JP2006348231A - Ink composition, method for forming image therewith, and recorded article - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ink composition which has excellent curability, excellent stability and excellent light resistance, and does not produce an aldehyde compound. <P>SOLUTION: This ink composition is characterized by containing at least a compound having a structure represented by general formula (1) [X is O, S, an alkylene or -N(R1)-; Y is O, S or -N(R2)-; R1 and R2 are each independently H or a substituent; Z is a linkage for bonding to X and Y; X, Y and Z form a ring together with the α-carbon of the vinyl group]. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an ink composition suitably used for inkjet recording, an image forming method using the same, and a recorded matter.

  Water-based ink-jet inks have poor water resistance when printed on plain paper and are likely to bleed. In addition, ink droplets adhere poorly when printed on non-water-absorbing recording media such as plastic. For this reason, image formation could not be performed, and drying of the solvent was extremely slow, so that it was necessary to dry without overlapping the recorded material immediately after printing, and the image was liable to blur.

  Ultraviolet curable inks using polyfunctional monomers with excellent adhesion to recording media have been developed as suitable for printing on non-water-absorbing recording media. Slow and insufficient to form a full color image. In order to solve the drying property, a method using a volatile organic solvent as an ink solvent has been carried out. However, from the viewpoint of odor and the like, a method not using such a highly volatile solvent has been desired. .

From these viewpoints, ink jet inks that are cured and fixed by active energy rays rather than volatilization of the ink solvent have been developed. For example, Patent Documents 1 to 3 disclose inks containing a monomer having a polymerizable group and an oil-soluble dye. Patent Document 4 discloses a photopolymerizable composition containing a photopolymerizable compound and a photopolymerization initiator. However, an ink composition having a high curing rate has been desired. In addition, it has been desired to improve curability with a thin film, particularly in the air.
Therefore, an ink using cationic polymerization that does not inhibit polymerization even in air is disclosed. For example, Patent Document 5 discloses an active energy ray-curable composition having oxirane and oxetane, but an ink composition having a higher curing rate has been desired. Patent Document 6 discloses an active energy ray-curable composition having oxirane, oxetane, and vinyl ether with improved curing speed, but the storage stability deteriorates, and vinyl ether decomposes to produce acetaldehyde. Therefore, an ink composition that has high storage stability and does not generate acetaldehyde has been desired. On the other hand, Patent Document 7 discloses an active energy ray-curable ink that uses a cyclic compound such as tetrahydrofuran, oxepane, and monocyclic acetal for the purpose of having storage stability. A composition was desired.
JP 2003-221528 A JP 2003-221532 A JP 2003-221530 A JP 2001-222105 A JP 2000-169552 A JP 2001-220526 A JP 2004-10625 A

  The problem to be solved by the present invention is to provide an ink composition which is excellent in curability and stability, a printed image formed using it is excellent in light resistance, and does not produce aldehyde. Another object of the present invention is to provide an image forming method and recorded matter using such an ink composition.

The present invention provides the following ink composition, image forming method and recorded matter.
(1) An ink composition comprising at least a compound having a structure represented by the following general formula (1) as a polymerizable compound.

(In General Formula (1), X represents an oxygen atom (—O—), a sulfur atom (—S—), an alkylene group, or —N (R 1) —, and Y represents an oxygen atom (—O—). , Sulfur atom (—S—) or —N (R 2) —, R 1 and R 2 each independently represents a hydrogen atom or a substituent, Z is a linking group bonded to X and Y. X , Y, and Z form a ring with the α-carbon of the vinyl group.)
(2) The ink composition according to item (1), which contains a photocationic polymerization initiator.
(3) The ink composition according to item (1) or (2), further comprising a compound having at least one of an oxirane ring and an oxetane ring.
(4) The ink composition according to any one of (1) to (3), further comprising a colorant.
(5) The ink composition according to item (4), wherein the colorant is selected from the group consisting of a pigment and an oil-soluble dye.
(6) The ink composition according to item (5), which contains an oil-soluble dye, wherein the oxidation potential of the oil-soluble dye is at least 1.0 V (vs SCE).
(7) The ink composition according to any one of (1) to (6), wherein the compound having a structure represented by the general formula (1) is contained in an amount of 35 to 45% by mass. .
(8) The ink composition according to any one of (1) to (7), which is for inkjet printing.
(9) An image forming method comprising an image recording step of recording an image on a recording medium by inkjet recording in which the ink composition according to any one of (1) to (8) is discharged.
(10) An image recording step of recording an image on a recording medium using the ink composition according to any one of (1) to (8);
An image curing step of irradiating and curing an active energy ray on the image recorded on the recording medium in the image recording step;
An image forming method comprising:
(11) The image forming method according to item (10), wherein the image recording step records the image by ink jet recording which discharges the ink composition.
(12) A recorded matter recorded using the ink composition according to any one of (1) to (8).

  Since the ink composition of the present invention includes a polymer compound having a structure represented by the general formula (1) having a high reactivity, it is possible to increase the curing speed and to have good ink stability. In addition, since the ink curing rate is sufficiently high and the ink stability is good, clogging is small and the adhesion to the recording medium is excellent, and a good character or image can be recorded on the recording medium.

  Furthermore, the present invention can provide an image forming method using such an ink composition and having excellent adhesion to a recording medium, and a recorded matter on which good characters or images are recorded.

Details of the present invention will be described below.
The ink composition of the present invention contains at least a compound having a structure represented by the general formula (1) as a polymerizable compound.
As the polymerizable compound of the present invention, a cationic polymerizable compound is preferably used.
Here, the cationically polymerizable compound refers to a compound that is polymerized by a cation species generated by a known photocationic polymerization initiator or a cation radical. The content of the polymerizable compound in the ink composition of the present invention is preferably in the range of 70% to 99.9% by mass with respect to the total mass of the ink composition, and is further 75% to 99% by mass. Preferably, 80% to 97% by mass is more preferable.
Next, the compound having the structure represented by the general formula (1) will be described.

General formula (1) Formula, X represents an oxygen atom (-O-), a sulfur atom (-S-), an alkylene group, or -N (R1)-, Y represents an oxygen atom (-O-), sulfur It represents an atom (-S-) or -N (R2)-. R1 and R2 each independently represents a hydrogen atom or a substituent. Z is a linking group that binds to X and Y. X, Y, and Z form a ring together with the α carbon of the vinyl group.
This structure increases the electron density on the vinyl group and improves the nucleophilicity of the vinyl group. For this reason, an ink having a high cationic polymerization rate and a high curing rate can be obtained. In cationic polymerization, it is known that the electron density on the vinyl group greatly affects the polymerization rate, and the structure of the general formula (1) in which the α-position is substituted with two electron-donating functional groups is a polymerization rate. It is an excellent structure in improving

In X, the alkylene group is preferably an unsubstituted methylene group or a substituted methylene group, and more preferably an unsubstituted methylene group from the viewpoint of steric hindrance.
Examples of the substituent for R1 and R2 include an alkyl group (for example, methyl, ethyl, butyl) and an aryl group (for example, phenyl, benzyl).
In the present invention, both X and Y do not become an alkylene group, but when both X and Y are alkylene groups, the electron donating property is reduced and the curing rate is lowered. Moreover, when -N (R1)-or -N (R2)-is selected for X and / or Y, R1 and R2 are preferably alkyl groups, and the alkyl group is more preferably one having 1 to 8 carbon atoms.
As a combination of X and Y, those in which X and Y are both oxygen atoms (—O—) or sulfur atoms (—S—) are preferable.

As the linking group represented by Z, a linking group that forms a 12-membered ring or less is preferably used, and a linking group that forms a 5- to 8-membered ring is preferably used. That is, the number of bonds of the linking group is preferably 9 or less, more preferably 2 to 5, between the atoms connecting X and Y.
Z is preferably an alkylene group, which may include an ether bond, an ester bond, a thioether bond or an amide bond, or may have a substituent. Examples of the substituent include an alkyl group, an alkenyl group, an aryl group, an alkoxy group, a carbonyloxy group, and an alkylsilyl group, which inhibit or prevent cationic polymerization of a hydroxyl group, a sulfonic acid group, a carboxylic acid group, and the like. It is preferred not to include the starting functional group.

  The polymerizable compound used in the present invention may be any of a monomer, an oligomer and a polymer as long as it has a structure represented by the general formula (1) in the molecule. The number of sites represented by the general formula (1) in this compound, that is, the number of functional groups, is preferably 1 to 4 from the viewpoints of curing speed and stability.

  Examples of the compound having the structure represented by the general formula (1) used in the present invention are shown below, but the present invention is not limited to these compound examples.

  The compound having the structure represented by the general formula (1) may be used alone or in combination with a plurality of compounds having the structure represented by the general formula (1). You may mix and use an ionic compound. The content of the compound having the structure represented by the general formula (1) is 5 to 95% by mass with respect to the total mass of the polymerizable compound in the ink composition from the viewpoints of curability and stability of the ink. Preferably, 10-80 mass% is more preferable, 10-50 mass% is especially preferable, and 35-45 mass% is the most preferable.

  As other cationically polymerizable compounds that can be used in combination with the compound having the structure represented by the general formula (1), monomers, oligomers, and polymer seeds can be selected as long as they are compounds having a generally known cationically polymerizable group. Can be used regardless. Examples of the cationic polymerizable compound include the compounds exemplified below, but the present invention is not limited to these, and any known cationic polymerizable compound can be used without any problem. Moreover, the cationically polymerizable compound can be used alone or in combination for the purpose of adjusting the reaction rate, ink physical properties, cured film physical properties and the like.

As the cationic polymerizable monomer, a known cationic polymerizable compound is used, and in addition to a styrene derivative and a vinyl ether, an oxirane ring-containing compound, an oxetane ring-containing compound, a tetrahydrofuran ring-containing compound, a lactam, a lactone, and the like are used. Among these, oxirane ring-containing compounds, oxetane ring-containing compounds, vinyl ethers or styrene derivatives are preferably used, and oxirane and oxetane are particularly preferable.
Further, as the oxirane ring-containing compound (oxirane compound, that is, epoxy compound) and the oxetane ring-containing compound (oxetane compound), one may be used in addition to the compound having the structure represented by the general formula (1). More than one species may be used in combination. From the viewpoint of improving the curing rate and the degree of curing, it is preferable to use at least one oxetane compound and an oxirane compound in combination. In this case, the ratio of the oxirane compound and the oxetane compound is preferably 10:90 to 60:40, respectively. An ink composition having a good balance between curability and curing speed can be obtained by setting between these values.

[Oxirane ring-containing compound]
Examples of the oxirane ring-containing compound include aromatic epoxides and alicyclic epoxides. Aromatic epoxides include di- or polyglycidyl ethers produced by the reaction of polyphenols having at least one aromatic nucleus or their alkylene oxide adducts and epichlorohydrin, such as bisphenol A or its alkylene oxides. Examples thereof include di- or polyglycidyl ethers of adducts, di- or polyglycidyl ethers of hydrogenated bisphenol A or alkylene oxide adducts thereof, and novolak type epoxy resins. Here, examples of the alkylene oxide include ethylene oxide and propylene oxide.

Examples of the alicyclic epoxide include cyclohexene oxide obtained by epoxidizing a compound having at least one cycloalkane ring such as cyclohexene or cyclopentene ring with an appropriate oxidizing agent such as hydrogen peroxide or peracid. Preferred examples include cyclopentene oxide-containing compounds.
Examples of the aliphatic epoxide include dihydric polyhydridyl ethers of aliphatic polyhydric alcohols or alkylene oxide adducts thereof, and typical examples thereof include diglycidyl ether of ethylene glycol, diglycidyl ether of propylene glycol or 1,6. -Diglycidyl ether of alkylene glycol such as diglycidyl ether of hexanediol, polyglycidyl ether of polyhydric alcohol such as di- or triglycidyl ether of glycerin or its alkylene oxide adduct, diglycidyl of polyethylene glycol or its adduct of alkylene oxide Polyalkylene glycol diglycol represented by diglycidyl ether of ether, polypropylene glycol or its alkylene oxide adduct Jill ether, and the like. Here, examples of the alkylene oxide include ethylene oxide and propylene oxide.
Among these oxirane compounds, aromatic epoxides and alicyclic epoxides are preferable from the viewpoint of excellent curing speed, and alicyclic epoxides are particularly preferable.
Further, among the oxirane ring-containing compounds, those having a small number of functional groups are preferable because they can simultaneously have solubility and viscosity adjusting effects as described above.

  Examples of monofunctional epoxides used in the present invention include, for example, 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- Examples include vinylcyclohexene oxide.

  Examples of polyfunctional epoxides include, for example, bisphenol A diglycidyl ether, bisphenol F diglycidyl ether, bisphenol S diglycidyl ether, brominated bisphenol A diglycidyl ether, brominated bisphenol F diglycidyl ether, 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-epoxycyclohexyl) Til) 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, ethylene glycol di (3,4-epoxycyclohexylmethyl) ether, ethylenebis (3,4-epoxycyclohexanecarboxylate) , Epoxyhexahydrophthalate dioctyl, epoxyhexahydrophthalate di-2-ethylhexyl, 1,4-butanediol diglycidyl ether, 1,6-hexanediol diglycidyl ether, Resin triglycidyl ether, trimethylolpropane triglycidyl ether, polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ethers, 1,1,3-tetradecadiene dioxide, limonene dioxide, 1,2,7,8-di Examples thereof include epoxy octane, 1,2,5,6-diepoxycyclooctane and the like.

[Oxetane ring-containing compound]
The oxetane ring-containing compound in the present invention refers to a compound having an oxetane ring, and arbitrarily selected from known oxetane compounds as described in JP-A Nos. 2001-220526, 2001-310937, and 2003-341217. Can be used.
As the compound having an oxetane ring that can be used in the ink composition of the present invention, a compound having 1 to 4 oxetane rings in its structure is preferable, and as described above, the viscosity and tackiness of the ink composition are particularly preferable. From the viewpoint, it is preferable to use a compound having one or two oxetane rings. By using such a compound, 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. .

  Examples of the compound having 1 to 2 oxetane rings in the molecule include compounds represented by the following general formulas (11) to (13).

R ^a1 represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, a fluoroalkyl group having 1 to 6 carbon atoms, an allyl group, an aryl group, a furyl group, or a thienyl group. When two R ^a1 are present in the molecule, they may be the same or different.
Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, and a butyl group. Preferred examples of the fluoroalkyl group include those in which any hydrogen of these alkyl groups is substituted with a fluorine atom.
R ^a2 is an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, a group having an aromatic ring, an alkylcarbonyl group having 2 to 6 carbon atoms, or an alkoxycarbonyl having 2 to 6 carbon atoms. Group represents an N-alkylcarbamoyl group having 2 to 6 carbon atoms. Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, and a butyl group. Examples of the alkenyl group include a 1-propenyl group, a 2-propenyl group, a 2-methyl-1-propenyl group, and 2-methyl-2. -Propenyl group, 1-butenyl group, 2-butenyl group, 3-butenyl group and the like. Examples of the group having an aromatic ring include phenyl group, benzyl group, fluorobenzyl group, methoxybenzyl group, phenoxyethyl group and the like. Can be mentioned. As the alkylcarbonyl group, an ethylcarbonyl group, a propylcarbonyl group, a butylcarbonyl group, etc., as an alkoxycarbonyl group, an ethoxycarbonyl group, a propoxycarbonyl group, a butoxycarbonyl group, etc., as an N-alkylcarbamoyl group, Examples thereof include an ethylcarbamoyl group, a propylcarbamoyl group, a butylcarbamoyl group, and a pentylcarbamoyl group.

R ^a3 represents a linear or branched alkylene group, a linear or branched poly (alkyleneoxy) group, a linear or branched unsaturated hydrocarbon group, an alkylene group containing a carbonyl group or a carbonyl group, a carboxyl group Represents an alkylene group containing, an alkylene group containing a carbamoyl group, or a group shown below. Examples of the alkylene group include an ethylene group, a propylene group, and a butylene group. Examples of the poly (alkyleneoxy) group include a poly (ethyleneoxy) group and a poly (propyleneoxy) group. Examples of the unsaturated hydrocarbon group include a propenylene group, a methylpropenylene group, and a butenylene group.

When R ^a3 is the above polyvalent group, R ^a4 is a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a halogen atom, a nitro group, a cyano group, a mercapto group, A lower alkyl carboxyl group, a carboxyl group, or a carbamoyl group is represented.
R ^a5 represents an oxygen atom, a sulfur atom, a methylene group, NH, SO, SO ₂ , C (CF ₃ ) ₂ , or C (CH ₃ ) ₂ .
R ^a6 represents an alkyl group having 1 to 4 carbon atoms or an aryl group, and n is an integer of 0 to 2000. R ^a7 represents an alkyl group having 1 to 4 carbon atoms, an aryl group, or a monovalent group having the following structure. In the following formula, R ^a8 is an alkyl group having 1 to 4 carbon atoms or an aryl group, and m is an integer of 0 to 100.

  Examples of the compound having 3 to 4 oxetane rings include compounds represented by the following general formula (14).

In the general formula (14), R ^a1 has the same ^{meaning as} in the general formula (11). In addition, examples of R ^a9 that is a polyvalent linking group include branched alkylene groups having 1 to 12 carbon atoms such as groups represented by A to C below, and branched poly ( An alkyleneoxy) group or a branched polysiloxy group such as a group represented by E below. j is 3 or 4.

In the above A, R ^a10 represents a methyl group, an ethyl group, or a propyl group. Moreover, in said D, p is an integer of 1-10.

  Another embodiment of the oxetane compound that can be suitably used in the present invention includes a compound represented by the following general formula (15) having an oxetane ring in the side chain.

In the general formula (15), R ^a1 and R ^a8 have the same ^{meaning as} in the above formula. R ^a11 is an alkyl group having 1 to 4 carbon atoms such as a methyl group, an ethyl group, a propyl group, or a butyl group, or a trialkylsilyl group, and r is 1 to 4.

  Examples of monofunctional oxetanes include oxetane compounds used in the present invention, such as 3-ethyl-3-hydroxymethyloxetane, 3- (meth) allyloxymethyl-3-ethyloxetane, and (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-ethyl Hexyl (3-ethyl-3-oxetanylmethyl) ether, ethyldiethylene 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-oxetanyl) Methyl) ether, 2-tetrabromophenoxyethyl (3-ethyl-3-oxetanylmethyl) ether, tribromophenyl (3-ethyl-3-oxetanylmethyl) ether, 2-tribromophenoxyethyl (3-ethyl) Ru-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 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, tri Ethylene glycol bis (3-ethyl-3-oxetanylmethyl) ether, tetraethylene glycol bis (3-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 pentakis ( 3-ethyl-3-oxetanylmethyl) ether, ditrimethylolpropanetetrakis (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) And polyfunctional oxetanes such as ru-3-oxetanylmethyl) ether and EO-modified bisphenol F (3-ethyl-3-oxetanylmethyl) ether.

[Examples of vinyl ether]
Further, in the present invention, a compound having a vinyl ether group may be further contained in order to impart a degree of curing. In this case, the compound having a vinyl ether group can be present in the ink composition in the range of 1% by mass to 20% by mass from the viewpoint of adjusting the surface physical properties of the cured product and the solubility of the ink composition.
Examples of monofunctional vinyl ethers used in the present invention include, for example, 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, Cyclohexylmethyl 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 , Methoxy polyethylene Recall 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, Examples include chloroethoxyethyl vinyl ether, phenylethyl vinyl ether, phenoxypolyethylene glycol vinyl ether, and the like.

  Examples of polyfunctional vinyl ethers include, for example, ethylene glycol divinyl ether, diethylene glycol divinyl ether, polyethylene glycol divinyl ether, propylene glycol divinyl ether, butylene glycol divinyl ether, hexanediol divinyl ether, bisphenol A alkylene oxide divinyl ether, bisphenol F alkylene oxide. Divinyl ethers such as divinyl ether; trimethylolethane trivinyl ether, trimethylolpropane trivinyl ether, ditrimethylolpropane tetravinyl ether, glycerin trivinyl ether, pentaerythritol tetravinyl ether, dipentaerythritol pentavinyl ether, dipentaerythritol hex Vinyl 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, propylene oxide-added penta And polyfunctional vinyl ethers such as erythritol tetravinyl ether, ethylene oxide-added dipentaerythritol hexavinyl ether, and propylene oxide-added dipentaerythritol hexavinyl ether.

  As the styrene derivative, a known compound is used. From the viewpoint of improving the electron density on the vinyl group, a styrene derivative in which at least one of p-position and o-position of the aromatic ring is substituted with an electron-donating functional group is preferable. Used. Here, the electron-donating functional group means one having a negative Hammett's rule substituent constant σ value, and examples of such a functional group include an amino group, a hydroxyl group, an alkoxy group, and an alkyl group. Among these, an alkoxy group, an alkyl group, and a dimethylamino group are preferably used because they hardly react with the active terminal during polymerization.

  Monofunctional styrene compounds include styrene, 2-methylstyrene, 4-methylstyrene, 2,6-methylstyrene, 2-ethylstyrene, 4-ethylstyrene, 2-ethylstyrene, 4-n-butylstyrene, 2 2-alkylstyrenes and 4-alkylstyrenes such as n-butylstyrene, 4-t-butylstyrene, 2-t-butylstyrene, 4-butenylstyrene, 4-octenylstyrene, 4-methoxystyrene, 2-alkoxystyrene such as 2-methoxystyrene and 4-t-butylstyrene, or 4-alkoxystyrenes, 4-acetoxystyrene, 4-dimethylaminostyrene, 4-dimethylaminomethylstyrene, 4-glycidylmethylstyrene, 4 -Hydroxystyrene, 2,4-dialkylstyrene, 2,4, - trialkyl styrene, 2,4-dialkoxy styrene, 2,4,6-alkoxy styrene.

  As polyfunctional styrene, divinylbenzene, bis (4-vinylphenyl) methane, bis (4-vinylphenyl) ethane, bis (4-vinylphenyl) butane, bis (4-vinylphenyl) hexane, bis (4-vinyl) Phenyl) heptane, bis (4-vinylphenyl) octane, bis (4-vinylphenoxy) hexane, bis (4-vinylbenzyl) diethylene glycol, ethylene glycol bis (4-vinylphenyl) ether, propylene glycol bis (4-vinylphenyl) ) Ether, 1,6-hexanediol bis (4-vinylphenyl) ether, 1,8-octanediol bis (4-vinylphenyl) ether, oligoethylene glycol bis (4-vinylphenyl) ether, polyethylene glycol (4- Vinyl pheni Ether), oligo propylene glycol bis (4-vinylphenyl) ether, polypropylene glycol bis (4-vinylphenyl) ether, glycerol tris (4-vinylphenyl) ether.

<Photocationic polymerization initiator>
The ink composition of the present invention preferably contains a cationic photopolymerization initiator. This cationic photopolymerization initiator refers to a compound that generates an acid upon irradiation with active energy rays to initiate cationic polymerization, and publicly known compounds and mixtures thereof can be appropriately selected and used.
As the photocationic polymerization initiator, those listed below may be used alone or in combination of two or more. The content of the present cationic photopolymerization initiator in the ink composition is preferably 0.1 to 20% by mass, more preferably 0.5 to 10% by mass, based on the total mass of the ink composition. preferable. If the content of the photocationic polymerization initiator is within the above range, the curability is high, and there is no problem of brittleness or acid generation due to the remaining initiator, which is preferable.

  Examples of the photocationic polymerization initiator in the present invention include diazonium salts, phosphonium salts, sulfonium salts, iodonium salts, imide sulfonates, oxime sulfonates, diazodisulfones, disulfones, and o-nitrobenzyl sulfonates.

Further, these photocationic polymerization initiators, or compounds obtained by introducing a group or compound having an equivalent function into the main chain or side chain of the polymer, for example, US Pat. No. 3,849,137, German Patent No. 3914407. JP, 63-26653, JP 55-164824, JP 62-69263, JP 63-146038, JP 63-163452, JP 62-153853, The compounds described in JP-A-63-146029 can be used.
Furthermore, compounds capable of generating an acid by light described in US Pat. No. 3,779,778, European Patent 126,712 and the like can also be used.

  Among the photocationic polymerization initiators, preferred compounds as the photoacid generator that can be used in the present invention include compounds represented by the following general formulas (b1), (b2), and (b3).

In general formula (b1), R ²⁰¹ , R ²⁰² and R ²⁰³ each independently represents an organic group.
X ⁻ represents a non-nucleophilic anion, preferably an organic anion having a carbon atom (for example, sulfonate anion, carboxylate anion, bis (alkylsulfonyl) amide anion, tris (alkylsulfonyl) methide anion), BF ₄ ⁻ , Examples thereof include PF ₆ ⁻ , SbF ₆ ^— and the groups shown below, and more preferably an organic anion having a carbon atom.

  Examples of the organic anion having a preferable carbon atom include organic anions represented by the following formula.

Rc ¹ represents an organic group.
Examples of the organic group in Rc ¹ include those having 1 to 30 carbon atoms, and preferably an alkyl group, a cycloalkyl group, an aryl group, or a plurality of these are a single bond, —O—, —CO ₂ —, —S—. , —SO ₃ —, —SO ₂ N (Rd ¹ ) — and the like.

Rd ¹ represents a hydrogen atom or an alkyl group.
Rc ³ , Rc ⁴ and Rc ⁵ each independently represents an organic group.
Preferred examples of the organic group for Rc ³ , Rc ⁴ , and Rc ⁵ include the same organic groups as those for Rc ¹ , and most preferably a perfluoroalkyl group having 1 to 4 carbon atoms.
Rc ³ and Rc ⁴ may be bonded to form a ring.
Examples of the group formed by combining Rc ³ and Rc ⁴ include an alkylene group and an arylene group. Preferably, it is a C2-C4 perfluoroalkylene group.

As the organic groups of Rc ¹ and Rc ^{3 to} Rc ⁵ , the most preferable one is an alkyl group substituted at the 1-position with a fluorine atom or a fluoroalkyl group, or a phenyl group substituted with a fluorine atom or a fluoroalkyl group. By having a fluorine atom or a fluoroalkyl group, the acidity of the acid generated by light irradiation is increased and the sensitivity is improved.

The carbon number of the organic group as R ²⁰¹ , R ²⁰² and R ²⁰³ is generally 1 to 30, preferably 1 to 20.
Two of R ^{201 to} R ²⁰³ may be bonded to form a ring structure, and the ring may contain an oxygen atom, a sulfur atom, an ester bond, an amide bond, or a carbonyl group. Examples of the group formed by combining two of R ^{201 to} R ²⁰³ include an alkylene group (eg, butylene group, pentylene group).

Specific examples of the organic group as R ²⁰¹ , R ²⁰² and R ²⁰³ include corresponding groups in the compounds (b1-1), (b1-2) and (b1-3) described later.
In addition, the compound which has two or more structures represented by general formula (b1) may be sufficient. For example, at least one of ^R 201 ^{to R 203} of the compound represented by the general formula (b1) is at least one directly with ^R 201 ^{to R 203} of another compound represented by formula (b1), or, It may be a compound having a structure bonded through a linking group.

  Further preferred examples of the component (b1) include compounds (b1-1), (b1-2), and (b1-3) described below.

Compound (b1-1) is in which at least one aryl group ^R 201 ^{to R 203} in formula (b1), arylsulfonium compound, i.e., a compound having arylsulfonium as a cation.

In the arylsulfonium compound, all of R ^{201 to} R ²⁰³ may be an aryl group, or a part of R ^{201 to} R ²⁰³ may be an aryl group, and the rest may be an alkyl group or a cycloalkyl group.

  Examples of the arylsulfonium compound include triarylsulfonium compounds, diarylalkylsulfonium compounds, aryldialkylsulfonium compounds, diarylcycloalkylsulfonium compounds, aryldicycloalkylsulfonium compounds, and the like.

  The aryl group of the arylsulfonium compound is preferably an aryl group such as a phenyl group or a naphthyl group, or a heteroaryl group such as an indole residue or a pyrrole residue, more preferably a phenyl group or an indole residue. When the arylsulfonium compound has two or more aryl groups, the two or more aryl groups may be the same or different.

The alkyl group that the arylsulfonium compound has as necessary is preferably a linear or branched alkyl group having 1 to 15 carbon atoms, such as a methyl group, an ethyl group, a propyl group, an n-butyl group, sec. -A butyl group, a t-butyl group, etc. can be mentioned.
The cycloalkyl group that the arylsulfonium compound has as necessary is preferably a cycloalkyl group having 3 to 15 carbon atoms, and examples thereof include a cyclopropyl group, a cyclobutyl group, and a cyclohexyl group.

The aryl group, alkyl group, and cycloalkyl group of R ^{201 to} R ²⁰³ are an alkyl group (eg, having 1 to 15 carbon atoms), a cycloalkyl group (eg, having 3 to 15 carbon atoms), an aryl group (eg, having 6 to 14 carbon atoms). ), An alkoxy group (for example, having 1 to 15 carbon atoms), a halogen atom, a hydroxyl group, or a phenylthio group as a substituent. Preferred substituents are linear or branched alkyl groups having 1 to 12 carbon atoms, cycloalkyl groups having 3 to 12 carbon atoms, and linear, branched or cyclic alkoxy groups having 1 to 12 carbon atoms, and most preferred. Is an alkyl group having 1 to 4 carbon atoms and an alkoxy group having 1 to 4 carbon atoms. The substituent may be substituted with any one of three R ^{201 to} R ²⁰³ , or may be substituted with all three. When R ^{201 to} R ²⁰³ are an aryl group, the substituent is preferably substituted at the p-position of the aryl group.

Next, the compound (b1-2) will be described.
The compound (b1-2) is a compound when R ^{201 to} R ²⁰³ in the formula (b1) each independently represents an organic group that does not contain an aromatic ring. Here, the aromatic ring includes an aromatic ring containing a hetero atom.
The organic group not containing an aromatic ring as R ^{201 to} R ²⁰³ generally has 1 to 30 carbon atoms, preferably 1 to 20 carbon atoms.
R ^{201 to} R ²⁰³ are each independently preferably an alkyl group, a cycloalkyl group, an allyl group, or a vinyl group, more preferably a linear, branched, cyclic 2-oxoalkyl group, or an alkoxycarbonylmethyl group, particularly preferably Is a linear, branched 2-oxoalkyl group.

The alkyl group as R ^{201 to} R ²⁰³ may be either linear or branched, and is preferably a linear or branched alkyl group having 1 to 10 carbon atoms (for example, methyl group, ethyl group, propyl group). Group, a butyl group, a pentyl group), and a linear, branched 2-oxoalkyl group, and an alkoxycarbonylmethyl group are more preferable.

The cycloalkyl group as R ^{201 to} R ²⁰³ preferably includes a cycloalkyl group having 3 to 10 carbon atoms (cyclopentyl group, cyclohexyl group, norbornyl group), and a cyclic 2-oxoalkyl group is more preferable.

Preferred examples of the linear, branched and cyclic 2-oxoalkyl group represented by R ^{201 to} R ²⁰³ include a group having> C═O at the 2-position of the above alkyl group or cycloalkyl group.
The alkoxy group in the alkoxycarbonylmethyl group as R ^{201 to} R ²⁰³ is preferably an alkoxy group having 1 to 5 carbon atoms (methoxy group, ethoxy group, propoxy group, butoxy group, pentoxy group).
R ^{201 to} R ²⁰³ may be further substituted with a halogen atom, an alkoxy group (eg, having 1 to 5 carbon atoms), a hydroxyl group, a cyano group, or a nitro group.

  The compound (b1-3) is a compound represented by the following general formula (b1-3), and is a compound having a phenacylsulfonium salt structure.

In General Formula (b1-3), R ^{1c to} R ^5c each independently represent a hydrogen atom, an alkyl group, a cycloalkyl group, an alkoxy group, or a halogen atom.
R ^6c and R ^7c each independently represents a hydrogen atom, an alkyl group or a cycloalkyl group.
R ^x and R ^y each independently represents an alkyl group, a cycloalkyl group, an allyl group, or a vinyl group.
Any two or more of R ^{1c to} R ^5c , R ^6c and R ^7c , and R ^x and R ^y may be bonded to each other to form a ring structure.
Zc ^- represents a non-nucleophilic anion, in the general formula (b1) X ^- can be the same as the non-nucleophilic anion.

The alkyl group as R ^{1c to} R ^7c may be either linear or branched, and for example, a linear and branched alkyl group having 1 to 20 carbon atoms, preferably 1 to 12 carbon atoms (for example, Methyl group, ethyl group, linear or branched propyl group, linear or branched butyl group, linear or branched pentyl group).

Preferred examples of the cycloalkyl group represented by R ^{1c to} R ^7c include cycloalkyl groups having 3 to 8 carbon atoms (for example, a cyclopentyl group and a cyclohexyl group).

The alkoxy group as R ^{1c to} R ^{5c may} be linear, branched or cyclic, for example, an alkoxy group having 1 to 10 carbon atoms, preferably a linear or branched alkoxy group having 1 to 5 carbon atoms. (For example, methoxy group, ethoxy group, linear or branched propoxy group, linear or branched butoxy group, linear or branched pentoxy group), C3-C8 cyclic alkoxy group (for example, cyclopentyloxy group, cyclohexyloxy group) ).

Examples of the group formed by combining any two or more of R ^{1c to} R ^5c , R ^6c and R ^7c , and R ^x and R ^y include a butylene group and a pentylene group. This ring structure may contain an oxygen atom, a sulfur atom, an ester bond, or an amide bond.

Preferably, any one of R ^{1c to} R ^5c is a linear or branched alkyl group, a cycloalkyl group, or a linear, branched, or cyclic alkoxy group, and more preferably the sum of the carbon number of R ^1c to R ^5c is 2-15. Thereby, solvent solubility improves more and generation | occurrence | production of a particle is suppressed at the time of a preservation | save.

^Examples of the alkyl group and cycloalkyl group as R ^x and R ^y include the same alkyl groups and cycloalkyl groups as R ^{1c to} R ^7c .
R ^x and R ^y are preferably a 2-oxoalkyl group or an alkoxycarbonylmethyl group.
Examples of the 2-oxoalkyl group include a group having> C═O at the 2-position of the alkyl group or cycloalkyl group as R ^{1c to} R ^5c .
The alkoxy group in the alkoxycarbonylmethyl group may be the same as the alkoxy group as R ^1c to R ^5c.

R ^x and R ^y are preferably an alkyl group or cycloalkyl group having 4 or more carbon atoms, more preferably 6 or more, and still more preferably 8 or more alkyl groups or cycloalkyl groups.

In the formula ^{(b2), (b3),} R 204 ~R 207 each independently represents an aryl group, an alkyl group or a cycloalkyl group. X ⁻ represents a non-nucleophilic anion, and examples thereof include the same non-nucleophilic anion as X ^{− in} formula (b1).

The aryl group for R ^{204 to} R ²⁰⁷ is preferably a phenyl group or a naphthyl group, and more preferably a phenyl group.
The alkyl group as R ^{204 to} R ²⁰⁷ may be either linear or branched, and is preferably a linear or branched alkyl group having 1 to 10 carbon atoms (for example, methyl group, ethyl group, propyl group). Group, butyl group, pentyl group). The cycloalkyl group as R ²⁰⁴ to R ²⁰⁷ is preferably, and a cycloalkyl group having 3 to 10 carbon atoms (e.g., cyclopentyl, cyclohexyl, norbornyl).
The R ²⁰⁴ to R ²⁰⁷ are substituents which may have, for example, an alkyl group (for example, 1 to 15 carbon atoms), a cycloalkyl group (for example, 3 to 15 carbon atoms), an aryl group (e.g., 6 carbon atoms 15), alkoxy groups (for example, having 1 to 15 carbon atoms), halogen atoms, hydroxyl groups, phenylthio groups and the like.

  Examples of the photocationic polymerization initiator that may be used further include compounds represented by the following general formulas (b4), (b5), and (b6).

In general formulas (b4) to (b6), Ar ³ and Ar ⁴ each independently represents an aryl group.
R ²⁰⁶ , R ²⁰⁷ and R ²⁰⁸ each independently represents an alkyl group, a cycloalkyl group or an aryl group.
A represents an alkylene group, an alkenylene group or an arylene group.

Preferable examples of the cationic photopolymerization initiator include compounds represented by general formulas (b1) to (b3).
Examples of particularly preferred photocationic polymerization initiators that can be used in the present invention are listed below.

Further, oxazole derivatives and s-triazine derivatives described in JP-A No. 2002-122994, paragraph numbers [0029] to [0030] are also preferably used.
The onium salt compounds and sulfonate compounds exemplified in JP-A-2002-122994, paragraphs [0037] to [0063] can also be suitably used in the present invention.

[Active energy rays]
As active energy rays for proceeding the polymerization of the ink composition of the present invention, α rays, γ rays, X rays, ultraviolet rays, visible rays, electron rays and the like can be used. Of these, ultraviolet rays and visible rays are preferably used from the viewpoint of cost and safety, and ultraviolet rays are more preferably used.
As a light source for generating ultraviolet rays, low-pressure mercury lamps, high-pressure mercury lamps, short arc discharge lamps, ultraviolet light-emitting diodes, and the like, which are known ultraviolet lamps, can be used. High pressure mercury lamps, metal halide lamps, and xenon lamps belonging to short arc discharge lamps are preferably used. Moreover, an ultraviolet light emitting diode is also preferably used from the viewpoint of energy saving.

[Polymerization inhibitor]
In the present invention, it is preferable to use in combination with a polymerization inhibitor that inhibits the progress of polymerization other than cationic polymerization in order to effectively progress the polymerization by the photocationic polymerization initiator.
Suitable polymerization inhibitors include phenolic hydroxyl group-containing compounds and quinones, N-oxide compounds, piperidine 1-oxyl free radical compounds, pyrrolidine 1-oxyl free radical compounds, N-nitrosophenylhydroxylamines, and cations. It is a compound selected from the group consisting of dyes. Preferred polymerization inhibitors include haloquinone, p-methoxyphenol, di-t-butyl-p-cresol, pyrogallol, resorcinol, catechol, t-butylcatechol, hydroquinone, benzoquinone, 4,4-thiobis (3-methyl-6- t-butylphenol), 2,2'-methylenebis (4-methyl-6-t-butylphenol)
2,2,6,6-tetramethylpiperidine and derivatives thereof, di-t-butyl nitroxide, 2,2,6,6-tetramethylpiperidine-N-oxide and derivatives thereof, piperidine 1-oxyl free radical, 2,2,6,6-tetramethylpiperidine 1-oxyl free radical, 4-oxo-2,2,6,6-tetramethylpiperidine 1-oxyl free radical, 4-hydroxy-2,2,6,6- Tetramethylpiperidine 1-oxyl free radical, 4-acetamido-2,2,6,6-tetramethylpiperidine 1-oxyl free radical, 4-maleimido-2,2,6,6-tetramethylpiperidine 1-oxyl free radical 4-phosphonoxy-2,2,6,6-tetramethylpiperidine 1-oxyl Lea radical, 3-carboxy-2,2,5,5-tetramethylpyrrolidine 1-oxyl free radical, N-nitrosophenylhydroxylamine cerium salt, N-nitrosophenylhydroxylamine aluminum salt, crystal violet, methyl violet, Examples include ethyl violet and Victoria pure blue BOH. The addition amount of the polymerization inhibitor is preferably about 0.01% by mass to about 5% by mass with respect to the total mass of the ink composition.

[Colorant]
A colorant can be preferably added to the ink composition of the present invention in order to form a visible image.
There is no restriction | limiting in particular in the coloring agent which can be used here, According to a use, well-known various color materials and (pigment, dye) can be selected suitably, and can be used. For example, when forming an image excellent in weather resistance, a pigment is preferable. As the dye, both water-soluble dyes and oil-soluble dyes can be used as long as they are soluble in the polymerizable compound. In the present invention, in order to form an image or characters, the ink composition of the present invention preferably contains a pigment or an oil-soluble dye as a colorant.
These colorants are preferably added in an amount of 0.5 to 20% by mass in the ink composition, more preferably 1 to 15% by mass, and still more preferably 5 to 15% by mass.

The pigment preferably used in the present invention will be described.
[Pigment]
The pigment is not particularly limited, and all commercially available organic and inorganic pigments or pigments dispersed in an insoluble resin or the like as a dispersion medium, or the resin is grafted onto the pigment surface Can be used. Moreover, what dye | stained the resin particle with dye can be used.
Examples of these pigments include, for example, “Dictionary of Pigments” edited by Seijiro Ito (2000), W. Herbst, K. Hunger, “Industrial Organic Pigments”, JP-A No. 2002-12607, JP-A No. 2002-188025. Examples thereof include pigments described in JP-A No. 2003-26978 and JP-A No. 2003-342503.

  Specific examples of organic pigments and inorganic pigments that can be used in the present invention include C.I. I. Pigment Yellow 1 (Fast Yellow G etc.), C.I. I. A monoazo pigment such as C.I. Pigment Yellow 74; I. Pigment Yellow 12 (disaji yellow AAA, etc.), C.I. I. Disazo pigments such as C.I. Pigment Yellow 17; I. Non-benzidine type azo pigments such as CI Pigment Yellow 180; I. Azo lake pigments such as C.I. Pigment Yellow 100 (eg Tartrazine Yellow Lake); I. Condensed azo pigments such as CI Pigment Yellow 95 (Condensed Azo Yellow GR, etc.); I. Acidic dye lake pigments such as C.I. Pigment Yellow 115 (such as quinoline yellow lake); I. Basic dye lake pigments such as CI Pigment Yellow 18 (Thioflavin Lake, etc.), anthraquinone pigments such as Flavantron Yellow (Y-24), isoindolinone pigments such as Isoindolinone Yellow 3RLT (Y-110), and quinophthalone yellow Quinophthalone pigments such as (Y-138), isoindoline pigments such as isoindoline yellow (Y-139), C.I. I. Nitroso pigments such as C.I. Pigment Yellow 153 (nickel nitroso yellow, etc.); I. And metal complex salt azomethine pigments such as CI Pigment Yellow 117 (copper azomethine yellow, etc.).

  C. As a thing which exhibits red or magenta color, C.I. I. Monoazo pigments such as CI Pigment Red 3 (Toluidine Red, etc.); I. Disazo pigments such as C.I. Pigment Red 38 (Pyrazolone Red B, etc.); I. Pigment Red 53: 1 (Lake Red C, etc.) and C.I. I. Azo lake pigments such as C.I. Pigment Red 57: 1 (Brilliant Carmine 6B); I. Condensed azo pigments such as C.I. Pigment Red 144 (condensed azo red BR, etc.); I. Acidic dye lake pigments such as C.I. Pigment Red 174 (Phloxine B Lake, etc.); 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 C.I. Pigment Red 88 (Thioindigo Bordeaux, etc.); I. Perinone pigments such as C.I. Pigment Red 194 (perinone red, etc.); I. Perylene pigments such as C.I. Pigment Red 149 (perylene scarlet, etc.); I. Pigment violet 19 (unsubstituted quinacridone), C.I. I. Quinacridone pigments such as CI Pigment Red 122 (quinacridone magenta, etc.); I. Isoindolinone pigments such as CI Pigment Red 180 (isoindolinone red 2BLT, etc.); I. And alizarin lake pigments such as CI Pigment Red 83 (Mada Lake, etc.).

  As a pigment exhibiting blue or cyan, C.I. I. Disazo pigments such as C.I. Pigment Blue 25 (Dianisidine Blue, etc.); I. Phthalocyanine pigments such as C.I. Pigment Blue 15 (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 (Viclotia Pure Blue BO Lake, etc.); I. Anthraquinone pigments such as C.I. Pigment Blue 60 (Indantron Blue, etc.); I. And alkali blue pigments such as CI Pigment Blue 18 (Alkali Blue V-5: 1).

As a pigment exhibiting green, C.I. I. Pigment green 7 (phthalocyanine green), C.I. I. Phthalocyanine pigments such as C.I. Pigment Green 36 (phthalocyanine green); I. And azo metal complex pigments such as CI Pigment Green 8 (Nitroso Green).
As a pigment exhibiting orange, C.I. I. An isoindoline pigment such as C.I. Pigment Orange 66 (isoindoline orange); I. And anthraquinone pigments such as CI Pigment Orange 51 (dichloropyrantron orange).

Examples of the black pigment include carbon black, titanium black, and aniline black.
Specific 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), Strontium titanate (SrTiO ₃ , so-called titanium strontium white) or the like can be used.

  Here, 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 large hiding power and coloring power as a pigment. Excellent durability against other environments. Therefore, it is preferable to use titanium oxide as the white pigment. Of course, other white pigments (may be other than the listed white pigments) may be used as necessary.

For dispersion of the pigment, for example, a dispersion device such as a ball mill, a sand mill, an attritor, a roll mill, a jet mill, a homogenizer, a paint shaker, a kneader, an agitator, a Henschel mixer, a colloid mill, an ultrasonic homogenizer, a pearl mill, or a wet jet mill is used. Can do.
It is also possible to add a dispersant when dispersing the pigment. Examples of the dispersant include a hydroxyl group-containing carboxylic acid ester, a salt of a long-chain polyaminoamide and a high molecular weight acid ester, a salt of a high molecular weight polycarboxylic acid, a high molecular weight unsaturated acid ester, a high molecular weight copolymer, a modified polyacrylate, an aliphatic polyacrylate. Carboxylic acid, naphthalenesulfonic acid formalin condensate, polyoxyethylene alkyl phosphate ester, pigment derivative and the like. It is also preferable to use a commercially available polymer dispersant such as the Solsperse series from Zeneca.
Moreover, it is also possible to use a synergist according to various pigments as a dispersion aid. These dispersants and dispersion aids are preferably added in an amount of 1 to 50 parts by mass with respect to 100 parts by mass of the pigment.

  In the ink composition, as a dispersion medium for various components such as pigments, a solvent may be added, and the cationic polymerizable compound that is a low molecular weight component without a solvent may be used as a dispersion medium. The ink composition of the present invention is an active energy ray-curable ink, and is preferably solvent-free 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 problem of VOC (Volatile Organic Compound) of the remaining solvent occurs. From such a viewpoint, it is preferable to use a cationically polymerizable compound as the dispersion medium, and in particular, to select a cationically polymerizable monomer having the lowest viscosity from the viewpoint of improving dispersibility and handling properties of the ink composition.

  The average particle diameter of the pigment is preferably 0.02 to 0.5 μm, and more preferably 0.08 to 0.5 μm. The selection of pigment, dispersant, dispersion medium, dispersion conditions, and filtration conditions are set so that the maximum particle size is 5 μm or less (preferably 3 μm or less). By controlling the particle size, clogging of the head nozzle can be suppressed, and ink storage stability, ink transparency, and curing sensitivity can be maintained.

[dye]
Next, the dyes preferably used as the colorant in the present invention will be described.
The dye can be appropriately selected from conventionally known compounds (dyes). Specific examples include dyes described in paragraphs [0023] to [0089] of JP-A No. 2002-114930.

  Examples of yellow dyes include, for example, phenols, naphthols, anilines, pyrazolones, pyridones, aryl or heteryl azo dyes having open-chain active methylene compounds as coupling components, for example, open-chain active methylene compounds as coupling components Azomethine dyes having, for example, methine dyes such as benzylidene dyes and monomethine oxonol dyes, for example, quinone dyes such as naphthoquinone dyes and anthraquinone dyes, and other dyes include quinophthalone dyes, nitro, Nitroso dyes, acridine dyes, acridinone dyes and the like can be mentioned.

  Examples of the magenta dye include phenols, naphthols, anilines, pyrazolones, pyridones, pyrazolotriazoles, and ring-closing active methylene compounds (for example, dimedone, barbituric acid, 4-hydroxycoumarin) as coupling components. Derivatives), electron-rich heterocycles (eg, pyrrole, imidazole, thiophene, thiazole derivatives), or aryl or heteryl azo dyes, eg, azomethine dyes having pyrazolones, pyrazolotriazoles as coupling components, eg, arylidene dyes, styryl Dyes, merocyanine dyes, methine dyes such as oxonol dyes, carbonium dyes such as diphenylmethane dyes, triphenylmethane dyes, xanthene dyes, such as naphthoquinone, anthraquinone, anthrone Quinone dyes such Rapiridon, it can be mentioned condensed polycyclic dyes such as, for example, dioxazine dye.

  Examples of cyan dyes include azomethine dyes such as indoaniline dyes and indophenol dyes, cyanine dyes, oxonol dyes, polymethine dyes such as merocyanine dyes, diphenylmethane dyes, triphenylmethane dyes, carbonium dyes such as xanthene dyes, Examples of phthalocyanine dyes and anthraquinone dyes include phenols, naphthols, anilines, pyrrolopyrimidin-one, aryl or heteryl azo dyes having pyrrolotriazin-one derivatives, and indigo / thioindigo dyes as coupling components.

  Each of the dyes may exhibit yellow, magenta, and cyan colors only after a part of the chromophore is dissociated. In this case, the counter cation is an inorganic cation such as an alkali metal or ammonium. Alternatively, it may be an organic cation such as pyridinium, quaternary ammonium salt, or a cationic polymer having a partial structure thereof.

  The dye used in the present invention is preferably oil-soluble. Specifically, it means that the solubility in water at 25 ° C. (the mass of the dye dissolved in 100 g of water) is 1 g or less, preferably 0.5 g or less, more preferably 0.1 g or less. Therefore, a so-called water-insoluble oil-soluble dye is preferably used.

The dye used in the present invention preferably has an oil-solubilizing group introduced into the above-described dye mother core in order to dissolve the necessary amount in the ink composition.
As the oil-solubilizing group, long chain, branched alkyl group, long chain, branched alkoxy group, long chain, branched alkylthio group, long chain, branched alkylsulfonyl group, long chain, branched acyloxy group, long chain, branched alkoxycarbonyl group, Long chain, branched acyl group, long chain, branched acylamino group long chain, branched alkylsulfonylamino group, long chain, branched alkylaminosulfonyl group and these long chains, aryl groups containing branched substituents, aryloxy groups, aryloxycarbonyl Group, arylcarbonyloxy group, arylaminocarbonyl group, arylaminosulfonyl group, arylsulfonylamino group and the like.
In addition, for water-soluble dyes having carboxylic acid and sulfonic acid, long chain, branched alcohol, amine, phenol, aniline derivatives are used as oil-solubilizing alkoxycarbonyl groups, aryloxycarbonyl groups, alkylaminosulfonyl groups, A dye may be obtained by conversion to an arylaminosulfonyl group.

  The oil-soluble dye preferably has a melting point of 200 ° C. or lower, more preferably has a melting point of 150 ° C. or lower, and still more preferably has a melting point of 100 ° C. or lower. By using an oil-soluble dye having a low melting point, the precipitation of dye crystals in the ink composition is suppressed, and the storage stability of the ink composition is improved.

  Further, it is desirable that the oxidation potential is noble (high) in order to improve fading, particularly resistance to oxidizing substances such as ozone and curing characteristics. For this reason, as the oil-soluble dye used in the present invention, those having an oxidation potential of at least 1.0 V (vs SCE) are preferably used. The oxidation potential is preferably higher, the oxidation potential is more preferably 1.1 V (vs SCE) to 2.0 V, and particularly preferably 1.15 V (vs SCE) to 2.0 V.

As the yellow dye, a compound having a structure represented by the general formula (Y-I) described in JP-A No. 2004-250483 is preferable.
Particularly preferred dyes are dyes represented by general formulas (Y-II) to (Y-IV) described in paragraph [0034] of JP-A No. 2004-250483. And the compounds described in paragraph numbers [0060] to [0071] of JP-A-250483. The oil-soluble dye of the general formula (Y-I) described in the publication may be used not only for yellow but also for any color ink such as black ink and red ink.

The magenta dye is preferably a compound having a structure represented by the general formulas (3) and (4) described in JP-A No. 2002-114930. Specific examples include paragraphs of JP-A No. 2002-114930. Examples include the compounds described in [0054] to [0073].
Particularly preferred dyes are azo dyes represented by the general formulas (M-1) to (M-2) described in paragraph numbers [0084] to [0122] of JP-A No. 2002-121414, and specific examples Examples thereof include compounds described in paragraph numbers [0123] to [0132] of JP-A No. 2002-121414. The oil-soluble dyes represented by the general formulas (3), (4) and (M-1) to (M-2) described in the publication are used not only for magenta but also for any color ink such as black ink and red ink. May be.

  Examples of the cyan dye include dyes represented by formulas (I) to (IV) described in JP-A No. 2001-181547, and paragraphs [0063] to [0078] of JP-A No. 2002-121414. The dyes represented by the general formulas (IV-1) to (IV-4) described above are preferred, and specific examples include paragraph numbers [0052] to [0066] of JP-A No. 2001-181547. Examples thereof include the compounds described in paragraph Nos. [0079] to [0081] of Kai 2002-121414.

  Particularly preferred dyes are phthalocyanine dyes represented by general formulas (CI) and (C-II) described in paragraphs [0133] to [0196] of JP-A No. 2002-121414, A phthalocyanine dye represented by formula (C-II) is preferred. Specific examples thereof include the compounds described in JP-A No. 2002-121414, paragraph numbers [0198] to [0201]. The oil-soluble dyes of the formulas (I) to (IV), (IV-1) to (IV-4), (CI) and (C-II) are not only cyan but also black ink or green ink. It may be used for inks of any color.

(Oxidation potential)
The oxidation potential value (Eox) of the dye in the present invention can be easily measured by those skilled in the art. Regarding this method, for example, “New Instrumental Methods in Electrochemistry” by P. Delahay (1954, published by Interscience Publishers), AJBard et al. “Electrochemical Methods” (1980, published by John Wiley & Sons), Akira Fujishima et al. It is described in the book "Electrochemical measurement method" (1984, published by Gihodo Publishing Co., Ltd.).

Specifically, the oxidation potential is measured by placing a test sample in a solvent such as dimethylformamide or acetonitrile containing a supporting electrolyte such as sodium perchlorate or tetrapropylammonium perchlorate in the range of 1 × 10 ⁻² to 1 × 10 ⁻⁶ mol / It is measured as a value relative to SCE (saturated calomel electrode) using various voltammetry (polarography using a dropping mercury electrode, cyclic voltammetry, a method using a rotating disk electrode, etc.). Although this value may be deviated by several tens of mil volts due to the influence of the liquid potential difference or the liquid resistance of the sample solution, the reproducibility of the potential can be guaranteed by inserting a standard sample (for example, hydroquinone).

  In the present invention, SCE (saturated calomel) is used as a reference electrode in N, N-dimethylformamide (concentration of dye is 0.001 mol / liter) containing 0.1 mol / liter of tetrapropylammonium perchlorate as a supporting electrolyte. Electrode), a value measured using a graphite electrode as a working electrode and a platinum electrode as a counter electrode (vsSCE) was defined as the oxidation potential of the dye.

The value of Eox represents the ease of electron transfer from the sample to the electrode, and the greater the value (the higher the oxidation potential), the more difficult the electron transfer from the sample to the electrode, in other words, the less easily oxidized. In relation to the structure of the compound, the oxidation potential becomes more noble by introducing an electron withdrawing group, and the oxidation potential becomes lower by introducing an electron donating group. In the present invention, in order to lower the reactivity with ozone as an electrophile, it is desirable to introduce an electron withdrawing group into the dye skeleton to make the oxidation potential more noble.
Specific examples of preferable dyes used in the present invention are shown below, but the dyes used in the present invention are not limited to the following specific examples.

[Other ingredients]
Hereinafter, various additives that can be contained in the ink composition of the present invention as needed are described.
[Ultraviolet absorber]
From the viewpoint of improving the weather resistance of the resulting image and preventing discoloration, an ultraviolet absorber can be used.
Examples of the ultraviolet absorber are described in JP-A-58-185679, JP-A-61-190537, JP-A-2-782, JP-A-5-97075, JP-A-9-34057, and the like. Benzotriazole compounds, benzophenone compounds described in JP-A No. 46-2784, JP-A No. 5-194433, US Pat. No. 3,214,463, etc., JP-B Nos. 48-30492 and 56-21141 Cinnamic acid compounds described in JP-A-10-88106, JP-A-4-298503, JP-A-8-53427, JP-A-8-239368, JP-A-10-182621, JP The triazine compounds described in JP-A-8-501291, Research Disclosure No. Examples thereof include compounds described in No. 24239, compounds that emit ultraviolet light by absorbing ultraviolet rays typified by stilbene and benzoxazole compounds, so-called fluorescent brighteners, and the like.
The addition amount is appropriately selected depending on the purpose, but is generally about 0.01 to 10% by mass with respect to the total mass of the ink composition.

〔Antioxidant〕
An antioxidant can be added to improve the stability of the ink composition. Examples of the antioxidant include European Published Patent No. 223739, No. 309401, No. 309402, No. 310551, No. 310552, No. 4594416, German Published Patent No. 3435443. JP, 54-85535, 62-262417, 63-113536, 63-163351, JP-A-2-262654, JP-A-2-71262, Examples thereof include those described in Kaihei 3-121449, JP-A-5-61166, JP-A-5-119449, US Pat. No. 4,814,262, US Pat. No. 4,980,275, and the like.
The addition amount is appropriately selected depending on the purpose, but is generally about 0.001 to 1% by mass with respect to the total mass of the ink composition.

[Anti-fading agent]
In the ink composition of the present invention, various organic and metal complex anti-fading agents can be used. Examples of the organic anti-fading agent include hydroquinones, alkoxyphenols, dialkoxyphenols, phenols, anilines, amines, indanes, chromans, alkoxyanilines, and heterocycles. Examples of the metal complex anti-fading agent include nickel complexes and zinc complexes. No. 17643, No. VII, I to J, ibid. 15162, ibid. No. 18716, page 650, left column, ibid. No. 36544, page 527, ibid. No. 307105, page 872, ibid. The compounds described in the patent cited in No. 15162 and the compounds included in the general formulas and compound examples of representative compounds described in JP-A-62-215272, pages 127 to 137 can be used. .
The amount added is appropriately selected according to the purpose, but is generally about 0.001 to 5% by mass with respect to the total mass of the ink composition.

[Conductive salts]
Conductive salts such as potassium thiocyanate, lithium nitrate, ammonium thiocyanate, and dimethylamine hydrochloride can be added to the ink composition of the present invention for the purpose of controlling ejection properties.
The addition amount is appropriately selected according to the purpose, but is generally about 0.001 to 1.0% by mass with respect to the total mass of the ink composition.

〔solvent〕
In order to improve the adhesion to the recording medium, it is also effective to add a very small amount of an organic solvent to the ink composition of the present invention.
Examples of the solvent include ketone solvents such as acetone, methyl ethyl ketone, and diethyl ketone, alcohol solvents such as methanol, ethanol, 2-propanol, 1-propanol, 1-butanol, and tert-butanol, and chlorine such as chloroform and methylene chloride. Solvents, aromatic solvents such as benzene and toluene, ester solvents such as ethyl acetate, butyl acetate and isopropyl acetate, ether solvents such as diethyl ether, tetrahydrofuran and dioxane, glycols such as ethylene glycol monomethyl ether and ethylene glycol dimethyl ether And ether solvents.
In this case, it is effective to add in a range that does not cause the problem of solvent resistance and VOC, and the amount thereof is preferably 0.1 to 5% by mass, more preferably 0.1 to 5% by mass with respect to the total mass of the ink composition. The range is 3% by mass.

[Polymer compound]
Various polymer compounds can be added to the ink composition in order to adjust film properties. Examples of the polymer compound include styrene polymers, acrylic polymers, cyclic ether polymers, polyvinyl butyral resins, polyurethane resins, polyamide resins, polyester resins, epoxy resins, phenol resins, polycarbonate resins, polyvinyl butyral resins, and polyvinyl formal resins. Shellac, vinyl resin, acrylic resin, rubber resin, wax, and other natural resins can be used. Two or more of these may be used in combination. Of these, copolymerization of styrene monomers, acrylic monomers, and cyclic ethers is preferred. Furthermore, as a copolymer composition of the polymer binder, a copolymer containing “cyclic ether group-containing monomer” and “vinyl ether group-containing monomer” as a structural unit is also preferably used.
The addition amount is appropriately selected according to the purpose, but is generally about 0.01 to 10.0% by mass with respect to the total mass of the ink composition.

[Surfactant]
Examples of the surfactant include those described in JP-A Nos. 62-173463 and 62-183457. For example, anionic surfactants such as dialkyl sulfosuccinates, alkyl naphthalene sulfonates, fatty acid salts, polyoxyethylene alkyl ethers, polyoxyethylene alkyl allyl ethers, acetylene glycols, polyoxyethylene / polyoxypropylene blocks Nonionic surfactants such as copolymers, and cationic surfactants such as alkylamine salts and quaternary ammonium salts. An organic fluoro compound may be used in place of the surfactant. The organic fluoro compound is preferably hydrophobic. Examples of the organic fluoro compounds include fluorine surfactants, oily fluorine compounds (eg, fluorine oil) and solid fluorine compound resins (eg, tetrafluoroethylene resin). No. (columns 8 to 17) and those described in JP-A Nos. 62-135826.
The addition amount is appropriately selected according to the purpose, but is generally about 0.001 to 5.0% by mass with respect to the total mass of the ink composition.

In addition to this, if necessary, for example, leveling additives, matting agents, waxes for adjusting film physical properties, polymerization to inhibit the adhesion to recording media such as polyolefin and PET, and the like, The tackifier which does not do can be contained.
As the tackifier, specifically, a high molecular weight adhesive polymer described in JP-A-2001-49200, 5-6p (for example, (meth) acrylic acid and an alkyl group having 1 to 20 carbon atoms). An ester with an alcohol having, an ester of (meth) acrylic acid with an alicyclic alcohol having 3 to 14 carbon atoms, a copolymer comprising an ester of (meth) acrylic acid with an aromatic alcohol having 6 to 14 carbon atoms) And a low molecular weight tackifying resin having a polymerizable unsaturated bond.

  The ink composition of the present invention preferably has an ink viscosity of 30 mPa · s or less, more preferably 5 to 20 mPa · s at the temperature at the time of ejection in consideration of ejection properties, so that it falls within the above range. It is preferable to adjust the composition ratio as appropriate. The temperature at the time of injection is generally 25 to 90 ° C, preferably 25 to 80 ° C, and particularly preferably 40 to 80 ° C. The ink viscosity at 25 to 30 ° C. is preferably 200 mPa · s or less, more preferably 7 to 100 mPa · s. By setting the viscosity at room temperature high, even when a porous recording medium is used, ink penetration into the recording medium can be prevented, uncured monomer can be reduced, and odor can be reduced. Dot bleeding at the time of landing can be suppressed, and as a result, the image quality is improved. When the ink viscosity at 25 to 30 ° C. is larger than 200 mPa · s, there may be a problem in the delivery of the ink liquid.

  The surface tension of the ink composition of the present invention is preferably 20 to 30 mN / m, more preferably 23 to 28 mN / m. When recording on various recording media such as polyolefin, PET, coated paper, and non-coated paper, 20 mN / m or more is preferable from the viewpoint of bleeding and penetration, and the wettability is preferably 30 mN / m or less.

The ink composition of the present invention thus adjusted is suitably used as an ink for inkjet recording. The ink composition is printed on a recording medium by an inkjet printer, and then the printed ink composition is irradiated with an active energy ray and cured to perform recording.
In the recorded matter obtained with this ink, the image portion is cured by irradiation with active energy rays such as ultraviolet rays, and the strength of the image portion is excellent. It can be used for various purposes such as formation of a layer (image portion).

The ink composition of the present invention can be suitably used as an ink for inkjet recording. There are no particular restrictions on the ink jet recording method, for example, a charge control method that ejects ink using electrostatic attraction, a drop-on-demand method (pressure pulse method) that uses the vibration pressure of a piezo element, and an electrical signal that is acoustic Either an acoustic ink jet system that irradiates ink by irradiating it with ink instead of using a beam, or a thermal ink jet system that uses ink to form bubbles by heating the ink and use the generated pressure. Also good. The inkjet recording method includes a method of ejecting a large number of low-density inks called photo inks in a small volume, a method of improving image quality using a plurality of inks having substantially the same hue and different concentrations, and colorless and transparent. A method using ink.
Among these, the ink is suitable as a drop-on-demand type (pressure pulse type) ink jet recording ink using a piezo element.

<Image forming method and recorded matter thereof>
The image forming method of the present invention includes an image recording step of recording an image on a recording medium using the ink composition of the present invention described above, and curing by irradiating the recorded image with active energy rays (active rays). And an image curing step to be provided. In the present invention, a polymerizable compound that contributes to imaging by using active energy rays in the image curing step, recording an image on a recording medium in the image recording step, and then irradiating the recorded image with active energy rays. As the polymerization and curing proceed, the image is cured well and an image having high fastness can be formed.
The recorded matter obtained with this ink has an image portion cured by irradiation with active energy rays such as ultraviolet rays and is excellent in strength of the image portion. For example, it is used as an ink receiving layer (image portion) of a lithographic printing plate. You can also.

  In the image recording step, it is preferable to apply an ink jet recording method using an ink jet printer. Specifically, an aspect in which the image is inkjet-recorded by discharging an ink composition in the image recording step is preferable. In the ink jet recording method, image recording is performed on a recording medium using the ink composition of the present invention, and there are no particular restrictions on the ink discharge nozzles (for example, for an ink jet printer) used at that time, and the purpose and application It can be appropriately selected according to the like. There is no restriction | limiting in particular in an inkjet recording system, and it is as above-mentioned specifically.

  In the image curing step, an exposure process for accelerating polymerization and curing can be performed using a light source that emits active energy rays in a wavelength region corresponding to the sensitive wavelength of the ink composition. Specifically, a light source that emits active rays belonging to a wavelength region of 240 to 450 nm, for example, LD, LED, fluorescent lamp, low-pressure mercury lamp, high-pressure mercury lamp, metal halide lamp, carbon arc lamp, xenon lamp, chemical lamp, etc. It can be suitably performed. Preferred light sources include LEDs, high pressure mercury lamps, and metal halide lamps. What is necessary is just to select an exposure time and light quantity suitably according to the grade of the polymerization hardening of the polymeric compound which concerns on this invention.

[Inkjet recording method and inkjet recording apparatus]
Next, an ink jet recording method and an ink jet recording apparatus that can be suitably employed in the ink composition of the present invention will be described below.
In the ink jet recording method, it is preferable that the ink composition is heated to 40 to 80 ° C. to lower the viscosity of the ink composition to 30 mPa · s or less, and then ejected. By using this method, high ejection stability is achieved. Can be realized. In general, an active energy ray-curable ink composition generally has a higher viscosity than a water-based ink, and thus has a large viscosity fluctuation range due to temperature fluctuations during printing. This viscosity variation of the ink composition directly affects the droplet size and droplet ejection speed as it is, which causes image quality deterioration. Therefore, it is necessary to keep the ink composition temperature as constant as possible during printing. is there. The control range of the ink composition temperature is preferably set temperature ± 5 ° C., more preferably set temperature ± 2 ° C., and particularly preferably set temperature ± 1 ° C.

One feature of the ink jet recording apparatus is that it includes a means for stabilizing the temperature of the ink composition, and the portion to be kept at a constant temperature is a piping system from an ink tank (an intermediate tank if there is an intermediate tank) to the nozzle ejection surface. All of the members are targeted.
The temperature control method is not particularly limited, but for example, it is preferable to provide a plurality of temperature sensors in each piping portion and perform heating control according to the ink composition flow rate and the environmental temperature. Moreover, it is preferable that the head unit to be heated is thermally shielded or insulated so that the apparatus main body is not affected by the temperature from the outside air. In order to shorten the printer start-up time 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.

Since the ink composition of the present invention contains the cationic photopolymerization initiator, it becomes an active energy ray-curable ink composition.
The irradiation conditions of active energy rays in such an ink will be described. A basic irradiation method is disclosed in JP-A-60-132767. Specifically, a light source is provided on both sides of the head unit, and the head and the light source are scanned by a shuttle method. Irradiation is performed after a certain period of time after ink landing. Further, the curing is completed by another light source that is not driven. In WO99 / 54415, as an irradiation method, a method using an optical fiber or a method in which a collimated light source is applied to a mirror surface provided on the side surface of the head unit to irradiate the recording unit with UV light is disclosed. These irradiation methods can be used in the ink composition of the present invention.

  In the ink composition of the present invention, the ink composition is heated to a constant temperature, and the time from landing to irradiation is desirably 0.01 to 0.5 seconds, preferably 0.01 to 0.00. It is to irradiate active energy rays after 3 seconds, more preferably from 0.01 to 0.15 seconds. Thus, by controlling the time from landing to irradiation to an extremely short time, it is possible to prevent the landing ink from bleeding before being cured. In addition, since the ink composition can be exposed to a porous recording medium before reaching the deep part where the light source does not reach, residual unreacted monomer can be suppressed, and as a result, odor can be reduced. Can do. By using the inkjet recording method described above and the ink composition of the present invention in combination, a great synergistic effect is brought about. In particular, when an ink composition having an ink viscosity of 200 mPa · s or less at 25 ° C. is used, a great effect can be obtained. By adopting such a recording method, the dot diameter of the landed ink can be kept constant even on various recording media having different surface wettability, and the image quality is improved. In addition, in order to obtain a color image, it is preferable to superimpose in order from the color with the lowest brightness. When inks with low lightness are stacked, it is difficult for the irradiation rays to reach the lower ink, and inhibition of curing sensitivity, increase of residual monomers, generation of odor, and deterioration of adhesion tend to occur. Irradiation can be performed by injecting all colors and exposing them together, but exposure for each color is preferable from the viewpoint of curing acceleration.

  There is no restriction | limiting in particular as an inkjet recording device which discharges the ink composition of this invention, A commercially available inkjet recording device can be used. That is, the ink composition of the present invention can be recorded on a recording medium using a commercially available inkjet recording apparatus.

[Recording medium]
The recording medium used in the present invention is not particularly limited, and examples thereof include an ink-permeable recording material and an ink-impermeable recording material, any of which can be used.

  Examples of the ink-permeable recording material include plain paper, inkjet exclusive paper, coated paper, electrophotographic co-paper, cloth, non-woven fabric, porous film, and polymer absorber. These are described as “recording materials” in Japanese Patent Application Laid-Open No. 2001-181549.

  From the viewpoint of effectively expressing the effects of the present invention, it is preferable to use a non-ink-permeable (non-absorbing) recording material. Examples of the ink-impermeable recording material include art paper, synthetic resin, rubber, resin-coated paper, glass, metal, earthenware, and wood. In addition, in terms of adding each function, a base material obtained by combining a plurality of these materials can also be used.

As the synthetic resin, any synthetic resin can be used. For example, polyester resin (polyethylene terephthalate, polybutadiene terephthalate, etc.), polyolefin resin (polyvinyl chloride, polystyrene, polyethylene, polyurethane, polypropylene, etc.), acrylic resin, Examples include polycarbonate, acrylonitrile-butadiene-styrene copolymer, diacetate, triacetate, polyimide, cellophane, celluloid, and polyvinyl alcohol.
There is no restriction | limiting in particular about the shape of the base material using a synthetic resin, and its thickness, Any of a film form, a card | curd shape, or a block shape may be sufficient, and it can select suitably according to the desired objective. The synthetic resin may be either transparent or opaque.

  As the usage form of the synthetic resin, it is one of the preferred forms used in the form of a film used for so-called soft packaging, and various non-absorbable plastics and films thereof can be used. Various plastics films include, for example, PET (polyethylene terephthalate) film, OPS (stretched polystyrene) film, OPP (stretched polypropylene) film, ONy (biaxially stretched nylon) film, PVC (polyvinyl chloride) film, PE (Polyethylene) film, TAC (triacetylcellulose) film, etc. can be mentioned.

  Examples of the resin-coated paper include a paper support in which one side or both sides of the paper is coated with a polyolefin resin and the like, and a paper support in which both sides of the paper are laminated with a polyolefin resin is particularly preferable.

  As described above, the recorded matter of the present invention can be obtained by image recording using the ink composition of the present invention (the image forming method of the present invention). The recorded matter of the present invention can be applied to a wide range of fields.

  EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, this invention is not limited to these Examples. Moreover,% in an Example is a mass reference | standard unless there is particular notice.

[Examples 1-6, Comparative Examples 1-3]
The polymerizable compound, the polymerization initiator, and the colorant were stirred and mixed under the parts by mass shown in Table 1 at 20 ° C. and atmospheric pressure to obtain an ink composition.
The compounds in the table are as follows.
* 1: Compound of formula-1. The synthesis was performed by the method described in Journal of Polymer Science: Part A 1999, Vol. 37, 2841.
* 2: Compound of formula-2. The compound was synthesized by the method described in Journal of Polymer Science: Part A 1999, vol.

* 3: 3,4-epoxycyclohexylmethyl-3 ′, 4′-epoxycyclohexanecarboxylate (Celoxide 2021A, manufactured by Daicel UCB)
* 4: 3,7-bis (3-oxetanyl) -5-oxa-nonane (OXT-221, manufactured by Toagosei Co., Ltd.)
* 5: Photocationic polymerization initiator, triphenylsulfonium salt (UVI-6992, manufactured by Dow Chemical Company)
* 6: The following compound M-1 oxidation potential 1.39V (measured with CH Instruments ALS Model 610A)
* 7: Pigment dispersion P-1 prepared as follows. 10 g of Pigment Yellow 12, 5 g of polymer dispersant (Avecia Solsprse series), and 85 g of OXT-221 (Toagosei Co., Ltd.) have an average particle diameter of pigment particles in the range of 0.2 to 0.3 μm. As described above, it was dispersed using a known dispersing device, and then obtained using a heating filter filtration.

The obtained ink composition was printed on art paper with an inkjet printer (printing density 300 dpi, droplet ejection frequency 4 kHz, nozzle number 64), and then 7.5 mJ / cm ² with a Deep UV lamp (US-7, SP-7). Or it exposed on the conditions used as the energy of 30 mJ / cm < ² >. Later 7.5mJ / cm ² of the conditions low-light sample what was exposed, referred to as high and low illumination sample those conditions exposure of 30mJ / cm ^2. All inks could be ejected stably.
Evaluation was performed using a sample having passed 10 minutes after printing, and using a high illuminance sample except for the curability test.

(Curable)
The printed surface was evaluated by a tack-free test. When the cured film was touched with a finger, the case where there was no stickiness was evaluated as A, the case where there was slightly stickiness was evaluated as B, and the case where it was extremely sticky was evaluated as C.
(Adhesiveness)
After cutting the cut surface in a grid pattern with a cutter, an adhesive tape was attached to the surface of the cured film, and then the remaining state of the cured film on the substrate when the adhesive tape was peeled was visually observed. The case where peeling was not observed was evaluated as A, the case where partial peeling was observed was evaluated as B, the case where remarkable peeling was observed was evaluated as C, and the case where curing was insufficient and could not be evaluated was evaluated as D.

(Light resistance evaluation)
The photographic paper on which the previous period image was formed was irradiated with xenon light (100,000 lx) for 3 days using a weather meter (Atlas C.165), and the image density before and after the xenon irradiation was measured using a reflection densitometer (X-Rite 310TR). It was measured and evaluated as a dye residual ratio. The reflection density was fixed at 1.0 and measured. The evaluation was made in three stages, with A being a dye residual ratio of 80% or more, B being less than 80%, and C being less than 70%.
(Ink stability)
1 g of the adjusted ink was placed in a 5 ml test tube and allowed to stand at room temperature for 2 weeks, but no sedimentation was observed in either case.
(Generation of aldehyde)
Ink containing no colorant was prepared in the same way, and after exposure on a silicon wafer under the conditions of a high illumination curing test, the cured product was extracted with 2-butanone to extract non-crosslinked components, and ¹ H NMR (Varian Technology) The production of aldehyde was confirmed using 300 MHz). The case where no aldehyde-derived signal was observed was evaluated as A, and the case where it was determined as D.

As shown in Table 1, when the ink composition of this example containing the polymerizable compound of the general formula (1) was used, all of the ejection stability, curability, adhesiveness, light resistance, and ink stability Good evaluation was obtained regarding the property. Moreover, the production | generation of the aldehyde was not recognized. On the other hand, generation of aldehyde was observed in the system using the vinyl ether of the comparative example. In addition, the low illuminance curability was remarkably reduced particularly in the inks not using the compound of the general formula (1) and divinyl ether. Thereby, by using the ink composition of this example, the ink stability is excellent, a good image can be formed, and the curability and the adhesion to the recording medium are excellent when a dye is used as the colorant. It was found that an inkjet recording ink and an inkjet recording method can be provided.

Claims (11)

An ink composition comprising at least a compound having a structure represented by the following general formula (1) as a polymerizable compound.

(In General Formula (1), X represents an oxygen atom (—O—), a sulfur atom (—S—), an alkylene group, or —N (R 1) —, and Y represents an oxygen atom (—O—). , Sulfur atom (—S—) or —N (R 2) —, R 1 and R 2 each independently represents a hydrogen atom or a substituent, Z is a linking group bonded to X and Y. X , Y, and Z form a ring with the α-carbon of the vinyl group.)   The ink composition according to claim 1, comprising a photocationic polymerization initiator.   The ink composition according to claim 1, further comprising a compound having at least one of an oxirane ring and an oxetane ring.   The ink composition according to claim 1, further comprising a colorant.   The ink composition according to claim 4, wherein the colorant is selected from the group consisting of a pigment and an oil-soluble dye.   The ink composition according to claim 5, comprising an oil-soluble dye, wherein the oxidation potential of the oil-soluble dye is at least 1.0 V (vs SCE).   The ink composition according to any one of claims 1 to 6, which is for inkjet printing.   An image forming method comprising: an image recording step of recording an image on a recording medium by ink jet recording which discharges the ink composition according to claim 1. An image recording step of recording an image on a recording medium using the ink composition according to claim 1;
An image curing step of irradiating and curing an active energy ray on the image recorded on the recording medium in the image recording step;
An image forming method comprising:   The image forming method according to claim 9, wherein the image recording step records the image by inkjet recording in which the ink composition is discharged. A recorded matter recorded using the ink composition according to claim 1.