JP2008222982A - Ink for inkjet and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ink for inkjet excellent in preservability and in discharge stability, and to provide a method for producing the ink for inkjet. <P>SOLUTION: The ink for inkjet comprises a colored resin fine particle and a dispersion medium for dispersing the colored resin fine particle, and the colored resin fine particle is produced by uniting a dispersoid in an emulsion wherein are dispersed a resin, a colorant, and an organic solvent in a dispersion medium, and the particle size distribution of the colored resin fine particle Dv/Dn is 1.00-1.15. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

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

The ink jet recording method is a printing method in which recording is performed by ejecting and adhering ink droplets onto a transfer paper. Since ink for inkjet recording is required to be stably ejected from the fine nozzles of the inkjet recording head, the viscosity is always in a certain range, and clogging due to drying and solidification at the nozzle tip does not occur. It will be necessary.
As an ink used in such an ink jet recording method, a pigment ink obtained by dispersing pigment fine particles in an aqueous dispersion medium or a nonpolar dispersion medium is widely used.

In such a pigment ink, since the color material is a pigment insoluble in the dispersion medium, when the ink is ejected onto the transfer paper, the pigment fine particles tend to stay on the surface of the transfer paper. As a result, the print quality can be made uniform regardless of the type of transfer paper.
However, in such a pigment ink, the dispersion stability of the pigment fine particles in the aqueous dispersion medium or the nonpolar dispersion medium is poor, and the pigment fine particles are aggregated to cause clogging of the nozzle portion of the ink discharge head. In addition, there is a problem that stable ejection cannot be performed due to a change in the viscosity of the ink.

In order to solve such problems, as a pigment ink, a pigment dispersion in which pigment and resin are dispersed in an insulating liquid is prepared, and a shearing force is applied to such a pigment dispersion to re-aggregate the pigment. There has been an attempt to use the same (see, for example, Patent Document 1).
In such a pigment ink, the pigment fine particles contained in the pigment ink have a pigment and a resin, and although the dispersion stability is improved as compared with the pigment ink in which the pigment is simply dispersed in the dispersion medium, It did not have sufficient dispersion stability and was inferior in ejection stability.

JP-A-5-186724

  An object of the present invention is to provide an inkjet ink having excellent storage stability and excellent ejection stability, and a method for producing an inkjet ink capable of producing the inkjet ink.

Such an object is achieved by the present invention described below.
The inkjet ink of the present invention has colored resin fine particles and a dispersion medium for dispersing the colored resin fine particles,
The colored resin fine particles are produced by combining the dispersoids in an emulsion in which a dispersoid containing a resin, a colorant, and an organic solvent is dispersed in an aqueous dispersion medium. To do.
As a result, it is possible to provide an ink-jet ink having excellent storage stability and excellent ejection stability.

In the ink-jet ink of the present invention, it is preferable that the colored resin fine particles are formed by adding an electrolyte to the emulsion.
As a result, the ink storage stability is particularly excellent, and the ink ejection stability is particularly excellent.
In the inkjet ink of the present invention, the particle size distribution Dv / Dn of the colored resin fine particles is preferably 1.00 to 1.15.
As a result, the ink storage stability is particularly excellent, clogging at the ink discharge head portion is more reliably prevented, and the discharge stability is particularly excellent. Further, the durability of the ink adhering to the recording medium is particularly excellent.

In the inkjet ink of the present invention, the average circularity R of the colored resin fine particles represented by the following formula (I) is preferably 0.98 to 1.
R = L ₀ / L ₁ (I)
(Wherein, L ₁ [μm] is the peripheral length of the projected image of the colored resin fine particles to be measured, and L ₀ [μm] is a perfect circle having an area equal to the area of the projected image of the colored resin fine particles to be measured. (Represents the perimeter of a complete geometric circle)
As a result, clogging at the ink discharge head portion is more reliably prevented, and the ink discharge stability is particularly excellent.

In the inkjet ink of the present invention, it is preferable that an average particle diameter of the colored resin fine particles is 0.2 to 10 μm.
As a result, even when the amount of ink adhering to the recording medium is small, higher density printing can be performed, and the long-term storage stability is particularly excellent.
In the inkjet ink of the present invention, it is preferable that the dispersion medium contains at least one of aliphatic hydrocarbon liquid, silicone oil, and fatty acid ester.
As a result, the ink storage stability is particularly excellent, and the ink ejection stability is particularly excellent.

The inkjet ink of the present invention preferably contains a polymer dispersant having a cationic functional group or an anionic functional group in addition to the colored resin fine particles and the dispersion medium.
As a result, the ink storage stability is particularly excellent, and the ink ejection stability is particularly excellent.
In the ink-jet ink of the present invention, the polymer dispersant preferably has a weight average molecular weight Mw of 10,000 to 100,000.
As a result, the ink storage stability is particularly excellent, and the ink ejection stability is particularly excellent.

In the inkjet ink of the present invention, the polymer dispersant is preferably compatible with the dispersion medium.
As a result, the ink storage stability is particularly excellent, and the ink ejection stability is particularly excellent.
In the inkjet ink of the present invention, the viscosity is preferably 3 to 40 mPa · s.
As a result, the ink storage stability is particularly excellent, and the ink ejection stability is particularly excellent.

The inkjet ink production method of the present invention includes a dispersion preparation step of preparing a dispersion in which a dispersoid containing a resin, a colorant, and an organic solvent is dispersed in an aqueous dispersion medium;
Coalescing a plurality of the dispersoids to obtain coalesced particles; and
Removing the organic solvent contained in the coalesced particles to obtain colored resin fine particles; and
A dispersion step of dispersing the colored resin fine particles in a dispersion medium.
Thereby, the manufacturing method of the inkjet ink excellent in discharge stability can be provided.

In the method for producing an inkjet ink according to the present invention, the dispersion is made into a W / O type emulsion by adding an aqueous liquid to a solution containing a resin, a colorant, and an organic solvent, and further the aqueous liquid is added. Therefore, it is preferable that the emulsion is an O / W type emulsion.
As a result, the ink storage stability is particularly excellent, clogging at the ink discharge head portion is more reliably prevented, and the ink discharge stability is particularly excellent. Further, the durability of the ink adhering to the recording medium is particularly excellent.

In the method for producing an inkjet ink of the present invention, it is preferable that the coalescing step is performed in the presence of a polymer dispersant having a cationic functional group or an anionic functional group.
As a result, the ink storage stability is particularly excellent, and the ink ejection stability is particularly excellent.
In the ink jet ink production method of the present invention, it is preferable to add an electrolyte in the coalescing step.
As a result, the ink storage stability is particularly excellent, and the ink ejection stability is particularly excellent.

Hereinafter, preferred embodiments of the present invention will be described in detail.
<Inkjet ink>
The ink jet ink of the present invention has colored resin fine particles containing at least a resin and a colorant, and a dispersion medium for dispersing the colored resin fine particles.
<Colored resin fine particles>
First, the colored resin fine particles will be described.
Such colored resin fine particles are made of a material containing a resin and a colorant.

In the present invention, the dispersoid in which the colored resin fine particles constituting the ink-jet ink (hereinafter also simply referred to as ink) include a resin and a colorant that are components of the colored resin fine particles in an aqueous dispersion medium, and an organic solvent. Is characterized by being obtained by uniting dispersoids in an emulsified liquid in which is dispersed.
By the way, an ink obtained by dispersing pigment fine particles in an aqueous dispersion medium or a nonpolar dispersion medium has a feature that the print quality can be made uniform regardless of the type of paper to be transferred. However, such an ink has poor dispersion stability of the pigment fine particles in the aqueous dispersion medium or nonpolar dispersion medium, and the pigment fine particles are aggregated to cause clogging of the nozzle portion of the ink discharge head. In addition, there is a problem that stable ejection cannot be performed due to a change in the viscosity of the ink. There is also an attempt to use an ink in which colored resin fine particles composed of a pigment and a resin are dispersed in a dispersion medium instead of the pigment. However, the colored resin fine particles in such an ink have a wide particle size distribution and are mixed with coarse particles and fine particles. Although such an ink has improved dispersion stability compared to an ink obtained by simply dispersing a pigment in a dispersion medium, it is not sufficient, and it tends to cause clogging at the ink discharge head, and discharge stability. Was not enough. In addition, when such ink is ejected onto the transfer paper, among the colored resin fine particles, fine particles permeate into the transfer paper, causing problems such as bleeding of the print portion or reduction in print density, Stable printing was difficult.

  On the other hand, the colored resin fine particles having the above-described characteristics have a uniform particle size in which coarse particles and fine particles are not mixed. Thereby, the dispersion stability of the ink is excellent, clogging at the ink discharge head portion is prevented, and the ink has excellent discharge stability and storage stability. Further, such colored resin fine particles have sufficiently high circularity. In such an ink in which the colored resin fine particles are dispersed, the aggregation of the colored resin fine particles is suitably suppressed even when stored for a long period of time. Therefore, excellent dispersion stability can be maintained over a long period of time. Further, the colored resin fine particles having a high degree of circularity can smoothly pass through the nozzle portion of the ink discharge head. For this reason, clogging in the ink discharge head portion can be prevented, and driving energy required when ink is discharged from the head portion can be reduced. Further, such colored resin fine particles can make the composition of each constituent particle uniform. In this way, by using ink in which colored resin fine particles having a uniform particle size and a uniform composition (content ratio between the colorant and the resin) between the particles are dispersed, the printing density of the printing portion is uniform. Can be. In addition, the particle diameter of pigments contained in currently widely used pigment inks is about several tens of nm to 100 nm, but in the ink of the present invention manufactured using a manufacturing method as described later. The particle diameter of the colored resin fine particles contained is about submicron to several tens of microns. As described above, the colored resin fine particles contained in the ink of the present invention are characterized by having a relatively large particle diameter, a uniform particle diameter, and a uniform composition among the particles. The ink in which the colored resin fine particles are dispersed is excellent in storage stability and ejection stability, and the colored resin fine particles in the ink discharged onto the transfer paper are reliably suppressed from penetrating into the transfer paper. The As a result, problems such as blurring of the print portion or reduction in print density can be prevented, and the resolution of the print portion can be improved. Further, even if the amount of ink discharged onto the transfer paper is reduced, the print density can be increased. Further, even when a transfer paper having different material, surface roughness, etc. is used, the print quality can be made uniform regardless of the type of the transfer paper.

  The resin constituting the colored resin fine particles is not particularly limited. For example, polystyrene, poly-α-methylstyrene, chloropolystyrene, styrene-chlorostyrene copolymer, styrene-propylene copolymer, styrene-butadiene copolymer, Styrene-vinyl chloride copolymer, styrene-vinyl acetate copolymer, styrene-maleic acid copolymer, styrene-acrylic acid ester copolymer, styrene-methacrylic acid ester copolymer, styrene-acrylic acid ester-methacrylic acid A styrene resin such as an ester copolymer, a styrene-α-chloromethyl acrylate copolymer, a styrene-acrylonitrile-acrylic acid ester copolymer, a styrene-vinyl methyl ether copolymer, or the like containing a styrene or a styrene substitution product. Polymer or copolymer, polyester Resin, epoxy resin, urethane modified epoxy resin, silicone modified epoxy resin, vinyl chloride resin, rosin modified maleic acid resin, phenyl resin, polyethylene resin, polypropylene, ionomer resin, polyurethane resin, silicone resin, ketone resin, ethylene-ethyl acrylate A copolymer, a xylene resin, a polyvinyl butyral resin, a terpene resin, a phenol resin, an aliphatic or alicyclic hydrocarbon resin, and the like can be used, and one or more of these can be used in combination.

Among these, the polyester resin has high transparency and can sufficiently express the color tone of the colorant described later. Therefore, by using an ink containing colored resin fine particles using a polyester resin as a resin as a constituent component, high density printing can be performed even if the amount of ink attached to the transfer paper is relatively small.
Further, the glass transition temperature Tg of the resin constituting the colored resin fine particles is not particularly limited, but is preferably 30 to 100 ° C, more preferably 55 to 85 ° C. When the glass transition temperature Tg of the resin constituting the colored resin fine particles is within the above range, aggregation of the colored resin fine particles in the ink can be more reliably prevented. As a result, the dispersion stability of the ink is excellent over a long period of time, the ink is excellent in storage stability and the discharge stability is excellent over a long period of time.

When the colored resin fine particles include a plurality of types of resin components, that is, when the resin includes a plurality of types of resin components, the glass transition temperature Tg [° C.] is a value of Tg obtained as a solution of the following simultaneous equations. Can be adopted.
100 / T = w1 / T1 + w2 / T2 + ...
Tg = T-273
However, in the above formula, the glass transition temperatures of the respective resin components (first component, second component,...) Constituting the resin are respectively expressed as absolute temperature T1 [K], T2 [K], , And the content ratio of each component (first component, second component,...) In the entire resin component constituting the resin A is w1 [wt%] and w2 [wt%], respectively. ...

The softening temperature of the resin constituting the colored resin fine particles is not particularly limited, but is preferably 60 to 220 ° C, more preferably 80 to 200 ° C. When the softening temperature T1 / 2 of the resin constituting the colored resin fine particles is within the above range, aggregation of the colored resin fine particles in the ink can be more reliably prevented. As a result, the dispersion stability of the ink is excellent over a long period of time, the ink is excellent in storage stability and the discharge stability is excellent over a long period of time. In the present specification, unless otherwise specified, the softening temperature T1 / 2 is as follows using a flow tester (CFT-500, manufactured by Shimadzu Corporation), which is a constant load extrusion type capillary rheometer. Refers to the required value. That is, as shown in FIG. 2A, a sample 8 (weight 1.5 g) is filled into a cylinder 7 having a nozzle 6 having a nozzle diameter D of 1.0 mm and a nozzle length (depth) L of 1.0 mm. When a load of 10 kg per unit area (cm ² ) is applied from the side opposite to the nozzle 6 and heated at a temperature rising rate of 6 ° C. per minute in that state, the stroke S of the load surface 9 (of the load surface 9 By measuring the sinking value), the relationship between the elevated temperature and the stroke S is obtained as shown in FIG. 2 (b). The outflow of the sample 8 from the nozzle 6 starts and the stroke S increases rapidly. When the temperature when the curve rises is Tfb [° C.], and when the temperature when the flow of the sample 8 from the nozzle 6 almost ends and the curve is bent is Tend [° C.], the stroke at Tfb Stroke S at Sfb and Tend The temperature at the intermediate value become S1 / 2 with nd, herein it employs as a softening temperature T1 / 2.

As the colorant constituting the colored resin fine particles, for example, pigments, dyes and the like can be used.
Examples of such pigments include C.I. I. Pigment Red 2,3,5,17,22,23,38,81, 48: 1, 48: 2, 48: 3, 48: 4, 49: 1, 52: 1, 53: 1, 57: 1. 63: 1,112,122,144,146,149,166,170,176,177,178,179,185,202,207,209,254,101,102,105,106,108,108: 1, C. I. Pigment green 7,36,15,17,18,19,26,50, C.I. I. Pigment blue 1,15,15: 1,15: 2,15: 3, 15: 4, 15: 6, 17: 1, 18, 60, 27, 28, 29, 35, 36, 80, C.I. I. Pigment Yellow 1, 3, 12, 13, 14, 17, 55, 73, 74, 81, 83, 93, 94, 95, 97, 108, 109, 110, 129, 138, 139, 150, 151, 153 154, 168, 184, 185, 34, 35, 35: 1, 37, 37: 1, 42, 43, 53, 157, C.I. I. Pigment violet 1, 3, 19, 23, 50, 14, 16, C.I. I. Pigment orange 5, 13, 16, 36, 43, 20, 20: 1, 104, C.I. I. And CI Pigment Brown 25, 7, 11, 33, and the like. Among these, one kind or two or more kinds can be used in combination.

Examples of such dyes include azo dyes, anthraquinone dyes, condensed polycyclic aromatic carbonyl dyes, indigoid dyes, carbonium dyes, phthalocyanine dyes, methine, and polymethine dyes. Specific examples of the dye include C.I. I. Solvent colors (yellow, magenta, cyan, black) and the like can be mentioned, and one or more of these can be used in combination.
As the colored resin fine particles, the pigments and dyes as described above can be used, but when the pigment is used, the durability (light resistance, gas resistance, water resistance) of the printed portion is excellent. It is possible to prevent the printing portion from fading.
In addition, when the above-described dye is used as the colored resin fine particles in the ink, it is possible to obtain an ink with more uniform print quality than the aqueous ink in which the dye is dissolved in the aqueous medium. In addition, depending on the type of paper to be transferred, the water-based ink has a problem that the dye penetrates into the inside of the paper, causing bleeding and a decrease in print density. However, the dye is used as the colored resin fine particles. Ink is less dependent on the paper type of print quality.

  The colored resin fine particles contain a colorant and a resin, and are obtained using a manufacturing method as described later. By adjusting the composition and content of the resin, the specific gravity of the colored resin fine particles can be easily made equal to the specific gravity of the dispersion medium for dispersing the colored resin fine particles described later. As a result, the ink has excellent storage stability and ejection stability. In addition, variation in the amount of ink droplets discharged onto the transfer paper can be reduced, and the print density can be uniform and high-resolution printing can be performed.

The colored resin fine particles may contain components other than those described above. Examples of such components include a charge control agent and magnetic powder.
Examples of the charge control agent include benzoic acid metal salts, salicylic acid metal salts, benzylic acid metal salts, alkylsalicylic acid metal salts, copper phthalocyanine, perylene, quinacridone, azo pigments, metal-containing bisazo dyes, and calixarene. Type phenolic condensate, cyclic polysaccharide, trimethylethane compound, catechol metal salt, nigrosine compound, tetraphenylborate derivative, quaternary ammonium salt, onium compound, toniphenylmethane compound, alkylpyridinium salt, chlorination Examples thereof include polyester and nitrofunic acid.

Examples of the magnetic powder include magnetite, maghemite, various ferrites, cupric oxide, nickel oxide, zinc oxide, zirconium oxide, titanium oxide, magnesium oxide, and other metal oxides, and magnetic materials such as Fe, Co, and Ni. The thing etc. which were comprised with the magnetic material containing a metal are mentioned.
In addition to the above materials, the constituent material (component) of the colored resin fine particles is, for example, zinc stearate, zinc oxide, cerium oxide, silica, titanium oxide, iron oxide, fatty acid, fatty acid metal salt, wax. Etc. may be used.

  The average particle size of the colored resin fine particles as described above is not particularly limited, but is preferably 0.2 to 10 μm, and more preferably 0.3 to 3 μm. When the average particle diameter of the colored resin fine particles is a value within the above range, the ink dispersion stability is particularly excellent, and the ink is particularly excellent in storage stability and ejection stability. Further, when ink droplets are ejected onto the transfer paper, the colored resin fine particles are more reliably prevented from penetrating into the transfer paper. As a result, it is possible to more reliably prevent problems such as blurring of the print portion and a decrease in print density, and an excellent resolution of the print portion. Furthermore, even if the amount of ink discharged onto the transfer paper is reduced, the print density can be increased. Further, even if different materials, surface roughness, etc. are used as the transfer paper, the print quality can be made uniform regardless of the type of the transfer paper.

Moreover, it is preferable that the average circularity R about the colored resin fine particles represented by the following formula (I) is 0.98 to 1.00. The ink in which the colored resin fine particles satisfying the above conditions are dispersed can maintain better dispersion stability over a long period of time, and the ink has particularly excellent storage stability and ejection stability. Further, such colored resin fine particles can pass through the nozzle portion of the ink discharge head more smoothly. For this reason, clogging in the ink discharge head portion can be prevented, and driving energy required when ink is discharged from the head portion can be further reduced.
R = L ₀ / L ₁ (I)
(Wherein, L ₁ [μm] is the peripheral length of the projected image of the colored resin fine particles to be measured, and L ₀ [μm] is a perfect circle having an area equal to the area of the projected image of the colored resin fine particles to be measured. (Represents the perimeter of a complete geometric circle)

The standard deviation of the circularity of the colored resin fine particles is preferably 0.04 or less.
As described above, when the standard deviation of the circularity is sufficiently small, the above-described effect becomes more remarkable.
Further, the particle diameter of the colored resin fine particles expressed as a numerical value (σ (DT) / DT) obtained by dividing the standard deviation (σ (DT)) of the colored resin fine particles by the average particle diameter (DT) of the colored resin fine particles. The coefficient of variation for is preferably 0.30 or less, and more preferably 0.20 or less. Thereby, the particle size distribution of the colored resin fine particles becomes particularly sharp. As a result, the dispersion stability of the ink is particularly excellent, and the ink is particularly excellent in storage stability and ejection stability. Further, when ink in which colored resin fine particles satisfying the above conditions are dispersed is ejected onto the transfer paper, the colored resin fine particles are held on the surface of the transfer paper. Such colored resin fine particles have excellent packing properties, and are particularly excellent in durability (abrasion resistance) of the printed portion.

  Further, when the 50% volume particle size of the colored resin fine particles is Dv (50) [μm] and the 50% number particle size is Dn (50) [μm], the value of Dv (50) / Dn (50) is 1.00 to 1.15, and more preferably 1.00 to 1.10. As a result, the dispersion stability of the ink is particularly excellent, and the ink is particularly excellent in storage stability and ejection stability. Further, when ink in which colored resin fine particles satisfying the above conditions are dispersed is ejected onto the transfer paper, the colored resin fine particles are held on the surface of the transfer paper. Such colored resin fine particles have excellent packing properties, and are particularly excellent in durability (abrasion resistance) of the printed portion.

In addition, the value of Dv (50) and Dn (50) can be calculated | required by the measurement using the multisizer II type | mold (aperture tube diameter: 100 micrometers) by a Coulter company, for example.
In addition, the content of the colorant in the ink is preferably 1 to 15 wt%, and more preferably 2 to 10 wt%. When the content of the colorant is within the above range, clogging at the ink discharge head portion is prevented, and the ink has particularly excellent discharge stability.

<Dispersion medium>
Next, a dispersion medium for dispersing the above-described colored resin fine particles will be described.
Examples of such a dispersion medium include, but are not limited to, polar liquids such as water and various alcohols, nonpolar liquids such as fatty acid esters such as aliphatic hydrocarbon liquids, silicone oils, fatty acid triglycerides, and fatty acid monoesters. These can be used alone or in combination of two or more.

  Among these, when an aliphatic hydrocarbon liquid is used as the dispersion medium, the following effects can be obtained. That is, the aliphatic hydrocarbon liquid is a liquid that is chemically stable and has low moisture absorption. For this reason, the ink using the aliphatic hydrocarbon liquid as a dispersion medium is prevented from being denatured (deteriorated) and maintains a constant viscosity over a long period of time. As a result, the ink has excellent ejection stability and can maintain stable printing quality. In addition, the aliphatic hydrocarbon liquid has a property of easily penetrating into the transfer paper. Therefore, when such ink is ejected from the ink ejection head onto the transfer paper, the colored resin fine particles remain on the surface of the transfer paper, while the aliphatic hydrocarbon liquid quickly penetrates into the transfer paper. Can do. Thereby, the amount of the aliphatic hydrocarbon liquid existing between the colored resin fine particles can be reduced, and the printed portion can be made clearer. In addition, the aliphatic hydrocarbon liquid has a high affinity with the colored resin fine particles as described above. Accordingly, the dispersion stability of the colored resin fine particles in the ink is particularly excellent, and the ink is particularly excellent in storage stability and ejection stability.

  The aliphatic hydrocarbon liquid that can be used for the dispersion medium is not particularly limited. For example, Isopar E, Isopar G, Isopar H, Isopar L (Isopar; trade name of Exxon Chemical Co., Ltd.), Cosmo White P-60 , Cosmo White P-70, Cosmo White P-120 (trade name of Cosmo Oil Lubricants), Dyna Fresia W-8, Daphne Oil CP, Daphne Oil KP, Transformer Oil H, Transformer Oil G, Transformer Oil A, Transformer Oil B, Transformer Oil S (trade name of Idemitsu Kosan Co., Ltd.), Cielsol 70, Cielsol 71 (Cielsol; trade name of Ciel Oil Co.), Amsco OMS, Amsco 460 solvent (trade name of Amsco; Spirits), low viscosity / high Viscosity flow Raffin (Wako Pure Chemical Industries), octane, isooctane, decane, isodecane, decalin, nonane, dodecane, isododecane, cyclohexane, cyclooctane, cyclodecane, etc. are used, and among these, one kind or a combination of two or more kinds is used. be able to.

Such an aliphatic hydrocarbon-based liquid is preferably a saturated hydrocarbon. The aliphatic hydrocarbon liquid that is a saturated hydrocarbon is a particularly chemically stable liquid. Therefore, an ink using such an aliphatic hydrocarbon liquid as a dispersion medium can maintain stable print quality for a longer period of time.
Moreover, it is preferable that the aliphatic hydrocarbon which comprises such an aliphatic hydrocarbon-type liquid has the branched chain of a hydrocarbon group. As a result, the aliphatic hydrocarbon liquid becomes chemically more stable. Therefore, an ink using such an aliphatic hydrocarbon liquid as a dispersion medium can maintain stable print quality for a longer period of time. This is considered to be because the structure of the aliphatic hydrocarbon constituting the aliphatic hydrocarbon-based liquid becomes bulky so that a chemical reaction hardly occurs.

  Further, when silicone oil is used as the dispersion medium, the following effects can be obtained. That is, silicone oil is a chemically stable liquid with little moisture absorption. For this reason, the ink using the aliphatic hydrocarbon liquid as a dispersion medium is prevented from being denatured (deteriorated) and maintains a constant viscosity over a long period of time. As a result, the ink has excellent ejection stability and can maintain stable printing quality. Silicone oil is generally a substance that has little influence on the human body, and can provide an environmentally friendly printed matter (printed paper to be transferred).

  Examples of silicone oils that can be used for the dispersion medium include KF96, KF4701, KF965, KS602A, KS603, KS604, KF41, KF54, FA630 (manufactured by Shin-Etsu Silicone), TSF410, TFS433, TFS434, TFS451, TSF437, and (Momentive). -Performance Materials Japan GK), SH200 (manufactured by Toray Industries, Inc.), and the like can be mentioned, and among these, one type or two or more types can be used in combination.

  Moreover, fatty acid ester can be used suitably as a dispersion medium. Examples of such fatty acid esters include fatty acid triglycerides which are triesters between higher fatty acids having 4 or more carbon atoms and glycerin, and monoesters between higher fatty acids having 4 or more carbon atoms and monohydric alcohols. There are certain fatty acid monoesters. When such a fatty acid ester is used as a dispersion medium, the following effects can be obtained. That is, such a fatty acid ester has high affinity with the resin that is a constituent component of the colored resin fine particles as described above. Accordingly, the dispersion stability of the colored resin fine particles in the ink using the fatty acid ester as the dispersion medium is particularly excellent, and the ink is particularly excellent in storage stability and ejection stability. In addition, such fatty acid esters are abundant in nature and are environmentally friendly components. Therefore, an ink using such a fatty acid ester as a dispersion medium is environmentally friendly.

  Examples of fatty acid esters that can be used in the dispersion medium include oleic acid, palmitoleic acid, linoleic acid, α-linolenic acid, γ-linolenic acid, arachidonic acid, docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA), and the like. Representative unsaturated fatty acid triglycerides, butyric acid, caproic acid, caprylic acid, capric acid, lauric acid, mytilic acid, palmitic acid, stearic acid, arachidic acid, behenic acid, lignoceric acid, and other saturated fatty acid triglycerides, olein Alkyls of unsaturated fatty acids represented by acids, palmitoleic acid, linoleic acid, α-linolenic acid, γ-linolenic acid, arachidonic acid, docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA), etc. (methyl, ethyl, propyl, Butyl) ester, butyric acid, capro Alkyl (methyl, ethyl, propyl, butyl, etc.) esters of saturated fatty acids such as acid, caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, arachidic acid, behenic acid, lignoceric acid, etc. 1 type selected from these, or 2 or more types can be used in combination.

Among the fatty acid esters described above, when fatty acid triglyceride is used as a dispersion medium, the affinity between the resin material constituting the colored resin fine particles as described above and the fatty acid triglyceride is particularly high, and ink storage stability and ejection stability. Is particularly excellent.
In addition, among the fatty acid esters described above, when a fatty acid monoester is used as a dispersion medium, the fatty acid monoester penetrates into the colored resin fine particles and exhibits a plasticizing effect. Due to this plasticizing effect, the colored resin fine particles enter the fibers near the surface of the transfer paper more reliably and are retained. Thereby, the durability (scratch resistance) of the printed portion is particularly excellent.

  Among such fatty acid esters, fatty acid esters whose fatty acid components are saturated fatty acids are not easily degraded and are chemically particularly stable. For this reason, an ink using a fatty acid ester as a dispersion medium is prevented from being denatured (deteriorated), and maintains a constant viscosity over a long period of time. As a result, the ink has excellent ejection stability and can maintain stable printing quality.

Moreover, as such a dispersion medium, components other than those described above may be included. For example, degradation products of fatty acid triglycerides such as glycerin and fatty acids, benzene, toluene, xylene, mesitylene and the like can be mentioned, and one or more of these can be used in combination.
Moreover, the viscosity at 25 ° C. of the dispersion medium constituting the ink is not particularly limited, but is preferably 2 to 30 mPa · s, and more preferably 3 to 15 mPa · s. Thereby, the dispersion stability of the ink becomes particularly excellent.

<Dispersant>
Further, the inkjet ink may contain a dispersant. Thereby, the dispersibility of the colored resin fine particles in the dispersion medium can be improved, and the dispersion stability of the ink can be further improved.
Examples of the dispersant include various low-molecular and high-molecular dispersants such as cationic, anionic, nonionic, amphoteric, silicone-based, and fluorine-based, and one or two or more selected from these are combined. Can be used. Among these, the dispersant is preferably a polymer dispersant having a cationic functional group or an anionic functional group.

Such a cationic or anionic polymer dispersant has high affinity with the colored resin fine particles as described above, and can make the dispersion stability of the colored resin fine particles in the ink particularly excellent. . As a result, the ink is particularly excellent in storage stability and ejection stability.
In addition, the weight average molecular weight Mw of such a polymer dispersant is preferably 10,000 to 100,000, more preferably 30,000 to 80,000. The polymer dispersant satisfying the above conditions has high affinity with the colored resin fine particles as described above, and can make the dispersion stability of the colored resin fine particles in the ink particularly excellent. As a result, the ink is particularly excellent in storage stability and ejection stability.

  Further, such a polymer dispersant is preferably compatible with the dispersion medium as described above. By including such a polymer dispersant in the ink, the viscosity of the ink can be lowered and a constant viscosity can be maintained over a long period of time. As a result, the dispersion stability of the ink is particularly excellent, and the ink is particularly excellent in storage stability and ejection stability.

  Further, the viscosity of the ink at 25 ° C. is not particularly limited, but is preferably 3 to 40 mPa · s, and more preferably 4 to 30 mPa · s. As a result, the dispersion stability of the ink is particularly excellent, clogging at the ink discharge head portion is more reliably prevented, and the ink has particularly excellent discharge stability. In addition, it is possible to stably discharge droplets having a uniform size, and the printing density of the printing unit can be made more uniform.

≪Inkjet ink manufacturing method≫
Next, a method for producing the inkjet ink of the present invention will be described.
In the method for producing colored resin fine particles according to the present embodiment, a dispersion (emulsified suspension) in which a dispersoid composed of a material containing a resin component and an organic solvent is dispersed (emulsified and / or suspended) in an aqueous dispersion medium. A step (emulsification suspension (dispersion) preparation step), a step of coalescing a plurality of dispersoids to obtain coalesced particles (a coalescence step), and an organic solvent contained in the coalesced particles. A step of removing and obtaining colored resin fine particles (solvent removal step), and a step of dispersing the colored resin fine particles in a dispersion medium (dispersing step). Thereby, it is possible to obtain colored resin fine particles having a uniform particle size (monodispersed particle size distribution) in which coarse particles and fine particles are not mixed.

Hereinafter, the manufacturing method of the colored resin fine particles of the present embodiment will be described in detail.
[Emulsion suspension preparation process (dispersion preparation process)]
First, the emulsion suspension preparation process will be described.
The emulsified suspension may be prepared by any method. For example, it is prepared by mixing a colored resin liquid, which is a liquid containing a resin, a colorant, and an organic solvent (organic solvent), with an aqueous medium. Can do.

As the resin component constituting the colored resin liquid, the resin as the constituent material of the colored resin fine particles described above can be used.
Moreover, as a coloring agent, what was illustrated as a constituent material of the colored resin fine particle mentioned above can be used.
Examples of the organic solvent (organic solvent) include ketone solvents such as methyl ethyl ketone (MEK), diethyl ketone, methyl isobutyl ketone (MIBK), methyl isopropyl ketone (MIPK), cyclohexanone, 3-heptanone, and 4-heptanone. n-butanol, i-butanol, t-butanol, 3-methyl-1-butanol, 1-pentanol, 2-pentanol, n-hexanol, cyclohexanol, 1-heptanol, 1-octanol, 2-octanol, 2 -Alcohol solvents such as methoxyethanol, allyl alcohol, furfuryl alcohol, phenol, diethyl ether, dipropyl ether, diisopropyl ether, dibutyl ether, 1,2-dimethoxyethane (DME), 1,4-dioxane, Ether solvent such as trahydropyran (THP), anisole, diethylene glycol dimethyl ether (diglyme), 2-methoxyethanol, cellosolv solvent such as methyl cellosolve, ethyl cellosolve, phenyl cellosolve, hexane, pentane, heptane, cyclohexane, methylcyclohexane, Aliphatic hydrocarbon solvents such as octane, didecane, methylcyclohexene, isoprene, aromatic hydrocarbon solvents such as toluene, xylene, benzene, ethylbenzene, naphthalene, dichloromethane, chloroform, 1,2-dichloroethane, trichloroethylene, chlorobenzene, four Halogenated solvents such as carbon chloride, ethyl acetate, methyl acetate, isopropyl acetate, isobutyl acetate, isopentyl acetate, ethyl chloroacetate, chlorovinegar Examples include butyl, isobutyl chloroacetate, ethyl formate, isobutyl formate, ethyl acrylate, methyl methacrylate, ethyl benzoate, and other ester solvents, acrylonitrile, acetonitrile, and other nitrile solvents, nitromethane, nitroethane, and other nitro solvents. , One or a mixture of two or more selected from these can be used.

As an organic solvent, it is preferable that the solubility with respect to 100 weight part water at 25 degreeC is 5-45 weight part, and it is more preferable that it is 5-40 weight part.
The boiling point of the organic solvent (boiling point at normal pressure (1 atm); hereinafter the same) is preferably lower than the boiling point of water. Thereby, the organic solvent can be recovered efficiently.
Examples of the organic solvent that satisfies the above conditions include methyl ethyl ketone, ethyl acetate, chloroform, dichloromethane, trichloroethylene, and the like. Among them, methyl ethyl ketone and ethyl acetate are preferable because the resin component (particularly polyester resin) has high solubility and dispersibility.

  The colored resin liquid can be obtained, for example, by mixing a material containing a resin component, a colorant, and an organic solvent with a stirrer such as a high-speed stirrer. The colored resin liquid may be prepared, for example, by kneading a composition containing a resin component and a colorant in advance and mixing the kneaded material obtained by kneading with an organic solvent. Examples of the stirrer that can be used for the preparation of the colored resin liquid include DESPA (manufactured by Asada Tekko), K. Robotics / T. K. Examples include Homo Desper 2.5 type wing (manufactured by Primex).

The blade tip speed during mixing using a stirrer is preferably, for example, 4 to 30 m / sec, and more preferably 10 to 25 m / sec. When the blade tip speed is a value within the above range, the resin component can be efficiently dissolved and dispersed in the organic solvent, and the colorant is dispersed more uniformly in the colored resin liquid. It can be. On the other hand, if the blade tip speed is less than the lower limit, depending on the resin component, the colorant, the composition of the organic solvent, etc., fine dispersion of the colorant in the colored resin liquid may be insufficient. On the other hand, when the blade tip speed exceeds the upper limit, heat generation due to shearing may increase depending on the composition of the organic solvent, and it may be difficult to perform uniform stirring in combination with volatilization of the organic solvent.
Moreover, it is preferable that the material temperature at the time of stirring is 20-60 degreeC, and it is more preferable that it is 30-50 degreeC.
In the obtained colored resin liquid, the resin component and the colorant are dissolved or dispersed in an organic solvent.

  Although the content rate of solid content in a colored resin liquid is not specifically limited, It is preferable that it is 40-75 wt%, it is more preferable that it is 50-73 wt%, and it is further more preferable that it is 50-70 wt%. When the solid content is within the above range, the dispersoid constituting the emulsified suspension described later can have a higher sphericity (a shape close to a true sphere), and finally The shape of the colored resin fine particles obtained in the above can be made more surely suitable.

The colored resin liquid may contain an emulsifier (dispersant). Thereby, the dispersibility of the dispersoid in the emulsified suspension described in detail later can be easily made particularly excellent.
As the emulsifier, those generally used as a dispersant, a dispersion stabilizer, and a surfactant can be applied. In the present invention, specific materials that can be applied as an emulsifier include, for example, polyoxyethylene nonyl phenyl ether, polyoxyethylene octyl phenyl ether, polyoxyethylene dodecyl phenyl ether, polyoxyethylene lauryl ether, polyoxyethylene Nonionic emulsifiers such as alkyl ethers, polyoxyethylene fatty acid esters, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, various pluronics, anionic emulsifiers such as alkyl sulfates, alkyl sulfonates, alkyl benzene sulfonates, Examples include cationic emulsifiers such as quaternary ammonium salts, and one or more selected from these can be used in combination. Of these, alkylbenzene sulfonate is preferred as the emulsifier. As a result, the dispersibility of the dispersoid in the emulsified suspension is particularly excellent, and even if the emulsifier remains in the final colored resin fine particles, the charging characteristics of the colored resin fine particles are adversely affected. Can be effectively prevented, and an increase in the amount of TVOC (volatile organic compound) can be effectively prevented. Examples of the alkyl group that the alkylbenzene sulfonate has include hexyl, heptyl, octyl, nonanyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl Group and the like, and a dodecyl group is preferable. That is, the alkylbenzene sulfonate is preferably dodecylbenzene sulfonate. As a result, the dispersibility of the dispersoid in the emulsified suspension is further improved, and even if the emulsifier remains in the final colored resin fine particles, the charging characteristics of the colored resin fine particles are adversely affected. Can be more effectively prevented, and an increase in the amount of TVOC (volatile organic compound) can be more effectively prevented.

  The amount of the emulsifier to be used is preferably 0.1 to 3.0 wt%, more preferably 0.3 to 2.0 wt%, and 0.3 to 1.5 wt% with respect to the solid content. More preferably. If the amount of the emulsifier to be used is less than the lower limit, the effect of preventing the generation of coarse particles may not be sufficiently obtained. On the other hand, when the amount of the emulsifier used exceeds the upper limit, in the coalescence step described later, coalescence of the dispersoid does not sufficiently proceed, and fine particles smaller than a predetermined particle size remain, yielding colored resin fine particles. May be reduced.

The colored resin liquid may contain wax, charge control agent, magnetic powder and the like as described above as components other than the resin component, the colorant, and the organic solvent.
In the preparation of the colored resin liquid, all the components of the colored resin liquid to be prepared may be mixed at the same time, or a part of the components of the colored resin liquid to be prepared may be mixed in advance. Master) and then the mixture (master) may be mixed with other ingredients. For example, a colorant and a resin component are mixed (kneaded) to obtain a colorant master, and then the colorant master, the resin component (additional resin), and an organic solvent are mixed to prepare a colored resin liquid. It may be prepared. Thereby, the colored resin liquid with which each component was mixed uniformly can be obtained more reliably. Moreover, when using a wax as a structural component of the colored resin liquid, for example, a material containing a wax, a resin component, and an organic solvent is mixed to obtain a wax master. This wax master is used as a colorant master, a resin component ( The colored resin liquid may be prepared by mixing with an additional resin) and an organic solvent. In preparation of the wax master, a wax dispersion liquid (so-called wax emulsion) in which wax particles are dispersed in an aqueous dispersion medium may be used.

An emulsified suspension is prepared by mixing the colored resin liquid as described above with an aqueous medium.
As the aqueous medium, those mainly composed of water can be used.
The aqueous medium may contain, for example, a solvent having excellent compatibility with water (for example, a solvent having a solubility in 100 parts by weight of water at 25 ° C. of 50 parts by weight or more).
The aqueous medium may contain an emulsifier (dispersant).

  In preparing the emulsified suspension, for example, a neutralizing agent may be used. Thereby, for example, the functional group (carboxyl group) possessed by the polyester resin can be neutralized, and the shape, size uniformity, and dispersibility of the dispersoid in the prepared emulsion suspension can be improved. It can be particularly excellent. In addition, by using a neutralizing agent, the dispersibility of the dispersoid can be sufficiently improved without using an emulsifier or without using an emulsifier. The occurrence of inconvenience due to can be prevented. For example, when a relatively large amount of emulsifier is used, a relatively high shearing force is required during preparation of the emulsion suspension, thereby generating coarse particles (coarse dispersoid) and particle size distribution of the dispersoid. However, such a problem can be prevented by performing neutralization with a neutralizing agent.

For example, the neutralizing agent may be added to the colored resin liquid, or may be added to the aqueous medium.
Further, the neutralizing agent may be added in a plurality of times in the preparation of the emulsion suspension. For example, after adding a neutralizing agent to the colored resin liquid prepared as described above, the colored resin liquid (colored resin liquid to which a neutralizing agent has been added) and an aqueous medium are mixed, and then, You may add a neutralizing agent in a liquid mixture. Thereby, it is possible to easily obtain an emulsified suspension in which the dispersoid is uniformly and finely dispersed while effectively suppressing an increase in the viscosity of the liquid during mixing of the colored resin liquid and the aqueous medium.

  As the neutralizing agent, a basic compound can be used. More specifically, for example, inorganic salts such as sodium hydroxide, potassium hydroxide and ammonia, and organic bases such as diethylamine, triethylamine and isopropylamine can be used. 1 type or 2 types or more selected from these can be used. The neutralizing agent may be an aqueous solution containing the above compound.

  Moreover, the usage-amount of a basic compound has the preferable quantity (1-3 equivalent) equivalent to 1-3 times of the quantity required in order to neutralize all the carboxyl groups which a polyester-type resin has, and 1-2 times. Corresponding amounts (1-2 equivalents) are preferred. Thereby, it is possible to effectively prevent the formation of irregular dispersoids, and it is possible to make the particle size distribution of the particles obtained in the coalescence step described in detail later sharper.

  Water after dripping water in the emulsified suspension obtained in this step (water used for emulsification, water from the wax dispersion (so-called wax emulsion) used to prepare the wax master, neutralized base) The ratio of the total amount of water and the like to the organic solvent is preferably 50:50 to 80:20, and more preferably 60:40 to 80:20, by volume ratio. As a result, the shape, size uniformity, and dispersibility of the dispersoid in the prepared emulsion suspension can be made particularly excellent.

  The mixing of the colored resin liquid and the aqueous medium may be performed by any method, but the aqueous medium is gradually added (dropped) to the colored resin liquid while shearing the colored resin liquid with a stirrer or the like. It is preferable to finally obtain a dispersion in which the dispersoid derived from the colored resin liquid is dispersed in the aqueous medium. Thereby, for example, an emulsified suspension in which the dispersoid is uniformly and finely dispersed can be obtained easily and reliably.

Examples of the stirrer that can be used for the preparation of the emulsified suspension include DESPA (manufactured by Asada Tekko Co., Ltd.), T.C. K. Robotics / T. K. Examples include a high-speed stirrer such as Homo Desper 2.5 type wing (manufactured by Primics), slasher (manufactured by Mitsui Mining), Cavitron (manufactured by Eurotech), or a high-speed disperser.
The blade tip speed during mixing using a stirrer is preferably, for example, 4 to 30 m / sec, and more preferably 10 to 25 m / sec. When the blade tip speed is a value within the above range, an emulsified suspension can be obtained efficiently, and the dispersion of the shape and size of the dispersoid in the emulsified suspension can be made particularly small. The uniform dispersibility of the dispersoid can be made particularly excellent. On the other hand, if the blade tip speed is less than the lower limit, it may be difficult to sufficiently achieve fine dispersion of the dispersoid in the emulsion suspension. On the other hand, if the blade tip speed exceeds the upper limit, the mixture liquid of the colored resin liquid and the aqueous medium may be scattered violently during mixing, and insoluble materials may be mixed.
Moreover, it is preferable that the material temperature at the time of stirring is 20-60 degreeC, and it is more preferable that it is 20-50 degreeC.

[Joint process]
Next, a plurality of dispersoids are coalesced to obtain coalesced particles (a coalescence step). The coalescence of dispersoids usually proceeds by fusion of dispersoids containing an organic solvent so that they are fused.
A method for combining a plurality of dispersoids is not particularly limited, but a method of adding an electrolyte to the dispersion is preferable. Thereby, coalesced particles can be obtained easily and reliably. In addition, the particle size of the coalesced particles (colored resin fine particles) can be controlled easily and reliably by adjusting the amount of electrolyte added.

  Examples of the electrolyte include magnesium sulfate, ammonium sulfate, potassium sulfate, sodium hydrogen sulfate, ammonium hydrogen sulfate, magnesium sulfate, sodium phosphate, sodium dihydrogen phosphate, sodium chloride, potassium chloride, ammonium chloride, calcium chloride, sodium hydrogen carbonate. And salts such as ammonium hydrogen carbonate and sodium acetate, and acidic substances such as hydrochloric acid, sulfuric acid, phosphoric acid, acetic acid and oxalic acid. One or more selected from these can be used in combination. . Of these, monovalent cation sulfates (for example, sodium sulfate and ammonium sulfate) and carbonates are preferable.

The addition of the electrolyte may be performed in a plurality of times. Thereby, colored resin fine particles (unified particles) of a desired size can be obtained easily and reliably, and the circularity of the obtained colored resin fine particles (unified particles) is surely sufficiently large. can do.
The amount of the electrolyte added in this step is not particularly limited, but is preferably 0.1 to 20 parts by weight with respect to 100 parts by weight of the solid content of the dispersion to which the electrolyte is added. More preferred are parts by weight.

The electrolyte is preferably added in the form of an aqueous solution. As a result, the electrolyte can be quickly diffused throughout the dispersion, and the amount of electrolyte added can be easily and reliably controlled.
In this step, a polymer dispersant having a cationic functional group or an anionic functional group as described above may be included as the dispersion. When coalescing the dispersoid, if the dispersion contains a polymer dispersant as described above, the polymer dispersant can be unevenly distributed in the vicinity of the surface of the finally formed colored resin fine particles. . Thereby, the dispersion stability of the ink is further improved, and the ink is particularly excellent in storage stability and ejection stability. In addition, when such a polymer dispersant is included in the ink as the final ink composition, the colored resin is used by the above-described method rather than adding the polymer dispersant together with the dispersion medium in the dispersion step described later. Inclusion of a polymer dispersant in the vicinity of the surface of the fine particles can lower the viscosity of the ink. Therefore, for example, even when it is desired to increase the content of the colored resin fine particles in the ink, the viscosity of the ink can be made appropriate.

  In addition, the weight average molecular weight Mw of such a polymer dispersant is preferably 10,000 to 100,000, more preferably 30,000 to 80,000. The polymer dispersant satisfying the above conditions is easily taken up by the dispersoid in the dispersion. Thereby, the polymer dispersant can be unevenly distributed near the surface of the resultant coalesced particles. Thereby, the dispersion stability of the ink is further improved, and the ink is particularly excellent in storage stability and ejection stability.

  Although the processing temperature in this process is not specifically limited, It is preferable that it is 10-50 degreeC, It is more preferable that it is 15-40 degreeC, It is further more preferable that it is 20-35 degreeC. When the treatment temperature is less than the lower limit, the coalescence progresses slowly, and the productivity of the colored resin fine particles may be reduced. On the other hand, when the treatment temperature exceeds the upper limit, undesired aggregates and coarse particles are likely to be generated.

This step is preferably performed while the dispersion is stirred. Thereby, coalesced particles with particularly small variations in shape and size among the particles can be obtained.
In this step, for example, an agitation blade such as an anchor blade, a turbine blade, a fiddler blade, a full zone blade, a max blend blade, or a half moon blade may be used. Among these, a max blend blade or a full zone blade is preferable. Thereby, it can prevent more reliably that the coalesced particle (colored resin fine particle) once formed collapse | disintegrates, uniting a dispersoid efficiently. As a result, coalesced particles with small variations in shape and particle size among the particles can be obtained efficiently.

  The blade tip speed of the stirring blade is, for example, preferably 0.1 to 10 m / second, more preferably 0.2 to 8 m / second, and further preferably 0.2 to 6 m / second. . When the blade tip speed is a value within the above range, it is possible to more reliably prevent the coalesced particles once formed from collapsing while more efficiently coalescing the dispersoid. As a result, coalesced particles with particularly small variations in shape and particle size among the particles can be obtained efficiently. On the other hand, when the blade tip speed is less than the lower limit, stirring is not uniform, and coarse particles coarsened more than necessary are likely to be generated. On the other hand, if the blade tip speed exceeds the upper limit, fine particles that do not contribute to the formation of coalesced particles tend to remain.

When the coalesced particles reach the desired particle size, coalescence is stopped. Thereby, the coalesced particle | grains of a desired particle size can be obtained reliably.
Methods for stopping coalescence include, for example, a method of increasing the stirring speed, a method of reducing the temperature of the dispersion (dispersion in which coalesced particles are dispersed), a method of adding water to the dispersion, The method etc. which combined 2 or more are mentioned. Among them, as a method for stopping coalescence, it is preferable to use a method of adding water to the dispersion. As a result, the coalescence of dispersoids can be quickly stopped while reliably preventing unintentional coalescence particles from further coalescence or collapse. As a result, it is possible to reliably obtain colored resin fine particles having a desired particle size and a sharp (monodispersed) particle size distribution. When the coalescence is stopped by adding water to the dispersion, the organic solvent contained in the dispersoid is extracted by the added water, and the dispersoid particles become hard. As a result, it is considered that coalescence is stopped and collapse of the coalesced particles is surely prevented.

In the case where coalescence is stopped by adding water to the dispersion, the total amount of water contained in the dispersion is 400 weights with respect to 100 parts by weight of the organic solvent contained in the dispersion. It is preferable to add so that it may become more than part, and it is more preferable to add so that it may become 500 parts by weight or more.
Further, when coalescence is stopped by adding water to the dispersion, water is added so that the solid content is 18 to 25 wt% after the addition of water (after the coalescence is stopped). Is preferred. Thereby, suitable colored resin fine particles with small variations in size and shape can be produced while sufficiently suppressing the amount of the organic solvent and water used when producing the colored resin fine particles.

[Desolvation (desolvation) step]
Thereafter, the organic solvent contained in the dispersion is removed (desolvent process). Thereby, colored resin fine particles are obtained.
The removal of the organic solvent may be performed by any method, but can be performed, for example, under reduced pressure. Thereby, the organic solvent can be efficiently removed while sufficiently preventing the modification of the constituent materials such as the resin component.

In addition, the treatment temperature in this step is lower than the glass transition point (Tg) of the resin component constituting the film (the resin component constituting the shell region of the finally obtained colored resin fine particles). preferable.
Moreover, you may perform this process in the state which added the antifoamer to the dispersion liquid. Thereby, an organic solvent can be removed efficiently.

Antifoaming agents include, for example, mineral oil-based antifoaming agents, polyether-based antifoaming agents, silicone-based antifoaming agents, lower alcohols, higher alcohols, fats and oils, fatty acids, fatty acid esters, phosphoric acid Esters can be used.
Although the usage-amount of an antifoamer is not specifically limited, It is preferable that it is 20-300 ppm by weight ratio with respect to the solid content contained in a dispersion liquid, and it is more preferable that it is 30-100 ppm.

In this step, at least a part of the aqueous medium may be removed together with the organic solvent.
In this step, unreacted raw materials (monomers and the like) contained in the dispersion can be removed together with the organic solvent. As a result, the amount of volatile organic compound (TVOC) in the colored resin fine particles finally obtained can be made particularly small.
In this step, it is not always necessary to remove all of the organic solvent (the total amount of the organic solvent contained in the dispersion). Even in such a case, the organic solvent remaining in the washing step and the drying step described later can be sufficiently removed.

[Washing process]
Next, the colored resin fine particles are cleaned (cleaning step).
By performing this step, even when an organic solvent, an unreacted raw material (monomer, etc.), etc. are contained as impurities, these can be efficiently removed. As a result, the amount of volatile organic compound (TVOC) in the colored resin fine particles finally obtained can be made particularly small.
In this step, for example, the colored resin fine particles are separated by solid-liquid separation (separation from the aqueous medium), and then the solid content (colored resin fine particles) is re-dispersed in water and solid-liquid separation (coloring from the aqueous medium). It can be carried out by separating resin fine particles. The redispersion of solids in water and solid-liquid separation may be repeated a plurality of times.

[Drying process]
Then, the final colored resin fine particles can be obtained by performing a drying process (drying step).
The drying step can be performed using, for example, a vacuum dryer (for example, ribocorn (manufactured by Okawara Seisakusho), nauter (manufactured by Hosokawa Micron) etc.), fluidized bed dryer (manufactured by Okawara Seisakusho), etc.

[Dispersing process]
Next, an inkjet ink can be obtained by dispersing the obtained colored resin fine particles in a dispersion medium (dispersing step).
As such a dispersion medium, those exemplified as the dispersion medium for dispersing the above-described colored resin fine particles can be used.

In this step, a dispersant for improving the dispersibility of the colored resin fine particles in the dispersion medium may be added. As a result, the dispersion stability of the ink is particularly excellent, and an ink having excellent storage stability and ejection stability can be produced.
A method of dispersing the colored resin fine particles in the dispersion medium can be obtained, for example, by mixing a material containing the colored resin fine particles and the dispersion medium with a stirrer such as a high-speed stirrer. As a stirrer which can be used for such a dispersion | distribution process, DESPA (made by Asada Tekko Co., Ltd.), T.E. K. Robotics / T. K. Examples include Homo Desper 2.5 type wing (manufactured by Primex).

As mentioned above, although this invention was demonstrated based on suitable embodiment, this invention is not limited to these.
For example, although the ink-jet ink of the present invention has been described as including a pigment or a dye as a colorant, the colorant may include either a pigment or a dye, or a pigment and a dye. Both may be included.

  In the above-described method for producing an inkjet ink, the coalescence step may be performed in the presence of a polymer dispersant. However, in the coalescence step, a part of the polymer dispersant is used. It may be included in the dispersion and united, and the remaining polymer dispersant may be added in the dispersion step. In particular, by reducing the amount of the polymer dispersant contained in the coalescence step, the coalescence of the dispersion can be made suitable, and the final ink dispersion stability is particularly excellent. can do.

[1] Manufacture of colored resin fine particles Prior to the manufacture of ink-jet ink, a resin and a dispersant were synthesized. Further, a colorant master and a mill base were prepared using the synthesized resin.
<Synthesis of Resin R1>
Raw materials such as acid, alcohol component and catalyst having the following composition were placed in a 5-liter reaction kettle equipped with a rectifying column, a stirrer, a nitrogen gas inlet, and a thermometer. The reaction was carried out for 12 hours. Thereafter, the pressure was reduced successively and the reaction was continued at 10 mmHg. The reaction was followed by the softening point based on ASTM E28-517, and the reaction was terminated when the softening point reached 160 ° C.

Terephthalic acid 3.9 parts by weight isophthalic acid 9.06 parts by weight ethylene glycol 2.54 parts by weight neopentyl glycol 4.26 parts by weight tetrabutyl titanate 0.1 part by weight Epicron 830 0.3 part by weight (Dainippon Ink & Chemicals, Inc. Bisphenol F type epoxy resin, epoxy equivalent 170 (g / eq)
Cardura E 0.1 parts by weight (alkyl glycidyl ester manufactured by Shell Japan) Epoxy equivalent 250 (g / eq)

  The obtained polymer is a colorless solid, and has an acid value of 11.0 KOHmg / g, a glass transition temperature (Tg) of 60 ° C., a softening point (T1 / 2) of 178 ° C., and a glass transition temperature (Tg) by DSC method. Was 58 ° C., and a polyester resin (resin R1) having a weight average molecular weight (Mw) of 250,000 by GPC method was obtained. The weight average molecular weight is determined by using a combination of TSK-GEL G5000HXL / G4000HXL / G3000HXL / G2000HXL manufactured by Tosoh as a separation column using a GPC measuring apparatus (HLC-8120GPC manufactured by Tosoh), column temperature: 40 ° C., solvent: tetrahydrofuran, solvent The molecular weight was determined by measuring at a concentration of 0.5% by weight, filter: 0.2 μm, flow rate: 1 ml / min, and conversion using standard polystyrene.

<Synthesis of Resin R2>
Raw materials such as acid, alcohol component and catalyst having the following composition were put into a 5 liter reaction kettle equipped with a rectifying column, a stirrer, a nitrogen gas inlet, and a thermometer. The reaction was carried out for 12 hours. Thereafter, the pressure was reduced successively and the reaction was continued at 10 mmHg. The reaction was followed by the softening point based on ASTM E28-517, and the reaction was terminated when the softening point reached 95 ° C.

Terephthalic acid 7.97 parts by weight Isophthalic acid 5.31 parts by weight Ethylene glycol 2.86 parts by weight Neopentyl glycol 4.8 parts by weight Tetrabutyl titanate 0.1 parts by weight

  The obtained polymer was a colorless solid having an acid value of 10.0, a glass transition temperature (Tg) of 55 ° C., and a softening point (T1 / 2) of 107 ° C. Further, the weight average molecular weight was measured by using a GPC measuring apparatus (HLC-8120GPC manufactured by Tosoh Corporation) as a separation column in combination with TSK-GEL G5000HXL / G4000HXL / G3000HXL / G2000HXL manufactured by Tosoh Corporation, column temperature: 40 ° C., solvent: tetrahydrofuran, solvent The molecular weight was determined by measuring at a concentration of 0.5% by mass, filter: 0.2 μm, flow rate: 1 ml / min, and conversion using standard polystyrene. As a result, the weight average molecular weight was 7740.

<Synthesis of Resins R3 and R4>
Except that the usage amount (usage ratio) of each raw material was as shown in Table 1, the reaction was carried out in the same manner as the synthesis of the resin R2 to obtain two types of resins R3 and R4.
Table 1 summarizes the synthesis conditions and physical properties of the resins synthesized as described above.

<Synthesis of Dispersant P-1>
Put a raw material such as vinyl monomer, polymerization initiator, chain transfer agent, etc. of the following composition into a 5 liter reaction kettle equipped with a rectifying column, a stirrer, a nitrogen gas inlet, and a thermometer, The reaction was performed at 70 ° C. for 12 hours under an air stream.
Stearyl methacrylate 48.0 parts by weight Styrene 50.0 parts by weight Methacrylic acid 2.0 parts by weight Stearyl mercaptan 1.0 part by weight Azobisisobutyronitrile 1.0 part by weight

  The obtained polymer was a colorless solid, and its weight average molecular weight was measured using a GPC measuring device (HLC-8120GPC manufactured by Tosoh Corporation), using TSK-GEL G5000HXL manufactured by Tosoh Corporation as a separation column, column temperature: 40 ° C., solvent: The molecular weight was determined by measuring with tetrahydrofuran / solvent concentration of 0.5 mass%, filter: 0.2 μm, flow rate: 1 ml / min, and conversion using standard polystyrene. As a result, the weight average molecular weight was 30000.

<Preparation of Colorant Master CM-1C>
Cyan pigment (Dai Nippon Ink Chemical Co., Ltd., KET BLUE 111 CI Pigment B-15: 3): 20 L Henschel mixer in which 2000 parts by weight and resin R1: 2000 parts by weight are set with ST / A0 blades (Mitsui Mining Co., Ltd.) and stirred at a rotational speed of 698 rpm for 2 minutes to obtain a mixture. Using the open roll continuous extrusion kneader (Mitsui Mining Co., Ltd., kneedex MOS140-800), the front roll rotation speed: 75 rpm, the rear roll rotation speed: 60 rpm, the inlet side clearance 0.1 mm, the outlet The colorant master PM-1C was obtained by melt-kneading with a side clearance of 0.3 mm and a discharge rate of 5.0-5.5 kg / h. The composition of the coloring master PM-1C was colorant: resin = 50: 50 by weight ratio. Moreover, when the obtained colorant master PM-1C was diluted with methyl ethyl ketone and observed for the finely dispersed state of the colorant and the presence or absence of coarse particles with a 400-fold optical microscope, the coarse particles were not recognized and were uniformly present. A state of fine dispersion was observed.

<Preparation of Colorant Master CM-2C>
PM-2C was prepared in the same manner as PM-1C except that resin R2 was used instead of resin R1.
<Preparation of Colorant Master CM-3C>
PM-3C was prepared in the same manner as PM-1C except that the resin R3 was used instead of the resin R1.
<Preparation of Colorant Master CM-4C>
PM-4C was prepared in the same manner as PM-1C except that the resin R4 was used instead of the resin R1.

<Preparation of Millbase MB-1C>
In a stainless steel container, methyl ethyl ketone: 35 parts by weight, resin R1: 45.5 parts by weight, colorant master CM-1C: 19.5 parts by weight, sodium dodecylbenzenesulfonate as an emulsifier: 0.25 parts by weight distilled water: 3 The aqueous solution dissolved in 25 parts by weight was charged and stirred for 2 hours with a rotation speed of 777 min ⁻¹ (blade tip speed: 8.5 m / sec) of a stirrer (Disper blade diameter 230 mm manufactured by Asada Iron Works) to dissolve each component. Dispersion was performed. Further, methyl ethyl ketone was additionally added so that the solid content was 65% by weight, and mill base MB-1C was obtained. In addition, the material temperature at the time of stirring was hold | maintained at 30-40 degreeC.
<Preparation of Millbase MB-2C-4C>
Using the resin and colorant master shown in Table 2, each mill base was prepared according to the indicated blending amount.
Table 2 shows the blending amounts of the materials constituting each manufactured mill base.

(Example 1)
Inkjet ink was produced as follows. In addition, about the process (process) in which temperature conditions are not described, it performed at room temperature (25 degreeC).
<< Emulsion suspension preparation process >>
46.15 parts by weight of Millbase MB-1C was charged into a cylindrical container equipped with a stirrer (Disper manufactured by Asada Iron Works) having a blade diameter of 230 mm, and then 1N ammonia water: 4 parts by weight as a basic substance Was added and the mixture was sufficiently stirred at 777 min ⁻¹ , and the temperature was adjusted to 30 ° C.

Subsequently, the stirring speed was changed to 1100 min ⁻¹ and 34 parts by weight of distilled water was added dropwise at a rate of 1.0 part by weight / min. The blade tip speed of the stirring blade at this time was 13.2 m / sec. As the distilled water was added, the viscosity of the system increased. However, the distilled water was taken into the system at the same time as the dropwise addition, and stirring and mixing could be performed uniformly. In addition, a phase inversion point at which the viscosity of the system suddenly decreased was observed when 26 parts by weight of distilled water was dropped. The content of methyl ethyl ketone (organic solvent) in the dispersion at this stage was 29.0 wt%. When this dispersion was observed with an optical microscope, it was observed that the resin was dissolved and the pigment and release agent fine particles were dispersed. Presence of coarse particles with poor dispersibility was not observed in this dispersion.

<< Unification process >>
The emulsified suspension was transferred to a cylindrical container attached to Max Blend Wing (registered trademark) having a blade diameter of 340 mm, and then the temperature was adjusted to 25 ° C. while maintaining the stirring speed at 85 min ⁻¹ . Thereafter, the rotational speed was adjusted to 120 min ⁻¹ , a 3.5 wt% sodium sulfate aqueous solution: 12 parts by weight was dropped at 1 part by weight / min, and 5 minutes after the completion of dropping, the rotational speed was 85 min ⁻¹ for 5 minutes, 65 min. ^The mixture was stirred at ^-1 for 5 minutes and stirred at 47 min ^-1 for 20 minutes. The blade tip speed of the stirring blade at this time was 0.47 m / sec. Subsequently, the rotational speed was adjusted to 120 min ⁻¹ , and 2.5 parts by weight of a sodium sulfate aqueous solution having a concentration of 5.0% by weight was dropped at 1 g / min, and 5 minutes after the completion of dropping, the rotational speed was 85 min ⁻¹ for 5 minutes. The mixture was stirred at 65 min ⁻¹ for 5 minutes, and then stirred at 47 min ⁻¹ for 20 minutes. Here, this dispersion was observed. As a result, a large number of coalesced particles (colored resin fine particles) in which a plurality of dispersoids were coalesced were confirmed. In addition, fine pigment particles have been incorporated in a finely dispersed state in a dispersoid composed of a resin-containing material. The particle diameter of the coalesced particles thus obtained was measured, and Dv (50) was 2.5 μm when the 50% volume particle diameter was Dv (50) [μm]. The particle size was measured with a Coulter Counter Multisizer TAII (Beckman Coulter, Inc.) using a 100 μm aperture tube.

<< Solvent removal process >>
Thereafter, 0.006 part by weight of silicone-based antifoaming agent (Toray Dow Corning Silicone, BY22-517) was added, the container used for the reaction was sealed, and a vacuum pump was attached. Next, the solvent was removed by reducing the pressure at room temperature (25 ° C.) using a vacuum pump at a reduced pressure of 2.7 kPa for 30 minutes. Next, while lowering the pressure, the vessel used for the reaction was heated for 90 minutes, and the internal material temperature was increased at a rate of 4 ° C./hr until the temperature in the vacuum vessel reached 21 ° C. . After 90 minutes, when the internal material temperature reached 21 ° C., the pressure was continuously reduced under the same pressure while maintaining the same temperature. Distillation under reduced pressure was performed until the liquid distilled off under reduced pressure became 138 vol% of the methyl ethyl ketone used to obtain a slurry of coalesced particles (colored resin fine particle slurry). At this time, the final degree of vacuum was 1.0 kPa.

《Dedispersing medium process》
The slurry obtained as described above was subjected to a dedispersion medium at a peripheral speed of 1250 min ⁻¹ using a basket type centrifuge. After performing the dedispersion medium, while continuing to rotate the basket-type centrifuge at the same peripheral speed, 6 times the amount of solids in the slurry (in terms of weight) is added and washed simply (hereinafter, rinse) The wet cake (colored resin fine particle cake) of coalesced particles was obtained.

《Cleaning and dehydration process》
A wet cake of coalesced particles was placed in the stirring phase. Distilled water was added so that the solid content in the mixture in the stirring tank was 15 to 20% by weight, and the temperature was adjusted so that the water temperature was 30 ° C. In this state, an edged turbine blade was used as a stirring blade, stirring was performed for 30 minutes so that the blade tip speed of the stirring blade was 8.2 m / s, and a redispersed slurry was obtained. Next, the redispersed slurry was dehydrated and rinsed in the same manner as in the dedispersing medium step. At this time, the distilled water used for rinsing was set to a three-fold amount (weight conversion) of the solid content of the redispersed slurry.

This operation was performed a total of three times to obtain a washed wet cake of coalesced particles. The distilled water used for the simple washing was 6 times the amount of solid content of the redispersed slurry (weight conversion). The moisture content of the wet cake was 35% by weight.
Further, the ratio d / D between the inner diameter D [cm] of the stirring vessel K1 used this time and the blade diameter d [cm] of the stirring blade K2 is 0.37, and the stirring energy per 1 L of the mixture is 0.25 [Wh]. / L].

<< Drying process >>
Thereafter, the wet cake was dried using a vacuum dryer to obtain coalesced particles. The obtained coalesced particles have a 50% volume particle diameter of Dv (50) [μm] and a 50% number particle diameter of Dn (50) [μm], Dv (50) is 2.5 μm, Dv ( 50) / Dn (50) was 1.10. The average circularity of the coalesced particles was 0.990. The particle size and particle size distribution were measured with a Coulter Counter Multisizer TAII (manufactured by Beckman Coulter, Inc.) using a 100 μm aperture tube. The other particles described below were similarly measured for particle size and particle size distribution. The average circularity was determined by measurement using a flow particle image analyzer (FPIP-1000, manufactured by Toa Medical Electronics Co., Ltd.). Moreover, the average circularity was calculated | required similarly about the other particle | grains demonstrated below.

≪Dispersing process≫
In a cylindrical container equipped with a stirrer having a blade diameter of 230 mm (Disper manufactured by Asada Iron Works), 40 parts by weight of the dispersant P-1 was dissolved in 300 parts by weight of Isopar H (manufactured by Exxon Chemical). The solution and 60 parts by weight of coalesced particles were charged, and stirred and dispersed for 2 hours at a rotation speed of 777 min ⁻¹ . The dispersion thus obtained was centrifuged (relative centrifugal acceleration: 2000 G, 30 minutes), and the supernatant liquid that became 20% by weight was taken out. The supernatant liquid: 25 parts by weight and Isopar H: 75 parts by weight Was added to obtain an inkjet ink having a solid content of 5 wt%.

(Examples 2 to 8)
As shown in Table 3, the mill base and dispersion medium corresponding to each example are used, and the circularity, particle size distribution, and particle size shown in Table 3 are obtained by changing the stirring speed and stirring time in the coalescence process. An inkjet ink was obtained in the same manner as in Example 1 except that the colored resin fine particles were used.

Example 9
An emulsified suspension was prepared as in Example 1.
Next, after the above emulsion suspension was transferred to a cylindrical container attached to Max Blend Wing (registered trademark) having a blade diameter of 340 mm, 8.7 parts by weight of Dispersant P-1 was added to the cylindrical container and stirred. The temperature was adjusted to 25 ° C. while maintaining the speed at 85 min ⁻¹ . Thereafter, the rotational speed was adjusted to 120 min ⁻¹ , a 3.5 wt% sodium sulfate aqueous solution: 12 parts by weight was dropped at 1 part by weight / min, and 5 minutes after the completion of dropping, the rotational speed was 85 min ⁻¹ for 5 minutes, 65 min. ^The mixture was stirred at ^-1 for 5 minutes and stirred at 47 min ^-1 for 20 minutes. The blade tip speed of the stirring blade at this time was 0.47 m / sec. Subsequently, the rotational speed was adjusted to 120 min ⁻¹ , and 2.5 parts by weight of a sodium sulfate aqueous solution having a concentration of 5.0% by weight was dropped at 1 g / min, and 5 minutes after the completion of dropping, the rotational speed was 85 min ⁻¹ for 5 minutes. The mixture was stirred at 65 min ⁻¹ for 5 minutes, and then stirred at 47 min ⁻¹ for 20 minutes. Here, this dispersion was observed. As a result, a large number of coalesced particles (colored resin fine particles) in which a plurality of dispersoids were coalesced were confirmed. In addition, fine pigment particles have been incorporated in a finely dispersed state in a dispersoid composed of a resin-containing material. Further, the particle size of the coalesced particles thus obtained was measured, and Dv (50) was 2.4 μm when the 50% volume particle size was Dv (50) [μm].
Thereafter, an ink jet ink was obtained in the same manner as in Example 1 except that the dispersant was not added in the dispersing step.

(Example 10)
An emulsified suspension was prepared as in Example 1.
Next, after transferring the above emulsion suspension to a cylindrical container attached to Max Blend Wing (registered trademark) having a blade diameter of 340 mm, 1.0 part by weight of the dispersant P-1 is added to the cylindrical container and stirred. The temperature was adjusted to 25 ° C. while maintaining the speed at 85 min ⁻¹ . Thereafter, the rotational speed was adjusted to 120 min ⁻¹ , a 3.5 wt% sodium sulfate aqueous solution: 12 parts by weight was dropped at 1 part by weight / min, and 5 minutes after the completion of dropping, the rotational speed was 85 min ⁻¹ for 5 minutes, 65 min. ^The mixture was stirred at ^-1 for 5 minutes and stirred at 47 min ^-1 for 20 minutes. The blade tip speed of the stirring blade at this time was 0.47 m / sec. Subsequently, the rotational speed was adjusted to 120 min ⁻¹ , and 2.5 parts by weight of a sodium sulfate aqueous solution having a concentration of 5.0% by weight was dropped at 1 g / min, and 5 minutes after the completion of dropping, the rotational speed was 85 min ⁻¹ for 5 minutes. The mixture was stirred at 65 min ⁻¹ for 5 minutes, and then stirred at 47 min ⁻¹ for 20 minutes. Here, this dispersion was observed. As a result, a large number of coalesced particles (colored resin fine particles) in which a plurality of dispersoids were coalesced were confirmed. In addition, fine pigment particles have been incorporated in a finely dispersed state in a dispersoid composed of a resin-containing material. Further, the particle size of the coalesced particles thus obtained was measured, and Dv (50) was 2.4 μm when the 50% volume particle size was Dv (50) [μm].
Thereafter, an inkjet ink was obtained in the same manner as in Example 1 except that the solvent removal step was changed to 35 parts by weight, except that the amount of the dispersant dissolved in Isopar H was changed to 35 parts by weight.

(Comparative Example 1)
Resin R-1: 25.5 parts by weight, cyan pigment (manufactured by Dainippon Ink & Chemicals, Inc. KET.BLUE.111): 4.5 parts by weight, methyl ethyl ketone: 16 parts by weight, distilled water: 54 parts by weight, as an emulsifier Sodium dodecylbenzenesulfonate: 0.1 part by weight was mixed and dispersed with Dynomill (Titania beads manufactured by Shinmaru Enterprises Co., Ltd., φ0.3 mm, filling rate 70%, peripheral speed 10 m / s).
Thereafter, the ink-jet ink was obtained in the same manner as in Example 1 after the solvent removal step.

(Comparative Example 2)
(Process 1)
First, 10 parts by weight of commercially available stearyl methacrylate, 6 parts by weight of acrylic acid and 6.0 parts by weight of vinylpepyridine are placed in 35 parts by weight of Isopar L manufactured by Exxon Petrochemical Co., Ltd., heated to 60 ° C. and stirred overnight. As a result, a copolymer resin solution of stearyl methacrylate and acrylic acid having an average molecular weight (weight basis) of 16000 was obtained.

  Next, 20 parts by weight of the cyan pigment of Example 1 was added to the solution A obtained in the above step, and the solution A was sufficiently infiltrated into the cyan pigment, and then an ultrasonic disperser (manufactured by Nippon Seiki Co., Ltd. RUS-300) to disperse the cyan pigment to the primary particle size. Next, the above dispersion was dispersed in a circulating horizontal mill M100 (bead mill manufactured by EIGER ENGINEERING LIMITED) 0.9 mm beads at 5000 rpm for 1 hour to obtain a dispersion B having an average pigment particle diameter of 2 μm.

(Process 2)
To 100 parts by weight of ISOPAR L, 2.5 parts by weight of stearyl methacrylate, 1.5 parts by weight of acrylic acid and 1.5 parts by weight of vinylpepyridine are added and stirred overnight for 60 days to average molecular weight (weight basis) 16000. A copolymer resin solution of stearyl methacrylate and acrylic acid was obtained. Thereafter, 2 parts by weight of sorbitan trioleate was added and dissolved to obtain Solution C.
Next, while stirring the dispersion B obtained in Step 1 with a stirrer HI-15 (Tokyo Science Instruments Co., Ltd.), the solution C is gradually added, and the dispersion pigment is combined with stearyl methacrylate and acrylic acid. The polymer resin is completely adsorbed.

Ink jet ink was obtained by the above steps 1 and 2.
Mill base, dispersant, dispersion medium used in the ink jet inks of the above Examples and Comparative Examples, and the circularity, particle size distribution Dv50 / Dn50, particle size Dv50 of the prepared colored resin fine particles, and ink jet ink Table 3 shows the viscosity and the like.
In Table 1, Isopar H is A, SH200FLUID100CS (made by Toray Dow Corning Silicone) as silicone oil, B, soybean oil (made by Nisshin Oilio Co.) as fat and oil, and soybean oil fatty acid as fatty acid monoester M (manufactured by Nisshin Oilio Co., Ltd.) is indicated by D.
Moreover, the viscosity in Table 1 was expressed according to the following three-stage criteria.

<Viscosity>
A: 4 mPa · s or more and 30 mPa · s or less.
○: 3 mPa · s or more and 40 mPa · s or less. (Except 4mPa · s to 30mPa · s)
Δ: Less than 3 mPa · s or greater than 40 mPa · s.

[2] Evaluation [2.1] Discharge stability The ink for ink jet obtained in each example and each comparative example was filled in an ink cartridge of an ink jet printer PM-G850 (manufactured by Seiko Epson) and mounted on the printer. A square solid of 2 cm × 2 cm was printed, and visually evaluated according to the following five-step criteria.

A: No disturbance in the printed part is observed.
A: Almost no disturbance is observed in the printed part.
○: Disturbance is slightly observed in the printed part, but it is within the allowable range.
Δ: Slight disturbance in the printed part
X: Disturbances can be clearly confirmed in the printed part.

[2.2] Evaluation of printing density The ink for ink jet obtained in each example and each comparative example was filled in an ink cartridge of an ink jet printer PM-G850 (manufactured by Seiko Epson) and mounted on the printer, and NPI fine paper A solid of 2 cm × 2 cm was printed on (manufactured by Nippon Paper Industries Co., Ltd.), and the print density was evaluated using a reflection densitometer RD-191 (manufactured by Sakata Inx Engineering Co., Ltd.) according to the following four criteria.
◎: 0.9 or more ○: 0.8 or more, less than 0.9 △: 0.7 or more, less than 0.8 ×: less than 0.7

[2.3] Resolution Evaluation The ink-jet ink obtained in each example and each comparative example was filled into an ink cartridge of an ink-jet printer PM-G850 (manufactured by Seiko Epson) and mounted on the printer. A thin wire bundle having a line width of 1 pixel was printed at a pitch of 5 pixels on a paper manufactured by Nippon Paper Industries Co., Ltd., and the blurring of the white background between the thin wires was visually evaluated according to the following four criteria.
A: No blur is seen at all.
○: Almost no blur is observed.
Δ: Slight blurring is observed.
X: The blur can be clearly confirmed.

[2.4] Long-term storability The ink-jet inks obtained in the above Examples and Comparative Examples were allowed to stand for 8 months in an environment at a temperature of 35 ° C. Thereafter, the appearance of the ink-jet ink was visually confirmed and evaluated according to the following four criteria.
A: No aggregation of colored resin fine particles in the ink is observed.
○: Aggregation of colored resin fine particles in the ink is hardly observed.
Δ: Slight aggregation of colored resin fine particles in ink is observed.
X: Aggregation of colored resin fine particles in the ink is clearly recognized.
The evaluation results of each example and comparative example are shown in Table 4.

As is clear from Table 4, the inkjet ink of the present invention has excellent storage stability and excellent ejection stability, and the printed portion printed on the transfer paper using the inkjet ink of the present invention is: The print density was high and the resolution was high. On the other hand, sufficient results were not obtained with the inkjet ink of the comparative example.
In addition, instead of the cyan pigment, the color pigment is a red pigment (manufactured by Clariant Japan, Permanent.Red P-F7RK), a green pigment (manufactured by Clariant Japan, Hostaperm.Green.GNX), carbon black (MA-100R, manufactured by Mitsubishi Chemical Corporation). When the toner was manufactured and evaluated in the same manner as described above except that (1) was used, results similar to the above were obtained.

Claims (14)

Having colored resin fine particles and a dispersion medium for dispersing the colored resin fine particles,
The colored resin fine particles are produced by combining the dispersoids in an emulsion in which a dispersoid containing a resin, a colorant, and an organic solvent is dispersed in an aqueous dispersion medium. Ink jet ink.   The inkjet ink according to claim 1, wherein the colored resin fine particles are formed by adding an electrolyte to the emulsion.   The inkjet ink according to claim 1 or 2, wherein a particle size distribution Dv / Dn of the colored resin fine particles is 1.00 to 1.15. The inkjet ink according to any one of claims 1 to 3, wherein an average circularity R of the colored resin fine particles represented by the following formula (I) is 0.98 to 1.
R = L ₀ / L ₁ (I)
(Wherein, L ₁ [μm] is the peripheral length of the projected image of the colored resin fine particles to be measured, and L ₀ [μm] is a perfect circle having an area equal to the area of the projected image of the colored resin fine particles to be measured. (Represents the perimeter of a complete geometric circle)   The inkjet ink according to any one of claims 1 to 4, wherein the colored resin fine particles have an average particle size of 0.2 to 10 µm.   The inkjet ink according to any one of claims 1 to 5, wherein the dispersion medium contains at least one of an aliphatic hydrocarbon-based liquid, a silicone oil, and a fatty acid ester.   The inkjet ink according to any one of claims 1 to 6, comprising a polymer dispersant having a cationic functional group or an anionic functional group in addition to the colored resin fine particles and the dispersion medium.   The inkjet ink according to claim 7, wherein the polymer dispersant has a weight average molecular weight Mw of 10,000 to 100,000.   The inkjet ink according to claim 7 or 8, wherein the polymer dispersant is compatible with the dispersion medium.   The inkjet ink according to any one of claims 1 to 9, which has a viscosity of 3 to 40 mPa · s. A dispersion preparation step of preparing a dispersion in which a dispersoid containing a resin, a colorant, and an organic solvent is dispersed in an aqueous dispersion medium;
Coalescing a plurality of the dispersoids to obtain coalesced particles; and
Removing the organic solvent contained in the coalesced particles to obtain colored resin fine particles; and
And a dispersion step of dispersing the colored resin fine particles in a dispersion medium.   The dispersion is made into a W / O emulsion by adding an aqueous liquid to a solution containing a resin, a colorant, and an organic solvent, and is further made into an O / W emulsion by adding the aqueous liquid. The method for producing an inkjet ink according to claim 11.   The method for producing an inkjet ink according to claim 11 or 12, wherein the coalescing step is performed in the presence of a polymer dispersant having a cationic functional group or an anionic functional group.   The method for producing an inkjet ink according to claim 11, wherein an electrolyte is added in the coalescing step.