JPH10292143A - Aqueous jet ink of colored microcapsule dispersion type - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an aqueous jet ink having a fine micro capsule diameter, excellent in dispersion stability and excellent in ink jetting characteristics, etc., by making the jet ink include colored microcapsules comprising a pigment coated with a specified coating film-forming resin in an aqueous medium. SOLUTION: This aqueous jet ink is obtained by dissolving (B) colored microcapsules produced by coating (A) a pigment (e.g. a quinacridone pigment) with a coating film-forming resin in (C) an aqueous solvent comprising water and, if necessary, an organic solvent. Therein, the content of an ink-soluble resin component in the component B is 0.01-2 wt.%. In order to satisfy the condition, the component B is preferably the neutralization product of a resin having an acid value of 50-180 and a weight-average mol.wt. of 1000-100000 with a base (e.g. triethanolamine), and the ink preferably has a pH of 7.5-9.0. The component A is preferably contained in an amount of 0.5-20 wt.% in the ink.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a colored microcapsule-dispersed aqueous jet ink.

[0002]

2. Description of the Related Art Ink jet recording inks are roughly classified into oil-based inks and water-based inks. 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 they are poor in water resistance and light resistance because a water-soluble dye is used as a colorant. In addition, since the dye is dissolved at the molecular level, when printing on so-called plain paper such as copy paper generally used in offices, bleeding called whisker-like feathering occurs, leading to a significant decrease in print quality. .

In order to improve the above drawbacks, various types of so-called water-based pigment inks have been proposed in the past. For example, a resin solution obtained by dispersing carbon black or an organic pigment using a water-soluble resin as a binder and dispersant has been proposed. Various types of resin-dispersed inks containing a colorant as a type ink, a polymer latex, or a microcapsule have been proposed.

[0005] As a water-based pigment ink for a jet printer, colorant particles dispersed as finely as possible are required. As a specific example of a resin-soluble water-based ink, Japanese Patent No. 2512861 discloses (a) ) Charging the pigment and the polymer dispersant into a 2-roll milling device;
(B) milling to obtain a dispersion of pigment and polymer dispersant;
Japanese Patent Application Laid-Open No. 3-153775 discloses a method for preparing an aqueous pigmented inkjet ink having improved properties, which comprises the step of (c) dispersing the pigment dispersion in an aqueous carrier medium. A water-based ink composition for inkjet printing containing a solid pigment preparation b) a water-dilutable organic solvent c) a humectant d) water containing a carboxyl group-containing polyacrylic resin.

[0006] However, these techniques are effective for making pigment fine particles, but due to the effect of dissolved dispersant resin, abnormal ejection due to an increase in ink viscosity near the nozzles due to water evaporation of the ink, and worst case Easy to clog,
The water resistance of the printed matter was remarkably poor.

[0007] A resin-dispersed water-based ink has the advantages that the increase in viscosity due to evaporation of water in the ink is relatively small and that the ink is excellent in water resistance. Specifically, Japanese Patent Application Laid-Open No. 58-452
No. 72 discloses an ink composition containing a urethane polymer latex containing a dye, and JP-A No. 62-95366 discloses a method in which a polymer and an oily dye are dissolved in a water-insoluble organic solvent and mixed with an aqueous solution containing a surfactant. An ink containing a dye encapsulated in polymer particles by evaporating the solvent after emulsification is proposed. Japanese Patent Application Laid-Open No. 62-254833 discloses an ink having an interfacial tension between an organic solvent and water at the time of encapsulation of 10%. There has been proposed a method for producing an aqueous suspension of a coloring agent by reducing the content to less than dyne, and JP-A-1-170672 proposes a recording liquid containing a macroencapsulated dye. The dispersion stability of the colored resin dispersion obtained is not always sufficient, and foaming is large due to the effect of the surfactant used during encapsulation. There was not always enough.

Japanese Patent Application 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 swelling in the dispersion medium. The sol-gel phase transition was apt to occur in the vicinity, and the dispersion stability of the particles was not always good, and injection abnormalities were likely to occur.

JP-A-5-247370 discloses that in a coloring composition for image recording containing a pigment and a resin, the pigment is
A coloring composition for image recording characterized by being a pigment substantially insoluble in a dispersion medium and coated with a thin film of a cured polymer having a polar group has been proposed. Due to the lack of self-dispersibility and fixing ability to recording paper, a resin as a dispersant and a fixing agent is essential, so that the dispersion stability is superior to a pigment not coated with a cured polymer. However, the disadvantages of insufficient jetting stability as an ink jet and poor water resistance were not improved.

[0010]

The problem to be solved by the present invention is to provide a colored microcapsule which is excellent in dispersion stability due to fine particle diameter, and excellent in ink jet ejection characteristics and fixation of capsule particles to a recording medium. It is to provide a dispersion type aqueous jet ink.

[0011]

Means for Solving the Problems The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result,
In the ink, a pigment-coated, free and dissolved film-forming resin component having a quantitative range that does not affect the ejection stability and contributes to the fixation of the capsule particles to the recording medium. Thus, the above-described problem has been solved.

That is, according to the present invention, in an ink containing an aqueous medium containing colored microcapsules in which a pigment is coated with a film-forming resin, the resin component soluble in the ink among the film-forming resins is 0.01 to 2% by mass. % Water-based jet ink with dispersed microcapsules.
In the present invention, the SI unit system is adopted as the unit system, and the weight is described as mass.

[0013] The ink is not limited to the ink of the present invention. For example, a colored microcapsule coated with a film-forming resin that does not dissolve the pigment in the dispersion medium, or a free microcapsule that does not dissolve in the dispersion medium not coated with the film-forming resin. Pigment particles, free film-forming resin-dispersed particles that do not dissolve in a dispersion medium that is not coated with pigment, film-forming resin dissolved in a dispersion medium, and a dispersion medium, and further, if necessary, a drying inhibitor and a penetrant. And the like.

The present invention is characterized in that, in the above-described ink composition, a dissolved film-forming resin is present in an aqueous medium as a dispersion medium within an optimum range.

However, if the resin component soluble in the ink in the film-forming resin is less than 0.01% by mass, the microcapsule particles in the ink layer obtained adhere to the recording paper when the ink is printed on the recording paper. Insufficient capacity and binding force between microcapsule particles are likely to result, resulting in poor durability such as friction of printed matter.

Conversely, if the resin component soluble in the ink exceeds 2% by mass of the film-forming resin, the microcapsule particles in the ink layer obtained adhere to the recording paper when the ink is printed on the recording paper. The capacity and the bonding force between the microcapsule particles are increased, but in addition to the disadvantage that the time required for the dissolved film-forming resin to become insoluble on the recording paper, that is, the time required for developing water resistance immediately after printing, is increased. As compared with a water-soluble resin such as a polymer dispersant, the film-forming resin is more likely to cause clogging due to water evaporation at the nozzle end face, and is more likely to suffer from a disadvantage that ink jet ejection stability becomes worse.

The amount of the resin component soluble in the ink in the film-forming resin is, for example, 0.01 to 2% by mass, more preferably 0.1 to 1% by mass, so that the ink is printed on the recording paper. The ability of the microcapsule particles in the obtained ink layer to adhere to the recording paper and the bonding force between the microcapsule particles are increased, and the durability of the printed matter, such as friction, is improved. As a result, ink jet ejection stability is greatly improved.

In the present invention, the aqueous medium may be water alone,
A medium containing water as a main component and optionally containing an organic solvent. In the present invention, it is preferable to select a chemical composition, a mass ratio of constituent components, and the like as an aqueous medium serving as a dispersion medium of the ink so as not to dissolve the film-forming resin as much as possible.

In the present invention, the film-forming resin used to coat the pigment may be any resin that forms a film, and is not limited to a natural resin or a synthetic resin, and various film-forming resins can be used. For example, a styrene resin, an acrylic resin, a polyester resin, and a polyurethane resin can be used.

However, in order to stably disperse the colored microcapsules in an aqueous medium, the film-forming resin needs to have a high hydrophilic property. Will dissolve in it. In this case, the dissolved resin may promote aggregation of the microcapsules due to long-term storage due to inter-particle crosslinking caused by entanglement with the resin layer covering the microcapsules. In addition, when ink-jet recording is performed, abnormal ejection is likely to occur due to an increase in the viscosity of the ink due to evaporation of water at the nozzle end surface and adhesion of the ink concentrate around the nozzle.

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

Therefore, it is often necessary to minimize the 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, there is also a method of using a film-forming resin having no or little hydrophilicity by using, for example, a surfactant or a dispersant. However, in view of the fact that the colored image exhibits more excellent water resistance and good ejection stability, it is preferable to prepare the colored image so as not to contain a surfactant, a dispersant and the like.

As a method for preparing the composition so as not to contain a surfactant or a dispersant, for example, a film-forming resin obtained by neutralizing a resin which can be dispersed in an aqueous medium by neutralization with a neutralizing agent is used. It is better to use it. As a film-forming resin obtained by neutralizing a resin dispersible in an aqueous medium by neutralization with a neutralizing agent, typically, a resin dispersible in an aqueous medium by neutralization with a base is 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, a dispersant, or the like may be referred to as a self-water dispersible resin.

In the present invention, it is preferable to use, as a film-forming resin, a self-water dispersible resin obtained by neutralizing a resin having an acid value with a base, for example. As the resin having an acid value, for example, a resin having an acid value of 50 to 180 is used. The acid value refers to the number of milligrams (mg) of potassium hydroxide (KOH) required to neutralize 1 g of the resin.
It is expressed in g · KOH / g (hereinafter, the unit is abbreviated). Such a resin can be obtained, for example, by neutralizing all or a part of the acid value of the resin having the specific acid value. In this case, the pH of the ink is 7.5 to 9.0. It is preferred that

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 Is apt to become insufficient due to swelling and the like, and the microcapsule particles are likely to aggregate or clog the nozzle, which is not suitable.

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 decrease, and when the pH is 9.0 or higher, the pigment coating of the colored microcapsule particles swells. For example, the microcapsule particles are unsuitable because they tend to be insufficient due to, for example, aggregation and clogging of nozzles.

Optimally, the film-forming resin component is added at 0.01
In order to obtain an ink in which the ink is dissolved by 2 to 2% by mass, a resin having an acid value of 50 to 180, a film-forming resin obtained by neutralizing the acid with a base, and a pH of the ink of 7.
A value of 5 to 9.0 shows a remarkable effect in the present invention.

The molecular weight range of the film-forming resin is not particularly limited, but is preferably in the range of 1,000 to 100,000 in terms of weight average molecular weight. The molecular weight of the film-forming resin is
If the molecular weight is less than 10,000, a sufficient film cannot be formed in many cases, which is not suitable because the nozzles are easily clogged due to agglomeration of the microcapsule particles. 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 present invention, a preferred film-forming resin is a styrene-based resin or a (meth) acrylic resin, for example, at least one monomer selected from the group consisting of styrene, substituted styrene and (meth) acrylate. Self-water-dispersible resin obtained by neutralizing at least a part of a copolymer with (meth) acrylic acid with a base.

(Meth) acrylic acid is a general term for acrylic acid and methacrylic acid. In the present invention, either one is essential, but more preferred film-forming resins are acrylic acid and methacrylic acid. It has a structure derived from both acids.

In the present invention, for example, in order to further reduce the dissolution of a self-water dispersible resin as a film-forming resin in an aqueous medium, it is preferable to use acrylic acid among all monomer components having a carboxyl group. Should be lower and the ratio of methacrylic acid should be higher.

That is, the self-water-dispersible resin as the most suitable film-forming resin contains at least one monomer selected from the group consisting of styrene, substituted styrene and (meth) acrylate, and contains acrylic acid and It is a copolymer with acrylic acid, and is a self-water-dispersible resin in which methacrylic acid is copolymerized more than acrylic acid and at least partially neutralized with a base.

In order to make the pH of the ink basic, it is sufficient to neutralize the resin which can be dispersed in the aqueous medium by neutralization, that is, to add a base. Examples of the base include hydroxides of alkali metals such as sodium hydroxide, potassium hydroxide and lithium hydroxide, basic substances such as ammonia, triethylamine and morpholine, as well as triethanolamine, diethanolamine and N-methyldiethanolamine. Alcohol amines can be used. As a base, it is easily volatile at such a high temperature that the film-forming resin does not decompose,
It is preferred to employ a volatile base.

However, if the resin having a higher acid value is neutralized with a stronger base, the solubility of the film-forming resin in the ink increases, and the strength and amount of the base (neutralization rate) are increased. ) Is preferably adjusted. In ink jet recording, alcohol amines, especially triethanolamine, which is a weak base, are particularly suitable because clogging of nozzles, dispersion stability during storage, and water resistance of printed matter are extremely small.

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

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.
For example, inorganic pigments such as carbon black, titanium black, titanium white, zinc sulfide and red iron oxide, azo pigments such as phthalocyanine pigments, monoazo and disazo pigments, and organic pigments such as phthalocyanine pigments and quinacridone pigments are used. When a color image is obtained, it is preferable to use a chromatic pigment as the ink.

The amount of the pigment to be used is not particularly limited as long as the effects of the present invention are achieved, but is usually adjusted to be 0.5 to 20% by mass in the finally obtained ink. Is preferred.

If necessary, the ink may contain an organic solvent which does not dissolve or hardly dissolves the film-forming resin. The organic solvent used for the ink is used, for example, as a drying inhibitor or a penetrant.

The anti-drying agent has the effect of preventing the ink from drying at the nozzles of the ink jet, and usually has a boiling point higher than the boiling point of water. As such an anti-drying agent, any known and commonly used ones can be used. For example, polyhydric alcohols such as ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, polyethylene glycol, polypropylene glycol and glycerin can be used. And so on.

In particular, glycerin is bonded to the film-forming resin on the surface of the microcapsule particles by strong hydrogen bonding to 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. On the other hand, it is more preferable in terms of preventing drying at the nozzle end face by binding with a strong hydrogen bond.

The penetrant controls the penetration of the ink into the recording medium and the dot diameter on the recording medium. Examples of the penetrant include lower alcohols such as ethanol and isopropyl alcohol, ethylene glycol hexyl ether, and the like. There are ethylene oxide adducts of alkyl alcohols such as diethylene glycol butyl ether and propylene oxide adducts of alkyl alcohols such as propylene glycol propyl ether.

Depending on the type and concentration of the film-forming resin or the combination of the organic solvent concentration in the aqueous medium, the organic solvent dissolves the resin coated on the pigment in an amount of 2% by mass or more to improve the jetting characteristics. The content in the ink may be 2% by mass or less depending on the type of the organic solvent.
More preferably, the amount of addition must be suppressed in consideration of the pH range of the ink so as to be 1% by mass or less.

The amount of the organic solvent to be added is 1 to 80% by mass in the case of the anti-drying agent and 0.1 in the case of the penetrant in the ink.
It is preferable to set the content to 1 to 10% by mass.

The method of measuring the components dissolved in the ink of the film-forming resin of the present invention is performed by, for example, setting the microcapsule particles to sedimentation using an ultracentrifuge if the solid components other than the resin are small. The supernatant can be sufficiently dried and measured directly as non-volatile components. If a large amount of a solid content or a high-boiling organic solvent other than the resin is present in the ink, the centrifuged sediment is sufficiently dried, and then the resin is analyzed by a thermal analyzer based on the difference in thermal decomposition temperature. By measuring the ratio of the resin and the pigment and converting the ratio of the resin and the pigment charged in the ink, the amount of the resin component dissolved in the ink can be obtained. The latter method is used when the dispersion in the aqueous medium is composed of only colored microcapsules and does not contain free pigment particles not coated with the film-forming resin or particles of only the film-forming resin containing no pigment. In
In particular, it can be measured with high accuracy. If the ink contains additives such as anti-drying agents and penetrants, the measurement should be performed after drying the former additives at a temperature that does not cause decomposition of the pigment and the film-forming resin. Thus, the measurement accuracy can be further increased.

As a specific method for obtaining the colored microcapsule-dispersed aqueous jet ink of the present invention, the following method is preferred when a pigment is coated using a film-forming resin having an acid value. According to this method, the components derived from the resin and the pigment dispersed in the aqueous medium are composed of only colored microcapsules, and free pigment particles not coated with the film-forming resin, It is possible to easily obtain a very small amount of ink containing no resin-containing particles or no dissolved film-forming resin at all.

In this method, 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 colored compound. (Kneading process)

In this step, the pigment is uniformly dissolved or dispersed in the resin in a solution or a heated and melted state using a kneading device such as a roll, a kneader, or a bead mill, which is conventionally known, and the pigment is finally dissolved. By removing the mixture as a solid kneaded material (solid colored compound).

In particular, when fine dispersion of the pigment in the resin is required, as a means for dispersing the pigment, any of the dispersion methods known in the art, which can form a state in which a relatively high shearing force is applied, is used. It is preferable to perform dispersion under high shearing force using a means, specifically, two rolls.

(2) At least water, an organic solvent that dissolves the resin, a base, and the solid coloring compound are mixed to 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 the organic solvent can be appropriately selected for the resin. Examples of the organic solvent include acetone, dimethyl ketone, and methyl ethyl ketone. Ketone solvents, alcohol solvents such as methanol, ethanol, and isopropyl alcohol; chlorine solvents such as chloroform and methylene chloride; aromatic solvents such as benzene and toluene; ester solvents such as ethyl acetate; ethylene glycol monomethyl ether Ether solvents such as ethylene glycol and ethylene glycol dimethyl ether;
Any material that can dissolve resins such as amides can be used.

The dispersion medium used in this step is mainly water that functions as a poor solvent for the film-forming resin.
Since it is used as an aqueous ink for inkjet recording, it preferably 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 the mixture is not uniform, a surfactant is used or O / W is mechanically performed, if necessary.
It is preferable to emulsify the mixture in a mold or use it in combination with a co-solvent to make it uniform. For the reasons described above, surfactants, if used, are kept to a minimum.

As the organic solvent for forming the dispersion medium and dissolving the resin used as needed, only the organic solvent may be used. However, only the organic solvent and water and base are used, and the pigment suspension having excellent dispersion stability is used. If it is difficult to obtain a turbid liquid, a hydrophilic organic solvent may be used in combination with the resin as a cosolvent to provide better emulsion stability. The organic solvent and the co-solvent that dissolve the resin may be used alone or in combination of two or more.

When the resin is a copolymer of at least one monomer selected from the group consisting of styrene, substituted styrene and (meth) acrylic acid ester with (meth) acrylic acid, a ketone such as methyl ethyl ketone is used. At least one combination selected from alcohol solvents such as isopropyl alcohol as a cosolvent mainly as a cosolvent is preferred.

The ratio of water to the organic solvent is not particularly limited as long as the effects of the present invention are achieved, but is preferably such that the weight ratio of water / organic solvent is 10/1 to 1/1.

By this step, the film-forming resin having an acid value, which is present on the surface of the solid colored compound, is gradually neutralized by a base at least partially or entirely with the acid value, and the solid of the compound is solidified. Due to its shape, the mixture is in suspension.

As a stirring method for obtaining a suspension, any known and commonly used method can be employed. For example, in addition to a conventional uniaxial propeller type stirring blade, a stirring blade having a shape suitable for the purpose or a stirring blade may be used. Usually, it can be easily suspended using a container.

In obtaining a suspension, there is a case where fine mixing is not effected by simple mixing and stirring in which a large shear force does not act.
When the pigment is relatively easily aggregated, a high shear force may be further applied to stabilize the fine particles. As a dispersing machine in this case, for example, a high-pressure homogenizer or a beadless dispersing machine known by trade names such as a microfluidizer and a nanomizer is preferably used, since reaggregation of the pigment is small.

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

This step is a step of depositing the dissolved resin component and the dispersed resin component present in the suspension on the surface of the pigment in the pigment suspension obtained in the suspension step. The “re-precipitation” in this step does not mean that the pigment or the particles in a semi-capsule state in which the dissolved resin or the dispersed resin is adsorbed on the pigment surface is separated and settled from the liquid medium of the suspension. Therefore, what is obtained in this step is not a mere mixture in which the solid component and the liquid component are clearly separated, but the microcapsules in which the dissolved resin or the dispersed resin is coated on the pigment surface are stably used in the liquid medium of the suspension. An aqueous dispersion of dispersed colored resin particles (colored microcapsules).

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

However, a method in which water or an aqueous medium that functions as a poor solvent for the resin is further added to the pigment suspension is preferable because it causes less aggregates. In the reprecipitation, by dropping water or an aqueous medium while the suspension is gently stirred, it is possible to reliably deposit (reprecipitate) the resin on the pigment surface while preventing the generation of aggregates.

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

In this way, the above (1) kneading step (2)
The colored resin particles having a desired particle diameter are obtained by the resuspension step (3) reprecipitation step.
It is 0.01 to 1 μm.

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

The aqueous dispersion of the colored resin particles obtained in the reprecipitation step can be used as it is, but since the colored resin particles are often in a swollen state due to the effect of the coexisting organic solvent, the storage stability is lowered. It is preferable to further remove the solvent for further improvement or for enhancing safety against fire and pollution.

The organic solvent thus removed can be used without incineration for continuous production, for example.
It can be recycled and reused in a closed system.

In the aqueous dispersion of colored resin particles (colored microcapsules) obtained through the steps (1) to (4), all the components derived from the resin and pigment used in the preparation are exclusively colored microparticles. It becomes an aqueous dispersion consisting only of capsules,
It does not substantially contain the three components of free pigment particles, particles of the film-forming resin alone, and dissolved film-forming resin. However, since it is extremely difficult to reduce the amount of the dissolved film-forming resin component to zero, its content is generally 0.01% by mass or more based on all components constituting the dispersion.

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

(5) Ink process The aqueous dispersion of colored resin particles of submicron order, which contains no or almost no liquid medium other than water, obtained by the above process, is basically used for ink jet recording. Although it can be used as an aqueous ink, it is preferable to further adjust the ink in consideration of dispersion stability and ejection characteristics.

The adjustment of the ink may be performed, for example, by adding the above-mentioned anti-drying agent or permeable organic solvent, adjusting the concentration and viscosity, and adjusting the ink.
An H adjuster, a surfactant for dispersing, defoaming, and penetrating into paper, a preservative, a chelating agent, a plasticizer, an antioxidant, an ultraviolet absorber, and the like can be added as necessary. However, various additives are selected from those which do not dissolve the film-forming resin present on the surface of the colored microcapsules, and only those having such properties are used, or even those which can dissolve the resin. It is necessary to take measures such as minimizing the amount of use to a concentration that does not substantially dissolve. Surfactant is used not only in the final adjustment, but also in all of the steps that can be adopted in the ink preparation of the present invention, so that it is not used at all from the viewpoint of the water resistance of an image obtained from the ink. preferable.

When the recording medium is other than impervious recording medium such as glass, metal, and film (penetrable recording medium), the film-forming resin is not affected so as not to affect the jetting stability. Alternatively, other water-soluble resins can also be added.

In order to avoid nozzle clogging due to coarse particles, it is usually necessary to remove the coarse particles by centrifugation or filter filtration after the solvent removal step (4).
After adjusting the ink in the ink step (5), the ink is filtered through a filter having a desired particle size.

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

The colored microcapsule-dispersed aqueous jet ink of the present invention is excellent in transparency, color development, and dispersion stability.
It can be applied to paints and color filters.

[0077]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention includes the following embodiments. 1. In an ink containing a pigmented microcapsule coated with a film-forming resin in an aqueous medium, the resin component of the film-forming resin that dissolves in the ink is 0.01 to 2 parts.
Colored microcapsule-dispersed aqueous jet ink in a mass%.

2. The acid value of the film-forming resin is 50 to 180.
And the pH of the ink is 7.5 to 9.0, wherein the colored microcapsule-dispersed aqueous jet ink is 1.

3. The colored microcapsule-dispersed aqueous jet ink of 1 or 2, wherein the film-forming resin has a molecular weight of 10,000 or more.

4. The aforementioned 1 containing glycerin in an aqueous medium.
Colored microcapsule-dispersed aqueous jet inks of Nos. 1 to 3.

5. The colored microcapsule-dispersed aqueous jet ink according to any one of 1 to 4, which is a self-water-dispersible resin obtained by neutralizing at least a part of a film-forming resin having an acid value of 50 to 180 with a base.

6. The colored microcapsule-dispersed aqueous jet ink according to the above item 5, wherein the base is an alcoholamine.

7. 6. The colored microcapsule-dispersed aqueous jet ink according to 6 above, wherein the alcoholamine is triethanolamine.

8. The colored microcapsule-dispersed aqueous jet ink according to any one of claims 5 to 7, which is neutralized at a neutralization rate of not more than 60 mol% of the acid groups of the film-forming resin.

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

(2) Methyl ethyl ketone is mainly used as water and a low boiling point organic solvent for dissolving the resin, and isopropyl alcohol is used in combination as a low boiling point water-soluble organic solvent functioning as a cosolvent for water and methyl ethyl ketone. As a base, 60 mol% of the acid groups of the film-forming resin
A solution containing water as a main liquid medium, which contains alcoholamine in an amount sufficient to make the film-forming resin self-water dispersible and glycerin as an anti-drying agent, having a neutralization ratio of a considerable amount or less, Then, the chips of the solid coloring compound of (1) are mixed and stirred to obtain a pigment suspension.
More preferably, the suspension is given a high shearing force, and is further dispersed into fine particles using a nanomizer (trademark), which is a dispersing machine capable of obtaining a more sufficient suspension state, without reaggregation. Do.

(3) While stirring the pigment suspension, an aqueous solution containing glycerin was dropped, and the components derived from the pigment and the film-forming resin were substantially in the range of 0.01 to 1 μm in average particle size.
An aqueous dispersion consisting of less than less colored resin particles (colored microcapsules) is obtained. (4) Methyl ethyl ketone and isopropyl alcohol are distilled off from the obtained aqueous dispersion of colored resin particles to prepare an ink base. (5) An ink adjusting agent was added to the ink base to adjust the concentration and physical properties, followed by filtration, and the colored microcapsules were 0.5 to 20% by mass in terms of pigment, pH 7.5 to 7.5.
11 is an aqueous ink for inkjet recording.

[0088]

Next, the present invention will be described more specifically with reference to examples and comparative examples. In addition, "part" in the following examples
Represents "parts by mass".

(Example 1) 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) 16 parts of this roll kneaded material
46 parts of water, 4 parts of glycerin, triethanolamine 1.
7 parts, a mixture of 18 parts of methyl ethyl ketone and 8 parts of isopropyl alcohol, stirred at room temperature for 3 hours, and further subjected to a dispersion treatment at 98 MPa using a dispersing machine Nanomizer (manufactured by Nanomizer) to obtain a pigment suspension. Was.

A mixture of 6 parts of glycerin and 69 parts of water was added dropwise to 93.7 parts of the obtained suspension at a rate of 5 ml / min with stirring to obtain an aqueous dispersion of magenta colored resin particles. . 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 aqueous dispersion of magenta colored resin particles.

To 92 parts of this aqueous dispersion, 3 parts of glycerin as a drying inhibitor and 5 parts of propylene glycol propyl ether as a penetrant were added, and the concentration was 2.7% by mass in terms of the pigment of the colored microcapsules in the ink. Then, the mixture was adjusted and stirred so as to obtain a water-based ink for inkjet recording by filtration using a 1 μm filter.

The microcapsules in the obtained aqueous ink had an average particle diameter of 0.15 μm and the pH was 8.4. The aqueous ink using the ultracentrifuge precipitated microcapsules particles by centrifugation conditions acceleration 9.8km / s ² · 3 hours, and the precipitate obtained was dried 140 hours at 105 ° C. in an oven, the film-forming After only the reactive resin and the pigment were determined, the ratio of the resin to the pigment was determined by a thermal analyzer, and only the film-forming resin dissolved in the ink was determined to be 0.4% by mass.

This ink shows stable dispersion without aggregation after storage at room temperature for one year, and printing using a piezo-type ink jet printer is stable, and the obtained printed matter has no bleeding and vivid magenta. Color (print density 1.3)
The printing density after immersing the recording paper immediately after printing in purified water for 24 hours was 1.3, which was no change from that before printing.

[0094]

According to the aqueous jet ink of the present invention, the resin component dissolved in the ink among the film-forming resins is 0.01 to 2% by mass.
It has a remarkable technical effect of being excellent in dispersion stability over time, jetting characteristics, and image fixability to a recording medium.

Therefore, in ink-jet recording, stable ink-jet ejection characteristics are achieved without losing the characteristics of, for example, a resin-dispersed water-based ink having excellent print quality, water resistance, and light fastness, and having excellent dispersion stability and without nozzle clogging. Enable.

Claims (8)

[Claims] In an ink containing an aqueous medium containing colored microcapsules in which a pigment is coated with a film-forming resin, a resin component of the film-forming resin that dissolves in the ink is:
A colored microcapsule-dispersed aqueous jet ink characterized in that the content is 0.01 to 2% by mass. 2. The film-forming resin having an acid value of 50 to 180.
And the pH of the ink is 7.5 to 9.0.
The colored microcapsule-dispersed aqueous jet ink described in the above. 3. The colored microcapsule-dispersed aqueous jet ink according to claim 1, wherein the molecular weight of the film-forming resin is 10,000 or more. 4. An aqueous medium containing glycerin.
The colored microcapsule-dispersed aqueous jet ink described in the above. 5. A colored microcapsule-dispersed aqueous jet ink according to claim 1, wherein the film-forming resin having an acid value of 50 to 180 is a self-water-dispersible resin obtained by neutralizing at least a part of the resin with a base. 6. The colored microcapsule-dispersed aqueous jet ink according to claim 5, wherein the base is an alcoholamine. 7. The colored microcapsule-dispersed aqueous jet ink according to claim 6, wherein the alcoholamine is triethanolamine. 8. The colored microcapsule-dispersed aqueous jet ink according to claim 5, which is neutralized at a neutralization rate of not more than 60 mol% of the acid groups of the film-forming resin.