JP2010111713A - Ink composition, ink composition for inkjet recording, method for inkjet recording, and recorded matter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ink composition polymerizable and curable by irradiation with an active energy ray after recording, and exhibiting high sensitivity; an ink composition suitably used for inkjet recording having good ejection stability and generating a recorded layer without showing fragility; and a method for forming an excellent image free from exfoliation of the layer recorded using the ink composition. <P>SOLUTION: This active energy ray-curable ink composition includes (A) a polymerizable compound having a molecular weight of ≤600 and containing ≥3 cationic polymerizable groups in a molecule, (B) a polymerizable compound containing one cationic polymerizable group in a molecule, and (C) a photo-cationic polymerization initiator; wherein the amount of the polymerizable compound (A) having a molecular weight of ≤600 and containing ≥3 cationic polymerizable groups in a molecule is in the range of 5-60 mass%. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an ink composition and an ink jet recording method that are suitably used for ink jet recording. Specifically, an active energy ray-curable ink composition suitable for inkjet recording, which is cured with high sensitivity to irradiation with actinic radiation and the cured product has sufficient flexibility even after ink curing, an inkjet recording method, And the recorded matter.

As an image recording method for forming an image on a recording medium such as paper based on an image data signal, there are an electrophotographic method, a sublimation type and a melt type thermal transfer method, an ink jet method and the like. The electrophotographic system requires a process of forming an electrostatic latent image on a photosensitive drum by charging and exposure, and there is a problem that the system becomes complicated and consequently the manufacturing cost becomes high. In addition, although the thermal transfer system is inexpensive, there are problems such as high running costs and waste materials due to the use of ink ribbons.
On the other hand, the ink jet method is an inexpensive apparatus and ejects ink only to a required image portion to form an image directly on a recording medium. Therefore, the ink can be used efficiently and the running cost is low. Furthermore, there is little noise and it is excellent as an image recording method.

  UV inks that are cured by ultraviolet (UV) irradiation are known as inkjet inks that are suitable for printing on non-water-absorbing recording media such as plastics (see, for example, Patent Documents 1 to 3). In comparison, there is an advantage that time and equipment for volatilizing the organic solvent are unnecessary. For curing using such an ink, a system using radical polymerization of monomer components is widely used. In recent years, ultraviolet curable ink jet inks using cationically polymerizable compounds have also been developed (see, for example, Patent Documents 4 and 5), and are made of a polyfunctional cationically polymerizable compound containing a trifunctional or higher functional polymerizable compound. Ink jet ink compositions having excellent properties have been proposed (see, for example, Patent Documents 4 and 5).

Cationic polymerization systems that are not subject to polymerization inhibition by oxygen can be cured with less energy compared to radical polymerization systems, reduce power consumption, extend life by reducing the load on the active radiation generator, and use UV as a light source. There is an advantage that a comparatively low energy light emitting diode can be used efficiently instead of a lamp. However, if a polyfunctional polymerizable compound is included in the ink composition with an emphasis on curability, it shows brittleness when irradiated with active energy rays, so it is easily cracked due to, for example, deformation of the substrate and has poor adhesion. There is a problem that the ink composition is easily peeled off from the printed matter by physical force such as rubbing, and there has been a demand for an active energy ray-curable ink composition that achieves both curability, appropriate flexibility, and adhesion. .
Japanese Patent Laid-Open No. 9-183927 JP 2003-246818 A JP 2003-292855 A JP-A-8-143806 JP 2004-256626 A

  The problem to be solved by the present invention is to provide an ink composition that can be polymerized and cured by irradiating an active energy ray after recording and exhibits high sensitivity, has good ejection stability, and has a recording layer. The present invention is to provide an ink composition suitably used for ink jet recording that does not exhibit the brittleness of the ink, and an excellent image forming method in which the recording layer does not peel off using the ink composition, and the recording obtained thereby Is to provide things.

  As a result of intensive studies, the inventors of the present invention have included two types of cationically polymerizable compounds having a specific structure in the ink composition, and by setting one of the cationically polymerizable compounds within a certain range, high sensitivity and It has been found that the ejection stability is exhibited, and the brittleness and adhesion of the recording layer can be improved.

The above problems of the present invention have been solved by the following means.
<1> (A) a polymerizable compound having a molecular weight of 600 or less and containing 3 or more cationic polymerizable groups in the molecule; and (B) a polymerizable compound containing one cationic polymerizable group in the molecule; (C) photocationic polymerization initiator, and (A) the molecular weight is 600 or less with respect to all cationically polymerizable compounds contained in the ink composition, and 3 or more cationic polymerizable groups in the molecule An active energy ray-curable ink composition containing a polymerizable compound in a range of 5 to 60% by mass.

<2> The polymerizable compound (A) having a molecular weight of 600 or less and containing three or more cationic polymerizable groups in the molecule, and (B) the polymerizable compound containing one cationic polymerizable group in the molecule. The active energy ray-curable ink composition according to <1>, wherein the cationically polymerizable group in is an oxirane ring, an oxetane ring, or a vinyl ether group.
<3> The polymerizable compound (A) having a molecular weight of 600 or less and having three or more cationic polymerizable groups in the molecule is a polymerizable compound having one or more oxetane rings in the molecule <1 > Or <2> The active energy ray-curable ink composition.

<4> The relationship between the content of the oxirane ring and the oxetane ring in the ink composition is in the range of 10:90 to 50:50 in the ratio of the total number of oxirane rings to the total number of oxetane rings. The active energy ray-curable ink composition according to any one of 3>.
<5> The active energy ray-curable ink composition according to any one of <1> to <4>, which is for inkjet recording.

<6> (a) a step of discharging the active energy ray-curable ink composition according to <5> onto a recording medium; and (b) active radiation to the discharged active energy ray-curable ink composition. A step of irradiating and curing the active energy ray-curable ink composition.
<7> A recorded matter obtained by the method according to <6>.

  In the present invention, by using an oxirane ring or an oxetane ring as a polymerizable group, it is characterized by being less susceptible to polymerization inhibition by oxygen and having a small volume shrinkage due to curing, and (A) a molecular weight of 600 or less, And a polymerizable compound containing three or more cationic polymerizable groups in the molecule and (B) a polymerizable compound containing one cationic polymerizable group in the molecule, and (A) the molecular weight is 600 or less, In addition, by containing a certain amount of a polymerizable compound containing three or more cationically polymerizable groups in the molecule, the cured ink composition has an appropriate crosslinking density, and the recording layer made of the ink composition is flexible as a whole. In addition, it is considered that the surface has high physical properties. As a result, it is considered that an ink composition having good ejection stability and high sensitivity was obtained, the adhesiveness of the recording layer was high, and peeling did not occur.

  According to the present invention, it is possible to provide an ink composition that can be polymerized and cured by irradiating active energy rays after recording, exhibit high sensitivity, good ejection stability, and exhibit brittleness of the recording layer. It is possible to provide an ink composition that is suitably used for inkjet recording. Furthermore, it is possible to provide an excellent image forming method in which the recording layer does not peel off using the ink composition, and a recorded matter obtained thereby.

Hereinafter, the ink composition of the present invention, the image forming method using the ink composition, and the recorded matter obtained thereby will be described in detail.
The ink composition of the present invention may be referred to as (A) a polymerizable compound having a molecular weight of 600 or less and having three or more cationic polymerizable groups in the molecule (hereinafter referred to as “specific polymerizable compound A”). ), (B) a polymerizable compound containing one cationic polymerizable group in the molecule (hereinafter sometimes referred to as “specific polymerizable compound B”), and (C) a photocationic polymerization initiator. It is characterized by that.

<(A) Polymerizable compound having a molecular weight of 600 or less and containing three or more cationic polymerizable groups in the molecule: specific polymerizable compound A>
The specific polymerizable compound A used in the present invention has a molecular weight of 600 or less, preferably 500 or less, and particularly preferably in the range of 200 to 400. If the molecular weight is too large, the viscosity of the ink composition may increase and the ejection stability may decrease. If the molecular weight is too small, volatility becomes a problem.

  The specific polymerizable compound A used in the present invention is a compound having three or more cationic polymerizable groups. Specific examples of the cationic polymerizable group include an oxirane ring, an oxetane ring, a vinyl ether group, an aziridine ring, an N-vinyl group (specific compounds such as N-vinylcarbazole and N-vinylcaprolactam), and a styryl group. , An oxirane ring, an oxetane ring, and a vinyl ether group are preferably used. One or more oxetane rings are more preferably included.

  The specific polymerizable compound A used in the present invention preferably has one or more oxetane rings in the molecule, and more preferably has three or four oxetane rings in the molecule. Examples of the compound having 3 to 4 oxetane rings include a compound represented by the following formula (1).

In Formula (1), R ¹ 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 ¹ 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. In addition, examples of R ⁹ 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.

  Specific examples of the oxetane compound of the specific polymerizable compound A preferably used in the present invention include compounds (a-5) and (a-6) described in JP2007-238644A and JP2007-238655A. And the compounds (a-5) and (a-6) described in the above.

  As a compound preferably used as an epoxy compound that is a compound containing three or more oxirane rings as the specific polymerizable compound A, Daicel Chemical Industries, Ltd., trade names Epolide GT-300 (trifunctional), Ephelide GT-400 (Tetrafunctional) and the like.

  Specific examples of vinyl ethers that are compounds containing three or more vinyl ether groups as the specific polymerizable compound A include trimethylol ethane trivinyl ether, trimethylol propane trivinyl ether, ditrimethylol propane tetravinyl ether, glycerin trivinyl ether, pentaerythritol tetra. Vinyl ether, dipentaerythritol pentavinyl ether, dipentaerythritol hexavinyl ether, ethylene oxide-added trimethylolpropane trivinyl ether, propylene oxide-added trimethylolpropane trivinyl ether, ethylene oxide-added ditrimethylolpropane tetravinyl ether, propylene oxide-added ditrimethylolpropane tetravinyl ether, Echile Oxide adduct of pentaerythritol tetravinyl ether, propylene oxide adduct of pentaerythritol tetravinyl ether, ethylene oxide adduct of dipentaerythritol hexavinyl ether, and propylene oxide adduct of dipentaerythritol hexavinyl ether.

  Furthermore, exemplary compounds [1-1] to [1-15] shown below are also given as specific examples of the specific polymerizable compound A that can be preferably used in the present invention. As the specific polymerizable compound A of the present invention, a compound in which two or more polymerizable groups selected from an oxirane ring, an oxetane ring, and a vinyl ether group coexist in the molecule is also a preferable embodiment. However, it is not limited to these.

<(B) Polymerizable compound containing one cationic polymerizable group in the molecule: specific polymerizable compound B>
The ink composition of the present invention contains (B) a polymerizable compound (specific polymerizable compound B) containing one cationic polymerizable group in the molecule. As the specific polymerizable compound B, any monomer species can be used as long as it is cured by cationic polymerization. However, it is preferable to select at least one species from the group consisting of epoxides, oxetane compounds, and vinyl ether compounds.

  Specific examples of the monofunctional epoxide that can be used as the specific polymerizable compound B 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, -Acryloyloxymethyl cyclohexene oxide, 3-vinylcyclohexene oxide, (alpha) -pinene oxide, etc. are mentioned.

  Specific examples of the oxetane compound that can be preferably used as the specific polymerizable compound B include a compound represented by the following formula (2).

In general formula (2), R ¹ has the same meaning as in general formula (1), and is 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, or furyl. Represents a group or a thienyl group.
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 ² is a hydrogen atom, 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 2 to 6 carbon atoms. Represents an alkoxycarbonyl group, and 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. Further, R ² may have a substituent, the substituent, 1 to 6 alkyl groups include fluorine atom.

  Specific examples of the monofunctional oxetane that can be used as the specific polymerizable compound B of the present invention include, for example, 3-ethyl-3-hydroxymethyloxetane (OXT-101: manufactured by Toagosei Co., Ltd.), 3-ethyl- 3- (2-ethylhexyloxymethyl) oxetane (OXT-212: manufactured by Toagosei Co., Ltd.), 3-ethyl-3-phenoxymethyloxetane (OXT-211: manufactured by Toagosei Co., Ltd.), 3- (meta ) Allyloxymethyl-3-ethyloxetane, (3-ethyl-3-oxetanylmethoxy) methylbenzene, 4-fluoro- [1- (3-ethyl-3-oxetanylmethoxy) methyl] benzene, 4-methoxy- [1 -(3-Ethyl-3-oxetanylmethoxy) methyl] benzene, [1- (3-Ethyl-3-oxetanylmethoxy) ethyl] phenyl ether, isobutoxymethyl (3-ethyl) -3-Oxetanylmethyl) ether, isobornyloxyethyl (3-ethyl-3-oxetanylmethyl) ether, isobornyl (3-ethyl-3-oxetanylmethyl) ether, 2-ethylhexyl (3-ethyl-3-oxetanylmethyl) ) Ether and the like.

  Specific examples of the monofunctional vinyl ether that can be used as the specific polymerizable compound B of the present invention include methyl vinyl ether, ethyl vinyl ether, propyl vinyl ether, n-butyl vinyl ether, t-butyl vinyl ether, 2-ethylhexyl vinyl ether, n-nonyl vinyl ether. , Lauryl vinyl ether, cyclohexyl vinyl ether, cyclohexyl methyl vinyl ether, 4-methylcyclohexyl methyl vinyl ether, benzyl vinyl ether, dicyclopentenyl vinyl ether, 2-dicyclopentenoxyethyl vinyl ether, methoxyethyl vinyl ether, ethoxyethyl vinyl ether, butoxyethyl vinyl ether, methoxyethoxy Ethyl vinyl ether, ethoxyethoxyethyl vinyl ether Methoxypolyethylene glycol vinyl ether, tetrahydrofurfuryl vinyl ether, 2-hydroxyethyl vinyl ether, 2-hydroxypropyl vinyl ether, 4-hydroxybutyl vinyl ether, 4-hydroxymethylcyclohexyl methyl vinyl ether, diethylene glycol monovinyl ether, polyethylene glycol vinyl ether, chloroethyl vinyl ether, chlorobutyl Examples include vinyl ether, chloroethoxyethyl vinyl ether, phenylethyl vinyl ether, phenoxy polyethylene glycol vinyl ether, and the like.

  The ink composition of the present invention includes both the specific polymerizable compound A and the specific polymerizable compound B. The total polymerizable compound A contained in the ink composition is 5 to 5 on a mass basis. It is the range of 60 mass%, the range of 10-50 mass% is preferable, and the range of 15-40 mass% is more preferable. Within this range, when cured with active energy rays, it has good curing sensitivity for practical use and can impart appropriate flexibility and adhesion, which is favorable.

  The ratio of the specific polymerizable compound B contained in the ink composition of the present invention is preferably in the range of 15 to 95% by mass with respect to the total cationic polymerizable compound contained in the ink composition. More preferably, it is in the range of -90% by mass, and more preferably in the range of 40-80% by mass. If the ratio of the specific polymerizable compound B is too high, the curing sensitivity is lowered and causes stickiness and the like, and if it is too low, the film becomes brittle and the flexibility is lowered.

  The ink composition of the present invention may further contain a polymerizable compound containing two cationic polymerizable groups in the molecule (hereinafter sometimes referred to as “bifunctional polymerizable compound”). The type of the bifunctional polymerizable compound is not limited, and any polymerizable compound can be used as long as it can be cured by cationic polymerization, but epoxide, oxetane compound, and vinyl ether compound are preferable. Moreover, the compound which has 2 types of polymeric groups in a molecule | numerator may be sufficient, for example, the compound which has both an oxirane ring and an oxetane ring in the same molecule described in Unexamined-Japanese-Patent No. 2005-2191 etc. is used preferably.

  Examples of the oxetane compound of the bifunctional polymerizable compound that can be preferably used in the present invention include compounds represented by the following formulas (3) and (4).

In general formulas (3) and (4), R ¹ has the same meaning as in general formula (1), and R ¹ is a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or a fluoroalkyl group having 1 to 6 carbon atoms. Represents an allyl group, an aryl group, a furyl group, or a thienyl group. Two R ¹ present in the molecule 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 ³ is an alkylene group containing a linear or branched alkylene group, a linear or branched poly (alkyleneoxy) group, a linear or branched unsaturated hydrocarbon group, 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.
Examples of R ³ include of a preferable example following structure.

When R ³ is a polyvalent group of the, R ⁴ is a hydrogen atom, alkyl group having 1 to 4 carbon atoms, 1 to 4 alkoxy groups 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.
R ⁵ represents an oxygen atom, a sulfur atom, a methylene group, NH, SO, SO ₂ , C (CF ₃ ) ₂ , or C (CH ₃ ) ₂ .
R ⁶ represents an alkyl group having 1 to 4 carbon atoms or an aryl group, and n is an integer of 0 to 2,000. R ⁷ 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 ⁸ is an alkyl group having 1 to 4 carbon atoms or an aryl group, and m is an integer of 0 to 100.

  Specific examples of the oxetane compound preferably used as the bifunctional polymerizable compound include, for example, bis (3-ethyl-3-oxetanylmethyl) ether (OXT-221: manufactured by Toagosei Co., Ltd.), 1,4-bis [ (3-Ethyl-3-oxetanylmethoxy) methyl] benzene (OXT-121: manufactured by Toagosei Co., Ltd.), 3,7-bis (3-oxetanyl) -5-oxa-nonane, 3,3 ′-(1 , 3- (2-Methylenyl) propanediylbis (oxymethylene)) bis- (3-ethyloxetane), 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 and the like.

  Specific examples of the vinyl ether compound preferably used as the bifunctional polymerizable compound include ethylene glycol divinyl ether, diethylene glycol divinyl ether, propylene glycol divinyl ether, butylene glycol divinyl ether, hexanediol divinyl ether, bisphenol A alkylene oxide divinyl ether, and bisphenol F. And divinyl ethers such as alkylene oxide divinyl ether.

  Examples of the epoxy compound preferably used as the bifunctional polymerizable compound include, for example, bisphenol A diglycidyl ether, bisphenol F diglycidyl ether, bisphenol S diglycidyl ether, brominated bisphenol A diglycidyl ether, and brominated bisphenol F. Diglycidyl ether, 3,4-epoxycyclohexylmethyl-3 ′, 4′-epoxycyclohexanecarboxylate, 2- (3,4-epoxycyclohexyl-5,5-spiro-3,4-epoxy) cyclohexane-meta-dioxane Bis (3,4-epoxycyclohexylmethyl) adipate, 3,4-epoxy-6-methylcyclohexyl-3 ', 4'-epoxy-6'-methylcyclohexanecarboxylate, methylenebis (3,4-epoxycyclohexane , Dicyclopentadiene diepoxide, ethylene bis (3,4-epoxycyclohexanecarboxylate), 1,4-butanediol diglycidyl ether, 1,6-hexanediol diglycidyl ether, limonene dioxide, 1,2,7, Examples include 8-diepoxyoctane and 1,2,5,6-diepoxycyclooctane.

  Although the selection and ratio of the cationic polymerizable group in the specific polymerizable compound A and the specific polymerizable compound B constituting the ink composition of the present invention are not limited, the polymerizable compound comprising the specific polymerizable compound A and the specific polymerizable compound B Preferably contains an oxirane ring and an oxetane ring. That is, if the specific polymerizable compound B is a compound containing an oxirane ring, the specific polymerizable compound A (in some cases a bifunctional polymerizable compound) is preferably a compound containing one or more oxetane rings. If Compound B is a compound containing an oxetane ring, the specific polymerizable compound A (in some cases a bifunctional polymerizable compound) is preferably a compound containing one or more oxirane rings. Moreover, the aspect which uses together the compound containing an oxirane ring and the compound containing an oxetane ring as the specific polymeric compound B is also preferable.

  The content relationship between the oxirane ring and the oxetane ring in the ink composition of the present invention is preferably in the range of 10:90 to 50:50 in the ratio of the total number of oxirane rings: total number of oxetane rings, It is more preferable that it is 20: 80-40: 60. In addition to the specific polymerizable compound A and the specific polymerizable compound B included in the ink composition, this ratio is obtained when a bifunctional polymerizable compound, an epoxy resin described later, or the like is used. Calculations are made including the oxirane and oxetane rings contained in epoxy resins and the like. When it is within this range, it is favorable from the viewpoint of obtaining sufficient curability. That is, if there are more oxirane rings than this range, the hardness of the polymer film tends to be low, and if there are more oxetane rings than this range, the monomer tends to remain and cause stickiness.

In the ink composition of the present invention, an epoxy resin having a cationic polymerizable group and a molecular weight exceeding 600 can be used within a range not exceeding 5% by mass with respect to the total polymerizable compounds contained in the ink composition. Usable epoxy resins are compounds having two or more oxirane rings in the molecule, such as bisphenol A type, cresol novolac type, biphenyl type, and alicyclic epoxy resin.
For example, as bisphenol A type, Epototo YD-115, YD-118T, YD-127, YD-128, YD-134, YD-8125, YD-7011R, ZX-1059, YDF-8170, YDF-170, etc. Toto Kasei Co., Ltd., Denacol EX-1101, EX-1102, EX-1103, etc. (more from Nagase Kasei), Plaxel G101, G102 (more from Daicel Chemical), and similar bisphenol F type and bisphenol S type Can also be mentioned. Epoxy acrylates such as Ebecryl 3700, 3701, 600 (manufactured by Daicel UC) may also be used.

The cresol novolak type includes Epototo YDPN-638, YDPN-701, YDPN-702, YDPN-703, YDPN-704, etc. (more from Toto Kasei), Denacol EM-125, etc. (more from Nagase Kasei), alicyclic epoxy Examples of the compound include EHPE-3150 (manufactured by Daicel Chemical), Santo Tote ST-3000, ST-4000, ST-5080, ST-5100 (manufactured by Tohto Kasei) and the like.
In addition, Epototo YH-434 and YH-434L, which are amine type epoxy resins, glycidyl ester in which dimer acid is modified in the skeleton of bisphenol A type epoxy resin can be used.

<Ink composition>
The ink composition of the present invention is configured such that a recorded image can be cured by irradiation with an active energy ray after recording an image on a recording material. The ink composition of the present invention may be a colorless ink that does not contain a colorant, but a configuration containing a colorant is preferred. In addition, the ink composition of the present invention can be constituted using other components such as various additives as necessary.

[Photocationic polymerization initiator]
The ink composition of the present invention contains a photocationic polymerization initiator that generates an acid upon irradiation with radiation (also referred to as a photoacid generator as appropriate). As the cationic photopolymerization initiator that can be used in the present invention, it is used as a photoinitiator for photocationic polymerization, a photoinitiator for radical photopolymerization, a photodecolorant for dyes, a photochromic agent, a microresist, or the like. By irradiation with light (400-200 nm ultraviolet light, far ultraviolet light, particularly preferably g-line, h-line, i-line, KrF excimer laser beam), ArF excimer laser beam, electron beam, X-ray, molecular beam or ion beam A compound that generates an acid can be appropriately selected and used.

  Such photocationic polymerization initiators include onium salt compounds such as diazonium salts, phosphonium salts, sulfonium salts, iodonium salts, imide sulfonates, oxime sulfonates, diazodisulfones, disulfones that decompose upon irradiation with radiation to generate acids. And sulfonate compounds such as o-nitrobenzyl sulfonate.

  Other examples of the cationic photopolymerization initiator used in the present invention include S.I. I. Schlesinger, Photogr. Sci. Eng. , 18, 387 (1974), T.A. S. Bal et al. , Polymer, 21, 423 (1980), etc., U.S. Pat. Nos. 4,069,055, 4,069,056, Re27,992, and JP-A-3-140140. Ammonium salts described in the above, and the like. C. Necker et al. , Macromolecules, 17, 2468 (1984), C.I. S. Wen et al. , Teh, Proc. Conf. Rad. Curing ASIA, p478 Tokyo, Oct (1988), U.S. Pat. Nos. 4,069,055 and 4,069,056, and the like. V. Crivello et al. , Macromolecules, 10 (6), 1307 (1977), Chem. & Eng. News, Nov. 28, p31 (1988), European Patent Nos. 104,143, 339,049, 410,201, JP-A-2-150848, JP-A-2-296514, etc. Of iodonium salt,

  J. et al. V. Crivello et al. , Polymer J. et al. 17, 73 (1985), J. Am. V. Crivello et al. , J .; Org. Chem. 43, 3055 (1978); R. Watt et al. , J .; Polymer Sci. , Polymer Chem. Ed. , 22, 1789 (1984), J. Am. V. Crivello et al. , Polymer Bull. 14, 279 (1985), J. Am. V. Crivello et al. , Macromolecules, 14 (5), 1141 (1981), J. MoI. V. Crivello et al. , J .; Polymer Sci. , Polymer Chem. Ed. 17, 2877 (1979), European Patent Nos. 370,693, 161,811, 410,201, 339,049, 233,567, 297,443, and 297,442. U.S. Pat.Nos. 3,902,114, 4,933,377, 4,760,013, 4,734,444, 2,833,827, German Patent 2, Nos. 904, 626, 3,604, 580, 3,604, 581, JP-A-7-28237, and 8-27102, etc.

  J. et al. V. Crivello et al. , Macromolecules, 10 (6), 1307 (1977), J. Am. V. Crivello et al. , J .; Polymer Sci. , Polymer Chem. Ed. , 17, 1047 (1979), etc., selenonium salts, C.I. S. Wen et al. , Teh, Proc. Conf. Rad. Curing ASIA, p478 Tokyo, Oct (1988) and other onium salts such as arsonium salts, US Pat. No. 3,905,815, Japanese Examined Patent Publication No. 46-4605, Japanese Unexamined Patent Publication No. 48-36281, JP 55-32070, JP 60-239736, JP 61-169835, JP 61-169837, JP 62-58241, JP 62-212401, JP 63 Organic halogen compounds described in JP-A-70243, JP-A-63-298339, and the like; Meier et al. , J .; Rad. Curing, 13 (4), 26 (1986), T.A. P. Gill et al. Inorg. Chem. , 19, 3007 (1980), D.M. Astruc, Acc. Chem. Res. , 19 (12), 377 (1986), JP-A-2-161445, etc., organometallic / organic halides,

  S. Hayase et al. , J .; Polymer Sci. 25, 753 (1987), E.I. Reichmanis et al. , J .; Polymer Sci. , Polymer Chem. Ed. , 23, 1 (1985), Q.M. Q. Zhu et al. , J .; Photochem. 36, 85, 39, 317 (1987), B.R. Amit et al. Tetrahedron Lett. , (24) 2205 (1973), D.M. H. R. Barton et al. , J .; Chem. Soc. , 3571 (1965), p. M.M. Collins et al. , J .; Chem. Soc. Perkin I, 1695 (1975), M .; Rudinstein et al. Tetrahedron Lett. , (17), 1445 (1975), J. MoI. W. Walker et al. , J .; Am. Chem. Soc. 110, 7170 (1988), S.A. C. Busman et al. , J .; Imaging Technol. 11 (4), 191 (1985), H. et al. M.M. Houlihan et al. , Macromolecules, 21, 2001 (1988), p. M.M. Collins et al. , J .; Chem. Soc. , Chem. Commun. 532 (1972), S.A. Hayase et al. , Macromolecules, 18, 1799 (1985), E.M. Reichmanis et al. , J .; Electrochem. Soc. , Solid State Sci. Technol. , 130 (6), F.M. M.M. Houlihan et al. , Macromolecules, 21, 2001 (1988), European Patent Nos. 0290,750, 046,083, 156,535, 271,851, 0,388,343, US Pat. No. 3,901. No. 710, No. 4,181,531, JP-A-60-198538, JP-A-53-133022 and the like, a photoacid generator having an O-nitrobenzyl type protecting group,

  M.M. TUNOOKA et al. , Polymer Preprints Japan, 35 (8), G. et al. Berner et al. , J .; Rad. Curing, 13 (4), W.M. J. et al. Mijs et al. , Coating Technol. , 55 (697), 45 (1983), Akzo, H .; Adachi et al. , Polymer Preprints, Japan, 37 (3), European Patent Nos. 0199,672, 84515, 044,115, 618,564, 0101,122, U.S. Pat. No. 4,371,605. No. 4,431,774, JP-A 64-18143, JP-A-2-245756, JP-A-3-140109, and the like. Compounds that generate sulfonic acid, disulfone compounds described in JP-A Nos. 61-166544 and 2-71270, JP-A-3-103854, JP-A-3-103856, and JP-A-210960 Examples thereof include diazoketosulfone and diazodisulfone compounds described in publications and the like.

  Further, a group which generates an acid by these light, or a compound in which a compound is introduced into the main chain or side chain of the polymer, for example, E. Woodhouse et al. , J .; Am. Chem. Soc. 104, 5586 (1982), S .; P. Pappas et al. , J .; Imaging Sci. , 30 (5), 218 (1986), S .; Kondo et al. , Makromol. Chem. , Rapid Commun. , 9, 625 (1988), Y. et al. Yamada et al. , Makromol. Chem. 152, 153, 163 (1972), J. Am. V. Crivello et al. , J .; Polymer Sci. , Polymer Chem. Ed. 17, 3845 (1979), U.S. Pat. No. 3,849,137, German Patent 3,914,407, JP-A 63-26653, JP-A 55-164824, JP The compounds described in JP-A-62-69263, JP-A-63-146038, JP-A-63-163452, JP-A-62-153853, JP-A-63-146029, etc. can be used. For example, photocationic polymerization with diazonium salt, ammonium salt, phosphonium salt, iodonium salt, sulfonium salt, selenonium salt, onium salt such as arsonium salt, organic halogen compound, organic metal / organic halide, o-nitrobenzyl type protecting group Examples thereof include a compound capable of generating a sulfonic acid by photolysis, such as an initiator and iminosulfonate, a disulfone compound, a diazoketosulfone, and a diazodisulfone compound.

  Furthermore, V. N. R. Pillai, Synthesis, (1), 1 (1980), A.M. Abad et al. Tetrahedron Lett. , (47) 4555 (1971), D.M. H. R. Barton et al. , J .; Chem. Soc. , (C), 329 (1970), U.S. Pat. No. 3,779,778, European Patent No. 126,712, etc., compounds that generate an acid by light can also be used.

  Preferred examples of the photocationic polymerization initiator that can be used in the present invention include compounds represented by the following formulas (b1), (b2), and (b3).

In the formula (b1), R ¹¹ , R ¹² and R ¹³ each independently represents an organic group.
X ⁻ represents a non-nucleophilic anion, preferably a sulfonate anion, a carboxylate anion, a bis (alkylsulfonyl) amide anion, a tris (alkylsulfonyl) methide anion, BF ₄ ⁻ , PF ₆ ⁻ , SbF ₆ ⁻ or the following It includes such groups shown, preferably _{^{BF 4 -, PF 6 -,}} SbF 6 - is.

  Preferable organic anions include organic anions represented by the following formula.

R ²¹ represents an organic group. 1 to 30 carbon atoms as an organic group of R ²¹ can be mentioned, preferably an alkyl group, a cycloalkyl group, an aryl group, or a plurality of these, a single _{bond, -O -, - CO 2 -} , - S- , —SO ₃ —, —SO ₂ N (R ²² ) — and the like.

R ²² represents a hydrogen atom or an alkyl group. R ²³ , R ²⁴ and R ²⁵ each independently represents an organic group. As the organic group for ^{R 23, R 24, R 25} , preferably may be mentioned the same as the preferred organic groups in ^{R 21,} and most preferably a perfluoroalkyl group having 1 to 4 carbon atoms. R ²³ and R ²⁴ may combine to form a ring. Examples of the group formed by combining R ²³ and R ²⁴ include an alkylene group and an arylene group. Preferably, it is a C2-C4 perfluoroalkylene group.

The organic group of R ²¹ and R ^{23 to} R ²⁵ is most preferably 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.

Carbon number of the organic group as R <^11> , R < ¹² > and R < ¹³ > is generally 1-30, preferably 1-20.
Two of R ^{11 to} R ¹³ 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. The two of the group formed by bonding of the R ¹¹ to R ^13, there can be mentioned an alkylene group (e.g., butylene, pentylene).

Specific examples of the organic group as R ¹¹ , R ¹² and R ¹³ 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 Formula (b1) may be sufficient. For example, at least one of ^R 11 ^{to R 13} of the compound represented by the general formula (b1) is at least one direct the ^R 11 ^{to R 13} in another compound represented by formula (b1), or, connected It may be a compound having a structure bonded through a group.

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

The compound (b1-1) is an arylsulfonium compound in which at least one of R ^{11 to} R ^{13 in} the formula (b1) is an aryl group, that is, a compound having arylsulfonium as a cation.

Arylsulfonium ^compound, all of R 11 ^{to R 13} may be an aryl group ^{or a} part of R 11 ^{to R 13} is an aryl group with the remaining being 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.

As the alkyl group that the arylsulfonium compound has as necessary, a linear or branched alkyl group having 1 to 15 carbon atoms is preferable. For example, 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 ^{11 to} R ¹³ are an alkyl group (for example, 1 to 15 carbon atoms), a cycloalkyl group (for example, 3 to 15 carbon atoms), an aryl group (for example, 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 may be substituted. 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 the three R ^{11 to} R ¹³ or may be substituted with all three. When R ^{11 to} R ¹³ are aryl groups, the substituent is preferably substituted at the p-position of the aryl group.

Next, the compound (b1-2) will be described.
Compound (b1-2) is, ^R 11 ^{to R 13} in Formula (b1) independently is a compound when it represents an organic group having no aromatic ring. Here, the aromatic ring includes an aromatic ring containing a hetero atom.
The organic group not containing an aromatic ring as R ^{11 to} R ¹³ generally has 1 to 30 carbon atoms, preferably 1 to 20 carbon atoms.
R ^{11 to} R ¹³ are each independently preferably an alkyl group, a cycloalkyl group, an allyl group or a vinyl group, more preferably a linear, branched or cyclic 2-oxoalkyl group or an alkoxycarbonylmethyl group, particularly preferably Is a linear, branched 2-oxoalkyl group.

The alkyl group as R ¹¹ to R ¹³ may be linear, it may be either branched, preferably a straight-chain or branched alkyl group (e.g., methyl group having 1 to 10 carbon atoms, an ethyl group, a propyl 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 ^{11 to} R ¹³ is preferably a cycloalkyl group having 3 to 10 carbon atoms (cyclopentyl group, cyclohexyl group, norbornyl group), and more preferably a cyclic 2-oxoalkyl group.

Preferred examples of the linear, branched, and cyclic 2-oxoalkyl group represented by R ^{11 to} R ¹³ 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 ¹¹ to R ^13, preferably can be mentioned an alkoxy group having 1 to 5 carbon atoms (a methoxy group, an ethoxy group, a propoxy group, a butoxy group, a pentoxy group).
R ¹¹ to R ¹³ is a halogen atom, an alkoxy group (for example, 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 formula (b1-3) and is a compound having a phenacylsulfonium salt structure.

In the formula ^{(b1-3), R} 31 ~R ³⁵ independently represents a hydrogen atom, an alkyl group, a cycloalkyl group, an alkoxy group, or a halogen atom.
R ³⁶ and ^{R 37} each independently represent a hydrogen atom, an alkyl group or a cycloalkyl group.
R ³⁸ and R ³⁹ each independently represents an alkyl group, a cycloalkyl group, an allyl group, or a vinyl group.
Any two or more of R ^{31 to} R ³⁵ , R ³⁶ and R ³⁷ , and R ³⁸ and R ³⁹ may be bonded to each other to form a ring structure.
Z ⁻ represents a non-nucleophilic anion, and examples thereof include the same as the non-nucleophilic anion of X ^{− in} formula (b1).

The alkyl group as R ^{31 to} R ³⁷ 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).

The cycloalkyl group of R ³¹ to R ^37, preferably, may be mentioned cycloalkyl group having 3 to 8 carbon atoms (e.g., cyclopentyl, cyclohexyl).

The alkoxy group as R ^{31 to} R ³⁵ 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 ^{31 to} R ³⁵ , R ³⁶ and R ³⁷ , and R ³⁸ and R ³⁹ 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 either a linear or branched alkyl group of R ³¹ to R ^35, a cycloalkyl group or a linear, branched or cyclic alkoxy group, and more preferably the sum of carbon atoms for R ³⁵ from R ³¹ 2-15. Solvent solubility is further improved, and generation of particles during storage is suppressed, which is preferable.

^Examples of the alkyl group and cycloalkyl group as R ³⁸ and R ^{39 are the same} as the alkyl group and cycloalkyl group as R ^{31 to} R ³⁷ .
R ³⁸ and R ³⁹ 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 ^{31 to} R ³⁵ .
As for the alkoxy group in the alkoxycarbonylmethyl group, the same alkoxy groups as R ^{31 to} R ³⁵ can be exemplified.

R ³⁸ and R ³⁹ 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 formulas (b2) and (b3), R ^{14 to} R ¹⁷ 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 ^{14 to} R ¹⁷ is preferably a phenyl group or a naphthyl group, and more preferably a phenyl group.
The alkyl group as R ^{14 to} R ¹⁷ 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 ¹⁴ to R ¹⁷ are preferably, and a cycloalkyl group having 3 to 10 carbon atoms (e.g., cyclopentyl, cyclohexyl, norbornyl).
Examples of the substituent that R ^{14 to} R ¹⁷ may have include, for example, an alkyl group (for example, 1 to 15 carbon atoms), a cycloalkyl group (for example, 3 to 15 carbon atoms), and an aryl group (for example, 6 to 6 carbon atoms). 15), alkoxy groups (for example, having 1 to 15 carbon atoms), halogen atoms, hydroxyl groups, phenylthio groups and the like.

  Although the preferable compound example [(b-1)-(b-96)] of the photocationic polymerization initiator which can be used for this invention is given below, this invention is not limited to these.

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.

A photocationic polymerization initiator can be used individually by 1 type or in combination of 2 or more types.
The content of the cationic photopolymerization initiator in the ink composition is preferably 0.1 to 20% by mass, more preferably 0.5 to 10% by mass, and still more preferably based on the total solid content of the ink composition. 1 to 7% by mass.

<Sensitizer>
A sensitizer that accelerates polymerization and curing may be further added to the ink composition of the present invention, and an anthracene compound is preferably used as the sensitizer. The anthracene compound may have a substituent.

  When the anthracene has a substituent, examples of the substituent include an alkyl group, an alkoxy group, an aryloxy group, etc. Among them, an alkoxy group having 1 to 4 carbon atoms is particularly preferable. The number of anthracene substituents is preferably 1 to 4, more preferably 1 to 2. In particular, the position of the substituent in the case of 1 substitution is preferably the 9th position, and the position of the substituent in the case of 2 substitutions is preferably the 9th and 10th positions. Among these, a 9,10-substituted anthracene compound which is the 9,10 position in the case of disubstitution is particularly preferable.

The content of the above anthracene compound is preferably 35 to 100% by mass of the cationic photopolymerization initiator, more preferably 40 to 80% by mass, and further preferably 44 to 70% by mass.
Moreover, it is preferable that the preferable content of the above-mentioned photocationic polymerization initiator and the preferable content of the anthracene compound are simultaneously within the range.

  In the present invention, a compound other than anthracene may be added as a sensitizer, and it can be used in combination with anthracene or used alone. Examples of sensitizers other than anthracene according to the present invention include those belonging to the compounds listed below and having an absorption wavelength in a wavelength region of 350 nm to 450 nm.

  For example, polynuclear aromatics (eg, pyrene, perylene, triphenylene, 2-ethyl-9,10-dimethoxyanthracene, etc.), xanthenes (eg, fluorescein, eosin, erythrosine, rhodamine B, rose bengal, etc.) , Cyanines (eg, thiacarbocyanine, oxacarbocyanine, etc.), merocyanines (eg, merocyanine, carbomerocyanine, etc.), thiazines (eg, thionine, methylene blue, toluidine blue, etc.), acridines (eg, Acridine orange, chloroflavin, acriflavine, etc.), anthraquinones (eg, anthraquinone, etc.), squaliums (eg, squalium, etc.), coumarins (eg, 7-diethylamino-4-methylcoumarin, etc.), etc. Mentioned That.

  The content of the sensitizer in the ink composition of the present invention is preferably 0.01 to 20% by mass, and preferably 0.1 to 15% by mass with respect to the total mass of the ink composition, from the viewpoint of ink colorability. Is more preferable, and still more preferably in the range of 0.5 to 10% by mass. The said sensitizer may be used individually by 1 type, and may use 2 or more types together. The content ratio of the sensitizer and the cationic photopolymerization initiator in the ink composition is a mass ratio from the viewpoint of improving the decomposition rate of the cationic photopolymerization initiator and the transparency of the irradiated light. Cationic polymerization initiator / sensitizer = 100 to 0.5 is preferable, 50 to 1 is more preferable, and 10 to 1.5 is still more preferable.

  The ink composition of the present invention may further contain a known compound having a function of further improving sensitivity or suppressing inhibition of polymerization by oxygen as a cosensitizer.

  Examples of co-sensitizers include amines such as M.I. R. Sander et al., “Journal of Polymer Society”, Vol. 10, 3173 (1972), Japanese Patent Publication No. 44-20189, Japanese Patent Publication No. 51-82102, Japanese Patent Publication No. 52-134692, Japanese Patent Publication No. 59-138205. No. 60-84305, JP-A 62-18537, JP-A 64-33104, Research Disclosure 33825, and the like. Specific examples include triethanolamine. P-dimethylaminobenzoic acid ethyl ester, p-formyldimethylaniline, p-methylthiodimethylaniline and the like.

  Other examples of co-sensitizers include thiols and sulfides such as thiol compounds described in JP-A-53-702, JP-B-55-500806, and JP-A-5-142277, No. 56-75643, such as 2-mercaptobenzothiazole, 2-mercaptobenzoxazole, 2-mercaptobenzimidazole, 2-mercapto-4 (3H) -quinazoline, β-mercapto. And naphthalene.

Other examples of the co-sensitizer include amino acid compounds (eg, N-phenylglycine), organometallic compounds described in JP-B-48-42965 (eg, tributyltin acetate), JP-B 55- No. 34414, a hydrogen donor described in JP-A-6-308727 (eg, trithiane), a phosphorus compound described in JP-A-6-250387 (eg diethylphosphite), Examples include Si-H and Ge-H compounds described in 191605.
The addition amount is appropriately selected according to the purpose, but is generally about 0.01 to 10% by mass with respect to the total amount (total mass) of the ink composition.

<Surfactant>
The ink composition of the present invention preferably contains a known surfactant. Examples of known surfactants include those described in JP-A Nos. 62-173463 and 62-183457. Specifically, for example, anionic surfactants such as dialkyl sulfosuccinates, alkyl naphthalene sulfonates, fatty acid salts, polyoxyethylene alkyl ethers, polyoxyethylene alkyl allyl ethers, acetylene glycols, polyoxyethylene -Nonionic surfactants such as polyoxypropylene block copolymers, and cationic surfactants such as alkylamine salts and quaternary ammonium salts. An organic fluoro compound may be used instead of the known 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.

<Colorant>
The ink composition of the present invention can form a visible image by adding a colorant. The colorant that can be used in the ink composition of the present invention is not particularly limited, and various known color materials (pigments and dyes) can be appropriately selected and used depending on the application. 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, but oil-soluble dyes are preferred.

<Pigment>
First, a pigment that is preferably used as a colorant in the present invention will be described.
The pigment is not particularly limited, and all commercially available organic pigments and inorganic pigments or pigments dispersed in an insoluble resin or the like as a dispersion medium, or a resin is grafted on 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, “Pigment Dictionary” (2000), edited by Seijiro Ito. Herbst, K.M. Hunger “Industrial Organic Pigments”, JP 2002-12607 A, JP 2002-188025 A, JP 2003-26978 A, and JP 2003-342503 A3.

  Specific examples of organic pigments and inorganic pigments that can be used in the present invention include, for example, 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. Pigment yellow 128, C.I. I. Pigment yellow 93, C.I. 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.).

  Examples of red or magenta colors include 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.).

  Examples of pigments exhibiting blue or cyan colors include 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).

Examples of green pigments include 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).
Examples of the orange pigment include 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 black pigments 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 Solsperse series manufactured by Lubrizol.
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 polymerizable compound which is a low molecular weight component without a solvent may be used as a dispersion medium. The ink composition of the invention is a radiation curable ink, and is preferably solvent-free in order to be cured after the ink 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, a polymerizable compound is used as the dispersion medium, and among them, it is preferable to select a cationically polymerizable monomer having the lowest viscosity from the viewpoint of improving dispersibility and handling properties of the ink composition.

  The volume average particle diameter of the pigment particles in the ink composition is preferably 0.02 to 0.60 μm, more preferably 0.02 to 0.10 μm. Further, the maximum particle size is preferably 3 μm or less, more preferably 1 μm or less, and the selection of the pigment, dispersant, dispersion medium, dispersion conditions, and filtration conditions are set so as to be in such a range. 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 the 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 and nitro dyes Nitroso dyes, acridine dyes, acridinone dyes and the like.

  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, 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, carbonium dyes such as diphenylmethane dyes, triphenylmethane dyes, and 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 above dyes may exhibit yellow, magenta, and cyan colors only after a part of the chromophore is dissociated, and the counter cation in that case 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 that can be used in the present invention is preferably oil-soluble. “Oil-soluble” specifically 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 matrix in order to dissolve the necessary amount in the ink composition.
Examples of the oil-solubilizing group include a long chain / branched alkyl group, a long chain / branched alkoxy group, a long chain / branched alkylthio group, a long chain / branched alkylsulfonyl group, a long chain / branched acyloxy group, and a 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 aryl groups including these long chain / branched substituents, aryloxy groups, aryl Examples include an oxycarbonyl group, an arylcarbonyloxy group, an arylaminocarbonyl group, an arylaminosulfonyl group, an arylsulfonylamino group.
In addition, for water-soluble dyes having carboxylic acid and sulfonic acid, long-chain / branched alcohols, amines, phenols, 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 preferable 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 1.0 V or more (noble than 1.0 V) when measured as a value with respect to a saturated calomel electrode are preferably used. The oxidation potential is preferably higher, more preferably 1.1 V or higher, and particularly preferably 1.15 V or higher.

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 paragraphs [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 inks of any color 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. 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 cyan dyes include dyes represented by formulas (I) to (IV) described in JP-A No. 2001-181547 and paragraph numbers [0063] to [0078] of JP-A No. 2002-121414. The dyes represented by the general formulas (IV-1) to (IV-4) described above are preferable, and specific examples include paragraph numbers [0052] to [0066] of JP-A No. 2001-181547. Examples 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 paragraph numbers [0133] to [0196] of JP-A No. 2002-121414, A phthalocyanine dye represented by formula (C-II) is preferred. Specific examples thereof include compounds described in paragraphs [0198] to [0201] of JP-A No. 2002-121414. 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. The ink may be used for any color ink.

  The colorant is preferably added in an amount of 0.05 to 20% by mass, more preferably 0.2 to 10% by mass, based on the total mass of the ink composition. When an oil-soluble dye is used as the colorant, the content is particularly preferably 0.2 to 6% by mass with respect to the total mass (including the solvent) of the ink composition.

<Additives>
In addition to the essential components, various additives can be used in combination with the ink composition of the present invention depending on the purpose. These optional components will be described.

[Polymerization inhibitor]
The ink composition of the present invention can contain at least one polymerization inhibitor.
Examples of the polymerization inhibitor include phenolic hydroxyl group-containing compounds, quinones, N-oxide compounds, piperidine-1-oxyl free radical compounds, pyrrolidine-1-oxyl free radical compounds, and N-nitrosophenylhydroxylamines. And a compound selected from the group consisting of cationic dyes.

  Specifically, haloquinone, p-methoxyphenol, di-t-butyl-p-cresol, pyrogallol, resorcinol, catechol, t-butylcatechol, hydroquinone monoalkyl ether (for example, hydroquinone monomethyl ether, hydroquinone monobutyl ether), Benzoquinone, 4,4-thiobis (3-methyl-6-tert-butylphenol), 2,2'-methylenebis (4-methyl-6-tert-butylphenol), 2,2,6,6-tetramethylpiperidine and its Derivatives, 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-o So-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 Free radical, 3-carboxy-2,2,5,5-tetramethylpyrrolidine 1-oxyl free radical, N-nitrosophenylhydroxylamine cerium salt, N-nitrosophenylhydroxylamine aluminum salt, crystal violet, methyl violet, Ethyl violet and bi Examples include cutria pure blue BOH.

  Of the above, hydroquinone monoalkyl ethers such as hydroquinone monomethyl ether and hydroquinone monobutyl ether, 4,4′-thiobis (3-methyl-6-tert-butylphenol), 2,2′-methylenebis (4-methyl-6-t) Hindered phenols such as -butylphenol) are preferred.

  The content of the polymerization inhibitor in the ink composition is preferably 50 to 30000 ppm, more preferably 100 to 10000 ppm, and more preferably 100 to 3000 ppm with respect to the total amount (total mass) of the ink composition.

[Ultraviolet absorber]
An ultraviolet absorber can be added to the ink composition of the present invention from the viewpoint of improving the weather resistance of the resulting image and preventing discoloration.
Examples of the ultraviolet absorber are described in JP-A Nos. 58-185677, 61-190537, JP-A-2-782, JP-A-5-97075, and JP-A-9-34057. 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. 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, Special Tables The triazine compounds described in JP-A-8-501291, Research Disclosure No. Examples thereof include compounds described in US Pat. No. 24239, compounds that emit fluorescence by absorbing ultraviolet rays typified by stilbene and benzoxazole compounds, and so-called fluorescent brighteners.
The addition amount is appropriately selected according to the purpose, but is generally about 0.01 to 10% by mass with respect to the total amount (total mass) of the ink composition.

[Antioxidant]
An antioxidant may be added to the ink composition of the present invention to improve stability. Examples of the antioxidant include European published patents, 223739, 309401, 309402, 310551, 310552, 359416, and 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 according to the purpose, but is generally about 0.01 to 10% by mass with respect to the total amount (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, i. 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 addition amount of the anti-fading agent is appropriately selected according to the purpose, but is generally about 0.01 to 10% by mass with respect to the total amount (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.

[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 where the solvent resistance does not deteriorate, and the amount is preferably 0.1 to 5% by mass, more preferably 0.1 to 3% by mass with respect to the entire ink composition. It is.

[Polymer compound]
Various polymer compounds can be added to the ink composition of the present invention in order to adjust film physical properties. High molecular compounds include acrylic polymers, polyvinyl butyral resins, polyurethane resins, polyamide resins, polyester resins, epoxy resins, phenol resins, polycarbonate resins, polyvinyl butyral resins, polyvinyl formal resins, shellacs, vinyl resins, acrylic resins. Rubber resins, waxes and other natural resins can be used. Two or more of these may be used in combination. Of these, vinyl copolymer obtained by copolymerization of acrylic monomers is preferred. Furthermore, a copolymer containing “carboxyl group-containing monomer”, “methacrylic acid alkyl ester”, or “acrylic acid alkyl ester” as a structural unit is also preferably used as the copolymer composition of the polymer binder.

In addition to the above, the ink composition of the present invention includes, for example, leveling additives, matting agents, waxes for adjusting film physical properties, and adhesion to recording media such as polyolefin and PET. In order to improve this, a tackifier or the like that does not inhibit the polymerization 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). Copolymers composed of esters with alcohols having an ester, esters of (meth) acrylic acid with alicyclic alcohols having 3 to 14 carbon atoms, and esters of (meth) acrylic acid with aromatic alcohols having 6 to 14 carbon atoms And low molecular weight tackifying resin having a polymerizable unsaturated bond.

<Preferred physical properties of ink composition>
When the ink composition of the present invention is applied to inkjet recording, the ink viscosity at the temperature at the time of ejection is preferably 5 to 30 mPa · s, and more preferably 7 to 20 mPa · s, in consideration of ejection properties. For this reason, it is preferable to adjust and determine a composition ratio suitably so that it may become the said range.
The viscosity of the ink composition at room temperature (25 to 30 ° C.) is preferably 7 to 120 mPa · s, and more preferably 10 to 80 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, image quality can be improved.

  The surface tension of the ink composition of the present invention is preferably 20 to 40 mN / m, and more preferably 20 to 30 mN / m. In addition, when recording the ink composition of the present invention on various recording media such as polyolefin, PET, coated paper, and uncoated paper, the surface tension is preferably 20 mN / m or more from the viewpoint of bleeding and penetration, and is wet. From the viewpoint of properties, it is preferably 30 mN / m or less.

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 is included.
Among the above, the ink composition of the present invention is suitable as a drop-on-demand ink jet recording ink using a piezoelectric element.

<Image forming method and recorded matter thereof>
The ink composition of the present invention includes an image forming method including an image recording step of recording an image on a recording material by ink jet recording that discharges the ink composition, and an image on a recording material using the ink composition of the present invention. Can be used in an image forming method including: an image recording step for recording the image; and an image curing step for irradiating an active energy ray (active ray) to the image recorded on the recording material in the image recording step to cure the image. .
That is, the image recording method of the present invention may be a method including only an image recording step of forming an image by ink jet recording, or a method combining this with an image curing step. Furthermore, a method in which an image is recorded by a method other than inkjet recording in the image recording process, and an image curing process is combined with this may be used.

In the image curing process of the present invention, active energy rays are used in the image curing process, and after recording an image on a recording material in the image recording process, the recorded image is irradiated with active energy rays for imaging. Polymerization and curing of the polymerizable compound that contributes can proceed, and an image that is cured well and has high fastness can be formed.
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. What is necessary is just to select a light source, exposure time, and a light quantity suitably according to the grade of the polymerization hardening of the polymeric compound which concerns on this invention.
The thickness of the image cured in the image curing step is preferably 2 to 30 μm. Here, “image thickness” refers to the thickness of a cured product obtained by curing an image formed by the ink composition. When the thickness of the image is 2 to 30 μm, an image having a low density to a high density can be expressed.

  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 emitting active rays belonging to a wavelength region of 250 to 450 nm, preferably 365 ± 20 nm, for example, LD, LED (light emitting diode), fluorescent lamp, low pressure mercury lamp, high pressure mercury lamp, metal halide lamp, carbon arc lamp , Xenon lamps, chemical lamps and the like. Preferred light sources include LEDs, high pressure mercury lamps, and metal halide lamps.

In the case of curing by radical polymerization, since the polymerization is inhibited by oxygen, it can be cured with low energy by exposure in a low oxygen concentration state, that is, in a gas atmosphere such as nitrogen.
In the recorded matter obtained with this ink, the image portion is cured by irradiation with radiation such as ultraviolet rays, and the strength of the image portion is excellent. For example, it can be used as an ink receiving layer (image portion) of a lithographic printing plate. it can.

  In the recording step, it is preferable to apply an ink jet recording method using an ink jet printer. Specifically, it is preferable that the image recording step records the image by inkjet recording in which the ink composition is discharged.

<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 image recording method of the present invention will be described below.

  The image forming method in the present invention includes (a) a step of ejecting the active energy ray-curable ink composition of the present invention onto a recording medium, and (b) the discharged active energy ray-curable ink composition. Preferably, the inkjet recording method includes a step of irradiating actinic radiation to cure the active energy ray-curable ink composition.

System As an ink jet recording system for ejecting ink, a form as shown in Japanese Patent Application Laid-Open No. 2002-11860 is given as an example, but the invention is not limited to this, and other forms may be used.

Ink holding means As a means for holding ink, it is preferable to fill a known ink cartridge, and it can be stored in a deformable container and used as a tank as disclosed in JP-A-5-16377. It is. Further, as disclosed in Japanese Patent Laid-Open No. 5-16382, if a sub tank is provided, the supply of ink to the head is further stabilized. Further, as disclosed in JP-A-8-174860, it is also possible to use a cartridge that supplies ink by moving a valve when the pressure in the ink supply chamber decreases. As a negative pressure applying method for appropriately maintaining the meniscus in the head with these ink holding means, a method based on the height of the ink holding means, that is, water head pressure, a method based on the capillary force of the filter provided in the ink flow path, In addition, a method of controlling the pressure with a pump or the like, and a method of holding the ink on the ink absorber and applying a negative pressure by this capillary force as disclosed in Japanese Patent Application Laid-Open No. 50-74341 are suitable. is there.

Ink supply path As a method of supplying ink from these ink holding means to the head, a method of directly connecting the holding means to the head unit or a method of connecting by a flow path such as a tube may be used. The ink holding means and the flow path are preferably made of a material having good wettability with respect to the ink or subjected to a surface treatment.

-As a method of ejecting head ink, as disclosed in Japanese Patent Laid-Open No. 5-104725, ink droplets are continuously ejected, and the droplets are deflected according to the image to land on the recording material. Alternatively, a method of selectively controlling whether or not to perform the operation may be used, or a so-called on-demand method, in which ink droplets are ejected only to a portion necessary as an image, may be used. As disclosed in JP-A-5-16349, the on-demand system may be a system that generates and discharges ink pressure by deformation of a structure using a piezoelectric element or the like. As disclosed, it may be a method of discharging at a pressure generated by expansion accompanying vaporization by thermal energy. Further, as disclosed in Japanese Patent Application Laid-Open No. 2001-277466, a method of controlling ejection to a recording material by an electric field may be used.

  In the ink jet recording method, image recording is performed on a recording material using the ink composition of the present invention, and there are no particular restrictions on the ink discharge nozzles and the like used at that time, which can be appropriately selected according to the purpose. it can. For example, a form described in JP-A-5-31908 can be applied to the nozzle. At this time, in order to eject ink of a plurality of colors, the nozzles are configured in a plurality of rows as described in JP-A-2002-316420, so that a color image can be formed at high speed. Furthermore, it is possible to further increase the speed by arranging a plurality of head units having a plurality of nozzle rows.

Further, as described in Japanese Patent Laid-Open No. 63-160849, the nozzles are arranged by a width equal to or larger than the width of the image to form a so-called line head, and the recording material is moved simultaneously with the droplet ejection from these nozzles. As a result, an image can be formed at high speed.
Further, the surface of the nozzle is subjected to a surface treatment as disclosed in Japanese Patent Laid-Open No. 5-116327, whereby it is possible to prevent ink droplets from adhering to the nozzle surface and ink droplets from adhering.

Even if such treatment is performed, dirt may still adhere, and therefore it is preferable to perform cleaning with a blade as disclosed in JP-A-6-71904.
In addition, the inks of the respective colors are not necessarily ejected from the nozzles uniformly, and specific inks may not be ejected for a long time. In such a case, in order to keep the meniscus stable, as disclosed in Japanese Patent Application Laid-Open No. 11-157102, ink is appropriately ejected outside the image area, and new ink is supplied to the head, thereby providing ink physical properties. Is preferably maintained at a suitable value.

Further, even if such treatment is performed, bubbles may enter the head or be generated in the head. In such a case, as described in JP-A-11-334092, by forcibly sucking ink from outside the head, the ink whose physical properties have changed is discarded, and bubbles are also discharged outside the head. be able to. In the case where the droplets are not ejected for a long time, the nozzle surface can be protected by covering the nozzle surface with a cap as disclosed in JP-A-11-138830. Even if these measures are taken, there is a case where the liquid is still not discharged.
If an image is printed in a state where some of the nozzles do not discharge, problems such as unevenness in the image occur. In order to avoid such a situation, it is effective to take a measure by detecting that no discharge has occurred, as disclosed in Japanese Unexamined Patent Publication No. 2000-343686.

  When the head unit is mechanically moved as described in Japanese Patent Laid-Open No. 6-115099 and the recording material is intermittently moved in the orthogonal direction in synchronization with the head unit, This has the effect of making it difficult to see the unevenness caused by the inaccuracy of the intermittent movement of the material, and can achieve high image quality. At this time, the relationship between the image quality and the recording speed can be set to a preferable relationship by appropriately setting the relationship between the moving speed of the head, the moving amount of the recording material, and the number of nozzles.

  On the other hand, the same effect can be obtained by fixing the head and mechanically reciprocating the recording material in a predetermined direction and intermittently moving the recording material in a direction orthogonal thereto.

-Temperature control The ink jet recording apparatus is preferably provided with a means for stabilizing the ink composition temperature, and the part to be kept at a constant temperature is a piping system from the ink tank (intermediate tank if there is an intermediate tank) to the nozzle ejection surface, All of the members are targeted.

  In the inkjet recording method, the ink composition is heated to 40 to 80 ° C., and the viscosity of the ink composition is reduced to 30 mPa · s or less, preferably 20 mPa · s or less, and then ejected. By using this, high injection stability can be realized. In general, radiation curable ink compositions generally have a higher viscosity than aqueous inks, so that the viscosity fluctuation range due to temperature fluctuations during printing is large. 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. For this purpose, it is preferable to have an ink temperature detecting means, an ink heating means, and a control means for controlling heating according to the detected ink temperature.

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.
Alternatively, it is also preferable to have means for controlling energy applied to the means for ejecting ink according to the ink temperature.

  The control range of the ink composition temperature is preferably set temperature ± 5 ° C., more preferably set temperature ± 2 ° C., and further preferably set temperature ± 1 ° C.

-Exposure As a light source, as above-mentioned, a mercury lamp, a metal halide lamp, etc. which are generally used may be used, and a light emitting diode, a semiconductor laser, a fluorescent lamp, etc. can be used. Further, a hot cathode tube, a cold cathode tube, an electron beam, an X-ray, or the like, a light source in which an ink polymerization reaction proceeds, an electromagnetic wave or the like can be used.

When using a metal halide lamp, the lamp should be designed 10~1000W / cm ^2, it is preferable that the illuminance of ^1mW / cm ^{2 ~100W} / cm 2 at the recording material surface.
Further, since high pressure mercury lamps, metal halide lamps and the like generate ozone with discharge, it is preferable to have an exhaust means. The exhaust means is preferably arranged so as to also collect ink mist generated during ink ejection.

  Next, preferable irradiation conditions of active energy rays will be described. A basic irradiation method is disclosed in JP-A-60-132767. Specifically, light sources are provided on both sides of the head unit, and the head and the light sources 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. International Publication No. 99/54415 pamphlet discloses a method using an optical fiber and a method of irradiating a recording unit with UV light by applying a collimated light source to a mirror surface provided on the side of the head unit. In the present invention, these irradiation methods can be used.

  When active energy rays for curing are applied to the ink discharge nozzles, ink mist attached to the surface of the nozzle surface may solidify and hinder ink discharge. In order to keep it, it is preferable to take measures such as shading. Specifically, it is preferable to provide a partition wall that prevents the nozzle plate from being irradiated, or to provide means for limiting the incident angle to the recording material so as to reduce stray light.

  In the present invention, the time from landing to irradiation is desirably 0.01 to 0.5 seconds, preferably 0.01 to 0.3 seconds, and more preferably 0.01 to 0.15 seconds later. Is to irradiate. 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. Also, since the ink composition can be exposed to a porous recording medium before it penetrates deeper than the light source reaches, unreacted monomer remains, 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. 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.

System parameters In forming an image, the ink landing diameter on the recording material is preferably between 10 and 500 μm, and for this purpose, the diameter of the ink droplets during ejection is from 5 to 250 μm. In this case, the nozzle diameter is preferably 15 to 100 μm.
In order to form an image, the number of pixels per inch is preferably 50 to 2400 dpi, and for that purpose, the nozzle density of the head is preferably 10 to 2400 dpi. Here, even if the nozzle density of the head is low, high-density landing can be achieved with a head with a large nozzle interval by tilting with respect to the recording material conveyance direction or by displacing multiple head units relative to each other. Is possible. In addition, by reciprocating the head or the recording material as described above, each time the head moves at a low nozzle pitch, the recording material is conveyed by a predetermined amount, and ink droplets are landed at different positions, thereby recording high-density images. Can be realized.

The amount of ink droplets to be recorded on the recording material is preferably controlled to an arbitrary amount between 0.05 and 25 g / m ² in order to express a good gradation. It is preferable to control the size and / or quantity of the ejected ink droplets from.

  If the distance between the head and the recording material is too wide, the flying of the ink droplets is disturbed by the air flow accompanying the movement of the head or the recording material, and the landing position accuracy decreases. On the contrary, if the interval is narrow, there is a risk that the head and the recording material come into contact with each other due to unevenness of the recording material, vibration due to the transport mechanism, and the like, and it is preferable to maintain the recording material at about 0.5 to 2 mm.

-Ink set The ink may be a single color, cyan, magenta, yellow, or four colors including black, or a specific color other than these called special color. Also good. The coloring material may be a dye or a pigment. These inks may be ejected in order of landing in order of increasing lightness, may be landed in order of increasing lightness, or are preferably ejected in an order suitable for image recording quality.

When the colors are stacked in order from the lightest color, the active energy ray easily reaches the lower ink, and it is difficult for inhibition of curing sensitivity, increase of residual monomers, generation of odor, and deterioration of adhesion. 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.
The image signal to be recorded is preferably subjected to signal processing to obtain good color reproduction, as described in, for example, Japanese Patent Laid-Open No. 6-210905.

  The ink composition of the present invention can be used not only for inkjet recording but also for three-dimensional modeling, and can also be used for can printing and food. For these uses, it is possible to form an image using a known method. For example, the description in Japanese Patent No. 2679586 can be referred to.

[Recording material]
As a recording medium to be recorded using the ink composition of the present invention, both an ink-permeable recording medium and an ink-impermeable recording medium can be used. Examples of the ink-permeable recording medium 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.

  Examples of the ink-impermeable recording medium include art paper, synthetic resin, rubber, resin-coated paper, glass, metal, earthenware, and wood. In addition, in order to add each function, a base material obtained by combining a plurality of these materials can be used.

  Although any synthetic resin can be used as the synthetic resin, for example, polyethylene terephthalate and polyester such as polybutadiene terephthalate; polyolefin such as polyvinyl chloride, polystyrene, polyethylene, polyurethane, and polypropylene; and acrylic resin, Examples include polycarbonate, acrylonitrile-butadiene-styrene copolymer, diacetate, triacetate, polyimide, cellophane, and celluloid.

  The shape (thickness) of the base material using the synthetic resin may be a film shape, a card shape or a block shape, and can be appropriately selected according to a desired purpose without particular limitation. These synthetic resins may be 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. Examples of plastic films include polyethylene terephthalate (PET) film, biaxially oriented polystyrene (OPS) film, biaxially oriented polypropylene (OPP) film, biaxially oriented nylon (ONy) film, and polyvinyl chloride (PVC). A film, a polyethylene (PE) film, and a triacetyl cellulose (TAC) film can be mentioned.

  Examples of the resin-coated paper include a transparent polyester film, an opaque polyester film, an opaque polyolefin resin film, and a paper support in which both sides of the paper are laminated with a polyolefin resin, and both sides of the paper are laminated with a polyolefin resin. A paper support is particularly preferred.

  As described above, according to the image recording using the ink composition of the present invention, an image having excellent brittleness and adhesiveness can be obtained. The obtained recorded matter, that is, the recorded matter of the present invention is brittle and adherent. It is excellent in performance.

  EXAMPLES Hereinafter, although an Example demonstrates this invention, this invention is not limited to these Examples. Unless otherwise specified, “part” is based on mass.

[Example 1]
The following components were stirred with a high-speed water-cooled stirrer to obtain a magenta ink composition for UV inkjet, and evaluated by the methods described below.
Colorant PR-122 (Chromophthal Jet Magenta DMQ manufactured by Ciba Specialty Chemicals) 5.0 parts Specific polymerizable compound A (Exemplified Compound 1-1) 30.0 parts Specific polymerizable compound B Glycidyl Phenyl ether (manufactured by Tokyo Chemical Industry Co., Ltd.) 20.0 parts, specific polymerizable compound B 3-ethyl-3- (2-ethylhexyloxymethyl) oxetane (manufactured by Toagosei Co., Ltd., trade name: OXT-212) 35.0 Parts / dispersant (Solsperse 32000 manufactured by Lubrizol) 2.0 parts / photocationic polymerization initiator (previously exemplified compound b-39) 5.0 parts (tris (4-chlorophenyl) sulfonium hexafluorophosphate)
Sensitizer 9,10-Butoxyanthracene (manufactured by Kawasaki Chemical Industries) 3.0 parts

[Examples 2-7, Comparative Examples 1-4]
Except for changing to the composition described in Table 1, the ink compositions of Examples 2 to 7 and Comparative Examples 1 to 4 were prepared in the same manner as the adjustment of the ink composition of Example 1, and the same as in Example 1. The method was evaluated.

  In Table 1, Exemplified Compounds 1-1, 1-6 and 1-13 are the compounds described above. The structure of the comparative compound P is shown below.

OXT-221 (manufactured by Toagosei Co., Ltd.) is a compound represented by the following structural formula, and has two oxetanes as cationically polymerizable groups.
The numbers of each compound in Table 1 are parts by mass.

<Printing and exposure>
Each ink composition obtained above was ejected using a piezo ink jet head. The head has a nozzle density of 150 per 25.4 mm and has 318 nozzles. By fixing these two nozzles in the nozzle row direction with a shift of 1/2 of the nozzle interval, 25 heads are arranged on the medium in the nozzle array direction. . 300 drops per 4 mm.

The head and ink are controlled so that the vicinity of the ejection portion is 50 ± 0.5 ° C. by circulating hot water in the head. Ink ejection from the head is controlled by a piezo drive signal applied to the head, and ejection of 6 to 42 pl per drop is possible. In this embodiment, the head is transported while the medium is conveyed at a position 1 mm below the head. More drops. The conveyance speed can be set in the range of 50 to 200 mm / s. The piezo drive frequency can be up to 4.6 kHz, and the droplet ejection amount can be controlled by these settings.
In this evaluation, by setting the transport speed to 90 mm / s and the drive frequency to 1.9 kHz, the ink discharge amount was controlled to 24 pl and droplets were ejected at 10 g / m ² to obtain a solid print image.

After the droplets are ejected, they are transported to an exposure unit and exposed by an ultraviolet light emitting diode (UV-LED). In this example, NUCA NCCU033 (trade name) was used as the UV-LED. This LED outputs ultraviolet light having a wavelength of 365 nm from one chip. When a current of about 500 mA is applied, light of about 100 mW is emitted from the chip. A plurality of these are arranged at intervals of 7 mm, and a power of 0.3 W / cm ² can be obtained on the media surface. The exposure time after the droplet ejection and the exposure time can be changed according to the transport speed of the medium and the distance between the head and the LED in the transport direction. In this embodiment, the exposure is performed about 0.5 seconds after landing. Depending on the setting of the distance to the medium and the conveyance speed, the exposure energy on the medium can be adjusted between 0.01 and 15 J / cm ² . In this embodiment, the exposure energy is adjusted according to the conveyance speed. For the measurement of exposure power and exposure energy, a spectroradiometer URS-40D (trade name) manufactured by USHIO ELECTRIC CO., LTD. Was used, and a value obtained by integrating between wavelengths 220 to 400 nm was used. In this evaluation, a PET film having a thickness or a sheet made of polyvinyl chloride is used as a medium. H. Conducted in a 60% environment. The thickness of the cured image was 19 μm.

<Evaluation>
The sensitivity, discharge stability, and brittleness were evaluated by the following methods, and the results are shown in Table 2.

1. Sensitivity Each ink composition was printed on a sheet made of polyvinyl chloride using the above-mentioned apparatus, the integrated exposure was adjusted by changing the conveying speed, and the ink was cured to obtain a printed matter. The exposure energy in curing was measured with a light quantity integrator (UV PowerMAP manufactured by EIT). Curability was judged by the presence or absence of surface stickiness of the printed matter, and the minimum integrated exposure amount at which stickiness disappeared was evaluated according to the following criteria.
A: 100mJ / cm ² less B: 100mJ / cm ² or more 250 mJ / cm ² less than C: 250 mJ / cm ² or more 500 mJ / cm ² less than D: The 500 mJ / cm ² or more practical evaluation of sensitivity is at least C Is preferably B or more, particularly preferably A.

2. When the obtained ink composition was stored at room temperature for 4 weeks, recording was performed on a recording medium using a commercially available inkjet recording apparatus having a piezo-type inkjet nozzle, and continuous printing was performed for 48 hours at room temperature. The presence or absence of missing dots and ink scattering was visually observed and evaluated according to the following criteria.
○: Dot drop or ink splatter does not occur or occurs 3 times or less △: Dot drop or ink splatter occurs 4 to 10 times ×: Dot drop or ink splatter occurs 11 times or more

3. Brittleness A sample in which each ink composition was printed on 175 μm PET was punched with a two-hole punch (Type C, trade name, manufactured by MAX), the state of the punched circular surface was observed, and evaluated according to the following criteria.
Rank 5: No peeling is observed.
Rank 4: A portion of the periphery is missing.
Rank 3: A part of the periphery is peeled off.
Rank 2: The periphery is peeled off.
Rank 1: The surface peels off.
Practically, the brittleness evaluation needs to be 4 or more, and 5 is preferable.

From the results shown in Table 2, Comparative Example 1 using a trifunctional polymerizable compound having a molecular weight exceeding 600 is inferior in ejection stability, and the trifunctional specific polymerizable compound A is only 3% by mass based on the total polymerizable compound. It can be seen that Comparative Example 2 which does not contain has low sensitivity. In Comparative Example 3 using the specific polymerizable compound C having two polymerizable groups without using the trifunctional specific polymerizable compound A2, the sensitivity was low and the brittleness was poor. Comparative Example 4 containing excessively trifunctional specific polymerizable compound A was inferior in brittleness.
On the other hand, Examples 1 to 8 using the present invention show that the ink composition has high sensitivity, good ejection stability, and excellent brittleness.
Comparison between Example 1 and Example 2 shows that a composition in which the ratio of the number of oxetane and oxirane is in a suitable range is more preferable in terms of both sensitivity and brittleness. From the comparison, it was found that the specific polymerizable compound A preferably has an oxetane ring.

Claims (7)

  (A) a polymerizable compound having a molecular weight of 600 or less and containing three or more cationic polymerizable groups in the molecule, (B) a polymerizable compound containing one cationic polymerizable group in the molecule, and (C) And (C) a polymer having a molecular weight of 600 or less and 3 or more cationically polymerizable groups in the molecule with respect to all cationically polymerizable compounds contained in the ink composition. An active energy ray-curable ink composition in which the compound is in the range of 5 to 60% by mass on a mass basis.   Cationic polymerization in (A) a polymerizable compound having a molecular weight of 600 or less and containing three or more cationic polymerizable groups in the molecule, and (B) a polymerizable compound containing one cationic polymerizable group in the molecule. The active energy ray-curable ink composition according to claim 1, wherein the functional group is an oxirane ring, an oxetane ring, or a vinyl ether group.   The (A) polymerizable compound having a molecular weight of 600 or less and having three or more cationic polymerizable groups in the molecule is a polymerizable compound having one or more oxetane rings in the molecule. Item 3. The active energy ray-curable ink composition according to Item 2.   The content relationship between the oxirane ring and the oxetane ring in the ink composition is in the range of 10:90 to 50:50 in the ratio of the total number of oxirane rings to the total number of oxetane rings. The active energy ray-curable ink composition according to any one of the above.   The active energy ray-curable ink composition according to any one of claims 1 to 4, which is for inkjet recording.   (A) a step of discharging the active energy ray curable ink composition according to claim 5 onto a recording medium; and (b) irradiating the discharged active energy ray curable ink composition with active radiation. And a step of curing the active energy ray-curable ink composition.   A recorded matter obtained by the method according to claim 6.