Electron beam curable varnish composition

Abstract

An object of the present invention is to provide an electron beam-curable varnish composition that can adequately protect a layer printed with an aqueous ink composition. [Solution] An electron beam-curable varnish composition containing: a (meth)acrylate compound (A) containing 3 to 6 (meth)acrylate groups in the molecule, having a homopolymer glass transition temperature of 25°C or higher but lower than 100°C, and a surface tension at 25°C of 30 mN / m or higher but lower than 41 mN / m; a (meth)acrylate compound (B) containing 2 to 3 (meth)acrylate groups in the molecule, having a homopolymer glass transition temperature of 100°C or higher, and a surface tension at 25°C of 30 mN / m or higher but lower than 42 mN / m; a polymerization inhibitor (C); a polysiloxane compound (D-1); and a wax (D-2), wherein the electron beam-curable varnish composition contains 4 to 60 mass% of the (meth)acrylate compound (A) and 35 mass% or higher but lower than 95 mass% of the (meth)acrylate compound (B).

Description

[Technical Field]

[0001] The present invention relates to an electron beam-curable varnish composition, preferably a varnish composition that can be cured by electron beams and is used by overprinting on a substrate. [Background technology]

[0002] Varnish compositions can be used to form a layer (film) for protecting (overcoating) a substrate. For example, Patent Document 1 describes the formation of an overprint varnish film on the surface of a flexographic printing layer formed on a plastic film, and describes that the overprint varnish film uses an ultraviolet / electron beam curable resin as a binder. Patent Document 2 describes overcoating the surface of a gravure printing layer formed on a substrate, and describes that the overcoat layer is a cured layer of an electron beam or ultraviolet beam curable coating agent.

[0003] Furthermore, Patent Document 3 discloses an electron beam curable overprint varnish composition containing dimethylpolysiloxane, and claims that a print varnish composition can be obtained that maintains basic properties such as curability, adhesion, and scratch resistance without containing a polymerization initiator. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-225083 [Patent Document 2] Japanese Patent Application Laid-Open No. 2005-153163 [Patent Document 3] Japanese Patent Application Publication No. 2020-147730 Summary of the Invention [Problem to be solved by the invention]

[0005] Varnish compositions are sometimes used to form layers (films) to protect the substrate, but they are also sometimes used as overcoats on printed layers made from ink compositions. With the recent trend toward environmentally friendly inks, aqueous ink compositions, such as aqueous flexographic inks and aqueous inkjet inks, are increasingly being used in ink compositions to form printed layers.

[0006] Because a printed layer made of an aqueous ink composition has high water affinity, even if it is overcoated with a conventional print varnish composition, the resulting print may not have sufficient resistance in various respects (alcohol resistance, abrasion resistance, heat resistance, oil resistance, etc.). This problem becomes even more pronounced when the overcoated print varnish composition is cured with an electron beam. Therefore, an object of the present invention is to provide an electron beam-curable varnish composition that can adequately protect a printed layer made of an aqueous ink composition. [Means for solving the problem]

[0007] That is, the present invention relates to the following electron beam-curable varnish composition. [1] An electron beam curable varnish composition comprising: a (meth)acrylate compound (A) containing 3 to 6 (meth)acrylate groups in the molecule, the homopolymer having a glass transition temperature of 25°C or higher but lower than 100°C, and a surface tension at 25°C of 30 mN / m or higher but lower than 41 mN / m; a (meth)acrylate compound (B) containing 2 to 3 (meth)acrylate groups in the molecule, the homopolymer having a glass transition temperature of 100°C or higher, and a surface tension at 25°C of 30 mN / m or higher but lower than 42 mN / m; a polymerization inhibitor (C); a polysiloxane compound (D-1); and a wax (D-2), The electron beam curable varnish composition contains 4 to 60 mass % of the (meth)acrylate compound (A) and 35 mass % or more but less than 95 mass % of the (meth)acrylate compound (B) relative to the electron beam curable varnish composition.

[0008] Preferably, the present invention relates to the following electron beam-curable varnish composition. [2] The electron beam-curable varnish composition according to [1] above, wherein the electron beam-curable varnish composition does not contain a polymerizable monomer component having a surface tension of 42 mN / m or more at 25°C. [3] The electron beam-curable varnish composition according to [1] or [2], wherein the molecular weight of the (meth)acrylate compound (A) is greater than the molecular weight of the (meth)acrylate compound (B), and the difference between the molecular weights is 50 or more. [4] The electron beam-curable varnish composition according to any one of [1] to [3] above, wherein the polysiloxane compound (D-1) includes a modified polysiloxane having a polymerizable functional group. [5] The electron beam-curable varnish composition according to any one of [1] to [4], wherein the polymerization inhibitor (C) is contained in an amount of 0.05% by mass to 1% by mass relative to the electron beam-curable varnish composition. [6] The electron beam-curable varnish composition according to any one of [1] to [5], wherein the wax (D-2) is contained in an amount of 0.05 mass % or more and less than 5 mass % relative to the electron beam-curable varnish composition. [7] The electron beam-curable varnish composition according to any one of [1] to [6] above, further comprising one or more components (E) selected from talc, silica, calcium carbonate, mica, barium sulfate, and magnesium carbonate.

[0009] The present invention further relates to the following electron beam-curable varnish composition. [8] The electron beam-curable varnish composition according to any one of [1] to [7] above, which is for overprinting. [9] The electron beam-curable varnish composition according to any one of [1] to [8] above, for overprinting on a water-based ink layer. [Effects of the Invention]

[0010] The electron beam-curable varnish composition of the present invention has high storage stability; and when the varnish composition is overprinted to protect a substrate, a printed item having sufficient resistance in various respects can be obtained. More preferably, even when the substrate has high water affinity (for example, the substrate is a printed layer (aqueous ink layer) formed by an aqueous ink composition), a printed item having sufficient resistance in various respects can be obtained; and the gloss of the overprinted surface of the printed item can be increased by the varnish composition. DETAILED DESCRIPTION OF THE INVENTION

[0011] [1. Composition of electron beam curable varnish composition] The electron beam-curable varnish composition of the present invention (also referred to as "varnish composition") contains a combination of a (meth)acrylate compound (A) and a (meth)acrylate compound (B) as polymerizable monomer components, and any other polymerizable monomer component; it also contains a polymerization inhibitor (C), a polysiloxane compound (D-1), and a wax (D-2); and may further contain a component (E) that can function as a gloss adjuster, as well as any other component.

[0012] [1-1. (Meth)acrylate Compound (A)] The (meth)acrylate compound (A) is a polymerizable monomer component having: A1) 3 to 6 (meth)acrylate groups in the molecule; A2) a homopolymer having a glass transition temperature of 25°C or higher and lower than 100°C; and A3) a surface tension at 25°C of 30 mN / m or higher and lower than 41 mN / m.

[0013] The (meth)acrylate compound (A) contains 3 to 6 (meth)acrylate groups in the molecule, preferably 4 to 6 (meth)acrylate groups. The number of (meth)acrylate groups in the (meth)acrylate compound (A) is preferably greater than the number of (meth)acrylate groups in the (meth)acrylate compound (B). The (meth)acrylate compound (A) is highly curable by polymerization reaction and easily polymerizes. Therefore, a cured layer containing the (meth)acrylate compound (A) tends to have high abrasion resistance.

[0014] The glass transition temperature of the homopolymer of the (meth)acrylate compound (A) is 25°C or higher and lower than 100°C, preferably 25°C or higher and 85°C or lower, and more preferably 25°C or higher and 70°C or lower. The glass transition temperature of the homopolymer of the (meth)acrylate compound (A) is preferably lower than the glass transition temperature of the homopolymer of the (meth)acrylate compound (B) (the difference in glass transition temperature is preferably 20°C or higher, more preferably 30°C or higher, and even more preferably 40°C or higher). A cured product of a varnish composition containing a (meth)acrylate compound (A) whose homopolymer glass transition temperature is lower than 100°C has high flexibility and tends to be less brittle. Therefore, it tends to have high abrasion resistance.

[0015] The surface tension of the (meth)acrylate compound (A) at 25°C is 30 mN / m or more but less than 41 mN / m, preferably 40 mmN / m or less, and more preferably 39 mmN / m or less. By adjusting the (meth)acrylate compound (A) to less than 41 mN / m, the surface tension of a varnish composition containing it can be reduced. As a result, even if the surface tension of the base to which the varnish composition is applied is highly hydrophilic, the varnish composition can be applied without being repelled by the base, resulting in a smooth coating film that, when cured, becomes a highly glossy cured layer.

[0016] The molecular weight of the (meth)acrylate compound (A) is preferably 350 or more, more preferably 370 or more, and even more preferably 400 or more; on the other hand, it is preferably 700 or less, more preferably 600 or less. The molecular weight of the (meth)acrylate compound (A) is preferably relatively larger than the molecular weight of the (meth)acrylate compound (B) (the difference between the molecular weights is preferably 50 or more, preferably 100 or more). The (meth)acrylate compound (A) has many functional groups and a relatively large molecular weight, so it can easily become a large polymer. Therefore, the cured product of a varnish composition containing the (meth)acrylate compound (A) is likely to have improved resistance to various frictions.

[0017] Examples of the (meth)acrylate compound (A) include dipentaerythritol hexaacrylate (DPHA), dipentaerythritol pentaacrylate (DPPA), ditrimethylolpropane tetraacrylate (Di-TMPTA), triacrylate of a 3-mol adduct of propylene oxide to trimethylolpropane (3PO-TMPTA), triacrylate of a 3-mol adduct of propylene oxide to glycerin (GPTA), triacrylate of a 6-mol adduct of propylene oxide to trimethylolpropane (6PO-TMPTA), and the like.

[0018] The (meth)acrylate compound (A) is contained in an amount of 4% by mass or more, preferably 9% by mass or more, relative to the electron beam curable varnish composition; on the other hand, it is contained in an amount of 60% by mass or less, preferably 50% by mass or less.

[0019] [1-2. (Meth)acrylate Compound (B)] The (meth)acrylate compound (B) is a polymerizable monomer component having: B1) two to three (meth)acrylate groups in the molecule; B2) a homopolymer having a glass transition temperature of 100°C or higher; and B3) a surface tension at 25°C of 30 mN / m or higher but lower than 42 mN / m.

[0020] The (meth)acrylate compound (B) contains 2 to 3 (meth)acrylate groups in the molecule, preferably 2. The number of (meth)acrylate groups in the (meth)acrylate compound (B) is preferably smaller than the number of (meth)acrylate groups in the (meth)acrylate compound (A).

[0021] The glass transition temperature of the homopolymer of the (meth)acrylate compound (B) is preferably 100°C or higher, but 200°C or lower. The glass transition temperature of the homopolymer of the (meth)acrylate compound (B) is preferably higher than the glass transition temperature of the homopolymer of the (meth)acrylate compound (A). A cured product of a varnish composition containing a (meth)acrylate compound (B) having a homopolymer glass transition temperature of 100°C or higher tends to have high heat resistance, high hardness, and improved abrasion resistance.

[0022] The surface tension of the (meth)acrylate compound (B) at 25°C is 30 mN / m or more but less than 42 mN / m, preferably 41 mN / m or less, more preferably 40 mN / m or less, and even more preferably 39 mN / m or less. By adjusting the (meth)acrylate compound (B) to less than 42 mN / m, the surface tension of the varnish composition containing it can be reduced. As a result, even if the surface tension of the substrate to which the varnish composition is applied is highly hydrophilic, the varnish composition can be applied without being repelled by the substrate, resulting in a smooth coating film that, when cured, becomes a highly glossy layer. Furthermore, cured products of varnish compositions containing the (meth)acrylate compound (B) tend to have high alcohol resistance.

[0023] The molecular weight of the (meth)acrylate compound (B) is preferably 400 or less, more preferably 360 or less, and even more preferably 330 or less. The molecular weight of the (meth)acrylate compound (B) is preferably smaller than the molecular weight of the (meth)acrylate compound (A), and more preferably 50 or more smaller than the molecular weight of the (meth)acrylate compound (A). The molecular weight of the (meth)acrylate compound (B) is relatively small and therefore has a low viscosity, so varnish compositions containing the (meth)acrylate compound (B) tend to have high leveling properties.

[0024] Examples of the (meth)acrylate compound (B) include diacrylates having a hydroxypivalic acid skeleton, such as hydroxypivalic acid neopentyl glycol diacrylate, dipropylene glycol diacrylate, and tricyclodecane dimethanol diacrylate.

[0025] The (meth)acrylate compound (B) is contained in an amount of 35% by mass or more, preferably 45% by mass or more, based on the electron beam curable varnish composition; on the other hand, it is contained in an amount of less than 95% by mass, preferably 80% by mass or less.

[0026] [1-3. Optional Other Polymerizable Monomer Components] The varnish composition of the present invention may contain other polymerizable monomer components in addition to the (meth)acrylate compound (A) and the (meth)acrylate compound (B). For example, it may contain a (meth)acrylate compound with a functionality of 1. However, it is preferable that the varnish composition of the present invention does not contain a polymerizable monomer component whose surface tension is 42 mN / m or more. When a varnish composition containing a polymerizable monomer component with a surface tension of 42 mN / m or more is applied to a highly hydrophilic substrate, it is likely to be repelled by the substrate, making it difficult to form a coating film or a cured product layer of uniform thickness.

[0027] [1-4. Polymerization inhibitor (C)] The electron beam-curable varnish composition of the present invention contains a polymerization inhibitor (C). The polymerization inhibitor (C) can prevent polymerization reactions from occurring during storage of the varnish composition and suppress thickening of the ink composition, thereby improving the storage stability of the varnish composition.

[0028] Examples of the polymerization inhibitor (C) include phenolic compounds (including quinone compounds) such as dibutylhydroxytoluene, tocopherol acetate, nitrosamine compounds, benzotriazole, hindered amines, etc., of which phenolic compounds (including quinone compounds) are more preferred. Examples of nitrosamine compounds include N-nitrosophenylhydroxylamine aluminum salt and ammonium N-nitrosophenylhydroxylamine. These can be contained in the varnish composition alone or in combination of two or more.

[0029] The content of the polymerization inhibitor (C) in the electron beam curable varnish composition is preferably about 0.05 to 1 mass % relative to the entire varnish composition in the case of a quinone-based compound; and may be about 0.05 to 0.1 mass % in the case of a nitrosamine-based compound.

[0030] [1-5. Polysiloxane Compound (D-1)] The polysiloxane compound (D-1) is a compound having a siloxane bond (-O-Si-) in the main chain. In the varnish composition of the present invention, the polysiloxane compound (D-1) is radicalized by electron beam irradiation, causing a copolymerization reaction with other polymerizable components, which is thought to result in improved abrasion resistance of the cured product of the varnish composition.

[0031] The polysiloxane compound (D-1) may be either an unmodified polysiloxane or a modified polysiloxane. Unmodified polysiloxanes include unmodified dimethylpolysiloxanes, which have a structure formed by polymerizing units consisting of dimethylsiloxane. Unmodified dimethylpolysiloxanes may have a molecular structure represented by the following structural formula: n in the following structural formula is 3 to 30, preferably 4 to 20, but is not particularly limited. [ka]

[0032] The unmodified dimethylpolysiloxane may also be a cyclic dimethylpolysiloxane such as octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, or dodecamethylcyclohexasiloxane.

[0033] The modified polysiloxane may be a polysiloxane having a substituent that does not have a polymerizable reactive group upon electron beam irradiation, or a polysiloxane having a polymerizable reactive group ((meth)acrylic group) upon electron beam irradiation. The polysiloxane having a substituent that does not have a polymerizable reactive group is, for example, a modified polysiloxane in which a hydroxyl group, an amino group, a (poly)ether group, an epoxy group, a carboxy group, a carbinol group, a mercapto group, a phenol group, an ester group, an alkoxy group, a halogen atom, an aralkyl group, an aralkyl group, a long-chain alkyl group, a higher fatty acid ester modified group, a higher aliphatic amide group, or the like is substituted on the side chain or terminal (one terminal or both terminals) of the unmodified dimethylpolysiloxane represented by the above structural formula.

[0034] Furthermore, polysiloxanes having polymerizable reactive groups are, for example, referred to as silicone (meth)acrylates, and are modified polysiloxanes in which one or more (meth)acrylic groups are substituted on the side chains or terminals (one terminal or both terminals) of the unmodified dimethylpolysiloxane represented by the above structural formula. The varnish composition of the present invention preferably contains a polysiloxane having polymerizable reactive groups, preferably a silicone (meth)acrylate, and more preferably a silicone acrylate, as the polysiloxane compound (D-1). In the cured product of the varnish composition, unpolymerized polysiloxanes are relatively free to move and may migrate to the interface, causing a mold release effect and reducing the adhesion of the cured varnish. However, polymerized polysiloxanes are less likely to migrate, making mold release less likely to occur, and therefore the adhesion of the cured varnish is less likely to decrease.

[0035] The polysiloxane (D-1) is preferably contained in an amount of 0.1% by mass or more, more preferably 0.3% by mass or more, and even more preferably 0.5% by mass or more, based on the varnish composition; on the other hand, the amount is preferably 3.5% by mass or less, more preferably 3.0% by mass or less, and even more preferably 2.5% by mass or less. The inclusion of polysiloxane (D-1) can promote electron beam curing of the varnish composition; however, if the content is high, polysiloxane (D-1) is unlikely to be uniformly present in the varnish composition, and it may become localized and liberated even in the cured product of the varnish composition.

[0036] [1-6. Wax (D-2)] Wax (D-2) can improve the scratch resistance of the cured product of the varnish composition of the present invention. Examples of wax (D-2) include animal and vegetable waxes such as beeswax, lanolin wax, spermaceti, candelilla wax, carnauba wax, rice wax, Japan wax, and jojoba oil; mineral waxes such as montan wax, ozogelite, ceresin, paraffin wax, microcrystalline wax, and petrolatum; petroleum waxes; synthetic hydrocarbon waxes such as Fischer-Tropsch wax, polyethylene wax, oxidized polyethylene wax, and oxidized polypropylene wax; modified waxes such as montan wax derivatives, paraffin wax derivatives, and microcrystalline wax derivatives; hydrogenated waxes such as hydrogenated castor oil and hydrogenated castor oil derivatives; and polytetrafluoroethylene wax. Wax (D-2) is preferably polytetrafluoroethylene wax or polyethylene wax.

[0037] To enhance scratch resistance, the wax (D-2) preferably has an average particle size of 8.0 μm or less, more preferably 6.0 μm or less, and even more preferably 4.0 μm or less, and may be in the range of 1.0 to 2.0 μm.

[0038] The content of wax (D-2) in the varnish composition is preferably 0.05% by mass or more, more preferably 0.1% by mass or more; on the other hand, it is preferably 5% by mass or less, more preferably 2% by mass or less.

[0039] [1-7. Ingredient (E)] The electron beam-curable varnish composition of the present invention may contain one or more components (E) selected from talc, silica, calcium carbonate, mica, barium sulfate, and magnesium carbonate. Component (E) can function as a gloss adjuster (or extender pigment) in the varnish composition. The content of the gloss adjuster may be approximately 1 to 10% by mass of the varnish composition, but is not particularly limited.

[0040] [1-8. Other ingredients] The electron beam-curable varnish composition of the present invention may contain other optional additives; examples of optional additives include surface conditioners (surfactants), color pigments, and dispersants. Examples of surfactants include silicone-based surface conditioners, fluorine-based surface conditioners, acrylic-based surface conditioners, and acetylene glycol-based surface conditioners. The color pigment can be blended into the varnish composition to the extent that it does not impair the transparency or translucency required of the varnish composition. For example, by incorporating a dispersant into a varnish composition containing component (E), the dispersibility of component (E) can be improved. Examples of dispersants include the DISPERBYK series (trade name, manufactured by BYK-Chemie).

[0041] The electron beam-curable varnish composition of the present invention does not usually contain a polymerization initiator. Since the varnish composition of the present invention is cured by irradiation with an electron beam, the curing reaction is possible even without containing a polymerization initiator. However, the electron beam-curable varnish composition of the present invention may also contain a polymerization initiator.

[0042] The electron beam-curable varnish composition of the present invention preferably contains no solvent or a small amount of solvent (for example, 3% by mass or less of the varnish composition). The solvent can reduce the viscosity of the varnish composition and adjust the ease with which the varnish spreads onto the substrate. Examples of solvents include water, glycol monoacetates, glycol diacetates, glycol ethers, and lactate esters.

[0043] [2. Physical properties of electron beam curable varnish composition] The electron beam-curable varnish composition of the present invention can be used to form (overprint) a protective layer to protect an underlying substrate, but it is preferable that the underlying substrate be visible through the protective layer, and therefore the varnish composition is often transparent or translucent.

[0044] The viscosity of the electron beam-curable varnish composition of the present invention may be appropriately set depending on the application method of the varnish composition. The viscosity of the varnish composition can be adjusted by selecting the polymerizable components ((meth)acrylate compound (A), (meth)acrylate compound (B), other polymerizable monomers), adding an oligomer or polymer, adding a solvent, etc.

[0045] The surface tension of the electron beam-curable varnish composition of the present invention is preferably less than 42 mN / m, more preferably less than 41 mN / m, even more preferably less than 40 mN / m, and may be 39 mN / m or less. A varnish composition with a surface tension of less than 42 mN / m is likely to form a coating film of uniform thickness even when applied to a highly hydrophilic substrate without being repelled by the substrate.

[0046] [3. Method for producing electron beam curable varnish composition] The manufacturing method (preparation method) of the electron beam-curable varnish composition of the present invention is not particularly limited. For example, the varnish composition can be prepared by adding all of the components and mixing them with a stirrer or the like. Furthermore, when the electron beam-curable varnish composition contains a pigment, the varnish composition can be prepared by adding all of the components and milling them using a roll mill or a bead mill. Furthermore, the varnish composition containing component (E) can be prepared by mixing component (E) with a portion of the (meth)acrylate compound (A) and / or (meth)acrylate compound (B) with a stirrer or the like to obtain a concentrated base, and then adding and mixing the remaining components.

[0047] [4. Uses of electron beam curable varnish compositions] The electron beam-curable varnish composition of the present invention can be used to overprint a substrate to protect the substrate, although this is not particularly limited. Overprinting refers to applying a second coat on a printed layer formed on a substrate. By overprinting the electron beam-curable varnish composition of the present invention on the printed layer, the printed layer can be protected.

[0048] The electron beam-curable varnish composition of the present invention is applied by a known method, and the resulting coating film is cured by irradiating it with electron beams. The varnish composition can be applied using techniques such as flexographic printing or gravure printing, but techniques such as inkjet printing can also be used. The coating film of the varnish composition is cured by irradiating it with electron beams. The conditions for electron beam irradiation are not particularly limited, and may be set so as to cure the coating film of the varnish composition. For example, the irradiation can be performed under conditions of an acceleration voltage of 50 to 150 kV, an irradiation dose of 15 to 50 kGy, and an oxygen concentration of 50 to 300 ppm.

[0049] The electron beam-curable varnish composition of the present invention can be overprinted onto a printed layer (aqueous ink layer) formed using an aqueous ink. Because a printed layer formed using an aqueous ink is highly hydrophilic, the surface tension of the printed layer is likely to be low. Therefore, if a varnish composition with high surface tension is overcoated onto the printed layer, the varnish composition will be repelled by the printed layer; as a result, it is difficult to achieve a uniform thickness of the varnish composition layer, and in some cases the varnish composition layer may become rough or an embossed varnish composition layer may be formed. This reduces the gloss of the cured surface of the varnish composition and tends to reduce various resistance properties.

[0050] In contrast, the electron beam-curable varnish composition of the present invention has a low surface tension, and therefore, even when overprinted onto a printed layer formed using a water-based ink, it blends well with the printed layer, facilitating the formation of a varnish composition layer of uniform thickness. As a result, the gloss of the cured surface of the varnish composition is enhanced, and various resistance properties are easily improved.

[0051] The material of the substrate onto which the electron beam-curable varnish composition of the present invention is applied may be plastic, paper (including carton), etc. The substrate may also be a composite substrate such as a laminate composed of multiple substrates.

[0052] The substrate onto which the electron beam curable varnish composition of the present invention is applied may be a plastic substrate. Examples of plastics include polyester polymers (e.g., polyethylene terephthalate (PET), polyethylene naphthalate, etc.), cellulose polymers (e.g., diacetyl cellulose, triacetyl cellulose (TAC), etc.), polycarbonate polymers, polyacrylic polymers (e.g., polymethyl methacrylate, etc.), vinyl chloride polymers, polyolefin polymers (e.g., polyethylene, polypropylene, polyolefin polymers having a cyclic or norbornene structure, ethylene propylene, etc.), and the like. copolymer polymers, etc.), polyamide polymers (e.g., nylon, aromatic polyamide polymers, etc.), polystyrene polymers (e.g., polystyrene, acrylonitrile-styrene copolymer polymers, etc.), polyimide polymers, polysulfone polymers, polyethersulfone polymers, polyetherketone polymers, polyphenylsulfide polymers, polyvinyl alcohol polymers, polyvinylidene chloride polymers, polyvinyl butyral polymers, polyarylate polymers, polyoxymethylene polymers, polyepoxy polymers, and blends of these polymers.

[0053] The substrate onto which the electron beam-curable varnish composition of the present invention is applied may be a paper substrate, and is preferably a paper substrate selected from uncoated paper, one-side glossy kraft paper in which one side of the substrate is treated, bleached kraft paper, unbleached kraft paper, etc., or cardboard such as carton.

[0054] The aqueous ink to be printed on the substrate is not particularly limited as long as it is a printing ink containing water as a solvent as a main component. The aqueous ink may contain, for example, a colorant such as a pigment or dye, a binder resin, and various additives. Printing with the aqueous ink can be performed by any method, and techniques such as flexographic printing, gravure printing, and inkjet printing can be used. [Example]

[0055] 1. Materials used in preparing the varnish composition The varnish compositions shown in Tables 1 to 5 were prepared using the materials shown below.

[0056] 1-1. (Meth)acrylate compound (A) DPHA: Dipentaerythritol hexaacrylate Number of functional groups: 6, homopolymer glass transition temperature: 54°C, surface tension: 39mN / m, Mw (molecular weight): 578.6 DPPA: Dipentaerythritol pentaacrylate Number of functional groups: 5, homopolymer glass transition temperature: 68°C, surface tension: 39mN / m, Mw: 524.5 Di-TMPTA: Ditrimethylolpropanetetraacrylate Functional group number 4, homopolymer glass transition temperature 42°C, surface tension 36mN / m, Mw 466.6 3PO-TMPTA: Triacrylate of 3-mol propylene oxide adduct of trimethylolpropane (trade name "MIRAMER M360", manufactured by Miwon) Functional group number 3, homopolymer glass transition temperature 27℃, surface tension 34mN / m, Mw 470 GPTA Triacrylate of propylene oxide 3 mole adduct of glycerin Functional group number 3, homopolymer glass transition temperature 35℃, surface tension 36mN / m, Mw 428

[0057] 1-2. (Meth)acrylate Compound (B) HPNDA: Diacrylate with a hydroxypivalic acid skeleton (trade name "MIRAMER M210", manufactured by Miwon) Number of functional groups: 2, homopolymer glass transition temperature: 111°C, surface tension: 33mN / m, Mw: 312 DPGDA: Dipropylene glycol diacrylate (trade name "MIRAMER M222", manufactured by Miwon) Number of functional groups: 2, homopolymer glass transition temperature: 102°C, surface tension: 34mN / m, Mw: 242 TCDDA (trade name "MIRAMER M262", tricyclodecane dimethanol diacrylate, manufactured by Miwon) Functional groups: 2, homopolymer glass transition temperature: 110°C, surface tension: 38mN / m, Mw: 304

[0058] 1-3. Other polymerizable monomer components 6EO-TMPTA: Triacrylate of 6 moles of ethylene oxide adduct of trimethylolpropane (trade name "MIRAMER M3130", manufactured by Miwon) Number of functional groups: 3, homopolymer glass transition temperature: 22°C, surface tension: 39mN / m 9EO-TMPTA: Triacrylate of 9 moles of ethylene oxide adduct of trimethylolpropane (trade name "MIRAMER M3130", manufactured by Miwon) Number of functional groups: 3, homopolymer glass transition temperature: -3°C, surface tension: 40mN / m 15EO-TMPTA: Triacrylate of 15 moles of ethylene oxide adduct of trimethylolpropane (trade name "MIRAMER M3150", manufactured by Miwon) Number of functional groups: 3, homopolymer glass transition temperature: -31°C, surface tension: 42mN / m PETA: Pentaerythritol triacrylate Number of functional groups: 3, homopolymer glass transition temperature: 42°C, surface tension: 41mN / m PETTA: Pentaerythritol tetraacrylate Number of functional groups: 3, homopolymer glass transition temperature: 36°C, surface tension: 41mN / m

[0059] 1-4. Polymerization inhibitor (C): Dibutylhydroxytoluene 1-5. Polysiloxane compound (D-1): Silicone acrylate (trade name "X-22-2445, manufactured by Shin-Etsu Chemical Co., Ltd.) 1-6. Wax (D-2): Polyethylene wax (product name "SB-395", manufactured by Shamrock Technologies) 1-7. Component (E): Talc (trade name "P-3", manufactured by Nippon Talc Co., Ltd.) gloss adjuster

[0060] 2. Preparation of Varnish Composition Each component was added according to the formulation (unit: parts by mass) shown in Tables 1 to 5, and the mixture was stirred and mixed with a stirrer to prepare a varnish composition.

[0061] 3. Storage stability of varnish composition Each varnish composition prepared in 2 above was left to stand and stored at 25°C for 365 days, and the storage stability was evaluated according to the following criteria. ○: No gelation observed after 365 days of storage ×: Gelation was observed after 365 days of storage

[0062] 4. Preparation and Evaluation of Cured Products 4-1. Preparation of cured product (laminate) A water-based ink (Ecoplata B) was applied to a printing substrate (product name "UF Coat", manufactured by Oji Paper Co., Ltd.) using a Maya Bar No. 5, and the coating film was dried using hot air from a hair dryer. Next, each varnish composition shown in Tables 1 to 5 was applied to the dried coating film formed on the printing substrate using a simple color developer (RI Tester, Toyoei Seiko Co., Ltd.). Specifically, each varnish composition shown in Tables 1 to 5 was applied to 3 cm 3 / m 2 A varnish composition layer was obtained by applying the coating amount to the dried aqueous ink coating film. The varnish composition layer was then irradiated with electron beams (EB irradiation device; acceleration voltage 90 kV, exposure dose 30 kGy) until the varnish composition layer was cured, and the cured product was obtained as a test piece.

[0063] 4-2. Gloss measurement For each test piece obtained in 4-1 above, the gloss (gloss B) of the cured coating surface of the varnish composition was measured. For the measurement, a Murakami digital gloss meter (manufactured by Murakami Color Research Institute) was used to measure the gloss reflected at an angle of 60° from the cured coating surface.

[0064] Separately, each varnish composition shown in Tables 1 to 5 was applied directly (without printing with aqueous ink) to a printing substrate (product name "UF Coat", manufactured by Oji Paper Co., Ltd.) using a simple color developer (RI Tester, manufactured by Toyoei Seiko Co., Ltd.) under the same conditions as in 4-1 above, and then cured. The gloss (gloss A) of the cured coating film surface of the varnish composition was measured for each sample obtained in the same manner as for gloss B. The measurement results are shown in Tables 1 to 5.

[0065] 4-3. Evaluation of abrasion resistance The rub resistance of each test piece obtained in 4-1 above was evaluated using a Gakushin-type rub fastness tester. Specifically, the test pieces were overlapped so that the cured coating surfaces of the varnish compositions were in contact with each other, and rubbed 500 times with a 500g weight. The condition of the coating immediately after this rubbing was visually observed and evaluated according to the following criteria. The evaluation results are shown in Tables 1 to 5. 5:20 Even with back-and-forth friction, the hardened coating on the coated surface could not be removed. 4: The hardened coating on the coated surface was removed by rubbing back and forth from 10 to 19 times. 3: The hardened coating on the coated surface was removed by rubbing back and forth 5 to 9 times. 2: The hardened coating on the coated surface was removed by rubbing back and forth 2 to 4 times. The hardened coating on the coated surface was removed by rubbing back and forth at 1:1.

[0066] 4-4. Evaluation of alcohol resistance and friction resistance The alcohol-rubbing resistance of each test piece obtained in 4-1 above was evaluated using a Gakushin-type rub fastness tester. Specifically, the cured coating surface of the varnish composition of each test piece was rubbed back and forth 20 times with a 200g weight through a patch cloth (Kanakin No. 3) soaked in three drops of ethanol. The condition of the coating immediately after this rubbing was visually observed and evaluated according to the following criteria. The evaluation results are shown in Tables 1 to 5. 5:20 Even with back-and-forth friction, the hardened coating on the coated surface could not be removed. 4: The hardened coating on the coated surface was removed by rubbing back and forth from 10 to 19 times. 3: The hardened coating on the coated surface was removed by rubbing back and forth 5 to 9 times. 2: The hardened coating on the coated surface was removed by rubbing back and forth 2 to 4 times. The hardened coating on the coated surface was removed by rubbing back and forth at 1:1.

[0067] 4-5. Heat resistance For each test piece obtained in 4-1 above, the cured coating surface of the varnish composition and the aluminum foil were sealed at a pressure of 2.0 kg / cm using a heat seal tester equipped with a hot plate with a thermal gradient of 80 to 300°C. 2The test piece was pressed for 1 second at a pressure of 0.05 psi. The heat resistance was evaluated based on the minimum temperature at which the varnish on the cured coating surface of the varnish composition transferred to the aluminum foil. The evaluation results are shown in Tables 1 to 5. 5: Over 250℃ 4: 240℃ or higher, but lower than 250℃ 3: 230℃ or higher, but lower than 240℃ 2: 210℃ or higher and lower than 230℃ 1: Less than 210℃

[0068] 4-6. Oil resistance and abrasion resistance The oil and rub resistance of each test piece obtained in 4-1 above was evaluated using a Gakushin-type rub fastness tester. Specifically, the cured coating surface of the varnish composition of each test piece was rubbed 20 times with a 200g weight, using a patch (Kanakin No. 3) soaked in three drops of edible oil (trade name "Canola Oil", manufactured by Nisshin Oillio Co., Ltd.). The condition of the cured coating film immediately after this rubbing was visually observed and evaluated according to the following criteria. The evaluation results are shown in Tables 1 to 5. 5:20 Even with back-and-forth friction, the hardened coating on the coated surface could not be removed. 4: The hardened coating on the coated surface was removed by rubbing back and forth from 10 to 19 times. 3: The hardened coating on the coated surface was removed by rubbing back and forth 5 to 9 times. 2: The hardened coating on the coated surface was removed by rubbing back and forth 2 to 4 times. The hardened coating on the coated surface was removed by rubbing back and forth at 1:1.

[0069] [Table 1]

[0070] [Table 2]

[0071] [Table 3]

[0072] [Table 4]

[0073] [Table 5]

[0074] As shown in Comparative Example 1 (Table 5), the varnish composition containing no polymerization inhibitor had poor storage stability, and gelation was observed after storage for one year. As shown in Comparative Examples 2 to 4 (Table 5), when a varnish composition containing no polysiloxane compound and / or wax was used, the abrasion resistance of the obtained cured product (laminate), including abrasion resistance, alcohol abrasion resistance, and oil abrasion resistance, was reduced.

[0075] As shown in Comparative Example 5 (Table 5), when a varnish composition containing 6EO-TMPTA but not the (meth)acrylate compound (B), a monomer component with a high glass transition temperature, was used, the abrasion resistance, alcohol abrasion resistance, and heat resistance of the resulting cured product (laminate) were reduced.

[0076] As shown in Comparative Examples 6 and 7 (Table 5), when a varnish composition containing 9EO-TMPTA or 15EO-TMPTA but not containing the (meth)acrylate compound (B) monomer component with a high glass transition temperature was used, the resulting cured product (laminate) exhibited reduced abrasion resistance, alcohol abrasion resistance, and heat resistance (similar to Comparative Example 5), and also exhibited reduced gloss B. The decrease in gloss B is due to the high surface tension of 9EO-TMPTA or 15EO-TMPTA, which causes the surface of the cured layer to become rough (roughened) when the varnish compositions of Comparative Examples 6 and 7 containing 9EO-TMPTA are applied to a highly hydrophilic aqueous ink coating and cured. It is believed that the roughened surface of the cured layer resulted in a further decrease in heat resistance compared to Comparative Example 5.

[0077] As shown in Comparative Examples 8 and 9 (Table 5), when a varnish composition containing PETA or PETTA but not a (meth)acrylate compound (B) monomer component with a high glass transition temperature was used, the abrasion resistance and alcohol abrasion resistance of the resulting cured product (laminate) decreased (similar to Comparative Example 5), and the gloss B decreased (similar to Comparative Examples 6 and 7). However, Comparative Examples 8 and 9 maintained heat resistance; this is thought to be because the glass transition temperature of PETA or PETTA is relatively high compared to that of 9EO-TMPTA or 15EO-TMPTA.

[0078] As shown in Comparative Examples 10 to 13 (Table 5), when a varnish composition containing 9EO-TMPTA but not containing a (meth)acrylate compound (B) was used, the abrasion resistance, alcohol abrasion resistance, and heat resistance of the obtained cured product (laminate) decreased, as in Comparative Example 6, and the gloss B also decreased.

[0079] As shown in Comparative Examples 14 to 15 (Table 5), when a varnish composition containing a combination of 6EO-TMTAP and 9EO-TMPTA or 15EO-TMPTA but not containing a (meth)acrylate compound (B) was used, the abrasion resistance, alcohol abrasion resistance, and heat resistance of the obtained cured product (laminate) decreased, as in Comparative Examples 6 and 7, and the gloss B also decreased.

[0080] As shown in Comparative Examples 16 and 17 (Table 5), when a varnish composition containing a combination of 6EO-TMTAP or 9EO-TMPTA and PETA or PETTA but not containing the (meth)acrylate compound (B) was used, the abrasion resistance and alcohol abrasion resistance of the obtained cured product (laminate) decreased, as in Comparative Examples 8 and 9, and the gloss B also decreased (as in Comparative Examples 6 and 7), but heat resistance was maintained.

[0081] As shown in Comparative Example 18 (Table 5), the composition contained DPHA as the (meth)acrylate compound (A) and TCDDA as the (meth)acrylate compound (B). When the DPHA content was high and the TCDDA content was low, gloss B was maintained, but the abrasion resistance, alcohol abrasion resistance, heat resistance, and oil abrasion resistance all decreased.

[0082] In contrast to these comparative examples, the varnish compositions of Examples 1 to 56, which contained a combination of a specified amount of (meth)acrylate compound (A) and (meth)acrylate compound (B), and further contained a polymerization inhibitor (C), a polysiloxane compound (D-1), and a wax (D-2), had good storage stability, and the cured products (laminates) obtained using these varnish compositions had high resistance in various respects, and also had a sufficiently high gloss B.

[0083] As shown in Examples 1 to 7 (Table 1), when a varnish composition containing a combination of DPHA ((meth)acrylate compound (A)) and TCDDA ((meth)acrylate compound (B)) was used, the resulting cured product (laminate) exhibited good resistance in various respects. However, as shown in Example 7, a decrease in the DPHA content tended to decrease the abrasion resistance.

[0084] As shown in Examples 8 to 13 (Table 1), when a varnish composition containing a combination of DPHA ((meth)acrylate compound (A)) and DPGDA ((meth)acrylate compound (B)) was used, the resulting cured product (laminate) had good resistance properties, similar to Examples 1 to 7. Furthermore, as shown in Example 13, a decrease in the DPHA content tended to decrease the abrasion resistance.

[0085] As shown in Examples 14 to 19 (Table 2), when a varnish composition containing a combination of DPHA ((meth)acrylate compound (A)) and HPNDA ((meth)acrylate compound (B)) was used, the cured product (laminate) obtained had good resistance properties, as in Examples 1 to 7. Furthermore, as shown in Example 19, a decrease in the DPHA content tended to decrease the abrasion resistance.

[0086] As shown in Examples 20 to 28 (Table 2), when a varnish composition containing a combination of DPPA ((meth)acrylate compound (A)) and various (meth)acrylate compounds (B) (TCDDA, DPGDA, or HPNDA) was used, the resulting cured product (laminate) had good resistance to various types of materials.

[0087] As shown in Examples 29 to 37 (Table 3), when a varnish composition containing a combination of Di-TMPTA ((meth)acrylate compound (A)) and various (meth)acrylate compounds (B) was used; as shown in Examples 38 to 46 (Table 3), when a varnish composition containing a combination of 3PO-TMPTA ((meth)acrylate compound (A)) and various (meth)acrylate compounds (B) was used; as shown in Examples 47 to 55, when a varnish composition containing a combination of multiple types of (meth)acrylate compounds (A) and various (meth)acrylate compounds (B) was used; and as shown in Example 56, when a varnish composition containing a combination of GPTA as the (meth)acrylate compound (A) and TCDDA as the (meth)acrylate compound (B) was used, the resulting cured product (laminate) exhibited good resistance in various respects. [Industrial Applicability]

[0088] The present invention provides a varnish composition for overprinting that protects a substrate. Printed matter overprinted with the varnish composition of the present invention exhibits excellent resistance properties, and even when the substrate has high hydrophilicity, it is possible to obtain a printed matter with excellent resistance properties and also to enhance its gloss. Therefore, the varnish composition of the present invention can be suitably used as an overprint varnish composition for protecting a substrate that includes a printed layer formed with an aqueous ink composition.

Claims

1. a (meth)acrylate compound (A) containing 3 to 6 (meth)acrylate groups in the molecule, having a homopolymer glass transition temperature of 25°C or higher and lower than 100°C, and having a surface tension at 25°C of 30 mN / m or higher and lower than 41 mN / m; a (meth)acrylate compound (B) containing 2 to 3 (meth)acrylate groups in the molecule, having a homopolymer glass transition temperature of 100°C or higher, and having a surface tension at 25°C of 30 mN / m or higher but lower than 42 mN / m; a polymerization inhibitor (C); a polysiloxane compound (D-1); Wax (D-2), An electron beam curable varnish composition comprising: The electron beam curable varnish composition contains 4 to 60 mass% of the (meth)acrylate compound (A) and 35 mass% or more but less than 95 mass% of the (meth)acrylate compound (B) relative to the electron beam curable varnish composition.

2. 2. The electron beam-curable varnish composition according to claim 1, wherein the electron beam-curable varnish composition does not contain a polymerizable monomer component having a surface tension of 42 mN / m or more at 25°C.

3. 3. The electron beam-curable varnish composition according to claim 1, wherein the molecular weight of the (meth)acrylate compound (A) is greater than the molecular weight of the (meth)acrylate compound (B), and the difference in molecular weight between them is 50 or more.

4. 3. The electron beam-curable varnish composition according to claim 1, wherein the polysiloxane compound (D-1) comprises a modified polysiloxane having a polymerizable functional group.

5. 3. The electron beam-curable varnish composition according to claim 1, wherein the polymerization inhibitor (C) is contained in an amount of 0.05% by mass to 1% by mass relative to the electron beam-curable varnish composition.

6. 3. The electron beam curable varnish composition according to claim 1, wherein the wax (D-2) is contained in an amount of 0.05% by mass or more and less than 5% by mass relative to the electron beam curable varnish composition.

7. 3. The electron beam-curable varnish composition according to claim 1, further comprising one or more components (E) selected from the group consisting of talc, silica, calcium carbonate, mica, barium sulfate, and magnesium carbonate.

8. 3. The electron beam-curable varnish composition according to claim 1, which is for overprinting.

9. 3. The electron beam-curable varnish composition according to claim 1, for overprinting an aqueous ink layer.

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