JP7694637B2 - Active energy ray curable composition and laminate using same - Google Patents

Description

The present invention relates to an active energy ray-curable composition and a laminate using the same.

In recent years, in the field of packaging that uses paper substrates (also known as paper containers), much research has been conducted into printing color inks on various substrates and then applying a coating varnish to impart durability and aesthetic appeal to printed matter. With regard to paper container packaging, after printing, there are cases where glossiness or a matte finish is required for aesthetic reasons when the product is displayed in stores. In particular, there has been an increase in demand for printed matter with a matte finish in recent years.

Conventionally, solvent-based matte coating varnishes containing resins, matting agents, and solvents have been used for matte coating varnishes for paper packaging, with the aim of imparting a high-quality look through high matte properties. Generally, with solvent-based matte coating varnishes, the volume of the varnish film decreases as the solvent components evaporate from the varnish film during the drying process after printing, and the matting agent is oriented on the surface of the varnish film, resulting in a high matte effect, but on the other hand, they are poor in workability and environmental friendliness. Furthermore, with solvent-based matte coating varnishes, the solid content of the ink changes as the solvent components evaporate during printing, which raises concerns about viscosity changes during printing and the risk of environmental pollution due to volatilized solvent.

In recent years, solvent-free activated energy ray matte coating varnishes that improve workability and environmental friendliness have been developed. For example, Patent Document 1 proposes an activated energy ray curable coating varnish that contains a photopolymerizable acrylate monomer, resin beads, and a photoinitiator, in which the resin beads are made of resin beads with two types of average particle size, and that produces printed matter with excellent matte finish and abrasion resistance.

Furthermore, Patent Document 2 proposes a solventless active energy ray-curable composition containing an active energy ray-curable compound, an inorganic matting agent, and an aluminum chelate compound, characterized in that the inorganic matting agent is silica having an average particle size of 1 to 15 μm, the thixotropic coefficient at 25°C is 2 or less, and the viscosity at the coating environment temperature is 1000 mPa·s or less.

In addition, Patent Document 3 proposes an active energy ray-curable resin composition that contains an organic filler and a urethane (meth)acrylate compound obtained by reacting a polyol compound, a hydroxyl group-containing (meth)acrylate compound, and a polyisocyanate compound, in which the polyol compound contains a polyol compound having a weight average molecular weight of 60 to 300 and a polyol compound having a weight average molecular weight of 3,000 to 20,000, and the organic filler is a combination of a polyurethane filler and a polyethylene filler.

Also, Patent Document 4 proposes an active energy ray curable composition containing a polyfunctional urethane (meth)acrylate, a monofunctional ethylenically unsaturated monomer, and resin fine particles, in which the weight average molecular weight of the polyfunctional urethane (meth)acrylate is 1000 to 7000, the composition does not contain an organic solvent or contains an organic solvent in an amount of 5 mass% or less of the total mass of the composition, the viscosity of the composition at 25°C is 250 to 2500 mPa·s, and the monofunctional ethylenically unsaturated monomer contains a hydroxyalkyl (meth)acrylate.

However, while the technologies disclosed in Patent Documents 1 and 2 above are solvent-free and have excellent workability and environmental friendliness, they do not have sufficient matte properties compared to the solvent-based matte coating varnishes that have traditionally been mainstream, and issues remain for use in paper packaging applications that require high matte properties in recent years.

In addition, while the above-mentioned Patent Document 3 is considered to have sufficient matte properties from the viewpoint of cosmetic properties, the composition contains a solvent to impart coatability, and issues remain in terms of workability and environmental friendliness.

On the other hand, the above-mentioned Patent Document 4 is a solvent-free type that is excellent in workability, environmental friendliness, and cosmetic properties, and is expected in this field to further improve adhesion to substrates and printed layers and abrasion resistance.

JP 2010-241954 A JP 2002-121210 A JP 2015-101609 A JP 2022-101753 A

The present invention aims to provide an active energy ray-curable composition for forming a cured layer that has excellent printability (viscosity stability) and, when printed and cured, has excellent adhesion to the substrate and the printed layer, abrasion resistance, and moist heat resistance.

As a result of extensive research into the above-mentioned problems, the inventors discovered that the problems could be solved by using the active energy ray-curable composition described below, and thus completed the present invention.

That is, the present invention provides an active energy ray-curable composition containing a polyfunctional urethane (meth)acrylate, a monofunctional ethylenically unsaturated monomer, and resin fine particles,
The weight average molecular weight of the polyfunctional urethane (meth)acrylate is 3,000 to 20,000;
The present invention relates to an active energy ray-curable composition, wherein the hydroxyl value of the solid content of the active energy ray-curable composition is 30 mgKOH/g or less.

The present invention also relates to the active energy ray-curable composition, in which the monofunctional ethylenically unsaturated monomer has a heterocyclic structure.

The present invention also relates to the active energy ray-curable composition, which further contains a photopolymerization initiator.

The present invention also relates to the active energy ray-curable composition, in which the multifunctional urethane (meth)acrylate has a structural unit derived from polyether.

The present invention also relates to the active energy ray-curable composition, in which the resin microparticles are urethane resin microparticles.

The present invention also relates to the active energy ray-curable composition, which further contains a silicon acrylate.

The present invention also relates to the active energy ray-curable composition for use on paper substrates.

The present invention also relates to a laminate having a printed layer and a cured layer formed from the active energy ray-curable composition on a paper substrate.

The present invention also relates to a method for producing a laminate in which the active energy ray-curable composition is applied to a substrate by any one of flexographic printing, screen printing, and roll coating, and then cured.

The present invention makes it possible to provide an active energy ray-curable composition for forming a cured layer that has excellent printability (viscosity stability) and, when printed and cured, has excellent adhesion to the substrate and the printed layer, abrasion resistance, and moist heat resistance.

The following describes in detail the embodiments of the present invention. However, the following description of the components is merely an example (representative example) of the embodiment of the present invention, and the present invention is not limited to these details as long as it does not exceed the gist of the invention.

In this specification, the "solid content of the active energy ray curable composition" refers to the total mass of the components excluding water and organic solvents from the active energy ray curable composition. The "solid content" includes polyfunctional urethane (meth)acrylates, monofunctional ethylenically unsaturated monomers, and resin fine particles.

In the following description, (meth)acrylic and (meth)acrylate refer to methacrylic and acrylic, and methacrylate and acrylate, respectively. Also, (meth)acryloyl refers to methacryloyl and acryloyl. Note that multifunctional urethane acrylate is synonymous with multifunctional urethane (meth)acrylate. Also, active energy ray-curable composition may be simply referred to as "composition," but these terms are synonymous.

The present invention relates to an active energy ray-curable composition containing a polyfunctional urethane (meth)acrylate, a monofunctional ethylenically unsaturated monomer, and resin fine particles, wherein the weight average molecular weight of the polyfunctional urethane (meth)acrylate is 3000 to 20000, and the hydroxyl value of the solid content of the composition is 30 mgKOH/g or less. Preferably, the composition does not contain an organic solvent or contains an organic solvent in an amount of 5 mass% or less of the total mass of the composition.
It is believed that by setting the weight-average molecular weight of the polyfunctional urethane acrylate within the applicable range and the hydroxyl value of the composition to 30 mgKOH/g or less, the cohesive force within the composition is alleviated, the intermolecular interactions with the substrate and the printed layer are improved, and the adhesion, abrasion resistance, and moist heat resistance are improved, and by setting the organic solvent in the total mass of the composition to 5 mass% or less, the viscosity stability is improved, improving the printability and coating properties of the printed matter, etc. Note that the above shows the effects based on chemical considerations, and the present invention is not limited to only the aspects showing these effects.

(Hydroxyl value)
In the present invention, the hydroxyl value refers to the amount of hydroxyl groups in 1 g of the composition calculated by esterifying or acetylating the hydroxyl groups in the composition and back titrating the remaining acid with an alkali, converted into mg of potassium hydroxide, and is a value measured in accordance with JIS K0070.
In order to make the hydroxyl value of the solid content of the composition 30 mgKOH/g or less, it is a preferred embodiment to use a polyfunctional urethane (meth)acrylate and a monofunctional ethylenically unsaturated monomer having a hydroxyl value of 30 mgKOH/g or less, and the hydroxyl value of the monofunctional ethylenically unsaturated monomer is preferably 30 mgKOH/g or less, more preferably 20 mgKOH/g or less, and more preferably 10 mgKOH/g or less. By being in the above range, the moist heat resistance is good.
The hydroxyl value of the solid content of the composition is preferably 20 mgKOH/g or less, more preferably 10 mgKOH/g or less, and particularly preferably 5 mgKOH/g or less. Note that a hydroxyl value of 30 mgKOH/g or less also includes a case where the hydroxyl value is 0 mgKOH/g or less. When the hydroxyl value is in the above preferred range, the moist heat resistance is good.

(Multifunctional urethane acrylate)
The weight average molecular weight of the polyfunctional urethane acrylate used in the present invention is 3000 to 20000. By having the weight average molecular weight in the above range, the viscosity of the composition is appropriately maintained to improve the coating suitability, and the cured layer formed from the ultraviolet curable resin composition is uniform without excessive penetration into the paper substrate. Furthermore, the hardness of the cured layer is appropriately maintained and it does not crack. In addition, the polyfunctionality provides good blocking resistance. The weight average molecular weight is preferably 3500 to 15000, and more preferably 4000 to 10000. In addition, the number of functional groups of the polyfunctional urethane acrylate is preferably 2 to 3, and more preferably 2. Here, the number of functional groups refers to a polymerizable (meth)acrylate group or other unsaturated double bond group. By having the number of functional groups in the above range, the adhesion of the cured layer is improved.

The weight average molecular weight mentioned above refers to a value measured by gel permeation chromatography, and can be measured, for example, using a GPC (gel permeation chromatography) "Shodex GPC System-21" manufactured by Showa Denko KK GPC (gel permeation chromatography) is a liquid chromatography that separates and quantifies substances dissolved in a solvent based on the difference in their molecular size. Tetrahydrofuran is preferably used as the solvent, and the weight average molecular weight is preferably determined in polystyrene equivalent.

The glass transition temperature (Tg) of the polyfunctional urethane acrylate is preferably -50 to 35°C, more preferably -45 to 30°C, and even more preferably -40 to 25°C. When it is within the above range, the adhesion and crease crack resistance of the cured layer are improved. The glass transition temperature is a value measured using a differential scanning calorimeter (DSC), and the midpoint between the end temperature and the start temperature of heat absorption based on the glass transition in the DSC curve is taken as the glass transition temperature.

The active energy ray curable composition preferably contains 5 to 40% by mass of the polyfunctional urethane acrylate, and more preferably 10 to 30% by mass. When the content is within the above range, the abrasion resistance is improved.

The polyfunctional urethane acrylate is preferably in the following form, for example, one obtained by reacting an isocyanate group-containing urethane prepolymer obtained by reacting a polyol with a polyisocyanate under conditions of excess isocyanate groups with a (meth)acrylate having a hydroxyl group, or one obtained by reacting a polyisocyanate with a (meth)acrylate having a hydroxyl group. Alternatively, it can also be obtained by reacting a hydroxyl group-containing urethane prepolymer obtained by reacting a polyol with a polyisocyanate under conditions of excess hydroxyl groups with a (meth)acrylate having an isocyanate group.

The polyol, hydroxyl group-containing (meth)acrylate, and polyisocyanate that make up the multifunctional urethane acrylate are described below.

<Polyol>
The polyol constituting the multifunctional urethane acrylate can be a known one, and suitable examples thereof include polyether polyol, polyester polyol, polyolefin polyol (polybutadiene polyol, polyisoprene polyol), polycarbonate polyol, polysiloxane polyol, (meth)acrylic polyol, etc., which may have an aliphatic structure or an alicyclic structure. Among these, polyether polyol is preferred, and when polyether polyol is used, the multifunctional urethane acrylate has a structural unit derived from polyether, improving adhesion. The multifunctional urethane acrylate preferably contains 20 to 99% by mass, more preferably 40 to 98% by mass, of a structural unit derived from polyether.
Furthermore, it is more preferable that the polyether polyol is polyethylene glycol. By using polyethylene glycol, the polyfunctional urethane (meth)acrylate has a structural unit derived from polyethylene glycol, and the adhesion can be further improved.

<Polyisocyanate>
As the polyisocyanate constituting the polyfunctional urethane acrylate, known polyisocyanates can be used, and examples of such polyisocyanates include aromatic diisocyanates, aliphatic diisocyanates, and alicyclic diisocyanates.
Examples of aromatic diisocyanates include 1,5-naphthylene diisocyanate, 4,4'-diphenylmethane diisocyanate (MDI), 4,4'-diphenyldimethylmethane diisocyanate, 4,4'-dibenzyl isocyanate, 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, tolylene diisocyanate, m-tetramethylxylylene diisocyanate, 4,4-diphenylmethane diisocyanate, xylylene diisocyanate, and 2,6-diisocyanate-benzyl chloride.
Examples of the aliphatic diisocyanate include butane-1,4-diisocyanate, hexamethylene diisocyanate, isopropylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, and lysine diisocyanate.
Examples of alicyclic diisocyanates include cyclohexane-1,4-diisocyanate, hydrogenated xylylene diisocyanate, isophorone diisocyanate, dimeryl diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, 1,3-bis(isocyanatemethyl)cyclohexane, methylcyclohexane diisocyanate, norbornane diisocyanate, and dimer diisocyanate in which the carboxy group of a dimer acid is converted into an isocyanate group.
These may form a trimer to form an isocyanurate ring structure. These polyisocyanates may be used alone or in combination of two or more kinds.
Among these, tolylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, hydrogenated xylylene diisocyanate, hexamethylene diisocyanate, and isocyanurates of hexamethylene diisocyanate are preferred.

<(Meth)acrylate Having a Hydroxyl Group>
Specific examples of the "(meth)acrylate having a hydroxyl group" constituting the polyfunctional urethane acrylate include trimethylolpropane di(meth)acrylate, trimethylolethane di(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol penta(meth)acrylate, 2-hydroxyethyl (meth)acrylate, 1-hydroxypropyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 1-hydroxybutyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, and 1-hydroxypropyl (meth)acrylate. Examples of the hydroxyl group-containing (meth)acrylic acid esters include 8-hydroxyoctyl acrylate, cyclohexanedimethanol mono(meth)acrylic acid ester, 10-hydroxydecyl (meth)acrylate, 12-hydroxylauryl (meth)acrylate, ethyl-α-(hydroxymethyl) (meth)acrylate, monofunctional glycerol (meth)acrylate, or (meth)acrylic acid esters having a hydroxyl group at the end obtained by ring-opening addition of these (meth)acrylates with ε-caprolactone lactone, and alkylene oxide-added (meth)acrylic acid esters obtained by repeatedly adding alkylene oxides such as ethylene oxide, propylene oxide, and butylene oxide to the above-mentioned hydroxyl group-containing (meth)acrylates. Among these, those containing at least one selected from 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate are preferred.

<Monofunctional ethylenically unsaturated monomer>
Examples of the monofunctional ethylenically unsaturated monomers used in the present invention include (alkyl)(meth)acrylates having 1 to 18 carbon atoms, such as methyl(meth)acrylate, ethyl(meth)acrylate, butyl(meth)acrylate, hexyl(meth)acrylate, octyl(meth)acrylate, dodecyl(meth)acrylate, and stearyl(meth)acrylate, as well as benzyl(meth)acrylate, alkylphenols such as butylphenol, octylphenol, nonylphenol, and dodecylphenol, and ethylene oxide adducts ( (meth)acrylate, isobornyl (meth)acrylate, cyclohexyl (meth)acrylate, tricyclodecane monomethylol (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, hydroxypentyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, 2-hydroxy-3-butoxypropyl (meth)acrylate acrylate, 2-hydroxy-3-methoxypropyl (meth)acrylate, diethylene glycol mono(meth)acrylate, triethylene glycol mono(meth)acrylate, polyethylene glycol mono(meth)acrylate, dipropylene glycol mono(meth)acrylate, polypropylene glycol mono(meth)acrylate, glycerin mono(meth)acrylate, acryloyloxyethyl phthalate, 2-(meth)acryloyloxyethyl-2-hydroxyethyl phthalate, 2-(meth)acryloyloxypropyl phthalate, β-carboxyethyl Examples include (meth)acrylate, (meth)acrylic acid dimer, ω-carboxy-polycaprolactone mono(meth)acrylate, dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, N-vinylformamide, (meth)acryloylmorpholine, N-vinylpyrrolidone, tetrahydrofurfuryl acrylate, cyclic trimethylolpropane formal acrylate, 3-ethyl-3-oxetanyl-methyl (meth)acrylate, (2-methyl-2-ethyl-1,3-dioxolan-4-yl)methyl acrylate, and the like.

Among them, it is preferable to include a monofunctional ethylenically unsaturated monomer having a heterocyclic structure, such as N-vinylpyrrolidone, acryloylmorpholine, tetrahydrofurfuryl acrylate, tetrahydrofurfuryl alcohol acrylic acid polymer ester, cyclic trimethylolpropane formal acrylate, 3-ethyl-3-oxetanyl-methyl (meth)acrylate, and (2-methyl-2-ethyl-1,3-dioxolan-4-yl)methyl acrylate. By including a heterocyclic structure, the viscosity of the composition can be appropriately maintained, and the resistance to moist heat is improved. The heterocyclic ring preferably includes a nitrogen atom or an oxygen element, and more preferably includes an oxygen atom. In addition, the heterocyclic ring preferably includes a 4- to 6-membered ring structure, and more preferably includes a 5-membered ring structure. A tetrahydrofuran ring structure is more preferable. By including a tetrahydro ring, the viscosity stability of the composition and the adhesion of the cured layer are improved.
The content of the monofunctional ethylenically unsaturated monomer having a heterocyclic structure in the total mass of the monofunctional ethylenically unsaturated monomer is preferably 60 to 100 mass%, more preferably 70 to 100 mass%, still more preferably 80 to 100 mass%, and particularly preferably 85 to 100 mass%.

The monofunctional ethylenically unsaturated monomer has the effect of significantly reducing the viscosity of the active energy ray curable composition, improving the smoothness of the coating film, and further improving the abrasion resistance. From the above viewpoint, the content of the monofunctional ethylenically unsaturated monomer in the total mass of the active energy ray curable composition is preferably 30 to 60 mass%, more preferably 35 to 55 mass%, and even more preferably 40 to 50 mass%. In addition, the mass ratio of the polyfunctional urethane acrylate to the monofunctional ethylenically unsaturated monomer is preferably 10:90 to 50:50, preferably 20:80 to 40:60, and even more preferably 25:75 to 35:65.

<Difunctional ethylenically unsaturated monomer>
The composition of the present invention also preferably contains a difunctional ethylenically unsaturated monomer. Suitable examples of the difunctional ethylenically unsaturated monomer include polyethylene glycol 200 diacrylate, polyethylene glycol 300 diacrylate, polyethylene glycol 400 diacrylate, polyethylene glycol 600 diacrylate, polyethylene glycol 1000 diacrylate, and tetraethylene glycol diacrylate, and those containing an ether structure are preferred. The difunctional ethylenically unsaturated monomer is preferably contained in an amount of 0 to 15% by mass, more preferably 0 to 7% by mass, based on the total mass of the composition.
The difunctional ethylenically unsaturated monomer does not include the above-mentioned polyfunctional urethane acrylate.

<Resin fine particles>
In the present invention, the resin fine particles are responsible for the functions of abrasion resistance, matte finish, and blocking resistance. The resin fine particles preferably have an average particle size of 1 to 10 μm, more preferably 1.5 to 8 μm, even more preferably 2 to 6 μm, and even more preferably 2 to 3 μm. The average particle size referred to here refers to the volume average particle size measured by a laser diffraction method, and can be measured, for example, using a T330EXII manufactured by Microtrack Bell.
The resin fine particles are contained in an amount of preferably 10 to 40% by mass, more preferably 15 to 35% by mass, and further preferably 20 to 30% by mass, based on the total mass of the active energy ray-curable composition.

Specific examples of suitable resin microparticles include, for example, urethane resin microparticles, silicone resin microparticles, melamine resin microparticles, melamine-benzoguanamine resin microparticles, acrylic resin microparticles (e.g., polymethyl methacrylate resin microparticles), acrylic-styrene copolymer resin microparticles, polycarbonate resin microparticles, polyethylene resin microparticles, polystyrene resin microparticles, and benzoguanamine resin microparticles. These may be used alone or in combination of two or more kinds. Among these, urethane resin microparticles are more preferred. The above resin microparticles may be used in combination of two or more kinds as necessary.

Specific examples of urethane resin microparticles include crosslinked urethane beads such as Art Pearl C-1000 transparent, Art Pearl C-600 transparent, Art Pearl C-400 transparent, Art Pearl C-800, Art Pearl MM-120T, Art Pearl JB-800T, Art Pearl JB-600T, Art Pearl P-800T, and Art Pearl P-400T (manufactured by Negami Chemical Industries Co., Ltd.).

Specific examples of silicone resin microparticles include KMP-594, KMP-597, KMP-598, KMP-600, KMP-601, and KMP-602 (manufactured by Shin-Etsu Chemical Co., Ltd.), Trefil E-506S, and EP-9215 (manufactured by Dow Corning Toray Co., Ltd.).

Specific examples of melamine resin fine particles include Eposter SS, Eposter S, Eposter FS, Eposter S6, and Eposter S12 (manufactured by Nippon Shokubai Co., Ltd.).
A specific example of the melamine-benzoguanamine resin fine particles is Eposter M30 (manufactured by Nippon Shokubai Co., Ltd.).

Specific examples of acrylic resin fine particles include Eposter MA1002, Eposter MA1004, Eposter MA1006, and Eposter MA1010 (manufactured by Nippon Shokubai Co., Ltd.), Tuftic FH-S005, Tuftic FH-S008, Tuftic FH-S010, Tuftic FH-S015, and Tuftic FH-S020 (manufactured by Toyobo Co., Ltd.), and Chemisnow M.
Examples of the polymerizable compound include X-80H3wT, MX-150, MX-180TA, MX-300, MX-500, MX-1000, MX-1500H, MX-2000, and MX-3000 (manufactured by Soken Chemical Engineering Co., Ltd.).

Specific examples of acrylic-styrene copolymer resin microparticles include Eposter MA2003 (manufactured by Nippon Shokubai Co., Ltd.), FS-102, FS-201, FS-301, MG-451, MG-351 (manufactured by Nippon Paint Industrial Coatings Co., Ltd.), etc.

Specific examples of polycarbonate resin microparticles include the microparticles described in JP-A-2014-125495, the microparticles obtained by the manufacturing method described in JP-A-2011-26471, and the microparticles obtained by the method described in JP-A-2001-213970.

Specific examples of polyethylene resin microparticles include Mipelon XM-220 and XM221U (manufactured by Mitsui Chemicals, Inc.), and Flow Beads LE-1080 (manufactured by Sumitomo Seika Chemicals, Inc.).

Specific examples of polystyrene-based microparticles include Chemisnow SX-130H, SX-350H, and SX-500H (manufactured by Soken Chemical & Engineering Co., Ltd.).

Specific examples of benzoguanamine resin microparticles include Eposter MS, Eposter M05, and Eposter L15 (manufactured by Nippon Shokubai Co., Ltd.).

<Photopolymerization initiator>
The active energy ray curable composition of the present invention also contains a photopolymerization initiator. The photopolymerization initiator generates radicals by active energy such as light irradiation or heating, and initiates a crosslinking reaction and a polymerization reaction of the acrylate group of the polyfunctional urethane acrylate or the monofunctional ethylenically unsaturated monomer. Suitable examples of the photopolymerization initiator include acetophenone-based photopolymerization initiators, alkylphenone-based photopolymerization initiators, benzoin-based photopolymerization initiators, benzophenone-based photopolymerization initiators, and acylphosphine oxide-based photopolymerization initiators, among which acetophenone-based photopolymerization initiators and acylphosphine oxide-based photopolymerization initiators are preferred. The photopolymerization initiator is preferably contained in an amount of 1 to 10% by mass, more preferably 2 to 7% by mass, and even more preferably 3 to 5% by mass, based on the total mass of the composition.

The acetophenone-based photopolymerization initiator may be 4-phenoxydichloroacetophenone, diethoxyacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-(4-isopropylphenyl)-2-hydroxy-2-methylpropan-1-one, 1-hydroxycyclohexylphenyl ketone, 4-(2-hydroxyethoxy)-phenyl(2-hydroxy-2-propyl)ketone, 2-methyl-[4-(methylthio)phenyl]-2-morpholino-1-propanone, or 2,2-dimethoxy-2-phenylacetophenone.

Examples of alkylphenone photopolymerization initiators include 2,2-dimethoxy-1,2-diphenylethane-1-one, 1-hydroxy-cyclohexyl-phenyl-ketone, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propan-1-one, 2-hydroxy-1-{4-[4-(2-hydroxy-2-methyl-propionyl)-benzyl]phenyl}-2-methyl-propan-1-one, 2-methyl-1-(4-methylthiophenyl)-2-morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone-1, 2-(dimethylamino)-2-[(4-methylphenyl)methyl]-1-[4-(4-morpholinyl)phenyl]-1-butanone, and the like.

Examples of benzoin-based photopolymerization initiators include benzoin, benzoin methyl ether, benzoin isoethyl ether, benzoin isopropyl ether, and benzoin isobutyl ether.

Examples of the benzophenone-based photopolymerization initiator (d-1) include benzophenone, 4-methylbenzophenone, 4,4'-bis(dimethylamino)benzophenone, 4,4'-bis(diethylamino)benzophenone, methyl-o-benzoylbenzoate, benzoylbenzoic acid, methyl benzoylbenzoate, 4-phenylbenzophenone, hydroxybenzophenone, 4-benzoyl-4'-methyldiphenyl sulfide, and 3,3-dimethyl-4-methoxybenzophenone. Of these, 4-methylbenzophenone is preferred.

Thioxanthone-based photopolymerization initiators include thioxanthone, 2-chlorothioxanthone, 2,4-dichlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, isopropylthioxanthone, and 2,4-diisopropylthioxanthone.

Anthraquinone-based photopolymerization initiators include α-acyloxime ester, benzil, methylbenzoyl formate ("Biacure 55"), 2-ethylanthraquinone, etc.

Examples of acylphosphine oxide photopolymerization initiators include 2,4,6-trimethylbenzoyldiphenylphosphine oxide ("OmniradTPO"), bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide ("Omnirad819"), etc.

The photopolymerization initiator may be used alone or in combination of two or more.

<Organic Solvent in Composition>
It is more effective in solving the problems of the present invention that the composition contains no organic solvent or has an organic solvent content of 5 mass % or less, because within this range, printability is improved and the coating properties of the printed matter are improved.

<Viscosity of Composition>
The viscosity of the composition is preferably 250 to 2500 mPa·s at 25°C, more preferably 500 to 2000 mPa·s. Within this range, the effect of suppressing excessive penetration into paper substrates and the like after coating by printing or the like is high. In addition, there is an advantage that the surface of the cured layer becomes a uniform film and is less likely to cause spots. In addition, the viscosity referred to here is an assumed value according to the method described in JIS K5600-2, and can be measured, for example, using a cone-plate type viscometer using a cone with a cone diameter of 35 mm and a cone angle of 2° at a shear rate of 100 per second in a 25°C environment.

<Additives>
The active energy ray-curable composition of the present invention can appropriately contain known additives. For example, a leveling agent, a polymerization inhibitor, an ultraviolet absorber, a light stabilizer, a sensitizer, a curing agent, a plasticizer, a wetting agent, an adhesion aid, an antifoaming agent, an antistatic agent, etc. can be used, and there are no particular limitations.

<Leveling Agent>
The active energy ray curable composition of the present invention preferably contains a leveling agent, and the leveling agent is preferably contained in an amount of 1 to 10 mass %, more preferably 2 to 8 mass %, and even more preferably 3 to 7 mass % of the total mass of the active energy ray curable composition. In addition, it is preferable to use a silicon acrylate as the leveling agent. By using a silicon acrylate, the friction resistance becomes good.

<Silicon acrylate>
Specific examples of silicone acrylates include TEGO Rad 2100, TEGO Rad 2200 N, TEGO Rad 2250, TEGO Rad 2300, TEGO Rad 2500, TEGO Rad 2550, TEGO Rad 2650, TEGO Rad 2700, TEGO Rad 2800 (manufactured by Evonik), BYK-UV 3500, BYK-UV 3505, BYK-UV 3530, BYK-UV 3570, BYK-UV 3575, and BYK-UV 3576 (manufactured by BYK).

<Production of active energy ray-curable composition>
The active energy ray curable composition can be produced by stirring a polyfunctional urethane acrylate having a weight average molecular weight of 3,000 to 20,000, a monofunctional ethylenically unsaturated monomer, resin fine particles, and a photopolymerization initiator for about 30 minutes to 3 hours using a bladed stirrer (disper), etc. If mixing is difficult and the viscosity, etc., tends to become non-uniform, a roller mill, ball mill, pebble mill, attritor, sand mill, etc. may be used.

When the active energy ray-curable composition of the present invention contains air bubbles or unexpectedly large particles, these particles deteriorate the quality of the printed matter, and therefore it is preferable to remove them by filtration, etc. As the filter, a conventionally known filter can be used.

<Production of Laminate>
The method for producing the laminate of the present invention is not particularly limited, but is preferably formed by coating and curing the active energy ray curable composition on a paper substrate or a film substrate. A printed layer made of a printing ink composition may be formed on the substrate, and the active energy ray curable composition of the present invention may be printed and cured on the printed layer to form a laminate. The cured layer formed from the active energy ray curable composition preferably has a thickness of 1 to 30 μm, more preferably 1 to 20 μm, even more preferably 1 to 10 μm, and particularly preferably 1 to 5 μm.

The method for applying the active energy ray-curable composition is not particularly limited, and examples include wet coating methods such as spraying, showering, dipping, flow coating, gravure printing, flexographic printing, roll coater, spin, dispenser, inkjet printing, screen printing, etc. Among these, flexographic printing, screen printing, and roll coater are preferred.

Ultraviolet rays for curing active energy ray-curable compositions include far ultraviolet rays, ultraviolet rays, and near ultraviolet rays. On the other hand, it is also possible to use electron beams or proton beams, in which case curing can be achieved without using a photopolymerization initiator, but curing by ultraviolet irradiation is preferred in terms of curing speed, ease of availability of irradiation equipment, cost, etc.

The method of curing by ultraviolet irradiation may be carried out using a high pressure mercury lamp, ultra-high pressure mercury lamp, carbon arc lamp, metal halide lamp, xenon lamp, chemical lamp, electrodeless discharge lamp, LED or the like that emits light in the wavelength range of 150 to 450 nm, with an integrated light quantity of 30 to 5000 mJ/cm ² , preferably 100 to 1000 mJ/cm ^2. After ultraviolet irradiation, heating may be carried out as necessary to ensure complete curing.

The film thickness when applying the active energy ray-curable composition (film thickness after curing) is usually preferably 1 to 50 μm, more preferably 1 to 30 μm, and particularly preferably 1 to 10 μm. Within this range, there is no curing inhibition, the UV irradiation time can be shortened, and productivity is good.

<Paper base material>
In the present invention, the substrate is preferably a paper substrate. The paper substrate is preferably ordinary paper or cardboard, and although there is no particular designation for the thickness, a substrate having a thickness of 0.2 mm to 1.0 mm can be preferably used, and the printed surface may be corona-treated. In addition, the surface of the paper substrate may be vapor-deposited with a metal such as aluminum for the purpose of imparting design, and may further be surface-coated with an acrylic resin, a urethane resin, a polyester resin, a polyolefin resin, or other resin, and may further be surface-treated, such as corona treatment. For example, coated cardboard and Marie-coated paper are preferably used.

<Film substrate>
The film substrate used in the present invention is preferably a normal PET (polyethylene terephthalate) or PVC (polyvinyl chloride), and is not particularly limited. The film thickness is preferably 0.02 mm to 1.0 mm, and the substrate surface may be corona-treated. The film substrate may be surface-coated with acrylic resin, urethane resin, polyester resin, polyolefin resin, or other resin, and may further be surface-treated, such as corona treatment. Examples include Cosmoshine A4300 (manufactured by Toyobo), E5101 (manufactured by Toyobo), and Crisper K2323 (manufactured by Toyobo).

<Printing ink composition>
Examples of the printing ink composition include known gravure ink compositions, flexographic ink compositions, ultraviolet-curable flexographic ink compositions, offset ink compositions, ultraviolet-curable offset ink compositions, and other ink compositions, and any printing ink composition may be used. Among them, when an ultraviolet-curable offset ink composition or an ultraviolet-curable flexographic ink composition is used, if an active energy ray-curable composition is laminated, a curing reaction caused by ultraviolet light or the like occurs between the layers, improving adhesion. Therefore, as the printing ink composition, an ultraviolet-curable offset ink composition or an ultraviolet-curable flexographic ink composition is more preferable.

<Printing with printing ink>
Known methods can be used as the printing method for the printing ink composition. Examples include gravure printing, flexographic printing, offset printing, and screen printing. The thickness of the ink layer is preferably 0.1 to 15 μm, and more preferably 0.5 to 12 μm. The printing ink composition may be either an organic solvent-based or water-based ink composition, or may be an ultraviolet-curable ink composition. The ink layer may be formed by combining the above printing ink compositions, and the printing layer can be formed by drying or ultraviolet curing after printing.

The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. Note that parts and % in the present invention represent parts by mass and % by mass unless otherwise noted.

<Hydroxyl value>
The measurement was performed according to the method described in JIS K0070.
<Weight average molecular weight>
The weight average molecular weight was determined by measuring the molecular weight distribution using a GPC (gel permeation chromatography) device (HLC-8220 manufactured by Tosoh Corporation) and calculating the molecular weight converted using polystyrene as a standard substance. The measurement conditions are shown below.
Columns: The following columns were used in series connection:
Tosoh Corporation TSKgel Super AW2500
Tosoh Corporation TSKgel Super AW3000
Tosoh Corporation TSKgel Super AW4000
Tosoh Corporation TSK gelguard column Super AWH
Detector: RI (differential refractometer)
Measurement conditions: column temperature 40°C
Eluent: tetrahydrofuran Flow rate: 1.0 mL/min

<Glass transition temperature>
The glass transition temperature (Tg) was determined by DSC (differential scanning calorimetry). The measurement was performed using a Rigaku Corporation DSC8231 instrument, with a measurement temperature range of −70 to 150° C., a heating rate of 10° C./min, and the midpoint between the endothermic start and end temperatures due to the glass transition in the DSC curve was taken as the glass transition temperature.

<Synthesis Example of Urethane Acrylate (UA1)>
In a reactor equipped with a thermometer, a stirrer, a reflux condenser, a stirring device and a nitrogen gas inlet tube, 1001 parts (4 moles) of diphenylmethane diisocyanate, 1000 parts (1 mole) of polyethylene glycol having a number average molecular weight of 1000 and 4000 parts (2 moles) of polyethylene glycol having a number average molecular weight of 2000 were mixed and reacted at 80°C for 4 hours while stirring to obtain a terminal isocyanate prepolymer. Next, 232 parts (2 moles) of 2-hydroxyethyl acrylate and 1.247 parts (500 ppm) of p-methoxyphenol were charged into the obtained terminal isocyanate prepolymer, and the mixture was stirred while feeding air and reacted at 80°C for 4 hours. After confirming the disappearance of the peak due to the isocyanate group in the IR spectrum and terminating the reaction, the mixture was cooled to 40°C to obtain a pale yellow liquid (UA1). The weight average molecular weight of the urethane acrylate UA1 was 5100, the Tg was -30°C and the number of functional groups was 2.

Urethane acrylates (UA2 to UA11) were synthesized in the same manner as in the above synthesis examples, except that the raw material compounds shown in Table 1 were used.
The abbreviations for each raw material compound in Table 1 are shown below.

MDI: diphenylmethane diisocyanate IPDI: isophorone diisocyanate Sumidur N3390: hexamethylene diisocyanate trimer (manufactured by Sumika Bayer Urethane Co., Ltd.)
PEG1000: Polyethylene glycol (polyether polyol) with a number average molecular weight of 1000
PEG2000: Polyethylene glycol (polyether polyol) with number average molecular weight of 2000
PEG6000: Polyethylene glycol (polyether polyol) with a number average molecular weight of 6000
PTG2000: Polytetramethylene glycol (polyether polyol) with a number average molecular weight of 2000
PMPA2000: Poly(3-methyl-1,5-pentane adipate)diol having a number average molecular weight of 2000 NISSO-PB G-1000: Polybutadiene having hydroxyl groups at both ends and having a number average molecular weight of 1400 (manufactured by Nippon Soda Co., Ltd.)
2HEA: 2-hydroxyethyl acrylate

(Example 1: Preparation of active energy ray-curable composition S1)
19 parts of urethane acrylate UA1, 47 parts of THFA (tetrahydrofurfuryl acrylate), 25 parts of ARTPEARL MM-120T (urethane-based fine particles, average particle size 2 μm, glass transition temperature "Tg" 22°C, manufactured by Negami Chemical Industrial Co., Ltd.), 3 parts of Omnirad184 (1-hydroxycyclohexyl phenyl ketone, manufactured by IGM), 1 part of Omnirad819 (bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, manufactured by IGM), and 5 parts of silicon acrylate (TEGO Rad 2100, manufactured by Evonik) as a leveling agent were mixed and stirred for 90 minutes with a bladed stirrer to obtain an active energy ray curable composition S1. The abbreviations of the raw materials in Table 2 are shown below.

<Monofunctional ethylenically unsaturated monomer>
・4HBA: 4-hydroxybutyl acrylate ・ACMO: acryloylmorpholine ・CTFA: cyclic trimethylolpropane formal acrylate <bifunctional ethylenically unsaturated monomer>
TEGDA: Tetraethylene diacrylate (resin particles)
・ARTPEARL C-800 transparent: urethane resin fine particles, average particle diameter 6 μm, Tg = -13 ° C, manufactured by Negami Chemical Industrial Co., Ltd. ・ARTPEARL C-1000 transparent: urethane resin fine particles, average particle diameter 3 μm, Tg = -13 ° C, manufactured by Negami Chemical Industrial Co., Ltd. ・ARTPEARL J-4P: acrylic resin fine particles, average particle diameter 2.2 μm, manufactured by Negami Chemical Industrial Co., Ltd. ・Sylosphere C-1504: spherical silica, average particle diameter 4.5 μm, manufactured by Fuji Silysia Chemical Co., Ltd. <Photopolymerization initiator>
Omnirad TPO: 2,4,6-trimethylbenzoyldiphenylphosphine oxide, manufactured by IGM Omnirad 1173: 2,4,6-trimethylbenzoyldiphenylphosphine oxide, manufactured by IGM <Additives>
Silicone type leveling agent: TEGO Glide 420, manufactured by Evonik Non-silicon leveling agent: BYK 350, manufactured by BYK <Organic solvent>
PGM-AC: Propylene glycol monomethyl ether acetate

(Examples 2 to 28: Preparation of active energy ray-curable compositions S2 to S28)
Active energy ray-curable compositions S2 to S28 were obtained in the same manner as in Example 1, except that the raw materials shown in Table 2-1 were used in the described blending ratios.

(Comparative Examples 1 to 5: Preparation of Active Energy Ray-Curable Compositions T1 to T5)
Active energy ray-curable compositions T1 to T5 were obtained in the same manner as in Example 1, except that the raw materials shown in Table 2-2 were used in the described blending ratios.

<Evaluation method and criteria>
Each of the active energy ray curable compositions obtained in the above Examples and Comparative Examples was printed using a sheet-fed printing machine "Lithrone 26 (manufactured by Komori Corporation)". First, a UV-curable offset ink "FD Carton X Ink M (manufactured by Toyo Ink Co., Ltd., containing a multifunctional (meth)acrylic monomer having three or more functionalities)" was printed on a paper substrate, Aurora Coat (coated paper high gloss type, paper thickness 81 μm, manufactured by Nippon Paper Industries Co., Ltd.), so that the ink density was 1.75 (measuring device: X-Rite eXact (manufactured by X-Rite Co., Ltd.), conditions: Illuminant D50, standard observer 2°, density status E, no filter), and cured with a UV lamp. The printing speed of the above printing was 8000 sheets/hour, the types of UV lamps were two air-cooled metal halide lamps and one high-pressure mercury lamp, and the intensity of the UV lamps was 160 W/cm for all three lamps (accumulated light amount 450 mJ/cm ² ).
Next, each active energy ray curable composition (S1 to S26, T1 to T5) was applied onto the printed matter of FD Karton X Ink M obtained above using a flexo coating unit of Lithrone 26, and cured with a UV lamp to obtain the corresponding laminate (G1 to G26, H1 to H5). The anilox roll of the coating unit had a trihelical engraved pattern, a line count of 90 lines/inch, and a cell volume of 25 ml/ ^m2 . During flexo coating, the printing speed was 8000 sheets/hour, and the temperature was controlled so that the liquid temperature of S1 was 25°C. The type, number, and intensity of the UV lamp were the same as those of the curing conditions for FD Karton X Ink M described above.

<Viscosity stability>
The viscosity change rate was measured for the active energy ray curable compositions obtained in the examples and comparative examples. The viscosity change rate is a value obtained by measuring the viscosity before and after heating, dividing the viscosity after heating by the viscosity before heating, and expressing the value as a percentage (%). The above-mentioned heating is a process in which the active energy ray curable composition is poured into a cylindrical metal container with an inner diameter of 9.6 cm and a height of 3.0 cm to a thickness of 1 cm, and then left in a 40°C environment for 30 minutes. The viscosity was measured using a cone-plate type viscometer under a liquid temperature condition of 25°C. The evaluation criteria are as follows.
5 (Excellent): Viscosity change rate of 0% or more but less than 3% 4 (Good): Viscosity change rate of 3% or more but less than 6% 3 (Acceptable): Viscosity change rate of 6% or more but less than 9% 2 (Unacceptable): Viscosity change rate of 9% or more but less than 12% 1 (Poor): Viscosity change rate of 12% or more Note that ratings of 3, 4 and 5 are suitable for practical use.

<Adhesion>
For the laminates obtained in the Examples and Comparative Examples, 100 cross-cuts of 1 ^mm2 were made on the cured layer using a checkerboard peeling test tool. Then, adhesive tape (LP24, manufactured by Nichiban Co., Ltd.) was attached to the cross-cuts and peeled off in a 90-degree direction, and the number of remaining checkerboards on the cured layer was counted. The evaluation criteria were as follows:
5 (Excellent): Number of remaining squares = 100 (no peeling)
4 (Good): Number of remaining squares = 96 or more but less than 100 3 (Acceptable): Number of remaining squares = 90 or more but less than 96 2 (Unacceptable): Number of remaining squares = 86 or more but less than 90 1 (Poor): Number of remaining squares = less than 86 Note that ratings of 3, 4 and 5 are suitable for practical use.

<Abrasion resistance>
The laminates obtained in the examples and comparative examples were set in a Southerland Rub Tester (manufactured by Toyo Seiki Seisakusho) so that the hardened layers were in contact with each other, and after a load of 2 pounds was applied and the laminates were reciprocated a predetermined number of times, the hardened layers were peeled off to reveal the base, and the abrasion resistance was evaluated by visually checking. The evaluation criteria were as follows.
5 (Excellent): The hardened layer did not peel off even after 10,000 reciprocations, and the base was not visible.
4 (good): After 10,000 strokes, the hardened layer peeled off and the base was visible, but after 9,000 strokes, the base was no longer visible.
3 (Fair): After 9,000 strokes, the hardened layer peeled off and the base was visible, but after 8,000 strokes, the base was not visible.
2 (unacceptable): After 8,000 strokes, the hardened layer peeled off and the base was visible, but after 7,000 strokes, the base was no longer visible.
1 (poor): Even after 7,000 strokes, the hardened layer peeled off and the base was visible.
The practically usable ratings are 3, 4 and 5.

<Moisture and heat resistance>
The laminates obtained in the examples and comparative examples were exposed to an atmosphere at 60°C and 90% humidity for 48 hours, and then 100 crosscuts of 1 ^mm2 were made on the cured layer using a checkerboard peeling test tool. Then, adhesive tape (LP24, manufactured by Nichiban Co., Ltd.) was attached to the crosscuts and peeled off in a 90° direction, and the number of remaining checkerboards on the cured layer was counted. The evaluation criteria were as follows.
5 (Excellent): Number of remaining squares = 90 or more4 (Good): Number of remaining squares = 80 to less than 903 (Acceptable): Number of remaining squares = 75 to less than 802 (Unacceptable): Number of remaining squares = 70 to less than 751 (Poor): Number of remaining squares = less than 70Note that ratings of 3, 4 and 5 are suitable for practical use.

A practically usable active energy ray curable composition is one that simultaneously satisfies stable printability and good film properties. In other words, it simultaneously satisfies a viscosity stability rating of 3 or higher and a rating of 3 or higher in all of the following categories: adhesion, abrasion resistance, and moist heat resistance.

From the above examples, an active energy ray curable composition containing a polyfunctional urethane (meth)acrylate, a monofunctional ethylenically unsaturated monomer, and resin fine particles, in which the weight average molecular weight of the polyfunctional urethane (meth)acrylate is 3,000 to 20,000, and the hydroxyl value of the solid content of the active energy ray curable composition is 30 mg KOH/g or less, has good printability (viscosity stability) and excellent cured film properties such as adhesion, abrasion resistance, and moist heat resistance, and can be obtained.

Since it does not contain organic solvents or uses only a small amount of them, this active energy ray-curable composition is useful as a low-gloss coating agent with low environmental impact.

Claims (9)

An active energy ray-curable matte coating varnish containing a multifunctional urethane (meth)acrylate, a monofunctional ethylenically unsaturated monomer, and resin fine particles,
the polyfunctional urethane (meth) acrylate has a weight average molecular weight of 3,000 to 20,000 and is contained in an amount of 5 to 40% by mass based on the total mass of the active energy ray-curable matte coating varnish;
the monofunctional ethylenically unsaturated monomer is contained in an amount of 30 to 60% by mass based on the total mass of the active energy ray-curable matte coating varnish;
the resin fine particles have a volume average particle diameter of 1 to 10 μm and are contained in an amount of 10 to 40% by mass based on the total mass of the active energy ray-curable matte coating varnish;
The active energy ray-curable matte coating varnish has a hydroxyl value of a solid content of 30 mgKOH/g or less.
(However, this does not include the case where the resin fine particles are black resin particles.) The active energy ray-curable matte coating varnish according to claim 1, wherein the monofunctional ethylenically unsaturated monomer has a heterocyclic structure. The active energy ray-curable matte coating varnish according to claim 1 further contains a photopolymerization initiator. The active energy ray-curable matte coating varnish according to claim 1, wherein the multifunctional urethane (meth)acrylate has a structural unit derived from polyether. The active energy ray-curable matte coating varnish according to claim 1, wherein the resin fine particles are urethane resin fine particles. The active energy ray-curable matte coating varnish according to claim 1 further contains silicone acrylate. The active energy ray-curable matte coating varnish according to claim 1, which is for use on paper substrates. A laminate having a printed layer and a cured layer formed from the active energy ray-curable matte coating varnish described in any one of claims 1 to 7 on a paper substrate. A method for producing a laminate, comprising applying the active energy ray-curable matte coating varnish according to any one of claims 1 to 7 onto a substrate by any one of flexographic printing, screen printing, and roll coating, and curing the applied coating varnish.