Inkjet ink and inkjet recording method

Abstract

Provided are: an inkjet ink containing water and particles containing a polymer (P) having an acid group and a polymerizable compound (A) having two or more ethylenically unsaturated groups in one molecule and having a weight-average molecular weight of 1000 or more;

Description

Technical Field

[0001] The present invention relates to an inkjet ink and an inkjet recording method. Background Art

[0002] Conventionally, various studies have been conducted on inkjet inks and inkjet recording methods.

[0003] For example, Japanese Patent No. 6584677 discloses an inkjet ink composition comprising water, a chain polymer including a specific structural unit (1), a specific structural unit (2) and a hydrophilic group, and particles including a polymerizable group.

[0004] Furthermore, Japanese Patent Gazette No. 6047904 discloses an inkjet recording method, which includes: a first step of ejecting droplets of a photocurable ink composition from a nozzle toward a recording medium and causing the droplets to land to form an image, wherein the photocurable ink composition contains a solvent, a polymerizable compound, and a photopolymerization initiator, and the polymerizable compound is particles dispersed in the solvent; a second step of evaporating the solvent contained in the photocurable ink composition constituting the image; and a third step of irradiating the image after the second step with light, wherein at the start of irradiation in the third step, the content of the polymerizable compound contained in the photocurable ink composition constituting the image after the second step is 20 to 90% by mass relative to the total mass of the ink composition. Summary of the invention

[0005] Technical issues to be solved by the invention

[0006] However, conventionally, it has been difficult to achieve both abrasion resistance and stretchability of an image recorded by an inkjet recording method.

[0007] The present invention has been made in view of such circumstances, and an object of the embodiments of the present invention is to provide an inkjet ink and an inkjet recording method capable of recording an image having excellent abrasion resistance and stretchability.

[0008] Means for solving technical problems

[0009] The present invention includes the following aspects.

[0010] <1>

[0011] An inkjet ink comprising water and particles containing a polymer P having an acid group and a polymerizable compound A.

[0012] The polymerizable compound A has two or more ethylenically unsaturated groups in one molecule and has a weight average molecular weight of 1,000 or more.

[0013] <2>

[0014] The inkjet ink according to <1>, wherein the ethylenically unsaturated group is a (meth)acryloyl group.

[0015] <3>

[0016] The inkjet ink according to <1> or <2>, wherein the polymerizable compound A is a urethane (meth)acrylate having two or more (meth)acryloyl groups in one molecule.

[0017] <4>

[0018] The inkjet ink according to any one of <1> to <3>, wherein the polymerizable compound A includes a polymerizable compound A1 having 6 or more ethylenically unsaturated groups in one molecule.

[0019] <5>

[0020] The inkjet ink according to <4>, wherein the polymerizable compound A1 has 10 or more ethylenically unsaturated groups in one molecule.

[0021] <6>

[0022] The inkjet ink according to any one of <1> to <5>, wherein the polymerizable compound A contains a polymerizable compound A2 having two or three ethylenically unsaturated groups in one molecule and having a weight average molecular weight of 2,000 or more.

[0023] <7>

[0024] The inkjet ink according to <6>, wherein the polymerizable compound A2 has two ethylenically unsaturated groups in one molecule and has a weight average molecular weight of 4,000 or more.

[0025] <8>

[0026] The inkjet ink according to any one of <1> to <7>, wherein the polymerizable compound A comprises: a polymerizable compound A1 having 6 or more ethylenically unsaturated groups in one molecule; and a polymerizable compound A2 having 2 or 3 ethylenically unsaturated groups in one molecule and a weight average molecular weight of 2000 or more.

[0027] <9>

[0028] The inkjet ink according to <8>, wherein a ratio of the content of the polymerizable compound A1 to the total content of the polymerizable compound A1 and the polymerizable compound A2 is 0.2 to 0.8.

[0029] <10>

[0030] The inkjet ink according to any one of <1> to <9>, wherein the ratio of the content of the polymerizable compound A to the total content of the polymer P having an acid group and the polymerizable compound A is 0.3 to 0.7.

[0031] <11>

[0032] The inkjet ink according to any one of <1> to <10>, wherein the particles further contain a polymerizable compound B which is a monofunctional polymerizable compound having a ring structure.

[0033] <12>

[0034] The inkjet ink according to <11>, wherein a ratio of the content of the polymerizable compound B to the total content of the polymerizable compound A and the polymerizable compound B is 0.2 to 0.5.

[0035] <13>

[0036] The inkjet ink according to any one of <1> to <12>, wherein a content of (meth)acrylic acid contained in the inkjet ink after the storage test is 0.1% by mass or less.

[0037] <14>

[0038] An inkjet recording method comprising the steps of: applying the inkjet ink described in any one of <1> to <13> to a substrate by an inkjet recording method; and irradiating the inkjet ink applied to the substrate with active energy rays.

[0039] Effects of the Invention

[0040] According to the present invention, there are provided an inkjet ink and an inkjet recording method capable of recording an image having excellent abrasion resistance and stretchability. DETAILED DESCRIPTION

[0041] In the present invention, a numerical range expressed using "to" indicates a range including the numerical values ​​before and after "to" as the minimum value and the maximum value, respectively.

[0042] In the present invention, when a plurality of substances corresponding to each component are present in the composition, the amount of each component in the composition represents the total amount of the plurality of substances present in the composition unless otherwise specified.

[0043] In the numerical ranges described stepwise in the present invention, the upper limit or lower limit described in a certain numerical range may be replaced by the upper limit or lower limit of another numerical range described stepwise, or may be replaced by the value shown in the Examples.

[0044] In the present invention, the term "process" includes not only an independent process but also a process that cannot be clearly distinguished from other processes as long as the intended purpose of the process can be achieved.

[0045] In the present invention, "*" in the chemical formula represents a bonding position.

[0046] In the present invention, the concept of "image" includes not only pattern images (eg, characters, symbols, or graphics) but also solid images.

[0047] In the present invention, "light" is a concept including active energy rays such as gamma rays, beta rays, electron beams, ultraviolet rays, and visible rays.

[0048] In the present invention, ultraviolet rays may be referred to as "UV (Ultra Violet) light".

[0049] In the present invention, light generated from an LED (Light Emitting Diode) light source may be referred to as “LED light”.

[0050] In the present invention, “(meth)acrylic acid” is a concept including both acrylic acid and methacrylic acid, “(meth)acrylate” is a concept including both acrylate and methacrylate, and “(meth)acryloyl” is a concept including both acryloyl and methacryloyl.

[0051] [Inkjet ink]

[0052] The inkjet ink of the present invention (hereinafter also simply referred to as "ink") contains water and particles including a polymer P having an acid group and a polymerizable compound A having two or more ethylenically unsaturated groups in one molecule and a weight average molecular weight of 1,000 or more.

[0053] By using the ink of the present invention, an image having excellent abrasion resistance and stretchability can be recorded. The reason why such effects can be exerted is presumed to be as follows.

[0054] In image recording in which an inkjet ink containing water and particles of a polymer or a polymerizable compound is deposited on a substrate and the deposited ink is cured by irradiation with active energy rays and / or application of heat to obtain an image, it is difficult to achieve both abrasion resistance and stretchability.

[0055] It is believed that if a polymerizable compound having more than two ethylenically unsaturated groups is contained in one molecule, it is polymerized by irradiation and / or impartation of active energy rays to form a three-dimensional network, and the strength of the ink film formed is improved, and the abrasion resistance is improved. However, in the past, if the strength of the ink film formed is improved, the ink film is difficult to follow the deformation of the substrate, and there is a tendency for the stretchability to decrease. In contrast, in the ink of the present invention, the weight-average molecular weight of the polymerizable compound A contained in the particles is more than 1000, so a network with a long distance between the crosslinking points is formed, so it is believed that the ink film is easy to follow the deformation of the substrate and can obtain stretchability. That is, by using the ink of the present invention, both abrasion resistance and stretchability can be taken into account.

[0056] On the other hand, Japanese Patent No. 6584677 discloses only particles containing a low molecular weight polymerizable monomer, and does not focus on achieving both abrasion resistance and stretchability. Japanese Patent No. 6047904 does not disclose particles containing a polymerizable compound, which is different from the technical concept of the present invention.

[0057] Hereinafter, each component contained in the ink of the present invention will be described.

[0058] <Water>

[0059] The ink of the present invention contains water.

[0060] The content of water can be, for example, 10% by mass or more and 99% by mass or less relative to the total amount of the ink of the present invention.

[0061] The water content is preferably 10% by mass or more, more preferably 20% by mass or more, further preferably 30% by mass or more, and particularly preferably 50% by mass or more, based on the total amount of the ink of the present invention.

[0062] The upper limit of the water content relative to the total amount of the ink of the present invention can be appropriately determined according to the contents of other components, and is, for example, 99% by mass, preferably 95% by mass, and more preferably 90% by mass.

[0063] <Particles>

[0064] The ink of the present invention contains at least one type of particles composed of a polymer P and a polymerizable compound A (hereinafter also referred to as “specific particles”).

[0065] In the ink of the present invention, the polymer P and the polymerizable compound A contained in the specific particles contribute to the storage stability of the ink.

[0066] A preferred embodiment of the ink of the present invention is an embodiment in which the polymerizable compound A stays in the specific particles in the ink before being applied to the substrate, and the polymerizable compound A oozes out from the specific particles in the ink applied to the substrate.

[0067] (Polymerizable compound A)

[0068] The specific particles contain at least one polymerizable compound A having two or more ethylenically unsaturated groups in one molecule and a weight average molecular weight of 1000 or more. Hereinafter, a polymerizable compound having two or more ethylenically unsaturated groups in one molecule and a weight average molecular weight of 1000 or more is also simply referred to as "polymerizable compound A".

[0069] In the ink of the present invention, the polymerizable compound A having two or more ethylenically unsaturated groups in one molecule contributes to the abrasion resistance of the image, and the polymerizable compound A having a weight average molecular weight of 1,000 or more contributes to the stretchability of the image.

[0070] In the present invention, the weight average molecular weight (Mw) refers to a value measured by gel permeation chromatography (GPC).

[0071] In the measurement based on GPC, HLC (registered trademark)-8020GPC (TOSOH CORPORATION) was used as a measuring device, three TSKgel (registered trademark) Super Multipore HZ-H (4.6 mmID×15 cm, TOSOH CORPORATION) were used as columns, and THF (tetrahydrofuran) was used as an eluent. In addition, as measurement conditions, the sample concentration was set to 0.45% by mass, the flow rate was set to 0.35 ml / min, the sample injection volume was set to 10 μL, and the measurement temperature was set to 40° C., and the measurement was performed using an RI detector.

[0072] The calibration curve was prepared using eight samples of "TSK standard, polystyrene" of TOSOH Corporation: "F-40", "F-20", "F-4", "F-1", "A-5000", "A-2500", "A-1000" and "n-propylbenzene".

[0073] The weight average molecular weight of the polymerizable compound A is 1000 or more, preferably 1500 or more, and more preferably 2000 or more. On the other hand, the upper limit of the weight average molecular weight of the polymerizable compound A is not particularly limited, but is preferably 20000 or less, and more preferably 15000 or less from the viewpoint of dispersion stability. The weight average molecular weight of the polymerizable compound A can be set in the range of 1000 to 20000.

[0074] As the ethylenically unsaturated group possessed by the polymerizable compound A, for example, a (meth)acryloyl group, a vinyl group, a vinyl ester group, and a vinyl ether group can be cited. From the viewpoint of reactivity, the ethylenically unsaturated group is preferably a (meth)acryloyl group or a vinyl group, and more preferably a (meth)acryloyl group. As the (meth)acryloyl group, for example, a (meth)acryloyloxy group and a (meth)acrylamide group can be cited. Among them, from the viewpoint of further improving the abrasion resistance of the image, the ethylenically unsaturated group is preferably a (meth)acryloyl group, more preferably an acryloyl group, and further preferably an acryloyloxy group.

[0075] In the ink of the present invention, from the viewpoint of obtaining an image with excellent stretchability, in the polymerizable compound A, the two or more ethylenically unsaturated groups contained in one molecule are preferably present at positions separated from each other, and may be in a form having two or more ethylenically unsaturated groups including two ethylenically unsaturated groups bonded to both ends of the molecule.

[0076] The number of ethylenically unsaturated groups possessed by the polymerizable compound A is not particularly limited as long as it is 2 or more. The upper limit of the number of ethylenically unsaturated groups is not particularly limited, and is, for example, 20. From the viewpoint of ease of synthesis, the number of ethylenically unsaturated groups is preferably 2, 3, 6, 9, 10, 15 or 20.

[0077] Furthermore, from the viewpoint of further improving the abrasion resistance of an image, the polymerizable compound A is preferably a urethane (meth)acrylate having two or more (meth)acryloyl groups in one molecule.

[0078] Urethane (meth)acrylate refers to a compound having a (meth)acryloyl group and a urethane bond. It is believed that if the polymerizable compound A contains a urethane bond, the adhesion to the substrate is improved, so the abrasion resistance of the image is improved. In addition, it is believed that the strength of the ink film is improved by hydrogen bonding between the urethane bonds, and as a result, the abrasion resistance of the image is improved.

[0079] Urethane (meth)acrylate can be produced by, for example, reacting a bifunctional isocyanate compound, a hydroxyl group-containing (meth)acrylate, and, in some cases, a polyol.

[0080] Examples of the bifunctional isocyanate compound include aliphatic diisocyanates such as methylene diisocyanate, dimethylene diisocyanate, trimethylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, dipropyl ether diisocyanate, 2,2-dimethylpentane diisocyanate, 3-methoxyhexane diisocyanate, octamethylene diisocyanate, 2,2,4-trimethylpentane diisocyanate, nonamethylene diisocyanate, decamethylene diisocyanate, 3-butoxyhexane diisocyanate, 1,4-butanediol dipropyl ether diisocyanate, and thiodihexyl diisocyanate; and m-phenylene glycol diisocyanate. diisocyanate, p-phenylene diisocyanate, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, dimethylphenyl diisocyanate, ethylphenyl diisocyanate, isopropylphenyl diisocyanate, dimethylbiphenyl diisocyanate, 1,4-naphthalene diisocyanate, 1,5-naphthalene diisocyanate, 2,6-naphthalene diisocyanate, 2,7-naphthalene diisocyanate, m-xylylene diisocyanate, p-xylylene diisocyanate, tetramethylxylylene diisocyanate and other aromatic diisocyanates; and hydrogenated xylylene diisocyanate, isophorone diisocyanate, dicyclohexylmethane 4,4'-diisocyanate and other alicyclic diisocyanates.

[0081] Examples of the hydroxyl group-containing (meth)acrylate include 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, phenyl glycidyl ether (meth)acrylate, pentaerythritol (meth)triacrylate, and dipentaerythritol penta(meth)acrylate.

[0082] As a preferred embodiment, the polymerizable compound A includes a polymerizable compound A1 having 6 or more ethylenically unsaturated groups in one molecule. Hereinafter, the polymerizable compound having 6 or more ethylenically unsaturated groups in one molecule is also referred to as "polymerizable compound A1". If the specific particles include the polymerizable compound A1, the crosslinking density is further increased by polymerization, and the abrasion resistance of the image is improved.

[0083] The number of ethylenically unsaturated groups in the polymerizable compound A1 is not particularly limited as long as it is 6 or more, but is more preferably 10 or more from the viewpoint of further improving the abrasion resistance of the image. The upper limit of the number of ethylenically unsaturated groups is not particularly limited, and is 20, for example.

[0084] Preferred embodiments of the ethylenically unsaturated group contained in polymerizable compound A1 are the same as those of the ethylenically unsaturated group contained in polymerizable compound A. That is, the ethylenically unsaturated group contained in polymerizable compound A1 is preferably a (meth)acryloyl group, more preferably an acryloyl group, and still more preferably an acryloyloxy group.

[0085] Furthermore, as another preferred embodiment, the polymerizable compound A contains a polymerizable compound A2 having two or three ethylenically unsaturated groups in one molecule and a weight average molecular weight of 2000 or more. Hereinafter, the polymerizable compound having two or three ethylenically unsaturated groups in one molecule and a weight average molecular weight of 2000 or more is also referred to as "polymerizable compound A2". If the specific particles contain the polymerizable compound A2, a network with a longer distance between crosslinking points is formed, so that the ink film easily follows the deformation of the substrate, and the stretchability is further improved.

[0086] Preferred embodiments of the ethylenically unsaturated group possessed by polymerizable compound A2 are the same as preferred embodiments of the ethylenically unsaturated group possessed by polymerizable compound A. That is, the ethylenically unsaturated group possessed by polymerizable compound A2 is preferably a (meth)acryloyl group, more preferably an acryloyl group, and still more preferably an acryloyloxy group.

[0087] The weight average molecular weight of polymerizable compound A2 is 2000 or more, preferably 4000 or more, and more preferably 10000 or more. On the other hand, the upper limit of polymerizable compound A2 is not particularly limited, but is preferably 30000 or less, and more preferably 20000 or less from the viewpoint of dispersion stability.

[0088] Furthermore, the number of ethylenically unsaturated groups contained in the polymerizable compound A2 is preferably 2.

[0089] Specifically, the polymerizable compound A2 preferably has two ethylenically unsaturated groups in one molecule and a weight average molecular weight of not less than 4000. When the number of ethylenically unsaturated groups is two and the weight average molecular weight is not less than 4000, the abrasion resistance and stretchability of the image can be improved simultaneously.

[0090] From the above viewpoints, the polymerizable compound A preferably contains polymerizable compound A1 and polymerizable compound A2. It is considered that polymerizable compound A1 mainly contributes to the abrasion resistance of the image, and polymerizable compound A2 contributes to the stretchability of the image.

[0091] When polymerizable compound A includes polymerizable compound A1 and polymerizable compound A2, the ratio of the content of polymerizable compound A1 to the total content of polymerizable compound A1 and polymerizable compound A2 is preferably 0.2 to 0.8, more preferably 0.3 to 0.7, from the viewpoint of achieving both abrasion resistance and stretchability of the image.

[0092] In the ink of the present invention, the content of the polymerizable compound A is preferably 1% by mass to 15% by mass, and more preferably 2% by mass to 8% by mass, based on the total amount of the ink.

[0093] (Polymerizable compound B)

[0094] The specific particles preferably further contain a monofunctional polymerizable compound having a ring structure. The monofunctional polymerizable compound having a ring structure is also simply referred to as "polymerizable compound B".

[0095] The ring structure contained in the polymerizable compound B may be an alicyclic structure or an aromatic ring structure. From the viewpoint of improving ejection properties while maintaining abrasion resistance, the ring structure is preferably an aromatic ring structure.

[0096] Examples of the alicyclic structure include a cyclohexane ring structure, a dicyclopentyl ring structure, a dicyclopentenyl ring structure, a norbornane ring structure, an isobornane ring structure, a norbornene ring structure, an isobornene ring structure, and an adamantane ring structure.

[0097] Examples of the aromatic ring structure include a naphthalene ring and a benzene ring.

[0098] In particular, from the viewpoint of improving ejection properties while maintaining abrasion resistance, the polymerizable compound B preferably has two or more aromatic rings, and more preferably has two or three aromatic rings.

[0099] From the viewpoint of improving ejectability, the viscosity of the polymerizable compound B is preferably 1000 mPa·s or less, more preferably 500 mPa·s or less, and even more preferably 200 mPa·s or less. The lower limit of the viscosity is, for example, 1 mPa·s.

[0100] In addition, the viscosity of the polymerizable compound B is a value measured using a viscometer.

[0101] As the viscometer, for example, VISCOMETER TV-22 (Toki Sangyo Co., Ltd.) can be used.

[0102] The molecular weight of the polymerizable compound B is preferably 100 to 300 from the viewpoint of improving ejection properties.

[0103] If the polymerizable compound B is included in addition to the polymerizable compound A, the viscosity increase is suppressed when the ink on the nozzle surface dries, and ejection failure (nozzle clogging) is less likely to occur. In addition, if the polymerizable compound B is included, the abrasion resistance can be maintained and ejection failure can be improved.

[0104] The ratio of the content of polymerizable compound B to the total content of polymerizable compound A and polymerizable compound B is preferably 0.2 to 0.5, and more preferably 0.3 to 0.5. If the above ratio is 0.2 or more, the ejection property is further improved. On the other hand, if the above ratio is 0.5 or less, the crosslinking density in the ink film becomes high, and the abrasion resistance is excellent.

[0105] (Polymer P having acid groups)

[0106] The specific particles contain at least one type of polymer P having an acid group (hereinafter, also simply referred to as “polymer P”).

[0107] The polymer P plays a role in retaining the polymerizable compound A in specific particles in the ink before being applied to the substrate, thereby contributing to improving the storage stability of the ink.

[0108] The polymer P may be a chain polymer or a cross-linked polymer.

[0109] In the present invention, a chain polymer refers to a polymer having no cross-linked structure, and a cross-linked polymer refers to a polymer having a cross-linked structure.

[0110] The chain polymer may have a cyclic structure or a branched structure.

[0111] Regarding specific particles containing polymer P which is a chain polymer, for example, Japanese Patent No. 6584677 can be referred to.

[0112] As a preferred embodiment of the specific particles when the polymer P is a cross-linked polymer, there can be mentioned microcapsules including a shell made of the polymer P which is a cross-linked polymer and a core including a polymerizable compound.

[0113] Regarding specific particles containing polymer P which is a cross-linked polymer, for example, Japanese Patent No. 6510681 can be referred to.

[0114] -Weight average molecular weight (Mw)-

[0115] The weight average molecular weight (Mw) of the polymer P is preferably 3,000 to 200,000, more preferably 4,000 to 150,000, further preferably 5,000 to 100,000, further preferably 8,000 to 80,000, further preferably 10,000 to 50,000.

[0116] When the Mw of the polymer P is 3000 or more, the storage stability of the ink is further improved. This is believed to be because, when the Mw of the polymer P is 3000 or more, the function of the polymer P (the function of retaining the polymerizable compound A in the specific particles, in other words, the function of inhibiting the exudation of the polymerizable compound A from the specific particles) is more effectively exerted in the ink before being applied to the substrate.

[0117] When the Mw of the polymer P is 200,000 or less, the blocking resistance of the image is further improved. This is believed to be because when the Mw of the polymer P is 200,000 or less, the fluidity of the ink applied to the substrate is suppressed from decreasing during the drying process (i.e., increasing viscosity), and as a result, the volatilization of the liquid component (i.e., water and a water-soluble organic solvent) from the ink is further promoted.

[0118] -Glass transition temperature (Tg)-

[0119] The glass transition temperature (Tg) of the polymer P is not particularly limited.

[0120] From the viewpoint of improving the mobility of the polymer P and further improving the image quality (specifically, suppressing the roughness of the image), the Tg of the polymer P is preferably 120°C or lower, more preferably 100°C or lower, further preferably 80°C or lower, and further preferably 70°C or lower.

[0121] On the other hand, the Tg of the polymer P is preferably 0°C or higher, more preferably 10°C or higher, further preferably 20°C or higher, and further preferably 30°C or higher.

[0122] In the present invention, the glass transition temperature (Tg) of a polymer refers to a value measured using a differential scanning calorimeter (DSC).

[0123] The specific measurement of the glass transition temperature is carried out in accordance with the method described in JIS K 7121 (1987) or JIS K 6240 (2011).

[0124] The glass transition temperature in the present invention is an extrapolated glass transition start temperature (hereinafter, sometimes referred to as Tig).

[0125] The method for measuring the glass transition temperature will be described in more detail.

[0126] When determining the glass transition temperature, maintain a temperature about 50°C lower than the expected glass transition temperature of the resin until the device is stable, and then heat at a heating rate of 20°C / min until a temperature about 30°C higher than the temperature at which the glass transition ends is reached to produce a differential thermal analysis (DTA) curve or a DSC curve.

[0127] The extrapolated glass transition starting temperature (Tig), i.e., the glass transition temperature in the present invention, is obtained as the temperature of the intersection of a straight line extending the baseline on the low temperature side to the high temperature side in a DTA curve or a DSC curve and the following tangent line, which is drawn from the point where the gradient of the curve of the step-shaped change part of the glass transition becomes the maximum.

[0128] When the ink contains two or more polymers P, the glass transition temperature (Tg) of the polymer P refers to the weighted average value of the glass transition temperatures of the individual polymers P.

[0129] Examples of the polymer P include urethane polymers, urethane urea polymers, urea polymers, acrylic polymers, polyesters, polyolefins, polystyrenes, polycarbonates, and polyamides.

[0130] Here, the urethane polymer refers to a polymer including a urethane bond and not including a urea bond, the urea polymer refers to a polymer including a urea bond and not including a urethane bond, and the urethane urea polymer refers to a polymer including a urethane bond and a urea bond.

[0131] The acrylic polymer refers to a polymer (homopolymer or copolymer) containing at least one raw material monomer selected from the group consisting of acrylic acid, acrylic acid derivatives (eg, acrylic acid esters, etc.), methacrylic acid, and methacrylic acid derivatives (eg, methacrylic acid esters, etc.).

[0132] -Key U-

[0133] The polymer P preferably includes at least one of a urethane bond and a urea bond, that is, a bond U. In other words, the polymer P is preferably a urethane polymer, a urethane urea polymer, or a urea polymer.

[0134] When the polymer P contains bonds U, in the ink landed on the substrate, the specific particles are likely to interact with each other through the interactions (e.g., hydrogen bonds) of the bonds U. Therefore, it is easier to connect the specific particles to each other by polymerization of the polymerizable compound A that oozes out from the specific particles. As a result, it is easier to solidify the specific particles, thereby further improving the abrasion resistance of the image.

[0135] Bond U preferably comprises a urethane bond.

[0136] In other words, the polymer P preferably includes a urethane bond and no urea bond, or includes a urethane bond and a urea bond.

[0137] -Acid group-

[0138] The polymer P preferably comprises at least one acid group.

[0139] This contributes to the dispersion stability of the specific particles in the ink, and as a result, the storage stability of the ink is further improved.

[0140] The acid groups may or may not be neutralized.

[0141] Examples of the unneutralized acid group include a carboxyl group, a sulfo group, a sulfate group, a phosphonic acid group, and a phosphoric acid group.

[0142] The neutralized acid group refers to an acid group in a "salt" form (e.g., a salt of a carboxyl group (e.g., -COONa)). Examples of the neutralized acid group include salts of carboxyl groups, salts of sulfonyl groups, salts of sulfate groups, salts of phosphonic acid groups, and salts of phosphoric acid groups.

[0143] Neutralization can be performed using, for example, an alkali metal hydroxide (eg, sodium hydroxide, potassium hydroxide, etc.) or an organic amine (eg, triethylamine, etc.).

[0144] As the acid group in the polymer P, from the viewpoint of further improving the storage stability of the ink, it is preferably selected from at least one of the group consisting of a carboxyl group, a salt of a carboxyl group, a sulfonate group, a salt of a sulfonate group, a sulfate group, a salt of a sulfate group, a phosphonic acid group, a salt of a phosphonic acid group, a phosphoric acid group and a salt of a phosphoric acid group, and more preferably selected from at least one of the group consisting of a carboxyl group, a salt of a carboxyl group, a sulfonate group and a salt of a sulfonate group.

[0145] As the "salt" among the salts of carboxyl group, sulfonate group, sulfate group, phosphonate group and phosphate group, an alkali metal salt or an organic amine salt is preferred, and an organic amine salt is more preferred.

[0146] As the organic amine in the organic amine salt, N,N-diisopropylethylamine or triethylamine is preferred.

[0147] Furthermore, when the total number of millimoles of acid groups (e.g., carboxyl groups and carboxyl salts) contained in 1 g of polymer P is set as the acid value of polymer P, from the viewpoint of dispersion stability, the acid value of polymer P is preferably 0.10 mmol / g to 2.00 mmol / g, and more preferably 0.30 mmol / g to 1.50 mmol / g.

[0148] Furthermore, the neutralization degree of the acid groups in the polymer P is preferably 50% to 100%, more preferably 70% to 100%.

[0149] Here, the degree of neutralization refers to the ratio of the "number of neutralized acid groups" in the polymer P to the "total number of unneutralized acid groups (e.g., carboxyl groups) and the number of neutralized acid groups (e.g., salts of carboxyl groups)" (i.e., the ratio [number of neutralized acid groups / (number of unneutralized acid groups + number of neutralized acid groups)]).

[0150] The degree of neutralization of the acid groups in the polymer P can be determined by neutralization titration.

[0151] -Polymerizable group-

[0152] The specific particles contain not only the polymer P but also the polymerizable compound A. Therefore, the polymer P does not necessarily need to contain a polymerizable group. However, from the viewpoint of further improving the abrasion resistance of the image, the polymer P may contain a polymerizable group.

[0153] As the polymerizable group which may be contained in the polymer P, a photopolymerizable group or a thermal polymerizable group is preferred.

[0154] As the photopolymerizable group, a free radical polymerizable group is preferred, a group containing an olefinic double bond is more preferred, and a (meth)acryloyl group, an allyl group, a styryl group or a vinyl group is further preferred. As the free radical polymerizable group, from the viewpoint of free radical polymerization reactivity and the hardness of the formed film, a (meth)acryloyl group is particularly preferred.

[0155] As the heat-polymerizable group, an epoxy group, an oxetanyl group, an aziridine group, an azetidinyl group, a keto group, an aldehyde group or a blocked isocyanate group is preferred.

[0156] The polymer P may contain only one type of polymerizable group, or may contain two or more types.

[0157] The polymer P contains a polymerizable group, which can be confirmed by, for example, Fourier transform infrared spectroscopy (FT-IR) analysis.

[0158] When the number of millimoles of olefinic double bonds in 1 g of polymer P is set as the C=C valence of polymer P, from the viewpoint of further improving the hardness of the image, the C=C valence of polymer P is preferably 0.05 mmol or more, more preferably 0.10 mmol / g or more, further preferably 0.30 mmol / g or more, and particularly preferably 0.50 mmol / g or more.

[0159] From the viewpoint of further improving the water resistance and alcohol resistance of the image, the C=C value of the polymer P is preferably 0.05 mmol or more, more preferably 0.10 mmol / g or more, further preferably 0.30 mmol / g or more, further preferably 0.50 mmol / g or more, further preferably 0.60 mmol / g or more, and particularly preferably 0.70 mmol / g or more.

[0160] On the other hand, from the viewpoint of improving the time-dependent curing property of the ink (i.e., inhibiting the decrease in curing property of the ink due to time), the C=C valence of the polymer P is preferably 4.00 mmol / g or less, more preferably 3.00 mmol / g or less, further preferably 2.00 mmol / g or less, and particularly preferably 1.50 mmol / g or less.

[0161] The polymer P may include other structures in addition to the above-mentioned structures (ie, the bond U, the hydrophilic group, and the polymerizable group).

[0162] Examples of other structures include a polysiloxane bond (ie, a divalent polysiloxane group), a monovalent polysiloxane group, a monovalent fluorinated hydrocarbon group, and a divalent fluorinated hydrocarbon group.

[0163] -Preferred Structure of Polymer P-

[0164] The polymer P preferably contains a structural unit derived from an isocyanate compound and a structural unit derived from a compound containing an active hydrogen group.

[0165] The polymer P of the above preferred embodiment includes a bond U formed by a reaction between an isocyanate group of an isocyanate compound and an active hydrogen group of an active hydrogen group-containing compound.

[0166] The active hydrogen group is preferably a hydroxyl group, a primary amino group or a secondary amino group.

[0167] For example, a urethane group is formed by the reaction between an isocyanate group and a hydroxyl group.

[0168] And, a urea group is formed by the reaction between the isocyanate group and the primary or secondary amino group.

[0169] Hereinafter, the isocyanate compound and the active hydrogen group-containing compound serving as raw materials of the polymer P having the above-mentioned preferred structure may be referred to as raw material compounds.

[0170] The isocyanate compound as a raw material compound may be only one kind or two or more kinds.

[0171] The active hydrogen group-containing compound as the raw material compound may be only one kind or two or more kinds.

[0172] At least one isocyanate compound among the raw material compounds is preferably a bifunctional or higher functional isocyanate compound.

[0173] At least one of the compounds containing an active hydrogen group as the raw material compound is preferably a compound containing two or more active hydrogen groups.

[0174] In the raw material compound, at least one of the isocyanate compound and the compound containing an active hydrogen group preferably contains a hydrophilic group. Thus, it is easy to produce a polymer P containing a hydrophilic group. In this case, at least a part of the hydrophilic groups in the finally obtained polymer P may be groups in which the hydrophilic groups in the raw material compound are neutralized.

[0175] A more preferred embodiment is an embodiment in which at least one of the compounds containing an active hydrogen group in the raw material compounds is a compound containing an active hydrogen group and a hydrophilic group.

[0176] When the polymer P contains a polymerizable group, it is preferred that at least one of the isocyanate compound and the compound containing an active hydrogen group among the raw material compounds contains a polymerizable group. This makes it easy to produce the polymer P containing a polymerizable group.

[0177] A more preferred embodiment is an embodiment in which at least one of the compounds containing an active hydrogen group in the raw material compounds is a compound containing an active hydrogen group and a polymerizable group.

[0178] As described above, the polymer P may be a chain polymer or a cross-linked polymer.

[0179] The chain polymer as the polymer P can be produced by reacting a bifunctional isocyanate compound with a compound containing two active hydrogen groups.

[0180] The crosslinked polymer as the polymer P can be produced by reacting a trifunctional or higher functional isocyanate compound with a compound containing two or more active hydrogen groups.

[0181] The crosslinked polymer as the polymer P can also be produced by reacting a bifunctional isocyanate compound with a compound containing three or more active hydrogen groups.

[0182] Preferred raw material compounds are described below.

[0183] -Isocyanate compounds-

[0184] As the isocyanate compound, a difunctional or higher-functional isocyanate compound is preferred, and a difunctional to hexafunctional isocyanate compound is more preferred.

[0185] When a bifunctional isocyanate compound is used as a raw material compound, the polymer P contains the following structural unit (P1) which is a structural unit derived from the bifunctional isocyanate compound.

[0186] [Chemical formula 1]

[0187]

[0188] In the structural unit (P1), L 1 represents a divalent organic group having 1 to 20 carbon atoms, and * represents a bonding position.

[0189] As L 1 Specific examples of include residues obtained by removing two isocyanate groups (NCO groups) from the bifunctional isocyanate compounds described in the following specific examples.

[0190] Specific examples of the bifunctional isocyanate compound are as follows. However, the bifunctional isocyanate compound is not limited to the following specific examples.

[0191] [Chemical formula 2]

[0192]

[0193] Furthermore, as the bifunctional isocyanate compound, the bifunctional isocyanate compound derived from the above-mentioned specific examples may be used, for example, Duranate (registered trademark) D101, D201, A101 (manufactured by Asahi Kasei Corporation) and the like.

[0194] Furthermore, the trifunctional or higher-functional isocyanate compound is preferably a reaction product of at least one selected from the group including bifunctional isocyanate compounds and at least one selected from the group including compounds containing three or more active hydrogen groups (for example, trifunctional or higher-functional polyol compounds, trifunctional or higher-functional polyamine compounds and trifunctional or higher-functional polythiol compounds).

[0195] The number of moles (number of molecules) of the bifunctional isocyanate compound to be reacted with the compound containing three or more active hydrogen groups is preferably 0.6 times or more, more preferably 0.6 times to 5 times, further preferably 0.6 times to 3 times, and further preferably 0.8 times to 2 times, relative to the number of moles of active hydrogen groups in the compound containing three or more active hydrogen groups (the equivalent number of active hydrogen groups).

[0196] Examples of the bifunctional isocyanate compound for forming a trifunctional or higher-functional isocyanate compound include the bifunctional isocyanate compounds described in the above specific examples.

[0197] Examples of the compound containing three or more active hydrogen groups for forming a trifunctional or higher functional isocyanate compound include compounds described in paragraphs 0057 to 0058 of International Publication No. 2016 / 052053.

[0198] Examples of the trifunctional or higher-functional isocyanate compound include addition-type trifunctional or higher-functional isocyanate compounds, isocyanurate-type trifunctional or higher-functional isocyanate compounds, and biuret-type trifunctional or higher-functional isocyanate compounds.

[0199] Examples of commercially available adduct-type trifunctional or higher-functional isocyanate compounds include Takenate (registered trademark) D-102, D-103, D-103H, D-103M2, P49-75S, D-110N, D-120N, D-140N, and D-160N (all from Mitsui Chemicals, Inc.), Desmodule (registered trademark) L75 and UL57SP (from Sumika Bayer Urethane Co., Ltd.), CORONATE (registered trademark) HL, HX, and L (from Nippon Polyurethane Industry Co., Ltd.), and P301-75E (from Asahi Kasei Corporation).

[0200] Examples of commercially available isocyanurate-type trifunctional or higher-functional isocyanate compounds include Takenate (registered trademark) D-127N, D-170N, D-170HN, D-172N, and D-177N (all from Mitsui Chemicals, Inc.), SUMIDUR N3300, Desmodule (registered trademark) N3600, N3900, and Z4470BA (all from Sumika Bayer Urethane Co., Ltd.), CORONATE (registered trademark) HX and HK (all from Nippon Polyurethane Industry Co., Ltd.), and Duranate (registered trademark) TPA-100, TKA-100, TSA-100, TSS-100, TLA-100, and TSE-100 (all from Asahi Kasei Corporation).

[0201] Examples of commercially available biuret-type trifunctional or higher-functional isocyanate compounds include Takenate (registered trademark) D-165N, NP1100 (Mitsui Chemicals, Inc.), Desmodule (registered trademark) N3200 (SumikaBayer Urethane Co., Ltd.), and Duranate (registered trademark) 24A-100 (Asahi Kasei Corporation).

[0202] At least one of the isocyanate compounds as the raw material compound may be an isocyanate compound containing a hydrophilic group. For the isocyanate compound containing a hydrophilic group, reference may be made to paragraphs 0112 to 0118 and 0252 to 0254 of International Publication No. 2016 / 052053.

[0203] At least one of the isocyanate compounds as the raw material compound may be an isocyanate compound containing a polymerizable group. For the isocyanate compound containing a polymerizable group, reference may be made to paragraphs 0084 to 0089, 0203, and 0205 of International Publication No. 2016 / 052053.

[0204] -Compounds containing active hydrogen groups-

[0205] As the compound containing an active hydrogen group, a compound containing two or more active hydrogen groups is preferred.

[0206] As the compound containing two or more active hydrogen groups, a polyol compound (ie, a compound having two or more hydroxyl groups) or a polyamine compound (ie, a compound having two or more amino groups) is more preferable.

[0207] When a compound containing an active hydrogen group and a hydrophilic group is used as a raw material compound, the polymer P preferably contains at least one structural unit (P0) described below.

[0208] [Chemical formula 3]

[0209]

[0210] In the structural unit (P0),

[0211] L 0 represents a divalent organic group,

[0212] Y 1 and Y 2 Each independently represents an oxygen atom, a sulfur atom or -NR 1 -base,

[0213] R 1 represents a hydrogen atom or a hydrocarbon group having 1 to 10 carbon atoms,

[0214] *Indicates bonding position.

[0215] In the structural unit (P0), L 0 The divalent organic group represented may be a group containing carbon atoms and hydrogen atoms, or may be a group containing carbon atoms and hydrogen atoms and a hetero atom (for example, an oxygen atom, a nitrogen atom, a sulfur atom, etc.).

[0216] L 0The divalent organic group represented may include at least one of a hydrophilic group and a polymerizable group.

[0217] As L 0 A specific example of is a residue obtained by removing two active hydrogen groups from the specific example of the compound containing two or more active hydrogen groups described later.

[0218] As R 1 , preferably a hydrogen atom or a hydrocarbon group having 1 to 6 carbon atoms, more preferably a hydrogen atom or a hydrocarbon group having 1 to 3 carbon atoms.

[0219] Y 1 and Y 2 are each independently preferably an oxygen atom or -NR 1 - group, more preferably an oxygen atom.

[0220] Specific examples of the diol compound as the compound containing an active hydrogen group are shown below, but the compound containing an active hydrogen group is not limited to the following specific examples.

[0221] [Chemical formula 4]

[0222]

[0223] In compounds (12) to (15), nC7H 15 、nC9H 19 、nC 11 H 23 and nC 17 H 35 They represent n-heptyl, n-nonyl, n-undecyl and n-heptadecyl, respectively.

[0224] Compound (16) PPG is polypropylene glycol, and n is the number of repetitions.

[0225] Compound (16-2) PEG is polyethylene glycol, and n is the number of repetitions.

[0226] Compound (17) PEs is a polyester diol, n is a repeating number, Ra and two Rb are independently a divalent hydrocarbon group having 2 to 25 carbon atoms. The n Ra in compound (17) PEs may be the same or different. The (n+1) Rb in compound (17) PEs may be the same or different.

[0227] Compound (18) PCD is a polycarbonate diol, n is the number of repetitions, and (n+1) Rcs are each independently an alkylene group having 2 to 12 carbon atoms (preferably 3 to 8, more preferably 3 to 6). The (n+1) Rcs in compound (18) PCD may be the same or different.

[0228] Compound (19) PCL is polycaprolactone diol, n and m are the repeating numbers, and Rd is an alkylene group having 2 to 25 carbon atoms.

[0229] -Compound containing an active hydrogen group and a polymerizable group-

[0230] Examples of the compound containing an active hydrogen group include compounds containing an active hydrogen group and a polymerizable group.

[0231] A compound containing an active hydrogen group and a polymerizable group is suitable as a compound for introducing a polymerizable group into the polymer P (hereinafter also referred to as a "polymerizable group-introducing compound").

[0232] Specific examples of the diol compound as the compound containing an active hydrogen group and a polymerizable group are shown below, but the compound containing an active hydrogen group and a polymerizable group is not limited to the following specific examples.

[0233] [Chemical formula 5]

[0234]

[0235] Regarding the compound containing an active hydrogen group and a polymerizable group, the description in paragraphs 0075 to 0089 of International Publication No. 2016 / 052053 may be appropriately referred to.

[0236] -Compounds containing active hydrogen groups and hydrophilic groups-

[0237] Examples of the compound containing an active hydrogen group include compounds containing an active hydrogen group and a hydrophilic group.

[0238] A compound containing an active hydrogen group and a hydrophilic group is suitable as a compound for introducing a hydrophilic group into the polymer P (hereinafter also referred to as a "hydrophilic group-introducing compound").

[0239] When a compound containing an active hydrogen group and a hydrophilic group is used as a raw material compound, the polymer P preferably contains the following structural unit (P2).

[0240] [Chemical formula 6]

[0241]

[0242] In the structural unit (P2),

[0243] L 21 represents a trivalent organic group having 1 to 20 carbon atoms,

[0244] L 22 represents a single bond or a divalent organic group having 1 to 20 carbon atoms,

[0245] A1 represents a carboxyl group, a carboxyl salt, a sulfonic group, or a sulfonic group salt,

[0246] *Indicates bonding position.

[0247] L 21 The trivalent organic group having 1 to 20 carbon atoms represented by is preferably 2 to 20 carbon atoms, more preferably 3 to 20 carbon atoms, and even more preferably 4 to 20 carbon atoms.

[0248] As L 21 The trivalent organic group represented is preferably a trivalent hydrocarbon group or a group in which at least one carbon atom in the trivalent hydrocarbon group is substituted with a heteroatom (preferably an oxygen atom, a sulfur atom or a nitrogen atom).

[0249] L 22 The number of carbon atoms in the divalent organic group having 1 to 20 carbon atoms represented by is preferably 1 to 10, more preferably 1 to 6.

[0250] As L 22 The divalent organic group represented is preferably a divalent hydrocarbon group (preferably an alkylene group) or a group in which at least one carbon atom in a divalent hydrocarbon group (preferably an alkylene group) is substituted with an oxygen atom or a sulfur atom (preferably an oxygen atom).

[0251] L 22 Can be a single key.

[0252] Specific examples of compounds containing active hydrogen groups and hydrophilic groups are shown below, but the compounds containing active hydrogen groups and hydrophilic groups are not limited to the following specific examples. The carboxyl group and sulfonic group in the following specific examples may be neutralized (that is, they may be salts of carboxyl groups and sulfonic groups).

[0253] [Chemical formula 7]

[0254]

[0255] Regarding the compound containing an active hydrogen group and a hydrophilic group, the description in paragraphs 0112 to 0118 and paragraphs 0252 to 0254 of International Publication No. 2016 / 052053 may be appropriately referred to.

[0256] The content of the polymer P is preferably 10 to 90% by mass, more preferably 20 to 80% by mass, further preferably 30 to 70% by mass, and further preferably 40 to 60% by mass, based on the total solid content of the specific particles.

[0257] In the present invention, the total solid content of the specific particles refers to the total amount of the specific particles excluding the solvent (ie, water and organic solvent). When the specific particles do not contain a solvent, the total solid content of the specific particles is consistent with the total amount of the specific particles.

[0258] The content of the polymer P is preferably 0.3% by mass to 20% by mass, more preferably 0.5% by mass to 15% by mass, and even more preferably 1% by mass to 10% by mass, relative to the total amount of the ink.

[0259] From the viewpoint of storage stability of the ink, the ratio of the content of the polymerizable compound A to the total content of the polymer P having an acid group and the polymerizable compound A is preferably 0.3 to 0.7, and more preferably 0.4 to 0.6. When the ratio is within the above range, the function of the polymer P (the function of retaining the polymerizable compound A in the specific particles, in other words, the function of inhibiting the exudation of the polymerizable compound A from the specific particles) is more effectively exerted.

[0260] (Polymerizable compounds other than polymerizable compound A and polymerizable compound B)

[0261] The specific particles may contain a polymerizable compound other than the polymerizable compound A and the polymerizable compound B (hereinafter also referred to as “other polymerizable compound”).

[0262] From the viewpoint of suppressing bleeding of other polymerizable compounds, the content of other polymerizable compounds is preferably 5% by mass or less, more preferably 3% by mass or less, and even more preferably 1% by mass or less, based on the total amount of ink.

[0263] The molecular weight of the other polymerizable compound is preferably less than 1000, more preferably 100 to 900, further preferably 100 to 800, and particularly preferably 150 to 750. The molecular weight of the other polymerizable compound can be calculated based on the types and numbers of atoms constituting the polymerizable compound.

[0264] As other polymerizable compounds which may be contained in the specific particles, photopolymerizable compounds are preferred, and radical polymerizable compounds are more preferred.

[0265] The radical polymerizable compound has a radical polymerizable group.

[0266] The radical polymerizable compound preferably has an ethylenically unsaturated group. Preferred embodiments of the ethylenically unsaturated group are the same as those of the ethylenically unsaturated group that the polymerizable compound A has.

[0267] The number of polymerizable groups possessed by other polymerizable compounds may be only one, or may be two or more.

[0268] Examples of other polymerizable compounds include (meth)acrylate compounds, styrene compounds, vinylnaphthalene compounds, N-vinyl heterocyclic compounds, unsaturated polyesters, unsaturated polyethers, unsaturated polyamides, and unsaturated urethanes.

[0269] Among them, the other polymerizable compound is preferably a polymerizable compound having a ClogP value of 4 or more.

[0270] The specific particles may contain a polymerizable compound having a ClogP value of less than 4 as another polymerizable compound. However, when containing a polymerizable compound having a ClogP value of less than 4, the content of the specific particles is preferably 3% by mass or less relative to the total amount of the ink. Furthermore, the specific particles more preferably do not contain a polymerizable compound having a ClogP value of less than 4 as another polymerizable compound.

[0271] If the content of the polymerizable compound having a ClogP value of less than 4 contained in the specific particles is 3% by mass or less, the polymerizable compound having a ClogP value of less than 4 oozes out from the specific particles and is hydrolyzed, thereby suppressing the formation of an acidic compound and suppressing changes in the physical properties of the ink (particularly, pH). As a result, storage stability of the ink can be obtained.

[0272] In the present invention, the ClogP value is calculated using the fragment method. As calculation software using the fragment method, ChemDraw Professional 16 (manufactured by PerkinElmer Informatics) was used.

[0273] As polymerizable compound A, when using carbamate acrylate with 6 acryloyl groups, the carbamate acrylate with 6 acryloyl groups is manufactured by, for example, using a mixture of pentaerythritol triacrylate and pentaerythritol tetraacrylate. At this time, pentaerythritol triacrylate reacts with isocyanate compounds, and pentaerythritol tetraacrylate does not react with isocyanate compounds. Therefore, in addition to the carbamate acrylate with 6 acryloyl groups, the product also contains pentaerythritol tetraacrylate. The ClogP value of pentaerythritol tetraacrylate is 3.5. Therefore, from the viewpoint of obtaining the storage stability of ink, in the case of manufacturing the carbamate acrylate with 6 acryloyl groups by the above method, the purification treatment of pentaerythritol tetraacrylate is removed, and preferably only the carbamate acrylate with 6 acryloyl groups is used in the preparation of ink.

[0274] Furthermore, when a urethane acrylate having 10 acryloyl groups is used as the polymerizable compound A, the urethane acrylate having 10 acryloyl groups is manufactured using, for example, dipentaerythritol pentaacrylate and dipentaerythritol hexaacrylate. At this time, dipentaerythritol pentaacrylate reacts with the isocyanate compound, and dipentaerythritol hexaacrylate does not react with the isocyanate compound. Therefore, in addition to the urethane acrylate having 10 acryloyl groups, the product also contains dipentaerythritol hexaacrylate. The ClogP value of dipentaerythritol hexaacrylate is 5.1. Therefore, when the urethane acrylate having 10 acryloyl groups is manufactured using the above method, the purification treatment for removing dipentaerythritol hexaacrylate may not be performed, and a mixture of urethane acrylate having 10 acryloyl groups and dipentaerythritol hexaacrylate may be used in the preparation of the ink.

[0275] (Free Radical Polymerization Initiator)

[0276] The specific particles preferably contain at least one free radical polymerization initiator.

[0277] In the present invention, the radical polymerization initiator refers to a compound that generates radicals by absorbing light.

[0278] When the specific particles contain a radical polymerization initiator, the abrasion resistance and adhesion of the ink film are further improved.

[0279] This is considered to be because the distance between the polymerizable compound A and the radical polymerization initiator becomes closer, and the curing sensitivity (hereinafter, also simply referred to as “sensitivity”) of the ink film increases.

[0280] Furthermore, when the specific particles contain a free radical polymerization initiator, a free radical polymerization initiator that was previously highly sensitive but difficult to use due to low dispersibility or low solubility in water (for example, a free radical polymerization initiator having a solubility in water of 1.0% by mass or less at 25° C.) can be used. Thus, the range of choices of the free radical polymerization initiator used is expanded, and the range of choices of the light source used is also expanded. Therefore, the curing sensitivity can be improved compared to the past.

[0281] Specific examples of the radical polymerization initiator that has high sensitivity but is difficult to use due to low dispersibility or solubility in water include carbonyl compounds and acylphosphine oxide compounds described below, and acylphosphine oxide compounds are preferred.

[0282] In the ink of the present invention, by making the specific particles contain a radical polymerization initiator having low solubility in water, the radical polymerization initiator can be contained in the ink of the present invention.

[0283] Furthermore, the ink in which the specific particles contain a radical polymerization initiator also has excellent storage stability compared to conventional photocurable compositions. This is believed to be because the radical polymerization initiator is contained in the specific particles, thereby suppressing aggregation or precipitation of the radical polymerization initiator.

[0284] As the radical polymerization initiator, for example, the description in paragraphs 0091 to 0094 of International Publication No. 2016 / 052053 can be appropriately referred to.

[0285] As the radical polymerization initiator, (a) a carbonyl compound such as an aromatic ketone or (b) an acylphosphine oxide compound is preferred. Examples of the radical polymerization initiator include bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide (e.g., product name “Omnirad 819”, manufactured by IGM Resins BV), 2-(dimethylamino)-1-(4-morpholinophenyl)-2-benzyl-1-butanone (e.g., product name “Omnirad 369”, manufactured by IGM Resins BV), 2-methyl-1-(4-methylthiophenyl)-2-morpholinopropan-1-one (e.g., product name “Omnirad 907”, manufactured by IGM Resins BV), 1-hydroxy-cyclohexyl-phenyl-ketone (e.g., product name “Omnirad 184”, manufactured by IGM Resins BV), 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide (e.g., product name “Omnirad TPO-H”, manufactured by IGM Resins BV), and 1-hydroxy-cyclohexyl-phenyl-ketone (e.g., product name “Omnirad 184”, manufactured by IGM Resins BV). BV), (2,4,6-trimethylbenzoyl)ethoxyphenylphosphine oxide (for example, product name "Omnirad TPO-L", manufactured by IGM Resins BV).

[0286] Among them, from the viewpoint of improving sensitivity and adaptability to LED light, the radical polymerization initiator is preferably (b) an acylphosphine oxide compound, and more preferably a monoacylphosphine oxide compound or a bisacylphosphine oxide compound.

[0287] The wavelength of the LED light is preferably 355 nm, 365 nm, 385 nm, 395 nm, or 405 nm.

[0288] The specific particles of the embodiment containing a polymerization initiator can be produced, for example, by emulsifying a mixture obtained by mixing an oil phase component and an aqueous phase component containing a polymer P (or a raw material compound for producing the polymer P), a polymerizable compound A, and a polymerization initiator.

[0289] The content of the radical polymerization initiator is preferably 0.1% by mass to 15% by mass, more preferably 0.5% by mass to 10% by mass, and even more preferably 1% by mass to 6% by mass, relative to the total solid content of the specific particles.

[0290] The content of the radical polymerization initiator is preferably 0.1% by mass to 3.0% by mass, more preferably 0.3% by mass to 2.0% by mass, and even more preferably 0.5% by mass to 1.5% by mass, relative to the total amount of the ink.

[0291] (Sensitizer)

[0292] The specific particles preferably contain at least one sensitizer.

[0293] When the specific particles contain a photopolymerization initiator, the specific particles preferably contain a sensitizer.

[0294] When the specific particles contain a sensitizer, decomposition of the photopolymerization initiator due to irradiation with active energy rays can be further accelerated.

[0295] The sensitizer is a substance that absorbs specific active energy rays and becomes an electronically excited state. The electronically excited sensitizer contacts the photopolymerization initiator and generates electron transfer, energy transfer, heat generation, etc. This promotes the chemical changes of the photopolymerization initiator, that is, decomposition, generation of free radicals, acid or base, etc.

[0296] Examples of the sensitizer include benzophenone, thioxanthone, isopropylthioxanthone, anthraquinone, 3-acylcoumarin derivatives, terphenyl, styryl ketone, 3-(aroylmethylene)thiazoline, camphorquinone, eosin, rhodamine, erythrosine, and the like.

[0297] Furthermore, as the sensitizer, a compound represented by the general formula (i) described in JP-A-2010-24276, a compound represented by the general formula (I) described in JP-A-6-107718, and the like can also be preferably used.

[0298] Among them, as a sensitizer, from the viewpoint of adaptability to LED light and reactivity with a photopolymerization initiator, at least one selected from thioxanthone, isopropyl thioxanthone and benzophenone is preferred, at least one selected from thioxanthone and isopropyl thioxanthone is more preferred, and isopropyl thioxanthone is further preferred.

[0299] When the specific particles contain a sensitizer, the content of the sensitizer is preferably 0.1 to 20% by mass, more preferably 0.2 to 15% by mass, and further preferably 0.3 to 10% by mass, relative to the solid content of the specific particles.

[0300] The content of the sensitizer is preferably 0.01% by mass to 0.5% by mass, more preferably 0.05% by mass to 0.3% by mass, and even more preferably 0.1% by mass to 0.2% by mass, relative to the total amount of the ink.

[0301] The specific particles containing a polymerization initiator and a sensitizer can be produced, for example, by emulsifying a mixture of an oil phase component containing a polymer P (or a raw material compound for producing the polymer P), a polymerizable compound A, a photopolymerization initiator and a sensitizer, and an aqueous phase component.

[0302] (Other ingredients)

[0303] The specific particles may further contain other components in addition to the above-mentioned components.

[0304] Examples of other components include compounds containing at least one selected from the group consisting of a polysiloxane bond (ie, a divalent polysiloxane group), a monovalent polysiloxane group, a monovalent fluorinated hydrocarbon group, and a divalent fluorinated hydrocarbon group.

[0305] (Method for producing aqueous dispersion of specific particles)

[0306] The ink of the present invention can be produced by preparing an aqueous dispersion of the specific particles containing the specific particles and water, and by adding other components to the obtained aqueous dispersion as necessary.

[0307] Furthermore, the ink of the present invention is one form of an aqueous dispersion of specific particles, and therefore, depending on the composition of the ink, the ink can be produced directly (that is, without adding other components) as an aqueous dispersion of specific particles.

[0308] The method for producing the aqueous dispersion of specific particles is not particularly limited.

[0309] As a method for producing an aqueous dispersion of specific particles, the following production method A and production method B are exemplified.

[0310] -Method A-

[0311] Preparation method A has a step of obtaining a water dispersion of specific particles by mixing and emulsifying an oil phase component including an organic solvent, a polymer P, and a polymerizable monomer and an aqueous phase component including water.

[0312] The production method A is suitable as a method for producing an aqueous dispersion of specific particles containing polymer P in the form of a chain polymer.

[0313] Regarding the production method A, reference may be made to known documents such as Japanese Patent No. 6584677.

[0314] -Method B-

[0315] Preparation method B has the following steps: an oil phase component containing an organic solvent, a raw material compound of the polymer P (for example, a trifunctional or higher-functional isocyanate compound, a compound having two or more active hydrogen groups, etc.) and a polymerizable monomer and an aqueous phase component containing water are mixed and emulsified to obtain an aqueous dispersion of specific particles.

[0316] The production method B is suitable as a method for producing an aqueous dispersion of specific particles (for example, microcapsules) containing the polymer P in the form of a cross-linked polymer.

[0317] Regarding Preparation Method B, reference may be made to known documents such as International Publication No. 2016 / 052053.

[0318] <Water-soluble organic solvent>

[0319] The ink of the present invention preferably comprises at least one water-soluble organic solvent.

[0320] This further ensures the ejection performance of ink from the inkjet head.

[0321] In the present invention, the "water-soluble" in the "water-soluble organic solvent" refers to a property of dissolving 1 g or more in 100 g of water at 25°C.

[0322] The amount of the water-soluble organic solvent that dissolves in 100 g of water at 25° C. is preferably 5 g or more, more preferably 10 g or more.

[0323] The content of the water-soluble organic solvent is preferably 1 to 35% by mass, more preferably 3 to 30% by mass, further preferably 5 to 20% by mass, and further preferably 7 to 15% by mass, relative to the total amount of the ink.

[0324] When the content of the water-soluble organic solvent is 1% by mass or more, the ejection properties of the ink are further improved.

[0325] When the content of the water-soluble organic solvent is 35% by mass or less, the storage stability of the ink is further improved.

[0326] Specific examples of the water-soluble organic solvent are as follows.

[0327] Alcohols (e.g., methanol, ethanol, propanol, isopropanol, butanol, isobutanol, sec-butanol, tert-butanol, pentanol, hexanol, cyclohexanol, benzyl alcohol, etc.)

[0328] Polyols (e.g., ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, butylene glycol, hexylene glycol, pentylene glycol, glycerol, hexanetriol, thiodiglycol, 2-methylpropanediol, etc.)

[0329] Polyol ethers (e.g., ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monoethyl ether, diethylene glycol monomethyl ether, diethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monobutyl ether, tripropylene glycol monomethyl ether, dipropylene glycol monomethyl ether, dipropylene glycol dimethyl ether, ethylene glycol monomethyl ether acetate, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monobutyl ether, ethylene glycol monophenyl ether, propylene glycol monophenyl ether, etc.)

[0330] Amines (e.g., ethanolamine, diethanolamine, triethanolamine, N-methyldiethanolamine, N-ethyldiethanolamine, morpholine, N-ethylmorpholine, ethylenediamine, diethylenediamine, triethylenetetramine, tetraethylenepentamine, polyethyleneimine, pentamethyldiethylenetriamine, tetramethylpropylenediamine, etc.)

[0331] Amides (e.g., formamide, N,N-dimethylformamide, N,N-dimethylacetamide, etc.)

[0332] Heterocyclic compounds (e.g., 2-pyrrolidone, N-methyl-2-pyrrolidone, cyclohexylpyrrolidone, 2-oxazolidinone, 1,3-dimethyl-2-imidazolidinone, γ-butyrolactone, etc.)

[0333] Sulfoxides (e.g. dimethyl sulfoxide, etc.),

[0334] Sulfones (e.g., sulfolane, etc.)

[0335] Others (urea, acetonitrile, acetone, etc.)

[0336] <Color>

[0337] The ink of the present invention may be an ink containing at least one coloring material (so-called "colored ink") or an ink containing no coloring material (so-called "clear ink").

[0338] When the ink contains a colorant, it is preferred that the colorant is contained outside the specific particles (that is, the specific particles do not contain a colorant).

[0339] The colorant is not particularly limited and can be arbitrarily selected from known colorants such as pigments, water-soluble dyes, and disperse dyes. Among them, the colorant is more preferably a pigment from the viewpoint of excellent weather resistance and rich color reproducibility.

[0340] The pigment is not particularly limited and can be appropriately selected according to the purpose, and examples thereof include known organic pigments and inorganic pigments, etc. In addition, examples of the pigment include resin particles dyed with dyes, commercially available pigment dispersions, and surface-treated pigments (for example, pigments dispersed in water, liquid compounds, insoluble resins, etc. as dispersion media, and pigments whose surfaces have been treated with resins, pigment derivatives, etc.).

[0341] Examples of the organic pigment and the inorganic pigment include yellow pigment, red pigment, magenta pigment, blue pigment, cyan pigment, green pigment, orange pigment, violet pigment, brown pigment, black pigment, and white pigment.

[0342] When a pigment is used as a colorant, a pigment dispersant may be used as necessary.

[0343] Furthermore, when a pigment is used as a colorant, a self-dispersible pigment having a hydrophilic group on the surface of the pigment particles can be used as the pigment.

[0344] Regarding the colorant and the pigment dispersant, paragraphs 0180 to 0200 of JP-A-2014-040529 and paragraphs 0122 to 0129 of WO 2016 / 052053 may be appropriately referred to.

[0345] When the ink of the present invention contains a colorant, the content of the colorant is preferably 0.1 to 20% by mass, more preferably 0.5 to 10% by mass, and particularly preferably 0.5 to 5% by mass, based on the total amount of the ink.

[0346] <Other ingredients>

[0347] The ink of the present invention may contain other components besides those described above as necessary.

[0348] Other components may or may not be contained in the specific particles.

[0349] The ink of the present invention may contain a surfactant, a polymerization inhibitor, an ultraviolet absorber, and the like as other components.

[0350] Furthermore, the ink of the present invention may contain a water-soluble polymerizable monomer, a water-soluble photopolymerization initiator, a water-soluble resin, etc., on the outside of the specific particles as necessary.

[0351] Regarding these components, for example, paragraphs 0134 to 0157 of International Publication No. 2016 / 052053 can be referred to.

[0352] (Preferred method for producing ink)

[0353] The method for producing the ink of the present invention is not particularly limited, but preferably includes the following steps: a step of producing an aqueous dispersion of specific particles by the above-mentioned method for producing an aqueous dispersion (production method A or production method B); and

[0354] A step of adding other components such as a pigment and a water-soluble organic solvent to a water dispersion of specific particles and mixing the mixture.

[0355] Furthermore, as another method for producing the ink of the present invention, there may be mentioned a process of producing an aqueous dispersion of specific particles by the above-mentioned method for producing an aqueous dispersion (Production Method A or Production Method B), or a method of directly producing the ink as an aqueous dispersion of specific particles (i.e., a method without adding other components to the aqueous dispersion of specific particles).

[0356] (Preferred physical properties of ink)

[0357] The viscosity of the ink of the present invention at 25° C. is preferably 3 mPa·s to 15 mPa·s, and more preferably 3 mPa·s to 13 mPa·s. In particular, the viscosity of the ink of the present invention at 25° C. is preferably 50 mPa·s or less. When the viscosity of the ink is within the above range, higher ejection stability can be achieved.

[0358] In addition, the viscosity of the ink is a value measured using a viscometer.

[0359] As the viscometer, for example, VISCOMETER TV-22 (Toki Sangyo Co., Ltd.) can be used.

[0360] In the ink of the present invention, the content of (meth)acrylic acid contained in the ink after the storage test is preferably 0.1% by mass or less. The storage test was performed by the following method.

[0361] The ink just prepared was placed in a sealed container, and the sealed container was placed in a constant temperature room at 60° C. and left to stand for 1 week, and then the sealed container was taken out.

[0362] The content of (meth)acrylic acid contained in the ink after the storage test was calculated by HPLC (high performance liquid chromatography) measurement. In the HPLC measurement, a Thermo Scientific UltiMate 3000HPLC (Thermo Fisher Scientific Inc.) was used as a measuring device, a TSKgel ODS-100V (4.6 mmID×15 cm, TOSOH CORPORATION) was used as a column, and a 0.1 mass % phosphoric acid methanol solution and a 0.1 mass % phosphoric acid aqueous solution were used as eluents.

[0363] The measurement conditions were as follows: the sample concentration was 1.5% by mass methanol solution, the flow rate was 1.0 mL / min, the sample injection volume was 3 μL, and the measurement temperature was 40° C., and a UV detector (detection wavelength 210 nm) was used. A calibration curve was prepared from five samples of 0.0001% by mass methanol solution, 0.0005% by mass methanol solution, 0.001% by mass methanol solution, 0.005% by mass methanol solution, and 0.01% by mass methanol solution of (meth)acrylic acid.

[0364] [Inkjet recording method]

[0365] The inkjet recording method of the present invention preferably includes: a step of imparting the ink to a substrate by inkjet recording (hereinafter also referred to as "imparting step"); and a step of irradiating the ink imparted to the substrate with active energy rays (hereinafter also referred to as "irradiation step").

[0366] Hereinafter, the operation of irradiating with active energy rays may be referred to as “exposure”.

[0367] In the inkjet recording method of the present invention, since the ink of the present invention is used, the same effects as those obtained by the ink of the present invention are exerted.

[0368] <Base material>

[0369] The substrate used in the inkjet recording method of the present invention is not particularly limited and may be either a non-permeable substrate or a permeable substrate, but is preferably a non-permeable substrate.

[0370] Here, the non-permeable substrate refers to a substrate having a water absorption rate (unit: mass %, measurement time: 24 hours) of less than 10 in ASTM D570 of the ASTM test method.

[0371] The water absorption of the impermeable substrate is preferably 5% by mass or less.

[0372] Examples of the impermeable substrate include paper laminated with plastic (e.g., polyethylene, polypropylene, polystyrene, etc.), polyester cloth, metal plates (e.g., plates of metals such as aluminum, zinc, and copper), plastic films (e.g., polyvinyl chloride (PVC: Polyvinyl Chloride) resin, cellulose diacetate, cellulose triacetate, cellulose propionate, cellulose butyrate, cellulose acetate butyrate, cellulose nitrate, polyethylene terephthalate (PET: Polyethylene Terephthalate), polyethylene (PE: Polyethylene), polystyrene (PS: Polystyrene), polypropylene (PP: Polypropylene), polycarbonate (PC: Polycarbonate), polyvinyl acetal, acrylic resin, etc.), paper laminated or vapor-deposited with the above metals, plastic films laminated or vapor-deposited with the above metals, and leather.

[0373] Examples of leather include natural leather (also referred to as "genuine leather"), synthetic leather (eg, PVC (polyvinyl chloride) leather, PU (polyurethane) leather), etc. For leather, for example, see paragraphs 0163 to 0165 of Japanese Patent Application Laid-Open No. 2009-058750.

[0374] For example, when an ink film is formed on leather (eg, vehicle seats, bags, shoes, wallets, etc.) or a plastic film as an impermeable substrate, the formed ink film is required to have excellent abrasion resistance and stretchability.

[0375] Furthermore, when an ink film is formed on a substrate other than leather and plastic film, the formed film may be required to have excellent abrasion resistance and stretchability.

[0376] According to the inkjet recording method of the present invention, such a requirement can be met. From this point of view, it is more effective to use PVC as the substrate.

[0377] From the viewpoint of increasing the surface energy, the substrate may be surface treated.

[0378] Examples of the surface treatment include corona treatment, plasma treatment, frame treatment, heat treatment, abrasion treatment, and light irradiation treatment (UV treatment), but the surface treatment is not limited to these.

[0379] The thickness of the substrate is not particularly limited, but is preferably 20 μm to 500 μm from the viewpoint of flexibility.

[0380] <Assignment process>

[0381] The applying step is a step of applying the ink of the present invention to a substrate by an inkjet recording method.

[0382] (Ink application conditions, etc.)

[0383] Application of ink by the inkjet recording method can be performed by ejecting ink from an inkjet head in a known inkjet recording device.

[0384] As the inkjet head, a piezoelectric inkjet head is preferable.

[0385] The resolution of the inkjet head is preferably 300 dpi or more, more preferably 600 dpi or more, and even more preferably 800 dpi or more.

[0386] Here, dpi (dot per inch) refers to the number of dots per 2.54 cm (1 inch).

[0387] The amount of droplets ejected from the ink jet head (the amount of droplets ejected per dot) is preferably 1 pL (picoliter) to 100 pL, more preferably 3 pL to 80 pL, and even more preferably 3 pL to 50 pL.

[0388] (Substrate temperature, etc.)

[0389] In the application step, the temperature of the substrate surface on the ink-impacted side is preferably 20 to 80°C, more preferably 25 to 75°C, further preferably 30 to 70°C, and further preferably 40 to 70°C.

[0390] When the temperature of the substrate surface on the ink landing side is 20° C. to 80° C., the image quality and abrasion resistance are further improved. This is probably because the effect of the polymerizable compound A bleeding out from the specific particles is more easily obtained.

[0391] (Heating of substrate)

[0392] The inkjet recording method of the present invention preferably satisfies at least one of the following conditions: a preheating step of heating the substrate before the imparting step; and heating the substrate and imparting the ink in the imparting step. When at least one of the above conditions is satisfied, it is easy to adjust the temperature of the substrate surface to the above preferred temperature.

[0393] By heating the substrate, the image quality and abrasion resistance of the image are further improved. The reason for this is believed to be that the effect of the polymerizable compound A bleeding out from the specific particles is more easily obtained.

[0394] In the heating in the preheating step and the heating in each of the imparting steps, the heating mechanism used to heat the substrate is not particularly limited, and examples thereof include a heating drum, warm air, an infrared lamp, an infrared LED, an infrared heater, a heating oven, a hot plate, an infrared laser, an infrared dryer, and the like.

[0395] (air supply to substrate)

[0396] The inkjet recording method of the present invention preferably includes a blowing step of blowing gas to the applied ink after the applying step. The blowing of gas further promotes the drying of the ink, and the image quality and abrasion resistance of the image are further improved.

[0397] The temperature of the gas to be blown is, for example, 20°C to 60°C.

[0398] The gas blowing of the ink can be carried out, for example, using a blower. The blower is preferably arranged at a position higher than the inkjet head arranged on the upper side of the substrate. The gas blown from the blower can not only dry the ink but also cool the inkjet head.

[0399] <Irradiation process>

[0400] The irradiation step is a step of irradiating the ink applied to the substrate with active energy rays (in other words, a step of exposing the ink applied to the substrate).

[0401] By irradiating the active energy rays in this step (i.e., exposure), the polymerizable compound A in the ink is polymerized and the ink is cured, thereby obtaining an image. More specifically, as described above, after the ink is deposited, the polymerizable compound A effectively oozes out from the specific particles, thereby sufficiently curing the specific particles (i.e., the specific particles are linked to each other), and as a result, an image with excellent image quality and abrasion resistance can be obtained.

[0402] Examples of active energy rays include ultraviolet rays (UV light), visible rays, and electron beams.

[0403] Among them, the active energy ray is preferably UV light.

[0404] The irradiation of the ink applied to the substrate with active energy rays can be performed in a state where the substrate and the ink applied to the substrate are heated. Furthermore, the irradiation of the ink applied to the substrate with active energy rays can be performed in a state where the substrate and the ink applied to the substrate are heated and gas is blown to the ink applied to the substrate by a blower.

[0405] The irradiation conditions and basic irradiation method of the active energy rays can be those disclosed in Japanese Patent Application Laid-Open No. 60-132767.

[0406] In the inkjet recording method of the present invention, the time from the time when the ink lands to the start of irradiation with the active energy ray is not particularly limited, and is, for example, 0.1 seconds to 1000 seconds.

[0407] The application of ink and the irradiation of active energy rays can be performed using an inkjet recording apparatus including a unit including an inkjet head and an active energy ray source disposed near the inkjet head.

[0408] Furthermore, in the inkjet recording apparatus, the inkjet head and the active energy ray source may be independently arranged.

[0409] Furthermore, the inkjet recording device may be equipped with a temporary curing light source (pinning light source) and a formal curing light source (curing light source). The temporary curing light source is a light source that irradiates active energy rays (preferably ultraviolet rays), which are used to temporarily cure the ink to the extent that adjacent droplets are not aligned with each other after the ink droplets ejected from the inkjet head land on the substrate. The ink irradiated with active energy rays from the temporary curing light source avoids landing interference, but is temporarily cured to the extent that the dots are spread (able to fully diffuse). The formal curing light source is a light source that performs additional exposure after temporary curing and irradiates active energy rays (preferably ultraviolet rays) for finally completely curing the ink (formal curing).

[0410] As light sources for active energy ray irradiation, there can be listed discharge lamps such as mercury lamps, metal halide lamps, high-pressure mercury lamps, medium-pressure mercury lamps, low-pressure mercury lamps, and ultraviolet fluorescent lamps; laser light sources such as gas lasers and solid-state lasers; and semiconductor light sources such as LED (light emitting diode) and LD (laser diode).

[0411] Among them, as the active energy ray irradiation light source, a metal halide lamp, a high pressure mercury lamp, a medium pressure mercury lamp, a low pressure mercury lamp or an ultraviolet LED (hereinafter also referred to as UV-LED) as a light source for ultraviolet irradiation is preferred.

[0412] The peak wavelength of ultraviolet rays is, for example, preferably from 200 nm to 405 nm, more preferably from 220 nm to 400 nm, and further preferably from 340 nm to 400 nm.

[0413] The peak wavelength of light from the LED light source (LED light) is preferably 200 nm to 600 nm, more preferably 300 nm to 450 nm, further preferably 320 nm to 420 nm, further preferably 340 nm to 405 nm, further preferably 355 nm, 365 nm, 385 nm, 395 nm or 405 nm.

[0414] As the UV-LED, for example, there can be mentioned a UV-LED manufactured by NICHIA CORPORATION whose main emission spectrum has a wavelength between 365 nm and 420 nm.

[0415] In addition, there can be mentioned UV-LEDs described in US Pat. No. 6,084,250 that emit active radiation centered between 300 nm and 370 nm.

[0416] Furthermore, by combining several UV-LEDs, it is possible to irradiate ultraviolet rays in different wavelength regions.

[0417] The irradiation energy (i.e., exposure amount) of the active energy ray is preferably 20 mJ / cm 2 More preferably, 100 mJ / cm 2 More preferably, 500 mJ / cm 2 above.

[0418] The upper limit of the exposure amount is not particularly limited and can be 5 J / cm 2 , or 1,500mJ / cm 2 .

[0419] The maximum illuminance of the LED on the substrate is preferably 10 mW / cm 2 ~8,000mW / cm 2 , more preferably 20 mW / cm 2~5,000mW / cm 2 , more preferably 30mW / cm 2 ~3000mW / cm 2 , more preferably 50mW / cm 2 ~1000mW / cm 2 .

[0420] The irradiation time of the active energy ray is preferably 0.01 to 120 seconds, more preferably 0.1 to 90 seconds.

[0421] <Drying process>

[0422] The inkjet recording method of the present invention preferably further includes a drying step of heating and drying the ink (ie, the image) irradiated with the active energy rays.

[0423] This further improves the abrasion resistance of the image and further suppresses the stickiness of the image.

[0424] The heating means for heating the ink is not particularly limited, and examples thereof include a heating drum, warm air, an infrared lamp, an infrared LED, an infrared heater, a heating oven, a hot plate, an infrared laser, and an infrared dryer.

[0425] The heating temperature in heat drying is preferably 40°C or higher, more preferably 40°C to 200°C, further preferably 40°C to 100°C, further preferably 40°C to 80°C, further preferably 45°C to 70°C.

[0426] The heating temperature refers to the temperature of the ink on the substrate, and can be measured using a thermal imager using an infrared thermal imaging device H2640 (manufactured by Nippon Avionics Co., Ltd.).

[0427] The heating time can be appropriately set in consideration of the heating temperature, ink composition, printing speed, etc. The heating time is preferably 5 seconds or longer, more preferably 5 seconds to 20 minutes, more preferably 10 seconds to 10 minutes, and even more preferably 20 seconds to 5 minutes.

[0428] Example

[0429] Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to the following Examples.

[0430] Unless otherwise specified, "room temperature" means 25°C.

[0431] <Preparation of polymer P>

[0432] Into a 1-liter three-necked flask equipped with a stirrer, a thermometer, and a reflux cooling tube, 187.9 g of methyl ethyl ketone, 137.4 g of isophorone diisocyanate, 32.3 g of tricyclodecane dimethanol, 91.8 g of epoxy acrylate (product name "EBECRYL600", manufactured by DAICEL-ALLNEX LTD.), 28.8 g of 2,2-bis(hydroxymethyl)propionic acid, 25.3 g of a hydroxyl-containing silicone compound (product name "SILAPLANE FM-DA11", manufactured by JNC Corporation), and 0.01 g of 2-tert-butyl-1,4-benzoquinone were placed, the temperature was raised to 70° C., and 0.5 g of tris(2-ethylhexanoate) bismuth (product name "NEOSTANN U-600", manufactured by DAICEL-ALLNEX LTD.) was added. Then, the temperature in the reaction container was kept at 70° C. and stirred for 8 hours.

[0433] Next, a solution containing 64.4 g of methyl ethyl ketone and 221.1 g of 2-propanol was added to the reaction container and stirred for 2 hours. Then, the temperature was lowered to 40°C, and 27.8 g of N,N-diisopropylethylamine was added. The temperature in the reaction container was maintained at 40°C and stirred for 1 hour to obtain a polymer P solution (polymer P content: 40% by mass).

[0434] [Example 1]

[0435] <Preparation of aqueous dispersion of specific particles>

[0436] -Preparation of oil phase components-

[0437] The following components were mixed and stirred at room temperature for 30 minutes to obtain an oil phase component.

[0438] 40 mass % solution of polymer P ... 38.7 g

[0439] Polymerizable compound A...15.5 g

[0440] Polymerization initiator: (2,4,6-trimethylbenzoyl)ethoxyphenylphosphine oxide (product name "Omnirad TPO-L", manufactured by IGM Resins BV, "TPO-L" in the table) ... 2.5 g

[0441] Sensitizer: Isopropylthioxanthone (ITX) ... 0.6g

[0442] Ethyl acetate...31.7 g

[0443] Methyl ethyl ketone......9.4g

[0444] - Preparation of aqueous dispersion of specific particles -

[0445] The oil phase component and 84.6 g of distilled water were mixed, and the obtained mixture was emulsified at room temperature at 7000 rpm for 30 minutes using a homogenizer to obtain an emulsion.

[0446] The obtained emulsion was added to distilled water (30.0 g), and the obtained liquid was heated to 50° C. and stirred at 50° C. for 4 hours, thereby distilling off ethyl acetate and methyl ethyl ketone from the liquid.

[0447] The liquid from which ethyl acetate and methyl ethyl ketone were distilled off was diluted with distilled water so that the solid content concentration became 25 mass %, thereby obtaining an aqueous dispersion of specific particles (content of specific particles: 25 mass %).

[0448] The volume average dispersed particle size of the specific particles is 100 nm.

[0449] <Ink Preparation>

[0450] The respective components were mixed to prepare ink.

[0451] · Aqueous dispersion of the above-mentioned specific particles (specific particle content 25% by mass) ... 44 parts by mass

[0452] Pigment dispersion: product name "Pro-jet Black APD4000", manufactured by FUJIFILM Imaging Colorants, pigment concentration 15 mass % ... 20 parts by mass

[0453] Surfactant: polyoxyethylene alkyl ether (product name "EMULGEN 707", manufactured by Kao Corporation, solid content concentration 100% by mass) ... 0.5 parts by mass

[0454] Water-soluble organic solvent: propylene glycol (PG) ... 10 parts by mass

[0455] · Water: The remainder of the total ink is 100 parts by mass

[0456] [Example 2 to Example 16, Comparative Example 1 to Comparative Example 2]

[0457] An ink was obtained by the same method as in Example 1 except that the polymerizable compound described in Table 1 or Table 2 was used instead of the bifunctional polyester acrylate.

[0458] The details of the polymerizable compound A and other polymerizable compounds described in Table 1 or Table 2 are as follows.

[0459] · 2-functional polyester acrylate: Product name "ARONIX M-6500", manufactured by TOAGOSEI CO., LTD.

[0460] · Bifunctional carbamate methacrylamide: a compound prepared by the following method

[0461] Into a 500 ml three-necked flask equipped with a stirrer, a thermometer and a reflux cooling tube, 100 g of methyl ethyl ketone, 20.0 g of isophorone diisocyanate, 22.1 g of N-(2-hydroxyethyl) methacrylamide and 0.01 g of 2-tert-butyl-1,4-benzoquinone were placed, the temperature was raised to 70°C, and 0.08 g of tris(2-ethylhexanoate) bismuth (product name "NEOSTANN U-600", manufactured by DAICEL-ALLNEXLTD.) was added. Then, the temperature in the reaction vessel was maintained at 70°C while stirring for 8 hours. Next, 10.0 g of 2-propanol was added to the reaction vessel and stirred for 2 hours. Then, methyl ethyl ketone and 2-propanol were distilled off by reduced pressure drying to obtain carbamate methacrylamide.

[0462] · Bifunctional urethane acrylate: product name "UN-2601", manufactured by Negami Chemical Industrial Co., Ltd.)

[0463] · Hexafunctional urethane acrylate: product name "UV-7630B", manufactured by Mitsubishi Chemical Corporation, 70% by mass

[0464] · 10-functional urethane acrylate: product name "MIRAMER SC2153", manufactured by Miwon Specialty Chemical Co., Ltd., 70% by mass

[0465] · Trifunctional urethane acrylate: Product name "UV-7550B", manufactured by Mitsubishi Chemical Corporation

[0466] · Bifunctional urethane acrylate (Mw=3000): product name "UV-6630B", manufactured by Mitsubishi Chemical Corporation

[0467] · Bifunctional urethane acrylate (Mw=11000): product name "UV-3520EA", manufactured by Mitsubishi Chemical Corporation

[0468] · TriPEA: A mixture of tripentaerythritol acrylate, monopentaerythritol acrylate, dipentaerythritol acrylate, and polypentaerythritol acrylate (product name: "Viscoat#802", manufactured by OSAKA ORGANIC CHEMICAL INDUSTRY LTD.)

[0469] TPGDA: tripropylene glycol diacrylate (product name "Viscoat#310HP", manufactured by OSAKA ORGANIC CHEMICAL INDUSTRY LTD.)

[0470] PETA: Pentaerythritol tetraacrylate (product name "UV-7630B", manufactured by Mitsubishi Chemical Corporation, 30% by mass)

[0471] DPHA: dipentaerythritol hexaacrylate (product name: "MIRAMER SC2153", manufactured by Miwon Specialty Chemical Co., Ltd., 30% by mass)

[0472] As described above, UV-7630B contains 70% by mass of hexafunctional urethane acrylate and 30% by mass of PETA. In Example 4, UV-7630B was used to prepare the ink. In Example 5, when UV-7630B was purified in advance to prepare the ink, only hexafunctional urethane acrylate was used.

[0473] As described above, "MIRAMER SC2153" contains 70% by mass of 10-functional urethane acrylate and 30% by mass of DPHA. In Example 6, "MIRAMER SC2153" was used in preparing the ink.

[0474] <Image record 1>

[0475] The ink cartridge attached to an inkjet recording apparatus (product name "DMP-2850", manufactured by Fujifilm Corporation) was filled with the above ink, and an image was recorded on a substrate by the following method.

[0476] As the substrate, a PVC (polyvinyl chloride) film (product name "LAG Jet P-282ZW", thickness 80 μm, manufactured by LINTEC Corporation) was used.

[0477] The substrate is heated so that the temperature of the surface to which the ink is applied (ie, the surface on which the ink lands) becomes 50° C. (preheating step). This preheating is performed by a platen heater in the inkjet recording apparatus.

[0478] The ink is ejected from the inkjet head of the inkjet recording device and applied to the heated substrate (application process). The ink ejection conditions are set to 900 dpi (dots per inch) and 10 pL per dot. The ink is applied while the substrate is heated, so that the ink lands on the surface of the substrate maintained at 50° C. The substrate is heated using a platen heater in the inkjet recording device.

[0479] Next, the applied ink was dried at 50° C. for 180 seconds to obtain an ink film (drying step). The ink was dried by bringing the surface of the substrate opposite to the ink applied surface into contact with a hot plate.

[0480] Finally, the dried ink film was exposed using a conveyor-type LED exposure device to an exposure dose of 1000 mJ / cm 2 , thereby obtaining an image record (irradiation step).

[0481] <Image Record 2>

[0482] A multi-channel (i.e., reciprocating scanning) inkjet recording device was prepared. A conveying roller for conveying a substrate was provided, and a platen heater was provided below the conveying roller. The inkjet head used was the inkjet head of FIG. 3 described in Japanese Patent Publication No. 2013-78862. With reference to the printer described in Japanese Patent Publication No. 2013-166271, a blower was provided above the inkjet head.

[0483] The ink cartridge included in the inkjet recording apparatus was filled with the above ink, and an image was recorded on a substrate by the following method.

[0484] As the substrate, a PVC (polyvinyl chloride) film (product name "LAG Jet P-282ZW", thickness 80 μm, manufactured by LINTEC Corporation) was used.

[0485] The substrate is heated so that the temperature of the surface to which the ink is applied (ie, the surface on which the ink lands) becomes 50° C. (preheating step). This preheating is performed by a platen heater located upstream of the inkjet head.

[0486] The ink is transported on the heated substrate, and the ink is ejected from the inkjet head of the inkjet recording device and applied to the heated substrate (application process). The ink ejection conditions are set to 900 dpi (dots per inch), 1 dot 10 pL, 8 channels, and bidirectional printing. Regarding the application of the ink, the temporary curing light source (32A, 32B in FIG. 3 described in Japanese Patent Publication No. 2013-78862) is turned off, and the substrate is heated on the platen heater, and the air is blown from the blower provided on the upper part of the inkjet head.

[0487] The substrate with the ink applied was transported to the lower part of the main curing light source (34A and 34B in FIG. 3 described in Japanese Patent Application Laid-Open No. 2013-78862) and the exposure amount was 1000 mJ / cm 2 The exposure is performed in a manner to obtain an image record (irradiation step). The exposure is performed while the substrate is heated by a platen heater, and the exposure is performed while a gas is blown from a blower.

[0488] The obtained image records were used to evaluate the abrasion resistance and tensile properties. In addition, the obtained ink was used to evaluate the storage stability. The evaluation method is as follows. In addition, the evaluation results of the image records obtained in Image Recording 1 and Image Recording 2 were the same.

[0489] <Abrasion resistance>

[0490] By the above-mentioned image recording method, a 10 cm×3 cm rectangular solid image was recorded on the substrate at a recording duty ratio of 100%, thereby obtaining an image recorded object. The obtained image recorded object was left to stand in an environment of 25° C. and 50% relative humidity for 24 hours.

[0491] Cotton cloth (Kanakin #3) was placed on the image recording surface of the image recording material after placement, and a load of 200 g was applied and rubbed back and forth 100 times using a Gakushin friction tester (manufactured by TESTER SANGYO CO., LTD.). The image recording surface after being rubbed was observed with the naked eye to confirm the rub marks and the peeling state of the image. The evaluation criteria are as follows. Evaluations 3, 4, and 5 are levels with no practical problems.

[0492] 5: There are no scratches in the image.

[0493] 4: There are scratches in the image but not to the substrate.

[0494] 3: There are scratches in the image, and part of the scratches reaches the substrate, but the area of ​​the visible substrate exceeds the area of ​​the original image recorded (30cm 2 ) is 0% and less than 5%.

[0495] 2: There are scratches on the image, and part of the scratches reaches the substrate. The area of ​​the substrate is the area of ​​the original image (30cm 2 ) is greater than 5% and less than 50%.

[0496] 1: There are scratches on the image, and part of the scratches reaches the substrate. The area of ​​the substrate is the area of ​​the original image (30cm 2 ) more than 50%.

[0497] <Stretchability>

[0498] By the above-mentioned image recording method, a 10 cm×3 cm rectangular solid image was recorded on the substrate at a recording duty ratio of 100%, thereby obtaining an image recorded object. The obtained image recorded object was left to stand in an environment of 25° C. and 50% relative humidity for 24 hours.

[0499] The image density of the image recorded material after being left to stand (that is, the image recorded material before being stretched) was measured using a fluorescence spectroscopic densitometer (product name: "FD-7", manufactured by KONICA MINOLTA JAPAN, INC.).

[0500] The image recorded material was placed using a tensile tester (product name "Autograph AG-IS 5kN Model", manufactured by SHIMADZU CORPORATION) with a distance between clips of 5 cm, and stretched at a tension rate of 300 mm / min until the distance between clips became 13 cm.

[0501] The image density of the image recorded after stretching was measured in the same manner as the image density of the image recorded before stretching. In addition, the image recorded after stretching was observed with the naked eye to confirm the presence or absence of cracks. The stretchability was evaluated based on the amount of change in the image density of the image recorded after stretching from the image density of the image recorded before stretching and the presence or absence of cracks. The evaluation criteria are as follows. Evaluations 3, 4, and 5 are levels with no practical problems.

[0502] Change in image density before and after stretching = Image density of image recorded material before stretching - Image density of image recorded material after stretching

[0503] 5: No cracks were observed in the image after stretching, and the change in image density before and after stretching was less than 0.5. 4: No cracks were observed in the image after stretching, and the change in image density before and after stretching was 0.5 or more and less than 0.8.

[0504] 3: No cracks in the image are observed after stretching, and the amount of change in image density before and after stretching is 0.8 or more and less than 1.1.

[0505] 2: No cracks were observed in the image after stretching, but the amount of change in image density before and after stretching was 1.1 or more.

[0506] 1: Cracks in the image are seen after stretching.

[0507] <Storage stability>

[0508] The average particle size of the ink (i.e., the ink before the storage test) was measured within 12 hours after the ink was prepared. The average particle size of the ink was measured at 25°C using a particle size measuring device (product name "nanoSAQLA", manufactured by Otsuka Electronics Co., Ltd.).

[0509] As a storage test, a sealed container containing ink was placed in a 60°C constant temperature room for 1 week. After 1 week, the average particle size of the ink after the storage test was measured in the same way as the average particle size of the ink before the storage test. Storage stability was evaluated based on the change in the average particle size of the ink before the storage test and the average particle size of the ink after the storage test. The evaluation criteria are as follows. Evaluations 3, 4, and 5 are levels with no practical problems.

[0510] 5: The absolute value of the change in the average particle size before and after the storage test is less than 5 nm.

[0511] 4: The absolute value of the change in the average particle size before and after the storage test is 5 nm or more and less than 10 nm.

[0512] 3: The absolute value of the change in the average particle size before and after the storage test is 10 nm or more and less than 20 nm.

[0513] 2: The absolute value of the change in the average particle size before and after the storage test is 20 nm or more.

[0514] 1: The ink after the storage test contained sediment and could not be measured.

[0515] Tables 1 and 2 show the evaluation results.

[0516]

[0517]

[0518] As shown in Table 1, it can be seen that in Examples 1 to 16, particles containing water, a polymer P having an acid group, and a polymerizable compound A, wherein the polymerizable compound A has two or more ethylenically unsaturated groups in one molecule and a weight-average molecular weight of more than 1,000, can obtain images with excellent abrasion resistance and stretchability.

[0519] On the other hand, in Comparative Examples 1 and 2, since the polymerizable compound A was not contained in the particles, both the abrasion resistance and the stretchability of the image could not be achieved.

[0520] In Example 3, it is found that the polymerizable compound A is a urethane (meth)acrylate having two or more (meth)acryloyl groups in one molecule, and that the abrasion resistance is superior to that of Examples 1 and 2.

[0521] It is found that Example 5, which includes the polymerizable compound A1 having 6 or more ethylenically unsaturated groups in one molecule, has superior abrasion resistance compared to Example 3.

[0522] It is found that Example 8, which contains the polymerizable compound A2 having two or three ethylenically unsaturated groups in one molecule and having a weight average molecular weight of 2,000 or more, has excellent stretchability compared to Example 3.

[0523] It is found that Example 9, which contains a polymerizable compound having two ethylenically unsaturated groups in one molecule and having a weight average molecular weight of 4,000 or more, has excellent stretchability compared to Example 8.

[0524] In Example 10, it was found that the polymerizable compound A1 and the polymerizable compound A2 were included, and that the abrasion resistance was superior to that of Example 9.

[0525] In Example 11, the ratio of the content of the polymerizable compound A1 to the total content of the polymerizable compound A1 and the polymerizable compound A2 was 0.8 or less, and the stretchability was excellent compared with Example 12. In addition, in Example 13, the ratio of the content of the polymerizable compound A1 to the total content of the polymerizable compound A1 and the polymerizable compound A2 was 0.2 or more, and the abrasion resistance was excellent compared with Example 14.

[0526] In Example 5, it was found that the content of (meth)acrylic acid contained in the inkjet ink after the storage test was 0.1% by mass or less, and that the storage stability was excellent compared to that of Example 4.

[0527] [Example 17 to Example 22]

[0528] Except having used each component described in Table 3, it carried out similarly to Example 1, and obtained the ink.

[0529] The details of the polymerizable compound B and other polymerizable compounds described in Table 3 are as follows.

[0530] Dicyclopentenyloxyethyl acrylate (product name "FA-512AS", manufactured by RESONAC Corporation)

[0531] Benzyl m-phenoxyacrylate (product name "POB-A", manufactured by KYOEISHA CHEMICAL CO., LTD.)

[0532] · Ethoxylated o-phenylphenol acrylate (product name "A-LEN-10", manufactured by Shin-Nakamura Chemical Co., Ltd.)

[0533] LA: Lauryl acrylate (product name "LA", manufactured by OSAKA ORGANIC CHEMICAL INDUSTRY LTD.)

[0534] Using the obtained ink, an image recorded material was obtained by the same method as in the above-mentioned Image Recording 1 and Image Recording 2.

[0535] The obtained image records were used to evaluate the abrasion resistance and stretchability. Furthermore, the obtained inks were used to evaluate the storage stability. The evaluation methods of abrasion resistance, stretchability and storage stability are as described above.

[0536] Then, the ejection stability was evaluated using the obtained ink. The evaluation method was as follows. The evaluation results of the image records obtained in Image Recording 1 and Image Recording 2 were the same.

[0537] Ink was ejected under the conditions described in the above-mentioned image recording 2. Before the start of image recording, a nozzle check pattern was printed to confirm that there were no non-ejecting nozzles. Then, an image of size 1m×5m was recorded at an image density of 5%. The nozzle check pattern was printed again. The number of non-ejecting nozzles was counted based on the printed nozzle check pattern, and the ejection stability was evaluated. The evaluation criteria are as follows. Evaluations 3, 4, and 5 are levels that are not problematic in practical use.

[0538] 5: No nozzle that does not spray.

[0539] 4: There are 1 or 2 nozzles that do not spray.

[0540] 3: The number of non-spraying nozzles is 3 to 5.

[0541] 2: The number of nozzles that do not eject is 6 or more and less than 20% of all nozzles.

[0542] 1: There are 6 or more nozzles that do not eject, which accounts for more than 20% of all nozzles.

[0543] Table 3 shows the evaluation results.

[0544]

[0545] As shown in Table 3, it can be seen that in Examples 17 to 22, particles containing water, a polymer P having an acid group, and a polymerizable compound A, wherein the polymerizable compound A has two or more ethylenically unsaturated groups in one molecule and a weight-average molecular weight of more than 1000, can obtain images with excellent abrasion resistance and stretchability.

[0546] Furthermore, it is found that Example 21 is excellent in discharge stability compared with Example 10 because the polymerizable compound B is contained.

[0547] Furthermore, in Examples 18 to 20, the ratio of the content of the polymerizable compound B to the total content of the polymerizable compound A and the polymerizable compound B was 0.2 or more, and the ejection stability was found to be superior to that of Example 21. Furthermore, in Examples 18 to 20, the ratio of the content of the polymerizable compound B to the total content of the polymerizable compound A and the polymerizable compound B was 0.5 or less, and the abrasion resistance was found to be superior to that of Example 22.

[0548] In addition, the disclosure of Japanese Patent Application No. 2022-138407 filed on August 31, 2022 is incorporated by reference in its entirety into this specification. Furthermore, all documents, patent applications, and technical standards described in this specification are incorporated by reference into this specification to the same extent as if each document, patent application, and technical standard were specifically and individually described as being incorporated by reference.

Claims

1. An inkjet ink comprising: Water; and Particles comprising a polymer P having an acid group and a polymerizable compound A, The polymerizable compound A has two or more ethylenically unsaturated groups in one molecule and has a weight average molecular weight of 1,000 or more.

2. The inkjet ink according to claim 1, wherein The ethylenically unsaturated group is a (meth)acryloyl group.

3. The inkjet ink according to claim 1, wherein The polymerizable compound A is a urethane (meth)acrylate having two or more (meth)acryloyl groups in one molecule.

4. The inkjet ink according to claim 1, wherein The polymerizable compound A includes a polymerizable compound A1 having six or more ethylenically unsaturated groups in one molecule.

5. The inkjet ink according to claim 4, wherein The polymerizable compound A1 has 10 or more ethylenically unsaturated groups in one molecule.

6. The inkjet ink according to claim 1, wherein The polymerizable compound A includes a polymerizable compound A2 having two or three ethylenically unsaturated groups in one molecule and having a weight average molecular weight of 2,000 or more.

7. The inkjet ink according to claim 6, wherein: The polymerizable compound A2 has two ethylenically unsaturated groups in one molecule and has a weight average molecular weight of 4,000 or more.

8. The inkjet ink according to claim 1, wherein The polymerizable compound A comprises: A polymerizable compound A1 having 6 or more ethylenically unsaturated groups in one molecule; and A polymerizable compound A2 having two or three ethylenically unsaturated groups in one molecule and having a weight average molecular weight of 2,000 or more.

9. The inkjet ink according to claim 8, wherein The ratio of the content of the polymerizable compound A1 to the total content of the polymerizable compound A1 and the polymerizable compound A2 is 0.2 to 0.

8.

10. The inkjet ink according to claim 1, wherein The ratio of the content of the polymerizable compound A to the total content of the polymer P having an acid group and the polymerizable compound A is 0.3 to 0.

7.

11. The inkjet ink according to claim 1, wherein The particles further contain a polymerizable compound B which is a monofunctional polymerizable compound having a ring structure.

12. The inkjet ink according to claim 11, wherein The ratio of the content of the polymerizable compound B to the total content of the polymerizable compound A and the polymerizable compound B is 0.2 to 0.

5.

13. The inkjet ink according to claim 1, wherein The content of (meth)acrylic acid contained in the inkjet ink after the storage test was 0.1% by mass or less.

14. An inkjet recording method comprising the following steps: imparting the inkjet ink according to any one of claims 1 to 13 to a substrate by inkjet recording; and The inkjet ink applied to the substrate is irradiated with active energy rays.

Images