JP2014024980A - Ink jet ink and image formation method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To inhibit oxygen hindrance of the curing of an ink jet ink including a charge-transfer complex polymerization-type composition and to enhance the storage stability of the ink.SOLUTION: Provided is an ink jet ink containing an electron-accepting monomer (A), an electron-donative monomer (D), and a (meth)acrylic acid ester group-containing polymerizable monomer (X); the electron-donative monomer (D) contains vinyl ether; the ratio of the combined sum of the electron-accepting monomer (A) and electron-donative monomer (D) with respect to the total sum of the electron-accepting monomer (A), electron-donative monomer (D), and polymerizable monomer (X) is 25-90 wt.%; the ratio of the functional group number of the electron-accepting monomer (A) with respect to the functional group number of the electron-donative monomer (D) [(A)/(D)] is 70/30-35/65.

Description

  The present invention relates to an inkjet ink and an image forming method using the same.

  In recent years, the inkjet recording method has been used in various printing fields such as photographs, various printing, marking, and special printing such as color filters from the viewpoint of being able to create an image easily and inexpensively.

  As an inkjet ink used in such an inkjet recording system, an aqueous inkjet ink containing water as a main solvent, a non-volatile solvent that does not volatilize at room temperature, an oil-based inkjet ink that does not substantially contain water, and volatilizes at room temperature. Non-water-based inkjet ink that contains mainly solvent and contains substantially no water, hot-melt ink that heats and melts solid ink at room temperature, and active energy ray-curable inkjet that cures with actinic rays such as ultraviolet rays after printing There are various types of ink-jet inks such as ink. These have been used properly depending on the application. Among them, the active energy ray-curable inkjet ink has a fast curing property and can print on a wide variety of recording media. The ink is attracting attention as a next-generation ink-jet ink that replaces the water-based ink-jet ink, the oil-based ink-jet ink, and the non-aqueous ink-jet ink whose recording medium is limited.

  In order to improve the image quality in the ink jet recording method, a base material that stabilizes the dot diameter of the ejected ink droplets is selected (for example, an absorbent base material is selected for water-based ink). , Use dark and light inks, or reduce the ink droplet size. Inkjet recording methods using active energy ray-curable inkjet inks record on various substrates, so there is no improvement in image quality by selecting the substrate. It is effective to reduce.

  With recent development of inkjet heads, ink droplets of less than 2 pl can be ejected, and active energy ray-curable inkjet inks are also ejected with several pl of ink droplets, and attempts have been made to form images. Yes.

  Active energy ray curable inkjet inks are roughly classified into radical polymerization type and cationic polymerization type inkjet inks. Radical polymerization type ink-jet inks are widely researched and developed and put to practical use because they have a wide range of material choices and a high degree of freedom in ink design. However, radical polymerization inks have the disadvantage of being susceptible to polymerization inhibition by oxygen, and are more susceptible to oxygen and humidity when the droplet size is reduced for higher image quality. Curing sensitivity is greatly reduced.

  On the other hand, attempts have been made to apply a charge transfer complex polymerization composition (CT polymerization composition) as a polymerization system that is not easily affected by oxygen and humidity to an active energy ray-curable composition (Non-patent Document 1). See). More specifically, a charge transfer complex polymerization composition comprising a combination of an electron-rich monomer (donor monomer) such as vinyl ether and an electron-deficient monomer (acceptor monomer) such as maleimide is an active energy ray-curable composition. It is used as a product (see Patent Documents 1 and 2).

  However, when the charge transfer complex polymerization composition is applied to an inkjet ink, it is difficult to reduce the viscosity to such an extent that it can be ejected by inkjet. Further, when the ink is stored for a long period of time or the storage environment of the ink fluctuates, the ink viscosity fluctuates. Due to these effects, it is difficult to obtain stable inkjet ejection properties even when the charge transfer complex polymerization composition is applied to inkjet ink.

  Ink-jet inks in which maleimide and various polymerizable compounds are combined are known (see Patent Document 3). However, oxygen inhibition of ink curing cannot be suppressed, and the storage stability of ink is poor. There was a problem.

Japanese Patent No. 3353020 Japanese Patent Laid-Open No. 11-124403 JP 2012-51992 A

Sonny Jonsson, et. Al, Polymer Materials Sci. & Enginer. 1995, 72, 470-472)

  The present invention relates to an inkjet ink containing a charge transfer complex polymerization composition, which suppresses oxygen inhibition of oxygen curing even when the amount of ejected ink droplets is reduced, and improves the storage stability of the ink. Objective. More preferably, the curing shrinkage of the ink cured product is suppressed. These provide high quality images printed with inkjet ink.

The present invention relates to the following inkjet ink.
[1] having an unsaturated bond a, an electron-accepting monomer (A) in which the maximum charge of the carbon atom constituting the unsaturated bond a is −0.30 or more, and an unsaturated bond d An electron donating monomer (D) having a minimum charge of carbon atoms constituting the unsaturated bond d of −0.50 or less, and a polymerizable monomer (X) having a (meth) acrylate group Including
The electron donating monomer (D) contains vinyl ether; the electron accepting monomer (A) with respect to the total amount of the electron accepting monomer (A), the electron donating monomer (D) and the polymerizable monomer (X). The ratio of the total amount of the electron-donating monomer (D) is 25 to 90% by weight; the ratio of the number of functional groups of the electron-accepting monomer (A) to the number of functional groups of the electron-donating monomer (D) (A) / (D) is actinic ray curable inkjet ink having 70/30 to 35/65.
[2] The actinic ray curable inkjet ink according to [1], further containing a photopolymerization initiator.
[3] The actinic ray curable inkjet ink according to [1], further containing a pigment.
[4] The actinic ray curable inkjet ink according to [1], which has a viscosity at 25 ° C. of 5 to 60 mPa · s.

Furthermore, the present invention relates to an image forming method described below.
[5] A step of spraying the actinic radiation curable ink according to [1] onto a recording medium from a nozzle of an inkjet recording head to form a coating film, and an activity on the coating film formed on the recording medium An image forming method, comprising: a step of irradiating and curing a light beam, wherein the light source of the active light beam is an LED.
[6] A step of spraying the actinic ray curable ink according to [1] onto a recording medium from a nozzle of an ink jet recording head to form a coating film, and an activity on the coating film formed on the recording medium. An image forming method, wherein the amount of ink droplets ejected from the nozzles of the inkjet recording head is 0.1 to 12 pl.

  The ink-jet ink of the present invention has high ink storage stability even when the ink is hardened to be inhibited by oxygen even when printing with a small droplet size. Furthermore, the curing shrinkage of the ink cured product can be suppressed.

1 is a front view of a serial head type ink jet recording apparatus and shows a main configuration of the apparatus. FIG. FIG. 2 is a top view of a line head type ink jet recording apparatus, showing the main configuration of the apparatus.

1. Inkjet ink The inkjet ink of the present invention comprises an electron-accepting monomer (A), an electron-donating monomer (D), and a polymerizable monomer having a (meth) acrylic acid ester group.

  Both the electron-accepting monomer (A) and the electron-donating monomer (D) have a functional group composed of an unsaturated bond, typically a double bond between a carbon atom and a carbon atom. The electron accepting monomer (A) means a monomer having a low electron density of unsaturated bonds contained therein; the electron donating monomer (D) means a monomer having a high electron density of unsaturated bonds contained therein. That is, the electron-accepting monomer (A) has an unsaturated bond to which an electron-withdrawing group is bonded; the electron-donating monomer (D) has an unsaturated bond to which an electron-donating group is bonded.

  The electron density of the unsaturated bond of each monomer means the charge of the carbon atom constituting the unsaturated bond. The charge of the carbon atom constituting the unsaturated bond refers to an atomic charge in the ground state obtained by calculation based on the molecular orbital theory. The charge on the carbon atom of the unsaturated bond in the ground state of the polymerizable monomer can be obtained by calculation using a computer. In the present invention, SPARTAN'08 for Windows (registered trademark) which is molecular orbital calculation software can be used, and the calculation method can be Equilibrium Geometry at Ground state with Hartree-Fock 3-21G in Vacuum. The value of the charge is Natural atomic charge.

  The “carbon constituting the unsaturated bond” in the electron-accepting monomer (A) means a carbon having a larger charge value among two carbons on the unsaturated bond to which the electron-withdrawing group is bonded. The “carbon constituting the unsaturated bond” in the electron donating monomer (D) means a carbon having a smaller charge value out of two carbons on the unsaturated bond to which the electron donating group is bonded. When a plurality of unsaturated bonds are present in one molecule of the polymerizable monomer, “carbon constituting the unsaturated bond” means an average value of electric charges of carbon constituting each unsaturated bond.

  Among the monomers of the electron-accepting monomer (A) contained in the ink jet of the present invention, X is the charge of the carbon atom constituting the unsaturated bond of the monomer having the smallest charge of the carbon atom constituting the unsaturated bond; Among the monomers of the electron donating monomer (D), Y is the charge of the carbon atom constituting the unsaturated bond of the monomer having the maximum charge of the carbon atom constituting the unsaturated bond. At this time, the difference between the charge X and the charge Y is preferably 0.24 or more and 0.46 or less. When the difference between the charge X and the charge Y is 0.24 or more, CT polymerization tends to occur. Further, when the difference between the charge X and the charge Y is 0.46 or less, the charge transfer complex is not excessively stabilized, and the polymerization rate is sufficiently high.

About electron-accepting monomer (A) The electron-accepting monomer (A) refers to a monomer having a low electron density of unsaturated bonds contained therein. The value of the atomic charge of the carbon atom constituting the unsaturated bond in the electron accepting monomer (A) is preferably −0.3 or more, more preferably −0.28 or more.

The electron-accepting monomer (A) contained in the inkjet ink of the present invention is preferably a compound represented by the general formula (4) or the general formula (5).

In General Formula (4) or General Formula (5), EWG ₁ and EWG ₂ each represent a partial structure in which an electron-withdrawing group is directly connected to an unsaturated bond. A part of EWG ₁ or EWG ₂ may be bonded to have a cyclic structure. The electron-withdrawing group represents a cyano group, a halogen group, a pyridyl group, a pyrimidyl group, a nitro group, a group represented by the following general formula (a), or a group represented by the following general formula (b).

Further, EWG ₁ and EWG ₂ may be bonded to each other to form the following electron-withdrawing linking group to form a cyclic structure. Examples of the electron-withdrawing linking group include —CO—O—CO—, —CO—N (R _X ) —CO—, —S (O) _n —O—CO—, —S (O) _n —. N (R) —CO—, —S (O) _n —O—S (O) _n —, or —S (O) _n —N (R _X ) —S (O) _n — and the like are included.

EWG ₁ and EWG ₂ may form a cyclic structure via a linking group such as a linear alkylene group, a branched alkylene group, a cyclic alkylene group, an alkylene group having a hydroxyl group, an arylene group or an arylalkylene group, and a substituent. You may have. Further, a part of EWG ₁ or EWG ₂ may form a polyfunctional polymerizable compound having two or more unsaturated bonds through a linking group.

In the general formulas (a) and (b), Q ₁ represents OH, OR ′, NR′R ″ or R ′. R ′ and R ″ each represent a hydrogen atom, a linear alkyl group, a branched alkyl group, a cyclic alkyl group, an alkyl group having a hydroxyl group, an aryl group or an arylalkyl group, and may further have a substituent.

  Specific examples of the compound represented by the general formula (4) or the general formula (5) include a vinylene imide compound, a vinylene dicarboxylic acid, a vinylene dicarboxylic acid ester, a vinylene monocarboxylic acid amide monocarboxylic acid, and a vinylene monocarboxylic acid amide monocarboxylic acid. Acid ester, vinylene dicarboxylic acid amide, vinylene nitrile compound substituted with nitrile groups at both ends of vinylene skeleton, vinyl halide compound substituted with halogen groups at both ends of vinylene skeleton, vinylene diketone compound substituted with carbonyl at both ends of vinylene skeleton, vinylene thiocarboxylic acid Acid anhydride, vinylene thioimide compound, vinylene thiocarboxylic acid, vinylene thiocarboxylic acid ester, vinylene monothiocarboxylic acid amide monothiocarboxylic acid, vinylene monothiocarboxylic acid amide monothiocarboxylic acid ester Ether, vinylene range thio carboxylic acid amide, compounds pyridyl group which is substituted vinylene backbone ends, but such compounds structure pyrimidyl group is substituted on vinylene skeleton ends include, but are not limited to.

  Examples of the electron-accepting monomer (A) include vinylene imides such as maleic anhydride and maleimide, vinylenedicarboxylic acids such as maleic acid and fumaric acid, and vinylene dicarboxylic acid esters such as maleic acid ester and fumaric acid ester.

The electron accepting monomer (A) can also be represented by the following general formulas (A-1) to (A-13).

In general formulas (A-1) to (A-13), R ₁ , R ₂ , R ₃ , and R ₄ are each independently a hydrogen atom, a linear alkyl group, a branched alkyl group, a cyclic alkyl group, or a hydroxyl group. Represents an alkyl group, an aryl group or an arylalkyl group having a substituent, and may further have a substituent. R ₁ , R ₂ , R ₃ and R ₄ can also be a linking group for forming a polyfunctional polymerizable compound having two or more unsaturated bonds. X ₁ represents a halogen atom.

  Although the electron-accepting monomer (A) represented by general formula (A-1)-general formula (A-13) is demonstrated below, it is not limited to these. The charge of the carbon atom of the unsaturated bond which the electron-accepting monomer (A) described below has has a value of −0.3 or more.

  Examples of the monofunctional electron-accepting monomer (A) represented by the general formulas (A-1) to (A-13) include maleic anhydride; vinyleneimide as an example of a compound having vinylene dicarboxylic anhydride. Examples of compounds are maleimide, N-methylmaleimide, N-ethylmaleimide, N-butylmaleimide, N-2-ethylhexylmaleimide, N-dodecylmaleimide, N-octadecylmaleimide, N-phenylmaleimide, N-cyclohexylmaleimide, N- (P-carbomethoxyphenyl) maleimide, 4,4′-dimaleimidobisphenol F, N-butylmaleimide, N- (2-chlorophenyl) maleimide, N- (4-chlorophenyl) maleimide, 2,3-dimethyl-1- N- (2-methacryloxyethylmaleimide; as an example of vinylene dicarboxylic acid, maleic acid, Malic acid: Examples of vinylene dicarboxylic acid esters include dimethyl maleate, diethyl maleate, diisopropyl maleate, di-n-butyl maleate, di-tert-butyl maleate, di (2-ethylhexyl) maleate, fumaric acid Examples include dimethyl, diethyl fumarate, diisopropyl fumarate, di-n-butyl fumarate, di-tert-butyl fumarate, and di (2-ethylhexyl) fumarate, but these are not limited to these specific examples.

  The polyfunctional electron-accepting monomer (A) may have a conventionally known linking group skeleton. For example, it may be a polyfunctional maleimide as described in US Pat. No. 6,034,150, JP-A-11-124403, and the like.

  The ink-jet ink of the present invention contains at least maleimide as the electron-accepting monomer (A) and at least one of maleate ester and fumarate ester.

  The maleimide is preferably a maleimide having a chiral structure in the molecule from the viewpoints of solubility in inkjet ink, low viscosity required for inkjet ink, and ejection stability required for inkjet ink.

The maleimide having a chiral group is not particularly limited as long as it has at least one chiral carbon atom in the molecule. As this preferred maleimide, a compound represented by the following general formula (1) is preferable.

In the general formula (1), R ₁ and R ₂ each independently represent a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and R ₁ and R ₂ may be linked to form a ring. Y ₁ , Y ₃ and Z represent a divalent organic linking group in which groups selected from an alkylene group, an alkyleneoxy group, a phenylene group, an ester group, an ether group and a thioether group are combined. Y ₂ represents a divalent group having an asymmetric carbon. n represents an integer of 1 to 6, n1 represents 0 or 1, and n2 represents 0 or 1.

Examples of the alkyl group represented by R ₁ and R ₂ include a methyl group, an ethyl group, a propyl group, a butyl group, and a hexyl group. R ₁ and R ₂ may combine to form a cyclopropylene ring, a cyclobutylene ring, a cyclopentene ring, a cyclohexene ring, or the like.

The divalent organic linking group represented by Y ₁ and Y ₃ is an alkylene group (eg, methylene group, ethylene group, butylene group, hexylene group, etc.), an alkyleneoxy group (eg, ethyleneoxy group, polyethyleneoxy group, Butyleneoxy group, polybutyleneoxy group), alkyleneoxycarbonyl group (for example, ethyleneoxycarbonyl group, hexyleneoxycarbonyl group, etc.), alkylene ester group (for example, methylene ester group, hexylene ester group, phenylene group), phenyl Group (for example, methylphenylene group, oxycarbonylphenylenecarbonyloxy group, carbonyloxyphenyleneoxycarbonyl group, etc.).

Y ₂ represents a divalent group having an asymmetric carbon (chiral carbon). Specifically, it is represented by the following formula.

  In the above formula, X represents an alkyl group having 1 to 18 carbon atoms, an alkenyl group having 1 to 18 carbon atoms, an alkyloxy group having 1 to 18 carbon atoms, an alkylcarbonyloxy group having 1 to 18 carbon atoms, or a hydroxyl group. Preferably, a C1-C4 methyl group, an ethyl group, a propyl group, and an isobutyl group are mentioned.

In the general formula (1), Z represents an n-valent linking group. In the case of n = 1, Z is a hydrogen atom, an alkyl group (methyl group, ethyl group, hexyl group), a hydroxyl group, a carboxyl group, or an alkyl ester group. In the case of n = 2, Z has the same meaning as the divalent organic linking group represented by Y ₁ or Y ₃ . In the case of n = 3, Z is a glycerol group, a trimethylol alkyl group, a triazine group, or the like. When n = 4, Z is a pentaerythritol group or the like, and when n = 6, Z is a bistrimethylolalkyl group or the like.

  In order to eject the inkjet ink from the inkjet head, the molecular weight of the maleimide having a chiral group is preferably 200 to 1000, more preferably 200 to 800. If it is smaller than 200, it is easy to crystallize and clogging is likely to occur during ejection. On the other hand, if the molecular weight is larger than 1000, the viscosity becomes high and ejection becomes difficult.

Further preferred examples of maleimides having a chiral group include maleimides represented by the following structural formula.

n11 and n12 are integers of 0 to 6, and n13 is preferably an integer of 1 to 30. R _{1, R 2,} Z is synonymous with _{R 1, R} 2, Z in the general formula (1). X has the same meaning as X in the formula given as an example of the divalent group having an asymmetric carbon (chiral carbon) represented by Y ₂ . Particularly preferably, R ₁ and R ₂ are a hydrogen atom, X is an alkyl group having 1 to 4 carbon atoms, n12 is 0, and Z is an alkylene or polyoxyalkylene having 1 to 18 carbon atoms.

Although the specific example of the maleimide which has a chiral group represented by General formula (1) below is shown, it is not limited to this.

  The methods for synthesizing these maleimides are known, and can be synthesized, for example, using the method described in JP-A No. 11-124403 or Macromolecular Chemical and physics, 2009, 210, 269-278.

In the inkjet ink of the present invention, as a maleimide that is more preferable as the electron-accepting monomer (A), a maleimide represented by the following general formula (2) is exemplified from the viewpoint of low viscosity, solubility, and ejection stability.

In the general formula (2), R ₁₁ and R ₁₂ each independently represent a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and R ₁₁ and R ₁₂ may be bonded to each other to form a ring. . A ₁₁ and A ₁₃ each independently represent an alkylene group, and A ₁₂ represents a trivalent hydrocarbon group having an asymmetric center. Y represents carbonyloxy (—C (═O) —O—) or oxycarbonyl (—O—C (═O) —). p represents 1 or 2. R ₁₃ represents an alkyl group or alkyleneoxy group having a molecular weight of 15 to 600 when p is 1, and an alkylene group or alkyleneoxy group having a molecular weight of 14 to 600 when p is 2. m represents 0 or 1, and n represents 0 or 1.

In the general formula (2), examples of the alkyl group represented by R ₁₁ and R ₁₂ include a methyl group, an ethyl group, a propyl group, a butyl group, and a hexyl group. R ₁₁ and R ₁₂ may be bonded to form a cyclopropene ring, a cyclobutylene ring, a cyclopentene ring, a cyclohexene ring, or the like.

Examples of the divalent organic linking group represented by A ₁₁ and A ₁₃ include a methylene group, an ethylene group, a butylene group, a hexylene group, an ethyleneoxy group, a polyethyleneoxy group, a butyleneoxy group, a polybutyleneoxy group, and an ethyleneoxycarbonyl group. Hexyleneoxycarbonyl group, methylene ester group, hexylene ester group, phenylene group, methylphenylene group, oxycarbonylphenylenecarbonyloxy group, and carbonyloxyphenyleneoxycarbonyl group.

A ₁₂ represents a trivalent group having an asymmetric carbon (chiral carbon).

In the general formula (2), A ₁₁ and A ₁₃ are preferably a methylene group, A ₁₂ is —CHR ₁₄ —, and R ₁₃ is an alkyl group having 2 to 12 carbon atoms or an alkylene group. At this time, R ₁₄ represents an alkyl group having 1 to 12 carbon atoms, an alkenyl group having 1 to 18 carbon atoms, an alkyloxy group having 1 to 18 carbon atoms, an alkylcarbonyloxy group having 1 to 18 carbon atoms, or a hydroxyl group. Preferably, R ₁₄ is an alkyl group having 1 to 4 carbon atoms (such as a methyl group, an ethyl group, a propyl group, or an isobutyl group).

When p is 1, the alkyl group having a molecular weight of 15 to 600 represented by R ₁₃ is a linear or branched alkyl group having 1 to 18 carbon atoms, specifically, methyl group, ethyl group, propyl group. Group, butyl group, hexyl, group, neopentyl group, dodecyl group, 2,2,4-octyl group, and the like.

The alkylene group having a molecular weight of 14 to 600 represented by R ₁₃ when p is 2 is a linear or branched alkylene group having 1 to 18 carbon atoms, specifically a methylene group, an ethylene group, or a propylene group. Butylene group, hexylene group, nepopentylene group, dodecylene group, 2,2,4-octylene group and the like.

Examples of the alkyleneoxy group represented by R ₁₃ when p is 1 include a hydroxy or alkoxy polyethyleneoxy group, a hydroxy or alkoxypolyproleneoxy group, a hydroxy or alkoxypolybutyleneoxy group, and the like. It is not limited.

R ₁₃ is preferably a linear or branched alkylene group having 1 to 18 carbon atoms, or a linear or branched alkyl group having 1 to 18 carbon atoms, and more preferably a linear or branched alkyl group having 4 to 12 carbon atoms. An alkylene group is a linear or branched alkyl group having 4 to 12 carbon atoms.

Further preferred maleimides include maleimides represented by the following general formulas (II) to (IV).

In the general formulas (II) to (IV), R ₁₄ is an alkyl group having 1 to 12 carbon atoms, an alkenyl group having 1 to 18 carbon atoms, an alkyloxy group having 1 to 18 carbon atoms, or an alkyl group having 1 to 18 carbon atoms. Represents an alkylcarbonyloxy group or a hydroxyl group. Preferably, an alkyl group having 1 to 4 carbon atoms (methyl group, ethyl group, propyl group, isobutyl group, etc.) can be used. p represents 1 or 2. R ₁₅ represents a linear alkyl group having 4 to 12 carbon atoms or an alkylene group.

Specific examples of the maleimide represented by the general formula (2) of the present invention are shown below.

Electron-donating monomer (D) The electron-donating monomer (D) contained in the inkjet ink of the present invention is a monomer having an electron-rich unsaturated bond. The value of the atomic charge of the carbon atom constituting the unsaturated bond of the electron donating monomer (D) is preferably −0.50 or less.

  The inkjet ink of the present invention contains vinyl ether as the electron donating monomer (D). The electron donating monomer (D) may be monofunctional or polyfunctional. The ratio of the weight of the vinyl ether to the total weight of the electron donating monomer (D) is preferably 80 to 100% by weight.

The monofunctional electron donating monomer (D) can be represented by the following general formula (6).

In the general formula (6), X represents —O—, —NR ₄ —, —S—, or —SO—. Y represents a hydrogen atom, a linear alkyl group, a branched alkyl group, a cycloalkyl group, an alkyl group having a hydroxyl group, an aryl group, or an arylalkyl group, and may further have a substituent. R ₁ , R ₂ , and R ₃ each independently represent a hydrogen atom, a linear alkyl group, a branched alkyl group, a cycloalkyl group, an alkyl group having a hydroxyl group, an aryl group, or an arylalkyl group; You may have. Further, a part of R ₂ or R ₃ and Y may be bonded to form a cyclic structure. Moreover, you may form the polyfunctional donor monomer which one part of Y has a 2 or more unsaturated bond through a coupling group.

  Specific examples of the monofunctional electron donating monomer (D) include, for example, alkenyl ethers such as vinyl ether and propenyl ether, alkenyl thioethers such as vinyl thioether and propenyl thioether, alkenyl sulfoxides such as vinyl sulfoxide and propenyl sulfoxide, Vinyl esters with a vinyl group bonded to the oxygen atom of the acid ester, vinylamines with a vinyl group bonded to the nitrogen atom of the amino group, vinylamides with a vinyl group bonded to the nitrogen atom of the amide group, vinyl to the nitrogen atom of the imidazole ring Examples include vinyl imidazole having a group bonded thereto, vinyl carbazole having a vinyl group bonded to a nitrogen atom of a carbazole ring, a cyclic 5-membered ring having a vinylene skeleton and an oxygen atom in the ring, and a cyclic 6-membered ring compound.

The monofunctional electron donating monomer (D) is more preferably a compound represented by the following general formulas (D-1) to (D-9).

In General Formulas (D-1) to (D-9), R ₅ to R ₉ are each independently a hydrogen atom, a linear alkyl group, a branched alkyl group, a cyclic alkyl group, an alkyl group having a hydroxyl group, or aryl. Represents a group or an arylalkyl group, and may further have a substituent. R ₅ to R ₉ may be a linking group for forming a polyfunctional polymerizable compound having two or more unsaturated bond moieties. Z represents —O—, —N (R ₁₀ ) — or —S—. R ₁₀ represents a hydrogen atom, a linear alkyl group, a branched alkyl group, a cyclic alkyl group, an alkyl group having a hydroxyl group, an aryl group, or an arylalkyl group, and may further have a substituent.

In General Formula (6), Y represents a hydrogen atom, a linear alkyl group, a branched alkyl group, a cycloalkyl group, an alkyl group having a hydroxyl group, an aryl group, or an arylalkyl group. X represents —O—, —N (R ₁₁ ) CO—, —NR ₄ —, —S—, or —SO—, R ₁₁ represents a hydrogen atom, an alkyl group, a cycloalkyl group, or an aryl group; R ₁₁ may be linked to Y to form a ring.

  Specific examples of the compound represented by the general formula (6) include vinyl thioether; vinyl methyl sulfoxide as a polymerizable monomer containing vinyl sulfoxide; vinyl-tert-butyl sulfide, vinyl methyl sulfide, vinyl ethyl sulfide and the like.

  The compound represented by the general formula (6) may be a polymerizable monomer having a vinylene skeleton and a 5-membered or 6-membered ring compound containing a nitrogen atom or an oxygen atom in the ring. Examples of the 5-membered or 6-membered ring compound include imidazole, pyrrole, furan, dihydrofuran, pyran, dihydropyran and the like.

  Specific examples of N-vinyl compounds having a structure in which a vinyl group is substituted on a nitrogen atom include N-vinylformamide, N-vinylcarbazole, N-vinylindole, N-vinylpyrrole, N-vinylacetamide, N-vinyl. Pyrrolidone, N-vinylcaprolactam, N-vinyl-N-ethylurea, N-vinyloxazolidone, N-vinylsuccinimide, N-vinylethylcarbamate and derivatives thereof are included. Among these compounds, N-vinylcaprolactam and N-vinylformamide are particularly preferable. N-vinylformamide can be obtained from, for example, Arakawa Chemical Industries, Ltd.

The monofunctional electron donating monomer (D) may be a monofunctional vinyl ether represented by the general formula (3). Monofunctional vinyl ethers are particularly preferred because they can increase the storage stability of inkjet inks.

In the formula (3), R ₃ , R ₄ and R ₅ represent a hydrogen atom, an alkyl group, a cycloalkyl group or an aryl group, and R ₆ represents an alkyl group, a cycloalkyl group or an aryl group.

  Examples of monofunctional vinyl ethers include n-propyl vinyl ether, isopropyl vinyl ether, n-butyl vinyl ether, isobutyl vinyl ether, 2-ethylhexyl vinyl ether, octadecyl vinyl ether, cyclohexyl vinyl ether, allyl vinyl ether, hydroxyethyl vinyl ether, hydroxybutyl vinyl ether, 9-hydroxynonyl Examples include vinyl ether, 4-hydroxycyclohexyl vinyl ether, cyclohexanedimethanol monovinyl ether, triethylene glycol monovinyl ether, triethylene glycol monomethyl vinyl ether, diethylene glycol monovinyl ether, and the like.

  The monofunctional vinyl ether may be other known various vinyl ethers. For example, a compound containing a (meth) acryloyl group and a vinyl ether group in the molecule disclosed in Japanese Patent No. 3461501, a vinyl ether having an alicyclic skeleton containing at least an oxygen atom disclosed in Japanese Patent No. 4037856, A vinyl ether having an alicyclic skeleton disclosed in Japanese Patent Application Laid-Open No. 2005-015396, 1-indanyl vinyl ether disclosed in Japanese Patent Application Laid-Open No. 2008-137974, 4 disclosed in Japanese Patent Application Laid-Open No. 2008-150341 -Acetoxycyclohexyl vinyl ether.

  The inkjet ink in the present invention may contain a polyfunctional electron donating monomer (D) together with the monofunctional electron donating monomer (D). Thereby, curing sensitivity, weather resistance and solvent resistance can be improved.

The polyfunctional electron donating monomer (D) is represented by the general formula (6). For example, in the general formulas (D-1) to (D-9) (preferably the general formula (D-1)), It is a polyfunctional polymerizable monomer having an electron-rich unsaturated bond in R ^{5 to} R ⁹ .

  Although the example of the polyfunctional electron donating monomer (D) represented by general formula (D-1)-(D-9) is shown, it is not limited to this. The electric charge which the carbon atom which comprises the unsaturated bond of the polyfunctional electron donating monomer (D) illustrated below has is -0.45 or less.

  Examples of bifunctional vinyl ethers include 1,4-butanediol divinyl ether, 1,6-hexanediol divinyl ether, neopentyl glycol divinyl ether, nonanediol divinyl ether, cyclohexane diol divinyl ether, cyclohexane dimethanol divinyl ether, diethylene glycol di Examples include vinyl ether, triethylene glycol divinyl ether (TEGDVE), trimethylolpropane divinyl ether, ethylene oxide-modified trimethylolpropane divinyl ether, pentaerythritol divinyl ether, and the like.

  Examples of the bifunctional vinyl ether include a vinyl ether having an alicyclic skeleton containing at least an oxygen atom disclosed in Japanese Patent No. 4037856, a vinyl ether having an alicyclic skeleton disclosed in Japanese Patent Laid-Open No. 2005-015396, There are 1-indanyl vinyl ether disclosed in JP-A-2008-137974, 4-acetoxycyclohexyl vinyl ether disclosed in JP-A-2008-150341, and the like.

  A compound in which a vinyl ether group of a bifunctional vinyl ether is substituted with a propenyl ether group, an isopropenyl ether group, a butenyl ether group or an isobutenyl ether group to introduce a substituent at the α-position or β-position of the vinyl ether group Can be used as a polyfunctional unsaturated compound.

  Among bifunctional vinyl ethers, when considering curability, adhesion, and surface hardness, diethylene glycol divinyl ether, triethylene glycol divinyl ether, cyclohexanediol divinyl ether, cyclohexane dimethanol divinyl ether, etc. are curable and compatible with various materials. In terms of odor and safety, it is preferable.

  Specific examples of trifunctional or higher polyfunctional vinyl ethers include trimethylolpropane trivinyl ether, ethylene oxide modified trimethylolpropane trivinyl ether, pentaerythritol trivinyl ether, pentaerythritol tetravinyl ether, ethylene oxide modified pentaerythritol trivinyl ether, ethylene oxide modified penta Examples include erythritol tetravinyl ether, dipentaerythritol hexavinyl ether, ethylene oxide-modified dipentaerythritol hexavinyl ether, and the like.

The trifunctional vinyl ether can be represented by the following general formula (A). As represented by the general formula (A), a compound having an oxyalkylene group in the molecule is preferable for obtaining compatibility and solubility with other ink components and adhesion to a substrate. The total number of oxyalkylene groups in the compound represented by formula (A) is preferably 10 or less. If it exceeds 10, the water resistance of the cured film may be lowered. The compound represented by the general formula (A) has an oxyethylene group, but the oxyethylene group may be another oxyalkylene group having a different carbon number. 1-4 are preferable and, as for carbon number of an oxyalkylene group, it is more preferable that it is 1 or 2.

In the general formula (A), R ₁₁ represents hydrogen or an organic group. Examples of the organic group represented by R ₁₁ include an alkyl group having 1 to 6 carbon atoms such as a methyl group, an ethyl group, a propyl group, or a butyl group, a fluoroalkyl group having 1 to 6 carbon atoms, an aryl group, and a furyl group. Or thienyl group, allyl group, 1-propenyl group, 2-propenyl group, 2-methyl-1-propenyl group, 2-methyl-2-propenyl group, 1-butenyl group, 2-butenyl group, 3-butenyl group, etc. An alkenyl group having 1 to 6 carbon atoms, phenyl group, benzyl group, fluorobenzyl group, aryl group such as methoxybenzyl group or phenoxyethyl group, alkoxy group such as methoxy group, ethoxy group and butoxy group, propylcarbonyl group, An alkylcarbonyl group having 1 to 6 carbon atoms such as a butylcarbonyl group or a pentylcarbonyl group, an ethoxycarbonyl group, a propoxycarbonyl group; Includes a group such as an alkoxycarbamoyl group having 1 to 6 carbon atoms such as a butoxycarbonyl group, an alkoxycarbamoyl group having 1 to 6 carbon atoms such as an ethoxycarbamoyl group, a propylcarbamoyl group or a butylpentylcarbamoyl group. It is not limited. Among these, as the organic group, a hydrocarbon group containing no hetero atom is preferable from the viewpoint of curability. Moreover, p, q, and r are 0 or an integer greater than or equal to 1, and p + q + r is an integer of 3-10.

Examples of the polyfunctional vinyl ether having 4 or more vinyl ether groups include compounds represented by the following general formulas (B) and (C).

In the general formula (B), R ₁₂ is a linking group containing any one of a methylene group, an alkylene group having 1 to 6 carbon atoms, an oxyalkylene group, and an ester group. p, q, l and m are each 0 or an integer of 1 or more, and the total number of p + q + l + m is an integer of 3 to 10.

In General Formula (C), R ₁₃ represents a linking group containing any of a methylene group, an alkylene group having 1 to 6 carbon atoms, an oxyalkylene group, and an ester group. p1, q1, r1, l1, m1, and s1 are each 0 or an integer of 1 or more, and the total number of p1 + q1 + r1 + l1 + m1 + s1 is an integer of 3 to 10.

  Although general formulas (B) and (C) show an oxyethylene group, the oxyethylene group may be an oxyalkylene group having a different carbon number. The oxyalkylene group preferably has 1, 3 or 4 carbon atoms.

  The ratio “(A) / (D)” of the functional group number of the electron-accepting monomer (A) to the functional group number of the electron-donating monomer (D) contained in the inkjet ink of the present invention is 70/30 to 35/65. It is. When the ratio “(A) / (D)” is too large, the adhesiveness of the image, which is a cured ink, is lowered, and the solvent resistance is easily lowered. When the ratio “(A) / (D)” is too small, the curing sensitivity of the ink is lowered, and the solvent resistance is easily lowered.

About the polymerizable monomer (X) which has a (meth) acrylic acid ester group The polymerizable monomer (X) has at least one (meth) acrylic ester group capable of radical polymerization in its molecule. That is, the polymerizable monomer (X) can be a monofunctional monomer having one (meth) acrylic acid ester group, a polyfunctional monomer having a plurality of (meth) acrylic acid ester groups, an oligomer or a polymer thereof. Depending on the type, various functions can be imparted when ink properties and on the substrate are cured.

  The ink-jet ink of the present invention may contain only one type of polymerizable monomer (X), and may contain two or more types of polymerizable monomers (X) at an arbitrary ratio in order to improve target properties. . It is preferable to use two or more kinds in combination for controlling performance such as reactivity and physical properties.

  The polymerizable monomer (X) has one or both of a methacrylic acid ester group and an acrylic acid ester group, but the skin irritation of the polymerizable monomer (X) having a methacrylic acid ester group is an acrylic acid ester group. Often, it is lower than the skin irritation of the polymerizable monomer (X) having.

  Examples of monofunctional polymerizable monomers (X) include aliphatic (meth) acrylates such as 2-ethylhexyl acrylate, lauryl acrylate, isooctyl acrylate and isostearyl acrylate; fats having cyclohexyl, tricyclodecanyl and isobornyl skeletons Cyclic (meth) acrylates; ether-based (meth) acrylates such as carbitol acrylate, 2-ethylhexyl carbitol acrylate and methoxytripropylene glycol acrylate; cyclic ether-based (meth) acrylates such as tetrahydrofurfuryl acrylate; 2-hydroxyethyl Examples include hydroxyl group-containing (meth) acrylates such as acrylate, 4-hydroxybutyl acrylate, and 2-hydroxypropyl acrylate.

  Specific examples of the monofunctional polymerizable monomer (X) include cyclohexyl acrylate, tetrahydrofurfuryl acrylate, benzyl acrylate, methylphenoxyethyl acrylate, 4-t-butylcyclohexyl acrylate, caprolactone-modified tetrahydrofurfuryl acrylate, tribromophenyl acrylate , Ethoxylated tribromophenyl acrylate, ethylene oxide adduct and propylene oxide adduct of 2-phenoxyethyl acrylate, acryloylmorpholine, phenoxydiethylene glycol acrylate, vinyl caprolactam, vinyl pyrrolidone, 2-hydroxy-3-phenoxypropyl acrylate, 1,4 -Cyclohexanedimethanol monoacrylate, 2-hydroxyethyl acrylate, 2-hydride Roxypropyl acrylate, 4-hydroxybutyl acrylate, isobutyl acrylate, t-butyl acrylate, isooctyl acrylate, 2-methoxyethyl acrylate, methoxytriethylene glycol acrylate, 2-ethoxyethyl acrylate, 3-methoxybutyl acrylate, ethoxyethoxyethyl acrylate , Butoxyethyl acrylate, ethoxydiethylene glycol acrylate, methoxydipropylene glycol acrylate, dipropylene glycol acrylate, β-carboxyl ethyl acrylate, ethyl diglycol acrylate, trimethylolpropane formal monoacrylate, imide acrylate, isoamyl acrylate, ethoxylated succinic acid acrylate, Trifluoroethyl Acrylate, cyclohexyl acrylate, 4-t-butyl cyclohexyl acrylate, isobornyl acrylate, 1,4-cyclohexanedimethanol monoacrylate, although etc. ω- carboxy polycaprolactone monoacrylate, but is not limited thereto.

  In some cases, the polyfunctional polymerizable monomer (X) is preferably a bifunctional monomer. Similar to the monofunctional monomer, the bifunctional monomer has a low viscosity and excellent dilutability, and can increase the strength of the ink cured product.

  Preferred examples of the bifunctional polymerizable monomer (X) include 1,4-butanediacrylate, 1,6-hexanediacrylate, 1,9-nonanediacrylate, branched neopentyl whose main skeleton is aliphatic. Glycol diacrylate is included. A bifunctional polymerizable monomer (X) obtained by subjecting an ethylene oxide adduct or a propylene oxide adduct to (meth) acrylate is preferable because of its low skin irritation. The bifunctional polymerizable monomer (X) is also preferably polyethylene glycol diacrylate or polypropylene glycol diacrylate. This is because it has a low molecular weight and a low viscosity.

  The bifunctional polymerizable monomer (X) having bisphenol A as the main skeleton is preferable because the cured shrinkage of the cured product containing the bisphenol A is small and the adhesion is enhanced and the toughness is increased. Tricyclodecane dimethanol diacrylate is preferred because it is excellent in scratch resistance and moisture resistance, and the cured product containing it has small cure shrinkage and less brittleness.

  The polyfunctional polymerizable monomer (X) having three or more (meth) acrylic acid ester groups is glycerin, trimethylolpropane, pentaerythritol, ditrimethylolpropane, dipentaerythritol, and their ethylene oxide adducts, propylene oxide. Examples include adducts, caprolactone adducts, alkylene adducts and the like obtained by (meth) acrylate conversion.

  The polyfunctional polymerizable monomer (X) is excellent in curability and has a high hardness of the cured product, but on the other hand, the curing shrinkage is large and the adhesion is poor. Many polyfunctional monomers have high viscosity and strong skin irritation. (Meth) acrylates such as ethylene oxide adducts, propylene oxide adducts, and caprolaclone adducts can reduce these disadvantages.

  Specific examples of the bifunctional polymerizable monomer (X) include dimethylol-tricyclodecane diacrylate, propoxylated bisphenol A di (meth) acrylate, ethoxylated bisphenol A di (meth) acrylate, cyclohexanedimethanol di (meth) ) Acrylate, dimethylol dicyclopentane diacrylate, ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, ethoxylated 1, 6-hexanediol diacrylate, neopentyl glycol di (meth) acrylate, polypropylene glycol diacrylate, 1,4-butanediol di (meth) acrylate, 1,9-nonanediol diacryl , Tetraethylene glycol diacrylate, 2-n-butyl-2-ethyl-1,3-propanediol diacrylate, neopentyl glycol diacrylate hydroxypivalate, 1,3-butylene glycol di (meth) acrylate, ethoxy Tripropylene glycol diacrylate, neopentyl glycol modified trimethylolpropane diacrylate, stearic acid modified pentaerythritol diacrylate, ethoxylated neopentyl glycol di (meth) acrylate, propoxylated neopentyl glycol di (meth) acrylate, tripropylene glycol Di (meth) acrylate, bisphenol A diacrylate, dimethylol-tricyclodecane diacrylate, propoxylated bisphenol A di (meth) acrylate , Ethoxylated bisphenol A di (meth) acrylate, bisphenol F diacrylate, ethoxylated bisphenol F diacrylate, propoxylated bisphenol F diacrylate, cyclohexanedimethanol di (meth) acrylate, dimethylol dicyclopentane diacrylate, isocyanuric acid di Examples thereof include, but are not limited to, acrylate and propoxylated isocyanuric acid diacrylate.

  Specific examples of the trifunctional or higher polyfunctional polymerizable monomer (X) include ethoxylated isocyanuric acid triacrylate, tri (2-hydroxyethyl isocyanurate) triacrylate, tri (meth) allyl isocyanurate, trimethylolpropane. Triacrylate, hydroxypivalate trimethylolpropane triacrylate, ethoxylated phosphate triacrylate, pentaerythritol triacrylate, tetramethylolpropane triacrylate, tetramethylol methane triacrylate, caprolactone modified trimethylolpropane triacrylate, propoxylate glyceryl triacrylate, Ethoxylated trimethylolpropane triacrylate, propoxylated trimethylolpropane triacrylate; tetramethylo Dimethylerythritol tetraacrylate, dipentaerythritol hydroxypentaacrylate, dipentaerythritol hexaacrylate, caprolactone-modified dipentaerythritol hexaacrylate; neo Examples include pentyl glycol oligoacrylate, 1,4-butanediol oligoacrylate, 1,6-hexanediol oligoacrylate, trimethylolpropane oligoacrylate, pentaerythritol oligoacrylate, and the like.

  The polymerizable monomer (X) may be an oligomer of a monomer having a (meth) acrylic acid ester group. Examples of the oligomer include an epoxy acrylate oligomer, a urethane acrylate oligomer, a polyester acrylate oligomer, and the like.

  Epoxy acrylate oligomers have a high curing rate and are not susceptible to air inhibition during curing. The cured product has high hardness and excellent heat resistance and chemical resistance. Moreover, since it has a hydroxyl group, the adhesiveness to a metal is also excellent. Epoxides containing a fluorene skeleton are less susceptible to oxygen inhibition than epoxides containing a bisphenol skeleton, have excellent curability, low cure shrinkage, and excellent adhesion.

  The urethane acrylate oligomer has high strength of the cured product and is excellent in extensibility and flexibility. Further, this physical property largely depends on the polyol, and various physical properties can be produced because of the rich variety of polyol components.

  The polyester acrylate oligomer is obtained by esterifying a polyester polyol composed of a polyol and a polybasic acid with acrylic acid. Polyester acrylate oligomers have a lower viscosity than other oligomers having the same molecular weight. Therefore, the polyester acrylate oligomer is easy to handle with no diluent. The hardness of the cured product of the polyester acrylate oligomer can be easily adjusted in a wide range from a flexible one to a high one.

  The polybutadiene acrylate oligomer is a hydrophobic oligomer, and the cured resin is excellent in water resistance and chemical resistance. Moreover, not only high toughness is shown, but also curing shrinkage is small and adhesion is good.

  Silicone acrylate oligomers may be blended into the ink alone, but they can be combined with other oligomers to impart weather resistance, abrasion resistance, water repellency, and flexibility to the cured ink. it can. The acrylate of phenylsiloxane improves the compatibility of other oligomers due to the effect of the phenyl group, and the cured product has a high refractive index and is also improved in flexibility and weather resistance.

  Furthermore, the polymerizable monomer (X) may be a commercially available product or a radically polymerizable and radically crosslinkable monomer, oligomer and polymer known in the industry. These are Shinzo Yamashita, “Cross-linking agent handbook” (Taisei, 1981); Kato Kiyomi, “UV / EB curing handbook (raw material)” (1985, Polymer publication society); , "Application and Market of UV / EB Curing Technology", p. 79, (1989, CMC); Eiichiro Takiyama, "Polyester Resin Handbook", (1988, Nikkan Kogyo Shimbun).

  The polymerizable monomer (X) has low skin irritation and sensitization (ease of rash) and has a relatively low viscosity. Therefore, a stable ink discharge property can be obtained by blending the polymerizable monomer (X) with the actinic ray curable ink, and the adhesion of the ink cured product to the substrate can be enhanced.

  Among them, many monofunctional polymerizable monomers (X) have a low viscosity. Therefore, it is preferably blended for adjusting the viscosity of the ink from the viewpoint of improving the emission property. Moreover, the crosslinking density of the ink cured product can be suppressed by blending the monofunctional polymerizable monomer (X). Therefore, the ink containing the monofunctional polymerizable monomer (X) can form a flexible cured film on a flexible substrate and can suppress the occurrence of curing shrinkage. In addition, the oligomer is easily dissolved in the monofunctional polymerizable monomer (X).

  Among monofunctional polymerizable monomers (X), inks containing acrylates having a cyclic skeleton such as tetrahydrofurfuryl acrylate and 2-phenoxyethyl acrylate have reduced cure shrinkage and increased adhesion and flexibility. . In particular, an ink blended with an acrylate having an alicyclic structure has low curing shrinkage, good weather resistance in addition to adhesion, and excellent heat resistance and wear resistance. Examples of the acrylate having an alicyclic structure include acrylates having a bicyclo ring structure or a tricyclo ring structure such as isobornyl acrylate, dicyclopentenyl acrylate, dicyclopentenyloxyethyl acrylate, and dicyclopentanyl acrylate.

  Moreover, the ink containing polyfunctional polymerizable monomer (X) and its oligomer has improved curing sensitivity, and the cured film has high scratch resistance, durability and weather resistance.

  The total amount of the electron-accepting monomer (A), the electron-donating monomer (D), and the polymerizable monomer (X) having a (meth) acrylate group in the ink is compared with the electron-accepting monomer (A) and the electron donating. The ratio of the total amount of the functional monomer (D) is preferably 25 to 90% by weight.

  The cured product of the charge transfer complex polymer composition containing the electron-accepting monomer (A) containing maleimide and the electron-donating monomer (D) containing vinyl ether or the like is rigid and can follow the flexible substrate. Problems such as difficulty in obtaining adhesion are likely to occur. On the other hand, since the inkjet ink of the present invention contains a certain amount of the polymerizable monomer (X), the ink cured product (image) has high flexibility, and the ink cured product has high adhesion to the substrate.

  The total amount of the electron accepting monomer (A) and the electron donating monomer (D) with respect to the sum of the electron accepting monomer (A), the electron donating monomer (D) and the polymerizable monomer (X) in the ink. When the ratio is high, the curing sensitivity increases. This is because charge transfer complex polymerization is likely to occur, and the curing sensitivity is less affected by the environment. Therefore, from the viewpoint of curing sensitivity, the electron-accepting monomer (A) and the electron-donating monomer (A), the electron-donating monomer (D), and the polymerizable monomer (X) are combined. It is preferable that the ratio of the total amount of D) is 50 to 90% by weight.

  On the other hand, the total of the electron-accepting monomer (A) and the electron-donating monomer (D) with respect to the total of the electron-accepting monomer (A), the electron-donating monomer (D), and the polymerizable monomer (X) in the ink. When the ratio of the amount is low, the flexibility of the ink cured film is increased and the curing shrinkage is also reduced. Therefore, in order to impart flexibility to the cured film, the electron-accepting monomer (A), the electron-accepting monomer (A), the electron-donating monomer (D), and the polymerizable monomer (X) are combined. The total amount of the electron donating monomer (D) is preferably 25 to 50% by weight.

  In the inkjet ink of the present invention, the electron-accepting monomer (A), the electron-donating monomer (B) and the polymerizable monomer (X) having a (meth) acrylic acid ester group, which are monomer components, and other components, For example, a photopolymerization initiator, a colorant such as a pigment, a dispersant, a radical polymerization inhibitor, and other additives may be included.

<Photopolymerization initiator>
The ink jet in the present invention preferably contains a photo radical polymerization initiator or a sensitizer as a photo polymerization initiator from the viewpoint of obtaining high sensitivity.

  The radical photopolymerization initiator contained in the inkjet ink of the present invention is preferably a molecular cleavage type or a hydrogen abstraction type. Specific examples of the radical photopolymerization initiator include benzoin isobutyl ether, 2,4-diethylthioxanthone, 2-isopropylthioxanthone, benzyl, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, 2-benzyl-2-dimethylamino- 1- (4-morpholinophenyl) -butan-1-one, bis (2,6-dimethoxybenzoyl) -2,4,4-trimethylpentylphosphine oxide, bis (2,4,6-trimethylbenzoyl) -phenylphosphine An oxide or the like is preferably used.

  Further, as molecular cleavage type photopolymerization initiators, 1-hydroxycyclohexyl phenyl ketone, benzoin ethyl ether, benzyldimethyl ketal, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1- (4-isopropylphenyl) -2-Hydroxy-2-methylpropan-1-one and 2-methyl-1- (4-methylthiophenyl) -2-morpholinopropan-1-one, 1- [4- (2-hydroxyethoxy) -phenyl] -2-Hydroxy-2-methyl-1-propan-1-one may be used in combination.

  Further, examples of the hydrogen abstraction type photopolymerization initiator include benzophenone, 4-phenylbenzophenone, isophthalphenone, 4-benzoyl-4′-methyl-diphenyl sulfide, and bis (2,4- 1,2-octanedione, a polymerization initiator of cyclopentadiene-1-yl) -bis (2,6-difluoro-3- (1H-pyrrol-1-yl) -phenyl) titanium, an oxime ester type -(4- (phenylthio) -2- (O-benzoyloxime)), ethanone, 1- (9-ethyl-6- (2-methylbenzoyl) -9H-carbazol-3-yl)-, 1- (O -Acetyl oxime).

  A sensitizer can be used in combination with the radical photopolymerization initiator. Examples of sensitizers include trimethylamine, methyldimethanolamine, triethanolamine, p-diethylaminoacetophenone, ethyl p-dimethylaminobenzoate, isoamyl p-dimethylaminobenzoate, N, N-dimethylbenzylamine and 4, Amines that do not cause an addition reaction with a radically polymerizable monomer such as 4′-bis (diethylamino) benzophenone are included. Of course, it is preferable to select and use a radical photopolymerization initiator and a sensitizer that are excellent in solubility in the polymerizable monomer.

  The content of the photo radical polymerization initiator and the sensitizer in the inkjet ink is preferably 0.1 to 20% by mass, more preferably 1 to 12% by mass with respect to the total mass of the inkjet ink.

  Other examples of the radical photopolymerization initiator include a type in which an amine-based initiator aid is bonded as an initiator structure to a dendrimer core described in European Patent 1,674,499A, European Patent 2,161. , 264A, European Patent 2,189,477A, an initiator having a polymerizable group, an amine-based initiator, a plurality of those described in European Patent 1,927,632B1 A type having an amine-based initiator in one molecule, a type having a plurality of thioxanthones in the molecule described in WO2009 / 060235, represented by ESACURE ONE and ESACUR KIP150 marketed by Lamberti An oligomer type polymerization initiator in which α-hydroxypropiophenone is bonded to the side chain is also included.

  Further, maleimide, which is a polymerizable monomer, can itself act as a photopolymerization initiator.

<Colorant>
When coloring the inkjet ink of this invention, it is preferable to contain a pigment as a coloring agent. The pigment may be a colorless inorganic pigment such as carbon black, titanium oxide, calcium carbonate, or a colored organic pigment.

  Examples of organic pigments include insoluble azo pigments such as toluidine red, toluidine maroon, Hansa yellow, benzidine yellow, pyrazolone red, soluble azo pigments such as ritol red, heliobordeaux, pigment scarlet, permanent red 2B; alizarin, indanthrone Derivatives from vat dyes such as thioindigo maroon; phthalocyanine organic pigments such as phthalocyanine blue and phthalocyanine green; quinacridone organic pigments such as quinacridone red and quinacridone magenta; perylene organic pigments such as perylene red and perylene scarlet; Isoindolinone organic pigments such as indolinone yellow and isoindolinone orange; pyranthrone organic pigments such as pyranthrone red and pyranthrone orange; thioindigo Machine pigments, condensed azo organic pigments, benzimidazolone organic pigments, quinophthalone organic pigments such as quinophthalone yellow; isoindoline organic pigments such as isoindoline yellow; other pigments such as flavanthron yellow, acylamide yellow, nickel Azo yellow, copper azomethine yellow, perinone orange, anthrone orange, dianthraquinonyl red, dioxazine violet and the like are included.

  Organic pigments are exemplified below by color index (CI) numbers.

C. I. Pigment Yellow 12, 13, 14, 17, 20, 24, 74, 83, 86, 93, 109, 110, 117, 120, 125, 128, 129, 137, 138, 139, 147, 148, 150, 151, 153, 154, 155, 166, 168, 180, 185;
C. I. Pigment orange 16, 36, 43, 51, 55, 59, 61;
C. I. Pigment Red 9, 48, 49, 52, 53, 57, 97, 122, 123, 149, 168, 177, 180, 192, 202, 206, 215, 216, 217, 220, 223, 224, 226, 227, 228, 238, 240;
C. I. Pigment violet 19, 23, 29, 30, 37, 40, 50;
C. I. Pigment blue 15, 15: 1, 15: 3, 15: 4, 15: 6, 22, 60, 64;
C. I. Pigment green 7, 36;
C. I. Pigment Brown 23, 25, 26.

  Among the above pigments, quinacridone-based, phthalocyanine-based, benzimidazolone-based, isoindolinone-based, condensed azo-based, quinophthalone-based, and isoindoline-based organic pigments are preferable because of excellent light resistance.

  The organic pigment is preferably fine particles having an average particle diameter in the ink of 10 to 150 nm as measured by laser scattering. When the average particle size of the pigment is less than 10 nm, the light resistance is lowered due to the small particle size, and when it exceeds 150 nm, it is difficult to maintain stable dispersion, and the precipitation of the pigment is likely to occur. Stability is lowered, and a problem that minute mist called satellite occurs. However, in the case of titanium oxide, the average particle diameter is 150 to 300 nm, preferably 180 to 250 nm, in order to provide whiteness and concealment.

  In addition, it is preferable that coarse particles are removed by sufficient dispersion or filtration so that the maximum particle size of the pigment in the ink does not exceed 1.0 μm. When coarse particles are present, the ejection stability tends to decrease.

  The organic pigment can be refined by the following method. That is, a mixture comprising at least three components of an organic pigment, a water-soluble inorganic salt of 3 mass times or more of the organic pigment, and a water-soluble solvent is made into a clay, kneaded with a kneader or the like, and then poured into water. Stir with a speed mixer to make a slurry. Next, filtration and washing of the slurry are repeated, and the water-soluble inorganic salt and the water-soluble solvent are removed by aqueous treatment. In the miniaturization step, a resin, a pigment dispersant and the like may be added.

  Examples of the water-soluble inorganic salt include sodium chloride and potassium chloride. These inorganic salts are used in the range of 3 to 20 times the mass of the organic pigment, but after the dispersion treatment, chlorine ions (halogen ions) are removed by washing with water. When the amount of the inorganic salt is less than 3 times by mass, a treated pigment having a desired size cannot be obtained. When the amount is more than 20 times by mass, the cleaning process in the subsequent step is enormous, and the substantial processing amount of the organic pigment is reduced.

  The water-soluble solvent is not particularly limited as long as it is a solvent that can be used for making an appropriate clay state of an organic pigment and a water-soluble inorganic salt used as a crushing aid and performing sufficient crushing efficiently, and is soluble in water. However, since the temperature rises during kneading and the solvent easily evaporates, a high boiling point solvent having a boiling point of 120 to 250 ° C. is preferable from the viewpoint of safety. As water-soluble solvent, 2- (methoxymethoxy) ethanol, 2-butoxyethanol, 2- (i-pentyloxy) ethanol, 2- (hexyloxy) ethanol, diethylene glycol, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether , Triethylene glycol, triethylene glycol monomethyl ether, liquid polyethylene glycol, 1-methoxy-2-propanol, 1-ethoxy-2-propanol, dipropylene glycol, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, low molecular weight Examples include polypropylene glycol.

  The pigment may be surface-treated by a known technique such as an acid treatment or a basic treatment, a synergist, or various coupling agents. This is because the adsorption with the pigment dispersant is promoted to ensure dispersion stability.

  The pigment content in the ink-jet ink is preferably 1.5 to 8% by mass in order to obtain a sufficient concentration and sufficient light resistance, but in the case of a white ink containing titanium oxide as a pigment, it is 10 to 30% by mass. % Is preferably included.

<Pigment dispersant>
Pigment dispersants include hydroxyl group-containing carboxylic acid esters, salts of long chain polyaminoamides and high molecular weight acid esters, salts of high molecular weight polycarboxylic acids, salts of long chain polyaminoamides and polar acid esters, high molecular weight unsaturated acid esters, Polymer copolymer, modified polyurethane, modified polyacrylate, polyether ester type anionic activator, naphthalene sulfonic acid formalin condensate salt, aromatic sulfonic acid formalin condensate salt, polyoxyethylene alkyl phosphate ester, polyoxyethylene nonyl Examples thereof include phenyl ether, stearylamine acetate, and pigment derivatives.

  Specific examples of the pigment dispersant include “Anti-Terra-U (polyaminoamide phosphate)”, “Anti-Terra-203 / 204 (high molecular weight polycarboxylate)” manufactured by BYK Chemie, “Disperbyk-101”. (Polyaminoamide phosphate and acid ester), 107 (hydroxyl group-containing carboxylic acid ester), 110 (copolymer containing an acid group), 130 (polyamide), 161, 162, 163, 164, 165, 166, 170 (high Molecular copolymer) ”,“ 400 ”,“ Bykumen ”(high molecular weight unsaturated acid ester),“ BYK-P104, P105 (high molecular weight unsaturated acid polycarboxylic acid) ”,“ P104S, 240S (high molecular weight unsaturated) Acid polycarboxylic acid and silicone) "," Lactimon (long-chain amine and unsaturated acid polycal And the like and phosphate Silicone) ".

  “Efka 44, 46, 47, 48, 49, 54, 63, 64, 65, 66, 71, 701, 764, 766” manufactured by Efka CHEMICALS, “Efka Polymer 100 (modified polyacrylate), 150 (aliphatic) Modified polymer), 400, 401, 402, 403, 450, 451, 452, 453 (modified polyacrylate), 745 (copper phthalocyanine type) ”;“ Floren TG-710 (urethane oligomer) ”manufactured by Kyoei Chemical Co., Ltd.,“ “Flonon SH-290, SP-1000”, “Polyflow No. 50E, No. 300 (acrylic copolymer)”; “Disparon KS-860, 873SN, 874 (polymer dispersing agent)” manufactured by Enomoto Kasei Co., Ltd., # 2150 (aliphatic polyvalent carboxylic acid), # 7004 (polyether ester type) "etc. are also pigments It can be a powder.

  Furthermore, “Demol RN, N (Naphthalenesulfonic acid formalin condensate sodium salt), MS, C, SN-B (aromatic sulfonic acid formalin condensate sodium salt), EP”, “Homogenol L-18” manufactured by Kao Corporation. (Polycarboxylic acid type polymer) "," Emulgen 920, 930, 931, 935, 950, 985 (polyoxyethylene nonyl phenyl ether) "," Acetamine 24 (coconut amine acetate), 86 (stearyl amine acetate) "; “Solspers 5000 (phthalocyanine ammonium salt type), 13240, 13940 (polyesteramine type), 17000 (fatty acid amine type), 24000, 32000, 7000” manufactured by Zeneca Corporation; “Nikkor T106 (polyoxyethylenesorbitan) manufactured by Nikko Chemical Mo Oleate), MYS-IEX (polyoxyethylene monostearate), Hexagline4-0 (hexaglyceryl ruthenate Huwei rate) ", also manufactured by Ajinomoto Fine-Techno Co., of AJISPER 821,822,824 etc. can be a pigment dispersing agent.

  The content of the pigment dispersant in the inkjet ink is 5 to 70 parts by mass, preferably 10 to 50 parts by mass with respect to 100 parts by mass of the pigment. If the amount is less than 5 parts by mass, dispersion stability may be difficult to obtain. If the amount is more than 70 parts by mass, the ejection stability may be deteriorated.

<Radical polymerization inhibitor>
The inkjet ink in the present invention may contain a radical polymerization inhibitor from the viewpoint of storage stability. Ink jet ink may generate radicals under the influence of heat or light during storage, and radical polymerization reaction may occur. By adding a radical polymerization inhibitor to the inkjet ink, radical polymerization that occurs during storage is suppressed. Since the ink-jet ink of the present invention is extremely excellent in photocurability, it is very preferable to add a radical polymerization inhibitor.

  Examples of radical polymerization inhibitors include phenolic hydroxyl group-containing compounds, methoquinone (hydroquinone monomethyl ether), hydroquinone, 4-methoxy-1-naphthol, hindered amine antioxidants, 1,1-diphenyl-2-picrylhydrazyl. Free radicals, N-oxide compounds, piperidine 1-oxyl free radical compounds, pyrrolidine 1-oxyl free radical compounds, N-nitrosophenylhydroxylamines, nitrogen-containing heterocyclic mercapto compounds, thioether antioxidants, hinders Dophenol antioxidants, ascorbic acids, zinc sulfate, thiocyanates, thiourea derivatives, various sugars, phosphate antioxidants, nitrites, sulfites, thiosulfates, hydroxylamine derivatives, dicyandiamide and polyalkylene poly Polycondensates of emissions, include phenothiazines, and the like.

  Specific examples of the radical polymerization inhibitor include the following compounds.

  Examples of phenolic compounds as radical polymerization inhibitors include phenol, alkylphenols such as o-, m- or p-cresol (methylphenol), 2-t-butyl-4-methylphenol, 6-t-butyl. -2,4-dimethylphenol, 2,6-di-t-butyl-4-methylphenol, 2-t-butylphenol, 4-t-butylphenol, 2,4-di-t-butylphenol, 2-methyl-4 -t-butylphenol, 4-t-butyl-2,6-dimethylphenol, or 2,2'-methylene-bis- (6-t-butyl-methylphenol), 4,4'-oxydiphenyl, 3,4 -Methylenedioxydiphenol (sesame oil), 3,4-dimethylphenol, benzcatechin (1,2-dihydroxybenzol), 2- (1'-methylcyclohexyl-1'-yl) -4,6-dimethylphenol 2- (1'-F Nyleth-1'-yl) phenol, 4- (1'-phenyleth-1'-yl) phenol, 2-t-butyl-6-methylphenol, 2,4,6-tris-t-butylphenol, 2,6 -Di-t-butylphenol, nonylphenol [CAS-Nr. 11066-49-2], octylphenol [CAS-Nr. 140-66-9], 2,6-dimethylphenol, bisphenol A, bisphenol B, bisphenol C, bisphenol F, bisphenol S, 3,3 ′, 5,5′-tetrabromobisphenol A, 2,6-di- t-Butyl-p-cresol, BASF Aktiengesellschaft, Koresin, 3,5-di-t-butyl-4-hydroxybenzoic acid methyl ester, 4-t-butylbenzcatechin, 2-hydroxybenzyl alcohol, 2- Methoxy-4-methylphenol, 2,3,6-trimethylphenol, 2,4,5-trimethylphenol, 2,4,6-trimethylphenol, 2-isopropylphenol, 4-isopropylphenol, 6-isopropyl-m- Cresol, n-octadecyl-β- (3,5-di-t-butyl-4-hydroxyphenyl) Pionate, 1,1,3-tris- (2-methyl-4-hydroxy-5-t-butylphenyl) butane, 1,3,5-trimethyl-2,4,6-tris- (3,5-di-) -t-butyl-4-hydroxybenzyl) benzol, 1,3,5-tris- (3,5-di-t-butyl-4-hydroxybenzyl) isocyanurate, 1,3,5-tris- (3, 5-Di-tert-butyl-4-hydroxyphenyl) propionyloxyethyl-isocyanurate, 1,3,5-tris- (2,6-dimethyl-3-hydroxy-4-tert-butylbenzyl) isocyanurate or penta Erythlit-tetrakis- [β- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], 2,6-di-t-butyl-4-dimethylaminomethylphenol, 6-s-butyl- 2,4-dinitrophenol, Firma Ciba Specialiaetenc Emie Irganox 565, 1010, 1076, 1141, 1192, 1222 and 1425, 3- (3 ′, 5′-di-t-butyl-4′-hydroxyphenyl) propionic acid octadecyl ester, 3- ( 3 ', 5'-di-t-butyl-4'-hydroxyphenyl) propionic acid hexadecyl ester, 3- (3', 5'-di-t-butyl-4'-hydroxyphenyl) propionic acid octyl ester, 3-thia-1,5-pentanediol-bis- [3 ′, 5′-di-t-butyl-4′-hydroxyphenyl) propionate], 4,8-dioxa-1,11-undecandiol-bis- [3 ', 5'-di-t-butyl-4'-hydroxyphenyl) propionate], 4,8-dioxa-1,11-undecandiol-bis-[(3'-t-butyl-4'-hydroxy -5′-methylphenyl) propionate], , 9-nonanediol-bis-[(3 ′, 5′-di-t-butyl-4′-hydroxyphenyl) propionate], 1,7-heptanediamine-bis [3- (3 ′, 5′-di -t-butyl-4'-hydroxyphenyl) propionic acid amide], 1,1-methanediamine-bis [3- (3 ', 5'-di-t-butyl-4'-hydroxyphenyl) propionic acid amide] 3- (3 ′, 5′-di-t-butyl-4′-hydroxyphenyl) propionic acid hydrazide, 3- (3 ′, 5′-dimethyl-4′-hydroxyphenyl) propionic acid hydrazide, bis- ( 3-t-butyl-5-ethyl-2-hydroxyphen-1-yl) methane, bis- (3,5-di-t-butyl-4-hydroxyphen-1-yl) methane, bis- [3- (1′-Methylcyclohex-1′-yl) -5-methyl-2-hydroxyphen-1-yl] methane, bis- (3-tert-butyl-2-hydroxy-5-methyl) Ruphen-1-yl) methane, 1,1-bis- (5-tert-butyl-4-hydroxy-2-methylphen-1-yl) ethane, bis- (5-tert-butyl-4-hydroxy-2-) Methylphen-1-yl) sulfide, bis- (3-tert-butyl-2-hydroxy-5-methylphen-1-yl) sulfide, 1,1-bis- (3,4-dimethyl-2-hydroxypheny-1) -Yl) -2-methylpropane, 1,1-bis- (5-tert-butyl-3-methyl-2-hydroxyphen-1-yl) butane, 1,3,5-tris- [1 ′-( 3 ", 5" -di-t-butyl-4 "-hydroxyphen-1" -yl) methy-1'-yl] -2,4,6-trimethylbenzol, 1,1,4- Aminophenols such as tris- (5′-t-butyl-4′-hydroxy-2′-methylphen-1′-yl) butane, t-butylcatechol, p-aminophenol, p-nitrosophenol and p-nitroso- -Nitrosophenol such as cresol, 2-methoxyphenol (guaiacol, benzcatechin monomethyl ether), 2-ethoxyphenol, 2-isopropoxyphenol, 4-methoxyphenol (hydroquinone monomethyl ether), mono- or di-t-butyl- 4-methoxyphenol, 3,5-di-t-butyl-4-hydroxyanisole, 3-hydroxy-4-methoxybenzyl alcohol, 2,5-dimethoxy-4-hydroxybenzyl alcohol (syringa alcohol), 4-hydroxy -3-Methoxybenzaldehyde (vanillin), 4-hydroxy-3-ethoxybenzaldehyde (ethylvanillin), 3-hydroxy-4-methoxybenzaldehyde (isovanillin), 1-((4-hydroxy-3-methoxyphenyl) ethanone (aceto Vanillin), Eugeno , Alkoxyphenols such as dihydroeugenol and isoeugenol, tocopherols such as α-, β-, γ-, δ- and ε-tocopherol, tocol, α-tocopherol hydroquinone, and 2,3-dihydro-2,2- Dimethyl-7-hydroxybenzofuran (2,2-dimethyl-7-hydroxycoumaran) and the like are included.

  Examples of quinones and hydroquinones as radical polymerization inhibitors include hydroquinone or hydroquinone monomethyl ether (4-methoxyphenol), methylhydroquinone, 2,5-di-t-butylhydroquinone, 2-methyl-p-hydroquinone, 2, 3-dimethylhydroquinone, trimethylhydroquinone 4-methylbenzcatechin, t-butylhydroquinone, 3-methylbenzcatechin, benzoquinone, 2-methyl-p-hydroquinone, 2,3-dimethylhydroquinone, trimethylhydroquinone, t-butylhydroquinone, 4 -Ethoxyphenol, 4-butoxyphenol, hydroquinone monobenzyl ether, p-phenoxyphenol, 2-methylhydroquinone, tetramethyl-p-benzoquinone, diethyl-1,4-cyclohexanedione-2,5-dicarboxylate, phenyl -p-benzoquinone, 2,5-dimethyl-3-benzyl-p-benzoquinone, 2-isopropyl-5-methyl-p-benzoquinone (thymoquinone), 2,6-diisopropyl-p-benzoquinone, 2,5-dimethyl- 3-hydroxy-p-benzoquinone, 2,5-dihydroxy-p-benzoquinone, embellin, tetrahydroxy-p-benzoquinone, 2,5-dimethoxy-1,4-benzoquinone, 2-amino-5-methyl-p-benzoquinone 2,5-bisphenylamino-1,4-benzoquinone, 5,8-dihydroxy-1,4-naphthoquinone, 2-anilino-1,4-naphthoquinone, anthraquinone, N, N-dimethylindoaniline, N, N -Diphenyl-p-benzoquinonediimine, 1,4-benzoquinonedioxime, cerlignon, 3,3'-di-t-butyl-5,5'-dimethyldiphenoquinone, p-rosoleic acid (orin), 2, 6- Di-t-butyl-4-benzylidene-benzoquinone, 2,5-di-t-butyl-amylhydroquinone and the like are included.

  Examples of N-oxyl compounds as radical polymerization inhibitors (nitroxyl- or N-oxyl-groups, compounds having at least one> NO- group) include 4-hydroxy-2,2,6, 6-tetramethylpiperidine-N-oxyl, 4-oxo-2,2,6,6-tetramethylpiperidine-N-oxyl, 4-methoxy-2,2,6,6-tetramethylpiperidine-N-oxyl, 4-acetoxy-2,2,6,6-tetramethylpiperidine-N-oxyl, 2,2,6,6-tetramethylpiperidine-N-oxyl, BASF Aktinengesellschaft Ubinul 4040P, 4,4 ′, 4 ″ -tris- (2,2,6,6-tetramethylpiperidine-N-oxyl) phosphite, 3-oxo-2,2,5,5-tetramethylpyrrolidine-N-oxyl, 1-oxyl- 2,2,6,6-tetramethyl-4-me Toxipiperidine, 1-oxyl-2,2,6,6-tetramethyl-4-trimethylsilyloxypiperidine, 1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl-2-ethylhexanoate 1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl-sebacate, 1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl-stearate, 1-oxyl- 2,2,6,6-tetramethylpiperidin-4-yl-benzoate, 1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl- (4-t-butyl) benzoate, bis- ( 1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl) succinate, bis- (1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl) adipate, 1,10 -Decandioic acid-bis- (1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl Esters, bis- (1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl) n-butylmalonate, bis- (1-oxyl-2,2,6,6-tetramethylpiperidine- 4-yl) phthalate, bis- (1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl) isophthalate, bis- (1-oxyl-2,2,6,6-tetramethylpiperidine -4-yl) terephthalate, bis- (1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl) hexahydroterephthalate, N, N′-bis- (1-oxyl-2,2, 6,6-tetramethylpiperidin-4-yl) adipinamide, N- (1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl) caprolactam, N- (1-oxyl-2,2) , 6,6-Tetramethylpiperidin-4-yl) dodecylsuccinimide, 2,4,6-tris- [N-butyl -N- (1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl] triazine, N, N'-bis- (1-oxyl-2,2,6,6-tetramethylpiperidine- 4-yl) -N, N′-bis-formyl-1,6-diaminohexane, 4,4′-ethylene-bis- (1-oxyl-2,2,6,6-tetramethylpiperazin-3-one ) Etc. are included.

  Examples of aromatic amines or phenylenediamines as radical polymerization inhibitors include N, N-diphenylamine, N-nitroso-diphenylamine, nitrosodiethylaniline, p-phenylenediamine, N, N′-diisobutyl-p-phenylenediamine, N, N′-dialkyl-p-phenylenediamine, such as N, N′-diisopropyl-p-phenylenediamine (the two alkyl groups may be the same or different, each containing 1 to 4 carbon atoms, Or Irganox 5057 (Firma Ciba Spezialitaetenchemie), N-phenyl-p-phenylenediamine, N, N′-diphenyl-p-phenylenediamine, N-isopropyl-N-phenyl-p-phenylenediamine N, N'-di-s-butyl-p-phenylenediamine (BASF Aktiengesellschaft's Kerobit BPD), N-pheny -N'-isopropyl-p-phenylenediamine (Vulkanox 4010 from Bayer AG), N- (1,3-dimethylbutyl) -N'-phenyl-p-phenylenediamine, N-phenyl-2-naphthylamine , Iminodibenzyl, N, N′-diphenylbenzidine, N-phenyltetraaniline, acridone, 3-hydroxydiphenylamine, 4-hydroxydiphenylamine and the like.

  Examples of imines as radical polymerization inhibitors include methylethylimine, (2-hydroxyphenyl) benzoquinoneimine, (2-hydroxyphenyl) benzophenoneimine, N, N-dimethylindoaniline, thionine (7-amino-3- Imino-3H-phenothiazine), methylene violet (7-dimethylamino-3-phenothiazine) and the like.

  Examples of sulfonamides as radical polymerization inhibitors include N-methyl-4-toluolsulfonamide, Nt-butyl-4-toluolsulfonamide, Nt-butyl-N-oxyl-4-toluene. Allsulfonamide, N, N′-bis (4-sulfanylamide) piperidine, 3-{[5- (4-aminobenzoyl) -2,4-dimethylbenzoylsulfonyl] ethylamino} -4-methylbenzolsulfonic acid, etc. Is included.

  Examples of oximes as radical polymerization inhibitors include aldoxime, ketoxime or amidoxime, preferably diethyl ketoxime, acetoxime, methyl ethyl ketoxime, cyclohexanone oxime, benzaldehyde oxime, benzyldioxime, dimethylglyoxime, 2-pyridine aldoxime, salicyl. Aldoxime, phenyl-2-pyridylketoxime, 1,4-benzoquinone dioxime, 2,3-butanedione dioxime, 2,3-butanedione monooxime, 9-fluorenone oxime, 4-t-butyl-cyclohexanone oxime N-ethoxy-acetimidic acid ethyl ester, 2,4-dimethyl-3-pentanone oxime, cyclododecanone oxime, 4-heptanone oxime and di-2-furanylethanedione dioxime. Other examples of oximes include their reaction with other aliphatic or aromatic oximes or alkyl transfer agents such as alkyl halogenides, -triflate, -sulfonate, -tosylate, -carbonate, -sulfate, -phosphate, etc. It may be a product.

  Examples of hydroxylamine as a radical polymerization inhibitor include N, N-diethylhydroxylamine, compounds described in the international patent application PCT / EP2003 / 03139.

  The urea derivative as the radical polymerization inhibitor is, for example, urea or thiourea.

  Examples of phosphorus-containing compounds as radical polymerization inhibitors include triphenylphosphine, triphenyl phosphite, hypophosphorous acid, trinonyl phosphite, triethyl phosphite or diphenylisopropylphosphine.

  Examples of sulfur-containing compounds as radical polymerization inhibitors include diphenyl sulfide, phenothiazine and sulfur-containing natural materials such as cysteine.

  Complexing agents based on tetraazaannulene (TAA) as radical polymerization inhibitors are described, for example, in Chem. Soc. Rev. 1998, 27, 105-115, for example, dibenzotetraaza [14] ring and porphyrin.

  Other examples of radical polymerization inhibitors include carbon salts, chlorides, dithiocarbamic acid, sulfuric acid, salicylic acid, acetic acid, stearic acid, ethylhexanoic acid and other metal salts (copper, manganese, cerium, nickel, chromium, etc.) It is.

  Further, the N-oxyl free radical compound having a vinyl ether functional group described in Macromol. Rapid Commun., 28, 1929 (2007) has both a polymerizable function and a radical scavenging function in the same molecule. N-oxyl free radical compounds can also be added to the inkjet ink of the present invention from the viewpoints of curability and ink storage stability. A polymer obtained by polymerization using an N-oxyl free radical compound has a free radical in the side chain. Such a polymer can also be added to the inkjet ink of the present invention from the viewpoints of cured film properties such as solvent resistance, scratch resistance, and weather resistance, and ink storage stability.

  The content of the radical polymerization inhibitor in the inkjet ink (per 1 g) is preferably 1.0 to 5000 μg, and more preferably 10 to 2000 μg. If it is 1.0 μg / g or more, desired storage stability can be obtained, ink thickening and liquid repellency with respect to the ink jet nozzle can be obtained, and this is preferable from the viewpoint of ejection stability. Moreover, if it is 5000 microgram / g ink or less, the high generation sensitivity can be maintained, without impairing the acid generation efficiency of a polymerization initiator.

<Other additives>
The ink-jet ink may further contain various additives as necessary. Examples of various additives include surfactants, lubricants, fillers, antifoaming agents, gelling agents, thickeners, specific resistance adjusting agents, film forming agents, ultraviolet absorbers, antioxidants, anti-fading agents, Anti-corrosive agent, rust preventive agent, etc. are included. These are added according to the purpose of improving ejection stability, compatibility with a print head or ink packaging container, storage stability, image storage stability, and other various performances. Furthermore, it can contain a small amount of solvent such as ester solvent, ether solvent, ether ester solvent, ketone solvent, aromatic hydrocarbon solvent, nitrogen-containing organic solvent.

  Specific examples of the solvent include dimethyl sulfoxide, diethyl sulfoxide, methyl ethyl sulfoxide, diphenyl sulfoxide, tetraethylene sulfoxide, dimethyl sulfone, methyl ethyl sulfone, methyl-isopropyl sulfone, methyl-hydroxyethyl sulfone, sulfolane, or N-methyl- 2-pyrrolidone, 2-pyrrolidone, β-lactam, N, N-dimethylformamide, N, N-diethylformamide, N, N-dimethylacetamide, 1,3-dimethyl-2-imidazolidinone, 3-methyl-2 -Oxazolidinone, γ-butyrolactone, γ-valerolactone, isophorone, cyclohexanone, propylene carbonate, anisole, methyl ethyl ketone, acetone, ethyl lactate, butyl lactate, dioxane, ethyl acetate, butyl acetate, diethylene glycol Methyl ether, dibasic ester, methoxybutyl acetate, and the like. When a solvent is added to the ink in an amount of 1.5 to 30%, preferably 1.5 to 15%, adhesion to a resin recording medium such as polyvinyl chloride is improved.

  Other specific examples of the solvent include alkylene glycol monoalkyl ethers such as diethylene glycol monoethyl ether, triethylene glycol monomethyl ether, dipropylene glycol monomethyl ether, tripropylene glycol monomethyl ether, ethylene glycol dibutyl ether, tetraethylene glycol dimethyl ether, etc. Alkylene glycol dialkyl ethers, alkylene glycol monoalkyl ether acetates such as ethylene glycol monobutyl ether acetate, diethylene glycol diethyl ether, dipropylene glycol dimethyl ether, dipropylene glycol diethyl ether, ethylene glycol diacetate, propylene glycol diacetate .

  Examples of the surfactant contained in the inkjet ink of the present invention include anionic surfactants such as dialkylsulfosuccinates, alkylnaphthalenesulfonates, fatty acid salts, polyoxyethylene alkyl ethers, polyoxyethylene alkyl allyl ethers , Nonionic surfactants such as acetylene glycols, polyoxyethylene / polyoxypropylene block copolymers, cationic surfactants such as alkylamine salts and quaternary ammonium salts, silicone-based and fluorine-based surfactants Etc. are included. In particular, a silicone-based or fluorine-based surfactant is preferable.

  By adding a silicone-based or fluorine-based surfactant, it is possible to further suppress ink mixing on recording media made of various hydrophobic resins such as vinyl chloride sheets and recording media that absorb slowly such as printing paper. And high-quality printed images can be obtained. These surfactants are particularly preferably used in combination with a water-soluble organic solvent having a low surface tension.

  Preferred examples of the silicone-based surfactant include polyether-modified polysiloxane compounds such as KF-351A, KF-642, X-22-4272 manufactured by Shin-Etsu Chemical Co., Ltd., BYK307, BYK345, BYK347 manufactured by Big Chemie. BYK348, TSF4452 manufactured by Toshiba Silicone Co., and the like.

  The fluorosurfactant means one obtained by substituting a part or all of hydrogen bonded to carbon of the hydrophobic group of a normal surfactant with fluorine. The fluorine-based surfactant preferably has a perfluoroalkyl group in the molecule.

  Fluorosurfactants are available from DIC under the name Megafac F; from Asahi Glass under the name Surflon; from Minnesota Mining & Manufacturing Company Fluorad Under the trade name FC; under the trade name Monflor from Imperial Chemical Industry; under the trade name Zonyls from EI DuPont Nemeras &Company; Ricobet from Farbeberke Hoechst (Licowet) under the trade name VPF; also commercially available from Neos under the trade name Fantage.

  The addition amount of the surfactant in the inkjet ink is preferably 0.1% by mass or more and less than 2.0% by mass with respect to the total mass of the ink.

  If the surface tension of the ink-jet ink is 15 mN / m or more (25 ° C.), the area around the nozzles of the ink-jet head is wet and the discharge capability is unlikely to decrease. Further, it is preferable that the surface tension of the ink-jet ink is less than 35 mN / m (25 ° C.) because it is well wetted with a coated paper or a resin-made recording medium whose surface energy is lower than that of normal paper, and whitening hardly occurs.

<Ink physical properties>
The ink-jet ink in the present invention preferably has the same physical properties as a normal active energy ray-curable ink-jet ink.

  The viscosity of the inkjet ink is preferably 20 to 500 mPa · s at 25 ° C., and more preferably 5 to 60 mPa · s. Furthermore, it is preferable that the share rate dependency be as small as possible.

  In order to increase the ejection stability of the ink, it is preferable to reduce the viscosity of the ink. On the other hand, by increasing the viscosity of inkjet ink at room temperature to some extent, it prevents ink from penetrating into absorbent recording media, reduces uncured monomer, reduces odor, and suppresses dot bleeding at impact Image quality can be improved. Moreover, even if the surface tension of the base material changes, similar dots can be formed, so that similar image quality can be formed.

  The ink-jet ink in the present invention preferably does not contain a gel-like substance having an average particle size exceeding 1.0 μm, excluding pigment particles.

  The electrical conductivity of the inkjet ink in the present invention is preferably 10 μS / cm or less. This is to suppress electrical corrosion inside the inkjet head. In the continuous type, the conductivity of the inkjet ink needs to be adjusted to 0.5 mS / cm or more. In this case, it is necessary to adjust the conductivity with the electrolyte.

  The ink-jet ink of the present invention does not show an exothermic peak with a calorific value per unit mass of 10 mJ / mg or more when DSC measurement of the ink is performed in a range of 25 ° C. to −25 ° C. at a rate of 5 ° C. per minute. It is preferable. By doing in this way, generation | occurrence | production of a gel and generation | occurrence | production of a precipitate can be suppressed when an inkjet ink is preserve | saved at low temperature. The calorific value in the DSC measurement is adjusted by selecting the components of the inkjet ink.

<Ink preparation method>
Ink-jet ink includes a polymerizable monomer containing an electron-accepting monomer (A) and an electron-donating monomer (D), an optional photopolymerization initiator, a colorant, and a pigment dispersion when the colorant is a pigment. And an agent are dispersed by using a normal dispersing machine such as a sand mill.

  Preferably, a pigment concentrate is prepared in advance, and the pigment concentrate is diluted with a polymerizable monomer to prepare an inkjet ink. According to this method, sufficient dispersion can be performed with a normal disperser, and excessive dispersion energy and a great amount of dispersion time are not required. As a result, it is possible to prepare an ink that is less likely to be deteriorated during the dispersion step and has excellent stability.

  The prepared ink is preferably filtered through a filter having a pore diameter of 3 μm or less (preferably 1 μm or less).

2. Image Forming Method An image forming method of the present invention includes a step of ejecting and landing the above-described inkjet ink from an inkjet head onto a recording medium, and a step of irradiating and curing the inkjet ink landed on the recording medium. .

  In the image forming method of the present invention, an inkjet ink is landed on a recording medium; the recording medium may be any of a wide range of synthetic resins conventionally used in various applications. Specific examples of the recording medium include polyester, polyvinyl chloride, polyethylene, polyurethane, polypropylene, acrylic resin, polycarbonate, polystyrene, acrylonitrile-butadiene-styrene copolymer, polyethylene terephthalate, polybutadiene terephthalate, and the like. The thickness and shape of these synthetic resin base materials are not limited at all. In addition, metals, glass, printing paper, etc. can be used.

  Specific examples of polyvinyl chloride which is one of the recording media in the image forming method of the present invention include KSM-VS, KSM-VST, KSM-VT (above, manufactured by Kimoto Co., Ltd.), P-223RW, and P-224RW. , P-249ZW, P-284ZC (manufactured by Lintec Corporation), MPI3023 (manufactured by Toyo Corporation), NIJ-CAPVC, NIJ-SPVCGT (manufactured by Nichie Corporation), JT5129PM, JT5728P, JT5822P, JT5829P , JT5829R, JT5829PM, JT5829RM, JT5929PM (manufactured by Mactac), VGL-137, SVGS-137, MD3-200, MD3-301M, MD5-100, MD5-101M, MD5-105 (manufactured by Metamark) 640M, 64 1G, 641M, 3105M, 3105SG, 3162G, 3164G, 3164M, 3164XG, 3164XM, 3165G, 3165SG, 3165M, 3169M, 3451SG, 3551G, 3551M, 3631, 3641M, 3651G, 3651M, 3651SG, 3951G, 3641M Product), IJ180CV2 (manufactured by 3M), and the like.

  The recording medium may be a resin substrate containing no plasticizer or a non-absorbing inorganic substrate. There are no particular restrictions on various properties such as the thickness, shape, color, softening temperature, and hardness of the substrate.

  Examples of resin substrates that do not contain a plasticizer include ABS resin, polycarbonate (PC) resin, polyacetal (POM) resin, polyamide (PA) resin, polyethylene terephthalate (PET) resin, polyimide (PI) resin, acrylic resin, Examples include polyethylene (PE) resin, polypropylene (PP) resin, and hard polyvinyl chloride (PVC) resin that does not contain a plasticizer.

  Examples of non-absorbing inorganic base materials include glass plates, metal plates such as iron and aluminum, ceramic plates, and the like. These inorganic substrates are characterized by not having an ink-absorbing layer on the surface.

  These substrates can be used alone or in combination of a plurality of types of substrates.

  In the image forming method of the present invention, the inkjet ink is ejected as droplets from a nozzle (ejection port) of the inkjet head onto a recording medium. The ink jet head system may be an on-demand system or a continuous system. The discharge method is an electro-mechanical conversion method (for example, single cavity type, double cavity type, bender type, piston type, shear mode type, shared wall type, etc.), electro-thermal conversion method (for example, thermal ink jet). Any of a type | mold, a bubble jet (trademark) type | mold etc. may be sufficient.

  The droplet size discharged from the nozzle of the inkjet head can be adjusted by the nozzle diameter of the head, the magnitude of the voltage applied to the inkjet head, and the pattern. For example, by using a “pulling” method in which the pressure chamber communicating with the nozzle opening is expanded and then contracted, the mass of the ink droplet can be reduced, so that the droplet size can be reduced.

  In order to form a high-definition and high-quality image with little unevenness, the amount of ink droplets is preferably 0.1 to 20 pl, and more preferably 0.1 to 12 pl. In the ink-jet ink of the present invention, even when the amount of ink droplets is reduced, the ink that has landed on the recording medium is less susceptible to oxygen inhibition.

  When the amount of ink droplets is smaller than 0.1 pl, the number of droplets for image formation becomes excessive, and the time required for image formation becomes long. There is also a problem that nozzle clogging is likely to occur. Further, when the ink droplet amount is smaller than 0.1 pl, the surface area per unit volume when the ink jet ink is ejected from the nozzle or when it is landed on the base material is increased. .

  On the other hand, when the droplet size is larger than 20 pl, the dot diameter per dot increases, so the resolution of the formed image decreases. For this reason, there are problems in the roughness of image quality and the reproducibility of fine characters when viewed from close.

  In the image forming method of the present invention, the inkjet ink may be ejected in a heated state. Since the viscosity of the inkjet ink is reduced by heating, the ejection stability is increased. The heating temperature of the inkjet ink is preferably 35 to 100 ° C, more preferably 35 to 80 ° C. A method for heating and keeping the ink-jet ink at a predetermined temperature is not particularly limited. For example, insulate the ink supply system such as the ink tank, supply pipe, front chamber ink tank just before the head, pipe with filter, piezo head, etc. that make up the inkjet head carriage, and use panel heater, ribbon heater, warm water, etc. There is a method of heating to a predetermined temperature.

  The inkjet ink is preferably heated and kept at a control width of a set temperature ± 5 ° C., more preferably a control width of a set temperature ± 2 ° C., and particularly preferably a control width of a set temperature ± 1 ° C. .

  The recording medium on which the ink jet ink lands is preferably heated. The recording medium may be heated before ink landing or may be heated after ink landing. By heating the recording medium, the ink component landed on the recording medium penetrates into the recording medium, and the adhesion between the ink cured product (image) and the recording medium is improved. In particular, when a vinyl chloride sheet is used as the recording medium and vinyl ether having a property of swelling vinyl chloride as an electron donating monomer (D) is added to the inkjet ink, the adhesion between the cured ink (image) and the recording medium is improved. Easy to improve.

<Irradiation of active energy rays to ink landed on recording medium>
The inkjet ink droplets discharged onto the recording medium are irradiated with active energy rays such as ultraviolet rays, and the components contained in the ink are cured.

  Examples of the active energy rays to be irradiated include ultraviolet rays, near ultraviolet rays, natural light (including filter cut products), and the like, and ultraviolet rays are preferable. Examples of the ultraviolet light irradiation light source include a light emitting diode (LED), a metal halide lamp, a xenon lamp, a carbon arc lamp, a chemical lamp, a low pressure mercury lamp, a high pressure mercury lamp, and the like. For example, H lamps, D lamps, V lamps, etc. manufactured by Fusion System are commercially available.

  The LED can be turned on instantaneously, has a long life, has little radiant heat, is easy to control the amount of light, has a very narrow emission wavelength width (half-value width), and has low power consumption. LED light sources are also commercially available. The wavelength of the irradiation light source is preferably 305 to 410 nm, and more preferably 350 to 410 nm. This is because it is safe because it is on the long wavelength side in the light ultraviolet region.

In the image forming method of the present invention, it is preferable that the cumulative amount of light applied to the ink jet ink droplets landed on the recording medium is in the range of ^{20 to} 200 mJ / cm ² per droplet. The inkjet ink according to the present invention can sufficiently undergo a curing reaction even when the integrated light amount per drop is 200 mJ / cm ² or less. Therefore, it is advantageous from the viewpoint of energy saving / space saving and cost.

In the image forming method of the present invention, the illuminance of the active energy ray irradiation light source is preferably 8 W / cm ² or less. A light source with an illuminance higher than 8 W / cm ² has a large amount of heat generation, which may cause problems such as deformation of a recording medium with low heat resistance, or increased leakage of light and curing of ink on the head nozzle surface. . In addition, a light source with high illuminance has high energy consumption, a large light source space, and cost increases.

  In the image forming method of the present invention, the active energy ray is preferably irradiated for 0.001 second to 1.0 second after the ink droplet has landed on the recording medium, and more preferably 0.001 second. Irradiation for ~ 0.5 seconds. In order to form a high-definition image, it is preferable that the interval from landing to irradiation is as short as possible.

  The irradiation method of an active energy ray is not specifically limited, For example, it can carry out with the following method. A light source is provided on both sides of the head unit, the head and the light source are scanned by a shuttle method, and irradiation is performed after a certain time from ink landing. Further, the curing is completed by irradiating light from another light source that is not driven (see Japanese Patent Application Laid-Open No. 60-132767). Alternatively, light may be irradiated using an optical fiber, or ultraviolet light from a collimated light source may be reflected by a mirror surface provided on the side of the head unit and irradiated to the recording unit (US Pat. No. 6, 145,979).

  Moreover, you may divide active energy ray irradiation into two steps. For example, a method of first irradiating active energy rays by the above-described method between 0.001 and 2.0 seconds after ink landing, and further irradiating active energy rays after the completion of all printing is one of preferred embodiments. is there. By dividing the irradiation of the active energy ray into two stages, it is possible to further suppress the shrinkage of the recording medium that occurs during ink curing.

  In the image forming method of the present invention, the total ink film thickness after the ink has landed on the recording medium and cured by irradiation with active energy rays is preferably 2 to 20 μm. This is for suppressing curling and wrinkling of the recording medium and changes in the texture of the recording medium. “Total ink film thickness” means the maximum value of the film thickness of ink drawn on a recording medium. Whether it is a single color or a two-color overlap (secondary color), a three-color overlap, or a four-color overlap (white ink base), the total ink film thickness is preferably 2 to 20 μm.

  The image forming method of the present invention uses an inkjet ink containing an electron-accepting monomer (A) and an electron-donating monomer (D) as a polymerizable monomer. The amount of drops can be relatively small. Although the light source is an LED and the amount of irradiation light is suppressed and the amount of ink droplets is reduced, the ink can be sufficiently cured. Furthermore, since the inkjet ink contains a certain amount of the polymerizable monomer (X) together with the electron-accepting monomer (A) and the electron-donating monomer (D), the curing shrinkage of the ink cured product is suppressed, and the flexibility is also improved. Rise.

  The image forming method of the present invention can be performed using an ink jet recording apparatus (ink jet printer). Examples of the ink jet recording apparatus include, but are not limited to, a serial head type recording apparatus and a line head type recording apparatus. Hereinafter, each recording apparatus will be described with reference to the drawings, but the ink jet recording apparatus is not limited thereto.

  FIG. 1 is a front view of a serial head type ink jet recording apparatus and shows a configuration of a main part of the apparatus. The recording apparatus 1 includes a head carriage 2, a recording head 3, an irradiation unit 4, a platen unit 5, and the like. In the recording apparatus 1, the platen unit 5 is installed under the recording medium P. The platen unit 5 has a function of absorbing ultraviolet rays, and absorbs the ultraviolet rays that have passed through the recording medium P. As a result, a high-definition image can be stably reproduced.

  The recording medium P is guided by the guide member 6 and moves from the front side to the back side in FIG. 1 by the operation of the conveying means (not shown). A head scanning means (not shown) scans the recording head 3 held by the head carriage 2 by reciprocating the head carriage 2 in the Y direction.

  The head carriage 2 is installed facing the upper side of the recording medium P, and includes a plurality of recording heads 3 according to the number of colors of images to be printed on the recording medium P. The recording head 3 is arranged with the ejection port 31 facing the recording medium P. The head carriage 2 of the recording apparatus of FIG. 1 accommodates four types of recording heads 3 of yellow (Y), magenta (M), cyan (C), and black (K), but is accommodated in the head carriage 2. The number of colors of the recording head 3 is appropriately set.

  A plurality of ink chambers are arranged inside the recording head 3, and each ink chamber is provided with an ejection means (not shown). The ejection unit is, for example, a piezo element. The ink chamber disposed inside the recording head 3 is supplied with active energy ray-curable ink by an ink supply means (not shown). The active energy ray-curable ink supplied to the ink chamber is ejected from the ejection port 31 toward the recording medium P by the operation of the ejection unit.

  The inkjet ink ejected from the ejection port 31 of the recording head 3 is the above-described active energy ray-curable inkjet ink, and when irradiated with the active energy ray, the polymerizable monomer is crosslinked or polymerized by the action of the polymerization initiator. It has the property of causing a reaction to cure.

  The recording head 3 can scan from one end to the other end of the recording medium P along the Y direction by driving the head scanning means. The recording head 3 ejects ink jet ink droplets to land on a certain area (landing possible area) of the recording medium P while scanning.

  After the recording head 3 is scanned as many times as necessary and ink is ejected to one landing possible area, the recording medium P is appropriately moved from the front side to the back side in FIG. Again, while the recording head 3 is being scanned, ink jet ink droplets are ejected and landed on the landable area adjacent to the one landable area by the recording head 3.

  By repeating the above-described operation, an image composed of an aggregate of inkjet ink droplets is formed on the recording medium P.

  The irradiation unit 4 is installed on both sides of the head carriage 2 so as to be fixed substantially parallel to the recording medium P. The irradiation means 4 includes an irradiation light source 8 that emits ultraviolet light in the specific wavelength region described above, and a filter (not shown) that transmits ultraviolet light of a specific wavelength.

  The irradiation area of the irradiation unit 4 may be the same as or larger than the landing possible area by the recording head 3.

  In order to suppress the light from being applied to the ejection port 31, the entire recording head 3 is shielded from light, and the ejection port 31 and the recording medium P of the recording head 3 are further separated from the distance h 1 between the irradiation unit 4 and the recording medium P. It is preferable to increase the distance h2 (h1 <h2) or to increase the distance between the recording head 3 and the irradiation means 4. Further, it is preferable that a bellows structure 7 is provided between the recording head 3 and the irradiation means 4.

  FIG. 2 is a top view of the line head type ink jet recording apparatus, and shows the main configuration of the apparatus. The recording apparatus 1 includes a head carriage 2 in which a plurality of recording heads 3 are fixedly disposed, and an irradiation unit 4.

  The plurality of recording heads 3 provided in the head carriage 2 are arranged so as to cover the entire width of the recording medium P.

  The irradiation unit 4 is disposed downstream of the head carriage 2 in the conveyance direction of the recording medium P. The irradiation means 4 has a plurality of LED light sources, and the plurality of LED light sources are arranged so as to cover the entire width of the recording medium P. That is, the irradiation means 4 is arranged so as to cover the entire area of the ink print surface. Each LED light source has a maximum illuminance, for example, at 395 nm.

  In the line head type ink jet recording apparatus 1, the head carriage 2 and the irradiation means 4 are fixed, and only the recording medium P is conveyed. The ink droplets ejected from the fixedly arranged recording head 3 land on the transported recording medium P, and light from the irradiation unit 4 is irradiated to the landed ink, and the ink is cured. Thereby, an image is formed.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto.

1. Preparation of ink Each component used for the preparation of the ink is shown below. The charge of the monomer whose charge value is described was obtained by the calculation method described above. In the case of an electron-accepting monomer, the charge of a carbon atom having a higher charge value out of two carbon atoms on a polymerizable unsaturated bond to which an electron-withdrawing group is bonded is shown. In the case of the electron donating monomer, the charge of the carbon atom having the lower charge value out of the two carbon atoms on the polymerizable unsaturated bond to which the electron donating group was bonded was shown. In the case of the polymerizable monomer having an acrylate group, the charge of the carbon atom to which the ester group is not bonded out of the two carbon atoms of the polymerizable unsaturated bond was shown.

[Color material]
Color material Y: C.I. I. pigment Yellow 150
Color material M: C.I. I. pigment Red 122
Color material C: C.I. I. pigment Blue 15: 4
Color material K: C.I. I. pigment Black 7

[Pigment dispersant]
D1: Pigment dispersant Solsperse 24000GR, manufactured by Lubrizol, Inc. D2: Pigment dispersant, BYKJET-9150, manufactured by Big Chemie Japan Co., Ltd. D3: Pigment dispersant, Azisper PB824, manufactured by Ajinomoto Fine Techno Co., Ltd.

[Basic compound] TIPA: Triisopropanolamine

[Polymerizable monomer (X) having (meth) acrylic acid ester group] etc. X-1: Phenoxyethyl acrylate X-2: Tetrahydrofurfuryl acrylate X-3: Isobornyl acrylate X-4: Tripropylene glycol diacrylate X-5: Polyethylene glycol # 600 diacrylate X-6: 6EO-modified trimethylolpropane triacrylate X-7: Amine-modified acrylate oligomer
X-8: Polyester acrylate oligomer
X-9: 1,6-hexane diacrylate X-10: 2-methoxyethyl acrylate X-11: benzyl acrylate

Ｍ−３：マレイミドＭ−３（電荷：−０．２７）

Ｍ−８：マレイミドＭ−８（電荷：−０．２７）

Ｍ−３５：マレイミドＭ−３５（電荷：−０．２７）

ＢＭＩ−５１００：３，３‘−ジメチル−５，５’−ジエチル−４，４‘−ジフェニルメタンビスマレイミド（電荷：−０．２７）
ＢＭＩ−ＴＭＨ：１，６‘−ビスマレイミド−（２，２，４−トリメチル）ヘキサン（電荷：−０．２７） [Electron-accepting monomer (A)]
M-2: Maleimide M-2 (Charge: -0.27)

M-3: Maleimide M-3 (charge: -0.27)

M-8: Maleimide M-8 (charge: -0.27)

M-35: Maleimide M-35 (Charge: -0.27)

BMI-5100: 3,3′-dimethyl-5,5′-diethyl-4,4′-diphenylmethane bismaleimide (charge: −0.27)
BMI-TMH: 1,6′-bismaleimide- (2,2,4-trimethyl) hexane (charge: −0.27)

  The maleimides used in the examples were synthesized with reference to Japanese Patent Application Nos. 2010-136977 and 2010-136978.

[Electron donating monomer (D)]
TEGDVE: Triethylene glycol divinyl ether (charge: -0.54)
DEGDVE: Diethylene glycol divinyl ether (charge: -0.59)
CHDMDVE: cyclohexanedimethanol divinyl ether (charge: -0.53)
DDVE: dodecyl vinyl ether (charge: -0.54)
DEGV: Diethylene glycol monovinyl ether (charge: -0.54)
HBVE: hydroxybutyl vinyl ether (charge: -0.53)
NVC: N-vinylcaprolactam (charge: -0.50)

[Photopolymerization initiator]
TPO: 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide Irg819: bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide ITX: 2-isopropylthioxanthone

[Surfactant] KF351: Side-chain polyether-modified silicone oil manufactured by Shin-Etsu Silicone Co., Ltd. [Polymerization inhibitor] Irgastab UV-10 manufactured by BASF

  Inks 1 to 36 having the compositions shown in Tables 1 to 5 were prepared according to the following method using the ink components described above. The ink compositions in Tables 1 to 5 represent mass%.

  Part of the dispersant, basic compound, and photopolymerizable monomer listed in Tables 1 to 5 are placed in a stainless beaker and stirred and mixed for 1 hour while heating on a hot plate at 60 ° C. to dissolve. It was. Next, coloring materials 1 to 4 described in Tables 1 to 5 were added to this solution. Thereafter, it was put in a plastic bottle together with zirconia beads having a diameter of 0.5 mm and sealed, and subjected to a dispersion treatment for 6 hours using a paint shaker. The zirconia beads were removed to obtain a pigment dispersion.

  A mixture of the remaining photopolymerizable monomer, photopolymerization initiator, surfactant, and polymerization inhibitor was added to the obtained pigment dispersion with stirring. Inks 1 to 36 were prepared by filtration through a 1 μm membrane filter.

2. Ink Evaluation Inks 1 to 36 were evaluated for viscosity, curing sensitivity, curing shrinkage, adhesion, and solvent resistance.

<Ink viscosity>
The viscosity of the prepared ink was measured using a rheometer MCR300 (manufactured by Physica) under the conditions of 25 ° C. and Shear Rate = 1000 (1 / s). All of the inks 1 to 36 were in the range of 20 to 40 mPa · s.

<Curing sensitivity>
For inks 1 to 36, each ink was loaded into a serial type ink jet recording apparatus equipped with a piezoelectric ink jet nozzle in an environment of 25 ° C./50% RH. A solid image having an image resolution of 1440 × 1440 dpi was formed. A PET film was used as the substrate.

  The ink supply system includes an ink tank, a supply pipe, a front chamber ink tank immediately before the head, a pipe with a filter, and a piezo head. The temperature from the front chamber ink tank to the head portion was heated by a heater, and the temperature was controlled so that the viscosity of the ink can be ejected (12 mPa · s or less). The nozzle pitch of the piezo head is 360 dpi (dpi represents the number of dots per inch), and droplet sizes of 4 pl, 6 pl, 14 pl, and 42 pl can be ejected from each nozzle.

Air-cooled LEDs (manufactured by Foseon) having a wavelength of 395 nm are mounted on both ends of the carriage. The head was scanned and irradiated with actinic rays within 0.5 seconds after ink landing. The exposure surface illuminance was 2 W / cm ² and the integrated light quantity was adjusted by changing the speed of the head carriage. The illuminance on the exposed surface and the integrated light amount were measured in the UVA2 region using UV POWER PUCKII manufactured by EIT.

The curing sensitivity of each ink was evaluated based on the integrated light amount value when no rub marks were made when the cured film surface was rubbed with a finger. The integrated light quantity value was calculated from the carriage speed. The evaluation results of the curing sensitivity are shown in Tables 1-5.
◎: 100mJ / cm ² without scratches in the following ○: 100mJ / cm ² ultra ~150mJ / cm ² or less by rubbing without trace △: 150mJ / cm ² ultra ~200mJ / cm ² or less with no scratches ×: 200mJ / cm Scratch remains even after ²

<Curing shrinkage>
A solid image was printed and cured on a PET substrate having a thickness of 38 μm using an inkjet recording apparatus (6 pl nozzle) used for evaluating the curing sensitivity, and an image was formed. The thickness of the ink layer at the time of curing was set to 20 μm. The created solid image was cut out together with the base material in a size of 100 mm in the vertical direction and 75 mm in the horizontal direction, and left at room temperature. On the next day, the curl amount of the cut out image was measured. The ratio (%) of the linear distance (string length) between both ends of the warped image to the lateral length (75 mm) of the cut substrate was determined, and this was used as the curl amount. From the curl amount, evaluation was made according to the following criteria.
A: Curling is 95 to 100% (100% is not curled at all)
○: Curling is 90% to less than 95% △: Curling is 80% to less than 90% (within practical tolerance)
X: Curling is less than 80% (practically unacceptable level)

<Adhesion>
A solid image having an image resolution of 1440 × 1440 dpi was formed on a polyvinyl chloride sheet (manufactured by IJ180 3M) using an inkjet recording apparatus (6 pl nozzle) used for evaluating the curing sensitivity. The solid image part was cut into a grid of 5 squares × 5 squares. A peel test was conducted by attaching Nichiban cello tape (registered trademark) to the cut image and peeling it off. The adhesion was evaluated according to the following criteria.
◎: No peeling of grids, no lifting or rubbing at cuts ○: No peeling of grids, slight lifting or rubbing at cuts △: Seeing peeling of 2 to 3 grids (Practically acceptable)
×: More than half of the cells were peeled off (practical problem level)

<Solvent resistance>
A 50% halftone image having an image resolution of 1440 × 1440 dpi was formed on a polyvinyl chloride sheet (manufactured by IJ180 3M) using an inkjet recording apparatus (6 pl nozzle) used for evaluating the curing sensitivity. The residual ratio of density when the surface of the image portion was wiped 10 times with a nonwoven fabric moistened with isopropyl alcohol was evaluated. From the residual rate, the solvent resistance was evaluated according to the following criteria.
A: Concentration residual ratio is 90% or more B: Concentration residual ratio is 80% to less than 90% Δ: Concentration residual ratio is 70% to less than 80% X: Concentration residual ratio is less than 70%

  Ink 32 as a comparative example had insufficient curing sensitivity because the total amount of the electron-accepting monomer (A) and the electron-donating monomer (D) was too small relative to the total amount of monomers. This is probably because the charge transfer complex polymerization reaction was difficult. On the other hand, in the ink 33 as a comparative example, the total amount of the electron accepting monomer (A) and the electron donating monomer (D) with respect to the total amount of the monomer was too large, so that the cured ink was cured and contracted. . For this reason, the adhesion of the image was also lowered.

  Ink 34 and 35, which are comparative examples, had a lower curing sensitivity because the number of functional groups of the electron-accepting monomer (A) was too small relative to the number of functional groups of the electron-donating monomer (D). Therefore, the ink was not sufficiently cured, and the adhesion and solvent resistance were reduced. On the other hand, the ink 36 as a comparative example has too many functional groups of the electron-accepting monomer (A) with respect to the number of functional groups of the electron-donating monomer (D), and therefore the electron-accepting monomer (A) other than the CT polymerization reaction. It is considered that reaction between each other occurred and an electron-accepting monomer (A) dimer or the like was excessively generated. As a result, the cured film is hard and brittle, and it is considered that the adhesiveness of the image and the decrease in solvent resistance are reduced.

  Inks 1 to 36, which are examples, were satisfactory in terms of each evaluation item. Furthermore, when the total amount of the electron-accepting monomer (A) and the electron-donating monomer (D) with respect to the total amount of monomers increases, the curing sensitivity becomes better; the electron-accepting monomer (A with respect to the total amount of monomers) ) And the electron donating monomer (D) were found to decrease the curing shrinkage (see inks 1 to 14 as examples).

Next, ink sets 1 and 2 were prepared. Each ink constituting the ink sets 1 and 2 was prepared in the same manner as the inks 1-36.

<Small droplet image performance, image durability 1>
The obtained ink sets 1 and 2 were filled into a serial type ink jet recording apparatus equipped with a four-color piezo-type head having ink nozzles capable of ejecting a droplet size of 6 pl. The temperature of the ink was controlled so as to be a jettable viscosity (about 10 mPa · s). In an environment of 25 ° C./50% RH, a color image (N3 “fruit basket”, a high-definition color digital standard image conforming to JISX 9201-1995) with a carriage speed of 500 mm / s and an image resolution of 1440 × 1440 dpi is obtained. Formed on a vinyl sheet. In image formation, the landed ink was exposed within 0.5 seconds after landing with LEDs (manufactured by Foseon, wavelength 395 nm, 2 W / cm 2) mounted on both ends of the carriage. The integrated light quantity on the substrate was 100 mJ / cm ² .

  The image output with the ink set 1 was free from rubbing when the printing surface was rubbed immediately after printing, and there was no blur between colors, and a clear image was obtained. Further, even when the image surface was wiped with a non-woven cloth moistened with a cleaner solution containing an alcohol solvent, no color transfer occurred and no change in the gloss of the image was observed.

  The image output by ink set 2 was rubbed when the printing surface was rubbed immediately after printing, and bleeding between colors was also observed. As a result, the image was totally blurred. Also, when wiped with the above cleaner liquid, an image was taken and white spots were lost.

<Small droplet image performance, image durability 2>
Ink sets 1 and 2 were loaded into a line head type ink jet recording apparatus having a four-color piezo-type head having ink nozzles capable of ejecting a droplet size of 6 pl. The following images (resolution 1400 dpi × 1440 dpi) were formed on art paper.
Image 1: 4 and 5 and 6 point MS Mincho Kanji characters "Mouth, Four, Day, Time, Cause, Difficulty, Country, Eye, Figure, Country" and letters (Y, M, C) , K)
Image 2: Color image (N3 “fruit basket” of high-definition color digital standard image conforming to JIS X 9201-1995)

In image formation, exposure was performed using an LED having a width wider than the width of the head (manufactured by Foseon, wavelength 395 nm, 4 W / cm 2). The LED light source was arranged in parallel to the head in the downstream direction in which the base material is conveyed (where the actinic ray hits after printing). The substrate was transported at a carriage speed such that the integrated light amount was 150 mJ / cm ² on the substrate, and printing was performed.

  Each image formed on the art paper was visually observed to evaluate character reproducibility and image quality. When ink set 1 was used, all four-point characters and blank characters were clearly recorded in detail, and a clear image was formed with good rubbing on the color image surface. Some images formed using the ink set 2 were illegible because 6-point characters and extracted characters were crushed, and the surface of the color image remained rubbing, and was an overall blurred image.

  The ink-jet ink of the present invention can suppress oxygen inhibition of ink curing and can improve the storage stability of the ink. Furthermore, the ink-jet ink of the present invention can be applied to printing on various recording media because the cured ink has little cure shrinkage and high flexibility.

DESCRIPTION OF SYMBOLS 1 Recording device 2 Head carriage 3 Recording head 31 Ejection port 4 Irradiation means 5 Platen part 6 Guide member 7 Bellows structure 8 Irradiation light source P Recording medium

Claims (6)

An electron-accepting monomer (A) having an unsaturated bond a and a maximum charge of the carbon atom constituting the unsaturated bond a being −0.30 or more; an unsaturated bond d; An electron-donating monomer (D) having a minimum charge of a carbon atom constituting a saturated bond d of −0.50 or less, and a polymerizable monomer (X) having a (meth) acrylate group,
The electron donating monomer (D) contains vinyl ether,
The total amount of the electron accepting monomer (A) and the electron donating monomer (D) with respect to the total amount of the electron accepting monomer (A), the electron donating monomer (D), and the polymerizable monomer (X). Is a proportion of 25 to 90% by weight,
The actinic ray curable inkjet, wherein the ratio (A) / (D) of the number of functional groups of the electron accepting monomer (A) to the number of functional groups of the electron donating monomer (D) is 70/30 to 35/65 ink.   The actinic ray curable inkjet ink according to claim 1, further comprising a photopolymerization initiator.   The actinic ray curable inkjet ink according to claim 1, further comprising a pigment.   The actinic-light curable inkjet ink of Claim 1 whose viscosity in 25 degreeC is 5-60 mPa * s. A step of spraying the actinic radiation curable ink according to claim 1 onto a recording medium from a nozzle of an ink jet recording head, and irradiating the coating film formed on the recording medium with actinic rays. And curing the process,
The image forming method, wherein the light source of the active light is an LED. A step of spraying the actinic radiation curable ink according to claim 1 onto a recording medium from a nozzle of an ink jet recording head, and irradiating the coating film formed on the recording medium with actinic rays. And curing the process,
An image forming method, wherein an amount of ink droplets ejected from a nozzle of the ink jet recording head is 0.1 to 12 pl.

Images