JP2010254750A - Active energy ray-curable inkjet ink and inkjet recording method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an active energy ray-curable inkjet ink having advantageous delivery stability, capable of performing printing excellent in curability, odor resistance of an image, solvent resistance, weatherability, and adhesion to a base material, and excellent in an image recording of a thin-film ink and recording properties by a multi-pass method even in a high humidity environment; and an inkjet image recording method using the same. <P>SOLUTION: This active energy ray-curable inkjet ink comprising an active energy ray-polymerizable compound includes 10 mass% or more and 70 mass% or less of neopentyl glycol divinyl ether. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an active energy ray-curable inkjet ink containing an active energy ray polymerizable compound and an inkjet recording method using the same.

  Conventionally, as the active energy ray curable ink jet ink, there are a radical polymerization type ink and a cation polymerization type ink. Among these, a solvent-free curable ink substantially free of a solvent and a low-viscosity solvent-diluted curable ink positively diluted with water or a solvent are known. Originally, active energy ray curable ink-jet inks are characterized by their quick-drying properties. Therefore, solvent-free curable ink-jet inks that do not require a solvent drying load during ink-jet recording or curable ink-jet inks with a slight addition of solvent are widely used. It has been put into practical use. Among these, radical polymerization type ink-jet ink has a wide range of material selection, and thus has a high degree of freedom in ink design, and has been widely researched and developed and put into practical use.

  On the other hand, since the cationic polymerization type ink-jet ink is not affected by the polymerization inhibition by oxygen, it is excellent in curability of small droplets and curability with a low energy light source, and obtains a cured film having relatively high flexibility. There is an advantage that you can.

  As cationically polymerizable ink-jet ink compositions, those using oxetane compounds, alicyclic epoxy compounds, and vinyl ether compounds as polymerizable compounds are widely known (for example, see Patent Document 1).

  In the ink-jet ink compositions disclosed therein, it is difficult to obtain sufficient curing sensitivity desired by the present inventors. In these ink jet compositions, it has been considered to increase the addition amount of the alicyclic epoxy compound in order to obtain sufficient curing sensitivity, but there are problems such as an increase in ink viscosity and a decrease in flexibility of the cured film. From the viewpoint of lowering the viscosity of the ink and obtaining the flexibility of the cured film, the vinyl ether compound is a useful monomer because the cured film has a relatively low viscosity and the flexibility of the cured film, and a curable inkjet ink containing vinyl ether has been proposed, (For example, refer patent documents 2-3).

  Patent Document 2 shows that an ink having a vinyl ether compound having an average molecular weight of 300 to 5,000 has good curability and high strength of a cured film.

  Patent Document 3 discloses an image forming method for curing with an LED light source using an inkjet ink containing triethylene glycol divinyl ether, a pigment, a dispersant, a diallyl phthalate prepolymer, a cationic polymerization initiator, and a sensitizer. ing.

  However, it is still difficult to obtain sufficient curing sensitivity desired by the present inventors. In particular, the present inventors pay attention to the fact that the compound containing a vinyl ether group has low viscosity and high-speed curability, referring to patent documents, blending such that the viscosity is low so as to be suitable for active energy ray curability and inkjet applications. The ink jet ink composition mainly composed of vinyl ether was studied. As a result, it was found that the ink mainly composed of vinyl ether has a problem specific to the ink jet recording method. When image formation is performed by a serial recording method that divides an image and forms an image by scanning a number of times, depending on the recording conditions, the cured film properties such as a specific decrease in curability, solvent resistance and substrate adhesion New problems such as reduction and odor generation occurred. As a result of intensive studies, it has been found that these problems are related to the curing characteristics of ink on ink irradiated with active energy rays. This phenomenon is prominent in curing in a high humidity environment, particularly when ink-jet recording of small droplets or thin film ink is cured.

  In addition to vinyl ether, it is possible to use a cationically polymerizable monomer such as an oxetane compound or an epoxidized compound, or a radically polymerizable monomer mainly composed of acrylate, but vinyl ether itself has poor copolymerizability with other monomers, It is difficult to obtain stable curing characteristics. Therefore, in the past, the application of vinyl ether to the ink jet system has inevitably limited its use range, for example, by suppressing the addition amount or limiting the curing conditions and processes.

Japanese Patent No. 3014251 Japanese Patent Laying-Open No. 2005-8758 JP 2008-280460 A

  The present invention has been made in view of the above problems, and its purpose is excellent in ejection stability, recording in an environment where the temperature and humidity during printing change, and recording small droplets by a multi-pass method. The present invention provides an active energy ray-curable inkjet ink and an inkjet recording method that are excellent in curing speed and cured film properties under a wide range of inkjet recording conditions.

  The above object of the present invention is achieved by the following configurations.

  1. An active energy ray-curable inkjet ink containing an active energy ray-polymerizable compound, wherein neopentyl glycol divinyl ether is contained in an amount of 10% by mass to 70% by mass.

2. As an active energy ray polymerization initiator, P (Rf _n F _(6-n) ) ⁻ (wherein Rf represents a fluorine-containing aliphatic group and n represents an integer of 1 to 5) as a counter anion. 2. The active energy ray-curable ink-jet ink as described in 1 above, which comprises an onium salt.

  3. 3. The active energy ray-curable inkjet ink as described in 1 or 2 above, wherein the water content is 0.5% by mass or less.

  4). The active energy ray-curable inkjet ink is applied with an active energy ray-curable inkjet ink on a substrate, the active energy ray is applied to the active energy ray-curable inkjet ink on the substrate, and the active energy ray is further irradiated. In the ink jet recording method for forming an image by applying an active energy ray-curable ink-jet ink on the ink and further irradiating the active energy ray, the active energy ray-curable ink-jet ink is used as the active energy ray-curable ink-jet ink. An inkjet recording method using the active energy ray-curable inkjet ink according to any one of the above.

  5. 4. The active energy ray curable inkjet ink on the substrate is irradiated with the active energy ray curable inkjet ink on the substrate within 0.5 seconds after the active energy ray curable inkjet ink is applied on the substrate. The inkjet recording method as described.

  According to the present invention, the substrate of the cured film that can be ejected with small droplets, has excellent ink ejection stability at a high frequency, has a fast curing speed and low odor in a wide printing environment from low humidity to high humidity. It was possible to provide an active energy ray-curable inkjet ink and an inkjet recording method capable of obtaining an image having excellent adhesion, flexibility and weather resistance.

  Hereinafter, embodiments for carrying out the present invention will be described in detail.

  As a result of intensive studies in view of the above problems, the inventor of the present invention includes an active energy ray-curable inkjet ink containing an active energy ray-polymerizable compound, and contains 10% by mass or more and 70% by mass or less of neopentyl glycol divinyl ether. By using the active energy ray-curable inkjet ink characterized by the above, even on the active energy ray-curable inkjet ink irradiated with the active energy ray, the ink has a high curing speed and the cured film has good characteristics. It has been found that an image can be formed.

The active energy ray-curable inkjet ink of the present invention (hereinafter also simply referred to as ink) contains neopentyl glycol divinyl ether as an essential component, and contains an active energy ray polymerization initiator that generates a polymerization active species by active energy rays. Conventionally known cationic polymerizable compounds and radical polymerizable compounds can be used in combination as the polymerizable compound. In particular, P (Rf _n F _(6-n) ) ⁻ is used as an active energy ray polymerization initiator. It is preferable to use an onium salt as a counter anion. Here, the Rf group represents an aliphatic group containing a fluorine atom, and preferably represents an alkyl group in which 80% or more of hydrogen atoms are substituted with a fluorine atom. n represents the number thereof and is an integer of 1 to 5. The n Rf may be the same or different.

  A specific form of the ink of the present invention is composed of a vinyl ether compound other than neopentyl glycol divinyl ether copolymerizable with neopentyl glycol divinyl ether, and the ink includes a color material component such as a pigment and various additives. Furthermore, the water content in the ink is preferably 0.5% by mass or less.

  Hereinafter, each component of the active energy ray-curable inkjet ink of the present invention and the inkjet recording method will be described in detail.

<Active energy ray-curable inkjet ink>
[Neopentyl glycol divinyl ether]
In the ink of the present invention, neopentyl glycol divinyl ether (hereinafter abbreviated as NPGDVE) is contained in an amount of 10% by mass to 70% by mass as an essential component. By containing NPGDVE, it is possible to improve curability, odor resistance during curing, solvent resistance of cured film, weather resistance, and adhesion to substrates in a wide range of environments from low humidity to high humidity. It becomes. If NPGDVE is 10% by mass or more, the object effect of the present invention can be obtained, and if it is 70% by mass or less, sufficient surface curability can be obtained even in a high humidity environment, and the odor at the time of curing can be obtained. Can be suppressed.

  The mechanism of action of NPGDVE in the present invention is not clear, but it is presumed that excessive chain transfer is suppressed in the polymerization process, and the degree of polymerization of the cured product is increased.

  In the present invention, in addition to neopentyl glycol divinyl ether, a bifunctional or higher polyfunctional vinyl ether can be used in combination.

[Bifunctional or higher polyfunctional vinyl ether compound]
Bifunctional vinyl ether compounds include 1,4-butanediol divinyl ether, 1,6-hexanediol divinyl ether, neopentyl glycol divinyl ether, nonanediol divinyl ether, cyclohexanediol divinyl ether, cyclohexanedimethanol divinyl ether, diethylene glycol divinyl ether. , Triethylene glycol divinyl ether (TEGDVE), trimethylolpropane divinyl ether, ethylene oxide-modified trimethylolpropane divinyl ether, pentaerythritol divinyl ether, and the like.

  In addition, a vinyl ether compound having an alicyclic skeleton containing at least an oxygen atom disclosed in Japanese Patent No. 4037856, a vinyl ether having an alicyclic skeleton disclosed in Japanese Patent Application Laid-Open No. 2005-015396, 1-indanyl vinyl ether disclosed in JP-A-137974, 4-acetoxycyclohexyl vinyl ether disclosed in JP-A-2008-150341, and the like.

  In addition, by introducing a substituent at the α-position or β of the vinyl ether group, such as by substituting the vinyl ether group of the above-mentioned divinyl ether with a propenyl ether group, an isopropenyl ether group, a butenyl ether group, or an isobutenyl ether group. You can also.

  Examples of the trifunctional or higher polyfunctional vinyl ether compound include compounds represented by the general formulas (1), (2), and (3).

In the general formula (1), R ₁ represents a hydrogen atom or an organic group. Among these, as the organic group, a hydrocarbon group not containing a hetero element is preferable from the viewpoint of curability.

  As the organic group, for example, 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 aryl group, a furyl group or a thienyl group, 1 carbon number such as allyl group, 1-propenyl group, 2-propenyl group, 2-methyl-1-propenyl group, 2-methyl-2-propenyl group, 1-butenyl group, 2-butenyl group or 3-butenyl group ~ 6 alkenyl groups, phenyl group, benzyl group, fluorobenzyl group, aryl group such as methoxybenzyl group or phenoxyethyl group, alkoxy group such as methoxy group, ethoxy group, butoxy group, propylcarbonyl group, butylcarbonyl group or C1-C6 alkylcarbonyl group such as pentylcarbonyl group, ethoxycarbonyl group, propoxycarbonyl Groups such as an alkoxycarbonyl group having 1 to 6 carbon atoms such as a group or butoxycarbonyl group, an alkoxycarbamoyl group having 1 to 6 carbon atoms such as an ethoxycarbamoyl group, a propylcarbamoyl group or a butylpentylcarbamoyl group. It is not limited to.

  P, q, and r are each a positive number of 0 or 1 or more, and p + q + r is a positive number of 3 to 10.

  Examples of the polyfunctional vinyl ether compound having four or more vinyl ether groups include compounds represented by the above general formulas (2) and (3).

In the general formulas (2) and (3), R ₂ is a linking group containing any one of a methylene group, an alkylene group having 1 to 6 carbon atoms, an oxyalkylene group, and an ester group, and p, q, l, Each m is a positive number of 0 or 1 or more, and the total number of p + q + l + m is a positive number of 3-10.

  In the present invention, the total amount of neopentyl glycol divinyl ether and the other bifunctional or higher polyfunctional vinyl ether is preferably 70% by mass or more in the ink as long as the curability is not impaired. By setting it as 70 mass% or more, improvement of cured film physical properties, such as an improvement of a cure rate and a weather resistance, can be anticipated.

  In the present invention, it is more preferable to use a trifunctional or higher polyfunctional vinyl ether together in order to obtain excellent curing characteristics such as humidity dependency of curing, solvent resistance and weather resistance of the cured film.

  In addition, the above-described trifunctional or higher polyfunctional vinyl ether may be a functional group represented by the following general formula (4) as a vinyl ether group to improve curing sensitivity, improve humidity dependency, and reduce odor. Is preferable.

In the general formula (4), R ₁ and R ₂ each represent a hydrogen atom or an organic group, and the total number of carbon atoms of the organic groups of R ₁ and R ₂ is an integer of 1 or more. An organic group is synonymous with the organic group in the said General formula (1).

[Other cationic polymerizable compounds]
In the ink of the present invention, other cationically polymerizable compounds, for example, conventionally known monofunctional vinyl ether compounds, epoxy compounds, oxetane ring-containing compounds, and the like can be used as long as the object effects of the present invention are not impaired.

  Examples of the monofunctional vinyl ether compound include n-propyl vinyl ether, isopropyl vinyl ether, n-butyl vinyl ether, isobutyl vinyl ether, 2-ethylhexyl vinyl ether, octadecyl vinyl ether, cyclohexyl vinyl ether, allyl vinyl ether, hydroxyethyl vinyl ether, hydroxybutyl vinyl ether, 9-hydroxy. Nonyl vinyl ether, 4-hydroxycyclohexyl vinyl ether, cyclohexane dimethanol monovinyl ether, triethylene glycol monovinyl ether and the like can be mentioned.

  In addition to the above, various vinyl ether compounds disclosed so far can be applied. For example, a compound containing a (meth) acryloyl group and a vinyl ether group in the molecule disclosed in Japanese Patent No. 3461501, a vinyl ether compound having an alicyclic skeleton containing at least an oxygen atom disclosed in Japanese Patent No. 4037856 , Vinyl ethers having an alicyclic skeleton disclosed in Japanese Patent Application Laid-Open No. 2005-015396, 1-indanyl vinyl ether disclosed in Japanese Patent Application Laid-Open No. 2008-137974, and Japanese Patent Application Laid-Open No. 2008-150341. 4-acetoxycyclohexyl vinyl ether and the like can be mentioned.

(Epoxy compound)
As the epoxy compound, any of monomers, oligomers, and polymers that are usually used as epoxy resins can be used. Specific examples include conventionally known aromatic epoxides, alicyclic epoxides and aliphatic epoxides. Hereinafter, the epoxide means a monomer or an oligomer thereof. You may use these compounds 1 type or 2 types or more as needed.

  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 thereof. Examples thereof include di- or polyglycidyl ethers of oxide adducts, di- or polyglycidyl ethers of hydrogenated bisphenol A or alkylene oxide adducts thereof, and novolak-type epoxy resins. Here, examples of the alkylene oxide include ethylene oxide and propylene oxide.

  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, and specific examples thereof include, for example, Celoxide 2021, Celoxide 2021A, Celoxide 2021P, Celoxide 2080, Celoxide 2000, Epoxide GT301, Epoxide GT302, Epoxide GT401, Epoxide GT403, EHPE- manufactured by Daicel Chemical Industries, Ltd. 3150, EHPEL3150CE; Union Carbide UVR-6105, UVR-6110, UVR-6128, UVR-6100, UVR-6216, VR-6000, and the like can be given.

  Preferable aliphatic epoxides include di- or polyglycidyl ethers of aliphatic polyhydric alcohols or alkylene oxide adducts thereof, and typical examples thereof include ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether or 1, Diglycidyl ether of alkylene glycol such as 6-hexanediol diglycidyl ether, polyglycidyl ether of polyhydric alcohol such as di- or triglycidyl ether of glycerin or its alkylene oxide adduct, diglycidyl of polyethylene glycol or its alkylene oxide adduct Diglycidyl of polyalkylene glycol such as ether, polypropylene glycol or diglycidyl ether of its alkylene oxide adduct Ether and the like. Here, examples of the alkylene oxide include ethylene oxide and propylene oxide.

  In addition to these compounds, monoglycidyl ethers of higher aliphatic alcohols and phenols, monoglycidyl ethers of cresol, and the like can also be used. Of these epoxides, aromatic epoxides and alicyclic epoxides are preferable, and alicyclic epoxides are particularly preferable in consideration of fast curability.

  These epoxy compounds are blended in a liquid component composed of an oxetane compound and a vinyl ether compound in an amount of 0 to 20% by mass, preferably 0 to 10% by mass. This is preferable.

(Oxetane compound)
An oxetane compound is a compound having one or more oxetane (trimethylene oxide) rings in the molecule. Specifically, 3-ethyl-3-hydroxymethyloxetane (manufactured by Toa Gosei Co., Ltd .: OXT101, etc.), 1,4-bis [(3-ethyl-3-oxetanyl) methoxymethyl] benzene (same as OXT121, etc.), 3- Ethyl-3- (phenoxymethyl) oxetane (same as OXT211), di (1-ethyl-3-oxetanyl) methyl ether (same as OXT221), 3-ethyl-3- (2-ethylhexyloxymethyl) oxetane (same as above) OX212, etc.), di (1-methyl-3-oxetanyl) methyl ether, etc. can be preferably used, especially 3-ethyl-3-hydroxymethyloxetane, 3-ethyl-3- (phenoxymethyl) oxetane, di (1 -Ethyl-3-oxetanyl) methyl ether is preferred. These can be used alone or in combination of two or more. These oxetane compounds are curable in a liquid component composed of an epoxy compound, an oxetane ring-containing compound, and a vinyl ether compound, preferably 0 to 10% by mass, curable, flexibility of cured film, base material From the viewpoint of adhesiveness.

  In addition to the above-mentioned vinyl ether, epoxy compound, and oxetane compound, the cationic polymerizable compound may contain a known cyclic compound capable of cationic polymerization. In the present invention, the vinyl ether compound, epoxy compound, oxetane compound and other cyclic compounds are referred to as cationic polymerizable compounds.

  In the present invention, the total amount of the vinyl ether compound in the ink is 70% by mass or more, and 70 to 98% by mass is particularly preferable. If it is less than 70% by mass, the copolymerization rate with other polymerizable monomers is small, so that the time required for curing becomes long, and it may be difficult to obtain sufficient film strength immediately after curing. is there. When it is more than 98% by mass, there is no room for blending other components in order to obtain suitability as an active curable inkjet ink.

[Radically polymerizable compound]
Since the active energy ray-curable ink-jet ink of the present invention contains a vinyl ether compound as a main component, it is possible to add a radical polymerizable compound. As the radically polymerizable compound, conventionally known compounds such as (meth) acrylic acid esters, maleic anhydride, thiol compounds, aryl compounds, and the like that can be copolymerized with an unsaturated double bond can be used.

  The radically polymerizable compound is preferably added within a range not impairing the cationic polymerizability of the present invention, and it is 20% by mass or less based on the whole ink.

[Active energy ray polymerization initiator]
As the active energy ray polymerization initiator that can be used in the ink of the present invention, a known photoacid generator can be used. Specifically, arylsulfonium salt derivatives (Syracure UVI-6990, Cyracure UVI-6974, manufactured by Union Carbide, Inc .; Adeka optomer SP-150, Adeka optomer SP-152, Adeka optomer SP-, manufactured by Asahi Denka Kogyo Co., Ltd.) 170, Adekaoptomer SP-172, Sun Apro CPI-100P, CPI-101A, CPI-110P, CPI-110A, CPI-200K, CPI-210S, Sanwa Chemical TS-91, Lamberti Esacure 1187, Esacure 1188, etc.), allyl iodonium salt derivatives (RP-2074, Rhodia, Irgacure 250, etc., Ciba Geigy), allene-ion complex derivatives (Irgacure 250, etc., Ciba Geigy), dia Salt derivatives, triazine type initiators and acid generator such as other halides.

Generally, PF ₆ ⁻ , AsF ₆ ⁻ , B (Ph) ₄ ^{− and the} like are used as the counter anion of the onium salt. In the present invention, particularly when P (Rf _n F _(6-n) ) ⁻ is cured. The odor resistance, the solvent resistance of the cured film, the weather resistance, and the adhesion to the substrate can be further improved, which is preferable. Rf represents a fluorine-containing aliphatic group, preferably an alkyl group in which 80% or more of hydrogen atoms are substituted with fluorine atoms. n represents the number thereof and represents an integer of 1 to 5. The n Rf may be the same or different.

  Specific examples of products include CPI-210K and CPI-210S manufactured by Sun Apro, but the cation structure is not limited thereto. A polymerization initiator disclosed in WO2005 / 116038 can also be used as appropriate.

  The active energy ray polymerization initiator is preferably contained at a ratio of 0.2 to 10 parts by mass, and further 0.5 to 5 parts by mass with respect to 100 parts by mass of the cationic polymerizable compound. If the content of the active energy ray polymerization initiator is 0.2 parts by mass or more, a desired cured product can be obtained, and if it is 10 parts by mass or less, the active energy ray polymerization initiator itself becomes an ultraviolet absorber. Thus, a sufficient curability improvement effect can be obtained without causing a shielding effect in the ink, and the storage stability of the ink at low and high temperatures can be maintained. These active energy ray polymerization initiators can be used alone or in combination of two or more.

  As a sensitizer of an active energy ray polymerization initiator, when a sulfonium salt is used as an active energy ray polymerization initiator, anthracene and anthracene derivatives (Adekaoptomer SP-100, diethoxyanthracene manufactured by Asahi Denka Kogyo Co., Ltd., And dibutoxyanthracene). When an iodonium salt is used as an active energy ray polymerization initiator, thioxanthones and the like can be used. These sensitizers can be used alone or in combination. The addition amount is preferably 0.2 to 10 parts by mass, more preferably 0.5 to 8 parts by mass with respect to 100 parts by mass of the cationic polymerizable compound. If it is 0.2 parts by mass or more, a sensitizing effect can be obtained, and if it is 5 parts by mass or less, coloring of the sensitizer itself and coloring by a sensitizer decomposition product can be suppressed.

  In addition, when a radical polymerizable compound is used in combination as the active energy ray polymerizable compound, a conventionally known radical polymerization initiator can be added.

[Colorant]
When coloring the ink of the present invention, it is preferable to use a pigment as a colorant. As the pigment, a colorless inorganic pigment such as carbon black, titanium oxide, calcium carbonate, or a colored organic pigment can be used. Examples of organic pigments include insoluble azo pigments such as toluidine red, toluidine maroon, Hansa yellow, benzidine yellow and pyrazolone red, soluble azo pigments such as ritole red, heliobordeaux, pigment scarlet, and permanent red 2B; alizarin, indanthrone, thio Derivatives from vat dyes such as indigo maroon; phthalocyanine organic pigments such as phthalocyanine blue and phthalocyanine green; quinacridone organic pigments such as quinacridone red and quinacridone magenta; perylene organic pigments such as perylene red and perylene scarlet; isoindolinone Isoindolinone organic pigments such as yellow and isoindolinone orange; Pyranthrone organic pigments such as pyranthrone red and pyranthrone orange; Thioindigo Machine pigments, condensed azo organic pigments, benzimidazolone organic pigments, quinophthalone organic pigments such as quinophthalone yellow; isoindoline organic pigments such as isoindoline yellow; other pigments such as flavanthron yellow, acylamide yellow, nickel Azo yellow, copper azomethine yellow, perinone orange, anthrone orange, dianthraquinonyl red, dioxazine violet and the like can be mentioned.

  An example of an organic pigment is Color Index (CI) No. The following is shown.

C. I. Pigment Yellow 12, 13, 14, 17, 20, 24, 74, 83, 86, 93, 109, 110, 117, 120, 125, 128, 129, 137, 138, 139, 147, 148, 150, 151, 153, 154, 155, 166, 168, 180, 185,
C. I. Pigment Orange 16, 36, 43, 51, 55, 59, 61,
C. I. Pigment Red 9, 48, 49, 52, 53, 57, 97, 122, 123, 149, 168, 177, 180, 192, 202, 206, 215, 216, 217, 220, 223, 224, 226, 227, 228, 238, 240,
C. I. Pigment violet 19, 23, 29, 30, 37, 40, 50,
C. I. Pigment Blue 15, 15: 1, 15: 3, 15: 4, 15: 6, 22, 60, 64,
C. I. Pigment Green 7, 36,
C. I. Pigment brown 23, 25, 26,
Among the above pigments, quinacridone-based, phthalocyanine-based, benzimidazolone-based, isoindolinone-based, condensed azo-based, quinophthalone-based, and isoindoline-based organic pigments are preferable because of their excellent light resistance.

  The organic pigment is preferably fine particles having an average particle diameter in the ink of 10 to 150 nm as measured by laser scattering. When the average particle size of the pigment is less than 10 nm, the light resistance is lowered due to the small particle size, and when it exceeds 150 nm, it is difficult to maintain stable dispersion, and the precipitation of the pigment is likely to occur. Stability is lowered, and a problem that minute mist called satellite occurs. However, in the case of titanium oxide, the average particle diameter is 150 to 300 nm, preferably 180 to 250 nm, in order to provide whiteness and concealment.

  In addition, it is preferable to remove coarse particles sufficiently by dispersion or filtration so that the maximum particle size of the pigment in the ink does not exceed 1 μm. If coarse particles are present, the ejection stability is also lowered.

  The organic pigment can be refined by the following method. That is, a mixture composed of at least three components of an organic pigment, a water-soluble inorganic salt of 3 mass times or more of the organic pigment, and a water-soluble solvent is made into a clay, and is kneaded strongly with a kneader or the like to be refined, and then poured into water. Stir with a high speed mixer or the like to form a slurry. Next, filtration and washing of the slurry are repeated to remove the water-soluble inorganic salt and the water-soluble solvent. In the miniaturization step, a resin, a pigment dispersant, or the like may be added.

  Examples of the water-soluble inorganic salt used in the refinement process include sodium chloride and potassium chloride. These inorganic salts are used in the range of 3 to 20 times the mass of the organic pigment. If the amount of the inorganic salt is less than 3 times by mass, a treated pigment having a desired size cannot be obtained, and if it is more than 20 times by mass, the washing process in the subsequent step is enormous, Processing amount is reduced.

  The water-soluble solvent is not particularly limited as long as it is a solvent that can be used for making an appropriate clay state of an organic pigment and a water-soluble inorganic salt used as a crushing aid and performing sufficient crushing efficiently, and is soluble in water. However, since the temperature rises during kneading and the solvent easily evaporates, a high boiling point solvent having a boiling point of 120 to 250 ° C. is preferable from the viewpoint of safety.

  As water-soluble solvents, 2- (methoxymethoxy) ethanol, 2-butoxyethanol, 2- (i-pentyloxy) ethanol, 2- (hexyloxy) ethanol, diethylene glycol, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether , Triethylene glycol, triethylene glycol monomethyl ether, liquid polyethylene glycol, 1-methoxy-2-propanol, 1-ethoxy-2-propanol, dipropylene glycol, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, low molecular weight Examples thereof include polypropylene glycol.

  In addition, in order to ensure the dispersion stability of the pigment, surface treatment by a known technique such as acidic treatment or basic treatment, synergist, various coupling agents in order to promote adsorption with the pigment dispersant on the surface thereof. Is preferable.

  In order to obtain a sufficient concentration and sufficient light resistance, the pigment is in the range of 1.5 to 8% by mass in the case of a color excluding white in the inkjet ink, and in the range of 10 to 30% by mass in the case of a white ink using titanium oxide. It is preferable that it is contained.

(Pigment dispersant)
Examples of the pigment dispersant include a hydroxyl group-containing carboxylic acid ester, a salt of a long chain polyaminoamide and a high molecular weight acid ester, a salt of a high molecular weight polycarboxylic acid, a salt of a long chain polyaminoamide and a polar acid ester, a high molecular weight unsaturated acid ester, Polymer copolymer, modified polyurethane, modified polyacrylate, polyether ester type anionic activator, naphthalene sulfonic acid formalin condensate salt, aromatic sulfonic acid formalin condensate salt, polyoxyethylene alkyl phosphate ester, polyoxyethylene nonyl Examples thereof include phenyl ether, stearylamine acetate, and pigment derivatives.

  Specific examples include “Anti-Terra-U (polyaminoamide phosphate)”, “Anti-Terra-203 / 204 (high molecular weight polycarboxylate)” manufactured by BYK Chemie, “Disperbyk-101 (polyaminoamide phosphate) Salt (acid ester), 107 (hydroxyl group-containing carboxylic acid ester), 110 (copolymer containing acid group), 130 (polyamide), 161, 162, 163, 164, 165, 166, 170 (polymer copolymer) ) "," 400 "," Bykumen "(high molecular weight unsaturated acid ester)," BYK-P104, P105 (high molecular weight unsaturated acid polycarboxylic acid) "," P104S, 240S (high molecular weight unsaturated acid polycarboxylic acid) And Lactimon (long chain amine, unsaturated acid polycarboxylic acid and silane) Con) "and the like.

  Further, “Efka CHEMICALS” “Efka 44, 46, 47, 48, 49, 54, 63, 64, 65, 66, 71, 701, 764, 766”, “Efka Polymer 100 (modified polyacrylate), 150 (fatty oil) Group modified polymer), 400, 401, 402, 403, 450, 451, 452, 453 (modified polyacrylate), 745 (copper phthalocyanine)); “Floren TG-710 (urethane oligomer)” manufactured by Kyoei Chemical Co., Ltd. "Flonon SH-290, SP-1000", "Polyflow No. 50E, No. 300 (acrylic copolymer)"; "Disparon KS-860, 873SN, 874 (polymer dispersing agent) manufactured by Enomoto Kasei Co., Ltd. , # 2150 (aliphatic polyvalent carboxylic acid), # 7004 (polyether ester type) ”, etc. And the like.

  Furthermore, “Demol RN, N (Naphthalenesulfonic acid formalin condensate sodium salt), MS, C, SN-B (aromatic sulfonic acid formalin condensate sodium salt), EP”, “Homogenol L-18” manufactured by Kao Corporation. (Polycarboxylic acid type polymer) "," Emulgen 920, 930, 931, 935, 950, 985 (polyoxyethylene nonyl phenyl ether) "," Acetamine 24 (coconut amine acetate), 86 (stearyl amine acetate) "; "Solspers 5000 (phthalocyanine ammonium salt type), 13240, 13940 (polyesteramine type), 17000 (fatty acid amine type), 24000, 32000, 7000" manufactured by Zeneca Corporation; "Nikkor T106 (polyoxyethylene sorbitan) manufactured by Nikko Chemical mono Rate), MYS-IEX (polyoxyethylene monostearate), Hexagline4-0 (hexaglyceryl ruthenate Huwei Rate) ", manufactured by Ajinomoto Fine-Techno Co., of AJISPER 821,822,824, and the like.

  These pigment dispersants are contained in an amount of 5 to 70% by mass, preferably 10 to 50% by mass, based on the pigment 100. By setting it to 5% or more, good dispersion stability can be obtained, and by setting it to 70% or less, it is possible to maintain good discharge stability.

  Furthermore, these pigment dispersants preferably have a solubility of 5% by mass or more with respect to the whole cationically polymerizable compound at 0 ° C. When the solubility is 5% by mass or more, when the ink is stored at low temperature, undesirable polymer gel or pigment soft agglomerates are unlikely to occur, and the storage stability and ejection stability of the ink are improved.

(Polymerization inhibitor)
In the ink of the present invention, it is preferable to add a cationic polymerization inhibitor. Since vinyl ether is highly reactive and a dark reaction is likely to proceed due to residual acid or acid generated slightly from the polymerization initiator during storage, it is preferable to intentionally add a polymerization inhibitor. Examples of the polymerization inhibitor include alkali metal compounds and / or alkaline earth metal compounds or amines. Since it is preferable not to add alkali metal ions as much as possible as described later, amines are suitable.

  Preferred amines are alkanolamines, N, N-dimethylalkylamines, N, N-dimethylalkenylamines, N, N-dimethylalkynylamines and the like. Isopropanolamine, tributanolamine, N-ethyldiethanolamine, propanolamine, n-butylamine, sec-butylamine, 2-aminoethanol, 2-methylaminoethanol, 3-methylamino-1-propanol, 3-methylamino-1, 2-propanediol, 2-ethylaminoethanol, 4-ethylamino-1-butanol, 4- (n-butylamino) -1-butanol, 2- (t-butylamino) ethanol, N, N-dimethylundeca Nord, N, N-dimethyldodecanol N, N-dimethyltridecanolamine, N, N-dimethyltetradecanolamine, N, N-dimethylpentadecanolamine, N, N-dimethylnonadecylamine, N, N-dimethylicosylamine, N, N-dimethyleicosylamine, N, N-dimethylhenecosylamine, N, N-dimethyldocosylamine, N, N-dimethyltricosylamine, N, N-dimethyltetracosylamine, N, N-dimethyl Pentacosylamine, N, N-dimethylpentanolamine, N, N-dimethylhexanolamine, N, N-dimethylheptanolamine, N, N-dimethyloctanolamine, N, N-dimethylnonanolamine, N, N -Dimethyldecanolamine, N, N-dimethylnonylamine, N, N-dimethyldecylami N, N-dimethylundecylamine, N, N-dimethyldodecylamine, N, N-dimethyltridecylamine, N, N-dimethyltetradecylamine, N, N-dimethylpentadecylamine, N, N-dimethyl Examples include hexadecylamine, N, N-dimethylheptadecylamine, and N, N-dimethyloctadecylamine. In addition to these, quaternary ammonium salts and the like can also be used. Among them, 2-methylaminoethanol is preferable because it can improve storage stability without reducing curability by adding a small amount.

  The addition amount of the cationic polymerization inhibitor is preferably 10 to 5000 ppm. By setting it to 10 ppm or more, good storage stability can be obtained, and it is preferable from the viewpoint that thickening of ink and good liquid repellency with respect to an ink jet nozzle can be obtained and discharge stability can be maintained. By setting it to 5000 ppm or less, the acid generation efficiency of the active energy ray initiator can be sufficiently maintained, and the curing sensitivity can be maintained.

  In the ink of the present invention, storage stability may be obtained by adding a radical polymerization inhibitor instead of the above cationic polymerization inhibitor. It is also preferable to use the cationic polymerization inhibitor and the radical polymerization inhibitor in combination. It has been found that by using a radical polymerization inhibitor in combination, the storage stability of the ink can be drastically improved even if impurities and residual acid are present in the ink. The ink of the present invention is mainly composed of vinyl ether as a cationically polymerizable compound, but since vinyl ether also has radical polymerizability, it is considered that the radical polymerization inhibitor exhibits a synergistic effect.

  Examples of radical polymerization inhibitors include methoquinone (hydroquinone monomethyl ether), hydroquinone, 4-methoxy-1-naphthol, hindered amine antioxidants, nitrogen-containing heterocyclic mercapto compounds, thioether antioxidants, and hindered phenols. Antioxidants, ascorbic acids, zinc sulfate, thiocyanates, thiourea derivatives, various sugars, phosphate antioxidants, nitrites, sulfites, thiosulfates, hydroxylamine derivatives, polycondensation of dicyandiamide and polyalkylene polyamines Such as things.

  In addition, 2,2,6,6-tetramethylpiperidinyl-N-oxyl (hereinafter abbreviated as TEMPO), which is an N-oxyl derivative, improves storage stability without reducing curability with a small amount of addition. This is preferable.

  The addition amount of the radical polymerization inhibitor is preferably 10 to 5000 ppm. By setting it to 10 ppm or more, good storage stability can be obtained, ink thickening and good liquid repellency with respect to the ink jet nozzle can be obtained, and this is preferable from the viewpoint that discharge stability can be maintained. By setting it to 5000 ppm or less, the acid generation efficiency of the active energy ray initiator can be sufficiently maintained, and the curing sensitivity can be maintained.

  In the ink of the present invention, the water content is preferably 0.5% by mass or less. More preferably, it is 0.3 mass% or less. Water acts as a cationic polymerization inhibitor and has the effect of improving the storage stability of the ink. However, by controlling the water content to 0.5% by mass or less in the ink of the present invention, overprinting can be performed in a high humidity environment. In this case, the curability, the odor during curing, the solvent resistance of the cured film, and the adhesion to the substrate can be further improved. When the amount is more than 0.5% by mass, the above-described effects are reduced, and there is a possibility that the storage stability is lowered, such as a decrease in pigment dispersibility and precipitation of a dispersant and various additives.

  As a method of setting the moisture content to 0.5% by mass or less, it can be achieved by preparing a raw material dehydrated in advance while avoiding contact with outside air and storing it in a moisture-proof packaging material. The moisture content can be measured by the Karl Fischer method, gas chromatography method, NMR measurement, electric conduction method, or the like.

〔Metal ions〕
In the ink of the present invention, the total amount of Na ions, Ca ions and Mg ions in the ink is preferably 100 ppm or less. These ions can be quantified by ion chromatography by mixing ink and pure water, separating the aqueous phase, and then extracting the ions extracted into the aqueous phase.

  These alkali metal ions do not cause any problems during normal ink storage, but are hardly soluble when the ink receives active energy rays and various decomposition products and active species are generated from the active energy ray polymerization initiator. May form salt. For this reason, when ink is ejected for a long period of time, a hardly soluble precipitate may be generated in the vicinity of the opening of the inkjet nozzle, which may reduce the ejection accuracy.

  The method for reducing the amount of alkali metal ions in the ink is achieved by purifying various materials used. In particular, generally available pigments, active energy ray polymerization initiators such as sulfonium salts, and cationic polymerization initiators such as vinyl ether / oxetane / epoxy may contain alkali metal ions as impurities in the production process. Therefore, it is preferable to use after each material is appropriately purified. By refining these alkali metals, the content of the counter anion is also reduced, and there is an effect that a decrease in cationic polymerizability due to impurities can be suppressed.

  It is also preferable to reduce halogen ion species such as chlorine as much as possible. Halogen ion species may significantly reduce the reactivity of the vinyl ether compound under high humidity conditions. The total amount of halogen ions is preferably less than 50 ppm, preferably less than 10 ppm, based on the total amount of ink. The reduction of the halogen ion species can be achieved by refining the raw material in the same manner as the reduction of the alkali metal ion species described above.

[Other additives]
The ink of the present invention may contain various additives such as a surfactant, a lubricant, a filler, a rust inhibitor, an antifoaming agent, a thickener, a gelling agent, and polymers as necessary.

  If necessary, a small amount of a solvent such as an ester solvent, an ether solvent, an ether ester solvent, a ketone solvent, an aromatic hydrocarbon solvent, or a nitrogen-containing organic solvent can be added.

[Ink properties]
The physical properties of the ink of the present invention preferably have the same physical properties as those of a normal curable inkjet ink. That is, the viscosity is 5 to 50 mPa · s at 25 ° C., the share rate dependency is as small as possible, the surface tension is in the range of 22 to 35 mN / m at 25 ° C., and the gel form exceeds 1 μm other than the pigment. It is preferable that there is no substance, the conductivity is 10 μS / cm or less, and the ink is free from electrical corrosion inside the head. In the continuous type, it is necessary to adjust the electric conductivity by the electrolyte. In this case, it is necessary to adjust the electric conductivity to 0.5 mS / cm or more.

  In addition, as a physical property of the ink of the present invention, a more preferable form is a calorific value of 10 mJ / unit mass when the DSC measurement of the ink is performed in the range of 25 ° C. to −25 ° C. at a rate of 5 ° C. per minute. It does not show an exothermic peak of more than mg. By selecting a material in accordance with the configuration of the present invention, it is possible to suppress a certain amount of heat generation in DSC measurement. By adopting such a configuration, even when the ink is stored at a low temperature, the generation of gel and the generation of precipitates can be suppressed.

[Ink preparation method]
The ink of the present invention is produced by thoroughly dispersing a pigment together with a vinyl ether and a pigment dispersant using an ordinary dispersing machine such as a sand mill. It is preferable to prepare a concentrated solution having a high pigment concentration in advance and dilute with an active energy ray-curable compound. Sufficient dispersion is possible even with dispersion by ordinary dispersers. Therefore, excessive dispersion energy is not applied and a large amount of dispersion time is not required, so it is difficult to cause deterioration during dispersion of ink components, and stability. Can be prepared. The prepared ink is preferably filtered through a filter having a pore diameter of 3 μm or less, and more preferably 1 μm or less.

<Inkjet recording method>
The ink of the present invention exhibits particularly preferable recording characteristics in a multipass serial recording method in which inks are stacked and cured. Specifically, the ink of the present invention is applied on a base material, and the ink on the base material is irradiated with active energy rays so that the ink is cured or semi-cured, and then the cured or semi-cured ink is applied to the ink. It includes a step of applying fresh ink and curing the ink with active energy rays. In particular, the present invention is effective in a recording method in which the film thickness of ink that is cured by a single irradiation of active energy rays is a thin film.

  Specifically, it is an ink jet recording method in which small droplets of about 1 to 20 pl are sequentially cured. Further, in the ink jet recording method using these small droplets, it is necessary to perform high-frequency ejection in order to obtain productivity. When performing such small droplets and high-frequency ejection, The active energy ray-curable ink-jet ink exhibits excellent ejection stability.

  As the active energy ray, when irradiating ultraviolet rays, for example, ultraviolet LED, ultraviolet laser, mercury arc lamp, xenon arc lamp, low pressure mercury lamp, fluorescent lamp, carbon arc lamp, tungsten-halogen copying lamp and sunlight are used. Can be used. In the case of curing with an electron beam, it is usually cured with an electron beam having an energy of 300 eV or less, but it can also be cured instantaneously with an irradiation amount of 1 to 5 Mrad.

  Furthermore, in the present invention, it is preferable to irradiate the ink with active energy rays within 0.5 seconds after the ink has landed on the substrate. By irradiating active energy rays in less than 0.5 seconds, it is possible to start curing before unnecessary moisture is taken into the ink from the outside air. It becomes possible to make solvent resistance and substrate adhesion better.

"Base material"
As a base material used for inkjet recording, all of a wide range of conventional synthetic resins used in various applications have been targeted. Specifically, for example, polyester, polyvinyl chloride, polyethylene, polyurethane, polypropylene, acrylic resin, polycarbonate , Polystyrene, acrylonitrile-butadiene-styrene copolymer, polyethylene terephthalate, polybutadiene terephthalate, etc., and the thickness and shape of these synthetic resin substrates are not limited at all. In addition, metals, glass, printing paper, etc. can be used.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. In addition, although the display of "part" or "%" is used in an Example, unless otherwise indicated, "part by mass" or "mass%" is represented.

<< Preparation of polyfunctional vinyl ether >>
J. et al. Chem. Soc. 1965 (2) 1560-1561, Am. Chem. Soc. Vol. 124, no. The following compounds VE1 to VE5 were prepared according to known synthesis methods described in 8, 1590-1591 (2002) and JP-A-2005-015396.

<< Details of each additive >>
The details of the additives abbreviated in the respective tables used in Examples 1 to 4 described later are as follows.

<Pigment>
PB15: 4 C.I. I. Pigment Blue 15: 4
<Pigment dispersant>
PB824: Azisper PB824, polymer dispersant, manufactured by Ajinomoto Fine Techno Co. <Vinyl ether compound according to the present invention>
NEPGDVE: Neopentyl glycol divinyl ether <Bifunctional vinyl ether>
TEGDVE: Triethylene glycol divinyl ether DEGDVE: Diethylene glycol divinyl ether CHDVE: Cyclohexanediol divinyl ether TEGDPE: Triethylene glycol dipropenyl ether <Other polymerizable compounds>
OXT221: oxetane 221, di [1-ethyl (3-oxetanyl)] methyl ether, manufactured by Toagosei Co., Ltd. C2021P: alicyclic epoxy compound manufactured by Daicel <polymerization initiator>
CPI-100P: Propylene carbonate 50% solution of triallylsulfonium salt, manufactured by Sun Apro, counter anion = PF6 ^- salt CPI-210S: Propylene carbonate 50% solution of triallyl sulfonium salt, manufactured by Sun Apro, counter anion _{= P (Rf n F (6} -n)) - salt <sensitizer>
DEA: Diethoxyanthracene <Cationic polymerization inhibitor>
MAE: 2-methylaminoethanol <Radical polymerization inhibitor>
TEMPO: 2,2,6,6-tetramethylpiperidine-N-oxyl <Surfactant>
KF351: Silicone surfactant, manufactured by Shin-Etsu Chemical Co., Ltd. Example 1
<Preparation of ink>
In the ink composition shown in Table 1, first, each component except an active energy ray polymerization initiator (simply indicated as a polymerization initiator), a sensitizer and a surfactant is placed in a sand mill and dispersed for 4 hours. Was distributed. Next, an active energy ray polymerization initiator, a sensitizer, and a surfactant were added and dissolved, and finally filtered with a membrane filter having an absolute filtration accuracy of 0.85 μm to prepare inks 1 to 6. The water content shown in Table 1 was measured by a gas chromatography method.

<Evaluation of ink>
Each of the prepared inks was evaluated according to the following method.

(Evaluation of continuous discharge stability)
Using a piezo head 512SH manufactured by Konica Minolta IJ, the head temperature was set so that the viscosity was 10 mPa · s, and each ink corresponding to 1 L was continuously ejected at a frequency of 20 kHz with a droplet size of 4 pl. Compared with the discharge property immediately after discharge, continuous discharge stability was evaluated according to the following criteria.

○: There was no change in the emission accuracy before and after continuous ejection. △: The accuracy error of ejection was slightly degraded after continuous ejection, but recovered by cleaning. ×: The accuracy error of ejection was degraded after continuous ejection. It did not recover even after cleaning (Evaluation of curability)
The image recording characteristics were evaluated using a serial UV curable printer equipped with a piezo head 512SH on a vinyl chloride sheet. Ink was fed from a moisture-proof metal tank, and the piping was also made of moisture-proof material so that humidity fluctuations did not occur until ink was discharged. Recording is performed with an image resolution of 720 × 720 dpi (dpi represents the number of dots per 2.54 cm), and a maximum of 4 droplets of 4 pl per pixel are applied to form a solid image of one color. Ink applied. The number of passes was 8, and the image was formed by repeating the ejection of ink and UV exposure for each pass. A 365 nm LED was used as the light source, and the UV exposure amount per pass was 10 mJ / cm ² to form an image. Note that the arrangement of the head and the light source and the scanning speed were set so that the timing at which the LED light was irradiated after the ink landed from the substrate was 0.1 to 0.4 seconds. The environment during image recording was a high humidity condition of 25 ° C. and 80%. About the solid image drawn, the film surface immediately after hardening was touched, the presence or absence of surface tack (adhesiveness) was confirmed, and sclerosis | hardenability evaluation was performed according to the following reference | standard.

○: Tack is not recognized at all △: Slightly tack is recognized ×: Clear tack is recognized (Evaluation of odor resistance)
The odor of the formed solid image was confirmed, and the odor resistance was evaluated according to the following criteria.

○: Almost no odor Δ: Slight odor is acceptable, but acceptable: Poor odor Next, as the cured film properties, the solvent resistance and weather resistance of the cured film were evaluated.

(Evaluation of solvent resistance)
The solvent resistance of each solid image was evaluated according to the following criteria.

○: Color does not fade even when rubbed 20 times or more with a cotton swab containing acetone. Δ: Slightly fades when rubbed 20 times with a cotton swab containing acetone. X: Film surface dissolves when rubbed 20 times with a cotton swab containing acetone. Sex assessment)
The solid image thus formed was subjected to a cycle of ultraviolet irradiation and humidification / condensation for one month using a QUV made by the accelerated weathering tester Q-Lab Corporation, and then the state of the cured film was visually observed, according to the following criteria: The weather resistance was evaluated.

○: No change is observed in the cured film Δ: Slight fluctuation in gloss of the cured film is observed ×: The cured film is washed away and the concentration is lowered (Evaluation of Adhesiveness of Substrate)
The adhesion of the solid image formed on the vinyl chloride sheet was evaluated by a cross-cut tape peeling test.

○: Peeling ratio is 2 or less in 25 blocks Δ: Peeling ratio is 3 to 5 in 25 blocks
X: The peeling ratio is 6 or more in 25 blocks.

  As is apparent from the results shown in Table 2, the ink of the present invention containing neopentyl glycol divinyl ether in an amount specified by the present invention is stable in continuous ejection in a recording method in which multiple passes are recorded with small droplets. It is clear that it has excellent properties, odor during curing, curability, solvent resistance, weather resistance, and substrate adhesion, all of which are superior to the comparative ink.

Example 2
<< Preparation of Inks 7-12 >>
Inks 7 to 12 were prepared in the same manner as in the preparation of each ink described in Example 1, except that the ink composition was changed as shown in Table 3.

<Evaluation of ink>
Each ink prepared above was evaluated in the same manner as in the method described in Example 1. However, the evaluation by inkjet recording is the same as the method described in Example 1 except that the number of printing passes is changed to 16 times, the current value of the LED is lowered, and the exposure energy per pass is set to 5 mJ / cm ^2. The same was done. This image forming condition is a severe condition in which the curability of the ink mainly composed of vinyl ether is lowered because the number of passes is large and the exposure energy per pass is smaller than that in the first embodiment.

  Table 4 shows the results obtained as described above.

Results from As is evident in Table 4, _P as a polymerization initiator _{(Rf n F (6-n} )) - neopentyl glycol divinyl ether onium salt (CPI-210S) with a salt as a counter anion (NEPGDVE) It can be seen that the inclusion in combination with the odor resistance during curing, the solvent resistance of the cured film, and the adhesion to the vinyl chloride sheet substrate are improved.

Example 3
<< Preparation of Inks 13-17 >>
Inks 13 to 17 were prepared in the same manner as in the preparation of each ink described in Example 1, except that the ink composition was changed to the configuration shown in Table 5.

<Evaluation of ink>
Each ink prepared above was evaluated in the same manner as in the method described in Example 2. However, in the image formation by inkjet recording, the same method as described in Example 2 was used except that the time from when the ink landed on the base material until the LED was exposed was set to 0.6 seconds. Since it takes a long time to irradiate the LED light, the ink is evaluated under severe conditions that are easily affected by humidity in the outside air.

  Table 6 shows the results obtained as described above.

  As is clear from the results shown in Table 6, by setting the water content of the ink to 0.5% or less, the curability in a high humidity environment, the odor resistance during curing, the solvent resistance of the cured film, the substrate adhesion It can be seen that the sex is improved.

Example 4
<< Preparation of inks 18 to 26 >>
Inks 18 to 26 were prepared in the same manner as in the preparation of each ink described in Example 1, except that the ink composition was changed to the configuration described in Table 7.

<Evaluation of ink>
Each ink prepared above was evaluated in the same manner as in the method described in Example 1.

  Table 8 shows the results obtained as described above.

  As is apparent from the results shown in Table 8, the ink of the present invention containing neopentyl glycol divinyl ether is a continuous discharge stability and resistance to odor during curing in a recording method in which multiple passes are recorded with small droplets. It can be seen that the curability, solvent resistance, weather resistance, and substrate adhesion are excellent.

Claims (5)

  An active energy ray-curable inkjet ink containing an active energy ray-polymerizable compound, wherein neopentyl glycol divinyl ether is contained in an amount of 10% by mass to 70% by mass. As an active energy ray polymerization initiator, P (Rf _n F _(6-n) ) ⁻ (wherein Rf represents a fluorine-containing aliphatic group and n represents an integer of 1 to 5) as a counter anion. The active energy ray-curable inkjet ink according to claim 1, further comprising an onium salt.   3. The active energy ray-curable inkjet ink according to claim 1, wherein the water content is 0.5% by mass or less.   The active energy ray-curable inkjet ink is applied with an active energy ray-curable inkjet ink on a substrate, the active energy ray is applied to the active energy ray-curable inkjet ink on the substrate, and the active energy ray is further irradiated. In an inkjet recording method for forming an image by applying an active energy ray-curable inkjet ink onto an ink and further irradiating the active energy ray, the active energy ray-curable inkjet ink is used as the active energy ray-curable inkjet ink. 4. An ink jet recording method using the active energy ray-curable ink jet ink according to any one of items 3 to 4.   5. The active energy ray-curable inkjet ink on the substrate is irradiated with the active energy ray-curable inkjet ink on the substrate within 0.5 seconds after the active energy ray-curable inkjet ink is applied on the substrate. The ink jet recording method described in 1.