Inkjet ink and inkjet recording method

Abstract

The present invention pertains to: an inkjet ink comprising water and particles containing a polymer that has an acid group and a (meth)acrylate that has a branched alkylene chain having 10 or more carbon atoms but does not have a cyclic structure; and an application for the inkjet ink.

Description

Inkjet ink and inkjet recording method

[0001] This disclosure relates to inkjet inks and inkjet recording methods.

[0002] Various studies have been conducted on inkjet inks. For example, International Publication No. 2024 / 048251 describes an inkjet ink containing water, a polymer P having an acid group, and particles containing a polymerizable compound A, wherein the polymerizable compound A has two or more ethylenically unsaturated groups in one molecule and has a weight-average molecular weight of 1000 or more.

[0003] There were instances where improved ink ejection performance was required for inks stored in low-temperature and high-temperature environments.

[0004] This disclosure has been made in view of these circumstances, and the problem that the embodiments of this disclosure aim to solve is to provide an inkjet ink and an inkjet recording method that exhibit excellent ejection properties when stored in low-temperature and high-temperature environments.

[0005] This disclosure includes the following embodiments: <1> An inkjet ink comprising water, a (meth)acrylate having a branched alkylene chain with 10 or more carbon atoms and not having a cyclic structure, and particles comprising a polymer having an acid group. <2> The inkjet ink according to <1>, wherein the (meth)acrylate is a compound represented by the following formula (1). In formula (1), R １ and R ２ Each of these is independently an alkyl group having 6 to 16 carbon atoms. <3> (Meth)acrylate has a hydrogen bonding term of solubility parameter of 2.5 MPa １／２The inkjet ink according to <1> or <2> below. <4> The inkjet ink according to any one of <1> to <3>, wherein the (meth)acrylate has a glass transition temperature of -30°C or higher when it is a homopolymer. <5> The inkjet ink according to any one of <1> to <4>, wherein the (meth)acrylate has a molecular weight of 300 to 1000. <6> The inkjet ink according to any one of <1> to <5>, wherein the particles further comprise a polymerizable monomer having a cyclic structure. <7> The polymerizable monomer having a cyclic structure has a hydrogen bonding term of 5.0 MPa in its solubility parameter. １／２ The inkjet ink described in <6> below. <8> The inkjet ink described in <6> or <7>, wherein the mass ratio of the content of polymerizable monomer having a cyclic structure to the content of (meth)acrylate is 0.1 to 3.0. <9> The inkjet ink described in any one of <1> to <8>, wherein the particles further comprise a polymerizable oligomer having a weight-average molecular weight of 3000 or more. <10> The inkjet ink described in <9>, wherein the polymerizable oligomer has a urethane structure. <11> The inkjet ink described in <9> or <10>, wherein the mass ratio of the content of polymerizable oligomer to the content of (meth)acrylate is 0.4 to 2.0. <12> The inkjet ink described in any one of <1> to <11>, wherein the particles further comprise a polyfunctional polymerizable monomer that does not fall under the category of (meth)acrylate, has a ClogP value of 3.0 or more, and does not have a cyclic structure. <13> The inkjet ink according to <12>, wherein the mass ratio of the content of polyfunctional polymerizable monomer to the content of (meth)acrylate is 0.1 to 3.0. <14> An inkjet recording method comprising the steps of: applying the inkjet ink according to any one of <1> to <13> onto a substrate using an inkjet recording method; and irradiating the inkjet ink applied onto the substrate with an active energy ray.

[0006] According to this disclosure, an inkjet ink and an inkjet recording method are provided that exhibit excellent ejection properties when stored in low-temperature and high-temperature environments.

[0007] Figure 1 shows the character image used to evaluate the image quality in the embodiment.

[0008] In this disclosure, numerical ranges indicated using "~" mean a range that includes the numbers before and after "~" as the minimum and maximum values, respectively. In this disclosure, the amount of each component in a composition means the total amount of multiple substances present in the composition, unless otherwise specified, if there are multiple substances corresponding to each component in the composition. In numerical ranges described in steps in this disclosure, the upper or lower limit stated in one numerical range may be replaced with the upper or lower limit of another numerical range described in steps, or with the values ​​shown in the examples. In this disclosure, the term "process" includes not only independent processes, but also processes that are not clearly distinguishable from other processes, as long as their intended purpose is achieved. In this disclosure, "*" in chemical formulas indicates a bond position.

[0009] In this disclosure, the concept of “image” includes not only pattern images (e.g., characters, symbols, or figures) but also solid images. In this disclosure, “light” is a concept that includes active energy rays such as gamma rays, beta rays, electron beams, ultraviolet rays, and visible light. In this disclosure, ultraviolet light may be referred to as “UV (Ultra Violet) light.” In this disclosure, light emitted from an LED (Light Emitting Diode) light source may be referred to as “LED light.” In this disclosure, “(meth)acrylic acid” is a concept that includes both acrylic acid and methacrylic acid, “(meth)acrylate” is a concept that includes both acrylate and methacrylate, and “(meth)acryloyl group” is a concept that includes both acryloyl group and methacryloyl group. In this disclosure, “ink ejection performance when stored in a low-temperature environment” means the performance of ink ejected when stored in a low-temperature environment. “Ink ejection performance when stored in a high-temperature environment” means the performance of ink ejected when stored in a high-temperature environment. A low-temperature environment refers to a temperature environment lower than room temperature (25°C), for example, an environment between -20°C and 0°C. A high-temperature environment refers to a temperature environment higher than room temperature (25°C), for example, an environment between 40°C and 70°C.

[0010] [Inkjet Ink] The inkjet ink of this disclosure contains water, a (meth)acrylate having a branched alkylene chain with 10 or more carbon atoms and no cyclic structure, and particles containing a polymer having an acid group.

[0011] The inkjet inks disclosed herein (hereinafter also simply referred to as "inks") exhibit excellent ejection properties when stored in both low-temperature and high-temperature environments. In other words, the inkjet inks disclosed herein exhibit excellent ejection properties when stored in a wide range of temperature environments. The reason for this effect is presumed to be as follows.

[0012] In an image recording method in which an ink containing water and particles containing polymers and polymerizable monomers is deposited onto a substrate, and the deposited ink is cured by irradiation with active energy rays and / or heat is applied to obtain an image, it is sometimes required that the ink has excellent ejection properties when stored in both low-temperature and high-temperature environments. In the above-described image recording method, the ink film hardens as polymerizable monomers leach out from the particles onto the substrate. On the other hand, it is desirable that polymerizable monomers do not leach out from the particles before the ink is ejected. In response to this, the ink of this disclosure contains (meth)acrylate particles having branched alkylene chains with 10 or more carbon atoms and no cyclic structure, and the (meth)acrylate in the ink is less likely to precipitate in low-temperature environments. Furthermore, the (meth)acrylate is less likely to hydrolyze and is less likely to leach out from the particles in high-temperature environments. Therefore, the ink of this disclosure has excellent ejection properties when stored in both low-temperature and high-temperature environments.

[0013] On the other hand, International Publication No. 2024 / 048251 describes an inkjet ink containing water and particles comprising a polymer P having an acid group and a polymerizable compound A, but its purpose is to achieve both abrasion resistance and stretchability of images in image recording materials, and therefore its technical concept differs from that of the inkjet ink of this disclosure.

[0014] The following provides a detailed explanation of each component contained in the ink.

[0015] (Water) The ink contains water. The water content relative to the total amount of ink is, for example, 10% to 99% by mass. Preferably, the water content relative to the total amount of ink is 10% by mass or more, more preferably 20% by mass or more, even more preferably 30% by mass or more, and particularly preferably 50% by mass or more.

[0016] The upper limit of the water content relative to the total amount of ink is determined appropriately depending on the content of other components, but is, for example, 99% by mass, preferably 95% by mass, and more preferably 90% by mass.

[0017] <Particles> The ink contains at least one type of particle. The particles include a (meth)acrylate having branched alkylene chains with 10 or more carbon atoms and no cyclic structure, and a polymer having acidic groups. Hereinafter, the particles contained in the ink will also be referred to as "specific particles." The (meth)acrylate having branched alkylene chains with 10 or more carbon atoms and no cyclic structure will also be referred to as "(meth)acrylate A." The inclusion of (meth)acrylate A and the polymer having acidic groups in the specific particles contributes to improving the ink's discharge performance when stored in low-temperature and high-temperature environments. A preferred embodiment of the ink is such that (meth)acrylate A remains in the specific particles in the ink before it is applied to the substrate, and (meth)acrylate A seeps out from the specific particles in the ink once it is applied to the substrate.

[0018] (A (meth)acrylate having a branched alkylene chain with 10 or more carbon atoms and not having a cyclic structure) The specified particle contains at least one type of (meth)acrylate A. The specified particle may contain only one type of (meth)acrylate A, or two or more types.

[0019] (Meth)acrylate A has branched alkylene chains with 10 or more carbon atoms and does not have a cyclic structure. (Meth)acrylate A has a low freezing point and does not precipitate easily at low temperatures. In addition, (meth)acrylate A is more hydrophobic and less susceptible to hydrolysis compared to (meth)acrylates with linear alkylene chains.

[0020] (Meth)acrylate A has a (meth)acryloyl group. The number of (meth)acryloyl groups may be one or two or more. From the viewpoint of image quality, it is preferable that (meth)acrylate A contains only one (meth)acryloyl group. Also, from the viewpoint of polymerizability, it is preferable that the (meth)acryloyl group contained in (meth)acrylate A is an acryloyl group.

[0021] The branched alkylene chain contained in (meth)acrylate A has 10 or more carbon atoms, preferably 16 or more, and more preferably 18 or more. The upper limit of the number of carbon atoms is, for example, 40.

[0022] Above all, from the viewpoint of further improving the ink ejectability when stored in low-temperature environments and high-temperature environments, (meth)acrylate A is preferably a compound represented by the following formula (1).

[0023]

[0024] In formula (1), R １ and R ２ are each independently an alkyl group having 6 to 16 carbon atoms.

[0025] R １ and R ２ represented alkyl groups may be either linear alkyl groups or branched alkyl groups. R １ and R ２ represented alkyl groups have 6 to 16 carbon atoms, and preferably 7 to 16 carbon atoms.

[0026] From the viewpoint of further improving the ink ejectability when stored in low-temperature environments and high-temperature environments, (meth)acrylate A preferably has a hydrogen bonding term of the solubility parameter of 2.5 MPa １／２ or less, and more preferably 2.0 MPa １／２ or less. The lower limit of the hydrogen bonding term of the solubility parameter is, for example, 1.5 MPa １／２ .

[0027] A solubility parameter (SP value) is a physical property value defined as the square root of cohesive energy density, and is a numerical value indicating the dissolution behavior of a substance. The HSP value (Hansen solubility parameter) is a parameter that considers the polarity of a substance by dividing the SP value into three components: a dispersion term (δD), a polarity term (δP), and a hydrogen bonding term (δH). The SP value is represented by "δ ２ = δD ２ + δP ２ + δH ２ ".

[0028] In the present disclosure, the dispersion term, polar term, and hydrogen bonding term of the SP value are calculated based on the structure of a compound using Hansen solubility parameter software (product name: HSPiP 5 ｔｈ Edition).

[0029] From the viewpoint of further improving ink ejection performance when stored under low-temperature environments and high-temperature environments, as well as scratch resistance and image quality, the glass transition temperature of (meth)acrylate A when formed into a homopolymer is preferably -40°C or higher, and more preferably -30°C or higher. The upper limit of the glass transition temperature is, for example, 100°C.

[0030] The glass transition temperature when (meth)acrylate A is formed into a homopolymer is measured by the following method. For (meth)acrylate A, a homopolymer having a weight average molecular weight of 10,000 to 20,000 is produced, and the glass transition temperature of the produced homopolymer is measured in accordance with the method described in JIS K7121:2012.

[0031] In the present disclosure, the glass transition temperature is measured using a differential scanning calorimeter, for example, using the product name "DSC-60" manufactured by Shimadzu Corporation. In the present disclosure, the weight average molecular weight is measured using gel permeation chromatography (GPC). For example, as GPC, HLC-8220GPC (manufactured by Tosoh Corporation) is used, three TSKgel Super Multipore HZ-H columns (manufactured by Tosoh Corporation, 4.6 mm ID × 15 cm) are used as columns, and THF (tetrahydrofuran) is used as an eluent. The measurement conditions are: sample concentration 0.45 mass%, flow rate 0.35 ml / min, sample injection volume 10 μl, measurement temperature 40°C, and detection is performed using a differential refractive index (RI) detector. A calibration curve is prepared using 8 samples manufactured by Tosoh Corporation as standard samples, which are product name "TSK Standard Polystyrene": "F-40", "F-20", "F-4", "F-1", "A-5000", "A-2500", "A-1000", and "n-propylbenzene".

[0032] The glass transition temperature of a homopolymer varies depending on its weight-average molecular weight, but when the weight-average molecular weight is between 10,000 and 20,000, the variation is negligibly small.

[0033] From the viewpoint of further improving ink ejection performance when stored in a low-temperature environment, the melting point of (meth)acrylate A is preferably -100°C to 0°C. In this disclosure, the melting point is measured using DSC-60 Plus (manufactured by Shimadzu Corporation).

[0034] From the viewpoint of further improving ink ejection performance, the viscosity of (meth)acrylate A is preferably 1 mPa·s to 150 mPa·s. In this disclosure, viscosity is measured using a viscometer. As a viscometer, for example, a VISCOMETER TV-22 (Toki Sangyo Co., Ltd.) can be used.

[0035] From the viewpoint of odor, (meth)acrylate A preferably has a molecular weight of 300 to 1000, and more preferably 300 to 600. The molecular weight is calculated from the types and number of atoms constituting (meth)acrylate A.

[0036] Examples of (meth)acrylate A include the following compounds. In Table 1, "number of carbon atoms" refers to the number of carbon atoms in the branched alkylene chain contained in (meth)acrylate A. "δH" refers to the hydrogen bonding term of the SP value, and the unit is "MPa". １／２ "Tg" refers to the glass transition temperature when it is a homopolymer, and its unit is "℃".

[0037]

[0038] Other examples of (meth)acrylate A include isocetyl acrylate (product name "Viscote #297", manufactured by Osaka Organic Chemical Industry Co., Ltd., 16 carbon atoms) and branched alkyl acrylate with a molecular weight exceeding 5000 (product name "Viscote HPB", manufactured by Osaka Organic Chemical Industry Co., Ltd., 100 or more carbon atoms).

[0039] The content of (meth)acrylate A is preferably 0.5% to 25% by mass, and more preferably 5% to 21% by mass, relative to the total solid content of the specific particles.

[0040] The content of (meth)acrylate A is preferably 0.1% to 5% by mass, and more preferably 0.8% to 4% by mass, based on the total amount of ink.

[0041] (Other polymerizable compounds) The specific particles may contain other polymerizable compounds other than (meth)acrylate A.

[0042] From the viewpoint of increasing the strength of the ink film, the specific particles preferably further contain polymerizable monomers having a cyclic structure. The cyclic structure may be an aliphatic cyclic structure or an aromatic cyclic structure. Hereinafter, the polymerizable monomer having a cyclic structure will also be referred to as "polymerizable monomer B".

[0043] Examples of monofunctional polymerizable monomers having a cyclic structure include 2-phenoxyethyl acrylate, cyclohexyl acrylate, tetrahydrofurfuryl acrylate, benzyl acrylate, isobornyl acrylate, dicyclopentenyl acrylate, dicyclopentenyloxyethyl acrylate, and dicyclopentanyl acrylate.

[0044] Furthermore, examples of bifunctional polymerizable monomers having a cyclic structure include tricyclodecane dimethanol di(meth)acrylate, bisphenol A ethylene oxide (EO) adduct di(meth)acrylate, bisphenol A propylene oxide (PO) adduct di(meth)acrylate, ethoxylated bisphenol A di(meth)acrylate, alkoxylated dimethylol tricyclodecane di(meth)acrylate, alkoxylated cyclohexanone dimethanol di(meth)acrylate, and cyclohexanone dimethanol di(meth)acrylate.

[0045] Furthermore, examples of trifunctional polymerizable monomers having a cyclic structure include ethoxylated isocyanuric acid triacrylate and ε-caprolactone-modified tris-(2-acryloxyethyl) isocyanurate.

[0046] In particular, from the viewpoint of further increasing the strength of the ink film, the number of polymerizable groups in polymerizable monomer B is preferably two or more, and more preferably two. That is, polymerizable monomer B is preferably a polyfunctional polymerizable monomer having a cyclic structure, and more preferably a bifunctional polymerizable monomer having a cyclic structure. Furthermore, from the viewpoint of scratch resistance, polymerizable monomer B is preferably a polymerizable monomer having an aliphatic cyclic structure, more preferably a polyfunctional polymerizable monomer having an aliphatic cyclic structure, and even more preferably a bifunctional polymerizable monomer having an aliphatic cyclic structure.

[0047] From the viewpoint of ink ejection performance and image quality when stored in a high-temperature environment, polymerizable monomer B has a hydrogen bonding term of 6.0 MPa in its SP value. １／２ Preferably, the following: 5.0 MPa １／２ It is more preferable that the following conditions be met: 4.0 MPa １／２ It is even more preferable that the lower limit of the hydrogen bonding term in the solubility parameter is, for example, 1.0 MPa. １／２ That is the case.

[0048] From the viewpoint of scratch resistance, polymerizable monomer B is preferably of -50°C or higher, and more preferably of 100°C or higher, when it is in the form of a homopolymer. The upper limit of the glass transition temperature is, for example, 250°C.

[0049] The molecular weight of polymerizable monomer B is not particularly limited, but is preferably between 250 and 1000.

[0050] Examples of polymerizable monomer B include the following compounds.

[0051]

[0052]

[0053] When specific particles contain polymerizable monomer B, the content of polymerizable monomer B is preferably 0.5% to 20% by mass, and more preferably 1% to 10% by mass, relative to the total solid content of the specific particles.

[0054] The content of polymerizable monomer B is preferably 0.1% to 5% by mass, and more preferably 0.3% to 3% by mass, based on the total amount of ink.

[0055] The mass ratio of polymerizable monomer B to (meth)acrylate A is preferably 0.01 to 10.0, more preferably 0.05 to 5.0, and even more preferably 0.1 to 3.0. When the above mass ratio is 0.01 or higher, scratch resistance is excellent. When the above mass ratio is 10.0 or lower, ink ejection performance and image quality are excellent when stored in a high-temperature environment.

[0056] From the viewpoint of enhancing the flexibility of the ink film, the specific particles preferably further contain polymerizable oligomers with a weight-average molecular weight of 3000 or more. Hereinafter, polymerizable oligomers with a weight-average molecular weight of 3000 or more will also be referred to as "polymerizable oligomer C".

[0057] The weight-average molecular weight of polymerizable oligomer C is 3000 or more, preferably 10000 or more. The upper limit of the weight-average molecular weight is, for example, 20000.

[0058] The number of polymerizable groups in polymerizable oligomer C is preferably two or more, more preferably 2 to 15, and even more preferably 2. That is, polymerizable oligomer C is preferably a polyfunctional polymerizable oligomer with a weight-average molecular weight of 3000 or more, and more preferably a bifunctional polymerizable oligomer with a weight-average molecular weight of 3000 or more.

[0059] From the viewpoint of further enhancing the flexibility of the ink film, polymerizable oligomer C is preferably a urethane structure, and more preferably a urethane (meth)acrylate oligomer.

[0060] When the specific particles contain polymerizable oligomer C, the content of polymerizable oligomer C is preferably 0.1% to 20% by mass, and more preferably 0.5% to 13% by mass, relative to the total solid content of the specific particles.

[0061] The content of polymerizable oligomer C is preferably 0.05% to 5% by mass, and more preferably 0.5% to 2% by mass, based on the total amount of ink.

[0062] The mass ratio of polymerizable oligomer C to (meth)acrylate A is preferably 0.05 to 5.0, more preferably 0.1 to 4.0, and even more preferably 0.4 to 2.0. When the above mass ratio is 0.05 or higher, scratch resistance is excellent. When the above mass ratio is 5.0 or lower, ink ejection performance and image quality are excellent when stored in a high-temperature environment.

[0063] From the viewpoint of improving ink ejection performance and image quality, it is preferable that the specific particles further include a polyfunctional polymerizable monomer that does not fall under (meth)acrylate A and does not have a cyclic structure.

[0064] Examples of polyfunctional polymerizable monomers that do not fall under (meth)acrylate A and do not have a cyclic structure include polyethylene glycol diacrylate, polypropylene glycol diacrylate, polytetramethylene glycol diacrylate, 1,3-butylene glycol diacrylate, 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate (hereinafter also referred to as "HDDA"), 1,9-nonanediol diacrylate (hereinafter also referred to as "NDDA"), and 1,10-decanediol diacrylate (hereinafter referred to as "DDD"). Difunctional acrylate compounds such as: 3-methylpentadiol diacrylate (also known as "A"), 3-methylpentadiol diacrylate (hereinafter also known as "3MPDDA"), neopentyl glycol diacrylate, hydroxyneopentyl glycol diacrylate, propoxylated neopentyl glycol diacrylate, alkoxylated hexanediol diacrylate, diethylene glycol diacrylate, tetraethylene glycol diacrylate, dipropylene glycol diacrylate, tripropylene glycol diacrylate (hereinafter also known as "TPGDA"), propylene oxide modified neopentyl glycol diacrylate, neopentyl glycol propylene oxide adduct diacrylate; trimethylolpropane triacrylate, pentaerythritol triacrylate, dipentaerythritol tetraacrylate, ditrimethylolpropane tetraacrylate (hereinafter also known as "DTMPTA"), dipentaerythritol pentaacrylate, dipentaerythritol hexaacrylate, caprolactone modified trimethylolpropane triacrylate, pentaerythritol Examples include tetraacrylate, pentaerythritol ethoxytetraacrylate, ethoxylated dipentaerythritol hexaacrylate, caprolactam-modified dipentaerythritol hexaacrylate, propoxylated glycerin triacrylate, ethoxylated trimethylolpropane triacrylate, trimethylolpropanepropylene oxide (average number of repetitions 1)-modified triacrylate (hereinafter also referred to as "POTMPTA"), propoxylated trimethylolpropane triacrylate, and other acrylate compounds with three or more functionalities.

[0065] The polyfunctional polymerizable monomer, which does not fall under (meth)acrylate A and does not have a cyclic structure, preferably has a ClogP value of 3.0 or higher from the viewpoint of improving the ejection performance and image quality of the ink film. That is, it is more preferable that the specific particles contain a polyfunctional polymerizable monomer (hereinafter also referred to as "polymerizable monomer D") that does not fall under (meth)acrylate A, has a ClogP value of 3.0 or higher, and does not have a cyclic structure. Since polymerizable monomer D has a ClogP value of 3.0 or higher, it is hydrophobic, and when polymerizable monomer D is contained in the specific particles, the ink film formed by applying ink to the substrate spreads easily, resulting in excellent curability. Furthermore, when polymerizable monomer D is contained in the specific particles, graininess of the ink image is suppressed. The ClogP value of polymerizable monomer D is more preferably 4 or higher, and even more preferably 4.5 or higher. The ClogP value of polymerizable monomer D is, for example, 20 or lower. In this disclosure, the ClogP value is calculated using the fragment method. ChemDraw Professional 16 is a computational software that uses the fragmentation method.

[0066] Examples of polymerizable monomer D include HDDA (ClogP value: 3.0), propylene oxide-modified neopentyl glycol diacrylate (ClogP value: 3.2), POTMPTA (ClogP value: 4.9), DDDA (ClogP value: 5.1), and DTMPTA (ClogP value: 5.7). Polymerizable monomer D preferably contains at least one selected from the group consisting of HDDA, propylene oxide-modified neopentyl glycol diacrylate, POTMPTA, DDDA, and DTMPTA, more preferably contains at least one selected from the group consisting of POTMPTA and DTMPTA, and even more preferably contains POTMPTA.

[0067] When specific particles contain polymerizable monomer D, the content of polymerizable monomer D is preferably 0.5% to 20% by mass, and more preferably 1% to 10% by mass, relative to the total solid content of the specific particles.

[0068] The content of polymerizable monomer D is preferably 0.1% to 5% by mass, and more preferably 0.3% to 3% by mass, based on the total amount of ink.

[0069] The mass ratio of polymerizable monomer D to (meth)acrylate A is preferably 0.01 to 10.0, more preferably 0.05 to 5.0, and even more preferably 0.1 to 3.0. When the above mass ratio is 0.01 or higher, the image quality is excellent. When the above mass ratio is 10.0 or lower, the ink discharge performance is excellent when stored in a high-temperature environment.

[0070] The specific particles may contain polymerizable compounds other than (meth)acrylate A, polymerizable monomer B, polymerizable oligomer C, and polymerizable monomer D.

[0071] (Polymers containing acidic groups) The specified particles contain at least one polymer containing acidic groups (hereinafter also simply referred to as "polymer P").

[0072] Polymer P plays a role in retaining polymerizable compounds such as (meth)acrylate A within specific particles in the ink before it is applied to the substrate.

[0073] Polymer P may be a chain polymer or a crosslinked polymer.

[0074] In this disclosure, "chain polymer" means a polymer that does not have a crosslinking structure, and "crosslinked polymer" means a polymer that has a crosslinking structure.

[0075] The chain polymer may have a cyclic structure or a branched structure.

[0076] For specific particles containing polymer P, which is a chain-like polymer, see, for example, Japanese Patent Publication No. 6584677.

[0077] A preferred embodiment of the specific particles when polymer P is a crosslinked polymer is a microcapsule comprising a shell made of polymer P which is a crosslinked polymer, and a core containing (meth)acrylate A.

[0078] For specific particles containing polymer P, which is a crosslinked polymer, see, for example, Japanese Patent Publication No. 6510681.

[0079] -Weight-average molecular weight (Mw)- The weight-average molecular weight (Mw) of polymer P is preferably 3,000 to 200,000, more preferably 4,000 to 150,000, even more preferably 5,000 to 100,000, particularly preferably 8,000 to 80,000, and most preferably 10,000 to 50,000.

[0080] When the Mw of polymer P is 3000 or higher, the storage stability of the ink is further improved. This is thought to be because, when the Mw of polymer P is 3000 or higher, the function of polymer P (the function of retaining (meth)acrylate A within specific particles; in other words, the function of suppressing the leaching of (meth)acrylate A from specific particles) is more effectively exerted in the ink before it is applied to the substrate.

[0081] When the Mw of polymer P is 200,000 or less, the image blocking resistance is further improved. This is thought to be because when the Mw of polymer P is 200,000 or less, the decrease in fluidity (i.e., thickening) during the drying process of the ink applied to the substrate is suppressed, and as a result, the evaporation of liquid components (i.e., water and water-soluble organic solvents) from the ink is further promoted.

[0082] -Glass transition temperature (Tg)- There are no particular restrictions on the glass transition temperature (Tg) of polymer P. From the viewpoint of improving the mobility of polymer P and further improving image quality (specifically, suppressing image graininess), the Tg of polymer P is preferably 120°C or lower, more preferably 100°C or lower, even more preferably 80°C or lower, and particularly preferably 70°C or lower.

[0083] On the other hand, the Tg of polymer P is preferably 0°C or higher, more preferably 10°C or higher, even more preferably 20°C or higher, and particularly preferably 30°C or higher.

[0084] In this disclosure, the glass transition temperature (Tg) of polymer P refers to a value measured using differential scanning calorimetry (DSC).

[0085] The specific measurement of the glass transition temperature is carried out in accordance with the methods described in JIS K 7121 (1987) or JIS K 6240 (2011). The glass transition temperature in this disclosure is the extrapolation glass transition onset temperature (hereinafter sometimes referred to as Tig). The method for measuring the glass transition temperature will be described in more detail. When determining the glass transition temperature, the apparatus is held at a temperature approximately 50°C lower than the expected glass transition temperature of the resin until it stabilizes, and then heated at a heating rate of 20°C / min to a temperature approximately 30°C higher than the temperature at which the glass transition ends, and a differential thermal analysis (DTA) curve or DSC curve is created. The extrapolation glass transition onset temperature (Tig), i.e., the glass transition temperature in this disclosure, is determined as the temperature at the intersection of a straight line drawn by extending the baseline on the low-temperature side of the DTA curve or DSC curve to the high-temperature side, and a tangent line drawn at the point where the slope of the curve of the step-like change portion of the glass transition is maximum. If the ink contains two or more polymers P, the glass transition temperature (Tg) of polymer P represents the weighted average of the glass transition temperatures of each individual polymer P.

[0086] Examples of polymer P include urethane polymer, urethane urea polymer, urea polymer, acrylic polymer, polyester, polyolefin, polystyrene, polycarbonate, and polyamide.

[0087] Here, urethane polymer means a polymer that contains urethane bonds but does not contain urea bonds, urea polymer means a polymer that contains urea bonds but does not contain urethane bonds, and urethane-urea polymer means a polymer that contains both urethane bonds and urea bonds.

[0088] Furthermore, acrylic polymer means a polymer (homopolymer or copolymer) of raw material monomers that includes at least one selected from the group consisting of acrylic acid, derivatives of acrylic acid (e.g., acrylic acid esters, etc.), methacrylic acid, and derivatives of methacrylic acid (e.g., methacrylic acid esters, etc.).

[0089] -Bond U- The polymer P preferably contains bond U, which is at least one of a urethane bond and a urea bond. In other words, the polymer P is preferably a urethane polymer, a urethane-urea polymer, or a urea polymer.

[0090] When polymer P contains bond U, specific particles tend to interact with each other in the ink that has landed on the substrate due to the interaction between bond Us (e.g., hydrogen bonding). Therefore, linking of specific particles by polymerization of (meth)acrylate A that seeps out from specific particles proceeds more easily. As a result, hardening between specific particles proceeds more easily, and the scratch resistance of the image is improved.

[0091] Bond U preferably includes a urethane bond. In other words, polymer P preferably includes a urethane bond and does not include a urea bond, or it preferably includes both a urethane bond and a urea bond.

[0092] - Acid Groups - Polymer P preferably contains at least one type of acid group. This contributes to the dispersion stability of specific particles in the ink, and as a result, the storage stability of the ink is further improved.

[0093] The acidic group may or may not be neutralized.

[0094] Examples of unneutralized acid groups include carboxyl groups, sulfo groups, sulfate groups, phosphonic acid groups, and phosphate groups.

[0095] A neutralized acid group refers to an acid group in the form of a "salt" (for example, a salt of a carboxyl group (e.g., -COONa)). Examples of neutralized acid groups include salts of acid groups such as carboxyl groups, sulfo groups, sulfate groups, phosphonic acid groups, and phosphate groups.

[0096] Neutralization can be carried out using, for example, alkali metal hydroxides (e.g., sodium hydroxide, potassium hydroxide, etc.) or organic amines (e.g., triethylamine, etc.).

[0097] As for the acid group in polymer P, from the viewpoint of further improving the storage stability of the ink, at least one selected from the group consisting of carboxyl group, salt of carboxyl group, sulfo group, salt of sulfo group, sulfate group, salt of sulfate group, phosphonic acid group, salt of phosphonic acid group, phosphate group, and salt of phosphate group is preferred, and at least one selected from the group consisting of carboxyl group, salt of carboxyl group, sulfo group, and salt of sulfo group is more preferred.

[0098] In the above-mentioned salts of carboxyl groups, sulfo groups, sulfate groups, phosphonic acid groups, and phosphate groups, alkali metal salts or organic amine salts are preferred as the "salt," and organic amine salts are more preferred.

[0099] In the organic amine salt, N,N-diisopropylethylamine or triethylamine are preferred as the organic amine.

[0100] Furthermore, if the total number of millimoles of acid groups (e.g., carboxyl groups and salts of carboxyl groups) contained in 1 g of polymer P is defined as the acid value of polymer P, then 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.

[0101] Furthermore, the degree of neutralization of the acid groups in polymer P is preferably 50% to 100%, and more preferably 70% to 100%.

[0102] Here, the degree of neutralization refers to the ratio of the number of neutralized acid groups (e.g., salts of carboxyl groups) to the total number of unneutralized acid groups (e.g., carboxyl groups) in polymer P (i.e., the ratio [number of neutralized acid groups / (number of unneutralized acid groups + number of neutralized acid groups)]). The degree of neutralization of acid groups in polymer P can be measured by neutralization titration.

[0103] -Polymerizable Groups- The specific particles include not only polymer P but also (meth)acrylate A. Therefore, polymer P does not necessarily need to contain polymerizable groups. However, from the viewpoint of further improving the scratch resistance of the image, polymer P may contain polymerizable groups.

[0104] The polymerizable groups that may be included in polymer P are preferably photopolymerizable groups or thermally polymerizable groups.

[0105] As the photopolymerizable group, a radical polymerizable group is preferred, a group containing an ethylenically double bond is more preferred, and (meth)acryloyl, allyl, styryl, or vinyl groups are even more preferred. As the radical polymerizable group, the (meth)acryloyl group is particularly preferred from the viewpoint of radical polymerization reactivity and the hardness of the formed film.

[0106] Preferred thermally polymerizable groups include epoxy groups, oxetanyl groups, azilidinyl groups, azetidinyl groups, ketone groups, aldehyde groups, or blocked isocyanate groups.

[0107] Polymer P may contain only one polymerizable group, or it may contain two or more polymerizable groups.

[0108] The presence of polymerizable groups in polymer P can be confirmed, for example, by Fourier transform infrared spectroscopy (FT-IR) analysis.

[0109] When the number of millimoles of ethylenic double bonds in 1 g of polymer P is defined as the C=C value of polymer P, the C=C value of polymer P is preferably 0.05 mmol / g or more, more preferably 0.10 mmol / g or more, even more preferably 0.30 mmol / g or more, and particularly preferably 0.50 mmol / g or more, from the viewpoint of further improving the hardness of the image.

[0110] From the viewpoint of further improving the water resistance and alcohol resistance of the image, the C=C value of polymer P is preferably 0.05 mmol / g or more, more preferably 0.10 mmol / g or more, even more preferably 0.30 mmol / g or more, particularly preferably 0.50 mmol / g or more, extremely preferably 0.60 mmol / g or more, and most preferably 0.70 mmol / g or more.

[0111] On the other hand, from the viewpoint of improving the curability of the ink over time (i.e., suppressing the decrease in the curability of the ink over time), the C=C value of polymer P is preferably 4.00 mmol / g or less, more preferably 3.00 mmol / g or less, even more preferably 2.00 mmol / g or less, and particularly preferably 1.50 mmol / g or less.

[0112] Polymer P may contain structures other than those described above (i.e., bond U, acid group, and polymerizable group). Examples of other structures include polysiloxane bonds (i.e., divalent polysiloxane groups), monovalent polysiloxane groups, monovalent fluorinated hydrocarbon groups, and divalent fluorinated hydrocarbon groups.

[0113] - Preferred structure of polymer P - Polymer P preferably comprises structural units derived from an isocyanate compound and structural units derived from a compound containing an active hydrogen group.

[0114] The polymer P in the above preferred embodiment contains a bond U formed by the reaction of an isocyanate group of an isocyanate compound and an active hydrogen group of a compound containing an active hydrogen group.

[0115] The active hydrogen group is preferably a hydroxyl group, a primary amino group, or a secondary amino group. For example, a urethane group is formed by the reaction of an isocyanate group with a hydroxyl group. Alternatively, a urea group is formed by the reaction of an isocyanate group with a primary or secondary amino group.

[0116] The isocyanate compounds and compounds containing active hydrogen groups that serve as raw materials for polymer P having the above-mentioned preferred structure may hereinafter be referred to as raw material compounds.

[0117] The isocyanate compound used as a raw material may be one type or two or more types. The compound containing an active hydrogen group used as a raw material may be one type or two or more types.

[0118] Among the isocyanate compounds used as raw material compounds, at least one isocyanate compound with two or more functions is preferred.

[0119] As the starting material compound, at least one compound containing active hydrogen groups is preferably a compound containing two or more active hydrogen groups.

[0120] Preferably, at least one of the raw material compounds, an isocyanate compound and a compound containing an active hydrogen group, contains a hydrophilic group. This facilitates the production of a polymer P containing a hydrophilic group. In this case, at least some of the hydrophilic groups in the final polymer P may be groups in which the hydrophilic groups in the raw material compound have been neutralized. A more preferred embodiment is one in which at least one of the raw material compounds containing an active hydrogen group is a compound containing both an active hydrogen group and a hydrophilic group.

[0121] When polymer P contains polymerizable groups, it is preferable that at least one of the raw material compounds, an isocyanate compound and a compound containing an active hydrogen group, contains polymerizable groups. This facilitates the production of polymer P containing polymerizable groups. A more preferred embodiment is one in which at least one of the raw material compounds containing an active hydrogen group is a compound containing both an active hydrogen group and a polymerizable group.

[0122] As mentioned above, polymer P may be a linear polymer or a crosslinked polymer. A linear polymer as polymer P can be produced by reacting a bifunctional isocyanate compound with a compound containing two active hydrogen groups. A crosslinked polymer as polymer P can be produced by reacting a trifunctional or more isocyanate compound with a compound containing two or more active hydrogen groups. A crosslinked polymer as polymer P can also be produced by reacting a bifunctional isocyanate compound with a compound containing three or more active hydrogen groups.

[0123] For preferred starting material compounds, for example, compounds disclosed in International Publication No. 2023 / 053593 can be used.

[0124] The polymer P content relative to the total solid content of specific particles is preferably 10% to 90% by mass, more preferably 20% to 80% by mass, even more preferably 30% to 70% by mass, and particularly preferably 40% to 60% by mass.

[0125] In this disclosure, the total solid content of a specific particle means the total amount of the specific particle excluding the solvent (i.e., water and organic solvents). If the specific particle does not contain a solvent, the total solid content of the specific particle is equal to the total amount of the specific particle.

[0126] The polymer P content is preferably 0.3% to 20% by mass, more preferably 0.5% to 15% by mass, and even more preferably 1% to 10% by mass, relative to the total amount of ink.

[0127] (Radical polymerization initiator) The specific particles preferably contain at least one type of radical polymerization initiator.

[0128] In this disclosure, a radical polymerization initiator means a compound that absorbs light and generates radicals.

[0129] When specific particles contain a radical polymerization initiator, the abrasion resistance and adhesion of the ink film are further improved. This is thought to be because the distance between (meth)acrylate A and the radical polymerization initiator becomes shorter, improving the curing sensitivity (hereinafter also simply referred to as "sensitivity") of the ink film.

[0130] Furthermore, when specific particles contain a radical polymerization initiator, it becomes possible to use radical polymerization initiators that were previously difficult to use due to their high sensitivity but low dispersibility or solubility in water (for example, radical polymerization initiators with a solubility in water of 1.0% by mass or less at 25°C). This broadens the range of radical polymerization initiators that can be used, and consequently, the range of light sources that can be used. As a result, curing sensitivity may be improved compared to conventional methods.

[0131] As mentioned above, radical polymerization initiators that are highly sensitive but difficult to use due to low dispersibility or solubility in water include, specifically, carbonyl compounds and acylphosphine oxide compounds, which will be described later, with acylphosphine oxide compounds being preferred.

[0132] By incorporating a radical polymerization initiator with low solubility in water into specific particles, the radical polymerization initiator can be incorporated into the ink.

[0133] Furthermore, inks in which specific particles contain a radical polymerization initiator exhibit superior storage stability compared to conventional photocurable compositions. This is thought to be because the inclusion of the radical polymerization initiator in the specific particles suppresses aggregation or sedimentation of the radical polymerization initiator.

[0134] For example, paragraphs 0091 to 0094 of International Publication No. 2016 / 052053 can be appropriately referenced as radical polymerization initiators.

[0135] As radical polymerization initiators, (a) carbonyl compounds such as aromatic ketones or (b) acylphosphine oxide compounds are preferred. Examples of radical polymerization initiators include bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (e.g., product name "Omnirad 819", manufactured by IGM Resins B.V.), 2-(dimethylamine)-1-(4-morpholinophenyl)-2-benzyl-1-butanone (e.g., product name "Omnirad 369", manufactured by IGM Resins B.V.), 2-methyl-1-(4-methylthiophenyl)-2-morpholinopropan-1-one (e.g., product name "Omnirad 907", manufactured by IGM Resins B.V.), and 1-hydroxycyclohexylphenyl ketone (product name "Omnirad 184", manufactured by IGM Resins B.V. Examples include (manufactured by IGM Resins B.V.), 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (e.g., product name "Omnirad TPO-H", manufactured by IGM Resins B.V.), and (2,4,6-trimethylbenzoyl)ethoxyphenylphosphine oxide (e.g., product name "Omnirad TPO-L", manufactured by IGM Resins B.V.).

[0136] In particular, from the viewpoint of improving sensitivity and compatibility with LED light, (b) acylphosphine oxide compounds are preferred as radical polymerization initiators, and monoacylphosphine oxide compounds or bisacylphosphine oxide compounds are more preferred.

[0137] Preferred wavelengths for LED light are 355 nm, 365 nm, 385 nm, 395 nm, or 405 nm.

[0138] Specific particles in an embodiment containing a polymerization initiator can be produced, for example, by emulsifying a mixture of an oil phase component containing polymer P (or a raw material compound for producing polymer P), (meth)acrylate A, and a polymerization initiator, and an aqueous phase component.

[0139] The content of the radical polymerization initiator is preferably 0.1% to 15% by mass, more preferably 0.5% to 10% by mass, and even more preferably 1% to 6% by mass, relative to the total solid content of the specific particles.

[0140] The content of the radical polymerization initiator is preferably 0.1% to 3.0% by mass, more preferably 0.3% to 2.0% by mass, and even more preferably 0.5% to 1.5% by mass, based on the total amount of ink.

[0141] (Sensitizer) The specific particles preferably contain at least one sensitizer.

[0142] If the specific particles contain a photopolymerization initiator, it is preferable that the specific particles also contain a sensitizer.

[0143] If specific particles contain a sensitizer, the decomposition of the photopolymerization initiator by irradiation with active energy rays may be further accelerated.

[0144] A sensitizer is a substance that absorbs specific active energy rays and enters an electronically excited state. When the electronically excited sensitizer comes into contact with a photopolymerization initiator, it undergoes processes such as electron transfer, energy transfer, and exothermic reactions. This accelerates the chemical changes of the photopolymerization initiator, namely decomposition, radical formation, and the generation of acids or bases.

[0145] Examples of sensitizers include benzophenone, thioxanthone, 2,4-diethylthioxanthone, isopropylthioxanthone, anthraquinone, 3-acylmarin derivatives, terphenyl, styrylketone, 3-(aloylmethylene)thiazoline, camphor quinone, eosin, rhodamine, and erythrosine.

[0146] Furthermore, as sensitizers, compounds represented by general formula (i) described in Japanese Patent Publication No. 2010-24276, compounds represented by general formula (I) described in Japanese Patent Publication No. Hei 6-107718, and the like can also be suitably used.

[0147] In particular, as a sensitizer, at least one selected from thioxanthone, 2,4-diethylthioxanthone, isopropylthioxanthone, and benzophenone is preferred from the viewpoint of compatibility with LED light and reactivity with photopolymerization initiators, at least one selected from thioxanthone, 2,4-diethylthioxanthone, and isopropylthioxanthone is more preferred, and 2,4-diethylthioxanthone is even more preferred.

[0148] If the specific particles contain a sensitizer, the sensitizer content is preferably 0.1% to 20% by mass, more preferably 0.2% to 15% by mass, and even more preferably 0.3% to 10% by mass, relative to the solid content of the specific particles.

[0149] The sensitizer content is preferably 0.01% to 0.5% by mass, more preferably 0.05% to 0.3% by mass, and even more preferably 0.1% to 0.2% by mass, relative to the total amount of ink.

[0150] Specific particles containing polymerization initiators and sensitizers can be produced, for example, by emulsifying a mixture of an oil phase component containing polymer P (or a raw material compound for producing polymer P), (meth)acrylate A, a photopolymerization initiator, and a sensitizer, and an aqueous phase component.

[0151] (Other Components) The specific particles may contain other components besides those described above. Examples of other components include compounds containing at least one selected from the group consisting of polysiloxane bonds (i.e., divalent polysiloxane groups), monovalent polysiloxane groups, monovalent fluorinated hydrocarbon groups, and divalent fluorinated hydrocarbon groups.

[0152] (Method for producing an aqueous dispersion of specific particles) The ink of this disclosure can be produced by producing an aqueous dispersion of specific particles containing the above-mentioned specific particles and water, and then adding other components to the obtained aqueous dispersion as necessary.

[0153] Furthermore, since the inks of this disclosure are in the form of aqueous dispersions of specific particles, depending on the composition of the ink, it is also possible to manufacture the ink directly as an aqueous dispersion of specific particles (i.e., without adding other components).

[0154] There are no particular restrictions on the method for producing the aqueous dispersion of specific particles. The following are examples of methods for producing the aqueous dispersion of specific particles: Method A and Method B.

[0155] -Method A- Method A comprises the step of mixing an oil phase component containing an organic solvent, polymer P, and polymerizable monomer with an aqueous phase component containing water, and emulsifying them to obtain an aqueous dispersion of specific particles. Method A is suitable as a method for producing an aqueous dispersion of specific particles containing polymer P in the form of a chain-like polymer. For Method A, refer to prior art such as Japanese Patent Publication No. 6584677.

[0156] -Method B- Method B involves mixing an oil phase component containing an organic solvent, a raw material compound for polymer P (for example, a trifunctional or higher isocyanate compound, a compound having two or more active hydrogen groups, etc.), and a polymerizable monomer with an aqueous phase component containing water, and emulsifying the mixture to obtain an aqueous dispersion of specific particles. Method B is suitable as a method for producing an aqueous dispersion of specific particles (for example, microcapsules) containing polymer P in a crosslinked polymer form. For more information on Method B, please refer to publicly available documents such as International Publication No. 2016 / 052053.

[0157] <Organic Solvents> The ink preferably contains at least one organic solvent (preferably a water-soluble organic solvent). This ensures better ink discharge performance.

[0158] In this disclosure, "water-soluble" in "water-soluble organic solvent" means the property of dissolving 1 g or more in 100 g of water at 25°C. The amount of 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.

[0159] The content of the water-soluble organic solvent is preferably 1% to 35% by mass, more preferably 3% to 30% by mass, even more preferably 5% to 20% by mass, and particularly preferably 7% to 15% by mass, based on the total amount of ink.

[0160] When the water-soluble organic solvent content is 1% by mass or more, the ink ejection performance is further improved.

[0161] When the water-soluble organic solvent content is 35% by mass or less, the storage stability of the ink is further improved.

[0162] Specific examples of water-soluble organic solvents are as follows: • Alcohols (e.g., methanol, ethanol, propanol, isopropanol, butanol, isobutanol, secondary butanol, tertiary butanol, pentanol, hexanol, cyclohexanol, benzyl alcohol, etc.) • Polyhydric alcohols (e.g., ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, butylene glycol, hexanediol, pentanediol, glycerin, hexanetriol, thiodiglycol, 2-methylpropanediol, etc.) - Polyhydric alcohol 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, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monobutyl ether, ethylene glycol monophenyl ether, propylene glycol monophenyl ether, etc.) - Amines (e.g., ethanolamine, diethanolamine, triethanolamine, N-methyldiethanolamine, N-ethyldiethanolamine, morpholine, N-ethylmorpholine, ethylenediamine, diethylenediamine, triethylenetetramine, tetraethylenepentamine, polyethyleneimine, pentamethyldiethylenetriamine, tetramethylpropylenediamine, etc.) - Amides (e.g., formamide, N,N-dimethylformamide, N,N-dimethylacetamide, etc.) • Heterocyclic compounds (e.g., 2-pyrrolidone, N-methyl-2-pyrrolidone, cyclohexylpyrrolidone, 2-oxazolidone, 1,3-dimethyl-2-imidazolidinone, γ-butyrolactone, etc.) • Sulfoxides (e.g., dimethyl sulfoxide) • Sulfones (e.g., sulfolane) • Others (urea, acetonitrile, acetone, etc.)

[0163] <Colorants> The ink may be an ink containing at least one colorant (so-called "colored ink") or an ink that does not contain a colorant (so-called "clear ink").

[0164] If the ink contains a colorant, it is preferable that the colorant is contained outside of the specific particles (i.e., the specific particles do not contain the colorant).

[0165] There are no particular restrictions on the colorant; any known colorants such as pigments, water-soluble dyes, and disperse dyes can be arbitrarily selected and used. Among these, pigments are more preferable as colorants due to their excellent weather resistance and rich color reproducibility.

[0166] There are no particular restrictions on the pigments used, and they can be appropriately selected according to the purpose. Examples include well-known organic and inorganic pigments. Other examples of pigments 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., using the pigment as a dispersion medium, and pigments whose surfaces have been treated with resins, pigment derivatives, etc.).

[0167] Examples of organic and inorganic pigments include yellow pigments, red pigments, magenta pigments, blue pigments, cyan pigments, green pigments, orange pigments, purple pigments, brown pigments, black pigments, and white pigments.

[0168] When using pigments as colorants, pigment dispersants may be used as needed. Furthermore, when using pigments as colorants, self-dispersing pigments having hydrophilic groups on the surface of the pigment particles may be used.

[0169] For colorants and pigment dispersants, paragraphs 0180 to 0200 of Japanese Patent Publication No. 2014-040529 and paragraphs 0122 to 0129 of International Publication No. 2016 / 052053 may be referenced as appropriate.

[0170] If the ink contains a colorant, the colorant content 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, relative to the total amount of ink.

[0171] <Other Ingredients> The ink may contain other ingredients not described above, as needed. These other ingredients may or may not be present in the specific particles. The ink may contain surfactants, polymerization inhibitors, UV absorbers, etc., as other ingredients.

[0172] Furthermore, the ink may contain, if necessary, water-soluble polymerizable monomers, water-soluble photopolymerization initiators, water-soluble resins, etc., outside of the specific particles. For these components, see, for example, paragraphs 0134 to 0157 of International Publication No. 2016 / 052053.

[0173] (Preferred method for manufacturing ink) There are no particular restrictions on the method for manufacturing ink, but preferably, the method includes the steps of: manufacturing an aqueous dispersion of specific particles by the above-described method for manufacturing aqueous dispersions (method A or method B); and adding and mixing other components such as pigments and water-soluble organic solvents to the aqueous dispersion of specific particles.

[0174] Another aspect of the method for manufacturing ink is to directly manufacture ink as an aqueous dispersion of specific particles by a step of manufacturing an aqueous dispersion of specific particles using the above-described method for manufacturing aqueous dispersions (method A or method B) (i.e., a method in which no other components are added to the aqueous dispersion of specific particles).

[0175] (Preferred physical properties of the ink) The viscosity of the ink at 25°C is preferably 3 mPa·s to 15 mPa·s, and more preferably 3 mPa·s to 13 mPa·s. When the viscosity of the ink is within the above range, higher ejection stability can be achieved.

[0176] [Inkjet Recording Method] The inkjet recording method of the present disclosure preferably includes a step of applying the ink of the present disclosure onto a substrate using an inkjet recording method (hereinafter also referred to as the "ink application step") and a step of irradiating the inkjet ink applied onto the substrate with active energy rays (hereinafter also referred to as the "active energy ray irradiation step").

[0177] <Ink Application Process> In the ink application process, the ink of this disclosure is applied to the substrate using an inkjet recording method. There are no particular restrictions on the substrate; it may be a non-permeable substrate or a permeable substrate.

[0178] Here, a non-permeable substrate refers to a substrate whose water absorption rate (unit: mass %) (measurement time: 24 hours) is less than 10 according to the ASTM D570 test method of the ASTM test method.

[0179] The water absorption rate of the non-permeable substrate is preferably 5% by mass or less.

[0180] Examples of non-permeable substrates 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., films made of polyvinyl chloride (PVC), cellulose diacetate, cellulose triacetate, cellulose propionate, cellulose butyrate, cellulose acetate butyrate, cellulose nitrate, polyethylene terephthalate (PET), polyethylene (PE), polystyrene (PS), polypropylene (PP), polycarbonate (PC), polyvinyl acetal, acrylic resin, etc.), paper laminated or vapor-deposited with the aforementioned metals, plastic films laminated or vapor-deposited with the aforementioned metals, leather, wallpaper, etc. Examples of wallpapers include vinyl chloride wallpaper, olefin wallpaper, and nonwoven wallpaper. Examples of permeable substrates include polyester substrates. In particular, it is preferable that the surface of the polyester substrate is coated with resin.

[0181] Examples of leather include natural leather (also called "genuine leather") and synthetic leather (for example, PVC (polyvinyl chloride) leather, PU (polyurethane) leather). For more information on leather, see, for example, paragraphs 0163 to 0165 of Japanese Patent Publication No. 2009-058750.

[0182] For example, when forming an ink film on a non-permeable substrate such as leather (e.g., vehicle seats, bags, shoes, wallets, etc.) or plastic film, the formed ink film is required to have excellent abrasion resistance and stretchability.

[0183] Furthermore, when forming ink films on substrates other than leather and plastic films, the resulting film may require excellent abrasion resistance and stretchability.

[0184] The inkjet recording method of this disclosure can satisfy such requirements. From this viewpoint, it is more effective when PVC is used as the substrate.

[0185] The substrate may be surface-treated to improve its surface energy. Examples of surface treatments include, but are not limited to, corona treatment, plasma treatment, flame treatment, heat treatment, abrasion treatment, and light irradiation treatment (UV treatment).

[0186] The thickness of the substrate is not particularly limited, but from the viewpoint of flexibility, it is preferably 20 μm to 500 μm.

[0187] The ink is preferably ejected using an inkjet recording device and an inkjet recording method.

[0188] The inkjet recording method is not particularly limited as long as it is a method capable of recording an image, and known methods can be used. Examples of inkjet recording methods include a charge control method that ejects ink using electrostatic attraction, a drop-on-demand method (pressure pulse method) that utilizes the vibration pressure of a piezoelectric element, an acoustic inkjet method that converts an electrical signal into an acoustic beam, irradiates the ink with it, and ejects the ink using the radiation pressure, and a thermal inkjet (bubble jet®) method that heats the ink to form bubbles and utilizes the resulting pressure.

[0189] Inkjet heads used in inkjet recording methods include a shuttle method, which uses a short serial head and records while scanning the head in the width direction of the substrate, and a line method, which uses a line head in which recording elements are arranged to cover the entire area of ​​one side of the substrate.

[0190] In the line method, the substrate can be scanned in a direction intersecting the arrangement direction of the recording elements, allowing for pattern formation across the entire substrate surface. This eliminates the need for a transport system such as a carriage that scans the short head. Furthermore, the line method eliminates the need for complex scanning control of the carriage and the substrate; only the substrate moves, resulting in faster recording speeds compared to the shuttle method.

[0191] The resolution of the inkjet head is preferably 300 dpi or higher, more preferably 600 dpi or higher, and even more preferably 800 dpi or higher. Here, dpi (dots per inch) represents the number of dots per 2.54 cm (1 inch).

[0192] The amount of ink droplets ejected from the inkjet head (amount of droplets per dot) is preferably 1 pL (picoliters) to 100 pL, more preferably 3 pL to 80 pL, and even more preferably 3 pL to 50 pL.

[0193] <Activated Energy Ray Irradiation Process> In the activated energy ray irradiation process, activated energy rays are irradiated onto the ink applied to the substrate.

[0194] In this process, irradiation with active energy rays (i.e., exposure) causes (meth)acrylate A and other materials to polymerize, hardening the ink and obtaining an image. More specifically, after the ink lands, (meth)acrylate A effectively seeps out from specific particles, allowing hardening between the specific particles (i.e., bonding between specific particles) to proceed sufficiently, resulting in an image with excellent image quality and scratch resistance.

[0195] The irradiation of the ink dispensed onto the substrate with active energy rays may be performed while the substrate and the ink dispensed onto the substrate are heated. Alternatively, the irradiation of the ink dispensed onto the substrate with active energy rays may be performed while the substrate and the ink dispensed onto the substrate are heated, and gas is blown onto the ink dispensed onto the substrate by a blower.

[0196] Active energy rays that can be used include alpha rays, gamma rays, electron beams, X-rays, ultraviolet rays, visible light, or infrared light.

[0197] Light sources that emit active energy rays include 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 LEDs (light-emitting diodes) and LDs (laser diodes).

[0198] In particular, the light source is preferably a light source for ultraviolet irradiation, such as a metal halide lamp, high-pressure mercury lamp, medium-pressure mercury lamp, low-pressure mercury lamp, or ultraviolet LED (hereinafter also referred to as UV-LED).

[0199] The peak wavelength of ultraviolet light is preferably, for example, 200 nm to 405 nm, more preferably 220 nm to 400 nm, and even more preferably 340 nm to 400 nm.

[0200] The peak wavelength of the light from the LED light source (LED light) is preferably 200 nm to 600 nm, more preferably 300 nm to 450 nm, even more preferably 320 nm to 420 nm, particularly preferably 340 nm to 405 nm, and most preferably 355 nm, 365 nm, 385 nm, 395 nm, or 405 nm.

[0201] Examples of UV-LEDs include those manufactured by Nichia Corporation, which have a primary emission spectrum with wavelengths between 365 nm and 420 nm. Another example is the UV-LED described in U.S. Patent No. 6,084,250, which can emit active radiation centered between 300 nm and 370 nm. Furthermore, by combining several UV-LEDs, it is possible to irradiate with ultraviolet light in different wavelength ranges.

[0202] The irradiation energy of the active energy rays (i.e., the exposure amount) is 20 mJ / cm². ２ Preferably, it is 100 mJ / cm² or higher. ２ It is more preferable that the concentration be 500 mJ / cm² or higher. ２ It is even more preferable that the above conditions are met.

[0203] There is no particular upper limit on the exposure amount, which is 5 J / cm². ２ It may also be 1,500 mJ / cm² ２ That's fine.

[0204] Furthermore, the active energy ray irradiation process may include a step of pre-curing the ink with a relatively small exposure dose and a step of fully curing the ink with a relatively large exposure dose. The exposure dose for pre-curing the ink is 50 mJ / cm². ２ ~500 mJ / cm ２ Preferably, it is 100 mJ / cm ２ ~300 mJ / cm ２ It is preferable that it be so.

[0205] The inkjet recording method of this disclosure may further include a step of heating a substrate (hereinafter also referred to as the "heating step").

[0206] In the heating process, the surface of the substrate opposite to the surface where the ink lands may be heated, the surface where the ink lands may be heated, or both sides of the substrate may be heated. From the viewpoint of causing (meth)acrylate A to seep out from specific particles contained in the ink, it is preferable to heat the surface of the substrate opposite to the surface where the ink lands during the heating process. For example, the surface of the substrate opposite to the surface where the ink lands may be heated by a platen located at the bottom of the substrate.

[0207] The substrate may be heated before the ink hits, heated at the time of ink impact, heated after the ink impact, or any combination thereof.

[0208] From the viewpoint of promoting the leaching of (meth)acrylate A, it is preferable that the substrate is preheated before the ink lands, and more preferably that it is preheated before the ink lands and is also heated at the time of ink lands.

[0209] The heating temperature is preferably 35°C to 60°C, and more preferably 40°C to 50°C.

[0210] The present disclosure will be described in detail below with reference to examples, but the present disclosure is not limited to the following examples.

[0211] Unless otherwise specified, "room temperature" refers to 25°C.

[0212] <Preparation of Polymer P> In a 1-liter three-necked flask equipped with a stirrer, thermometer, and reflux condenser, charge 187.9 g of methyl ethyl ketone, 116.4 g of isophorone diisocyanate, 13.9 g of cyclohexyl dimethanol, 82.9 g of epoxy acrylate (product name "EBECRYL600", manufactured by Daicel Ornex), 26.0 g of 2,2-bis(hydroxymethyl)propionic acid, 45.6 g of hydroxyl group-containing silicone compound (product name "Cylaprene FM-DA11", manufactured by JNC), and 0.01 g of 2-tert-butyl-1,4-benzoquinone. Heat to 70°C and add 0.5 g of bismastris (2-ethylhexanoate) (product name "Neostan U-600", manufactured by Daicel Ornex). Then, stir for 8 hours while maintaining the temperature in the reaction vessel at 70°C. Next, a solution consisting of 64.4 g of methyl ethyl ketone and 221.1 g of 2-propanol is added to the reaction vessel and stirred for 2 hours. Then, the temperature is lowered to 40°C and 25.1 g of N,N-diisopropylethylamine is added. While maintaining the temperature in the reaction vessel at 40°C, the mixture is stirred for 1 hour to obtain a polymer P solution (polymer P content: 40% by mass). Polymer P is a polymer having a carboxyl group.

[0213] [Example 1] <Preparation of aqueous dispersion of specific particles> -Preparation of oil phase component- The following components are mixed and stirred at room temperature for 30 minutes to obtain the oil phase component. Polymer P 40% by mass solution …98.77 g C32A: Product name "DOD-A", manufactured by Shin Nakamura Chemical Industry Co., Ltd. …14.4 g Polymerization initiator: (2,4,6-trimethylbenzoyl)ethoxyphenylphosphine oxide (Product name "Omnirad TPO-L", manufactured by IGM Resins B.V.) …2.4 g Polymerization initiator: Bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide (Product name "Omnirad 819", manufactured by IGM Resins B.V.) …2.4 g Sensitizer: 2,4-diethylthioxanthone (Product name "SpeedCure DETX", manufactured by Arkema) …4.8 g Ethyl acetate …58.85 g Methyl ethyl ketone …117.38 g

[0214] - Preparation of aqueous dispersion of specific particles - The above oil phase components and 84.6 g of distilled water are mixed, and the resulting mixture is emulsified at room temperature using a homogenizer at 7000 rpm (revolutions per minute) for 30 minutes to obtain an emulsion. The obtained emulsion is added to distilled water (30.0 g), and the resulting liquid is heated to 50°C and stirred at 50°C for 4 hours to remove ethyl acetate and methyl ethyl ketone from the liquid by distillation. The liquid from which ethyl acetate and methyl ethyl ketone have been removed is diluted with distilled water to a solid content concentration of 25% by mass to obtain aqueous dispersion of specific particles 1 (content of specific particles: 25% by mass). The volume-average dispersion particle diameter of the specific particles is 100 nm.

[0215] <Ink Preparation> Mix each component to prepare the ink.

[0216] - Aqueous dispersion of the above-mentioned specific particles (content of specific particles: 25% by mass) ... 40 parts by mass - Pigment dispersion Bk: Product name "Pro-jet Black APD1000", manufactured by FUJIFILM Imaging Colorants, pigment concentration 15% by mass ... 13 parts by mass - Surfactant: Polyoxyethylene alkyl ether (Product name "Emulgen 707", manufactured by Kao Corporation, solid content concentration 100% by mass) ... 0.9 parts by mass - Surfactant: Acetylene glycol (Product name "Surfinol 440", manufactured by EVONIK, solid content concentration 100% by mass) ... 0.9 parts by mass - Surfactant: Acetylene glycol (Product name "Surfinol 420", manufactured by EVONIK, solid content concentration 100% by mass) ... 0.9 parts by mass - Wax: Product name "Hi-Tec E6314", manufactured by Toho Chemical Industry Co., Ltd. (solid content concentration 35%) ...0.57 parts by mass, water-soluble organic solvent: propylene glycol (PG) ...14 parts by mass, water ...remaining amount equal to 100 parts by mass of the total ink

[0217] [Examples 2 to 51, Comparative Examples 1 to 3] An aqueous dispersion of specific particles was prepared in the same manner as in Example 1, and ink was obtained in the same manner as in Example 1, such that the content (mass%) of each component contained in the ink was as shown in Tables 4 to 10. Tables 4 to 10 list only polymer P, (meth)acrylate A, polymerizable monomer B, polymerizable oligomer C, polymerizable monomer D, and other polymerizable compounds among the components contained in the ink. In Examples 2 to 51, the amounts of (meth)acrylate A, polymerizable monomer B, polymerizable oligomer C, polymerizable monomer D, and other polymerizable compounds contained in the aqueous dispersion of specific particles were changed compared to Example 1, while the content of other components was the same as in Example 1.

[0218] Details of (meth)acrylate A, polymerizable monomer B, polymerizable oligomer C, polymerizable monomer D, and other polymerizable compounds contained in the ink are as follows: (meth)acrylate A means a (meth)acrylate having a branched alkylene chain with 10 or more carbon atoms and not having a cyclic structure. Polymerizable monomer B means a polymerizable monomer having a cyclic structure. Polymerizable oligomer C means a polymerizable oligomer with a weight-average molecular weight of 3000 or more. Polymerizable monomer D means a monomer that does not fall under (meth)acrylate A and does not have a cyclic structure.

[0219] -(meth)acrylate A- ・C32A: Product name "DOD-A", manufactured by Shin Nakamura Chemical Industry Co., Ltd.

[0220]

[0221] - Multi-branch ISTA: Product name "S-1800ALC", manufactured by Shin Nakamura Chemical Industry Co., Ltd.

[0222]

[0223] ・C28A: Product name “DHD-A”, manufactured by Shin Nakamura Chemical Industry Co., Ltd.

[0224]

[0225] - C34DA: Product name "J20Y-745", manufactured by Nikka Chemical Co., Ltd.

[0226]

[0227] ・C24A: Product name “DTD-A”, manufactured by Shin-Nakamura Chemical Industry Co., Ltd.

[0228]

[0229] • Terminal ISTA: Product name "ISA-001", manufactured by HanNong Chemicals.

[0230]

[0231] • C16A: Product name "MT-1522", Toagosei Co., Ltd.

[0232]

[0233] • IDA F: Product name "Isodecyl Acrylate F", manufactured by BASF.

[0234]

[0235] • 2-PHA: Product name "2-Propylheptyl Acrylate", manufactured by BASF.

[0236]

[0237] -Polymerizable monomer B- • TCDMA: Tricyclodecanedimethanol diacrylate, product name "SR833", manufactured by Arkema.

[0238]

[0239] ・DOGDA: Product name "Dioxaneglycol diacrylate", manufactured by Tokyo Chemical Industry Co., Ltd.

[0240]

[0241] • BPAEODA: EO-modified bisphenol A diacrylate, product name "Ebecryl 150", manufactured by Daicel Corporation.

[0242]

[0243] -Polymerizable Oligomer C- • UA1: Urethane acrylate oligomer, product name "CN8887", manufactured by Arkema • UA2: Urethane acrylate oligomer, product name "CN8888", manufactured by Arkema • UA3: Urethane acrylate oligomer, product name "UV3520EA", manufactured by Mitsubishi Chemical Corporation • UA4: Urethane acrylate oligomer, product name "UV-3500BA", manufactured by Mitsubishi Chemical Corporation • UA5: Urethane acrylate oligomer, product name "GU7400", manufactured by Qualipoly Chemical • UA6: Urethane acrylate oligomer, product name "GU7500", manufactured by Qualipoly Chemical • EA1: Epoxy acrylate oligomer, product name "CN186", manufactured by Arkema Corporation

[0244] -Polymerizable monomer D- • POTMPTA: Trimethylolpropanepropylene oxide (average number of repetitions 1) modified triacrate, product name "M-310", manufactured by Toagosei Co., Ltd. (ClogP value: 4.9)

[0245]

[0246] DTMPTA: Ditrimethylolpropanetetraacrylate, product name "M-408", manufactured by Toagosei Co., Ltd. (ClogP value: 5.7)

[0247]

[0248] - Other polymerizable compounds - LC16A: Product name "Bremmer CA", manufactured by NOF Corporation

[0249]

[0250] LC10A: Product name "Decyl acrylate", manufactured by Tokyo Chemical Industry Co., Ltd.

[0251]

[0252] • 2EHA: Product name "2-ethylhexyl acrylate", manufactured by Tokyo Chemical Industry Co., Ltd.

[0253]

[0254] <Inkjet Recording> A vinyl chloride substrate P282 (Lintec Corporation) is used as the substrate. Droplets are applied to the substrate using a Kyocera head KJ4B1200 while it is heated to 45°C with a platen heater. After application, it is dried with air. After it has dried to a certain extent, an illuminance of 2000 mW / cm is applied using a 385 nm UV-LED. ２ , irradiation energy 1000 mJ / cm ２ The material is then irradiated with ultraviolet light. After that, it is heated to 50°C with a post-heater and dried for 2 minutes to obtain an image record.

[0255] The prepared ink will be used to evaluate its ejection performance (low and high temperatures). The resulting image recordings will be used to evaluate image quality, odor, and scratch resistance. The evaluation method is as follows:

[0256] <Ejection Performance (Low Temperature)> The ink is stored at -20°C for one month. After that, it is left at 25°C for one day, then the ink is set in an inkjet recording device, an image with a halftone dot density of 1% is recorded for 30 minutes, and nozzle clogs are checked afterward. The evaluation criteria are as follows: 5... 0 clogs. 4... 1 or fewer clogs. 3... 3 or fewer clogs. 2... 5 or fewer clogs. 1... More than 5 clogs.

[0257] <Ejection Performance (High Temperature)> Store the ink at 70°C for 3 days. Then, load the ink into an inkjet recording device, record an image with a halftone dot density of 1% for 30 minutes, and check for nozzle clogs afterward. The evaluation criteria are as follows: 5... 0 clogs. 4... 1 or fewer clogs. 3... 3 or fewer clogs. 2... 5 or fewer clogs. 1... More than 5 clogs.

[0258] <Image Quality> Under the image recording conditions described above, the character image shown in Figure 1 was recorded in 5-point, 6-point, 7-point, and 8-point sizes. The character image of each size was observed using a 10x magnification craft magnifying glass (manufactured by Etsumi Co., Ltd.). Based on the observation results, the image detail was evaluated according to the following evaluation criteria. In the following evaluation criteria, the best image quality is 5. -Evaluation Criteria for Image Quality- 5: The character image shown in Figure 1 at 5-point size is formed without distortion or blurring. 4: The character image shown in Figure 1 at 6-point size is formed without distortion or blurring (except in cases corresponding to evaluation 5). 3: The character image shown in Figure 1 at 7-point size is formed without distortion or blurring (except in cases corresponding to evaluations 4 and 5). 2: The character image shown in Figure 1 at 8-point size is formed without distortion or blurring (except in cases corresponding to evaluations 3 to 5). 1: The character image shown in Figure 1, with a size of 8 points, is formed in a distorted or blurred manner.

[0259] <Odor> Place the image recordings in an A4-sized bag. Store at 60°C for 1 hour. Afterwards, open the bag and evaluate the odor. The evaluation criteria are as follows: 5... Only the odor of the substrate is present; no ink odor is detected. 3... A slight ink odor is detected. 1... An ink odor is detected.

[0260] <Scratch Resistance> The image recording material is scratched with a 0.1 mm sapphire needle under a load of 100 g, and the length of the scratch is measured. 5... The scratch length is 10 mm or less. 4... The scratch length is more than 10 mm but 15 mm or less. 3... The scratch length is more than 15 mm but 20 mm or less. 2... The scratch length is more than 20 mm but 25 mm or less. 1... The scratch length is more than 25 mm but 30 mm or less. 0... The scratch length is more than 30 mm.

[0261] Tables 4 to 10 show the evaluation results. In the tables, the number of functional groups refers to the number of polymerizable groups. The number of carbon atoms in (meth)acrylate A refers to the number of carbon atoms in the alkylene chain of (meth)acrylate A. δH is the hydrogen bonding term of the solubility parameter, and its unit is MPa. １／２Tg is the glass transition temperature when the material is homopolymer, and its unit is °C.

[0262]

[0263]

[0264]

[0265]

[0266]

[0267]

[0268]

[0269] As shown in Tables 4 to 10, in Examples 1 to 51, the ink contains water, (meth)acrylate A, and polymer P particles, and exhibits excellent discharge properties when stored in low-temperature and high-temperature environments. On the other hand, in Comparative Examples 1 to 3, (meth)acrylate A is not included, and the discharge properties when stored in low-temperature or high-temperature environments are inferior.

[0270] In Example 1, (meth)acrylate A is a compound represented by formula (1), and it can be seen that it exhibits superior discharge properties when stored in low-temperature and high-temperature environments compared to Example 6.

[0271] In Example 1, the hydrogen bonding term of the solubility parameter of (meth)acrylate A was 2.5 MPa. １／２ The results are as follows, and it can be seen that, compared to Example 7, it exhibits superior dispensing performance when stored in a high-temperature environment.

[0272] In Example 1, the glass transition temperature of the homopolymer of (meth)acrylate A was -30°C or higher, and it can be seen that it has superior image quality and scratch resistance compared to Example 5.

[0273] In Example 1, the molecular weight of (meth)acrylate A is 300 to 1000, and it can be seen that it is superior in terms of dischargeability, odor, image quality, and scratch resistance when stored in a high-temperature environment compared to Examples 8 and 9.

[0274] Examples 37 to 39 further contain polymerizable monomer B, and it can be seen that they have superior scratch resistance compared to Example 1.

[0275] In Examples 37 and 38, the hydrogen bonding term of the solubility parameter of polymerizable monomer B was 5.0 MPa. １／２ The following results show that the image quality is superior compared to Example 39.

[0276] In Examples 24 to 27, the mass ratio of polymerizable monomer B to (meth)acrylate A was 0.1 or higher, indicating superior scratch resistance compared to Example 23. In Examples 24 to 27, the mass ratio of polymerizable monomer B to (meth)acrylate A was 3.0 or lower, indicating superior discharge performance and image quality when stored in a high-temperature environment compared to Example 28.

[0277] In Example 11, polymerizable oligomer C is further included, and it can be seen that it has superior scratch resistance compared to Example 1.

[0278] Examples 20 and 21 include urethane (meth)acrylate as polymerizable oligomer C, and it can be seen that they have superior scratch resistance compared to Example 22.

[0279] In Example 11, the mass ratio of polymerizable oligomer C to (meth)acrylate A was 0.4 or higher, indicating superior scratch resistance compared to Example 10. In Example 13, the mass ratio of polymerizable oligomer C to (meth)acrylate A was 2.0 or lower, indicating superior discharge performance and image quality when stored in a high-temperature environment compared to Example 14.

[0280] Examples 50 and 51 further contain polymerizable monomer D, and it can be seen that they have superior scratch resistance compared to Example 1.

[0281] Examples 40 to 46 further contain polymerizable monomer D, and compared to Example 13, they exhibit superior discharge properties, image quality, and scratch resistance when stored in a high-temperature environment.

[0282] [Example 101] An ink is prepared in the same manner as in Example 17, except that the following pigment dispersion C is used instead of pigment dispersion Bk. • Pigment dispersion C: Product name "Pro-jet Cyan APD1000", manufactured by FUJIFILM Imaging Colorants, pigment concentration 15% by mass…13 parts by mass

[0283] [Example 102] Ink is prepared in the same manner as in Example 17, except that 20 parts by mass of the following pigment dispersion M are used instead of 13 parts by mass of pigment dispersion Bk, and the amount of water is adjusted. • Pigment dispersion M: Product name "Pro-jet Magenta APD1000", manufactured by FUJIFILM Imaging Colorants, pigment concentration 15% by mass…20 parts by mass

[0284] [Example 103] Instead of using 13 parts by mass of pigment dispersion Bk, the following pigment dispersion Y is used in 20 parts by mass, C32A is used in 2.2 parts by mass, and the amount of water is adjusted, except that the ink is prepared in the same manner as in Example 17. • Pigment dispersion Y: Product name "Pro-jet Yellow APD1000LF", manufactured by FUJIFILM Imaging Colorants, pigment concentration 15% by mass…20 parts by mass

[0285] The inks of Examples 101 to 103 were evaluated using the same method as in Example 1. All evaluation results were "5".

[0286] Furthermore, the disclosure of Japanese Patent Application No. 2025-048931, filed on March 24, 2025, is incorporated herein by reference in its entirety. In addition, all documents, patent applications, and technical standards described herein are incorporated herein by reference to the same extent as if each individual document, patent application, and technical standard were specifically and individually noted to be incorporated by reference.

Claims

1. An inkjet ink containing water, a (meth)acrylate having a branched alkylene chain with 10 or more carbon atoms and no cyclic structure, and particles containing a polymer having an acid group.

2. The inkjet ink according to claim 1, wherein the (meth)acrylate is a compound represented by the following formula (1). In formula (1), R １ and R ２ Each of these is independently an alkyl group having 6 to 16 carbon atoms.

3. The (meth)acrylate has a hydrogen bonding term of solubility parameter of 2.5 MPa. １／２ The inkjet ink according to claim 1, which is as follows:

4. The inkjet ink according to claim 1, wherein the (meth)acrylate has a glass transition temperature of -30°C or higher when it is a homopolymer.

5. The inkjet ink according to claim 1, wherein the (meth)acrylate has a molecular weight of 300 to 1000.

6. The inkjet ink according to claim 1, wherein the particles further comprise a polymerizable monomer having a cyclic structure.

7. The polymerizable monomer having the cyclic structure has a hydrogen bonding term of 5.0 MPa in its solubility parameter. １／２ The inkjet ink according to claim 6, which is as follows:

8. The inkjet ink according to claim 6, wherein the mass ratio of the content of the polymerizable monomer having a cyclic structure to the content of the (meth)acrylate is 0.1 to 3.

0.

9. The inkjet ink according to claim 1, wherein the particles further comprise a polymerizable oligomer having a weight-average molecular weight of 3000 or more.

10. The inkjet ink according to claim 9, wherein the polymerizable oligomer has a urethane structure.

11. The inkjet ink according to claim 9, wherein the mass ratio of the polymerizable oligomer content to the (meth)acrylate content is 0.4 to 2.

0.

12. The inkjet ink according to claim 1, wherein the particles further comprise a polyfunctional polymerizable monomer that does not fall under the (meth)acrylate, has a ClogP value of 3.0 or higher, and does not have a cyclic structure.

13. The inkjet ink according to claim 12, wherein the mass ratio of the content of the polyfunctional polymerizable monomer to the content of the (meth)acrylate is 0.1 to 3.

0.

14. An inkjet recording method comprising the steps of: applying an inkjet ink according to any one of claims 1 to 13 onto a substrate using an inkjet recording method; and irradiating the inkjet ink applied onto the substrate with an active energy ray.

Images