JP2001064563A - Aqueous pigment dispersion and ink jet ink - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aqueous pigment dispersion excellent in shelf stability, jetting stability and resistance to clogging and an ink jet ink. SOLUTION: The subject aqueous pigment dispersion is obtained by dispersing a quinacridone-based pigment (A) having a surface area of 80 m2/g-120 m2/g in an aqueous medium (C) in the presence of a dispersant (B) comprising an alkali metal salt or an ammonium salt of a sulfated product of a polyethylene oxide styrenized methyl phenyl ether. Desirably, the dispersion comprises 13-18 wt.% of the quinacridone-based pigment (A), 2.5-5.5 wt.% of the dispersant (B) and 76.5-84.5 wt.% of the aqueous medium (C).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aqueous pigment dispersion containing a quinacridone pigment and an ink-jet ink using the same.

[0002]

2. Description of the Related Art Conventionally, a dye ink obtained by dissolving a dye in an aqueous medium has been used as an ink jet ink used for ink jet recording. Such a dye ink has good storage stability of the ink, stability of ejection from a printer nozzle, clearness of printed matter, and good color development, but has a problem in that the water resistance and light resistance of the printed matter are poor. To solve such problems, a method of increasing the water resistance by applying a water-resistant coating agent to a printing material, and a method of discharging a water-resistant agent together with ink have been proposed, but such methods are expensive. However, there has been no fundamental approval, and light resistance has not been resolved. On the other hand, in recent years, pigment inks having good water resistance and light resistance have been studied. This is obtained by dispersing an insoluble pigment in a medium such as water, but is inferior in storage stability, ejection stability, and clogging resistance of the ink compared to the dye ink, and a satisfactory ink has been obtained. Absent.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned conventional problems and to provide an aqueous pigment dispersion and an ink-jet ink which are excellent in storage stability, discharge stability and clogging resistance. is there. The present inventors have found that the use of an alkali metal salt or ammonium salt of polyethylene oxide styrenated methyl phenyl ether sulfonate as a dispersant is extremely effective in stabilizing the aqueous dispersion of fine quinacridone pigments. Invented the invention.

[0004]

That is, the present invention relates to a method for preparing a quinacridone pigment (A) having a specific surface area of 80 m2 / g to 120 m2 / g by converting an alkali metal salt or an ammonium salt of polyethylene oxide styrenated methylphenyl ether sulfonate. And an aqueous dispersion of the pigment dispersed in the aqueous medium (C) in the presence of the dispersant (B).

Further, the present invention relates to a quinacridone pigment (A)
Is 13 to 18% by weight, the dispersant (B) is 2.5 to 5.5% by weight, and the aqueous medium (C) is 76.5 to 84.5% by weight. Further, according to the present invention, the integrated particle size 1% value by the laser light scattering method is 20 to 40 nm,
The present invention relates to the aqueous pigment dispersion having a 50% value of 50 to 70 nm and a 99% value of 250 nm or less. Further, the present invention
The present invention relates to the aqueous pigment dispersion having a viscosity at 5 ° C of 2 to 6 cps. Further, the present invention relates to an inkjet ink containing the aqueous pigment dispersion.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The quinacridone pigments of the present invention include unsubstituted or substituted quinacridones such as unsubstituted quinacridone, 2,9-dimethylquinacridone and 4,11-dichloroquinacridone, and solid solutions thereof.
I. When expressed in numbers, Pigment Violet 1
9, Pigment Red 122, Pigment Red 20
7, Pigment Orange 48, Pigment Orange 4
9, Pigment Red 209, Pigment Red 20
6, Pigment Violet 42 and the like.

As for the particle size of the quinacridone pigment, a fine particle is suitable as an ink jet ink, and the specific surface area, which is an index indicating the particle size of the pigment, is 80 m2 / g to 120 m2 / g.
m2 / g is preferred. When the specific surface area is less than 80 m2 / g, the dispersed particle size becomes large, and sedimentation of the pigment tends to occur. When the specific surface area is more than 120 m2 / g, the light fastness of the ink deteriorates. In the present invention, the specific surface area is measured by a nitrogen adsorption method.

The alkali metal salt or ammonium salt of the polyethylene oxide styrenated methyl phenyl ether sulfonate of the present invention is a polyethylene oxide having an average degree of polymerization of 4 to 30 which can substitute a benzene ring via an ether bond at the α-position. It is a water-soluble polymer in which a methylphenyl group having 1 to 3 styrenes attached at positions is bonded, and a sulfonic acid group forming an alkali metal salt or an ammonium salt is bonded at the ω position.

The alkali metal salt or ammonium salt of polyethylene oxide styrenated methyl phenyl ether sulfonate is incorporated in the aqueous pigment dispersion in an amount of 2.5 to 5.5% by weight. If it is not obtained, and if it is too large, the water resistance of the ink jet ink will be deteriorated.

The aqueous medium of the present invention comprises water or a mixture of water and an aqueous solvent. In the case of a mixture, the aqueous solvent accounts for 50% by weight or less of the aqueous medium. The aqueous solvent can be selected according to the use of the aqueous pigment dispersion. For example, when the use is an inkjet ink, an aqueous solvent described below can be used.

The aqueous pigment dispersion of the present invention comprises a quinacridone pigment, an alkali metal salt or an ammonium salt of polyethylene oxide styrenated methylphenyl ether sulfonate and an aqueous medium, a disperser, a homomixer, a paint shaker, a sand mill, a roll mill, a nanomizer, etc. Obtained by dispersing with a dispersing machine.

The aqueous pigment dispersion has an integrated particle size 1% value of 20 to 40 nm and a 50% value of 50 to 50% by a laser light scattering method.
Preferably, the thickness is 70 nm and the 99% value is 250 nm or less. If the amount of the excessively fine particles is too large, the storage stability of the dispersion may be deteriorated. If the amount of the coarse particles is too large, sedimentation of the pigment particles easily occurs, which is not suitable as an ink jet ink. Pigment aqueous dispersion of the present invention,
It is preferable that the viscosity at 25 ° C. is from 2 to 6 cps, and it is difficult to adjust the viscosity range of a pigment-based aqueous dispersion exceeding 6 cps as an inkjet ink.

The aqueous pigment dispersion of the present invention can be used as an ink-jet ink by mixing with an aqueous medium, various additives and the like and adjusting the physical properties. The aqueous medium is composed of water and optionally an aqueous solvent.
As the water, ion-exchanged water or distilled water from which metal ions and the like have been removed is used in the range of 49 to 95% by weight of the ink.

The aqueous solvent includes an aqueous solvent that acts as a humectant to prevent drying of the ink at the nozzle portion, solidification of the ink, stable ejection of the ink, and prevention of drying of the nozzle over time. An aqueous solvent that acts as a penetrant to stop the penetration of the ink into the paper and speed up the apparent dryness when the ink substrate is a permeable material such as paper;
There are aqueous solvents that act as drying accelerators to speed the drying of the ink on paper.

Aqueous solvents acting as humectants include 1,1
3-propanediol, 1,2-hexanediol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, dipropylene glycol, 2,4,6-hexanetriol,
Examples include glycerin, tetrafurfuryl alcohol, ketone alcohol, N-methyl-2-pyrrolidone, substituted pyrrolidone, 4-methoxy-4-methylpentanone and the like. These aqueous solvents are used alone or as a mixture in an amount of 1 to 50% by weight of the ink, preferably 2 to 25% by weight of the ink.

Examples of the aqueous solvent acting as a penetrant include glycol ethers such as diethylene glycol monobutyl ether, ethylene glycol monobutyl ether, and ethylene glycol monoethyl ether; glycol glycols of polyethylene glycol monolauryl ether;
Examples include alkylene glycols such as ethylene glycol and propylene glycol.

These aqueous solvents are used alone or as a mixture in an amount of 0 to 5% by weight, preferably 1 to 5% by weight of the ink. Aqueous solvent that acts as a penetrant has a sufficient effect at the above usage amount, and if it is more than this, bleeding of printing,
Paper loss (print-through) occurs, which is not preferable.
Aqueous solvents that act as drying accelerators include methanol,
Lower alcohols such as ethanol and isopropyl alcohol can be exemplified. These aqueous solvents may be used alone or as a mixture in an amount of 0.1 to 20% by weight of the ink, preferably 1 to 1%.
It is used in the range of 0% by weight.

Further, the ink-jet ink of the present invention has a nonionic, anionic, cationic or zwitterionic interface in order to impart surface tension, wettability with a liquid contact material of a printer, and ejection stability. An activator can be added.

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, Nonionic activators such as glycerin fatty acid ester, polyoxyethylene fatty acid ester, polyoxyethylene alkylamine, fluorine-based, and silicon-based are exemplified.

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 phosphorus. 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 cationic surfactant include an alkylamine salt, a quaternary ammonium salt, an alkylpyridinium salt, an alkylimidazolium salt and the like. Examples of the amphoteric surfactant include alkyl betaine, alkyl amine oxide, phosphadyl choline and the like.

Among the surfactants, anionic surfactants such as sodium lauryl sulfate, sodium dodecylbenzenesulfonate, sodium oleate, and sodium dioctylsulfosuccinate reduce the permeability of the ink into the permeable print medium. It also acts as a penetrant to speed up apparent dryness. The content of the anionic surfactant which also functions as a penetrant in the ink is 0.1 to 5%.
Preferably it is in the range of weight%. The amount of the anionic surfactant which also functions as a penetrant has a sufficient effect at the above-mentioned amount, and if the amount is more than this, bleeding of printing and paper loss (print-through) occur, which is not preferable.

Various additives such as a fungicide and a chelating agent can be added to the ink-jet ink of the present invention. The antifungal agent prevents the generation of mold on the ink, and includes sodium dehydroacetate, sodium benzoate, sodium pyridine thione-1-oxide, zinc pyridine thione-1-oxide, 1,2-benzisothiazoline. Amine salts of 3-one, 1-benzisothiazolin-3-one and the like are used. These are used in the range of 0.05 to 1.0% by weight of the ink.

The chelating agent blocks metal ions in the ink and prevents the deposition of metal at the nozzle portion and the deposition of insoluble substances in the ink, and the like. Ethylenediaminetetraacetic acid, ethylenediaminetetraacetate, etc. Sodium salts of tick acid, diammonium salts of ethylenediaminetetraacetic acid, tetraammonium salts of ethylenediaminetetraacetic acid, and the like are used. These are 0.005-0.
It is used in the range of 5% by weight. Further, for the purpose of adjusting the hue, imparting the concentration, and the like, the dye can be used in such a manner that there is no problem in water resistance and light resistance.

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, or a buffer such as phosphoric acid is used. be able to. Further, an antifoaming agent can be added in order to prevent the circulation and movement of the ink or the generation of bubbles during the production of the ink. Also, water resistance,
For the purpose of imparting fixability to recording paper, other water-soluble resins,
A water-dispersible resin can be added.

The ink-jet ink of the present invention is obtained by mixing an aqueous medium and additives as necessary with the aqueous pigment dispersion of the present invention, and stirring the mixture with a disper, sand mill, homogenizer, ball mill, paint shaker, ultrasonic disperser or the like. Can be produced by dispersing and mixing. The inkjet ink of the present invention is preferably sufficiently filtered 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. It is also possible to carry out filtration by centrifugation prior to filter filtration, thereby reducing clogging in filter filtration and filter replacement. The viscosity of the ink is preferably 0.8 to 40 centipoise at 25 ° C., although it depends on the type of the recording apparatus.

[0027]

The present invention will be specifically described below with reference to examples. In Examples, “parts” and “%” represent “parts by weight” and “% by weight”, respectively. (Example 1) 15 parts of a dimethylquinacridone pigment having a specific surface area of 90 m2 / g, 3 parts of a sodium salt of polyethylene oxide styrenated 3-methylphenyl ether sulfonate having an average degree of polymerization of ethylene oxide of 7, and an average addition number of styrene of 1.5, ions 82 parts of exchanged water was charged into a mayonnaise bottle, and 4 parts were charged with a sand mill filled with 1 mm glass beads.
Time-dispersion was performed to obtain a red pigment aqueous dispersion having a viscosity of 4 cps at 25 ° C., an integrated particle size 1% value of 35 nm, a 50% value of 60 nm, and a 99% value of 180 nm by a laser light scattering method. The obtained pigment aqueous dispersion did not show any change in viscosity and particle size even after storage at 60 ° C. for 3 weeks. Next, 20 parts of the obtained pigment aqueous dispersion, 20 parts of glycerin as a humectant, 0.5 part of sodium dioctylsulfosuccinate as a penetrant, and an amine salt of 1-benzisothiazolin-3-one as a fungicide 0.1 Part, acrylic resin as a binder resin (TOKURIL W-
261: manufactured by Toyo Ink Mfg. Co., Ltd.), 0.5 parts of ion-exchanged water and 58.9 parts of ion-exchanged water were stirred and mixed by a disper, and then filtered through a nylon 66 0.45 μm membrane filter to obtain an ink-jet ink. Obtained. The obtained inkjet ink had a viscosity at 25 ° C. of 1.8 cps and an average particle size of 60 nm.
No change in viscosity and particle size after storage for 3 weeks was observed, and no sediment was observed. In addition, the obtained inkjet ink was used with a Hewlett Packard DeskJet 7
When injected into a cartridge for 20C and subjected to a printing test, good printed matter was obtained, and clogging did not occur even after printing at room temperature for one week.

(Example 2) 15 parts of a quinacridone pigment having a specific surface area of 100 m2 / g, 4 parts of a sodium salt of a styreneated 3-methylphenyl ether sulfonated product of polyethylene oxide having an average degree of polymerization of ethylene oxide of 7, and an average addition number of styrene of 1.5. , 81 parts of ion-exchanged water were charged into a mayonnaise bottle, and dispersed for 4 hours by a sand mill filled with 1 mm glass beads, and the viscosity at 25 ° C. was 5 cps.
The integrated particle size 1% value by the laser light scattering method is 30 nm, 5
A red pigment aqueous dispersion having a 0% value of 55 nm and a 99% value of 170 nm was obtained. The obtained pigment aqueous dispersion did not show any change in viscosity and particle size even after storage at 60 ° C. for 3 weeks. Next, 20 parts of the obtained pigment aqueous dispersion, 20 parts of glycerin as a humectant, 0.5 part of sodium dioctylsulfosuccinate as a penetrant, and an amine salt of 1-benzisothiazolin-3-one as a fungicide 0.1 Parts, 0.5 part of an acrylic emulsion (Tokuril W-261: manufactured by Toyo Ink Mfg. Co., Ltd.) as a binder resin,
58.9 parts of ion-exchanged water was stirred and mixed by a disper, and then filtered through a nylon 66 0.45 μm membrane filter to obtain an inkjet ink. The obtained inkjet ink was heated at 25 ° C.
Has a viscosity of 2.0 cps and an average particle size of 55 nm,
No change in viscosity and particle size after storage at 60 ° C for 3 weeks,
No sediment was observed. The obtained inkjet ink was injected into a cartridge for DeskJet 720C manufactured by Hewlett-Packard Company, and a printing test was performed. As a result, a good printed matter was obtained, and even after printing for one week at room temperature, clogging was observed. Did not occur.

Comparative Example 1 As in Example 1, 15 parts of a quinacridone pigment having a specific surface area of 100 m 2 / g, 5 parts of sodium polyethylene oxide β-naphthol ether sulfonate having an average degree of polymerization of ethylene oxide of 13 and 80 parts of ion-exchanged water were used. When the dispersion was carried out at 25 ° C., the viscosity at 25 ° C. was 2.5 cps, the integrated particle size by laser light scattering was 1 nm at 30 nm, 50% at 50 nm, and 99% at 210 n.
m of a red pigment aqueous dispersion. When the obtained pigment aqueous dispersion was stored at 60 ° C., gelation occurred after one week.

Comparative Example 2 15 parts of a dimethylquinacridone pigment having a specific surface area of 60 m 2 / g, a sodium salt of a styreneated 3-methylphenyl ether sulfonated product of polyethylene oxide having an average degree of polymerization of ethylene oxide of 7, and an average addition number of styrene of 1.5 3 And 82 parts of ion-exchanged water were charged into a mayonnaise bottle and dispersed for 4 hours by a sand mill filled with 1 mm glass beads, and the viscosity at 25 ° C.
5 cps, integrated particle size 1% value by laser light scattering method is 5
0 nm, 50% value is 120 nm, 99% value is 400 nm
To obtain a red pigment aqueous dispersion. A sediment was observed in the obtained aqueous pigment dispersion after storage at 60 ° C. for 2 weeks. Next, 20 parts of the obtained pigment aqueous dispersion, 20 parts of glycerin as a humectant, 0.5 part of sodium dioctylsulfosuccinate as a penetrant, and an amine salt of 1-benzisothiazolin-3-one as a fungicide 0.1 Part, acrylic resin as a binder resin (TOKURIL W-
261: Toyo Ink Mfg. Co., Ltd.) 0.5 parts and ion-exchanged water 58.9 parts were stirred and mixed by a disper, and then filtered through a nylon 66 0.45 μm membrane filter to obtain an inkjet ink. Obtained. The obtained inkjet ink had a viscosity at 25 ° C. of 1.7 cps, an average particle diameter of 120 nm, and a viscosity of 60 nm.
No change was observed in the viscosity and particle size after storage at 3 ° C. for 3 weeks, but sediment was observed. In addition, the obtained ink-jet ink was used with a Hewlett Packard DeskJet 7
When the ink was injected into a cartridge for 20C and a printing test was performed, the direction of the ink at the time of ejection was disturbed, and the image could not be reproduced. Also, after printing for one week at room temperature,
Clogging has occurred.

According to the present invention, a quinacridone-based pigment is miniaturized, and an alkali metal salt or an ammonium salt of polyethylene oxide styrenated methyl phenyl ether sulfonate is used as a dispersant, whereby a pigment having storage stability and low viscosity is obtained. An aqueous dispersion was obtained, and an inkjet ink having excellent storage stability, discharge stability, and clogging resistance was obtained by using the pigment aqueous dispersion.

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Claims (5)

[Claims] 1. A specific surface area of 80 m2 / g to 120 m2 / g
g of quinacridone pigment (A) dispersed in an aqueous medium (C) in the presence of a dispersant (B) composed of an alkali metal salt or ammonium salt of polyethylene oxide styrenated methylphenyl ether sulfonate. A pigment-based aqueous dispersion comprising: 2. The quinacridone-based pigment (A) has a content of 13 to 18.
The aqueous pigment dispersion according to claim 1, wherein the aqueous dispersion (B) comprises 2.5 to 5.5% by weight of the dispersant (B) and 76.5 to 84.5% by weight of the aqueous medium (C). 3. An integrated particle size of 1% value of 20 to 40 nm, a 50% value of 50 to 70 nm and 9% by a laser light scattering method.
The aqueous pigment dispersion according to claim 1 or 2, wherein the 9% value is 250 nm or less. 4. The aqueous pigment dispersion according to claim 1, which has a viscosity at 25 ° C. of 2 to 6 cps. 5. An inkjet ink comprising the aqueous pigment dispersion according to claim 1.