JP2023056486A - Inkjet recording method and inkjet recording device - Google Patents

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

The present invention relates to an inkjet recording method and an inkjet recording apparatus.

In recent years, the inkjet recording method has been increasingly used in the field of signs and displays, such as recording of posters and large-sized advertisements. In this field, polyvinyl chloride sheets, polyethylene terephthalate (PET) sheets, and the like are often used as recording media from the viewpoint of durability and cost of recording media. These recording media have no or almost no water-based ink absorbing layer on the recording surface of the recording medium. recording medium (recording medium with low water-based ink absorption). Solvent-based inks, curable inks, and the like have conventionally been used to record images on these recording media. However, from the viewpoint of reducing environmental load and odor, there is an increasing need for water-based inks using water-based media.

Various techniques for recording good images on non-absorbent recording media have been investigated. For example, a recording method using a reaction liquid containing an aggregating agent for aggregating components in the ink has been proposed in order to quickly fix the ink adhering to the recording medium and record a high-quality image with suppressed unevenness. (Patent Document 1). In addition, an ink containing resin fine particles and a nonionic surfactant and ensuring storage stability has been proposed in order to record an image with excellent scratch resistance when used with a reaction liquid (Patent Document 2).

JP 2018-162341 A JP 2018-165314 A

However, in the case of the method proposed in Patent Document 1, the present inventors have studied and found that the image clarity of the image recorded with the ink before storage is different from the image clarity of the image recorded with the ink after storage. It was found that the image clarity of the image recorded using the ink after storage was poor. Further, when using the ink proposed in Patent Document 2, it was found to be difficult to record an image exhibiting the required level of image clarity. Furthermore, it was found that the image clarity of the image recorded with the ink before storage differs from the image clarity of the image recorded with the ink after storage.

Accordingly, an object of the present invention is to provide a low-to-non-absorbent image that exhibits excellent image clarity and, even when using the ink after storage, exhibits the same image clarity as when using the ink before storage. To provide an ink jet recording method capable of recording on a flexible recording medium. Another object of the present invention is to provide an inkjet recording apparatus for use in this inkjet recording method.

That is, according to the present invention, there is provided an inkjet recording method in which a water-based ink and a water-based reaction liquid that reacts with the water-based ink are ejected from an ink-jet recording head and applied to a recording medium to record an image, a step of ejecting the ink from the recording head to apply it to the recording medium; and a step of ejecting the reaction liquid from the recording head to apply it to the recording medium, wherein the water-based ink contains an anionic group. containing resin particles and polyoxyethylene alkyl ether having an amount of 150 μmol/g or less, the polyoxyethylene alkyl ether having an alkyl group having 16 or more carbon atoms, and an HLB value determined by the Griffin method of 14.0 As described above, there is provided an inkjet recording method, wherein the recording medium has a water absorption amount of 10 mL/m ² or less from the start of contact until 30 msec ^1/2 in the Bristow method.

According to the present invention, an image having excellent image clarity and exhibiting the same image clarity as that obtained when the ink before storage is used even when the ink after storage is used is formed with a low to non-absorbent ink. An inkjet recording method capable of recording on a recording medium can be provided. Further, according to the present invention, it is possible to provide an inkjet recording apparatus used for this inkjet recording method.

1 is a perspective view schematically showing an embodiment of an inkjet recording apparatus of the present invention; FIG. 1 is a side view schematically showing an embodiment of an inkjet recording apparatus of the present invention; FIG.

The present invention will be further described in detail below with reference to preferred embodiments. In the present invention, when the compound is a salt, the salt is dissociated into ions in the ink, but for convenience, it is expressed as "containing the salt." In addition, water-based ink for inkjet is sometimes simply referred to as "ink". Unless otherwise specified, physical property values are values at normal temperature (25° C.) and normal pressure (1 atm).

In the present specification, the term "unit" means a unit structure corresponding to one monomer, unless otherwise specified. "(Meth)acrylic acid" and "(meth)acrylate" shall mean "acrylic acid, methacrylic acid" and "acrylate, methacrylate", respectively. Polyester resins commonly used for water-based inkjet inks are composed of a unit derived from a polyhydric alcohol and a unit derived from a polycarboxylic acid. A structure containing an ester bond (--COO--) composed of a unit derived from a polyhydric alcohol and a unit derived from a polycarboxylic acid is sometimes called an "ester unit."

Furthermore, in this specification, low-absorption to non-absorption recording media may be collectively referred to as "non-absorption recording medium". A low-absorption to non-absorption recording medium is defined as having a water absorption of 10 mL/m ² or less from the start of contact to 30 msec ^1/2 in the Bristow method.

In order to obtain good image quality on a non-absorbing recording medium, it is necessary to use a combination of ink and reaction liquid, which is a so-called "reaction system" in which ink and reaction liquid are combined. In the case of recording an image with improved image clarity by a reaction system, for example, an ink containing resin particles is used. Considering the storage stability of the ink, resin particles having a relatively small amount of anionic groups are used. However, since resin particles having a small amount of anionic groups tend to aggregate due to reaction with the reactant in the reaction liquid, it is difficult to improve image clarity. As a result of investigations, the present inventors have found that the use of an ink containing polyoxyethylene alkyl ether as a surfactant improves image clarity. However, when an image was recorded using the ink after storage, it was found that the image clarity was lower than that of the image recorded using the ink before storage. The reason for this is presumed by the present inventors as follows.

The alkyl group of the polyoxyethylene alkyl ether is adsorbed to the resin particles, thereby easing the reaction between the resin particles in the ink and the reactant (aggregating component) in the reaction liquid, thereby improving the image clarity. However, when the ink is stored, the surfactant adsorbed to the resin particles is desorbed, so that the resin particles and the reactant tend to react with each other, and the resin particles aggregate to reduce image clarity. The present inventors paid attention to the number of carbon atoms in the alkyl groups constituting the polyoxyethylene alkyl ether and the HLB value of the polyoxyethylene alkyl ether, and made further studies. As a result, by including in the ink a polyoxyethyl alkyl ether having an alkyl group with a carbon number of 16 or more and an HLB value of 14.0 or more, the image clarity is improved even when the ink is used after storage. I found that it becomes difficult to change. The reason for this is presumed by the present inventors as follows.

A resin particle having a small amount of anionic groups has a large number of hydrophobic moieties. A polyoxyethyl alkyl ether having an alkyl group with a large number of carbon atoms is considered to be difficult to detach from the resin particles because it is stabilized by being adsorbed on the hydrophobic portions of the resin particles at multiple points. In addition, since polyoxyethylene alkyl ethers with small HLB values are poorly soluble in aqueous media, the cohesiveness of the ink changes before and after storage of the ink, and the image clarity of the obtained image is also considered to change. On the other hand, a polyoxyethylene alkyl ether having an HLB value of 14.0 or more readily adsorbs to the resin particles and is less likely to detach from the resin particles even after the ink is stored. Conceivable.

<Inkjet recording method and inkjet recording apparatus>
The inkjet recording method of the present invention is a method of ejecting a water-based ink and a water-based reaction liquid that reacts with the water-based ink from a recording head of an ink jet system, and applying the liquid to a recording medium to record an image. The inkjet recording method of the present invention has a step of ejecting a water-based ink from a recording head to apply it to a recording medium, and a step of ejecting a reaction liquid from a recording head to apply it to a recording medium. The water-based 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 with 16 or more carbon atoms and an HLB value of 14.0 or more as determined by the Griffin method. Further, the inkjet recording apparatus of the present invention is an apparatus used in an inkjet recording method in which a water-based ink and a water-based reaction liquid that reacts with the water-based ink are ejected from an ink-jet recording head and applied to a recording medium to record an image. . The inkjet recording apparatus of the present invention is an apparatus suitable for use in the above recording method. The inkjet recording method and inkjet recording apparatus (hereinafter also simply referred to as "recording method and recording apparatus") of the present invention will be described in detail below.

(water-based ink)
The ink contains resin particles and polyoxyethylene alkyl ether. Each component constituting the ink will be described in detail below.

[Resin particles]
The resin particles have an anionic group content of 150 μmol/g or less. The “amount of anionic groups in resin particles” is a physical property value represented by the amount (μmol) of anionic groups present on the particle surface of resin particles per unit mass (g). When the amount of the anionic group exceeds 150 μmol/g, the polyoxyethylene alkyl ether becomes difficult to be adsorbed to the resin particles, and the effect of improving the image clarity may be weakened. Image clarity is lost. The amount of anionic groups in the resin particles can be measured by colloidal titration using a potential difference.

The content (% by mass) of the resin particles in the ink is preferably 0.1% by mass or more and 15.0% by mass or less, and 1.0% by mass or more and 10.0% by mass or less, based on the total mass of the ink. More preferably: The resin particles are present in the ink in a dispersed state, that is, in the form of a resin emulsion. It is preferable that the resin particles do not contain a coloring material.

As used herein, the term “resin particles” refers to a resin that is insoluble in the aqueous medium that constitutes the ink. means a resin that may be present in On the other hand, "water-soluble resin" refers to a resin that is soluble in the aqueous medium that constitutes the ink. means a resin that may be present in "Resin particles" can also be rephrased as "water-dispersible resin (water-insoluble resin)".

Whether or not a certain resin is a "resin particle" can be determined according to the method described below. First, a liquid containing a resin to be determined (resin content: 10% by mass) is prepared. Next, a sample is prepared by diluting the prepared liquid 10-fold (by volume) with deionized water. Then, when the particle size of the resin in the sample is measured by the dynamic light scattering method, if particles having a particle size are measured, the particles are determined to be "resin particles" (water-dispersible resin). . On the other hand, if particles having a particle size are not measured, it is determined that the resin is not a "resin particle" (is a "water-soluble resin"). The measurement conditions at this time can be, for example, SetZero: 30 seconds, number of measurements: 3, measurement time: 180 seconds, shape: spherical, refractive index: 1.59. As the particle size distribution analyzer, a particle size analyzer using dynamic light scattering (for example, trade name “Nanotrack UPA-EX150” manufactured by Nikkiso Co., Ltd.) can be used. Of course, the particle size distribution measuring device and measurement conditions are not limited to those described above.

Examples of the resin constituting the resin particles include acrylic resins, urethane resins, olefin resins, and polyester resins. Among them, polyester resin is preferable. That is, the resin particles contained in the ink are preferably polyester resin particles. Among the resin particles, polyester resin particles have a good affinity with polyoxyethylene alkyl ether, so that the polyoxyethylene alkyl ether is less likely to be released from the resin particles even when the ink is stored. Therefore, it is possible to further suppress the change in image clarity of the image recorded with the ink after storage.

[acrylic resin]
The acrylic resin preferably has a hydrophilic unit and a hydrophobic unit as structural units. Among them, a resin having a hydrophilic unit derived from (meth)acrylic acid and a hydrophobic unit derived from at least one of a monomer having an aromatic ring and a (meth)acrylic acid ester is preferred. In particular, a resin having a hydrophilic unit derived from (meth)acrylic acid and a hydrophobic unit derived from at least one monomer of styrene and α-methylstyrene is preferred. Since these resins easily interact with pigments, they can be suitably used as resin dispersants for dispersing pigments.

A hydrophilic unit is a unit having a hydrophilic group such as an anionic group. A hydrophilic unit can be formed, for example, by polymerizing a hydrophilic monomer having a hydrophilic group. Specific examples of hydrophilic monomers having a hydrophilic group include acidic monomers having a carboxylic acid group such as (meth)acrylic acid, itaconic acid, maleic acid and fumaric acid, and anhydrides of these acidic monomers. and anionic monomers such as compounds and salts. Examples of cations constituting salts of acidic monomers include ions such as lithium, sodium, potassium, ammonium and organic ammonium. A hydrophobic unit is a unit that does not have a hydrophilic group such as an anionic group. A hydrophobic unit can be formed, for example, by polymerizing a hydrophobic monomer that does not have a hydrophilic group such as an anionic group. Specific examples of hydrophobic monomers include monomers having aromatic rings such as styrene, α-methylstyrene, and benzyl (meth)acrylate; methyl (meth)acrylate, butyl (meth)acrylate, (meth)acrylate, ) (meth)acrylate monomers such as 2-ethylhexyl acrylate.

[Urethane resin, olefin resin]
A urethane resin can be obtained, for example, by reacting a polyisocyanate and a polyol. Moreover, what made the chain extension agent further react may be used. Examples of olefin resins include polyethylene and polypropylene.

[Polyester resin]
A polyester resin is usually composed of a unit derived from a polyhydric alcohol and a unit derived from a polycarboxylic acid. An unreacted hydroxy group or carboxylic acid group exists at the end of the polyester resin. The sum of the proportion (% by mass) of the units derived from the polyhydric alcohol and the proportion (% by mass) of the units derived from the polycarboxylic acid in the polyester resin is preferably 90.0% by mass or more. Moreover, it is more preferably 95.0% by mass or more, and may be 100.0% by mass.

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

Divalent to tetravalent polyvalent carboxylic acids can be mentioned as the polyvalent carboxylic acid. Examples of polyvalent carboxylic acids include polyvalent carboxylic acids having an aliphatic group, polyvalent carboxylic acids having an aromatic group, and nitrogen-containing polyvalent carboxylic acids. Examples of polyvalent carboxylic 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; tetravalent carboxylic acid; and the like. Oligomers (low-molecular-weight polymers with a molecular weight of 1,000 or less) can also be used as polyvalent carboxylic acids. The ratio (% by mass) of units derived from polyvalent carboxylic acid in the polyester resin is preferably 40.0% by mass or more and 60.0% by mass or less.

The weight average molecular weight of the polyester resin particles (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 chain of the polyester resin is too short, the polyoxyethylene alkyl ether is likely to be eliminated, and the effect of improving the image clarity of the image recorded with the ink after storage is somewhat weak. may become. On the other hand, when the weight-average molecular weight exceeds 70,000, the molecular chain of the polyester resin is too long, so that molecular movement is difficult to occur and interaction with the polyoxyethylene alkyl ether is difficult to occur, resulting in poor image clarity of the recorded image. may be slightly weaker. The weight average molecular weight in this specification is a polystyrene-equivalent value measured by gel permeation chromatography.

[Analysis of resin particles]
The composition of the resin that constitutes the resin particles can be analyzed, for example, by the method described below. 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 to be dissolved in the organic solvent may be in an aqueous dispersion state or in a dry state. The prepared sample is analyzed by analysis methods such as nuclear magnetic resonance (NMR) spectroscopy and matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) to determine the type of unit (monomer) that constitutes the resin. and the ratio can be known. Also, by analyzing the resin particles by pyrolysis gas chromatography, it is possible to detect the units (monomers) that constitute the resin. When preparing a sample, if an insoluble matter that does not dissolve in an organic solvent is generated, the generated insoluble matter can be analyzed by pyrolysis gas chromatography to detect the units (monomers) that constitute the resin.

[Other resins]
The ink may further contain a resin (another resin) other than the resin particles. The type and form of other resins may be those that can stably exist in the water-based ink. Specific examples of other resins include water-soluble resins. Examples of other resins include (meth)acrylic resins, polyamide resins, polyester resins, polyvinyl alcohol resins, and polyolefin resins. A base may be added to the ink to improve the solubility of these resins. Examples of bases that can be used include organic amines such as monoethanolamine, diethanolamine, triethanolamine, aminemethylpropanol, and N,N-dimethylethanolamine; inorganic bases such as potassium hydroxide and sodium hydroxide;

[Polyoxyethylene alkyl ether]
The ink contains polyoxyethylene alkyl ether having an alkyl group (hydrocarbon group) with 16 or more carbon atoms. Polyoxyethylene alkyl ether is a component that functions as a so-called surfactant, and is represented by the following general formula (1), for example. If the number of carbon atoms in the alkyl group is less than 16, the image clarity of the recorded image is poor, and the resin particles are likely to be released from the resin particles during storage, impairing the image clarity of the image recorded with the ink after storage. The number of carbon atoms in the polyoxyethylene alkyl ether is preferably 30 or less, more preferably 24 or less. Hydrocarbon groups include alkyl groups and alkenyl groups. n is preferably 10 or more and 50 or less, more preferably 15 or more and 30 or less.
R—O—(CH ₂ CH ₂ O) _n —H (1)
(In general formula (1), R represents a hydrocarbon group having 16 or more carbon atoms, and n represents a natural number)

The HLB value of the polyoxyethylene alkyl ether determined by the Griffin method is 14.0 or more. If the HLB value of the polyoxyethylene alkyl ether is less than 14.0, the effect of improving the clarity of the recorded image may be weakened. In addition, the solubility in an aqueous medium decreases, and the adsorption to the resin particles progresses slowly, so that 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 less. A polyoxyethylene alkyl ether having an HLB value of 16.0 or less is not too soluble in an aqueous medium, and is difficult to detach from the resin particles even when the ink is stored. Therefore, it is possible to further suppress the change in image clarity of the image recorded with the ink after storage. In addition, in order to facilitate adsorption of polyoxyethylene alkyl ether to resin particles, when using acrylic resin particles, it is preferable to use polyoxyethylene alkyl ether having an HLB value of 16.0 or less.

The HLB value according to the Griffin method can be calculated from the following formula (2). The HLB value determined by the Griffin method is a physical property value representing the degree of hydrophilicity or lipophilicity of a surfactant, and ranges from 0.0 to 20.0. The smaller the HLB value, the higher the lipophilicity, and the larger the HLB value, the higher the hydrophilicity.
HLB value = 20 x (formula weight of hydrophilic group of surfactant/molecular weight of surfactant) (2)

The content (% by mass) of the polyoxyethylene alkyl ether in the ink is preferably 0.1% by mass or more and 1.0% by mass or less, and 0.1% by mass or more and 0.1% by mass or less, based on the total mass of the ink. It is preferably 8% by mass or less. The content (% by mass) of the polyoxyethylene alkyl ether in the ink is preferably 0.10 times or less, and preferably 0.05 times or less, as a mass ratio with respect to the content (% by mass) of the resin particles. is more preferred. If the above mass ratio exceeds 0.10 times, the polyoxyethylene alkyl ether may tend to form micelles, and the effect of improving the image clarity of the image recorded with the ink after storage may be slightly weakened. . The above mass ratio is preferably 0.01 times or more.

[Color material]
The ink can contain coloring materials such as pigments and dyes. Among them, pigments are preferable as the coloring material, and resin-dispersed pigments, which will be described later, are particularly preferable. The content (% by mass) of the coloring material in the ink is preferably 0.1% by mass or more and 15.0% by mass or less, and 1.0% by mass or more and 10.0% by mass or less, based on the total mass of the ink. More preferably:

Specific examples of pigments include inorganic pigments such as carbon black and titanium oxide; and organic pigments such as azo, phthalocyanine, quinacridone, isoindolinone, imidazolone, diketopyrrolopyrrole, dioxazine and perinone. Among the pigments, carbon black and organic pigments are preferably used.

Examples of the method of dispersing the pigment include a resin-dispersed pigment using a resin as a dispersant, and a self-dispersing pigment in which a hydrophilic group is bonded to the particle surface of the pigment. Other examples include resin-bonded pigments in which an organic group containing a resin is chemically bonded to the surface of pigment particles, and microcapsule pigments in which the surfaces of pigment particles are coated with resin or the like.

As the resin dispersant for dispersing the pigment in the aqueous medium, it is preferable to use one that can disperse the pigment in the aqueous medium by the action of an anionic group. A water-soluble resin is preferably used as the resin dispersant. Examples of resin dispersants include acrylic resins and urethane resins. Among them, acrylic resins are preferable, and acrylic resins composed of units derived from (meth)acrylic acid or (meth)acrylic acid ester are more preferable.

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.

[Aqueous medium]
The ink is an aqueous ink containing at least water as an aqueous medium. The ink can contain water or an aqueous medium that is a mixed solvent of water and a water-soluble organic solvent. As water, it is preferable to use deionized water or ion-exchanged water. The water content (% by 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.

As the water-soluble organic solvent, alcohols, (poly)alkylene glycols, glycol ethers, nitrogen-containing compounds, sulfur-containing compounds, and the like, which can be used for inkjet inks, can be used. Generally, the term "water-soluble organic solvent" refers to liquids, but in the present invention, those that are solid at 25°C (normal temperature) are also included in water-soluble organic solvents. Examples of water-soluble organic solvents that are commonly used for water-based inks and are solid at 25° C. include 1,6-hexanediol, trimethylolpropane, ethylene urea, urea, and polyethylene glycol having a number average molecular weight of 1,000. be able to. As the water-soluble organic solvent, it is preferable to use one having a boiling point higher than that of water.

The content (% by mass) of the water-soluble organic solvent in the ink is preferably 3.0% by mass or more and 50.0% by mass or less, and 10.0% by mass or more and 30.0% by mass, based on the total mass of the ink. % by mass or less is more preferable. The content (% by mass) of the water-soluble organic solvent in the ink is preferably 1.0 to 4.0 times the content (% by mass) of the polyester resin particles. If the above mass ratio is less than 1.0 times, the amount of the water-soluble organic solvent is too small relative to the polyester resin particles, so that the polyester resin particles are less likely to be softened by the water-soluble organic solvent, resulting in an effect of improving image clarity. may become weaker. On the other hand, if the mass ratio is more than 4.0 times, the amount of the water-soluble organic solvent is too large for the polyester resin particles, and the water-soluble organic solvent remaining on the recording medium causes the polyester resin particles to move. In some cases, the effect of improving image clarity may be weakened.

The ink preferably further contains a first water-soluble organic solvent having a boiling point of 220° C. or less. 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. At this time, if the compatibility between the water-soluble organic solvent and the resin particles is high, the resin particles are softened and the image clarity tends to increase. Then it is easy to occur. The boiling point of the first water-soluble organic solvent is preferably higher than 100°C. Examples of the first water-soluble organic solvent having 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.), propylene glycol (188° C.) and the like. Among them, 1,2-butanediol is preferably used as the first water-soluble organic solvent because of its excellent image clarity.

[Other ingredients]
If necessary, the ink may contain surfactants (other surfactants) other than the above-mentioned polyoxyethylene alkyl ethers, pH adjusters, antifoaming agents, rust inhibitors, antiseptics, antifungal agents, antioxidants, Various additives such as agents, anti-reducing agents, and chelating agents may also be included. 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 the surfactant (including the polyoxyethylene alkyl ether described above) in the ink is preferably 0.1% by mass or more and 5.0% by mass or less based on the total mass of the ink. , more preferably 0.1% by mass or more and 2.0% by mass or less.

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

(Reaction solution)
The reaction liquid contains a reactant that reacts with the ink when it comes into contact with the ink and aggregates components in the ink (components having anionic groups such as resins and self-dispersing pigments).

[Reactant]
Examples of the reaction solution include cationic components such as polyvalent metal ions and cationic resins; organic acids; and the like. Among them, the reactive agent is preferably an organic acid and a polyvalent carboxylic acid having a valence of 2 or more (which may be a salt or a hydrogen salt).

Polyvalent metal ions include divalent metal ions such as ^{Ca 2+ ,} Cu ²⁺ , Ni ²⁺ , Mg ²⁺ , Sr ²⁺ , ^{Ba 2+} and Zn ^{2+ ;} trivalent metal ions; In order to contain polyvalent metal ions in the reaction solution, a polyvalent metal salt (which may be a hydrate) composed of a combination of polyvalent metal ions and anions can be used. Examples of anions include Cl ⁻ , Br ⁻ , I ^{− ,} ClO − , ClO ₂ ⁻ , ClO ₃ ⁻ , ClO ₄ ⁻ , NO ₂ ⁻ , NO ₃ ⁻ , SO ₄ ²⁻ , CO ₃ ²⁻ , HCO ₃ ^- , PO ₄ ^3- , HPO ₄ ^2- , and H ₂ PO ₄ ^- ; HCOO ^- , (COO ^- ) ₂ , COOH(COO ^- ), CH ₃ COO ^- , C ₂ H ₄ (COO ^- ) ₂ , C ₆ H ₅ COO ⁻ , C ₆ H ₄ (COO ⁻ ) ₂ , and CH ₃ SO ₃ ^— ; When polyvalent metal ions are used as the reactant, the content (% by mass) in terms of polyvalent metal salt in the reaction solution is 1.0% by mass or more and 20.0% by mass or less based on the total mass of the reaction solution. Preferably.

The reaction liquid containing the organic acid has a buffering capacity in the acidic region (pH less than 7.0, preferably pH 2.0 to 5.0), so that the anionic groups of the components present in the ink are efficiently converted into an acid form. can be agglomerated. Examples of organic acids include formic acid, acetic acid, propionic acid, butyric acid, benzoic acid, glycolic acid, lactic acid, salicylic acid, pyrrolecarboxylic acid, furancarboxylic acid, picolinic acid, nicotinic acid, thiophenecarboxylic acid, levulinic acid, and coumaric acid. monocarboxylic acids and their salts; oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, maleic acid, fumaric acid, itaconic acid, sebacic acid, phthalic acid, malic acid, tartaric acid and dicarboxylic acids and their salts and hydrogen salts; tricarboxylic acids such as citric acid and trimellitic acid, salts and hydrogen salts thereof; tetracarboxylic acids such as pyromellitic acid and salts and hydrogen salts thereof; The content (% by mass) of the organic acid in the reaction liquid is preferably 1.0% by mass or more and 50.0% by mass or less based on the total mass of the reaction liquid.

Examples of cationic resins include resins having a primary to tertiary amine structure and resins having a quaternary ammonium salt structure. Specific examples include resins having structures such as vinylamine, allylamine, vinylimidazole, vinylpyridine, dimethylaminoethyl methacrylate, ethyleneimine, and guanidine. In order to increase the solubility in the reaction solution, a cationic resin and an acidic compound may be used together, or a cationic resin subjected to a quaternary treatment may be used. When a cationic resin is used as a reactant, the content (% by mass) of the cationic resin in the reaction liquid is 1.0% by mass or more and 10.0% by mass or less based on the total mass of the reaction liquid. preferable.

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

[Other ingredients]
In addition to the above components, the reaction solution may optionally contain surfactants, pH adjusters, antifoaming agents, rust inhibitors, preservatives, anti-mold agents, antioxidants, anti-reduction agents, and chelating agents. may contain various additives.

(recoding media)
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 tested according to JAPAN TAPPI Paper Pulp Test Method No. 51, "Liquid absorption test method for paper and paperboard", the recording medium has a water absorption of 10 mL/m ² or less from the start of contact to 30 msec ^1/2 according to the Bristow method. In the present invention, a recording medium that satisfies the water absorption condition is defined as a "non-absorbing recording medium". Recording media for inkjet recording (glossy paper, matte paper, etc.) having a coat layer (ink receiving layer) formed of inorganic particles and plain paper having no coat layer have a water absorption of 10 mL/m ² . It is an "absorbent recording medium" that exceeds

Examples of low to non-absorbent recording media include plastic films; recording media in which a plastic film is adhered 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. ; and the like can be used. Among these, a plastic film is preferable, and a recording medium in which an organic resin coat layer as an organic resin layer is provided on the recording surface of a substrate containing cellulose pulp is also preferable.

Since the reaction liquid used in the recording method and the recording apparatus of the present invention quickly permeates an absorbent recording medium when applied, the reaction liquid can be used to produce an image even when compared to a non-absorbent recording medium. Hard to improve quality. On the other hand, when an absorptive recording medium is used, the reaction between the ink and the reaction liquid is less likely to occur, and the surface of the image tends to be smoother. Note that the term "recording medium" as used herein refers not to a transfer medium but to a recording medium on which an image as a recorded matter is recorded.

(Inkjet recording device)
FIG. 1 is a perspective view schematically showing one embodiment of the inkjet recording apparatus of the present invention. FIG. 2 is a side view schematically showing an embodiment of the inkjet recording apparatus of the invention. As shown in FIGS. 1 and 2, the printing apparatus of the present embodiment includes an inkjet printing head 22 that ejects ink and reaction liquid. Examples of the recording head include a recording head that ejects ink and reaction liquid by the action of mechanical energy, and a recording head that ejects ink and reaction liquid by the action of thermal energy. Among them, a recording head that ejects ink and reaction liquid by the action of thermal energy is preferable. The recording head, which ejects ink and reaction liquid by the action of thermal energy, is a thermal type in which thermal energy is applied to the ink and reaction liquid by applying an electric pulse to the electrothermal conversion element, and the ink and reaction liquid are ejected from the ejection port. is a recording head. The thermal print head preferably has a mechanism (temperature control mechanism) for heating the water-based ink ejected from the print head and applied to the print medium to a predetermined temperature.

[Heating process]
The recording method of the present invention preferably further includes a step of heating (heating) the recording medium to which the ink has been applied. By heating the recording medium to which the ink and the reaction liquid have been applied, film formation of the resin particles is promoted, and an image with excellent image clarity can be recorded. The heating temperature of the recording medium to which the ink is applied is preferably 90° C. or lower, and preferably 50° C. or higher. The heating temperature of the ink-applied recording medium may be read by a sensor incorporated at a position corresponding to the heating means of the recording apparatus, or may be obtained by determining the amount of heat determined according to the type of ink and recording medium and the temperature of the recording medium. You may judge from the relationship with temperature.

The heating means is not particularly limited, and can be performed by, for example, known heating means such as a heater, air blowing means such as a dryer, or a combination thereof. That is, the inkjet recording apparatus preferably has a mechanism (heating means) for heating the recording medium to which the ink and the reaction liquid have been applied. Examples of the heating means include the above-described heating means, air blowing means, and means in which these are combined. As a method of heat treatment, a method of applying heat by a heater or the like from the opposite side (back surface) of the recording medium to the recording surface (ink and reaction liquid application surface), and a method of applying warm air or hot air to the recording surface of the recording medium. , a method of heating using an infrared heater from the recording surface or the back surface, and the like. Moreover, you may combine these plural.

In the printing apparatus shown in FIGS. 1 and 2, a heater 25 supported by a frame (not shown) is located downstream in the sub-scanning direction A from the position where the print head 22 reciprocates in the main scanning direction B. are placed. A heater 25 can heat the recording medium 1 to which the ink and the reaction liquid have been applied. Specific examples of the heater 25 include sheathed heaters and halogen heaters. The heater 25 is covered with a heater cover 26 . The heater cover 26 is a member for efficiently irradiating the recording medium 1 with heat generated by the heater 25 . Furthermore, the heater cover 26 is also a member that protects the heater 25 . The recording medium 1 to which the ink and the reaction liquid ejected from the recording head 22 are applied is taken up by the take-up spool 27 to form a roll-shaped take-up medium 24 .

EXAMPLES The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited by the following examples as long as the gist thereof is not exceeded. "Parts" and "%" regarding component amounts are based on mass unless otherwise specified.

<Preparation of pigment dispersion>
(Pigment dispersion liquid 1)
A styrene/acrylic acid copolymer (composition (mol) ratio = 33:67), which is a water-soluble resin, is dissolved in ion-exchanged water by adding sodium hydroxide with an acid value and an equimolar amount, and the resin content is An aqueous solution of resinous dispersant at 20.0% was prepared. This water-soluble resin has a weight average molecular weight of 10,000 and an acid value of 200 mgKOH/g. A mixture of 15.0 parts of a pigment (carbon black), 30.0 parts of an aqueous solution of a resin dispersant, and 55.0 parts of water was placed in a sand grinder and dispersed for 1 hour. Thereafter, centrifugal separation treatment was performed to remove coarse particles, pressure filtration was performed using a microfilter with a pore size of 3.0 μm (manufactured by FUJIFILM Corporation), and an appropriate amount of ion-exchanged water was added to obtain a pigment dispersion liquid 1. . The pigment content in Pigment Dispersion Liquid 1 was 15.0%, and the resin content was 6.0%.

(Pigment dispersion liquid 2)
A solution prepared by dissolving 5.0 g of concentrated hydrochloric acid in 5.5 g of water was cooled to 5° C., and 1.5 g of 4-amino-1,2-benzenedicarboxylic acid was added in this state. The container containing this solution was placed in an ice bath, and a solution obtained by dissolving 1.8 g of sodium nitrite in 9.0 g of water at 5°C was added while stirring to keep the temperature of the solution below 10°C. . After stirring for 15 minutes, 6.0 g of carbon black (D50=100 nm) having a specific surface area of 220 m ² /g and a DBP oil absorption of 105 mL/100 g was added under stirring. Stirred for an additional 15 minutes to obtain a slurry. The resulting slurry was filtered through a filter paper (trade name “Standard Filter Paper No. 2”, manufactured by Advantech), and the particles were thoroughly washed with water and dried in an oven at 110°C. After that, sodium ions were replaced with potassium ions by an ion exchange method to obtain a self-dispersing pigment in which —C ₆ H ₃ —(COOK) ₂ groups were bonded to the particle surfaces of the pigment. An appropriate amount of water was added to adjust the pigment content, and a pigment dispersion liquid 2 having a pigment content of 15.0% was obtained.

(Pigment dispersion liquid 3)
500.0 g of ion-exchanged water and 15.0 g of carbon black were mixed and stirred at 15,000 rpm for 30 minutes to prewet the pigment (carbon black). 4,485 g of ion-exchanged water was added and dispersed with a high-pressure homogenizer to obtain a dispersion liquid. The D50 of the pigment in dispersion was 100 nm. The resulting dispersion was placed in a high-pressure vessel and pressurized at a pressure of 3.0 MPa, and then ozone water having 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 liquid to 10.0 using potassium hydroxide, the solid content concentration was adjusted to obtain a pigment dispersion liquid 3. Pigment Dispersion Liquid 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%.

<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, dissolved at 25° C. for 24 hours, and filtered through a membrane filter to prepare a sample. The resin content in the sample was adjusted to about 0.3%. The prepared sample was analyzed by gel permeation chromatography under the conditions shown below, and the number average molecular weight was calculated using a molecular weight calibration curve prepared using a standard polystyrene resin. As the standard polystyrene resin, the product name "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 device: trade name “2695 Separations Module” (manufactured by Waters)
・ Differential refractive index (RI) detector: trade name “2414 detector” (manufactured by Waters)
・Column: Quadruple column with the trade name “GPC KF-806M” (manufactured by Showa Denko)
・Eluent: tetrahydrofuran ・Flow rate: 1.0 mL/min
・Oven temperature: 40℃
・Sample injection volume: 100 μL

(Determination of whether resin is resin particles)
A resin-containing liquid was diluted with deionized water to prepare a sample having a resin content of about 1.0%. With respect to this sample, the particle size of the resin particles (volume-based cumulative 50% particle size D ₅₀ ) was measured using a particle size distribution analyzer based on the dynamic light scattering method under the following measurement conditions. As the particle size distribution analyzer, a trade name "Nanotrack WAVE II-Q" (manufactured by Microtrack Bell) was used. When particles having a particle size were measured by this measurement method, the resin was determined to be "resin particles"("water-dispersibleresin"). On the other hand, when particles having a particle size were not measured by this measurement method, it was determined that the resin was not a "resin particle" (a "water-soluble resin").
[Measurement condition]:
・Set Zero: 30s
・Number of measurements: 3 ・Measurement time: 180 seconds ・Shape: true sphere ・Refractive index: 1.6
・Density: 1.0

(Amount of anionic groups in resin particles)
Using a dispersion of resin particles as a sample, the amount of anionic groups in the resin particles (the amount of anionic groups on the surface of the particles) was measured by colloidal titration using a potential difference. For colloidal titration, an automatic potentiometric titrator (trade name: "AT510", manufactured by Kyoto Electronics Industry) equipped with a streaming potential titration unit (trade name: "PCD-500", manufactured by Kyoto Electronics Industry) was used. A 0.005 mol/L methyl glycol chitosan solution was used as a titration reagent.

<Production of resin particles>
60.0 parts of ethylene glycol, 40.0 parts of neopentyl glycol, 54.5 parts of terephthalic acid, and 54.5 parts of isophthalic acid are placed in a reaction vessel installed in an autoclave and heated at 220° C. for 4 hours to form an ester. reaction was carried out. The temperature was raised to 240° C., and the pressure inside the autoclave was reduced to 13 Pa over 90 minutes. After the esterification (dehydration-condensation) reaction was continued at 240° C. and a reduced pressure of 13 Pa for 5 hours, nitrogen gas was introduced into the autoclave to restore the normal pressure. After lowering the temperature in the reaction vessel to 220° C., a catalyst (tetra-n-butyl titanate) and 1.0 part of trimetic acid were added, and the mixture was heated at 220° C. for 2 hours to carry out a transesterification reaction. The amount (mol) of the catalyst was defined as “3×10 ⁻⁴ ×total amount (mol) of polyvalent carboxylic acid used”. Thereafter, nitrogen gas was introduced into the autoclave to pressurize it, and the sheet-like resin was taken out. After the resin was taken out and cooled to 25° C., it was pulverized with a crusher to obtain a polyester resin.

A stirrer (trade name “Tornado Stirrer Standard SM-104” manufactured by AS ONE) was set in a 2 L beaker. 200 g of polyester resin and methyl ethyl ketone (MEK) were put into this beaker and stirred at 30° C. to dissolve the polyester resin. Then, 15.9 g of 5% potassium hydroxide aqueous solution was added and stirred for 30 minutes. While stirring at 30° C., 500 g of deionized water was added dropwise at a rate of 20 mL/min. After heating to 60° C., MEK and some water were distilled off. After cooling to 25° C., the mixture was filtered through a 150-mesh wire mesh, and deionized water was added to obtain a dispersion liquid of polyester resin particles 1 having a resin particle content of 30.0%.

In addition, the amount of trimellitic acid used was appropriately changed so that the amount of anionic group (μmol/g) became the value shown in Table 1, and the reaction time was adjusted so that the weight average molecular weight became the value shown in Table 1. It was adjusted. Dispersions of polyester resin particles 2 to 8 having a resin particle content of 30.0% were obtained in the same manner as polyester resin particles 1 except for the above.

(Acrylic resin particles)
1,160 mL of water was added to the reactor 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 placed in a reaction vessel and stirred. Separately, 159.4 mL of water was mixed with 183 g of styrene, 80 g of benzyl acrylate, 1.5 g of methacrylic acid, 1.6 g of isooctylthioglycolate (chain transfer agent), and 9.98 g of a 30% aqueous solution of emulsifier. to prepare a monomer mixture. As the emulsifier, an aliphatic phosphate ester (addition mole number of ethylene oxide group: 10), trade name "Rhodafac RS 710" (manufactured by Rhodia Novecare) was used. This mixture was added dropwise to the reaction vessel over 30 minutes under stirring. Concurrently, 129.4 g of initiator solution was added dropwise to the reaction vessel over 30 minutes. The reaction was stirred and maintained at 90° C. for 3 hours to react. After that, it was cooled to 50°C. Potassium hydroxide (50% in water) was then added to bring the pH of the liquid containing the resin particles to 8.5. After cooling to 25° C. and filtering using a 200-mesh filter, an appropriate amount of ion-exchanged water was added to obtain a dispersion of acrylic resin particles having a resin particle content of 30.0%.

<Structure and physical properties of surfactant (polyoxyethylene alkyl ether)>
Surfactants of the types shown in Table 2 were prepared. All of the prepared surfactants are manufactured by Nikko Chemicals. The HLB value is a value calculated by the Griffin method.

<Ink preparation>
(Inks 1-34)
Each component (unit: %) shown in Tables 3-1 to 3-3 was mixed, thoroughly stirred, and filtered under pressure through a cellulose acetate filter (manufactured by Advantech) with a pore size of 0.8 μm to prepare each ink. bottom. In Tables 3-1 to 3-3, "Zonyl FS-3100" is the trade name of a fluorine-based surfactant manufactured by Chemours, and "BYK348" is the trade name of a silicone-based surfactant manufactured by BYK-Chemie. . "Proxel GXL(S)" is a trade name of an antifungal agent manufactured by Arch Chemicals.

(ink 35)
Ink 35 was prepared according to the preparation method of "Ink 3" described in Patent Document 1. Resin emulsion 1 is resin particles made of acrylic resin, and the amount of anionic groups is 440 μmol/g. Surfynol 465 (trade name, surfactant) is an ethylene oxide adduct of acetylene glycol manufactured by Nissin Kagaku Kogyo. The hydrocarbon group of the ethoxylated fatty alcohol has 16-18 carbon atoms.
・Pigment dispersion (solid content): 5.00%
・ Resin emulsion 1 (solid 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 fatty alcohol (surfactant A, nonionic): 0.24%
・Ion-exchanged water: 53.70%

(ink 36)
Ink 36 was prepared according to the ink preparation method of "Example 1" described in Patent Document 2. Dispersant resin 2 is a water-soluble acrylic resin. Resin emulsion 1 is resin particles made of an acrylic resin, and the amount of anionic groups is 18 μmol/g. Surfactant 1 is polyoxyethylene stearyl ether (trade name “EMULGEN 320P” manufactured by Kao Corporation), and has a hydrocarbon group with 18 carbon atoms and an HLB value of 13.9.
・Pigment 1 (solid content): 4.0%
・Dispersant resin 2 (solid content): 0.5%
・Resin emulsion 1 (solid 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%

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

<Preparing recording media>
The following recording media were prepared.
- Recording medium 1: A sheet made of polyvinyl chloride, manufactured by 3M, under the trade name of "Scotchcal Graphic Film IJ1220". This recording medium 1 is a non-absorbent recording medium having a water absorption of 10 mL/m ² or less from the start of contact to 30 msec ^1/2 in the Bristow method.
- Recording medium 2: Product name "GL-101", manufactured by Canon, glossy paper. This recording medium is an absorptive recording medium having a water absorption of more than 10 mL/m ² from the start of contact to 30 msec ^1/2 in the Bristow method.

<Evaluation>
An ink jet recording apparatus (trade name “image PROGRAF PRO-2000”, manufactured by Canon Inc.) with a built-in heating mechanism was used for the following evaluations. This inkjet recording apparatus is defined to have a recording duty of 100% for a solid image recorded under the condition that one droplet of 4 ng of ink is applied to a unit area of 1/1,200 inch×1/1,200 inch. Each of the ink and the reaction liquid was filled in an ink cartridge, and the combinations shown in Table 5 were mounted in the ink jet recording apparatus. On the recording medium shown in Table 5, a 2 cm × 2 cm solid image of the reaction liquid with a recording duty of 20% and a 2 cm × 2 cm solid ink image with a recording duty of 100% were superimposed on each other to record an image. bottom. In the present invention, in the evaluation criteria for each item shown below, "AA", "A" and "B" were defined as acceptable levels, and "C" was defined as an unacceptable level. Table 5 shows the evaluation results.

(image clarity)
Two fluorescent lamps spaced at intervals of 5 cm and 10 cm were used as observation light sources, and the fluorescent lamps were projected onto the image from a position separated by 2 m. The shape of the fluorescent lamp projected on the image was visually confirmed under the conditions of an illumination angle of 45 degrees and an observation angle of 45 degrees, and the image clarity of the image was evaluated according to the following evaluation criteria.
AA: Two projected fluorescent lamps with an interval of 5 cm were clearly projected on the image.
A: The edges of the projected two fluorescent lamps spaced 5 cm apart were blurred, but the boundaries were recognizable.
B: The boundary between the two projected fluorescent lamps spaced 5 cm apart was not recognized, but the boundary between the two projected fluorescent lamps spaced 10 cm apart was discernible.
C: The boundary between two projected fluorescent lamps spaced 10 cm apart was not recognized.

(Change in clarity)
The above image clarity was defined as "rank before storage". In addition, using the ink stored at 60° C. for 2 weeks, the image clarity was evaluated in the same manner, and the result was defined as “rank after storage”. Then, the ranks before and after storage were compared, and changes in image clarity were evaluated according to the evaluation criteria shown below.

(Evaluation criteria)
A: The rank of image clarity was the same before and after storage.
B: The rank of image clarity was different before and after storage, but the image clarity after storage was ranked A or B.
C: The rank of image clarity was different before and after storage, and the image clarity after storage was C rank.

Since Reference Examples 1 to 3 did not use a reaction liquid, the image quality was inferior to any of the Examples. In Reference Examples 4 to 6, in which an absorbent recording medium was used, the reaction liquid permeated the recording medium, so that the image quality was better than that in Reference Examples 1 to 3. was inferior. However, the image clarity of the images recorded in Reference Examples 4 to 6 was the same regardless of the type of ink.

The disclosure of this embodiment includes the following methods and configurations.
(Method 1) An inkjet recording method in which a water-based ink and a water-based reaction liquid that reacts with the water-based ink are ejected from an ink-jet recording head and applied to a recording medium to record an image,
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 water-based 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 with 16 or more carbon atoms and an HLB value of 14.0 or more as determined by the Griffin method,
An inkjet recording method, wherein the recording medium has a water absorption amount of 10 mL/m ² or less from the start of contact to 30 msec ^1/2 in the Bristow method.
(Method 2) Method 1, wherein the content (% by mass) of the polyoxyethylene alkyl ether in the water-based ink is 0.10 times or less as a mass ratio with respect to the content (% by mass) of the resin particles. Inkjet recording method.
(Method 3) The inkjet recording method according to Method 1 or 2, wherein the polyoxyethylene alkyl ether has an HLB value determined by the Griffin method of 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 of a polyester resin having a weight average molecular weight of 30,000 or more and 70,000 or less.
(Method 6)
the water-based ink further contains a water-soluble organic solvent,
The inkjet according to Method 4 or 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 as a mass ratio. Recording method.
(Method 7) The inkjet recording method of any one of Methods 1 to 6, wherein the water-based ink further contains a first water-soluble organic solvent having a boiling point of 220° C. or less.
(Method 8) The inkjet recording method according to Method 7, wherein the first water-soluble organic solvent is 1,2-butanediol.
(Method 9) The inkjet recording method according to any one of Methods 1 to 8, wherein the water-based ink further contains a pigment.
(Arrangement 1) An inkjet recording apparatus used in an inkjet recording method for recording an image by ejecting a water-based ink and a water-based reaction liquid that reacts with the water-based ink from an ink-jet recording head and applying the ink to a recording medium to record an image,
The water-based 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 with 16 or more carbon atoms and an HLB value of 14.0 or more as determined by the Griffin method,
An inkjet recording apparatus, wherein the recording medium has a water absorption amount of 10 mL/m ² or less from the start of contact to 30 msec ^1/2 in the Bristow method.

Claims (10)

An inkjet recording method for recording an image by ejecting a water-based ink and a water-based reaction liquid that reacts with the water-based ink from an ink-jet recording head and applying it to a recording medium,
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 water-based 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 with 16 or more carbon atoms and an HLB value of 14.0 or more as determined by the Griffin method,
An inkjet recording method, wherein the recording medium has a water absorption amount of 10 mL/m ² or less from the start of contact to 30 msec ^1/2 in the Bristow method. 2. The inkjet recording according to claim 1, wherein the content (% by mass) of the polyoxyethylene alkyl ether in the water-based ink is 0.10 times or less as a mass ratio with respect to the content (% by mass) of the resin particles. Method. 3. The ink jet recording method according to claim 1, wherein the polyoxyethylene alkyl ether has an HLB value determined by the Griffin method of 16.0 or less. 3. The inkjet recording method according to claim 1, wherein the resin particles are polyester resin particles. 5. The ink jet recording method according to claim 4, wherein the polyester resin particles are formed of a polyester resin having a weight average molecular weight of 30,000 or more and 70,000 or less. the water-based ink further contains a water-soluble organic solvent,
5. The inkjet recording according to claim 4, wherein the content (% by mass) of the water-soluble organic solvent is 1.0 times or more and 4.0 times or less as a mass ratio with respect to the content (% by mass) of the polyester resin particles. Method. 3. The inkjet recording method according to claim 1, wherein the water-based ink further contains a first water-soluble organic solvent having a boiling point of 220[deg.] C. or less. 8. The inkjet recording method according to claim 7, wherein the first water-soluble organic solvent is 1,2-butanediol. 3. The inkjet recording method according to claim 1, wherein the water-based ink further contains a pigment. An inkjet recording apparatus for use in an inkjet recording method for recording an image by ejecting a water-based ink and a water-based reaction liquid that reacts with the water-based ink from an ink-jet recording head and applying it to a recording medium to record an image,
The water-based 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 with 16 or more carbon atoms and an HLB value of 14.0 or more as determined by the Griffin method,
An inkjet recording apparatus, wherein the recording medium has a water absorption amount of 10 mL/m ² or less from the start of contact to 30 msec ^1/2 in the Bristow method.

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