JPH08109344A - Production of ink for ink-jet printing and ink for ink-jet printing - Google Patents

Abstract

PURPOSE: To enable prompt preparation of an ink for ink-jet printing which gives printed matters of high fineness and exactness because of its fine particle sizes of pigments, stabilized dispersion and high water resistance by executing a specific treatment to a dispersion which is prepared by dispersing the pigments and a dispersant in a dispersion solvent preliminarily. CONSTITUTION: At first, the pigments and a dispersant [preferably a compound of the formula (n is 3-10)] are preliminarily dispersed in a dispersion solvent (preferably water and/or a solvent soluble in water such as ethylene glycol). Then, the pigment dispersion is pressurized with a hydraulic pressure over 100kg/cm<2> to pass through a chamber which has only one flow path 1, 2, 3 with two more corners of 45-135 deg. angles a, b to miniaturize the particle size of the pigment by collision to the corners a and b and the friction with the walls of the flow path to give this ink. It is preferred that the temperature of the dispersion is kept at 5-40 deg.C before and after the passage through the chamber from the view points of dispersion efficiency and stability.

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 inkjet ink having excellent pigment dispersion stability. More specifically, an ink jet ink that can form an image with high resolution while maintaining good water resistance of an ink using a pigment as a coloring material and that has good long-term storage stability of the ink is promptly provided. Manufacturing method.

[0002]

2. Description of the Related Art Ink jet printing systems have been remarkably popularized in industrial applications and OA applications in recent years because they are non-contact printing systems for printing materials and are capable of high-speed printing. From the development of image processing systems,
In particular, there is an increasing demand for high-definition, full-color, high-quality printed matter for OA applications. Inkjet printing systems are required to reduce the diameter of nozzles that form ink droplets as the resolution of printed images becomes higher, and it is therefore necessary for ink to be less prone to nozzle clogging. It is a characteristic. Since inks that use dyes as coloring materials generally have better characteristics than those that use pigments, ink-jet inks have hitherto been used as water-soluble dyes such as acid dyes, direct dyes, and basic dyes. It is often used that glycol is dissolved in a glycol solvent and water (JP-A-53-61412).
JP-A-54-89811, JP-A-55-
No. 65269).

However, a printed matter printed with a dye-based ink generally has poor water resistance due to the good solubility of the ink in water, and spilling water easily causes bleeding of the dye in the recording portion. was there. In order to improve such poor water resistance, it has been attempted to change the structure of the dye or prepare a strongly basic inkjet ink (Japanese Patent Laid-Open No. 56-57862). Further, it has 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 and JP-A-57).
-36692, JP-A-59-20696,
JP-A-59-146889).

Although these methods are remarkably effective for a certain type of ink jet recording paper, there is a strong demand for printing on ordinary paper in the ink jet method, and therefore an ink jet ink using a water-soluble dye is used. Does not provide sufficient water resistance of the printed matter.
Further, the use of the recording paper for exclusive use of inkjet has a drawback that the running cost becomes high. In addition, dyes generally have poor light resistance to sunlight and the like, and there is a need to solve this point as well.

Since the ink jet ink using the dye as the color material has such drawbacks, the ink jet ink using the pigment as the color material has been developed. A printed matter printed with an inkjet ink using a pigment as a coloring material has good water resistance even if the paper is not an inkjet recording paper, and also has good light resistance. Inkjet inks that use pigments (hereinafter abbreviated as pigment-based inkjet inks) do not cause clogging and provide stable ejection characteristics in response to the reduction in nozzle diameter that is associated with higher resolution printing. In order to keep the pigment particles, it is necessary that the pigment particles do not settle and the particle diameter is sufficiently small.

As an attempt to reduce the pigment particle size of the pigment-based ink jet ink, a method using a dispersing machine such as a ball mill, a sand mill, a homogenizer, or a roll mill has been studied. However, these methods have drawbacks such that the particle size of the pigment cannot be made sufficiently small, and even if it becomes small, it takes a long time. As a method for improving these conventional drawbacks, US Pat.
In Japanese Patent No. 27,27, the pre-dispersed ink mixture is introduced into the chamber under high pressure, and the ink mixture interacts with each other by passing through at least a plurality of nozzles in the chamber. A method for producing a stable pigment-based inkjet ink has been proposed, but it is recognized that further improvement is necessary in terms of pressure loss due to having a plurality of flow paths and a short chamber life.

[0007]

DISCLOSURE 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 a high-definition printed matter having good water resistance on any paper. To provide a rapid manufacturing method.

[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 at} a temperature of 45 degrees or higher. Pass through a chamber with only one flow path that has at least two angle-change parts below
It is characterized in that the particle diameter of the pigment is made smaller than that during pre-dispersion by the effect of the collision of the dispersion with the wall surface of the angle changing portion in the flow path and the effect of friction between the dispersion and the inner 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 flow path, the applied pressure energy is less likely to drop, and the applied pressure energy can be effectively transmitted to the pigment particles. Therefore, since the applied pressure energy is not reduced as compared with the system having a plurality of flow paths and a small angle of deviation, the pigment particles can be made finer and dispersed. Further, since the structure of the chamber is simple, the dispersion is clogged in the chamber, the workability of the repair accompanying it becomes easy, and the life of the chamber is extended. This, in turn, has the effect of promoting higher quality ink jet ink and lowering manufacturing costs.

The chamber used in the present invention is
As shown in FIG. 1, one flow channel has a structure in which a and b are two divergent portions in the middle. The pre-dispersed pigment dispersion is applied with a high pressure (at least a liquid pressure of 100 Kg / cm ² ) from the entrance of the chamber, collides at high speed with the wall surfaces of the inflectional portions a and b in the flow path, and By virtue of such energy, the pigment particles are made finer and uniformly dispersed. The angle of variation of a and b is 45 degrees or more and 135 degrees or less, but is generally 90 degrees because of the ease of working the chamber. The flow passage 2 connecting a and b has a smaller cross-sectional area and a flat wall surface than the flow passage 1 from the inlet and the flow passage 3 to the outlet, which is effective in rapidly increasing the flow velocity. It is easy to obtain the effect of the shearing force obtained from the friction with the inner wall of the flow path and the effect of the collision at the bending portion.

The flow passage in the chamber preferably has a structure in which the cross-sectional area of the flow passage 2 is smaller than the cross-sectional area of the flow passage 1, and the area ratio is utilized to increase the pressure applied to the flow passage 1. It can be transmitted to the flow path 2. The larger the pressure on the flow path 2 side than the flow path 1, the more efficiently the atomization and dispersion in the chamber progress. The pressure applied to the 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 inside the chamber must be made of a material that can withstand high pressures, including ceramics such as sintered metal or sintered diamond, metal oxides, borides, carbides, nitrides or mixtures thereof. Etc.

The chamber used in the present invention is not limited to the one shown in FIG. 1, but may be one having three or more bending portions (four in FIG. 2) as shown in FIG. A high pressure pump is used to introduce the predispersed pigment dispersion into the chamber. When the pigment is not sufficiently made into fine particles by only passing it once through the chamber, the object can be achieved by performing an appropriate number of circulations. The liquid temperature of the dispersion before and after passing through the chamber is 5 to 40.
It is preferable to maintain the temperature in the range of ° C from the viewpoint of dispersion efficiency and stability of the dispersion. If the liquid temperature rises above this, cool the chamber and the pipes before and after it.

The dispersing solvent and the diluting solvent include odor,
Water and / or a water-soluble solvent is used from the viewpoint of safety. The water-soluble solvent may be used together with water when preliminarily dispersing the pigment and the dispersant, or may be added after dispersing the pigment and the dispersant in water. Further, the pigment dispersion after the preliminary dispersion can be added during the process of circulating the pigment dispersion in the chamber. The water-soluble solvent is a moisturizer to prevent the inkjet ink from drying at the nozzle part and solidification of the inkjet ink, and to perform stable jetting of the inkjet ink, and a drying to accelerate the drying on the printing material. Agents, viscosity modifiers, dissolution stabilizers and the like can be contained.

As the water-soluble solvent, 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 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 in a mixture of 2 to 50% by weight of the inkjet ink. Examples of desiccants for speeding up the drying include alcohols such as methanol, ethanol and isopropyl alcohol. As water, deionized water or distilled water from which metal ions and the like have been removed is used.

As the pigment, various pigments used in 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 pigment 7, 3
6, CI brown pigments 23, 25, 26, CI black pigment 7, titanium black (indicated by color index (CI) number), and the like. Such pigments are
It may be used in the state of an aqueous slurry after pigment formation, or may be powdered by drying such as spray drying. Further, a surface-treated pigment having a functional group added to the surface of the pigment may be used.

The ink-jet ink of the present invention has a water resistance and a pigment for the purpose of adjusting the hue of the pigment and imparting the concentration.
Dyes can be used in combination so that there is no problem in light resistance. However, the use of the dye may deteriorate the stability of dispersion of the pigment, so that the amount of the dye used should be 40% by weight or less, preferably 25% by weight or less. As the dye, an acid dye, a basic dye, a direct dye, a reactive dye, a disperse dye, a metal-containing dye or the like is used. The dye is
Purified dyes free of inorganic salts 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, etc. can be illustrated.

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

Embedded image

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

[Chemical 4]

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

As the nonionic activator, polyoxyethylene alkyl ether, polyoxyethylene alkylaryl 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 alkylamine salts, quaternary ammonium salts, alkylpyridinium salts, alkylimidazolium salts and the like. Examples of the zwitterionic activator include alkylbetaine, alkylamine oxide, phosphadylcholine and the like.

A water-based resin, a penetrating agent, a mildew-proofing agent, a chelating agent, a pH adjusting agent, a defoaming agent, a neutralizing agent for the water-based resin and the like can be added to the ink jet ink of the present invention. The water-based resin improves the stability of dispersion of the pigment and the fixability of the inkjet ink to the printing medium,
A water-soluble resin that is soluble in water and a resin that is dispersible in water can be used alone or in combination. As the water-based resin, a water-soluble resin such as an acrylic resin, a styrene-acrylic resin, a polyester resin, a polyamide resin, or a polyurethane resin which is soluble in water and a resin which is dispersible in water are used.
In order to neutralize the water-based resin, a neutralizing agent such as ammonia, amine, or inorganic alkali can be appropriately adjusted and added to the inkjet ink of the present invention.

When the material to be printed with the inkjet ink is a permeable material such as paper, a penetrating agent may be added in order to stop the penetration of the inkjet ink into the material to be printed and to accelerate the apparent drying property. it can. 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, etc. Can be used. These are sufficiently effective when used in an amount of 5% by weight or less of the ink jet ink, and if the amount is more than this amount, it causes bleeding of printing and paper dropout (print through), which is not preferable.

The mildew-proofing agent is for preventing the generation of mildew on ink jet inks, and includes sodium dehydroacetate, sodium benzoate and sodium pyridinethione-1.
-Oxide, zinc pyridinethion-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 inkjet ink and prevents the deposition of metal at the nozzle portion or the insoluble matter in the inkjet ink. Ethylenediamine tetraacetic acid, ethylenediamine tetra The sodium salt of acetic acid, the diammonium salt of ethylenediaminetetraacetic acid, the tetraammonium salt of ethylenediaminetetraacetic acid, etc. are used. These are 0.00% of inkjet ink.
Used in the range of 5 to 0.5% by weight.

Further, in order to adjust the pH of the inkjet ink and obtain stability of the inkjet ink or stability with the inkjet ink pipe in the recording apparatus,
Amine, an inorganic salt, a regulator such as ammonia, and a buffer solution such as phosphoric acid can be used. Further, an antifoaming agent may be added to prevent the circulation and movement of the inkjet ink or the generation of bubbles during the production of the inkjet ink. Other additives such as urea and dimethylurea may be added. The inkjet ink has a viscosity of 0.8 to 15 cp depending on the type of recording device.
It is prepared as a liquid of s (25 ° C). The surface tension is 25
Is about 60 dyn / cm. The pH is not particularly limited, but is in the range of 4 to 12, weakly acidic to neutral of 5 to 7,
It is preferably 7 to 9 neutral to weakly alkaline. In the present invention, the preliminary dispersion before passing through the chamber can be carried out by using a general dispersion method such as a mixer equipped with stirring blades, ultrasonic waves, a paint shaker, a sand mill, and a ball mill.

[0026]

The present invention will be described in more detail based on the following examples. In the examples, parts and% represent parts by weight and% by weight, respectively. A particle size distribution meter "DLS-700" manufactured by Otsuka Electronics Co., Ltd. was used to measure the average particle size of the dispersion. Example 1 The following raw materials were mixed and preliminarily dispersed using a sand mill to prepare an aqueous pigment dispersion. When the average particle size is measured by sampling at this stage, it is 266n.
It was m. Using 250 ml of the aqueous pigment dispersion, a chamber having a single flow path having two 90 ° angle changing parts (FIG. 1), an inlet temperature of 25 ° C. and a pressure of 700 kg /
cm ² and outlet temperature 50 ° C. for 20 cycles (liquid flow rate 360
ml / min, processing time 14 minutes). The average particle size of the dispersion subjected to this treatment was 125 nm. Blue pigment (“Rionol Blue 7351” manufactured by Toyo Ink Mfg. Co., Ltd.) 15 parts Acrylic resin solution 1.5 parts (“PDX6101” manufactured by Johnson Polymer Co., NV = 27.5%) Compound represented by general formula (II) Mixture of compounds represented by general formula (III) (weight ratio of (II) and (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 μ membrane filter and then through a 0.45 μ membrane filter to produce an inkjet ink. The viscosity is 2.
It was 0 cps (25 ° C). Mixture of compound represented by general formula (II) and compound represented by general formula (III) (weight ratio of (II) and (III) is 5: 1, average of n is 6) 0.2 part Acrylic resin dispersion Body 2.0 parts (Nippon Polymer Co., Ltd. "Touryl W-215", NV = 45%) Ethylene glycol 10 parts Antifungal agent (Ohlin Chemical's "Sodium omazine") 0.15 parts Ethylenediamine tetraacetic 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 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. When ink bleeding was examined by dripping water on the recording surface, there was no ink bleeding or running out, and the ink had sufficient water resistance. Further, when the head was left as it was for one week and recording was performed again, good recording could be performed.

[Comparative Example 1] A pre-dispersed water-based pigment was prepared in the same manner as in Example 1 except that the chamber was changed to a chamber having two channels having a 90 ° angle changing portion (Fig. 3). The dispersion was processed. The average particle size of the treated dispersion was 148 nm. 13.5 parts of the dispersion after treatment was mixed with the same as in Example 1 and filtered in the same manner to produce an inkjet ink. Filtration with a 0.45μ filter took 1.5 times as long as in Example 1.

Example 2 The following raw materials were mixed and sanded.
Preliminary dispersion using a mill to make an aqueous pigment dispersion
Was. Sampling is performed at this stage to measure the average particle size.
Then, it was 407 nm. 250 ml of aqueous pigment dispersion
Is a channel with one flow path having two 90-degree bends.
Using a chamber (Fig. 1), inlet temperature 15 ° C, pressure 70
0 kg / cm ²20 cycles at outlet temperature of 50 ° C (liquid flow
Volume 360 ml / min, processing time 14 minutes)). this
The average particle size of the treated dispersion was 215 nm.
Was. Yellow pigment ("Rionol Yellow 22-2845" manufactured by Toyo Ink Mfg. Co., Ltd.) 20 parts Acrylic resin solution 1.5 parts ("PDX6101" manufactured by Johnson Polymer, NV = 27.5%) Compound represented by general formula (II) And a compound represented by the general formula (III) (the weight ratio of (II) and (III) is 5: 1, the 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 μ membrane filter and then through a 0.45 μ membrane filter to produce an inkjet ink. The viscosity is 2.
It was 1 cps (25 ° C). Mixture of compound represented by general formula (II) and compound represented by general formula (III) (weight ratio of (II) and (III) is 10: 1, average of n is 6) 0.2 part Acrylic resin dispersion Body 2.2 parts (Nippon Polymer Co., Ltd. "Touryl W-215", NV = 45%) Ethylene glycol 10 parts Antifungal agent (Ohlin Chemical Co., Ltd. "Sodium omazine") 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 put in a cartridge of an ink jet printer ("HG5130" manufactured by Seiko Epson Corporation) and recording was performed, a good recorded matter was obtained. When ink bleeding was examined by dripping water on the recording surface, there was no ink bleeding or runoff, and it had sufficient water resistance. Further, when the head was left as it was for one week and recording was performed again, 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 with a sand mill using 0.5 mm glass beads as a medium. The average particle size of the treated dispersion was 357 nm. After the treatment, 11.5 parts of the dispersion was mixed with the same material as in Example 2 and the same filtration was performed. During filtration with a 0.8 μ membrane filter, pigment was deposited on the filter surface, necessitating replacement of the filter. The amount filtered with a 0.45μ filter was small. The filtrate concentration was about 93% of that of Example 2.

[Comparative Example 3] Preliminarily dispersed aqueous pigment was prepared in the same manner as in Example 2 except that the chamber was changed to a chamber having two channels having a 90 ° angle changing portion (Fig. 3). The dispersion was processed. The average particle size of the treated dispersion was 247 nm. 11.5 parts of the dispersion after treatment was mixed with the same as in Example 2 and filtered in the same manner to produce an inkjet ink. Filtration with a 0.45μ filter took approximately twice as long as in Example 2.

Example 3 The following raw materials were mixed and sanded.
Preliminary dispersion using a mill to make an aqueous pigment dispersion
Was. Sampling is performed at this stage to measure the average particle size.
Then, it was 223 nm. 250 ml of aqueous pigment dispersion
Is a channel with one flow path having two 90-degree bends.
Using a chamber (Fig. 1), the inlet temperature is 15 ° C and the pressure is 60.
0 kg / cm ², Outlet temperature 45 ° C, 15 cycles (liquid flow
The amount was 340 ml / min, the processing time was 11 minutes). This place
The average particle size of the treated dispersion was 115 nm. Blue pigment (“Ryonor 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%) Shown by the general formula (II). Mixture of compound and compound represented by general formula (III) (weight ratio of (II) and (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 μ membrane filter and then through a 0.45 μ membrane filter to produce an inkjet ink. The viscosity is 2.
It was 0 cps (25 ° C). Mixture of compound represented by general formula (II) and compound represented by general formula (III) (weight ratio of (II) and (III) is 10: 1, average of n is 6) 0.2 part Acrylic resin dispersion Body 1.8 parts (Nippon Polymer Co., Ltd. “Touryl W-215”, NV = 45%) Diethylene glycol 10 parts Antifungal agent (Ohlin Chemical Co., Ltd. “Sodium Omazine”) 0.15 parts Ethylenediaminetetraacetic acid acid 0.02 parts 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 in a cartridge of an ink jet printer ("HG5130" manufactured by Seiko Epson Corp.) and recording was performed, a good recorded matter was obtained. When ink bleeding was examined by dripping water on the recording surface, there was no ink bleeding or runoff, and it had sufficient water resistance. Further, when the head was left as it was for one week and recording was performed again, 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 channels having a 90 ° angle changing portion (Fig. 3). The dispersion was processed. The average particle size of the treated dispersion was 131 nm. 12.5 parts of the treated dispersion was mixed with the same dispersion as in Example 3 and the same filtration was carried out to produce an inkjet ink. Filtration with a 0.45μ filter took about 1.3 times as long as in Example 3.

An aqueous sodium hydroxide solution was added to the ink jet inks obtained in Examples 1 to 3 to adjust the conductivity to 0.
Adjusted to 8 mS or more. This ink can perform stable printing from the 35μ nozzle of a continuous jet type (suite type) inkjet printer, and the recorded characters are
Good water resistance was exhibited without running or bleeding even when water was dripped. The inks obtained in Examples 1 to 3 were stored at -40 ° C for one week and then naturally thawed, but the initial viscosity was maintained and stable jetting characteristics were exhibited. Also, 60
Although it was stored in a constant temperature bath at ℃ for 1 month, the initial viscosity was maintained and stable injection characteristics were exhibited. The inks obtained in Examples 1 to 3 were mixed with each other while giving a temperature change of -40 ° C to 60 ° C.
After a cycle of 3 days (holding for 3 hours), no deposit was generated in any of the inks, and the good initial state was maintained. Therefore, good printing and stable ejection characteristics were exhibited.

[0040]

According to the present invention, an inkjet ink having a small pigment particle size and a stable dispersion can be produced. The inkjet ink obtained by the production method of the present invention can be applied to high-definition printing images, and is extremely good in water resistance even though it is water-based. It can be used in a wide range of fields such as writing, cardboard marking, numbering, and bar code.
Further, it has better light resistance than an ink jet ink produced by a dye, and can form a color image having excellent storage stability of recorded matter.

[0041]

[Brief description of drawings]

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

FIG. 2 is a schematic view of the 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

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Shinya Fujimatsu 2-33 Kyobashi, Chuo-ku, Tokyo Toyo Inki Manufacturing Co., Ltd. (72) Inventor Yasuharu Iida 2-3-13 Kyobashi, Chuo-ku, Tokyo Toyo Inki Manufacturing Co., Ltd.

Claims (8)

[Claims] 1. A pigment dispersion prepared by preliminarily dispersing a pigment and a dispersant in a dispersion solvent, at least 100 kg / cm ^2.
Liquid pressure is applied to pass through a chamber having only one flow path having at least two angle changing parts of 45 degrees or more and 135 degrees or less, and the dispersion collides with the wall surface of the angle changing part in the flow path. And a method for producing an ink jet ink, characterized in that the particle size of the pigment is made smaller than that at 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 the pigment concentration is adjusted to 0.5 to 10% by weight using a diluting solvent after or before passing through the chamber. The method for producing an inkjet ink according to claim 1, wherein 3. The method for producing an ink jet ink according to claim 1, wherein the temperature of the dispersion after passing through the chamber or before passing through the chamber is maintained in the range of 5 to 40 ° C. 4. The method for producing an ink jet ink according to claim 1, wherein the cross-sectional area of the flow path in the chamber is different from that before and after the angle changing portion. 5. The dispersion solvent and the diluting solvent are water and / or a water-soluble solvent.
A method for producing the inkjet ink described above. 6. The method for producing an inkjet ink according to claim 1, wherein the dispersant is a compound represented by the general formula (I). Embedded image 7. An ink-jet ink produced by the method according to any one of claims 1 to 6. 8. A compound of the general formula (I)
Contains 10% by weight and has a viscosity of 0.8 to 15 centipoise (25
C.) The inkjet ink according to claim 7. Embedded image