JP5005216B2 - Ink composition - Google Patents

Description

  The present invention is an ink composition having high sensitivity, capable of forming a high-quality image and having good storage stability, particularly a radiation-curable ink composition for ink jet recording, an ink jet recording method using the same, and It relates to printed matter. The present invention also relates to a lithographic printing plate that requires no development processing, has high printing durability, and can form a high-quality image, and a method for producing the same.

  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 system is an inexpensive apparatus and ejects ink only to a required image portion to form an image directly on a recording medium, so that ink can be used efficiently and running cost is low. Furthermore, there is little noise and it is excellent as an image recording method.

As one of the ink jet methods, there is a recording method using an ink for ink jet recording that can be cured by irradiation of radiation.
For example, the ultraviolet curable ink jet system 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. The following Patent Document 1 discloses a specific acrylate compound group for the purpose of providing a relatively highly sensitive ink for ink jet recording even on a support that is usually difficult to directly record by the ink jet recording method. There has been proposed a composition containing a polymerizable compound comprising a coloring agent and a colorant.
If high sensitivity can be achieved, there are many benefits such as high curability, reduction of power consumption of the radiation source, longer life by reducing the load on the radiation source, prevention of low molecular weight substances caused by insufficient curing, etc. With the prior art such as the technique disclosed in Patent Document 1, it is difficult to obtain these benefits. That is, the present situation is that further enhancement of sensitivity remains an important issue.

JP 2003-192943 A

Accordingly, an object of the present invention is an ink composition that is very sensitive to radiation irradiation, can form a high-quality image, and has good storage stability, particularly an ink composition for inkjet recording, and To provide an ink jet recording method and a printed matter using the same.
Another object of the present invention is to provide a method for preparing a lithographic printing plate and a lithographic printing plate that do not require a development treatment, and that can form a high printing durability and high-quality image.

The object is achieved by an ink composition comprising (a) a polymerizable compound represented by the general formula (I), (b) a polymerization initiator, and (c) a colorant.
In a preferred embodiment of the present invention, the ink composition is an ink composition for ink jet recording.
Furthermore, the present invention provides an ink jet recording method comprising the steps of jetting and landing the ink composition on a recording medium, and the step of irradiating the ink composition with radiation to cure the ink composition. .
The present invention also provides a printed material obtained by jetting and landing the ink composition on a recording medium and then irradiating the ink composition to cure the ink composition.
The present invention also provides a lithographic printing plate characterized in that a hydrophobic region is formed by spraying the ink composition onto a hydrophilic support, landing, and then curing the ink by irradiation with radiation. A manufacturing method is provided.
The present invention further includes a lithographic printing plate having a hydrophobic region formed by jetting and landing the ink composition on a hydrophilic support and then curing the ink composition by irradiation with radiation. I will provide a.

Since the polymerizable compound represented by the formula (I) used as the polymerizable compound is not high in thermal polymerization without a polymerization initiator as compared with an acrylic compound, it is excellent in storage stability.
Therefore, according to the present invention, an ink composition for inkjet recording that is highly sensitive to radiation irradiation, can form a high-quality image, has good storage stability, and development processing is unnecessary. A method for producing a lithographic printing plate capable of forming a high printing durability and high-quality image is provided.

According to the present invention, it is possible to obtain an ink composition that has high sensitivity, has good adhesion to a recording medium such as a support or paper, and can form a high-quality image.
The ink composition containing the polymerizable compound represented by the specific formula (I) of the present invention has remarkably high curing sensitivity as compared with an ink composition containing an acrylic compound as described in Patent Document 1. The reason for this is that the polymerizable compound represented by formula (I) has higher polymerizability than acrylic compounds and is less susceptible to oxygen polymerization inhibition, and therefore has high curability due to ultraviolet rays and electron beam irradiation. In particular, it is considered that the curing characteristics become remarkable in ultraviolet curing that is cured in the air. In addition, the polymerizable compound represented by the formula (I) of the present invention has a bulky substituent such as a tertiary alkyl group containing a ring structure in the molecule, so that the polymerization termination rate is reduced. It is thought to be the cause of improvement.
In the lithographic printing plate using the ink composition of the present invention, the curing strength of the image area is increased and the adhesion between the image area and the support is higher than that of the conventional one. The reason is that the self-aggregating property of the polymerizable compound represented by the formula (I) works after curing, the curing strength is increased, and the polymerizable compound represented by the formula (I) is chelated with the support surface atoms. It is presumed that high chemical interaction occurs and adhesion with the support is enhanced.

(1) Ink composition The ink composition of the present invention contains a polymerizable compound represented by formula (I), a polymerization initiator, and a colorant.
The ink composition of the present invention is preferably an ink composition that can be cured by irradiation with radiation. The “radiation” broadly means α rays, γ rays, X rays, ultraviolet rays, visible rays, electron rays, etc., among which ultraviolet rays and electron beams are preferable, and ultraviolet rays are more preferable.

式中、Ｒ^a、Ｒ^bは各々独立して、水素原子、ハロゲン原子、シアノ基、炭化水素基、置換オキシ基、置換チオ基、置換アミノ基、置換カルボニル基、又はカルボキシラート基を表し、Ｒは環構造を含む、炭素数が７以上の２級もしくは３級の炭化水素基を表す。ＹはＣＮまたはＣＯＸを表し、Ｘはヘテロ原子を介してカルボニル基に結合している基また
はハロゲン原子を表す。また、ＲとＹ、Ｒ^aとＲ^b、またはＲとＲ^aあるいはＲ^bとが互いに結合して環状構造を形成してもよい。 (A) [Polymerizable compound]
One of the characteristics of the ink composition of the present invention is that it contains a polymerizable compound represented by the following formula (I) (hereinafter also referred to as α-heteromethacrylic compound) as the polymerizable compound.

In the formula, R ^a and R ^b each independently represent a hydrogen atom, a halogen atom, a cyano group, a hydrocarbon group, a substituted oxy group, a substituted thio group, a substituted amino group, a substituted carbonyl group, or a carboxylate group, R represents a secondary or tertiary hydrocarbon group containing a ring structure and having 7 or more carbon atoms. Y represents CN or COX, and X represents a group or halogen atom bonded to the carbonyl group through a hetero atom. R and Y, R ^a and R ^b , or R and R ^a or R ^b may be bonded to each other to form a cyclic structure.

The structure represented by the formula (I) may be a monovalent or divalent or higher substituent, and R ^a , R ^b , R and Y in the formula (I) all represent end groups, It may be one compound by itself. When the structure represented by formula (I) is a monovalent or divalent or higher substituent, at least one of R ^a , R ^b , R, and Y in formula (I) is one or more. Have a bond. Further, R and Y may be a linking group having n connectable sites, and n groups of the formula (I) may be connected to the terminal (n is an integer of 2 or more) ( Multimers).

  Further, at least one of R and Y may be bonded to the polymer chain. That is, the polymer chain may take a form in which the structure represented by the formula (I) is present in the side chain. Here, a linear organic high molecular polymer is mentioned as a polymer chain. Specific examples include vinyl polymers such as polyurethane, novolac, and polyvinyl alcohol, polyhydroxystyrene, polystyrene, poly (meth) acrylic acid ester, poly (meth) acrylic acid amide, and polyacetal. These polymers may be homopolymers or copolymers (copolymers).

  In the formula (I), R represents a secondary or tertiary hydrocarbon group containing a ring structure and having 7 or more carbon atoms, Y represents CN or COX, and X is bonded to the carbonyl group via a hetero atom. Or a halogen atom, which may be a terminal group or a linking group, and other substituents (wherein the substituents include the structure of formula (I), (Including polymer chains).

The compound represented by the above formula (I) is preferably a polymerizable compound represented by the following formulas (II) to (IV) and having an α-heteromethacrylic structure and at least one polymerizable group.

In formula (II), R ^a1 and R ^b1 each independently represent a hydrogen atom, a halogen atom, a cyano group, or a monovalent hydrocarbon group, a substituted oxy group, a substituted thio group, a substituted amino group, a substituted carbonyl group, Or a carboxylate group, R ¹ represents a secondary or tertiary monovalent hydrocarbon group containing a ring structure and having 7 or more carbon atoms, Y ¹ represents CN or COX ¹ , and X ¹ represents hetero A monovalent group or a halogen atom which is bonded to a carbonyl group through an atom. R ¹ and Y ¹ , R ^a1 and R ^b1 , or R ¹ and R ^a1 or R ^b1 may be bonded to each other to form a cyclic structure.

In the formula (III), m represents an integer of 2 to 6, and R ^a2 and R ^b2 each independently represent a hydrogen atom, a halogen atom, a cyano group, or a monovalent hydrocarbon group, a substituted oxy group, a substituted thio group. Represents a group, a substituted amino group, a substituted carbonyl group, or a carboxylate group, R ² represents a secondary or tertiary monovalent or divalent hydrocarbon group having 7 or more carbon atoms, including a ring structure; ² represents CN or COX ² ; X ² represents a monovalent or divalent group or a halogen atom bonded to the carbonyl group via a hetero atom; R ^d represents a divalent to hexavalent hydrocarbon group; To express. However, at least one of R ² and Y ² is a divalent group. A dotted line represents a bond when there is a bond between R ² or Y ² and R ^d, and the number of bonds is 2 to 6 in the entire structure of formula (III). Further, R ² and Y ² , R ^a2 and R ^b2 , or R ² and R ^a2 or R ^b2 may be bonded to each other to form a cyclic structure.

  A more preferable compound represented by the formula (III) is a compound represented by the following formula (III-1) or (III-2).

式(III-1)または(III-2)において、ｍは２〜６の整数を表し、Ｒ^a2、Ｒ^b2、Ｒ²、Ｙ²、及びＲ^dの定義は式(III)におけるものと同義である。
式（III-1）、(III-2)におけるＲ^dの好ましい例としては、

In the formula (III-1) or (III-2), m represents an integer of 2 to 6, and the definitions of R ^a2 , R ^b2 , R ² , Y ² , and R ^d are the same as those in the formula (III). It is.
Preferred examples of R ^d in formulas (III-1) and (III-2) include

が挙げられる。

Is mentioned.

In the formula (IV), B represents a repeating unit of the polymer chain. In the formula A, R ^a3 and R ^b3 each independently represent a hydrogen atom, a halogen atom, a cyano group, a monovalent hydrocarbon group, a substituted oxy Represents a group, a substituted thio group, a substituted amino group, a substituted carbonyl group, or a carboxylate group, and R ³ includes a ring structure, and a monovalent or divalent hydrocarbon group having a secondary or tertiary carbon number of 7 or more. Y ³ represents CN or COX ³ , and X ³ represents a monovalent or divalent group or a halogen atom bonded to the carbonyl group via a hetero atom. However, at least one of R ³ and Y ³ is a divalent group. The dotted line represents a bond present depending on the valence of R ³ and Y ^3. R ³ and Y ³ , R ^a3 and R ^b3 , or R ³ and R ^a3 or R ^b3 may be bonded to each other to form a cyclic structure.

  In the general formula (IV), B represents a repeating unit of a polymer chain. Examples of the polymer chain include linear organic high molecular polymers. Specific examples include vinyl polymers such as polyurethane, novolac, and polyvinyl alcohol, polyhydroxystyrene, polystyrene, poly (meth) acrylic acid ester, poly (meth) acrylic acid amide, and polyacetal. These polymers may be homopolymers or copolymers (copolymers).

Y, Y ¹ , Y ² and Y ³ in the above general formulas (I) to (IV) represent CN, COX ¹ , COX ² or COX ³ , preferably CN, X ¹ , X ² , X ^{In this case, 3} is a monovalent or divalent group bonded to a carbonyl group via a hetero atom. The “heteroatom” is preferably a nonmetallic atom, and specifically includes an oxygen atom, a sulfur atom, and a nitrogen atom, and more preferably an oxygen atom and a nitrogen atom. The “monovalent group bonded to the carbonyl group through a heteroatom” is preferably a hydroxyl group, a heterocyclic group (but linked by a heteroatom), a substituted oxy group, a mercapto group, a substituted thio group An amino group and a substituted amino group, more preferably a substituted oxy group and a substituted amino group. A “bivalent or more group bonded to a carbonyl group through a heteroatom” is a group derived from the monovalent group by replacing a hydrogen atom or other atom or group with a bond.

  The heterocyclic group, substituted oxy group, substituted thio group, substituted amino group, substituted carbonyl group, and carboxylate group in the definition of each group of the general formulas (I) to (IV) are used as follows.

In the present specification, the heterocyclic group means a monovalent group obtained by removing one hydrogen on the heterocyclic ring, and further removing one hydrogen from the monovalent group so that the substituent in the above substituted alkyl group is bonded. A monovalent group (substituted heterocyclic group). Examples of preferred heterocycles include the groups shown below.

As the substituted oxy group in the present specification, a group represented by R ⁵ O—, wherein R ⁵ is a monovalent nonmetallic atomic group excluding hydrogen can be used. Preferred examples of the substituted oxy group include an alkoxy group, an aryloxy group, an acyloxy group, and an arylsulfoxy group. Specific examples of preferred substituted oxy groups include methoxy, ethoxy, propyloxy, isopropyloxy, butyloxy, phenoxy, tolyloxy, xylyloxy, mesityloxy, cumenyloxy, methoxyphenyloxy, ethoxyphenyloxy Group, chlorophenyloxy group, bromophenyloxy group, acetyloxy group, benzoyloxy group, naphthyloxy group, phenylsulfonyloxy group, and the like.

As the substituted thio group in the present specification, those represented by R ⁷ S—, wherein R ⁷ is a monovalent nonmetallic atomic group excluding hydrogen can be used. Examples of preferred substituted thio groups include alkylthio groups and arylthio groups. Specific examples of preferable substituted thio groups include a methylthio group, an ethylthio group, a phenylthio group, an ethoxyethylthio group, a carboxyethylthio group, and a methoxycarbonylthio group.

The substituted amino group in the present specification is represented by R ⁸ NH—, (R ⁹ ) (R ¹⁰ ) N—, and R ⁸ , R ⁹ , R ¹⁰ are monovalent nonmetallic atomic groups excluding hydrogen. Can be used. Preferable examples of the substituted amino group include N-alkylamino group, N, N-dialkylamino group, N-arylamino group, acylamino group and the like. Specific examples of preferred substituted amino groups include methylamino group, ethylamino group, diethylamino group, morpholino group, piperidino group, pyrrolidino group, phenylamino group, benzoylamino group, acetylamino group and the like.

In the present specification, a substituted carbonyl group represented by R ¹¹ —CO—, wherein R ¹¹ is a monovalent nonmetallic atomic group can be used. Preferred examples of the substituted carbonyl group include formyl group, acyl group, carboxyl group, alkoxycarbonyl group, aryloxycarbonyl group, carbamoyl group, N-alkylcarbamoyl group, N, N-dialkylcarbamoyl group, N-arylcarbamoyl group, Is mentioned. Specific examples of preferred substituted carbonyl groups include formyl group, acetyl group, benzoyl group, carboxyl group, methoxycarbonyl group, allyloxycarbonyl group, N-methylcarbamoyl group, N-phenylcarbamoyl group, N, N-diethylcarbamoyl group. And a morpholinocarbonyl group.

The carboxylate group (—CO ₂ ⁻ ) in the present specification means a conjugate base anion group of a carboxyl group (CO ₂ H), and is usually preferably used together with a counter cation. Examples of such counter cations include those generally known, that is, various oniums (ammonium compounds, sulfonium compounds, phosphonium compounds, iodonium compounds, azinium compounds, etc.), and metal ions (Na ⁺ , K ⁺ , Ca). ²⁺ , Zn ^2+, etc.).

  In the present specification, examples of the “monovalent hydrocarbon group” include alkyl groups, substituted alkyl groups, aryl groups, substituted aryl groups, alkenyl groups, substituted alkenyl groups, alkynyl groups, and substituted alkynyl groups. In the present specification, a “divalent hydrocarbon group” or “bivalent or higher hydrocarbon group” is a group derived from a monovalent hydrocarbon group by replacing a hydrogen atom or other atom or group with a bond. is there.

Examples of the alkyl group include linear, branched, or cyclic alkyl groups having 1 to 20 carbon atoms. Specific examples thereof include a methyl group, an ethyl group, a propyl group, a butyl group, Pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, hexadecyl, octadecyl, eicosyl, isopropyl, isobutyl, s-butyl, t-butyl Groups, isopentyl group, neopentyl group, 1-methylbutyl group, isohexyl group, 2-ethylhexyl group, 2-methylhexyl group, cyclohexyl group, cyclopentyl group and 2-norbornyl group.
Among these, linear alkyl groups having 1 to 12 carbon atoms, branched alkyl groups having 3 to 12 carbon atoms, and cyclic alkyl groups having 5 to 10 carbon atoms are more preferable.

  Examples of the aryl group include those in which 1 to 3 benzene rings form a condensed ring, and those in which a benzene ring and a 5-membered unsaturated ring form a condensed ring. Specific examples include a phenyl group, A naphthyl group, an anthryl group, a phenanthryl group, an indenyl group, an acenaphthenyl group, and a fluorenyl group can be exemplified, and among these, a phenyl group and a naphthyl group are more preferable.

Examples of the alkenyl group include vinyl, allyl, propenyl, isopropenyl, 2-methyl-1-propenyl, 2-methylallyl, 2-buteinyl and the like.
Examples of the alkynyl group include ethynyl, 2-propynyl, 2-butynyl and the like.

  Examples of the substituent in the substituted alkyl group, substituted aryl group, substituted alkenyl group and substituted alkynyl group include a halogen atom (—F, —B, —Cl, —I), a hydroxyl group, an alkyl group, an aryl group, an alkoxy group, and aryloxy. Group, amino group, cyano group, nitro group and the like.

  Specific examples of the monovalent hydrocarbon group having a secondary or tertiary carbon number of 7 or more and including a ring structure in the general formulas (I) to (IV) include a cyclohexyl group substituted with an alkyl group. , Adamantyl group, noradamantyl group, decalin residue, tricyclodecanyl group, tetracyclododecanyl group, norbornyl group, cedrol group, cycloheptyl group, cyclooctyl group, cyclodecanyl group, cyclododecanyl group . More preferred are a cyclohexyl group, adamantyl group, norbornyl group, cycloheptyl group, cyclooctyl group, cyclodecanyl group, and cyclododecanyl group substituted with an alkyl group. In the general formulas (I) to (IV), the secondary or tertiary hydrocarbon group having a secondary or tertiary carbon number of 7 or more and including a ring structure is a hydrogen atom or other atom or group from the monovalent group. Is a group derived by substituting for a bond.

  The monovalent hydrocarbon group having a secondary or tertiary carbon number of 7 or more may further have a substituent. The substituent is preferably an alkyl group, and the alkyl group is more preferably a lower alkyl group such as a methyl group, an ethyl group, a propyl group, an isopropyl group, or a t-butyl group.

Next, examples of a cyclic structure formed by combining R and Y, R ^a and R ^b , or R and R ^a or R ^b are shown. Examples of the aliphatic ring formed by combining R and Y, R ^a and R ^b , or R and R ^a or R ^b with each other include 5-membered, 6-membered, 7-membered and 8-membered aliphatic A ring can be mentioned, More preferably, a 5-membered ring and a 6-membered aliphatic ring can be mentioned. These may further have a substituent on the carbon atoms constituting them, and a part of the ring carbon is substituted with a hetero atom (oxygen atom, sulfur atom, nitrogen atom, etc.). Also good. Furthermore, a part of the aliphatic ring may form a part of the aromatic ring.

In the present invention, specific examples of the compound having the structure represented by the general formulas (I) to (IV) are shown below, but the present invention is not limited thereto.

  The α-heteromethacrylic compound used in the present invention is used in a proportion of 3 to 95% by mass, preferably 5 to 70% by mass in the ink composition.

In addition, in a polymeric compound, polymeric compounds other than the said alpha-heteromethacrylic compound can also be used, for example, a monoacrylate compound, a polyfunctional acrylate monomer, a polyfunctional acrylate oligomer, etc. can be used together. These other polymerizable compounds include isomyristyl acrylate, isostearyl acrylate, lauryl acrylate, isoamyl acrylate, stearyl acrylate, ethoxy-diethylene glycol acrylate, methoxy-polyethylene glycol acrylate, methoxydipropylene glycol acrylate, and 2 (2-ethoxyethoxy). Ethyl acrylate, butoxyethyl acrylate, isobornyl acrylate, phenoxy-polyethylene glycol acrylate, 2-ethylhexyl-diglycol acrylate, 2-acryloyloxyethylphthalic acid, 2-acryloyloxyethyl-2-hydroxyethylphthalic acid, ethoxylation Phenyl acrylate, 2-acryloyloxyethyl succinic acid, nonylphenol Tylene oxide adduct acrylate, 2-acryloyloxyethyl hexahydrophthalic acid, lactone-modified towable acrylate, polytetramethylene glycol diacrylate, tetraethylene glycol diacrylate, hydroxypivalate neopentyl glycol diacrylate, dimethylol tricyclo Decane diacrylate, dimethylol dicyclopentane diacrylate, propylene glycol diglycidyl ether acrylic acid adduct, bisphenol A diglycidyl ether (meth) acrylic acid adduct, bisphenol A propylene oxide adduct diacrylate, bisphenol A ethylene oxide Modified bisphenol A diacrylate such as adduct diacrylate, glycerin propoxytriacrylate, Intererythritol tetraacrylate, pentaerythritol ethoxytetraacrylate, dipentaerythritol hexaacrylate, caprolactone modified dipentaerythritol hexaacrylate, ethylene oxide modified trimethylolpropane triacrylate, caprolactone modified trimethylolpropane triacrylate, ditrimethylolpropane tetraacrylate, amine modified Examples thereof include polyester tetraacrylate, pentaerythritol triacrylate tolylene diisocyanate urethane prepolymer, and pentaerythritol triacrylate hexamethylene diisocyanate urethane prepolymer. These may be used in combination with a polymerizable monomer or oligomer having a molecular weight of 400 or more (for example, an acrylate monomer or acrylate oligomer having a molecular weight of 400 or more). Among other polymerizable compounds, isomyristyl acrylate, isostearyl acrylate, lauryl acrylate, isoamyl acrylate, stearyl acrylate, ethoxy-diethylene glycol acrylate, methoxy-polyethylene glycol acrylate, methoxydipropylene glycol acrylate, 2 (2-ethoxyethoxy) At least one selected from ethyl acrylate and lactone-modified flexible acrylate is preferred.
The content of other polymerizable compounds that can be used in combination with the α-heteromethacrylic compound of the present invention is preferably 5 to 85% by mass, more preferably 5 to 70% by mass of the entire polymerizable compound.

(B) [Polymerization initiator]
Examples of the polymerization initiator in the present invention include known radical polymerization photopolymerization initiators used in radiation curable ink compositions. Other photopolymerization initiators that can be used in combination with the present invention are compounds that generate radicals through chemical action through the action of light or interaction with the electronically excited state of a sensitizing dye. Specific photopolymerization initiators known among those skilled in the art can be used without limitation. Specifically, for example, Bruce M. Monroe et al., Chemical Review, 93, 435 (1993), RSD Davidson, Journal of Photochemistry and biology A: Chemistry, 73, 81 (1993), JP Faussier "Photoinitiated Polymerization" -Theory and Applications ": Rapra Review vol. 9, Report, Rapra Technology (1998) and M. Tsunooka et al., Prog. Polym. Sci., 21, 1 (1996). Further, many compounds used for chemically amplified photoresists are described in (Organic Electronics Materials Research Group, “Organic Materials for Imaging”, Bunshin Publishing (1993), pages 187 to 192). Furthermore, FDSaeva, Topics in Current Chemistry, 156, 59 (1990), GG Maslak, Topics in Current Chemistry, 168, 1 (1993), HB Shuster et al, J. Am. Chem. Soc., 112, 6329 ( 1990), IDFEaton et al, J. Am. Chem. Soc, 102, 3298 (1980) and the like, through the interaction with the electronically excited state of the sensitizing dye, oxidatively or reductively. A group of compounds that cause bond cleavage is also known.

  Preferred photopolymerization initiators include (a) aromatic ketones, (b) aromatic onium salt compounds, (c) organic peroxides, (d) hexaarylbiimidazole compounds, (e) ketoxime ester compounds, (F) a borate compound, (g) an azinium compound, (h) a metallocene compound, (i) an active ester compound, (j) a compound having a carbon halogen bond, and the like.

  (A) Preferable examples of aromatic ketones include compounds having a benzophenone skeleton or a thioxanthone skeleton described in “RADIATION CURING IN POLYMER SCIENCE AND TECHNOLOGY” J. P. FOUASSIER J. F. RABEK (1993), p77-117. More preferable examples of (a) aromatic ketones include α-thiobenzophenone compounds described in JP-B-47-6416, benzoin ether compounds described in JP-B-47-3981, and JP-B-47-22326. Α-substituted benzoin compounds, benzoin derivatives described in JP-B-47-23664, aroylphosphonic acid esters described in JP-A-57-30704, dialkoxybenzophenones described in JP-B-60-26483, Benzoin ethers described in JP-A-60-26403, JP-A-62-81345, JP-B-1-34242, US Pat. No. 4,318,791, and α-aminobenzophenones described in European Patent 0284561A1, P-di (dimethyla) described in JP-A-2-211452 Nobenzoyl) benzene, thio-substituted aromatic ketone described in JP-A-61-194062, acylphosphine sulfide described in JP-B-2-9597, acylphosphine described in JP-B-2-9596, JP-B-63- Examples thereof include thioxanthones described in Japanese Patent No. 61950, and coumarins described in Japanese Patent Publication No. 59-42864.

  (B) As aromatic onium salt compounds, elements of Groups 15, 16 and 17 of the periodic table, specifically N, P, As, Sb, Bi, O, S, Se, Te, or I fragrances Group onium salts are included. For example, iodonium salts described in European Patent No. 104143, US Pat. No. 4,837,124, Japanese Patent Laid-Open No. 2-150848, Japanese Patent Laid-Open No. 2-96514, European Patent Nos. 370693, 233567, and 297443 are disclosed. The diazonium salts described in the specifications of U.S. Pat. Nos. 2,974,279, 279210, and 422570, U.S. Pat. Nos. 3,902,144, 4,933,377, 4,760013, 4,734,444, and 2,833,827. Benzenediazonium which may have a substituent), diazonium salt resins (formaldehyde resin of diazodiphenylamine, etc.), N-alkoxypyridinium salts, etc. (for example, US Pat. No. 4,743,528, JP-A-63) -138345, JP-A-63 142345, JP-A-63-142346, and JP-B-46-42363, specifically 1-methoxy-4-phenylpyridinium tetrafluoroborate, etc. The compounds described in JP-A 52-147277, 52-14278, and 52-14279 are preferably used. Generates radicals and acids as active species.

  (C) The organic peroxide includes almost all organic compounds having one or more oxygen-oxygen bonds in the molecule. Examples thereof include 3,3′4,4′-tetra- (t -Butylperoxycarbonyl) benzophenone, 3,3'4,4'-tetra- (t-amylperoxycarbonyl) benzophenone, 3,3'4,4'-tetra- (t-hexylperoxycarbonyl) benzophenone, 3,3′4,4′-tetra- (t-octylperoxycarbonyl) benzophenone, 3,3′4,4′-tetra- (cumylperoxycarbonyl) benzophenone, 3,3′4,4′-tetra Peroxide esters such as-(p-isopropylcumylperoxycarbonyl) benzophenone and di-t-butyldiperoxyisophthalate are preferred.

  (D) Examples of hexaarylbiimidazole compounds include lophine dimers described in JP-B Nos. 45-37377 and 44-86516, such as 2,2′-bis (o-chlorophenyl) -4,4 ′, 5,5′-tetraphenylbiimidazole, 2,2′-bis (o-bromophenyl) -4,4 ′, 5,5′tetraphenylbiimidazole, 2,2′-bis (o, p-dichlorophenyl) -4,4 ', 5,5'-tetraphenylbiimidazole, 2,2'-bis (o-chlorophenyl) -4,4', 5,5'-tetra (m-methoxyphenyl) biimidazole, 2, 2′-bis (o, o′-dichlorophenyl) -4,4 ′, 5,5′-tetraphenylbiimidazole, 2,2′-bis (o-nitrophenyl) -4,4 ′, 5,5 ′ − Traphenylbiimidazole, 2,2′-bis (o-methylphenyl) -4,4 ′, 5,5′-tetraphenylbiimidazole, 2,2′-bis (o-trifluorophenyl) -4,4 Examples include ', 5,5'-tetraphenylbiimidazole.

  (E) Examples of ketoxime ester compounds include 3-benzoyloxyiminobutan-2-one, 3-acetoxyiminobutan-2-one, 3-propionyloxyiminobutan-2-one, and 2-acetoxyiminopentane-3. -One, 2-acetoxyimino-1-phenylpropan-1-one, 2-benzoyloxyimino-1-phenylpropan-1-one, 3-p-toluenesulfonyloxyiminotan-2-one, 2-ethoxy And carbonyloxyimino-1-phenylpropan-1-one.

  (F) Examples of borate compounds include those described in the specifications of US Pat. Nos. 3,567,453, 4,343,891, European Patents 109,772, and 109,773. Can be mentioned.

  (G) Examples of azinium salt compounds include JP-A 63-138345, JP-A 63-142345, JP-A 63-142346, JP-A 63-143537, and JP-B 46-42363. The compound group which has NO bond of each gazette description can be mentioned.

  (H) Examples of metallocene compounds include titanocenes described in JP-A-59-152396, JP-A-61-151197, JP-A-63-41484, JP-A-2-249, and JP-A-2-4705. Examples thereof include iron-arene complexes described in JP-A-1-304453 and JP-A-1-152109.

  Specific examples of the titanocene compound include di-cyclopentadienyl-Ti-di-chloride, di-cyclopentadienyl-Ti-bis-phenyl, and di-cyclopentadienyl-Ti-bis-2,3. 4,5,6-pentafluorophen-1-yl, di-cyclopentadienyl-Ti-bis-2,3,5,6-tetrafluorophen-1-yl, di-cyclopentadienyl-Ti- Bis-2,4,6-trifluorophen-1-yl, di-cyclopentadienyl-Ti-2,6-difluorophen-1-yl, di-cyclopentadienyl-Ti-bis-2,4 -Difluorophen-1-yl, di-methylcyclopentadienyl-Ti-bis-2,3,4,5,6-pentafluorophen-1-yl, di-methylcyclopentadienyl-Ti- -2,3,5,6-tetrafluorophen-1-yl, di-methylcyclopentadienyl-Ti-bis-2,4-difluorophen-1-yl, bis (cyclopentadienyl) -bis (2,6-difluoro-3- (pyridin-1-yl) phenyl) titanium, bis (cyclopentadienyl) bis [2,6-difluoro-3- (methylsulfonamido) phenyl] titanium, bis (cyclopenta And dienyl) bis [2,6-difluoro-3- (N-butylbialoyl-amino) phenyl] titanium.

  (I) Examples of active ester compounds include the specifications of European Patent Nos. 0290750, 046083, 156153, 271851, and 0388343, U.S. Pat. Nos. 3,901,710, and 4,181,531. Nitrobenzol ester compounds described in JP-A-60-198538 and JP-A-53-133022, European Patents 0199672, 84515, 199672, 0441115, and 0101122. No. 4,618,564, U.S. Pat. No. 4,371,605, and U.S. Pat. No. 4,431,774, and JP-A 64-18143, JP-A-2-245756, and JP-A-4-365048. Iminosulfonate compound, Japanese Examined Patent Publication No. 62-6223, Japanese Examined Publication No. 63 No. 14340, and compounds, and the like described in the JP-A No. 59-174831.

  (J) Preferable examples of the compound having a carbon halogen bond include, for example, compounds described in Wakabayashi et al., Bull. Chem. Soc. Japan, 42, 2924 (1969), compounds described in British Patent No. 1388492, Examples thereof include compounds described in Japanese Utility Model Publication No. 53-133428, compounds described in German Patent No. 3337024, and the like.

Further, compounds described in J. Org. Chem., 29, 1527 (1964) by FC Schaefer et al., Compounds described in JP-A-62-258241, compounds described in JP-A-5-281728, and the like can be mentioned. it can. A compound as described in German Patent No. 2641100, a compound described in German Patent No. 3333450, a compound group described in German Patent No. 3021590, or a compound group described in German Patent No. 3021599, etc. Can be mentioned.
Preferable specific examples of the compounds represented by the above (a) to (j) include those shown below.

In the structural formula of the above compound, Ar represents a phenyl group, a paramethoxyphenyl group, or a dimethylaminophenyl group.

When the other polymerization initiators described above are used in combination, the content thereof is preferably 0.1 to 20% by mass with respect to the total solid content of the ink composition.
As the polymerization initiator, various known compounds can be used, but it is preferable to select one that is soluble in the polymerizable compound according to the present invention. Specific examples of the polymerization initiator include xanthone or Examples thereof include thioxanthone polymerization initiators, benzophenone polymerization initiators, quinone synthesis initiators, and phosphine oxide polymerization initiators.

  Moreover, it is preferable to add 200-20000 ppm of a polymerization inhibitor from a viewpoint of improving storability. When the ink composition of the present invention is used as an ink composition for ink jet recording, it is preferably heated and reduced in viscosity in the range of 40 to 80 ° C., and polymerization is prohibited to prevent head clogging due to thermal polymerization. It is preferable to add an agent. Examples of the polymerization inhibitor include hydroquinone, benzoquinone, p-methoxyphenol, TEMPO, TEMPOL, and cuperon Al.

(C) [Colorant]
The ink composition of the present invention contains a colorant. Although there is no restriction | limiting in particular as a coloring agent which can be used in this invention, Although the pigment excellent in the weather resistance is preferable, Arbitrary well-known coloring agents, such as a soluble dye and an oil-based dye, can be used.

  The pigment preferably used in the present invention will be described. The ink composition of the present invention does not necessarily have a high color developability (color density per added density), and in addition, it is difficult to produce a homogeneous fine particle dispersion. Therefore, ink jet inks that have not been put into practical use can be used. Although not particularly limited, for example, organic or inorganic pigments having the following numbers described in the color index can be used in the present invention.

  Examples of red or magenta pigments include Pigment Red 3, 5, 19, 22, 31, 38, 43, 48: 1, 48: 2, 48: 3, 48: 4, 48: 5, 49: 1, and 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, 16, 1 -1, 22, 27, 28, 29, 36, 60, Pigment Green 7, 26, 36, 50 as a green pigment, Pigment Yellow 1, 3, 12, 13, 14, 17, 34 as a yellow pigment , 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.

  For the dispersion of the pigment, 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 pigment. 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. These dispersants and dispersion aids are preferably added in an amount of 1 to 50 parts by mass with respect to 100 parts by mass of the pigment. The dispersion medium is a solvent or a polymerizable compound according to the present invention. In the radiation curable ink used in the present invention, it is preferable that the dispersion medium be solvent-free because it reacts and cures immediately after ink landing. When the solvent remains in the cured image, there arises a problem of deterioration of solvent resistance and VOC (Volatile Organic Compound) of the remaining solvent. Therefore, it is preferable in view of dispersibility that the dispersion medium is not a solvent, but a polymerizable compound, and a monomer having the lowest viscosity among them is selected.

  The average particle size of the pigment particles is preferably 0.08 to 0.5 μm, and the maximum particle size is 0.3 to 10 μm, preferably 0.3 to 3 μm. Set selection, dispersion conditions, and filtration conditions. By controlling the particle size, clogging of the head nozzle can be suppressed, and ink storage stability, ink transparency, and curing sensitivity can be maintained. The colorant is preferably added in an amount of 1 to 10% by mass, more preferably 2 to 8% by mass, based on the total ink mass.

  In addition to the above-described explanation, other components can be added to the ink composition of the present invention as necessary.

(D) [Other components]
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. In addition, the ink composition of the present invention is preferably ejected by heating and lowering the viscosity in the range of 40 to 80 ° C. In order to prevent clogging of the head due to thermal polymerization, it is preferable to add a polymerization inhibitor. The polymerization inhibitor is preferably added in an amount of 200 to 20000 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.

The ink composition of the present invention preferably contains no solvent from the viewpoint of solvent resistance and VOC. However, in order to improve the adhesion to the recording medium, a very small amount of organic matter is used as long as the above problem does not occur. It is also effective to add a solvent.
Examples of the solvent include ketone solvents such as acetone, methyl ethyl ketone, and diethyl ketone, alcohol solvents such as methanol, ethanol, 2-propanol, 1-propanol, 1-butanol, and tert-butanol, and chlorine such as chloroform and methylene chloride. Solvents, aromatic solvents such as benzene and toluene, ester solvents such as ethyl acetate, butyl acetate and isopropyl acetate, ether solvents such as diethyl ether, tetrahydrofuran and dioxane, glycols such as ethylene glycol monomethyl ether and ethylene glycol dimethyl ether And ether solvents.
In this case, the amount of the solvent used is preferably from 0.1 to 5% by mass, more preferably from 0.1 to 3% by mass, based on the entire ink composition.
In order to further increase the curing sensitivity, a radical polymerizable compound and a radical polymerization initiator may be used in combination, that is, a radical / cation hybrid type curable ink may be used.

  In addition to this, 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]
When the ink composition is used as an ink composition for ink jet recording, the viscosity is, for example, 7 to 7 at a temperature at the time of ejection (for example, 40 to 80 ° C., preferably 25 to 30 ° C.) in consideration of ejection properties. 30 mPa · s, preferably 7 to 20 mPa · s. For example, the viscosity of the ink composition of the present invention at room temperature (25 to 30 ° C.) is 35 to 500 mPa · s, preferably 35 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, ink bleeding at the time of ink droplet landing can be suppressed, and as a result, the image quality is improved.

  The surface tension of the ink composition of the present invention is, for example, 20 to 30 mN / m, 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.

(2) Inkjet recording method and apparatus An inkjet recording method and an inkjet recording apparatus that can be suitably employed in the present invention will be described below.
(2-1) Inkjet recording method The present invention is to form an image by ejecting the ink composition onto a recording medium, irradiating the ink landed on the support with radiation, and curing the ink composition. Provide a way to do it. That is, the present invention
(a) applying the ink composition onto a recording medium;
(b) The ink composition has a peak wavelength of 200 to 600 nm, preferably 300 to 450 nm, more preferably 350 to 420 nm, and is 2000 mJ / cm ² or less, preferably 10 to 2000 mJ / cm ² . more preferably, more preferably 20~1000mJ / cm ^2, a step of curing the ink composition by irradiation at an output of 50 to 800 mJ / cm ^2; and by (c) cured ink composition onto a recording medium A process of forming an image;
Relates to a method comprising:

  The recording medium is not particularly limited, and papers such as ordinary non-coated paper and coated paper, various non-absorbing resin materials used for so-called soft packaging, or resin films obtained by forming them into a film shape are used. Examples of the various plastic films include PET film, OPS film, OPP film, ONy film, PVC film, PE film, and TAC film. In addition, examples of the plastic that can be used as a recording medium material include polycarbonate, acrylic resin, ABS, polyacetal, PVA, and rubbers. Metals and glasses can also be used as the recording medium.

  In the ink composition of the present invention, when a material with low thermal shrinkage at the time of curing is selected, the adhesive property between the cured ink composition and the recording medium is excellent. Films that tend to curl and deform, such as heat-shrinkable PET film, OPS film, OPP film, ONy film, PVC film, etc., have the advantage that a high-definition image can be formed.

[Example of a method for ejecting and landing an ink composition]
As a method for ejecting and landing an ink composition on a recording medium, an ink jet method in which dedicated ink is ejected as fine droplets from a nozzle and adhered to a sheet is preferable. Ink jet heads include a bubble jet (registered trademark) method that generates bubbles by applying a voltage to a heater and pushes ink, a thermal ink jet method, and a piezo element method that pushes ink by vibration of a piezo element. The ink composition can be used in any of these systems.

Further, the ink jet recording method of the present invention will be described by taking as an example a method for preparing a lithographic printing plate including injecting an ink composition onto the lithographic printing plate to form an image.
The lithographic printing plate of the present invention has a hydrophilic support and a hydrophobic region (image) formed on the hydrophilic support using the ink composition of the present invention. This lithographic printing plate production method comprises the following steps:
(1) a step of ejecting the ink composition of the present invention onto the hydrophilic support; and
(2) Radiation is applied to the surface of the hydrophilic support on which the ink has been ejected to cure the ink, thereby forming a hydrophobic region (image) formed by curing the ink on the hydrophilic support. And a process.

(2-1-1) Lithographic printing plate Here, the lithographic printing plate has a hydrophilic support and an image formed on the support.
Conventionally, so-called PS plates having a configuration in which a lipophilic photosensitive resin layer is provided on a hydrophilic support have been widely used as lithographic printing plates. As a method for producing the PS plate, a desired printing plate is usually obtained by performing mask exposure (surface exposure) through a lith film and then dissolving and removing the non-exposed portion. However, in recent years, digitization techniques for electronically processing, storing, and outputting image information using a computer have become widespread, and a new image output method corresponding to the technique has been demanded. In particular, Computer-to-Plate (CTP) technology has been developed that scans highly-preferred light such as laser light according to digitized image information without using a lithographic film, and directly produces printing plates. Yes.

  As a method for obtaining a lithographic printing plate that enables such scanning exposure, a method of directly producing a lithographic printing plate with an ink composition can be mentioned. This is because ink is ejected onto a support, preferably a hydrophilic support, by an ink jet method or the like, and exposed to radiation, whereby a portion of the ink composition is exposed to form a desired image (preferably hydrophobic). A printing plate having a sex image) is obtained. An ink composition suitable for such a system is the ink composition of the present invention.

  The support (recording medium) on which the ink composition of the present invention is ejected is not particularly limited as long as it is a dimensionally stable plate-like support. The support is preferably a hydrophilic support. 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 on which the above-mentioned metal is laminated or deposited. Preferable supports include 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 an 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, but completely pure aluminum is difficult to manufacture in terms of refining technology, and therefore 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 from 0.1 to 0.6 mm, more preferably from 0.15 to 0.4 mm.
Prior to using the aluminum plate, it is preferable to perform a surface treatment such as roughening treatment or anodizing treatment. By the surface treatment, it is easy to improve hydrophilicity and secure adhesion between the image recording layer 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.

  As the support used in the present invention, the substrate having the above-mentioned surface treatment and having an anodized film may be used as it is, but for further improvement in adhesion to the upper layer, hydrophilicity, resistance to contamination, heat insulation and the like. If necessary, the surface of the anodized film described in JP-A-2001-253181 and JP-A-2001-322365 may be enlarged or sealed, and immersed in an aqueous solution containing a hydrophilic compound. A hydrophilic treatment or the like can be appropriately selected and performed. Of course, the large treatment and the sealing treatment are not limited to those described above, and any conventionally known methods 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.
Of these, sealing treatment with an aqueous solution containing an inorganic fluorine compound, sealing treatment with water vapor, and sealing treatment with hot water are preferable. Each will be described below.

<Sealing treatment with an aqueous solution containing an 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. Of 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, more preferably 0.05% by mass or more, from the viewpoint of sufficiently sealing the micropores of the anodized film. Further, in terms of stain resistance, it is preferably 1% by mass or less, and more preferably 0.5% by mass or less.
It is preferable that the aqueous solution containing an 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.

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. Of 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. Is preferred.
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, from the viewpoint of improving on-press developability and stain resistance. Further, in terms of solubility, it is preferably 20% by mass or less, and more preferably 5% by 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, preferably 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.

The 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 the treatment is performed using the dipping method, the treatment time is preferably 1 second or longer, more preferably 3 seconds or longer, and preferably 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).
Further, 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, more preferably 20 seconds or shorter.

<Sealing treatment with hot water>
Examples of the sealing treatment with 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, more preferably 100 seconds or shorter, and even more preferably 20 seconds or shorter.

Examples of the hydrophilization treatment used in the present invention include US Pat. Nos. 2,714,066, 3,181,461, 3,280,734 and 3,902,734. There is an alkali metal silicate method as described in the book. 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.
The support that can be used in the present invention preferably has a center line average roughness of 0.10 to 1.2 μm. Within this range, good adhesion to the image recording layer, good printing durability and good stain resistance can be obtained.

(2-1-2) Step of ejecting the ink composition onto the recording medium When the ink composition of the present invention is ejected onto the surface of the recording medium such as a hydrophilic support, the ink composition It is preferable that the ink composition is ejected after being heated to -80 ° C, preferably 25-30 ° C, to lower the viscosity of the ink composition to 7-30 mPa · s, preferably 7-20 mPa · s. In particular, when an ink composition having an ink viscosity of 35 to 500 mPa · s at 25 ° C. is used, a great effect can be obtained. By using this method, high injection stability can be realized. A radiation curable ink composition such as the ink composition of the present invention generally has a higher viscosity than water-based inks used in ordinary ink-jet recording ink compositions, and therefore has a large viscosity variation due to temperature variations during printing. The ink viscosity fluctuation has a great influence on the change in the droplet size and the change in the ejection speed of the droplets, thereby causing deterioration of the image quality. Therefore, it is necessary to keep the temperature of ink at the time of printing as constant as possible. Therefore, it is appropriate that the control range of the temperature of the present invention is the set temperature ± 5 ° C., preferably the set temperature ± 2 ° C., more preferably the set temperature ± 1 ° C.

(2-1-3) A step of irradiating the recording medium on which the ink has been ejected to cure the ink The ink ejected on the surface of the recording medium such as a hydrophilic support is irradiated with radiation. To cure. This is because the sensitizing dye in the polymerization initiation system contained in the ink composition of the present invention absorbs radiation to be in an excited state, and the polymerization initiator is decomposed by contact with the polymerization initiator in the polymerization initiation system. This is because the polymerizable compound is cured by radical polymerization.

Here, α-rays, γ-rays, electron beams, X-rays, ultraviolet rays, visible light, infrared light, or the like can be used as the radiation used. The peak wavelength of the radiation is, for example, 200 to 600 nm, preferably 300 to 450 nm, more preferably 350 to 450 nm, depending on the absorption characteristics of the sensitizing dye. In addition, the polymerization initiation system of the present invention has sufficient sensitivity even with low output radiation. Thus, the output of radiation, for example, 2000 mJ / cm ² or less, preferably, 10 to 2000 mJ / cm ^2, more preferably, 20~1000mJ / cm ^2, more preferably, irradiation energy of 50 to 800 mJ / cm ² It is appropriate to be. Moreover, it is appropriate that the radiation is irradiated at an exposure surface illuminance of, for example, 10 to 2000 mW / cm ² , preferably 20 to 1000 mW / cm ² .

The ink composition of the present invention is appropriately irradiated with such radiation for, for example, 0.01 to 120 seconds, preferably 0.1 to 90 seconds.
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 of 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 a porous recording medium before the ink penetrates to a deep part where the light source does not reach, residual unreacted monomer can be suppressed, and as a result, odor can be reduced. .

  Further, the curing may be completed by another light source that is not driven. In WO99 / 54415, as an irradiation method, a method using an optical fiber or a method in which a collimated light source is applied to a mirror surface provided on the side surface of the head unit to irradiate the recording unit with UV light is disclosed.

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. Irradiation can be performed by injecting all colors and exposing them together, but exposure for each color is preferable from the viewpoint of curing acceleration.
In this way, the ink composition of the present invention is cured by irradiation with radiation to form a hydrophobic image on the surface of the hydrophilic support.

(2-2) Inkjet recording apparatus The inkjet recording apparatus used in the present invention is not particularly limited, and a commercially available inkjet recording apparatus can be used. That is, in the present invention, recording can be performed on a recording medium using a commercially available inkjet recording apparatus.
The ink jet recording apparatus of the present invention includes, for example, an ink supply system, a temperature sensor, and a 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 inject 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 has a constant temperature for the ejected ink, heat insulation and heating can be performed from the ink supply tank to the inkjet head portion. The temperature control method is not particularly limited, but for example, it is preferable to provide a plurality of temperature sensors at each piping site 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 thermal energy, it is preferable to insulate from other parts and reduce the heat capacity of the entire heating unit.

  As a radiation source, a mercury lamp, a gas / solid laser or the like is mainly used, and a mercury lamp and a metal halide lamp are widely known as ultraviolet light curable ink jets. 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 photocurable ink jets.

  In addition, a light emitting diode (LED) and a laser diode (LD) can be used as a 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 launched 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 radiation centered between 300 nm and 370 nm. Other ultraviolet LEDs are also available and can emit radiation in different ultraviolet bands. Particularly preferred radiation sources in the present invention are UV-LEDs, and particularly preferred are UV-LEDs having a peak wavelength in the range of 350 to 420 nm.

  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.

Example 1
<< Preparation of pigment dispersion >>
According to the method described below, yellow, magenta, cyan and black pigment dispersions 1 were prepared. The dispersion conditions are adjusted appropriately using a known dispersion device so that the average particle diameter of each pigment particle is in the range of 0.2 to 0.3 μm, and then filtered under heating. Prepared by filtration.

(Yellow pigment dispersion 1)
(C) C.I. I. Pigment Yellow 12 10 parts by weight Polymer Dispersant (Solsperse series manufactured by Zeneca) 5 parts by weight Lauryl acrylate 85 parts by weight (magenta pigment dispersion 1)
(C) C.I. I. Pigment Red 57: 1 15 parts by mass Polymer dispersant (Solsperse series manufactured by Zeneca) 5 parts by mass Lauryl acrylate 80 parts by mass (Cyan Pigment Dispersion 1)
(C) C.I. I. Pigment Blue 15: 3 20 parts by mass Polymer dispersing agent (Solsperse series manufactured by Zeneca) 5 parts by mass Lauryl acrylate 75 parts by mass (Black pigment dispersion 1)
(C) C.I. I. Pigment Black 7 20 parts by mass Polymer dispersant (Solsperse series manufactured by Zeneca) 5 parts by mass Lauryl acrylate 75 parts by mass

<Preparation of ink>
Each color ink was prepared using each of the dispersions 1 prepared above according to the method described below.

(Yellow ink 1)
(Contains (c)) Yellow pigment dispersion 20 parts by mass (a) Polymerizable compound I-1 30 parts by mass 1,6-hexanediol diacrylate 40 parts by mass Caprolactone-modified dipentaerythritol hexaacrylate 5 parts by mass (b) Polymerization initiator (Ciba Specialty Chemicals,
IRGACURE 184) 5 parts by mass

(Magenta ink 1)
(Containing (c)) magenta pigment dispersion 1 20 parts by mass (a) polymerizable compound I-1 30 parts by mass 1,6-hexanediol diacrylate 40 parts by mass caprolactone-modified dipentaerythritol hexaacrylate 5 parts by mass (b ) Polymerization initiator (Ciba Specialty Chemicals,
IRGACURE 184) 5 parts by mass

(Cyan ink 1)
(Contains (c)) Cyan pigment dispersion 1 15 parts by mass (a) Polymerizable compound I-1 30 parts by mass 1,6-hexanediol diacrylate 45 parts by mass Caprolactone-modified dipentaerythritol hexaacrylate 5 parts by mass (b ) Polymerization initiator (Ciba Specialty Chemicals,
IRGACURE 184) 5 parts by mass

(Black ink 1)
(Contains (c)) Black pigment dispersion 1 15 parts by mass (a) Polymerizable compound I-1 30 parts by mass 1,6-hexanediol diacrylate 45 parts by mass Caprolactone-modified dipentaerythritol hexaacrylate 5 parts by mass (b ) Polymerization initiator (Ciba Specialty Chemicals,
IRGACURE 184) 5 parts by mass Each color ink 1 prepared as described above was filtered with a filter having an absolute filtration accuracy of 2 μm to obtain ink 1 of each color.

<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, a supply pipe, 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. In the present invention, dpi represents the number of dots per 2.54 cm.

Each color ink prepared above was ejected in the order of black → cyan → magenta → yellow at an ambient temperature of 25 ° C. and irradiated with ultraviolet rays for each color. In order to eliminate tackiness by palpation, the exposure was performed with a total exposure energy per color of 300 mJ / cm ² as the energy for complete curing. 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).

Examples 2-5
<Preparation of ink>
Magenta inks 2-5 were prepared according to the method described below.

(Magenta ink 2)
(Containing (c)) magenta pigment dispersion 1 20 parts by mass (a) polymerizable compound I-6 30 parts by mass 1,6-hexanediol diacrylate 40 parts by mass caprolactone-modified dipentaerythritol hexaacrylate 5 parts by mass (b ) Polymerization initiator (Ciba Specialty Chemicals,
IRGACURE 184) 5 parts by mass

(Magenta ink 3)
(Containing (c)) magenta pigment dispersion 1 20 parts by mass (a) polymerizable compound I-7 30 parts by mass 1,6-hexanediol diacrylate 40 parts by mass caprolactone-modified dipentaerythritol hexaacrylate 5 parts by mass (b ) Polymerization initiator (Ciba Specialty Chemicals,
IRGACURE 184) 5 parts by mass

<Preparation of magenta pigment dispersion 2>
A magenta pigment dispersion 2 was prepared in the same manner as in the preparation of the magenta pigment dispersion 1 described in Example 1, except that isobornyl acrylate was used instead of lauryl acrylate.

(Magenta ink 4)
(Containing (c)) magenta pigment dispersion 2 20 parts by mass (a) polymerizable compound I-8 30 parts by mass 1,6-hexanediol diacrylate 40 parts by mass caprolactone-modified dipentaerythritol hexaacrylate 5 parts by mass (b ) Polymerization initiator (Ciba Specialty Chemicals,
IRGACURE 184) 5 parts by mass

(Magenta ink 5)
(Containing (c)) magenta pigment dispersion 2 20 parts by mass (a) polymerizable compound I-1 30 parts by mass 1,6-hexanediol diacrylate 40 parts by mass caprolactone-modified dipentaerythritol hexaacrylate 5 parts by mass (b ) Polymerization initiator (Ciba Specialty Chemicals,
IRGACURE 184) 5 parts by mass

Comparative Example << Preparation of ink >>
Magenta ink 6 was prepared according to the method described below.
(Magenta ink 6: Comparative example)
(Containing (c)) magenta pigment dispersion 1 20 parts by mass 1,6-hexanediol diacrylate 70 parts by mass caprolactone-modified dipentaerythritol hexaacrylate 5 parts by mass (b) polymerization initiator (manufactured by Ciba Specialty Chemicals,
IRGACURE 184) 5 parts by mass

  In the ink compositions prepared in the above examples and comparative examples, the ink viscosity at the ejection temperature was in the range of 7 to 20 mPa · s.

<Inkjet image recording>
Using the magenta inks 2 to 6 prepared as described above and the magenta ink 1 prepared in Example 1, magenta image printing was performed in the same manner as in the method described in Example 1.

<Evaluation of inkjet image>
Next, for each formed image, in accordance with the method described below, sensitivity required for curing, permeability in commercially available recycled paper, ink bleeding on a grained aluminum support, adhesion, printing durability, storage The stability was evaluated.

(Measurement of curing sensitivity)
The amount of exposure energy (mJ / cm ² ) at which the sticky feeling disappears on the image surface after ultraviolet irradiation was defined as the curing sensitivity. The smaller the value, the higher the sensitivity.

(Permeability evaluation for commercial recycled paper)
For images printed on commercially available recycled paper, permeability was evaluated according to the following criteria.
○: Almost no penetration and no residual monomer odor △: Slight penetration and slight residual monomer odor X: Clearly the ink penetrates the back side and the residual monomer odor is strong

(Evaluation of ink bleeding on grained aluminum support)
For images printed on a grained aluminum support, ink bleeding was evaluated according to the following criteria.
○: No blur between adjacent dots Δ: Slightly blur dots ×: Dot blurs and the image is clearly blurred

(Evaluation of adhesion in grained aluminum support)
With respect to the print image created above, a sample that does not scratch the print surface at all, and in accordance with JISK 5400, 11 cuts are made on the print surface at 1 mm intervals vertically and horizontally, and a 1 mm square grid 100 is formed. Individual samples were prepared, and a cellophane tape was applied to each printing surface. The sample was peeled off quickly at an angle of 90 degrees, and the state of the printed image remaining without peeling or the grid pattern was evaluated according to the following criteria.
○: No peeling of the printed image was observed even in the cross cut test. Δ: Some ink peeling was observed in the cross cut test, but almost no peeling was observed unless the ink surface was scratched. Easy to peel off with cello tape (registered trademark)

(Evaluation of printing durability)
The image printed on the grained aluminum support prepared above was used as a printing plate, and after printing with a Heidel KOR-D machine, the number of finished sheets was relatively compared as an index of printing durability (Example 1 was set to 100). ). A larger numerical value is preferable because it provides higher printing durability.

(Evaluation of storage stability)
The prepared ink was stored at 75% RH and 60 ° C. for 3 days, the ink viscosity at the injection temperature was measured, and the increase in the ink viscosity was expressed as the 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.
These evaluation results are shown in Table 1.

  As is clear from Table 1, the ink composition using the α-heteromethacrylic compound of the present invention is highly sensitive to radiation irradiation and forms a high-quality image even in image-forming properties on paper. In addition, the storage stability was good, and even when used for producing a printing plate, images with high printing durability and high image quality were formed (Examples 1 to 5). On the other hand, an ink composition using only a conventional acrylate compound as a polymerizable compound has low curing sensitivity, high permeability to paper, and ink bleeding was observed. In addition, the storage stability is low, and when used for the production of a printing plate, the printing durability is low and a high-quality image can be formed.

Claims (11)

An ink composition comprising: (a) a polymerizable compound represented by the following general formula (I); (b) a polymerization initiator; and (c) a colorant.

Formula (I)
In the formula, R ^a and R ^b each independently represent a hydrogen atom, a halogen atom, a cyano group, a hydrocarbon group, a substituted oxy group, a substituted thio group, a substituted amino group, a substituted carbonyl group, or a carboxylate group, R represents a secondary or tertiary hydrocarbon group containing a ring structure and having 7 or more carbon atoms. The substituted oxy group represented by R ^a and R ^b is selected from an alkoxy group, an aryloxy group, an acyloxy group, and an arylsulfoxy group, the substituted thio group is selected from an alkylthio group and an arylthio group, and the substituted amino group is an N-alkylamino group. Group, N, N-dialkylamino group, N-arylamino group, and acylamino group, the substituted carbonyl group is formyl group, acyl group, carboxyl group, alkoxycarbonyl group, aryloxycarbonyl group, carbamoyl group, N- It is selected from alkylcarbamoyl groups, N, N-dialkylcarbamoyl groups, and N-arylcarbamoyl groups. Y represents CN or COX, and X represents a group or halogen atom bonded to the carbonyl group through a hetero atom. R and Y, R ^a and R ^b , or R and R ^a or R ^b may be bonded to each other to form a cyclic structure. Substituted oxy groups are methoxy, ethoxy, propyloxy, isopropyloxy, butyloxy, phenoxy, tolyloxy, xylyloxy, mesityloxy, cumenyloxy, methoxyphenyloxy, ethoxyphenyloxy, chlorophenyloxy The ink composition according to claim 1, wherein the ink composition is selected from bromophenyloxy group, acetyloxy group, benzoyloxy group, naphthyloxy group, and phenylsulfonyloxy group. The ink composition according to claim 1, wherein the substituted thio group is selected from a methylthio group, an ethylthio group, a phenylthio group, an ethoxyethylthio group, a carboxyethylthio group, and a methoxycarbonylthio group. The substituted amino group is selected from a methylamino group, an ethylamino group, a diethylamino group, a morpholino group, a piperidino group, a pyrrolidino group, a phenylamino group, a benzoylamino group, and an acetylamino group. The ink composition as described. Substituted carbonyl groups are formyl group, acetyl group, benzoyl group, carboxyl group, methoxycarbonyl group, allyloxycarbonyl group, N-methylcarbamoyl group, N-phenylcarbamoyl group, N, N-diethylcarbamoyl group, and morpholinocarbonyl group. The ink composition according to claim 1, wherein the ink composition is selected from the group consisting of: R ^a And R ^b The ink composition according to claim 1, wherein is an hydrogen atom. The ink composition according to any one of claims 1 to 6, which is for inkjet recording. It includes a step of ejecting and landing the ink composition according to any one of claims 1 to 7 on a recording medium, and a step of irradiating the ink composition with radiation to cure the ink composition. Inkjet recording method. A printed matter obtained by ejecting and landing the ink composition according to any one of claims 1 to 6 on a recording medium and then irradiating the ink composition to cure the ink composition. A hydrophobic region is formed by spraying the ink composition according to any one of claims 1 to 6 onto a hydrophilic support, landing the ink composition, and then curing the ink by irradiation with radiation. A method for preparing a lithographic printing plate characterized by Hydrophobic formed by ejecting the ink composition according to any one of claims 1 to 6 onto a hydrophilic support, landing and then curing the ink composition by irradiation with radiation. A lithographic printing plate with areas.