JP2018030985A - Infrared-absorbing particle dispersion liquid, aqueous ink, ink cartridge, recording device and recording method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an infrared-absorbing particle dispersion liquid in which an infrared absorber is contained in a stably dispersed manner.SOLUTION: A dispersion liquid contains, in an aqueous medium, an infrared-absorbing particle that contains a compound represented by general formula (1), and a polymer containing a constitutional unit represented by general formula (2) and an alkyl (meth) acrylate-derived constitutional unit and having an acid value of 6-100 mgKOH/g.SELECTED DRAWING: None

Description

  The present invention relates to an infrared absorbing particle dispersion, an aqueous ink, an ink cartridge, a recording apparatus, and a recording method.

  A composition containing an infrared absorber is known as an ink or a toner that is fixed to a recording medium by light irradiation.

  For example, Patent Document 1 discloses a dye-donor element for laser-induced thermal dye transfer containing a squarylium-based infrared absorber.

  For example, Patent Document 2 discloses a synthetic resin aqueous dispersion containing a resin in which a compound that absorbs a wavelength in the near infrared region is chemically bound in a resin skeleton.

  For example, Patent Document 3 discloses an aqueous solid particle dispersion containing a polymer, an infrared absorber, and a surfactant that stabilizes the dispersion.

Japanese Patent Laid-Open No. 06-210972 JP 11-021460 A JP 2003-231819 A

  2. Description of the Related Art Conventionally, in order to contain an infrared absorbent in an aqueous medium, a technique is known in which an infrared absorbent and a polymer are formed into particles containing both and dispersed in an aqueous medium. However, in the process of making both particles into an aqueous medium and dispersing them in the aqueous medium, agglomerates are generated and the yield of particles exhibiting infrared absorptivity decreases, or the particle size of particles exhibiting infrared absorptivity increases. was there.

  In the present invention, the polymer containing the structural unit represented by the general formula (2) and the structural unit derived from alkyl (meth) acrylate has a general formula of less than 6 mg KOH / g or more than 100 mg KOH / g. It is an object of the present invention to provide an infrared absorbing particle dispersion liquid in which the compound represented by (1) is stably dispersed in an aqueous medium.

  Specific means for solving the above-described problems include the following modes.

The invention according to claim 1
An aqueous medium;
Infrared absorbing particles dispersed in the aqueous medium, comprising a compound represented by the following general formula (1), a structural unit represented by the following general formula (2) and a structural unit derived from an alkyl (meth) acrylate Infrared absorbing particles containing a polymer having an acid value of from 6 mgKOH / g to 100 mgKOH / g,
Infrared absorbing particle dispersion liquid.

In General Formula (1), R ^a represents a group represented by General Formula (1-R), and R ^b , R ^c, and R ^d each independently represents an alkyl group. In General Formula (1-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 (2), R ¹ represents hydrogen, a methyl group or —X—R ² —A ¹ , R ³ represents hydrogen or —X—R ² —A ¹ , X represents a single bond, —CO— , —C (═O) O—, —CONH—, —OC (═O) — or a phenylene group, R ² represents a single bond or a divalent linking group, and A ¹ represents —COOH, —SO _3. It represents H or -OPO ₃ H _2. When two or more —X—R ² —A ¹ are present in a single structural unit, X, R ² and A ¹ may be the same as or different from each other.

The invention according to claim 2
The structural unit represented by the general formula (2) is a structural unit derived from 2-carboxyethyl (meth) acrylate, a structural unit derived from styrenesulfonic acid, 2- (meth) acrylamide-2-methylpropanesulfonic acid The infrared-absorbing particle dispersion liquid according to claim 1, which is at least one of a structural unit derived from the above and a structural unit derived from mono 2- (meth) acryloyloxyethyl phosphate.

The invention according to claim 3
The infrared-absorbing particle dispersion according to claim 1 or 2, wherein the pH is 6.0 or more and 9.5 or less.

The invention according to claim 4
The infrared-absorbing particle dispersion according to any one of claims 1 to 3, wherein the polymer contains a benzene ring in a range of 3% by mass to 50% by mass with respect to the total mass.

The invention according to claim 5
An aqueous medium;
Infrared absorbing particles dispersed in the aqueous medium, comprising a compound represented by the following general formula (1), a structural unit represented by the following general formula (2) and a structural unit derived from an alkyl (meth) acrylate Infrared absorbing particles containing a polymer having an acid value of from 6 mgKOH / g to 100 mgKOH / g,
Water-based ink containing.

In General Formula (1), R ^a represents a group represented by General Formula (1-R), and R ^b , R ^c, and R ^d each independently represents an alkyl group. In General Formula (1-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 (2), R ¹ represents hydrogen, a methyl group or —X—R ² —A ¹ , R ³ represents hydrogen or —X—R ² —A ¹ , X represents a single bond, —CO— , —C (═O) O—, —CONH—, —OC (═O) — or a phenylene group, R ² represents a single bond or a divalent linking group, and A ¹ represents —COOH, —SO _3. It represents H or -OPO ₃ H _2. When two or more —X—R ² —A ¹ are present in a single structural unit, X, R ² and A ¹ may be the same as or different from each other.

The invention according to claim 6
The structural unit represented by the general formula (2) is a structural unit derived from 2-carboxyethyl (meth) acrylate, a structural unit derived from styrenesulfonic acid, 2- (meth) acrylamide-2-methylpropanesulfonic acid The water-based ink according to claim 5, wherein the water-based ink is at least one of a structural unit derived from the above and a structural unit derived from mono 2- (meth) acryloyloxyethyl phosphate.

The invention according to claim 7 provides:
The water-based ink according to claim 5 or 6, wherein the polymer contains a benzene ring in a range of 3% by mass to 50% by mass with respect to the total mass.

The invention according to claim 8 provides:
An ink cartridge containing the water-based ink according to any one of claims 5 to 7.

The invention according to claim 9 is:
Ink applying means for containing the water-based ink according to any one of claims 5 to 7, and applying the water-based ink to a recording medium;
Infrared irradiation means for irradiating the water-based ink applied to the recording medium with infrared rays;
A recording apparatus comprising:

The invention according to claim 10 is:
An ink application step of applying the water-based ink according to any one of claims 5 to 7 to a recording medium;
An infrared irradiation step of irradiating the water-based ink applied to the recording medium with infrared rays;
A recording method.

  According to the inventions according to claims 1 and 2, the acid value of the polymer containing the structural unit represented by the general formula (2) and the structural unit derived from alkyl (meth) acrylate is less than 6 mg KOH / g or more than 100 mg KOH / g. Compared with the case where it is, the infrared rays absorptive particle dispersion liquid in which the compound represented by General formula (1) is stably disperse | distributed and contained in an aqueous medium is provided.

  According to the invention of claim 3, there is provided an infrared-absorbing particle dispersion in which a decrease in the infrared-absorbing performance over time is suppressed as compared with a case where the pH is less than 6.0 or more than 9.5.

  According to the invention which concerns on Claim 4, the polymer containing the structural unit represented by General formula (2) and the structural unit derived from alkyl (meth) acrylate is less than 3 mass% with respect to the total mass, or 50 Compared with the case where it is contained in a range exceeding mass%, an infrared absorbing particle dispersion liquid in which the compound represented by the general formula (1) is stably dispersed in an aqueous medium is provided.

  According to the invention which concerns on Claim 5, 6, the acid value of the polymer containing the structural unit represented by General formula (2) and the structural unit derived from alkyl (meth) acrylate is less than 6 mgKOH / g or more than 100 mgKOH / g. Compared with the case where it is, the water-based ink in which the compound represented by General formula (1) is stably disperse | distributed and contained in an aqueous medium is provided.

  According to the invention which concerns on Claim 7, the polymer containing the structural unit represented by General formula (2) and the structural unit derived from an alkyl (meth) acrylate is less than 3 mass% with respect to the total mass, or 50 Compared with the case where it is contained in a range exceeding mass%, an aqueous ink in which the compound represented by the general formula (1) is stably dispersed and contained in an aqueous medium is provided.

  According to the invention which concerns on Claim 8, the acid value of the polymer containing the structural unit represented by General formula (2) and the structural unit derived from alkyl (meth) acrylate is less than 6 mgKOH / g or more than 100 mgKOH / g. As compared with the case, an ink cartridge containing an aqueous ink in which the compound represented by the general formula (1) is stably dispersed in an aqueous medium is provided.

  According to the invention of claim 9, the acid value of the polymer containing the structural unit represented by the general formula (2) and the structural unit derived from alkyl (meth) acrylate is less than 6 mg KOH / g or more than 100 mg KOH / g. As compared with the case, a recording apparatus using an aqueous ink in which the compound represented by the general formula (1) is stably dispersed in an aqueous medium is provided.

  According to the invention which concerns on Claim 10, the acid value of the polymer containing the structural unit represented by General formula (2) and the structural unit derived from alkyl (meth) acrylate is less than 6 mgKOH / g or more than 100 mgKOH / g. Compared to the case, a recording method using a water-based ink in which the compound represented by the general formula (1) is stably dispersed in an aqueous medium is provided.

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

  Embodiments of the invention will be described below. These descriptions and examples illustrate embodiments and do not limit the scope of the invention.

  In the present disclosure, 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, the plurality of the substances present in the composition unless otherwise specified. It means the total amount of substance.

In the present disclosure, “alkane”, “alkyl”, “alkylene”, “alkene” and “alkenyl” include not only chain hydrocarbons but also cyclic hydrocarbons.
In this disclosure, “(meth) acryl” means that either “acryl” or “methacryl” may be used.

  In the present disclosure, the “aqueous medium” means water or a mixed solvent of water and other solvents and a mixed solvent containing water as a main solvent. In the present disclosure, the “main solvent” refers to a solvent having the largest mass among all the solvents constituting the mixed solvent.

<Infrared absorbing particle dispersion>
The infrared absorbing particle dispersion according to this embodiment is a dispersion including an aqueous medium and infrared absorbing particles dispersed in the aqueous medium, and the infrared absorbing particles are represented by the general formula (1). A compound and a polymer having a structural unit represented by the general formula (2) and a structural unit derived from alkyl (meth) acrylate and having an acid value of 6 mgKOH / g or more and 100 mgKOH / g or less are contained.

Conventionally, in order to contain an organic compound having a property insoluble or hardly soluble in water in an aqueous medium, a technique for forming the organic compound and a polymer into particles containing both of them and dispersing them in an aqueous medium is known. It has been.
This embodiment includes a compound represented by the general formula (1), a structural unit represented by the general formula (2), and a structural unit derived from alkyl (meth) acrylate, and has an acid value of 6 mgKOH / g or more and 100 mgKOH / The polymer represented by the general formula (1) is obtained by making a polymer having a molecular weight of g or less into particles containing both, and stably dispersing the compound represented by the general formula (1) in an aqueous medium. And a dispersion of infrared absorbing particles containing the polymer.

  Hereinafter, in the present disclosure, a polymer having a structural unit represented by the general formula (2) and a structural unit derived from alkyl (meth) acrylate and having an acid value of 6 mgKOH / g or more and 100 mgKOH / g or less is referred to as “specific polymer”. "

  In this embodiment, the acid value of the specific polymer is 6 mgKOH / g or more and 100 mgKOH / g or less. When the acid value of the polymer containing the structural unit represented by the general formula (2) and the structural unit derived from alkyl (meth) acrylate is less than 6 mgKOH / g, the dispersibility of the polymer in an aqueous medium is relatively Since it is low, the dispersion stability of the infrared absorbing particles is poor. On the other hand, when the acid value of the polymer containing the structural unit represented by the general formula (2) and the structural unit derived from alkyl (meth) acrylate is more than 100 mgKOH / g, the water solubility of the polymer is relatively high. Further, particles containing the polymer and the compound represented by the general formula (1) are hardly formed, and therefore, it is difficult to obtain infrared absorbing particles that are stably dispersed in an aqueous medium. From these viewpoints, the acid value of the specific polymer is 6 mg KOH / g or more as the lower limit, more preferably 8 mg KOH / g or more, further preferably 10 mg KOH / g or more, and the upper limit is 100 mg KOH / g or less, and 80 mg KOH / g. g or less is more preferable, and 60 mgKOH / g or less is still more preferable.

  This embodiment is excellent in the dispersion stability of infrared absorbing particles. Therefore, according to this embodiment, in the process of preparing the dispersion of infrared absorbing particles, aggregates are hardly generated and the yield of infrared absorbing particles is high. Moreover, according to this embodiment, a dispersion liquid in which infrared absorbing particles having a small particle diameter (for example, a volume average particle diameter of 150 nm or less) is dispersed is obtained.

In the present embodiment, the dispersion state of the infrared absorbing particles may be emulsification in which liquid particles are dispersed, or may be suspension in which solid particles are dispersed. From the viewpoint of dispersion stability, suspension in which solid particles are dispersed is preferable. .
That is, the infrared-absorbing particle dispersion according to the present embodiment may be an emulsion (emulsion) in which infrared-absorbing particles are dispersed in an aqueous medium in a liquid state, or a suspension in which infrared-absorbing particles are dispersed in an aqueous medium in a solid state. It may be a turbid liquid (suspension) and is preferably a suspension from the viewpoint of dispersion stability of the infrared absorbing particles.

  Hereinafter, components, compositions, manufacturing methods, and the like of the infrared-absorbing particle dispersion according to the present embodiment will be described in detail.

[Compound represented by general formula (1)]
The compound represented by the general formula (1) hardly deteriorates in infrared absorption performance even when stored for a long period of time or under a high temperature. The following is presumed as this mechanism.

A compound having a squarylium skeleton is contained in an aqueous composition such as a photofixable ink for reasons such as high infrared absorption performance. However, the squarylium skeleton is invaded by a solvent and other materials (dispersant, surfactant, etc.). May decompose.
In contrast, in the compound represented by the general formula (1), at least one of the four alkyl groups is a branched alkyl group having 3 or more carbon atoms, so that molecules that invade the squarylium skeleton are unlikely to approach the squarylium skeleton. It is considered to be. Therefore, the compound represented by the general formula (1) is unlikely to be decomposed in the aqueous composition, and it is presumed that the infrared absorption performance is not easily lowered even when stored for a long period of time or at a high temperature.

In General Formula (1), R ^a represents a group represented by General Formula (1-R).
The total carbon number of the group represented by the general formula (1-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 General Formula (1-R), R ^e represents hydrogen or a methyl group. R ^e is preferably a methyl group. When R ^e is a methyl group, the group represented by the general formula (1-R) has a structure in which the terminal is branched into three, and the infrared absorption performance is further reduced as compared with the case where R ^e is hydrogen. Is suppressed. This degradation towards the structure R ^e is methyl group, compared with the structure R ^e is hydrogen, molecules that invade the squarylium skeleton is hardly approach the squarylium skeleton, the compound represented by the general formula (1) This is thought to be due to the fact that this is suppressed.

  In general formula (1-R), n represents an integer of 0 or more and 3 or less. n is preferably an integer of 0 or more and 2 or less, more preferably 0 or 1, and still more preferably 0. The smaller n is, the lower the infrared absorption performance is suppressed. This is because, as the value of n is smaller, the distance between the branched structure portion in the group represented by the general formula (1-R) and the squarylium skeleton is closer, so that molecules that invade the squarylium skeleton are less likely to approach the squarylium skeleton. It is considered that the decomposition of the compound represented by the general formula (1) is suppressed.

  Specific examples of the group represented by the general formula (1-R) include 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 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 preferable, and a tert-butyl group is more preferable.

In general formula (1), R ^b , R ^c and R ^d each independently represents an alkyl group. R ^b , R ^c and R ^d are preferably at least one group represented by the general formula (1-R), and all of R ^b , R ^c and R ^d are represented by the general formula (1-R). It is more preferred that As the number of groups represented by the general formula (1-R) in the general formula (1) increases, the decrease in the infrared absorption performance is further suppressed. This is because, as the number of groups represented by the general formula (1-R) increases, molecules that invade the squarylium skeleton are less likely to approach the squarylium skeleton, and the decomposition of the compound represented by the general formula (1) is suppressed. Conceivable.

When one of R ^b , R ^c and R ^d is a group represented by the general formula (1-R), any of R ^b , R ^c and R ^d is represented by the general formula (1-R). It may be a group. When two of R ^b , R ^c and R ^d are groups represented by the general formula (1-R), any of R ^b , R ^c and R ^d is represented by the general formula (1-R). It may be a group.

When two or more of R ^{a to} R ^d are a group represented by the general formula (1-R), a plurality of groups represented by the general formula (1-R) may have the same structure. It may be.

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

The alkyl group in the case where at least one of R ^b , R ^c and R ^d is other than the group represented by the general formula (1-R) may be any of linear, branched and cyclic structures. Good. In this case, the alkyl group preferably has a larger number of branches, and the carbon chain is preferably shorter. As carbon number, 1 or more and 10 or less are preferable, 2 or more and 8 or less are more preferable, and 3 or more and 6 or less are still more preferable.
Specific examples of the alkyl group include methyl, ethyl, n-propyl, n-butyl, n-pentyl, n-hexyl, sec-butyl, 2-methylbutan-2-yl, 3- 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 and the like Is mentioned. Among these, a 2-methylbutan-2-yl group and a 3-methylpentan-3-yl group are preferable.

Specific examples of the compound represented by the general formula (1) are shown below.
Compounds (Ia-1) to (Ia-7), Compounds (Ib-1) to (Ib-21), Compounds (Ic-1) to (Ic-21) Is a compound having four groups represented by the general formula (1-R). Compounds (Id-1) to (Id-4) are compounds having two groups represented by the general formula (1-R).

  Among the above specific examples, compounds (Ia-1) to (Ia-7), compounds (Ib-1) to (Ib-6), compounds (Ic-1) to (Ic-6) is preferred, Compound (Ia-1), Compound (Ib-3), and Compound (Ic-3) are more preferred, and Compound (Ia-1) is most preferred preferable.

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

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

  First, the starting material 1 is allowed to act dropwise on an organic solvent (eg, tetrahydrofuran) solution of an organic magnesium halide (Grignard reagent, eg, ethylmagnesium chloride) under an inert atmosphere and cooling. 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 hereinafter in this description) or higher. Subsequently, a formic acid derivative (for example, ethyl formate etc.) is dropped and allowed to act under cooling. Thereafter, the temperature may be returned to room temperature or higher in order to complete the reaction. An organic substance 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 (such as manganese oxide) are added to a solvent (such as cyclohexane), and the mixture is reacted by heating under reflux. 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.

  Next, the cycloaddition reaction is performed on intermediate B. For example, sodium hydrogen monosulfide n hydrate is added to a solvent (for example, ethanol), and the intermediate B is added dropwise under cooling. Then, it is made to react at room temperature, After removing a solvent from a reaction liquid, salt is added until it is saturated, and it liquid-separates, collect | recovers organic phases, The intermediate body C is obtained from an organic phase. Purification may be performed when obtaining intermediate C.

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

  Next, in an inert atmosphere, intermediate D and squaric acid are dispersed in a solvent (such as a mixed solvent of cyclohexane and isobutanol), a basic compound (such as pyridine) is added, and the mixture is heated to reflux to obtain compound (I). -A is obtained. Water generated during the reaction may be removed. Further, purification, isolation, concentration and the like may be performed.

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

  Under an inert atmosphere and under cooling, the starting material 1 is added dropwise to a solution of a Grignard reagent (for example, ethyl magnesium bromide) in an organic solvent (for example, tetrahydrofuran), and then the additional material 2 is added dropwise to react. A strong acid (such as 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 in obtaining intermediate A '.

(3) Compounds in which R ^a and R ^b are the same group and R ^c and R ^d are the same group (R ^a and R ^c are different groups)
As an intermediate D in the reaction scheme of (1), two types of compounds having different R ¹ structures are prepared, and these two types 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 ^{a to} R ^d are the same group, a compound in which two are the same group and the remaining two are different groups, and a compound in which all four groups are different can be synthesized according to the above reaction scheme.

The maximum absorption wavelength (λ _max ) of the compound represented by the general formula (1) (tetrahydrofuran solution) is preferably a wavelength of 760 nm or more and 1200 nm or less, more preferably a wavelength of 780 nm or more and 1100 nm or less, and a wavelength of 800 nm or more. More preferably, it is 1000 nm or less.

The molar extinction coefficient (ε _max ) at the maximum absorption wavelength (λ _max ) of the compound represented by the general formula (1) (tetrahydrofuran solution) is 1 × 10 ⁵ Lmol ⁻¹ cm ⁻¹ or more and 6 × 10 ⁵ Lmol ^−1. It is preferably cm ⁻¹ or less, more preferably 2 × 10 ⁵ Lmol ⁻¹ cm ⁻¹ or more and 6 × 10 ⁵ Lmol ⁻¹ cm ⁻¹ or less, and 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.

[Specific polymer]
In the present embodiment, the specific polymer may be a polymer dispersed in an aqueous medium in a liquid state or a polymer dispersed in an aqueous medium in a solid state. From the viewpoint of dispersion stability, a polymer dispersed in an aqueous medium in a solid state may be used. preferable.

In the present embodiment, the specific polymer acts as a dispersant for the compound represented by the general formula (1). The specific polymer includes at least a structural unit represented by the general formula (2) and a structural unit derived from alkyl (meth) acrylate, and has an acid value of 6 mgKOH / g or more and 100 mgKOH / g or less. The lower limit of the acid value of the specific polymer is more preferably 8 mgKOH / g or more, still more preferably 10 mgKOH / g or more, and the upper limit is more preferably 80 mgKOH / g or less, still more preferably 60 mgKOH / g or less.
In this embodiment, the acid value of the polymer is a value determined by the neutralization titration method defined in JIS K0070: 1992.

The polymer containing the structural unit represented by the general formula (2) is stably dispersed as compared with the polymer containing the structural unit derived from (meth) acrylic acid instead of the structural unit represented by the general formula (2). . Moreover, the polymer containing the structural unit represented by the general formula (2) is stably dispersed when the pH of the aqueous medium is near neutral (for example, pH 6.0 to 9.5). This is probably because the anionic group of the structural unit represented by the general formula (2) has a smaller dissociation constant pKa than the anionic group of the structural unit derived from (meth) acrylic acid.
The compound represented by the general formula (1) is more likely to be decomposed as the pH of the medium goes away from neutrality. By using a polymer containing the structural unit represented by the general formula (2), infrared absorbing particle dispersion Since the pH of the liquid can be set in the vicinity of neutrality, according to the present embodiment, decomposition of the compound represented by the general formula (1) can be suppressed, and deterioration of infrared absorption performance over time can be suppressed. .

In General Formula (2), R ¹ represents hydrogen, a methyl group, or —X—R ² —A ^1, and preferably hydrogen or a methyl group. X in ^{-X-R 2 -A 1, R} 2 and ^{A 1} are as described below.

In General Formula (2), R ³ represents hydrogen or —X—R ² —A ¹ , and hydrogen is preferable. X in ^{-X-R 2 -A 1, R} 2 and ^{A 1} are as described below.

  In General Formula (2), X represents a single bond, —CO—, —C (═O) O—, —CONH—, —OC (═O) —, or a phenylene group.

In general formula (2), R ² represents a single bond or a divalent linking group. Examples of the divalent linking group include an alkylene group having 1 to 4 carbon atoms (methylene group, ethylene group, n-propylene group, isopropylene group, n-butylene group, isobutylene group, sec-butylene group, tert- Butylene group, etc.), -C (= O) O-, -OC (= O)-, 1,2-phenylene group, 1,4-phenylene group, 1,2-cyclohexylene group, 1,4-cyclohexylene Groups, and combinations thereof.

In the general formula (2), ^{A 1} is -COOH (carboxy group), - represents a _SO 3 H (sulfonic acid group), or -OPO ₃ H ₂ (phosphorous acid).

When two or more —X—R ² —A ¹ are present in a single structural unit, a plurality of X, R ² and A ¹ present in a single structural unit may be the same as or different from each other. .

  The specific polymer may contain 1 type as a structural unit represented by General formula (2) in a single polymer molecule, and may contain 2 or more types.

Specific examples of the structural unit represented by the general formula (2) include the following. In the following structural formula, R ¹¹ represents hydrogen or a methyl group, and R ¹² represents a 1,2-phenylene group, a 1,4-phenylene group, a 1,2-cyclohexylene group, or a 1,4-cyclohexylene group. N represents an integer of 1 to 10, and m represents an integer of 1 to 10. n is preferably an integer of 1 to 5, more preferably an integer of 1 to 3, and particularly preferably 1. m is preferably an integer of 1 to 6, and more preferably an integer of 2 to 4.

  The specific polymer is obtained by polymerizing at least a monomer that is a structural unit represented by the general formula (2) and an alkyl (meth) acrylate. The specific polymer may have a monomer other than the monomer that is the structural unit represented by the general formula (2) and an alkyl (meth) acrylate as a polymerization component. There is no particular limitation on the polymerization method of the specific polymer, and the monomer mixture may be copolymerized by a known polymerization method.

  Examples of the monomer that is a structural unit represented by the general formula (2) and has a structural unit having —COOH (carboxy group) include styrene carboxylic acid (vinyl benzoic acid), α-methylstyrene carboxylic acid, 2- Examples thereof include carboxyethyl (meth) acrylate, 2- (meth) acryloyloxyethyl hexahydrophthalic acid, and 2- (meth) acryloyloxyethyl phthalic acid.

Examples of the monomer represented by the general formula (2), which is a structural unit having —SO ₃ H (sulfonic acid group), include styrene sulfonic acid, α-methyl styrene sulfonic acid, and vinyl benzyl sulfonic acid. , (Meth) acryloyloxyethanesulfonic acid, (meth) acryloyloxypropanesulfonic acid, (meth) acryloyloxybutanesulfonic acid, 2- (meth) acrylamide-2-methylethanesulfonic acid, 2- (meth) acrylamide-2 -Methylpropanesulfonic acid, 2- (meth) acrylamide-2-methylbutanesulfonic acid and the like.

Examples of the monomer that is a structural unit represented by the general formula (2) and has a structural unit having —OPO ₃ H ₂ (phosphate group) include, for example, mono 2- (meth) acryloyloxyethyl phosphate, phosphoric acid And monovinyl.

From the viewpoint of excellent dispersibility in an aqueous medium, the alkyl group in the alkyl (meth) acrylate is preferably an alkyl group having 1 to 8 carbon atoms, more preferably an alkyl group having 1 to 4 carbon atoms, The alkyl group preferably has no substituent.
Examples of the alkyl (meth) acrylate include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, Examples include sec-butyl (meth) acrylate, tert-butyl (meth) acrylate, pentyl (meth) acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, octyl (meth) acrylate, and the like. It is done. 1 type may be used for alkyl (meth) acrylate and it may use 2 or more types together.

From the viewpoint of more stably dispersing the compound represented by the general formula (1), the specific polymer preferably has an aromatic ring in the molecule, and preferably includes an aromatic ring-containing monomer as a polymerization component.
Aromatic ring-containing monomers include styrene, α-methyl styrene, dimethyl styrene, trimethyl styrene, ethyl styrene, isopropyl styrene, chloro styrene, dichloro styrene, chloromethyl styrene, bromo styrene, methoxy styrene, acetoxy styrene, methyl styrene carboxylate ( Styrenic monomers such as methyl vinyl benzoate); macromonomers having polystyrene structural units; phenyl (meth) acrylate, benzyl (meth) acrylate, naphthyl (meth) acrylate, 2-phenoxyethyl (meth) acrylate, 2-hydroxy- Aromatic group-containing (meth) acrylates such as 3-phenoxypropyl (meth) acrylate; One type of aromatic ring-containing monomer may be used, or two or more types may be used in combination.

  The aromatic ring contained in the specific polymer is preferably a monocyclic benzene ring, and the specific polymer preferably contains the benzene ring in the range of 3% by mass to 50% by mass with respect to the total mass. When the benzene ring content is in the above range, the specific polymer is easy to form and disperse in the aqueous medium, and the dispersion of the compound represented by the general formula (1) becomes more stable. From the above viewpoint, the benzene ring content of the specific polymer is more preferably 4% by mass or more as a lower limit, further preferably 5% by mass or more, more preferably 45% by mass or less, and further more preferably 40% by mass or less. preferable.

  Examples of monomers other than the above that form the specific polymer include the following. 1 type may be used for the following monomer and it may use 2 or more types together.

  (Meth) acrylic acid esters other than alkyl (meth) acrylates. Specifically, furfuryl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, hydroxybutyl (meth) acrylate, hydroxypentyl (meth) acrylate, hydroxyhexyl ( (Meth) acrylate, 2,2-dimethyl-3-hydroxypropyl (meth) acrylate, 2,2,2-tetrafluoroethyl (meth) acrylate, glycidyl (meth) acrylate, 2-methoxyethyl (meth) acrylate, 2- (2-methoxyethoxy) ethyl (meth) acrylate, ethoxytriethylene glycol (meth) acrylate, methoxypolyethylene glycol (molecular weight 200 to 1000) mono (meth) acrylate, poly Ethylene glycol (molecular weight 200 to 1000) mono (meth) acrylate.

  Carboxy group-containing monomer. Specifically, acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, citraconic acid, crotonic acid, itaconic acid monoalkyl ester (for example, itaconic acid monomethyl, itaconic acid monoethyl, itaconic acid monobutyl etc.), maleic acid And monoalkyl esters (for example, monomethyl maleate, monoethyl maleate, monobutyl maleate, etc.).

  Vinyl esters. Specific examples include vinyl acetate, vinyl propionate, vinyl butyrate, vinyl isobutyrate, vinyl caproate, vinyl chloroacetate, vinyl methoxyacetate, vinyl phenyl acetate, vinyl benzoate, and vinyl salicylate.

  (Meth) acrylamides. Specifically, (meth) acrylamide, methyl (meth) acrylamide, ethyl (meth) acrylamide, propyl (meth) acrylamide, butyl (meth) acrylamide, cyclohexyl (meth) acrylamide, phenyl (meth) acrylamide, benzyl (meth) Acrylamide, hydroxymethyl (meth) acrylamide, methoxymethyl (meth) acrylamide, butoxymethyl (meth) acrylamide, methoxyethyl (meth) acrylamide, dimethyl (meth) acrylamide, diethyl (meth) acrylamide, β-cyanoethyl (meth) acrylamide, N- (2-acetoacetoxyethyl) (meth) acrylamide, diacetone (meth) acrylamide, etc. are mentioned.

  Olefins. Specific examples include dicyclopentadiene, ethylene, propylene, 1-butene, 1-pentene, vinyl chloride, vinylidene chloride, isoprene, chloroprene, butadiene, and 2,3-dimethylbutadiene.

  Vinyl ethers. Specific examples include methyl vinyl ether, butyl vinyl ether, hexyl vinyl ether, methoxyethyl vinyl ether and the like.

  In addition, butyl crotonate, hexyl crotonate, dimethyl itaconate, dibutyl itaconate, dimethyl maleate, diethyl maleate, dibutyl maleate, dimethyl fumarate, diethyl fumarate, dibutyl fumarate, methyl vinyl ketone, phenyl vinyl ketone , Methoxyethyl vinyl ketone, N-vinyl oxazolidone, N-vinyl pyrrolidone, vinylidene chloride, methylenemalon nitrile and the like.

  From the viewpoint of controlling, for example, the glass transition temperature of a specific polymer, the solubility in an organic solvent, or the affinity for the compound represented by the general formula (1), the monomers listed above are selected from one or more types. select.

  Hereinafter, specific examples of the specific polymer will be exemplified by describing polymerization components. The parentheses indicate the mass ratio of the polymerization components. The present invention is not limited to these compounds P01 to P23.

P01: Phenoxyethyl acrylate / methyl methacrylate / acrylic acid / 2-carboxyethyl acrylate copolymer (50/44/1/5)
P02: Phenoxyethyl acrylate / benzyl methacrylate / isobutyl methacrylate / styrene carboxylic acid copolymer (30/35/25/10)
P03: Phenoxyethyl methacrylate / isobutyl methacrylate / 2-acrylamido-2-methylpropanesulfonic acid copolymer (50/44/6)
P04: Styrene / butyl acrylate / ethyl methacrylate / 2-carboxyethyl acrylate copolymer (30/15/49/6)
P05: styrene / butyl acrylate / ethyl methacrylate / sodium styrene sulfonate copolymer (30/20/44/6)
P06: Styrene / phenoxyethyl acrylate / methyl methacrylate / 2-carboxyethyl acrylate copolymer (10/50/35/5)
P07: benzyl acrylate / methyl methacrylate / 2-carboxyethyl acrylate copolymer (55/40/5)
P08: Phenoxyethyl methacrylate / benzyl acrylate / styrene carboxylic acid copolymer (45/47/8)
P09: Styrene / phenoxyethyl acrylate / butyl methacrylate / 2-carboxyethyl acrylate copolymer (5/48/40/7)
P10: benzyl methacrylate / phenoxyethyl methacrylate / methyl methacrylate / mono 2-methacryloyloxyethyl phosphate copolymer (30/30/30/10)
P11: benzyl acrylate / methyl methacrylate / butyl acrylate / 2-acrylamido-2-methylpropane sulfonic acid copolymer (12/50/30/8)
P12: Styrene / ethyl methacrylate / 2-carboxyethyl acrylate copolymer (30/60/10)
P13: Styrene / phenoxyethyl methacrylate / butyl acrylate / 2-carboxyethyl acrylate copolymer (15/76/5/4)
P14: Methyl methacrylate / phenoxyethyl methacrylate / benzyl acrylate / 2-carboxyethyl acrylate copolymer (50/30/15/5)
P15: Methyl methacrylate / butyl methacrylate / 2-acrylamido-2-methylpropanesulfonic acid copolymer (56/40/4)
P16: benzyl acrylate / 2-carboxyethyl acrylate copolymer (90/10)
P17: Methyl methacrylate / methoxyethyl acrylate / benzyl methacrylate / itaconic acid copolymer (44/15/35/6)
P18: Ethyl methacrylate / styrene / maleic acid copolymer (46/50/4)
P19: Methyl methacrylate / benzyl methacrylate / methoxypolyethylene glycol methacrylate (n = 23) / 2-acrylamido-2-methylpropanesulfonic acid copolymer (74/15/5/6)
P20: benzyl methacrylate / ethoxytriethylene glycol methacrylate / mono 2-methacryloyloxyethyl phosphate phosphate copolymer (65/30/5)
P21: Methyl methacrylate / butyl acrylate / 2-carboxyethyl acrylate copolymer (75/19/6)
P22: Phenoxyethyl acrylate / benzyl methacrylate / isobutyl methacrylate / sodium styrene sulfonate copolymer (30/35/29/6)
P23: Styrene / ethyl methacrylate / mono-methacryloyloxyethyl phosphate copolymer (30/60/10)

  A specific polymer contains the structural unit represented by General formula (2) in the range from which an acid value will be 6 mgKOH / g or more and 100 mgKOH / g or less. Content of the structural unit represented by General formula (2) in a specific polymer is 2 mass% or more and 50 mass% or less, for example, and 3 mass% or more and 30 mass% or less are preferable.

  Content of the structural unit derived from the alkyl (meth) acrylate in a specific polymer is 15 to 80 mass%, for example, and 30 to 70 mass% is preferable.

The molecular weight range of the specific polymer is preferably 3000 or more and 200,000 or less, more preferably 5000 or more and 150,000 or less, and still more preferably 10,000 or more and 100,000 or less as a weight average molecular weight. When the weight average molecular weight is 3000 or more, the content ratio of the water-soluble component described later is reduced, which is suitable for the dispersion of the compound represented by the general formula (1). On the other hand, when the weight average molecular weight is 200,000 or less, the solubility of the polymer solution dissolved in the organic solvent is excellent and the viscosity of the polymer solution dissolved in the organic solvent can be suppressed. The dispersion of the infrared absorbing particles is thus excellent.
The weight average molecular weight of the polymer is measured by gel permeation chromatography (GPC) and calculated in terms of polystyrene.

  The glass transition temperature of the specific polymer is preferably 40 ° C or higher and 150 ° C or lower. When the glass transition temperature is 40 ° C. or higher, the image formed using the ink containing the specific polymer is excellent in scratch resistance and blocking resistance, and when the glass transition temperature is 150 ° C. or lower, the ink containing the specific polymer is used. Excellent in abrasion resistance of the image formed by using. In this respect, the glass transition temperature of the specific polymer is more preferably 60 ° C. or higher and 140 ° C. or lower, and further preferably 70 ° C. or higher and 130 ° C. or lower.

When the specific polymer is a polymer dispersion, the ratio of the water-soluble component to the solid content contained in the dispersion is preferably 10% by mass or less.
Usually, the individual molecules constituting the polymer aggregate have variations in the composition of the constituent units, and therefore the individual molecules have variations in water solubility. A polymer molecule having a relatively high solubility in water corresponds to the “water-soluble component” referred to herein. A water-soluble component, that is, a polymer molecule having a relatively high solubility in water is not suitable for the dispersion of the compound represented by the general formula (1). Therefore, when a specific polymer is used as a polymer dispersion, The smaller the water-soluble component contained, the better. Further, from the viewpoint of suppressing the swelling of particles containing the specific polymer and adhesion between the particles, and maintaining stable dispersion, the specific polymer is a water-soluble component contained in the dispersion when used as a polymer dispersion. The smaller the number, the better. From these viewpoints, when the specific polymer is used as a dispersion, the ratio of the water-soluble component to the solid content contained in the dispersion is preferably 10% by mass or less, more preferably 8% by mass or less, and 5% by mass or less. Is more preferable, and the smaller is more preferable.

The ratio of the water-soluble component is measured by the following method.
A polymer dispersion in which a polymer is dispersed in water (solid content concentration: 10% by mass, liquid temperature: 23 ± 0.5 ° C.) is prepared. At that time, a neutralizing agent is used as needed for dispersing the polymer. The polymer dispersion is centrifuged into a dispersoid and a medium using a centrifugal ultrafiltration filter unit, the separated medium is dried, the mass of the dried product is measured, and the solid content of the polymer dispersion (= The ratio of the amount of dry solids of the medium to the amount of polymer used in the preparation of the polymer dispersion + the weight of the neutralizing agent used in the process of preparing the polymer dispersion) is calculated and used as the ratio (mass%) of the water-soluble component.

[Aqueous medium]
The medium of the infrared-absorbing particle dispersion is water or a mixed solvent containing water as a main solvent. The mixed solvent is, for example, a mixture of water and a water-soluble organic solvent.

  The water is preferably purified water such as distilled water, ion-exchanged water, or ultrafiltered water from the viewpoint of suppressing contamination with impurities or generation of microorganisms.

  Examples of the water-soluble organic solvent include alcohols, polyhydric alcohols, polyhydric alcohol derivatives, nitrogen-containing solvents, and sulfur-containing solvents. The water-soluble organic solvent contained in the infrared absorbing particle dispersion is, for example, the residue of the organic solvent used for dissolving the compound represented by the general formula (1) or the specific polymer in the production process of the infrared absorbing particle dispersion. It is.

The content of water is preferably 50% by mass or more and 95% by mass or less, and more preferably 60% by mass or more and 90% by mass or less with respect to the total mass of the infrared absorbing particle dispersion.
The content of the water-soluble organic solvent is preferably 30% by mass or less and more preferably 10% by mass or less with respect to the total mass of the infrared-absorbing particle dispersion.

[Other ingredients]
The infrared-absorbing particle dispersion according to this embodiment is a compound having infrared absorbing ability other than the compound represented by the general formula (1) (for example, squarylium dye, croconium dye, naphthalocyanine dye, cyanine dye) , Aminium-based dyes, etc.), UV-absorbing compounds (for example, benzotriazole compounds, benzophenone compounds, etc.), colorants, neutralizers, surfactants, dispersion stabilizers, polymers other than specific polymers, etc. You may go out.

[Method for producing infrared-absorbing particle dispersion]
Examples of the method for producing the infrared-absorbing particle dispersion include a phase inversion emulsification method and an impregnation method in which a specific polymer particle is impregnated with a compound having infrared absorbing ability, and the phase inversion emulsification method is preferable.

  In the phase inversion emulsification method, a solution in which a compound having infrared absorbing ability and a specific polymer are dissolved in an organic solvent is prepared, a neutralizing agent is added to the solution to neutralize the specific polymer, and then water is gradually mixed. This is a method in which a compound having an infrared absorbing ability and a specific polymer are made into particles containing both to form 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, a suspension in which solid particles are dispersed is preferable. The organic solvent is removed from the viewpoint of dispersion stability of the infrared absorbing particles when the solubility of the organic solvent in water is 10% by mass or less, or when the vapor pressure of the organic solvent is higher than water. It is preferable. Neutralization is not an essential step, but when the specific polymer has an unneutralized dissociable group, it is preferably performed from the viewpoint of pH adjustment of the dispersion.

  The impregnation method involves preparing a particle dispersion of a specific polymer, mixing the particle dispersion and a solution in which a compound having infrared absorbing ability is dissolved in an organic solvent, and then gradually removing the organic solvent to remove infrared absorbing ability. This is a method for impregnating particles of a specific polymer into particles of a specific polymer to obtain infrared absorbing particles. The particles of the specific polymer may be liquid particles or solid particles, and solid particles are preferable from the viewpoint of dispersion stability. The particle dispersion of the specific polymer is prepared, for example, by preparing a solution in which the specific polymer 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 compound represented by the general formula (1) and the solubility of the specific polymer. 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 Chlorine solvents; 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. These organic solvents may be used alone or in combination of two or more.

  As the usage-amount of an organic solvent, 10 mass parts or more and 2000 mass parts or less are preferable with respect to 100 mass parts of specific polymers, and 100 mass parts or more and 1000 mass parts or less are more preferable. When the amount of the organic solvent used is 10 parts by mass or more with respect to 100 parts by mass of the specific polymer, the dispersion of the particles is stable, and when the amount of the organic solvent used is 2000 parts by mass or less with respect to 100 parts by mass of the specific polymer, The process of removing the solvent is unnecessary or takes a short time.

Examples of the neutralizing agent used in the phase inversion emulsification method and the impregnation method include organic bases and inorganic alkalis because the specific polymer has an anionic group. Examples of the organic base include triethanolamine, diethanolamine, N-methyldiethanolamine, dimethylethanolamine and the like. Examples of the inorganic alkali include alkali metal hydroxides (for example, sodium hydroxide, lithium hydroxide, potassium hydroxide, etc.), carbonates (for example, sodium carbonate, sodium hydrogencarbonate, etc.), ammonia and the like.
The addition amount of the neutralizing agent is preferably such that the pH of the infrared-absorbing particle dispersion is in the range described later, from the viewpoint of dispersion stability of the infrared-absorbing particles.

  The amount of the specific polymer used in the phase inversion emulsification method and the impregnation method and the content of the specific polymer contained in the infrared absorbing particle dispersion are 100 parts by mass or more and 9900 parts by mass with respect to 100 parts by mass of the compound having infrared absorbing ability. Part or less, preferably 300 parts by weight or more and 4900 parts by weight or less. When the amount of the specific polymer used (content of the specific polymer) is 100 parts by mass or more with respect to 100 parts by mass of the compound having infrared absorbing ability, the dispersion of the compound having infrared absorbing ability becomes stable, and the amount of the specific polymer used ( When the content of the specific polymer is 9900 parts by mass or less with respect to 100 parts by mass of the compound having infrared absorbing ability, the infrared absorbing efficiency of the infrared absorbing particle dispersion is good.

  In the phase inversion emulsification method and impregnation method, an organic compound other than the compound represented by the general formula (1) is also used, and the compound is granulated together with the compound represented by the general formula (1) and the specific polymer. You may form the particle | grains to contain. Examples of the organic compound that forms particles together include, for example, dyes and compounds having infrared absorbing ability other than the compound represented by the general formula (1) (for example, squarylium dyes, croconium dyes, naphthalocyanine dyes, cyanine dyes) , Aminium-based dyes, etc.), and compounds having ultraviolet absorbing ability (for example, benzotriazole-based compounds, benzophenone-based compounds, etc.).

[Physical properties of infrared absorbing particle dispersion]
The volume average particle diameter of the infrared absorbing particles contained in the infrared absorbing particle dispersion is preferably 10 nm to 150 nm, more preferably 10 nm to 120 nm, and still more preferably 10 nm to 100 nm. When the volume average particle diameter is 10 nm or more, the light resistance is excellent, and when the volume average particle diameter is 150 nm or less, the droplet ejection characteristics of the ink jet system are excellent. The particle size distribution may be either a wide particle size distribution or a monodisperse particle size distribution. The average particle size and particle size distribution of the infrared absorbing particles are measured using, for example, a light scattering method.

The pH of the infrared-absorbing particle dispersion according to the present embodiment is 9.5 or less from the viewpoint of suppressing decomposition of the compound represented by the general formula (1) and suppressing deterioration of infrared absorption performance over time. Preferably, it is 9.0 or less, more preferably 8.5 or less, and even more preferably 8.0 or less. On the other hand, from the viewpoint of stably dispersing the specific polymer and the infrared absorbing particles, the pH of the infrared absorbing particle dispersion according to the present embodiment is preferably 6.0 or more, more preferably 6.5 or more, and 7 0.0 or more is more preferable.
Moreover, since a general water-based ink is alkaline (pH of about 8 to 10), the infrared absorptivity according to this embodiment is also used from the viewpoint of preparing a water-based ink using the infrared-absorbing particle dispersion according to this embodiment. The pH of the particle dispersion is preferably in the above range.
In this embodiment, the pH of the infrared-absorbing particle dispersion is measured under an environment of a temperature of 23 ± 0.5 ° C. and a relative humidity of 55 ± 5%.

  The surface tension of the infrared-absorbing particle dispersion according to this embodiment is preferably 20 mN / m or more and 40 mN / m or less, and more preferably 25 mN / m or more and 35 mN / m or less. In this embodiment, the surface tension of the infrared-absorbing particle dispersion is measured using a Wilhelmy surface tension meter in an environment of a temperature of 23 ± 0.5 ° C. and a relative humidity of 55 ± 5%.

The viscosity of the infrared-absorbing particle dispersion according to this embodiment is preferably 1 mPa · s to 30 mPa · s, and more preferably 2 mPa · s to 20 mPa · s. In this embodiment, the viscosity of the infrared-absorbing particle dispersion is measured under the conditions of a temperature of 23 ± 0.5 ° C. and a shear rate of 1400 s ⁻¹ using a TV-20 viscometer (Toki Sangyo) as a measuring device.

<Water-based ink>
The water-based ink according to the present embodiment is a water-based ink containing an aqueous medium and infrared-absorbing particles dispersed in the aqueous medium, and the infrared-absorbing particles include a compound represented by the general formula (1), A polymer having a structural unit represented by the formula (2) and a structural unit derived from an alkyl (meth) acrylate and having an acid value of 6 mgKOH / g or more and 100 mgKOH / g or less.

  The details of the compound represented by the general formula (1), the specific polymer, and the infrared absorbing particles in the aqueous ink according to the present embodiment are as described for the infrared absorbing particle dispersion according to the present embodiment.

  The water-based ink according to this embodiment includes, for example, the infrared-absorbing particle dispersion itself according to this embodiment; a composition obtained by adding at least a colorant to the infrared-absorbing particle dispersion according to this embodiment; And a composition to which the infrared-absorbing particle dispersion according to the present embodiment is added.

[Aqueous medium]
The aqueous ink medium is water or a mixed solvent containing water as a main solvent. The mixed solvent is, for example, a mixture of water and a water-soluble organic solvent. Examples of the water-soluble organic solvent include alcohols, polyhydric alcohols, polyhydric alcohol derivatives, nitrogen-containing solvents, and sulfur-containing solvents. Details of water and the water-soluble organic solvent in the water-based ink are the same as those described for the infrared-absorbing particle dispersion.

The content of water is preferably 40% by mass or more and 80% by mass or less, and more preferably 50% by mass or more and 80% by mass or less with respect to the total mass of the water-based ink.
The content of the water-soluble organic solvent is preferably 50% by mass or less and more preferably 40% by mass or less with respect to the total mass of the water-based ink.

[Colorant]
Examples of the colorant include pigments and dyes, and pigments are preferable from the viewpoint of light resistance of an image.

  When a pigment is used as the colorant, it is preferable to use a pigment dispersant together. Examples of the pigment dispersant include all known polymer dispersants and surfactants. One type of pigment dispersant may be used, or two or more types may be used in combination. Although the content of the pigment dispersant varies depending on the type of pigment and the type of pigment dispersant, it cannot be generally stated, but it is preferably 0.1% by mass to 100% by mass with respect to the pigment content.

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

  Examples of the pigment include so-called microcapsule pigments 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, white, etc .; metallic luster pigments such as gold and silver; colorless or light extender pigments; plastic pigments; dyes or pigments on the surface of silica, alumina, or polymer beads Insoluble raked dyes; colored emulsions; colored latexes; and the like.

  When a dye is used as the colorant, it is preferable that the dye is made into particles together with a polymer dispersant (for example, the specific polymer of the present disclosure), and the particles are included 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 1% by mass or more and 25% by mass or less, and more preferably 2% by mass or more and 20% by mass or less with respect to the total mass of the water-based ink.

[Additive]
The water-based ink according to this embodiment may contain various additives as necessary. Examples of the additive include a polymer, a surfactant, a penetrating agent, a viscosity adjusting agent, a pH adjusting agent, a pH buffering agent, an antioxidant, an ultraviolet absorber, an antiseptic, and an antifungal agent. The water-based ink according to this embodiment may contain a compound having infrared absorbing ability other than the compound represented by the general formula (1).

[Physical properties of water-based ink]
The volume average particle diameter of the infrared absorbing particles contained in the aqueous ink is preferably 10 nm or more and 150 nm or less, more preferably 10 nm or more and 120 nm or less, and further preferably 10 nm or more and 100 nm or less. When the volume average particle diameter is 10 nm or more, the light resistance is excellent, and when the volume average particle diameter is 150 nm or less, the droplet ejection characteristics of the ink jet system are excellent. The particle size distribution may be either a wide particle size distribution or a monodisperse particle size distribution. The average particle size and particle size distribution of the infrared absorbing particles are measured using, for example, a light scattering method.

  The pH of the water-based ink according to this embodiment 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. In this embodiment, the pH of the water-based ink is measured under an environment of a temperature of 23 ± 0.5 ° C. and a relative humidity of 55 ± 5%.

  The surface tension of the water-based ink according to this embodiment is preferably 20 mN / m or more and 40 mN / m or less, and more preferably 25 mN / m or more and 35 mN / m or less. In this embodiment, the surface tension of the water-based ink is measured using a Wilhelmy surface tension meter in an environment of a temperature of 23 ± 0.5 ° C. and a relative humidity of 55 ± 5%.

The viscosity of the water-based ink according to the present embodiment is preferably 1 mPa · s to 30 mPa · s, and more preferably 2 mPa · s to 20 mPa · s. In this embodiment, the viscosity of the water-based ink is measured under the conditions of a temperature of 23 ± 0.5 ° C. and a shear rate of 1400 s ⁻¹ using a TV-20 viscometer (Toki Sangyo) as a measuring device.

<Ink cartridge>
The ink cartridge according to the present embodiment is a cartridge that contains the water-based ink according to the present embodiment. The ink cartridge according to the present embodiment is provided in a form that can be attached to and detached from, for example, an ink jet recording apparatus.

<Recording apparatus and recording method>
The recording apparatus according to the present embodiment contains the water-based ink according to the present embodiment, an ink applying unit that applies the water-based ink to the recording medium, and an infrared irradiation unit that irradiates the water-based ink applied to the recording medium with infrared rays. With. The recording apparatus according to the present embodiment realizes a recording method including an ink application process for applying the water-based ink according to the present embodiment to a recording medium, and an infrared irradiation process for irradiating the water-based 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 rolls, sprays, sponges, and the like; a printing unit using offset printing, screen printing, gravure printing, letterpress printing, and the like. It is done.

  The ink application unit in the present embodiment is preferably an ejection unit that ejects ink by an inkjet method. A recording apparatus and a recording method to which the ink jet system is applied are excellent in ejection stability by using the water-based ink according to the present embodiment.

  The recording apparatus according to the present embodiment includes an infrared irradiation unit as a drying unit that dries the aqueous ink applied to the recording medium. In the recording apparatus according to the present embodiment, as the drying unit, in addition to the infrared irradiation unit, a contact heating unit such as a heating roll, a heating drum, and a heating belt; a hot air blowing unit including a heating element and a blower; a combination thereof 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 accommodates the water-based ink according to the present embodiment and is made into a cartridge so as to be attached to and detached 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. A recording apparatus 12 shown in FIG. 1 is an ink jet recording apparatus.

  A recording apparatus 12 shown in FIG. 1 includes a container 16 that accommodates a recording medium P before image recording, an endless conveyance belt 28 that is stretched around a driving roll 24 and a driven roll 26, and a housing 14. Ink ejection heads (ink ejection heads 30Y, 30M, 30C, 30K, collectively referred to as ink ejection heads 30), which are examples of ink application means, and infrared irradiation devices (infrared irradiation devices 60Y, 60M, 60C, 60K). And collectively referred to as an infrared irradiation device 60) and a container 40 for storing 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 taking out the recording medium P one by one from the container 16, and a recording. A plurality of roll pairs 20 that convey the medium P are arranged. A charging roll 32 is disposed on the upstream side of the conveyance belt 28. The charging roll 32 is driven while sandwiching the conveyance belt 28 and the recording medium P with the driven roll 26, generates a potential difference with the grounded driven roll 26, and applies an electric charge to the recording medium P to convey the conveyance belt. 28 is electrostatically adsorbed.

  The ink discharge head 30 is disposed above the conveyance belt 28 so as to face the flat portion of the conveyance belt 28. A region where the ink discharge head 30 and the conveyance belt 28 face each other is a region where ink droplets are discharged from the ink discharge head 30.

  Ink discharge heads 30Y, 30M, 30C, and 30K are respectively a head that records a Y (yellow) color image, a head that records an M (magenta) color image, a head that records a C (cyan) color image, and K This is a head for recording a (black) color image. The ink discharge heads 30Y, 30M, 30C, and 30K are arranged from the upstream side to the downstream side of the conveyance belt 28 in this order, for example. The ink ejection heads 30Y, 30M, 30C, and 30K are connected to the ink cartridges 31Y, 31M, 31C, and 31K of each color that are attached to and detached from the recording apparatus 12 through supply tubes (not shown), and the inks of the respective colors are supplied from the ink cartridge. Supplied to the discharge head.

  As the ink discharge head 30, for example, an effective recording area (arrangement area of nozzles that discharge ink) is longer than the width of the recording medium P (the length in the direction orthogonal to the conveyance direction of the recording medium P). And a carriage head that is shorter than the width of the recording medium P and moves in the width direction of the recording medium P to eject ink.

  As the ink jet system employed by the ink ejection head 30, a piezoelectric system that utilizes the vibration pressure of the piezoelectric element; a charge control system that ejects ink using electrostatic attraction; an electrical signal is converted into an acoustic beam and the ink is irradiated And an acoustic ink jet method in which ink is ejected using radiation pressure; a thermal ink jet method in which bubbles are formed by heating the ink and the generated pressure is used; and the like.

  The ink discharge head 30 is, for example, a low-resolution recording head (for example, a 600 dpi recording head) that discharges ink droplets in a range of 10 pL to 15 pL, and discharges ink droplets in a range of less than 10 pL. This is a recording head for high resolution (for example, a recording head of 1200 dpi). dpi means “dots per inch”.

  The recording apparatus 12 is not limited to a form including four ink ejection heads. The recording apparatus 12 may have a form including four or more ink discharge heads obtained by adding intermediate colors to YMCK; a form including one ink discharge head and recording an image of only one color.

  Infrared irradiation means 60Y, 60M, 60C, and 60K are disposed on the downstream side of the ink discharge head 30 above the transport belt 28 for each color ink discharge head. The infrared irradiation device 60 (an example of infrared irradiation means) irradiates the ink on the recording medium P with infrared rays 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 irradiation device 60, for example, a long infrared irradiation device in which an effective infrared irradiation region (arrangement region of a light source for irradiating infrared rays) is equal to or larger than the width of the recording region by the ink discharge head 30; And a carriage-type infrared irradiation device that moves in the width direction of the recording medium P and irradiates infrared rays.

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 condition, the irradiation condition for drying the water content in the ink applied on the recording medium P to 10% by mass or less is 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 The irradiation time is from 0.1 milliseconds to 10 seconds (preferably from 10 milliseconds to 100 milliseconds).

  The recording device 12 is not limited to a mode including an infrared irradiation device for each color ink discharge head, and may be a mode including only one infrared irradiation device on the downstream side of the most downstream ink discharge head.

  The recording device 12 may include at least one of a contact-type heating unit and a hot-air blowing unit as an ink drying unit together with the infrared irradiation device 60. The contact-type heating means or hot air blowing means performs drying under conditions that raise the surface temperature of the recording medium to a range of 50 ° C. or higher and 120 ° C. or lower, for example.

  A peeling plate 34 is disposed on the downstream side of the infrared irradiation device 60 so as to face the drive roll 24. The peeling plate 34 peels the recording medium P from the conveyance belt 28.

  Between the conveyance belt 28 and the container 40 is a conveyance path 36 through which the recording medium P after image recording is conveyed, and a plurality of pairs of rolls 38 that convey the recording medium P are arranged in the conveyance path 36. .

The operation of the recording device 12 will be described.
The recording medium P before image recording is taken out one by one from the container 16 by the roll 18 and is conveyed to the conveying belt 28 by the plural roll pairs 20.
Next, the recording medium P is electrostatically attracted to the conveyance belt 28 by the charging roll 32, and is conveyed below the ink discharge head 30 by the rotation of the conveyance 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 by absorbing infrared rays, the ink temperature rises, and the ink is dried.
Next, the recording medium P on which the ink is dried and the image is fixed is peeled off from the transport belt 28 by the peeling plate 34 and is transported to the container 40 by a plurality of roll pairs 38.

  The recording apparatus according to the present embodiment is not limited to a mode in which ink is directly applied to the recording medium from the ink applying unit, and after the ink is applied from the ink applying unit to the intermediate transfer member, the ink on the intermediate transfer member is applied to the recording medium. A form to be transferred may be used.

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

  Hereinafter, embodiments of the present invention will be described in detail by way of examples, but the 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 of Compound Represented by General Formula (1)>
[Synthesis of Compound (Ia-1)]
Compound (Ia-1) was synthesized according to the following reaction scheme.

  A Dean-Stark trap, a reflux condenser, a stirring seal, and a stirring rod were installed in a three-necked flask to prepare a reaction vessel. 2,2,8,8-Tetramethyl-3,6-nonadiin-5-ol and cyclohexane were placed in a reaction vessel. 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 2,2,8,8-tetramethyl-3,6-nonadiin-5-ol remaining. The reaction mixture was allowed to cool and then filtered under reduced pressure to obtain a yellow filtrate (F1). The filtered solid was transferred to another container, ethyl acetate was added, and the operation of ultrasonically dispersing and filtering was repeated 4 times to obtain an ethyl acetate extract (F2). The ethyl acetate extract (F2) and the filtrate (F1) were mixed and concentrated with 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 installed in a three-necked flask to prepare a reaction vessel. Sodium hydrogen monosulfide n hydrate was added to ethanol and stirred at room temperature (20 ° C.) until dissolved, followed by cooling with ice water. When the internal temperature reached 5 ° C., a mixture of intermediate 1 and ethanol was added dropwise little by little. The liquid changed from yellow to orange by the dropwise addition. Since the internal temperature increased due to heat generation, the internal temperature was dropped within the range of 5 ° C. or higher and 7 ° C. or lower while adjusting the dropping amount. Thereafter, the ice water bath was removed, and the mixture was stirred while allowing the temperature to rise naturally at room temperature (20 ° C.). Water was added to the reaction solution, and ethanol was removed by a rotary evaporator. Thereafter, sodium chloride was added until saturation, and the mixture was separated with ethyl acetate to recover the organic phase. The organic phase was washed twice with saturated ammonium chloride and dried over magnesium sulfate. After drying, the solution was concentrated under reduced pressure to recover a brown liquid. The brown liquid was distilled under reduced pressure. A distillate begins to come out at 200 ° C., but since the purity of the target component is low in the initial distillate, the main distillate was selected when the amount of steam increased. A yellow liquid (Intermediate 2) was distilled.

  A stir bar and intermediate 2 were placed in a three-necked flask, and a nitrogen inlet tube and a reflux condenser were attached to replace the nitrogen. Under a nitrogen atmosphere, anhydrous tetrahydrofuran was added with a syringe, and a 1M tetrahydrofuran solution of methylmagnesium bromide 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. The reaction solution was allowed to cool under a nitrogen atmosphere, and then a solution of ammonium bromide dissolved in water was added dropwise while cooling in an ice-water bath. The reaction mixture was further stirred at room temperature (20 ° C.), n-hexane was added, and the mixture was 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 then vacuum dried to obtain Intermediate 3.

  Under a nitrogen atmosphere, Intermediate 3 and squaric acid were dispersed in a mixed solvent of cyclohexane and isobutanol, and pyridine was added and heated to reflux. Then isobutanol was added and the reaction mixture was further heated to reflux. Water generated during the reaction was removed by azeotropic distillation. The reaction mixture was allowed to cool and then 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 this was vacuum-dried to obtain compound (I-a-1).

[Synthesis of Compound (Ia-2)]
In the synthesis of compound (Ia-1), 2,2,10,10-tetramethyl-4,7- instead of 2,2,8,8-tetramethyl-3,6-nonadiin-5-ol Compound (Ia-2) was synthesized in the same procedure except that undecadiin-6-ol was used.

[Synthesis of Compound (Ia-5)]
In the synthesis of compound (Ia-1), 2,10-dimethyl-4,7-undecadiin-6-ol instead of 2,2,8,8-tetramethyl-3,6-nonadiin-5-ol Compound (Ia-5) was synthesized in the same procedure except that was used.

<Polymer synthesis>
[Synthesis of Polymer P12]
A three-necked flask equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen gas inlet tube was charged with 25 parts of methyl ethyl ketone and heated to 80 ° C. While maintaining the temperature in the reaction vessel at 80 ° C., 30 parts of styrene (manufactured by Wako Pure Chemical Industries), 60 parts of ethyl methacrylate (manufactured by Wako Pure Chemical Industries), 2-carboxyethyl acrylate (manufactured by Solvay Nikka, SIPomer β-CEA) A mixed solution consisting of 10 parts, 70 parts of methyl ethyl ketone, and 2 parts of a polymerization initiator (Wako Pure Chemical Industries, V-601, the same applies hereinafter) was added dropwise over 2 hours. After completion of the dropwise addition, a solution consisting of 0.4 part of a polymerization initiator and 10 parts of methyl ethyl ketone was added and stirred at 80 ° C. for 2 hours. Further, a solution consisting of 0.4 part of a polymerization initiator and 10 parts of methyl ethyl ketone was added, and 80 ° C. The mixture was stirred for 2 hours, then heated to 85 ° C. and stirred for 2 hours. Thus, a polymer P12 solution in which the polymer P12 was dissolved in methyl ethyl ketone was obtained. The weight average molecular weight (Mw) of the polymer P12 was 34000 (calculated in terms of polystyrene by GPC), the acid value was 34 mgKOH / g, and the solid content concentration of the polymer P12 solution was 48% by mass.

[Synthesis of Polymers P12-1 to 7, P04, and P21]
Each polymer solution was obtained in the same manner as the synthesis of polymer P12 except that the type and amount of the monomer were changed according to Table 1.

[Synthesis of Polymer P15]
10 parts of ethanol was charged into a three-necked flask equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen gas introduction tube, and the temperature was raised to 80 ° C. While maintaining the temperature in the reaction vessel at 80 ° C., 4 parts 2-acrylamido-2-methylpropanesulfonic acid (Wako Pure Chemical Industries), 56 parts methyl methacrylate (Wako Pure Chemical Industries), n-butyl methacrylate (Wako Pure) A mixed solution consisting of 40 parts of Yakuhin Kogyo Co., 60 parts of ethanol, 6 parts of water, and 1 part of a polymerization initiator (manufactured by Wako Pure Chemical Industries, V-601; the same applies hereinafter) was added dropwise over 2 hours. After completion of the dropwise addition, a solution consisting of 0.2 parts of a polymerization initiator and 10 parts of methyl ethyl ketone was added and stirred at 80 ° C. for 2 hours. Further, a solution consisting of 0.2 parts of a polymerization initiator and 10 parts of methyl ethyl ketone was added, and 80 ° C. The mixture was stirred for 2 hours, then heated to 85 ° C. and stirred for 2 hours. Thus, a polymer P15 solution in which the polymer P15 was dissolved in the organic solvent was obtained. The weight average molecular weight (Mw) of the polymer P15 was 25000 (calculated in terms of polystyrene by GPC), the acid value was 11 mgKOH / g, and the solid content concentration of the polymer P15 solution was 48% by mass.

[Synthesis of Polymers P15-1 and P2, P05, and P23]
Each polymer solution was obtained in the same manner as the synthesis of polymer P15 except that the type and amount of the monomer were changed according to Table 1.

<Example 1: Production of infrared absorbing particle dispersion>
[Production of Infrared Absorbing Particle Dispersion AD-1]
20 parts of the squarylium compound which is the compound (Ia-1) was put in a flask. Thereto, 3600 parts of tetrahydrofuran was added, and a stir bar was added and stirred. Subsequently, 800 parts of polymer P12-1 solution (solid content concentration 48% by mass) was added, and further 800 parts of methyl ethyl ketone and 80 parts of isopropyl alcohol were added and stirred and mixed. Next, a 10% by mass aqueous solution of sodium hydroxide was added with stirring, 0.8 equivalent of all carboxy groups contained in the polymer P12-1. Next, 10000 parts of water was gradually added while stirring, and water was mixed. After the mixture becomes nearly uniform, a distillation tube and a vacuum pump are attached to the flask, and the mixture is heated to 30 ° C to 35 ° C and depressurized while stirring. Part was distilled off. The operation of concentrating while replacing the organic solvent with water was repeated until the odor of the organic solvent disappeared while adjusting the amount of water added so that the solid content concentration calculated from the material did not exceed 7% by mass. The concentrated solution was filtered through a 230 mesh nylon mesh to obtain an infrared absorbing particle dispersion. About this infrared absorptive particle dispersion liquid, the amount of solid content was measured by the method as described in "(1) Yield" mentioned later, and the yield was calculated | required. Based on the measured solid content, water was added to the infrared-absorbing particle dispersion to adjust the solid content concentration to 5% by mass to obtain an infrared-absorbing particle dispersion AD-1. When converted from the amount of the compound (Ia-1) used for the production of the infrared absorbing particle dispersion and the amount of the polymer, the concentration of the compound (Ia-1) in the infrared absorbing particle dispersion AD-1 is 0. .25% by mass.

[Production of Infrared Absorbing Particle Dispersions AD-2 to 15, 20, and 21]
Infrared absorbing particle dispersion AD, except that the type of polymer and the degree of neutralization (addition amount (equivalent) of sodium hydroxide to all acidic groups contained in the polymer) and the compound having infrared absorbing ability were changed according to Table 1. In the same manner as in the production of -1, each infrared absorbing particle dispersion was obtained. “Ia-2” in Table 1 is the compound (Ia-2), “Ia-5” is the compound (Ia-5), and “II” is the following structural formula. Compound (II) represented.

[Production of Infrared Absorbing Particle Dispersion AD-16]
20 parts of the squarylium compound which is the compound (Ia-1) was put in a flask. Thereto, 3600 parts of tetrahydrofuran was added, and a stir bar was added and stirred. Next, 800 parts of a polymer P05 solution (solid content concentration: 48% by mass) was added, and 2700 parts of tetrahydrofuran was further added, followed by stirring and mixing. Next, 10000 parts of water was gradually added while stirring, and water was mixed. After the mixture becomes nearly uniform, a distillation tube and a vacuum pump are attached to the flask, and the mixture is heated to 30 ° C to 35 ° C and depressurized while stirring. Part was distilled off. The operation of concentrating while replacing the organic solvent with water was repeated until the odor of the organic solvent disappeared while adjusting the amount of water added so that the solid content concentration calculated from the material did not exceed 7% by mass. The concentrated solution was filtered through a 230 mesh nylon mesh to obtain an infrared absorbing particle dispersion. About this infrared absorptive particle dispersion liquid, the amount of solid content was measured by the method as described in "(1) Yield" mentioned later, and the yield was calculated | required. Based on the measured solid content, water was added to the infrared-absorbing particle dispersion to adjust the solid content concentration to 5% by mass to obtain an infrared-absorbing particle dispersion AD-16. When converted from the amount of the compound (Ia-1) and the amount of polymer used for the production of the infrared absorbing particle dispersion, the concentration of the compound (Ia-1) in the infrared absorbing particle dispersion AD-16 is 0. .25% by mass.

[Production of Infrared Absorbing Particle Dispersion Liquid AD-17-19]
Except having changed the kind of polymer according to Table 1, it carried out similarly to manufacture of infrared absorbing particle dispersion liquid AD-16, and obtained each infrared absorbing particle dispersion liquid.

[Evaluation]
(1) Yield A part of the infrared-absorbing particle dispersion is heated and dried at 120 ° C. for 2 hours under atmospheric pressure, the solid content (mass) is measured, and the yield is obtained according to the following formula. Classified.
Formula: solid content of infrared-absorbing particle dispersion ÷ (amount of compound having infrared absorbing ability used for production of infrared-absorbing particle dispersion + solid content of polymer solution used for production of infrared-absorbing particle dispersion + 100 mass of sodium hydroxide used for neutralization in the manufacturing process of the infrared absorbing particle dispersion) × 100

G1: The yield is 90% or more.
G2: Yield 80% or more and less than 90%.
G3: The yield is 70% or more and less than 80%.
G4: Yield less than 70%.

(2) Particle size Volume-based median of particles dispersed in an infrared-absorbing particle dispersion (solid content concentration 5 mass%) using a dynamic light scattering particle size distribution analyzer LB-500 (Horiba Seisakusho) The diameter (nm) was measured.

(3) Decreasing rate of infrared absorption amount The infrared absorbing particle dispersion (solid content concentration 5 mass%) was diluted 5 times and stored at a temperature of 60 ° C. for 14 days. For each infrared absorbing particle dispersion before and after storage, the amount of absorption at a wavelength of 818 nm was measured using a spectrophotometer (Hitachi, U-4100), and the rate of decrease in the amount of infrared absorption was calculated according to the following formula: The classification was as follows.
Formula: Reduction rate of infrared absorption (%) = ((infrared absorption before storage−infrared absorption after storage) ÷ infrared absorption before storage) × 100

G1: Reduction rate is less than 10%.
G2: Decrease rate of 10% or more and less than 30%.
G3: The reduction rate is 30% or more and less than 50%.
G4: The reduction rate is 50% or more.

The meanings of the abbreviations in Table 1 are as follows.
St: styrene, MMA: methyl methacrylate, EMA: ethyl methacrylate, BMA: n-butyl methacrylate, BA: n-butyl acrylate, CEA: Shipomer β-CEA (2-carboxyethyl acrylate), AMPS: 2-acrylamide-2- Methylpropanesulfonic acid, NaSS: sodium styrenesulfonate, MOEP: mono 2-methacryloyloxyethyl phosphate

<Example 2: Production of infrared absorbing ink (light fixing ink)>
[Preparation of Cyan Pigment Dispersion Liquid CD1]
In a reaction vessel, 6 parts of styrene, 11 parts of stearyl methacrylate, 4 parts of styrene macromer AS-6 (Toagosei), 5 parts of Blenmer PP-500 (Nippon Oil), 5 parts of methacrylic acid, 0.05 part of 2-mercaptoethanol 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 Bremer PP-500 (NOF), 10 parts of methacrylic acid, 0.13 part of 2-mercaptoethanol, 56 of methyl ethyl ketone And a mixed solution consisting of 1.2 parts of 2,2′-azobis (2,4-dimethylvaleronitrile) was prepared and placed in a dropping funnel.
While stirring the mixed solution in the reaction vessel under a nitrogen atmosphere, the temperature was raised to 75 ° C., and the mixed solution in the dropping funnel was dropped over 1 hour. 2 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. Further, the mixture was aged at 80 ° C. for 2 hours to obtain a polymer solution.
5 parts of polymer solution obtained (in terms of solid content), 10 parts of Pigment Blue 15: 3 (Daiichi Seika Kogyo), 40 parts of methyl ethyl ketone, 8 parts of 1 mol / L aqueous sodium hydroxide solution and 82 parts of ion-exchanged water 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 to a pigment concentration of 10% by mass. Thus, a cyan pigment dispersion liquid CD1 in which the cyan pigment whose surface was coated with the polymer dispersant was dispersed was obtained. The volume average particle size of the cyan pigment dispersion liquid CD1 was 77 nm.

[Production of Cyan Ink C-1]
After the following materials were mixed, coarse particles were removed with a 5 μm filter to obtain cyan ink C-1. As the infrared-absorbing particle dispersion AD-1, a dispersion immediately after production was used. The pH of cyan ink C-1 was 8.8.

-Cyan pigment dispersion CD1 6% by mass (solid content conversion)
Infrared absorbing particle dispersion AD-1 1% by mass (solid content conversion)
・ Diethylene glycol 5% by mass
・ Propanediol 25% by mass
・ Orphine E1010 (Nisshin Chemical Industry) 1.2% by mass
・ Ion-exchanged water Remaining amount of 100% by mass

[Production of Cyan Inks C-2 to 17]
Except for changing the infrared absorbing particle dispersion AD-1 to any one of the infrared absorbing particle dispersions AD-2 to 5, 7, 9 to 13, 15 to 18, 20, and 21, the cyan ink C- In the same manner as in No. 1, cyan inks C-2 to C-17 were obtained. As the infrared absorbing particle dispersion, a dispersion immediately after production was used.

[Print test]
Cyan ink C-1 to 17 immediately after manufacture were refilled into a cartridge of an Epson inkjet printer PX-1004, and printed on Tokishi Art Double Side N (Mitsubishi Paper) with an inkjet printer PX-1004. In all of -17, there was no ejection failure and good printing could be performed. When infrared irradiation was performed on the image under the conditions of a center wavelength of 810 nm, an irradiation intensity of 3 J / cm ² , and an irradiation time of 200 milliseconds, images with no blur were obtained in all of the cyan inks C-1 to C-17. .

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 ejection 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 Container 60Y, 60M, 60C, 60K Infrared irradiation device (an example of infrared irradiation means)
P Recording medium

Claims (10)

An aqueous medium;
Infrared absorbing particles dispersed in the aqueous medium, comprising a compound represented by the following general formula (1), a structural unit represented by the following general formula (2) and a structural unit derived from an alkyl (meth) acrylate Infrared absorbing particles containing a polymer having an acid value of from 6 mgKOH / g to 100 mgKOH / g,
Infrared absorbing particle dispersion liquid.

In General Formula (1), R ^a represents a group represented by General Formula (1-R), and R ^b , R ^c, and R ^d each independently represents an alkyl group. In General Formula (1-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 (2), R ¹ represents hydrogen, a methyl group or —X—R ² —A ¹ , R ³ represents hydrogen or —X—R ² —A ¹ , X represents a single bond, —CO— , —C (═O) O—, —CONH—, —OC (═O) — or a phenylene group, R ² represents a single bond or a divalent linking group, and A ¹ represents —COOH, —SO _3. It represents H or -OPO ₃ H _2. When two or more —X—R ² —A ¹ are present in a single structural unit, X, R ² and A ¹ may be the same as or different from each other.   The structural unit represented by the general formula (2) is a structural unit derived from 2-carboxyethyl (meth) acrylate, a structural unit derived from styrenesulfonic acid, 2- (meth) acrylamide-2-methylpropanesulfonic acid The infrared-absorbing particle dispersion liquid according to claim 1, which is at least one of a structural unit derived from the above and a structural unit derived from mono 2- (meth) acryloyloxyethyl phosphate.   The infrared-absorbing particle dispersion according to claim 1 or 2, wherein the pH is 6.0 or more and 9.5 or less.   The infrared-absorbing particle dispersion according to any one of claims 1 to 3, wherein the polymer contains a benzene ring in a range of 3% by mass to 50% by mass with respect to the total mass. An aqueous medium;
Infrared absorbing particles dispersed in the aqueous medium, comprising a compound represented by the following general formula (1), a structural unit represented by the following general formula (2) and a structural unit derived from an alkyl (meth) acrylate Infrared absorbing particles containing a polymer having an acid value of from 6 mgKOH / g to 100 mgKOH / g,
Water-based ink containing.

In General Formula (1), R ^a represents a group represented by General Formula (1-R), and R ^b , R ^c, and R ^d each independently represents an alkyl group. In General Formula (1-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 (2), R ¹ represents hydrogen, a methyl group or —X—R ² —A ¹ , R ³ represents hydrogen or —X—R ² —A ¹ , X represents a single bond, —CO— , —C (═O) O—, —CONH—, —OC (═O) — or a phenylene group, R ² represents a single bond or a divalent linking group, and A ¹ represents —COOH, —SO _3. It represents H or -OPO ₃ H _2. When two or more —X—R ² —A ¹ are present in a single structural unit, X, R ² and A ¹ may be the same as or different from each other.   The structural unit represented by the general formula (2) is a structural unit derived from 2-carboxyethyl (meth) acrylate, a structural unit derived from styrenesulfonic acid, 2- (meth) acrylamide-2-methylpropanesulfonic acid The water-based ink according to claim 5, wherein the water-based ink is at least one of a structural unit derived from the above and a structural unit derived from mono 2- (meth) acryloyloxyethyl phosphate.   The water-based ink according to claim 5 or 6, wherein the polymer contains a benzene ring in a range of 3% by mass to 50% by mass with respect to the total mass.   An ink cartridge containing the water-based ink according to any one of claims 5 to 7. Ink applying means for containing the water-based ink according to any one of claims 5 to 7, and applying the water-based ink to a recording medium;
Infrared irradiation means for irradiating the water-based ink applied to the recording medium with infrared rays;
A recording apparatus comprising: An ink application step of applying the water-based ink according to any one of claims 5 to 7 to a recording medium;
An infrared irradiation step of irradiating the water-based ink applied to the recording medium with infrared rays;
A recording method.