Inkjet ink composition and recording method

Abstract

This invention provides an inkjet ink composition with excellent redispersibility, storage stability, clogging recovery, and abrasion resistance. [Solution] The solution contains a pigment, a resin binder, and an organic solvent, wherein the pigment includes a resin-dispersed pigment dispersed in a crosslinked resin, the resin binder includes a self-emulsifying resin binder, and the organic solvent has an octanol / water partition coefficient logP ow An inkjet ink composition containing an organic solvent with a value between 0 and 1.

Description

[Technical Field]

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

[0002] Inkjet recording methods are rapidly developing in various fields because they enable the recording of high-resolution images with relatively simple equipment. For example, Patent Document 1 discloses an ink composition comprising a pigment, an organic compound, and water, with the aim of providing an ink composition that suppresses the generation of foreign matter at the gas-liquid interface, resulting in excellent continuous printing stability and excellent image fastness. The resolubility index, which is the time it takes for the ink viscosity to return to its original state when the mass decreases to 50% and the viscosity increases, by adding the same amount of water as the decreased mass, is 0.5 minutes or more and 10 minutes or less. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2018-109119 [Overview of the project] [Problems that the invention aims to solve]

[0004] As described in Patent Document 1, adding resin particles to the ink composition can be considered from the viewpoint of improving image robustness, such as resistance to line markers. However, on the other hand, the addition of resin particles tends to cause clogging of the inkjet head. [Means for solving the problem]

[0005] The inkjet ink composition of the present invention contains a pigment, a resin binder, and an organic solvent, wherein the pigment comprises a resin-dispersed pigment dispersed in a crosslinked resin, the resin particles comprise a self-emulsifying resin binder, and the organic solvent comprises an octanol / water partition coefficient logP owAn inkjet ink composition, which is an aqueous ink containing an organic solvent having a value of 0 to 1.

[0006] The recording method of the present invention is to attach ink using the above inkjet ink composition to a recording medium.

Brief Description of Drawings

[0007] [Figure 1] It is Table 1 showing the composition of each composition used in the examples and the evaluation results thereof. [Figure 2] It is Table 2 showing the composition of each composition used in the examples and the evaluation results thereof. [Figure 3] It is Table 3 showing the composition of each composition used in the examples and the evaluation results thereof. [Figure 4] It is a diagram showing an example of a recording apparatus used in the recording method of the present embodiment.

Modes for Carrying Out the Invention

[0008] Hereinafter, the present embodiment will be described in detail with reference to the drawings as necessary. However, the present invention is not limited thereto, and various modifications are possible without departing from the gist thereof. In the drawings, the same elements are denoted by the same reference numerals, and redundant descriptions are omitted. Also, the positional relationships such as up, down, left, and right are based on the positional relationships shown in the drawings unless otherwise specified. Furthermore, the dimensional ratios in the drawings are not limited to the illustrated ratios.

[0009] 1. Inkjet Ink Composition The inkjet ink composition according to the present embodiment contains a pigment, a resin binder, and an organic solvent. The pigment includes a resin-dispersed pigment dispersed in a crosslinked resin. The resin binder includes a self-emulsifying resin binder. The organic solvent includes an organic solvent having an octanol / water partition coefficient logP ow value (hereinafter, also referred to as "logP ow value") of 0 to 1.

[0010] When the abrasion resistance of the recording material is low, ink peeling is likely to occur when the recording material is rubbed, and bleeding is likely to occur when tracing the recording surface with a line marker. To improve this, it is conceivable to use resin particles, but there is a problem that the addition of resin particles tends to cause clogging of the inkjet head.

[0011] Therefore, in the present embodiment, a resin-dispersed pigment dispersed in a crosslinked resin, a self-emulsifying resin binder, and an organic solvent having a predetermined logP ow value are used in combination.

[0012] The self-emulsifying resin binder is excellent in redispersibility and clogging recovery while improving abrasion resistance. However, in order to disperse such a self-emulsifying resin binder in water, an organic solvent having a high logP ow value (hereinafter also referred to as "high logP ow solvent") needs to be used in combination. However, the high logP ow solvent dissolves the dispersant resin that disperses the pigment, which may cause problems such as a decrease in the dispersion stability of the pigment, deterioration of storage stability, and deterioration of clogging recovery. Therefore, as the pigment, a resin-dispersed pigment in which the pigment is dispersed by a crosslinked resin is used. Since such resin-dispersed pigments have the dispersant resins that disperse the pigments crosslinked together, they are difficult to peel from the pigment and are difficult to dissolve in high logP ow solvents. This enables the combined use of the self-emulsifying resin binder and the high logP ow solvent.

[0013] Hereinafter, the components that can be included and the manufacturing method in the ink composition according to the present embodiment will be described in detail.

[0014] 1.1. Pigment Generally, pigments can be broadly classified into two types based on their dispersion form: self-dispersing pigments, which disperse on their own without the use of a dispersant, and resin-dispersed pigments, which are dispersed by a dispersant. Resin-dispersed pigments are pigments that are dispersed in a solvent by the dispersant adsorbing, adhering to, or coating the pigment surface. Typical resins used as dispersants include water-insoluble resins and water-soluble resins. In this embodiment, a crosslinked resin is used as the dispersant for the pigment. Hereinafter, pigments dispersed by a crosslinked resin will also be called "crosslinked resin-dispersed pigments." Because the pigment surface is at least partially coated with the crosslinked resin in this way, the dispersant is less likely to detach from the pigment surface upon dissolution, resulting in a high logP ow Dispersion breakdown becomes less likely even in the presence of solvents. As a result, high logP ow This ink exhibits excellent pigment dispersion stability even in the presence of solvents, resulting in improved storage stability and clogging recovery.

[0015] The method for producing a crosslinked resin dispersion pigment 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 resin with a crosslinking agent to coat the surface of the pigment.

[0016] The crosslinked resin used as a dispersant 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 groups that react with the reactive functional group.

[0017] Examples of monomers constituting a resin having reactive functional groups include monomers having ionic groups and hydrophobic monomers, and other monomers may also be included. The resin having reactive functional groups may also be a copolymer of monomers having ionic groups and hydrophobic monomers.

[0018] 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.

[0019] Among these, anionic monomers are preferred as monomers having an ionic group, unsaturated carboxylic acid monomers are preferred, and acrylic acid and methacrylic acid are more preferred.

[0020] The content of 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 monomers. When the content of monomers having ionic groups is within the above range, redispersibility, clogging recovery, and storage stability tend to be further improved.

[0021] 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.

[0022] Among these, styrene-based monomers are preferred as hydrophobic monomers, with styrene, α-methylstyrene, and 2-methylstyrene being more preferred.

[0023] The hydrophobic monomer content is preferably 30-99% by mass, 50-90% by mass, 60-80% by mass, or 65-75% by mass, relative to the total amount of monomers. When the hydrophobic monomer content is within the above range, redispersibility, clogging recovery, and storage stability tend to be improved.

[0024] 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]. These can be used individually or in combination of two or more.

[0025] The chain transfer agent used when polymerizing resins having reactive functional groups is not particularly limited, but examples include anionic polymer chain transfer agents 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; 1-amino-2-methyl-2-propanethol, 2-aminoethanethiol, 2-diethylaminoethanethiol, Examples of polymerization chain transfer agents include those having cationic groups such as 2-dimethylaminoethanethiol, 4-aminothiophenol, dithiodianiline, 3,4,5,6-tetrahydro-2-pyrimidinethiol, and 2-mercaptothiazoline; and those 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.

[0026] Furthermore, 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. The number of reactive functional groups in the crosslinking agent is preferably two or more, and preferably three or more. By using a resin crosslinked with such a compound, the storage stability and clogging recovery properties of the inkjet ink composition tend to be further improved.

[0027] While such crosslinking agents are not particularly limited, compounds having two or more epoxy groups, oxazoline groups, or isocyanate groups in their molecules are more preferred. Using resins crosslinked with such compounds tends to improve the storage stability and clogging recovery properties of inkjet ink compositions.

[0028] Among these, there are no particular limitations on the polyfunctional epoxy compounds, 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, hydrogenated bisphenol A type diglycidyl ether, and the like.

[0029] 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.

[0030] There are no particular restrictions on the pigments used in the crosslinked resin dispersion pigments, but for example, CI Pigment Yellow 12, 13, 14, 17, 20, 24, 74, 83, 86, 93, 94, 95, 97, 109, 110, 117, 120, 125, 128, 129, 137, 138, 139, 147, 148, 150, 151, 153, 154, 155, 166, 168, 175, 180, 181, 185, 191; CI Pigment Orange 16, 36, 43, 51, 55, 59, 61, 64, 71, 73; CI Pigment Red 4, 5, 9, 23, 48, 49, 52, 53, 57, 97, 112, 122, 12 Examples include 3, 144, 146, 147, 149, 150, 166, 168, 170, 176, 177, 180, 184, 185, 192, 202, 207, 214, 215, 216, 217, 220, 221, 223, 224, 226, 227, 228, 238, 240, 242, 254, 255, 264, 269, 272, CI Pigment Violet 19, 23, 29, 30, 37, 40, 50, CI Pigment Blue 15, 15:1, 15:3, 15:4, 15:6, 22, 60, 64, CI Pigment Green 7, 36, CI Pigment Black 7, CI Pigment White 6, and others.

[0031] The content of the crosslinked resin dispersion pigment is preferably 1 to 10% by mass, 3 to 8% by mass, and 4 to 6% by mass, relative to the total amount of the inkjet ink composition. By setting the content of the crosslinked resin dispersion pigment within the above range, redispersibility, clogging recovery, and storage stability tend to be further improved.

[0032] 1.2. Resin Binder Typically, resin binders include self-emulsifying resin binders that stabilize as a resin emulsion on their own without the use of emulsifiers, and emulsifier-type resin binders that stabilize as a resin emulsion using emulsifiers, depending on their dispersion form.

[0033] Self-emulsifying resin binders have a high water concentration in the ink and self-emulsify, but water evaporates at nozzles, etc., resulting in high logPow The self-emulsifying resin binder dissolves when the solvent concentration increases. Then, when the water concentration increases again due to the supply of new ink, it self-emulsifies and redisperses again. In this way, the self-emulsifying resin binder contributes to improved abrasion resistance of the resulting recording material, and because dissolution and dispersion are reversible, the ink does not become a foreign substance or cause clogging even after drying, and it has excellent redispersibility and clogging recovery properties.

[0034] The monomers constituting the self-emulsifying resin binder are not particularly limited, and hydrophobic monomers and hydrophilic monomers can be used. While not particularly limited, examples of hydrophobic monomers 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, and tert-butyl (meth)acrylate. Examples include alkyl(meth)acrylates such as lylate, isoamyl(meth)acrylate, isooctyl(meth)acrylate, isodecyl(meth)acrylate, isododecyl(meth)acrylate, isostearyl(meth)acrylate, and dicyclopentanyl(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.

[0035] Furthermore, hydrophilic monomers 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 phosphate monomers such as vinyl phosphonic acid, vinyl phosphate, bis(methacryloxyethyl) phosphate, diphenyl-2-acryloyloxyethyl phosphate, and diphenyl-2-methacryloyloxyethyl phosphate; and N,N-dimethylaminoethyl (meth)acrylate. Examples include unsaturated tertiary amine-containing monomers such as 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 ionic monomers such as 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.

[0036] The self-emulsifying resin binder may be a copolymer of hydrophilic monomers, hydrophobic monomers, etc. The copolymer may be a random polymer or a block polymer. Furthermore, the block polymer may be a diblock polymer, a triblock polymer, or have more than one block. In addition, the block may be composed of a single monomer or of two or more types of monomers. In the case of a block containing two or more types of monomers, the two or more monomers may be arranged randomly.

[0037] Among these, it is preferable that the self-emulsifying resin binder contains a block polymer consisting of an A block and a B block with a higher acid value than the A block. Examples of such AB block polymers include those having a highly hydrophobic A block and a highly hydrophilic B block. As a result, the self-emulsifying resin binder is more likely to adopt a micelle structure in which the hydrophobic block faces the center and the hydrophilic block faces the outside, which tends to improve solubility in water, as well as redispersibility, clogging recovery, and storage stability. Furthermore, having a hydrophobic portion allows for a high logP ow Due to its excellent solubility in solvents, it tends to have improved clogging recovery and redispersibility.

[0038] In this embodiment, the acid value can be calculated from the proportion of monomers containing acidic groups among the monomers in the block.

[0039] The monomers constituting block B may include monomers having an acidic group, as well as monomers without an acidic group, if necessary. Similarly, the monomers constituting block A may include monomers having an acidic group, as long as the acid value does not exceed that of block B, in addition to monomers without an acidic group.

[0040] Examples of monomers having an acidic group 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, which are among the hydrophilic monomers mentioned above; unsaturated sulfonic acid monomers such as styrene sulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, and 3-sulfopropyl (meth)acrylate; and unsaturated phosphoric acid monomers such as vinylphosphonic acid, vinyl phosphate, bis(methacryloxyethyl) phosphate, diphenyl-2-acryloyloxyethyl phosphate, and diphenyl-2-methacryloyloxyethyl phosphate.

[0041] Furthermore, while there are no particular limitations on monomers that do not have an acidic group, other monomers such as hydrophobic monomers can be mentioned.

[0042] The content of monomers having acidic groups in block B is preferably 1 to 50% by mass, 5 to 40% by mass, 10 to 30% by mass, and 15 to 25% by mass, relative to the total amount of monomers in block B. When the content of monomers having acidic groups in block B is within the above range, the abrasion resistance, clogging recovery, and redispersibility tend to be further improved.

[0043] In this embodiment, the block polymer consisting of block A and block B, which has a higher acid value than block A, is preferably a block polymer having two types of hydrophobic monomers, or a block polymer having one type each of hydrophobic monomers and hydrophilic monomers. The hydrophobic monomers contained in block A and block B may be the same.

[0044] Methods for obtaining such polymers are not particularly limited, but include free radical polymerization and living radical polymerization. Among these, living radical polymerization is preferred in order to obtain a precise polymer structure. Living radical polymerization methods are not particularly limited, but include the NMP method using nitroxides, the ATRP method utilizing the redox reaction of metal complexes, the RAFT method using dithiocarboxylic acid esters, methods using cobalt catalysts, the TERP method using tellurium compounds, iodine transfer polymerization using iodine, and the RTCP method using iodide as an initiator and an organic compound as a catalyst.

[0045] The initiator is not particularly limited as long as it is a known initiator used in radical polymerization, but examples include azo compounds such as azobis(isobutyronitrile) and 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile); and peroxides of benzoyl peroxide and dicumyl peroxide.

[0046] The self-emulsifying resin binder preferably has an octanol / water partition coefficient logP ow It is solvent polymerized in an organic solvent with a value of 0 to 1. Using such a self-emulsifying resin binder tends to improve redispersibility and clogging resistance. Note that logP used here ow Organic solvents with a value between 0 and 1 are included in the ink's logP ow It may be the same as or different from organic solvent A, whose value is between 0 and 1.

[0047] The content of the self-emulsifying resin binder is preferably 0.1 to 7% by mass, 0.5 to 5% by mass, and 1.5 to 3% by mass, relative to the total amount of the inkjet ink composition. By setting the content of the self-emulsifying resin binder within the above range, the abrasion resistance and clogging recovery tend to be further improved.

[0048] 1.3. Organic Solvents The ink composition of this embodiment has an octanol / water partition coefficient logP ow Contains organic solvent A with a value between 0 and 1, and optionally logP ow It may also contain organic solvent B with a value other than 0 to 1.

[0049] logP of organic solvent A ow The values ​​are preferably 0.1 to 1, 0.2 to 0.9, 0.3 to 0.8, 0.4 to 0.7, and 0.5 to 0.6. logP of organic solvent A ow The value being within the above range results in excellent clogging recovery. Organic solvent A is logP ow A value greater than or equal to 0 indicates high resin solubility, and logP ow A value of 1 or less indicates excellent compatibility with water. Therefore, redispersibility and clogging recovery are improved.

[0050] In this embodiment, the octanol / water partition coefficient logP ow The value refers to the value defined in OECD Test Guideline 107. logP owA higher value indicates higher hydrophobicity, while a lower value indicates higher hydrophilicity.

[0051] logP of compounds ow The 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).

[0052] Organic solvents A and B are not particularly limited, but examples include monoalcohols, glycols, ketones, ethers, trihydric alcohols, and lactam compounds.

[0053] Examples of ethers include dimethyl ether, methyl ethyl ether, diethyl ether, isopropyl methyl ether, isopropyl ethyl ether, and glycol ethers.

[0054] Glycol ethers can be any monoether or diether of alkylene glycol, for example, 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, tripropylene Examples include alkylene glycol monoalkyl ethers such as ethylene glycol monomethyl ether and 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.

[0055] 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.

[0056] Glycols include alkanediols and condensates of alkanediols, which have a structure in which the hydroxyl groups between molecules are condensed. They are also called alkylene glycols.

[0057] Alkanediols are formed in which an alkane is substituted with two hydroxyl groups. Alkanediols of alkanes having 2 to 10 carbon atoms are preferred. Furthermore, alkanediols of alkanes having 5 to 9 carbon atoms are preferred, and alkanediols of alkanes having 6 to 8 carbon atoms are preferred. On the other hand, alkanediols of alkanes having 2 to 4 carbon atoms are also preferred. In addition, 1,2-alkanediols are preferred.

[0058] Condensates having a structure in which the hydroxyl groups of alkanediols are fused together are preferably condensates having a structure in which the hydroxyl groups of diols of alkanes having 2 to 4 carbon atoms are fused together.

[0059] Glycols include, for example, ethylene glycol, propylene glycol, 1,2-propanediol, 1,2-butanediol, 1,2-pentanediol, 1,2-hexanediol, 1,2-octanediol, alkanediols such as 1,3-propanediol, 1,4-butanediol, and 1,6-hexanediol; and glycols such as tetramethylene glycol, hexamethylene glycol, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, polypropylene glycol, and (poly)tetramethylene glycol.

[0060] Examples of ketones include acetone, methyl ethyl ketone, and diethyl ketone.

[0061] Examples of trihydric alcohols include glycerin and trimethylolpropane.

[0062] Examples of lactam compounds include 2-pyrrolidone, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, and N-hydroxyethylpyrrolidone (HEP).

[0063] Organic solvent A is one of the organic solvents mentioned above, with an octanol / water partition coefficient logP. ow These are values ​​between 0 and 1.

[0064] Among these, organic solvent A is preferably one of alkanediols, monoalcohols, ketones, or ethers, and more preferably one of glycol ethers or alkanediols. Including such an organic solvent tends to further improve storage stability and clogging recovery.

[0065] Examples of such organic solvent A include isopropyl methyl ether, diethylene glycol monobutyl ether, 1,2-hexanediol methyl ethyl ketone, isopropyl alcohol, and methyl ethyl ketone.

[0066] The content of organic solvent A is preferably 0.5 to 15% by mass, 3 to 11% by mass, 5 to 9% by mass, or 6 to 8% by mass, relative to the total amount of ink. When the content of organic solvent A is within the above range, the redispersibility and clogging recovery tend to be further improved.

[0067] The content of organic solvent B is preferably 0-24% by mass, 5-22% by mass, 10-20% by mass, or 15-19% by mass, relative to the total amount of ink. When the content of organic solvent B is within the above range, the discharge stability tends to improve and the compatibility with organic solvent A tends to improve.

[0068] The total content of organic solvents, including organic solvents A and B, is preferably 0.5 to 30% by mass, 5 to 29% by mass, 10 to 28% by mass, 15 to 27% by mass, and 20 to 26% by mass, relative to the total amount of ink. When the organic solvent content is within the above range, the discharge stability tends to improve and the compatibility of organic solvent A tends to improve.

[0069] 1.4. Surfactants The ink composition in this embodiment may contain a surfactant. Examples of surfactants include silicone-based surfactants, acetylene glycol-based surfactants, and fluorine-based surfactants. One surfactant may be used alone, or two or more may be used in combination.

[0070] Among these, acetylene glycol-based surfactants are preferred. Commercially available acetylene glycol-based surfactants are not particularly limited, but examples include Olfin E1010, EXP4200, Surfinol SE, Surfinol 440, and Surfinol 104 (manufactured by Nisshin Chemical Industry Co., Ltd.). Commercially available silicone-based surfactants are not particularly limited, but examples include KF-640 and KF-6013 (manufactured by Shin-Etsu Silicone Co., Ltd.).

[0071] The ink composition in this embodiment preferably contains an acetylene glycol-based surfactant having an HLB value of 5 or less. The inclusion of an acetylene glycol-based surfactant with an HLB value of 5 or less improves the ink's penetration into the recording medium. Furthermore, it enhances the wettability of the ink to the material in the ink supply system, removing air bubbles, thus tending to improve clogging recovery. On the other hand, acetylene glycol-based surfactants with an HLB value of 5 or less generally have low solubility in water and are prone to phase separation; however, in this embodiment, a high logP surfactant is used. ow By using a solvent, the solubility of acetylene glycol-based surfactants can be increased, and phase separation can be suppressed.

[0072] In this embodiment, the HLB (Hydrophile-Lipophile Balance) value is a value proposed by Davis et al. to evaluate the hydrophilicity of a compound, and is a numerical value obtained by the Davis method as defined in the literature "JTDavies and EKRideal, "Interface Phenomena" 2nd ed. Academic Press, New York 1963," and is shown as the value calculated by the following formula. The HLB value is a value that evaluates the hydrophilicity of a compound, and the larger the HLB value, the higher the hydrophilicity, and the smaller the HLB value, the higher the hydrophobicity. HLB value = 7 + Σ[1] - Σ[2] (In the formula, [1] represents the number of hydrophilic groups, and [2] represents the number of hydrophobic groups.)

[0073] Commercially available acetylene glycol-based surfactants with an HLB value of 5 or less are not particularly limited, but examples include Surfinol 104 (manufactured by Nisshin Chemical Industry Co., Ltd.).

[0074] The content of the acetylene glycol-based surfactant is preferably 0.1 to 3% by mass, 0.5 to 2.5% by mass, or 1.0 to 2.0% by mass, relative to the total amount of the ink composition. By keeping the surfactant content within the above range, the clogging recovery performance tends to improve further.

[0075] The surfactant content is preferably 0.1 to 4.0% by mass, 0.3 to 3.0% by mass, 0.5 to 2.5% by mass, or 1.0 to 2.0% by mass, relative to the total amount of the ink composition. Keeping the surfactant content within these ranges tends to further improve the clogging recovery performance.

[0076] 1.5. pH adjusters The inkjet ink composition in this embodiment may optionally contain a pH adjuster. Examples of pH adjusters include inorganic acids (e.g., sulfuric acid, hydrochloric acid, nitric acid, etc.), inorganic bases (e.g., lithium hydroxide, sodium hydroxide, potassium hydroxide, ammonia, etc.), organic acids (e.g., adipic acid, citric acid, succinic acid, etc.), and organic bases (triethanolamine, diethanolamine, monoethanolamine, triisopropanolamine, diisopropanolamine, trishydroxymethylaminomethane). A single pH adjuster may be used, or two or more may be used in combination.

[0077] 1.6.Water The inkjet ink composition of this embodiment is a water-based ink containing water. A water-based inkjet ink composition is an inkjet ink composition that contains at least water as the main solvent component of the ink.

[0078] The water content is preferably 40-99% by mass, 50-98% by mass, 60-95% by mass, 63-85% by mass, 64-75% by mass, 65-70% by mass, or 66-68% by mass, relative to the total amount of the inkjet ink composition. Keeping the water content within these ranges tends to improve storage stability.

[0079] 1.7. 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.

[0080] 2. Inkjet recording method The inkjet recording method according to this embodiment includes a step of using a predetermined inkjet head to eject the inkjet ink composition from the inkjet head and deposit it onto a recording medium.

[0081] 3. Inkjet recording device The inkjet recording apparatus of this embodiment comprises the above-mentioned ink composition and an inkjet head having a nozzle for ejecting the above-mentioned ink composition onto a recording medium, and preferably further comprises a supply channel through which the above-mentioned ink composition flows and is connected to the inkjet head, and a filter unit provided in the supply channel of the inkjet head.

[0082] Figure 4 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 4. In the XYZ coordinate system shown in Figure 4, 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.

[0083] 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 8, 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.

[0084] 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.

[0085] 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.

[0086] 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.

[0087] 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.

[0088] The recording unit 8 comprises a line-type inkjet head 48 and a head holder 46 that holds the inkjet head 48. The recording unit 8 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 opposite 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.

[0089] 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 8. 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 8 so that the side opposite to the original recording surface faces the inkjet head 48.

[0090] 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.

[0091] 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.

[0092] 4. Recording media The recording medium used in this embodiment is not particularly limited and includes, for example, an absorbent recording medium, a low-absorbent recording medium, or a non-absorbent recording medium, with an absorbent recording medium being preferred.

[0093] Examples of absorbent recording media include plain paper such as electrophotographic paper with high ink permeability, and inkjet paper (inkjet-specific paper equipped with an ink-absorbing layer composed of silica particles or alumina particles, or an ink-absorbing layer composed of hydrophilic polymers such as polyvinyl alcohol (PVA) or polyvinylpyrrolidone (PVP)).

[0094] 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.

[0095] 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; metal plates or plastic films made by vapor deposition of these metals; plates of alloys 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.

[0096] 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 redispersibility, storage stability, clogging recovery, and abrasion resistance. [Examples]

[0097] 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.

[0098] Figures 1 to 3 are shown, along with Tables 1 to 3, which illustrate the composition of each ink composition in the examples and comparative examples, and the evaluation results thereof.

[0099] 1. Preparation of inkjet ink composition A dispersion was prepared by mixing and stirring the ingredients 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 percentages. Furthermore, in the table, each numerical value represents the mass percentage of the solid content of the component.

[0100] The details of the product ingredients used in Tables 1 and 3 are as follows.

[0101] [Pigments] • Cross-linked resin dispersion material (see adjustment example below) [binder] • Resin binder (see adjustment example below) [Organic solvents] • BDG (Diethylene glycol monobutyl ether, logP ow (Value 0.56) ·12HD(1,2-hexanediol, logP ow (Value 0.57) IPA (isopropyl alcohol, logP ow (Value 0.05) • MEK (methyl ethyl ketone, logP) ow (Value 0.29) • MIPE (isopropyl methyl ether, logP ow (Value 1.0) Gly (glycerin, logP) ow (Value -1.8) TEG (Triethylene Glycol, logP) ow (Value -1.8) ·2P(2-pyrrolidone, logP) ow (Value -0.9) [Surfactants] • S104 (Surfinol 104, acetylene glycol-based surfactant, HLB value 4, manufactured by Nisshin Chemical Industry Co., Ltd.) • E1010 (Acetylene glycol-based surfactant, HLB value 13-14, manufactured by Nisshin Chemical Industry Co., Ltd.) [pH adjuster] • TEA (triethanolamine) [water] • Ion-exchanged water

[0102] 1.1. Preparation of Crosslinked Resin Dispersed Pigments <Preparation of Crosslinked Resin Dispersed Pigment C1> (1) Preparation of polymer solution [Polymer Solution 1] 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 polymer solution containing carboxyl groups (solid content concentration 55% by mass, weight-average molecular weight of polymer: 13900).

[0103] [Polymer Solution 2] Polymer solution 2 is obtained by the same procedure as polymer solution 1, except that the monomer mixture is obtained by mixing 31 parts by mass of acrylic acid, 57 parts by mass of styrene, and 12 parts by mass of α-methylstyrene.

[0104] (2) Preparation of Pigment Aqueous Dispersion [Pigment aqueous dispersion 1] The polymer solution 1 obtained above is dried under reduced pressure to obtain 24 parts by mass of polymer. 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 polymer, and the mixture is neutralized so that the ratio of moles of sodium hydroxide to moles of carboxyl groups of the polymer 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 polymer dispersion (average particle size of polymer particles: 15 nm, solid content concentration 11% by mass).

[0105] To the obtained polymer dispersion, 76 parts by mass of cyanide pigment (PB15:3, manufactured by Dainichi Seika Kogyo Co., Ltd.) is added, and the mixture is 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 obtained mixture is dispersed in 10 passes at a pressure of 200 MPa using a microfluidizer (manufactured by Microfluidics). The obtained 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, and then ion-exchanged water is added to obtain pigment aqueous dispersion 1 (average particle size of pigment-containing polymer particles: 121 nm) (pigment: 76% by mass, polymer: 24% by mass).

[0106] [Pigment aqueous dispersion 2] Pigment aqueous dispersion 2 is obtained using the same procedure as for pigment aqueous dispersion 1, except that magenta pigment (PV-19, manufactured by Dainichi Seika Kogyo Co., Ltd.) is used as the pigment.

[0107] [Pigment aqueous dispersion 3] Pigment aqueous dispersion 3 is obtained using the same procedure as for pigment aqueous dispersion 1, except that yellow pigment (PY-74, manufactured by Dainichi Seika Kogyo Co., Ltd.) is used as the pigment.

[0108] [Pigment aqueous dispersion 4] Pigment aqueous dispersion 4 is obtained using the same procedure as for pigment aqueous dispersion 1, except that black pigment (PBk-7, manufactured by Dainichi Seika Kogyo Co., Ltd.) is used as the pigment.

[0109] [Pigment aqueous dispersion 5] Pigment aqueous dispersion 5 is obtained using the same procedure as for pigment aqueous dispersion 1, except that the amount of 5N sodium hydroxide aqueous solution added to the polymer solution is 7.3 parts by mass.

[0110] [Pigment aqueous dispersion 6] A pigment aqueous dispersion 6 is obtained using the same procedure as for pigment aqueous dispersion 1, except that polymer solution 2 is used.

[0111] (3) Preparation of crosslinked resin dispersed pigments [Crosslinked resin dispersed pigment C1] 100 parts by mass (22% solids) of the pigment aqueous dispersion 1 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 polymer 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 crosslinked resin dispersed pigment C1.

[0112] [Crosslinked resin dispersed pigment M] Using the aqueous pigment dispersion 2, the same procedure as for the crosslinked resin dispersed pigment C1 is followed to obtain the crosslinked resin dispersed pigment M.

[0113] [Crosslinked resin dispersed pigment K] Using the pigment aqueous dispersion 3, the same procedure as for the crosslinked resin dispersed pigment C1 is followed to obtain the crosslinked resin dispersed pigment K.

[0114] [Crosslinked resin dispersed pigment Y] Using the pigment aqueous dispersion 4, the same procedure as for the crosslinked resin dispersed pigment C1 is followed to obtain the crosslinked resin dispersed pigment Y.

[0115] [Crosslinked resin dispersed pigment C2] Using the pigment aqueous dispersion 5, the same procedure as for the crosslinked resin dispersed pigment C1 is followed to obtain the crosslinked resin dispersed pigment C2.

[0116] [Crosslinked resin dispersed pigment C3] Using the pigment aqueous dispersion 6, the same procedure as for the crosslinked resin dispersed pigment C1 is followed to obtain the crosslinked resin dispersed pigment C3.

[0117] 1.2. Adjustment of the resin binder [Resin Binder 1] In a 1 L separable flask equipped with a stirring blade, condenser, thermometer, and nitrogen inlet tube, add 350.5 parts by mass of diethylene glycol monobutyl ether (logPow value 0.30), 1.0 part by mass of iodine, 3.7 parts by mass of 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), 0.1 part by mass of iodosuccinimide as a catalyst, 52.8 parts by mass of benzyl methacrylate, and 99.4 parts by mass of isobutyl methacrylate, stir, and heat to 45°C.

[0118] After 2 hours, once the brown color of iodine has disappeared, polymerization is carried out for another 3 hours while maintaining the above temperature to obtain random copolymer A of benzyl methacrylate and isobutyl methacrylate. The number-average molecular weight of random copolymer A is 11200, and the degree of dispersion is 1.19. The number-average molecular weight and degree of dispersion are measured by GPC using tetrahydrofuran as the developing solvent.

[0119] Next, the solution of random copolymer A obtained above was cooled to 40°C, and then 15.1 parts by mass of methacrylic acid and 61.6 parts by mass of benzyl methacrylate were added. Polymerization was then carried out at 40°C for 4 hours, and block B, in which methacrylic acid and benzyl methacrylate were randomly copolymerized, was extended to the end of random copolymer A (block A) to obtain AB block polymer. The acid value in block B was calculated to be 128.4 mgKOH / g. The acid value in chain B was calculated as follows.

[0120] First, determine the amount of methacrylic acid per 1 part by mass of composition in block B. 15.1 / (15.1+61.6)=0.197 parts by mass Next, assuming a molecular weight of 86.1 for methacrylic acid and 56.1 for potassium hydroxide (KOH), the acid value in the B block polymer chain is calculated as follows. (0.197 / 86.1)×56.1×1000=128.4mgKOH / g

[0121] This AB block polymer solution has a solid content of 50.0% by mass, confirming a polymerization rate of nearly 100%. Furthermore, the number-average molecular weight of the AB block polymer is 17,500, and its dispersion degree is 1.33. The formation of the AB block polymer can be confirmed by observing the increase in molecular weight compared to random copolymer A.

[0122] [Resin Binder 2] Resin binder 2 is obtained by the same procedure as resin binder 1, except that block polymer A is synthesized using 76.1 parts by mass of dicyclopentanyl methacrylate and 76.1 parts by mass of dodecyl methacrylate instead of a monomer mixture of benzyl methacrylate and isobutyl methacrylate.

[0123] [Resin Binder 3] Resin binder 3 is obtained using the same procedure as for resin binder 1, except that block polymer A is synthesized using 152.2 parts by mass of benzyl methacrylate instead of a monomer mixture of benzyl methacrylate and isobutyl methacrylate.

[0124] [Resin Binder 4] In a reaction vessel equipped with a stirrer, reflux condenser, dropper, and thermometer, 900 g of deionized water and 1 g of sodium lauryl sulfate are charged, and the temperature is raised to 70°C while stirring and purging with nitrogen. Maintaining the internal temperature at 70°C, 4 g of potassium persulfate is added as a polymerization initiator and dissolved. After dissolution, an emulsion prepared by adding 450 g of deionized water, 3 g of sodium lauryl sulfate, 20 g of acrylamide, 365 g of styrene, 545 g of butyl acrylate, and 30 g of methacrylic acid to 450 g of deionized water and 3 g of sodium lauryl sulfate, while stirring, is continuously added dropwise to the reaction solution over 4 hours. After the dropwise addition is complete, the mixture is allowed to mature for 3 hours. After the obtained resin emulsion is cooled to room temperature, deionized water and aqueous sodium hydroxide solution are added to adjust the solid content to 40% by mass and the pH to 8 to obtain resin binder 4.

[0125] 3. Evaluation Method 3.1. Redispersibility The inkjet ink composition is dropped onto a glass slide and left to dry at 60°C for one day. Then, the glass slide with the dried ink is immersed in a sample bottle containing ink water, and the redispersion behavior of the dried ink is visually observed. Care should be taken to avoid agitating the ink water during the procedure. Note that "ink water" refers to the mixture in Examples Tables 1-3 that does not contain pigment or resin binder. The evaluation criteria for redispersibility are shown below. (Evaluation Criteria) A: The dried ink is completely redispersible in the ink solution, and no aggregates or precipitates are observed. B: Some of the dried ink has redispersed in the ink solution, but some aggregates and precipitates are visible. C: Dried ink cannot be redispersed in the ink solution, resulting in aggregates or sedimentation.

[0126] 3.2.Abrasion resistance Each ink composition was filled into the PX-M791FT printer (manufactured by Seiko Epson Corporation), and Xerox P paper (Fuji Xerox copy paper, basis weight 64 g / m²) was used. 2Twenty-six 20-point size alphabet characters are recorded onto a recording medium on paper with a thickness of 88 μm. Immediately after recording, the recording medium is fixed to a flat surface where it is placed horizontally. Five minutes after recording, the character areas are rubbed with an OPTEX CARE highlighter (manufactured by Zebra Co., Ltd.), and the abrasion resistance is evaluated based on the degree of ink bleeding according to the following evaluation criteria. (Evaluation Criteria) A: No color bleeding occurs even after rubbing twice. B: No color bleeding occurs after rubbing once, but color bleeding occurs after rubbing twice. C: Color bleeding occurs when rubbed once.

[0127] 3.3. Storage Stability The ink composition is left in a 60°C environment for one week. Then, the percentage change in the average particle size of pigment particles in the ink after the period of exposure compared to the average particle size of pigment particles in the ink before exposure is calculated and evaluated according to the following criteria. (Evaluation Criteria) A: The percentage of change is less than ±10%. B: The percentage change is ±10% or more, and less than ±20%. C: Fluctuation rate of ±20% or more.

[0128] 3.4. Clogging recovery After filling the PX-M791FT printer (manufactured by Seiko Epson Corporation) with ink and performing a nozzle check to confirm that all nozzles are ejecting ink, the printer head will be defapped and left at 40°C for one week. After this period, the number of cleaning cycles required for all nozzles to recover will be evaluated. (Evaluation Criteria) A: No more than 3 cleaning sessions. B: Cleaning done 4 to 5 times. C: More than 5 cleaning cycles, or the nozzle does not fully recover.

[0129] 4. Evaluation Results Figures 1-3 show the composition of the inkjet inks used in each example, as well as the evaluation results. From Figures 1-3, the inkjet inks contain a pigment, a resin binder, and an organic solvent. The pigment includes a resin-dispersed pigment dispersed in a crosslinked resin, the resin binder includes a self-emulsifying resin binder, and the organic solvent has an octanol / water partition coefficient logP. ow In all of the examples, which are inkjet ink compositions containing organic solvent A with a value of 0 to 1 and being water-based inks, it can be seen that they have excellent clogging recovery and abrasion resistance. Furthermore, they also have good redispersibility and storage stability.

[0130] In contrast, the comparative examples, which are inkjet ink compositions that do not meet these criteria, all show inferiority in either clogging recovery or abrasion resistance. [Explanation of symbols]

[0131] 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, a resin binder, and an organic solvent. The aforementioned pigment includes a resin-dispersed pigment dispersed in a crosslinked resin, The aforementioned resin binder includes a self-emulsifying resin binder. The aforementioned organic solvent has an octanol / water partition coefficient logP ｏｗ It contains organic solvent A whose value is between 0 and 1. It is a water-based ink. Inkjet ink composition.

2. The resin binder comprises a block polymer having block A and block B having a higher acid value than block A. The inkjet ink composition according to claim 1.

3. The aforementioned crosslinked resin is a resin crosslinked with a crosslinking agent having two or more epoxy groups, oxazoline groups, or isocyanate groups in its molecule. The inkjet ink composition according to claim 1.

4. The aforementioned organic solvent A contains any of the following: alkanediols, monoalcohols, ketones, or ethers. The inkjet ink composition according to claim 1.

5. The content of the organic solvent A is 0.5 to 15% by mass relative to the total amount of the inkjet ink composition. The inkjet ink composition according to claim 1.

6. The self-emulsifying resin binder has an octanol / water partition coefficient logP ｏｗ It is a product of solution polymerization in an organic solvent with a value between 0 and 1. The inkjet ink composition according to claim 1.

7. Contains an acetylene glycol-based surfactant with an HLB value of 5 or less. The inkjet ink composition according to claim 1.

8. The process includes the step of ejecting the inkjet ink composition according to any one of claims 1 to 7 from an inkjet head and adhering it to a recording medium. Recording method.

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