Ink composition, pigment dispersion, ink set, printed material, inkjet recording device, recording method, and method for manufacturing printed material

Abstract

The present invention provides an active energy ray curable ink composition that contains polymerizable compounds and exhibits high storage stability and ejection stability. An active energy ray curable ink composition ejected by an inkjet method, comprising a polymerizable compound, wherein the pH of the aqueous suspension measured by the following test method is 6.0 or higher and 8.0 or lower. Test method: The ink composition is mixed with water to prepare an aqueous suspension of the ink composition, and the pH of the aqueous suspension is measured.

Description

Technical Field

[0001] The present invention relates to an ink composition, a pigment dispersion, an ink set, a printed matter, an inkjet recording apparatus, a recording method, and a method for manufacturing a printed matter.

Background Art

[0002] In recent years, there has been a trend towards small-lot, multi-variety production of printed matter. As an alternative to the conventional offset printing method, the inkjet printing method, which is an on-demand printing method, has attracted attention. The inkjet printing method is simpler compared to the conventional offset printing method and has advantages such as waste reduction, economic efficiency, and energy savings.

[0003] On the other hand, in the inkjet printing method, it is required that the ink has good storage stability and a small viscosity change. If the viscosity changes, the ejection from the inkjet head may deteriorate.

[0004] Conventionally, in aqueous inkjet inks, pH adjustment has been carried out to maintain the dispersion stability of pigments and resins (Prior Art Documents 1 to 5), and pH adjusters have been added for the purpose of suppressing the corrosion of electrodes, nozzle plates, and head nozzle members (Prior Art Documents 6 to 9).

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Patent Document 6

[0006] Among inkjet printing methods, there are active energy ray-curable ink compositions in which polymerizable compounds harden when exposed to ultraviolet light, electron beams, or other active energy rays. Because active energy ray-curable ink compositions are fast-drying, ink bleeding can be prevented even when printing on substrates that do not absorb ink or absorb very little ink, such as plastics, glass, and coated paper.

[0007] On the other hand, in the case of active energy ray-curable ink compositions, the viscosity of the ink composition may increase even when the ink composition is not irradiated with active energy rays during unused or storage periods, which can prevent inkjet ejection, and the cause of this was unknown.

[0008] The present invention aims to provide an active energy ray curable ink composition that contains polymerizable compounds and exhibits high storage stability and discharge stability. [Means for solving the problem]

[0009] The inventors of the present invention conducted diligent research to solve the above problems and found that the above problems can be solved by controlling the components and their content so that the pH of the aqueous suspension obtained from the ink composition is within a specific range, thereby completing the present invention.

[0010] (1) An active energy ray-curable ink composition ejected by an inkjet method, containing a polymerizable compound, and having a pH of the aqueous suspension measured by the following test method of 6.0 or more and 8.0 or less. Test method: Mix the ink composition and water so that the content of the ink composition is 10% by mass fraction to prepare an aqueous suspension of the ink composition, and measure the pH of the aqueous suspension.

[0011] (2) The ink composition according to (1), containing a coloring material.

[0012] (3) The ink composition according to (1), not containing a coloring material.

[0013] (4) A pigment dispersion used for an active energy ray-curable ink composition ejected by an inkjet method, containing a pigment, a polymerizable compound, and a pigment dispersant, and having a pH of the aqueous suspension measured by the following test method of 6.0 or more and 8.0 or less. Test method: Mix the pigment dispersion and water so that the content of the pigment dispersion is 10% by mass fraction to produce an aqueous suspension of the pigment dispersion, and measure the pH of the aqueous suspension.

[0014] (5) An active energy ray-curable ink composition ejected by an inkjet method, containing the pigment dispersion according to (4) and a polymerization initiator.

[0015] (6) The ink composition according to any one of (1) to (3) and (5), having a water content of 5.0% by mass or less in the total amount of the ink composition.

[0016] (7) An ink set containing the ink composition according to any one of (1) to (3), (5) and (6).

[0017] (8) A printed matter printed with the ink composition according to any one of (1) to (3), (5) and (6).

[0018] An inkjet recording apparatus comprising a storage mechanism filled with the ink composition according to any one of (1) to (3), (5), and (6) in (9).

[0019] (10) A recording method of discharging the ink composition according to any one of (1) to (3), (5), and (6) by an inkjet method.

[0020] (11) A method for manufacturing a printed matter by discharging the ink composition according to any one of (1) to (3), (5), and (6) by an inkjet method. [Effect of the Invention]

[0021] According to the present invention, it is possible to provide an active energy ray-curable ink composition excellent in storage stability and ejection stability. [Modes for Carrying Out the Invention]

[0022] Hereinafter, specific embodiments of the present invention will be described in detail. However, the present invention is not limited to the following embodiments, and can be implemented with appropriate modifications within the scope of the object of the present invention.

[0023] ≪1. Active Energy Ray-Curable Ink Composition≫ The active energy ray-curable ink composition according to the present embodiment contains a polymerizable compound, and is characterized in that the pH of an aqueous suspension measured by the following test method is 6.0 or more and 8.0 or less.

[0024] Test method: Mix the ink composition and water so that the content of the ink composition becomes 10% by mass fraction to produce an aqueous suspension of the ink composition, and measure the pH of the aqueous suspension.

[0025] Active energy ray-curable ink compositions, after being applied to a substrate, become fixed to the substrate due to the polymerization of polymerizable compounds, which increases their viscosity. However, even when unused or stored, active energy ray-curable ink compositions containing polymerizable compounds may undergo polymerization reactions of the polymerizable compounds even without irradiation with active energy rays, which can lead to increased viscosity of the ink composition, the formation of gels, or the inability to eject inkjet ink.

[0026] The exact cause is unknown, and generally, the only way to address it is to add polymerization inhibitors, which is not sufficient to prevent it completely. On the other hand, if the amount of polymerization initiator added is reduced or the amount of polymerization inhibitor added is increased in order to suppress the polymerization reaction, the polymerization reaction may not proceed well even when irradiated with active energy rays, resulting in poor curability or deterioration of the coating film's physical properties.

[0027] The inventors of this invention conducted diligent research to solve the above problems and found that by controlling the components and their content so that the pH (also called the hydrogen ion index, hydrogen ion concentration index, or hydrogen index) of the aqueous suspension obtained from the ink composition or pigment dispersion falls within a specific range, an ink composition with excellent storage stability and discharge stability can be obtained. Polymerizable compounds undergo a dark reaction even without the application of active energy ray irradiation energy, which can lead to an increase in ink viscosity, gelation, and the formation of aggregates. The inventors' research revealed that the progression of such dark reactions in polymerizable compounds is due to the pH of the aqueous suspension obtained from the ink composition. The novel aspect of this invention lies in the discovery that the pH of the suspension water affects the stability of an active energy ray curable ink composition that does not inherently contain water.

[0028] Therefore, by controlling the components and their content so that the pH of the aqueous suspension obtained from the ink composition falls within a specific range, an ink composition with excellent storage stability and dispensing stability can be obtained. In this specification, for convenience, the pH of a 10% mass fraction aqueous suspension obtained from the ink composition may be simply referred to as "pH of the ink composition," etc.

[0029] In other words, in the active energy ray curable ink composition according to this embodiment, the pH of the ink composition is set to the neutral range (pH range of 6.0 to 8.0). This makes it possible to obtain an ink composition with excellent storage stability and discharge stability. If the pH of the ink composition is in the acidic range (pH range of less than 6.0) or the basic range (pH range of greater than 8.0), the reactivity of polymerizable compounds in the ink composition may increase, and polymerization reactions may proceed even without irradiation with active energy rays, which may cause the viscosity of the ink composition to increase or gel to form. In addition, if the acidity or basicity of the ink composition becomes too strong, the dispersibility of colorants and other materials may deteriorate, which may cause gel or precipitate to form or the viscosity of the ink composition to increase.

[0030] The pH of the ink composition is "Japanese Industrial Standard JIS K5101-17- 2 The pH of the pigment is measured using a room-temperature extraction method similar to the method for measuring the pH of pigments in accordance with "2004 Pigment Test Method - Part 17: pH Value - Section 2: Room Temperature Extraction Method". Specifically, a 10% aqueous suspension of the ink composition (or pigment dispersion) to be tested is prepared using water in a container such as a glass container equipped with a stopper. The container is then stoppered and shaken vigorously for 1 minute. After standing for 5 minutes, the stopper is removed and the pH of the suspension is measured.

[0031] For example, "Japanese Industrial Standard JIS K5101-17- 2Using a pH measuring device conforming to "2004 Pigment Test Method - Part 17: pH Value - Section 2: Room Temperature Extraction Method", water, and a 50 ml glass bottle with a lid, place 3.0 g of the sample to be measured (additives such as colorants, dispersants, polymerization initiators, polymerizable compounds, and surfactants) and 27.0 g of 25°C water into the glass bottle, close the lid, shake vigorously for 1 minute, and let stand for 5 minutes to prepare an aqueous suspension. Then remove the stopper and measure the pH of the suspension.

[0032] Methods for controlling the components and their amounts so that the pH of the ink composition falls within a specific range include the following: Specifically, among the components (polymerizable compounds, colorants, dispersants, binder resins, surfactants, etc.) that are candidates to be included in the ink composition (or pigment dispersion), the Japanese Industrial Standard JIS K5101-17- 2 The pH is measured using a room-temperature extraction method similar to the pH measurement method for pigments in accordance with 2004. The ink composition is then manufactured by determining the components and their amounts so that the predicted pH of the ink composition (or pigment dispersion), inferred from the pH of the components, falls within a predetermined range. If the pH of the aqueous suspension obtained from the ink composition does not fall within the desired pH range, it is possible to control the pH of the aqueous suspension obtained from the ink composition to fall within a specific range by, for example, adding a pH adjuster to the composition or adjusting the amounts of acidic or basic components.

[0033] The pH of the active energy ray-curable ink composition according to this embodiment may be 6.0 or more and 8.0 or less, but it is preferably 6.2 or more and more preferably 6.4 or more. The pH of the ink composition is preferably 7.8 or less and more preferably 7.6 or less. The pH of the ink composition is preferably 6.2 or more and 7.8 or less and more preferably 6.4 or more and 7.6 or less.

[0034] Furthermore, the active energy ray curable ink composition according to this embodiment may also be a colored ink containing a colorant. In this specification, "colorant" includes dyes and pigments, and is used as a concept that includes, for example, dyes or pigments contained in colored inks that form images such as yellow, magenta, cyan, black, red, orange, violet, blue, green, and intermediate or light colors thereof, as well as white dyes or white pigments contained in white inks and luminous colorants contained in metallic inks.

[0035] This colored ink may be a colored ink that forms an image in colors such as yellow, magenta, cyan, black, red, orange, violet, blue, green, and intermediate or light shades thereof. Alternatively, the colored ink may be a white ink containing a white pigment, or a metallic ink containing a luminous pigment, etc.

[0036] Furthermore, if the active energy ray-curable ink composition according to this embodiment contains a colorant, it may also contain a dispersant that disperses at least a portion of the colorant in the ink composition.

[0037] Furthermore, the active energy ray curable ink composition according to this embodiment may be a clear ink that does not contain a colorant. Specifically, it may be a primer ink for forming a primer layer on the surface of a substrate, an overcoat ink for forming an overcoat layer on the surface of a recording, a matte ink composition for removing the gloss of a recording (substrate), an ink composition for imparting gloss or texture, or an ink containing an ultraviolet absorber or light stabilizer for forming a weather-resistant layer.

[0038] In this embodiment, the water content of the active energy ray-curable ink composition is preferably 5.0% by mass or less, more preferably 3.0% by mass or less, and even more preferably 1.0% by mass or less of the total amount of ink composition. The term "water" here refers to water that is not intentionally added but is present as a result of the raw materials or manufacturing process.

[0039] The following describes each component included in the active energy ray curable ink composition according to this embodiment.

[0040] [Polymerizable compound] The active energy ray curable ink composition according to this embodiment contains a polymerizable compound. A polymerizable compound is a compound (polymerizable monomer) that has one or more ethylenically unsaturated double bonds and polymerizes to form a cured product when irradiated with active energy rays. Active energy rays include electromagnetic waves such as far ultraviolet rays, ultraviolet rays, near ultraviolet rays, visible light, infrared rays, X-rays, and gamma rays, as well as electron beams, proton beams, and neutron beams. This polymerizable compound is mainly in liquid form and has the function of polymerizing to form a cured product, as well as the function of a dispersion medium or solvent for the ink composition.

[0041] The polymerizable compound may be a monofunctional polymerizable compound having one ethylenically unsaturated double bond, or a polyfunctional polymerizable compound having two or more ethylenically unsaturated double bonds.

[0042] Furthermore, the polymerizable compound may be a polymerizable compound with a relatively large molecular weight, such as an oligomer.

[0043] Examples of monofunctional polymerizable compounds include tetrahydrofurfuryl (meth)acrylate, cyclic trimethylolpropane formal (meth)acrylate, (2-methyl-2-ethyl-1,3-dioxolan-4-yl) (meth)acrylate, (2-methyl-2-isobutyl-1,3-dioxolan-4-yl) (meth)acrylate, (cyclohexanespiro-2-(1,3-dioxolan-4-yl)) (meth)acrylate, alkylcycloalkyl acrylates such as 4-t-butylcyclohexyl (meth)acrylate and n-butylcyclohexyl ( Meth)acrylate, benzyl(meth)acrylate, phenoxyethyl(meth)acrylate, isobornyl(meth)acrylate, dicyclopentanyl(meth)acrylate, dicyclopentenyl(meth)acrylate, dicyclopentenyloxyethyl(meth)acrylate, γ-butyrolactone(meth)acrylate, cresol(meth)acrylate, 2-acryloyloxyethyl phthalate, 2-acryloyloxyethyl-2-hydroxyethyl phthalate, 2-acryloyloxyethylhexahydrophthalate, 2-acryloyloxypropyl Pyrphthalate, paracumylphenoxyethylene glycol (meth)acrylate, nonylphenoxypolyethylene glycol (meth)acrylate, 1-adamantyl (meth)acrylate, cyclohexyl (meth)acrylate, cyclooctyl (meth)acrylate, hydroxycyclohexyl (meth)acrylate, 3-3-5-trimethylcyclohexyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth), N-vinylpyrrole acrylate, acryloylmorpholine, N-vinylcaprolactam, imido (meth) Acrylate, isooctyl (meth)acrylate, tridecyl (meth)acrylate, lauryl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, stearyl (meth)acrylate, isodecyl (meth)acrylate, caprolactone (meth)acrylate, methoxypolyethylene glycol (meth)acrylate, methoxypolypropylene glycol (meth)acrylate, 2-methoxyethyl (meth)acrylate, ethyl carbitol (meth)acrylate, 2-ethylhexyl (meth)acrylate, vinylcyclohexane,tert-butyl-4-ethynylcyclohexane, cycloheptyl (meth)acrylate, cyclopentyl (meth)acrylate, cyclobutyl (meth)acrylate, phenyl (meth)acrylate, styrene, N-vinylpyrrolidone, N-vinyloxazolidone, 2-vinyl-2-oxazoline N-vinylpyridine, N-vinylimidazole, 2-isopropenyl-2-oxazoline, methyl (meth)acrylate, butyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, te rt-butylcyclohexyl (meth)acrylate, octyl (meth)acrylate, trifluoroethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxyethyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, methyl α-(hydroxymethyl) (meth)acrylate, ethyl α-(hydroxymethyl) (meth)acrylate, n-butyl α-(hydroxymethyl) (meth)acrylate, dimethylaminoethyl (meth)acrylate, methyl Luaminoethyl (meth)acrylate, N-vinyl succinimide, N-vinyl methyl carbamate, N,N-methylvinyl acetamide, (meth)acryloyloxyethyltrimethylammonium chloride, (meth)acrylonitrile, N,N-dimethyl (meth)acrylamide, N,N-diethyl (meth)acrylamide, N-ethyl-N-methyl-(meth)acrylamide, N,N-diisopropyl (meth)acrylamide, N,N-dipropyl (meth)acrylamide, N,N-dibutyl (meth)acrylamide, N-ethyl-N-butyl - Acrylamide, N-isopropyl(meth)acrylamide, N-propyl(meth)acrylamide, N-butyl(meth)acrylamide, N-hexyl(meth)acrylamide, N-octyl(meth)acrylamide, N-2-ethylhexyl(meth)acrylamide, N-(2-hydroxyethyl)(meth)acrylamide, N-[3-(dimethylamino)propyl](meth)acrylamide, diacetone(meth)acrylamide, N-tert-butyl(meth)acrylamide, N-(dibutylaminomethyl)(meth)acrylamide, andExamples of these acrylates include those that have undergone various modifications such as alkoxy modification and caprolactone modification. Other examples include acid group-containing monomers such as 2-(meth)acryloyloxy)ethyl phosphate, 2-(meth)acryloyloxyethyl succinic acid, 2-(meth)acryloyloxyethyl-2-hydroxyethyl phthalic acid, and 2-(meth)acryloyloxyethyl hexahydrophthalic acid. For example, the pH of ink compositions and pigment dispersions can be adjusted using basic monomers containing basic functional groups such as amines and amides, and acidic monomers. These polymerizable compounds may be used individually or in combination. Note that "(meth)acrylate" refers to both "acrylate" and "methacrylate."

[0044] Examples of polyfunctional polymerizable compounds include ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, long-chain aliphatic di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,5-pentanediol di(meth)acrylate, 3-methyl-1,5-pentanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, and 1,6-hexanediol di(meth)acrylate. Ethylene oxide modified (EO modified) (2), ethylene oxide modified (EO modified) 1,6-hexanediol di(meth)acrylate (3), ethylene oxide modified (EO modified) 1,6-hexanediol di(meth)acrylate (5), propylene oxide modified (PO modified) 1,6-hexanediol di(meth)acrylate (2), propylene oxide modified (PO modified) 1,6-hexanediol di(meth)acrylate (3), 1,9-nonanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate T, Neopentyl glycol di(meth)acrylate modified with ethylene oxide (EO) (2), Neopentyl glycol di(meth)acrylate modified with ethylene oxide (EO) (3), Neopentyl glycol di(meth)acrylate modified with propylene oxide (PO) (2), Neopentyl glycol di(meth)acrylate modified with propylene oxide (PO) (8), Neopentyl glycol di(meth)acrylate modified with propylene oxide (PO) (16), Neopentyl glycol hydroxypivalate Di(meth)acrylate, neopentyl glycol hydroxypivalate di(meth)acrylate modified with caprolactone (2), neopentyl glycol hydroxypivalate di(meth)acrylate modified with caprolactone (4), polyalkylene glycol diacrylate, polyalkylene glycol diacrylate modified with ethylene oxide (EO) (4), polyalkylene glycol diacrylate modified with ethylene oxide (EO) (9), polyalkylene glycol diacrylate modified with ethylene oxide (EO) (14),Polyalkylene glycol diacrylate modified with ethylene oxide (EO) (23), polyalkylene glycol diacrylate modified with ethylene oxide (EO) (46), polyalkylene glycol diacrylate modified with propylene oxide (PO) (3), polyalkylene glycol diacrylate modified with propylene oxide (PO) (7), polyalkylene glycol diacrylate modified with propylene oxide (PO) (12), polyalkylene glycol diacrylate modified with ethylene oxide and propylene Polyalkylene oxide modification (PO modification (12) & EO modification (6)), ethylene oxide and propylene oxide modification of polyalkylene glycol diacrylate (PO modification (6) & EO modification (12)), ethylene oxide and propylene oxide modification of polyalkylene glycol diacrylate (PO modification (4) & EO modification (12)), ethylene oxide and propylene oxide modification of polyalkylene glycol diacrylate (PO modification (4) & EO modification (17)), ethylene oxide and propylene oxide modification of polyalkylene glycol diacrylate Polyalkylene oxide modified (PO modified (13) & EO modified (5)), butylene oxide modified (BO modified) of polyalkylene glycol diacrylate (3.5), butylene oxide modified (BO modified) of polyalkylene glycol diacrylate (9), butylene oxide modified (BO modified) of polyalkylene glycol diacrylate (14), stearic acid modified pentaerythritol di(meth)acrylate, propylene glycol di(meth)acrylate, glycerol di(meth)acrylate, triethylene glycol di(meth)acrylate 2-(2-vinyloxyethoxy)ethyl acrylate, tetraethylene glycol di(meth)acrylate, tetramethylene glycol di(meth)acrylate, butylene glycol di(meth)acrylate, propoxylated neopentyl glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, polypropylene di(meth)acrylate, triglycerol di(meth)acrylate, neopentyl glycol modified trimethylolpropane di(meth)acrylate, allylated cyclohexyl di(meth)acrylate,Methoxylated cyclohexyl di(meth)acrylate, acrylic isocyanurate, bis(acryloxyneopentyl glycol) adipate, bisphenol A di(meth)acrylate, ethylene oxide modified (EO modified) bisphenol A di(meth)acrylate (2), ethylene oxide modified (EO modified) bisphenol A di(meth)acrylate (3), ethylene oxide modified (EO modified) bisphenol A di(meth)acrylate (4), ethylene oxide modified (EO modified) bisphenol A di(meth)acrylate Modified (10), ethylene oxide modified (EO modified) bisphenol A di(meth)acrylate (20), ethylene oxide modified (EO modified) bisphenol A di(meth)acrylate (30), propylene oxide modified (PO modified) bisphenol A di(meth)acrylate (3), ethylene oxide and propylene oxide modified bisphenol A di(meth)acrylate (PO modified (6) & EO modified (3)), tetrabromobisphenol A di(meth)acrylate, bisphenol S di(meth)acrylate, pig Diol di(meth)acrylate, phthalate di(meth)acrylate, phosphate di(meth)acrylate, zinc di(meth)acrylate, pentaerythritol tetra(meth)acrylate, ethylene oxide modified (EO modified) pentaerythritol tetra(meth)acrylate (4), ethylene oxide modified (EO modified) pentaerythritol tetra(meth)acrylate (35), propylene oxide modified (PO modified) pentaerythritol tetra(meth)acrylate (4), pentaerythritol tetra(meth)acrylate Propylene oxide modified (PO modified) of ditrimethylolpropanetetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, ethylene oxide modified (EO modified) of dipentaerythritol hexa(meth)acrylate (6), ethylene oxide modified (EO modified) of dipentaerythritol hexa(meth)acrylate (12), ethylene oxide modified (EO modified) of dipentaerythritol hexa(meth)acrylate (18),Dipentaerythritol hexa(meth)acrylate modified with ethylene oxide (EO) (24), dipentaerythritol hexa(meth)acrylate modified with ethylene oxide (EO) (48), dipentaerythritol hexa(meth)acrylate modified with propylene oxide (PO) (6), dipentaerythritol hexa(meth)acrylate modified with caprolactone (2), dipentaerythritol hexa(meth)acrylate modified with caprolactone (3), dipentaerythritol hexa(meth)acrylate Caprolactone-modified trimethylolpropane (6), caprolactone-modified dipentaerythritol hexa(meth)acrylate (12), trimethylolpropane tri(meth)acrylate, ethylene oxide-modified trimethylolpropane tri(meth)acrylate (3), ethylene oxide-modified trimethylolpropane tri(meth)acrylate (6), ethylene oxide-modified trimethylolpropane tri(meth)acrylate (9), ethylene oxide-modified trimethylolpropane tri(meth)acrylate Oxide-modified (EO-modified) (15), Ethylene oxide-modified (EO-modified) trimethylolpropane tri(meth)acrylate (20), Ethylene oxide-modified (EO-modified) trimethylolpropane tri(meth)acrylate (30), Propylene oxide-modified (PO-modified) trimethylolpropane tri(meth)acrylate (3), Propylene oxide-modified (PO-modified) trimethylolpropane tri(meth)acrylate (6), Pentaerythritol tri(meth)acrylate, Glycerin tri(meth)acrylate , ethylene oxide modification (EO modification) of glycerin tri(meth)acrylate (3), ethylene oxide modification (EO modification) of glycerin tri(meth)acrylate (6), ethylene oxide modification (EO modification) of glycerin tri(meth)acrylate (9), ethylene oxide modification (EO modification) of glycerin tri(meth)acrylate (20), propylene oxide modification (PO modification) of glycerin tri(meth)acrylate (3), propylene oxide modification (PO modification) of glycerin tri(meth)acrylate (5.5),Examples include glycerin tri(meth)acrylate modified with propylene oxide (PO modification) (6), glycerin tri(meth)acrylate modified with propylene oxide (PO modification) (9), dimethylol tricyclodecanediaacrylate, and (meth)acrylates with different modification levels, modification species, and structural differences.

[0045] The pH of a 10% mass fraction aqueous suspension of polymerizable compounds is not particularly limited. It can be adjusted by using multiple polymerizable compounds in combination, or by combining them with colorants, dispersants, polymerization initiators, additives, etc. It is also possible to adjust the pH by adding acidic or basic components after ink preparation. However, to make it easier to adjust the pH of the ink to between 6.0 and 8.0, the pH of the 10% mass fraction aqueous suspension of polymerizable compounds (hereinafter sometimes simply referred to as the pH of the polymerizable compound) is preferably 5.0 or higher, more preferably 6.0 or higher, and even more preferably 6.2 or higher. Among these polymerizable compounds, the pH is preferably 9.0 or lower, more preferably 8.0 or lower, and even more preferably 7.8 or lower. Among these polymerizable compounds, the pH is preferably 5.0 to 9.0, more preferably 6.0 to 8.0, and even more preferably 6.2 to 7.8. The pH of the polymerizable compound can be measured by the same method as the room temperature extraction method described above.

[0046] The active energy ray curable ink composition according to this embodiment preferably contains a monofunctional polymerizable compound and a bifunctional or polyfunctional polymerizable compound (polyfunctional monomer) as polymerizable compounds. When a monofunctional polymerizable compound and a polyfunctional polymerizable compound are included, there are no particular restrictions on the content of the bifunctional polymerizable compound, but the content of the trifunctional or polyfunctional polymerizable compound is preferably 50% by mass or less, and more preferably 40% by mass or less, of the total amount of the ink composition. When a tetrafunctional or polyfunctional polymerizable compound (polyfunctional monomer) is included, its content is preferably 30% by mass or less, more preferably 25% by mass or less, and even more preferably 20% by mass or less, of the total amount of the ink composition. If the content of the trifunctional or polyfunctional polymerizable compound (polyfunctional monomer) is too high, curing shrinkage may occur, where the volume shrinks due to curing. When curing shrinkage occurs, the ink coating (cured film) may become relatively easier to peel off from the substrate, and the printed material may become relatively more prone to cracking and warping. By having a content of four or more polyfunctional polymerizable compounds (polyfunctional monomers) within the above range, peeling of the cured film due to curing shrinkage can be more effectively suppressed, resulting in the formation of a cured film with higher adhesion to the substrate.

[0047] Furthermore, it is preferable to include a polymerizable oligomer as the polymerizable compound. A polymerizable oligomer generally refers to a polymer in which a relatively small number of monomers are bonded together. An example of a polymerizable oligomer is a compound in which several to tens of constituent unit molecules are polymerized and has a weight-average molecular weight of 10,000 or less. By including a predetermined amount of polymerizable oligomer, it is possible to adjust the curability and viscosity of the ink composition.

[0048] Examples of polymerizable oligomers include urethane acrylates, epoxy acrylates, polyester acrylates, and polymer-type acrylates (acrylic acrylates), which can be obtained from companies such as Rahn AG, Sartomer, Daicel Corporation, Taisei Fine Chemicals, Mitsubishi Chemical Corporation, Daiichi Kogyo Seiyaku Co., Ltd., Kyoeisha Chemical Co., Ltd., and Shin Nakamura Chemical Co., Ltd.

[0049] If polymerizable oligomers are included, the polymerizable oligomer content is preferably 1.0% by mass or more, more preferably 1.3% by mass or more, and even more preferably 1.5% by mass or more, based on the total amount of the ink composition. The polymerizable oligomer content is preferably 20.0% by mass or less, more preferably 17.0% by mass or less, and even more preferably 15.0% by mass or less, based on the total amount of the ink composition. The polymerizable oligomer content is preferably 1.0% by mass or more and 20.0% by mass or less, more preferably 1.3% by mass or more and 17.0% by mass or less, and even more preferably 1.5% by mass or more and 15.0% by mass or less, based on the total amount of the ink composition.

[0050] These polymerizable compounds may be solid or liquid at room temperature. Among these, it is preferable that the polymerizable compounds contained in the ink composition according to this embodiment are liquid at room temperature. The liquid state of the polymerizable compound allows it to act as a solvent (dispersion medium) for dissolving or dispersing each component contained in the ink composition.

[0051] The content of polymerizable compounds is not particularly limited, but is preferably 40% by mass or more, more preferably 50% by mass or more, and even more preferably 60% by mass or more of the total ink composition. A polymerizable compound content of 40% by mass or more of the total ink composition can improve the curability of the cured film of the glossy layer formed when irradiated with active energy rays. The polymerizable compound content is preferably 90% by mass or less of the total ink composition, more preferably 87% by mass or less, and even more preferably 85% by mass or less. A polymerizable compound content of 90% by mass or less of the total ink composition allows for a relative increase in the content of colorants, etc., thereby imparting desired properties to the ink composition and the resulting printed material. The polymerizable compound content is preferably 40% by mass or more and 90% by mass or less of the total ink composition, more preferably 50% by mass or more and 87% by mass or less, and even more preferably 60% by mass or more and 85% by mass or less.

[0052] [Polymerization initiator] The active energy ray curable ink composition according to this embodiment may optionally contain a polymerization initiator. A polymerization initiator is used to promote the polymerization reaction of polymerizable compounds in the ink composition by irradiation with active energy rays. In the ink composition according to this embodiment, a polymerization initiator is not necessarily required; for example, if an electron beam is used as the active energy ray, a polymerization initiator may not be used.

[0053] Specific examples of polymerization initiators include, for example, bisacyl phosphine oxides such as bis-(2,6-dichlorobenzoyl)phenylphosphine oxide, bis-(2,6-dichlorobenzoyl)-2,5-dimethylphenylphosphine oxide, bis-(2,6-dichlorobenzoyl)-4-propylphenylphosphine oxide, bis-(2,6-dichlorobenzoyl)-1-naphthylphosphine oxide, bis-(2,6-dimethoxybenzoyl)phenylphosphine oxide, bis-(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide, bis-(2,6-dimethoxybenzoyl)-2,5-dimethylphenylphosphine oxide, and bis-(2,4,6-trimethylbenzoyl)-phenylphosphine oxide; and 2,6-dimethoxybenzoyldiphenylphosphine oxide, 2,6-dichlorobenzoyldiphenylphosphine oxide. Acyl phosphine oxide polymerization initiators such as diphenyl-2,4,6-trimethylbenzoylphenylphosphinate methyl ester, 2-methylbenzoyldiphenylphosphine oxide, pivaloylphenylphosphinate isopropyl ester, diphenyl-2,4,6-trimethylbenzoylphosphine oxide, and 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one, 2-benzyl-2-dimethylamino- Examples of such polymerization initiators include aminoacetophenone-based polymerization initiators such as 1-(4-morpholinophenyl)-butan-1-one and 2-(dimethylamino)-2-(4-methylbenzyl)-1-(4-morpholinophenyl)butan-1-one, and thioxanthone-based polymerization initiators such as 2-methylthioxanthone, 2-ethylthioxanthone, 2-chlorothioxanthone, 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, and 2-isopropylthioxanthone.

[0054] The pH of a 10% aqueous suspension of polymerization initiator is not particularly limited. It can be adjusted by using multiple polymerization initiators in combination, or by combining them with colorants, dispersants, polymerizable compounds, additives, etc. It is also possible to adjust the pH by adding acidic or basic components after ink preparation. However, to make it easier to adjust the pH of the ink to 6.0 to 8.0, the pH of a 10% aqueous suspension of polymerization initiator (hereinafter sometimes simply referred to as the pH of the polymerization initiator) is preferably 5.0 or higher, more preferably 6.0 or higher, and even more preferably 6.2 or higher. Among these polymerization initiators, the pH is preferably 9.0 or lower, more preferably 8.0 or lower, and even more preferably 7.8 or lower. Among these polymerization initiators, the pH is preferably 5.0 to 9.0, more preferably 6.0 to 8.0, and even more preferably 6.2 to 7.8. The pH of the polymerization initiator can be measured by the same method as the room temperature extraction method described above.

[0055] Furthermore, diphenyl-2,4,6-trimethylbenzoylphosphine oxide, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butan-1-one, and 2-(dimethylamino)-2-(4-methylbenzyl)-1-(4-morpholinophenyl)butan-1-one can more effectively promote the polymerization reaction of polymerizable compounds, but they are candidates for inclusion as substances of very high concern listed in Annex XIV of the REACH Regulation established by the European Union. For this reason, it is preferable to include polymerization initiators other than these.

[0056] Polymerization initiators that are not candidates for inclusion as substances of very high concern listed in Annex XIV of the REACH Regulation established by the European Union include polymerization initiators containing phosphine oxide derivatives containing two or more alkylbenzene structures in the molecule, polymerization initiators containing alkoxyphosphine oxide derivatives, and fluorenylaminoketone polymerization initiators. Examples include Omnirad 819 (manufactured by IGM Resins BV), A-TPO-N (manufactured by Diroid Materials), SpeedCure TPO-L (manufactured by Sartomer), SpeedCure XKm (manufactured by Sartomer), NPI-20400 (manufactured by TRONLY), SPEEDCURE BMS (manufactured by Sartomer), and Omnirad ITX (manufactured by IGM Resins).

[0057] As polymerization initiators that are not candidates for listing as substances of very high concern, those having the following structures, for example, can be preferably used.

[0058] [ka]

[0059] [ka] In formula (2), R4 is a branched alkyl group having 1 to 10 carbon atoms, and R5 is a branched alkyl group having 1 to 10 carbon atoms.

[0060] [ka] In formula (3), R6 is a branched alkyl group having 1 to 10 carbon atoms.

[0061] [ka] In formula (4), R7 is a branched alkyl group having 1 to 10 carbon atoms.

[0062] [ka] In formula (5), R8 is a branched alkyl group having 1 to 10 carbon atoms, and R9 is a branched alkyl group having 1 to 10 carbon atoms.

[0063] [ka] In formula (6), R 10 This is a branched alkyl group having 1 to 10 carbon atoms.

[0064] [ka] In formula (7), R 11 R is a branched alkyl group having 1 to 10 carbon atoms, 12 This is a branched alkyl group having 1 to 10 carbon atoms.

[0065] When the active energy ray curable ink composition according to this embodiment contains a polymerization initiator, the content of the polymerization initiator is not particularly limited, but is preferably 1.0% by mass or more, more preferably 1.5% by mass or more, and even more preferably 2.0% by mass or more, based on the total amount of the ink composition. The content of the polymerization initiator is preferably 15.0% by mass or less, more preferably 12.0% by mass or less, and even more preferably 10.0% by mass or less, based on the total amount of the ink composition. The content of the polymerization initiator is preferably 1.0% by mass or more and 15.0% by mass or less, more preferably 1.5% by mass or more and 12.0% by mass or less, and even more preferably 2.0% by mass or more and 10.0% by mass or less, based on the total amount of the ink composition.

[0066] [Polymerization inhibitor] The ink composition according to this embodiment may optionally contain a polymerization inhibitor. The polymerization inhibitor is not particularly limited, and for example, diphenylpicryl hydrazide, tri-p-nitrophenylmethyl, p-benzoquinone, p-tert-butylcatechol, picric acid, copper chloride, methyl hydroquinone, methoquinone, tert-butylhydroquinone, phenothiazines, nitrosamines, and other polymerization inhibitors can be used.

[0067] The pH of a 10% aqueous suspension of polymerization inhibitor is not particularly limited. It can be adjusted by using multiple polymerizable compounds in combination, or by combining it with colorants, dispersants, polymerizable compounds, additives, etc. It is also possible to adjust the pH by adding acidic or basic components after ink preparation. However, to make it easier to adjust the pH of the ink to 6.0 to 8.0, the pH of a 10% aqueous suspension of polymerization inhibitor (hereinafter sometimes simply referred to as the pH of the polymerization initiator) is preferably 5.0 or higher, more preferably 6.0 or higher, and even more preferably 6.2 or higher. Among these polymerization inhibitors, the pH is preferably 9.0 or lower, more preferably 8.0 or lower, and even more preferably 7.8 or lower. Among these polymerization inhibitors, the pH is preferably 5.0 to 9.0, more preferably 6.0 to 8.0, and even more preferably 6.2 to 7.8. The pH of the polymerization inhibitor can be measured by the same method as the room temperature extraction method described above.

[0068] [Colorants] The active energy ray-curable ink composition according to this embodiment may contain a colorant as needed. When the active energy ray-curable ink composition according to this embodiment contains a colorant, the colorant is not particularly limited and may be a dye-based or a pigment-based colorant, but it is preferable to use a pigment (pigment-based colorant) from the viewpoint of good resistance such as water resistance and light resistance of the recorded material. The pigments that can be used in the active energy ray-curable ink composition according to this embodiment are not particularly limited and include organic pigments or inorganic pigments used in conventional ink compositions. These may be used individually or in combination of two or more. The ink composition according to this embodiment does not have to contain a colorant. Alternatively, the pigment or dye may be incorporated into the resin and used.

[0069] In the active energy ray curable ink composition according to this embodiment, when a pigment is used, the dispersion stability of the pigment can be improved by using dispersants, dispersing aids (pigment derivatives), and surfactants described later.

[0070] Specific examples of organic pigments include, for instance, insoluble azo pigments, soluble azo pigments, derivatives from dyes, phthalocyanine organic pigments, quinacridone organic pigments, perylene organic pigments, perinone organic pigments, azomethine organic pigments, anthraquinone organic pigments (anthrone organic pigments), xanthene organic pigments, diketopyrrolopyrrole organic pigments, dioxazine organic pigments, nickel azo pigments, isoindolinone organic pigments, pyranthrone organic pigments, thioindigo organic pigments, condensed azo organic pigments, benzimidazolon organic pigments, quinophthalone organic pigments, isoindoline organic pigments, quinacridone solid solution pigments, perylene solid solution pigments and other organic solid solution pigments, as well as other pigments such as lake pigments and carbon black.

[0071] Examples of organic pigments using Color Index (CI) numbers include: CI Pigment Yellow 1, 2, 3, 12, 13, 14, 16, 17, 20, 24, 73, 74, 75, 83, 93, 95, 97, 98, 109, 110, 114, 117, 120, 125, 128, 129, 130, 137, 138, 139, 147, 148, 150, 151, 153, 154, 155, 166, 168, 180, 185, 213, 214; CI Pigment Red 5, 7, 9, 12, 48, 49, 52, 53, 57:1, 97, 112, 122, 123, 146, 149, 150, 168, 177, 180, 184 Examples include 192, 202, 206, 208, 209, 215, 216, 217, 220, 223, 224, 226, 227, 228, 238, 240, 254, 255, 269, 291, CI Pigment Orange 16, 36, 43, 51, 55, 59, 61, 64, 71, 73, CI Pigment Violet 19, 23, 29, 30, 37, 40, 50, CI Pigment Blue 15, 15:1, 15:3, 15:4, 15:6, 16, 22, 60, 64, CI Pigment Green 7, 36, 58, 59, 62, 63, CI Pigment Brown 23, 25, 26, CI Pigment Black 7, etc.

[0072] Specific examples of dyes that can be used in the active energy ray curable ink composition according to this embodiment include azo dyes, benzoquinone dyes, naphthoquinone dyes, anthraquinone dyes, cyanine dyes, squarylium dyes, croconium dyes, merocyanine dyes, stilbene dyes, diarylmethane dyes, triarylmethane dyes, fluorane dyes, spiropyran dyes, phthalocyanine dyes, indigo dyes such as indigoids, fulgide dyes, nickel complex dyes, and azulene dyes.

[0073] In the active energy ray curable ink composition according to this embodiment, specific examples of inorganic pigments that can be used include titanium dioxide, barium sulfate, calcium carbonate, zinc oxide, barium carbonate, silica, talc, clay, synthetic mica, alumina, zinc oxide, lead sulfate, lead yellow, zinc yellow, red iron(III) oxide, ultramarine, Prussian blue, chromium oxide green, cobalt green, amber, titanium black, aluminum, titanium, indium, nickel, chromium, gold, silver, copper, synthetic iron black, iron oxide, mica, fish scale foil, bismuth acid chloride, inorganic solid solution pigments, and the like. In addition to the above pigments, other materials with optical properties or functionalities other than decorative purposes, such as conductive pigments, insulating pigments, pigments that absorb specific wavelengths, and pigments that emit or reflect specific wavelengths, can also be used.

[0074] The pH of colorants (pigments) is specified in Japanese Industrial Standards JIS K5101-17- 2 It can be measured by a room-temperature extraction method in accordance with 2004. Colorants may be modified or surface-treated with acidic or basic compounds to improve wettability and dispersibility in the dispersion medium (JP 2001-011341, JP 2002-121411, JP 2005-523985, Japanese Patent Re-6892947, etc.). When colorants (pigments) are surface-treated in this way, the pH of the colorant (pigment) changes, and even if the color index name is the same, it varies depending on the manufacturer and product specifications, and the pH value shown also varies.

[0075] The pH of a 10% mass fraction aqueous suspension of colorants (pigments) is not particularly limited. It can be adjusted by using multiple colorants (pigments) in combination, or by combining them with dispersants, polymerizable compounds, polymerization initiators, additives, etc. It is also possible to adjust the pH by adding acidic or basic components after ink preparation. However, to make it easier to adjust the pH of the ink to between 6.0 and 8.0, the pH of the 10% mass fraction aqueous suspension of colorants (pigments) (hereinafter sometimes simply referred to as the pH of the colorant) is preferably 3.0 or higher, more preferably 4.0 or higher, and even more preferably 5.0 or higher. Among these colorants, the pH is preferably 9.0 or lower, more preferably 8.0 or lower, and even more preferably 7.8 or lower. Among these colorants, the pH is preferably between 3.0 and 9.0, more preferably 4.0 and 8.0, and even more preferably 5.0 and 7.8. The pH of the colorant can be measured by the same method as the room temperature extraction method described above.

[0076] In the active energy ray curable ink composition according to this embodiment, the average particle size of the pigment that can be contained is not particularly limited, as long as it enables the desired color development. Although it varies depending on the type of pigment used, from the viewpoint of good dispersibility and dispersion stability of the pigment and obtaining sufficient coloring power, the average particle size is preferably in the range of 5 nm or more, more preferably 20 nm or more, and even more preferably 30 nm or more. The lightfastness of the ink composition can be improved by having the average particle size above the above lower limit. From the viewpoint of dispersion stability in the ink composition and inkjet ejection performance, the average particle size is preferably in the range of 1000 nm or less, more preferably 800 nm or less, even more preferably 500 nm or less, and even more preferably 350 nm. The average particle size of the pigment is preferably in the range of 5 nm or more and 1000 nm or less, more preferably 20 nm or more and 800 nm or less, and even more preferably 30 nm or more and 500 nm or less.

[0077] In this embodiment, the volume-average particle diameter of the pigment is the volume-based cumulative 50% particle diameter (D50) measured under 25°C conditions using a particle size distribution analyzer (such as the NANOTRACWAVE particle size analyzer manufactured by Microtrac Bell Co., Ltd., the "FPIA-3000S" manufactured by Sysmex Corporation, or the "FPAR-1000" manufactured by Otsuka Electronics Co., Ltd.). In this specification, "volume-based cumulative 50% particle diameter (D50)" refers to the particle diameter at which the cumulative volume calculated from the smallest diameter side becomes 50%. "Volume-based cumulative 50% particle diameter (D50)" may also be referred to as "volume-average particle diameter," "average particle diameter," or "median diameter."

[0078] In the active energy ray curable ink composition according to this embodiment, the pigment content is not particularly limited as long as it is possible to form the desired image, and can be adjusted as appropriate. Specifically, although it varies depending on the type of pigment, it is preferably in the range of 0.05% by mass or more, more preferably in the range of 0.08% by mass or more, and even more preferably in the range of 0.1% by mass or more, in the range of 0.1% by mass or more, in the range of 20% by mass or less, more preferably in the range of 15% by mass or less, and even more preferably in the range of 10% by mass or less, in the range of 0.05% by mass or more and 20% by mass or less, in the range of 0.08% by mass or more and 15% by mass or less, and even more preferably in the range of 0.1% by mass or more and 10% by mass or less, in the range of 0.05% by mass or more and 20% by mass or less, in the range of 20% by mass or less, which allows for an excellent balance between the dispersion stability of the pigment and the coloring power.

[0079] Furthermore, the active energy ray-curable ink composition according to this embodiment is not particularly limited in the colors to be recorded (printed), and may be selected and combined according to the purpose. The colors can be various inks such as yellow, magenta, cyan, black, red, orange, violet, blue, and green, as well as light magenta, light cyan, light black, white, clear, and glossy inks. In this case, the same type of colorant may be selected for the ink set containing the active energy ray-curable ink composition according to this embodiment.

[0080] [Dispersant] In the active energy ray curable ink composition according to this embodiment, a dispersant may be used as needed. Any dispersant used in the ink composition can be used as the dispersant. It is preferable to use a polymer dispersant. Such dispersants have a main chain made of polyester, polyacrylic, polyurethane, polyamine, polycaprolactone, etc., and side chains that have polar groups such as amino groups, carboxyl groups, sulfone groups, and hydroxyl groups. Examples of polyacrylic dispersants include Disperbyk-2000, 2001, 2008, 2009, 2010, 2020, 2020N, ​​2022, 2025, 2050, 2070, 2095, 2150, 2151, 2155, 2163, 2164, BYKJET-9130, 9131, 9132, 9133, 9151, 9152 (manufactured by BYK), EfkaPX4310, PX4320, PX4330, PA4401, 4402, PA4403, 4570, 7411, 7477, PX4700, PX4701, PX4703 (manufactured by BASF), and TREPLUS. Products such as D-1200, D-1410, D-1420, MD-1000 (manufactured by Otsuka Chemical Co., Ltd.), Floren DOPA-15BHFS, 17HF, 22, G-700, 900, NC-500, and GW-1500 (manufactured by Kyoeisha Chemical Co., Ltd.) are used. Examples of polycaprolactone-based dispersants include Ajisper PB821, PB822, PB881 (manufactured by Ajinomoto Fine Techno Co., Ltd.), Hinoact KF-1000, T-6000, T-7000, T-8000, T-8000E, T-9050 (manufactured by Kawaken Fine Chemical Co., Ltd.), Solsperse 20000, 24000, 32000, 32500, 32550, 32600, 33000, 33500, 34000, 35200, 36000, 37500, 39000, 71000, 76400, 76500, 86000, 88000, J180, J200 (manufactured by Lubrizol), and TEGO. Dispers 652, 655, 685, 688, and 690 (manufactured by EVONIK) are used.Preferred dispersants include PB881, BYKJET-9130, 9131, 9132, 9133, 9151, 9152, EfkaPX4310, PX4320, PX4330, PX4700, PX4701, PX4703, Solsperse20000, 24000, 32000, 33000, 33500, 34000, 35200, 39000, 71000, 76500, 86000, 88000, J180, J200, TEGO Dispers655, 685, 688, 690, etc. These can be used individually or in mixtures thereof.

[0081] The pH of a 10% mass fraction aqueous suspension of a dispersant is not particularly limited. It can be adjusted by using multiple dispersants in combination, or by combining them with colorants, polymerizable compounds, polymerization initiators, additives, etc. It is also possible to adjust the pH by adding acidic or basic components after ink preparation. However, to make it easier to adjust the pH of the ink to between 6.0 and 8.0, it is preferable that the pH of the aqueous suspension containing a 10% mass fraction of a dispersant (hereinafter sometimes simply referred to as the pH of the dispersant) be 4.0 or higher, more preferably 5.0 or higher, and even more preferably 6.0 or higher. Among these dispersants, it is preferable that the pH be 12.0 or lower, more preferably 11.0 or lower, and even more preferably 10.0 or lower. Among these dispersants, it is preferable that the pH be between 4.0 and 12.0, more preferably 5.0 and 11.0, and even more preferably 6.0 and 10.0. The pH of the dispersant can be measured by the same method as the room temperature extraction method described above.

[0082] The amount of dispersant is not particularly limited, but it is preferable to adjust it according to the amount of colorant contained in the ink composition.

[0083] There are no particular limitations on the lower limit of the dispersant content. When the colorant is an organic colorant, the upper limit of the dispersant content is preferably 80 parts by mass or less, more preferably 75 parts by mass or less, even more preferably 50 parts by mass or less, and even more preferably 35 parts by mass or less, per 100 parts by mass of the colorant.

[0084] When the colorant is an inorganic colorant, the upper limit of the dispersant content is preferably 50 parts by mass or less, more preferably 30 parts by mass or less, and even more preferably 20 parts by mass or less, per 100 parts by mass of the colorant.

[0085] In the active energy ray curable ink composition according to this embodiment, it is preferable to adjust the amount of dispersant so that the amount of colorant is greater than the amount of dispersant (i.e., the amount of dispersant is less than the amount of colorant). This makes it possible to effectively disperse the colorant in the ink composition, thereby improving the storage stability and discharge stability of the ink composition.

[0086] [Dispersing agent] The active energy ray curable ink composition according to this embodiment may optionally contain a dispersion aid. The dispersion aid is adsorbed onto the surface of the colorant (pigment), and its functional groups enhance its affinity for polymerizable compounds and dispersants in the ink composition, thereby improving dispersion stability. As the dispersion aid, known pigment derivatives having functional groups such as acidic groups, basic groups, and neutral groups in the organic pigment residues can be used.

[0087] The pH of a 10% mass fraction aqueous suspension of a dispersing agent is not particularly limited. It can be adjusted by combinations with colorants, dispersants, polymerizable compounds, polymerization initiators, additives, etc., and it is also possible to adjust the pH by adding acidic or basic components after ink preparation. However, to make it easier to adjust the pH of the ink to between 6.0 and 8.0, it is preferable that the pH of the aqueous suspension containing a 10% mass fraction of a dispersing agent (hereinafter sometimes simply referred to as the pH of the dispersing agent) be 4.0 or higher, more preferably 5.0 or higher, and even more preferably 5.5 or higher. Among these dispersing agents, it is preferable that the pH be 11.0 or lower, more preferably 10.0 or lower, and even more preferably 9.5 or lower. Among these dispersing agents, it is preferable that the pH be between 4.0 and 8.0, more preferably 5.0 and 7.7, and even more preferably 5.5 and 9.5. The pH of the dispersing agent can be measured by the same method as the room temperature extraction method described above.

[0088] [Surfactants] The ink composition according to this embodiment may optionally contain a surfactant. While not particularly limited to surfactants, specific examples include BYK's "BYK-306", "BYK-307", "BYK-331", "BYK-333", "BYK-354", "BYK-361N", "BYK-371", "BYK-377", "BYK-378", "BYK-399", "BYK-3455", "BYK-UV3500", "BYK-UV3505", "BYK-UV3510", "BYK-UV3535", "BYK-UV3570", "BYK-UV3575", and "BYK-UV3576" containing dimethylpolysiloxane; and EVONIK's "TEGO Flow425", "TEGO Glide100", "TEGO Glide110", "TEGO Glide130", "TEGO Glide432", "TEGO Glide435", "TEGO Glide440", "TEGO Glide450", and "TEGO Examples include "GlideZG400", "TEGO Twin4000", "TEGO Twin4200", "TEGO Wet270", "TEGO Rad2010", "TEGO Rad2100", "TEGO Rad2200N", "TEGO Rad2250", "TEGO Rad2300", "TEGO Rad2500", and "TEGO Rad2700"; Kyoeisha Chemical's "Polyflow KL-401", "Polyflow KL-402", "Polyflow KL-403", and "Polyflow KL-404"; and among acrylic polymer-based products, Kyoeisha Chemical's "Polyflow No.75", "Polyflow No.77", "Polyflow No.90", "Polyflow No.95", and "Polyflow No.99C"; and EVONIK's "TEGO Wet500", etc.

[0089] The pH of a 10% mass fraction aqueous suspension of surfactant is not particularly limited. It can be adjusted by combination with colorants, dispersants, polymerizable compounds, polymerization initiators, additives, etc., and it is also possible to adjust the pH by adding acidic or basic components after ink preparation. However, in order to maintain the dispersion state of the pigment and ensure good stability of the ink composition, among these surfactants, the pH of the aqueous suspension containing 10% mass fraction of surfactant (hereinafter sometimes simply referred to as the pH of the surfactant) is preferably 4.0 or higher, more preferably 4.5 or higher, and even more preferably 5.0 or higher. Among these surfactants, the pH is preferably 12.0 or lower, more preferably 11.5 or lower, and even more preferably 11.0 or lower. Among these surfactants, the pH is preferably 4.0 or higher and 12.0 or lower, more preferably 4.5 or higher and 11.5 or lower, and even more preferably 5.0 or higher and 11.0 or lower. The pH of the surfactant can be measured by the same method as the room temperature extraction method described above.

[0090] The surfactant content is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, and even more preferably 0.3% by mass or more, based on the total amount of the ink composition. Furthermore, the surfactant content is preferably 5.0% by mass or less, more preferably 4.5% by mass or less, and even more preferably 4.0% by mass or less, based on the total amount of the ink composition. By setting the surfactant content to 0.1% by mass or more, or 5.0% by mass or less, the ink composition will have favorable wettability with respect to thermoplastic resin substrates, etc., and when recording (forming an image) on the substrate, the active energy ray curable ink composition will be able to wet and spread without causing repulsion, making it a particularly preferable ink composition. The surfactant content is preferably 0.1% by mass or more and 5.0% by mass or less, more preferably 0.2% by mass or more and 4.5% by mass or less, and even more preferably 0.3% by mass or more and 4.0% by mass or less, based on the total amount of the ink composition.

[0091] [Binder resin] The active energy ray curable ink composition according to this embodiment may optionally contain a binder resin. Here, "binder resin" refers to a non-polymerizable resin distinct from monomers, oligomers, and additives. The binder resin is not particularly limited, but examples include acrylic resins, polystyrene resins, polyester resins, polyethylene terephthalate resins, vinyl chloride resins, vinyl acetate resins, vinyl chloride vinyl acetate copolymer resins, polyethylene resins, polyurethane resins, rosin-modified resins, phenolic resins, xylene resins, terpene resins, polyamide resins, vinyltoluene-α-methylstyrene copolymers, ethylene-vinyl acetate copolymers, cellulose resins, silicone resins, acrylamide resins, epoxy resins, diallyl phthalate resins, allyl resins, or copolymers or mixtures thereof. Among these, a mixture containing one or more of vinyl chloride-vinyl acetate copolymer resins, polyethylene terephthalate resins, diallyl phthalate resins, acrylic resins, allyl resins, and cellulose resins is preferred. The molecular weight of the binder resin is preferably 10,000 or more, and more preferably 15,000 or more. The molecular weight of the binder resin is preferably 500,000 or less, and more preferably 300,000 or less. Having a molecular weight within this range allows for good storage stability, discharge properties, and coating film properties of the ink composition.

[0092] The pH of a 10% mass fraction aqueous suspension of binder resin is not particularly limited. It can be adjusted by combining it with colorants, dispersants, polymerizable compounds, polymerization initiators, additives, etc., and it is also possible to adjust the pH by adding acidic or basic components after ink preparation. However, in order to maintain the dispersion state of the pigment and ensure good stability of the ink composition, among these binder resins, the pH of an aqueous suspension containing 10% mass fraction binder resin (hereinafter sometimes simply referred to as the pH of the binder resin) is preferably 5.0 or higher, more preferably 5.5 or higher, and even more preferably 6.0 or higher. Among these binder resins, the pH is preferably 9.0 or lower, more preferably 8.5 or lower, and even more preferably 8.0 or lower. Among these binder resins, the pH is preferably 5.0 to 9.0, more preferably 5.5 to 8.5, and even more preferably 6.0 to 8.0. The pH of the binder resin can be measured by the same method as the room temperature extraction method described above.

[0093] When the active energy ray curable ink composition according to this embodiment contains a binder resin, the binder resin content is not particularly limited, but is preferably 0.05% by mass or more of the total ink composition, more preferably 0.08% by mass or more, even more preferably 0.1% by mass or more, and still more preferably 0.3% by mass or more. The binder resin content is preferably 20.0% by mass or less of the total ink composition, more preferably 15.0% by mass or less, even more preferably 10.0% by mass or less, and still more preferably 5.0% by mass or less. The binder resin content is preferably 0.05% by mass or more and 20.0% by mass or less of the total ink composition, more preferably 0.08% by mass or more and 15.0% by mass or less, and still more preferably 0.1% by mass or more and 10.0% by mass or less.

[0094] [Other additives] The ink composition according to this embodiment may also contain various additives such as acidic compounds, basic compounds, organic solvents, plasticizers, light stabilizers, waxes, ultraviolet absorbers, antioxidants, orientation agents, antibacterial agents, and antiviral agents.

[0095] Furthermore, the ink composition according to this embodiment may contain a volatile organic solvent, but if the polymerizable compound contained is liquid at room temperature, the polymerizable compound acts as a solvent (dispersion medium) that dissolves or disperses each component, so it is not necessary to contain a volatile organic solvent. If the polymerizable compound contained is liquid at room temperature, the content of the volatile organic solvent is preferably 20.0% by mass or less, more preferably 10.0% by mass or less, even more preferably 5.0% by mass or less, and still more preferably 1.0% by mass or less of the total amount of the ink composition. By containing a polymerizable compound that is liquid at room temperature and having a volatile organic solvent content of 20.0% by mass or less of the total amount of the ink composition, it is possible to suppress the precipitation of components due to the evaporation of the ink composition in the inkjet nozzle and the increase in viscosity, thereby further improving the inkjet ejection performance.

[0096] Furthermore, the ink composition according to this embodiment may contain a pH adjusting agent to adjust the pH of a 10% mass fraction aqueous suspension to 6.0 or higher and 8.0 or lower. Specifically, it may include compounds containing acidic functional groups such as carboxylic acids, sulfonic acids, nitric acid, and phosphoric acid as acidic compounds, and compounds containing basic functional groups such as amino groups and amide groups as basic compounds. In addition, it may contain various acids and their salts, hydroxides and other salts, ammonia, amino alcohols, amines, etc.

[0097] (Viscosity and surface tension of the ink composition) The viscosity of the ink composition according to this embodiment is preferably 30 mPa·s or less, more preferably 25 mPa·s or less, and even more preferably 22 mPa·s or less at the ejection temperature (e.g., 40°C) from the viewpoint of inkjet ejection performance and ejection stability. Furthermore, the viscosity of the ink composition according to this embodiment is preferably 3 mPa·s or more, more preferably 5 mPa·s or more, and even more preferably 8 mPa·s or more at the ejection temperature (e.g., 40°C), but it is preferable to adjust it appropriately according to the inkjet head used. Viscosity can be measured with a vibrating viscometer, rheometer, falling ball viscometer, etc.

[0098] Furthermore, the surface tension of the ink composition according to this embodiment is preferably 20 mN / m or more, more preferably 23 mN / m or more, and even more preferably 25 mN / m or more at 25°C, from the viewpoint of inkjet ejection performance, ejection stability, and leveling performance to the substrate. Furthermore, the surface tension of the ink composition according to this embodiment is preferably 40 mN / m or less, more preferably 37 mN / m or less, and even more preferably 35 mN / m or less.

[0099] The method for producing the active energy ray curable ink composition of one embodiment of the present invention is not particularly limited, and conventionally known methods can be used. For example, a polymerizable compound, a colorant, and a dispersant as needed are mixed and dispersed using a disperser, and then a polymerization initiator, a polymerization inhibitor as needed, a leveling agent, etc. are added and the mixture is uniformly stirred to obtain a mixture, and then the mixture is filtered to obtain the ink composition.

[0100] ≪2. Pigment Dispersion≫ The pigment dispersion according to this embodiment is a pigment dispersion used in an active energy ray curable ink composition ejected by the inkjet method described above. Specifically, the pigment dispersion according to this embodiment is a pigment dispersion used in the manufacture of an ink composition, and can be used to manufacture an ink composition by incorporating other components contained in the ink composition (e.g., polymerization initiators) such as polymerization initiators.

[0101] Furthermore, the pigment dispersion according to this embodiment contains a pigment, a polymerizable compound, and a pigment dispersant, and is characterized in that the pH of the aqueous suspension, as measured by the following test method, is 6.0 or higher and 8.0 or lower.

[0102] Test method: A pigment dispersion is prepared by mixing the pigment dispersion with water so that the pigment dispersion content is 10% by mass fraction, and the pH of the aqueous suspension is measured.

[0103] By controlling the composition and content of the pigment dispersion so that the pH of the resulting aqueous suspension falls within a specific range, a pigment dispersion with excellent storage stability can be obtained. For convenience, in this specification, the pH of a 10% mass fraction aqueous suspension obtained from the pigment dispersion may simply be referred to as "pH of the pigment dispersion."

[0104] The pH of the pigment dispersion should be between 6.0 and 8.0, but preferably 6.3 or higher, and more preferably 6.5 or higher. The pH of the pigment dispersion should preferably be 7.7 or lower, and more preferably 7.5 or lower. The pH of the pigment dispersion should preferably be between 6.3 and 7.7, and more preferably 6.5 or higher, and more preferably 7.5.

[0105] The pH of the pigment dispersion is specified in Japanese Industrial Standard JIS K5101-17- 2 The pH is measured by a room-temperature extraction method similar to the pH measurement method for pigments in accordance with :2004. Specifically, it can be measured in the same way as the pH of the ink composition described above.

[0106] The method for controlling the components and their amounts so that the pH of the pigment dispersion falls within a specific range can be controlled in the same way as the method for controlling the components and their amounts so that the pH of the ink composition falls within a specific range as described above.

[0107] Furthermore, by using a pigment dispersion with a controlled pH of 6.0 to 8.0 and incorporating other components of the ink composition, such as polymerization initiators, to produce an active energy ray-curable ink composition, it becomes easier to manufacture an active energy ray-curable ink composition with a controlled pH of 6.0 to 8.0.

[0108] Furthermore, the pigment, polymerizable compound, and pigment dispersant contained in the pigment dispersion according to this embodiment can be the same as those contained in the active energy ray curable ink composition ejected by the inkjet method described above.

[0109] ≪3. Ink Set≫ The above-described active energy ray-curable ink composition may be a colored ink, a clear ink without colorants, a primer ink, or an overcoat ink. The ink set according to this embodiment may be an ink set that combines these ink compositions.

[0110] In this embodiment, the ink set is sufficient if the pH of at least one ink composition contained in the ink set is 6.0 or higher and 8.0 or lower.

[0111] Furthermore, the ink set may be a combination of colored ink compositions containing colorants, for example, a combination of multiple ink compositions selected from yellow, magenta, cyan, black, red, orange, violet, blue, green, intermediate or light colors thereof, a white ink composition containing a white colorant, or a metallic ink containing a glossy colorant.

[0112] ≪4. Recording Method≫ The recording method according to this embodiment is a recording method in which an ink composition having a pH of 6.0 or more and 8.0 or less is applied to a substrate by an inkjet method.

[0113] Furthermore, the recording method according to this embodiment may include an ejection step of inkjet ejecting the above-mentioned ink composition onto the surface of a surface-treated resin substrate.

[0114] The process may also include an irradiation step in which the ink composition applied to the surface of the substrate is irradiated with active energy rays. This irradiation causes a cured product of the ink composition to form on the surface of the substrate. Active energy rays can include electromagnetic waves such as far ultraviolet rays, ultraviolet rays, near ultraviolet rays, visible light, infrared rays, X-rays, and gamma rays, as well as electron beams, proton beams, and neutron beams. Among these, active energy rays with a peak wavelength of 365 nm to 395 nm are preferred.

[0115] The light source for irradiating with active energy rays is not particularly limited and includes, for example, high-pressure mercury lamps, metal halide lamps, low-pressure mercury lamps, ultra-high-pressure mercury lamps, ultraviolet lasers, sunlight, and LED lamps. From the standpoint of energy saving and greater design flexibility for printing equipment, it is more preferable to use LED lamps as the light source.

[0116] To obtain a surface-treated resin substrate, the process may include a pretreatment step in which the surface of the substrate is subjected to a surface treatment beforehand.

[0117] Examples of surface treatment methods include corona treatment, flame treatment, plasma treatment, ultraviolet irradiation treatment, and silane coupling treatment. Two or more surface treatments may be combined.

[0118] The substrate to be pretreated may be either a non-absorbent substrate or an absorbent substrate, as described later.

[0119] Furthermore, the inkjet ejection method for the ink composition of the present invention may be any method, such as a piezo method or an electrostatic method. The inkjet method may be a serial head method or a line head method, and is not particularly limited.

[0120] Alternatively, the material may be applied to the substrate by means other than inkjet, such as spraying or using a dispenser.

[0121] ≪5. Method of Manufacturing Printed Materials≫ The recording method described above can also be defined as a method for manufacturing printed materials by applying the above-described ink composition onto a substrate using an inkjet method. Alternatively, printed materials can also be manufactured by applying the ink onto the substrate using methods other than inkjet, such as spraying or using a dispenser.

[0122] ≪6.Printed materials≫ The printed material according to this embodiment is a printed material on which the ink composition according to the above embodiment is printed on the surface of a substrate. Specifically, the printed material obtained using the ink composition according to the above embodiment comprises a substrate (recording medium) and a cured film of the ink composition laminated on the surface of the substrate (recording medium). The cured film contains a cured product of a polymerizable compound contained in the ink composition according to the above embodiment.

[0123] [Substrate (recording medium)] The substrate (recording medium) included in the recording material according to this embodiment is not particularly limited and may be a non-absorbent substrate such as a resin substrate, a metal plate, or glass, an absorbent substrate such as paper or cloth, or a substrate with a surface coating such as a substrate with a receiving layer, and various substrates can be used.

[0124] Examples of non-absorbent substrates include resin substrates such as polyester resins, polyethylene terephthalate resins, polyethylene naphthalate resins, polypropylene synthetic paper, polyolefin resins (polypropylene resins, polyethylene resins, etc.), acrylic resins, polystyrene resins, polycarbonate resins, ABS resins, vinyl chloride resins, and polyimide resins, as well as metals, metal foil coated paper, glass, synthetic rubber, and natural rubber. Among these, it is preferable that the resin substrate contains at least one selected from the group consisting of polypropylene resins, polycarbonate resins, polystyrene resins, polyethylene resins, ABS resins, vinyl chloride resins, polyethylene terephthalate resins, and acrylic resins.

[0125] In particular, ink compositions containing polymerizable compounds with a pH of 6.0 to 8.0 can form cured films that have high adhesion to polyvinyl chloride resins and acrylic resin substrates, so it is especially preferable that the substrate (recording medium) is a polyethylene terephthalate resin, polyvinyl chloride resin, or acrylic resin substrate.

[0126] Absorbent base materials include newsprint, medium-quality paper, fine-quality paper, synthetic paper, cotton, synthetic fiber fabrics, silk, hemp, woven fabrics, nonwoven fabrics, leather, and the like.

[0127] Examples of substrates with surface coatings include coated paper, art paper, cast paper, lightweight coated paper, and lightly coated paper.

[0128] [Cured film of ink composition] The cured film of an ink composition is formed by the polymerization of polymerizable compounds contained in the ink composition. For example, if the ink composition contains a colorant, it becomes a decorative layer or its underlayer that forms a desired image. In this specification, the shape of the "cured film" is not limited to, for example, a flat or layered shape, but may have irregularities, may have pores in some parts, or may have a cured film formed on a part of the surface. Furthermore, for convenience, a cured film of an ink composition that is absorbed by an absorbent substrate and is substantially like a part of the substrate will also be referred to as the cured film of an ink composition.

[0129] When the ink composition is used as an overcoat ink, it forms an overcoat layer on the surface of the recording material. In this case, the ink composition that forms the recording layer on the recording material may be the ink composition of the present invention or an ink composition different from the present invention.

[0130] The thickness of the cured product of the ink composition (e.g., the recording layer or overcoat layer) is not particularly limited, but is preferably 1 μm or more, more preferably 3 μm or more, and even more preferably 5 μm or more. The thickness of the cured product of the ink composition (e.g., the recording layer or overcoat layer) is preferably 1000 μm or less, more preferably 500 μm or less, and even more preferably 100 μm or less. The thickness of the cured product of the ink composition is preferably 1 μm or more and 1000 μm or less, more preferably 3 μm or more and 500 μm or less, and even more preferably 5 μm or more and 100 μm or less. Desired functions can be imparted to the cured product of the ink composition. Note that the thickness of the cured product is the average value of the thickness measured at multiple arbitrary locations on the surface of the cured product.

[0131] ≪7. Inkjet Recording Devices≫ The inkjet recording device according to this embodiment is an inkjet recording device equipped with a storage mechanism filled with the above-mentioned ink composition having a pH of 6.0 or more and 8.0 or less.

[0132] The inkjet recording apparatus according to this embodiment may be a multi-pass (or serial head) inkjet recording apparatus in which the inkjet head moves back and forth to eject the ink composition, or it may be a single-pass (or line head) inkjet recording apparatus in which the inkjet head does not move to eject the ink composition onto the recording medium (substrate).

[0133] The storage mechanism mounted in the inkjet recording device according to this embodiment is not particularly limited, and examples include containers such as ink bottles, pouches, bag-in-boxes, and drums. Furthermore, these containers may be further housed in cartridges or the like. The material of the storage container is not particularly limited, and may be made of conventionally known resin, or a material that includes some metal material (for example, an aluminum pouch with an aluminum vapor deposition layer).

[0134] Furthermore, the discharge method at each discharge unit may be any of the following: piezoelectric, thermal, electrostatic, etc.

[0135] The inkjet recording apparatus according to this embodiment may be equipped with a light source that emits active energy rays. The light source that emits active energy rays is not particularly limited and examples include high-pressure mercury lamps, metal halide lamps, low-pressure mercury lamps, ultra-high-pressure mercury lamps, ultraviolet lasers, sunlight, LED lamps, etc. From the viewpoint of energy saving and high degree of freedom in the design of the printing apparatus, it is more preferable to use an LED lamp as the light source. [Examples]

[0136] The present invention will be described in more detail below with reference to examples, but the present invention is not limited in any way to these descriptions.

[0137] 1-1. Production of Pigment Dispersion Pigment dispersions for experimental and comparative examples were prepared. Specifically, the pigment dispersions for the examples and comparative examples were prepared with the colorant (pigment mill base), dispersant, polymerizable compound, additive, and polymerization inhibitor in the proportions shown in the table below. The units in the table are mass percent. Note that each component was previously specified in accordance with Japanese Industrial Standard JIS K5101-17- 2 The pH of a 10% aqueous suspension was measured using a room-temperature extraction method similar to the pH measurement method for pigments in accordance with 2004.

[0138] 1-2. Evaluation of Pigment Dispersions (Storage stability) The storage stability of the pigment dispersions of the examples and comparative examples was evaluated. Specifically, the pigment dispersions of the examples and comparative examples were sealed in light-shielding glass bottles and stored at 60°C for 7 days. After storage, the pigment dispersions were visually inspected for the formation of precipitates and aggregates. Furthermore, the viscosity of the pigment dispersions was measured before and after storage, and the viscosity change rate was evaluated. [Evaluation Criteria] A: No precipitates or aggregates were formed, and the viscosity change rate was less than 10%. B: No precipitates or aggregates were formed, and the viscosity change rate was between 10% and 20%. C: Precipitates or aggregates were observed, or the viscosity change rate was 20% or more. A and B are within the usable range.

[0139] [Table 1]

[0140] [Table 2]

[0141] In Tables 1 and 2, "P-1" refers to Mitsubishi Chemical's CARBON BLACK MA-8, which is a carbon black (pigment). The pH of a 10% mass fraction aqueous suspension was 3.2.

[0142] In Tables 1 and 2, "P-2" refers to HP RED 2574 manufactured by Shanghai Honor Industrial Co Ltd, which is CI Pigment Red 122 (pigment). The pH of the 10% mass fraction aqueous suspension was 6.8.

[0143] In Tables 1 and 2, "P-3" refers to DIC's FASTOGEN® SUPER MAGENTA JM04, which is CI Pigment Red 122 / 19 (pigment). The pH of the 10% mass fraction aqueous suspension was 7.6.

[0144] In Tables 1 and 2, "P-4" refers to LIONOL® BLUE FG-7400-G manufactured by Toyo Color, which is a CI pigment blue 15:4 (pigment). The pH of the 10% mass fraction aqueous suspension was 7.4.

[0145] In Tables 1 and 2, "P-5" refers to DIC FASTOGEN® BLUE 5452-SK, which is a CI pigment blue 15:4 (pigment). The pH of the 10% mass fraction aqueous suspension was 4.6.

[0146] In Tables 1 and 2, "D-1" refers to BYKJET® 9151 manufactured by BYK. The pH of the 10% mass fraction aqueous suspension was 7.0.

[0147] In Tables 1 and 2, "D-2" refers to EVONIK's TEGO® Disprse 685. The pH of the 10% mass fraction aqueous suspension was 8.0.

[0148] In Tables 1 and 2, "D-3" refers to Solsperse® 20000 manufactured by Lubrizol. The pH of the 10% mass fraction aqueous suspension was 11.2.

[0149] In Tables 1 and 2, "PHEA" refers to phenoxyethyl acrylate (a polymerizable compound). The pH of a 10% aqueous suspension was 7.0.

[0150] In Tables 1 and 2, "HXDA" refers to 1,6-hexanediol diacrylate (a polymerizable compound). The pH of the 10% aqueous suspension was 5.0.

[0151] In Tables 1 and 2, "TPGDA" refers to tripropylene glycol diacrylate (a polymerizable compound). The pH of a 10% aqueous suspension was 7.0.

[0152] In Tables 1 and 2, "IBXA" refers to isobornyl acrylate (a polymerizable compound). The pH of a 10% aqueous suspension was 7.0.

[0153] In Tables 1 and 2, "MPDA" refers to 3-methyl-1,5-pentanediol diacrylate (a polymerizable compound). The pH of the 10% mass fraction aqueous suspension was 6.0.

[0154] In Tables 1 and 2, "DPGDA" refers to dipropylene glycol diacrylate (a polymerizable compound). The pH of a 10% aqueous suspension was 5.0.

[0155] In Tables 1 and 2, "A-3" refers to phenylphosphonic acid (an acidic pH adjuster). The pH of a 10% aqueous suspension was 1.6.

[0156] In Tables 1 and 2, "A-2" refers to triethanolamine (a basic pH adjuster). The pH of the 10% aqueous suspension was 10.6.

[0157] In Tables 1 and 2, "S-1" refers to phenothiazine (polymerization inhibitor). The pH of the 10% mass fraction aqueous suspension was 6.2.

[0158] 2-1. Manufacturing of Ink Composition (Clear Ink Composition) Ink compositions (clear ink compositions) for experimental and comparative examples were prepared. Specifically, polymerizable compounds, polymerization initiators, and additives were added to prepare pigment dispersions for the examples and comparative examples in the proportions shown in the table below. The units in the table are mass%. The ink compositions for the examples and comparative examples were prepared by adding these components. Note that each component was previously specified in accordance with Japanese Industrial Standard JIS K5101-17- 2 The pH of a 10% aqueous suspension was measured using a room-temperature extraction method similar to the pH measurement method for pigments in accordance with 2004.

[0159] 2-2. Evaluation of Ink Compositions (Storage stability) The storage stability of the ink compositions of the examples and comparative examples was evaluated. Specifically, the ink compositions of the examples and comparative examples were sealed in light-shielding glass bottles and stored at a temperature of 60°C for 7 days. After storage, the formation of precipitates and aggregates in the ink compositions was visually inspected. Furthermore, the viscosity of the ink compositions before and after storage was measured, and the viscosity change rate was evaluated. [Evaluation Criteria] A: No precipitates or aggregates were formed, and the viscosity change rate was less than 10%. B: No precipitates or aggregates were formed, and the viscosity change rate was between 10% and 20%. C: Precipitates or aggregates were observed, or the viscosity change rate was 20% or more. A and B are within the usable range.

[0160] (Dischargeability) The ejection performance (inkjet ejection performance) of the ink compositions of the examples and comparative examples was evaluated. Specifically, the ink compositions of the examples and comparative examples were inkjet ejected from an inkjet head for 10 minutes using an ImageXpert droplet observation device, and the incidence of non-ejection, bending, and scattering of ink from the inkjet head was evaluated. [Evaluation Criteria] A: The rate of dispensing failures is less than 3%. B: Dispensing failure rate is between 3% and 10%. C: Dispensing failure rate is 10% or higher. A and B are within the usable range.

[0161] (curable) The curability of the ink compositions of the examples and comparative examples was evaluated. Specifically, the ink compositions of the examples and comparative examples were ejected onto the surface of PET film (Toyobo Co., Ltd. Cosmo Shine A4300) using an inkjet recording device, Fujifilm Corporation's "Material Printer DMP-2850," and evaluated with a 385nm wavelength LED lamp at a peak illuminance of 250mW / cm². 2 , cumulative light intensity 650 mJ / cm 2 The PET film was irradiated with active energy rays to form a cured product of the ink composition on its surface, and the curability of the cured product was evaluated according to the following evaluation criteria. [Evaluation Criteria] A: Even when I rubbed it with a cotton swab, no ink came off. B: Although it was slightly sticky, no ink came off when I rubbed it with a cotton swab. C: When rubbed with a cotton swab, ink came off. A and B are within the usable range.

[0162] [Table 3]

[0163] In Table 3, "VEEA" refers to 2-(vinyloxyethoxy)ethyl acrylate. The pH of the 10% aqueous suspension was 5.0.

[0164] In Table 3, "IBXA" refers to isobornyl acrylate (a polymerizable compound). The pH of the 10% mass fraction aqueous suspension was 7.0.

[0165] In Table 3, "DEAA" refers to diethylacrylamide. The pH of the 10% mass fraction aqueous suspension was 6.0.

[0166] In Table 3, "HXDA" refers to 1,6-hexanediol diacrylate (a polymerizable compound). The pH of the 10% aqueous suspension was 5.0.

[0167] In Table 3, "TPGDA" refers to tripropylene glycol diacrylate (a polymerizable compound). The pH of a 10% aqueous suspension was 7.0.

[0168] In Table 3, "DPHA" refers to dipentaerythritol hexaacrylate (a polymerizable compound). The pH of the 10% mass fraction aqueous suspension was 7.0.

[0169] In Table 3, "PETA" refers to pentaerythritol triacrylate (a polymerizable compound). The pH of the 10% mass fraction aqueous suspension was 7.0.

[0170] In Table 3, "MPDA" refers to 3-methyl-1,5-pentanediol diacrylate (a polymerizable compound). The pH of the 10% mass fraction aqueous suspension was 6.0.

[0171] In Table 3, "DPGDA" refers to dipropylene glycol diacrylate (a polymerizable compound). The pH of the 10% aqueous suspension was 5.0.

[0172] In Table 3, "O-1" refers to oligomer: aliphatic urethane acrylate CN996 manufactured by Sartomer. The pH of the 10% mass fraction aqueous suspension was 5.0.

[0173] In Table 3, "TPO-L" refers to SpeedCure® TPO-L (polymerization initiator represented by formula (3)) manufactured by Sartomer. The pH of the 10% mass fraction aqueous suspension was 3.7.

[0174] In Table 3, "819" refers to Omnirad® 819 (a polymerization initiator represented by formula (1)) manufactured by IGM Resins BV. The pH of the 10% mass fraction aqueous suspension was 7.3.

[0175] In Table 3, "DETX" refers to SpeedCure® DETX (a polymerization initiator represented by formula (7)) manufactured by Sartomer. The pH of the 10% mass fraction aqueous suspension was 8.0.

[0176] In Table 3, "TMO" refers to PhiCure® TMO (polymerization initiator represented by formula (2)) manufactured by Diloid Materials. The pH of the 10% mass fraction aqueous suspension was 7.8.

[0177] In Table 3, "A-1" refers to a silicon-based nonionic additive, a polyether-modified polysiloxane with a weight-average molecular weight of 1000. The pH of the 10% aqueous suspension was 7.0.

[0178] In Table 3, "A-2" refers to triethanolamine (a basic pH adjuster). The pH of the 10% aqueous suspension was 10.6.

[0179] In Table 3, "A-3" refers to phenylphosphonic acid (an acidic pH adjuster). The pH of the 10% aqueous suspension was 1.6.

[0180] 3-1. Manufacturing of ink compositions (colored ink compositions) Ink compositions (colored ink compositions) for experimental and comparative examples were prepared. Specifically, 20 parts by mass of the pigment dispersion shown in Table 1 above, a polymerizable compound, a polymerization initiator, and additives were mixed in the proportions shown in the table below to prepare the ink compositions for the examples and comparative examples. Note that each component was previously specified in accordance with Japanese Industrial Standard JIS K5101-17- 2 The pH of a 10% aqueous suspension was measured using a room-temperature extraction method similar to the pH measurement method for pigments in accordance with 2004.

[0181] 3-2. Evaluation of Ink Composition (Storage stability) The storage stability of the ink compositions of the examples and comparative examples was evaluated. Specifically, the ink compositions of the examples and comparative examples were sealed in light-shielding glass bottles and stored at a temperature of 60°C for 7 days. After storage, the formation of precipitates and aggregates in the ink compositions was visually inspected. Furthermore, the viscosity of the ink compositions before and after storage was measured, and the viscosity change rate was evaluated. [Evaluation Criteria] A: No precipitates or aggregates were formed, and the viscosity change rate was less than 5%. B: No precipitates or aggregates were formed, and the viscosity change rate was between 5% and 10%. C: Precipitates or aggregates were observed, or the viscosity change rate was 10% or more. A and B are within the usable range.

[0182] (Dischargeability) The ejection performance (inkjet ejection performance) of the ink compositions of the examples and comparative examples was evaluated. Specifically, the ink compositions of the examples and comparative examples were inkjet ejected from an inkjet head for 10 minutes using an ImageXpert droplet observation device, and the rate of ejection defects such as non-ejection, bending, and scattering from the inkjet head was evaluated. [Evaluation Criteria] A: The rate of dispensing failures is less than 3%. B: Dispensing failure rate is between 3% and 10%. C: Dispensing failure rate is 10% or higher. A and B are within the usable range.

[0183] (curable) The curability of the ink compositions of the examples and comparative examples was evaluated. Specifically, the ink compositions of the examples and comparative examples were ejected onto the surface of PET film (Toyobo Co., Ltd. Cosmo Shine A4300) using an inkjet recording device, Fujifilm Corporation's "Material Printer DMP-2850," and evaluated with a 385nm wavelength LED lamp at a peak illuminance of 250mW / cm². 2 , cumulative light intensity 650 mJ / cm 2The PET film was irradiated with active energy rays to form a cured product of the ink composition on its surface, and the curability of the cured product was evaluated according to the following evaluation criteria. [Evaluation Criteria] A: Even when I rubbed it with a cotton swab, no ink came off. B: Although it was slightly sticky, no ink came off when I rubbed it with a cotton swab. C: When rubbed with a cotton swab, ink came off. A and B are within the usable range.

[0184] [Table 4]

[0185] [Table 5]

[0186] In Tables 4 and 5, "VEEA" refers to 2-(vinyloxyethoxy)ethyl acrylate. The pH of the 10% aqueous suspension was 5.0.

[0187] In Tables 4 and 5, "IBXA" refers to isobornyl acrylate (a polymerizable compound). The pH of a 10% aqueous suspension was 7.0.

[0188] In Tables 4 and 5, "DEAA" refers to diethylacrylamide. The pH of the 10% mass fraction aqueous suspension was 6.0.

[0189] In Tables 4 and 5, "HXDA" refers to 1,6-hexanediol diacrylate (a polymerizable compound). The pH of the 10% mass fraction aqueous suspension was 5.0.

[0190] In Tables 4 and 5, "4HBA" refers to 4-hydroxybutyl acrylate. The pH of the 10% aqueous suspension was 5.0.

[0191] In Tables 4 and 5, "TPGDA" refers to tripropylene glycol diacrylate (a polymerizable compound). The pH of a 10% aqueous suspension was 7.0.

[0192] In Tables 4 and 5, "DPHA" refers to dipentaerythritol hexaacrylate (a polymerizable compound). The pH of the 10% mass fraction aqueous suspension was 7.0.

[0193] In Tables 4 and 5, "PETA" refers to pentaerythritol triacrylate (a polymerizable compound). The pH of the 10% mass fraction aqueous suspension was 7.0.

[0194] In Tables 4 and 5, "MPDA" refers to 3-methyl-1,5-pentanediol diacrylate (a polymerizable compound). The pH of a 10% aqueous suspension was 6.0.

[0195] In Tables 4 and 5, "DPGDA" refers to dipropylene glycol diacrylate (a polymerizable compound). The pH of a 10% aqueous suspension was 5.0.

[0196] In Tables 4 and 5, "O-1" refers to oligomer: aliphatic urethane acrylate CN996 manufactured by Sartomer. The pH of the 10% mass fraction aqueous suspension was 5.0.

[0197] In Tables 4 and 5, "TPO-L" refers to SpeedCure® TPO-L (a polymerization initiator represented by formula (3)) manufactured by Sartomer. The pH of the 10% mass fraction aqueous suspension was 3.7.

[0198] In Tables 4 and 5, "819" refers to Omnirad® 819 (a polymerization initiator represented by formula (1)) manufactured by IGM Resins BV. The pH of the 10% mass fraction aqueous suspension was 7.3.

[0199] In Tables 4 and 5, "DETX" refers to SpeedCure® DETX (a polymerization initiator represented by formula (7)) manufactured by Sartomer. The pH of the 10% mass fraction aqueous suspension was 8.0.

[0200] In Tables 4 and 5, "TMO" refers to PhiCure® TMO (polymerization initiator represented by formula (2)) manufactured by Diloid Materials. The pH of the 10% mass fraction aqueous suspension was 7.8.

[0201] In Tables 4 and 5, "NPI" refers to TRONLY's NPI-20400 (registered trademark) (a polymerization initiator represented by formula (5)). The pH of the 10% mass fraction aqueous suspension was 7.2.

[0202] In Tables 4 and 5, "BMS" refers to Lunacure® BMS (a polymerization initiator represented by formula (6)) manufactured by DKSH. The pH of the 10% mass fraction aqueous suspension was 8.0.

[0203] In Tables 4 and 5, "A-1" refers to a silicon-based nonionic additive, a polyether-modified polysiloxane with a weight-average molecular weight of 1000. The pH of a 10% aqueous suspension was 7.0.

[0204] In Tables 4 and 5, "A-2" refers to triethanolamine (a basic pH adjuster). The pH of the 10% aqueous suspension was 10.6.

[0205] In Tables 4 and 5, "A-3" refers to phenylphosphonic acid (an acidic pH adjuster). The pH of a 10% aqueous suspension was 1.6.

[0206] As can be seen from the results above, pigment dispersions and ink compositions in which the components and their amounts are controlled so that the pH is within a specific range exhibit excellent storage stability and dispensing stability.

Claims

1. A method for producing an active energy ray curable ink composition ejected by an inkjet method, The aforementioned ink composition contains a polymerizable compound, The process includes adjusting the type and amount of each component so that the pH of the aqueous suspension, as measured by the following test method, is between 6.2 and 7.

8. The above process is, Step A involves measuring the pH of a 10% aqueous suspension of each component by a room temperature extraction method in accordance with Japanese Industrial Standard JIS K5101-17-2:2004, Step B involves determining the type and content of each component so that the pH of the 10% aqueous suspension of the completed ink composition is between 6.2 and 7.8, based on the pH measured in step A. including, A method for producing an ink composition. Test method: The ink composition is mixed with water to prepare an aqueous suspension of the ink composition, and the pH of the aqueous suspension is measured.

2. The aforementioned ink composition contains a colorant. A method for producing the ink composition according to claim 1.

3. The aforementioned ink composition does not contain a colorant. A method for producing the ink composition according to claim 1.

4. A method for producing a pigment dispersion used in an active energy ray curable ink composition ejected by an inkjet method, The aforementioned pigment dispersion contains a pigment, a polymerizable compound, and a pigment dispersant. The process includes adjusting the type and amount of each component so that the pH of the aqueous suspension, as measured by the following test method, is between 6.3 and 7.

7. The above process is, Step A involves measuring the pH of a 10% aqueous suspension of each component by a room temperature extraction method in accordance with Japanese Industrial Standard JIS K5101-17-2:2004, Step B involves determining the type and content of each component so that the pH of the completed 10% aqueous suspension of pigment dispersion is between 6.3 and 7.7, based on the pH measured in step A. including, A method for producing a pigment dispersion. Test method: A pigment dispersion is mixed with water to produce an aqueous suspension of the pigment dispersion, and the pH of the aqueous suspension is measured.

5. A method for producing an active energy ray curable ink composition ejected by an inkjet method, A pigment dispersion produced by the method for producing a pigment dispersion according to claim 4, and a polymerization initiator, A method for producing an ink composition.

6. A method for producing an ink composition according to any one of claims 1 to 3 and 5, wherein the water content is 5.0% by mass or less of the total amount of the ink composition.

7. The ink composition comprises an ink composition produced by the method for producing an ink composition described in any one of claims 1 to 3, 5, and 6. A method for manufacturing ink sets.

8. An ink composition produced by the method for producing an ink composition according to any one of claims 1 to 3, 5, and 6 is printed on the surface of a substrate. A method for manufacturing printed materials.

9. A storage mechanism filled with an ink composition manufactured by the method for manufacturing an ink composition described in any one of claims 1 to 3, 5, and 6, A method for manufacturing an inkjet recording device.

10. The ink composition produced by the method for producing an ink composition according to any one of claims 1 to 3, 5, and 6 is ejected by an inkjet method. Recording method.

11. The ink composition produced by the method for producing an ink composition according to any one of claims 1 to 3, 5, and 6 is ejected by an inkjet method. A method for manufacturing printed materials.

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