JP7707660B2 - Method for manufacturing active energy ray curable screen printing ink, printed matter, and molded printed matter - Google Patents

Description

The present invention relates to an active energy beam-curable screen printing ink and a printed article using the same. In particular, the present invention relates to an active energy beam-curable screen printing ink that has good adhesion to plastic substrates, is excellent in chemical resistance, post-processing properties, and flexibility of the cured coating film, and contains 10% by mass or more of biomass-derived components, and to a printed article using the same.

Conventionally, active energy ray-curable screen printing inks can be cured by short-term exposure to active energy rays such as ultraviolet rays, visible light, and electron beams, and are widely used in fields where durability is required because they are highly productive and can provide high coating resistance.

When the substrate to be printed is a plastic substrate, this active energy ray curable screen printing ink faces the problem that good adhesion cannot be obtained depending on the type of plastic, particularly with olefin-based substrates such as polyethylene and polypropylene, which have low polarity, and with polyethylene substrates, and there are also required physical properties such as chemical resistance, flexibility, and suitability for post-processing as coating performance, and various studies are being conducted.

On the other hand, in recent years, as part of efforts to reduce the environmental impact, the Japan Organics Resources Association has established a new biomass mark system, which calls for replacing raw materials in inks with biomass-derived raw materials and increasing their ratio. However, when the ratio of biomass-derived raw materials is increased in active energy ray-curable inks, there is an issue that physical properties such as sufficient adhesion to the substrate and coating resistance cannot be obtained.

For example, Patent Document 1 discloses an active energy ray-curable resin composition that contains 5 to 95% by weight of rosin epoxy acrylate, 5 to 95% by weight of a polyurethane resin having a number average molecular weight of 1,000 to 50,000 and a carbon-carbon unsaturated bond group, and 0 to 70% by weight of a reactive diluent. However, although the biomass ratio is increased by using rosin epoxy acrylate, the adhesion to plastic substrates is insufficient. Furthermore, since both the rosin epoxy acrylate and the polyurethane resin are monofunctional, there are problems with the coating resistance.

For example, Patent Document 2 discloses an active energy ray-curable resin composition containing a monofunctional polyether-based polymerizable oligomer. However, although the use of a monofunctional oligomer having a flexible polyether structure improves adhesion to a polyethylene terephthalate substrate, there are problems with adhesion to a polystyrene substrate. In addition, biomass-derived raw materials are not used, and it can be said that the environmental friendliness is insufficient.

Japanese Patent Application Publication No. 8-143635 JP 2004-339487 A

The present invention provides an active energy ray-curable screen printing ink and printed matter that have good adhesion to plastic substrates, excellent chemical resistance, post-processing properties, and flexibility of the cured coating film, and that contain biomass-derived components in an amount of 10% by mass or more.

As a result of extensive research into solving the above problems, the inventors discovered that the above problems could be solved by the active energy ray-curable screen printing ink and printed matter described below, and thus completed the present invention.

That is, the present invention relates to an active energy ray-curable screen printing ink that contains a colorant, a binder resin containing a plant-based modified acrylate, and resin particles.

The present invention also relates to the above-mentioned active energy ray-curable screen printing ink, in which the plant component-modified acrylate includes a rosin-modified polyester acrylate and/or a vegetable oil-modified polyepoxy acrylate.

The present invention also relates to the above-mentioned active energy ray-curable screen printing ink, in which the content of the plant component-modified acrylate is 5 to 30 mass % based on the total mass of the active energy ray-curable screen printing ink.

The present invention also relates to the above-mentioned active energy ray-curable screen printing ink, in which the binder resin further contains a urethane acrylate.

The present invention also relates to the above-mentioned active energy ray-curable screen printing ink, in which the glass transition temperature of the urethane acrylate alone cured product is -50 to 50°C.

The present invention also relates to the above-mentioned active energy ray-curable screen printing ink, in which the resin particles are biomass resin particles.

The present invention also relates to the above-mentioned active energy ray-curable screen printing ink, which further contains a non-silicone compound defoamer in an amount of 0.1 to 5 mass % based on the total amount of the ink.

The present invention also relates to a printed material having a cured printing layer made of the above-mentioned active energy ray-curable screen printing ink on a substrate.

The present invention also relates to the above printed material, in which the substrate is a molded plastic.

The present invention also relates to a method for producing a molded printed product, which includes a step of printing the above-mentioned active energy ray-curable screen printing ink on molded plastic.

The present invention makes it possible to provide an active energy beam-curable screen printing ink and printed matter that have good adhesion to plastic substrates, excellent chemical resistance, post-processing properties, and flexibility of the cured coating film, and that contain 10% or more by mass of biomass-derived components in the ink.

The constituent elements of the present invention are described in detail below, but the following description is only a part of the embodiment of the present invention and is not limited to these. In addition, unless otherwise specified, "parts" means "parts by mass" and "%" means "% by mass."

In the following description, "(meth)acrylic" refers to "acrylic and/or methacrylic", "(meth)acrylate" refers to "methacrylate and/or acrylate", and "(meth)acroyl" refers to "methacryloyl and/or acryloyl".
In the following description, a polymerizable oligomer refers to a compound having a polymerizable group and a molecular weight of 1,000 or more, and a polymerizable monomer refers to a compound having a polymerizable group and a molecular weight of less than 1,000. A polymerizable group refers to an acrylate group, a methacrylate group, or another polymerizable unsaturated double bond group.

[Active energy ray curable screen printing ink]
The active energy ray-curable screen printing ink of the present invention is characterized by comprising a colorant, a binder resin containing a plant-component modified acrylate, and resin particles.
By including a plant-component modified acrylate in the binder resin, pigment dispersibility, coating film flexibility, and biomass degree are improved, and by including resin particles, printability and coating film flexibility are improved, and preferably, by including biomass resin particles, the biomass degree is improved.

The following describes the components that are or can be included in the active energy ray-curable screen printing ink of this embodiment (hereinafter, sometimes simply referred to as "screen ink" or "ink").

[Coloring agent]
The active energy ray-curable screen printing ink of the present invention contains a colorant. As the colorant, at least one of a pigment and a dye can be used. From the viewpoint of light resistance, a pigment is preferred.
The pigment that can be used in the present invention is not particularly limited, and any known pigment can be used. Both inorganic and organic pigments can be used.

The above inorganic pigments include carbon blacks such as furnace black, lamp black, acetylene black, and channel black, iron oxide, and titanium oxide.

The above organic pigments include soluble azo pigments such as β-naphthol, β-oxynaphthoic acid, β-oxynaphthoic acid anilide, acetoacetate anilide, and pyrazolone; Insoluble azo pigments such as β-naphthol, β-oxynaphthoic acid anilide, acetoacetate anilide monoazo, acetoacetate anilide disazo, and pyrazolone; phthalocyanine pigments such as copper phthalocyanine blue, halogenated (e.g., chlorinated or brominated) copper phthalocyanine blue, sulfonated copper phthalocyanine blue, and metal-free phthalocyanine; polycyclic pigments and heterocyclic pigments such as quinacridone, dioxazine, threne (pyranthrone, anthanthrone, indanthrone, anthrapyrimidine, flavanthrone, thioindigo, anthraquinone, perinone, perylene, etc.), isoindolinone, metal complex, quinophthalone, and diketopyrrolopyrrole.

More specifically, in terms of the C.I. Color Index, black pigments include C.I. Pigment Black 1, 6, 7, 9, 10, 11, 28, 26, 31, etc.

White pigments include C.I. Pigment White 5, 6, 7, 12, 28, etc.

Examples of yellow pigments include C.I. Pigment Yellow 1, 2, 3, 12, 13, 14, 16, 17, 18, 24, 73, 74, 75, 83, 93, 95, 97, 98, 100, 108, 109, 110, 114, 120, 128, 129, 138, 139, 174, 150, 151, 154, 155, 167, 180, 185, and 213.

Blue or cyan pigments include C.I. Pigment Blue 1, 2, 14, 15, 15:1, 15:2, 15:3, 15:4, 60, 62, etc.

Red or crimson pigments include C.I. Pigment RED 1, 3, 5, 19, 21, 22, 31, 38, 42, 43, 48:1, 48:2, 48:3, 48:4, 48:5, 49:1, 50, 52, 53:1, 57:1, 57:2, 58:4, 63:1, 81, 81:1, 81:2, 81:3, 81:4, 83, 90, 104, 10 8, 112, 114, 122, 144, 146, 148, 149, 150, 166, 168, 169, 170, 172, 173, 176, 177, 178, 184, 185, 187, 193, 202, 209, 214, 242, 254, 255, 264, 266, 269, C.I. Pigment Violet 19, etc.

Green pigments include C.I. Pigment Green 1, 2, 3, 4, 7, 8, 10, 15, 17, 26, 36, 45, 50, etc.

Examples of purple pigments include C.I. Pigment Violet 1, 2, 3, 4, 5:1, 12, 13, 15, 16, 17, 19, 23, 25, 29, 31, 32, 36, 37, 39, and 42.
Orange pigments include C.I. Pigment Orange 13, 16, 20, 34, 36, 38, 39, 43, 51, 61, 63, 64, 74, and the like.

In the present invention, the above pigments may be used alone or in combination of two or more.

In the present invention, the pigment can be used in any content as long as the desired concentration can be reproduced on the printed surface, and it is preferably 1 to 40% by mass, more preferably 5 to 30% by mass, based on the total mass of the ink.

[Binder resin]
In the present invention, the binder resin refers to a resin that can function as a binding agent in the screen printing ink, and includes plant-based modified acrylates. Note that many plant-based modified acrylates are binder resins that fall under the category of polymerizable oligomers.

[Plant-modified acrylate]
The plant-modified acrylate contained in the active energy ray-curable screen printing ink of the present invention can be any plant-modified acrylate having a (meth)acrylate group. The plant-modified acrylate can improve pigment dispersibility and coating film flexibility, and can also increase the biomass ratio. Suitable examples of the plant-modified acrylate include rosin-modified polyester acrylate and/or vegetable oil-modified polyepoxy acrylate, and vegetable oil-modified urethane acrylate.

[Rosin modified polyester acrylate]
The rosin-modified polyester acrylate preferably has a ratio of rosin-derived structural units (hereinafter also referred to as "rosin content") of 40 to 80% by mass, and more preferably 40 to 60% by mass from the viewpoint of chemical resistance, of the total mass of the rosin-modified polyester acrylate. The weight-average molecular weight of the rosin-modified polyester acrylate is preferably 1,000 to 10,000, and more preferably 1,000 to 8,000. The rosin-modified polyester acrylate preferably has 2 to 6 (meth)acroyl groups, and more preferably has 3 to 6 (meth)acroyl groups.

Examples of rosin-modified polyester acrylate include, but are not limited to, those obtained by reacting a rosin-modified polyester compound obtained by subjecting a conjugated rosin acid to a Diels-Alder addition reaction with an ethylenically unsaturated double bond-containing compound having a carboxy group, and then esterifying the carboxy group of the reacting compound with a hydroxyl group of a polyol, with a (meth)acrylate compound having a hydroxyl group. Examples of the rosin-modified polyester acrylate include the "ETERCURE" series manufactured by Choko Materials Co., Ltd. and the "EBECRYL" series manufactured by Daicel-Allnex Corporation.

[Vegetable oil modified polyepoxy acrylate]
The vegetable oil-modified polyepoxy acrylate may be a known compound obtained by adding (meth)acrylic acid to the epoxy group of an epoxidized vegetable oil in which the double bonds of the unsaturated vegetable oil are epoxidized with peracetic acid or perbenzoic acid. The vegetable oil to be modified is preferably soybean oil, rapeseed oil, sunflower oil, corn oil, or the like. The vegetable oil-modified polyepoxy acrylate preferably has a vegetable oil-derived structure content of 40 to 80% by mass, more preferably 60 to 80% by mass. The weight-average molecular weight of the vegetable oil-modified polyepoxy acrylate is preferably 1,000 to 10,000, more preferably 1,000 to 8,000. The vegetable oil-modified polyepoxy acrylate preferably has 2 to 5 (meth)acryloyl groups, more preferably 2 to 4 (meth)acryloyl groups from the viewpoint of coating film flexibility.
Examples of the vegetable oil-modified polyepoxy acrylate include the "PHOTOMER" series manufactured by IGM Resins and the "EBECRYL" series manufactured by Daicel Allnex Corporation.

[Urethane acrylate]
In the screen ink of the present invention, the binder resin preferably further contains a urethane acrylate. Note that many urethane acrylates are polymerizable oligomers. The urethane acrylate has a (meth)acrylate group, and can be obtained, for example, by reacting a diisocyanate with a (meth)acrylate having a hydroxyl group, or by reacting a polyol with a polyisocyanate under conditions of excess isocyanate groups to obtain an isocyanate group-containing urethane prepolymer, with a (meth)acrylate having a hydroxyl group. Alternatively, it can be obtained by reacting a polyol with a polyisocyanate under conditions of excess hydroxyl groups to obtain a hydroxyl group-containing urethane prepolymer, with a (meth)acrylate having an isocyanate group.
In addition, urethane acrylates made from compounds modified from plant components, such as vegetable oil-modified diols, are treated as "plant component-modified acrylates."
The weight average molecular weight of the urethane acrylate is preferably 1,000 to 50,000, more preferably 1,000 to 30,000. The urethane acrylate preferably has 2 to 5 (meth)acroyl groups, more preferably 2 to 4. The glass transition temperature of the urethane acrylate alone cured product is preferably -50 to 50°C, more preferably -40 to 40°C from the viewpoint of a coating film performance with a good balance between flexibility and chemical resistance. The method for measuring the glass transition temperature will be described later.
Examples of the urethane acrylate include the "Shiko" series manufactured by Mitsubishi Chemical Corporation and the "AER RESIN" series manufactured by Negami Chemical Industries, Ltd.

In the present invention, the content of the urethane acrylate is preferably 1 to 50% by mass, and more preferably 10 to 30% by mass, based on the total mass of the screen ink.

The mass ratio of the plant-based modified acrylate to the urethane acrylate is preferably 10:90 to 80:20, and more preferably 30:70 to 80:20. The total mass of the screen ink preferably contains 20 to 80 mass% of the plant-based modified acrylate and urethane acrylate, and more preferably 20 to 60 mass%.

[Resin particles]
The resin particles used in the screen ink of the present invention are not limited as long as they are effective in the coating film performance such as the surface protection and chemical resistance of the ink layer and are particles (may be fine particles) made of resin. The resin particles are preferably biomass resin particles, and preferably contain, for example, a compound that is a natural product (including a plant-based compound). Suitable examples of the structure of the biomass resin particles include resin particles containing starch, cellulose, polylactic acid (PLA), polyglycolic acid (PGA), polyhydroxybutyric acid (PHB), and other polyhydroxyalkanoic acid (PHA). Resin particles containing polyhydroxyalkanoic acid (PHA) are more preferable. In addition, biomass resin particles using the above-mentioned natural product (including a plant-based compound) as a raw material and having a biomass degree of more than 0% (preferably 10% or more, or 20% or more) and less than 100% can also be suitably used.
The average particle size of the biomass resin particles is preferably 1 to 20 μm, more preferably 1 to 15 μm, and even more preferably 2 to 12 μm. The average particle size refers to the measured value of D50 in a laser diffraction/scattering method.
From the viewpoint of coating film performance, the melting point is preferably 100°C or higher and 250°C or lower, or 120°C or higher and 220°C or lower.
Examples of such resin particles include the "ARBOCEL" series manufactured by RETTENMAIER.

In the present invention, the above resin particles may be used alone or in combination of two or more types.

In the present invention, the content of the resin particles is preferably 1 to 20% by mass, more preferably 1 to 10% by mass, based on the total mass of the ink.

[Polymerization initiator]
The active energy ray curable ink of the present invention preferably contains a polymerization initiator. The polymerization initiator preferably contains a radical polymerization initiator, and more preferably contains a photopolymerization initiator. The polymerization initiator of the present invention is a compound that undergoes a chemical change through the action of light or through interaction with the electronically excited state of the sensitizing dye, generating, for example, radicals, and among these, a photoradical polymerization initiator is preferable from the viewpoint of being able to initiate polymerization by exposure to light. However, when the active energy ray is an electron beam or the like, a polymerization initiator may not be required.

In the present invention, the photoradical polymerization initiator is not particularly limited, and any known initiator can be used. Specific examples include benzophenone compounds, dialkoxyacetophenone compounds, α-hydroxyalkylphenone compounds, α-aminoalkylphenone compounds, acylphosphine oxide compounds, and thioxanthone compounds.

The above-mentioned benzophenone compounds include benzophenone, 4-methylbenzophenone, 4-phenylbenzophenone, 4,4'-bis(diethylamino)benzophenone, 4,4'-bis(dimethylamino)benzophenone, and [4-(methylphenylthio)phenyl]-phenylmethanone.

Examples of the dialkoxyacetophenone compounds include 2,2-dimethoxy-2-phenylacetophenone, dimethoxyacetophenone, and diethoxyacetophenone.

Examples of the α-hydroxyalkylphenone compounds include 1-hydroxy-cyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, 1-[4-(2-hydroxymethoxy)-phenyl]-2-hydroxy-2-methyl-1-propan-1-one, and 2-hydroxy-1-{4-[4-(2-hydroxy-2-methyl-propionyl)-benzyl]phenyl}-2-methyl-propan-1-one.

Examples of the α-aminoalkylphenone compounds include 2-methyl-1-[4-(methoxythio)-phenyl]-2-morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone-1, and 2-(dimethylamino)-2-[(4-methylphenyl)methyl]-1-[4-(4-morpholinyl)phenyl-1-butanone.

Examples of the acylphosphine oxide compounds include diphenylacylphenylphosphine oxide, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, and bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide.

Examples of the thioxanthone compounds include 2-isopropylthioxanthone, 2,4-dimethylthioxanthone, and 2,4-diethylthioxanthone.

In the present invention, the above polymerization initiators may be used alone or in combination of two or more.

In the present invention, the content of the polymerization initiator is preferably 0.5 to 20% by mass, more preferably 1 to 10% by mass, based on the total mass of the ink.

[Polymerizable monomer]
The screen ink of the present invention preferably contains a polymerizable monomer in addition to the above. In the present invention, the term "polymerizable monomer" refers to a polymerizable monomer having a molecular weight of less than 1000 (excluding the case of plant component modified acrylate and urethane acrylate). Hereinafter, the term may also be simply referred to as "monomer". The monomer is preferably a compound having a polymerizable group selected from a (meth)acryloyl group, an allyl group, a vinyl group, and a vinyl ether group in the molecule. Among them, an acrylate monomer, which is a compound having a (meth)acryloyl group as the polymerizable group, is more preferable.
Specific examples of the monomer include 2-ethylhexyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, β-carboxyethyl (meth)acrylate, 4-tert-butylcyclohexyl (meth)acrylate, tetrahydrofurfuryl acrylate, alkoxylated tetrahydrofurfuryl acrylate, caprolactone (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, isoamyl (meth)acrylate, 2-phenoxyethyl (meth)acrylate, isodecyl (meth)acrylate, 3,3,5-trimethylcyclohexanol (meth)acrylate, and the like. ) acrylate, cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, norbornyl (meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclopentenyl (oxyethyl) (meth)acrylate, 1,4-cyclohexanedimethanol (meth)acrylate, cyclic trimethylolpropane formal (meth)acrylate, benzyl (meth)acrylate, EO-modified (2) nonylphenol acrylate, 2-methyl-2-ethyl-1,3-dioxolan-4-yl) methyl acrylate, acryloyl morpholine, and other monofunctional (meth)acrylate monomers having one (meth)acryloyl group in the molecule;
Preferred are monofunctional monomers, such as monofunctional vinyl monomers having one vinyl group in the molecule, such as N-vinylcarbazole, 1-vinylimidazole, N-vinyl-2-pyrrolidone, N-vinylcaprolactam, and N-vinylformamide.
1,3-butylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 3-methyl-1,5-pentanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, 1,10-decanediol di(meth)acrylate, 1,2-dodecanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, polyethylene glycol (200) di(meth)acrylate, polyethylene glycol (300) di(meth)acrylate, polyethylene glycol (400) di(meth)acrylate, polyethylene glycol (600) di(meth)acrylate, hydroxypivalic acid neopentyl glycol di(meth)acrylate, dipropylene glycol Preferred are bifunctional monomers such as bifunctional (meth)acrylate monomers having two (meth)acryloyl groups in the molecule, such as ricol di(meth)acrylate, tripropylene glycol di(meth)acrylate, EO-modified (2) 1,6-hexanediol di(meth)acrylate, PO-modified (2) neopentyl glycol di(meth)acrylate, (neopentyl glycol-modified) trimethylolpropane di(meth)acrylate, dimethyloltricyclodecane di(meth)acrylate, EO-modified (4) bisphenol A di(meth)acrylate, PO-modified (4) bisphenol A di(meth)acrylate, cyclohexanedimethanol di(meth)acrylate, dimethylol-tricyclodecane di(meth)acrylate, and dicyclopentanyl di(meth)acrylate.
trifunctional (meth)acrylate monomers having three (meth)acryloyl groups in the molecule, such as trimethylolpropane tri(meth)acrylate, EO-modified (3) trimethylolpropane tri(meth)acrylate, PO-modified (3) trimethylolpropane tri(meth)acrylate, ε-caprolactone-modified tris-(2-acryloxyethyl)isocyanurate, ethoxylated isocyanuric acid tri(meth)acrylate, tris(2-hydroxyethyl)isocyanurate tri(meth)acrylate, and pentaerythritol tri(meth)acrylate;
tetrafunctional (meth)acrylate monomers having four acryloyl groups in the molecule, such as pentaerythritol tetra(meth)acrylate and ditrimethylolpropane tetra(meth)acrylate;
Pentafunctional (meth)acrylate monomers having five (meth)acryloyl groups in the molecule, such as dipentaerythritol penta(meth)acrylate;
and hexafunctional (meth)acrylate monomers having six (meth)acryloyl groups in the molecule, such as dipentaerythritol hexa(meth)acrylate.

Among these monomers, from the viewpoint of flexibility and adhesion, it is preferable to contain a bifunctional monomer and/or a monofunctional monomer, and it is more preferable to contain a bifunctional monomer and a monofunctional monomer. It is sufficient that the bifunctional monomer and the monofunctional monomer are contained in a mass ratio of 10:90 to 80:20, preferably 10:90 to 70:30.

When a monofunctional monomer is contained, its content is preferably 30% by mass or less, and more preferably 20% by mass or less, based on the total mass of the active energy ray-curable screen printing ink, from the viewpoint of chemical resistance.
When a tri- or higher functional (meth)acrylate monomer is contained, its content is preferably 30% by mass or less, and more preferably 20% by mass or less, based on the total mass of the active energy ray-curable screen printing ink, from the viewpoint of flexibility.

In addition, in order to improve chemical resistance, flexibility, and adhesion in screen inks, the mass ratio of polymerizable oligomer to polymerizable monomer is preferably 5:95 to 95:5. It is even more preferable that the mass ratio is 30:70 to 95:5.

[Plant-based modified acrylates, polymerizable oligomers other than urethane acrylates (other polymerizable oligomers)]
The present invention also preferably includes a polymerizable oligomer other than the plant component modified acrylate and urethane acrylate. The polymerizable oligomer may be a compound having not only an acrylate group but also a polymerizable group such as an allyl group, a vinyl group, a vinyl ether group, or an internal double bond group (e.g., maleic acid) in the molecule.
Other polymerizable oligomers include, for example, petroleum-derived acrylic acrylate, polyester acrylate, polyepoxy acrylate, etc. From the viewpoint of abrasion resistance, polyepoxy acrylate is preferable, and polyepoxy acrylate having a bisphenol A structure is more preferable. The polymerizable oligomer may be used alone or in combination of two or more kinds.

The other polymerizable oligomer preferably has a (meth)acryloyl group as a polymerizable group in one molecule, and in this case, the number of (meth)acryloyl groups per molecule is preferably 1 to 6, and more preferably 2 to 4, from the viewpoint of flexibility. The weight average molecular weight of the other polymerizable oligomer is preferably 1,000 to 50,000, and more preferably 1,000 to 30,000.

In the present invention, the "weight average molecular weight" can be determined as a styrene-equivalent molecular weight by general gel permeation chromatography (hereinafter, referred to as GPC).
The GPC measurement method is as follows. HLC-8020 manufactured by Tosoh Corporation was used, and a calibration curve was created using a standard polystyrene sample. Tetrahydrofuran was used as the eluent, and three TSKgel Super HM-M columns (manufactured by Tosoh Corporation) were used. The measurement can be performed at a flow rate of 0.6 ml/min, an injection volume of 10 μl, and a column temperature of 40° C.

[Antifoaming agent]
The screen printing ink of the present invention preferably contains a defoaming agent. The content is preferably 0.1 to 5 mass % of the total mass of the screen ink. Suitable compounds constituting the defoaming agent include at least one defoaming agent selected from acrylic resins, vinyl ether resins, butadiene resins, silicone resins, fluorine-based resins, and modified resins thereof (excluding the above-mentioned binder resins). The defoaming agent is preferably a non-silicone resin, and preferably contains at least one resin selected from acrylic resins, vinyl ether resins, and butadiene resins.
For example, commercially available defoaming agents include the BYK series (manufactured by BYK Japan KK) and the FLORAN series (manufactured by Kyoeisha Chemical Co., Ltd.).

[Leveling agent]
The screen printing ink of the present invention preferably further contains a leveling agent. The content is preferably 0.1 to 1% by mass of the total mass of the screen printing ink. The compound constituting the leveling agent is preferably an acrylic resin and/or a silicone resin (but does not include the above-mentioned binder resin). For example, commercially available leveling agents include the Polyflow series (manufactured by Kyoeisha Chemical Co., Ltd.). These may be used alone or in combination of two or more types.

[Other ingredients]
The active energy ray-curable screen printing ink of the present invention may contain, in addition to the above-mentioned components, extender pigments, pigment dispersants, other polymerizable compounds, sensitizers, waxes, polymerization inhibitors, surface tension adjusters, defoamers, ultraviolet absorbers, antioxidants, and the like, as necessary, within the range in which the effects of the present invention are not impaired.

[Pigment dispersant]
In the present invention, the ink preferably contains a pigment dispersant in order to improve the pigment dispersibility. There is no particular limitation on the pigment dispersant, and any known pigment dispersant can be used. Among them, a resin-type pigment dispersant having a basic functional group is preferable, and examples of the basic functional group include a primary, secondary, or tertiary amino group, and nitrogen-containing heterocycles such as pyridine, pyrimidine, and pyrazine.
Further, as the skeleton constituting the resin-type pigment dispersant, a fatty acid amine skeleton and/or a urethane skeleton are more preferable since good pigment dispersibility can be easily obtained.

The pigment dispersants can be obtained from the Ajisper series (Ajisper PB821, PB822, PB824, etc.) manufactured by Ajinomoto Fine-Techno Co., Ltd., the Solsperse series (Solsperse 24000, Solsperse 32000, Solsperse 38500, etc.) manufactured by Lubrizol Corporation, and the Disperbyk series (BYK-162, BYK-168, BYK-183, etc.) manufactured by BYK-Chemie.

The content of the pigment dispersant is preferably 0.1 to 10% by mass, and more preferably 0.5 to 5% by mass, based on the total mass of the ink.

[Sensitizer]
In the present invention, the ink may contain a sensitizer to improve the curing property. There are no particular limitations on the sensitizer, and any known sensitizer may be used. Specific examples include triethanolamine, methyldiethanolamine, triisopropanolamine, aliphatic amines, ethyl 2-dimethylaminobenzoate, ethyl 4-dimethylaminobenzoate, isoamyl 4-dimethylaminobenzoate, dibutylethanolamine, and 4,4-bis(dimethylamino)benzophenone.

The content of the polymerization initiator aid is preferably 0.1 to 5 mass% of the total mass of the ink, and more preferably 0.5 to 3 mass%.

[wax]
In the present invention, the ink preferably contains a wax in order to improve the abrasion resistance, blocking prevention, smoothness, and scratch prevention. There are no particular limitations on the wax, and any known wax can be used. For example, natural wax and synthetic wax are available.
Examples of natural waxes include carnauba wax, Japan wax, lanolin, montan wax, paraffin wax, and microcrystalline wax.
Examples of synthetic waxes include Fischer-Tropsch wax, polyethylene wax, polypropylene wax, polytetrafluoroethylene wax, polyamide wax, and silicone compounds.

The wax content is preferably 0.1 to 5% by mass based on the total mass of the ink.

[Polymerization inhibitor]
In the present invention, the ink may contain a polymerization inhibitor in order to enhance storage stability. As the polymerization inhibitor, a hindered phenol compound, a phenothiazine compound, a hindered amine compound, or a phosphorus compound is particularly preferably used.
Specific examples include 4-methoxyphenol, hydroquinone, methylhydroquinone, t-butylhydroquinone, 2,6-di-t-butyl-4-methylphenol, phenothiazine, and aluminum salts of N-nitrosophenylhydroxylamine.
Among these, it is preferable that the composition contains a hindered phenol compound and/or a phenothiazine compound, and it is more preferable that the composition contains 2,6-di-t-butyl-4-methylphenol and phenothiazine.

The content of the polymerization inhibitor is preferably 0.01 to 2% by mass relative to the total mass of the ink, from the viewpoint of maintaining curability while improving storage stability.

In the present invention, it is preferable that the ink contains substantially no organic solvents from the viewpoint of reducing the environmental impact. "Substantially no organic solvents" means that a small amount of organic solvent unintentionally mixed in corresponds to "substantially no organic solvents", and if a small amount of organic solvent is contained, it is less than 3% by mass, more preferably less than 1% by mass, of the total mass of the screen ink.

[Biomass ratio]
The biomass degree can be calculated using the following formula.
Biomass ratio (%) = ("mass of biomass component of plant-component modified acrylate used" + "mass of biomass component of biomass resin particles used") x 100 / "total mass of active energy ray-curable screen printing ink"
The biomass degree is preferably 10% or more. In the present invention, the means for achieving a biomass degree of 10% by mass or more is not particularly limited other than the use of the above-mentioned specific compounds, and a method such as the addition of a known biomass compound can be appropriately used.

[Production of screen printing ink]
The screen printing ink of the present invention can be prepared by any known dispersion method. For example, the ink can be prepared by mixing the required amounts of binder resin, pigment, organic solvent and additives, thoroughly stirring the mixture with a stirrer or the like, and then using a dispersing machine such as a three-roller, paint shaker, attritor, sand mill, etc. Among these, the ink is preferably prepared using a three-roller dispersing machine.

[Base material]
The substrate used to form the printed matter in the present invention is not particularly limited, and examples thereof include inorganic substrates such as glass, polyester substrates such as polyethylene terephthalate, polyolefin substrates such as polyethylene, polypropylene, ethylene-vinyl acetate, and other substrates, nylon substrates such as polyamide, acrylic substrates, polyvinyl chloride substrates, polycarbonate substrates, polyurethane substrates, and resin substrates such as epoxy substrates. Vapor deposition substrates in which inorganic compounds such as silica, alumina, and aluminum are vapor-deposited on the substrate can also be used, and the vapor deposition surface may be further coated with polyvinyl alcohol or the like. Corona treatment, frame treatment, and stretching treatment may also be performed. In particular, good adhesion can be obtained to molded plastics.

[Molded plastic substrate]
The molding method for the molded plastic substrate of the present invention is not particularly limited, and any known molding method can be used, including injection molding, direct blow molding, injection blow molding, and insert molding.

[Printed material]
The printed article of the present invention refers to a printed article in which a printed layer is formed on the substrate by a screen printing method using the screen ink, and the printed layer is cured by exposure to active energy rays. The printing method is preferably a screen printing method, and printing conditions are preferably such that a cylinder press printing machine or a semi-automatic printing machine is used as the printing machine, and a resin material such as nylon or polyester, or a resin material such as stainless steel is used as the printing plate.

In the present invention, the method for curing the screen ink is not particularly limited as long as it uses active energy rays, and any known method can be used. Specifically, the ink can be cured by irradiating it with α rays, γ rays, electron beams, X-rays, ultraviolet rays, visible light, infrared light, or the like. Of these, ultraviolet rays and electron beams are preferred, and ultraviolet rays are more preferred. The peak wavelength of the ultraviolet rays is preferably 200 to 600 nm, and more preferably 350 to 420 nm.

There are no particular limitations on the source of active energy rays, and any known source can be used. Specific examples include mercury lamps, xenon lamps, metal halide lamps, LEDs (light-emitting diodes) such as ultraviolet light-emitting diodes (UV-LEDs) and ultraviolet laser diodes (UV-LDs), as well as gas and solid-state lasers.

[Glass transition temperature]
The glass transition temperature (Tg) is a value determined by DSC (differential scanning calorimetry). The measurement was performed using a Rigaku Corporation DSC8231 instrument, with a measurement temperature range of -70 to 250°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.
The glass transition temperature of a single cured product of the plant component modified acrylate, rosin modified polyester acrylate and/or vegetable oil modified polyepoxy acrylate, is preferably 0 to 100° C., more preferably 0 to 70° C. The glass transition temperature of a single cured product of the urethane acrylate is preferably −50 to 50° C., more preferably −40 to 40° C.
Here, the term "homo-cured product" refers to a product obtained by homopolymerizing the raw material polymerizable oligomer.
This is because within the above range, a coating film performance that is well balanced between flexibility and chemical resistance can be obtained.

The present invention will be specifically described below using examples, but the present invention is not limited to the following examples. In the present invention, unless otherwise specified, "parts" and "%" represent "mass parts" and "mass %", respectively.
It should be noted that Example 3 is a reference example.

Example 1 Preparation of active energy ray curable screen printing ink S1
Rosin-modified polyester acrylate (biomass ratio 30% by mass, "ETERCURE" manufactured by Choko Materials Industry Co., Ltd., weight average molecular weight 2,000 to 3,000, trifunctional) 15 parts, urethane acrylate (Shikoh UV-3200B manufactured by Mitsubishi Chemical Corporation, glass transition temperature of single cured product -8°C, weight average molecular weight 10,000, bifunctional) 25 parts, biomass resin particles A (natural product-based, resin particles containing polyhydroxyalkanoic acid, biomass ratio 100% by mass, average particle diameter 5 μm) as biomass resin particles A screen printing ink (S1) was prepared by uniformly mixing 6 parts of methyl 2,4-diethylthioxanthone (melting point 170° C.) as a monomer, 10 parts of N-vinylcaprolactam, 10 parts of 1,6-hexanediol diacrylate, 3 parts of 2,4-diethylthioxanthone as a polymerization initiator, 3 parts of ethyl 2-dimethylaminobenzoate as a sensitizer, 2 parts of BYK-057 (butadiene copolymer, manufactured by BYK-Chemie Japan) as a non-silicone antifoaming agent, 6 parts of a colorant (C.I. Pigment Blue 15:4), and 20 parts of an extender pigment (barium sulfate) using a mixer rotary stirrer.

<Examples 2 to 17, Comparative Examples 1 to 6> [Preparation of screen printing inks S2 to S17, T1 to T6]
The screen printing inks shown in Tables 1 and 2 were prepared in the same manner as in Example 1. The abbreviations in the tables are as follows. The numerical values in the tables represent "parts" unless otherwise specified, and blanks represent unused values.
Soybean oil modified polyepoxy acrylate (manufactured by Daicel Allnex Corporation, functional group number 4, weight average molecular weight 1200, glass transition temperature of single cured product 13°C, biomass ratio 64% by mass)
Shikou UV-3000B (manufactured by Mitsubishi Chemical Corporation, bifunctional, urethane acrylate, glass transition temperature of single cured product -39°C, weight average molecular weight 18,000)
Shiko UV-7000B (manufactured by Mitsubishi Chemical Corporation, 2-3 functional, urethane acrylate, glass transition temperature of single cured product 52°C, weight average molecular weight 3,500)
ART RESIN UN-6200 (manufactured by Negami Chemical Industries, bifunctional, urethane acrylate, glass transition temperature of single cured product -52°C, weight average molecular weight 6,500)
EBECRYL 1830 (manufactured by Daicel Allnex Corporation, 6-functional polyester acrylate, glass transition temperature of single cured product 77°C, weight average molecular weight 1,000)
Biomass resin particles B (plant-based, biomass content including polylactic acid: 100% by mass, average particle size: 3 μm)
Shin-Etsu Silicon KF-96-1000CS: Silicone-based defoamer (manufactured by Shin-Etsu Chemical Co., Ltd.)

<Printing with screen printing ink S1>
A molded plastic that had been subjected to a frame treatment was used as the substrate, and the above-mentioned active energy ray curable screen printing ink S1 was screen-printed onto the substrate using a screen printing plate (NBC Meshtec, L-SCREEN, 140-030/355PW) to form a pattern. The screen printing ink was then cured with UV light (light source: metal halide lamp) at a conveyor speed of 10 m/min, 120 W/cm, and an irradiation distance of 15 mm to prepare a test sample. A screen print was produced.
The flame treatment can be carried out by a conventional method, but the flame treatment is carried out by using a burner with a flame power of 35 to 40 μA, setting the distance between the tip of the burner and the molded plastic surface at about 25 to 75 mm, and uniformly heat-treating the molded plastic surface for 0.5 to 2.0 seconds. The molded plastic surface after the flame treatment has a surface tension in the range of 40 to 60 mN/m to ensure wettability suitable for printing.

<Examples 1 to 17, Comparative Examples 1 to 6> [Printing with screen printing inks S1 to S15, T1 to T6]
Printed bodies were prepared in the same manner as in Example 1, except that the screen printing ink S1 used in Example 1 was changed to the screen printing inks shown in Tables 1 and 2.

<Evaluation of screen printing ink and its prints>
The screen printing inks and printed matter obtained in the above Examples and Comparative Examples were evaluated as follows. The evaluation results are shown in Tables 1 and 2.

[Chemical resistance]
Evaluations were carried out using the prints obtained in Examples 1 to 17 and Comparative Examples 1 to 6. The print surface was rubbed back and forth 100 times with a cotton swab soaked in 99.5% ethanol, and the number of times the substrate was exposed was evaluated.
A (excellent): 100 times or more B (good): 50 times or more but less than 100 times C (poor): less than 50 times Furthermore, the industrially applicable levels are A and B.

[Flexibility]
Evaluations were carried out using the prints obtained in Examples 1 to 17 and Comparative Examples 1 to 6. The printed surface was folded 180° and then returned to its original state, and the state of cracks on the printed surface was visually judged. The judging criteria for the evaluation results were as follows:
A (Excellent): Less than 10% of the coating film cracks at the fold line, no whitening of the coating film. B (Good): 10% to 20% of the coating film cracks at the fold line, slight whitening of the coating film. C (Poor): 20% or more of the coating film cracks at the fold line, with pieces falling off. Furthermore, A and B are at the industrially usable levels.

[Adhesion]
Evaluations were carried out using the prints obtained in Examples 1 to 17 and Comparative Examples 1 to 6. A 12 mm wide adhesive tape (cellophane tape manufactured by Nichiban Co., Ltd.) was applied to the printed surface, and the appearance of the printed surface was judged visually when the tape was quickly peeled off. The evaluation results were judged based on the following criteria.
A (Excellent): Peeling of the ink film on the printed surface is less than 5%.
B (Good): The peeled area of the ink film is 5% or more and less than 20%.
C (bad): The peeled area of the ink film is 20% or more.
The industrially applicable levels are A and B.

[Post-processability]
Evaluations were carried out using the prints obtained in Examples 1 to 17 and Comparative Examples 1 to 6. In the following evaluations, the post-processability refers to the ratio of the area of the foil (evaporated foil manufactured by Murata Gold Foil Co., Ltd.) transferred per unit area. The criteria for the evaluation results were as follows:
A (Excellent): The transfer rate of the transferred foil is 90% by mass or more.
B (good): The transfer rate of the transferred foil is 80% by mass or more and less than 90% by mass.
C (poor): The transfer rate of the transferred foil is less than 80% by mass.
The industrially applicable levels are A and B.

The present invention has been made to solve the above problems, and Examples S1 to S17, which include a colorant, a binder resin containing a plant-component modified acrylate, and resin particles, make it possible to provide an active energy ray-curable screen printing ink and a printed material that are excellent in chemical resistance, flexibility, adhesion, and post-processability.
Comparative Examples T1, T4, and T5, which do not contain plant-component modified acrylate, were poor in flexibility and adhesion, while Comparative Examples T2, T3, and T6, which do not contain biomass resin particles, were poor in chemical resistance and adhesion.

Claims (9)

An active energy ray-curable screen printing ink comprising a colorant, a binder resin containing a plant-based modified acrylate, and resin particles,
The resin particles include biomass resin particles,
The biomass resin particles contain at least one selected from the group consisting of starch, cellulose, polylactic acid, polyglycolic acid, polyhydroxybutyric acid, and polyhydroxyalkanoic acid,
The present invention further provides an active energy ray-curable screen printing ink, which contains a defoaming agent that is a non-silicone compound. The active energy ray-curable screen printing ink according to claim 1, wherein the plant component-modified acrylate comprises a rosin-modified polyester acrylate and/or a vegetable oil-modified polyepoxy acrylate. The active energy beam-curable screen printing ink according to claim 1 or 2, wherein the content of the plant component-modified acrylate is 5 to 30 mass % based on the total mass of the active energy beam-curable screen printing ink. The active energy ray-curable screen printing ink according to any one of claims 1 to 3, wherein the binder resin further contains a urethane acrylate. The active energy ray-curable screen printing ink according to claim 4, wherein the glass transition temperature of the urethane acrylate alone when cured is -50 to 50°C. 6. The active energy ray-curable screen printing ink according to claim 1 , wherein the antifoaming agent which is a non- silicone compound is contained in an amount of 0.1 to 5% by mass based on the total amount of the ink. A printed material having a cured printing layer made of the active energy ray-curable screen printing ink according to any one of claims 1 to 6 on a substrate. The printed article according to claim 7 , wherein the substrate is a molded plastic. A method for producing a molded printed product, comprising the step of printing the active energy ray-curable screen printing ink according to any one of claims 1 to 6 on a molded plastic.