JP6644996B2 - Water-based ink for inkjet recording - Google Patents

Description

  The present invention relates to an aqueous ink for inkjet recording and a method for producing the aqueous ink.

  The ink jet recording system is a recording system in which ink droplets are directly ejected from a very fine nozzle onto a recording medium and adhered to obtain characters and images. This method has many advantages such as easy full color printing, low cost, use of plain paper as a recording medium, and non-contact with printed materials, making it ideal for consumer printing for general consumers. In recent years, it has recently begun to be applied to commercial printing and industrial printing fields.

However, in the ink jet recording system, due to the structure in which the ink passes through a fine discharge nozzle, for example, if a very small amount of impurities is present in the pigment, problems such as blockage of the discharge nozzle are likely to occur. As a method for removing such a trace amount of impurities, methods such as a centrifugal separation method, a filtration method, and an ion exchange method are known. Generally, various raw materials used in the production of aqueous inks for inkjet recording are purified and used by a known method before mixing them.
For example, a crystallization method is known as a method for removing impurities contained in dyes and pigments.

Patent Literature 1 discloses that a high-quality water-soluble phthalocyanine compound is substituted with a substituted phthalonitrile, a substituted 1,3-, for the purpose of reducing the content of an inorganic compound which is an impurity without using an ion exchange treatment device or the like. A method for producing a water-soluble phthalocyanine compound, comprising reacting one or more compounds selected from diiminoisoindoline and the like with a specific metal derivative, crystallizing the reaction mixture with a hydrophilic organic solvent, and crystallization. I have.
Patent Literature 2 discloses a pigment, a dispersant having an acid value larger than an amine value, a polymerizable compound, and a light-curable ink jet ink that is stable, can be ejected with good landing accuracy, and has excellent storage stability. There is disclosed an ultraviolet curable ink jet ink containing a polymerization initiator, in which cationic impurities, metal impurities, and the like are individually removed by a method such as crystallization, and the total amount of impurities is 500 ppm or less.
Patent Document 3 discloses that a dye is added to a yellow pigment without a chemical reaction in order to obtain an ink jet recording liquid having excellent dispersibility using a yellow pigment, good printability, and storage stability. There is disclosed an inkjet recording liquid containing a substance which is reversibly adsorbed at not less than 02 g / g and in which a nonionic surfactant and an anionic surfactant coexist.

JP 2005-75778 A JP 2005-200560 A JP-A-2004-27204

In Patent Documents 1 and 2, the raw materials are individually purified, and a simple method capable of removing impurities in one step at the time of producing an aqueous ink is not known.
Further, Patent Document 3 discloses that after removing organic impurities by crystallization or the like prior to use of a dye, the resultant is mixed with a pigment, water, or the like, and subjected to ultrasonic dispersion treatment to form an aqueous ink. Since the treatment is performed, an adverse effect on the performance of the aqueous ink is inevitable.
An object of the present invention is to provide a water-based ink for ink-jet recording having excellent ejection properties, and a method for producing the water-based ink.

The present inventors have found that, in aqueous ink for inkjet recording, when the liquid medium portion of the ink was measured by a high-performance liquid chromatograph equipped with an ultraviolet / visible detector having an absorption wavelength of 400 nm, C.I. I. Pigment Yellow 74 with respect to the area of the peak (A ₇₄ ). I. It was found that when the ratio of the total area (A _E74 ) of the peaks other than Pigment Yellow 74 was 1.4 or less, there was little nozzle chipping in the ink jet recorded matter.
That is, the present invention provides the following [1] and [2].
[1] C.I. I. Pigment Yellow 74, which is a water-based ink for ink-jet recording, and has a C.I. I. Pigment Yellow 74 with respect to the area of the peak (A ₇₄ ). I. An aqueous ink for inkjet recording, wherein the ratio (A _E74 / A ₇₄ ) of the total area (A _E74 ) of peaks other than Pigment Yellow 74 is 1.4 or less.
(Measurement method by liquid chromatography)
Ion-exchanged water was added to 4 g of the aqueous ink to make 200 g, 2 g of ethylene oxide 2 mol adduct of 2,7-dimethyl-4-octyne-4,5-diol was added, and after stirring for 24 hours, 2 g of the sample was collected. After centrifugation, 1.3 g of diethyl ether was added to collect the diethyl ether phase, and the diethyl ether was volatilized. 1.0 g of acetonitrile was added to obtain a sample, which was subjected to high-performance liquid chromatography equipped with an ultraviolet / visible detector. In the graph, an ODS column was used, column temperature: 40 ° C., eluent: acetonitrile / 10 mM ammonium formate buffer (pH: 3) = 80/20 (volume ratio), flow rate: 1.00 ml / min, detection wavelength: It is measured under the condition of 400 nm.
[2] The method for producing an aqueous ink for inkjet recording according to the above [1], comprising the following steps I to III.
Step I: water-insoluble polymer, organic solvent, C.I. I. After the mixture containing CI Pigment Yellow 74 and water was subjected to high-pressure dispersion treatment at a pressure of 60 MPa or more, the mixture was kept at 30 ° C. or less for 15 hours or more. I. Step of Obtaining a Dispersion of Water-Insoluble Polymer Particles Containing Pigment Yellow 74 Step II: Removing the Organic Solvent from the Dispersion Obtained in Step I I. Step of Obtaining an Aqueous Dispersion of Water-Insoluble Polymer Particles Containing Pigment Yellow 74 Step III: Combining the Water Dispersion Obtained in Step II with One or More Selected from Water and a Water-Soluble Organic Solvent

  ADVANTAGE OF THE INVENTION According to this invention, the aqueous ink for inkjet recording which is excellent in discharge property, and the manufacturing method of this aqueous ink can be provided.

FIG. 4 is a view showing a measurement result by a liquid chromatograph of Example 1. FIG. 9 is a view showing a measurement result by a liquid chromatograph of Example 2. FIG. 9 is a view showing a result of measurement by a liquid chromatograph of Comparative Example 3. FIG. 9 is a view showing a measurement result by liquid chromatography of Comparative Example 1. FIG. 8 is a view showing a result of measurement by liquid chromatography of Comparative Example 2.

[Aqueous ink for inkjet recording]
The water-based ink for ink-jet recording of the present invention includes C.I. I. Pigment Yellow 74 (hereinafter, also referred to as “PY74” or simply “pigment”), which is based on the area of the peak (A ₇₄ ) of PY74 measured by the following liquid chromatography method. This is an aqueous ink jet recording ink having a ratio (A _E74 / A ₇₄ ) of the total area (A _E74 ) of peaks other than PY74 to 1.4 or less.
(Measurement method by liquid chromatography)
Ion-exchanged water was added to 4 g of the aqueous ink to make 200 g, 2 g of ethylene oxide 2 mol adduct of 2,7-dimethyl-4-octyne-4,5-diol was added, and after stirring for 24 hours, 2 g of the sample was collected. After centrifugation, 1.3 g of diethyl ether was added to collect the diethyl ether phase, and the diethyl ether was volatilized. 1.0 g of acetonitrile was added to obtain a sample, which was subjected to high-performance liquid chromatography equipped with an ultraviolet / visible detector. In the graph, an ODS column was used, column temperature: 40 ° C., eluent: acetonitrile / 10 mM ammonium formate buffer (pH: 3) = 80/20 (volume ratio), flow rate: 1.00 ml / min, detection wavelength: It is measured under the condition of 400 nm.

<Measurement by liquid chromatography>
In the present invention, the measuring method by liquid chromatography is as described above.
PY74 absorbs ultraviolet light and visible light in the range of 350 nm to 500 nm to make human eyes recognize yellow. Here, an ultraviolet-visible detector is a device that irradiates a specimen with ultraviolet light, visible light, or near-infrared light, and measures the absorbance to clarify the presence of a substance, using an ultraviolet-visible light detector. When PY74 is analyzed by using the method, the wavelength of the detector is set to 400 nm.
In the analysis by high-performance liquid chromatography, ghost peaks derived from electric noise, dissolved gas in the sample, and the like appear, but these ghost peaks are identified by a known method, and are not included in peaks other than the peak corresponding to PY74. . Under the measurement conditions according to the present invention, a ghost peak is detected at a retention time of about 2.5 minutes when the time of injecting the sample is set to 0 minute. Therefore, in the measurement method using a liquid chromatograph according to the present invention, the time when the sample is injected is set to 0 minute, and the peak whose retention time is detected from 2.7 minutes to 10.0 minutes is targeted. The peak of PY74 is detected at around 7.4 minutes.
Since the peak detected by the measurement method according to the present invention has an absorption around 400 nm, it is presumed to have a chemical structure similar to that of PY74, but it is difficult to identify the structure.

In the measurement method according to the present invention, the measurement is performed in a state containing a poorly water-soluble organic solvent from the viewpoint of transferring organic impurities present in the aqueous ink to the organic solvent phase and suppressing a change in mass during the measurement process. As the poorly water-soluble organic solvent, a 2-mol ethylene oxide adduct of 2,7-dimethyl-4-octyne-4,5-diol is used.
When the above-mentioned poorly water-soluble organic solvent is used, the polymer dispersant and the surfactant are preferentially transferred into the poorly water-soluble organic solvent, which may adversely affect the measurement. To prevent this, 4 g of the aqueous ink is diluted with water to 200 g before adding the poorly water-soluble organic solvent.
Before starting the measurement, a liquid portion and a solid portion made of PY74, a polymer dispersant, or the like are separated by centrifugation. The intensity of the centrifugation is preferably 10,000 G hours or more, preferably 100,000 G hours or more, and 1,000,000 G hours or less, preferably 500,000 G hours or less, from the viewpoint of efficient measurement. .
In addition, from the viewpoint of suppressing the decomposition of the analysis target substance and improving the accuracy, after adding a water-insoluble and volatile organic solvent, the organic solvent is volatilized at normal temperature and normal pressure before measurement.
Diethyl ether is used as the water-insoluble and volatile organic compound.

ADVANTAGE OF THE INVENTION According to this invention, the aqueous ink for inkjet recording which is excellent in discharge property can be provided. Although the reason is not always clear, it is considered as follows.
Commercially available PY74 used for aqueous inks for inkjet recording generally contains various organic compounds by-produced during the production thereof as impurities. Examples of the by-produced organic compound include a diazo compound by-produced during a diazo coupling reaction in the production of PY74, and a compound which has undergone a nucleophilic reaction with the diazo compound. More specifically, in a method of diazotizing 4-nitro-o-anisidine and performing a coupling reaction with acetoacetic acid-o-anisidide, 2-[(2-methoxy-4-nitrophenyl) azo] -N- ( Organic compounds such as 2-methoxyphenyl) ethanamide are by-produced as impurities. Other impurities include pigment derivatives added when preparing PY74. If the aqueous ink contains a large amount of impurities resulting from the production of such a pigment, it is considered that the impurities cause various problems such as ejection failure during inkjet recording. By using the index of the amount of impurities based on the peak detected by the liquid chromatographic measurement method according to the present invention, it is possible to obtain an aqueous inkjet ink having excellent ejection properties.

Here, impurities (organic compounds) other than PY74 are separated and removed by high-pressure dispersion treatment or the like in the presence of an organic solvent, and when the amount of PY74 is used as a reference, the amount of the organic compounds other than PY74 as an impurity is a specific ratio. When the water content is below, it is considered that the water-based ink becomes excellent in ejection property. More specifically, the ratio (A _E74 / A ₇₄ ) of the total area (A _E74 ) of the peaks other than PY _{74 to} the area (A ₇₄ ) of the PY ₇₄ peak measured by the method using liquid chromatography is 1.4 or less. When, the aqueous ink is considered to be excellent in ejection property.
The ratio of the peak areas (A _E74 / A ₇₄ ) is preferably 1.3 or less, more preferably 1.2 or less, from the viewpoint of eliminating defects such as clogging of the inkjet discharge nozzle and improving dischargeability. It is still more preferably 1.1 or less, and from the viewpoint of maintaining vivid color and suppressing blemishes, preferably 0.1 or more, more preferably 0.2 or more, and still more preferably 0.4 or more. Even more preferably, it is 0.6 or more.
As means for reducing the peak area ratio (A _E74 / A ₇₄ ), a method of selecting PY74 from a lot containing less impurities other than PY74, a method of separating and removing impurities other than PY74 by high-pressure dispersion treatment in the presence of an organic solvent And the like.

<C. I. Pigment Yellow 74>
PY74 used in the present invention is a kind of monoazo pigment, and is a name included in the color index. Similarly, the color index number set by the color index is assigned CI11741.
PY74 is a compound represented by the following formula (I).

  In the formula (I), a wavy line indicates that the geometric isomer of the adjacent double bond is at least one selected from E-form and Z-form. The compound represented by the formula (I) is preferably 2-[(2-methoxy-4-nitrophenyl) azo] -N- (2-methoxyphenyl) -3-oxobutanamide.

(Manufacturing method of PY74)
As a method for producing PY74, for example, a production method (A) in which 4-nitro-o-anisidine is diazotized and subjected to a coupling reaction with acetoacetic acid-o-anisidide.
In this coupling reaction, impurities such as 2-[(2-methoxy-4-nitrophenyl) azo] -N- (2-methoxyphenyl) ethanamide are by-produced.
The production method (A) preferably has the following steps (1) to (3).
Step (1): Step of obtaining product A by diazotization reaction of 4-nitro-o-anisidine Step (2): After mixing acetoacetate-o-anisidide, sodium hydroxide and water, acetic acid is added, Thereafter, a step of obtaining a product B by further adding sodium acetate Step (3): mixing the product A obtained in the step (1) and the product B obtained in the step (2), Step of performing a coupling reaction

The diazotization reaction in the step (1) can be performed, for example, by reacting 4-nitro-o-anisidine with nitrous acid or a salt thereof under acidic conditions.
In step (2), the amount of by-products can be adjusted to some extent by adjusting the amount of acetic acid and sodium acetate used, but it is difficult to sufficiently reduce the amount of by-products.
The step (3) is a step of mixing the product A obtained in the step (1) and the product B obtained in the step (2) and performing a coupling reaction, and preferably the step (2). Is added to the product B obtained in the step (1).
The temperature of the coupling reaction is preferably 0 ° C. or higher, and is preferably 25 ° C. or lower, more preferably 20 ° C. or lower, still more preferably 15 ° C. or lower, and even more preferably 10 ° C. or lower.
After the coupling reaction in the step (3), post-treatment such as adjusting the crystal, particle shape, particle diameter, and the like of the product to a desired range can be performed, if necessary.

In the present invention, PY74 is preferably dispersed in an aqueous medium using a polymer dispersant from the viewpoint of improving storage stability and incorporation into ink. Here, the polymer dispersant includes a water-soluble polymer or a water-insoluble polymer. PY74 is in the form of (i) PY74 dispersed with a water-soluble polymer, (ii) water-insoluble polymer particles containing PY74, or the like. Used. Among them, it is preferable to use in the form of (ii) water-insoluble polymer particles containing PY74 (hereinafter, also referred to as “pigment-containing polymer particles”) from the viewpoint of scratch resistance.
The “aqueous medium” refers to a medium in which water accounts for the largest proportion of the medium in which the pigment is dispersed.

(I) PY74 dispersed with a water-soluble polymer
PY74 dispersed with a water-soluble polymer is an aqueous dispersion in which PY74 is dispersed with a water-soluble polymer such as a copolymer having a carboxyl group containing acrylic acid or methacrylic acid. Commercial products of the water-soluble polymer used include JONCRYL67, JONCRYL678, JONCRYL683, JONCRYL60J (all manufactured by BASF Japan Ltd.) and the like.
PY74 dispersed in a water-soluble polymer is obtained by adding PY74 to an aqueous medium in which a water-soluble polymer is dissolved, and dispersing PY74 by applying shear stress with a kneader, a high-pressure homogenizer, a media type disperser, or the like. It is preferably used as a dispersion.

(Ii) PY74-Containing Water-Insoluble Polymer Particles The form of PY74-containing water-insoluble polymer particles (pigment-containing polymer particles) is not particularly limited, as long as the particles are formed by at least PY74 and the water-insoluble polymer. For example, a particle form in which PY74 is included in the water-insoluble polymer, a particle form in which PY74 is uniformly dispersed in the water-insoluble polymer, a particle form in which PY74 is exposed on the surface of the water-insoluble polymer particles, and Mixture forms are also included.

(Water-insoluble polymer: polymer dispersant)
The water-insoluble polymer constituting the pigment-containing polymer particles preferably has a function as a dispersant for dispersing PY74 in an aqueous medium and stably maintaining the dispersion, and a function as a fixing agent for the recording medium.
The “water-insoluble” of the water-insoluble polymer means that the water-insoluble polymer aqueous dispersion is not transparent. Even if the aqueous dispersion of the water-insoluble polymer looks transparent visually, it is judged to be water-insoluble if the Tyndall phenomenon is observed by observation with laser light or ordinary light. In the case where the polymer is ionic, the determination of “water-insoluble” is made in the case of an anionic polymer in a state where the anionic group of the polymer is 100% neutralized with sodium hydroxide, and in the case of a cationic polymer, The reaction is carried out in a state where the acidic groups are 100% neutralized with hydrochloric acid.
The water-insoluble polymer used in the present invention is preferably a polymer having a salt-forming group (anionic group or cationic group) in the polymer chain from the viewpoint of improving dispersibility. Examples of the salt-forming group include an anionic group such as a carboxy group, a sulfonic group, and a phosphoric group, and a cationic group such as an amino group and an ammonium group.
It is preferable that the polymer dispersant which is a water-insoluble polymer has a salt-forming group, and at least a part of the salt-forming group is neutralized with a basic compound.

Examples of the water-insoluble polymer include polyester, polyurethane, and vinyl polymers. Alternatively, a commercially available dispersion of water-insoluble polymer particles can be used.
As a commercially available dispersion of water-insoluble polymer particles, a dispersion of particles composed of an acrylic resin, a urethane resin, a styrene-butadiene resin, a styrene-acryl resin, and a vinyl chloride resin is preferable. Specific examples include acrylic resins such as Neocryl A1127 (manufactured by DSM NeoResins, anionic self-crosslinking water-based acrylic resin), JONCRYL390 (manufactured by BASF Japan), WBR-2018, WBR-2000U (manufactured by Taisei Fine Chemical Co., Ltd.) And styrene-butadiene resins such as SR-100 and SR-102 (all manufactured by Nippon A & L Co., Ltd.); styrene-acrylic resins such as JONCRYL7100, JONCRYL734 and JONCRYL538 (all manufactured by BASF Japan Co., Ltd.), and And vinyl chloride resins such as VinyBlan 701 (manufactured by Nissin Chemical Industry Co., Ltd.).
The water-insoluble polymer is preferably a water-insoluble vinyl polymer obtained by addition polymerization of at least one vinyl monomer selected from a vinyl compound, a vinylidene compound, and a vinylene compound, from the viewpoint of improving the storage stability of the ink.

Examples of the water-insoluble vinyl polymer include (a) a structural unit derived from an ionic monomer (hereinafter also referred to as “component (a)”) and (b) a structural unit derived from a macromonomer (hereinafter also referred to as “(b) component”). And a vinyl-based polymer containing a (c) component, and a structural unit derived from (c) a hydrophobic monomer (hereinafter also referred to as “component (c)”) and a nonionic monomer (d) (hereinafter also referred to as “(d) component”). ) Are preferred.
The water-insoluble polymer is obtained by, for example, addition polymerization of (a) an ionic monomer, (b) a macromonomer, and, if necessary, (c) a hydrophobic monomer and (d) a nonionic monomer by a known method. be able to.

<(A) ionic monomer>
(A) The ionic monomer can be used as a monomer component from the viewpoint of improving the storage stability of the aqueous ink.
(A) Examples of the ionic monomer include an anionic monomer and a cationic monomer, and an anionic monomer is preferable from the viewpoints of storage stability and dischargeability of the aqueous ink. Examples of the anionic monomer include a carboxylic acid monomer, a sulfonic acid monomer, and a phosphoric acid monomer, and a carboxylic acid monomer having a carboxy group is preferable.
Examples of the carboxylic acid monomer include acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid, citraconic acid, 2-methacryloyloxymethyl succinic acid and the like, and one type selected from acrylic acid and methacrylic acid The above is more preferred, and methacrylic acid is still more preferred.

<(B) Macromonomer>
(B) The macromonomer is a compound having a polymerizable functional group at one end and having a number average molecular weight of 500 to 100,000, and is preferably used from the viewpoint of improving the storage stability of the aqueous ink. As the polymerizable functional group present at one terminal, an acryloyloxy group or a methacryloyloxy group is preferable, and a methacryloyloxy group is more preferable.
(B) The number average molecular weight of the macromonomer is preferably 1,000 or more and 10,000 or less. The number average molecular weight is measured by gel permeation chromatography using chloroform containing 1 mmol / L dodecyldimethylamine as a solvent, and using polystyrene as a standard substance.
(B) As the macromonomer, from the viewpoint of improving the storage stability of the aqueous ink, an aromatic group-containing monomer macromonomer and a silicone macromonomer are preferable, and an aromatic group-containing monomer macromonomer is more preferable.
Examples of the aromatic group-containing monomer constituting the aromatic group-containing monomer-based macromonomer include the aromatic group-containing monomers described in (c) Hydrophobic monomer below, and styrene and benzyl (meth) acrylate are preferable. Is more preferred.
Specific examples of the styrene-based macromonomer include AS-6 (S), AN-6 (S), HS-6 (S) (trade name of Toagosei Co., Ltd.) and the like.
Examples of the silicone-based macromonomer include an organopolysiloxane having a polymerizable functional group at one end.

<(C) hydrophobic monomer>
From the viewpoint of improving the storage stability of the aqueous ink, it is preferable to further use (c) a hydrophobic monomer as a monomer component in the water-insoluble polymer. Examples of the hydrophobic monomer include an alkyl (meth) acrylate and an aromatic group-containing monomer.
As the alkyl (meth) acrylate, those having an alkyl group having 1 to 22 carbon atoms, preferably 6 to 18 carbon atoms are preferable. For example, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate Acrylate, butyl (meth) acrylate, amyl (meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, octyl (meth) acrylate, decyl (meth) acrylate, dodecyl (meth) acrylate, stearyl (meth) Acrylate, isopropyl (meth) acrylate, isobutyl (meth) acrylate, tertiary butyl (meth) acrylate, isoamyl (meth) acrylate, isooctyl (meth) acrylate, isodecyl (meth) acrylate , Isododecyl (meth) acrylate, isostearyl (meth) acrylate.
In addition, "(meth) acrylate" means one or more types selected from acrylate and methacrylate. “(Meta)” in the following is also synonymous.

As the aromatic group-containing monomer, a vinyl monomer having an aromatic group having 6 to 22 carbon atoms which may have a substituent containing a hetero atom is preferable, and a styrene-based monomer and an aromatic group-containing (meth) acrylate Is more preferred.
As the styrene-based monomer, styrene, 2-methylstyrene, vinyltoluene, and divinylbenzene are preferable, and styrene and 2-methylstyrene are more preferable.
As the aromatic group-containing (meth) acrylate, phenyl (meth) acrylate, benzyl (meth) acrylate, phenoxyethyl (meth) acrylate and the like are preferable, and benzyl (meth) acrylate is more preferable.
(C) As the hydrophobic monomer, two or more of the above monomers may be used, or a styrene monomer and an aromatic group-containing (meth) acrylate may be used in combination.

<(D) Nonionic monomer>
From the viewpoint of improving the storage stability of the aqueous ink, it is preferable to further use (d) a nonionic monomer (component (d)) as the monomer component in the water-insoluble polymer.
As the component (d), 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, and polypropylene glycol (n = 2 to 30, where n represents the average number of moles of the oxyalkylene group, the same applies hereinafter) Polyalkylene glycol (meth) acrylates such as (meth) acrylate, polyethylene glycol (n = 2-30) (meth) acrylate, methoxy polyethylene glycol (n = 1-30) (meth) acrylate, polyethylene glycol methacrylate 2-ethylhexyl ether And phenoxy (copolymerization of ethylene glycol and propylene glycol) (n = 1 to 30, ethylene glycol therein: n = 1 to 29) (meth) acrylate. I can do it. Among them, polypropylene glycol (n = 2 to 30) (meth) acrylate and polyethylene glycol (n = 2 to 6) methacrylate 2-ethylhexyl ether are more preferable.

Specific examples of the commercially available component (d) include NK esters M-20G, 40G, 90G, 230G, EH-4E and the like (manufactured by Shin-Nakamura Chemical Co., Ltd.), Blemmer PE-90 , 200, 350, etc., PME-100, 200, 400, etc., PP-500, 800, 1000, etc., AP-150, 400, 550, etc., 50 PEP-300, 50 POEP-800B, 43 PAPE -600B (manufactured by NOF CORPORATION). Among these, NK ester EH-4E (polyethylene glycol [n = 4] methacrylate 2-ethylhexyl ether) is preferable, particularly from the viewpoint of print density. The above components (a) to (d) may be used alone or in combination of two or more. These can be used in combination.

(Content of each component or constituent unit in the monomer mixture or the water-insoluble polymer)
It is derived from the content of the above components (a) to (d) in the monomer mixture (content as an unneutralized amount) or the components (a) to (d) in the water insoluble polymer during production of the water-insoluble polymer. The content of the structural unit is as follows from the viewpoint of improving the dispersion stability of the pigment-containing polymer particles in the aqueous ink.
The content of the component (a) is preferably at least 3% by mass, more preferably at least 5% by mass, even more preferably at least 7% by mass, and preferably at most 35% by mass, more preferably at most 30% by mass. , More preferably 25% by mass or less.
The content of the component (b) is preferably 3% by mass or more, more preferably 4% by mass or more, still more preferably 5% by mass or more, and preferably 30% by mass or less, more preferably 25% by mass or less. , More preferably 20% by mass or less.
When the component (c) is contained, the content of the component (c) is preferably at least 10% by mass, more preferably at least 20% by mass, even more preferably at least 30% by mass, and preferably at least 60% by mass. Or less, more preferably 55% by mass or less, further preferably 50% by mass or less.
When component (d) is contained, the content of component (d) is preferably at least 10% by mass, more preferably at least 15% by mass, even more preferably at least 20% by mass, and preferably at least 50% by mass. Or less, more preferably 45% by mass or less, still more preferably 40% by mass or less.
Further, the mass ratio of [(a) component / [(b) component + (c) component]] is preferably 0.01 or more, more preferably 0.05 or more, and still more preferably 0.10 or more, And it is preferably 1.0 or less, more preferably 0.80 or less, and still more preferably 0.60 or less.

(Production of water-insoluble polymer)
The water-insoluble polymer is produced by copolymerizing the monomer mixture by a known polymerization method such as a bulk polymerization method, a solution polymerization method, a suspension polymerization method, and an emulsion polymerization method. Among these polymerization methods, a solution polymerization method is preferable.
The solvent used in the solution polymerization method is not particularly limited, but a polar organic solvent is preferred. When the polar organic solvent has water miscibility, it can be used by mixing with water. Examples of the polar organic solvent include aliphatic alcohols having 1 to 3 carbon atoms, ketones, ethers, and esters having 3 to 5 carbon atoms. Among them, aliphatic alcohols, ketones, or a mixed solvent thereof with water is preferable, and methyl ethyl ketone or a mixed solvent thereof with water is preferable.
At the time of polymerization, a polymerization initiator or a polymerization chain transfer agent can be used.
Examples of the polymerization initiator include azo compounds such as 2,2′-azobisisobutyronitrile and 2,2′-azobis (2,4-dimethylvaleronitrile), t-butylperoxyoctoate, and benzoyl peroxide. And a known chain transfer agent such as mercaptans such as octyl mercaptan and 2-mercaptoethanol, and thiuram disulfides.
Further, there is no limitation on the mode of the chain of the polymerization monomers, and any polymerization mode such as random, block, or graft may be used.

Preferred polymerization conditions vary depending on the type of polymerization initiator, monomer, solvent used and the like, but usually the polymerization temperature is preferably 30 ° C or higher, more preferably 50 ° C or higher, and preferably 95 ° C or lower, 80 ° C. or less. The polymerization time is preferably at least 1 hour, more preferably at least 2 hours, and preferably at most 20 hours, more preferably at most 10 hours. The polymerization atmosphere is preferably a nitrogen gas atmosphere or an inert gas atmosphere such as argon.
After the completion of the polymerization reaction, the produced polymer can be isolated from the reaction solution by a known method such as reprecipitation or solvent evaporation.
The weight average molecular weight of the water-insoluble polymer is preferably 6,000 or more, more preferably 8,000 or more, and still more preferably 10,000 or more, from the viewpoint of the adsorptivity to the pigment and the dispersion stability. Preferably it is 200,000 or less, more preferably 100,000 or less, more preferably 80,000 or less.
The measurement of the weight average molecular weight can be performed by the method described in Examples.

(Production of pigment-containing polymer particles)
The water-insoluble polymer particles (pigment-containing polymer particles) containing PY74 can be efficiently produced as a water dispersion by a method having the following steps I and II.
Step I: A mixture containing a water-insoluble polymer, an organic solvent, PY74, and water (hereinafter, also referred to as a “pigment mixture”) is subjected to a high-pressure dispersion treatment at a pressure of 60 MPa or more, and then kept at 30 ° C. or less for 15 hours or more. Step of Obtaining a Dispersion of Pigment-Containing Polymer Particles Step II: Removing the organic solvent from the dispersion obtained in Step I to obtain an aqueous dispersion of PY74-containing water-insoluble polymer particles (hereinafter referred to as “pigment aqueous dispersion”). Process to obtain the body)

(Step I)
In Step I, first, the water-insoluble polymer is dissolved in an organic solvent, and then PY74, water, and, if necessary, a neutralizing agent, a surfactant, and the like are added to the obtained organic solvent solution, mixed, and mixed with water. A method for obtaining an oil-type dispersion is preferred. The order of adding the water-insoluble polymer to the organic solvent solution is not limited, but it is preferable to add water, the neutralizing agent, and PY74 in this order.
There is no limitation on the organic solvent in which the water-insoluble polymer is dissolved, but aliphatic alcohols having 1 to 4 carbon atoms, ketones having 3 to 8 carbon atoms, ethyl ether, propyl ether, butyl ether, ethers such as tetrahydrofuran, methyl acetate, methyl acetate, Esters such as ethyl acetate are exemplified. Among them, ketones having 4 to 6 carbon atoms are more preferable from the viewpoints of wettability to PY74, solubility of the water-insoluble polymer, and adsorptivity of the water-insoluble polymer to PY74, and methyl ethyl ketone and methyl isobutyl ketone are more preferable. Preferably, methyl ethyl ketone is even more preferred. When the water-insoluble polymer is synthesized by a solution polymerization method, the solvent used in the polymerization may be used as it is.

(Neutralization)
When neutralizing at least a part of a salt-forming group, for example, a carboxy group of the water-insoluble polymer, the pH is preferably adjusted to 7 or more and 11 or less.
As the neutralizing agent, an alkali metal hydroxide is used from the viewpoint of storage stability and dischargeability of the obtained aqueous ink. As the alkali metal hydroxide, sodium hydroxide and potassium hydroxide are preferable. Further, the water-insoluble polymer may be neutralized in advance.
The neutralizing agent is preferably used as a neutralizing agent aqueous solution from the viewpoint of sufficiently and uniformly promoting neutralization. In view of the above, the concentration of the neutralizing agent aqueous solution is preferably 3% by mass or more, more preferably 10% by mass or more, still more preferably 15% by mass or more, and preferably 30% by mass or less, and 25% by mass or less. More preferred.
The degree of neutralization of the carboxy group of the water-insoluble polymer is preferably 30 mol% or more, more preferably 40 mol% or more, and still more preferably 50 mol% or more, from the viewpoint of storage stability and dischargeability of the obtained aqueous ink. And preferably at most 300 mol%, more preferably at most 200 mol%, even more preferably at most 150 mol%.
Here, the degree of neutralization is a value obtained by dividing the molar equivalent number of the alkali metal hydroxide by the molar equivalent number of the carboxy group of the water-insoluble polymer. Originally, the degree of neutralization does not exceed 100 mol%, but in the present invention, since it is calculated from the amount of the neutralizing agent used, when the neutralizing agent is used in excess, it exceeds 100 mol%.

(Dispersion treatment of pigment mixture)
In step I, the pigment mixture is subjected to a dispersion treatment to obtain a dispersion of pigment-containing polymer particles. There is no particular limitation on the dispersion method for obtaining the dispersion. Although it is possible to atomize the average particle size of the PY74 particles only to the desired particle size by the main dispersion alone, preferably after pre-dispersing the pigment mixture, the main dispersion is further performed by applying a strong shear stress, It is preferable to control the average particle size of the PY74 particles to a desired particle size.
The temperature in the preliminary dispersion in Step I is preferably 0 ° C. or higher, and is preferably 40 ° C. or lower, more preferably 30 ° C. or lower, further preferably 25 ° C. or lower, and the dispersion time is preferably 0.5 hour. The above is more preferably 0.8 hours or more, and preferably 30 hours or less, more preferably 10 hours or less, and further preferably 5 hours or less.
When the pigment mixture is pre-dispersed, a commonly used mixing and stirring device such as an anchor blade and a disper blade can be used, and among them, a high-speed stirring and mixing device is preferable.

Examples of means for applying the shear stress of the dispersion include kneading machines such as a roll mill and a kneader, a high-pressure homogenizer such as a microfluidizer (manufactured by Microfluidic), an ultimateizer (manufactured by Sugino Machine Co., Ltd.), a paint shaker, and a bead mill. Media type dispersing machines can be mentioned. Examples of commercially available media type dispersers include Ultra Apex Mill (manufactured by Kotobuki Industries Co., Ltd.) and Picomill (manufactured by Asada Iron Works Co., Ltd.). These devices can also be used in combination. Among these, it is preferable to use a high-pressure homogenizer from the viewpoint of reducing the particle size of PY74. In this case, the PY 74 can be controlled to have a desired particle size by controlling the processing pressure and the number of passes.
The treatment pressure is preferably 60 MPa or more, more preferably 100 MPa or more, further preferably 130 MPa or more, and preferably 200 MPa or less, more preferably 180 MPa or less from the viewpoint of productivity and economy.
The number of passes is preferably 3 or more, more preferably 10 or more, and is preferably 30 or less, more preferably 25 or less.

In the present invention, a mixture containing a water-insoluble polymer, an organic solvent, PY74, and water is mixed at a temperature of 30 ° C. or lower from the start of the first high-pressure dispersion treatment in Step I to before the organic solvent is removed in Step II described below. Hold for more than an hour.
By holding for 15 hours or more in the presence of the organic solvent, peak components other than PY74 are extracted into the organic solvent, and, for example, by removing the peak components other than PY74 by an operation such as filtering a solid content. Conceivable.
In the present invention, the holding time at 30 ° C. or less after the high pressure dispersion treatment is the time kept at 30 ° C. or less from the start of the first high pressure dispersion treatment in Step I to before removing the organic solvent in Step II. Sum up. The holding time may be set collectively after the end of the high-pressure dispersion, or a holding operation may be set a plurality of times during a plurality of high-pressure dispersions.
From the viewpoint of removing peak components other than PY74, the holding temperature is preferably 10 ° C or higher, more preferably 15 ° C or higher, and preferably 25 ° C or lower.
The holding time is preferably 20 hours or more, from the viewpoint of removing peak components other than PY74, and preferably 180 hours or less, more preferably 100 hours, from the viewpoint of vivid coloration and suppression of blemishes. It is as follows.
At the time of holding, stirring is preferable from the viewpoint of removing peak components other than PY74. The rotation speed of the stirring is preferably 12 rotations / minute or more, and preferably 120 rotations / minute or less.

(Step II)
In Step II, an aqueous dispersion of pigment-containing polymer particles (pigment aqueous dispersion) can be obtained by removing the organic solvent from the dispersion obtained in Step I. It is preferable that the organic solvent in the obtained pigment aqueous dispersion is substantially removed.
Examples of the method of removing the organic solvent include a method of distilling the organic solvent under reduced pressure conditions, and a method of filtering solids and redispersing them in water.
From the viewpoint of removing peak components other than PY74 from the pigment aqueous dispersion, the pigment aqueous dispersion obtained by distilling off the organic solvent is preferably further filtered to re-disperse solids in water.

The concentration of the non-volatile component (solid content) of the obtained aqueous pigment dispersion is preferably 10% by mass or more from the viewpoint of improving the dispersion stability of the aqueous pigment dispersion and facilitating the preparation of the aqueous ink. It is preferably at least 15% by mass, more preferably at most 30% by mass, more preferably at most 25% by mass.
The solid content of the aqueous pigment dispersion is measured by the method described in Examples.
The average particle diameter of the pigment-containing polymer particles in the pigment aqueous dispersion is preferably 50 nm or more, more preferably 60 nm or more, and still more preferably 70 nm or more, from the viewpoint of reducing coarse particles and improving the ejection stability of the aqueous ink. And preferably 200 nm or less, more preferably 160 nm or less, and still more preferably 150 nm or less.
The average particle size of the pigment-containing polymer particles is measured by the method described in Examples.
Further, the average particle size of the pigment-containing polymer particles in the aqueous ink is preferably such that swelling and shrinkage of the particles and aggregation between the particles do not occur, and more preferably the same as the average particle size in the pigment aqueous dispersion. . The preferred embodiment of the average particle size of the pigment-containing polymer particles in the aqueous ink is the same as the preferred embodiment of the average particle size in the aqueous pigment dispersion.
In the present invention, from the viewpoint of improving the water resistance, storage stability, ejection properties, and the like of the obtained aqueous ink, a part of the salt-forming group of the water-insoluble polymer constituting the pigment-containing polymer particles is converted into a water-insoluble polyfunctional epoxy compound. It is also preferred that the surface layer of the pigment-containing polymer particles is crosslinked to form a crosslinked structure by reacting with a crosslinking agent such as

[Production method of aqueous ink for inkjet recording]
The aqueous dispersion of the water-insoluble polymer particles containing PY74 (pigment aqueous dispersion) obtained by the method having the above-mentioned steps I and II can be used as it is as an aqueous ink. It is preferable to produce an aqueous ink by the method used.
Step III: A step of mixing one or more selected from water and a water-soluble organic solvent with the aqueous dispersion obtained in Step II. In the aqueous ink production method of the present invention, the concentration of the aqueous ink is adjusted, From the viewpoint of improving the properties, it is preferable to mix at least water.

(Water-soluble organic solvent)
“Water-soluble” of a water-soluble organic solvent means a property that can be mixed with water at an arbitrary ratio.
As the water-soluble organic solvent, those having a boiling point of 100 ° C. or more and 270 ° C. or less are preferably used. When a plurality of organic solvents having different boiling points are used, the weighted average of the boiling points of the organic solvents is 100 ° C. or more and 270 ° C. It is more preferable to use in a range of not more than ° C.
The weighted average boiling point of the water-soluble organic solvent is more preferably 150 ° C. or higher, still more preferably 180 ° C. or higher, and further preferably 260 ° C. or lower, more preferably 255 ° C. or less.
Examples of the water-soluble organic solvent include polyhydric alcohols, polyhydric alcohol alkyl ethers, nitrogen-containing heterocyclic compounds, amides, amines, and sulfur-containing compounds.
Examples of the polyhydric alcohol include ethylene glycol, diethylene glycol, polyethylene glycol having a molecular weight of 200 to 600, propylene glycol, dipropylene glycol, polypropylene glycol having a molecular weight of 300 to 1200, 1,2-propanediol, 1,3-propanediol, 2-butanediol, 1,3-butanediol, 1,4-butanediol, 3-methyl-1,3-butanediol, 1,2-pentanediol, 1,5-pentanediol, 1,2-hexanediol 1,6-hexanediol, 2-methyl-2,4-pentanediol, 1,2,6-hexanetriol, 1,2,4-butanetriol, 1,2,3-butanetriol, trimethylolpropane, Petriol and the like.
Among these, 1,2-hexanediol (boiling point: 224 ° C.), trimethylolpropane (boiling point: 160 ° C.), polyethylene glycol having a molecular weight of 200 to 600 (boiling point: 250 C) and diethylene glycol (boiling point: 244 ° C).
A water-soluble organic solvent having a boiling point of more than 270 ° C. such as pentaerythritol (boiling point 276 ° C.), triethylene glycol (boiling point 287 ° C.), tripropylene glycol (boiling point 273 ° C.), glycerin (boiling point 290 ° C.) It can be used in combination with a compound having a temperature lower than 260 ° C.

Examples of the polyhydric alcohol alkyl ether include ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monoisopropyl ether, diethylene glycol monobutyl ether, triethylene glycol monomethyl ether, triethylene glycol monoisobutyl ether, Examples thereof include tetraethylene glycol monomethyl ether, propylene glycol monoethyl ether, dipropylene glycol monobutyl ether, tripropylene glycol monomethyl ether, and tripropylene glycol monobutyl ether. Further, triethylene glycol monobutyl ether (boiling point: 276 ° C.) or the like can be used in combination with a water-soluble organic solvent having a boiling point of less than 270 ° C. Among these, polyethylene glycol monoalkyl ethers such as diethylene glycol monoisopropyl ether are preferred from the viewpoint of reducing the amount of impurities and improving the dischargeability.
Among these, one or more compounds selected from polyhydric alcohols and polyhydric alcohol alkyl ethers are preferable, and a combination use of one or more polyhydric alcohols and one or more polyhydric alcohol alkyl ethers is more preferable.

In the method for producing an aqueous ink for ink-jet recording of the present invention, if necessary, a surfactant for adjusting the surface tension, a penetrant for controlling the wetting spread and the permeability to the print medium, which is usually used for the aqueous ink, Add various additives such as humectants, wetting agents, dispersants, viscosity modifiers, defoamers, preservatives, fungicides, rust inhibitors, etc., which suppress the drying of the ink, and then perform filtration treatment with a filter etc. It can be carried out.
The content and physical properties of each component of the aqueous ink obtained by the production method of the present invention are as follows.

(Content of PY74 (pigment))
The content of the pigment in the aqueous ink is preferably 1.0% by mass or more, more preferably 2.0% by mass or more, and still more preferably 2.5% by mass or more, from the viewpoint of improving the print density of the aqueous ink. is there. In addition, from the viewpoint of lowering the viscosity of the ink when the solvent is volatilized and improving the ejection stability and storage stability, it is preferably 15.0% by mass or less, more preferably 10.0% by mass or less, and further preferably 7.0% by mass. % Or less.
(Total content of pigment and water-insoluble polymer)
The total content of the pigment and the water-insoluble polymer in the aqueous ink is preferably 2.0% by mass or more, more preferably 2.5% by mass or more, still more preferably 3.0% by mass or more, and still more preferably 3% by mass or more. 0.5% by mass or more, and preferably 17.0% by mass or less, more preferably 12.0% by mass or less, further preferably 10.0% by mass or less, further more preferably 8.0% by mass or less, It is even more preferably at most 6.0% by mass.
(Content of water-soluble organic solvent)
The content of the water-soluble organic solvent in the aqueous ink is preferably 5% by mass or more, and more preferably 10% by mass, from the viewpoint of reducing the content of the organic compound as an impurity and the storage stability of the ink composition. %, More preferably 15% by mass or more, and from the viewpoint of the printing density of the ink composition, it is preferably 40% by mass or less, more preferably 30% by mass or less, and even more preferably 25% by mass or less.
(Water content)
The content of water in the aqueous ink is preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 65% by mass or more from the viewpoint of storage stability of the ink composition. From the viewpoint of the print density of the product, the content is preferably 99% by mass or less, more preferably 90% by mass or less, and further preferably 80% by mass or less.

(Physical properties of aqueous ink)
The viscosity of the aqueous ink at 32 ° C. is preferably 2.0 mPa · s or more, more preferably 3.0 mPa · s or more, and still more preferably 5.0 mPa · s, from the viewpoint of improving the storage stability of the ink. s or more, and preferably 12 mPa · s or less, more preferably 9.0 mPa · s or less, and still more preferably 7.0 mPa · s or less.
The pH of the aqueous ink is preferably 7.0 or more, more preferably 8.0 or more, and even more preferably 8.5 or more, from the viewpoint of improving the storage stability of the ink. Further, from the viewpoints of member resistance and skin irritation, the pH is preferably 11.0 or less, more preferably 10.0 or less, and further preferably 9.5 or less.

With respect to the above-described embodiment, the present invention further discloses the following aqueous ink for inkjet recording and a method for producing the aqueous ink for inkjet recording.
<1> C.I. I. Pigment Yellow 74, which is a water-based ink for ink-jet recording, and has a C.I. I. Pigment Yellow 74 with respect to the area of the peak (A ₇₄ ). I. An aqueous ink for inkjet recording, wherein the ratio (A _E74 / A ₇₄ ) of the total area (A _E74 ) of peaks other than Pigment Yellow 74 is 1.4 or less.
(Measurement method by liquid chromatography)
Ion-exchanged water was added to 4 g of the aqueous ink to make 200 g, 2 g of ethylene oxide 2 mol adduct of 2,7-dimethyl-4-octyne-4,5-diol was added, and after stirring for 24 hours, 2 g of the sample was collected. After centrifugation, 1.3 g of diethyl ether was added to collect the diethyl ether phase, and the diethyl ether was volatilized. 1.0 g of acetonitrile was added to obtain a sample, which was subjected to high-performance liquid chromatography equipped with an ultraviolet / visible detector. In the graph, an ODS column was used, column temperature: 40 ° C., eluent: acetonitrile / 10 mM ammonium formate buffer (pH: 3) = 80/20 (volume ratio), flow rate: 1.00 ml / min, detection wavelength: It is measured under the condition of 400 nm.

<2> The ratio of the peak area _(A E74 _/ A ₇₄₎ is preferably 0.1 or more, more preferably 0.2 or more, more preferably 0.4 or more, even more preferably be 0.6 or higher The aqueous ink according to <1>, wherein the aqueous ink is preferably 1.3 or less, more preferably 1.2 or less, and still more preferably 1.1 or less.
<3> C.I. I. Pigment Yellow 74 is obtained by a method of diazotizing 4-nitro-o-anisidine and performing a coupling reaction with acetoacetic acid-o-anisidide, wherein the aqueous ink according to the above <1> or <2>.
<4> C.I. I. The aqueous ink according to any one of the above items <1> to <3>, wherein Pigment Yellow 74 is dispersed in an aqueous medium by a polymer dispersant.
<5> C.I. I. Pigment Yellow 74 is C.I. I. The aqueous ink according to any one of the above items <1> to <4>, which is used in the form of water-insoluble polymer particles containing Pigment Yellow 74.
<6> The aqueous ink according to <5>, wherein the water-insoluble polymer is a polymer having a salt-forming group in a polymer chain.
<7> Any of the above <5> or <6>, wherein the water-insoluble polymer is a water-insoluble vinyl-based polymer obtained by addition polymerization of at least one vinyl monomer selected from a vinyl compound, a vinylidene compound, and a vinylene compound. A water-based ink according to Crab.
<8> The water-insoluble vinyl polymer is preferably a vinyl polymer containing (a) a structural unit derived from an ionic monomer and (b) a structural unit derived from a macromonomer, and more preferably (c) a hydrophobic polymer. The aqueous ink according to any one of the above items <5> to <7>, which is a vinyl-based polymer containing at least one structural unit derived from a nonionic monomer and (d) a structural unit derived from a nonionic monomer.

<9> The content of the structural unit derived from the ionic monomer (a) in the water-insoluble polymer is preferably 3% by mass or more, more preferably 5% by mass or more, further preferably 7% by mass or more, and The aqueous ink according to any one of the above items <5> to <8>, wherein the amount is preferably 35% by mass or less, more preferably 30% by mass or less, and still more preferably 25% by mass or less.
<10> The content of the structural unit (b) derived from the macromonomer in the water-insoluble polymer is preferably 3% by mass or more, more preferably 4% by mass or more, still more preferably 5% by mass or more, and preferably Is 30% by mass or less, more preferably 25% by mass or less, further preferably 20% by mass or less, the aqueous ink according to any one of the above <5> to <9>.
<11> When the water-insoluble polymer contains (c) a structural unit derived from a hydrophobic monomer, the content of the structural unit (c) derived from the hydrophobic monomer is preferably 10% by mass or more, more preferably 20% by mass. Any of the above <5> to <10>, which is more preferably 30% by mass or more, and preferably 60% by mass or less, more preferably 55% by mass or less, and still more preferably 50% by mass or less. 2. The aqueous ink according to item 1.
<12> When the water-insoluble polymer contains (d) a structural unit derived from a nonionic monomer, the content of the structural unit derived from (d) the nonionic monomer is preferably 10% by mass or more, and more preferably 15% by mass. Any of the above <5> to <11>, which is more preferably 20% by mass or more, and preferably 50% by mass or less, more preferably 45% by mass or less, and still more preferably 40% by mass or less. 2. The aqueous ink according to item 1.
<13> The mass ratio of [(a) component / [(b) component + (c) component]] is preferably 0.01 or more, more preferably 0.05 or more, and further preferably 0.10 or more. The aqueous ink according to any one of the above items <8> to <12>, wherein the aqueous ink is preferably 1.0 or less, more preferably 0.80 or less, and still more preferably 0.60 or less.
<14> The weight-average molecular weight of the water-insoluble polymer is preferably 6,000 or more, more preferably 8,000 or more, further preferably 10,000 or more, and preferably 200,000 or less, more preferably 100 or more. The aqueous ink according to any one of the above items <5> to <13>, wherein the aqueous ink is not more than 2,000, more preferably not more than 80,000.
<15> C.I. I. Pigment Yellow 74 is preferably at least 1.0% by mass, more preferably at least 2.0% by mass, even more preferably at least 2.5% by mass, and preferably at most 15.0% by mass, The aqueous ink according to any one of the above items <1> to <14>, more preferably 10.0% by mass or less, still more preferably 7.0% by mass or less.
<16> C.I. I. Pigment Yellow 74 and the water-insoluble polymer have a total content of preferably 2.0% by mass or more, more preferably 2.5% by mass or more, still more preferably 3.0% by mass or more, and still more preferably 3.5% by mass. % By mass or more, and preferably 17.0% by mass or less, more preferably 12.0% by mass or less, further preferably 10.0% by mass or less, still more preferably 8.0% by mass or less, and further more The aqueous ink according to any one of the above items <5> to <15>, which is preferably 6.0% by mass or less.

<17> The method for producing a water-based ink for inkjet recording according to any one of <1> to <16>, comprising the following steps I to III.
Step I: water-insoluble polymer, organic solvent, C.I. I. After the mixture containing CI Pigment Yellow 74 and water was subjected to high-pressure dispersion treatment at a pressure of 60 MPa or more, the mixture was kept at 30 ° C. or less for 15 hours or more. I. Step of Obtaining a Dispersion of Water-Insoluble Polymer Particles Containing Pigment Yellow 74 Step II: Removing the Organic Solvent from the Dispersion Obtained in Step I I. Step of Obtaining an Aqueous Dispersion of Water-Insoluble Polymer Particles Containing Pigment Yellow 74 Step III: A step of blending one or more selected from water and a water-soluble organic solvent with the aqueous dispersion obtained in Step II <18> The pressure of the high-pressure dispersion treatment in the step I is preferably 60 MPa or more, more preferably 100 MPa or more, still more preferably 130 MPa or more, and preferably 200 MPa or less, more preferably 180 MPa or less, described in <17> above. A method for producing an aqueous ink.
<19> The production of the aqueous ink according to <17> or <18>, wherein the holding temperature in step I is preferably 10 ° C or higher, more preferably 15 ° C or higher, and preferably 25 ° C or lower. Method.
<20> The aqueous solution according to any one of the above <17> to <19>, wherein the retention time in step I is preferably 20 hours or more, and is preferably 180 hours or less, more preferably 100 hours or less. Ink manufacturing method.
<21> The method for producing a water-based ink according to any one of <17> to <20>, wherein the water-soluble organic solvent used in Step III has a boiling point of 100 ° C to 270 ° C.
<22> The water-soluble organic solvent is preferably one or more selected from polyhydric alcohols and polyhydric alcohol alkyl ethers, and more preferably a combination of one or more polyhydric alcohols and one or more polyhydric alcohol alkyl ethers. The method for producing an aqueous ink according to any one of <17> to <21>.
<23> The content of the water-soluble organic solvent in the aqueous ink is preferably 5% by mass or more, more preferably 10% by mass or more, still more preferably 15% by mass or more, and preferably 40% by mass or less. The method for producing a water-based ink according to any one of the above items <17> to <22>, more preferably 30% by mass or less, still more preferably 25% by mass or less.

In the following Production Examples, Examples and Comparative Examples, “parts” and “%” are “parts by mass” and “% by mass” unless otherwise specified. In addition, the weight average molecular weight of the polymer was measured by the following method.
(1) Method for measuring weight average molecular weight of polymer Gel chromatography method [manufactured by Tosoh Corporation] using N, N-dimethylformamide containing 60 mmol / L phosphoric acid and 50 mmol / L lithium bromide as a solvent as a solvent. The measurement was carried out using a GPC apparatus (HLC-8120GPC), a column (TSK-GEL, α-M × 2), flow rate: 1 mL / min, manufactured by Tosoh Corporation, using monodisperse polystyrene having a known molecular weight as a standard substance.
(2) Measurement of average particle diameter of pigment-containing polymer particles Cumulant analysis was performed using a laser particle analysis system “ELS-8000” (manufactured by Otsuka Electronics Co., Ltd.) to measure. The measurement conditions were a temperature of 25 ° C., an angle between the incident light and the detector of 90 °, and the number of times of integration was 100 times. The refractive index of water (1.333) was input as the refractive index of the dispersion solvent. The dilution was performed with water so that the measured concentration was 5 × 10 ⁻³ mass% (in terms of solid content concentration).
(3) Measurement of solid content concentration of pigment aqueous dispersion 1 g of an aqueous dispersion of pigment-containing polymer particles and 10 g of sodium sulfate (Glauber's salt) are uniformly mixed and spread evenly on an evaporating dish (10.5 cm ² ). The solution was dried under reduced pressure at -0.07 MPa at 105 ° C. for 2 hours, the weight of the dried aqueous dispersion was measured, and the solid content concentration (% by mass) was determined by the following equation.
Solid content concentration (%) = (mass of aqueous dispersion after drying / mass of aqueous dispersion before drying) × 100

Production Example 1 (Production of polymer dispersant)
In a reaction vessel, 20 parts of methyl ethyl ketone, 0.03 part of a polymerization chain transfer agent (2-mercaptoethanol), and 10% of a total of 200 parts of each monomer shown in Table 1 were mixed and sufficiently replaced with nitrogen gas. , To obtain a mixed solution.
On the other hand, the remaining 90% of the monomers shown in Table 1 were charged into the dropping funnel, and 0.27 parts of the polymerization chain transfer agent, 60 parts of methyl ethyl ketone and a radical polymerization initiator (2,2′-azobis (2,4-dimethyl Valeronitrile), 1.2 parts of V-65 (manufactured by Wako Pure Chemical Industries, Ltd.) were added and mixed, and the mixture was sufficiently purged with nitrogen gas to obtain a mixed solution.
Under a nitrogen atmosphere, the temperature of the mixed solution in the reaction vessel was raised to 65 ° C. while stirring, and the mixed solution in the dropping funnel was gradually dropped over 3 hours. After 2 hours at 65 ° C from the end of the dropping, a solution prepared by dissolving 0.3 part of the radical polymerization initiator in 5 parts of methyl ethyl ketone was added, and the mixture was further aged at 65 ° C for 2 hours and at 70 ° C for 2 hours to obtain a weight average molecular weight of 62. 2,000 polymer solutions were obtained. Table 1 shows the results.

The details of the compounds shown in Table 1 are as follows.
(B) Styrene macromer: manufactured by Toagosei Co., Ltd., trade name: AS-6 (S), number average molecular weight: 6000, polymerizable functional group: methacryloyloxy group, solid content concentration 50%
(D) Polyethylene glycol monomethacrylate 2-ethylhexyl ether: manufactured by Shin-Nakamura Chemical Co., Ltd., trade name: NK ester EH-4E, average addition mole number of ethylene oxide = 4, terminal: 2-ethylhexyl group

Example 1 (Production of water-based ink (1))
(1) Production of aqueous ink (1) 25 parts of a polymer obtained by drying the polymer solution obtained in Production Example 1 under reduced pressure was dissolved in 50 parts of methyl ethyl ketone, and a neutralizing agent (5N sodium hydroxide solution, 6.7 parts of Wako Pure Chemical Industries, Ltd. (for volume analysis) and 250 parts of ion-exchanged water were added to neutralize the salt-forming group (neutralization degree: 75 mol%). I. Pigment Yellow 74 (manufactured by Clariant Co., Ltd., trade name: HANSA BRILL. YELLOW 5GXW) (75 parts) is added, and the number of revolutions is 8000 using TK Robomix (trade name) + TK Homodisper 2.5 as a preliminary dispersion. / Min for 60 minutes. The obtained dispersion was subjected to a 10-pass dispersion treatment at 150 MPa using a microfluidizer (trade name, manufactured by Microfluidics) as a main dispersion.
While this dispersion was repeated for 10 passes, the dispersion was maintained at 20 ° C. for 0.5 hour while stirring using a magnetic stirrer (rotational speed: 60 rpm). After the main dispersion, the dispersion was further kept at 20 ° C. while stirring using a magnetic stirrer (rotation speed: 60 rpm). The time kept at 20 ° C. or lower was 48 hours in total.
250 parts of ion-exchanged water is added to the obtained dispersion, methyl ethyl ketone is removed under reduced pressure at 60 ° C., a part of the water is removed, and the dispersion is concentrated to a solid concentration of 25%. An aqueous pigment dispersion in the form of particles was obtained.
300 g of the obtained pigment aqueous dispersion was put into a centrifugal sedimentation tube 500PA bottle using Hitachi Koki Co., Ltd. cooling centrifuge "himacCR22G" and a rotor (R12A, radius: 15.1 cm), and 12,000 rpm. A centrifugal acceleration of 24300 G was applied at a rate of / min, and this state was maintained for 6 minutes.
The supernatant liquid obtained by centrifugation is collected and a 25 mL capacity syringe without needle (manufactured by Terumo Corporation) equipped with a surface filtration type filter (acetyl cellulose membrane, outer diameter: 2.5 cm, manufactured by Sartorius) having a nominal filtration accuracy of 5 μm. After the solid content was filtered, the mixture was appropriately diluted with ion-exchanged water to adjust the solid content concentration to 20%, to obtain an aqueous dispersion (1) of water-insoluble polymer particles containing PY74. The average particle size of the pigment-containing polymer particles in this aqueous dispersion (1) was 121 nm.
This aqueous dispersion (1) can be used as it is as the aqueous ink for analysis (1).

(2) Analysis of water-based ink (1) 4 g of the water-based ink (1) obtained in the above (1) was placed in a screw tube No. 7 (volume: 50 ml) manufactured by Maruem Co., Ltd., and ion-exchanged water was added to 200 g. 2 g of an ethylene oxide 2 mol adduct of 2,7-dimethyl-4-octyne-4,5-diol (trade name: Surfynol 420, water-insoluble, manufactured by Nissin Chemical Co., Ltd.) was added thereto, and the mixture was added at room temperature (23 ° C.). ) For 24 hours, and 2 g of the mixture is collected, placed in a centrifugal sedimentation tube (part No. S404332A) manufactured by Hitachi Koki Co., Ltd. And centrifuged at 110,000 rpm for 28 minutes.
After completion of the centrifugation, 1.3 g of diethyl ether (reagent, manufactured by Wako Pure Chemical Industries, Ltd.) was added to the centrifugal sedimentation tube, the diethyl ether phase was recovered, and nitrogen gas was blown to volatilize the diethyl ether, followed by acetonitrile. (For HPLC, manufactured by Wako Pure Chemical Industries, Ltd.) Add ultra-high-speed single quadrupole mass spectrometer compatible with high-performance liquid chromatograph equipped with UV / visible detector As a result of analysis by LCMS-2020 manufactured by Shimadzu Corporation, four peaks were detected at 3.0 minutes, 4.1 minutes, 4.9 minutes, and 7.4 minutes.
The results are shown in FIG. The peak at 2.5 minutes in FIG. 1 is a ghost peak.
(Analysis conditions for high-performance liquid chromatography)
-Column: ODS (chemically bonded porous spherical silica gel surface-modified with octadecylsilyl group) Shodex C18M 4E (4.6 mm x 250 mm, 5 m) manufactured by Showa Denko KK
-Column temperature: 40 ° C
-Eluent: acetonitrile / 10 mM ammonium formate buffer (pH: 3) = 80/20 (volume ratio)
・ Flow rate: 1.00 ml / min
・ Detection wavelength: 400 nm

On the other hand, C.I. I. Pigment Yellow 74 (manufactured by Clariant, trade name: HANSA BRILL. YELLOW 5GXW) was added to acetonitrile, stirred at room temperature (23 ° C.) for 24 hours, and filtered through a 0.2 μm PTFE membrane filter. As a result of analysis by high performance liquid chromatography, a peak was detected at 7.4 minutes. This is C.I. I. Pigment Yellow 74 has a peak at a position of 7.4 minutes under the present conditions.
The total area (A _E74 ) of the three peaks other than PY74 at 3.1 minutes, 4.1 minutes, and 5.0 minutes, the peak area of PY74 at 7.4 minutes (A ₇₄ ), and the peak area Table 2 shows the ratio (A _E74 / A ₇₄ ).

Examples 2-3 and Comparative Examples 1-2 (Production of aqueous inks for analysis (2)-(5))
The aqueous inks for analysis (2) to (2) were prepared in the same manner as in Example 1 except that the holding time after the main dispersion by the microfluidizer was changed to change the total holding time as shown in Table 2. (5) was obtained. Table 2 shows the results.

<Evaluation of aqueous ink for inkjet recording>
25 parts of the aqueous inks obtained in Examples 1 to 3 and Comparative Examples 1 and 2 were mixed with 7 parts of glycerin, 7 parts of triethylene glycol and 5 parts of trimethylolpropane (the weighted average of the boiling points of the water-soluble organic solvents was , 254.7 ° C.), and acetylenol E100 (manufactured by Kawaken Fine Chemical Co., Ltd., nonionic surfactant, addition of 10 mol of ethylene oxide of 2,4,7,9-tetramethyl-5-decyne-4,7-diol) to ethylene oxide Product) 0.5 part and 55.5 parts of ion-exchanged water are mixed, and a 25 mL syringe with a surface filtration type filter (manufactured by acetyl cellulose, outer diameter: 2.5 cm, manufactured by Sartorius) having a nominal filtration accuracy of 5 μm is attached. To obtain aqueous inks for evaluation (1) to (5).
Using the obtained aqueous ink, the ejection property was evaluated by the following method. Table 2 shows the results.
(Evaluation of dischargeability)
Using a commercially available ink jet printer (manufactured by Seiko Epson Corporation, trade name: EM930C, piezo method), the water-based ink was solid-printed on plain paper (manufactured by Xerox Corporation, trade name: 4200) in 10 sheets in the “fast mode”. The printing state of the tenth sheet was observed, and the number of streaks (the number of nozzles that did not discharge normally) was recorded.
The smaller the number of streaks (the number of missing nozzles), the better the ejection performance without the occurrence of a non-ejection phenomenon due to problems such as nozzle blockage.

  From the comparison of Examples 1 to 3 and Comparative Examples 1 and 2 in Table 2, the aqueous inks obtained in Examples 1 to 3 are more suitable for inkjet recordings than the aqueous inks obtained in Comparative Examples 1 and 2. It can be seen that there is no nozzle chipping and the ejection properties are excellent.

Claims (3)

A method for producing a water-based ink for ink-jet recording , comprising the following steps I to III, wherein C.I. I. Pigment Yellow 74 with respect to the area of the peak (A ₇₄ ). I. A method for producing a water-based ink for inkjet recording, wherein the ratio (A _E74 / A ₇₄ ) of the total area (A _E74 ) of peaks other than Pigment Yellow 74 is 1.4 or less .
Step I: water-insoluble polymer, organic solvent, C.I. I. After the mixture containing CI Pigment Yellow 74 and water was subjected to high-pressure dispersion treatment at a pressure of 60 MPa or more, the mixture was kept at 30 ° C. or less for 15 hours or more. I. Step of Obtaining a Dispersion of Water-Insoluble Polymer Particles Containing Pigment Yellow 74 Step II: Removing the Organic Solvent from the Dispersion Obtained in Step I I. Step of Obtaining an Aqueous Dispersion of Water-Insoluble Polymer Particles Containing Pigment Yellow 74 Step III: After Centrifuging the Aqueous Dispersion Obtained in Step II and Filtering the Supernatant , Water and a Water-Soluble Organic A step of blending at least one selected from solvents
(Measurement method by liquid chromatography)
Ion-exchanged water was added to 4 g of the aqueous ink to make 200 g, 2 g of ethylene oxide 2 mol adduct of 2,7-dimethyl-4-octyne-4,5-diol was added, and after stirring for 24 hours, 2 g of the sample was collected. After centrifugation, 1.3 g of diethyl ether was added to collect the diethyl ether phase, and the diethyl ether was volatilized. 1.0 g of acetonitrile was added to obtain a sample, which was then subjected to high-performance liquid chromatography equipped with an ultraviolet / visible detector. In the graph, using an ODS column, column temperature: 40 ° C., eluent: acetonitrile / 10 mM ammonium formate buffer (pH: 3) = 80/20 (volume ratio), flow rate: 1.00 ml / min, detection wavelength: It is measured under the condition of 400 nm. The peak area ratio (A _E74 / A ₇₄ The method for producing a water-based ink for ink-jet recording according to claim 1, wherein (a) is from 0.1 to 1.3. C. in aqueous ink I. The method according to claim 1, wherein the total content of CI Pigment Yellow 74 and the water-insoluble polymer is 2.0% by mass or more and 17.0% by mass or less.