Active energy ray curable black ink for offset rotary printing and printed matter

Abstract

To provide black ink for active energy ray-curable offset rotary printing which improves paper peeling of a paper base material, especially, woody paper, and improves ink setting property, and has excellent dot reproducibility, and a hue approximate to oily ink, and a printed matter using the same.SOLUTION: Black ink for active energy ray-curable offset rotary printing contains a pigment, a resin, and a (meth)acrylate compound, wherein the pigment contains 13-16% of a carbon black pigment having an average particle diameter of 40-50 nm and a DBP absorption of 65-75 cm3 / 100 g, the resin contains a diallyl phthalate resin, and viscosity of the ink is 8-22 Pa s.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an actinic radiation-curable black ink for web offset printing, and to a printed matter using the same. [Background technology]

[0002] In recent years, demand for actinic radiation-curable inks has been increasing in place of oil-based inks due to their quick drying properties and ease of use, allowing for post-processing immediately after printing, and there is a demand for ink coatings that are equivalent to those of oil-based inks. Furthermore, for active energy ray-curable offset web printing inks, the high-speed printing process requires a relatively soft ink finish to prevent paper peeling during printing and ink adhesion. Furthermore, when the substrate is wood paper, this adversely affects the printability more significantly. On the other hand, a soft ink can also lead to a decrease in halftone dot reproducibility, so the balance between ink viscosity and fluidity is also important.

[0003] As a method for improving such paper peeling and ink receptivity of a substrate, for example, Patent Document 1 discloses a method for improving paper peeling in an offset printing ink containing a rosin-modified phenolic resin and a vegetable oil component. Also, Patent Document 2 discloses a method for maintaining excellent curability and fluidity without paper peeling in an active energy ray-curable ink containing a photopolymerization initiator, a (meth)acrylate monomer, a binder, and an extender pigment.

[0004] Furthermore, for example, Patent Document 3 discloses a method for improving paper peeling and ink adhesion in a lithographic printing ink containing a rosin-modified phenolic resin obtained by reacting rosins, a novolak-resol type phenolic resin, and recycled vegetable oil.

[0005] However, while the methods described in Patent Documents 1 and 2 improve paper peeling, they have the problem of being insufficient in terms of dot reproducibility. Also, the method described in Patent Document 3 does not sufficiently improve ink receptivity during high-speed printing or on low-grade paper with weak paper strength, such as recycled paper. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-241866 [Patent Document 2] Japanese Patent Publication No. 2020-019915 [Patent Document 3] Japanese Patent Application Laid-Open No. 2013-023618 Summary of the Invention [Problem to be solved by the invention]

[0007] The object of the present invention is to provide an actinic ray-curable black ink for offset web printing that improves paper peeling and ink receptivity on paper substrates, particularly wood paper, and has excellent dot reproducibility and a hue similar to that of oil-based inks, as well as to provide printed matter using the same. [Means for solving the problem]

[0008] As a result of extensive research into solving the above-mentioned problems, the present inventors have found that the above-mentioned problems can be solved by the actinic radiation-curable black ink for web offset printing described below, and by a printed matter using the same, and have thus completed the present invention.

[0009] That is, the present invention provides an actinic ray-curable black ink for web offset printing, which contains a pigment, a resin, and a (meth)acrylate compound, The pigment has an average particle size of 40 to 50 nm and a DBP absorption of 65 to 75 cm 3 / 100g contains 13-16% carbon black pigment, the resin comprises a diallyl phthalate resin; The present invention relates to an actinic ray-curable black ink for web offset printing, having an ink viscosity of 8 to 22 Pa·s.

[0010] The present invention also relates to the above-mentioned actinic ray-curable black ink for web offset printing, wherein the resin further contains a rosin-modified resin.

[0011] The present invention also relates to the above-mentioned actinic ray-curable black ink for web offset printing, wherein the rosin-modified resin is a reaction product of an addition reaction product of a rosin acid (A) and an α,β-unsaturated carboxylic acid or its acid anhydride (B), and a polyol (C).

[0012] The present invention also relates to the above-mentioned actinic ray-curable black ink for web offset printing, wherein the (meth)acrylate compound comprises an alkylene oxide-modified (meth)acrylate compound having two or more (meth)acryloyl groups in the molecule.

[0013] The present invention also relates to the above-mentioned actinic ray-curable black ink for web offset printing, which further contains silica.

[0014] The present invention also relates to a printed matter obtained by printing the above-mentioned active energy ray-curable black ink for web offset printing on a paper substrate and curing it with active energy rays.

[0015] The present invention also relates to the above printed matter, wherein the paper substrate is wood paper. [Effects of the Invention]

[0016] The present invention has made it possible to provide an actinic ray-curable black ink for web offset printing that improves paper peeling and ink receptivity on paper substrates, particularly wood paper, and has excellent dot reproducibility and a hue similar to that of oil-based ink, as well as printed matter using the same. DETAILED DESCRIPTION OF THE INVENTION

[0017] The present invention will be described in detail below. Note that the present invention is not limited to the following embodiments and can be practiced with various modifications within the scope of the spirit thereof. Furthermore, unless otherwise specified, "parts" means "parts by mass" and "%" means "% by mass." <Active energy ray curable black ink for web offset printing> The actinic ray-curable black ink for web offset printing of the present invention contains a pigment, a resin, and a (meth)acrylic compound.

[0018] Hereinafter, the components that are or can be contained in the active energy ray-curable black ink for web offset printing of the present invention (hereinafter also simply referred to as "ink") will be described.

[0019] <Pigments> The active energy ray curable black ink for web offset printing of the present invention has an average particle diameter of 40 to 50 nm and a DBP absorption of 65 to 75 cm 3 Carbon black pigment is used in an amount of 13 to 16% by mass per 100g of ink. By using a carbon black pigment that satisfies this condition, ink acceptance and flowability are improved. The average particle size is the average diameter calculated by measuring small spherical components (which have a microcrystalline outline and cannot be separated) that make up the carbon black aggregates using an electron microscope.

[0020] <Resin> The active energy ray-curable black ink for web offset printing of the present invention contains a resin. When the ink contains a resin, the viscosity and emulsification resistance of the ink are improved. The resin is preferably a resin that is compatible with and soluble in (meth)acrylate compounds.

[0021] <Diallyl phthalate resin> The present invention includes a diallyl phthalate resin as the resin, which significantly improves ink flowability. The diallyl phthalate resin may be either an orthodiallyl phthalate resin or an isodiallyl phthalate resin, and may be used alone or in combination of two or more types, but preferably contains an isodiallyl phthalate resin.

[0022] <Rosin-modified resin> The resin of the present invention preferably further contains a rosin-modified resin. The rosin-modified resin in the present invention refers to a resin containing a skeleton derived from rosin in the resin skeleton. The inclusion of the rosin-modified resin maintains a balanced flowability and improves the ink emulsification rate.

[0023] Furthermore, the rosin-modified resin in the present invention is preferably a rosin-modified resin formed by reaction with a hydroxyl group of a compound obtained by the Diels-Alder reaction of an organic acid having a conjugated double bond contained in the rosin acids (A) with an α,β-unsaturated carboxylic acid or its acid anhydride (B), an organic acid among the rosin acids (A) that does not have a conjugated double bond, or another organic acid, or a compound formed by reaction of a carboxylic acid in each of these with a polyol (C) to form an ester bond.

[0024] <Rosin acids (A)> The rosin acids (A) used to obtain the rosin-modified resin of the present invention refer to monobasic acids having a cyclic diterpene skeleton. These include rosin acid, disproportionated rosin acid, hydrogenated rosin acid, and alkali metal salts of these compounds. Specific examples include abietic acid, which has a conjugated double bond, and its conjugated compounds, such as neoabietic acid, palustric acid, and levopimaric acid, as well as pimaric acid, isopimaric acid, sandaracopimaric acid, and dehydroabietic acid, which do not have a conjugated double bond. Examples of natural resins containing these rosin acids (A) include gum rosin, wood rosin, and tall oil rosin.

[0025] The amount of rosin acid (A) used to obtain the rosin-modified resin of the present invention is preferably 20 to 70 mass %, more preferably 30 to 60 mass %, based on the total amount of resin raw materials. If the amount of rosin acid (A) is 20 mass % or more, the gloss of the active energy ray-curable coating varnish containing the resin will be good, and if the amount is 70 mass % or less, the abrasion resistance of the active energy ray-curable coating varnish will be good.

[0026] <α,β-Unsaturated carboxylic acid or its acid anhydride (B)> Examples of the α,β-unsaturated carboxylic acid or its acid anhydride (B) used to obtain the rosin-modified resin of the present invention include maleic acid, fumaric acid, citraconic acid, itaconic acid, crotonic acid, isocrotonic acid, etc., and their acid anhydrides. In view of the reactivity with the rosin acids (A), maleic acid or its acid anhydride is preferred.

[0027] In the present invention, the blending amount of the α,β-unsaturated carboxylic acid or its acid anhydride (B) is preferably in the range of 60 to 200 mol %, more preferably in the range of 70 to 180 mol %, and particularly preferably in the range of 80 to 155 mol %, relative to the rosin acids (A). When the blending amount of the α,β-unsaturated carboxylic acid or its acid anhydride (B) is adjusted within the above range, it is easy to obtain a rosin-modified resin having excellent friction resistance and adhesion.

[0028] <Carboxylic acids other than (A) and (B) (hereinafter also referred to as "other organic acids")> In order to obtain the rosin-modified resin of the present invention, in addition to the rosin acids (A) and the α,β-unsaturated carboxylic acid or its acid anhydride (B), other organic acids may be used alone or in combination of two or more. The blending amount of the other organic acids is preferably 0 to 30% by mass, more preferably 0 to 20% by mass, based on the total blending amount of the resin raw materials.

[0029] Specific examples of other organic acids include, but are not limited to, the following:

[0030] <Organic monobasic acid> aromatic monobasic acids such as benzoic acid, methylbenzoic acid, tertiary butylbenzoic acid, naphthoic acid, and orthobenzoylbenzoic acid; Compounds that have conjugated double bonds but do not have a cyclic diterpene skeleton, such as conjugated linoleic acid, eleostearic acid, parinaric acid, and calendic acid etc.

[0031] <Alicyclic polybasic acid or its acid anhydride> Examples thereof include 1,2,3,6-tetrahydrophthalic acid, 3-methyl-1,2,3,6-tetrahydrophthalic acid, 4-methyl-1,2,3,6-tetrahydrophthalic acid, 1,2-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, and acid anhydrides thereof.

[0032] (Other organic polybasic acids or their acid anhydrides) Examples of the acid anhydride include alkenylsuccinic acids such as oxalic acid, malonic acid, succinic acid, glutaric acid, pimelic acid, sebacic acid, azelaic acid, dodecenylsuccinic acid, and pentadecenylsuccinic acid, o-phthalic acid, terephthalic acid, trimellitic acid, pyromellitic acid, and acid anhydrides thereof.

[0033] <Polyol (C)> The polyol (C) forms an ester bond by reaction with a compound obtained by the Diels-Alder reaction between an organic acid having a conjugated double bond contained in the rosin acids (A) and an α,β-unsaturated carboxylic acid or its acid anhydride (B), an organic acid of the rosin acids (A) that does not have a conjugated double bond, or another organic acid. To obtain the rosin-modified resin of the present invention, the following polyols can be used alone or in combination. Specific examples of polyols include, but are not limited to, the following:

[0034] (Linear alkylene dihydric polyol) 1,2-ethanediol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,4-butanediol, 1,2-pentanediol, 1,5-pentanediol, 1,6-hexanediol, 1,2-hexanediol, 1,5-hexanediol, 2,5-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,2-octanediol, 1,9-nonanediol, 1,2-decanediol, 1,10-decanediol, 1,12-dodecanediol, 1,2-dodecanediol, 1,14-tetradecanediol, 1,2-tetradecanediol, 1,16-hexadecanediol, 1,2-hexadecanediol, and the like.

[0035] <Branched alkylene dihydric polyol> 2-methyl-2,4-pentanediol, 3-methyl-1,5-pentanediol, 2-methyl-2-propyl-1,3-propanediol, 2-butyl-2-ethyl-1,3-propanediol, 2,4-dimethyl-2,4-pentanediol, 2,2-dimethyl-1,3-propanediol, 2,2,4-trimethyl-1,3-pentanediol, dimethylol octane, 2-ethyl-1,3-hexanediol, 2,5-dimethyl-2,5-hexanediol, 2-methyl-1,8-octanediol, 2-butyl-2-ethyl-1,3-propanediol, 2,4-diethyl-1,5-pentanediol, and the like.

[0036] <Cyclic dihydric polyol> Cyclic alkylene dihydric polyols such as 1,2-cycloheptanediol, tricyclodecane dimethanol, 1,2-cyclohexanediol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanediol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, hydrogenated bisphenol A, hydrogenated bisphenol F, hydrogenated bisphenol S, hydrogenated catechol, hydrogenated resorcinol, and hydrogenated hydroquinone; aromatic dihydric polyols such as bisphenol A, bisphenol F, bisphenol S, catechol, resorcinol, and hydroquinone.

[0037] <Other dihydric polyols> Divalent polyether polyols such as polyethylene glycol (n=2 to 20), polypropylene glycol (n=2 to 20), and polytetramethylene glycol (n=2 to 20), polyester polyols, and the like.

[0038] <Trivalent polyol> Glycerin, trimethylolpropane, 1,2,6-hexanetriol, 3-methylpentane-1,3,5-triol, hydroxymethylhexanediol, trimethylol octane, etc.

[0039] <Trivalent or higher polyols> Linear, branched, and cyclic polyols having tetrahydric or higher valences, such as pentaerythritol, diglycerin, ditrimethylolpropane, dipentaerythritol, sorbitol, inositol, and tripentaerythritol.

[0040] The rosin-modified resin in the present invention preferably has a weight-average molecular weight of 3,000 to 30,000, more preferably 3,000 to 15,000. When the weight-average molecular weight is 3,000 to 30,000, good abrasion resistance and adhesion are achieved.

[0041] The rosin-modified resin in the present invention preferably has an acid value of 20 to 80 mgKOH / g, more preferably 30 to 80 mgKOH / g, even more preferably 40 to 80 mgKOH / g, and particularly preferably 50 to 80 mgKOH / g. When the acid value of the rosin-modified resin is within the above range, an active energy ray-curable coating varnish using the resin has excellent adhesion.

[0042] The melting point of the rosin-modified resin is preferably 50° C. or higher, more preferably in the range of 60 to 100° C. The melting point can be measured using a BUCHI Melting Point M-565 at a temperature rise rate of 0.5° C. / min.

[0043] <(Meth)acrylate compounds> In this specification, unless otherwise specified, the terms "(meth)acryloyl," "(meth)acrylic acid," "(meth)acrylate," and "(meth)acryloyloxy" mean "acryloyl and / or methacryloyl," "acrylic acid and / or methacrylic acid," "acrylate and / or methacrylate," and "acryloyloxy and / or methacryloyloxy," respectively. Additionally, "PO" represents "propylene oxide," and "EO" represents "ethylene oxide."

[0044] The active energy ray-curable black ink for web offset printing of the present invention contains a (meth)acrylate compound. The (meth)acrylate compound that can be used in the present invention is not particularly limited as long as it is a compound having one or more (meth)acryloyl groups, and includes any of the forms of a monomer, oligomer, and polymer. In the present invention, the (meth)acrylate compound may be used alone or in combination of two or more kinds.

[0045] In the present invention, the content of the (meth)acrylate compound is preferably 40 to 80 mass %, more preferably 45 to 70 mass %, relative to the total mass of the ink.

[0046] <Monomer> In the present invention, it is preferable that the (meth)acrylate compound contains a monomer. In the present invention, the term "monomer" refers to a compound that is the smallest structural unit for constituting an oligomer or a polymer. Specifically, the monomer may be 2-ethylhexyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, β-carboxylethyl (meth)acrylate, 4-tert-butylcyclohexyl (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, or the like. Monofunctional (meth)acrylate monomers having one (meth)acryloyl group in the molecule, such as acrylate, cyclohexyl (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, and acryloylmorpholine, Monofunctional vinyl monomers having one vinyl group in the molecule, such as 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, neopentyl glycol di(meth)acrylate hydroxypivalate , 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, dimethyloltricyclodecane di(meth)acrylate, dicyclopentanyl di(meth)acrylate, and other bifunctional (meth)acrylate monomers having two (meth)acryloyl groups in the molecule; Trifunctional (meth)acrylate monomers having three (meth)acryloyl groups in the molecule, such as trimethylolpropane tri(meth)acrylate, EO-modified (3) trimethylolpropane tri(meth)acrylate, EO-modified (6) trimethylolpropane tri(meth)acrylate, PO-modified (3) 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 (meth)acrylate monomers having four acryloyl groups in the molecule, such as pentaerythritol tetra(meth)acrylate, EO-modified (4) pentaerythritol tetra(meth)acrylate, and ditrimethylolpropane tetra(meth)acrylate; Pentafunctional (meth)acrylate monomers having five (meth)acryloyl groups in the molecule, such as dipentaerythritol penta(meth)acrylate; Examples include hexafunctional (meth)acrylate monomers having six (meth)acryloyl groups in the molecule, such as dipentaerythritol hexa(meth)acrylate.

[0047] Among these, it is preferable that the (meth)acrylate compound contains a difunctional to hexafunctional (meth)acrylate monomer from the viewpoint of flowability.

[0048] The total content of di- to hexafunctional (meth)acrylate monomers is preferably 70% by mass or more, more preferably 80% by mass or more, and particularly preferably 90% by mass or more, based on the total mass of the (meth)acrylate compound.

[0049] When a monofunctional (meth)acrylate monomer is contained, from the viewpoint of curability, the content thereof is preferably 10% by mass or less, and more preferably 5% by mass or less, based on the total mass of the active energy ray-curable black ink for offset web printing.

[0050] <Oligomer> The present invention may contain an oligomer as the (meth)acrylate compound. In the present invention, the "oligomer" refers to a polymer having structural units based on 2 to 100 monomers.

[0051] The oligomer is preferably a compound having a (meth)acryloyl group as a polymerizable group in the molecule, and in this case, the number of (meth)acryloyl groups per molecule is preferably 1 to 6, and more preferably 2 to 4, from the viewpoint of flexibility.

[0052] The weight average molecular weight of the oligomer is preferably 400 to 10,000, more preferably 500 to 5,000. Here, the "weight average molecular weight" can be determined as a styrene-equivalent molecular weight by general gel permeation chromatography (hereinafter, referred to as GPC).

[0053] Examples of the oligomer include urethane acrylate oligomers such as aliphatic urethane acrylate oligomers and aromatic urethane acrylate oligomers, acrylic ester oligomers, polyester acrylate oligomers, and epoxy acrylate oligomers. The oligomers may be used alone or in combination of two or more.

[0054] The (meth)acrylate compound of the present invention preferably contains an alkylene oxide-modified (meth)acrylate compound having two or more (meth)acryloyl groups in the molecule. By containing an alkylene oxide-modified (meth)acrylate compound having two or more (meth)acryloyl groups, the ink can be made to have a low viscosity, which is expected to improve paper peeling and ink receptivity.

[0055] <Photopolymerization initiator> The active energy ray-curable black ink for web offset printing of the present invention may contain a photopolymerization initiator. There are no particular limitations on the photopolymerization initiator that can be used in the present invention, and known photopolymerization initiators can be used. Specific examples include benzophenone-based compounds, dialkoxyacetophenone-based compounds, α-hydroxyalkylphenone-based compounds, α-aminoalkylphenone-based compounds, acylphosphine oxide-based compounds, and thioxanthone-based compounds. The photopolymerization initiator may be used alone or in combination of two or more.

[0056] Examples of the benzophenone compounds include benzophenone, 4-methylbenzophenone, 4-phenylbenzophenone, 4,4'-bis(diethylamino)benzophenone, 4,4'-bis(dimethylamino)benzophenone, and [4-(methylphenylthio)phenyl]-phenylmethanone.

[0057] Examples of the dialkoxyacetophenone compounds include 2,2-dimethoxy-2-phenylacetophenone, dimethoxyacetophenone, and diethoxyacetophenone.

[0058] Examples of the α-hydroxyalkylphenone compounds include 1-hydroxycyclohexylphenyl ketone, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, 1-[4-(2-hydroxymethoxy)-phenyl]-2-hydroxy-2-methyl-1-propan-1-one, and 2-hydroxy-1-{4-[4-(2-hydroxy-2-methyl-propionyl)-benzyl]phenyl}-2-methyl-propan-1-one.

[0059] Examples of the α-aminoalkylphenone compounds include 2-methyl-1-[4-(methoxythio)-phenyl]-2-morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone-1, and 2-(dimethylamino)-2-[(4-methylphenyl)methyl]-1-[4-(4-morpholinyl)phenyl]-1-butanone.

[0060] Examples of the acylphosphine oxide compounds include diphenylacylphenylphosphine oxide, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, and bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide.

[0061] Examples of the thioxanthone compounds include 2-isopropylthioxanthone, 2,4-dimethylthioxanthone, and 2,4-diethylthioxanthone.

[0062] The content of the photopolymerization initiator is preferably 1 to 20% by mass, and more preferably 5 to 15% by mass, based on the total mass of the ink.

[0063] <Silica> The active energy ray-curable black ink for web offset printing of the present invention preferably contains silica. By including silica, improvement in halftone dot reproducibility can be expected. The content of the silica is preferably 0.4 to 2 mass %, more preferably 0.5 to 1.5 mass %, based on the total mass of the ink.

[0064] The silica may be AEROSIL 90, AEROSIL 130, AEROSIL 150, AEROSIL 200, AEROSIL 255, AEROSIL 300, AEROSIL 380, AEROSIL OX50, AEROSIL TT600, AEROSIL 200Pharma, AEROSIL 300Pharma, AEROSIL R972, AEROSIL L974, AEROSIL R104, AEROSIL R106, AEROSIL L202, AEROSIL R805, AEROSIL L812, AEROSIL R812S, AEROSIL R816, AEROSIL R7200, AEROSIL R8200, AEROSIL L9200, AEROSIL R711, AEROSIL RY50, AEROSIL NY50, AEROSIL L7200, AEROSIL L7200, AEROSIL L711, AEROSIL L720 ... Examples include AEROSIL RY200, AEROSIL RY200S, AEROSIL RX50, AEROSIL NAX50, AEROSIL RX200, AEROSIL RX300, AEROSIL R504, AEROSIL R972Pharma, and Nipsil LP manufactured by Tosoh Silica Corporation.

[0065] <Other ingredients> The active energy ray-curable black ink for web offset printing of the present invention may contain, in addition to the above components, a sensitizer, a polymerization inhibitor, an extender pigment, and the like, as required.

[0066] <Sensitizer> The active energy ray-curable black ink for web offset printing of the present invention may contain a sensitizer. By containing a sensitizer, curability can be further improved. Specific examples of sensitizers include triethanolamine, methyldiethanolamine, triisopropanolamine, aliphatic amines, ethyl 2-dimethylaminobenzoate, ethyl 4-dimethylaminobenzoate, isoamyl 4-dimethylaminobenzoate, and dibutylethanolamine.

[0067] <Polymerization inhibitor> The actinic ray-curable black ink for web offset printing of the present invention may contain a polymerization inhibitor, such as 4-methoxyphenol, hydroquinone, methylhydroquinone, t-butylhydroquinone, 2,6-di-t-butyl-4-methylphenol, phenothiazine, or an aluminum salt of N-nitrosophenylhydroxylamine.

[0068] The content of the polymerization inhibitor is preferably 0.01 to 2% by mass relative to the total mass of the ink, from the viewpoint of maintaining curability and enhancing the stability of the ink.

[0069] In the present invention, the active energy ray-curable black ink for web offset printing preferably contains substantially no water, which means that the amount of water contained is 3% by mass or less relative to the total mass of the ink.

[0070] <Extender pigment> The active energy ray-curable black ink for web offset printing of the present invention may contain an extender pigment (except silica). Examples of the extender pigment include clay, talc, barium sulfate, calcium carbonate, ground calcium carbonate, barium carbonate, magnesium carbonate, and bentonite.

[0071] <Ink viscosity> The viscosity of the actinic radiation-curable black ink for web offset printing of the present invention is 8 to 22 Pa·s. With a viscosity in this range, paper peeling and deterioration of ink receptivity can be suppressed even on low-grade paper such as wood paper.

[0072] <Printed material> The printed matter of the present invention can be obtained by printing an actinic ray-curable black ink for web offset printing on a substrate and curing it with actinic ray.

[0073] The substrate of the present invention is not particularly limited as long as it is a paper substrate, and known substrates can be used. Specific examples include coated papers such as art paper, coated paper, and cast paper, wood-free paper, medium-quality paper, and recycled paper such as newsprint, and synthetic papers such as Yupo paper.

[0074] In the present invention, it is particularly preferable to use wood paper, since it is highly effective in terms of ink receptivity and dot reproducibility.

[0075] In the present invention, the method for curing the active energy ray-curable black ink for offset web printing is not particularly limited, and known methods can be used. For example, the ink can be cured by irradiation with α-rays, γ-rays, electron beams, X-rays, ultraviolet light, visible light, or infrared light. Among these, ultraviolet light and electron beams are preferred, and ultraviolet light is more preferred. The peak wavelength of the ultraviolet light is preferably 200 to 600 nm, and more preferably 350 to 420 nm.

[0076] The active energy ray source is not particularly limited and may be any known source. Specific examples include mercury lamps, xenon lamps, metal hydride lamps, LEDs (light-emitting diodes) such as ultraviolet light-emitting diodes (UV-LEDs) and ultraviolet laser diodes (UV-LDs), and gas / solid-state lasers. Among these, ultraviolet light-emitting diodes (UV-LEDs) are preferred. [Example]

[0077] The present invention will be specifically described below with reference to examples and comparative examples. However, the present invention is not limited to the following examples. In the examples and comparative examples, "parts" and "%" represent "parts by mass" and "% by mass", respectively.

[0078] <Preparation of resin varnish> 30 parts of diallyl phthalate resin (Daiso DAP A, manufactured by Daiso Co., Ltd.) having a weight average molecular weight of 50,000 was dissolved in 70 parts of ditrimethylolpropane tetraacrylate, and the mixture was heated and mixed (80° C.) to prepare a resin varnish.

[0079] <Preparation of active energy ray curable black ink for offset web printing> Example 1 A black ink was prepared by mixing 15 parts of #25 carbon black, 15 parts of EO (3) modified trimethylol propane triacrylate and 15 parts of EO modified (4) bisphenol A di(meth)acrylate as (meth)acrylate compounds, 3 parts of Omnirad 379, 2 parts of Omirad OMBB, 2 parts of Omnirad DETX, and 3 parts of Omnirad EMK as photopolymerization initiators, 1.5 parts of Nipsil LP as silica, 2 parts of talc and 1.2 parts of magnesium carbonate as extender pigments, 0.3 parts of Q-1301 as a polymerization inhibitor, and 40 parts of resin varnish. The mixture was stirred and mixed using a butterfly mixer, and then dispersed using a three-roll mill so that the maximum particle size was 7.5 μm or less.

[0080] Examples 2 to 13, Comparative Examples 1 to 8 Black inks of Examples 2 to 17 were obtained in the same manner as in Example 1, except that the raw materials and amounts shown in Table 1 were changed. Note that blank cells indicate that no ingredients were blended.

[0081] [Table 1]

[0082] [Table 1]

[0083] In Table 1, the notations are explained as follows: [resin] iso-DAP: TFH-2833, manufactured by Toshin Yushi Co., Ltd. o-DAP: Toyochem Co., Ltd., KFH-2858 Rosin-modified resin 1: Resin 4 described in paragraph 0076 of WO 2017 / 164246 was used. Rosin-modified resin 2: Resin 5 described in paragraph 0076 of WO 2017 / 164246 was used. Acrylic resin: Arakawa Chemical Industries, Ltd., Beamset 271 [Carbon black pigment] #25: Carbon black pigment manufactured by Mitsubishi Chemical Corporation, #25 MA-14: Carbon black pigment manufactured by Mitsubishi Chemical Corporation, MA-14 MA-11: Mitsubishi Chemical Corporation carbon black pigment, MA-11 Laven 1080: Birla Carbon's carbon black pigment, Laven 1080 Ultra Powder Nerox 555: Orion Engineered Carbon carbon black pigment, Nerox 555 [(Meth)acrylate compounds] TMP(EO)TA: EO(3) modified trimethylolpropane triacrylate: BASF, LAROMER LR8863 BisA: EO modified (4) Bisphenol A di(meth)acrylate: Photomer 4028 manufactured by IGM TMP(PO)TA: PO(3) modified trimethylolpropane triacrylate: Etamer 2381, manufactured by Choko Materials Co., Ltd. DiTMPTA: Ditrimethylolpropanetetraacrylate: EBECRYL 1142 manufactured by Daicel-Allnex Co., Ltd. [Photopolymerization initiator] Omnirad379: iGM Resins, Omnirad379 (2-dimethylamino-2-(4-methylbenzyl)-1-(4-morpholinophenyl)-butan-1-one) OmniradOMBB: OmniradOMBB (methyl-O-benzoyl benzoate), manufactured by iGM RESINS OmniradDETX: OmniradDETX (2,4-dimethylthioxanthone), manufactured by iGM RESINS OmniradEMK: OmniradEMK (4,4'-bis(diethylamino)benzophenone), manufactured by iGM RESINS [silica] Nipsil LP: manufactured by Tosoh Silica Corporation, Nipsil LP: hydrophilic wet silica [others] (extender pigment) High Filler 5000PJ: Manufactured by Matsumura Sangyo Co., Ltd. High Filler 5000PJ: Talc Magnesium carbonate: Magnesium carbonate manufactured by Naikai Salt Industry Co., Ltd. (polymerization inhibitor) Q-1301: N-nitrosophenylhydroxylamine aluminum

[0084] The performance of the obtained active energy ray-curable black ink for offset web printing was evaluated by the following method. The results are shown in Table 2. [Liquidity] 3 g of the obtained active energy ray-curable black ink for offset web printing was dropped onto a brass inclined plate tilted at 60°C in an atmosphere of 25°C, and the distance that the ink flowed from the point where it landed in 10 minutes was measured and evaluated as static fluidity. The evaluation criteria were that the longer the length that the ink flowed, the better the performance. 5: The static flow is 120 mm or more 4: The static flow is 90 mm or more and less than 120 mm 3: Static flow is 60mm or more and less than 90mm 2: The static flow is 30 mm or more and less than 60 mm 1: Static flow is less than 30 mm

[0085] [How to create a test sample] Using an RI tester (manufactured by Tester Sangyo Co., Ltd.), a solid image was printed using the obtained active energy ray-curable black ink for offset web printing at a volume of 0.30 ml onto the substrates listed in Table 2. The ink was then cured at a conveyor speed of 60 m / min using an LED lamp ("XP-9" manufactured by Air Motion Systems Co., Ltd., irradiation distance 10 mm, output 70%) to prepare a test sample. Note that an RI tester is a testing machine that prints ink onto paper or film, and is capable of adjusting the amount of ink transfer and printing pressure. The substrates used were as follows: SS Comics: SS Comics, produced by Marusumi Paper Co., Ltd. OK Top Coat: Made by Oji Paper Co., Ltd. Maricoat: Maricoat, manufactured by Hokuetsu Corporation

[0086] [Ink receptivity] Using the test piece prepared by the above method, the ink adhesion to the paper surface is evaluated visually. A score of 4 or higher is considered to be at a level that presents no practical problems. 4: White areas are visible in less than 10% of the solid image area. 3: White areas are visible in 10% to 30% of the solid image area. 2: White areas are visible in 30% to less than 70% of the solid image area. 1: White areas are visible in more than 70% of the solid image area.

[0087] [Dot reproducibility / dot gain] The test was carried out using a Mitsubishi BT2-800NEO web offset press under the following printing conditions with a typical image and density. After the density stabilized, the printed matter was sampled and the dot gain was evaluated. A value of 3 or above is considered to be at a level that is acceptable for practical use. 5: The dot gain of 80% halftone dots is less than 10% 4: The dot gain of 80% halftone dots is 10% or more and less than 15% 3: The dot gain of 80% halftone dots is 15% or more and less than 20% 2: The dot gain of 80% halftone dots is 20% or more and less than 25% 1: The dot gain of 80% halftone dots is 25% or more.

[0088] [Paper peeling] The test was carried out on a Mitsubishi BT2-800NEO web offset press with a general image and density under the following printing conditions, and after the density had stabilized, the printed material was sampled to check for the occurrence of paper peeling. If no paper peeling occurred, it was marked as ◯, and if it did occur, it was marked as ×. 〇. No peeling of paper occurs ×. Paper peeling has occurred

[0089] (Printing conditions) Printing machine: Mitsubishi BT2-800NEO web offset printing machine (manufactured by Mitsubishi Heavy Industries) Paper: SS comic paper (127.9g / m 2 ) (Marusumi Paper Co., Ltd.) Dampening solution: Tap water / Astromark UV44+ (FFGS) mixed in a 98 / 2 mass ratio Lamp: LED lamp (manufactured by iGraphics, output 100%, two lamps used) Printing temperature: 25±1℃ Print speed: 13000 sheets / hour Version: XP-F (FFGS)

[0090] [Table 2]

[0091] From the above, it was found that the active energy ray-curable black ink for web offset printing of the present invention has excellent fluidity and ink receptivity, and is therefore excellent in printability.

Claims

1. An actinic ray-curable black ink for web offset printing, comprising a pigment, a resin, and a (meth)acrylate compound, The pigment has an average particle size of 40 to 50 nm and a DBP absorption of 65 to 75 cm ３ / 100g of carbon black pigment in an amount of 13 to 16 mass %, the resin comprises a diallyl phthalate resin; An active energy ray curable black ink for offset rotary printing, having an ink viscosity of 8 to 22 Pa·s.

2. 2. The actinic ray-curable black ink for web offset printing according to claim 1, wherein the resin further comprises a rosin-modified resin.

3. 3. The active energy ray-curable black ink for web offset printing according to claim 2, wherein the rosin-modified resin is a reaction product of an addition reaction product of a rosin acid (A) and an α,β-unsaturated carboxylic acid or its acid anhydride (B), and a polyol (C).

4. The active energy ray-curable black ink for web offset printing according to any one of claims 1 to 3, wherein the (meth)acrylate compound comprises an alkylene oxide-modified (meth)acrylate compound having two or more (meth)acryloyl groups in the molecule.

5. The actinic ray-curable black ink for web offset printing according to any one of claims 1 to 4, further comprising silica.

6. A printed matter obtained by printing the black ink for web offset printing according to any one of claims 1 to 5 onto a paper substrate and curing it with actinic energy rays.

7. The printed matter according to claim 6, wherein the paper substrate is wood paper.

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