Active energy ray-curable ink composition and printed matter

Abstract

To provide an active energy ray-curable ink composition which has excellent adhesion to a substrate and processability and has surface curability which hardly causes scratching even when rubbed and a printed matter having excellent adhesion to a surface protective layer formed on a printed layer.SOLUTION: There are provided: an active energy ray-curable ink composition which comprises a pigment, a photopolymerizable compound and a photopolymerization initiator, wherein the photopolymerizable compound contains a nitrogen-containing monofunctional polymerizable compound (A-1) in which the nitrogen (N) atom has an active hydrogen, a nitrogen-containing monofunctional polymerizable compound (A-2) in which the nitrogen (N) atom has no active hydrogen and a polyfunctional polymerizable compound (B) and the content of the polyfunctional polymerizable compound (B) is 50 mass% or less based on the total mass of the photopolymerizable compound; and a printed matter 1 having a printing layer 12 using the same.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an actinic ray-curable ink composition and a printed matter. [Background technology]

[0002] Ink compositions for inkjet printing have been widely used as materials for imparting design properties to metal substrates. Currently, in terms of productivity, inkjet printing is often performed using actinic radiation-curable ink compositions that are cured by UV rays or the like to form printed materials. For example, when an actinic radiation-curable ink composition is printed on a metal substrate by an inkjet method, adhesion to the substrate and surface abrasion resistance can become issues. Furthermore, the metal substrate may be subjected to processing such as bending, and it is necessary that cracking and peeling do not occur during processing. Furthermore, in some cases, a surface protective layer may be applied for protection, and excellent adhesion to the surface protective layer is required.

[0003] For example, Patent Document 1 discloses a method for producing a printed matter in which an underlayer containing a functional group capable of reacting with a compound having a specific structure as a monomer having an ethylenically unsaturated group is used, thereby reacting the compound present in the printing layer with the functional group contained in the underlayer, thereby improving the interlayer adhesion between the printing layer and the underlayer. Furthermore, Patent Document 2 discloses a photocurable ink composition that contains at least (A) a specific silicon-containing compound, (B) a nitrogen-containing polymerizable monomer, and (C) a photopolymerization initiator, and that can form a printed film that is excellent in heat yellowing resistance and adhesion even when subjected to a heat treatment after printing and curing on a heat-resistant substrate.

[0004] Furthermore, Patent Document 3 discloses an actinic ray-curable inkjet ink composition that contains an alicyclic monofunctional (meth)acrylate (A) having different glass transition temperatures, a hydroxyl group-containing monofunctional (meth)acrylate (B), and a tri- or higher functional polyfunctional (meth)acrylate (C) having a (meth)acrylic equivalent of 100 to 250, and that is capable of forming a film (inkjet printing layer) that has excellent adhesion to substrates such as glass substrates, sufficient hardness, and is scratch-resistant. Furthermore, Patent Document 4 discloses an ink composition that contains (component A) N-vinylcaprolactam, (component B) a monofunctional acrylate having an aromatic ring, (component C) a monofunctional acrylate having an aliphatic hydrocarbon ring, and the like, and that has excellent adhesion to substrates, blocking resistance of the resulting printed matter, and suitability for vacuum forming, and can suppress post-processing cracking of molded printed matter after vacuum forming. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2018-083343 [Patent Document 2] Patent Publication No. 2021-161148 [Patent Document 3] Japanese Patent Publication No. 2020-055901 [Patent Document 4] JP 2014-172971 A (Patent No. 5980702) Summary of the Invention [Problem to be solved by the invention]

[0006] However, Patent Documents 1 to 3 have the problem that the processability is insufficient because the printed layer formed by inkjet printing may crack or peel during processing, and further, the surface hardening property for scratch resistance is insufficient. Furthermore, although Patent Document 4 has excellent processability and surface hardening properties for the printed layer, it has the problem that the adhesion to the surface protection layer provided on the printed layer is insufficient.

[0007] Therefore, an object of the present invention is to provide an actinic ray-curable ink composition that has excellent adhesion to a substrate and processability, and also has surface curability that makes it resistant to scratches even when rubbed. Another object of the present invention is to provide a printed matter that has excellent adhesion to a surface protective layer formed on the printed layer. [Means for solving the problem]

[0008] The features of the present invention are listed below. (1) An active energy ray-curable ink composition comprising a pigment, a photopolymerizable compound, and a photopolymerization initiator, wherein the photopolymerizable compound comprises a nitrogen-containing monofunctional polymerizable compound (A-1) in which the nitrogen (N) atom has active hydrogen, a nitrogen-containing monofunctional polymerizable compound (A-2) in which the nitrogen (N) atom does not have active hydrogen, and a polyfunctional polymerizable compound (B), and the content of the polyfunctional polymerizable compound (B) is 50 mass% or less with respect to the total amount of the photopolymerizable compound. (2) The actinic ray-curable ink composition according to (1), wherein the photopolymerizable compound further comprises a nitrogen-free monofunctional polymerizable compound (C) having an alicyclic structure. (3) The actinic ray-curable ink composition according to (2), wherein the monofunctional polymerizable compound (C) has a glass transition temperature (Tg) in the range of 0 to 90°C. (4) A printed matter comprising: a substrate; a printed layer formed on the substrate by printing the actinic ray-curable ink composition according to any one of (1) to (3); and a surface protective layer formed on the printed layer. (5) The printed matter according to (4), wherein the substrate is a metal substrate. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide an actinic ray-curable ink composition that has excellent adhesion to a substrate and processability, and also has surface curability that makes it resistant to scratches even when rubbed. Furthermore, according to the present invention, it is possible to provide a printed matter that has excellent adhesion to the surface protective layer formed on the printed layer. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a schematic diagram illustrating the structure of a printed matter using an ink composition of the present invention. [Figure 2] FIG. 1 is a schematic diagram showing another configuration of a printed matter using the ink composition of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0011] The actinic energy ray-curable ink composition of the present invention and a printed matter having a printed layer using the actinic energy ray-curable ink composition will be described in detail below.

[0012] <Actinic energy ray-curable ink composition> The present invention provides an actinic ray-curable ink composition comprising a pigment, a photopolymerizable compound, and a photopolymerization initiator, wherein the photopolymerizable compound comprises a nitrogen-containing monofunctional polymerizable compound (A-1) in which the nitrogen (N) atom has active hydrogen, a nitrogen-containing monofunctional polymerizable compound (A-2) in which the nitrogen (N) atom does not have active hydrogen, and a polyfunctional polymerizable compound (B), and the content of the polyfunctional polymerizable compound (B) is 50 mass% or less based on the total amount of the photopolymerizable compound. The actinic ray-curable ink composition of the present invention (hereinafter simply referred to as "ink composition") is an ink composition for inkjet printers, and is an ink composition containing a photopolymerizable compound that can be cured by irradiation with actinic ray such as ultraviolet light, visible light, or electron beam.

[0013] Photopolymerizable compounds are classified into monofunctional polymerizable compounds and polyfunctional polymerizable compounds. Here, examples of the monofunctional polymerizable compound include a monofunctional polymerizable monomer having one functional group that shows reactivity when irradiated with active energy rays (for example, a monofunctional polymerizable monomer having one polymerizable unsaturated group), and a monofunctional polymerizable oligomer having one functional group that shows reactivity when irradiated with active energy rays (for example, a monofunctional polymerizable oligomer having one polymerizable unsaturated group). Examples of the polyfunctional polymerizable compound include a polyfunctional polymerizable monomer having two or more functional groups that show reactivity when irradiated with active energy rays (for example, a polyfunctional polymerizable monomer having two or more polymerizable unsaturated groups), and a polyfunctional polymerizable oligomer having two or more functional groups that show reactivity when irradiated with active energy rays (for example, a polyfunctional polymerizable oligomer having two or more polymerizable unsaturated groups).

[0014] <Nitrogen-containing monofunctional polymerizable compound (A-1) in which the nitrogen (N) atom has an active hydrogen atom> In the present invention, when a nitrogen (N) atom has active hydrogen, it means that it has an N-H bond, and when a nitrogen (N) atom does not have active hydrogen, it means that it does not have an N-H bond. By using a nitrogen-containing monofunctional polymerizable compound, photopolymerization is promoted, which improves curability and abrasion resistance, and the presence of hydrogen bonds tends to improve interlayer adhesion with the substrate or resin layer.

[0015] The nitrogen-containing monofunctional polymerizable compound (A-1) in which the nitrogen (N) atom has an active hydrogen atom (hereinafter simply referred to as "(nitrogen-containing monofunctional polymerizable compound (A-1))") may be a monomer having a functional group containing a nitrogen (N) atom, such as an amino group, an amide group, an imide group, a urea group, or a urethane group. The nitrogen-containing monofunctional polymerizable compound (A-1) may be a single monomer having a functional group containing a nitrogen (N) atom, or a combination of two or more monomers. By including the nitrogen-containing monofunctional polymerizable compound (A-1) in the ink composition, adhesion can be ensured regardless of the substrate material, such as a metal, used for the underlayer. Furthermore, adhesion can be ensured not only to metal substrates but also to surface treatment layers, such as water-based paints, solvent-based paints, photocurable paints, and powder paints, applied to the surface of metal substrates. If the amount of the nitrogen-containing monofunctional polymerizable compound (A-1) is less than 1% by mass, adhesion of the printed layer to the substrate or underlayer may be insufficient. If it exceeds 30% by mass, cracking may become more pronounced when the film is thick. The content is preferably 1 to 30% by mass, more preferably 1 to 20% by mass, and particularly preferably 1 to 10% by mass. The molecular weight of the nitrogen-containing monofunctional polymerizable compound (A-1) is in the range of 100 to 1000, and preferably in the range of 100 to 300. From the viewpoint of suppressing cure shrinkage, it is preferable to use a nitrogen-containing monofunctional polymerizable compound (A-1) having a relatively high molecular weight.

[0016] Examples of the nitrogen-containing monofunctional polymerizable compound (A-1) having an amino group include a monomer containing a nitrogen-containing group in which two hydrogen atoms of a primary amino group are substituted with two protecting groups, a nitrogen-containing group in which one hydrogen atom of a secondary amino group is substituted with one protecting group, etc.

[0017] The nitrogen-containing monofunctional polymerizable compound (A-1) preferably has an amide group, and specific examples thereof include Nn-butoxymethylacrylamide, N-isobutoxymethylacrylamide, N-methoxymethylacrylamide, N-isopropylacrylamide, 2-hydroxyethylacrylamide, and N-methylolacrylamide, with Nn-butoxymethylacrylamide, N-methoxymethylacrylamide, and N-methylolacrylamide being particularly preferred.

[0018] <Nitrogen-containing monofunctional polymerizable compound (A-2) in which the nitrogen (N) atom does not have an active hydrogen atom> The ink composition of the present invention also contains a nitrogen-containing monofunctional polymerizable compound (A-2) containing a nitrogen (N) atom that does not have an active hydrogen. The nitrogen-containing monofunctional polymerizable compound (A-2) in which the nitrogen (N) atom does not have an active hydrogen (hereinafter simply referred to as "nitrogen-containing monofunctional polymerizable compound (A-2)") refers to a compound that has a nitrogen atom but does not have an active hydrogen bonded to the nitrogen atom. "Not having an active hydrogen" refers to a hydrogen atom bonded to an atom other than carbon, such as oxygen or nitrogen. In particular, compounds containing a functional group such as an amino group, a group having a carbon-nitrogen double bond, or a nitrogen-containing heterocyclic group are preferred. Furthermore, the inclusion of the nitrogen-containing monofunctional polymerizable compound (A-2) ensures surface abrasion resistance. If the amount of the nitrogen-containing monofunctional polymerizable compound (A-2) is less than 1% by mass, surface abrasion resistance may be insufficient, and if it exceeds 30% by mass, cracking may become more pronounced in thick films. The nitrogen-containing monofunctional polymerizable compound (A-2) is contained in an amount of preferably 1 to 30% by mass, more preferably 1 to 20% by mass, and particularly preferably 1 to 10% by mass. The molecular weight of the nitrogen-containing monofunctional polymerizable compound (A-2) is in the range of 100 to 1000, and preferably in the range of 100 to 300. From the viewpoint of suppressing cure shrinkage, it is preferable to use a nitrogen-containing monofunctional polymerizable compound (A-2) having a relatively high molecular weight.

[0019] For example, nitrogen-containing monomers such as vinyl monomers having an amide group without active hydrogen and vinyl monomers having an amino group without active hydrogen can be mentioned. Other examples of nitrogen-containing monomers that do not have active hydrogen include acrylic monomers containing an N,N-dialkyl-substituted amino group or an N,N-dialkyl-substituted amide group, N-vinyl-substituted lactams such as N-vinylpyrrolidone and N-vinylcaprolactam, and N-(meth)acryloyl-substituted cyclic amines such as N-(meth)acryloylmorpholine. Specific examples include N-vinylcaprolactam, N,N-dimethylacrylamide, and acryloylmorpholine (ACMO) (registered trademark).

[0020] <Polyfunctional polymerizable compound (B)> The ink composition of the present invention contains a polyfunctional polymerizable compound (B). The polyfunctional polymerizable compound (B) may be a polyfunctional polymerizable monomer having two or more radically polymerizable functional groups, or a polyfunctional polymerizable oligomer having two or more radically polymerizable functional groups, and is particularly preferably a methacrylate or acrylate compound. Specific examples of bifunctional polymerizable monomers include 1,3-butylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,5-pentanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,7-heptanediol di(meth)acrylate, 1,8-octanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, 1,10-decanediol di(meth)acrylate, 1,12-dodecanediol di(meth)acrylate, 2-butyl-2-ethyl-1,3-propanediol di(meth)acrylate, 3-methyl-1,5-pentanediol di(meth)acrylate, 2-methyl-1,8-octanediol di(meth)acrylate, diethylene glycol di(meth)acrylate, and dipropylene glycol. di(meth)acrylate, triethylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, hydroxypivalic acid neopentyl glycol di(meth)acrylate, PO (propylene oxide)-modified neopentyl glycol di(meth)acrylate, cyclohexanedimethanol diacrylate, tricyclodecane dimethanol diacrylate, dimethylol-tricyclodecane di(meth)acrylate, dicyclopentanyl diacrylate, bisphenol A di(meth)acrylate, polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, polytetramethylene glycol di(meth)acrylate, and the like.

[0021] Specific examples of trifunctional or higher polyfunctional polymerizable monomers include trimethylolpropane tri(meth)acrylate, ethoxylated trimethylolpropane tri(meth)acrylate, propoxylated trimethylolpropane tri(meth)acrylate, ethoxylated glycerin tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, ethoxylated pentaerythritol tetra(meth)acrylate, EO-modified diglycerin tetra(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, EO-modified dipentaerythritol hexa(meth)acrylate, and glycerin tri(meth)acrylate.

[0022] The content of the polyfunctional polymerizable compound (B) is 50% by mass or less based on the total amount of the photopolymerizable compounds. In the ink composition of the present invention, the ratio of the polyfunctional polymerizable compound (B) to the total amount of photopolymerizable compounds, including nitrogen-containing monofunctional polymerizable compounds (A-1, A-2), is set to 50% by mass or less. This allows for adjustment of the number of polymerization reactions of the polyfunctional polymerizable compound (B) and the resulting crosslink density. This reduces shrinkage caused by curing of the printed layer. Furthermore, by ensuring a certain degree of flexibility, the adhesion of the printed layer itself to the substrate can be improved. Furthermore, adhesion to various substrates, surface treatment layers on the substrate, and surface protection layers applied to the printed layer can be ensured. Furthermore, by setting the amounts of the monofunctional polymerizable compound and the polyfunctional polymerizable compound in a specific ratio, processability and surface hardening properties against cracking and peeling during processing can be ensured. In addition, adjusting the amount of nitrogen-containing monofunctional polymerizable compounds (A-1, A-2) relative to the total photopolymerizable compounds can improve adhesion and processability. Furthermore, a high ratio of nitrogen-containing monofunctional polymerizable compounds (A-1, A-2) can suppress surface hardening against scratches due to rubbing, so the ratio of monofunctional polymerizable compounds, including nitrogen-containing monofunctional polymerizable compounds (A-1, A-2), relative to the total photopolymerizable compounds is preferably 50% by mass or more. It is even more preferable that the amount of monofunctional polymerizable compounds relative to the total polymerizable compounds is 70% by mass or more.

[0023] The polyfunctional polymerizable compound (B) contained in the ink composition of the present invention has a molecular weight in the range of 100 to 1,000, preferably in the range of 200 to 500. From the viewpoint of suppressing cure shrinkage, it is preferable to use a polyfunctional polymerizable compound (B) having a relatively high molecular weight. In particular, the molecular weight of the bifunctional polymerizable compound is preferably 200 to 1,000, more preferably 200 to 400. The amount of the bifunctional polymerizable compound having a molecular weight of 300 to 1,500 relative to the total polymerizable compounds is more preferably 5 to 20 mass%.

[0024] <Monofunctional polymerizable compound having an alicyclic structure (C)> The ink composition of the present invention contains a nitrogen-free monofunctional polymerizable compound (C) having an alicyclic structure (hereinafter simply referred to as "monofunctional polymerizable compound (C)"). The monofunctional polymerizable compound (C) having an alicyclic structure may be a monofunctional polymerizable monomer or oligomer having a functional group exhibiting radical polymerizability. Alicyclic structures refer to saturated or unsaturated carbocyclic rings that are not aromatic. For example, cycloalkyl groups, preferably C 4-20 Cycloalkyl groups, more preferably C 4-10It is a cycloalkyl group. Examples of the monofunctional polymerizable compound (C) having an alicyclic hydrocarbon group include cycloalkyl (meth)acrylates such as cyclohexyl (meth)acrylate, alkyl cycloalkyl (meth)acrylates such as 4-methylcyclohexyl (meth)acrylate, t-butylcyclohexyl acrylate, and trimethylcyclohexyl acrylate, cycloalkyl alkyl (meth)acrylates such as cyclohexylmethyl (meth)acrylate, cyclohexylethyl (meth)acrylate, cyclohexylpropyl (meth)acrylate, and 4-methylcyclohexylmethyl (meth)acrylate, and crosslinked cyclic (meth)acrylates such as isobornyl (meth)acrylate and adamantyl (meth)acrylate. Among these, t-butylcyclohexyl acrylate and trimethylcyclohexyl acrylate are particularly preferred.

[0025] The monofunctional polymerizable compound (C) may be used alone or in combination of two or more. The amount of the monofunctional polymerizable compound (C) in the photopolymerizable compound is preferably 20% by mass or more, more preferably in the range of 25 to 70% by mass. If the amount of the monofunctional polymerizable compound (C) in the photopolymerizable compound is too high, peeling from the substrate and cracking of the printed material may occur during processing. If the amount of the monofunctional polymerizable compound (C) is too low, the surface curability of the printed material may decrease. The monofunctional polymerizable compound (C) in the ink composition of the present invention preferably contains at least 30% by mass of a monofunctional polymerizable compound having an alicyclic hydrocarbon group selected from compounds other than isobornyl acrylate.

[0026] The monofunctional polymerizable compound (C) in the ink composition of the present invention preferably has a glass transition temperature (Tg) in the range of 0 to 90°C. Examples of monofunctional polymerizable compounds (C) having an alicyclic hydrocarbon group and having a homopolymer Tg in the range of 0 to 90°C include t-butylcyclohexyl acrylate (TBCHA) and trimethylcyclohexyl acrylate. The monofunctional polymerizable compounds (C) may be used alone or in combination of two or more. Monofunctional polymerizable compounds (C) having a Tg in the range of 0 to 90°C provide a printed layer with strong tackiness and excellent adhesion. If the monofunctional polymerizable compound (C) has a glass transition temperature (Tg) exceeding 90°C, it will be impossible to obtain excellent adhesion to a wide range of substrates such as metals and plastics, and to the surface protective layer formed on the printed layer. If the glass transition temperature (Tg) is less than 0°C, the hardness of the printed matter will decrease, and excellent surface curing properties will not be obtained.

[0027] When a monomer whose glass transition temperature is unknown is used, the glass transition temperature (Tg) of the monomer can be determined by differential scanning calorimetry (DSC), differential thermal analysis (DTA), thermomechanical analysis (TMA), or the like.

[0028] <Other monofunctional polymerizable compounds> The ink composition of the present invention may further contain a monofunctional polymerizable compound other than the nitrogen-containing monofunctional polymerizable compound (A-1, A-2) and the monofunctional polymerizable compound (C). The content of other monofunctional polymerizable compounds in the photopolymerizable compound is not particularly limited, but is preferably 10% by mass or more. The total amount of the nitrogen-containing monofunctional polymerizable compounds (A-1, A-2), the monofunctional polymerizable compound (C), and other monofunctional polymerizable compounds in the photopolymerizable compound is preferably 50% by mass or more, and more preferably 70% by mass or more.

[0029] The photopolymerizable compound contained in the ink composition of the present invention has an average functionality of 1.2 or less, preferably 1.05 to 1.20. The ink composition of the present invention reduces the number of reactive sites in the entire ink composition, suppressing curing shrinkage of the printed layer while providing an appropriate crosslinked structure, thereby ensuring surface curability of the printed layer. Furthermore, by controlling the average number of functional groups of the photopolymerizable compound contained in the ink composition, the number of polymerization reactions and the resulting crosslink density can be adjusted, thereby suppressing curing shrinkage of the printed layer. Furthermore, the adhesion of the printed layer itself can be significantly improved, and adhesion to various substrates and coatings, such as a surface protective layer provided on the printed layer, and surface curability of the printed layer can be ensured.

[0030] Specific examples of the monofunctional polymerizable compound include the following monomers: 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, polyoxyethylene mono(meth)acrylate, polyoxypropylene mono(meth)acrylate, polyoxybutylene mono(meth)acrylate, stearyl (meth)acrylate, tridecyl (meth)acrylate, lauryl (meth)acrylate, decyl (meth)acrylate, phenoxyethyl (meth)acrylate, phenoxydiethylene glycol (meth)acrylate, benzyl (meth)acrylate, isodecyl (meth)acrylate, (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, octyl (meth)acrylate, 2-ethylhexyl-diglycol (meth)acrylate, EO (ethylene oxide)-modified 2-ethylhexyl (meth)acrylate, neopentyl glycol (meth)acrylic acid benzoate, tetrahydrofurfuryl (meth)acrylate, methoxydipropylene glycol (meth)acrylate, (2-methyl-2-ethyl-1,3-dioxolan-4-yl)methyl (meth)acrylate, cyclic trimethylolpropane formal (meth)acrylate, and ethoxy-diethylene glycol (meth)acrylate.

[0031] In the present invention, the term "(meth)acrylate" means methacrylate or acrylate. When a prefix indicating plural is added to (meth)acrylate, such as di(meth)acrylate or tri(meth)acrylate, each (meth)acrylate may be the same or different.

[0032] <Photopolymerization initiator> The ink composition of the present invention contains a photopolymerization initiator. The photopolymerization initiator has the effect of initiating polymerization of the photopolymerizable compounds (A-1, A-2, B, and C) upon irradiation with active energy rays. Furthermore, the content of the photopolymerization initiator in the ink composition of the present invention is preferably 1 to 25% by mass, more preferably 3 to 20% by mass, and even more preferably 3 to 15% by mass. If the content of the photopolymerization initiator is less than 1% by mass, the printed layer will not cure properly and the surface curability will be reduced. If the content of the photopolymerization initiator is more than 25% by mass, the curing reaction will be accelerated, resulting in poor adhesion of the printed layer to the substrate, cracking of the printed layer, and reduced processability. Furthermore, when used in an inkjet system, the ejection stability of the inkjet head will be reduced. Furthermore, to promote the initiation reaction of the photopolymerization initiator, an auxiliary agent such as a photosensitizer can be used in combination.

[0033] Specific examples of suitable photopolymerization initiators include acylphosphine oxides, α-hydroxyketones, benzyl dimethyl ketals, α-aminoalkylphenones, and thioxanthones. While these photopolymerization initiators may be used alone, it is preferable to use a combination of two or more. When the photopolymerization initiator is at least two selected from the group consisting of acylphosphine oxides, α-hydroxyketones, benzyl dimethyl ketals, α-aminoalkylphenones, and thioxanthones, the photopolymerization initiator can efficiently absorb the emission wavelength of the active energy ray light source. Furthermore, a photopolymerization initiator that exhibits excellent internal curing properties and a photopolymerization initiator that exhibits excellent surface curing properties can be used in combination, thereby further increasing the hardness of the printed layer. Among the suitable photopolymerization initiators, examples of photopolymerization initiators that exhibit excellent internal curing properties include acylphosphine oxides and α-aminoalkylphenones, while examples of photopolymerization initiators that exhibit excellent surface curing properties include α-hydroxyketones and benzyl dimethyl ketals. For this reason, the photopolymerization initiator is preferably at least two selected from the group consisting of acylphosphine oxides, α-hydroxyketones, benzyl dimethyl ketals, α-aminoalkylphenones, and thioxanthones, and particularly preferably a combination of at least one photopolymerization initiator selected from the group consisting of acylphosphine oxides and α-aminoalkylphenones and at least one photopolymerization initiator selected from the group consisting of α-hydroxyketones and benzyl dimethyl ketals.

[0034] <Pigments> The ink composition of the present invention may contain a colorant such as a dye or pigment. Since the ink composition of the present invention requires weather resistance when used in an inkjet system, it preferably contains a pigment. The pigment is not particularly limited, and pigments commonly used in the paint industry can be used. Specific examples include inorganic pigments such as titanium dioxide, iron oxide, and carbon black, and organic pigments such as phthalocyanine copper, azo pigments, and condensed polycyclic pigments. The coloring pigments may be used alone or in combination of two or more. The content of the colorant in the ink composition is 0.1 to 15% by mass. The colorant may be used alone or in combination of two or more. Colorants also include aluminum flakes, glass flakes, and pearl pigments. The ink composition of the present invention may contain various compounds for the purpose of imparting functionality. For example, it may contain calcium carbonate, barium sulfate, etc. in order to increase the hardness of the resulting film, it may contain tin-doped indium oxide (ITO), antimony-doped tin oxide (ATO), nanoparticles of gold or silver, etc. in order to impart a heat ray absorption function to the resulting film, and it may contain titanium oxide, zirconium oxide, hollow particles, etc. in order to adjust the refractive index of the resulting film. The pigment particles dispersed in the ink composition preferably have a volume average particle diameter of 0.05 to 0.9 μm and a volume maximum particle diameter of 0.2 to 1 μm. If the volume average particle diameter is greater than 0.9 μm and the volume maximum particle diameter is greater than 1 μm, it tends to be difficult to stably eject the composition. The volume average particle diameter and volume maximum particle diameter can be measured using a measuring device that uses dynamic light scattering.

[0035] <Pigment dispersant> The ink composition of the present invention may further contain a pigment dispersant as needed to disperse the pigment. The dispersant is not particularly limited, but is preferably a high molecular weight compound. The pigment dispersant may be a resin having a structure containing a functional group having affinity for the pigment and a functional group having affinity for the solvent. Examples of the functional group having affinity include nonionic, cationic, and anionic functional groups. The pigment dispersant may contain two or more types of the functional groups in one molecule. Examples of nonionic functional groups include hydroxyl groups, amide groups, and polyoxyalkylene groups. Examples of cationic functional groups include amino groups, imino groups, and hydrazino groups. Examples of anionic functional groups include carboxyl groups, sulfo groups, and phosphate groups. The weight-average molecular weight of the pigment dispersant is preferably 1,000 to 100,000, more preferably 2,000 to 100,000, and even more preferably 4,000 to 50,000. The content of the pigment dispersant in the ink composition is 0.1 to 5.0% by mass, preferably 1.0 to 3.0% by mass. The pigment dispersants may be used alone or in combination of two or more.

[0036] The pigment dispersant is not particularly limited, but it is preferable to use one that can efficiently disperse the pigment with a small amount of the pigment dispersant. For example, Solsperse 32000, Solsperse J180, Solsperse J200, Solsperse X300 (all manufactured by Lubrizol), BYK-P104, BYK-P104S, BYK-P105, BYK-9076, BYK-9077, BYK-220S, BYKJET-9150, BYKJET-9151, DISPERBYK-168 (all manufactured by BYK Japan), Disparlon DA-7301, Disparlon DA-325, Disparlon DA-375, Disparlon DA-234 (all manufactured by Kusumoto Chemicals), Florene AF-1000, Florene NC-500, Florene WK-13E (all manufactured by Kyoeisha Chemical), LIPOTIN DB, LIPOTIN Examples include SB (all manufactured by Evonik Degussa), PB821, PB822, PN411, and PA111 (all manufactured by Ajinomoto Fine-Techno Co., Ltd.).

[0037] <Surface conditioner> The ink composition of the present invention may further contain a surfactant to improve adhesion of the printing layer to the substrate. The surface conditioner in the ink composition of the present invention has a hydrophilic moiety and a hydrophobic moiety in its molecular structure, and its addition can adjust the surface tension of the composition. The surface conditioner is not particularly limited, and suitable examples include fluorine-based surfactants, silicone-based surfactants, and acrylic polymer-based surfactants. The content of the surfactant in the ink composition of the present invention is, for example, 0.01 to 1% by mass, and from the viewpoint of adhesion, etc., preferably 0.1 to 0.7% by mass. The surfactant may be used alone or in combination of two or more types.

[0038] In the ink composition of the present invention, an acrylic polymer surfactant is preferably used as the surface conditioner, which is capable of orienting on the coating surface and reducing the surface tension of the coating surface, thereby exhibiting a leveling effect.

[0039] <Other ingredients> The ink composition of the present invention may contain, as other components, additives such as other resins, adhesion imparting agents, antioxidants, plasticizers, rust inhibitors, solvents, fillers, defoaming agents, charge control agents, stress relaxation agents, penetrating agents, light-guiding materials, glittering materials, magnetic materials, fluorescent materials, antibacterial agents, antiviral agents, and anti-algae agents, as needed.

[0040] <Characteristics of ink composition> The ink composition of the present invention can be used in various inkjet printers. Examples of inkjet printers include inkjet printers that eject the ink composition using a charge control system or a piezoelectric system. The ink composition of the present invention can also be applied to inkjet printers intended for printing on articles produced by large-format inkjet printers. Therefore, the ink composition of the present invention has the following properties, which will be explained below.

[0041] <Viscosity of Ink Composition> Ink jet printers often use heads equipped with a mechanism for heating the ink composition before ejecting it, and the temperature of the ink composition during printing is generally set to 30 to 50° C. Therefore, the temperature for measuring the viscosity of the ink composition of the present invention is set to 40° C. The ink composition of the present invention was adjusted to a liquid temperature of 40°C, and then its viscosity (X) at a shear rate of 10 s-1 and its viscosity (Y) at a shear rate of 100 s-1 were measured. The unit of viscosity is mPa·s. The ink composition of the present invention preferably has a viscosity (X) at a shear rate of 10 s-1 of 3 to 20 mPa·s and a viscosity (Y) at a shear rate of 100 s-1 of 3 to 20 mPa·s. The viscosity was measured using a rheometer (ARES rheometer manufactured by TA Instruments) after the liquid temperature was adjusted to 40°C.

[0042] In inkjet printers producing precise or continuous images, if the viscosity (X) at a shear rate of 10 s-1 at 40°C is less than 3 mPa·s, mist is likely to form during ejection, causing a decrease in image quality. If the viscosity (X) at a shear rate of 100 s-1 exceeds 20 mPa·s, the ejection stability of the ink is impaired.

[0043] <Surface tension of ink composition> The ink composition of the present invention is not particularly limited as long as it can be ejected from the head of an inkjet printer, and from the viewpoint of improving wettability to a substrate, the surface tension at 25° C. is preferably 20 to 50 mN / m, and more preferably 30 to 40 mN / m. The surface tension of the ink is measured by the plate method.

[0044] <Specific gravity of ink composition> From the viewpoint of stably ejecting the ink composition from the head of an inkjet printer, the ink composition of the present invention preferably has a specific gravity of 1.00 to 1.25 relative to water at 4° C. In this specification, the specific gravity of the ink refers to that measured by the hydrometer method.

[0045] <Printed material> Next, a printed matter using the ink composition of the present invention will be described in detail. The printed matter of the present invention comprises a substrate, a printed layer formed on the substrate by printing the ink composition described above, and a surface protective layer formed on the printed layer. FIG. 1 is a schematic diagram showing the structure of a printed matter using the ink composition of the present invention. The printed matter 1 of the present invention is a printed matter 1 comprising a substrate 11 and a printed layer 12 formed on the substrate 11 using the ink composition of the present invention. The ink composition of the present invention can provide printed matter that does not crack or peel even when processed, has good surface curing properties, and is excellent in abrasion resistance.

[0046] FIG. 2 is a schematic diagram showing another configuration of a printed matter using the ink composition of the present invention. The abrasion resistance of the printed matter 1 of the present invention can be further improved by providing a surface protective layer 13 on the printed layer 12. By using the ink composition of the present invention, a printed matter having excellent adhesion between the printed layer 12 and the surface protective layer 13 can be obtained. The surface protective layer 13 may have a photocatalyst layer or an overcoat layer containing a water repellent, a hydrophilic agent, or the like, on the outermost surface layer.

[0047] The substrate 11 constituting the printed matter using the ink composition of the present invention is not particularly limited, and in the present invention, a substrate 11 used in an industrial line is preferred. The shape of the substrate 11 may be, for example, a plate or a thin shape. Since the method for producing the printed matter 1 includes a processing step after curing the printed layer 12, a substrate 11 that is not damaged by deformation during processing is preferred. Examples of materials for the substrate 11 include aluminum, magnesium, copper, iron, stainless steel, and glass.

[0048] The surface of the substrate 11 may be subjected to pretreatment such as degreasing, chemical conversion treatment, and polishing, or may be coated with a sealer or primer. For example, if the substrate 11 is a ceramic building material or other material that may excessively absorb paint or ink, the surface of the substrate 11 may be coated with a sealer, and a sealer layer may be formed on the substrate 11. Furthermore, if the substrate 11 is a metal building material or the like, the surface of the substrate 11 may be coated with a primer, and a treatment layer may be formed on the substrate 11.

[0049] Furthermore, the printed matter 1 printed using the ink composition of the present invention is provided with a surface protective layer 13 to protect the printed layer 12. The surface protective layer 13 improves resistance to swelling and shrinkage of the underlying printed layer 12 and substrate 11 and to changes in outdoor environmental temperature, and can prevent cracks from occurring in the surface protective layer 13, ensuring a high level of weather resistance over a long period of time. The surface protective layer 13 preferably contains a resin, such as an acrylic resin, a silicone resin, an acrylic silicone resin, a styrene-acrylic copolymer resin, a polyester resin, or a fluororesin. The resin may be used alone or in combination of two or more. Furthermore, the surface protective layer 13 preferably contains an ultraviolet absorber and a radical scavenger for weather resistance, as long as the appearance of the printed layer 12 is not impaired. The surface protective layer 13 may also contain a colorant, an antioxidant, a plasticizer, a rust inhibitor, a filler, a charge control agent, a light-guiding material, a lustrous material, a magnetic material, a phosphor, wax, or the like, as needed.

[0050] The printed layer 12 using the ink composition of the present invention is formed by curing the actinic energy ray-curable inkjet ink composition of the present invention by irradiation with actinic energy rays. The printed matter 1 of the present invention can provide a printed matter having a printed layer 12 that is excellent in processability, that does not crack or peel when processed into the printed layer 12, that has excellent surface curability, that is resistant to scratches even when rubbed, and that is also excellent in adhesion to the substrate 11 and to the treatment layer or surface protection layer 13 on the substrate surface.

[0051] In the printing process, when the ink composition of the present invention is irradiated with active energy rays, the photopolymerizable compound in the molecule undergoes a radical polymerization reaction and is cured to form a printed layer 12. Examples of light sources used for irradiating active energy rays include mercury lamps, high-pressure mercury lamps, metal halide lamps, xenon lamps, and LEDs. [Example]

[0052] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples in any way.

[0053] <Preparation of Ink Compositions of Examples and Comparative Examples> The materials shown in Table 1 were blended (values ​​are in parts by mass) and dispersed in a bead mill to obtain an active energy ray-curable ink composition.

[0054] Details of the materials used are given below. <Pigments> 1) Pigment Black 7: Raven 450 (Columbian Carbon Japan Co., Ltd.) 2) Pigment Yellow 74: Sico Yellow FR1252HD (BASF Japan Ltd.) 3) Pigment Blue 15; 4: Heliogen Blue L7080 (BASF Japan Ltd.) 4) Pigment Red 122: SicoFast Red 3855 (BASF Japan Ltd.) 5) Pigment White 6: CR-90 (Ishihara Sangyo Kaisha, Ltd.)

[0055] (Photopolymerizable compound) <Nitrogen-containing monofunctional polymerizable compound (A-1)> 6) NBM: N-butoxymethylacrylamide (KJ Chemicals Co., Ltd.) 7) HEAA: N-(2-hydroxyethyl)acrylamide (KJ Chemicals Co., Ltd.) 8) NIPAM: N-isopropylacrylamide (KJ Chemicals Co., Ltd.)

[0056] <Nitrogen-containing monofunctional polymerizable compound (A-2)> 9) NVC: N-vinylcaprolactam (BASF Japan Ltd.) 10) ACMO: Acryloylmorpholine (KJ Chemicals Co., Ltd.) 11) DMAA: N,N-dimethylacrylamide (KJ Chemicals Co., Ltd.)

[0057] <Polyfunctional polymerizable compound (B)> 12) DPGDA: Dipropylene glycol diacrylate (Daicel-Allnex Corporation, bifunctional) 13) 1,6-HDDA: 1,6-hexanediol diacrylate (Kyoeisha Chemical Co., Ltd., bifunctional) 14) TPGDA: Tripropylene glycol diacrylate (Sartomer Corporation, bifunctional)

[0058] <Monofunctional polymerizable compound (C)> 15) TBCHA: 4-tert-butylcyclohexyl acrylate (KJ Chemicals, Tg = 77°C) 16) IBOA: Isobornyl acrylate (Kyoeisha Chemical Co., Ltd., Tg = 94°C) 17) CHA: Cyclohexyl acrylate (Osaka Organic Chemical Industry Co., Ltd., Tg=15℃)

[0059] <Other monofunctional polymerizable compounds> 18) POA: Phenoxyethyl acrylate (Kyoeisha Chemical Co., Ltd.) 19) ECA: Ethyl carbitol acrylate (Kyoeisha Chemical Co., Ltd.)

[0060] <Polymerization initiator> 20)Omnirad TPO H(IGM Resine BV) 21) Speedcure DETX (Nippon Kayaku Co., Ltd.)

[0061] <Pigment dispersant> 22) DISPERBYK-168 (BYK Japan Co., Ltd.)

[0062] [Table 1]

[0063] <Sample preparation> Furthermore, the ink compositions of Examples 1 to 21 and Comparative Examples 1 to 3 were set in an inkjet printer, and a solid image (printing layer) was printed on an aluminum substrate of 0.3 mm × 100 mm × 50 mm. Then, an LED lamp with a dominant wavelength of 385 nm was used to irradiate the solid image with an actinic energy ray of 2000 mJ / cm. 2 After irradiation and curing, a printed layer with a thickness of 5 μm was obtained. Next, the following evaluation tests were carried out, and the results are shown in Table 2.

[0064] [Table 2]

[0065] <Adhesion to substrate> The test was conducted using the printed layer prepared in the above "Preparation of Materials." The test was conducted in accordance with JIS-K5600-5-6 (Adhesion (Cross-Cut Method)) and evaluated according to the following criteria. If the result was Class 2 or higher, it was determined that there would be no problems in practical use. ○: Classification 0, 1. △: Classification 2. ×: Classification 3~5.

[0066] <Surface hardening> The test used the printed layer prepared in the above "Preparation of Materials." The appearance of the printed surface was evaluated using the following criteria when it was lightly rubbed with a cotton swab. If the substrate surface was not exposed when rubbed, it was determined that there would be no problem in practical use. ○: The printed film does not peel off and no rubbing marks remain. △: The printed film does not peel off, but scratches remain. ×: The printed film peeled off and part of the substrate surface was visible.

[0067] <Workability> The test was conducted using the printing layer prepared in the above <Preparation of Materials>. The test was conducted in accordance with JIS-K5600-5-1 (Flexibility (Cylindrical Mandrel Method)) and evaluated according to the following criteria. The better the flexibility, the better the processability. The higher the processability, the less problems were judged to occur in practical use. ○: No cracking or peeling occurs at a diameter of 2 mm. △: Cracks and peeling occurred at a diameter of 2 mm, but no cracks or peeling occurred at a diameter of 5 mm. ×: Cracks and peeling occurred at a diameter of 5 mm.

[0068] <Adhesion to surface protective layer> The diluted solution was applied to the printed matter prepared in the above <Preparation of Samples> using a Daito Paint Daitron #1517 bar coater, and then heated until the substrate surface reached 180°C, and heated at that temperature for 10 minutes to form a surface protective layer with a dry film thickness of 10 μm, which was used as a test panel. Using this test panel, adhesion was evaluated in accordance with JIS-K5600-5-6 (Adhesion (cross-cut method)), and was evaluated according to the following criteria. ○: Classification 0, 1. △: Classification 2. ×: Classification 3~5.

[0069] From the above results, it can be determined that Examples 1 to 21 present no practical problems in all evaluation items regarding adhesion to the substrate, processability, surface hardening property, and adhesion to the surface protective layer. In contrast, Comparative Example 1 does not contain a nitrogen-containing monofunctional polymerizable compound (A-1) in which the nitrogen (N) atom has active hydrogen, and therefore the adhesion to the surface protective layer is reduced. Furthermore, it is clear that Comparative Example 2 does not contain the nitrogen-containing monofunctional polymerizable compound (A-2) in which the nitrogen (N) atom does not have active hydrogen, and therefore the surface curability is reduced. In addition, in Comparative Example 3, the content of the polyfunctional polymerizable compound (B) exceeds 50 mass% relative to the total amount of the photopolymerizable compound, and therefore, although the surface curability is excellent, the adhesion to the substrate and the processability are reduced.

[0070] Therefore, the present invention can provide an ink composition and a printed matter that are excellent in adhesion to the substrate or surface protective layer of the printed matter, processability, and surface curability. [Explanation of symbols]

[0071] 1 Printed matter 11 Base material 12 printing layer 13 Surface protective layer

Claims

1. An actinic ray-curable ink composition comprising a pigment, a photopolymerizable compound, and a photopolymerization initiator, The photopolymerizable compound is a nitrogen-containing monofunctional polymerizable compound (A-1) in which the nitrogen (N) atom has an active hydrogen; a nitrogen-containing monofunctional polymerizable compound (A-2) in which the nitrogen (N) atom does not have an active hydrogen atom; Contains a polyfunctional polymerizable compound (B), The actinic ray-curable ink composition, wherein the content of the polyfunctional polymerizable compound (B) is 50 mass % or less with respect to the total amount of the photopolymerizable compound.

2. The actinic ray-curable ink composition according to claim 1 , wherein the photopolymerizable compound further comprises a nitrogen-free monofunctional polymerizable compound (C) having an alicyclic structure.

3. 3. The actinic ray-curable ink composition according to claim 2, wherein the monofunctional polymerizable compound (C) has a glass transition temperature (Tg) in the range of 0 to 90°C.

4. A substrate; a printed layer formed on the substrate by printing the actinic ray-curable ink composition according to any one of claims 1 to 3; and A surface protective layer formed on the printing layer.

5. The printed matter according to claim 4 , wherein the substrate is a metal substrate.

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