JP2011162614A - Inkjet ink and method for manufacturing the inkjet ink - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet ink excellent in storage stability, discharge stability, and scratch resistance; and to provide a method for manufacturing the same. <P>SOLUTION: The method for manufacturing the inkjet ink includes: a dispersion step in which a mixture obtained by mixing a dispersion liquid containing a water-insoluble colorant, a first surfactant and water with a dispersion liquid containing an oil monomer, a second surfactant and water, is dispersed to obtain a dispersion liquid containing the water-insoluble colorant, the first surfactant, the second surfactant, and the oil monomer; and a microencapsulation step in which a microcapsule is obtained by polymerizing the oil monomer contained in the dispersion liquid obtained in the dispersion step. The method is characterized in that the first and second surfactants are a multi-chain and multi-hydrophilic group type surfactant containing a hydrophilic group, a linking group, and a plurality of anionic hydrophilic groups. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

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

  Improve water resistance and scratch resistance by adding fine particles (hereinafter also referred to as microcapsules) in which ink is a core and resin is a shell to ink-jet ink (hereinafter also simply referred to as ink). Has been proposed. One method for producing such microcapsules is emulsion polymerization.

  Patent Document 1 proposes a method of obtaining microcapsules by performing emulsion polymerization using a monomer containing an alkylene oxide group and a pigment.

JP 2004-155818 A

  When the present inventors examined the technique described in Patent Document 1, the discharge stability could be obtained at a certain level. However, with higher image quality in recent years, there is a demand for ink with higher ejection stability.

  Accordingly, in view of the above-described problems of the prior art, an object of the present invention is to provide an inkjet ink excellent in storage stability, ejection stability, and scratch resistance, and a method for producing the inkjet ink.

  The above-mentioned subject is achieved by the following invention. That is, the present invention disperses a mixture obtained by mixing a dispersion containing a water-insoluble colorant, a first surfactant and water, and a dispersion containing an oily monomer, a second surfactant and water. A dispersion step of obtaining a dispersion containing the water-insoluble colorant, the first and second surfactants and the oily monomer, and the oily monomer contained in the dispersion obtained by the dispersion step. A method for producing an inkjet ink having a microencapsulation step of obtaining a microcapsule by polymerization, wherein the first and second surfactants comprise a hydrophobic group, a linking group, and a plurality of anionic hydrophilic groups A method for producing an ink-jet ink, wherein the surfactant is a multi-chain poly-hydrophilic type surfactant.

  ADVANTAGE OF THE INVENTION According to this invention, when using for an inkjet ink, the manufacturing method of the inkjet ink which is excellent in storage stability, discharge stability, and abrasion resistance, and an inkjet ink can be provided.

  Hereinafter, the present invention will be described in more detail with reference to preferred embodiments.

<Inkjet ink manufacturing method>
[Multi-chain, multi-hydrophilic surfactant]
In the method for producing an ink-jet ink of the present invention, the first and second surfactants used in the dispersion step and the microencapsulation step shown below are a multi-chain multi-chain having a hydrophobic group and a plurality of anionic hydrophilic groups. A hydrophilic type surfactant is used. In the present invention, the multi-chain polyhydrophilic group-type surfactant refers to a surfactant having a hydrophobic group, a plurality of hydrophilic groups and a linking group.

  Examples of the hydrophobic group of the multi-chain polyhydrophilic group-type surfactant include a hydrocarbon group having 4 to 20 carbon atoms (a linear or branched alkyl group, alkylaryl group, aryl group, alkenyl group, phenyl group, etc. And a fluorine-containing hydrocarbon group having 4 to 20 carbon atoms (such as a fluoroalkyl group, a fluoroalkenyl group, and a fluoroaryl group).

  In addition, examples of the anionic group of the multi-chain polyhydrophilic group-type surfactant include a carboxyl group, a sulfonic acid group, and a phosphoric acid group.

  In addition, the linking group of the multi-chain polyhydrophilic group-type surfactant is not particularly limited as long as it is an organic group, but a tetravalent or pentavalent organic group, a carbon bond, an ester bond, an amide bond, an ether bond, and a urethane bond. Examples thereof include organic groups.

  Examples of the multi-chain polyhydrophilic surfactant of the present invention include a 2-chain 2-hydrophilic surfactant, a 2-chain 3-hydrophilic surfactant, and a 3-chain 3-hydrophilic surfactant. . Specific examples of the multi-chain polyhydrophilic group-type surfactant include compounds represented by the following formula (1), compounds represented by the following formula (2), JP-A Nos. 11-217583 and 2007-146108. And compounds described in JP2007-238905A. In the present invention, it is preferable to use a compound represented by the following formula (1) or (2).

  Formula (1)

(In the formula, X is H or Na.)
Formula (2)

(In the formula, X is H or Na.)

  The compound of the formula (1) has a carboxyl group that is three anionic hydrophilic groups, a lauroyl group is a hydrophobic group, and a chain obtained by removing a carboxyl group from glutamic acid-lysine-glutamic acid is a two-chain 3 A hydrophilic group type surfactant. The compound of the formula (1) can be purchased under the trade name of Perisea manufactured by Asahi Kasei Chemicals Corporation.

  The compound of formula (2) is a two-chain two-hydrophilic surfactant having two anionic hydrophilic groups, a dodecyl group being a hydrophobic group, and C—C being a linking group. The compound of the formula (2) can be purchased under the trade name of Gemsufα142 manufactured by Chukyo Yushi Co., Ltd.

  The ink-jet ink obtained through the method for producing an ink-jet ink of the present invention preferably contains 0.01% by mass or more and 5% by mass or less of the multi-chain polyhydrophilic group type surfactant with respect to the total mass of the ink.

  In the present invention, the first surfactant and the second surfactant may be different multi-chain polyhydrophilic surfactants, but are the same multi-chain polyhydrophilic surfactant. Is preferred.

[Dispersion process]
In the present invention, the dispersion step includes a dispersion obtained by mixing a solution containing a water-insoluble colorant, a first surfactant, and water, an oily monomer, a second surfactant, and water. By dispersing the mixture obtained by mixing the dispersion obtained by mixing the solution, a dispersion in which the water-insoluble colorant, the oily monomer, and the first and second surfactants are dispersed is obtained. It is a process. Hereinafter, a solution containing a water-insoluble colorant, a first surfactant, and water is also referred to as a water-insoluble colorant dispersion, and particularly a pigment dispersion when a pigment is used as the colorant. A solution containing an oily monomer, a second surfactant and water is also referred to as a monomer emulsion. The water-insoluble colorant dispersion is preferably subjected to ultrasonic irradiation after mixing the respective components. Also in a monomer emulsion, it is preferable to perform ultrasonic irradiation after mixing each component. The first and second surfactants used in this step are the above-described multi-chain polyhydrophilic group-type surfactants. Further, the amount of the multi-chain polyhydrophilic group-type surfactant added in the dispersion step is 0.1% by mass or more and 10% by mass or less based on the total amount of the water-insoluble colorant dispersion and the monomer emulsion. Is preferred.

[Microencapsulation process]
In the present invention, the microencapsulation step is a step of obtaining a microcapsule by polymerizing an oily monomer contained in a dispersion obtained by the dispersion step. By the microencapsulation process, a microcapsule dispersion containing a polymer obtained by polymerizing an oil-based monomer with a water-insoluble colorant as a core and a microcapsule having the above-described multi-chain polyhydrophilic surfactant as a shell is obtained. be able to. In the present invention, it is not necessary for the shell to cover the entire surface of the core, as long as it covers at least part of the surface of the core (the surface of the water-insoluble colorant).

  The hydrophobic group of the multi-chain polyhydrophilic surfactant in the microcapsule obtained through the dispersion step and the microencapsulation step is closer to the core of the microcapsule than the polymer constituting the outermost peripheral portion of the microcapsule shell. It can be present in a portion, that is, in a state of being taken inside the microcapsule. In such a state, the multi-chain polyhydrophilic group-type surfactant present in the microcapsule is a multi-chain polyhydrophilic group-type interface in which the multi-chain polyhydrophilic surfactant is adsorbed on the surface of the shell. Since it is firmly fixed as compared with the active agent, it is difficult to detach from the microcapsule. Therefore, it is possible to reduce the detachment of the surfactant due to the shearing force applied to the microcapsule when discharging from the nozzle by the ink jet method, and it is possible to obtain excellent discharge stability.

  Moreover, although a detailed reason is unknown, microcapsules having a relatively small average particle diameter can be obtained by using the dispersion step and the microencapsulation step of the present invention. Specifically, microcapsules having an average particle size of 50 nm or more and 200 nm or less can be obtained. In the present invention, the average particle diameter of the microcapsules can be obtained by measuring the D50 particle diameter, which is the median diameter. Examples of the method for measuring the D50 particle size include a method using a particle size distribution measuring machine (Nikkiso Microtrac UPA EX-150).

  The weight average molecular weight of the polymer constituting the microcapsule shell can be calculated by the following method. The microcapsule dispersion is separated into microcapsules by centrifugation, and the microcapsules are dissolved in THF (tetrahydrofuran). Then, it is made to isolate | separate with a centrifuge, The supernatant liquid is filtered, The filtrate is measured by the gel permeation chromatography (GPC) of polystyrene conversion (column Shodex GPC KF-806, K-806L by Showa Denko). The weight average molecular weight of the polymer constituting the shell of the microcapsule can be calculated. In the present invention, the polymer constituting the shell of the microcapsule preferably has a weight average molecular weight of 400,000 or more and 700,000 or less.

  In addition, when the multi-chain polyhydrophilic surfactant in the microcapsule in the ink obtained by the method for producing an ink-jet ink of the present invention has an acid value, the acid value of the microcapsule is calculated by the following method. be able to.

  Centrifugation is performed, and the precipitates are collected to take out the microcapsules in the ink. Thereafter, the microcapsules are dispersed in water to prepare a dispersion aqueous solution. The aqueous dispersion is adjusted so that the content of the microcapsules is 0.3% by mass with respect to the total mass of the aqueous dispersion. Thereafter, 7 g of the aqueous dispersion is taken, diluted with 238 g of pure water, and prepared with an aqueous potassium hydroxide solution so that the pH of the diluted aqueous dispersion is 10. Thereafter, methyl glycol chitosan N / 200 is dropped while measuring the potential difference of the obtained preparation using a potentiometric titrator AT-510 (Kyoto Electronics Co., Ltd.). As methyl glycol chitosan N / 200 is dropped, the potential difference fluctuates, and an inflection point of the potential difference appears at a specific drop amount. The acid value of the microcapsule is calculated from the titration amount of methyl glycol chitosan N / 200 used until the inflection point appears. The acid value measurement method described above is hereinafter also referred to as colloid titration method.

  The acid value of the microcapsules obtained by the colloid titration method is preferably 50 μmol or more and 400 μmol or less with respect to 1 g of the color material.

<Inkjet ink>
As described above, a microcapsule dispersion containing microcapsules can be obtained after the microencapsulation step. In the present invention, this microcapsule dispersion may be used as it is as an inkjet ink, but it is preferable to prepare an inkjet ink by adding a component such as a water-soluble organic solvent described later to the microcapsule dispersion.

  Hereinafter, each component that can be used in the ink-jet ink of the present invention will be described in detail.

[Water-insoluble colorant]
The color material of the present invention is insoluble in water in an environment of normal temperature and normal pressure. As the water-insoluble colorant of the present invention, specifically, a known pigment or a known oily dye can be used. The amount of the water-insoluble colorant added in the dispersion step is preferably 0.5% by mass or more and 20% by mass or less based on the total amount of the pigment dispersion and the monomer emulsion. The amount of the water-insoluble colorant contained in the inkjet ink of the present invention is preferably 0.5% by mass or more and 5% by mass or less based on the total mass of the ink.

[Oil monomer]
The present invention uses an oily monomer as a raw material for the polymer. The oily monomer is not particularly limited, and a known oily monomer can be used. Preferable oil-based monomers are specifically styrene, methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, i-propyl (meth) acrylate, i-butyl (meth) acrylate acrylate, n -Butyl (meth) acrylate acrylate etc. are mentioned. In particular, it is preferable to use n-butyl methacrylate or styrene. Moreover, in this invention, you may perform a dispersion | distribution process and a microencapsulation process using several types of oil-based monomers. That is, the resin constituting the shell of the microcapsule may be a homopolymer obtained from one kind of oily monomer or a copolymer obtained from two or more kinds of oily monomers. The amount of the oily monomer added in the dispersing step is preferably 5% by mass or more and 150% by mass or less based on the total mass of the water-insoluble colorant.

[Other monomers]
In the present invention, it is sufficient if the oily monomer described above is included in the dispersion step, but another monomer may be added in addition to the oily monomer. Therefore, the resin constituting the shell of the microcapsule may be a copolymer of an oily monomer and another monomer. The other monomer other than the oily monomer is not particularly limited, and any monomer may be used. Specific examples of the other monomer include acrylic acid, methacrylic acid, itaconic acid, crotonic acid, maleic acid and the like. The amount of the other monomer added in the dispersion step is preferably 1% by mass or more and 30% by mass or less based on the total mass of the oily monomer.

[Hydrohove]
In the method for producing an inkjet ink of the present invention, a hydrophobe may be added to the dispersion during the dispersion step in order to stably polymerize the oily monomer in the microencapsulation step. In the present invention, the hydrophobe refers to an oily compound having a solubility in water (normal temperature and normal pressure environment) of 1 g or less with respect to 100 g of water. Hydrophobes are a dispersion containing a water-insoluble colorant, an oily monomer, and water, a dispersion containing a multi-chain polyhydrophilic surfactant, an oily monomer, and water, a water-insoluble colorant, and a multi-chain polyhydrophilic. What is necessary is just to add to either of the dispersion liquid containing a basic surfactant, an oil-based monomer, and water. Specific examples of the hydrophobe of the present invention include hexadecane, dodecyl methacrylate, stearyl methacrylate, chlorobenzene, dodecyl mercaptan, olive oil, blue dye (Blue 70), polymethyl methacrylate, and polyacrylic acid. The amount of hydrophobe added in the dispersion step is preferably 1% by mass or more and 20% by mass or less based on the total mass of the oily monomer.

[Polymerization initiator]
In the microencapsulation process of the present invention, a polymerization initiator can be used to polymerize the oily monomer. It does not specifically limit as a polymerization initiator, A well-known water-soluble and oil-soluble polymerization initiator can be used. Specific examples of the polymerization initiator include potassium persulfate, 2, 2′azobis (2-isobutyronitryl), 2′′azobis (2-methylbutyronitryl), and the like. The amount of the polymerization initiator added in the dispersion step is preferably 1% by mass or more and 10% by mass or less based on the total mass of the oily monomer.

[Aqueous medium]
The ink-jet ink obtained through the method for producing an ink-jet ink of the present invention contains water. The inkjet ink of the present invention may contain water, but it is preferable to use a mixed solvent of water and a water-soluble organic solvent as the aqueous medium. The water-soluble organic solvent is not particularly limited, and any known organic solvent can be used. Specific examples of the water-soluble organic solvent include hexanediol, polyethylene glycol, 2-pyrrolidone, and glycerin. Further, the content of the water-soluble organic solvent in the ink is preferably 5% by mass or more and 40% by mass or less based on the total mass of the ink. The water of the present invention is preferably deionized water. Further, the content of water in the ink is preferably 40% by mass or more and 90% by mass or less based on the total mass of the ink.

[Surfactant]
The ink-jet ink of the present invention may contain a surfactant other than the above-described multi-chain polyhydrophilic group-type surfactant. Specific examples of the surfactant include acetylenol EH (manufactured by Kawaken Fine Chemical Co., Ltd.). The amount of the surfactant other than the polychain polyhydrophilic surfactant in the ink is preferably 0.01% by mass or more and 5.0% by mass or less based on the total mass of the ink, and 0.1% by mass. More preferably, it is 3.0 mass% or less.

  EXAMPLES Next, although an Example and a comparative example are given and this invention is demonstrated more concretely, this invention is not limited by the following Example, unless the summary is exceeded. In the text, “parts” and “%” are based on mass unless otherwise specified.

<Preparation of pigment dispersion>
(Pigment dispersion A)
After adding 10 g of carbon black FW18 (manufactured by Evonik Degussa Japan Co., Ltd.) 10 g of a 2-chain 3-hydrophilic surfactant (compound of the above formula (1); Perisea Asahi Kasei Chemicals Co., Ltd.) to 81 g of water, The pigment dispersion A was obtained by ultrasonic irradiation for 15 minutes.

(Pigment dispersion B)
Carbon black FW18 (Evonik Degussa Japan Co., Ltd.) 10 g, 2-chain 2-hydrophilic surfactant (compound of the above formula (2). Gemsurf α142, Chukyo Yushi Co., Ltd.) 3 g was added to 110 g of water, and then ultrasonicated for 15 minutes. Irradiation was performed to obtain a pigment dispersion B.

(Pigment dispersion C)
After adding 10 g of carbon black FW18 (manufactured by Evonik Degussa Japan) and 3 g of Antox-MS-60 (Nippon Emulsifier Co., Ltd.) to 110 g of water, ultrasonic dispersion was performed for 15 minutes to obtain pigment dispersion C. Note that Antox-MS-60 is a compound represented by the following formula (3), which is a multi-chain polyhydrophilic group-type surfactant, but does not have a plurality of anionic hydrophilic groups. .

  Formula (3)

(Pigment dispersion D)
After adding 10 g of carbon black FW18 (manufactured by Evonik Degussa Japan) and 3 g of sodium dodecyl sulfate to 110 g of water, ultrasonic dispersion was performed for 15 minutes to obtain pigment dispersion D.

<Preparation of monomer emulsion>
(Monomer emulsion A)
10 g of n-butyl methacrylate, 2 chain 3 hydrophilic group type surfactant (compound of the above formula (1), Perisea Asahi Kasei Chemicals Co., Ltd.) 3 g of 30% aqueous solution, 1 g of hexadecane, 2, 2′azobis (2-methylbutyronitrile) ) After adding 0.5 g to 61 g of water, ultrasonic irradiation was performed for 1 minute for emulsification to obtain monomer emulsion A.

(Monomer emulsion B)
70 g of 2 g of n-butyl methacrylate 10 g, 2 chain 2 hydrophilic group type surfactant (compound of the above formula (2). Chukyo Yushi Gemsurfα142) 1 g, hexadecane 1 g, 2 and 2 ′ azobis (2-methylbutyronitrile) After being added to water, the mixture was emulsified by ultrasonic irradiation for 1 minute to obtain monomer emulsion B.

(Monomer emulsion C)
After adding 10 g of styrene, 1 g of Antox-MS-60 (manufactured by Nippon Emulsifier Co., Ltd.), 1 g of hexadecane, 0.5 g of 2,2′azobis (2-methylbutyronitrile) to 70 g of water, ultrasonic irradiation was performed for 1 minute. Emulsification was performed to obtain monomer emulsion C.

(Monomer emulsion D)
After adding 10 g of n-butyl methacrylate, 1 g of sodium dodecyl sulfate, 1 g of hexadecane, 0.5 g of 2,2′azobis (2-methylbutyronitryl) to 70 g of water, the mixture is emulsified by ultrasonic irradiation for 1 minute, and monomer emulsion D was obtained.

<Preparation of microcapsule dispersion>
(Microcapsule dispersion A)
50 g of pigment dispersion A and 40 g of monomer emulsion A were mixed and emulsified for 4 minutes by ultrasonic irradiation, and then polymerized at 70 ° C. for 8 hours in a nitrogen atmosphere to obtain microcapsule dispersion A.

(Microcapsule dispersion B)
50 g of Pigment Dispersion B and 40 g of Monomer Emulsion B were mixed, emulsified for 4 minutes by ultrasonic irradiation, and then polymerized at 70 ° C. for 8 hours in a nitrogen atmosphere to obtain Microcapsule Dispersion B.

(Microcapsule dispersion C)
50 g of pigment dispersion C and 40 g of monomer emulsion C were mixed, emulsified for 4 minutes by ultrasonic irradiation, and then polymerized at 70 ° C. for 8 hours in a nitrogen atmosphere to obtain microcapsule dispersion C.

(Microcapsule dispersion D)
50 g of pigment dispersion D and 40 g of monomer emulsion D were mixed, emulsified for 4 minutes by ultrasonic irradiation, and then polymerized at 70 ° C. for 8 hours in a nitrogen atmosphere to obtain microcapsule dispersion D.

<Preparation of ink>
The components shown in Table 1 were mixed and stirred for 30 minutes, and then filtered through a membrane filter having a pore size of 5 μm to obtain inks of Examples and Comparative Examples.

<Physical properties of inkjet ink>
(Measurement of average particle size)
Using the inks of Examples and Comparative Examples, the average particle diameters of the microcapsules and the color material in the ink were measured. For each ink, the particle size distribution measuring machine (Nikkiso Microtrac UPA EX-150) was used to measure the D50 particle size, which is the median diameter. The results are shown in Table 2.

(Measurement of acid value)
The inks of Examples and Comparative Examples were centrifuged, and the precipitates were collected to take out the microcapsules in each ink. Thereafter, the microcapsules were dispersed in water to prepare a dispersion aqueous solution. The aqueous dispersion was adjusted so that the content of microcapsules was 0.3% by mass with respect to the total mass of the aqueous dispersion. Thereafter, 7 g of the aqueous dispersion was taken, diluted with 238 g of pure water, and prepared with an aqueous potassium hydroxide solution so that the pH of the diluted aqueous dispersion was 10. Thereafter, methyl glycol chitosan N / 200 was added dropwise while measuring the potential difference of the obtained preparation using a potentiometric titrator AT-510 (Kyoto Electronics Co., Ltd.). The acid value of the microcapsules was calculated from the titration amount of methyl glycol chitosan N / 200 used until the inflection point appeared. The results are shown in Table 2.

(Measurement of molecular weight of polymer forming shell)
By centrifuging the inks of Examples and Comparative Examples, only the microcapsules in the ink were taken out, and the microcapsules alone were dissolved in THF. Thereafter, the pigment, which is the core of the microcapsule, and the polymer, which is the shell, are further separated by a centrifuge, the supernatant is filtered, and the filtrate is converted into polystyrene-equivalent GPC (column Shodex GPC KF-806, K manufactured by Showa Denko). -806L), the weight average molecular weight of the polymer forming the microcapsule shell was calculated. The results are shown in Table 2.

<Evaluation of inkjet ink>
[Evaluation of storage stability]
The average particle diameters of the microcapsules and the coloring material in the inks of Examples and Comparative Examples (hereinafter also referred to as the average particle diameter before storage) were measured using the same method as the above-described average particle diameter measuring method. Then, each ink was preserve | saved at 60 degreeC for 7 days, and the average particle diameter of the microcapsule and color material in the ink after preservation | save was measured. The average particle size of the microcapsules and the coloring material in the ink after storage (hereinafter, also simply referred to as the average particle size after storage) was measured using a method similar to the method for measuring the average particle size before storage. For each ink, the average particle size before storage was divided by the average particle size after storage and multiplied by 100 to calculate the change rate of the average particle size.

In the present invention, if the above-mentioned rate of change of the average particle diameter is A or B, it is said that sufficient storage stability is obtained. The results are shown in Table 2.
A: Change rate of average particle diameter is less than 10% before and after holding B: Change rate of average particle diameter is 10% or more and less than 20% before and after holding C: Change rate of average particle diameter is 20% before and after holding more than.

[Evaluation of ejection stability]
Using an ink jet printer PIXUS iP4300 (manufactured by Canon Inc.), the ink of the ink jet printer was loaded with the inks of Examples and Comparative Examples, respectively, and printing was performed.

Using an inkjet printer PIXUS iP4300 (manufactured by Canon Inc.), first, a vertical line of 1 dot was printed on a recording sheet. After that, the ink in the ink cartridge is ejected from the nozzles, and the ink is consumed. Immediately before the ink runs out, the recording paper other than the recording paper on which the vertical line is printed first (vertical line) Please specify whether or not was used.) After that, the recording paper on which the vertical lines are printed first and the recording paper on which the vertical lines are printed just before the ink is used are arranged, visually observed from a distance of 25 cm, and the printed matter is evaluated according to the following criteria. Thus, the ejection stability was evaluated. In the present invention, if it is A or B in the following evaluation criteria, sufficient discharge stability is assumed. The results are shown in Table 2.
A: There is almost no difference between the two. B: Although the dot landing deviation is recognized in a part of the vertical line printed on the cartridge immediately before the end of use, it can be recognized as a straight line. C: The dot is printed on the vertical line printed on the cartridge immediately before the end of use. Landing misalignment is clearly recognized, and the vertical line is misaligned.

(Evaluation of scratch resistance)
[Evaluation of scratch resistance immediately after printing]
A solid image was formed in an area excluding 20 mm from the edge of the recording medium using the ink cartridges in which the inks of Examples and Comparative Examples were mounted. PIXUS iP4300 (manufactured by Canon Inc.) was used as the ink jet recording apparatus, and professional photo paper PR-101 (manufactured by Canon Inc.) was used as the recording medium. After 15 seconds of printing, Sylbon paper was placed on the obtained printed matter, and a weight having a side of 5 cm and a weight of 1 kg was placed thereon, and then the Sylbon paper was pulled. The scratch resistance of each ink was evaluated by visually observing whether or not the recording paper edge (white background portion) and the silver paper were stained when the paper was pulled. In the present invention, A is considered to have sufficient scratch resistance. The results are shown in Table 2.
A: No stain was observed on the white background and the Sylbon paper. B: Stain was observed only on the Sylbon paper. C: Stain was observed on both the white background and the Silbon paper.

[Evaluation of scratch resistance after 1 hour of printing]
After the solid image was formed, the printed matter on which the solid image was formed was left at room temperature for 1 hour. The same method as the evaluation of scratch resistance immediately after printing described above was used. Evaluation was performed. Using the same criteria as the evaluation of scratch resistance immediately after printing, the scratch resistance was evaluated 1 hour after printing. The results are shown in Table 2.

Claims (5)

By dispersing a mixture obtained by mixing a dispersion containing a water-insoluble colorant, a first surfactant and water, and a dispersion containing an oily monomer, a second surfactant and water, the water A dispersion step of obtaining a dispersion containing the insoluble colorant, the first and second surfactants and the oily monomer, and a microcapsule by polymerizing the oily monomer contained in the dispersion obtained by the dispersion step A process for producing an ink jet ink having a microencapsulation step,
The method for producing an inkjet ink, wherein the first and second surfactants are multi-chain polyhydrophilic surfactants having a hydrophobic group, a linking group, and a plurality of anionic hydrophilic groups. The method for producing an inkjet ink according to claim 1, wherein the multi-chain polyhydrophilic surfactant is a compound represented by the following formula (1) or (2).
Formula (1)

(In the formula, X is H or Na.)
Formula (2)

(In the formula, X is H or Na.)   The method for producing an inkjet ink according to claim 1 or 2, wherein an acid value obtained by a colloid titration method of the microcapsule is 50 µmol or more and 400 µmol or less with respect to 1 g of the color material in the microcapsule. An ink-jet ink comprising microcapsules comprising a water-insoluble colorant, a surfactant and a polymer,
At least a part of the surface of the water-insoluble colorant is coated with the surfactant and the polymer;
The polymer is a polymer obtained by polymerizing a monomer containing at least an oily monomer,
The inkjet ink according to claim 1, wherein the surfactant is a multi-chain polyhydrophilic surfactant having a hydrophobic group, a linking group, and a plurality of anionic hydrophilic groups.   The inkjet ink according to claim 4, wherein the polymer has a weight average molecular weight obtained by gel permeation chromatography in terms of polystyrene of 400000 or more and 700000 or less.