Radiation-curable ink-jet ink, decorative sheet, and method for producing the decorative sheet

Abstract

To provide a radiation curable inkjet ink which has good surface curability even in air, and is capable of providing a cured product having low odor, good flexibility, and low-temperature impact resistance.SOLUTION: In particular, the radiation curable inkjet ink includes 20-40 pts.mass of a bifunctional urethane (meth)acrylate oligomer and 50-80 pts.mass of a monofunctional monomer, based on 100 pts.mass of polymerizable components, and further includes an α-hydroxyketone oligomer and a benzophenone compound as photoinitiators.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a radiation curable inkjet ink, a decorative sheet, and a method for producing a decorative sheet. [Background technology]

[0002] Decorative sheets are used to decorate the interior and exterior walls of buildings. In recent years, there has been an increasing demand in the construction and building industry for interior finishing materials that can provide a real texture and unique design. In order to achieve such a real texture with decorative sheets, it is necessary to form height differences (asperities) on the surface of the decorative sheet. By performing color printing and surface texture (2.5D surface) formation using UV-curable inkjet ink, it is possible to impart a real surface texture and unique design to the decorative sheet. Inkjet printing is advantageous in terms of shortening lead times and producing small lots.

[0003] US Patent Application Publication No. 2010 / 0285282 describes a radiation-curable inkjet ink that contains at least 50% by weight of cyclic trimethylolpropane formal acrylate (CTFA), further contains a free radical photoinitiator, and is substantially free of volatile compounds.

[0004] Patent Document 2 (JP 2012-162615 A) describes an inkjet ink composition comprising: "a polymerizable monomer polymerizable by active energy rays; and a photopolymerization initiator, wherein the polymerizable monomer contains, in all monomers, 0.5 to 13 mass% of a polymerizable phosphate ester compound having a phosphate ester group and an ethylenic double bond group in the molecule, and 10 to 75 mass% of a monofunctional monomer having one ethylenic double bond group in the molecule and no phosphate ester group, and the photopolymerization initiator comprises an acylphosphine oxide initiator and an α-hydroxyketone initiator having one or less phenyl groups in the skeleton, and has a viscosity at 25°C of 3 to 50 mPa s."

[0005] Patent Document 3 (JP 2007-321034 A) describes "an ultraviolet-curable ink composition for inkjet recording, which contains a pigment, a photopolymerizable compound having an ethylenic double bond, a mixture of oxy-phenyl-acetic acid 2-[2-oxo-2-phenyl-acetoxy-ethoxy]-ethyl ester and oxy-phenyl-acetic acid 2-[2-hydroxy-ethoxy]-ethyl ester as a photopolymerization initiator, and an acylphosphine oxide compound, and an amine as a photoinitiator assistant." [Prior art documents] [Patent documents]

[0006] [Patent Document 1] US Patent Application Publication No. 2010 / 0285282 [Patent Document 2] JP 2012-162615 A [Patent Document 3] JP 2007-321034 A Summary of the Invention [Problem to be solved by the invention]

[0007] Generally, the cured product of UV-curable ink has an odor. From the viewpoint of health and safety in indoor applications, it is desirable to reduce the odor of the cured product as much as possible. The odor of the cured product of UV-curable ink is mainly derived from unreacted monomers, photoinitiators and their decomposition products. Therefore, in general printing systems such as flexographic printing and gravure printing, printing is performed under an inert gas atmosphere such as a nitrogen gas atmosphere in order to sufficiently proceed with the reaction with a smaller amount of photoinitiator.

[0008] To create a 2.5D surface by inkjet printing, the ink must be cured quickly before the ink droplets spread onto the substrate or onto the ink that has already been printed and cured. However, it is difficult to print in an inert gas atmosphere in a multi-pass inkjet printer. In inkjet printing, the curing process is performed with the print head located in an inert gas atmosphere. In this case, the ink on the print head is easily cured by stray ultraviolet light used for curing, causing nozzle clogging.

[0009] Interior materials are often installed to cover not only flat surfaces of structures but also curved surfaces or corners in environments ranging from 10° C. to 40° C. To prevent damage during installation and use, interior materials are required to have good flexibility, elongation properties, for example, and low-temperature impact resistance.

[0010] The present disclosure provides a radiation-curable inkjet ink that has good surface curing properties even in air and is capable of providing a cured product that has low odor, good flexibility, and low-temperature impact resistance. [Means for solving the problem]

[0011] According to one embodiment, there is provided a radiation-curable inkjet ink comprising, based on 100 parts by mass of a polymerizable component, 20 to 40 parts by mass of a bifunctional urethane (meth)acrylate oligomer and 50 to 80 parts by mass of a monofunctional monomer, and an α-hydroxyketone oligomer and a benzophenone compound as a photoinitiator.

[0012] According to another embodiment, there is provided a decorative sheet having a printed layer comprising a cured product of the above-mentioned radiation-curable ink-jet ink.

[0013] According to yet another embodiment, there is provided a method for producing a decorative sheet, comprising: preparing a substrate; inkjet printing the above-mentioned radiation-curable inkjet ink onto the substrate to form a printed layer on the substrate; and irradiating the printed layer with radiation to cure the printed layer. Effect of the Invention

[0014] The radiation-curable inkjet ink of the present disclosure has good surface curing properties even in air, and can provide a cured product that has low odor, good flexibility, and low-temperature impact resistance. The radiation-curable inkjet ink of the present disclosure can be suitably used in the production of decorative sheets.

[0015] It should be noted that the above description should not be construed as a disclosure of all embodiments of the present invention and all advantages related to the present invention. [Brief description of the drawings]

[0016] [Figure 1] 1 is a schematic cross-sectional view of a decorative sheet according to one embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] The present invention will be described in more detail below for the purpose of illustrating representative embodiments thereof, but the present invention is not limited to these embodiments.

[0018] In this disclosure, "monofunctional monomer" means a compound that has only one reactive functional group, generally having a molecular weight of less than 1000.

[0019] In the present disclosure, "oligomer" refers to a compound having a plurality of units derived from a monomer, and generally has a molecular weight of about 350 or more, or about 500 or more. For example, a urethane (meth)acrylate oligomer is a compound that contains a plurality of units having a urethane bond and has a (meth)acryloyloxy group.

[0020] In this disclosure, "texture" means the three-dimensional features on a surface that an observer can sense by sight or touch.

[0021] In this disclosure, "transparent" means that a material or article has a total light transmittance of about 70% or more, about 80% or more, or about 90% or more in the wavelength range of 400 to 700 nm. The total light transmittance is determined in accordance with JIS K 7361-1:1997 (ISO 13468-1:1996).

[0022] In this disclosure, "(meth)acrylic" means acrylic or methacrylic, "(meth)acryloyl" means acryloyl or methacryloyl, and "(meth)acrylate" means acrylate or methacrylate.

[0023] The radiation-curable inkjet ink of one embodiment contains, based on 100 parts by mass of the polymerizable component, 20 to 40 parts by mass of a bifunctional urethane (meth)acrylate oligomer and 50 to 80 parts by mass of a monofunctional monomer, and an α-hydroxyketone oligomer and a benzophenone compound as a photoinitiator. By using a specific combination of photoinitiators and containing specific amounts of a bifunctional urethane (meth)acrylate oligomer and a monofunctional monomer as the polymerizable components, it is possible to provide a cured product that has good surface curing properties even in air, low odor, good flexibility, and low-temperature impact resistance. The radiation-curable inkjet ink is a radical polymerization type acrylic ink, and the cured product thereof has excellent transparency, strength, weather resistance, etc., and is advantageous when using a decorative sheet as an interior material, for example.

[0024] A bifunctional urethane (meth)acrylate oligomer is a urethane oligomer that is a reaction product of a diol and a diisocyanate, and has (meth)acryloyl groups introduced at both ends thereof. The (meth)acryloyl groups react with (meth)acryloyl groups of other bifunctional urethane (meth)acrylate oligomers or monofunctional monomers to form a cured product. The bifunctional urethane (meth)acrylate oligomer can impart flexibility and low-temperature impact resistance to the cured product of the radiation-curable inkjet ink, and also contributes to improving surface curing in air due to its relatively large molecular weight. The bifunctional urethane (meth)acrylate oligomer may be one type or a combination of two or more types. The diol and diisocyanate constituting the urethane oligomer may be one type or a combination of two or more types.

[0025] Diols include, for example, polyester polyols, polyether polyols, polycarbonate polyols, and polycaprolactone polyols.

[0026] The diol may include a low molecular weight diol, such as ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, 1,3-butanediol, 1,4-butanediol, 2-methyl-1,3-propanediol, 1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, 1,4-cyclohexanedimethanol, bisphenol A, bisphenol F, hydrogenated bisphenol A, hydrogenated bisphenol F, 1,2-cyclopentanediol, and tricyclo[5.2.1.0]. 2,6 ]Decanedimethanol is an example.

[0027] The diisocyanate may be an aliphatic diisocyanate or an aromatic diisocyanate. Examples of the aliphatic diisocyanate include tetramethylene diisocyanate, hexamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, decamethylene diisocyanate, 1,3-cyclohexane diisocyanate, 1,4-cyclohexane diisocyanate, isophorone diisocyanate, and 4,4'-methylenebis(cyclohexylisocyanate). Examples of aromatic diisocyanates include 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, methylene diphenyl 4,4'-diisocyanate, 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, 3,3'-dimethyldiphenylmethane-4,4'-diisocyanate, diphenylmethane-2,2'-diisocyanate, diphenylmethane-2,4'-diisocyanate, 4,4'-diisocyanato-3,3'-dimethylbiphenyl, 1,5-naphthalene diisocyanate, and 2-methyl-1,5-naphthalene diisocyanate.

[0028] By using aliphatic compounds as both the diol and the diisocyanate, it is possible to improve the weather resistance of the cured product of the radiation-curable inkjet ink, and of the printed layer containing the cured product.

[0029] The introduction of the (meth)acryloyl group can be carried out by reacting the isocyanato terminal of the urethane oligomer with a hydroxyl group-containing (meth)acrylate. Examples of the hydroxyl group-containing (meth)acrylate include 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, 2-hydroxybutyl acrylate, 2-hydroxybutyl methacrylate, dipropylene glycol monoacrylate, and dipropylene glycol monomethacrylate. The hydroxyl group-containing (meth)acrylate can be used alone or in combination of two or more. In this embodiment, it is desirable to use an excess of diisocyanate relative to the diol during the synthesis of the urethane oligomer, that is, to make the molar ratio of NCO group / OH group greater than 1.

[0030] The introduction of the (meth)acryloyl group can also be carried out by reacting the hydroxyl group terminal of the urethane oligomer with an isocyanato group-containing (meth)acrylate. Examples of the isocyanato group-containing (meth)acrylate include 2-isocyanatoethyl acrylate and 2-isocyanatoethyl methacrylate. In this embodiment, it is desirable to use an excess of diol relative to diisocyanate during the synthesis of the urethane oligomer, that is, to set the molar ratio of NCO group / OH group to less than 1.

[0031] Examples of bifunctional urethane (meth)acrylate oligomers include polyester urethane di(meth)acrylate oligomers, polycarbonate urethane di(meth)acrylate oligomers, and polyether urethane di(meth)acrylate oligomers.

[0032] The difunctional urethane (meth)acrylate oligomer is preferably a difunctional urethane acrylate oligomer, since this provides excellent surface curing properties in air for the radiation-curable inkjet ink.

[0033] The difunctional urethane (meth)acrylate oligomer is advantageously a difunctional aliphatic urethane acrylate oligomer, which can improve the surface curing properties of the radiation-curable inkjet ink in air and provide a cured product with excellent weather resistance.

[0034] The number average molecular weight Mn of the bifunctional urethane (meth)acrylate oligomer is generally about 500 or more, about 1000 or more, or about 1200 or more, and about 5000 or less, about 4000 or less, or about 3000 or less. The weight average molecular weight Mw of the bifunctional urethane (meth)acrylate oligomer is generally about 500 or more, about 1000 or more, or about 1200 or more, and about 5000 or less, about 4000 or less, or about 3000 or less. The number average molecular weight Mn and the weight average molecular weight Mw are values ​​calculated in terms of standard polystyrene by gel permeation chromatography. Since a cured product having excellent low-temperature impact resistance and elongation properties can be obtained, the weight average molecular weight Mw of the bifunctional urethane (meth)acrylate oligomer is preferably 500 to 5000.

[0035] The radiation curable inkjet ink contains about 20 parts by mass or more and about 40 parts by mass or less of the bifunctional urethane (meth)acrylate oligomer based on 100 parts by mass of the polymerizable component. The radiation curable inkjet ink desirably contains about 22 parts by mass or more, or about 24 parts by mass or more, and about 35 parts by mass or less, or about 30 parts by mass or less of the bifunctional urethane (meth)acrylate oligomer based on 100 parts by mass of the polymerizable component. By making the content of the bifunctional urethane (meth)acrylate oligomer about 20 parts by mass or more based on 100 parts by mass of the polymerizable component, the flexibility and low-temperature impact resistance of the cured product of the radiation curable inkjet ink can be further improved, and the surface curing property in air can be further improved. By making the content of the bifunctional urethane (meth)acrylate oligomer about 40 parts by mass or less based on 100 parts by mass of the polymerizable component, good inkjet ejection properties can be obtained. In the present disclosure, the term "polymerizable component" encompasses difunctional urethane (meth)acrylate oligomers, monofunctional monomers, and other polymerizable monomers and oligomers.

[0036] The monofunctional monomer forms a cured product together with a bifunctional urethane (meth)acrylate oligomer as a polymerizable component, and also functions as a viscosity adjusting component of the radiation curable inkjet ink. Examples of the monofunctional monomer include linear alkyl (meth)acrylates, branched alkyl (meth)acrylates, alicyclic (meth)acrylates, (meth)acrylates having a dioxane moiety or a dioxolane moiety, phenoxyalkyl (meth)acrylates, alkoxyalkyl (meth)acrylates, cyclic monoether-containing (meth)acrylates, hydroxyl group-containing (meth)acrylates, nitrogen-containing (meth)acryloyl compounds, and (meth)acrylic acid. The monofunctional monomer may be one type or a combination of two or more types.

[0037] Examples of linear alkyl (meth)acrylates include methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, n-hexyl (meth)acrylate, n-octyl (meth)acrylate, n-decyl (meth)acrylate, and n-dodecyl (meth)acrylate.

[0038] Examples of branched alkyl (meth)acrylates include isoamyl (meth)acrylate, 2-methylbutyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, and isononyl (meth)acrylate.

[0039] Alicyclic (meth)acrylates include, for example, cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, and 3,3,5-trimethylcyclohexyl (meth)acrylate.

[0040] Examples of (meth)acrylates having a dioxane moiety include (5-ethyl-1,3-dioxane-5-yl)methyl (meth)acrylate (also referred to as cyclic trimethylolpropane formal acrylate), (2-methyl-5-ethyl-1,3-dioxane-5-yl)methyl (meth)acrylate, (2,2-dimethyl-5-ethyl-1,3-dioxane-5-yl)methyl (meth)acrylate, (2-methyl-2,5-diethyl-1,3-dioxane-5-yl)methyl (meth)acrylate, (2,2,5-triethyl-1,3-dioxane-5-yl)methyl (meth)acrylate, (2,5-diethyl-1,3-dioxane-5-yl)methyl (meth)acrylate, and polyethylene glycol (meth)acrylate having a 1,3-dioxane ring. Examples of (meth)acrylates having a dioxolane moiety include (2-methyl-2-ethyl-1,3-dioxolan-4-yl)methyl (meth)acrylate, (2-cyclohexyl-1,3-dioxolan-4-yl)methyl (meth)acrylate, (2,2-dimethyl-1,3-dioxolan-4-yl)methyl (meth)acrylate, (2-methyl-2-isobutyl-1,3-dioxolan-4-yl )methyl (meth)acrylate, (2-methyl-2-acetonyl-1,3-dioxolan-4-yl)methyl (meth)acrylate, (2-oxo-1,3-dioxolan-4-yl)methyl (meth)acrylate, 2-(2-oxo-1,3-dioxolan-4-yl)ethyl (meth)acrylate, and 3-(2-oxo-1,3-dioxolan-4-yl)propyl (meth)acrylate.

[0041] An example of the phenoxyalkyl (meth)acrylate is phenoxyethyl (meth)acrylate.

[0042] Alkoxyalkyl (meth)acrylates include, for example, methoxypropyl (meth)acrylate, 2-methoxybutyl (meth)acrylate, and 2-(2-ethoxyethoxy)ethyl (meth)acrylate.

[0043] Cyclic monoether-containing (meth)acrylates include, for example, glycidyl (meth)acrylate and tetrahydrofurfuryl (meth)acrylate.

[0044] Examples of hydroxyl group-containing (meth)acrylates include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate.

[0045] Nitrogen-containing (meth)acryloyl compounds include, for example, (meth)acrylamide and N,N-diethyl(meth)acrylamide.

[0046] Other monofunctional monomers include, for example, vinyl compounds such as vinyl acetate, vinyl propionate, styrene, and vinyl toluene; unsaturated nitriles such as acrylonitrile and methacrylonitrile; and unsaturated carboxylic acids such as crotonic acid, itaconic acid, fumaric acid, citraconic acid, and maleic acid.

[0047] Since the weather resistance and low-temperature impact resistance of the cured product can be improved, the monofunctional monomer is preferably at least one selected from the group consisting of linear or branched alkyl (meth)acrylates, alicyclic (meth)acrylates, and (meth)acrylates having a dioxane moiety or a dioxolane moiety.

[0048] The monofunctional monomer is preferably an acrylate monomer, since this provides excellent surface curing properties in air for the radiation-curable ink-jet ink.

[0049] The radiation curable inkjet ink contains a monofunctional monomer in an amount of about 50 parts by mass or more and about 80 parts by mass or less, based on 100 parts by mass of the polymerizable component. The radiation curable inkjet ink desirably contains a monofunctional monomer in an amount of about 55 parts by mass or more, or about 60 parts by mass or more and about 78 parts by mass or less, or about 75 parts by mass or less, based on 100 parts by mass of the polymerizable component. By making the content of the monofunctional monomer about 50 parts by mass or more, based on 100 parts by mass of the polymerizable component, good inkjet ejection properties can be obtained. By making the content of the monofunctional monomer about 80 parts by mass or less, based on 100 parts by mass of the polymerizable component, the flexibility and low-temperature impact resistance of the cured product of the radiation curable inkjet ink can be further increased, and the surface curability in air can be further improved.

[0050] The radiation curable inkjet ink may further contain a polyfunctional (meth)acrylate monomer. The polyfunctional (meth)acrylate monomer functions as a crosslinking agent to improve the surface curing property of the radiation curable inkjet ink in air and to increase the strength and durability of the cured product. By crosslinking using the polyfunctional (meth)acrylate monomer, it may be possible to increase the adhesion of the cured product to a substrate.

[0051] Examples of polyfunctional (meth)acrylate monomers include bifunctional (meth)acrylates such as 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, ethylene glycol di(meth)acrylate, cyclohexanedimethanol di(meth)acrylate, diethylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, and polyethylene glycol di(meth)acrylate; trifunctional (meth)acrylates such as glycerol tri(meth)acrylate, trimethylolpropane tri(meth)acrylate, and pentaerythritol tri(meth)acrylate; and (meth)acrylates having four or more functional groups such as ditrimethylolpropane tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, and pentaerythritol tetra(meth)acrylate.

[0052] The polyfunctional (meth)acrylate monomer is preferably a polyfunctional acrylate monomer, since this provides excellent surface curing properties in air for the radiation-curable inkjet ink.

[0053] In embodiments in which the radiation curable inkjet ink comprises a multifunctional (meth)acrylate monomer, the radiation curable inkjet ink can comprise about 0.1 parts by weight or more, about 1 part by weight or more, or about 2 parts by weight or more, about 10 parts by weight or less, about 8 parts by weight or less, or about 5 parts by weight or less of the multifunctional (meth)acrylate monomer, based on 100 parts by weight of the polymerizable component.

[0054] The radiation-curable inkjet ink may further contain other polymerizable oligomers other than the bifunctional urethane (meth)acrylate oligomer. Examples of other polymerizable oligomers include polyester (meth)acrylate and epoxy (meth)acrylate. These polymerizable oligomers may be monofunctional or polyfunctional.

[0055] In embodiments in which the radiation curable inkjet ink includes the other polymerizable oligomer, the radiation curable inkjet ink can include about 0.1 parts by weight or more, about 1 part by weight or more, or about 2 parts by weight or more, about 10 parts by weight or less, about 8 parts by weight or less, or about 5 parts by weight or less of the other polymerizable oligomer, based on 100 parts by weight of the polymerizable component.

[0056] The radiation-curable inkjet ink contains a combination of an α-hydroxyketone oligomer and a benzophenone compound as a photoinitiator. The α-hydroxyketone oligomer is an intramolecular cleavage type photoinitiator, and the benzophenone compound is a hydrogen abstraction type photoinitiator. By combining these photoinitiators, the surface curing property in air can be improved, and thus the generation of odor derived from unreacted monofunctional monomers can be suppressed. The α-hydroxyketone oligomer has a relatively large molecular weight, and at least one of the residues after intramolecular cleavage remains in the cured product, so that the generation of odor derived from the photoinitiator and its decomposition products can be suppressed. The α-hydroxyketone oligomer and the benzophenone compound can be used alone or in combination of two or more kinds.

[0057] The α-hydroxyketone oligomer is a polymer such as a dimer or trimer of a monomer containing an α-hydroxyketone moiety. Examples of monomers containing an α-hydroxyketone moiety include derivatives in which an α-hydroxyketone compound such as 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-hydroxycyclohexyl phenyl ketone, and 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methylpropanone is substituted with a polymerizable group. Examples of polymerizable groups include vinyl groups, 1-methylvinyl groups, (meth)acryloyloxy groups, (meth)acryloyloxyethoxy groups, and glycidyloxy groups. Examples of such monomers include 2-hydroxy-2-methyl-1-[4-(1-methylvinyl)phenyl]propanone and 2-hydroxy-2-methyl-1-[4-(2-acryloyloxyethoxy)phenyl]propanone.

[0058] The number average molecular weight of the α-hydroxyketone oligomer is preferably about 350 or more and about 1000 or less. When the number average molecular weight of the α-hydroxyketone oligomer is about 350 or more, a cured product with low odor can be formed. When the number average molecular weight of the α-hydroxyketone oligomer is about 1000 or less, compatibility with the polymerizable component of the radiation-curable inkjet ink can be improved.

[0059] The α-hydroxyketone oligomer preferably has a 2-hydroxy-2-methyl-1-oxopropyl group. The α-hydroxyketone oligomer having a 2-hydroxy-2-methyl-1-oxopropyl group undergoes intramolecular cleavage upon exposure to ultraviolet light to generate acetone, which has a relatively low boiling point and therefore evaporates quickly. The other residue remains in the cured product because it is a constituent part of the oligomer. This effectively suppresses the odor of the cured product.

[0060] Examples of α-hydroxyketone oligomers include oligo(2-hydroxy-2-methyl-1-[4-(1-methylvinyl)phenyl]propanone) (Esacure™ ONE, IGM Resins BV, Waalwijk, The Netherlands).

[0061] The radiation curable inkjet ink desirably contains about 1 part or more, or about 2 parts or more, and about 15 parts or less, or about 10 parts or less, by weight of the α-hydroxyketone oligomer, based on 100 parts by weight of the polymerizable component.

[0062] The benzophenone compound may be a compound having a substituted or unsubstituted benzophenone structure in the molecule, and may be an oligomer or a polymer.

[0063] The molecular weight of the benzophenone compound is preferably about 182 g / mol or more and about 1000 g / mol or less. By having the molecular weight of the benzophenone compound in the above range, the mobility of the excited benzophenone compound or benzophenone radical in the radiation curable inkjet ink can be increased, and the surface curability in air can be further improved.

[0064] Examples of benzophenone compounds include benzophenone, 4-methylbenzophenone, 2,4,6-trimethylbenzophenone, 4-methoxybenzophenone, benzoylbenzoic acid, methyl-o-benzoylbenzoate, 4-benzoyl-4'-methyldiphenyl sulfide, 4,4'-dihydroxybenzophenone, 4,4'-dichlorobenzophenone, diesters of carboxymethoxybenzophenone and polytetramethylene glycol (e.g., Omnipol BP, IGM Resins BV, Waalwijk, The Netherlands), and polymers of benzophenone derivatives (e.g., Omnipol 2702, IGM Resins BV, Waalwijk, The Netherlands).

[0065] The radiation curable inkjet ink desirably contains about 1 part by weight or more, or about 2 parts by weight or more, and about 15 parts by weight or less, or about 10 parts by weight or less of the benzophenone compound, based on 100 parts by weight of the polymerizable component.

[0066] The radiation curable inkjet ink may contain optional components such as light stabilizers, polymerization inhibitors, UV absorbers, defoamers, antifouling agents, surface conditioners, and fillers.

[0067] The radiation curable inkjet ink is advantageous in terms of environmental load, workability and curability because it is a solvent-free ink. As the radiation curable inkjet ink, a water-based ink or a solvent-based ink can be used.

[0068] The radiation curable inkjet ink may be transparent, translucent or opaque, and may be colorless or colored. In one embodiment, the radiation curable inkjet ink is transparent, and when a cured product having a thickness of 50 μm is formed, the cured product has a total light transmittance of about 70% or more, about 80% or more, or about 90% or more in the wavelength range of 400 to 700 nm.

[0069] The viscosity of the radiation curable inkjet ink can be about 5 mPa·s or more, or about 15 mPa·s or more, and about 60 mPa·s or less, or about 50 mPa·s or less at 25° C. By setting the viscosity of the radiation curable inkjet ink at 25° C. within the above range, the shape of the ink droplets can be maintained when they land, and a printed layer having a three-dimensional shape can be efficiently formed.

[0070] The viscosity of the radiation curable inkjet ink can be about 1 mPa·s or more, or about 3 mPa·s or more, and about 15 mPa·s or less, or about 10 mPa·s or less at 55° C. By setting the viscosity of the radiation curable inkjet ink at 55° C. to within the above range, it is possible to ensure ink fluidity when ink droplets are ejected, and to improve the printability of the radiation curable inkjet ink.

[0071] The printed layer of the decorative sheet can be formed using a radiation-curable inkjet ink. In one embodiment, the decorative sheet has a printed layer including a cured product of the radiation-curable inkjet ink.

[0072] A method for producing a decorative sheet in one embodiment includes preparing a substrate, inkjet printing a radiation-curable inkjet ink onto the substrate to form a printed layer on the substrate, and irradiating the printed layer with radiation to cure the printed layer.

[0073] The substrate may be a sheet or film made of various materials such as synthetic resin, paper, metal, or cloth.

[0074] As the radiation, ultraviolet light is generally used because it is easy to combine a radiation source with an inkjet printing device. As the ultraviolet light source, a high pressure mercury lamp, a metal halide lamp, a fusion lamp (Hbulb), etc. can be used. The illuminance of the ultraviolet light source is, for example, about 10 mW / cm. 2 Above, about 50mW / cm 2 or more than 100mW / cm 2 Approximately 10,000mW / cm 2 Below, approximately 5,000mW / cm 2 or less than 3,000mW / cm 2 The irradiation dose can be, for example, about 1 mJ / cm 2 More than about 10mJ / cm 2 or more, or about 50 mJ / cm 2 Approximately 100,000mJ / cm 2 Below, approximately 50,000mJ / cm 2 or less than 30,000 mJ / cm 2 The radiation-curable inkjet ink can be cured by irradiation with ultraviolet light in air, but the irradiation with ultraviolet light may be carried out in an inert gas atmosphere.

[0075] In one embodiment, the decorative sheet includes a base film layer as a substrate, a printing layer disposed on the base film layer, and a protective layer having a texture disposed on the printing layer. The protective layer is formed using a radiation-curable inkjet ink. In the present disclosure, "disposed on" includes not only a case where it is directly disposed on top, but also a case where it is indirectly disposed on top. For example, one or more other layers may be included between the printing layer and the protective layer. The layer disposed on top may be partially disposed.

[0076] A decorative sheet according to one embodiment is shown in a schematic cross-sectional view in Fig. 1. The decorative sheet 10 includes a base film layer 12, a printing layer 14 disposed on the base film layer 12, and a protective layer 16 disposed on the printing layer 14. The protective layer 16 includes a cured product of a radiation-curable inkjet ink that has been inkjet-printed, and the three-dimensional shape of the protective layer 16 imparts a texture to the decorative sheet. Although the printing layer 14 is shown completely covered by the protective layer 16 in Fig. 1, a part of the printing layer 14 may be exposed to the outside. The printing layer 14 and the protective layer 16 may each be continuous or discontinuous.

[0077] As the base film layer, films containing various resins, for example, acrylic resins including polymethyl methacrylate (PMMA), polyurethane (PU), polyvinyl chloride (PVC), polycarbonate (PC), polyolefins such as polyethylene (PE) and polypropylene (PP), polyesters such as polyethylene terephthalate (PET) and polyethylene naphthalate, fluororesins, copolymers such as ethylene-vinyl acetate copolymer (EVA), ethylene-acrylic acid copolymer, ethylene-ethyl acrylate copolymer, ethylene-vinyl acetate copolymer, acrylonitrile-butadiene rubber (NBR), and acrylonitrile-butadiene-styrene copolymer (ABS), or mixtures thereof, can be used.

[0078] From the viewpoints of strength, impact resistance, etc., a film containing polyurethane, polyvinyl chloride, polyethylene terephthalate, acrylonitrile-butadiene-styrene copolymer, or polycarbonate can be advantageously used as the base film layer. The base film layer can also function as a receptor layer for printing ink and / or as a protective layer that protects the surface of the adherend from external punctures, impacts, etc. When the base film layer functions as a receptor layer for printing ink, it is advantageous in terms of printability, solvent resistance (e.g., alcohol resistance), etc. for the base film layer to be a polyvinyl chloride film or a polyurethane film. From the viewpoints of flame retardancy, flexibility, etc., a polyvinyl chloride film can be advantageously used as the base film layer.

[0079] The thickness of the base film layer may vary, but from the viewpoint of the strength and handling of the decorative sheet, it can generally be about 10 μm or more, about 20 μm or more, or about 50 μm or more, about 500 μm or less, about 200 μm or less, or about 100 μm or less. When the base film layer is not flat, the thickness of the base film layer means the thickness of the thinnest part of the base film layer. For example, the base film layer may be embossed. The depth of the embossing can be about 1 μm or more, about 2 μm or more, or about 5 μm or more, about 50 μm or less, about 20 μm or less, or about 10 μm or less, generally within the range less than the thickness of the base film layer.

[0080] The base film layer may be transparent, translucent or opaque, and may be colorless or colored. In one embodiment, the base film layer is colored white. This embodiment is advantageous in terms of clarity, color development, etc. of the image produced by the printing layer disposed directly or indirectly on the base film layer.

[0081] The printing layer is used to impart decorativeness or design to the decorative sheet with a picture, pattern, etc. The printing layer can be formed by printing on the base film layer directly or via another layer using a colorant such as toner or ink. When the base film layer is transparent or translucent, the printing layer can also be formed between the base film layer and the adhesive layer. The printing layer can be formed by using a printing technique such as gravure printing, electrostatic printing, screen printing, inkjet printing, and offset printing. As the printing ink, a solvent-based ink or a UV-curable ink can be used.

[0082] In one embodiment, the printed layer is an inkjet printed layer. In another embodiment, the printed layer is formed by inkjet printing with UV-curable inks. Inkjet printing, particularly inkjet printing with UV-curable inks, allows for short-run, on-demand manufacturing.

[0083] The thickness of the printed layer may vary, and generally, when a solvent-based ink is used, the thickness may be about 1 μm or more, or about 2 μm or more, and about 10 μm or less, or about 5 μm or less, and when a UV-curable ink is used, the thickness may be about 1 μm or more, or about 5 μm or more, and about 50 μm or less, or about 30 μm or less.

[0084] The printed layer may be continuous or discontinuous. The printed layer may be disposed so as to cover the entire surface of the decorative sheet, or may be disposed so as to cover a portion or a plurality of portions thereof.

[0085] The protective layer containing the cured product of the radiation-curable ink-jet ink is disposed on the printing layer, and has a texture formed by ink-jet printing the radiation-curable ink-jet ink. The texture of the protective layer is generally sensed visually or tactilely by an observer due to the protective layer having a three-dimensional shape.

[0086] A protective layer having a texture can be formed by inkjet printing a radiation-curable inkjet ink directly or via another layer onto a base film layer, and curing the ink by irradiating it with radiation such as ultraviolet light or an electron beam. The radiation-curable inkjet ink may be printed onto at least a portion of the printed layer, or may be printed onto the entire printed layer. The radiation-curable inkjet ink may be printed locally or over the entire surface multiple times to increase the thickness of the protective layer.

[0087] The thickness of the protective layer may vary, but in some embodiments, it is at least partially about 7 μm or more, about 20 μm or more, or about 30 μm or more. By providing the protective layer with a portion having a thickness of about 7 μm or more, it is possible to impart a texture with a real texture or a three-dimensional unevenness matching the design of the decorative sheet to the surface of the decorative sheet.

[0088] In some embodiments, the maximum thickness of the protective layer is about 500 μm or less, about 300 μm or less, or about 100 μm or less. By making the maximum thickness of the protective layer about 500 μm or less, the flexibility of the protective layer, for example, the elongation property, can be made suitable.

[0089] In some embodiments, the maximum height roughness Rz of the protective layer is about 0.5 μm or more, about 1 μm or more, or about 1.5 μm or more, and about 20 μm or less, about 15 μm or less, or about 10 μm or less. By setting the maximum height roughness Rz of the protective layer in the above range, it is possible to impart a texture with a real texture or three-dimensional unevenness matching the design of the decorative sheet to the surface of the decorative sheet.

[0090] The protective layer may be transparent or translucent. It is desirable that the protective layer is transparent. In some embodiments, the total light transmittance of the protective layer is about 90% or more, about 92% or more, or about 95% or more, and the haze is about 2% or less, about 1.5% or less, or about 1.0% or less. When the total light transmittance and haze are in the above ranges, the image provided by the printing layer of the decorative sheet can be made clearer. The haze is determined in accordance with JIS K 7136:2000 (ISO 14782:1999).

[0091] The decorative sheet may further include an adhesive layer disposed on the base film layer opposite the printed layer. Figure 1 shows an adhesive layer 18 disposed on the base film layer 12 opposite the printed layer 14. The adhesive layer can generally be formed using a solvent-based, emulsion-based, pressure-sensitive, heat-sensitive, heat-curing, or UV-curing adhesive, such as an acrylic-based, polyolefin-based, polyurethane-based, polyester-based, or rubber-based adhesive.

[0092] The thickness of the adhesive layer can generally be about 3 μm or more, about 5 μm or more, or about 10 μm or more, and about 100 μm or less, about 80 μm or less, or about 50 μm or less.

[0093] In one embodiment, the adhesive layer is a pressure-sensitive adhesive layer. In order to adjust the adhesive strength of the pressure-sensitive adhesive layer, the pressure-sensitive adhesive layer may contain elastic microspheres including polyester, polystyrene, acrylic resin, polyurethane, etc.

[0094] A liner may be disposed on the surface of the adhesive layer. Examples of the liner include paper such as kraft paper, polymers such as polyethylene, polypropylene, polyester, and cellulose acetate, and paper coated with these polymers. These liners may have a release-treated surface with silicone, fluorocarbon, and the like. The thickness of the liner can generally be about 5 μm or more, about 15 μm or more, or about 25 μm or more, and about 300 μm or less, about 200 μm or less, or about 150 μm or less.

[0095] The adhesive layer may have a microstructured surface with interconnecting channels extending to the outer edge of the adhesive layer. When the decorative sheet is applied to the adherend, air bubbles trapped between the decorative sheet and the adherend can be discharged to the outside through the interconnecting channels of the microstructured surface. In this embodiment, the liner may have a relief structure on its release surface that corresponds to the microstructured surface of the adhesive layer. The liner may be the same as or different from the one used to form the microstructured surface of the adhesive layer.

[0096] Other layers, such as a decorative layer such as a metal layer, a receptor layer for printing ink, etc., may be laminated on the base film layer. These layers may be bonded together by a bonding layer. The decorative layer may be disposed so as to correspond to the entire surface of the decorative sheet, or to correspond to a part or a plurality of parts.

[0097] The metal layer can be formed by depositing a metal such as indium, tin, or chromium on the base film layer or other layers of the decorative sheet by vapor deposition, sputtering, or the like. A metal mask or the like can be used during vapor deposition or sputtering to form a pattern or design. The thickness of the metal layer can vary, and can generally be about 5 nm or more, about 10 nm or more, or about 20 nm or more, and about 10 μm or less, about 5 μm or less, or about 2 μm or less.

[0098] Various resin films can be used as the receptor layer for the printing ink. The resin constituting the receptor layer is not particularly limited, but may be an acrylic polymer, a polyolefin, a polyvinyl acetal, a phenoxy resin, or the like. The glass transition temperature of the resin forming the receptor layer can generally be about 0°C or higher and about 100°C or lower. By setting the glass transition temperature within the above range, a clear image can be obtained by transferring the toner or printing the ink without impairing the flexibility of the entire decorative sheet. The thickness of the receptor layer can generally be about 2 μm or higher, about 5 μm or higher, or about 10 μm or higher, and about 50 μm or lower, about 40 μm or lower, or about 30 μm or lower.

[0099] The bonding layer that bonds the layers that make up the decorative sheet generally contains a solvent-based, emulsion-based, pressure-sensitive, heat-sensitive, heat-curable, or UV-curable adhesive, such as an acrylic-based, polyolefin-based, polyurethane-based, polyester-based, rubber-based, etc. The thickness of the bonding layer can generally be about 1 μm or more, about 2 μm or more, or about 5 μm or more, and about 50 μm or less, about 40 μm or less, or about 30 μm or less.

[0100] In one embodiment, the printing layer has a two-dimensional design pattern, the protective layer has a three-dimensional shape pattern, and the two-dimensional design pattern and the three-dimensional shape pattern are in harmony. By having the two-dimensional design pattern of the printing layer and the three-dimensional shape pattern of the protective layer in harmony, the texture can be further emphasized from both visual and tactile aspects.

[0101] A decorative sheet in which the two-dimensional design pattern of the printing layer and the three-dimensional shape pattern of the protective layer are in harmony can be manufactured by a method including, for example, the steps of providing image data for the printing layer, converting the image data for the printing layer to grayscale to generate grayscale image data, inverting the tone of the grayscale image data to generate image data for the protective layer, adjusting the tone curve of the image data for the protective layer as necessary, forming a printing layer having a two-dimensional design pattern on a base film layer by inkjet printing using UV-curable CMYK inks based on the image data for the printing layer, and forming a protective layer on the printing layer by inkjet printing using radiation-curable inkjet inks based on the image data for the protective layer.

[0102] The step of forming the printed layer and the step of forming the protective layer may be performed consecutively. The step of forming the printed layer and the step of forming the protective layer may be performed in one device equipped with multiple inkjet print heads. In order to form a protective layer having a large difference in height of the unevenness of the surface by repeating the step of forming the protective layer multiple times, the inkjet printing device may be equipped with a conveying device capable of moving the printed material (e.g., the film of the base film layer) back and forth, and may be equipped with multiple inkjet print heads for the protective layer.

[0103] The two-dimensional design pattern of the printing layer and the three-dimensional shape pattern of the protective layer can be more accurately synchronized by arranging the inkjet printing head for the printing layer and the inkjet printing head for the protective layer in series in an inkjet printing device and printing the printing layer and the protective layer successively based on the image data of the printing layer and the image data of the protective layer, respectively, obtained by the above-mentioned method.

[0104] The two-dimensional design pattern of the printing layer and the three-dimensional shape pattern of the protective layer may be repeated or non-repeated in one decorative sheet. By using inkjet printing, not only repeating patterns but also non-repeated patterns can be easily formed. In embossing using an embossing roll, it is not possible to form a non-repeated three-dimensional shape pattern longer than the circumference of the embossing roll. By using a non-repeated pattern, the design freedom is increased, and a decorative sheet having a unique design can be produced.

[0105] In one embodiment, the decorative sheet has an elongation at break of about 50% or more, about 60% or more, or about 70% or more at 20° C. The elongation at break can be determined by cutting the decorative sheet to a length of 102 mm and a width of 25.4 mm, and conducting a tensile test using a tensile tester with a clamp gap of 50 mm and a tensile speed of 300 mm / min at 20° C., using the formula (length at break of decorative sheet−length of decorative sheet before elongation) / (length of decorative sheet before elongation)×100(%).

[0106] The total thickness of the decorative sheet can generally be about 50 μm or more, about 60 μm or more, or about 70 μm or more, and about 700 μm or less, about 600 μm or less, or about 500 μm or less. The total thickness of the decorative sheet does not include the thickness of the liner.

[0107] In one embodiment, the impact resistance of the decorative sheet at 5°C (low-temperature impact resistance) is 40 in lbs (about 4.52 Nm) or more. In this embodiment, the components and composition of the radiation-curable ink-jet ink used to form the protective layer are determined so that the decorative sheet has such impact resistance. The thickness of the protective layer, the material and thickness of the base film layer, and the like may also affect the impact resistance of the decorative sheet, and the components and composition of the radiation-curable ink-jet ink may be determined taking these factors into consideration.

[0108] The impact resistance of the decorative sheet at 5°C is preferably about 50 in·lbs (about 5.65 Nm) or more, more preferably about 60 in·lbs (about 6.78 Nm) or more. In some embodiments, the impact resistance of the decorative sheet at 5°C is about 200 in·lbs (about 22.6 Nm) or less, about 150 in·lbs (about 17.0 Nm) or less, or about 100 in·lbs (about 11.3 Nm) or less. The impact resistance is determined by cutting the decorative sheet to a length of 150 mm and a width of 70 mm, attaching it to an aluminum plate of length 150 mm, width 70 mm, and thickness 1 mm at 25°C, leaving the decorative sheet at 5°C for 24 hours, setting it in an impact resistance tester, dropping a 2-pound weight onto the surface of the decorative sheet at a temperature of 5°C while changing the height from 5 inches to 40 inches, and observing the appearance of the decorative sheet to determine the moment (in·lbs) at which cracks occur.

[0109] The decorative sheet can be provided in a variety of forms, including individual sheets, rolls, stacks of multiple decorative sheets, etc. In one embodiment, the decorative sheet is in the form of a roll.

[0110] The decorative sheet can be adhered to the surface of various adherends, and can be applied to, for example, concrete, glass, painted boards, flooring materials, wallpaper, plaster boards, etc. The adherend may be a part of a building structure, for example, a wall, a window, a floor, a ceiling, a pillar, etc. EXAMPLES

[0111] The following examples illustrate specific embodiments of the disclosure, but the invention is not limited thereto. All parts and percentages are by weight unless otherwise specified.

[0112] The materials and reagents used in this example are shown in Table 1. [Table 1]

[0113] Preparation of radiation curable inkjet inks The radiation curable inkjet inks of Examples 1 to 9 and Comparative Examples 1 to 9 were prepared according to the following procedure. The monofunctional and polyfunctional monomers, bifunctional urethane (meth)acrylate oligomers, and polymerization inhibitors shown in Table 2 were stirred in a mixer for 20 minutes to obtain a premix solution. Then, a photoinitiator was added to the premix solution, and the solution was stirred for 30 minutes to obtain a radiation curable inkjet ink. The values ​​in Table 2 indicate the blending amount (parts by mass) of each component.

[0114] The viscosity of the radiation-curable inkjet ink was measured using a rheometer (Discovery HR-2, TA Instruments Japan, Shinagawa-ku, Tokyo, Japan) at a temperature of 55 °C and a shear rate of 5000 s -1 The viscosity of the radiation-curable inkjet inks of Examples 1 to 9 was 15 mPa·s or less at 55° C., and they were suitable for inkjet printing.

[0115] Preparation of film sample - Coating 1 The radiation-curable inkjet inks of Examples 1 to 8 and Comparative Examples 1 to 9 were coated onto HK-31WF PET film (Higashiyama Film Co., Ltd., Nagoya, Aichi Prefecture, Japan) using a #20 wire bar. The fusion lamp (H bulb) (UVA: 1000 mW / cm 2 , irradiation amount 600mJ / cm 2 The coating was cured by irradiating it with ultraviolet light at 350 nm to obtain a film sample. The thickness of the cured ink layer was about 30 μm. The film sample was used for odor testing and TVOC (total volatile organic compounds) analysis.

[0116] Preparation of film sample - Coating 2 As a protective layer, the radiation-curable inkjet inks of Examples 1 to 8 and Comparative Examples 1 to 9 were coated on 3M (registered trademark) Scotchcal (registered trademark) Graphic Film IJ180Cv3-10XR (polyvinyl chloride film, 3M Japan Co., Ltd., Shinagawa-ku, Tokyo, Japan) using a #20 wire bar. Fusion lamp (H bulb) (UVA: 1000 mW / cm 2, irradiation amount 600mJ / cm 2 The protective layer was cured by irradiating it with ultraviolet light at 1000 K (1000 psi) to obtain a film sample. The thickness of the cured protective layer was about 30 μm. The film sample was used for abrasion resistance test, elongation test, low-temperature impact resistance test, and color difference measurement.

[0117] Preparation of film samples - inkjet printing As a protective layer, the radiation-curable inkjet ink of Example 9 was printed on 3M (registered trademark) Scotchcal (registered trademark) Graphic Film IJ180Cv3-10 (polyvinyl chloride film, 3M Japan Co., Ltd., Shinagawa-ku, Tokyo, Japan) using a UV inkjet printer (print head: KM1024iLMHB, 720 x 720 dpi, Konica Minolta Inc., Chiyoda-ku, Tokyo, Japan). 2 , irradiation amount 731mJ / cm 2 The protective layer was cured by irradiating it with ultraviolet light at 1000 K (1000 psi) to obtain a film sample. The thickness of the cured protective layer was about 45 μm. The film sample was used for odor tests, scratch resistance tests, elongation tests, low-temperature impact resistance tests, and color difference measurements.

[0118] The odor, TVOC analysis, scratch resistance, elongation properties, low-temperature impact resistance, and color difference of the film samples were evaluated according to the following procedures. The evaluation results are shown in Table 2.

[0119] <Evaluation method> 1. Odor test The prepared film samples were left to stand for 24 hours at 25° C. After that, the odor level was evaluated according to the following criteria. AA: No odor or very weak odor A: Weak odor B: Strong odor C: The odor is very strong

[0120] 2. TVOC (Total Volatile Organic Compounds) Analysis The film samples were cut into small pieces of 5 mm x 5 mm and measured using TD-GC / MS at 25°C for 10 minutes.

[0121] 3. Scratch resistance test The film sample was cut into 1 inch (25.4 mm) x 6 inch (152 mm), attached to a 1 inch (25.4 mm) x 8 inch (203 mm) HK-31WF PET film, and set in a Gakushin-type friction fastness tester (AB-301, Tester Sangyo Co., Ltd., Miyoshi-machi, Iruma-gun, Saitama, Japan). Cotton (Kanakin No. 3) was clipped onto the surface of the friction element of the tester. The film sample was rubbed back and forth for 100 strokes with a friction element with a load of 500 g. The appearance of the protective layer after rubbing was observed with the naked eye. Those without scratches were rated as "good" and those with scratches were rated as "poor."

[0122] 4. Elongation test (elongation at break) Film samples were cut into 1 inch (25.4 mm) x 4 inches (102 mm) and the elongation at the time of film break was measured using a tensile testing machine (Tensilon Universal Testing Machine, Model: RTC-1210A, A&D Co., Ltd., Toshima-ku, Tokyo, Japan) with a clamp gap of 50 mm, a tensile speed of 300 mm / min, and 20°C. The elongation at break was determined from the formula: (length of film sample at break - length of film sample before elongation) / (length of film sample before elongation) x 100(%).

[0123] 5. Low temperature impact resistance test The film sample was cut to a length of 150 mm and a width of 70 mm, and attached to an aluminum plate of length 150 mm, width 70 mm, and thickness 1 mm at 25°C. After leaving the film sample at 5°C for 24 hours, it was set in an impact resistance tester (IM-IG-1120, The Paul N. Gardner Company, Inc., Pompano Beach, Florida, USA) and a 2-pound weight was dropped onto the film surface at a temperature of 5°C while changing the height from 5 inches to 40 inches. The appearance of the film sample was observed and the moment (in·lbs) at which cracking occurred was recorded.

[0124] 6.Color difference measurement Film sample L * , a * , b* The value of L1 was measured using a spectrophotometer (CM-3700d, Konica Minolta Japan, Inc., Minato-ku, Tokyo, Japan). The value of the area where the radiation curable inkjet ink was not printed was L1. * , a1 * , b1 * Let the value of the printed area be L2 * , a2 * , b2 * When * was calculated using the following formula: Color difference ΔE * =[(L2 * -L1 * ) 2 +(a2 * -a1 * ) 2 +(b2 * -b1 * ) 2 ] 1 / 2

[0125] [Table 2-1]

[0126] [Table 2-2]

[0127] [Table 2-3] [Explanation of symbols]

[0128] 10 Decorative Sheet 12 Base film layer 14 Printing layer 16 Protective layer 18 Adhesive layer

Claims

1. Based on 100 parts by mass of the polymerizable component, 20 to 40 parts by mass of a bifunctional urethane (meth)acrylate oligomer and 50 to 80 parts by mass of a monofunctional monomer; With α-hydroxyketone oligomer and benzophenone compound as photoinitiator 1. A radiation curable inkjet ink comprising: the benzophenone compound is selected from benzophenone, 4-methylbenzophenone, 2,4,6-trimethylbenzophenone, 4-methoxybenzophenone, benzoylbenzoic acid, methyl-o-benzoylbenzoate, 4-benzoyl-4'-methyldiphenylsulfide, 4,4'-dihydroxybenzophenone, 4,4'-dichlorobenzophenone, diesters of carboxymethoxybenzophenone and polytetramethylene glycol, and polymers of benzophenone derivatives; the bifunctional urethane (meth)acrylate oligomer comprises a polyester urethane di(meth)acrylate oligomer, The radiation curable inkjet ink has a viscosity of 15 mPa·s or less at 55° C.

2. 2. The radiation-curable ink-jet ink according to claim 1, wherein the monofunctional monomer is at least one selected from the group consisting of linear or branched alkyl (meth)acrylates, alicyclic (meth)acrylates, and (meth)acrylates having a dioxane moiety or a dioxolane moiety.

3. 3. The radiation-curable ink-jet ink according to claim 1, wherein the α-hydroxyketone oligomer has a number average molecular weight of 350 to 1,000.

4. The radiation-curable ink-jet ink according to any one of claims 1 to 3, wherein the α-hydroxyketone oligomer has a 2-hydroxy-2-methyl-1-oxopropyl group.

5. 5. The radiation curable ink-jet ink according to claim 1, wherein the molecular weight of the benzophenone compound is from 182 g / mol to 1000 g / mol.

6. The radiation-curable inkjet ink according to any one of claims 1 to 5, wherein the bifunctional urethane (meth)acrylate oligomer has a weight average molecular weight of 500 to 5,000.

7. The radiation-curable ink-jet ink according to any one of claims 1 to 6, further comprising a polyfunctional (meth)acrylate monomer.

8. A decorative sheet having a printed layer comprising a cured product of the radiation-curable ink-jet ink according to any one of claims 1 to 7.

9. Providing a substrate; forming a printing layer on the substrate by inkjet printing the radiation curable inkjet ink according to any one of claims 1 to 7; irradiating the printed layer with radiation to cure the printed layer; A method for producing a decorative sheet comprising the steps of:

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