JP7480924B1 - UV-curable varnish composition - Google Patents

Abstract

Provided is a material capable of forming a surface layer that can impart a dry, comfortable feel and texture that does not catch on fingers to the surfaces of articles such as interior building materials, home appliances, precision instruments, electronic devices, etc. The ultraviolet-curable varnish composition contains a urethane (meth)acrylate (A), an epoxy resin (B), a filler (C) containing resin beads and/or inorganic beads, a polyethylene wax (D), and a silicone (E), and the ultraviolet-curable varnish composition has a dynamic friction coefficient of 0.6 or less, measured by touching the dried coated surface with a human hand after application of the ultraviolet-curable varnish composition.

Description

The present invention relates to an ultraviolet-curable varnish composition that can be coated on the surfaces of items such as interior building materials, home appliances, precision instruments, and electronic devices to form a surface layer.

Coating agents are applied to items such as interior building materials, home appliances, precision instruments, and electronic devices to provide surface protection against scratches and dirt, or to make them comfortable to the touch, forming a surface layer.

Meanwhile, interest in sensory value, which adds new value to products, is growing, and many industries are actively working on creating sensory value. The pleasant feel of a product, which is perceived as a touch sensation, is attracting attention as an important factor in adding value to a product.
For example, an aqueous ultraviolet-curable overprint varnish composition has been disclosed that can impart a moist, soft, velvet-like or suede-like feel to the surface of a printed material such as paper by applying it thereto (see, for example, Patent Document 1).

Japanese Patent No. 5712338

The feel and texture desired by individuals on the surfaces of items such as interior building materials, home appliances, precision instruments, and electronic devices varies widely.
When evaluating the surfaces of interior building materials, home appliances, precision instruments, electronic devices, and other products based on their wet/dry tactile sensations, some people prefer a dry, comfortable sensation that does not catch on their fingers.
Here, there are a considerable number of people who prefer the comfortable dry feeling that does not catch on the fingers, rather than the comfortable moist feeling of a moist sensation.
Additionally, a dry surface makes it easier to brush off dust, which helps to remove bacteria and viruses that may be attached to the dust, and also makes it less likely for dirt to stick to the surface in the first place.
Therefore, in order to meet the needs of people who prefer this dry, comfortable feeling, there is a demand for materials that can form a surface layer that can impart a dry, comfortable feel to the touch and touch of the surface of articles in the fields of interior building materials, home appliances, precision instruments, electronic devices, and the like.

However, the composition described in Patent Document 1 is intended to meet the needs of people who prefer a moist, soft feel and a comfortable moist sensation, but does not meet the needs of people who prefer a dry, comfortable sensation that does not catch on the fingers.
In addition, the composition described in Patent Document 1 is specified using the value of the dynamic friction coefficient measured using a device with a friction element. However, although there is a JIS standard for the friction measurement itself, there is no standard for the friction element, so the value of the friction coefficient varies greatly depending on the friction element selected by the measurer. Therefore, it cannot be said that there is a sufficient correlation between the value of the friction coefficient and the tactile sensation.

The problem that this invention aims to solve is to provide a material that can form a surface layer on the surfaces of articles such as interior building materials, home appliances, precision instruments, and electronic devices, which can provide a dry, comfortable feel to the touch and skin that does not catch on the fingers.

As a result of extensive research to solve the above problems, the inventors discovered that the above problems could be solved by using an ultraviolet-curable varnish composition containing specific components as a material for forming a surface layer to be coated on the surfaces of articles such as interior building materials, home appliances, precision instruments, and electronic devices, and the ultraviolet-curable varnish composition is defined using a dynamic friction coefficient measured by human hand, and thus completed the present invention.

That is, the present invention includes the following aspects.
[1] An ultraviolet-curable varnish composition comprising a urethane (meth)acrylate (A), an epoxy resin (B), a filler including resin beads and/or inorganic beads (C), a polyethylene wax (D), and a silicone (E),
The ultraviolet-curable varnish composition has a dynamic friction coefficient of 0.6 or less when measured by touching the dried coated surface of the ultraviolet-curable varnish composition with a human hand.
[2] An ultraviolet-curable varnish composition as described in [1], in which the coefficient of dynamic friction measured by a human touching the dried coated surface after application of the ultraviolet-curable varnish composition increases by 0.05 or less when the measurement speed is increased from 30 mm/s to 60 mm/s.
[3] An ultraviolet-curable varnish composition according to [1], comprising 50 to 90 parts by mass of a urethane (meth)acrylate (A), 1 to 10 parts by mass of an epoxy resin (B), and 5 to 30 parts by mass of a filler (C) including resin beads and/or inorganic beads.
[4] An ultraviolet-curable varnish composition according to [3], comprising 50 to 90 parts by mass of a urethane (meth)acrylate (A), 1 to 10 parts by mass of an epoxy resin (B), 5 to 30 parts by mass of a filler (C) containing resin beads and/or inorganic beads, 0.2 to 2 parts by mass of a polyethylene wax (D), and 0.1 to 1 part by mass of a silicone (E).
[5] The ultraviolet-curable varnish composition according to [3], further comprising 1 to 5 parts by mass of a photopolymerization initiator and 0.1 to 1 part by mass of a photopolymerization inhibitor.
[6] The ultraviolet-curable varnish composition according to [4], further comprising 1 to 5 parts by mass of a photopolymerization initiator and 0.1 to 1 part by mass of a photopolymerization inhibitor.
[7] A laminate having a laminate film on which the ultraviolet-curable varnish composition according to any one of [1] to [6] is coated and dried.
[8] The laminate according to [7], wherein the average roughness (Ra) of the dried coated surface after coating of the ultraviolet-curable varnish composition is 2.50 μm or less.

The present invention provides a material that can form a surface layer on the surfaces of items such as interior building materials, home appliances, precision instruments, and electronic devices, which provides a dry, comfortable feel to the touch and skin that does not catch on the fingers.

FIG. 2 is a schematic diagram showing an example of a configuration diagram of a tactile sensation detection device used in the present invention, as viewed from the side. 1 is a schematic diagram showing an example of a configuration diagram of a tactile sensing device used in the present invention, as viewed from above. 1 is a photograph showing a tactile sensing device used in the present invention as viewed from above. FIG. 1 is a diagram showing an example of a data map in which friction coefficients are classified for each speed/load category.

The present invention will be described in detail below. Note that the explanation of the components described below is merely an example for explaining the present invention, and the present invention is not limited to these contents.

(UV-curable varnish composition)
The ultraviolet-curable varnish composition of the present invention contains a urethane (meth)acrylate (A), an epoxy resin (B), a filler including resin beads and/or inorganic beads (C), a polyethylene wax (D), and a silicone (E).
The ultraviolet-curable varnish composition of the present invention has a dynamic friction coefficient of 0.6 or less, measured by touching the dried coated surface of the ultraviolet-curable varnish composition with a human hand.

<Urethane (meth)acrylate (A)>
The urethane (meth)acrylate (A) is effective as a component for imparting flexibility to the coating film and maintaining the properties of the filler. As the urethane (meth)acrylate (A), for example, a compound obtained by reacting a polyol (a1), a polyisocyanate (a2), and a (meth)acrylic compound (a3) having a hydroxyl group or an isocyanate group can be used.

In the present invention, "urethane (meth)acrylate" refers to urethane acrylate and/or urethane methacrylate, "(meth)acrylic compound" refers to methacrylic compound and/or acrylic compound, "(meth)acrylate" refers to methacrylate and/or acrylate, "(meth)acryloyl group" refers to methacryloyl group and/or acryloyl group, and "(meth)acrylic acid" refers to methacrylic acid and/or acrylic acid.

As the polyol (a1), for example, polyether polyol, polyester polyol, polycarbonate polyol, etc. can be used. These polyols may be used alone or in combination of two or more. The polyol (a1) is appropriately determined depending on the type of substrate to be adhered, but when a polycarbonate substrate, which is in high demand as a substrate, is used, it is preferable to use a polycarbonate polyol from the viewpoint of adhesion.

As the polyisocyanate (a2), for example, aromatic polyisocyanates such as xylylene diisocyanate, phenylene diisocyanate, tolylene diisocyanate, diphenylmethane diisocyanate, and naphthalene diisocyanate; aliphatic or alicyclic polyisocyanates such as hexamethylene diisocyanate, lysine diisocyanate, cyclohexane diisocyanate, isophorone diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, diisocyanatomethylcyclohexane, and tetramethylxylylene diisocyanate can be used. These polyisocyanates may be used alone or in combination of two or more. Among these, it is preferable to use an alicyclic polyisocyanate from the viewpoint of further improving adhesion, and it is more preferable to use one or more polyisocyanates selected from the group consisting of 4,4'-dicyclohexylmethane diisocyanate, isophorone diisocyanate, cyclohexane diisocyanate, and diisocyanatomethylcyclohexane.

The (meth)acrylic compound (a3) having an isocyanate group or a hydroxyl group is used for the purpose of introducing a (meth)acryloyl group into the urethane (meth)acrylate (A).

Examples of (meth)acrylic compounds having an isocyanate group that can be used as the (meth)acrylic compound (a3) include 2-(meth)acryloyloxyethyl isocyanate, 2-(2-(meth)acryloyloxyethyloxy)ethyl isocyanate, 1,1-bis((meth)acryloyloxymethyl)ethyl isocyanate, and the like. These compounds may be used alone or in combination of two or more. Among these, it is preferable to use 2-(meth)acryloyloxyethyl isocyanate from the viewpoint of ease of obtaining raw materials, and it is more preferable to use 2-acryloyloxyethyl isocyanate from the viewpoint of curability.

Examples of (meth)acrylic compounds having a hydroxyl group that can be used as the (meth)acrylic compound (a3) include (meth)acrylic acid alkyl esters having a hydroxyl group such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, and hydroxyethylacrylamide; polyfunctional (meth)acrylates having a hydroxyl group such as trimethylolpropane di(meth)acrylate, pentaerythritol tri(meth)acrylate, and dipentaerythritol penta(meth)acrylate; polyethylene glycol monoacrylate, polypropylene glycol monoacrylate, and the like. These compounds may be used alone or in combination of two or more. Among these, from the viewpoints of ease of raw material availability, curability, and adhesion, it is preferable to use an acrylic acid (meth)alkyl ester having a hydroxyl group, and it is more preferable to use 2-hydroxyethyl acrylate and/or 4-hydroxybutyl acrylate.

When a (meth)acrylic compound having an isocyanate group is used as the (meth)acrylic compound (a3), a method for producing the urethane (meth)acrylate (A) can be exemplified by, for example, preparing a polyol (a1) and a polyisocyanate (a2) in the absence of a solvent, reacting them to obtain a urethane prepolymer having a hydroxyl group, and then supplying a (meth)acrylic compound (a3) having an isocyanate group, mixing, and reacting the mixture. The reaction is preferably carried out at a temperature of 20 to 120°C for 30 minutes to 24 hours.

Examples of the method for producing urethane (meth)acrylate (A) when a (meth)acrylic compound having a hydroxyl group is used as the (meth)acrylic compound (a3) include a method in which, in the absence of a solvent, polyol (a1) and (meth)acrylic compound (a3) are charged into a reaction system, and then polyisocyanate (a2) is supplied, mixed, and reacted; a method in which, in the absence of a solvent, polyol (a1) and polyisocyanate (a2) are reacted to obtain a urethane prepolymer having an isocyanate group, and then (meth)acrylic compound (a3) having a hydroxyl group is supplied, mixed, and reacted. The above reaction is preferably carried out, for example, at 20 to 120°C for 30 minutes to 24 hours.

When producing urethane (meth)acrylate (A), a polymerization inhibitor, a urethane catalyst, etc. may be used as necessary.

Examples of polymerization inhibitors that can be used include 3,5-bis(tertiary butyl)-4-hydroxytoluene, hydroquinone, methylhydroquinone, hydroquinone monomethyl ether (methoquinone), para-tertiary butylcatechol methoxyphenol, 2,6-di-tertiary butylcresol, phenothiazine, tetramethylthiuram disulfide, diphenylamine, dinitrobenzene, etc. These polymerization inhibitors may be used alone or in combination of two or more.

Examples of urethane-forming catalysts that can be used include nitrogen-containing compounds such as triethylamine, triethylenediamine, and N-methylmorpholine; metal salts such as potassium acetate, zinc stearate, and tin octoate; and organometallic compounds such as dibutyltin laurate and zirconium tetraacetylacetonate. These urethane-forming catalysts may be used alone or in combination of two or more.

In addition, when producing the urethane (meth)acrylate (A), an alcohol such as methanol may be added at the end in order to deactivate any isocyanate groups remaining in the urethane (meth)acrylate (A).

The weight average molecular weight of the urethane (meth)acrylate (A) is preferably in the range of 500 to 50,000, more preferably in the range of 3,000 to 40,000, from the viewpoints of flexibility and suppression of cure shrinkage. The weight average molecular weight of the urethane (meth)acrylate (A) is a value measured by gel permeation chromatography (GPC) under the following conditions:

Measurement apparatus: high-speed GPC apparatus ("HLC-8220GPC" manufactured by Tosoh Corporation) Column: The following columns manufactured by Tosoh Corporation were used, connected in series.
"TSKgel G5000" (7.8mm I.D. x 30cm) x 1 "TSKgel G4000" (7.8mm I.D. x 30cm) x 1 "TSKgel G3000" (7.8mm I.D. x 30cm) x 1 "TSKgel G2000" (7.8mm I.D. x 30cm) x 1 Detector: RI (differential refractometer)
Column temperature: 40°C
Eluent: tetrahydrofuran (THF)
Flow rate: 1.0 mL/min Injection volume: 100 μL (sample concentration 0.4% by mass in tetrahydrofuran solution)
Standard sample: Prepare a calibration curve using the following standard polystyrene.

[Standard polystyrene]
"TSKgel Standard Polystyrene A-500" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene A-1000" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene A-2500" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene A-5000" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene F-1" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene F-2" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene F-4" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene F-10" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene F-20" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene F-40" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene F-80" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene F-128" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene F-288" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene F-550" manufactured by Tosoh Corporation

As the urethane (meth)acrylate (A), it is preferable to use a so-called bifunctional urethane (meth)acrylate having two (meth)acryloyl groups, since this reduces the crosslinking density and further suppresses cure shrinkage.

It is preferable that the glass transition point of the urethane (meth)acrylate (A) is in the range of 30 to 60°C from the viewpoint of the feel of the coating film.

<Epoxy resin (B)>
Examples of the epoxy resin (B) include various epoxy resins that are generally commercially available, such as epi-bis type, novolak type, β-methyl epichlorohydrin type, cyclic oxirane type, glycidyl ether type, glycidyl ester type, polyglycol ether type, glycol ether type, epoxidized fatty acid ester type, polyvalent carboxylate ester type, aminoglycidyl type, resorcinol type, etc. Among these, epi-bis type epoxy resins are preferably used because of their good scratch resistance of the coating film.

Commercially available epoxy resins (B) include bisphenol A (BPA) type products such as EPIKOAT 1001, EPIKOAT 1004, EPICLON N-865, and EPICLON N-870.
As the modified novolac type epoxy resin, examples of the epoxy resin (C-1) not containing bisphenol A include phenol novolac type epoxy resins such as EPICLON N-730, EPICLON N-740, and EPICLON N-770 manufactured by DIC Corporation, and cresol novolac type epoxy resins such as EPICLON N-660, EPICLON N-665, EPICLON N-670, EPICLON N-673, EPICLON N-680, EPICLON N-690, and EPICLON N-695 manufactured by Asahi Kasei Epoxy Corporation, and AER ECN-1273 and AER ECN-1299 manufactured by the same company.
Furthermore, an epoxy resin that does not contain bisphenol A is preferable, particularly from the viewpoint of hygiene and food applications, since it does not leach out unreacted bisphenol A. The epoxy resin that does not contain bisphenol A means an epoxy resin that does not contain a structure derived from a bisphenol A skeleton.

As the epoxy resin (B), it is preferable that it is a bifunctional epoxy resin from the viewpoint of promoting crosslinking and maintaining scratch resistance.

<Filler (C)>
The filler (C) may be an inorganic filler, an organic filler, or resin beads. These may be used alone or in combination of two or more.
The average particle size of the filler (C) is not particularly limited, but is preferably, for example, 10 μm or less, for example, in the range of 0.1 to 10 μm, and more preferably in the range of 0.8 to 6 μm. If the particle size is small, the filler is buried in the coating film and a good feel cannot be obtained, whereas if the particle size is large, problems such as poor abrasion resistance, product stability (sedimentation), and coating unevenness occur.

<<Organic filler (resin beads)>>
The organic filler or resin beads include, for example, organic fillers or resin beads selected from acrylic resin, urethane resin, nylon resin, polypropylene resin, or urea resin.
Among these, urethane resin beads and silica (silicon dioxide) are preferred from the viewpoint of feel.

The urethane resin beads used in the present invention are formed by molding urethane resin into beads, and have an average particle size in the range of 2 to 10 μm. The reason for this is that, when the beads are exposed on the coating surface, this particle size range allows the desired tactile sensation to be felt when touched by a person with their hands. Furthermore, a range of 5 to 8 μm is more preferable from the viewpoint of tactile sensation.
The glass transition point of the urethane resin beads is preferably in the range of -80 to 0°C. The reason for this is that at this glass transition point, when the beads are exposed to the coating surface, a person feels dry and comfortable when touching them with their hands. Furthermore, if the glass transition point is in the range of -60 to -20°C, blocking and the like are unlikely to occur when the beads are exposed to the coating surface, and the beads can be used preferably.
The glass transition point (Tg) can be determined from the inflection point of the heat flow curve when, for example, about 7 mg of the measurement target is placed in an aluminum pan under a nitrogen atmosphere, the pan is compressed and sealed, and the temperature is scanned in the range of −100 to +150° C. at a heating rate of 10° C./min using a DSC822e manufactured by Mettler Toledo.

<<Inorganic filler>>
Inorganic fillers include, for example, inorganic fillers selected from silica (silicon dioxide), clay, ground calcium carbonate, precipitated calcium carbonate, precipitated barium sulfate, calcium silicate, synthetic silicates, and finely divided silicic acid powder.

<Polyethylene wax (D)>
The ultraviolet-curable varnish composition of the present invention contains polyethylene wax.
From the viewpoints of the lubricity, scratch resistance and feel of the coating film, polyethylene wax is preferably used.
The average particle size of the polyethylene wax is preferably in the range of, for example, 2 to 8 μm. If the average particle size of the polyethylene wax is 2 μm or more, the area of the polyethylene wax floating on the coating film surface is small, and the problem of insufficient scratch resistance and lubricity can be prevented. On the other hand, if the average particle size of the polyethylene wax is 8 μm or less, the problem of unevenness on the coating film surface being prominent, which may cause poor appearance, can be prevented.

<Silicone (E)>
The ultraviolet-curable varnish composition of the present invention contains a silicone (polysiloxane).
Examples of silicones include various silicone oils such as methylpolysiloxane, methylphenylpolysiloxane, methylhydrogenpolysiloxane, methylcyclopolysiloxane, octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, dodecamethylcyclohexasiloxane, octamethyltrisiloxane, tetradecamethylhexasiloxane, dimethylsiloxane-methyl(polyoxyethylene)siloxane-methyl(polyoxypropylene)siloxane copolymer, dimethylsiloxane-methyl(polyoxyethylene)siloxane copolymer, dimethylsiloxane-methyl(polyoxypropylene)siloxane copolymer, dimethylsiloxane-methylcetyloxysiloxane copolymer, and dimethylsiloxane-methylstearoxysiloxane copolymer. Among these, methylhydrogenpolysiloxane and methylpolysiloxane are preferred.

<Other ingredients>
The ultraviolet-curable varnish composition of the present invention must contain a photopolymerization initiator in order to cure it with ultraviolet light. In the present invention, it is also important that the composition contains a photopolymerization inhibitor.

Examples of photopolymerization initiators that can be used in the present invention include benzoin isobutyl ether, benzil, 1-hydroxycyclohexyl phenyl ketone, benzoin ethyl ether, 2,2-dimethoxy-1,2-diphenylethane-1-one, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-(4-isopropylphenyl)-2-hydroxy-2-methylpropan-1-one, 2-methyl-1-(4-methylthiophenyl)-2-morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone-1, 2-hydroxy-1-{4-[4-(2-hydroxy-2-methyl-propionyl)-benzyl]-phenyl} 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propan-1-one, phenylglyoxylic acid methyl ester, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide and other molecular cleavage type photopolymerization initiators; benzophenone, 4-phenylbenzophenone, isophthalphenone, 4-benzoyl-4'-methyl-diphenyl sulfide, 2,4-diethylthioxanthone, 2-isopropylthioxanthone and other hydrogen abstraction type photopolymerization initiators; these may be used alone or in combination of two or more.

Photopolymerization inhibitors are added to prevent polymerization reactions in the coating liquid when the paint is stored or kept, or during the coating process. Examples of this component include hydroquinone (HQ), methylhydroquinone (MEHQ), 3,5-dibutyl-4-hydroxytoluene (BHT), butylhydroxyanisole, etc., which can be blended in appropriate amounts.

The ultraviolet-curable varnish composition of the present invention exhibits a low viscosity suitable for coating even in the absence of solvent, but an organic solvent may be added if necessary. Examples of such organic solvents include ketones such as acetone, methyl ethyl ketone, and methyl isobutyl ketone; cyclic ethers such as tetrahydrofuran and dioxolane; esters such as methyl acetate, ethyl acetate, and butyl acetate; aromatics such as toluene and xylene; and alcohols such as carbitol, cellosolve, methanol, toluene, isopropanol, butanol, and propylene glycol monomethyl ether. These may be used alone or in combination of two or more types.
Furthermore, the ultraviolet-curable varnish composition of the present invention may contain various additives, as necessary, such as leveling agents, thixotropy-imparting agents, waxes other than those mentioned above, drying agents, thickeners, anti-sagging agents, plasticizers, dispersants, anti-settling agents, defoamers, ultraviolet absorbers, light stabilizers, release agents, inorganic pigments, organic pigments, and extender pigments.

The ultraviolet-curable varnish composition of the present invention is prepared by mixing the above-mentioned components in a desired ratio. There is no particular restriction on the mixing ratio, but for example, the ultraviolet-curable varnish composition preferably contains 50 to 90 parts by mass of urethane (meth)acrylate (A), more preferably 70 to 85 parts by mass. The ultraviolet-curable varnish composition preferably contains 1 to 10 parts by mass of epoxy resin (B), more preferably 5 to 7 parts by mass. The ultraviolet-curable varnish composition preferably contains 5 to 30 parts by mass of filler (C) including resin beads and/or inorganic beads, more preferably 9 to 12 parts by mass. The ultraviolet-curable varnish composition preferably contains 0.2 to 2 parts by mass of polyethylene wax (D), more preferably 0.4 to 1 part by mass. The ultraviolet-curable varnish composition preferably contains 0.1 to 1 part by mass of silicone (E), more preferably 0.1 to 0.5 parts by mass.
Furthermore, the ultraviolet-curable varnish composition of the present invention may contain a photopolymerization initiator and a photopolymerization inhibitor. The ultraviolet-curable varnish composition preferably contains 1 to 5 parts by mass of the photopolymerization initiator, and more preferably contains 1.5 to 3.5 parts by mass. The ultraviolet-curable varnish composition preferably contains 0.1 to 1 part by mass of the photopolymerization inhibitor, and more preferably contains 0.1 to 0.5 parts by mass.

A preferred embodiment of the mixing ratio of each component of the ultraviolet-curable varnish composition is an ultraviolet-curable varnish composition in which 50 to 90 parts by mass of urethane (meth)acrylate (A), 1 to 10 parts by mass of epoxy resin (B), and 5 to 30 parts by mass of filler (C) containing resin beads and/or inorganic beads are mixed.
Another example is an ultraviolet-curable varnish composition obtained by mixing 50 to 90 parts by mass of urethane (meth)acrylate (A), 1 to 10 parts by mass of epoxy resin (B), 5 to 30 parts by mass of filler (C) containing resin beads and/or inorganic beads, 0.2 to 2 parts by mass of polyethylene wax (D), and 0.1 to 1 part by mass of silicone (E).
Furthermore, when the ultraviolet-curable varnish composition of the present invention contains a photopolymerization initiator and a photopolymerization inhibitor, a preferred embodiment of the mixing ratio of each component of the ultraviolet-curable varnish composition is an ultraviolet-curable varnish composition mixed in a ratio of 50 to 90 parts by mass of urethane (meth)acrylate (A), 1 to 10 parts by mass of epoxy resin (B), 5 to 30 parts by mass of filler (C) containing resin beads and/or inorganic beads, 1 to 5 parts by mass of photopolymerization initiator, and 0.1 to 1 part by mass of photopolymerization inhibitor.
Further, an example of an ultraviolet-curable varnish composition is a mixture of 50 to 90 parts by mass of urethane (meth)acrylate (A), 1 to 10 parts by mass of epoxy resin (B), 5 to 30 parts by mass of filler (C) containing resin beads and/or inorganic beads, 0.2 to 2 parts by mass of polyethylene wax (D), 0.1 to 1 part by mass of silicone (E), 1 to 5 parts by mass of a photopolymerization initiator, and 0.1 to 1 part by mass of a photopolymerization inhibitor.

<Characteristics of UV-curable varnish composition>
The dynamic friction coefficient measured by touching the dried coated surface of the ultraviolet-curable varnish composition of the present invention with a human hand is 0.6 or less, more specifically, the dynamic friction coefficient at a measurement speed of 50 mm/s is 0.6 or less.
Furthermore, the coefficient of dynamic friction measured by touching the dried coated surface after application of the ultraviolet-curable varnish composition of the present invention with a human hand preferably increases by 0.065 or less, and more preferably by 0.05 or less, when the measurement speed is increased from 30 mm/s to 60 mm/s.
As a result, the ultraviolet-curable varnish composition of the present invention can form a surface layer that does not snag on the fingers and provides a dry, comfortable feel to the touch and skin.

<<Dynamic friction coefficient>>
In the present invention, the dynamic friction coefficient is not measured using a device with a friction element, but is measured directly by touching with a human hand. This allows the tactile sensation of the measurement sample to be quantified and evaluated, taking into account the tactile sensation caused by the movement of a human finger, and therefore friction data that is more closely correlated with the human tactile sensation can be obtained.
In addition, the conventional method of measuring the dynamic friction coefficient by touching with a human hand has the advantage that it is highly likely to obtain friction data that correlates well with the human sense of touch. However, it is also difficult to systematically evaluate friction because it is impossible to control the speed and load and there is a possibility that random friction data is obtained.
However, in the present invention, by using the measurement method described below, stable friction data can be extracted from random friction data, even in the case where the dynamic friction coefficient is measured directly by touching with a human hand, and friction data results that are well correlated with the human tactile sensation can be obtained.

<<<<Dynamic friction coefficient measuring device (tactile detection device)>>>
The measuring device (tactile detection device) used in the method for measuring the dynamic friction coefficient can include a plate on which the measurement sample is placed, a plurality of load detection sensors that detect the load applied to the plate, a load calculation means that uses the load detection sensors to detect the load in the XYZ directions when a finger contacts the measurement sample, and a movement state calculation means that calculates the movement speed of the load position applied to the measurement sample from the loads applied to the plurality of load detection sensors. For example, a measuring device described in JP 2019-144213 A can be used.
A more preferred embodiment of the measuring device is a tactile sensing device 1 as shown in FIGS.
The tactile sensation detection device 1 is adapted to quantify and evaluate the tactile sensation of a measurement sample 4, and is configured to include a flat plate 2 for placing the measurement sample 4, and load detection sensors 3 provided near the four corners of the plate 2, as shown in Fig. 1 and Fig. 2. Characteristically, when the measurement sample 4 placed and fixed on the plate 2 is moved in a tracing manner while being pressed with a finger, the device detects the load in the vertical downward direction of the plate 2 and the load along the planar direction of the plate 2, and obtains the COP (center of pressure), which is the part pressed by the finger, from the load detection sensors 3 provided near the four corners. The device detects the moving speed of the finger from the moving time of the COP, and calculates the dynamic friction coefficient and the like from the load in the vertical downward direction and the load and moving speed in the planar direction of the plate 2 to quantify the tactile sensation.
In addition, in FIGS. 1 and 2, reference numeral 41 denotes a fixture for fixing the measurement sample 4 to the plate 2 .
1 and 2, when viewed from above, it appears as shown in the photograph of FIG.
A commercially available product may be used as the measuring device used in the method for measuring the dynamic friction coefficient. For example, the tactile force plate TF-2020 sold by Tech Gihansha Co., Ltd. may be used.

<<<<Method for measuring dynamic friction coefficient>>>>
(1) Using the above-mentioned measuring device, a friction test is performed by, for example, sliding the index finger of the right hand over the measurement sample 4 in one direction perpendicular to the longitudinal direction of the finger, as if tracing the surface of the measurement sample 4, to measure the friction coefficient.
・Measuring device: For example, a tactile force plate TF-2020-GVS from Tech Gihansha Co., Ltd. is used. ・Measurers: For example, 10 men and women in their 20s to 50s are used as subjects (Note that the experimental results use the average value of the measurers).
Place the measurement sample on the plate and trace it with your index finger from left to right while changing the speed and load. Repeat this for 30 seconds, for example.
・Using a measuring device, monitor the coordinates of the touched position, horizontal force, and vertical force at 1000 Hz. For example, the data will be 30 s x 1000 Hz = 30,000 points. The friction coefficient can be calculated by dividing the horizontal force by the vertical force, and the speed can be calculated from the coordinates.
From the obtained data, for example, the average value of the normal load, the average value of the friction coefficient, and the time dependency of the speed are calculated for a window of 50 data points (0.05 s) and set as Data 1.
(2) The following data is removed from Data 1 to obtain Data 2. This corresponds to preprocessing to remove unnecessary data.
- Excluding data such as friction coefficient of 0, vertical load below a certain value (20 g), speed above a certain value (400 mm/s), and rate of change of friction coefficient per unit time (2.0/s).
(3) Data 2 is grouped into intervals of speed and normal load. The number of data in each group and the average value of the friction coefficient are calculated and used as Data 3.
For example, the speeds are 5-15, 15-25, ... 395-405 mm/s (in 10 mm/s intervals), and the loads are 12.5-37.5, 37.5-62.5 ... 387.5-412.5 (in 25 g intervals). However, in the above classifications, in the case of "up to 15" and "15+", 15 will not be classified into both, but only into one. For example, by interpreting "up to 15" as less than 15 and "15+" as 15 or greater, 15 will only be classified into "15+".
(4) Based on the grouping results, the average friction coefficient is calculated.
For example, in Data 3, if the number of data is sufficient (e.g., 200 or more), the friction coefficient is reliable. The friction coefficient with different loads and speeds can be obtained from a single measurement. If necessary, the friction coefficient of load vs. speed is mapped. For example, the data map of the friction coefficient of Data 3 is shown in Figure 4.
(5) By mapping the obtained data, (a) a statistical kinetic friction coefficient with consistent speed and vertical load can be obtained, (b) the rate of change of the kinetic friction coefficient with respect to the speed and vertical load can be related to the tactile sensation, and (c) the reliability of the data can be evaluated from the kinetic friction coefficient map with different speeds and vertical loads.
In this way, by sorting the Data 3 along the axes of speed and load, stable friction data can be extracted from chaotic friction data. In the present invention, by classifying and mapping the kinetic friction coefficient measured by human touch in this way according to the speed of the moving hand and the pressing load, it is possible to obtain a result of the kinetic friction coefficient that correlates very well with the tactile sensation.
For example, from the results of Fig. 4, the dynamic friction coefficient can be obtained when the vertical load is between 175 and 225 g and the speed is between 20 and 100 mm/s. More preferably, the average value (0.52) of the dynamic friction coefficient at a vertical load of 200 g and a speed of 50 mm/s can be obtained as the measurement result.

<<<<Method for measuring the rate of increase in the dynamic friction coefficient>>>
From the map of dynamic friction coefficients obtained by the above method, the dynamic friction coefficients at a vertical load of 200 g and a speed of 30 mm/s (FC30) and at a vertical load of 200 g and a speed of 60 mm/s (FC60) were obtained, and the rate of increase in the dynamic friction coefficient was calculated by the following formula.

If the rate of increase in the dynamic friction coefficient is 0 or more, it means that the dynamic friction coefficient increases as the speed increases, and more resistance is felt. On the other hand, if the rate of increase in the dynamic friction coefficient is 0 or less, it means that the dynamic friction coefficient decreases as the speed increases, and you can slide without feeling any resistance.

(Laminated film)
The ultraviolet-curable varnish composition of the present invention can be used to form a surface layer (also called a laminated film) by coating the ultraviolet-curable varnish composition on a substrate or the surface of an article.
Examples of methods for applying the ultraviolet-curable varnish composition include bar coater coating, roll coater coating, spray coating, gravure coating, reverse gravure coating, offset printing, flexographic printing, and screen printing, and any of these methods may be used.
The amount of the UV-curable varnish composition to be applied, when it is used as a coating material to be applied directly to a substrate, should be 5 to 20 g/ ^m2 , preferably 8 to 15 g/ ^m2 in terms of solids. When it is used as an overprint varnish for film, the amount should be 3 to 12 g/ ^m2 , preferably 5 to 10 g/ ^m2 .

The ultraviolet-curable composition can be cured by irradiation with energy rays such as ultraviolet rays.
The irradiation energy of energy rays such as ultraviolet rays is preferably in the range of 0.1 to 10 J/cm ² , more preferably in the range of 0.2 to 5 J/cm ² , and even more preferably in the range of 0.25 to 3 J/cm ² , from the viewpoint of ultraviolet curing properties.
The illuminance of energy rays such as ultraviolet rays is preferably in the range of 0.001 to 2 W/cm ² , more preferably in the range of 0.01 to 1.5 W/cm ² , and even more preferably in the range of 0.05 to 1 W/cm ² , from the viewpoint of adhesion and curing properties.
Examples of sources of ultraviolet rays that can be used include known lamps such as xenon lamps, xenon-mercury lamps, metal halide lamps, high-pressure mercury lamps, low-pressure mercury lamps, LEDs, etc. The irradiation energy and illuminance of ultraviolet rays are based on values measured in the wavelength range of 320 to 390 nm using a UV checker; UV Power PucK (II) (manufactured by Electronic Instrumentation and Technology Co., Ltd.).

(Laminate)
The present invention also provides a laminate having a surface layer (laminated film) formed using the ultraviolet-curable varnish composition of the present invention.
The laminate of the present invention has a laminate film on which the ultraviolet-curable varnish composition of the present invention is coated and dried.
The average roughness (Ra) of the dried coated surface after application of the ultraviolet-curable varnish composition is preferably 2.50 μm or less, and more preferably within the range of 0.20 to 2.00 μm.
When the average roughness (Ra) of the dried coated surface is 0.20 μm or more, it is possible to easily sense a comfortable touch, and when the average roughness (Ra) is 2.00 μm or less, it is possible to easily sense a touch that does not catch on the fingers.
The average roughness (Ra) of the dried coated surface can be measured using a contact type roughness meter in accordance with JIS B0601 and JIS B0633. As the contact type roughness meter, for example, a commercially available device such as SURFCOM NEX manufactured by Tokyo Seimitsu Co., Ltd. can be used.

<Applications of the laminate>
The ultraviolet-curable varnish composition of the present invention can be suitably used as a coating agent for the surfaces of articles such as interior building materials, home appliances, precision instruments, and electronic devices.
Therefore, a laminate having a surface layer (laminate film) formed from the ultraviolet-curable varnish composition of the present invention can be applied to various articles such as interior building materials, home appliances, precision instruments, and electronic devices.

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. In the following examples, "%" in the compositions means "% by mass".
The following raw materials were mixed in the proportions shown in Tables 1 and 2 below (the numbers in the tables indicate the solid mass ratios), and stirred in a dispersion stirrer at a rotation speed of 3,000 rpm for a time of 3 minutes to prepare varnish composition samples for the examples and comparative examples.

Urethane acrylate (A): Luxidia manufactured by DIC Corporation (Tg: 50° C.)
Bifunctional epoxy resin (B): Epicron manufactured by DIC Corporation Filler (C)
- Urethane resin beads: Art Pearl manufactured by Negami Chemical Industries, Ltd. Particle size: 15 μm
Acrylic resin beads: Art Pearl manufactured by Negami Chemical Industries, Particle size: 10 μm
Nylon resin beads: Orgasol manufactured by Arkema Particle size: 30 μm
Silicon dioxide beads: Silica manufactured by Fuji Silysia Particle size: 4 μm
Polyethylene wax: Clariant Ceridust Particle size: 8 μm
Silicone: KF series manufactured by Shin-Etsu Chemical Co., Ltd. Photo-radical polymerization initiator: Adeka Arcles manufactured by ADEKA Corporation Photo-polymerization inhibitor: Photo-polymerization inhibitor manufactured by Tokyo Chemical Industry Co., Ltd.

(Preparation of measurement samples)
The varnish compositions having the mixing ratios shown in Examples 1 to 6, Reference Examples 7 and 8, and Comparative Examples 1 to 5 were applied to a 50 μm-thick PET film E-5102 manufactured by Toyobo Co., Ltd. using a bar coater so that the dry coating amount was 4 to 6 g/ ^m2 , and the film was dried and heated at 100°C for 5 seconds to volatilize the solvent (methyl ethyl ketone), and then treated with a UV irradiation device manufactured by Fusion UV Systems Co., Ltd. at an accumulated light amount of 300 mJ/ ^cm2 .

The coefficient of dynamic friction and the feel of the laminated film made of the UV-curable varnish composition prepared as described above were measured using the methods described below.

(Measurement of dynamic friction coefficient)
The dynamic friction coefficient was measured by touching the surface with the human hand using the TF-2020-GVS tactile force plate manufactured by Tech Gihan Co., Ltd. The dynamic friction coefficient was measured by mapping the friction coefficient of load vs. speed and extracting stable friction data.

(Hand feel (evaluation of wet and dry feeling))
A questionnaire survey was conducted to evaluate the feel of the coating surface of the varnish composition of the present invention. The subjects touched the coating surface with their hands and fingers, and the percentage of subjects who felt "a comfortable dry feeling without any catching on the fingers" was tallied, and this was used as the evaluation standard.
<Evaluation criteria>
◎: Strongly feels comfortable with a dry feeling. ◯: Feels comfortable with a dry feeling. △: Feels slightly comfortable with a dry feeling. ×: Does not feel comfortable with a dry feeling.

Table 1 shows the compositions and evaluation results of the ultraviolet-curable varnish compositions of Examples 1 to 6, Reference Examples 7 and 8, and Table 2 shows the compositions and evaluation results of the ultraviolet-curable varnish compositions of Comparative Examples 1 to 5.

As is clear from the results of the above examples, it has been found that the ultraviolet-curable varnish composition of the present invention can form a surface layer on the surface of an article that provides a dry, comfortable feel and texture that does not catch on the fingers.

When the ultraviolet-curable varnish composition of the present invention is used to coat the surfaces of articles such as interior building materials, home appliances, precision instruments, and electronic devices, it not only imparts a comfortable dry feel to the touch and texture, but also imparts an effect of making it easy to brush off dust with one's hands to, for example, interior building materials (kitchens, washstands, furniture, wall materials, etc.), home appliances (television housings, refrigerators, rice cookers, humidifiers), precision instruments (cameras, watches, and other office automation equipment), and electronic devices (PCs, smartphones, tablets). Also, it has the effect of imparting a cool feel to the touch and texture to beverage cans.
In this way, a laminate film using the ultraviolet-curable varnish composition of the present invention can be widely deployed in a wide range of applications.

1: Touch detection device 2: Plate 3: Load detection sensor 4: Measurement sample 41: Fixture

Claims (8)

An ultraviolet-curable varnish composition comprising a urethane (meth)acrylate (A), an epoxy resin (B), a filler (C) containing urethane resin beads and/or silicon dioxide beads, a polyethylene wax (D), and a silicone (E),
the coefficient of dynamic friction measured by touching the dried coated surface of the ultraviolet-curable varnish composition with a human hand is 0.6 or less;
The dynamic friction coefficient is obtained by calculating a horizontal force/vertical force from a horizontal force and a vertical force measured when a human moves his/her hand on the measurement sample while changing the speed and load, using a measurement device having a load calculation means for detecting a load in the XYZ directions when the hand contacts the measurement sample using a load detection sensor that detects the load, and a movement state calculation means for calculating a movement speed of the load position applied to the measurement sample,
This ultraviolet-curable varnish composition determines the dynamic friction coefficient by extracting the friction coefficient value that ensures the desired number of data points based on a classification of the measurement results of hand speed and load measured using the measuring device. The ultraviolet-curable varnish composition according to claim 1, wherein the coefficient of dynamic friction measured by touching the dried coating surface after application of the ultraviolet-curable varnish composition with a human hand increases by 0.05 or less when the measurement speed is increased from 30 mm/s to 60 mm/s. 2. The ultraviolet-curable varnish composition according to claim 1, comprising 50 to 90 parts by mass of a urethane (meth)acrylate (A), 1 to 10 parts by mass of an epoxy resin (B), and 5 to 30 parts by mass of a filler (C) containing urethane resin beads and/or silicon dioxide beads. 4. The ultraviolet-curable varnish composition according to claim 3, comprising 50 to 90 parts by mass of a urethane (meth)acrylate (A), 1 to 10 parts by mass of an epoxy resin (B), 5 to 30 parts by mass of a filler (C) containing urethane resin beads and/or silicon dioxide beads, 0.2 to 2 parts by mass of a polyethylene wax (D), and 0.1 to 1 part by mass of a silicone (E). The ultraviolet-curable varnish composition according to claim 3 further contains 1 to 5 parts by mass of a photopolymerization initiator and 0.1 to 1 part by mass of a photopolymerization inhibitor. The ultraviolet-curable varnish composition according to claim 4, further comprising 1 to 5 parts by mass of a photopolymerization initiator and 0.1 to 1 part by mass of a photopolymerization inhibitor. A laminate having a laminate film on which the ultraviolet-curable varnish composition according to any one of claims 1 to 6 has been applied and dried. The laminate according to claim 7, wherein the average roughness (Ra) of the dried coating surface after coating with the ultraviolet-curable varnish composition is 2.50 μm or less.