JP2008081516A - Radiation-curing type ink composition for ink jet, method for ink-jet recording, method for producing lithographic printing plate and lithographic printing plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radiation-curing type ink composition for ink jets capable of curing by irradiation of active radiation with high sensitivity and forming an image having excellent adhesiveness to a medium to be recorded and flexibility, to provide a method for ink-jet recording using the ink composition, to provide a lithographic printing plate obtained by using the ink composition for the ink jets and capable of affording a plurality of prints of high image quality and to provide a method for producing the lithographic printing plate. <P>SOLUTION: The radiation-curing type ink composition for the ink jets comprises a radiation-curing compound having a content of urethane bonds in the molecule within the range of 1-12 mass%. The method for ink-jet recording is obtained by using the ink composition. The lithographic printing plate and the method for producing the lithographic printing plate are provided by using the ink composition. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a radiation curable inkjet ink composition, an inkjet recording method using the ink composition, a lithographic printing plate obtained using the ink composition, and a method for producing a lithographic printing plate. .

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

  Ink compositions that can be cured by irradiation with actinic radiation such as ultraviolet rays (radiation curable ink compositions), such as ink compositions for ink jet recording, can be cured with high sensitivity and form high-quality images. It has been demanded. By achieving high sensitivity, high curability is imparted by irradiation with actinic radiation, so that sufficient curing is achieved in addition to reducing power consumption and extending life by reducing the load on the actinic radiation generator. As a result, there are various advantages such as suppression of volatilization of uncured low molecular weight substances and reduction in the strength of the formed image. Further, the improvement in the image strength by increasing the sensitivity results in high printing durability in the image area when this ink composition is used for forming the image area of a lithographic printing plate.

  The curable inkjet method using ultraviolet light has been attracting attention in recent years because it has a relatively low odor and can record on a recording medium having no quick drying and no ink absorption. In particular, benzyl, benzoin, benzoin ethyl ether, Michler ketone, anthraquinone, acridine, phenazine, benzophenone, 2-ethylanthraquinone, and the like have been generally used as photopolymerization initiators (for example, see Non-Patent Document 1). However, when these photopolymerization initiators are used, it takes a long time for image exposure in image formation because the photopolymerizable composition has low curing sensitivity. For this reason, in the case of a fine image, if there is a slight vibration in the operation, an image with good image quality cannot be reproduced, and the amount of energy emitted from the light source of the exposure must be increased. It was necessary to consider radiation.

Even for a support that is usually difficult to directly record with an ink jet recording method, it is possible to record an image with no blur, high sensitivity, high adhesion to a recording medium, and skin irritation and sensitization. For the purpose of providing an ink composition with low safety and high safety, an ink containing a polymerizable compound consisting of a specific acrylate compound group has been proposed (for example, see Patent Document 1).
However, in the ink composition for ink jet recording, it has been difficult to improve the adhesion of the cured film to the recording medium and the flexibility of the cured film.
JP 2003-192943 A Bruce M. Monroe et al., Chemical Reviews, Vol. 93, (1993), p. 435-448.

The objects of the present invention made in view of the above problems are as follows.
That is, an object of the present invention is to provide a radiation curable inkjet ink composition which can be cured with high sensitivity to irradiation with actinic radiation and can form an image excellent in adhesion and flexibility to a recording medium, and An object of the present invention is to provide an ink jet recording method using an ink composition.
Another object of the present invention is to provide a lithographic printing plate obtained by using the ink jet ink composition described above and capable of obtaining a large number of high-quality printed materials, and a method for producing the lithographic printing plate. It is in.

As a result of intensive studies, the present inventors have used an ink composition in which the adhesion of the formed image to a recording medium and its flexibility are enhanced by using a specific curable compound in the ink composition. Was found and the present invention was completed.
That is, the radiation curable inkjet ink composition of the present invention is characterized by containing a radiation curable compound having a urethane bond content in the range of 1 to 12% by mass.
Moreover, it is preferable that the curable group of this radiation-curable compound contains at least one selected from the group consisting of a (meth) acrylate group, a vinyl group, and a ring-opening polymerizable group.

Although the operation of the present invention is not clear, it is estimated as follows.
In the present invention, the radiation curable compound contains a urethane bond in the range of 1 to 12% by mass. Thus, it is estimated that the sclerosing | hardenable compound which contains a urethane bond by specific content forms an intermolecular interaction in the urethane bond part. As a result, the increase in the viscosity of the composition accompanying the polymerization reaction is promoted by the interaction property, so that the sensitivity becomes high and the ink jet aptitude is excellent.
On the other hand, in order to hold a cured film (image) formed by curing the ink composition, an interaction caused by urethane bonds is used, so that it is not necessary to increase the degree of polymerization in the cured film. As a result, the flexibility of the cured film can be maintained, and the interaction due to the urethane bond is also effective in developing the interaction with the recording medium, so that the adhesion to the recording medium is excellent.

  The radiation curable ink composition for inkjet according to the present invention preferably further contains a colorant.

The inkjet recording method of the present invention includes (a) a step of ejecting the radiation curable inkjet ink composition of the present invention onto a recording medium, and (b) actinic radiation to the ejected ink composition. Irradiating and curing the ink composition.
The method for producing a lithographic printing plate of the present invention comprises: (a ′) a step of discharging the radiation curable inkjet ink composition of the present invention onto a hydrophilic support; and (b ′) the discharged ink composition. Irradiating actinic radiation to the ink composition to cure the ink composition, thereby forming a hydrophobic image formed by curing the ink composition on the hydrophilic support.
The lithographic printing plate of the present invention is produced by the method for producing a lithographic printing plate of the present invention.

As described above, according to the present invention, a radiation curable inkjet ink composition that can be cured with high sensitivity to irradiation with actinic radiation and can form an image excellent in adhesion and flexibility to a recording medium. And an ink jet recording method using the ink composition.
In addition, by using the inkjet ink composition of the present invention as described above, it is possible to obtain a large number of high-quality printed materials having an image portion excellent in adhesion to a support and flexibility. A lithographic printing plate and a method for producing a lithographic printing plate can be provided.

<Radiation curable ink composition for inkjet>
The radiation curable inkjet ink composition of the present invention (hereinafter sometimes simply referred to as “ink composition”) has a radiation curable content in the range of 1 to 12% by mass of urethane bonds in the molecule. It is characterized by containing a compound.
First, a radiation curable compound (hereinafter, appropriately referred to as “specific urethane compound”) in which the content of urethane bonds in the molecule is in the range of 1 to 12% by mass will be described in detail.

[(A) Radiation-curable compound (specific urethane compound) in which the content of urethane bonds in the molecule is in the range of 1 to 12% by mass]
As the specific urethane compound in the present invention, any compound can be used as long as it contains a urethane bond in the range of 1 to 12% by mass and has a curable group that is cured by at least one radiation. You can also.
In addition, when the content of the urethane bond is less than 1% by mass, the adhesion to the support and the flexibility are insufficient. On the other hand, when the content exceeds 12% by mass, the ink jet recording apparatus has a high viscosity that cannot be printed. There is a risk.

Here, the content of urethane bonds in the present invention is the content of urethane bonds (—O—C (═O) —NH—) relative to the molecular weight of the specific urethane compound. When there are two or more urethane bonds in the molecule, the total content is shown.
Thus, in order to calculate the content of the urethane bond in the specific urethane compound, the structure of the specific urethane compound is identified using the ⁱ H-NMR spectrum, ¹³ C-NMR spectrum, IR spectrum, etc., and the molecular weight Need to be calculated.

  Here, in the specific urethane compound, a curable group that is cured by radiation (hereinafter sometimes simply referred to as “curable group”) includes a radical polymerizable group, a cationic polymerizable group, a condensation reactive crosslinking group, and the like. Is mentioned. The curable group is preferably a (meth) acrylate group, a vinyl group, or a ring-opening polymerizable group. It is preferable that 1 or 2 of such curable groups exist in one molecule, and when it is in this range, the storage stability of the ink composition of the present invention is good and the film physical properties after curing are excellent. It is preferable because it is good.

  The specific urethane compound in the present invention is preferably a compound represented by the following general formula (a).

In the general formula (a), X and Y each independently represent a hydrogen atom, a hydroxy group, a monovalent organic group, or a curable group, and at least one of X and Y is a curable group. Cost. X and Y may be the same or different.
When X or Y is a monovalent organic group, the monovalent organic group includes an alkyl group having 2 to 18 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, an aryl group having 6 to 14 carbon atoms, Examples thereof include an alkoxy group having 1 to 18 carbon atoms, an aryloxy group having 6 to 10 carbon atoms, an alkylamino group having 1 to 18 carbon atoms, and an arylamino group having 6 to 10 carbon atoms. From the viewpoint of affinity, alkyl groups such as methyl group, ethyl group, octyl group, dodecyl group and octadecyl group are preferred.
When X and / or Y is a curable group, examples of the curable group include a (meth) acrylate group, a vinyl group, and a ring-opening polymerizable group.

In the general formula (a), R ¹ and R ² represent a divalent organic group, and preferred divalent organic groups include an alkylene group having 2 to 18 carbon atoms and a cycloalkylene having 3 to 12 carbon atoms. Group, an arylene group having 6 to 14 carbon atoms, and a polyalkyleneoxy group having a repeating unit of an alkylene oxide structure having 2 to 6 carbon atoms. Among these, from the viewpoint of the flexibility of the cured film and the adhesion to the printing medium, a polyalkyleneoxy group having a C 2-18 alkylene group or a C 2-6 alkylene oxide structure as a repeating unit is preferred. The number of repeating units of the oxy group is preferably about 4-20.

  Specific examples of the specific urethane compound in the present invention are shown below, but the present invention is not limited thereto. The urethane bond content is also shown.

The specific urethane compound represented by the general formula (a) can be synthesized by reacting an isocyanate group-containing compound with a compound having a photocurable group, an isocyanate group, and a reactive group. .
As the isocyanate group-containing compound, those having an aliphatic chain are preferred from the viewpoint of low viscosity. Specifically, monofunctional isocyanates such as n-octadecyl isocyanate and bifunctional isocyanates (organic diisocyanates) as shown below are preferred. Compound).
Examples of organic diisocyanate compounds include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, xylene-1,4-diisocyanate, xylene-1,3-diisocyanate, 4-4′-diphenylmethane diisocyanate, 4, 4-diphenyl ether diisocyanate, 2-nitrodiphenyl-4,4′-diisocyanate, 2,2′-diphenylpropane-4,4′-diisocyanate, 4,4′-diphenylpropane diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate , Aromatic diisocyanates such as naphthylene-1,4-diisocyanate, naphthylene-1,5-diisocyanate, 3,3′-dimethoxydiphenyl-4,4′-diisocyanate, tetramethylene diisocyanate And alicyclic diisocyanates such as aliphatic diisocyanates such as hexamethylene diisocyanate and lysine diisocyanate, isophorone diisocyanate, hydrogenated tolylene diisocyanate and hydrogenated diphenylmethane diisocyanate.

  Examples of the compound having a photocurable group, an isocyanate group, and a reactive group (for example, a hydroxyl group) include 2-hydroxyethyl methacrylate, 2-hydroxyethyl acrylate, pentaerythritol triacrylate, and pentaerythritol trimethacrylate. Can be mentioned.

When synthesizing the specific urethane compound in the present invention, it is possible to use another skeleton having an isomer structure having a branched structure. Specifically, a compound having a 2,2,4-trimethyloctamethylenediol skeleton and a 2,4,4-trimethyloctamethylenediol skeleton may be used.
By having a branched structure in the specific urethane compound, it is difficult to crystallize compared to a straight chain type having no branched structure, and a good viscosity can be obtained.

  The specific urethane compound in the present invention preferably has a mass average molecular weight in the range of 500 to 100,000, more preferably in the range of 500 to 50,000, from the viewpoint of adhesion of the cured film to the recording medium.

The content of the specific urethane compound in the ink composition of the present invention is preferably in the range of 1 to 25% by mass, more preferably in the range of 2 to 20% by mass in terms of solid content, from the viewpoint of ejection stability and flexibility.
When the content of the specific urethane compound exceeds 25% by mass, the viscosity becomes incapable of printing (discharging) in the ink jet recording apparatus, and when the content is less than 1% by mass, the adhesiveness to the recording medium and flexibility are increased. The property becomes insufficient.
Moreover, a specific urethane compound may be used independently and may use 2 or more types together.

[(B) polymerization initiator]
The ink composition of the present invention preferably contains a polymerization initiator. As the polymerization initiator, a known polymerization initiator can be used. In particular, in the present invention, it is preferable to use a radical polymerization initiator.
The polymerization initiator used in the ink composition of the present invention is a compound that absorbs external energy and generates a polymerization initiating species. External energy used for initiating polymerization is roughly divided into heat and (active) radiation, and a thermal polymerization initiator and a photopolymerization initiator are used, respectively. Examples of (active) radiation include γ rays, β rays, electron beams, ultraviolet rays, visible rays, and infrared rays.
Known compounds can be used as the thermal polymerization initiator and the photopolymerization initiator.

(B-1) Radical polymerization initiator Preferred radical polymerization initiators that can be used in the present invention include (a) aromatic ketones, (b) acylphosphine compounds, (c) aromatic onium salt compounds, (d) organic Peroxide, (e) thio compound, (f) hexaarylbiimidazole compound, (g) ketoxime ester compound, (h) borate compound, (i) azinium compound, (j) metallocene compound, (k) active ester Compounds, (l) compounds having a carbon halogen bond, and (m) alkylamine compounds.
The radical polymerization initiator in the present invention may be used alone or in combination.

(B-2) Cationic Polymerization Initiator As a preferred cationic polymerization initiator (photoacid generator) that can be used in the present invention, for example, a chemical amplification type photoresist or a compound used for photocationic polymerization is used (organic). (See "Organic Materials for Imaging" edited by Electronics Materials Research Group, Bunshin Publishing (1993), pages 187-192).
Examples of the cationic polymerization initiator suitable for the present invention are listed below.
That is, first, diazonium, ammonium, iodonium, sulfonium, aromatic onium compounds such as phosphonium ^{_{B (C 6 F 5) 4}} -, PF 6 -, AsF 6 -, SbF 6 -, CF 3 SO 3 - salt Can be mentioned.
Secondly, sulfonated products that generate sulfonic acid can be mentioned.
Thirdly, a halide that generates hydrogen halide can also be used.
Fourthly, an iron allene complex can be mentioned.
Such cationic polymerization initiators may be used alone or in combination of two or more.

The polymerization initiator in the present invention is preferably 0.01 to 20 parts by mass, more preferably 0.1 to 20 parts by mass, and still more preferably 0 to 100 parts by mass of the total polymerizable compound including the specific urethane compound. It is suitable to contain in the range of 5-10 mass parts.
Moreover, in this invention, a polymerization initiator is mass ratio of a polymerization initiator: sensitizing dye with respect to (E) sensitizing dye mentioned later, 200: 1-1: 200, Preferably, it is 50: 1. It is suitable that it is contained in an amount of 1:50, more preferably 20: 1 to 1: 5.

In the ink composition of the present invention, in addition to the essential components described above, other components can be used in combination for the purpose of improving physical properties as long as the effects of the present invention are not impaired.
Hereinafter, these optional components will be described below.

[(C) Other polymerizable compound]
In the ink composition of the present invention, it is preferable to use other polymerizable compound in combination with the specific urethane compound. Examples of other polymerizable compounds that can be used in combination with the present invention include radical polymerizable compounds and / or cationic polymerizable compounds.
Other polymerizable compounds may be appropriately selected and used in relation to the objective properties or the structure of the specific urethane compound.

(C-1) Radical polymerizable compound The radical polymerizable compound is a compound having an ethylenically unsaturated bond capable of radical polymerization, and having at least one ethylenically unsaturated bond capable of radical polymerization in the molecule. Any type may be used, including those having chemical forms such as monomers, oligomers, and polymers. Only one kind of radically polymerizable compound may be used, or two or more kinds thereof may be used in combination at an arbitrary ratio in order to improve desired properties. In addition, a polyfunctional compound having two or more functional groups is preferable to a monofunctional compound. More preferably, two or more polyfunctional compounds are used in combination for controlling performance such as reactivity and physical properties.

  Examples of the polymerizable compound having an ethylenically unsaturated bond capable of radical polymerization include unsaturated carboxylic acids such as acrylic acid, methacrylic acid, itaconic acid, crotonic acid, isocrotonic acid, maleic acid, and salts thereof, Examples thereof include radically polymerizable compounds such as anhydrides having a saturated group, acrylonitrile, styrene, various unsaturated polyesters, unsaturated polyethers, unsaturated polyamides, and unsaturated urethanes.

  Specifically, 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, butoxyethyl acrylate, carbitol acrylate, cyclohexyl acrylate, tetrahydrofurfuryl acrylate, benzyl acrylate, bis (4-acryloxypolyethoxyphenyl) propane, neopentyl glycol Diacrylate, 1,6-hexanediol diacrylate, ethylene glycol diacrylate, diethylene glycol diacrylate, triethylene glycol diacrylate, tetraethylene glycol diacrylate, polyethylene glycol diacrylate, polypropylene glycol diacrylate, pentaerythritol triacrylate, pentaerythritol Tetraacrylate, dipentaery Acrylic acid derivatives such as lithol tetraacrylate, trimethylolpropane triacrylate, tetramethylolmethane tetraacrylate, oligoester acrylate, N-methylol acrylamide, diacetone acrylamide, epoxy acrylate, methyl methacrylate, n-butyl methacrylate, 2-ethylhexyl methacrylate , Lauryl methacrylate, allyl methacrylate, glycidyl methacrylate, benzyl methacrylate, dimethylaminomethyl methacrylate, 1,6-hexanediol dimethacrylate, ethylene glycol dimethacrylate, triethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, polypropylene glycol dimethacrylate, trimethylol Methacryl derivatives such as tan trimethacrylate, trimethylolpropane trimethacrylate, 2,2-bis (4-methacryloxypolyethoxyphenyl) propane, and other derivatives of allyl compounds such as allyl glycidyl ether, diallyl phthalate, triallyl trimellitate More specifically, Shinzo Yamashita, “Cross-linking agent handbook”, (1981 Taiseisha); Kato Kiyomi, “UV / EB curing handbook (raw material)” (1985, Polymer publication) ); Rad-Tech Study Group, “Application and Market of UV / EB Curing Technology”, p. 79, (1989, CMC); Eiichiro Takiyama, “Polyester Resin Handbook”, (1988, Nikkan Kogyo Shimbun) Commercially available products described in the above, or radically polymerizable or crosslinkable monomers known in the industry, Ligomers and polymers can be used.

  Examples of the radical polymerizable compound include those described in JP-A-7-159983, JP-B-7-31399, JP-A-8-224982, JP-A-10-863, JP-A-9-134011 and the like. Photocurable polymeric compound materials used in the described photopolymerizable compositions are known and can also be applied to the ink compositions of the present invention.

(C-2) Cationic polymerizable compound The ink composition of the present invention may be used in combination with a cationic polymerizable compound, if necessary.
The cationically polymerizable compound used in the present invention is not particularly limited as long as it is a compound that initiates a polymerization reaction with an acid generated from a photoacid generator and cures, and various known cationic polymerizations known as photocationically polymerizable monomers. Sex monomers can be used. Examples of the cationic polymerizable monomer include JP-A-6-9714, JP-A-2001-31892, JP-A-2001-40068, JP-A-2001-55507, JP-A-2001-310938, JP-A-2001-310937, and 2001-2001. Examples thereof include epoxy compounds, vinyl ether compounds, oxetane compounds and the like described in each publication such as No. 220526.

Examples of the epoxy compound include aromatic epoxides, alicyclic epoxides, and aliphatic 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 its alkylene oxide adducts, and novolak-type epoxy resins. Here, examples of the alkylene oxide include ethylene oxide and propylene oxide.

  As the alicyclic epoxide, 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. Or a cyclopentene oxide containing compound is mentioned preferably.

  Examples of the aliphatic epoxide include dihydric polyglycidyl ethers of aliphatic polyhydric alcohols or alkylene oxide adducts thereof. Typical examples include diglycidyl ether of ethylene glycol, diglycidyl ether of propylene glycol or diglycidyl ether of alkylene glycol such as diglycidyl ether of 1,6-hexanediol, di- or tri- or di- or tri-glycol or adducts thereof. Polyglycidyl ether of polyhydric alcohol such as glycidyl ether, diglycidyl ether of polyethylene glycol or alkylene oxide adduct thereof, diglycidyl ether of polyalkylene glycol represented by diglycidyl ether of polypropylene glycol or alkylene oxide adduct thereof, etc. Can be mentioned. Here, examples of the alkylene oxide include ethylene oxide and propylene oxide.

The epoxy compound may be monofunctional or polyfunctional.
Examples of monofunctional epoxy compounds that can be 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 -Vinylcyclohexene oxide etc. are mentioned.

  Examples of polyfunctional epoxy compounds 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, and brominated bisphenol. S diglycidyl ether, epoxy novolac resin, hydrogenated bisphenol A diglycidyl ether, hydrogenated bisphenol F diglycidyl ether, hydrogenated bisphenol S diglycidyl ether, 3,4-epoxycyclohexylmethyl-3 ′, 4′-epoxycyclohexanecarboxy 2- (3,4-epoxycyclohexyl-5,5-spiro-3,4-epoxy) cyclohexane-meta-dioxane, bis (3,4-epoxy Hexylmethyl) adipate, vinylcyclohexene oxide, 4-vinylepoxycyclohexane, bis (3,4-epoxy-6-methylcyclohexylmethyl) adipate, 3,4-epoxy-6-methylcyclohexyl-3 ', 4'-epoxy- 6'-methylcyclohexanecarboxylate, methylenebis (3,4-epoxycyclohexane), dicyclopentadiene diepoxide, ethylene glycol di (3,4-epoxycyclohexylmethyl) ether, ethylenebis (3,4-epoxycyclohexanecarboxylate) ), Dioctyl epoxyhexahydrophthalate, di-2-ethylhexyl epoxyhexahydrophthalate, 1,4-butanediol diglycidyl ether, 1,6-hexanediol diglycidyl Ether, glycerin triglycidyl ether, trimethylolpropane triglycidyl ether, polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ethers, 1,1,3-tetradecadiene dioxide, limonene dioxide, 1,2,7,8 -Diepoxyoctane, 1,2,5,6-diepoxycyclooctane and the like.

  Among these epoxy compounds, aromatic epoxides and alicyclic epoxides are preferable from the viewpoint of excellent curing speed, and alicyclic epoxides are particularly preferable.

  Examples of the vinyl ether compound include ethylene glycol divinyl ether, diethylene glycol divinyl ether, triethylene glycol divinyl ether, propylene glycol divinyl ether, dipropylene glycol divinyl ether, butanediol divinyl ether, hexanediol divinyl ether, cyclohexanedimethanol divinyl ether, Di- or trivinyl ether compounds such as methylolpropane trivinyl ether, ethyl vinyl ether, n-butyl vinyl ether, isobutyl vinyl ether, octadecyl vinyl ether, cyclohexyl vinyl ether, hydroxybutyl vinyl ether, 2-ethylhexyl vinyl ether, cyclohexane dimethanol monovinyl ether, n-propyl Pills vinyl ether, isopropyl vinyl ether, isopropenyl ether -o- propylene carbonate, dodecyl vinyl ether, diethylene glycol monovinyl ether, and octadecyl vinyl ether.

The vinyl ether compound may be monofunctional or polyfunctional.
Specifically, examples of monofunctional vinyl ethers 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 , Methoxypolyethyleneglycol 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 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, and bisphenol F. Divinyl ethers such as alkylene oxide divinyl ether; trimethylolethane trivinyl ether, trimethylolpropane trivinyl ether, ditrimethylolpropane tetravinyl ether, glycerin trivinyl ether, pentaerythritol tetravinyl ether, dipentaerythritol pentavinyl ether, dipentaerythritol Hexavinyl ether, ethylene oxide-added trimethylolpropane trivinyl ether, propylene oxide-added trimethylolpropane trivinyl ether, ethylene oxide-added ditrimethylolpropane tetravinyl ether, propylene oxide-added ditrimethylolpropane tetravinyl ether, ethylene oxide-added pentaerythritol tetravinyl ether, propylene oxide addition Examples thereof include polyfunctional vinyl ethers such as pentaerythritol tetravinyl ether, ethylene oxide-added dipentaerythritol hexavinyl ether, and propylene oxide-added dipentaerythritol hexavinyl ether.

  As the vinyl ether compound, a di- or trivinyl ether compound is preferable from the viewpoints of curability, adhesion to a recording medium, surface hardness of the formed image, and the like, and a divinyl ether compound is particularly preferable.

The oxetane compound in the present invention refers to a compound having an oxetane ring, and a known oxetane compound can be arbitrarily selected and used as described in JP-A Nos. 2001-220526, 2001-310937, and 2003-341217. .
The compound having an oxetane ring that can be used in the ink composition of the present invention is preferably a compound having 1 to 4 oxetane rings in the structure. By using such a compound, it becomes easy to maintain the viscosity of the ink composition within a good handling range, and obtain high adhesion between the cured ink composition and the recording medium. Can do.

  Examples of the compound having 1 to 2 oxetane rings in the molecule include compounds represented by the following 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 a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, a group having an aromatic ring, an alkylcarbonyl group having 2 to 6 carbon atoms, or 2 to 6 carbon atoms. Represents an alkoxycarbonyl group, and an N-alkylcarbamoyl group having 2 to 6 carbon atoms. Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, and a butyl group. Examples of the alkenyl group include a 1-propenyl group, a 2-propenyl group, a 2-methyl-1-propenyl group, and 2-methyl-2. -Propenyl group, 1-butenyl group, 2-butenyl group, 3-butenyl group and the like. Examples of the group having an aromatic ring include phenyl group, benzyl group, fluorobenzyl group, methoxybenzyl group, phenoxyethyl group and the like. Can be mentioned. As the alkylcarbonyl group, an ethylcarbonyl group, a propylcarbonyl group, a butylcarbonyl group, etc., as an alkoxycarbonyl group, an ethoxycarbonyl group, a propoxycarbonyl group, a butoxycarbonyl group, etc., as an N-alkylcarbamoyl group, Examples thereof include an ethylcarbamoyl group, a propylcarbamoyl group, a butylcarbamoyl group, and a pentylcarbamoyl group. R ^a2 may have a substituent, and examples of the substituent include an alkyl group of 1 to 6 and a fluorine atom.

R ^a3 is 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, Represents a lower alkyl carboxyl group, a carboxyl group, or a carbamoyl group.
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 2,000. 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 monovalent group, 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.

  As a compound represented by the formula (1), 3-ethyl-3-hydroxymethyloxetane (OXT-101: manufactured by Toagosei Co., Ltd.), 3-ethyl-3- (2-ethylhexyloxymethyl) oxetane (OXT) -212: manufactured by Toagosei Co., Ltd.) and 3-ethyl-3-phenoxymethyloxetane (OXT-211: manufactured by Toagosei Co., Ltd.). Examples of the compound represented by the formula (2) include 1,4-bis [(3-ethyl-3-oxetanylmethoxy) methyl] benzene (OXT-121: Toagosei Co., Ltd.). ), Bis (3-ethyl-3-oxetanylmethyl) ether (OXT-221: Toagosei Co., Ltd.) is exemplified.

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

In Formula (4), R ^a1 has the same ^meaning as in Formula (1). In addition, examples of Ra ⁹ that is a polyvalent linking group include branched alkylene groups having 1 to 12 carbon atoms such as groups represented by A to C below, and branched poly groups such as groups represented by D below. Examples include (alkyleneoxy) groups or branched polysiloxy groups such as groups 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 formula (5) having an oxetane ring in the side chain.

In the formula ^{(5), R a1} and ^{R a8} are the same meaning as ^{R a1} and ^{R a8} 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.

Such a compound having an oxetane ring is described in detail in paragraphs [0021] to [0084] of JP-A No. 2003-341217, and the compound described here can be suitably used in the present invention. it can.
Oxetane compounds described in JP 2004-91556 A can also be used in the present invention. It is described in detail in paragraph numbers [0022] to [0058] of the publication.
Among the oxetane compounds used in the present invention, it is preferable to use a compound having one oxetane ring from the viewpoint of the viscosity and tackiness of the ink composition.

  In addition, as the cationic polymerizable compound, for example, a polymerizable compound applied to a cationic polymerization type photocurable resin is known, and recently, a photo cationic polymerization type sensitized in a visible light wavelength region of 400 nm or more. Examples of the polymerizable compound applied to the photocurable resin are disclosed in JP-A-6-43633 and JP-A-8-324137. These can also be applied to the ink composition of the present invention.

  The cationically polymerizable compound that can be used in the present invention may be used alone or in combination of two or more. From the viewpoint of effectively suppressing shrinkage during ink curing, an oxetane compound. And at least one compound selected from epoxy compounds and a vinyl ether compound are preferably used in combination.

  In the present invention, regarding the selection of a polymerizable compound including a polymerization initiator and a specific urethane compound, as a means for preventing a decrease in sensitivity due to the light-shielding effect of the colorant used in the ink composition, a cationic polymerizable compound and a cationic polymerization are used. In addition to a combination with an initiator and a combination of a radical polymerizable compound and a radical polymerization initiator, a radical / cation hybrid type curable ink using these polymerizable compound and a polymerization initiator in combination may be used.

(C-3) Other preferred polymerizable compounds Other polymerizable compounds in the present invention include (meth) acrylic monomers or prepolymers, epoxy monomers or prepolymers, urethane monomers or prepolymers (meth). Acrylic acid esters (hereinafter referred to as acrylate compounds as appropriate) are preferred. More preferably, they are the following compounds.

  That is, 2-ethylhexyl-diglycol acrylate, 2-hydroxy-3-phenoxypropyl acrylate, 2-hydroxybutyl acrylate, hydroxypivalate neopentyl glycol diacrylate, 2-acryloyloxyethyl phthalate, methoxy-polyethylene glycol acrylate, Tetramethylol methane triacrylate, 2-acryloyloxyethyl-2-hydroxyethylphthalic acid, dimethylol tricyclodecane diacrylate, ethoxylated phenyl acrylate, 2-acryloyloxyethyl succinic acid, nonylphenol EO adduct acrylate, modified glycerin Triacrylate, bisphenol A diglycidyl ether acrylic acid adduct, modified bisphenol A diacrylate, phenoxy-poly Tylene glycol acrylate, 2-acryloyloxyethylhexahydrophthalic acid, PO adduct diacrylate of bisphenol A, EO adduct diacrylate of bisphenol A, dipentaerythritol hexaacrylate, pentaerythritol triacrylate tolylene diisocyanate urethane prepolymer Lactone-modified flexible acrylate, butoxyethyl acrylate, propylene glycol diglycidyl ether acrylic acid adduct, pentaerythritol triacrylate hexamethylene diisocyanate urethane prepolymer, 2-hydroxyethyl acrylate, methoxydipropylene glycol acrylate, ditrimethylolpropane Tetraacrylate, pentaerythritol triacrylate hexamethyl Nji diisocyanate urethane prepolymer, stearyl acrylate, isoamyl acrylate, isomyristyl acrylate, isostearyl acrylate, lactone-modified acrylate.

  These acrylate compounds have less skin irritation and sensitization (ease of rashes) than conventional polymerizable compounds used in UV curable inks, and can relatively lower the viscosity, providing stable ink ejection. The polymerization sensitivity and the adhesion to the recording medium are also good.

  The monomers listed above have low sensitization even at low molecular weight, and have high reactivity, low viscosity, and excellent adhesion to a recording medium.

  In order to further improve the sensitivity, bleeding, and adhesion to the recording medium, it is preferable to use monoacrylate in combination with a polyfunctional acrylate monomer or polyfunctional acrylate oligomer having a molecular weight of 400 or more, preferably 500 or more. In addition, the embodiment in which at least three polymerizable compounds of monofunctional, bifunctional, and trifunctional or higher polyfunctional monomers are used in combination further improves sensitivity, bleeding, and adhesion to the recording medium while maintaining safety. From the viewpoint that it can be further improved, it is mentioned as a preferred embodiment.

  In particular, in an ink composition used for recording on a flexible recording medium such as a PET film or a PP film, (B) one selected from a specific urethane compound and a mono selected from the above compound group The combined use of an acrylate and a polyfunctional acrylate monomer or polyfunctional acrylate oligomer is preferable because the film strength can be increased while the film is made flexible to improve adhesion.

As monoacrylates, stearyl acrylate, isoamyl acrylate, isomistyl acrylate, and isostearyl acrylate have high sensitivity and low shrinkage to prevent curling, while preventing bleeding, odor of printed matter, and cost reduction of irradiation equipment. preferable.
Moreover, as an oligomer which can be used in combination with a monoacrylate, an epoxy acrylate oligomer and a urethane acrylate oligomer are particularly preferable.
In addition, methacrylate has better skin irritation than acrylate.
Among the above compounds, when alkoxy acrylate is used in an amount of 70% by mass or less and the balance is acrylate, it is preferable because it has good sensitivity, bleeding characteristics, and odor characteristics.

  In the present invention, when the acrylate compound is used as (C) the other polymerizable compound, the acrylate compound is 30% by mass or more based on the total mass of the other polymerizable compound (that is, the total amount of the component (C)). It is preferable that it is 40 mass% or more, and it is still more preferable that it is 50 mass% or more. Moreover, (C) all the other polymerizable compounds used together can also be made into the said acrylate compound.

[Content of polymerizable compound]
In the present invention, the total content of the polymerizable compound, that is, the total amount of the (A) specific urethane compound and the added amount of (C) another polymerizable compound that can be used in combination with the specific urethane compound is the ink composition of the present invention. It is 1-97 mass% with respect to the mass of the whole thing, More preferably, it is 30-95 mass%.

  In the ink composition of the present invention, the specific urethane compound (A) contains the total content of polymerizable compounds contained in the ink composition (that is, the total content of the components (A) and (C)). ) To 30% by mass or more, more preferably 40% by mass or more, and still more preferably 50% by mass or more.

[(D) Colorant]
When the ink composition of the present invention is used for forming an image portion of a lithographic printing plate, it is not particularly necessary to form a colored image. However, in order to improve the visibility of the formed image portion, or the ink composition When it is going to form a colored image using a thing, (D) a coloring agent can be contained.
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, but oil-soluble dyes are preferred.
The colorant that can be suitably used in the ink composition of the present invention preferably does not function as a polymerization inhibitor in a polymerization reaction that is a curing reaction. This is because the sensitivity of the curing reaction by actinic radiation is not reduced.

[Pigment]
Although it does not necessarily limit as a pigment which can be used for this invention, For example, the organic or inorganic pigment of the following number described in a color index can be used.

  That is, as the red or magenta pigment, Pigment Red 3, 5, 19, 22, 31, 38, 43, 48: 1, 48: 2, 48: 3, 48: 4, 48: 5, 49: 1, 53 : 1, 57: 1, 57: 2, 58: 4, 63: 1, 81, 81: 1, 81: 2, 81: 3, 81: 4, 88, 104, 108, 112, 122, 123, 144 146, 149, 166, 168, 169, 170, 177, 178, 179, 184, 185, 208, 216, 226, 257, Pigment Violet 3, 19, 23, 29, 30, 37, 50, 88, Pigment Orange 13, 16, 20, 36, blue or cyan pigments include Pigment Blue 1, 15, 15: 1, 15: 2, 15: 3, 15: 4, 15: 6, 1 6, 17-1, 22, 27, 28, 29, 36, 60, as green pigment, Pigment Green 7, 26, 36, 50, as yellow pigment, Pigment Yellow 1, 3, 12, 13, 14, 17, 34, 35, 37, 55, 74, 81, 83, 93, 94, 95, 97, 108, 109, 110, 137, 138, 139, 153, 154, 155, 157, 166, 167, 168, 180, 185, 193, Pigment Black 7, 28, 26 as the black pigment, and Pigment White 6, 18, 21, etc. as the white pigment can be used according to the purpose.

[Oil-soluble dye]
The oil-soluble dye that can be used in the present invention will be described below.
The oil-soluble dye that can be used in the present invention means a dye that is substantially insoluble in water. Specifically, the solubility in water at 25 ° C. (the mass of the dye that can be dissolved in 100 g of water) is 1 g or less, preferably 0.5 g or less, more preferably 0.1 g or less. Accordingly, the oil-soluble dye means a so-called water-insoluble pigment or oil-soluble dye, and among these, an oil-soluble dye is preferable.

  In the present invention, the oil-soluble dye may be used alone or in combination of several kinds. In addition, other water-soluble dyes, disperse dyes, pigments, and other colorants may be contained as necessary as long as the effects of the present invention are not impaired.

  Among the oil-soluble dyes that can be used in the present invention, any yellow dye can be used. For example, phenols, naphthols, anilines, pyrazolones, pyridones, aryl or heteryl azo dyes having open-chain active methylene compounds as coupling components; for example, azomethine dyes having open-chain active methylene compounds as coupling components 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 dye species such as quinophthalone dyes, nitro dyes -A nitroso dye, an acridine dye, an acridinone dye, etc. can be mentioned.

  Of the oil-soluble dyes that can be used in the present invention, any magenta dye can be used. For example, aryl or heteryl azo dyes having phenols, naphthols, anilines as coupling components; for example, azomethine dyes having pyrazolones, pyrazolotriazoles as coupling components; for example, arylidene dyes, styryl dyes, merocyanine dyes, Methine dyes such as oxonol dyes; carbonium dyes such as diphenylmethane dyes, triphenylmethane dyes and xanthene dyes; quinone dyes such as naphthoquinone, anthraquinone and anthrapyridone; A ring dye; and the like.

  Among the oil-soluble dyes that can be used in the present invention, any cyan dye can be used. For example, indoaniline dyes, indophenol dyes or azomethine dyes having pyrrolotriazoles as coupling components; polymethine dyes such as cyanine dyes, oxonol dyes, merocyanine dyes; carboniums such as diphenylmethane dyes, triphenylmethane dyes, xanthene dyes Examples include dyes; phthalocyanine dyes; anthraquinone dyes; aryl or heteryl azo dyes having phenols, naphthols, and anilines as coupling components; indigo / thioindigo dyes;

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

  Although not limited to the following, preferred specific examples include C.I. I. Solvent Black 3, 7, 27, 29 and 34; C.I. I. Solvent Yellow 14, 16, 19, 29, 30, 56, 82, 93 and 162; C.I. I. Solvent Red 1, 3, 8, 18, 24, 27, 43, 49, 51, 72, 73, 109, 122, 132 and 218; I. Solvent Violet 3; C.I. I. Solvent Blue 2,11,25,35,38,67 and 70; I. Solvent Green 3 and 7; I. Solvent orange 2; and the like. Particularly preferred among these are: Nubian Black PC-0850, Oil Black HBB, Oil Yellow 129, Oil Yellow 105, Oil Pink 312, Oil Red 5B, Oil Scallet 308, Vali Fast Blue chemistry 2606e B2 (Manufactured by Co., Ltd.), Aizen Spiron Blue GNH (manufactured by Hodogaya Chemical Co., Ltd.), Neopen Yellow 075, Neopen Magenta SE1378, Neopen Blue 808, Neopen Blue FF4012, and Neo42 Cy FF4012.

  In the present invention, a disperse dye can be used as long as it is soluble in a water-immiscible organic solvent. Preferred examples thereof include C.I. I. Disperse Yellow 5,42,54,64,79,82,83,93,99, 100,119,122,124,126,160,184: 1,186,198,199,201,204,224 and 237 C. I. Disperse Orange 13, 29, 31: 1, 33, 49, 54, 55, 66, 73, 118, 119 and 163; I. Disperse Red 54, 60, 72, 73, 86, 88, 91, 92, 93, 111, 126, 127, 134, 135, 143, 145, 152, 153, 154, 159, 164, 167: 1,177 , 181, 204, 206, 207, 221, 239, 240, 258, 277, 278, 283, 311, 323, 343, 348, 356 and 362; I. Disperse Violet 33; C.I. I. Disperse Blue 56, 60, 73, 87, 113, 128, 143, 148, 154, 158, 165, 165: 1, 165: 2, 176, 183, 185, 197, 198, 201, 214, 224, 225 , 257, 266, 267, 287, 354, 358, 365 and 368; I. Disperse Green 6: 1 and 9;

  Particularly preferred oil-soluble dyes include azo or azomethine dyes represented by the following formula (i) or formula (ii). The dye represented by the following formula (ii) is known as a dye formed from a coupler and a developing agent by oxidation in a photographic material.

In the formula (i) and the formula (ii), R ¹ , R ² , R ³ and R ⁴ are each independently a hydrogen atom, a halogen atom, an aliphatic group, an aromatic group, a heterocyclic group, a cyano group, Hydroxy group, nitro group, amino group, alkylamino group, alkoxy group, aryloxy group, amide group, arylamino group, ureido group, sulfamoylamino group, alkylthio group, arylthio group, alkoxycarbonylamino group, sulfonamide group Carbamoyl group, sulfamoyl group, sulfonyl group, alkoxycarbonyl group, heterocyclic oxy group, azo group, acyloxy group, carbamoyloxy group, silyloxy group, aryloxycarbonyl group, aryloxycarbonylamino group, imide group, heterocyclic thio group , Sulfinyl group, phosphoryl group, acyl group, carboxyl Or a sulfo group.

In the formula (i) and the formula (ii), in particular, R ² is a hydrogen atom, a halogen atom, an aliphatic group, an alkoxy group, an aryloxy group, an amide group, a ureido group, a sulfamoylamino group among the above substituents. It is preferably a group, an alkoxycarbonylamino group or a sulfonamide group.

In the present invention, the aliphatic group means an alkyl group, a substituted alkyl group, an alkenyl group, a substituted alkenyl group, an alkynyl group, a substituted alkynyl group, an aralkyl group and a substituted aralkyl group. The aliphatic group may have a branch or may form a ring. The number of carbon atoms in the aliphatic group is preferably 1-20, and more preferably 1-18. The aryl part of the aralkyl group and the substituted aralkyl group is preferably phenyl or naphthyl, particularly preferably phenyl. Examples of the substituent of the alkyl moiety of the substituted alkyl group, the substituted alkenyl group, the substituted alkynyl group, and the substituted aralkyl group include the substituents exemplified in the description of R ^{1 to} R ⁴ . The example of the substituent of the aryl part of a substituted aralkyl group is the same as the example of the substituent of the following substituted aryl group.

In the present invention, the aromatic group means an aryl group and a substituted aryl group. The aryl group is preferably phenyl or naphthyl, particularly preferably phenyl. The aryl part of the substituted aryl group is the same as the above aryl group. Examples of the substituent of the substituted aryl group include the substituents cited for explanation of R ¹ to R ^4.

In the formula (i) and the formula (ii), A represents —NR ⁵ R ⁶ or a hydroxy group, and R ⁵ and R ⁶ each independently represents a hydrogen atom, an aliphatic group, an aromatic group or a heterocyclic group. To express. A is preferably —NR ⁵ R ⁶ . R ⁵ and R ⁶ may be bonded to each other to form a ring. Each of R ⁵ and R ⁶ is more preferably a hydrogen atom, an alkyl group, a substituted alkyl group, an aryl group or a substituted aryl group, and a hydrogen atom, an alkyl group having 1 to 18 carbon atoms, or a carbon atom number of 1 Most preferred is a substituted alkyl group of ˜18.

In formula (i) and formula (ii), B ¹ represents ═C (R ³ ) — or ═N—, and B ² represents —C (R ⁴ ) ═ or —N═. It is preferable that B ¹ and B ² are not simultaneously -N =, and it is more preferable that B ¹ is = C (R ³ )-and B ² is -C (R ⁴ ) =. Any of R ¹ and R ⁵ , R ³ and R ⁶ and R ¹ and R ² may be bonded to each other to form an aromatic ring or a heterocyclic ring.

In the formula (i), Y represents an unsaturated heterocyclic group. Y is preferably a 5-membered or 6-membered unsaturated heterocyclic ring. The heterocyclic ring may be condensed with an aliphatic ring, an aromatic ring or another heterocyclic ring. N, O, and S can be mentioned as an example of the hetero atom of a heterocyclic ring.
Examples of the unsaturated heterocyclic ring include pyrazole ring, imidazole ring, thiazole ring, isothiazole ring, thiadiazole ring, thiophene ring, benzothiazole ring, benzoxazole ring, benzoisothiazole ring, pyrimidine ring, pyridine ring, and quinoline. A ring or the like is preferable. Moreover, the said unsaturated heterocyclic group may have the substituent quoted by said R < ¹ > -R < ⁴ >.

In the formula (ii), X represents a color photographic coupler residue. The following are preferred as the residues of the color photographic coupler.
Yellow coupler: U.S. Pat. Nos. 3,933,501, 4,022,620, 4,326,024, 4,401,752, 4,248,961, and JP-B-58-10939 British Patents 1,425,020, 1,476,760, U.S. Patents 3,973,968, 4,314,023, 4,511,649, European Patent 249,473A, Couplers represented by formulas (I) and (II) of No. 502,424A, couplers represented by formulas (1) and (2) of No. 513,496A (particularly Y-28 on page 18), No. 568,037A, the coupler represented by the formula (I) of claim 1, US Pat. No. 5,066,576, column 1, line 45 to 55, the coupler represented by the general formula (I), General of paragraph 0008 of 274425 A coupler represented by (I), a coupler described in claim 1 on page 40 of European Patent 498,381A1 (particularly D-35 on page 18), and represented by formula (Y) on page 4 of 447,969A1. Couplers (especially Y-1 (page 17), Y-54 (page 41)), represented by the formulas (II) to (IV) in columns 7 to 58 of column 7 of US Pat. No. 4,476,219. Couplers (particularly II-17, 19 (column 17), II-24 (column 19)).

  Magenta couplers: US Pat. Nos. 4,310,619, 4,351,897, European Patent 73,636, US Pat. Nos. 3,061,432, 3,725,067, Research Disclosure No. 24220 (June 1984), ibid. 24230 (June 1984), JP-A-60-33552, JP-A-60-43659, JP-A-61-72238, JP-A-60-35730, JP-A-55-118034, JP-A-60-185951, U.S. Pat. No. 500,630, No. 4,540,654, No. 4,556,630, International Publication No. WO88 / 04795, JP-A-3-39737 (L-57 (page 11, lower right), L-68 (12 (Lower right of page), L-77 (lower right of page 13)), [A-4] -63 (page 134), [A-4] -73, -75 (page 139) of European Patent 456,257, 486, 965, M-4, -6 (page 26), M-7 (page 27), 571, 959A, M-45 (page 19), and JP-A-5-204106, M-1 (Page 6), paragraph 0237 M- 2, US Pat. No. 3,061,432 and No. 3,725,067.

  Cyan coupler: U.S. Pat. Nos. 4,052,212, 4,146,396, 4,228,233, 4,296,200, European Patent 73,636, Japanese Patent Laid-Open No. 4-204843 CX-1,3,4,5,11,12,14,15 (pages 14 to 16); JP-A-4-43345, C-7,10 (page 35), 34,35 (page 37), ( I-1), (I-17) (pages 42-43); a coupler represented by general formula (Ia) or (Ib) of claim 1 of JP-A-6-67385.

  Other couplers described in JP-A-62-215272 (page 91), JP-A-2-33144 (pages 3, 30), EP 355,660A (pages 4, 5, 45, 47) Is also useful.

  Of the oil-soluble dyes represented by the formula (i), a dye represented by the following formula (iii) is particularly preferably used as the magenta dye.

In the formula (iii), Z ¹ represents an electron-withdrawing group having a Hammett's substituent constant σp value of 0.20 or more. Z ¹ is preferably an electron-withdrawing group having a σp value of 0.30 or more and 1.0 or less. Specific examples of the preferred substituent include an electron-withdrawing substituent described later. Among them, an acyl group having 2 to 12 carbon atoms, an alkyloxycarbonyl group having 2 to 12 carbon atoms, a nitro group, a cyano group, An alkylsulfonyl group having 1 to 12 carbon atoms, an arylsulfonyl group having 6 to 18 carbon atoms, a carbamoyl group having 1 to 12 carbon atoms, and a halogenated alkyl group having 1 to 12 carbon atoms are preferable. Particularly preferred are a cyano group, an alkylsulfonyl group having 1 to 12 carbon atoms, and an arylsulfonyl group having 6 to 18 carbon atoms, and most preferred is a cyano group.

In the formula (iii), Z ² represents a hydrogen atom, an aliphatic group or an aromatic group.
In said formula (iii), R < ¹ > -R < ⁶ > is synonymous with each of the said formula (i).

In the formula (iii), Q represents a hydrogen atom, an aliphatic group, an aromatic group or a heterocyclic group. Among these, Q is preferably a group composed of a nonmetallic atom group necessary for forming a 5- to 8-membered ring. Among these, an aromatic group or a heterocyclic group is particularly preferable. The 5- to 8-membered ring may be substituted, may be a saturated ring, or may have an unsaturated bond. Preferred nonmetallic atoms include nitrogen atoms, oxygen atoms, sulfur atoms or carbon atoms. Specific examples of such a ring structure include, for example, a benzene ring, cyclopentane ring, cyclohexane ring, cycloheptane ring, cyclooctane ring, cyclohexene ring, pyridine ring, pyrimidine ring, pyrazine ring, pyridazine ring, triazine ring, imidazole ring. , A benzimidazole ring, an oxazole ring, a benzoxazole ring, an oxane ring, a sulfolane ring, and a thiane ring. When these rings further have a substituent, the substituent is the substituent of the formula (i). The group illustrated by R < ¹ > -R < ⁴ > is mentioned.

  In addition, about the preferable structure of the compound represented by the said formula (iii), it describes in Unexamined-Japanese-Patent No. 2001-335714.

  Of the dyes represented by the formula (ii), a dye represented by the following formula (iv) is particularly preferably used as the magenta dye.

  In the above formula (iv), G is a hydrogen atom, aliphatic group, aromatic group, heterocyclic group, cyano group, alkoxy group, aryloxy group, alkylthio group, arylthio group, ester group, amino group, carbamoyl group, sulfonyl group Represents a group, a sulfamoyl group, a ureido group, a urethane group, an acyl group, an amide group or a sulfonamide group.

In the formula (iv), R ¹ , R ² , A, B ¹ and B ² have the same meanings as those in the formula (ii), and preferred ranges thereof are also the same.

  In the formula (iv), L represents an aliphatic group, aromatic group, heterocyclic group, cyano group, alkoxy group, aryloxy group, alkylthio group, arylthio group, ester group, amino group, carbamoyl group, sulfonyl group, sulfamoyl. Represents a group of atoms that form a 5- or 6-membered nitrogen-containing heterocycle optionally substituted with at least one of a group, a ureido group, a urethane group, an acyl group, an amide group, and a sulfonamide group, Furthermore, a condensed ring may be formed with another ring.

In the compound represented by the formula (iv), A is preferably —NR ⁵ R ⁶ , L preferably forms a 5-membered nitrogen-containing heterocyclic ring, and examples of the 5-membered nitrogen-containing heterocyclic ring include imidazole. Rings, triazole rings and terazole rings are included.

Examples of magenta dye compounds (M-0 to 6, a-21 to 25) among the dyes represented by the formula (i) and the formula (ii) are shown below. It is for explaining in detail, and the present invention is not limited by these.
Moreover, as a magenta dye in this invention, it is preferable to use M-0, M-4, M-6, and a-21, and M-4, M-6, and a-21 can be used especially preferably.

  Other examples of the colorant compound that can be used in the present invention are described in JP-A Nos. 2001-240763, 2001-181549, and JP-A-2001-335714. It is not limited.

The compound represented by the formula (iii) can be synthesized with reference to, for example, methods described in JP-A Nos. 2001-335714 and 55-161856.
The compound represented by the formula (4) can be referred to, for example, the methods described in JP-A-4-1267772 and JP-B-7-94180 and JP-A-2001-240763. Can be synthesized.

  Of the dyes represented by the formula (ii), a pyrrolotriazole azomethine dye represented by the following formula (v) is particularly preferably used as the cyan dye.

In the formula (v), A, R ¹ , R ² , B ¹ and B ² have the same meanings as those in the formula (iv), and preferred ranges thereof are also the same.

In the formula (v), Z ³ and Z ⁴ are independently the same as G in the formula (iv). Z ³ and Z ⁴ may be bonded to each other to form a ring structure. It is more preferable that Z ³ is an electron-withdrawing group having a Hammett substituent constant σp value of 0.30 or more because the absorption is sharp. Z ³ is more preferably an electron-withdrawing group having a Hammett substituent constant σp value of 0.45 or more, and most preferably an electron-withdrawing group having a Hammett substituent constant σp value of 0.60 or more. Further, those having a sum of Hammett substituent constants σp values of Z ³ and Z ⁴ of 0.70 or more exhibit an excellent hue as cyan, and are more preferable.

In the formula (v), M is an atomic group forming a 1,2,4-triazole ring fused to the 5-membered ring in the formula (v), and two atoms in the condensed part with the 5-membered ring One of B ³ and B ⁴ is a nitrogen atom and the other is a carbon atom.

  The compound represented by the formula (v) is preferably used as a cyan dye, but can also be used as a magenta dye by changing a substituent.

  Here, Hammett's substituent constant σp value used in this specification will be described. Hammett's rule was found in 1935 by L. L. in order to quantitatively discuss the effect of substituents on the reaction or equilibrium of benzene derivatives. P. A rule of thumb proposed by Hammett, which is widely accepted today. Substituent constants determined by Hammett's rule include a σp value and a σm value, and these values can be found in many general books. A. Dean, “Lange's Handbook of Chemistry”, 12th edition, 1979 (Mc Graw-Hill) and “Chemicals” special edition, 122, 96-103, 1979 (Nankodo). In the present invention, each substituent is limited or explained by Hammett's substituent constant σp, but this is limited to only a substituent having a known value that can be found in the above-mentioned book. Needless to say, it also includes substituents that would be included in the range when measured based on Hammett's rule even if the value is unknown. The formulas (i) to (v) include those that are not benzene derivatives, but the σp value is used as a scale indicating the electronic effect of the substituent regardless of the substitution position. In the present invention, the σp value is used in this sense.

  Examples of the electron-withdrawing group having a Hammett substituent constant σp value of 0.60 or more include a cyano group, a nitro group, and an alkylsulfonyl group (for example, a methanesulfonyl group and an arylsulfonyl group (for example, a benzenesulfonyl group)). As the electron withdrawing group having a Hammett σp value of 0.45 or more, in addition to the above, an acyl group (for example, acetyl group), an alkoxycarbonyl group (for example, dodecyloxycarbonyl group), an aryloxycarbonyl group (for example, m-chlorophenoxy) Carbonyl), alkylsulfinyl group (for example, n-propylsulfinyl), arylsulfinyl group (for example, phenylsulfinyl), sulfamoyl group (for example, N-ethylsulfamoyl, N, N-dimethylsulfamoyl), halogenated alkyl group (For example, a trif (Loromethyl).

  As the electron-withdrawing group having a Hammett substituent constant σp value of 0.30 or more, in addition to the above, an acyloxy group (for example, acetoxy), a carbamoyl group (for example, N-ethylcarbamoyl, N, N-dibutylcarbamoyl), halogen Alkoxy group (for example, trifluoromethyloxy), halogenated aryloxy group (for example, pentafluorophenyloxy), sulfonyloxy group (for example, methylsulfonyloxy group), halogenated alkylthio group (for example, difluoromethylthio), 2 An aryl group (eg, 2,4-dinitrophenyl, pentachlorophenyl) substituted with one or more electron-withdrawing groups having a σp value of 0.15 or more, and a heterocyclic ring (eg, 2-benzoxazolyl, 2- Benzothiazolyl, 1-phenyl-2-benzimidazolyl) Can do. Specific examples of the electron-withdrawing group having a σp value of 0.20 or more include a halogen atom in addition to the above.

  Moreover, in this invention, the oil-soluble dye represented by a following formula (AI) can be used preferably.

In the above formula (AI), X ₁ , X ₂ , X ₃ and X ₄ are each independently —SO—Z, —SO ₂ —Z, —SO ₂ NR ₁ R ₂ , —CONR ₁ R _2. represents a group selected from _-CO 2 _{R 1} and a sulfo group. Here, Z is a substituted or unsubstituted alkyl group, a substituted or unsubstituted cycloalkyl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted aralkyl group, a substituted or unsubstituted aryl group, or a substituted or unsubstituted group. Represents a substituted heterocyclic group. R ₁ and R ₂ are each independently a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted cycloalkyl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted aralkyl group, substituted or unsubstituted It represents a substituted aryl group or a substituted or unsubstituted heterocyclic group. However, R ₁ and R ₂ are not both hydrogen atoms. M represents a hydrogen atom, a metal element, a metal oxide, a metal hydroxide, or a metal halide. Y ₁ , Y ₂ , Y ₃ and Y ₄ each independently represent a hydrogen atom or a monovalent substituent. _{a 1 ~a 4, b 1 ~b} 4 _represents the number of _{X 1 ~X 4, Y 1 ~Y} 4, each independently, an integer of 0-4. However, the sum of a _{1 to} a ₄ is 2 or more.

  Of the oil-soluble dyes represented by the formula (AI), an oil-soluble dye represented by the following formula (A-II) can be particularly preferably used.

The formula (A-II) _{in: X 11 ~X 14, Y 11} ~Y 18 and M is a _{X 1 ~X 4, Y 1 ~Y} 4, M respectively synonymous in Formula (A-I) is there. a ₁₁ ~a ₁₄ each independently represent a integer of 1 or 2.

  Illustrative compound (AII-17) is shown as a specific example of formula (A-II), but this is for the purpose of illustrating the present invention in detail, and the present invention is not limited thereby. .

  In the present invention, it is preferable to use an oil-soluble dye having an oxidation potential nobler than 1.0 V (SCE). The oxidation potential is more preferable as it is noble, the oxidation potential is more noble than 1.1 V (SCE), more preferably 1.2 V (SCE).

  A person skilled in the art can easily measure the value (Eox) of the oxidation potential. Regarding this method, see, for example, P.I. Delahay's “New Instrumental Methods in Electrochemistry” (1954, published by Interscience Publishers) and A.C. J. et al. "Electrochemical Methods" by Bard et al. (1980, published by John Wiley & Sons), Akira Fujishima et al., "Electrochemical Measurement Methods" (1984, published by Gihodo Publishing Co., Ltd.).

Specifically, the oxidation potential is measured by placing a test sample in a solvent such as dimethylformamide or acetonitrile containing a supporting electrolyte such as sodium perchlorate or tetrapropylammonium perchlorate in the range of 1 × 10 ⁻⁴ to 1 × 10 ⁻⁶ mol / Approximate the oxidization wave in a straight line by dissolving 1 liter and sweeping to the oxidation side (noble side) using carbon (GC) as the working electrode and rotating platinum electrode as the counter electrode by cyclic voltammetry and DC polarography equipment Then, the intersection of this straight line and the residual current / potential line and the intersection of the straight line and the saturation current line (or the intersection of the straight line parallel to the vertical axis passing through the peak potential value) The potential value is measured as a value relative to SCE (saturated calomel electrode). This value may be deviated by several tens of milvolts 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). . The supporting electrolyte and solvent to be used can be selected appropriately depending on the oxidation potential and solubility of the test sample. The supporting electrolyte and the solvent that can be used are described in pages 101 to 118 of Akira Fujishima et al., “Electrochemical measurement method” (1984, published by Gihodo Publishing Co., Ltd.).
In the concentration range of the measurement solvent and the phthalocyanine compound sample, the oxidation potential in a non-association state is measured.

The value of Eox represents the ease of electron transfer from the sample to the electrode, and the larger the value (the oxidation potential is noble), the less the electron transfer from the sample to the electrode, in other words, the less easily oxidized. .
When a dye having a low oxidation potential is used, polymerization inhibition by the dye is large and curability is lowered. When a dye having a noble oxidation potential is used, there is almost no polymerization inhibition.

The colorant that can be used in the present invention is preferably appropriately dispersed in the ink after being added to the ink composition of the present invention. For dispersing the colorant, for example, a dispersion device such as a ball mill, a sand mill, an attritor, a roll mill, an agitator, a Henschel mixer, a colloid mill, an ultrasonic homogenizer, a pearl mill, a wet jet mill, or a paint shaker can be used.
It is also possible to add a dispersant when dispersing the colorant. The type of the dispersant is not particularly limited, but a polymer dispersant is preferably used, and examples of the polymer dispersant include Solsperse series manufactured by Zeneca. Moreover, it is also possible to use a synergist according to various pigments as a dispersion aid. In the present invention, these dispersant and dispersion aid are preferably added in an amount of 1 to 50 parts by mass with respect to 100 parts by mass of the colorant.
The colorant may be added directly to the ink composition of the present invention, but may be added in advance to a dispersion medium such as a solvent or a polymerizable compound used in the present invention in order to improve dispersibility. In the present invention, in order to avoid the problem of deterioration of solvent resistance when the solvent remains in the cured image and the problem of VOC (Volatile Organic Compound) of the remaining solvent, the colorant contains a specific urethane compound. It is preferable to add to the polymerizable compound to contain. Further, as a polymerizable compound to be used, it is preferable in view of dispersion suitability to select a monomer having the lowest viscosity.

  In the present invention, the colorant particles have an average particle diameter of preferably 0.005 to 0.5 μm, more preferably 0.01 to 0.45 μm, and still more preferably 0.015 to 0.3 μm. It is preferable to select the agent, dispersant, dispersion medium, dispersion conditions, and filtration conditions. This particle size control is preferable because clogging of the head nozzle can be suppressed and ink storage stability, ink transparency, and curing sensitivity can be maintained.

  The colorant is preferably added in an amount of 1 to 10% by mass in terms of solid content in the ink composition, and more preferably 2 to 8% by mass.

[(E) Sensitizing dye]
A sensitizing dye (E) can be added to the ink composition of the present invention in order to promote the decomposition of the (B) polymerization initiator by irradiation with actinic rays. A sensitizing dye absorbs specific actinic radiation and enters an electronically excited state. The sensitizing dye in an electronically excited state is brought into contact with the polymerization initiator to cause effects such as electron transfer, energy transfer, and heat generation. As a result, the polymerization initiator undergoes a chemical change, that is, decomposes to generate radicals, acids, or bases.

As the sensitizing dye, a compound corresponding to the wavelength of actinic radiation that generates an initiation species in the polymerization initiator (B) used in the ink composition may be used, but it is used for a curing reaction of a general ink composition. In view of the above, examples of preferable sensitizing dyes include those belonging to the following compounds and having an absorption wavelength in the 350 nm to 450 nm region.
That is, polynuclear aromatics (for example, pyrene, perylene, triphenylene), xanthenes (for example, fluorescein, eosin, erythrosine, rhodamine B, rose bengal), cyanines (for example, 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 (for example, 7-diethylamino-4-methylcoumarin) and the like can be mentioned.

  More preferable examples of the sensitizing dye include compounds represented by the following formulas (I) to (V).

(In the formula (I), A ¹ represents a sulfur atom or NR ⁵⁰ , R ⁵⁰ represents an alkyl group or an aryl group, and L ² represents the basic nucleus of the dye in combination with the adjacent A ¹ and the adjacent carbon atom. Represents a non-metallic atomic group to be formed, R ⁵¹ and R ⁵² each independently represent a hydrogen atom or a monovalent non-metallic atomic group, and R ⁵¹ and R ⁵² are bonded to each other to form an acidic nucleus of the dye. W represents an oxygen atom or a sulfur atom.)

(In the formula (II), Ar ¹ and Ar ² each independently represent an aryl group and are linked via a bond with —L ³ —, where L ³ represents —O— or —S—. W is synonymous with that shown in formula (I).)

(In the formula (III), A ² represents a sulfur atom or NR ⁵⁹ , L ⁴ represents a non-metallic atomic group that forms a basic nucleus of the dye in combination with adjacent A ² and a carbon atom, R ⁵³ , R ⁵⁴ , R ⁵⁵ , R ⁵⁶ , R ⁵⁷ and R ⁵⁸ each independently represent a monovalent nonmetallic atomic group, and R ⁵⁹ represents an alkyl group or an aryl group.)

(In Formula (IV), A ³ and A ⁴ each independently represent —S— or —NR ⁶² — or —NR ⁶³ —, and R ⁶² and R ⁶³ each independently represent a substituted or unsubstituted alkyl group, substituted Or an unsubstituted aryl group, and L ⁵ and L ⁶ each independently represent a nonmetallic atomic group that forms a basic nucleus of a dye together with adjacent A ³ , A ⁴ and an adjacent carbon atom; ⁶⁰ and R ⁶¹ are each independently a hydrogen atom or a monovalent nonmetallic atomic group, or can be bonded to each other to form an aliphatic or aromatic ring.)

(In the formula (V), 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 represents a hydrogen atom or a monovalent nonmetallic atomic group, and R ⁶⁷ and R ⁶⁴ , and R ⁶⁵ and R ⁶⁷ can be bonded to each other to form an aliphatic or aromatic ring. .)

  Preferable specific examples of the compounds represented by formulas (I) to (V) include those shown below.

  The sensitizing dye is preferably added to the ink composition in an amount of 0 to 20% by mass, and more preferably 0.1 to 10% by mass.

[(F) Co-sensitizer]
The ink composition of the present invention can also contain a co-sensitizer. In the present invention, the co-sensitizer has functions such as further improving the sensitivity of the sensitizing dye to actinic radiation or suppressing polymerization inhibition of the polymerizable compound by oxygen.
Examples of such co-sensitizers include amines such as M.I. R. Sander et al., “Journal of Polymer Society”, Vol. 10, 3173 (1972), Japanese Patent Publication No. 44-20189, Japanese Patent Publication No. 51-82102, Japanese Patent Publication No. 52-134692, Japanese Patent Publication No. 59-138205. No. 60-84305, JP-A 62-18537, JP-A 64-33104, Research Disclosure 33825, and the like. Specific examples include triethanolamine. P-dimethylaminobenzoic acid ethyl ester, p-formyldimethylaniline, p-methylthiodimethylaniline and the like.

  Other examples of co-sensitizers include thiols and sulfides, for example, thiol compounds described in JP-A-53-702, JP-B-55-500806, JP-A-5-142773, and JP-A-56. And the like. Specific examples include 2-mercaptobenzothiazole, 2-mercaptobenzoxazole, 2-mercaptobenzoimidazole, 2-mercapto-4 (3H) -quinazoline, β-mercaptonaphthalene. Etc.

  Other examples include amino acid compounds (eg, N-phenylglycine), organometallic compounds described in Japanese Patent Publication No. 48-42965 (eg, tributyltin acetate), and hydrogen described in Japanese Patent Publication No. 55-34414. Donors, sulfur compounds described in JP-A-6-308727 (eg, trithiane), phosphorus compounds described in JP-A-6-250387 (diethyl phosphite, etc.), Si-H described in JP-A-8-65779 , Ge—H compounds and the like.

  The co-sensitizer is preferably added in an amount of 0 to 15% by mass, more preferably 0.1 to 10% by mass in the ink composition.

[(G) Other ingredients]
If necessary, other components can be added to the ink composition of the present invention. Examples of other components include a polymerization inhibitor and a solvent.
A polymerization inhibitor may be added from the viewpoint of enhancing the storage stability. The ink composition of the present invention is preferably discharged in the range of 40 to 80 ° C. by heating and reducing the viscosity, and a polymerization inhibitor is preferably added to prevent clogging of the head due to thermal polymerization. The polymerization inhibitor is preferably added in an amount of 200 to 20,000 ppm based on the total amount of the ink composition of the present invention. Examples of the polymerization inhibitor include hydroquinone, benzoquinone, p-methoxyphenol, TEMPO, TEMPOL, and cuperon Al.

In view of the fact that the ink composition of the present invention is a radiation curable type, it is preferable that no solvent is contained so that the ink composition can react quickly and be cured immediately after landing of the ink composition. However, a predetermined solvent can be included as long as the curing rate of the ink composition is not affected. In the present invention, an organic solvent or water can be used as the solvent. In particular, the organic solvent can be added in order to improve the adhesion to the recording medium (support such as paper). The addition of an organic solvent is effective because the VOC problem can be avoided.
The amount of the organic solvent is, for example, 0.1 to 5% by mass, preferably 0.1 to 3% by mass with respect to the mass of the entire ink composition of the present invention.

  In addition, a known compound can be added to the ink composition of the present invention as necessary. For example, surfactants, leveling additives, matting agents, polyester resins for adjusting film properties, polyurethane resins, vinyl resins, acrylic resins, rubber resins, waxes and the like are appropriately selected and added. be able to. In order to improve the adhesion to a recording medium such as polyolefin or PET, it is also preferable to contain a tackifier that does not inhibit the polymerization. Specifically, a high molecular weight adhesive polymer described in JP-A-2001-49200, pages 5 to 6 (for example, (meth) acrylic acid and an alcohol having an alkyl group having 1 to 20 carbon atoms). An ester, a copolymer of (meth) acrylic acid and an alicyclic alcohol having 3 to 14 carbon atoms, a copolymer of an ester of (meth) acrylic acid and an aromatic alcohol having 6 to 14 carbon atoms), and polymerizability. Examples thereof include a low molecular weight tackifying resin having an unsaturated bond.

[Properties of ink composition]
As described above, the ink composition of the present invention contains a specific urethane compound as an essential component, and further contains a polymerization initiator, a sensitizing dye, a colorant, and the like. These components are preferably (A) a total polymerizable compound containing a specific urethane compound, based on the total mass of the ink composition, preferably 1 to 97% by mass, more preferably 30 to 95% by mass, and (B) polymerization. The initiator is preferably 0.01 to 20% by mass, more preferably 0.1 to 20% by mass, still more preferably 0.5 to 10% by mass, based on the total polymerizable compound including the specific urethane compound ( D) The colorant is preferably 1 to 10% by mass, more preferably 2 to 8% by mass, and (E) the sensitizing dye is preferably 0.1 to 12% by mass, more preferably 0.5 to It is suitable to contain so that it may become 11 mass%.

Since the ink composition of the present invention is applied for inkjet recording, the viscosity of the ink composition is determined at a discharge temperature (for example, 40 to 80 ° C., preferably 25 to 30 ° C.) in consideration of discharge properties. , Preferably 4 to 30 mPa · s, more preferably 5 to 20 mPa · s. For example, the viscosity of the ink composition of the present invention at room temperature (25 to 30 ° C.) is preferably 4 to 500 mPa · s, more preferably 5 to 200 mPa · s.
It is preferable that the composition ratio of the ink composition of the present invention is appropriately adjusted so that the viscosity is in the above range. By setting the viscosity at room temperature high, even when a porous recording medium is used, ink penetration into the recording medium can be avoided, and uncured monomers and odors can be reduced. Furthermore, it is preferable because bleeding of ink at the time of ink droplet landing can be suppressed, and as a result, the image quality of the obtained printed matter is improved.

  The surface tension of the ink composition of the present invention is, for example, 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>
The ink jet recording method of the present invention and the ink jet recording apparatus applicable to the ink jet recording method will be described below.
In the inkjet recording method of the present invention, the ink composition of the present invention is ejected onto a recording medium (support, recording material, etc.), and the ink composition ejected onto the recording medium is irradiated with actinic radiation. Is a method of forming an image by curing.

That is, the inkjet recording method of the present invention comprises (a) a step of ejecting the ink composition of the present invention onto a recording medium, and (b) irradiating the ejected ink composition with actinic radiation, And a step of curing the ink composition.
By including the steps (a) and (b), the ink jet recording method of the present invention forms an image with the ink composition cured on the recording medium.

  In the step (a) in the inkjet recording method of the present invention, an inkjet recording apparatus described in detail below can be used.

[Inkjet recording device]
There is no restriction | limiting in particular as an inkjet recording device used for the inkjet recording method of this invention, The well-known inkjet recording device which can achieve the target resolution can be selected arbitrarily and can be used. That is, any known inkjet recording apparatus including a commercially available product can eject ink onto a recording medium in step (a) of the inkjet recording method of the present invention.
Examples of the ink jet recording apparatus that can be used in the present invention include an apparatus including an ink supply system, a temperature sensor, and an actinic radiation source.
The ink supply system includes, for example, an original tank containing the ink composition of the present invention, a supply pipe, an ink supply tank immediately before the inkjet head, a filter, and a piezo-type inkjet head. The piezo-type inkjet head has a multi-size dot of 1 to 100 pl, preferably 8 to 30 pl, for example, 320 × 320 to 4000 × 4000 dpi, preferably 400 × 400 to 1600 × 1600 dpi, and more preferably 720 × 720 dpi. It can drive so that it can discharge with the resolution of. In the present invention, dpi represents the number of dots per 2.54 cm.

  As described above, since it is desirable that the radiation-curable ink, like the ink composition of the present invention, has a constant temperature for the ink to be ejected, heat insulation and heating are performed from the ink supply tank to the inkjet head portion. It can be carried out. 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 flow rate and the environmental temperature. The temperature sensor can be provided in the vicinity of the ink supply tank and the nozzle of the inkjet head. 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 heat energy, it is preferable to insulate from other parts and reduce the heat capacity of the entire heating unit.

Using the above inkjet recording apparatus, the ink composition of the present invention is ejected by heating the ink composition to 40 to 80 ° C., more preferably 25 to 50 ° C. Preferably it is performed after lowering to 7-30 mPa · s, more preferably 7-25 mPa · s. In particular, it is preferable to use an ink composition having an ink viscosity at 25 ° C. of 35 to 500 mPa · s as the ink composition of the present invention because a large effect can be obtained. By using this method, high ejection stability can be realized.
Radiation curable inks such as the ink composition of the present invention generally have a higher viscosity than water-based inks that are usually used in ink jet recording inks, and therefore have a large viscosity fluctuation due to temperature fluctuations during ejection. The ink viscosity fluctuation has a great influence on the change of the droplet size and the change of the droplet discharge speed, and causes the image quality deterioration. Therefore, it is necessary to keep the temperature of the ink at the time of ejection as constant as possible. Therefore, in the present invention, it is appropriate that the control range of the ink temperature is ± 5 ° C. of the set temperature, preferably ± 2 ° C. of the set temperature, more preferably ± 1 ° C. of the set temperature.

Next, (b) the step of irradiating the ejected ink composition with actinic radiation to cure the ink composition will be described.
The ink composition ejected on the recording medium is cured by irradiation with actinic radiation. This is because the (B) polymerization initiator contained in the ink composition of the present invention is decomposed by irradiation with actinic radiation to generate initiating species such as radicals, acids, bases, and the like (A This is because the polymerization reaction of the specific urethane compound or the other polymerizable compound (C) used in combination as desired occurs and is accelerated. At this time, when (E) a sensitizing dye is present together with (B) the polymerization initiator in the ink composition, (E) the sensitizing dye in the system absorbs actinic radiation to be in an excited state, and (B) the polymerization initiator. (B) can accelerate | stimulate decomposition | disassembly of a polymerization initiator and can achieve a more highly sensitive hardening reaction.

  Here, α rays, γ rays, electron beams, X rays, ultraviolet rays, visible light, infrared rays, or the like can be used as the active radiation used. Although the peak wavelength of actinic radiation is based also on the absorption characteristic of a sensitizing dye, it is preferable that it is 200-600 nm, for example, it is more preferable that it is 300-450 nm, and it is still more preferable that it is 350-420 nm.

In addition, the polymerization initiation system of the ink composition of the present invention has sufficient sensitivity even with a low output actinic radiation. Thus, the output of the active radiation is preferably 2,000 mJ / cm ² or less, more preferably from 10 to 2,000 mJ / cm ^2, more preferably be 20 to 1,000 mJ / cm ² Particularly preferably, it is 50 to 800 mJ / cm ² .
Furthermore, the actinic radiation is, the exposure surface illuminance of, for example, 10 to 2,000 mW / cm ^2, preferably, suitably be irradiated at 20 to 1,000 mW / cm ^2.

Mercury lamps and gas / solid lasers are mainly used as actinic radiation sources, and mercury lamps and metal halide lamps are widely known as light sources used for curing UV photocurable ink jet recording inks. Yes. However, from the viewpoint of environmental protection, mercury-free is strongly desired, and replacement with a GaN-based semiconductor ultraviolet light-emitting device is very useful industrially and environmentally. Furthermore, LED (UV-LED) and LD (UV-LD) are small, have a long life, have high efficiency, and are low in cost, and are expected as light sources for photo-curable ink jets.
Further, a light emitting diode (LED) and a laser diode (LD) can be used as the active radiation source. In particular, when an ultraviolet light source is required, an ultraviolet LED and an ultraviolet LD can be used. For example, Nichia Corporation has introduced a purple LED whose main emission spectrum has a wavelength between 365 nm and 420 nm. When even shorter wavelengths are required, US Pat. No. 6,084,250 discloses an LED that can emit actinic radiation centered between 300 nm and 370 nm. Other ultraviolet LEDs are also available and can emit radiation in different ultraviolet bands. The actinic radiation source particularly preferred in the present invention is a UV-LED, particularly preferably a UV-LED having a peak wavelength at 350 to 420 nm.
Incidentally, it is preferable that maximum illumination intensity of the LED on a recording medium is 10 to 2,000 mW / cm ^2, more preferably 20 to 1,000 mW / cm ^2, particularly preferably 50 to 800 mW / cm ² .

The ink composition of the present invention is suitably irradiated with such actinic radiation for, for example, 0.01 to 120 seconds, preferably 0.1 to 90 seconds.
Actinic radiation irradiation conditions and a basic irradiation method are disclosed in JP-A-60-132767. Specifically, the light source is provided on both sides of the head unit including the ink ejection device, and the head unit and the light source are scanned by a so-called shuttle method. Irradiation with actinic radiation takes a certain time (for example, 0.01 to 0.5 seconds, preferably 0.01 to 0.3 seconds, more preferably 0.01 to 0.15 seconds) after ink landing. Will be done. In this way, by controlling the time from ink landing to irradiation to an extremely short time, it is possible to prevent the ink that has landed on the recording medium from spreading before curing. Further, since the ink can be exposed to the porous recording medium before the ink penetrates to a deep part where the light source does not reach, the residual unreacted monomer can be suppressed, and as a result, the odor can be reduced. .
Further, the curing may be completed by another light source that is not driven. WO99 / 54415 pamphlet discloses a method using an optical fiber and a method of applying a collimated light source to a mirror surface provided on the side surface of the head unit and irradiating the recording unit with UV light as an irradiation method. The curing method can also be applied to the ink jet recording method of the present invention.

By adopting the ink jet recording method as described above, 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. By superimposing the inks in the order of low lightness, the irradiation line can easily reach the lower ink, and good curing sensitivity, reduction of residual monomers, reduction of odor, and improvement of adhesion can be expected. In addition, irradiation can be performed by discharging all colors and collectively exposing, but exposure for each color is preferable from the viewpoint of promoting curing.
In this manner, the ink composition of the present invention can form an image on the surface of a recording medium by being cured with high sensitivity by irradiation with actinic radiation.

<Lithographic printing plate and manufacturing method thereof>
It is possible to produce a lithographic printing plate by applying the ink composition of the present invention on a hydrophilic support and curing using the inkjet recording method of the present invention.
Hereinafter, a method for producing a lithographic printing plate (a method for producing a lithographic printing plate of the present invention) to which the inkjet recording method of the present invention is applied, and a lithographic printing plate obtained by the method (lithographic printing plate of the present invention) will be described.

The lithographic printing plate of the present invention has a hydrophilic support and a hydrophobic image formed on the hydrophilic support. This method for producing a lithographic printing plate includes the following steps.
(A ′) a step of discharging the ink composition of the present invention onto a hydrophilic support; and (b ′) irradiating the discharged ink composition with actinic radiation to cure the ink composition. In this step, a hydrophobic image formed by curing the ink composition is formed on the hydrophilic support.
That is, a lithographic printing plate can be produced in the same manner as in the ink jet recording method of the present invention except that a support having a hydrophilic surface suitable for a lithographic printing plate support is used as the recording medium. .

Conventionally, a lithographic printing plate is obtained by exposing a so-called PS plate having a structure in which a lipophilic photosensitive resin layer is provided on a hydrophilic support as described above, and solubilizing or curing the exposed portion. It was manufactured by forming an image and dissolving and removing non-image areas.
On the other hand, the lithographic printing plate of the present invention is applied directly to the surface of the hydrophilic support according to the digitized image information by applying the lithographic printing plate production method of the present invention (inkjet recording method of the present invention). A hydrophobic image portion can be formed by injecting an object and curing it. This makes it possible to produce a lithographic printing plate more easily than in the past.

[Hydrophilic support used for lithographic printing plates]
The lithographic printing plate of the present invention has a hydrophilic support and a hydrophobic image formed on the surface of the support by the ink composition of the present invention.

The support for a lithographic printing plate on which the ink composition of the present invention is discharged is not particularly limited, and any plate-like support that is dimensionally stable can be used. In view of the image quality, it is preferable that the surface is a hydrophilic support.
The material used as the support can be used as the support as it is when it has hydrophilicity, and when it does not have hydrophilicity, the surface thereof may be subjected to water immersion treatment.
Materials used for the support include, for example, paper, paper laminated with plastic (eg, polyethylene, polypropylene, polystyrene, etc.), metal plate (eg, aluminum, zinc, copper, etc.), plastic film (eg, cellulose diacetate) Cellulose triacetate, cellulose propionate, cellulose butyrate, cellulose acetate butyrate, cellulose nitrate, polyethylene terephthalate, polyethylene, polystyrene, polypropylene, polycarbonate, polyvinyl acetal, etc.), paper or plastic film laminated or vapor-deposited with the above metals, etc. Is mentioned. A preferable support includes a polyester film and an aluminum plate. Among these, an aluminum plate that has good dimensional stability and is relatively inexpensive is preferable.

  The aluminum plate is a pure aluminum plate, an alloy plate containing aluminum as a main component and containing a trace amount of foreign elements, or a plastic laminated on a thin film of aluminum or aluminum alloy. Examples of foreign elements contained in the aluminum alloy include silicon, iron, manganese, copper, magnesium, chromium, zinc, bismuth, nickel, and titanium. The content of foreign elements in the alloy is preferably 10% by mass or less. In the present invention, a pure aluminum plate is preferable. However, since completely pure aluminum is difficult to manufacture in terms of refining technology, it may contain a slightly different element. The composition of the aluminum plate is not specified, and a known material can be used as appropriate.

The thickness of the support is preferably 0.1 to 0.6 mm, and more preferably 0.15 to 0.4 mm.
Prior to using the aluminum plate, it is preferable to perform surface treatment such as roughening treatment or anodizing treatment. By the surface treatment, it becomes easy to improve hydrophilicity and secure adhesion between the hydrophobic image and the support. Prior to roughening the aluminum plate, a degreasing treatment with a surfactant, an organic solvent, an alkaline aqueous solution or the like for removing rolling oil on the surface is performed as desired.

The surface roughening treatment of the aluminum plate is performed by various methods. For example, mechanical surface roughening treatment, electrochemical surface roughening treatment (surface roughening treatment for dissolving the surface electrochemically), chemical treatment, etc. Surface roughening treatment (roughening treatment that chemically selectively dissolves the surface).
As a method for the mechanical surface roughening treatment, a known method such as a ball polishing method, a brush polishing method, a blast polishing method, or a buff polishing method can be used. Also, a transfer method in which the uneven shape is transferred with a roll provided with unevenness in the aluminum rolling step may be used.
Examples of the electrochemical surface roughening treatment include a method in which an alternating current or a direct current is used in an electrolytic solution containing an acid such as hydrochloric acid or nitric acid. Another example is a method using a mixed acid as described in JP-A-54-63902.
The surface-roughened aluminum plate is subjected to an alkali etching treatment using an aqueous solution of potassium hydroxide, sodium hydroxide or the like, if necessary, further neutralized, and if desired, wear resistant. In order to increase the anodic oxidation treatment.

As the electrolyte used for the anodizing treatment of the aluminum plate, various electrolytes that form a porous oxide film can be used. In general, sulfuric acid, hydrochloric acid, oxalic acid, chromic acid or a mixed acid thereof is used. The concentration of these electrolytes is appropriately determined depending on the type of electrolyte.
The conditions for anodizing treatment vary depending on the electrolyte used and cannot be specified in general. In general, however, the electrolyte concentration is 1 to 80% by mass solution, the liquid temperature is 5 to 70 ° C., and the current density is 5 to 60 A / day. dm ² , voltage 1 to 100 V, and electrolysis time 10 seconds to 5 minutes are preferable. The amount of the anodized film formed is preferably from 1.0 to 5.0 g / ^{m 2,} and more preferably 1.5 to 4.0 g / ^{m 2.} Within this range, good printing durability and good scratch resistance of the non-image area of the lithographic printing plate can be obtained, which is preferable.

  As the support used in the present invention, a substrate that has been surface-treated as described above and has an anodized film may be used as it is. However, adhesion to a hydrophobic image, hydrophilicity, stain resistance, etc. are further improved. In order to improve, if necessary, the micropore enlargement treatment or sealing treatment of the anodized film described in JP-A-2001-253181 and JP-A-2001-322365, and a hydrophilic compound are contained. A surface hydrophilization treatment immersed in an aqueous solution can be selected as appropriate. Of course, the enlargement process and the sealing process are not limited to those described above, and any conventionally known method can be performed.

(Sealing treatment)
Sealing treatment includes vapor sealing, single treatment with zirconic fluoride, treatment with an aqueous solution containing an inorganic fluorine compound such as treatment with sodium fluoride, vapor sealing with addition of lithium chloride, sealing with hot water. Hole processing is also possible.
Among these, a sealing treatment with an aqueous solution containing an inorganic fluorine compound, a sealing treatment with water vapor, and a sealing treatment with hot water are preferable. Each will be described below.

-Sealing treatment with aqueous solution containing inorganic fluorine compound-
As the inorganic fluorine compound used for the sealing treatment with an aqueous solution containing an inorganic fluorine compound, a metal fluoride is preferably exemplified.
Specifically, for example, sodium fluoride, potassium fluoride, calcium fluoride, magnesium fluoride, sodium fluoride zirconate, potassium fluoride zirconate, sodium fluoride titanate, potassium fluoride titanate, zircon fluoride Ammonium acid, ammonium fluoride titanate, potassium fluoride titanate, fluorinated zirconate, fluorinated titanate, hexafluorosilicic acid, nickel fluoride, iron fluoride, phosphor fluoride, ammonium fluoride phosphate It is done. Among these, sodium fluorinated zirconate, sodium fluorinated titanate, fluorinated zirconic acid, and fluorinated titanic acid are preferable.

The concentration of the inorganic fluorine compound in the aqueous solution is preferably 0.01% by mass or more, and more preferably 0.05% by mass or more in terms of sufficiently sealing the micropores of the anodized film. Further, in terms of stain resistance, the content is preferably 1% by mass or less, and more preferably 0.5% by mass or less.
It is preferable that the aqueous solution containing the inorganic fluorine compound further contains a phosphate compound. When the phosphate compound is contained, the hydrophilicity of the surface of the anodized film is improved, so that on-machine developability and stain resistance can be improved, which is preferable.

Suitable examples of the phosphate compound include phosphates of metals such as alkali metals and alkaline earth metals.
Specifically, for example, zinc phosphate, aluminum phosphate, ammonium phosphate, diammonium hydrogen phosphate, ammonium dihydrogen phosphate, monoammonium phosphate, monopotassium phosphate, monosodium phosphate, dihydrogen phosphate Potassium, dipotassium hydrogen phosphate, calcium phosphate, sodium ammonium hydrogen phosphate, magnesium hydrogen phosphate, magnesium phosphate, ferrous phosphate, ferric phosphate, sodium dihydrogen phosphate, sodium phosphate, hydrogen phosphate Disodium, lead phosphate, diammonium phosphate, calcium dihydrogen phosphate, lithium phosphate, phosphotungstic acid, ammonium phosphotungstate, sodium phosphotungstate, ammonium phosphomolybdate, sodium phosphomolybdate, sodium phosphite , Tripolyphosphate Potassium, and sodium pyrophosphate. Among these, sodium dihydrogen phosphate, disodium hydrogen phosphate, potassium dihydrogen phosphate, and dipotassium hydrogen phosphate are preferable.
The combination of the inorganic fluorine compound and the phosphate compound is not particularly limited, but the aqueous solution contains at least sodium zirconate fluoride as the inorganic fluorine compound and contains at least sodium dihydrogen phosphate as the phosphate compound. It is preferable.
The concentration of the phosphate compound in the aqueous solution is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, in terms of improvement in on-press developability and stain resistance. Moreover, it is preferable that it is 20 mass% or less at a soluble point, and it is more preferable that it is 5 mass% or less.

The ratio of each compound in the aqueous solution is not particularly limited, but the mass ratio of the inorganic fluorine compound and the phosphate compound is preferably 1/200 to 10/1, and preferably 1/30 to 2/1. Is more preferable.
The temperature of the aqueous solution is preferably 20 ° C. or higher, more preferably 40 ° C. or higher, 100 ° C. or lower, more preferably 80 ° C. or lower.
The aqueous solution preferably has a pH of 1 or more, more preferably has a pH of 2 or more, preferably has a pH of 11 or less, and more preferably has a pH of 5 or less.
A method for sealing with an aqueous solution containing an inorganic fluorine compound is not particularly limited, and examples thereof include an immersion method and a spray method. These may be used alone or in combination, or may be used in combination of two or more.
Of these, the dipping method is preferred. When processing using the dipping method, the processing time is preferably 1 second or longer, more preferably 3 seconds or longer, 100 seconds or shorter, and 20 seconds or shorter. More preferred.

-Sealing treatment with water vapor-
Examples of the sealing treatment with water vapor include a method of bringing pressurized or normal pressure water vapor into contact with the anodized film continuously or discontinuously.
The temperature of the water vapor is preferably 80 ° C. or higher, more preferably 95 ° C. or higher, and preferably 105 ° C. or lower.
The water vapor pressure is preferably in the range (1.008 × 10 ^{5 to} 1.043 × 10 ⁵ Pa) from (atmospheric pressure−50 mmAq) to (atmospheric pressure + 300 mmAq).
The time for which the water vapor is contacted is preferably 1 second or longer, more preferably 3 seconds or longer, 100 seconds or shorter, and more preferably 20 seconds or shorter.

-Sealing treatment with hot water-
Examples of the sealing treatment with hot water (water vapor) include a method in which an aluminum plate on which an anodized film is formed is immersed in hot water.
The hot water may contain an inorganic salt (for example, phosphate) or an organic salt.
The temperature of the hot water is preferably 80 ° C. or higher, more preferably 95 ° C. or higher, and preferably 100 ° C. or lower.
Further, the time of immersion in hot water is preferably 1 second or longer, more preferably 3 seconds or longer, 100 seconds or shorter, more preferably 20 seconds or shorter.

  As the hydrophilization treatment for the support in the present invention, U.S. Pat. Nos. 2,714,066, 3,181,461, 3,280,734, and 3,902,734 are each used. There are alkali metal silicate methods as described in the specification. In this method, the support is immersed in an aqueous solution such as sodium silicate or electrolytically treated. In addition, the treatment with potassium zirconate fluoride described in JP-B 36-22063, U.S. Pat. Nos. 3,276,868, 4,153,461 and 4,689, And a method of treating with polyvinylphosphonic acid as described in each specification of No.272.

In the present invention, the support preferably has a center line average roughness of 0.10 to 1.2 μm. Within this range, good adhesion to a hydrophobic image, good printing durability and good stain resistance are obtained, which is preferable.
A method for producing a lithographic printing plate using such a lithographic printing plate support (hydrophilic support) will be described below.

(A ′) Step of discharging the ink composition of the present invention onto the hydrophilic support First, the ink composition of the present invention is discharged onto the hydrophilic support. In this step, a conventionally known ink jet recording apparatus can be used as described in the ink jet recording method. In addition, when ink is ejected using this ink jet recording apparatus, preferred ranges of ink temperature and viscosity, and the control methods thereof are also the same.

(B ′) a step of irradiating the ejected ink composition with actinic radiation to cure the ink composition, thereby forming a hydrophobic image formed by curing the ink composition Surface of the hydrophilic support The ink composition discharged above is cured by irradiation with actinic radiation. The details of the curing mechanism are the same as those described in the ink jet recording method. Further, the actinic radiation source used for curing the ink composition or the preferable irradiation condition thereof is also the same as described in the ink jet recording method.

  Through the above steps, a hydrophobic image formed by curing the ink composition of the present invention is formed on the surface of the hydrophilic support, and a lithographic printing plate is obtained.

In this way, by applying the inkjet recording method of the present invention to produce a lithographic printing plate, the dot diameter of the landed ink is constant even for various lithographic printing plate supports having different surface wettability. As a result, a hydrophobic image can be accurately formed.
In addition, as described above, the ink composition of the present invention has a low viscosity, excellent storage stability and dischargeability, and further cured with high sensitivity by actinic radiation, so that it can adhere to a support, A hydrophobic region (hydrophobic image) having excellent film quality such as impact resistance and flexibility can be formed.
For these reasons, the planographic printing plate of the present invention has high image quality and excellent printing durability.
In addition, it cannot be overemphasized that the ink composition of this invention is useful not only as an image part of such a lithographic printing plate but as a generally used ink composition.

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to the embodiments in these examples.
The following examples relate to UV inkjet inks of each color.

(Synthesis Example 1: Synthesis of specific urethane compound U-1)
20 g of n-octadodecyl isocyanate was dissolved in 100 ml of tetrahydrofuran, 17.7 g of a terminal epoxy group compound (Compound A) having the following structure was added and stirred, and 100 μl of Neostan U-600 (manufactured by Nitto Kasei) was added thereto. Then, after stirring at 50 degreeC for 1 hour, the solvent was depressurizingly distilled and 37.7g of specific urethane compounds U-1 of the following structure were obtained.
The structure of the obtained specific urethane compound U-1 was identified by ¹ H-NMR and ¹³ C-NMR. Moreover, content of the urethane bond of this specific urethane compound U-1 was 10.4 mass%.

(Synthesis Example 2: Synthesis of specific urethane compound U-2)
20 g of n-octadodecyl isocyanate was dissolved in 100 ml of tetrahydrofuran, 17.3 g of a terminal oxetane group compound (Compound B) having the following structure was added and stirred, and 100 μl of Neostan U-600 (manufactured by Nitto Kasei) was added thereto. Then, after stirring at 50 degreeC for 1 hour, the solvent was depressurizingly distilled and 37.3g of specific urethane compounds U-2 of the following structure were obtained.
The structure of the obtained specific urethane compound U-2 was identified by the same method as in Synthesis Example 1. Moreover, content of the urethane bond of this specific urethane compound U-2 was 10.7 mass%.

(Synthesis Example 3: Synthesis of specific urethane compound U-3)
10 g of hexamethylene diisocyanate was dissolved in 100 ml of tetrahydrofuran, 72.4 g of Blemmer PP500 (Compound C, manufactured by NOF Corporation) having the following structure was added and stirred, and 100 μl of Neostan U-600 (manufactured by Nitto Kasei) was added thereto. Then, after stirring at 50 degreeC for 1 hour, the solvent was depressurizingly distilled and 82.4g of specific urethane compounds U-3 of the following structure were obtained.
The structure of the obtained specific urethane compound U-3 was identified by the same method as in Synthesis Example 1. Moreover, content of the urethane bond of this specific urethane compound U-3 was 4.3 mass%.

(Synthesis Example 4: Synthesis of Specific Urethane Compound U-4)
20 g of n-octadodecyl isocyanate was dissolved in 100 ml of tetrahydrofuran, 17.5 g of Ebecryl 111 (Daicel Chemical) was added and stirred, and 100 μl of Neostan U-600 (Nitto Kasei) was added thereto. Then, after stirring at 50 degreeC for 1 hour, the solvent was depressurizingly distilled and 37.5g of specific urethane compounds U-4 of the following structure were obtained.
The structure of the obtained specific urethane compound U-4 was identified by the same method as in Synthesis Example 1. Moreover, content of the urethane bond of this specific urethane compound U-4 was 10.7 mass%.

(Synthesis Example 5: Synthesis of Comparative Compound R-1)
Esterification was performed using 21.1 g of Eicanoic Acid containing a terminal carboxyl group instead of n-octadodecyl isocyanate used in Synthesis Example 1 to obtain 38.6 g of Comparative Compound R-1 having the following structure. .
The structure of the obtained comparative compound R-1 was identified by the same method as in Synthesis Example 1. Moreover, content of the urethane bond of this comparative compound R-1 was 0 mass%.

(Synthesis Example 6: Synthesis of Comparative Compound R-2)
20 g of hexamethylene diisocyanate was dissolved in 100 ml of tetrahydrofuran, 13.8 g of allyl alcohol was added and stirred, and 100 μl of Neostan U-600 (Nitto Kasei) was added thereto. Then, after stirring at 50 degreeC for 1 hour, the solvent was depressurizingly distilled and 33.8g of comparative compound R-2 of the following structure was obtained.
The structure of the obtained comparative compound R-2 was identified by the same method as in Synthesis Example 1. Moreover, content of the urethane bond of this comparative compound R-2 was 43.7% by mass.

(Synthesis Example 7: Synthesis of Comparative Compound R-3)
Dissolve 3.0 g of n-octadodecyl isocyanate in 200 ml of acetone, add 156.0 g of a polyester terminal acrylate group compound (compound D, Mw15600) having the following structure, stir, and add 100 μl of Neostan U-600 (Nitto Kasei). Added. Then, after stirring at 50 degreeC for 1 hour, the solvent was depressurizingly distilled and 159.0g of comparative compound R-3 of the following structure was obtained.
The structure of the obtained comparative compound R-3 was identified by the same method as in Synthesis Example 1. In addition, the content of urethane bonds in the comparative compound R-3 was 0.4% by mass.

≪Preparation of ink≫
[Example 1]
A mixture of the following components was filtered through a filter having an absolute filtration accuracy of 2 μm to prepare magenta ink 1.

(Magenta ink 1)
C. I. Pigment Red 57: 1 5 parts by mass Divinyl ether 52 parts by mass Specific urethane compound U-2 13 parts by mass 3,4-epoxycyclohexylmethyl-3 ′, 4′-
20 parts by mass of epoxycyclohexanecarboxylate (Celoxide 2021A: manufactured by Daicel UCB)
Polymerization initiator (CSC, IRGACURE 184, following structure) 5 parts by mass Polymerization initiator (CSC, IRGACURE 250, following structure) 5 parts by mass

[Example 2]
A mixture of the following components was filtered through a filter having an absolute filtration accuracy of 2 μm to prepare magenta ink 2.

(Magenta ink 2)
C. I. Pigment Red 57: 1 5 parts by mass Specific urethane compound U-1 7 parts by mass Specific urethane compound U-2 13 parts by mass OXT221 (manufactured by Toagosei Co., Ltd.) 65 parts by mass Polymerization initiator (CSC, IRGACURE 184, the above structure ) 5 parts by mass Polymerization initiator (CSC, IRGACURE 250, the structure) 5 parts by mass

Example 3
A mixture of the following components was filtered through a filter having an absolute filtration accuracy of 2 μm to prepare yellow ink 1.

(Yellow ink 1)
C. I. Pigment Yellow 13 5 parts by mass Specific urethane compound U-3 13 parts by mass 1,6-hexanediol diacrylate 72 parts by mass Polymerization initiator (CSC, IRGACURE 184, the above structure) 5 parts by mass

Example 4
A mixture of the following components was filtered through a filter having an absolute filtration accuracy of 2 μm to prepare magenta ink 3.

(Magenta ink 3)
C. I. Pigment Red 57: 1 5 parts by mass Specific urethane compound U-3 13 parts by mass 1,6-hexanediol diacrylate 72 parts by mass Polymerization initiator (manufactured by CSC, IRGACURE 184, the above structure) 5 parts by mass

Example 5
A mixture of the following components was filtered through a filter having an absolute filtration accuracy of 2 μm to obtain cyan ink 1.

(Cyan ink 1)
C. I. Pigment Blue 15: 3 5 parts by mass Specific urethane compound U-3 13 parts by mass 1,6-hexanediol diacrylate 72 parts by mass Polymerization initiator (manufactured by CSC, IRGACURE 184, the structure) 5 parts by mass

Example 6
A mixture of the following components was filtered through a filter having an absolute filtration accuracy of 2 μm to prepare black ink 1.

(Black ink 1)
C. I. Pigment Black 7 5 parts by mass Specific urethane compound U-3 13 parts by mass 1,6-hexanediol diacrylate 72 parts by mass Polymerization initiator (CSC, IRGACURE 184, the above structure) 5 parts by mass

Example 7
A mixture of the following components was filtered through a filter having an absolute filtration accuracy of 2 μm to prepare magenta ink 4.

(Magenta ink 4)
C. I. Pigment Red 57: 1 5 parts by mass Specific urethane compound U-4 7 parts by mass 1,6-hexanediol diacrylate 83 parts by mass Polymerization initiator (manufactured by CSC, IRGACURE 184, the above structure) 5 parts by mass

[Comparative Example 1]
A magenta ink 5 of Comparative Example 1 was prepared in the same manner as in Example 1 except that the specific urethane compound U-2 was replaced with the comparative compound R-1 in Example 1.

[Comparative Example 2]
A magenta ink 6 of Comparative Example 2 was prepared in the same manner as in Example 1 except that the specific urethane compound U-2 was replaced with the comparative compound R-2 in Example 1.

[Comparative Example 3]
A magenta ink 7 of Comparative Example 3 was prepared in the same manner as in Example 1 except that the specific urethane compound U-2 was replaced with the comparative compound R-3 in Example 1.

  The viscosity, storage stability, ejection stability, and curability of the ink compositions of Examples and Comparative Examples were evaluated by the following methods. Moreover, the following methods evaluated the adhesiveness to a recording medium and the softness | flexibility of hardened | cured material with respect to the cured film of the ink composition of an Example and a comparative example. The evaluation results are shown in Table 2 below.

[Evaluation of ink composition]
(1. Viscosity)
About each ink composition of an Example and a comparative example, the viscosity in 40 degreeC was measured using the E-type viscosity meter (made by Toki Sangyo).
The evaluation index is as follows.
A: Less than 30 mPas B: 30 mPas or more, less than 100 mPas C: 100 mPas or more (a level causing a discharge problem)

(2. Storage stability)
Each of the ink compositions of Examples and Comparative Examples was stored at 75% RH and 60 ° C. for 3 days, and then the ink viscosity at the ejection temperature (room temperature: 25 ° C.) was measured. It was expressed as a viscosity ratio after storage / before storage. If the viscosity does not change and is close to 1.0, the storage stability is good, and if it exceeds 1.5, clogging may occur at the time of injection, which is not preferable.

(3. Discharge stability)
Each of the ink compositions of Examples and Comparative Examples was continuously printed for 60 minutes with an inkjet printer (UJF-605C, manufactured by MIMAKI ENGINEERING CO., LTD.). Evaluation was performed with a three-stage evaluation of 2 and a case where a nozzle missing occurred as 1.

Subsequently, each ink composition was printed on art paper using a piezo-type inkjet head (CA3 head, manufactured by TOSHIBA TEC, printing density 300 dpi, droplet ejection frequency 4 kHz, nozzle number 64), and then a deep UV lamp (USHIO). Manufactured, SP-7) under the condition of energy of 15 mJ / cm ² to obtain a print sample.
Samples that had passed 10 minutes after printing were evaluated for the following evaluation items (curability, adhesion, flexibility).

(4. Curability)
The printed surface was evaluated by a tack-free test. The cured film was touched with a finger, and a five-step evaluation was performed, assuming that there was no stickiness and that the case was markedly sticky.

(5. Adhesion of cured film to recording medium)
After making a cut in a grid pattern on the cured film with a cutter, an adhesive tape was attached to the surface, and then the remaining state of the cured film on the substrate when the adhesive tape was peeled was visually observed.
The case where peeling was not observed was evaluated as 5, the case where partial peeling was observed was evaluated as a three-stage evaluation of 4 to 2, the case where remarkably peeling was observed as 1, and the case where curing was insufficient and could not be evaluated was evaluated as 0.

(6. Flexibility of cured film)
The evaluation of the flexibility was also evaluated by the degree of cracks generated in the cured film after bending the printed sample sheet 10 times. This bending test was performed in a five-step evaluation with 5 points indicating a state where no cracks occurred, and 4 points or more were evaluated as having no practical problems.

As is apparent from Table 2, all of the ink compositions of Examples 1 to 7 have low viscosity, excellent ejection stability, cure with high sensitivity, image portion curability, and adhesion to the recording medium. The film was excellent both in the property and the flexibility of the image (film).
On the other hand, the ink composition of Comparative Example 1 containing a curable compound containing no urethane bond did not have sufficient adhesion to the recording medium.
Further, the ink composition of Comparative Example 2 containing a curable compound having a high urethane bond content showed good adhesion to the recording medium, but the viscosity of the ink composition was high and the ejection stability was high. At the same time, since the flexibility of the cured film was insufficient, the cured film was markedly cracked by bending the sheet, causing a practical problem.
Further, the ink composition of Comparative Example 3 containing a small amount of urethane bonds and containing a curable compound did not have sufficient adhesion to the recording medium.

<Inkjet image recording>
Next, recording on a recording medium was performed using a commercially available inkjet recording apparatus having a piezoelectric inkjet nozzle. The ink supply system was composed of an original tank, supply piping, an ink supply tank immediately before the inkjet head, a filter, and a piezo-type inkjet head, and heat insulation and heating were performed from the ink supply tank to the inkjet head portion. Temperature sensors were provided near the ink supply tank and the nozzles of the ink jet head, respectively, and temperature control was performed so that the nozzle portions were always 70 ° C. ± 2 ° C. The piezo-type inkjet head was driven so that 8 to 30 pl multi-size dots could be ejected at a resolution of 720 × 720 dpi. After landing, UV-A light is condensed to an exposure surface illuminance of 100 mW / cm ² , and the exposure system, main scanning speed, and ejection frequency are adjusted so that irradiation starts 0.1 seconds after ink landing on the recording medium. . Further, the exposure time was variable, and exposure energy was irradiated. For the exposure, a metal halide lamp Vzero085 manufactured by Integration Technology was used.
In the present invention, dpi represents the number of dots per 2.54 cm.

Using each of the prepared color inks (magenta ink 1, yellow ink 1, cyan ink 1, and black ink 1) at an environmental temperature of 25 ° C., black, cyan, magenta, yellow are emitted in the order of ultraviolet rays for each color. Irradiated. The exposure was performed at a total exposure energy of 100 mJ / cm ² uniformly for each color as energy for complete curing so that tackiness disappeared by palpation. As recording media, each color image was recorded on a grained aluminum support, a transparent biaxially stretched polypropylene film having a printability, a soft vinyl chloride sheet, cast coated paper, and commercially available recycled paper. However, in both cases, a high-resolution image without dot bleeding was obtained. Furthermore, even on high-quality paper, the ink was sufficiently cured without causing the ink to turn around, and there was almost no odor due to unreacted monomers. Further, the ink recorded on the film had sufficient flexibility, and the ink was not cracked even when it was bent, and there was no problem in the adhesion test by peeling the cello tape (registered trademark).

Example 8
(Production of support)
Si: 0.06 mass%, Fe: 0.30 mass%, Cu: 0.025 mass%, Mn: 0.001 mass%, Mg: 0.001 mass%, Zn: 0.001 mass%, Ti: It contains 0.03% by mass, and the balance is prepared by using an aluminum alloy of Al and inevitable impurities. After the molten metal treatment and filtration, an ingot having a thickness of 500 mm and a width of 1200 mm is obtained by a DC casting method. Produced. After the surface was shaved with a chamfering machine with an average thickness of 10 mm, it was kept soaked at 550 ° C. for about 5 hours, and when the temperature dropped to 400 ° C., rolling with a thickness of 2.7 mm using a hot rolling mill A board was used. Furthermore, after performing heat processing using a continuous annealing machine at 500 degreeC, it finished by cold rolling to 0.24 mm in thickness, and obtained the aluminum plate of JIS1050 material. The obtained aluminum had an average crystal grain size with a minor axis of 50 μm and a major axis of 300 μm. After making this aluminum plate width 1030mm, it used for the surface treatment shown below and created the aluminum support body.

[surface treatment]
In the surface treatment, the following various treatments (a) to (j) were continuously performed. In addition, after each process and water washing, the liquid draining was performed with the nip roller.

(A) Mechanical surface roughening treatment While supplying a suspension of a polishing agent (pumice) having a specific gravity of 1.12 and water as a polishing slurry liquid to the surface of the aluminum plate, mechanical roughening is performed by a rotating nylon brush. Surface treatment was performed. The average particle size of the abrasive was 30 μm, and the maximum particle size was 100 μm. The material of the nylon brush was 6 · 10 nylon, the hair length was 45 mm, and the hair diameter was 0.3 mm. The nylon brush was planted so as to be dense by making a hole in a stainless steel tube having a diameter of 300 mm. Three rotating brushes were used. The distance between the two support rollers (φ200 mm) at the bottom of the brush was 300 mm. The brush roller was pressed until the load of the drive motor for rotating the brush became 7 kW plus with respect to the load before the brush roller was pressed against the aluminum plate. The rotating direction of the brush was the same as the moving direction of the aluminum plate. The rotation speed of the brush was 200 rpm.

(B) Alkali etching treatment The aluminum plate obtained above was subjected to an etching treatment by spraying using an aqueous solution having a caustic soda concentration of 2.6% by mass, an aluminum ion concentration of 6.5% by mass and a temperature of 70 ° C. / M ^{2 was} dissolved. Then, water washing by spraying was performed.

(C) Desmutting treatment The desmutting treatment was performed by spraying with a 1% by mass aqueous solution of nitric acid at a temperature of 30 ° C. (containing 0.5% by mass of aluminum ions), and then washed with water by spraying. The nitric acid aqueous solution used for the desmut treatment was a waste liquid from a process of performing an electrochemical surface roughening treatment using alternating current in a nitric acid aqueous solution.

(D) Electrochemical roughening treatment An electrochemical roughening treatment was carried out continuously using an alternating voltage of 60 Hz. The electrolytic solution at this time was a 10.5 g / L aqueous solution of nitric acid (containing 5 g / L of aluminum ions and 0.007% by mass of ammonium ions) at a liquid temperature of 50 ° C. AC power supply waveform is 0.8 msec until the current value reaches the peak from zero, duty ratio is 1: 1, and trapezoidal rectangular wave alternating current is used to perform electrochemical surface roughening treatment with the carbon electrode as the counter electrode. went. Ferrite was used for the auxiliary anode.
The current density was 30 A / dm ² at the peak current value, and the amount of electricity was 220 C / dm ² in terms of the total amount of electricity when the aluminum plate was the anode. 5% of the current flowing from the power source was shunted to the auxiliary anode. Then, water washing by spraying was performed.

(E) Alkali etching treatment The aluminum plate was subjected to etching treatment at 32 ° C. using an aqueous solution having a caustic soda concentration of 26 mass% and an aluminum ion concentration of 6.5 mass%, and the aluminum plate was dissolved at 0.50 g / m ² . Removes the smut component mainly composed of aluminum hydroxide that was generated when electrochemical roughening treatment was performed using the alternating current of the previous stage, and also melted the edge part of the generated pit to smooth the edge part. did. Then, water washing by spraying was performed.

(F) Desmut treatment Desmut treatment was performed by spraying with a 15% by weight aqueous solution of nitric acid at a temperature of 30 ° C. (containing 4.5% by weight of aluminum ions), and then washed with water by spraying. The nitric acid aqueous solution used in the desmut was the waste liquid from the step of electrochemical surface roughening using alternating current in the nitric acid aqueous solution.

(G) Electrochemical roughening treatment An electrochemical roughening treatment was carried out continuously using an alternating voltage of 60 Hz. The electrolytic solution at this time was a hydrochloric acid 5.0 g / L aqueous solution (containing 5 g / L of aluminum ions) at a temperature of 35 ° C. The AC power supply waveform has a time until the current value reaches a peak from zero, 0.8 msec, a duty ratio of 1: 1, and a trapezoidal trapezoidal wave alternating current is used to perform an electrochemical surface roughening treatment using a carbon electrode as a counter electrode. went. Ferrite was used for the auxiliary anode.
The current density was 25 A / dm ² at the peak current value, and the amount of electricity was 50 C / dm ² in terms of the total amount of electricity when the aluminum plate was the anode. Then, water washing by spraying was performed.

(H) Alkaline etching treatment An aluminum plate was subjected to an etching treatment by spraying at 32 ° C. using an aqueous solution having a caustic soda concentration of 26 mass% and an aluminum ion concentration of 6.5 mass%, and the aluminum plate was dissolved by 0.12 g / m ² . Removes the smut component mainly composed of aluminum hydroxide that was generated when electrochemical roughening treatment was performed using the alternating current of the previous stage, and also melted the edge part of the generated pit to smooth the edge part. did. Then, water washing by spraying was performed.

(I) Desmutting treatment A desmutting treatment by spraying was performed with a 25% by weight aqueous solution of sulfuric acid at a temperature of 60 ° C. (containing 0.5% by weight of aluminum ions), followed by washing with water by spraying.

(J) Anodizing treatment Anodizing treatment is performed using an anodizing apparatus (first and second electrolysis section length 6 m, first and second feeding section length 3 m, first and second feeding section length 2.4 m each). It was. Sulfuric acid was used as the electrolytic solution supplied to the first and second electrolysis units. All electrolytes had a sulfuric acid concentration of 50 g / L (containing 0.5 mass% of aluminum ions) and a temperature of 20 ° C. Then, water washing by spraying was performed. The final oxide film amount was 2.7 g / m ² .

(Preparation and evaluation of lithographic printing plates)
On the aluminum support produced above, printing was performed with the ink composition of Example 1 (magenta ink 1), and an image was formed and cured in the same manner as in Example 1. This was used as a planographic printing plate to evaluate the image.

a. Evaluation of Image A lithographic printing plate prepared using the ink compositions of Examples and Comparative Examples was applied to a Heidel KOR-D machine, and ink [VALUES-G Beni for Sheetfed (Dainippon Ink Co., Ltd.)] and A dampening solution [Ecolity 2 (manufactured by Fuji Photo Film Co., Ltd.)] was supplied for printing. When the printed material after printing 100 sheets was visually evaluated, it was confirmed that the image had no white spots in the image area and no stain in the non-image area.
b. Evaluation of printing durability When printing is continued as it is, it is possible to obtain 10,000 or more high-quality prints with no white spots in the image area and stains in the non-image area. It was confirmed that.

Claims (6)

  A radiation curable inkjet ink composition comprising a radiation curable compound having a urethane bond content in a range of 1 to 12% by mass.   The radiation according to claim 1, wherein the curable group of the radiation curable compound includes at least one selected from the group consisting of a (meth) acrylate group, a vinyl group, and a ring-opening polymerizable group. A curable inkjet ink composition.   The radiation curable inkjet ink composition according to claim 1 or 2, further comprising a colorant. (A) a step of discharging the radiation-curable ink composition for ink jet according to any one of claims 1 to 3 onto a recording medium; and (b) actinic radiation to the discharged ink composition. Irradiating the ink composition to cure the ink composition;
An inkjet recording method comprising: (A ′) a step of discharging the radiation-curable inkjet ink composition according to any one of claims 1 to 3 onto a hydrophilic support; and (b ′) the discharged ink composition. Irradiating active radiation to the ink composition to cure the ink composition, thereby forming a hydrophobic image formed by curing the ink composition on the hydrophilic support;
A method for producing a lithographic printing plate comprising   A lithographic printing plate produced by the lithographic printing plate production method according to claim 5.