Method for producing matte coating film

Abstract

To provide a method for producing a coating film having sufficient matte effect, scratch resistance and contamination resistance.SOLUTION: A method for producing a matte coating film includes a step (I) of coating an active energy ray-curable composition onto a base material and forming a coating film, a step (II) of irradiating the coating film with ultraviolet light while controlling peak illuminance to 30 to 80 mW / cm2 in the atmosphere, and a step (III) of irradiating the coating film with an electron beam or ultraviolet light in the inert gas atmosphere, wherein the active energy ray-curable composition contains a compound having a (meth)acryloyl group, a photopolymerization initiator, and a matte agent, and the average number of (meth)acryloyl groups of the compound having the (meth)acryloyl groups is more than 2 and less than 2.5.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for producing a matte coating film using an active energy ray-curable composition. [Background technology]

[0002] Decorative panels and sheets are used in the interior decoration of furniture and buildings for the purpose of surface protection and beautification. As a surface protective layer for these products, solvent-free coating agents that can be applied and cured with active energy rays such as electron beams and ultraviolet rays (active energy ray curable coating agents) are used to reduce VOCs, etc. In recent years, there has been a high demand for low-gloss (also called matte or matte finish) products to prevent reflections from lighting fixtures and to reproduce the appearance of wood surfaces. It is known that active energy ray-curable coating agents are also applied with the aim of imparting a matte aesthetic appearance by adding a matting agent (see, for example, Patent Document 1). Furthermore, a method is also known in which, when curing a coating agent with a matting agent added, the oxygen concentration is varied in multiple stages in an oxygen-containing inert gas atmosphere, and the electron beam-curable clear coat is irradiated with electron beams to cure the coating, thereby obtaining a sufficient matte effect and a highly weather-resistant matte decorative panel with significantly superior weather resistance (see, for example, Patent Document 2). However, there is still room for further study to achieve both a sufficient matte effect and the physical properties desired for decorative plates and sheets, such as scratch resistance and stain resistance. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-69332 [Patent Document 2] Japanese Patent Application Laid-Open No. 2001-87703 Summary of the Invention [Problem to be solved by the invention]

[0004] The problem to be solved by the present invention is to provide a production method for obtaining a coating film having sufficient matte effect, scratch resistance, and stain resistance by using a solvent-free active energy ray-curable composition. [Means for solving the problem]

[0005] The present inventors have found that the above-mentioned problems can be solved by a method for producing a matte coating film, which includes, in this order, a step (I) of forming a coating film using an active energy ray-curable composition having a specific formulation provided on a substrate, a step (II) of irradiating with ultraviolet rays in the atmosphere, and a step (III) of irradiating with active energy rays.

[0006] That is, the present invention provides a method for producing a coating film by applying an active energy ray-curable composition to a substrate (I), and applying a peak irradiance of 30 to 80 mW / cm to the coating film under atmospheric pressure. 2 and (III) irradiating the coating film with ultraviolet light while controlling the temperature of the coating film to be heated to 1000°C or higher, and irradiating the coating film with ultraviolet light either by electron beam irradiation or in an inert gas atmosphere, in this order. The active energy ray-curable composition contains a compound having a (meth)acryloyl group, a photopolymerization initiator, and a matting agent, and the compound having a (meth)acryloyl group has an average number of (meth)acryloyl groups of more than 2 and less than 2.5. [Effects of the Invention]

[0007] The production method of the present invention makes it possible to obtain a coating film having a sufficient matte effect, scratch resistance, and stain resistance. DETAILED DESCRIPTION OF THE INVENTION

[0008] (base material) The substrate used in the present invention is not particularly limited as long as it is a substrate for which a matte design is desired. For example, in the case of a decorative sheet for building materials, a general-purpose substrate sheet used for decorative sheets can be used as the substrate. There are no particular limitations on the base sheet, and a sheet (film) or paper made of a general-purpose thermoplastic resin such as a general decorative sheet can be used. Examples of sheets (films) formed from thermoplastic resins include polyolefin resins such as polyethylene, ethylene-α-olefin copolymer, polypropylene, polymethylpentene, polybutene, ethylene-propylene copolymer, propylene-butene copolymer, ethylene-vinyl acetate copolymer, saponified ethylene-vinyl acetate copolymer, ethylene-(meth)acrylic acid copolymer, and ethylene-(meth)acrylic acid ester copolymer, as well as polyvinyl chloride, polyethylene terephthalate (PET), polybutylene terephthalate, polyamide, polycarbonate, polyethylene naphthalate, ionomer, acrylic acid ester polymer, and methacrylic acid ester polymer. The substrate sheet may be formed using these resins alone or in combination of two or more.

[0009] The substrate sheet may be colored and, if necessary, may contain various additives such as fillers, matting agents, foaming agents, flame retardants, lubricants, antistatic agents, antioxidants, ultraviolet absorbers, light stabilizers, etc. The thickness of the substrate sheet can be appropriately set depending on the application and usage method of the final product, but is generally preferably 20 to 300 μm.

[0010] One or both sides of the substrate sheet may be subjected to a surface treatment such as corona discharge treatment, ozone treatment, plasma treatment, ionizing radiation treatment, or dichromate treatment, as needed. For example, when corona discharge treatment is performed, the surface tension of the substrate sheet surface may be set to 30 dyne or more, preferably 40 dyne or more. The surface treatment may be performed according to a conventional method for each treatment.

[0011] Examples of types of paper substrates for decorative sheets include tissue paper, plain paper, reinforced paper, resin-impregnated paper, titanium paper, and the like.

[0012] The substrate may also be a wood veneer or the like that is commonly used for decorative boards. Examples of wood substrates for wood veneers include known materials such as plywood, particle board, hardboard, and MDF that have traditionally been used as wooden substrates for decorative boards, furniture, building materials, etc. Furthermore, it does not matter what manufacturing method was used to obtain these known substrates. Further, examples of non-combustible materials that can be used as the substrate include perforated board building materials made from gypsum board, gypsum plate, calcium silicate plate, etc.; ceramic plates such as pottery, porcelain, stoneware, earthenware, glass, and enamel; and metal plates such as iron plate, galvanized steel plate, polyvinyl chloride sol-coated steel plate, aluminum plate, and copper plate.

[0013] (Coating film made of active energy ray-curable composition) The coating film made of the active energy ray-curable composition is a coating film made of a coating agent made of the active energy ray-curable composition. Hereinafter, the coating agent made of the active energy ray-curable composition used in the present invention will be referred to as "active energy ray-curable coating agent."

[0014] The active energy ray-curable coating agent used in the present invention contains a compound having a (meth)acryloyl group and a photopolymerization initiator. In the present invention, the term "(meth)acryloyl group" refers to either or both of an acryloyl group and a methacryloyl group. A "compound having a (meth)acryloyl group" may also be referred to as a (meth)acrylate. The term "(meth)acrylate" refers to either or both of an acrylate and a methacrylate.

[0015] (Compounds having a (meth)acryloyl group) The compound having a (meth)acryloyl group used in the present invention is not particularly limited, and any compound having a (meth)acryloyl group that can be cured with known active energy rays (hereinafter, sometimes simply referred to as "active energy ray-curable") can be used. Examples of monofunctional (meth)acrylates that are monofunctional monomers include ethyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, nonyl (meth)acrylate, lauryl (meth)acrylate, tridecyl (meth)acrylate, hexadecyl (meth)acrylate, octadecyl (meth)acrylate, isoamyl (meth)acrylate, isodecyl (meth)acrylate, isostearyl (meth)acrylate, cyclohexyl (meth)acrylate, benzyl (meth)acrylate, methoxyethyl (meth)acrylate, butoxyethyl (meth)acrylate, phenoxyethyl (meth)acrylate, and phenoxydiethylene glycol (meth)acrylate. tetrahydrofurfuryl (meth)acrylate, glycidyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, 3-chloro-2-hydroxypropyl (meth)acrylate, diethylaminoethyl (meth)acrylate, nonylphenoxyethyl tetrahydrofurfuryl (meth)acrylate, caprolactone-modified tetrahydrofurfuryl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, and ethoxyethoxyethanol acrylic acid polymer esters.

[0016] Examples of bifunctional (meth)acrylates that are bifunctional monomers include 1,4-butanediol di(meth)acrylate, 3-methyl-1,5-pentanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 2-methyl-1,8-octanediol di(meth)acrylate, 2-butyl-2-ethyl-1,3-propanediol di(meth)acrylate, tricyclodecane dimethanol di(meth)acrylate, ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, and triethylene glycol di(meth)acrylate. di(meth)acrylates of dihydric alcohols such as dipropylene glycol di(meth)acrylate and tripropylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, di(meth)acrylate of tris(2-hydroxyethyl)isocyanurate, di(meth)acrylates of diols obtained by adding 4 moles or more of ethylene oxide or propylene oxide to 1 mole of neopentyl glycol, and di(meth)acrylates of diols obtained by adding 2 moles of ethylene oxide or propylene oxide to 1 mole of bisphenol A.

[0017] Examples of the trifunctional or higher functional (meth)acrylate that is a trifunctional monomer include poly(meth)acrylates of trihydric or higher polyalcohols such as trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, and poly(meth)acrylate of dipentaerythritol; poly(meth)acrylates of polyoxyalkylene polyols such as triol tri(meth)acrylates obtained by adding 3 moles or more of ethylene oxide or propylene oxide to 1 mole of glycerin, di- or tri(meth)acrylates of triols obtained by adding 3 moles or more of ethylene oxide or propylene oxide to 1 mole of trimethylolpropane, and di(meth)acrylates of diols obtained by adding 4 moles or more of ethylene oxide or propylene oxide to 1 mole of bisphenol A.

[0018] Furthermore, a mixture of dipentaerythritol hexaacrylate and dipentaerythritol pentaacrylate (sometimes abbreviated as DPHA), which corresponds to a bifunctional or higher functional (meth)acrylate, ditrimethylolpropane tetraacrylate (sometimes abbreviated as DTMPTA), trimethylolpropane ethylene oxide adduct tri(meth)acrylate, which is a triol tri(meth)acrylate obtained by adding 3 moles or more of ethylene oxide to 1 mole of trimethylolpropane, etc. A representative example of the trimethylolpropane ethylene oxide adduct tri(meth)acrylate is trimethylolpropane ethylene oxide (hereinafter, ethylene oxide may be referred to as "EO")-modified (n≒3) triacrylate.

[0019] Furthermore, if necessary, a polymerizable oligomer may be used, such as amine-modified acrylates such as urethane (meth)acrylate, amine-modified polyether acrylate, amine-modified epoxy acrylate, amine-modified aliphatic acrylate, amine-modified polyester acrylate, and amino (meth)acrylate, polyester (meth)acrylate, polyether (meth)acrylate, polyolefin (meth)acrylate, polystyrene (meth)acrylate, and epoxy (meth)acrylate.

[0020] The compound having a (meth)acryloyl group is preferably a polyfunctional monomer, and more preferably 1,6-hexanediol di(meth)acrylate, EO-modified 1,6-hexanediol di(meth)acrylate, tripropylene glycol di(meth)acrylate, EO-modified trimethylolpropane tri(meth)acrylate, or DPHA. Furthermore, the polymerizable oligomer is preferably urethane (meth)acrylate, polyester (meth)acrylate, or epoxy (meth)acrylate. Furthermore, a combination of a bifunctional monomer and a trifunctional monomer is preferred, and specifically, a combination of EO-modified 1,6-hexanediol di(meth)acrylate, tripropylene glycol di(meth)acrylate, and EO-modified trimethylolpropane tri(meth)acrylate is preferred, with the ratios preferably being 51% by mass to 90% by mass of the bifunctional monomer and 10% by mass to 49% by mass of the trifunctional monomer, and more preferably 70% by mass to 90% by mass of the bifunctional monomer and 10% by mass to 30% by mass of the trifunctional monomer. A combination of EO-modified 1,6-hexanediol di(meth)acrylate, tripropylene glycol di(meth)acrylate and DPHA is also preferred, with the ratio preferably being 90% to 95% by mass of the bifunctional monomer and 5% to 10% by mass of DPHA. Combinations of polymerizable oligomers and monomers are also preferred, and a combination of EO-modified 1,6-hexanediol di(meth)acrylate, tripropylene glycol di(meth)acrylate, EO-modified trimethylolpropane tri(meth)acrylate, and epoxy (meth)acrylate oligomer is preferred, with the ratio preferably being 70% by mass to 95% by mass of monomer and 5% by mass to 30% by mass of epoxy (meth)acrylate oligomer.

[0021] (Average number of (meth)acryloyl groups) The active energy ray-curable coating agent used in the present invention is characterized in that when the compounds having the (meth)acryloyl group are combined, the average number of (meth)acryloyl groups is more than 2 and less than 2.5. By setting the average number of (meth)acryloyl groups within this range and using a production method that includes the steps described below, it is possible to obtain a coating film that has sufficient matte effect, scratch resistance, and stain resistance, which are the objectives of the present invention.

[0022] In the present invention, the average number of (meth)acryloyl groups is a numerical value representing the number of (meth)acryloyl groups in the active energy ray-curable compounds contained in the active energy ray-curable coating agent. When several types of active energy ray-curable compounds are contained, they are respectively represented as active energy ray-curable compounds (A1) to (An). In this case, the average number of (meth)acryloyl groups is expressed by the following formula (1):

[0023]

number

[0024] In formula (1), Fi is the number of (meth)acryloyl groups (hereinafter may be simply referred to as "functional groups") in each of the active energy ray-curable compounds (A1) to (An), Mi is the part by mass of each of the active energy ray-curable compounds (A1) to (An), and M is the sum of the parts by mass of the active energy ray-curable compounds (A1) to (An) contained in the active energy ray-curable coating agent.

[0025] When the average number of (meth)acryloyl groups in the active energy ray-curable compound is greater than 2.0, stain resistance and scratch resistance can be maintained, whereas when it is less than 2.5, the low gloss behavior according to the present invention tends to be exhibited.

[0026] (Photopolymerization initiator) The method for producing a matte coating film of the present invention includes a step (II) of irradiating with ultraviolet light in the atmosphere as described below, and therefore the active energy ray-curable coating agent used contains a photopolymerization initiator. Any known photopolymerization initiator may be used.

[0027] Among these, radical polymerization type photopolymerization initiators are preferred, and α-hydroxyalkyl ketone-based photopolymerization initiators are preferred because they do not color the solution when the active energy ray-curable compound is dissolved and do not yellow over time. Examples of α-hydroxyalkyl ketone-based photopolymerization initiators include 1-phenyl-2-hydroxy-2-methylpropan-1-one, 1-(4-i-propylphenyl)-2-hydroxy-2-methylpropan-1-one, 4-(2-hydroxyethoxy)phenyl-(2-hydroxy-2-propyl)ketone, and 1-hydroxycyclohexyl phenyl ketone. Furthermore, phenylglyoxolate-based photopolymerization initiators are also preferred. Examples of phenylglyoxolate-based photopolymerization initiators include methylbenzoyl formate. Among these, 1-hydroxycyclohexyl phenyl ketone is preferred.

[0028] As other radical polymerization type photopolymerization initiators, monoacylphosphine oxide-based photopolymerization initiators having an absorption wavelength in the long wavelength region of ultraviolet light may be used in combination as appropriate. The monoacylphosphine oxide photopolymerization initiator excludes bisacylphosphine oxides that become colored when dissolved in an active energy ray-curable compound, and examples thereof include monoacylphosphine oxides such as 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, 2,6-dimethoxybenzoyl-diphenylphosphine oxide, 2,6-dichlorobenzoyl-diphenylphosphine oxide, 2,4,6-trimethylbenzoyl-phenylphosphine acid methyl ester, 2-methylbenzoyl-diphenylphosphine oxide, and pivaloylphenylphosphine acid isopropyl ester. Of these, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide is particularly preferred because it has a UV absorption wavelength that matches the emission wavelength region of UV-LEDs that have emission wavelengths of 385 nm or 395 nm, thereby achieving suitable curability and causing little yellowing of the cured film.

[0029] The photopolymerization initiators may be used alone or in combination of two or more. The total amount of the photopolymerization initiators added is preferably in the range of 0.1% by mass to 30% by mass relative to the total amount of the coating agent, and more preferably in the range of 0.25% by mass to 20% by mass relative to the total amount of the coating agent.

[0030] (organic solvent) In the method for producing a matte coating film of the present invention, the active energy ray-curable coating agent used is preferably solvent-free, but an organic solvent can be added as a diluent if necessary. Any organic solvent can be used as long as it dissolves the compound having a (meth)acryloyl group used. Examples of the organic solvent include aromatic hydrocarbons such as toluene and xylene, aliphatic or alicyclic hydrocarbons such as n-hexane, cyclohexane, methylcyclohexane, and ethylcyclohexane, esters such as ethyl acetate, butyl acetate, and propyl acetate, alcohols such as methanol, ethanol, isopropyl alcohol, and n-butanol, ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone, alkylene glycol monoalkyl ethers such as ethylene glycol monoethyl ether and propylene glycol monomethyl ether, and ether esters such as propylene glycol monomethyl ether acetate. However, if the goal is to thoroughly reduce the amount of organic solvents evaporated into the atmosphere, i.e., to reduce volatile organic compounds (VOCs), it is more preferable to not include the above organic solvents.

[0031] In the method for producing a matte coating film of the present invention, from the viewpoint of coatability, it is preferable to adjust the viscosity to a level that allows coating in the method for producing a decorative sheet for building materials of the present invention described below. The viscosity is preferably adjusted to 40 to 4,000 mPa·s at 25°C. Since most of the compounds having a (meth)acryloyl group generally have low molecular weights, dilution with an organic solvent is not necessary if the viscosity can be adjusted without dilution with an organic solvent. On the other hand, when a polymerizable oligomer with a high molecular weight and high viscosity is used in combination, the viscosity can be adjusted by diluting with an organic solvent or heating as necessary. When the active energy ray-curable coating agent used contains an organic solvent, the organic solvent can be dried off appropriately in the coating film in step (I) described below. In particular, in step (I), in the step of heating the formed coating film, heating and drying of the organic solvent can be performed simultaneously. In this case, the surface temperature of the coating film after drying can be measured.

[0032] (Matting agent) The matting agent used in the present invention may be any known organic and / or inorganic material, and may be used alone or in combination without any particular limitation. Specific examples include inorganic particles such as silica, titanium oxide, alumina particles (aluminum oxide), calcium carbonate, barium sulfate, and glass; organic particles such as acrylic resin, urethane resin, polycarbonate resin, silicone resin, and polystyrene resin; and silicone beads. Preferred inorganic particles that can be expected to provide a high matting effect include silica and aluminosilicate beads, and organic particles such as acrylic resin beads, urethane resin beads, and silicone beads. Adding beads to the silica matting agent can provide design features such as a moderate low gloss and a comfortable feel, as well as improved scratch resistance of the coating surface.

[0033] (silica) The silica used in the present invention is not particularly limited, and any known silica can be used as long as it has an average particle size of 25 μm or less. In the present invention, the average particle size is a value measured by laser diffraction. Specifically, amorphous silica is more preferred as silica. Examples of the amorphous silica include diatomaceous earth and activated clay. Among the amorphous silicas, synthetic amorphous silica such as dry silica, wet silica, and silica gel can be used. Among them, wet silica produced by neutralizing and decomposing an aqueous solution of sodium silicate with an acid or an alkali metal salt is preferred. Surface-treated wet silica can also be used. The method for surface-treating the silica particles is not particularly limited, and any known method can be used. Examples include surface-treated wet silica with wax or a silane coupling agent. A mixture of the surface-treated and untreated wet silicas may be used.

[0034] The average particle size of the wet silica used as the matting agent is 25 μm or less, and more preferably 15 μm or less. If the average particle size is larger than 25 μm, gloss changes and scratches are likely to occur due to particle dropout.

[0035] The silica content is preferably 0.5 to 50 mass % and more preferably 1 to 30 mass % in terms of solid content of the total amount of the coating agent. If the content is less than 0.5 mass %, a sufficient matting effect is not obtained, and if it exceeds 50 mass %, the silica tends to easily fall off from the surface of the coating film, which is not preferable.

[0036] The average particle size of the beads used as the matting agent is 50 μm or less, and more preferably 15 μm or less. If the average particle size is larger than 50 μm, the beads are likely to fall off or become embedded, causing changes in gloss and scratches.

[0037] The content of beads is preferably 0.5 to 50 mass % in terms of solid content of the total amount of the coating agent, and more preferably 0.5 to 30 mass %. If the content exceeds 50 mass %, the beads tend to easily fall off from the coating surface, which is not preferred.

[0038] (additives) In addition, in the method for producing a matte coating film of the present invention, it is possible to contain a polymerization inhibitor, a leveling agent, a thixotropy imparting agent, a wax, a drying agent, a thickener, an anti-sagging agent, a plasticizer, a dispersant, an anti-settling agent, an antifoaming agent, an ultraviolet absorber, a light stabilizer, etc.

[0039] (Production of active energy ray curable coating agents) The active energy ray-curable coating agent used in the present invention can be produced by mixing, kneading, and dispersing a compound having a (meth)acryloyl group, a photopolymerization initiator, a matting agent, fine particles, and various other additives, etc. As the dispersing machine, for example, a known dispersing machine such as a roller mill, a ball mill, a pebble mill, an attritor, or a sand mill can be used. If the coating agent contains air bubbles or unexpectedly large particles, these will deteriorate the quality of the coated product, so it is preferable to remove them by filtration, etc. Any conventionally known filter can be used.

[0040] (Process (I)) In the present invention, step (I) is a step of applying an active energy ray-curable composition onto the substrate to form a coating film.

[0041] The method for forming a coating film of the active energy ray-curable composition on the substrate is not particularly limited, and known coating methods such as a roll coater, gravure coater, gravure offset coater, flexo coater, air doctor coater, blade coater, air knife coater, squeeze coater, impregnation coater, transfer roll coater, kiss coater, curtain coater, cast coater, spray coater, die coater, offset printing machine, and screen printing machine can be used. When the coating agent used contains an organic solvent, the organic solvent may be dried in a drying oven or the like.

[0042] There are no particular limitations on the thickness of the coating film, but it is generally preferred that the coating film be formed to a thickness of 0.1 to 100 μm, and more preferably 0.5 to 50 μm.

[0043] (Step (II) of irradiating with ultraviolet light in the atmosphere) In the present invention, step (II) is a step of irradiating the coating film that has been subjected to step (I) with ultraviolet light in the atmosphere. Ultraviolet irradiation can be carried out by a known method. For example, ultraviolet light is irradiated from a light source such as a germicidal lamp, an ultraviolet fluorescent lamp, an ultraviolet light-emitting diode (UV-LED), a carbon arc, a metal halide lamp, a xenon lamp, a chemical lamp, a low-pressure mercury lamp, a high-pressure mercury lamp for copying, a medium-pressure or high-pressure mercury lamp, an ultra-high-pressure mercury lamp, an electrodeless lamp, a metal halide lamp, or natural light. The ultraviolet light intensity during curing is 20 mJ / cm. 2 If it is more than this, the curing efficiency is good.

[0044] In the present invention, the peak irradiance of the ultraviolet irradiation in step (II) is 30 to 80 mW / cm 2It is characterized in that the irradiation is performed within the range of . By setting the irradiation within this range, the effect of the present invention can be maximized, which is preferable. In the present invention, the peak irradiance refers to the irradiation intensity received per unit area, and refers to the maximum irradiance obtained by concentrating light directly below the lamp, etc.

[0045] In addition, the cumulative amount of ultraviolet light in step (II) is 20 mJ / cm 2 ~200mJ / cm 2 It is preferable that the integrated light amount is in the range of 40 mJ / cm. 2 ~80mJ / cm 2 It is more preferable that the range is:

[0046] The thickness of the coating film thus obtained is preferably in the range of 0.1 to 100 μm, most preferably in the range of 0.5 to 50 μm. By keeping the thickness in this range, the effects of the present invention can be maximized.

[0047] (Step (III) of irradiating with active energy rays) After the step (II), a step (III) of irradiating with active energy rays is essential. When electron beams are used as the active energy rays, an electron beam irradiator is used. The irradiation dose is preferably about 10 to 230 kGy, more preferably about 10 to 100 kGy, and even more preferably in a gas atmosphere with an oxygen concentration of less than 8%.

[0048] The reason why the desired matte coating film can be efficiently obtained by the production method of the present invention is presumed to be as follows. Because the coating film has a low average functional group number of the active energy ray-curable compound, less than 2.5, it is estimated that when UV light is irradiated in the atmosphere in the next step (II), the curing reaction on the surface of the coating film is slow to progress, while curing begins to progress inside the coating film. As curing progresses inside the coating film, the matting agent inside is pushed up and moves closer to the surface of the coating film, and unevenness is efficiently formed near the soft surface where curing has not progressed. In this case, the peak irradiance of UV light is set to 30 to 80 mW / cm. 2By keeping the temperature within this range, the curing process inside the coating film progresses sufficiently, while the surface of the coating film remains uncured and soft, which is presumably why the unevenness is formed efficiently. It is presumed that the unevenness is fixed by step (III), which involves irradiating the surface with electron beams or ultraviolet rays in this state, and a coating film with a sufficient matte effect, scratch resistance, and stain resistance is obtained. The peak irradiance of ultraviolet light is 30 mW / cm 2 If the peak irradiance is less than 80mW / cm, the internal curing will not progress sufficiently, making it difficult for the matting agent to be pushed up to the surface of the coating. 2 If the thickness is larger, curing will proceed not only inside the coating film but also near the surface of the coating film, and it is thought that the matting agent will not be pushed up to the surface of the coating film, making it difficult to form unevenness.

[0049] The manufacturing method of the present invention can be widely applied not only to the aforementioned building material applications such as decorative sheets, but also to surface coating applications for furniture, musical instruments, office supplies, sporting goods, toys, etc. [Example]

[0050] The present invention will be described in more detail below with reference to examples, in which parts and parts by mass represent mass %. The average particle size of the fine particles was measured using a nanoparticle particle size distribution analyzer Nanotrac UPA EX-150 manufactured by Nikkiso Co., Ltd.

[0051] (Preparation Example 1: Active Energy Ray-Curable Composition) 50 parts by mass of a bifunctional acrylate monomer "Miramer M202" manufactured by MIWON, 33 parts by mass of a bifunctional acrylate monomer "Miramer M220" manufactured by MIWON, 17 parts by mass of a trifunctional acrylate monomer "Miramer M3130" manufactured by MIWON, 1.5 parts by mass of a photopolymerization initiator 1-hydroxy-cyclohexyl-phenyl-ketone "Omnirad 184" manufactured by IGM Resins BV, and 15 parts by mass of silica Nipsil E170 (average particle size 3 μm) manufactured by Tosoh Silica Corporation were mixed and stirred with a stirrer for about 1 hour to prepare a total of 116.5 parts by mass of an active energy ray-curable composition (1). The average number of (meth)acryloyl groups (also expressed as the average number of functional groups) according to the formula (1) was 2.2.

[0052] The active energy ray-curable compositions of Preparation Examples 2 to 6 and Preparation Comparative Examples 1 to 4 were also prepared in the same manner as Preparation Example 1 according to the formulations shown in Tables 1 to 3. The average number of (meth)acryloyl groups was determined for each composition in the same manner as Preparation Example 1. The DPA-600T and Ebecryl3708 are as follows: DPA-600T: Hexafunctional acrylate, dipentaerythritol hexaacrylate, manufactured by Zhangjiagang Dongdaic Biochemical Co., Ltd. Ebecryl 3708 (EpAc): Difunctional bisphenol A epoxy acrylate oligomer, manufactured by Daicel-Allnext Co., Ltd. In addition, for Preparations 2 to 6 and Comparative Preparations 1 to 4, the photopolymerization initiator was replaced with an acylphosphine oxide photopolymerization initiator, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide "Omnirad TPO H" manufactured by IGM Resins BV, in place of "Omnirad 184."

[0053] Each preparation example and preparation comparison example and the average number of (meth)acryloyl groups for each are shown in Tables 1 to 3. Note that blank spaces in the tables indicate that no compound was added.

[0054] [Table 1]

[0055] [Table 2]

[0056] [Table 3]

[0057] The abbreviations in the table are as follows: Miramer M202 (EO-HDDA): Bifunctional acrylate monomer, ethylene oxide modified 1,6-hexanediol diacrylate, manufactured by Miwon Miramer M220 (TPGDA): Bifunctional acrylate monomer, tripropylene glycol diacrylate, manufactured by Miwon Miramer M3130 (EO-TMPTA): Trifunctional acrylate monomer, ethylene oxide modified trimethylolpropane triacrylate, manufactured by Miwon DPA-600T: Hexafunctional acrylate, dipentaerythritol hexaacrylate, manufactured by Zhangjiagang Dongdaic Biochemical Co., Ltd. Ebecryl 3708 (EpAc): Difunctional bisphenol A epoxy acrylate oligomer, manufactured by Daicel-Allnext Co., Ltd. Omnirad 184: 1-hydroxycyclohexyl phenyl ketone, manufactured by IGM Resins BV Omnirad TPO H: 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, manufactured by IGM Resins BV Nipsil E170: Silica manufactured by Tosoh Silica Corporation, average particle size 3 μm

[0058] [Method for producing coating film] (Process (I)) The active energy curable composition obtained in the above Preparation Example was applied to an easily adhesive treated polyethylene terephthalate film (hereinafter referred to as PET film, manufactured by Toyobo Co., Ltd., A4300, thickness 100 μm) by a bar coater coating method to form a coating layer of 15 μm.

[0059] (Step (II) of irradiating the coating film with ultraviolet light in the atmosphere) The coating layer after step (I) was irradiated with ultraviolet light using an ultraviolet irradiation device manufactured by GS Yuasa Corporation. The peak irradiance measuring device (illuminance meter) used was the "Industrial UV Checker UVR-N1" ultraviolet integrating actinometer manufactured by GS Yuasa Corporation. The light receiving unit used was the "UD-36T2" (measurement wavelength range: 300-390 nm, peak sensitivity wavelength: approximately 355 nm).

[0060] (Step (III) of irradiating the coating film with electron beams or ultraviolet rays in an inert gas atmosphere) The coating layer after the step (III) was irradiated with electron beams at 50 kGy in a gas atmosphere with an oxygen concentration of less than 8% using an electron beam irradiation device "Electrocurtain EC250 / 15 / 180L" manufactured by Iwasaki Electric Co., Ltd. In Example 12 and Comparative Example 11, instead of the electron beam irradiation, ultraviolet irradiation was performed in a gas atmosphere with an oxygen concentration of less than 8% using an ultraviolet irradiation device manufactured by GS Yuasa Corporation. The cumulative ultraviolet light dose was 56 mJ / cm. 2 It was confirmed that it was. In this way, a matte coating film was obtained.

[0061] (Evaluation item 1: Gloss) The gloss of the resulting coating film was measured using the following equipment and conditions. The lower the gloss, the better the matte effect. Equipment used: Konica Minolta "MULTI GLOSS 268A" Measurement conditions: incident angle 60° reflection angle 60° The evaluation criteria for the gloss loss rate are as follows: A value of 25 or less is considered to be an acceptable product. (Evaluation criteria) ○:25 or less ×: Exceeding 25

[0062] (Evaluation item 2: Scratch resistance) A steel wool ("BON STAR No. 0000" manufactured by Nippon Steel Wool Co., Ltd.) was applied with a load of 1.5 kg and moved back and forth on the surface of the obtained coating film. The extent of scratches on the coating film was evaluated according to the following three-level evaluation criteria. A grade of △ or higher was considered to be an acceptable product. (Evaluation criteria) ○: No change, or slight change in gloss, but no streaky scratches. △: Streak-like scratches cover less than half the area of ​​the friction surface. ×: Streak-like scratches cover almost the entire friction surface, and the coating film turns white to the extent that it is unusable.

[0063] (Evaluation item 3: Stain resistance) In accordance with the JAS Special Plywood Staining Test A, stains were applied to the surface of the decorative panel, and after 4 hours, the surface was wiped with an alcohol-based cloth and the remaining stain was visually observed. Commercially available black marker, red crayon, and blue ink were used as stains. (Evaluation criteria) ○: No contaminants remain. △: Contaminants remain, but they are minor and do not pose any practical problems. ×: Significant contaminants remain.

[0064] Tables 4 to 7 show the evaluation results of the coating films prepared using each preparation example.

[0065] [Table 4]

[0066] [Table 5]

[0067] [Table 6]

[0068] [Table 7]

[0069] According to the method for producing a matte coating film of the present invention, the average number of functional groups of the active energy ray-curable compound is more than 2 but less than 2.5, and the peak irradiance under atmospheric conditions is 30 to 80 mW / cm 2 The matte coating film irradiated with UV light while controlling the temperature showed a high gloss reduction rate, a sufficient matte effect, and both scratch resistance and stain resistance.

Claims

1. a step (I) of applying an active energy ray-curable composition onto a substrate to form a coating film; The coating film is exposed to a peak irradiance of 30 to 80 mW / cm under atmospheric pressure. ２ a step (II) of irradiating the substrate with ultraviolet light while controlling the temperature; a step (III) of irradiating the coating film with an electron beam or ultraviolet light in an inert gas atmosphere; A method for producing a matte coating film having the following in this order: The method for producing a matte coating film is characterized in that the active energy ray-curable composition contains a compound having a (meth)acryloyl group, a photopolymerization initiator, and a matting agent, and the compound having a (meth)acryloyl group has an average number of (meth)acryloyl groups of more than 2 and less than 2.

5.

2. The ultraviolet irradiation conditions in the step (II) are 20 mJ / cm ２ ~200 mJ / cm ２ and the dose of electron beam irradiation in the step (III) of irradiating with active energy rays is in the range of 20 to 230 kGy.

3. 2. The method for producing a matte coating film according to claim 1, wherein the compound having a (meth)acryloyl group is at least one compound selected from the group consisting of ethylene oxide-modified 1,6-hexanediol acrylate, tripropylene glycol diacrylate, ethylene oxide-modified trimethylolpropane diacrylate, dipentaerythritol hexaacrylate, and epoxy acrylate oligomer.

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