Inkjet ink composition, recording method, ink set, pigment dispersion

Abstract

This invention provides an inkjet ink composition with excellent storage stability, ejection stability, clogging recovery, and abrasion resistance. [Solution] An inkjet ink composition comprising a pigment which is bio-derived carbon black, a solvent, wherein the pigment is a resin-dispersed pigment dispersed in a crosslinked resin, and the solvent contains water, making it a water-based ink.

Description

[Technical Field]

[0001] This invention relates to an inkjet ink composition, a recording method, an ink set, and a pigment dispersion. [Background technology]

[0002] Inkjet recording methods enable the recording of high-resolution images with relatively simple equipment and are undergoing rapid development in various fields. For example, Patent Document 1 aims to provide an aqueous inkjet ink composition that is excellent in environmental compatibility and storage stability, and is an aqueous inkjet ink composition comprising a bio-derived colorant, a bio-derived dispersant, and a bio-derived organic solvent, wherein the organic solvent has a solubility parameter of 24.0 (cal / cm³) based on the Hansen method. 3 ) 1 / 2 The above describes an inkjet ink composition containing a compound having a hydroxyl group. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2023-128719 [Overview of the project] [Problems that the invention aims to solve]

[0004] In water-based inkjet inks containing pigments, there is a desire to improve ejection stability and other properties. [Means for solving the problem]

[0005] The inkjet ink composition of the present invention contains a pigment which is bio-derived carbon black and a solvent, wherein the pigment is a resin-dispersed pigment dispersed in a crosslinked resin, and the solvent contains water, making it an aqueous ink.

[0006] The recording method of the present invention includes an adhesion step of ejecting ink using the above-mentioned inkjet ink composition from an inkjet head and adhering it to a recording medium.

[0007] The ink set of the present invention comprises the above-mentioned inkjet ink composition. The pigment dispersion of the present invention is a pigment dispersion used for preparing an inkjet ink composition, and contains a pigment which is bio-derived carbon black and a solvent, wherein the pigment is a resin-dispersed pigment dispersed in a crosslinked resin, and the solvent contains water, making it an aqueous pigment dispersion. [Brief explanation of the drawing]

[0008] [Figure 1] This figure shows an example of a recording device used in this embodiment. [Figure 2] Table 1 shows the composition of each composition used in the examples and the evaluation results thereof. [Modes for carrying out the invention]

[0009] The present invention will be described in detail below, with reference to the drawings as necessary. However, the present invention is not limited thereto, and various modifications are possible without departing from its essence. In the drawings, the same elements will be denoted by the same reference numerals, and redundant explanations will be omitted. Furthermore, unless otherwise specified, positional relationships such as up, down, left, and right will be based on the positional relationships shown in the drawings. Moreover, the dimensional ratios in the drawings are not limited to those shown.

[0010] 1. Inkjet ink composition The inkjet ink composition according to this embodiment contains a pigment which is bio-derived carbon black (hereinafter also referred to as "bio-derived CB") and a solvent, wherein the pigment is a resin-dispersed pigment dispersed in a crosslinked resin, and the solvent contains water, making it an aqueous ink.

[0011] Efforts are being made to develop environmentally friendly inks by using colorants derived from natural products, such as bio-based CBs like biochar and bio-oil char, to reduce petroleum-derived components and CO2 emissions from petroleum-derived components. Biochar is charcoal obtained by carbonizing biomass. Bio-oil char is charcoal obtained by carbonizing bio-derived oil. Bio-oil is biomass converted to oil or oil obtained from biomass. Biochar is a solid such as charcoal obtained by carbonizing biomass and is not bio-oil. Biomass refers to living organisms such as animals, plants, and microorganisms and does not include those derived from underground resources such as petroleum.

[0012] Biochar has many surface irregularities and a large specific surface area. Also, during the manufacturing process, it is often pulverized, making it easy for active sites to increase on the surface. Due to these factors, plant charcoal tends to aggregate, which can reduce storage stability, ejection stability, and clogging recovery.

[0013] In addition, bio-oil char contains more organic substances, which are impurities, compared to petroleum-derived carbon black. When the evaporation of water in the ink makes the organic components such as organic solvents and surfactants rich, interactions occur between the organic substances contained in bio-oil CB and these organic components, which can weaken the hydrophobic interaction between bio-oil char and the dispersant resin. As a result, the dispersant resin can elute (become free), and the pigment tends to aggregate, which can reduce storage stability, ejection stability, and clogging recovery.

[0014] Furthermore, high molecular weight organic substances, which are impurities, may adhere to the surface of pigments derived from bio-oil char. Such impurities are likely to peel off from the pigment in the ink. The peeled pigment surface tends to be highly hydrophobic and is likely to become a starting point for pigment aggregation. Examples of such high molecular weight organic substances include fulvic acid.

[0015] From the perspective of improving the storage stability, discharge stability, and clogging recovery properties of pigments derived from bio-oils and coals, it is conceivable to increase the amount of dispersant resin used. However, this would result in a larger amount of dispersant resin being free in the ink, which could actually decrease discharge stability and clogging recovery properties.

[0016] Therefore, in this embodiment, bio-derived CB is used as a resin-dispersed pigment dispersed in a crosslinked dispersant resin. The crosslinked dispersant resin has high adsorption stability to the pigment and excellent dispersion stability of the pigment, which suppresses aggregation, resulting in an ink with excellent storage stability, discharge stability, and clogging recovery. In particular, the ink maintains the above effects even when the ink dries and becomes rich in organic components. Furthermore, it is possible to reduce the total amount of dispersant resin used.

[0017] The biomass content of the ink composition in this embodiment is preferably 50-100% by mass, 55-99% by mass, 65-97% by mass, 70-95% by mass, and 75-93% by mass. Having a biomass content within the above range contributes even more to reducing CO2 emissions. Here, biomass content refers to the mass ratio of bio-derived components to solid content in the ink.

[0018] Bio-derived components are organic resources derived from plants and animals, excluding fossil fuels. In this embodiment, plant-derived carbon dioxide (CB) is an example of a bio-derived component.

[0019] Biomass content was measured by accelerator mass spectrometry (AMS). 14 It can be measured by known methods based on the concentration of C. More specifically, it can be measured by the method described in the examples.

[0020] The components that may be included in the ink composition according to this embodiment will be described in detail below.

[0021] 1.1. Pigments Pigments can be classified into self-dispersing pigments, which disperse on their own without the use of a dispersant, and dispersant-dispersed pigments, which are dispersed by a dispersant. Dispersants are materials that disperse pigments in this way. Among dispersant-dispersed pigments, those in which the pigment is dispersed by a resin are called resin-dispersed pigments. Resin-dispersed pigments are pigments in which a resin is dispersed in a solvent by adsorption, attachment, or coating of the pigment surface. Typically, water-insoluble resins and water-soluble resins are used as dispersants. In this embodiment, a crosslinked resin is used as the dispersant for the pigment. Hereinafter, the pigment dispersed by the crosslinked resin will also be called a "crosslinked resin-dispersed pigment." Because the pigment surface is at least partially coated with the crosslinked resin in this way, the resin is less likely to detach from the pigment surface even when plant-derived CB is used as the pigment. As a result, dispersion stability is improved, resulting in an ink with excellent storage stability, discharge stability, and clogging recovery.

[0022] The method for producing the crosslinked resin dispersion pigment in this embodiment is not particularly limited, but examples include a method comprising the steps of polymerizing a resin having reactive functional groups such as carboxyl groups and hydroxyl groups, mixing the resin with a pigment, and crosslinking the reactive functional groups.

[0023] In this embodiment, the crosslinked resin used as the dispersant resin is not particularly limited, but may be obtained by reacting a resin having a reactive functional group such as a carboxyl group or a hydroxyl group with a crosslinking agent having two or more functional groups that react with the reactive functional group. Among these, it is desirable that the crosslinked resin includes an acrylic resin. An acrylic resin is a general term for a polymer that contains at least one constituent unit derived from an acrylic monomer. Acrylic monomers are monomers having a (meth)acryloyl group, such as (meth)acrylic acid, (meth)acrylate, (meth)acrylamide, and (meth)acrylonitrile. The inclusion of acrylic resin in the crosslinked resin tends to improve storage stability, dispensing stability, and clogging recovery. The resin and crosslinking agent may be reacted beforehand and then mixed with the pigment, or the resin may be mixed with the pigment and then reacted with the crosslinking agent.

[0024] Examples of monomers constituting a resin having reactive functional groups include monomers having ionic groups and hydrophobic monomers. The resin having reactive functional groups may also be a copolymer of monomers having ionic groups or hydrophobic monomers.

[0025] The monomers having ionic groups are not particularly limited, but examples include unsaturated carboxylic acid monomers such as acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid, citraconic acid, and 2-methacryloyloxymethyl succinic acid; unsaturated sulfonic acid monomers such as styrene sulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, and 3-sulfopropyl (meth)acrylate; unsaturated phosphoric acid monomers such as vinyl phosphonic acid, vinyl phosphate, bis(methacryloxyethyl) phosphate, diphenyl-2-acryloyloxyethyl phosphate, and diphenyl-2-methacryloyloxyethyl phosphate; and N,N-dimethylamino Examples include unsaturated tertiary amine-containing monomers such as ethyl (meth)acrylate, N,N-dimethylaminopropyl (meth)acrylate, N,N-diethylaminoethyl (meth)acrylate, N,N-dimethylaminopropyl (meth)acrylamide, N,N-dimethylarylamine, vinylpyrrolidone, 2-vinylpyridine, 4-vinylpyridine, 2-methyl-6-vinylpyridine, and 5-ethyl-2-vinylpyridine; and unsaturated ammonium salt-containing monomers such as N,N-dimethylaminoethyl (meth)acrylate quaternary, N,N-diethylaminoethyl (meth)acrylate quaternary, and N,N-dimethylaminopropyl (meth)acrylate quaternary.

[0026] The content of constituent units derived from monomers having ionic groups is preferably 1 to 80% by mass, 10 to 50% by mass, 20 to 40% by mass, and 25 to 35% by mass, relative to the total amount of the dispersant resin. When the content of constituent units derived from monomers having ionic groups is within the above range, storage stability, discharge stability, and clogging recovery tend to be further improved.

[0027] Furthermore, the hydrophobic monomers are not particularly limited, but examples include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, amyl (meth)acrylate, cyclohexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, decyl (meth)acrylate, dodecyl (meth)acrylate, stearyl (meth)acrylate, isopropyl (meth)acrylate, isobutyl (meth)acrylate, te Examples include alkyl(meth)acrylates such as rt-butyl(meth)acrylate, isoamyl(meth)acrylate, isooctyl(meth)acrylate, isodecyl(meth)acrylate, isododecyl(meth)acrylate, and isostearyl(meth)acrylate; and aromatic group-containing monomers such as styrene, α-methylstyrene, 2-methylstyrene, vinyltoluene, divinylbenzene, chlorostyrene, phenyl(meth)acrylate, benzyl(meth)acrylate, and phenoxyethyl(meth)acrylate.

[0028] The content of constituent units derived from hydrophobic monomers is preferably 30-99% by mass, 50-90% by mass, 60-80% by mass, and 65-75% by mass, relative to the total amount of the dispersant resin. When the content of constituent units derived from hydrophobic monomers is within the above range, storage stability, discharge stability, and clogging recovery tend to be further improved.

[0029] The polymerization initiator used when polymerizing resins having reactive functional groups is not particularly limited, but examples include 2,2'-azobis(2-amidinopropane)dibasic acid, 4,4'-azobis(4-cyanovaleric acid), 2,2'-azobis[2-(5-methyl-2-imidazolin-2-yl)propane]dihydrochloride, 2,2'-azobis[2-(2-imidazolin-2-yl)propane]dihydrochloride, 2,2'-azobis[2-(2-imidazolin- Examples include 2-yl)propane disulfate dihydrate, 2,2'-azobis[2-(3,4,5,6-tetrahydropyrimidine-2-yl)propane]dihydrochloride, 2,2'-azobis[2-(1-(2-hydroxyethyl)-2-yl)propane]dihydrochloride, 2,2'-azobis(2-methylpropionamidin)dihydrochloride, and 2,2'-azobis[N-(2-carboxyethyl)-2-methylpropionamide].

[0030] The polymerization chain transfer agent used when polymerizing resins having reactive functional groups is not particularly limited, but examples include polymerization chain transfer agents having anionic groups such as 2-mercaptopropionic acid, 3-mercaptopropionic acid, mercaptosuccinic acid, thioglycolic acid, thiolactic acid, 4,4'-dithiobtyric acid, 3,3'-dithiopropionic acid, and dithioglycolic acid; and 1-amino-2-methyl-2-propanethol, 2-aminoethanethiol, and 2-diethylaminoethanethiol. Examples include polymerization chain transfer agents having cationic groups such as 2-dimethylaminoethanethiol, 4-aminothiophenol, dithiodianiline, 3,4,5,6-tetrahydro-2-pyrimidinethiol, and 2-mercaptothiazoline; and polymerization chain transfer agents having amphoteric ionic groups such as thiol-containing amino acids and their derivatives, including DL-penicillamine, N-(2-mercaptopropionyl)glycine, DL-cysteine, DL-homocysteine, cystamine, and DL-cystine.

[0031] Examples of crosslinking agents include those that react with the reactive functional groups of the resin to form ester bonds, thioester bonds, amide bonds, amino bonds, ether bonds, thioether bonds, carbonyl bonds, thiocarbonyl bonds, and sulfonyl bonds.

[0032] Such crosslinking agents are not particularly limited, but include compounds having two or more functional groups in their molecule, such as epoxy groups, isocyanate groups, azilidino groups, amino groups, and oxazoline groups. Among these, compounds having two or more of one or more functional groups selected from the group consisting of epoxy groups, isocyanate groups, azilidino groups, amino groups, and oxazoline groups are preferred. Using such compounds tends to improve storage stability, discharge stability, and clogging recovery.

[0033] Such crosslinking agents are not particularly limited, but examples include polyfunctional epoxy compounds having two or more epoxy groups in the molecule. Examples of polyfunctional epoxy compounds are not particularly limited, but examples include polypropylene glycol diglycidyl ether, glycerol polyglycidyl ether, polyglycerol polyglycidyl ether, trimethylolpropane polyglycidyl ether, sorbitol polyglycidyl ether, pentaerythritol polyglycidyl ether, resorcinol diglycidyl ether, neopentyl glycol diglycidyl ether, and hydrogenated bisphenol A type diglycidyl ether.

[0034] The amount of crosslinking agent added is preferably 20-80 mol%, 25-60 mol%, 30-50 mol%, and 35-45 mol% relative to the total amount of reactive functional groups in the resin. Adding the crosslinking agent within the above range tends to further improve redispersibility, clogging recovery, and storage stability.

[0035] The volume-average particle size D50 corresponding to a 50% pigment accumulation is preferably between 30 nm and 200 nm, between 50 nm and 110 nm, between 70 nm and 105 nm, between 80 nm and 100 nm, and between 87 nm and 95 nm. When the volume-average particle size D50 is within the above range, storage stability, discharge stability, and clogging recovery tend to be improved.

[0036] The volume-average particle diameter in this embodiment can be measured using a particle size distribution analyzer that employs dynamic light scattering as its measurement principle. Alternatively, it can be measured using a particle size distribution analyzer that employs dynamic and electrophoretic light scattering as its measurement principles. Examples of such particle size distribution analyzers include the "ELSZ-2000ZS" (product name) manufactured by Otsuka Electronics Co., Ltd., which employs a homodyne optical system as its frequency analysis method.

[0037] The pigment content is preferably 0.1 to 15% by mass, 1 to 12% by mass, 2 to 9% by mass, or 3 to 7% by mass, relative to the total amount of the ink composition. A pigment content within these ranges tends to improve storage stability, discharge stability, and clogging recovery.

[0038] The dispersant resin content is preferably 0.1 to 10% by mass, 0.3 to 5% by mass, 1 to 4% by mass, and 2 to 3% by mass, relative to the total amount of the ink composition. When the dispersant resin content is within the above range, storage stability, discharge stability, and clogging recovery tend to be improved.

[0039] The mass ratio of the dispersant resin to the pigment is preferably 0.05 to 0.8, 0.1 to 0.7, 0.2 to 0.6, or 0.25 to 0.5. When the mass ratio of the dispersant resin to the pigment is within the above range, storage stability, discharge stability, and clogging recovery tend to be further improved.

[0040] 1.1.1.Biological CB The resin-dispersed pigment in this embodiment includes bio-derived carbon black (CB). Bio-derived CB is carbon black derived from living organisms. Because it is carbon black derived from natural products, it can reduce petroleum-derived components and contribute to reducing CO2 emissions from petroleum-derived components. While not particularly limited, bio-derived CB includes, as mentioned above, bio-carbon and bio-oil-carbon. Organisms include animals, plants, and microorganisms, but among biologically derived CBs, plant-derived CBs, which use plants as raw materials, are preferred and useful because the raw materials are relatively homogeneous and readily available in relatively large quantities, they are easy to handle, and they are easy to store. Plant-derived carbon charcoal (CB) includes plant charcoal obtained by carbonizing plants, and plant oil charcoal obtained by carbonizing plant oil (plant-derived oil). In the case of biochar, if the biosource is plants, it is called food charcoal, and in the case of bio oil charcoal, if the biosource is plant oil, it is called food oil charcoal. As mentioned above, plant charcoal has many irregularities on the pigment surface, resulting in a large specific surface area. Furthermore, pulverization during the manufacturing process tends to increase the number of active sites on the surface. Due to these factors, storage stability, discharge stability, and clogging recovery properties tend to be particularly reduced. Furthermore, vegetable oil charcoal contains many organic impurities, and as the water in the ink evaporates, the organic components such as organic solvents and surfactants become richer. Interactions occur between the organic components in the vegetable oil charcoal and these organic components, which can weaken the hydrophobic interaction between the vegetable oil charcoal and the dispersant resin. This can cause the dispersant resin to dissolve (be released), making the pigment more prone to aggregation, and thus potentially reducing storage stability, discharge stability, and clogging recovery. However, according to this embodiment, even when using plant-derived CB, excellent storage stability, discharge stability, and clogging recovery properties can be obtained, making this embodiment particularly useful.

[0041] The content of bio-derived CB is preferably 0.1 to 15% by mass, 1 to 12% by mass, 2 to 9% by mass, and 3 to 7% by mass, relative to the total amount of the ink composition. When the content of bio-derived CB is within the above range, storage stability, discharge stability, and clogging recovery tend to improve.

[0042] 1.1.1.1. Vegetable charcoal The resin-dispersed pigment in this embodiment preferably contains plant charcoal. While not particularly limited, examples of plant charcoal include binchotan charcoal, bamboo charcoal, activated carbon, white charcoal, black charcoal, molded wood charcoal, sawdust charcoal, plum charcoal, activated carbon, oak charcoal, Douglas fir charcoal, seaweed charcoal, mangrove charcoal, and coconut shell charcoal. While not particularly limited, a method for producing plant charcoal includes treating plants under high-temperature conditions to carbonize them. High-temperature conditions are not particularly limited as long as they allow for the carbonization of plants, but examples include high-temperature conditions of 250°C or higher, known as "charcoal burning," which can reduce bamboo and wood to ash; high-temperature conditions of 350°C or higher, where uncarbonized components are said to disappear; or high-temperature conditions of 700°C or higher using a charcoal kiln.

[0043] The amount of plant charcoal is preferably 0.1 to 15% by mass, 1 to 12% by mass, 2 to 9% by mass, or 3 to 7% by mass, relative to the total amount of the ink composition. When the amount of plant charcoal is within the above range, storage stability, discharge stability, and clogging recovery tend to be improved.

[0044] 1.1.1.2. Vegetable oil charcoal In this embodiment, the resin-dispersed pigment preferably contains vegetable oil carbon. Vegetable oil carbon is produced by carbonizing vegetable oil to make carbon black, and its manufacturing process is similar to that of petroleum-derived carbon black, as it involves burning a liquid to produce carbon black, making it relatively easy to manufacture.

[0045] There are no particular limitations on the method for producing vegetable oil coal, but known methods such as the furnace method, channel method, and lamp method can be used. In addition, in the process of preparing the raw materials for vegetable oil or its modified products, it is possible to control the structure of vegetable oil coal by adding alkaline agents such as potassium hydroxide or sodium hydroxide, in addition to conditions such as heating temperature and sample amount.

[0046] The raw materials for the vegetable oil charcoal are not particularly limited, but examples include tall oil, wood tar, plant seed oil, and modified products such as hydrogenated or derivative products of the above substances. A modified product is a vegetable oil modified to the extent that the effects of this embodiment can be obtained.

[0047] The vegetable oil and carbon content is preferably 0.1 to 15% by mass, 1 to 12% by mass, 2 to 9% by mass, and 3 to 7% by mass, relative to the total amount of the ink composition. When the vegetable oil and carbon content is within the above range, storage stability, discharge stability, and clogging recovery tend to be further improved.

[0048] 1.2. Fixing resin The ink composition in this embodiment preferably contains a fixing resin. The fixing resin is a resin that enhances the fixation of the pigment to the recording medium, and the ink composition tends to have improved properties such as abrasion resistance when it contains a fixing resin. In this embodiment, the fixing resin is distinguished from the dispersant resin. On the other hand, when ink contains a fixing resin, ejection stability, clogging recovery, and storage stability may decrease. However, in this embodiment, excellent ejection stability, clogging recovery, and storage stability are obtained, making this embodiment particularly useful.

[0049] The fixing resin is not particularly limited, but examples include acrylic resins, urethane resins, polyester resins, polyether resins, and polyolefin resins. The fixing resin may be a self-emulsifying resin that stabilizes itself as a resin emulsion without the use of an emulsifier, or an emulsifying resin that stabilizes itself as a resin emulsion using an emulsifier. The fixing resin may be a water-soluble resin dissolved in the solvent components of the ink, including water. The fixing resin is not a resin for dispersing the pigment; it does not adhere to or adsorb to the pigment in the ink, but is dissolved in the solvent components or dispersed as resin particles. For the fixing resin, resins dispersed as resin particles in the ink, resin emulsions, etc., are preferred because they offer superior abrasion resistance and other properties.

[0050] The fixing resin content is preferably 0.1 to 10% by mass, 0.1 to 5% by mass, 0.3 to 3% by mass, 0.5 to 2% by mass, and 0.7 to 1.5% by mass, relative to the total amount of the ink composition. When the fixing resin content is within the above range, the ejection stability and abrasion resistance tend to be further improved.

[0051] 1.2.1. Acrylic resins Acrylic resins are a general term for polymers that contain at least one constituent unit derived from acrylic monomers. Examples include resins obtained from acrylic monomers and copolymers of acrylic monomers with other monomers. Suitable acrylic monomers include monomers having a (meth)acryloyl group, such as (meth)acrylic acid, (meth)acrylate, (meth)acrylamide, and (meth)acrylonitrile. Other monomers may also be used as constituent units in combination with acrylic monomers. Examples of other monomers include vinyl monomers such as styrene. Acrylic resins have a high affinity for plant oil carbon CB, and therefore, using acrylic resins as a fixing resin tends to improve abrasion resistance.

[0052] The acrylic resin may be a self-emulsifying resin. A self-emulsifying acrylic resin can be obtained, for example, by emulsion polymerization of an unsaturated monomer in water in the presence of a polymerization initiator and a surfactant.

[0053] Examples of unsaturated monomers include acrylic acid ester monomers, methacrylic acid ester monomers, aromatic vinyl monomers, vinyl ester monomers, vinyl cyanide compound monomers, halogenated monomers, olefin monomers, and diene monomers, which are commonly used in emulsion polymerization. Specific examples include (meth)acrylic acid ester monomers such as methyl (meth)acrylate, ethyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, n-amyl (meth)acrylate, isoamyl (meth)acrylate, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, decyl (meth)acrylate, dodecyl (meth)acrylate, octadecyl (meth)acrylate, cyclohexyl (meth)acrylate, phenyl (meth)acrylate, benzyl (meth)acrylate, and glycidyl (meth)acrylate; vinyl ester monomers such as vinyl acetate; acrylonitrile; meth Examples include vinyl cyanide compounds such as crironitrile; halogenated monomers such as vinylidene chloride and vinyl chloride; aromatic vinyl monomers such as styrene, α-methylstyrene, vinyltoluene, 4-t-butylstyrene, chlorostyrene, vinylanisole, and vinylnaphthalene; olefins such as ethylene and propylene; dienes such as butadiene and chloroprene; vinyl monomers such as vinyl ether, vinyl ketone, and vinylpyrrolidone; unsaturated carboxylic acids such as acrylic acid, methacrylic acid, itaconic acid, fumaric acid, and maleic acid; acrylamides such as acrylamide, methacrylamide, and N,N'-dimethylacrylamide; and hydroxyl group-containing monomers such as 2-hydroxyethyl (meth)acrylate and 2-hydroxypropyl (meth)acrylate.

[0054] In addition, crosslinkable monomers having two or more polymerizable double bonds can also be used. Examples of crosslinkable monomers having two or more polymerizable double bonds include polyethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, 1,3-butylene glycol di(meth)acrylate, 1,4-butylene glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, polypropylene glycol di(meth)acrylate, 2,2'-bis(4-(meth)acryloxypropyloxyphenyl)propane, and 2,2'-bis(4-(meth)acryloxydiol Examples include di(meth)acrylate compounds such as toxyphenyl)propane; tri(meth)acrylate compounds such as trimethylolpropane tri(meth)acrylate, trimethylolethane tri(meth)acrylate, and tetramethylolmethane tri(meth)acrylate; tetra(meth)acrylate compounds such as ditrimethyloltetra(meth)acrylate, tetramethylolmethane tetra(meth)acrylate, and pentaerythritol tetra(meth)acrylate; hexa(meth)acrylate compounds such as dipentaerythritol hexa(meth)acrylate; methylenebisacrylamide, divinylbenzene, etc.

[0055] During emulsion polymerization, in addition to polymerization initiators and surfactants, chain transfer agents and neutralizing agents may also be used. Examples of neutralizing agents include ammonia and hydroxides of inorganic alkalis, such as sodium hydroxide and potassium hydroxide.

[0056] The acrylic resin content is preferably 0.1 to 10% by mass, 0.1 to 5% by mass, 0.3 to 3% by mass, 0.5 to 2% by mass, and 0.7 to 1.5% by mass, relative to the total amount of the ink composition. When the acrylic resin content is within the above range, the ejection stability and abrasion resistance tend to improve.

[0057] 1.2.2. Urethane resins Urethane resins are a general term for resins having a urethane skeleton, and refer to resins containing urethane bonds, urea bonds, or allophanate bonds formed by the reaction of isocyanate groups with active hydrogen-containing groups such as hydroxyl groups, amino groups, urethane bonding groups, and carboxyl groups. In addition to urethane skeletons, urethane resins also include polyether-type urethane resins containing an ether skeleton in the main chain, polyester-type urethane resins containing an ester skeleton in the main chain, and polycarbonate-type urethane resins containing a carbonate skeleton in the main chain. Using urethane resins as a fixing resin tends to improve abrasion resistance.

[0058] The urethane resin may be a self-emulsifying resin. Examples of urethane-based self-emulsifying fixing resins include urethane resins to which hydrophilic groups or hydrophilic segments are provided. An example of a commercially available urethane-based self-emulsifying fixing resin is Superflex 460 (trade name, isocyanate carbonate-based urethane resin, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.).

[0059] The urethane resin content is preferably 0.1 to 10% by mass, 0.1 to 5% by mass, 0.3 to 3% by mass, 0.5 to 2% by mass, and 0.7 to 1.5% by mass, relative to the total amount of the ink composition. When the urethane resin content is within the above range, the discharge stability, clogging recovery, and abrasion resistance tend to be further improved. A polyester resin is any resin that has a polyester structure in its backbone. A polyether resin is any resin that has a polyether structure in its backbone. A polypolyolefin resin is any resin that has a polyolefin structure in its backbone.

[0060] 1.3. solvent The ink composition in this embodiment contains a solvent. The solvent is a liquid component that disperses or dissolves pigments, fixing resins, etc. The solvent contains at least water and may also contain organic solvents. When simply referred to as "solvent," it means the solvent itself. 1.3.1. Organic Solvents The ink composition in the present embodiment may contain an organic solvent as a solvent. The organic solvent in the present embodiment preferably contains an organic solvent A having an octanol / water partition coefficient logP ow value of 0 to 1. When the ink composition contains the organic solvent A, when the drying of the ink proceeds and the content of the organic component becomes dominant, the fixing resin and the pigment are more likely to dissolve in the ink, and the storage stability and clogging recovery property tend to be further improved. Further, in the process of the ink drying on the recording medium, the fixing resin and the pigment are more likely to bind in the organic solvent A, so the abrasion resistance tends to be further improved. The ink composition in the present embodiment may contain an organic solvent B having a logP ow value other than 0 to 1 as necessary. The organic solvent B is an organic solvent other than the organic solvent A. The octanol / water partition coefficient logP ow value is also referred to as the octanol / water partition coefficient or the logP ow value and the like.

[0061] The logP ow value of the organic solvent A is preferably 0.1 to 1, 0.2 to 0.9, 0.3 to 0.8, 0.4 to 0.7, or 0.5 to 0.6. Since the logP ow value is 0 or more, the solubility of the fixing resin becomes higher, and since the logP ow value is 1 or less, the compatibility with water tends to be more excellent. Therefore, when the logP ow value is within the above range, the storage stability, abrasion resistance, and clogging recovery property of the ink composition tend to be further improved.

[0062] In the present embodiment, the octanol / water partition coefficient logP ow value refers to the value defined in OECD Test Guideline 107. The octanol / water partition coefficient is represented as logP ow or logK ow and the like. The higher the logP ow value, the higher the hydrophobicity, and the lower the value, the higher the hydrophilicity.

[0063] The logP owThe value can be determined by various methods; for example, it can be obtained by measuring according to the measurement method specified in JIS Z 7260-117. It can also be calculated using Hansen Solubility Parameter Software (HSPIP).

[0064] Organic solvents A and B are not particularly limited, but examples include monoalcohols, polyols, ethers, amides, and lactam compounds.

[0065] Examples of monoalcohols include methanol, ethanol, n-propyl alcohol, isopropyl alcohol, n-butanol, 2-butanol, tert-butanol, isobutanol, n-pentanol, 2-pentanol, 3-pentanol, and tert-pentanol, 2-phenoxyethanol, benzyl alcohol, and phenoxypropanol.

[0066] Polyols are organic solvents having two or more hydroxyl groups. Examples include glycols having two hydroxyl groups and polyols having three or more hydroxyl groups. Examples of glycols include alkanediols and condensates of alkanediols having a structure in which the hydroxyl groups between molecules are condensed. Alkanediols are those in which an alkane is substituted with two hydroxyl groups. Alkanediols preferably have two or more carbon atoms, preferably four or more, and more preferably five to eight. 1,2-alkanediols are also preferred. Examples of condensates having a structure in which the hydroxyl groups between molecules of alkanediols are fused together include condensates of diols of alkanes having 2 to 4 carbon atoms, in which the hydroxyl groups between molecules are fused together.

[0067] Examples of glycols include ethylene glycol, propylene glycol, alkanediols such as ethylene glycol, propylene glycol, 1,2-propanediol, 1,2-butanediol, 1,2-pentanediol, 1,2-hexanediol, 1,2-octanediol, 1,3-propanediol, 1,4-butanediol, and 1,6-hexanediol; and condensates of alkanediols such as tetramethylene glycol, hexamethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, dipropylene glycol, tripropylene glycol, polypropylene glycol, and (poly)tetramethylene glycol, which have a structure in which the hydroxyl groups between molecules are condensed.

[0068] Examples of ethers include alkyl ethers and glycol ethers, although they are not particularly limited. Examples of alkyl ethers include dimethyl ether, methyl ethyl ether, diethyl ether, isopropyl methyl ether, and isopropyl ethyl ether.

[0069] Examples of glycol ethers include ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monobutyl ether, tetraethylene glycol monomethyl ether, tetraethylene glycol monoethyl ether, tetraethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol monopropyl ether, dipropylene glycol monobutyl ether, and tripropylene glycol monomethyl ether. Examples include alkylene glycol monoalkyl ethers such as tripropylene glycol monobutyl ether; and alkylene glycol dialkyl ethers such as ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol dibutyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol dibutyl ether, diethylene glycol methyl ethyl ether, diethylene glycol methyl butyl ether, triethylene glycol dimethyl ether, triethylene glycol diethyl ether, triethylene glycol dibutyl ether, triethylene glycol methyl butyl ether, tetraethylene glycol dimethyl ether, tetraethylene glycol diethyl ether, tetraethylene glycol dibutyl ether, propylene glycol dimethyl ether, propylene glycol diethyl ether, dipropylene glycol dimethyl ether, dipropylene glycol diethyl ether, and tripropylene glycol dimethyl ether.

[0070] Examples of polyols having three or more hydroxyl groups include glycerin. Examples of ketones include acetone, methyl ethyl ketone, and diethyl ketone. Examples of amides include lactam compounds and other amides. Examples of lactam compounds include 2-pyrrolidone, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, and N-hydroxyethylpyrrolidone (HEP).

[0071] Organic solvent A is one of the organic solvents mentioned above, with an octanol / water partition coefficient logP. ow The value is between 0 and 1. Examples of such organic solvents A include isopropyl methyl ether, diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, 1,2-hexanediol methyl ethyl ketone, isopropyl alcohol, and methyl ethyl ketone.

[0072] The content of organic solvent A is preferably 1 to 15% by mass, 2 to 11% by mass, 4 to 9% by mass, or 5 to 7% by mass, relative to the total amount of the ink composition. When the content of organic solvent A is within the above range, storage stability, abrasion resistance, and clogging recovery tend to be improved.

[0073] Organic solvent B may be any of the organic solvents mentioned above, but the octanol / water partition coefficient logP ow Those whose value is less than 0. The content of organic solvent B is preferably 0.5 to 20% by mass, 10 to 19% by mass, 12 to 18% by mass, 13 to 17% by mass, and 14 to 16% by mass, relative to the total amount of the ink composition. When the content of organic solvent B is within the above range, storage stability, abrasion resistance, and clogging recovery tend to be improved.

[0074] When organic solvents A and B are included, the total content of the included organic solvents is preferably 5-45% by mass, 10-40% by mass, 15-35% by mass, 17-30% by mass, and 19-25% by mass, relative to the total amount of the ink composition. Having the organic solvent content within the above range tends to improve storage stability, abrasion resistance, and clogging recovery.

[0075] 1.3.2.Water The inkjet ink composition of this embodiment is an aqueous ink containing water. An aqueous ink is defined as a composition that contains at least water as its main solvent component.

[0076] The water content is preferably 40-99% by mass, 50-90% by mass, 55-85% by mass, 60-80% by mass, or 65-75% by mass, relative to the total amount of the inkjet ink composition. By keeping the water content within the above range, storage stability, abrasion resistance, and clogging recovery tend to be further improved.

[0077] 1.4. Surfactants The ink composition in this embodiment may contain a surfactant. The surfactant is not particularly limited, but examples include silicone-based surfactants, acetylene glycol-based surfactants, and fluorine-based surfactants.

[0078] Examples of acetylene glycol-based surfactants include, but are not limited to, 2,4,7,9-tetramethyl-5-decine-4,7-diol and alkylene oxide adducts of 2,4,7,9-tetramethyl-5-decine-4,7-diol. Examples of commercially available acetylene glycol-based surfactants include Orfin E1010, EXP4200, EXP4300, Surfinol SE, Surfinol 440, Surfinol 104, and Surfinol 465 (product names of Nisshin Chemical Industry Co., Ltd.).

[0079] Examples of fluorinated surfactants include perfluoroalkyl sulfonates, perfluoroalkyl carboxylates, perfluoroalkyl phosphate esters, perfluoroalkyl ethylene oxide adducts, perfluoroalkyl betaines, and perfluoroalkylamine oxide compounds.

[0080] Examples of silicone-based surfactants are not particularly limited, but include polysiloxane compounds and polyether-modified organosiloxanes. Examples of commercially available silicone-based surfactants include BYK-306, BYK-307, BYK-333, BYK-341, BYK-345, BYK-346, BYK-348, BYK-UV3500, BYK-UV3510, BYK-UV3530, and BYK-UV3570 (product names of BYK Corporation).

[0081] The surfactant content is preferably 0.1 to 3% by mass, 0.3 to 2% by mass, and 0.5 to 1.5% by mass, relative to the total amount of the ink composition. When the surfactant content is within the above range, storage stability, discharge stability, and clogging recovery tend to improve.

[0082] 1.5. pH adjusters The inkjet ink composition in this embodiment may contain a pH adjuster. The pH adjuster is not particularly limited, but examples include inorganic acids such as sulfuric acid, hydrochloric acid, and nitric acid; inorganic bases such as lithium hydroxide, sodium hydroxide, potassium hydroxide, and ammonia; organic acids such as adipic acid, citric acid, and succinic acid; and organic bases such as triethanolamine, diethanolamine, monoethanolamine, triisopropanolamine, diisopropanolamine, and trishydroxymethylaminomethane.

[0083] The pH adjusting agent content is preferably 0.1 to 3% by mass, 0.3 to 2% by mass, and 0.5 to 1.5% by mass, relative to the total amount of the ink composition. When the pH adjusting agent content is within the above range, storage stability, discharge stability, and clogging recovery tend to improve.

[0084] 1.6. Other ingredients The ink composition may contain components other than those described above. Various additives such as solubilizers, viscosity modifiers, antioxidants, preservatives, fungicides, and corrosion inhibitors may be added as appropriate.

[0085] 2. Recording Method The recording method in this embodiment includes an adhesion step in which the inkjet ink composition is ejected from a predetermined inkjet head and adhered to a recording medium using a predetermined inkjet head.

[0086] 3. Recording device The recording device in this embodiment comprises the above-described ink composition and an inkjet head having a nozzle for ejecting the above-described ink composition onto a recording medium, and preferably further comprises a supply channel through which the above-described ink composition flows and is connected to the inkjet head, and a filter unit provided in the supply channel of the inkjet head.

[0087] Figure 1 shows an example of an inkjet recording apparatus that can be used in this embodiment. The inkjet recording apparatus according to this embodiment will be described in more detail with reference to Figure 1. In the XYZ coordinate system shown in Figure 1, the X direction represents the length direction of the recording medium, the Y direction represents the width direction of the recording medium in the transport path within the recording apparatus, and the Z direction represents the height direction of the apparatus.

[0088] As an example, the recording device 10 is a line-type inkjet printer capable of high-speed and high-density printing. The recording device 10 includes a feeding unit 12 for storing a recording medium P such as paper, a transport unit 14, a belt transport unit 16, a recording unit 18, an Fd (face down) ejection unit 20 as an "ejection unit", an Fd (face down) placement unit 22 as a "placement unit", an inversion path unit 24 as an "inversion transport mechanism", a Fu (face up) ejection unit 26, and a Fu (face up) placement unit 28.

[0089] The feeding unit 12 is located at the bottom of the recording device 10. The feeding unit 12 includes a feeding tray 30 for storing recording media P and a feeding roller 32 for sending the recording media P stored in the feeding tray 30 to the transport path 11.

[0090] The recording medium P stored in the feeding tray 30 is fed along the transport path 11 to the transport unit 14 by the feeding roller 32. The transport unit 14 is equipped with a transport drive roller 34 and a transport driven roller 36. The transport drive roller 34 is rotationally driven by a drive source (not shown). In the transport unit 14, the recording medium P is nipped between the transport drive roller 34 and the transport driven roller 36 and transported to the belt transport unit 16 located downstream of the transport path 11.

[0091] The belt conveying unit 16 includes a first roller 38 located upstream in the conveying path 11, a second roller 40 located downstream, an endless belt 42 rotatably mounted on the first roller 38 and the second roller 40, and a support 44 that supports the upper section 42a of the endless belt 42 between the first roller 38 and the second roller 40.

[0092] The endless belt 42 is driven by a first roller 38 or a second roller 40, driven by a drive source (not shown), to move in the upper section 42a from the +X direction to the -X direction. As a result, the recording medium P conveyed from the conveying section 14 is further conveyed downstream of the conveying path 11 in the belt conveying section 16.

[0093] The recording unit 18 comprises a line-type inkjet head 48 and a head holder 46 that holds the inkjet head 48. The recording unit 18 may also be a serial-type unit in which the inkjet head is mounted on a carriage that reciprocates in the Y-axis direction. The inkjet head 48 is positioned to face the upper section 42a of an endless belt 42 supported by a support 44. When the recording medium P is transported along the upper section 42a of the endless belt 42, the inkjet head 48 ejects ink toward the recording medium P and performs recording. While recording is taking place, the recording medium P is transported downstream of the transport path 11 by the belt transport unit 16.

[0094] A first branching section 50 is provided downstream of the transport path 11 of the belt transport section 16. The first branching section 50 is configured to switch between a transport path 11 that transports the recording medium P to the Fd discharge section 20 or the Fu discharge section 26, and an inversion path 52 of an inversion path section 24 that inverts the recording surface of the recording medium P and transports the recording medium P back to the recording section 18. When the recording medium P is transported after being switched to the inversion path 52 by the first branching section 50, the recording surface is inverted during the transport process in the inversion path 52, and it is transported back to the recording section 18 so that the side opposite to the original recording surface faces the inkjet head 48.

[0095] A second branch section 54 is provided downstream of the first branch section 50 along the transport path 11. The second branch section 54 is configured to switch the transport direction of the recording medium P so as to transport the recording medium P toward the Fd discharge section 20 or toward the Fu discharge section 26.

[0096] The recording medium P transported toward the Fd discharge section 20 at the second branching section 54 is discharged from the Fd discharge section 20 and placed on the Fd mounting section 22. At this time, the recording surface of the recording medium P is placed facing the Fd mounting section 22. The recording medium P transported toward the Fu discharge section 26 at the second branching section 54 is discharged from the Fu discharge section 26 and placed on the Fu mounting section 28. At this time, the recording surface of the recording medium P is placed facing away from the Fu mounting section 28.

[0097] 4. Recording media The recording medium used in this embodiment is not particularly limited, but examples include absorbent recording media, low-absorbent recording media, or non-absorbent recording media, and is preferably an absorbent recording medium.

[0098] Examples of absorbent recording media include ordinary paper such as electrophotographic paper with high ink permeability and an ink-absorbing layer composed of silica particles or alumina particles, or inkjet-specific paper equipped with an ink-absorbing layer composed of a hydrophilic polymer such as polyvinyl alcohol or polyvinylpyrrolidone.

[0099] Examples of low-absorption recording media include art paper, coated paper, and cast paper, which are commonly used in offset printing and have relatively low ink permeability.

[0100] Examples of non-absorbent recording media include films and plates of plastics such as polyvinyl chloride, polyethylene, polypropylene, polyethylene terephthalate (PET), polycarbonate, polystyrene, and polyurethane; plates of metals such as iron, silver, copper, and aluminum; or metal plates or plastic films made by vapor deposition of these metals, or alloy plates such as stainless steel and brass; and recording media in which films of plastics such as polyvinyl chloride, polyethylene, polypropylene, polyethylene terephthalate (PET), polycarbonate, polystyrene, and polyurethane are bonded (coated) to a paper substrate.

[0101] 5. Records The recording material of this embodiment is obtained by adhering the above-described ink composition to a recording medium. The recording material of this embodiment using the above-described ink composition can be recorded with an ink that has excellent storage stability, color development, transfer resistance, abrasion resistance, clogging recovery, and bubble discharge properties.

[0102] 6. Ink Set The ink set of this embodiment is a set of two or more inks, each containing at least the above-described inkjet ink composition, and is used as a set for recording. The ink set may also contain other ink compositions that exhibit a different color from the above-described inkjet ink composition. For example, cyan ink, yellow ink, magenta ink, etc. This enables color printing. 7. Pigment dispersion The pigment dispersion of this embodiment is a pigment dispersion used for preparing an inkjet ink composition, and contains a pigment which is bio-derived carbon black and a solvent, wherein the pigment is a resin-dispersed pigment dispersed in a crosslinked resin, and the solvent contains water, making it an aqueous pigment dispersion. This pigment dispersion is used to prepare an inkjet ink composition with other components necessary for the inkjet ink composition. The pigment dispersion is also called a pigment dispersion body. The pigment and solvent are the same as those contained in the inkjet ink composition of this embodiment described above. Since the pigment dispersion contains the aforementioned pigment and solvent, it is preferable that an inkjet ink composition containing the aforementioned pigment and solvent can be easily prepared by preparing the inkjet ink composition using this pigment dispersion. The inkjet ink composition may be the inkjet ink composition of this embodiment described above. The pigment dispersion may, if necessary, contain components that may be included in the inkjet ink composition of this embodiment as described above. [Examples]

[0103] The present invention will be described more specifically below using examples and comparative examples. The present invention is not limited in any way by the following examples.

[0104] Figure 2 shows Table 1, which illustrates the composition of each ink composition in the examples and comparative examples, as well as their evaluation results.

[0105] 1. Preparation of inkjet ink composition A dispersion was prepared by mixing and stirring the components to obtain the inkjet ink compositions for each example, as shown in Table 1. Unless otherwise specified, the numerical values ​​for each component in the table represent mass percent. In addition, in the table, each numerical value represents the mass percent of the solid content of the component (or the amount of solvent component in the case of the solvent).

[0106] The details of the product ingredients used in Table 1 are as follows:

[0107] [Pigments] • Binchotan charcoal, vegetable oil coal, petroleum CB (see adjustment examples below) [Dispersant resin] • Crosslinked type, non-crosslinked type (dispersant resin, see adjustment examples below) [Fixing resin] • Acrylic EM (see adjustment example below) • Urethane EM (product name "Superflex 460", manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) [Organic solvents] ·12HD(1,2-hexanediol, logP ow (Value 0.57) • BDG (Diethylene glycol monobutyl ether, logP ow (Value 0.56) • MEK (methyl ethyl ketone, logP) ow (Value 0.29) Gly (glycerin, logP) ow (Value -1.76) TEG (Triethylene Glycol, logP) ow (Value -1.75) [Surfactants] • E1010 (Product name "Orphine E1010", acetylene glycol-based surfactant, manufactured by Nisshin Chemical Industry Co., Ltd.) • S104 (Product name "Surfinol 104", acetylene glycol-based surfactant, manufactured by Nisshin Chemical Industry Co., Ltd.) [pH adjuster] • TEA (triethanolamine) [water] • Ion-exchanged water

[0108] 1.1. Preparation of Crosslinked Resin Dispersed Pigments <Preparation of resin solution> Mix 31 parts by mass of acrylic acid and 69 parts by mass of styrene to prepare a monomer mixture. In the reaction vessel, mix 5 parts by mass of methyl ethyl ketone, 0.25 parts by mass of 3-mercaptopropionic acid (polymerization chain transfer agent), and 10% by mass of the above monomer mixture (3.1 parts by mass of acrylic acid and 6.9 parts by mass of styrene), and thoroughly purge with nitrogen gas. Next, prepare a mixture in a dropping funnel containing the remaining 90% by mass of the above monomer mixture (28.9 parts by mass of acrylic acid and 62.1 parts by mass of styrene), 2.25 parts by mass of 3-mercaptopropionic acid, 75 parts by mass of methyl ethyl ketone, and 1.5 parts by mass of 4,4'-azobis(4-cyanovaleric acid) (azo radical polymerization initiator, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.). Under a nitrogen atmosphere, raise the temperature in the reaction vessel to 77°C while stirring, and add the mixture in the dropping funnel dropwise over 5 hours. After the dropwise addition is complete, a solution prepared by dissolving 0.5 parts by mass of 4,4'-azobis(4-cyanovaleric acid) in 5 parts by mass of methyl ethyl ketone is added, and the mixture is reacted at 77°C for 2 hours to obtain a resin solution containing a carboxyl group.

[0109] <Preparation of resin dispersions> The resin solution obtained above is dried under reduced pressure to obtain 24 parts by mass of resin. 200 parts by mass of ion-exchanged water and 9.7 parts by mass of 5N sodium hydroxide aqueous solution (sodium hydroxide solid content 16.9% by mass) are added to 24 parts by mass of the resin, and the mixture is neutralized so that the ratio of moles of sodium hydroxide to moles of carboxyl groups in the resin is 40% (degree of neutralization 40 mol%). The aqueous solution is heated at 90°C for 5 hours while stirring at 150 rpm to obtain a resin dispersion.

[0110] <Preparation of Pigment Dispersion> To the obtained resin dispersion, Binchotan charcoal (manufactured by Kiriya Chemical Co., Ltd.) is added so that the mass ratio of the resin to the Binchotan charcoal is as shown in Table 1. The mixture is then stirred for 60 minutes at 20°C with the disperser blades rotating at 7000 rpm using a disperser (Ultra Disperser, manufactured by Asada Iron Works Co., Ltd.). The resulting mixture is dispersed in 10 passes at a pressure of 200 MPa using a microfluidizer (manufactured by Microfluidics). The resulting dispersion is filtered using a 25 mL needleless syringe (manufactured by Terumo Corporation) fitted with a 5 μm filter (acetylcellulose membrane, outer diameter: 2.5 cm, manufactured by Fujifilm Corporation) to remove coarse particles. Then, ion-exchanged water is added to obtain a pigment dispersion with a solid content concentration of 22% by mass. When using vegetable charcoal as the pigment, carbon black (vegetable oil-based, manufactured by Orion Engineered Carbons) is used instead of Binchotan charcoal. When using petroleum-derived CB (petroleum-derived carbon black) as a pigment, use petroleum-derived carbon black (CI Pigment Black 7, manufactured by Mitsubishi Chemical Corporation) instead of Binchotan charcoal.

[0111] <Crosslinking of resins> 100 parts by mass of the pigment dispersion obtained above are placed in a screw-top glass bottle, and 1.27 parts by mass of trimethylolpropane polyglycidyl ether (Denacol EX-321, manufactured by Nagase ChemteX Corporation, molecular weight 302, epoxy equivalent 139, water solubility 27%), a crosslinking agent having 3 epoxy groups in one molecule, is added so that 40 mol% of the total carboxyl groups of the resin are crosslinked. The bottle is then tightly sealed and heated at 70°C for 5 hours while stirring with a stirrer. After 5 hours, the temperature is lowered to room temperature, and the mixture is filtered using a 25 mL needleless syringe (manufactured by Terumo Corporation) fitted with a 5 μm filter (acetylcellulose membrane, outer diameter: 2.5 cm, manufactured by Fujifilm Corporation) to obtain a crosslinked resin dispersion pigment.

[0112] 1.2. Preparation of non-crosslinked resin-dispersed pigments In the above, the non-crosslinked resin dispersed pigment was prepared in the same manner as the crosslinked resin dispersed pigment, except that the <resin crosslinking> step was omitted.

[0113] 1.3. Adjustment of Acrylic EM In a reaction vessel equipped with a stirrer, reflux condenser, dropper, and thermometer, 900 g of deionized water and 3 g of sodium lauryl sulfate were charged, and the temperature was raised to 70°C while stirring and purging with nitrogen. Maintaining the internal temperature at 70°C, 4 g of potassium persulfate was added as a polymerization initiator. After dissolution, an emulsion prepared by stirring 450 g of deionized water, 3 g of sodium lauryl sulfate, 20 g of acrylamide, 130 g of styrene, 780 g of 2-ethylhexyl acrylate, 30 g of methacrylic acid, and 2 g of ethylene glycol dimethacrylate was continuously added dropwise to the reaction solution over 4 hours. After the addition was complete, the mixture was allowed to mature for 3 hours. After the resin dispersion was cooled to room temperature, deionized water and aqueous ammonia were added to adjust the solid content to 40% by weight and the pH to 8.

[0114] 2. Evaluation Method 2.1. Storage Stability Each ink composition is left in a 60°C environment for one week. Then, the range of variation in the volume-average particle diameter of pigment particles in the ink after the period of exposure is calculated compared to the volume-average particle diameter of pigment particles in the ink before exposure, and evaluated according to the following criteria. The volume-average particle diameter is measured using the ELSZ-1000 (product name, dynamic scattering particle size analyzer, manufactured by Otsuka Electronics Co., Ltd.). (Evaluation Criteria) A: The fluctuation range is less than ±5%. B: The fluctuation range is ±5% or more, and less than ±10%. C: Fluctuation range is ±10% or more, and less than ±20%. D: Fluctuation range of ±20% or more.

[0115] 2.2. Clogging recovery The ink composition was filled into a modified PX-M791FT printer (manufactured by Seiko Epson Corporation), and a nozzle check was performed to confirm that all nozzles were ejecting ink. After that, the print head was left in a defapped state at 40 degrees Celsius for 7 days. After this period, the number of cleaning cycles required for all nozzles to recover was evaluated according to the evaluation criteria below. (Evaluation Criteria) A: Cleaning done no more than twice. B: Cleaned 3 times. C: Cleaning cycle: 4 or 5 times. D: The problem did not resolve after 5 cleaning attempts.

[0116] 2.3.Abrasion resistance Each ink composition was filled into a modified PX-M791FT printer (manufactured by Seiko Epson Corporation), and Xerox P paper (Fuji Xerox copy paper, basis weight 64 g / m²) was used for testing. 2 26 letters of the alphabet in 20-point size are recorded on a recording medium (paper thickness 88 μm). Immediately after recording, the recording medium is fixed to a flat surface where it is placed horizontally. Five minutes after recording, the letters are rubbed with a line marker "OPTEX CARE" (product name manufactured by Zebra Co., Ltd.), and then evaluated according to the following evaluation criteria based on the degree of ink bleeding. (Evaluation Criteria) A: No color bleeding occurs even after rubbing it three times. B: No color bleeding occurs after rubbing twice, but color bleeding occurs after rubbing three times. C: No color bleeding occurs after rubbing once, but color bleeding occurs after rubbing twice. D: Color bleeding occurs when rubbed once.

[0117] 2.4.Discharge stability The SC-T3150 modified printer (manufactured by Seiko Epson Corporation) is filled with the ink after the storage stability evaluation described above. After checking the nozzles to confirm that all nozzles are ejecting ink, a 5-hour recording is performed on a recording medium (thin plain paper roll; manufactured by Epson), and an ejection test is performed after recording. (Evaluation Criteria) A: The number of nozzles that do not dispense is 3% or less of the total number of nozzles. B: The number of nozzles that do not dispense fluid relative to the total number of nozzles is between 3% and 7%. C: The number of nozzles that did not dispense more than 7% of the total number of nozzles.

[0118] 2.5. Biomass content The biomass content of each component of the ink composition is determined in accordance with ASTM D6866. 12 It is an isotope of C. 14The calculation is based on the concentration of C. 14 The concentration of C is measured by accelerator mass spectrometry (AMS). The biomass content of the solids in the ink composition is calculated based on the biomass content of each component of the solids in the ink composition.

[0119] 3. Evaluation Results Table 1 shows that all of the examples of inkjet ink compositions of this embodiment, which contain a bio-derived carbon black pigment and are resin-dispersed pigments in which the pigment is dispersed in a cross-linked resin, exhibit excellent ejection stability. Furthermore, storage stability, clogging recovery, and abrasion resistance tend to be improved as well. In contrast, the comparative examples that are not resin-dispersed pigments in which the pigment is dispersed in a cross-linked resin all exhibit poor discharge stability. Furthermore, some also have inferior storage stability, clogging recovery, and abrasion resistance. Furthermore, a reference example that does not contain bio-derived carbon black pigment does not exhibit inferior discharge stability despite not being a resin-dispersed pigment in which the pigment is dispersed in a cross-linked resin. [Explanation of Symbols]

[0120] 10...Recording device, 11...Transport path, 12...Feeding section, 14...Transporting section, 16...Belt transport section, 18...Recording section, 20...Fd discharge section, 22...Fd mounting section, 24...Reversal path section, 26...Fu discharge section, 28...Fu mounting section, 30...Feeding tray, 32...Feeding roller, 34...Transporting drive roller, 36...Transporting driven roller, 38...First roller, 40...Second roller, 42...Endless belt, 42a...Upper section of endless belt, 44...Support, 46...Head holder, 48...Inkjet head, 50...First branching section, 52...Reversal path, 54...Second branching section, 56...Discharge roller pair, 64...Discharge drive roller, 68...Drive shaft, 76...Mounting surface, 78...Convex section, 80...First biasing member, 82...Second biasing member, 84, 86...Support shaft, P...Recording medium.

Claims

1. It contains a pigment that is bio-derived carbon black and a solvent. The aforementioned pigment is a resin-dispersed pigment dispersed in a crosslinked resin. The solvent includes water, An inkjet ink composition, which is a water-based ink.

2. The aforementioned pigment contains plant-derived carbon black. The inkjet ink composition according to claim 1.

3. The aforementioned resin is a resin crosslinked with a compound having two or more functional groups selected from the group consisting of epoxy groups, isocyanate groups, azilidino groups, amino groups, and oxazoline groups in its molecule. The inkjet ink composition according to claim 1.

4. The aforementioned resin includes an acrylic resin. The inkjet ink composition according to claim 1.

5. The solvent includes organic solvent A having an octanol / water partition coefficient of 0 to 1. The inkjet ink composition according to claim 1.

6. The volume-average particle size of the pigment is 110 nm or less. The inkjet ink composition according to claim 1.

7. The mass ratio of the resin to the pigment is 0.1 to 0.

7. The inkjet ink composition according to claim 1.

8. Contains fixing resin, The inkjet ink composition according to claim 1.

9. The invention comprises an ink application step of ejecting an inkjet ink composition according to any one of claims 1 to 8 from an inkjet head and adhering it to a recording medium. Recording method.

10. An inkjet ink composition according to any one of claims 1 to 8, Ink set.

11. A pigment dispersion used for preparing an inkjet ink composition according to any one of claims 1 to 8, It contains a pigment that is bio-derived carbon black and a solvent. The aforementioned pigment is a resin-dispersed pigment dispersed in a crosslinked resin. The solvent includes water, It is an aqueous pigment dispersion. Pigment dispersion.

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