JP2005105034A - Active ray-curable ink, ink-jet printer, and ink-jet recording method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an active ray-curable ink-jet printing ink which is excellent in the storage stability and in the picture durability after the curing. <P>SOLUTION: The active ray-curable ink which contains a cationically polymerizable compound, a cationic photopolymerization initiator and a coloring material, is characterized in that the coloring material is an oil-soluble dyestuff. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an actinic ray curable ink containing an oil-soluble dye and curable by actinic ray irradiation, and to an ink jet printer and an ink jet recording method using the ink.

  In recent years, the ink jet recording system can create images easily and inexpensively, and thus has been applied to various printing fields such as photographs, various printing, marking, and special printing such as color filters. In general, water-soluble dyes are widely used for vivid color reproduction, but it has been pointed out that special paper is required to obtain high-quality images and that light resistance is insufficient. .

  Even when a pigment is used to improve light resistance, special paper is still necessary to obtain a high-quality image, and the ejection stability of the ink is slightly deteriorated. Therefore, it has been proposed to use oil-soluble dyes.

  For example, it is described that the injection stability is improved by using an oil-soluble dye in an ultraviolet curable inkjet ink using a radical polymerizable monomer.

  For example, solvent-free photocurable inks using a photo-radically polymerizable compound and an oil-soluble dye having a specific structure and an inkjet recording method (see Patent Document 1), an ethylenically unsaturated monomer in a dispersion in an aqueous dispersion of colored fine particles Ink containing ink and oil-soluble dye and polymerizing monomer after recording and ink jet recording method (see Patent Document 2), (meth) acryloyl, allyl, vinyl polymerizable monomer / oil-soluble dye / storage stabilizer-containing ink An ink containing an oil-soluble dye dissolved in an ink and a solvent-free ink (see Patent Document 3), an ink containing a radical polymerizable monomer and an oil-soluble phthalocyanine dye (see Patent Document 4), and the like.

However, in the photocurable ink using these photoradically polymerizable compounds, the durability of the image is not sufficient particularly when an image is recorded on an ink non-absorbing substrate such as plastic.
JP 2003-221528 A JP 2003-221529 A JP 2003-221530 A Japanese Patent Laid-Open No. 2003-221531

  An object of the present invention is to solve the above-described problems and achieve the following objects. That is, an object of the present invention is to provide an actinic ray curable inkjet ink having excellent storage stability and excellent image durability after curing, an inkjet printer using the ink, and an inkjet recording method.

The above object of the present invention is achieved by the following means.
(Claim 1)
An actinic ray curable ink comprising a cationic polymerizable compound, a cationic photopolymerization initiator, and a color material, wherein the color material is an oil-soluble dye.
(Claim 2)
2. The actinic ray curable ink according to claim 1, wherein the cationic polymerizable compound is at least one compound selected from an alicyclic epoxy compound, an oxetane compound, and a vinyl ether compound.
(Claim 3)
The actinic ray curable ink according to claim 1, wherein the oil-soluble dye is represented by the general formula (I).

(In the formula, Q represents an atomic group necessary for the compound represented by the general formula (I) to absorb light in the visible region or near infrared region, A represents —NR ⁵ R ⁶ or a hydroxyl group, R ⁵ and R ⁶ each independently represents a hydrogen atom, an alkyl group, an aryl group or a heterocyclic group, B ¹ represents ═C (R ³ ) — or ═N—, and B ² represents —C (R ⁴ ). R ¹ , R ² , R ³ and R ⁴ each independently represents a hydrogen atom or a substituent, R ¹ and R ² , R ¹ and R ⁵ , R ⁵ and R ⁶ , R ³ and R ⁵ and R ³ and R ⁴ may be bonded to each other to form a ring.)
(Claim 4)
4. An ink jet printer having an ink ejection unit that ejects ink onto a recording medium, a transport unit for transporting the recording medium, and a light source unit for curing ink after ink landing. An ink-jet printer using the actinic ray curable ink described.
(Claim 5)
The image forming method for forming an image with the ink jet printer according to claim 4 using the actinic ray curable ink according to any one of claims 1 to 3, wherein the light irradiated from the light source unit for ink curing, the ink jet recording method, wherein the illuminance on the recording medium surface is ^{0.1mW / cm 2 ~50mW / cm 2} .

  According to the present invention, when an image is recorded on a non-ink-absorbing substrate having excellent storage stability, an actinic ray curable ink excellent in durability of an image after curing and an ink jet recording method using the ink are obtained. It is done.

  The best mode for carrying out the present invention will be described below, but the present invention is not limited thereto.

  First, the oil-soluble dye according to the present invention will be described.

<Oil-soluble dye>
As the oil-soluble dye of the present invention, dyes described in paragraphs (0014) to (0084) of JP-A No. 2001-262039 can be used. In paragraph (0040) of JP-A No. 2001-262039, the description of a substituted or unsubstituted indolinin-1-yl group shall be read as a substituted or unsubstituted indolin-1-yl group.

In the present invention, a compound represented by general formula (I) (hereinafter also referred to as compound (I)) is used as the oil-soluble dye. Q represents an atomic group necessary for the compound represented by the general formula (I) to absorb light in the visible region and / or near infrared region, and preferably represents a residue of a diazo component. A represents -NR ⁵ R ⁶ or a hydroxyl group, preferably a -NR ⁵ R ^6. R ⁵ and R ⁶ each independently represents a hydrogen atom, an alkyl group, an aryl group or a heterocyclic group, B ¹ represents ═C (R ³ ) — or ═N—, and B ² represents —C (R ⁴ ). = Or -N =, and R ¹ , R ² , R ³ and R ⁴ each independently represents a hydrogen atom or a substituent. R ¹ and R ² , R ¹ and R ⁵ , R ⁵ and R ⁶ , R ³ and R ^5, and R ³ and R ⁴ may be bonded to each other to form a ring. The substituent for R ¹ , R ² , R ³ and R ⁴ is not particularly limited, but is a halogen atom, aliphatic group, aromatic group, heterocyclic group, cyano group, carbamoyl group, alkoxycarbonyl group, aryloxycarbonyl Group, heterocyclic oxycarbonyl group, acyl group, hydroxyl group, alkoxy group, aryloxy group, heterocyclic oxy group, silyloxy group, acyloxy group, carbamoyloxy group, alkoxycarbonyloxy group, aryloxycarbonyloxy group, alkyl group or Amino group substituted by aryl group or heterocyclic group, acylamino group, ureido group, sulfamoylamino group, alkoxycarbonylamino group, aryloxycarbonylamino group, alkyl or arylsulfonylamino group, heterocyclic sulfonylamino group, nitro Group Examples include an alkyl or aryl sulfonyl group, an alkyl or aryl sulfonyl group, a heterocyclic sulfonyl group, an alkyl or aryl sulfinyl group, a heterocyclic sulfinyl group, and a sulfamoyl group, and each group may be further substituted.

  Among these, what is represented by the following general formula (I-1) as an oil-soluble dye of this invention is preferable.

  In general formula (I-1), D represents a 5-membered heterocyclic group. Examples of the hetero atom of the 5-membered heterocycle include N, O, and S. Preferably it is a nitrogen-containing 5-membered heterocycle, and the heterocycle may be condensed with an aliphatic ring, an aromatic ring or other heterocycle. Examples of preferable heterocycle of D include pyrazole ring, imidazole ring, thiazole ring, isothiazole ring, thiadiazole ring, benzothiazole ring, benzoxazole ring, and benzoisothiazole ring. Each heterocyclic group may further have a substituent. Of these, the pyrazole ring, imidazole ring, isothiazole ring, thiadiazole ring and benzothiazole ring represented by the following general formulas (a) to (f) are preferable.

In the general formulas (a) to (f), R ⁷ to R ²⁰ represent a hydrogen atom or a substituent, and examples of the substituent include the same substituents as those described for R ¹ , R ^2, or R ^4. It is done. Of the general formulas (a) to (f), preferred are the pyrazole ring and isothiazole ring represented by the general formulas (a) and (b), and the most preferred is represented by the general formula (a). It is a pyrazole ring.

Preferable substituents represented by R ¹ and R ² include a hydrogen atom, an alkyl group, an alkoxycarbonyl group, a carbamoyl group, and a cyano group. Each group may further have a substituent.

Preferred substituents represented by R ⁴ include a hydrogen atom, a halogen atom, an aliphatic group, an aromatic group, a hydroxy group, an alkoxy group, an aryloxy group, an acyloxy group, a heterocyclic oxy group, an alkyl group, an aryl group, or a heterocyclic group. An amino group substituted with a cyclic group, an acylamino group, a ureido group, a sulfamoylamino group, an alkoxycarbonylamino group, an aryloxycarbonylamino group, an alkyl or aryl or a heterocyclic thio group, and more preferably a hydrogen atom, A halogen atom, an alkyl group, a hydroxy group, an alkoxy group, an aryloxy group, an acyloxy group, an amino group substituted with an alkyl group, an aryl group or a heterocyclic group, or an acylamino group, among which a hydrogen atom, an arylamino group, an amide The group is most preferred. Each group may further have a substituent.

R ⁵ and R ⁶ are preferably a hydrogen atom, an aryl group, or a heterocyclic group. Each group may further have a substituent. However, it is preferable that either R ⁵ or R ⁶ is not a hydrogen atom.

R ¹ and R ⁵ , or R ⁵ and R ⁶ may combine to form a 5- to 6-membered ring. In the case where each substituent represented by D, R ¹ , R ² , R ⁴ , R ⁵ , R ⁶ further has a substituent, the substituents mentioned in the above R ¹ , R ² , R ⁴ Can be mentioned.

  In the present specification, an 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 and may form a ring. The number of carbon atoms in the aliphatic group is preferably 1-20, and more preferably 1-16. The aryl part of the aralkyl group and the substituted aralkyl group is preferably phenyl or naphthyl, particularly preferably phenyl. Examples of the aliphatic group include methyl, ethyl, butyl, isopropyl, t-butyl, hydroxyethyl, methoxyethyl, cyanoethyl, trifluoromethyl, cyclohexyl group, benzyl group, 2-phenethyl group, vinyl group, and allyl group. The group can be mentioned.

  In the present specification, the aromatic group means an aryl group and a substituted aryl group. The aryl group is preferably phenyl or naphthyl, particularly preferably phenyl. The number of carbon atoms in the aromatic group is preferably 6 to 20, and more preferably 6 to 16. Examples of the aromatic group include phenyl, p-tolyl, p-methoxyphenyl, o-chlorophenyl and the like.

  The heterocyclic group includes a heterocyclic group having a substituent and an unsubstituted heterocyclic group. The heterocycle may be condensed with an aliphatic ring, an aromatic ring or another heterocycle. The heterocyclic group is preferably a 5-membered or 6-membered heterocyclic group. Examples of the substituent include aliphatic groups, halogen atoms, alkyl and arylsulfonyl groups, acyl groups, acylamino groups, sulfamoyl groups, carbamoyl groups, and the like. Examples of the heterocyclic group include a 2-pyridyl group, a 2-thienyl group, a 2-thiazolyl group, a 2-benzothiazolyl group, a 2-benzoxazolyl group, and a 2-furyl group.

  The alkyl and arylsulfonyl groups include substituted alkyl and arylsulfonyl groups, unsubstituted alkyl and arylsulfonyl groups. Examples of the alkyl and arylsulfonyl groups include a methanesulfonyl group and a phenylsulfonyl group, respectively.

  Alkyl and arylsulfinyl groups include substituted alkyl and arylsulfinyl groups, unsubstituted alkyl and arylsulfinyl groups. Examples of the alkyl and arylsulfinyl groups include a methanesulfinyl group and a phenylsulfinyl group, respectively.

  The acyl group includes an acyl group having a substituent and an unsubstituted acyl group. The acyl group is preferably an acyl group having 1 to 12 carbon atoms. Examples of the acyl group include an acetyl group and a benzoyl group.

  Examples of the halogen atom include a fluorine atom, a chlorine atom, and a bromine atom.

  The amino group substituted with an alkyl group, an aryl group or a heterocyclic group includes an amino group substituted with one or two groups selected from an alkyl group, an aryl group and a heterocyclic group, and an alkyl group , Aryl group and heterocyclic group may further have a substituent. Unsubstituted amino groups are not included. As the alkylamino group, an alkylamino group having 1 to 6 carbon atoms is preferable. Examples of the alkylamino group include a methylamino group and a diethylamino group. The arylamino group includes an arylamino group having a substituent and an unsubstituted arylamino group. The arylamino group is preferably an arylamino group having 6 to 12 carbon atoms. Examples of the substituent include a halogen atom. Examples of the arylamino group include an anilino group and a 2-chloroanilino group.

  The alkoxy group includes an alkoxy group having a substituent and an unsubstituted alkoxy group. As said alkoxy group, a C1-C12 alkoxy group is preferable. Examples of the substituent include an alkoxy group and a hydroxyl group. Examples of the alkoxy group include methoxy group, ethoxy group, isopropoxy group, methoxyethoxy group, hydroxyethoxy group and the like.

  The aryloxy group includes an aryloxy group having a substituent and an unsubstituted aryloxy group. The aryloxy group is preferably an aryloxy group having 6 to 12 carbon atoms. Examples of the substituent include an alkoxy group. Examples of the aryloxy group include a phenoxy group, a p-methoxyphenoxy group, and an o-methoxyphenoxy group.

  The silyloxy group is preferably a silyloxy group substituted with an aliphatic group or aromatic group having 1 to 12 carbon atoms. Examples of the silyloxy group include trimethylsilyloxy and diphenylmethylsilyloxy.

  The heterocyclic oxy group includes a heterocyclic oxy group having a substituent and an unsubstituted heterocyclic oxy group. The heterocyclic oxy group is preferably a heterocyclic oxy group having 2 to 12 carbon atoms. Examples of the substituent include an alkyl group and an alkoxy group. Examples of the heterocyclic oxy group include a 3-pyridyloxy group and a 3-thienyloxy group.

  The alkoxycarbonyloxy group includes an alkoxycarbonyloxy group having a substituent and an unsubstituted alkoxycarbonyloxy group. The alkoxycarbonyloxy group is preferably an alkoxycarbonyloxy group having 2 to 12 carbon atoms. Examples of the alkoxycarbonyloxy group include a methoxycarbonyloxy group and an isopropoxycarbonyloxy group.

  The aryloxycarbonyloxy group includes an aryloxycarbonyloxy group having a substituent and an unsubstituted aryloxycarbonyloxy group. The aryloxycarbonyloxy group is preferably an aryloxycarbonyloxy group having 7 to 12 carbon atoms. Examples of the aryloxycarbonyloxy group include a phenoxycarbonyloxy group.

  The acylamino group includes an acylamino group having a substituent and an unsubstituted acylamino group. The acylamino group is preferably an acylamino group having 2 to 12 carbon atoms. Examples of the acylamino group include acetylamino group, propionylamino group, benzoylamino group, N-phenylacetylamino and the like.

  The ureido group includes a ureido group having a substituent and an unsubstituted ureido group. The ureido group is preferably a ureido group having 1 to 12 carbon atoms. Examples of the substituent include an alkyl group and an aryl group. Examples of the ureido group include a 3-methylureido group, a 3,3-dimethylureido group, and a 3-phenylureido group.

  The sulfamoylamino group includes a sulfamoylamino group having a substituent and an unsubstituted sulfamoylamino group. Examples of the substituent include an alkyl group. Examples of the sulfamoylamino group include N, N-dipropylsulfamoylamino group.

  The alkoxycarbonylamino group includes an alkoxycarbonylamino group having a substituent and an unsubstituted alkoxycarbonylamino group. The alkoxycarbonylamino group is preferably an alkoxycarbonylamino group having 2 to 12 carbon atoms. Examples of the alkoxycarbonylamino group include an ethoxycarbonylamino group.

  The alkyl or arylsulfonylamino group includes an alkyl or arylsulfonylamino group having a substituent and an unsubstituted alkyl or arylsulfonylamino group. The sulfonylamino group is preferably a sulfonylamino group having 1 to 12 carbon atoms. Examples of the sulfonylamino group include a methanesulfonylamino group, an N-phenylmethanesulfonylamino group, and a benzenesulfonylamino group.

  The carbamoyl group includes a carbamoyl group having a substituent and an unsubstituted carbamoyl group. Examples of the substituent include an alkyl group. Examples of the carbamoyl group include a methylcarbamoyl group and a dimethylcarbamoyl group.

  The sulfamoyl group includes a sulfamoyl group having a substituent and an unsubstituted sulfamoyl group. Examples of the substituent include an alkyl group. Examples of the sulfamoyl group include a dimethylsulfamoyl group and a di- (2-hydroxyethyl) sulfamoyl group.

  The alkoxycarbonyl group includes an alkoxycarbonyl group having a substituent and an unsubstituted alkoxycarbonyl group. The alkoxycarbonyl group is preferably an alkoxycarbonyl group having 2 to 12 carbon atoms. Examples of the alkoxycarbonyl group include a methoxycarbonyl group and an ethoxycarbonyl group.

  The acyloxy group includes an acyloxy group having a substituent and an unsubstituted acyloxy group. The acyloxy group is preferably an acyloxy group having 1 to 12 carbon atoms. Examples of the acyloxy group include an acetoxy group and a benzoyloxy group.

  The carbamoyloxy group includes a carbamoyloxy group having a substituent and an unsubstituted carbamoyloxy group. Examples of the substituent include an alkyl group. Examples of the carbamoyloxy group include an N-methylcarbamoyloxy group.

  The aryloxycarbonyl group includes an aryloxycarbonyl group having a substituent and an unsubstituted aryloxycarbonyl group. The aryloxycarbonyl group is preferably an aryloxycarbonyl group having 7 to 12 carbon atoms. Examples of the aryloxycarbonyl group include a phenoxycarbonyl group.

  The aryloxycarbonylamino group includes an aryloxycarbonylamino group having a substituent and an unsubstituted aryloxycarbonylamino group. The aryloxycarbonylamino group is preferably an aryloxycarbonylamino group having 7 to 12 carbon atoms. Examples of the aryloxycarbonylamino group include a phenoxycarbonylamino group.

  Alkyl or aryl or heterocyclic thio groups include substituted alkyl, aryl, and heterocyclic thio groups, and unsubstituted alkyl, aryl, and heterocyclic thio groups. The alkyl, aryl, and heterocyclic thio groups preferably have 1 to 12 carbon atoms. Examples of the alkyl, aryl, and heterocyclic thio groups include a methylthio group, a phenylthio group, and a 2-pyridylthio group.

  The heterocyclic oxycarbonyl group includes a substituted heterocyclic oxycarbonyl group and an unsubstituted heterocyclic oxycarbonyl group. The heterocyclic oxycarbonyl group is preferably a heterocyclic oxycarbonyl group having 2 to 12 carbon atoms. Examples of the heterocyclic oxycarbonyl group include a 2-pyridyloxycarbonyl group.

  The heterocyclic sulfonylamino group includes a substituted heterocyclic sulfonylamino group and an unsubstituted heterocyclic sulfonylamino group. The heterocyclic sulfonylamino group is preferably a heterocyclic sulfonylamino group having 1 to 12 carbon atoms. Examples of the heterocyclic sulfonylamino group include a 2-thiophenesulfonylamino group and a 3-pyridinesulfonylamino group.

  The heterocyclic sulfonyl group includes a heterocyclic sulfonyl group having a substituent and an unsubstituted heterocyclic sulfonyl group. The heterocyclic sulfonyl group is preferably a heterocyclic sulfonyl group having 1 to 12 carbon atoms. Examples of the heterocyclic sulfonyl group include a 2-thiophenesulfonyl group and a 3-pyridinesulfonyl group.

  The heterocyclic sulfinyl group includes a heterocyclic sulfinyl group having a substituent and an unsubstituted heterocyclic sulfinyl group. The heterocyclic sulfinyl group is preferably a heterocyclic sulfinyl group having 1 to 12 carbon atoms. Examples of the heterocyclic sulfinyl group include a 4-pyridinesulfinyl group.

  In the present invention, a particularly preferred structure is represented by the following general formula (I-1a).

In general formula (I-1a), 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, more preferably 0.45 or more, and particularly preferably an electron-withdrawing group of 0.60 or more. It is desirable not to exceed zero. 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. Z ² represents a hydrogen atom, an aliphatic group, an aromatic group or a heterocyclic group. Z ³ represents a hydrogen atom, an aliphatic group, an aromatic group or a heterocyclic group. Among these, Z ³ is preferably a group composed of a nonmetallic atom group necessary for forming a 5- to 8-membered ring.

  The 5- to 8-membered ring may be substituted, may be a saturated ring, or may have an unsaturated bond. Of these, aromatic groups and heterocyclic groups are particularly preferred. 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. , Benzimidazole ring, oxazole ring, benzoxazole ring, thiazole ring, benzothiazole ring, oxane ring, sulfolane ring and thiane ring.

R ¹ , R ² , R ⁵ and R ⁶ have the same meanings as those in formula (I-1). R ⁴¹ and R ⁴² each independently represents a hydrogen atom or a substituent. Examples of the substituent include an aliphatic group, an aromatic group, a heterocyclic group, an acyl group, an alkoxycarbonyl group, an aryloxycarbonyl group, a carbamoyl group, an alkyl group, and an alkyl group. An arylsulfonyl group and a sulfamoyl group are mentioned. Of these, a hydrogen atom, aromatic group, heterocyclic group, acyl group, alkyl and arylsulfonyl group are preferred, and a hydrogen atom, aromatic group and heterocyclic group are particularly preferred.

Each group described in formula (I-1a) may further have a substituent. When each of these groups further has a substituent, examples of the substituent include the substituents described in the general formula (I-1), groups exemplified by R ¹ , R ² , and R ⁴ .

  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 (McGraw-Hill) and “Chemicals” special edition, 122, 96-103, 1979 (Nankodo). In the present invention, each substituent is limited or explained by the Hammett's substituent constant σp value, 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. In addition, the general formulas (I-1) to (I-1a) of the present invention include those that are not benzene derivatives. However, as a measure showing the electronic effect of the substituent, the σp value is independent of the substitution position. Is used. 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, an alkylsulfonyl group (for example, methanesulfonyl group), and an arylsulfonyl group (for example, benzenesulfonyl group). it can. Examples of the electron-withdrawing group having a Hammett σp value of 0.45 or more include an acyl group (for example, acetyl group), an alkoxycarbonyl group (for example, dodecyloxycarbonyl group), an aryloxycarbonyl group (for example, m-chlorophenoxycarbonyl) in addition to the above. ), An alkylsulfinyl group (for example, n-propylsulfinyl), an arylsulfinyl group (for example, phenylsulfinyl), a sulfamoyl group (for example, N-ethylsulfamoyl, N, N-dimethylsulfamoyl), a halogenated alkyl group ( For example, trifluoromethyl) can be mentioned. 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 heterocycle (eg, 2-benzoxazolyl, 2- Benzothiazolyl, 1-phenyl-2-benzimidazolyl) be able to. 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.

In the particularly preferred combination of substituents as the azo dye represented by the general formula (I-1), R ¹ and R ² are preferably a hydrogen atom, a halogen atom, a cyano group, a carbamoyl group, an alkyl group, a hydroxyl group, An alkoxy group, more preferably a hydrogen atom, a cyano group, a carbamoyl group, or an alkoxy group. R ⁴ is preferably a hydrogen atom, halogen atom, alkyl group, hydroxyl group, amino group or amide group, more preferably a hydrogen atom, halogen atom, amino group or amide group, most preferably a hydrogen atom, amino group Group, an amide group. Of these, D is preferably a pyrazole ring, an imidazole ring, an isothiazole ring, a thiadiazole ring, or a benzothiazole ring, more preferably a pyrazole ring or an isothiazole ring, and most preferably a pyrazole ring. R ⁵ and R ⁶ are preferably a hydrogen atom, an aryl group, or a heterocyclic group, and R ⁵ and R ⁶ are not both hydrogen atoms.

  In addition, about the preferable combination of a substituent of the compound represented by the said general formula (I-1), the compound whose at least 1 of various substituents is the said preferable group is preferable, and more various substituents are The compound which is the said preferable group is more preferable, and the compound whose all the substituents are the said preferable group is the most preferable.

  Specific examples of the azo dye represented by the general formula (I-1) are shown below, but the azo dye used in the present invention is not limited to the following examples.

  These dyes can be produced by known production methods for producing azo dyes known in the dye industry.

  The content of these oil-soluble dyes is preferably 0.05 to 15% by mass in the ink, more preferably 0.1 to 10% by mass, and particularly preferably 0.2 to 6% by mass.

  In the present invention, a cationic polymerizable compound is used as one of the polymerizable compounds. Various known cationic polymerizable monomers can be used as the cationic polymerizable compound. For example, the epoxies exemplified in JP-A-6-9714, JP-A-2001-31892, JP-A-2001-40068, JP-A-2001-55507, JP-A-2001-310938, JP-A-2001-310937, JP-A-2001-220526 Compounds, vinyl ether compounds, oxetane compounds and the like.

  A preferable aromatic epoxide is a di- or polyglycidyl ether produced by the reaction of a polyhydric phenol having at least one aromatic nucleus or an alkylene oxide adduct thereof and epichlorohydrin, such as bisphenol A or an alkylene oxide thereof. Examples thereof include di- or polyglycidyl ethers of adducts, di- or polyglycidyl ethers of hydrogenated bisphenol A or alkylene oxide adducts thereof, and novolak type epoxy resins. Here, examples of the alkylene oxide include ethylene oxide and propylene oxide.

  The alicyclic epoxide can be 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. Cyclohexene oxide or cyclopentene oxide-containing compounds are preferred.

  Preferred aliphatic epoxides include di- or polyglycidyl ethers of aliphatic polyhydric alcohols or alkylene oxide adducts thereof, and typical examples thereof 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, polyglycidyl ether of polyhydric alcohol such as di- or triglycidyl ether of glycerin or its alkylene oxide adduct, polyethylene glycol or its alkylene oxide adduct Of polyalkylene glycols such as diglycidyl ether, polypropylene glycol or diglycidyl ether of its alkylene oxide adduct Glycidyl ether, and the like. Here, examples of the alkylene oxide include ethylene oxide and propylene oxide.

  Among these epoxides, in view of fast curability, aromatic epoxides and alicyclic epoxides are preferable, and alicyclic epoxides are particularly preferable. In the present invention, one of the epoxides may be used alone, or two or more may be used in appropriate combination.

  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.

  Among these vinyl ether compounds, in consideration of curability, adhesion, and surface hardness, di- or trivinyl ether compounds are preferable, and divinyl ether compounds are particularly preferable. In the present invention, one of the above vinyl ether compounds may be used alone, or two or more thereof may be used in appropriate combination.

  In the present invention, it is preferable to contain at least one oxetane compound as a photopolymerizable compound for the purpose of suppressing shrinkage of the recording material during ink curing.

  The oxetane compound according to the present invention is a compound having an oxetane ring, and any known oxetane compound as introduced in JP-A Nos. 2001-220526 and 2001-310937 can be used.

  In the oxetane compound according to the present invention, when a compound having 5 or more oxetane rings is used, the viscosity of the ink composition becomes high, so that handling becomes difficult, and the glass transition temperature of the ink composition becomes high. The resulting cured product will not be sufficiently sticky. The compound having an oxetane ring used in the present invention is preferably a compound having 1 to 4 oxetane rings.

  Hereinafter, although the specific example of the compound which has an oxetane ring based on this invention is demonstrated, this invention is not limited to these.

  An example of the compound having one oxetane ring is a compound represented by the following general formula (1).

In the general formula (1), R ¹ is a hydrogen atom, an alkyl group having 1 to 6 carbon atoms such as a methyl group, an ethyl group, a propyl group, or a butyl group, a fluoroalkyl group having 1 to 6 carbon atoms, an allyl group, or an aryl group. , Furyl group or thienyl group. R ² is an alkyl group having 1 to 6 carbon atoms such as methyl group, ethyl group, propyl group, butyl group, 1-propenyl group, 2-propenyl group, 2-methyl-1-propenyl group, 2-methyl- C2-C6 alkenyl group such as 2-propenyl group, 1-butenyl group, 2-butenyl group, 3-butenyl group, phenyl group, benzyl group, fluorobenzyl group, methoxybenzyl group, phenoxyethyl group, etc. A group having an aromatic ring, an alkylcarbonyl group having 2 to 6 carbon atoms such as an ethylcarbonyl group, a propylcarbonyl group, and a butylcarbonyl group, an alkylcarbonyl group having 2 to 6 carbon atoms such as an ethoxycarbonyl group, a propoxycarbonyl group, and a butoxycarbonyl group; Alkoxycarbonyl group, ethylcarbamoyl group, propylcarbamoyl group, butylcarbamoyl group, pentylcarbamoyl Is N- alkylcarbamoyl group having a carbon number of 2-6 and the like. As the oxetane compound used in the present invention, it is particularly preferable to use a compound having one oxetane ring because the resulting composition has excellent tackiness, low viscosity and excellent workability.

  An example of a compound having two oxetane rings includes a compound represented by the following general formula (2).

In the general formula (2), R ¹ is the same group as that in the general formula (1). R ³ is, for example, a linear or branched alkylene group such as an ethylene group, a propylene group or a butylene group, a linear or branched poly (alkyleneoxy) such as a poly (ethyleneoxy) group or a poly (propyleneoxy) group. ) Group, propenylene group, methylpropenylene group, butenylene group or other linear or branched unsaturated hydrocarbon group, alkylene group containing carbonyl group or carbonyl group, alkylene group containing carboxyl group, alkylene containing carbamoyl group Group.

Moreover, as R < ³ >, the polyvalent group selected from the group shown by the following general formula (3), (4) and (5) can also be mentioned.

In the general formula (3), R ⁴ represents a hydrogen atom, an alkyl group having 1 to 4 carbon atoms such as a methyl group, an ethyl group, a propyl group, or a butyl group, a methoxy group, an ethoxy group, a propoxy group, or a butoxy group. An alkoxy group having 1 to 4 carbon atoms, a halogen atom such as a chlorine atom or a bromine atom, a nitro group, a cyano group, a mercapto group, a lower alkoxycarbonyl group, a carboxyl group, or a carbamoyl group.

In the general formula (4), R ⁵ represents an oxygen atom, a sulfur atom, a methylene group, NH, SO, SO ₂ , C (CF ₃ ) ₂ , or C (CH ₃ ) ₂ .

In General formula (5), R < ⁶ > is a C1-C4 alkyl group, such as a methyl group, an ethyl group, a propyl group, a butyl group, or an aryl group. n is an integer of 0-2000. R ⁷ is a methyl group, an ethyl group, a propyl group, a butyl group having 1 to 4 carbon atoms, or an aryl group. R ⁷ may further include a group selected from the group represented by the following general formula (6).

In General formula (6), R < ⁸ > is a C1-C4 alkyl group, such as a methyl group, an ethyl group, a propyl group, a butyl group, or an aryl group. m is an integer of 0-100.

  Specific examples of the compound having two oxetane rings include the following compounds.

Illustrative compound 1 is a compound in which R ¹ is an ethyl group and R ³ is a carboxyl group in the general formula (2). Exemplary compound 2 is a compound in which, in the general formula (2), R ¹ is an ethyl group, R ³ is the general formula (5), R ⁶ and R ⁷ are methyl groups, and n is 1.

Among the compounds having two oxetane rings, preferred examples other than the above compounds include compounds represented by the following general formula (7). In general formula (7), R ¹ has the same meaning as R ¹ in the general formula (1).

  An example of a compound having 3 to 4 oxetane rings is a compound represented by the following general formula (8).

In the general formula (8), R ¹ is the same meaning as R ¹ in the general formula (1). As R ⁹ , for example, a branched alkylene group having 1 to 12 carbon atoms such as groups represented by the following A to C, a branched poly (alkyleneoxy) group such as a group represented by the following D, or the following E And branched polysiloxy groups such as those shown. j is 3 or 4.

In A above, R ¹⁰ is a lower alkyl group such as a methyl group, an ethyl group or a propyl group. Moreover, in said D, p is an integer of 1-10.

  Illustrative compound 3 is an example of a compound having 3 to 4 oxetane rings.

  Furthermore, examples of the compound having 1 to 4 oxetane rings other than those described above include compounds represented by the following general formula (9).

In the general formula (9), R ⁸ has the same meaning as R ⁸ in the general formula (6). R ¹¹ 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.

  Preferable specific examples of the oxetane compound used in the present invention include the following compounds.

  The production method of each compound having an oxetane ring described above is not particularly limited, and may be a conventionally known method, for example, Pattisson (DB Pattison, J. Am. Chem. Soc., 3455, 79). (1957)) discloses a method for synthesizing an oxetane ring from a diol. In addition to these, compounds having 1 to 4 oxetane rings having a high molecular weight of about 1000 to 5000 are also included. Examples of these specific compounds include the following compounds.

  The content of the cationically polymerizable oxetane compound in the whole cationically polymerizable composition is preferably 1 to 100% by mass, more preferably 30 to 95% by mass.

  As the cationic polymerization initiator used in the present invention, for example, a chemical amplification type photoresist or a compound used for photocationic polymerization is used (edited by Organic Electronics Materials Research Group, “Organic Materials for Imaging”, Bunshin Publishing (1993). Year), pages 187-192). Examples of compounds suitable for the present invention are listed below.

First, B (C ₆ F ₅ ) ₄ ⁻ , PF ₆ ⁻ , AsF ₆ ⁻ , SbF ₆ ⁻ , CF ₃ SO ₃ ⁻ salt of aromatic onium compounds such as diazonium, ammonium, iodonium, sulfonium, phosphonium, etc. be able to.

  Specific examples of onium compounds that can be used in the present invention are shown below.

  Secondly, sulfonated substances that generate sulfonic acid can be mentioned, and specific compounds thereof are exemplified below.

  Thirdly, halides that generate hydrogen halide can also be used, and specific compounds thereof are exemplified below.

  Fourthly, an iron allene complex can be mentioned.

  It is preferable to contain the said photocationic polymerization initiator in the ratio of 0.1-20 mass% with respect to an oxetane compound, More preferably, it is 0.1-10 mass%.

  Moreover, when it contains the compound which has the above-mentioned epoxy group or vinyl ether group, it is 0.1-20 mass% with respect to the total amount of an oxetane compound, a compound which has an epoxy group, or a compound which has a vinyl ether group. It is preferable to contain in the ratio, More preferably, it is 0.1-10 mass%. When the cationic polymerization initiator is less than 0.1% by mass, the curability is not sufficient. On the other hand, when it exceeds 20% by mass, the light transmittance becomes poor and uniform curing cannot be performed. The smoothness of the coating surface may be lost.

  In addition, the ink composition according to the present invention is cured by irradiation with ultraviolet rays, but a photosensitizer may be used in combination in order to perform the curing reaction more efficiently. Examples of such a photosensitizer include triethanolamine, methyldiethanolamine, triisopropanolamine, methyl 4-dimethylaminobenzoate, ethyl 4-dimethylaminobenzoate, isoamyl 4-dimethylaminobenzoate, benzoic acid ( 2-dimethylamino) ethyl, 4-dimethylaminobenzoic acid (n-butoxy) ethyl, amines such as 4-dimethylaminobenzoic acid 2-ethylhexyl, cyanine, phthalocyanine, merocyanine, porphyrin, spiro compound, ferrocene, fluorene, fulgide Imidazole, perylene, phenazine, phenothiazine, polyene, azo compound, diphenylmethane, triphenylmethane, polymethine acridine, coumarin, ketocoumarin, quinacridone, indigo, styryl, pyriri Compounds, pyromethene compounds, pyrazolotriazole compounds, benzothiazole compounds, barbituric acid derivatives, thiobarbituric acid derivatives, and the like, and further, European Patent No. 568,993, US Patent No. 4,508,811, The compounds described in JP-A-5,227,227, JP-A-2001-125255, JP-A-11-271969 and the like can also be used. The usage-amount of a photosensitizer has the preferable range of 0.01-10.00 mass% in actinic-light curable composition.

  In the ink according to the present invention, various additives other than those described above can be used. For example, leveling additives, matting agents, polyester resins for adjusting film properties, polyurethane resins, vinyl resins, acrylic resins, rubber resins, and waxes can be added. In addition, known basic compounds can be used for the purpose of improving storage stability, but typical examples include basic organic compounds such as basic alkali metal compounds, basic alkaline earth metal compounds, and amines. Etc. It is also possible to combine a radically polymerizable monomer and an initiator into a radical / cation hybrid type curable ink.

  As a base material that can be used in the ink jet recording method of the present invention, various non-absorbable plastics and films used for so-called soft packaging can be used in addition to ordinary uncoated paper, coated paper, and the like. Examples of the plastic film include polyethylene terephthalate (PET) film, stretched polystyrene (OPS) film, stretched polypropylene (OPP) film, stretched nylon (ONy) film, polyvinyl chloride (PVC) film, polyethylene (PE) film, An acetyl cellulose (TAC) film etc. can be mentioned. As other plastics, polycarbonate, acrylic resin, ABS, polyacetal, polyvinyl alcohol (PVA), rubbers and the like can be used. Moreover, it is applicable also to metals and glass. Among these substrates, the structure of the present invention is effective particularly when an image is formed on a PET film, an OPS film, an OPP film, an ONy film, or a PVC film that can be shrunk by heat. These substrates are not only susceptible to curling and deformation of the film due to ink curing shrinkage and heat generation during the curing reaction, but also the ink film is difficult to follow the substrate shrinkage.

  The surface energies of these various plastic films differ greatly, and it has been a problem in the past that the dot diameter after ink landing varies depending on the substrate. With the configuration of the present invention, good high-definition images can be formed with a wide range of recording materials with a surface energy of 35 to 60 mN / m, including OPP films with low surface energy, OPS films, and PET with relatively high surface energy. it can.

  Next, an image forming method that can be used in the present invention will be described.

  In the image forming method according to the present invention, as described above, the above ink is ejected and drawn on a substrate by an ink jet recording method, and then within 1.0 second, 0.05 second or more, 5.0 In this method, the ink is cured by irradiating with an actinic ray such as ultraviolet rays, which takes a time of less than a second. When irradiation is started after elapse of 1.0 second or more, the characters are crushed and the turbidity becomes conspicuous at the boundary line where the two colors overlap.

Further, the active ray emitted from the light source unit for ink curing, the illuminance in the substrate (recording medium) surface may be used any light source capable of irradiating in a range of 0.1mW / cm ² ~500mW / cm ² but faster curing in the cationically polymerizable ink according to the present invention, preferred because it is possible to use a relatively low intensity of ^{0.1mW / cm 2 ~50mW / cm 2} .

  In the present invention, the total ink film thickness after the ink has landed on the substrate and cured by irradiation with actinic rays is preferably 2 to 20 μm. In the actinic ray curable ink jet recording in the screen printing field, the total ink film thickness currently exceeds 20 μm, but in the flexible packaging printing field where the base material is often a thin plastic material, the above-mentioned base material is used. In addition to the problem of curling and wrinkles, there is a problem in that the entire printed material is changed in its strain and texture.

  Here, the “total ink film thickness” means the maximum value of the film thickness of the ink drawn on the base material, and even for a single color, other two-color superposition (secondary color), three-color superposition, four colors Even when recording is performed by an ink jet recording method such as superposition, the meaning of the total ink film thickness is the same.

  As the ink discharge conditions, it is preferable from the viewpoint of discharge stability that the ink jet recording head and the ink are heated to 35 to 100 ° C. and discharged. Actinic ray curable ink has a large viscosity fluctuation range due to temperature fluctuation, and the viscosity fluctuation directly affects the droplet size and droplet ejection speed, causing image quality degradation. It is necessary to keep on. The control range of the ink temperature is set temperature ± 5 ° C., preferably set temperature ± 2 ° C., more preferably set temperature ± 1 ° C.

  In the present invention, it is preferable that the minimum amount of droplets discharged from each nozzle is 2 to 15 pl. Originally, in order to form a high-definition image, it is necessary for the amount of droplets to be within this range, but when discharging with this amount of droplets, the above-described discharge stability becomes particularly severe.

  A basic method of actinic ray irradiation is disclosed in JP-A-60-132767. According to this, the light source is provided on both sides of the head unit, and the head and the light source are scanned by the shuttle method. Irradiation is performed after a certain period of time after ink landing. Further, the curing is completed by another light source that is not driven. In US Pat. No. 6,145,979, as an irradiation method, a method using an optical fiber or a method of applying a collimated light source to a mirror surface provided on the side of the head unit and irradiating the recording unit with UV light is disclosed. Yes. Any of these irradiation methods can be used in the image forming method according to the present invention.

  Next, an ink jet recording apparatus (hereinafter simply referred to as a recording apparatus) that can be used in the present invention will be described.

  Hereinafter, a recording apparatus according to the present invention will be described with reference to the drawings as appropriate. Note that the recording apparatus in the drawings is only one aspect of the recording apparatus that can be preferably used in the present invention, and the present invention is not limited to the drawing of the recording apparatus exemplified here.

  FIG. 1 is a front view showing an example of a configuration of a main part used in a serial printing method in an ink jet recording apparatus that can be used in the present invention. The recording apparatus 1 includes a head carriage 2, a recording head 3, an irradiation unit 4, a platen unit 5, and the like. In the recording apparatus 1, the platen unit 5 is installed under the base material P. The platen unit 5 has a function of absorbing ultraviolet rays, and absorbs excess ultraviolet rays that have passed through the substrate P. As a result, a high-definition image can be reproduced very stably.

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

  The head carriage 2 is installed on the upper side of the substrate P, and stores a plurality of recording heads 3 to be described later according to the number of colors used for image printing on the substrate P, with the discharge ports arranged on the lower side. The head carriage 2 is installed with respect to the main body of the recording apparatus 1 in such a manner that it can reciprocate in the Y direction in FIG. 1, and reciprocates in the Y direction in FIG. 1 by driving the head scanning means.

  In FIG. 1, the head carriage 2 is illustrated as accommodating the recording heads 3 of yellow (Y), magenta (M), cyan (C), and black (K). The number of colors of the recording head 3 housed in the head carriage 2 can be determined as appropriate.

  The recording head 3 is operated by a discharge means (not shown) provided with a plurality of actinic ray curable inks (for example, UV curable ink) supplied by an ink supply means (not shown). It discharges toward the base material P from a discharge outlet. The UV ink ejected by the recording head 3 is composed of a coloring material, a polymerizable monomer, an initiator, and the like, and the monomer crosslinks when the initiator acts as a catalyst when irradiated with ultraviolet rays. It has the property of being cured by a polymerization reaction.

  The recording head 3 has a certain region (landing possible region) on the substrate P during scanning of moving from one end of the substrate P to the other end of the substrate P in the Y direction in FIG. ), UV ink is ejected as ink droplets, and ink droplets are landed on the landable area.

  The above scanning is performed as many times as necessary, and after UV ink is ejected toward one landable area, the substrate P is appropriately moved from the front to the back in FIG. 1 by the conveying means, and scanning by the head scanning means is performed again. 1, the recording head 3 discharges UV ink to the next landable area adjacent in the depth direction in FIG.

  By repeating the above-described operation and discharging the UV ink from the recording head 3 in conjunction with the head scanning unit and the conveying unit, an image composed of an aggregate of UV ink droplets is formed on the substrate P.

  The irradiation unit 4 includes an ultraviolet lamp that emits ultraviolet light in a specific wavelength region with stable exposure energy and a filter that transmits ultraviolet light of a specific wavelength. Here, as the ultraviolet lamp, a mercury lamp, a metal halide lamp, an excimer laser, an ultraviolet laser, a hot cathode tube, a cold cathode tube, a black light, an LED (light emitting diode), etc. can be applied. Cathode tubes, mercury lamps or black lights are preferred.

  The irradiating means 4 has substantially the same shape as the maximum one that can be set by the recording apparatus (UV inkjet printer) 1 among the landable areas in which the recording head 3 ejects UV ink by one scan driven by the head scanning means. , Having a shape larger than the landable area.

  The irradiating means 4 is fixed on both sides of the head carriage 2 so as to be substantially parallel to the substrate P.

  As described above, as means for adjusting the illuminance of the ink discharge portion, not only the entire recording head 3 is shielded, but in addition, the ink discharge of the recording head 3 is determined from the distance h1 between the irradiation means 4 and the substrate P. It is effective to increase the distance h2 between the portion 31 and the substrate P (h1 <h2), or to increase the distance d between the recording head 3 and the irradiation means 4 (d is increased). Further, it is more preferable to provide a bellows structure 7 between the recording head 3 and the irradiation means 4.

  Here, the wavelength of the ultraviolet rays irradiated by the irradiation means 4 can be changed as appropriate by replacing the ultraviolet lamp or filter provided in the irradiation means 4.

  As described above, in FIG. 1, the serial printing method has been described as an example, but in addition, an ink jet recording apparatus of each ink jet printing method as shown in FIG. 2 can be used.

  In FIG. 2, a) in FIG. 2 is a method (line head method) in which the recording head 19 is arranged in the width direction of the substrate 20 and actinic rays are irradiated from the printing and irradiation means 24 while conveying the recording medium. 2b is a method (flat head method) in which the recording head 19 performs printing while moving in the sub-scanning direction, and further irradiates actinic rays from the irradiating means 24 (c) in FIG. This is a method (serial printing method) in which the recording head 24 described performs printing while scanning in the width direction on the base material, and further irradiates actinic rays from the irradiation means 24 provided at both ends. it can.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated concretely, this invention is not limited to these examples.

Example 1
<Preparation of ink>
A cationically polymerizable ink 1 having the following constitution was prepared.

Oil-soluble dye (a-21) 4 parts Cationic polymerizable compound (Aron Oxetane OXT-221 manufactured by Toagosei Co., Ltd.) 70 parts Cationic polymerizable compound (made by Vikoflex 9040 ATOFINA) 30 parts Cationic polymerization initiator (manufactured by UVI6992 Dow Chemical) 8 parts In addition, the oil-soluble dye (a-21) C.I. I. In place of Pigment Blue 15: 4, a cationic polymerizable compound and a cationic polymerization initiator are combined with a radical polymerizable compound and a radical polymerization initiator (that is, a cationic polymerizable compound (Alonoxetane) with the oil-soluble dye and the pigment. OXT-221) is a radical polymerizable compound (PO-A: manufactured by Kyoei Chemical Co., Ltd.), and a cationic polymerizable compound (Vikoflex 9040) is a radical polymerizable compound (KAYARAD DPCA30: caprolactam-modified dipentaerythritol hexaacrylate manufactured by Nippon Kayaku Co., Ltd. In addition, the cationic polymerization initiator (UVI6992) was replaced with a radical polymerization initiator (Irgacure-819: 2-methyl-1 [4- (methylthio) phenyl] -2-morpholinopropan-1-one Ci Inks 2 to 4 were prepared as shown in Table 1 instead of (made by ba).

  In the case of a radical polymerizable compound, 0.12 part of Ajisper PB822 Ajinomoto Finetech was added as a dispersant.

<< Inkjet image formation >>
(Inkjet recording device)
A serial type ink jet recording apparatus having the structure shown in FIG. 1 is used, and the above-prepared cationic polymerizable inks 1 and 2 and radical polymerizable inks 3 and 4 are loaded, respectively. An image sample containing the image was printed.

The irradiation means of the ultraviolet, a high pressure mercury lamp Vzero 085 (Integration Technology Inc.) illuminance 400 mW / cm ² using, or a hot cathode tube (manufactured by Nippo) so as to be 40 mW / cm ² using (according to Table 1 ) The output voltage was adjusted as appropriate, and the following four types (also shown in Table 2) were used as the base materials. The timing from the ink landing on the substrate to the ultraviolet irradiation is 0.2 seconds for the ink ejected from the nozzle close to the light source, 0.5 seconds for the ink ejected from the distant nozzle, that is, 0.2 second to 0. The distance between the light source (irradiation means) and the recording head (the d) and the carriage speed were adjusted so as to be in the range of 5 seconds.

OPP: OPP film Toray: Trefan Thickness 100μm
PET: Polyethylene terephthalate film Thickness 100 μm
PVC: Polyvinyl chloride film Thickness 100μm
Art paper; manufactured by Mitsubishi Paper Industries, Tokuhishi Art (basis weight 127.9 g / m ² )
The recording head was equipped with a piezo-type inkjet nozzle capable of emitting different ink droplet sizes within a nozzle pitch range of 360 dpi and 4 to 24 pl, and printing was performed under the condition that the ink droplet size was 8 pl. Further, the ink supply unit, the ink flow path, and the ink jet nozzle can be heated up to 55 ° C. by a heater. In addition, dpi as used in the field of this invention represents the number of dots per 2.54 cm.

(Evaluation of adhesion)
A solid image on the substrate when the solid image (reflection density 1.5) formed above is cut with a cutter in a grid pattern, an adhesive tape is attached to the surface, and then the adhesive tape is peeled off The remaining state was visually observed, and the adhesion was evaluated according to the following criteria.

○: No change in image due to tape peeling △: Some images are missing due to tape peeling ×: Most images are missing due to tape peeling Each result obtained above It is shown in 2.

  When used as a photocurable ink, the cationic polymerizable ink (ink 1) according to the present invention had better adhesion than the radical polymerizable ink (inks 3 and 4). Further, although it is the same cationically polymerizable, the ink 1 is excellent in adhesion as compared with the ink 2 which is an ink using a pigment, and the color shift in each direction when bidirectional printing is small is preferable. It was color reproduction. Moreover, when the irradiation light source 1 was used, about what used OPP as the base material, a slight wrinkle generate | occur | produced in the boundary of an image part and a non-image part.

  In the same manner, however, the 4-point characters were noticeably crushed in each recording material when ultraviolet irradiation was performed for 1.5 seconds to 2.0 seconds after ink landing.

(Evaluation of ink storage stability)
<< Preparation of preservation sample >>
The ink prepared as described above was placed in an LDPE (low density polyethylene) container in an environment of 0.09% absolute humidity and a temperature of 23 ° C., and sealed with a lid made of the same material to prepare a sample. .

In addition, the moisture permeability of LDPE used for sample preparation was 19 g / m < ² > * 24hr (40 degreeC * 90% RH) in 25 micrometers in thickness as a result of measuring by the method prescribed | regulated to JISZ0208. The water content of the ink was 0.16%.

<Evaluation of stored sample>
The above-prepared sample was stored at a high temperature and low humidity for 7 days in an environment of 60 ° C. and 20% relative humidity, and the viscosity difference was measured for each ink immediately after being put in a storage container and after 7 days of storage. The results are shown in Table 2.

The viscosity was measured using a vibration viscometer (VISCOMATE VM-1G-MH, manufactured by YAMAICHI.CO.LTD) at 25 ° C. and a share rate of 1000 sec ⁻¹ . The water content was determined by the Karl Fischer method.

  The results for ink storability are shown in Table 3.

  The ink of the present invention has little change in viscosity and good storage stability.

It is a front view which shows an example of a structure of the principal part used with a serial printing system with the inkjet recording device which can be used by this invention. It is the schematic which shows the example of the inkjet printing system which can be used by this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Recording device 2 Head carriage 3, 19 Recording head 4, 24 Irradiation means 5 Platen part 6 Guide member 7 Bellows structure P, 20 Base material

Claims (5)

An actinic ray curable ink comprising a cationic polymerizable compound, a cationic photopolymerization initiator, and a color material, wherein the color material is an oil-soluble dye. 2. The actinic ray curable ink according to claim 1, wherein the cationic polymerizable compound is at least one compound selected from an alicyclic epoxy compound, an oxetane compound, and a vinyl ether compound. The actinic ray curable ink according to claim 1, wherein the oil-soluble dye is represented by the general formula (I).

(In the formula, Q represents an atomic group necessary for the compound represented by the general formula (I) to absorb light in the visible region or near infrared region, A represents —NR ⁵ R ⁶ or a hydroxyl group, R ⁵ and R ⁶ each independently represents a hydrogen atom, an alkyl group, an aryl group or a heterocyclic group, B ¹ represents ═C (R ³ ) — or ═N—, and B ² represents —C (R ⁴ ). R ¹ , R ² , R ³ and R ⁴ each independently represents a hydrogen atom or a substituent, R ¹ and R ² , R ¹ and R ⁵ , R ⁵ and R ⁶ , R ³ and R ⁵ and R ³ and R ⁴ may be bonded to each other to form a ring.) 4. An ink jet printer having an ink ejection unit that ejects ink onto a recording medium, a transport unit for transporting the recording medium, and a light source unit for curing ink after ink landing. An ink jet printer using the actinic ray curable ink described. The image forming method for forming an image with the ink jet printer according to claim 4 using the actinic ray curable ink according to any one of claims 1 to 3, wherein the light irradiated from the light source unit for ink curing, the ink jet recording method, wherein the illuminance on the recording medium surface is ^{0.1mW / cm 2 ~50mW / cm 2} .

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