JP2019056066A - Ink, method for producing ink and recording apparatus - Google Patents

Abstract

To achieve both drying property and stable infrared absorption performance in an ink which includes an infrared absorber and is dried by irradiation with infrared rays.SOLUTION: The ink comprises a coloring agent, an aqueous solvent, an infrared absorber and a water-soluble organic solvent having a boiling point higher than that of water in which the water-soluble organic solvent includes at least one kind of compounds represented by the general formula (I) and by the general formula (II) in a range of 4 mass% to 14 mass%. Formula (I): R-(O-CH-CH)-O-R(in the general formula (I), in the case of n=2, both of Rand Rrepresent an alkyl group and in the case of n=3 to 12, at least one of Rand Rrepresents an alkyl group and the other thereof represents a hydrogen atom or an alkyl group.) Formula (II): R-(O-CH-CH-CH)-O-R(in the general formula (II), both of Rand Rrepresent an alkyl group.)SELECTED DRAWING: None

Description

  The present invention relates to ink, an ink manufacturing method, and a recording apparatus.

  In Patent Document 1, in an ink containing a colorant, a wetting agent, and a polyol and / or glycol ether having 8 to 11 carbon atoms, the polyol and / or glycol ether having 8 to 11 carbon atoms is added to the total weight of the ink. An ink containing 0.1 to 10.0% by weight with respect to the ink is disclosed.

JP 2002-327141 A

  In an ink containing an infrared absorber and dried by infrared irradiation, an organic solvent having a boiling point higher than that of water may be added in order to suppress curing of the ink during storage. However, depending on the type and amount of the organic solvent added to the ink, the drying property of the ink and the infrared absorption performance of the ink may be affected. For example, when an organic solvent having a low SP value is used, the drying property of the ink can be improved. On the other hand, depending on the type and addition amount of the organic solvent, the infrared absorption performance decreases when stored under high temperature conditions. There is a fear.

  An object of the present invention is to realize both a drying property and a stable infrared absorption performance in an ink containing an infrared absorber and dried by infrared irradiation.

The invention according to claim 1 contains a colorant, an aqueous solvent, an infrared absorber, and a water-soluble organic solvent having a boiling point higher than that of water, and the water-soluble organic solvent is represented by the general formula (I) or An ink containing at least one compound represented by formula (II) in a range of 4% by mass to 14% by mass with respect to the total amount of the ink.
R ¹ — (O—CH ₂ —CH ₂ ) _n —O—R ² ... Formula (I)
(In general formula (I), n is an integer of 2 or more and 12 or less. When n = 2, R ¹ and R ² both represent an alkyl group, and when n = 3 to 12, at least one of R ¹ and R ² is An alkyl group, and the other represents a hydrogen atom or an alkyl group.)
R ³ — (O—CH ₂ —CH ₂ —CH ₂ ) ₂ —O—R ⁴ —General Formula (II)
(In general formula (II), R ³ and R ⁴ both represent an alkyl group.)

（一般式（ＩＩＩ）において、Ｒ^a、Ｒ^b、Ｒ^c、Ｒ^dは、それぞれ独立にアリール基またはアルキル基を表す。）

（一般式（ＩＶ）において、Ｒ^e、Ｒ^f、Ｒ^g、Ｒ^hは、それぞれ独立にアルキル基を表し、Ｒ^eとＲ^f、およびＲ^gとＲ^hは、互いに結合して環を形成していてもよい。） The invention according to claim 2 is the ink according to claim 1, wherein the infrared absorber includes a compound represented by general formula (III) or general formula (IV).

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

(In the general formula (IV), R ^e , R ^f , R ^g and R ^h each independently represents an alkyl group, and R ^e and R ^f , and R ^g and R ^h are bonded to each other to form a ring. You may do it.)

The invention according to claim 3 is characterized in that the infrared absorber includes R ^a , R ^b , R ^c and R ^d in the general formula (III), or R ^e , R ^f , R ^g in the general formula (IV) and The ink according to claim 2, wherein R ^h is a t-butyl group.
The invention according to claim 4 is characterized in that the infrared absorber is dispersed in a fine particle state together with a resin having an acid value with respect to the aqueous solvent and the water-soluble organic solvent. Ink.
In the invention according to claim 5, in the compound represented by the general formula (I) or the general formula (II), the alkyl group constituting R ¹ , R ² , R ³ and R ⁴ has 1 carbon atom. The ink according to claim 1, wherein the ink is 9 or less.
The invention according to claim 6 is characterized in that the SP value of the compound represented by the general formula (I) or the general formula (II) is in the range of 17 or more and 23 or less. Ink.
The invention according to claim 7 is characterized in that the water-soluble organic solvent contains at least one of triethylene glycol monomethyl ether, tetraethylene glycol monomethyl ether or tetraethylene glycol dimethyl ether represented by the general formula (I). The ink according to claim 5.
The invention according to claim 8 is characterized in that the water-soluble organic solvent further includes another water-soluble organic solvent having a boiling point different from that of the compound represented by the general formula (I) or the general formula (II). The total content of the compound represented by the formula (I) or the general formula (II) and the other water-soluble organic solvent is 40% by mass or less based on the total amount of the ink. 1. The ink according to 1.

The invention according to claim 9 includes a step of adjusting a colorant dispersion in which a colorant is dispersed, a step of adjusting an infrared absorber dispersion in which an infrared absorber is dispersed, the colorant dispersion, and the infrared absorption. Including a step of mixing an agent dispersion, an aqueous solvent, and a water-soluble organic solvent having a boiling point higher than that of water. In the mixing step, the water-soluble organic solvent may be represented by the general formula (I) or the general formula ( II) The range of 4 mass% or more and 14 mass% or less with respect to the whole quantity which match | combined the said colorant dispersion liquid, the said infrared absorber dispersion liquid, the said water-system solvent, and the said water-soluble organic solvent with at least 1 type of a compound represented. The ink production method is characterized in that the ink is mixed.
R ¹ — (O—CH ₂ —CH ₂ ) _n —O—R ² ... Formula (I)
(In general formula (I), n is an integer of 2 or more and 12 or less. When n = 2, R ¹ and R ² both represent an alkyl group, and when n = 3 to 12, at least one of R ¹ and R ² is An alkyl group, and the other represents a hydrogen atom or an alkyl group.)
R ³ — (O—CH ₂ —CH ₂ —CH ₂ ) ₂ —O—R ⁴ —General Formula (II)
(In general formula (II), R ³ and R ⁴ both represent an alkyl group.)

According to a tenth aspect of the present invention, there is provided an ink storage portion for storing the ink according to any one of the first to eighth aspects, and an ink jet for discharging the ink stored in the ink storage portion toward a recording medium. A recording apparatus includes a head and an infrared irradiation apparatus that irradiates infrared rays having a central wavelength in a range of 750 mm to 900 mm with respect to ink ejected to the recording medium.
The invention according to claim 11 is characterized in that the ink jet head ejects ink to a coated paper on which a surface layer containing a filler or a binder resin is formed as a recording medium. Recording device.

According to the invention which concerns on Claim 1, in the ink which contains an infrared absorber and is dried by irradiation of infrared rays, coexistence with drying property and stable infrared absorption performance is realizable.
According to the second aspect of the present invention, compared with the case where the compound represented by the general formula (III) or the general formula (IV) is not included as the infrared absorber, the deterioration of the infrared absorption performance of the ink is suppressed. Can do.
According to the invention of claim 3, R ^a , R ^b , R ^c and R ^d in the general formula (III), or R ^e , R ^f , R ^g and R ^h in the general formula (IV) are t-butyl. Compared with the case of a group other than the group, the decomposition of the infrared absorbent in the ink can be suppressed.
According to the invention which concerns on Claim 4, the infrared absorption efficiency by an infrared absorber can be improved compared with the case where the infrared absorber is not disperse | distributed with a dispersing agent.
According to the invention of claim 5, the general formula (I) or the general formula (II) is compared with the case where the alkyl group constituting R ¹ , R ² , R ³ and R ⁴ has 10 or more carbon atoms. ) And the miscibility between the aqueous solvent and the aqueous solvent can be improved.
According to the invention of claim 6, the penetration of the water-soluble organic solvent into the recording material is greater than when the SP value of the compound represented by the general formula (I) or (II) exceeds 23. Can be promoted.
According to the invention which concerns on Claim 7, compared with the case where compounds other than the triethylene glycol monomethyl ether, tetraethylene glycol monomethyl ether, and tetraethylene glycol dimethyl ether represented by general formula (I) are included as a water-soluble organic solvent. Both the drying property of the ink and the stability of the infrared absorbent in the ink can be improved.
According to the eighth aspect of the present invention, the total content of the compound represented by the general formula (I) or the general formula (II) and the other water-soluble organic solvent exceeds 40% by mass with respect to the total amount of the ink. Compared to the case, the drying property of the ink can be improved.
According to the ninth aspect of the present invention, it is possible to achieve both dryness and stable infrared absorption performance in an ink containing an infrared absorber and dried by infrared irradiation.
According to the tenth aspect of the present invention, there is provided a recording apparatus that includes an infrared absorber and is dried by irradiation with infrared rays, and that forms an image with an ink having drying properties and stable infrared absorption performance. be able to.
According to the invention which concerns on Claim 11, even if it is a case where an ink is apply | coated with respect to the coated paper into which a solvent does not osmose | permeate, penetration of a solvent can be promoted.

1 is an overall configuration diagram illustrating an example of a recording apparatus to which an exemplary embodiment is applied.

Next, embodiments of the present invention will be described.
<Ink configuration>
The ink to which the exemplary embodiment is applied is used in an ink jet printer that forms an image by ejecting ink onto a recording material by an ink jet head, for example. The ink of the present embodiment is a water-based ink using an aqueous solvent and a water-soluble organic solvent as a solvent. Further, as will be described later, the ink of the present embodiment includes an infrared absorber that absorbs light in the near infrared region. The ink according to the present embodiment is dried by being irradiated with infrared rays by an infrared laser or the like after being ejected onto a recording material by an inkjet head. In the description of this embodiment, the light in the near infrared region may be simply referred to as infrared rays.

Ink containing an infrared absorber exhibits infrared absorptivity. Specifically, the infrared absorber contained in the ink generates heat by absorbing infrared rays, and volatilizes the solvent in the ink by heating.
Here, the ink applied on the recording material made of coated paper such as coated paper or art paper is dried by removing the solvent contained in the ink, and an image is formed on the recording material. The solvent contained in the ink is removed from the ink by two phenomena: volatilization by heating and penetration into the recording material.

The ink used in the ink jet printer contains a water-soluble organic solvent having a boiling point higher than that of water in order to suppress clogging due to drying in the ink jet head or curing due to drying during storage.
Among such water-soluble organic solvents, it is preferable to use a water-soluble organic solvent having a low SP value (solubility parameter) in order to promote penetration of the solvent into the recording material and promote ink drying. That is, the water-soluble organic solvent having a low SP value has a high affinity with the constituent materials (filler and binder resin) of the surface layer formed on the surface of the recording material. For this reason, the penetration of the solvent contained in the ink into the recording material is promoted, and the drying of the ink is promoted.

However, depending on the type (structure) of the water-soluble organic solvent and the amount added to the ink, the stability of the infrared absorbent in the ink may be lowered. Specifically, the infrared absorber may aggregate in the ink depending on the type and amount of the water-soluble organic solvent. And when an infrared absorber aggregates in an ink, the infrared absorptivity by an infrared absorber may become difficult to express.
For this reason, depending on the type (structure) of the water-soluble organic solvent and the amount added to the ink, for example, if the ink is stored for a long time under high temperature conditions, the infrared absorption performance by the infrared absorbent may be lowered.

Therefore, in an ink containing an infrared absorber, it is necessary to select a water-soluble organic solvent in order to achieve both the drying property of the ink by the penetration of the solvent into the recording material and the maintenance of the stable infrared absorption performance of the ink.
In the ink of the present embodiment, at least one compound represented by the general formula (I) or (II) described later as a water-soluble organic solvent is in a range of 4% by mass to 14% by mass with respect to the total amount of the ink. By including, the said subject is solved.

Hereinafter, the components of the ink according to the present embodiment will be described in detail.
The ink of the present embodiment includes a colorant, an aqueous solvent, a water-soluble organic solvent, and an infrared absorber. Moreover, the ink of this Embodiment may contain other additives, such as surfactant, as needed.
In addition, the color of the ink of the present embodiment is not particularly limited. In addition to black, cyan, magenta, yellow, etc., specific colors such as red, green, blue, brown, white, and metallic luster such as gold, silver, etc. It can be a color or the like. However, in the case of the black ink, depending on the type of the colorant, since it also has an absorption wavelength in the near infrared region, it may not contain an infrared absorber. Therefore, the present invention is particularly effective for color inks other than black.

(Coloring agent)
The “colorant” is a substance that develops a predetermined color in the ink, and examples thereof include pigments and dyes. Among these, although it does not specifically limit as a pigment, An organic pigment or an inorganic pigment can be used.

  Specific examples of the black pigment include Raven7000, Raven5750, Raven5250, Raven5000 ULTRAII, Raven3500, Raven2000, Raven1500, Raven1250, Raven1200, Raven1125, Raven1125, Raven10, Raven10 Regal 330R, Regal 660R, Mogul L, Black Pearls L, Monarch 700, Monarch 800, Monarch 880, Monarch 900, Monarch 1000, Monarch 1100, Monarch 1300, Monarch 400 (manufactured by Cabot Corp.), Color Black FW1, Color Black FW2, Color Black FW2V, Color Black 18, Color Black FW200, Color Black S150, Color Black P160, Color Black P160, Color Black FW2P, Color Black FW2V, Color Black FW2V, Color Black FW2 Printex 140V, Special Black 6, Special Black 5, Special Black 4A, Special Black 4 (manufactured by Evonik Japan), No. 25, no. 33, no. 40, no. 47, no. 52, no. 900, no. 2300, MCF-88, MA600, MA7, MA8, MA100 (manufactured by Mitsubishi Chemical Corporation) and the like, but are not limited thereto.

  Specific examples of the cyan pigment include C.I. I. Pigment Blue-1, -2, -3, -15, -15: 1, -15: 2, -15: 3, -15: 4, -16, -22, -60, and the like. It is not limited.

  Specific examples of the magenta color pigment include C.I. I. Pigment Red-5, -7, -12, -48, -48: 1, -57, -112, -122, -123, -146, -168, -177, -184, -202, C.I. I. Pigment Violet-19 and the like, but are not limited thereto.

  Specific examples of yellow pigments include C.I. I. Pigment Yellow-1, -2, -3, -12, -13, -14, -16, -17, -73, -74, -75, -83, -93, -95, -97, -98, -114, -128, -129, -138, -151, -154, -180, and the like, but are not limited thereto.

  Here, when a pigment is used as the colorant, the pigment is preferably dispersed in the ink by a pigment dispersant. As the pigment dispersant, a polymer dispersant, a surfactant or the like can be used.

The polymer dispersant has a function of suppressing aggregation of pigment particles by adsorbing to the surface of the pigment.
As the polymer dispersant, a polymer having a hydrophilic structure portion and a hydrophobic structure portion is preferably used. As the polymer having a hydrophilic structure portion and a hydrophobic structure portion, a condensation polymer and an addition polymer can be used. Examples of the condensation polymer include known polyester dispersants. Examples of the addition polymer include addition polymers of monomers having an α, β-ethylenically unsaturated group. Polymer of interest by copolymerizing monomer having α, β-ethylenically unsaturated group having hydrophilic group and monomer having α, β-ethylenically unsaturated group having hydrophobic unit in combination A dispersant is obtained. A homopolymer of a monomer having an α, β-ethylenically unsaturated group having a hydrophilic group can also be used.

  Monomers having an α, β-ethylenically unsaturated group having a hydrophilic group include monomers having a carboxyl group, a sulfonic acid group, a hydroxyl group, a phosphoric acid group, such as acrylic acid, methacrylic acid, and crotonic acid. , Itaconic acid, itaconic acid monoester, maleic acid, maleic acid monoester, fumaric acid, fumaric acid monoester, vinyl sulfonic acid, styrene sulfonic acid, sulfonated vinyl naphthalene, vinyl alcohol, acrylamide, methacryloxyethyl phosphate, bismethacrylic acid Examples include roxyethyl phosphate, methacrylooxyethyl phenyl acid phosphate, ethylene glycol dimethacrylate, and diethylene glycol dimethacrylate.

  Examples of the monomer having an α, β-ethylenically unsaturated group having a hydrophobic group include styrene derivatives such as styrene, α-methylstyrene, vinyltoluene, vinylcyclohexane, vinylnaphthalene, vinylnaphthalene derivatives, alkyl acrylate esters, Examples include methacrylic acid alkyl esters, methacrylic acid phenyl esters, methacrylic acid cycloalkyl esters, crotonic acid alkyl esters, itaconic acid dialkyl esters, maleic acid dialkyl esters, and the like.

Examples of desirable copolymers used as polymer dispersants include styrene-styrene sulfonic acid copolymers, styrene-maleic acid copolymers, styrene-methacrylic acid copolymers, styrene-acrylic acid copolymers, Vinyl naphthalene-maleic acid copolymer, vinyl naphthalene-methacrylic acid copolymer, vinyl naphthalene-acrylic acid copolymer, alkyl acrylate ester-acrylic acid copolymer, alkyl methacrylate ester-methacrylic acid copolymer, styrene -Methacrylic acid alkyl ester-Methacrylic acid copolymer, Styrene-Acrylic acid alkyl ester-Acrylic acid copolymer, Styrene-Methacrylic acid phenyl ester-Methacrylic acid copolymer, Styrene-Methacrylic acid cyclohexyl ester-Methacrylic acid copolymer Etc. . Moreover, you may copolymerize the monomer which has a polyoxyethylene group and a hydroxyl group with these polymers.
Examples of the polymer dispersant include those having a weight average molecular weight of 2,000 to 50,000.

  Specific examples of the surfactant will be described later.

  These pigment dispersants may be used alone or in combination of two or more. The amount of the pigment dispersant added varies greatly depending on the pigment, so it cannot be generally stated. However, in general, the total amount is 0.1% by mass or more and 100% by mass or less based on the pigment.

As the pigment, a pigment that is self-dispersible in water (hereinafter referred to as a self-dispersing pigment) may be used.
The self-dispersing pigment refers to a pigment that has many water-solubilizing groups on the pigment surface and disperses in water without the presence of a polymer dispersant. Specifically, self-dispersed pigments can be obtained by subjecting ordinary so-called pigments to surface modification treatment such as acid / base treatment, coupling agent treatment, polymer graft treatment, plasma treatment, oxidation / reduction treatment, etc. It is done.

  Further, as pigments that can be self-dispersed in water, in addition to pigments obtained by subjecting the above pigments to surface modification treatment, Cab-o-jet-200, Cab-o-jet-300, IJX- manufactured by Cabot Corporation Commercially available self-dispersing pigments such as 157, IJX-253, IJX-266, IJX-273, IJX-444, IJX-55, Cabot 260, Microjet Black CW-1, CW-2 manufactured by Orient Chemical Co., etc. can also be used.

  The self-dispersing pigment is desirably a pigment having at least sulfonic acid, sulfonate, carboxylic acid, or carboxylate as a functional group on the surface thereof. More desirably, the pigment has at least a carboxylic acid or a carboxylate as a functional group on the surface.

Examples of the pigment include a pigment coated with a resin. This is called a microcapsule pigment, and commercially available microcapsule pigments such as those manufactured by DIC and Toyo Ink can be used.
In addition, examples of the pigment include resin-dispersed pigments in which a polymer substance is physically adsorbed or chemically bonded to the pigment.
In addition to black, cyan, magenta, and yellow primary pigments, the pigments include specific color pigments such as red, green, blue, brown, and white, metallic luster pigments such as gold and silver, and colorless or light-colored constitutions. Examples include pigments and plastic pigments.
Examples of the pigment include particles in which silica, alumina, polymer beads or the like are used as a core, and a dye or pigment is fixed on the surface thereof, an insoluble lake of the dye, a colored emulsion, a colored latex, or the like.

  As colorants, in addition to pigments, other hydrophilic anionic dyes, direct dyes, cationic dyes, reactive dyes, polymer dyes and oil-soluble dyes, wax powders and resin powders colored with dyes And emulsions, fluorescent dyes and pigments, infrared absorbers (infrared absorbers other than the compounds represented by formula (III) or formula (IV)), ultraviolet absorbers, and ferromagnetism represented by ferrite and magnetite Examples thereof include semiconductors and photocatalysts represented by magnetic substances such as titanium, titanium oxide and zinc oxide, and other organic and inorganic electronic material particles.

  The volume average particle diameter of the colorant is, for example, 10 nm or more and 1000 nm or less.

  The volume average particle diameter of the colorant refers to the particle diameter of the colorant itself, or the particle diameter to which the additive has adhered when an additive such as a dispersant is attached to the colorant. A Microtrac UPA particle size analyzer 9340 (manufactured by Lees & Northrup) can be used as the volume average particle diameter measuring apparatus. The measurement is performed according to the measuring method of the measuring device by putting 4 ml of ink into the measuring cell. As input values at the time of measurement, the viscosity is the viscosity of the ink, and the density of the dispersed particles is the density of the colorant.

  The content (concentration) of the colorant can be, for example, in the range of 5% by mass to 30% by mass with respect to the total amount of ink.

(Aqueous solvent)
“Aqueous solvent” means a solvent mainly composed of water. Here, the solvent mainly composed of water refers to containing 50% or more of water.
Examples of the aqueous solvent include water such as ion exchange water, ultrapure water, distilled water, and ultrafiltration water. Moreover, as an aqueous solvent, you may use together the solvent excellent in the solubility with water with water. Examples of such a solvent having excellent solubility in water include lower alcohols such as methanol, ethanol, butanol and isopropyl alcohol, and lower ketones such as acetone. One of these solvents having excellent solubility with water may be blended alone, or two or more thereof may be blended.

(Water-soluble organic solvent)
The “water-soluble organic solvent” means an organic solvent that is excellent in compatibility with water and can be mixed with water at an arbitrary ratio.
The ink of the present embodiment includes a water-soluble organic solvent having a boiling point higher than that of water. Specifically, the ink of the present embodiment contains at least one compound represented by the following general formula (I) or general formula (II) as a water-soluble organic solvent having a boiling point higher than that of water. It is included in the range of 4% by mass to 14% by mass with respect to the total amount.
R ¹ — (O—CH ₂ —CH ₂ ) _n —O—R ² ... Formula (I)
(In general formula (I), n is an integer of 2 or more and 12 or less. When n = 2, R ¹ and R ² both represent an alkyl group, and when n = 3 to 12, at least one of R ¹ and R ² is An alkyl group, and the other represents a hydrogen atom or an alkyl group.)
R ³ — (O—CH ₂ —CH ₂ —CH ₂ ) ₂ —O—R ⁴ —General Formula (II)
(In general formula (II), R ³ and R ⁴ both represent an alkyl group.)

In the description of the present embodiment, the “compound represented by the general formula (I) or the general formula (II)” refers to a compound in which R ^{1 to} R ⁴ satisfy the above-described requirements. That is, the compound in which R ^{1 to} R ⁴ do not satisfy the above-described requirements in general formula (I) or general formula (II) is represented by “general formula (I) or general formula (II)” in the present embodiment. It is not included in “compound”.

In the compound represented by the general formula (I) or the general formula (II), the alkyl group represented by R ¹ , R ² , R ³ and R ⁴ may be either linear or branched, You may have. The number of carbon atoms of the alkyl group represented by R ¹ , R ² , R ³ and R ⁴ is preferably 1 or more and 9 or less, and more preferably 1 or 2. When the alkyl group represented by R ¹ , R ² , R ³ and R ⁴ has 10 or more carbon atoms, the miscibility between the compound represented by the general formula (I) or the general formula (II) and the aqueous solvent decreases. There is a fear.

Specific examples of the alkyl group represented by R ¹ , R ² , R ³ and R ⁴ include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, t-butyl group, n- Examples include, but are not limited to, a pentyl group, an isopentyl group, a t-pentyl group, an n-hexyl group, an isohexyl group, and a t-hexyl group.

  Specific examples of the compound represented by the general formula (I) include diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol ethyl methyl ether, triethylene glycol monomethyl ether, triethylene glycol dimethyl ether, triethylene glycol monoethyl ether, and triethylene glycol diethyl. Ether, tetraethylene glycol monomethyl ether, tetraethylene glycol dimethyl ether, tetraethylene glycol monoethyl ether, tetraethylene glycol diethyl ether, polyethylene glycol monomethyl ether, polyethylene glycol dimethyl ether, polyethylene glycol monoethyl ether, polyethylene glycol diethyl ether, etc. But it is lower, but the invention is not limited thereto.

  Specific examples of the compound represented by the general formula (II) include, but are not limited to, dipropylene glycol dimethyl ether and dipropylene glycol diethyl ether.

  In this Embodiment, it is preferable to use the compound represented by general formula (I) among the compounds represented by the said general formula (I) or general formula (II). Among the compounds represented by the general formula (I), it is more preferable to use triethylene glycol monomethyl ether, tetraethylene glycol monomethyl ether, or tetraethylene glycol dimethyl ether.

Moreover, you may mix and use the multiple types of compound represented by the said general formula (I) or general formula (II). That is, the compound represented by the general formula (I) and the compound represented by the general formula (II) may be used in combination, and in the compound represented by the general formula (I) or the general formula (II), carbon Compounds having different numbers n, R ¹ , R ² , R ³ or R ⁴ may be used in combination.

  In the ink of the present embodiment, by using the compound represented by the general formula (I) or the general formula (II) as the water-soluble organic solvent, the water-soluble organic solvent for the recording material such as coated paper or art paper is used. Penetration can be promoted. Thus, when an image is formed on a recording material using the ink of the present embodiment, for example, only a compound other than the compound represented by the general formula (I) or the general formula (II) as a water-soluble organic solvent is used. Compared with the case of using the ink, the drying property of the ink can be improved.

More specifically, a surface layer is formed of a filler and a binder resin on the surface of a recording material (coated paper) such as coated paper or art paper. As the filler, for example, calcium carbonate, magnesium carbonate, kaolin, talc, silica, alumina, titanium dioxide, aluminum hydroxide, zinc oxide and the like are used. Moreover, as binder resin, latex, such as a styrene butadiene copolymer and an acrylonitrile butadiene copolymer, is used, for example.
The compound represented by the general formula (I) or the general formula (II) has a low SP value and a high affinity with the filler and binder resin constituting the surface layer formed on the surface of the recording material. Therefore, by using the compound represented by the general formula (I) or the general formula (II) as the water-soluble organic solvent, it is possible to promote the penetration of the ink into the recording material.

Further, in the ink of the present embodiment, the use of the compound represented by the general formula (I) or the general formula (II) as the water-soluble organic solvent can suppress a decrease in the infrared absorption performance of the ink. .
That is, as described above, depending on the type of the water-soluble organic solvent, the stability of the infrared absorbent in the ink may be reduced, and the infrared absorbent may aggregate. In this case, for example, if the ink is stored for a long time under high temperature conditions, the infrared absorption performance of the ink may be reduced.

On the other hand, the ink of the present embodiment contains the compound represented by the general formula (I) or the general formula (II) as a water-soluble organic solvent, so that the stability of the infrared absorber in the ink is improved. The decrease is suppressed, and the aggregation of the infrared absorber is suppressed.
Thereby, for example, even when the ink is stored for a long time under a high temperature condition, compared with the case where the compound represented by the general formula (I) or the general formula (II) is not included as the water-soluble organic solvent. A decrease in the infrared absorption performance of the ink is suppressed.

  Moreover, the ink of this Embodiment contains the compound represented by general formula (I) or general formula (II) as a water-soluble organic solvent, The pigment aggregation is suppressed, and it becomes easy to come loose. Thereby, the plasticity of the ink is improved as compared with the case where the water-soluble organic solvent does not contain the compound represented by the general formula (I) or the general formula (II), and clogging of the ink in the inkjet head is suppressed. .

In the present embodiment, the amount of the compound represented by the general formula (I) or the general formula (II) is in the range of 4% by mass to 14% by mass with respect to the total amount of the ink.
When the amount of the compound represented by the general formula (I) or the general formula (II) is less than 4% by mass with respect to the total amount of the ink, the penetration of the ink into the recording material becomes insufficient. There is a risk of drying.

  On the other hand, when the amount of the compound represented by the general formula (I) or the general formula (II) exceeds 14% by mass with respect to the total amount of the ink, the infrared absorption performance of the ink may be deteriorated. That is, since the compound represented by the general formula (I) or the general formula (II) has low polarity, when the amount added to the ink exceeds 14% by mass, the general formula (I) or the general formula (II) The polarity of the solvent containing the represented compound will be reduced. In this case, the stability of the infrared absorbent in the ink may be reduced, and the infrared absorption performance of the ink may be reduced.

  The SP value of the compound represented by the general formula (I) or the general formula (II) is preferably 17 or more and 23 or less. By using a compound having an SP value of 17 or more and 23 or less as the water-soluble organic solvent, for example, the penetration of the water-soluble organic solvent into the surface layer formed on the surface of the recording material as compared with a case where the SP value is higher than 23. Improves. Thereby, the drying property of the ink is improved. The SP value of the compound represented by the general formula (I) or the general formula (II) is more preferably 19 or more and 23 or less.

  Moreover, as a water-soluble organic solvent, in addition to the compound represented by the general formula (I) or the general formula (II), another water-soluble organic solvent having a boiling point higher than that of water may be used. Examples of other water-soluble organic solvents include polyhydric alcohols, polyhydric alcohol derivatives other than the compounds represented by formula (I) or formula (II), nitrogen-containing solvents, sulfur-containing solvents, and the like.

  As polyhydric alcohols, ethylene glycol, diethylene glycol, propylene glycol, butylene glycol, triethylene glycol, polyethylene glycol, 1,5-pentanediol, 1,2-hexanediol, 1,2,6-hexanetriol, glycerin, Examples thereof include sugar alcohols such as trimethylolpropane and xylitol, and sugars such as xylose, glucose and galactose.

  Examples of the polyhydric alcohol derivatives other than the compound represented by the general formula (I) or (II) include ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether. , Diethylene glycol monobutyl ether, propylene glycol monobutyl ether, dipropylene glycol monobutyl ether and the like.

Examples of the nitrogen-containing solvent include 2-pyrrolidone, N-methyl-2-pyrrolidone, N-hydroxyethyl-2-pyrrolidone, cyclohexyl pyrrolidone, triethanolamine and the like.
Examples of the sulfur-containing solvent include thiodiethanol, thiodiglycerol, sulfolane, dimethyl sulfoxide and the like.

In the ink of the present embodiment, the total content of the water-soluble organic solvent including the compound represented by the general formula (I) or the general formula (II) and the other water-soluble organic solvent is the total amount of the ink. It is preferable that it is 4 mass% or more and 40 mass% or less of range.
When the total content of the water-soluble organic solvent exceeds 40% by mass, the ratio of the compound having a boiling point higher than that of water in the ink is increased, so that the drying property of the ink may be lowered.

(Infrared absorber)
The ink of the present embodiment contains an infrared absorber. Here, the “infrared absorber” is a compound having a property of absorbing light (infrared rays) in the near infrared region. More specifically, the infrared absorber is a compound having a functional group or a skeleton that absorbs infrared rays.
In the present embodiment, the infrared absorber preferably includes a compound having a squarylium skeleton, more specifically a compound represented by the general formula (III) or the general formula (IV).

（一般式（ＩＩＩ）において、Ｒ^a、Ｒ^b、Ｒ^c、Ｒ^dは、それぞれ独立にアリール基またはアルキル基を表す。）

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

（一般式（ＩＶ）において、Ｒ^e、Ｒ^f、Ｒ^g、Ｒ^hは、それぞれ独立にアルキル基を表し、Ｒ^eとＲ^f、およびＲ^gとＲ^hは、互いに結合して環を形成していてもよい。）

(In the general formula (IV), R ^e , R ^f , R ^g and R ^h each independently represents an alkyl group, and R ^e and R ^f , and R ^g and R ^h are bonded to each other to form a ring. You may do it.)

In the description of the present embodiment, “a compound represented by general formula (III) or general formula (IV)” refers to a compound in which R ^{a to} R ^h satisfy the above-described requirements. That is, the compound in which R ^{a to} R ^h do not satisfy the above-described requirements in the general formula (III) or the general formula (IV) is represented by the “general formula (III) or the general formula (IV) in the present embodiment. It is not included in “compound”.

In the ink of the present embodiment, the drying property of the ink can be improved by using the compound represented by the general formula (III) or the general formula (IV) as the infrared absorber.
If it demonstrates concretely, the compound represented by general formula (III) or general formula (IV) is excellent in the near-infrared absorptivity of wavelength 700nm -1200nm. Therefore, in the ink of the present embodiment, by using the compound represented by the general formula (III) or the general formula (IV) as the infrared absorber, the volatilization of the solvent by the infrared irradiation is promoted, and the ink is dried. Can be urged.

  Moreover, the compound represented by the general formula (III) or the general formula (IV) as an infrared absorber has high particle stability when it is made into fine particles together with a resin having an acid value, and hardly decomposes with time. Therefore, in the ink according to the present embodiment, the use of the compound represented by the general formula (III) or the general formula (IV) as the infrared absorber can suppress a decrease in the infrared absorption performance of the ink. .

An alkyl group represented by R ^a , R ^b , R ^c and R ^d in the compound represented by the general formula (III), or R ^e , R ^f , R ^g and R ^{h in the} compound represented by the general formula (IV) The alkyl group represented by may be either linear or branched, and may have a ring. The number of carbon atoms of the alkyl group represented by R ^a , R ^b , R ^c and R ^d or R ^e , R ^f , R ^g and R ^h is preferably 1 or more and 8 or less. It is more preferable.

Specific examples of the alkyl group represented by R ^a , R ^b , R ^c and R ^d or R ^e , R ^f , R ^g and R ^h include methyl, ethyl, n-propyl, isopropyl and n-butyl. Group, isobutyl group, sec-butyl group, t-butyl group, n-pentyl group, isopentyl group, neopentyl group, 1,2-dimethyl-propyl group, n-hexyl group, isohexyl group, sec-hexyl group, n- A heptyl group, an isoheptyl group, a sec-heptyl group, an n-octyl group, etc. are mentioned, However, It is not limited to these.

Among these, the alkyl group represented by R ^a , R ^b , R ^c and R ^d or R ^e , R ^f , R ^g and R ^h is preferably a t-butyl group. When the alkyl group represented by R ^a , R ^b , R ^c and R ^d or R ^e , R ^f , R ^g and R ^h is a t-butyl group, it is represented by the general formula (III) or the general formula (IV). Is prevented from being decomposed in the ink, and the deterioration of the infrared absorption performance by the infrared absorber is further suppressed.

In the compound represented by the general formula (III), the aryl group represented by R ^a , R ^b , R ^c and R ^d preferably has 6 to 12 carbon atoms, and preferably 6 to 10 carbon atoms. More preferred.
Specific examples of the aryl group represented by R ^a , R ^b , R ^c and R ^d include phenyl group, phenethyl group, o-tolyl group, m-tolyl group, p-tolyl group, 2,3-xylyl group, 2 , 4-xylyl group, mesityl group, naphthyl group and the like, but are not limited thereto.

The content of the infrared absorber in the ink is preferably in the range of 0.01% by mass to 0.2% by mass with respect to the total amount of the ink.
When the content of the infrared absorber is less than 0.01% by mass, the infrared absorption performance of the ink may be insufficient. In this case, the amount of heat generated by the absorption of infrared rays by the infrared absorbent becomes insufficient, and the solvent of the ink becomes difficult to volatilize, which may reduce the drying properties of the ink.
On the other hand, when the content of the infrared absorber exceeds 0.2% by mass, the formed image may be affected by the color of the infrared absorber itself.

  The compound represented by the general formula (III) or the general formula (IV) preferably has a maximum absorption wavelength in the tetrahydrofuran solution in the range of 700 nm to 1200 nm, and in the range of 800 nm to 1000 nm. More preferably.

In the ink of the present embodiment, it is preferable that the infrared absorbent (the infrared absorbent represented by the general formula (III) or the general formula (IV)) is dispersed in a fine particle state in the ink.
As a method for preparing an infrared absorbent dispersion, a method in which an infrared absorbent and a resin having an acid value are dissolved in a solvent such as tetrahydrofuran, methyl ethyl ketone, isopropyl alcohol, and the solution is dropped into the solvent, or resin fine particles And a solution in which the infrared absorbent is dissolved, and then the organic solvent is gradually removed to impregnate the resin fine particles with the infrared absorbent to form infrared absorbent fine particles.

(Resin having acid value)
As the resin having an acid value used for the preparation of the infrared absorbent dispersion, a resin that forms a dispersion in a volume average particle size of 10 nm or more and 150 nm or less in water or ink can be used. Specifically, acrylic resin, polyurethane, polyester, polyamide, polyurea and polycarbonate can be used. The acid value is preferably in the range of 5 mgKOH / g to 50 mgKOH / g.

(Other additives)
The ink of the present embodiment may contain a surfactant as another additive. By including the surfactant, it is possible to further promote the penetration of the ink into the recording material.
Examples of the surfactant include an anionic surfactant, a nonionic surfactant, a cationic surfactant, and an amphoteric surfactant. Among these, it is preferable to use an anionic surfactant or a nonionic surfactant.

Examples of the anionic surfactant include alkylbenzene sulfonate, alkylphenyl sulfonate, alkylnaphthalene sulfonate, higher fatty acid salt, sulfate of higher fatty acid ester, sulfonate of higher fatty acid ester, sulfuric acid of higher alcohol ether. Examples thereof include ester salts and sulfonates, higher alkyl sulfosuccinates, polyoxyethylene alkyl ether carboxylates, polyoxyethylene alkyl ether sulfates, alkyl phosphates, polyoxyethylene alkyl ether phosphates, and the like.
Among these, as anionic surfactants, dodecylbenzenesulfonate, isopropylnaphthalenesulfonate, monobutylphenylphenol monosulfonate, monobutylbiphenylsulfonate, monobutylbiphenylsulfonate, dibutylphenylphenol It is preferable to use a disulfonate.

Nonionic surfactants include polyoxyethylene alkyl ethers, polyoxyethylene alkyl phenyl ethers, polyoxyethylene fatty acid esters, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, polyoxyethylene sorbitol fatty acid esters, glycerin fatty acid esters, poly Examples thereof include oxyethylene glycerin fatty acid ester, polyglycerin fatty acid ester, sucrose fatty acid ester, polyoxyethylene alkylamine, polyoxyethylene fatty acid amide, alkyl alkanol amide, polyethylene glycol polypropylene glycol block copolymer, acetylene glycol and the like.
Among these, nonionic surfactants include polyoxyethylene nonylphenyl ether, polyoxyethylene octylphenyl ether, polyoxyethylene dodecylphenyl ether, polyoxyethylene alkyl ether, polyoxyethylene fatty acid ester, sorbitan fatty acid ester, polyoxyethylene It is preferable to use oxyethylene sorbitan fatty acid ester, fatty acid alkylolamide, polyethylene glycol polypropylene glycol block copolymer, and acetylene glycol.

  The addition amount of the surfactant in the ink of the present embodiment can be in the range of 0.001% by mass to 5% by mass and 0.01% by mass to 3% by mass with respect to the total amount of the ink. It is preferable to be in the range.

  In addition, the ink of the present embodiment includes, as other additives, a stabilizer, a polymerization inhibitor, a dispersant, an antioxidant, a surface conditioner, an adhesion imparting agent, a plasticizer, a rust preventive agent, a solvent, a non-reaction Additives such as conductive polymers, fillers, pH adjusters, antifoaming agents, charge control agents, stress relaxation agents, penetrating agents, light guide materials, glittering materials, magnetic materials, and phosphors may be added as necessary. Good.

In the above description, the use of the ink of the present embodiment is exemplified by the formation of an image by an ink jet method using an ink jet head or the like, but the use of the ink is not limited to this. The ink of the present embodiment may be used for, for example, offset printing, gravure printing, letterpress printing, screen printing, and the like.
However, as described above, since the ink of the present embodiment has the above-described configuration, clogging due to drying in the inkjet head can be suppressed, and therefore, it can be preferably used for image formation by an inkjet method.

<Ink production method>
The ink of the present embodiment can be obtained by mixing a colorant, an aqueous solvent, a water-soluble organic solvent (a compound represented by general formula (I) or general formula (II)) and an infrared absorber. More specifically, the ink of the present embodiment is prepared by, for example, preparing a colorant dispersion in which a colorant is dispersed and an infrared absorbent dispersion in which an infrared absorber is dispersed, and an aqueous solvent and a water-soluble solution. It can be obtained by mixing an organic solvent or the like.
A dispersion machine can be used to adjust the dispersion. The disperser is not particularly limited, and for example, a ball mill, a sand mill, a roll mill, a bead mill or the like can be used.

<Recording device>
The ink described above is stored in an ink storage container such as an ink cartridge, and is used in a recording apparatus that forms an image on a recording medium. Next, an example of a recording apparatus that uses the ink of the present embodiment will be described.
FIG. 1 is an overall configuration diagram illustrating an example of a recording apparatus 1 to which the exemplary embodiment is applied.

  The recording apparatus 1 is an ink jet recording apparatus that forms an image by a so-called ink jet method. As shown in FIG. 1, the recording apparatus 1 includes an image forming unit 10 that forms an image on a recording material based on image data, a recording material supply unit 20 that supplies the recording material to the image forming unit 10, and an image. An ink cartridge 30 that supplies ink to the forming unit 10 and an infrared irradiation device 50 that irradiates the ink applied to the recording material in the image forming unit 10 with infrared rays are provided. The recording apparatus 1 also includes a control unit 70 that controls the operation of the entire recording apparatus 1.

  As shown in FIG. 1, the image forming unit 10 includes an inkjet head 11 that forms an image by ejecting ink onto a recording material. The ink-jet head 11 includes ink-jet heads 11 (ink-jet heads 11Y, 11M, 11C, and 11K) that respectively correspond to four color inks of yellow (Y), magenta (M), cyan (C), and black (K). The The inkjet heads 11Y, 11M, 11C, and 11K for the respective colors are provided side by side in the recording material conveyance direction. Each inkjet head 11 forms an image on a recording material by ejecting ink droplets based on control by the control unit 70.

  More specifically, each ink jet head 11 is formed with a plurality of ink discharge ports (not shown) arranged along the width direction of the recording material (the direction intersecting the recording material conveyance direction). Each of the inkjet heads 11 ejects ink droplets from the ink ejection port to a recording material supplied from the recording material supply unit 20 and conveyed by a conveyance roll (not shown). The ink droplet ejection method by the inkjet head 11 is not particularly limited. For example, a thermal method in which ink droplets are ejected by heat, or a piezoelectric method in which ink droplets are ejected by pressure using a piezoelectric element or the like. A method etc. can be adopted.

  The ink cartridge 30 includes ink cartridges 31Y, 31M, 31C, and 31K that correspond to four colors of ink of yellow (Y), magenta (M), cyan (C), and black (K), respectively. Each ink cartridge 31 contains the ink of each color described above. Specifically, the ink cartridge 31Y contains yellow ink, the ink cartridge 31M contains magenta ink, the ink cartridge 31C contains cyan ink, and the ink cartridge 31K contains black ink. Is housed.

  Each ink cartridge 31 is configured to be detachable from the apparatus main body of the recording apparatus 1 and is connected to the corresponding inkjet head 11. Each ink cartridge 31 supplies ink of each color to each inkjet head 11 based on control by the control unit 70.

The infrared irradiation device 50 irradiates the ink applied on the recording material with infrared rays.
In the infrared irradiation device 50, a light source (not shown) is arranged along the width direction of the recording material. The light source of the infrared irradiation device 50 is not particularly limited, and for example, an infrared laser, a halogen lamp, a ceramic heater, an LED (Light Emitting Diode), or the like can be used.

Irradiation conditions such as the wavelength, irradiation intensity, and irradiation time of the light source of the infrared irradiation device 50 are selected in accordance with the ink configuration described above. For example, the wavelength of the light source of the infrared radiator 50 may be a 1000nm the range above 800 nm, irradiation intensity can be 0.1 J / cm ² or more 10J / cm ² or less in the range of irradiation time Can be in the range of 0.1 milliseconds to 1 second.

  In addition, in the recording apparatus of the present embodiment, as a recording material for forming an image, in addition to non-coated paper, coated paper such as coated paper or art paper having lower ink absorbability than non-coated paper is used. In contrast, an image can be formed.

Subsequently, the operation of the recording apparatus 1 of the present embodiment will be described.
In the recording apparatus 1, when an image formation instruction is received, the recording material is supplied from the recording material supply unit 20 based on control by the control unit 70. Then, in accordance with the timing at which the recording material is conveyed to the image forming unit 10, ink is ejected toward the recording material by each inkjet head 11. As a result, an image is formed on the recording material with ink.

Subsequently, the recording material on which the ink is ejected and the image is formed is conveyed to the infrared irradiation device 50, and the infrared irradiation device 50 irradiates the ink on the recording material with infrared rays. As a result, the infrared absorbent in the ink absorbs infrared rays to generate heat, and the ink temperature rises. Then, the solvent (aqueous solvent, water-soluble organic solvent) contained in the ink is volatilized and reduced, the ink is dried, and the image is fixed on the recording material.
The recording material on which the image is fixed is transported to a transport roll (not shown) and discharged outside the recording apparatus 1.

  Here, in the recording apparatus 1 of the present embodiment, drying of ink can be promoted by using the ink having the above-described configuration as the ink contained in the ink cartridge 31 and ejected by the inkjet head 11. That is, in the ink of the present embodiment, the compound represented by the general formula (I) or the general formula (II) as a water-soluble organic solvent is in a range of 4% by mass to 14% by mass with respect to the total amount of the ink. Including. Thereby, the penetration of the water-soluble organic solvent into the recording material can be promoted with respect to the ink ejected by the inkjet head 11.

In particular, the compound represented by the general formula (I) or the general formula (II) has high affinity with the filler and binder resin constituting the surface layer in coated paper such as coated paper and art paper. Therefore, even if the recording apparatus 1 uses a coated paper having a lower ink absorbency than the non-coated paper as the recording material, the permeability of the water-soluble organic solvent to the recording material can be promoted. .
As a result, the drying of the ink can be promoted as compared with the case where the ink does not have the above configuration. Further, since the drying of the ink can be promoted, for example, the irradiation intensity of infrared rays irradiated by the infrared irradiation device 50 can be lowered, or the irradiation time can be shortened.

  Further, by using the ink having the above-described configuration, aggregation of the pigment is suppressed and the ink is easily loosened. Thereby, compared with the case where the ink does not have the said structure, the plasticity of an ink improves and the clogging of the ink in the inkjet head 11 is suppressed.

  In the recording apparatus 1 according to the present embodiment, the infrared irradiation unit 50 collectively irradiates infrared rays to the inks of the respective colors ejected onto the recording material by the inkjet heads 11Y, 11M, 11C, and 11K of the respective colors. It is said. However, the configuration of the recording apparatus 1 is not limited to this. For example, the infrared irradiation device 50 may be arranged on the downstream side of the ink jet heads 11Y, 11M, 11C, and 11K for each color in the conveyance direction of the recording material, and infrared rays may be irradiated for each ink.

Subsequently, the present invention will be described in more detail using examples. The present invention is not limited to the following examples.
[Example 1 to Example 8, Comparative Example 1 to Comparative Example 8]
(1) Preparation of ink According to Table 1 and Table 2 described later, inks of Examples 1 to 8 and Comparative Examples 1 to 8 were prepared according to the following procedure. In the following description, “part” means “mass part” which is a mass reference.
(Preparation of cyan pigment dispersion)
In a reaction vessel, 6 parts of styrene, 11 parts of stearyl methacrylate, 4 parts of styrene macromer AS-6 (manufactured by Toa Gosei Co., Ltd.), 5 parts of Blenmer PP-500 (manufactured by NOF Corporation), 5 parts of methacrylic acid, 2-mercapto Ethanol 0.05 part and methyl ethyl ketone 24 parts were mixed to obtain a mixed solution 1.
Also, 14 parts of styrene, 24 parts of stearyl methacrylate, 9 parts of styrene macromer AS-6 (manufactured by Toagosei Co., Ltd.), 9 parts of Blenmer PP-500 (manufactured by NOF Corporation), 10 parts of methacrylic acid, 0 of 2-mercaptoethanol 0 .13 parts, 56 parts of methyl ethyl ketone, and 1.2 parts of 2,2′-azobis (2,4-dimethylvaleronitrile) were mixed into a dropping funnel.

Next, under a nitrogen atmosphere, the mixed solution 1 in the reaction vessel was heated to 75 ° C. while stirring, and the mixed solution 2 in the dropping funnel was gradually dropped into this over 1 hour. After completion of dropping, the mixture was allowed to stand at 75 ° C. for 2 hours.
Subsequently, a solution prepared by dissolving 1.2 parts of 2,2′-azobis (2,4-dimethylvaleronitrile) in 12 parts of methyl ethyl ketone was gradually added dropwise to this solution over 3 hours.
Thereafter, the mixture was further reacted at 75 ° C. for 2 hours and then aged at 80 ° C. for 2 hours to obtain a polymer solution.

  Part of the polymer solution obtained is isolated by removing the solvent, and the solid content obtained is diluted to 0.1% by mass with tetrahydrofuran, and the weight average molecular weight is measured by GPC (Gel Permeation Chromatography). As a result, the weight average molecular weight in terms of polystyrene was 25000.

  In addition, 5 parts of the obtained polymer solution in terms of solid content, 10 parts of cyan pigment (Pigment Blue 15: 3, manufactured by Dainichi Seika Kogyo Co., Ltd.), 40 parts of methyl ethyl ketone, 8 parts of 1 mol / L sodium hydroxide aqueous solution, ions 82 parts of exchange water was filled in a vessel together with 300 g of 0.1 mm zirconia beads, and dispersed at 1000 rpm for 6 hours using a ready mill disperser (manufactured by Imex Corporation).

Subsequently, the obtained dispersion was concentrated under reduced pressure using an evaporator so that methyl ethyl ketone was removed and the pigment concentration was 10% by mass.
As described above, a cyan pigment dispersion A1 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 in the obtained cyan pigment dispersion A1 was 77 nm.

(Preparation of infrared absorber dispersion)
Add 16.7 parts of P-1 methyl ethyl ketone solution (resin solid content 35%) to the flask, add 6 parts of methyl ethyl ketone and 2 parts of tetrahydrofuran, and 0.09 part of the infrared absorber shown in Table 1 and stir. , Mixed. Next, a 10% by mass aqueous solution of sodium hydroxide was added with stirring so as to neutralize 0.8 equivalent of the total amount of all carboxyl groups contained in the resin. Subsequently, 60 parts of water (ion-exchanged water) was gradually added while mixing and mixed.
P-1: Copolyester of terephthalic acid / isophthalic acid / trimellitic acid / dodecenyl succinic acid / bisphenol A ethylene oxide 2 mol adduct / bisphenol A propylene oxide 2 mol adduct (copolymerization molar ratio: 45/45/8/2/50) / 50). Number average molecular weight 6500, acid value 12 mgKOH / g

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 distilling and concentrating the organic solvent while substituting with water is repeated until the organic solvent odor disappears while adjusting the amount of water added so that the solid content converted from the material does not exceed 17% by mass. It was.

  The obtained concentrated liquid was filtered through a nylon mesh having 230 meshes. And the amount of solid content of the filtered concentrated liquid was measured, and based on the measurement result, water was added to the concentrated liquid to adjust the solid content concentration to 10% by mass. Thus, an infrared absorbent dispersion in which the infrared absorbent was dispersed with the resin was obtained.

(Preparation of cyan ink)
After mixing the following materials based on Table 1, coarse particles were removed with a 5 μm filter to obtain a cyan ink.
-Cyan pigment dispersion 3% by mass (solid content conversion)
・ Infrared absorber dispersion 5% by mass (solid content conversion)
・ 26% by mass of propylene glycol (Wako Pure Chemical Industries, Ltd.)
-Organic solvent represented by general formula (I) or (II) described in Table 1 Addition amount (% by mass) described in Table 1
・ Surfactant ・ Surfinol 440 (Nissin Chemical Industry Co., Ltd.) 0.5% by mass
・ Surfinol 465 (manufactured by Nissin Chemical Industry Co., Ltd.) 1.5% by mass
・ Silface SAG503 (manufactured by Nissin Chemical Industry Co., Ltd.) 0.05% by mass
・ Ion-exchanged water The remaining amount of materials is 100% by mass

(2) Evaluation test (dryness test)
Using the ink prepared in Example 1 to Example 8 and Comparative Examples 1 to 8, coated paper (manufactured by Oji Paper Co., Ltd., OK topcoat paper (basis weight ^{127g / cm 2, 73g / cm} 2) On the other hand, an image was formed as follows: In other words, after the prepared ink was discharged at 5 ml / cm ² to a 50 mm × 50 mm region, the irradiation energy was 1.6 J / cm ² . An infrared ray was irradiated with infrared rays having a wavelength of 820 nm to form an image.
After applying plain paper (Fuji Xerox Co., Ltd., C2 paper) to the surface of the obtained sample and rubbing the image surface for 2 cm with a pressure of 20 N applied vertically to the image. The density state of the image was visually observed to evaluate the drying property.

The dryness was evaluated according to the following criteria.
A: Image deterioration is not observed.
B: Slight wear deterioration is observed in a part of the image.
C: Peeling is observed in part of the image.
Of the dryness evaluations, A and B are evaluations having no problem in actual use.

(Infrared absorption maintenance test)
The inks produced in Examples 1 to 8 and Comparative Examples 1 to 8 were put in a sealed container and stored in a thermostatic bath at 60 ° C. for 2 weeks. Before and after storage, the infrared absorbance of the ink (absorption peak value observed at a wavelength of 810 nm to 830 nm) was measured with a spectrophotometer, and the ratio (%) of the absorbance after storage to the absorbance before storage was the absorbance maintenance rate. Calculated as

The evaluation of infrared absorption maintenance was performed according to the following criteria.
A: The maintenance ratio of absorbance is 90% or more B: The maintenance ratio of absorbance is 80% or more and less than 90% C: The maintenance ratio of absorbance is less than 80% Of the evaluation of infrared absorption maintenance, A and B are actually used It is an evaluation with no problem.

(3) Evaluation Results Table 1 shows the configurations and evaluation results of the inks of Examples 1 to 8, and Table 2 shows the configurations and evaluation results of the inks of Comparative Examples 1 to 8.

  The polyethylene glycol dimethyl ether 500 used as the water-soluble organic solvent in Example 5 is mainly composed of the compound represented by n = 10 in the general formula (I), and the compound represented by the general formula n = 10 ± 2. 90 mass% or more is included.

As shown in Table 1, an ink containing the compound represented by the general formula (I) or (II) as a water-soluble organic solvent in a range of 4% by mass to 14% by mass with respect to the total amount of the ink is dry. In addition, both of the evaluations of the absorption maintenance property were A or B, and it was confirmed that it was possible to achieve both the drying property by infrared irradiation and the stable infrared absorption performance.
On the other hand, as shown in Table 2, Comparative Examples 1 to 7 using compounds other than the general formulas (I) and (II) as the water-soluble organic solvent, and the general formula (I) as the water-soluble organic solvent In Comparative Example 8 containing more than 14% by mass of the compound represented by formula (C), the evaluation of at least one of drying property or absorption maintenance property was C.

  Further, Examples 1 to 6 having different types of compounds represented by the general formula (I) or the general formula (II) used as the water-soluble organic solvent are compared with each other. In Examples 2 to 4 using triethylene glycol monomethyl ether, tetraethylene glycol monomethyl ether, and tetraethylene glycol dimethyl ether represented by the general formula (I) as the water-soluble organic solvent, evaluation of drying property and absorption maintenance property was performed. Both were A, and it was confirmed that the drying property by infrared irradiation and the stable infrared absorption performance were better.

DESCRIPTION OF SYMBOLS 1 ... Recording device, 10 ... Image formation part, 11 ... Inkjet head, 20 ... Recording material supply part, 30 ... Ink cartridge, 50 ... Infrared irradiation apparatus, 70 ... Control part

Claims (11)

Containing a colorant, an aqueous solvent, an infrared absorber, and a water-soluble organic solvent having a boiling point higher than that of water,
The water-soluble organic solvent is an ink containing at least one compound represented by general formula (I) or general formula (II) in a range of 4% by mass to 14% by mass with respect to the total amount of the ink.
R ¹ — (O—CH ₂ —CH ₂ ) _n —O—R ² ... Formula (I)
(In general formula (I), n is an integer of 2 or more and 12 or less. When n = 2, R ¹ and R ² both represent an alkyl group, and when n = 3 to 12, at least one of R ¹ and R ² is An alkyl group, and the other represents a hydrogen atom or an alkyl group.)
R ³ — (O—CH ₂ —CH ₂ —CH ₂ ) ₂ —O—R ⁴ —General Formula (II)
(In general formula (II), R ³ and R ⁴ both represent an alkyl group.) The ink according to claim 1, wherein the infrared absorber contains a compound represented by the general formula (III) or the general formula (IV).

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

(In the general formula (IV), R ^e , R ^f , R ^g and R ^h each independently represents an alkyl group, and R ^e and R ^f , and R ^g and R ^h are bonded to each other to form a ring. You may do it.) In the infrared absorber, R ^a , R ^b , R ^c and R ^d in the general formula (III) or R ^e , R ^f , R ^g and R ^h in the general formula (IV) are t-butyl groups. The ink according to claim 2, wherein   The ink according to claim 2, wherein the infrared absorber is dispersed in a fine particle state together with a resin having an acid value with respect to the aqueous solvent and the water-soluble organic solvent. In the compound represented by the general formula (I) or the general formula (II), the alkyl group constituting R ¹ , R ² , R ³ and R ⁴ has 1 to 9 carbon atoms. The ink according to claim 1.   6. The ink according to claim 5, wherein the SP value of the compound represented by the general formula (I) or the general formula (II) is in a range of 17 or more and 23 or less.   6. The ink according to claim 5, wherein the water-soluble organic solvent contains at least one of triethylene glycol monomethyl ether, tetraethylene glycol monomethyl ether and tetraethylene glycol dimethyl ether represented by the general formula (I). .   The water-soluble organic solvent further includes another water-soluble organic solvent having a boiling point different from that of the compound represented by the general formula (I) or the general formula (II), and the general formula (I) or the general formula The ink according to claim 1, wherein the content of the compound represented by (II) and the other water-soluble organic solvent is 40% by mass or less based on the total amount of the ink. Adjusting the colorant dispersion in which the colorant is dispersed;
A step of preparing an infrared absorbent dispersion in which an infrared absorbent is dispersed;
Mixing the colorant dispersion, the infrared absorbent dispersion, an aqueous solvent, and a water-soluble organic solvent having a boiling point higher than that of water,
In the mixing step, as the water-soluble organic solvent, at least one compound represented by the general formula (I) or the general formula (II) is used as the colorant dispersion, the infrared absorbent dispersion, or the aqueous solvent. And a method of producing an ink, comprising mixing in a range of 4% by mass to 14% by mass with respect to the total amount of the water-soluble organic solvent.
R ¹ — (O—CH ₂ —CH ₂ ) _n —O—R ² ... Formula (I)
(In general formula (I), n is an integer of 2 or more and 12 or less. When n = 2, R ¹ and R ² both represent an alkyl group, and when n = 3 to 12, at least one of R ¹ and R ² is An alkyl group, and the other represents a hydrogen atom or an alkyl group.)
R ³ — (O—CH ₂ —CH ₂ —CH ₂ ) ₂ —O—R ⁴ —General Formula (II)
(In general formula (II), R ³ and R ⁴ both represent an alkyl group.) An ink storage unit for storing the ink according to any one of claims 1 to 8,
An ink jet head that discharges ink stored in the ink storage portion toward a recording medium;
A recording apparatus comprising: an infrared irradiation apparatus that irradiates an ink discharged onto a recording medium with an infrared ray having a central wavelength in a range of 750 mm to 900 mm.   The recording apparatus according to claim 10, wherein the ink jet head ejects ink to a coated paper on which a surface layer containing a filler or a binder resin is formed as a recording medium.

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