JP2007084637A - Active ray curable ink for inkjet, inkjet recording device, and method for forming image - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an active ray curable ink for inkjet providing a cured film excellent in flexibility free from causing troubles such as cracks, etc., in printing on various recording materials by inkjet printing method using the ink being cured by irradiating with an active ray, and to provide a method for forming an inkjet image and an inkjet recording device. <P>SOLUTION: The active ray curable ink for inkjet comprises a photopolymerizing compound, a photopolymerization initiator and a pigment, wherein the photopolymerizing compound is an epoxy compound with two or more functional groups and having a connecting group with a structure represented by general formula (1): -(R-O-)<SB>n</SB>-. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an actinic ray curable inkjet ink excellent in flexibility after curing, an image forming method using the same, and an inkjet recording apparatus.

  In recent years, the inkjet recording method can be easily and inexpensively produced images, and thus has been applied to various printing fields such as photographs, various printing, marking, and special printing such as color filters. In particular, a recording device that emits and controls fine dots, ink that has improved color reproduction gamut, durability, and emission suitability, and ink absorbability, coloring material color development, surface gloss, etc. have been dramatically improved. It is also possible to obtain image quality comparable to silver halide photography using special paper. The image quality improvement of today's ink jet recording system is achieved only when all of the recording apparatus, ink, and special paper are available.

  However, in an inkjet system that requires dedicated paper, the recording medium is limited, and the cost of the recording medium increases. Therefore, many attempts have been made to record on a transfer medium different from dedicated paper by an ink jet method. Specifically, a phase change inkjet method using a solid wax ink at room temperature, a solvent-based inkjet method using an ink mainly composed of a fast-drying organic solvent, and an activity of crosslinking by ultraviolet (UV) light or an electron beam after recording. For example, a light-curing inkjet method.

  Among these, the UV inkjet method has been attracting attention in recent years because it has a relatively low odor compared to the solvent-based inkjet method, and can be recorded on a recording medium having no quick drying and no ink absorption. No. 200204 and JP 2000-504778 A disclose an ultraviolet curable inkjet ink.

In ultraviolet curable ink-jet inks, for example, an ink using a cationic polymerizable compound has characteristics that it is superior in safety and does not receive an oxygen inhibiting action as compared with an ink using a radical polymerizable compound. (For example, see Patent Documents 1 to 3) However, the adhesion of the cured film to the substrate, the hardness of the film, and the flexibility are still insufficient. In particular, when printing is performed on a flexible substrate, there are problems such as failure to follow and cracking.
JP 2001-220526 A (Claims, Examples) JP 2002-188025 A (claims, examples) JP-A-2002-317139 (Claims, Examples)

  The present invention has been made in view of the above-mentioned problems, and the object of the present invention is that the cured film has good flexibility even when ink that is cured by actinic rays is printed on various recording materials by an inkjet recording method. An object of the present invention is to provide an actinic ray curable inkjet ink, an inkjet image forming method, and an inkjet recording apparatus that do not cause problems such as cracks.

  The above object of the present invention can be achieved by the following constitution.

  (1) In the actinic ray curable inkjet ink containing a photopolymerizable compound, a photopolymerization initiator, and a pigment, the photopolymerizable compound has a linking group having a structure represented by the following general formula (1) An actinic ray curable inkjet ink comprising a functional or higher epoxy compound.

General formula (1)
-(-R-O-) _n-
(In the formula, n represents an integer of 2 or more, and R represents an alkylene group which may have a substituent having 1 to 15 carbon atoms, or an aliphatic cyclic group which may have a substituent having 6 to 17 carbon atoms. Represents a hydrocarbon group.)
(2) About the bifunctional or more functional epoxy compound having a linking group having the structure represented by the general formula (1), n represents an integer of 2 to 5, and the activity described in the above item (1) Light curable inkjet ink.

  (3) About the bifunctional or more functional epoxy compound which has a coupling group which has a structure represented by the said General formula (1), R represents the alkylene group which may have a C1-C15 substituent. The actinic ray curable inkjet ink as described in (1) or (2) above,

  (4) Any one of the above (1) to (3), which contains a bifunctional or higher functional epoxy compound other than the bifunctional epoxy compound having a linking group having a structure represented by the general formula (1) The actinic ray curable inkjet ink according to claim 1.

  (5) The actinic ray curable inkjet ink described in any one of (1) to (4) above, which contains an oxetane compound.

  (6) The actinic ray curable inkjet ink described in any one of (1) to (5) above, which contains a monofunctional epoxy compound.

  (7) The actinic ray curable inkjet ink as described in any one of (1) to (6) above, which contains an alicyclic epoxy compound as an epoxy compound.

  (8) Any one of (1) to (7) above, containing 5 to 30% by mass of a bifunctional or higher functional epoxy compound having a linking group having a structure represented by the general formula (1) 2. The actinic ray curable inkjet ink according to item 1.

  (9) The actinic ray curable inkjet ink according to any one of (1) to (8), wherein the actinic ray curable inkjet ink has a viscosity at 25 ° C. of 10 to 70 mPa · s.

  (10) An image forming method in which the actinic radiation curable inkjet ink according to any one of (1) to (9) is ejected from a inkjet recording head onto a recording material and printing is performed on the recording material. An image forming method comprising irradiating a lamp within 0.001 to 2.0 seconds after the actinic ray curable inkjet ink has landed.

  (11) An image forming method in which the actinic radiation curable inkjet ink according to any one of (1) to (9) is ejected from a inkjet recording head onto a recording material and printing is performed on the recording material. A total ink film thickness after the actinic ray curable inkjet ink has landed and cured by irradiation with a lamp is 2 to 20 μm.

  (12) An image forming method in which the actinic radiation curable inkjet ink according to any one of (1) to (9) is ejected from a inkjet recording head onto a recording material and printing is performed on the recording material. An image forming method, wherein the amount of ink droplets ejected from each nozzle of the recording head is 1 to 15 pl.

  (13) An actinic ray curable inkjet ink according to any one of (1) to (9) and an inkjet recording apparatus, wherein the recording head is heated to 35 to 100 ° C. and then discharged.

  (14) The actinic ray curable inkjet according to any one of (1) to (9), wherein the inkjet recording apparatus is used in the image forming method according to any one of (10) to (12). An ink jet recording apparatus, wherein the ink and the recording head are heated to 35 to 100 ° C. and then discharged.

  According to the present invention, an actinic ray curable inkjet ink having good flexibility of a cured film and causing no problems such as cracking even when an ink curable by actinic rays is printed on various recording materials by an inkjet recording method, An inkjet image forming method and an inkjet recording apparatus can be provided.

  Hereinafter, although the best mode for carrying out the present invention will be described, the present invention is not limited to these.

  Hereinafter, the present invention will be described in detail.

  The ink used in the present invention will be described.

  The ink used in the present invention comprises at least a photopolymerizable compound, a photopolymerization initiator, and a pigment.

  The actinic ray curable inkjet ink of the present invention contains a bifunctional or higher functional epoxy compound having a linking group having a structure represented by the general formula (1) as a photopolymerizable compound. In the present invention, a bifunctional or higher functional epoxy compound and a bifunctional to tetrafunctional epoxy compound are preferable because the viscosity of the ink does not become too high.

  The content of the bifunctional or higher epoxy compound is preferably 5 to 30% by mass. If it is less than 5% by mass, the intended effect is small, and if it exceeds 30% by mass, the curability of the ink is lowered. Preferably it contains 5-20 mass%.

  In the bifunctional or higher functional epoxy compound having a linking group having the structure represented by the general formula (1), R is preferably a C2-C4 alkylene group, more preferably R is an ethyl group or a propyl group. And n is an integer of 2 or more. n is preferably an integer of 2 to 5. When n is smaller than 2, the effect of the present invention may be reduced. On the other hand, if it exceeds 5, the curability of the ink may decrease.

  Specific examples of the bifunctional or higher functional epoxy compound having a linking group having a structure represented by the general formula (1) include, but are not limited to, the following.

  The production method of the epoxy compound of the present invention is not limited. For example, Maruzen KK Publishing, 4th edition Experimental Chemistry Course 20 Organic Synthesis II, 213, 1992, Ed. By Alfred Hasfner, The Chemistry of Heterocyclic compounds, Vol. 30, Advertisement, Small Ring Heterocycle part3 Oxilane, John & Wiley and Sons, An Inc No. 5, 42, 1986, Yoshimura, Adhesion, Vol. 30, No. 7, 42, 1986, Japanese Patent Application Laid-Open No. 11-100388, Japanese Patent Application No. 2-140732, Japanese Patent Application No. 2-182124, Japanese Patent Application Laid-Open No. 2004-262874. It can synthesize | combine with reference to literatures.

  The actinic ray curable inkjet ink of the present invention contains a compound (hereinafter referred to as a photoacid generator) that generates an acid upon irradiation with actinic rays as a photopolymerization initiator.

  Specific examples of the photoacid generator according to the present invention include, for example, chemically amplified photoresists and compounds used for photocationic polymerization (edited by Organic Electronics Materials Research Group, “Organic Materials for Imaging”, Bunshin Publishing ( 1993), 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 ⁻ , p-CH ₃ C ₆ H ₄ of aromatic onium compounds such as diazonium, ammonium, iodonium, sulfonium, and phosphonium. SO ₃ ^- salt, CF ₃ SO ₃ ^- and sulfonic acid salts such as salts.

Those having a borate compound as a counter anion and PF ₆ ^- salt acid generation capability higher preferred. Specific examples of the onium compound are shown below.

  Secondly, sulfonated products that generate sulfonic acid can be mentioned. Specific compounds are exemplified below.

  Thirdly, a halide that generates hydrogen halide can also be used. Specific compounds are exemplified below.

  Fourthly, an iron allene complex can be mentioned.

  Examples of the photoacid generator used in the present invention include arylsulfonium salt derivatives (for example, Cyracure UVI-6990, Cyracure UVI-6974 manufactured by Union Carbide, Adekaoptomer SP-150 manufactured by Asahi Denka Kogyo Co., Ltd., and Adekatop. Mer SP-152, Adekaoptomer SP-170, Adekaoptomer SP-172), allyl iodonium salt derivatives (for example, RP-2074 manufactured by Rhodia), allene-ion complex derivatives (for example, Irgacure 261 manufactured by Ciba Geigy) ), Acid generators such as diazonium salt derivatives, triazine initiators and other halides. It is preferable to contain a photo-acid generator in the ratio of 0.2-20 mass parts with respect to 100 mass parts of compounds which have cationic polymerizability. When the content of the photoacid generator is less than 0.2 parts by mass, it is difficult to obtain a cured product, and even if the content exceeds 20 parts by mass, there is no further effect of improving curability. These photoacid generators can be used alone or in combination of two or more.

  A more preferable structure of the sulfonium salt compound includes a sulfonium salt represented by the following general formula (I-1).

In the general formula _{(I-1), R 11} , R 12, R 13 represents a substituent, m, n, p is an integer of 0 to 2. X ₁₁ ⁻ represents a counter ion.

Furthermore, the sulfonium salt represented by the general formula (I-1) will be described. In the general formula (I-1), R ₁₁ , R ₁₂ and R ₁₃ each represent a substituent. Examples of the substituent include a halogen atom (for example, chlorine atom, bromine atom, fluorine atom, etc.), an alkyl group having 1 to 6 carbon atoms (for example, methyl group, ethyl group, propyl group, isopropyl group, butyl group, etc.) ), A cycloalkyl group having 3 to 6 carbon atoms (for example, cyclopropyl group, cyclobutyl group, cyclopentyl group, cyclohexyl group, etc.), an alkenyl group having 1 to 6 carbon atoms (for example, vinyl group, 1-propenyl group, 2-propenyl group, 2-butenyl group, etc.), C1-C6 alkynyl group (for example, acetylenyl group, 1-propynyl group, 2-propynyl group, 2-butynyl group, etc.), C1-6 Alkoxy groups (for example, methoxy group, ethoxy group, n-propoxy group, iso-propoxy group, n-butoxy group, tert-butoxy group, etc.), having 1 to 6 carbon atoms Alkylthio group (for example, methylthio group, ethylthio group, n-propylthio group, iso-propylthio group, n-butylthio group, tert-butylthio group, etc.), aryl group having 6 to 14 carbon atoms (for example, phenyl group, naphthyl group, Anthracenyl group etc.), C6-C10 aryloxy groups (e.g. phenoxy group, naphthoxy group etc.), C6-C10 arylthio groups (e.g. phenylthio group, naphthylthio group etc.), acyl groups (e.g. acetyl) Group, propionyl group, trifluoroacetyl group, benzoyl group, etc.), acyloxy group (eg, acetoxy group, propionyloxy group, trifluoroacetoxy group, benzoyloxy group, etc.), alkoxycarbonyl group (eg, methoxycarbonyl group, ethoxycarbonyl) Group, tert-butoxy Carbonyl group and the like), hetero atom-containing aromatic Hajime Tamaki having 4 to 8 carbon atoms (e.g., furyl group, a thienyl group, etc.), a nitro group, a cyano group, and the like.

Preferred examples of the substituent include a halogen atom, an alkyl group, an alkyloxy group, an aryl group, an aryloxy group, an arylthio group, and an acyl group. Of these substituents, possible ones may be further substituted. m, n and p each represents an integer of 0 to 2, and each is preferably 1 or more. X ₁₁ ⁻ represents a counter anion. Counter anions include complex ions such as BF ₄ ⁻ , B (C ₆ F ₅ ) ₄ ⁻ , PF ₆ ⁻ , AsF ₆ ⁻ and SbF ₆ ⁻ , p-CH ₃ C ₆ H ₄ SO ₃ ⁻ and CF ₃ SO. ₃ ^- sulfonate ion and the like. As the counter anion, borate ion and PF ₆ ^- are preferable because of their high acid generation ability.

  Specific examples of the sulfonium salt according to the present invention are shown below, but the present invention is not limited thereto.

  The actinic ray curable ink of the present invention contains various known pigments.

  The pigments that can be preferably used in the present invention are listed below.

C. I. Pigment Yellow 1, 2, 3, 12, 13, 14, 16, 17, 73, 74, 75, 81, 83, 87, 93, 95, 97, 98, 109, 114, 120, 128, 129, 138, 150, 151, 154, 180, 185
C. I. Pigment Red 5, 7, 12, 22, 38, 48: 1, 48: 2, 48: 4, 49: 1, 53: 1, 57: 1, 63: 1, 101, 112, 122, 123, 144, 146, 168, 184, 185, 202
C. I. Pigment Violet 19, 23
C. I. Pigment Blue 1, 2, 3, 15: 1, 15: 2, 15: 3, 15: 4, 18, 22, 27, 29, 60
C. I. Pigment Green 7,36
C. I. Pigment White 6, 18, 21
C. I. Pigment Black 7
In the present invention, it is preferable to use white ink in order to improve the color concealment property on a transparent substrate such as a plastic film. In particular, it is preferable to use white ink in soft packaging printing and label printing.

  For the dispersion of the pigment, for example, a ball mill, sand mill, attritor, roll mill, agitator, Henschel mixer, colloid mill, ultrasonic homogenizer, pearl mill, wet jet mill, paint shaker, or the like can be used. Further, a dispersing agent can be added when dispersing the pigment. As the dispersant, a polymer dispersant is preferably used, and examples of the polymer dispersant include Avecia's Solsperse series and Ajinomoto Fine-Techno's Azisper PB series. 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 used using a solvent or a polymerizable compound, but the actinic ray curable ink used in the present invention is preferably solvent-free because it reacts and cures immediately after ink landing. If the solvent remains in the cured image, the solvent resistance deteriorates and the VOC of the remaining solvent arises. Therefore, it is preferable in view of dispersibility that the dispersion medium is not a solvent but a polymerizable compound, and among them, a monomer having the lowest viscosity is selected.

  The pigment is preferably dispersed so that the average particle diameter of the pigment particles is 0.08 to 0.5 μm, and the maximum particle diameter is 0.3 to 10 μm, preferably 0.3 to 3 μm. The selection of the dispersion medium, the dispersion conditions, and the filtration conditions are appropriately set. 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.

  In the ink according to the present invention, the pigment concentration is preferably 1 to 10% by mass of the whole ink.

  The actinic ray curable inkjet ink of the present invention may contain a bifunctional epoxy compound other than the bifunctional epoxy compound having a structure represented by the general formula (1) as a bonding group, or a monofunctional epoxy compound.

  Examples of the epoxy compound include the following aromatic epoxides, alicyclic epoxides, and aliphatic epoxides.

  Preferred as the 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 its alkylene oxide adducts, and novolak-type epoxy resins. Here, examples of the alkylene oxide include ethylene oxide and propylene oxide.

  As the alicyclic epoxide, cyclohexene oxide obtained by epoxidizing a compound having at least one cycloalkane ring such as cyclohexene or cyclopentene ring with a suitable oxidizing agent such as hydrogen peroxide or peracid. Or a cyclopentene oxide containing compound is preferable.

  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 Diglycidyl ethers of polyalkylene glycols such as diglycidyl ethers, polypropylene glycols or diglycidyl ethers of adducts thereof Tel 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.
In the actinic ray curable ink of the present invention, it is possible to use an alicyclic epoxy compound, including a bifunctional epoxy compound having a structure represented by the general formula (1) as a bonding group. It is preferable because safety such as the above is improved.

  The actinic ray curable ink-jet ink of the present invention preferably contains an oxetane compound (in the present specification, also referred to as an oxetane ring-containing compound or an oxetane compound, both of which represent synonymous compounds). The oxetane ring represents a cyclic 4-membered ether structure.

  In the present invention, an oxetane compound represented by the following general formula (3) is preferable.

In General formula (3), R < ₁ > -R < ₆ > represents a hydrogen atom or a substituent respectively. However, all of R _{1 to} R ₆ do not represent hydrogen atoms at the same time.

In the general formula (3), examples of the substituent represented by R _{1 to} R ₆ include an alkyl group (methyl group, ethyl group, propyl group, isopropyl group, tert-butyl group, pentyl group, hexyl group, octyl group). Group, dodecyl group, tridecyl group, tetradecyl group, pentadecyl group, cyclopentyl group, cyclohexyl group, etc.), alkenyl group (for example, vinyl group, 1-propenyl group, 2-propenyl group, 2-butenyl group, allyl group, etc.), Alkynyl group (for example, acetylenyl group, 1-propynyl group, 2-propynyl group, 2-butynyl group, propargyl group, etc.), alkoxy group (for example, methoxy group, ethoxy group, propyloxy group, pentyloxy group, hexyloxy group) , Octyloxy group, dodecyloxy group, cyclopentyloxy group, cyclohexyloxy Group), aromatic hydrocarbon group (eg phenyl group, naphthyl group, anthracenyl group etc.), heteroaromatic group (eg furyl group, thienyl group, pyridyl group, pyridazinyl group, pyrimidyl group, pyrazyl group, triazyl group). Imidazolyl group, pyrazolyl group, thiazolyl group, benzoimidazolyl group, benzoxazolyl group, quinazolyl group, phthalazyl group, pyrrolyl group, 2-quinolyl group, 1-isoquinylyl group, etc.), heterocyclic group (for example, pyrrolidyl group, imidazolidyl group) Group, morpholyl group, oxazolidyl group, 2-tetrahydrofuranyl group, 2-tetrahydrothienyl group, 2-tetrahydropyranyl group, 3-tetrahydropyranyl group, etc.), halogen atom (for example, chlorine atom, bromine atom, fluorine atom, etc.) ), Fluorinated hydrocarbon groups (eg, fluoromethyl group, trif A fluoromethyl group, a pentafluoroethyl group, a pentafluorophenyl group, and the like). R ₁ and R ₂ , R ₃ and R ₄ , R ₅ and R ₆ may be bonded to each other to form a divalent group and form a ring. Preferable substituents represented by R _{1 to} R ₆ are alkyl groups, alkoxy groups, acyloxy groups, alkoxycarbonyl groups, aromatic hydrocarbon groups, heteroaromatic groups, halogen atoms, and fluorinated hydrocarbon groups. is there. Particularly preferred are an alkyl group and an aromatic hydrocarbon group.

Each group represented by R _{1 to} R ₆ may further have a substituent.

Examples of groups that can be substituted for the substituents represented by R _{1 to} R ₆ include alkyl groups (methyl group, ethyl group, propyl group, isopropyl group, tert-butyl group, pentyl group, hexyl group, octyl group, dodecyl group). Group, tridecyl group, tetradecyl group, pentadecyl group, cyclopentyl group, cyclohexyl group, etc.), alkenyl group (for example, vinyl group, 1-propenyl group, 2-propenyl group, 2-butenyl group, allyl group, etc.), alkynyl group ( For example, acetylenyl group, 1-propynyl group, 2-propynyl group, 2-butynyl group, propargyl group, etc.), aromatic hydrocarbon group (for example, phenyl group, naphthyl group, anthracenyl group, etc.), heteroaromatic group (for example, , Furyl group, thienyl group, pyridyl group, pyridazinyl group, pyrimidyl group, pyrazyl group, triazyl group, imidazo Group, pyrazolyl group, thiazolyl group, benzimidazolyl group, benzoxazolyl group, quinazolyl group, phthalazyl group, pyrrolyl group, 2-quinolyl group, 1-isoquinylyl group, etc.), heterocyclic group (for example, pyrrolidyl group, imidazolidyl group) , Morpholyl group, oxazolidyl group, 2-tetrahydrofuranyl group, 2-tetrahydrothienyl group, 2-tetrahydropyranyl group, 3-tetrahydropyranyl group, etc.), alkoxy group (for example, methoxy group, ethoxy group, propyloxy group, Pentyloxy group, hexyloxy group, octyloxy group, dodecyloxy group, cyclopentyloxy group, cyclohexyloxy group, etc.), aryloxy group (eg, phenoxy group, naphthyloxy group, etc.), alkylthio group (eg, methylthio group, ethylthio group) Group, propyl Thio group, pentylthio group, hexylthio group, octylthio group, dodecylthio group, cyclopentylthio group, cyclohexylthio group, etc.), arylthio group (eg, phenylthio group, naphthylthio group, etc.), alkoxycarbonyl group (eg, methyloxycarbonyl group, ethyl group) Oxycarbonyl group, butyloxycarbonyl group, octyloxycarbonyl group, dodecyloxycarbonyl group, etc.), aryloxycarbonyl group (eg, phenyloxycarbonyl group, naphthyloxycarbonyl group, etc.), sulfamoyl group (eg, aminosulfonyl group, methyl) Aminosulfonyl group, dimethylaminosulfonyl group, butylaminosulfonyl group, hexylaminosulfonyl group, cyclohexylaminosulfonyl group, octylaminosulfonyl group, dode Ruaminosulfonyl group, phenylaminosulfonyl group, naphthylaminosulfonyl group, 2-pyridylaminosulfonyl group, etc.), acyl group (for example, acetyl group, ethylcarbonyl group, propylcarbonyl group, pentylcarbonyl group, cyclohexylcarbonyl group, octylcarbonyl group) 2-ethylhexylcarbonyl group, dodecylcarbonyl group, phenylcarbonyl group, naphthylcarbonyl group, pyridylcarbonyl group, etc.), acyloxy group (for example, acetyloxy group, ethylcarbonyloxy group, butylcarbonyloxy group, octylcarbonyloxy group, dodecyl) Carbonyloxy group, phenylcarbonyloxy group, etc.), amide group (for example, methylcarbonylamino group, ethylcarbonylamino group, dimethylcarbonylamino group, Pyrcarbonylamino group, pentylcarbonylamino group, cyclohexylcarbonylamino group, 2-ethylhexylcarbonylamino group, octylcarbonylamino group, dodecylcarbonylamino group, phenylcarbonylamino group, naphthylcarbonylamino group, etc.), carbamoyl group (for example, amino Carbonyl group, methylaminocarbonyl group, dimethylaminocarbonyl group, propylaminocarbonyl group, pentylaminocarbonyl group, cyclohexylaminocarbonyl group, octylaminocarbonyl group, 2-ethylhexylaminocarbonyl group, dodecylaminocarbonyl group, phenylaminocarbonyl group, Naphthylaminocarbonyl group, 2-pyridylaminocarbonyl group, etc.), ureido group (for example, methylureido group, ethylureido) Group, pentylureido group, cyclohexylureido group, octylureido group, dodecylureido group, phenylureido group, naphthylureido group, 2-pyridylaminoureido group, etc.), sulfinyl group (for example, methylsulfinyl group, ethylsulfinyl group, butylsulfinyl group) , Cyclohexylsulfinyl group, 2-ethylhexylsulfinyl group, dodecylsulfinyl group, phenylsulfinyl group, naphthylsulfinyl group, 2-pyridylsulfinyl group, etc.), alkylsulfonyl group (for example, methylsulfonyl group, ethylsulfonyl group, butylsulfonyl group, cyclohexyl) Sulfonyl group, 2-ethylhexylsulfonyl group, dodecylsulfonyl group, etc.), arylsulfonyl group (phenylsulfonyl group, naphthylsulfonyl group, 2 Pyridylsulfonyl group, etc.), amino group (for example, amino group, ethylamino group, dimethylamino group, butylamino group, cyclopentylamino group, 2-ethylhexylamino group, dodecylamino group, anilino group, naphthylamino group, 2-pyridylamino group) Group), halogen atom (eg fluorine atom, chlorine atom, bromine atom etc.), fluorinated hydrocarbon group (eg fluoromethyl group, trifluoromethyl group, pentafluoroethyl group, pentafluorophenyl group etc.), cyano Group, nitro group, hydroxy group, mercapto group, silyl group (for example, trimethylsilyl group, triisopropylsilyl group, triphenylsilyl group, phenyldiethylsilyl group, etc.), hydroxyl group, nitro group, carboxyl group, etc. The substituents are each represented by R _{1 to} R ₆ described above. These substituents may be further substituted with groups having the same meanings as those of the substitutable groups, and a plurality of these substituents may be bonded to each other to form a ring.

A group that can be substituted with the substituent represented by R _{1 to} R ₆ is preferably a halogen atom, an alkyl group, an alkoxy group, an acyloxy group, an alkoxycarbonyl group, an aromatic hydrocarbon group, a heteroaromatic group, a hydroxyl group, It is a fluorinated hydrocarbon group. At least one of the substituents represented by R _{1 to} R ₆ may have a bifunctional or higher polyfunctional oxetane compound having an oxetane ring as a substituent.

  The oxetane compound according to the present invention preferably has a substituent at the 2-position or 3-position of the oxetane ring.

  The substituent that can be substituted at the 2-position of the oxetane ring is not particularly limited, but is preferably an aromatic group, and examples of the aromatic group include the above-described aromatic hydrocarbon groups (for example, phenyl group, naphthyl group). , Anthracenyl group, etc.), heteroaromatic groups (for example, furyl, thienyl, pyridyl, pyridazinyl, pyrimidyl, pyrazyl, triazyl, imidazolyl, pyrazolyl, thiazolyl, benzoimidazolyl, benzoxazolyl Group, quinazolyl group, phthalazyl group, pyrrolyl group, 2-quinolyl group, 1-isoquinylyl group and the like). These aromatic groups may further have a substituent, and examples of the substituent are the same groups as those described above for the halogen atom, alkyl group, alkoxy group, acyloxy group, and alkoxycarbonyl group. When the substituent at the 2-position is an aromatic group, it may further have a substituent at the 3-position, and examples of preferred substituents are the same groups as the alkyl group and alkoxy group described above.

  The oxetane compound having a substituent at the 2-position is more preferably an oxetane compound represented by the following general formula (A) or the following general formula (B).

In the general formula _(A), Q A represents (m _A + n _A) valent aromatic group, R _A1 to R _A4 each represent a hydrogen atom or a substituent, R _A5 represents a substituent, m _A is Represents an integer of 1 to 3, and n _A represents an integer of 0 to 5. The aromatic group represented by Q _A represents a group having the same meaning as the above-described aromatic group having a (m _A + n _A ) value. The substituent represented by R _{A1 to} R _A4 represents the same group as the substituent represented by R _{1 to} R ₆ described above, and is preferably a hydrogen atom, an alkyl group, or an alkoxy group. The substituent represented by R _A5 represents a group having the same meaning as the substituent represented by R _{1 to} R ₆ described above, and the plurality of R _A5 may be the same or different, and may be bonded to each other to form a divalent group. And may form a ring. R _A5 is preferably an alkyl group or an alkoxy group, and at least one of the plurality of R _A5 is more preferably an alkoxy group. m _A is preferably an integer of 1 to 2, n _A is preferably an integer of 0 to 3, more preferably an integer of 0 to 2, and m _A + n _A is an integer of 1 to 6. Is more preferable, and an integer of 1 to 3 is more preferable.

In the general formula _(B), Q B represents the (n _B +2) valent aromatic group, R _B1 to R _B4 each represents a hydrogen atom or a substituent, R _B5 represents a substituent, L _B is m _{A B-} valent linking group is represented, m _B represents an integer of 2 to 4, and n _B represents an integer of 0 to 4.

The aromatic group represented by Q _B represents a group having the same meaning as the (n _B +2) -valent aromatic group described above. The substituents represented by R _{B1 to} R _B4 represent the same groups as the substituents represented by R _{1 to} R ₆ described above, and each of R _{B1 to} R _B4 is preferably a hydrogen atom, an alkyl group, or an alkoxy group. It is. The substituent represented by R _B5 represents a group having the same meaning as the substituent represented by R _{1 to} R ₆ described above, and the plurality of R _B5 may be the same or different, and may be bonded to each other to form a divalent group. And may form a ring. R _B5 is more preferably an alkyl group or an alkoxy group. mB is preferably an integer of 2 or 3, and nB is preferably an integer of 0 to 3, more preferably an integer of 0 to 2.

L _B may preferably be a main chain oxygen atom or a sulfur atom which may contain a 0-15 carbon atoms m _B-valent linking group or a single bond, also contain an oxygen atom or a sulfur atom in the main chain 2 Examples of the valent linking group include the following groups and groups formed by combining these groups with a plurality of —O— groups, —S— groups, —CO— groups, and —CS— groups.

A methylene group [—CH ₂ ⁻ ],
An ethylidene group [> CHCH ₃ ],
Isopropylidene [> C (CH ₃ ) ₂ ]
1,2-ethylene group [—CH ₂ CH ₂ ⁻ ],
1,2-propylene group [—CH (CH ₃ ) CH ₂ ⁻ ],
1,3-propanediyl group [—CH ₂ CH ₂ CH ₂ ⁻ ],
2,2-dimethyl-1,3-propanediyl group [—CH ₂ C (CH ₃ ) ₂ CH ₂ ⁻ ],
2,2-dimethoxy-1,3-propanediyl group [—CH ₂ C (OCH ₃ ) ₂ CH ₂ ⁻ ],
2,2-dimethoxymethyl-1,3-propanediyl group [—CH ₂ C (CH ₂ OCH ₃ ) ₂ CH ₂ ⁻ ],
1-methyl-1,3-propanediyl group [—CH (CH ₃ ) CH ₂ CH ₂ ⁻ ],
1,4-butanediyl group [—CH ₂ CH ₂ CH ₂ CH ₂ ⁻ ],
1,5-pentanediyl group [—CH ₂ CH ₂ CH ₂ CH ₂ CH ₂ ⁻ ],
An oxydiethylene group [—CH ₂ CH ₂ OCH ₂ CH ₂ ⁻ ],
A thiodiethylene group [—CH ₂ CH ₂ SCH ₂ CH ₂ ⁻ ],
3-oxothiodiethylene group [—CH ₂ CH ₂ SOCH ₂ CH ₂ ⁻ ],
3,3-dioxothiodiethylene group [—CH ₂ CH ₂ SO ₂ CH ₂ CH ₂ ⁻ ],
1,4-dimethyl-3-oxa-1,5-pentanediyl group [—CH (CH ₃ ) CH ₂ OCH (CH ₃ ) CH ₂ ⁻ ],
3-oxopentanediyl group [—CH ₂ CH ₂ COCH ₂ CH ₂ ⁻ ],
1,5-dioxo-3-oxa-pentane diyl group ^{_{[-COCH 2 OCH 2 CO -]}} ,
4-oxa-1,7-heptanediyl group [—CH ₂ CH ₂ CH ₂ OCH ₂ CH ₂ CH ₂ ⁻ ],
3,6-dioxa-1,8-octanediyl group [—CH ₂ CH ₂ OCH ₂ CH ₂ OCH ₂ CH ₂ ⁻ ],
1,4,7-trimethyl-3,6-dioxa-1,8-octanediyl group [—CH (CH ₃ ) CH ₂ OCH (CH ₃ ) CH ₂ OCH (CH ₃ ) CH ₂ ⁻ ],
5,5-dimethyl-3,7-dioxa-1,9-nonanediyl group [—CH ₂ CH ₂ OCH ₂ C (CH ₃ ) ₂ CH ₂ OCH ₂ CH ₂ ⁻ ],
5,5-dimethoxy-3,7-dioxa-1,9-nonanediyl group [—CH ₂ CH ₂ OCH ₂ C (OCH ₃ ) ₂ CH ₂ OCH ₂ CH ₂ ⁻ ],
5,5-dimethoxymethyl-3,7-dioxa-1,9-nonanediyl group [—CH ₂ CH ₂ OCH ₂ C (CH ₂ OCH ₃ ) ₂ CH ₂ OCH ₂ CH ₂ ⁻ ],
4,7-dioxo-3,8-dioxa-1,10-decandiyl group [—CH ₂ CH ₂ O—COCH ₂ CH ₂ CO—OCH ₂ CH ₂ ⁻ ],
3,8-dioxo-4,7-dioxa-1,10-decandiyl group [—CH ₂ CH ₂ CO—OCH ₂ CH ₂ O—COCH ₂ CH ₂ ⁻ ],
1,3-cyclopentane-diyl group ^{_{[-1,3-C 5 H 8 -}} ],
1,2-cyclohexane-diyl group ^{_{[-1,2-C 6 H 10 -}} ],
1,3-cyclohexanediyl group [-1,3-C ₆ H ₁₀ ⁻ ],
1,4-cyclohexanediyl group [-1,4-C ₆ H ₁₀ ⁻ ],
2,5-tetrahydrofurandiyl group [2,5-C ₄ H ₆ O ⁻ ]
p- phenylene ^{_{[-p-C 6 H 4 -}} ],
m- phenylene group ^{_{[-m-C 6 H 4 -}} ],
α, α'-o- xylylene group _{[-o-CH 2 -C 6 H} 4 -CH 2 -],
α, α'-m- xylylene group _{[-m-CH 2 -C 6 H} 4 -CH 2 -],
α, α'-p- xylylene group _{[-p-CH 2 -C 6 H} 4 -CH 2 -],
Furan-2,5-diyl - bismethylene group _{[2,5-CH 2 -C 4 H} 2 O-CH 2 -]
Thiophene-2,5-diyl-bismethylene group [2,5-CH ₂ —C ₄ H ₂ S—CH ₂ —]
Isopropylidenebis -p- phenylene group _{[-p-C 6 H 4 -C} (CH 3) 2 -p-C 6 H 4 -]
Examples of the trivalent or higher valent linking group include a group formed by removing as many hydrogen atoms as necessary from the divalent linking groups listed above, and an —O— group, —S— group, —CO—. And a group formed by combining a plurality of groups and -CS- groups.

  The production method of the oxetane compound described above is not particularly limited, and may be a conventionally known method, which can be synthesized according to the method described in the following literature.

(1) Hu Xianming, Richard M. et al. Kellogg, Synthesis, 533-538, May (1995)
(2) A. O. Fitton, J .; Hill, D.C. Ejane, R.A. Miller, Synth. , 12, 1140 (1987)
(3): Toshiro Imai and Shinya Nishida, Can. J. et al. Chem. Vol. 59, 2503-2509 (1981)
(4): Nobujiro Shimizu, Shintaro Yamaoka and Yuho Tsuno, Bull. Chem. Soc. Jpn. 56, 3853-3854 (1983)
(5): Walter Fisher and Cyril A. Grob, Helv. Chim. Acta. , 61, 2336 (1978)
(6): Chem. Ber. 101, 1850 (1968)
(7): “Heterocyclic Compounds with Three- and Four-membered Rings”, Part Two, Chapter IX, Interscience Publishers, John Wiley & Son, N
(8): Bull. Chem. Soc. Jpn. 61, 1653 (1988)
(9): Pure Appl. Chem. , A29 (10), 915 (1992)
(10) J: Pure Appl. Chem. , A30 (2 &amp; 3), 189 (1993)
(11): Japanese Patent Laid-Open No. 6-16804 (12): German Patent No. 1,021,858 The oxetane represented by the following general formula (3), general formula (A), and general formula (B) Although the example of a compound is given, this invention is not limited to these.

  The substituent that can be substituted at the 3-position of the oxetane ring is not particularly limited, but preferably the above-described alkyl group, alkoxy group, acyloxy group, alkoxycarbonyl group, aromatic hydrocarbon group, heteroaromatic group, halogen atom, Examples thereof include a group having the same meaning as a fluorinated hydrocarbon group.

  As the oxetane compound having a substituent at the 3-position, an oxetane compound not substituted at the 2-position is more preferable. As an example of the oxetane compound in which the 2-position is not substituted, a compound represented by the following general formula (101) can be given.

In General Formula (101), 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-2. -Alkenyl groups having 2 to 6 carbon atoms such as propenyl group, 1-butenyl group, 2-butenyl group and 3-butenyl group, aromatic groups such as phenyl group, benzyl group, fluorobenzyl group, methoxybenzyl group and phenoxyethyl group A group having a ring, an alkylcarbonyl group having 2 to 6 carbon atoms such as an ethylcarbonyl group, a propylcarbonyl group and a butylcarbonyl group, an alkoxy having 2 to 6 carbon atoms such as an ethoxycarbonyl group, a propoxycarbonyl group and a butoxycarbonyl group Carbonyl group, ethylcarbamoyl group, propylcarbamoyl group, butylcarbamoyl group, pentylcarbamoyl group Number 2-6 carbons of an N- alkylcarbamoyl group. 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 (102).

In the general formula (102), R ¹ is the same group as that in the general formula (101). 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 (103), (104) and (105) can also be mentioned.

In the general formula (103), R ⁴ is 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, or a carbon such as a methoxy group, an ethoxy group, a propoxy group, or a butoxy group. A C 1-4 alkoxy group, a halogen atom such as a chlorine atom or a bromine atom, a nitro group, a cyano group, a mercapto group, a lower alkyl carboxyl group, a carboxyl group, or a carbamoyl group.

In the general formula (104), 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 (105), R ⁶ 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 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. Examples of R ^{7 also} include a group selected from the group represented by the following general formula (106).

In General Formula (106), R ⁸ 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 an aryl group. m is an integer of 0-100.

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

Exemplary compound 11 is a compound in which R ¹ is an ethyl group and R ³ is a carboxyl group in the general formula (102). The exemplified compound 12 is a compound in which R ¹ is an ethyl group, R ³ is the general formula (105), R ⁶ and R ⁷ are methyl groups, and n is 1 in the general formula (102).

  In the compound having two oxetane rings, a preferred example other than the above compound is a compound represented by the following general formula (107).

In formula (107), R ¹ has the same meaning as R ¹ in the general formula (101).

  Moreover, as an example of a compound having 3 to 4 oxetane rings, a compound represented by the following general formula (108) can be given.

In formula (108), R ¹ has the same meaning as R ¹ in the general formula (101). 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 the above A, 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 13 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 (109).

In formula (109), R ⁸ has the same meaning as R ⁸ in the general formula (106). 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, Pattison (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.

  Various additives other than those described above can be used in the actinic ray curable inkjet ink of the present invention. For example, surfactants, leveling additives, matting agents, polyester resins for preparing film properties, polyurethane resins, vinyl resins, acrylic resins, rubber resins, and waxes can be added.

  In the ink of the present invention, the viscosity at 25 ° C. is preferably 10 to 70 mPa · s in order to obtain good curability. The viscosity in the present invention is a value of a shear rate of 1000 (1 / s) measured with a viscoelasticity measuring apparatus MCR300 manufactured by Physica.

  As a recording material that can be used in the present invention, in addition to ordinary uncoated paper, coated paper, etc., various non-absorbable plastics and films used for so-called soft packaging can be used. Examples thereof include PET film, OPS film, OPP film, ONy film, PVC film, PE film, and TAC film. As other plastics, polycarbonate, acrylic resin, ABS, polyacetal, PVA, rubbers and the like can be used. Moreover, it is applicable also to metals and glass.

  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 recording material. With the configuration of the present invention, a good high-definition image can be formed on a wide range of recording materials having a surface energy of 35 to 60 mN / m, including OPP films having a low surface energy, OPS films, and PET having a relatively large surface energy. .

  In the present invention, it is more advantageous to use a long (web) recording material in terms of the cost of the recording material such as packaging cost and production cost, the production efficiency of the print, and the ability to cope with printing of various sizes. is there.

  Next, the image forming method of the present invention will be described.

  In the image forming method of the present invention, a method is preferred in which the ink is ejected and drawn on a recording material by an ink jet recording method, and then the ink is cured by irradiation with an actinic ray such as ultraviolet rays.

(Total ink film thickness after ink landing)
In the present invention, the total ink film thickness after the ink has landed on the recording material and cured by irradiation with actinic rays is preferably 2 to 20 μm. In the actinic ray curable inkjet recording in the screen printing field, the total ink film thickness currently exceeds 20 μm, but in the flexible packaging printing field where the recording material is often a thin plastic material, the recording material described above 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, “total ink film thickness” means the maximum value of the film thickness of the ink drawn on the recording material, and even for a single color, other two colors are superimposed (secondary color), three colors are superimposed, four colors are used. Even when recording is performed by the overlapping (white ink base) inkjet recording method, the meaning of the total ink film thickness is the same.

(Ink ejection conditions)
In the case of forming an image using the ink of the present invention, it is preferable from the viewpoint of ejection stability that the ink is ejected by heating the recording head and the ink to 35 to 100 ° C. Actinic radiation curable ink has a large viscosity fluctuation range due to temperature fluctuations, and the viscosity fluctuations directly affect the droplet size and droplet ejection speed, causing image quality degradation. It is necessary to keep. The control range of the ink temperature is set temperature ± 5 ° C., preferably set temperature ± 2 ° C., more preferably set temperature ± 1 ° C.

  Moreover, in this invention, it is preferable that the amount of droplets discharged from each nozzle is 1 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. According to the present invention, even when ejection is performed with a small droplet amount such as 1 to 15 pl, the ejection stability is improved and a high-definition image can be stably formed.

(Light irradiation conditions after ink landing)
In the image forming method of the present invention, the active light is preferably irradiated for 0.001 second to 2.0 seconds after landing of the ink, more preferably 0.001 second to 1 as the active light irradiation condition. 0.0 seconds, and more preferably 0.001 seconds to 0.5 seconds. In order to form a high-definition image, it is particularly important that the irradiation timing is as early as possible.

  As a method for irradiating actinic rays, the basic method 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 of the present invention.

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

  The recording apparatus of the present invention will be described below with reference to the drawings as appropriate. Note that the recording apparatus of the drawings is merely one aspect of the recording apparatus of the present invention, and the recording apparatus of the present invention is not limited to this drawing.

  FIG. 1 is a front view showing the configuration of the main part of the recording apparatus of 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 recording material P. The platen unit 5 has a function of absorbing ultraviolet rays, and absorbs excess ultraviolet rays that have passed through the recording material P. As a result, a high-definition image can be reproduced very stably.

  The recording 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 recording material 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 recording material 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 white (W), yellow (Y), magenta (M), cyan (C), black (K), light yellow (Ly), light magenta (Lm), and light cyan (Lc). Although the drawing is carried out assuming that the recording heads 3 of light black (Lk) and white (W) are accommodated, the number of colors of the recording heads 3 accommodated in the head carriage 2 is determined as appropriate. Is.

  The recording head 3 has a discharge port by operating 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). To the recording material P. 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.

  During the scanning in which the recording head 3 moves from one end of the recording material P to the other end of the recording material P in the Y direction in FIG. 1 by driving the head scanning means, a certain area (landing possible area) in the recording material P On the other hand, 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 recording material P is appropriately moved from the front to the back in FIG. 1, the recording head 3 discharges UV ink to the next landable area adjacent in the depth direction in FIG.

  By repeating the above operation and ejecting the UV ink from the recording head 3 in conjunction with the head scanning means and the conveying means, an image composed of an aggregate of UV ink droplets is formed on the recording material 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 electrodeless lamp, an excimer laser, an ultraviolet laser, a cold cathode tube, a hot cathode tube, a black light, an LED (light emitting diode), and the like are applicable.

  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 irradiation means 4 is fixed on both sides of the head carriage 2 so as to be substantially parallel to the recording material P.

  As described above, as a 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 recording material P. It is effective to increase the distance h2 between the portion 31 and the recording material 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.

  The ink of the present invention has excellent ejection stability and is particularly effective when an image is formed using a line head type recording apparatus.

  FIG. 2 is a top view illustrating another example of the configuration of the main part of the ink jet recording apparatus.

  The ink jet recording apparatus shown in FIG. 2 is called a line head system, and a plurality of ink jet recording heads 3 of each color are fixedly arranged on the head carriage 2 so as to cover the entire width of the recording material P. ing.

  On the other hand, on the downstream side of the head carriage 2, there is provided irradiation means 4 arranged so as to cover the entire width of the recording material P and cover the entire area of the ink printing surface. As the ultraviolet lamp used in the illuminating means 4, the same one as described in FIG. 1 can be used.

  In this line head system, the head carriage 2 and the irradiating means 4 are fixed, and only the recording material P is conveyed, and ink ejection and curing are performed to form an image.

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

Example 1
<< Preparation of pigment dispersion >>
The pigment is dispersed with the following composition.

  The following two compounds were put in a stainless beaker and dissolved by heating on a 60 ° C. hot plate.

Azisper PB822 (dispersant manufactured by Ajinomoto Fine Techno Co., Ltd.) 8 parts by mass Aron Oxetane OXT-221 (Oxetane compound manufactured by Toagosei Co., Ltd.) 72 parts by mass 200 g of the zirconia beads were sealed in a glass bottle and sealed with a paint shaker for the following time, after which the zirconia beads were removed to prepare each pigment dispersion.

Pigment 1: Pigment Black 7 (Mitsubishi Chemical Corp., MA7) 10 hours Pigment 2: Pigment Blue 15: 4 (Daiichi Seika Co., Ltd., special order) 6 hours Pigment 3: Pigment Red 122 (Daisei Seika Co., Ltd., special order) 10 hours Pigment 4: Pigment Yellow 180 (manufactured by Dainichi Seika Co., Ltd., special order) 10 hours Pigment 5: Titanium oxide (anatase type: particle size 0.2 μm) 10 hours << Preparation of ink composition >>
Each color ink was prepared with the ink composition described in Tables 1 to 19 using each of the prepared pigment dispersions.

  Each color ink was mixed with all additives other than the pigment dispersion, and after confirming that it was sufficiently dissolved, the resulting mixture was added to the pigment dispersion little by little and stirred for 15 minutes. Filtration was performed with a PP3 μm disk filter manufactured by Loki Techno Co., Ltd. Each ink viscosity is as shown in Tables 1-19.

  *: Bifunctional epoxy compound (comparative compound) other than “bifunctional epoxy compound having a linking group having a structure represented by the general formula (1) of the present invention”.

<< Inkjet image forming method >>
Each ink prepared above is loaded into the ink jet recording apparatus having the configuration shown in FIG. 1 having a piezo type ink jet nozzle, and continuous recording of each color solid image is performed on a long polyethylene terephthalate film having a width of 600 mm and a length of 500 m. I went there. The ink supply system was composed of an ink tank, a supply pipe, a front chamber ink tank immediately before the head, a pipe with a filter, and a piezo head. The ink was insulated from the front chamber tank to the head portion and heated at 55 ° C. The piezo head was driven so that 2 to 15 pl multi-size dots could be ejected at a resolution of 720 × 720 dpi, and each ink was ejected continuously. After landing, irradiation (curing) is performed under the conditions described in Table 20 and Table 21. After recording, the total ink film thickness was measured and found to be in the range of 10 to 13 μm. In the present invention, dpi represents the number of dots per 2.54 cm. The inkjet image was formed in an environment of 25 ° C. and 50% RH according to the above method.

  Also, a solid image was formed using the line head recording type ink jet recording apparatus shown in FIG. 2 in exactly the same manner.

<Evaluation of inkjet recording image>
The following evaluation was performed on each image recorded by the image forming method.

(Ink curability)
In the ink jet recording apparatus shown in FIG. 1, the ink curability is determined by the maximum carriage speed at which the ink is cured, and in the ink jet recording apparatus of the line head recording system shown in FIG. 2, the maximum recording material conveyance speed at which the ink is cured. Judged.

(Flexibility of cured film)
Based on JIS K5600-5-1 (cylindrical mandrel method), the bending resistance of the cured film was confirmed.

(Recording material curl)
The curling state of the recording material after image formation (after curing) was visually evaluated.

○: No curling Δ: Slight curling is observed, but there is no practical problem. ×: Curling is severe, unusable level Table 22 shows the results.

* 1: Electrodeless lamp (Power Cure One manufactured by Fusion UV Systems)
* 2: Measured 254 nm illuminance with UVPF-A1 (Iwasaki Electric Co., Ltd.)

* 3: 120W / cm metal halide lamp (manufactured by Nippon Battery MAL 400NL)
* 2: Measured 254 nm illuminance with UVPF-A1 (Iwasaki Electric Co., Ltd.)

  As is apparent from Table 22, the ink of the present invention is excellent in flexibility after curing. And it turns out that problems, such as a crack and curl, do not arise.

It is a front view which shows an example of a structure of the principal part of the inkjet recording device of this invention. It is a top view which shows another example of a structure of the principal part of the inkjet recording device of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Inkjet recording device 2 Head carriage 3 Inkjet recording head 31 Ink ejection port 4 Irradiation means 5 Platen part 6 Guide member 7 Bellows structure P Recording material

Claims (14)

In the actinic ray curable inkjet ink containing a photopolymerizable compound, a photopolymerization initiator, and a pigment, the photopolymerizable compound has a bifunctional or higher functional group having a linking group having a structure represented by the following general formula (1). An actinic ray curable inkjet ink comprising an epoxy compound.
General formula (1)
-(-R-O-) _n-
(In the formula, n represents an integer of 2 or more, and R represents an alkylene group which may have a substituent having 1 to 15 carbon atoms, or an aliphatic cyclic group which may have a substituent having 6 to 17 carbon atoms. Represents a hydrocarbon group.) 2. The actinic ray curable inkjet ink according to claim 1, wherein n represents an integer of 2 to 5 for the bifunctional or higher functional epoxy compound having a linking group having the structure represented by the general formula (1). . The bifunctional or higher functional epoxy compound having a linking group having a structure represented by the general formula (1) is characterized in that R represents an alkylene group which may have a substituent having 1 to 15 carbon atoms. The actinic ray curable inkjet ink according to claim 1 or 2. The activity according to any one of claims 1 to 3, comprising a bifunctional or higher functional epoxy compound other than the bifunctional epoxy compound having a linking group having a structure represented by the general formula (1). Light curable inkjet ink. The actinic ray curable inkjet ink according to claim 1, comprising an oxetane compound. The actinic ray curable inkjet ink according to claim 1, comprising a monofunctional epoxy compound. The actinic ray curable inkjet ink according to claim 1, comprising an alicyclic epoxy compound as the epoxy compound. The actinic ray according to any one of claims 1 to 7, comprising 5 to 30% by mass of a bifunctional or higher functional epoxy compound having a linking group having a structure represented by the general formula (1). A curable inkjet ink. The actinic ray curable inkjet ink according to any one of claims 1 to 8, wherein the actinic ray curable inkjet ink has a viscosity of 10 to 70 mPa · s at 25 ° C. An actinic ray curable inkjet ink according to any one of claims 1 to 9, wherein the actinic ray curable inkjet ink is ejected from a inkjet recording head onto a recording material, and printing is performed on the recording material. An image forming method comprising irradiating a lamp for 0.001 to 2.0 seconds after the curable inkjet ink has landed. An actinic ray curable inkjet ink according to any one of claims 1 to 9, wherein the actinic ray curable inkjet ink is ejected from a inkjet recording head onto a recording material, and printing is performed on the recording material. An image forming method, wherein the total ink film thickness after the curable inkjet ink has landed and cured by irradiation with a lamp is 2 to 20 μm. An image forming method for performing printing on a recording material by ejecting the actinic ray curable inkjet ink according to any one of claims 1 to 9 onto the recording material from an inkjet recording head, comprising: An image forming method, wherein the amount of ink droplets ejected from each nozzle is 1 to 15 pl. An actinic ray curable inkjet ink according to claim 1 and a recording head are heated to 35 to 100 ° C. and then discharged. It is an inkjet recording device used for the image forming method of any one of Claims 10-12, Comprising: Actinic-light curable inkjet ink of any one of Claims 1-9, and a recording head are 35-100. An ink jet recording apparatus which discharges after heating to ° C.

Images