JP2008031301A - Active energy ray-curable inkjet ink, and image-forming method and recorded matter using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide active energy ray-curable inkjet ink that is low in viscosity and excellent in jetting stability and does not suffer from brittle fracture even if bent after recording on various base materials and curing, and to provide an inkjet recording method and recorded matter using the active energy ray-curable inkjet ink. <P>SOLUTION: The active energy ray-curable ink composition comprises a compound represented by general formula (I) (wherein R<SB>1</SB>-R<SB>5</SB>are each independently a hydrogen atom or a substituent group). <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an active energy ray-curable inkjet ink, an image forming method using the same, and a recorded matter.

In recent years, printing by an inkjet printer that does not use a plate has been used for the production of a limited number of copies such as regional advertisements and large posters. As inks for inkjet printing, water-based inks, solvent-based inks, and ultraviolet curable inks are generally used. Water-based ink-jet inks have poor water resistance when printed on plain paper, are likely to bleed, and ink droplets adhere poorly when printed on non-water-absorbing recording media such as plastic. In addition, image formation defects are liable to occur, and the drying of the solvent is extremely slow, so that it is necessary to dry the printed matter without overlapping immediately after printing.
On the other hand, solvent-based inks are suitable for printing on non-water-absorbing recording media such as plastics, but since the solvent needs to be dried, not only does it take time to dry, but also volatilizes the organic solvent. There was a drawback that an exhaust facility and a solvent recovery mechanism had to be provided.

In order to solve these problems, inkjet inks that are cured and fixed by radiation rather than volatilization of the ink solvent have been developed. For example, Patent Documents 1 to 3 disclose inks containing a monomer having a polymerizable group and an oil-soluble dye. Patent Document 4 discloses a photopolymerizable composition containing a photopolymerizable compound and a photopolymerization initiator. However, since these inks are radical polymerization systems, the polymerization is hindered by oxygen, and poor curing tends to occur in the air, and improvement has been desired.
Therefore, an ink using cationic polymerization that is not inhibited by oxygen is disclosed. For example, Patent Documents 5 and 6 disclose active energy ray-curable compositions having oxirane and oxetane, but the curability is not sufficient, the brittleness, and the adhesion are insufficient. Patent Document 7 discloses an active energy ray-curable composition having oxirane, oxetane, and vinyl ether. However, the curability is relatively good, but it is brittle and has insufficient adhesion. Since odor is generated, it has been desired to develop a material that can increase sensitivity without using vinyl ether.
In addition, oxirane and oxetane used in the active energy ray-curable ink are relatively high viscosity compounds, and it has been difficult to provide sufficient ejection stability. Patent Document 8 also discloses an ink-jet ink containing a lower alkyl ether having two oxetane groups. However, the ink viscosity is high, and the nozzle is clogged during continuous printing, resulting in ejection failure. The ejection stability with an inexpensive print head with low driving force was insufficient. In order to provide sufficient ejection stability, a special print head having a high ejection force is required, and there is a problem that the printing apparatus becomes large. As an ink for improving ink discharge performance in an inkjet printer, for example, Patent Document 9 discloses an ink having a resin liquid having a photoreactive monomer and a colorant, and the viscosity of the resin liquid is adjusted to be low. Things are disclosed. However, this ink has the drawbacks of low sensitivity and easy shrinkage during curing.
JP 2003-221528 A JP 2003-221532 A JP 2003-221530 A JP 2001-222105 A JP 2000-169552 A JP 2001-220526 A JP 2002-317139 A JP 2003-119414 A JP 2001-288387 A

  The problem to be solved by the present invention is to provide an active energy ray-curable ink-jet ink having a low viscosity and excellent ejection stability, which does not cause brittle fracture even if it is bent on various substrates after recording and curing. Moreover, it is providing the inkjet recording method and recorded matter using such an active energy ray hardening-type inkjet ink. In the present invention, “ejection stability” means that the inkjet ink is continuously ejected stably without causing ejection failure due to nozzle clogging.

The problems of the present invention have been solved by the following means.
(1) An active energy ray-curable ink composition comprising a compound represented by the following general formula (I):

(In the formula, R _{1 to} R ₅ each independently represents a hydrogen atom or a substituent.)
(2) The active energy ray-curable ink composition according to (1), wherein the compound represented by the general formula (I) is a compound represented by the following general formula (II).

(In the formula, R _{1 to} R ₄ and R ₆ each independently represent a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, an aromatic hydrocarbon group, a heteroaromatic group, or a heterocyclic group.)
(3) The active energy ray according to (1) or (2), wherein the compound represented by the general formula (I) or (II) is a compound represented by the following general formula (III): A curable ink composition.

(In the formula, R ₆ represents a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, an aromatic hydrocarbon group, a heteroaromatic group, or a heterocyclic group.)
(4) The active energy ray curing according to (1) to (3), wherein the compounds represented by the general formulas (I) to (III) have a viscosity at 25 ° C. of 1 to 10 mPa · s. Type ink composition.
(5) The active energy ray-curable ink composition according to any one of (1) to (4), further comprising any one of an oxirane ring-containing compound and an oxetane ring-containing compound.
(6) The active energy ray-curable ink composition according to any one of (1) to (5), further comprising at least one polymerization initiator and at least one photosensitizer. .
(7) The active energy ray-curable ink composition according to any one of (1) to (6), wherein the viscosity at 25 ° C. is 2 to 20 mPa · s.
(8) An inkjet ink comprising the active energy ray-curable ink composition according to any one of (1) to (7).
(9) An image forming method comprising an image recording step of recording an image by inkjet recording in which the active energy ray-curable inkjet ink according to (8) is discharged.
(10) An image recording process for recording an image on a recording material using an active energy ray-curable inkjet ink, and an image recorded on the recording material in the image recording step is irradiated with active energy rays to be cured. The image forming method according to (9), further comprising an image curing step.
(11) The image forming method according to (10), wherein the active energy ray irradiation light source is a light emitting diode or a semiconductor laser.
(12) The image forming method according to (9) or (10), wherein a center wavelength of the active energy ray is 365 ± 20 nm.
(13) The recorded matter according to any one of (10) to (12), wherein the image cured by the image curing step has a thickness of 2 to 30 μm.
(14) A recorded matter formed using the active energy ray-curable inkjet ink according to (8).

The active energy ray-curable ink composition of the present invention is characterized in that the viscosity of the composition can be significantly reduced by containing an oxetane compound in which at least one of the 3-position substituents on the oxetane ring is a methyl group. is there. Therefore, without using a solvent, the viscosity of the ink is kept low, so that the ejection stability is excellent, and a good character or image can be recorded on the recording medium. In addition, it is excellent in flexibility after curing, and even if the recorded matter recorded on the film is subjected to bending deformation, it does not crack.
According to the present invention, there is provided an active energy ray-curable inkjet ink having a low ink clay when ink composition is used as an ink composition, excellent ejection stability, and causing no brittle fracture of a recording surface even when bent after curing. be able to. Moreover, the inkjet recording method and recorded matter using such an active energy ray hardening-type inkjet ink can be provided.

Hereinafter, the present invention will be described in detail.
The active energy ray-curable ink composition of the present invention can be used as a jet ink. The aspect made into the inkjet ink is demonstrated.
The ink composition of the present invention is preferably an active energy ray-curable ink-jet ink containing a compound represented by the following general formula (I).

(In the formula, R _{1 to} R ₅ each independently represents a hydrogen atom or a substituent.)

In the general formula (I), R _{1 to} R ₅ each independently represents a hydrogen atom or a substituent. Examples of the substituent include an alkyl group, an alkenyl group, an alkynyl group, an aromatic hydrocarbon group, and a heteroaromatic group. Group, heterocyclic group, alkoxy group, aryloxy group, alkylthio group, arylthio group, alkoxycarbonyl group, aryloxycarbonyl group, sulfamoyl group, acyl group, acyloxy group, amide group, carbamoyl group, ureido group, alkylsulfonyl group , Arylsulfonyl group, amino group, halogen atom, fluorinated hydrocarbon group, cyano group, nitro group, hydroxy group, mercapto group, silyl group, etc., and these substituents are further substituted by the above-mentioned substituents. These substituents may be bonded to each other to form a ring. Alternatively, R _{1 to} R ₅ may form a ring by arbitrarily combining the terminal portions of each substituent, and the ring is preferably an aliphatic hydrocarbon ring, and the ring includes the above-described substituents. The group may be substituted. R _{1 to} R ₅ are preferably a hydrogen atom or an alkyl group.

In the general formula (I), the alkyl group represented by R _{1 to} R ₄ may be linear, branched, or cyclic. For example, a methyl group, an ethyl group, a propyl group, Examples include an isopropyl group, a tert-butyl group, a pentyl group, a hexyl group, an octyl group, a dodecyl group, a tridecyl group, a tetradecyl group, a pentadecyl group, a cyclopentyl group, and a cyclohexyl group, and are alkyl groups having 1 to 3 carbon atoms. Is more preferable, a methyl group or an ethyl group is more preferable, and a methyl group is particularly preferable.
In the general formula (I), the alkyl group represented by R ₅ may be linear, branched or cyclic, such as methyl, ethyl, propyl, methyloxymethyl. Group, ethyloxymethyl group, propyloxymethyl group, butyloxymethyl group, tert-butyloxymethyl group, pentyloxymethyl group, hexyloxymethyl group, octyloxymethyl group, 2-ethylhexyloxymethyl group, dodecyloxymethyl group , Tridecyloxymethyl group, tetradecyloxymethyl group, pentadecyloxymethyl group, cyclopentyloxymethyl group, cyclohexyloxymethyl group, benzyloxymethyl group, phenyloxymethyl group, 4-methylphenyloxy group, 4-tert- Butylphenyloxymethyl, etc., carbon number It is preferably an alkyl group of ˜20, more preferably a butyloxymethyl group, a hexyloxymethyl group, an octyloxymethyl group, a 2-ethylhexyloxymethyl group, a cyclohexyloxymethyl group, a benzyloxymethyl group, a phenyloxymethyl group. It is.

In the general formula (I), examples of the alkenyl group represented by R _{1 to} R ₅ include a vinyl group and an allyl group. Examples of the alkynyl group include an ethynyl group and a propargyl group. For example, as a heteroaromatic group such as phenyl group, naphthyl group and the like, for example, furyl group, thienyl group, pyridyl group, pyridazyl group, pyrimidyl group, pyrazyl group, triazyl group, imidazolyl group, pyrazolyl group, thiazolyl group, benzoimidazolyl group, Benzoxazolyl group, quinazolyl group, phthalazyl group, etc., as heterocyclic group, for example, pyrrolidyl group, imidazolidyl group, morpholyl group, oxazolidyl group, etc., as alkoxy group, for example, methoxy group, ethoxy group, propyloxy group, pentyl Oxy group, hexyloxy group, octyloxy group, dode As an aryloxy group, for example, a phenoxy group, a naphthyloxy group, etc., as an alkylthio group, for example, a methylthio group, an ethylthio group, a propylthio group, a pentylthio group, a hexylthio group, an octylthio group, a dodecylthio group, etc. For example, phenylthio group, naphthylthio group, etc., as alkoxycarbonyl group, for example, methyloxycarbonyl group, ethyloxycarbonyl group, butyloxycarbonyl group, octyloxycarbonyl group, dodecyloxycarbonyl group, etc., as aryloxycarbonyl group, for example As the sulfamoyl group such as phenyloxycarbonyl group, naphthyloxycarbonyl group, etc., for example, aminosulfonyl group, methylaminosulfonyl group, dimethylaminosulfonyl group, Examples of acyl groups such as tilaminosulfonyl group, hexylaminosulfonyl group, cyclohexylaminosulfonyl group, octylaminosulfonyl group, dodecylaminosulfonyl group, phenylaminosulfonyl group, naphthylaminosulfonyl group, 2-pyridylaminosulfonyl group, etc. include acetyl group Examples of acyloxy groups such as ethylcarbonyl group, propylcarbonyl group, pentylcarbonyl group, cyclohexylcarbonyl group, octylcarbonyl group, 2-ethylhexylcarbonyl group, dodecylcarbonyl group, phenylcarbonyl group, naphthylcarbonyl group, pyridylcarbonyl group, etc. Acetyloxy group, ethylcarbonyloxy group, butylcarbonyloxy group, octylcarbonyloxy group, dodecylcarbonyloxy group, phenyl Examples of the amide group such as a carbonyloxy group include a methylcarbonylamino group, an ethylcarbonylamino group, a dimethylcarbonylamino group, a propylcarbonylamino group, a pentylcarbonylamino group, a cyclohexylcarbonylamino group, a 2-ethylhexylcarbonylamino group, and an octylcarbonyl group. Examples of the carbamoyl group such as amino group, dodecylcarbonylamino group, phenylcarbonylamino group, naphthylcarbonylamino group, etc. include aminocarbonyl group, methylaminocarbonyl group, dimethylaminocarbonyl group, propylaminocarbonyl group, pentylaminocarbonyl group, cyclohexyl Aminocarbonyl group, octylaminocarbonyl group, 2-ethylhexylaminocarbonyl group, dodecylaminocarbonyl group, phenyl Examples of ureido groups such as minocarbonyl group, naphthylaminocarbonyl group, 2-pyridylaminocarbonyl group, etc. include methylureido group, ethylureido group, pentylureido group, cyclohexylureido group, octylureido group, dodecylureido group, phenylureido group, Examples of alkylsulfonyl groups such as naphthylureido group and 2-pyridylaminoureido group include, for example, methylsulfonyl group, ethylsulfonyl group, butylsulfonyl group, cyclohexylsulfonyl group, 2-ethylhexylsulfonyl group, dodecylsulfonyl group, and arylsulfonyl groups Is a phenylsulfonyl group, a naphthylsulfonyl group, a 2-pyridylsulfonyl group, etc. Examples of the amino group include an amino group, an ethylamino group, a dimethylamino group, and a butylamino group. Group, cyclopentylamino group, 2-ethylhexylamino group, dodecylamino group, anilino group, naphthylamino group, 2-pyridylamino group, etc., as halogen atoms, for example, fluorine atom, chlorine atom, bromine atom, etc., fluorinated hydrocarbon group Examples of the silyl group include a fluoromethyl group, a trifluoromethyl group, a pentafluoroethyl group, and a pentafluorophenyl group. Examples of the silyl group include a trimethylsilyl group, a triisopropylsilyl group, a triphenylsilyl group, and a phenyldiethylsilyl group. It is done.

  Further, the compound represented by the general formula (I) is preferably represented by the following general formula (II).

(In the formula, R _{1 to} R ₄ and R ₆ each independently represent a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, an aromatic hydrocarbon group, a heteroaromatic group, or a heterocyclic group.)
Preferred examples of R _{1 to} R ₄ are the same as in the case of the general formula (I).
In the general formula (I), each R ₆ independently represents a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, an aromatic hydrocarbon group, a heteroaromatic group, or a heterocyclic group. These substituents are further alkoxy groups, aryloxy groups, alkylthio groups, arylthio groups, alkoxycarbonyl groups, aryloxycarbonyl groups, sulfamoyl groups, acyl groups, acyloxy groups, amide groups, carbamoyl groups, ureido groups, alkylsulfonyl groups. , An arylsulfonyl group, a halogen atom, a fluorinated hydrocarbon group, a cyano group, a nitro group, a silyl group, etc., and these substituents are bonded to any _one of the substituents R _{1 to} R _4. To form a ring. The ring is preferably an aliphatic hydrocarbon ring, and the above-described substituent may be substituted on the ring.

In the general formula (I), the alkyl group represented by R ₆ may be linear, branched, or cyclic. For example, a methyl group, an ethyl group, a propyl group, an isopropyl group, Examples include butyl, tert-butyl, pentyl, hexyl, octyl, 2-ethylhexyl, dodecyl, tridecyl, tetradecyl, pentadecyl, cyclopentyl, cyclohexyl, benzyl, etc. It is preferably an alkyl group of 1 to 20, more preferably a butyl group, a hexyl group, an octyl group, a 2-ethylhexyl group, a cyclohexyl group or a benzyl group.

In the general formula (I), examples of the alkenyl group represented by R ₆ include vinyl and allyl groups, examples of the alkynyl group include ethynyl group and propargyl group, and examples of the aromatic hydrocarbon group include phenyl. Examples of the heteroaromatic group such as a group, a naphthyl group, etc. include a furyl group, a thienyl group, a pyridyl group, a pyridazyl group, a pyrimidyl group, a pyrazyl group, a triazyl group, an imidazolyl group, a pyrazolyl group, a thiazolyl group, a benzoimidazolyl group, and a benzoxazolyl group. Examples of the heterocyclic group such as a ruthel group, a quinazolyl group, and a phthalazyl group include a pyrrolidyl group, an imidazolidyl group, a morpholyl group, and an oxazolidyl group.

(In the formula, R ₆ represents a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, an aromatic hydrocarbon group, a heteroaromatic group, or a heterocyclic group.)
Preferred examples of R ₆ are the same as in the case of the general formula (II).

  The viscosity of the compound represented by general formula (I), (II), or (III) can be measured using, for example, a RE80 viscometer (trade name, manufactured by Toki Sangyo Co., Ltd.). The viscosity of the compound represented by formula (I) at 25 ° C. is preferably 1 to 30 mPa · s, more preferably 1 to 15 mPa · s, and particularly preferably 1 to 8 mPa · s.

  Specific examples of the compound represented by the general formula (I), (II), or (III) used in the present invention are shown below, but the present invention is not limited to these compounds.

  The compound represented by the above general formula (I) according to the present invention can be synthesized by a known synthesis method such as those disclosed in JP-A-6-16804, Japanese Patent No. 3403354 and J.P. Am. Chem. Soc. , 1957, 79 can be synthesized, but a typical example of synthesis is given below.

(Synthesis Example of Compound I-5)
Sodium hydride (5.2 g) was suspended in 100 mL of DMF under ice cooling, and 10.2 g of 3-methyl-3-oxetanemethanol was added dropwise. After stirring for 30 minutes, 20.3 g of 1-bromo-2-ethylhexane was added dropwise. After stirring for 30 minutes, the mixture was warmed to room temperature and stirred for 6 hours. The reaction mixture was poured into water and extracted with ethyl acetate. The ethyl acetate layer was washed with water, washed with saturated brine, and dried over magnesium sulfate. Ethyl acetate was distilled off and the residue was purified by column chromatography to obtain 4,9 g of compound I-5.
¹ H-NMR (300 MHz, CDCl ₃ , δ): 4.52 (dd, 2H), 4.37 (dd, 2H), 3.40 (s, 2H), 3.35 (d, 2H), 1 .52 (m, 1H), 1.40-1.22 (m, 11H), 0.95-0.84 (m, 6H).
It was 2.4 mPa * s when the viscosity at 25 degrees C of compound I-5 was measured using RE80 type viscometer (brand name, Toki Sangyo Co., Ltd. make).

(Synthesis Example of Compound I-9)
Sodium hydride (5.2 g) was suspended in 100 mL of DMF under ice cooling, and 10.2 g of 3-methyl-3-oxetanemethanol was added dropwise. After stirring for 30 minutes, 18.0 g of benzyl bromide was added dropwise. After stirring for 30 minutes, the mixture was warmed to room temperature and stirred for 3 hours. The reaction mixture was poured into water and extracted with ethyl acetate. The ethyl acetate layer was washed with water, washed with saturated brine, and dried over magnesium sulfate. Ethyl acetate was distilled off and the residue was purified by column chromatography to obtain 17.9 g of compound I-9.
¹ H-NMR (300 MHz, CDCl ₃ , δ): 7.38 (m, 5H), 4.57 (s, 2H), 4.52 (dd, 2H), 4.38 (dd, 2H), 3 .55 (s, 2H), 1.34 (s, 3H).
It was 5.6 mPa * s when the viscosity at 25 degrees C of compound I-9 was measured using RE80 type viscometer (brand name, Toki Sangyo Co., Ltd. make).

In the composition of the present invention, the content of the compound represented by the general formula (I) can be arbitrarily set, but from the viewpoint of viscosity and curability, 3 mass of the total amount of the active energy ray-curable ink composition. % To 50% by mass is preferable, and 5% to 40% by mass is more preferable.
The compound represented by the general formula (I) used in the present invention may be used not only alone but also as a mixture, or as a mixture with other cationically polymerizable compounds. The total amount of the compound represented by the general formula (I) and other cationically polymerizable compounds is preferably 70% by mass or more and 99% by mass or less, and more preferably 75% by mass or more and 98% by mass or less with respect to the total amount of the ink composition. Preferably, 80 mass% or more and 95 mass% or less are the most preferable.

  The ratio of the compound represented by the general formula (I) to the total amount of the polymerizable compound can be arbitrarily set, but is preferably 3% by mass or more and 60% by mass or less from the viewpoint of curability, viscosity, and physical properties of the cured product. 5 mass% or more and 40 mass% or less are more preferable, and 10 mass% or more and 35 mass% or less are especially preferable.

  Any other cationically polymerizable compound that can be used in combination with the compound represented by formula (I) can be used regardless of the type of monomer, oligomer, or polymer, as long as it is a compound having a generally known cationically polymerizable group. can do. Examples of the cationic polymerizable compound include the compounds exemplified below, but the present invention is not limited to these, and any known cationic polymerizable compound can be used without any problem. Moreover, the cationically polymerizable compound can be used alone or in combination for the purpose of adjusting the reaction rate, ink physical properties, cured film physical properties and the like.

As the cationically polymerizable compound, a known cationically polymerizable compound is used, and in addition to styrene derivatives and vinyl ethers, oxirane, oxetane, tetrahydrofuran, lactam, lactone, and the like are used. Of these, oxirane, oxetane, vinyl ether or styrene derivatives are preferably used, and oxirane and oxetane are particularly preferred.
Further, as the oxirane ring-containing compound (oxirane compound, that is, epoxy compound) and the oxetane ring-containing compound (oxetane compound), one may be used in addition to the compound represented by the general formula (I). You may use together. From the viewpoint of improving the curing rate and the degree of curing, it is preferable to use at least one oxetane compound and an oxirane compound in combination. In this case, the ratio of the oxirane compound and the oxetane compound is preferably 10:90 to 70:30. An ink composition having a good balance between curability and curing speed can be obtained by setting between these values.

  From the viewpoint of stably ejecting the ink composition, the other cationic polymerizable compound used in the present invention is preferably one having a low viscosity, and may contain other monofunctional cationic polymerizable compound. As the monofunctional cationically polymerizable compound, oxirane, oxetane, and vinyl ether are preferably used, and it is particularly preferable to use one or both of oxirane and oxetane. If the monofunctional cation polymerizable compound is too much, the curability is lowered, and if it is less, the viscosity of the ink composition, for example, an inkjet ink is increased. In combination with the compound represented by the general formula (I), it is preferably used in a proportion of 3% by mass or more and 50% by mass or less of the total amount of the ink composition, most preferably 5% by mass or more and 40% by mass or less.

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

  Examples of the alicyclic epoxide include cyclohexene oxide obtained by epoxidizing a compound having at least one cycloalkane ring such as cyclohexene or cyclopentene ring with a suitable oxidizing agent such as hydrogen peroxide or peracid. Preferred examples include cyclopentene oxide-containing compounds.

Examples of the aliphatic epoxides include aliphatic polyhydric alcohols or di- or polyglycidyl ethers of alkylene oxide adducts thereof. Typical examples thereof include diglycidyl ether of ethylene glycol, diglycidyl ether of propylene glycol, or 1,6. -Diglycidyl ether of alkylene glycol such as diglycidyl ether of hexanediol, polyglycidyl ether of polyhydric alcohol such as di- or triglycidyl ether of glycerin or its alkylene oxide adduct, diglycidyl of polyethylene glycol or its alkylene oxide adduct Polyalkylene glycol diglycol represented by diglycidyl ether of ether, polypropylene glycol or its alkylene oxide adduct Jill ether, and the like. Here, examples of the alkylene oxide include ethylene oxide and propylene oxide.
Among these oxirane compounds, aromatic epoxides and alicyclic epoxides are preferable from the viewpoint of excellent curing speed, and alicyclic epoxides are particularly preferable.

  Examples of monofunctional epoxides used in the present invention include, for example, phenyl glycidyl ether, p-tert-butylphenyl glycidyl ether, butyl glycidyl ether, 2-ethylhexyl glycidyl ether, allyl glycidyl ether, 1,2-butylene oxide, 1 , 3-butadiene monooxide, 1,2-epoxydodecane, epichlorohydrin, 1,2-epoxydecane, styrene oxide, cyclohexene oxide, 3-methacryloyloxymethylcyclohexene oxide, 3-acryloyloxymethylcyclohexene oxide, 3- Examples include vinylcyclohexene oxide.

  Examples of polyfunctional epoxides include, for example, bisphenol A diglycidyl ether, bisphenol F diglycidyl ether, bisphenol S diglycidyl ether, brominated bisphenol A diglycidyl ether, brominated bisphenol F diglycidyl ether, brominated bisphenol S diglycidyl. Ether, epoxy novolac resin, hydrogenated bisphenol A diglycidyl ether, hydrogenated bisphenol F diglycidyl ether, hydrogenated bisphenol S diglycidyl ether, 3,4-epoxycyclohexylmethyl-3 ′, 4′-epoxycyclohexanecarboxylate, 2 -(3,4-epoxycyclohexyl-5,5-spiro-3,4-epoxy) cyclohexane-meta-dioxane, bis (3,4-epoxycyclohexyl) Til) adipate, vinylcyclohexene oxide, 4-vinylepoxycyclohexane, bis (3,4-epoxy-6-methylcyclohexylmethyl) adipate, 3,4-epoxy-6-methylcyclohexyl-3 ′, 4′-epoxy-6 '-Methylcyclohexanecarboxylate, methylenebis (3,4-epoxycyclohexane), dicyclopentadiene diepoxide, di (3,4-epoxycyclohexylmethyl) ether of ethylene glycol, ethylenebis (3,4-epoxycyclohexanecarboxylate) , Epoxyhexahydrophthalate dioctyl, epoxyhexahydrophthalate di-2-ethylhexyl, 1,4-butanediol diglycidyl ether, 1,6-hexanediol diglycidyl ether, Resin triglycidyl ether, trimethylolpropane triglycidyl ether, polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ethers, 1,1,3-tetradecadiene dioxide, limonene dioxide, 1,2,7,8-di Examples thereof include epoxy octane, 1,2,5,6-diepoxycyclooctane and the like.

[Oxetane compounds]
The oxetane compound that can be used in the present invention refers to a compound having an oxetane ring, and can be selected from the compounds described in JP-A Nos. 2001-220526, 2001-310937, and 2003-341217.
As the compound having an oxetane ring that can be used in the ink composition of the present invention, a compound having 1 to 4 oxetane rings in its structure is preferable, and as described above, the viscosity and tackiness of the ink composition are particularly preferable. From the viewpoint, it is preferable to use a compound having one or two oxetane rings. By using such a compound, it becomes easy to maintain the viscosity of the ink composition in a good handling property range, and it is possible to obtain high adhesion of the cured ink to the recording medium. .

  Examples of the compound having 1 to 2 oxetane rings in the molecule include compounds represented by the following general formulas (1) to (3).

R ^a1 represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, a fluoroalkyl group having 1 to 6 carbon atoms, an allyl group, an aryl group, a furyl group, or a thienyl group. When two R ^a1 are present in the molecule, they may be the same or different.
Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, and a butyl group. Preferred examples of the fluoroalkyl group include those in which any hydrogen of these alkyl groups is substituted with a fluorine atom.

R ^a2 is an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, a group having an aromatic ring, an alkylcarbonyl group having 2 to 6 carbon atoms, or an alkoxycarbonyl having 2 to 6 carbon atoms. Group represents an N-alkylcarbamoyl group having 2 to 6 carbon atoms. Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, and a butyl group. Examples of the alkenyl group include a 1-propenyl group, a 2-propenyl group, a 2-methyl-1-propenyl group, and 2-methyl-2. -Propenyl group, 1-butenyl group, 2-butenyl group, 3-butenyl group and the like. Examples of the group having an aromatic ring include phenyl group, benzyl group, fluorobenzyl group, methoxybenzyl group, phenoxyethyl group and the like. Can be mentioned. As the alkylcarbonyl group, an ethylcarbonyl group, a propylcarbonyl group, a butylcarbonyl group, etc., as an alkoxycarbonyl group, an ethoxycarbonyl group, a propoxycarbonyl group, a butoxycarbonyl group, etc., as an N-alkylcarbamoyl group, Examples thereof include an ethylcarbamoyl group, a propylcarbamoyl group, a butylcarbamoyl group, and a pentylcarbamoyl group.

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

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

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

In general formula (4), R ^a1 has the same ^meaning as in general formula (1). In addition, as R ^a9 which is a polyvalent linking group, for example, a branched polyalkylene group having 1 to 12 carbon atoms such as groups represented by the following A to C, a branched poly ( An alkyleneoxy) group or a branched polysiloxy group such as a group represented by E below. j is 3 or 4.

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

  Another embodiment of the oxetane compound that can be suitably used in the present invention includes a compound represented by the following general formula (5) having an oxetane ring in the side chain.

In the general formula (5), R ^a1 and R ^a8 have the same ^{meaning as} in the above formula. R ^a11 is an alkyl group having 1 to 4 carbon atoms such as a methyl group, an ethyl group, a propyl group, or a butyl group, or a trialkylsilyl group, and r is 1 to 4.

  Examples of monofunctional oxetanes include oxetane compounds used in the present invention, such as 3-ethyl-3-hydroxymethyloxetane, 3- (meth) allyloxymethyl-3-ethyloxetane, and (3-ethyl-3 -Oxetanylmethoxy) methylbenzene, 4-fluoro- [1- (3-ethyl-3-oxetanylmethoxy) methyl] benzene, 4-methoxy- [1- (3-ethyl-3-oxetanylmethoxy) methyl] benzene, [ 1- (3-ethyl-3-oxetanylmethoxy) ethyl] phenyl ether, isobutoxymethyl (3-ethyl-3-oxetanylmethyl) ether, isobornyloxyethyl (3-ethyl-3-oxetanylmethyl) ether, isobornyl (3-Ethyl-3-oxetanylmethyl) ether, 2-ethyl Hexyl (3-ethyl-3-oxetanylmethyl) ether, ethyldiethylene glycol (3-ethyl-3-oxetanylmethyl) ether, dicyclopentadiene (3-ethyl-3-oxetanylmethyl) ether, dicyclopentenyloxyethyl (3- Ethyl-3-oxetanylmethyl) ether, dicyclopentenyl (3-ethyl-3-oxetanylmethyl) ether, tetrahydrofurfuryl (3-ethyl-3-oxetanylmethyl) ether, tetrabromophenyl (3-ethyl-3-oxetanyl) Methyl) ether, 2-tetrabromophenoxyethyl (3-ethyl-3-oxetanylmethyl) ether, tribromophenyl (3-ethyl-3-oxetanylmethyl) ether, 2-tribromophenoxyethyl (3-ethyl) Ru-3-oxetanylmethyl) ether, 2-hydroxyethyl (3-ethyl-3-oxetanylmethyl) ether, 2-hydroxypropyl (3-ethyl-3-oxetanylmethyl) ether, butoxyethyl (3-ethyl-3- Oxetanylmethyl) ether, pentachlorophenyl (3-ethyl-3-oxetanylmethyl) ether, pentabromophenyl (3-ethyl-3-oxetanylmethyl) ether, bornyl (3-ethyl-3-oxetanylmethyl) ether, and the like. .

  Examples of the polyfunctional oxetane include 3,7-bis (3-oxetanyl) -5-oxa-nonane, 3,3 ′-(1,3- (2-methylenyl) propanediylbis (oxymethylene)) bis. -(3-ethyloxetane), 1,4-bis [(3-ethyl-3-oxetanylmethoxy) methyl] benzene, 1,2-bis [(3-ethyl-3-oxetanylmethoxy) methyl] ethane, 1, 3-bis [(3-ethyl-3-oxetanylmethoxy) methyl] propane, ethylene glycol bis (3-ethyl-3-oxetanylmethyl) ether, dicyclopentenylbis (3-ethyl-3-oxetanylmethyl) ether, tri Ethylene glycol bis (3-ethyl-3-oxetanylmethyl) ether, tetraethylene glycol bis (3-ethyl) -3-oxetanylmethyl) ether, tricyclodecanediyldimethylene (3-ethyl-3-oxetanylmethyl) ether, trimethylolpropane tris (3-ethyl-3-oxetanylmethyl) ether, 1,4-bis (3- Ethyl-3-oxetanylmethoxy) butane, 1,6-bis (3-ethyl-3-oxetanylmethoxy) hexane, pentaerythritol tris (3-ethyl-3-oxetanylmethyl) ether, pentaerythritol tetrakis (3-ethyl-3 -Oxetanylmethyl) ether, polyethylene glycol bis (3-ethyl-3-oxetanylmethyl) ether, dipentaerythritol hexakis (3-ethyl-3-oxetanylmethyl) ether, dipentaerythritol pentakis (3-ethyl) 3-oxetanylmethyl) ether, dipentaerythritol tetrakis (3-ethyl-3-oxetanylmethyl) ether, caprolactone-modified dipentaerythritol hexakis (3-ethyl-3-oxetanylmethyl) ether, caprolactone-modified dipentaerythritol pentakis ( 3-ethyl-3-oxetanylmethyl) ether, ditrimethylolpropanetetrakis (3-ethyl-3-oxetanylmethyl) ether, EO-modified bisphenol A bis (3-ethyl-3-oxetanylmethyl) ether, PO-modified bisphenol A bis ( 3-ethyl-3-oxetanylmethyl) ether, EO-modified hydrogenated bisphenol A bis (3-ethyl-3-oxetanylmethyl) ether, PO-modified hydrogenated bisphenol A bis (3-ethyl) And polyfunctional oxetanes such as ru-3-oxetanylmethyl) ether and EO-modified bisphenol F (3-ethyl-3-oxetanylmethyl) ether.

[Vinyl ether]
Further, in the present invention, a compound having a vinyl ether group may be further contained in order to impart a degree of curing. In this case, the compound having a vinyl ether group can be present in the ink composition in the range of 1% by mass to 20% by mass from the viewpoint of adjusting the surface physical properties of the cured product and the solubility of the ink composition.
Examples of monofunctional vinyl ethers used in the present invention include, for example, methyl vinyl ether, ethyl vinyl ether, propyl vinyl ether, n-butyl vinyl ether, t-butyl vinyl ether, 2-ethylhexyl vinyl ether, n-nonyl vinyl ether, lauryl vinyl ether, cyclohexyl vinyl ether, Cyclohexylmethyl vinyl ether, 4-methylcyclohexyl methyl vinyl ether, benzyl vinyl ether, dicyclopentenyl vinyl ether, 2-dicyclopentenoxyethyl vinyl ether, methoxyethyl vinyl ether, ethoxyethyl vinyl ether, butoxyethyl vinyl ether, methoxyethoxyethyl vinyl ether, ethoxyethoxyethyl vinyl ether , Methoxy polyethylene Recall vinyl ether, tetrahydrofurfuryl vinyl ether, 2-hydroxyethyl vinyl ether, 2-hydroxypropyl vinyl ether, 4-hydroxybutyl vinyl ether, 4-hydroxymethylcyclohexyl methyl vinyl ether, diethylene glycol monovinyl ether, polyethylene glycol vinyl ether, chloroethyl vinyl ether, chlorobutyl vinyl ether, Examples include chloroethoxyethyl vinyl ether, phenylethyl vinyl ether, phenoxypolyethylene glycol vinyl ether, and the like.

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

[Styrene derivatives]
In the present invention, a styrene derivative may be further contained. In this case, a known compound is used as the styrene derivative. From the viewpoint of improving the electron density on the vinyl group, styrene in which at least one of the p-position and the o-position of the aromatic ring is substituted with an electron-donating functional group. Derivatives are preferably used. Here, the electron-donating functional group means a group having a negative Hammett's rule substituent constant σ value, and examples of such a functional group include an amino group, a hydroxyl group, an alkoxy group, and an alkyl group. Among these, an alkoxy group, an alkyl group, and a dimethylamino group are preferably used because they hardly react with the active terminal during polymerization.

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

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

The ink composition of the present invention preferably contains at least one polymerization initiator and at least one photosensitizer from the viewpoint of curability.
[Polymerization initiator]
The polymerization initiator preferably used in the present invention is a photocationic polymerization initiator. A photocationic polymerization initiator refers to a compound that generates an acid upon irradiation with actinic rays or radiation to initiate cationic polymerization, and publicly known compounds and mixtures thereof can be appropriately selected and used.
As the photocationic polymerization initiator, those listed below may be used alone or in combination of two or more. The content of the present cationic photopolymerization initiator in the ink composition is preferably 0.1 to 20% by mass, and more preferably 0.5 to 10% by mass. When the content of the photocationic polymerization initiator is 0.1% or less, the amount of acid generated is reduced, so that the curability may be lowered. When the content of the photocationic polymerization initiator is 20% or more, the brittleness of the cured product is reduced. And the generation of acid by the remaining initiator may cause a problem, which is not preferable.

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

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

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

In the general formula (b1), R ²⁰¹ , R ²⁰² and R ²⁰³ each independently represents an organic group.
X ⁻ represents a non-nucleophilic anion, preferably a sulfonate anion, a carboxylate anion, a bis (alkylsulfonyl) amide anion, a tris (alkylsulfonyl) methide anion, BF ₄ ⁻ , PF ₆ ⁻ , SbF ₆ ⁻ or the following The organic anion which has a carbon atom is preferable.

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

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

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

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

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

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

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

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

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

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

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

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

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

Next, the compound (b1-2) will be described.
The compound (b1-2) is a compound in the case where R ^{201 to} R ²⁰³ in the formula (b1) each independently represents an organic group not containing an aromatic ring. Here, the aromatic ring includes an aromatic ring containing a hetero atom.
The organic group having no aromatic ring as R ²⁰¹ to R ²⁰³ is preferably 1 to 30 carbon atoms, more preferably 1 to 20 carbon atoms.
R ^{201 to} R ²⁰³ are each independently preferably an alkyl group, a cycloalkyl group, an allyl group or a vinyl group, more preferably a linear, branched or cyclic 2-oxoalkyl group, an alkoxycarbonylmethyl group, particularly A linear or branched 2-oxoalkyl group is preferred.

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

The cycloalkyl group as R ²⁰¹ to R ²⁰³ is preferably a cycloalkyl group having 3 to 10 carbon atoms (a cyclopentyl group, a cyclohexyl group, a norbornyl group) can be exemplified, more preferably a cyclic 2-oxoalkyl group.

Linear R ²⁰¹ to R ^203, branched, or a cyclic 2-oxoalkyl group, preferably, may be mentioned 2-position group having> C = O at the above-described alkyl or cycloalkyl group.
The alkoxy group in the alkoxycarbonylmethyl group as R ²⁰¹ to R ^203, preferably may be mentioned alkoxy groups having 1 to 5 carbon atoms (a methoxy group, an ethoxy group, a propoxy group, a butoxy group, a pentoxy group).
R ^{201 to} R ²⁰³ may be further substituted with a halogen atom, an alkoxy group (for example, having 1 to 5 carbon atoms), a hydroxyl group, a cyano group, or a nitro group.

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

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

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

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

The alkoxy group as R ^{1c to} R ^{5c may} be linear, branched or cyclic, for example, an alkoxy group having 1 to 10 carbon atoms, preferably a linear or branched alkoxy group having 1 to 5 carbon atoms. Group (for example, methoxy group, ethoxy group, linear or branched propoxy group, linear or branched butoxy group, linear or branched pentoxy group), cyclic alkoxy group having 3 to 8 carbon atoms (for example, cyclopentyloxy group) Cyclohexyloxy group).

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

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

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

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

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

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

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

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

Preferable examples of the photocationic polymerization initiator include compounds represented by general formulas (b1) to (b3).
Specific examples of particularly preferable photocationic polymerization initiators that can be used in the present invention are listed below, but the present invention is not limited thereto.

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

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

[Photosensitizer]
In the present invention, it is preferable to add a photosensitizer for the purpose of improving the sensitivity of the photopolymerization initiator. Preferable photosensitizers include sensitizing dyes belonging to the following compounds and those having an absorption wavelength in the 350 nm to 450 nm region.
Polynuclear aromatics (eg, pyrene, perylene, triphenylene), xanthenes (eg, fluorescein, eosin, erythrosine, rhodamine B, rose bengal), cyanines (eg, thiacarbocyanine, oxacarbocyanine), merocyanines ( For example, merocyanine, carbomerocyanine), thiazines (for example, thionine, methylene blue, toluidine blue), acridines (for example, acridine orange, chloroflavin, acriflavine), anthraquinones (for example, anthraquinone), squalium (for example, squalium) ), Coumarins (eg 7-diethylamino-4-methylcoumarin).

  More preferable examples of the sensitizing dye include compounds represented by the following general formulas (IX) to (XIII).

In formula (IX), A ¹ represents a sulfur atom or NR ⁵⁰ , R ⁵⁰ represents an alkyl group or an aryl group, and L ² forms a basic nucleus of the dye together with the adjacent A ¹ and the adjacent carbon atom. R ⁵¹ and R ⁵² each independently represent a hydrogen atom or a monovalent nonmetallic atomic group, and R ⁵¹ and R ⁵² may be bonded to each other to form an acidic nucleus of the dye. Good. W represents an oxygen atom or a sulfur atom.
In formula (X), Ar ¹ and Ar ² each independently represent an aryl group and are linked via a bond with —L ³ —. Here, L ³ represents —O— or —S—. W is synonymous with that shown in the general formula (IX).
In the formula (XI), A ² represents a sulfur atom or NR ⁵⁹ , L ⁴ represents a nonmetallic atomic group that forms a basic nucleus of the dye together with the adjacent A ² and carbon atom, R ⁵³ , R ⁵⁴ , R ⁵⁵ , R ⁵⁶ , R ⁵⁷ and R ⁵⁸ each independently represents a monovalent nonmetallic atomic group, and R ⁵⁹ represents an alkyl group or an aryl group.

In formula (XII), A ³ and A ⁴ each independently represent —S— or —NR ⁶² — or —NR ⁶³ —, wherein R ⁶² and R ⁶³ each independently represent a substituted or unsubstituted alkyl group, substituted or represents an unsubstituted aryl group, L to ^5, L ⁶ are each independently, together with the adjacent a ^3, a ⁴ and adjacent carbon atoms represents a nonmetallic atom group necessary for forming a basic nucleus of a dye, R ⁶⁰ , R ⁶¹ each independently represents a hydrogen atom or a monovalent non-metallic atomic group, or may be bonded to each other to form an aliphatic or aromatic ring.
In formula (XIII), R ⁶⁶ represents an aromatic ring or a hetero ring which may have a substituent, and A ⁵ represents an oxygen atom, a sulfur atom or —NR ⁶⁷ —. R ⁶⁴ , R ⁶⁵ and R ⁶⁷ each independently represent a hydrogen atom or a monovalent nonmetallic atomic group, and R ⁶⁷ and R ⁶⁴ , and R ⁶⁵ and R ⁶⁷ each represent an aliphatic or aromatic ring. Can be combined to form.

  Preferred specific examples of the compounds represented by the general formulas (IX) to (XIII) include the exemplified compounds (A-1) to (A-20) shown below.

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

The pigment preferably used in the present invention will be described.
[Pigment]
The pigment is not particularly limited, and all commercially available organic and inorganic pigments or pigments dispersed in an insoluble resin or the like as a dispersion medium, or the resin is grafted onto the pigment surface Can be used. Moreover, what dye | stained the resin particle with dye can be used.
Examples of these pigments include, for example, “Pigment Dictionary” (2000), edited by Seijiro Ito. Herbst, K.M. Hunger, “Industrial Organic Pigments”, JP 2002-12607 A, JP 2002-188025 A, JP 2003-26978 A, JP 2003-342503 A, and the like.

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

  C. As a thing which exhibits red or magenta color, C.I. I. Monoazo pigments such as CI Pigment Red 3 (Toluidine Red, etc.); I. Disazo pigments such as C.I. Pigment Red 38 (Pyrazolone Red B, etc.); I. Pigment Red 53: 1 (Lake Red C, etc.) and C.I. I. Azo lake pigments such as C.I. Pigment Red 57: 1 (Brilliant Carmine 6B); I. Condensed azo pigments such as C.I. Pigment Red 144 (condensed azo red BR, etc.); I. Acidic dye lake pigments such as C.I. Pigment Red 174 (Phloxine B Lake, etc.); I. Basic dye lake pigments such as C.I. Pigment Red 81 (Rhodamine 6G 'lake, etc.); I. Anthraquinone pigments such as C.I. Pigment Red 177 (eg, dianthraquinonyl red); I. Thioindigo pigments such as C.I. Pigment Red 88 (Thioindigo Bordeaux, etc.); I. Perinone pigments such as C.I. Pigment Red 194 (perinone red, etc.); I. Perylene pigments such as C.I. Pigment Red 149 (perylene scarlet, etc.); I. Pigment violet 19 (unsubstituted quinacridone), C.I. I. Quinacridone pigments such as CI Pigment Red 122 (quinacridone magenta, etc.); I. Isoindolinone pigments such as CI Pigment Red 180 (isoindolinone red 2BLT, etc.); I. And alizarin lake pigments such as CI Pigment Red 83 (Mada Lake, etc.).

  As a pigment exhibiting blue or cyan, C.I. I. Disazo pigments such as C.I. Pigment Blue 25 (Dianisidine Blue, etc.); I. Phthalocyanine pigments such as C.I. Pigment Blue 15 (phthalocyanine blue, etc.); I. Acidic dye lake pigments such as C.I. Pigment Blue 24 (Peacock Blue Lake, etc.); I. Basic dye lake pigments such as C.I. Pigment Blue 1 (Viclotia Pure Blue BO Lake, etc.); I. Anthraquinone pigments such as C.I. Pigment Blue 60 (Indantron Blue, etc.); I. And alkali blue pigments such as CI Pigment Blue 18 (Alkali Blue V-5: 1).

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

Examples of the black pigment include carbon black, titanium black, and aniline black.
Specific examples of white pigments include basic lead carbonate (2PbCO ₃ Pb (OH) ₂ , so-called silver white), zinc oxide (ZnO, so-called zinc white), titanium oxide (TiO ₂ , so-called titanium white), strontium titanate (SrTiO ₃ , so-called titanium strontium white) can be used.

  Here, titanium oxide has a smaller specific gravity than other white pigments, a large refractive index, and is chemically and physically stable, so that it has a large hiding power and coloring power as a pigment. Excellent durability against other environments. Therefore, it is preferable to use titanium oxide as the white pigment. Of course, other white pigments (may be other than the listed white pigments) may be used as necessary.

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

  In the ink composition, as a dispersion medium for various components such as pigments, a solvent may be added, and the cationic polymerizable compound that is a low molecular weight component without a solvent may be used as a dispersion medium. The ink composition of the invention is a radiation curable ink, and is preferably solvent-free in order to be cured after the ink is applied to a recording medium. This is because if the solvent remains in the cured ink image, the solvent resistance is deteriorated or a VOC (Volatile Organic Compound) problem of the remaining solvent occurs. From such a viewpoint, it is preferable to use a cationically polymerizable compound as the dispersion medium, and in particular, to select a cationically polymerizable monomer having the lowest viscosity from the viewpoint of dispersion suitability and handling property of the ink composition.

The average particle diameter of the pigment used here is preferably about 0.01 to 0.4 [mu] m, more preferably 0.02 to 0.2 [mu] m, because the finer the particle, the better the color developability. The selection of pigment, dispersant, dispersion medium, dispersion conditions, and filtration conditions are set so that the maximum particle diameter is 3 μm or less, preferably 1 μm or less. By controlling the particle size, clogging of the head nozzle can be suppressed, and ink storage stability, ink transparency, and curing sensitivity can be maintained.
The particle size of the pigment in the ink composition can be measured by a known measurement method. Specifically, it can be measured by a centrifugal sedimentation light transmission method, an X-ray transmission method, a laser diffraction / scattering method, a dynamic light scattering method, or a counting method using a transmission electron microscope. In the present invention, a value obtained by a counting method using a transmission electron microscope is employed.
The pigment is preferably added in an amount of 1 to 20% by mass in terms of solid content in the ink composition, and more preferably 2 to 10% by mass.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

  The value of Eox represents the ease of electron transfer from the sample to the electrode, and the greater the value (the higher the oxidation potential), the more difficult the electron transfer from the sample to the electrode, in other words, the less easily oxidized. In relation to the structure of the compound, the oxidation potential becomes more noble by introducing an electron withdrawing group, and the oxidation potential becomes lower by introducing an electron donating group. In the present invention, in order to lower the reactivity with ozone as an electrophile, it is desirable to introduce an electron withdrawing group into the dye skeleton to make the oxidation potential more noble.

[Other ingredients]
Hereinafter, various additives that can be contained in the ink composition of the present invention as needed are described.
[Ultraviolet absorber]
From the viewpoint of improving the weather resistance of the resulting image and preventing discoloration, an ultraviolet absorber can be used.
Examples of the ultraviolet absorber are described in JP-A-58-185679, JP-A-61-190537, JP-A-2-782, JP-A-5-97075, JP-A-9-34057, and the like. Benzotriazole compounds, benzophenone compounds described in JP-A No. 46-2784, JP-A No. 5-194843, US Pat. No. 3,214,463, etc., JP-B Nos. 48-30492 and 56-21141 Cinnamic acid compounds described in JP-A-10-88106, JP-A-4-298503, JP-A-8-53427, JP-A-8-239368, JP-A-10-182621, JP The triazine compounds described in JP-A-8-501291, Research Disclosure No. Examples thereof include compounds described in No. 24239, compounds that emit ultraviolet light by absorbing ultraviolet rays typified by stilbene and benzoxazole compounds, so-called fluorescent brighteners, and the like.
The amount added is appropriately selected according to the purpose, but is generally about 0.01 to 10% by mass of the ink composition.

〔Antioxidant〕
An antioxidant can be added to improve the stability of the ink composition. Examples of the antioxidant include European published patents, 223739, 309401, 309402, 310551, 310552, 359416, and 3435443. JP, 54-85535, 62-262417, 63-113536, 63-163351, JP-A-2-262654, JP-A-2-71262, Examples thereof include those described in Kaihei 3-121449, JP-A-5-61166, JP-A-5-119449, US Pat. No. 4,814,262, US Pat. No. 4,980,275, and the like.
The addition amount is appropriately selected according to the purpose, but is generally about 0.001 to 1% by mass of the ink composition.

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

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

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

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

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

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

[Preferred physical properties of ink composition]
When the ink composition of the present invention is applied to ink jet recording, the ink temperature during ejection is maintained at a substantially constant temperature in the range of 15 to 90 ° C., and the viscosity at that time is 1 to 20 mPa · s. More preferably, it is 2-12 mPa * s, More preferably, it is 2-10 mPa * s. It is preferable to adjust the composition ratio appropriately so as to be in the above range. The ink viscosity at 25 ° C. is preferably 1 to 50 mPa · s, more preferably 2 to 20 mPa · s, and still more preferably 2 to 12 mPa · s.

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

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

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

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

  In the recorded matter obtained using the ink composition of the present invention, the image portion is cured by irradiation with radiation such as ultraviolet rays, and the strength of the image portion is excellent. It can be used for various purposes such as formation of an ink receiving layer (image portion) of a plate.

  Next, an ink jet recording method and an ink jet recording apparatus that can be suitably employed in the present invention will be described below.

  In the ink jet recording method of the present invention, recording is performed using the ink for ink jet recording, but there are no particular limitations on the ink nozzles and the like used at that time, and they can be appropriately selected according to the purpose. As an example of a system for printing using the above ink, a mode as disclosed in JP-A-2002-11860 is given as an example, but the present invention is not limited to this, and other modes may be used.

  One feature of the ink jet recording apparatus is that it includes a means for stabilizing the temperature of the ink composition, and the portion to be kept at a constant temperature is a piping system from an ink tank (an intermediate tank if there is an intermediate tank) to the nozzle ejection surface. All of the members are targeted.

  The temperature control method is not particularly limited, but for example, it is preferable to provide a plurality of temperature sensors in each piping portion and perform heating control according to the ink composition flow rate and the environmental temperature. Moreover, it is preferable that the head unit to be heated is thermally shielded or insulated so that the apparatus main body is not affected by the temperature from the outside air. In order to shorten the printer start-up time required for heating or to reduce the loss of thermal energy, it is preferable to insulate from other parts and reduce the heat capacity of the entire heating unit.

Next, radiation conditions will be described. A basic irradiation method is disclosed in JP-A-60-132767. Specifically, a light source is provided on both sides of the head unit, and the head and the light source are scanned by a shuttle method. Irradiation is performed after a certain period of time after ink landing. Further, the curing is completed by another light source that is not driven. In WO99 / 54415, as an irradiation method, a method using an optical fiber or a method in which a collimated light source is applied to a mirror surface provided on the side surface of the head unit to irradiate the recording unit with UV light is disclosed. In the present invention, these irradiation methods can be used. As the active energy ray to be irradiated, a commonly used mercury lamp, metal halide lamp, or the like may be used, or a light source such as a light emitting diode (LED), a semiconductor laser, or a fluorescent lamp may be used. Further, a hot cathode tube, a cold cathode tube, an electron beam, an X-ray, or the like, a light source in which an ink polymerization reaction proceeds, an electromagnetic wave, or the like can be used.
In the present invention, it is preferable to use an LED or a semiconductor laser as a light source. The LED or semiconductor laser is characterized by its small size. In particular, LEDs have the advantages of long life, low calorific value, low power consumption, no generation of ozone, and immediate use when turned on. In addition, a light source of 365 nm ± 20 nm is advantageous in terms of cost, and an existing photopolymerization initiation system can be used.
When using a metal halide lamp, the lamp should be designed 10~1000W / cm ^2, it is preferable that the illuminance of 1mW / cm ² ~100W / cm ² at the media surface. The exposure energy is preferably 0.1 mJ / cm ^{2 to} 100 J / cm ² .
Further, in a mercury lamp, a metal halide lamp, or the like that uses high-pressure discharge, ozone is generated due to discharge, and therefore it is preferable to have an exhaust means. The exhaust means is preferably arranged so as to also collect ink mist generated during ink ejection.
In the case of curing by radical polymerization, since the polymerization is inhibited by oxygen, it can be cured with low energy by exposure in a low oxygen concentration state, that is, in a gas atmosphere such as nitrogen.
When energy such as light for curing is applied to the ink discharge nozzle, the ink mist adhering to the surface of the nozzle may solidify, which may hinder ink discharge. In order to keep it to a minimum, it is preferable to take measures such as shading. Specifically, it is preferable to provide a partition that prevents the nozzle plate from being irradiated, or to provide a means for limiting the incident angle to the medium so as to reduce stray light.

  In the present invention, when used as an inkjet ink, the ink composition is heated to a constant temperature, and the time from landing to irradiation is preferably from 0.01 to 0.5 seconds, more preferably from 0.01 to Radiation is irradiated after 0.3 seconds, more preferably from 0.01 to 0.15 seconds. Thus, by controlling the time from landing to irradiation to an extremely short time, it is possible to prevent the landing ink from bleeding before curing. In addition, since the ink composition can be exposed to a porous recording medium before reaching the deep part where the light source does not reach, residual unreacted monomer can be suppressed, and as a result, odor can be reduced. Can do. By using the inkjet recording method described above and the ink composition of the present invention in combination, a great synergistic effect is brought about. In particular, when an ink composition having an ink viscosity of 35 to 500 mPa · s at 25 ° C. is used, a great effect can be obtained. By adopting such a recording method, the dot diameter of the landed ink can be kept constant even on various recording media having different surface wettability, and the image quality is improved. In addition, in order to obtain a color image, it is preferable to superimpose in order from the color with the lowest brightness. When inks with low lightness are stacked, it is difficult for the irradiation rays to reach the lower ink, and inhibition of curing sensitivity, increase of residual monomers, generation of odor, and deterioration of adhesion tend to occur. Irradiation can be performed by injecting all colors and exposing them together, but exposure for each color is preferable from the viewpoint of curing acceleration.

  There is no restriction | limiting in particular as an inkjet recording device used for this invention, A commercially available inkjet recording device can be used. That is, in the present invention, recording can be performed on a recording medium using a commercially available inkjet recording apparatus.

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

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

  As a method for ejecting ink, as disclosed in Japanese Patent Application Laid-Open No. 5-104725, whether or not ink droplets are continuously ejected and deflected according to an image to land on a medium is determined. A selection control method may be used, or a so-called on-demand method may be used, in which ink droplets are ejected only to a portion necessary as an image. As disclosed in JP-A-5-16349, the on-demand system may be a system that generates and discharges ink pressure by deformation of a structure using a piezoelectric element or the like. As disclosed in Japanese Patent No. 234255, a method of discharging at a pressure generated by expansion accompanying vaporization by thermal energy may be used. Further, as disclosed in Japanese Patent Laid-Open No. 2001-277466, a method of controlling ejection to a medium by an electric field may be used.

  For example, a mode described in Japanese Patent Laid-Open No. 5-31908 can be applied to the nozzle. At this time, in order to eject ink of a plurality of colors, the nozzles are configured in a plurality of rows as described in JP-A-2002-316420, so that a color image can be formed at high speed. Furthermore, it is possible to further increase the speed by arranging a plurality of head units having a plurality of nozzle rows.

  Furthermore, as described in JP-A-63-160849, nozzles are arranged by a width equal to or greater than the width of the image, so-called line heads are formed, and the media is moved simultaneously with the droplet ejection from these nozzles. Therefore, it is possible to form an image at high speed. Further, the surface of the nozzle is subjected to a surface treatment as disclosed in JP-A-5-116327, thereby preventing ink droplets from adhering to the nozzle surface and ink droplets from being adhered. Even if such treatment is performed, dirt may still adhere, and therefore it is preferable to perform cleaning with a blade as disclosed in JP-A-6-71904. In addition, the inks of the respective colors are not necessarily ejected from the nozzles uniformly, and specific inks may not be ejected for a long time. In such a case, in order to keep the meniscus stable, as disclosed in Japanese Patent Application Laid-Open No. 11-157102, ink is appropriately ejected outside the image region, and new ink is supplied to the head, thereby providing ink physical properties. Is preferably maintained at a suitable value. Further, even if such treatment is performed, bubbles may enter the head or be generated in the head. In such a case, as described in Japanese Patent Application Laid-Open No. 11-334092, by forcibly sucking ink from the outside of the head, the ink whose physical properties have changed is discarded, and bubbles are also discharged outside the head. be able to. In the case where the droplets are not ejected for a long time, the nozzle surface can be protected by covering the nozzle surface with a cap as disclosed in JP-A-11-138830. Even if these measures are taken, there is a case where the liquid is still not discharged. If an image is printed in a state where some of the nozzles do not discharge, problems such as unevenness in the image occur. In order to avoid such a situation, it is effective to take a measure by detecting that no discharge has occurred, as disclosed in Japanese Unexamined Patent Publication No. 2000-343686.

  In discharging the ink, it is preferable to keep the ink temperature constant with a predetermined accuracy in order to keep the viscosity constant. For this purpose, it is preferable to have an ink temperature detecting means, an ink heating means, and a control means for controlling heating according to the detected ink temperature. It is also preferable to have a means for controlling energy applied to the means for ejecting ink according to the ink temperature. When the head unit is mechanically moved as described in Japanese Patent Laid-Open No. 6-115999, and superimposed droplet ejection is performed by intermittently moving the medium in the orthogonal direction in synchronization with the head unit, the medium intermittently This has the effect of making it difficult to see the unevenness caused by poor movement accuracy, and can achieve high image quality. At this time, the relationship between the image quality and the recording speed can be set to a preferable relationship by appropriately setting the relationship between the moving speed of the head, the moving amount of the medium, and the number of nozzles. On the contrary, the same effect can be obtained by fixing the head and mechanically reciprocating the medium in a predetermined direction and intermittently moving the medium in a direction orthogonal thereto.

[System parameters]
In forming an image, the ink landing diameter on the medium is preferably between 10 and 500 μm, and for this purpose, the diameter of the ink droplet at the time of ejection is preferably 5 to 250 μm. The nozzle diameter is preferably 15 to 100 μm. In order to form an image, the number of pixels per inch is preferably 50 to 2400 dpi, and for that purpose, the nozzle density of the head is preferably 10 to 2400 dpi. Here, even if the nozzle density of the head is low, it is possible to achieve high-density landing with a head with a large nozzle interval by tilting with respect to the media transport direction or by disposing a plurality of head units relative to each other. Is possible. In addition, by reciprocating the head or media as described above, each time the head moves at a low nozzle pitch, the media is transported by a predetermined amount, and ink droplets are landed at different positions, thereby realizing high-density image recording. Can do.
In order to express good gradation, it is preferable that the amount of ink ejected onto the medium can be controlled to an arbitrary amount between 0.05 and 25 g / m ² . It is preferable to control the size and / or quantity of the ejected ink droplets.
As for the distance between the head and the medium, if the distance is too wide, the flight of ink droplets is disturbed by the air flow accompanying the movement of the head or the medium, and the landing position accuracy is lowered. On the other hand, if the interval is narrow, there is a risk that the head and the medium come into contact with each other due to unevenness of the medium, vibration caused by the transport mechanism, and the like, and it is preferably maintained at about 0.5 to 2 mm.

[Ink set]
The ink may be a single color, may be cyan, magenta, or yellow, or may be four colors including black or a specific color other than these, called a special color. The coloring material may be a dye or a pigment. These inks may be ejected in order of landing in order of increasing lightness, may be landed in order of increasing lightness, or are preferably ejected in an order suitable for image recording quality. The image signal to be recorded is preferably subjected to signal processing to obtain good color reproduction, as described in, for example, Japanese Patent Laid-Open No. 6-210905.

[Recording material]
The ink composition of the present invention can be suitably recorded on a known recording material.
The recording material to which the ink composition of the present invention can be applied is not particularly limited, and is used for ordinary plain paper, uncoated paper, coated paper, inkjet paper, electrophotographic paper, and other so-called soft packaging. Various non-absorbable resin materials used or resin films obtained by forming them into a film can be used. Examples of various plastic films include PET (polyethylene terephthalate) film, OPS (stretched polystyrene) film, and OPP (stretched). Polypropylene) film, ONy (biaxially stretched nylon) film, PVC (polyvinyl chloride) film, PE (polyethylene) film, TAC (triacetyl cellulose) film and the like. In addition, examples of the plastic that can be used as the recording material include polycarbonate, acrylic resin, ABS, polyacetal, PVA, and rubbers. Metals, glasses, fabrics, ceramics, etc. can also be used as recording materials. As the recording material, those described in paragraph numbers (0228) to (0246) of JP-A Nos. 2001-181549 and 2001-279141 can also be used.

  EXAMPLES Hereinafter, although an Example demonstrates this invention, this invention is not limited to these Examples. In this example, an example of producing ink for inkjet recording is shown as an example of the ink composition.

<Preparation of pigment dispersion>
First, the pigment and the dispersant shown in Table 1 were placed in a ball mill and dispersed for 16 hours using zircon beads having a diameter of 0.6 mm to obtain a pigment dispersion. The average particle diameter of the pigment particles in the pigment dispersion was measured by measuring the length of the particle major axis of 100 arbitrary particles with a transmission electron microscope (TEM) and indicating the number average. The measurement results are shown in Table 1.

(Preparation of sample 100)
The following components were stirred and mixed, and filtered through a 5.0 μm membrane filter to obtain a cyan ink sample 100.
<Sample 100 ink composition component>
Monomer A: 70 g of alicyclic epoxy group-containing compound of the following formula
(Celoxide 3000, trade name, manufactured by Daicel UCB)
Monomer B: 30 g of bis (3-ethyl-3-oxetanylmethyl) ether
(Aron Oxetane OXT-221, trade name, manufactured by Toa Gosei)
Pigment dispersion: 10 g of pigment dispersion-1 in Table 1
Photopolymerization initiator: (4-isobutylphenyl) 4-methylphenyliodonium hexafluorophosphate and propylene carbonate 6.0 g
(Irgacure 250, trade name, manufactured by Ciba Specialty Chemicals)
Sensitizer: 9,10-dibutoxyanthracene 3.0 g
Surfactant: BYK307 (trade name, manufactured by BYK Chemie) 0.2 g

(Preparation of samples 101-108)
Cyan ink samples 101 to 108 were produced in the same manner as the sample 100 except that a part of the monomer A and the monomer B in the sample 100 was changed as shown in Table 2.

<Evaluation>
1. Viscosity of Ink Liquid The viscosity of the ink liquid at a temperature of 25 ° C. was measured with a RE80 viscometer (trade name, manufactured by Toki Sangyo Co., Ltd.).
2. Printing, exposure test The ink obtained in the examples and comparative examples was ejected using a piezo-type head (Toshiba Tec Printhead CA-3 (trade name)). The head has a nozzle density of 150 per 25.4 mm and has 318 nozzles. By fixing these two nozzles in the nozzle row direction with a shift of 1/2 of the nozzle interval, 25 heads are arranged on the medium in the nozzle array direction. . 300 drops per 4 mm.

The droplets were ejected at a temperature of the head and the ink liquid of 25 ° C. ± 1 ° C. Moreover, UV light was cut at the time of droplet ejection.
Ink ejection from the head is controlled by a piezo drive signal applied to the head, and ejection of 6 to 42 pl per drop is possible. In this embodiment, the medium is conveyed from the head while being transported at a position 1 mm below the head. Dropped. The conveyance speed can be set in the range of 50 to 200 mm / s. The piezo drive frequency can be up to 4.6 kHz, and the droplet ejection amount can be controlled by these settings. In this example, by setting the transport speed to 90 mm / s and the driving frequency to 1.9 kHz, the ink ejection amount was controlled to 24 pl and droplets were ejected at 10 g / m ² to obtain a solid print image of 7 cm × 12 cm.

After the droplets were ejected, the media were transported to an exposure section and exposed by an ultraviolet light emitting diode (UV-LED). In this example, NUCA NCCU033 (trade name) was used as the UV-LED. This LED outputs ultraviolet light having a wavelength of 365 nm from one chip. When a current of about 500 mA is applied, light of about 100 mW is emitted from the chip. A plurality of these are arranged at intervals of 7 mm, and a power of 0.3 W / cm ² can be obtained on the media surface. The exposure time after the droplet ejection and the exposure time can be changed according to the transport speed of the medium and the distance between the head and the LED in the transport direction. In this example, exposure was performed about 0.5 seconds after landing.
Depending on the setting of the distance to the medium and the conveyance speed, the exposure energy on the medium can be adjusted between 0.01 and 15 J / cm ² . In this embodiment, the exposure energy is adjusted according to the conveyance speed.
For measurement of these exposure power and exposure energy, a spectroradiometer URS-40D (trade name) manufactured by USHIO ELECTRIC CO., LTD. Was used, and a value obtained by integrating between wavelengths 220 nm to 400 nm was used.
In this embodiment, a PET film having a thickness of 100 μm and 8 cm × 15 cm is used as a medium. H. Conducted in a 60% environment. The cured images had a thickness of 9 μm.

3. Evaluation of Curability A high quality paper was superimposed on a print sample immediately after exposure, and the following evaluation was performed according to the degree of transfer of the color material to the high quality paper when passing through a pressure roller (50 kg / cm ² ). The evaluation results are shown in Table 3.
○: No transfer at all.
Δ: Partially transferred.
X: Almost all transferred.

4). Nozzle discharge performance evaluation 2. Under the same conditions as the above printing conditions, a grid-like line drawing (nozzle check pattern) was printed for 1 hour instead of the ink-jet paper (manufactured by Fuji Photo Film, “paint” gloss finish). The number of nozzles that were clogged after the printing for 1 hour continuously or the jump direction was greatly shifted was measured by comparing and observing the grid image after printing for 1 hour. The defective ejection% of the printer head nozzle was calculated by the number of ejection failure nozzles relative to the total number of nozzles (318), and the ejection failure from the nozzles was evaluated. The evaluation results are shown in Table 3.
○: 0% to 5% of the printer head nozzles were not discharged.
Δ: More than 5% and 20% or less of the printer head nozzles were not discharged.
X: 20% of the printer head nozzles were not discharged.

5. Bending resistance evaluation of cured film Print samples that were not transferred at the lowest energy with each ink at 23 ° C and 60% relative humidity were stored for one day, and then the center of the screen was bent by hand to 180 ° and cured. The presence or absence of cracks in the film was observed and evaluated as follows. The evaluation results are shown in Table 3.
○: No change Δ: Slight cracking occurs in the recording part at the bent portion.
X: The cured film of the recording material peels off at the bent portion

  The evaluation results for the cyan ink samples 100 to 108 are summarized.

As is apparent from the results in Table 3, the sample 100 made of an oxetane compound having an ethyl group at the 3-position has poor curability, bending resistance of the cured film, and ejection stability. Similar samples 102, 104, 106 and 108 have increased ink viscosity and deteriorated ejection stability. In contrast, Samples 101, 103, 105, and 107 of the present invention contain a predetermined amount of an oxetane compound having a methyl group at the 3-position, thereby reducing any of ink viscosity, resistance to bending of a cured film, and ejection stability. It turns out that it will be excellent.

Claims (14)

An active energy ray-curable ink composition comprising a compound represented by the following general formula (I):

(In the formula, R _{1 to} R ₅ each independently represents a hydrogen atom or a substituent.) The active energy ray-curable ink composition according to claim 1, wherein the compound represented by the general formula (I) is a compound represented by the following general formula (II).

(In the formula, R _{1 to} R ₄ and R ₆ each independently represent a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, an aromatic hydrocarbon group, a heteroaromatic group, or a heterocyclic group.) The active energy ray-curable ink composition according to claim 1 or 2, wherein the compound represented by the general formula (I) or (II) is a compound represented by the following general formula (III): .

(In the formula, R ₆ represents a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, an aromatic hydrocarbon group, a heteroaromatic group, or a heterocyclic group.)   The active energy ray-curable ink composition according to claim 1, wherein the compounds represented by the general formulas (I) to (III) have a viscosity at 25 ° C. of 1 to 10 mPa · s.   The active energy ray-curable ink composition according to claim 1, further comprising any one of an oxirane ring-containing compound and an oxetane ring-containing compound.   The active energy ray-curable ink composition according to claim 1, further comprising at least one polymerization initiator and at least one photosensitizer.   The active energy ray-curable ink composition according to any one of claims 1 to 6, wherein the viscosity at 25 ° C is 2 to 20 mPa · s.   An inkjet ink comprising the active energy ray-curable ink composition according to any one of claims 1 to 7.   An image forming method comprising: an image recording step of recording an image by inkjet recording in which the active energy ray-curable inkjet ink according to claim 8 is discharged.   An image recording step of recording an image on a recording material using an active energy ray-curable inkjet ink, and an image curing step of irradiating and curing an active energy ray on the image recorded on the recording material in the image recording step The image forming method according to claim 9, further comprising:   The image forming method according to claim 10, wherein the irradiation source of the active energy ray is a light emitting diode or a semiconductor laser.   11. The image forming method according to claim 9, wherein a center wavelength of the active energy ray is 365 ± 20 nm.   The recorded matter according to any one of claims 10 to 12, wherein a thickness of the image cured by the image curing step is 2 to 30 µm. A recorded matter formed using the active energy ray-curable inkjet ink according to claim 8.