JP2000273383A - Aqueous pigment dispersion and recording liquid for inkjet - Google Patents

Abstract

(57) Abstract: An aqueous pigment dispersion excellent in water dispersibility and dispersion stability over time, a method for producing the same, and an ink-jet recording liquid using the pigment dispersion, which are used for light resistance after printing,
Provided is an aqueous inkjet recording liquid having excellent water resistance, hue, print density, color gamut reproduction range when printed on plain paper, and excellent ejection stability at a nozzle. An aqueous liquid, quinacridone pigment particles dispersed in the aqueous liquid, a water-soluble quinacridone derivative adsorbed on the surface of the quinacridone pigment particles, and an unadsorbed water-soluble quinacridone derivative. The unadsorbed water-soluble quinacridone derivative is contained in the quinacridone-based pigment at a predetermined pigment blending amount within a range of 2 to 25% by weight based on the total amount of the aqueous liquid and the quinacridone-based pigment. An aqueous pigment dispersion, wherein the pigment is dissolved in the aqueous liquid in an amount smaller than the critical concentration at which flocculation occurs.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to an aqueous pigment dispersion having excellent water dispersibility and stability over time, and a method for producing the same.
Further, the present invention relates to an ink jet recording liquid which is excellent in light resistance, water resistance and hue after printing, and has good ejection stability at a nozzle.

[0002]

2. Description of the Related Art Conventionally, a water-based ink or a water-based paint is prepared by using a surfactant, a dispersant, or a dispersion resin to disperse a pigment in water. However, in the case of a surfactant, there is a problem of foaming and it is necessary to use a defoaming agent in combination to improve the foaming property, compatibility with the defoaming agent and the surfactant, leveling property at the time of drying after printing. There is a problem in the balance of ink performance due to the combined use of activators and additives. In addition, in the case of a dispersion resin, a highly effective dispersion stabilizing effect is recognized in a relatively high-viscosity ink and a coating system, but a low-viscosity dispersion is greatly affected by the viscosity of the resin dissolved in a solvent of the resin. There is a limit to viscosity.

On the other hand, there is known a method of using a pigment derivative as a pigment dispersant and performing a surface treatment. The pigment derivative treatment method is a method in which an acidic group or a basic group is introduced as a substituent into a compound of the same kind as the pigment to be dispersed and adsorbed on the pigment to increase the polarity, improve the wetting, and improve the dispersibility. . The derivative treatment method has a remarkable improvement in dispersibility compared to other dispersants and surfactants, but since the derivative is soluble in solvents, there are problems with bleeding and color mixing during coating and printing of paints and inks. . This problem is due to the fact that the pigment derivative treatment method uses an additive before dispersing like a dispersant and a surfactant, and the part that adsorbs to the pigment improves the dispersing effect. This is because phenomena such as bleeding and color mixing during coating and reduction in solvent resistance occur due to the large number of portions. As described above, when a dispersant, a surfactant, or a pigment derivative is used, an addition amount that is greater than or equal to the amount adsorbed on the pigment is required to enhance the dispersibility effect. Furthermore, the dispersion system becomes thixotropic by flocculation due to the interaction between the structure of the derivative and the solvent or the solubility, and it is difficult to improve the dispersibility by using the derivative alone. As a countermeasure, it is improved by the combined use with a surfactant, the addition of an organic solvent and an additive. However, in many cases, there are problems such as complicating the dispersion system and repelling when the coating film is dried.

[0004] In addition to the above-mentioned method, a method of chemically modifying the surface of a pigment powder has been proposed. Examples of industrial processes include the treatment of carbon black by a gas phase method and a liquid phase method. The purpose of the gas phase method is to express polar functional groups by oxidation treatment such as ozone treatment or plasma treatment. . In the case of the liquid phase method, it is used when stronger treatment is required than the oxidation treatment normally performed by the gas phase method, and strong oxidizing agents such as nitric acid, sodium nitrite, sodium hypochlorite, permanganate, etc. You are using By these treatments, the pigment can be dispersed in an aqueous system without using a dispersant or a resin, and the range of application is widened. However, there is a disadvantage that the production cost is high due to the characteristics of the treatment process, and the range of use is limited because the technology cannot be applied to organic pigments.

[0005] On the other hand, as disclosed in JP-A-53-61412, JP-A-54-89811, and JP-A-55-65269, an ink jet recording liquid includes an acid dye, a direct dye, In many cases, a water-soluble dye such as a basic dye is dissolved in a glycol-based solvent and water, and the recorded matter is generally poor in water resistance due to its easy solubility in water. However, there is a problem that the bleeding of the dye in the recording portion occurs. Further, there is a problem that light resistance is poor due to the structural characteristics of the dye. Items required for these aqueous ink jet recording liquids are: high-quality recorded images without bleeding; fast drying and fixing speed of the recording liquid; clogging of nozzles and recording liquid flow paths. It is particularly important that the recording liquid is ejected stably without recording, that the storage stability of the recording liquid is good, that the recording density is high, that the printed matter has good weather resistance and water resistance, and the like.

In order to improve such poor water resistance,
As disclosed in JP-A-56-57862, attempts have been made to change the structure of a dye or to prepare a recording solution having a strong basicity. Also, Japanese Patent Application Laid-Open No. 50-490
No. 04, JP-A-57-36692 and JP-A-5-36969.
As disclosed in Japanese Patent Application Laid-Open No. 9-20696 and Japanese Patent Application Laid-Open No. Sho 59-146889, improvement of water resistance has also been attempted by making good use of the reaction between a recording paper and a recording liquid. Although these methods have a remarkable effect on specific recording paper, they lack versatility in that they are restricted by recording paper, and when a non-specific recording paper is used, a water-soluble dye is used. In many cases, the recording liquid cannot provide sufficient water resistance of the recorded matter.

[0007] Examples of recording liquids having good water resistance include those in which an oil-soluble dye is dispersed or dissolved in a high boiling point solvent and those in which an oil-soluble dye is dissolved in a volatile solvent. There is a problem of emission of water, which is environmentally unfavorable.
In addition, there is a problem that solvent recovery or the like is required depending on a case where a large amount of recording is performed or where the apparatus is installed. Therefore, in order to improve the water resistance of the recorded matter, a recording liquid in which an organic pigment is dispersed in an aqueous medium has been developed.

However, unlike pigments, it is very difficult to disperse pigments as fine particles and to maintain a stable dispersion state. On the other hand, in the recording liquid for ink jet, the nozzle diameter is becoming smaller as the resolution of the printer is increased, and accordingly, the particle diameter of the pigment particles needs to be reduced. However, in the case of the pigment type, it is difficult to satisfy all the necessary items of the ejection stability from the nozzle, the re-dissolution (dispersion) property, and the coloring property after printing.
This is a problem of the pigment type ink jet recording liquid.

As an example having both the dispersibility of the pigment type ink jet recording liquid and the vivid color tone of the dye, see JP-B-60-4.
No. 5667, JP-B-60-45668 and JP-B-60-45669, a water-soluble dye having the same color as the pigment to be used is used in combination with the pigment, and a polymer dispersion having a molecular weight of 1,000 to 100,000 is used. Recording liquids using agents have been proposed. This technique is improved in terms of water resistance and light resistance by containing a pigment as compared with the case where the dye is used alone, but the dye is used at a pigment ratio of 1:10 to 10: 1. No bleeding, color mixing, or fundamental improvement in water resistance has been made as a printed material for use. Furthermore, although the thixotropic property is improved as compared with the case of the pigment alone, the tendency required to be associated with an increase in the dye concentration, and there are restrictions on the application surface such as thickening, etc. Rather than satisfying, it is an intermediate performance between dye and pigment. Also,
The combination use of a dye having a sulfonic acid group or a sulfonic acid group and a pigment disclosed in JP-A-5-247391 is considered to be equivalent to the above technique.

As an improvement of the above-mentioned combined recording liquid of pigment and dye, as disclosed in Japanese Patent Application Laid-Open No. 9-151344, by positively adsorbing the dye to the pigment, the color reproduction range is larger than that of the pigment. Pigment inks that are widely used and have better water resistance and light resistance than dyes have been proposed. The adsorption of the dye to the organic pigment is performed by using a reactive dye as the dye, by using a reactive dye as the dye, or a part of the functional group of the dye and the functional group in the pigment structure (that is, if the pigment is an acidic functional group, the dye is a (Or vice versa). Although this technique is very useful, it depends on the functional group of the pigment, and in the case of an organic pigment, there are many limitations particularly in utilizing its effect. In the example of the above publication, it is stated that a dye having a basic group is adsorbed when the pigment has an acidic group in the molecular structure, and a dye having an acidic group is adsorbed when the pigment has a basic group in the molecular structure. At this time, when the dye acts as a dispersant for improving dispersibility in consideration of dispersibility as an aqueous dispersion medium, it is necessary to use a basic medium for an acidic dye and an acidic medium for a basic dye. And there is a limitation due to the combination of the pigment and the dye. Usually, the aqueous recording liquid for inkjet is a basic medium. In the case of the above example, an acid dye is required in consideration of dispersibility, and a pigment having a carboxyl group or a sulfonic acid group cannot be used. On the other hand, in the case of a pigment having the opposite weak basicity, the acidic groups of the dye and the pigment, the basicity of the dispersion medium is in a competitive adsorption state, and the dispersion medium having a lower basicity than the basicity of the pigment is used. Need to be used.

[0011]

SUMMARY OF THE INVENTION It is an object of the present invention to provide storage stability over time, ejection stability at a nozzle, and a sufficient color reproducibility range when printed, and the excellent properties of the pigment type. Another object of the present invention is to provide a pigment-type ink jet recording liquid which is self-dispersible in an aqueous system while having both excellent water resistance and light resistance.

[0012]

DISCLOSURE OF THE INVENTION The present invention is a proposal for achieving the above object, that is, an aqueous liquid, quinacridone-based pigment particles dispersed in the aqueous liquid, and a quinacridone-based pigment. A water-soluble quinacridone derivative adsorbed on the surface of the particles, and the water-soluble quinacridone derivative not adsorbed, wherein the unadsorbed water-soluble quinacridone derivative is based on the total amount of the aqueous liquid and the quinacridone pigment; The quinacridone pigment is dissolved in the aqueous liquid in an amount less than the critical concentration at which flocculation occurs at a predetermined pigment content in the range of 2 to 25% by weight of the pigment. Production method having an aqueous pigment dispersion and a step of removing unadsorbed derivatives, and ink jet using the aqueous dispersion The present invention relates to a recording liquid.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention are as follows. (1) The water-soluble quinacridone derivative is a quinacridone containing an acidic functional group or a salt thereof. (2) The quinacridone-based pigment is unsubstituted, lower alkyl-substituted or halogen-substituted quinacridone. (3) The primary particles of the quinacridone pigment are from 10 to 100.
nm. (4) The water-soluble quinacridone derivative is adsorbed at 0.01 to 1.5 mmol / g per quinacridone-based pigment weight.

The major difference of the present invention from the prior art is that self-dispersible pigments found in the chemical surface modification of oxidized carbon black and organic pigments can be easily and inexpensively prepared. It differs greatly from the system in design as a pigment dispersion. Furthermore, the conventional dye adsorption type pigment dispersion has a narrow range of application, and the pigment dispersion of the present invention is a novel surface-modifying technology for easily dispersible pigments in an aqueous system in comparison with the dispersing effect and ink physical properties. It can be said. In the adsorption of the pigment and the pigment derivative in the present invention, it is considered that the aromatic rings of the respective chemical structures approach each other due to hydrophobic interaction and are adsorbed by π-π stacking. Conventionally, regarding the pigment derivative treatment method, it was introduced that a pigment derivative having a skeleton similar to that of a pigment has been used as an effective dispersant because of its extremely large adsorptivity to the pigment. The point is that instead of using it as a dispersant, the derivative is aligned on the pigment surface as a single layer of adsorption, so that there is no conventional pigment concentration in a high range, without using other dispersants or resins, with low viscosity. This is to invent a water-based pigment dispersant having high surface tension and high dispersion stability over time.

As the pigment used in the present invention, a quinacridone pigment can be used. As a specific example, C.I. I.
Pigment Red 122, C.I. I. Pigment Red 2
02, C.I. I. Pigment Red 206, C.I. I. Pigment Red 207, C.I. I. Pigment Red 20
9, C.I. I. Pigment Violet 19, C.I. I. Pigment Violet 42, etc., and any pigment having a quinacridone skeleton can be used including its solid solution. The particle size of the pigment particles used is preferably from 50 to 0.01 μm, and the recording liquid for inkjet is preferably from 1 to 0.005 μm. For finer pigment particles and particle size control, salt milling or solvent milling is preferred. It is preferable to perform the pulverization of the primary particles by wet pulverization or dry pulverization before the treatment. Further, performing the derivative treatment in the above-mentioned pulverizing step is more preferable as an advantage due to adsorption efficiency and simplification of the step.

As the pigment derivative used in the present invention, a water-soluble quinacridone derivative can be used. Examples of the water-soluble quinacridone pigment derivative include a compound represented by the following general formula [I]. General formula []

[0017]

Embedded image

(Wherein X 1 and X 2 are independently —CH 3,
-Cl and -H, wherein Y1 and Y2 are independently -COO
H, -COONa, -COOK, -SO3H, -SO3
Na, -SO3K, an acidic amine salt of the following general formula [II], wherein n1 and n2 are integers of 1 to 4, and m1 and m2 are 1 to 2
Where m1 + n1 = 4, m2 + n2 = 4,1
≦ m1 + m2 ≦ 4, preferably m1 + m2 = 1 to 2. ) General formula [II]

[0019]

Embedded image

(Wherein R1, R2, R3 and R4 each independently represent a hydrogen atom, an alkyl group having 1 to 4 carbon atoms,
Alkanol group, an alkyl group having 1 to 4 carbon atoms and an alkyl alkanol group substituted with an alkanol group having 1 to 3 carbon atoms. )

As the type of amine, primary amine, secondary amine, tertiary amine and quaternary amine can be used. As the recording liquid for inkjet, in addition to ammonia, a water-soluble amine compound is preferable, and specifically, dimethylamine, trimethylamine, monoethylamine,
Diethylamine, triethylamine, propylamine,
Examples include isopropylamine, dipropylamine, butylamine, isobutylamine, sec-butylamine, monoethanolamine, diethanolamine, triethanolamine, triisopropanolamine, isopropanolamine, dimethylethanolamine, diethylethanolamine, and N-butyldiethanolamine. Other water-soluble amine compounds include N, N-dimethyl-1,3-diaminopropane, N, N-diethyl-1,3-diaminopropane and the like.

For the adsorption treatment of the water-soluble quinacridone derivative on the quinacridone pigment, a dispersing machine usually used for dispersing pigments can be used. In the adsorption treatment, the water-soluble quinacridone derivative is dissolved in predetermined water within a basic range, and the adsorption treatment proceeds by adding and dispersing the pigment into the solution. In this case, as the water to be used, it is preferable to use purified water having no divalent or higher valent metal salt, pure water or water equivalent thereto. This is because tap water and water containing mineral components contain a divalent metal salt, and this metal salt becomes insoluble by binding to an acidic group of the water-soluble quinacridone derivative, thereby preventing water-based dispersion. Examples of the dispersing machine used for the adsorption treatment include a paint conditioner (manufactured by Red Devil Co., Ltd.), a ball mill, a sand mill ("Dyno Mill" manufactured by Shinmaru Enterprises Co., Ltd.), an attritor,
Pearl mill (e.g., "DCP mill" manufactured by Erich), Koball mill, homomixer, homogenizer ("Clearmix", manufactured by M Technique), wet jet mill ("Genus PY" manufactured by Genus, "Nanomizer" manufactured by Nanomizer) Etc. can be used. Glass beads, zirconia beads, alumina beads, magnetic beads, and styrene beads can be used for those using media as a dispersing machine.

The pigment dispersion adsorbed by the dispersing machine is in a state where the chemical structure and the acidic functional group in the water-soluble derivative are liable to cause flocculation in water due to the action of van der Waals force, such as viscosity increase and aggregation. Poor stability. Furthermore, use of the ink as an ink is limited due to excessive water-soluble derivatives, such as bleeding during printing, color mixing, and deterioration of water resistance of printed matter. In the present invention, the dispersibility, the stability with time, and the characteristics as a printed matter can be achieved at the same time by removing the water-soluble derivative not adsorbed on the pigment to the extent that the above-mentioned adverse effect is not caused. As a method for removing the unadsorbed water-soluble derivative, centrifugation and ultrafiltration can be used.

By separating the non-adsorbed derivative using ultrafiltration or centrifugation, a pigment dispersion having excellent dispersion stability can be obtained. In the case of a water-soluble quinacridone derivative, the basic aqueous solution and the derivative cause solvation due to the chemical structure of the derivative, so that the aqueous solution of the water-soluble quinacridone derivative becomes a very viscous purine state. When the water-soluble pigment derivative is dispersed and adsorbed on the pigment, the pH is usually adjusted to 11
Adjust to around 8. In this state, even if the amount of the water-soluble derivative added is reduced to the lower limit at which the dispersibility is improved in any pH range, a dispersion having a high thixotropy due to flocculation is obtained. However, by separating the non-adsorbed derivative, the thixotropic property is lost and a pigment dispersion having a very low viscosity can be obtained. FIG. 1 is a graph showing the concentration of an unadsorbed pigment derivative in a dispersion and the concentration of the pigment in the dispersion. As shown in this figure, flocculation is caused by the pigment derivative concentration and the distance between the pigment particles. Therefore, the higher the pigment concentration, the more easily flocculation occurs, and there is a critical concentration at which flocculation occurs. The concentration gradient changes depending on the particle diameter of the pigment particles, the pigment specific surface area, the amount of adsorbed derivative, the amount of functional group in the derivative, and the like. By controlling each factor, a stable dispersion region can be secured.

When the pigment dispersion of the present invention is used as a recording liquid for ink-jet recording, the pigment concentration is generally used in the range of 2 to 5% by weight. Therefore, the lower limit of the derivative concentration is limited. This is because, when the pigment concentration in the dispersion is as low as 2 to 5% by weight, the lower limit of flocculation can be tolerated as a high derivative concentration. 3 to 20 c for an aqueous pigment dispersion having a pigment concentration of 15 to 20% by weight
The viscosity can be as low as ps, and the number of functional groups of the water-soluble pigment derivative is preferably 2 or less. In this case, the critical concentration of flocculation is such that the concentration of the unadsorbed pigment derivative is about 10 mmol / kg or less, preferably 1 mmol / kg or less at a pigment concentration of 15 wt%. The amount of the pigment derivative adsorbed on the pigment is 0.01 to 1.5 per pigment.
mmol / g, preferably 0.05 to 0.5 mm
ol / g.

When used as an ink jet recording liquid, the surface-treated pigment dispersion has an average particle diameter of 10 to 300 n as measured by a laser light scattering particle size distribution meter.
m and coarse particles of 500 nm or more are 3% by weight of all the particles.
The following is preferred. If the average dispersed particle size is too large, there are disadvantages such as impaired ejection stability as an inkjet recording liquid and precipitation, and the smaller the coarse particles, the better. The pigment dispersion of the present invention is 0.5 to 10 parts by weight, more preferably 2 to 5 parts by weight, in 100 parts by weight of the inkjet recording liquid.
It is preferred that it be contained by weight. If the amount of the pigment is too small, a sufficient density as a recording liquid cannot be obtained, and if the amount is too large, the ejection stability and the nozzle clogging resistance required for the recording liquid are impaired.

The recording liquid for ink-jet recording of the present invention is used in order to improve the fixability to paper and the water resistance of the ink coating film.
An aqueous resin can be used. Aqueous resins that can be used can be broadly classified into water-soluble resins and water-dispersible resins, each of which includes an acrylic resin, a styrene-acrylic resin, a vinyl acetate resin, a polyester resin, a polyamide resin, a polyurethane resin, an epoxy resin, and a butadiene resin. Resins such as resins, petroleum resins, and fluorine resins, and water-dispersible resins.

The dispersed particle size of the water-dispersible resin can be variously changed by a polymerization operation, a surfactant and the like.
A particle size of several thousand nm is obtained. In order to eliminate clogging in the nozzle, the average particle diameter of the water-dispersible resin measured by a laser light scattering particle size distribution analyzer is 20 to 300 nm, and coarse particles of 500 nm or more are 3% by weight or less of all resin particles, and Has an average particle size of 50 to 200 nm and 500
It is preferable that the coarse particles having a size of not less than nm are 2% by weight or less of all the resin particles. The water-soluble resin or the water-dispersible resin is preferably contained in an amount of 0.05 to 5 parts by weight, more preferably 0.1 to 3 parts by weight, per 100 parts by weight of the ink jet recording liquid. If the amount of the resin is too small, it is difficult to obtain satisfactory water resistance. If the amount of the resin is too large, the ejection stability required as a recording liquid for inkjet is impaired, and troubles such as clogging of nozzles occur.

In the ink jet recording liquid of the present invention, an anionic, cationic, nonionic, amphoteric or amphoteric surfactant or a polymer surfactant is used for adjusting the surface tension and adjusting the permeability to paper. be able to. The surfactant has an effect on the stability of the recording liquid and the permeability to paper for the ink jet recording liquid in which the pigment is dispersed using the surfactant, but the pigment derivative is adsorbed on the pigment surface. When the amount of the surfactant is large, the dispersion stability of the pigment may be impaired.

Examples of the anionic surfactant include fatty acid salts, alkyl sulfate salts, alkyl aryl sulfonates, alkyl naphthalene sulfonates, dialkyl sulfonates, dialkyl sulfosuccinates, alkyl diaryl ether disulfonates, and alkyl phosphates. Acid salt, polyoxyethylene alkyl ether sulfate, polyoxyethylene alkyl aryl ether sulfate, naphthalenesulfonic acid formalin condensate, polyoxyethylene alkyl phosphate ester salt, glycerol borate fatty acid ester, polyoxyethylene glycerol fatty acid ester, etc. Can be exemplified.

Examples of the nonionic surfactant include polyoxyethylene alkyl ether, polyoxyethylene alkyl aryl ether, polyoxyethylene oxypropylene block copolymer, sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester, and polyoxyethylene sorbitol fatty acid ester. And non-ionic surfactants such as glycerin fatty acid ester, polyoxyethylene fatty acid ester, polyoxyethylene alkylamine, fluorine type and silicon type.

Examples of the cationic surfactant include an alkylamine salt, a quaternary ammonium salt, an alkylpyridinium salt, and an alkylimidazolium salt. Examples of the amphoteric surfactant include alkyl betaine, alkyl amine oxide, phosphadyl choline and the like. Examples of the polymer surfactant include an acrylic water-soluble resin, a styrene / acrylic water-soluble resin, a water-soluble polyester resin, and a water-soluble polyamide resin. If necessary, two or more surfactants such as anionic surfactants, cationic surfactants, nonionic surfactants, and polymer surfactants may be used in combination.

The aqueous pigment dispersion and ink jet recording liquid of the present invention are composed of an aqueous medium, a surface-treated pigment, an aqueous resin, and if necessary, other additives. The aqueous medium refers to water, an organic solvent miscible with water, and a mixture thereof. Examples of the water include ion-exchanged water or distilled water from which metal ions or the like have been removed, and an aqueous pigment dispersion or an inkjet recording liquid. It is used in the range of up to 95% by weight. Aqueous solvent refers to an organic solvent that is miscible with water in the present specification, which prevents drying at the nozzle portion as an inkjet recording liquid, prevents solidification of the recording liquid, and ensures stable ejection of the recording liquid and aging at the nozzle. Is used alone or in a mixture of 1 to 50% by weight, preferably 2 to 25% by weight of the recording liquid.

As the aqueous solvent, ethylene glycol,
Diethylene glycol, propylene glycol, 1,3
-Propanediol, triethylene glycol, polyethylene glycol, glycerin, tetraethylene glycol, dipropylene glycol, ketone alcohol, diethylene glycol monobutyl ether, ethylene glycol monobutyl ether, triethylene glycol monobutyl ether, ethylene glycol monoethyl ether, 1,2-hexane Examples thereof include diol, N-methyl-2-pyrrolidone, pyrrolidone, 2,4,6-hexanetriol, tetrafurfuryl alcohol, and 4-methoxy-4-methylpentanone. For the purpose of accelerating the drying of the recording liquid, alcohols such as methanol, ethanol and isopropyl alcohol can be used.

The following various additives can be used in the ink jet recording liquid of the present invention, if necessary. When the printing medium of the recording liquid is a permeable material such as paper, a penetrating agent can be added to accelerate the penetration of the recording liquid into the paper and the apparent drying property. Examples of the penetrant include glycol ethers such as diethylene glycol monobutyl ether exemplified as the aqueous solvent, alkylene glycol, and polyethylene glycol monolauryl ether.
Sodium lauryl sulfate, sodium dodecylbenzenesulfonate, sodium oleate, sodium dioctylsulfosuccinate and the like can be used. These are used in the range of 0 to 5% by weight, preferably 0.1 to 5% by weight of the recording liquid. The penetrant has a sufficient effect at the above-mentioned usage amount, and if it is more than this, the printing is blurred and the paper comes out (print-through), which is not preferable.

Preservatives are added for the purpose of preventing the generation of mold and bacteria in the recording liquid. Examples of the antifungals include sodium dehydroacetate, sodium benzoate, sodium pyridinethione-1-oxide, zinc pyridinethione. -1-oxide, 1,2-benzisothiazolin-3-one, 1
-Amine salts of benzisothiazolin-3-one and the like are used. These are 0.05 to 1.0% by weight in the recording liquid.
Is preferably included in the range.

The chelating agent blocks the metal ions in the recording liquid, and prevents the deposition of metal at the nozzle portion and the deposition of insoluble substances in the recording liquid. Tick acid, a sodium salt of ethylenediaminetetraacetic acid, a diammonium salt of ethylenediaminetetraacetic acid, a tetraammonium salt of ethylenediaminetetraacetic acid, and the like are used. These are used in a range of 0.005 to 0.5% by weight in the recording liquid.

Further, in order to adjust the pH of the recording liquid and obtain stability of the recording liquid or stability with the recording liquid piping in the recording apparatus, a pH adjuster such as amine, inorganic salt, ammonia, etc. Buffers can be used. Further, an antifoaming agent can be added in order to prevent the recording liquid from circulating or moving inside the pipe or inside the pipe, or from generating bubbles during the production of the recording liquid.

The ink jet recording liquid of the present invention can be produced by dispersing a pigment dispersion and an aqueous resin in an aqueous medium, appropriately diluting with water, and mixing other additives. Dispersion can be performed using a disper, sand mill, homogenizer, ball mill, paint shaker, ultrasonic disperser, or the like. In addition, mixing and stirring can be performed by a high-speed disperser, emulsifier, or the like, in addition to stirring by a stirrer using ordinary blades.

It is preferable that the mixed recording liquid is sufficiently filtered before or after dilution with a filter having a pore size of 0.65 μm or less, and more preferably a filter having a pore size of 0.45 μm or less. Filtration by centrifugation can be performed prior to filter filtration, whereby clogging in filter filtration can be reduced and filter replacement can be reduced. The recording liquid has a viscosity of 0.8, depending on the type of the recording apparatus.
It is preferable to adjust as a liquid of １５15 cps (25 ° C.). The surface tension is preferably adjusted to 25 to 73 dyn / cm. The pH is not particularly limited, but is 7-1.
A weak alkalinity of 0 is preferred.

The aqueous pigment dispersion of the present invention can be used in a wide range of fields such as printing inks, paints, cosmetics, writing inks, toners, liquid developers, and electrophotographic materials, in addition to ink jet recording liquids. .

[0042]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to the examples. In the examples, parts and% represent parts by weight and% by weight, respectively. In addition, the measurement method of the particle diameter and viscosity of the aqueous pigment dispersion obtained in the examples and comparative examples, storage stability, re-dissolvability of dry powder, particle diameter of ink jet recording liquid, viscosity, storage stability, The following methods were used to evaluate the discharge stability, water resistance, and clogging resistance, and the quality of printing on ordinary people.

(1) Particle Size The average particle size (d99) was measured using a laser diffraction type particle size distribution meter (“Microtrack UPA” manufactured by Nikkiso Co., Ltd.).
), And the content of coarse particles of 500 nm or more was calculated. (2) Viscosity In the low viscosity range, a vibrating viscometer (“VM-1” manufactured by Yamaichi Electric Co., Ltd.)
A "), 25 ° C. using a B-type viscometer for medium viscosity or higher
Was measured.

(3) Storage stability The aqueous pigment dispersion exhibited a storage period in which the change in particle size at 50 ° C. was less than 15 nm and the change in viscosity was less than 0.5 cps. The case where the storage stability was one day or less was indicated by x. With respect to the ink jet recording liquid, storage stability was evaluated from changes in particle size and viscosity after storage at 50 ° C. for 3 months (（: change in particle size was less than 15 nm and change in viscosity was less than 0.2 cps; (Change of 15 nm or more or change of viscosity 0.2 cps or more). (4) Foamability 30 aqueous pigment dispersions were placed in a 50 ml screw tube with a lid.
ml, shake vigorously up and down 20 times and evaluate the foaming property in the state of the foam after 3 minutes (（: foam disappeared, ○: foam slightly on the inner surface of screw tube, Δ: foam foam on entire surface Height 3mm
Less than, ×: foam is on the entire surface and foam height is 3 mm or more). (5) Surface tension: Use a surface tensiometer (“CBVP-Z” manufactured by Kyowa Interface Chemical Co., Ltd.)
The surface tension at 5 ° C. was measured. (6) Ejection stability The recording liquid for inkjet was packed in a cartridge of an inkjet printer (“HG-5130” manufactured by Epson Corporation), printed on plain paper (“K” manufactured by Xerox Corporation), and the ejection stability was evaluated. . (○: stable continuous ejection from the nozzle for 120 minutes or more; Δ: disturbance in the landing position of the droplet within 120 minutes of continuous ejection; ×: stable ejection from the nozzle).

(7) Water resistance The printed matter obtained in (4) was wetted with water, rubbed with a finger, and visually evaluated for changes in the printed matter (○: no bleeding or peeling of ink was observed). ×: Bleeding and peeling of the ink are observed). (8) Clogging resistance In the same manner as in (6), the cap of the printer was removed after printing, printing was performed again after 1 hour, and the presence or absence of clogging was evaluated. Clogging). (9) Print quality The ink jet recording liquid was packed in a cartridge of an ink jet printer (“EP-750C” manufactured by Epson) and printed on plain paper (“4024” manufactured by Xerox) to evaluate the feathering property of the ink. did. (○:
There is almost no feathering and the next to "dragon" can be distinguished without blurring. X: There is feathering, and the character of "dragon" is difficult to distinguish due to blurring.

Example 1 I. Pigment Red 122 having an average primary particle size of 30 nm or less by salt milling.
g, 2 g of a sulfonated quinacridone derivative (average sulfonic acid group introduction amount = 1) and 110 g of ion-exchanged water, and sodium hydroxide is added so that the pH of the mixed solution becomes 9 or more. Paint is performed using zirconia beads as a medium. The dispersion was performed for about 5 hours using a shaker. The pigment dispersion has a permeate derivative concentration of 0.9 mmol / k by ultrafiltration.
g of the pigment dispersion and the solid content of the pigment dispersion is 15% by weight when the pH of the reflux water is about 8.5.
And concentrated.

Example 2 I. Pigment Violet 19 by salt milling to reduce the average primary particle size to 30 nm or less.
0 g, 1.6 g of sulfonated quinacridone derivative (average sulfonic acid group introduction amount = 1.2), 110 g of ion-exchanged water
g, and sodium hydroxide was added so that the pH of the mixture became 9 or more, and the mixture was dispersed for about 5 hours using a zirconia bead as a medium using a paint shaker. The pigment dispersion has a derivative concentration of permeated water of 1.4 mm by ultrafiltration.
The resultant was washed while adding ion-exchanged water to ol / kg or less, and concentrated so that the solid content of the pigment dispersion became 15% by weight when the pH of the reflux water was around 9.0.

Embodiment 3 C.I. I. Pigment Red 202 having an average primary particle size of 30 nm or less by salt milling.
g, 2.4 g of a sulfonated dichloroquinacridone derivative (average sulfonic acid group introduction amount = 0.9) and 110 g of ion-exchanged water, and sodium hydroxide was added so that the pH of the mixture became 9 or more. The beads were dispersed in a medium using a paint shaker for about 5 hours. The pigment dispersion had a derivative concentration of 0.1% in the permeated water by ultrafiltration.
Washing was performed while adding ion-exchanged water to 4 mmol / kg or less, and the solution was concentrated so that the solid content of the pigment dispersion became 15% by weight when the pH of the reflux water was around 9.0.

Comparative Example 1 C.I. I. Pigment Red 122 having an average primary particle size of 30 nm or less by salt milling.
g, C.I. I. 4 g of Acid Red 259 and 110 g of ion-exchanged water are mixed, and sodium hydroxide is added so that the pH of the mixed solution becomes 9 or more, and the mixture is dispersed for about 5 hours using a zirconia bead as a medium using a paint shaker. And

Comparative Example 2 C.I. I. Pigment Red 122 having an average primary particle size of 30 nm or less by salt milling.
g, C.I. I. 6 g of Acid Red 154 and 110 g of ion-exchanged water are mixed, and sodium hydroxide is added so that the pH of the mixed solution becomes 9 or more, and the mixture is dispersed for about 5 hours using a zirconia bead as a medium using a paint shaker. And

Comparative Example 3 C.I. I. Pigment Red 122 having an average primary particle size of 30 nm or less by salt milling.
g, 2 g of a sulfonated quinacridone derivative (average sulfonic acid group introduction amount = 1) and 110 g of ion-exchanged water, and sodium hydroxide is added so that the pH of the mixed solution becomes 9 or more. Paint is performed using zirconia beads as a medium. The dispersion was performed for about 5 hours using a shaker.

[0052]

[Table 1]

(Examples 4 to 6 and Comparative Examples 4 to 6) Raw materials having the compositions shown in Table 2 were charged into a stirring tank, stirred and mixed by a disper, then filtered through a 0.45 μm membrane filter, and ink-jetted. A recording liquid for use was obtained. The particle size and viscosity of the obtained ink jet recording liquid were measured, and storage stability, ejection stability, water resistance, and clogging resistance were evaluated. Table 2 shows the results.

[0054]

[Table 2]

Water-soluble resin solution: Styrene / acrylic water-soluble resin aqueous solution manufactured by Johnson Polymer Co., Ltd., "Johncryl J-62", solid content: about 34% Activator: Anionic surfactant manufactured by Kao Corporation Perex 0T-P ”, about 70% solid content Fungicide:“ Placcel GXL ”manufactured by Zeneca Corporation

[0056]

The aqueous pigment dispersion of the present invention, when used in an ink jet recording liquid, has excellent water resistance and storage stability, does not cause clogging in a nozzle, and provides stable ejection for a long period of time. give. Further, it has a sufficient density in print quality printed on paper, has a wide color gamut reproduction range, and is excellent in light resistance as compared with the dye type. Therefore, it can be used in a wide range of fields as a color print in fields such as office document preparation, postal address writing, cardboard marking, numbering, and bar code addition. further,
The aqueous pigment dispersion can be used in gravure inks, aqueous paints, and other printing ink fields.

[Brief description of the drawings]

FIG. 1 shows the relationship between the pigment concentration of the flocculation critical concentration and the concentration of an unadsorbed pigment derivative in an aqueous pigment dispersion.

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Akimitsu Mochizuki 2-3-1, Kyobashi, Chuo-ku, Tokyo F-term in Toyo Ink Manufacturing Co., Ltd. 4J037 AA30 CB28 DD05 DD23 DD24 EE02 EE28 EE33 EE43 FF15 FF22 FF23 FF25 FF30 4J039 AD03 AD04 AD08 AD09 AD10 AD15 AD18 AE04 AE05 AE06 AE07 AE08 BA29 BC05 BC12 BC13 BC16 BC19 BC20 BC27 BC33 BC35 BC50 BC51 BC54 BC56 BC57 BC65 BC69 BE01 BE22 CA06 DA02 DA08 EA35 EA38 EA43 EA42 EA43 EA43 EA42 EA43 EA42 EA43 EA42 EA42 EA43 EA43 EA42 EA42 EA43 EA42 EA43 EA42 EA43 EA43 EA42 EA43 EA42 EA42

Claims (7)

[Claims] 1. An aqueous liquid, particles of a quinacridone pigment dispersed in the aqueous liquid, a water-soluble quinacridone derivative adsorbed on the surface of the quinacridone pigment particles, and an unadsorbed water-soluble quinacridone derivative. Wherein the unadsorbed water-soluble quinacridone derivative is contained in the quinacridone at a predetermined pigment blending amount in the range of 2 to 25% by weight of the total amount of the aqueous liquid and the quinacridone pigment. An aqueous pigment dispersion, wherein the aqueous pigment is dissolved in the aqueous liquid in an amount smaller than the critical concentration at which flocculation occurs. 2. The aqueous pigment dispersion according to claim 1, wherein the water-soluble quinacridone derivative is a quinacridone containing an acidic functional group or a salt thereof. 3. The aqueous pigment dispersion according to claim 1, wherein the quinacridone pigment is an unsubstituted, lower alkyl-substituted or halogen-substituted quinacridone. 4. The quinacridone pigment particles having a particle size of 10 to 1
4. The aqueous pigment dispersion according to claim 1, which has a thickness of 00 nm. 5. The adsorption amount of the water-soluble quinacridone derivative is 0.01 to 1.5 mmol based on the quinacridone pigment.
The aqueous pigment dispersion according to any one of claims 1 to 4, wherein the amount is 1 / g. 6. A step of dispersing quinacridone pigment particles in an aqueous liquid in which a water-soluble quinacridone derivative is dissolved and adsorbing the quinacridone pigment particles on the surface of the quinacridone pigment particles; The water-soluble quinacridone derivative not adsorbed so that the amount of the quinacridone pigment is less than the critical concentration at which the quinacridone pigment reaggregates at a predetermined pigment blending amount within the range of 2 to 25% by weight based on the total amount. And a process for producing an aqueous pigment dispersion. 7. An ink jet recording liquid comprising the aqueous pigment dispersion according to claim 1, an activator and / or an aqueous resin.