JP2002220557A - Process printing ink set - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a water-based ink set containing pigments as the corresponding colorants, excellent in balance between the corresponding hues of the pigments to be used for process three primary colors, with wide reproducible color range, and capable of reproducing high-density and high-grade full-color image. SOLUTION: This process printing ink set contains, as the corresponding colorants, self-dispersible pigments dispersed in an aqueous medium through the electrostatic repulsion between the acidic functional groups introduced onto the surface of each of the particles of each of the pigments, and is characterized by comprising an yellow ink with a benzimidazolone yellow pigment as the 1st colorant, a cyanogen ink with a phthalocyanine blue pigment as the 2nd colorant and a fuchsine ink with a quinacridone red pigment as the 3rd colorant.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aqueous ink set having excellent water dispersibility, dispersion stability with time, color reproducibility, ejection stability at a nozzle when used as an inkjet ink, and the like.

[0002]

2. Description of the Related Art Conventionally, process printing using oil-based ink has been performed in offset printing and gravure printing. In this process printing, a monoazo lake pigment is used for the magenta ink, and a disazo pigment is used for the yellow ink. However, in a water-based ink such as an ink-jet ink, when a pigment having excellent light resistance, water resistance, etc. is used as a coloring agent, it is necessary to stabilize the pigment in dispersion in an aqueous medium and obtain practicality as an ink. There are many problems as follows. For this reason, it has been difficult to select a pigment having both practicality of dispersion stability and a pigment as a colorant for a process printing colorant and an aqueous ink.

[0003] Techniques for dispersing pigments in aqueous media are known in the art. For example, a water-based ink or a water-based paint has a pigment 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.

JP-A-56-155261 and JP-A-56-155262 disclose aqueous pigment dispersions 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 paint and ink cause problems such as color mixing and bleeding.

In the case of ink-jet inks, the nozzle diameter is becoming finer as the resolution of the printer is increased, and accordingly, it is necessary to reduce the particle diameter of the pigment particles. 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 ink, such as ejection stability from a nozzle, re-dissolution (dispersion) properties, and color development after printing. Was.

[0006]

DISCLOSURE OF THE INVENTION The present invention uses a pigment as a colorant to reproduce a full-color image of a high density and high quality with a wide balance of reproducible color gamut, excellent color balance of the pigment used in the three primary colors of the process. The present invention provides a set of water-based inks that can be used. Further, the present invention provides a water-based ink that uses a pigment having excellent light fastness and water fastness, has good storage stability of the ink, does not clog the ink in a nozzle or a recording liquid flow path, and can discharge the ink stably. provide.

[0007]

According to the present invention, there is provided a water-based ink for process printing using a self-dispersion type pigment which is dispersed in an aqueous medium by electrostatic repulsion of an acidic functional group introduced on the surface of a pigment particle as a coloring agent. Wherein the set of inks comprises a yellow ink using a benzimidazolone yellow pigment as a colorant, a cyan ink using a phthalocyanine blue pigment as a colorant, and a magenta ink using quinacridone red pigment as a colorant. To a set of process printing inks.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The pigment used as a colorant in the ink set of the present invention is a benzimidazolone yellow pigment as a yellow ink, a phthalocyanine blue pigment as a cyan ink, and a quinacridone red pigment as a magenta ink. When a black ink is included, carbon black is preferred as the colorant.

More specifically, as a benzimidazolone yellow pigment, C.I. I. Pigment Yellow 180,
C. I. Pigment Yellow 151 or C.I. I. Pigment Yellow 154 is C.I. I. Pigment Blue 15: 3 is used as a quinacridone red pigment as C.I. I. Pigment Red 122 or C.I. I. Pigment Violet 19 is preferably used.

[0010] The dispersed particle diameter of the pigment particles to be incorporated in the colored ink of the present invention is such that the average particle diameter measured by a laser light scattering particle size distribution analyzer is 10 to 150 nm, and coarse particles having a diameter of 250 nm or more account for 1% by weight of all the particles. Hereinafter, also, 50 nm <D
50 <150 nm and 150 nm <D99 <400 nm
Preferably, 150 nm <D99 <250 nm. If the average dispersed particle size is too large, when used as an inkjet recording liquid, there are disadvantages such as impaired ejection stability and precipitation, and the smaller the coarse particles, the better. In order to adjust the pigment having such a particle size, it is preferable to perform a fine treatment of the pigment by performing wet grinding or dry grinding such as salt milling or solvent milling on a crude pigment or a pigment of pigment quality.

In the present invention, the term "self-dispersion type" means that an acidic functional group is introduced into pigment particles to increase the water affinity of the pigment surface, and that the acidic functional group undergoes ion dissociation in an aqueous medium to cause electrostatic repulsion. , A property of being stably dispersed in water without the need for an external dispersing aid such as a dispersant, a surfactant, or a water-soluble resin. However, in order to improve the dispersion stability of the pigment, a necessary amount of a surfactant may be blended. The amount of surfactant incorporated for this purpose is not more than 20% by weight, based on the pigment.

In order to introduce an acidic functional group into the pigment particles in the present invention, an acidic functional group may be directly introduced into the surface of the pigment particles by chemical means, or the same or similar chemical structure as the pigment may be introduced. An acidic functional group may be introduced into the compound to be adsorbed on the surface of the pigment particles. Whichever method is employed, it is important to modify only the surface of the pigment. Examples of the acidic functional group include a carboxylic acid group, a sulfonic acid group, and a phosphoric acid group.

The self-dispersible pigment of the present invention can be obtained, for example, by adsorbing a pigment derivative having a sulfonic acid group introduced into a pigment having the same chemical structure as the pigment to be dispersed, on the surface of the pigment particles. Adsorption is achieved by mixing the pigment and the sulfonic acid group-containing pigment derivative in water.
The amount of the sulfonic acid group-containing pigment derivative to be used is preferably 3 to 30 parts by weight, more preferably 5 to 25 parts by weight, based on 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 larger, the viscosity of the dispersion increases and the dispersibility decreases. The concentration of the self-dispersion pigment in the aqueous dispersion in which the self-dispersion pigment is concentrated is 10 to 30% by weight.

The sulfonic acid group-containing pigment derivative preferably has only one sulfonic acid group in the molecule. 2 in the molecule
Pigment derivatives having two or more sulfonic acid groups have a high solubility in water, so the adsorption force on the pigment particle surface becomes small, and not only cannot contribute to the dispersion stability of the pigment, but also the molecules dissolved in the water It is necessary to remove as much as possible because it hinders dispersion stability.

In order to introduce a sulfonic acid group into the pigment, for example, a sulfonating agent such as fuming sulfuric acid, concentrated sulfuric acid or chlorosulfuric acid may be applied to 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 to form an aqueous pigment dispersion, and then to water by a technique such as ultrafiltration. The pigment derivative containing two or more sulfonic acid groups dissolved in the sulfonic acid group may be removed, or a dispersion of only the sulfonic acid group-containing pigment derivative may be adjusted before the dispersion of the pigment. More than one pigment derivative may be removed. or,
The sulfonic acid group-containing pigment derivative is such that the derivative having only one sulfonic acid group in the molecule is 60% or more, preferably 70% or more, based on the pigment into which the sulfonic acid group is to be introduced, and 2 The content of the pigment derivative having a sulfonic acid group is 20% or less, preferably 15% or less.

In the present invention, the acidic functional group introduced on the pigment particle surface forms an alkali metal salt, an ammonium salt or an organic amine salt in an aqueous dispersion or in an ink. Examples of the organic amine include dimethylamine, trimethylamine, monoethylamine, diethylamine, triethylamine, propylamine, isopropylamine, dipropylamine, butylamine, isobutylamine, se
c-butylamine, monoethanolamine, diethanolamine, triethanolamine, triisopropanolamine, isopropanolamine, dimethylethanolamine, diethylethanolamine, N-butyldiethanolamine, N, N-dimethyl-1,3-diaminopropane, N, N -Diethyl-1,3-diaminopropane and the like.

In the ink of the present invention, in order to maintain good dispersion stability of the pigment, Ca, Mg, Fe, B
It is preferable to eliminate metal ions having two or more valences such as a, Al, and Ni, chloride ions, and sulfate ions as much as possible. Removal of these contaminating ions can be achieved by ultrafiltration purification, semi-filtration, purification of a concentrated aqueous dispersion of an acidic functional group-containing pigment derivative, an aqueous dispersion of a pigment chemically treated with a surface modification, or an aqueous dispersion of a concentrated pigment. It can be achieved by performing membrane purification, ion exchange resin purification, chelate purification, acid washing, and the like.

The ink of the present invention is preferably prepared by preparing a concentrated aqueous dispersion of a self-dispersible pigment, and then formulating the ink by blending the aqueous dispersion with other additives. The concentrated aqueous dispersion of the self-dispersible pigment is, for example,
It can be obtained by subjecting a pigment to be dispersed in the presence of an acidic functional group-containing pigment derivative to a dispersion treatment in water containing a base such as an alkali metal, ammonia or an organic amine. That is, the water for dispersing the pigment is adjusted to have a pH of preferably 7 to 11, more preferably 8 to 10 with the above base. 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 dispersing 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.

An aqueous resin can be used in the ink of the present invention in order to improve the fixing property to paper and the water resistance of the ink coating film. 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,
Examples include water-soluble resins and water-dispersible resins such as epoxy resins, butadiene resins, petroleum resins, and fluorine 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 used in an amount of 0.05 to 20 parts by weight, preferably 0.1 to 20 parts by weight, per 100 parts by weight of the ink.
1 to 10 parts by weight may be contained.

The ink of the present invention may contain an anionic, cationic, nonionic or amphoteric surfactant to enhance the dispersion stability of the pigment, or to adjust the surface tension of the ink, or to adjust the permeability to paper. And a polymeric surfactant.

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,
Polyoxyethylene sorbitol fatty acid ester, glycerin fatty acid ester, polyoxyethylene fatty acid ester, polyoxyethylene alkylamine, fluorine-based,
Examples include nonionic surfactants such as silicon-based surfactants.

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 medium of the present invention represents water or a mixture of an organic solvent miscible with water, and the water refers to ion-exchanged water or distilled water from which metal ions and the like have been removed.

An organic solvent miscible with water prevents drying at the nozzle portion and solidification of the recording liquid when the ink is used as an ink jet ink, thereby preventing stable ink jetting and drying over time at the nozzle. 1 to 50% by weight, preferably 2 to 50% by weight of the ink.
It is used in the range of ２５25% by weight.

Examples of the water-miscible organic solvent include ethylene glycol, diethylene glycol, propylene glycol, 1,3-propanediol, triethylene glycol, polyethylene glycol, glycerin, tetraethylene glycol, dipropylene glycol, ketone alcohol, and diethylene glycol monoethylene glycol. Butyl ether, ethylene glycol monobutyl ether, triethylene glycol monobutyl ether, ethylene glycol monoethyl ether, 1,2-hexanediol, N
-Methyl-2-pyrrolidone, 2,4,6-hexanetriol, tetrafurfuryl alcohol, 4-methoxy-
4-methylpentanone and the like can be exemplified. For the purpose of accelerating the drying of the ink, methanol, ethanol,
Alcohols such as isopropyl alcohol can also be used.

In the ink of the present invention, various additives as described below can be used as needed. When the ink substrate is a permeable material such as paper, a penetrant can be added to accelerate the penetration of the ink into the paper and the apparent dryness. As a penetrant, glycol ethers such as diethylene glycol monobutyl ether,
Alkylene glycol, polyethylene glycol monolauryl ether. Sodium lauryl sulfate, sodium dodecylbenzene sulfonate, sodium oleate,
Sodium dioctyl sulfosuccinate and the like can be used. These are used in the ink in the range of 0 to 5% by weight, preferably 0.1 to 5% by weight. 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 molds 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 ink.
Is preferably included in the range.

The chelating agent blocks metal ions in the ink, prevents the deposition of metal at the nozzle portion and the deposition of insoluble substances in the ink, etc., and comprises ethylenediaminetetraacetic acid. For example, 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 the ink in the range of 0.005 to 0.5% by weight.

Further, in order to adjust the pH of the ink and obtain the stability of the ink or the stability with the ink piping in the recording apparatus, a pH adjuster such as an amine, an inorganic salt or ammonia, and a buffer such as phosphoric acid are used. be able to. When the ink is used for ink jet, an antifoaming agent can be added to prevent circulation or movement of the ink at the time of discharging the ink or inside the piping, or generation of bubbles during the production of the ink.

The ink of the present invention comprises a pigment-concentrated aqueous dispersion and optionally an aqueous resin dispersed in an aqueous medium,
It can be produced by 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.

It is preferable that the mixed ink is sufficiently filtered before or after dilution through 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 ink 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 a weak alkaline of 7 to 10 is preferable.

The ink of the present invention has excellent water resistance and storage stability when used as an ink-jet ink.
There is no clogging in the nozzle, and stable ejection is provided for a long 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. The ink of the present invention can be used as a printing ink such as an inkjet ink or a gravure ink.

[0039]

The present invention will be described below with reference to examples. In the examples, parts represent parts by weight. Incidentally, the component ratio in the pigment derivative containing a sulfonic acid group, the dispersion average particle size of the pigment in the pigment derivative ink, viscosity, surface tension, storage stability, ejection stability, water resistance, evaluation of clogging resistance, The measurement of print quality on plain paper was performed by the following method.

(1) Component Ratio in Pigment Derivative Having Sulfonic Acid Group The pigment derivative is dissolved in a polar compound such as methanol, dimethylformamide, or water, and reverse phase HPLC (column:
Separation and measurement were performed using Crest Pack C185 manufactured by JASCO Corporation. (2) Dispersion average particle diameter The dispersion average particle diameter was measured using a laser diffraction type particle size distribution meter (“Microtrack UPA” manufactured by Nikkiso Co., Ltd.).

(3) Viscosity In the low viscosity region, a vibrating viscometer (“VM-1” manufactured by Yamaichi Electric Co., Ltd.)
A ") was used to measure the viscosity at 25 ° C.

(4) Storage stability The 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; ×: The change in particle size is 15 nm or more or the change in viscosity is 0.2 cps or more).

(5) Discharge Stability The ink jet ink was packed in a cartridge of an ink jet printer (“HG-5130” manufactured by Epson) and printed on plain paper (“K” manufactured by Xerox) to evaluate the discharge stability. did. (○: 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).

(6) Water resistance The printed matter obtained in the same manner as in (5) was wetted with water, rubbed with a finger, and visually evaluated for changes in the printed matter (○: bleeding and peeling of ink). Not recognized, x: bleeding and peeling of ink are recognized).

(7) Clogging resistance After printing was performed in the same manner as in (5), the cap of the printer was removed, and after 1 hour, printing was performed again to evaluate the presence or absence of clogging (評 価: no clogging of nozzles) , X: nozzle clogged).

(8) Printing Quality The ink-jet ink is packed in a cartridge of an ink-jet printer (“PM-750C” manufactured by Epson) and printed on plain paper (“4024” manufactured by Xerox) in a character size of 10P by MS Mincho. Then, 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.

Production Example 1 (Benzimidazolone Yellow Pigment) (Production of Pigment Derivative) I. Pigment Yellow 18
050 parts of 95% by weight sulfuric acid was added at 10 ° C. or lower. Next, the mixture was heated and stirred at 15 ° C. for 2 hours, and then poured into ice water to precipitate. The precipitate was filtered and washed with 5% by weight saline to obtain 294 parts of an aqueous paste of a sulfonic acid group-containing pigment derivative (53 parts when dried). This sulfonic acid group-containing pigment derivative had a derivative component ratio having one sulfonic acid group of 90%, a derivative component ratio having two sulfonic acid groups of 8%, and the rest was unsubstituted. Next, the water paste of this pigment derivative was reslurried with ion-exchanged water to obtain 1% by weight.
It was adjusted to an aqueous dispersion, and desalted and washed using an ultrafilter.
Next, 10 parts of the dried pigment derivative purified above was added to a solution of 2.0 parts of sodium hydroxide in 200 parts of ion-exchanged water, and 15 parts of triethanolamine was added. Then, the resultant was washed with ion-exchanged water to form a triethanolamine salt, and an aqueous dispersion having a concentration of 3% by weight of the triethanolamine salt of the pigment derivative was prepared. (Preparation of aqueous dispersion of pigment) C.I. having an average primary particle size of 80 nm. I. 20 g of CI Pigment Yellow 180, 53 g of the aqueous dispersion of the pigment derivative obtained above and 59 g of ion-exchanged water are mixed, and triethanolamine is added so that the pH of the mixed solution becomes 9.0, and zirconia beads are used as a medium. The mixture was dispersed using a paint shaker for about 5 hours to obtain an aqueous dispersion (Y) of a pigment.

Production Example 2 (Phthalocyanine blue pigment) (Production of pigment derivative) I. Pigment Blue 15:
3 200 parts were added to 1500 parts of 22% by weight fuming sulfuric acid and 400 parts of 98% by weight sulfuric acid at 20 ° C. or lower. Next, the mixture was heated and stirred at 47 ° C. for 5 hours, and then poured into 3500 parts of ice water to precipitate. The precipitate was filtered and washed with 6000 parts of 5% by weight hydrochloric acid to obtain 1520 parts of a water paste of a sulfonated pigment (310 parts when dried). In the pigment derivative containing a sulfonic acid group, the ratio of the derivative component containing one sulfonic acid group is 90%, and the ratio of the derivative component containing two sulfonic acid groups is 8%.
%, And the rest were unsubstituted. Next, the aqueous paste of the pigment derivative was reslurried with ion-exchanged water to prepare a 1% by weight aqueous dispersion, followed by desalting and washing, and then concentrated to prepare a 3% by weight aqueous solution of the pigment derivative. . (Preparation of aqueous dispersion of pigment) C.I. having an average primary particle size of 80 nm. I. Pigment Blue 15: 3 20 g, 70 g of a 3% aqueous dispersion of the pigment derivative obtained above and 40 g of ion-exchanged water were mixed, and triethanolamine was added so that the pH of the mixture became 9.0, and zirconia was added. The beads were used as a medium and dispersed for about 7 hours using a paint shaker to obtain an aqueous dispersion (C) of the pigment. Production Example 3 (Quinacridone red pigment) (Production of pigment derivative) I. Pigment Violet 19 (200 parts) was added to 2,000 parts of 98% by weight sulfuric acid at 20 ° C. or lower. Next, the mixture was heated and stirred at 80 ° C. for 2.5 hours, and then poured into ice water to precipitate. The precipitate was filtered and washed with saline to obtain 1520 parts (310 parts when dried) of an aqueous paste of a pigment derivative containing sulfonic acid. This pigment derivative has a derivative component ratio of 95% containing one sulfonic acid group,
The derivative component ratio containing two sulfonic acid groups was 4%, and the rest were unsubstituted. Next, the aqueous paste of the pigment derivative was reslurried with ion-exchanged water to prepare an 8% by weight aqueous dispersion, and after desalting and washing, ion-exchanged water was added to disperse the pigment derivative in water at a concentration of 3% by weight. The liquid was adjusted. (Adjustment of aqueous dispersion of pigment) C.I. having an average primary particle size of 90 nm. I. 20 g of CI Pigment Red 122, 55 g of the aqueous dispersion of the pigment derivative obtained above and 60 g of ion-exchanged water, ammonia water is added so that the pH of the mixed solution becomes 9.0, and the mixture is painted using zirconia beads as a medium. The mixture was dispersed using a shaker for about 7 hours to obtain a pigment aqueous dispersion (M1).

Production Example 4 (Quinacridone Red Pigment) (Production of Pigment Derivative) I. Pigment Violet 19 is C.I. I. Pigment Red 12
A water paste of a pigment derivative having a sulfonic acid group was obtained by sulfonation in the same manner as in Production Example 3 except that the composition was changed to 2. In this pigment derivative, the ratio of the derivative component having one sulfonic acid group is 90%, and the ratio of the derivative component having two sulfonic acid groups is 3%.
%, And the rest were unsubstituted. Next, the aqueous paste of the pigment derivative was reslurried with ion-exchanged water to prepare an 8% by weight aqueous dispersion, and after desalting and washing, ion-exchanged water was added to disperse the pigment derivative in water at a concentration of 3% by weight. The liquid was adjusted. (Preparation of aqueous dispersion of pigment) C.I. having an average primary particle size of 90 nm. I. Pigment Red 122 (20 g) is mixed with the above-obtained aqueous dispersion of the pigment derivative (110 g) and ion-exchanged water (50 g), ammonia water is added so that the pH of the mixture becomes 9.0, and zirconia beads are used as a medium to paint. The mixture was dispersed using a shaker for about 7 hours to obtain an aqueous dispersion of a pigment (M2).

Production Example 5 (Carbon Black) Carbon black "Black Pearls 8" manufactured by Cabot Corporation
00 ”was added to 100 parts of fuming nitric acid.
Heat and stir for hours, then cool, ion-exchange water 100
0 parts were added and the decantation was repeated 10 times, followed by desalting and washing, and then neutralized with an aqueous sodium hydroxide solution.
After adjusting the pH to 8, the mixture was concentrated to a pigment content of 20% to obtain a pigment aqueous dispersion (BK). Example A raw material having the composition shown in Table 1 was charged into a stirring tank, stirred and mixed by a disper, and then filtered through a 0.8 μm membrane filter to obtain an inkjet ink. The particle size and viscosity of the obtained ink-jet ink were measured, and storage stability, ejection stability, water resistance, and clogging resistance were evaluated. Table 1 shows the results.

[0051]

[Table 1] ¹⁾ Water-soluble resin solution: styrene / acrylic water-soluble resin aqueous solution, Johnson Polymer J-62, manufactured by Johnson Polymer Co., Ltd., solid content of about 34% ²⁾ DEGE: diethylene glycol monobutyl ether ³⁾ Activator: Nippon Emulsifier Co., Ltd. ⁴⁾ Anti-fungal agent: “Placcel GXL” manufactured by Zeneca Corporation

Printing Test 1 Using the yellow ink (Y ink), cyan ink (C ink), magenta ink (MI ink), and black ink (B ink) obtained above, an inkjet printer (“PM” manufactured by Epson Corporation) was used. -750C ") cartridge and plain paper (" 402 "manufactured by Xerox Corporation).
4)), full-color printing with good reproducibility was obtained.

Printing Test 2 When full-color printing was performed in the same manner as in Example 1 except that the M1 ink was changed to the M2 ink in the printing test 1, full-color printing with good reproducibility was obtained.

[0054]

The ink set of the present invention uses a pigment as a colorant and is excellent in the hue balance of the pigment used in the three primary colors of the process, so that a wide color gamut can be reproduced and a high-density and high-quality full-color image can be reproduced. . Further, the pigment used for coloring the ink of the present invention retains self-dispersibility due to the acidic functional group introduced on the surface of the pigment particles, so that the storage stability of the ink is good, and the ink is clogged with the nozzle or the recording liquid flow path. Without this, the ink can be discharged stably, and the printed image obtained is excellent in weather resistance and water resistance. Further, since the pigment used in the ink set of the present invention does not contain any chlorine, even if the printed matter is incinerated, there is no danger of generating harmful substances to the human body.

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[Procedure amendment]

[Submission date] February 23, 2001 (2001.2.2)
3)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0009

[Correction method] Change

[Correction contents]

More specifically, the benzimidazolone yellow pigment includes C.I. I. Pigment Yellow 180,
C. I. Pigment Yellow 151 or C.I. I. Pigment Yellow 154, C. as phthalocyanine blue pigment I. Pigment Blue 15: 3 and C.I. I. Pigment Red 12
2 or C.I. I. Pigment Violet 19 is preferred
Often used.

 ──────────────────────────────────────────────────の Continued on the front page F term (reference) 2C056 EA13 FC02 2H086 BA53 BA55 4J037 AA02 AA30 CA20 EE02 EE28 FF05 FF06 FF07 FF08 FF22 FF23 FF25 4J039 BA04 BC16 BC37 BC50 BC51 BC60 BC65 BC69 BE01 EA15 EA16 EA17 EA16 EA44 GA03 GA24

Claims (8)

[Claims] 1. A set of aqueous inks for process printing using a self-dispersion type pigment which is dispersed in an aqueous medium by electrostatic repulsion of an acidic functional group introduced on the surface of pigment particles as a colorant, and the set of inks is A process printing ink set, comprising: a yellow ink using a benzimidazolone yellow pigment as a colorant; a cyan ink using a phthalocyanine blue pigment as a colorant; and a magenta ink using quinacridone red pigment as a colorant. 2. The method according to claim 1, wherein the introduction of the acidic functional group onto the surface of the pigment particle is
2. The ink set according to claim 1, wherein the ink set is physical adsorption on the surface of the pigment particles by a pigment derivative having an acidic functional group. 3. The ink set according to claim 1, wherein the acidic functional group is a sulfonic acid group, and the sulfonic acid group forms an amine salt, an ammonium salt or a monovalent metal salt. 4. A benzimidazolone yellow pigment comprising C.I.
I. Pigment yellow 180, C.I. I. Pigment Yellow 151 or C.I. I. Pigment Yellow 154
The ink set according to any one of claims 1 to 3, wherein 5. A phthalocyanine blue pigment comprising C.I. I. Pigment Blue 15: 3. 6. The quinacridone red pigment is C.I. I. Pigment Red 122 or C.I. I. The ink set according to any one of claims 1 to 5, which is CI Pigment Violet 19. 7. The ink set according to claim 1, further comprising a black ink containing carbon black as a coloring agent. 8. A concentrated aqueous dispersion of a self-dispersible pigment for incorporation into the ink set according to claim 1. Description: