JP3031179B2 - Method for producing ink-jet ink and ink-jet ink - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an ink jet ink having excellent pigment dispersion stability. More specifically, an ink using a pigment as a coloring material can form a high-resolution image while maintaining the good water resistance of the ink, and quickly provide an ink-jet ink having good long-term storage stability of the ink. Manufacturing method.

[0002]

2. Description of the Related Art In recent years, an ink jet printing system has been remarkably spread in industrial use and OA use since it is a non-contact printing system for a printing medium and can perform high-speed printing. Due to the development of image processing systems,
In particular, there is an increasing demand for obtaining high-definition, full-color, high-quality printed matter for OA applications. Ink jet printing systems are required to reduce the diameter of the nozzles that form ink droplets as the print image becomes higher definition, and therefore it is necessary for ink to be less likely to cause nozzle clogging. It is a characteristic. Since inks using dyes as coloring materials generally have better properties than those using pigments, water-soluble dyes such as acid dyes, direct dyes, and basic dyes have been conventionally used as inkjet inks. Which is dissolved in a glycol-based solvent and water is often used (JP-A-53-61412).
JP, JP-A-54-89811, JP-A-55-89811
No. 65269).

However, printed matter printed with a dye-based ink generally has poor water resistance due to the good solubility of the ink in water, and the spilling of water easily causes dye bleeding of a recording portion. was there. In order to improve such poor water resistance, attempts have been made to change the structure of the dye or to prepare a highly basic inkjet ink (JP-A-56-57862). It has also been attempted to improve the water resistance by making good use of the reaction between the inkjet paper and the inkjet ink (JP-A-50-49004, JP-A-57 / 1979).
-36692, JP-A-59-20696,
JP-A-59-146889).

[0004] These methods have a remarkable effect on certain types of recording paper dedicated to ink-jet printing. However, in ink-jet printing, since there is a strong demand for printing on ordinary paper, ink-jet inks using water-soluble dyes are used. However, the printed matter does not have sufficient water resistance.
Further, there is a disadvantage that the use of the recording paper exclusive for the ink jet increases the running cost. In addition, dyes generally have poor light resistance to sunlight and the like, and a solution is also required for this point.

[0005] Ink jet inks using dyes as coloring materials have such disadvantages, and therefore, ink jet inks using pigments as coloring materials have been conventionally developed. Printed matter printed with an inkjet ink using a pigment as a coloring material has good water resistance and good light fastness even if the paper is not a recording paper dedicated to inkjet. In response to the reduction in nozzle diameter in response to higher definition printing, ink jet inks using pigments (hereinafter abbreviated as pigment ink jet inks) are expected to have stable ejection characteristics without clogging. In order to make the pigment particles durable, it is necessary that the pigment particles do not settle and have a sufficiently small particle size.

[0006] As an attempt to reduce the pigment particle size of the pigment-based inkjet ink, methods using a dispersing machine such as a ball mill, a sand mill, a homogenizer, and a roll mill have been studied. However, these methods have the disadvantage that the pigment particle size does not become sufficiently small, and even if the particle size becomes small, it takes much time. As a method of improving these conventional disadvantages, US Pat.
No. 27 discloses that a pre-dispersed ink mixture is introduced into a chamber under high pressure, and the ink mixture interacts by passing through at least a plurality of nozzles in the chamber. Although a method for producing a stable pigment-based ink-jet ink has been proposed, it is recognized that further improvement is necessary in terms of pressure loss due to having a plurality of flow paths and a short service life of the chamber.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide an ink jet ink having a small pigment particle size and a stable dispersion for obtaining high-definition printed matter having good water resistance to any paper. To provide a rapid manufacturing method for

[0008]

That is, according to the present invention, a pigment dispersion prepared by preliminarily dispersing a pigment and a dispersant in a dispersion solvent is subjected to a liquid pressure of at least 100 kg / cm ^{2 and} a pressure of 45 ° to 135 °. Passing through a chamber with only one channel with at least two bends less than or equal to degrees,
The particle diameter of the pigment is reduced as compared with the time of pre-dispersion due to the collision of the dispersion with the wall of the bent portion in the flow path and the effect of friction between the dispersion and the wall of the flow path. The present invention relates to a method for producing an inkjet ink and an inkjet ink produced by the method.

According to the present invention, since the chamber has only one channel, the applied pressure energy is less reduced and the applied pressure energy can be effectively transmitted to the pigment particles. Accordingly, the applied pressure energy is not reduced as compared with the system having a plurality of flow paths and a small angle of change portion, so that the pigment particles can be made finer and dispersed. Furthermore, since the structure of the chamber is simple, clogging of the dispersion in the chamber, the workability of repair accompanying the dispersion becomes easy, and the life of the chamber is prolonged. As a result, there is an effect that the quality of the inkjet ink is improved and the manufacturing cost is reduced.

[0010] The chamber used in the present invention comprises:
As shown in FIG. 1, one flow path has a structure having two bent portions a and b in the middle. The pre-dispersed pigment dispersion is applied with a high pressure (a liquid pressure of at least 100 kg / cm ² ) and enters through the entrance of the chamber, collides at high speed with the wall surfaces of the bent portions a and b in the flow path, and its dynamics Fine energy and uniform dispersion of the pigment particles are promoted by high energy. The angle of the deflection angle of a and b is 45 degrees or more and 135 degrees or less, but is generally 90 degrees from the viewpoint of ease of working the chamber. The flow path 2 connecting a and b has a smaller cross-sectional area and a flat wall as compared with the flow path 1 from the entrance and the flow path 3 from the exit. It is easy to obtain the effect of the shear force resulting from the friction with the inner wall of the flow path and the effect of the collision at the bent portion.

The flow path in the chamber preferably has a structure in which the cross-sectional area of the flow path 2 is smaller than the cross-sectional area of the flow path 1. By utilizing this area ratio, the pressure applied to the flow path 1 is increased. It can be transmitted to the channel 2. The higher the pressure on the side of the flow path 2 than on the flow path 1, the more efficiently the atomization and dispersion in the chamber proceeds. Pressure applied to channel 1 is at least 10
0 kg / cm ² suffices, but actually easy to handle pressure is 500~3000Kg / cm ^2. The flow path in the chamber must be made of a material that can withstand high pressure, such as ceramics such as sintered metals and diamonds, metal oxides, borides, carbides, nitrides, and mixtures thereof. And the like.

The chamber used in the present invention is not limited to the one shown in FIG. 1, but may have three or more (four in FIG. 2) bent portions as shown in FIG. A high-pressure pump is used to introduce the predispersed pigment dispersion into the chamber. If the pigment is not sufficiently atomized by a single pass through the chamber, the object can be achieved by performing circulation a suitable number of times. The liquid temperature of the dispersion before and after passing through the chamber is 5 to 40
It is preferable to keep the temperature within the range of ° C from the viewpoint of dispersion efficiency and dispersion stability. If the liquid temperature rises above this, cool the chamber and the piping before and after it.

As the dispersing solvent and the diluting solvent, odor,
Water and / or a water-soluble solvent are used from the viewpoint of safety and the like. The water-soluble solvent may be used together with water when preliminarily dispersing the pigment and the dispersant, or may be added after the pigment and the dispersant are dispersed in water. In addition, it can be added in the process of circulating the pigment dispersion after the preliminary dispersion in the chamber. Water-soluble solvents include humectants to prevent drying at the nozzles of the inkjet ink and solidification of the inkjet ink, to ensure stable jetting of the inkjet ink, and to speed up drying on the printing substrate. Agents, viscosity modifiers, dissolution stabilizers and the like.

Examples of the water-soluble solvent include ethylene glycol, diethylene glycol, propylene glycol, triethylene glycol, polyethylene glycol, glycerin, tetraethylene glycol, dipropylene glycol, ketone alcohol, diethylene glycol monobutyl ether, ethylene glycol monobutyl ether and ethylene glycol monoethyl ether. , 1,2-hexanediol, N-methyl-2-pyrrolidone, substituted pyrrolidone, 2,4,6-hexanetriol, tetrafurfuryl alcohol, 4-methoxy-4-methylpentanone and the like. The water-soluble solvent is used alone or as a mixture in the range of 2 to 50% by weight of the ink for inkjet. Examples of the drying agent for speeding up drying include alcohols such as methanol, ethanol, and isopropyl alcohol. As the water, ion-exchanged water or distilled water from which metal ions and the like have been removed is used.

As the pigment, various pigments used for printing inks and paints can be used. Such pigments include CI yellow pigments 20, 24, 86, 93, 10
9, 110, 117, 125, 137, 138, 14
7, 148, 153, 154, 166, 168, CI orange pigments 36, 43, 51, 55, 59, 61, CI
Red pigments 9, 97, 122, 123, 149, 168,
177, 180, 192, 215, 216, 217, 2
20, 223, 224, 226, 227, 228, 24
0, CI violet pigments 19, 23, 29, 30, 3
7, 40, 50, CI blue pigment 15, 15: 1, 15:
4, 15: 6, 22, 60, 64, CI green pigments 7, 3
6, CI brown pigments 23, 25, 26, CI black pigment 7, titanium black (shown by a color index (CI) number), and the like. Such pigments are
The slurry may be used in the form of an aqueous slurry after the pigment is formed, or the slurry may be powdered by drying such as spray drying. Further, a surface-treated pigment obtained by adding a functional group to the surface of the pigment may be used.

The ink-jet ink of the present invention has water resistance,
Dyes can be used in such a form that there is no problem in light resistance. However, since the use of the dye may deteriorate the dispersion stability of the pigment, the amount of the pigment used must be limited to 40% by weight or less, preferably 25% by weight or less of the pigment. As the dye, an acid dye, a basic dye, a direct dye, a reactive dye, a disperse dye, a metal-containing dye and the like are used. The dye is
Purified dyes from which inorganic salts have been removed are preferred.

As a dye, CI Direct Black 1
7, 19, 32, 51, 71, 108, 146, 15
4, 166, CI Acid Black 2, 7, 24, 2
6, 31, 52, 63, 112, 118, CI Basic Black 2, CI Direct Blue 6, 22, 25,
71, 90, 106, CI Acid Blue 9, 22, 4
0, 59, 93, 102, 104, 113, 117, 1
20, 167, 229, 234, CI Basic Blue 1, 3, 5, 7, 9, 24, 25, 26, 28, 29,
CI Direct Red 1, 4, 17, 28, 83, CI
Acid Red 1, 6, 32, 37, 51, 52, 8
0, 85, 87, 92, 94, 115, 180, 25
6, 315, 317, CI Basic Red 1, 2,
9, 12, 13, 14, 37, CI Direct Yellow 1
2, 24, 26, 98, CI Acid Yellow 11, 1
7, 23, 25, 29, 42, 61, 71, CI Basic Yellow 11, 28. CI Direct Orange 34,
39, 44, 46, 60, CI Direct Violet 47, 48, CI Direct Brown 109, CI Direct Green 59, CI Acid Orange 7, 19,
CI Acid Violet 49, CI Basic Violet 7, 14, 27 and the like can be exemplified.

As the dispersant, a compound represented by the following general formula (I) is preferably used. The compound represented by the general formula (I) has a function of achieving good pigment dispersion and improving the dispersion stability of the pigment over time, and is contained in the ink for inkjet in the range of 0.1 to 10% by weight. Preferably.

Embedded image

The compound represented by the general formula (I) is a single compound or a mixture of the compound represented by the general formula (II) and the compound represented by the general formula (III), and the compound represented by the general formula (II): The weight ratio of the compound represented by the general formula (III) is preferably from 30 to 50:10 to 3.

Embedded image

As the pigment dispersant, a surfactant such as an anionic, nonionic, cationic or amphoteric surfactant can be used. When a surfactant is used in combination with the compound represented by the general formula (I), better pigment dispersion can be achieved. Examples of the anionic activator include fatty acid salts, alkyl sulfate salts, alkyl aryl sulfonates, alkyl naphthalene sulfonates, dialkyl sulfonates, dialkyl sulfosuccinates, alkyl diaryl ether disulfonates, alkyl phosphates, and polyphosphates. Oxyethylene alkyl ether sulfate, polyoxyethylene alkyl aryl ether sulfate, naphthalene sulfonic acid formalin condensate, polyoxyethylene alkyl phosphate ester salt, glycerol borate fatty acid ester, polyoxyethylene glycerol fatty acid ester and the like can be exemplified.

Examples of the nonionic activator 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, Examples thereof include glycerin fatty acid ester, polyoxyethylene fatty acid ester, polyoxyethylene alkylamine, fluorine-based, and silicon-based nonionic activators. Examples of the cationic activator include an alkylamine salt, a quaternary ammonium salt, an alkylpyridinium salt, and an alkylimidazolium salt. Examples of the zwitterionic activator include alkyl betaine, alkyl amine oxide, phosphadyl choline and the like.

The ink-jet ink of the present invention may contain an aqueous resin, a penetrant, a fungicide, a chelating agent, a pH adjuster, a defoamer, a neutralizer for the aqueous resin, and the like. Aqueous resin is intended to improve the stability of the dispersion of the pigment and the fixability of the inkjet ink to a printing medium,
A water-soluble resin soluble in water and a water-dispersible resin can be used alone or as a mixture. As the aqueous resin, a water-soluble resin such as an acrylic resin, a styrene-acrylic resin, a polyester resin, a polyamide resin, a polyurethane resin, or the like, which dissolves in water, and a resin dispersible in water are used.
In order to neutralize the aqueous resin, a neutralizing agent such as ammonia, an amine, or an inorganic alkali can be appropriately adjusted and added to the inkjet ink of the present invention.

When the substrate for ink-jet ink is a permeable material such as paper, a penetrating agent may be added to the ink-jet ink to stop the ink-jet ink from penetrating into the substrate and to improve the apparent dryness. it can. Examples of such penetrants include glycol ethers such as diethylene glycol monobutyl ether described as water-soluble solvents, alkylene glycols, polyethylene glycol monolauryl ether, sodium lauryl sulfate, sodium dodecylbenzenesulfonate, sodium oleate, sodium dioctylsulfosuccinate, and the like. Can be used. These have a sufficient effect when used in an amount of 5% by weight or less of the ink for ink jet. If the amount is more than this, bleeding of printing and paper loss (print through) occur, which is not preferable.

The antifungal agent is used to prevent the generation of fungi in the ink jet ink, and includes sodium dehydroacetate, sodium benzoate and sodium pyridinethione-1.
-Oxide, zinc pyridinethione-1-oxide, 1,2-benzisothiazolin-3-one, 1-benzisothiazolin-3-one amine salt and the like are used. These are 0.05 to 1.
Used in the range of 0% by weight. The chelating agent blocks metal ions in the ink for ink jet, and prevents deposition of metal at the nozzle portion and precipitation of insoluble substances in the ink for ink jet. A sodium salt of acetic acid, a diammonium salt of ethylenediaminetetraacetylic acid, a tetraammonium salt of ethylenediaminetetraacetic acid, and the like are used. These are 0.00 of the ink for inkjet.
Used in the range of 5 to 0.5% by weight.

Also, in order to adjust the pH of the ink for ink jet and to obtain stability of the ink for ink jet or stability with the ink jet ink pipe in the recording apparatus,
Modifiers such as amines, inorganic salts and ammonia, and buffers such as phosphoric acid can be used. Further, an antifoaming agent may be added to prevent circulation and movement of the ink for ink jet or generation of bubbles at the time of manufacturing the ink for ink jet. As other additives, urea, dimethyl urea and the like can be added. Ink jet inks have a viscosity of 0.8 to 15 cp, depending on the type of recording device.
Adjust as a liquid of s (25 ° C.). Surface tension is 25
６０60 dyn / cm. The pH is not particularly limited, but is in the range of 4 to 12, and is slightly acidic to neutral of 5 to 7,
Neutral to weak alkali of 7 to 9 is preferred. In the present invention, the preliminary dispersion before passing through the chamber can be performed using a general dispersion method such as a mixer equipped with stirring blades, an ultrasonic wave, a paint shaker, a sand mill, and a ball mill.

[0026]

The present invention will be described below in further detail with reference to examples. In the examples, parts and% represent parts by weight and% by weight, respectively. For the measurement of the average particle size of the dispersion, a particle size distribution meter “DLS-700” manufactured by Otsuka Electronics Co., Ltd. was used. [Example 1] The following raw materials were mixed and predispersed using a sand mill to prepare an aqueous pigment dispersion. At this stage, sampling was performed to measure the average particle size.
m. 250 ml of the aqueous pigment dispersion was placed in a chamber having a single flow path having two 90 ° bends (FIG. 1) at an inlet temperature of 25 ° C. and a pressure of 700 kg /.
cm ^2, an outlet temperature of 50 ° C. for 20 cycles (liquid flow rate 360
ml / min, treatment time 14 minutes). The dispersion having been subjected to this treatment had an average particle size of 125 nm. 15 parts of blue pigment ("Lionol Blue 7351" manufactured by Toyo Ink Mfg. Co., Ltd.) 1.5 parts of acrylic resin solution ("PDX6101" manufactured by Johnson Polymer Co., NV = 27.5%) Compound represented by general formula (II) Mixture of compounds represented by formula (III) (weight ratio of (II) to (III) is 5: 1, average of n is 6) 3.0 parts Purified water 74.5 parts Glycerin 6.0 parts

13.5 parts of the treated dispersion were mixed with: After mixing, the mixture was filtered through a 0.8 μm membrane filter, and then filtered through a 0.45 μm membrane filter to produce an inkjet ink. The viscosity is 2.
It was 0 cps (25 ° C.). A mixture of the compound represented by the general formula (II) and the compound represented by the general formula (III) (weight ratio of (II) to (III) is 5: 1, average of n is 6) 0.2 parts Acrylic resin dispersion Body 2.0 parts ("Torkuril W-215" manufactured by Nippon Polymer Co., NV = 45%) Ethylene glycol 10 parts Antifungal agent ("Sodium Omazine" manufactured by Olin Chemical Co.) 0.15 parts Ethylenediaminetetraacetic acid 0.02 Part Purified water 63.53 parts 2-ethylhexanol 0.1 part 2,4,7,9-tetramethyl-5-decyne-4,7-diol 0.1 part

When this ink was placed in a cartridge of an ink jet printer (“HG5130” manufactured by Seiko Epson Corporation) and recording was performed, a good recorded matter was obtained. Water was dripped on the recording surface to examine the bleeding of the ink. As a result, there was no bleeding or running out of the ink, and the ink had sufficient water resistance. Furthermore, when the recording was performed again after the head was left as it was for one week, good recording could be performed.

Comparative Example 1 A predispersed aqueous pigment was prepared in the same manner as in Example 1 except that the chamber was changed to a chamber having two flow paths having a 90-degree bend (FIG. 3). The dispersion was processed. The average particle diameter of the treated dispersion was 148 nm. 13.5 parts of the dispersion after the treatment was mixed with the same dispersion as in Example 1, and the same filtration was performed to produce an inkjet ink. Filtration through a 0.45μ filter required 1.5 times as long as in Example 1.

Example 2 The following materials were mixed, and
Pre-dispersion using a mill to make an aqueous pigment dispersion
Was. At this stage, perform sampling to measure the average particle size.
It was 407 nm. 250 ml of aqueous pigment dispersion
With a single channel having two 90-degree bends
Inlet temperature 15 ° C, pressure 70
0Kg / cm ^Two20 cycles at 50 ° C outlet temperature (liquid flow
360 ml / min, treatment time 14 min)). this
The average particle size of the treated dispersion was 215 nm.
Was. 20 parts of yellow pigment ("Lionol Yellow 22-2845" manufactured by Toyo Ink Mfg. Co., Ltd.) 1.5 parts of acrylic resin solution ("PDX6101" manufactured by Johnson Polymer, NV = 27.5%) Compound represented by general formula (II) And a compound of the general formula (III) (weight ratio of (II) and (III) is 5: 1, average of n is 5) 3.0 parts Purified water 74.5 parts Glycerin 6.0 parts Non 2.1 parts of ionic surfactant ("Emulgen 420" manufactured by Kao Corporation)

11.5 parts of the treated dispersion were mixed with: After mixing, the mixture was filtered through a 0.8 μm membrane filter, and then filtered through a 0.45 μm membrane filter to produce an inkjet ink. The viscosity is 2.
It was 1 cps (25 ° C.). A mixture of the compound represented by the general formula (II) and the compound represented by the general formula (III) (weight ratio of (II) to (III) is 10: 1, average of n is 6) 0.2 parts Acrylic resin dispersion Body 2.2 parts ("Torkuril W-215", manufactured by Nippon Polymer Co., NV = 45%) Ethylene glycol 10 parts Fungicide ("Sodium Omazine", manufactured by Ohlin Chemical Co.) 0.15 parts Ethylenediaminetetraacetic acid 0.02 Part Purified water 63.53 parts 2-ethylhexanol 0.1 part 2,4,7,9-tetramethyl-5-decyne-4,7-diol 0.1 part

When this ink was put into a cartridge of an ink jet printer (“HG5130” manufactured by Seiko Epson Corporation) and recording was performed, a good recorded matter was obtained. Water was dripped on the recording surface to examine the bleeding of the ink. As a result, the bleeding of the ink and the outflow did not occur, and the ink had sufficient water resistance. Furthermore, when the recording was performed again after the head was left as it was for one week, good recording could be performed.

Comparative Example 2 Aqueous pigment dispersion 2 of Example 2
Dispersion of 50 ml was further continued for 1 hour in a sand mill using 0.5 mm glass beads as a medium. The average particle size of the dispersion after the treatment was 357 nm. 11.5 parts of the dispersion after the treatment was mixed with the same one as in Example 2, and the same filtration was performed. At the time of filtration with a 0.8 μm membrane filter, pigment was deposited on the filter surface, and the filter had to be replaced. The amount of filtration with a 0.45μ filter was small. The concentration of the filtrate was about 93% of that of Example 2.

Comparative Example 3 A predispersed aqueous pigment was prepared in the same manner as in Example 2 except that the chamber was changed to a chamber having two flow paths having a 90-degree bend (FIG. 3). The dispersion was processed. The treated dispersion had an average particle size of 247 nm. After the treatment, 11.5 parts of the dispersion was mixed with the same dispersion as in Example 2, and the same filtration was performed to produce an inkjet ink. Filtration through a 0.45μ filter took about twice as long as in Example 2.

Example 3 The following materials were mixed, and
Pre-dispersion using a mill to make an aqueous pigment dispersion
Was. At this stage, perform sampling to measure the average particle size.
It was 223 nm. 250 ml of aqueous pigment dispersion
With a single channel having two 90-degree bends
Using a chamber (Fig. 1), inlet temperature 15 ° C, pressure 60
0Kg / cm ^Two, 15 cycles at an outlet temperature of 45 ° C (liquid flow
Volume 340 ml / min, treatment time 11 minutes). This place
The average particle size of the treated dispersion was 115 nm. Blue pigment ("Lionol Blue KLH-T" manufactured by Toyo Ink Mfg. Co., Ltd.) 20 parts Acrylic resin solution 2.8 parts ("PDX6101" manufactured by Johnson Polymer Co., NV = 27.5%) Formula (II) Mixture of compound and compound represented by formula (III) (weight ratio of (II) to (III) is 5: 1, average of n is 6) 4.0 parts Purified water 74.5 parts Glycerin 6.0 parts

12.5 parts of the treated dispersion were mixed with: After mixing, the mixture was filtered through a 0.8 μm membrane filter, and then filtered through a 0.45 μm membrane filter to produce an inkjet ink. The viscosity is 2.
It was 0 cps (25 ° C.). A mixture of the compound represented by the general formula (II) and the compound represented by the general formula (III) (weight ratio of (II) to (III) is 10: 1, average of n is 6) 0.2 parts Acrylic resin dispersion Body 1.8 parts (Torkuril W-215, manufactured by Nippon Polymer Co., NV = 45%) Diethylene glycol 10 parts Fungicide (Sodium Omazine, manufactured by Ohlin Chemical Co.) 0.15 parts Ethylenediaminetetraacetic acid 0.02 parts Purified water 63.53 parts 2-ethylhexanol 0.1 parts 2,4,7,9-tetramethyl-5-decyne-4,7-diol 0.1 parts

When this ink was placed in a cartridge of an ink jet printer ("HG5130" manufactured by Seiko Epson Corporation) and recording was performed, a good recorded matter was obtained. Water was dripped on the recording surface to examine the bleeding of the ink. As a result, the bleeding of the ink and the outflow did not occur, and the ink had sufficient water resistance. Furthermore, when the recording was performed again after the head was left as it was for one week, good recording could be performed.

[Comparative Example 4] A pre-dispersed aqueous pigment was prepared in the same manner as in Example 3 except that the chamber was changed to a chamber having two flow paths having a 90-degree bend (FIG. 3). The dispersion was processed. The average particle size of the treated dispersion was 131 nm. After the treatment, 12.5 parts of the dispersion was mixed with the same dispersion as in Example 3, and the same filtration was performed to produce an inkjet ink. Filtration with a 0.45μ filter required about 1.3 times as long as in Example 3.

An aqueous solution of sodium hydroxide was added to the ink-jet inks obtained in Examples 1 to 3 to adjust the conductivity to 0.1.
Adjusted to 8 ms or more. This ink can perform stable printing from the 35μ nozzle of the continuous jet type (sweet type) inkjet printer, and the recorded characters are
Good water resistance was exhibited without causing run-off or bleeding even if the water was dropped. The inks obtained in Examples 1 to 3 were stored at −40 ° C. for one week and then naturally thawed, but maintained the initial viscosity and exhibited stable ejection characteristics. Also, 60
Although stored in a constant temperature bath at ℃ for one month, the initial viscosity was maintained and stable injection characteristics were exhibited. The inks obtained in Examples 1 to 3 were subjected to a temperature change of −40 ° C. to 60 ° C.
A cycle of 3 days (holding for 3 hours) was performed, and all of the inks were free of precipitates and maintained a good initial state. Therefore, good printing and stable ejection characteristics were exhibited.

[0040]

According to the present invention, an inkjet ink having a small pigment particle diameter and a stable dispersion can be produced. The inkjet ink obtained by the production method of the present invention can cope with high-definition of a printed image and is extremely excellent in water resistance while being water-based. It can be used in a wide range of fields such as writing, cardboard marking, numbering, and barcode.
In addition, the ink has good light fastness as compared with ink-jet inks manufactured using dyes, and can form a color image having excellent storage stability of recorded matter.

[0041]

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a chamber of the present invention.

FIG. 2 is a schematic view of a chamber of the present invention.

FIG. 3 is a schematic view of a chamber having a plurality of flow paths.

[Explanation of symbols]

 1: Flow path 1: 2: Flow path 2: 3: Flow path 3 a: Deflection part b: Deflection part c: Deflection part

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Yasuharu Iida 2-3-1-13 Kyobashi, Chuo-ku, Tokyo Toyo Ink Manufacturing Co., Ltd. Examiner Chiyako Inoue (56) References JP-A-8-41395 (JP, A) JP-A-6-87220 (JP, A) JP-A-5-59188 (JP, A) JP-A-5-76743 (JP, A) JP-A-5-170852 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) C09D 11/00-11/20 B01F 3/08

Claims (8)

(57) [Claims] 1. A pigment dispersion comprising a pigment and a dispersant preliminarily dispersed in a dispersing solvent, at least 100 kg / cm ^2.
Liquid through the chamber having only one flow path having at least two bends of 45 degrees or more and 135 degrees or less, and collision of the dispersion with the wall of the bend in the flow path And a method for producing an ink-jet ink, characterized in that the particle size of the pigment is reduced as compared with the time of preliminary dispersion by the effect of friction between the dispersion and the inner wall surface of the flow path. 2. The pigment concentration during predispersion is 1 to 40% by weight, and after passing through the chamber or before passing through the chamber, the pigment concentration is adjusted to 0.5 to 10% by weight using a diluting solvent. The method for producing an inkjet ink according to claim 1, wherein: 3. The method according to claim 1, wherein the temperature of the dispersion after or before passing through the chamber is maintained in the range of 5 to 40 ° C. 4. The method according to claim 1, wherein the cross-sectional area of the flow path in the chamber is different before and after the bent portion. 5. The method according to claim 1, wherein the dispersing solvent and the diluting solvent are water and / or a water-soluble solvent.
A method for producing the inkjet ink according to the above. 6. The method according to claim 1, wherein the dispersant is a compound represented by formula (I). Embedded image 7. A compound represented by the general formula (1):
7. The method for producing an ink-jet ink according to claim 6, which contains 10% by weight. 8. A viscosity of 0.8 to 15 centipoise (25 ° C.)
The method for producing an inkjet ink according to any one of claims 1 to 7, wherein