JP4876901B2 - Method for producing jet ink and dispersion of colored fine particles for jet ink - Google Patents

Description

The present invention relates to a method for producing a dispersion of jet ink and colored fine particles for the jet ink. In particular, the present invention relates to a colored microcapsule dispersed aqueous jet ink.

  Ink jet recording inks are roughly classified into oil-based inks and water-based inks, but oil-based inks have problems in terms of odor and toxicity, and water-based inks are becoming mainstream.

  However, many of the conventional water-based inks have a drawback that water resistance and light resistance are poor because a water-soluble dye is used as a colorant. In addition, since the dye is dissolved at the molecular level, printing on so-called plain paper such as copy paper commonly used in offices causes bleeding called wrinkle-like feathering, which causes a significant decrease in print quality. .

  Various so-called water-based pigment inks have been proposed in the past to improve the above-mentioned drawbacks. For example, resin-dissolved inks in which carbon black or organic pigments are dispersed using a water-soluble resin as a binder / dispersant. Various resin-dispersed inks containing a colorant as polymer latex or microcapsules have been proposed.

  As water-based pigment inks for jet printers, colorant particles dispersed in a fine particle size as much as possible are required. As a specific example of a resin-soluble water-based ink, Japanese Patent No. 2512861 discloses (1) a pigment and (2) grinding to obtain a dispersion of pigment and polymer dispersant; and (3) dispersing the pigment dispersion in an aqueous carrier medium. A method for preparing an aqueous pigmented ink-jet ink having improved properties is disclosed in JP-A-3-153775 as follows: a) Solid pigment preparation b containing a pigment and a carboxyl group-containing polyacrylic resin b A water-based ink composition for ink jet printing has been proposed which contains a) an organic solvent dilutable with water c) a wetting agent d) water.

  However, these technologies are effective for finer pigments, but due to the effect of the dissolved dispersant resin, abnormal ink jets due to increased ink viscosity near the nozzles and worst nozzle clogging occur due to the evaporation of ink moisture. It was easy and the water resistance of the printed matter was extremely inferior.

  Resin-dispersed water-based inks have the advantages of relatively little increase in viscosity due to water evaporation of the ink and excellent water resistance. Specifically, JP-A-58-45272 discloses an ink composition containing a urethane polymer latex containing a dye, and JP-A-62-95366 discloses a method in which a polymer and an oily dye are dissolved in a water-insoluble organic solvent. Furthermore, an ink containing a dye encapsulated in polymer particles by evaporating the solvent after mixing with an aqueous solution containing a surfactant and emulsifying is proposed. Japanese Patent Application Laid-Open No. Sho 62-254833 discloses an organic solvent for encapsulation. A method for producing an aqueous colorant suspension by reducing the interfacial tension between water and water to 10 dynes or less has been proposed. JP-A-1-170672 also discloses a recording liquid containing a macroencapsulated dye, etc. However, the dispersion stability of the colored resin dispersions obtained from them is not always sufficient, and foaming is caused by the influence of the surfactant used during encapsulation. Hear, jetting characteristics of the ink jet it is not necessarily sufficient.

  Japanese Patent Laid-Open No. 3-240586 proposes an image forming material characterized in that the surface of particles dispersed in a dispersion medium is coated with a resin that swells in the dispersion medium. -Gel phase transition was likely to occur, and the dispersion stability of the particles was not always good, and injection abnormalities were likely to occur.

  In JP-A-5-247370, in a coloring composition for image recording comprising a pigment and a resin, the pigment is substantially insoluble in a dispersion medium and is coated with a thin film of a cured polymer having a polar group In the present invention, the pigment itself is insufficient in self-dispersibility and fixing ability to recording paper, so that it can be used as a dispersant and a fixing agent. Resin is indispensable. Therefore, although the dispersion stability is excellent as compared with the pigment not coated with the cured polymer, the disadvantage that the jetting stability as an ink jet is insufficient and the water resistance is inferior has not been improved.

  Japanese Patent Application Laid-Open No. 2-255875 discloses a “resin in which a water-soluble resin is fixed to the surface of a pigment with a relatively weak force in a water-based ink for inkjet recording containing a pigment, a water-soluble resin, a water-soluble organic solvent, and water. "Adsorbed pigment particles" are dispersed in an aqueous medium, and further dissolved in the aqueous medium so that the water-soluble resin is not adsorbed by the pigment and is not more than 2% by weight in the ink.

  In the method of adsorbing the water-soluble resin to the pigment surface as described above, the degree of fixation between the pigment surface and the adsorption resin is still insufficient, and the “resin-adsorbed pigment particles” thus obtained are more advanced in an aqueous medium. Dispersion stability cannot be expected.

In addition, when such “resin adsorbing pigment particles” are used, excellent ink jet ejection characteristics are obtained when the amount of the water-soluble resin not adsorbed on the pigment and dissolved in the ink is 2% by weight or less. And excellent adhesion to a recording medium cannot be achieved.
Japanese Patent Laid-Open No. 6-157554 Japanese Patent Laid-Open No. 3-153775 JP 58-45272 A JP-A-62-95366 JP 62-254833 A JP-A-1-170672 JP-A-3-240586 Japanese Patent Laid-Open No. 5-247370 JP-A-2-255875

  The problem to be solved by the present invention is to provide a colored microcapsule-dispersed water-based jet ink having a fine particle size, excellent dispersion stability, excellent ink jetting characteristics, and excellent adhesion of capsule particles to a recording medium. It is in.

  The present invention enables stable ink jet ejection characteristics without sacrificing the characteristics of a resin-dispersed water-based ink excellent in printing quality, water resistance, and light resistance, excellent in dispersion stability, and without nozzle clogging.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have improved the dispersion stability in ink by coating the pigment fine particles instead of adsorbing the resin. Colored fine particles whose fine particles are coated with a resin (hereinafter sometimes referred to as colored microcapsules) have a specific particle size in the ink, and excludes the ink liquid medium in which the colored fine particles are dispersed. It has been found that it is effective to change the particle size of the colored fine particles dispersed in the liquid medium before and after being dispersed again in the same liquid medium after drying.

  As a means for doing so, the present inventors do not affect the ejection stability of a film-forming resin component that is not coated with a pigment and that is free and dissolved, and the recording medium By making the quantitative range that contributes to the fixation of capsule particles to the surface, the above-mentioned problems have been solved.

  More specifically, instead of using “resin-adsorbing pigment particles” in which a water-soluble resin is fixed to the pigment surface with a relatively weak force as described above, the pigment is coated with a self-dispersible film-forming resin. As a result, it has been found that, as a result of “colored microcapsules” having a higher degree of fixation than adsorption, a higher degree of dispersion stability of the pigment component in the aqueous medium can be achieved.

  In addition, as an aqueous jet ink in which the “colored microcapsules” are dispersed in an aqueous medium, the amount of the water-soluble resin that is not adsorbed by the pigment and dissolved in the ink is 2% by mass or less. It has been found that both the inkjet jetting characteristics and the adhesion to the recording medium can be improved compared to the case where “is used,” and the present invention has been completed.

  That is, the present invention provides the following inventions. In a jet ink in which colored fine particles (d) formed by coating pigment fine particles (a) with a film-forming resin (b) having a carboxyl group are dispersed in an aqueous medium, (1) the colored fine particles (d) are It has a quaternized carboxyl group on its surface and a volume average particle diameter of 0.5 μm or less, (2) “Volume average of colored fine particles (d) in a redispersion of dry ink A jet ink characterized in that the "increase rate of particle size" is 50% or less.

  (1) (i) a colored compound (V) obtained by kneading a pigment and a carboxyl group-containing film-forming resin (b), (ii) water, and an organic that can dissolve the film-forming resin (b) An aqueous medium (W) composed of a solvent (e) and (iii) a basic compound (c) are mixed uniformly to form (2) a film-forming resin in which the pigment fine particles (a) have a carboxyl group. A colored fine particle dispersion (X) is produced in which colored fine particles (d) coated with (b) and having quaternized carboxyl groups on the coated surface are dispersed in an aqueous medium (W). Then, (3) removing the organic solvent (e) from the dispersion (X), a method for producing a dispersion of colored fine particles for jet ink.

  The colored fine particles in the colored fine particle aqueous dispersion obtained by the method for producing the colored fine particle aqueous dispersion of the present invention have a fine particle size and extremely excellent dispersion stability. For example, when applied to a water-based ink for inkjet recording, the printing quality and water resistance are improved. This makes it possible to achieve stable ink jet ejection characteristics without sacrificing the features of resin-dispersed water-based inks that are excellent in light resistance and light resistance, excellent dispersion stability, and nozzle clogging.

  The colored microcapsule-dispersed water jet ink of the present invention has a film-forming resin component dissolved in the ink of 2% by mass or less, and as a result, coloring in the re-dispersed liquid of the dry ink The rate of increase of the volume average particle diameter of the fine particles is 50% or less, and there is a particularly remarkable technical effect that the dispersion stability over time is excellent, and the jetting characteristics and the image fixing property to the recording medium are also excellent.

  Therefore, in inkjet recording, for example, without sacrificing the features of resin-dispersed water-based inks with excellent print quality, water resistance, and light resistance, it has excellent dispersion stability and nozzle clogging, enabling stable inkjet ejection characteristics. To do.

  The jet ink of the present invention is a colored fine particle (d) formed by coating a pigment fine particle (a) with a film-forming resin (b) having a carboxyl group in a dispersed state in an aqueous medium as a dispersion medium. ) "Has a volume average particle diameter of 0.5 μm or less, but preferably has a volume average particle diameter in the range of 0.01 to 0.3 μm.

  In the present invention, the colored fine particles (d) may be referred to as microcapsule particles, colored microcapsules, or simply microcapsules.

  In order to stably use the ink jet using the pigment, it is necessary to overcome nozzle clogging caused by drying of the ink at the nozzle end face. Ink obtained by a technique of stably dispersing pigment fine particles by adsorption using a conventional water-soluble resin as a pigment dispersant tends to cause aggregation of the pigment fine particles as the water evaporates. Once agglomeration of the pigment fine particles occurs, even if water or the same ink is added again and moistened, it cannot be redispersed again, resulting in nozzle clogging. When preparing a dispersion liquid (redispersion liquid) that is re-dispersed in the same liquid medium after evaporating the ink liquid medium, is the pigment fine particles or colored fine particles dispersed at the same level as the original ink? It can be a measure of the difficulty of nozzle clogging.

  As an evaluation method of the aggregation state of the colored fine particles, an increase in the particle size over time may be examined. For example, an average particle size, a median (50% particle size), an increase in a coarse particle portion (for example, 90% particle size) and the like can be mentioned. However, the present inventors have found that the average particle diameter, particularly the volume average particle diameter, most accurately reflects the correlation with nozzle clogging.

  As used in this specification, the term “rate of increase in volume average particle diameter of colored fine particles (d) in the redispersion of dry ink” means [(S2 / S1) -1] × 100. The definitions of S2 and S1 are as follows. That is, a slide glass provided with holes (diameter 14-16 mm, deepest part depth 0.4-0.8 mm) on the surface, or a mini petri dish (diameter 14-16 mm, height 10-15 mm cylindrical) 10 μl of jet ink is placed in the medium) and left for 7 days in an atmosphere of a temperature of 25 ° C. and a relative humidity of 20% to dry the ink, and then the dried ink present in the hole is put into 10 ml of pure water. Redisperse (diluted 1000 times). The volume average particle diameter of the colored fine particles (d) contained in the diluted redispersion liquid (hereinafter, simply referred to as “dry ink redispersion liquid”) is measured, and the measured value is defined as S2. On the other hand, as a blank, 10 μl of the same ink as the jet ink is diluted with 10 ml of pure water (diluted 1000 times). The volume average particle diameter of the colored fine particles (d) contained in the diluted solution is measured, and the measured value is defined as S1.

  For the measurement of the particle diameter of these colored fine particles (d), known and conventional ones can be used. In the present invention, a microtrack particle size analyzer (LEEDS AND NORTHRUP, MICRO ULTRAFINE ANALYZER) manufactured by Leeds and Northrup is used. Is preferred.

  The jet ink of the present invention refers to an ink having a “rate of increase in volume average particle diameter of colored fine particles (d) in a redispersion of dry ink” of 50% or less. The rate of increase is preferably 40% or less, and more preferably 20% or less, particularly in view of the effect.

  In order to perform the two tests, each ink is preferably sampled from the same container. In the present invention, when the ink is used, the container is opened for the first time, and the volume average particle diameter of the colored fine particles (d) of the ink immediately measured can be, for example, the blank S1. The volume average particle diameter is preferably 0.3 μm or less in both cases of S2 and S1.

  In the “frequency distribution of the particle diameter of the colored fine particles (d) in the re-dispersion liquid of the dry ink”, the standard deviation (sd) of the volume particle diameter is 0.15 or less, and particularly 0.1 or less. It is preferable to do so. Of course, this range is preferable even under the condition of S1.

  The term “frequency distribution of the particle size of the colored fine particles (d) in the redispersion of dry ink” used in this specification is the definition of the colored fine particles (d) in the “redispersion of dry ink” as defined above. It means frequency distribution of particle diameter. Preferably, a frequency distribution of volume particle sizes is used.

  In the present invention, the SI unit system is adopted as the unit system, and the weight is described as mass.

  The ink is not limited to that of the present invention. For example, “colored microcapsules coated with a film-forming resin that does not dissolve the pigment in the dispersion medium” or “free that does not dissolve in the dispersion medium that is not coated with the film-forming resin” Pigment fine particles ”,“ free film-forming resin dispersion particles not coated with pigment, not dissolved in dispersion medium ”,“ film-forming resin dissolved in dispersion medium ”, and dispersion medium, and further used as necessary And an anti-drying agent, a penetrating agent, and the like.

  In order to solve the above-mentioned problems, in the present invention, a jet in which colored fine particles (d) obtained by coating pigment fine particles (a) with a film-forming resin (b) having a carboxyl group are dispersed in an aqueous medium. In the ink, (1) the colored fine particles (d) have a quaternized carboxyl group on the surface thereof and a volume average particle size of 0.5 μm or less; The “increase rate of the volume average particle diameter of the colored fine particles (d) in the redispersion liquid” must be 50% or less.

  In the present invention, as a more specific means, in the above ink configuration, it is effective to make the dissolved film-forming resin in the aqueous medium as the dispersion medium absent or within an allowable range. .

  As a means for this, it is preferable that the aqueous medium as a dispersion medium has as little dissolved film-forming resin as possible, and the amount thereof is preferably 2% by mass or less based on the ink weight.

  However, it is relatively difficult to make the resin component dissolved in the ink out of the film-forming resin less than 0.01% by mass, and when that happens, it is formed on the surface of the recording paper when the ink is printed on the recording paper. It is estimated that the microcapsule particles in the ink layer are insufficiently fixed to the recording paper and the bonding force between the microcapsule particles is insufficient, and as a result, there is a disadvantage that the durability such as friction of the printed matter is inferior.

  On the contrary, when the resin component dissolved in the ink exceeds 2% by mass in the film-forming resin, the recording of the microcapsule particles in the ink layer formed on the surface of the recording paper when the ink is printed on the recording paper. Although the fixing ability to paper and the bonding force between microcapsule particles are increased, the time until the dissolved film-forming resin is insolubilized on the recording paper, that is, the time until the water resistance immediately after printing is increased, is disadvantageous. In addition, the film-forming resin is more susceptible to clogging due to water evaporation at the nozzle end face than water-soluble resins such as polymer dispersants, and the ink jet stability is likely to be worse.

  When the resin component dissolved in the ink in the film-forming resin is, for example, 0.01-2% by mass, more preferably 0.1-1% by mass, when the ink is printed on the recording paper, the recording paper The adhesion of the microcapsule particles in the ink layer formed on the surface to the recording paper and the bonding force between the microcapsule particles are increased, and the durability of the printed matter is improved. There is no clogging, and the stability of inkjet ejection is greatly improved.

  The film-forming resin component dissolved in the ink represents the absolute amount contained in the ink as a content rate (hereinafter sometimes referred to as the absolute content rate).

  In the present invention, the aqueous medium means only water or a medium containing water as a main component and an organic solvent and other additives as necessary. In the present invention, it is preferable to select the chemical composition, the mass ratio of the constituent components, and the like so as not to dissolve the film-forming resin as much as possible as the aqueous medium serving as the ink dispersion medium.

  The film-forming resin may be any resin that forms a film, and is not limited to natural resins or synthetic resins, and various film-forming resins can be used, such as styrene resins, acrylic resins, polyester resins, Examples thereof include polyurethane resins. The resin may have a reversible cross-linking that is cross-linked at room temperature but becomes non-cross-linked by heat.

  Something like ionomer resins show this reversible cross-linking behavior. However, the film-forming resin is preferably a linear and substantially thermoplastic film-forming resin, and is not preferably one that is permanently crosslinked without heat dependency.

  However, in order to stably disperse the colored microcapsules in an aqueous medium, the film-forming resin needs to have a highly hydrophilic property, and thus a large amount of the film-forming resin is often dissolved in the ink. Will do. In this case, the dissolved resin may promote the aggregation of the microcapsules by long-term storage due to cross-linking between particles accompanying the entanglement of the resin layer covering the microcapsules. In addition, when ink jet recording is performed, ejection abnormalities are liable to occur due to an increase in the viscosity of ink accompanying the evaporation of moisture at the nozzle end face and adhesion of ink concentrate around the nozzle.

  Examples of the ejection abnormality include ink ejection abnormality and nozzle clogging.

  On the other hand, when the hydrophilicity of the film-forming resin is low, the dispersion stability of the colored microcapsules in which the pigment is coated with the film-forming resin in the aqueous medium becomes lower.

  Therefore, it is preferable to minimize dissolution of the film-forming resin in the aqueous medium and to enable stable dispersion in the aqueous medium.

  In order to stably disperse the colored microcapsules in an aqueous medium, for example, there may be a method of using a film-forming resin which is originally hydrophilic or poor in hydrophilicity using a surfactant or a dispersant. From the viewpoint that the image exhibits better water resistance and good ejection stability, it is preferable to prepare the image so as not to contain a surfactant or a dispersant.

  As a method for preparing the surfactant or dispersant so as not to contain it, for example, a film-forming resin obtained by neutralizing a resin that can be dispersed in an aqueous medium by neutralization with a neutralizer is used. Good to do. As a film-forming resin obtained by neutralizing a resin that can be dispersed in an aqueous medium by neutralization with a neutralizing agent, the resin that can be dispersed in an aqueous medium by neutralization with a base is typically neutralized with a base. And a film-forming resin. In the present invention, this resin that can be stably dispersed in an aqueous medium by itself without the aid of a surfactant or a dispersant may be referred to as a self-water dispersible resin.

  In the present invention, for example, a self-water dispersible resin obtained by neutralizing a resin having an acid value with a base is preferably used as the film-forming resin.

  A typical film-forming resin having an acid group is a film-forming resin (b) having a carboxyl group. The colored fine particles (d) obtained by coating the pigment fine particles (a) with the film-forming resin (b) having a carboxyl group include an aqueous medium of the film-forming resin (b) covering the pigment fine particles (a). The carboxyl group on the surface in contact is mainly quaternized to become a salt, so that it is stably dispersed in the aqueous medium. The film-forming resin (b) having a carboxyl group can be either a water-soluble resin or a self-water dispersible resin depending on the degree of quaternization of the amount of the carboxyl group determined by the acid value. However, the effect of the present invention is unique when the film-forming resin (b) present on the surface of the pigment fine particles (a) is not substantially dissolved in the aqueous medium, that is, is a self-water dispersible resin. .

  The acid value of a preferable resin is 10 to 280.

  Particularly preferably, an acid value of 50 to 180 is used.

  The acid value refers to the number of milligrams (mg) of potassium hydroxide (KOH) necessary to neutralize 1 g of resin, and is expressed in mg · KOH / g (hereinafter, the unit is abbreviated). Such a resin can be obtained, for example, by neutralizing all or part of the acid value of the resin having the specific acid value.

  At this time, it is preferable to adjust the pH of the ink to 7.5 to 9.0.

  When the acid value is less than 50, the surface hydrophilicity of the microcapsule particles is poor, and the dispersion stability tends to be insufficient. When the acid value exceeds 180, the hydrophilicity of the resin is remarkably increased, and the coating of the pigment with the resin is difficult. This is inappropriate because it tends to be insufficient due to swelling or the like, and tends to cause aggregation of the microcapsule particles or clogging of the nozzles.

  On the other hand, when the pH of the ink is lower than 7.5, the dispersion stability of the colored microcapsule particles tends to be lowered, and when the pH exceeds 9.0, the pigment coating of the colored microcapsule particles is unsatisfactory due to swelling or the like. This is not suitable because it tends to be sufficient, and the microcapsule particles tend to aggregate and clog the nozzles.

  Optimally, a self-water-dispersible resin obtained by using a resin having an acid value of 50 to 180 and neutralizing it with a base to make an ink in which 0.01 to 2% by mass of a film-forming resin component is dissolved. Is used as a film-forming resin, and the pH of the ink is 7.5 to 9.0, which shows a remarkable effect in the present invention.

  The molecular weight range of the film-forming resin is not particularly limited, but is preferably a molecular weight range of 1000 to 100,000 in terms of weight average molecular weight. If the molecular weight of the film-forming resin is less than 10,000, sufficient film formation is often not achieved, and this is inappropriate because it tends to cause nozzle clogging due to aggregation of microcapsule particles.

  Moreover, if it is less than 10,000, the water resistance of the printed matter is also deteriorated, which is inappropriate.

  In particular, in order to sufficiently coat the pigment with the film-forming resin, the molecular weight of the resin is preferably 10,000 or more and 100,000 or less.

  In the case of a styrene resin or an acrylic resin, those having a molecular weight of 1000 or more and 100,000 or less are more preferable.

  The weight average molecular weight of the resin is preferably 10,000 or more and 100,000 or less, and particularly preferably 30,000 or more and 100,000 or less from the viewpoint of obtaining superior water resistance.

  In the present invention, a preferred film-forming resin is a styrene resin or a (meth) acrylic resin.

  Preferred examples of the resin having an acid value include a copolymer of (meth) acrylic acid with at least one monomer selected from the group consisting of styrene, substituted styrene, and (meth) acrylic acid ester.

  In the present invention, as a film-forming resin comprising a self-water dispersible resin obtained by neutralizing a resin having an acid value with a base, preferably, for example, from styrene, substituted styrene, (meth) acrylic acid ester Examples thereof include a self-water dispersible resin obtained by neutralizing at least one monomer selected from the group consisting of a copolymer of (meth) acrylic acid with a base.

  (Meth) acrylic acid is a generic term for acrylic acid and methacrylic acid, and in the present invention, either one is essential, but more suitable film-forming resins are used for both acrylic acid and methacrylic acid. It has a derived structure.

  In the present invention, for example, in order to reduce the dissolution of the self-water dispersible resin as a film-forming resin in an aqueous medium, the ratio of acrylic acid among the monomer components having all carboxyl groups is changed. The amount of methacrylic acid should be increased more and less.

  That is, the self-water dispersible resin as the optimum film-forming resin is mainly composed of at least one monomer selected from the group consisting of styrene, substituted styrene, and (meth) acrylic acid ester, and includes acrylic acid and methacrylic acid. This is a self-water-dispersible resin in which methacrylic acid is copolymerized more than acrylic acid and is at least partially neutralized with a base.

  In order to make the pH of the ink basic, neutralization, that is, a base may be added to the resin that can be dispersed in an aqueous medium by neutralization.

  A base is used in the suspending step in a more preferable method for producing an aqueous jet ink (this will be described in detail later).

  Examples of the base (sometimes referred to as a basic compound in the present invention) include alkali metal hydroxides such as sodium hydroxide, potassium hydroxide and lithium hydroxide, and basic substances such as ammonia, triethylamine and morpholine. Alcohol amines such as triethanolamine, diethanolamine, N-methyldiethanolamine can be used.

  As the base, it is preferable to employ a volatile base that is easily volatile at a high temperature at which the film-forming resin does not decompose.

  However, neutralizing a higher acid number resin with a stronger base increases the solubility of the film-forming resin in the ink, so the strength of the base and the amount used (neutralization rate) are adjusted. It is preferable to do.

  In the case of a high acid value resin, since the solubility of the resin in the suspension increases as the neutralization rate with the base increases, the amount of base used depends on the degree of dissolution in the liquid medium and the final dispersion of the aqueous dispersion. Adjust appropriately based on the intended size of the particle.

  Neutralizing a high acid value resin with a strong base increases the solubility of the resin in water. However, in the reprecipitation step in the more preferable method for producing an aqueous jet ink, the resin is not sufficiently deposited on the pigment surface. Therefore, it is preferable to adjust the strength and amount of use (neutralization rate) of the base so that the amount of the water-soluble resin component does not increase in the suspension.

  In the case of water-based ink for ink jet recording, it is preferable to keep the water-soluble resin component to a minimum because clogging of nozzles, dispersion stability during storage, and water resistance of printed matter are adversely affected.

  Alcoholamines, especially triethanolamine, are weak bases and are less likely to produce the water-soluble resin component, and are optimal bases for the preparation of water-based inks for ink jet recording.

  In inkjet recording, alcohol bases, particularly triethanolamine, are the most suitable bases because they have very little adverse effects on nozzle clogging, dispersion stability during storage, and water resistance of printed matter.

  The neutralization rate with the base in the suspending step in the more preferable method for producing a water-based jet ink is not limited as long as the resin having an acid value in the resin coloring step is self-emulsified in the suspension. It is 10 mol% or more of the group.

  In the present invention, the neutralization rate of the film-forming resin with respect to the acid groups is 100 mol% or less, preferably 60 mol% or less. It is particularly preferable to use alcoholamine as a base so that the neutralization rate of the film-forming resin with respect to the acid groups is 60 mol% or less.

  In the present invention, the film-forming resin having an acid value is a film-forming resin having an acid value of 50 to 180 mg · KOH / g, and the neutralization rate of the film-forming resin with respect to acid groups is 60 mol%. It is preferable to use a self-water dispersible resin that is not more than a considerable amount.

  As the colored fine particles (d), when a film-forming resin (b) having a carboxyl group and having an acid value of 50 to 180 is used, a part or all thereof is an organic amine compound and is quaternary ammonium. What is made into the salt is preferable.

  The method for producing a more preferred aqueous jet ink in the present invention is not particularly limited, and any known and commonly used colorant can be used. The use of a pigment makes it easier to obtain a colored resin film having excellent water resistance than the use of a dye.

  The colored microcapsule of the present invention using a pigment can provide a colored resin film having superior water resistance and light resistance than colored resin particles using a dye.

  The pigment used in the colored microcapsule-dispersed aqueous jet ink of the present invention is not particularly limited, and any known and commonly used pigment can be used. This pigment exists as pigment fine particles (a) in the colored fine particles (d) in the present invention.

  Examples of the pigment include inorganic pigments such as carbon black, titanium black, titanium white, zinc sulfide, and bengara; azo pigments such as phthalocyanine pigments, monoazo and disazo pigments, and organic pigments such as phthalocyanine pigments and quinacridone pigments. .

  As will be described in detail later, any one of carbon black, phthalocyanine pigment, halogenated phthalocyanine pigment, quinacridone pigment, benzimidazolone pigment, perinone pigment, and isoindolinone pigment is used as the pigment used to obtain the ink. Is preferred.

  In order to obtain achromatic colored fine particles, particularly black colored fine particles, only carbon black or a colorant mainly composed of carbon black may be used. To obtain chromatic colored fine particles, an organic pigment may be used. preferable.

  When obtaining a color image, it is preferable to use a chromatic pigment.

  In order to perform color image formation, particularly full color image formation, the color tone of the pigment to be used must be at least a combination of three colors of cyan (blue), magenta (red) and yellow, preferably black. It is possible to form an image using four colors of ink, or to form an image by adding a complementary color to the three or four colors.

  The cyan pigment is preferably a phthalocyanine pigment from the viewpoint of color tone and weather resistance. Specific examples of the phthalocyanine pigment include metal-free phthalocyanine, copper phthalocyanine or chlorinated copper phthalocyanine, and other various metal phthalocyanines. Among these, copper phthalocyanine is preferable, and C.I. I. Pigment Blue 15: 4 is more preferable.

  The magenta color pigment is preferably a quinacridone pigment from the viewpoint of color tone and weather resistance. Specific examples of the quinacridone pigment include dimethylquinacridone and dichloroquinacridone. Among these, C.I. is particularly preferred in terms of color tone and dispersibility when combined with other color pigments. I. Pigment Red 122 is preferable.

  The yellow color pigment is preferably a benzimidazolone pigment from the viewpoint of color tone and weather resistance. Specific examples of benzimidazolone pigments include C.I. I. Pigment yellow 120, C.I. I. Pigment yellow 151, C.I. I. Pigment yellow 154, C.I. I. Pigment yellow 156, C.I. I. Pigment yellow 175. Among these, C.I. is preferable in terms of color tone, dispersibility and light resistance when combined with other color pigments. I. Pigment Yellow 151 is most preferable.

  The black pigment is not particularly limited, but carbon black is preferable from the viewpoint of color tone and weather resistance.

  An image obtained by forming a color image by combining an ink containing carbon black as a colorant and each of at least three colors of a phthalocyanine pigment, a quinacridone pigment, and a benzimidazolone pigment has almost no color tone change due to photobleaching. And extremely high image quality stability.

  In particular, C.I. I. Pigment Blue 15: 4, C.I. I. Pigment Red 122 and benzimidazolone pigments such as C.I. I. An image obtained by performing color image formation by combining carbon black with pigment yellow 151 and, if necessary, carbon black is particularly preferable for image quality stability.

  Each of the color pigments can be used alone or in combination, and if necessary, other types of pigments can be used in combination to form an ink.

  In the present invention, it is preferable to form an image on a recording medium using each of the above-described water-based inks using the four preferred pigments and further using each of the water-based inks of intermediate colors. As described above, it is preferable to use a halogenated phthalocyanine pigment, an imidazolone pigment, a perinone pigment, or an isoindolinone pigment as an intermediate color pigment. As an intermediate color aqueous ink using such a pigment, a colored microcapsule dispersion type is used. Some of them are not, but the following are preferred.

  (A) A microcapsule-dispersed green aqueous jet ink containing a colored microcapsule coated with a film-forming resin on halogenated phthalocyanine pigment fine particles in an aqueous medium, (B) an imidazolone pigment, a perinone pigment, or an isoindolinone pigment. A microcapsule-dispersed orange aqueous jet ink comprising colored microcapsules obtained by coating fine particles of any one pigment with a film-forming resin in an aqueous medium.

  In these inks (A) and (B), among the film-forming resins, those having a resin component dissolved in the ink in the range of 0.01 to 2% by mass are combined with the above water-based inks. Is preferable.

  The amount of the pigment used is not particularly defined as long as the effect of the present invention is achieved, but it is preferably prepared so that the amount is usually 0.5 to 20% by mass in the finally obtained ink. .

  These pigments are preferably all coated with a film-forming resin if the surface is at least partly formed, and the ratio varies depending on the specific surface area of the pigment and the thickness of the coating resin. 5 to 2 parts by mass is preferable. In the present invention, since there are very few free pigments that are not resin-coated in the ink, almost all of the pigments used can be approximated by the content as only colored microcapsules.

  When both are used so that the pigment and the film-forming resin having an acid value have almost the same mass, more preferable results can be obtained in the preferred method for producing an aqueous ink for inkjet recording described below. The range includes a case where both have the same mass or the pigment is within a range of ± 15% of the mass of the resin.

  If necessary, the ink may contain an organic solvent that does not dissolve or hardly dissolve the film-forming resin. The organic solvent used for the ink is used as an anti-drying agent or a penetrating agent as an example.

  The anti-drying agent has an effect of preventing the ink from drying at the jet nozzle opening of the ink jet, and usually has a boiling point equal to or higher than the boiling point of water. As such an anti-drying agent, any conventionally known ones can be used. For example, polyhydric alcohols such as ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, polyethylene glycol, polypropylene glycol, and glycerin. There is kind.

  When glycerin is an anti-drying agent, the most excellent anti-drying effect is exhibited.

  In particular, glycerin is bonded to the film-forming resin on the surface of the microcapsule particles by strong hydrogen bonds to further enhance the dispersion stability of the microcapsule particles, and at the same time, even if a small amount of the film-forming resin is dissolved in the ink, Further, it is more preferable in that it is connected with a strong hydrogen bond to prevent drying at the nozzle end face.

  The penetrant is for penetrating ink into the recording medium and adjusting the dot diameter on the recording medium. Examples of penetrants include lower alcohols such as ethanol and isopropyl alcohol, ethylene glycol hexyl ether, diethylene glycol butyl ether, and the like. Examples thereof include ethylene oxide adducts of alkyl alcohols and propylene oxide adducts of alkyl alcohols such as propylene glycol propyl ether.

  An organic solvent having excellent permeability to a recording medium often destroys the microcapsule and impairs the stability of the ink. Among them, in particular, 1 mol of monoalcohol propylene oxide alone (k), 1 carbon atom At least 1 selected from the group consisting of 3 to 10 monopropylene oxide monoaddition polymers (1) to 6 monoalcohols and 1 mole monoadduct (m) of ethylene alcohol to 4 to 8 monoalcohols. The stability of the microcapsules can be maintained by using an appropriate amount of seeds or more in the ink. Among them, it is preferable to select and use two groups of substances in each group of (k), (l), and (m).

  The water-based jet ink is not limited to that of the present invention, and a silicone-based emulsion-dispersed antifoaming agent is added to the recording medium to suppress bleeding, to suppress foaming, and to improve ink ejection stability. However, in place of the silicone-based emulsification-dispersed antifoaming agent, the use of each substance of each group is particularly effective.

  Examples of the monoalcohol propylene oxide 1 mol single adduct (k) include propylene oxide (1 mol) single adduct of propanol.

  Examples of the propylene oxide 10-40 mol homoaddition polymer (1) of monoalcohol having 1 to 6 carbon atoms include butanol propylene oxide (17.7 mol) addition polymer.

  Examples of the monoalcohol ethylene oxide 1 mol single adduct (m) include butanol ethylene oxide (1 mol) single adduct, hexanol ethylene oxide (1 mol) single adduct, and the like.

  The contents of (l), (m), and (n) in the ink are preferably added so as to minimize the foaming of the ink, and the addition amount may be suppressed to a level that does not cause layer separation on the ink surface. Although not particularly limited, it is generally in the range of about 0.01 to 10% by mass.

  The amount of the organic solvent added is preferably 1 to 80% by mass when used as an anti-drying agent in the ink and 0.01 to 10% by mass when used as a penetrant.

  Depending on the type and concentration of the film-forming resin, or the concentration of the organic solvent in the aqueous medium, the organic solvent dissolves the resin coated on the pigment in excess of 2% by mass and deteriorates the jetting characteristics. In some cases, the amount added in the ink is determined in consideration of the pH range of the ink so that the content in the ink is 2% by mass or less, more preferably 1% by mass or less, depending on the type of the organic solvent. It is necessary to suppress it.

  The finally obtained dispersion medium of the ink is preferably an aqueous medium that substantially does not contain the organic solvent (e) that dissolves the film-forming resin and consists essentially of water. Further, when the organic solvent (e) that dissolves the film-forming resin is included in the ink, the resin (b) having a quaternized salt structure on the surface of the dispersed colored fine particles (d). It is preferable to keep the content contained in the ink low so as not to dissolve.

  In the method of measuring the component dissolved in the ink of the film-forming resin of the present invention, when there are few solid components other than the resin, for example, the microcapsule particles are precipitated by an ultracentrifuge, Can be dried and measured directly as a non-volatile content. In addition, if there is a large amount of solids or high-boiling organic solvents other than the resin in the ink, the centrifugal sediment is thoroughly dried, and then the resin is analyzed with a thermal analyzer based on the difference in thermal decomposition temperature. The amount of the resin component dissolved in the ink can be determined by measuring the ratio of the pigment and the pigment and converting the ratio from the ratio of the resin and the pigment charged in the ink. In the latter method, the dispersion in the aqueous medium is composed only of colored microcapsules, and does not include free pigment fine particles not coated with a film-forming resin or “particles containing only a film-forming resin without a pigment”. In some cases, it can be measured with particularly high accuracy. If the ink contains additives such as anti-drying agents and penetrants, the former additive should be dried and removed at a temperature that will not cause the pigment and film-forming resin to decompose. , The measurement accuracy can be increased.

  As a specific method for obtaining the colored microcapsule-dispersed aqueous jet ink of the present invention, the following method is preferable particularly when the pigment is coated with a film-forming resin having an acid value. According to this method, a resin and a component derived from a pigment dispersed in an aqueous medium consist only of colored microcapsules, and “free pigment fine particles not coated with a film-forming resin” or “a film containing no pigment”. An extremely small amount of ink can be easily obtained even if it contains no or only “particles of the forming resin” or “dissolved film-forming resin”.

  The following method is based on a phase inversion emulsification method in which a pigment fine particle is dispersed in an organic solvent solution of a self-water dispersible resin, and an aqueous medium is added to perform phase inversion emulsification to remove the organic solvent. However, it is possible to more easily obtain a very small amount of ink even if it contains no pigment-containing film-forming resin-only particles or no or no dissolved film-forming resin.

[1] A resin coloring step in which a solid coloring compound is obtained by dispersing at least a pigment in a film-forming resin having an acid value.
[2] A pigment suspension in which at least water, an organic solvent that dissolves the film-forming resin, a base, and the solid coloring compound obtained in the resin coloring step are mixed and at least a part of the resin is dissolved by dispersion. Obtaining a suspension step.
[3] A reprecipitation step of depositing a dissolved resin component on the pigment surface in the pigment suspension obtained in the suspension step.

Specifically, for example, the following <1> to <5> can be performed in this order.
<1> A pigment is dispersed in a film-forming resin having an acid value to obtain a solid coloring compound. (Kneading process)

  In this step, for example, the pigment is uniformly dispersed in the resin in a solution or heated and melted using a conventionally known kneading apparatus such as a roll, a kneader, or a bead mill, and finally a solid kneaded product (solid It can be performed by taking it out as a colored compound.

  In particular, when fine dispersion of the pigment in the resin is necessary, as a means for dispersing the pigment, a dispersion means that forms a state in which a relatively high shear force is applied can be used. Specifically, it is preferable to perform dispersion under a high shear force using two rolls.

  <2> Mix at least water, an organic solvent that dissolves the resin, a base, and the solid coloring compound, and obtain a pigment suspension in which at least a part of the resin is dissolved by dispersion. (Suspension process)

  The organic solvent that dissolves the resin functions as a good solvent for the resin and can be appropriately selected for the resin. For example, ketone solvents such as acetone, dimethyl ketone, and methyl ethyl ketone, methanol, ethanol , Alcohol solvents such as isopropyl alcohol, chlorine solvents such as chloroform and methylene chloride, aromatic solvents such as benzene and toluene, ester solvents such as ethyl acetate, glycol ethers such as ethylene glycol monomethyl ether and ethylene glycol dimethyl ether Any solvent can be used as long as it dissolves a resin such as a system solvent or an amide.

  The dispersion medium used in this step is mainly water that functions as a poor solvent for the film-forming resin and is preferably used as water-based ink for ink jet recording, and therefore has a purity higher than that of ion-exchanged water.

  In this step, it is preferable that the mixture of water and the organic solvent is uniform. If not uniform, if necessary, a surfactant may be used, or the mixture may be mechanically emulsified into an O / W type. It is preferable to use a solvent in a uniform manner.

  If it is difficult to obtain a pigment suspension with excellent dispersion stability using only an organic solvent that dissolves the resin, water, and a base, a hydrophilic organic solvent that does not dissolve the resin is partially used as a cosolvent. And you may make it have better emulsification stability. In addition, the organic solvent and cosolvent which melt | dissolve the said resin may use together 1 type, or 2 or more types.

  In the case where the resin is a copolymer of (meth) acrylic acid and at least one monomer selected from the group consisting of styrene, substituted styrene, and (meth) acrylic acid ester, for example, a ketone solvent such as methyl ethyl ketone is used. Mainly, at least one combination selected from alcohol solvents such as isopropyl alcohol is preferably used as a cosolvent.

  The ratio of water and organic solvent is not particularly defined as long as the effect of the present invention is achieved, but is preferably such an amount that the weight ratio of water / organic solvent is 10/1 to 1/1.

  Through this step, a pigment suspension in which a film-forming resin having an acid value including a pigment is self-emulsified with the help of an organic solvent and a base and at least partly dissolved from the surface of the solid coloring compound. Is obtained.

  When the resin is completely dissolved in the liquid medium in the suspension, the pigment surface is exposed, but when the resin is self-emulsified, at least a part of the pigment surface is resin. It is thought that it is covered.

  By this step, the film-forming resin having an acid value that is present on the surface of the solid coloring compound is gradually neutralized by the base with at least a part or all of the acid value, and from the solid form of the compound, The mixture becomes suspended.

  As a stirring method for obtaining a suspension, any known and commonly used method can be adopted. For example, in addition to a uniaxial propeller type stirring blade, a stirring blade or a stirring container having a shape suitable for the purpose can be used. Can be suspended.

  When obtaining a suspension, if the mixture is not finely divided by simple mixing and stirring where no large shearing force is applied, or if the pigment is relatively easy to agglomerate, the particles may be stabilized by applying a higher shearing force. . As a disperser in this case, for example, a high-pressure homogenizer, a beadless disperser known by a trade name of microfluidizer or nanomizer, and the like are preferably used because of less pigment re-aggregation.

  For example, when a pigment suspension dispersed in a relatively small particle size is obtained as a compound in the suspension step <2>, the reprecipitation step <3> can be immediately performed. On the other hand, when a solid color compound obtained using an organic pigment as a pigment is used as a compound, or when a solid color compound using an inorganic pigment such as carbon black is used, the suspension step <2> and <3> In order to increase the dispersion stability of the suspension obtained from the former compound and to reduce the particle size of the pigment fine particles in the pigment suspension obtained from the latter compound during It is preferable to provide a step of exposing and dispersing the suspension under force.

  <3> The film-forming resin component dissolved in the pigment suspension is deposited on the pigment surface. (Reprecipitation process)

  By doing so, the film-forming resin component dissolved in the pigment suspension is deposited on the pigment surface to obtain microcapsules.

  This step is a step of depositing the dissolved resin component present in the suspension on the surface of the pigment in the pigment suspension obtained in the suspension step.

  “Reprecipitation” in this step does not mean that the pigment or the semi-encapsulated particles in which the dissolved resin is adsorbed on the pigment surface are separated and settled from the liquid medium of the suspension. Therefore, what is obtained in this step is not a simple mixture in which the solid component and the liquid component are clearly separated, but the microcapsules coated with the dissolved resin or the dispersed resin on the pigment surface are stable in the liquid medium of the suspension. Colored fine particles (colored microcapsules) dispersed in water.

  That is, the deposition of the dissolved resin on the surface of the pigment fine particles whose surface is coated with the free pigment surface and / or the self-water dispersible resin in the pigment suspension is the surface of the free pigment and / or the self-water dispersible resin. The pigment fine particles coated with are dispersed in an aqueous medium.

  The deposition of the dissolved resin on the free pigment surface and / or the pigment fine particle surface coated with the self-water-dispersible resin in the pigment suspension in this suspension step is the resin component of the dissolved resin component in the aqueous medium. This can be done by lowering the solubility of.

  As a method of reducing the solubility of the resin component in the aqueous medium of the dissolved resin component, a necessary amount of a poor solvent for the resin is added to the aqueous medium in which the resin component is dissolved, or the resin component contained in the aqueous medium A method is generally used in which a necessary amount of a chemical component that dissolves is removed from the system. By doing so, the dissolved resin preferentially approaches the surface of the free pigment fine particles and / or the surface of the pigment fine particles coated with a self-water dispersible resin, which are dispersed in the system. It accumulates on each surface and deposits as if pressed against it.

  Deposition of the dissolved resin on the surface of the pigment in the pigment suspension in this suspending step is, for example, at least partly in the pigment suspension in which the film-forming resin is dissolved, It can be easily carried out by adding an aqueous medium that functions as an organic solvent and / or by removing the organic solvent from the pigment suspension.

  The resin is deposited on the surface of the colored microcapsule by, for example, an aqueous medium functioning as a poor solvent for the resin in a pigment suspension in which the film-forming resin is dissolved and / or dispersed. It can be easily carried out by adding and / or removing the organic solvent from the pigment suspension.

  However, a method in which an aqueous medium that functions as a poor solvent for the resin is added to the pigment suspension is preferable because there is little aggregate. In the reprecipitation, the aqueous medium is dropped while the suspension is gently stirred, thereby making it possible to reliably deposit (reprecipitate) the resin on the pigment surface while preventing the formation of aggregates.

  In performing the deposition, an aqueous medium that functions as a poor solvent for the resin is added to the pigment suspension in which the film-forming resin is dissolved and / or dispersed. It is preferable to remove the organic solvent from the suspension.

  In order to prevent the obtained dispersion from drying, it is preferable that an anti-drying agent is present in the aqueous medium in advance or is added after reprecipitation.

  When the finally obtained colored fine particle dispersion is used as jet ink, the jet ink is designed to realize stable ejection without clogging.

  When the dispersion liquid thus obtained is used as an inkjet recording liquid, the average particle diameter is set to the submicron order (less than 1 μm).

  The submicron-order colored fine particle aqueous dispersion obtained by the method for producing a colored fine particle aqueous dispersion of the present invention exhibits ink jet aptitude excellent in dispersion stability and jetting characteristics when used as an aqueous ink for ink jet recording. As will be described in detail later, when the method for producing an aqueous dispersion of colored fine particles of the present invention is applied thereto, the suspension in the suspending step (2) contains an anti-drying agent so that the dispersion stability is extremely excellent. Suspensions, aqueous dispersions, and water-based inks can be obtained.

  In this manner, colored fine particles having a desired particle size can be obtained by the above <1> kneading step <2> suspension step <3> reprecipitation step. Usually, the average particle size range is 0.01 or more to It is less than 1 μm.

  <4> Removal and / or concentration of low boiling point organic solvent from the microcapsule dispersion obtained in the reprecipitation step (solvent removal step)

  The colored fine particle aqueous dispersion obtained in the reprecipitation step can be used as it is, but since the colored fine particles are often in a swollen state due to the coexisting organic solvent, in order to further improve the storage stability, In order to further improve safety against fire and pollution, it is preferable to remove the solvent.

  The organic solvent thus removed can be recycled and reused in a closed system without being incinerated for the purpose of continuous production, for example.

The colored fine particle (colored microcapsule) aqueous dispersion obtained through the steps <1> to <4> is exclusively composed of “colored microcapsules” in which all components derived from the resin and pigment used in the preparation thereof are exclusively used. It is an aqueous dispersion consisting of the above, and is substantially free from the three components of “free pigment fine particles”, “particles of film-forming resin only” and “dissolved film-forming resin”. However, since it is extremely difficult to make the dissolved film-forming resin component zero, the content is generally 0.01% by mass or more based on the total components of the dispersion.

  The dispersion thus obtained usually consists essentially of colored microcapsules in which a pigment is coated with a film-forming resin and a dispersion medium alone. The content of the colored microcapsules in the dispersion is usually 10 to 40% by mass relative to the total of the dispersion and the dispersion medium. Of course, when various additives are included in the steps so far, they are also included in the dispersion.

  In the present invention, in a jet ink in which colored fine particles (d) obtained by coating pigment fine particles (a) with a film-forming resin (b) having a carboxyl group are dispersed in an aqueous medium, (1) the colored fine particles (D) has a quaternized carboxyl group on its surface and a volume average particle diameter of 0.5 μm or less, (2) “colored fine particles in a redispersion of dry ink (d )) Is obtained by the following production method in that the ink having such characteristics can be easily obtained. It is preferable to do this.

  (1) (i) a colored compound (V) obtained by kneading a pigment and a carboxyl group-containing film-forming resin (b), (ii) water, and an organic that can dissolve the film-forming resin (b) An aqueous medium (W) composed of a solvent (e) and (iii) a basic compound (c) are mixed uniformly to form (2) a film-forming resin in which the pigment fine particles (a) have a carboxyl group. A colored fine particle dispersion (X) is produced in which colored fine particles (d) coated with (b) and having quaternized carboxyl groups on the coated surface are dispersed in an aqueous medium (W). Then, (3) by adding a poor solvent of the film-forming resin (b) to the dispersion liquid (X) of the colored fine particles, a film formation dissolved in the aqueous medium of the dispersion liquid (X) of the colored fine particles The functional resin (b) is deposited on the surface of the colored fine particles (d); Removing the organic solvent (e) from dispersion liquid (X), the production method of the dispersion of the jet ink coloring fine particles, characterized in that.

  Of course, in the step (3), the dispersion (X) contains no quaternized carboxyl group (ie, salt structure) and dissolved film-forming resin. When the dispersion stability of the colored fine particles (d) dispersed in (X) is good, it is not necessary to add the poor solvent of the film-forming resin (b), and only the organic solvent (e) is removed. But you can.

<5> Ink process The submicron-order colored fine particle aqueous dispersion containing no or almost no liquid medium other than water obtained by the above <4> process is basically an aqueous ink for ink jet recording. It can be used as ink.

  The obtained dispersion is preferably further adjusted for ink in consideration of dispersion stability and ejection characteristics.

  Usually, as will be described later, for example, the ink is passed through a filter having a desired particle diameter, filtered, and used as an aqueous ink for inkjet recording in which only particles smaller than the nozzle diameter of the inkjet recording apparatus are dispersed in a liquid medium.

  Ink adjustment includes, for example, addition of the above-mentioned anti-drying agent and penetrating organic solvent, concentration adjustment / viscosity adjustment, pH adjusting agent, surfactant for dispersion / defoaming / penetration into paper, preservative, Chelating agents, plasticizers, antioxidants, ultraviolet absorbers and the like can be added as necessary. However, various additives may be selected from those that do not dissolve the film-forming resin present on the surface of the colored microcapsules and use only those having such properties, or those that can dissolve the resin. It is necessary to devise measures such as minimizing the amount used so that it does not substantially dissolve.

  Also, if the recording medium is something other than impervious (glass, metal, film, etc.) (permeable recording medium), it differs from the film-forming resin to the extent that it does not affect the jetting stability. Other water-soluble resins can also be added.

  In order to avoid clogging of nozzles due to coarse particles, ordinarily, coarse particles are removed by centrifugation or filtration after the solvent removal step <4>, or desired after ink adjustment in the ink step <5>. Filter with a filter of particle size.

  The colored microcapsule-dispersed water-based jet ink of the present invention can be employed in a known and commonly used ink jet recording system printer such as a piezo system or an on-demand system. The ink can be used for forming an image on a known and commonly used recording material such as paper, resin-coated paper, ink-jet recording paper, glass, metal, film, ceramics and the like.

  The colored microcapsule-dispersed water jet ink of the present invention is excellent in transparency, color developability, and dispersion stability, and can be applied to other general inks, paints, and color filters in addition to inkjet recording.

The present invention includes the following embodiments.
1. Realized stable injection without clogging of the nozzle, which is made of a colored fine particle aqueous dispersion smaller than the nozzle diameter of the ink jet recording apparatus obtained in the following process, dispersion stability during storage, water resistance of the printed matter Good colored fine particle dispersed aqueous jet ink.
[1] A resin coloring step in which a solid coloring compound is obtained by dispersing at least a pigment in a film-forming resin having an acid value.
[2] At least water, an organic solvent that dissolves the film-forming resin, a base that minimizes the amount of the water-soluble resin component, and the solid coloring compound obtained in the resin coloring step are mixed, and the film-forming resin A suspension step for obtaining a pigment suspension which is dispersed in water and adjusted so that at least a part of the resin is dissolved.
[3] After adding an aqueous medium that functions as a poor solvent to the resin, the organic solvent that dissolves the resin is removed from the suspension, and the pigment suspension obtained in the suspension step A reprecipitation process that deposits dissolved resin components on the pigment surface to minimize water-soluble resin components.

  2. An ink containing a pigmented microcapsule coated with a self-dispersible film-forming resin in an aqueous medium, and the film-forming resin component dissolved in the ink is 0.01 to 2% by mass A colored microcapsule-dispersed water-based jet ink characterized by

  3. An ink containing a pigmented microcapsule coated with a self-dispersible film-forming resin in an aqueous medium, and the film-forming resin component dissolved in the ink is 0.1 to 1% by mass A colored microcapsule-dispersed water-based jet ink characterized by

  4). An ink containing pigmented microcapsules coated with a self-water-dispersible film-forming resin in an aqueous medium, wherein the absolute content of the film-forming resin component dissolved in the ink is 0.01 to 2 mass %, A colored microcapsule-dispersed water-based jet ink.

  5. An ink containing pigmented microcapsules coated with a self-dispersible film-forming resin in an aqueous medium, wherein the absolute content of the film-forming resin component dissolved in the ink is 0.1 to 1 mass %, A colored microcapsule-dispersed water-based jet ink.

  6). 6. The ink according to the above 1, 2, 3, 4 and 5 having a pH of 7.5 to 9.0.

  7). 7. The ink according to 1, 2, 3, 4, 5, or 6, wherein the self-water dispersible film-forming resin has a weight average molecular weight of 30,000 to 100,000.

8). 8. The ink according to 2, 3, 4, 5, 6 and 7, wherein the colored microcapsule is obtained by sequentially performing the following steps.
[1] A resin coloring step in which a solid coloring compound is obtained by dispersing at least a pigment in a film-forming resin having an acid value.
[2] At least water, an organic solvent that dissolves the film-forming resin, a base, and the solid coloring compound obtained in the resin coloring step are mixed, and the film-forming resin is self-water-dispersed and at least a part of the resin is dissolved. A suspension step of obtaining a pigment suspension adjusted to
[3] A reprecipitation step of depositing a dissolved resin component on the pigment surface in the pigment suspension obtained in the suspension step.

9. 8. The ink according to 2, 3, 4, 5, 6 and 7, wherein the colored microcapsule is obtained by sequentially performing the following steps.
[1] A resin coloring step in which a solid coloring compound is obtained by dispersing at least a pigment in a film-forming resin having an acid value.
[2] At least water, an organic solvent that dissolves the film-forming resin, a base, and the solid coloring compound obtained in the resin coloring step are mixed, and the film-forming resin is self-water-dispersed and at least a part of the resin is dissolved. A suspension step of obtaining a pigment suspension adjusted to
[3] A reprecipitation step in which the dissolved resin component is deposited on the pigment surface in the pigment suspension obtained in the suspension step by reducing the solubility of the resin component in the aqueous medium.

10. 8. The ink according to 2, 3, 4, 5, 6 and 7, wherein the colored microcapsule is obtained by sequentially performing the following steps.
<1> A resin coloring step for obtaining a solid coloring compound by dispersing at least a pigment in a film-forming resin having an acid value.
<2> At least water, an organic solvent that dissolves the film-forming resin, a base, and the solid coloring compound obtained in the resin coloring step are mixed, and the film-forming resin is self-water-dispersed and at least a part of the resin is dissolved. A suspension step of obtaining a pigment suspension adjusted to
<3> An aqueous medium that functions as a poor solvent for the dissolved resin is added to the surface of the pigment in the pigment suspension obtained in the suspension step, and the organic solvent is removed from the suspension to remove the suspension. A reprecipitation process in which the dissolved resin component is deposited on the pigment surface in the pigment suspension obtained in the turbid process.

11. 8. The ink according to 2, 3, 4, 5, 6 and 7, wherein the colored microcapsule is obtained by sequentially performing the following steps.
<1> A resin coloring step for obtaining a solid coloring compound by dispersing at least a pigment in a film-forming resin having an acid value.
<2> At least water, an organic solvent that dissolves the film-forming resin, a base, and the solid coloring compound obtained in the resin coloring step are mixed, and the film-forming resin is self-water-dispersed and at least a part of the resin is dissolved. A suspension step of obtaining a pigment suspension adjusted to
<3> After an aqueous medium that functions as a poor solvent is added to the surface of the pigment in the pigment suspension obtained in the suspension step to form a film, an organic solvent that dissolves the resin is added to the surface of the pigment. The solvent is removed from the suspension, and the dissolved resin component is deposited on the pigment surface in the pigment suspension obtained in the suspension step by reducing the solubility of the resin component in the aqueous medium. Reprecipitation process.

  12 The above 1, 2, 3, 4, 5, 6, wherein the pigment and the film-forming resin having an acid value are the same mass, or the pigment mass is ± 15% of the mass of the resin. The ink according to 7, 8, 9, 10 and 11.

  13. The above-mentioned 2 wherein the self-water dispersible film-forming resin is neutralized at a neutralization rate equal to or less than 60 mol% of the acid groups of the resin having an acid value of 50 to 180 mg · KOH / g. The ink according to 3, 4, 5, 6 and 7.

  14 The film-forming resin having an acid value is a resin having an acid group with an acid value of 50 to 180 mg · KOH / g, and is neutralized with a base so that the neutralization rate is less than or equal to 60 mol% of the acid group. The ink according to 1, 8, 9, 10 and 11 above.

  15. In a jet ink in which colored fine particles (d) formed by coating pigment fine particles (a) with a film-forming resin (b) having a carboxyl group are dispersed in an aqueous medium, (1) the colored fine particles (d) are It has a quaternized carboxyl group on its surface and a volume average particle diameter of 0.5 μm or less, (2) “Volume average of colored fine particles (d) in a redispersion of dry ink A jet ink characterized in that the "increase rate of particle size" is 50% or less.

  16. 16. The jet ink according to 15 above, wherein the amount of the film-forming resin (b) dissolved in the aqueous medium is 2% or less with respect to the ink weight.

  17. 17. The jet ink according to the above 15 and 16, wherein the standard deviation value in the “frequency distribution of the particle diameter of the colored fine particles (d) in the redispersed liquid of dry ink” is 0.15 or less.

  18. 18. The said 15, 16, 17 that film formation resin (b) which has a carboxyl group has an acid value of 50-180, and the one part or all part is made into the quaternary ammonium salt with the organic amine compound. Jet ink.

  19. (1) (i) a colored compound (V) obtained by kneading a pigment and a carboxyl group-containing film-forming resin (b), (ii) water, and an organic that can dissolve the film-forming resin (b) An aqueous medium (W) composed of a solvent (e) and (iii) a basic compound (c) are mixed uniformly to form (2) a film-forming resin in which the pigment fine particles (a) have a carboxyl group. A colored fine particle dispersion (X) is produced in which colored fine particles (d) coated with (b) and having quaternized carboxyl groups on the coated surface are dispersed in an aqueous medium (W). Then, (3) removing the organic solvent (e) from the dispersion (X), a method for producing a dispersion of colored fine particles for jet ink.

  20. By adding the poor solvent of the film-forming resin (b) to the dispersion liquid (X) of the colored fine particles, the film-forming resin (b) dissolved in the aqueous medium of the dispersion liquid (X) of the colored fine particles is colored. 20. The production method according to 19 above, wherein the organic solvent (e) is deposited on the surface of the fine particles (d) and then the organic solvent (e) is removed from the dispersion (X).

  21. 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 using 1 mol of propylene oxide monoalcohol adduct. And the ink according to 20.

  22. 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, using a monoadduct of propylene oxide of a monoalcohol having 1 to 6 carbon atoms, The ink according to 15, 16, 17, 18, 19, 20, and 21.

  23. 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, which contains a single adduct of 1 to 4 moles of ethylene oxide of monoalcohol having 4 to 8 carbon atoms, The ink according to 15, 16, 17, 18, 19, 20, 21, and 22.

  24. 1 mol of propylene oxide monoadduct of monoalcohol, 10 to 40 mol of propylene oxide monoaddition polymer of monoalcohol having 1 to 6 carbon atoms, and 1 mol of ethylene oxide monoadduct of monoalcohol having 4 to 8 carbon atoms 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, comprising at least two selected from the group The ink according to 19, 20, 21, 22, and 23.

  25. The above 1, 2, 3, 4, 5, 6, wherein the pigment is any one of carbon black, phthalocyanine pigment, halogenated phthalocyanine pigment, quinacridone pigment, benzimidazolone pigment, perinone pigment, and isoindolinone pigment. Inks according to 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23 and 24.

  26. The method for producing a jet ink according to 19, 20, 21, 22, 23, 24 and 25, comprising a step of removing coarse particles exceeding 0.5 μm from the dispersion.

A preferred embodiment of the present invention will be described as an example where it is applied to an ink for ink jet recording.
(1) A pigment is dispersed in a film-forming styrene- (meth) acrylic acid copolymer resin having an acid value of 50 to 180 based on a carboxyl group and having a weight average molecular weight of 1 to 100,000 using two rolls. , Get a solid coloring compound.

  (2) Water, methyl ethyl ketone is mainly used as a low-boiling organic solvent for dissolving the resin, and isopropyl alcohol is used in combination as a low-boiling water-soluble organic solvent that functions as a co-solvent for the water and methyl ethyl ketone. Water containing an alcoholamine in an amount sufficient to make the film-forming resin self-dispersible, and a glycerin as an anti-drying agent, with a neutralization rate equal to or less than 60 mol% of the acid groups of the film-forming resin. Is prepared as a main liquid medium, and the solid colored compound chips of (1) above are mixed therein, and a pigment suspension is obtained by stirring. More preferably, the suspension can be further finely divided so that there is no re-aggregation using Nanomizer (trademark), which is a disperser capable of giving a high shearing force and obtaining a sufficient suspension state. Do.

  (3) While stirring the pigment suspension, an aqueous solution containing glycerin is dropped, and the components derived from the pigment and the film-forming resin are substantially fine particles having an average particle diameter of 0.01 to less than 1 μm (colored micro An aqueous dispersion consisting only of capsules is obtained. The content of the film-forming resin component dissolved in this dispersion is 0.1 to 1% by mass.

  (4) Methyl ethyl ketone and isopropyl alcohol are distilled off from the obtained colored fine particle aqueous dispersion to form an ink base.

  (5) An ink adjusting agent is added to the ink base to adjust the concentration and physical properties, followed by filtration, and the colored microcapsules are 0.5 to 20% by mass in terms of pigment and pH 7.5 to 11 is used for ink jet recording. Use water-based ink. The content of the film-forming resin component dissolved in the ink is also 0.1 to 1% by mass.

Next, the present invention will be described more specifically with reference to examples and comparative examples. In the following examples, “part” represents “part by mass”. In Examples and the like, the particle diameters of the colored fine particles (colored microcapsules) were measured using the above-described “Microtrack particle size analyzer manufactured by Leeds and Northrup Co .. Further, the volume average particle diameter S2 of the colored fine particles was measured. In each case, a slide glass in which holes defined in the specification were provided on the surface was used.

Example 1 (Example of magenta ink)
16 parts of a two-roll kneaded product of 8 parts of quinacridone pigment and 8 parts of styrene-acrylic acid-methacrylic acid resin (styrene / acrylic acid / methacrylic acid = 77/10/13; molecular weight 50,000 / acid value 160) Place in a mixed solution of 46 parts of water, 4 parts of glycerin, 1.7 parts of triethanolamine (equivalent to 50 mol% of acid groups), 18 parts of methyl ethyl ketone, and 8 parts of isopropyl alcohol, and stir at room temperature for 3 hours. Dispersion treatment was performed at a pressure of 98 MPa using a nanomizer (manufactured by Nanomizer) to obtain a pigment suspension.

  While stirring, a mixed liquid of 6 parts of glycerin and 69 parts of water was dropped into 93.7 parts of the obtained suspension at a rate of 5 ml / min to obtain a magenta colored fine particle aqueous dispersion. Methyl ethyl ketone, isopropyl alcohol and a part of water were distilled off from the obtained capsule liquid using a rotary evaporator to obtain the final magenta colored fine particle aqueous dispersion.

  To 92 parts of this aqueous dispersion, 3 parts of glycerin as an anti-drying agent and 5 parts of propylene glycol propyl ether as a penetrant are added, so that the concentration is 2.7% by mass in terms of pigment of the colored microcapsules in the ink. After adjustment and stirring, the mixture was filtered using a 1 μm filter to obtain a water-based ink for inkjet recording.

  The microcapsules in the obtained water-based ink had an average particle diameter of 0.15 μm and the pH was 8.4. Form microcapsule particles with aqueous ink using an ultracentrifuge at an acceleration rate of 9.8 km / s 2 · 3 hours, and dry the resulting precipitate in an oven at 105 ° C for 140 hours to form a film. After only the resin and the pigment were obtained, the ratio of the resin and the pigment was obtained using a thermal analyzer, and only the film-forming resin component dissolved in the ink was obtained.

To 100 parts of this ink, 0.1 part of propylene oxide addition polymer of butanol (average number of moles of propylene oxide added 17.7) was added and stirred sufficiently to obtain an ink. The microcapsules in the obtained water-based ink have an average particle size of 0.15 μm, and the pH is 8.
4.

  This ink shows stable dispersion without agglomerates after storage for 1 year at room temperature, and printing using a piezo ink jet printer is more stable than the above ink without the addition of propylene oxide addition polymer of butanol. The obtained printed matter shows a bright magenta color (print density 1.30) without bleeding, and the print density after immersion of the recording paper immediately after printing in purified water for 1.24 hours is 1.30 before printing. There was no change at all.

(Example 2) (Magenta ink example 2)
One part of ethylene glycol hexyl ether was added to 100 parts of the ink of Example 1 and stirred sufficiently to obtain an ink.

The microcapsules in the obtained water-based ink had an average particle diameter of 0.15 μm and the pH was 8.4. When the film-forming resin content dissolved in the ink was determined in the same manner as in Example 1, it was 0.6% by mass.

  This ink shows stable dispersion without agglomerates after storage for 1 year at room temperature, printing using a piezo ink jet printer is more stable than Example 1, and drying immediately after printing on a recording paper It was extremely fast and instantaneous compared to The obtained printed matter showed moderate bleeding, and was excellent in the smoothness of the solid print portion compared to the ink in which Example 1 was changed so as not to contain the propylene oxide addition polymer of butanol and Example 1; A bright magenta color (print density 1.35) was exhibited, and the print density after immersing the recording paper immediately after printing in purified water for 24 hours was 1.35, which was completely unchanged from that before printing.

Example 3 (Cyan ink example)
C. I. Pigment Blue 15: 4 8 parts and styrene-acrylic acid-methacrylic acid resin (styrene / acrylic acid / methacrylic acid = 77/10/13; molecular weight 50,000 / acid value 160) 8 rolls kneaded mixture 16 parts are put into a mixed solution of 46 parts of water, 4 parts of glycerin, 1.7 parts of triethanolamine (equivalent to 50 mol% of acid groups), 18 parts of methyl ethyl ketone and 8 parts of isopropyl alcohol, and stirred at room temperature for 3 hours. Further, dispersion treatment was performed at a pressure of 98 MPa using a disperser Nanomizer (manufactured by Nanomizer) to obtain a pigment suspension.

  While stirring, a mixed solution of 6 parts of glycerin and 69 parts of water was dropped into 93.7 parts of the obtained suspension at a rate of 5 ml per minute to obtain a cyan colored fine particle aqueous dispersion. Methyl ethyl ketone, isopropyl alcohol and a part of water were distilled off from the obtained capsule liquid using a rotary evaporator to obtain the final cyan colored fine particle aqueous dispersion.

  To 92 parts of this aqueous dispersion, 3 parts of glycerin as an anti-drying agent and 5 parts of propylene glycol propyl ether as a penetrating agent are added, so that the concentration is 2.5% by mass in terms of pigment of the colored microcapsules in the ink. After adjustment and stirring, the mixture was filtered using a 1 μm filter to obtain a water-based ink for inkjet recording.

  The microcapsules in the obtained water-based ink had an average particle diameter of 0.17 μm and the pH was 8.6. When the film-forming resin content dissolved in the ink was determined in the same manner as in Example 1, it was 0.2% by mass.

  This ink shows a stable dispersion without agglomerates even after storage for 1 year at room temperature, printing using a piezo-type ink jet printer is stable, and the resulting printed matter has a bright cyan color (printing) The print density after the recording paper immediately after printing was immersed in purified water for 24 hours was 1.30, which was completely unchanged from that before printing.

  The obtained ink was stable in a glass container even when left at room temperature for 1 year. It did not generate agglomerates, and as a result of a jet test using a piezo-type ink jet printer, the nozzle was not clogged and stable jetting. The printed paper obtained was vivid and excellent in water resistance.

Example 4 (Yellow ink example)
C. I. 16 parts of a two-roll kneaded product of 8 parts of Pigment Yellow 151 and 8 parts of styrene-acrylic acid-methacrylic acid resin (styrene / acrylic acid / methacrylic acid = 77/10/13; molecular weight 50,000 / acid value 160) Is put into a mixed solution of 46 parts of water, 4 parts of glycerin, 1.7 parts of triethanolamine (equivalent to 50 mol% of acid groups), 18 parts of methyl ethyl ketone, and 8 parts of isopropyl alcohol, and stirred at room temperature for 3 hours. Dispersion treatment was performed at a pressure of 98 MPa using a disperser Nanomizer (manufactured by Nanomizer) to obtain a pigment suspension.

  While stirring, a mixed solution of 6 parts of glycerin and 69 parts of water was dropped into 93.7 parts of the obtained suspension at a rate of 5 ml / min to obtain a yellow colored fine particle aqueous dispersion. Methyl ethyl ketone, isopropyl alcohol and a part of water were distilled off from the obtained capsule liquid using a rotary evaporator to obtain a final yellow colored fine particle aqueous dispersion.

  To 92 parts of this aqueous dispersion, 3 parts of glycerin as an anti-drying agent and 5 parts of propylene glycol propyl ether as a penetrant are added, so that the concentration becomes 3.3% by mass in terms of pigment of the colored microcapsules in the ink. After adjustment and stirring, the mixture was filtered using a 1 μm filter to obtain a water-based ink for inkjet recording.

  The microcapsules in the obtained water-based ink had an average particle diameter of 0.18 μm and the pH was 8.4. When the film-forming resin content dissolved in the ink was determined in the same manner as in Example 3, it was 0.5% by mass.

  This ink exhibits stable dispersion without agglomerates even after storage for 1 year at room temperature, printing using a piezo-type ink jet printer is stable, and the resulting printed matter has a bright yellow color (print density) 1.17), and the printing density after the recording paper immediately after printing was immersed in purified water for 24 hours was 1.17, which was completely unchanged from that before printing.

  The obtained ink was stable in a glass container even when left at room temperature for 1 year. It did not generate agglomerates, and as a result of a jet test using a piezo-type ink jet printer, the nozzle was not clogged and stable jetting. The printed paper obtained was vivid and excellent in water resistance.

(Example 5) (Example of black ink)
16 parts of a two-roll kneaded product of 8 parts of carbon black and 8 parts of styrene-acrylic acid-methacrylic acid resin (styrene / acrylic acid / methacrylic acid = 77/10/13; molecular weight 50,000 / acid value 160) , 46 parts of water, 4 parts of glycerin, 1.7 parts of triethanolamine (equivalent to 50 mol% of acid groups), 18 parts of methyl ethyl ketone, and 8 parts of isopropyl alcohol, stirred for 3 hours at room temperature, and further dispersed Dispersion treatment was performed at a pressure of 98 MPa using a machine nanomizer (manufactured by Nanomizer) to obtain a pigment suspension.

  While stirring, a mixed solution of 6 parts of glycerin and 69 parts of water was dropped into 93.7 parts of the obtained suspension at a rate of 5 ml per minute to obtain a black colored fine particle aqueous dispersion. Methyl ethyl ketone, isopropyl alcohol and a part of water were distilled off from the obtained capsule liquid using a rotary evaporator to obtain the final black colored fine particle aqueous dispersion.

  To 92 parts of this aqueous dispersion, 3 parts of glycerin as an anti-drying agent and 5 parts of propylene glycol propyl ether as a penetrant are added, so that the concentration becomes 3.7% by mass in terms of pigments of colored microcapsules in ink After adjustment and stirring, the mixture was filtered using a 1 μm filter to obtain a water-based ink for inkjet recording.

  The microcapsules in the obtained water-based ink had an average particle size of 0.09 μm and the pH was 8.5. When the film-forming resin content dissolved in the ink was determined in the same manner as in Example 1, it was 0.6% by mass.

  This ink shows stable dispersion without agglomerates even after storage for 1 year at room temperature, printing using a piezo-type ink jet printer is stable, and the obtained printed matter is black with almost no black (no blurring) The printing density was 1.32), and the recording density after the recording paper immediately after printing was immersed in purified water for 24 hours was 1.35, which was rather higher than before printing.

  In each example, the volume average particle diameter of the colored fine particles in the ink immediately after preparation, “the increase rate of the volume average particle diameter of the colored fine particles in the re-dispersed liquid of the dried ink”, and the standard deviation of the volume particle diameter ( sd) is summarized below.

  In addition, each of the inks in the above examples can be regarded as having no change in the volume average particle diameter even if the ink just after preparation and the ink just after preparation are filled in a container, sealed and left at room temperature for 1 year. It was about.

3 is a frequency distribution diagram of volume particle diameters of colored fine particles in the ink of Example 1. FIG. 3 is a frequency distribution diagram of volume particle diameters of colored fine particles in a re-dispersed liquid of dry ink using the jet ink of Example 1. FIG. 6 is a frequency distribution diagram of volume particle diameters of colored fine particles in the ink of Example 3. FIG. 6 is a frequency distribution diagram of volume particle diameters of colored fine particles in a re-dispersed liquid of dry ink using the jet ink of Example 3. FIG. 6 is a frequency distribution diagram of volume particle diameters of colored fine particles in the ink of Example 4. FIG. 6 is a frequency distribution diagram of volume particle diameters of colored fine particles in a re-dispersed liquid of dry ink using the jet ink of Example 4. FIG.

Claims (4)

A jet ink in which pigmented fine particles (a) are coated with a film-forming resin (b) having a carboxyl group and colored fine particles (d) are dispersed in an aqueous medium, and a film having a pigment and a carboxyl group is formed. By uniformly mixing an alcoholic amine with an aqueous medium composed of a solid coloring compound obtained by kneading the functional resin (b), water and an organic solvent capable of dissolving the film-forming resin (b), Production of a dispersion of colored fine particles in which colored fine particles are dispersed in an aqueous medium, and if necessary, a film forming resin dissolved in the aqueous medium of the dispersion of colored fine particles by adding a poor solvent for the film-forming resin. The resin is deposited on the surface of the colored fine particles and then removed by removing the organic solvent. (1) The carbo is obtained by neutralizing the colored fine particles (d) with alcohol amine on the surface. It has a xyl group and a volume average particle size of 0.5 μm or less, and (2) “rate of increase in volume average particle size of colored fine particles (d) in the re-dispersed liquid of dry ink” is 50 Jet ink, characterized in that it is less than a percentage. The jet ink according to claim 1, wherein the alcohol amine is triethanolamine. The jet ink according to claim 1 or 2 , wherein a standard deviation value in "frequency distribution of particle diameter of colored fine particles in re-dispersed liquid of dry ink" is 0.15 or less. The jet ink according to any one of claims 1 to 3 , wherein the resin having a carboxyl group is a styrene-acrylic acid-methacrylic acid resin.

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