Active energy ray-curable ink composition and printed matter

Abstract

To provide an active energy ray-curable ink composition capable of achieving both good film strength and visibility of the degree of curing, and to provide a printed matter having a layer of a cured product of the active energy ray-curable ink composition.SOLUTION: An active energy ray-curable ink composition comprising a leuco dye and a radically polymerizable compound, wherein the content of the leuco dye is 0.1 to 2% by mass based on the total amount of the composition, the content of the radically polymerizable compound is 35% by mass or more based on the total amount of the composition, and the content of the radically polymerizable compound having one (meth) acryloyl group in the molecule is 25% by mass or less based on the total amount of the composition, in particular, it is suitable as an ink for detecting the irradiation amount of an active energy ray.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an active energy ray-curable ink composition and a printed matter using the active energy ray-curable ink composition. [Background technology]

[0002] Printing is a method for producing decorative printed materials and includes various processes. Among these, the process of solidifying (drying, curing, etc.) printed inks, varnishes, etc. to fix them to the substrate is a critical process that determines the design and performance of the printed material. In particular, in methods of curing active energy ray-curable inks, varnishes, etc. (hereinafter also referred to as active energy ray-curable compositions) with active energy rays, a satisfactory cured state has been achieved by supplying more than sufficient energy. A satisfactory cured state prevents degradation of the design due to, for example, offset or rubbing between paper surfaces. Furthermore, ensuring a satisfactory cured state is an important factor, particularly for food packaging materials, because insufficient curing can result in offset of low-molecular-weight compounds in the coating film or migration of the packaged product due to penetration into the substrate.

[0003] Recently, with the growing trend to curb environmental destruction caused by the rapid increase in energy consumption, there has been growing interest in reducing energy consumption in printing as well, including by controlling the excessive energy supply required for curing and by launching active energy ray-curable compositions that can be cured with less energy than conventional methods.

[0004] However, when controlling the energy supply required for curing, small unpredictable problems can result in less than the required amount of energy being supplied to some printed materials, raising concerns that the quality of the printed materials may not be guaranteed.

[0005] Label indicator products are used to measure the amount of energy involved in curing during printing. Examples include the ultraviolet detection material "UV Label" (registered trademark) manufactured by Nitto Giken Kogyo Co., Ltd., and the radiation label "XR Label" (registered trademark) for confirming blood irradiation manufactured by the same company. The former changes color from colorless to color when exposed to ultraviolet light, while the latter changes color from yellow to red when exposed to radiation. Furthermore, an electron beam irradiation dose measurement material using a leuco dye has been proposed as a material for detecting electron beam irradiation dose (Patent Document 1).

[0006] Furthermore, a method for measuring the coloration of a leuco dye has been proposed as a method for evaluating the degree of cure of an active energy ray-curable composition (Patent Document 2). [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-275345 [Patent Document 2] Japanese Patent Application Laid-Open No. 2010-195985 Summary of the Invention [Problem to be solved by the invention]

[0008] When using label indicator products to measure the amount of energy required for curing during printing, they must be attached to the printing substrate beforehand, which poses challenges such as having to rewind the substrate film after attachment and re-stack the substrate paper.Attaching the label in real time during printing requires the introduction of attachment equipment and significant changes to the printing environment, making it unrealistic to introduce attachment equipment to existing printing machines.

[0009] Patent Document 1 discloses a material for measuring electron beam irradiation dose that contains a leuco dye, but contains an organic halide or the like as a radical generator. These organic halides contribute to the generation of environmentally hazardous substances when incinerated, and there is a growing movement to promote their removal from inks. Patent Document 2 discloses an active energy ray-curable resin composition that contains a leuco dye, but the coating film structure, in which inorganic fillers and monofunctional radically polymerizable compounds substantially account for the majority of the formulation, results in low coating film strength and may cause staining of printed materials.

[0010] After printing, if the degree of curing of the printed matter is checked at fixed points and poor curing is found in a specific area, it takes a great deal of effort to identify the poorly cured area. Furthermore, if the poorly cured area is not identified when a malfunction of the active energy ray irradiation equipment is found, the largest area where poor curing is thought to have occurred must be discarded in order to prevent the poorly cured product from being distributed on the market, which leads to resource waste.

[0011] Therefore, an object of the present invention is to provide an active energy ray-curable ink composition that can achieve both good film strength and visibility of the degree of cure, and a printed matter having a layer of a cured product of the active energy ray-curable ink composition. [Means for solving the problem]

[0012] As a result of extensive research into solving the above problems, the present inventors have found that the above problems can be solved by the active energy ray-curable ink composition shown below, and have thus completed the present invention.

[0013] That is, the present invention provides an active energy ray-curable ink composition containing a leuco dye and a radical polymerizable compound, the content of the leuco dye is 0.1 to 2% by mass based on the total amount of the composition; the radical polymerizable compound is present in an amount of 35% by mass or more based on the total amount of the composition; The present invention relates to an active energy ray-curable ink composition, wherein, among the radical polymerizable compounds, a radical polymerizable compound having one (meth)acryloyl group in the molecule accounts for 25 mass % or less based on the total amount of the composition.

[0014] The present invention also relates to the above actinic ray-curable ink composition, wherein the radical polymerizable compound has an average of 2 to 5 (meth)acryloyl groups in its molecule.

[0015] The present invention also relates to the above active energy ray-curable ink composition, wherein the (meth)acryloyl group concentration is 2 to 12 mmol / g.

[0016] The present invention also relates to the above-mentioned actinic ray-curable ink composition, wherein the actinic ray is an electron beam.

[0017] The present invention also relates to the above active energy ray-curable ink composition, which is substantially free of a photopolymerization initiator.

[0018] The present invention also relates to the above-mentioned actinic ray-curable ink composition, which is an ink for detecting the amount of actinic ray irradiation.

[0019] The present invention also relates to a printed matter having a layer of the cured product of the above-mentioned active energy ray-curable ink composition on a substrate. [Effects of the Invention]

[0020] According to the present invention, it is possible to provide an active energy ray-curable ink composition that can achieve both good film strength and visibility of the degree of cure, and a printed matter having a layer of a cured product of the active energy ray-curable ink composition, and by using the active energy ray-curable ink composition of the present invention for printing, it is possible to quickly identify the range in which the degree of cure does not meet the standard. DETAILED DESCRIPTION OF THE INVENTION

[0021] Hereinafter, embodiments of the present invention will be described in detail. Note that the present invention is not limited to the following embodiments, and various modifications can be made within the scope of the present invention.

[0022] The terms used in this embodiment will be explained below. "(Meth)acryloyl" means acryloyl and / or methacryloyl (methacryloyl), and "(meth)acrylate" means acrylate and / or methacrylate (methacrylate).

[0023] EO refers to ethylene oxide, and EO-modified refers to ethylene oxide-modified. PO refers to propylene oxide, and PO-modified refers to propylene oxide-modified. Additionally, in the names of radical polymerizable compounds, (XO)n (X is E or P) and XO-modified (n), n refers to the average number of XO-modified units in one molecule.

[0024] The degree of discoloration is a value obtained by quantifying the discoloration of the detection printing ink before and after curing using a color mode. Here, color mode refers to RGB color, CMYK color, Lab color, etc., and is not limited as long as the discoloration can be quantified. In one embodiment, for example, when an active energy ray-curable ink composition is applied to a substrate and then exposed to active energy rays, the color difference ΔE is calculated from the Lab color under irradiation conditions that make the coating tack-free, and the Lab color under irradiation conditions that do not make the coating tack-free.

[0025] In this embodiment, a numerical range indicated using "to" includes the numerical values ​​before and after "to" as the minimum and maximum values, respectively. In multiple numerical ranges described in stages in this embodiment, the upper limit or lower limit of a numerical range in a certain stage can be arbitrarily combined with the upper limit or lower limit of a numerical range in another stage. Furthermore, unless otherwise specified, the materials and compounds exemplified in this embodiment may be used alone or in combination of two or more types.

[0026] The actinic ray-curable ink composition of the present invention contains a leuco dye and a radically polymerizable compound, and the printed matter has a layer of a cured product of the actinic ray-curable ink composition on a substrate.

[0027] <Leuco dye> The leuco dye is colorless before being irradiated with active energy rays, but when irradiated with active energy rays and radicals are supplied from the radically polymerizable compound, etc., an ionization reaction occurs in the leuco dye contained therein, causing the leuco dye to change color. Since this color change reaction is irreversible, by storing the ink, particularly in a light-shielded environment, it is possible to record the history of active energy ray irradiation and the degree of hardening of the printing ink for a long period of time.

[0028] The leuco dye according to the present invention is preferably one or more selected from the group consisting of leuco crystal violet, leuco malachite green, benzoyl leuco methylene blue, leuco crystal violet lactone, leuco quinizarin, 2'-(2-chloroanilino)-6'-(dibutylamino)fluoran, and 3',6'-bis(dimethylamino)-2-(4-nitrophenyl)spiro[isoindole-1,9'-xanthene]-3-one. The above substances significantly discolor the active energy ray-curable ink composition of the present invention, allowing the degree of cure to be evaluated with high accuracy.

[0029] Leuco crystal violet is particularly preferred because it has a large difference in color change between the amount of radicals that generally tend to cause poor curing and the amount of radicals that is generally necessary and sufficient for curing, and has high visibility.

[0030] In one embodiment, the content of the leuco dye is 0.1 to 2 mass %, preferably 0.2 to 1.8 mass %, and more preferably 0.5 to 1.5 mass %, based on the total amount of the composition. If the content of the leuco dye is less than 0.1 mass %, the degree of discoloration will saturate even with a small amount of radicals, narrowing the range in which the degree of cure can be detected. If the content of the leuco dye exceeds 2 mass %, residual leuco dye and precipitates will be generated, and the heat during curing will increase the solubility of the leuco dye in the radical polymerizable compound, increasing the concentration of the leuco dye in the system, making the degree of discoloration unstable and reducing visibility.

[0031] <Radical polymerizable compound> The radical polymerizable compound is a compound having a radically polymerizable ethylenically unsaturated bond, and may be any compound having at least one ethylenically unsaturated bond in the molecule, including those having chemical forms such as monomers, oligomers, and polymers. The radical polymerizable compound may be used alone or in combination of two or more. Examples of radical polymerizable compounds include unsaturated carboxylic acids such as (meth)acrylic acid, itaconic acid, and maleic acid, and salts thereof, anhydrides having an ethylenically unsaturated group, acrylonitrile, styrene, and various unsaturated polyesters, unsaturated polyethers, unsaturated polyamides, and unsaturated urethanes. More specifically, the radical polymerizable compound may include 2-ethylhexyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, β-carboxyethyl (meth)acrylate, 4-tert-butylcyclohexanol (meth)acrylate, tetrahydrofurfuryl acrylate, alkoxylated tetrahydrofurfuryl acrylate, caprolactone (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, isoamyl (meth)acrylate, 2-phenoxyethyl (meth)acrylate, isodecyl (meth)acrylate, 3,3,5-trimethylcyclohexanol (meth)acrylate, cyclohexyl monofunctional radical polymerizable compounds such as methyl (meth)acrylate, isobornyl (meth)acrylate, norbornyl (meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclopentenyl (oxyethyl) (meth)acrylate, 1,4-cyclohexanedimethanol (meth)acrylate, cyclic trimethylolpropane formal (meth)acrylate, benzyl (meth)acrylate, EO-modified (2) nonylphenol acrylate, (2-methyl-2-ethyl-1,3-dioxolan-4-yl)methyl acrylate, acryloylmorpholine, N-vinylcarbazole, 1-vinylimidazole, N-vinyl-2-pyrrolidone, N-vinylcaprolactam, and N-vinylformamide; 1,3-butylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 3-methyl-1,5-pentanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, 1,10-decanediol di(meth)acrylate, 1,2-dodecanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, polyethylene glycol (200) di(meth)acrylate, polyethylene glycol (300) di(meth)acrylate, polyethylene glycol (400) di(meth)acrylate, polyethylene glycol (600) di(meth)acrylate, Bifunctional radical polymerizable compounds such as hydroxypivalic acid neopentyl glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, EO-modified (2) 1,6-hexanediol di(meth)acrylate, PO-modified (2) neopentyl glycol di(meth)acrylate, (neopentyl glycol-modified) trimethylolpropane di(meth)acrylate, dimethyloltricyclodecane di(meth)acrylate, EO-modified (4) bisphenol A di(meth)acrylate, PO-modified (4) bisphenol A di(meth)acrylate, cyclohexanedimethanol di(meth)acrylate, dicyclopentanyl di(meth)acrylate, and (2-(2-vinyloxyethoxy)ethyl acrylate); Trifunctional radical polymerizable compounds such as trimethylolpropane tri(meth)acrylate, EO-modified (3), trimethylolpropane tri(meth)acrylate, EO-modified (6), trimethylolpropane tri(meth)acrylate, EO-modified (9), trimethylolpropane tri(meth)acrylate, PO-modified (3), trimethylolpropane tri(meth)acrylate, PO-modified (6), trimethylolpropane tri(meth)acrylate, PO-modified (9), trimethylolpropane tri(meth)acrylate, ε-caprolactone-modified tris-(2-acryloxyethyl)isocyanurate, ethoxylated isocyanuric acid tri(meth)acrylate, tris(2-hydroxyethyl)isocyanurate tri(meth)acrylate, and pentaerythritol tri(meth)acrylate; tetrafunctional radical polymerizable compounds such as pentaerythritol tetra(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, EO-modified (4) pentaerythritol tetra(meth)acrylate, PO-modified (4) pentaerythritol tetra(meth)acrylate, EO-modified (4) ditrimethylolpropane tetra(meth)acrylate, and PO-modified (4) ditrimethylolpropane tetra(meth)acrylate; Pentafunctional radical polymerizable compounds such as dipentaerythritol penta(meth)acrylate, EO-modified (5) dipentaerythritol penta(meth)acrylate, and PO-modified (5) dipentaerythritol penta(meth)acrylate; Examples of such compounds include hexafunctional radical polymerizable compounds such as dipentaerythritol hexa(meth)acrylate, EO-modified (6) dipentaerythritol hexa(meth)acrylate, and PO-modified (6) dipentaerythritol hexa(meth)acrylate. The radical polymerizable compound may be a compound modified with mono- or polyalkylene oxide other than those mentioned above. In addition, as the radical polymerizable compound, urethane acrylates such as aliphatic urethane acrylate and aromatic urethane acrylate can be used as unsaturated urethanes; polyester acrylates and the like can be used as unsaturated polyesters; polyether acrylates and the like can be used as unsaturated polyethers, and epoxy acrylates and the like can also be used.

[0032] In one embodiment, the content of the radical polymerizable compound is 35 to 99.9 mass %, preferably 45 to 99.5 mass %, and more preferably 50 to 98.5 mass %, based on the total amount of the composition. In one embodiment, the content of the radical polymerizable compound having one (meth)acryloyl group in the molecule is 25% by mass or less (may be 0% by mass) and preferably 15% by mass or less (may be 0% by mass) based on the total amount of the composition. When the content of the radical polymerizable compound having one (meth)acryloyl group in the molecule is in this range, good film strength can be imparted to the coating film after curing.

[0033] Furthermore, in one embodiment, the average number of (meth)acryloyl groups in the molecule of the radical polymerizable compound is preferably 2 to 5. When the average number of (meth)acryloyl groups in the molecule of the radical polymerizable compound is 2 to 5, the amount of radicals generated from the (meth)acryloyl groups falls within a preferred range, resulting in a large degree of discoloration of the leuco dye, good visibility, and good film strength.

[0034] In one embodiment, the (meth)acryloyl group concentration of the active energy ray-curable ink composition is preferably 2 to 12 mmol / g, and more preferably 2.5 to 10 mmol / g. When the (meth)acryloyl group concentration of the active energy ray-curable ink composition is 2 to 12 mmol / g, the amount of radicals generated from the (meth)acrylate functional groups falls within a preferred range, resulting in a large degree of discoloration of the leuco dye and good visibility. The (meth)acryloyl group concentration of an active energy ray-curable ink composition is the concentration of the number of moles of (meth)acryloyl groups (Y (mmol)) contained in the active energy ray-curable ink composition (X (g)) [(Y (mmol)) / (X (g))]. The (meth)acryloyl group concentration can be calculated, for example, using the mass of the raw materials used in the production of the active energy ray-curable ink composition and the number of moles of (meth)acryloyl groups contained in the raw materials. In this case, the molecular weight of the radical polymerizable compound used to calculate the (meth)acryloyl group may be the value listed in the manufacturer's catalog or a theoretical molecular weight calculated from the structure. If an organic solvent is contained, it is not substantially contained in the cured coating film of the active energy ray-curable ink composition, and therefore is not included in the calculation of X (g).

[0035] The actinic ray-curable ink of the present invention may contain a photopolymerization initiator if necessary, but when electron beams are used as the actinic ray, it is preferable that the ink does not substantially contain a photopolymerization initiator. Here, "substantially free of" photopolymerization initiators means that they are not intentionally added to the composition and that the content due to unintentional addition is less than 1% by mass. Unintentional addition includes trace amounts in the raw materials, contamination during the composition manufacturing process, and the process for producing printed matter.

[0036] When a photopolymerization initiator is used, examples of the photopolymerization initiator that can be used include, but are not particularly limited to, a photocleavage initiator, a hydrogen abstraction initiator, and a hybrid type such as a photopolymerization initiator in which a cleavage site and a hydrogen abstraction site coexist in the molecule, or a photopolymerization initiator in which a hydrogen abstraction site and a proton donor site coexist. The photopolymerization initiator may be used alone or in combination of two or more.

[0037] Examples of photocleavage initiators include α-aminoalkylphenone compounds, α-hydroxyalkylphenone compounds, and acylphosphine oxide compounds.

[0038] More specifically, examples of the α-aminoalkylphenone compound include 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butan-1-one, 2-dimethylamino-2-(4-methyl-benzyl)-1-(4-morpholin-4-yl-phenyl)-butan-1-one, 2-benzyl-2-dimethylamino-1-(4-piperidinophenyl)-butan-1-one, 1-[4-(butylsulfanyl)phenyl]-2-methyl-2-(morpholin-4-yl)propan-1-one, 3,6-bis(2-methyl-2-morpholinopropanonyl)-9-butylcarbazole, and 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one. These compounds may be used alone or in combination of two or more.

[0039] Examples of α-hydroxyalkylphenone compounds include 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, 1-[4-(2-hydroxymethoxy)-phenyl]-2-hydroxy-2-methyl-1-propan-1-one, 2-hydroxy-1-[4-[4-(2-hydroxy-2-methyl-propionyl)-benzyl]phenyl]-2-methyl-propan-1-one, etc. These may be used alone or in combination of two or more.

[0040] Examples of acylphosphine oxide compounds include diphenylacylphenylphosphine oxide, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, 2,4,6-trimethylbenzoyl-bis(4-methylphenyl)phosphine oxide, ethoxyphenyl(2,4,6-trimethylbenzoyl)phosphine oxide, etc. These may be used alone or in combination of two or more.

[0041] Furthermore, examples of the hydrogen abstraction type polymerization initiator include dialkylbenzophenone compounds and thioxanthone compounds.

[0042] More specifically, examples of the dialkylaminobenzophenone compound include 4,4'-dialkylaminobenzophenones such as 4,4'-bis-(dimethylamino)benzophenone and 4,4'-bis-(diethylamino)benzophenone, and 4-benzoyl-4'-methyldiphenyl sulfide. The dialkylaminobenzophenone compound may be used alone or in combination of two or more types. Examples of thioxanthone compounds include 2,4-diethylthioxanthone, 2,4-dimethylthioxanthone, 2,4-diisopropylthioxanthone, 2-isopropylthioxanthone, 4-diisopropylthioxanthone, 2-isopropylthioxanthone, 4-isopropylthioxanthone, 2,4-dichlorothioxanthone, 2-chlorothioxanthone, 1-chloro-4-propoxythioxanthone, 2-hydroxy-3-(3,4-dimethyl-9-oxo-9H-thioxanthone-2-yloxy-N,N,N-trimethyl-1-propanamine hydrochloride, and the like. These compounds may be used alone or in combination of two or more.

[0043] Sensitizers include benzophenone, 4-methylbenzophenone, 2,4,6-trimethylbenzophenone, 2,3,4-trimethylbenzophenone, 4-phenylbenzophenone, 3,3'-dimethyl-4-methoxybenzophenone, 4-(1,3-acryloyl-1,4,7,10,13-pentaoxotridecyl)benzophenone, methyl-o-benzoylbenzoate, [4-(methylphenylthio)phenyl]phenylmethanone, (4-benzoylbenzyl)trimethylammonium chloride, 2-hydroxy- Examples include 2-methyl-1-phenylpropan-1-one, 1-(4-isopropylphenyl)2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-hydroxycyclohexylphenyl ketone, 2-hydroxy-2-methyl-1-styrylpropan-1-one polymer, diethoxyacetophenone, dibutoxyacetophenone, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether, benzoin normal butyl ether, etc. These may be used alone or in combination of two or more.

[0044] For example, in applications requiring reduced migration of low molecular weight substances, such as food applications, high molecular weight initiators can also be used. Examples of high molecular weight initiators include Omnipol BP, Genopol BP, Omnipol ASA, Genopol AB, Omnipol 910, Omnipol TX, and Omnipol TP. These may be used alone or in combination of two or more.

[0045] When an active energy ray-curable ink composition contains a photopolymerization initiator in addition to a radical polymerizable compound, it is presumed that upon irradiation with active energy rays, radicals are generated from the photopolymerization initiator in preference to the radical polymerizable compound, causing the leuco dye to discolor.

[0046] In one embodiment, the photopolymerization initiator is preferably 15% by mass or less, more preferably 12.5% ​​by mass or less, and even more preferably 10% by mass or less, based on the total amount of the composition. Since the amount of radicals generated during the initiation reaction is thought to have the greatest effect on the discoloration of the leuco dye, when the photopolymerization initiator is 15% by mass or less, the amount of radicals that can be generated in preference to the radical polymerizable compound falls within a range that improves the visibility of the discoloration of the leuco dye. The lower limit is 0% by mass.

[0047] In one embodiment, when the active energy ray-curable ink composition of the present invention contains a photopolymerization initiator, the generation of radicals from the photopolymerization initiator is promoted by the influence of room light, and therefore it is preferable to block light, particularly during long-term storage.

[0048] <Other ingredients> The actinic ray-curable ink composition of the present invention can contain a colored pigment having coloring power. The colored pigment may be either an inorganic pigment or an organic pigment, and various known pigments can be used. Examples of inorganic pigments include yellow lead, zinc yellow, iron blue, cadmium red, titanium oxide, zinc white, red iron oxide, ultramarine, carbon black, graphite, aluminum powder, and red iron oxide.

[0049] Examples of organic pigments include soluble azo pigments such as β-naphthols, β-oxynaphthoic acid pigments, β-oxynaphthoic acid anilide pigments, acetoacetate anilide pigments, and pyrazolone pigments; insoluble azo pigments such as β-naphthols, β-oxynaphthoic acid anilide pigments, acetoacetate anilide monoazo pigments, acetoacetate anilide disazo pigments, and pyrazolone pigments; phthalocyanine pigments such as copper phthalocyanine blue, halogenated (chlorinated or brominated) copper phthalocyanine blue, sulfonated copper phthalocyanine blue, and metal-free phthalocyanine; polycyclic pigments and heterocyclic pigments such as quinacridones, dioxazines, threnes (pyranthrones, anthranthrones, indanthrones, anthrapyrimidines, flavanthrones, thioindigo pigments, anthraquinones, perinones, perylenes, and the like), isoindolinones, metal complex pigments, and quinophthalone pigments.

[0050] Even when a pigment with coloring power is used, if there is a difference in the discoloration caused by the leuco dye before and after curing or due to differences in the intensity of the active energy rays, the color difference ΔE can be calculated using the formula described below.

[0051] The active energy ray-curable ink composition of the present invention may contain an extender pigment that does not have coloring power. The use of an extender pigment makes it possible to adjust the fluidity and coating strength of the printing ink and to suppress paper surface smearing during printing. Examples of extender pigments include barium sulfate, magnesium silicate, alumina white, calcium carbonate, magnesium carbonate, aluminum silicate, magnesium silicate, silicon dioxide, and aluminum hydroxide.

[0052] The active energy ray-curable ink composition of the present invention can contain a resin. The use of a resin can impart appropriate elasticity to the printing ink and contribute to the dispersion of color pigments. Examples of resins that can be contained in the present invention include polyvinyl chloride, acrylic resins, epoxy resins, polyester resins, polyurethane resins, cellulose derivatives (e.g., ethyl cellulose, cellulose acetate, nitrocellulose), vinyl chloride-vinyl acetate copolymers, polyamide resins, polyvinyl acetal resins, diallyl phthalate resins, alkyd resins, rosin-modified alkyd resins, petroleum resins, urea resins, and synthetic rubbers such as butadiene-acrylonitrile copolymers. Furthermore, these resins can also be modified before use. Specific examples include chlorinated, brominated, amine-modified, and carboxylic acid-modified resins. The resins can be used alone or in combination of two or more. The content of the resin is preferably 3 to 50% by mass, more preferably 5 to 40% by mass, of the total amount of the composition.

[0053] A radical polymerization inhibitor may be added to the active energy ray-curable ink composition of the present invention. Examples of radical polymerization inhibitors include (alkyl)phenols, hydroquinone, catechol, resorcinol, p-methoxyphenol, t-butylcatechol, t-butylhydroquinone, pyrogallol, 1,1-picrylhydrazyl, phenothiazine, p-benzoquinone, nitrosobenzene, 2,5-di-tert-butyl-p-benzoquinone, dithiobenzoyl disulfide, picric acid, cupferron, aluminum N-nitrosophenylhydroxylamine, tri-p-nitrophenylmethyl, N-(3-oxyanilino-1,3-dimethylbutylidene)aniline oxide, dibutyl cresol, cyclohexanone oxime cresol, guaiacol, o-isopropylphenol, butyraldoxime, methyl ethyl ketoxime, cyclohexanone oxime, etc. These may be used alone or in combination of two or more. The content of the radical polymerization inhibitor is preferably 0.01 to 5 mass %, more preferably 0.05 to 3 mass %, of the total amount of the composition.

[0054] Wax may be added to the actinic ray-curable ink composition of the present invention. Examples of waxes include natural waxes such as carnauba wax, Japan wax, lanolin, montan wax, paraffin wax, and microcrystalline wax, and synthetic waxes such as Fischer-Tropsch wax, polyethylene wax, polypropylene wax, polytetrafluoroethylene wax, polyamide wax, and silicone compounds. The content of the wax is preferably 0.1 to 10% by mass, more preferably 0.3 to 7% by mass, of the total amount of the composition.

[0055] A leveling agent can be added to the active energy ray-curable ink composition of the present invention. The leveling agent is not particularly limited as long as it has the desired leveling effect, i.e., the effect of suppressing coating defects such as cissing during printing and the effect of smoothing the surface of the coating layer to be formed. In one embodiment, examples of the leveling agent include silicone-based leveling agents, fluorine-based leveling agents, acrylic-based leveling agents, siloxane-modified acrylic-based leveling agents, and vinyl-based leveling agents. The content of the leveling agent is preferably 0.01 to 10% by mass, and more preferably 0.05 to 7% by mass, based on the total amount of the composition.

[0056] A dispersant can be added to the active energy ray-curable ink composition of the present invention. There are no particular limitations on the pigment dispersant, and known pigment dispersants can be used. Among them, resin-type pigment dispersants having a basic functional group are preferred, and examples of the basic functional group include primary, secondary, or tertiary amino groups, and nitrogen-containing heterocycles such as pyridine, pyrimidine, and pyrazine.

[0057] Examples of the pigment dispersant include the Ajisper series (Ajisper PB821, PB822, PB824, etc.) manufactured by Ajinomoto Fine-Techno Co., Ltd., the Solsperse series (Solsperse00, Solsperse32000, Solsperse38500, etc.) manufactured by Lubrizol, and the Disperbyk series (DISPERBYK-111, DISPERBYK-180, DISPERBYK-162, DISPERBYK-168, etc.) manufactured by BYK-Chemie. The content of the dispersant is preferably 0.1 to 15% by mass, more preferably 0.5 to 10% by mass, of the total amount of the composition.

[0058] The active energy ray-curable ink composition of the present invention may further contain, as necessary, a dispersant, a colorant, an antistatic agent, a surfactant, an antifoaming agent, an ultraviolet absorber, an antioxidant, an antioxidant (preservative), and the like.

[0059] In one embodiment, the active energy ray-curable composition may contain an organic solvent, and when the organic solvent is contained, the leuco dye dissolves in the organic solvent as well as the radical polymerizable compound. If the organic solvent volatilizes during printing or from the coating film, the leuco dye may precipitate, and the precipitate may further redissolve due to the heat of the printing or curing process, which may result in a decrease in the reproducibility of the degree of discoloration.

[0060] In one embodiment, the active energy ray-curable composition preferably does not substantially contain an organic solvent. Here, "substantially does not contain" an organic solvent means that the organic solvent is not intentionally added to the composition and the content due to unintentional addition is less than 5% by mass. Examples of unintentional addition include trace amounts of organic solvent contained in each raw material, or contamination during the composition production process or the printed matter production process.

[0061] The active energy ray-curable ink composition of the present invention can be used as an ink for detecting the amount of active energy ray irradiation. There is a correlation between the amount of radicals generated and the discoloration of the leuco dye. There is also a correlation between the amount of radicals generated by irradiation with active energy rays and the degree of curing of the printing ink. In other words, the degree of polymerization of the radically polymerizable compound contained in the printing ink can be directly confirmed through the degree of discoloration of the leuco dye.

[0062] The active energy ray-curable ink composition may be produced by the same method as that for conventional active energy ray-curable ink compositions, for example, by using the ink components described above at a temperature between room temperature and 100° C. For production, a kneader, a three-roll mill, an attritor, a sand mill, a gate mixer, a scandex, or other equipment for milling, mixing, and / or preparation may be used.

[0063] <Active energy rays> The actinic energy rays used to cure the actinic energy ray-curable ink composition of the present invention refer to energy rays such as ultraviolet rays and electron beams that have the property of causing chemical changes in the irradiated material. Examples include energy rays generated by mercury lamps, xenon lamps, metal hydride lamps, ultraviolet light-emitting diodes (UV-LEDs), ultraviolet laser diodes (UV-LDs), and other LEDs (light-emitting diodes) with wavelengths of 365 nm, 385 nm, 395 nm, or 405 nm, as well as gas and solid-state lasers. Among these, electron beams are preferred as actinic energy rays from the perspectives of improving reaction efficiency and performance of the final product, such as by virtue of their high irradiation energy and ability to reduce shrinkage of printed materials due to heat generation.

[0064] <Base material> The substrate for printing the active energy ray-curable ink composition of the present invention may be any material on which the printing ink can be printed. Examples of the paper substrate include ordinary paper or cardboard, and the thickness is not particularly limited. The surface of the paper substrate may be vapor-deposited with a metal such as aluminum to impart a design. The paper substrate may also be surface-coated with an acrylic resin, a urethane resin, a polyester resin, a polyolefin resin, or other resin, and may further be surface-treated by a corona treatment or other treatment. Specific examples of surface-treated paper substrates include coated paper and art paper.

[0065] Examples of resin substrates include polyolefin substrates such as polyethylene and polypropylene, polyester substrates such as polyethylene terephthalate and polylactic acid, polycarbonate substrates, polystyrene-based substrates such as polystyrene, AS resin and ABS resin, nylon substrates, polyamide substrates, polyvinyl chloride substrates, polyvinylidene chloride substrates, cellophane substrates, paper substrates, aluminum substrates, and substrates made of composite materials of these.

[0066] Alternatively, the substrate may be a vapor-deposited substrate in which an inorganic compound such as silica, alumina, or aluminum is vapor-deposited onto the substrate. Furthermore, the vapor-deposited surface may be coated with polyvinyl alcohol or the like.

[0067] The substrate preferably has been subjected to an adhesion-facilitating treatment on the surface to be printed (the surface in contact with the printing layer). Specific examples of adhesion-facilitating treatments include corona discharge treatment, ultraviolet / ozone treatment, plasma treatment, oxygen plasma treatment, and primer treatment. Furthermore, if sufficient adhesion cannot be obtained with a polyethylene terephthalate substrate, the substrate may be subjected to a surface treatment such as an acrylic coating treatment, polyester treatment, or polyvinylidene chloride treatment.

[0068] <Printed material> Examples of printing methods for the active energy ray-curable ink composition of the present invention include lithographic printing (normal lithographic printing using dampening water and waterless lithographic printing not using dampening water), letterpress printing, intaglio printing, and stencil printing.

[0069] In an embodiment of the present invention, the printed matter has a substrate and a layer of a cured product of the active energy ray-curable ink composition. The cured product can be formed by printing the active energy ray-curable ink composition by the above-mentioned printing method and curing it.

[0070] <Example> The present invention will be described in more detail below with reference to examples, but the following examples are not intended to limit the scope of the invention. In the present invention, "parts" means "parts by mass" and "%" means "% by mass".

[0071] Details of the materials listed in Table 1 are provided below. <Pigments> Titanium oxide: CR-50: manufactured by Ishihara Sangyo Kaisha, Ltd. <Radical polymerizable compound> Acryloylmorpholine: ACMO: Manufactured by KJ Chemicals Co., Ltd. PEG400DA: Miramer M280: Polyethylene glycol diacrylate manufactured by Miwon HD(EO)2DA: Miramer M202: 1,6-hexanediol EO-modified diacrylate manufactured by Miwon TMP(EO)3TA: Miramer M3130: Trimethylolpropane EO modified triacrylate manufactured by Miwon TMP(EO)15TA: Miramer M3150: Trimethylolpropane EO modified triacrylate manufactured by Miwon TMP(EO)20TA: AT-20E: Trimethylolpropane EO modified triacrylate manufactured by Shin-Nakamura Chemical Co., Ltd. GPTA: Miramer M320: Glycerin propoxytriacrylate manufactured by Miwon DiTMPTA: M-408: Ditrimethylolpropanetetraacrylate manufactured by Toagosei Co., Ltd. DPHA: Miramer M600: Dipentaerythritol hexaacrylate manufactured by Miwon <Resin> Rosin-modified resin: Resin 4 described in paragraph 0079 of WO 2017 / 164246 was used. The resin was dissolved in a radically polymerizable compound and then blended, and the blending amount in the final actinic energy ray-curable ink composition was as shown in Table 1. <Leuco dye> Leuco Crystal Violet: TCI M0344: manufactured by Tokyo Chemical Industry Co., Ltd. Leucomalachite Green: TCI M0419: Tokyo Chemical Industry Co., Ltd. Benzoyl leucomethylene blue: TCI B0207: manufactured by Tokyo Chemical Industry Co., Ltd. <Photopolymerization initiator> TPO: TCI D3358: Diphenyl (2,4,6-trimethylbenzoyl) phosphine oxide manufactured by Tokyo Chemical Industry Co., Ltd. DETX: TCI D2375: 2,4-diethylthioxanthen-9-one manufactured by Tokyo Chemical Industry Co., Ltd. EMK:TCI B0139: 4,4'-bis(diethylamino)benzophenone manufactured by Tokyo Chemical Industry Co., Ltd. 379: TCI M3451: 2-Dimethylamino-2-(4-methyl-benzyl)-1-(4-morpholin-4-yl-phenyl)-butan-1-one manufactured by Tokyo Chemical Industry Co., Ltd. <Wax> PTFE wax: FluoroSLIP 511-RC: manufactured by Shamrock Technologies Inc. <Leveling agent> Silicone: DOWSIL TM 8526 Additive <Dispersant> Alkylolamine salt: DISPERBYK-180: BYK <Inhibitor> Tertiary butylhydroquinone: t-butylhydroquinone: Fujifilm Wako Pure Chemical Industries, Ltd.

[0072] Example 1 According to the formulation in Table 1, 99.1 parts of TMP(EO)3TA as a radical polymerizable compound, 0.1 parts of leuco crystal violet, 0.5 parts of PTFE wax, 0.2 parts of silicone, and 0.1 parts of tertiary butyl hydroquinone were blended, followed by 35 parts of 1 mm diameter zirconia beads. After heating at 60°C for 20 minutes, the mixture was dispersed using a Scandex for 1 hour. The mixture was immediately filtered through a nylon mesh 60 (openings 263 μm) to obtain an active energy beam-curable ink composition.

[0073] <Examples 2 to 27 and Comparative Examples 1 to 5> According to the formulations in Table 1, the active energy ray-curable ink compositions of Examples 2 to 27 and Comparative Examples 1 to 5 were obtained by dispersing with Scandex.

[0074] [Table 1]

[0075] [Table 1]

[0076] [Table 1]

[0077] The obtained active energy ray-curable ink composition was evaluated. The evaluation included "solubility," "discoloration," and "visual visibility" as "visibility," and "crack resistance" and "blocking resistance" as "film strength." The results are also shown in Table 1.

[0078] <Visibility evaluation> <Method for evaluating solubility> The resulting actinic radiation-curable ink composition was left to stand in the dark at room temperature of 25°C and humidity of 50% RH, and the presence or absence of leuco dye precipitation was evaluated on a three-point scale after 24 hours. Observed precipitation is undesirable because the heat from the printing and curing processes causes the precipitate to redissolve, reducing the accuracy of the discoloration index. A practical level is 2 or higher. (Evaluation criteria) 3: No precipitation observed 2: Slightly precipitated 1: A lot of precipitate

[0079] <Creating printed materials> The resulting active energy ray-curable composition was applied to coated paper (OK Top Coat Plus, manufactured by Oji Paper Co., Ltd.) using a 4-section roll of an RI tester (manufactured by Tester Sangyo Co., Ltd.) and 0.25 ml of ink. The printed coating was immediately cured using an electron beam irradiator EC250 / 15 / 180L manufactured by Iwasaki Electric Co., Ltd., at an acceleration voltage of 110 kV and an electron beam dose of 15 kGy to 60 kGy, yielding a printed product. The photopolymerization initiator-containing active energy ray-curable ink compositions of Examples 11 to 14 were cured by irradiating the printed surface with ultraviolet light at varying cumulative doses using a single air-cooled mercury lamp manufactured by Toshiba Corporation, instead of electron beams, to yield printed products. The cumulative dose was determined using a UV Power Pack manufactured by EIT Inc., and was calculated as the sum of the values ​​measured in the UVA, UVB, UVC, and UVV wavelength ranges.

[0080] <<Evaluation method for discoloration>> The color values ​​L*, a*, and b* were measured using a spectrophotometer (X-rite eXact2, manufactured by X-rite). The color values ​​of the active energy ray-curable ink composition before curing were also measured in the same manner. The color difference ΔE was calculated using the following formula and used as the degree of discoloration. Here, when the active energy ray is an electron beam, L* nkGy represents the brightness of the print cured at each electron dose nkGy. 、 a* nkGy and b* nkGy indicates the hue and saturation of the print cured at nkGy. The values ​​before curing are L* 0kGy , a*0kGy , b* 0kGy It is expressed as: In addition, if the active energy rays are ultraviolet rays, L* nmJ / cm2 is the cumulative light intensity nmJ / cm 2 represents the brightness of the cured print, and a* nmJ / cm2 and b* nmJ / cm2 is nmJ / cm 2 The values ​​before curing are L* 0mJ / cm2 , a* 0mJ / cm2 , b* 0mJ / cm2 It is expressed as:

[0081] In this example, the curing temperature was 15 kGy or 30 mJ / cm 2 , which was below the curing state where the coating became tack-free. 2 The L*a*b* values ​​of the prints produced at 60kGy or 1000mJ / cm2 were compared with the L*a*b* values ​​of the prints produced at 60kGy or 1000mJ / cm2, which were completely tack-free. 2 The L*a*b* values ​​of the printed matter produced in the above were used for the calculation. (Formula 1) Color difference ΔE 15kGy―0kGy =((L* 15kGy -L* 0kGy ) 2 +(a* 15kGy -a* 0kGy ) 2 +(b* 15kGy -b* 0kGy ) 2 ) 1 / 2 (Formula 2) Color difference ΔE 60kGy―15kGy =((L* 60kGy -L* 15kGy ) 2 +(a* 60kGy -a* 15kGy ) 2 +(b* 60kGy -b* 15kGy ) 2 ) 1 / 2 (Equation 3) Slope A = ΔE 15kGy―0kGy ÷ΔE 60kGy―15kGy (Formula 4) Color difference ΔE 30mJ / cm2―0mJ / cm2 =((L* 30mJ / cm2 -L* 0mJ / cm2 ) 2 +(a* 30mJ / cm2 -a* 0mJ / cm2 )2 +(b* 30mJ / cm2 -b* 0mJ / cm2 ) 2 ) 1 / 2 (Formula 5) Color difference ΔE 1000mJ / cm2―30mJ / cm2 =((L* 1000mJ / cm2 -L* 30mJ / cm2 ) 2 +(a* 1000mJ / cm2 -a* 30mJ / cm2 ) 2 +(b* 1000mJ / cm2 -b* 30mJ / cm2 ) 2 ) 1 / 2 (Equation 6) Slope A = ΔE 30mJ / cm2―0mJ / cm2 ÷ΔE 1000mJ / cm2―30mJ / cm2

[0082] ΔE calculated using (Equation 1) or (Equation 4) 15kGy―0kGy or ΔE 30mJ / cm2―0mJ / cm2 When the value is large, it means that the leuco dye has colored well when exposed to active energy rays. ΔE calculated using (Equation 2) or (Equation 5) 60kGy―15kGy or ΔE 1000mJ / cm2―30mJ / cm2 When the value is large, it means that the discoloration of the printed material cured with a low amount of actinic energy radiation is different from the discoloration of the printed material cured with a high amount of actinic energy radiation. A larger quotient calculated by (Equation 3) or (Equation 6) means that the degree of discoloration in the high active energy ray region is smaller than that in the low active energy ray region, which is an indicator of poor visibility, and was evaluated on a three-level scale: 2 or higher is a practical level. (Evaluation criteria) Less than 3:8.0 2:8.0 or more and less than 10.0 1:10.0 or higher

[0083] <<Evaluation method for visual visibility>> Ten evaluators were asked to view each print for three seconds and evaluate whether they could distinguish the differences in color using the following evaluation criteria. The print was evaluated based on the most common evaluation (in the case of a tie, the lower evaluation was used). A practical level is 2 or above. (Evaluation criteria) 3: The difference is clearly discernible 2: You can tell the difference by looking closely 1: I can't tell the difference

[0084] <Method for evaluating film strength> <<Crack resistance>> The obtained active energy ray-curable composition was applied to an OPP film (biaxially oriented polypropylene film manufactured by Futamura Chemical Co., Ltd., thickness 20 μm) using a 4-section roll of an RI tester (manufactured by Tester Sangyo Co., Ltd.) and an ink volume of 0.25 ml. The printed coating was immediately cured using an electron beam irradiator EC250 / 15 / 180L manufactured by Iwasaki Electric Co., Ltd., at an acceleration voltage of 110 kV and an electron beam dose of 60 kGy to obtain a printed product. Furthermore, for the photopolymerization initiator-containing active energy ray-curable ink compositions of Examples 10 to 12, instead of an electron beam, a single air-cooled mercury lamp manufactured by Toshiba Corporation was used to irradiate the printed surface with an accumulated light dose of 1000 (mJ / cm2). 2 ) and cured by irradiating with ultraviolet light to obtain a printed matter. When the printed material was rolled up tightly to create a wrinkle, the strength of the film was evaluated on a 4-point scale, with a practical level of 2 or higher. (Evaluation criteria) 4: No cracks in the printed material 3: Tiny cracks appear on the print 2: Small cracks appear on the print 1: Large cracks appear on the print

[0085] <<Evaluation method for blocking resistance>> The printed matter obtained using the same method as the crack resistance evaluation method described above was cut into 4cm x 4cm squares, and the films were stacked together. Then, the test pieces were placed at a room temperature of 25°C, humidity of 50%, and a load of 2kg / cm 2 The printed matter was then left for 24 hours and the condition of the printed matter was evaluated on a 4-point scale, with 2 or above being at a practically acceptable level. (Evaluation criteria) 4: No change in the printed surface 3: Peeling is observed on less than 30% of the printed area. 2: Peeling is observed on 30% or more but less than 65% of the printed area. 1: Peeling is observed on more than 65% of the printed area.

[0086] All of Examples 1 to 27 were excellent in solubility, visibility, and film strength. In Comparative Example 1, the content of the leuco dye was low, and the visual visibility evaluation result did not reach a practical level. Comparative Example 2 has a low content of radically polymerizable compound, and the film strength is low, not meeting the practical standard. In Comparative Examples 3 and 5, the content of monofunctional radically polymerizable compounds in the active energy ray-curable compound was very high, and even when irradiated with sufficient active energy rays to become tack-free, the blocking resistance did not reach the practical standard. Comparative Example 4 contains a large amount of leuco dye, which increases the solubility and does not meet the practical standards.

[0087] As described above, the present invention makes it possible to provide an active energy ray-curable ink composition that can achieve both good film strength and high visibility of the degree of cure, and a printed matter having a layer of a cured product of the active energy ray-curable ink composition.

Claims

1. An active energy ray-curable ink composition comprising a leuco dye and a radical polymerizable compound, the content of the leuco dye is 0.1 to 2% by mass based on the total amount of the composition; the radical polymerizable compound is present in an amount of 35% by mass or more based on the total amount of the composition; an active energy ray-curable ink composition, wherein, among the radical polymerizable compounds, a radical polymerizable compound having one (meth)acryloyl group in the molecule accounts for 25 mass% or less based on the total amount of the composition.

2. 2. The active energy ray-curable ink composition according to claim 1, wherein the radical polymerizable compound has an average of 2 to 5 (meth)acryloyl groups in its molecule.

3. 2. The active energy ray-curable ink composition according to claim 1, wherein the (meth)acryloyl group concentration is 2 to 12 mmol / g.

4. The actinic ray-curable ink composition according to claim 1, wherein the actinic ray is an electron beam.

5. 2. The actinic ray-curable ink composition according to claim 1, which is substantially free of a photopolymerization initiator.

6. 2. The actinic ray-curable ink composition according to claim 1, which is an ink for detecting the amount of actinic ray irradiation.

7. A printed matter having a layer of a cured product of the actinic ray-curable ink composition according to any one of claims 1 to 5 on a substrate.

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