JP7556180B2 - Active energy ray curable composition and method for producing matte coating film - Google Patents

Description

The present invention relates to an active energy ray-curable composition and a method for producing a matte coating film using the composition.

Generally, "decorative sheets" are used for furniture, residential interiors, vehicle interior materials, etc. as a material that can give an appearance (design) close to that of natural materials by being attached to the surface of a base material.
The coating agent constituting the outermost layer of the decorative sheet is required to have a matte finish (sometimes referred to as low gloss) to prevent reflection in lighting fixtures and to reproduce a wood surface, as well as physical properties such as good viscosity in terms of scratch resistance, stain resistance, and processability to protect the base material and decorative layer.
On the other hand, most of the current coating agents are two-component curing paints containing organic solvents, but in recent years, active energy ray curing type solventless paints have been attracting attention from the viewpoint of environmental friendliness. However, in solventless paints, the mechanism of matting agents orienting to the coating surface layer when the solvent evaporates, which reduces gloss, cannot be used, so matting agents with large particle sizes according to the coating thickness must be used, which is an issue in that a sufficiently low gloss cannot be obtained.
It is known to apply a coating agent containing an electron beam curable (sometimes referred to as EB curable) or ultraviolet ray curable (sometimes referred to as UV curable) matting agent onto a substrate (see, for example, Patent Document 1).
Also, when curing a coating agent containing a matting agent, a method is known in which the oxygen concentration is changed in multiple stages in an oxygen-containing inert gas atmosphere, and an electron beam is irradiated to cure an electron beam curable clear, thereby obtaining a sufficient matting effect and obtaining a highly weather-resistant matte decorative panel with significantly superior weather resistance (see, for example, Patent Document 2).
However, even these methods are still not sufficient to provide a desired matte effect while also providing scratch resistance, stain resistance, and a viscosity that is favorable in terms of processability.

JP 2002-69332 A JP 2001-87703 A

The problem that the present invention aims to solve is to provide an active energy ray-curable composition that has a viscosity that allows it to be applied as a coating agent, low gloss that provides a matte effect, contamination resistance, and scratch resistance, and a method for producing a matte coating film using the active energy ray-curable composition.

The inventors have discovered that an active energy ray-curable composition containing a specific amount of a specific active energy ray-curable compound, a photopolymerization initiator, and a specific amount of a matting agent of a specific particle size solves the above-mentioned problems.

That is, the present invention provides an active energy ray-curable composition containing an active energy ray-curable compound, a photopolymerization initiator, and a matting agent, the active energy ray-curable composition being characterized in that it satisfies (1) and (2).
(1) As the active energy ray curable compound, the composition contains 10 to 50 mass % of ethylene oxide modified 1,6-hexanediol diacrylate based on the total mass of the active energy ray curable compound, and 10 to 50 mass % of ethylene oxide modified trimethylolpropane triacrylate based on the total mass of the active energy ray curable compound.
(2) The matting agent has a particle size of 1 to 10 μm, and is contained in an amount of 5 to 20% by mass based on the total mass of the active energy ray-curable compound.
(3) The active energy ray-curable compound contains a monofunctional monomer in an amount of 1 to 30% by mass based on the total mass of the active energy ray-curable compound.

The present invention also provides the above-described active energy ray-curable composition, which contains dipentaerythritol hexaacrylate in an amount of 1 to 20 mass % based on the total mass of the active energy ray-curable compound.

The present invention also provides the active energy ray-curable composition described above, which contains at least one (meth)acrylic oligomer selected from the group consisting of urethane (meth)acrylate, epoxy (meth)acrylate, and acrylic (meth)acrylate in an amount of 1 to 20 mass % based on the total mass of the active energy ray-curable compound.

The present invention also provides the active energy ray-curable composition described above, wherein the monofunctional monomer contains at least one selected from the group consisting of ethoxydiethylene glycol acrylate, 2-2-(phenoxyethoxy)ethyl acrylate, 2-(4-nonylphenoxy)ethyl acrylate, n-octyl acrylate, and 2-methyl-2-ethyl-1,3-dioxolan-4-ylmethyl acrylate.

The present invention also provides a method for producing a matte coating film, comprising the steps of: (I) forming a coating film of an active energy ray-curable composition on a substrate; (II) irradiating the coating film with ultraviolet light in the atmosphere; and (III) irradiating the coating film with active energy rays, in that order; wherein the active energy ray-curable composition is the active energy ray-curable composition described above.

The active energy ray curable composition of the present invention has a viscosity that allows it to be applied as a coating agent even without solvent, and it has low gloss that provides a matte effect, as well as contamination resistance and scratch resistance.

The active energy ray-curable composition of the present invention is an active energy ray-curable composition containing an active energy ray-curable compound, a photopolymerization initiator, and a matting agent, and is characterized in that it satisfies (1) and (2).
(1) As the active energy ray curable compound, the composition contains 10 to 50 mass % of ethylene oxide modified 1,6-hexanediol diacrylate based on the total mass of the active energy ray curable compound, and 10 to 50 mass % of ethylene oxide modified trimethylolpropane triacrylate based on the total mass of the active energy ray curable compound.
(2) The matting agent has a particle size of 1 to 10 μm, and is contained in an amount of 5 to 20% by mass based on the total mass of the active energy ray-curable compound.
(3) The active energy ray-curable compound contains a monofunctional monomer in an amount of 1 to 30% by mass based on the total mass of the active energy ray-curable compound.

(Matte coating film made of a cured product of an active energy ray-curable composition)
The matte coating film of the present invention is a matte coating film made of a cured product of a coating agent made of an 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 matte coating agent".
In the present invention, the term "(meth)acrylate" refers to either or both of an acrylate and a methacrylate.

(Active energy ray curable compound)
The active energy ray curable compound used in the present invention must contain 10 to 50 mass % of ethylene oxide modified 1,6-hexanediol diacrylate and 10 to 50 mass % of ethylene oxide modified trimethylolpropane triacrylate, based on the total mass of the active energy ray curable compound.
When the amount of ethylene oxide modified 1,6-hexanediol diacrylate is 10% by mass or more based on the total mass of the active energy ray curable compound, low gloss tends to be maintained, and when it is 50% by mass or less, scratch resistance tends to be maintained.
When the amount of ethylene oxide modified trimethylolpropane triacrylate is 10% by mass or more based on the total mass of the active energy ray curable compound, scratch resistance tends to be maintained, and when it is 50% by mass or less, low gloss tends to be maintained.

In ethylene oxide-modified 1,6-hexanediol diacrylate, the amount of alkylene oxide added in the modification is preferably 1 to 2 moles. In ethylene oxide-modified trimethylolpropane triacrylate, the amount of alkylene oxide added in the modification is preferably 1 to 3 moles, more preferably 2 to 3 moles.

Furthermore, the active energy ray-curable compound used in the present invention must contain a monofunctional monomer in an amount of 1 to 30% by mass based on the total mass of the active energy ray-curable compound.
When the monofunctional monomer is 1% by mass or more based on the total mass of the active energy ray-curable compound, low gloss tends to be maintained, and when it is 30% by mass or less, scratch resistance tends to be maintained.

As the monofunctional monomer, ethoxydiethylene glycol acrylate, 2-2-(phenoxyethoxy)ethyl acrylate, 2-(4-nonylphenoxy)ethyl acrylate, n-octyl acrylate, and 2-methyl-2-ethyl-1,3-dioxolan-4-ylmethyl acrylate are preferred, and among these, ethoxydiethylene glycol acrylate, 2-2-(phenoxyethoxy)ethyl acrylate, and 2-(4-nonylphenoxy)ethyl acrylate are preferred.
These may be used alone or in combination of two or more.

Furthermore, dipentaerythritol hexaacrylate may be contained in an amount of 1 to 20% by mass based on the total mass of the active energy ray-curable compound.
When dipentaerythritol hexaacrylate is 1% by mass or more based on the total mass of the active energy ray-curable compound, stain resistance tends to be maintained, and when it is 20% by mass or less, low gloss tends to be maintained.

Furthermore, a (meth)acrylic oligomer may be used as necessary. Examples of the (meth)acrylic oligomer include urethane (meth)acrylate, acrylic (meth)acrylate, epoxy (meth)acrylate, amine-modified polyether acrylate, amine-modified epoxy acrylate, amine-modified aliphatic acrylate, amine-modified polyester acrylate, amine-modified acrylate such as amino (meth)acrylate, polyester (meth)acrylate, polyether (meth)acrylate, polyolefin (meth)acrylate, polystyrene (meth)acrylate, etc.
Among these, urethane (meth)acrylate, epoxy (meth)acrylate, and acrylic (meth)acrylate are preferred, and urethane (meth)acrylate is more preferred in that it has a viscosity that allows it to be applied as a coating agent, low gloss, stain resistance, and scratch resistance.

The molecular weight of the (meth)acrylic oligomer is preferably in the number average molecular weight range of 150 to 100,000, and more preferably in the number average molecular weight range of 200 to 10,000.

It is preferable that at least one (meth)acrylic oligomer selected from the group consisting of urethane (meth)acrylate, epoxy (meth)acrylate, and acrylic (meth)acrylate is contained in an amount of 1 to 20% by mass based on the total mass of the active energy ray curable compound. By containing the (meth)acrylic oligomer in an amount of 1% by mass or more based on the total mass of the active energy ray curable compound, scratch resistance tends to be maintained, and if it is contained in an amount of 20% by mass or less, viscosity suitable for application as a coating agent tends to be maintained.

(Photopolymerization initiator)
The active energy ray-curable composition of the present invention generally uses a photopolymerization initiator. As the photopolymerization initiator to be used in this case, a known photopolymerization initiator may be used.

Among them, radical polymerization type photopolymerization initiators are preferred, and examples thereof include α-hydroxyalkyl ketone-based photopolymerization initiators, which 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 them, 1-hydroxycyclohexyl phenyl ketone is preferred.

In addition, other radical polymerization type photopolymerization initiators may be used in appropriate combination with monoacylphosphine oxide-based photopolymerization initiators that have an absorption wavelength in the long wavelength region of ultraviolet light. Examples of the monoacylphosphine oxide photopolymerization initiator 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, excluding bisacylphosphine oxides that become colored when dissolved in an active energy ray-curable compound. Among these, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide is particularly preferred in that it has a UV absorption wavelength that matches the emission wavelength region of UV-LEDs having an emission wavelength of 385 nm or 395 nm, thereby obtaining suitable curability and causing less yellowing of the cured film.

The above-mentioned 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 0.01 to 5.0% by mass of the total amount of the active energy ray curable composition. If it is 0.01% by mass or more, good curability can be obtained. In addition, in conventional active energy ray curable matte coating agents used in decorative sheets, etc., the photopolymerization initiator is generally added in an amount of 5.0 to 10.0% by mass of the total amount of solids in the coating agent. In the present invention, by setting it to 5.0% by mass or less, the fluidity of the coating agent is maintained, and processability and workability are maintained. In addition, the surface of the matte coating film tends to be semi-cured by the step (II) of irradiating ultraviolet rays under atmospheric conditions, and the fine particles of the matte agent are efficiently aligned by surface orientation, making it easier to obtain a matte effect.

Furthermore, the curing speed can be increased by adding a tertiary amine compound selected from aliphatic amine derivatives and/or benzoic acid amine derivatives as a sensitizer. Tertiary amine compounds are known to increase reactivity and prevent reaction inhibition by oxygen. Suitable tertiary amine compounds include free alkylamines such as triethylamine, methyldiethanolamine, and triethanolamine, aromatic amines such as 2-ethylhexyl-4-dimethylaminobenzoate and ethyl-4-dimethylaminobenzoate, and active energy ray polymerizable compounds such as polymeric unsaturated amines (e.g., (meth)acrylated amines), which are considered to be preferred due to their low odor, low volatility, and ability to be incorporated into the polymer matrix by curing, thereby suppressing yellowing.

The tertiary amine compound can be used in an amount of preferably 0.1 to 10% by mass, and more preferably 0.3 to 3% by mass, based on the total amount of the paint including the organic solvent.

(Matting agent with average particle size of 1 to 10 μm)
The matting agent used in the present invention may be any known one having an average particle diameter of 1 to 10 μm, and may be used alone or in combination, without particular limitation, based on organic and/or inorganic systems. Specifically, for example, inorganic particles such as silica, titanium oxide, alumina particles (aluminum oxide), calcium carbonate, barium sulfate, glass, etc., organic particles such as acrylic resin, urethane resin, polycarbonate resin, silicone resin, polystyrene resin, silicone beads, etc., may be used. As those that can be expected to have a high matting effect, preferred inorganic particles include silica and aluminosilicate beads, and organic particles include acrylic resin beads, urethane resin beads, etc., and silicone beads, etc.
The amount of the matting agent added is preferably 5 to 20% by mass, more preferably 10 to 18% by mass, based on the total mass of the active energy ray-curable compound. If the content is 5% by mass or more, a sufficient matting effect is obtained, and if it is 20% by mass or less, the viscosity and scratch resistance that can be applied as a coating agent tend to be maintained.

(silica)
The silica used in the present invention is not particularly limited as long as it has an average particle size in the range of 1 to 10 μm, and any known silica can be used. In the present invention, the average particle size is a value measured by a laser diffraction method.
Specifically, amorphous silica is more preferable. Examples of the amorphous silica include diatomaceous earth and activated clay. Among the amorphous silica, dry silica, wet silica, silica gel, etc. can be used as synthetic amorphous silica. Among them, wet silica produced by neutralizing and decomposing an aqueous solution of sodium silicate with an acid or an alkali metal salt is preferable. The wet silica can also be surface-treated. The method of surface-treating the silica particles is not particularly limited and may be any known method. Examples include surface-treated silica with wax or a silane coupling agent. The wet silica may be used by mixing a plurality of the surface-treated and non-surface-treated silicas.

The average particle size of the wet silica used as the matting agent is 1 to 10 μm, more preferably 1.5 to 8 μm. If the average particle size is less than 1 μm, the viscosity increases significantly and it becomes difficult to obtain a viscosity suitable for coating. If the average particle size is more than 10 μm, the effect of orienting the silica on the surface of the coating film is lost, resulting in an insufficient matte finish.

The silica content is preferably 5 to 20% by mass, and more preferably 10 to 18% by mass, of the total mass of the active energy ray-curable compound. If the content is less than 5% by mass, a sufficient matte effect is not obtained, and if it exceeds 20% by mass, it tends to be difficult to maintain a viscosity and scratch resistance that allows application as a coating agent, which is not preferable.

(beads)
When beads are used in the present invention, there is no particular limitation and known beads can be used. Specifically, acrylic resin beads, silicone beads, glass beads, aluminosilicate beads, etc. can be used. By adding beads to the silica as the matting agent, it is possible to improve the scratch resistance of the coating surface in addition to a moderate low gloss. Although beads as the matting agent are required in larger amounts than silica, another advantage is that it is easier to fine-tune the gloss level by changing the amount of beads added. Among them, acrylic resin beads are preferred.

The active energy ray-curable composition of the present invention is preferably used without solvent in light of recent environmental considerations, but an organic solvent can also be added if necessary.

(Organic Solvent)
As the organic solvent, any solvent can be used as long as it dissolves the active energy ray-curable composition used.
Examples of the 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, when the objective is to thoroughly reduce the amount of organic solvents evaporated into the atmosphere, that is, to reduce volatile organic compounds (VOCs), it is more preferable to not contain the above organic solvents.

From the viewpoint of coatability, it is preferable to adjust the viscosity of the active energy ray curable composition of the present invention to a level that allows coating in the method for producing a matte coating film of the present invention described below. The viscosity is preferably adjusted to 300 to 10,000 mPa·s, more preferably 2,000 to 10,000 mPa·s, and even more preferably 300 to 2,000 mPa·s. The active energy ray curable compounds generally have low molecular weights, and if the viscosity can be adjusted without dilution with an organic solvent, there is no need to dilute with an organic solvent. On the other hand, when a polymerizable oligomer having a high molecular weight and high viscosity is used in combination, the viscosity can be adjusted by diluting with an organic solvent or by heating.

(Additives)
In addition, the active energy ray-curable composition used in the present invention may contain, as necessary, a polymerization inhibitor, a leveling agent, a thixotropy imparting agent, a wax, a drying agent, a thickening agent, an anti-sagging agent, a plasticizer, a dispersant, an anti-settling agent, an antifoaming agent, an ultraviolet absorbing agent, a light stabilizer, and the like.

(Production of active energy ray-curable composition)
The active energy ray-curable composition of the present invention can be produced by mixing, kneading, and dispersing the active energy ray-curable compound, the photopolymerization initiator, the matting agent, and various other additives.
The active energy ray-curable composition of the present invention can be adjusted by appropriately adjusting the size of the grinding media of the dispersing machine, the packing rate of the grinding media, the dispersion treatment time, etc. As the dispersing machine, a commonly used one, for example, a roller mill, a ball mill, a pebble mill, an attritor, a sand mill, etc. can be used.
When air bubbles or unexpectedly large particles are contained in the coating agent, they deteriorate the quality of the coating product, so it is preferable to remove them by filtration, etc. As the filter, a conventionally known filter can be used.

(Method of forming a matte coating film)
The active energy ray curable composition of the present invention can form a coating film by a known coating/printing method.Specific examples of the coating method include a roll coater, a gravure coater, a gravure offset coater, a flexo coater, an air doctor coater, a blade coater, an air knife coater, a squeeze coater, an impregnation coater, a transfer roll coater, a kiss coater, a curtain coater, a cast coater, a spray coater, a die coater, an offset printing machine, a screen printing machine, and the like.

When the coating agent used contains an organic solvent, the matte coating film formed by the above-mentioned method can be obtained by drying the solvent in a drying oven or the like and then curing the coating with active energy rays to obtain a hardened coating film, but this is not necessary when the coating agent is solvent-free.

(Base material)
The substrate used in the present invention can be any 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 for decorative sheets can be used as the substrate.
There are no particular limitations on the base sheet, and a typical decorative sheet such as a sheet (film) made of a general-purpose thermoplastic resin or paper can be used.
Examples of sheets (films) formed from thermoplastic resins include polyolefin resins such as polyethylene, ethylene-α-olefin copolymers, polypropylene, polymethylpentene, polybutene, ethylene-propylene copolymers, propylene-butene copolymers, ethylene-vinyl acetate copolymers, saponified ethylene-vinyl acetate copolymers, ethylene-(meth)acrylic acid copolymers, and ethylene-(meth)acrylic acid ester copolymers, polyvinyl chloride, polyethylene terephthalate (PET), polybutylene terephthalate, polyamide, polycarbonate, polyethylene naphthalate, ionomers, acrylic acid ester polymers, and methacrylic acid ester polymers. The substrate sheet may be formed by using these resins alone or in combination of two or more.

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

One or both sides of the base sheet may be subjected to a surface treatment such as corona discharge treatment, ozone treatment, plasma treatment, ionizing radiation treatment, or dichromate treatment, as necessary. For example, when performing corona discharge treatment, the surface tension of the base sheet surface may be set to 30 dynes or more, preferably 40 dynes or more. The surface treatment may be performed according to the usual method for each treatment.

Types of paper substrates for decorative sheets include, for example, thin paper, plain paper, reinforced paper, resin-impregnated paper, titanium paper, etc.

The substrate may also be a wood veneer or the like that is commonly used for decorative boards. Examples of the wood substrate for the wood veneer include known materials such as plywood, particle board, hardboard, and MDF that have been used as wooden substrates for decorative boards, furniture, building materials, etc. It does not matter by what method these known substrates are obtained.
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.

(Step (I))
The active energy ray curable composition is applied to a substrate selected from the substrates described above depending on the purpose of use, and a coating film is formed on the substrate by using any of the coating methods described above.

(Step (II))
Next, the coating film is preferably irradiated with ultraviolet light in the atmosphere.

Here, ultraviolet irradiation in the atmosphere can be performed by a known method, for example, by irradiating ultraviolet light 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 or high pressure mercury lamp, an ultra-high pressure mercury lamp, an electrodeless lamp, a metal halide lamp, natural light, or the like.
In the step (2), the cumulative light amount of the ultraviolet light is preferably in the range of 20 to 1000 mJ/ ^cm2 in order to maximize the effect of the present invention. In particular, the cumulative light amount is more preferably in the range of 40 to 800 mJ/ ^cm2 .
If it is 20 mJ/cm ² or more, the curing efficiency is good, and if it is 1000 mJ/cm ² or less, damage to the substrate due to heat generation can be prevented.
By semi-curing the surface of the matte coating film of the present invention in step (II), the matte effect can be easily obtained efficiently due to the surface orientation of the matte agent, and a matte effect similar to that of a solvent-based paint can be obtained even without a solvent.

(Step (III)
After the step (II), the matte coating film is completely cured in the step (III) of irradiating it with active energy rays, which may be electron beams or ultraviolet rays.
In the case of ultraviolet irradiation, it is more preferable to irradiate in an atmosphere with an oxygen concentration of less than 5%.
Here, an atmosphere with an oxygen concentration of less than 5% means an atmosphere filled with an inert gas containing oxygen, the oxygen concentration of which is less than 5%. As the inert gas, one or more of nitrogen gas, carbon dioxide gas, argon gas, etc. may be used. In addition, there is no problem if a small amount of other gases such as carbon dioxide contained in air is contained.

Ultraviolet light is irradiated in an atmosphere with an oxygen concentration of less than 5%. The cumulative light amount of the ultraviolet light in step (III) is preferably in the range of 20 to 1000 mJ/ ^cm2 , since this maximizes the effects of the present invention. In particular, the cumulative light amount is more preferably in the range of 40 to 800 mJ/ ^cm2 .

On the other hand, when electron beams are used, an electron beam irradiation device is used. The irradiation dose is preferably about 10 to 230 kGy, and more preferably about 10 to 100 kGy. When irradiating with electron beams, it is preferable that the oxygen concentration in the atmosphere is 2% or less.

The thickness of the coating film thus obtained is preferably in the range of 0.1 to 100 μm, and 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.

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

The present invention will be described in more detail below with reference to the following examples. Note that the parts and parts by weight in the following examples represent mass %.

The average particle size of silica was measured using a nanoparticle size distribution analyzer Nanotrac UPA EX-150 manufactured by Nikkiso Co., Ltd.

(Preparation of active energy ray-curable composition)
Example 1
Photomer 6184 (manufactured by IGM Resins B.V.) 10 parts, monofunctional monomer Miramer M170 (ethoxydiethylene glycol acrylate (EOEOEA, manufactured by MIWON)) 5 parts, ethylene oxide modified 1,6-hexanediol diacrylate Miramer A total of 116.5 parts of M202 (manufactured by MIWON Corporation) 50 parts, ethylene oxide modified trimethylolpropane triacrylate M3130 (manufactured by MIWON Corporation) 35 parts, photopolymerization initiator 1-hydroxycyclohexylphenylketone "Omnirad184" (manufactured by BASF Corporation) 1.5 parts, organic surface-treated silica (wet silica) Nipsil E170 (average particle size: 3 μm, manufactured by Tosoh Silica Corporation) as a matting agent were stirred and mixed for 1 hour using a stirrer to prepare active energy ray curable composition 1.

[Examples 2 to 14, Comparative Examples 1 to 8]
According to the formulations shown in Tables 1 to 4, each active energy ray-curable composition was prepared in the same manner as in Example 1.

<Formation of coating film by step (I)>
A polypropylene film (manufactured by Okamoto Corporation, 0.5 mm thick) was used as a substrate, and the active energy ray-curable compositions prepared in Examples 1 to 14 and Comparative Examples 1 to 8 were applied using a bar coater (10 μm) to the coated products, which were then subjected to a step (II) of irradiating with ultraviolet light in the atmosphere and a step (III) of irradiating with active energy rays in accordance with Tables 1 to 4.

<Ultraviolet light irradiation in step (II)>
Using a UV irradiation device (GS Yuasa Corporation) equipped with an air-cooled high-pressure mercury lamp (output 120 W/cm, 1 lamp) and a belt conveyor, the coated product was placed on the conveyor and passed directly under the lamp (irradiation distance 11 cm) in air at a speed of 25 meters per minute, thereby semi-curing the coating film.
The ultraviolet ray exposure was confirmed to be 55 mJ/ ^cm2 using an ultraviolet ray integrating light meter (GS Yuasa Corporation, Industrial UV Checker UVR-N1).

<Electron beam irradiation in step (III)>
Next, using a curtain-type electron beam irradiation device ("Electrocurtain EC250/15/180L" manufactured by Iwasaki Electric Co., Ltd.), the coating film was irradiated with electron beams at an exposure dose of 50 kGy to completely cure the coating film.

[Evaluation method]
The active energy ray-curable composition of the present invention and the method for evaluating the prepared matte coating film will be described below.

[Evaluation item 1: Viscosity]
The active energy ray-curable composition adjusted to 25° C. was measured using a digital B-type viscometer (TVB-10M manufactured by Toki Sangyo Co., Ltd.) with an M3 rotor at 60 rpm.
(Evaluation Criteria)
◎: 300 mPa·s or more, but less than 2000 mPa·s ○: 2000 mPa·s or more, but less than 10000 mPa·s ×: Less than 300 mPa·s or 10000 mPa·s or more

[Evaluation item 2: Glossiness]
The completely cured matte coating film surface was subjected to measurement of the specular gloss in accordance with JIS Z8741 using a gloss meter ("MULTI GLOSS 268A" manufactured by Konica Minolta, Inc.) to measure the gloss value.
The gloss value was measured under conditions of an incident angle of 60° and a reflection angle of 60°.
(Evaluation Criteria)
◎: Less than 10% ○: 10% to less than 20% ×: 20% or more

[Evaluation item 3: Stain resistance]
In accordance with the JAS Special Plywood Stain A Test, a stain was applied to the surface of the decorative board, and after 4 hours, the surface was wiped off with a cloth containing alcohol, and the remaining stain was visually observed. Commercially available black marker pen was used as the stain.
(Evaluation Criteria)
◎: No remaining contaminants ○: Some remaining contaminants are minor and do not pose a problem in practical use ×: Significant remaining contaminants

[Evaluation item 4: Scratch resistance]
The surface of the obtained coating film was evaluated using a Hoffman scratch tester (manufactured by BYK Gardner). Specifically, a scratch blade was set at an angle of 45° on the surface of the coating film, and the tester was moved. The load was gradually increased, and the load at which scratches or indentations were generated on the surface was measured.
(Evaluation Criteria)
◎: Load 400g or more ○: Load 200g or more, less than 400g ×: Load less than 200g

The compositions of the active energy ray-curable compositions and the evaluation results of the matte coating films thus produced are shown in Tables 1 to 4.
In addition, all values in the table are in parts by mass or percent by mass, and blank spaces indicate that no component was blended.
In addition, N.D. in Table 4 indicates that the viscosity was too high to be evaluated.

The abbreviations in the table are as follows:
Photomer 6184: Urethane acrylate oligomer manufactured by IGM Resins B.V. Miramer M170: Ethoxydiethylene glycol acrylate (EOEOEA) manufactured by MIWON
・M-101A: 2-2-(phenoxyethoxy)ethyl acrylate manufactured by Toagosei Co., Ltd. ・M-113: 2-(4-nonylphenoxy)ethyl acrylate manufactured by Toagosei Co., Ltd. ・NOAA: n-octyl acrylate manufactured by Osaka Organic Chemical Industry Co., Ltd. ・MEDOL-10: 2-methyl-2-ethyl-1,3-dioxolan-4-ylmethyl acrylate manufactured by Osaka Organic Chemical Industry Co., Ltd. ・Miramer M202: ethylene oxide modified 1,6-hexanediol diacrylate manufactured by MIWON Co., Ltd. ・Miramer M220: tripropylene glycol diacrylate manufactured by MIWON Co., Ltd. ・Miramer M3130: ethylene oxide modified trimethylolpropane triacrylate manufactured by MIWON Co., Ltd. ・DPA600T: manufactured by Zhangjiagang Toa Di Chemical Co., Ltd. Dipentaerythritol hexaacrylate, Omnirad 184: Photopolymerization initiator manufactured by BASF 1-Hydroxy-cyclohexyl-phenyl-ketone, Nipsil E170: Silica manufactured by Tosoh Silica Corporation, average particle size 3 μm
Syloid ED-50: Silica manufactured by W. R. Grace, average particle size 8 μm
NIPGEL BY-001: Silica manufactured by Tosoh Silica Corporation, average particle size 14 μm

The active energy ray-curable composition of the present invention has a viscosity that allows it to be applied as a coating agent without using organic solvents, while also providing low gloss, contamination resistance, and scratch resistance that provide a matte effect.

Claims (4)

A step (I) of forming a coating film of an active energy ray-curable composition on a substrate;
(II) a step of irradiating the coating film with ultraviolet light under atmospheric conditions;
A step (III) of irradiating the coating film with an electron beam;
A method for producing a matte coating film, characterized in that:
The substrate is a sheet formed of a thermoplastic resin.
The active energy ray-curable composition comprises
A method for producing a matte coating film, comprising an active energy ray-curable composition containing an active energy ray-curable compound, a photopolymerization initiator, and a matte agent, the method being characterized in that the composition satisfies (1), (2), and (3).
(1) As the active energy ray curable compound, the composition contains 10 to 50 mass % of ethylene oxide modified 1,6-hexanediol diacrylate based on the total mass of the active energy ray curable compound, and 10 to 50 mass % of ethylene oxide modified trimethylolpropane triacrylate based on the total mass of the active energy ray curable compound.
(2) The matting agent has a particle size of 1 to 10 μm, and is contained in an amount of 5 to 20% by mass based on the total mass of the active energy ray-curable compound.
(3) The active energy ray-curable compound contains a monofunctional monomer in an amount of 1 to 30% by mass based on the total mass of the active energy ray-curable compound. The method for producing a matte coating film according to claim 1, wherein the dipentaerythritol hexaacrylate is contained in an amount of 1 to 20% by mass based on the total mass of the active energy ray-curable compound. The method for producing a matte coating film according to claim 1 or 2, which contains 1 to 20% by mass of at least one (meth)acrylic oligomer selected from the group consisting of urethane (meth)acrylate, epoxy (meth)acrylate, and acrylic (meth)acrylate, based on the total mass of the active energy ray curable compound. The method for producing a matte coating film according to claim 1, wherein the monofunctional monomer contains at least one selected from the group consisting of ethoxydiethylene glycol acrylate, 2-2-(phenoxyethoxy)ethyl acrylate, 2-(4-nonylphenoxy)ethyl acrylate, n-octyl acrylate, and 2-methyl-2-ethyl-1,3-dioxolan-4-ylmethyl acrylate.