JP2020002308A - Aqueous ink, ink cartridge, recording device and recording method - Google Patents

Abstract

To provide aqueous ink which has fixability of an image by infrared rays and suppresses lowering of re-dispersion property.SOLUTION: Aqueous ink contains a colorant, infrared absorbable particles containing a polyester resin and an infrared absorber, and glycol ether having an octanol/water distribution coefficient logP of 0.6 or more and 2.0 or less.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a water-based ink, an ink cartridge, a recording device, and a recording method.

  In recent years, the inkjet printing technology has greatly increased its share in the printing field because of its wide width and high speed. Above all, there is an increasing demand for recording with a water-based inkjet ink on media such as coated printing paper, which have a low liquid penetration (slow penetration media, non-penetration media).

  For example, Patent Literature 1 discloses “a coloring material, an antifoaming agent selected from glycol-based and glycol ether-based compounds having a water-octanol partition coefficient of 2.0 to 5.0, and a water-octanol partition coefficient of 0. A first solvent selected from a glycol-based compound and a glycol ether-based compound having a zeta potential of −65 mV to −15 mV, and a first solvent selected from glycol-based and glycol ether-based compounds having a zeta potential of −65 mV to −15 mV. And a resin particle having a polyoxyethylene chain. "

  Patent Document 2 discloses that “a first solvent that is a propanediol having a water-octanol partition coefficient of 0.5 to 2.0 and having a phenoxy group or a benzyloxy group, A second solvent which is a water-soluble organic solvent of not less than 1.0 and not more than 1.0, water and a coloring material, and the content of the first solvent is 0.05% by mass to 0.5% by mass And a liquid composition in which the content of the second solvent is 0.5% by mass or more and 15% by mass or less ”.

  Patent Document 3 discloses that “a pigment that contains at least a pigment, a glycol ether, a water-soluble emulsion, and water, and that can be dispersed and / or dissolved in water without a dispersant. And the glycol ethers are one or two selected from the group consisting of diethylene glycol mono-n-butyl ether, triethylene glycol mono-n-butyl ether, propylene glycol mono-n-butyl ether, and dipropylene glycol mono-n-butyl ether. An ink composition, which is a mixture of the above, is disclosed.

JP 2017-141388 A JP-A-2017-014443 Patent No. 3505718

Conventionally, water and a colorant, for an aqueous ink containing a polyester resin and infrared absorbing particles containing an infrared absorbing agent, by drying the ink using heat generated from infrared absorption, 2. Description of the Related Art A technique for improving the fixing property of an image is known. However, in this aqueous ink, when a part of the water contained in the aqueous ink evaporates and is concentrated, the infrared-absorbing particles are aggregated. It is difficult to disperse, and the dispersibility of the infrared absorbing particles tends to be lower than before the concentration (hereinafter, also referred to as “redispersibility lowering”).
Therefore, in the present invention, "water, a colorant, infrared-absorbing particles containing a polyester resin and an infrared absorber, and a glycol ether having an octanol / water partition coefficient logP of less than 0.6 or more than 2.0 are used. Aqueous ink containing '' or `` water, a colorant, infrared absorbing particles containing a polyester resin and an infrared absorbing agent, and glycol ether, a step of concentrating 2.5 g of the aqueous ink to obtain a concentrate, And re-dispersing the product in 2.5 g of the aqueous ink to produce a re-dispersed liquid, the aqueous residue having a solid residue exceeding 0.042 g when the re-dispersed liquid is filtered using a filter paper. " An object of the present invention is to provide a water-based ink which has an image fixing property by infrared rays and suppresses a decrease in re-dispersibility as compared with the above.

  Means for solving the above problems include the following embodiments.

<1> Water and
A coloring agent,
Infrared absorbing particles comprising a polyester resin and an infrared absorbing agent,
A glycol ether having an octanol / water partition coefficient logP of 0.6 or more and 2.0 or less;
Aqueous ink containing.

<2> Water and
A coloring agent,
Infrared absorbing particles comprising a polyester resin and an infrared absorbing agent,
Glycol ether,
Including
Concentrating 2.5 g of the aqueous ink to obtain a concentrate; and re-dispersing the concentrate in 2.5 g of the aqueous ink to prepare a redispersion. An aqueous ink having a solid residue from 0 g to 0.042 g when filtered.

<3> the infrared absorbent includes a compound having a squarylium skeleton;
The aqueous ink according to <1> or <2>.

<4> The compound having a squarylium skeleton is
Including a compound represented by the general formula (1),
The aqueous ink according to <3>.

(In the general formula (1), R ^1a , R ^1b , R ^1c and R ^1d each independently represent an alkyl group or an aryl group.)

<5> the glycol ether includes a glycol ether having an alkyl ether chain having 3 to 10 carbon atoms,
The aqueous ink according to any one of <1> to <4>.

<6> the glycol ether includes at least one selected from propylene glycol-n-butyl ether, dipropylene glycol-n-butyl ether and diethylene glycol hexyl ether;
The aqueous ink according to any one of <1> to <5>.

<7> The content of the infrared absorbent is
0.5% by mass or more and 2.5% by mass or less based on the infrared absorbing particles;
The aqueous ink according to any one of <1> to <6>.

<8> The content of the infrared absorbent is
1.0% by mass or more and 2.0% by mass or less based on the infrared absorbing particles,
The aqueous ink according to <7>.

<9> The content of the glycol ether is
4% by mass or more and 15% by mass or less based on the aqueous ink.
The aqueous ink according to any one of <1> to <8>.

<10> The content of the glycol ether is
80% by mass or more and 300% by mass or less based on the infrared absorbing particles,
The aqueous ink according to any one of <1> to <9>.

<11> The content of the infrared absorbing particles is
4% by mass or more and 15% by mass or less based on the aqueous ink.
The aqueous ink according to any one of <1> to <10>.

<12> An ink cartridge containing the aqueous ink according to any one of <1> to <11>.

<13> An ink applying unit which contains the aqueous ink according to any one of <1> to <11>, and applies the aqueous ink to a recording medium.
Infrared irradiating means for irradiating the aqueous ink applied to the recording medium with infrared light,
A recording device comprising:

<14> The ink applying unit includes an inkjet head that ejects the aqueous ink,
A means for ejecting the aqueous ink from the inkjet head and applying it to a recording medium,
The recording device according to <13>.

<15> an ink applying step of applying the aqueous ink according to any one of <1> to <11> to a recording medium;
An infrared irradiation step of irradiating the aqueous ink applied to the recording medium with infrared light,
A recording method having:

<16> The recording method according to <15>, wherein the ink applying step is a step of ejecting the aqueous ink from an inkjet head to apply the aqueous ink to a recording medium.

  According to the invention described in <1>, <3> or <4>, water, a colorant, infrared absorbing particles containing a polyester resin and an infrared absorbing agent, and an octanol / water partition coefficient logP of 0.6 are used. A water-based ink having an image fixing property by infrared rays and suppressing a decrease in re-dispersibility as compared with a water-based ink containing a glycol ether of less than or more than 2.0.

  According to the invention described in <2>, <3> or <4>, the aqueous ink contains water, a colorant, infrared absorbing particles including a polyester resin and an infrared absorbing agent, and glycol ether. Through a step of concentrating 5 g to obtain a concentrate and a step of re-dispersing the concentrate in 2.5 g of the aqueous ink to prepare a re-dispersion liquid, by filtering the re-dispersion liquid using a filter paper. A water-based ink is provided which has an image fixing property by infrared rays and suppresses a decrease in redispersibility as compared with a water-based ink having a solid residue of more than 0.042 g.

  According to the invention described in <5> or <6>, compared to the case where the glycol ether contains a glycol ether having an alkyl ether chain having 2 or less carbon atoms or 11 or more, the glycol ether has an image fixing property by infrared rays. And a water-based ink that suppresses a decrease in redispersibility.

  According to the invention described in <7>, compared with the case where the content of the infrared absorbent is less than 0.5% by mass or more than 2.5% by mass with respect to the infrared absorbing particles, A water-based ink having image fixability and suppressing a decrease in redispersibility is provided.

  According to the invention described in <8>, the content of the infrared absorber is less than 1.0% by mass or more than 2.0% by mass with respect to the infrared-absorbing particles. A water-based ink having image fixability and suppressing a decrease in redispersibility is provided.

  According to the invention described in <9>, compared to the case where the content of the glycol ether is less than 4% by mass or more than 15% by mass with respect to the aqueous ink, the fixing property of an image by infrared rays is improved. And a water-based ink that suppresses a decrease in redispersibility.

  According to the invention described in <10>, the fixability of an image with infrared rays is improved as compared with the case where the content of the glycol ether is less than 80% by mass or more than 300% by mass with respect to the infrared absorbing particles. A water-based ink which has and suppresses a decrease in redispersibility is provided.

  According to the invention described in <11>, the fixing property of the image by infrared rays is improved as compared with the case where the content of the infrared absorbing particles is less than 4% by mass or more than 15% by mass with respect to the aqueous ink. A water-based ink which has and suppresses a decrease in redispersibility is provided.

  According to the invention described in <12>, <13>, <14>, <15> or <16>, "water, a colorant, infrared-absorbing particles containing a polyester resin and an infrared absorber, and octanol / Aqueous ink containing glycol ether having distribution coefficient logP of less than 0.6 or more than 2.0 "or" water, a colorant, infrared absorbing particles containing a polyester resin and an infrared absorbing agent, and glycol Containing ether and a step of concentrating 2.5 g of the aqueous ink to obtain a concentrate, and a step of redispersing the concentrate in 2.5 g of the aqueous ink to prepare a redispersion liquid, using a filter paper. Compared with the case of using "aqueous ink having a solid residue exceeding 0.042 g when the redispersion liquid is subjected to filtration treatment", the redispersion liquid has an image fixing property by infrared rays and suppresses a decrease in redispersibility. aqueous Ink cartridge using the ink, a recording apparatus or recording method is provided.

FIG. 1 is a schematic configuration diagram illustrating an example of an image forming apparatus according to an embodiment.

  In the present specification, when referring to the amount of each component in the composition, when there are a plurality of substances corresponding to each component in the composition, unless otherwise specified, the plurality of substances present in the composition Means the total amount of

  Hereinafter, an embodiment which is an example of the present invention will be described.

-Aqueous ink-
The aqueous ink according to the first embodiment (hereinafter, also simply referred to as “aqueous ink”) has water, a colorant, infrared absorbing particles including a polyester resin and an infrared absorbing agent, and an octanol / water partition coefficient logP. Glycol ether of 0.6 or more and 2.0 or less (hereinafter also referred to as “specific glycol ether”). The aqueous ink according to the first embodiment may contain other additives.

  Conventionally, water and a colorant, for an aqueous ink containing a polyester resin and infrared absorbing particles containing an infrared absorbing agent, by drying the ink using heat generated from infrared absorption, 2. Description of the Related Art A technique for improving the fixing property of an image is known. However, in this aqueous ink, when a part of the water contained in the aqueous ink evaporates and is concentrated, the infrared-absorbing particles are aggregated. It is difficult to disperse, and the re-dispersibility of the infrared absorbing particles tends to be lower than before the concentration. When the redispersibility of the aqueous ink is reduced and aggregates are formed, for example, when the aqueous ink is used in a droplet discharge method (inkjet method), clogging may occur in an ejection port (inkjet head).

  On the other hand, the water-based ink according to the first embodiment has the above-described configuration, has an image fixing property by infrared rays, and suppresses a decrease in redispersibility. The cause of the decrease in redispersibility is not necessarily clear, but can be considered as follows.

  Specific glycol ethers tend to have high affinity with polyester resins. Therefore, the dispersibility of the infrared absorbing particles including the infrared absorbing agent and the polyester resin in the aqueous ink tends to be increased. Thereby, it is considered that aggregation of the infrared absorbing particles in the aqueous ink is easily suppressed. As a result, it is considered that the image has the fixing property of the image by the infrared rays and the decrease in the redispersibility is suppressed.

  The aqueous ink according to the second embodiment includes water, a colorant, infrared absorbing particles including a polyester resin and an infrared absorbing agent, and glycol ether. The aqueous ink according to the second embodiment has a step of concentrating 2.5 g of the aqueous ink to obtain a concentrate, and a step of redispersing the concentrate in 2.5 g of the aqueous ink to prepare a redispersion liquid. , And the solid residue when the redispersion liquid is filtered using a filter paper is 0 g or more and 0.042 g or less. The aqueous ink according to the second embodiment may contain other additives.

  As described above, in the conventional aqueous ink, when a part of the water contained in the aqueous ink is evaporated and concentrated, the redispersibility tends to decrease. More specifically, even after the above-mentioned aqueous ink is once dried, even if it is re-dispersed in the aqueous ink again to prepare a re-dispersion liquid, the re-dispersibility is reduced, so that a large amount of solid residue tends to be generated. .

  On the other hand, in the water-based ink according to the second embodiment, the dispersibility of the infrared-absorbing particles tends to be improved by adopting the above configuration. As a result, it is considered that the image has the fixing property of the image by the infrared rays and the decrease in the redispersibility is suppressed. In addition, aggregation of the infrared absorbing particles is easily suppressed.

  Hereinafter, the configuration of the aqueous ink according to the first and second embodiments (hereinafter, collectively referred to as “the present embodiment” for convenience) will be described in detail. The description will be omitted with reference numerals omitted.

  The aqueous ink according to the first embodiment includes water, a colorant, infrared absorbing particles including a polyester resin and an infrared absorbing agent, and a specific glycol ether.

  The aqueous ink according to the second embodiment includes a step of concentrating 2.5 g of the aqueous ink to obtain a concentrate, and a step of redispersing the concentrate in 2.5 g of the aqueous ink to prepare a redispersion liquid. The solid residue when filtering the redispersion liquid using a filter paper is 0 g or more and 0.042 g or less.

  The fact that the solid residue obtained through the above steps is 0.042 g or less means that the dispersibility of the aggregate of the infrared absorbing particles contained in the concentrate of the aqueous ink with respect to the non-concentrated aqueous ink is high. Represents that. In other words, it means that an aqueous ink in which a decrease in redispersibility is suppressed can be obtained.

Each of the above steps is performed in the following manner.
2.5 g of the aqueous ink is placed in a glass petri dish having a diameter of 5 cm and heated to 40 ° C. to obtain a concentrate having a solid content concentration of 40% by mass. The concentrate is allowed to cool to room temperature (23 ° C.), and 2.5 g of an aqueous ink is added to a petri dish containing the concentrate at room temperature to obtain a redispersion of the concentrate. Next, this redispersed liquid was filtered with a filter paper No. 2 (qualitative filter paper specified in Japanese Industrial Standards JIS P3801 (2017 edition): 125 g / m ² , thickness 0.26 mm, drainage time 80 seconds, water absorption 80 cm). The residue is dried in a desiccator (Auto Dry Desiccator OH-3S, manufactured by AS ONE Corporation) to obtain a solid residue.

  In addition, in an aqueous ink containing water, a colorant, an infrared absorbing particle containing a polyester resin and an infrared absorbing agent, and a glycol ether, the solid residue after redispersing the aqueous ink in an amount within the above range. For example, a method using a specific glycol ether described later as the glycol ether may be used. However, the type of glycol ether is not particularly limited as long as the amount of the solid residue after redispersion of the aqueous ink can be set within the above range.

  The pH of the aqueous ink is preferably 6.5 or more and 11.0 or less, more preferably 7.0 or more and 10.5 or less, and even more preferably 8.0 or more and 10.0 or less. The pH of the aqueous ink is measured in an environment at a temperature of 23 ± 0.5 ° C. and a relative humidity of 55 ± 5%.

  The surface tension of the aqueous ink is preferably from 20 mN / m to 40 mN / m, and more preferably from 25 mN / m to 35 mN / m. In the present embodiment, the surface tension of the particle dispersion and the aqueous ink is measured using a Wilhelmy surface tensiometer under an environment of a temperature of 23 ± 0.5 ° C. and a relative humidity of 55 ± 5%.

The viscosity of the aqueous ink is preferably from 1 mPa · s to 30 mPa · s, and more preferably from 2 mPa · s to 20 mPa · s. In the present embodiment, the viscosities of the particle dispersion liquid and the aqueous ink are measured using a TV-20 viscometer (manufactured by Toki Sangyo Co., Ltd.) at a temperature of 23 ± 0.5 ° C. and a shear rate of 1400 s ⁻¹ . Measure.

[water]
The aqueous ink contains water.
As the water, purified water such as distilled water, ion-exchanged water, or ultrafiltration water is preferable from the viewpoint of suppressing contamination of impurities or generation of microorganisms.

  The water content is preferably from 40% by mass to 75% by mass, more preferably from 45% by mass to 70% by mass, and more preferably from 50% by mass to 70% by mass, based on the total mass of the particle dispersion or the aqueous ink. % Or more and 65% by mass or less.

[Colorant]
The aqueous ink contains a colorant.

  Examples of the colorant include a pigment and a dye, and a pigment is preferable from the viewpoint of light fastness of an image.

  When a pigment is used as the colorant, it is preferable to use a pigment dispersant. Examples of the pigment dispersant include all known polymer dispersants, surfactants, and the like. One type of pigment dispersant may be used, or two or more types may be used in combination. Since the content of the pigment dispersant varies depending on the type of the pigment and the type of the pigment dispersant, it cannot be specified unconditionally, but is preferably 0.1% by mass or more and 100% by mass or less based on the content of the pigment.

  Examples of the pigment include a pigment that is self-dispersed in water (hereinafter, referred to as a “self-dispersible pigment”). The self-dispersion type pigment refers to a pigment having a hydrophilic group on the surface of the pigment and dispersing in water even without a pigment dispersant. Examples of the self-dispersion type pigment include all known self-dispersion type pigments obtained by subjecting the pigment to a surface modification treatment such as a coupling agent treatment, a polymer graft treatment, a plasma treatment, an oxidation treatment, and a reduction treatment. Pigments.

  Examples of the pigment include a so-called microcapsule pigment coated with a resin. Commercially available microcapsule pigments include those manufactured by DIC and Toyo Ink.

  Examples of the pigment include a resin-dispersed pigment in which a polymer compound is physically adsorbed or chemically bonded to the pigment.

  Specific pigments such as red, green, brown, and white pigments; metallic luster pigments such as gold and silver; colorless or light-colored extender pigments; plastic pigments; dyes or pigments on the surface of silica, alumina, or polymer beads; Fixed dyes; insoluble lakes of dyes; colored emulsions; colored latexes, and the like.

  When a dye is used as the colorant, it is preferable that the dye is formed into particles together with a polymer dispersant (for example, the polymer of the present disclosure), and the particles are contained in the aqueous ink.

  When the colorant is a granular material, the volume average particle diameter is, for example, 10 nm or more and 200 nm or less.

  The content of the colorant is preferably from 1% by mass to 25% by mass, more preferably from 2% by mass to 20% by mass, based on the total mass of the aqueous ink.

[Specific glycol ether]
The aqueous ink according to the first embodiment contains a specific glycol ether.
The aqueous ink according to the second embodiment may contain a specific glycol ether.

  The octanol / water partition coefficient logP of the specific glycol ether is 0.6 or more and 2.0 or less, preferably 0.8 or more and 1.8 or less, more preferably 1.0 or more and 1.7 or less. preferable.

  The octanol / water partition coefficient logP is a numerical value indicating the hydrophilicity / hydrophobicity of the solvent. The larger the octanol / water partition coefficient logP, the more hydrophobic the solvent, and the smaller the octanol / water partition coefficient logP, the more hydrophilic the solvent. is there.

When the octanol / water partition coefficient logP of the specific glycol ether is 0.6 or more, the hydrophilicity of the specific glycol ether tends to increase. Therefore, the affinity between the aqueous solution containing the specific glycol ether and the polyester resin contained in the infrared absorbing particles tends to increase. As a result, a decrease in the redispersibility of the aqueous ink is suppressed.
On the other hand, if the octanol / water partition coefficient logP of the specific glycol ether is 2.0 or less, the specific glycol ether tends to suppress the hydrophobicity from becoming too high. Therefore, the elution of the infrared absorbent contained in the infrared absorbing particles into the liquid is suppressed, and an aqueous ink having an image fixing property by infrared rays can be obtained.

  The octanol / water partition coefficient log P of the specific glycol ether is determined according to OECD Test Guideline No. 107 (or a value obtained by a flask shaking method specified in JIS Z7260-107, which is a Japanese translation of the guideline).

  The specific glycol ether is a compound in which both terminals or one terminal of glycol and an alkyl group are bonded by an ether bond.

  The specific glycol ether may be a glycol ether in which both terminals of glycol are ether-bonded to an alkyl group, or a glycol ether in which one terminal of glycol is ether-bonded to an alkyl group.

  The specific glycol ether may be, for example, a glycol ether in which one end of the glycol is ether-bonded to an alkyl group, and the octanol / water partition coefficient of the specific glycol ether may be within the above specific range.

  Examples of the glycol in the specific glycol ether include an aliphatic glycol, an aromatic glycol, and an alicyclic glycol. Among the above, the glycol in the specific glycol ether is preferably an aliphatic glycol.

Although it does not specifically limit as an aliphatic glycol, For example, the C2-C20 aliphatic glycol is mentioned.
Examples of the aliphatic glycol having 2 to 20 carbon atoms include ethylene glycol, diethylene glycol, triethylene glycol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol, 1,5 -Pentanediol, 1,6-hexanediol, 1,3-propylene glycol, 1,10-decanediol, 1,12-dodecanediol, 1,18-octanedecadiol, 1,20-icosanediol and the like. Can be

  As the specific glycol ether, for example, a glycol ether having a linear or branched alkyl ether chain having 1 to 20 carbon atoms (-OR, R represents an alkyl group having 1 to 20 carbon atoms) Is mentioned.

  Specific examples of the linear alkyl ether chain include a methyl ether group, an ethyl ether group, an n-propyl ether group, an n-butyl ether group, an n-pentyl ether group, an n-hexyl ether group, an n-heptyl ether group, n-octyl ether group, n-nonyl ether group, n-decyl ether group, n-decyl ether group, n-dodecyl ether group, n-hexadecyl ether group, n-octadecyl ether group, n-icosyl ether group, etc. Is mentioned.

  Specific examples of the branched alkyl ether chain include an isopropyl ether group, an isobutyl ether group, a sec-butyl ether group, a tert-butyl ether group, an isopentyl ether group, a neopentyl ether group, a tert-pentyl ether group, and an isohexyl ether group. , Sec-hexyl ether group, tert-hexyl ether group, isoheptyl ether group, sec-heptyl ether group, tert-heptyl ether group, isooctyl ether group, sec-octyl ether group, tert-octyl ether group, isononyl ether Group, sec-nonyl ether group, tert-nonyl ether group, isodecyl ether group, sec-decyl ether group, tert-decyl ether group and the like.

  Among the above, the specific glycol ether is a straight-chain or branched carbon atom having a carbon number of 3 or more and 10 or less (more preferably 3 or more and 8 or less; More preferably, it has an alkyl ether chain having 4 to 6 carbon atoms).

  The specific glycol ether preferably contains at least one selected from propylene glycol-n-butyl ether, dipropylene glycol-n-butyl ether and diethylene glycol hexyl ether, from the viewpoint of suppressing a decrease in redispersibility in the aqueous ink. .

  The content of the glycol ether is preferably from 80% by mass to 300% by mass, more preferably from 90% by mass to 270% by mass, and more preferably from 100% by mass to 250% by mass, based on the infrared absorbing particles. It is more preferred that:

  When the content of the glycol ether is 80% by mass or more based on the infrared absorbing particles, aggregation of the infrared absorbing particles tends to be suppressed even when the aqueous ink is concentrated. As a result, a decrease in redispersibility of the aqueous ink tends to be suppressed. On the other hand, when the content of the glycol ether is 300% by mass or less with respect to the infrared absorbing particles, the elution of the infrared absorbing agent contained in the infrared absorbing particles tends to be suppressed.

  The content of the glycol ether is from 4% by mass to 15% by mass with respect to the aqueous ink, from the viewpoint of obtaining an aqueous ink having an image fixing property by infrared rays and suppressing a decrease in redispersibility. Is preferably 4.5% by mass or more and 12% by mass or less, and more preferably 5% by mass or more and 10% by mass or less.

[Infrared absorbing particles]
The aqueous ink contains infrared absorbing particles.
The infrared absorbing particles include a polyester resin and an infrared absorbing agent.

(Polyester resin)
The infrared absorbing particles include a polyester resin.
When the infrared absorbing particles contain a polyester resin, precipitation of the infrared absorbing agent in the aqueous ink tends to be suppressed.

  A polyester resin is generally synthesized by dehydration condensation of a dicarboxylic acid and a diol.

  The polyester resin preferably has a dissociable group from the viewpoint of dispersibility in water. As the dissociable group, an anionic group is preferable, and a carboxy group and a sulfonic acid group are particularly preferable. The introduction of the dissociable group into the polyester resin is performed, for example, by using a dicarboxylic acid or diol having a sulfonic acid group as a raw material for dehydration condensation.

  Examples of the dicarboxylic acid having a sulfonic acid group include 3-sulfophthalic acid, 4-sulfophthalic acid, 4-sulfoisophthalic acid, 5-sulfoisophthalic acid, 2-sulfoterephthalic acid, sulfosuccinic acid, and 4-sulfo-1,8. -Naphthalenedicarboxylic acid, 7-sulfo-1,5-naphthalenedicarboxylic acid, 2,4-di (2-hydroxy) ethyloxycarbonylbenzenesulfonic acid, and salts thereof. These dicarboxylic acids may be used alone or in combination of two or more.

  Other dicarboxylic acids include, for example, oxalic acid, malonic acid, succinic acid, glutaric acid, dimethylmalonic acid, adipic acid, pimelic acid, α, α-dimethylsuccinic acid, acetonedicarboxylic acid, sebacic acid, 1,9- Nonanedicarboxylic acid, fumaric acid, maleic acid, itaconic acid, citraconic acid, phthalic acid, isophthalic acid, terephthalic acid, 2-butylterephthalic acid, tetrachloroterephthalic acid, acetylenedicarboxylic acid, poly (ethylene terephthalate) dicarboxylic acid, 1, Examples include 2-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, ω-poly (ethylene oxide) dicarboxylic acid, p-xylylenedicarboxylic acid, and the like. These dicarboxylic acids may be subjected to dehydration condensation in the form of alkyl esters, acid chlorides or acid anhydrides. These dicarboxylic acids may be used alone or in combination of two or more.

  Examples of the diol having a sulfonic acid group and other diols include the compounds described above as raw materials for polyurethane. One type of diol may be used, or two or more types may be used in combination.

  The polyester resin is synthesized by selecting a monomer species from the viewpoint of controlling, for example, the acid value of the polyester resin, the glass transition temperature, the solubility in an organic solvent, the affinity for an infrared absorbent, and the like.

  Hereinafter, specific examples of the polyester resin will be described by describing a polymerization component. However, irrespective of the polymerization components, dicarboxylic acids, diols, and the like which are constituent units of the polyester resin are described. The numbers in parentheses are the molar ratios of the polymerization components. The present invention is not limited to these specific examples.

-Terephthalic acid / isophthalic acid / cyclohexanedimethanol / 1,4-butanediol / ethylene glycol (25/25/25/15/10)
-Terephthalic acid / isophthalic acid / 2,2'-bis (4-hydroxyphenyl) propane / tetraethylene glycol / ethylene glycol (30/20/20/15/15)
-Terephthalic acid / isophthalic acid / cyclohexanedimethanol / neopentyl glycol / diethylene glycol (20/30/25/15/10)
-Terephthalic acid / isophthalic acid / 4,4'-benzenedimethanol / diethylene glycol / neopentyl glycol (25/25/25/15/10)
-Terephthalic acid / isophthalic acid / 5-sulfoisophthalic acid / ethylene glycol / neopentyl glycol (24/24/2/25/25)
-Terephthalic acid / isophthalic acid / 5-sulfoisophthalic acid / cyclohexanedimethanol / 1,4-butanediol / ethylene glycol (22/22/6/25/15/10)
・ Isophthalic acid / 5-sulfoisophthalic acid / cyclohexanedimethanol / ethylene glycol (40/10/40/10)
・ Cyclohexanedicarboxylic acid / isophthalic acid / 2,4-di (2-hydroxy) ethyloxycarbonylbenzenesulfonic acid / cyclohexanedimethanol / ethylene glycol (30/20/5/25/20)

The molecular weight of the polyester resin is preferably from 1,000 to 200,000 as a weight average molecular weight, more preferably from 1500 to 100,000, and still more preferably from 2,000 to 50,000.
When the weight average molecular weight is 1,000 or more, the content of the water-soluble component described below is reduced, and the composition is suitable for dispersing an infrared absorbent. On the other hand, when the weight average molecular weight is 200,000 or less, the solubility in a water-soluble organic solvent is excellent, and the viscosity of a polymer solution dissolved in the water-soluble organic solvent is suppressed. Dispersion of the particles becomes easy, and therefore, the dispersion stability of the particles is excellent.
The weight average molecular weight of the polyester resin is measured by gel permeation chromatography (GPC) and calculated in terms of polystyrene.

  The glass transition temperature of the polyester resin is preferably from 40 ° C to 150 ° C. When the glass transition temperature is 40 ° C. or higher, an image formed using an ink containing a polyester resin is excellent in scratch resistance and blocking resistance. When the glass transition temperature is 150 ° C. or lower, an aqueous ink containing a polyester resin is used. Excellent in abrasion resistance of an image formed using In this respect, the glass transition temperature of the polyester resin is more preferably from 60 ° C to 140 ° C, and still more preferably from 70 ° C to 130 ° C.

The glass transition temperature Tg of the polyester resin is obtained using a differential scanning calorimeter (DSC-60A, manufactured by Shimadzu Corporation) in accordance with ASTM D3418. The temperature was increased at a rate of 10 ° C./min, maintained at 200 ° C. for 5 minutes, decreased from 200 ° C. to 0 ° C. at −10 ° C./minute using liquid nitrogen, maintained at 0 ° C. for 5 minutes, and re-started at 0 ° C. The temperature is raised from 10 ° C to 200 ° C at 10 ° C / min. Analysis is performed from the endothermic curve at the time of the second temperature increase, and the temperature is the temperature at the intersection of the extension of the base line below Tg and the tangent to the endothermic curve near Tg.
The softening temperature Tm of the resin was measured using a flow tester (CFT-500C, manufactured by Shimadzu Corporation) with a load of 10 kgf / cm ² , a nozzle diameter of 1 mm, a nozzle length of 1 mm, and a preheating temperature of 80 ° C. for 5 minutes, and a heating rate. When a sample amount of 1 g is measured and recorded at 6 ° C./min, the temperature at a half of the height of the S-shaped curve in the plunger drop amount-temperature curve of the flow tester (1/2 outflow temperature) is defined as the softening temperature.
In these measurements, the infrared-absorbing particles were taken out of the state of the aqueous ink (for example, the infrared-absorbing particles were taken out by a method such as drying water and a specific glycol ether by drying), and the obtained infrared-absorbing particles were obtained. This is performed using

The glass transition temperature Tg of the polyester resin is controlled by, for example, adjusting the composition of the monomer which is a raw material of the polyester resin, and adding a material having a plasticizing effect such as a plasticizer or a highly compatible material.
The softening temperature Tm of the polyester resin is controlled by, for example, the glass transition temperature Tg, the molecular weight of the polyester resin, the molecular weight distribution, the addition of a material having a plasticizing effect such as a plasticizer or a highly compatible material, and the addition of a crosslinking agent. Is done.

(Infrared absorber)
The infrared absorbing particles include an infrared absorbing agent.
The infrared absorbing agent may be any as long as it has a light absorption peak in an infrared region from a wavelength of 780 nm to a wavelength of 1000 nm. Examples of the infrared absorber include conventional cyanine compounds, merocyanine compounds, benzenethiol metal complexes, mercaptophenol metal complexes, aromatic diamine metal complexes, diimonium compounds, aminium compounds, nickel complex compounds, phthalocyanine compounds, anthraquinone compounds, and naphthalocyanine compounds. Known infrared absorbers may be used.

  As the infrared absorber, for example, an organic or inorganic near infrared absorber may be used. Examples of the organic near-infrared absorber include a diimonium dye, a phthalocyanine dye, a dithiol metal complex dye, a substituted benzenedithiol metal complex dye, a cyanine dye, and a squarylium dye. Examples of the inorganic near-infrared absorber include ATO (antimony-doped tin oxide) and ITO (tin-doped indium oxide).

  Among the above, it is preferable to include a compound having a squarylium skeleton, which is a squarylium dye.

  As the compound having a squarylium skeleton, a commercially available product may be used, or a synthetic product may be used.

Examples of the compound having a squarylium skeleton include, for example, a thiopyran-based squarylium compound (that is, a compound having a thiopyran skeleton and a squarylium skeleton), a perimidine-based squarylium compound (that is, a compound having a perimidine skeleton and a squarylium skeleton), and a flavone-based squarylium compound (ie, , A compound having a flavone skeleton and a squarylium skeleton). Among these, as the compound having a squarylium skeleton, a thiopyran-based squarylium compound and a perimidine-based squarylium compound are preferable, and a thiopyran-based squarylium compound is more preferable.
As the compound having a squarylium skeleton, one type may be used alone, or two or more types may be used in combination.

  Examples of the thiopyran-based squarylium compound include a compound represented by the following general formula (1).

In Formula (1), R ^1a , R ^1b , R ^1c , and R ^1d each independently represent an aryl group or an alkyl group.

The alkyl group represented by R ^1a , R ^1b , R ^1c , and R ^1d is preferably an alkyl group having 1 to 12 carbon atoms, more preferably an alkyl group having 1 to 10 carbon atoms, and more preferably 3 or more carbon atoms. An alkyl group having 6 or less is more preferable, and an alkyl group having 4 to 6 carbon atoms is more preferable.

The alkyl group represented by R ^1a , R ^1b , R ^1c , and R ^1d may be any of linear, branched, and cyclic alkyl groups, such as a methyl group, an ethyl group, and an n-type alkyl group. -Propyl group, isopropyl group, n-butyl group, isobutyl group (2-methylpropyl group), sec-butyl group (1-methylpropyl group), tert-butyl group (1,1-dimethylethyl group), n- Pentyl group, isopentyl group (3-methylbutyl group), neopentyl group (2,2-dimethylpropyl group), tert-pentyl group (1,1-dimethylpropyl group), n-hexyl group, isohexyl group, sec-hexyl group Tert-hexyl group, n-heptyl group, isoheptyl group, sec-heptyl group, tert-heptyl group, n-octyl group, isooctyl group, sec -Octyl group, 2-ethylhexyl group, tert-octyl group, n-nonyl group, isononyl group, sec-nonyl group, tert-nonyl group, n-decyl group, isodecyl group, sec-decyl group, tert-decyl group, Examples include an n-undecyl group, an isoundecyl group, an n-dodecyl group, an isododecyl group, a cyclopropyl group, a cyclopentyl group, a cyclohexyl group, and a bicyclo [2,2,2] octyl group.

Examples of the aryl group represented by R ^1a , R ^1b , R ^1c , and R ^1d include a phenyl group and an alkyl-substituted phenyl group.
In the alkyl-substituted phenyl group, the phenyl group may be substituted with one alkyl group or a plurality of alkyl groups, but an alkyl-substituted phenyl group in which only one alkyl group is substituted is more preferred. preferable.
As the alkyl group as the substituent, an alkyl group having 1 to 10 carbon atoms is preferable. For example, a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group Tert-butyl group, n-pentyl group, isopentyl group, neopentyl group, tert-pentyl group, n-hexyl group, isohexyl group, sec-hexyl group, tert-hexyl group, n-heptyl group, isoheptyl group, sec- Heptyl group, tert-heptyl group, n-octyl group, isooctyl group, sec-octyl group, tert-octyl group, n-nonyl group, isononyl group, sec-nonyl group, tert-nonyl group, n-decyl group, isodecyl Group, sec-decyl group, tert-decyl group and the like.

  Specific examples of the aryl group include a phenyl group, a 4-methylphenyl group, a 4-ethylphenyl group, a 4-propylphenyl group, a 4-butylphenyl group (particularly, a 4-tert-butylphenyl group), and a 3-methylphenyl group. And a 2-methylphenyl group, among which a phenyl group is preferred.

The alkyl group and the aryl group represented by R ^1a , R ^1b , R ^1c , and R ^1d may be substituted with a halogen atom (for example, fluorine or chlorine).

In the compound represented by the general formula (1), at least one of the groups represented by R ^1a , R ^1b , R ^1c , and R ^1d has a branched chain from the viewpoint of suppressing a decrease in infrared absorption ability of the aqueous ink. It is preferably an alkyl group, and more preferably a compound represented by the following general formula (1a).

In the general formula (1a), ^{R a} represents a group represented by the general formula ^(1a-R), representing a R b, ^{R c,} and ^{R d} are each independently an alkyl group. In the general formula (1a-R), ^Re represents hydrogen or a methyl group, and n represents an integer of 0 or more and 3 or less.

In the general formula (1a), ^{R a} represents a group represented by formula (1a-R).
The total number of carbon atoms of the group represented by the general formula (1a-R) is preferably 6 or less, more preferably 5 or less, still more preferably 4 or less, and particularly preferably 4. The lower limit of the total carbon number is 3.
In the general formula ^(1a-R), R ^e represents hydrogen or a methyl group. ^Re is preferably a methyl group.
In the general formula (1a-R), n represents an integer of 0 to 3. n is preferably an integer of 0 or more and 2 or less, more preferably 0 or 1, and still more preferably 0.

  Specific examples of the group represented by the general formula (1a-R) include, for example, isopropyl group, isobutyl group, tert-butyl group, 3-methylbutyl group (3-methylbutan-1-yl group), 2,2- Dimethylpropyl group (2,2-dimethylpropan-1-yl group), 4-methylpentyl group (4-methylpentan-1-yl group), 3,3-dimethylbutyl group (3,3-dimethylbutan-1 -Yl group) and a 4,4-dimethylpentyl group (4,4-dimethylpentan-1-yl group). Among these, an isopropyl group, an isobutyl group and a tert-butyl group are more preferred, and a tert-butyl group is even more preferred.

In the general formula (1a), R ^b , R ^c , and R ^d each independently represent an alkyl group. Preferably, at least one of R ^b , R ^c , and R ^d is a group represented by the general formula (1a-R), and all of R ^b , R ^c , and R ^d are represented by the general formula (1a-R) More preferably, it is a group represented by
When one of R ^b , R ^c , and R ^d is a group represented by the general formula (1a-R), any one of R ^b , R ^c , and R ^d is represented by the general formula (1a-R). May be a group to be formed. When two of R ^b , R ^c , and R ^d are groups represented by the general formula (1a-R), any of R ^b , R ^c , and R ^d is represented by the general formula (1a-R) May be a group to be formed.
When two or more of R ^a , R ^b , R ^c , and R ^d are groups represented by the general formula (1a-R), the structure of a group represented by a plurality of general formulas (1a-R) May be the same or different.

The preferred structure when at least one of R ^b , R ^c and R ^d is a group represented by the general formula (1a-R) is as described above for ^Ra .

When at least one of R ^b , R ^c, and R ^d is other than the group represented by the general formula (1a-R), the alkyl group may have any of a linear, branched, and cyclic structure. Good. In this case, the alkyl group preferably has a large number of branches, and the carbon chain is preferably short. The number of carbon atoms is preferably 1 or more and 10 or less, more preferably 2 or more and 8 or less, and still more preferably 3 or more and 6 or less.
Specific examples of the alkyl group include methyl, ethyl, n-propyl, n-butyl, n-pentyl, n-hexyl, sec-butyl, 2-methylbutan-2-yl, 3-methyl Methylbutan-2-yl group, 3,3-dimethylbutan-2-yl group, 3-pentyl group, 2-methylpentan-3-yl group, 3-methylpentan-3-yl group, cyclopentyl group, cyclohexyl group, etc. Is mentioned. Among these, a 2-methylbutan-2-yl group and a 3-methylpentan-3-yl group are preferred.

  Hereinafter, specific examples of the compound represented by the general formula (1) (compounds (1-a-1) to (1-a-10)) are shown.

  The compound represented by the general formula (1) is synthesized, for example, according to the following reaction scheme.

(1) Compounds in which R ^1a , R ^1b , R ^1c and R ^1d are all the same group

  First, a starting material 1 is added dropwise to a solution of an organic magnesium halide (eg, Grignard reagent, eg, ethyl magnesium chloride) in an organic solvent (eg, tetrahydrofuran) under an inert atmosphere and cooled. Thereafter, in order to complete the reaction, the temperature may be returned to room temperature (for example, 20 ° C. to 25 ° C .; the same applies in the present description) or higher. Next, a formic acid derivative (for example, ethyl formate or the like) is added dropwise under cooling. Thereafter, the temperature may be returned to room temperature or higher to complete the reaction. The organic matter is extracted from the mixture after the reaction, and Intermediate A is obtained from the separated organic layer.

  Next, the intermediate A and an oxidizing reagent (eg, manganese oxide) are added to a solvent (eg, cyclohexane), and the mixture is heated and refluxed to cause a reaction. Water generated during the reaction may be removed. Intermediate B is obtained from the organic layer of the reaction mixture. Purification may be performed when obtaining the intermediate B.

  Then, the intermediate B is subjected to a cycloaddition reaction. For example, sodium hydrogen sulfide n-hydrate is added to a solvent (for example, ethanol or the like), and the intermediate B is added dropwise under cooling. Thereafter, the reaction is carried out at room temperature, the solvent is removed from the reaction solution, and then sodium chloride is added until the solution is saturated, and the mixture is separated to recover the organic phase, whereby Intermediate C is obtained from the organic phase. Purification may be performed when obtaining the intermediate C.

  Then, under an inert atmosphere, a solvent (for example, anhydrous tetrahydrofuran or the like) and the intermediate C are mixed, and a Grignard reagent (for example, methylmagnesium bromide or the like) is added dropwise. After completion of the dropwise addition, the reaction solution is heated to reflux, and then, under cooling, ammonium bromide is added dropwise. The separated organic layer is dried and concentrated to give Intermediate D.

  Then, under an inert atmosphere, the intermediate D and squaric acid are dispersed in a solvent (for example, a mixed solvent of cyclohexane and isobutanol), a basic compound (for example, pyridine, etc.) is added, and the mixture is heated to reflux to give the compound (1) -A is obtained. Water generated during the reaction may be removed. Further, purification, isolation, concentration and the like may be performed.

(2) Compound in which R ^1a and R ^1d are the same group and R ^1b and R ^1c are the same group (R ^1a and R ^1b are different groups)
The process of obtaining the intermediate A in the reaction scheme of the above (1) is changed to the following process.

  Under an inert atmosphere and under cooling, a starting material 1 is added dropwise to a solution of a Grignard reagent (for example, ethyl magnesium bromide, etc.) in an organic solvent (for example, tetrahydrofuran, etc.), and an additional substance 2 is further added and reacted. A strong acid (for example, hydrochloric acid) is added to the solution after the reaction under cooling, and then ether is added at room temperature to obtain an intermediate A 'from the organic layer. Purification may be performed when obtaining the intermediate A '.

(3) Compound in which R ^1a and R ^1b are the same group and R ^1c and R ^1d are the same group (R ^1a and R ^1c are different groups)
As the intermediate D in the reaction scheme of the above (1), two kinds of compounds having different structures of R ¹ are prepared, and the two kinds of compounds are reacted with squaric acid to obtain a compound represented by the general formula (1). Get.

A compound in which three of R ^{1a to} R ^1d have the same group, a compound in which two are the same and the remaining two have different groups, and a compound in which all four are different can also be synthesized according to the above reaction scheme.

The maximum absorption wavelength (λ _max ) of the compound having a squarylium skeleton in a tetrahydrofuran solution is preferably 760 nm to 1200 nm, more preferably 780 nm to 1100 nm, and more preferably 800 nm to 1000 nm. Is more preferred.

The molar extinction coefficient (ε _max ) of the compound having a squarylium skeleton at the maximum absorption wavelength (λ _max ) in a tetrahydrofuran solution is from 1 × 10 ⁵ Lmol ⁻¹ cm ^{−1 to} 6 × 10 ⁵ Lmol ⁻¹ cm ^−1. And more preferably 2 × 10 ⁵ Lmol ⁻¹ cm ⁻¹ or more and 6 × 10 ⁵ Lmol ⁻¹ cm ⁻¹ or less, more preferably 2.5 × 10 ⁵ Lmol ⁻¹ cm ⁻¹ or more and 6 × 10 ⁵ Lmol ⁻¹ cm. ^-1 or less is more preferable.

  The content of the compound having a squarylium skeleton with respect to the infrared absorber is preferably from 90% by mass to 100% by mass, and more preferably from 98% by mass to 100% by mass.

  The content of the infrared absorbent is preferably 0.5% by mass or more and 2.5% by mass or less with respect to the infrared absorbing particles from the viewpoint of obtaining an aqueous ink having an image fixability by infrared rays. It is more preferably from 7% by mass to 2.3% by mass, and further preferably from 1.0% by mass to 2.0% by mass.

The volume average particle diameter of the infrared absorbing particles is preferably from 50 nm to 1000 nm, more preferably from 50 nm to 500 nm, and even more preferably from 50 nm to 150 nm.
When the volume average particle diameter of the infrared absorbing particles is in the above range, the droplet ejection characteristics of the ink jet system are excellent as compared with the case where the volume is larger than the above range, and the light resistance is excellent as compared with the case where the size is smaller than the above range.
The volume average particle diameter of the infrared absorbing particles is a value measured as a volume-based median diameter (nm) by using a dynamic light scattering particle size distribution analyzer LB-500 (Horiba, Ltd.).

  The content of the infrared-absorbing particles is 4% by mass or more and 15% by mass or less with respect to the aqueous ink from the viewpoint of obtaining an aqueous ink having an image fixing property by infrared rays and suppressing a decrease in redispersibility. Is preferably 4.5% by mass or more and 12% by mass or less, and more preferably 5% by mass or more and 10% by mass or less.

[Other additives]
The aqueous ink may contain various additives as necessary. Additives include polymers, surfactants, dispersion stabilizers, penetrants, viscosity modifiers, neutralizers, pH regulators, pH buffers, antioxidants, ultraviolet absorbers, preservatives, fungicides, etc. No.

[Method for producing aqueous ink]
As a method for producing the aqueous ink according to this embodiment, for example, after producing an infrared-absorbing particle dispersion, the dispersion is mixed with water, a specific glycol ether, a colorant, and other components as necessary. It is manufactured by doing.

  Examples of the method for preparing the infrared absorbing particle dispersion include a phase inversion emulsification method and an impregnation method, and the phase inversion emulsification method is preferable.

  The phase inversion emulsification method is to prepare a solution in which an infrared absorbing agent and a polyester resin are dissolved in an organic solvent, neutralize the polyester resin by adding a neutralizing agent to the solution, and then gradually mix water with the infrared absorbing agent. This is a method of forming particles containing both the polyester resin and the polyester resin into a dispersed state. The dispersion state here may be emulsification in which liquid particles are dispersed or suspension in which solid particles are dispersed. From the viewpoint of dispersion stability, suspension in which solid particles are dispersed is preferable. The organic solvent used in the phase inversion emulsification method is such that the SP value of the organic solvent is less than 24 or more than 32, the solubility of the organic solvent in water is 10% by mass or less, or the vapor of the organic solvent is When the pressure is higher than water, it is preferably removed from the viewpoint of dispersion stability of the infrared absorbing particles. Neutralization is not an essential step, but when the polyester resin has an unneutralized dissociable group, it is preferable to perform neutralization from the viewpoint of adjusting the pH of the dispersion.

  In the impregnation method, a polyester resin particle dispersion is prepared, and a polyester resin particle dispersion and a solution in which an infrared absorbent is dissolved in an organic solvent are mixed. This is a method of impregnating particles into infrared absorbing particles. The polyester resin particles may be liquid particles or solid particles, and solid particles are preferred from the viewpoint of dispersion stability. The polyester resin particle dispersion is prepared, for example, by preparing a solution in which the polyester resin is dissolved, neutralizing the solution by adding a neutralizing agent, and then removing the organic solvent while gradually mixing water.

  The organic solvent used for the phase inversion emulsification method and the impregnation method is selected based on the solubility of the infrared absorbent and the solubility of the polyester resin. Specifically, for example, ketone solvents such as acetone, methyl ethyl ketone and diethyl ketone; alcohol solvents such as methanol, ethanol, 2-propanol, 1-propanol, 1-butanol and tert-butanol; chloroform, methylene chloride and the like Aromatic solvents such as benzene and toluene; ester solvents such as ethyl acetate, butyl acetate and isopropyl acetate; ether solvents such as diethyl ether, tetrahydrofuran and dioxane; ethylene glycol monomethyl ether and ethylene glycol dimethyl ether Glycol ether solvents; and the like. One of these organic solvents may be used alone, or two or more thereof may be used in combination.

  The amount of the organic solvent used in the phase inversion emulsification method and the impregnation method is preferably from 10 parts by mass to 2,000 parts by mass, and more preferably from 100 parts by mass to 1,000 parts by mass with respect to 100 parts by mass of the polyester resin. Is more preferred. When the amount of the organic solvent is at least 10 parts by mass with respect to 100 parts by mass of the polyester resin, the dispersibility of the infrared absorbing particles is stable, and the amount of the organic solvent is at most 2,000 parts by mass with respect to 100 parts by mass of the polyester resin. If so, the step of removing the organic solvent is unnecessary or short.

  When the polyester resin has an anionic group, an organic base or an inorganic alkali is preferable as the neutralizing agent used in the phase inversion emulsification method and the impregnation method. Examples of the organic base include triethanolamine, diethanolamine, N-methyldiethanolamine, dimethylethanolamine and the like. Examples of the inorganic alkali include hydroxides of alkali metals (eg, sodium hydroxide, lithium hydroxide, potassium hydroxide, etc.), carbonates (eg, sodium carbonate, sodium hydrogen carbonate, etc.), and ammonia. From the viewpoint of the dispersion stability of the infrared absorbing particles, the addition amount of the neutralizing agent is preferably such that the pH of the infrared absorbing particle dispersion is in the above range.

  The amount of the polyester resin used in the phase inversion emulsification method and the impregnation method is preferably 100 parts by mass or more and 9900 parts by mass or less, and 300 parts by mass or more and 4900 parts by mass or less with respect to 100 parts by mass of the compound having infrared absorptivity. Is more preferable. When the amount of the polyester resin used (content of the polyester resin) is 100 parts by mass or more with respect to 100 parts by mass of the compound having the infrared absorbing property, the dispersion of the compound having the infrared absorbing property is stabilized, and the amount of the polyester resin used ( When the content of the polyester resin is 9900 parts by mass or less with respect to 100 parts by mass of the compound having an infrared absorbing property, the infrared absorption efficiency of the aqueous ink is good.

  In the phase inversion emulsification method and the impregnation method, an organic compound other than the infrared absorbing agent may be used, and the compound may be formed into particles together with the infrared absorbing agent and the polyester resin to form infrared absorbing particles containing the three components. Examples of the organic compound that forms particles together include a dye, a compound having an ultraviolet absorbing ability (eg, a benzotriazole-based compound, a benzophenone-based compound, and the like).

-Ink cartridge-
The ink cartridge according to the present embodiment is a cartridge containing the aqueous ink according to the present embodiment. The ink cartridge according to the present embodiment is provided, for example, in a form detachable from an ink jet recording apparatus.

-Recording device and recording method-
The recording apparatus according to the present embodiment contains an aqueous ink according to the present embodiment, an ink applying unit that applies the aqueous ink to a recording medium, and an infrared irradiation unit that irradiates infrared rays to the aqueous ink applied to the recording medium. And The recording apparatus according to the present embodiment realizes a recording method including an ink applying step of applying the aqueous ink according to the embodiment to a recording medium and an infrared irradiation step of irradiating the aqueous ink applied to the recording medium with infrared light. Is done.

  Examples of the ink application unit in the present embodiment include: an ejection unit that ejects ink by an inkjet method; an application unit using a roll, a spray, a sponge, or the like; a printing unit using offset printing, screen printing, gravure printing, relief printing, or the like. Can be

  As the ink applying unit in the present embodiment, a discharging unit that discharges ink by an inkjet method is preferable. A recording apparatus and a recording method to which the ink jet method is applied have excellent ejection stability by using the aqueous ink according to the present embodiment.

  The recording apparatus according to the present embodiment includes an infrared irradiation unit as a drying unit for drying the aqueous ink applied to the recording medium. The recording apparatus according to this embodiment includes, as the drying unit, a contact-type heating unit such as a heating roll, a heating drum, and a heating belt in addition to the infrared irradiation unit; a hot-air blowing unit including a heating element and a blower; May be provided.

  Examples of the recording medium include paper; paper coated with resin; films and plates made of resin, metal, glass, ceramics, silicon, rubber, and the like.

  The recording apparatus according to the present embodiment may include an ink cartridge that contains the aqueous ink according to the present embodiment and is formed into a cartridge so as to be detachable from the recording apparatus.

  Hereinafter, an example of a recording apparatus and a recording method according to the present embodiment will be described with reference to the drawings.

  FIG. 1 is a schematic configuration diagram illustrating an example of a recording apparatus according to the present embodiment. The recording device 12 shown in FIG. 1 is an inkjet recording device.

  The recording apparatus 12 shown in FIG. 1 includes a container 16 for storing a recording medium P before image recording, an endless transport belt 28 stretched around a driving roll 24 and a driven roll 26, inside a housing 14, Ink ejection heads (ink ejection heads 30Y, 30M, 30C, and 30K; collectively referred to as ink ejection heads 30) and an infrared irradiation device (infrared irradiation devices 60Y, 60M, 60C, and 60K), which are examples of ink applying means. A generic name is referred to as an infrared irradiation device 60), and a container 40 for accommodating the recording medium P after image recording.

  Between the container 16 and the transport belt 28 is a transport path 22 through which the recording medium P before image recording is transported. The transport path 22 includes a roll 18 for removing the recording medium P one by one from the container 16 and a recording path. A plurality of roll pairs 20 for transporting the medium P are arranged. On the upstream side of the transport belt 28, a charging roll 32 is disposed. The charging roll 32 is driven while sandwiching the transport belt 28 and the recording medium P between the charging roll 32 and the driven roll 26 to generate a potential difference between the charging roll 32 and the driven roll 26 that is grounded. 28 is electrostatically adsorbed.

  The ink ejection head 30 is disposed above the transport belt 28 so as to face a flat portion of the transport belt 28. The area where the ink ejection head 30 and the conveyance belt 28 face each other is the area where ink droplets are ejected from the ink ejection head 30.

  The ink ejection heads 30Y, 30M, 30C, and 30K are a head for recording a Y (yellow) color image, a head for recording an M (magenta) color image, a head for recording a C (cyan) color image, and a K, respectively. A head for recording a (black) color image. The ink ejection heads 30Y, 30M, 30C, and 30K are arranged, for example, in this order from the upstream side to the downstream side of the transport belt 28. The ink ejection heads 30Y, 30M, 30C, and 30K are respectively connected to ink cartridges 31Y, 31M, 31C, and 31K of respective colors that are attached to and detached from the recording device 12 through supply pipes (not shown). It is supplied to the ejection head.

  The ink ejection head 30 is, for example, a long one in which an effective recording area (area where nozzles for ejecting ink are arranged) is equal to or larger than the width of the recording medium P (length in a direction orthogonal to the transport direction of the recording medium P). Head; a head that is shorter than the width of the recording medium P and that moves in the width direction of the recording medium P to eject ink.

  The ink jet system adopted by the ink ejection head 30 includes a piezo system using a vibration pressure of a piezo element; a charge control system for ejecting ink using an electrostatic attraction; Acoustic ink-jet method in which ink is ejected using radiant pressure, and thermal ink-jet method in which ink is heated to form bubbles and the generated pressure is used.

  The ink ejection head 30 ejects ink droplets in a range of, for example, an ink droplet amount of 10 pL or more and 15 pL or less (for example, a recording head of 600 dpi), and ejects ink droplets in an ink droplet amount of less than 10 pL. It is a recording head for high resolution (for example, a recording head of 1200 dpi). dpi means “dots per inch”.

  The recording device 12 is not limited to a mode including four ink ejection heads. The recording device 12 may be configured to include four or more ink ejection heads obtained by adding an intermediate color to YMCK; or to include one ink ejection head and record an image of only one color.

  On the downstream side of the ink ejection head 30, above the transport belt 28, infrared irradiation means devices 60Y, 60M, 60C, and 60K are arranged for each color ink ejection head. The infrared irradiator 60 (an example of an infrared irradiator) irradiates the ink on the recording medium P with infrared to dry the ink.

  Examples of the light source of the infrared irradiation device 60 include a light emitting diode, a semiconductor laser, a surface emitting semiconductor laser, a halogen lamp, and a xenon lamp.

  As the infrared irradiating device 60, for example, a long infrared irradiating device in which an effective infrared irradiating region (an arrangement region of a light source for irradiating infrared) is equal to or larger than the width of a recording region by the ink discharging head 30; And a carriage-type infrared irradiation device that moves in the width direction of the recording medium P and irradiates infrared light.

The irradiation conditions of the infrared irradiation device 60 are set according to the infrared absorption performance of the ink, the amount of water in the ink, and the like. As the irradiation conditions, irradiation conditions for drying the water content of the ink applied onto the recording medium P to 10% by mass or less are preferable. Specifically, for example, a central wavelength of 700nm or more 1200nm or less (preferably not more than 780nm or 980 nm), irradiation intensity 0.1 J / cm ² or more 10J / cm ² or less (preferably 1 J / cm ² or more 3J / cm ² ), And the irradiation time is from 0.1 ms to 10 seconds (preferably from 10 ms to 100 ms).

  The recording device 12 is not limited to a mode in which an infrared irradiation device is provided for each color ink ejection head, and may be a mode in which only one infrared irradiation device is provided downstream of the most downstream ink ejection head.

  The recording device 12 may include at least one of a contact heating device and a hot air blowing device as a drying device for the ink, together with the infrared irradiation device 60. The contact-type heating unit or the hot-air blowing unit performs the drying under the condition that the surface temperature of the recording medium is raised to a range of 50 ° C. or more and 120 ° C. or less.

  On the downstream side of the infrared irradiation device 60, a peeling plate 34 is disposed so as to face the drive roll 24. The release plate 34 separates the recording medium P from the transport belt 28.

  Between the transport belt 28 and the container 40 is a transport path 36 through which the recording medium P after image recording is transported. In the transport path 36, a plurality of roll pairs 38 that transport the recording medium P are arranged. .

The operation of the recording device 12 will be described.
The recording medium P before the image recording is taken out one by one from the container 16 by the roll 18, and is conveyed to the conveyance belt 28 by a plurality of roll pairs 20.
Next, the recording medium P is electrostatically attracted to the transport belt 28 by the charging roll 32, and is transported below the ink ejection head 30 by the rotation of the transport belt 28.
Next, ink is ejected from the ink ejection head 30 onto the recording medium P, and an image is recorded.
Next, the ink on the recording medium P is irradiated with infrared rays from the infrared irradiation device 60, the ink generates heat due to absorption of infrared rays, the ink temperature rises, and the ink dries.
Next, the recording medium P on which the ink has dried and the image has been fixed is separated from the transport belt 28 by the release plate 34, and is transported to the container 40 by the plurality of roll pairs 38.

  The recording apparatus according to the present embodiment is not limited to a form in which ink is directly applied to a recording medium from an ink applying unit.After applying ink to the intermediate transfer body from the ink applying unit, the ink on the intermediate transfer body is applied to the recording medium. The transfer form may be used.

  The recording apparatus according to the present embodiment is not limited to a sheet-fed machine in which the recording apparatus 12 shown in FIG. 1 is an example, and may be a rotary press.

  Hereinafter, embodiments of the present invention will be described in detail with reference to examples, but embodiments of the present invention are not limited to these examples. In the following description, all “parts” are based on mass unless otherwise specified.

-Synthesis example-
[Synthesis of squarylium dye compound: (Ia-1)]
As the compound represented by the general formula (Ia), compound (Ia-1) was synthesized according to the reaction scheme of compound (1) -A described above.

  A three-necked flask was equipped with a Dean-Stark trap, a reflux condenser, a stirring seal, and a stirring rod, and used as a reaction vessel. A reaction vessel was charged with 2,2,8,8-tetramethyl-3,6-nonaziin-5-ol and cyclohexane. Manganese (IV) oxide powder was added, stirred with a three-one motor, and heated to reflux. Water formed during the reaction was removed by azeotropic distillation. It was confirmed by thin layer chromatography that there was no remaining 2,2,8,8-tetramethyl-3,6-nonadiyn-5-ol. After allowing the reaction mixture to cool, it was filtered under reduced pressure to obtain a yellow filtrate (F1). The filtered solid was transferred to another container, ethyl acetate was added, the operation of ultrasonic dispersion and filtration was repeated four times to obtain an ethyl acetate extract (F2). The ethyl acetate extract (F2) and the filtrate (F1) were mixed and concentrated by a rotary evaporator and then a vacuum pump to obtain an orange liquid. The orange liquid was distilled under reduced pressure to obtain a pale yellow liquid (intermediate 1).

  A thermometer and a dropping funnel were set in a three-necked flask to obtain a reaction vessel. Sodium hydrogen monosulfide n-hydrate was added to ethanol, stirred at room temperature (20 ° C.) until dissolved, and then cooled with ice water. When the internal temperature reached 5 ° C, a mixed solution of Intermediate 1 and ethanol was added dropwise little by little. The liquid changed from yellow to orange by dropping. Since the internal temperature rises due to heat generation, the temperature was dropped within the range of 5 ° C. or more and 7 ° C. or less while adjusting the amount of dropping. Thereafter, the ice water bath was removed, and the mixture was stirred while the temperature was naturally raised at room temperature (20 ° C.). Water was added to the reaction solution, and ethanol was removed with a rotary evaporator. Thereafter, sodium chloride was added until saturation, and the mixture was separated with ethyl acetate to collect an organic phase. The organic phase was washed twice with saturated ammonium chloride and dried over magnesium sulfate. After drying, the mixture was concentrated under reduced pressure to recover a brown liquid. The brown liquid was distilled under reduced pressure. A distillate starts to be produced at 200 ° C., but the first distillate has a low purity of the target component. The yellow liquid (intermediate 2) was distilled.

  The stirring rod and the intermediate 2 were placed in a three-necked flask, and a nitrogen inlet tube and a reflux condenser were attached, followed by purging with nitrogen. Under a nitrogen atmosphere, anhydrous tetrahydrofuran was added with a syringe, and a 1M solution of methylmagnesium bromide in tetrahydrofuran was added dropwise with a syringe while stirring at room temperature (20 ° C.). After completion of the dropwise addition, the reaction solution was heated and stirred and refluxed. After allowing the reaction solution to cool under a nitrogen atmosphere, a solution of ammonium bromide in water was added dropwise while cooling in an ice water bath. After the reaction mixture was further stirred at room temperature (20 ° C.), n-hexane was added and dried over sodium sulfate. After drying, the n-hexane / tetrahydrofuran solution was taken out with a syringe, and the inorganic layer was washed with ethyl acetate to obtain an extract. The n-hexane / tetrahydrofuran solution and the extract from the inorganic layer were mixed, concentrated under reduced pressure, and dried in vacuo to obtain Intermediate 3.

  Under a nitrogen atmosphere, Intermediate 3 and squaric acid were dispersed in a mixed solvent of cyclohexane and isobutanol, pyridine was added, and the mixture was heated to reflux. Thereafter, isobutanol was added, and the reaction mixture was further heated to reflux. The water formed during the reaction was removed by azeotropic distillation. After allowing the reaction mixture to cool, it was filtered under reduced pressure to remove hardly soluble substances. The filtrate was concentrated on a rotary evaporator. Methanol was added to the residue, heated to 40 ° C, and then cooled to -10 ° C. Crystals were obtained by filtration and dried under vacuum to obtain compound (I-a-1).

[Polyester resin: synthesis of PES]
-90.1 parts of dimethyl terephthalate-90.1 parts of dimethyl isophthalate-21.0 parts of methyl fumarate-146.2 parts of bisphenol A ethylene oxide 2 mol adduct-162.2 parts of bisphenol A propylene oxide 2 mol adduct Ethylene glycol 22.0 parts Into a three-necked flask equipped with a stirrer and a distillation tube, the above-mentioned raw materials, 0.1 part of calcium acetate and 0.1 part of antimony (III) oxide as a condensation catalyst were put, and then placed under a nitrogen stream. The temperature was raised while distilling off the generated methanol and ethylene glycol, and the mixture was stirred for 30 minutes while maintaining the temperature at 150 ° C., and further stirred for 1 hour while maintaining the temperature at 200 ° C. Next, the temperature was lowered to 150 ° C., and the pressure in the reaction system was gradually reduced by a pump under stirring, and while maintaining the pressure in the reaction system in a range of 10 Pa or more and 40 Pa or less, the inside of the reaction system was distilled off while ethylene glycol was distilled off. The temperature was raised, and the reaction was further performed at 240 ° C. for 3 hours. The product was taken out and cooled to obtain a polyester resin. The polyester resin (PES) had a weight average molecular weight (Mw) of 16,000 and an acid value of 16 mgKOH / g.

[Synthesis of acrylic resin: Ac]
・ N-butyl methacrylate: 90 parts ・ acrylic acid: 0.5 parts ・ 1,10-decanediol diacrylate: 0.5 parts ・ dodecanethiol: 0.8 parts In a three-necked flask equipped with a stirrer and a distillation tube, The above-mentioned raw materials and 0.5 part of potassium persulfate were added, and the mixture was stirred for 60 minutes while maintaining the temperature at 72 ° C under a nitrogen stream, and further stirred for 5 hours while maintaining the temperature at 80 ° C. Next, the temperature was lowered to 30 ° C., and the product was taken out and cooled to obtain an acrylic resin. The acrylic resin (Ac) had a weight average molecular weight (Mw) of 60000 and an acid value of 7 mgKOH / g.

-Preparation of each dispersion-
[Example 1]
(Preparation of Infrared Absorbing Particle Dispersion: IR1)
1.5 parts of the compound (Ia-1) having a squarylium skeleton was placed in a flask. Thereto, 14 parts of tetrahydrofuran was added, and a stirring bar was put therein and stirred. Next, 5 parts of a polyester resin was added, and 10 parts of methyl ethyl ketone was further added, followed by stirring and mixing. Next, an 8% aqueous solution of sodium hydroxide was added with stirring to 0.9 equivalents (90% neutralization degree) of all carboxy groups contained in the polyester resin. Next, 130 parts of water was gradually added while stirring was continued, and mixed with water. Thereafter, a distillation tube and a vacuum pump were attached to the flask, and the mixture was heated to 42 ° C. or higher and 52 ° C. or lower, and the pressure was reduced while stirring to remove the organic solvent. The process was repeated until the organic solvent odor disappeared while adjusting the amount of water added so that the solid content concentration did not exceed 11% by mass. The concentrate was filtered through a 230 mesh nylon mesh to obtain an infrared absorbing particle dispersion. The solid content of this infrared-absorbing particle dispersion was measured, and water was added to adjust the solid concentration to 10% by mass based on the measured solid content to obtain a dispersion (IR1) of infrared-absorbing particles. When converted from the amount of the compound having a squarylium skeleton (I-a-1) and the amount of the polyester resin, the concentration of the compound having a squarylium skeleton (I-a-1) with respect to the infrared absorbing particles was 15% by mass. .

(Production of polymer-coated cyan pigment (1))
In a reaction vessel, 6 parts of styrene, 11 parts of stearyl methacrylate, 4 parts of styrene macromer AS-6 (manufactured by Toagosei), 5 parts of Blenmer PP-500 (manufactured by NOF Corporation), 5 parts of methacrylic acid, 0.05 part of 2-mercaptoethanol 0.05 And a mixed solution consisting of 24 parts of methyl ethyl ketone was prepared. Separately, 14 parts of styrene, 24 parts of stearyl methacrylate, 9 parts of styrene macromer AS-6 (Toagosei), 9 parts of Blemmer PP-500 (NOF), 10 parts of methacrylic acid, 0.13 part of 2-mercaptoethanol, and methyl ethyl ketone 56 And a mixed solution composed of 1.2 parts of 2,2′-azobis (2,4-dimethylvaleronitrile) was prepared and placed in a dropping funnel.

  Under a nitrogen atmosphere, the temperature of the mixed solution in the reaction vessel was raised to 75 ° C. while stirring, and the mixed solution in the dropping funnel was dropped over 1 hour. Two hours after the completion of the dropwise addition, a solution prepared by dissolving 1.2 parts of 2,2′-azobis (2,4-dimethylvaleronitrile) in 12 parts of methyl ethyl ketone was added dropwise over 3 hours, and reacted at 75 ° C. for 2 hours. The mixture was further aged at 80 ° C. for 2 hours to obtain a polymer solution.

  5 parts (solid content conversion) of the obtained polymer solution, 10 parts of Pigment Blue 15: 3 (Dainichi Seika Kogyo), 40 parts of methyl ethyl ketone, 8 parts of a 1 mol / L sodium hydroxide aqueous solution and 82 parts of ion-exchanged water were added to 0.1 part. The mixture was charged into a bead mill disperser together with 300 parts of 1 mm zirconia beads and dispersed for 6 hours. The obtained dispersion was concentrated under reduced pressure using an evaporator to remove methyl ethyl ketone and to concentrate the pigment to a concentration of 10% by mass. Thus, a dispersion in which the polymer-coated cyan pigment (1) was dispersed was obtained. The volume average particle diameter of the polymer-coated cyan pigment (1) contained in the dispersion was 77 nm.

(Production of water-based ink)
After mixing the following materials, coarse particles were removed with a 5 μm filter to obtain an aqueous ink. The pH of the aqueous ink was 6.

-Infrared absorbing particle dispersion: 33 parts of IR1-15 parts of dispersion of polymer-coated cyan pigment (1)-15 parts of propylene glycol-1 part of Olfin E1010 (Nissin Chemical Industry)-26 parts of ion-exchanged water-propylene glycol- 10 parts of n-butyl ether (PnB) (partition coefficient of octanol / water log P = 1.15)

[Example 2]
An aqueous ink was obtained in the same manner as in Example 1, except that diethylene glycol monohexyl ether (hexyl carbitol, HCBT) having an octanol / water partition coefficient log P = 1.7 was used in the production of the aqueous ink.

[Example 3]
An aqueous ink was obtained in the same manner as in Example 1, except that propylene glycol-n-butyl ether (PnB) in Example 1 was changed to dipropylene glycol-n-butyl ether (DPnB).

[Example 4]
An aqueous ink was obtained in the same manner as in Example 1 except that propylene glycol-n-butyl ether (PnB) in Example 1 was changed to diethylene glycol diethyl ether (DEDE).

[Example 5]
Except that the content of the infrared absorbing agent with respect to the infrared absorbing particles in Example 1 was changed to 0.4 part and the amount of ion exchange water was adjusted so that the total amount of the aqueous ink became 100 parts. In the same manner as in Example 1, an aqueous ink was obtained.

[Example 6]
Except that the content of the infrared absorbing agent with respect to the infrared absorbing particles in Example 1 was changed to 2.6 parts and the amount of ion exchange water was adjusted so that the total amount of the aqueous ink became 100 parts. In the same manner as in Example 1, an aqueous ink was obtained.

[Example 7]
In Example 1, the content of propylene glycol-n-butyl ether (PnB) in the aqueous ink was changed to 3 parts, and the amount of ion-exchanged water was adjusted so that the total amount of the aqueous ink became 100 parts. A water-based ink was obtained in the same manner as in Example 1 except that the above operation was performed.

Example 8
In Example 1, the content of propylene glycol-n-butyl ether (PnB) with respect to the aqueous ink was changed to 17 parts, and the amount of ion-exchanged water was adjusted so that the total amount of the aqueous ink became 100 parts. A water-based ink was obtained in the same manner as in Example 1 except that the above operation was performed.

[Example 9]
Example 1 was repeated except that the content of the infrared absorbing particles with respect to the aqueous ink in Example 1 was changed to 3 parts and the amount of ion exchange water was adjusted so that the total amount of the aqueous ink became 100 parts. A water-based ink was obtained in the same manner as in Example 1.

[Example 10]
Example 1 was repeated except that the content of the infrared-absorbing particles with respect to the aqueous ink in Example 1 was changed to 16 parts, and the amount of ion-exchanged water was adjusted so that the total amount of the aqueous ink became 100 parts. A water-based ink was obtained in the same manner as in Example 1.

[Comparative Example 1]
In the production of the water-based ink, the water-based ink was prepared in the same manner as in Example 1, except that the specification was such that the glycol ether was not used and the amount of the ion-exchanged water was adjusted so that the total of the water-based ink was 100 parts. Obtained.

[Comparative Example 2]
An aqueous ink was obtained in the same manner as in Example 1, except that diethylene glycol monobutyl ether (butyl carbitol, BCBT) having an octanol / water partition coefficient log P = 0.56 was used in the production of the aqueous ink.

[Comparative Example 3]
Diethylene glycol monobutyl ether (butyl carbitol, BCBT) having an octanol / water partition coefficient logP = 0.56 is used in the production of the aqueous ink, and an acrylic resin is used instead of the polyester resin in the preparation of the infrared absorbing particle dispersion. A water-based ink was obtained in the same manner as in Example 1 except that the specifications were used.

[Comparative Example 4]
In the production of the aqueous ink, diethylene glycol monobutyl ether (butyl carbitol, BCBT) having an octanol / water partition coefficient logP = 0.56 was used, and the amounts of the polyester resin and the infrared absorbent were adjusted in the preparation of the infrared absorbent particle dispersion. A water-based ink was obtained in the same manner as in Example 1, except that each part was 3 parts.

-Evaluation of the amount of solid residue-
The amount of solid residue was evaluated for the aqueous inks of each example using the above-described method (Table 1).

−Evaluation of precipitation of infrared absorber−
The precipitation of the infrared absorbent in each example was evaluated as follows (Table 1).
The obtained cyan ink was stored in an environment at a temperature of 60 ° C. for 10 days. After storage, the presence or absence of a precipitate (that is, a precipitate) was visually observed and evaluated according to the following criteria. In addition, when the composition of the precipitate was confirmed for the cyan ink in which a large amount of the precipitate was generated, all the precipitates contained an infrared absorbent (a compound having a squarylium skeleton) as a main component. A and B are acceptable.
(Evaluation criteria)
A: No precipitate is generated.
B: A precipitate was slightly generated.
C: Many precipitates were generated.

-Evaluation of redispersibility of aqueous ink-
2.5 g of the aqueous ink of each example was placed in a glass Petri dish (the lid side of FS-60 manufactured by FLAT), heated at 40 ° C., and concentrated to 40% by mass. Thereafter, in an environment at a temperature of 23 ° C., 20 g of ion-exchanged water (temperature of 23 ° C.) was added to dilute the ink to the original amount, followed by standing overnight. The state of the diluent was visually observed and classified based on the following evaluation criteria (Table 1). Note that G1 to G4 are acceptable.

G1: No solid matter can be confirmed on the petri dish. Aggregates in the diluent cannot be confirmed.
G2: Slight solids can be confirmed on the Petri dish, but no aggregates in the diluent can be confirmed.
G3: Solids can be confirmed on the Petri dish, and aggregates can be slightly confirmed in the diluent.
G4: Solids can be confirmed on the petri dish, and aggregates can be confirmed in the diluent, but within an acceptable range.
G5: Solids can be confirmed on the Petri dish, and aggregates are present in the diluent in an unacceptable range.

  From the above results, Examples 1 to 4 containing water, a colorant, infrared absorbing particles containing a polyester resin and an infrared absorbing agent, and a glycol ether having an octanol / water partition coefficient logP of 0.6 or more and 2.0 or less. The aqueous inks of Example 3 and Examples 5 to 10 have an image fixing property by infrared rays and are redispersed as compared with the aqueous inks of Comparative Examples 1 to 4 not having the configuration of the present invention. It was found that the deterioration of the property was suppressed. Further, the aqueous inks of Examples 1 to 2 and 4 to 10 in which the amount of the solid residue when the redispersion liquid of the aqueous ink was filtered was 0 g or more and 0.042 g or less. It has also been found that, compared to the aqueous inks of Comparative Examples 1 to 2 and Comparative Example 4 in which the amount of Was.

Reference Signs List 12 recording device 14 housing 16 container 18 roll 20 roll pair 22 transport path 24 drive roll 26 driven roll 28 transport belts 30Y, 30M, 30C, 30K ink discharge head (an example of ink applying means)
31Y, 31M, 31C, 31K Ink cartridge 32 Charging roll 34 Release plate 36 Transport path 38 Roll pair 40 Containers 60Y, 60M, 60C, 60K Infrared irradiation device (an example of an infrared irradiation device)
P Recording medium

Claims (16)

water and,
A coloring agent,
Infrared absorbing particles comprising a polyester resin and an infrared absorbing agent,
A glycol ether having an octanol / water partition coefficient logP of 0.6 or more and 2.0 or less;
Aqueous ink containing. water and,
A coloring agent,
Infrared absorbing particles comprising a polyester resin and an infrared absorbing agent,
Glycol ether,
Including
Concentrating 2.5 g of the aqueous ink to obtain a concentrate; and re-dispersing the concentrate in 2.5 g of the aqueous ink to prepare a redispersion. An aqueous ink having a solid residue from 0 g to 0.042 g when filtered. The infrared absorber comprises a compound having a squarylium skeleton,
The aqueous ink according to claim 1 or 2. The compound having the squarylium skeleton,
Including a compound represented by the general formula (1),
The aqueous ink according to claim 3.

(In the general formula (1), R ^1a , R ^1b , R ^1c and R ^1d each independently represent an alkyl group or an aryl group.) The glycol ether includes a glycol ether having an alkyl ether chain having 3 to 10 carbon atoms,
The aqueous ink according to any one of claims 1 to 4. The glycol ether comprises at least one selected from propylene glycol-n-butyl ether, dipropylene glycol-n-butyl ether and diethylene glycol hexyl ether,
The aqueous ink according to any one of claims 1 to 5. The content of the infrared absorber,
0.5% by mass or more and 2.5% by mass or less based on the infrared absorbing particles;
The aqueous ink according to any one of claims 1 to 6. The content of the infrared absorber,
1.0% by mass or more and 2.0% by mass or less based on the infrared absorbing particles,
The aqueous ink according to claim 7. The content of the glycol ether,
4% by mass or more and 15% by mass or less based on the aqueous ink.
The aqueous ink according to any one of claims 1 to 8. The content of the glycol ether,
80% by mass or more and 300% by mass or less based on the infrared absorbing particles,
The aqueous ink according to any one of claims 1 to 9. The content of the infrared absorbing particles,
4% by mass or more and 15% by mass or less based on the aqueous ink.
The aqueous ink according to any one of claims 1 to 10.   An ink cartridge containing the aqueous ink according to claim 1. An ink application unit that stores the aqueous ink according to any one of claims 1 to 11, and applies the aqueous ink to a recording medium.
Infrared irradiating means for irradiating the aqueous ink applied to the recording medium with infrared light,
A recording device comprising: The ink applying unit includes an inkjet head that ejects the aqueous ink,
A means for ejecting the aqueous ink from the inkjet head and applying it to a recording medium,
The recording device according to claim 13. An ink applying step of applying the aqueous ink according to any one of claims 1 to 11 to a recording medium,
An infrared irradiation step of irradiating the aqueous ink applied to the recording medium with infrared light,
A recording method having:   The recording method according to claim 15, wherein the ink applying step is a step of ejecting the aqueous ink from an inkjet head and applying the aqueous ink to a recording medium.