Ultraviolet-curable water-based ink, dispersion, ultraviolet-curable water-based composition, and printed matter

Abstract

Provided is an ultraviolet-curable water-based ink that is excellent in film properties, particularly scratch resistance, and also excellent in substrate versatility. An ultraviolet-curable water-based ink containing at least an ultraviolet-curable oligomer, a colorant, and a water-soluble multifunctional (meth)acrylamide compound, wherein the ultraviolet-curable oligomer has a structural unit from a water-soluble compound and a structural unit from a compound containing two or more polymerizable unsaturated bonds, respectively. Alternatively, an ultraviolet-curable water-based ink wherein the ultraviolet-curable oligomer contains four or more polymerizable unsaturated bonds and has a structural unit from a compound capable of bonding with a polyisocyanate compound (A), or the ultraviolet-curable oligomer has a structural unit from a compound represented by the following formula (1) (in formula (1), X is an alkylene group, Y is any one of a (meth)acryloyl group, an allyl group, and an acyl group; n is an integer of two or more).[Chemical Formula 1]

Description

Technical Field

[0001] This invention relates to a UV-curable water-based ink, and further to printed matter using the UV-curable water-based ink, and more particularly to UV-curable water-based compositions and dispersions suitable for the UV-curable water-based ink. Background Technology

[0002] Inkjet printers have the following characteristics: easy to achieve full color printing, low noise, ability to obtain high-resolution images at low cost, high-speed printing, printing on curved surfaces as well as flat surfaces, and easy printing on large areas. Therefore, they are not limited to personal use and have been rapidly gaining popularity in recent years as commercial inkjet printers for signatures, window films, posters, car wraps, wallpapers, and more.

[0003] In commercial inkjet printers, the printed materials are required to have characteristics such as (1) high image quality, (2) high coating quality, (3) high printing speed, (4) substrate versatility, and (5) environmental / safety. When printing large-area printed materials or printed materials for outdoor use, the printing film is required to have excellent coating properties such as water resistance, alcohol resistance, coating strength, and light resistance.

[0004] Currently, the inks used for printing in commercial inkjet printers include the following: water-based inks that disperse pigments in an aqueous medium; solvent-based UV inks that disperse or dissolve pigments and UV-curable monomers in an organic solvent; solvent-free UV inks that disperse pigments in UV-curable monomers without solvents; water-based latex inks that disperse pigments and resins in an aqueous medium; UV-curable water-based inks that disperse pigments and UV-curable oligomers in an aqueous medium; and so on.

[0005] Among these inks, water-based inks offer excellent image quality and environmental / safety. However, they suffer from poor film-forming properties, high-speed printing performance, and substrate versatility, particularly weaker film strength, making them unsuitable for large-area printing or outdoor applications.

[0006] In such water-based inks, as a component for improving the curability after image formation, ink compositions containing (A) a tetrafunctional (meth)acrylamide polymerizable compound having a defined structure and (B) a polymerization initiator have been developed (see Patent Document 1 below).

[0007] In addition, as a component to improve the curing performance of ink, an active energy ray curable water-based ink has been developed, which contains water and a (meth)acrylamide polymeric substance with a specified structure (see Patent Document 2 below).

[0008] As an ink with improved abrasion resistance, an ink composition has been developed that comprises pigments, polymer particles, and water-soluble polymeric compounds such as polyfunctional acrylamide polymerized by active energy rays (see Patent Document 3 below).

[0009] Furthermore, an inkjet ink composition containing a water-soluble polymer, a multifunctional (meth)acrylamide-type polymeric compound having a defined structure, a colorant, and water has been developed, wherein the water-soluble polymer is selected from at least one of polyethylene glycol having a number average molecular weight of 1,000 to 100,000, and a block copolymer of ethylene glycol and propylene glycol (see Patent Document 4 below).

[0010] Existing technical documents

[0011] Patent documents

[0012] Patent Document 1: Japanese Patent Application Publication No. 2013-18846

[0013] Patent Document 2: Japanese Patent Application Publication No. 2005-307198

[0014] Patent Document 3: Japanese Patent Application Publication No. 2010-70693

[0015] Patent Document 4: Japanese Patent Application Publication No. 2015-52084 Summary of the Invention

[0016] The problem that the invention aims to solve

[0017] Therefore, the object of the present invention is to provide a UV-curable water-based ink that, compared with previous UV-curable water-based inks, has better film performance, especially excellent scratch resistance and excellent substrate versatility, among UV-curable water-based inks that have a better balance of all properties.

[0018] Technical solutions to the problem

[0019] Through repeated and dedicated research, the inventors discovered that by using UV-curable oligomers and incorporating water-soluble polyfunctional (meth)acrylamide compounds as additives, it is possible to achieve UV-curable water-based inks with excellent coating properties, particularly scratch resistance, and excellent substrate versatility.

[0020] This invention is based on this discovery, and its main points are as follows.

[0021] [1] An ultraviolet-curable water-based ink, comprising at least an ultraviolet-curable oligomer, a colorant and a water-soluble polyfunctional (meth)acrylamide compound, wherein the ultraviolet-curable oligomer has structural units derived from the water-soluble compound and structural units derived from a compound containing two or more polymeric unsaturated bonds.

[0022] [2] An ultraviolet-curable water-based ink comprising at least an ultraviolet-curable oligomer, a colorant and a water-soluble polyfunctional (meth)acrylamide compound, wherein the ultraviolet-curable oligomer contains four or more polymerizable unsaturated bonds and has structural units derived from compounds capable of bonding with polyisocyanate compound (A).

[0023] [3] According to the UV-curable water-based ink of [2], the compound that can bond with the polyisocyanate compound (A) is a compound having any group among hydroxyl, amino and carboxyl groups.

[0024] [4] An ultraviolet-curable water-based ink comprising at least an ultraviolet-curable oligomer, a colorant and a water-soluble polyfunctional (meth)acrylamide compound, wherein the ultraviolet-curable oligomer has a structural unit derived from a compound represented by the following formula (1).

[0025] [Chemistry 1]

[0026]

[0027] (In formula (1), X is an alkylene group, Y is any one of (meth)acryloyl, allyl, or acyl; n is an integer greater than or equal to 2.)

[0028] [5] The UV-curable water-based ink according to any one of [1] to [4], wherein the water-soluble polyfunctional (meth)acrylamide compound has two or more and four or fewer functional groups.

[0029] [6] The UV-curable water-based ink according to any one of [1] to [5], wherein the content of the water-soluble polyfunctional (meth)acrylamide compound is 0.05% by mass or more and 10% by mass or less.

[0030] [7] The UV-curable water-based ink according to any one of [1] to [6] further comprises one or more of a polymerization initiator, a sensitizer and a surfactant.

[0031] [8] According to the UV-curable water-based ink of [7], at least a portion of the polymerization initiator and / or sensitizer is contained within the UV-curable oligomer.

[0032] [9] The UV-curable water-based ink according to any one of [1] to [8], wherein the UV-curable oligomer is nonionic.

[0033]

[10] The UV-curable water-based ink according to any one of [1] to [9], wherein the UV-curable oligomer exists in the form of particles.

[0034]

[11] The UV-curable water-based ink according to any one of [1] to

[10] , wherein the average particle size of the UV-curable oligomer is 10 nm or more and 200 nm or less.

[0035]

[12] A printed matter having a cured material formed on a recording medium by any one of [1] to

[11] of the UV-curable water-based ink.

[0036]

[13] A dispersion is a dispersion of an ultraviolet-curable oligomer, wherein the dispersion contains 0.1% by mass and 20% by mass and a water-soluble polyfunctional (meth)acrylamide compound, wherein the ultraviolet-curable oligomer has structural units derived from the water-soluble compound and structural units derived from a compound containing two or more polymeric unsaturated bonds.

[0037]

[14] A dispersion is a dispersion of a UV-curable oligomer, wherein the dispersion contains 0.1% by mass and 20% by mass and less than 20% by mass of a water-soluble polyfunctional (meth)acrylamide compound, wherein the UV-curable oligomer contains four or more polymerizable unsaturated bonds and has structural units derived from compounds capable of bonding with a polyisocyanate compound (A).

[0038]

[15] A dispersion is a dispersion of a UV-curable oligomer, wherein the dispersion contains 0.1% by mass and 20% by mass and a water-soluble polyfunctional (meth)acrylamide compound, the UV-curable oligomer having structural units derived from compounds represented by the following formula (1).

[0039] [Chemistry 1]

[0040]

[0041] (In formula (1), X is an alkylene group, Y is any one of (meth)acryloyl, allyl, or acyl; n is an integer greater than or equal to 2.)

[0042]

[16] The dispersion according to any one of

[13] to

[15] , wherein the number of functional groups of the water-soluble polyfunctional (meth)acrylamide compound is 2 or more and 4 or less.

[0043]

[17] An ultraviolet-curable aqueous composition comprising: any one or more of a polymerization initiator, a sensitizer and a surfactant; an ultraviolet-curable oligomer; and a water-soluble polyfunctional (meth)acrylamide compound, wherein the ultraviolet-curable oligomer has structural units derived from the water-soluble compound and structural units derived from a compound containing two or more polymerizable unsaturated bonds.

[0044]

[18] An ultraviolet-curable aqueous composition comprising: any one or more of a polymerization initiator, a sensitizer and a surfactant; an ultraviolet-curable oligomer; and a water-soluble polyfunctional (meth)acrylamide compound, wherein the ultraviolet-curable oligomer contains four or more polymerizable unsaturated bonds and has structural units derived from compounds capable of bonding with polyisocyanate compound (A).

[0045]

[19] An ultraviolet-curable aqueous composition comprising: any one or more of a polymerization initiator, a sensitizer and a surfactant; an ultraviolet-curable oligomer; and a water-soluble polyfunctional (meth)acrylamide compound, wherein the ultraviolet-curable oligomer has a structural unit derived from a compound represented by the following formula (1).

[0046] [Chemistry 1]

[0047]

[0048] (In formula (1), X is an alkylene group, Y is any one of (meth)acryloyl, allyl, or acyl; n is an integer greater than or equal to 2.)

[0049]

[20] The UV-curable aqueous composition according to any one of

[17] to

[19] , wherein the number of functional groups of the water-soluble polyfunctional (meth)acrylamide compound is 2 or more and 4 or less.

[0050]

[21] The UV-curable aqueous composition according to any one of

[17] to

[20] comprises a polymerization initiator and / or a sensitizer, at least a portion of which is contained within the UV-curable oligomer.

[0051]

[22] The UV-curable aqueous composition according to any one of

[17] to

[21] , wherein the UV-curable oligomer is nonionic.

[0052] The effects of the invention

[0053] The UV-curable water-based ink of the present invention not only meets the requirements for printing ink in a good balance, but also has excellent coating performance, especially scratch resistance, and excellent substrate versatility. Detailed Implementation

[0054] The following describes one embodiment of the present invention. However, the present invention is not limited to this embodiment.

[0055] In this invention, when expressed as "X~Y" (X and Y are arbitrary numbers), unless otherwise specified, it includes the meaning of "X or more and Y or less", and also includes the meaning of "preferably greater than X" and "preferably less than Y".

[0056] [UV-curable water-based inks]

[0057] In a first embodiment of the ink of the present invention, the UV-curable water-based ink of the present invention (hereinafter, sometimes referred to as "the ink of the present invention") contains at least a UV-curable oligomer, a colorant, and a water-soluble polyfunctional (meth)acrylamide compound, wherein the UV-curable oligomer has structural units derived from the water-soluble compound and structural units derived from a compound containing two or more polymeric unsaturated bonds.

[0058] In a second embodiment of the ink of the present invention, it is characterized by containing at least a UV-curable oligomer, a colorant, and a water-soluble polyfunctional (meth)acrylamide compound, wherein the UV-curable oligomer contains four or more polymerizable unsaturated bonds and has structural units derived from compounds capable of bonding with the polyisocyanate compound (A).

[0059] In a third embodiment of the ink of the present invention, it is characterized by containing at least a UV-curable oligomer, a colorant, and a water-soluble polyfunctional (meth)acrylamide compound, wherein the UV-curable oligomer has a structural unit derived from a compound represented by the following formula (1).

[0060] [Chemistry 1]

[0061]

[0062] (In formula (1), X is an alkylene group, Y is any one of (meth)acryloyl, allyl, or acyl; n is an integer greater than or equal to 2.)

[0063] In this invention, "(meth)acrylamide" refers to acrylamide or methacrylamide.

[0064] It should be noted that although the ink of the present invention is UV-curable, the active energy rays used for curing are not limited to ultraviolet light.

[0065] When curing the ink of the present invention, it is not limited to curing by using active energy rays, but also by curing by heat.

[0066] In addition, the ink of the present invention is suitable for inkjet printing.

[0067] [UV-curable oligomers]

[0068] There is no particular limitation on whether the UV-curable oligomer used in this invention is ionic; it can be nonionic or ionic (anionic, cationic, or amphoteric). However, by being nonionic, it is possible to inhibit pigment aggregation and improve the preservation stability of the printing ink. Here, nonionic means, for example, that the hydrophilic groups of the UV-curable oligomer are composed of ether bonds and hydroxyl groups that do not undergo ionic dissociation in water. Ionic (anionic, cationic, or amphoteric) means, for example, that the UV-curable oligomer has carboxyl or amino groups that can undergo ionic dissociation in water. More specifically, anionic UV-curable oligomers include, for example, UV-curable oligomers containing carboxyl groups.

[0069] There are no particular limitations on the UV-curable oligomers used in this invention, but those with excellent UV curability, fixing properties, water dispersion stability, pigment aggregation inhibition effect, and alcohol resistance are preferred, for example, those described below. <1> ~ <4> The UV-curable oligomer shown.

[0070] <1> They respectively have structural units derived from water-soluble compounds and structural units derived from compounds containing two or more polymeric unsaturated bonds;

[0071] <2> It contains four or more polymerizable unsaturated bonds and has structural units derived from compounds that can bond with polyisocyanate compound (A);

[0072] <3> It has structural units derived from compounds represented by the following formula (1);

[0073] [Chemistry 1]

[0074]

[0075] (In formula (1), X is an alkylene group, Y is any one of (meth)acryloyl, allyl, or acyl; n is an integer greater than or equal to 2.)

[0076] <4> It has structural units from polyisocyanate compound (A), structural units from compound (B') shown below, and structural units from compound (C') shown below.

[0077] To clarify, the above <4> The UV-curable oligomers shown are typically manufactured by reacting polyisocyanate compounds (A), (B'), and (C').

[0078] Compound (B'): A compound containing two or more polymerizable unsaturated bonds that can bond with polyisocyanate compound (A);

[0079] Compound (C'): A water-soluble compound that can bond with polyisocyanate compound (A).

[0080] Furthermore, the UV-curable oligomer used in this invention preferably has structural units derived from (meth)acrylates, and particularly preferably has structural units derived from polyfunctional (meth)acrylates. It is even more preferable to have structural units derived from both polyfunctional (meth)acrylates and polyalkylene glycols. That is, from a reactivity perspective, compound (B') is preferably a hydroxyl-containing polyfunctional (meth)acrylate (B). Furthermore, from a water dispersibility perspective, compound (C') is preferably a polyalkylene glycol (C). Such UV-curable oligomers are typically manufactured by reacting a polyisocyanate compound (A), a hydroxyl-containing polyfunctional (meth)acrylate (B), and a polyalkylene glycol (C).

[0081] It should be noted that in this invention, "(meth)acrylate" refers to acrylate or methacrylate.

[0082] In this invention, "structural unit from X" refers to a structural unit introduced into the molecular structure of a UV-curable oligomer by using compound X as a raw material and reacting compound X with other compounds. It should be noted that "structural unit from X" is not necessarily limited to using compound X as a raw material. That is, even if formed from raw materials other than X, as long as the chemical structure is the same, it is still considered a "structural unit from X".

[0083] In the aforementioned UV-curable oligomers, the structural unit portion from the polyisocyanate compound (A) contributes to the adhesion of the printed film to the recording medium.

[0084] The structural unit portion from compound (B') contributes to UV curability. Furthermore, in the case where compound (B') is a hydroxyl-containing polyfunctional (meth)acrylate (B), the (meth)acryloyl group contained in the structural unit of this hydroxyl-containing polyfunctional (meth)acrylate (B) contributes to UV curability.

[0085] The structural unit portion from compound (C') contributes to the water dispersibility of oligomers in the ink. Furthermore, in the case where compound (C') is a polyalkylene glycol (C), the polyalkylene glycol chains from the structural units of this polyalkylene glycol (C) contribute to the water dispersibility of oligomers in the ink.

[0086] The aforementioned UV-curable oligomers contain all of these structural units within the same molecule, and are therefore preferred.

[0087] Furthermore, to ensure excellent solvent resistance, such as alcohol resistance, it is preferable that the structural units from the polyisocyanate compound (A) are bonded via urethane bonds to structural units from the hydroxyl-containing polyfunctional (meth)acrylate (B) and the polyalkylene glycol (C), respectively. Through these measures, the UV-curable oligomers of the present invention exhibit excellent UV curability, coating properties, substrate fixing properties, and water dispersion stability.

[0088] As described above, a preferred embodiment of compound (B') is a polyfunctional (meth)acrylate (B) containing hydroxyl groups, but a preferred embodiment of compound (B') may also be "a compound (B) containing hydroxyl groups and having two or more polymerizable unsaturated bonds".

[0089] The "compound capable of bonding with polyisocyanate compound (A)" in compound (B') can be a compound formed by replacing the hydroxyl group of compound (B') with a carboxyl group, amino group, or the like. Furthermore, examples of polymerizable unsaturated bonds include carbon-carbon double bonds and carbon-carbon triple bonds, with carbon-carbon double bonds being preferred. More specifically, carbon-carbon double bonds derived from vinyl groups, (meth)acryloyl groups, etc., can be cited.

[0090] The water-soluble compounds in compound (C') include water-soluble polymers, specifically including: polyglycerol, polyhydroxy (meth)acrylates, polyamines, quaternized polystyrene, sulfonated polystyrene, polyethers, polyalkylene glycols, etc. Among these, polyglycerol, polyhydroxy (meth)acrylates, and polyalkylene glycols, which are nonionic water-soluble compounds, are preferred, and polyalkylene glycols are particularly preferred. These water-soluble compounds can each be copolymers. Compound (C') has the structure of such a water-soluble compound and the structure of a "compound capable of bonding with polyisocyanate compound (A)". Here, the structure of the "compound capable of bonding with polyisocyanate compound (A)" can be selected from the same structure exemplified above as compound (B').

[0091] In addition, the structural unit from the polyisocyanate compound (A) forms a urethane bond by combining with the structural unit from the hydroxyl-containing polyfunctional (meth)acrylate (B) and the structural unit from the polyalkylene glycol (C), but the urethane bond can be replaced by a urea bond or an amide bond, respectively.

[0092] In the case of forming a urea bond, the hydroxyl group in the hydroxyl-containing polyfunctional (meth)acrylate (B) is replaced with an amino group as compound (B'), or the hydroxyl terminus of the polyalkylene glycol (C) is replaced with an amino group as compound (C').

[0093] In the case of forming an amide bond, the hydroxyl group in the hydroxyl-containing polyfunctional (meth)acrylate (B) can be replaced with a carboxyl group as compound (B'), or the hydroxyl terminus constituting the polyalkylene glycol (C) can be replaced with a carboxyl group as compound (C'). It should be noted that substantially the same chemical structure can also be formed.

[0094] As mentioned above, the structural units from the polyisocyanate compound (A) contribute to the adhesion of the printed film to the recording medium, but as mentioned above, it is believed to be due to the formation of polar sites such as urethane bonds, urea bonds, or amide bonds by the isocyanate groups in the UV-curable oligomer.

[0095] In this invention, when the hydroxyl-containing polyfunctional (meth)acrylate (B) is the above-described compound (B') or compound (B''), or when the polyalkylene glycol (C) is the above-described compound (C'), the preferred or specific method can also be the use of the hydroxyl-containing polyfunctional (meth)acrylate (B) or polyalkylene glycol (C) described later as a preferred or specific method.

[0096] The following describes the compounds that constitute the UV-curable oligomers. In this invention, "oligomer" is not limited to a specific molecular weight range, but simply refers to any compound having the structure shown below.

[0097] It should be noted that the ink of the present invention may contain only one type of UV-curable oligomer, or it may contain two or more types.

[0098] <Polyisocyanate compound (A)>

[0099] A polyisocyanate compound (A) is a compound having a total of two or more isocyanate groups in one molecule.

[0100] There are no particular limitations on the type of polyisocyanate compound (A), and examples include: chain aliphatic polyisocyanates, aromatic polyisocyanates, and alicyclic polyisocyanates. Among them, from the perspective of weather resistance and hardness, polyisocyanate compound (A) is preferably a trimer compound containing polyisocyanates.

[0101] Chain aliphatic polyisocyanates are compounds having a chain aliphatic structure and two or more isocyanate groups. Chain aliphatic polyisocyanates are preferred from the perspectives of weather resistance and tensile strength. The chain aliphatic structure in chain aliphatic polyisocyanates is not particularly limited, but it is preferably a straight-chain or branched alkylene group with 1 or more and 12 or fewer carbon atoms, and more preferably 1 or more and 6 or fewer carbon atoms. Examples of chain aliphatic polyisocyanates include, for example, tetramethylene diisocyanate, hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, dimer diisocyanate, and other aliphatic diisocyanates, or trimer compounds of these polyisocyanates.

[0102] Aromatic polyisocyanates are compounds having an aromatic structure and two or more isocyanate groups. From the perspective of coating strength, aromatic polyisocyanates are preferred. The aromatic structure in aromatic polyisocyanates is not particularly limited, but it is preferably an aromatic structure with 6 or more but less than 13 carbon atoms. Examples of aromatic polyisocyanates include, for example, toluene diisocyanate, xylene diisocyanate, diphenylmethane diisocyanate, isophenylene diisocyanate, naphthalene diisocyanate, and other aromatic diisocyanates, or trimer compounds of these polyisocyanates.

[0103] Alicyclic polyisocyanates are compounds having an alicyclic structure and two or more isocyanate groups. The alicyclic structure in alicyclic polyisocyanates is not particularly limited, but it typically has 5 or more carbon atoms, preferably 6 or more, typically 15 or less, preferably 14 or less, and more preferably 13 or less. The alicyclic structure is particularly preferably cyclohexane. Examples of alicyclic polyisocyanates include bis(isocyanate-methyl)cyclohexane, cyclohexane diisocyanate, bis(isocyanate-cyclohexyl)methane, isophorone diisocyanate, and other diisocyanates having an alicyclic structure, or trimer compounds of these polyisocyanates.

[0104] UV-curable oligomers may use only one of these polyisocyanate compounds (A), or they may use two or more in combination. Furthermore, as polyisocyanate compound (A), polyisocyanates having two or more of the following structures may also be used: chain aliphatic structure, aromatic structure, and alicyclic structure.

[0105] As the polyisocyanate compound (A), it is particularly preferable to have 3 or more but 6 or fewer isocyanate groups, from the perspective of adhesion to the substrate. Furthermore, as the polyisocyanate compound (A), it is preferable to be a trimer obtained by trimerization reaction of hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, phenyl diisocyanate, etc., and it is especially preferable to be a trimer of hexamethylene diisocyanate.

[0106] <Compounds containing polymeric unsaturated bonds>

[0107] In the first and second embodiments of the present invention, the UV-curable oligomer has structural units derived from compounds containing polymeric unsaturated bonds.

[0108] In compounds containing polymerizable unsaturated bonds, the number of polymerizable unsaturated bonds is preferably one or more, more preferably two or more, and even more preferably four or more. On the other hand, it is preferably eight or less, more preferably six or less.

[0109] Furthermore, the compound containing polymerizable unsaturated bonds is preferably a compound capable of bonding with the polyisocyanate compound (A). As a compound capable of bonding with said polyisocyanate compound (A), a compound having any of the following groups: hydroxyl, amino, and carboxyl groups is preferred.

[0110] (Compound (B'))

[0111] Compound (B') is a compound containing two or more polymerizable unsaturated bonds that can bond with polyisocyanate compound (A).

[0112] Compound (B') can be any compound having any of the following groups: hydroxyl, amino, and carboxyl. Furthermore, compounds (B') can include: polyfunctional vinyl monomers, polyfunctional allyl monomers, and polyfunctional (meth)acrylates. Among these, a hydroxyl-containing polyfunctional (meth)acrylate (B) is preferred as compound (B').

[0113] <Hydroxy-containing polyfunctional (meth)acrylates (B)>

[0114] Hydroxyl-containing polyfunctional (meth)acrylates (B) have one or more hydroxyl groups and two or more (meth)acryloyl groups. Specifically, (meth)acrylic acid partial esters of polyols can be cited as examples. In the curing reaction, multiple (meth)acryloyl groups participate in the curing reaction of hydroxyl-containing polyfunctional (meth)acrylates, thereby forming a good cross-linking structure, which improves physical properties such as stain resistance and abrasion resistance.

[0115] The number of hydroxyl-containing polyfunctional (meth)acrylates (B) is preferably 3 or less, more preferably 2 or less, and even more preferably 1. The number of (meth)acryloyl groups in the hydroxyl-containing polyfunctional (meth)acrylates (B) is preferably 8 or less, more preferably 6 or less.

[0116] Examples of hydroxyl-containing polyfunctional (meth)acrylates (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-dimethacryloyloxypropane, 2-hydroxy-3-acryloyloxypropyl methacrylate, etc.

[0117] In the manufacture of UV-curable oligomers, only one of these hydroxyl-containing polyfunctional (meth)acrylates (B) may be used, or two or more may be used together.

[0118] As a hydroxyl-containing polyfunctional (meth)acrylate (B), especially from the perspective of the coating strength of the obtained cured film, it is preferable to have one hydroxyl group and three or more but less than five (meth)acryloyl groups, such as pentaerythritol penta(meth)acrylate and pentaerythritol tri(meth)acrylate. In particular, from the perspective of forming a good crosslinking structure and improving the mechanical strength of the cured film, pentaerythritol penta(meth)acrylate is preferred.

[0119] <Water-soluble compounds>

[0120] In a first embodiment of the present invention, the UV-curable oligomer has structural units derived from a water-soluble compound.

[0121] (Compound (C'))

[0122] Compound (C') is a water-soluble compound that can bond with polyisocyanate compound (A).

[0123] To achieve good water dispersibility, the preferred compound (C') is one containing a hydroxyl terminus.

[0124] As the compound (C'), as described above, examples include water-soluble polymers, of which polyalkylene glycols (C) are particularly preferred.

[0125] The polyalkylene glycol (C) is not limited, but a monosubstituted structure is preferred. That is, preferably, one of the hydroxyl groups in the glycol is substituted. As a substituted structure, a structure that does not bond with isocyanate is preferred.

[0126] Polyalkylene glycols (C) can also be a mixture of monosubstituted and non-monosubstituted compounds.

[0127] The structure of the monosubstituted product is not limited, but from the perspective of making the UV-curable oligomer non-ionic, it is preferred to use a polyalkylene glycol monosubstituted ether, more preferably a polyethylene glycol monosubstituted ether, a polytrimethylene glycol monosubstituted ether or a polypropylene glycol monosubstituted ether, and even more preferably a polyethylene glycol monosubstituted ether.

[0128] The molecular weight (in the case of non-single) of polyalkylene glycol (C) is not limited, but is generally 100 or more, preferably 200 or more, generally 5000 or less, preferably 2000 or less.

[0129] More preferably, in the case of polyalkylene glycol monosubstituted ethers, the ether portion does not contain ionic substituents. For example, it is even more preferably a compound represented by the following general formula (1).

[0130] [Chemistry 1]

[0131]

[0132] (In formula (1), X is an alkylene group, Y is any one of alkyl, (meth)acryloyl, allyl, or acyl; n is an integer greater than or equal to 2.)

[0133] As specific examples of polyalkylene glycol monosubstituted ethers represented by the above general formula (1), the following compounds can be cited.

[0134] Compounds with Y = alkyl group: polyethylene glycol monomethyl ether, polyethylene glycol lauryl ether, polyethylene glycol cetyl ether, polyethylene glycol stearyl ether, polyethylene glycol tridecyl ether, polyethylene glycol oil ether, polyethylene glycol octylphenyl ether, polyoxyethylene oil-based cetyl ether, polypropylene glycol monomethyl ether, etc.

[0135] Compounds with Y = (meth)acryloyl group: polyethylene glycol mono(meth)acrylate, polypropylene glycol mono(meth)acrylate, poly(ethylene glycol-propylene glycol) mono(meth)acrylate, poly(ethylene glycol-tetramethylene glycol) mono(meth)acrylate, poly(propylene glycol-tetramethylene glycol) mono(meth)acrylate, etc.

[0136] Compounds with Y = allyl group: polyethylene glycol monoallyl ether, polypropylene glycol monoallyl ether, poly(ethylene glycol-propylene glycol) monoallyl ether, etc.

[0137] Compounds with a Y = acyl group: polyethylene glycol monolaurate, polypropylene glycol monolaurate, poly(ethylene glycol-propylene glycol) monolaurate, polyethylene glycol monostearate, polyethylene glycol monooleate, etc.

[0138] In these, X in general formula (1) is preferably an alkylene group with 1 or more but less than 3 carbon atoms, more preferably ethylene, trimethylene, or propylene, and from the perspective of pigment dispersion stability or storage stability at high temperatures, ethylene is even more preferred. In addition, from the perspective of coating strength, Y is preferably (meth)acryloyl, allyl, or acyl, more preferably allyl.

[0139] From the perspective of the coating strength of the obtained cured film, n in general formula (1) is usually 2 or more, preferably 5 or more, more preferably 6 or more, usually 500 or less, preferably 100 or less, more preferably 50 or less.

[0140] In the third embodiment of the present invention, it is preferable to have structural units derived from compounds represented by the above formula (1), where X in the above formula (1) is an alkylene group, Y is any one of (meth)acryloyl, allyl, and acyl, and n is an integer of 2 or more.

[0141] In the manufacture of UV-curable oligomers, only one of these polyalkylene glycols (C) may be used, or two or more may be used in combination. The polyalkylene glycols (C) may be a mixture of compounds with different molecular weights (n in general formula (1)).

[0142] <Method for manufacturing UV-curable oligomers>

[0143] The method for manufacturing UV-curable oligomers is not particularly limited, but it is preferred to manufacture them by reacting the above-mentioned polyisocyanate compounds (A), (B') and (C') to form chemical bonds respectively.

[0144] When compound (B') is a hydroxyl-containing polyfunctional (meth)acrylate (B) and compound (C') is a polyalkylene glycol (C), it is preferable to manufacture the product by reacting the above-mentioned polyisocyanate compound (A), the hydroxyl-containing polyfunctional (meth)acrylate (B), and the polyalkylene glycol (C) so that the isocyanate group of the polyisocyanate compound (A) forms a urethane bond with the hydroxyl groups of the hydroxyl-containing polyfunctional (meth)acrylate (B) and the polyalkylene glycol (C), respectively.

[0145] In this invention, from the perspective of pigment dispersion stability and coating strength of the obtained cured film, it is preferred to be an oligomer formed by two hydroxyl-containing polyfunctional (meth)acrylates (B) and one polyalkylene glycol (C) forming urethane bonds relative to the polyisocyanate compound (A).

[0146] It should be noted that the UV-curable oligomer only needs to have structural units from polyisocyanate compound (A), structural units from hydroxyl-containing polyfunctional (meth)acrylate (B), and structural units from polyalkylene glycol (C), and may additionally have other structures.

[0147] <Weight-average molecular weight>

[0148] From the perspective of the performance and processability of the formed coating film, the weight-average molecular weight of the UV-curable oligomer converted from polystyrene by gel permeation chromatography (GPC) is preferably 1,000 or more, more preferably 2,000 or more, more preferably 100,000 or less, and more preferably 50,000 or less.

[0149] <Average Particle Size>

[0150] In the ink, the dispersion (oligomer dispersion) described later, and the aqueous composition of the present invention, the UV-curable oligomer exists in the form of particles, more preferably in the form of particles with an average particle size of 10 nm or more and 200 nm or less, and even more preferably in the form of particles with an average particle size of 20 nm or more and 150 nm or less. When the average particle size of the UV-curable oligomer is within the above-mentioned range, the dispersion stability becomes good.

[0151] Here, the average particle size of the UV-curable oligomer is, for example, the volume average particle size (D) measured by a particle size analyzer based on dynamic light scattering. 50 ).

[0152] It should be noted that in the embodiments described later, the average particle size of the UV-curable oligomer particles in the UV-curable oligomer aqueous dispersion was measured, but the average particle size of the oligomer particles in the aqueous dispersion is substantially equal to the average particle size of the oligomer particles in the ink.

[0153] In the ink, dispersion (oligomer dispersion) and aqueous composition of the present invention, if the UV-curable oligomer exists in the form of particles, even if there is aggregation, even if other substances are contained within the particles, it is included in the above-mentioned state of "existing in the form of particles".

[0154] In addition, the average particle size of the UV-curable oligomer mentioned above refers to the particle size (primary particle size) of the UV-curable oligomer particles.

[0155] The following describes the components in the ink of the present invention other than the UV-curable oligomers.

[0156] [Coloring agent]

[0157] The ink of this invention contains a colorant.

[0158] As the colorant used in the ink of the present invention, various dyes or pigments known as colorants used in inkjet inks can be used, but from the perspective of ultraviolet irradiation and long-term preservation durability of printed images, pigments are preferred.

[0159] <Dye>

[0160] There are no particular limitations on the dyes that can be used in this invention, and examples include water-soluble dyes such as acid dyes, direct dyes, and reactive dyes, as well as disperse dyes. Among these, anionic dyes are preferred.

[0161] (Water-soluble dyes)

[0162] Examples of water-soluble dyes include: azo dyes, methylene dyes, azomethyl base dyes, xanthan dyes, quinone dyes, phthalocyanine dyes, triphenylmethane dyes, and diphenylmethane dyes. Specific compounds are shown below, but the examples are not limited to these.

[0163] <CI 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

[0165] <CI 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

[0167] <CI 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

[0169] <CI Acid Purple> 17, 19, 21, 42, 43, 47, 48, 49, 54, 66, 78, 90, 97, 102, 109, 126

[0171] <CI 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

[0173] <CI Acid Green> 9, 12, 16, 19, 20, 25, 27, 28, 40, 43, 56, 73, 81, 84, 104, 108, 109

[0175] <CI Acid Brown> 2, 4, 13, 14, 19, 28, 44, 123, 224, 226, 227, 248, 282, 283, 289, 294, 297, 298, 301, 355, 357, 413

[0177] <CI 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

[0179] <CI 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

[0181] <CI Direct Orange> 6, 26, 27, 34, 39, 40, 46, 102, 105, 107, 118

[0183] <CI 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

[0185] <CI Direct Purple> 9, 35, 51, 66, 94, 95

[0187] <CI 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

[0189] <CI Direct Green> 26, 28, 59, 80, 85

[0191] <CI Direct Brown> 44, 106, 115, 195, 209, 210, 222, 223

[0193] <CI Direct Black> 17, 19, 22, 32, 51, 62, 108, 112, 113, 117, 118, 132, 146, 154, 159, 169

[0195] <CI Basic Yellow> 1, 2, 11, 13, 15, 19, 21, 28, 29, 32, 36, 40, 41, 45, 51, 63, 67, 70, 73, 91

[0197] <CI Basic Orange> 2, 21, 22

[0199] <CI Basic Red> 1, 2, 12, 13, 14, 15, 18, 23, 24, 27, 29, 35, 36, 39, 46, 51, 52, 69, 70, 73, 82, 109

[0201] <CI Basic Violet> 1, 3, 7, 10, 11, 15, 16, 21, 27, 39

[0203] <CI 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

[0205] <CI Basic Green> 1, 4

[0207] <CI Basic Brown> 1

[0209] <CI Active 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

[0211] <CI Active 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

[0213] <CI Active 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

[0215] <CI Reactive Purple> 1, 2, 4, 5, 6, 22, 23, 33, 36, 38

[0217] <CI Active 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

[0219] <CI Active Green> 8, 12, 15, 19, 21

[0221] <CI Active Brown> 2, 7, 9, 10, 11, 17, 18, 19, 21, 23, 31, 37, 43, 46

[0223] <CI Active Black> 5, 8, 13, 14, 31, 34, 39

[0225] <CI Food Black> 1, 2

[0227] Pigments

[0228] As pigments, existing known organic and inorganic pigments can be used. Examples include: azo pigments such as azo lakes, insoluble azo pigments, condensed azo pigments, and chelated azo pigments; polycyclic pigments such as phthalocyanine pigments, perylene and perylene pigments, anthraquinone pigments, quinacridone pigments, diazine pigments, thioindole pigments, isoindolineone pigments, and quinophthalone 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 dioxide, and iron oxide pigments, but anionic pigments are preferred.

[0229] (Organic pigments)

[0230] Specific examples of organic pigments are shown below.

[0231] <Magenta or Red pigment>

[0232] CI Pigment Red 2, CI Pigment Red 3, CI Pigment Red 5, CI Pigment Red 6, CI Pigment Red 7, CI Pigment Red 15, CI Pigment Red 16, CI Pigment Red 48:1, CI Pigment Red 53:1, CI Pigment Red 57:1, CI Pigment Red 122, CI Pigment Red 123, CI Pigment Red 139, CI Pigment Red 144, CI Pigment Red 149, CI Pigment Red 166, CI Pigment Red 177, CI Pigment Red 178, CI Pigment Red 222, etc.

[0233] <Orange or yellow pigment>

[0234] CI Pigment Orange 31, CI Pigment Orange 43, CI Pigment Yellow 12, CI Pigment Yellow 13, CI Pigment Yellow 14, CI Pigment Yellow 15, CI Pigment Yellow 17, CI Pigment Yellow 74, CI Pigment Yellow 93, CI Pigment Yellow 94, CI Pigment Yellow 128, CI Pigment Yellow 138, CC.I. Pigment Yellow 155, etc.

[0235] <Pigments for green or cyan>

[0236] CI Pigment Blue 15, CI Pigment Blue 15:2, CI Pigment Blue 15:3, CI Pigment Blue 16, CI Pigment Blue 60, CI Pigment Green 7, etc.

[0237] These dyes and pigments can be used in single or multiple ways.

[0238] [Water-soluble polyfunctional (meth)acrylamide compounds]

[0239] The ink of the present invention contains a water-soluble polyfunctional (meth)acrylamide compound.

[0240] The ink of the present invention, by containing a water-soluble polyfunctional (meth)acrylamide compound, becomes an ink with excellent scratch resistance. The reasoning is as follows: In UV-curable water-based inks, the water-soluble polyfunctional (meth)acrylamide compound is considered to act as a crosslinking agent. Specifically, the water-soluble polyfunctional (meth)acrylamide compound exists between the particles of the UV-curable oligomer, thereby crosslinking the particles and increasing the crosslinking density between particles. Therefore, it is believed that an ink with improved film strength and excellent scratch resistance can be obtained.

[0241] Water-soluble polyfunctional (meth)acrylamides include not only water-soluble polyfunctional (meth)acrylamides, but also water-dispersed and emulsified polyfunctional (meth)acrylamides, or water-soluble polyfunctional (meth)acrylamides dissolved in alkaline water. Here, "water-soluble" means any substance that is slightly soluble in water, but preferably polyfunctional (meth)acrylamides whose water solubility is within the range described later. Furthermore, "dispersed and emulsified in water" means that the polyfunctional (meth)acrylamide, when dispersed alone in water, can be dispersed into particles with a particle size of 0.2 μm or less.

[0242] The water-soluble multifunctional (meth)acrylamide can have two or more functional groups, preferably two or more but less than six, and most preferably four or less, with a maximum of two, three, or four functional groups. Here, "number of functional groups" refers to the number of (meth)acrylamide structures present in one molecule.

[0243] Even with water-soluble (meth)acrylamide compounds, monofunctional water-soluble (meth)acrylamides (e.g., acrylamide morpholine) do not function as crosslinking agents, thus the ink film becomes hard and brittle, and no improvement in scratch resistance can be expected. However, this does not preclude the inclusion of monofunctional water-soluble (meth)acrylamides in the inks of the present invention.

[0244] Furthermore, even with multifunctional structures that can function as crosslinking agents, if they are not water-soluble multifunctional (meth)acrylamides but rather water-soluble multifunctional (meth)acrylates with PEG chains (polyethylene glycol chains), crosslinking can occur between UV-curable oligomer particles. Sometimes, the PEG chain portion swells due to water or solvents, causing the ink film to disintegrate from that portion. This weakens the coating strength and reduces alcohol resistance. Additionally, because the ink film tends to become more flexible, it is susceptible to cracking upon friction.

[0245] Examples of water-soluble multifunctional (meth)acrylamides include: N-[tris(3-acrylamidopropoxymethyl)methyl](meth)acrylamide, N,N-bis(2-acrylamidoethyl)acrylamide, N,N-[oxybis(2,1-ethanedioxy-3,1-propanediyl)]bisacrylamide, N,N-1,2-ethanediylbis{N-[2-(acryloylamino)ethyl]acrylamide}, N,N'-methylenebisacrylamide, N,N'-(1,2-dihydroxyethylene)bisacrylamide, etc. Among these, from the perspective of solubility in inks, dispersions, and aqueous compositions, N-[tris(3-acrylamidopropoxymethyl)methyl](methyl)acrylamide, N,N-bis(2-acrylamidoethyl)acrylamide, N,N-[oxybis(2,1-ethylenedioxy-3,1-propanediyl)]bisacrylamide, and N,N-1,2-ethanediylbis{N-[2-(acryloylamino)ethyl]acrylamide} are preferred. From the perspective of crosslinking structure formation, N-[tris(3-acrylamidopropoxymethyl)methyl](methyl)acrylamide, N,N-bis(2-acrylamidoethyl)acrylamide, and N,N-1,2-ethanediylbis{N-[2-(acryloylamino)ethyl]acrylamide} are more preferred.

[0246] Commercially available water-soluble multifunctional (meth)acrylamides include, for example: FOM-03006 (N-[tris(3-acrylamidopropoxymethyl)methyl]acrylamide), FOM-03007 (N,N-bis(2-acrylamidoethyl)acrylamide), FOM-03008 (N,N-[oxybis(2,1-ethanedioxy-3,1-propanediyl)]bisacrylamide), FOM-03009 (N,N-1,2-ethanediylbis{N-[2-(acryloylamino)ethyl]acrylamide}) (all manufactured by Fujifilm and Koujun Pharmaceutical Co., Ltd.); N,N'-methylenebisacrylamide (manufactured by Fujifilm and Koujun Pharmaceutical Co., Ltd., Shin-Ming Co., Ltd., etc.), etc.

[0247] From the perspective of uniform dissolution in inks, dispersions, and aqueous compositions, the solubility of water-soluble polyfunctional (meth)acrylamide in water is preferably 3% by mass or more, more preferably 10% by mass or more, and even more preferably 15% by mass or more.

[0248] Furthermore, from the viewpoint that the ink can be stably preserved without reacting with other components or causing agglomeration, the ionic form of water-soluble polyfunctional (meth)acrylamide is preferably nonionic.

[0249] The ink of the present invention may contain one of the above-mentioned water-soluble polyfunctional (meth)acrylamide compounds alone, or may contain two or more compounds in combination.

[0250] [Aqueous media]

[0251] The ink of this invention is a water-based ink. "Water-based ink" refers to an ink that contains a water-based medium. A water-based medium refers to water and / or water-soluble organic solvents.

[0252] The aqueous medium used in this invention is preferably water, or a mixture of water and a water-soluble organic solvent.

[0253] Water-soluble organic solvents include solvents that function as moisturizing solvents to improve the moisturizing and wetting properties of inks, and solvents that function as water-based media to adjust the viscosity of inks and improve their processability and dischargeability. However, there is no clear distinction between the two. Water-soluble organic solvents used as moisturizing solvents also function as water-based media.

[0254] It should be noted that, in this invention, water-soluble organic solvents refer to compounds that are soluble in water. The solubility in water is not limited, but compounds that can dissolve in water in any proportion are preferred. Furthermore, even compounds that are difficult to use as solvents on their own (e.g., compounds that are solid at room temperature or have high viscosity) are included in the category of water-soluble organic solvents, as long as they can be used as solvents by uniformly mixing with water.

[0255] Examples of water-soluble organic solvents include: polyols, polyol alkyl ethers, polyol aryl ethers, nitrogen-containing heterocyclic compounds, amides, amines, and sulfur-containing compounds.

[0256] Specific examples of water-soluble organic solvents include: ethylene glycol, diethylene glycol, 1,2-propanediol, 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- Polyols including pentanediol, 1,5-pentanediol, 1,2-hexanediol, 1,6-hexanediol, 1,3-hexanediol, 2,5-hexanediol, 1,5-hexanediol, glycerol, 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, pentanetriol, etc.; ethylene glycol monoethyl ether, Polyol alkyl ethers such as ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, tetraethylene glycol monomethyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, and diethylene glycol ethyl methyl ether; polyol aryl ethers such as ethylene glycol monophenyl ether and ethylene glycol monobenzyl ether; nitrogen-containing heterocyclic compounds such as 2-pyrrolidone, N-methyl-2-pyrrolidone, N-hydroxyethyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolinone, 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 thiodiethanolamine; propylene carbonate and ethylene carbonate.

[0257] As a water-soluble organic solvent, it is preferable to use an organic solvent with a boiling point below 250°C, considering that it not only functions as a moisturizing solvent but also provides good drying properties.

[0258] As a water-soluble organic solvent, polyol compounds with 8 or more carbon atoms, as well as glycol ether compounds, can also be used appropriately.

[0259] Specific examples of polyol compounds with 8 or more carbon atoms include 2-ethyl-1,3-hexanediol and 2,2,4-trimethyl-1,3-pentanediol.

[0260] Specific examples of glycol ether compounds include: 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, propylene glycol monoethyl ether, diethylene glycol ethyl methyl ether, and other polyol alkyl ethers; ethylene glycol monophenyl ether, ethylene glycol monobenzyl ether, and other polyol aryl ethers.

[0261] These water-soluble organic solvents can be used alone or in combination with two or more.

[0262] [Polymerization initiator]

[0263] The ink of the present invention preferably contains a polymerization initiator.

[0264] A polymerization initiator is a photoradical polymerization initiator that generates free radicals as active species by utilizing the energy of light (ultraviolet light) received from ultraviolet radiation, thereby initiating the photopolymerization of ultraviolet-curable oligomers. As a result, ink present on the surface of the recording medium can be cured to form an image.

[0265] The polymerization initiator can be included in the ink either in a state where it is not encapsulated within the UV-curable oligomer, or in a state where it is encapsulated within particles of the UV-curable oligomer. Furthermore, it can be included in both states.

[0266] As a polymerization initiator, it can be a fat-soluble polymerization initiator (hereinafter, sometimes referred to as "fat-soluble initiator") or a water-soluble polymerization initiator (hereinafter, sometimes referred to as "water-soluble initiator").

[0267] Here, "lipid-soluble initiator" refers to a polymerization initiator that is compatible with UV-curable oligomers or soluble in organic solvents; "water-soluble initiator" refers to an initiator that dissolves in water at a concentration of 1% or more by mass. The same applies to "lipid-soluble sensitizer" and "water-soluble sensitizer" as described later.

[0268] The polymerization initiators used in this invention are not limited to the following, but examples include: aromatic ketones, acylphosphine oxide compounds, aromatic onium salt compounds, organic peroxides, thiolated compounds (thioxanthone compounds, phenyl thio-containing compounds), α-aminoalkylphenyl ketone compounds, hexaaryl biimidazole compounds, ketoxime ester compounds, borate ester compounds, azazine compounds, metallocene compounds, active ester compounds, compounds having carbon-halogen bonds, and alkylamine compounds.

[0269] Among these, the polymerization initiator preferably contains at least one of an acylphosphine oxide compound and a thioxanthone compound. By using such a polymerization initiator, it is possible to achieve better curability of the ink.

[0270] As a lipid-soluble polymerization initiator, it is not limited to the following, but examples include: acetophenone, 2,2-diethoxyacetophenone, p-dimethylaminoacetophenone, benzophenone, 2-chlorobenzophenone, p,p'-dichlorobenzophenone, p,p'-bis(diethylamino)benzophenone, michlerone, benzoin, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin n-propyl ether, benzoin isobutyl ether, benzoin n-butyl ether, benzyl methyl ketone, 2,2-dimethoxy-1,2-diphenylethane-1-one, 1-hydroxycyclohexylphenyl ketone, 2-hydroxy-1-{4-[4-(2-hydroxy-2-methylpropanoyl)benzyl]phenyl}2-methylpropano-1-one, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)butanone-1- 2-Dimethylamino-2-(4-methylbenzyl)-1-(4-morpholin-4-yl-phenyl)butane-1-one, 2,4,6-trimethylbenzoyl diphenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide, 2-methyl-1-[4-(methylthio)phenyl]2-morpholinopropane-1-one, thioxanone, 2-chlorothioxanone, 2-methylthioxanone, 2-isopropylthioxanone, 4-isopropylthioxanone, 2-hydroxy-2-methyl-1-phenyl-1-one, 1-(4-isopropylphenyl)-2-hydroxy-2-methylpropane-1-one, methyl benzoylformate, azobisisobutyronitrile, benzoyl peroxide, and di-tert-butyl peroxide, etc.

[0271] As a water-soluble polymerization initiator, it is not limited to the following, but examples include: 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propane-1-one, sodium phenyl(2,4,6-trimethylbenzoyl)phosphonate, 2-(3-dimethylamino-2-hydroxypropoxy)-3,4-dimethyl-9H-thioxanone-9-one methyl chloride, etc.

[0272] Commercially available polymerization initiators include, for example, GENOPOL TX-2 manufactured by RAHN, and Irgacure 369, Irgacure 500, and Irgacure 2959 manufactured by Ciba Specialty Chemicals.

[0273] Polymerization initiators can be used alone or in combination with two or more. For example, a lipid-soluble initiator can be used in combination with a water-soluble initiator, so that the lipid-soluble initiator is encapsulated in the particles of the UV-curable oligomer, and the water-soluble initiator is dissolved in an aqueous medium.

[0274] In addition to the photoradical polymerization initiator described above, a thermal radical polymerization initiator can also be used as a polymerization initiator.

[0275] [surfactant]

[0276] To ensure the flatness of the resulting coating and its wettability with the substrate, the ink of the present invention preferably contains a surfactant.

[0277] As a surfactant, any one of the following can be used: organosilicon surfactant, fluorinated surfactant, amphoteric surfactant, nonionic surfactant, or anionic surfactant.

[0278] Organosilicon surfactants are not particularly limited and can be appropriately selected depending on the purpose. Among them, surfactants that do not decompose at high pH are preferred, such as side-chain modified polydimethylsiloxanes, bi-terminated polydimethylsiloxanes, single-terminated polydimethylsiloxanes, and bi-terminated side-chain polydimethylsiloxanes. Organosilicon surfactants having polyoxyethylene, polyoxyethylene, or polyoxypropylene groups as modifying groups are particularly preferred because they exhibit good properties as aqueous surfactants. Polyether-modified organosilicon surfactants can also be used, such as compounds formed by introducing a polyoxyethylene structure into the Si-side chain of a dimethylsiloxane.

[0279] As a fluorinated surfactant, it is preferred to be a compound with 2 or more and 16 or less carbon atoms substituted with fluorine, and more preferably a compound with 4 or more and 16 or less carbon atoms substituted with fluorine.

[0280] As fluorinated surfactants, perfluoroalkyl sulfonic acid compounds, perfluoroalkyl carboxylic acid compounds, perfluoroalkyl phosphate ester compounds, perfluoroalkyl epoxy alkyl adducts, and polyoxyalkylene ether polymer compounds with perfluoroalkyl ether groups on the side chains are preferred due to their low foaming properties. Examples of perfluoroalkyl sulfonic acid compounds include perfluoroalkyl sulfonic acids and perfluoroalkyl sulfonates. 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 epoxy alkyl adducts include perfluoroalkyl ethylene oxide adducts. Examples of polyoxyalkylene ether polymer compounds with perfluoroalkyl ether groups on the side chains include sulfate salts of polyoxyalkylene ether polymers with perfluoroalkyl ether groups on the side chains and salts of polyoxyalkylene ether polymers with perfluoroalkyl ether groups on the side chains. Examples of counterions to the salts of these fluorinated surfactants include: Li, Na, K, NH4, NH3CH2CH2OH, NH2(CH2CH2OH)2, and NH(CH2CH2OH)3.

[0281] Among these, polyoxyalkylene ether polymer compounds with perfluoroalkyl ether groups on the side chains are more preferred due to their particularly low foaming properties, and fluorinated surfactants represented by the following general formulas (3A) and (3B) are particularly preferred.

[0282] CF3CF2(CF2CF2) s -CH2CH2O(CH2CH2O) t H…(3A)

[0283] In compounds represented by general formula (3A), in order to impart water solubility, 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.

[0284] C r F 2r+1 -CH2CH(OH)CH2-O-(CH2CH2O) c -Z…(3B)

[0285] In compounds represented by the general formula (3B), Z is H or C. d F 2d+1 Where d is an integer greater than 1 and less than 6, or CH2CH(OH)CH2-C e F 2e+1 Where e is an integer greater than 4 and less than 6, or is C. f H 2f+1 Where f is an integer greater than or equal to 1 and less than or equal to 19. In addition, r is an integer greater than or equal to 1 and less than or equal to 6, and c is an integer greater than or equal to 4 and less than or equal to 14.

[0286] Commercially available products can be used as fluorinated surfactants. Examples of commercially available products include: Surflon S-111, S-112, S-113, S-121, S-131, S-132, S-141, and S-145 (all manufactured by Asahi Glass); Fluorad FC-93, FC-95, FC-98, FC-129, FC-135, FC-170C, FC-430, and FC-431 (all manufactured by Sumitomo 3M); MEGAFAC F-470, F-1405, F-474 (all manufactured by DIC); Zonyl (Zonyl) TBS, FSP, FSA, FSN-100, FSN, FSO-100, FSO, FS-300, UR (all manufactured by DuPont); FT-110, FT-250, FT-251, FT-400S, FT-150, FT-400SW (all manufactured by NEOS); PolyFox PF-136A, PF-156A, PF-151N, PF-154, PF-159 (manufactured by OMNOVA); NOIGEN FN-1287 (manufactured by Daiichi Kogyo Pharmaceutical Co., Ltd.); UNIDYNE DSN-403N (manufactured by Daikin Industries, Ltd.); LE-604, LE-605, LE-606, LE-607 (Kyoeisha Chemical Co., Ltd.), etc.

[0287] Examples of amphoteric surfactants include lauryl aminopropionate, lauryl dimethyl betaine, stearyl dimethyl betaine, and lauryl dihydroxyethyl betaine.

[0288] 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, alkynyl alcohol derivatives, and alkynyl diol derivatives.

[0289] Examples of anionic surfactants include: polyoxyethylene alkyl ether acetates, dodecylbenzene sulfonates, laurates, and salts of polyoxyethylene alkyl ether sulfates.

[0290] These can be used individually or in combination with two or more.

[0291] As mentioned above, there are no particular limitations on silicone surfactants, and they can be appropriately selected according to the purpose. However, polyether-modified silicone surfactants with polyoxyethylene, polyoxyethylene, or polyoxypropylene groups as modifying groups are particularly preferred surfactants because they exhibit good properties as aqueous surfactants.

[0292] Such surfactants can be appropriately synthesized compounds or commercially available products. Commercially available products can be obtained, for example, from BYK Corporation, Shin-Etsu Chemical Co., Ltd., Toray D. Corning Silicones Co., Ltd., Emulsion Corporation of Japan, and Kyoei Chemical Co., Ltd.

[0293] There are no particular limitations on polyether-modified organosilicon surfactants, and they can be appropriately selected according to the purpose. For example, compounds formed by introducing a polyoxyethylene structure into the Si side chain of a dimethylpolysiloxane, represented by the following general formula (2), can be cited.

[0294] [Chemistry 2]

[0295]

[0296] Q = -R(C₂HO),(CaHO),R

[0297] (In equation (2), p, q, a, and b represent integers; R and R' represent hydrocarbon groups.)

[0298] Commercially available products can be used as polyether-modified silicone surfactants. Examples of commercially available products include: KF-618, KF-642, KF-643 (Shin-Etsu Chemical Co., Ltd.); SAG001, SAG002, SAG003, SAG005, SAG503, SAG008 (Nikshin Chemical Co., Ltd.); EMLEX-SS-5602, SS-1906EX (Emulsion Corporation of Japan); FZ-2105, FZ-2118, FZ-2154, FZ-2161, FZ-2162, FZ-2163, FZ-2164 (Toray Corning Silicones Co., Ltd.); BYK-33, BYK-387 (BYK Corporation); TSF4440, TSF4452, TSF4453 (Toshiba Silicones Co., Ltd.), etc.

[0299] [Sensitizer]

[0300] The ink of the present invention may also contain a sensitizer. When the sensitizer is present in the ink along with the polymerization initiator, the sensitizer in the system absorbs active energy rays and is in an excited state, and promotes the decomposition of the polymerization initiator by contacting it, thereby enabling a curing reaction with higher sensitivity.

[0301] Sensitizers can be either fat-soluble, like polymerization initiators, or water-soluble. If the sensitizer is fat-soluble, it can be encapsulated within the particles of the UV-curable oligomer.

[0302] As sensitizers, aliphatic amines, amines with aromatic groups, or cyclic amines such as piperidine can be used; thioxanthone compounds, alkoxyanthracene compounds, and urea compounds such as o-tolylthiourea; sulfur compounds such as sodium diethylthiophosphate or soluble salts of aromatic sulfinic acids; nitrile compounds such as N,N'-disubstituted p-aminobenzonitrile; phosphorus compounds such as tri-n-butylphosphine or sodium diethyldithiophosphate; and nitrogen compounds such as mischlerone, N-nitrosohydroxylamine derivatives, oxazolidine compounds, tetrahydro-1,3-oxazine compounds, and condensates of formaldehyde or acetaldehyde with diamines.

[0303] These sensitizers can be used in single or multiple ways.

[0304] [Other oligomers, resins, monomers]

[0305] In addition to the components described above, the ink of the present invention may, as needed, contain oligomer components other than UV-curable oligomers, any resin components, and any monomer components (collectively referred to as "other resin components"). Other resin components may be encapsulated within the particles of the UV-curable oligomers, dissolved in an aqueous medium, or dispersed alone or combined with other components in the ink.

[0306] [Other Additives]

[0307] In addition to the components described above, the ink of the present invention may also contain other additives as needed.

[0308] Other additives include, for example, well-known additives such as: anti-fading agents, emulsion stabilizers, penetration enhancers, UV absorbers, preservatives, mildew inhibitors, rust inhibitors, pH adjusters, viscosity adjusters, dispersants, dispersion stabilizers, defoamers, solid wetting agents, and chelating agents. These various additives can be added directly after ink preparation or during ink preparation.

[0309] For other additives, please refer to paragraphs 0088 to 0096 of Japanese Patent Application Publication No. 2010-65205 and paragraphs 0083 to 0090 of Japanese Patent Application Publication No. 2010-70669.

[0310] [Content of each ingredient]

[0311] The water content in the ink of the present invention is not particularly limited and can be appropriately selected according to the purpose. However, from the perspective of ink drying and discharge reliability, it is usually 10% by mass or more, preferably 20% by mass or more, usually 90% by mass or less, and preferably 80% by mass or less.

[0312] Furthermore, when the ink of the present invention contains a water-soluble organic solvent, its content (the total content of the water-soluble organic solvent used as a moisturizing solvent and the water-soluble organic solvent used as an aqueous medium) is not particularly limited, and can be appropriately selected according to the type and purpose of the water-soluble organic solvent used. However, from the perspective of drying performance, discharge reliability, and wettability with the substrate, it is generally 10% by mass or more, generally 50% by mass or less, and preferably 40% by mass or less.

[0313] From the perspective of drying performance and discharge reliability, in the ink of the present invention, the concentration of all solid components other than water and / or water-soluble organic solvents is generally adjusted to 5% by mass or more, preferably 7% by mass or more, more preferably 9% by mass or more, generally 30% by mass or less, preferably 25% by mass or less, more preferably 20% by mass or less, and even more preferably 15% by mass or less.

[0314] Furthermore, from the perspective of improving drying and drainage, when using a mixture of water and a water-soluble organic solvent as an aqueous medium, the ratio of water to water-soluble organic solvent (the total of water-soluble organic solvent used as a moisturizing solvent and water-soluble organic solvent used as an aqueous medium) is preferably such that the ratio of water to water-soluble organic solvent is typically 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).

[0315] From the perspective of the obtained printing coating performance and UV curability, the content of UV curable oligomers in the ink of the present invention is generally 3% by mass or more, preferably 5% by mass or more, and more preferably 7% by mass or more. On the other hand, from the perspective of discharge stability, it is generally 20% by mass or less, preferably 15% by mass or less, and more preferably 12% by mass or less.

[0316] Furthermore, from the same perspective, the content of UV-curable oligomers in all solid components of the ink of the present invention is generally 30% by mass or more, preferably 50% by mass or more, more preferably 60% by mass or more, generally 90% by mass or less, preferably 85% by mass or less, more preferably 80% by mass or less.

[0317] Here, all solid components in the ink of the present invention can be referred to as constituent components of the cured film (printed film) formed by the ink of the present invention, and the numerical ranges described above can be used in the same way. The content of each component in all solid components is substantially equal to the content of that component in the cured film (printed film) formed by the ink of the present invention.

[0318] Therefore, the content of UV-curable oligomers in all solid components of the ink of the present invention is generally 30% by mass or more, preferably 50% by mass or more, more preferably 60% by mass or more, generally 90% by mass or less, preferably 85% by mass or less, more preferably 80% by mass or less. This can also be regarded as the content of the component derived from UV-curable oligomers in the cured film (printed film) formed by the ink of the present invention being generally 30% by mass or more, preferably 50% by mass or more, more preferably 60% by mass or more, generally 90% by mass or less, preferably 85% by mass or less, more preferably 80% by mass or less.

[0319] The same applies to the content of the following colorants, water-soluble polyfunctional (meth)acrylamide compounds, and other ingredients.

[0320] From the perspective of improving image density, good fixing properties, and discharge stability, the content of colorant in the ink of the present invention is usually 0.1% by mass or more, preferably 1% by mass or more, usually 8% by mass or less, and preferably 6% by mass or less.

[0321] Furthermore, from the same perspective, the content of colorant in all solid components of the ink of the present invention is generally 1% by mass or more, preferably 5% by mass or more, generally 40% by mass or less, and preferably 30% by mass or less.

[0322] From the perspective of improving the coating strength of the ink by crosslinking the UV-curable oligomers through its function as a crosslinking agent, the content of the water-soluble polyfunctional (meth)acrylamide compound in the ink of the present invention is generally 0.01% by mass or more, preferably 0.05% by mass or more, more preferably 0.2% by mass or more, and from the perspective of improving the alcohol resistance of the ink film, it is even more preferably 0.6% by mass or more. On the other hand, from the perspective of improving the storage stability of the ink, it is generally 10% by mass or less, preferably 8% by mass or less, more preferably 6% by mass or less.

[0323] Furthermore, from the same perspective, the content of water-soluble polyfunctional (meth)acrylamide compounds in all solid components of the ink of the present invention is generally 0.05% by mass or more, preferably 0.25% by mass or more, more preferably 1% by mass or more, further preferably 4% by mass or more, generally 40% by mass or less, preferably 35% by mass or less, and more preferably 30% by mass or less.

[0324] When the ink of the present invention contains a polymerization initiator, its content is generally 0.05% by mass or more, preferably 0.1% by mass or more, more preferably 0.3% by mass or more, even more preferably 0.4% by mass or more, generally 8% by mass or less, preferably 5% by mass or less, more preferably 3% by mass or less, even more preferably 2% by mass or less, and particularly preferably 1% by mass or less. By keeping the content of the polymerization initiator within this range, the curing speed can be sufficiently improved, and coloring due to undissolved residues of the polymerization initiator and the polymerization initiator can be avoided.

[0325] Furthermore, from the same perspective, the content of polymerization initiator in all solid components of the ink of the present invention is generally 0.5% by mass or more, preferably 1% by mass or more, more preferably 2% by mass or more, even more preferably 3% by mass or more, generally 20% by mass or less, more preferably 15% by mass or less, even more preferably 10% by mass or less, and particularly preferably 8% by mass or less.

[0326] When the ink of the present invention contains a surfactant, its content is not particularly limited and can be appropriately selected according to the purpose. However, from the perspective of improving wettability, excellent discharge stability and image quality, the content of surfactant in the ink is usually 0.001% by mass or more, preferably 0.01% by mass or more, more preferably 0.03% by mass or more, usually 5% by mass or less, preferably 3% by mass or less, and more preferably 1% by mass or less.

[0327] Furthermore, from the same perspective, the content of surfactant in all solid components of the ink of the present invention is generally 0.01% by mass or more, preferably 0.1% by mass or more, more preferably 0.2% by mass or more, generally 10% by mass or less, preferably 5% by mass or less, more preferably 3% by mass or less.

[0328] When the ink of the present invention contains a sensitizer, its content is generally 0.01% by mass or more, preferably 0.03% by mass or more, more preferably 0.05% by mass or more, generally 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. If the content of the sensitizer is within the above range, the effect brought by the sensitizer is fully obtained.

[0329] Furthermore, from the same perspective, the content of sensitizer in all solid components of the ink of the present invention is generally 0.05% by mass or more, preferably 0.1% by mass or more, more preferably 0.3% by mass or more, even more preferably 0.5% by mass or more, generally 8% by mass or less, preferably 6% by mass or less, and more preferably 5% by mass or less.

[0330] [UV-curable water-based composition]

[0331] In a first embodiment of the aqueous composition of the present invention, the ultraviolet-curable aqueous composition of the present invention (hereinafter, sometimes referred to as "the aqueous composition of the present invention") contains one or more of a polymerization initiator, a sensitizer, and a surfactant; an ultraviolet-curable oligomer; and a water-soluble polyfunctional (meth)acrylamide compound, wherein the ultraviolet-curable oligomer has structural units derived from the water-soluble compound and structural units derived from a compound containing two or more polymerizable unsaturated bonds.

[0332] In a second embodiment of the aqueous composition of the present invention, the composition is characterized by containing: any one or more of a polymerization initiator, a sensitizer, and a surfactant; a UV-curable oligomer; and a water-soluble polyfunctional (meth)acrylamide compound, wherein the UV-curable oligomer contains four or more polymerizable unsaturated bonds and has structural units derived from compounds capable of bonding with the polyisocyanate compound (A).

[0333] In a third embodiment of the aqueous composition of the present invention, there is an ultraviolet-curable aqueous composition comprising: any one or more of a polymerization initiator, a sensitizer and a surfactant; an ultraviolet-curable oligomer; and a water-soluble polyfunctional (meth)acrylamide compound, wherein the ultraviolet-curable oligomer has a structural unit derived from a compound represented by the following formula (1).

[0334] [Chemistry 1]

[0335]

[0336] (In formula (1), X is an alkylene group, Y is any one of (meth)acryloyl, allyl, or acyl; n is an integer greater than or equal to 2.)

[0337] The UV-curable aqueous composition of the present invention is an aqueous composition, containing an aqueous medium similar to the ink of the present invention. Furthermore, in the aqueous composition of the present invention, the UV-curable oligomer is preferably nonionic, preferably a UV-curable oligomer having structural units from a polyisocyanate compound (A), structural units from a compound (B') shown below, and structural units from a compound (C') shown below, and particularly preferably a UV-curable (meth)acrylate oligomer having structural units from a polyisocyanate compound (A), structural units from a hydroxyl-containing polyfunctional (meth)acrylate (B), and structural units from a polyalkylene glycol (C).

[0338] That is, the above-described aqueous composition of the present invention belongs to the type of ink of the present invention that does not contain colorants. The UV-curable oligomers, water-soluble polyfunctional (meth)acrylamide compounds, aqueous media, polymerization initiators, sensitizers, surfactants and other additives contained in the aqueous composition of the present invention are the same as those described in the ink item of the present invention above, and their contents are also the same as those of the components other than colorants in the ink of the present invention above.

[0339] The method of using the aqueous composition of the present invention is not particularly limited, but it is preferred to use it by adding the above-described colorant to the aqueous composition of the present invention to prepare the ink of the present invention. The added colorant can be one color or two or more colors. By adding any two or more colorants, the hue of the ink can be adjusted to the desired hue.

[0340] In addition, the aqueous composition of the present invention can be used as a transparent ink.

[0341] [Ink manufacturing method]

[0342] The manufacturing method of the ink of the present invention is not particularly limited, but the following methods can be cited: preparing a dispersion (hereinafter, sometimes referred to as "oligomer particles") formed by dispersing ultraviolet-curable oligomer particles in an aqueous medium and a dispersion (hereinafter, sometimes referred to as "pigment dispersion") formed by dispersing colorants such as pigments in an aqueous medium; and mixing the oligomer dispersion and pigment dispersion with a polymerization initiator (water-soluble initiator), a water-soluble polyfunctional (meth)acrylamide compound, other additives, and an organic solvent. Furthermore, methods of adding colorants to the aqueous composition of the present invention can also be cited, but inks with the same properties can be obtained by using any method.

[0343] In a first embodiment of the dispersion of the present invention, there is a dispersion of an ultraviolet-curable oligomer, characterized in that the dispersion contains 0.1% by mass and more and 20% by mass and less of a water-soluble polyfunctional (meth)acrylamide compound, wherein the ultraviolet-curable oligomer has structural units derived from the water-soluble compound and structural units derived from a compound containing two or more polymerizable unsaturated bonds.

[0344] In a second embodiment of the dispersion of the present invention, there is a dispersion of an ultraviolet-curable oligomer, characterized in that the dispersion contains 0.1% by mass and 20% by mass and less of a water-soluble polyfunctional (meth)acrylamide compound, wherein the ultraviolet-curable oligomer contains four or more polymerizable unsaturated bonds and has structural units derived from compounds capable of bonding with polyisocyanate compound (A).

[0345] In a third embodiment of the dispersion of the present invention, there is a dispersion of an ultraviolet-curable oligomer, characterized in that the dispersion contains 0.1% by mass and 20% by mass and less of a water-soluble polyfunctional (meth)acrylamide compound, wherein the ultraviolet-curable oligomer has structural units derived from compounds represented by the following formula (1).

[0346] [Chemistry 1]

[0347]

[0348] (In formula (1), X is an alkylene group, Y is any one of (meth)acryloyl, allyl, or acyl; n is an integer greater than or equal to 2.)

[0349] By adding and mixing a lipid-soluble initiator and a lipid-soluble sensitizer during the preparation of the oligomer dispersion, these components can be encapsulated within the oligomer particles. Alternatively, the lipid-soluble initiator and sensitizer can be separately prepared as a solution dissolved in an organic solvent at a concentration of approximately 0.1% to 10% by mass and then mixed with the other components.

[0350] The dispersion of the present invention can be prepared by adding a water-soluble polyfunctional (meth)acrylamide compound to a dispersion of a UV-curable oligomer during the manufacturing process of such an ink.

[0351] In this case, as long as the amount of water-soluble polyfunctional (meth)acrylamide compound added in the ink of the present invention is the amount of the preferred content described above, it is acceptable. For example, the ratio (mass ratio) of the UV-curable oligomer to the water-soluble polyfunctional (meth)acrylamide compound is used in an amount of about 50:1 to 1:1. It is preferable that the dispersion contains 0.02% by mass or more of the water-soluble polyfunctional (meth)acrylamide compound, more preferably 0.1% by mass or more. On the other hand, it is preferable that the content is 20% by mass or less, more preferably 15% by mass or less.

[0352] <Preparation of Oligopolymer Dispersions>

[0353] Oligopolymer dispersions can be prepared by mixing UV-curable oligomers with an aqueous medium (preferably water).

[0354] By adjusting the temperature and stirring speed, the average particle size of the resulting oligomer particles can be adjusted.

[0355] From an operational perspective, the oligomer particle concentration of the oligomer dispersion prepared in this way is preferably between 10% by mass and about 30% by mass.

[0356] By further adding and mixing a lipophilic initiator and a lipophilic sensitizer during the preparation of the oligomer dispersion, a dispersion containing oligomer particles encapsulating these components can be obtained. In this case, to prevent the formation of particles containing only the sensitizer and not the oligomer initiator, it is preferable to add the lipophilic initiator and / or the lipophilic sensitizer to the UV-curable oligomer before mixing it with an aqueous medium such as water. When preparing a product containing the lipophilic initiator and / or the lipophilic sensitizer, from the perspective of manufacturing stability, it is preferable that the content of the lipophilic initiator and / or the lipophilic sensitizer in the oligomer particles is approximately 0.1% by mass or more and 8% by mass or less relative to the UV-curable oligomer.

[0357] <Preparation of Pigment Dispersion>

[0358] Pigment dispersions can be prepared by adding colorants such as pigments to an aqueous medium such as water and mixing them.

[0359] From the perspective of processability and storage stability, the concentration of pigments and other colorants in pigment dispersions is usually 5% by mass or more, preferably 10% by mass or more, usually 40% by mass or less, and preferably 35% by mass or less.

[0360] It should be noted that commercially available products can be used directly as pigment dispersions.

[0361] [Method for manufacturing the aqueous composition]

[0362] The method for manufacturing the aqueous composition of the present invention is not particularly limited, but the following method can be cited: preparing an oligomer dispersion in the same manner as the ink manufacturing method of the present invention described above, and mixing one or more of a water-soluble polyfunctional (meth)acrylamide compound, a polymerization initiator (water-soluble initiator), a sensitizer and a surfactant, other additives as needed, and an organic solvent in the prepared oligomer dispersion.

[0363] As described above, by adding and mixing a lipid-soluble initiator and a lipid-soluble sensitizer during the preparation of the oligomer dispersion, these components can be encapsulated within the oligomer particles. Furthermore, the lipid-soluble initiator and lipid-soluble sensitizer can also be separately prepared as solutions dissolved in an organic solvent at a concentration of approximately 0.1% to 10% by mass and then mixed with the other components.

[0364] The preparation method of the oligomer dispersion and the preparation method of the dispersion of oligomer particles containing lipophilic initiators and lipophilic sensitizers are the same as the manufacturing method of the ink of the present invention described above.

[0365] [Ink viscosity]

[0366] From the perspective of excellent pigment dispersion stability, the viscosity of the ink of the present invention can be kept low. As a result, the ink discharge properties are also good during high-speed printing. The viscosity of the ink of the present invention 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. It should be noted that the lower limit value is not particularly limited, but it is preferably 1 mPa·sec or more, and more preferably 2 mPa·sec or more.

[0367] [Viscosity of the aqueous composition]

[0368] The viscosity of the aqueous composition of the present invention at 25°C is preferably 50 mPa·sec or less, more preferably 30 mPa·sec or less, and even more preferably 20 mPa·sec or less. It should be noted that the lower limit is not particularly limited, but is preferably 0.5 mPa·sec or more, and more preferably 1 mPa·sec or more.

[0369] [Ink container]

[0370] The ink of this invention can be contained in ink cartridges or ink bottles, thus eliminating the need for direct contact with the ink during ink transportation and exchange, preventing contamination of fingers and clothing. Furthermore, it prevents foreign matter such as dust from contaminating the ink.

[0371] The shape, size, and material of the ink container itself are not particularly limited as long as they are suitable for the inkjet printer to which they are used. However, it is desirable that the material be an opaque light-blocking material or that the container be covered with a light-blocking sheet.

[0372] [Inkjet Recording Method]

[0373] The inkjet recording method using the ink of the present invention preferably includes the following steps: a step of discharging the ink of the present invention from the ejector nozzle of an inkjet printer and adhering it to a recording medium; a heating step of heating the recording medium with the ink adhering to it; and an irradiation step of irradiating the ink adhering to the recording medium with active energy rays. It should be noted that the step of adhering the ink of the present invention to the recording medium is not limited to adhering the ink to the recording medium in a mist (foam, spray) form, but is not necessarily limited to using an inkjet printer.

[0374] <Recorded medium>

[0375] There are no particular limitations on the recording medium to which the ink of the present invention can be applied, and it is possible to form high-quality printed images with good adhesion to various substrates such as polyesters such as polyethylene terephthalate (PET); plastic materials such as polyvinyl chloride (PVC), polyethylene (PE), and polypropylene (PP); and paper, textiles (cloth, fabric), leather, glass, ceramics, wood, metal, or composites thereof.

[0376] <Heating Process>

[0377] In the heating process, the recording medium coated with the ink of the present invention is preferably heated to 40°C or higher. More preferably, the heating temperature is 45°C or higher, and even more preferably 50°C or higher. By performing the above heating, volatile components such as water in the ink can be dried, which tends to further improve curability. There is no particular upper limit to the heating temperature, but since poor ink removal usually occurs due to the drying of the ink on the nozzle surface in the presence of the heating mechanism, it is preferably 120°C or lower, more preferably 100°C or lower. Here, the heating temperature is the surface temperature of the recording surface of the recording medium.

[0378] There are no particular limitations on heating mechanisms, but examples include: ceramic heaters, halogen heaters, quartz tube heaters, etc.

[0379] The heating can be performed at any time, such as before, during, or after the ink of the present invention is applied to the recording medium, or more preferably, during the entire process of application.

[0380] <Irradiation Process>

[0381] In the irradiation process, the polymerization reaction of UV-curable oligomers is initiated by irradiation with active energy rays. Furthermore, the polymerization initiator contained in the ink decomposes upon irradiation with active energy rays, generating free radicals, acids, bases, and other initiating species. The polymerization reaction of the UV-curable oligomers is promoted by these initiating species. At this time, when a sensitizer is present in the ink along with the polymerization initiator, the sensitizer in the system absorbs the active energy rays and enters an excited state. Through contact with the polymerization initiator, it promotes the decomposition of the polymerization initiator, enabling a more sensitive curing reaction.

[0382] Mercury lamps, metal halide lamps, and gas / solid-state lasers are well-known light sources (active energy radiation sources). However, from an environmental protection perspective, there is a strong desire for mercury-free alternatives, making GaN-based semiconductor ultraviolet light-emitting devices highly useful in both industrial and environmental applications. Furthermore, ultraviolet light-emitting diodes (UV-LEDs) and ultraviolet laser diodes (UV-LDs) are expected to be suitable as light sources for ultraviolet-curable inkjet printing due to their small size, long lifespan, high efficiency, and low cost. Among these, UV-LEDs are preferred.

[0383] The preferred wavelength of the emission peak of the irradiated active energy X-ray source is in the range of 350–450 nm, and the irradiation energy is 20 J / cm². 2 The following values ​​are preferred, for example, 0.5 to 10 J / cm. 2 .

[0384] It should be noted that there may be one or more emission peak wavelengths within the wavelength range mentioned above.

[0385] Furthermore, the irradiation process is not limited to the process intended as described above; it can also be, for example, sunlight exposure through outdoor exposure. Moreover, in cases where the reactivity (curability) of the UV-curable oligomer of the present invention is high, a heating process may be performed without the irradiation process. That is, the ink of the present invention is not limited to use in printing methods that include an irradiation process, as long as it possesses UV curability.

[0386] [use]

[0387] The ink of this invention is water-based, thus offering excellent environmental and safety characteristics. It achieves a good balance of the required properties for printing inks, particularly inkjet printer inks, such as high image quality, high coating performance, high-speed printability, and substrate versatility. Furthermore, it exhibits excellent coating strength, including scratch resistance. Therefore, it enables high-quality printing of images with excellent coating performance on various recording media with high productivity. Based on these advantages, it can be used for a wide range of applications, including posters, road signs, signs, billboards, outdoor and indoor display boards, building materials (exterior and interior surfaces, walls, floors, ceilings, windows, etc.), vehicle exteriors (automobiles, railways, airplanes, etc.), furniture, surface materials for office automation equipment, and printed paper.

[0388] Example

[0389] The following describes one embodiment of the present invention. However, the present invention is not limited to this embodiment.

[0390] First, embodiments and comparative examples of the first and second embodiments of the present invention will be described.

[0391] [Preparation of UV-curable oligomer 1]

[0392] A nonionic UV-curable oligomer 1 is prepared by reacting 0.4 mol of hexamethylene diisocyanate trimer, 0.8 mol of pentaerythritol pentaacrylate and 0.4 mol of polyethylene glycol monoallyl ether (n = 30-40 in the above general formula (1)).

[0393] [Preparation of UV-curable oligomer aqueous dispersion 1 encapsulated with a lipid-soluble initiator]

[0394] The UV-curable oligomer 1 obtained above and GENOPOL TX-2 manufactured by RAHN Corporation, used as a lipid-soluble initiator, were stirred and mixed at 60°C. Ion-exchanged water preheated to 60°C was then added dropwise while stirring to obtain an aqueous dispersion 1 (UV-curable oligomer concentration 20% by mass) containing 1% by mass of the lipid-soluble initiator relative to the UV-curable oligomer particles. The average particle size (D) of the UV-curable oligomer particles in this aqueous dispersion is... 50 The particle size distribution was measured using a MICROTRAC UPA (MODEL: 9340-UPA, manufactured by Nikkiso Corporation), and the result was 36 nm.

[0395] [Water-soluble polyfunctional (meth)acrylamide compounds]

[0396] The following compounds are used as water-soluble polyfunctional (meth)acrylamide compounds.

[0397] (1) Trifunctional Acrylamide: N,N-bis(2-acrylamidoethyl)acrylamide, manufactured by Fujifilm and Kazumitsu Pharmaceutical Co., Ltd., FOM-03007

[0398] (2) Difunctional Acrylamide: N,N-[oxybis(2,1-ethanedioxy-3,1-propanediyl)]bisacrylamide, manufactured by Fujifilm and Kako Pure Chemical Industries, Ltd., FOM-03008

[0399] (3) Tetrafunctional acrylamide: N-[tris(3-acrylamidopropoxymethyl)methyl]acrylamide, manufactured by Fujifilm and Koh Genuine Chemicals Co., Ltd., FOM-03006

[0400] [Example 1]

[0401] Ion-exchanged water, the above-mentioned lipid-soluble initiator-encapsulated UV-curable oligomer aqueous dispersion 1, N,N-bis(2-acrylamidoethyl)acrylamide as a water-soluble polyfunctional (meth)acrylamide compound, 1,2-butanediol as a moisturizing solvent, propylene glycol as a water-soluble organic solvent, a water-soluble initiator, a water-soluble sensitizer, NOIGEN FN1287 manufactured by Daiichi Kogyo Pharmaceutical Co., Ltd. as a surfactant[1], LE-605 manufactured by Kyoeisha Chemical Co., Ltd. as a surfactant[2], and EMACOL SF CYAN AE2034F manufactured by Sanyo Pigment Co., Ltd. as a pigment dispersion were added and mixed to obtain ink composition liquid 1.

[0402] [Examples 2-5]

[0403] Except for changing the proportion of N,N-bis(2-acrylamidoethyl)acrylamide as shown in Table 1, ink composition liquids 2 to 5 were obtained in the same manner as in Example 1.

[0404] [Example 6]

[0405] Except for replacing N,N-bis(2-acrylamidoethyl)acrylamide with N,N-[oxybis(2,1-ethanedioxy-3,1-propanediyl)]bisacrylamide, ink composition liquid 6 was obtained in the same manner as in Example 2.

[0406] [Example 7]

[0407] Except for replacing N,N-bis(2-acrylamidoethyl)acrylamide with N-[tris(3-acrylamidopropoxymethyl)methyl]acrylamide, ink composition liquid 7 was obtained in the same manner as in Example 2.

[0408] [Comparative Example 1]

[0409] Except that N,N-bis(2-acrylamidoethyl)acrylamide was not added, ink composition liquid 8 was obtained in the same manner as in Example 1.

[0410] [Comparative Example 2]

[0411] Except for replacing N,N-bis(2-acrylamidoethyl)acrylamide with ACMO (registered trademark) manufactured by Kj Chemical Company (acryloylmorpholine (monofunctional acrylamide)), the ink composition liquid 9 was obtained in the same manner as in Example 2.

[0412] [Comparative Example 3]

[0413] Except for replacing N,N-bis(2-acrylamidoethyl)acrylamide with NK oligoUA-W2A (water-soluble urethane acrylate oligomer) manufactured by Shin-Nakamura Chemical Co., Ltd., ink composition liquid 10 was obtained in the same manner as in Example 2.

[0414] [Comparative Example 4]

[0415] Except for replacing N,N-bis(2-acrylamidoethyl)acrylamide with NK ester A-GLY-20E (water-soluble trifunctional ethoxylated glycerol triacrylate [1]) manufactured by Shin-Nakamura Chemical Co., Ltd., ink composition liquid 11 was obtained in the same manner as in Example 2.

[0416] [Comparative Example 5]

[0417] Except for replacing N,N-bis(2-acrylamidoethyl)acrylamide with NK ester A-GLY-9E (water-soluble trifunctional ethoxylated glycerol triacrylate [2]) manufactured by Shin-Nakamura Chemical Co., Ltd., ink composition liquid 12 was obtained in the same manner as in Example 2.

[0418] [Comparative Example 6]

[0419] Ion-exchanged water, the above-mentioned lipid-soluble initiator-encapsulated UV-curable oligomer aqueous dispersion 1, diethylene glycol ethyl methyl ether as a moisturizing solvent, propylene glycol as a water-soluble organic solvent, BYK347 manufactured by BYK Chemical Japan Co., Ltd. as a surfactant [1], 1,3,5-triacryloylhexahydro-1,3,5-triazine (non-water-soluble acrylamide) manufactured by Tokyo Chemical Industry Co., Ltd. as an additive, and EMACOL SF CYAN AE2034F manufactured by Sanyo Pigment Co., Ltd. as a pigment dispersion were added and mixed to obtain ink composition liquid 13. Although the above operation was performed, there were undissolved residues of non-water-soluble acrylamide, and the ink composition liquid could not be obtained.

[0420] [Comparative Example 7]

[0421] Except for changing the proportion of 1,3,5-triacryloylhexahydro-1,3,5-triazine (aqua-insoluble acrylamide) manufactured by Tokyo Chemical Industry Co., Ltd. to that shown in Table 1, ink composition liquid 14 was obtained in the same manner as in Comparative Example 6.

[0422] [Table 1]

[0423]

[0424] [Evaluation of the ink's composition]

[0425] The ink compositions obtained in Examples 1-7 and Comparative Examples 1-5 and 7 were evaluated as follows, and the results are shown in Table 2.

[0426] Evaluation of the alcohol resistance and scratch resistance of the cured film

[0427] The cured film is formed by the following method (1), and the scratch resistance is evaluated by the following method (2), and the alcohol resistance is evaluated by the following method (3).

[0428] (1) LED curing

[0429] The ink composition liquid prepared above was applied to a PVC film with a film thickness of 15 μm and a thickness of approximately 50 cm using a bar coater. 2 Heating at 80°C for 10 minutes, then irradiating with an LED with a peak wavelength of 385nm at 7J / cm² 2 Irradiation with ultraviolet light forms a cured film.

[0430] In addition, the ink compositions of Examples 2, 4, 5 and Comparative Example 1 were also cured on polymethyl methacrylate (PMMA) films in the same way.

[0431] It should be noted that, for Comparative Example 6, the ink composition liquid described above could not be obtained, therefore a cured film could not be formed, and the scratch resistance and alcohol resistance evaluation described later could not be carried out.

[0432] (2) Evaluation of the scratch resistance of the cured film

[0433] The scratch resistance was evaluated using the cured film on the PVC film and the cured film on the PMMA film obtained above.

[0434] The evaluation was conducted as follows: A Tribo Gear HEIDON-14DR tribometer (manufactured by Shin-Tung Science & Technology Co., Ltd.) was used. An abrasive film with a grit size of #1000 (manufactured by TRUSCO Zhongshan Co., Ltd.) was placed on a circular terminal with a ground plane diameter of 27 mm. The cured film surface was rubbed 10 times in 10 seconds at a test distance of 50 mm under a 400g load. Image analysis software was used to binarize the peeling of the cured film, and the percentage of peeled portion in the area of ​​the cured film was calculated. The results are shown in Table 2.

[0435] In this evaluation test, a curing content of 1.30% or less was considered acceptable for cured films on PVC films, and a curing content of 1.00% or less was considered acceptable for cured films on PMMA films. It should be noted that PMMA film is considered to be a material that adheres to ink more easily than PVC film, hence separate acceptance criteria were set for each.

[0436] (3) Evaluation of the alcohol resistance of the cured film

[0437] The cured film on the PVC film obtained above was used for the evaluation of alcohol resistance.

[0438] The evaluation was conducted as follows: Absorbent cotton was immersed in absolute ethanol, and when rubbing the surface of the cured film without load or with a load of 200 g, visual observation was carried out to check for color migration to the absorbent cotton, and the evaluation was carried out according to the following evaluation criteria. The results are shown in Table 2. It should be noted that in this evaluation test, when it is "△" or above, it is evaluated as qualified.

[0439] ◎: There is no color migration to the absorbent cotton in any of the tests.

[0440] ○: There is no color migration to the absorbent cotton without load, and there is color migration to the absorbent cotton with a load of 200 g.

[0441] △: There is very little color migration to the absorbent cotton without load, and there is color migration to the absorbent cotton with a load of 200 g.

[0442] ×: There is color migration to the absorbent cotton in any of the tests, and there are problems in practical use.

[0443] [Table 2]

[0444]

[0445] As can be seen from Table 2, the ink of the present invention containing a water-soluble polyfunctional (meth)acrylamide compound can form a printed image with excellent abrasion resistance and excellent coating film properties.

[0446] In contrast, it can be seen that in Comparative Examples 1 to 5 and 7 without a water-soluble polyfunctional (meth)acrylamide compound, the abrasion resistance is poor.

[0447] In addition, from Examples 2, 4, and 5, it can be seen that the ink of the present invention has excellent abrasion resistance and high substrate versatility when coated on either a PVC film or a PMMA film.

[0448] Furthermore, from Examples 1 to 5, it can be seen that when the content of the water-soluble polyfunctional (meth)acrylamide is increased, the alcohol resistance becomes good.

[0449] [Preparation of ultraviolet curable oligomer 2]

[0450] 0.4 mol of a trimer of hexamethylene diisocyanate, 0.8 mol of dipentaerythritol pentaacrylate, and 0.4 mol of polyethylene glycol monomethyl ether (n = 20 - 30 in the above general formula (1)) were reacted to produce a nonionic ultraviolet curable oligomer 2.

[0451] [Preparation of ultraviolet curable oligomer 3]

[0452] A nonionic UV-curable oligomer 3 was produced by reacting 0.75 mol of isophorone diisocyanate, 0.90 mol of pentaerythritol pentaacrylate and 0.52 mol of polyethylene glycol (n = 15 to 25 in the above general formula (1)).

[0453] [Preparation of UV-curable oligomer 4]

[0454] An anionic, UV-curable oligomer containing carboxyl groups was produced by reacting 0.87 mol of isophorone diisocyanate, 1.0 mol of pentaerythritol pentaacrylate, 0.30 mol of polyethylene glycol (n = 10-20 in the above general formula (1)), 0.13 mol of 2,2-bis(hydroxymethyl)propionic acid and 0.12 mol of 2,2-bis(hydroxymethyl)butyric acid.

[0455] [Preparation of UV-curable oligomer aqueous dispersion 2 encapsulated with a lipid-soluble initiator]

[0456] Except for changing UV-curable oligomer 1 to UV-curable oligomer 2, a UV-curable oligomer aqueous dispersion 2 containing a lipophilic initiator is obtained in the same way as the lipophilic initiator-encapsulated UV-curable oligomer aqueous dispersion 1.

[0457] The average particle size (D50) of the UV-curable oligomer particles in the aqueous dispersion was measured using a particle size analyzer (Nanotrac Wave II EX-150, manufactured by Microtrac MRB), and the result was 26 nm.

[0458] [Preparation of UV-curable oligomer aqueous dispersion 3 encapsulated with a lipid-soluble initiator]

[0459] Except for changing UV-curable oligomer 1 to UV-curable oligomer 3, a UV-curable oligomer aqueous dispersion 3 containing a lipophilic initiator is obtained in the same way as the UV-curable oligomer aqueous dispersion 1 containing a lipophilic initiator.

[0460] The average particle size (D50) of the UV-curable oligomer particles in the aqueous dispersion was measured using a particle size analyzer (Nanotrac Wave II EX-150, manufactured by Microtrac MRB), and the result was 25 nm.

[0461] [Preparation of UV-curable oligomer aqueous dispersion 4 encapsulated with a lipid-soluble initiator]

[0462] Except for changing UV-curable oligomer 1 to UV-curable oligomer 4 and adding 1.25 mol equivalents of sodium hydroxide relative to 1 molar equivalent of the carboxyl groups contained in UV-curable oligomer 4 for neutralization, the same as the lipophilic initiator-encapsulated UV-curable oligomer aqueous dispersion 1 is obtained.

[0463] The average particle size (D50) of the UV-curable oligomer particles in the aqueous dispersion was measured using a particle size analyzer (Nanotrac Wave II EX-150, manufactured by Microtrac MRB), and the result was 134 nm.

[0464] [Example 8]

[0465] Ion-exchanged water, the aforementioned lipid-soluble initiator-encapsulated UV-curable oligomer aqueous dispersion 2, N,N-bis(2-acrylamidoethyl)acrylamide as a water-soluble polyfunctional (meth)acrylamide compound, diethylene glycol ethyl methyl ether as a moisturizing solvent, propylene glycol as a water-soluble organic solvent, a water-soluble initiator, a water-soluble sensitizer, BYK-347 manufactured by BYK Chemicals Japan Co., Ltd. as a surfactant, and EMACOL SF CYAN AE2034F manufactured by Sanyo Pigment Co., Ltd. as a pigment dispersion were added and mixed to obtain ink composition liquid 15.

[0466] [Example 9]

[0467] Except for changing the lipid-soluble initiator-encapsulated UV-curable oligomer aqueous dispersion 2 to the lipid-soluble initiator-encapsulated UV-curable oligomer aqueous dispersion 3, the ink composition liquid 16 was obtained in the same manner as in Example 8.

[0468] [Example 10]

[0469] Except for changing the lipid-soluble initiator-encapsulated UV-curable oligomer aqueous dispersion 2 to the lipid-soluble initiator-encapsulated UV-curable oligomer aqueous dispersion 4, the ink composition liquid 17 was obtained in the same manner as in Example 8.

[0470] [Comparative Example 8]

[0471] Except that N,N-bis(2-acrylamidoethyl)acrylamide was not added, ink composition liquid 18 was obtained in the same manner as in Example 8.

[0472] [Comparative Example 9]

[0473] Except that N,N-bis(2-acrylamidoethyl)acrylamide was not added, ink composition liquid 19 was obtained in the same manner as in Example 9.

[0474] [Comparative Example 10]

[0475] Except that N,N-bis(2-acrylamidoethyl)acrylamide was not added, ink composition liquid 20 was obtained in the same manner as in Example 10.

[0476] [Table 3]

[0477]

[0478] [Evaluation of the ink's composition]

[0479] The ink compositions obtained in Examples 8-10 and Comparative Examples 8-10 were evaluated as follows, and the results are shown in Table 4.

[0480] Evaluation of the alcohol resistance and scratch resistance of the cured film

[0481] The cured film is formed by the following method (1), and the scratch resistance is evaluated by the following method (2), and the alcohol resistance is evaluated by the following method (3).

[0482] (1) LED curing

[0483] Cured films are formed on PVC films and PMMA films using the methods described above.

[0484] (2) Evaluation of the scratch resistance of the cured film

[0485] The scratch resistance was evaluated using the cured film on the PVC film and the cured film on the PMMA film obtained above.

[0486] The evaluation was conducted as follows: A Tribo Gear HEIDON-14DR friction and wear testing machine (manufactured by Shin-Tung Science Co., Ltd.) was used. BONSTAR steel wool No. 0000 (manufactured by STEEL WOOL) was applied to a circular terminal with a ground plane diameter of 27 mm. The cured film surface was rubbed 10 times in 10-second cycles at a test distance of 50 mm under a 400g load. Image analysis software was used to binarize the peeling of the cured film, and the percentage (%) of the peeled portion in the cured film area was calculated. The results are shown in Table 4.

[0487] Compared to the test using the aforementioned abrasive film, this test using BONSTAR steel wool presents more stringent abrasion conditions. Therefore, in this evaluation test, a curing percentage of 10.00% or less is considered acceptable for cured films on PVC films, and a curing percentage of 1.50% or less is considered acceptable for cured films on PMMA films. It should be noted that PMMA film is considered to adhere to inks more readily than PVC film in both cases, hence separate acceptance criteria are set for each.

[0488] (3) Evaluation of the alcohol resistance of the cured film

[0489] The alcohol resistance of the cured film on the PVC film obtained above was evaluated.

[0490] The evaluation was carried out as follows: Absorbent cotton was impregnated with absolute ethanol, and when rubbing the surface of the cured film without load or with a load of 200 g, the color migration to the absorbent cotton was visually observed and evaluated according to the following evaluation criteria. The results are shown in Table 4. It should be noted that in this evaluation test, it was evaluated as qualified when it was "△" or above.

[0491] ◎: There was no color migration to the absorbent cotton in any of the tests.

[0492] ○: There was no color migration to the absorbent cotton without load, and there was a slight color migration to the absorbent cotton with a load of 200 g.

[0493] △: There was no color migration to the absorbent cotton without load, and there was a color migration to the absorbent cotton with a load of 200 g.

[0494] ×: There was no color migration to the absorbent cotton without load, and the coating film peeled off to expose the substrate with a load of 200 g.

[0495] ××: There was color migration to the absorbent cotton or the coating film was exposed without load, which was a problem in practical use.

[0496] [Table 4]

[0497]

[0498] As can be seen from Table 4, the ink of the present invention containing a water-soluble polyfunctional (meth) acrylamide compound can form a printed image with excellent abrasion resistance and excellent coating film properties regardless of the structure of the ultraviolet curable oligomer.

[0499] In addition, it can be seen that the ink of the present invention has excellent abrasion resistance and high substrate versatility when coated on either a PVC film or a PMMA film.

[0500] In contrast, it can be seen that in Comparative Examples 8 to 10 that do not contain a water-soluble polyfunctional (meth) acrylamide compound, the abrasion resistance, substrate versatility, and alcohol resistance are poor.

[0501] Next, the examples and comparative examples of the third embodiment of the present invention will be described.

[0502] [Examples 2-1 to 2-7, Comparative Examples 2-1 to 2-7]

[0503] The ink formulations were obtained in the same manner as in Examples 1-7 and Comparative Examples 1-7 described above. It should be noted that Comparative Examples 2-6 could not produce ink formulations in the same manner as in Comparative Example 6 described above.

[0504] [Table 5]

[0505]

[0506] [Evaluation of the ink's composition]

[0507] For the ink compositions obtained in Examples 2-1 to 2-7 and Comparative Examples 2-1 to 2-5 and 2-7, the alcohol resistance and scratch resistance of the cured films were evaluated using the same method as in Examples 1 to 7 and Comparative Examples 1 to 7, and the results are shown in Table 6.

[0508] [Table 6]

[0509]

[0510] As shown in Table 6, the inks of the present invention containing water-soluble polyfunctional (meth)acrylamide compounds can form printed images with excellent scratch resistance and excellent coating performance.

[0511] In contrast, Comparative Examples 2-1 to 2-5 and 2-7, which do not contain water-soluble polyfunctional (meth)acrylamide compounds, exhibit poor scratch resistance.

[0512] Furthermore, as can be seen from Examples 2-2, 2-4, and 2-5, the ink of the present invention exhibits excellent scratch resistance and high substrate versatility when coated on either PVC film or PMMA film.

[0513] Furthermore, as can be seen from Examples 2-1 to 2-5, when the content of water-soluble polyfunctional (meth)acrylamide is increased, the alcohol resistance becomes good.

Claims

1. A UV-curable water-based ink, comprising at least a UV-curable oligomer, a colorant, and a water-soluble polyfunctional (meth)acrylamide compound, wherein, The ratio of the UV-curable oligomer to the water-soluble polyfunctional (meth)acrylamide compound is 50:1 to 2:1 by mass. The UV-curable oligomers respectively have structural units derived from water-soluble compounds, structural units derived from compounds containing two or more polymerizable unsaturated bonds, and structural units derived from polyisocyanate compound A, wherein the water-soluble compounds are compounds represented by the following formula (1). [Chemistry 1] In formula (1), X is an alkylene group, Y is any one of (meth)acryloyl, allyl, or acyl; n is an integer greater than or equal to 2.

2. A UV-curable water-based ink, comprising at least a UV-curable oligomer, a colorant, and a water-soluble polyfunctional (meth)acrylamide compound, wherein, The ratio of the UV-curable oligomer to the water-soluble polyfunctional (meth)acrylamide compound is 50:1 to 2:1 by mass. The UV-curable oligomer has structural units derived from compounds containing four or more polymerizable unsaturated bonds, structural units derived from polyisocyanate compound A, and structural units derived from compounds represented by the following formula (1). [Chemistry 1] In formula (1), X is an alkylene group, Y is any one of (meth)acryloyl, allyl, or acyl; n is an integer greater than or equal to 2.

3. The ultraviolet-curable water-based ink according to claim 2, wherein, The compound containing four or more polymerizable unsaturated bonds is a compound having any of the following groups: hydroxyl, amino, and carboxyl.

4. A UV-curable water-based ink, comprising at least a UV-curable oligomer, a colorant, and a water-soluble polyfunctional (meth)acrylamide compound, wherein, The ratio of the UV-curable oligomer to the water-soluble polyfunctional (meth)acrylamide compound is 50:1 to 2:1 by mass. The UV-curable oligomer has structural units derived from polyisocyanate compound A and structural units derived from compounds represented by the following formula (1). [Chemistry 1] In formula (1), X is an alkylene group, Y is any one of (meth)acryloyl, allyl, or acyl; n is an integer greater than or equal to 2.

5. The ultraviolet-curable water-based ink according to any one of claims 1, 2, 4, wherein, In formula (1), Y is allyl.

6. The UV-curable water-based ink according to any one of claims 1, 2, and 4, wherein, The water-soluble polyfunctional (meth)acrylamide compound has two or more but fewer than four functional groups.

7. The UV-curable water-based ink according to any one of claims 1, 2, and 4, wherein, The content of the water-soluble polyfunctional (meth)acrylamide compound is 0.05% by mass or more and 10% by mass or less.

8. The UV-curable water-based ink according to any one of claims 1, 2, and 4, further comprising one or more of a polymerization initiator, a sensitizer, and a surfactant.

9. The UV-curable water-based ink according to claim 8, wherein, At least a portion of the polymerization initiator and / or sensitizer is encapsulated within the UV-curable oligomer.

10. The UV-curable water-based ink according to any one of claims 1, 2, and 4, wherein, The UV-curable oligomer is non-ionic.

11. The UV-curable water-based ink according to any one of claims 1, 2, and 4, wherein, The UV-curable oligomer exists in the form of particles.

12. The UV-curable water-based ink according to any one of claims 1, 2, and 4, wherein, The average particle size of the UV-curable oligomer is greater than 10 nm and less than 200 nm.

13. The UV-curable water-based ink according to any one of claims 1, 2, and 4, wherein, Compound A comprises a trimer of a polyisocyanate.

14. A printed matter having a cured product formed on a recording medium by any one of claims 1 to 13 of the UV-curable water-based ink.

15. A dispersion, which is a dispersion of a UV-curable oligomer, wherein, The dispersion contains 0.1% by mass and less than 20% by mass of a water-soluble polyfunctional (meth)acrylamide compound. The ratio of the UV-curable oligomer to the water-soluble polyfunctional (meth)acrylamide compound is 50:1 to 2:1 by mass. The UV-curable oligomers respectively have structural units derived from water-soluble compounds, structural units derived from compounds containing two or more polymerizable unsaturated bonds, and structural units derived from polyisocyanate compound A. The water-soluble compound is a compound represented by the following formula (1). [Chemistry 1] In formula (1), X is an alkylene group, Y is any one of (meth)acryloyl, allyl, or acyl; n is an integer greater than or equal to 2.

16. A dispersion, which is a dispersion of a UV-curable oligomer, wherein, The dispersion contains 0.1% by mass and less than 20% by mass of a water-soluble polyfunctional (meth)acrylamide compound. The ratio of the UV-curable oligomer to the water-soluble polyfunctional (meth)acrylamide compound is 50:1 to 2:1 by mass. The UV-curable oligomer has structural units derived from compounds containing four or more polymerizable unsaturated bonds, structural units derived from polyisocyanate compound A, and structural units derived from compounds represented by the following formula (1). [Chemistry 1] In formula (1), X is an alkylene group, Y is any one of (meth)acryloyl, allyl, or acyl; n is an integer greater than or equal to 2.

17. A dispersion, which is a dispersion of a UV-curable oligomer, wherein, The dispersion contains 0.1% by mass and less than 20% by mass of a water-soluble polyfunctional (meth)acrylamide compound. The ratio of the UV-curable oligomer to the water-soluble polyfunctional (meth)acrylamide compound is 50:1 to 2:1 by mass. The UV-curable oligomer has structural units derived from polyisocyanate compound A and structural units derived from compounds represented by the following formula (1). [Chemistry 1] In formula (1), X is an alkylene group, Y is any one of (meth)acryloyl, allyl, or acyl; n is an integer greater than or equal to 2.

18. The dispersion according to any one of claims 15 to 17, wherein, In Formula 1, Y is allyl.

19. The dispersion according to any one of claims 15 to 17, wherein, The water-soluble polyfunctional (meth)acrylamide compound has two or more but fewer than four functional groups.

20. The dispersion according to any one of claims 15 to 17, wherein, Compound A comprises a trimer of a polyisocyanate.

21. A UV-curable waterborne composition comprising: any one or more of a polymerization initiator, a sensitizer, and a surfactant; a UV-curable oligomer; and a water-soluble polyfunctional (meth)acrylamide compound, wherein, The ratio of the UV-curable oligomer to the water-soluble polyfunctional (meth)acrylamide compound is 50:1 to 2:1 by mass. The UV-curable oligomers respectively have structural units derived from water-soluble compounds, structural units derived from compounds containing two or more polymerizable unsaturated bonds, and structural units derived from polyisocyanate compound A. The water-soluble compound is a compound represented by the following formula (1). [Chemistry 1] In formula (1), X is an alkylene group, Y is any one of (meth)acryloyl, allyl, or acyl; n is an integer greater than or equal to 2.

22. A UV-curable waterborne composition comprising: any one or more of a polymerization initiator, a sensitizer, and a surfactant; a UV-curable oligomer; and a water-soluble polyfunctional (meth)acrylamide compound, wherein, The ratio of the UV-curable oligomer to the water-soluble polyfunctional (meth)acrylamide compound is 50:1 to 2:1 by mass. The UV-curable oligomer has structural units derived from compounds containing four or more polymerizable unsaturated bonds, structural units derived from polyisocyanate compound A, and structural units derived from compounds represented by the following formula (1). [Chemistry 1] In formula (1), X is an alkylene group, Y is any one of (meth)acryloyl, allyl, or acyl; n is an integer greater than or equal to 2.

23. A UV-curable waterborne composition comprising: any one or more of a polymerization initiator, a sensitizer, and a surfactant; a UV-curable oligomer; and a water-soluble polyfunctional (meth)acrylamide compound, wherein, The ratio of the UV-curable oligomer to the water-soluble polyfunctional (meth)acrylamide compound is 50:1 to 2:1 by mass. The UV-curable oligomer has structural units derived from polyisocyanate compound A and structural units derived from compounds represented by the following formula (1). [Chemistry 1] In formula (1), X is an alkylene group, Y is any one of (meth)acryloyl, allyl, or acyl; n is an integer greater than or equal to 2.

24. The UV-curable aqueous composition according to any one of claims 21 to 23, wherein, In Formula 1, Y is allyl.

25. The UV-curable aqueous composition according to any one of claims 21 to 23, wherein, The water-soluble polyfunctional (meth)acrylamide compound has two or more but fewer than four functional groups.

26. The UV-curable aqueous composition according to any one of claims 21 to 23, comprising a polymerization initiator and / or a sensitizer, at least a portion of which is encapsulated within the UV-curable oligomer.

27. The UV-curable aqueous composition according to any one of claims 21 to 23, wherein, The UV-curable oligomer is non-ionic.

28. The UV-curable aqueous composition according to any one of claims 21 to 23, wherein, Compound A comprises a trimer of a polyisocyanate.

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