JP2005105225A - Active-ray curable ink-jet ink composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an active-ray curable ink-jet ink composition capable of stably recording images excellent in durability. <P>SOLUTION: In the active-ray curable ink-jet ink composition comprising a photo-acid generator, a photopolymerizable compound and a pigment, the photo-acid generator is an onium salt which does not produce benzene by active-ray irradiation; the photopolymerizable compound is a compound having the oxetane ring; and the pigment is at least one selected from the group consisting of C.I. PY74, PY93, PY120, PY128, PY138, PY139, PY151, PY166, PY180, PY185, PR122, PR177, PV19, PB15:3, PB15:4, and PBk7. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an actinic ray curable inkjet ink composition excellent in durability of an image to be obtained.

  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 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 ink jet method using a wax ink solid at room temperature, a solvent ink jet method using an ink mainly composed of a fast-drying organic solvent, a UV ink jet method in which crosslinking is performed by ultraviolet (UV) light after recording, etc. It is.

  Among them, the UV inkjet method has been attracting attention in recent years in that 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, JP 2000-504778 discloses an ultraviolet curable inkjet ink.

However, in an ultraviolet curable ink-jet ink, for example, in an image created with an ink using a cationic polymerizable compound as described in Patent Documents 1 to 3, it is exposed to sunlight or the like for a long period of time due to outdoor use. In such a case, there may be a problem in the durability of the image such as stickiness on the surface.
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 problems, and an object of the present invention is to provide an actinic ray curable inkjet ink composition capable of recording an image having excellent durability very stably.

The above object of the present invention has been achieved by the following constitution.
(Claim 1)
In the actinic ray curable inkjet ink composition containing a photoacid generator, a photopolymerizable compound, and a pigment, the photoacid generator is an onium salt that does not generate benzene by actinic ray irradiation, and the photopolymerizable compound is oxetane A compound having a ring, and the pigment is C.I. I. (Color Index) At least one selected from the group consisting of PY74, PY93, PY120, PY128, PY138, PY139, PY151, PY166, PY180, PY185, PR122, PR177, PV19, PB15: 3, PB15: 4, and PBk7. An actinic ray curable inkjet ink composition characterized by the above.
(Claim 2)
The actinic ray curable inkjet ink composition according to claim 1, wherein the onium salt that does not generate benzene is a sulfonium salt.
(Claim 3)
The actinic ray curable inkjet ink composition according to claim 1, wherein the onium salt that does not generate benzene is an iodonium salt.
(Claim 4)
The actinic ray curable inkjet ink composition according to claim 2, wherein the sulfonium salt is at least one of compounds represented by the following general formulas [1] to [4].

[Wherein, R _{1 to} R ₁₇ each represent a hydrogen atom or a substituent, R _{1 to} R ₃ do not simultaneously represent a hydrogen atom, and R _{4 to} R ₇ do not simultaneously represent a hydrogen atom, R _{8 to} R ₁₁ do not represent hydrogen atoms at the same time, and R _{12 to} R ₁₇ do not represent hydrogen atoms at the same time. X represents a non-nucleophilic anionic residue. ]
(Claim 5)
The actinic ray curable inkjet ink, wherein the sulfonium salt represented by the general formulas [1] to [4] is at least one sulfonium salt selected from the following general formulas [5] to [13] Composition.

[X represents a non-nucleophilic anionic residue. ]
(Claim 6)
The average particle diameter of a pigment is 200 nm or less, The actinic-light curable inkjet ink composition of any one of Claims 1-5 characterized by the above-mentioned.
(Claim 7)
The average particle diameter of a pigment is 150 nm or less, The actinic-light curable inkjet ink composition of Claim 6 characterized by the above-mentioned.

  The present inventor contains a photoacid generator that does not generate benzene by actinic ray irradiation in an actinic ray curable inkjet ink composition, and a compound having an oxetane ring as a photopolymerizable compound, and further as a pigment C. I. By containing at least one selected from the group consisting of PY74, PY93, PY120, PY128, PY138, PY139, PY151, PY166, PY180, PY185, PR122, PR177, PV19, PB15: 3, PB15: 4, and PBk7. It has been found that an image having excellent durability can be obtained, and has reached the present invention.

  Conventionally, a cationically polymerizable ink composition has been used using UVI6992 (manufactured by Dow Chemical Co., Ltd., triarylsulfonium salt) as a center and a photoacid generator that generates benzene as a decomposition product after irradiation with actinic rays. . However, the ink composition is rarely used in the food field because it generates benzene, and when the amount of photoacid generator added is reduced in order to suppress the amount of benzene generated, it is particularly suitable for outdoor use. It was impossible to form an image that was durable and excellent in durability. Further, as onium salts (photoacid generators) that do not generate benzene, IRGACURE250 (Ciba Specialty Chemicals, diaryl iodonium salt) and CI 5102 (Nihon Soda Co., diaryl iodonium salt) are known. Including these, there has been no practical example of an inkjet ink composition capable of forming an image having excellent durability using an onium salt that does not generate benzene by irradiation with actinic rays.

  According to the present invention, it is possible to provide an actinic ray curable inkjet ink composition capable of stably recording an image having excellent durability.

  Hereinafter, the present invention will be described in detail.

  First, an onium salt (photoacid generator) that does not generate benzene by actinic ray irradiation will be described.

In the present invention, “does not generate benzene by irradiation with actinic rays” means that benzene is not substantially generated. Specifically, the ink composition contains 5% by mass of an onium salt (photoacid generator). Of the benzene generated when an image of a thickness of 15 μm and about 100 m ² is printed using the prepared ink and irradiated with actinic rays in an amount sufficient to decompose the photoacid generator with the ink film surface kept at 30 ° C. It means that the amount is very little or less than 5 μg. The onium salt is preferably a sulfonium salt or an iodonium salt, and satisfies the above conditions as long as it has a substituent on the benzene ring bonded to S ⁺ or I ⁺ . The sulfonium salt is preferably a sulfonium salt compound represented by the above general formulas [1] to [4], and satisfies the above condition as long as it has a substituent on the benzene ring bonded to S ⁺ .

In the general formulas [1] to [4], R _{1 to} R ₁₇ each represent a hydrogen atom or a substituent, R _{1 to} R ₃ do not simultaneously represent a hydrogen atom, and R _{4 to} R ₇ represent simultaneously. It does not represent a hydrogen atom, R _{8 to} R ₁₁ do not represent a hydrogen atom at the same time, and R _{12 to} R ₁₇ do not represent a hydrogen atom at the same time.

The substituent represented by R _{1 to} R ₁₇ is preferably an alkyl group such as a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a t-butyl group, a pentyl group, or a hexyl group, Alkoxy groups such as methoxy group, ethoxy group, propyl group, butoxy group, hexyloxy group, decyloxy group, dodecyloxy group, acetoxy group, propionyloxy group, decylcarbonyloxy group, dodecylcarbonyloxy group, methoxycarbonyl group, ethoxycarbonyl Group, carbonyl group such as benzoyloxy group, phenylthio group, halogen atom such as fluorine, chlorine, bromine and iodine, cyano group, nitro group and hydroxy group.

X represents a non-nucleophilic anion residue, for example, a halogen atom such as F, Cl, Br, or I, B (C ₆ F ₅ ) ₄ , R ₁₈ COO, R ₁₉ SO ₃ , SbF ₆ , AsF ₆ , PF ₆ , BF _{4 and the} like. However, R ₁₈ and R ₁₉ are each an alkyl group such as a methyl group, an ethyl group, a propyl group or a butyl group, a halogen atom such as fluorine, chlorine, bromine or iodine, a nitro group, a cyano group, a methoxy group or an ethoxy group. Represents an alkyl group or a phenyl group which may be substituted with an alkoxy group or the like. Among these, B (C ₆ F ₅ ) ₄ and PF ₆ are preferable from the viewpoint of safety.

  The above compounds can be obtained from THE CHEMICAL SOCIETY OF JAPAN Vol. 71No. 11, 1998, as well as the photoacid generator described in “Organic Materials for Imaging”, edited by Organic Electronics Materials Research Group, Bunshin Publishing (1993), can be easily synthesized by a known method.

  In the present invention, the sulfonium salt represented by the general formulas [I] to [4] is particularly preferably at least one of the sulfonium salts selected from the structural formulas [5] to [13].

Exemplary compounds including iodonium salts include the following compounds in addition to X = PF _{6 in} the general formulas (5) to (13).

  In the ink of the present invention, the photopolymerizable monomer contains a compound having at least one oxetane ring.

  As the compound having an oxetane ring that can be used in the present invention, any known oxetane compound as disclosed in JP-A Nos. 2001-220526 and 2001-310937 can be used.

  In the present invention, it is preferable to contain an epoxy compound having at least one oxirane group in order to further improve image durability.

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

  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 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 present invention, from the viewpoint of safety such as AMES and sensitization, the epoxy compound is preferably at least one of an epoxidized fatty acid ester and an epoxidized fatty acid glyceride.

The epoxidized fatty acid ester and the epoxidized fatty acid glyceride are not particularly limited as long as an epoxy group is introduced into the fatty acid ester or fatty acid glyceride.
The epoxidized fatty acid ester is produced by epoxidizing an oleic acid ester, and examples thereof include methyl epoxy stearate, butyl epoxy stearate, octyl epoxy stearate and the like. Similarly, the epoxidized fatty acid glyceride is produced by epoxidizing soybean oil, linseed oil, castor oil and the like, and epoxidized soybean oil, epoxidized linseed oil, epoxidized castor oil and the like are used.

  Furthermore, any known vinyl ether compound may be used in the present invention.

  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, and trimethylol. Di- or trivinyl ether compounds such as propane 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-pro 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 use a compound represented by the following general formula (1) as the oxetane compound in order to obtain high image durability.

In general formula (1), R < ₁ > -R < ₆ > represents a hydrogen atom or a substituent, respectively, and R < ₃ > -R < ₆ > does not represent a hydrogen atom simultaneously.

  Examples of the compound having one oxetane ring in the molecule include compounds represented by the following general formulas (2) to (5).

In the general formulas (2) to (5), Z is independent of each other, oxygen or sulfur atom, or a divalent hydrocarbon group that may contain oxygen or sulfur atom in the main chain, and R _{1 to} R ₆ are hydrogen. C1-C6 alkyl group such as atom, fluorine atom, methyl group, ethyl group, propyl group or butyl group, C1-C6 fluoroalkyl group, allyl group, aryl group, furyl group or thienyl group , R ₇ and R ₈ are each 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 1-propenyl group, a 2-propenyl group, a 2-methyl-1-propenyl group, C1-C6 alkenyl group such as 2-methyl-2-propenyl group, 1-butenyl group, 2-butenyl group or 3-butenyl group, phenyl group, benzyl group, fluorobenzyl group, methoxybenzyl group or phenoxy ethyl Aryl group such as propylcarbonyl group, butylcarbonyl group or pentylcarbonyl group, etc., alkylcarbonyl group having 1 to 6 carbon atoms, alkoxy having 1 to 6 carbon atoms such as ethoxycarbonyl group, propoxycarbonyl group or butoxycarbonyl group An alkoxycarbamoyl group having 1 to 6 carbon atoms such as a carbonyl group, an ethoxycarbamoyl group, a propylcarbamoyl group, or a butylpentylcarbamoyl group is represented.

As the oxetane ring-containing compound used in the present invention, in the above general formulas (2) to (5), R ₁ is a lower alkyl group, particularly ethyl group, R ₇ and R ₈ are propyl group, butyl group, phenyl group or A benzyl group and Z are preferably hydrocarbon groups containing no oxygen or sulfur atom. Moreover, R < ₃ > -R < ₆ > does not represent a hydrogen atom simultaneously.

  Examples of the compound having two or more oxetane rings in the molecule include compounds represented by the following general formulas (6), (7) and (13).

(In the general formulas (6) and (7), m is 2, 3 or 4, Z is independent, oxygen or sulfur atom, or a divalent hydrocarbon group which may contain oxygen or sulfur atom, R ₁ is a hydrogen atom, a fluorine atom, a methyl group, an ethyl group, a propyl group or a butyl group, such as an alkyl group having 1 to 6 carbon atoms, a phenyl group, a fluoroalkyl group having 1 to 6 carbon atoms, an allyl group, an aryl group Or a furyl group, R ₉ is, for example, a linear or branched alkylene group having 1 to 12 carbon atoms represented by the following formula (8), a linear or branched poly (alkyleneoxy) group,

(In the general formula (8), R ₁₀ represents a lower alkyl group such as a methyl group, an ethyl group or a propyl group.)
Or the polyvalent group selected from the group which consists of following General formula (9), (11) and (12) is represented.

(In general formula (9), n is 0 or an integer of 1 to 2000, R ₁₁ is an alkyl group having 1 to 10 carbon atoms such as a methyl group, an ethyl group, a propyl group or a butyl group, and the following general formula (10) R ₁₂ represents an alkyl group having 1 to 10 carbon atoms such as a methyl group, an ethyl group, a propyl group or a butyl group.

(In the general formula (10), j represents 0 or an integer of 1 to 100, and R ₁₃ represents an alkyl having 1 to 10 carbon atoms.)

(In the general formula (11), R ₁₄ is a hydrogen atom, an alkyl group having 1 to 10 carbon atoms such as a methyl group, an ethyl group, a propyl group or a butyl group, an alkoxy group having 1 to 10 carbon atoms, or a halogen atom. Represents a nitro group, a cyano group, a mercapto group, a lower alkyl carboxylate group or a carboxyl group.)

(In the general formula (12), R ₁₅ represents an oxygen atom, a sulfur atom, NH, SO, SO ₂ , CH ₂ , C (CH ₃ ) ₂ or C (CF ₃ ) _2. )
Oxetane ring-containing compound used in the present invention, in the above formula (6) (7), R ₁ is a lower alkyl group, particularly an ethyl group, R ₉ is, R ₁₄ is a hydrogen atom in the general formula (10) In the general formula (8), R ₁₀ is an ethyl group, in general formula (9), R ₁₂ and R ₁₃ are methyl groups, and Z is a hydrocarbon group containing no oxygen or sulfur atom. .

In the general formula (13), r is an integer of 25 to 200, R ₁₆ is an alkyl group or a trialkylsilyl group having 1 to 4 carbon atoms. R _{3 to} R ₆ do not represent a hydrogen atom at the same time.

  Specific examples of the compound containing an oxetane ring represented by the general formula (1) include, but are not limited to, those shown below.

These compounds can be easily synthesized by referring to the following literature, including the method described in the fourth lecture of “Catchball of Polymer Science and Organic Chemistry”.
1) Hu Xianming, Richard M. et al. Kellogg, Synthesis, 533-538, May (1995)
2) A. O. Fitton, J .; Hill, D.C. Ejan, 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 & Sons, New Y19 (19Y)
8) H.M. A. J. et al. Curless, “Synthetic Organic Photochemistry”, Plenum, New York (1984).
9) M.M. Braun, Nachr. Chem. Tech. Lab. 33, 213 (1985)
10) S.M. H. Schroeter, J. et al. Org. Chem. , 34, 5, 1181 (1969)
11) D. R. Arnold, Adv. Photochem. 6,301 (1968)
12) “Heterocyclic Compounds with Three-and Four-membered Rings”, Part Two, Chapter IX, Interscience Publishers, John Wiley & Sons, NewYor (1964).
Further, it is more preferable to use a monofunctional oxetane compound containing one oxetane ring and a polyfunctional oxetane compound containing two or more oxetane rings in order to improve image durability. However, if a compound having 5 or more oxetane rings is used, the viscosity of the ink composition becomes high, which makes it difficult to handle, and the glass transition temperature of the ink composition becomes high. Sex is not enough. The compound having an oxetane ring used in the present invention is preferably a compound having 1 to 4 oxetane rings.

  The actinic ray curable ink of the present invention contains a pigment together with the actinic ray curable composition described above.

  The pigments used in the present invention are listed below.

C. I Pigment Yellow-74, 93, 120, 128, 138, 139, 151, 166, 180, 185
C. I Pigment Red-122, 177
C. I Pigment Violet-19
C. I Pigment Blue-15: 3, 15: 4
C. I Pigment Black-7
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. Examples of the polymer dispersant include Avecia's Solsperse series, Ajinomoto Fine Techno's Adisper series, BYK Chemie's Disperbyk series, and Enomoto Kasei's Disparon. Series, PLAAD series and the like. 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 60 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. However, the radiation 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 durability of the image deteriorates and the VOC problem of the remaining solvent occurs. 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.

  In the pigment dispersion, the average particle size of the pigment particles is preferably 200 nm or less, and more preferably 150 nm or less. When the average particle diameter exceeds 200 nm, the image durability is greatly deteriorated. Moreover, selection of a pigment, a dispersing agent, a dispersion medium, dispersion conditions, and filtration conditions are appropriately set so that the maximum particle diameter is 0.3 to 10 μm, preferably 0.3 to 3 μm. In the ink according to the present invention, the color material concentration is preferably 1% by mass to 10% by mass of the entire ink.

  Various additives other than those described above can be used in the actinic ray curable ink of the present invention. For example, surfactants, 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, for the purpose of improving storage stability, any known basic compound can be used, but representative examples include basic organic compounds such as basic alkali metal compounds, basic alkaline earth metal compounds, and amines. Compounds and the like. It is also possible to combine a radically polymerizable monomer and an initiator into a radical / cation hybrid type curable ink.

  In the ink of the present invention, it is preferable that the viscosity at 25 ° C. is 7 to 50 mPa · s in order to obtain stable discharge and good curability regardless of the curing environment (temperature / humidity).

  As a recording material that can be used in the present invention, various non-absorbable plastics and films thereof can be used in addition to ordinary uncoated paper, coated paper, etc. Examples of various plastic films include PET films, An OPS film, an OPP film, an ONy film, a PVC film, a PE film, and a TAC film can be exemplified. 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.

  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, an image forming method using the ink of the present invention will be described.

  In the image forming method of the present invention, the ink composition 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.

  As ink discharge conditions, it is preferable from the viewpoint of discharge stability that the head and ink are heated to 35 to 100 ° C. and discharged. The actinic ray curable ink has a large viscosity fluctuation range due to temperature fluctuation. Viscosity fluctuations directly affect the droplet size and droplet ejection speed as they are, causing image quality degradation. Therefore, it is necessary to keep the ink temperature as constant as possible while raising the ink temperature. The control range of the ink temperature is set temperature ± 5 ° C., preferably set temperature ± 2 ° C., more preferably set temperature ± 1 ° C.

  Next, as an irradiation method, a basic irradiation method is disclosed in JP-A-60-132767. According to this, light sources as irradiation means are provided on both sides of the head unit, and the head and the light sources 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.

  The recording apparatus of the present invention will be described below with reference to the drawings as appropriate. In addition, the recording apparatus of drawing is only an example and is not this limitation.

  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 a composition containing a coloring material, a polymerizable monomer, an initiator, etc., and crosslinking of the monomer accompanying the action of the initiator 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 excimer laser, an ultraviolet laser, a cold cathode tube, a black light, an LED (light emitting diode) and the like can be applied, and a strip-shaped metal halide lamp tube, a cold cathode tube, A mercury lamp tube or black light is preferred. In particular, a cold cathode tube and black light emitting ultraviolet light having a wavelength of 365 nm are preferable because they can prevent bleeding, control the dot diameter efficiently, and reduce wrinkles during curing. By using a black light as an irradiation source of the irradiation unit 4, the irradiation unit 4 for curing the UV ink can be manufactured at low cost.

  The irradiating means 4 is substantially the same as the maximum one that can be set by the recording apparatus (for example, 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 It has a shape that is 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.

  Examples of the present invention will be specifically described below, but the embodiments of the present invention are not limited to these examples.

(Preparation of pigment dispersion)
A pigment dispersion having the composition described in Table 1 was prepared. Table 2 shows a list of pigments used for each pigment dispersion.

  A bead mill was used as a disperser, and zirconia beads were used as the beads. The dispersion time was set until the average particle size was stabilized.

Examples 1-6, Comparative Examples 1-4
(Preparation of ink)
Inks having the compositions described in Table 3 were prepared. The ink was prepared by gradually adding a solution obtained by dissolving a photoacid generator in a photopolymerizable compound while stirring the pigment dispersion.

(Preparation of sample for evaluation)
Each of the inks prepared above was loaded into a recording apparatus having the configuration shown in FIG. 1 equipped with a piezo-type inkjet nozzle, and the following image recording was performed on an OPP film. 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 50 ° C. The piezo head is driven so that multi-size dots of 2 to 15 pl can be ejected at a resolution of 720 × 720 dpi (dpi represents the number of dots per 2.54 cm), each ink is continuously ejected, and the reflection density is 1.0. A solid image was formed. After landing, it is cured instantaneously (less than 2 seconds after landing) by the lamp units on both sides of the carriage. The inkjet image was formed in an environment of 25 ° C. and 50% RH according to the above method.

(Evaluation of image durability)
Each evaluation sample obtained by the above method is put into a Xe fade meter (illuminance 70000 lx, internal environment 23 ° C., 60% RH), and the time until the sample surface is touched with a finger and feels sticky is confirmed. did. The results are shown in Table 4.

  It can be seen that a highly durable image can be obtained by employing the configuration of the present invention.

Examples 7-19
Inks having the compositions shown in Table 5 were prepared, and image durability was evaluated in the same manner. The results are shown in Table 6.

  It can be seen that a highly durable image can be obtained by employing the configuration of the present invention.

It is a front view which shows the structure of the principal part of the recording device of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Recording device 2 Head carriage 3 Recording head 4 Irradiation means 5 Platen 6 Guide member P Recording material

Claims (7)

In the actinic ray curable inkjet ink composition comprising a photoacid generator, a photopolymerizable compound, and a pigment, the photoacid generator is an onium salt that does not generate benzene by irradiation with actinic rays, and the photopolymerizable compound is oxetane A compound having a ring, and the pigment is C.I. I. (Color Index) At least one selected from the group consisting of PY74, PY93, PY120, PY128, PY138, PY139, PY151, PY166, PY180, PY185, PR122, PR177, PV19, PB15: 3, PB15: 4, and PBk7. An actinic ray curable inkjet ink composition characterized by the above. The actinic ray curable inkjet ink composition according to claim 1, wherein the onium salt that does not generate benzene is a sulfonium salt. The actinic ray curable inkjet ink composition according to claim 1, wherein the onium salt that does not generate benzene is an iodonium salt. The actinic ray curable inkjet ink composition according to claim 2, wherein the sulfonium salt is at least one of compounds represented by the following general formulas [1] to [4].

[Wherein, R _{1 to} R ₁₇ each represent a hydrogen atom or a substituent, R _{1 to} R ₃ do not simultaneously represent a hydrogen atom, and R _{4 to} R ₇ do not simultaneously represent a hydrogen atom, R _{8 to} R ₁₁ do not represent hydrogen atoms at the same time, and R _{12 to} R ₁₇ do not represent hydrogen atoms at the same time. X represents a non-nucleophilic anionic residue. ] The actinic ray curable inkjet ink, wherein the sulfonium salt represented by the general formulas [1] to [4] is at least one sulfonium salt selected from the following general formulas [5] to [13] Composition.

[X represents a non-nucleophilic anionic residue. ] The average particle diameter of a pigment is 200 nm or less, The actinic-light curable inkjet ink composition of any one of Claims 1-5 characterized by the above-mentioned. The average particle diameter of a pigment is 150 nm or less, The actinic-light curable inkjet ink composition of Claim 6 characterized by the above-mentioned.

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