Radiation-curable inks, ink sets, and image recording methods

Abstract

This invention provides an active energy radiation-curable ink and its application. The active energy radiation-curable ink comprises a polymerizable compound and a colorant. The polymerizable compound comprises an N-vinyl compound, a monofunctional polymerizable compound having a Tg of -30°C to 30°C when forming a homopolymer, and compounds selected from the group consisting of difunctional (meth)acrylates and polymerizable organosilicon surfactants. The total content of monofunctional polymerizable compounds other than N-vinyl compounds, having a Tg below -30°C when forming a homopolymer, and monofunctional polymerizable compounds having a Tg above 30°C when forming a homopolymer, is less than 10% by mass relative to the total amount of polymerizable compounds. The total content of compounds selected from the group consisting of difunctional (meth)acrylates and polymerizable organosilicon surfactants is 0.1% to 2% by mass relative to the total amount of polymerizable compounds.

Description

Technical Field

[0001] This disclosure relates to an active energy radiation-curable ink, an ink assembly, and an image recording method. Background Technology

[0002] It has long been known that when using ink to record images on a substrate, a method is used to cure the ink using active energy rays.

[0003] For example, Japanese Patent Application Publication No. 2015-47748 discloses 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 with a glass transition temperature of 40°C to 90°C, a photopolymerization initiator, and a pigment, wherein the content of the aforementioned acrylic resin is 0.5% by mass or more and 5% by mass or less. Japanese Patent Application Publication No. 2009-84313 discloses an active ray-curable ink composition, wherein, relative to the ink composition, it contains 65% by weight or more of a monofunctional olefin unsaturated compound having only one olefinic unsaturated bond within its molecule, and 7.5% by weight or less of a photopolymerization initiator with a molecular weight of 1000 or less and without an olefinic unsaturated bond within its molecule. Summary of the Invention

[0004] The technical problem to be solved by the invention

[0005] Image recordings are obtained by recording images on a substrate using ink. When the substrate is flexible, bending or other bending processes can cause the image recordings to deform. Therefore, it is necessary to maintain the image even when the image recording is deformed. Furthermore, from the perspective of ease of handling the image recordings, it is sometimes necessary to suppress image stickiness.

[0006] This disclosure was made in view of this situation. According to one embodiment of the present invention, an active energy radiation curable ink, an ink group, and an image recording method are provided that are capable of recording images with excellent flexibility and excellent anti-blocking properties.

[0007] means for solving technical problems

[0008] This disclosure includes the following schemes.

[0009] <1> An active energy radiation-curable ink, comprising a polymeric compound and a colorant.

[0010] Polymerizable compounds include N-vinyl compounds, monofunctional polymerizable compounds with a glass transition temperature of -30°C to 30°C when formed into homopolymers, and compounds selected from the group consisting of difunctional (meth)acrylates and polymerizable organosilicon surfactants.

[0011] Furthermore, the total content of monofunctional polymerizable compounds (excluding N-vinyl compounds) with a glass transition temperature below -30°C when formed into homopolymers and monofunctional polymerizable compounds with a glass transition temperature above 30°C when formed into homopolymers is less than 10% by mass relative to the total amount of polymerizable compounds.

[0012] The total content of compounds selected from the group consisting of difunctional (meth)acrylates and polymerizable organosilicon surfactants is 0.1% to 2% by mass relative to the total amount of polymerizable compounds.

[0013] <2> according to <1> The active energy ray curable ink, wherein,

[0014] The content of N-vinyl compounds is 10% to 35% by mass relative to the total amount of polymerizable compounds.

[0015] The content of monofunctional polymeric compounds with glass transition temperatures of -30℃ to 30℃ when forming homopolymers is 60% to 85% by mass relative to the total amount of polymeric compounds.

[0016] <3> according to <1> or <2> The active energy ray curable ink, wherein,

[0017] N-vinyl compounds contain N-vinylcaprolactam.

[0018] <4> according to <1> ~ <3> The active energy ray curable ink described in any one of the following statements, wherein,

[0019] Monofunctional polymeric compounds with a glass transition temperature of -30℃ to 30℃ when formed into homopolymers include phenoxyethyl acrylate.

[0020] <5> according to <1> ~ <4> The active energy ray curable ink described in any one of the following statements, wherein,

[0021] The number of carbon atoms in the part other than the (meth)acryloyl group of difunctional (meth)acrylates is 4 to 36.

[0022] <6> according to <1> ~ <5> The active energy ray curable ink described in any one of the following statements, wherein,

[0023] Polymerizable compounds include polymerizable organosilicon surfactants.

[0024] <7> An ink assembly having <1> ~ <6> The active energy ray curable ink and pretreatment liquid as described in any one of the following.

[0025] <8> according to <7> The ink group, wherein,

[0026] The pretreatment solution contains polymeric compounds and polyester resins.

[0027] <9> according to <7> The ink group, wherein,

[0028] The pretreatment solution contains a polymeric compound A, which has an acid group.

[0029] <10> according to <8> or <9> The ink group, wherein,

[0030] The proportion of monofunctional polymeric compounds in polymeric compounds is more than 80% by mass.

[0031] <11> An image recording method, comprising:

[0032] Apply to substrate <1> ~ <6> The process of the active energy ray curable ink as described in any one of the following; and

[0033] The process of irradiating an ink that is cured by applied active energy rays with active energy rays.

[0034] <12> according to <11> The image recording method, wherein,

[0035] The thickness of the substrate is 1mm or more.

[0036] <13> according to <11> or <12> The image recording method, wherein,

[0037] The substrate can be metal, plastic, synthetic leather, or rubber.

[0038] <14> An image recording method that uses <7> ~ <10> The ink group described in any one of the following statements,

[0039] It includes:

[0040] The process of applying a pretreatment liquid and the ink to a substrate using an inkjet recording method; and

[0041] The process of irradiating the pretreatment solution and ink with active energy rays.

[0042] Invention Effects

[0043] According to one embodiment of the present invention, an active energy X-ray curable ink, an ink group, and an image recording method are provided that are capable of recording images with excellent flexibility and excellent anti-blocking properties. Detailed Implementation

[0044] The following provides a detailed description of the active energy ray curable ink, ink group, and image recording method disclosed herein.

[0045] In this specification, the numerical range indicated by “~” means the range that includes the values ​​before and after “~” as the minimum and maximum values, respectively.

[0046] In the numerical ranges described in this specification, the upper or lower limit value recorded in a certain numerical range can be replaced with the upper or lower limit value of other numerical ranges described in different segments. Additionally, the upper or lower limit value recorded in a certain numerical range described in this specification can be replaced with the value shown in the embodiments.

[0047] In this specification, when a composition contains multiple substances equivalent to each component, unless otherwise specified, the amount of each component in the composition refers to the total amount of the multiple substances present in the composition.

[0048] In this specification, a combination of two or more preferred solutions is a more preferred solution.

[0049] In this specification, the term "process" includes not only independent processes, but also processes that cannot be clearly distinguished from other processes, as long as the desired purpose of the process is achieved.

[0050] In this specification, "image" means the entire film formed by applying ink, and "image recording" means the formation of an image (i.e., the film).

[0051] In addition, the concept of "image" in this specification also includes solid image.

[0052] In this specification, "(meth)acrylate" is a concept that includes both acrylate and methacrylate. Additionally, "(meth)acrylic acid" is a concept that includes both acrylic acid and methacrylic acid.

[0053] [Ink]

[0054] The active energy ray curable inkjet ink (hereinafter, also simply "ink") according to one embodiment of this disclosure comprises a polymerizable compound and a colorant. The polymerizable compound comprises an N-vinyl compound, a monofunctional polymerizable compound whose glass transition temperature (hereinafter, also referred to as "Tg") when forming a homopolymer is -30°C to 30°C (hereinafter, the glass transition temperature when forming a homopolymer is sometimes referred to as the "Tg" of the monofunctional polymerizable compound), and compounds selected from the group consisting of difunctional (meth)acrylates and polymerizable organosilicon surfactants. The total content of monofunctional polymerizable compounds other than the N-vinyl compound, whose glass transition temperature when forming a homopolymer is below -30°C, and monofunctional polymerizable compounds whose glass transition temperature when forming a homopolymer is above 30°C, is 10% by mass or less relative to the total amount of the polymerizable compound. The total content of compounds selected from the group consisting of difunctional (meth)acrylates and polymerizable organosilicon surfactants is 0.1% by mass to 2% by mass relative to the total amount of the polymerizable compound.

[0055] After applying the ink, as an embodiment of this disclosure, to a substrate, and then irradiating it with active energy rays, an image recorder can be obtained in which an ink film is formed on the substrate as an image. Since the ink, as an embodiment of this disclosure, contains a polymerizable compound, a polymerization reaction occurs through irradiation with active energy rays.

[0056] N-vinyl compounds have a strong ability to capture oxygen atoms that inhibit polymerization. Therefore, when inks contain N-vinyl compounds, surface curing properties are excellent, and image stickiness is suppressed. Furthermore, when inks contain monofunctional polymerizable compounds with a Tg of -30°C to 30°C, the ink film formed through the curing reaction exhibits excellent flexibility. That is, images with excellent flexibility can be obtained. While N-vinyl compounds tend to have high Tg due to their amide bonds, by simultaneously including monofunctional polymerizable compounds with a Tg of -30°C to 30°C in the ink along with N-vinyl compounds, both anti-blocking and flexibility can be achieved. Additionally, images with excellent adhesion are formed.

[0057] Furthermore, when the ink contains compounds selected from the group consisting of difunctional (meth)acrylates and polymerizable silicone surfactants, image stickiness is suppressed, resulting in an image with excellent anti-blocking properties. When the ink contains difunctional (meth)acrylates, a cross-linking reaction occurs within the ink film, making the ink film more robust and thus suppressing image stickiness. On the other hand, when the ink contains polymerizable silicone surfactants, the polymerizable silicone surfactants float to the surface of the ink, thus improving the surface curing properties of the ink film. Therefore, image stickiness is suppressed, and anti-blocking properties are excellent. Additionally, adhesion is also improved.

[0058] In particular, by selecting compounds from the group consisting of difunctional (meth)acrylates and polymerizable organosilicon surfactants, the total content of which is 0.1% by mass or more relative to the total amount of polymerizable compounds, anti-blocking properties are ensured. Furthermore, by having a total content of 2% by mass or less, an image with excellent flexibility is formed.

[0059] Furthermore, the total content of monofunctional polymeric compounds with a glass transition temperature below -30°C when forming homopolymers and monofunctional polymeric compounds with a glass transition temperature above 30°C when forming homopolymers (excluding N-vinyl compounds) is 10% by mass or less relative to the total amount of polymeric compounds. This indicates that they are not included as the main components of the polymeric compounds. By setting the above total content to 10% by mass or less, the image exhibits excellent flexibility.

[0060] On the other hand, the ink described in Japanese Patent Application Publication No. 2015-47748 contains, as a main component, a monofunctional polymerizable compound with a glass transition temperature exceeding 30°C when forming a homopolymer, which differs from the technical concept of this application. Furthermore, the ink described in Japanese Patent Application Publication No. 2009-84313 does not contain compounds selected from the group consisting of difunctional (meth)acrylates and polymerizable organosilicon surfactants, which also differs from the technical concept of this application.

[0061] Hereinafter, the components contained in the ink as an embodiment of the present disclosure will be described.

[0062] The ink described in one embodiment of this disclosure is an active energy radiation curable ink. That is, the ink described in one embodiment of this disclosure is cured by irradiation with active energy radiation. Examples of active energy radiation include gamma rays, beta rays, electron beams, ultraviolet light, and visible light. Ultraviolet light is preferred among these active energy rays. The ink described in one embodiment of this disclosure is preferably an ultraviolet-curable ink.

[0063] <Polymerizing compounds>

[0064] The ink, as one embodiment of this disclosure, comprises a polymerizable compound. The polymerizable compound may be contained in the ink as a single compound or in two or more compounds.

[0065] The polymerizable groups in a polymerizable compound can be cationic polymerizable groups or free radical polymerizable groups; from the viewpoint of curability, free radical polymerizable groups are preferred. Furthermore, from the viewpoint of curability, free radical polymerizable groups are preferably olefinic unsaturated groups.

[0066] Polymerizable compounds can be monofunctional polymerizable compounds with one polymerizable group, or polyfunctional polymerizable compounds with two or more polymerizable groups.

[0067] In the ink of 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 into a homopolymer, and a compound selected from the group consisting of difunctional (meth)acrylates and polymerizable organosilicon surfactants.

[0068] N-vinyl compounds have a strong ability to capture oxygen atoms that inhibit polymerization. Therefore, inks containing N-vinyl compounds exhibit excellent surface curing properties, suppressing image stickiness. Furthermore, inks containing monofunctional polymerizable compounds with a Tg of -30°C to 30°C result in ink films with excellent flexibility formed through the curing reaction. In other words, images with excellent flexibility can be obtained. While N-vinyl compounds tend to have high Tg due to their amide bonds, by simultaneously including monofunctional polymerizable compounds with a Tg of -30°C to 30°C in the ink along with N-vinyl compounds, both anti-blocking properties and flexibility can be achieved.

[0069] Furthermore, when the ink contains compounds selected from the group consisting of difunctional (meth)acrylates and polymerizable silicone surfactants, image stickiness is suppressed. When the ink contains difunctional (meth)acrylates, a cross-linking reaction occurs within the ink film, making the ink film more robust, thus suppressing image stickiness. On the other hand, when the ink contains polymerizable silicone surfactants, the polymerizable silicone surfactants float to the surface of the ink, thus improving the surface curability of the ink film. Therefore, image stickiness is suppressed.

[0070] From the viewpoint of curability, the content of polymeric compounds relative to the total amount of ink is preferably 70% to 95% by mass, more preferably 75% to 90% by mass.

[0071] (N-vinyl compounds)

[0072] Examples of N-vinyl compounds include N-vinylpyrrolidone, N-vinylcaprolactam, N-vinylformamide, and N-vinylphthalimide. Among these, N-vinylcaprolactam is preferred from the viewpoint of further improving surface curing properties.

[0073] From the viewpoint of further improving flexibility and anti-blocking properties, the content of N-vinyl compound is preferably 10% to 35% by mass relative to the total amount of polymerizable compound, and the content of monofunctional polymerizable compound with a glass transition temperature of -30°C to 30°C when forming homopolymer is preferably 60% to 85% by mass relative to the total amount of polymerizable compound.

[0074] Furthermore, from the viewpoint of further improving flexibility and anti-blocking properties, the content of N-vinyl compounds is more preferably 15% to 30% by mass relative to the total amount of polymerizable compounds, and the content of monofunctional polymerizable compounds with a glass transition temperature of -30°C to 30°C when forming homopolymers is more preferably 65% ​​to 80% by mass relative to the total amount of polymerizable compounds.

[0075] (A monofunctional polymeric compound whose Tg is -30℃ to 30℃ when it is made into a homopolymer)

[0076] A monofunctional polymerizable compound is a compound having a single polymerizable group. From the viewpoint of curability, a monofunctional polymerizable compound is preferably a monofunctional free radical polymerizable compound, and more preferably a monofunctional olefinic unsaturated compound.

[0077] Examples of monofunctional olefinic unsaturated compounds include monofunctional (meth)acrylates, monofunctional (meth)acrylamides, monofunctional aromatic vinyl compounds, and monofunctional vinyl ethers.

[0078] As examples of monofunctional polymerizable compounds whose Tg is -30℃ to 30℃ when forming homopolymers, the following specific examples of monofunctional polymerizable compounds are compounds whose Tg is -30℃ to 30℃ when forming homopolymers.

[0079] Examples of monofunctional (meth)acrylates include methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, hexyl methacrylate, 2-ethylhexyl methacrylate, tert-octyl methacrylate, isoamyl methacrylate, decyl methacrylate, isodecyl methacrylate, dodecyl methacrylate, octadecyl methacrylate, isooctadecyl methacrylate, cyclohexyl methacrylate, 4-n-butylcyclohexyl methacrylate, 4-tert-butylcyclohexyl methacrylate, borneol methacrylate, and isobutyl methacrylate. Borneol, 2-ethylhexyl diethylene glycol (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-methoxyethoxy)(meth)acrylate, 2-(2-butoxyethoxy)(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, methylpropionate... 3-Hydroxybutyl acrylate, 4-Hydroxybutyl acrylate, Cyclic Trimethylolpropane Methylacetal (meth)acrylate, Phenylacetic Glycidyl 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)acrylates, dipropylene glycol (meth)acrylates, polyoxypropylene monoalkyl ether (meth)acrylates, 2-methacryloyloxyethyl succinic acid, 2-methacryloyloxyhexahydrophthalic acid, 2-methacryloyloxyethyl-2-hydroxypropyl phthalate, ethoxydiethylene glycol (meth)acrylates, butoxydiethylene glycol (meth)acrylates, trifluoroethyl (meth)acrylate, perfluorooctyl ethyl (meth)acrylates, 2-hydroxy-3-phenoxypropyl (meth)acrylates, ethylene oxide (EO) modified phenol (meth)propylene Ester, 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, dicyclopentyl (meth)acrylate, (3-ethyl-3-oxetanebutylmethyl) (meth)acrylate, phenoxyethylene glycol (meth)acrylate, 2-carboxyethyl (meth)acrylate, and 2-(meth)acryloyloxyethyl succinate.

[0080] Examples of monofunctional (meth)acrylamides include (meth)acrylamide, N-methyl (meth)acrylamide, N-ethyl (meth)acrylamide, N-propyl (meth)acrylamide, N-n-butyl (meth)acrylamide, N-tert-butyl (meth)acrylamide, N-butoxymethyl (meth)acrylamide, N-isopropyl (meth)acrylamide, N-hydroxymethyl (meth)acrylamide, N,N-dimethyl (meth)acrylamide, N,N-diethyl (meth)acrylamide, and (meth)acryloylmorpholine.

[0081] Examples of monofunctional aromatic vinyl compounds include styrene, dimethylstyrene, trimethylstyrene, isopropylstyrene, chloromethylstyrene, methoxystyrene, acetoxystyrene, chlorostyrene, dichlorostyrene, bromostyrene, methyl vinyl benzoate, 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, isopropylstyrene, butenylstyrene, octenylstyrene, 4-tert-butoxycarbonylstyrene, and 4-tert-butoxystyrene.

[0082] Examples of monofunctional vinyl ethers include methyl vinyl ether, ethyl vinyl ether, propyl vinyl ether, n-butyl vinyl ether, tert-butyl vinyl ether, 2-ethylhexyl vinyl ether, n-nonyl vinyl ether, dodecyl 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, methoxy polyethylene 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 phenoxy polyethylene glycol vinyl ether.

[0083] The glass transition temperature of the homopolymer prepared from the monofunctional polymeric compound was determined using the following method. First, a homopolymer with a weight-average molecular weight of 10,000 to 20,000 was prepared using the monofunctional polymeric compound. The glass transition temperature of the prepared homopolymer was determined according to the method described in JIS K7121:2012. The glass transition temperature was determined using a differential scanning calorimeter, for example, using a product named "DSC-60" manufactured by Shimadzu Corporation. The weight-average molecular weight was determined using gel permeation chromatography (GPC). For example, an HLC-8220 GPC (manufactured by Tosoh Corporation) was used as the GPC, three TSKgel Super Multipore HZ-H (manufactured by Tosoh Corporation, 4.6 mm ID × 15 cm) columns were used as the column, and THF (tetrahydrofuran) was used as the eluent. The conditions were as follows: sample concentration set to 0.45% by mass, flow rate set to 0.35 ml / min, sample loading volume set to 10 μl, measurement temperature set to 40 °C, and detection using a differential refractive index (RI) detector. Calibration curves were prepared using eight samples manufactured by Tosoh Corporation under the product name "TSK Standard Polystyrene": "F-40", "F-20", "F-4", "F-1", "A-5000", "A-2500", "A-1000", and "n-propylbenzene". Furthermore, the glass transition temperature of the homopolymer varies depending on the weight-average molecular weight of the homopolymer, but the variation is negligible when the weight-average molecular weight is between 10,000 and 20,000.

[0084] The molecular weight of the monofunctional polymerizable compound with a Tg of -30°C to 30°C when forming a homopolymer is preferably 1000 or less, more preferably 500 or less. When the molecular weight is 1000 or less, it is possible to record images with better flexibility and anti-blocking properties.

[0085] From the viewpoint of curability, monofunctional polymerizable compounds with a Tg of -30°C to 30°C when forming homopolymers are preferably monofunctional acrylates. Examples of monofunctional acrylates with a Tg of -30°C to 30°C when forming homopolymers include benzyl acrylate (6°C), cyclohexyl acrylate (15°C), 2-methyl-2-ethyl-1,3-dioxolane-4-yl)methacrylate (-7°C), tetrahydrofurfuryl acrylate (-15°C), dodecyl acrylate (-30°C), 3,3,5-trimethylcyclohexyl acrylate (-29°C), phenoxyethyl acrylate (5°C), and 2-acryloyloxyethyl succinic acid (17°C). Furthermore, the Tg in parentheses indicates the Tg when forming a homopolymer.

[0086] From the viewpoint of further improving the flexibility of the image, the monofunctional polymerizable compound with a Tg of -30℃ to 30℃ when forming a homopolymer is preferably phenoxyethyl acrylate.

[0087] (Compounds selected from the group consisting of difunctional (meth)acrylates and polymeric organosilicon surfactants)

[0088] As one embodiment of this disclosure, the ink comprises a compound selected from the group consisting of difunctional (meth)acrylates and polymerizable silicone surfactants. The ink may contain only difunctional (meth)acrylates, only polymerizable silicone surfactants, or both. In any case, the anti-blocking properties of the image are improved. From the viewpoint of further improving anti-blocking properties, the ink preferably contains a polymerizable silicone surfactant.

[0089] -Difunctional (meth)acrylates-

[0090] Difunctional (meth)acrylates are compounds having two (meth)acryloyl groups. A difunctional (meth)acrylate can be any of a compound having an acryloyl group, a compound having a methacryloyl group, or a compound having both an acryloyl and a methacryloyl group. In this disclosure, it is understood that difunctional (meth)acrylates do not contain an organosilicon structure. Therefore, they are distinguished from polymerizable organosilicon surfactants. Organosilicon surfactants having two acryloyl groups are equivalent to polymerizable organosilicon surfactants.

[0091] Examples of difunctional (meth)acrylates include ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, propylene glycol dimethacrylate, dipropylene glycol dimethacrylate, tripropylene glycol dimethacrylate, polypropylene glycol dimethacrylate, butanediol dimethacrylate, tetraethylene glycol dimethacrylate, neopentyl glycol dimethacrylate, 3-methyl-1,5-pentanediol dimethacrylate, hexanediol dimethacrylate, heptaethylene glycol dimethacrylate, and 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, glycerol di(meth)acrylate, pentaerythritol di(meth)acrylate, ethylene glycol diglycidyl ether di(meth)acrylate, diethylene glycol diglycidyl ether di(meth)acrylate, and tricyclodecanediethanol di(meth)acrylate.

[0092] The difunctional (meth)acrylate preferably has 4 to 36 carbon atoms in the portion excluding the (meth)acryloyl group, more preferably 5 to 15. When the number of carbon atoms is 4 or more, the softness 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 anti-blocking property of the image is improved.

[0093] -Polymerizable silicone surfactants-

[0094] In this disclosure, "polymerizable organosilicon surfactant" refers to an organosilicon surfactant having polymerizable groups.

[0095] The polymerizable groups in polymerizable silicone surfactants can be cationic polymerizable groups or free radical polymerizable groups; from the viewpoint of curability, free radical polymerizable groups are preferred. Furthermore, from the viewpoint of curability, free radical polymerizable groups are preferably olefinic unsaturated groups. Specifically, the polymerizable groups in polymerizable surfactants are preferably vinyl or (meth)acryloyl groups; from the viewpoint of curability, (meth)acryloyl groups are more preferred.

[0096] From the viewpoint of anti-blocking properties, the number of polymeric groups in the polymerizable surfactant is preferably 2 or more. The upper limit of the number of polymeric groups in the polymerizable surfactant is not particularly limited, but from the viewpoint of ink ejection properties when ink is ejected using an inkjet recording method, it is, for example, 5.

[0097] That is, regarding the type and number of polymerizable groups, polymerizable organosilicon surfactants are preferably organosilicon surfactants having two or more (meth)acryloyl groups.

[0098] Examples of polymerizable organosilicon surfactants include compounds with polymerizable groups bonded to the main chain or side chain of polyether-modified dimethylsiloxane.

[0099] Commercially available polymerizable silicone surfactants include, for example, 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 Allnex), KP-410, 411, 412, 413, 414, 415, 416, 418, 420, 422, 423 (manufactured by Shin-Etsu Silicones), which are silicone surfactants containing (meth)acryloyl groups.

[0100] In the ink, the total content of compounds selected from the group consisting of difunctional (meth)acrylates and polymerizable silicone surfactants is 0.1% to 2% by mass relative to the total amount of polymerizable compounds, preferably 0.5% to 1.8% by mass, and more preferably 1.0% to 1.5% by mass. When the total content is 0.1% by mass or more, an image with excellent anti-blocking properties can be obtained. On the other hand, when the total content is 2% by mass or less, an image with excellent softness can be obtained.

[0101] (Other polymeric compounds)

[0102] As one embodiment of the present disclosure, the ink may also contain other polymeric compounds besides N-vinyl compounds, monofunctional polymeric compounds with a Tg of -30°C to 30°C when formed into homopolymers, and compounds selected from the group consisting of difunctional (meth)acrylates and polymeric organosilicon surfactants.

[0103] Other examples of polymerizable compounds include monofunctional polymers with a glass transition temperature (Tg) below -30°C when formed into homopolymers and monofunctional polymers with a glass transition temperature (Tg) above 30°C when formed into homopolymers. Furthermore, the method for determining Tg is as described above.

[0104] Examples of monofunctional polymerizable compounds with a glass transition temperature (Tg) below -30°C and a glass transition temperature (Tg) above 30°C when formed into homopolymers can be cited as specific examples of the aforementioned monofunctional polymerizable compounds.

[0105] The total content (excluding the content of N-vinyl compounds) of monofunctional polymeric compounds with a glass transition temperature below -30°C and monofunctional polymeric compounds with a glass transition temperature above 30°C when forming homopolymers is 10% by mass or less, preferably 5% by mass or less, relative to the total amount of polymeric compounds. The lower limit of the total content is not particularly limited, for example, it can be 0% by mass. When the total content is in the range of 10% by mass or less, images with excellent flexibility can be obtained.

[0106] In addition, other polymerizable compounds include multifunctional polymerizable compounds other than difunctional (meth)acrylates.

[0107] A multifunctional polymerizable compound is not particularly limited as long as it has two or more polymerizable groups. From the viewpoint of curability, a multifunctional polymerizable compound is preferably a multifunctional free radical polymerizable compound, and more preferably a multifunctional olefinic unsaturated compound.

[0108] Examples of polyfunctional olefinic unsaturated compounds other than difunctional (meth)acrylates include trifunctional (meth)acrylates and difunctional polyfunctional vinyl ethers.

[0109] Examples of trifunctional or higher (meth)acrylates include trimethylolethane tri(meth)acrylate, trimethylolpropane tri(meth)acrylate, trimethylolpropane EO addition 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, glycerol polyglycidyl ether poly(meth)acrylate, and tris(2-acryloyloxyethyl)isocyanurate.

[0110] Examples of multifunctional vinyl ethers include 1,4-butanediol diethylene ether, ethylene glycol diethylene ether, diethylene glycol diethylene ether, triethylene glycol diethylene ether, polyethylene glycol diethylene ether, propylene glycol diethylene ether, butanediol diethylene ether, hexanediol diethylene ether, 1,4-cyclohexanediethanol diethylene ether, bisphenol A epoxy diethylene ether, bisphenol F epoxy diethylene ether, trimethylolethane triethylene ether, trimethylolpropane triethylene ether, and ditrimethylolpropane tetraethylene ether. Ethers, triethylene glycerol, pentaerythritol tetraethylene ether, dipentaerythritol pentaethylene ether, dipentaerythritol hexaethylene ether, EO addition trimethylolpropane triethylene ether, PO addition trimethylolpropane triethylene ether, EO addition ditrimethylolpropane tetraethylene ether, PO addition ditrimethylolpropane tetraethylene ether, EO addition pentaerythritol tetraethylene ether, PO addition pentaerythritol tetraethylene ether, EO addition dipentaerythritol hexaethylene ether, and PO addition dipentaerythritol hexaethylene ether.

[0111] The total content of polyfunctional polymeric compounds other than difunctional acrylates is preferably 10% by mass or less, more preferably 5% by mass or less, relative to the total amount of polymeric compounds. The lower limit of the total content is not particularly limited, for example, it can be 0% by mass. When the total content is 10% by mass or less, the softness of the image is improved.

[0112] <Coloring agent>

[0113] As one embodiment of this disclosure, the ink contains a colorant. The colorant may be contained in the ink as a single type or as two or more types.

[0114] Dyes and pigments can be cited as coloring agents. From the viewpoint of durability, such as heat resistance, light resistance, and water resistance, pigments are preferred as coloring agents.

[0115] When using pigments as colorants, the pigments can be contained in the ink as pigment dispersions. A pigment dispersion is a liquid obtained by dispersing the pigment in a liquid medium using a dispersant, and it comprises at least a pigment, a dispersant, and a liquid medium. Details regarding dispersants will be described later. Furthermore, the liquid medium can be an organic solvent or a polymeric compound.

[0116] As pigments, both commercially available organic and inorganic pigments can be used. Examples of pigments include those listed in Seishiro Itō's "Dictionary of Pigments" (2000), W. Herbst, K. Hunger's "Industrial Organic Pigments", Japanese Patent Application Publication Nos. 2002-12607, 2002-188025, 2003-26978, and 2003-342503.

[0117] The content of colorant relative to the total amount of ink is preferably 0.5% to 15% by mass, more preferably 1% to 10% by mass.

[0118] <Dispersant>

[0119] When using pigments as colorants, the pigments can be contained in inks as pigment dispersions. Pigments can be dispersed in a liquid medium using a dispersant. Commonly known substances can be used as dispersants. From the viewpoint of dispersion stability, the dispersant is preferably a compound having both hydrophilic and hydrophobic structures.

[0120] Examples of dispersants include high fatty acid salts, alkyl sulfates, alkyl ester sulfates, alkyl sulfonates, sulfosuccinates, naphthalene sulfonates, alkyl phosphates, polyoxyethylene alkyl ether phosphates, polyoxyethylene alkylphenyl ethers, polyoxyethylene polyoxypropylene glycol, glycerol fatty acid esters, dehydrated sorbitan fatty acid esters, polyoxyethylene fatty acid amides, and amine oxides, which are low molecular weight dispersants with a molecular weight of less than 1000.

[0121] In addition, as a dispersant, examples include high molecular weight dispersants with a weight-average molecular weight of 10,000 or more, obtained by copolymerizing hydrophilic and hydrophobic monomers. Furthermore, the weight-average molecular weight is determined using the same method as described above. From the viewpoint of dispersion stability, the hydrophilic monomer is preferably a monomer containing a dissociable group, and more preferably a monomer containing a dissociable group and an olefinic unsaturated bond. Examples of monomers containing a dissociable group include, for example, carboxyl-containing monomers, sulfonic acid-containing monomers, and phosphate-containing monomers. From the viewpoint of dispersion stability, the hydrophobic monomer is preferably a monomer containing an aromatic group and an olefinic unsaturated bond, or a monomer containing an aliphatic hydrocarbon group and an olefinic unsaturated bond. The polymer can be either a random copolymer or a block copolymer.

[0122] Dispersants can be commercially available products. Examples of commercially available products include:

[0123] 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 (the above are by BYK Chemie Corporation); and

[0124] SOLSPERSE3000, SOLSPERSE5000, SOLSPERSE9000, SOLSPERSE12000, SOLSPERSE13240, SOLSPERSE13940, SOLSPERSE17000, SOLSPERSE22000, SOLSPERSE24000, SOLSPERSE26000, SOLSPERSE28000, SOLSPERSE32000, SOLSPERSE36000, SOLSPERSE39000, SOLSPERSE41000, SOLSPERSE71000 (all manufactured by Lubrizol).

[0125] As a dispersing device for dispersing pigments, known dispersing devices can be used, such as ball mills, sand mills, bead mills, roller mills, jet mills, paint mixers, grinders, ultrasonic dispersers, and dispersers.

[0126] From the viewpoint of dispersion stability, the ratio of dispersant content to pigment content in ink is preferably 0.05 to 1.0 by mass standard.

[0127] <Polymerization initiator>

[0128] The ink, as one embodiment of this disclosure, may contain at least one polymerization initiator. The polymerization initiator is preferably a free radical polymerization initiator that generates free radicals.

[0129] Examples of free radical polymerization initiators, including photoradical polymerization initiators and thermal free radical polymerization initiators, include alkyl phenyl ketone compounds, acylphosphine compounds, aromatic onium salt compounds, organic peroxides, thio compounds, hexaaryl biimidazole compounds, ketoxime ester compounds, borate ester compounds, azazine compounds, metallocene compounds, active ester compounds, compounds with carbon-halogen bonds, and alkylamine compounds.

[0130] 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 thioxanone compounds.

[0131] Examples of acylphosphine oxide compounds include monoacylphosphine oxide compounds and diacylphosphine oxide compounds.

[0132] Examples of monoacylphosphine oxide compounds include isobutyryl diphenylphosphine oxide, 2-ethylhexanoyl diphenylphosphine oxide, 2,4,6-trimethylbenzoyl diphenylphosphine oxide, (2,4,6-trimethylbenzoyl)ethoxyphenylphosphine oxide, o-toluyl diphenylphosphine oxide, p-tert-butylbenzoyl diphenylphosphine oxide, 3-pyridylcarbonyl diphenylphosphine oxide, acryloyl diphenylphosphine oxide, benzoyl diphenylphosphine oxide, and neopentyl phenylphosphine acid. Vinyl ester, adipyl bis(diphenylphosphine oxide), neopentyl diphenylphosphine oxide, p-toluyl diphenylphosphine oxide, 4-(tert-butyl)benzoyl diphenylphosphine oxide, terephthalyl bis(diphenylphosphine oxide), 2-methylbenzoyl diphenylphosphine oxide, tert-carbonyl diphenylphosphine oxide, 2-methyl-2-ethylhexanoyl diphenylphosphine oxide, 1-methyl-cyclohexanoyl diphenylphosphine oxide, neopentyl phenylphosphine methyl ester, and neopentyl phenylphosphine isopropyl ester.

[0133] Examples of diacylphosphine 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)-2-naphthylphosphine oxide. 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-dichlorophenylphosphine oxide -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-naphthyl)-2,5-dimethylphenylphosphine oxide, bis(2-methyl-1-naphthyl)-4-ethoxyphenylphosphine oxide, bis(2-methyl-1-naphthyl) Bis(2-methyl-1-naphthyl)-2-naphthylphosphine oxide, bis(2-methyl-1-naphthyl)-4-propylphenylphosphine oxide, bis(2-methyl-1-naphthyl)-2,5-dimethylphenylphosphine oxide, bis(2-methoxy-1-naphthyl)-4-ethoxyphenylphosphine oxide, bis(2-chloro-1-naphthyl)-2,5-dimethylphenylphosphine oxide, and bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide.

[0134] The preferred acylphosphine oxide compound is 2,4,6-trimethylbenzoyl diphenylphosphine oxide (e.g., the product name "Omnirad TPO-H" manufactured by IGM Resins BV) or bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (e.g., the product name "Omnirad 819" manufactured by IGM Resins BV).

[0135] Examples of 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, 4-butoxycarbonylthioxanthone, 3-butoxycarbonyl-7-methylthioxanthone, 1-cyano-3-chlorothioxanthone, 1-ethoxycarbonyl-3-chlorothioxanthone, 1-ethoxycarbonyl-3-ethoxythioxanthone, 1-ethoxycarbonyl-3-aminothioxanthone, 1-ethoxycarbonyl-3-phenylthioxanthone, 3,4-bis[2-(2-methoxyethoxy)ethoxycarbonyl]thioxanthone, and 1-ethoxycarbonyl -3-(1-methyl-1-morpholinylethyl)thioxanthone, 2-methyl-6-dimethoxymethylthioxanthone, 2-methyl-6-(1,1-dimethoxybenzyl)thioxanthone, 2-morpholinylmethylthioxanthone, 2-methyl-6-morpholinylmethylthioxanthone, n-allylthioxanthone-3,4-dicarboxymethylimide, n-octylthioxanthone-3,4-dicarboxymethylimide, N-(1,1,3,3-tetramethylbutyl)thioxanthone-3,4-dicarboxymethylimide, 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-propaneammonium chloride.

[0136] Thioxanone compounds are commercially available products. Examples of commercially available products include the SPEEDCURE series manufactured by Lambson (e.g., SPEEDCURE 7010, SPEEDCURE CPTX, SPEEDCURE ITX, etc.).

[0137] From the viewpoint of improving curability, the content of polymerization initiator relative to the total amount of ink is preferably 2% by mass or more, more preferably 5% by mass or more. The upper limit of the polymerization initiator content is not particularly limited, for example, it is 15% by mass.

[0138] <Polymerization inhibitors>

[0139] As one embodiment of this disclosure, the ink preferably contains at least one polymerization inhibitor.

[0140] Examples of polymerization inhibitors include hydroquinone compounds, phenothiazines, catechols, alkylphenols, alkyl bisphenols, zinc dimethyl dithiocarbamate, copper dimethyl dithiocarbamate, copper dibutyl dithiocarbamate, copper salicylate, thiodipropionate, mercaptobenzimidazole, phosphites, nitrosamine compounds, hindered amine compounds, and nitryl radicals.

[0141] The polymerization inhibitor is further preferably a nitrosamine compound.

[0142] Examples of nitrosamine compounds include aluminum salts of N-nitroso-N-phenylhydroxylamine and N-nitroso-N-phenylhydroxylamine. The preferred nitrosamine compound is the aluminum salt of N-nitroso-N-phenylhydroxylamine.

[0143] From the viewpoint of improving the long-term stability of ink, the content of the polymerization inhibitor is preferably 0.05% to 1.0% by mass relative to the total amount of ink.

[0144] <Additives>

[0145] As one embodiment of this disclosure, the ink may also contain additives such as resin, co-sensitizer, ultraviolet absorber, antioxidant, anti-fading agent, conductive salt, solvent, and alkaline compound, as needed.

[0146] The viscosity of the ink is preferably 0.5 mPa·s to 50 mPa·s, more preferably 5 mPa·s to 40 mPa·s, more preferably 7 mPa·s to 35 mPa·s, and even more preferably 8 mPa·s to 30 mPa·s. The viscosity is measured using a viscometer at 25°C. For example, a TV-22 type viscometer manufactured by Toki Sangyo Co., Ltd. can be used as the viscometer.

[0147] 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 tension meter at 25°C via the plate method. For example, an automatic surface tension meter (product name "DY-300") manufactured by Kyowa Interface Science Co., Ltd. can be used.

[0148] [Ink Set]

[0149] As one embodiment of this disclosure, the ink group preferably includes the aforementioned ink and a pretreatment liquid. The pretreatment liquid is a liquid applied to the substrate before applying the ink. By applying the pretreatment liquid to the substrate in advance, the flexibility to repeated bending is improved.

[0150] (Option 1)

[0151] As a first option, 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 can be attributed to the fact that, due to the effect of the polyester resin, the generation of residual stress caused by curing shrinkage is suppressed.

[0152] -Polyester resin-

[0153] Polyester resin refers to polymers with ester bonds in their main chain. Polyester resins are typically obtained by reacting dicarboxylic acids with polyols. Examples of dicarboxylic acids include fumaric acid, itaconic acid, adipic acid, sebacic acid, terephthalic acid, isophthalic acid, sulfoisophthalic acid, naphthalic acid, tetrahydrophthalic acid, and cyclohexanedicarboxylic acid. Examples of polyols include ethylene glycol, propylene glycol, glycerol, glycerol, butanediol, hexanediol, 1,4-cyclohexanediethanol, bisphenol A, and hydrogenated bisphenol A.

[0154] The polyester resin is preferably a polyester resin obtained by reacting a dicarboxylic acid having a cyclic structure with a polyol having a cyclic structure. Examples of such polyester resins include DIACHLON FC1588 (manufactured by Mitsubishi Chemical Corporation), NICHIGO-POLYESTER TP219 (manufactured by Mitsubishi Chemical Corporation), UVAD081 (manufactured by OSAKA SODA Corporation), and DIACHLON ER-535 (manufactured by Mitsubishi Chemical Corporation).

[0155] Information about polyester resin and its raw materials is available in, for example, the "Polyester Resin Handbook" (written by Eiichiro Takiyama, published by Nikkan Kogyo Shimbun, 1944).

[0156] In addition, examples of polyester resins include polyhydroxybutyrate (PHB) based, polycaprolactone (PCL) based, polycaprolactone butylene succinate based, polybutylene succinate (PBS) based, polybutylene adipate succinate (PBSA) based, polybutylene succinate-carbonate based, polyethylene terephthalate succinate based, polybutylene adipate terephthalate based, polytetramethylene adipate terephthalate based, polybutylene adipate terephthalate based, polyethylene succinate (PES) based, polyglycolic acid (PGA) based, and polylactic acid (PLA) based polyesters, carbonate copolymers of aliphatic polyesters, and copolymers of aliphatic polyesters and polyamides.

[0157] The weight-average molecular weight of the polyester resin is, for example, 1500 to 10000. The weight-average molecular weight is determined by the same method as described above.

[0158] The content of polyester resin relative to the total amount of pretreatment liquid is preferably 0.5% to 15% by mass, more preferably 1% to 10% by mass.

[0159] -Polymerizing compounds-

[0160] The polymerizable compound contained in the pretreatment solution is not particularly limited and can be either a monofunctional or polyfunctional polymerizable compound. Examples of monofunctional and polyfunctional polymerizable compounds include those that are the same as those that can be contained in the inks described above.

[0161] From the viewpoint of further improving the adhesion between the substrate and the image, the proportion of the monofunctional polymeric compound in the pretreatment solution is preferably 80% by mass or more, more preferably 90% by mass or more. The upper limit of the above proportion is not particularly limited and can be 100% by mass.

[0162] From the viewpoint of odor suppression, the pretreatment liquid preferably contains a monofunctional polymerizable compound as a polymerizable compound comprising at least one structure selected from the group consisting of cyclic ether structures and alicyclic structures, more preferably contains a monofunctional polymerizable compound comprising a cyclic ether structure, and even more preferably contains a monofunctional (meth)acrylate comprising a cyclic ether structure.

[0163] Examples of cyclic ether structures include furan ring structures, pyran ring structures, ethylene oxide ring structures, oxobutane ring structures, dioxane ring structures, dioxopentane ring structures, and morpholine ring structures.

[0164] The number of carbon atoms in the ring constituting the alicyclic structure is not particularly limited, but is preferably 5 to 10. Examples of alicyclic structures include cyclohexane ring structure, bicyclopentyl ring structure, bicyclopentenyl ring structure, norbornane ring structure, isobornane ring structure, norbornene ring structure, isobornene ring structure, and adamantane ring structure.

[0165] Examples of (meth)acrylates containing a cyclic ether structure include acryloylmorpholine, cyclic trimethylolpropane methyl acetal (meth)acrylate, (meth)acrylate-1,4-dioxospiro[4,5]silane-2-yl methyl ester, (meth)acrylate tetrahydrofurfuryl ester, and (2-methyl-2-ethyl-1,3-dioxolane-4-yl)(meth)acrylate methyl ester.

[0166] The content of the monofunctional polymerizable compound comprising at least one structure selected from the group consisting of cyclic ether structures and alicyclic structures is preferably 70% to 90% by mass, more preferably 80% to 85% by mass, relative to the total amount of the pretreatment liquid.

[0167] Furthermore, the pretreatment solution preferably contains a polymerizable silicone surfactant as a polymerizable compound. When the pretreatment solution contains a polymerizable silicone surfactant, image bleeding is suppressed, and scratch resistance is improved.

[0168] As polymerizable silicone surfactants, examples of surfactants that are the same as those that may be included in the aforementioned inks can be cited.

[0169] The content of polymeric organosilicon surfactant relative to the total amount of pretreatment liquid is preferably 3% to 20% by mass, more preferably 5% to 15% by mass.

[0170] From the viewpoint of curability, the content of polymeric compounds is 70% to 95% by mass, more preferably 80% to 90% by mass, relative to the total amount of the pretreatment liquid.

[0171] In the first embodiment, the pretreatment liquid may also contain other components besides polymerizable compounds and polyester resins. Examples of other components include, for instance, polymerization initiators, polymerization inhibitors, and additives. Examples of polymerization initiators, polymerization inhibitors, and additives are the same substances that may be contained in the aforementioned inks.

[0172] (Option 2)

[0173] As a second option, the pretreatment solution preferably contains a polymeric compound A having acid groups. The presence of polymeric compound A with acid groups improves adhesion to the substrate. This can be attributed to the interaction between the acid groups in polymeric compound A and the substrate surface.

[0174] Examples of acid groups in polymeric compounds include carboxyl, sulfonyl, phosphonic acid, phosphate, and sulfonamide groups.

[0175] Examples of polymeric 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.

[0176] Examples of polymeric compounds with sulfonyl groups 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.

[0177] Examples of polymeric compounds having phosphate groups include 2-phosphonoethyl ester of (meth)acrylic acid.

[0178] Among them, polymeric compound A having an acid group is preferably a polymeric compound having a carboxyl group.

[0179] The polymerizable compound A having an acid group can be a monofunctional polymerizable compound having an acid group or a polyfunctional polymerizable compound having an acid group. Preferably, it is 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.

[0180] The content of polymeric compound A with acid groups is preferably 3% to 20% by mass relative to the total amount of ink, more preferably 5% to 15% by mass.

[0181] In the second approach, the pretreatment solution may contain polymerizable compounds other than polymerizable compound A with acid groups as polymerizable compounds.

[0182] Other polymerizable compounds are not particularly limited and may be either monofunctional or polyfunctional polymerizable compounds. Examples of monofunctional and polyfunctional polymerizable compounds include those that are the same as those that may be included in the inks described above.

[0183] From the viewpoint of further improving the adhesion between the substrate and the image, other polymeric compounds preferably include monofunctional polymeric compounds.

[0184] From the viewpoint of odor suppression, the pretreatment liquid preferably contains a monofunctional polymeric compound comprising at least one structure selected from the group consisting of cyclic ether structures and alicyclic structures as other polymeric compounds, more preferably contains a monofunctional polymeric compound comprising a cyclic ether structure, and even more preferably contains a monofunctional (meth)acrylate comprising a cyclic ether structure.

[0185] The content of a monofunctional polymerizable compound comprising at least one of the structures selected from the group consisting of cyclic ether structures and alicyclic structures is preferably 65% ​​to 85% by mass, more preferably 70% to 80% by mass, relative to the total amount of the pretreatment liquid.

[0186] In addition, the pretreatment solution preferably contains polymerizable organosilicon surfactants as other polymerizable compounds.

[0187] As polymerizable silicone surfactants, examples of surfactants that are the same as those that may be included in the aforementioned inks can be cited.

[0188] The content of polymeric organosilicon surfactant relative to the total amount of pretreatment liquid is preferably 3% to 20% by mass, more preferably 5% to 15% by mass.

[0189] From the viewpoint of curability, the content of polymeric compounds relative to the total amount of the pretreatment liquid is preferably 70% to 95% by mass, more preferably 80% to 90% by mass.

[0190] From the viewpoint of further improving the adhesion between the substrate and the image, the proportion of the monofunctional polymeric compound in the pretreatment solution is preferably 80% by mass or more, more preferably 90% by mass or more. The upper limit of the above proportion is not particularly limited and can be 100% by mass.

[0191] In the second embodiment, the pretreatment liquid may contain components other than polymerizable compounds. Examples of such components include polymerization initiators, polymerization inhibitors, and additives. Examples of polymerization initiators, polymerization inhibitors, and additives include substances identical to those found in the inks described above.

[0192] Alternatively, the pretreatment solution may be a solution containing either a polyester resin or a polymeric compound A having acid groups.

[0193] 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, more preferably 7 mPa·s to 35 mPa·s, and even more preferably 8 mPa·s to 30 mPa·s. The viscosity is measured using a viscometer at 25°C. For example, a TV-22 type viscometer manufactured by Toki Sangyo Co., Ltd. can be used as the viscometer.

[0194] The surface tension of the pretreatment liquid is preferably below 60 mN / m, 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 tension meter at 25°C via the plate method. For example, an automated surface tension meter (product name "DY-300") manufactured by Kyowa Interface Science Co., Ltd. can be used.

[0195] [Image recording method]

[0196] The image recording method according to the first embodiment of this disclosure preferably includes: a step of applying the ink to a substrate using an inkjet recording method (hereinafter also referred to as the "ink application step"); and a step of irradiating the applied ink with active energy rays (hereinafter also referred to as the "active energy ray curing step").

[0197] (Ink application process)

[0198] In the ink application process, the ink is applied using an inkjet recording method.

[0199] The type of substrate is not particularly limited; commonly known substrates 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, polycyclic olefin resin, polyimide resin, polycarbonate resin, and polyvinyl acetal. The plastic film can be a film containing only one of these resins, or a film composed of a mixture of two or more of these resins.

[0200] According to the ink described in one embodiment of this disclosure, images with excellent flexibility can be recorded, and therefore, it can also be applied to substrates that are deformable at room temperature. The image with excellent flexibility can follow the deformation of the substrate at room temperature, thus reducing the likelihood of image cracking.

[0201] From the perspective that it can be applied to substrates that are deformable at room temperature, the substrate is preferably metal, plastic, synthetic leather or rubber, and more preferably rubber.

[0202] The thickness of the substrate is not particularly limited. The ink, as an embodiment of this disclosure, is capable of recording images with excellent flexibility; therefore, it can also be applied 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.

[0203] Inkjet recording methods are not particularly limited as long as they are capable of recording images, and can use known methods. Examples of inkjet recording methods include charge control methods that use electrostatic attraction to eject ink, on-demand inkjet methods (pressure pulse methods) that use the vibration pressure of piezoelectric elements, acoustic inkjet methods that convert electrical signals into sound beams to irradiate ink and eject ink using radiation pressure, and thermal inkjet methods (bubble jet, a registered trademark) that heat ink to form bubbles and use the resulting pressure.

[0204] Examples of inkjet heads for inkjet recording include: a shuttle type that uses a short, serial head to scan along the width of the substrate while recording; and a linear type that uses a linear head with recording elements arranged in an overall area corresponding to one side of the substrate.

[0205] In linear scanning, patterns can be formed on the entire surface of the substrate by scanning the substrate in a direction intersecting with the arrangement direction of the recording elements, eliminating the need for a transport system such as a carriage with short scanning sections. Furthermore, linear scanning eliminates the need for carriage movement and complex scanning control of the substrate; only the substrate moves. Therefore, compared to shuttle scanning, it enables significantly higher recording speeds.

[0206] The amount of ink ejected from the inkjet head is preferably 1 pL (picoli) to 100 pL, more preferably 3 pL to 80 pL, and even more preferably 3 pL to 50 pL.

[0207] (Active Energy X-ray Curing Process)

[0208] In the active energy ray curing process, the ink is irradiated with active energy rays.

[0209] Examples of active energy rays include gamma rays, beta rays, electron beams, ultraviolet light, and visible light. Among these, ultraviolet light is preferred.

[0210] The peak wavelength of the ultraviolet light is preferably 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 highest intensity in the ultraviolet band (e.g., 200 nm to 405 nm).

[0211] Mercury lamps, gas lasers, and solid-state lasers are commonly used as light sources for ultraviolet (UV) irradiation, with mercury lamps, metal halide lamps, and UV fluorescent lamps being widely known. Additionally, UV-LEDs (ultraviolet light-emitting diodes) and UV-LDs (ultraviolet laser diodes) are promising candidates for use as UV irradiation light sources 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 UV irradiation light sources.

[0212] In this disclosure, the polymerization of only a portion of the polymerizable compounds in the ink is referred to as "temporary curing," and the irradiation of the active energy rays used for temporary curing is referred to as "fixed exposure."

[0213] In this disclosure, the process of substantially all polymerizing the polymerizable compounds in the ink is referred to as "formal curing," and the irradiation by active energy rays used for formal curing is referred to as "formal exposure."

[0214] In the process of irradiating with active energy rays, it is preferable to temporarily cure the ink before formally curing it. Specifically, it is preferable to apply the ink, subject it to fixed exposure, and then perform formal exposure.

[0215] The reaction rate of the ink after fixed exposure is preferably 10% to 80%.

[0216] Here, the reaction rate of ink refers to the polymerization rate of the polymeric compounds contained in the ink, as determined by high-performance liquid chromatography.

[0217] Because the ink has a reaction rate of over 10%, the interference between ink droplets is suppressed, resulting in improved image quality.

[0218] In addition, since the ink reaction rate is below 80%, insufficient dot diffusion is suppressed, resulting in improved graininess of the final image.

[0219] From the viewpoint of further improving the image quality of the final image, the ink reaction rate is preferably 15% or higher.

[0220] From the viewpoint of further improving the graininess of the final image, the ink reaction rate is preferably 75% or less, more preferably 50% or less, more preferably 40% or less, more preferably 30% or less, and even more preferably 25% or less.

[0221] The reaction rate of the ink after formal exposure is preferably greater than 80% and less than 100%, more preferably 85% to 100%, and even more preferably 90% to 100%.

[0222] When the reaction rate exceeds 80%, the sealing performance is further improved.

[0223] The reaction rate of the ink was determined by the following method.

[0224] A substrate was prepared for operation until the irradiation of the ink with active energy rays was completed. A 20 mm × 50 mm sample (hereinafter referred to as the irradiated sample) was cut from the area of ​​the substrate where the ink film was present. The cut irradiated sample was immersed in 10 mL of THF (tetrahydrofuran) for 24 hours to obtain the eluent after ink elution. The amount of polymerizable compound (hereinafter referred to as "amount of compound after irradiation X1") was determined from the obtained eluent by high performance liquid chromatography.

[0225] In addition, except that the ink on the substrate is not irradiated with active energy rays, the same operation as above is performed to determine the amount of polymerizable monomer (hereinafter referred to as "amount of compound without irradiation X1").

[0226] Based on the amount of compound X1 after irradiation and the amount of compound X1 before irradiation, the reaction rate (%) of the ink is calculated using the following formula.

[0227] Ink reaction rate (%) = ((Compound amount before irradiation X1 - Compound amount after irradiation X1) / Compound amount before irradiation X1) × 100

[0228] From the viewpoint that it is easier to achieve the above-mentioned ink reaction rate, the exposure amount of the active energy rays used for fixed exposure is preferably 10 mJ / cm. 2 ~100mJ / cm 2 More preferably 20 mJ / cm 2 ~60mJ / cm 2 .

[0229] From the viewpoint of ensuring complete curing of the ink, the exposure dose of the active energy rays used for formal exposure is preferably 50 mJ / cm. 2 ~1000mJ / cm 2 More preferably 200 mJ / cm 2 ~800mJ / cm 2 .

[0230] In formal exposure, from the viewpoint of improving adhesion to the substrate, it is preferable to irradiate with active energy rays in an atmosphere with an oxygen concentration of less than 1 vol%. More preferably, the oxygen concentration is 0.5 vol% or less, and even more preferably 0.3 vol% or less.

[0231] 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 drips. In the case of fixed exposure and formal exposure, it is preferable to irradiate with active energy rays used for fixed exposure within 0.1 to 5 seconds from the time the ink drips. More preferably, the time from the time the ink drips to the irradiation with active energy rays (in the case of fixed exposure and formal exposure) is within 0.2 to 1 second.

[0232] Next, the image recording method using the above-described ink set will be explained.

[0233] The image recording method according to the second embodiment of this disclosure preferably uses the above-described ink group, which includes: a step of applying the pretreatment liquid and the ink to a substrate using an inkjet recording method; and a step of irradiating the pretreatment liquid and the ink with active energy rays after applying them respectively.

[0234] The process of applying the pretreatment solution and the process of applying the ink are the same as the ink application process described above.

[0235] In the process of irradiating with active energy rays, it is preferable to first apply a pretreatment solution, then fix and expose the pretreatment solution, apply ink to the temporarily cured pretreatment solution, fix and expose the ink after applying the ink, and finally perform formal exposure.

[0236] The preferred methods for fixed exposure and formal exposure are the same as those for fixed exposure and formal exposure in the above-mentioned active energy X-ray curing process.

[0237] [Example]

[0238] The present disclosure will be further described in detail below through embodiments, but the present disclosure is not limited to the following embodiments as long as it does not depart from its spirit.

[0239] The details of the components contained in the inks prepared in the examples and comparative examples are described below.

[0240] (Monofunctional polymeric compounds)

[0241] • NVC: N-vinylcaprolactam (manufactured by BASF)

[0242] • PEA: Phenoxyethyl acrylate (product name "SR339A", manufactured by Sartomer)

[0243] • CHA: Cyclohexyl acrylate (product name "VISCOAT#155, CHA", manufactured by Osaka Organic Chemical Industry Co., Ltd.)

[0244] • TMCHA: Trimethylcyclohexyl acrylate (product name "SR420", manufactured by Sartamomer)

[0245] THFA: Tetrahydrofurfuryl acrylate (product name "SR285", manufactured by Sartamomer)

[0246] •LA: Dodecyl acrylate (product name "SR335", manufactured by Sartomer)

[0247] • CTFA: Cyclic trimethylolpropane methyl acetal acrylate (product name "SR531", manufactured by Sartamomer)

[0248] • IBOA: Isoborneol acrylate (product name "SR506", manufactured by Sartomer)

[0249] • 4-HBA: 4-Hydroxybutyl acrylate (product name "4-HBA", manufactured by Osaka Organic Chemical Industry Co., Ltd.)

[0250] • IOA: Isooctyl acrylate (product name "SR440", manufactured by Sartamomer)

[0251] • A-SA: 2-Acryloyloxyethylsuccinic acid (product name "NK ESTER A-SA", manufactured by Shin-Nakamura Chemical Industry Co., Ltd.; a polymeric compound A containing an acid group)

[0252] (Difunctional polymeric compounds)

[0253] • HDDA: 1,6-Hexanediol diacrylate (product name "VISCOAT#230, HDDA", manufactured by Osaka Organic Chemical Industry Co., Ltd.)

[0254] •DDDA: 1,10-decanediol diacrylate (product name "A-DOD-N", manufactured by Shin-Nakamura Chemical Industry Co., Ltd.)

[0255] •PEGDA200: Polyethylene glycol #200 diacrylate (product name "A-200", manufactured by Shin-Nakamura Chemical Industry Co., Ltd.)

[0256] • PEGDA600: Polyethylene glycol #600 diacrylate (product name "A-600", manufactured by Shin-Nakamura Chemical Industry Co., Ltd.)

[0257] • PPGDA700: Polypropylene glycol #700 diacrylate (product name "APG-700", manufactured by Shin-Nakamura Chemical Industry Co., Ltd.)

[0258] • NPGDA: Neopentyl glycol diacrylate (product name "light acrylate NP-A", manufactured by Kyoeisha Chemical Co., Ltd.)

[0259] • TCDDMDA: Tricyclodecanedimethyl diacrylate (product name "EBECRYL 130", manufactured by Daicel Allnex)

[0260] HMPA: 2-Hydroxy-3-acrylate (product name "701A", manufactured by Shin-Nakamura Chemical Industry Co., Ltd.)

[0261] •PEGDA1000: Polyethylene glycol #1000 diacrylate (product name "A-1000", manufactured by Shin-Nakamura Chemical Industry Co., Ltd.)

[0262] (Polymerizable silicone surfactants)

[0263] • Tegorad 2100 (manufactured by Evonik)

[0264] ·Tegorad2010 (Made by Evonik)

[0265] (pigment)

[0266] • White pigment: Titanium dioxide (product name "KRONOS2300", manufactured by KRONOS Corporation)

[0267] • Cyan pigment: Pigment Blue 15:4 (product name "Heliogen Blue D7110F", manufactured by BASF JAPAN)

[0268] • Magenta pigment: Product name "CINQUASIA MAGENTA L4540", manufactured by BASF JAPAN

[0269] • Yellow pigment: Pigment Yellow 155 (product name "Inkjet Yellow 4GC", manufactured by Clariant)

[0270] • Black pigment: Carbon black (product name "Mogul E", manufactured by Cabot Corporation)

[0271] (Dispersant)

[0272] SOLSPERSE41000 (made by Lubrizol)

[0273] SOLSPERSE 32000 (made by Lubrizol)

[0274] ·Efka7731 (Made by BASF JAPAN)

[0275] • BYKJET9151 (Made by BYK Corporation)

[0276] (Polymerization initiator)

[0277] • Omn.184: 1-Hydroxycyclohexyl-phenyl ketone (product name "Omnirad184", manufactured by IGM Resins BV)

[0278] • Omn. 819: Bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (product name "Omnirad 819", manufactured by IGMresins BV)

[0279] • ITX: Isopropylthioxanthone (product name "SPEEDCURE ITX", manufactured by Lambson)

[0280] • TPO: 2,4,6-Trimethylbenzoyl diphenylphosphine oxide (product name "Omnirad TPO-H", manufactured by IGMresins BV)

[0281] (polymerization inhibitor)

[0282] • UV12: Aluminum salt of N-nitroso-N-phenylhydroxylamine (product name "FLORSTAB UV12", manufactured by Kromachem)

[0283] (additive)

[0284] • BR113: Acrylic resin (product name "Dianal BR113", manufactured by Mitsubishi Chemical Corporation)

[0285] -Ink Preparation-

[0286] <Example 1>

[0287] First, a white pigment dispersion was prepared. Specifically, the following components were loaded into an electric stirred mill M50 (manufactured by EIGER), and dispersed using 0.65 mm diameter zirconia beads at a circumferential speed of 9 m / s for 4 hours to obtain a white pigment dispersion.

[0288] White pigment…50 parts by weight

[0289] Dispersant (product name "SOLSPERSE41000", manufactured by Lubrizol)...3.53 parts by weight; PEA...45.47 parts by weight

[0290] UV12…1 part by weight

[0291] Next, mix the following ingredients. Using a mixer (product name "L4R", manufactured by SIVERSON), stir the mixture for 20 minutes at 25°C and 5000 rpm to obtain white ink.

[0292] • The prepared white pigment dispersion…15 parts by weight

[0293] ·PEA…49.6 parts by weight

[0294] ·HDDA…1 part by weight

[0295] ·NVC…21.5 parts by weight

[0296] ·BR113…2.4 parts by weight

[0297] ·UV12…0.42 parts by weight

[0298] ·Omni.184…2.8 parts by weight

[0299] ·TPO…8 parts by weight

[0300] <Examples 2 to 17, Comparative Examples 1 to 6>

[0301] The content of each polymeric compound in the ink was adjusted to the levels recorded in Tables 1 to 3, and the ink was otherwise obtained using the same method as in Example 1. Tables 1 to 3 list the proportions (mass %) of each component based on the total amount of polymeric compounds. In Examples 2 to 17 and Comparative Examples 1 to 6, the types and contents of components other than polymeric compounds in the ink were the same as in Example 1.

[0302] -Image Recording-

[0303] The prepared white ink was introduced into the white throttling element of an inkjet recording device (product name "Acuity LED 1600R", manufactured by Fujifilm). Synthetic leather (product name "Captain", manufactured by YAMPLAS, 1mm thick) and stainless steel plate (product name "Stainless Steel Plate <<Stainless Steel Plate>>", manufactured by Yahata Neji, 1mm thick) were used as substrates. The ink application conditions were set to 1200 dpi × 1200 dpi, 48 passes, and bidirectional printing, recording 100% solid image. Here, dpi is short for dots per inch.

[0304] By setting the lamp work on the inkjet recording device, the ink applied to the substrate is sequentially irradiated with ultraviolet light (peak wavelength 385nm) for fixed exposure and ultraviolet light (peak wavelength 385nm) for final exposure. The exposure dose for fixed exposure is set to 400mJ / cm². 2 The official exposure level was set at 1200 mJ / cm². 2 .

[0305] Based on the above conditions, the ink applied to the substrate is subjected to fixed exposure and formal exposure in sequence to obtain image recordings. The image recording with the image on the synthetic leather is designated as "Image Recording 1", and the image recording with the image on the stainless steel plate is designated as "Image Recording 2".

[0306] [evaluate]

[0307] For each embodiment and comparative example, the obtained image recordings were evaluated for flexibility, anti-adhesion, and adhesion. The evaluation methods are described below.

[0308] <Flexibility>

[0309] Image recording 1 was bent 180 degrees at room temperature (23°C). After bending, the presence of cracks and peeling of the image was visually inspected.

[0310] The image recording material 2 was stamped at room temperature (23°C) and bent at 90 degrees. After bending, the presence of cracks and peeling of the image was visually inspected.

[0311] The evaluation criteria are as follows.

[0312] A: Absolutely no cracks or peeling.

[0313] B: At least one of the cracks and spalling is present in small amounts.

[0314] C: At least one of the cracks and spalling can be identified as numerous.

[0315] <Anti-adhesion>

[0316] In image recordings 1 and 2, the stickiness of the image surface was confirmed by touch. The evaluation criteria are as follows.

[0317] A: It's not sticky at all.

[0318] B: It is slightly sticky.

[0319] C: Very sticky.

[0320] <Seamlessness>

[0321] Image recordings 1 and 2 were subjected to a scribing test according to ISO 2409 (cross-scribing method). In the cross-scribing test, the scribing interval was set to 1 mm, forming 25 square grids of 1 mm each. The tightness was evaluated based on the percentage (%) of grid peeling off. The percentage (%) of grid peeling off was calculated using the following formula. The total number of grids in the following formula is 25.

[0322] Percentage of cells peeling off (%) = [(Number of cells peeling off) / (Total number of cells)] × 100

[0323] The evaluation criteria are as follows.

[0324] A: The percentage of grid lines peeling off is 0%.

[0325] B: The percentage of grid peeling (%) is greater than 0% and less than 5%.

[0326] C: The percentage of grid peeling (%) exceeds 5%.

[0327] The evaluation results are shown in Tables 1 to 3.

[0328] In Tables 1-3, the glass transition temperature (Tg) for preparing homopolymers is listed for monofunctional polymerizable compounds other than N-vinyl compounds. For difunctional (meth)acrylates, the number of carbon atoms in the moiety excluding the (meth)acryloyl group is listed. 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.

[0329] [Table 1]

[0330]

[0331] [Table 2]

[0332]

[0333] [Table 3]

[0334]

[0335] As shown in Tables 1 and 2, in Examples 1 to 17, polymerizable compounds and colorants were included. The polymerizable compounds included N-vinyl compounds, monofunctional polymerizable compounds with a Tg of -30°C to 30°C when forming homopolymers, and compounds selected from the group consisting of difunctional (meth)acrylates and polymerizable organosilicon surfactants. The total content of monofunctional polymerizable compounds other than N-vinyl compounds with a Tg below -30°C when forming homopolymers and monofunctional polymerizable compounds with a Tg above 30°C when forming homopolymers was less than 10% by mass relative to the total amount of polymerizable compounds. The total content of compounds selected from the group consisting of difunctional (meth)acrylates and polymerizable organosilicon surfactants was 0.1% to 2% by mass relative to the total amount of polymerizable compounds. Therefore, images with softness and excellent anti-blocking properties were obtained.

[0336] On the other hand, as shown in Table 3, in Comparative Example 1 and Comparative Example 2, the total content of monofunctional polymeric compounds with a Tg exceeding 30°C when forming homopolymers exceeded 10% by mass, resulting in poor image flexibility.

[0337] It can be seen that in Comparative Examples 3 and 4, the total content of monofunctional polymeric compounds with a Tg lower than -30°C when forming homopolymers exceeded 10% by mass, resulting in poor anti-blocking properties of the images.

[0338] It can be seen that in Comparative Example 5, the images do not contain compounds selected from the group consisting of difunctional (meth)acrylates and polymeric organosilicon surfactants, resulting in poor anti-adhesion properties.

[0339] It can be seen that in Comparative Example 6, the total content of the compounds selected from the group consisting of difunctional (meth)acrylates and polymeric organosilicon surfactants exceeded 2% by mass relative to the total amount of polymeric compounds, resulting in poor image softness.

[0340] It can be seen that in Example 1, the content of N-vinyl compound is 10% to 35% by mass relative to the total amount of polymerizable compound, and the content of monofunctional polymerizable compound with glass transition temperature of -30°C to 30°C when making homopolymer is 60% to 85% by mass relative to the total amount of polymerizable compound. Therefore, compared with Example 2 and Example 3, the anti-blocking property is excellent.

[0341] It is known that Example 1 contains phenoxyethyl acrylate, and therefore has excellent adhesion compared to Examples 4 to 7.

[0342] It is known that in Example 1, the number of carbon atoms in the (meth)acryloyl portion of the difunctional (meth)acrylate is 4 or more, thus exhibiting superior softness compared to Example 14. Furthermore, it is also known that in Example 1, the number of carbon atoms in the (meth)acryloyl portion of the difunctional (meth)acrylate is 36 or less, thus exhibiting superior anti-blocking properties compared to Example 15.

[0343] <Example 101>

[0344] The components in the white pigment dispersion were changed to the following components, and cyan pigment dispersion, magenta pigment dispersion, yellow pigment dispersion and black pigment dispersion were prepared using the same method as the white pigment dispersion.

[0345] (Cyan pigment dispersion)

[0346] • Cyan pigment…30 parts by weight

[0347] ·PEA…52 parts by weight

[0348] SOLSPERSE 32000 (manufactured by Noveon)... 17 parts by weight

[0349] ·UV12…1 part by weight

[0350] (Magenta pigment dispersion)

[0351] • Magenta pigment…30 parts by weight

[0352] ·PEA…56 parts by weight

[0353] SOLSPERSE 32000…12.5 parts by weight

[0354] ·UV12…1.5 parts by weight

[0355] (Yellow pigment dispersion)

[0356] Yellow pigment…33.9 parts by weight

[0357] ·PEA…58.2 parts by weight

[0358] SOLSPERSE 32000…6.8 parts by weight

[0359] ·UV12…1.1 parts by weight

[0360] (Black pigment dispersion)

[0361] Black pigment…40 parts by weight

[0362] ·PEA…45.47 parts by weight

[0363] ·Efka7731…3.53 parts by weight

[0364] ·UV12…1 part by weight

[0365] The components of the white ink are changed to the following components, and cyan ink, magenta ink, yellow ink and black ink are prepared using the same method as the white ink.

[0366] (Cyan ink)

[0367] • The prepared cyan pigment dispersion… 8.3 parts by weight

[0368] ·PEA…58.07 parts by weight

[0369] ·HDDA…1 part by weight

[0370] ·NVC…21.7 parts by weight

[0371] BR113…2.98 parts by weight

[0372] ·UV12…0.35 parts by weight

[0373] ·ITX…1 part by weight

[0374] ·Omni.184…2.8 parts by weight

[0375] ·Omni.819…3.8 parts by weight

[0376] (Magenta ink)

[0377] • Prepared magenta pigment dispersion…13.5 parts by weight • PEA…55.24 parts by weight

[0378] ·HDDA…1 part by weight

[0379] ·NVC…21.7 parts by weight

[0380] BR113…1.58 parts by weight

[0381] ·UV12…0.18 parts by weight

[0382] BYKJET9151…0.9 parts by weight

[0383] ·ITX…1 part by weight

[0384] ·Omni.184…1.4 parts by weight

[0385] • Omni.819…3.5 parts by weight (yellow ink)

[0386] • The prepared yellow pigment dispersion…7.6 parts by weight • PEA…57.86 parts by weight

[0387] ·HDDA…1 part by weight

[0388] ·NVC…21.7 parts by weight

[0389] BR113…2.7 parts by weight

[0390] ·UV12…0.34 parts by weight

[0391] ·BYKJET9151…1 part by weight

[0392] ·ITX…1 part by weight

[0393] ·Omni.184…2.9 parts by weight

[0394] • Omni.819…3.9 parts by weight (black ink)

[0395] • The prepared black pigment dispersion…7.6 parts by weight • PEA…58.55 parts by weight

[0396] ·HDDA…1 part by weight

[0397] ·NVC…21.7 parts by weight

[0398] ·BR113…3 parts by weight

[0399] ·UV12…0.35 parts by weight

[0400] ·ITX…1 part by weight

[0401] ·Omni.184…2.9 parts by weight

[0402] ·Omni.819…3.9 parts by weight

[0403] The prepared cyan ink, magenta ink, yellow ink, black ink, and white ink from Example 1 were introduced into the cyan, magenta, yellow, black, and white throttling elements of an inkjet recording device (product name "Acuity LED 1600R", manufactured by Fujifilm). Synthetic leather (product name "Captain", manufactured by YAMPLAS, 1mm thick) and stainless steel plate (product name "Stainless Steel Plate <<Stainless Steel Plate>>", manufactured by Yahata Neji, 1mm thick) were used as substrates. The ink application conditions were set to 1200dpi × 1200dpi, 48 passes, and bidirectional printing. The dot ratio of the white ink was set to 100%, and the dot ratios of the cyan, magenta, yellow, and black inks were each set to 50%, recording solid images.

[0404] By setting the lamp work on the inkjet recording device, the ink applied to the substrate is sequentially irradiated with ultraviolet light (peak wavelength 385nm) for fixed exposure and ultraviolet light (peak wavelength 385nm) for final exposure. The exposure dose for fixed exposure is set to 400mJ / cm². 2 The official exposure level was set at 1200 mJ / cm². 2 .

[0405] Based on the above conditions, white ink, yellow ink, magenta ink, cyan ink, and black ink are sequentially applied to the substrate. After applying each ink, a fixed exposure is performed. After the final fixed exposure, a formal exposure is performed to obtain the image record.

[0406] In Example 101, the softness, anti-adhesion, and adhesion were evaluated using the same method as in Example 1. In either case, whether the substrate was synthetic leather or metal, the evaluation for softness, anti-adhesion, and adhesion was "A".

[0407] <Example 201, Example 202>

[0408] As in Example 201, an ink set comprising pretreatment liquid 1 and white ink of Example 1 is prepared.

[0409] As in Example 202, an ink set comprising pretreatment liquid 2 and white ink of Example 1 is prepared.

[0410] [Preparation of Pretreatment Solution 1]

[0411] Mix the following ingredients. Stir the mixture for 20 minutes at 25°C and 5000 rpm using a mixer (product name "L4R", manufactured by SIVERSON) to obtain pretreatment solution 1.

[0412] ·CTFA…83 parts by weight

[0413] • Polyester resin (product name "DIACHLON FC-1588", manufactured by Mitsubishi Chemical Corporation)...3 parts by weight

[0414] ·Tegorad 2100…10 parts by weight

[0415] ·Omn.819…3.8 parts by weight

[0416] ·UV12…0.2 parts by weight

[0417] [Preparation of Pretreatment Solution 2]

[0418] Mix the following ingredients. Stir the mixture for 20 minutes at 25°C and 5000 rpm using a mixer (product name "L4R", manufactured by SIVERSON) to obtain pretreatment solution 2.

[0419] ·CTFA…76 parts by weight

[0420] ·A-SA…10 parts by weight

[0421] ·Tegorad 2100…10 parts by weight

[0422] ·Omn.819…3.8 parts by weight

[0423] ·UV12…0.2 parts by weight

[0424] The prepared pretreatment liquid and the white ink from Example 1 were introduced into the transparent and white throttling element of the inkjet recording device (product name "Acuity LED 1600R", manufactured by Fujifilm). In Example 201, pretreatment liquid 1 was introduced as the pretreatment liquid, and in Example 202, pretreatment liquid 2 was introduced as the pretreatment liquid. Synthetic leather (product name "Captain", manufactured by YAMPLAS, 1 mm thick) and stainless steel plate (product name "Stainless Steel Plate", manufactured by Yahata Neji, 1 mm thick) were used as substrates. The pretreatment liquid and ink were applied at 1200 dpi × 1200 dpi, 48 passes, and bidirectional printing, recording 100% solid images.

[0425] By setting the lamp work on the inkjet recording device, the ink applied to the substrate is sequentially irradiated with ultraviolet light (peak wavelength 385nm) for fixed exposure and ultraviolet light (peak wavelength 385nm) for final exposure. The exposure dose for fixed exposure is set to 400mJ / cm². 2 The official exposure level was set at 1200 mJ / cm². 2 .

[0426] Based on the above conditions, a pretreatment liquid and white ink are sequentially applied to the substrate. After applying the pretreatment liquid and white ink, fixed exposure is performed respectively. After the final fixed exposure, formal exposure is performed to obtain the image record.

[0427] In Examples 201 and 202, the softness, anti-adhesion, and adhesion were evaluated using the same method as in Example 1. In either case where the substrate was synthetic leather or metal, the evaluation for softness, anti-adhesion, and adhesion was "A".

[0428] Furthermore, when using synthetic leather as the base material, the suppleness was evaluated through repeated bending. The evaluation method is described below.

[0429] <Through the flexibility of repeated bending>

[0430] Image recordings using synthetic leather as the substrate were bent 180 degrees at room temperature (23°C) and then returned to their original state. This operation was repeated 100 times. After 100 operations, the presence of cracks or peeling in the image was visually inspected.

[0431] In either Example 201 or Example 202, no cracks or peeling were observed in the evaluation of flexibility during repeated bending.

[0432] Furthermore, the publication of Japanese Patent Application No. 2021-135103, filed on August 20, 2021, is incorporated herein by reference in its entirety. Additionally, all documents, patent applications, and technical standards described in this specification are incorporated herein by reference to the extent that each document, patent application, and technical standard incorporated herein by reference is specifically and separately described therein.

Claims

1. An active energy radiation-curable ink, comprising a polymerizable compound and a colorant, The polymerizable compounds include N-vinyl compounds, monofunctional polymerizable compounds with a glass transition temperature of -30°C to 30°C when formed into homopolymers, and compounds selected from the group consisting of difunctional (meth)acrylates and polymerizable organosilicon surfactants. Furthermore, the total content of monofunctional polymeric compounds other than the aforementioned N-vinyl compounds, whose glass transition temperature when forming homopolymers is below -30°C, and monofunctional polymeric compounds whose glass transition temperature when forming homopolymers exceeds 30°C, is 0% to 10% by mass relative to the total amount of polymeric compounds. The total content of the compounds selected from the group consisting of the difunctional (meth)acrylate and the polymerizable organosilicon surfactant is 0.5% to 2% by mass relative to the total amount of the polymerizable compounds. The content of the monofunctional polymeric compound with a glass transition temperature of -30°C to 30°C when the homopolymer is formed is 71.5% to 85% by mass relative to the total amount of the polymeric compound.

2. The active energy radiation-curable ink according to claim 1, wherein, The content of the N-vinyl compound is 10% to 35% by mass relative to the total amount of the polymerizable compound.

3. The active energy radiation curable ink according to claim 1 or claim 2, wherein, The N-vinyl compound contains N-vinylcaprolactam.

4. The active energy radiation curable ink according to claim 1 or claim 2, wherein, The monofunctional polymeric compound having a glass transition temperature of -30°C to 30°C when forming a homopolymer includes phenoxyethyl acrylate.

5. The active energy radiation curable ink according to claim 1 or claim 2, wherein, The difunctional (meth)acrylate has 4 to 36 carbon atoms in the portion other than the (meth)acryloyl group.

6. The active energy radiation curable ink according to claim 1 or claim 2, wherein, The polymeric compound contains the polymeric organosilicon surfactant.

7. An ink assembly comprising an active energy radiation-curable ink and a pretreatment liquid, said pretreatment liquid comprising a polymerizable compound and a polyester resin. The active energy ray curable ink contains polymeric compounds and colorants. The polymerizable compounds include N-vinyl compounds, monofunctional polymerizable compounds with a glass transition temperature of -30°C to 30°C when formed into homopolymers, and compounds selected from the group consisting of difunctional (meth)acrylates and polymerizable organosilicon surfactants. Furthermore, the total content of monofunctional polymeric compounds other than the aforementioned N-vinyl compounds, whose glass transition temperature when forming homopolymers is below -30°C, and monofunctional polymeric compounds whose glass transition temperature when forming homopolymers exceeds 30°C, is 0% to 10% by mass relative to the total amount of polymeric compounds. The total content of the compounds selected from the group consisting of the difunctional (meth)acrylate and the polymerizable organosilicon surfactant is 0.5% to 2% by mass relative to the total amount of polymerizable compounds.

8. The ink group according to claim 7, wherein, The content of the N-vinyl compound is 10% to 35% by mass relative to the total amount of the polymerizable compound. The content of the monofunctional polymeric compound with a glass transition temperature of -30°C to 30°C when the homopolymer is formed is 60% to 85% by mass relative to the total amount of the polymeric compound.

9. The ink assembly according to claim 7, wherein, The pretreatment solution contains a polymeric compound A having an acid group.

10. The ink assembly according to claim 7, wherein, The monofunctional polymerizable compound accounts for 80% to 100% by mass of the polymerizable compound contained in the pretreatment solution.

11. The ink set according to any one of claims 7 to 10, wherein, The N-vinyl compound contains N-vinylcaprolactam.

12. The ink set according to any one of claims 7 to 10, wherein, The monofunctional polymeric compound having a glass transition temperature of -30°C to 30°C when forming a homopolymer includes phenoxyethyl acrylate.

13. The ink set according to any one of claims 7 to 10, wherein, The difunctional (meth)acrylate has 4 to 36 carbon atoms in the portion other than the (meth)acryloyl group.

14. The ink set according to any one of claims 7 to 10, wherein, The polymeric compound contains the polymeric organosilicon surfactant.

15. An image recording method, comprising: A process of applying an active energy ray curable ink according to any one of claims 1 to 6 onto a substrate; as well as The process of irradiating an ink that is cured by applied active energy rays with active energy rays.

16. The image recording method according to claim 15, wherein, The thickness of the substrate is 1mm to 5mm.

17. The image recording method according to claim 15, wherein, The substrate is metal, plastic, synthetic leather, or rubber.

18. An image recording method using the ink set according to any one of claims 7 to 14, It includes: The process of applying the pretreatment liquid and the ink to a substrate using an inkjet recording method; as well as The process of irradiating the pretreatment liquid and the ink with active energy rays.

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