Active energy ray curable ink, ink set, and image recording method

Abstract

An active-energy-ray-curable ink and the application thereof, in which: the active-energy-ray-curable ink includes a polymerizable compound and a colorant; the polymerizable compound includes an N-vinyl compound, a monofunctional polymerizable compound having a Tg when made into a homopolymer of -30 to 30°C, and a compound selected from the group consisting of difunctional (meth)acrylates and polymerizable silicone surfactants; the total content, excluding the N-vinyl compound, of monofunctional polymerizable compounds having a Tg when made into a homopolymer of less than -30°C and monofunctional polymerizable compounds having a Tg when made into a homopolymer of more than 30°C is 10 mass% or less relative to the total amount of polymerizable compounds; and the total content of compounds selected from the group consisting of difunctional (meth)acrylates and polymerizable silicone surfactants is 0.1-2 mass% relative to the total amount of polymerizable compounds.

Description

[Technical Field]

[0001] This disclosure relates to an active energy ray curable ink, an ink set, and an image recording method. [Background technology]

[0002] Conventionally, when recording an image on a substrate using ink, a method of curing it using active energy rays is known.

[0003] For example, Japanese Patent Publication No. 2015-47748 describes an ink containing N-vinylcaprolactam, a monofunctional acrylate having an aromatic ring, a monofunctional acrylate having an aliphatic hydrocarbon ring, a polysiloxane compound, an acrylic resin having a glass transition temperature of 40°C to 90°C, a photopolymerization initiator, and a pigment, wherein the content of the acrylic resin is 0.5% by mass or more and 5% by mass or less. Japanese Patent Publication No. 2009-84313 describes an active-ray curable ink composition containing 65% by weight or more of a monofunctional ethylenically unsaturated compound having only one ethylenically unsaturated bond in its molecule, and 7.5% by weight or less of a photopolymerization initiator having a molecular weight of 1000 or less and not having an ethylenically unsaturated bond in its molecule. [Overview of the project] [Problems that the invention aims to solve]

[0004] Image recordings are obtained by recording images on a substrate using ink. If the substrate is flexible, the image recording may deform due to bending or other means. Therefore, it is required that the image be maintained even when the image recording is deformed. In addition, from the standpoint of ease of handling the image recording, it may be necessary to suppress the stickiness of the image.

[0005] This disclosure has been made in view of the above circumstances, and according to one embodiment of the present invention, an active energy ray curable ink, an ink set, and an image recording method are provided that can record images that are highly flexible and highly resistant to blocking. [Means for solving the problem]

[0006] This disclosure includes the following aspects. <1> Contains polymerizable compounds and colorants, The polymerizable compound includes an N-vinyl compound, a monofunctional polymerizable compound having a glass transition temperature of -30°C to 30°C when homopolymerized, and a compound selected from the group consisting of a bifunctional (meth)acrylate and a polymerizable silicone-based surfactant. Excluding N-vinyl compounds, the total content of monofunctional polymerizable compounds having a glass transition temperature of less than -30°C when homopolymerized, and monofunctional polymerizable compounds having a glass transition temperature of more than 30°C when homopolymerized, is 10% by mass or less of the total amount of polymerizable compounds. An active energy ray curable ink in which the total content of compounds selected from the group consisting of bifunctional (meth)acrylates and polymerizable silicone-based surfactants is 0.1% to 2% by mass relative to the total amount of polymerizable compounds. <2> The N-vinyl compound content is 10% to 35% by mass relative to the total amount of polymerizable compounds. The content of monofunctional polymerizable compounds with a glass transition temperature of -30°C to 30°C when formed as homopolymers is 60% to 85% by mass relative to the total amount of polymerizable compounds. <1> The activated energy ray curing ink described above. <3> N-vinyl compounds include N-vinylcaprolactam. <1> or <2> The activated energy ray curing ink described above. <4> Monofunctional polymerizable compounds with a glass transition temperature of -30°C to 30°C when homopolymerized include phenoxyethyl acrylate. <1> ~ <3> An active energy ray curing ink as described in one of the following. <5> A difunctional (meth)acrylate has 4 to 36 carbon atoms in the part excluding the (meth)acryloyl group. <1> ~ <4> An active energy ray curing ink as described in one of the following. <6> Polymerizable compounds include polymerizable silicone-based surfactants. <1> ~ <4> An active energy ray curing ink as described in one of the following. <7> <1> ~ <6> An ink set comprising an active energy ray curable ink as described in any one of the above, and a pretreatment solution. <8> The pretreatment solution contains polymerizable compounds and polyester resins. <7> The ink set described above. <9> The pretreatment solution contains a polymerizable compound containing polymerizable compound A having an acid group. <7> The ink set described above. <10> The proportion of monofunctional polymerizable compounds in the total polymerizable compounds is 80% by mass or more. <8> or <9> The ink set described above. <11> On the substrate, <1> ~ <6> A step of applying an active energy ray curable ink as described in any one of the following, An image recording method comprising the step of irradiating a modified active energy ray-curable ink with active energy rays. <12> The base material has a thickness of 1 mm or more. <11> The image recording method described above. <13> The base material is metal, plastic, synthetic leather, or rubber. <11> or <12> The image recording method described above. <14> <7> ~ <10> The ink set described in one of the following is used: A process of applying a pretreatment solution and recording ink onto a substrate using an inkjet recording method, The process involves applying a pretreatment solution and ink, respectively, and then irradiating them with active energy rays. An image recording method that includes [a specific feature / method]. [Effects of the Invention]

[0007] According to one embodiment of the present invention, there is an active energy ray curable ink, an ink set, and an image recording method that can record images with excellent flexibility and excellent blocking resistance. [Modes for carrying out the invention]

[0008] The active energy ray curable ink, ink set, and image recording method of this disclosure will be described in detail below.

[0009] In this specification, a numerical range indicated using "~" means a range that includes the numerical values described before and after "~" as the minimum value and the maximum value, respectively. In a numerical range described stepwise in this specification, the upper limit value or the lower limit value described in a certain numerical range may be replaced with the upper limit value or the lower limit value of the numerical range described in other stepwise descriptions. Further, in the numerical range described in this specification, the upper limit value or the lower limit value described in a certain numerical range may be replaced with the value shown in the examples.

[0010] In this specification, the amount of each component in the composition means the total amount of the plurality of substances present in the composition when there are a plurality of substances corresponding to each component in the composition, unless otherwise specified. In this specification, a combination of two or more preferred embodiments is a more preferred embodiment. In this specification, the term "step" includes not only an independent step but also, even when it cannot be clearly distinguished from other steps, as long as the intended purpose of the step is achieved.

[0011] In this specification, "image" means the entire film formed by applying ink, and "image recording" means the formation of an image (i.e., a film). Further, the concept of "image" in this specification also includes a solid image.

[0012] In this specification, "(meth)acrylate" is a concept that includes both acrylate and methacrylate. Also, "(meth)acrylic" is a concept that includes both acrylic and methacrylic.

[0013] [Ink] An active energy ray-curable inkjet ink (hereinafter, also simply referred to as "ink") according to an embodiment of the present disclosure contains a polymerizable compound and a colorant. The polymerizable compound includes an N-vinyl compound, a monofunctional polymerizable compound having a glass transition temperature (hereinafter, also referred to as "Tg") of -30°C to 30°C when made into a homopolymer (hereinafter, the glass transition temperature when made into a homopolymer may be simply referred to as the "Tg" of the monofunctional polymerizable compound), and a compound selected from the group consisting of a bifunctional (meth)acrylate and a polymerizable silicone-based surfactant. The total content of the monofunctional polymerizable compound having a glass transition temperature of less than -30°C and the monofunctional polymerizable compound having a glass transition temperature of more than 30°C when made into a homopolymer, excluding the N-vinyl compound, is 10% by mass or less based on the total amount of the polymerizable compound. The total content of the compound selected from the group consisting of a bifunctional (meth)acrylate and a polymerizable silicone-based surfactant is 0.1% by mass to 2% by mass based on the total amount of the polymerizable compound.

[0014] By applying the ink according to an embodiment of the present disclosure, for example, onto a substrate and then irradiating it with active energy rays, an image recording article having an ink film formed as an image on the substrate can be obtained. Since the ink according to an embodiment of the present disclosure contains a polymerizable compound, a polymerization reaction proceeds upon irradiation with active energy rays.

[0015] The N-vinyl compound has a high function of capturing oxygen atoms that inhibit polymerization. Therefore, when the N-vinyl compound is contained in the ink, the surface curability is excellent and the stickiness of the image is suppressed. Also, when the ink contains a monofunctional polymerizable compound having a Tg of -30°C to 30°C, the ink film formed by the curing reaction is excellent in flexibility. That is, an image excellent in flexibility can be obtained. Since the N-vinyl compound has an amide bond, it tends to have a high Tg. However, by containing a monofunctional polymerizable compound having a Tg of -30°C to 30°C together with the N-vinyl compound in the ink, both blocking resistance and flexibility can be achieved. Also, the adhesion is excellent.

[0016] Furthermore, if the ink contains a compound selected from the group consisting of bifunctional (meth)acrylates and polymerizable silicone-based surfactants, the stickiness of the image is suppressed and the ink exhibits excellent blocking resistance. When bifunctional (meth)acrylates are included in the ink, a cross-linking reaction proceeds within the ink film, making the ink film stronger and thus suppressing image stickiness. On the other hand, when polymerizable silicone-based surfactants are included in the ink, the polymerizable silicone-based surfactants rise to the surface of the ink, improving the curability of the ink film surface. Therefore, image stickiness is suppressed and the ink exhibits excellent blocking resistance. Adhesion is also improved.

[0017] In particular, blocking resistance can be ensured by ensuring that the total content of compounds selected from the group consisting of bifunctional (meth)acrylates and polymerizable silicone-based surfactants is 0.1% by mass or more relative to the total amount of polymerizable compounds. Furthermore, if the total content is 2% by mass or less, excellent flexibility is achieved.

[0018] Furthermore, the total content of monofunctional polymerizable compounds with a glass transition temperature of less than -30°C when homopolymerized, and monofunctional polymerizable compounds with a glass transition temperature of more than 30°C when homopolymerized (excluding N-vinyl compounds), being 10% by mass or less of the total amount of polymerizable compounds indicates that they are not included as the main components of the polymerizable compounds. By keeping the above total content at 10% by mass or less, the flexibility of the image is excellent.

[0019] On the other hand, the ink described in Japanese Patent Publication No. 2015-47748 mainly contains a monofunctional polymerizable compound whose glass transition temperature when homopolymerized exceeds 30°C, and therefore differs in technical concept from the present application. Furthermore, the ink described in Japanese Patent Publication No. 2009-84313 does not contain a compound selected from the group consisting of bifunctional (meth)acrylates and polymerizable silicone-based surfactants, and therefore differs in technical concept from the present application.

[0020] The following describes each component contained in the ink, which is one embodiment of this disclosure.

[0021] One embodiment of the present disclosure is an active energy ray curable ink. That is, the ink according to one embodiment of the present disclosure is cured by irradiation with active energy rays. Examples of active energy rays include gamma rays, beta rays, electron beams, ultraviolet rays, and visible light. Among these, ultraviolet rays are preferred as the active energy ray. The ink according to one embodiment of the present disclosure is preferably an ultraviolet-curable ink.

[0022] <Polymerizable compound> An ink, which is one embodiment of the present disclosure, contains a polymerizable compound. The polymerizable compound may be present in the ink alone or in two or more forms.

[0023] The polymerizable group in a polymerizable compound may be either a cationic polymerizable group or a radical polymerizable group, but from the viewpoint of curability, a radical polymerizable group is preferable. Furthermore, from the viewpoint of curability, the radical polymerizable group is preferably an ethylenically unsaturated group.

[0024] The polymerizable compound may be a monofunctional polymerizable compound having one polymerizable group, or a polyfunctional polymerizable compound having two or more polymerizable groups.

[0025] In an ink according to one embodiment of the present disclosure, the polymerizable compound includes an N-vinyl compound, a monofunctional polymerizable compound having a glass transition temperature (Tg) of -30°C to 30°C when formed as a homopolymer, and a compound selected from the group consisting of bifunctional (meth)acrylates and polymerizable silicone-based surfactants.

[0026] N-vinyl compounds have a high ability to capture oxygen atoms that inhibit polymerization. Therefore, when N-vinyl compounds are included in the ink, surface hardening is excellent and stickiness of the image is suppressed. Furthermore, when monofunctional polymerizable compounds with a Tg of -30°C to 30°C are included in the ink, the ink film formed by the curing reaction has excellent flexibility. In other words, an image with excellent flexibility can be obtained. N-vinyl compounds tend to have a high Tg because they have amide bonds, but by including monofunctional polymerizable compounds with a Tg of -30°C to 30°C together with N-vinyl compounds in the ink, it is possible to achieve both blocking resistance and flexibility.

[0027] Furthermore, if the ink contains a compound selected from the group consisting of difunctional (meth)acrylates and polymerizable silicone-based surfactants, the stickiness of the image is suppressed. When difunctional (meth)acrylates are included in the ink, a cross-linking reaction proceeds within the ink film, making the ink film stronger and thus suppressing the stickiness of the image. On the other hand, when polymerizable silicone-based surfactants are included in the ink, the polymerizable silicone-based surfactants float to the surface of the ink, improving the curability of the ink film surface. Therefore, the stickiness of the image is suppressed.

[0028] From the viewpoint of curability, the content of polymerizable compounds is preferably 70% to 95% by mass, and more preferably 75% to 90% by mass, based on the total amount of ink.

[0029] (N-vinyl compound) Examples of N-vinyl compounds include N-vinylpyrrolidone, N-vinylcaprolactam, N-vinylformamide, and N-vinylphthalimide. Among these, N-vinylcaprolactam is preferred as the N-vinyl compound from the viewpoint of further improving surface hardening properties.

[0030] From the viewpoint of further improving flexibility and blocking resistance, the content of the N-vinyl compound is preferably 10% to 35% by mass relative to the total amount of polymerizable compounds, and the content of the monofunctional polymerizable compound having a glass transition temperature of -30°C to 30°C when formed as a homopolymer is preferably 60% to 85% by mass relative to the total amount of polymerizable compounds.

[0031] Furthermore, from the viewpoint of further improving flexibility and blocking resistance, the content of the N-vinyl compound is more preferably 15% to 30% by mass relative to the total amount of polymerizable compounds, and the content of the monofunctional polymerizable compound having a glass transition temperature of -30°C to 30°C when formed as a homopolymer is more preferably 65% ​​to 80% by mass relative to the total amount of polymerizable compounds.

[0032] (Monofunctional polymerizable compounds with a Tg of -30°C to 30°C when homopolymerized) A monofunctional polymerizable compound is a compound having one polymerizable group. From the viewpoint of curability, a monofunctional polymerizable compound is preferably a monofunctional radical polymerizable compound, and more preferably a monofunctional ethylenically unsaturated compound.

[0033] Examples of monofunctional ethylenically unsaturated compounds include monofunctional (meth)acrylates, monofunctional (meth)acrylamides, monofunctional aromatic vinyl compounds, and monofunctional vinyl ethers.

[0034] Examples of monofunctional polymerizable compounds with a Tg of -30°C to 30°C when homopolymerized include those listed below as specific examples of monofunctional polymerizable compounds with a Tg of -30°C to 30°C when homopolymerized.

[0035] Examples of monofunctional (meth)acrylates include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, tert-octyl (meth)acrylate, isoamyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, isostearyl (meth)acrylate, cyclohexyl (meth)acrylate. 4-n-butylcyclohexyl (meth)acrylate, 4-tert-butylcyclohexyl (meth)acrylate, bornyl (meth)acrylate, isobornyl (meth)acrylate, 2-ethylhexyl diglycol (meth)acrylate, butoxyethyl (meth)acrylate, 2-chloroethyl (meth)acrylate, 4-bromobutyl (meth)acrylate, cyanoethyl (meth)acrylate, benzyl (meth)acrylate, butoxymethyl (meth)acrylate, 3-methoxybutyl (meth)acrylate, 2-(2-methoxymethyl (Thiethoxy)ethyl (meth)acrylate, 2-(2-butoxyethoxy)ethyl (meth)acrylate, 2,2,2-tetrafluoroethyl (meth)acrylate, 1H,1H,2H,2H-perfluorodecyl (meth)acrylate, 4-butylphenyl (meth)acrylate, phenyl (meth)acrylate, 2,4,5-tetramethylphenyl (meth)acrylate, 4-chlorophenyl (meth)acrylate, 2-phenoxymethyl (meth)acrylate, 2-phenoxyethyl (meth)acrylate, glycidyl (meth)acrylate Glycidyloxybutyl (meth)acrylate, glycidyloxyethyl (meth)acrylate, glycidyloxypropyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, cyclic trimethylolpropaneformal (meth)acrylate,Phenylglycidyl ether (meth)acrylate, dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, dimethylaminopropyl (meth)acrylate, diethylaminopropyl (meth)acrylate, trimethoxysilylpropyl (meth)acrylate, trimethylsilylpropyl (meth)acrylate, polyethylene oxide monomethyl ether (meth)acrylate, polyethylene oxide (meth)acrylate, polyethylene oxide monoalkyl ether (meth)acrylate, dipropylene glycol (meth)acrylate, polypropylene oxide monoalkyl ether (meth)acrylate, 2-methacryloyloxyethyl succinate, 2-methacryloyloxyhexahydrophthalate, 2-methacryloyloxyethyl-2-hydroxypropyl phthalate, ethoxydiethylene glycol (meth)acrylate, butoxydi Examples include ethylene glycol (meth)acrylate, trifluoroethyl (meth)acrylate, perfluorooctylethyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, ethylene oxide (EO)-modified phenol (meth)acrylate, EO-modified cresol (meth)acrylate, EO-modified nonylphenol (meth)acrylate, propylene oxide (PO)-modified nonylphenol (meth)acrylate, EO-modified 2-ethylhexyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, dicyclopentanyl (meth)acrylate, (3-ethyl-3-oxetanylmethyl) (meth)acrylate, phenoxyethylene glycol (meth)acrylate, 2-carboxyethyl (meth)acrylate, and 2-(meth)acryloyloxyethyl succinate.

[0036] Examples of monofunctional (meth)acrylamides include (meth)acrylamide, N-methyl(meth)acrylamide, N-ethyl(meth)acrylamide, N-propyl(meth)acrylamide, Nn-butyl(meth)acrylamide, Nt-butyl(meth)acrylamide, N-butoxymethyl(meth)acrylamide, N-isopropyl(meth)acrylamide, N-methylol(meth)acrylamide, N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, and (meth)acryloylmorpholin.

[0037] Examples of monofunctional aromatic vinyl compounds include styrene, dimethylstyrene, trimethylstyrene, isopropylstyrene, chloromethylstyrene, methoxystyrene, acetoxystyrene, chlorostyrene, dichlorostyrene, bromostyrene, methyl vinylbenzoate, 3-methylstyrene, 4-methylstyrene, 3-ethylstyrene, 4-ethylstyrene, 3-propylstyrene, 4-propylstyrene, 3-butylstyrene, 4-butylstyrene, 3-hexylstyrene, 4-hexylstyrene, 3-octylstyrene, 4-octylstyrene, 3-(2-ethylhexyl)styrene, 4-(2-ethylhexyl)styrene, allylstyrene, isopropenylstyrene, butenylstyrene, octenylstyrene, 4-t-butoxycarbonylstyrene, and 4-t-butoxystyrene.

[0038] Examples of monofunctional vinyl ethers include methyl vinyl ether, ethyl vinyl ether, propyl vinyl ether, n-butyl vinyl ether, t-butyl vinyl ether, 2-ethylhexyl vinyl ether, n-nonyl vinyl ether, lauryl vinyl ether, cyclohexyl vinyl ether, cyclohexylmethyl vinyl ether, 4-methylcyclohexylmethyl vinyl ether, benzyl vinyl ether, dicyclopentenyl vinyl ether, 2-dicyclopentenoxyethyl vinyl ether, methoxyethyl vinyl ether, ethoxyethyl vinyl ether, butoxyethyl vinyl ether, methoxyethoxyethyl vinyl ether, ethoxyethoxyethyl vinyl ether, methoxypolyethylene glycol vinyl ether, tetrahydrofurfuryl vinyl ether, 2-hydroxyethyl vinyl ether, 2-hydroxypropyl vinyl ether, 4-hydroxybutyl vinyl ether, 4-hydroxymethylcyclohexylmethyl vinyl ether, diethylene glycol monovinyl ether, polyethylene glycol vinyl ether, chloroethyl vinyl ether, chlorobutyl vinyl ether, chloroethoxyethyl vinyl ether, phenylethyl vinyl ether, and phenoxypolyethylene glycol vinyl ether.

[0039] The glass transition temperature of a homopolymer made from a monofunctional polymerizable compound is measured by the following method. First, a homopolymer with a weight-average molecular weight of 10,000 to 20,000 is prepared using a monofunctional polymerizable compound. The glass transition temperature of the prepared homopolymer is measured according to the method described in JIS K7121:2012. The glass transition temperature is measured using a differential scanning calorimeter, for example, a Shimadzu Corporation product named "DSC-60". The weight-average molecular weight is measured using gel permeation chromatography (GPC). For example, an HLC-8220GPC (Tosoh Corporation) is used as the GPC, three TSKgel, Super Multipore HZ-H columns (Tosoh Corporation, 4.6 mm ID × 15 cm) are used as columns, and THF (tetrahydrofuran) is used as the eluent. The conditions were a sample concentration of 0.45% by mass, a flow rate of 0.35 ml / min, a sample injection volume of 10 μl, and a measurement temperature of 40°C, and detection was performed using a differential refractive index (RI) detector. A calibration curve was prepared using eight samples as standard samples: "TSK Standard Polystyrene" manufactured by Tosoh Corporation: "F-40", "F-20", "F-4", "F-1", "A-5000", "A-2500", "A-1000", and "n-propylbenzene". Note that the glass transition temperature of the homopolymer varies depending on the weight-average molecular weight of the homopolymer, but when the weight-average molecular weight is between 10,000 and 20,000, the variation is negligibly small.

[0040] Monofunctional polymerizable compounds with a Tg of -30°C to 30°C when homopolymerized preferably have a molecular weight of 1000 or less, and more preferably 500 or less. A molecular weight of 1000 or less allows for the recording of images with superior flexibility and blocking resistance.

[0041] For monofunctional polymerizable compounds with a Tg of -30°C to 30°C when homopolymerized, monofunctional acrylates are preferred from the viewpoint of curability. Examples of monofunctional acrylates with a Tg of -30°C to 30°C when homopolymerized include benzyl acrylate (6°C), cyclohexyl acrylate (15°C), 2-methyl-2-ethyl-1,3-dioxolan-4-yl)methyl acrylate (-7°C), tetrahydrofurfuryl acrylate (-15°C), lauryl acrylate (-30°C), 3,3,5-trimethylcyclohexyl acrylate (-29°C), phenoxyethyl acrylate (5°C), and 2-acryloyloxyethyl succinic acid (17°C). The values ​​in parentheses indicate the Tg when homopolymerized.

[0042] In particular, among monofunctional polymerizable compounds with a Tg of -30°C to 30°C when homopolymerized, phenoxyethyl acrylate is preferred from the viewpoint of further improving the flexibility of the image.

[0043] (A compound selected from the group consisting of bifunctional (meth)acrylates and polymerizable silicone-based surfactants) An ink, which is one embodiment of the present disclosure, comprises a compound selected from the group consisting of difunctional (meth)acrylates and polymerizable silicone-based surfactants. The ink may contain only a difunctional (meth)acrylate, only a polymerizable silicone-based surfactant, or both a difunctional (meth)acrylate and a polymerizable silicone-based surfactant. In any case, the image blocking resistance is improved. In particular, from the viewpoint of further improving blocking resistance, it is preferable that the ink contains a polymerizable silicone-based surfactant.

[0044] -2 Sensory (Meth)acrylate- A difunctional (meth)acrylate is a compound having two (meth)acryloyl groups. A difunctional (meth)acrylate may be any of the following: a compound having two acryloyl groups, a compound having two methacryloyl groups, or a compound having one acryloyl group and one methacryloyl group. In this disclosure, a difunctional (meth)acrylate does not include a silicone structure. Therefore, it is distinguished from polymerizable silicone surfactants. Silicone surfactants having two acryloyl groups are polymerizable silicone surfactants.

[0045] Examples of difunctional (meth)acrylates include ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, butylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 3-methyl-1,5-pentanediol di(meth)acrylate, hexanediol di(meth)acrylate, and heptanediol di(meth)acrylate. Examples include EO-modified neopentyl glycol di(meth)acrylate, PO-modified neopentyl glycol di(meth)acrylate, EO-modified hexanediol di(meth)acrylate, PO-modified hexanediol di(meth)acrylate, octanediol di(meth)acrylate, nonanediol di(meth)acrylate, decanediol di(meth)acrylate, dodecanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, glycerin di(meth)acrylate, pentaerythritol di(meth)acrylate, ethylene glycol diglycidyl ether di(meth)acrylate, diethylene glycol diglycidyl ether di(meth)acrylate, and tricyclodecanedimethanol di(meth)acrylate.

[0046] The bifunctional (meth)acrylate preferably has 4 to 36 carbon atoms in the portion excluding the (meth)acryloyl group, and more preferably 5 to 15 carbon atoms. When the number of carbon atoms is 4 or more, the flexibility of the image is improved. On the other hand, when the number of carbon atoms is 36 or less, the increase in ink viscosity is suppressed and the blocking resistance of the image is improved.

[0047] - Polymerizable silicone-based surfactants - In this disclosure, "polymerizable silicone-based surfactant" means a silicone-based surfactant having polymerizable groups.

[0048] The polymerizable group in a polymerizable silicone surfactant may be a cationic polymerizable group or a radical polymerizable group, but from the viewpoint of curability, a radical polymerizable group is preferable. Furthermore, from the viewpoint of curability, the radical polymerizable group is preferably an ethylenically unsaturated group. Among these, the polymerizable group in a polymerizable surfactant is preferably a vinyl group or a (meth)acryloyl group, and from the viewpoint of curability, a (meth)acryloyl group is more preferable.

[0049] From the viewpoint of blockage resistance, the number of polymerizable groups in a polymerizable surfactant is preferably two or more. There is no particular upper limit to the number of polymerizable groups in a polymerizable surfactant, but from the viewpoint of ejection performance when ejecting ink in an inkjet recording method, it is, for example, five.

[0050] In other words, with respect to the type and number of polymerizable groups, it is preferable that the polymerizable silicone-based surfactant is a silicone-based surfactant having two or more (meth)acryloyl groups.

[0051] Examples of polymerizable silicone-based surfactants include compounds in which polymerizable groups are bonded to the main chain or side chain of a polyether-modified dimethylsiloxane.

[0052] Examples of commercially available polymerizable silicone-based surfactants include BYK-UV3500, 3505, 3530, 3570, 3575, 3576 (manufactured by BYK), Tegorad2100, 2200, 2250, 2300, 2500, 2600, 2700, 2800, 2010, 2011 (manufactured by Evonik), EBECRYL350, 1360 (manufactured by Daicel Ornex), and KP-410, 411, 412, 413, 414, 415, 416, 418, 420, 422, 423 (manufactured by Shin-Etsu Silicone Co., Ltd.), which are silicone-based surfactants having (meth)acryloyl groups.

[0053] In the ink, the total content of compounds selected from the group consisting of bifunctional (meth)acrylates and polymerizable silicone surfactants is preferably 0.1% to 2% by mass, more preferably 0.5% to 1.8% by mass, and more preferably 1.0% to 1.5% by mass, relative to the total amount of polymerizable compounds. When the total content is 0.1% by mass or more, an image with excellent blocking resistance is obtained. On the other hand, when the total content is 2% by mass or less, an image with excellent flexibility is obtained.

[0054] (Other polymerizable compounds) An ink according to one embodiment of the present disclosure may contain other polymerizable compounds other than those selected from the group consisting of N-vinyl compounds, monofunctional polymerizable compounds with a Tg of -30°C to 30°C when homopolymerized, and bifunctional (meth)acrylates and polymerizable silicone-based surfactants.

[0055] Other polymerizable compounds include monofunctional polymerizable compounds with a glass transition temperature (Tg) of less than -30°C when homopolymerized, and monofunctional polymerizable compounds with a glass transition temperature (Tg) of more than 30°C when homopolymerized. The method for measuring Tg is as described above.

[0056] Monofunctional polymerizable compounds having a glass transition temperature of less than -30°C when homopolymerized, and monofunctional polymerizable compounds having a glass transition temperature of more than 30°C when homopolymerized, include, among the above-mentioned monofunctional polymerizable compounds, those with a Tg of less than -30°C and those with a Tg of more than 30°C.

[0057] The total content (excluding the content of N-vinyl compounds) of monofunctional polymerizable compounds having a glass transition temperature of less than -30°C when homopolymerized, and monofunctional polymerizable compounds having a glass transition temperature of more than 30°C when homopolymerized, is 10% by mass or less, and preferably 5% by mass or less, relative to the total amount of polymerizable compounds. The lower limit of the total content is not particularly limited and is, for example, 0% by mass. When the total content is in the range of 10% by mass or less, images with excellent flexibility can be obtained.

[0058] Other polymerizable compounds include polyfunctional polymerizable compounds other than difunctional (meth)acrylates.

[0059] The polyfunctional polymerizable compound is not particularly limited as long as it is a compound having two or more polymerizable groups. From the viewpoint of curability, the polyfunctional polymerizable compound is preferably a polyfunctional radical polymerizable compound, and more preferably a polyfunctional ethylenically unsaturated compound.

[0060] Examples of polyfunctional ethylenically unsaturated compounds other than difunctional (meth)acrylates include trifunctional or more (meth)acrylates and difunctional or more polyfunctional vinyl ethers.

[0061] Examples of (meth)acrylates with three or more functions include trimethylolethane tri(meth)acrylate, trimethylolpropane tri(meth)acrylate, trimethylolpropane EO-added tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, tri(meth)acryloyloxyethoxytrimethylolpropane, glycerin polyglycidyl ether poly(meth)acrylate, and tris(2-acryloyloxyethyl) isocyanurate.

[0062] Examples of polyfunctional vinyl ethers include 1,4-butanediol divinyl ether, ethylene glycol divinyl ether, diethylene glycol divinyl ether, triethylene glycol divinyl ether, polyethylene glycol divinyl ether, propylene glycol divinyl ether, butylene glycol divinyl ether, hexanediol divinyl ether, 1,4-cyclohexanedimethanol divinyl ether, bisphenol A alkylene oxide divinyl ether, bisphenol F alkylene oxide divinyl ether, trimethylolethane trivinyl ether, trimethylolpropane trivinyl ether, and ditrimethylolpropanethet. Examples include trivinyl ether, glycerin trivinyl ether, pentaerythritol tetravinyl ether, dipentaerythritol pentavinyl ether, dipentaerythritol hexanyl ether, EO-added trimethylolpropane trivinyl ether, PO-added trimethylolpropane trivinyl ether, EO-added ditrimethylolpropane tetravinyl ether, PO-added ditrimethylolpropane tetravinyl ether, EO-added pentaerythritol tetravinyl ether, PO-added pentaerythritol tetravinyl ether, EO-added dipentaerythritol hexanyl ether, and PO-added dipentaerythritol hexanyl ether.

[0063] The total content of polyfunctional polymerizable compounds other than bifunctional acrylates is preferably 10% by mass or less, and more preferably 5% by mass or less, relative to the total amount of polymerizable compounds. The lower limit of the total content is not particularly limited and is, for example, 0% by mass. When the total content is 10% by mass or less, the flexibility of the image is improved.

[0064] <Coloring agent> An ink, which is one embodiment of the present disclosure, includes a colorant. The colorant may be present in the ink alone or in two or more types.

[0065] Examples of colorants include dyes and pigments. From the viewpoint of durability such as heat resistance, light resistance, and water resistance, the colorant is preferably a pigment.

[0066] When pigments are used as colorants, they can be included in the ink as a pigment dispersion. A pigment dispersion is a liquid obtained by dispersing a pigment in a liquid medium using a dispersant, and it contains at least a pigment, a dispersant, and a liquid medium. Details of the dispersant will be described later. The liquid medium may be an organic solvent or a polymerizable compound.

[0067] As pigments, either commercially available organic or inorganic pigments can be used. Examples of pigments include those described in "Dictionary of Pigments" edited by Seijiro Ito (published in 2000), "Industrial Organic Pigments" by W. Herbst and K. Hunger, and Japanese Patent Publication Nos. 2002-12607, 2002-188025, 2003-26978, and 2003-342503.

[0068] The colorant content is preferably 0.5% to 15% by mass, and more preferably 1% to 10% by mass, relative to the total amount of ink.

[0069] <Dispersant> When pigments are used as colorants, they can be included in the ink as a pigment dispersion. Pigments can also be dispersed in a liquid medium using a dispersant. Commonly known dispersants can be used. From the viewpoint of dispersion stability, the dispersant is preferably a compound that has both a hydrophilic and a hydrophobic structure.

[0070] Examples of dispersants include low molecular weight dispersants with a molecular weight of less than 1000, such as higher fatty acid salts, alkyl sulfates, alkyl ester sulfates, alkyl sulfonates, sulfosuccinates, naphthalene sulfonates, alkyl phosphates, polyoxyalkylene alkyl ether phosphates, polyoxyalkylene alkylphenyl ethers, polyoxyethylene polyoxypropylene glycol, glycerin fatty acid esters, sorbitan fatty acid esters, polyoxyethylene fatty acid amides, and amine oxides.

[0071] Furthermore, as a dispersant, a high molecular weight dispersant with a weight-average molecular weight of 10,000 or more, obtained by copolymerizing a hydrophilic monomer and a hydrophobic monomer, is mentioned. The weight-average molecular weight is measured by the same method as described above. From the viewpoint of dispersion stability, the hydrophilic monomer is preferably a dissociable group-containing monomer, and more preferably a dissociable group-containing monomer having a dissociable group and an ethylenically unsaturated bond. Examples of dissociable group-containing monomers include carboxyl group-containing monomers, sulfonic acid group-containing monomers, and phosphate group-containing monomers. From the viewpoint of dispersion stability, the hydrophobic monomer is preferably an aromatic group-containing monomer having an aromatic group and an ethylenically unsaturated bond, or an aliphatic hydrocarbon group-containing monomer having an aliphatic hydrocarbon group and an ethylenically unsaturated bond. The polymer is random It may be either a copolymer or a block copolymer.

[0072] The dispersant may be a commercially available product. For example, DISPERBYK-101, DISPERBYK-102, DISPERBYK-103, DISPERBYK-106, DISPERBYK-110, DISPERBYK-111, DISPERBYK-161, DISPERBYK-162, DISPERBYK-163, DISPERBYK-164, DISPERBYK-166, DISPERBYK-167, DISPERBYK-168, DISPERBYK-170, DISPERBYK-171, DISPERBYK-174, DISPERBYK-182 (all manufactured by BYK Chemie); and Examples include SOLSPERSE3000, SOLSPERSE5000, SOLSPERSE9000, SOLSPERSE12000, SOLSPERSE13240, SOLSPERSE13940, SOLSPERSE17000, SOLSPERSE22000, SOLSPERSE24000, SOLSPERSE26000, SOLSPERSE28000, SOLSPERSE32000, SOLSPERSE36000, SOLSPERSE39000, SOLSPERSE41000, and SOLSPERSE71000 (all manufactured by Lubrizol).

[0073] Known dispersion devices can be used to disperse pigments, including, for example, ball mills, sand mills, bead mills, roll mills, jet mills, paint shakers, attritors, ultrasonic dispersers, and dispersers.

[0074] From the viewpoint of dispersion stability, the content of the dispersant relative to the pigment content in the ink is preferably 0.05 to 1.0 by mass.

[0075] <Polymerization initiator> An ink according to one embodiment of the present disclosure may contain at least one polymerization initiator. The polymerization initiator is preferably a radical polymerization initiator that generates radicals.

[0076] Radical polymerization initiators include photoradical polymerization initiators and thermal radical polymerization initiators, and examples include alkylphenone compounds, acylphosphine compounds, aromatic onium salt compounds, organic peroxides, thio compounds, hexaarylbiimidazole compounds, ketoxime ester compounds, borate compounds, azinium compounds, metallocene compounds, active ester compounds, compounds having carbon-halogen bonds, and alkylamine compounds.

[0077] In particular, the polymerization initiator is preferably at least one selected from the group consisting of acylphosphine compounds and thio compounds, and more preferably at least one selected from the group consisting of acylphosphine oxide compounds and thioxanthone compounds.

[0078] Examples of acylphosphine oxide compounds include monoacylphosphine oxide compounds and bisacylphosphine oxide compounds.

[0079] Examples of monoacylphosphine oxide compounds include isobutyryldiphenylphosphine oxide, 2-ethylhexanoyldiphenylphosphine oxide, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, (2,4,6-trimethylbenzoyl)ethoxyphenylphosphine oxide, o-toluyldiphenylphosphine oxide, pt-butylbenzoyldiphenylphosphine oxide, 3-pyridylcarbonyldiphenylphosphine oxide, acryloyldiphenylphosphine oxide, benzoyldiphenylphosphine oxide, pivaloylphenylphosphine vinyl ester, and Examples include dipoylbisdiphenylphosphine oxide, pivaloyldiphenylphosphine oxide, p-toluyldiphenylphosphine oxide, 4-(t-butyl)benzoyldiphenylphosphine oxide, terephthaloylbisdiphenylphosphine oxide, 2-methylbenzoyldiphenylphosphine oxide, versatoyldiphenylphosphine oxide, 2-methyl-2-ethylhexanoyldiphenylphosphine oxide, 1-methylcyclohexanoyldiphenylphosphine oxide, methyl pivaloylphenylphosphinate, and isopropyl pivaloylphenylphosphinate.

[0080] Examples of bisacylphosphine oxide compounds include bis(2,6-dichlorobenzoyl)phenylphosphine oxide, bis(2,6-dichlorobenzoyl)-2,5-dimethylphenylphosphine oxide, bis(2,6-dichlorobenzoyl)-4-ethoxyphenylphosphine oxide, bis(2,6-dichlorobenzoyl)-4-propylphenylphosphine oxide, bis(2,6-dichlorobenzoyl)-2-naphthylphosphine oxide, and bis(2,6-dichlorobenzoyl) Bis(2,6-dichlorobenzoyl)-1-naphthylphosphine oxide, bis(2,6-dichlorobenzoyl)-4-chlorophenylphosphine oxide, bis(2,6-dichlorobenzoyl)-2,4-dimethoxyphenylphosphine oxide, bis(2,6-dichlorobenzoyl)decylphosphine oxide, bis(2,6-dichlorobenzoyl)-4-octylphenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)-2, 5-Dimethylphenylphosphine oxide, bis(2,6-dichloro-3,4,5-trimethoxybenzoyl)-2,5-dimethylphenylphosphine oxide, bis(2,6-dichloro-3,4,5-trimethoxybenzoyl)-4-ethoxyphenylphosphine oxide, bis(2-methyl-1-naphthoyl)-2,5-dimethylphenylphosphine oxide, bis(2-methyl-1-naphthoyl)-4-ethoxyphenylphosphine oxide, bis(2-methyl-1-naphthoyl)-2- Examples include naphthylphosphine oxide, bis(2-methyl-1-naphthoyl)-4-propylphenylphosphine oxide, bis(2-methyl-1-naphthoyl)-2,5-dimethylphenylphosphine oxide, bis(2-methoxy-1-naphthoyl)-4-ethoxyphenylphosphine oxide, bis(2-chloro-1-naphthoyl)-2,5-dimethylphenylphosphine oxide, and bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide.

[0081] In particular, the acylphosphine oxide compound is preferably 2,4,6-trimethylbenzoyldiphenylphosphine oxide (for example, product name "Omnirad TPO-H" from IGM Resins BV) or bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (for example, product name "Omnirad 819" from IGM Resins BV).

[0082] Thioxanthone compounds include thioxanthone, 2-isopropylthioxanthone, 4-isopropylthioxanthone, 2-chlorothioxanthone, 2,4-dichlorothioxanthone, 2-dodecylthioxanthone, 2,4-diethylthioxanthone, 2,4-dimethylthioxanthone, 1-methoxycarbonylthioxanthone, 2-ethoxycarbonylthioxanthone, 3-(2-methoxyethoxycarbonyl)thioxanthone, and 4-butoxycarbonyl Bonylthioxanthone, 3-butoxycarbonyl-7-methylthioxanthone, 1-cyano-3-chlorothioxanthone, 1-ethoxycarbonyl-3-chlorothioxanthone, 1-ethoxycarbonyl-3-ethoxythioxanthone, 1-ethoxycarbonyl-3-aminothioxanthone, 1-ethoxycarbonyl-3-phenylsulfurylthioxanthone, 3,4-di[2-(2-methoxyethoxy)ethoxycarbonyl]thioxanthone, 1-E Toxycarbonyl-3-(1-methyl-1-morpholinoethyl)thioxanthone, 2-methyl-6-dimethoxymethylthioxanthone, 2-methyl-6-(1,1-dimethoxybenzyl)thioxanthone, 2-morpholinomethylthioxanthone, 2-methyl-6-morpholinomethylthioxanthone, n-allylthioxanthone-3,4-dicarboximide, n-octylthioxanthone-3,4-dicarboximide, N-(1,1,3,3-tetra Examples include methylbutyl)thioxanthone-3,4-dicarboximide, 1-phenoxythioxanthone, 6-ethoxycarbonyl-2-methoxythioxanthone, 6-ethoxycarbonyl-2-methylthioxanthone, thioxanthone-2-polyethylene glycol ester, and 2-hydroxy-3-(3,4-dimethyl-9-oxo-9H-thioxanthone-2-yloxy)-N,N,N-trimethyl-1-propaneaminium chloride.

[0083] The thioxanthone compound may be a commercially available product. Examples of commercially available products include Lambson's SPEEDCURE series (e.g., SPEEDCURE 7010, SPEEDCURE CPTX, SPEEDCURE ITX, etc.).

[0084] From the viewpoint of improving curability, the content of the polymerization initiator is preferably 2% by mass or more, and more preferably 5% by mass or more, relative to the total amount of ink. The upper limit of the polymerization initiator content is not particularly limited, but for example, it is 15% by mass.

[0085] <Polymerization inhibitor> An ink, which is one embodiment of the present disclosure, preferably contains at least one polymerization inhibitor.

[0086] Examples of polymerization inhibitors include hydroquinone compounds, phenothiazines, catechols, alkylphenols, alkylbisphenols, zinc dimethyldithiocarbamate, copper dimethyldithiocarbamate, copper dibutyldithiocarbamate, copper salicylate, thiodipropionates, mercaptobenzimidazole, phosphates, nitrosamine compounds, hindered amine compounds, and nitroxyl radicals.

[0087] In particular, the polymerization inhibitor is more preferably a nitrosamine compound.

[0088] Examples of nitrosamine compounds include N-nitroso-N-phenylhydroxylamine aluminum salt and N-nitroso-N-phenylhydroxylamine. Among these, the nitrosamine compound is preferably N-nitroso-N-phenylhydroxylamine aluminum salt.

[0089] From the viewpoint of improving the long-term stability of the ink, the content of the polymerization inhibitor is preferably 0.05% to 1.0% by mass relative to the total amount of ink.

[0090] <Additives> An ink according to one embodiment of the present disclosure may optionally contain additives such as resins, co-sensitizers, ultraviolet absorbers, antioxidants, fade inhibitors, conductive salts, solvents, and basic compounds.

[0091] The viscosity of the ink is preferably 0.5 mPa·s to 50 mPa·s, more preferably 5 mPa·s to 40 mPa·s, preferably 7 mPa·s to 35 mPa·s, and even more preferably 8 mPa·s to 30 mPa·s. The viscosity is measured at 25°C using a viscometer. As a viscometer, for example, a TV-22 viscometer manufactured by Toki Sangyo Co., Ltd. can be used.

[0092] The surface tension of the ink is preferably 60 mN / m or less, more preferably 20 mN / m to 50 mN / m, and even more preferably 25 mN / m to 45 mN / m. The surface tension is measured using a surface tensimeter by the plate method at 25°C. As the surface tensimeter, for example, an automatic surface tensimeter (product name "DY-300") manufactured by Kyowa Interface Science Co., Ltd. can be used.

[0093] [Ink Set] An ink set according to one embodiment of the present disclosure preferably comprises the above-mentioned ink and a pretreatment liquid. The pretreatment liquid is a liquid that is applied to the substrate in advance before applying the ink to the substrate. By applying the pretreatment liquid to the substrate in advance, the flexibility against repeated bending is improved.

[0094] (First aspect) In the first embodiment, the pretreatment solution preferably contains a polymerizable compound and a polyester resin. When the pretreatment solution contains a polyester resin, the adhesion to the substrate is improved. This is thought to be because the polyester resin suppresses the generation of residual stress due to curing shrinkage.

[0095] -Polyester resin- Polyester resin refers to a polymer having ester bonds in its main chain. Polyester resin is usually obtained by reacting a dicarboxylic acid with a polyol. Examples of dicarboxylic acids include fumaric acid, itaconic acid, adipic acid, sebacic acid, terephthalic acid, isophthalic acid, sulfisoisophthalic acid, naphthalenedicarboxylic acid, tetrahydrophthalic acid, and cyclohexanedicarboxylic acid. Examples of polyols include ethylene glycol, propylene glycol, glycerin, hexanetriol, butanediol, hexanediol, and 1,4-cyclohexanedimethanol, bisphenol A, and hydrogenated bisphenol A.

[0096] In particular, the polyester resin is preferably a polyester resin obtained by reacting a dicarboxylic acid having a ring structure with a polyol having a ring structure. Examples of such polyester resins include Diacron FC1588 (manufactured by Mitsubishi Chemical Corporation), Nichigo Polyester TP219 (manufactured by Mitsubishi Chemical Corporation), UVAD081 (manufactured by Osaka Soda Co., Ltd.), and Diacron ER-535 (manufactured by Mitsubishi Chemical Corporation).

[0097] Information about polyester resins and their raw materials can be found, for example, in the "Polyester Resin Handbook" (authored by Eiichiro Takiyama, published by Nikkan Kogyo Shimbun in 1988).

[0098] Examples of polyester resins include polyhydroxybutyrate (PHB), polycaprolactone (PCL), polycaprolactone butylene succinate, polybutylene succinate (PBS), polybutylene succinate adipate (PBSA), polybutylene succinate carbonate, polyethylene terephthalate succinate, polybutylene adipate terephthalate, polytetramethylene adipate terephthalate, polybutylene adipate terephthalate, polyethylene succinate (PES), polyglycolic acid (PGA), and polylactic acid (PLA) polyesters, as well as aliphatic polyester carbonate copolymers and copolymers of aliphatic polyesters and polyamides.

[0099] The weight-average molecular weight of polyester resin is, for example, 1500 to 10000. The weight-average molecular weight is measured by the same method as described above.

[0100] The polyester resin content is 0.5% to 15% by mass relative to the total volume of the pretreatment solution. It is preferable that it be present, and more preferably 1% to 10% by mass.

[0101] -Polymerizable compound- The polymerizable compounds contained in the pretreatment solution are not particularly limited and may be monofunctional polymerizable compounds or polyfunctional polymerizable compounds. Examples of monofunctional polymerizable compounds and polyfunctional polymerizable compounds are the same as those that may be contained in the ink described above.

[0102] From the viewpoint of further improving the adhesion between the substrate and the image, the proportion of monofunctional polymerizable compounds in the polymerizable compounds contained in the pretreatment solution is preferably 80% by mass or more, and more preferably 90% by mass or more. The upper limit of the above proportion is not particularly limited and may be 100% by mass.

[0103] From the viewpoint of suppressing odor, the pretreatment solution preferably contains a monofunctional polymerizable compound as a polymerizable compound, which includes at least one structure selected from the group consisting of cyclic ether structures and alicyclic structures; more preferably contains a monofunctional polymerizable compound including a cyclic ether structure; and even more preferably contains a monofunctional (meth)acrylate including a cyclic ether structure.

[0104] Examples of cyclic ether structures include furan ring structures, pyran ring structures, oxirane ring structures, oxetane ring structures, dioxane ring structures, dioxolane ring structures, and morpholine ring structures.

[0105] The number of carbon atoms constituting the ring in the alicyclic structure is not particularly limited, but it is preferably 5 to 10. Examples of alicyclic structures include cyclohexane ring structures, dicyclopentanyl ring structures, dicyclopentenyl ring structures, norbornane ring structures, isobornane ring structures, norbornene ring structures, isobornene ring structures, and adamantane ring structures.

[0106] Examples of (meth)acrylates containing a cyclic ether structure include acryloylmorpholine, cyclic trimethylolpropaneformal (meth)acrylate, 1,4-dioxaspiro[4,5]decane-2-ylmethyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, and (2-methyl-2-ethyl-1,3-dioxolan-4-yl)methyl (meth)acrylate.

[0107] The content of the monofunctional polymerizable compound, which includes at least one structure selected from the group consisting of cyclic ether structures and alicyclic structures, is preferably 70% to 90% by mass, and more preferably 80% to 85% by mass, based on the total amount of the pretreatment solution.

[0108] Furthermore, it is preferable that the pretreatment solution contains a polymerizable silicone-based surfactant as a polymerizable compound. When the pretreatment solution contains a polymerizable silicone-based surfactant, image blurring is suppressed and scratch resistance is improved.

[0109] Examples of polymerizable silicone-based surfactants include those similar to those that may be included in the above-mentioned inks.

[0110] The content of polymerizable silicone surfactant is preferably 3% to 20% by mass, and more preferably 5% to 15% by mass, based on the total amount of the pretreatment solution.

[0111] From the viewpoint of curability, the content of polymerizable compounds is preferably 70% to 95% by mass, and more preferably 80% to 90% by mass, based on the total amount of the pretreatment solution.

[0112] In the first embodiment, the pretreatment solution may contain other components besides polymerizable compounds and polyester resins. Examples of other components include polymerization initiators, polymerization inhibitors, and additives. Examples of polymerization initiators, polymerization inhibitors, and additives are the same as those that may be included in the above-mentioned ink.

[0113] (Second aspect) In a second embodiment, the pretreatment solution preferably contains a polymerizable compound containing polymerizable compound A having an acidic group. The presence of polymerizable compound A having an acidic group improves adhesion to the substrate. This is thought to be because the acidic group in polymerizable compound A interacts with the surface of the substrate.

[0114] Examples of acidic groups in polymerizable compounds containing acidic groups include carboxyl groups, sulfo groups, phosphonic acid groups, phosphoric acid groups, and sulfonamide groups.

[0115] Examples of polymerizable compounds having a carboxyl group include 2-(meth)acryloyloxyethyl succinic acid, 2-(meth)acryloyloxyethyl phthalic acid, 2-(meth)acryloyloxyethyl hexahydrophthalic acid, 2-(meth)acryloyloxypropyl phthalic acid, 2-(meth)acryloyloxypropyl hexahydrophthalic acid, 2-carboxyethyl (meth)acrylate, and (meth)acrylic acid.

[0116] Examples of polymerizable compounds having a sulfo group include 2-hydroxy-3-sulfopropyl(meth)acrylate, 2-(meth)acrylamide-2-methylpropanesulfonic acid, 2-sulfoethyl(meth)acrylate, 3-sulfopropyl(meth)acrylate, and 4-styrenesulfonic acid.

[0117] Examples of polymerizable compounds having a phosphate group include 2-phosphonooxyethyl (meth)acrylate and 2-(meth)acryloyloxyethyl acid phosphate.

[0118] In particular, polymerizable compound A having an acid group is preferably a polymerizable compound having a carboxyl group.

[0119] Polymerizable compound A having an acid group may be a monofunctional polymerizable compound having an acid group, or a polyfunctional polymerizable compound having an acid group. In particular, it is preferably a monofunctional polymerizable compound having an acid group, more preferably a monofunctional polymerizable compound having a carboxyl group, and even more preferably a monofunctional (meth)acrylate having a carboxyl group.

[0120] The content of polymerizable compound A having an acid group is preferably 3% to 20% by mass, and more preferably 5% to 15% by mass, based on the total amount of ink.

[0121] In the second embodiment, the pretreatment solution may contain polymerizable compounds other than polymerizable compound A having an acid group as the polymerizable compound.

[0122] Other polymerizable compounds are not particularly limited and may be monofunctional polymerizable compounds or polyfunctional polymerizable compounds. Examples of monofunctional polymerizable compounds and polyfunctional polymerizable compounds are the same as those that may be included in the above-mentioned ink.

[0123] From the viewpoint of further improving the adhesion between the substrate and the image, it is preferable that the other polymerizable compounds include monofunctional polymerizable compounds.

[0124] From the viewpoint of suppressing odor, the pretreatment solution preferably contains, as other polymerizable compounds, a monofunctional polymerizable compound having at least one structure selected from the group consisting of cyclic ether structures and alicyclic structures, more preferably a monofunctional polymerizable compound having a cyclic ether structure, and even more preferably a monofunctional (meth)acrylate having a cyclic ether structure.

[0125] The content of the monofunctional polymerizable compound, which includes at least one structure selected from the group consisting of cyclic ether structures and alicyclic structures, is preferably 65% ​​to 85% by mass, and more preferably 70% to 80% by mass, based on the total amount of the pretreatment solution.

[0126] Furthermore, the pretreatment solution preferably contains a polymerizable silicone-based surfactant as another polymerizable compound.

[0127] Examples of polymerizable silicone-based surfactants include those similar to those that may be included in the above-mentioned inks.

[0128] The content of polymerizable silicone surfactant is preferably 3% to 20% by mass, and more preferably 5% to 15% by mass, based on the total amount of the pretreatment solution.

[0129] From the viewpoint of curability, the content of polymerizable compounds is preferably 70% to 95% by mass, and more preferably 80% to 90% by mass, based on the total amount of the pretreatment solution.

[0130] From the viewpoint of further improving the adhesion between the substrate and the image, the proportion of monofunctional polymerizable compounds in the polymerizable compounds contained in the pretreatment solution is preferably 80% by mass or more, and more preferably 90% by mass or more. The upper limit of the above proportion is not particularly limited and may be 100% by mass.

[0131] In a second embodiment, the pretreatment solution may contain other components besides polymerizable compounds. Examples of other components include polymerization initiators, polymerization inhibitors, and additives. Examples of polymerization initiators, polymerization inhibitors, and additives are the same as those that may be contained in the ink described above.

[0132] Furthermore, the pretreatment solution may also contain both a polyester resin and a polymerizable compound A having an acidic group.

[0133] The viscosity of the pretreatment solution is preferably 0.5 mPa·s to 50 mPa·s, more preferably 5 mPa·s to 40 mPa·s, preferably 7 mPa·s to 35 mPa·s, and even more preferably 8 mPa·s to 30 mPa·s. The viscosity is measured at 25°C using a viscometer. As a viscometer, for example, a TV-22 viscometer manufactured by Toki Sangyo Co., Ltd. can be used.

[0134] The surface tension of the pretreatment solution is preferably 60 mN / m or less, more preferably 20 mN / m to 50 mN / m, and even more preferably 25 mN / m to 45 mN / m. The surface tension is measured using a surface tensimeter by the plate method at 25°C. As the surface tensimeter, for example, an automatic surface tensimeter (product name "DY-300") manufactured by Kyowa Interface Science Co., Ltd. can be used.

[0135] [Image recording method] The first embodiment of the image recording method of this disclosure preferably includes the steps of applying the above-mentioned ink to a substrate using an inkjet recording method (hereinafter also referred to as the "ink application step") and irradiating the applied ink with active energy rays (hereinafter also referred to as the "active energy ray curing step").

[0136] (Ink application process) In the ink application process, the above-mentioned ink is applied using an inkjet recording method. The type of substrate is not particularly limited, and any commonly known substrate can be used. Examples of substrates include glass, quartz, and plastic films. Examples of resins constituting the plastic film include cellulose diacetate, cellulose triacetate, cellulose propionate, cellulose butyrate, cellulose acetate butyrate, cellulose nitrate, acrylic resin, chlorinated polyolefin resin, polyethersulfone resin, polyethylene terephthalate (PET), polyethylene naphthalate, nylon, polyethylene, polystyrene, polypropylene, polycycloolefin resin, polyimide resin, polycarbonate resin, and polyvinyl acetal. The plastic film may contain only one of these resins, or it may be a film containing a mixture of two or more of these resins.

[0137] According to one embodiment of the present disclosure, an ink can record an image with excellent flexibility, and is therefore applicable to substrates that can be deformed at room temperature. Because the image with excellent flexibility can follow the deformation of the substrate at room temperature, image cracking is less likely to occur.

[0138] Since the application is possible to a substrate that can be deformed at room temperature, the substrate is preferably metal, plastic, synthetic leather, or rubber, and more preferably rubber.

[0139] The thickness of the substrate is not particularly limited. According to one embodiment of the present disclosure, the ink can record images with excellent flexibility and is therefore applicable to substrates with thickness. The lower limit of the substrate thickness is, for example, 1 μm. In terms of applicability to substrates with thickness, the substrate thickness is preferably 1 mm or more. The upper limit of the substrate thickness is, for example, 5 mm.

[0140] The inkjet recording method is not particularly limited as long as it is a method capable of recording an image, and known methods can be used. Examples of inkjet recording methods include a charge control method that ejects ink using electrostatic attraction, a drop-on-demand method (pressure pulse method) that utilizes the vibration pressure of a piezoelectric element, an acoustic inkjet method that converts an electrical signal into an acoustic beam, irradiates the ink with it, and ejects the ink using the radiation pressure, and a thermal inkjet (bubble jet®) method that heats the ink to form bubbles and utilizes the resulting pressure.

[0141] Inkjet heads used in inkjet recording methods include a shuttle method, which uses a short serial head and records while scanning the head in the width direction of the substrate, and a line method, which uses a line head in which recording elements are arranged to cover the entire area of ​​one side of the substrate.

[0142] In the line method, the substrate can be scanned in a direction intersecting the arrangement direction of the recording elements, allowing for pattern formation across the entire substrate surface. This eliminates the need for a transport system such as a carriage that scans the short head. Furthermore, the line method eliminates the need for complex scanning control of the carriage and the substrate; only the substrate moves, resulting in faster recording speeds compared to the shuttle method.

[0143] The amount of ink droplets ejected from the inkjet head is preferably 1 pL (picoliters) to 100 pL, more preferably 3 pL to 80 pL, and even more preferably 3 pL to 50 pL.

[0144] (Activated energy ray curing process) In the active energy ray curing process, the applied ink is irradiated with active energy rays. Examples of active energy rays include gamma rays, beta rays, electron beams, ultraviolet rays, and visible light. Among these, ultraviolet rays are preferred as the active energy ray.

[0145] The peak wavelength of ultraviolet light is preferably, for example, 200 nm to 405 nm, more preferably 250 nm to 400 nm, and even more preferably 300 nm to 400 nm. The peak wavelength refers to the wavelength at the maximum intensity of the waveform with the greatest intensity in the ultraviolet region (for example, 200 nm to 405 nm).

[0146] Mercury lamps, gas lasers, and solid-state lasers are the main light sources used for ultraviolet irradiation, with mercury lamps, metal halide lamps, and ultraviolet fluorescent lamps being widely known. UV-LEDs (ultraviolet light-emitting diodes) and UV-LDs (ultraviolet laser diodes) are also promising light sources for ultraviolet irradiation due to their small size, long lifespan, high efficiency, and low cost. Among these, metal halide lamps, high-pressure mercury lamps, medium-pressure mercury lamps, low-pressure mercury lamps, or UV-LEDs are preferred as light sources for ultraviolet irradiation.

[0147] In this disclosure, polymerizing only a portion of the polymerizable compounds in the ink is also referred to as "pre-curing," and the irradiation of active energy rays for pre-curing is also referred to as "pinning exposure." In this disclosure, the polymerization of substantially all of the polymerizable compounds in the ink is also referred to as "main curing," and the irradiation of active energy rays for main curing is also referred to as "main exposure."

[0148] In the process of irradiating with active energy rays, it is preferable to pre-cur the ink and then fully cure it. Specifically, it is preferable to apply the ink, perform pinning exposure on the ink, and finally perform full exposure.

[0149] The ink reaction rate after pinning exposure is preferably 10% to 80%.

[0150] Here, the reaction rate of the ink refers to the polymerization rate of the polymerizable compounds contained in the ink, as determined by high-performance liquid chromatography.

[0151] A reaction rate of 10% or higher for the ink suppresses droplet interference between ink dots, resulting in improved image quality in the final product.

[0152] Furthermore, by keeping the ink reaction rate below 80%, insufficient dot spreading is suppressed, resulting in improved granularity of the final image.

[0153] The ink reaction rate is preferably 15% or higher, from the viewpoint of further improving the image quality of the final image.

[0154] From the viewpoint of further improving the granularity of the final image, the ink reaction rate is preferably 75% or less, more preferably 50% or less, preferably 40% or less, more preferably 30% or less, and even more preferably 25% or less.

[0155] The reaction rate of the ink after exposure is preferably between 80% and 100%, more preferably between 85% and 100%, and even more preferably between 90% and 100%. When the reaction rate exceeds 80%, adhesion improves further.

[0156] The ink reaction rate is determined by the following method. A substrate is prepared that has been subjected to the procedure up to the end of irradiation with active energy rays on the ink. A sample piece measuring 20 mm x 50 mm (hereinafter referred to as the post-irradiation sample piece) is cut from the area of ​​the substrate where the ink film is present. The cut post-irradiation sample piece is immersed in 10 mL of THF (tetrahydrofuran) for 24 hours to obtain an eluate from which the ink has been dissolved. The amount of polymerizable compound (hereinafter referred to as "post-irradiation compound amount X1") is determined from the obtained eluate by high-performance liquid chromatography. Separately, the same procedure as above is performed, except that the ink on the substrate is not irradiated with active energy rays, to determine the amount of polymerizable monomer (hereinafter referred to as "amount of compound X1 before irradiation"). Based on the amount of compound after irradiation X1 and the amount of compound before irradiation X1, the reaction rate (%) of the ink is calculated using the following formula. Ink reaction rate (%) = ((Amount of compound before irradiation x1 - Amount of compound after irradiation x1) / Amount of compound before irradiation x1) × 100

[0157] The exposure dose of the active energy ray for pinning exposure is 10 mJ / cm², from the viewpoint of more easily achieving the aforementioned ink reaction rate. 2 ~100 mJ / cm 2 Preferably, it is 20 mJ / cm². 2 ~60 mJ / cm² 2 It is preferable that this be the case.

[0158] The amount of active energy radiation used for this exposure is 50 mJ / cm², from the viewpoint of completely curing the ink. 2 ~1000 mJ / cm 2 Preferably, it is 200 mJ / cm². 2 ~800 mJ / cm 2 It is preferable that this be the case.

[0159] In this exposure procedure, it is preferable to irradiate the substrate with active energy rays in an atmosphere with an oxygen concentration of less than 1 volume%. The oxygen concentration is more preferably 0.5 volume% or less, and even more preferably 0.3 volume% or less.

[0160] In the process of irradiating with active energy rays, from the viewpoint of image quality, it is preferable to irradiate with active energy rays within 0.1 to 5 seconds from the time the ink lands. When performing both pinning exposure and main exposure, it is preferable to irradiate with active energy rays for pinning exposure within 0.1 to 5 seconds from the time the ink lands. It is more preferable that the time from the time the ink lands until the irradiation of active energy rays (or, in the case of performing both pinning exposure and main exposure, the active energy rays for pinning exposure) is within 0.2 to 1 second.

[0161] Next, we will explain the image recording method using the above ink set.

[0162] A second embodiment of the present disclosure of the image recording method preferably includes the steps of using the above ink set, applying the above pretreatment liquid and the above ink onto a substrate using an inkjet recording method, and irradiating with active energy rays after the above pretreatment liquid and the above ink have been applied, respectively.

[0163] The step of applying the pretreatment solution and the step of applying the ink are the same as the ink application step described above.

[0164] In the process of irradiating with active energy rays, it is preferable to apply a pretreatment solution, then perform pinning exposure on the pretreatment solution, apply ink to the pre-cured pretreatment solution, apply the ink again, perform pinning exposure on the ink, and finally perform the main exposure.

[0165] Preferred embodiments of pinning exposure and main exposure are the same as preferred embodiments of pinning exposure and main exposure in the active energy ray curing process described above. [Examples]

[0166] The present disclosure will be further described below with reference to examples, but the present disclosure is not limited to the following examples unless it exceeds the spirit of the disclosure.

[0167] The details of each component contained in the inks prepared in the examples and comparative examples are as follows.

[0168] (Monofunctional polymerizable compound) • NVC: N-vinylcaprolactam (manufactured by BASF) • PEA: Phenoxyethyl acrylate (product name "SR339A", manufactured by Sartomer) • CHA: Cyclohexyl acrylate (product name "Viscote #155, CHA", manufactured by Osaka Organic Chemical Industry Co., Ltd.) • TMCHA: Trimethylcyclohexyl acrylate (product name "SR420", manufactured by Sartomer) • THFA: Tetrahydrofurfurylacrylate (product name "SR285", manufactured by Sartomer) • LA: Lauryl acrylate (product name "SR335", manufactured by Sartomer) • CTFA: Cyclic trimethylolpropaneform acrylate (product name "SR531", manufactured by Sartomer) • IBOA: Isobornyl acrylate (product name "SR506", manufactured by Sartomer) · 4-HBA: 4-hydroxybutyl acrylate (product name "4- HBA (manufactured by Osaka Organic Chemical Industry Co., Ltd.) • IOA: Isooctyl acrylate (product name "SR440", manufactured by Sartomer) • A-SA: 2-Acryloyloxyethyl succinic acid (product name "NK ester A-SA", manufactured by Shin Nakamura Chemical Industry Co., Ltd.; polymerizable compound A with an acid group)

[0169] (bifunctional polymerizable compound) • HDDA: 1,6-Hexanediol diacrylate (Product name "Viscote #230, HDDA", manufactured by Osaka Organic Chemical Industry Co., Ltd.) • DDDA: 1,10-decanediol diacrylate (product name "A-DOD-N", manufactured by Shin-Nakamura Chemical Industry Co., Ltd.) • PEGDA200: Polyethylene glycol #200 diacrylate (product name "A-200", manufactured by Shin Nakamura Chemical Industry Co., Ltd.) • PEGDA600: Polyethylene glycol #600 diacrylate (product name "A-600", manufactured by Shin Nakamura Chemical Industry Co., Ltd.) • PPGDA700: Polypropylene glycol #700 diacrylate (product name "APG-700", manufactured by Shin Nakamura Chemical Industry Co., Ltd.) • NPGDA: Neopentyl glycol diacrylate (product name "Light Acrylate NP-A", manufactured by Kyoeisha Chemical Co., Ltd.) • TCDDMDA: Tricyclodecanedimethanol diacrylate (product name "EBECRYL 130", manufactured by Daicel Ornex Co., Ltd.) • HMPA: 2-hydroxy-3-methacrylate (product name "701A", manufactured by Shin-Nakamura Chemical Industry Co., Ltd.) • PEGDA1000: Polyethylene glycol #1000 diacrylate (product name "A-1000", manufactured by Shin Nakamura Chemical Industry Co., Ltd.)

[0170] (Polymerizable silicone-based surfactant) • Tegorad 2100 (manufactured by Evonik) • Tegorad2010 (manufactured by Evonik)

[0171] (Pigment) • White pigment: Titanium dioxide (product name "KRONOS 2300", manufactured by KRONOS) • Cyan pigment: Pigment Blue 15:4 (Product name "Heliogen Blue D 7110 F", manufactured by BASF Japan) • Magenta pigment: Product name "CINQUASIA MAGENTA L4540", manufactured by BASF Japan. • Yellow pigment: Pigment Yellow 155 (product name "Inkjet Yellow 4GC", manufactured by Clariant) • Black pigment: Carbon black (product name "Mogul E", manufactured by Cabot)

[0172] (Dispersant) • SOLSPERSE41000 (manufactured by Lubrizol) • SOLSPERSE32000 (manufactured by Lubrizol) • Efka7731 (manufactured by BASF Japan) • BYKJET9151 (manufactured by BYK)

[0173] (Polymerization initiator) • Omn.184: 1-Hydroxycyclohexyl-phenyl ketone (product name "Omnirad184", manufactured by IGM Resins BV) • Omn.819: Bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (product name "Omnirad819", manufactured by IGM Resins BV) • ITX: Isopropylthioxanthone (product name "SPEEDCURE ITX", manufactured by Lambson) • TPO: 2,4,6-trimethylbenzoyldiphenylphosphine oxide (product name "Omnirad TPO-H", manufactured by IGM Resins BV)

[0174] (Polymerization inhibitor) • UV12: N-nitroso-N-phenylhydroxylamine aluminum salt (product name "FLORSTAB UV12", manufactured by Kromachem)

[0175] (Additives) • BR113: Acrylic resin (product name "Dianal BR113", manufactured by Mitsubishi Chemical Corporation)

[0176] -Ink preparation- <Example 1> First, a white pigment dispersion was prepared. Specifically, the following components were placed in a disperser motor mill M50 (manufactured by Eiger), and dispersed using zirconia beads with a diameter of 0.65 mm at a peripheral speed of 9 m / s for 4 hours to obtain a white pigment dispersion.

[0177] White pigment…50 parts by mass Dispersant (product name "SOLSPERSE41000", manufactured by Lubrizol) ... 3.53 parts by mass PEA…45.47 parts by mass UV12…1 part by mass

[0178] Next, the following ingredients were mixed. The mixture was stirred using a mixer (product name "L4R", manufactured by Silverson) at 25°C and 5000 revolutions per minute for 20 minutes to obtain white ink. • Prepared white pigment dispersion ... 15 parts by mass ·PEA…49.6 parts by mass ·HDDA…1 part by mass ·NVC…21.5 parts by mass ·BR113…2.4 parts by mass ·UV12…0.42 parts by mass ·Omni.184…2.8 parts by mass ·TPO…8 parts by mass

[0179] <Examples 2-17, Comparative Examples 1-6> The ink was obtained in the same manner as in Example 1, except that the content of each polymerizable compound in the ink was adjusted to the content shown in Tables 1 to 3. Tables 1 to 3 show the percentage (mass%) of each component relative to the total amount of polymerizable compounds. In Examples 2 to 17 and Comparative Examples 1 to 6, the types and content of components other than polymerizable compounds in the ink are the same as in Example 1.

[0180] -Image Record- A prepared white ink was introduced into the white slot of an inkjet recording device (product name "Acuity LED 1600R," manufactured by Fujifilm Corporation). Synthetic leather (product name "Cappuccino," manufactured by Yamaplus Co., Ltd., 1 mm thick) and stainless steel plate (product name "Stainless Steel Plate," manufactured by Yawata Screw Co., Ltd., 1 mm thick) were used as substrates. The ink application conditions were 1200 dpi x 1200 dpi, 48 passes, and bidirectional printing, and a 100% solid image was recorded. Here, dpi stands for dots per inch. By setting the lamp work of the inkjet recording apparatus, ultraviolet rays for pinning exposure (peak wavelength: 385 nm) and ultraviolet rays for main exposure (peak wavelength: 385 nm) were irradiated onto the ink applied on the substrate in this order. The exposure amount for pinning exposure was 400 mJ / cm 2 and the exposure amount for main exposure was 1200 mJ / cm 2 . Under the above conditions, pinning exposure and main exposure were sequentially performed on the ink applied on the substrate to obtain an image recording material. The image recording material with an image recorded on the leatherette was designated as "Image Recording Material 1", and the image recording material with an image recorded on the stainless steel plate was designated as "Image Recording Material 2".

[0181] [Evaluation] For each example and comparative example, using the obtained image recording materials, evaluations of flexibility, blocking resistance, and adhesion were performed. The evaluation methods are as follows.

[0182] [Flexibility] Image Recording Material 1 was bent 180 degrees at room temperature (23 °C). After bending, the presence or absence of cracks and peeling of the image was visually observed. For Image Recording Material 2, press working was performed at room temperature (23 °C) and then bent 90 degrees. After bending, the presence or absence of cracks and peeling of the image was visually observed. The evaluation criteria are as follows. A: There are no cracks or peeling at all. B: There is slight cracking or peeling in at least one of them. C: Cracking or peeling in at least one of them can be confirmed significantly.

[0183] [Blocking Resistance] In Image Recording Material 1 and Image Recording Material 2, the stickiness of the image surface was confirmed by touch. The evaluation criteria are as follows. A: There is no stickiness at all. B: There is slight stickiness. C: It is very sticky.

[0184] [Adhesion] A cross-hatch test was performed on image recording material 1 and image recording material 2 in accordance with ISO 2409 (cross-cut method). In the cross-hatch test, the cut interval was set to 1 mm, and 25 1 mm square grids were formed. Adhesion was evaluated based on the percentage of grids that peeled off. The percentage of grids that peeled off was calculated using the following formula. The total number of grids in the following formula is 25. Percentage of lattice detachment (%) = [(Number of detached lattices) / (Total number of lattices)] × 100 The evaluation criteria are as follows: A: The percentage of the grid that had peeled off was 0%. B: The percentage of the grid that had peeled off was greater than 0% and less than or equal to 5%. C: The percentage of lattice detachment was over 5%.

[0185] The evaluation results are shown in Tables 1 to 3.

[0186] Tables 1 to 3 show the glass transition temperature (Tg) when homopolymerized for monofunctional polymerizable compounds other than N-vinyl compounds. For bifunctional (meth)acrylates, the number of carbon atoms in the portion excluding the (meth)acryloyl group is indicated. The evaluation results for image recording 1 are listed in the "Synthetic Leather" column, and the evaluation results for image recording 2 are listed in the "Metal" column.

[0187] [Table 1]

[0188] [Table 2]

[0189] [Table 3]

[0190] As shown in Tables 1 and 2, Examples 1 to 17 contain polymerizable compounds and colorants. The polymerizable compounds include N-vinyl compounds, monofunctional polymerizable compounds with a Tg of -30°C to 30°C when homopolymerized, and compounds selected from the group consisting of difunctional (meth)acrylates and polymerizable silicone surfactants. The total content of monofunctional polymerizable compounds with a Tg of less than -30°C when homopolymerized (excluding N-vinyl compounds) and monofunctional polymerizable compounds with a Tg of more than 30°C when homopolymerized is 10% by mass or less of the total amount of polymerizable compounds. The total content of compounds selected from the group consisting of difunctional (meth)acrylates and polymerizable silicone surfactants is 0.1% by mass to 2% by mass of the total amount of polymerizable compounds. As a result, images with excellent flexibility and blocking resistance were obtained.

[0191] On the other hand, as shown in Table 3, in Comparative Example 1 and Comparative Example 2, the total content of monofunctional polymerizable compounds with a Tg of over 30°C when homopolymerized was over 10% by mass, indicating inferior flexibility in the image.

[0192] In Comparative Examples 3 and 4, the total content of monofunctional polymerizable compounds with a Tg of less than -30°C when homopolymerized exceeded 10% by mass, resulting in poor image blocking resistance.

[0193] Comparative Example 5 did not contain any compounds selected from the group consisting of bifunctional (meth)acrylates and polymerizable silicone-based surfactants, and it was found to have poor image blocking resistance.

[0194] In Comparative Example 6, the total content of compounds selected from the group consisting of bifunctional (meth)acrylates and polymerizable silicone-based surfactants was found to be more than 2% by mass relative to the total amount of polymerizable compounds, resulting in inferior image flexibility.

[0195] In Example 1, the N-vinyl compound content was 10% to 35% by mass relative to the total amount of polymerizable compound, and the monofunctional polymerizable compound content, which has a glass transition temperature of -30°C to 30°C when homopolymerized, was 60% to 85% by mass relative to the total amount of polymerizable compound. Therefore, it was found to have superior blocking resistance compared to Examples 2 and 3.

[0196] In Example 1, because phenoxyethyl acrylate was included, it was found to have superior adhesion compared to Examples 4 to 7.

[0197] In Example 1, the number of carbon atoms in the portion of the difunctional (meth)acrylate excluding the (meth)acryloyl group is 4 or more, so it was found to have superior flexibility compared to Example 14. Also, in Example 1, the number of carbon atoms in the portion of the difunctional (meth)acrylate excluding the (meth)acryloyl group is 36 or less, so it was found to have superior blocking resistance compared to Example 15.

[0198] <Example 101> Cyanite pigment dispersions, magenta pigment dispersions, yellow pigment dispersions, and black pigment dispersions were prepared in the same manner as the white pigment dispersion, except that the components contained in the white pigment dispersion were changed to the components listed below.

[0199] (Cyanide pigment dispersion) Cyan pigment ... 30 parts by mass ·PEA...52 parts by mass • SOLSPERSE32000 (manufactured by Noveon) ... 17 parts by mass ·UV12…1 part by mass

[0200] (Magenta pigment dispersion) Magenta pigment…30 parts by mass ·PEA...56 parts by mass ·SOLSPERSE32000…12.5 parts by mass ·UV12…1.5 parts by mass

[0201] (Yellow pigment dispersion) • Yellow pigment…33.9 parts by mass ·PEA...58.2 parts by mass ·SOLSPERSE32000…6.8 parts by mass ·UV12…1.1 parts by mass

[0202] (Black pigment dispersion) • Black pigment…40 parts by mass ·PEA...45.47 parts by mass ·Efka7731 …3.53 parts by mass ·UV12…1 part by mass

[0203] Cyan, magenta, yellow, and black inks were prepared in the same manner as the white ink, except that the components of the white ink were changed to the components listed below.

[0204] (Cyan ink) • Prepared cyanide pigment dispersion ... 8.3 parts by mass ·PEA…58.07 parts by mass ·HDDA…1 part by mass ·NVC…21.7 parts by mass ·BR113…2.98 parts by mass ·UV12…0.35 parts by mass ·ITX…1 part by mass ·Omni.184…2.8 parts by mass ·Omni.819 …3.8 parts by mass

[0205] (Magenta ink) • Prepared magenta pigment dispersion ... 13.5 parts by mass ·PEA…55.24 parts by mass ·HDDA…1 part by mass ·NVC…21.7 parts by mass ·BR113…1.58 parts by mass ·UV12…0.18 parts by mass ·BYKJET9151 …0.9 parts by mass ·ITX…1 part by mass • Omni.184 …1.4 Quality Department • Omni.819 …3.5 Quality Department

[0206] (イエローインク) ·Preparation of したイエロー pigment dispersion...7.6 Quality Department ·PEA …57.86 Quality Department HDDA…1 Quality Department •NVC …21.7 Quality Department ·BR113 …2.7 Quality Department • UV12 …0.34 Quality Department ·BYKJET9151 …1 Quality Department ·ITX …1 Quality Department • Omni.184 …2.9 Quality Department • Omni.819 …3.9 Quality Department

[0207] (ブラックインク) ·Prepared したブラック pigment dispersion...7.6 Quality Department ·PEA …58.55 Quality Department HDDA…1 Quality Department •NVC …21.7 Quality Department ·BR113 …3 Quality Department ·UV12 …0.35 Quality Department ·ITX …1 Quality Department • Omni.184 …2.9 Quality Department • Omni.819 …3.9 Quality Department

[0208] Cyan, magenta, yellow, black, and white inks prepared were introduced into the cyan, magenta, yellow, black, and white throttles of an inkjet recording apparatus (product name: "Acuity LED 1600R", manufactured by Fujifilm Corporation). As substrates, synthetic leather (product name: "Cappuccino", manufactured by Yamaplas Co., Ltd., thickness 1 mm) and a stainless steel plate (product name: "Stainless Steel Plate <<Stainless Steel Band>>", manufactured by Yawata Screw Co., Ltd., thickness 1 mm) were used. The conditions for ink application were 1200 dpi × 1200 dpi, 48 passes, and bi-directional printing. The dot percentage of the white ink was set at 100%, and the dot percentages of the cyan, magenta, yellow, and black inks were each set at 50% to record solid images. Depending on the setting of the lamp work of the inkjet recording apparatus, ultraviolet rays for pinning exposure (peak wavelength 385 nm) and ultraviolet rays for main exposure (peak wavelength 385 nm) were irradiated onto the ink applied on the substrate in this order. The exposure amount for pinning exposure was 400 mJ / cm 2 and the exposure amount for main exposure was 1200 mJ / cm 2 was set. Under the above conditions, white ink, yellow ink, magenta ink, cyan ink, and black ink were applied onto the substrate in this order. After each ink was applied, pinning exposure was performed, and after the last pinning exposure, main exposure was performed to obtain an image recording.

[0209] In Example 101, evaluations of flexibility, blocking resistance, and adhesion were performed in the same manner as in Example 1. In both cases where the substrate was synthetic leather and where the substrate was metal, the evaluations of flexibility, blocking resistance, and adhesion were "A".

[0210] <Examples 201, Example 202> As Example 201, an ink set comprising pretreatment liquid 1 and the white ink of Example 1 was prepared. As Example 202, an ink set comprising pretreatment liquid 2 and the white ink of Example 1 was prepared.

[0211] [Preparation of pretreatment solution 1] The following components were mixed. The mixture was stirred using a mixer (product name "L4R", manufactured by Silverson) at 25°C and 5000 rpm for 20 minutes to obtain pretreatment solution 1. ·CTFA…83 parts by mass • Polyester resin (product name "Diaclone FC-1588", manufactured by Mitsubishi Chemical Corporation) ... 3 parts by mass ·Tegorad2100…10 parts by mass ·Omn.819 …3.8 parts by mass ·UV12…0.2 parts by mass

[0212] [Preparation of pretreatment solution 2] The following components were mixed. The mixture was stirred using a mixer (product name "L4R", manufactured by Silverson) at 25°C and 5000 rpm for 20 minutes to obtain pretreatment solution 2. ·CTFA…76 parts by mass ·A-SA…10 parts by mass ·Tegorad2100…10 parts by mass ·Omn.819 …3.8 parts by mass ·UV12…0.2 parts by mass

[0213] The prepared pretreatment solution and the white ink from Example 1 were introduced into the clear and white slots of an inkjet recording device (product name "Acuity LED 1600R", manufactured by Fujifilm Corporation). In Example 201, pretreatment solution 1 was introduced as the pretreatment solution, and in Example 202, pretreatment solution 2 was introduced as the pretreatment solution. Synthetic leather (product name "Cappuccino", manufactured by Yamaplus Co., Ltd., 1 mm thick) and stainless steel plate (product name "Stainless Steel Van", manufactured by Yawata Screw Co., Ltd., 1 mm thick) were used as the substrates. The application conditions for the pretreatment solution and ink were 1200 dpi x 1200 dpi, 48 passes, and bidirectional printing, and a 100% solid image was recorded. By setting the lamp work of the inkjet recording apparatus, ultraviolet rays for pinning exposure (peak wavelength 385 nm) and ultraviolet rays for main exposure (peak wavelength 385 nm) were irradiated to the ink applied on the substrate in this order. The exposure amount of the pinning exposure was 400 mJ / cm 2 and the exposure amount of the main exposure was 1200 mJ / cm 2 . Under the above conditions, a pretreatment liquid and white ink were applied to the substrate in this order. After applying the pretreatment liquid and white ink, pinning exposure was performed respectively, and after the last pinning exposure, main exposure was performed to obtain an image recording object.

[0214] In Example 201 and Example 202, the flexibility, blocking resistance, and adhesion were evaluated in the same manner as in Example 1. In both cases where the substrate was synthetic leather and where the substrate was metal, the evaluations of flexibility, blocking resistance, and adhesion were "A".

[0215] Furthermore, when using synthetic leather as the substrate, the flexibility was evaluated by repeated bending. The evaluation method is as follows.

[0216] <Flexibility by repeated bending> The image recording object when using synthetic leather as the substrate was bent 180 degrees at room temperature (23°C), and then the operation of returning to the state before bending was performed 100 times. After 100 operations, the presence or absence of cracks and peeling of the image was visually observed.

[0217] In both Example 201 and Example 202, in the evaluation of flexibility by repeated bending, there were no cracks and peeling at all.

[0218] Furthermore, the disclosure of Japanese Patent Application No. 2021-135103, filed on August 20, 2021, is incorporated herein by reference in its entirety. In addition, all documents, patent applications, and technical standards described herein are incorporated herein by reference to the same extent as if each individual document, patent application, and technical standard had been specifically and individually indicated as being incorporated by reference.

Claims

1. Contains polymerizable compounds and colorants, The polymerizable compound comprises an N-vinyl compound, a monofunctional polymerizable compound having a glass transition temperature of -30°C to 30°C when formed as a homopolymer, and a compound selected from the group consisting of a bifunctional (meth)acrylate and a polymerizable silicone-based surfactant. Excluding the aforementioned N-vinyl compound, the total content of monofunctional polymerizable compounds having a glass transition temperature of less than -30°C when homopolymerized, and monofunctional polymerizable compounds having a glass transition temperature of more than 30°C when homopolymerized, is 10% by mass or less of the total amount of polymerizable compounds. An active energy ray curable ink in which the total content of a compound selected from the group consisting of the aforementioned bifunctional (meth)acrylate and the aforementioned polymerizable silicone-based surfactant is 0.5% to 2% by mass relative to the total amount of polymerizable compound.

2. The content of the N-vinyl compound is 10% to 35% by mass relative to the total amount of the polymerizable compound. The active energy ray curable ink according to claim 1, wherein the content of the monofunctional polymerizable compound having a glass transition temperature of -30°C to 30°C when used as the homopolymer is 60% to 85% by mass relative to the total amount of the polymerizable compound.

3. The active energy ray curable ink according to claim 1, wherein the N-vinyl compound comprises N-vinylcaprolactam.

4. The active energy ray curable ink according to claim 1, wherein the monofunctional polymerizable compound having a glass transition temperature of -30°C to 30°C when used as a homopolymer contains phenoxyethyl acrylate.

5. The active energy ray curable ink according to claim 1, wherein the bifunctional (meth)acrylate has 4 to 36 carbon atoms in the portion excluding the (meth)acryloyl group.

6. The active energy ray curable ink according to claim 1, wherein the polymerizable compound comprises the polymerizable silicone-based surfactant.

7. The active energy ray curable ink according to claim 1, wherein the polymerizable compound comprises the bifunctional (meth)acrylate.

8. An ink set comprising an active energy ray curable ink according to any one of claims 1 to 7, and a pretreatment solution.

9. The ink set according to claim 8, wherein the pretreatment solution comprises a polymerizable compound and a polyester resin.

10. The ink set according to claim 8, wherein the pretreatment solution contains a polymerizable compound containing polymerizable compound A having an acid group.

11. The ink set according to claim 9, wherein the proportion of monofunctional polymerizable compounds in the polymerizable compounds contained in the pretreatment solution is 80% by mass or more.

12. A step of applying an active energy ray curable ink according to any one of claims 1 to 7 onto a substrate, The process involves irradiating the applied active energy ray-curable ink with active energy rays, An image recording method that includes [a specific feature / method].

13. The image recording method according to claim 12, wherein the substrate has a thickness of 1 mm or more.

14. The image recording method according to claim 12, wherein the substrate is metal, plastic, synthetic leather, or rubber.

15. The ink set described in claim 8 is used, A step of applying the pretreatment liquid and the active energy ray curable ink onto a substrate using an inkjet recording method, The process involves applying the aforementioned pretreatment solution and the aforementioned active energy ray-curable ink, and then irradiating them with active energy rays. An image recording method that includes [a specific feature / method].

Images