Ultraviolet-curable composition, method for producing cured product, cured product, ultraviolet-curable ink, method for producing printed matter, and printed matter

Abstract

Provided is an ultraviolet-curable composition containing at least a radical-polymerizable compound, a polymerization initiator, and a solvent, wherein the radical-polymerizable compound does not contain an emulsion polymer, is present as particles, and further contains resin particles having a urethane skeleton. The resin particles having a urethane skeleton do not have a polymerizable functional group and have a glass transition temperature of -10°C or lower. Also provided is an ultraviolet-curable composition containing a radical-polymerizable compound, resin particles having a urethane skeleton, a polymerization initiator, a surfactant, and a solvent, wherein the radical-polymerizable compound is present as particles, the resin particles having a urethane skeleton do not have a polymerizable functional group and have a glass transition temperature of -10°C or lower, and the surfactant is a silicone-based surfactant.

Description

Ultraviolet-curable composition, method for producing cured product, cured product, ultraviolet-curable ink, method for producing printed material, and printed material

[0001] The present invention relates to an ultraviolet-curable composition and an ultraviolet-curable ink. The present invention also relates to a cured product obtained by curing the ultraviolet-curable composition and a printed material obtained by curing the ultraviolet-curable ink.

[0002] In fields such as inks, adhesives, and coating agents, the use of products containing large amounts of organic solvents has been associated with problems such as occupational health and safety during work and air pollution. One solution to these problems is the development of water-based products. However, compared to products using organic solvents, water-based products may produce coatings with insufficient water resistance, solvent resistance, and hardness. One solution involves blending a component that cures under ultraviolet light into a water-based product to form an ultraviolet-curable composition, which is then applied and cured by ultraviolet light to form a coating (see, for example, Patent Documents 1 and 2).

[0003] Among the above-mentioned products, demand for inks for inkjet printers has been increasing in recent years. Inkjet printers have various advantages, such as easy full-color printing, low noise, ability to produce high-resolution images at low cost, high-speed printing, ability to print on curved surfaces as well as flat surfaces, and ease of printing on large areas. Therefore, inkjet printers are not limited to personal use, but have also been rapidly gaining popularity in recent years as commercial inkjet printers for signage, window films, posters, car wrapping, wallpaper, and the like.

[0004] Commercial inkjet printers are required to print products with the following characteristics: (1) high image quality, (2) high coating properties, (3) high-speed printing, (4) substrate versatility, and (5) environmental and safety properties. When printing large-area prints or prints for outdoor use, commercial inkjet printers are also required to print films with excellent coating properties, such as water resistance, alcohol resistance, coating film strength, and light resistance.

[0005] Conventional printing inks for commercial inkjet printers include aqueous inks in which a pigment is dispersed in an aqueous medium; solvent UV inks in which a pigment and an ultraviolet-curable monomer are dispersed or dissolved in an organic solvent; solventless UV inks in which a pigment is dispersed in an ultraviolet-curable monomer without a solvent; aqueous latex inks in which a pigment and a resin are dispersed in an aqueous medium; and ultraviolet-curable aqueous inks in which a pigment and a UV-curable oligomer are dispersed in an aqueous medium (Patent Documents 1 and 2).

[0006] Among these, UV-curable water-based inks have a relatively good balance of all properties. However, water-based inkjet inks have the problem that they require heating at high temperatures for a long time to fix the ink to the substrate. If the ink does not fix to the substrate sufficiently, for example, in the case of fabric, the washing fastness of the printed material will be poor, causing color fading.

[0007] As a solution to the problem of the need for high-temperature, long-term heating to fix the ink, inks containing polymerizable compounds as particles (resin particles having polymerizable functional groups) have been proposed. However, the ink compositions proposed to date have not been able to sufficiently improve washing fastness when heated at low temperatures for a short period of time.

[0008] JP 2004-209976 A JP 2013-199110 A

[0009] An object of the present invention is to provide an ultraviolet-curable composition and an ultraviolet-curable ink that can provide a water-based inkjet ink that can give printed items with high washing fastness without requiring high-temperature, long-term heating to fix the ink to a substrate.

[0010] The present inventors have found that by using a combination of resin particles having a polymerizable functional group and resin particles having a urethane skeleton that does not have a polymerizable functional group and has a glass transition temperature (Tg) of −10° C. or lower, it is possible to realize a water-based inkjet ink that can produce printed matter with high washing fastness without requiring long-term heating at high temperatures to fix the ink.

[0011] [1] An ultraviolet-curable composition containing at least a radically polymerizable compound, a polymerization initiator, and a solvent, wherein the radically polymerizable compound does not contain an emulsion polymer and exists as particles, and the ultraviolet-curable composition further contains resin particles having a urethane skeleton, wherein the resin particles having a urethane skeleton do not have a polymerizable functional group and have a glass transition temperature of −10° C. or lower.

[0012] [2] An ultraviolet-curable composition containing a radically polymerizable compound, resin particles having a urethane skeleton, a polymerization initiator, a surfactant, and a solvent, wherein the radically polymerizable compound is present as particles, the resin particles having a urethane skeleton have no polymerizable functional group and a glass transition temperature of −10° C. or lower, and the surfactant is a silicone-based surfactant.

[0013] [3] The ultraviolet-curable composition according to [1] or [2], wherein the radically polymerizable compound contains a (meth)acrylate.

[0014] [4] The ultraviolet-curable composition according to any one of [1] to [3], wherein the content of the resin particles having a urethane skeleton is 0.1% by mass or more and 10% by mass or less, based on the total mass of the ultraviolet-curable composition.

[0015] [5] The ultraviolet-curable composition according to any one of [1] to [4], wherein the content of the radical polymerizable compound is 5% by mass or more and 20% by mass or less, based on the total mass of the ultraviolet-curable composition.

[0016] [6] The ultraviolet-curable composition according to any one of [1] to [5], wherein the resin particles having a urethane skeleton have an average particle size of 10 nm or more and 250 nm or less.

[0017] [7] The ultraviolet-curable composition according to any one of [1] to [6], wherein the radically polymerizable compound has a urethane bond.

[0018] [8] The ultraviolet-curable composition according to any one of [1] to [7], wherein the solvent contains water.

[0019] [9] The ultraviolet-curable composition according to [8], wherein the solvent further contains a water-soluble organic solvent, and the mass ratio of water to the water-soluble organic solvent (water:water-soluble organic solvent) is 1:0.05 to 1:1.5.

[0020]

[10] The ultraviolet-curable composition according to any one of [1] to [9], wherein the concentration of the total solid content other than the solvent is 5% by mass or more and 23% by mass or less.

[0021]

[11] The ultraviolet-curable composition according to any one of [1] to

[10] , which is for use in an inkjet ink.

[0022]

[12] A method for producing a cured product, comprising applying or printing the ultraviolet-curable composition according to any one of [1] to

[11] onto a surface of a substrate, and then irradiating the substrate with active energy rays.

[0023]

[13] A cured product obtained by curing the ultraviolet-curable composition according to any one of [1] to

[11] .

[0024]

[14] An ultraviolet-curable ink containing at least a radically polymerizable compound, a polymerization initiator, a colorant, and a solvent, wherein the radically polymerizable compound does not contain an emulsion polymer and exists as particles, and the ink further contains resin particles having a urethane skeleton, wherein the resin particles having a urethane skeleton do not have a polymerizable functional group and have a glass transition temperature of −10° C. or lower.

[0025]

[15] An ultraviolet-curable ink containing a radically polymerizable compound, resin particles having a urethane skeleton, a polymerization initiator, a surfactant, a colorant, and a solvent, wherein the radically polymerizable compound is present as particles, the resin particles having a urethane skeleton have no polymerizable functional group and a glass transition temperature of −10° C. or lower, and the surfactant contains a silicone-based surfactant.

[0026]

[16] The ultraviolet-curable ink according to

[14] or

[15] , wherein the radically polymerizable compound contains a (meth)acrylate.

[0027]

[17] The ultraviolet-curable ink according to any one of

[14] to

[16] , wherein the content of the resin particles having a urethane skeleton is 0.1% by mass or more and 10% by mass or less relative to the total mass of the ultraviolet-curable ink.

[0028]

[18] The ultraviolet-curable ink according to any one of

[14] to

[17] , wherein the content of the radically polymerizable compound is 5% by mass or more and 20% by mass or less relative to the total mass of the ultraviolet-curable ink.

[0029]

[19] The ultraviolet-curable composition according to any one of

[14] to

[18] , wherein the resin particles having a urethane skeleton have an average particle size of 10 nm or more and 250 nm or less.

[0030]

[20] The ultraviolet-curable ink according to any one of

[14] to

[19] , wherein the radically polymerizable compound has a urethane bond.

[0031]

[21] The ultraviolet-curable ink according to any one of

[14] to

[20] , wherein the solvent contains water.

[0032]

[22] The ultraviolet-curable ink according to

[21] , wherein the solvent further contains a water-soluble organic solvent, and the mass ratio of water to the water-soluble organic solvent (water:water-soluble organic solvent) is 1:0.05 to 1:1.5.

[0033]

[23] The ultraviolet-curable ink according to any one of

[14] to

[22] , wherein the concentration of all solids other than the solvent is 5% by mass or more and 23% by mass or less.

[0034]

[24] The ultraviolet-curable ink according to any one of

[14] to

[23] , which is for inkjet printing.

[0035]

[25] A method for producing a printed matter, comprising applying or printing the ultraviolet-curable ink according to any one of

[14] to

[24] onto a surface of a substrate, and then irradiating the substrate with active energy rays.

[0036]

[26] A printed matter obtained by curing the ultraviolet curable ink according to any one of

[14] to

[24] .

[0037] According to the present invention, there are provided an ultraviolet-curable composition and an ultraviolet-curable ink that can provide a water-based inkjet ink that can give printed items with high washing fastness without requiring long-term heating at high temperatures to fix the ink.

[0038] An embodiment of the present invention will be described below, but the present invention is not limited to this embodiment.

[0039] In the present invention, when the expression "X to Y" (X and Y are any numbers) is used, it includes the intention of "X or more and Y or less", as well as "preferably greater than X" and "preferably smaller than Y", unless otherwise specified. In the present invention, when the expression "X or more" (X is any number) or "Y or less" (Y is any number) is used, it also includes the intention of "preferably greater than X" or "preferably less than Y".

[0040] [UV-Curable Composition] An UV-curable composition according to a first embodiment of the present invention (hereinafter may be referred to as "UV-Curable Composition I") is an UV-curable composition containing at least a radically polymerizable compound, a polymerization initiator, and a solvent, wherein the radically polymerizable compound does not contain an emulsion polymer and exists as particles, and further contains particles of a resin having a urethane skeleton (hereinafter may be referred to as "urethane resin"), and the resin particles having a urethane skeleton do not have a polymerizable functional group and have a glass transition temperature of -10°C or lower.

[0041] An ultraviolet-curable composition according to a second embodiment of the present invention (hereinafter, may be referred to as "ultraviolet-curable composition II") is an ultraviolet-curable composition containing a radical-polymerizable compound, resin particles having a urethane skeleton, a polymerization initiator, a surfactant, and a solvent, characterized in that the radical-polymerizable compound is present in the form of particles, the resin particles having a urethane skeleton do not have a polymerizable functional group and have a glass transition temperature of -10°C or lower, and the surfactant contains a silicone-based surfactant.

[0042] Hereinafter, UV-curable composition I and UV-curable composition II may be collectively referred to as "UV-curable composition of the present invention" or "composition of the present invention."

[0043] The form of use of the ultraviolet-curable composition of the present invention is not particularly limited, and it can be used as a coating material, adhesive, paint, clear ink, etc.

[0044] An ultraviolet-curable ink (hereinafter, sometimes referred to as "ultraviolet-curable ink of the present invention" or "ink of the present invention") can be prepared by adding a colorant described below to the ultraviolet-curable composition of the present invention. The colorant to be added may be one color or two or more colors. By optionally adding two or more colorants, the color of the ink can be adjusted to a desired color.

[0045] An ultraviolet-curable ink according to a first embodiment of the present invention (hereinafter, sometimes referred to as "ultraviolet-curable ink I") is an ultraviolet-curable ink containing at least a radically polymerizable compound, a polymerization initiator, a colorant, and a solvent, and is characterized in that it does not contain the radically polymerizable compound or emulsion polymer, but exists as particles, and further contains resin particles having a urethane skeleton, and the resin particles having a urethane skeleton do not have a polymerizable functional group and have a glass transition temperature of -10°C or less.

[0046] An ultraviolet-curable ink according to a second embodiment of the present invention (hereinafter, sometimes referred to as "ultraviolet-curable ink II") is an ultraviolet-curable ink containing a radically polymerizable compound, resin particles having a urethane skeleton, a polymerization initiator, a surfactant, a colorant, and a solvent, characterized in that the radically polymerizable compound is present in the form of particles, the resin particles having a urethane skeleton have no polymerizable functional groups and have a glass transition temperature of -10°C or lower, and the surfactant contains a silicone-based surfactant.

[0047] Hereinafter, UV-curable ink I and UV-curable ink II may be collectively referred to as "UV-curable ink of the present invention" or "ink of the present invention."

[0048] The ink of the present invention is suitable for use in ink jet printing.

[0049] The ultraviolet-curable composition and ultraviolet-curable ink of the present invention are ultraviolet-curable, but the actinic energy rays used for curing are not limited to ultraviolet rays. When curing the ultraviolet-curable composition and ultraviolet-curable ink of the present invention, they may be cured not only by actinic energy rays but also by heat, for example.

[0050] [Mechanism] <Issues with conventional inks> In inks containing resin particles, the dispersed particles condense as the solvent evaporates after impacting the substrate, causing deformation and fusion of the particles, resulting in interdiffusion of polymer chains between the fused particles and the formation of a coating film. However, if drying is insufficient, the dispersed particles do not condense. Even if drying is sufficient, if the polymer particles have high heat resistance, the particles do not deform. This poses the issue of not being able to form a uniform coating film. For this reason, conventional inks require high-temperature, long-term heating to form a uniform coating film, and if heating is insufficient, a uniform coating film is not formed, resulting in insufficient coating film strength and substrate adhesion. As a result, the wash fastness of the printed material is poor.

[0051] <Reason why the above-mentioned problem can be solved by adding urethane resin particles that have no polymerizable functional groups and a Tg of −10°C or less> The inventors' investigations have revealed that the above-mentioned problem can be solved by combining resin particles that have polymerizable functional groups with resin particles that have a urethane skeleton that has no polymerizable functional groups and a Tg of −10°C or less. While the details of the reason for this are unclear, it is thought that the following may be the reason. The urethane bond sites of the urethane resin form hydrogen bonds with functional groups (e.g., hydroxyl groups of cellulose in cotton) of the substrate, such as fabric, thereby contributing to improved adhesion between the ink and the surface of the substrate, such as fabric. Furthermore, by using urethane resin particles with a Tg of −10°C or less, the majority of the urethane resin molecular chains exist in a rubbery state near room temperature, exhibiting a relatively flexible mechanical state. As a result, cracking of the ink coating on the fiber is less likely to occur. At the same time, the low Tg is thought to allow the urethane resin particles to easily fuse together, even near room temperature, as the solvent dries. Therefore, by applying the ink to a substrate and then curing it with UV light, both the durability provided by UV curing and the adhesion provided by the urethane resin are achieved, resulting in the formation of an ink coating film with high washing durability.

[0052] [Radical Polymerizable Compound] The radical polymerizable compound used in the present invention may be nonionic or ionic (anionic, cationic, or amphoteric). The radical polymerizable compound used in the present invention may be ionic like other materials, or may be nonionic, thereby suppressing aggregation with other materials and improving the storage stability of the ultraviolet-curable composition or ultraviolet-curable ink. Here, "nonionic" means, for example, that the hydrophilic group of the radical polymerizable compound is composed of an ether bond or a hydroxyl group that does not ionize in water. "Ionic" (anionic, cationic, or amphoteric) means, for example, that the radical polymerizable compound has a carboxyl group or an amino group that can ionize in water. More specifically, anionic radical polymerizable compounds include, for example, radical polymerizable compounds containing a carboxyl group.

[0053] The radical polymerizable compound is not particularly limited as long as it has one or more radical polymerizable groups in the molecule. The number of radical polymerizable groups in the molecule is preferably 2 or more, more preferably 3 or more, and on the other hand, preferably 15 or less.

[0054] Examples of the radically polymerizable group possessed by the radically polymerizable compound include a (meth)acryloyl group, a vinyl group, and a vinyl ether group. Among these, a (meth)acryloyl group is preferred from the viewpoint of ease of radical polymerization. That is, the radically polymerizable compound used in the present invention preferably contains a (meth)acrylate described below. When the radically polymerizable compound used in the present invention contains a (meth)acrylate, a higher effect in terms of washing fastness can be achieved when used in combination with the urethane resin particles described below.

[0055] In the present invention, "(meth)acrylate" means acrylate or methacrylate. The same applies to "(meth)acryloyl".

[0056] The radical polymerizable compound may be used alone or in combination of two or more kinds.

[0057] The radical polymerizable compound is not particularly limited to a compound having a radical polymerizable group having one (meth)acryloyl group in the molecule. Examples of the radical polymerizable compound include isoamyl (meth)acrylate, stearyl (meth)acrylate, lauryl (meth)acrylate, octyl (meth)acrylate, decyl (meth)acrylate, isomyristyl (meth)acrylate, isostearyl (meth)acrylate, 2-ethylhexyl-diglycol (meth)acrylate, 2-hydroxybutyl (meth)acrylate, butoxyethyl (meth)acrylate, ethoxydiethylene glycol (meth)acrylate, methoxydiethylene glycol (meth)acrylate, methoxypolyethylene glycol (meth)acrylate, methoxypropyl (meth)acrylate, methyl ... Examples of the acrylates include propylene glycol (meth)acrylate, phenoxyethyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, isobornyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, lactone-modified flexible (meth)acrylate, t-butylcyclohexyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, glycidyl (meth)acrylate, and isobornyl (meth)acrylate.

[0058] The radical polymerizable compound having a radical polymerizable group with two (meth)acryloyl groups in the molecule is not particularly limited. Examples of the radical polymerizable compound include triethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, dimethylol-tricyclodecane di(meth)acrylate, ethylene oxide (EO) adduct di(meth)acrylate of bisphenol A, propylene oxide (PO) adduct di(meth)acrylate of bisphenol A, neopentyl glycol hydroxypivalate di(meth)acrylate, and polytetramethylene glycol di(meth)acrylate.

[0059] The radical polymerizable compound is not particularly limited to a compound having a radical polymerizable group having three or more (meth)acryloyl groups in the molecule. Examples of the radical polymerizable compound include trimethylolpropane tri(meth)acrylate, ethylene oxide modified trimethylolpropane tri(meth)acrylate, propylene oxide modified trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, glycerol tri ... Examples of the acrylates include glycerin ethoxy tri(meth)acrylate, glycerin propoxy tri(meth)acrylate, caprolactone-modified trimethylolpropane tri(meth)acrylate, pentaerythritol ethoxy tetra(meth)acrylate, epichlorohydrin-modified trimethylolpropane tri(meth)acrylate, tripetaerythritol octa(meth)acrylate, tetrapentaerythritol deca(meth)acrylate, polypentaerythritol poly(meth)acrylate, and caprolactone-modified dipentaerythritol hexa(meth)acrylate.

[0060] As the radical polymerizable compound, an oligomer or polymer having one or more radical polymerizable groups in the molecule can also be used. Among them, an oligomer or polymer having one or more (meth)acryloyl groups in the molecule is preferred. The oligomer or polymer having one or more (meth)acryloyl groups in the molecule is not particularly limited. Examples of the oligomer or polymer include polyester (meth)acrylate, urethane (meth)acrylate, epoxy (meth)acrylate, acrylic resin (meth)acrylate, polyether (meth)acrylate, oligo(meth)acrylate, alkyd (meth)acrylate, and polyol (meth)acrylate.

[0061] The radical polymerizable compound used in the present invention exists as particles in the ultraviolet-curable composition or ultraviolet-curable ink. In the present invention, "existing as particles" means that when the particle size distribution is measured by dynamic light scattering using a particle size distribution meter (e.g., NANOTRAC WAVE II: manufactured by Microtrac Bell Co., Ltd.), a peak is observed in a region of particle sizes greater than 1 nm. Furthermore, in the present invention, as long as the radical polymerizable compound exists as particles, it is included in the state of "existing as particles" even if there is aggregation or other substances are contained within the particles.

[0062] The radical polymerizable compound exists as particles in the ultraviolet-curable composition or ultraviolet-curable ink, so that it does not penetrate too far and remains near the surface, even when the substrate is a water-absorbent substrate such as fabric, etc. As a result, a decrease in image density can be suppressed, and a cured product or printed product having excellent resistance properties such as water resistance and abrasion resistance can be formed.

[0063] Furthermore, the radical polymerizable compound used in the present invention is preferably water-insoluble. Here, "water-insoluble" means that the solubility of the polymerizable compound in water at 25°C is less than 0.1 g / mL. The solubility in water can be adjusted by the type and content of hydrophilic functional groups possessed by the radical polymerizable compound. The water-insoluble radical polymerizable compound can exist as particles in an aqueous medium.

[0064] Since the radical polymerizable compound exists stably as particles, an amphipathic radical polymerizable compound may be used as the radical polymerizable compound. The amphipathic radical polymerizable compound is not particularly limited as long as it is a compound having a radical polymerizable group and a hydrophilic group. Examples of the amphipathic radical polymerizable compound include a macromonomer or urethane (meth)acrylate having a (meth)acryloyl group or a vinyl ether group as the radical polymerizable group and a polyalkylene glycol or an ionic group as the hydrophilic group, and a compound produced by reacting a polyisocyanate compound (A) described below with a compound (B') and a compound (C') described below. Compound (B'): A compound containing a polymerizable unsaturated bond and capable of bonding to the polyisocyanate compound (A). Compound (C'): A water-soluble compound capable of bonding to the polyisocyanate compound (A).

[0065] The compound produced by reacting the polyisocyanate compound (A), the compound (B') and the compound (C') will be described in more detail below.

[0066] Examples of the structure of compound (B') that can bond to polyisocyanate compound (A) include a hydroxyl group, a carboxyl group, and an amino group. Examples of the polymerizable unsaturated bond include a carbon-carbon double bond and a carbon-carbon triple bond, and among these, a carbon-carbon double bond is preferred. More specific examples include carbon-carbon double bonds derived from a vinyl group, a (meth)acryloyl group, or the like.

[0067] The water-soluble compound in compound (C') includes a water-soluble polymer. Specific examples of compound (C') include polyglycerin, polyhydroxy(meth)acrylate, polyamine, quaternary aminated polystyrene, sulfonated polystyrene, polyether, polyalkylene glycol, etc. Among these, polyglycerin, polyhydroxy(meth)acrylate, and polyalkylene glycol are preferred, and polyalkylene glycol is particularly preferred. Each of these water-soluble compounds may be a copolymer. Compound (C') has the structure of such a water-soluble compound and a structure capable of bonding to polyisocyanate compound (A). Here, the "structure capable of bonding to polyisocyanate compound (A)" is the same as that of compound (B') described above. Polyisocyanate compound (A), compound (B'), and compound (C') may additionally have other structures.

[0068] <Polyisocyanate Compound (A)> The polyisocyanate compound (A) is a compound having a total of two or more isocyanate groups in one molecule.

[0069] The type of polyisocyanate compound (A) is not particularly limited, and examples thereof include chain aliphatic polyisocyanates, aromatic polyisocyanates, alicyclic polyisocyanates, etc. Among these, it is preferable that the polyisocyanate compound (A) contains a polyisocyanate trimer compound from the viewpoints of weather resistance and hardness.

[0070] The chain aliphatic polyisocyanate is a compound having a chain aliphatic structure and two or more isocyanate groups. The chain aliphatic polyisocyanate is preferred from the viewpoints of weather resistance and stretchability. The chain aliphatic structure in the chain aliphatic polyisocyanate is not particularly limited, but is preferably a linear or branched alkylene group having 1 to 12 carbon atoms, preferably 1 to 6 carbon atoms. Examples of the chain aliphatic polyisocyanate include aliphatic diisocyanates such as tetramethylene diisocyanate, hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, and dimer acid diisocyanate, as well as trimer compounds of these polyisocyanates.

[0071] Aromatic polyisocyanates are compounds having an aromatic structure and two or more isocyanate groups. Aromatic polyisocyanates are preferred from the viewpoint of the strength of the cured product. The aromatic structure in aromatic polyisocyanates is not particularly limited, but aromatic structures having 6 to 13 carbon atoms are preferred. Examples of aromatic polyisocyanates include aromatic diisocyanates such as tolylene diisocyanate, xylylene diisocyanate, diphenylmethane diisocyanate, m-phenylene diisocyanate, and naphthalene diisocyanate, as well as trimer compounds of these polyisocyanates.

[0072] Alicyclic polyisocyanates are compounds having an alicyclic structure and two or more isocyanate groups. The alicyclic structure in the alicyclic polyisocyanate is not particularly limited, but the carbon number thereof is usually 5 or more, preferably 6 or more, and usually 15 or less, preferably 14 or less, more preferably 13 or less. The alicyclic structure is particularly preferably a cycloalkylene group. Examples of alicyclic polyisocyanates include diisocyanates having an alicyclic structure such as bis(isocyanatomethyl)cyclohexane, cyclohexane diisocyanate, bis(isocyanatocyclohexyl)methane, and isophorone diisocyanate, as well as trimer compounds of these polyisocyanates.

[0073] These polyisocyanate compounds (A) may be used alone or in combination of two or more thereof. As the polyisocyanate compound (A), polyisocyanates having two or more structures selected from a chain aliphatic structure, an aromatic structure, and an alicyclic structure may also be used.

[0074] From the viewpoint of adhesion to a substrate in particular, the polyisocyanate compound (A) preferably has 3 or more isocyanate groups, and more preferably has 6 or less isocyanate groups. As the polyisocyanate compound (A), a trimer obtained by trimerization of hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, phenylene diisocyanate, or the like is preferred, and a trimer of hexamethylene diisocyanate is particularly preferred.

[0075] <Compound (B')> The compound (B') is a compound that contains a polymerizable unsaturated bond and can bond with the polyisocyanate compound (A).

[0076] Compound (B') is preferably a hydroxyl group-containing (meth)acrylate because it has excellent UV curability, fixability, aqueous dispersion stability, solvent resistance, etc. When compound (B') is a hydroxyl group-containing (meth)acrylate, the hydroxyl group of the hydroxyl group-containing (meth)acrylate reacts with the isocyanate group of polyisocyanate compound (A) to form a urethane bond. Furthermore, when the hydroxyl group-containing (meth)acrylate is a hydroxyl group-containing polyfunctional (meth)acrylate (B), it is preferable because it forms a good crosslinked structure and can improve the physical properties of the cured product, such as contamination resistance and abrasion resistance.

[0077] The number of hydroxyl groups in the hydroxyl group-containing (meth)acrylate is preferably 3 or less, more preferably 2 or less, and even more preferably 1. The upper limit of the number of (meth)acryloyl groups in the hydroxyl group-containing polyfunctional (meth)acrylate (B) is preferably 8 or less, more preferably 6 or less. On the other hand, the lower limit is preferably 2 or more, more preferably 3 or more.

[0078] Examples of the hydroxyl group-containing polyfunctional (meth)acrylate (B) include pentaerythritol tri(meth)acrylate, dipentaerythritol penta(meth)acrylate, caprolactone-modified dipentaerythritol penta(meth)acrylate, caprolactone-modified pentaerythritol tri(meth)acrylate, ethylene oxide-modified dipentaerythritol penta(meth)acrylate, ethylene oxide-modified pentaerythritol tri(meth)acrylate, 2-hydroxy-1,3-dimethacryloxypropane, and 2-hydroxy-3-acryloyloxypropyl methacrylate.

[0079] These hydroxyl group-containing polyfunctional (meth)acrylates (B) may be used alone or in combination of two or more.

[0080] As the hydroxyl group-containing polyfunctional (meth)acrylate (B), particularly from the viewpoint of the strength of the obtained cured product, those having one hydroxyl group and 3 to 5 (meth)acryloyl groups, such as dipentaerythritol penta(meth)acrylate and pentaerythritol tri(meth)acrylate, are preferred. Dipentaerythritol penta(meth)acrylate is particularly preferred as the hydroxyl group-containing polyfunctional (meth)acrylate (B) because it forms a good crosslinked structure and increases the mechanical strength of the cured film.

[0081] <Compound (C')> The compound (C') is a water-soluble compound that can bond with the polyisocyanate compound (A).

[0082] As described above, the compound (C') may be a water-soluble polymer, and among these, the polyalkylene glycol (C) is particularly preferred. The hydroxyl group of the polyalkylene glycol (C) can react with the isocyanate group of the polyisocyanate compound (A) to form a urethane bond.

[0083] The polyalkylene glycol (C) is not limited, but preferably has a mono-substituted structure. That is, it is preferable that one of the hydroxyl groups of the glycol is substituted. The substituted structure is preferably a structure that does not bond with isocyanate. The polyalkylene glycol (C) may be a mixture of a compound having a mono-substituted structure and a compound having a non-mono-substituted structure.

[0084] The molecular weight of the polyalkylene glycol (C) (if it is not a single molecule, it means the number average molecular weight) is not limited, but is usually 100 or more, preferably 200 or more, and usually 5000 or less, preferably 2000 or less.

[0085] Among the polyalkylene glycols (C), polyalkylene glycol mono-substituted ethers are preferred, and among the polyalkylene glycol mono-substituted ethers, polyalkylene glycol mono-substituted ethers that do not contain an ionic substituent in the ether moiety are more preferred. As the polyalkylene glycol (C), for example, one represented by the following formula (1) is more preferred.

[0086]

[0087] In formula (1), Alk is preferably an alkylene group having 1 to 3 carbon atoms, and among these, an ethylene group, a trimethylene group, or a propylene group is more preferable, and from the viewpoint of storage stability, an ethylene group is even more preferable. From the viewpoint of strength of the cured product, J is preferably a (meth)acryloyl group, an allyl group, or an acyl group, and more preferably an allyl group.

[0088] In terms of the strength of the resulting cured product, g in formula (1) is usually 2 or more, preferably 5 or more, more preferably 6 or more, and usually 500 or less, preferably 100 or less, more preferably 50 or less.

[0089] These polyalkylene glycols (C) may be used alone or in combination of two or more. The polyalkylene glycol (C) may be a mixture of compounds having different molecular weights (compounds having different g in the formula (1)).

[0090] In order for the radical polymerizable compound to exist stably as particles in the composition or ink of the present invention, it is preferable that the radical polymerizable compound does not contain a structure obtained by reacting the following compound (D) with the following compound (E): Compound (D): a tertiary amine or a salt thereof, or a quaternary ammonium salt Compound (E): a compound having a polymerizable unsaturated bond and a glycidyl group

[0091] <Weight-average molecular weight> When the radically polymerizable compound is a polymer, from the viewpoint of the performance and handleability of the cured product, the weight-average molecular weight, calculated as polystyrene by gel permeation chromatography (GPC), is preferably 1,000 or more, more preferably 2,000 or more, and preferably 100,000 or less, more preferably 50,000 or less. However, for commercially available products, catalog values ​​can be used.

[0092] <Average particle size> In the ultraviolet-curable composition and ultraviolet-curable ink of the present invention, the radical-polymerizable compound exists as particles. The average particle size of the particles is preferably 10 nm or more and 250 nm or less, and more preferably 20 nm or more and 200 nm or less. When the average particle size of the radical-polymerizable compound is within the above range, the dispersion stability is good.

[0093] The average particle size of the radical polymerizable compound is, for example, the volume average particle size (D ５０ )

[0094] In the examples described later, the average particle size of the radical polymerizable compound particles in an aqueous dispersion of the radical polymerizable compound is measured, and the average particle size of the radical polymerizable compound particles in this aqueous dispersion is substantially the same as the average particle size of the radical polymerizable compound particles in the ultraviolet-curable composition and ultraviolet-curable ink. The above average particle size of the radical polymerizable compound means the particle size (primary particle size) of the radical polymerizable compound particles.

[0095] [Resin Particles Having a Urethane Skeleton] The ultraviolet-curable composition and ultraviolet-curable ink of the present invention contain resin particles having a urethane skeleton (urethane resin particles). The urethane resin particles have no polymerizable functional groups and have a glass transition temperature (Tg) of −10° C. or lower.

[0096] From the viewpoint of the aforementioned effect of the urethane resin in improving the adhesion of the ink coating film, the glass transition temperature (Tg) of the urethane resin particles is preferably −20° C. or lower, more preferably −30° C. or lower, even more preferably −40° C. or lower, and particularly preferably −50° C. or lower. On the other hand, from the viewpoint of liquid stability, the lower limit of the Tg of the urethane resin particles is usually −100° C. or higher, and preferably −80° C. or higher.

[0097] The Tg of the urethane resin particles can be measured by the method described in the Examples section below. Specifically, the Tg is determined by the temperature at which the gradient of the stepwise change observed during the second heating process becomes maximum in a graph of the endothermic heat release and temperature obtained by differential scanning calorimetry (DSC). The stepwise change refers to the portion of the DSC curve where the curve moves from the previous low-temperature baseline to a new high-temperature baseline.

[0098] The average particle size of the urethane resin particles is preferably 10 nm or more and 250 nm or less, and more preferably 20 nm or more and 200 nm or less. When the average particle size of the urethane resin particles is within the above range, the dispersion stability is improved. Here, the average particle size of the urethane resin particles is, for example, the volume average particle size (D ５０ ) However, if the product is commercially available, the catalog value can be used. The average particle size of the urethane resin particles refers to the particle size (primary particle size) of the urethane resin particles.

[0099] The ionicity of the urethane resin particles may be nonionic, anionic, or cationic, and among these, the ionicity of the urethane resin particles is preferably nonionic or anionic.

[0100] The urethane resin particles may be commercially available as an aqueous dispersion of urethane resin particles. Examples of commercially available urethane resin particles suitable for the present invention include Takelac (registered trademark) W-6110, Takelac (registered trademark) WS-6021 (manufactured by Mitsui Chemicals, Inc.), DISPERCOLL (registered trademark) U53, DISPERCOLL (registered trademark) U56, DISPERCOLL (registered trademark) U8755, IMPRANIL (registered trademark) DL3040, IMPRANIL (registered trademark) DLI, NeoRez (registered trademark) R-600 (manufactured by Sumika Covestro Urethane Co., Ltd.), Superflex (registered trademark) 300, Superflex (registered trademark) 460, Superflex (registered trademark) 500M, Superflex (registered trademark) E-2000 (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.), and DAOTAN (registered trademark) TW. 6450 / 30WA (manufactured by Daicel Allnex Co., Ltd.), ETERNACOLL (registered trademark) UW-5002E (manufactured by UBE Corporation), ADEKA BONTITAR (registered trademark) HUX-370, ADEKA BONTITAR (registered trademark) HUX-564, ADEKA BONTITAR (registered trademark) HUX-567 (manufactured by ADEKA Corporation). However, the urethane resin particles that can be used in the present invention are not limited to the above.

[0101] These urethane resin particles may be used alone or in combination of two or more kinds.

[0102] [Colorant] The ultraviolet-curable ink of the present invention contains a colorant. As the colorant used in the ultraviolet-curable ink of the present invention, various dyes or pigments known as colorants used in inks can be used. From the viewpoints of ultraviolet irradiation and long-term storage durability of printed images, it is preferable to use a pigment as the colorant.

[0103] <Dye> Dyes that can be used in the present invention are not particularly limited, and examples thereof include water-soluble dyes such as acid dyes, direct dyes, and reactive dyes, disperse dyes, etc. Among these, anionic dyes are preferred.

[0104] (Water-soluble dyes) Examples of water-soluble dyes include azo dyes, methine dyes, azomethine dyes, xanthene dyes, quinone dyes, phthalocyanine dyes, triphenylmethane dyes, diphenylmethane dyes, etc. Specific compounds thereof are as shown below, but the present invention is not limited to these exemplified compounds.

[0105] <C.I. Acid Yellow> 1, 3, 11, 17, 18, 19, 23, 25, 36, 38, 40, 42, 44, 49, 59, 61, 65, 67, 72, 73, 79, 99, 104, 110, 114, 116, 118, 121, 127, 129, 135, 137, 141, 143, 151, 155, 158, 159, 169, 176, 184, 193, 200, 204, 207, 215, 219, 220, 230, 232, 235, 241, 242, 246 <C.I. Acid Orange > 3, 7, 8, 10, 19, 24, 51, 56, 67, 74, 80, 86, 87, 88, 89, 94, 95, 107, 108, 116, 122, 127, 140, 142, 144, 149, 152, 156, 162, 166, 168 <C.I. Acid Red > 88, 97, 106, 111, 114, 118, 119, 127, 131, 138, 143, 145, 151, 183, 195, 198, 211, 215, 217, 225, 226, 249, 251, 254, 256, 257, 260, 261, 265, 266, 274, 276, 277, 289, 296, 299, 315, 318, 336, 337, 357, 359, 361, 362, 364, 366, 399, 407, 415 <C.I. Acid Violet > 17, 19, 21, 42, 43, 47, 48, 49, 54, 66, 78, 90, 97, 102, 109, 126

[0106] <C.I. Acid Blue> 1, 7, 9, 15, 23, 25, 40, 62, 72, 74, 80, 83, 90, 92, 103, 104, 112, 113, 114, 120, 127, 128, 129, 138, 140, 142, 156, 158, 171, 182, 185, 193, 199, 201, 203, 204, 205, 207, 209, 220, 221, 224, 225, 229, 230, 239, 249, 258, 260, 264, 278, 279, 280, 284, 290, 296, 298, 300, 317, 324, 333, 335, 338, 342, 350 <C.I. Acid Green> 9, 12, 16, 19, 20, 25, 27, 28, 40, 43, 56, 73, 81, 84, 104, 108, 109 <C.I. Acid Brown> 2, 4, 13, 14, 19, 28, 44, 123, 224, 226, 227, 248, 282, 283, 289, 294, 297, 298, 301, 355, 357, 413 <C.I. Acid Black > 1, 2, 3, 24, 26, 31, 50, 52, 58, 60, 63, 107, 109, 112, 119, 132, 140, 155, 172, 187, 188, 194, 207, 222

[0107] <C.I. Direct Yellow> 8, 9, 10, 11, 12, 22, 27, 28, 39, 44, 50, 58, 79, 86, 87, 98, 105, 106, 130, 132, 137, 142, 147, 153 <C.I. Direct Orange> 6, 26, 27, 34, 39, 40, 46, 102, 105, 107, 118 <C.I. Direct Red> 2, 4, 9, 23, 24, 31, 54, 62, 69, 79, 80, 81, 83, 84, 89, 95, 212, 224, 225, 226, 227, 239, 242, 243, 254 <C.I. Direct Violet > 9, 35, 51, 66, 94, 95 <C.I. Direct Blue> 1, 15, 71, 76, 77, 78, 80, 86, 87, 90, 98, 106, 108, 160, 168, 189, 192, 193, 199, 200, 201, 202, 203, 218, 225, 229, 237, 244, 248, 251, 270, 273, 274, 290, 291 <C.I. Direct Green> 26, 28, 59, 80, 85 <C.I. Direct Brown> 44, 106, 115, 195, 209, 210, 222, 223 <C.I. Direct Black > 17, 19, 22, 32, 51, 62, 108, 112, 113, 117, 118, 132, 146, 154, 159, 169

[0108] <C.I. Basic Yellow> 1, 2, 11, 13, 15, 19, 21, 28, 29, 32, 36, 40, 41, 45, 51, 63, 67, 70, 73, 91 <C.I. Basic Orange> 2, 21, 22 <C.I. Basic Red> 1, 2, 12, 13, 14, 15, 18, 23, 24, 27, 29, 35, 36, 39, 46, 51, 52, 69, 70, 73, 82, 109 <C.I. Basic Violet> 1, 3, 7, 10, 11, 15, 16, 21, 27, 39 <C.I. Basic Blue > 1, 3, 7, 9, 21, 22, 26, 41, 45, 47, 52, 54, 65, 69, 75, 77, 92, 100, 105, 117, 124, 129, 147, 151 <C.I. Basic Green> 1, 4 <C.I. Basic Brown> 1

[0109] <C.I. Reactive Yellow> 2, 3, 7, 15, 17, 18, 22, 23, 24, 25, 27, 37, 39, 42, 57, 69, 76, 81, 84, 85, 86, 87, 92, 95, 102, 105, 111, 125, 135, 136, 137, 142, 143, 145, 151, 160, 161, 165, 167, 168, 175, 176 <C.I. Reactive Orange > 1, 4, 5, 7, 11, 12, 13, 15, 16, 20, 30, 35, 56, 64, 67, 69, 70, 72, 74, 82, 84, 86, 87, 91, 92, 93, 95, 107 <C.I. Reactive Red > 2, 3, 5, 8, 11, 21, 22, 23, 24, 28, 29, 31, 33, 35, 43, 45, 49, 55, 56, 58, 65, 66, 78, 83, 84, 106, 111, 112, 113, 114, 116, 120, 123, 124, 128, 130, 136, 141, 147, 158, 159, 171, 174, 180, 183, 184, 187, 190, 193, 194, 195, 198, 218, 220, 222, 223, 228, 235 <C.I. Reactive Violet > 1, 2, 4, 5, 6, 22, 23, 33, 36, 38 <C.I. Reactive Blue > 2, 3, 4, 5, 7, 13, 14, 15, 19, 21, 25, 27, 28, 29, 38, 39, 41, 49, 50, 52, 63, 69, 71, 72, 77, 79, 89, 104, 109, 112, 113, 114, 116, 119, 120, 122, 137, 140, 143, 147, 160, 161, 162, 163, 168, 171, 176, 182, 184, 191, 194, 195, 198, 203, 204, 207, 209, 211, 214, 220, 221, 222, 231, 235, 236 <C.I. C.I. Reactive Green > 8, 12, 15, 19, 21 C.I. Reactive Brown > 2, 7, 9, 10, 11, 17, 18, 19, 21, 23, 31, 37, 43, 46 C.I. Reactive Black > 5, 8, 13, 14, 31, 34, 39 C.I. Food Black > 1, 2

[0110] <Pigment> Conventional organic and inorganic pigments can be used as the pigment. Examples of the pigment include azo pigments such as azo lakes, insoluble azo pigments, condensed azo pigments, and chelate azo pigments; polycyclic pigments such as phthalocyanine pigments, perylene and perylene pigments, anthraquinone pigments, quinacridone pigments, dioxane pigments, thioindigo pigments, isoindolinone pigments, and quinophthaloni pigments; dye lakes such as basic dye lakes and acid dye lakes; organic pigments such as nitro pigments, nitroso pigments, aniline black, and daylight fluorescent pigments; and inorganic pigments such as carbon black, titanium oxide, and iron oxide pigments. Anionic pigments are preferred as the pigment.

[0111] (Organic Pigments) Specific examples of organic pigments are listed below.

[0112] <Pigments for magenta or red> C.I. Pigment Red 2, C.I. Pigment Red 3, C.I. Pigment Red 5, C.I. Pigment Red 6, C.I. Pigment Red 7, C.I. Pigment Red 15, C.I. Pigment Red 16, C.I. Pigment Red 48:1, C.I. Pigment Red 53:1, C.I. Pigment Red 57:1, C.I. Pigment Red 122, C.I. Pigment Red 123, C.I. Pigment Red 139, C.I. Pigment Red 144, C.I. Pigment Red 149, C.I. Pigment Red 166, C.I. Pigment Red 177, C.I. Pigment Red 178, C.I. Pigment Red 222, etc.

[0113] <Orange or yellow pigments> C.I. Pigment Orange 31, C.I. Pigment Orange 43, C.I. Pigment Yellow 12, C.I. Pigment Yellow 13, C.I. Pigment Yellow 14, C.I. Pigment Yellow 15, C.I. Pigment Yellow 17, C.I. Pigment Yellow 74, C.I. Pigment Yellow 93, C.I. Pigment Yellow 94, C.I. Pigment Yellow 128, C.I. Pigment Yellow 138, C.I. Pigment Yellow 155, etc.

[0114] <Pigments for green or cyan> C.I. Pigment Blue 15, C.I. Pigment Blue 15:2, C.I. Pigment Blue 15:3, C.I. Pigment Blue 16, C.I. Pigment Blue 60, C.I. Pigment Green 7, etc.

[0115] These dyes and pigments may be used alone or in combination of two or more.

[0116] [Solvent] The ultraviolet-curable composition and ultraviolet-curable ink of the present invention contain a solvent. The solvent preferably contains water, and more preferably further contains a water-soluble organic solvent. That is, the solvent used in the present invention is more preferably a mixture of water and a water-soluble organic solvent.

[0117] Water-soluble organic solvents include those that function as moisturizing solvents to increase moisture retention and wettability, and those that are used as aqueous media to adjust viscosity, improve handling, and improve inkjet ejection properties. The two are not clearly distinguished, and water-soluble organic solvents used as moisturizing solvents also function as solvents.

[0118] In the present invention, the water-soluble organic solvent means a compound that is soluble in water, and although the solubility in water is not limited, a compound that can dissolve in water at any ratio is preferred. Furthermore, even if a compound is difficult to have the properties of a solvent by itself (for example, a compound that is solid or has a high viscosity at room temperature), the compound is included in the water-soluble organic solvent as long as it can be used as a solvent by being uniformly mixed with water.

[0119] Examples of the water-soluble organic solvent include polyhydric alcohols; ethers such as polyhydric alcohol alkyl ethers and polyhydric alcohol aryl ethers; nitrogen-containing heterocyclic compounds; amides; amines; and sulfur-containing compounds.

[0120] Specific examples of the water-soluble organic solvent include ethylene glycol, diethylene glycol, 1,2-propanediol (propylene glycol), 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 3-methyl-1,3-butanediol, triethylene glycol, polyethylene glycol, polypropylene glycol, 1,2-pentanediol, 1,3-pentanediol, 1,4-pentanediol, 2,4-pentanediol, 1,5-pentanediol, and 1,6-pentanediol. Polyhydric alcohols such as hexanediol, 1,2-hexanediol, 1,6-hexanediol, 1,3-hexanediol, 2,5-hexanediol, 1,5-hexanediol, glycerin, 1,2,6-hexanetriol, 2-ethyl-1,3-hexanediol, ethyl-1,2,4-butanetriol, 1,2,3-butanetriol, 2,2,4-trimethyl-1,3-pentanediol, and petriol; ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether polyhydric alcohol alkyl ethers such as ethylene glycol monophenyl ether, ethylene glycol monobenzyl ether, and the like; polyhydric alcohol aryl ethers such as ethylene glycol monophenyl ether, ethylene glycol monobenzyl ether, and the like; nitrogen-containing heterocyclic compounds such as 2-pyrrolidone, N-methyl-2-pyrrolidone, N-hydroxyethyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, ε-caprolactam, and γ-butyrolactone; amides such as formamide, N-methylformamide, N,N-dimethylformamide, 3-methoxy-N,N-dimethylpropionamide, and 3-butoxy-N,N-dimethylpropionamide; amines such as monoethanolamine, diethanolamine, and triethylamine; sulfur-containing compounds such as dimethyl sulfoxide, sulfolane, and thiodiethanol; propylene carbonate, ethylene carbonate, and the like.

[0121] Among these, propylene glycol and diethylene glycol ethyl methyl ether are preferred.

[0122] As the water-soluble organic solvent, it is preferable to use an organic solvent having a boiling point of 250° C. or less, since this not only functions as a moisturizing solvent but also provides good drying properties.

[0123] As the water-soluble organic solvent, polyol compounds having 8 or more carbon atoms and glycol ether compounds are also preferably used.

[0124] Specific examples of polyol compounds having 8 or more carbon atoms include 2-ethyl-1,3-hexanediol and 2,2,4-trimethyl-1,3-pentanediol.

[0125] Specific examples of glycol ether compounds include polyhydric alcohol alkyl ethers such as ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, diethylene glycol monoisobutyl ether, tetraethylene glycol monomethyl ether, and propylene glycol monoethyl ether; and polyhydric alcohol aryl ethers such as ethylene glycol monophenyl ether and ethylene glycol monobenzyl ether.

[0126] These water-soluble organic solvents may be used alone or in combination of two or more.

[0127] [Polymerization initiator] The polymerization initiator used in the present invention is preferably a photoradical polymerization initiator that generates radicals as active species by the energy of light (ultraviolet rays) received upon irradiation with ultraviolet rays, thereby initiating photopolymerization of the radically polymerizable compound, thereby curing the ultraviolet-curable composition or ultraviolet-curable ink.

[0128] The polymerization initiator may be dissolved in the solvent without being encapsulated in particles of the radical polymerizable compound, or may be contained in the solvent in a state encapsulated in particles of the radical polymerizable compound, or may be contained in both of these states.

[0129] The polymerization initiator may be a fat-soluble polymerization initiator (hereinafter may be referred to as a "fat-soluble initiator") or a water-soluble polymerization initiator (hereinafter may be referred to as a "water-soluble initiator"). Here, the term "fat-soluble initiator" refers to a polymerization initiator that is compatible with a polymerizable compound such as an ultraviolet-curable oligomer or that is soluble in an organic solvent. The term "water-soluble initiator" refers to an initiator that is soluble in water at a concentration of 1% by mass or more. The same applies to the "fat-soluble sensitizer" and "water-soluble sensitizer" described below.

[0130] The polymerization initiator used in the present invention is not limited to the following, but examples thereof include aromatic ketones, acylphosphine oxide compounds, aromatic onium salt compounds, organic peroxides, thio compounds (thioxanthone compounds, thiophenyl group-containing compounds), α-aminoalkylphenone compounds, hexaarylbiimidazole compounds, ketoxime ester compounds, borate compounds, azinium compounds, metallocene compounds, active ester compounds, compounds having a carbon-halogen bond, and alkylamine compounds.

[0131] The polymerization initiator used in the present invention may be used alone or in combination of two or more. For example, a fat-soluble initiator and a water-soluble initiator may be used in combination, and the fat-soluble initiator may be encapsulated in particles of a polymerizable compound such as an ultraviolet-curable oligomer, and the water-soluble initiator may be dissolved in an aqueous medium. In addition to the photoradical polymerization initiator as described above, a thermal radical polymerization initiator may also be used in combination as the polymerization initiator.

[0132] [Surfactant] The ultraviolet-curable composition I and ultraviolet-curable ink I of the present invention preferably contain a small amount of surfactant to ensure the flatness of the cured product and printed material to be formed and wettability with the substrate, to the extent that water resistance and washing fastness are not impaired. The ultraviolet-curable composition II and ultraviolet-curable ink II of the present invention preferably contain a small amount of surfactant to ensure the flatness of the cured product and printed material to be formed and wettability with the substrate, to the extent that water resistance and washing fastness are not impaired.

[0133] As the surfactant, any of nonionic surfactants such as silicone surfactants and fluorine surfactants, amphoteric surfactants, and anionic surfactants can be used. Among these, nonionic surfactants are preferred from the viewpoint of preventing unexpected aggregation with other components in the composition or ink of the present invention, and among nonionic surfactants, silicone surfactants are more preferred from the viewpoint of environmental compatibility. In particular, when comparing silicone surfactants with fluorine surfactants, silicone surfactants are more preferred because silicone surfactants suppress aggregation of other components in the composition or ink of the present invention.

[0134] The silicone surfactant is not particularly limited and can be appropriately selected depending on the purpose. Among them, those that do not decompose even at high pH are preferred, such as side-chain modified polydimethylsiloxane, both-end modified polydimethylsiloxane, one-end modified polydimethylsiloxane, and both-end modified polydimethylsiloxane of side chain. Furthermore, those having a polyoxyethylene group or a polyoxyethylene polyoxypropylene group as the modifying group are particularly preferred because they exhibit good properties as aqueous surfactants. Polyether-modified silicone surfactants can also be used as the silicone surfactant, such as a compound in which a polyalkylene oxide structure is introduced into the Si part side chain of dimethylsiloxane.

[0135] The fluorine-based surfactant is preferably a compound having 2 to 16 fluorine-substituted carbon atoms, more preferably a compound having 4 to 16 fluorine-substituted carbon atoms.

[0136] As fluorine-based surfactants, for example, perfluoroalkyl sulfonic acid compounds, perfluoroalkyl carboxylic acid compounds, perfluoroalkyl phosphate ester compounds, perfluoroalkyl alkylene oxide adducts, and polyoxyalkylene ether polymer compounds having perfluoroalkyl ether groups on the side chain are preferred because of their low foaming properties. Examples of perfluoroalkyl sulfonic acid compounds include perfluoroalkyl sulfonic acid and perfluoroalkyl sulfonate salts. Examples of perfluoroalkyl carboxylic acid compounds include perfluoroalkyl carboxylic acids and perfluoroalkyl carboxylate salts. Examples of perfluoroalkyl phosphate ester compounds include perfluoroalkyl phosphate esters and perfluoroalkyl phosphate ester salts. Examples of perfluoroalkyl alkylene oxide adducts include perfluoroalkyl ethylene oxide adducts. Examples of polyoxyalkylene ether polymer compounds having perfluoroalkyl ether groups on the side chain include sulfate ester salts of polyoxyalkylene ether polymers having perfluoroalkyl ether groups on the side chains, and salts of polyoxyalkylene ether polymers having perfluoroalkyl ether groups on the side chains. Counter ions of the salts in these fluorine-based surfactants include Li, Na, K, NH ４ , N.H. ３ CH ２ CH ２ OH, NH ２ (CH ２ CH ２ OH) ２ , NH(CH ２ CH ２ OH) ３ etc.

[0137] Among these, polyoxyalkylene ether polymer compounds having perfluoroalkyl ether groups in the side chains are more preferred because they have particularly low foaming properties, and fluorine-based surfactants represented by the following formulas (2A) and (2B) are particularly preferred.

[0138] CF ３ CF ２(CF ２ CF ２ ) ｓ -CH ２ CH ２ O (CH ２ CH ２ O) ｔ H (2A) In the compound represented by formula (2A), s is preferably an integer of 0 or more and 10 or less, and t is preferably an integer of 0 or more and 40 or less, in order to impart water solubility.

[0139] C ｒ F ２ｒ＋１ -CH ２ CH(OH)CH ２ -O-(CH ２ CH ２ O) ｃ -Z ... (2B) In the compound represented by formula (2B), Z is H, C ｄ F ２ｄ＋１ , C.H. ２ CH(OH)CH ２ -C ｅ F ２ｅ＋１ , or C ｆ H ２ｆ＋１ It is. C ｄ F ２ｄ＋１ In the formula, d is an integer of 1 to 6. ２ CH(OH)CH ２ -C ｅ F ２ｅ＋１ In the formula, e is an integer of 4 or more and 6 or less. ｆ H ２ｆ＋１ In the formula, f is an integer of 1 or more and 19 or less, r is an integer of 1 or more and 6 or less, and c is an integer of 4 or more and 14 or less.

[0140] Commercially available fluorine-based surfactants can be used, such as Surflon S-111, S-112, S-113, S-121, S-131, S-132, S-141, and S-145 (manufactured by AGC Seimi Chemical Co., Ltd.), Fullard FC-93, FC-95, FC-98, FC-129, FC-135, FC-170C, FC-430, and FC-431 (manufactured by Sumitomo 3M Limited), Megafac F-470, F-1405, and F-474 (manufactured by DIC Corporation), Zonyl TBS, FSP, FSA, FSN-100, FSN, and FSO-100, Examples of suitable cellulose acetate copolymers include FSO, FS-300, and UR (manufactured by DuPont); FT-110, FT-250, FT-251, FT-400S, FT-150, and FT-400SW (manufactured by Neos Co., Ltd.), Polyfox PF-136A, PF-156A, PF-151N, PF-154, and PF-159 (manufactured by Omnova), Noigen FN-1287 (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.), Unidyne DSN-403N (manufactured by Daikin Industries, Ltd.), and LE-604, LE-605, LE-606, and LE-607 (manufactured by Kyoeisha Chemical Co., Ltd.).

[0141] Examples of amphoteric surfactants include lauryl aminopropionate, lauryl dimethyl betaine, stearyl dimethyl betaine, and lauryl dihydroxyethyl betaine.

[0142] Examples of nonionic surfactants include polyoxyethylene alkylphenyl ethers, polyoxyethylene alkyl esters, polyoxyethylene alkylamines, polyoxyethylene alkylamides, polyoxyethylene propylene block polymers, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, acetylene alcohol derivatives, and acetylene glycol derivatives.

[0143] Examples of anionic surfactants include polyoxyethylene alkyl ether acetates, dodecylbenzenesulfonates, laurates, and salts of polyoxyethylene alkyl ether sulfates.

[0144] These may be used alone or in combination of two or more.

[0145] As described above, the silicone surfactant is not particularly limited and can be appropriately selected depending on the purpose. Polyether-modified silicone surfactants having a polyoxyethylene group or a polyoxyethylene polyoxypropylene group as a modifying group are particularly preferred because they exhibit good properties as aqueous surfactants.

[0146] Such surfactants may be synthesized appropriately or commercially available products, such as those available from BYK Corporation, Shin-Etsu Chemical Co., Ltd., Dow Corning Toray Co., Ltd., Nippon Emulsion Co., Ltd., and Kyoeisha Chemical Co., Ltd.

[0147] The polyether-modified silicone surfactant is not particularly limited and can be appropriately selected depending on the purpose. For example, it may be a surfactant represented by the following formula (2) in which a polyalkylene oxide structure is introduced into the Si moiety side chain of dimethylpolysiloxane.

[0148]

[0149] Commercially available polyether-modified silicone surfactants can be used, such as KF-618, KF-642, and KF-643 (Shin-Etsu Chemical Co., Ltd.), SAG001, SAG002, SAG003, SAG005, SAG503, and SAG008 (Nissin Chemical Industry Co., Ltd.), EMALEX-SS-5602 and SS-1906EX (Nippon Emulsion Co., Ltd.), FZ-2105, FZ-2118, and FZ-21 54, FZ-2161, FZ-2162, FZ-2163, FZ-2164 (Dow Corning Toray Co., Ltd.), BYK-199, BYK-333, BYK-347, BYK-348, BYK-349, BYK-378 (BYK-Chemie Co., Ltd.), TSF4440, TSF4452 (Momentive Performance Materials, Inc.), and the like.

[0150] [Sensitizer] The ultraviolet-curable composition and ultraviolet-curable ink of the present invention may contain a sensitizer. When a sensitizer is present in the ultraviolet-curable composition and ultraviolet-curable ink together with a polymerization initiator, the sensitizer in the system absorbs actinic energy rays to become excited, and upon contact with the polymerization initiator, promotes decomposition of the polymerization initiator, thereby enabling a curing reaction with higher sensitivity.

[0151] The sensitizer may be either fat-soluble or water-soluble. If the sensitizer is fat-soluble, it can be encapsulated in the radical polymerizable compound particles.

[0152] Examples of sensitizers that can be used include aliphatic amines, amines having an aromatic group, and cyclic amine compounds such as piperidine; alkoxyanthracene compounds, urea compounds such as o-tolylthiourea; sulfur compounds such as sodium diethylthiophosphate and soluble salts of aromatic sulfinic acids; nitrile compounds such as N,N'-disubstituted-p-aminobenzonitrile; phosphorus compounds such as tri-n-butylphosphine and sodium diethyldithiophosphate; Michler's ketone, N-nitrosohydroxylamine derivatives, oxazolidine compounds, tetrahydro-1,3-oxazine compounds; and nitrogen compounds such as condensates of formaldehyde or acetaldehyde with diamines.

[0153] These sensitizers may be used alone or in combination of two or more.

[0154] [Other Oligomers, Resins, and Monomers] In addition to the components described above, the ultraviolet-curable composition and ultraviolet-curable ink of the present invention may contain, as necessary, any resin component, any oligomer component, or any monomer component (collectively referred to as "other resin components"). The other resin components may be encapsulated in particles of the radical-polymerizable compound, may be dissolved in a solvent, or may be dispersed alone or in a complex with other components in the composition or ink.

[0155] [Other Additives] In addition to the above components, the ultraviolet-curable composition and ultraviolet-curable ink of the present invention may contain other additives, if necessary.

[0156] Examples of other additives include known additives such as anti-fading agents, emulsion stabilizers, penetration enhancers, ultraviolet absorbers, preservatives, antifungal agents, rust inhibitors, pH adjusters, viscosity adjusters, dispersants, dispersion stabilizers, antifoaming agents, solid wetting agents, chelating agents, etc. These various additives may be added after or during preparation.

[0157] For other additives, reference can be made to the descriptions in paragraphs 0088 to 0096 of JP-A No. 2010-65205 and paragraphs 0083 to 0090 of JP-A No. 2010-70669, as appropriate.

[0158] [Content of each component] The content of water in the ultraviolet-curable composition and ultraviolet-curable ink of the present invention is not particularly limited and can be appropriately selected depending on the purpose. When used as an inkjet ink, the content of water in the ultraviolet-curable composition and ultraviolet-curable ink of the present invention is usually 40% by mass or more, preferably 50% by mass or more, and usually 90% by mass or less, preferably 80% by mass or less, from the viewpoint of drying properties and ejection reliability of the ink.

[0159]

[0042] When the ultraviolet-curable composition and ultraviolet-curable ink of the present invention contain a water-soluble organic solvent, the content thereof (the total content of the water-soluble organic solvent that also serves as a moisturizing solvent and the water-soluble organic solvent that is used as an aqueous medium) is not particularly limited and can be appropriately selected depending on the type of water-soluble organic solvent used and the purpose. When used as an inkjet ink, the content of the water-soluble organic solvent is usually 10% by mass or more and usually 50% by mass or less, preferably 40% by mass or less, based on the total mass of the ultraviolet-curable composition and ultraviolet-curable ink, from the viewpoints of drying property, ejection reliability, wettability with a substrate, etc.

[0160] The total solids concentration, which is the concentration of components other than the solvent in the ultraviolet-curable composition and ultraviolet-curable ink of the present invention, is not particularly limited and can be appropriately selected depending on the purpose. From the viewpoint of coatability, the total solids concentration is adjusted to usually 40% by mass or less, preferably 35% by mass or less, based on the total mass of the ultraviolet-curable composition and ultraviolet-curable ink. When used as an inkjet ink, from the viewpoints of drying property and ejection reliability, the total solids concentration is adjusted to usually 5% by mass or more, preferably 7% by mass or more, more preferably 9% by mass or more, and usually 30% by mass or less, preferably 25% by mass or less, more preferably 23% by mass or less, even more preferably 20% by mass or less, and particularly preferably 15% by mass or less, based on the total mass of the ultraviolet-curable composition and ultraviolet-curable ink.

[0161] When a mixture of water and a water-soluble organic solvent is used as the solvent, the ratio of water to the water-soluble organic solvent (the total of the water-soluble organic solvent that also serves as a moisturizing solvent and the water-soluble organic solvent used as a solvent) is preferably such that the ratio of water to water-soluble organic solvent is usually 1:0.05 to 1:1.5 (mass ratio), preferably 1:0.1 to 1:1.2 (mass ratio), and more preferably 1:0.15 to 1:1.1 (mass ratio), from the viewpoint of improving drying properties and ejection properties during inkjet printing.

[0162]

[0033] The content of the radical polymerizable compound in the ultraviolet-curable composition and ultraviolet-curable ink of the present invention is preferably 5% by mass or more, more preferably 6% by mass or more, and even more preferably 7% by mass or more, based on the total mass of the ultraviolet-curable composition and ultraviolet-curable ink, from the viewpoints of the performance of the cured product and printed material obtained and ultraviolet curability. On the other hand, when used as an inkjet ink, the content of the radical polymerizable compound is usually 20% by mass or less, preferably 15% by mass or less, and more preferably 12% by mass or less, based on the total mass of the ultraviolet-curable composition and ultraviolet-curable ink, from the viewpoint of ejection stability. From the same viewpoint, the content of the radical polymerizable compound in the total solids content of the ultraviolet-curable composition and ultraviolet-curable ink of the present invention is preferably 40% by mass or more, more preferably 45% by mass or more, and even more preferably 50% by mass or more, and is usually 95% by mass or less, preferably 90% by mass or less, and more preferably 85% by mass or less.

[0163] The total solids content in the UV-curable composition and UV-curable ink of the present invention can be rephrased as the components of the cured product and printed material formed from the UV-curable composition and UV-curable ink of the present invention, and the above-mentioned numerical ranges can be similarly adopted. The content of each component in the total solids content is approximately equal to the content of that component in the cured product and printed material formed from the UV-curable composition and UV-curable ink of the present invention. Therefore, the content of the radically polymerizable compound in the total solids content of the UV-curable composition and UV-curable ink of the present invention is preferably 40% by mass or more, more preferably 45% by mass or more, and even more preferably 50% by mass or more, and usually 95% by mass or less, preferably 90% by mass or less, and more preferably 85% by mass or less, relative to the total mass of the UV-curable composition and UV-curable ink. This can be interpreted as meaning that the content of components derived from the radically polymerizable compound in the cured product and printed material formed from the UV-curable composition and UV-curable ink of the present invention is preferably 40% by mass or more, more preferably 45% by mass or more, and even more preferably 50% by mass or more, and usually 95% by mass or less, preferably 90% by mass or less, and more preferably 85% by mass or less. The same applies to the contents of the colorants and other components described below.

[0164]

[0033] From the viewpoint of the effect of improving washing fastness by using the urethane resin particles, the content of urethane resin particles in the ultraviolet-curable composition and ultraviolet-curable ink of the present invention is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, even more preferably 0.4% by mass or more, and particularly preferably 0.5% by mass or more, relative to the total mass of the ultraviolet-curable composition and ultraviolet-curable ink. On the other hand, when used as an inkjet ink, from the viewpoint of ejection stability, the content of urethane resin particles is usually 10% by mass or less, preferably 7.5% by mass or less, and more preferably 5% by mass or less, relative to the total mass of the ultraviolet-curable composition and ultraviolet-curable ink. From the same viewpoint, the content of urethane resin particles in the total solid content of the ultraviolet-curable composition of the present invention is preferably 1% by mass or more, more preferably 2% by mass or more, even more preferably 3% by mass or more, and particularly preferably 10% by mass or more, and is usually 50% by mass or less, preferably 40% by mass or less, and more preferably 30% by mass or less.

[0165] The content of urethane resin particles in the ultraviolet-curable composition and ultraviolet-curable ink of the present invention is preferably 3% by mass or more, more preferably 3.5% by mass or more, and even more preferably 4% by mass or more, relative to the content of the radical-polymerizable compound. On the other hand, the content of urethane resin particles is preferably 30% by mass or less, more preferably 28% by mass or less, and even more preferably 26% by mass or less, relative to the content of the radical-polymerizable compound. When the content of urethane resin particles relative to the radical-polymerizable compound is equal to or greater than the above-mentioned lower limit, the effect of improving washing fastness by using the urethane resin particles is excellent, and when it is equal to or less than the above-mentioned upper limit, storage stability is excellent.

[0166]

[0043] From the viewpoints of improving image density, good fixability, and ejection stability, the content of the colorant in the ultraviolet-curable ink of the present invention is usually 0.1% by mass or more, preferably 1% by mass or more, and usually 8% by mass or less, preferably 6% by mass or less. From the same viewpoints, the content of the colorant in the total solid content of the ultraviolet-curable ink of the present invention is usually 1% by mass or more, preferably 5% by mass or more, and usually 40% by mass or less, preferably 30% by mass or less.

[0167] The total content of all polymerization initiators in the ultraviolet-curable composition and ultraviolet-curable ink of the present invention is usually 0.06% by mass or more, preferably 0.13% by mass or more, and more preferably 0.35% by mass or more, relative to the total mass of the ultraviolet-curable composition and ultraviolet-curable ink. It is usually 12% by mass or less, preferably 8% by mass or less, more preferably 4% by mass or less, and even more preferably 2.7% by mass or less. When the total content of all polymerization initiators is within the above range, curability can be improved. From the same viewpoint, the total content of all polymerization initiators in the total solids content of the ultraviolet-curable composition and ultraviolet-curable ink of the present invention is usually 0.55% by mass or more, preferably 1.1% by mass or more, more preferably 2.3% by mass or more, and even more preferably 3.5% by mass or more. It is usually 28% by mass or less, preferably 21% by mass or less, and more preferably 15% by mass or less.

[0168]

[0033] When the ultraviolet-curable composition I and ultraviolet-curable ink I of the present invention contain a surfactant, the content of the surfactant in the ultraviolet-curable composition II and ultraviolet-curable ink II of the present invention is not particularly limited, and can be appropriately selected depending on the purpose, as long as it does not impair water resistance or washing fastness. From the viewpoint of improving wettability, surface smoothness after application, and ejection stability during inkjet printing, the content of the surfactant in the ultraviolet-curable composition and ultraviolet-curable ink is usually 0.001% by mass or more, preferably 0.01% by mass or more, and more preferably 0.03% by mass or more, relative to the total mass of the ultraviolet-curable composition and ultraviolet-curable ink, and usually 5% by mass or less, preferably 3% by mass or less, and more preferably 1% by mass or less. From the same viewpoint, the content of the surfactant in the total solids content of the ultraviolet-curable composition and ultraviolet-curable ink of the present invention is usually 0.01% by mass or more, preferably 0.1% by mass or more, and more preferably 0.2% by mass or more, and usually 10% by mass or less, preferably 5% by mass or less, and more preferably 3% by mass or less.

[0169] When the ultraviolet-curable composition and ultraviolet-curable ink of the present invention contain a sensitizer, the content thereof is usually 0.01% by mass or more, preferably 0.03% by mass or more, more preferably 0.05% by mass or more, and usually 4% by mass or less, preferably 3% by mass or less, more preferably 1% by mass or less, and even more preferably 0.7% by mass or less, relative to the total mass of the ultraviolet-curable composition and ultraviolet-curable ink. If the content of the sensitizer is within the above range, the effect of the sensitizer can be sufficiently obtained. From the same viewpoint, the content of the sensitizer in the total solids content of the ultraviolet-curable composition and ultraviolet-curable ink of the present invention is usually 0.05% by mass or more, preferably 0.1% by mass or more, more preferably 0.3% by mass or more, and even more preferably 0.5% by mass or more, and usually 8% by mass or less, preferably 6% by mass or less, and more preferably 5% by mass or less.

[0170] [Method for Producing UV-Curable Composition and UV-Curable Ink] There are no particular limitations on the method for producing the UV-curable composition and UV-curable ink of the present invention. For example, the UV-curable composition and UV-curable ink of the present invention can be produced by preparing a dispersion in which a radically polymerizable compound is dispersed as particles in an aqueous medium (hereinafter, sometimes referred to as a "radical-polymerizable compound dispersion") and, if necessary, a dispersion in which a colorant such as a pigment is dispersed in an aqueous medium (hereinafter, sometimes referred to as a "colorant dispersion"), and then mixing the radically polymerizable compound dispersion with urethane resin particles (as described above, a commercially available aqueous dispersion of urethane resin particles can be used), a polymerization initiator, and, if necessary, a surfactant, other additives, an organic solvent, and the colorant dispersion. Even if a colorant is added to the UV-curable composition of the present invention, a UV-curable ink with similar performance can be obtained.

[0171] [Preparation of Radical Polymerizable Compound Dispersion] The radical polymerizable compound dispersion can be prepared by known methods such as high-pressure emulsification and phase inversion emulsification. Various known emulsifiers and dispersants may be used as needed to prepare the radical polymerizable compound dispersion, as long as the effects of the present invention are not impaired. The high-pressure emulsification method involves premixing an aqueous phase, an oil phase, and an amphipathic substance such as a surfactant, and emulsifying the mixture using a high-pressure emulsifier such as a homogenizer. The phase inversion emulsification method involves dissolving and dispersing an amphipathic substance such as a surfactant in an oil phase, and then adding an aqueous phase to obtain an O / W emulsion. When two or more radical polymerizable compounds are used, it is preferable to premix them before preparing the dispersion. From the standpoint of ease of handling, the solids concentration of the radical polymerizable compound dispersion thus prepared is preferably approximately 10% by mass or more and 40% by mass or less.

[0172] Two or more kinds of radical polymerizable compounds may be used. Each radical polymerizable compound may be separately prepared into a dispersion and mixed at any ratio, but it is preferable to premix the radical polymerizable compounds before preparing the dispersion. In addition, other components, such as a non-radical polymerizable polymer, a polymerization initiator, a preservative, etc., may be premixed and then prepared into a dispersion.

[0173] In addition to the above-mentioned emulsification method, emulsion polymerization is also a method for preparing a radically polymerizable compound dispersion. Emulsion polymerization is a polymerization method in which an aqueous medium, a water-insoluble radically polymerizable monomer such as a vinyl monomer, and an emulsifier are mixed together, and radical polymerization is carried out in an emulsion state. However, emulsion polymerization makes it difficult to obtain emulsion particles stably dispersed in an aqueous medium while controlling and retaining radically polymerizable groups in the polymer. Furthermore, since a large amount of emulsifier remains in the system, there is a concern that the water resistance and washfastness of the resulting cured product or printed material may be significantly impaired, or that environmentally harmful components may be gradually released. For this reason, it is preferable not to use radically polymerizable compounds obtained by emulsion polymerization, i.e., radically polymerizable compounds that are emulsion polymers, as the radically polymerizable compounds used in the present invention. The UV-curable composition I and UV-curable ink I of the present invention use radically polymerizable compounds that do not contain emulsion polymers. That is, the radical polymerizable compound particles used in the present invention are preferably obtained not by emulsion polymerization but by an emulsification method other than emulsion polymerization, such as high-pressure emulsification or phase inversion emulsification.

[0174] [Preparation of Colorant Dispersion] The colorant dispersion can be prepared by adding a colorant such as a pigment to a solvent such as water and mixing them. From the viewpoints of handling and storage stability, the concentration of the colorant such as a pigment in the colorant dispersion is usually 5% by mass or more, preferably 10% by mass or more, and usually 40% by mass or less, preferably 35% by mass or less.

[0175] As the colorant dispersion, a commercially available product may be used as it is.

[0176] [Viscosity of UV-curable composition] The viscosity of the UV-curable composition of the present invention can be adjusted as desired depending on the application and usage form. When the UV-curable composition of the present invention is used in an inkjet printer, the viscosity at 25°C is preferably 25 mPa·sec or less, more preferably 20 mPa·sec or less, and even more preferably 10 mPa·sec or less. The lower limit of the viscosity of the UV-curable composition of the present invention is not particularly limited, but is preferably 1 mPa·sec or more, more preferably 2 mPa·sec or more.

[0177] [Viscosity of UV-curable ink] The viscosity of the UV-curable ink of the present invention can be adjusted as desired depending on the application and mode of use. When the UV-curable ink of the present invention is used in an inkjet printer, the viscosity at 25°C is preferably 25 mPa·sec or less, more preferably 20 mPa·sec or less, and even more preferably 10 mPa·sec or less. The lower limit of the viscosity of the UV-curable ink of the present invention is not particularly limited, but is preferably 1 mPa·sec or more, and more preferably 2 mPa·sec or more.

[0178] [Substrate] The substrate to which the ultraviolet-curable composition and ultraviolet-curable ink of the present invention can be applied is not particularly limited, and examples thereof include plastic materials such as polyesters such as polyethylene terephthalate (PET), polyolefins such as polyvinyl chloride (PVC), polyethylene (PE), and polypropylene (PP), paper, textiles (cloth and fabrics), leather, glass, ceramics, wood, metal, rubber, and composites thereof. The ultraviolet-curable composition and ultraviolet-curable ink of the present invention can form cured products and printed products that have good adhesion to various substrates and excellent strength, such as washing fastness.

[0179] As described in the mechanism above, the ultraviolet-curable composition and ultraviolet-curable ink of the present invention contain urethane resin particles, which effectively enables the urethane resin of the urethane resin particles to exhibit good adhesion to the fibers of a water-absorbent substrate such as a fabric, and therefore it is effective to use a water-absorbent substrate such as a fabric as the substrate.

[0180] [Cured Products and Printed Products] Cured products and printed products can be obtained by curing the UV-curable composition and UV-curable ink of the present invention. Methods for curing the UV-curable composition and UV-curable ink of the present invention to obtain cured products and printed products include applying the UV-curable composition and UV-curable ink to a substrate using known methods such as a coater such as a spin coater or a bar coater, or various printing methods such as inkjet printing, and then irradiating the substrate with active energy rays. Alternatively, a method can be used in which the composition is first applied to a substrate such as a film, then transferred to another substrate, and then irradiated with active energy rays. Furthermore, patterns of cured products and printed products can be created by photolithography. Irradiation with active energy rays decomposes the polymerization initiator to generate radicals, and the polymerization reaction of the radically polymerizable compound proceeds.

[0181] A drying step may be added before or after the irradiation of the active energy rays, or before, after, or simultaneously with the irradiation. In the drying step, for example, the substrate is heated. The heating temperature when heating the substrate in the drying step is preferably 25°C or higher, more preferably 30°C or higher, and even more preferably 35°C or higher. By carrying out the heating, volatile components such as solvents can be dried, and curability tends to be further improved. The upper limit of the heating temperature is not particularly limited. Since the ultraviolet-curable composition and ultraviolet-curable ink of the present invention contain urethane resin particles, high-temperature, long-term heating is unnecessary. Therefore, the heating conditions are preferably 25 to 120°C, particularly 30 to 100°C, for about 1 to 60 minutes.

[0182] The heating means is not particularly limited, but examples thereof include a ceramic heater, a halogen heater, and a quartz tube heater.

[0183] As described above, the timing of heating may be any time before, during, or after the ultraviolet-curable composition or ultraviolet-curable ink of the present invention is applied to a substrate. However, it is more preferable to continue heating throughout the entire process, before, during, and after application.

[0184] The drying step may involve not only heating the substrate as described above, but also further including, for example, air drying or reduced pressure drying in a normal temperature and humidity environment, or may involve only air drying or reduced pressure drying without heating.

[0185] [Light Source (Activated Energy Ray Source)] Mercury lamps, metal halide lamps, gas / solid-state lasers, etc. are widely known as light sources (activated energy ray sources). However, there is currently a strong demand for mercury-free devices from the perspective of environmental protection, and replacement with GaN-based semiconductor ultraviolet light-emitting devices would be extremely useful from both an industrial and environmental perspective. Furthermore, ultraviolet light-emitting diodes (UV-LEDs) and ultraviolet laser diodes (UV-LDs) are small, have a long life, are highly efficient, and are low cost, and are expected to be used as light sources for ultraviolet-curable inkjet printers. Among these, UV-LEDs are preferred.

[0186] The emission peak wavelength of the active energy ray source to be irradiated is preferably in the range of 350 to 450 nm. The irradiation energy is 20 J / cm ２ For example, 0.5 to 10 J / cm ２ is preferred.

[0187] The emission peak wavelength may be one or more within the above wavelength range. The irradiation of active energy rays is not limited to the above-mentioned intentional process, but may also be, for example, outdoor exposure to sunlight. When the radical polymerizable compound used in the present invention has high reactivity (curability), heating alone is sufficient without irradiation with active energy rays. In other words, it is sufficient for the ultraviolet-curable composition or ink of the present invention to have ultraviolet curability, and it is not limited to being used in a printing method including a step of irradiating active energy rays.

[0188] [Inkjet Ink Storage Container] The ultraviolet-curable ink of the present invention can be stored in an ink cartridge or ink bottle, which eliminates the need to directly touch the ink during operations such as ink transport and ink replacement, preventing staining of fingers and clothing. It also prevents foreign matter such as dust from getting mixed into the ink. The shape, size, material, etc. of the ink storage container itself are not particularly limited, as long as they are suitable for, for example, the inkjet printer to which they are applied. It is desirable that the material of the ink storage container be a light-blocking material that does not transmit light, or that the container be covered with a light-blocking sheet or the like.

[0189] [Inkjet Recording Method] The UV-curable ink of the present invention can be suitably used in an inkjet recording method. The inkjet recording method using the UV-curable ink of the present invention preferably comprises a step of ejecting the UV-curable ink of the present invention from an ejection nozzle of an inkjet printer to adhere to a substrate, a heating step of heating the substrate to which the ink has adhered, and an irradiation step of irradiating the ink adhered to the substrate with actinic energy rays.

[0190] The step of applying the ultraviolet-curable ink of the present invention to a substrate is not necessarily limited to a method using an inkjet printer, as long as the ink is applied to the substrate in a mist (mist or spray form). In the heating step, the presence of a heating means generally tends to cause the ink on the nozzle surface to dry, resulting in ejection defects, so the heating temperature is preferably 120°C or lower, and more preferably 100°C or lower.

[0191] [Applications] The UV-curable composition and UV-curable ink of the present invention are water-based, which makes them environmentally friendly and safe, and they provide a good balance of required performance, while also providing excellent water resistance and solvent resistance to cured and printed products. When used as an ink, they are characterized by their ability to print images with high image quality and excellent cured film performance on various substrates with high productivity, and can be used in a variety of applications, including posters, road signs, signboards, billboards, various outdoor and indoor display boards, building materials (surface materials for exteriors, interiors, walls, floors, ceilings, windows, etc.), exteriors of vehicles (automobiles, trains, aircraft, etc.), surface materials for furniture and office equipment, and paper prints. The applications of the UV-curable composition of the present invention are not limited to inks, but can also be used in coating materials, adhesives, paints, etc.

[0192] In particular, the ultraviolet-curable composition and ultraviolet-curable ink of the present invention can form a printed coating film with excellent coating film strength, particularly high washing fastness, due to the urethane resin particles contained therein. Therefore, the ultraviolet-curable composition and ultraviolet-curable ink of the present invention can be suitably used for various applications such as fabrics for clothing such as T-shirts, other textiles that may become wet with water, wallpaper for interior use, and home furnishings.

[0193] An embodiment of the present invention will be described below, but the present invention is not limited to this embodiment.

[0194] <<Measurement Methods>> The following measurements were carried out on the raw materials used in the Examples and Comparative Examples.

[0195] <Tg of Urethane Resin Particles> The Tg of the urethane resin particles used in the examples and comparative examples was measured using a differential scanning calorimeter (DSC) (DSC7000X, manufactured by Hitachi High-Tech Science Corporation) using the following method. (Measurement Conditions) A dried film of a dispersion of urethane resin particles was prepared as a measurement sample, and 5 to 10 mg was placed in an aluminum sample pan and measured under a nitrogen atmosphere. During measurement, the starting temperature was 30°C, and the temperature was increased to 120°C at 10°C / min, and then decreased to -100°C at 10°C / min. A second temperature increase was then performed at 10°C / min, and measurements were made up to 120°C. From the graph of heat absorption and heat generation obtained under the above conditions, the temperature at which the gradient of the stepwise change curve observed during the second temperature increase was greatest was determined as the Tg.

[0196] <Volume average particle size (D ５０ )> Volume average particle diameter (D ５０ ) was measured using a particle size distribution analyzer NANOTRAC WAVE II-EX150 (manufactured by Microtrac Bell Co., Ltd.) by dynamic light scattering.

[0197] <<Test Example 1>> [Urethane Resin Particles] The following urethane resin particles were used.

[0198] <For Examples> IMPRANIL (registered trademark) DL3040: Aqueous dispersion of urethane resin particles (Tg: -55°C, volume average particle size (D ５０ IMPRANIL (registered trademark) DLI: polyurethane resin particle water dispersion (Tg: -52°C, volume average particle diameter (D ５０ Takelac (registered trademark) W-6110: Aqueous dispersion of urethane resin particles (Tg: -36°C, volume average particle diameter (D ５０ DISPERCOLL (registered trademark) U53: Aqueous dispersion of urethane resin particles (Tg: -52°C, volume average particle diameter (D ５０DISPERCOLL (registered trademark) U56: Aqueous dispersion of urethane resin particles (Tg: -55°C, volume average particle diameter (D ５０ DISPERCOLL (registered trademark) U8755: Aqueous dispersion of urethane resin particles (Tg: -55°C, volume average particle diameter (D ５０ Superflex (registered trademark) 300: Aqueous dispersion of urethane resin particles (Tg: -52°C, volume average particle diameter (D): 140 nm) manufactured by Daiichi Kogyo Seiyaku Co., Ltd. ５０ Superflex (registered trademark) 500M: Aqueous dispersion of urethane resin particles (Tg: -57°C, volume average particle diameter (D): 58 nm) manufactured by Daiichi Kogyo Seiyaku Co., Ltd. ５０ DAOTAN (registered trademark) TW 6450 / 30WA: Aqueous dispersion of urethane resin particles (Tg: -28°C, volume average particle diameter (D ５０ ): 32 nm)

[0199] <For Comparative Examples> TAKELAC (registered trademark) WS-4000: Aqueous dispersion of urethane resin particles manufactured by Mitsui Chemicals, Inc. (Tg: undetectable) TAKELAC (registered trademark) W-605: Aqueous dispersion of urethane resin particles manufactured by Mitsui Chemicals, Inc. (Tg: undetectable) TAKELAC (registered trademark) W-5030: Aqueous dispersion of urethane resin particles manufactured by Mitsui Chemicals, Inc. (Tg: undetectable) IMPRANIL (registered trademark) DLP-R: Aqueous dispersion of urethane resin particles manufactured by Sumika Covestro Urethane Co., Ltd. (Tg: -6°C, volume average particle diameter (D ５０ DISPERCOLL (registered trademark) U42: Urethane resin particle water dispersion (Tg: -6°C) manufactured by Sumika Covestro Urethane Co., Ltd.

[0200] [Preparation of Radically Polymerizable Compound 1] 0.4 mol of hexamethylene diisocyanate trimer, 0.8 mol of dipentaerythritol pentaacrylate, and 0.4 mol of polyethylene glycol monoallyl ether (in the formula (1) above, Alk=ethylene group, J=allyl group, and g=30 to 40) were reacted to produce radically polymerizable compound 1.

[0201] [Preparation of Aqueous Dispersion of Radical Polymerizable Compound 1] The radical polymerizable compound 1 was kept at 60°C, and GENOPOL TX-2 manufactured by RAHN was added as a polymerization initiator A in an amount of 1 mass % relative to the radical polymerizable compound. While stirring and mixing, ion-exchanged water preheated to 60°C was added to prepare an aqueous dispersion of the radical polymerizable compound 1. The volume average particle diameter (D ５０ The solid content of this aqueous dispersion was 20% by mass.

[0202] [Preparation of Ink 1] Ink 1 was obtained by adding and mixing ion-exchanged water, an aqueous dispersion of radically polymerizable compound 1, IMPRANIL (registered trademark) DL3040 manufactured by Sumika Covestro Urethane Co., Ltd., 10 parts by mass each of diethylene glycol ethyl methyl ether and propylene glycol as water-soluble organic solvents, 1.0 part by mass of a polymerization initiator mixture different from polymerization initiator A, 0.12 parts by mass of BYK-347 manufactured by BYK Japan KK as a silicone surfactant, and 2.5 parts by mass of black pigment (C.I. Pigment Black 7) in the amounts shown in Table 1. Note that the ion-exchanged water was added in an amount (i.e., the remainder) obtained by subtracting the total parts by mass of the aforementioned materials other than ion-exchanged water from 100 parts by mass when the total parts by mass of all the aforementioned materials including ion-exchanged water is taken as 100 parts by mass.

[0203] The values ​​of the contents of the radical polymerizable compound and urethane resin particles in the ultraviolet curable ink in Table 1 are values ​​of the contents of the radical polymerizable compound and urethane resin particles converted from the contents of the radical polymerizable compound and urethane resin particles in the respective aqueous dispersions. The same applies to Table 2.

[0204] [Preparation of Inks 2 to 21] Inks 2 to 21 were obtained in the same manner as Ink 1, except that the type and / or content of urethane resin particles and the content of radical polymerizable compound 1 were changed as shown in Table 1.

[0205] The composition obtained by removing the black pigment from the prepared ink corresponds to the ultraviolet-curable composition of the present invention.

[0206] [Example 1-1] A white fabric (cotton) was used as the substrate, and 5 μL of ink 1 was measured with a micropipette and dropped onto the substrate heated to 40° C. on a hot plate. After heating for 10 minutes, the substrate was irradiated with 7 J / cm 2 of an LED having a peak wavelength of 385 nm. ２ The coating was irradiated with ultraviolet light having an irradiation energy of 1000 kJ / cm to form a cured film.

[0207] Examples 1-2 to 1-15, Comparative Examples 1-1 to 1-6 Cured films were obtained in the same manner as in Example 1-1, except that the type of ink was changed as shown in Table 1.

[0208] [Evaluation of washing fastness of cured film (washing fastness 1)] Evaluation of washing fastness was carried out by scrubbing cotton with a cured film obtained in each Example and Comparative Example while wetting the cured film with running water, and visually observing the cotton after scrubbing. The observation results were evaluated according to the following evaluation criteria. The results are shown in Table 1. In the present invention, a grade of B or higher was considered "pass". (Evaluation criteria) A: The cured film was not peeled off, and the white side of the fabric was not visible. B: The cured film was slightly peeled off, and part of the white side of the fabric was visible. C: The cured film was peeled off, and most of the white side of the fabric was exposed.

[0209]

[0210] It can be seen from Table 1 that UV-curable inks using the UV-curable composition of the present invention can produce cured films with good washing fastness. In contrast, Comparative Example 1-1, which does not contain urethane resin particles, Comparative Examples 1-2 to 1-4, which use urethane resin particles with an undetectable Tg, and Comparative Examples 1-5 and 1-6, which use urethane resin particles with a Tg higher than -10°C, show poor washing fastness.

[0211] <<Test Example 2>> [Radical Polymerizable Compound] In Test Example 2, in addition to the raw materials used in Test Example 1, the following radical polymerizable compound was used.

[0212] <For Examples> UCECOAT (registered trademark) UC7655: Aqueous dispersion of urethane acrylate resin particles (solid content: 35% by mass, volume average particle diameter (D ５０UCECOAT (registered trademark) UC7788: Aqueous dispersion of urethane acrylate resin particles (solid content: 40% by mass, volume average particle diameter (D ５０ Beamset (registered trademark) EM-90: Arakawa Chemical Industries, Ltd., urethane acrylate resin particle aqueous dispersion (solid content concentration: 40 mass%, volume average particle diameter (D ５０ Beamset (registered trademark) EM-94: Arakawa Chemical Industries, Ltd., urethane acrylate resin particle aqueous dispersion (solid content: 50% by mass, volume average particle diameter (D ５０ ): 64 nm)

[0213] <For Comparative Examples> NK Ester (registered trademark) A-GLY-20E: Trifunctional alkoxylated glycerin acrylate (solid content: 100% by mass) manufactured by Shin-Nakamura Chemical Co., Ltd.

[0214] [Preparation of Ink 22] 8 parts by mass of radical polymerizable compound 1 was used, and the polymerization initiator A was added so that the amount was 1% by mass relative to the radical polymerizable compound 1. While stirring and mixing at 60°C, ion-exchanged water that had been preheated to 60°C was added to prepare an aqueous dispersion. Further, to this aqueous dispersion, 0.9 parts by mass of a polymerization initiator mixture different from the polymerization initiator A, 0.1 parts by mass of BYK-349 manufactured by BYK Japan KK as a silicone surfactant, 0.5 parts by mass of Olfine E1010 manufactured by Nissin Chemical Industry Co., Ltd. as an acetylene glycol surfactant, and 5.0 parts by mass of propylene glycol as a water-soluble organic solvent were mixed. Next, DISPERCOLL (registered trademark) U53 manufactured by Sumika Covestro Urethane Co., Ltd., which is an aqueous dispersion of urethane resin particles, 0.5 parts by mass of BYK-199 manufactured by BYK Japan KK as a silicone surfactant, 2.5 parts by mass of a black pigment dispersion (C.I. Pigment Black 7) as a colorant, and 15.5 parts by mass of propylene glycol as a water-soluble organic solvent were mixed, and the contents of the radical polymerizable compound and urethane resin particles were added and mixed to obtain the contents shown in Table 2, thereby obtaining Ink 22. Note that the ion-exchanged water was added in an amount (i.e., the remainder) obtained by subtracting the total parts by mass of the aforementioned materials other than ion-exchanged water from 100 parts by mass, where the total parts by mass of all the aforementioned materials including ion-exchanged water is taken as 100 parts by mass.

[0215] [Preparation of Inks 23 to 28, 30 to 32] Inks 23 to 28 and Inks 31 to 32 were prepared in the same manner as Ink 22, except that the type and content of urethane resin particles and the type and content of radically polymerizable compound were changed as shown in Table 2. Ink 30 was prepared in the same manner as Ink 24, except that urethane resin particles were not used.

[0216] [Preparation of Inks 29 and 33] An aqueous dispersion was prepared by adding ion-exchanged water preheated to 60°C while stirring and mixing 8 parts by mass of radical polymerizable compound 1, 0.8 parts by mass of TPO (2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide) as a polymerization initiator, and 0.08 parts by mass of ITX (2-isopropylthioxanthone) at 60°C. Further, 0.1 parts by mass of BYK-349 manufactured by BYK Japan KK as a silicone surfactant, 0.5 parts by mass of Olfine E1010 manufactured by Nissin Chemical Industry Co., Ltd. as an acetylene glycol surfactant, and 5.0 parts by mass of propylene glycol as a water-soluble organic solvent to the aqueous dispersion. Next, DISPERCOLL (registered trademark) U53 manufactured by Sumika Covestro Urethane Co., Ltd., which is an aqueous dispersion of urethane resin particles, 0.5 parts by mass of BYK-199 manufactured by BYK Japan KK as a silicone surfactant, 2.5 parts by mass of a black pigment (C.I. Pigment Black 7) as a colorant, and 15.5 parts by mass of propylene glycol as a water-soluble organic solvent were mixed, and the contents of the radical polymerizable compound and urethane resin particles were added and mixed to obtain the contents shown in Table 2, thereby obtaining Ink 29. Note that the amount of ion-exchanged water added was determined by subtracting the total parts by mass of the aforementioned materials other than ion-exchanged water from 100 parts by mass (i.e., the remainder), assuming that the total parts by mass of all the aforementioned materials, including ion-exchanged water, was 100 parts by mass. Ink 33 was obtained in the same manner as Ink 29, except that urethane resin particles were not used.

[0217] [Example 2-1] A white fabric (cotton) was used as the substrate, and 5 μL of ink 22 was measured with a micropipette and dropped onto the substrate heated to 80° C. on a hot plate. After heating for 10 minutes, the substrate was irradiated with 7 J / cm 2 of an LED having a peak wavelength of 365 nm. ２ The coating was irradiated with ultraviolet light having an irradiation energy of 1000 kJ / cm to form a cured film.

[0218] Examples 2-2 to 2-8, Comparative Examples 2-1 to 2-4 Cured films were obtained in the same manner as in Example 2-1, except that the type of ink was changed as shown in Table 2.

[0219] [Image Density of Cured Film] The image density (ID value) of the cured film portion of the cotton obtained in each Example and Comparative Example was measured using a spectrophotometer ("eXact Advanced" manufactured by X-rite). The results are shown in Table 2. In the present invention, the image density (ID value) before scrubbing was ０ ) was rated as "pass" if it was 1.2 or more, and as "fail" if it was less than 1.2.

[0220] [Evaluation of Washing Fastness of Cured Film (Washing Fastness 2)] The following evaluation was carried out for washing fastness 2. That is, for the cotton with the cured film obtained in each Example and Comparative Example, the image density (ID) of the cured film portion was measured using a spectrophotometer ("eXact Advanced" manufactured by X-rite Corporation) as described above. ０ After measuring the image density (ID), the cured film was wetted in a water tank and another cotton pad prepared for scrubbing was rubbed back and forth on the cured film 60 times to wash it, and the image density (ID) of the cured film after scrubbing was measured in the same way. １ The image density (ID) before scrubbing was measured. ０ ) and image density after scrubbing (ID １ ) into the following general formula (1) to determine the rate of change in image density (ΔID), and a ΔID of less than 40% was evaluated as "good (◯)" and a ΔID of 40% or more was evaluated as "poor (×)". The results are shown in Table 2. In Comparative Example 2-3, the image density (ID ０ ) was low and the initial image density was unacceptable, so evaluation of washing fastness 2 was not performed. １ -ID ０ ) / ID ０ ]|×100 ... (1)

[0221]

[0222] From Table 2, it was found that the UV-curable ink using the UV-curable composition of the present invention can provide a cured film with good washing fastness. In contrast, Comparative Examples 2-1 and 2-4, which do not contain urethane resin particles, and Comparative Example 2-2, which uses urethane resin particles with undetectable Tg, were inferior in washing fastness. Furthermore, in Comparative Example 2-3, the radical polymerizable compound is not present as particles in the ink, but is dissolved in the solvent. Therefore, the image density (ID) was already high at the stage before scrubbing. ０ ) and the image density was low, making it impractical.

[0223] As described above, the ultraviolet-curable composition of the present invention can be used to prepare the ultraviolet-curable ink of the present invention by adding a colorant. It is believed that even an ultraviolet-curable composition to which no colorant is added can achieve the same effects as the ultraviolet-curable inks shown in the examples.

[0224] Although the present invention has been described in detail using specific embodiments, it will be apparent to those skilled in the art that various modifications can be made without departing from the spirit and scope of the present invention. This application is based on Japanese Patent Application No. 2023-195828, filed on November 17, 2023, and is incorporated by reference in its entirety.

Claims

1. An ultraviolet-curable composition containing at least a radically polymerizable compound, a polymerization initiator, and a solvent, wherein the radically polymerizable compound does not contain an emulsion polymer and exists as particles, and further contains resin particles having a urethane skeleton, wherein the resin particles having a urethane skeleton do not have a polymerizable functional group and have a glass transition temperature of -10°C or lower.

2. An ultraviolet-curable composition containing a radically polymerizable compound, resin particles having a urethane skeleton, a polymerization initiator, a surfactant, and a solvent, wherein the radically polymerizable compound is present as particles, the resin particles having a urethane skeleton have no polymerizable functional groups and have a glass transition temperature of -10°C or lower, and the surfactant includes a silicone-based surfactant.

3. The ultraviolet-curable composition according to claim 1 or 2, wherein the radically polymerizable compound comprises a (meth)acrylate.

4. An ultraviolet-curable composition according to claim 1 or 2, wherein the content of the resin particles having a urethane skeleton is 0.1 mass % or more and 10 mass % or less relative to the total mass of the ultraviolet-curable composition.

5. The ultraviolet-curable composition according to claim 1 or 2, wherein the content of the radically polymerizable compound is 5% by mass or more and 20% by mass or less based on the total mass of the ultraviolet-curable composition.

6. The ultraviolet-curable composition according to claim 1 or 2, wherein the resin particles having a urethane skeleton have an average particle size of 10 nm or more and 250 nm or less.

7. The ultraviolet-curable composition according to claim 1 or 2, wherein the radically polymerizable compound has a urethane bond.

8. The ultraviolet-curable composition according to claim 1 or 2, wherein the solvent comprises water.

9. The ultraviolet-curable composition according to claim 8, wherein the solvent further contains a water-soluble organic solvent, and the mass ratio of water to the water-soluble organic solvent (water:water-soluble organic solvent) is 1:0.05 to 1:1.

5.

10. The ultraviolet-curable composition according to claim 1 or 2, wherein the concentration of the total solid content other than the solvent is 5% by mass or more and 23% by mass or less.

11. The ultraviolet-curable composition according to claim 1 or 2, which is for use in an ink-jet ink.

12. A method for producing a cured product, comprising coating or printing the ultraviolet-curable composition according to claim 1 or 2 on a surface of a substrate, and then irradiating the substrate with active energy rays.

13. A cured product obtained by curing the ultraviolet-curable composition according to claim 1 or 2.

14. An ultraviolet-curable ink containing at least a radically polymerizable compound, a polymerization initiator, a colorant, and a solvent, wherein the radically polymerizable compound does not contain an emulsion polymer and exists as particles, and further contains resin particles having a urethane skeleton, wherein the resin particles having a urethane skeleton do not have a polymerizable functional group and have a glass transition temperature of -10°C or lower.

15. An ultraviolet-curable ink containing a radically polymerizable compound, resin particles having a urethane skeleton, a polymerization initiator, a surfactant, a colorant and a solvent, wherein the radically polymerizable compound is present as particles, the resin particles having a urethane skeleton have no polymerizable functional groups and have a glass transition temperature of -10°C or lower, and the surfactant includes a silicone-based surfactant.

16. The ultraviolet-curable ink according to claim 14 or 15, wherein the radically polymerizable compound includes a (meth)acrylate.

17. An ultraviolet-curable ink according to claim 14 or 15, wherein the content of the resin particles having a urethane skeleton is from 0.1% by mass to 10% by mass relative to the total mass of the ultraviolet-curable ink.

18. The ultraviolet-curable ink according to claim 14 or 15, wherein the content of the radically polymerizable compound is 5% by mass or more and 20% by mass or less relative to the total mass of the ultraviolet-curable ink.

19. The ultraviolet-curable composition according to claim 14 or 15, wherein the resin particles having a urethane skeleton have an average particle size of 10 nm or more and 250 nm or less.

20. The ultraviolet-curable ink according to claim 14 or 15, wherein the radically polymerizable compound has a urethane bond.

21. The ultraviolet curable ink of claim 14 or 15, wherein the solvent comprises water.

22. The ultraviolet-curable ink according to claim 21, wherein the solvent further contains a water-soluble organic solvent, and the mass ratio of water to the water-soluble organic solvent (water:water-soluble organic solvent) is 1:0.05 to 1:1.

5.

23. The ultraviolet-curable ink according to claim 14 or 15, wherein the concentration of all solids other than the solvent is 5% by mass or more and 23% by mass or less.

24. The ultraviolet-curable ink according to claim 14 or 15, which is for ink-jet printing.

25. A method for producing a printed matter, comprising applying or printing the ultraviolet-curable ink according to claim 14 or 15 onto a surface of a substrate, and then irradiating the substrate with active energy rays.

26. A printed matter obtained by curing the ultraviolet-curable ink according to claim 14 or 15.