting an orange color. I. Pigment Orange 66 (Isoindoline Orange) and the like, C.I. I. Anthraquinone pigments such as C.I. Pigment Orange 51 (dichloropyrantron orange); I. Pigment orange 2, C.I. I. Pigment orange 3, C.I. I.オ レ ン ジ -naphthol pigments such as CI Pigment Orange 5; I. Pigment orange 4, C.I. I. Pigment orange 22, C.I. I. Pigment orange 24, C.I. I. Pigment orange 38, C.I. I. Naphthol AS pigments such as CI Pigment Orange 74; I. Pigment Orange 61 and other isoindolinone pigments, C.I. I. Perinone pigments such as CI Pigment Orange 43; I. Pigment orange 15, C.I. I. Disazo pigments such as CI Pigment Orange 16; I. Pigment orange 48, C.I. I. Quinacridone pigments such as CI Pigment Orange 49; I. Pigment orange 36, C.I. I. Pigment orange 62, C.I. I. Pigment orange 60, C.I. I. Pigment orange 64, C.I. I. An acetolone pigment such as C.I. Pigment Orange 72; I. Pigment orange 13, C.I. I. And pyrazolone pigments such as CI Pigment Orange 34.

The brown pigment is a pigment exhibiting a brown color. I. Pigment brown 25, C.I. I. And naphthron pigments such as CI Pigment Brown 32.
The violet pigment is a pigment exhibiting a purple color. I. Naphtholone pigments such as CI Pigment Violet 32, C.I. I. Perylene pigments such as CI Pigment Violet 29, C.I. I. Pigment violet 13, C.I. I. Pigment violet 17, C.I. I. Naphthol AS pigments such as CI Pigment Violet 50, C.I. I. Pigment violet 23, C.I. I. And dioxazine pigments such as CI Pigment Violet 37.

  The black pigment is a pigment exhibiting black color, such as carbon black, titanium black, C.I. I. Indazine pigments such as CI Pigment Black 1 (aniline black); I. Pigment black 31, C.I. I. And perylene pigments such as CI Pigment Black 32.

Examples of the white pigment include basic lead carbonate (2PbCO ₃ Pb (OH) ₂ , so-called silver white), zinc oxide (ZnO, so-called zinc white), titanium oxide (TiO ₂ , so-called titanium white), and titanium. Examples thereof include strontium acid (SrTiO ₃ , so-called titanium strontium white). The inorganic particles used for the white pigment may be a simple substance or, for example, oxides such as silicon, aluminum, zirconium and titanium, organometallic compounds, and composite particles with organic compounds.
Among them, the titanium oxide has a smaller specific gravity than other white pigments, a large refractive index, and is chemically and physically stable, so that it has a high hiding power and coloring power as a pigment, and further, an acid or an alkali. Since it is excellent in durability against other environments, it is preferably used. In addition to the titanium oxide, another white pigment (may be other than the white pigment described above) may be used in combination.

For dispersion of these pigments, for example, ball mill, sand mill, attritor, roll mill, jet mill, homogenizer, paint shaker, kneader, agitator, Henschel mixer, colloid mill, ultrasonic homogenizer, pearl mill, wet jet mill, etc. The apparatus can be preferably used.
In the present invention, it is particularly preferable to add the specific polymer (a) described above when dispersing the pigment.
Further, when dispersing the pigment, a synergist according to various pigments may be added as a dispersion aid, if necessary.
As content in the pigment dispersion of a dispersing aid, 1 mass part-50 mass parts are preferable with respect to 100 mass parts of (b) pigments.

The average particle size of the pigment is not particularly limited and may be appropriately selected depending on the intended purpose. However, since the finer the color development, the better the color developability, and about 0.01 to 0.4 μm is preferable. .2 μm is more preferable. The maximum particle size of the pigment is preferably 3 μm, and more preferably 1 μm. The particle size of the pigment can be adjusted by selecting the pigment, the dispersant, the dispersion medium, setting the dispersion conditions, and the filtration conditions. By controlling the particle size of the pigment, when the pigment dispersion of the present invention is applied to an ink composition for inkjet application, clogging of the head nozzle is suppressed, ink storage stability, ink transparency, and curing sensitivity. Can be maintained.
In the present invention, since (a) a specific polymer for enhancing the dispersibility of the pigment and its stability is included, a uniform and stable ink composition can be obtained even when a fine pigment is used.
The particle diameter of the pigment dispersion and the ink composition of the pigment can be measured by a known measurement method. Specifically, it can be measured by a centrifugal sedimentation light transmission method, an X-ray transmission method, a laser diffraction / scattering method, and a dynamic light scattering method.

<Dispersion medium>
In the present invention, (b) the dispersion medium used when dispersing the pigment is not particularly limited and may be appropriately selected depending on the intended purpose. For example, a low molecular weight polymerizable compound may be used as the dispersion medium. Alternatively, a solvent may be used as a dispersion medium.
However, when the pigment dispersion of the present invention is applied to a radiation curable ink, it is preferable not to include a non-curable solvent in order to cure the ink after it is applied to a recording medium. This is because if the solvent remains in the cured ink image, the solvent resistance is deteriorated or a VOC (Volatile Organic Compound) problem of the remaining solvent occurs. When applied to such applications, a polymerizable compound is used as a dispersion medium, and it is preferable to select a polymerizable compound having the lowest viscosity in terms of dispersion suitability and handling properties of the ink composition. .

  The pigment dispersion of the present invention contains (a) a specific polymer and (b) a pigment, and (a) the specific polymer improves (b) the dispersibility of the pigment and its stability. Therefore, a pigment dispersion having a clear color tone can be obtained.

[Ink composition]
The ink composition of the present invention comprises the pigment dispersion of the present invention, that is, (a) a specific polymer and (b) a pigment.
In such an ink composition, (b) the pigment functions as a coloring material, and the pigment having a fine particle diameter is uniform in the ink composition by the function of (a) the specific polymer, And it is stably dispersed. As a result, the ink composition of the present invention is excellent in color developability, has a clear color tone, has high coloring power, and can obtain a high-quality image.

The ink composition of the present invention can be applied to various uses such as oil-based ink, water-based ink, and curable ink.
Among these, since it is excellent in the dispersibility and dispersion stability of the fine pigment, it is preferably applied to curable ink, and more preferably applied to inkjet applications among curable inks.

<Pigment dispersion>
The pigment dispersion in the ink composition of the present invention is preferably used so that the pigment is in the following range.
That is, when the pigment is an organic pigment, the content of the organic pigment in the ink composition is preferably 1% by mass to 20% by mass and more preferably 2% by mass to 10% by mass in terms of solid content.
Further, when the pigment is an organic pigment, the content of the organic pigment in the ink composition is preferably 1% by mass to 30% by mass and more preferably 2% to 25% by mass in terms of solid content.

  Hereinafter, the case where the ink composition of the present invention is applied to a curable ink which is a suitable application will be specifically described. The ink composition of the present invention is not limited to this application and aspect.

In addition to the pigment dispersion of the present invention, the ink composition of the present invention can contain other components appropriately selected as necessary. Preferred components include (c) a polymerizable compound and (D) a polymerization initiator. By including these components, the ink composition of the present invention is cured by irradiation with active energy rays.
The active energy ray for curing the ink composition of the present invention is not particularly limited as long as it can impart energy capable of generating a starting species of a curing reaction in the ink composition by irradiation. Can be appropriately selected according to the above, and examples include α rays, γ rays, X rays, ultraviolet rays, visible rays, and electron beams. In the present invention, among these, ultraviolet rays and electron beams are preferable from the viewpoint of curing sensitivity and device availability, and ultraviolet rays are particularly preferable.
Hereinafter, constituent components when the ink composition of the present invention is applied to a curable ink will be described.

<(C) Polymerizable compound>
(C) The polymerizable compound is not particularly limited as long as it is a curable compound that causes a polymerization reaction by external stimulus, for example, application of some energy, and can be appropriately selected according to the purpose. It can be used regardless of the type of oligomer or polymer, but is known as a photocationically polymerizable monomer or photoradically polymerizable monomer that causes a polymerization reaction depending on the polymerization initiation species generated from the polymerization initiator (d). Various known polymerizable monomers are preferred.

One type of polymerizable compound may be used alone, or two or more types may be used in combination for the purpose of adjusting reaction rate, ink physical properties, cured film physical properties, and the like.
Moreover, as a polymeric compound, a monofunctional compound may be sufficient and a polyfunctional compound may be sufficient.

-Photo cationic polymerizable monomer-
Examples of the photocationically polymerizable monomer that can be used as the polymerizable compound include, for example, JP-A-6-9714, JP-A-2001-31892, JP-A-2001-40068, JP-A-2001-55507, JP-A-2001-310938, and JP-A-2001-310937. An epoxy compound, a vinyl ether compound, an oxetane compound and the like described in each publication such as JP-A-2001-220526 are preferable.

The epoxy compound may be a monofunctional epoxy compound or a polyfunctional epoxy compound.
Examples of the monofunctional epoxy compound include phenyl glycidyl ether, p-tert-butylphenyl glycidyl ether, butyl glycidyl ether, 2-ethylhexyl glycidyl ether, allyl glycidyl ether, 1,2-butylene oxide, 1,3-butadiene monooxide. 1,2-epoxydodecane, epichlorohydrin, 1,2-epoxydecane, styrene oxide, cyclohexene oxide, 3-methacryloyloxymethylcyclohexene oxide, 3-acryloyloxymethylcyclohexene oxide, 3-vinylcyclohexene oxide, etc. It is done.

Examples of the polyfunctional epoxy compound include bisphenol A diglycidyl ether, bisphenol F diglycidyl ether, bisphenol S diglycidyl ether, brominated bisphenol A diglycidyl ether, brominated bisphenol F diglycidyl ether, and brominated bisphenol S diglycidyl ether. Epoxy novolac resin, hydrogenated bisphenol A diglycidyl ether, hydrogenated bisphenol F diglycidyl ether, hydrogenated bisphenol S diglycidyl ether, 3,4-epoxycyclohexylmethyl-3 ′, 4′-epoxycyclohexanecarboxylate, 2- (3,4-epoxycyclohexyl-5,5-spiro-3,4-epoxy) cyclohexane-meta-dioxane, bis (3,4-epoxycyclohexylme A) Adipate, vinylcyclohexene oxide, 4-vinylepoxycyclohexane, bis (3,4-epoxy-6-methylcyclohexylmethyl) adipate, 3,4-epoxy-6-methylcyclohexyl-3 ′, 4′-epoxy-6 '-Methylcyclohexanecarboxylate, methylenebis (3,4-epoxycyclohexane), dicyclopentadiene diepoxide, di (3,4-epoxycyclohexylmethyl) ether of ethylene glycol, ethylenebis (3,4-epoxycyclohexanecarboxylate) , Epoxyhexahydrophthalate dioctyl, epoxyhexahydrophthalate di-2-ethylhexyl, 1,4-butanediol diglycidyl ether, 1,6-hexanediol diglycidyl ether, glycerin Triglycidyl ether, trimethylolpropane triglycidyl ether, polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ethers, 1,1,3-tetradecadiene dioxide, limonene dioxide, 1,2,7,8-diepoxy Examples include octane, 1,2,5,6-diepoxycyclooctane, and the like.
Among these epoxy compounds, an aromatic epoxy compound and an alicyclic epoxy compound are preferable, and an alicyclic epoxy compound is particularly preferable in terms of excellent curing speed.

The vinyl ether compound may be a monofunctional vinyl ether compound or a polyfunctional vinyl ether compound.
Examples of the monofunctional vinyl ether compound include methyl vinyl ether, ethyl vinyl ether, propyl vinyl ether, n-butyl vinyl ether, t-butyl vinyl ether, 2-ethylhexyl vinyl ether, n-nonyl vinyl ether, lauryl vinyl ether, cyclohexyl vinyl ether, cyclohexyl methyl vinyl ether, 4- Methylcyclohexyl methyl vinyl ether, benzyl vinyl ether, dicyclopentenyl vinyl ether, 2-dicyclopentenoxyethyl vinyl ether, methoxyethyl vinyl ether, ethoxyethyl vinyl ether, butoxyethyl vinyl ether, methoxyethoxyethyl vinyl ether, ethoxyethoxyethyl vinyl ether, methoxypolyethylene glycol vinyl Ether, tetrahydrofurfuryl vinyl ether, 2-hydroxyethyl vinyl ether, 2-hydroxypropyl vinyl ether, 4-hydroxybutyl vinyl ether, 4-hydroxymethylcyclohexyl methyl vinyl ether, diethylene glycol monovinyl ether, polyethylene glycol vinyl ether, chloroethyl vinyl ether, chlorobutyl vinyl ether, chloro Examples thereof include ethoxyethyl vinyl ether, phenylethyl vinyl ether, phenoxy polyethylene glycol vinyl ether, and the like.

Examples of the polyfunctional vinyl ether compound include ethylene glycol divinyl ether, diethylene glycol divinyl ether, triethylene glycol divinyl ether, polyethylene glycol divinyl ether, propylene glycol divinyl ether, butylene glycol divinyl ether, hexanediol divinyl ether, bisphenol A alkylene oxide divinyl ether. , Divinyl ethers such as bisphenol F alkylene oxide divinyl ether; trimethylolethane trivinyl ether, trimethylolpropane trivinyl ether, ditrimethylolpropane tetravinyl ether, glycerin trivinyl ether, pentaerythritol tetravinyl ether, dipentaerythritol penta Nyl ether, dipentaerythritol hexavinyl ether, ethylene oxide-added trimethylolpropane trivinyl ether, propylene oxide-added trimethylolpropane trivinyl ether, ethylene oxide-added ditrimethylolpropane tetravinyl ether, propylene oxide-added ditrimethylolpropane tetravinyl ether, ethylene oxide-added pentaerythritol tetravinyl ether Examples thereof include polyfunctional vinyl ethers such as vinyl ether, propylene oxide-added pentaerythritol tetravinyl ether, ethylene oxide-added dipentaerythritol hexavinyl ether, and propylene oxide-added dipentaerythritol hexavinyl ether.
Among these vinyl ether compounds, di- or trivinyl ether compounds are preferable and divinyl ether compounds are particularly preferable in terms of curability, adhesion to a recording medium, surface hardness of the formed image, and the like.

The oxetane compound means a compound having an oxetane ring, and preferred examples thereof include known oxetane compounds described in JP-A Nos. 2001-220526, 2001-310937, and 2003-341217.
In the present invention, the oxetane compound is preferably a compound having 1 to 4 oxetane rings in its structure. When such a compound is used, it becomes easy to maintain the viscosity of the ink composition in a good handling property range, and it is possible to obtain high adhesion of the cured ink to the recording medium. It is advantageous.

The oxetane compound may be a monofunctional oxetane compound or a polyfunctional oxetane compound.
Examples of monofunctional oxetane compounds include 3-ethyl-3-hydroxymethyloxetane, 3- (meth) allyloxymethyl-3-ethyloxetane, (3-ethyl-3-oxetanylmethoxy) methylbenzene, 4-fluoro- [1- (3-ethyl-3-oxetanylmethoxy) methyl] benzene, 4-methoxy- [1- (3-ethyl-3-oxetanylmethoxy) methyl] benzene, [1- (3-ethyl-3-oxetanylmethoxy) ) Ethyl] phenyl ether, isobutoxymethyl (3-ethyl-3-oxetanylmethyl) ether, isobornyloxyethyl (3-ethyl-3-oxetanylmethyl) ether, isobornyl (3-ethyl-3-oxetanylmethyl) ether 2-ethylhexyl (3-ethyl-3-oxetani Methyl) ether, ethyl diethylene glycol (3-ethyl-3-oxetanylmethyl) ether, dicyclopentadiene (3-ethyl-3-oxetanylmethyl) ether, dicyclopentenyloxyethyl (3-ethyl-3-oxetanylmethyl) ether, Dicyclopentenyl (3-ethyl-3-oxetanylmethyl) ether, tetrahydrofurfuryl (3-ethyl-3-oxetanylmethyl) ether, tetrabromophenyl (3-ethyl-3-oxetanylmethyl) ether, 2-tetrabromophenoxy Ethyl (3-ethyl-3-oxetanylmethyl) ether, tribromophenyl (3-ethyl-3-oxetanylmethyl) ether, 2-tribromophenoxyethyl (3-ethyl-3-oxetanylmethyl) ether 2-hydroxyethyl (3-ethyl-3-oxetanylmethyl) ether, 2-hydroxypropyl (3-ethyl-3-oxetanylmethyl) ether, butoxyethyl (3-ethyl-3-oxetanylmethyl) ether, pentachlorophenyl (3 -Ethyl-3-oxetanylmethyl) ether, pentabromophenyl (3-ethyl-3-oxetanylmethyl) ether, bornyl (3-ethyl-3-oxetanylmethyl) ether, and the like.

  Examples of the polyfunctional oxetane compound include 3,7-bis (3-oxetanyl) -5-oxa-nonane, 3,3 ′-(1,3- (2-methylenyl) propanediylbis (oxymethylene). ) Bis- (3-ethyloxetane), 1,4-bis [(3-ethyl-3-oxetanylmethoxy) methyl] benzene, 1,2-bis [(3-ethyl-3-oxetanylmethoxy) methyl] ethane, 1,3-bis [(3-ethyl-3-oxetanylmethoxy) methyl] propane, ethylene glycol bis (3-ethyl-3-oxetanylmethyl) ether, dicyclopentenylbis (3-ethyl-3-oxetanylmethyl) ether , Triethylene glycol bis (3-ethyl-3-oxetanylmethyl) ether, tetraethylene glycol bis ( -Ethyl-3-oxetanylmethyl) ether, tricyclodecanediyldimethylene (3-ethyl-3-oxetanylmethyl) ether, trimethylolpropane tris (3-ethyl-3-oxetanylmethyl) ether, 1,4-bis ( 3-ethyl-3-oxetanylmethoxy) butane, 1,6-bis (3-ethyl-3-oxetanylmethoxy) hexane, pentaerythritol tris (3-ethyl-3-oxetanylmethyl) ether, pentaerythritol tetrakis (3-ethyl) -3-oxetanylmethyl) ether, polyethylene glycol bis (3-ethyl-3-oxetanylmethyl) ether, dipentaerythritol hexakis (3-ethyl-3-oxetanylmethyl) ether, dipentaerythritol pentakis (3 Ethyl-3-oxetanylmethyl) ether, dipentaerythritol tetrakis (3-ethyl-3-oxetanylmethyl) ether, caprolactone-modified dipentaerythritol hexakis (3-ethyl-3-oxetanylmethyl) ether, caprolactone-modified dipentaerythritol pentane Kis (3-ethyl-3-oxetanylmethyl) ether, ditrimethylolpropane tetrakis (3-ethyl-3-oxetanylmethyl) ether, EO-modified bisphenol A bis (3-ethyl-3-oxetanylmethyl) ether, PO-modified bisphenol A Bis (3-ethyl-3-oxetanylmethyl) ether, EO-modified hydrogenated bisphenol A bis (3-ethyl-3-oxetanylmethyl) ether, PO-modified hydrogenated bisphenol A bis ( 3-ethyl-3-oxetanylmethyl) ether, EO-modified bisphenol F (3-ethyl-3-oxetanylmethyl) ether, and the like.

Further, as the oxetane compound, compounds described in detail in JP-A-2003-341217, paragraph numbers [0021] to [0084] can be preferably used in the present invention.
Among the oxetane compounds described above, in the present invention, a compound having 1 to 2 oxetane rings is preferable from the viewpoint of viscosity and adhesiveness of the ink composition.

  In the ink composition of the present invention, the photocationically polymerizable monomer may be used alone or in combination of two or more, but the viewpoint of effectively suppressing shrinkage during ink curing Is preferably used in combination with at least one oxetane compound and at least one compound selected from an epoxy compound and a vinyl ether compound.

-Photo radical polymerizable monomer-
Examples of the photoradical polymerizable monomer that can be used as the polymerizable compound (c) include (meth) acrylates, (meth) acrylamides, and aromatic vinyls. In this specification, when referring to both and / or “acrylate” and “methacrylate”, it refers to “(meth) acrylate” and “acryl” and / or “methacryl”. May be described respectively.

The (meth) acrylates may be monofunctional (meth) acrylates or polyfunctional (meth) acrylates.
Examples of monofunctional (meth) acrylates include hexyl group (meth) acrylate, 2-ethylhexyl (meth) acrylate, tert-octyl (meth) acrylate, isoamyl (meth) acrylate, decyl (meth) acrylate, and isodecyl (meth). ) Acrylate, stearyl (meth) acrylate, isostearyl (meth) acrylate, cyclohexyl (meth) acrylate, 4-n-butylcyclohexyl (meth) acrylate, bornyl (meth) acrylate, isobornyl (meth) acrylate, benzyl (meth) acrylate 2-ethylhexylglycol (meth) acrylate, butoxyethyl (meth) acrylate, 2-chloroethyl (meth) acrylate, 4-bromobutyl (meth) acrylate, cyano Chill (meth) acrylate, benzyl (meth) acrylate, butoxymethyl (meth) acrylate, 3-methoxybutyl (meth) acrylate, alkoxymethyl (meth) acrylate, alkoxyethyl (meth) acrylate, 2- (2-methoxyethoxy) ethyl (Meth) acrylate, 2- (2-butoxyethoxy) ethyl (meth) acrylate, 2,2,2-tetrafluoroethyl (meth) acrylate, 1H, 1H, 2H, 2H perfluorodecyl (meth) acrylate, 4- Butylphenyl (meth) acrylate, phenyl (meth) acrylate, 2,4,5-tetramethylphenyl (meth) acrylate, 4-chlorophenyl (meth) acrylate, phenoxymethyl (meth) acrylate, phenoxyethyl (meth) acrylate Relate, glycidyl (meth) acrylate, glycidyloxybutyl (meth) acrylate, glycidyloxyethyl (meth) acrylate, glycidyloxypropyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, hydroxyalkyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 3-hydroxypropyl ( (Meth) acrylate, dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, dimethylaminopropyl (meth) acrylate, diethylaminopropyl (meth) T) acrylate, trimethoxysilylpropyl (meth) acrylate, trimethylsilylpropyl (meth) acrylate, polyethylene oxide monomethyl ether (meth) acrylate, oligoethylene oxide monomethyl ether (meth) acrylate, polyethylene oxide (meth) acrylate, oligoethylene oxide (meth) Acrylate, oligoethylene oxide monoalkyl ether (meth) acrylate, polyethylene oxide monoalkyl ether (meth) acrylate, dipropylene glycol (meth) acrylate, polypropylene oxide monoalkyl ether (meth) acrylate, oligopropylene oxide monoalkyl ether (meth) acrylate 2-methacryloyloxytyl succinic acid, 2-methacrylic acid Leuoxyhexahydrophthalic acid, 2-methacryloyloxyethyl-2-hydroxypropyl phthalate, butoxydiethylene glycol (meth) acrylate, trifluoroethyl (meth) acrylate, perfluorooctylethyl (meth) acrylate, 2-hydroxy-3- Phenoxypropyl (meth) acrylate, EO modified phenol (meth) acrylate, EO modified cresol (meth) acrylate, EO modified nonylphenol (meth) acrylate, PO modified nonylphenol (meth) acrylate, EO modified-2-ethylhexyl (meth) acrylate, Etc. Examples include dicyclopentenyl (meth) acrylate, dicyclopentanyl (meth) acrylate, and dicyclopentenyloxyethyl (meth) acrylate.

Examples of the polyfunctional (meth) acrylate include bifunctional, trifunctional, tetrafunctional, pentafunctional, and hexafunctional ones.
Examples of the bifunctional (meth) acrylate include 1,6-hexanediol di (meth) acrylate, 1,10-decanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, and 2,4-dimethyl. -1,5-pentanediol di (meth) acrylate, butylethylpropanediol (meth) acrylate, ethoxylated cyclohexanemethanol di (meth) acrylate, polyethylene glycol di (meth) acrylate, oligoethylene glycol di (meth) acrylate, Ethylene glycol di (meth) acrylate, 2-ethyl-2-butyl-butanediol di (meth) acrylate, hydroxypivalic acid neopentyl glycol di (meth) acrylate, EO-modified bisphenol A di (meth) acrylate Bisphenol F polyethoxydi (meth) acrylate, polypropylene glycol di (meth) acrylate, oligopropylene glycol di (meth) acrylate, 1,4-butanediol di (meth) acrylate, 2-ethyl-2-butylpropanediol di (Meth) acrylate, 1,9-nonane di (meth) acrylate, propoxylated ethoxylated bisphenol A di (meth) acrylate, tricyclodecane di (meth) acrylate, dipropylene glycol di (meth) acrylate, propoxylated neopentyl glu Examples include cold di (meth) acrylate.

Examples of the trifunctional (meth) acrylate include trimethylolpropane tri (meth) acrylate, trimethylolethane tri (meth) acrylate, trimethylolpropane alkylene oxide-modified tri (meth) acrylate, and pentaerythritol tri (meth) acrylate. , Dipentaerythritol tri (meth) acrylate, trimethylolpropane tri ((meth) acryloyloxypropyl) ether, isocyanuric acid alkylene oxide modified tri (meth) acrylate, propionate dipentaerythritol tri (meth) acrylate, tri ((meta ) Acryloyloxyethyl) isocyanurate, hydroxypivalaldehyde-modified dimethylolpropane tri (meth) acrylate, sorbitol tri (meth) a Relate, propoxylated trimethylolpropane tri (meth) acrylate, ethoxylated glycerin triacrylate, and the like.
Examples of the tetrafunctional (meth) acrylate include pentaerythritol tetra (meth) acrylate, sorbitol tetra (meth) acrylate, ditrimethylolpropane tetra (meth) acrylate, dipentaerythritol tetra (meth) acrylate propionate, and ethoxylated penta And erythritol tetra (meth) acrylate.
Examples of pentafunctional (meth) acrylates include sorbitol penta (meth) acrylate and dipentaerythritol penta (meth) acrylate.
Examples of hexafunctional (meth) acrylates include dipentaerythritol hexa (meth) acrylate, sorbitol hexa (meth) acrylate, phosphazene alkylene oxide-modified hexa (meth) acrylate, and captolactone-modified dipentaerythritol hexa (meth) acrylate. , Etc.

  Examples of the (meth) acrylamides include (meth) acrylamide, N-methyl (meth) acrylamide, N-ethyl (meth) acrylamide, N-propyl (meth) acrylamide, Nn-butyl (meth) acrylamide, N-t-butyl (meth) acrylamide, N-butoxymethyl (meth) acrylamide, N-isopropyl (meth) acrylamide, N-methylol (meth) acrylamide, N, N-dimethyl (meth) acrylamide, N, N-diethyl (Meth) acrylamide, (meth) acryloylmorpholine, etc. are mentioned.

  Examples of the aromatic vinyls include styrene, methyl styrene, dimethyl styrene, trimethyl styrene, ethyl styrene, isopropyl styrene, chloromethyl styrene, methoxy styrene, acetoxy styrene, chloro styrene, dichloro styrene, bromo styrene, vinyl benzoic acid. Methyl ester, 3-methylstyrene, 4-methylstyrene, 3-ethylstyrene, 4-ethylstyrene, 3-propylstyrene, 4-propylstyrene, 3-butylstyrene, 4-butylstyrene, 3-hexylstyrene, 4- Hexyl styrene, 3-octyl styrene, 4-octyl styrene, 3- (2-ethylhexyl) styrene, 4- (2-ethylhexyl) styrene, allyl styrene, isopropenyl styrene, butenyl styrene, octet Rusuchiren, 4-t-butoxycarbonyl styrene, 4-methoxystyrene, 4-t-butoxystyrene, and the like.

  Examples of the photo-radically polymerizable monomer include vinyl esters [vinyl acetate, vinyl propionate, vinyl versatate, etc.], allyl esters [eg, allyl acetate], halogen-containing monomers [vinylidene chloride, vinyl chloride, etc.], Vinyl ether [methyl vinyl ether, butyl vinyl ether, hexyl vinyl ether, methoxy vinyl ether, 2-ethylhexyl vinyl ether, methoxyethyl vinyl ether, cyclohexyl vinyl ether, chloroethyl vinyl ether, triethylene glycol divinyl ether, etc.], vinyl cyanide [(meth) acrylonitrile, etc.], olefin [Ethylene, propylene, etc.] can also be used.

  Among these, (meth) acrylates and (meth) acrylamides are preferable from the viewpoint of curing speed, tetrafunctional or higher (meth) acrylates are more preferable, and polyfunctional (in terms of viscosity of the ink composition). It is preferable to use a combination of (meth) acrylate with monofunctional or bifunctional (meth) acrylate and (meth) acrylamide.

  In the ink composition of the present invention, the content of the polymerizable compound (c) is preferably 50% by mass to 95% by mass, more preferably 60% by mass to 92% by mass with respect to the total mass of the ink composition, and 70 A mass% to 90 mass% is particularly preferred.

<(D) Polymerization initiator>
The ink composition of the present invention preferably contains (d) a polymerization initiator.
The polymerization initiator may be selected in accordance with (c) the polymerizable compound, and is preferably a polymerization initiator for radical polymerization or cationic polymerization, and a photopolymerization initiator is particularly preferable.

The photopolymerization initiator generates a chemical change through the action of light or the interaction with the electronically excited state of the sensitizing dye, and generates at least one of radical, acid, and base as an active species. It is a compound.
Examples of the photopolymerization initiator include actinic rays to be irradiated, for example, 400 to 200 nm ultraviolet rays, far ultraviolet rays, g rays, h rays, i rays, KrF excimer laser rays, ArF excimer laser rays, electron rays, X rays, Those having sensitivity to a molecular beam, an ion beam and the like can be appropriately selected and used.

  Specific examples of the photopolymerization initiator include Bruce M. et al. Monroe et al., Chemical Review, 93, 435 (1993). R. S. By Davidson, Journal of Photochemistry and biologic A: Chemistry, 73.81 (1993). J. P. Faussier “Photoinitiated Polymerization—Theory and Applications”: Rapra Review vol. 9, Report, Rapra Technology (1998). M. Tsunooka et al. , Prog. Polym. Sci. , 21, 1 (1996). Compounds described in the above, chemical amplification type photoresists described in "Organic Materials for Imaging" edited by Organic Electronics Materials Research Group (see pages 187 to 192) (1993)), compounds used for photocationic polymerization, Etc. Further, F.I. D. Saeva, Topics in Current Chemistry, 156, 59 (1990). G. G. Maslak, Topics in Current Chemistry, 168, 1 (1993). H., et al. B. Shuster et al, JACS, 112, 6329 (1990). I. D. F. Eaton et al, JACS, 102, 3298 (1980). And the like, which are described in the above and the like, and compounds that generate bond cleavage oxidatively or reductively through interaction with the electronically excited state of the sensitizing dye.

  Among these photopolymerization initiators, (1) aromatic ketone compounds, (2) aromatic onium salt compounds, (3) organic peroxides, (4) hexaarylbiimidazole compounds, (4) ketoxime ester compounds And (5) borate compounds, (6) azinium compounds, (7) metallocene compounds, (8) active ester compounds, (9) compounds having a carbon-halogen bond, and the like.

  (1) As the aromatic ketone compound, for example, “RADIATION CURING IN POLYMER SCIENCE AND TECHNOLOGY” J. Org. P. FOUASSIER J.M. F. A compound having a benzophenone skeleton or a thioxanthone skeleton described in p77 to 117 of RABEK (1993), an α-thiobenzophenone compound described in Japanese Patent Publication No. 47-6416, a benzoin ether compound described in Japanese Patent Publication No. 47-3981, and Japanese Patent Publication No. 47-22326 Α-substituted benzoin compounds, benzoin derivatives described in JP-B-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-62-181345, JP-B-1-34242, US Pat. No. 4,318,791, α-aminobenzophenones described in European Patent 0284561A1, 2-2114 P-di (dimethylaminobenzoyl) benzene described in JP-A No. 2; thio-substituted aromatic ketones described in JP-A-61-194062; acylphosphine sulfides described in JP-B-2-9597; Acylphosphine described in Japanese Patent Publication No. 63-61950, thioxanthones described in Japanese Patent Publication No. 63-61950, coumarins described in Japanese Patent Publication No. 59-42864, monoacyl described in Japanese Patent Publication No. 60-8047, and Japanese Patent Publication No. 63-40799. Examples thereof include phosphine oxides and bisacylphosphine oxides described in JP-A-3-101686, JP-A-5-345790, and JP-A-6-298818.

  (2) As an aromatic onium salt compound, for example, elements of Group V, VI and VII of the periodic table, specifically N, P, As, Sb, Bi, O, S, Se, Te, or Specific examples of the iodonium described in European Patent No. 104143, US Pat. No. 4,837,124, Japanese Patent Laid-Open No. 2-150848, and Japanese Patent Laid-Open No. 2-96514. Salts, European Patent Nos. 370693, 233567, 297443, 297442, 279210, and 422570, U.S. Patents 3902144, 4933377, 4760013, 4734444, and No. 2,833,827 sulfonium salts, diazonium salts (benzenediazo which may have a substituent) ), Diazonium salt resins (formaldehyde resin of diazodiphenylamine, etc.), N-alkoxypyridinium salts, etc. (for example, U.S. Pat. No. 4,743,528, JP-A 63-138345, JP-A 63- No. 142345, JP-A-63-142346, JP-B-46-42363, etc., specifically, 1-methoxy-4-phenylpyridinium tetrafluoroborate etc.), JP-B-52 Preferred examples include the compounds described in JP-A Nos. 147277, 52-14278, and 52-14279. These compounds generate radicals and acids as active species.

  (3) Organic peroxide includes, for example, an organic compound having one or more oxygen-oxygen bonds in the molecule. Specifically, 3,3′4,4′-tetra- (t-butyl Peroxycarbonyl) benzophenone, 3,3′4,4′-tetra- (t-amylperoxycarbonyl) benzophenone, 3,3′4,4′-tetra- (t-hexylperoxycarbonyl) benzophenone, 3, 3'4,4'-tetra- (t-octylperoxycarbonyl) benzophenone, 3,3'4,4'-tetra- (cumylperoxycarbonyl) benzophenone, 3,3'4,4'-tetra- ( Suitable examples include peroxide compounds such as (p-isopropylcumylperoxycarbonyl) benzophenone and di-t-butyldiperoxyisophthalate.

  (4) Examples of hexaarylbiimidazole compounds include lophine dimers described in JP-B-45-37377 and JP-B-44-86516, specifically, 2,2′-bis (o-chlorophenyl). ) -4,4 ′, 5,5′-tetraphenylbiimidazole, 2,2′-bis (o-bromophenyl) -4,4 ′, 5,5′-tetraphenylbiimidazole, 2,2′- Bis (o, p-dichlorophenyl) -4,4 ′, 5,5′-tetraphenylbiimidazole, 2,2′-bis (o-chlorophenyl) -4,4 ′, 5,5′-tetra (m- Methoxyphenyl) biimidazole, 2,2′-bis (o, o′-dichlorophenyl) -4,4 ′, 5,5′-tetraphenylbiimidazole, 2,2′-bis (o-nitrophenyl) -4 4 ', 5,5'-tetraphenylbiimidazole, 2,2'-bis (o-methylphenyl) -4,4', 5,5'-tetraphenylbiimidazole, 2,2'-bis (o- (Trifluorophenyl) -4,4 ′, 5,5′-tetraphenylbiimidazole and the like are preferable.

  (4) Examples of the ketoxime ester compound include 3-benzoyloxyiminobutane-2-one, 3-acetoxyiminobutan-2-one, 3-propionyloxyiminobutan-2-one, and 2-acetoxyiminopentane. -3-one, 2-acetoxyimino-1-phenylpropan-1-one, 2-benzoyloxyimino-1-phenylpropan-1-one, 3-p-toluenesulfonyloxyiminobutan-2-one, 2 -Ethoxycarbonyloxyimino-1-phenylpropan-1-one, and the like.

(5) Examples of the borate compound include compounds described in US Pat. Nos. 3,567,453 and 4,343,891, European Patents 109,772 and 109,773, and the like.
(6) Examples of azinium compounds are described in JP-A-63-138345, JP-A-63-142345, JP-A-63-142346, JP-A-63-143537, and JP-B-46-42363. And a compound having an N—O bond.

(7) Examples of the metallocene compounds described in JP-A Nos. 59-152396, 61-151197, 63-41484, 2-249, and 2-4705 Examples thereof include titanocene compounds and iron-arene complexes described in JP-A-1-304453 and JP-A-1-152109.
Specific examples of the titanocene compound include di-cyclopentadienyl-Ti-di-chloride, di-cyclopentadienyl-Ti-bis-phenyl, and di-cyclopentadienyl-Ti-bis-2,3. 4,5,6-pentafluorophen-1-yl, di-cyclopentadienyl-Ti-bis-2,3,5,6-tetrafluorophen-1-yl, di-cyclopentadienyl-Ti- Bis-2,4,6-trifluorophen-1-yl, di-cyclopentadienyl-Ti-2,6-difluorophen-1-yl, di-cyclopentadienyl-Ti-bis-2,4 -Difluorophen-1-yl, di-methylcyclopentadienyl-Ti-bis-2,3,4,5,6-pentafluorophen-1-yl, di-methylcyclopentadienyl-Ti- -2,3,5,6-tetrafluorophen-1-yl, di-methylcyclopentadienyl-Ti-bis-2,4-difluorophen-1-yl, bis (cyclopentadienyl) -bis (2,6-difluoro-3- (pyridin-1-yl) phenyl) titanium, bis (cyclopentadienyl) bis [2,6-difluoro-3- (methylsulfonamido) phenyl] titanium, bis (cyclopenta And dienyl) bis [2,6-difluoro-3- (N-butylbialoyl-amino) phenyl] titanium.

  (8) As the active ester compound, for example, the specifications of European Patent Nos. 0290750, 046083, 156153, 271851, and 0388343, the specifications of U.S. Pat. Nos. 3,901,710 and 4,181,531, Nitrobenzester compounds described in JP-A-60-198538 and JP-A-53-133022, European Patent Nos. 0199672, 84515, 199672, 0441115 and 0101122 U.S. Pat. Nos. 4,618,564, 4,371,605, and 4,431,774, JP-A 64-18143, JP-A-2-245756, and JP-A-4-365048, respectively. , Shoko 62-6223, Shoko 63-1 Compounds described in JP 340 JP and JP 59-174831, and the like.

  (9) Examples of the compound having a carbon-halogen bond include Wakabayashi et al., Bull. Chem. Soc. Japan, 42, 2924 (1969), a compound described in British Patent 1388492, a compound described in JP-A-53-133428, a compound described in German Patent 3337024, F . C. J. Schaefer et al. Org. Chem. 29, 1527 (1964), a compound described in JP-A-62-258241, a compound described in JP-A-5-281728, a compound described in German Patent 2641100, a German patent 3333450 , Compounds described in German Patent No. 3021590, compounds described in German Patent No. 3021599, and the like.

  In addition, the preferable specific example of each compound of (1)-(8) is as follows.

A polymerization initiator may be used individually by 1 type, and may use 2 or more types together.
The content of the polymerization initiator (d) in the ink composition of the present invention is preferably 0.1% by mass to 20% by mass, and 0.5% by mass to 10% by mass with respect to the total mass of the ink composition. More preferably, 1% by mass to 7% by mass is particularly preferable.

<Other ingredients>
The ink composition of the present invention contains (a) a specific copolymer, (b) a pigment, (c) a polymerizable compound, (d) a polymerization initiator, and other components appropriately selected according to the purpose. can do.
Examples of other components include sensitizing dyes, co-sensitizers, resins, surfactants, ultraviolet absorbers, antioxidants, anti-fading agents, ejection stabilizers, adhesion improvers, leveling additives, matting agents. , Etc. These may be used individually by 1 type and may use 2 or more types together.

-Sensitizing dye-
When the ink composition of the present invention contains a photopolymerization initiator (d) as a polymerization initiator, it is preferable to contain a sensitizing dye for the purpose of improving the sensitivity of the photopolymerization initiator.
Suitable examples of the sensitizing dye include those that absorb light having a wavelength of 350 to 450 nm.
Examples of the sensitizing dye include polynuclear aromatics (for example, pyrene, perylene, triphenylene), xanthenes (for example, fluorescein, eosin, erythrosine, rhodamine B, rose bengal), cyanines (for example, thiacarbocyanine, Oxacarbocyanine), merocyanines (eg, merocyanine, carbomerocyanine), thiazines (eg, thionine, methylene blue, toluidine blue), acridines (eg, acridine orange, chloroflavin, acriflavine), anthraquinones (eg, anthraquinones) ), Squalium (eg, squalium), coumarins (eg, 7-diethylamino-4-methylcoumarin), and the like.
Preferable specific examples of the sensitizing dye include compounds represented by the following general formulas (IX) to (XIII).

In the above general formula (IX), A ¹ represents a sulfur atom or NR ⁵⁰ . R ⁵⁰ represents an alkyl group or an aryl group. L ² represents a nonmetallic atomic group that forms a basic nucleus of a dye together with adjacent A ² and a carbon atom. R ⁵¹ and R ⁵² each independently represent a hydrogen atom or a monovalent nonmetallic atomic group, and these may combine with each other to form an acidic nucleus of the dye. W represents an oxygen atom or a sulfur atom.
In the general formula (X), Ar ¹ and Ar ² each independently represent an aryl group, and are linked via a bond with —L ³ —. L ³ represents —O— or S—. W is synonymous with that shown in the general formula (IX).
In the above general formula (XI), A ² represents a sulfur atom or NR ⁵⁹ , and L ⁴ represents a nonmetallic atomic group that forms a basic nucleus of the dye together with adjacent A ² and a carbon atom. R ⁵³ , R ⁵⁴ , R ⁵⁵ , R ⁵⁶ , R ⁵⁷ and R ⁵⁸ each independently represent a monovalent nonmetallic atomic group. R ⁵⁹ represents an alkyl group or an aryl group.
In the general formula (XII), A ³ and A ⁴ each independently represent —S— or —NR ⁶² —. ^R62 represents a substituted or unsubstituted alkyl group or a substituted or unsubstituted aryl group. L ⁵ and L ⁶ each independently represent a nonmetallic atomic group that forms a basic nucleus of a dye together with adjacent A ³ , A ⁴ and a carbon atom. R ⁶⁰ and R ⁶¹ each independently represent a hydrogen atom or a monovalent nonmetallic atomic group. R ⁶⁰ and R ⁶¹ may be bonded to each other to form an aliphatic or aromatic ring.
In the general formula (XIII), R ⁶⁶ represents an aromatic ring or a hetero ring which may have a substituent. A ⁵ represents an oxygen atom, a sulfur atom or ═NR ⁶⁷ . R ⁶⁴ , R ⁶⁵ and R ⁶⁷ each independently represent a hydrogen atom or a monovalent nonmetallic atomic group. R ⁶⁷ and R ⁶⁴ , and R ⁶⁵ and R ⁶⁷ may be bonded to each other to form an aliphatic or aromatic ring.

  Specific preferred examples of the compounds represented by the general formulas (IX) to (XIII) include the following exemplified compounds A-1 to A-24.

-Co-sensitizer-
The ink composition of the present invention may contain a co-sensitizer for the purpose of further improving sensitivity or suppressing polymerization inhibition due to oxygen.
Examples of the co-sensitizer include, for example, amines (for example, M. R. Sander et al., “Journal of Polymer Society”, Vol. No. 5, JP-A 52-134692, JP-A 59-138205, JP-A 60-84305, JP-A 62-18537, JP 64-33104, Research Disclosure. And the compound described in No. 33825). Specific examples of the amines include triethanolamine, p-dimethylaminobenzoic acid ethyl ester, p-formyldimethylaniline, p-methylthiodimethylaniline, and the like.

Examples of co-sensitizers include thiols and sulfides (for example, thiol compounds described in JP-A-53-702, JP-B-55-500806, and JP-A-5-142277, A suitable example is the disulfide compound of JP 56-75643.
Specific examples of thiols and sulfides include 2-mercaptobenzothiazole, 2-mercaptobenzoxazole, 2-mercaptobenzimidazole, 2-mercapto-4 (3H) -quinazoline, β-mercaptonaphthalene, and the like.
Examples of co-sensitizers include amino acid compounds (for example, N-phenylglycine), organometallic compounds described in Japanese Patent Publication No. 48-42965 (for example, tributyltin acetate), and Japanese Patent Publication No. 55-. 34414, a hydrogen donor described in JP-A-6-308727, a sulfur compound (eg, trithiane), a phosphorus compound described in JP-A-6-250387 (such as diethyl phosphite), Examples thereof include Si—H and Ge—H compounds described in Japanese Patent Application No. 6-191605.

-Resin-
The ink composition of the present invention may contain (a) a resin different from the specific polymer for the purpose of adjusting film physical properties of the recorded image.
As this resin, for example, acrylic polymer, polyvinyl butyral resin, polyurethane resin, polyamide resin, polyester resin, epoxy resin, phenol resin, polycarbonate resin, polyvinyl butyral resin, polyvinyl formal resin, shellac, vinyl resin, acrylic resin Examples thereof include resins, rubber resins, waxes, and other natural resins. These may be used individually by 1 type and may use 2 or more types together. In the present invention, known waxes may be used in place of the resin.

-Surfactant-
The ink composition of the present invention may contain a surfactant for the purpose of adjusting the liquid properties of the ink composition.
Examples of the surfactant include nonionic surfactants, cationic surfactants, anionic surfactants, betaine surfactants, and organic fluoro compounds.

-UV absorber-
The ink composition of the present invention preferably contains an ultraviolet absorber from the viewpoint of improving the weather resistance of recorded images and preventing discoloration, and also from the viewpoint of improving the stability of the ink composition. From the viewpoint of preventing fading of recorded images, it is preferable to contain an antifading agent (for example, various organic and metal complex compounds), and inkjet In the case of recording, from the viewpoint of ejection stability, it is preferable to contain an ejection stabilizer (for example, conductive salts such as potassium thiocyanate, lithium nitrate, ammonium thiocyanate, dimethylamine hydrochloride). From the viewpoint of improving the adhesion to the recording medium, it may contain an adhesion improver (for example, a very small amount of organic solvent or a tackifier that does not inhibit the polymerization) If necessary, a leveling additive, may contain such matting agent.

-Solvent-
The ink composition of the present invention may contain a solvent. However, in the case where the ink composition of the present invention is a curable ink, it is preferable that the ink be applied without a solvent and be solvent-free in order to cure the ink after it is applied to the recording medium. This is because if the solvent remains in the cured ink image, the solvent resistance is deteriorated or a VOC (Volatile Organic Compound) problem of the remaining solvent occurs.
Therefore, the pigment dispersion of the present invention contained in the ink composition of the present invention preferably uses the polymerizable compound (c) used in the curing reaction as a dispersion medium, and among them, the polymerization having the lowest viscosity It is preferable to select a functional compound from the viewpoints of dispersion suitability and improved handling of the ink composition.

<Physical properties>
-Viscosity-
The viscosity of the ink composition of the present invention is not particularly limited and may be appropriately selected depending on the intended purpose. However, in view of ejection stability, the temperature at the time of ejection is preferably 30 mPa · s or less, preferably 20 mPa · s. S or less is more preferable.
Further, the viscosity of the ink composition of the present invention at room temperature (25 ° C.) is preferably 200 mPa · s or less, and more preferably 100 mPa · s or less.
By setting the viscosity at room temperature (25 ° C.) high, even when a porous recording medium is used, ink penetration into the recording medium can be prevented, and uncured monomers can be reduced and odor can be reduced. Furthermore, it is advantageous in that dot bleeding at the time of ink droplet landing can be suppressed, and as a result, high image quality can be obtained.
On the other hand, if the viscosity at room temperature (25 ° C.) exceeds 200 mPa · s, there may be a problem in delivery of the ink composition.
The viscosity can be measured using, for example, a conical plate type rotational viscometer (E type viscometer).

-Surface tension-
There is no restriction | limiting in particular as surface tension of the ink composition of this invention, Although it can select suitably according to the objective, For example, 20-30 mN / m is preferable and 23-28 mN / m is more preferable.
In addition, when recording the ink composition of the present invention on various recording media such as polyolefin, PET, coated paper, uncoated paper and the like, it is preferably 20 mN / m or more in terms of bleeding and penetration, and the point of wettability. Is preferably 30 mN / m or less.
The surface tension can be measured using, for example, a Wilhelmy surface tension meter or a Du Nouy surface tension meter.

<Preparation of ink composition>
There is no restriction | limiting in particular as a preparation method of the ink composition of this invention, According to the objective, it can select suitably, For example, it can manufacture by mixing each above-mentioned component. In addition, mixing can be performed according to a well-known method using a well-known mixer etc.

<Usage>
The ink composition of the present invention can be suitably used as an ink for various image recordings, and is particularly suitable for inkjet applications when it is a curable ink.
In this case, the ink composition of the present invention is printed on a recording medium by an ink jet printer, and then the printed ink composition is irradiated with actinic radiation to be cured and image recording is performed.
By applying the ink composition of the present invention to an ink jet system, a high-quality image can be directly formed on a non-absorbable recording medium based on digital data. Therefore, the ink composition of the present invention has a large area. It is also suitably used for the production of printed materials.

Moreover, the printed matter obtained using the ink composition of the present invention is excellent in strength because the image portion is cured by irradiation with active radiation such as ultraviolet rays. For this reason, besides image recording (image formation), for example, it can be suitably used for various applications such as formation of an ink receiving layer (image part) of a lithographic printing plate.
For example, since the ink composition of the present invention can be used for normal printing to form a sharp image with excellent color developability, not only high-quality printed materials can be obtained, but also resists, color filters, and optical disks. It can be suitably used for production and is also useful as an optical modeling material.

-Inkjet recording-
Here, ink jet recording using the ink composition of the present invention will be described.
The method and conditions for inkjet recording are not particularly limited and may be appropriately selected depending on the intended purpose. For example, the ink composition of the present invention is heated to 40 to 80 ° C. After adjusting the viscosity to 30 mPa · s or less, discharging from the ink nozzle head is preferable in terms of excellent discharge stability. Generally, a radiation curable ink composition such as the ink composition of the present invention generally has a higher viscosity than a general water-based ink, and thus has a large viscosity fluctuation range due to temperature fluctuations during image recording (printing). The viscosity variation of the ink composition has a great influence on the droplet size and the droplet ejection speed as it is, which causes image quality deterioration. For this reason, it is necessary to keep the temperature of the ink composition at the time of image recording (printing) as constant as possible. The control range of the temperature of the ink composition is preferably set temperature ± 5 ° C, more preferably set temperature ± 2 ° C, and particularly preferably set temperature ± 1 ° C.

  There is no restriction | limiting in particular as an inkjet recording device used for inkjet recording, It can select suitably from well-known things, A commercial item can be used conveniently, For example, the temperature of the said ink composition is sufficient. It is preferable to provide stabilizing means. In this case, it is preferable that the part where the ink composition is kept at a constant temperature is the entire piping system and members from the ink tank (intermediate tank if there is an intermediate tank) to the nozzle ejection surface.

  The method for controlling the temperature of the ink composition is not particularly limited, but for example, it is preferable to provide a plurality of temperature sensors in each piping region and perform heating control according to the flow rate of the ink composition and the environmental temperature. The ink nozzle head for discharging the ink composition is preferably heated, and in this case, the ink jet recording apparatus main body may be thermally blocked or insulated so as not to be affected by the temperature from the outside air. More preferred. In order to shorten the startup time of the ink jet recording apparatus (printer) required for heating, or to reduce the loss of thermal energy, it is preferable to insulate from other parts and reduce the heat capacity of the entire heating unit.

-Ink composition ejection conditions-
When the ink composition of the present invention is used for ink jet recording, it is preferable to warm the ink composition of the present invention to a constant temperature and to shorten the time from ejection of the ink composition to irradiation with actinic radiation.
The time from ejection of the ink composition to irradiation with actinic radiation (hereinafter sometimes referred to as “pre-irradiation time”) is preferably 0.01 to 0.5 seconds, for example, 0.01 to 0.3. The second is more preferable, and 0.01 to 0.15 second is particularly preferable.
By controlling the pre-irradiation time within the above-mentioned range, it is possible to effectively prevent the ejected ink composition from spreading before curing, and the light source of the porous recording medium can also be prevented. It is advantageous in that it can be irradiated with actinic radiation before the ink composition penetrates to a deep part that does not reach, and the residual unreacted monomer can be suppressed, and as a result, odor can be reduced. .

By using the ink composition of the present invention and discharging under the above-mentioned discharge conditions, etc., the dot diameter of the ink composition discharged in the form of droplets can also be applied to various recording media having different surface wettability. This is advantageous in that it can be kept constant and high image quality can be obtained.
In order to obtain a color image, it is preferable that the ink composition of the present invention is overlaid in order from a color with low brightness. When inks with low lightness are stacked, actinic radiation does not easily reach the lower ink, and the curing sensitivity may be hindered, residual monomers may increase, odor may be generated, and adhesion may be deteriorated. Irradiation with actinic radiation may be performed in a lump after all the inks of all colors have been ejected, but it is preferably performed for each color from the viewpoint of promoting curing.

  According to the above, although the ink composition of the present invention is repeatedly heated and cooled, (a) the case where it is stored under such temperature conditions due to the action or function of the specific polymer. However, it is advantageous in that a decrease in dispersibility of the pigment is effectively suppressed, excellent color developability is obtained over a long period of time, and a decrease in ejection stability due to aggregation of the pigment is also effectively suppressed. is there.

-Curing-
The ink composition of the present invention is cured by irradiation with actinic radiation after image recording, but the irradiation conditions of the actinic radiation in this case are not particularly limited and may be appropriately selected according to the purpose. Can do.
A method of irradiating actinic radiation is described in, for example, Japanese Patent Application Laid-Open No. 60-132767. Specifically, light sources are provided on both sides of the head unit, and the head and the light source are scanned by a shuttle method. Irradiation with actinic radiation is performed after a certain period of time after ink landing. Further, the curing is completed by another light source that is not driven. Also, WO99 / 54415 describes a method of irradiating UV light to a recording unit by applying a method using an optical fiber or a collimated light source to a mirror surface provided on the side of the head unit as a method of irradiating active radiation. ing. In the present invention, these irradiation methods can be employed.

-Recording medium-
The recording medium on which an image is recorded by discharging the ink composition of the present invention is not particularly limited and can be appropriately selected according to the purpose. Examples include various non-absorbable resin materials used for so-called soft packaging, or resin films obtained by forming them into a film. As the resin film, for example, PET film, OPS film, OPP film, ONy film, PVC film, PE film, TAC film, polycarbonate film, acrylic film, ABS film, polyacetal film, PVA film, rubber film, Etc. Further, metals, glasses and the like can be used as the recording medium.

  Examples of the present invention will be described below, but the present invention is not limited to these examples.

<Synthesis of specific polymer>
-Synthesis of the monomer (M-7)-
To a 1500 mL acetonitrile solution of 25.0 g of 4-hydroxymethyl-1,3dioxolan-2-one and 25.5 g of triethylamine, a mixed solution of 20.9 g of acrylic acid chloride and 200 mL of acetonitrile was added at room temperature to 40 mL. The solution was added dropwise so as not to exceed 0 ° C., and then stirred at room temperature for 8 hours. The resulting reaction mixture was filtered off and washed with 300 mL of ethyl acetate, and the solvent was distilled off from the filtrate under reduced pressure.
The resulting oily product was purified by silica gel column chromatography (Wako gel ^(R) C-300HG, ^(Ltd.) manufactured by Wako Pure Chemical Industries, Ltd., developing solvent: hexane / ethyl acetate = 1/1) to afford monomer of interest ( 25.2 g of M-7) was obtained as an oil.

-Graft polymer 1: Synthesis of the specific example (9)-
1 g of a monomer represented by M-7, 19.0 g of polybutyl acrylate having a methacryloyl group at the end (AB-6: manufactured by Toagosei Co., Ltd.), 20.0 g of methyl ethyl ketone, 48 mg of normal-dodecyl mercaptan are replaced with nitrogen The mixture was introduced into the three-necked flask, stirred with a stirrer (Shinto Kagaku Co., Ltd .: Three-One Motor), heated to 65 ° C. while flowing nitrogen into the flask. Separately prepared initiator solution of 1,4.5 mg of 2,2-azobis (2,4-dimethylvaleronitrile) (V-65 manufactured by Wako Pure Chemical Industries, Ltd.) and 4.0 g of methyl ethyl ketone was added dropwise over 10 minutes. . After dropping, the mixture was heated and stirred at 65 ° C. for 2 hours. Thereafter, an initiator solution of V-65, 14.5 mg, and methyl ethyl ketone 4.0 g was added dropwise over 10 minutes, and the mixture was heated and stirred at 65 ° C. for 4 hours. The obtained reaction mixture was dried at 60 ° C. under reduced pressure to synthesize graft polymer 1: specific example (9).

-Graft polymer 2: Synthesis of specific example (10)-
In the synthesis of the graft copolymer 1, the monomer (M-7) was changed to the monomer (M-8) (TCMA: manufactured by Kyowa Hakko Kogyo Co., Ltd.), and “polybutyl having a methacryloyl group at the terminal” was used. Graft polymer 2: the above-mentioned specific example, except that “acrylate” was changed to “polymethyl methacrylate having a methacryloyl group at the end (AA-6: manufactured by Toa Gosei Co., Ltd.)” Example (10) was synthesized.

-Graft polymer 3: Synthesis of specific example (11)-
The monomer (M-7) is changed to the monomer (M-11), and “polybutyl acrylate having a methacryloyl group at a terminal” is changed to “polymethyl methacrylate having a methacryloyl group at a terminal (AA-6: manufactured by Toa Gosei Co., Ltd.). The graft polymer 3: the specific example (11) was synthesized in the same manner as the synthesis of the graft copolymer 1 except that the composition was changed to “)”.

-Graft polymer 4: Synthesis of specific example (23)-
In the synthesis of the graft copolymer 1, “19.0 g of polybutyl acrylate having a methacryloyl group at the terminal” was changed to “18.0 g of polybutyl acrylate having a methacryloyl group at the terminal”, and mono-2- ( Graft polymer 4: The specific example (23) was synthesized in the same manner as the synthesis of the graft copolymer 1 except that 1.0 g of (acryloxy) ethyl succinate was added.

Example 1
The synthesized graft polymer 1 is dissolved in the following polymerizable compounds (1) to (3), put into a motor mill M50 (manufactured by Eiger) together with the following pigment, and zirconia beads having a diameter of 0.65 mm are used. Dispersion was carried out at a speed of 9 m / s for 6 hours to obtain a stock solution of curable ink. Next, the following polymerization initiator was added to the stock solution of the curable ink, mixed gently, and then filtered under pressure with a membrane filter to obtain the curable inkjet ink of Example 1 (the ink composition of the present invention). ) Was manufactured.
The content of each component in the ink composition of Example 1 is as follows.

[Composition of Ink Composition of Example 1]
・ Graft copolymer 1 0.5g
Polymerizable compound:
(1) 30.0 g of propoxylated neopentyl glycol diacrylate
(NPPGODA: Sartomer Co., Ltd.)
(2) Dipropylene glycol diacrylate 30.0g
(DPGDA: manufactured by Daicel Cytec Co., Ltd.)
(3) 29.5 g of phenoxyethyl acrylate
(AMP-10G: Shin-Nakamura Chemical Co., Ltd.)
・ Pigment: 5.0 g of quinacridone pigment (PR122)
-Polymerization initiator: Acylphosphine oxide compound 5.0 g
(Lucirin TPO-L: manufactured by BASF Japan)

(Examples 2, 3, and 4)
In Example 1, Example 2, 3, 4 was carried out in the same manner as in Example 1 except that the graft copolymer 1 was changed to graft copolymers 2, 3, 4 synthesized as described above, respectively. The curable inkjet ink (ink composition of the present invention) was obtained.

(Comparative Example 1)
In Example 1, the curable inkjet ink of Comparative Example 1 was used in the same manner as in Example 1 except that the graft copolymer 1 was changed to a commercially available pigment dispersant (SOLRSPERSE 24000GR, manufactured by Nihon Librizol Corporation). Obtained.

(Comparative Example 2)
In Example 1, the curable inkjet ink of Comparative Example 2 was used in the same manner as in Example 1 except that the graft copolymer 1 was changed to a commercially available pigment dispersant (SOLRSPERSE 32000, manufactured by Nihon Librizol Corporation). Obtained.

(Examples 5 to 8 and Comparative Examples 3 and 4)
Examples 1 to 4 and Comparative Examples 1 and 2, respectively, except that “quinacridone pigment (PR122)” used in Examples 1 to 4 and Comparative Examples 1 and 2 was changed to “condensed azo pigment (PY128)”. Similarly, the curable inkjet inks of Examples 5 to 8 and Comparative Examples 3 and 4 were produced.

(Examples 9 to 12 and Comparative Examples 5 and 6)
Examples 1-4 and Comparative Example 1 except that the polymerizable compounds (1) to (3) and the polymerization initiator used in Examples 1 to 4 and Comparative Examples 1 and 2 were changed to those shown below. 2, curable inkjet inks of Examples 9 to 12 and Comparative Examples 5 and 6 were produced in the same manner as in No. 2 and No. 2, respectively.

Polymerizable compound:
(A) Oxetane compound (OXT-221: manufactured by Toa Gosei Co., Ltd.) 70.0 g
(B) Epoxy compound 17.5 g
(Celoxide 3000: manufactured by Daicel Chemical Industries, Ltd.)
-Polymerization initiator: Triphenylsulfonium salt 5.0 g
(UVI-6992, manufactured by Dow Chemical Company)

(Examples 13 to 16 and Comparative Examples 7 and 8)
In Examples 9 to 12 and Comparative Examples 5 and 6, Examples 9 to 12 and Comparative Examples 5 and 6 were changed except that “quinacridone pigment (PR122)” was changed to “phthalocyanine pigment (PB15: 3)”. In the same manner, curable inkjet inks of Examples 13 to 16 and Comparative Examples 7 and 8 were produced.

-Evaluation of ink composition-
Each obtained ink composition (curable inkjet ink) was evaluated according to the following method. The results are shown in Table 1.

<Viscosity>
The viscosity at 40 ° C. of each ink composition was measured using an E-type viscometer. The viscosity was evaluated according to the following criteria.
A: Less than 30 mPas B: 30 mPas or more and less than 100 mPas

<Dispersion stability>
After each ink composition was stored at 25 ° C. for 1 month and after being stored at 70 ° C. for 24 hours, the dispersion state was evaluated by visual observation and change in viscosity. Evaluation was made according to the following criteria.
◎: Precipitation does not occur and viscosity does not increase ○: Precipitation does not occur and viscosity increases slightly, but there is no problem with ejection performance △: Precipitation does not occur, but ejection performance decreases due to increase in viscosity And practically problematic level ×: occurrence of precipitates is observed

<Average particle size>
About the pigment in each ink composition, the volume reference average particle diameter D50 was measured using a light scattering diffraction type particle size distribution measuring device (LA910, manufactured by Horiba, Ltd.), and evaluated according to the following criteria.
A: D50 is less than 100 nm B: D50 is 100 nm or more and less than 200 nm C: D50 is 200 nm or more

<Curing property>
Each ink composition obtained was recorded (printed) on art paper using an ink jet printer (printing density 300 dpi, droplet ejection frequency 4 kHz, nozzle number 64), and then a Deep UV lamp (US-7, SP-7). Was used to irradiate the recorded image with ultraviolet rays as active radiation under the condition of an energy of 100 mJ / cm ² to obtain a recorded image.
The obtained recorded image was touched with a finger, and the presence or absence of stickiness was evaluated according to the following criteria.
A: No stickiness B: Slightly sticky C: Remarkably sticky

(Example 17)
The graft copolymer 1 synthesized as described above is dissolved in the following polymerizable compounds (4) and (5), and together with the following pigment, put into a motor mill M50 (manufactured by Eiger), and zirconia having a diameter of 0.65 mm. Using beads, dispersion was performed at a peripheral speed of 5 m / s for 2 hours to obtain a stock solution of curable ink. Next, the following polymerization initiator was added to the stock solution of the curable ink, mixed gently, and then pressure-filtered with a membrane filter to obtain the curable inkjet ink of Example 17 (the ink composition of the present invention). ) Was manufactured.
In addition, the content of each component in the ink composition of Example 17 is as follows.

[Composition of Ink Composition of Example 17]
・ Graft copolymer 1 2.0g
Polymerizable compound:
(4) Phenoxyethyl acrylate 32.0 g
(AMP-10G: Shin-Nakamura Chemical Co., Ltd.)
(5) Dipropylene glycol diacrylate 40.0g
(DPGDA: manufactured by Daicel Cytec Co., Ltd.)
・ White pigment: Titanium oxide (CR-60-2 manufactured by Ishihara Sangyo Co., Ltd.) 20g
-Polymerization initiator: Acylphosphine oxide compound 5.0 g
(Lucirin TPO-L: manufactured by BASF)
・ Sensitizer: Isopropylthioxanthone 2.0g
(DAROCUR ITX: Ciba Specialty Chemicals)

(Examples 18 to 20)
In Example 17, the curable inkjet inks of Examples 18 to 20 (of the present invention) were used in the same manner as Example 17 except that the graft copolymer 1 was changed to graft copolymers 2, 3, and 4, respectively. Ink composition) was obtained.

(Comparative Examples 9 and 10)
In Example 17, except that the graft copolymer 1 was changed to a commercially available pigment dispersant (SORPERSE 26000, manufactured by Nihon Librizol Corporation) and a commercially available pigment dispersant (SORPERSE 28000, manufactured by Nihon Lubrizol Corporation), respectively. In the same manner as in Example 17, the curable inkjet inks of Comparative 9 and 10 were obtained.

-Evaluation of ink composition-
Each of the obtained ink compositions was evaluated according to the following method. The results are shown in Table 1.

<Viscosity>
The viscosity at 25 ° C. of each ink composition was measured using an E-type viscometer. The viscosity was evaluated according to the following criteria.
A: Less than 30 mPas B: 30 mPas or more and less than 100 mPas

<Stability>
10 g of each ink composition is put into a screw mouth bottle (SV-15: manufactured by Nippon Denka Glass Co., Ltd.), stored at 25 ° C. for 7 days, and stored at 70 ° C. for 24 hours. Was evaluated visually and by viscosity change. Evaluation was made according to the following criteria.
◎: Precipitation is not generated and viscosity is not increased. ○: Precipitation is generated, but when the precipitate is stirred with a spatula, it can be easily redispersed. Level where precipitation occurs and cannot be redispersed even with stirring with a spatula, causing problems with ejection

<Curing property>
Each ink composition obtained was recorded (printed) on art paper using an inkjet printer (printing density 300 dpi, droplet ejection frequency 4 kHz, nozzle number 64), and then a Deep UV lamp (made by Ushio, SP-7) was used. The recorded image was irradiated with ultraviolet rays as active radiation under the condition that the recorded image had an energy of 1000 mJ / cm ² to obtain a recorded image.
The obtained recorded image was touched with a finger, and the presence or absence of stickiness was evaluated according to the following criteria.
A: No stickiness B: Slightly sticky C: Remarkably sticky

From Tables 1 and 2, the ink compositions of the examples can be suitably image-recorded by ink-jet recording, are cured with high sensitivity to irradiation with actinic radiation (ultraviolet rays), and have high image quality without stickiness. It can be seen that it can be recorded. In addition, it was found that the ink compositions of the examples were good in both dispersibility and dispersion stability of the pigment without causing thickening due to a decrease in dispersibility of the pigment even under long-term storage conditions. .
As described above, since the ink compositions of the examples are excellent in the dispersibility and dispersion stability of the pigment, this effect results in a clear color tone and high coloring power, and can form a high-quality image. I guess that.
On the other hand, in the case of the ink of the comparative example using a commercially available polymer dispersant, the storage stability (stability (70 ° C.)) under high temperature conditions was inferior, and it was at a level causing a practical problem.
In the examples, each synthesized graft copolymer is composed of an interaction site with a pigment and a graft chain (macromonomer), and the graft chain (macromonomer) is more dispersed in the dispersion medium than the pigment. It was considered that it functions or functions as a steric repulsive group that exhibits affinity and sterically prevents particles from aggregating in the dispersion. In the present invention, since the graft copolymer has the same configuration as the graft copolymer used in the examples, it has the same functions and functions as the graft copolymer used in each example. Inferred.

Claims (5)

A pigment dispersion comprising at least (a) a polymer containing a repeating unit represented by the following general formula (1), and (b) a pigment.

(In General Formula (1), R ¹ represents a hydrogen atom or an alkyl group. R ² , R ³ , and R ⁴ each independently represents an alkylene group or a phenylene group. V represents —O. —, —CO—, —C (═O) O—, —CONR ⁵ —, —OC (═O) —, and a phenylene group are represented, and R ⁵ represents a hydrogen atom, an alkyl group, or an aryl group. W and X are each independently —O—, —C (═O) O—, —CONH—, —NHCO—, —NHC (═O) O—, —NHC (═O) NH. -, -OC (= O)-, and any one of a phenylene group, l, m, n, o, and p each independently represent 0 or 1. Y represents a single bond or an alkylene group. Z ¹ , Z ² , and Z ³ are each independently any one of NH, NR ⁶ , O, and S. And R ⁶ represents an alkyl group or an aryl group.) In the general formula (1), R ¹ represents a hydrogen atom or a methyl group, R ² , R ³ , and R ⁴ each independently represent an alkylene group having 1 to 12 carbon atoms or a phenylene group, W represents —C (═O) O—, —OC (═O) —, or a phenylene group, and X represents —O—, —NHC (═O) O—, —NHC (═O) NH—. Or -C (= O) O-, wherein l, m, n, o, and p each independently represent 0 or 1;   An ink composition comprising the pigment dispersion according to claim 1.   The ink composition according to claim 3, further comprising (c) a polymerizable compound.   The ink composition according to claim 3 or 4, further comprising (d) a photopolymerization initiator.