Electron beam curable offset printing ink composition

Abstract

The present invention addresses the problem of providing an active energy beam (preferably an electron beam) curable offset printing ink composition exhibiting a sufficient suitability for "water allowance", preferably an ink composition which is excellent in various performances as an active energy beam curable offset printing ink composition, for example, curing performance, adhesiveness to a printing target, and suitability for lamination. Provided as a solution to the problem is an electron beam curable offset printing ink composition which includes a ketone resin (A), a (meth)acrylate compound (B), and an extender pigment (C), and substantially does not include a photopolymerization initiator. The electron beam curable offset printing ink composition does not contain water or contains not more than 3 mass% of water. The ketone resin (A) is: a resin obtained by condensation between a ketone and formaldehyde; or a hydrogenated product thereof.

Description

Electron beam curable offset printing ink composition

[0001] The present invention relates to an electron beam curable offset printing ink composition and a laminate film using the same.

[0002] An active energy ray-curable ink composition cures when irradiated with energy rays such as ultraviolet rays, and is fixed as an image on a substrate. Active energy ray-curable ink compositions can basically be made into solvent-free inks, which has the advantage of being environmentally friendly, but can sometimes result in poor image adhesion to the printing surface of a substrate.

[0003] On the other hand, offset printing is a printing technique sometimes called lithographic printing, and basically involves: 1) ink and dampening water are supplied to a plate (lithographic plate) wrapped around a plate cylinder, with the ink (or a water-in-oil emulsion of ink and dampening water) adhering to areas corresponding to image areas and the dampening water adhering to areas corresponding to non-image areas; 2) the ink (or the water-in-oil emulsion of ink and dampening water) from the ink and dampening water adhering to the plate is transferred to a blanket wrapped around a blanket cylinder (off-step); 3) the ink (or the water-in-oil emulsion of ink and dampening water) transferred to the blanket is transferred to a substrate to be printed (setting step). Furthermore, if the ink is an active energy ray-curable ink composition, the ink composition transferred to the substrate is irradiated with active energy rays to cure it, thereby fixing the image to the substrate.

[0004] The supply ratio of ink to dampening water supplied to the plate is variable depending on the image pattern (such as the proportion of the image area). When the supply ratio of ink to dampening water changes, the emulsification state of the ink and dampening water may change, or ink may adhere to areas corresponding to non-image areas. When the emulsification state of the ink and dampening water changes, ink transfer becomes more difficult. Thus, offset printing can experience problems such as a deterioration in the quality of the printed image depending on the supply ratio of ink to dampening water (see Patent Documents 1 and 2).

[0005] In offset printing, "water width" refers to the acceptable range of the ink to dampening water supply ratio that can produce good image quality in printed matter. In other words, the wider the "water width," the easier it is to change the ink to dampening water supply ratio. Widening this water width (improving water width suitability) is one of the common challenges for offset printing ink compositions.

[0006] Several active energy ray-curable ink compositions for offset printing have been proposed to date (Patent Documents 3 to 5). Patent Document 3 proposes using an active energy ray-curable composition containing a polymerizable compound having a specific (meth)acryloyl group as an ink for offset printing. Patent Document 4 describes that a composition containing an acid group-containing urethane (meth)acrylate resin and a metal complex can be used as a raw material for an active energy ray-curable printing ink, and that the ink can be suitably used for lithographic offset printing. Patent Document 5 proposes using a white ink composition containing an ink vehicle containing an acrylate compound, a polyol adhesive composition, a photoinitiator, and a white colorant for digital offset printing.

[0007] Japanese Patent Application Laid-Open No. 2010-229299 Japanese Patent No. 6971421 Japanese Patent Application Laid-Open No. 2020-33465 International Publication No. 2019 / 17270 Japanese Patent Application Laid-Open No. 2022-98468

[0008] As described above, several actinic ray-curable ink compositions for offset printing have been proposed; however, these proposed ink compositions have had problems with offset printing, particularly in that they were unable to ensure sufficient "water compatibility." Therefore, an object of the present invention is to provide an actinic ray (preferably, electron beam)-curable ink composition for offset printing that has sufficient "water compatibility." More preferably, an ink composition is provided that exhibits various properties required for actinic ray-curable ink compositions, such as high curability, adhesion to a substrate, and lamination suitability. An ink composition with high adhesion to a substrate is preferably used, for example, as an ink for front printing, and an ink composition with high lamination suitability is preferably used, for example, as an ink for reverse printing.

[0009] That is, the present invention relates to the following electron beam-curable offset printing ink composition: <1> An electron beam-curable offset printing ink composition comprising a ketone resin (A), a (meth)acrylate compound (B), and an extender pigment (C), and substantially no photopolymerization initiator, wherein the electron beam-curable offset printing ink composition contains no water or 3 mass % or less of water, and the ketone resin (A) is a resin obtained by condensation of a ketone with formaldehyde, or a hydrogenated product thereof.

[0010] The present invention further relates to the following electron beam-curable offset printing ink composition: <2> The electron beam-curable offset printing ink composition according to <1> above, wherein the ketone comprises at least one selected from the group consisting of aromatic ketones, alicyclic ketones, and aliphatic ketones. <3> The electron beam-curable offset printing ink composition according to <1> or <2> above, wherein the (meth)acrylate compound (B) comprises at least one polyfunctional (meth)acrylate compound selected from the group consisting of alkylene oxide-modified trimethylolpropane tri(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, alkylene oxide-modified glycerin (meth)acrylate, soybean oil-modified acrylate, and urethane acrylate. <4> The electron beam-curable offset printing ink composition according to any one of <1> to <3>, wherein the content of the body pigment (C) is 0.1 to 10 mass % relative to the total mass of the ink composition. <5> The electron beam-curable offset printing ink composition according to any one of <1> to <4>, wherein the body pigment (C) comprises one or more selected from the group consisting of calcium carbonate, magnesium carbonate, and magnesium silicate, and silicon dioxide.

[0011] The electron beam-curable offset printing ink composition of the present invention can be used for the following applications: <6> The electron beam-curable offset printing ink composition according to any one of <1> to <5> above, which is for surface printing. <7> The electron beam-curable offset printing ink composition according to any one of <1> to <5> above, which is for lamination.

[0012] The present invention also relates to the following laminate film: <8> A laminate film comprising, in this order, a substrate, a printed layer, an adhesive layer, and a sealant layer, wherein the printed layer is a cured layer of the electron beam-curable offset printing ink composition according to any one of <1> to <5>.

[0013] The electron beam-curable offset printing ink composition of the present invention can be printed on a substrate by offset printing and cured with an electron beam to form an image on the substrate. Furthermore, since the electron beam-curable offset printing ink composition of the present invention has high water resistance suitability in offset printing, it can form high-quality images even if the offset printing conditions vary. More preferably, the electron beam-curable offset printing ink composition of the present invention has good suitability for lamination and can be used, for example, as an ink for forming a printed layer on a laminate film.

[0014] [1. Electron beam-curable offset printing ink composition] The electron beam-curable offset printing ink composition of the present invention (the ink composition of the present invention) contains a ketone resin (A), a (meth)acrylate compound (B), and an extender pigment (C), and the electron beam-curable offset printing ink composition contains no water or not more than 3 mass% of water. Furthermore, the ink composition of the present invention may contain other optional components. However, it is preferable that the ink composition of the present invention is substantially free of a photopolymerization initiator.

[0015] [1-1. Ketone Resin (A)] The ketone resin (A) contained in the ink composition of the present invention is a resin obtained by the condensation reaction of a ketone with formaldehyde, or a resin obtained by subjecting such a resin to a hydrogenation reaction. The condensation reaction of a ketone with formaldehyde refers to a reaction in which formaldehyde is added to the α-carbon of a ketone to convert the ketone to a hydroxymethyl (-CHOH) group, and the hydroxymethyl then attacks the α-carbon of another ketone, forming a methylene (-CH-) chain. The conditions for the condensation reaction in producing the ketone resin (A) are not particularly limited; for example, the ketone resin (A) can be obtained by reacting a ketone with formaldehyde in the presence of an alkali.

[0016] The ketone to be condensed is not particularly limited as long as it can undergo a condensation reaction with formaldehyde, and examples thereof include aromatic ketones, alicyclic ketones, and aliphatic ketones, with aromatic ketones and alicyclic ketones being preferred.

[0017] Examples of aromatic ketones include acetophenone or a derivative thereof, benzophenone or a derivative thereof, methyl naphthyl ketone, propiophenone, and the like.

[0018] Examples of the derivatives of acetophenone include o-hydroxymethoxyacetophenone, m-hydroxymethoxyacetophenone, p-hydroxymethoxyacetophenone, o-aminoacetophenone, m-aminoacetophenone, p-aminoacetophenone, 2'-trifluoromethylacetophenone, 3'-trifluoromethylacetophenone, p-t-butylacetophenone, 4'-cyclohexylacetophenone, 2'-phenylacetophenone, 3-acetylbiphenyl, 4-acetylbiphenyl, 2'-(benzyloxy)acetophenone, 3-benzyloxyacetophenone, 4'-(benzyloxy)acetophenone, acetophenone, 2'-iodoacetophenone, 3'-iodoacetophenone, 4-iodoacetophenone, p-nitroacetophenone, 2-bromoacetophenone, 2-hydroxy-1-phenylethanone, 2-phenylacetophenone, 2,2,2-trifluoroacetophenone, 4'-(imidazol-1-yl)acetophenone, and the like.

[0019] Examples of benzophenone derivatives include dihydroxybenzophenone, 2-methylbenzophenone, p-methylbenzophenone, 2-(trifluoromethyl)benzophenone, 3-(trifluoromethyl)benzophenone, 3,3'-bis(trifluoromethyl)benzophenone, 4,4'-di-tert-butylbenzophenone, 3-fluorobenzophenone, 3,3'-difluorobenzophenone, 4-fluorobenzophenone, 4,4'-difluorobenzophenone, 3-chlorobenzophenone, 2,2'-dichlorobenzophenone, 3,3'-dichlorobenzophenone, p-chlorobenzophenone, benzophenone, 3-bromobenzophenone, 4-bromobenzophenone, 4,4'-dibromobenzophenone, 2-iodobenzophenone, 3-iodobenzophenone, 4-iodobenzophenone, 3-hydroxybenzophenone, p-hydroxybenzophenone, bis(4-hydroxy)benzophenone, 2-aminobenzophenone, 3-aminobenzophenone, 4-aminobenzophenone, 2-(morpholinomethyl)benzophenone, 4-morpholinobenzophenone, p-nitrobenzophenone, 3,3'-dinitrobenzophenone, p-cyanobenzophenone, and the like.

[0020] Examples of alicyclic ketones include compounds having a cyclopentanone skeleton, compounds having a cyclohexanone skeleton, and compounds having a cyclooctanone skeleton, which may be substituted with a lower alkyl group or a halogen atom. For example, examples of alicyclic ketones having a cyclohexanone skeleton include cyclohexanone, 2-methylcyclohexanone, 3-methylcyclohexanone, 4-methylcyclohexanone, 2-ethylcyclohexanone, 2-n-butylcyclohexanone, 3-n-butylcyclohexanone, 3-tert-butylcyclohexanone, 4-n-butylcyclohexanone, 4-sec-butylcyclohexanone, 4-tert-butylcyclohexanone, 2,6-dimethylcyclohexanone, 3,3,5-trimethylcyclohexanone, 2,4,6-trimethylcyclohexanone, 2-chlorocyclohexanone, 3-chlorocyclohexanone, 4-chlorocyclohexanone, 2-fluorocyclohexanone, 2-bromocyclohexanone, and 2-iodocyclohexanone.

[0021] Examples of aliphatic ketones include acetone, methyl ethyl ketone, methyl isobutyl ketone, ethyl methyl ketone, diethyl ketone, t-butyl methyl ketone, chloroacetone, 1,1,1-trifluoroacetone, 3-bromo-1,1,1-trifluoroacetone, hexafluoroacetone, hydroxyacetone, 2-cyclopentenyl-1-acetone, 1-(1-adamantyl)acetone, 1-(4-methylpiperazin-1-yl)acetone, 1-(1-piperidinyl)acetone, 1-morpholin-4-yl-acetone, and the like.

[0022] The ketone resin (A) may be a resin obtained by hydrogenating a resin that is a condensation product of a ketone and formaldehyde. The condensation product undergoes a hydrogenation reaction in which a carbonyl group (-C(=O)-) derived from the ketone is reduced to form a hydroxyl group (-CH(-OH)-). Furthermore, the ketone resin (A) may be a resin obtained by hydrogenating the condensation product and crosslinking the hydroxyl groups of the resin obtained by hydrogenating the condensation product via a linker.

[0023] The ketone resin (A) may be a commercially available resin. Examples of commercially available ketone resin (A) include the TEGO VARIPLUS series (VARIPLUS AP, SK, CA, TC, etc.) (EVONIK), K90 (Arakawa Chemical Industries), the Halon series (Halon 80, 110H, etc.) (Honshu Chemical), and the Laropearl series (Laropearl A81, 101, K80, etc.) (BASF).

[0024]

[0033] The content of the ketone resin (A) in the ink composition of the present invention is, in terms of solids content relative to the mass of the ink composition, preferably 5% by mass or more, more preferably 10% by mass or more, and even more preferably 15% by mass or more; and preferably 55% by mass or less, more preferably 50% by mass or less, and even more preferably 45% by mass or less. The ketone resin (A) can improve the curability of the ink composition of the present invention, the adhesion of the ink composition to a substrate to be printed (particularly a resin film or the like), and the lamination suitability, and can further improve the offset printing suitability (particularly water resistance suitability) of the ink composition of the present invention.

[0025] The ketone resin (A) preferably has a glass transition temperature (Tg) of 200° C. or lower, more preferably 150° C. or lower, and even more preferably 100° C. or lower; on the other hand, it is preferably 30° C. or higher. By adjusting the glass transition temperature of the ketone resin to a certain level or lower, the lamination suitability of the ink composition of the present invention can be improved.

[0026] The ketone resin (A) may have a hydroxyl value (mgKOH / g) of 0 or more, preferably 1.0 or more, and preferably 500 or less, more preferably 300 or less, and even more preferably 100 or less. A ketone resin (A) having a hydroxyl value of a certain level or less may easily improve the offset printability (particularly water repellency) of the ink composition.

[0027] [1-2. (Meth)acrylate Compound (B)] The (meth)acrylate compound (B) contained in the ink composition of the present invention may be a compound having a (meth)acrylate group that undergoes a curing reaction upon irradiation with an electron beam. The (meth)acrylate group refers to a methacrylic group and / or an acrylic group. The (meth)acrylate compound (B) may have one or more (meth)acrylate groups, but preferably has two or more (meth)acrylate groups, and more preferably has two or three (meth)acrylate groups. The (meth)acrylate compound (B) may be a monomer or an oligomer.

[0028] Specific examples of the monofunctional (meth)acrylate compound (B) include ethyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, nonyl (meth)acrylate, lauryl (meth)acrylate, tridecyl (meth)acrylate, hexadecyl (meth)acrylate, octadecyl (meth)acrylate, isoamyl (meth)acrylate, isodecyl (meth)acrylate, isostearyl (meth)acrylate, cyclohexyl (meth)acrylate, benzyl (meth)acrylate, methoxyethyl (meth)acrylate, butoxyethyl (meth)acrylate, phenoxyethyl (meth)acrylate, and phenoxydiethyleneglycol. tetrahydrofurfuryl (meth)acrylate, nonylphenoxyethyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, glycidyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, 3-chloro-2-hydroxypropyl (meth)acrylate, diethylaminoethyl (meth)acrylate, nonylphenoxyethyl tetrahydrofurfuryl (meth)acrylate, caprolactone-modified tetrahydrofurfuryl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, and the like.

[0029] Specific examples of the polyfunctional (meth)acrylate compound (B) include 1,4-butanediol di(meth)acrylate, 3-methyl-1,5-pentanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 2-methyl-1,8-octanediol di(meth)acrylate, 2-butyl-2-ethyl-1,3-propanediol di(meth)acrylate, tricyclodecane dimethanol di(meth)acrylate, ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, di(meth)acrylates of dihydric alcohols such as diol di(meth)acrylate, triethylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, and tripropylene glycol di(meth)acrylate; di(meth)acrylates of polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, and tris(2-hydroxyethyl)isocyanurate; di(meth)acrylates of diols obtained by adding 4 or more moles of ethylene oxide or propylene oxide to 1 mole of neopentyl glycol; acrylate, di(meth)acrylate of a diol obtained by adding 2 moles of ethylene oxide or propylene oxide to 1 mole of bisphenol A; poly(meth)acrylate of a trihydric or higher polyhydric alcohol such as trimethylolpropane tri(meth)acrylate, glycerin tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, poly(meth)acrylate of dipentaerythritol; Examples of suitable poly(meth)acrylates include poly(meth)acrylates of polyoxyalkylene polyols such as triol tri(meth)acrylates obtained by adding 1 mole or more of ethylene oxide or propylene oxide to 1 mole of trimethylolpropane, di- or tri(meth)acrylates of triols obtained by adding 3 moles or more of ethylene oxide or propylene oxide to 1 mole of trimethylolpropane, and di(meth)acrylates of diols obtained by adding 4 moles or more of ethylene oxide or propylene oxide to 1 mole of bisphenol A; and vegetable oil (e.g., soybean oil) epoxy acrylates.

[0030] Specific examples of the (meth)acrylate compound (B) which is an oligomer include amine-modified acrylates such as amine-modified polyether acrylates, amine-modified epoxy acrylates, amine-modified aliphatic acrylates, amine-modified polyester acrylates, and amino(meth)acrylates, thiol-modified acrylates such as thiol-modified polyester acrylates and thiol(meth)acrylates, polyester(meth)acrylates, polyether(meth)acrylates, polyolefin(meth)acrylates, polystyrene(meth)acrylates, epoxy(meth)acrylates, and urethane(meth)acrylates.

[0031] Preferably, at least a portion of the (meth)acrylate compound (B) is a polyfunctional (meth)acrylate compound. For example, 50% by mass or more of the (meth)acrylate compound (B), more preferably 60% by mass or more, and even more preferably 80% by mass or more, is a polyfunctional (meth)acrylate compound. The polyfunctional (meth)acrylate compound can improve the curability of the ink composition with an electron beam. Suitable examples of the polyfunctional (meth)acrylate compound include alkylene oxide-modified trimethylolpropane tri(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, alkylene oxide-modified glycerin (meth)acrylate, soybean oil-modified acrylate, urethane acrylate, etc.

[0032] At least a portion of the (meth)acrylate compound (B) contained in the ink composition of the present invention is preferably a compound having a low glass transition temperature (for example, 100°C or less, preferably 60°C or less). For example, 50% by mass or more, more preferably 60% by mass or more of the (meth)acrylate compound (B) is a compound having a low glass transition temperature. A (meth)acrylate compound (B) having a low glass transition temperature can improve the lamination suitability of the ink composition. Examples of the (meth)acrylate compound (B) having a low glass transition temperature include di- or tri(meth)acrylates of triols obtained by adding 3 moles or more of ethylene oxide or propylene oxide to 1 mole of trimethylolpropane.

[0033] The content of the (meth)acrylate compound (B) in the ink composition of the present invention is, in terms of solid content, preferably 10% by mass or more, more preferably 20% by mass or more, and even more preferably 25% by mass or more, relative to the mass of the ink composition; and is preferably 65% ​​by mass or less, more preferably 60% by mass or less, and even more preferably 55% by mass or less.

[0034] In the ink composition of the present invention, the total content of the ketone resin (A) and the (meth)acrylate compound (B) is preferably 30% by mass or more, more preferably 40% by mass or more, and even more preferably 50% by mass or more, relative to the mass of the ink composition; on the other hand, it is preferably 95% by mass or less, and more preferably 85% by mass or less. In addition, in the ink composition of the present invention, the content ratio of the ketone resin (A) to the (meth)acrylate compound (B) ((A):(B)) is, for example, preferably in the range of 1.0:0.5 to 1.0:15.0, more preferably in the range of 1.0:0.7 to 1.0:5.0, and even more preferably in the range of 1.0:1.0 to 1.0:2.0.

[0035] [1-3. Extender Pigment (C)] The extender pigment (C) contained in the ink composition of the present invention is inorganic fine particles, and examples of the extender pigment (C) include titanium oxide, graphite, zinc, lime carbonate powder, calcium carbonate, gypsum, clay, silica (silicon dioxide), diatomaceous earth, talc, kaolin, alumina white, barium sulfate, aluminum stearate, magnesium carbonate, magnesium silicate, baryte powder, and glass beads.

[0036] The extender pigment (C) preferably contains calcium carbonate, magnesium carbonate, or magnesium silicate in combination with silica (silicon dioxide). This combination of extender pigments can reduce the stringiness of the ink composition.

[0037] The content of the extender pigment (C) in the ink composition of the present invention is preferably 0.1% by mass or more, more preferably 1.0% by mass or more, and even more preferably 3.0% by mass or more, relative to the mass of the ink composition; and is preferably 10% by mass or less.

[0038] The extender pigment (C) can adjust the rheological properties of the ink composition of the present invention, and by being localized on the surface (outer surface) of the cured coating film formed by the ink composition of the present invention, the extender pigment (C) can prevent sticking and the like of the printed matter.

[0039] [1-4. Other Optional Components] The ink composition of the present invention may contain other optional components; examples of other optional components include colorants, pigment dispersants, polymerization inhibitors, surfactants, solvents, waxes, ultraviolet absorbers, antibacterial agents, resins other than the ketone resin (A), and the like.

[0040] The colorant may be a color pigment or a dye. The color pigment may be an inorganic pigment or an organic pigment. Examples of inorganic pigments include colored pigments such as titanium oxide, red iron oxide, antimony red, cadmium yellow, cobalt blue, Prussian blue, ultramarine blue, carbon black, and graphite, and extender pigments such as silica, calcium carbonate, kaolin, clay, barium sulfate, aluminum hydroxide, and talc. Examples of organic pigments include soluble azo pigments, insoluble azo pigments, azo lake pigments, condensed azo pigments, copper phthalocyanine pigments, and condensed polycyclic pigments. Examples of dyes include dye lakes such as basic reaction lakes and acid dye lakes, and nitro pigments.

[0041] The pigment dispersant may be a polymeric dispersant. The polymeric pigment dispersant is preferably a pigment dispersant containing a basic group. Examples of pigment dispersants containing a basic group include polymeric pigment dispersants such as basic group-containing polyester pigment dispersants, basic group-containing acrylic pigment dispersants, basic group-containing urethane pigment dispersants, and basic group-containing carbodiimide pigment dispersants, as well as anionic surfactants. The polymeric pigment dispersant is not particularly limited, but may be a linear polymer having a pigment-affinity moiety composed of a basic group at least at one or both ends of the main chain due to a block or graft structure.

[0042] The polymerization inhibitor can prevent polymerization reactions from occurring during storage of the ink composition, and can suppress thickening of the ink composition. Examples of polymerization inhibitors include phenolic compounds (including quinone compounds) such as dibutylhydroxytoluene, tocopherol acetate, nitrosamine compounds, benzotriazole, hindered amines, etc.; among these, quinone compounds and nitrosamine compounds are more preferred. The content of the polymerization inhibitor in the ink composition is set appropriately depending on the type of polymerization inhibitor, but for example, in the case of a quinone compound, it can be approximately 0.3 to 2.0 parts by mass when the total curable components are 100 parts by mass.

[0043] Examples of surfactants include nonionic surfactants, cationic surfactants, anionic surfactants, betaine surfactants, etc. Specific examples of surfactants include silicone surfactants such as polyether-modified silicone oil, polyester-modified polydimethylsiloxane, and polyester-modified methylalkylpolysiloxane, fluorine-based surfactants, and acetylene-based surfactants. The surfactants can be used alone or in combination of two or more.

[0044] The ink composition of the present invention is curable by irradiation with an electron beam and may contain no polymerization initiator, preferably substantially no polymerization initiator, and more preferably no polymerization initiator at all. Here, "substantially no polymerization initiator" means that the ink composition does not contain a "catalytic amount of photopolymerization initiator." Examples of polymerization initiators include acylphosphine oxide compounds, thioxanthone compounds, aromatic ketones, aromatic onium salt compounds, organic peroxides, thio compounds (e.g., thiophenyl group-containing compounds), α-aminoalkylphenone compounds, hexaarylbiimidazole compounds, ketoxime ester compounds, borate compounds, azinium compounds, metallocene compounds, active ester compounds, compounds having a carbon-halogen bond, and alkylamine compounds.

[0045] The ink composition of the present invention may not contain a solvent such as water or an organic solvent, or may contain a small amount of a solvent (for example, 3 mass % or less relative to the mass of the ink composition). In particular, the ink composition of the present invention may be free of water or contain 3 mass % or less of water, thereby enhancing the stability of the ink composition.

[0046] [1-5. Physical Properties of Ink Composition] The viscosity of the ink composition of the present invention is preferably 100.0 Pa·s or less, and more preferably 1.0 Pa·s to 90.0 Pa·s. This viscosity may be measured using a cone-plate viscometer at 25°C and a shear rate of 100 / s. If the viscosity exceeds the above-mentioned value, the fluidity and transferability of the ink composition will decrease, which may reduce the stability of the ink composition supplied to the roller in offset printing and result in impaired printing workability. Furthermore, if the viscosity exceeds the above-mentioned value, the leveling ability of the ink composition transferred to the printing substrate will decrease, which may result in quality problems such as gloss deterioration, and this is undesirable. Furthermore, an increase in the viscosity of the ink composition will also increase the tack value of the ink, which may result in poor transfer to the printing substrate and make it difficult to ensure stable printing workability.

[0047] The ink composition of the present invention has the property of being cured by irradiation with an electron beam (curability). The degree of curability is not particularly limited, but it is preferable that, for example, when formed into a coating film, it is completely cured at an irradiation dose of 20 to 40 kGy.

[0048] [1-6. Method for producing ink composition] The ink composition of the present invention can be obtained by dissolving the ketone resin (A) in the (meth)acrylate compound (B), dispersing the extender pigment (C), and mixing other optional components. The mixing means, etc. are not particularly limited.

[0049] [2. Printing Method of the Present Invention] The printing method of the present invention comprises a step of offset printing the ink composition of the present invention onto a printing substrate (offset printing step), and a step of curing the offset-printed coating film with an electron beam (curing step).

[0050] The printing substrate in the offset printing process is not particularly limited and may be a resin substrate, a metal substrate, a paper substrate, etc. Examples of metals in metal substrates include aluminum, zinc, copper, iron, tin, etc. Paper substrates may be synthetic paper, art paper, coated paper, cast paper, wood chip paper, resin-laminated paper, metal-vapor-deposited paper, metal oxide-vapor-deposited paper, etc.

[0051] Considering the effects of the present invention, such as improved adhesion to the substrate to be printed and lamination suitability, resin substrates, particularly resin films, may be preferred. Examples of resins constituting the resin substrate are not particularly limited, but include films or sheets of polyester resins (e.g., polyethylene terephthalate), acrylic resins, vinyl chloride resins, vinylidene chloride resins, polyvinyl alcohol, polyethylene, polypropylene, polyacrylonitrile, ethylene-vinyl acetate copolymers, ethylene-vinyl alcohol copolymers, ethylene-methacrylic acid copolymers, nylon, polylactic acid, polycarbonate, etc., cellophane, aluminum foil, and various other resins conventionally used as printing substrates. The resin film may be stretched (uniaxially stretched, biaxially stretched, etc.).

[0052] The offset printing process may be carried out in accordance with known printing process techniques, and may include, for example, A) a step of supplying the ink composition of the present invention and dampening water to a plate, B) a step of transferring the ink composition supplied to the plate to a blanket (off-step), and C) a step of fixing the ink composition transferred to the blanket to a printing substrate (setting step).

[0053] The dampening solution supplied to the plate is a solution containing water as its main component, and may contain optional components such as pH adjusters, water-soluble organic solvents, chelating compounds, and water-soluble polymers.

[0054] In step A of supplying the ink composition and the dampening water to the plate, for example, the ink composition can be supplied to the plate wound around the plate cylinder by an ink roller, and the dampening water can be supplied by a water roller. The plate has a portion to which the ink composition adheres (lipophilic image portion) and a portion to which the dampening water adheres (hydrophilic non-image portion). The ink composition adheres to the image portion of the plate, and the ink composition that adheres is often an emulsion of the ink composition and the dampening water (water-in-oil emulsion).

[0055] Furthermore, in the offset printing process, the supply ratio of the ink composition to the fountain solution supplied to the plate is not constant but variable. If this supply ratio changes, the emulsification state of the ink composition emulsion adhering to the image area of ​​the plate may change, or the ink composition may also adhere to the non-image area of ​​the plate. As a result, the quality of the image printed on the printing substrate may deteriorate. In contrast, with the ink composition of the present invention, even if the supply ratio of the ink composition to the fountain solution changes, the emulsification state of the emulsion changes little, and the ink composition is less likely to adhere to the non-image area of ​​the plate. The mechanism behind this is not limited, but it can be considered that the high polarity of the ketone resin (A) contained in the ink composition of the present invention stabilizes the emulsification state with the fountain solution.

[0056] The ink composition (or emulsion with fountain solution) adhering to the image area of ​​the plate is transferred to the blanket (step B). The fountain solution adhering to the non-image area of ​​the plate is collected without being transferred to the blanket cylinder. Furthermore, the ink composition (or emulsion with fountain solution) transferred to the blanket is usually pressed against the substrate to be printed by an impression cylinder and fixed to the substrate to form a coating (step C).

[0057] The coating film formed on the substrate by offset printing is cured by irradiation with an electron beam to form a cured film, which is fixed as an image. The acceleration voltage of the irradiated electron beam is preferably in the range of 80 kV to 170 kV, more preferably in the range of 80 kV to 110 kV, in order to suitably suppress the penetration of the electron beam into the substrate and to suppress damage to the substrate. The irradiation dose of the irradiated electron beam is preferably in the range of 20 to 40 kGy in order to reliably cure the coating film and to suppress poor adhesion to the substrate due to excessive curing.

[0058] [3. Uses of Ink Composition] The ink composition of the present invention is printed on a substrate to be printed and cured to form a printed layer, thereby giving a printed matter. The ink composition may be printed by reverse printing, front printing, or other printing methods.

[0059] When an ink composition is printed by front printing, the printing layer is exposed on the surface of the printed material, and therefore high adhesion between the printing layer and the substrate to be printed is required. The printing layer obtained from the ink composition of the present invention has high adhesion to the substrate to be printed, and therefore can be suitably used in front printing. On the other hand, when an ink composition is printed by reverse printing, the printed material generally has a laminate layer covering the printing layer. Therefore, the printed material obtained by reverse printing is required to have high laminate strength (the laminate layer is not easily peeled off). The printing layer obtained from the ink composition of the present invention can be strongly adhered to the laminate layer via an adhesive or the like, and therefore can be suitably used in reverse printing.

[0060] The mechanism by which the adhesion and lamination suitability of the printed layer of the ink composition of the present invention are improved is not particularly limited, but it can be considered that ketone resins are generally used as adhesive components, and their adhesive function is exerted.

[0061] The ink composition of the present invention may be used as an ink composition for lamination. That is, a laminate film (a laminate film comprising, in this order, a substrate film as a substrate to be printed, a cured product layer of the ink composition, an adhesive layer, and a sealant layer) can be obtained by fixing a cured product of the ink composition of the present invention to a substrate film as a substrate to be printed to form an image, applying an adhesive to cover the cured product to form an adhesive layer, and further laminating a sealant layer on the adhesive layer.

[0062] The substrate film, which is the printing substrate, is preferably made of a resin, but is not particularly limited and can be selected depending on the application of the resulting laminate film. The adhesive layer is a cured product of an adhesive composition, but the composition of the adhesive composition is not particularly limited. The sealant layer, which is disposed so as to cover the adhesive layer, is preferably made of a resin, such as a polyolefin, but can be selected depending on the application of the laminate film.

[0063] The sealant layer may be formed by any of dry lamination, solventless lamination, and extrusion lamination, but in order to effectively exhibit the effects of the ink composition of the present invention (high adhesion to the printing substrate and high lamination suitability), it may be preferable to form the sealant layer by the dry lamination method.

[0064] The laminate film thus obtained has the advantage that sufficient laminate strength can be easily ensured because of the high adhesion between the printing substrate and the cured product layer of the ink composition, and also the high adhesion between the cured product layer of the ink composition and the adhesive layer. The laminate film thus obtained can be used for any purpose, such as food packaging, pouches for lithium ion batteries, building sheets, and other laminate applications.

[0065] The present invention will be described in more detail below with reference to examples, but the scope of the present invention should not be construed as being limited by these examples. The numerical values ​​of the blending amounts shown in each table are in parts by mass.

[0066] A. Preparation of Electron Beam-Curable Offset Printing Ink Compositions The materials used to prepare the electron beam-curable offset printing ink compositions of the Examples and Comparative Examples are listed below.

[0067] A-1. Resins (ketone resins and other resins) AP: condensation resin of acetophenone and formaldehyde (trade name "TEGO VARIPLUS AP (EVONIK)"), hydroxyl value 5 mg KOH / g SK: hydrogenated product of the above AP (trade name "TEGO VARIPLUS SK (EVONIK)"), hydroxyl value 325 mg KOH / g CA: condensation resin of cyclohexanone and formaldehyde (trade name "TEGO VARIPLUS CA (EVONIK)"), hydroxyl value 110 mg KOH / g TC: condensation resin of cyclohexanone skeleton-containing ketone (3,3,5-trimethylcyclohexanone) and formaldehyde (trade name "TEGO VARIPLUS TC (EVONIK Co., Ltd.)) Hydroxyl value: up to 10 mgKOH / g Daiso DAP A: Diallyl phthalate polymer (trade name: Daiso DAP A (Osaka Soda Co., Ltd.)) VS-1063: Polystyrene, Mw=5,500 (trade name: VS-1063 (Seiko PMC Co., Ltd.)) MSB: Sucrose benzoate ester (trade name: MIRAMER SB (Miwon Co., Ltd.))

[0068] A-2. Polymerizable compounds ((meth)acrylate compounds) M3130: Triacrylate of an ethylene oxide 3-mol adduct of trimethylolpropane (trade name "MIRAMER M3130 (Miwon Co., Ltd.)") M3160: Triacrylate of an ethylene oxide 6-mol adduct of trimethylolpropane (trade name "MIRAMER M3160 (Miwon Co., Ltd.)") M3190: Triacrylate of an ethylene oxide 9-mol adduct of trimethylolpropane (trade name "MIRAMER M3190 (Miwon Co., Ltd.)") M340: Triacrylate of pentaerythritol (trade name "MIRAMER M340 (Miwon Co., Ltd.)") M360: Triacrylate of a propylene oxide 3-mol adduct of trimethylolpropane (trade name "MIRAMER M360 (Miwon Co., Ltd.)") M320: Triacrylate of propylene oxide 3-mol adduct of glycerin (trade name "MIRAMER M320 (Miwon Co., Ltd.)") PE310: Soybean oil epoxy acrylate (trade name "MIRAMER PE310 (Miwon Co., Ltd.)") PU5000: Aliphatic trifunctional acrylate (trade name "MIRAMER PU5000 (Miwon Co., Ltd.)") M170: Ethoxydiethylene glycol acrylate (trade name "MIRAMER M170 (Miwon Co., Ltd.)") M144: Phenol ethylene oxide modified acrylate (trade name "MIRAMER M144 (Miwon Co., Ltd.)") M1140: Isobornyl acrylate (trade name "MIRAMER M1140 (Miwon Co., Ltd.)")

[0069] A-3. Extender pigments T-DD: calcium carbonate (product name "Hakuenka T-DD (Shiraishi Calcium Co., Ltd.)") L-1: talc (product name "L-1 (Nippon Talc Co., Ltd.)") CP-102: silica (product name "Reolosil CP102 (Tokuyama Corporation)")

[0070] A-4. Others Pigment MA-70 (carbon black, product name MA-70, manufactured by Mitsubishi Chemical Corporation) Pigment dispersant Solsperse 33000 (copolymer containing basic functional groups, amine value 43.0 mg KOH / g, acid value 27 mg KOH / g, active ingredient 100% by mass, manufactured by Lubrizol Japan) Polymerization inhibitor BHT (dibutylhydroxytoluene)

[0071] The components were blended to obtain the formulations (% by mass) shown in Tables 1 to 3, and the blended components were kneaded using a three-roll mill, thereby obtaining actinic ray-curable printing ink compositions of Examples and Comparative Examples.

[0072] [B. Evaluation of Electron Beam-Curable Offset Printing Ink Compositions] The ink compositions of the examples and comparative examples were evaluated as shown in B-1 to B-5. The results are shown in Tables 1 to 3.

[0073] B-1. Water Width Suitability Using the ink compositions of each Example and Comparative Example, prints were produced on printing paper according to the following procedures and conditions: Printing machine: 4-color, single-sided, 100-inch format, manufactured by Komori Corporation Printing speed: 12,000 sph Printing plate: XP-F (CTP plate) AM175 line, manufactured by Fujifilm Global Graphic Systems Co., Ltd. Printing paper: OK Coat L, manufactured by Nippon Paper Industries Co., Ltd.

[0074] First, printing was started with the dampening water feed rate dial value of the printing press set to 30, and when 10,000 sheets had been printed, the dampening water feed rate dial value was lowered to 15 (the amount of dampening water supplied was reduced). The ink stain density (OD value) in the plain areas (non-image areas) of the prints obtained when the dial value was lowered was measured, and the water balance suitability was evaluated according to the following criteria.

[0075] 5: Ink stain density in plain areas is less than 0.01 4: Ink stain density in plain areas is 0.01 or more and less than 0.05 3: Ink stain density in plain areas is 0.05 or more and less than 0.1 2: Ink stain density in plain areas is 0.1 or more and less than 0.2 1: Ink stain density in plain areas is 0.2 or more

[0076] B-2. Density Stability Printed matter was produced under the same conditions as in B-1 above using the ink compositions of each Example and Comparative Example. However, the amount of dampening water supplied was changed in 10% increments between 10 and 60% (increasing the amount of dampening water supplied), and the print density (OD value) of the image portion of the printed matter obtained at each amount of dampening water supplied was measured. The amount of dampening water supplied represents the number of rotations (%) of the water roller. The rate of decrease in optical density (OD value) was calculated using the following formula:

[0077] 5: The rate of decrease in concentration is 0%. 4: The rate of decrease in concentration is more than 0% and is 5% or less. 3: The rate of decrease in concentration is more than 5% and is 10% or less. 2: The rate of decrease in concentration is more than 10% and is 15% or less. 1: The rate of decrease in concentration is more than 15%.

[0078] B-3. ​​Curability Printed materials were produced under the same conditions as in B-1 above using the ink compositions of each Example and Comparative Example. However, electron beam irradiation (EB irradiation device; acceleration voltage 90 kV, exposure dose 30 kGy) was repeated until the ink coating film printed on the printed material cured, and the number of passes was counted. The ink coating film was judged to have cured when the ink no longer adhered to the coating film when rubbed with a cotton swab.

[0079] 5:1 pass 4:2 pass 3:3 pass 2:4 pass 1:5 pass or more

[0080] B-4. Tape Adhesion The ink composition (0.1 cc) of each Example and Comparative Example was taken and spread on each of the following films using an RI spreader (two-split roll, manufactured by Akira Seisakusho Co., Ltd.) to form an ink coating film, which was then irradiated with an electron beam (irradiated with electron beam irradiation until the ink coating film cured, in the same manner as in the curing test in B-3 above) to form a cured film, thereby obtaining a printed matter. OPP: Stretched polypropylene film (trade name "P2161 (Toyobo Co., Ltd.)") MDOPE: uniaxially oriented polyethylene film (JINDAL Co., Ltd.) OPA: Stretched nylon film (trade name "Emblem ONM-15 (Unitika Ltd.)") PET: polyethylene terephthalate film (trade name "E-5102 (Toyobo Co., Ltd.)")

[0081] Cellophane tape (product name: Cellotape (registered trademark), manufactured by Nichiban Co., Ltd.) was applied to the cured coating surface of the resulting printed product and then peeled off in one go. The peeled area of ​​the cured coating was evaluated on a 5-point scale according to the following criteria. The smaller the peeled area, the better the adhesion between the cured coating and the resin film.

[0082] 5: No peeling at all 4: Peeling of the cured film is more than 0% but not more than 20% of the area 3: Peeling of the cured film is more than 20% but not more than 50% of the area 2: Peeling of the cured film is more than 50% but not more than 75% of the area 1: Peeling of the cured film is more than 75% of the area

[0083] B-5. Lamination Suitability In the same manner as in B-4, the ink composition (0.1 cc) of each Example and Comparative Example was taken and spread on each film using an RI spreader (two-split roll, manufactured by Akira Seisakusho Co., Ltd.) to form an ink coating film, and the ink coating film was then irradiated with electron beams to obtain a printed matter. An adhesive (Takelac A969V / Takenate A-5 manufactured by Mitsui Chemicals, Inc.) was applied to the cured film surface of the obtained printed matter at a solid content of 3.5 g / m ２ The coating was applied in an amount of 1000 ppm, and a non-oriented polypropylene film ("GLC" manufactured by Mitsui Chemicals Tocello, Inc., thickness 40 μm) was laminated using a dry laminator. The tensile strength of the resulting laminated film was measured using a tensile tester (Yasuda Seiki Seisakusho, Ltd.) at a measurement temperature of 25° C. and a tensile speed of 200 mm / min.

[0084] 5: Peel strength is 1.5 N / 15 mm or more 4: Peel strength is 1.0 N / 15 mm or more and less than 1.5 N / 15 mm 3: Peel strength is 0.5 N / 15 mm or more and less than 1.0 N / 15 mm 2: Peel strength is 0.1 N / 15 mm or more and less than 0.5 N / 15 mm 1: Peel strength is less than 0.1 N / 15 mm

[0085]

[0086]

[0087]

[0088]

[0089] Comparative Examples 1 to 8 in Table 4 are ink compositions containing other resins but not ketone resin, and all of them exhibit poor tape adhesion and lamination suitability. In contrast, Examples 1 to 31 in Tables 1 to 3 are ink compositions containing ketone resin, and exhibit good tape adhesion and lamination suitability. This shows that the ketone resin imparts tape adhesion and lamination suitability to the ink composition.

[0090] Furthermore, Comparative Examples 2 to 8 in Table 3 all received poor evaluations for water compatibility and also received poor evaluations for curability. In contrast, Examples 1 to 31 in Tables 1 to 3 showed improvements in both evaluations. This shows that the ketone resin improves the water compatibility and curability of the ink composition.

[0091] The ink compositions of Examples 22 to 24 (Table 3), which contained a monofunctional compound as the polymerizable compound, exhibited slightly reduced curability by electron beam. In contrast, the ink compositions of Examples 1 to 21 (Tables 1 and 2), which contained a monofunctional compound as the polymerizable compound, all exhibited sufficient curability by electron beam. This shows that the inclusion of a polyfunctional compound is preferable to obtain an electron beam-curable ink composition with high curability.

[0092] The ink compositions of Examples 25 and 26 (Table 3), which had a low content of polymerizable compound relative to the ketone resin content (a weight ratio of 45:25 for "ketone resin:polymerizable compound"), exhibited slightly reduced curability with electron beams. The ink compositions of Examples 1 to 21 (Tables 1 and 2), which had a weight ratio of 30:40 for "ketone resin:polymerizable compound", exhibited sufficient curability with electron beams. On the other hand, as the content of polymerizable compound relative to the ketone resin content increased, the ink composition's water compatibility and concentration stability decreased, and curability also tended to decrease. Furthermore, the evaluations of adhesion and lamination suitability also deteriorated (see Examples 27 to 31 (Table 3)). As such, the ratio of ketone resin to polymerizable compound can be appropriately set depending on the physical properties desired for the ink composition.

[0093] As can be seen from a comparison of Examples 1 to 4 (Table 1) and Examples 8 to 11 (Table 1), when AP and TC, among the ketone resins, are blended, the evaluations of water compatibility and concentration stability are higher. This suggests that the inclusion of a ketone resin with a low hydroxyl value tends to improve the evaluations of water compatibility and concentration stability, but the mechanism of improvement is not particularly limited.

[0094] Furthermore, as shown in Examples 1 to 31, it is clear that ink compositions that meet necessary and sufficient evaluation standards can be obtained by arbitrarily combining multiple types of ketone resins and multiple types of polymerizable compounds.

[0095] The electron beam-curable offset printing ink composition of the present invention can be used as an offset printing ink to print high-quality images with high adhesion to a substrate. The electron beam-curable offset printing ink composition of the present invention can be used for front printing, back printing, and other printing methods. For example, by using the electron beam-curable offset printing ink composition of the present invention as a laminating ink, a laminate film with high lamination strength can be obtained, and the resulting laminate film can be used for various applications.

Claims

1. An electron beam-curable offset printing ink composition comprising a ketone resin (A), a (meth)acrylate compound (B), and an extender pigment (C), and substantially free of a photopolymerization initiator, wherein the electron beam-curable offset printing ink composition contains no water or not more than 3 mass% of water, and the ketone resin (A) is a resin obtained by condensation of a ketone with formaldehyde, or a hydrogenated product thereof.

2. The electron beam curable offset printing ink composition according to claim 1, wherein the ketone comprises at least one selected from the group consisting of aromatic ketones, alicyclic ketones, and aliphatic ketones.

3. The electron beam curable offset printing ink composition according to claim 1 or 2, wherein the (meth)acrylate compound (B) comprises one or more polyfunctional (meth)acrylate compounds selected from the group consisting of alkylene oxide-modified trimethylolpropane tri(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, and dipentaerythritol hexa(meth)acrylate, alkylene oxide-modified glycerin (meth)acrylate, soybean oil-modified acrylate, and urethane acrylate.

4. The electron beam curable offset printing ink composition according to claim 1 or 2, wherein the content of the extender pigment (C) is 0.1 to 10 mass % based on the total mass of the ink composition.

5. The electron beam curable offset printing ink composition according to claim 1 or 2, wherein the extender pigment (C) comprises one or more selected from the group consisting of calcium carbonate, magnesium carbonate, and magnesium silicate, and silicon dioxide.

6. The electron beam curable offset printing ink composition according to claim 1 or 2, which is for surface printing.

7. The electron beam curable offset printing ink composition according to claim 1 or 2, which is for lamination.

8. A laminate film comprising a substrate, a printing layer, an adhesive layer, and a sealant layer in this order, wherein the printing layer is a cured layer of the electron beam curable offset printing ink composition according to claim 1 or 2.

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