JP2002121419A - Method for producing water-based pigment dispersion - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a water-based pigment dispersion having excellent water- dispersibility and dispersion stability with time, and a method for producing the dispersion, and further to provide a method for producing a water-based pigment dispersion having excellent light resistance, water resistance, hue and print density after the printing, and a reproduction range of the color range when being printed on regular paper, further having good jetting stability at a nozzle, and usable for a water-based recording liquid for inkjet, in the recording liquid for the inkjet by using the water-based pigment dispersion. SOLUTION: This method for producing the water-based pigment dispersion is characterized in that the method comprises a step for sulfonating a pigment to introduce one or more sulfo groups into the molecule, a step for removing pigment derivatives having two or more sulfo groups from the reaction product to concentrate the sulfo group-containing organic pigment derivative having only one sulfo group, and a step for dispersing a pigment having the molecular structure of the pigment akin to the sulfo group-containing pigment derivative in the presence of the sulfo group-containing pigment derivative obtained at the above step, in water.

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.
Furthermore, the present invention relates to a method for producing a dispersion used in an inkjet recording liquid having excellent light fastness, water fastness, and hue after printing, and having good ejection stability at a nozzle.

[0002]

2. Description of the Related Art Conventionally, in a water-based ink or a water-based paint, a pigment is dispersed in water using a surfactant, a dispersing resin or the like. However, surfactants have the problem of foaming,
When an antifoaming agent is used in combination to suppress foaming, there has been a problem that the leveling property is reduced. Further, the dispersing resin is effective for a pigment dispersion having a relatively high viscosity, but only a limited effect was observed for a pigment dispersion having a low viscosity.

[0003] A technique is known in which a pigment is dispersed in water using a dye or pigment derivative that is soluble in water. For example, JP-A-56-155261, JP-A-56-15526
No. 2 discloses an aqueous pigment dispersion containing a pigment and a dye having the same color tone as the pigment. According to this method, the dispersion stability of the pigment in water is improved by absorbing part of the dye on the surface of the pigment, but the solubility of the dye in water is higher than the affinity of the pigment particle surface. Too much
In the case of paints and inks, problems such as color mixing and bleeding occur.

[0004] Japanese Patent Application Laid-Open No. Hei 10-36641 discloses an aqueous pigment dispersion containing a phthalocyanine pigment and a phthalocyanine compound into which a carboxylic acid group has been introduced. According to this technique, the problem of bleeding is improved, but there is still a problem in the dispersion stability of the pigment. JP-A-11-499
No. 74 discloses an aqueous pigment dispersion comprising a pigment and a pigment derivative having a sulfonic acid group bonded to an inorganic ion. According to this method, the dispersion stability of the pigment is obtained by the electrostatic repulsion of the divalent metal ion salt-formed with the sulfonic acid group of the pigment derivative integrated with the pigment.
However, it has been difficult in terms of production technology to control the dispersion stability with a trace amount of divalent metal ions mixed in the pigment dispersion step.

[0005] Further, in the recording liquid for ink jet, the nozzle diameter has been reduced as the resolution of the printer has been increased, and accordingly, the particle diameter of the pigment particles has to be reduced. However, in the case of an ink jet recording liquid containing a pigment, it is difficult to simultaneously satisfy the requirements required for the ink jet recording liquid such as ejection stability from a nozzle, re-dissolution (dispersion) properties, and color development after printing. Met.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide an aqueous pigment dispersion having excellent storage stability over time. Further, the present invention has a discharge stability at a nozzle when used for a recording liquid for an ink jet ink, a sufficient color reproducibility range when printing, and excellent performance of both water resistance and light resistance. It is an object of the present invention to provide a method for producing a dispersion used for a pigment-type ink jet recording liquid having the same.

[0007]

According to the present invention, there is provided a process for sulfonating a pigment to introduce one or more sulfonic acid groups into a molecule, and removing a pigment derivative having two or more sulfonic acid groups from a reaction product. Condensing the sulfonic acid group-containing pigment derivative having only one sulfonic acid group, and in the presence of the sulfonic acid group-containing pigment derivative obtained in the above step, a molecule of a pigment similar to the sulfonic acid group-containing pigment derivative Dispersing a pigment having a structure in water.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The pigments of the present invention include phthalocyanine, quinacridone, quinacridone quinone, isoindolinone, quinophthalone, diketopyrrolopyrrole, benzimidazolone, insoluble azo, and condensed azo. And organic pigments such as soluble azo, perylene, perinone, indigo, thioindigo, dioxazine, anthraquinone, pyranthrone, anthuanthrone, flavanthrone and indanthrone.

The pigment of the present invention includes a compound having a substituent at any substitutable position of the pigment molecular skeleton forming the above-mentioned pigment. These substituents include a methyl group,
A lower alkyl group such as an ethyl group, a methoxy group, a lower alkoxy group such as an ethoxy group, chlorine, a halogen element such as bromine, a halogen-substituted alkyl group, a carboxylate group,
Examples include an acetyl group and a hydroxyl group.

Specific examples of the pigment of the present invention include C.I. I. Pigment number. Examples of phthalocyanine pigments include C.I. I. Pigment Blue 15, 15: 2, 1
5: 3, 15: 4, 15: 5, 15: 6, 16, C.I.
I. Pigment Green 7, 36 and the like.

The quinacridone pigments include C.I. I. Pigment Violet 19, 42, C.I. I. Pigment Red 122, 192, 202, 206, 207, 20
9, C.I. I. Pigment Orange 48, 49 and the like.
Isoindolinone pigments include C.I. I. Pigment Yellow 109, 110, 173, C.I. I. Pigment Orange 61 and the like.

The isoindoline pigments include C.I. I.
Pigment Yellow 139, 185, C.I. I. Pigment orange 66, 69, C.I. I. Pigment Red 26
0, C.I. I. Pigment Brown 38 and the like.

The quinophthalone pigments include C.I. I. Pigment Yellow 138. Diketopyrrolopyrrole pigments include C.I. I. Pigment Red 254, 2
55, 264, 272, C.I. I. Pigment Orange 7
1, 73, etc.

The benzimidazolone pigments include C.I.
I. Pigment Yellow 120, 151, 154, 15
6, 175, 180, 181, 194, C.I. I. Pigment Orange 36, 60, 62, 72, C.I. I. Pigment Red 171, 175, 176, 185, 208,
C. I. Pigment Violet 32, C.I. I. Pigment Brown 25 and the like.

Examples of the insoluble azo pigments include C.I. I. Pigment Red 1, 2, 3, 4, 5, 6, 7, 8, 9, 1
0, 11, 12, 13, 14, 15, 16, 17, 1
8, 20, 21, 22, 23, 31, 32, 37, 3
8, 41, 95, 111, 112, 114, 119, 1
36, 146, 147, 148, 150, 164, 17
0, 184, 187, 188, 210, 212, 21
3, 222, 223, 238, 245, 253, 25
6, 258, 261, 266, 267, 268, 26
9, C.I. I. Pigment Orange 1, 2, 5, 6, 1
3, 15, 16, 22, 24, 34, 38, 44, C.I.
I. Pigment Violet 13, 25, 44, 50,
C. I. Pigment Brown 1, C.I. I. Pigment Yellow 1, 2, 3, 5, 6, 10, 12, 13, 14,
17, 49, 55, 60, 63, 65, 73, 74, 7
5, 81, 83, 87, 90, 97, 98, 106, 1
11, 113, 114, 116, 121, 124, 12
6, 127, 130, 136, 152, 165, 16
7, 170, 171, 172, 174, 176, 18
8, C.I. I. Pigment Blue 25 and the like.

Examples of the condensed azo pigments include C.I. I. Pigment Yellow 93, 94, 95, 128, 166, C.I.
I. Pigment Orange 31, C.I. I. Pigment Red 144, 166, 214, 220, 221, 242,
248, 262, C.I. I. Pigment Brown 23, 4
1, 42 and the like.

The perylene pigments include C.I. I. Pigment Red 123, 149, 178, 179, 190,
224, C.I. I. Pigment Violet 29, C.I.
I. Pigment Black 31, 32 and the like. Perinone pigments include C.I. I. Pigment Orange 43, C.I.
I. Pigment Red 194, Bat Red 14, and the like. Indigo pigments include C.I. I. Pigment Blue 63, 73015: X and the like. Thioindigo pigments include C.I. I. Pigment Red 88, 181 and the like. Examples of the dioxazine pigment include C.I. I. Pigment Violet 23, 37 and the like. Anthraquinone pigments include C.I. I. Pigment Yellow 99, 10
8, 123, 147, 193, 199, C.I. I. Pigment Red 83, 89, 177 and the like. Pyranthrone pigments include C.I. I. Pigment Red 216, 2
26, C.I. I. Pigment Orange 40, 51 and the like.

Ansuanthrone pigments include C.I.
I. Pigment Red 168, C.I. I. Pigment Violet 31, Bat Orange 3, and the like. Flavanthrone pigments include C.I. I. Pigment Yellow 2
4, bat yellow 1 and the like. Examples of indanthrone-based pigments include C.I. I. Pigment Blue 60, 64, and Bat Blue 4. Examples of metal complex pigments include C.I.
I. Pigment Green 10, C.I. I. Pigment Yellow 117, 129, 150, 153, 177, 17
9, 257, 271, C.I. I. Pigment Orange 5
9, 65, 68 and the like. Diketopyrrolopyrrole pigments include C.I. I. Pigment Red 254, 255,
264, 272, C.I. I. Pigment Orange 71, 7
There are 3 etc.

The average primary particle size of the pigment particles in the aqueous pigment dispersion of the present invention is preferably from 1000 to 5 nm, more preferably from 150 to 5 nm. In order to adjust the pigment having such a particle diameter, a coarse pigment or a pigment of a pigment grade is subjected to wet pulverization or dry pulverization such as salt milling or solvent milling to perform a finer pigment treatment. Salt milling is a process in which a small amount of a water-soluble solvent is added to a mixture of an organic pigment and a water-soluble inorganic salt, and the mixture is kneaded vigorously by a kneader or the like while controlling the temperature to 30 to 65 ° C. by water cooling or the like. The pulverized mixture is poured into water to dissolve and remove water-soluble inorganic salts and water-soluble solvents.

The water-soluble inorganic salt is added as a grinding aid for the organic pigment, and is used in an amount of 2 to 20 times, preferably 3 to 10 times the weight of the organic pigment. Examples of the water-soluble inorganic salt include sodium chloride, potassium chloride, and sodium sulfate. The water-soluble solvent is added for preventing caking and crystallization, and the amount of the water-soluble solvent in the mixture is 0.5 to 5 times by weight of the organic pigment, preferably 0.5 to 5 times.
Use 3 weight times. As the water-soluble solvent, for example,
Examples include diethylene glycol, dipropylene glycol and their monoalkyl ethers. In the present invention, the pigment can be refined in the presence of the sulfonic acid group-containing pigment derivative.

The dispersed particle size of the pigment in the aqueous pigment dispersion is as follows:
The average particle size measured by a laser light scattering particle size distribution analyzer is 1
Coarse particles of 0 to 150 nm and 250 nm or more account for 1% by weight or less of all particles, and 50 nm <D50 <150 nm
And 150 nm <D99 <400 nm, preferably 15
0 nm <D99 <250 nm. If the average dispersed particle size is too large, there are drawbacks such as impaired ejection stability and precipitation when used as a recording liquid for ink-jet printing. The smaller the coarse particles, the better.

In the aqueous pigment dispersion of the present invention, the pigment and the sulfonic acid group-containing pigment derivative preferably have the same chemical structure. This not only means that the pigment derivative is of the same type as the pigment to be dispersed, but also that it is advantageous to select a pigment and a pigment derivative of the same type that have the same structure as the basic skeleton. I do. For example, some benzimidazolone pigments have different basic skeletons as shown in the following (1) to (3), and therefore, for the sulfonic acid group-containing pigment derivative, those having the same basic skeleton as the pigment to be dispersed may be selected. preferable. It is considered that when the pigments to be dispersed and the pigment derivative have the same basic molecular skeleton, the adsorbing power of the pigment derivative on the particle surface of the pigment is increased, so that the dispersion stability is improved. Equation (1)

[0023]

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Equation (2)

[0025]

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Equation (3)

[0027]

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The pigment derivative of the present invention has only one sulfonic acid group in the molecule. Pigment derivatives having two or more sulfonic acid groups in the molecule have high solubility in water, so the adsorption force on the pigment particle surface is small, and not only cannot contribute to the dispersion stability of the pigment, but also dissolve in water. Molecules hinder the dispersion stability of the pigment and must be removed as much as possible.

In addition, the storage stability of ink-jet recording liquid over time is also a problem. this is,
It was found that n = 2 (compound containing two sulfonic acid groups) contained in the pigment derivative deteriorated the stability.

The introduction of a sulfonic acid group into the pigment may be effected by, for example, allowing a sulfonating agent such as fuming sulfuric acid, concentrated sulfuric acid, or chlorosulfuric acid to act on the pigment. In the sulfonation, it is preferable to control reaction conditions such as reaction temperature and reaction time so that the ratio of introducing only one sulfonic acid group into the pigment molecule is maximized. However, it is difficult to introduce only one sulfonic acid group into all the pigment molecules in the sulfonation step, and usually, a compound having two or more sulfonic acid groups introduced in one molecule and an unreacted product are not allowed. Obtained as a mixture. Therefore, it is necessary to remove the pigment derivative having two or more sulfonic acid groups in a subsequent step. For example, a pigment derivative containing a sulfonic acid (including a compound containing two or more sulfonic acid groups) is used to disperse the pigment into an aqueous pigment dispersion, and then an ultrafiltration membrane or a semipermeable membrane is used. The pigment derivative containing two or more sulfonic acid groups dissolved in water may be removed by using a reverse osmosis membrane or the like, or only the sulfonic acid group-containing pigment derivative may be dispersed before the pigment is dispersed. The body may be adjusted to remove pigment derivatives having two or more sulfonic acid groups. Further, by boiling the dispersion liquid of the sulfonic acid group-containing pigment derivative or the aqueous pigment dispersion, the solubility of the pigment derivative having two or more sulfonic acid groups in water is increased, and these are then removed by ultrafiltration. Can be removed. In addition, the pigment derivative having two or more sulfonic acid groups is two to the pigment derivative having only one sulfonic acid group.
0% by weight, preferably 15% by weight or less.

Usually, in ultrafiltration, the dispersion used for purification can be used after being heated to some extent as long as the temperature is below the temperature resistance of the ultrafiltration membrane. 5 ° C or more and 80 ° C
Below, preferably within the range of 10 ° C. or more and 60 ° C. or less, it is possible to purify efficiently by using the mixture in a high temperature range.

In the sulfonic acid group-containing pigment derivative, the pigment derivative having only one sulfonic acid group in the molecule is at least 60%, preferably at least 70%, based on the pigment into which the sulfonic acid group is to be introduced. The content of the pigment derivative having two or more sulfonic acid groups is 20% or less, preferably 15% or less.

When the sulfonic acid group-containing pigment derivative of the present invention is a pigment derivative obtained by a coupling reaction such as an azo type or benzimidazolone type, first, a base component or a coupler component having one sulfonic acid group is added. The sulfonic acid group-containing pigment derivative of the present invention can also be obtained by producing and then coupling the two.

Representative examples of the pigment derivative used in the present invention are shown below.

Quinacridone pigment derivative (a)

[0036]

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Diketopyrrolopyrrole pigment derivative (b)

[0038]

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The sulfonic acid group-containing pigment derivative of the present invention comprises
In the aqueous pigment dispersion, at least 15 of all sulfonic acid groups
%, Preferably at least 30%, is present in the free state. That is, the sulfonic acid groups are present in a substantially free state in their entirety, or the sulfonic acid groups in an amount of not more than 85%, preferably not more than 70% of the total, are alkali metal salts such as Na and K, ammonium salts or organic salts. Forms amine salts.

In the present invention, the pigment to which the sulfonic acid group-containing pigment derivative is adsorbed is considered to be negatively charged on the surface of the pigment and dispersed in water due to its electrostatic repulsion. Is preferably a monovalent metal having a high degree of dissociation. In addition, the pigment derivative in the aqueous pigment dispersion of the present invention may be dissolved or dispersed in an aqueous medium in addition to those adsorbed on the pigment, and these unadsorbed pigment derivatives may also affect the stability of the dispersion. It is presumed to have made some contribution. The aqueous pigment dispersion of the present invention increases the water affinity of the pigment surface by modifying the surface of the pigment particles, and requires an external dispersing aid such as a dispersant, a surfactant, and a water-soluble resin. It is a self-dispersion type pigment dispersion which is stable in water without performing.

In the present invention, the amount of the sulfonic acid group-containing pigment derivative used is preferably 3 to 30 parts by weight, more preferably 5 to 25 parts by weight, per 100 parts by weight of the pigment. When the content of the sulfonic acid group-containing pigment derivative with respect to the pigment is smaller than the above value, the dispersion stability of the pigment is insufficient, and when it is too large, the viscosity of the dispersion increases and the dispersibility decreases. The pigment concentration of the aqueous pigment dispersion of the present invention is preferably from 10 to 30% by weight.

In the aqueous pigment dispersion of the present invention, in order to maintain good dispersion stability of the pigment, Ca, M
It is preferable to eliminate divalent or higher valent metal ions such as g, Fe, Ba, Al and Ni, chloride ions and sulfate ions as much as possible. Removal of these contaminating ions can be performed by purifying the aqueous dispersion of the sulfonic acid group-containing pigment derivative or the finally obtained pigment dispersion with ultrafiltration purification, semipermeable membrane purification, ion exchange resin purification, chelate purification, acid washing. And so on. However, since these contaminant ions are mixed in the process of synthesizing the pigment or the pigment derivative or in the process of producing the aqueous pigment dispersion, it is inevitable that a certain amount of these ions exist. According to the present invention, the divalent or higher valent metal ion in the solid content of the aqueous pigment dispersion is 500 ppm or less,
It is preferable that the total of chloride ion and sulfate ion is 100 ppm or less, preferably 70 ppm or less in the aqueous pigment dispersion. If the amount of the contaminating ions is larger than the above value, the tendency of the pigment to aggregate and precipitate cannot be avoided.

The aqueous pigment dispersion of the present invention can be obtained by dispersing a pigment in water in the presence of a sulfonic acid group-containing pigment derivative. At this time, it is preferable that water contains a smaller amount of monovalent metal ions than all the sulfonic acid groups in the sulfonic acid group-containing pigment derivative. That is, the water in which the pigment is dispersed is preferably adjusted to have a pH of 7 to 11, preferably 8 to 10 with a monovalent metal compound. As the water to be used, purified water containing no divalent or higher-valent metal ions, pure water or water equivalent thereto is used.

The dispersing machine used in the dispersion step includes a paint conditioner (manufactured by Red Devil Co., Ltd.), a ball mill, a sand mill (such as "Dyno Mill" manufactured by Shinmaru Enterprises Co., Ltd.), an attritor, and a pearl mill ("DCP Mill" manufactured by Erich Co.) Etc.), a coball mill, a homomixer, a homogenizer ("Clearmix" manufactured by M Technique Co., Ltd.), a wet jet mill ("Genus PY" manufactured by Genus, "Nanomizer" manufactured by Nanomizer) and the like 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.

In the aqueous pigment dispersion of the present invention, since the sulfonic acid group-containing pigment derivative exhibits a high degree of dissociation, if the alkalinity is too strong, the amount of counter ions with respect to the sulfonic acid group becomes excessive, and the pigment derivative dissolves in water. Since the hydrophilicity or hydrophilicity increases, the adsorptivity to the pigment surface decreases, and the dispersion stability decreases. For this reason, the pH of the aqueous pigment dispersion
Is preferably not more than 11.

In the present invention, the surface tension of the aqueous pigment dispersion is 60 mN / m or more, preferably 60 to 75 mN / m.
It can be. This makes it possible to prepare an inkjet recording liquid having a wide range of surface tension. In general, when an activator or an aqueous dispersion resin is used in an aqueous pigment dispersion, the surface tension decreases. Therefore, an aqueous pigment dispersion using an activator or a water-soluble dispersion resin as the pigment dispersant has a surface tension of 25 to 50 mN. / M, the surface tension of the inkjet recording liquid is limited to a narrow range. Further, the aqueous pigment dispersion of the present invention has a pH of 7 to 10,
Conductivity is 600 μS / cm or less and viscosity is 4.0 mPa ·
s or less, preferably 1.0 to 4.0 mPa · s.

The aqueous pigment dispersion of the present invention is preferably contained in an amount of 0.5 to 10 parts by weight, more preferably 2 to 8 parts by weight, per 100 parts by weight of the ink jet recording liquid. 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.

In order to improve the fixability to paper and the water resistance of the ink coating film, the ink jet recording liquid of the present invention is
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. Water-soluble resins such as resins, petroleum resins, and fluorine-based 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 may be contained in an amount of 0.05 to 5 parts by weight, or even 0.1 to 3 parts by weight, per 100 parts by weight of the ink jet recording liquid.

In the ink jet recording liquid of the present invention, an anionic, cationic, nonionic, amphoteric or amphoteric surfactant or a polymeric surfactant is used for adjusting the surface tension and adjusting the permeability to paper. be able to.

Examples of the anionic surfactant include a fatty acid salt, an alkyl sulfate salt, an alkyl aryl sulfonate, an alkyl naphthalene sulfonate, a dialkyl sulfonate, a dialkyl sulfosuccinate, an alkyl diaryl ether disulfonate, and an alkyl phosphate. 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 polymeric 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 the ink jet recording liquid of the present invention are composed of a pigment, a pigment derivative and, if necessary, a water-based resin and other additives in a water-based medium. 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.

In the present invention, the aqueous solvent is an organic solvent which is miscible with water, which prevents drying at the nozzle portion as an ink jet recording liquid, prevents solidification of the recording liquid, and ensures stable jetting of the recording liquid and jetting at the nozzle. It prevents drying over time, and is used alone or as a mixture in the range 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, 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 occurrence 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 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, sodium salt of ethylenediaminetetraacetylic acid, diammonium salt of ethylenediaminetetraacetic acid, 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., and a buffer such as phosphoric acid. Liquids 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 a normal blade.

The mixed recording liquid is preferably 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 is preferably adjusted as a liquid having a viscosity of 0.8 to 15 cps (at 25 ° C.), depending on the type of the recording apparatus. Surface tension is 25 to 73 dyn / cm
It is preferable to adjust to. The pH is not particularly limited, but is preferably weakly alkaline of 7 to 10.

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 clog nozzles, and provides stable ejection for a long period of time. 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 the field of gravure inks, aqueous paints, and other printing inks.

[0067]

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 represent parts by weight. In addition, the measurement of the component ratio of the compound having one sulfonic acid group (n = 1) in the pigment derivative, the content of divalent or higher metal ions, particle size, viscosity, surface tension, conductivity, storage stability, Measurement of foaming property, zeta potential, particle size, viscosity, surface tension, storage stability, ejection stability, water resistance, clogging resistance of ink jet recording liquid, measurement of print quality on plain paper, etc. The procedure was as follows.

(1) Measurement of Component Ratio of Compound Having One Sulfonate Group (n = 1) in Pigment Derivative The pigment derivative was dissolved in a polar solvent such as methanol, dimethylformamide, or water, and reverse phase HPLC (HPLC Column: Separation and measurement using Crestpak C18S manufactured by JASCO Corporation.

(2) Measurement of the amount of metal ions having a valence of 2 or more The pigment, the pigment derivative and the pigment dispersion were dried, and the dried powder was acid-decomposed with an aqueous solution of nitric acid and perchloric acid. The amount of magnesium, the amount of iron, the amount of barium, the amount of aluminum, and the amount of nickel were analyzed, and the total amount thereof was defined as the amount of divalent or higher metal ions.

(3) Measurement of Chloride Ion Content and Sulfate Ion Content The pigment dispersion was diluted with purified water to a measurable range, and an ion chromatograph (Dionex 2010) was used.
i), column (IonPacAS4 manufactured by DIONEX)
Using A), the chloride ion and sulfate ion content of the pigment dispersion was measured.

(4) Average Particle Diameter of Pigment The pigment was dispersed in a solvent, applied onto a cell, and observed by a transmission electron microscope (TEM) to determine the average particle diameter.

(5) Dispersion Particle Size D50 and D99 were measured using a laser diffraction type particle size distribution meter (“Microtrack UPA” manufactured by Nikkiso Co., Ltd.).

(6) Viscosity In the low viscosity region, a vibrating viscometer (“VM-1” manufactured by Yamaichi Electric Co., Ltd.)
A "), the viscosity at 25 ° C. was measured using a B-type viscometer for the medium viscosity region and above.

(7) Surface tension The surface tension was measured using a surface tensiometer (“CBVP-Z” manufactured by Kyowa Interface Science Co., Ltd.).
The surface tension at 5 ° C. was measured.

(8) Conductivity Measurement The conductivity at 25 ° C. was measured using a conductivity meter (“DS-12” manufactured by HORIBA).

(9) Storage Stability The aqueous pigment dispersion exhibited a storage period in which the change in particle size at 60 ° 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 60 ° 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).

(10) Foaming property The aqueous pigment dispersion was placed in a 50 ml screw-cap screw tube.
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).

(11) Measurement of Zeta Potential The pigment dispersion was diluted with purified water to a measurable range, and the zeta potential of the pigment dispersion was measured with a zeta potential measuring device (“Zeta PALS” manufactured by Nikkiso Co., Ltd.). (12) 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).

(13) Water resistance The printed matter obtained in (12) was wet with water, rubbed with a finger, and visually evaluated for changes in the printed matter (○: no ink bleeding or peeling was observed). ×: Bleeding and peeling of the ink are observed).

(14) Clogging resistance In the same manner as in (12), the cap of the printer was removed after printing, and printing was performed again one hour later, and the presence or absence of clogging was evaluated (（: no nozzle clogging, × : Clogged nozzle).

(15) Print Quality The recording liquid for ink jet is packed in a cartridge of an ink jet printer (“PM-750C” manufactured by Epson), and MS is printed on plain paper (“4024” manufactured by Xerox).
Printing was performed at a character size of 10 P by the morning, and the feathering property of the ink was evaluated. (○: almost no feathering, character of “dragon” can be distinguished without blurring, ×: there is feathering, and character of “dragon” is difficult to distinguish due to blurring.

Example 1 (Quinacridone pigment) (Production of pigment derivative (a)) I. Pigment Violet 19 200 parts in 98% by weight sulfuric acid 2000 parts 2
Added below 0 ° C. Next, the mixture was heated and stirred at 85 ° C. for 2.5 hours, and then poured into ice water to precipitate. Filter the precipitate,
Washed with saline and water paste of sulfonated pigment 150
0 parts (300 parts when dried) were obtained. The n = 1 (compound containing one sulfonic acid group) component ratio of the sulfonated product of this pigment is 59%, the n = 2 (compound containing two sulfonic acid groups) component ratio is 22%, and the rest is unsubstituted. Body. next,
The water paste of the sulfonated pigment was reslurried with ion-exchanged water to prepare a 2% by weight aqueous dispersion (150 L), and the mixture was boiled for 3 hours. The aqueous dispersion was returned to normal temperature, and ultrafiltration purification was performed using 150 L of 4 times the amount of ion-exchanged water. The steps of boiling and ultrafiltration were repeated until the component ratio of n = 2 (compound containing two sulfonic acid groups) of the sulfonated pigment reached 3%. The n = 1 (compound containing one sulfonic acid group) component ratio of the sulfonated product of the pigment finally obtained is 72%, and the n = 2 (compound containing two sulfonic acid groups) component ratio is 3%. And the rest were unsubstituted. The content of divalent or higher valent metal ions was 730 ppm, and the total content of chloride ions and sulfate ions was 56 ppm. Further, from the results of the emission spectrometry, the sulfur content and the sodium content were each 13600.
ppm (425 μmol / g) and 9900 ppm (247
μmol / g), the neutralization ratio was 58%. This pigment derivative (a) was concentrated to prepare an aqueous dispersion having a concentration of 3% by weight.

(Preparation of Aqueous Pigment Dispersion) I. Pigment Red 122 (the content of metal ions having a valence of 2 or more is 38
20 g, containing 5 ppm), the above-mentioned pigment derivative (a)
Of an aqueous dispersion of 80 g and ion-exchanged water 60 g,
Using zirconia beads as a medium, the mixture was dispersed for about 7 hours using a paint shaker to obtain an aqueous pigment dispersion.

Example 2 (Quinacridone-based pigment) (Preparation of aqueous pigment dispersion) I. Pigment Red 1
22 (containing 400 ppm of a metal ion having a valence of 2 or more), 60 g of an aqueous dispersion of the pigment derivative (a), and 60 g of ion-exchanged water were mixed so that the neutralization ratio of the pigment derivative became 100%. 9 g of 2% by weight triethanolamine was added, and the mixture was dispersed for about 7 hours using a zirconia bead as a medium using a paint shaker to obtain an aqueous pigment dispersion.

Example 3 (Diketopyrrolopyrrole-based pigment) (Production of pigment derivative (b)) I. Pigment Red 264 (200 parts) is added to 1500 parts of 22% by weight fuming sulfuric acid.
Added below 0 ° C. Next, the mixture was heated and stirred at 75 ° C. for 5 hours, and then poured into 3500 parts of ice water to precipitate. The precipitate was filtered and washed with saline to obtain 1500 parts of a water paste of a sulfonated pigment (271 parts when dried). The n = 1 (compound containing one sulfonic acid group) component ratio of the sulfonated product of this pigment is 70%, the n = 2 (compound containing two sulfonic acid groups) component ratio is 16%, and the rest is unsubstituted. Body. Next, the aqueous paste of the sulfonated pigment was reslurried with ion-exchanged water to prepare a 2% by weight aqueous dispersion (136%).
L) and boiled for 3 hours. This aqueous dispersion was returned to normal temperature, and ultrafiltration was performed using 136 L of ion-exchanged water. The boiling and ultrafiltration were repeated until the component ratio of n = 2 (compound containing two sulfonic acid groups) of the sulfonated product of the pigment became 4%. The n = 1 (compound containing one sulfonic acid group) component ratio of the sulfonated product of the finally obtained pigment is 82%, and the n = 2 (compound containing two sulfonic acid groups) component ratio is 4%. And the rest were unsubstituted. The content of divalent or higher metal ions is 47
8 ppm, total content of chloride ion and sulfate ion is 7
It was 0 ppm. Furthermore, from the emission spectroscopy results,
Sulfur content and sodium content are each 15300ppm
(478 μmol / g) and 13000 ppm (325 μmo
l / g), the neutralization ratio was 68%. This pigment derivative (a) was concentrated to prepare an aqueous dispersion having a concentration of 3% by weight.

(Preparation of Aqueous Pigment Dispersion) I. Pigment Red 264 (477pp for metal ions with a valence of 2 or more)
20 g), an aqueous dispersion 80 of the pigment derivative (b)
g and 60 g of ion-exchanged water were mixed and dispersed for about 7 hours using a zirconia bead as a medium using a paint shaker to obtain a pigment dispersion.

Example 4 (Diketopyrrolopyrrole-based pigment) (Preparation of aqueous pigment dispersion) I. Pigment Red 2
64 (containing 520 ppm of divalent or higher metal ions)
20 g, 60 g of an aqueous dispersion of the pigment derivative (b) of Example 3
And 60 g of ion-exchanged water, 11 g of 2% by weight triethanolamine was added so that the neutralization ratio of the pigment derivative became 100%, and the mixture was dispersed for about 7 hours using a zirconia bead as a medium with a paint shaker to obtain a pigment dispersion. I got

Comparative Example 1 (Quinacridone Pigment) (Production of Pigment Derivative (c)) A water paste of a sulfonated pigment was prepared in the same manner as in Example 1 except that boiling and ultrafiltration were not performed. I got N = 1 (compound containing one sulfonic acid group) component ratio of the sulfonated product of this pigment is 59%, and n = 2 (2
The compound ratio was 22%, and the remainder was unsubstituted. The content of divalent or higher metal ions is 760p
pm, total content of chloride ion and sulfate ion is 70p
pm. Further, from the results of the emission spectrometry, the sulfur content and the sodium content were 24500 ppm (7
65 μmol / g) and 15900 ppm (398 μmol / g)
Therefore, the neutralization ratio was 52%. This pigment derivative (c) was concentrated to prepare an aqueous dispersion having a concentration of 3% by weight.

(Preparation of Aqueous Pigment Dispersion) I. Pigment Red 122 (with a divalent or higher valent metal ion content of 44)
20 g, containing the above-mentioned pigment derivative (c)
Of an aqueous dispersion of 80 g and ion-exchanged water 60 g,
Using zirconia beads as a medium, the mixture was dispersed for about 7 hours using a paint shaker to obtain an aqueous pigment dispersion.

Comparative Example 2 (Quinacridone Pigment) (Preparation of Aqueous Pigment Dispersion) I. Pigment Red 1
22 (containing 420 ppm of a metal ion having a valence of 2 or more), 60 g of an aqueous dispersion of the pigment derivative (c) of Comparative Example 1 and 60 g of ion-exchanged water were mixed, and 2% by weight was mixed.
10 g of triethanolamine was added, and the mixture was dispersed for about 7 hours using a zirconia bead as a medium using a paint shaker to obtain an aqueous pigment dispersion.

Comparative Example 3 (Diketopyrrolopyrrole Pigment) (Production of Pigment Derivative (d)) The same procedure as in Example 3 was carried out except that boiling and ultrafiltration purification were not carried out. A water paste of the compound was obtained. The n = 1 (compound containing one sulfonic acid group) component ratio of the sulfonated product of this pigment is 70%, the n = 2 (compound containing two sulfonic acid groups) component ratio is 16%, and the rest is unsubstituted. Body. The content of divalent or higher metal ions is 50
0 ppm, total content of chloride ion and sulfate ion is 7
It was 8 ppm. Furthermore, from the emission spectroscopy results,
23600ppm of sulfur and sodium respectively
(737 μmol / g) and 17800 ppm (442 μmo
l / g), the neutralization ratio was 60%. This pigment derivative (d) was concentrated to prepare a 3% by weight aqueous dispersion.

(Preparation of Aqueous Pigment Dispersion) I. Pigment Red 264 (480 ppm of divalent or higher metal ions)
20 g), 80 g of the aqueous dispersion of the above-mentioned pigment derivative (d), and 60 g of ion-exchanged water were mixed and dispersed using a paint shaker with zirconia beads as a medium for about 7 hours to obtain a pigment dispersion.

Comparative Example 4 (Diketopyrrolopyrrole-based pigment) (Preparation of aqueous pigment dispersion) I. Pigment Red 2
64 (contains 505 ppm of divalent or higher metal ions)
20 g, 60 g of an aqueous dispersion of the pigment derivative (d) of Example 3
And 60 g of ion-exchanged water, and 8 g of 2 wt% triethanolamine was added so that the neutralization ratio of the pigment derivative was 100%. The mixture was dispersed for about 7 hours using a zirconia bead as a medium and a paint shaker to obtain a pigment dispersion. I got Table 1 shows the evaluation results of the aqueous pigment dispersions obtained in each example.

[0094]

[Table 1]

Examples 5 to 8 and Comparative Examples 5 to 8 Raw materials having the compositions shown in Table 2 were charged into a stirring tank, stirred and mixed by a disper, and then filtered through a 0.8 μm membrane filter to obtain an ink jet recording. A liquid 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.

[0096]

[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 ", solid content about 70% Fungicide:" Placcel GXL "manufactured by Zeneca Corporation

[0098]

The aqueous pigment dispersion of the present invention comprises a step of sulfonating a pigment to introduce one or more sulfonic acid groups in a molecule, and a step of preparing a pigment derivative having two or more sulfonic acid groups from a reaction product. A step of concentrating the sulfonic acid group-containing pigment derivative having only one sulfonic acid group by removing using an ultrafiltration method, and containing the sulfonic acid group-containing pigment derivative in the presence of the sulfonic acid group-containing pigment derivative obtained in the step. Dispersing a pigment having a molecular structure of a pigment of the same type as the pigment derivative in water, by using a method for producing an aqueous pigment dispersion, which has a high pigment concentration range, a low conductivity, and a high surface. An aqueous pigment dispersion having tension and excellent in stability over time was obtained. The present invention also provides: a high-quality recorded image without bleeding; a high drying and fixing speed of the recording liquid; a stable recording liquid without clogging in a nozzle or a recording liquid distribution path. Aqueous pigments that can be used in aqueous inkjet recording liquids that meet the required characteristics, such as discharge of liquid, good storage stability of recording liquid, high recording density, good weatherability and good water resistance of printed matter A method for producing a dispersion could be provided.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Takashi Negishi 2-3-13 Kyobashi, Chuo-ku, Tokyo Inside Toyo Ink Manufacturing Co., Ltd. (72) Inventor Seiji 2-3-1-13 Kyobashi, Chuo-ku, Tokyo F-term (reference) in Toyo Ink Manufacturing Co., Ltd. 4J037 EE28 FF15 4J039 BA17 BC33 BE01 EA14 EA35 EA38 GA24

Claims (8)

[Claims] 1. A step of sulfonating a pigment to introduce one or more sulfonic acid groups into a molecule, and removing a pigment derivative having two or more sulfonic acid groups from a reaction product to remove only one sulfonic acid group. Concentrating the sulfonic acid group-containing pigment derivative having, and dispersing, in water, a pigment having the same molecular structure as the sulfonic acid group-containing pigment derivative in the presence of the sulfonic acid group-containing pigment derivative obtained in the step. A process for producing an aqueous pigment dispersion. 2. The method according to claim 1, wherein the step of removing the pigment derivative having two or more sulfonic acid groups from the reaction product is an ultrafiltration method. 3. The method according to claim 1, wherein the pigment is a condensed polycyclic pigment. 4. The production method according to claim 1, wherein the dispersion is carried out in water containing a monovalent metal ion, ammonia or an organic amine. 5. The production method according to claim 1, wherein the content of divalent or higher valent metal ions in the solid content of the aqueous pigment dispersion is 500 ppm or less. 6. The pigment has an average primary particle diameter of 150 n.
The method according to any one of claims 1 to 5, wherein m is not more than m. 7. The method according to claim 1, wherein the pigment has a particle diameter of 50 nm <50 nm.
D50 <150nm and 150nm <D99 <400n
7. The method according to claim 1, wherein m is m. 8. An aqueous pigment dispersion obtained by the production method according to claim 1.