Inkjet recording method and inkjet recording device

Abstract

To provide an inkjet recording method capable of recording an image having excellent image clarity and exhibiting the same image clarity as that obtained using the ink before storage even when the ink after storage is used on a low- to non-absorbent recording medium.SOLUTION: There is provided an inkjet recording method for recording an image by applying an aqueous ink and a reaction liquid onto a recording medium, which comprises: a step of ejecting an aqueous ink from a recording head to apply the aqueous ink onto a recording medium; and a step of ejecting a reaction liquid from a recording head to apply the reaction liquid onto a recording medium, wherein the aqueous ink contains resin particle having an anionic group content of 150 μmol / g or less and a polyoxyethylene alkyl ether, the polyoxyethylene alkyl ether has an alkyl group having 16 or more carbon atoms and has an HLB value determined by the Griffin method of 14.0 or more and the recording medium has a water absorption amount from the start of contact up to 30 msec1 / 2 of 10 mL / m2 or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This invention relates to an inkjet recording method and an inkjet recording apparatus. [Background technology]

[0002] In recent years, inkjet recording methods have been increasingly used in the signage and display field, such as for recording posters and large-sized advertisements. In this field, polyvinyl chloride sheets and polyethylene terephthalate (PET) sheets are often used as recording media due to their durability and cost. These are recording media that do not have or have very little of an absorbent layer for water-based ink on their recording surface, and are called so-called non-absorbent recording media (recording media that do not absorb water-based ink) or low-absorbent recording media (recording media with low absorbency of water-based ink). When recording images on these recording media, solvent-based inks and curable inks have traditionally been used. However, from the perspective of reducing environmental impact and odor, there is a growing need for water-based inks using water-based media.

[0003] Various methods have been investigated for recording good images on non-absorbent recording media. For example, a recording method has been proposed that uses a reaction solution containing a coagulant that aggregates components in the ink in order to quickly fix the ink attached to the recording media and record high-quality images with suppressed unevenness (Patent Document 1). In addition, an ink containing resin fine particles and a nonionic surfactant has been proposed to ensure storage properties in order to record images with excellent scratch resistance when used together with the reaction solution (Patent Document 2). [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2018-162341 [Patent Document 2] Japanese Patent Publication No. 2018-165314 [Overview of the project]

Problems to be Solved by the Invention

[0005] However, in the case of the method proposed in Patent Document 1, as examined by the present inventors, the mapping property of the image recorded with the ink before storage is different from the mapping property of the image recorded with the ink after storage, and it has been clarified that the mapping property of the image recorded with the ink after storage is inferior. Also, when using the ink proposed in Patent Document 2, it has been found that it is difficult to record an image showing the required level of mapping property. Furthermore, it has also been found that the mapping property of the image recorded with the ink before storage is different from the mapping property of the image recorded with the ink after storage.

[0006] Therefore, an object of the present invention is to provide an inkjet recording method capable of recording an image with excellent mapping property and showing the same mapping property as when using the ink before storage even when using the ink after storage on a low- to non-absorbent recording medium. Another object of the present invention is to provide an inkjet recording apparatus used for this inkjet recording method.

Means for Solving the Problems

[0007] That is, according to the present invention, there is provided an inkjet recording method in which an aqueous ink and an aqueous reaction liquid that reacts with the aqueous ink are ejected from an inkjet recording head, applied to a recording medium, and an image is recorded, the method including a step of ejecting the aqueous ink from the recording head and applying it to the recording medium, and a step of ejecting the reaction liquid from the recording head and applying it to the recording medium, the aqueous ink containing resin particles having an anionic group amount of 150 μmol / g or less and polyoxyethylene alkyl ether, the polyoxyethylene alkyl ether having an alkyl group with 16 or more carbon atoms and having an HLB value determined by the Griffin method of 14.0 or more, and the recording medium having a water absorption amount of 10 mL / m from the start of contact to 30 msec in the 1 / 2 up to 2 or less, characterized by the above.

Advantages of the Invention

[0008] According to the present invention, it is possible to record an image that is excellent in mapping property and exhibits the same mapping property as when using the ink before storage even when using the ink after storage on a low to non-absorbent recording medium, thereby providing an inkjet recording method. Further, according to the present invention, it is possible to provide an inkjet recording apparatus used for this inkjet recording method.

Brief Description of the Drawings

[0009] [Figure 1] FIG. 1 is a perspective view schematically showing an embodiment of the inkjet recording apparatus of the present invention. [Figure 2] FIG. 2 is a side view schematically showing an embodiment of the inkjet recording apparatus of the present invention.

Modes for Carrying Out the Invention

[0010] Hereinafter, the present invention will be described in more detail by way of preferred embodiments. In the present invention, when the compound is a salt, although the salt dissociates into ions and exists in the ink, for convenience, it is expressed as "containing a salt". Also, the aqueous ink for inkjet may be simply referred to as "ink". Physical property values are values at normal temperature (25 ° C) and normal pressure (1 atm) unless otherwise specified.

[0011] Furthermore, in this specification, "unit" means a unit structure corresponding to one monomer unless otherwise specified. When "(meth)acrylic acid" or "(meth)acrylate" is written, it refers to "acrylic acid, methacrylic acid" and "acrylate, methacrylate," respectively. Polyester resins commonly used in water-based inkjet inks are composed of units derived from polyhydric alcohols and units derived from polyhydric carboxylic acids. A structure containing an ester bond (-COO-) composed of a unit derived from a polyhydric alcohol and a unit derived from a polyhydric carboxylic acid is sometimes called an "ester unit."

[0012] Furthermore, in this specification, low-absorption to non-absorbent recording media may be collectively referred to as "non-absorbent recording media." Low-absorption to non-absorbent recording media are identified in the Bristow method by the time of contact for 30 msec. 1 / 2 Up to 10 mL / m² of water absorption capacity 2 It is defined as follows:

[0013] To obtain good image quality on non-absorbent recording media, it is necessary to use a combination of ink and a reaction solution, a so-called "reaction system." When recording images with improved image quality using a reaction system, for example, an ink containing resin particles is used. Furthermore, considering the storage stability of the ink, resin particles with a relatively small amount of anionic groups are used. However, resin particles with a small amount of anionic groups tend to aggregate due to reaction with the reactant in the reaction solution, making it difficult to improve the image quality. As a result of our investigation, the inventors found that the image quality of images improved by using an ink to which polyoxyethylene alkyl ether, a surfactant, was added. However, it was found that when images were recorded using the ink after storage, the image quality was lower compared to images recorded using the ink before storage. The inventors speculate on the reason for this as follows.

[0014] The adsorption of the alkyl group of polyoxyethylene alkyl ether onto the resin particles mitigates the reaction between the resin particles in the ink and the reactant (aggregating component) in the reaction solution, thereby improving image clarity. However, when the ink is stored, the surfactant adsorbed onto the resin particles detaches, making the resin particles more susceptible to reaction with the reactant, leading to aggregation of the resin particles and a decrease in image clarity. The inventors focused on the number of carbon atoms in the alkyl group constituting the polyoxyethylene alkyl ether and the HLB value of the polyoxyethylene alkyl ether and conducted further investigations. As a result, they found that by including polyoxyethyl alkyl ether having an alkyl group with 16 or more carbon atoms and an HLB value of 14.0 or higher in the ink, the image clarity is less likely to change even when the ink is used after storage. The inventors speculate on the reason for this as follows.

[0015] Resin particles with a low amount of anionic groups have a large number of hydrophobic regions. Polyoxyethyl alkyl ethers with alkyl groups that have a large number of carbon atoms are thought to be stable because they adsorb to the hydrophobic regions of the resin particles at multiple points and are therefore less likely to detach from the resin particles. Furthermore, polyoxyethylene alkyl ethers with low HLB values ​​have poor solubility in aqueous media, so their cohesiveness changes before and after ink storage, and the image quality of the resulting image is also thought to change. In contrast, polyoxyethylene alkyl ethers with an HLB value of 14.0 or higher are easily adsorbed to resin particles and are less likely to detach from the resin particles even after ink storage, so the image quality of the resulting image is thought to be stable.

[0016] <Inkjet recording method and inkjet recording device> The present invention relates to an inkjet recording method in which an image is recorded by ejecting an aqueous ink and an aqueous reaction solution that reacts with the aqueous ink from an inkjet recording head and applying them to a recording medium. The present invention relates to an inkjet recording method which comprises the steps of ejecting aqueous ink from a recording head and applying it to a recording medium, and ejecting a reaction solution from a recording head and applying it to a recording medium. The aqueous ink contains resin particles with an anionic group amount of 150 μmol / g or less and a polyoxyethylene alkyl ether. The polyoxyethylene alkyl ether has an alkyl group with 16 or more carbon atoms and has an HLB value of 14.0 or higher as determined by the Griffin method. The present invention relates to an inkjet recording apparatus which is used in an inkjet recording method in which an image is recorded by ejecting aqueous ink and an aqueous reaction solution that reacts with the aqueous ink from an inkjet recording head and applying them to a recording medium. The present invention relates to an inkjet recording apparatus which is suitably used in the above recording method. The present invention relates to an inkjet recording method and an inkjet recording apparatus which (hereinafter also simply referred to as "recording method and recording apparatus") which will be described in detail below.

[0017] (Water-based ink) The ink contains resin particles and polyoxyethylene alkyl ether. The following provides a detailed explanation of each component that makes up the ink.

[0018] [Resin particles] The resin particles have an anionic group content of 150 μmol / g or less. "Amount of anionic groups in resin particles" is a physical property value expressed as the amount (μmol) of anionic groups present on the particle surface of the resin particles per unit mass (g). If the amount of anionic groups exceeds 150 μmol / g, polyoxyethylene alkyl ether becomes less adsorbent to the resin particles, potentially weakening the effect of improving image quality, and impairing the image quality of images recorded with the ink after storage. The amount of anionic groups in resin particles can be measured by colloidal titration using potential difference.

[0019] The resin particle content (mass%) in the ink is preferably 0.1% to 15.0% by mass, and more preferably 1.0% to 10.0% by mass, based on the total mass of the ink. The resin particles exist in the ink in a dispersed state, i.e., in the form of a resin emulsion. It is preferable that the resin particles do not contain colorants.

[0020] In this specification, "resin particles" refers to resins that do not dissolve in the aqueous medium that constitutes the ink, and specifically means resins that can exist in the aqueous medium in a state in which particles whose particle size can be measured by dynamic light scattering are formed. On the other hand, "water-soluble resin" refers to resins that can dissolve in the aqueous medium that constitutes the ink, and specifically means resins that can exist in the aqueous medium in a state in which particles whose particle size can not be measured by dynamic light scattering are not formed. "Resin particles" can also be rephrased as "water-dispersible resin (water-insoluble resin)".

[0021] Whether a resin is a "resin particle" or not can be determined according to the following method. First, prepare a liquid containing the resin to be judged (resin content: 10% by mass). Next, prepare a sample by diluting the prepared liquid 10 times (by volume) with deionized water. Then, measure the particle size of the resin in the sample using dynamic light scattering. If particles with a particle size are measured, those particles are judged to be "resin particles" (water-dispersible resin). On the other hand, if particles with a particle size are not measured, the resin is judged not to be a "resin particle" ("water-soluble resin"). The measurement conditions in this case can be, for example, SetZero: 30 seconds, Number of measurements: 3, Measurement time: 180 seconds, Shape: Spherical, Refractive index: 1.59. As a particle size distribution analyzer, a particle size analyzer using dynamic light scattering (for example, product name "NanoTrack UPA-EX150", manufactured by Nikkiso) can be used. Of course, the particle size distribution analyzer and measurement conditions are not limited to those described above.

[0022] Examples of resins that make up the resin particles include acrylic resin, urethane resin, olefin resin, and polyester resin. Among these, polyester resin is preferred. In other words, it is preferable that the resin particles contained in the ink be polyester resin particles. Among resin particles, polyester resin particles have good affinity with polyoxyethylene alkyl ether, so even when the ink is stored, the polyoxyethylene alkyl ether is less likely to leach out than from the resin particles. Therefore, it is possible to further suppress changes in the image quality of images recorded with the ink after storage.

[0023] [Acrylic resin] As for the acrylic resin, it is preferable to have hydrophilic units and hydrophobic units as constituent units. In particular, resins having hydrophilic units derived from (meth)acrylic acid and hydrophobic units derived from at least one of a monomer having an aromatic ring and (meth)acrylic acid ester are preferred. Especially preferred are resins having hydrophilic units derived from (meth)acrylic acid and hydrophobic units derived from at least one of the monomers of styrene and α-methylstyrene. Because these resins readily interact with pigments, they can be suitably used as resin dispersants for dispersing pigments.

[0024] Hydrophilic units are units that have hydrophilic groups, such as anionic groups. Hydrophilic units can be formed, for example, by polymerizing hydrophilic monomers that have hydrophilic groups. Specific examples of hydrophilic monomers that have hydrophilic groups include acidic monomers having carboxylic acid groups, such as (meth)acrylic acid, itaconic acid, maleic acid, and fumaric acid, and anionic monomers such as anhydrides and salts of these acidic monomers. Cations that constitute salts of acidic monomers include ions such as lithium, sodium, potassium, ammonium, and organic ammonium. Hydrophobic units are units that do not have hydrophilic groups, such as anionic groups. Hydrophobic units can be formed, for example, by polymerizing hydrophobic monomers that do not have hydrophilic groups, such as anionic groups. Specific examples of hydrophobic monomers include monomers having aromatic rings, such as styrene, α-methylstyrene, and benzyl (meth)acrylate; and (meth)acrylic acid ester monomers, such as methyl (meth)acrylate, butyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate.

[0025] [Urethane resin, olefin resin] Urethane resins can be obtained, for example, by reacting polyisocyanate with a polyol. Alternatively, they may be obtained by further reacting with a chain extender. Examples of olefin resins include polyethylene and polypropylene.

[0026] [Polyester resin] Polyester resins are typically composed of units derived from polyhydric alcohols and units derived from polyhydric carboxylic acids. Unreacted hydroxyl groups or carboxylic acid groups are present at the ends of the polyester resin. The sum of the proportion (by mass) of units derived from polyhydric alcohols and units (by mass) derived from polyhydric carboxylic acids in the polyester resin is preferably 90.0% by mass or more. It is even more preferably 95.0% by mass or more, and may be 100.0% by mass.

[0027] Examples of polyhydric alcohols include dihydric to tetrahydric polyhydric alcohols. Examples of polyhydric alcohols include polyhydric alcohols having aliphatic groups, polyhydric alcohols having aromatic groups, and sugar alcohols. Examples of dihydric alcohols include ethylene glycol [1,2-ethanediol], neopentyl glycol [2,2-dimethyl-1,3-propanediol], 1,3-propanediol, 1,4-butanediol, benzenediol, and 2,2-bis(4-hydroxyphenyl)propane [bisphenol A]; trihydric alcohols include glycerin, trimethylolethane, and trimethylolpropane; and tetrahydric alcohols include pentaerythritol. Oligomers (low molecular weight polymers with a molecular weight of 1,000 or less) can also be used as polyhydric alcohols. The proportion (mass%) of units derived from polyhydric alcohols in the polyester resin is preferably 40.0% by mass or more and 60.0% by mass or less.

[0028] Examples of polycarboxylic acids include divalent to tetravalent polycarboxylic acids. Examples of polycarboxylic acids include polycarboxylic acids having aliphatic groups, polycarboxylic acids having aromatic groups, and nitrogen-containing polycarboxylic acids. Examples of polycarboxylic acids include divalent carboxylic acids such as glutaric acid, adipic acid, terephthalic acid, isophthalic acid, and 2,6-naphthalenedicarboxylic acid; trivalent carboxylic acids such as trimellitic acid; and tetravalent carboxylic acids such as ethylenediaminetetraacetic acid. Oligomers (low molecular weight polymers with a molecular weight of 1,000 or less) can also be used as polycarboxylic acids. The proportion (mass%) of units derived from polycarboxylic acids in the polyester resin is preferably 40.0% by mass or more and 60.0% by mass or less.

[0029] The weight-average molecular weight of the polyester resin particles (the polyester resin constituting the polyester resin particles) is preferably 30,000 or more and 70,000 or less. If the weight-average molecular weight is less than 30,000, the molecular chains of the polyester resin are too short, making it easier for the polyoxyethylene alkyl ether to detach, which may slightly weaken the effect of improving the image quality of the image recorded with the ink after storage. On the other hand, if the weight-average molecular weight is greater than 70,000, the molecular chains of the polyester resin are too long, making it difficult for molecular motion to occur and difficult for interaction with the polyoxyethylene alkyl ether to occur, which may slightly weaken the image quality of the recorded image. The weight-average molecular weight in this specification is a polystyrene-converted value measured by gel permeation chromatography.

[0030] [Analysis of resin particles] The composition of the resin constituting the resin particles can be analyzed, for example, by the following methods. First, a sample is prepared by dissolving the resin particles in an organic solvent such as tetrahydrofuran that can dissolve the resin particles. The resin particles dissolved in the organic solvent may be in an aqueous dispersion or in a dry state. By analyzing the prepared sample using analytical methods such as nuclear magnetic resonance (NMR) spectroscopy or matrix-assisted laser desorption / ionization mass spectrometry (MALDI-MS), the types and proportions of the units (monomers) constituting the resin can be determined. In addition, the units (monomers) constituting the resin can also be detected by analyzing the resin particles with pyrolysis gas chromatography. If insoluble matter that does not dissolve in the organic solvent is generated when preparing the sample, the resulting insoluble matter can also be analyzed with pyrolysis gas chromatography to detect the units (monomers) constituting the resin.

[0031] [Other resins] The ink may further contain resins other than resin particles (other resins). The type and form of the other resins are acceptable as long as they can be stably present in the water-based ink. Specifically, other resins include water-soluble resins. Examples of other resins include (meth)acrylic resins, polyamide resins, polyester resins, polyvinyl alcohol resins, and polyolefin resins. To improve the solubility of these resins, a base may be added to the ink. Suitable bases include organic amines such as monoethanolamine, diethanolamine, triethanolamine, aminemethylpropanol, and N,N-dimethylethanolamine; and inorganic bases such as potassium hydroxide and sodium hydroxide.

[0032] [Polyoxyethylene alkyl ether] The ink contains a polyoxyethylene alkyl ether having an alkyl group (hydrocarbon group) with 16 or more carbon atoms. The polyoxyethylene alkyl ether is a component that functions as a so-called surfactant and is represented, for example, by the following general formula (1). If the number of carbon atoms in the alkyl group is less than 16, the image quality of the recorded image will be poor, and it will be more likely to detach from the resin particles during storage, impairing the image quality of the image recorded with the ink after storage. The number of carbon atoms in the polyoxyethylene alkyl ether is preferably 30 or less, and more preferably 24 or less. Examples of hydrocarbon groups include alkyl groups and alkenyl groups. n is preferably 10 to 50, and more preferably 15 to 30. RO-(CH2CH2O) n -H ···(1) (In general formula (1), R represents a hydrocarbon group with 16 or more carbon atoms, and n represents a natural number.)

[0033] The HLB value of polyoxyethylene alkyl ether determined by the Griffin method is 14.0 or higher. If the HLB value of the polyoxyethylene alkyl ether is less than 14.0, the effect of improving the image clarity of the recorded image may be weakened. In addition, solubility in aqueous media decreases, and adsorption to resin particles proceeds slowly, so the image clarity of the image recorded with the ink after storage is impaired. The HLB value of the polyoxyethylene alkyl ether is preferably 16.0 or lower. Polyoxyethylene alkyl ether with an HLB value of 16.0 or lower does not have excessively high solubility in aqueous media and is less likely to detach from resin particles even when the ink is stored. Therefore, changes in the image clarity of the image recorded with the ink after storage can be further suppressed. Furthermore, in order to facilitate the adsorption of polyoxyethylene alkyl ether to resin particles, when using acrylic resin particles, it is preferable to use polyoxyethylene alkyl ether with an HLB value of 16.0 or lower.

[0034] The HLB value obtained by the Griffin method can be calculated using the following formula (2). The HLB value obtained by the Griffin method is a physical property value that represents the degree of hydrophilicity or lipophilicity of a surfactant, and takes a value between 0.0 and 20.0. A smaller HLB value indicates higher lipophilicity, and a larger HLB value indicates higher hydrophilicity. HLB value = 20 × (formula weight of hydrophilic group of surfactant / molecular weight of surfactant) ... (2)

[0035] The polyoxyethylene alkyl ether content (mass%) in the ink is preferably 0.1% to 1.0% by mass, and more preferably 0.1% to 0.8% by mass, based on the total mass of the ink. The polyoxyethylene alkyl ether content (mass%) in the ink is preferably 0.10 times or less, and more preferably 0.05 times or less, as a mass ratio to the resin particle content (mass%). If the above mass ratio exceeds 0.10 times, the polyoxyethylene alkyl ether may be more prone to micelle formation, and the effect of improving the image quality of the image recorded with the ink after storage may be slightly weakened. The above mass ratio is preferably 0.01 times or more.

[0036] [Colorants] The ink may contain colorants such as pigments and dyes. Among these, pigments are preferred as colorants, and resin-dispersed pigments, as described later, are particularly preferred. The colorant content (mass%) in the ink is preferably 0.1% by mass or more and 15.0% by mass or less, and more preferably 1.0% by mass or more and 10.0% by mass or less, based on the total mass of the ink.

[0037] Specific examples of pigments include inorganic pigments such as carbon black and titanium dioxide; and organic pigments such as azo, phthalocyanine, quinacridone, isoindolinone, imidazolon, diketopyrrolopyrrole, dioxazine, and perinone. Among the pigments, carbon black and organic pigments are preferred.

[0038] Examples of pigment dispersion methods include resin-dispersed pigments, which use resins as dispersants, and self-dispersing pigments, in which hydrophilic groups are bonded to the surface of the pigment particles. Other examples include resin-bonded pigments, in which organic groups containing resin are chemically bonded to the surface of the pigment particles, and microcapsule pigments, in which the surface of the pigment particles is coated with resin or other materials.

[0039] For dispersing pigments in an aqueous medium, it is preferable to use a resin dispersant that can disperse pigments in the aqueous medium through the action of anionic groups. It is preferable to use a water-soluble resin as the resin dispersant. Examples of resin dispersants include acrylic resins and urethane resins. Among these, acrylic resins are preferred, and acrylic resins composed of units derived from (meth)acrylic acid or (meth)acrylic acid esters are even more preferred.

[0040] Specific examples of dyes include direct dyes, acid dyes, basic dyes, disperse dyes, and food dyes. Specific examples of dye skeletons include azo, triphenylmethane, phthalocyanine, azaphthalocyanine, xanthene, and anthrapyridone.

[0041] [Aqueous medium] The ink is an aqueous ink containing at least water as an aqueous medium. The ink may contain an aqueous medium which is water or a mixed solvent of water and a water-soluble organic solvent. Deionized water or ion-exchanged water is preferably used as the water. The water content (mass%) in the ink is preferably 50.0% by mass or more and 95.0% by mass or less, based on the total mass of the ink.

[0042] As the water-soluble organic solvent, any of the following can be used for inkjet inks: alcohols, (poly)alkylene glycols, glycol ethers, nitrogen-containing compounds, sulfur-containing compounds, etc. While "water-soluble organic solvent" usually refers to a liquid, in this invention, substances that are solid at 25°C (room temperature) are also included. Examples of water-soluble organic solvents that are commonly used in water-based inks and are solid at 25°C include 1,6-hexanediol, trimethylolpropane, ethylene urea, urea, and polyethylene glycol with a number-average molecular weight of 1,000. It is preferable to use a water-soluble organic solvent with a boiling point higher than that of water.

[0043] The content (mass%) of water-soluble organic solvent in the ink is preferably 3.0% by mass or more and 50.0% by mass or less, and more preferably 10.0% by mass or more and 30.0% by mass or less, based on the total mass of the ink. Furthermore, the content (mass%) of water-soluble organic solvent in the ink is preferably 1.0 to 4.0 times the mass ratio of the polyester resin particle content (mass%). If the above mass ratio is less than 1.0 times, the amount of water-soluble organic solvent is too small relative to the polyester resin particles, making it difficult for the polyester resin particles to soften due to the water-soluble organic solvent, which may weaken the effect of improving image quality. On the other hand, if the above mass ratio is greater than 4.0 times, the amount of water-soluble organic solvent is too large relative to the polyester resin particles, which may make the polyester resin particles more prone to movement due to the water-soluble organic solvent remaining on the recording medium, which may weaken the effect of improving image quality.

[0044] Preferably, the ink further contains a first water-soluble organic solvent having a boiling point of 220°C or lower. When the ink is applied to the recording medium, liquid components such as water evaporate, and the resin particles and water-soluble organic solvent are concentrated. In this case, if the compatibility between the water-soluble organic solvent and the resin particles is high, the resin particles tend to soften, and the image quality tends to improve. This phenomenon is more likely to occur when a first water-soluble organic solvent with a boiling point of 220°C or lower is present. Preferably, the boiling point of the first water-soluble organic solvent is above 100°C. Examples of first water-soluble organic solvents with a boiling point of 220°C or lower include 1,3-propanediol (214°C), 2-methyl-1,3-propanediol (214°C), diethylene glycol monoethyl ether (202°C), ethylene glycol (198°C), diethylene glycol monomethyl ether (194°C), 1,2-butanediol (193°C), and propylene glycol (188°C). In particular, 1,2-butanediol is preferred as the first water-soluble organic solvent because it offers excellent image rendering capabilities.

[0045] [Other ingredients] The ink may contain various additives as needed, such as surfactants other than the polyoxyethylene alkyl ether mentioned above (other surfactants), pH adjusters, defoamers, rust inhibitors, preservatives, fungicides, antioxidants, reduction inhibitors, and chelating agents. Examples of other surfactants include silicone-based surfactants and fluorine-based surfactants. Other surfactants can be used, for example, to adjust the surface tension of the ink. The content (by mass) of surfactants (including the polyoxyethylene alkyl ether mentioned above) in the ink is preferably 0.1% by mass or more and 5.0% by mass or less, and more preferably 0.1% by mass or more and 2.0% by mass or less, based on the total mass of the ink.

[0046] [Physical properties of ink] Since the ink is ejected from an inkjet recording head, it is preferable that its physical properties are appropriately controlled. For example, the surface tension of the ink at 25°C, as measured by the plate method, is preferably 20 mN / m to 60 mN / m, and more preferably 25 mN / m to 45 mN / m. The viscosity of the ink at 25°C is preferably 1.0 mPa·s to 10.0 mPa·s, and more preferably 1.0 mPa·s to 5.0 mPa·s. The pH of the ink at 25°C is preferably 7.0 to 10.0.

[0047] (Reaction solution) The reaction solution contains a reactant that reacts with the ink upon contact, causing the components in the ink (components with anionic groups, such as resins and self-dispersing pigments) to aggregate.

[0048] [Reactive agent] Examples of reaction solutions include polyvalent metal ions, cationic components such as cationic resins, and organic acids. Among these, organic acids and divalent or higher polycarboxylic acids (which may be salts or hydrogen salts) are preferred as reactants.

[0049] As for polyvalent metal ions, Ca 2+ Cu2+ , Ni 2+ , Mg 2+ , Sr 2+ , Ba 2+ , and divalent metal ions such as Zn; Fe 2+ , Cr 3+ , Y 3+ , and trivalent metal ions such as Al; can be mentioned. In order to contain polyvalent metal ions in the reaction solution, a polyvalent metal salt (which may be a hydrate) composed of a polyvalent metal ion and an anion can be used. As the anion, for example, Cl 3+ , Br 3+ , I - , ClO - , ClO2 - , ClO3 - , ClO4 - , NO2 - , NO3 - , SO4 - , CO3 - , HCO3 2- , PO4 2- , HPO4 - , and inorganic anions such as H2PO4 3- , HCOO 2- , (COO - )2, COOH(COO - ), CH3COO - ), C2H4(COO - ), C6H5COO - ), C6H4(COO - ), and organic anions such as CH3SO3 - [[ID=6j]] - ), and CH3SO3 - can be mentioned. When using polyvalent metal ions as the reactant, the content (mass%) of the polyvalent metal salt in the reaction solution, based on the total mass of the reaction solution, is preferably 1.0 mass% or more and 20.0 mass% or less.

[0050] ​The reaction solution containing an organic acid has buffering capacity in the acidic range (pH less than 7.0, preferably pH 2.0 to 5.0), which allows for the efficient conversion of the anionic groups of components present in the ink into acidic forms and subsequent aggregation. Examples of organic acids include monocarboxylic acids and their salts such as formic acid, acetic acid, propionic acid, butyric acid, benzoic acid, glycolic acid, lactic acid, salicylic acid, pyrrole carboxylic acid, furanic acid, picolinic acid, nicotinic acid, thiophene carboxylic acid, levulinic acid, and coumaric acid; dicarboxylic acids and their salts or hydrogen salts such as oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, maleic acid, fumaric acid, itaconic acid, sebacic acid, phthalic acid, malic acid, and tartaric acid; tricarboxylic acids and their salts or hydrogen salts such as citric acid and trimellitic acid; and tetracarboxylic acids and their salts or hydrogen salts such as pyromellitic acid. The content (by mass) of organic acids in the reaction solution is preferably 1.0% by mass or more and 50.0% by mass or less, based on the total mass of the reaction solution.

[0051] Examples of cationic resins include resins having primary to tertiary amine structures and resins having quaternary ammonium salt structures. Specifically, resins having structures such as vinylamine, allylamine, vinylimidazole, vinylpyridine, dimethylaminoethyl methacrylate, ethyleneimine, and guanidine can be used. To improve solubility in the reaction solution, cationic resins can be used in combination with acidic compounds, or cationic resins that have undergone quaternization treatment can be used. When a cationic resin is used as a reactant, the content (mass%) of the cationic resin in the reaction solution is preferably 1.0% by mass or more and 10.0% by mass or less, based on the total mass of the reaction solution.

[0052] [Aqueous medium] The reaction solution is an aqueous liquid containing at least water as the aqueous medium. The reaction solution may contain an aqueous medium that is water or a mixed solvent of water and a water-soluble organic solvent. Deionized water or ion-exchanged water is preferred as the water. The water content (mass%) in the reaction solution is preferably 50.0% by mass or more and 95.0% by mass or less based on the total mass of the reaction solution. The water-soluble organic solvent content (mass%) in the reaction solution is preferably 3.0% by mass or more and 50.0% by mass or less, and more preferably 5.0% by mass or more and 30.0% by mass or less based on the total mass of the reaction solution. As the water-soluble organic solvent, any of those usable in inkjet inks, such as alcohols, (poly)alkylene glycols, glycol ethers, nitrogen-containing compounds, and sulfur-containing compounds, can be used. It is preferable to use at least the same type of water-soluble organic solvent used in the ink as the water-soluble organic solvent constituting the reaction solution.

[0053] [Other ingredients] In addition to the above components, the reaction solution may contain various additives as needed, such as surfactants, pH adjusters, defoamers, rust inhibitors, preservatives, fungicides, antioxidants, reduction inhibitors, and chelating agents.

[0054] (Recording medium) In the recording method and recording apparatus of the present invention, a non-absorbent recording medium (low to non-absorbent recording medium) is used as the recording medium. The non-absorbent recording medium is used in the Bristow method described in JAPAN TAPPI Paper and Pulp Test Method No. 51, "Test Method for Liquid Absorbency of Paper and Paperboard," from the start of contact for 30 msec. 1 / 2 Up to 10 mL / m² of water absorption capacity 2 The following are the recording media. In this invention, recording media that satisfy the above water absorption amount conditions are defined as "non-absorbent recording media." Recording media for inkjet recording (glossy paper, matte paper, etc.) having a coating layer (ink receiving layer) made of inorganic particles, and plain paper without a coating layer, have a water absorption amount of 10 mL / m². 2 It is an "absorbent recording medium" that exceeds [a certain limit].

[0055] As low-to-non-absorbent recording media, the following can be used: plastic films; recording media in which a plastic film is bonded to the recording surface of a substrate; and recording media in which an organic resin coating layer is provided on the recording surface of a substrate containing cellulose pulp. Among these, plastic films are preferred, and recording media in which an organic resin coating layer is provided as an organic resin layer on the recording surface of a substrate containing cellulose pulp are also preferred.

[0056] The reaction solution used in the recording method and recording apparatus of the present invention penetrates rapidly when applied to an absorbent recording medium, and therefore, compared to non-absorbent recording media, it is difficult to improve image quality even when using the reaction solution. On the other hand, when an absorbent recording medium is used, the reaction between the ink and the reaction solution is less likely to occur, and the image surface tends to become smoother, thus reducing the problem of poor image rendering quality. In this specification, the term "recording medium" refers to a recording medium on which an image as a recording object is recorded, not a transfer medium.

[0057] (Inkjet recording device) Figure 1 is a schematic perspective view showing one embodiment of the inkjet recording apparatus of the present invention. Figure 2 is a schematic side view showing one embodiment of the inkjet recording apparatus of the present invention. As shown in Figures 1 and 2, the recording apparatus of this embodiment includes an inkjet recording head 22 that ejects ink and reaction liquid. Examples of recording heads include recording heads that eject ink and reaction liquid by the action of mechanical energy, and recording heads that eject ink and reaction liquid by the action of thermal energy. Among these, recording heads that eject ink and reaction liquid by the action of thermal energy are preferred. A recording head that ejects ink and reaction liquid by the action of thermal energy is a thermal recording head that imparts thermal energy to the ink and reaction liquid by applying an electric pulse to an electrothermal conversion element, and ejects the ink and reaction liquid from the ejection port. This thermal recording head preferably includes a mechanism (temperature control mechanism) that heats the aqueous ink ejected from the recording head and applied to the recording medium to a predetermined temperature.

[0058] [Heating process] The recording method of the present invention preferably further includes a step of heating (heat treatment) the recording medium to which the ink has been applied. Heating the recording medium to which the ink and reaction solution have been applied promotes the formation of a resin particle film, and allows for the recording of an image with superior image quality. The heating temperature of the recording medium to which the ink has been applied is preferably 90°C or lower, and preferably 50°C or higher. The heating temperature of the recording medium to which the ink has been applied may be read by a sensor incorporated at a position corresponding to the heating means of the recording device, or it may be determined from the relationship between the amount of heat and the temperature of the recording medium, which is determined according to the type of ink and recording medium.

[0059] The means of heating are not particularly limited and can be used by known heating means such as heaters, air blowing means such as dryers, and means combining these. In other words, it is preferable that the inkjet recording device is equipped with a mechanism (heating means) for heating the recording medium to which the ink and reaction solution have been applied. Examples of heating means include the heating means, air blowing means, and means combining these. Examples of heating methods include applying heat from the side (back side) opposite to the recording surface (the surface to which the ink and reaction solution have been applied) of the recording medium with a heater, applying warm air or hot air to the recording surface of the recording medium, and heating from the recording surface or back side using an infrared heater. A combination of these methods may also be used.

[0060] In the recording apparatus shown in Figures 1 and 2, a heater 25 supported by a frame (not shown) is positioned downstream in the sub-scanning direction A from the position where the recording head 22 reciprocates in the main scanning direction B. The recording medium 1, to which ink and reaction liquid have been applied, can be heated by the heater 25. Specific examples of the heater 25 include sheath heaters and halogen heaters. The heater 25 is covered by a heater cover 26. The heater cover 26 is a component that efficiently irradiates the recording medium 1 with the heat generated from the heater 25. Furthermore, the heater cover 26 also serves as a component that protects the heater 25. The recording medium 1, to which ink and reaction liquid have been applied after being ejected from the recording head 22, is wound up by a take-up spool 27 to form a roll-shaped winding medium 24. [Examples]

[0061] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited in any way by the following examples unless it exceeds the gist of the invention. Unless otherwise specified, amounts of components indicated in "parts" and "%" are based on mass.

[0062] <Preparation of Pigment Dispersion> (Pigment dispersion 1) A water-soluble resin, a styrene / acrylic acid copolymer (composition (molar) ratio = 33:67), was dissolved in deionized water with sodium hydroxide equimolar to the acid value to prepare an aqueous solution of resin dispersant with a resin content of 20.0%. The weight-average molecular weight of this water-soluble resin was 10,000, and the acid value was 200 mgKOH / g. A mixture of 15.0 parts pigment (carbon black), 30.0 parts of the aqueous solution of resin dispersant, and 55.0 parts water was placed in a sand grinder and dispersed for 1 hour. After that, coarse particles were removed by centrifugation, and the mixture was pressure filtered through a 3.0 μm pore size microfilter (manufactured by Fujifilm). An appropriate amount of deionized water was added to obtain pigment dispersion 1. The pigment content in pigment dispersion 1 was 15.0%, and the resin content was 6.0%.

[0063] (Pigment dispersion 2) A solution of 5.0g concentrated hydrochloric acid dissolved in 5.5g water was cooled to 5°C, and 1.5g of 4-amino-1,2-benzenedicarboxylic acid was added. The container of this solution was placed in an ice bath and stirred to maintain the solution temperature below 10°C, while a solution of 1.8g sodium nitrite dissolved in 9.0g of 5°C water was added. After stirring for 15 minutes, the specific surface area was 220m². 2 6.0 g of carbon black (D50=100 nm) with a DBP oil absorption of 105 mL / 100 g was added under stirring. The mixture was stirred for another 15 minutes to obtain a slurry. The obtained slurry was filtered through filter paper (product name "Standard Filter Paper No. 2", manufactured by Advantec), the particles were thoroughly washed with water, and the mixture was dried in an oven at 110°C. Subsequently, sodium ions were replaced with potassium ions by ion exchange to obtain a self-dispersing pigment in which two -C6H3-(COOK) groups were bonded to the surface of the pigment particles. The pigment content was adjusted by adding an appropriate amount of water to obtain pigment dispersion 2 with a pigment content of 15.0%.

[0064] (Pigment dispersion 3) 500.0 g of deionized water and 15.0 g of carbon black were mixed and stirred at 15,000 rpm for 30 minutes to pre-wet the pigment (carbon black). 4,485 g of deionized water was added and dispersed using a high-pressure homogenizer to obtain a dispersion. The D50 of the pigment in the dispersion was 100 nm. The obtained dispersion was placed in a high-pressure container, pressurized to 3.0 MPa, and then ozonated water with an ozone concentration of 100 ppm was introduced to perform ozone oxidation treatment to obtain a pigment dispersion. After adjusting the pH of the pigment dispersion to 10.0 using potassium hydroxide, the solid content concentration was adjusted to obtain pigment dispersion 3. Pigment dispersion 3 contained a self-dispersing pigment in which -COOK groups were bonded to the surface of carbon black particles, and the pigment content was 15.0%.

[0065] <Method for measuring physical properties> (Weight-average molecular weight of resin) The weight-average molecular weight of the resin (particles) was measured according to the following procedure. The resin was added to tetrahydrofuran and dissolved at 25°C for 24 hours, then filtered through a membrane filter to prepare the sample. The resin content in the sample was adjusted to approximately 0.3%. The prepared sample was analyzed by gel permeation chromatography according to the conditions shown below, and the number-average molecular weight was calculated using a molecular weight calibration curve created using standard polystyrene resin. The standard polystyrene resin used was "TSK Standard Polystyrene F-850, F-450, F-288, F-128, F-80, F-40, F-20, F-10, F-4, F-2, F-1, A-5000, A-2500, A-1000, A-500" (manufactured by Tosoh). • HPLC system: Product name "2695 Separations Module" (manufactured by Waters) • Differential refractive index (RI) detector: Product name "2414 detector" (manufactured by Waters) • Column: 4-row column of product name "GPC KF-806M" (manufactured by Showa Denko) • Eluent: Tetrahydrofuran ·Flow rate: 1.0mL / min Oven temperature: 40℃ • Sample injection volume: 100 μL

[0066] (Determining whether the resin is resin particles or not) A sample containing approximately 1.0% resin was prepared by diluting a resin-containing liquid with deionized water. The particle size of the resin particles (cumulative 50% particle size by volume) was measured using a dynamic light scattering particle size analyzer according to the following measurement conditions. 50 The particle size was measured. The particle size analyzer used was the "NanoTrac WAVE II-Q" (manufactured by MicroTrac-Bell). If particles with a particle size were measured using this method, the resin was determined to be "resin particles" ("water-dispersible resin"). On the other hand, if particles with a particle size were not measured using this method, the resin was determined not to be "resin particles" ("water-soluble resin"). [Measurement conditions]: SetZero: 30s • Number of measurements: 3 • Measurement time: 180 seconds ·Shape: true spherical • Refractive index: 1.6 ·Density: 1.0

[0067] (Amount of anionic groups in resin particles) A dispersion of resin particles was used as the sample, and the amount of anionic groups in the resin particles (amount of anionic groups on the particle surface) was measured by colloidal titration using potentiometry. For colloidal titration, a potentiometric automatic titrator (product name "AT510", manufactured by Kyoto Electronics Manufacturing Co., Ltd.) equipped with a flow potentiometry titration unit (product name "PCD-500", manufactured by Kyoto Electronics Manufacturing Co., Ltd.) was used. A 0.005 mol / L methyl glycol chitosan solution was used as the titration reagent.

[0068] <Manufacturing of resin particles> In a reaction vessel set up inside an autoclave, 60.0 parts ethylene glycol, 40.0 parts neopentyl glycol, 54.5 parts terephthalic acid, and 54.5 parts isophthalic acid were added, and the mixture was heated at 220°C for 4 hours to carry out the esterification reaction. The temperature was raised to 240°C, and the pressure inside the autoclave was reduced to 13 Pa over 90 minutes. The esterification (dehydration condensation) reaction was continued by maintaining the reduced pressure of 240°C and 13 Pa for 5 hours, after which nitrogen gas was introduced into the autoclave to return to atmospheric pressure. After lowering the temperature inside the reaction vessel to 220°C, a catalyst (tetra-n-butyl titanate) and 1.0 part trimetic acid were added, and the mixture was heated at 220°C for 2 hours to carry out the transesterification reaction. The amount of catalyst (moles) was 3 × 10⁻⁶. -4 The formula was "Total amount of polycarboxylic acid used (mol)". Then, nitrogen gas was introduced into the autoclave to create a pressurized state, and the sheet-like resin was extracted. After the extracted resin was cooled to 25°C, it was crushed in a crusher to obtain polyester resin.

[0069] A stirrer (product name "Tornado Stirrer Standard SM-104", manufactured by AS ONE) was set up in a 2L beaker. 200g of polyester resin and methyl ethyl ketone (MEK) were added to this beaker and stirred at 30°C to dissolve the polyester resin. Next, 15.9g of 5% potassium hydroxide aqueous solution was added and stirred for 30 minutes. While stirring at 30°C, 500g of deionized water was added dropwise at a rate of 20mL / min. After raising the temperature to 60°C, the MEK and some of the water were removed by distillation. After cooling to 25°C, the solution was filtered through a 150-mesh wire mesh, and deionized water was added to obtain a dispersion of polyester resin particles 1 with a resin particle content of 30.0%.

[0070] Furthermore, the amount of trimellitic acid used was appropriately adjusted so that the amount of anionic groups (μmol / g) was as shown in Table 1, and the reaction time was adjusted so that the weight-average molecular weight was as shown in Table 1. Except for these factors, dispersions of polyester resin particles 2 to 8 with a resin particle content of 30.0% were obtained in the same manner as described above for polyester resin particle 1.

[0071] (Acrylic resin particles) 1,160 mL of water was placed in the reaction vessel and heated to 90°C. Separately, a solution was prepared by dissolving 1.39 g of potassium persulfate (initiator) in 160 mL of water. First, 32 mL of this solution was added to the reaction vessel and stirred. Separately, a monomer mixture was prepared by mixing 183 g of styrene, 80 g of benzyl acrylate, 1.5 g of methacrylic acid, 1.6 g of isooctyl thioglycolate (chain transfer agent), and 9.98 g of a 30% aqueous solution of emulsifier in 159.4 mL of water. As the emulsifier, the product name "Rhodafac RS 710" (manufactured by Rhodia Novecare), an aliphatic phosphate ester (10 moles of ethylene oxide groups added), was used. This mixture was added dropwise to the reaction vessel over 30 minutes under stirring. In parallel, 129.4 g of the initiator solution was added dropwise to the reaction vessel over 30 minutes. The reaction mixture was stirred and maintained at 90°C for 3 hours to allow the reaction to proceed. Afterward, it was cooled to 50°C. Then, potassium hydroxide (50% in water) was added to adjust the pH of the liquid containing the resin particles to 8.5. After cooling to 25°C and filtering through a 200-mesh filter, an appropriate amount of deionized water was added to obtain a dispersion of acrylic resin particles with a resin particle content of 30.0%.

[0072] TIFF2023056486000001.tif82170

[0073] <Structure and properties of surfactants (polyoxyethylene alkyl ethers)> The types of surfactants shown in Table 2 were prepared. All of the prepared surfactants were manufactured by Nikko Chemicals. The HLB values ​​were calculated using the Griffin method.

[0074] TIFF2023056486000002.tif88170

[0075] <Ink preparation> (Ink 1-34) Each ink was prepared by mixing the components (in %) shown in Tables 3-1 to 3-3, stirring thoroughly, and then pressure filtering through a 0.8 μm pore size cellulose acetate filter (manufactured by Advantec). In Tables 3-1 to 3-3, "Zonyl FS-3100" is the trade name for a fluorine-based surfactant manufactured by Chemours, and "BYK348" is the trade name for a silicone-based surfactant manufactured by Big Chemie. Also, "Proxel GXL(S)" is the trade name for a fungicide manufactured by Arch Chemicals.

[0076] TIFF2023056486000003.tif164170

[0077] TIFF2023056486000004.tif175170

[0078] TIFF2023056486000005.tif176170

[0079] (Ink 35) Ink 35 was prepared according to the preparation method for "Ink 3" described in Patent Document 1. Resin emulsion 1 is resin particles formed from acrylic resin, with an anionic group content of 440 μmol / g. Surfinol 465 (trade name, surfactant) is an ethylene oxide adduct of acetylene glycol manufactured by Nisshin Chemical Industry Co., Ltd. The hydrocarbon group of the ethoxylated aliphatic alcohol has 16 to 18 carbon atoms. • Pigment dispersion (solids): 5.00% • Resin emulsion 1 (solids content): 5.00% • Wax emulsion 3 (solid content): 3.00% Glycerin (boiling point 290°C): 15.00% • Diethylene glycol (boiling point 246°C): 10.00% • 1,2-Hexanediol (boiling point 223°C): 2.00% Trimethylolpropane (boiling point 296°C): 5.00% • Surfinol 465: 1.00% • Sodium lauryl sulfate (surfactant A, ionic): 0.06% • Ethoxylated aliphatic alcohol (surfactant A, nonionic): 0.24% • Ion-exchanged water: 53.70%

[0080] (Ink 36) Ink 36 was prepared according to the method for preparing the ink described in "Example 1" in Patent Document 2. The dispersant resin 2 is a water-soluble acrylic resin. The resin emulsion 1 is resin particles formed from acrylic resin, with an anionic group content of 18 μmol / g. The surfactant 1 is polyoxyethylene stearyl ether (trade name "Emulgen 320P", manufactured by Kao Corporation), with 18 carbon atoms in the hydrocarbon group and an HLB value of 13.9. Pigment 1 (solids): 4.0% • Dispersant resin 2 (solids): 0.5% • Resin emulsion 1 (solids content): 6.0% • Surfactant 1:0.5% • 2-Pyrrolidone (boiling point 245°C): 8.0% • 1,2-Pentanediol (boiling point 210°C): 3.0% • Diethylene glycol (boiling point 246°C): 7.0% • Ion-exchanged water: 71.5%

[0081] <Preparation of reaction solution> Each component (in %) shown in Table 4 was mixed and thoroughly stirred, then pressure filtered through a 3.0 μm pore size cellulose acetate filter (manufactured by Advantec) to prepare each reaction solution. In Table 4, "Zonyl FS-3100" is the trade name of a fluorine-based surfactant manufactured by Chemours.

[0082] TIFF2023056486000006.tif81170

[0083] <Preparing the recording medium> The following recording media were prepared. • Recording medium 1: Product name "Scotchcal Graphic Film IJ1220", manufactured by 3M, a sheet made of polyvinyl chloride. This recording medium 1 was contacted from the start of contact for 30 msec in the Bristow method. 1 / 2 Up to 10 mL / m² of water absorption capacity 2 The following are non-absorbent recording media. • Recording medium 2: Product name "GL-101", manufactured by Canon, glossy paper. This recording medium is used in the Bristow method from the start of contact for 30 msec. 1 / 2 Up to 10 mL / m² of water absorption capacity 2 It is a recording medium with absorbency exceeding [a certain limit].

[0084] <Rating> The following evaluation was performed using an inkjet recording device (product name "imagePROGRAF PRO-2000", manufactured by Canon) with a built-in heating mechanism. This inkjet recording device is defined as having a recording duty cycle of 100% for solid images recorded under the condition that one drop of 4 ng of ink is applied to a unit area of ​​1 / 1,200 inch × 1 / 1,200 inch. The ink and reaction solution were each filled into ink cartridges and mounted on the above inkjet recording device in the combinations shown in Table 5. On the recording medium shown in Table 5, a solid image of the reaction solution with a recording duty cycle of 20% and a solid image of the ink with a recording duty cycle of 2cm × 2cm were superimposed to record an image. In this invention, "AA", "A", and "B" were defined as acceptable levels in the evaluation criteria for each item shown below, and "C" was defined as an unacceptable level. The evaluation results are shown in Table 5.

[0085] (Mapping property) Two fluorescent lamps, spaced 5 cm and 10 cm apart, were used as observation light sources, and the fluorescent lamps were projected onto an image from a distance of 2 m. The shape of the projected fluorescent lamps was visually confirmed under conditions of a 45-degree illumination angle and a 45-degree observation angle, and the image quality was evaluated according to the evaluation criteria shown below. AA: Two fluorescent lights, spaced 5cm apart, were clearly projected onto the image. A: The edges of the two projected fluorescent lights, spaced 5cm apart, were blurred, but the boundary between them was discernible. B: The boundary between two fluorescent lights spaced 5cm apart was not discernible, but the boundary between two fluorescent lights spaced 10cm apart could be identified. C: I couldn't see the boundary between the two projected fluorescent lights that were 10cm apart.

[0086] (Changes in mapping properties) The mapping properties described above were defined as the "rank before preservation." Furthermore, the mapping properties were evaluated similarly using ink stored at 60°C for two weeks, and this was defined as the "rank after preservation." The ranks before and after preservation were then compared, and the change in mapping properties was evaluated according to the evaluation criteria shown below.

[0087] (Evaluation Criteria) A: The mapping rank was the same before and after saving. B: The mapping quality rank differed before and after preservation, but the mapping quality after preservation was rank A or B. C: The mapping quality rank differed before and after preservation, with the mapping quality after preservation being rank C.

[0088] TIFF2023056486000007.tif153170

[0089] In Reference Examples 1-3, no reaction solution was used, resulting in inferior image quality compared to all of the other examples. Furthermore, in Reference Examples 4-6, which used an absorbent recording medium, the reaction solution permeated the recording medium, resulting in better image quality than in Reference Examples 1-3, but still inferior to all of the other examples. However, the image quality of the images recorded in Reference Examples 4-6 was comparable regardless of the type of ink used.

[0090] This embodiment includes the following methods and configurations. (Method 1) An inkjet recording method in which an aqueous ink and an aqueous reaction solution that reacts with the aqueous ink are ejected from an inkjet recording head and applied to a recording medium to record an image, A step of ejecting the aqueous ink from the recording head and applying it to the recording medium, The process includes discharging the reaction solution from the recording head and applying it to the recording medium, The aqueous ink contains resin particles and polyoxyethylene alkyl ether having an anionic group amount of 150 μmol / g or less. The polyoxyethylene alkyl ether has an alkyl group with 16 or more carbon atoms, and its HLB value, as determined by the Griffin method, is 14.0 or higher. The recording medium, in the Bristow method, from the start of contact for 30 msec 1 / 2 Up to 10 mL / m² of water absorption capacity 2 An inkjet recording method characterized by the following: (Method 2) The inkjet recording method according to Method 1, wherein the content (mass%) of the polyoxyethylene alkyl ether in the aqueous ink is 0.10 times or less in mass ratio to the content (mass%) of the resin particles. (Method 3) The inkjet recording method according to Method 1 or 2, wherein the HLB value of the polyoxyethylene alkyl ether determined by the Griffin method is 16.0 or less. (Method 4) The inkjet recording method according to any one of Methods 1 to 3, wherein the resin particles are polyester resin particles. (Method 5) The inkjet recording method according to Method 4, wherein the polyester resin particles are formed from a polyester resin having a weight-average molecular weight of 30,000 or more and 70,000 or less. (Method 6) The aforementioned aqueous ink further contains a water-soluble organic solvent, The inkjet recording method according to method 4 or 5, wherein the content (mass%) of the water-soluble organic solvent is 1.0 times or more and 4.0 times or less in mass ratio to the content (mass%) of the polyester resin particles. (Method 7) An inkjet recording method according to any one of Methods 1 to 6, wherein the aqueous ink further contains a first water-soluble organic solvent having a boiling point of 220°C or lower. (Method 8) The inkjet recording method according to Method 7, wherein the first water-soluble organic solvent is 1,2-butanediol. (Method 9) An inkjet recording method according to any one of Methods 1 to 8, wherein the aqueous ink further contains a pigment. (Configuration 1) An inkjet recording apparatus used in an inkjet recording method in which an aqueous ink and an aqueous reaction solution that reacts with the aqueous ink are ejected from an inkjet recording head and applied to a recording medium to record an image, The aqueous ink contains resin particles and polyoxyethylene alkyl ether having an anionic group amount of 150 μmol / g or less. The polyoxyethylene alkyl ether has an alkyl group with 16 or more carbon atoms, and its HLB value, as determined by the Griffin method, is 14.0 or higher. The recording medium, in the Bristow method, from the start of contact for 30 msec 1 / 2 Up to 10 mL / m² of water absorption capacity 2 An inkjet recording apparatus characterized by the following:

Claims

1. An inkjet recording method in which an aqueous ink and an aqueous reaction liquid that reacts with the aqueous ink are ejected from an inkjet recording head and applied to a recording medium to record an image, comprising: a step of ejecting the water-based ink from the recording head and applying it to the recording medium; a step of ejecting the reaction liquid from the recording head and applying it to the recording medium, the aqueous ink contains resin particles having an anionic group content of 150 μmol / g or less and polyoxyethylene alkyl ether; the polyoxyethylene alkyl ether has an alkyl group having 16 or more carbon atoms and an HLB value determined by the Griffin method of 14.0 or more, The recording medium is １／２ Water absorption up to 10 mL / m ２ An inkjet recording method characterized by the following:

2. 2. The inkjet recording method according to claim 1, wherein the content (% by mass) of the polyoxyethylene alkyl ether in the aqueous ink is 0.10 or less times the content (% by mass) of the resin particles in terms of a mass ratio.

3. An inkjet recording method as described in Claim 2, wherein the content (mass %) of the polyoxyethylene alkyl ether in the aqueous ink is 0.01 times or more in mass ratio to the content (mass %) of the resin particles.

4. 4. The ink jet recording method according to claim 1, wherein the polyoxyethylene alkyl ether has an HLB value of 16.0 or less as determined by the Griffin method.

5. 4. The ink jet recording method according to claim 1, wherein the resin particles are polyester resin particles.

6. 6. The ink jet recording method according to claim 5, wherein the polyester resin particles are formed from a polyester resin having a weight average molecular weight of 30,000 or more and 70,000 or less.

7. the water-based ink further contains a water-soluble organic solvent, The inkjet recording method according to claim 5, wherein the content (% by mass) of the water-soluble organic solvent is 1.0 to 4.0 times the content (% by mass) of the polyester resin particles in terms of a mass ratio.

8. 4. The inkjet recording method according to claim 1, wherein the aqueous ink further contains a first water-soluble organic solvent having a boiling point of 220[deg.] C. or lower.

9. 9. The ink jet recording method according to claim 8, wherein the first water-soluble organic solvent is 1,2-butanediol.

10. The inkjet recording method according to claim 1 , wherein the water-based ink further contains a pigment.

11. An inkjet recording method described in any one of claims 1 to 3, wherein the content (mass %) of the resin particles in the aqueous ink is 0.1 mass % or more and 15.0 mass % or less, based on the total mass of the ink.

12. An inkjet recording method described in any one of claims 1 to 3, wherein the content (mass %) of the polyoxyethylene alkyl ether in the aqueous ink is 0.1 mass % or more and 1.0 mass % or less, based on the total mass of the ink.

13. An inkjet recording apparatus used in an inkjet recording method in which an aqueous ink and an aqueous reaction liquid that reacts with the aqueous ink are ejected from an inkjet recording head and applied to a recording medium to record an image, comprising: the aqueous ink contains resin particles having an anionic group content of 150 μmol / g or less and polyoxyethylene alkyl ether; the polyoxyethylene alkyl ether has an alkyl group having 16 or more carbon atoms and an HLB value determined by the Griffin method of 14.0 or more, The recording medium is １／２ Water absorption up to 10 mL / m ２ An inkjet recording apparatus characterized by the following:

Images