Oily inkjet ink

Abstract

To provide oily inkjet ink which can reduce roller transfer contamination of a printed matter.SOLUTION: Oily inkjet ink contains colored resin particles and a non-aqueous solvent, and satisfies at least one of the following (i) and (ii): (i) the colored resin particles contain colloidal silica; and (ii) the oily inkjet ink further contains uncolored resin particles containing colloidal silica.SELECTED DRAWING: None

Description

[Technical Field]

[0001] SUMMARY OF THE INVENTION An embodiment of the present invention relates to an oil-based inkjet ink. [Background technology]

[0002] Inkjet recording, in which highly fluid inkjet ink is ejected as droplets from minute nozzles to record an image on a substrate placed opposite the nozzle, has rapidly become popular in recent years due to its low-noise, high-speed printing capabilities. Inks used in inkjet recording include aqueous inks containing water as the primary solvent, ultraviolet-curable inks (UV inks) containing a high content of polymerizable monomers as the primary component, and hot-melt inks (solid inks) containing a high content of wax as the primary component, as well as so-called non-aqueous inks containing a non-aqueous solvent as the primary solvent. Non-aqueous inks can be classified into solvent-based inks, which contain a volatile organic solvent as the primary solvent, and oil-based inks, which contain a low-volatility or non-volatile organic solvent as the primary solvent. Solvent inks dry on the substrate primarily through the evaporation of the organic solvent, whereas oil-based inks dry primarily through penetration into the substrate.

[0003] When an oil-based ink is used, if the permeability of the solvent into the substrate improves, the colorant component may easily penetrate into the substrate, which may result in a decrease in the color development, etc. of the printed matter. Patent Document 1 discloses a colored resin particle dispersion containing colored resin particles, a basic dispersant, and a non-aqueous solvent, in which the colored resin particles contain a colorant and a (meth)acrylic resin specified by a predetermined unit, and an inkjet ink containing the same, and describes that the colored resin particles released from the solvent remain on the surface of the substrate, thereby improving the color development, etc. of the printed matter. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2018-053069 Summary of the Invention [Problem to be solved by the invention]

[0005] Oil-based ink applied to a substrate may adhere to conveying rollers or the like before it dries, and the ink adhering to the conveying rollers may be transferred to the subsequent substrate being conveyed, causing stains on the printed material. This phenomenon is called roller transfer staining. When printing many sheets in succession, the stains on the rollers tend to accumulate, worsening the staining of the printed material.

[0006] An object of an embodiment of the present disclosure is to provide an oil-based inkjet ink that can reduce roller transfer stains on printed matter. [Means for solving the problem]

[0007] One embodiment of the present disclosure is an oil-based inkjet ink that contains colored resin particles and a non-aqueous solvent and satisfies at least one of the following (i) or (ii): (i) The colored resin particles contain colloidal silica. (ii) The oil-based inkjet ink further contains non-colored resin particles containing colloidal silica. [Effects of the Invention]

[0008] According to an embodiment of the present disclosure, an oil-based inkjet ink that can reduce roller transfer stains on printed matter can be provided. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, several embodiments of the present invention will be described, but the examples in the following description of the embodiments do not limit the present invention.

[0010] According to one embodiment, there is provided an oil-based inkjet ink comprising colored resin particles and a non-aqueous solvent, and satisfying at least one of the following (i) or (ii): (i) The colored resin particles contain colloidal silica. (ii) The oil-based inkjet ink further comprises non-pigmented resin particles containing colloidal silica.

[0011] Hereinafter, oil-based inkjet inks will also be referred to as "ink" or "oil-based ink." In this disclosure, (meth)acrylic resin collectively refers to resins obtained by polymerizing acrylic acid, methacrylic acid, and derivatives thereof, either alone or in combination. (Meth)acrylic acid and (meth)acrylic acid ester collectively refer to acrylic acid and methacrylic acid, and acrylic acid ester and methacrylic acid ester, respectively. In this disclosure, a dispersant used to disperse a pigment as a colorant when producing colored resin particles will be referred to as a pigment dispersant. In this disclosure, a dispersant used to disperse colored resin particles and / or non-colored resin particles when producing oil-based inkjet ink will be referred to as a dispersant.

[0012] The oil-based inkjet ink of this embodiment can reduce roller transfer stains on printed matter, and the reason for this is presumed to be as follows.

[0013] Colored resin particles containing colloidal silica and non-colored resin particles containing colloidal silica tend to have increased affinity for the substrate and decreased affinity for the solvent due to the influence of silanol groups (—SiOH). Therefore, when colloidal silica is contained in colored resin particles in an oil-based ink, the fixation of the colored resin particles to the substrate and the releasability from the solvent are improved. When colloidal silica is contained in non-colored resin particles, the fixation of the non-colored resin particles to the substrate and the releasability from the solvent are improved. Furthermore, because colloidal silica has self-dispersing groups on its particle surface, it is not necessary to use a significant amount of dispersant to disperse the colloidal silica particles and adsorb them to the particle surface, as is the case when powdered silica is used. Therefore, the effect of such dispersants on the release of the colored resin particles and non-colored resin particles from the solvent is minimal, further improving their releasability from the solvent. Thus, it is presumed that when colored resin particles in an oil-based ink contain colloidal silica, the fixation of the colored resin particles to the substrate and the releasability from the solvent are improved, making it possible to reduce roller transfer stains. On the other hand, when the oil-based ink contains non-colored resin particles containing colloidal silica, the fixability of the non-colored resin particles to the substrate and the releasability from the solvent are improved, and the non-colored resin particles containing colloidal silica act as an intermediary between the fixation of the colored resin particles to the substrate and the substrate and as a filler for the colored resin particles. This is thought to improve the fixability of the colored resin particles to the substrate and the releasability from the solvent, thereby reducing roller transfer stains. In this way, even when printing a large number of sheets in succession, it is possible to produce printed matter with reduced roller transfer stains.

[0014] Colloidal silica The ink may contain colloidal silica. In the ink, the colored resin particles may contain colloidal silica, and / or the ink may further contain non-colored resin particles that contain colloidal silica. From the viewpoint of a more excellent effect of reducing roller transfer stains, it is preferable that the colored resin particles in the ink contain colloidal silica.

[0015] Colloidal silica can be obtained, for example, as a dispersion in water. Alternatively, the colloidal silica can be blended as a dispersion during the production of ink. When a water dispersion is used, it is preferable that the water contained in the water dispersion is removed during the ink production process.

[0016] From the viewpoints of improving imaging properties such as image density, strike-through, and sharpness, and of improving the effect of reducing roller transfer stains, the average particle size of the colloidal silica is preferably 100 nm or less, more preferably 80 nm or less, even more preferably 60 nm or less, still more preferably 40 nm or less, and even more preferably 20 nm or less. When the average particle size of the colloidal silica is reduced, the colloidal silica particles become smaller, thereby increasing the particle surface area and enabling the silanol effect to be obtained more efficiently, which is thought to further improve imaging properties and the effect of reducing roller transfer stains. The average particle size of the colloidal silica may be, for example, 2 nm or more, or 5 nm or more.

[0017] From the viewpoints of improving abrasion resistance, improving image quality, and more effectively reducing roller transfer stains, the average particle size of the colloidal silica is preferably from 5 to 100 nm, more preferably from 5 to 80 nm, even more preferably from 5 to 60 nm, still more preferably from 5 to 40 nm, and still more preferably from 5 to 20 nm.

[0018] In the present disclosure, the average particle size of colloidal silica refers to the volume-based particle size value (median size) in the particle size distribution measured by dynamic light scattering. This average particle size of colloidal silica can be measured using a dispersion of colloidal silica. Specifically, for example, a nanoparticle analyzer, nano Partica SZ-100 (Horiba, Ltd.), is used as a dynamic light scattering particle size distribution measuring device. The colloidal silica is diluted with water to a concentration of 0.5% by mass, and the measurement can be performed at 25°C under the following conditions: refractive index of the dispersion medium: 1.333, refractive index of the sample: 1.430, and calculation conditions: polydispersity standard.

[0019] The surface property of the colloidal silica may be, for example, anionic or cationic, with anionic being preferred. Counter ions used for neutralization include, for example, ammonium ions and alkali metal ions, with alkali metal ions such as sodium ions being preferred.

[0020] Commercially available colloidal silica products include, for example, "Snowtex ST-XS," "Snowtex ST-NS," "Snowtex ST-S," "Snowtex ST-30," "Snowtex ST-30L," "Snowtex ST-50-T," "Snowtex ST-OXS," "Snowtex ST-OS," "Snowtex ST-O," and "Snowtex ST-AK" manufactured by Nissan Chemical Industries, Ltd.; "Quattron PL-1" manufactured by Fuso Chemical Co., Ltd.; and "Surfloid 20" and "Surfloid 30" manufactured by Aichi Sodium Silicate Industry Co., Ltd. (all trade names).

[0021] The colloidal silica may be used alone or in combination of two or more kinds. From the viewpoint of image quality and abrasion resistance, the colloidal silica content is, for example, preferably 0.005% by mass or more and less than 5.0% by mass, more preferably 0.01% by mass or more and less than 5.0% by mass, even more preferably 0.05% by mass or more and less than 5.0% by mass, and even more preferably 0.1% by mass or more and less than 5% by mass, and may be, for example, 0.1% by mass or more and 4.0% by mass or less, 0.3% by mass or more and 3.0% by mass or less, 0.3% by mass or more and 2.0% by mass or less, 0.3% by mass or more and 1.0% by mass or less, or 0.3% by mass or more and 0.5% by mass or less, relative to the total amount of ink. The colloidal silica content may be, for example, 0.005% by mass or more, 0.01% by mass or more, 0.05% by mass or more, 0.1% by mass or more, or 0.3% by mass or more, relative to the total amount of ink. On the other hand, the content of colloidal silica may be, for example, less than 5.0% by mass, 4.0% by mass or less, 3.0% by mass or less, 2.0% by mass or less, 1.0% by mass or less, or 0.5% by mass or less relative to the total amount of ink.

[0022] For example, when colloidal silica is contained in the colored resin particles, from the viewpoints of image quality and abrasion resistance, the amount of colloidal silica contained in the colored resin particles is preferably 0.1% by mass or more and less than 5.0% by mass, more preferably 0.2% by mass or more and 4.0% by mass or less, and even more preferably 0.3% by mass or more and 3.0% by mass or less, relative to the total amount of ink. For example, when colloidal silica is contained in the non-colored resin particles, the colloidal silica contained in the non-colored resin particles is preferably 0.005% by mass or more and 2.0% by mass or less, more preferably 0.01% by mass or more and 1.0% by mass or less, and even more preferably 0.05% by mass or more and 0.5% by mass or less, relative to the total amount of ink. When colloidal silica is contained in the colored resin particles and the non-colored resin particles, the total amount of colloidal silica contained in the colored resin particles and the colloidal silica contained in the non-colored resin particles relative to the total amount of ink may be, for example, within any of the ranges described above.

[0023] When colloidal silica is contained in the colored resin particles, the amount of colloidal silica may be, for example, 0.1 to 30.0 mass %, 0.5 to 25.0 mass %, or 1.0 to 20.0 mass % relative to the total amount of the colored resin particles containing colloidal silica. When colloidal silica is contained in the non-colored resin particles, the amount of colloidal silica may be, for example, 0.1 to 30.0 mass %, 0.5 to 25.0 mass %, or 1.0 to 20.0 mass % relative to the total amount of the non-colored resin particles containing colloidal silica.

[0024] "Colored resin particles" The colored resin particles may contain a colorant and a resin. As described above, the colored resin particles may further contain colloidal silica.

[0025] "Colorant" The colored resin particles contained in the oil-based ink may contain a pigment, a dye, or a combination thereof as a coloring material.

[0026] Pigments can be used in the present invention, including organic pigments such as azo pigments, phthalocyanine pigments, polycyclic pigments, and dye lake pigments, as well as inorganic pigments such as carbon black and metal oxides. Examples of azo pigments include soluble azo lake pigments, insoluble azo pigments, and condensed azo pigments. Examples of phthalocyanine pigments include metal phthalocyanine pigments and metal-free phthalocyanine pigments. Examples of polycyclic pigments include quinacridone pigments, perylene pigments, perinone pigments, isoindoline pigments, isoindolinone pigments, dioxazine pigments, thioindigo pigments, anthraquinone pigments, quinophthalone pigments, metal complex pigments, and diketopyrrolopyrroles (DPPs). Examples of carbon black include furnace carbon black, lamp black, acetylene black, and channel black. Examples of metal oxides include titanium oxide and zinc oxide. These pigments can be used alone or in combination.

[0027] From the viewpoint of storage stability and ejection stability, the average particle size of the pigment is preferably 300 nm or less, and more preferably 200 nm or less. For example, the average particle size of the pigment may be 50 to 300 nm, or 100 to 200 nm. In the case of carbon black, from the viewpoint of color development, the primary particle size is preferably 30 nm or less, more preferably 25 nm or less, and even more preferably 20 nm or less.

[0028] For example, when producing an oil-based ink using the method of drying a water-in-oil (W / O) emulsion in oil described below, the pigment can be preferably used in the form of an aqueous dispersion in which the pigment is dispersed in water. The pigment may be a self-dispersing pigment, in which a water-solubilizing group such as a carboxyl group, a carbonyl group, a hydroxyl group, or a sulfo group is bonded to the pigment surface, thereby dispersing the pigment itself in water. For example, an aqueous dispersion of a self-dispersing pigment can be preferably used. Alternatively, it is also preferable to disperse the pigment in water using, for example, a pigment dispersant. Examples of the pigment dispersant that can be used include the pigment dispersants described below, and preferred examples include (meth)acrylic resins with pigment dispersibility and water-soluble nonionic pigment dispersants. When an aqueous dispersion is used, the water contained in the aqueous dispersion is preferably removed during the ink production process.

[0029] Any dye commonly used in the art can be used. From the viewpoint of reducing strike-through, it is preferable that the dye is poorly soluble or insoluble in the non-aqueous solvent contained in the ink. When an oil-based ink is produced by a method using the in-oil drying method of a water-in-oil (W / O) emulsion, it is preferable to use a dye that is soluble or dispersible in water.

[0030] As the dye, water-soluble dyes and water-soluble dyes made water-soluble by reduction or the like can be preferably used from among basic dyes, acid dyes, direct dyes, soluble vat dyes, acid mordant dyes, mordant dyes, reactive dyes, vat dyes, sulfur dyes, etc. Also preferably used are disperse dyes such as azo-based, anthraquinone-based, azomethine-based, and nitro-based dyes. These may be used alone or in combination.

[0031] From the viewpoint of color development, the colorant is preferably 10% by mass or more, more preferably 30% by mass or more, even more preferably 40% by mass or more, and even more preferably 50% by mass or more, based on the total amount of the colored resin particles. The colorant may be, for example, 90% by mass or less, 80% by mass or less, or 70% by mass or less, based on the total amount of the colored resin particles. The colorant may be 10 to 90% by mass, 30 to 80% by mass, 40 to 80% by mass, or 50 to 70% by mass, based on the total amount of the colored resin particles. The coloring material may be present in an amount of 0.01 to 20% by mass relative to the total amount of ink, and from the viewpoint of image quality, it is preferably present in an amount of 1 to 15% by mass, and more preferably present in an amount of 5 to 10% by mass.

[0032] "Resin contained in colored resin particles" The resin contained in the colored resin particles forms the colored resin particles in the oil-based ink and is preferably oil-insoluble in the non-aqueous solvent contained in the oil-based ink. For example, the amount of resin contained in the colored resin particles that can dissolve in 100 g of the non-aqueous solvent contained in the oil-based ink at 23° C. is preferably 3 g / 100 g or less, 1 g / 100 g or less, or 0.5 g / 100 g or less.

[0033] When the resin contained in the colored resin particles is an oil-insoluble resin, the elution of the resin component from the colored resin particles in the oil-based ink is easily suppressed, the dispersion performance of the colored resin particles can be more sufficiently maintained, and the suppression of the elution of the resin component can further suppress an increase in the viscosity of the oil-based ink. Furthermore, the oil-insolubility of the resin enhances solvent releasability when the oil-based ink lands on a substrate, more effectively reducing roller transfer stains and further improving image quality.

[0034] The resin contained in the colored resin particles may be, for example, a water-dispersible resin or a water-soluble resin. Being water-dispersible means that the resin has the property of being able to be dispersed in particulate form without dissolving in water. Examples of water-dispersible resins include resins having units with hydrophilic groups, resins having hydrophilic groups at the terminals, resins having side chains with hydrophilic groups, and resins whose surfaces have been hydrophilically treated with surfactants or the like. Examples of hydrophilic groups include acidic groups, basic groups, nonionic groups, and combinations thereof. For example, when an oil-based ink is produced by a method using a water-in-oil (W / O) emulsion drying in oil, the resin may be a water-soluble resin, a water-dispersible resin, or a combination thereof.

[0035] The resin contained in the colored resin particles is not particularly limited, and examples thereof include urethane resin, (meth)acrylic resin, polyester resin, vinyl chloride resin, polyolefin resin, etc. The colored resin particles may contain one type of resin alone or two or more types of resin in combination. The colored resin particles preferably contain, for example, a urethane resin, a (meth)acrylic resin, or a combination thereof. For example, in terms of suitability for non-aqueous solvents, the colored resin particles preferably contain a urethane resin. For example, colored resin particles containing colloidal silica preferably contain a urethane resin.

[0036] Urethane resin is a polymer containing urethane bonds. Generally, urethane resin can be synthesized by polyaddition of polyisocyanate and polyol. Examples of urethane resin include polyether-type urethane resins containing ether bonds in the main chain, polyester-type urethane resins containing ester bonds in the main chain, polycarbonate-type urethane resins containing carbonate bonds in the main chain, and polyester-ether-type urethane resins containing ester and ether bonds in the main chain.

[0037] The urethane resin may be a urethane urea resin having a urea bond in addition to a urethane bond. The urethane urea resin can be obtained, for example, by reacting a urethane prepolymer obtained from a material containing a polyol and a polyisocyanate with water and / or a polyamine compound, whereby the isocyanate groups of the urethane prepolymer react with the water and / or the polyamine compound to generate urea bonds and extend the chain.

[0038] The urethane resin may be any of acidic urethane resin, basic urethane resin, and nonionic urethane resin. The acidic urethane resin is a urethane resin having an acidic group, the basic urethane resin is a urethane resin having a basic group, and the nonionic urethane resin is a urethane resin having neither an acidic group nor a basic group. The acidic urethane resin is preferred. Examples of the acidic group include a carboxy group, a sulfo group, and a phosphate group.

[0039] The urethane resin is preferably an oil-insoluble urethane resin. Specifically, the urethane resin is preferably oil-insoluble in the non-aqueous solvent contained in the oil-based ink. For example, at 23°C, the amount of urethane resin that can be dissolved in 100 g of the non-aqueous solvent contained in the oil-based ink is preferably 3 g / 100 g or less, 1 g / 100 g or less, or 0.5 g / 100 g or less.

[0040] The urethane resin is preferably a water-dispersible urethane resin. Examples of water-dispersible urethane resins include urethane resins having units with hydrophilic groups, urethane resins having hydrophilic groups at their terminals, urethane resins having side chains with hydrophilic groups, and urethane resins whose surfaces have been hydrophilically treated with surfactants or the like. Examples of hydrophilic groups include acidic groups, basic groups, nonionic groups, and combinations thereof. For example, when producing oil-based inks using a method that uses a water-in-oil (W / O) emulsion drying-in-oil method, it is preferable to use a water-dispersible urethane resin as the urethane resin.

[0041] The glass transition temperature (Tg) of the urethane resin coating may be −60 to 100° C., −50 to 50° C., or −40 to 10° C. In the present disclosure, the glass transition temperature is a value measured using a differential scanning calorimeter (DSC).

[0042] Examples of commercially available water-dispersible urethane resins include "Takelac WS-5984," "Takelac WS-4022," and "Takelac W-635" manufactured by Mitsui Chemicals, Inc.; "Superflex 740," "Superflex 150H," "Superflex 620," "Superflex 500M," and "Superflex 650" manufactured by Daiichi Kogyo Seiyaku Co., Ltd.; "U-coat UWS-145" manufactured by Sanyo Chemical Industries, Ltd.; and "DAOTAN TW-6493," "DAOTAN TW-6490," and "DAOTAN TW-6491" manufactured by Daicel-Allnex Co., Ltd. (all trade names). In the colored resin particles, the urethane resin may be used alone or in combination of two or more types.

[0043] The colored resin particles may contain, for example, urethane resin in an amount of 10 to 100 mass %, 10 to 90 mass %, 20 to 80 mass %, or 40 to 60 mass % relative to the total amount of resin contained in the colored resin particles.

[0044] The (meth)acrylic resin is preferably an oil-insoluble (meth)acrylic resin. Specifically, the (meth)acrylic resin is preferably oil-insoluble in the non-aqueous solvent contained in the oil-based ink. For example, at 23° C., the amount of the (meth)acrylic resin that can be dissolved in 100 g of the non-aqueous solvent contained in the oil-based ink is preferably 3 g / 100 g or less, 1 g / 100 g or less, or 0.5 g / 100 g or less.

[0045] The (meth)acrylic resin may be, for example, a water-soluble (meth)acrylic resin or a water-dispersible (meth)acrylic resin. Examples of water-dispersible (meth)acrylic resins include (meth)acrylic resins having units with hydrophilic groups, (meth)acrylic resins having hydrophilic groups at their terminals, (meth)acrylic resins having side chains with hydrophilic groups, and (meth)acrylic resins whose surfaces have been treated to be hydrophilic with a surfactant or the like. For example, when an oil-based ink is produced by a method using a water-in-oil (W / O) emulsion drying method in oil, a water-soluble (meth)acrylic resin or a water-dispersible (meth)acrylic resin may be used as the (meth)acrylic resin.

[0046] The main chain of the (meth)acrylic resin is not particularly limited. For example, the main chain of the (meth)acrylic resin may be obtained by polymerizing acrylic acid, methacrylic acid, and derivatives thereof, either alone or in combination of two or more. For example, the (meth)acrylic resin may contain acrylic acid units, methacrylic acid units, acrylate units, and methacrylate units, either alone or in combination of two or more.

[0047] The (meth)acrylic resin may contain one or more selected from a nonionic polyoxyalkylene chain, an acidic group, and a pigment-affinity group. For example, the (meth)acrylic resin may contain a nonionic polyoxyalkylene chain and an acidic group. The (meth)acrylic resin may further contain a pigment-affinity group. In the production process of colored resin particles, the (meth)acrylic resin having the pigment-affinity group also functions as a pigment dispersant, improving pigment dispersibility in the aqueous phase and allowing colored resin particles with higher miscibility and adhesion to be obtained.

[0048] The (meth)acrylic resin may contain one or more units selected from a unit having a nonionic polyoxyalkylene chain, a unit having an acidic group, and a unit having a pigment affinity group. For example, the (meth)acrylic resin may contain a unit having a nonionic polyoxyalkylene chain and a unit having an acidic group. This (meth)acrylic resin may further contain other units. The (meth)acrylic resin may be a polymer of a monomer mixture containing a monomer having a nonionic polyoxyalkylene chain and a monomer having an acidic group, or may be a polymer of a monomer mixture containing further other monomers. Examples of other units include units having a pigment affinity group. Examples of other monomers include monomers having a pigment affinity group. Examples of units that may be contained in the (meth)acrylic resin are described below.

[0049] In the nonionic polyoxyalkylene chain, the number of moles of alkylene oxide (AO) added is not particularly limited, but is preferably 2 to 50, more preferably 2 to 30, and even more preferably 6 to 30. Within this range, the miscibility of the colored resin particles with the urethane resin is improved, the component uniformity of the colored resin particles is improved, and the storage stability of the ink and the circulation stability when the ink is circulated in an ink path such as a tube by a pump in a printing device can be improved. The alkylene oxide group preferably has 1 to 10 carbon atoms, more preferably 1 to 8 carbon atoms, even more preferably 2 to 4 carbon atoms, and still more preferably 2 or 3 carbon atoms. Examples of alkylene oxide groups include methylene oxide, ethylene oxide, propylene oxide, and butylene oxide. Among these, ethylene oxide, propylene oxide, and combinations thereof are preferred, with ethylene oxide being more preferred. Furthermore, one polyoxyalkylene chain may contain a combination of two or more alkylene oxide groups. Specifically, it is preferable that the copolymer has a polyoxyethylene chain, a polyoxypropylene chain, a polyoxyethylene polyoxypropylene chain, or the like, and from the viewpoint of miscibility with the urethane resin, a polyoxyethylene chain is more preferable.

[0050] The polyoxyalkylene chain is preferably nonionic, and specifically, it is preferred that no ionic group is introduced. For example, the terminal of the polyoxyalkylene chain may be a hydroxy group, or a nonionic functional group may be introduced into the hydroxy group. Specifically, a hydrocarbon group may be introduced into the terminal hydroxy group of the polyoxyalkylene chain. The hydrocarbon group is an alkyl group having 1 to 20 carbon atoms, and more preferably an alkyl group having 1 to 10 carbon atoms. The alkyl group having 1 to 10 carbon atoms is preferably a linear or branched alkyl group having 1 to 10 carbon atoms, preferably 1 to 8 carbon atoms, and more preferably 1 to 4 carbon atoms. Examples thereof include a methyl group, an ethyl group, a trimethyl group, a propyl group, an n-butyl group, a tert-butyl group, and a sec-butyl group, and preferably a methyl group or an ethyl group.

[0051] The monomer having a polyoxyalkylene chain may contain one polyoxyalkylene chain in one molecule, or may contain two or more polyoxyalkylene chains. The monomer having a polyoxyalkylene chain can be (meth)acrylic acid, (meth)acrylate, (meth)acrylamide, or a compound in which a polyoxyalkylene chain has been introduced into a derivative thereof, thereby providing a copolymer whose main chain is a (meth)acrylic skeleton. Examples include ethers of (meth)acrylic acid and polyalkylene glycol, (meth)acrylates modified with polyalkylene glycol, etc. Polyalkylene glycol-modified (meth)acrylates can be obtained, for example, by reacting polyalkylene glycol with (meth)acrylate into which a functional group that serves as a starting point for an isocyanate group or the like has been introduced.

[0052] The molecular weight of the monomer having a nonionic polyoxyalkylene chain is preferably 800 to 3,000, more preferably 1,000 to 2,000.

[0053] For example, the nonionic polyoxyalkylene chain may have a structure represented by the following general formula: 10 is a hydrogen atom or an alkyl group having 1 to 8 carbon atoms, n is an integer of 2 to 4, and m is an integer that satisfies the condition 2≦m≦30. * is a bonding position. *-O-(C n H 2n-1 O) m -R 10

[0054] Specific examples of monomers having a polyoxyalkylene chain include polyethylene glycol mono(meth)acrylate, methoxypolyethylene glycol mono(meth)acrylate, ethoxypolyethylene glycol mono(meth)acrylate, octoxypolyethylene glycol mono(meth)acrylate, stearoxypolyethylene glycol mono(meth)acrylate; polyethylene glycol-modified 2-isocyanatoethyl (meth)acrylate, polypropylene glycol mono(meth)acrylate, polyethylene glycol-propylene glycol-mono(meth)acrylate, polyethylene glycol-trimethylene glycol-mono(meth)acrylate; polyethylene glycol-allyl ether, methoxypolyethylene glycol-allyl ether, polyethylene glycol-polypropylene glycol-allyl ether, polypropylene glycol-allyl ether, polyethylene glycol-diallyl ether, polypropylene glycol-diallyl ether; and methoxypolyethylene glycol acrylamide.

[0055] Examples of commercially available products of monomers having a polyoxyalkylene chain include "ADEKA REASOAP ER-20" manufactured by ADEKA CORPORATION, "BLEMMER PME1000" manufactured by NOF CORPORATION, "NK ESTER M-230G", "M-90G", and "M-130G" manufactured by Shin-Nakamura Chemical Co., Ltd., "BLEMMER PME-4000", "BLEMMER PE-200", "BLEMMER PP-1000", and "BLEMMER PME-1000" manufactured by NOF CORPORATION, and "LIGHT ESTER 041MA" manufactured by Kyoeisha Chemical Co., Ltd. (all trade names).

[0056] In the (meth)acrylic resin, the unit having a polyoxyalkylene chain may be contained alone or in combination of two or more. In the polymerization of the (meth)acrylic resin, the above-mentioned monomers may be used alone or in combination of two or more.

[0057] Examples of the acidic group include a carboxy group, a sulfo group, and a phosphate group, and the (meth)acrylic resin preferably has a carboxy group. The (meth)acrylic resin may contain one type of acidic group alone or two or more types in combination.

[0058] The (meth)acrylic resin may be a (meth)acrylic resin containing a unit having an acidic group, a (meth)acrylic resin having an acidic group at its terminal, or a (meth)acrylic resin having a side chain having an acidic group. Preferably, it is a (meth)acrylic resin containing a unit having an acidic group. In this case, the acid value of the (meth)acrylic resin can be adjusted by changing the proportion of the unit having an acidic group.

[0059] In the (meth)acrylic resin, the acidic group may be directly bonded to a carbon atom of the carbon chain, or may be bonded to a carbon atom of the carbon chain via a linking group. Examples of monomers having an acidic group include methacrylic acid, acrylic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid, and citraconic acid. Other examples include β-carboxyethyl (meth)acrylate, 4-[2-(methacryloyloxy)ethoxy]-4-oxo-2-butenoic acid, 2-acryloyloxyethyl succinic acid, 2-acryloyloxyethyl hexahydrophthalic acid, 2-acryloyloxypropyl phthalic acid, 2-acryloyloxypropyl hexahydrophthalic acid, methacryloyloxymethyl succinic acid, methacryloyloxyethyl succinic acid, methacryloyloxyethyl phthalic acid, methacryloyloxyethyl hexahydrophthalic acid, methacryloyloxypropyl phthalic acid, and methacryloyloxypropyl hexahydrophthalic acid. The monomer is preferably (meth)acrylic acid or a derivative thereof. In the polymerization of the (meth)acrylic resin, the monomers may be used alone or in combination of two or more.

[0060] Examples of other units include units having a pigment affinity group, units having an alkyl group, etc. Examples of the pigment affinity group include aromatic ring-containing groups and β-dicarbonyl groups.

[0061] In the aromatic ring-containing group, examples of the aromatic ring include a benzene ring, a naphthalene ring, an anthracene ring, or a substituted version thereof, with a benzene ring being preferred. Examples of the aromatic ring-containing group include a benzyl group, a phenyl group, and a phenylethyl group, with a benzyl group being preferred. The aromatic ring-containing group may be contained in the (meth)acrylic resin either alone or in combination of two or more.

[0062] The unit having an aromatic ring-containing group may be a unit derived from a monomer having an aromatic ring-containing group, such as benzyl (meth)acrylate, phenyl (meth)acrylate, phenylethyl (meth)acrylate, or phenoxyethyl methacrylate.

[0063] Examples of the alkyl group include alkyl groups having 1 to 24 carbon atoms, 1 to 12 carbon atoms, 1 to 8 carbon atoms, and 1 to 4 carbon atoms.

[0064] For example, when producing oil-based ink using the drying-in-liquid method, a (meth)acrylic resin may be used as the resin solution, and in this case, a (meth)acrylic resin having an alkyl group with a low carbon number may be used to exhibit hydrophilicity. In this case, preferred alkyl groups include, for example, methyl, ethyl, propyl, and trimethyl groups.

[0065] The unit having an alkyl group may be a unit derived from a monomer having an alkyl group. Examples of the monomer having an alkyl group include alkyl(meth)acrylates, and specific examples thereof include methyl(meth)acrylate, ethyl(meth)acrylate, propyl(meth)acrylate, and trimethyl(meth)acrylate.

[0066] Further, specific examples of other monomers include styrene-based monomers such as styrene and α-methylstyrene, vinyl ether-based monomers such as vinyl acetate, vinyl benzoate, and butyl vinyl ether, maleic acid esters, fumaric acid esters, acrylonitrile, methacrylonitrile, α-olefins, etc. Units derived from these monomers may be contained in the (meth)acrylic resin.

[0067] The amount of units having a nonionic polyoxyalkylene chain relative to all units of the (meth)acrylic resin may be 1 to 60 mass %, 10 to 40 mass %, or 15 to 30 mass %.

[0068] The amount of units having an acidic group relative to the total amount of units in the (meth)acrylic resin may be 10 to 60 mass%, 20 to 50 mass%, or 30 to 40 mass%, within these ranges, making it easier to adjust the acid value of the (meth)acrylic resin (A). The amount of units having a pigment affinity group relative to all units of the (meth)acrylic resin may be 10 to 80 mass %, 20 to 60 mass %, or 30 to 50 mass %, and it is particularly preferable that the amount of units having an aromatic ring-containing group is within this range. The amount of units having an alkyl group relative to the total amount of units in the (meth)acrylic resin may be 0 to 30% by mass, or 0 to 20% by mass, and it is particularly preferable that the total amount of units having an alkyl group with 1 to 4 carbon atoms is within this range.

[0069] The weight-average molecular weight (Mw) of the (meth)acrylic resin is preferably 10,000 to 200,000, and more preferably 30,000 to 150,000. In the present disclosure, the weight-average molecular weight is a value determined by GPC using standard polystyrene standards. The same applies to the weight-average molecular weights of resins and the like described below.

[0070] The (meth)acrylic resin can be obtained by polymerizing a monomer mixture containing the above-mentioned monomers. During the polymerization reaction, a polymerization initiator, a chain transfer agent, a polymerization inhibitor, a polymerization accelerator, etc. can be added to the reaction system as appropriate to adjust the reaction rate. Examples of polymerization initiators that can be used include thermal polymerization initiators such as azo compounds such as AIBN (azobisisobutyronitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), and 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile); and peroxides such as t-butylperoxybenzoate and t-butylperoxy-2-ethylhexanoate. Photopolymerization initiators that generate radicals upon irradiation with active energy rays can also be used. In addition, the molecular weight of the resulting (meth)acrylic resin can be adjusted by using a chain transfer agent in the reaction system. Preferred examples of the chain transfer agent include thiols such as n-butyl mercaptan, lauryl mercaptan, stearyl mercaptan, and cyclohexyl mercaptan.

[0071] The polymerization solvent (reaction solvent) used in solution polymerization is not particularly limited, but is preferably one that can dissolve the resin obtained by polymerization. When the proportion of monomers having acidic groups is high, it is preferable to carry out polymerization using a polar organic solvent. As the polar organic solvent, one or a combination of two or more of those described below for oil-based inks can be used. Furthermore, when producing an oil-based ink using the drying-in-liquid method, it is preferable to use a low-boiling polar organic solvent as the polymerization solvent to facilitate solvent substitution in order to prepare an aqueous resin composition of a (meth)acrylic resin. The low-boiling polar organic solvent may be a polar organic solvent with a boiling point of less than 100°C, 95°C or less, 90°C or less, 80°C or less, 70°C or less, or 60°C or less, such as ethanol, methyl ethyl ketone, and ethyl acetate.

[0072] The method for providing an aqueous resin composition containing a (meth)acrylic resin by solvent substitution from a composition containing a polymerization solvent and a (meth)acrylic resin is not particularly limited. For example, an appropriate amount of water is added to a composition containing a polymerization solvent and a (meth)acrylic resin, and a low-boiling polar organic solvent is further added and mixed, and then the low-boiling polar organic solvent is removed from this composition using an evaporator or the like, thereby obtaining an aqueous resin composition containing a (meth)acrylic resin.

[0073] When the (meth)acrylic resin contains an acidic group, the acidic group may be neutralized to improve electrostatic repulsion. The acidic group of the (meth)acrylic resin can be neutralized using a water-soluble basic compound as a neutralizing agent. From the viewpoint of the stability of the (meth)acrylic resin, a monovalent water-soluble basic compound is preferred. By neutralizing the acidic group, the monovalent water-soluble basic compound exhibits an electrostatic repulsion effect and can further suppress the aggregation of coloring materials in the production of colored resin particles. Examples of water-soluble basic compounds include inorganic bases such as ammonium hydroxide, sodium hydroxide, and potassium hydroxide; and amines such as aminomethylpropanol, aminoethylpropanol, dimethylethanolamine, triethylamine, diethylethanolamine, dimethylaminopropanol, and triethanolamine. When preparing an aqueous resin composition containing a (meth)acrylic resin, a neutralizing agent may be added in the process of mixing a composition containing a (meth)acrylic resin and a polymerization solvent with water. The polymerization solvent is then removed to obtain a (meth)acrylic resin with neutralized acidic groups.

[0074] The degree of neutralization of the acidic groups in the (meth)acrylic resin may be 20 to 90 mol%, 40 to 80 mol%, or 50 to 60 mol%. The degree of neutralization of the acidic groups in the (meth)acrylic resin is preferably 40 mol% or more, and more preferably 50 mol% or more. In the present disclosure, the "degree of neutralization of acidic groups" refers to the ratio (mol%) of the number of molar equivalents of water-soluble basic compounds to the number of molar equivalents of acidic groups before neutralization.

[0075] The acid value of the (meth)acrylic resin may be, for example, 50 mgKOH / g or more, and from the viewpoint of improving image quality, it is preferably 120 mgKOH / g or more, more preferably 150 mgKOH / g or more, even more preferably 160 mgKOH / g or more, and even more preferably 175 mgKOH / g or more. When a (meth)acrylic resin with a high acid value is contained in the colored resin particles, separation of the colored resin particles from the non-aqueous solvent on the substrate surface is promoted, thereby improving the image quality of the printed matter.

[0076] The acid value of the (meth)acrylic resin may be, for example, 400 mgKOH / g or less, 300 mgKOH / g or less, or 280 mgKOH / g or less. In order to maintain better ink stability when the ink is circulated in an ink path such as a tube by a pump in a printing device, the acid value of the (meth)acrylic resin may be 250 mgKOH / g or less, 200 mgKOH / g or less, or 190 mgKOH / g or less.

[0077] For example, the acid value of the (meth)acrylic resin may be 50 mgKOH / g or more and 400 mgKOH / g or less, 120 mgKOH / g or more and 400 mgKOH / g or less, 150 mgKOH / g or more and 300 mgKOH / g or less, 160 mgKOH / g or more and 280 mgKOH / g or less, 170 mgKOH / g or more and 250 mgKOH / g or less, 180 mgKOH / g or more and 200 mgKOH / g or less, or 180 mgKOH / g or more and 190 mgKOH / g or less.

[0078] Here, the acid value is expressed as the number of milligrams (mg) of potassium hydroxide required to neutralize the acidic components contained in 1 g of sample. The acid value of (meth)acrylic resin can be measured according to JIS K0070:1992 "Testing methods for acid value, saponification value, ester value, iodine value, hydroxyl value and unsaponifiable matter of chemical products."

[0079] Commercially available (meth)acrylic resins may be used. For example, commercially available water-dispersible (meth)acrylic resins include "Movinyl 745" (trade name) manufactured by Japan Coating Resins Co., Ltd.

[0080] The colored resin particles may contain, for example, 10 to 100 mass %, 10 to 90 mass %, 20 to 80 mass %, or 40 to 60 mass % of the (meth)acrylic resin relative to the total amount of resin contained in the colored resin particles.

[0081] The resin contained in the colored resin particles is, for example, preferably 10% by mass or more, more preferably 15% by mass or more, and even more preferably 20% by mass or more, based on the total amount of the colored resin particles. On the other hand, the resin contained in the colored resin particles may be, for example, 70% by mass or less, 60% by mass or less, or 50% by mass or less, based on the total amount of the colored resin particles. The resin contained in the colored resin particles may be, for example, 10 to 70% by mass, 15 to 60% by mass, or 20 to 50% by mass, based on the total amount of the colored resin particles. The amount of resin contained in the colored resin particles may be, for example, 0.5 to 30% by mass, 1 to 20% by mass, or 2 to 10% by mass relative to the total amount of the ink.

[0082] "Pigment dispersant" The pigmented resin particles may include a pigment dispersant. In one embodiment of the pigmented resin particles, the pigmented resin particles include a pigment and a pigment dispersant. The pigment dispersant may be any of a basic dispersant, an acidic dispersant, an amphoteric dispersant, and a nonionic dispersant.

[0083] The pigment dispersant is preferably oil-insoluble in the non-aqueous solvent contained in the oil-based ink. For example, the amount of resin contained in the colored resin particles that can dissolve in 100 g of the non-aqueous solvent contained in the oil-based ink at 23°C is preferably 3 g / 100 g or less, 1 g / 100 g or less, or 0.5 g / 100 g or less. The pigment dispersant is preferably a water-soluble pigment dispersant. When an oil-based ink is produced by the submerged drying method described below, the use of a water-soluble pigment dispersant can improve dispersion stability of the colorant and resin in water.

[0084] In one example, among (meth)acrylic resins, a (meth)acrylic resin exhibiting pigment dispersibility can be used as the pigment dispersant. For example, a (meth)acrylic resin having a pigment affinity group can be used as the pigment dispersant. The (meth)acrylic resin used as the pigment dispersant is preferably a water-soluble pigment dispersant.

[0085] In another example, a water-soluble nonionic pigment dispersant can be used as the pigment dispersant. Water-soluble nonionic pigment dispersants are dispersants in which the hydrophilic group does not exhibit ionic dissociation. Examples of water-soluble nonionic pigment dispersants include ester-type water-soluble nonionic pigment dispersants, ether-type water-soluble nonionic pigment dispersants, and ester-ether-type water-soluble nonionic pigment dispersants, depending on the main bond type within the molecule.

[0086] Ester-type water-soluble nonionic pigment dispersants have a structure in which a polyhydric alcohol such as glycerin, sorbitol, or sucrose is ester-bonded to a fatty acid, and examples thereof include glycerin fatty acid esters, sorbitan fatty acid esters, and sucrose fatty acid esters.

[0087] Ether-type water-soluble nonionic pigment dispersants can be produced by adding ethylene oxide to raw materials with hydroxyl groups, such as higher alcohols, alkylphenols, arylphenols, and arylalkylphenols, and examples include polyglycol ethers (e.g., aryl polyglycol ethers and alkyl polyglycol ethers). More specific examples include polyoxyethylene alkyl ethers, polyoxyethylene alkyl phenyl ethers, polyoxyethylene aryl phenyl ethers, polyoxyethylene aryl alkyl phenyl ethers, and aryl alkyl biphenylol polyglycol ethers.

[0088] Ester-ether type water-soluble nonionic pigment dispersants are compounds in which ethylene oxide is added to an ester of a polyhydric alcohol, such as glycerin or sorbitol, and a fatty acid. They contain both ester and ether bonds in the molecule. For example, fatty acid polyethylene glycol ether esters can be mentioned. Other water-soluble nonionic pigment dispersants that can be used include polycarboxylic acid polymers and polysiloxane copolymers. These water-soluble nonionic pigment dispersants can be used alone or in combination of two or more.

[0089] As the water-soluble nonionic pigment dispersant, fatty acid polyethylene glycol ether ester, polyglycol ether (for example, aryl polyglycol ether), and the like are more preferred.

[0090] Commercially available pigment dispersants include, for example, "Solsperse 27000" manufactured by Lubrizol Japan Co., Ltd. and "Borchi Gen DFN" manufactured by Borchers.

[0091] In the colored resin particles, the pigment dispersant can be used alone or in combination of two or more. The amount of pigment dispersant in the colored resin particles can be appropriately set. For example, the pigment dispersant can be blended in a mass ratio of 0.01 to 3 parts by mass of pigment to 1 part by mass of pigment, preferably 0.01 to 1, and more preferably 0.1 to 0.5. The pigment dispersant may be, for example, 1 to 30 mass%, 5 to 25 mass%, or 10 to 20 mass% relative to the total amount of the colored resin particles. When a (meth)acrylic resin is used as the pigment dispersant, it is preferable that the total amount of the (meth)acrylic resin and other pigment dispersants satisfy these ranges.

[0092] "Uncolored resin particles containing colloidal silica" The oil-based ink may contain non-pigmented resin particles including colloidal silica. The non-pigmented resin particles containing colloidal silica may comprise a resin and colloidal silica.

[0093] "Resin contained in uncolored resin particles containing colloidal silica" The resin contained in the non-colored resin particles containing colloidal silica forms the non-colored resin particles in the oil-based ink, and is preferably oil-insoluble in the non-aqueous solvent contained in the oil-based ink. For example, the amount of resin contained in the non-colored resin particles containing colloidal silica that can dissolve in 100 g of the non-aqueous solvent contained in the oil-based ink at 23° C. is preferably 3 g / 100 g or less, 1 g / 100 g or less, or 0.5 g / 100 g or less.

[0094] When the resin contained in the non-colored resin particles containing colloidal silica is an oil-insoluble resin, the elution of the resin component from the non-colored resin particles in the oil-based ink is easily suppressed, making it possible to more fully maintain the dispersibility of the non-colored resin particles, and by suppressing the elution of the resin component, it is possible to more effectively suppress an increase in the viscosity of the oil-based ink. Furthermore, the oil-insolubility of the resin enhances solvent releasability when the oil-based ink lands on a substrate, more effectively reducing roller transfer stains and further improving image quality.

[0095] The resin contained in the non-colored resin particles containing colloidal silica may be, for example, a water-dispersible resin or a water-soluble resin. Being water-dispersible means that the resin has the property of being able to be dispersed in particulate form without dissolving in water. Examples of water-dispersible resins include resins having units with hydrophilic groups, resins having hydrophilic groups at the terminals, resins having side chains with hydrophilic groups, and resins whose surfaces have been hydrophilically treated with surfactants or the like. Examples of hydrophilic groups include acidic groups, basic groups, nonionic groups, and combinations thereof. For example, when an oil-based ink is produced by a method using a water-in-oil (W / O) emulsion drying in oil, the resin may be a water-soluble resin, a water-dispersible resin, or a combination thereof.

[0096] The resin contained in the non-colored resin particles containing colloidal silica is not particularly limited, and examples thereof include urethane resin, (meth)acrylic resin, polyester resin, vinyl chloride resin, polyolefin resin, etc. The non-colored resin particles containing colloidal silica may contain one type of resin alone or two or more types of resin in combination. The non-colored resin particles containing colloidal silica preferably contain, for example, a urethane resin, a (meth)acrylic resin, or a combination thereof. For example, in terms of suitability for non-aqueous solvents, the non-colored resin particles containing colloidal silica preferably contain a urethane resin.

[0097] Examples of the urethane resin and (meth)acrylic resin include the resins described above as the resin contained in the colored resin particles. For example, when producing an oil-based ink using a method that uses a water-in-oil (W / O) emulsion to dry in oil, it is preferable to use a water-dispersible resin as the resin for the non-colored resin particles containing colloidal silica, and it is preferable to use a water-dispersible urethane resin, a water-dispersible (meth)acrylic resin, or a combination thereof.

[0098] An example of a commercially available water-dispersible (meth)acrylic resin is "Movinyl 745" (trade name) manufactured by Japan Coating Resins Co., Ltd.

[0099] The amount of resin contained in the uncolored resin particles containing colloidal silica may be, for example, 50 to 99 mass % or 70 to 99 mass % relative to the total amount of the uncolored resin particles containing colloidal silica. The amount of resin contained in the non-colored resin particles containing colloidal silica may be, for example, 0.1 to 10% by mass, 0.2 to 5% by mass, or 0.5 to 2% by mass relative to the total amount of ink.

[0100] Oil-based inkjet ink The oil-based inkjet ink may contain colored resin particles and a non-aqueous solvent. The oil-based inkjet ink may (i) contain colloidal silica in the colored resin particles, and / or (ii) further contain non-colored resin particles containing colloidal silica. The oil-based inkjet ink may further contain a dispersant from the viewpoint of dispersion stability of the colored resin particles and the optionally contained non-colored resin particles containing colloidal silica.

[0101] The amount of colored resin particles relative to the total amount of the oil-based ink is preferably 1% by mass or more, 3% by mass or more, 5% by mass or more, or 10% by mass or more. The amount of colored resin particles relative to the total amount of the oil-based ink is preferably 40% by mass or less, 30% by mass or less, 25% by mass or less, or 20% by mass or less. For example, the amount of colored resin particles relative to the total amount of oil-based ink may be 1 to 40% by mass, 3 to 30% by mass, 5 to 25% by mass, or 10 to 20% by mass.

[0102] From the viewpoint of image quality of printed matter, the average particle diameter of the colored resin particles is preferably 100 nm or more, more preferably 150 nm or more, and even more preferably 200 nm or more. On the other hand, from the viewpoint of storage stability and circulation stability of the ink, the average particle diameter of the colored resin particles is preferably 400 nm or less, more preferably 350 nm or less, and even more preferably 300 nm or less. For example, the average particle diameter of the colored resin particles may be 100 to 400 nm, 150 to 350 nm, or 200 to 300 nm.

[0103] In the present disclosure, the particle diameter (D50) of the colored resin particles and the non-colored resin particles including colloidal silica described below is a volume-based median diameter measured by a laser diffraction / scattering method, and can be measured using, for example, a laser diffraction / scattering particle size distribution analyzer "Partica LA-950 (manufactured by Horiba, Ltd.)" manufactured by Horiba, Ltd.

[0104] The amount of non-colored resin particles containing colloidal silica relative to the total amount of the oil-based ink is preferably 0.1% by mass or more, 0.2% by mass or more, 0.4% by mass or more, or 0.5% by mass or more. The amount of non-colored resin particles containing colloidal silica relative to the total amount of the oil-based ink is preferably 20% by mass or less, 10% by mass or less, 5% by mass or less, or 2% by mass or less. For example, the amount of non-colored resin particles containing colloidal silica relative to the total amount of oil-based ink may be 0.1 to 20% by mass, 0.2 to 10% by mass, 0.4 to 5% by mass, or 0.5 to 2% by mass.

[0105] The average particle size of the non-colored resin particles containing colloidal silica is preferably 150 nm or more, more preferably 175 nm or more. On the other hand, the average particle size of the non-colored resin particles containing colloidal silica is preferably 350 nm or less, more preferably 325 nm or less. For example, the average particle size of the non-colored resin particles containing colloidal silica may be 150 to 350 nm or 175 to 325 nm.

[0106] "Dispersant" The dispersant for dispersing the colored resin particles and the non-colored resin particles, including colloidal silica, which may be optionally contained, is not particularly limited as long as it can be incorporated into the oil-based ink. From the viewpoint of stability in the oil-based ink, the dispersant preferably exhibits solubility in the non-aqueous solvent contained in the oil-based ink, and more preferably dissolves uniformly in the non-aqueous solvent without separating into two phases. From this viewpoint, the dispersant is preferably a polymer compound.

[0107] The dispersant may be any of a basic dispersant, an acidic dispersant, and a nonionic dispersant, but is preferably a basic dispersant. A basic dispersant is a dispersant having a basic group. For example, when a (meth)acrylic resin with a high acid value is contained in the colored resin particles, the use of a basic dispersant can further contribute to the stability of the oil-based ink.

[0108] Examples of basic groups include amino groups, amido groups, imino groups, imido groups; and nitrogen-containing heterocyclic groups such as pyrrolidone groups, pyridine groups, and morpholino groups. Examples of amino groups include unsubstituted amino groups and substituted amino groups such as monoalkylamino groups or dialkylamino groups (e.g., dimethylamino groups). Substituents such as alkyl groups may be further substituted with hydroxyl groups, aryl groups, and other substituents. Examples of amido groups include unsubstituted amido groups and substituted amido groups such as monoalkylamido groups or dialkylamido groups (e.g., dimethylamido groups). Substituents such as alkyl groups may be further substituted with hydroxyl groups, aryl groups, and other substituents. The basic dispersant may contain one basic group alone or two or more basic groups in combination.

[0109] The basic dispersant may be, for example, a polymer compound having a hydrocarbon group having 6 or more carbon atoms, or a hydrocarbon group having 6 or more carbon atoms and having a substituent such as a hydroxyl group or an aryl group, and a basic group.

[0110] The basic dispersant may be, for example, a basic dispersant having an alkanolamine structure. For example, when an oil-based ink is produced using a water-in-oil (W / O) emulsion drying-in-oil method, it is preferable to use a basic dispersant having an alkanolamine structure.

[0111] The alkanolamine structure may be, for example, a structure represented by the following formula (1): In this case, the alkanolamine structure may be a monoalkanolamine structure or a dialkanolamine structure, but is preferably a dialkanolamine structure.

[0112] [ka]

[0113] In formula (1), R 1 R may be a hydroxyalkyl group having 1 to 4 carbon atoms, a hydroxyalkylene oxide group having 1 to 4 carbon atoms, or a hydroxypolyalkylene oxide group having 1 to 4 carbon atoms. 2 may be an alkyl group having 1 to 10 carbon atoms, an ether bond-containing group having 1 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms, or an arylalkyl group having 7 to 10 carbon atoms. n is 1 or 2. When n=2, R 1 The groups represented by the following formula may be the same or different. * indicates a bonding site to another structure.

[0114] R 1is preferably a hydroxyalkyl group having 1 to 4 carbon atoms, and may be, for example, a functional group in which a hydrogen atom of any of a methyl group, an ethyl group, a propyl group, a trimethylene group, an n-butyl group, an iso-butyl group, a tert-butyl group, or a sec-butyl group has been substituted with a hydroxy group. More preferably, it is a hydroxyalkyl group having 1 or 2 carbon atoms, and may be, for example, a hydroxymethyl group, a 1-hydroxyethyl group, or a 2-hydroxyethyl group, and even more preferably a 1-hydroxyethyl group.

[0115] R 2 is preferably an alkyl group having 1 to 10 carbon atoms, such as a methyl group, ethyl group, propyl group, trimethylene group, n-butyl group, iso-butyl group, tert-butyl group, sec-butyl group, pentyl group, isopentyl group, neopentyl group, hexyl group, heptyl group, octyl group, isooctyl group, 2-ethylhexyl group, nonyl group, isononyl group, decyl group, isodecyl group, etc. More preferably, it is an alkyl group having 1 to 8 or 1 to 4 carbon atoms, and even more preferably, it is a methyl group or an ethyl group. R 2 The ether bond-containing group having 1 to 10 carbon atoms may be an alkyloxy group or a polyalkylene oxide group. R 2 The aryl group having 6 to 10 carbon atoms may have a substituent, and examples thereof include a phenyl group, a methylphenyl group, and an ethylphenyl group. R 2 As the arylalkyl group having 7 to 10 carbon atoms, it may have a substituent, and examples thereof include a phenylmethyl group and a phenylethyl group.

[0116] The alkanolamine structure is preferably a structure derived from N-methylethanolamine, N-ethylethanolamine, N-propylethanolamine, N-isopropylethanolamine, N-butylethanolamine, N-ethylbutanolamine, diethanolamine, diisopropanolamine, or the like.

[0117] The basic dispersant having an alkanolamine structure is preferably a polymeric compound, and is preferably a polymeric compound in which an alkanolamine is bonded to the main chain of a polymer such as a (meth)acrylic resin, a urethane resin, or an olefin resin by an addition reaction.

[0118] Specifically, the basic dispersant having an alkanolamine structure is preferably a polymer compound obtained by using a polymer having a unit having a reactive functional group reactive with an amino group and a unit having a lipophilic group, and bonding an amino alcohol to the reactive functional group by an addition reaction.

[0119] The amino alcohol used in the reaction may be a compound represented by the general formula (1) in which the binding site * is a hydrogen atom. More specific examples include N-methylethanolamine, N-ethylethanolamine, N-propylethanolamine, N-isopropylethanolamine, N-butylethanolamine, N-ethylbutanolamine, diethanolamine, and diisopropanolamine.

[0120] Examples of reactive functional groups reactive with amino groups include epoxy groups and β-dicarbonyl groups. The epoxy group may be a glycidyl group. Examples of β-dicarbonyl groups include β-diketone groups and β-keto acid ester groups. Examples of β-diketone groups include acetoacetyl groups and propionacetyl groups, and examples of β-keto acid ester groups include acetoacetoxy groups and propionacetoxy groups.

[0121] Examples of units having a lipophilic group include long-chain alkyl groups having 6 to 30, 8 to 22, or 10 to 20 carbon atoms. The basic dispersant having an alkanolamine structure may have other structural units, such as a unit having an aromatic ring. The aromatic ring exhibits affinity for colored resin particles, and is therefore expected to contribute more to dispersibility.

[0122] From the viewpoint of stability in oil-based inks, the basic dispersant having an alkanolamine structure preferably has a (meth)acrylic resin skeleton. For example, the main carbon chain may have an alkanolamine structure bonded to a reactive functional group via an ester bond. Alternatively, the main carbon chain may have another functional group, such as a lipophilic group, via an ester bond.

[0123] A basic dispersant having an alkanolamine structure can be obtained by polymerizing a monomer mixture. The monomer mixture will be described below. Examples of monomers having a reactive functional group reactive with an amino group include monomers having an epoxy group, a β-dicarbonyl group, etc. Specific examples of monomers having an epoxy group include glycidyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate glycidyl ether, and 3,4-epoxycyclohexylmethyl (meth)acrylate. Furthermore, examples of monomers having a β-dicarbonyl group include acetoacetoxyalkyl (meth)acrylates such as acetoacetoxyethyl (meth)acrylate, acetoacetoxypropyl (meth)acrylate, and acetoacetoxybutyl (meth)acrylate; ethylene glycol monoacetoacetate mono(meth)acrylate, 2,3-di(acetoacetoxy)propyl (meth)acrylate, and 2,4-hexadione (meth)acrylate; allyl acetoacetate; vinyl acetoacetate; and acetoacetoxyalkyl (meth)acrylamides such as acetoacetoxyethyl (meth)acrylamide.

[0124] Examples of monomers having a lipophilic group include monomers having a long-chain alkyl group having 6 to 30 carbon atoms, and specific examples include hexyl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, dodecyl (meth)acrylate, isododecyl (meth)acrylate, stearyl (meth)acrylate, isostearyl (meth)acrylate, behenyl (meth)acrylate, and cyclohexyl (meth)acrylate.

[0125] With respect to all units of the basic dispersant having an alkanolamine structure, the unit having an alkanolamine structure is, for example, preferably from 1 to 50 mass %, more preferably from 2 to 40 mass %, and even more preferably from 2 to 30 mass %. The unit having a lipophilic group preferably accounts for 10 to 95 mass %, more preferably 20 to 90 mass %, and even more preferably 40 to 85 mass %, of all units of the basic dispersant having an alkanolamine structure. The other units are optionally contained in the total units of the basic dispersant having an alkanolamine structure, and are, for example, preferably 1 to 90 mass %, more preferably 5 to 50 mass %, and even more preferably 5 to 30 mass %. Each unit may be of one type alone or in combination of two or more types.

[0126] There is no particular limitation on the weight average molecular weight (Mw) of the basic dispersant having an alkanolamine structure, but from the viewpoint of ink viscosity, it is preferably 8,000 to 50,000.

[0127] Other examples of basic dispersants include basic dispersants that are linear or branched polymers having a basic group at the end of the main chain; basic dispersants that are polymers having a basic group and a plurality of side chains containing polyester moieties (hereinafter sometimes referred to as "basic comb dispersants"); etc. From the viewpoint of dispersion stability, basic comb dispersants are preferred.

[0128] In the basic comb dispersant, the polyester moiety in the side chain may be, for example, a structure derived from a hydroxycarboxylic acid or a mixture of a hydroxycarboxylic acid and a carboxylic acid not containing a hydroxy group, or a polymer containing a carbonyl-C3-C6-alkyleneoxy group unit. An example of a structure derived from a mixture of a hydroxycarboxylic acid and a carboxylic acid not containing a hydroxy group is a carbonyl-C17-alkyleneoxy group derived from a self-condensation product of 12-hydroxystearic acid. An example of the carbonyl-C3-C6-alkyleneoxy group is a carbonyl-C5-alkyleneoxy group, and for example, a polymer containing a carbonyl-C5-alkyleneoxy group unit can be obtained by ring-opening polymerization of ε-caprolactone. The degree of polymerization of the polyester portion is not particularly limited, and may be, for example, about 2 to 80.

[0129] The basic comb dispersant may contain basic groups in the main chain backbone, for example in the form of a polyamine backbone, and / or may contain basic groups attached to the main chain directly or via a linking group. When the basic comb dispersant contains a basic group bonded to the main chain directly or via a linking group, the basic comb dispersant may have one or more basic groups, but preferably has two or more basic groups. The type of basic group bonded to the main chain directly or via a linking group is not particularly limited, and for example, the basic groups described above can be used, with amino groups and morpholino groups being preferred, and amino groups being more preferred. Examples of basic comb-shaped dispersants include basic dispersants that are polymers having a main chain containing a polyamine skeleton and having a plurality of side chains containing polyester moieties, and basic dispersants that are polymers having basic groups bonded to the main chain directly or via a linking group and having a plurality of side chains containing polyester moieties.

[0130] As another example of the basic dispersant, a (meth)acrylic polymer dispersant having a basic group may be used. For example, a (meth)acrylic polymer dispersant having a unit having a basic group, a unit having a pigment affinity group, or a unit having a long-chain alkyl group having 6 to 30 carbon atoms may be used. Each of these units may be partly or entirely derived from a (meth)acrylate.

[0131] Examples of the basic group include an amino group, an amido group, an imino group, an imido group, and nitrogen-containing heterocyclic groups such as a pyrrolidone group, a pyridine group, and a morpholino group. Examples of the pigment-affinitive group include an aromatic ring-containing group and a β-dicarbonyl group. As the long-chain alkyl group having 6 to 30 carbon atoms, one or more of those described above for the basic dispersant having an alkanolamine structure may be selected and used.

[0132] The amount of units having a basic group relative to all units of the (meth)acrylic polymer dispersant having a basic group is preferably from 5 to 30 mass %, more preferably from 10 to 20 mass %. The unit having a pigment-affinitive group preferably accounts for 5 to 30 mass %, more preferably 10 to 20 mass %, of all units of the (meth)acrylic polymer dispersant having a basic group. The unit having a long-chain alkyl group having 6 to 30 carbon atoms is preferably 40 to 90 mass %, more preferably 50 to 90 mass %, and even more preferably 60 to 80 mass % or more of the total units of the (meth)acrylic polymer dispersant having a basic group. Each unit may be of one type alone or in combination of two or more types.

[0133] The weight average molecular weight (Mw) of the basic (meth)acrylic dispersant is not particularly limited, but is preferably 5,000 to 30,000 from the viewpoint of ink stability and ink viscosity.

[0134] Commercially available basic dispersants include, for example, Solsperse 11200, Solsperse 13940, Solsperse 16000, Solsperse 17000, Solsperse 18000, Solsperse 19000, Solsperse 24000, Solsperse 32000, Solsperse 38500, Solsperse 39000, Solsperse 71000, Solsperse 22000, and Solsperse 28000 (all trade names) manufactured by Lubrizol Japan Co., Ltd.; Disperse BYK109 (trade name) manufactured by BYK Japan Co., Ltd.; Acetamine 24 and Acetamine 86 (trade names) manufactured by Kao Corporation; Hypermer KD3 and Hypermer KD11 (trade names) manufactured by Croda Japan Co., Ltd.; Ajinomoto Fine-Techno Co., Ltd.; Antaron V-216 and Antaron V-220" (both trade names).

[0135] The oil-based ink may contain one dispersant alone or two or more dispersants in combination. The amount of dispersant can be adjusted as appropriate. The amount of dispersant is preferably 0.1% by mass or more, more preferably 1% by mass or more, and even more preferably 2% by mass or more, relative to the total amount of ink. On the other hand, the amount of dispersant is preferably 10% by mass or less, more preferably 7% by mass or less, and may be, for example, 5% by mass or less, relative to the total amount of ink. For example, the amount of dispersant may be, for example, 0.1 to 10% by mass, 1 to 7% by mass, or 2 to 5% by mass, relative to the total amount of ink. The amount of dispersant may be 1 to 60 parts by mass, 5 to 50 parts by mass, 10 to 40 parts by mass, or 10 to 30 parts by mass relative to 100 parts by mass in total of the colored resin particles and the non-colored resin particles that may optionally contain colloidal silica.

[0136] "Non-aqueous solvent" As the non-aqueous solvent, either a non-polar organic solvent or a polar organic solvent can be used. These can be used alone or in combination. In the present disclosure, it is preferable to use a water-insoluble organic solvent that is not uniformly mixed with the same volume of water at 20°C under 1 atmosphere as the non-aqueous solvent.

[0137] Preferred examples of the non-polar organic solvent include petroleum hydrocarbon solvents such as aliphatic hydrocarbon solvents, alicyclic hydrocarbon solvents, and aromatic hydrocarbon solvents. Examples of aliphatic hydrocarbon solvents and alicyclic hydrocarbon solvents include non-aqueous solvents such as paraffins, isoparaffins, and naphthenes. Commercially available products include No. 0 Solvent L, No. 0 Solvent M, No. 0 Solvent H, Cactus normal paraffin N-10, Cactus normal paraffin N-11, Cactus normal paraffin N-12D, Cactus normal paraffin N-13, Cactus normal paraffin N-14, Cactus normal paraffin YHNP, Cactus normal paraffin SHNP, Isozol 300, Isozol 400, Teclain N16, Teclain N20, Teclain N22, AF Solvent No. 4, AF Solvent No. 5, AF Solvent No. 6, AF Solvent No. 7, Naphtesol 160, Naphtesol 200, and Naphtesol 220 (all trade names manufactured by ENEOS Corporation); Isopar G, Isopar H Preferred examples of the solvent include BHT, Isopar L, Isopar M, Exxol D40, Exxol D60, Exxol D80, Exxol D110, and Exxol D130 (all trade names manufactured by ExxonMobil Corporation); Moresco White P-60, Moresco White P-70, Moresco White P-80, Moresco White P-100, Moresco White P-120, Moresco White P-150, Moresco White P-200, Moresco White P-260, and Moresco White P-350P (all trade names manufactured by MORESCO Corporation). Preferred examples of the aromatic hydrocarbon solvent include Solvesso 100, Solvesso 150, Solvesso 200, and Solvesso 200ND (all trade names manufactured by ExxonMobil Corporation). The initial boiling point of the petroleum hydrocarbon solvent is preferably 100°C or higher, more preferably 150°C or higher, and even more preferably 200°C or higher. The initial boiling point of distillation can be measured in accordance with JIS K0066 "Testing method for distillation of chemical products."

[0138] Preferred examples of polar organic solvents include fatty acid ester solvents, higher alcohol solvents, and higher fatty acid solvents. For example, isononyl isononanoate, isodecyl isononanoate, isotridecyl isononanoate, methyl laurate, isopropyl laurate, hexyl laurate, isopropyl myristate, isopropyl palmitate, hexyl palmitate, isooctyl palmitate, isostearyl palmitate, methyl oleate, ethyl oleate, isopropyl oleate, butyl oleate, hexyl oleate, methyl linoleate, ethyl linoleate, isobutyl linoleate, butyl stearate, hexyl stearate, isooctyl stearate, isopropyl isostearate, 2-octyldecyl pivalate, soybean oil fatty acid methyl esters, soybean Examples of such solvents include fatty acid ester solvents having 13 or more carbon atoms per molecule, preferably 16 to 30, such as oil fatty acid isobutyl ester, tall oil fatty acid methyl ester, and tall oil fatty acid isobutyl ester; higher alcohol solvents having 6 or more carbon atoms per molecule, preferably 12 to 20, such as isomyristyl alcohol, isopalmityl alcohol, isostearyl alcohol, oleyl alcohol, isoeicosyl alcohol, and decyltetradecanol; and higher fatty acid solvents having 12 or more carbon atoms per molecule, preferably 14 to 20, such as lauric acid, isomyristic acid, palmitic acid, isopalmitic acid, α-linolenic acid, linoleic acid, oleic acid, and isostearic acid. The boiling points of polar organic solvents such as fatty acid ester solvents, higher alcohol solvents, and higher fatty acid solvents are preferably 150°C or higher, more preferably 200°C or higher, and even more preferably 250°C or higher. Non-aqueous solvents having a boiling point of 250°C or higher also include non-aqueous solvents that do not exhibit a boiling point.

[0139] These non-aqueous solvents may be used alone or in combination of two or more types as long as they form a single phase. In addition, other organic solvents may be contained within the range that allows the non-aqueous solvent to form a single phase.

[0140] In addition to the above components, the oil-based ink may contain various additives. Examples of additives that can be added include nozzle clogging inhibitors, antioxidants, conductivity modifiers, viscosity modifiers, surface tension modifiers, and oxygen absorbers. The types of these additives are not particularly limited, and any additives commonly used in the relevant fields can be used.

[0141] The amount of water in the ink is preferably 1% by mass or less, more preferably less than 1% by mass, even more preferably 0.5% by mass or less, and even more preferably 0.1% by mass or less, based on the total amount of the ink.

[0142] The suitable range of viscosity of oil-based inkjet inks varies depending on factors such as the nozzle diameter of the ejection head of the inkjet recording system and the ejection environment, but in general, the viscosity is preferably 5 to 30 mPa·s at 23°C, and more preferably 5 to 15 mPa·s.

[0143] "Method of manufacturing oil-based inkjet ink"

[0033] Hereinafter, an embodiment of a method for producing an oil-based inkjet ink will be described. Note that the above-mentioned oil-based inkjet ink is characterized by being specified by the above-mentioned components, regardless of the production method. Furthermore, the method for producing the oil-based inkjet ink is not particularly limited, and the ink may be produced, for example, using the embodiment of the production method described below.

[0144] Methods for producing oil-based inks containing colored resin particles are generally broadly divided into methods using chemical techniques and methods using physicochemical techniques. For example, chemical techniques include the interfacial polycondensation method, the interfacial reaction method (in situ polymerization method), and the liquid-cured coating method (orifice method). Physicochemical techniques include the liquid-drying method (water-drying method, oil-drying method), the coacervation method, and the melt-dispersion-cooling method. In producing the oil-based ink, the submerged drying method can be preferably used, and the submerged drying method of a water-in-oil (W / O) emulsion can be particularly preferably used.

[0145] An example of a method for producing an oil-based ink using the oil-in-oil drying method for a water-in-oil emulsion includes a step of preparing a water-in-oil emulsion containing an oil phase containing a non-aqueous solvent and an aqueous phase containing a resin, a colorant, and water (hereinafter sometimes referred to as "step 1"), and a step of removing water from the water-in-oil emulsion (hereinafter sometimes referred to as "step 2"). When the colored resin particles contain colloidal silica, the aqueous phase may contain colloidal silica. The aqueous phase may contain a pigment dispersant. When the oil-based ink contains non-colored resin particles containing colloidal silica, the method may further include a step of preparing a water-in-oil emulsion containing an oil phase containing a non-aqueous solvent and an aqueous phase containing a resin and water (hereinafter sometimes referred to as "step 3"), and a step of removing water from the water-in-oil emulsion (hereinafter sometimes referred to as "step 4"). In each of the water-in-oil emulsions of Step 1 and Step 3, an emulsifier may further be contained in the oil phase. The emulsifier contained in the oil phase is preferably a lipophilic emulsifier. In this method, the above-mentioned dispersant for dispersing the colored resin particles or non-colored resin particles may be used as the emulsifier.

[0146] This method, which uses the in-oil drying method of a water-in-oil emulsion, does not require the use of volatile organic solvents and is therefore safe. Furthermore, this method, which uses the in-oil drying method of a water-in-oil emulsion, makes it possible to produce inks with low viscosity. This is thought to be because this method makes it possible to produce inks containing colored resin particles with a small average particle size and a narrow particle size distribution.

[0147] In step 2, the aqueous phase contains a colorant, a resin, and optionally colloidal silica, and the water from the aqueous phase is removed while the aqueous phase forms droplets in the oil phase, thereby forming a mixture in the colored resin particles containing the colorant, resin, and optionally colloidal silica.In step 3, the aqueous phase contains a resin and colloidal silica, and the water from the aqueous phase is removed while the aqueous phase forms droplets in the oil phase, thereby forming a mixture in the resin particles containing the resin and colloidal silica.

[0148] In steps 1 and 3, the resin is preferably hydrophilic from the viewpoint of stably incorporating the resin into the aqueous phase. The resin is preferably a water-soluble resin or a water-dispersible resin. The resin may be added to the aqueous phase as an aqueous solution or a water dispersion of the resin.

[0149] The non-aqueous solvent, resin, colorant, pigment dispersant, and colloidal silica described above as components of oil-based inks can be used. Tap water, ion-exchanged water, deionized water, etc. can be used as water. The emulsifier that may be optionally included can be the same as the dispersant described above for dispersing colored resin particles.

[0150] In the water-in-oil emulsion obtained in step 1 and the water-in-oil emulsion obtained in step 3, the mass ratio of the aqueous phase (dispersed phase) to the oil phase (continuous phase) may be, for example, 10:90 to 90:10, 20:80 to 80:20, 25:75 to 55:45, or 30:70 to 45:55, respectively.

[0151] In the water-in-oil emulsion obtained in step 1, the total amount of the colorant, resin, optionally contained colloidal silica, and optionally contained pigment dispersant may be 1 to 60 mass %, 10 to 50 mass %, or 20 to 40 mass % relative to the total amount of the aqueous phase. When other components are further contained, the total amount of nonvolatile components in the aqueous phase should preferably fall within this range.

[0152] In the water-in-oil emulsion obtained in step 3, the total amount of the resin and colloidal silica may be 1 to 60 mass%, 10 to 50 mass%, or 20 to 40 mass% of the total aqueous phase. When other components are further contained, the total amount of nonvolatile components contained in the aqueous phase should preferably fall within this range.

[0153] In the water-in-oil emulsion obtained in step 1, the amount of emulsifier that may be optionally contained in the oil phase may be 0.1 to 10 mass %, 0.5 to 8 mass %, or 1 to 5 mass % relative to the total mass of the water-in-oil emulsion. The amount of this emulsifier may be 1 to 20 mass parts, 2 to 15 mass parts, or 3 to 12 mass parts relative to 100 mass parts of the aqueous phase.

[0154] In the water-in-oil emulsion obtained in step 3, the amount of emulsifier that may be optionally contained in the oil phase may be 0.1 to 10 mass %, 0.5 to 8 mass %, or 1 to 5 mass % relative to the total mass of the water-in-oil emulsion. The amount of this emulsifier may be 1 to 30 mass parts, 5 to 25 mass parts, or 10 to 22 mass parts relative to 100 mass parts of the aqueous phase.

[0155] In each of steps 1 and 3, the water-in-oil emulsion can be produced, for example, by mixing and emulsifying the above-mentioned water phase and oil phase. It is preferable to prepare the aqueous phase and the oil phase separately in advance. Then, it is preferable to add the aqueous phase to the oil phase and emulsify it. The emulsification may be carried out, for example, using an ultrasonic homogenizer while adding the aqueous phase to the oil phase, or may be carried out after adding the aqueous phase to the oil phase.

[0156] In each of Steps 1 and 3, a water-in-oil emulsion may be obtained by, for example, preparing an aqueous phase, adding it to the oil phase, and then emulsifying. Alternatively, a water-in-oil emulsion may be obtained by adding all the components at once and then emulsifying.

[0157] Water is removed from the aqueous phase of the water-in-oil emulsion in each of steps 2 and 4. As a result, it is believed that colored resin particles containing the aqueous phase component from which the water has been removed are obtained in step 2, and that non-colored resin particles containing the aqueous phase component from which the water has been removed are obtained in step 4. Methods for removing water include, for example, reducing pressure and / or heating, or bubbling a gas into the liquid to promote evaporation, or a combination of these. The conditions for reducing pressure and / or heating can be such that water is removed but the non-aqueous solvent in the oil phase remains. An evaporator can be used for reducing pressure, for example. The heating temperature is preferably 30°C or higher, more preferably 40 to 100°C, and even more preferably 60 to 90°C. In steps 2 and 4, the amount of water removed from the aqueous phase is preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, and even more preferably 99% by mass or more, based on the amount before removal.

[0158] In the case where a dispersion of colored resin particles containing colloidal silica is obtained in steps 1 and 2, this dispersion of colored resin particles may be used as ink as is. The method for producing the ink may further include a step of mixing the colored resin particle dispersion obtained in step 2 with the non-colored resin particle dispersion obtained in step 4.

[0159] "Printing method" The printing method using the oil-based inkjet ink is not particularly limited, and may be any method such as a piezoelectric method, an electrostatic method, a thermal method, etc. When an inkjet recording device is used, it is preferable to eject the ink according to this embodiment from an inkjet head based on a digital signal, and to cause the ejected ink droplets to adhere to a substrate.

[0160] In the present embodiment, the substrate is not particularly limited, and examples thereof include printing paper such as plain paper, coated paper, and special paper, cloth, inorganic sheet, film, OHP sheet, and adhesive sheet having an adhesive layer on the back surface of the substrate, etc. Among these, printing paper such as plain paper and coated paper can be preferably used from the viewpoint of ink permeability.

[0161] Here, plain paper refers to paper on which no ink-receiving layer or film layer is formed. Examples of plain paper include fine paper, medium-quality paper, PPC paper, wood paper, recycled paper, etc. Plain paper has paper fibers with a thickness of several μm to several tens of μm that form voids of several tens to several hundreds of μm, making it easy for ink to penetrate.

[0162] Furthermore, as the coated paper, inkjet coated paper such as matte paper, glossy paper, and semi-glossy paper, as well as so-called coated printing paper, can be preferably used. Here, coated printing paper refers to printing paper that has traditionally been used in letterpress printing, offset printing, gravure printing, and the like, and is printing paper in which a coating layer is provided on the surface of fine or medium-quality paper using a paint containing an inorganic pigment such as clay or calcium carbonate and a binder such as starch. Coated printing paper is classified into lightly coated paper, fine lightweight coated paper, medium lightweight coated paper, fine coated paper, medium coated paper, art paper, cast coated paper, and the like, depending on the amount of paint applied and the coating method.

[0163] Some embodiments of the present disclosure are set forth below. <1> An oil-based inkjet ink comprising colored resin particles and a non-aqueous solvent, and satisfying at least one of the following (i) or (ii): (i) the colored resin particles include colloidal silica; (ii) The oil-based inkjet ink further contains non-colored resin particles containing colloidal silica. <2> Satisfies the above (i); <1> 1. An oil-based inkjet ink according to claim 1. <3> Satisfies the above (ii), <1> or <2> 1. An oil-based inkjet ink according to claim 1. <4> The average particle size of the colloidal silica is 5 to 80 nm. <1> ~ <3> 10. The oil-based inkjet ink according to any one of claims 1 to 9. [Example]

[0164] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples. Unless otherwise specified, common components are the same throughout the following Examples and Comparative Examples. Unless otherwise specified, "%" indicates "% by mass."

[0165] <Ink materials> The materials of the inks in the examples and comparative examples are shown below.

[0166] Carbon black 1: "MOGUL L" (trade name), Cabot Specialty Chemicals. Carbon Black 2: "NEROX505" (trade name), manufactured by Orion Engineered Carbons. Copper phthalocyanine 1: "FASTGEN Blue LA5380" (product name), DIC Corporation.

[0167] Water-based pigment dispersion 1: Prepared according to the following procedure: 20% pigment, 6% pigment dispersant. Self-dispersing pigment water dispersion 1: "BONJET BLACK CW-1" (trade name), manufactured by Orient Chemical Industries, Ltd., 15% self-dispersing pigment. Pigment dispersant 1: "Solsperse 27000" (trade name), Lubrizol Japan Co., Ltd., 100% active ingredient.

[0168] Aqueous resin composition AC1 / (meth)acrylic resin AC1: Produced according to the following procedure. Solid content of aqueous resin composition AC1: 20%. Aqueous resin composition AC2 / (meth)acrylic resin AC2: Produced according to the following procedure. Aqueous resin composition AC2 had a solids content of 20%. Aryl polyglycol ether: "Borchi Gen DFN" (trade name), Borchers (water-soluble, aryl alkyl biphenylol polyglycol ether, 100% active ingredient).

[0169] Urethane resin water dispersion 1 / urethane resin 1: "Takelac WS-5984" (product name), Mitsui Chemicals, Inc., 40% solid content of urethane resin water dispersion 1. Urethane resin aqueous dispersion 2 / urethane resin 2: "Superflex 740" (trade name), Daiichi Kogyo Seiyaku Co., Ltd., 40% solid content of urethane resin aqueous dispersion 2. Urethane resin water dispersion 3 / urethane resin 3: "DAOTAN TW6491" (trade name), Daicel-Allnex Corporation, urethane resin water dispersion 3 solids content 33%. Urethane resin water dispersion 4 / urethane resin 4: "Superflex 650" (trade name), Daiichi Kogyo Seiyaku Co., Ltd., urethane resin water dispersion 4 solids content 26%. (Meth)acrylic resin water dispersion 1 / (meth)acrylic resin 1: "Movinyl 745" (trade name), manufactured by Japan Coating Resins Co., Ltd., solid content of (meth)acrylic resin water dispersion 1: 38%.

[0170] Colloidal silica water dispersion 1 / colloidal silica 1: "Snowtex ST-S", manufactured by Nissan Chemical Co., Ltd., solid content of colloidal silica water dispersion 1: 20%, average particle size: 14 nm. Colloidal silica water dispersion 2 / colloidal silica 2: "Snowtex ST-30", manufactured by Nissan Chemical Co., Ltd., solid content of colloidal silica water dispersion 2: 30%, average particle size: 23 nm. Colloidal silica water dispersion 3 / colloidal silica 3: "Snowtex ST-NS", manufactured by Nissan Chemical Co., Ltd., solid content of colloidal silica water dispersion 3: 20%, average particle size: 20 nm. Colloidal silica water dispersion 4 / colloidal silica 4: "Snowtex ST-50-T", manufactured by Nissan Chemical Co., Ltd., solid content of colloidal silica water dispersion 4: 48%, average particle size: 42 nm. Colloidal silica water dispersion 5 / colloidal silica 5: "Snowtex ST-30L", manufactured by Nissan Chemical Co., Ltd., solid content of colloidal silica water dispersion 5: 30%, average particle size: 86 nm.

[0171] The average particle size of colloidal silica is the volume-based particle size value (median size) in the particle size distribution measured by dynamic light scattering. The value was measured at 25°C using a nanoparticle analyzer, nano Partica SZ-100 (Horiba, Ltd.), as a dynamic light scattering particle size distribution measuring device, by diluting each colloidal silica aqueous dispersion with water to a colloidal silica concentration of 0.5 mass%, with the refractive index of the dispersant set to 1.333, the refractive index of the sample set to 1.430, and the calculation conditions set to polydispersity standard.

[0172] Aqueous silica dispersion 1: Prepared according to the following procedure: 20% powdered silica. Oil-based colloidal silica dispersion 1: Prepared according to the following procedure: 10% colloidal silica. Powdered silica 1: "Aerosil R104" (trade name), manufactured by Nippon Aerosil Co., Ltd.

[0173] Dispersant solution 1: Resin solution a-1 prepared according to the following procedure, active ingredient 50%, solvent is fatty acid ester solvent 1 described below. Dispersant solution 2: "Solsperse 13940" (trade name), Lubrizol Japan Co., Ltd., active ingredient 40%, solvent is petroleum-based solvent.

[0174] Fatty acid ester solvent 1: Isotridecyl isononanoate, Kokyu Alcohol Kogyo Co., Ltd. Petroleum-based hydrocarbon solvent 1: "Isopar M" (trade name), ExxonMobil Corporation.

[0175] Stearyl methacrylate is available from Shin-Nakamura Chemical Co., Ltd., 2-ethylhexyl methacrylate (2-ethylhexyl methacrylate) is available from Mitsubishi Chemical Corporation, glycidyl methacrylate (glycidyl methacrylate) is available from NOF Corporation, and methacrylic acid (MAA), methyl methacrylate (MMA), and benzyl methacrylate (BMA) are available from Tokyo Chemical Industry Co., Ltd.

[0176] Methoxypolyethylene glycol methacrylate: "M-90G" (trade name), number of added moles approximately 9, Shin-Nakamura Chemical Co., Ltd.

[0177] NaOH aqueous solution 1: 10% aqueous solution of NaOH.

[0178] <Production of resin solution a-1> A 300 ml four-neck flask was charged with 87.5 g of fatty acid ester solvent 1, and the temperature was raised to 110°C while aerating nitrogen gas and stirring. Next, while maintaining the temperature at 110°C, a mixture of 100.0 g of a monomer mixture having the composition shown below, 16.5 g of fatty acid ester solvent 1, and 4 g of perhexyl O (t-hexylperoxy 2-ethylhexanoate (manufactured by NOF Corporation)) was added dropwise over 3 hours. Thereafter, the mixture was stirred for 2 hours while maintaining the temperature at 110°C, yielding a resin solution a with a solids content of 50% by mass.

[0179] (Monomer mixture formulation) Stearyl methacrylate: 40 parts by mass. 2-Ethylhexyl methacrylate: 30 parts by mass. Glycidyl methacrylate: 30 parts by mass. Total: 100 parts by mass.

[0180] 200 g of resin solution a was placed in a 500 ml four-neck flask, and the mixture was heated to 110°C while aerating with nitrogen gas and stirring. 12 g of diisopropanolamine (Tokyo Chemical Industry Co., Ltd.) was added, and the mixture was allowed to react at 110°C for 2 hours. After that, 12 g of fatty acid ester solvent 1 was added, and resin solution a-1 with a solid content of 50 mass% was obtained.

[0181] <Production of Aqueous Resin Composition AC1 / (Meth)acrylic Resin AC1 and Aqueous Resin Composition AC2 / (Meth)acrylic Resin AC2> Table 1 shows the formulation of the monomer mixture. In Table 1, the amounts of each material are shown in parts by mass. 39.2 g of methyl ethyl ketone and 19.6 g of ethanol were charged into a 500 ml four-neck flask, and the mixture was heated to 65°C while aerating nitrogen gas and stirring. A monomer composition was prepared by adding 9.8 g of methyl ethyl ketone and 4.9 g of ethanol to 30.0 g of the monomer mixture mixed in the proportions shown in Table 1. 1.5 g of V-65 (2,2'-azobis(2,4-dimethylvaleronitrile)) was added to the flask, and then the monomer composition was added dropwise over 3 hours while maintaining the temperature at 65°C. After the dropwise addition, the mixture was aged at 70°C for 3 hours, yielding colorless, transparent resin compositions No. 1 and No. 2 with a solids content of 30%.

[0182] The resin compositions No. 1 and No. 2 obtained above were mixed with methyl ethyl ketone, ethanol, NaOH aqueous solution 1, and ion-exchanged water in the amounts shown in Table 2. Then, the methyl ethyl ketone and ethanol were evaporated using an evaporator to obtain aqueous resin compositions AC1 and AC2 with a solid content of 20%. In Table 2, the blending amount of each material is shown in parts by mass. The formulation in Table 2 is the formulation before removal of the solvents (methyl ethyl ketone and ethanol).

[0183] [Table 1]

[0184] [Table 2]

[0185] <Production of Water-Based Pigment Dispersion 1> The materials were mixed according to the following formula, and the pigment was thoroughly dispersed using a bead mill "Dyno Mill KDL-A" (manufactured by Shinmaru Enterprises Co., Ltd.) for a residence time of 15 minutes. Next, coarse particles were removed using a membrane filter, and aqueous pigment dispersion 1 (20% pigment, 6% pigment dispersant) was obtained.

[0186] (Formulation of water-based pigment dispersion 1) Carbon black 2: 20 parts by mass. Pigment dispersant 1:6 parts by weight. Water: 74 parts by mass. Total: 100 parts by mass.

[0187] <Production of Aqueous Silica Dispersion 1> The materials were mixed according to the following formula, and the powdered silica was thoroughly dispersed using a bead mill "Dyno Mill KDL-A" (manufactured by Shinmaru Enterprises Co., Ltd.) for a residence time of 15 minutes. Next, coarse particles were removed using a membrane filter, and aqueous silica dispersion 1 (20% powdered silica, 10% pigment dispersant) was obtained.

[0188] (Formulation of aqueous silica dispersion 1) Powdered silica 1:20 parts by mass. Pigment dispersant 1:10 parts by mass. Water: 70 parts by mass. Total: 100 parts by mass.

[0189] <Production of Oil-Based Colloidal Silica Dispersion 1> 84.5 parts by mass of petroleum-based hydrocarbon solvent 1 and 5.5 parts by mass of dispersant solution 1 were mixed to obtain an oil phase mixture. 33.3 parts by mass of colloidal silica aqueous dispersion 5 and 20.0 parts by mass of water were mixed to obtain an aqueous phase mixture. While stirring the oil phase mixture with a magnetic stirrer, the aqueous phase mixture was added dropwise and irradiated with an ultrasonic homogenizer "Ultrasonic Processor VC-750" (manufactured by Sonics Corporation) for 10 minutes to obtain 143.3 parts by mass of a water-in-oil (W / O) emulsion. The mixture was ice-cooled during ultrasonic irradiation. The water in the aqueous phase was removed from the obtained emulsion under reduced pressure using an evaporator to obtain 100.0 parts by mass of oil-based colloidal silica dispersion 1. The colloidal silica content in the obtained oil-based colloidal silica dispersion 1 was 10%.

[0190] <Preparation of oil-based ink> [Examples 1 to 8, Comparative Examples 1 to 3] The materials listed for the oil phase in Table 3 were mixed in the amounts shown in the table to obtain an oil phase mixture. The materials listed for the aqueous phases 1 and 2 in Table 3 were mixed in the amounts shown in the table to obtain an aqueous phase 1 mixture and an aqueous phase 2 mixture. While stirring the oil phase mixture with a magnetic stirrer, the aqueous phase 1 mixture and the aqueous phase 2 mixture were added dropwise in that order while irradiating the mixture with an ultrasonic homogenizer "Ultrasonic Processor VC-750" (manufactured by Sonics Corporation) for 10 minutes to obtain a water-in-oil (W / O) emulsion. The mixture was ice-cooled during ultrasonic irradiation. The water in the aqueous phase was removed from the resulting emulsion while reducing the pressure in an evaporator to obtain a colored resin particle dispersion. This colored resin particle dispersion was used as an ink. The formulation of the resulting ink is shown in the bottom row of Table 3. In Table 3, the amount of each material is shown in parts by mass.

[0191] [Table 3]

[0192] [Examples 9 to 18, Comparative Examples 4 to 5] (Preparation of colored resin particle dispersion) The materials shown in Aqueous Phase 1 in Table 4 were mixed in the amounts shown in the table, and the pigment was thoroughly dispersed using a bead mill "Dyno Mill KDL-A" (manufactured by Shinmaru Enterprises Co., Ltd.) for a residence time of 12 minutes to obtain an Aqueous Phase 1 mixture. The materials shown in Aqueous Phase 2 in Table 4 were mixed with this Aqueous Phase 1 mixture in the amounts shown in the table to obtain an Aqueous Phase mixture. The materials shown in Table 4 for the oil phase were mixed in the blending ratios shown in the table to obtain an oil phase mixture.

[0193] While stirring the oil phase mixture with a magnetic stirrer, the aqueous phase mixture was added dropwise to the mixture, and the mixture was subjected to ultrasonic irradiation with an "Ultrasonic Processor VC-750" (manufactured by Sonics Corporation) for 10 minutes to obtain a water-in-oil (W / O) emulsion. The mixture was ice-cooled during ultrasonic irradiation. The water in the aqueous phase was removed from the resulting emulsion under reduced pressure using an evaporator to obtain a colored resin particle dispersion. The formulation of the colored resin particle dispersion obtained is shown in the lower part of Table 4. In Table 4, the blending ratio of each material is shown in parts by mass.

[0194] [Table 4]

[0195] (Preparation of non-colored resin particle dispersion) The materials shown in Table 5 for the oil phase were mixed in the amounts shown in the table to obtain an oil phase mixture. The materials shown in Table 5 for the water phase were mixed in the amounts shown in the table to obtain an water phase mixture. While stirring the oil phase mixture with a magnetic stirrer, the aqueous phase mixture was added dropwise to the mixture, and the mixture was subjected to ultrasonic irradiation with an "Ultrasonic Processor VC-750" (manufactured by Sonics Corporation) for 10 minutes to obtain a water-in-oil (W / O) emulsion. The mixture was ice-cooled during ultrasonic irradiation. The water in the aqueous phase was removed from the resulting emulsion under reduced pressure using an evaporator to obtain a non-colored resin particle dispersion. The formulation of the non-colored resin particle dispersion obtained is shown in the bottom row of Table 5. In the table, the blending ratio of each material is shown in parts by mass.

[0196] [Table 5]

[0197] (Preparation of oil-based ink) The colored resin particle dispersion and uncolored resin particle dispersion obtained as described above were mixed in the amounts shown in Tables 6 and 7 to obtain oil-based inks of Examples 9 to 18 and Comparative Examples 4 and 5. In Tables 6 and 7, the amounts of the colored resin particle dispersion and uncolored resin particle dispersion are shown in parts by mass.

[0198] [Table 6]

[0199] [Table 7]

[0200] [Evaluation method] (Roller transfer stains) The ink obtained as described above was loaded into an inkjet printer "Comphis GD9630" (manufactured by Riso Kagaku Corporation), and 300 solid images were printed on plain paper "Riso Paper Multi" (manufactured by Riso Kagaku Corporation) to obtain 300 prints. The 300th print was visually observed and evaluated according to the following criteria. The results are shown in Tables 8 to 10. A: Almost no contamination around the image B: Slight contamination around the image C: Contamination around the image is visible

[0201] (Image quality) The ink obtained as described above was loaded into a line-type inkjet printer "Comphis GD9630" (Riso Kagaku Corporation), and a solid chart (600 x 600 dpi, 8 pI / dot) was printed on plain paper "Riso Paper Multi" (Riso Kagaku Corporation) to obtain a print. The resulting print was left at room temperature for one day, and then the image density (OD value) of the solid image area on the printed surface (front side) of the print was measured using an Xrite exact (Videojet X-Rite) and evaluated according to the following criteria. The results are shown in Tables 8 to 10. A:OD value is 1.15 or more B:OD value is 1.05 or more and less than 1.15 C:OD value is less than 1.05

[0202] [Table 8]

[0203] [Table 9]

[0204] [Table 10]

[0205] As shown in the table, it was demonstrated that the oil-based inks of each example were able to reduce roller transfer stains on printed matter.

[0206] In contrast to this, in Comparative Example 1, in which colloidal silica was not added to the ink, the image density was high and the image quality was excellent, but roller transfer staining was observed. Furthermore, roller transfer stains were observed in Comparative Example 2, in which an ink containing powdered silica added to colored resin particles was used. This is presumably because the presence of the powdered silica dispersant inhibited the interaction between the paper fibers and the silica, preventing the full effect of the silanol from being obtained. Roller transfer stains were also observed in Comparative Example 3, which used an ink in which colloidal silica was directly dispersed in a non-aqueous solvent, rather than being blended with colored or non-colored resin particles. This is presumably because the contribution of the colored resin particles to fixation was reduced due to the influence of penetration. Roller transfer stains were also observed in Comparative Example 4, which contained colored resin particles without colloidal silica but no uncolored resin particles, and in Comparative Example 5, which contained colored resin particles and uncolored resin particles but no colloidal silica. This is presumably due to insufficient solvent releasability.

Claims

1. An oil-based inkjet ink comprising colored resin particles and a non-aqueous solvent, and satisfying at least one of the following (i) or (ii): (i) the colored resin particles contain colloidal silica; (ii) The oil-based inkjet ink further contains non-colored resin particles containing colloidal silica.

2. The oil-based inkjet ink according to claim 1 , which satisfies the condition (i).

3. The oil-based inkjet ink according to claim 1 , which satisfies the condition (ii).

4. 4. The oil-based inkjet ink according to claim 1, wherein the colloidal silica has an average particle size of 5 to 80 nm.

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