JP3069550B2 - Method for producing aqueous pigment-based 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 pigment dispersion which can be used as a coloring agent suitable for a writing instrument, a recording instrument such as a printer for a computer or a copier, or a recording apparatus, and more particularly to an ink jet apparatus. And a method for producing a pigment dispersion ink.

[0002]

2. Description of the Related Art Conventionally, a solution of an aqueous dye containing a black dye has been used as an ink for an ink jet printer. In recent years, from the perspective of seeking storage durability and color fastness of printed matter, conversion from dyes to pigments as the black colorant, that is, efforts have been made to develop aqueous pigment inks using carbon black as the black pigment. It is well known.

It is a well-known fact that the surface of a commercially available carbon black for coloring is originally lipophilic and adapts well to oil, but has no affinity for water, and as a result tends to repel water. Therefore, in general, (1) a method using a carbon black surface which has been subjected to a hydrophilization treatment by some means, or (2) a method using a dispersant having chemical characteristics as a dispersant, Etc. are adopted.

The method (1) is, for example, a method in which the surface of carbon black is treated with an oxidizing agent or the surface of which is treated with a humate. (2) is a method of selecting a dispersant suitable for the selected pigment without specifying the pigment, for example, using an amine-based dispersant, or using an aqueous acrylic resin as a dispersant, In this method, carbon black is dispersed in an aqueous medium using a resin such as a styrene-acrylic resin or a styrene-maleic resin, and of course, using various dispersers suitable for dispersion.

[0005] Of the above, examples of developments in which the dispersant is characterized are disclosed in JP-A-56-147663 and JP-A-56-14863.
147868, JP-A-61-200182, and JP-A-4-18461. Japanese Patent Application Laid-Open (JP-A) No. 61-2354 discloses an example of devising dispersion stability.
No. 78, JP-A-61-246271, JP-A-62-116678 and the like.

[0006] Japanese Patent Application Laid-Open Nos. 56-147859 and 1-204979 disclose the dispersion particle size.
Japanese Patent Application Laid-Open No. Hei 3-234772 describes the use of pigment ink in an ink jet recording system in these systems.

[0007]

The ink jet recording system is a system in which a droplet is stably generated from the tip of a fine orifice of a recording head, and the droplet flies. Therefore, the conditions imposed on the water-based ink are (1) stable operation even under long-time continuous ejection conditions, (2) stable ejection under sufficient changes in the driving conditions of the recording head,
(3) In particular, in the bubble jet method, the orifice is not filled with heat stability without causing coagulation or carbonization on the heating surface in the head, and (4) Blackness is reduced due to sucking into the paper surface generated by pigment fine particles. (5) The recording medium has sufficient water resistance.

In order to satisfy the above five conditions, the pigment dispersed particles themselves are dispersed in ultrafine particles in the binder to be dispersed, but the composite of the pigment and the binder has a relatively large particle diameter, And how to provide a material having a large particle size and a cohesion stability against mechanical shear in water and a coagulation and carbonization stability against heat>. From this point of view, a conventional carbon black CBHA surface-treated with a humate,
In BL-P80 (S) and BL-P80 (both manufactured by Terunite Co., Ltd.), carbon black as a pigment and the humate are subjected to a mixing treatment in the absence of water,
Alternatively, even if water coexists, the amount is small, and as a result, it is a processed product obtained in a powder state or a water-containing flake state, and does not include a step of once separating carbon black, so that the above-described ordinary method, Even when dispersed by chemical selection of a dispersant, a large amount of undissolved substances is present, and the completion condition of <> is not satisfied. The present inventors first determined the appropriate conditions of humic acid under the condition that carbon black can be disintegrated using a relatively large amount of water. A method of using an organic solvent or an organic additive having a function, that is, a method that transcends common-sense techniques and finds a method that satisfies the above-mentioned completion conditions, has been repeated through trial and error, and has led to the completion of the present invention. Was.

[0009]

Accordingly, the technical concept of the present invention is integrated into the following technical means. (1) dispersing any aggregation of the pigment itself into fine particles that the pigment can reach using the power of a high-share disperser in the presence of a humate salt in water,
(2) Then, a binder resin group (resin or additive) capable of enclosing the dispersed fine particles or adsorbing on the surface is mixed to satisfy the above-mentioned completion conditions. That is, in the present invention, a humate dissolved in water is added and mixed in a liquid medium mainly containing water containing 60% or more of water so that the humate is 0.6 to 4 mg / m ² per specific surface area of carbon black. The average particle diameter of the carbon black pigment obtained by dispersing with a high-speed rotation media mill having a volume filling rate of 100% of the medium is in the range of 0.06 to 0.17 μm, and the maximum particle diameter is 0. This is a method for producing an aqueous pigment-based ink for inkjet, comprising mixing an organic solvent and an organic compound-based additive with a dispersion having a particle size of 0.6 μm or less.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The inventors of the present invention must first achieve the water resistance and weather resistance of an ink of the present invention by using a conventional dye type. Determined that it would not be. Next, the above-mentioned contents, which are technical problems in the pigment system, are based on grasping and controlling the degree of micronization, which involves applying energy by heat or a piezo effect imposed as a printing characteristic condition to obtain fine pores. From the selection of organic solvent and organic additive, and its pigment, which is compatible with an inkjet printer that uses ink droplets as a discharge source,
As a result of pursuing research on the relationship between these chemical properties and the coarse particles in the ink composed of these and the causal relationship that these two factors have on printing performance, the present invention was led to the present invention. The process is as follows.

First, a poorly dispersed mass of pigment in the ink,
In particular, when coarse particles having a maximum diameter of more than 0.6 μm are included, as the number of printed sheets increases, the printing becomes faint, the density becomes low, and the discharge of the ink itself stops. It has been found that by setting the thickness to 6 μm or less, it is possible to print stably for a long time without closing the fine holes of the recording head with coarse particles.
Second, when the average particle size of the dispersion exceeds 0.17 μm,
The average particle size of the dispersion needs to be 0.17 μm or less because it is difficult to exist as a uniform dispersion in the liquid for a long period of time, and the pigment easily adheres to the heat-acting surface in the bubble jet discharged by thermal energy. It was also found that when the average particle diameter was 0.06 μm or less, the pigment was absorbed into the paper greatly, and a high print density could not be obtained.
Third, by using alkaline ionized water having a cleaning effect on the dispersion medium, the cleaning effect is large at the time of head cleaning, and the ejection of ink is stably kept clean until the next cleaning time, It has been found that stable printing can be performed for a longer time. Fourthly, in preparing this pigment dispersion, (1) in the step of dispersing, first, the pigment particles are brought into contact with an aqueous solution of a surface treating agent such as a humic acid salt in water to disperse them by a strong mechanical dispersing force. (2) As mechanical conditions, carbon black is dispersed in a media mill in which the volume filling ratio of the media is 100% with respect to the above mixed solution (preferably at a rotational speed of a peripheral speed of 8 to 12 m / s). In order to obtain a dispersion in which the average particle diameter of the pigment obtained by dispersion is in the range of 0.06 to 0.17 μm and the maximum particle diameter is 0.6 μm or less, the dispersion is performed in a short time, efficiently, and stably. The present invention has been achieved by the combination of the above four, that is, to obtain an excellent dispersion and (3) to add an organic additive satisfying the particle size distribution to the obtained dispersion.

The pigments used in the ink of the present invention include:
Conventionally known carbon black can be used, but preferably, the oil absorption is 60 to 200 ml / 100 g, and the specific surface area is 50.
To 300 m ² / g, more preferably 80 to 200 m ² / g.
120 ml / 100 g, specific surface area 80-200 m ² / g
The powdered carbon black in the above range can be suitably used. When carbon black as a pigment is dispersed in water, the content of the pigment is 5 to 30% by weight, preferably 10 to 30% by weight.
It is used in the range of 20% by weight.

On the other hand, as the humic acid salt which is a surface treating agent for the above-mentioned pigment, a salt of humic acid which is a non-agricultural and not nitric acid-treated polyphenol type polycarboxylic acid is preferable, and CHA-02 and CHA- 07 (all trade names; manufactured by Terunite Co., Ltd.) are preferably used. It is preferable that the humate is dissolved in water in advance while adjusting the pH, and the pigment is added. The dissolution of the humate is 0.1 to 30% by weight, preferably 1.0 to 30% by weight based on the aqueous medium.
It is used in the range of 10% by weight. When dissolving the humate, a general device such as disperser stirring or a homomixer can be used. After dissolution, for example, a 100-200 mesh stainless steel net can be used to remove undissolved substances in the solution.

As the water used here, desalinated water having an electric conductivity of 0.1 μs / cm or less is preferably used after being filtered with a filter of 1 μm or less. More preferably, alkaline ionized water can be used. Unless otherwise specified in the present invention, simply referring to water means demineralized water having the above characteristics. Examples of the pH adjustment (agent) include ammonia water, alkali metal hydroxides such as diethanolamine, triethanolamine, triethylamine, and sodium hydroxide.

The amount of the humate added to the pigment is preferably in the range of 0.6 to 4 mg / m ^{2 based on} the specific surface area of the pigment. If the amount is less than this range, the dispersion stability becomes poor, and if added in a larger amount, not only is there no effect on the dispersion, but also the water resistance and the color density are undesirably reduced.

After the above-obtained mixed volume is subjected to a preliminary dispersion treatment, the main dispersion treatment is carried out, and the pigment is dispersed to the dispersion level of the present invention. The predispersing machine used is preferably a high-speed dissolver, a homomixer or the like. In particular, a continuous homomixer such as a TK homomic line mill (manufactured by Tokushu Kika Kogyo Co., Ltd.) can be suitably used. By performing the preliminary dispersion, 44
A μm stainless steel net can be easily passed, and introduction into the dispersing apparatus in the next step becomes easy.

In the present invention, a high-speed media mill is preferably used for dispersion. As the filling medium (medium) used here, zirconia beads having a diameter of 0.2 to 2.0 mm, preferably 0.3 to 1.0 mm, are used. Speed is 5-15m /
A disperser having equipment that can be set in the range of s can be suitably used. If the filling factor of the medium is less than 100%, it takes a long time to obtain a desired dispersion, and it is not possible to obtain a desired particle size distribution of the dispersion. On the other hand, if the peripheral speed is low, it takes time for dispersion, which is not preferable. Can not be done.

The pigment dispersion obtained as described above is subjected to a filtration treatment using a filter having a particle capture rate of 1 μm or more and 99.5% or more, to obtain a dispersion used for ink design. Hereinafter, this is referred to as a pigment dispersion stock solution. A desired inkjet ink is prepared by adding an organic solvent and an organic compound-based additive (a water-soluble additive), for example, a pH adjuster, a water-soluble resin, a resin emulsion, and a preservative to the obtained pigment dispersion stock solution. Is done.

The organic solvent used here is a water-soluble organic solvent, for example, methyl alcohol, ethyl alcohol, n-butyl alcohol, isopropyl alcohol,
alkyl alcohols having 1 to 4 carbon atoms such as n-propyl alcohol and isopropyl alcohol; ethers such as tetrahydrofuran dioxane; dimethylformamide;
Amides such as diacetamide, polyalkylene glycols such as polyethylene glycol and polypropylene glycol; alkylene glycols such as ethylene glycol, propylene glycol, butylene glycol and diethylene glycol; glycerin; ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, diethylene glycol methyl Lower alkyl ethers of polyhydric alcohols such as ether, diethylene glycol ethyl ether and triethylene glycol ethyl ether; N-methyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidin and the like. Of these many water-soluble organic solvents, lower alkyl ethers of polyhydric alcohols are preferred. Further, in the bubble jet method, ethanol or isopropyl alcohol can be added as needed in order to improve ejection stability.

Examples of the pH adjusting agent include ammonia water, diethanolamine, triethanolamine, triethylamine, and alkali metal hydroxides such as sodium hydroxide. As the organic compound-based additive, a resin, a surfactant, an antifoaming agent, a preservative, and the like can be added as needed in order to maintain desired physical properties in addition to the above components. Examples of the resin include a water-soluble resin and a resin emulsion.Examples of the water-soluble resin include casein, polyvinyl ether, polyvinyl pyrrolidone, methyl cellulose, hydroxyethyl cellulose, polyethylene glycol, and polyvinyl alcohol.
Styrene-acrylates, polyacrylates, polymethacrylates, and resin emulsions include polyacrylates, polymethacrylates, styrene-acrylic acid copolymers, and styrene-maleic acid copolymers , Urethane-acrylic acid copolymer, vinyl acetate, ethylene-vinyl acetate copolymer, vinyl acetate-acrylic acid copolymer, acrylonitrile-butadiene copolymer and the like.

However, if the surface tension is reduced to 35 dyne / cm or less by adding these additives, the ink absorbability to paper is high and ink strike-through or O
Since the D value decreases, the addition amount must be determined so as to be in the range of 40 to 60 dyne / cm.

Thus, the additives are mixed and stirred as described above,
Filtration was performed using a filter having a capture rate of particles exceeding 0.6 μm of 99.8% or more, and this was used as an aqueous pigment ink. According to the present invention, prints recorded using this water-based pigment ink are excellent in water resistance and light resistance as compared with conventional dye-based inks, and long-term dispersion, which is a problem in water-based pigment inks. The stability was excellent, and the launch stability and the storage stability were improved.
Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto.

[0023]

Example 1 0.7 parts of aqueous ammonia was added to 72.3 parts of ion-exchanged water of 0.1 μS / cm or less, and a humate (trade name: CHA-07; manufactured by Ternite) 7 was stirred. Part. After dissolving and stirring for 30 minutes, filtration was performed with a 150 mesh SUS filter. Next, 20 parts of carbon black was charged while stirring the obtained filtrate to prepare a mill base. The properties of the carbon black used here are specific surface area 134 m ² / g, DBP adsorption amount 100 cc / 100 g
It is. When the carbon black was sufficiently wet, preliminary dispersion was performed for 30 minutes using a continuous homomixer. Next, the mill base was dispersed by a media mill. The dispersing condition is as follows.
The filling was performed at a peripheral speed of 8 m / s and a residence time of 25 min. After dispersion, the mill base was filtered with a filter, and the filtrate was used as a dispersion stock solution.

The above-prepared dispersion stock solution was mixed in the following order to prepare an ink composition. Part by weight pigment dispersion stock solution 20 Deionized water 56 Ethyl alcohol 3 Diethyl glycol 5 Glycerin 15 Preservative 0.1 Next, the prepared ink was filtered, and the filtrate was set in an ink jet recording apparatus to perform printing.

Example 2 0.7 parts of aqueous ammonia was added to 72.3 parts of ion-exchanged water of 0.1 μS / cm or less, and 7 parts of a humate (trade name: CHA-02; manufactured by Ternite) were stirred. Input.
Thereafter, a dispersion stock solution was obtained in the same manner as in Example 1. Next, the prepared dispersion stock solution was mixed in the following order to prepare an ink composition. Part by weight pigment dispersion stock solution 20 Deionized water 56 Ethyl alcohol 3 Diethyl glycol 5 Glycerin 15 Preservative 0.1 Next, the prepared ink was filtered, and the filtrate was set in an ink jet recording apparatus to perform printing.

Example 3 1.0 part of aqueous ammonia was added to 68.5 parts of ion-exchanged water of 0.1 μS / cm or less, and humic acid salt (trade name: CHA-07; manufactured by Ternite Co.) with stirring. Insert 5 copies. Thereafter, a dispersion stock solution was obtained in the same manner as in Example 1. Next, the prepared dispersion stock solution was mixed in the following order to prepare an ink composition. Part by weight pigment dispersion stock solution 20 Deionized water 56 Ethyl alcohol 3 Diethyl glycol 5 Glycerin 15 Preservative 0.1 Next, the prepared ink was filtered, and the filtrate was set in an ink jet recording apparatus to perform printing.

Comparative Example 1 0.7 parts of ammonia water was added to 72.3 parts of ion-exchanged water of 0.1 μS / cm or less, and 7.0 parts of a nonylphenyl nonionic surfactant was added with stirring. Thereafter, a dispersion stock solution was obtained in the same manner as in Example 1. Next, the prepared dispersion stock solution was mixed in the following order to prepare an ink composition. Part by weight pigment dispersion stock solution 20 Deionized water 56 Ethyl alcohol 3 Diethyl glycol 5 Glycerin 15 Preservative 0.1 Next, the prepared ink was filtered, and the filtrate was set in an ink jet recording apparatus to perform printing.

Comparative Example 2 0.7 parts of ammonia water was added to 72.3 parts of ion-exchanged water of 0.1 μS / cm or less, and 7.0 parts of a polycarboxylic acid-based anionic surfactant was added with stirring. Thereafter, a dispersion stock solution was obtained in the same manner as in Example 1. Next, the prepared dispersion stock solution was mixed in the following order to prepare an ink composition. Part by weight pigment dispersion stock solution 20 Deionized water 56 Ethyl alcohol 3 Diethyl glycol 5 Glycerin 15 Preservative 0.1 Next, the prepared ink was filtered, and the filtrate was set in an ink jet recording apparatus to perform printing.

Comparative Example 3 1.5 parts of aqueous ammonia was added to 63.5 parts of ion-exchanged water of 0.1 μS / cm or less, and humic acid salt (trade name: CHA-07; manufactured by Ternite) was added with stirring. Insert 0 copies. Thereafter, a dispersion stock solution was obtained in the same manner as in Example 1. Next, the prepared dispersion stock solution was mixed in the following order to prepare an ink composition. Part by weight pigment dispersion stock solution 20 Deionized water 56 Ethyl alcohol 3 Diethyl glycol 5 Glycerin 15 Preservative 0.1 Next, the prepared ink was filtered, and the filtrate was set in an ink jet recording apparatus to perform printing.

Comparative Example 4 0.7 parts of aqueous ammonia was added to 72.3 parts of ion-exchanged water of 0.1 μS / cm or less, and humic acid salt (trade name: CHA-07; manufactured by Ternite) was stirred. Insert 5 copies. Thereafter, a dispersion stock solution was obtained in the same manner as in Example 1. Next, the prepared dispersion stock solution was mixed in the following order to prepare an ink composition. Part by weight pigment dispersion stock solution 20 Deionized water 56 Ethyl alcohol 3 Diethyl glycol 5 Glycerin 15 Preservative 0.1 Next, the prepared ink was filtered, and the filtrate was set in an ink jet recording apparatus to perform printing.

The inks prepared in the above Examples and Comparative Examples were evaluated by the following methods. As the property values of the ink, the surface tension was measured by a plate method at room temperature, and the average particle diameter was measured by a laser Doppler method. For the evaluation of physical properties, the solid part of the printed matter was
The value was measured. Also, for the rubbing property, the printed surface was rubbed with paper and the amount of transferred ink was measured. For the line pen property, the bleeding after the marker was measured with an aqueous highlighter pen. After drying, the bleeding was measured, and each was evaluated on a five-point scale from poor 1 to excellent 5. In addition, the printability was evaluated by printing continuously and evaluating the blurred state. As for storage stability, a change in liquid properties after 60 ° C. × 1 month was confirmed. The property values and physical property evaluation results of the inks prepared in Examples 1 to 3 and Comparative Examples 1 to 4 are shown below.

[0032]

[Table 1]

In Comparative Example 1, when a pigment dispersion stock solution was prepared using a nonionic surfactant, there was no significant difference in print quality, but an increase in viscosity and generation of coarse particles were observed during storage. Comparative Example 2 is an ink dispersed using an anionic surfactant and has a high O
No D value was obtained. As for storage stability, an increase in viscosity was observed. Comparative Example 3 was an ink obtained by dispersing using a large amount of humates, and resulted in low water resistance of printed matter. In Comparative Example 4, the ink dispersed with a small amount of humate had poor storage stability, and an increase in average particle diameter and generation of coarse particles were observed.

Example 4 In the same manner as in Example 1, 0.6 part of ammonia water was added to 73.9 parts of ion-exchanged water, and 5.5 of humic acid salt (trade name: CHA-07; manufactured by Ternite) was stirred. Part
The mixture was dissolved and stirred for 0 min. After filtration through 150 mesh SUS, the resulting filtrate was stirred while the specific surface area was 110 m ^2.
/ G and DBP adsorption amount of 125 cc / 100 g of carbon black were added to prepare a mill base. Hereinafter, Example 1
A dispersion stock solution was prepared in the same manner as described above. Next, the obtained dispersion stock solution was mixed in the following order to prepare an ink composition. Part by weight pigment dispersion stock solution 20 Deionized water 57 Ethyl alcohol 3 Diethylene glycol 5 Glycerin 15 Preservative 0.1 Next, the prepared ink was filtered, and the filtrate was set in an ink jet recording apparatus to perform printing.

Example 5 In the same manner as in Example 1, 1.1 parts of ammonia water was added to 67.9 parts of ion-exchanged water, and then 11 parts of a humic acid salt (trade name: CHA-07; manufactured by Ternite) was added with stirring. Throw in, 30
The mixture was stirred for min. After filtration with 150 mesh SUS,
While stirring the obtained filtrate, the specific surface area is 210 m ² /
g, DBP adsorption amount of 68 cc / 100 g of carbon black was added to prepare a mill base. Thereafter, a dispersion stock solution was prepared in the same manner as in Example 1. Next, the obtained dispersion stock solution was mixed in the following order to prepare an ink composition. Part by weight pigment dispersion stock solution 20 Deionized water 56 Ethyl alcohol 3 Diethylene glycol 5 Glycerin 15 Preservative 0.1 Next, the prepared ink was filtered, and the filtrate was set in an ink jet recording apparatus to perform printing.

Example 6 5 parts of triethanolamine was added to 74.3 parts of ion-exchanged water of 0.1 μS / cm or less, and then 7 parts of humic acid salt (trade name: CHA-07; manufactured by Ternite) was added with stirring. I put it in. After dissolving and stirring for 30 minutes, filtration was performed with 150 mesh SUS. Thereafter, dispersion was carried out in the same manner as in Example 1, and this was used as a dispersion stock solution. The dispersion stock solution prepared above was mixed in the following order to prepare an ink composition. Part by weight pigment dispersion stock solution 20 Deionized water 56 Ethyl alcohol 3 Diethyl glycol 5 Glycerin 15 Preservative 0.1 Next, the prepared ink was filtered, and the filtrate was set in an ink jet recording apparatus to perform printing.

Example 7 0.5 part of aqueous ammonia was added to 72.0 parts of alkaline ionized water, and then a humic acid salt (trade name: CHA-0) was stirred.
7; manufactured by Ternite Co.). 30min
After dissolution and stirring, filtration was performed with 150 mesh SUS. Thereafter, dispersion was carried out in the same manner as in Example 1, and this was used as a dispersion stock solution. According to the following order of the dispersion stock solution prepared above,
By mixing, an ink composition was prepared. Parts by weight of pigment dispersion liquid 20 Alkaline ionized water 56 Ethyl alcohol 3 Diethyl glycol 5 Glycerin 15 Preservative 0.1 Next, the prepared ink was filtered, and the filtrate was set in an ink jet recording apparatus to perform printing.

Example 8 0.7 parts of aqueous ammonia was added to 72.3 parts of ion-exchanged water of 0.1 μS / cm or less, and 7 parts of humic acid salt (trade name: CHA-07; manufactured by Ternite) were stirred. Was introduced. After dissolving and stirring for 30 minutes, filtration was performed with 150 mesh SUS. Next, while stirring the obtained filtrate, carbon black was charged to prepare a mill base. The characteristic of the carbon black used here is a specific surface area of 134 m ² /
g, DBP adsorption amount was 100 cc / 100 g. When the carbon black was sufficiently wet, preliminary dispersion was performed for 30 minutes using a continuous homomixer. Next, the mill base was dispersed by a media mill. The dispersing conditions were as follows.
% And a peripheral speed of 12 m / s and a residence time of 15 mi
n. After the dispersion, the mill base was filtered, and the filtrate was used as a dispersion stock solution. The dispersion stock solution prepared above was mixed in the following order to prepare an ink composition. Part by weight pigment dispersion stock solution 20 Deionized water 56 Ethyl alcohol 3 Diethyl glycol 5 Glycerin 15 Preservative 0.1 Next, the prepared ink was filtered, and the filtrate was set in an ink jet recording apparatus to perform printing. .

Comparative Example 5 0.7 parts of aqueous ammonia was added to 72.3 parts of ion-exchanged water of 0.1 μS / cm or less, and then 7 parts of a humate (trade name: CHA-07; manufactured by Ternite) with stirring. Was introduced. After dissolving and stirring for 30 minutes, carbon black was charged to prepare a mill base. The characteristics of the carbon black used here are specific surface area 134 m ² / g, DBP adsorption amount 10
It was 0 cc / 100 g. When the carbon black was sufficiently wet, preliminary dispersion was performed for 30 minutes using a continuous homomixer. Next, the mill base was dispersed by a media mill. As dispersion conditions, zirconia beads having a diameter of 0.5 mm were filled as a medium at a filling rate of 100%. This was performed at a peripheral speed of 8 m / s for a residence time of 15 min, and this was used as a dispersion stock solution without filtration. The dispersion stock solution prepared above was mixed in the following order to prepare an ink composition. Weight part pigment dispersion stock solution 20 ion-exchanged water 56 ethyl alcohol 3 diethyl glycol 5 glycerin 15 preservative 0.1 Next, the prepared ink was filtered through a 20 μm filter,
This was set in an ink jet recording apparatus and printing was performed. The property values and physical property evaluation results of the inks prepared in Examples 4 to 8 and Comparative Example 5 are shown below.

[0040]

[Table 2]

In Comparative Example 5, printing was blurred from the first sheet, and printing became impossible immediately. Further, generation of aggregates was observed at the bottom over time.

Example 9 0.7 parts of aqueous ammonia was added to 72.8 parts of ion-exchanged water of 0.1 μS / cm or less, and humic acid salt (trade name: CHA-07; manufactured by Ternite) was stirred. 5 parts were charged, and after dissolving and stirring for 30 minutes, filtration was performed with 150 mesh SUS. Next, while stirring the obtained filtrate, carbon black was charged to prepare a mill base. The characteristics of the carbon black used here are specific surface area 125 m ² /
g, DBP adsorption amount was 110 cc / 100 g. When the carbon black was sufficiently wet, preliminary dispersion was performed for 30 minutes using a continuous homomixer. Next, the mill base was dispersed by a media mill. The dispersion conditions were as follows: 0.5 mm diameter zirconia beads were used as the medium and the filling rate was 100%.
%, The peripheral speed is 12 m / s and the residence time is 25 mi
n. After the dispersion, the mill base was filtered, and the filtrate was used as a dispersion stock solution.

The stock dispersion solution prepared above was mixed in the following order to prepare an ink composition. The acrylic emulsion used here had an average particle size of 0.04 μm,
It was a soapless microemulsion having a pH of 8.5 and a Tg of 78 ° C. Parts by weight of pigment dispersion liquid 20 Deionized water 20 Ion-exchanged water 47 Ethyl alcohol 3 Diethyl glycol 5 Glycerin 15 Acrylic EM 10 Preservative 0.1 Next, the prepared ink is filtered, and the filtrate is set in an ink jet recording apparatus to perform printing. Was.

Example 9 An ink composition was prepared by mixing the stock dispersion solution prepared in Example 8 in the following order. The acrylic emulsion used here had an average particle diameter of 0.04 μm and a pH of 8.
5. It was a saw press microemulsion having a Tg of 78 ° C. Parts by weight of pigment dispersion liquid 20 Deionized water 20 Ion-exchanged water 53 Ethyl alcohol 2 Diethylene glycol 10 Glycerin 5 Acrylic EM 10 Preservative 0.1 Next, the prepared ink was filtered, and the filtrate was set in an ink jet recording apparatus to perform printing. .

Comparative Example 6 An ink composition was prepared by mixing the stock dispersion prepared in Example 8 in the following order. Part by weight of pigment dispersion stock solution 20 Deionized water 80 Preservative 0.1 Next, the prepared ink was filtered, and the filtrate was set in an ink jet recording apparatus to perform printing.

The property values and physical properties of the inks prepared in Examples 9 and 10 and Comparative Example 7 are shown below.

[0047]

[Table 3]

In both Examples 9 and 10, the addition of the acrylic emulsion improved the OD value, abrasion, line pen properties and water resistance of the printed matter. However, there was a tendency that the launching property was slightly deteriorated. The storage stability was good. In Comparative Example 6, printing was possible, but the printed matter was poor in abrasion and line pen properties.

[0049]

According to the present invention, when used for ink jet, a water-based pigment ink having excellent printability, robust printed matter, and long-term stability is provided.

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Claims (3)

(57) [Claims] 1. A humic acid salt dissolved in water is added to a liquid medium containing water as a main component and containing not less than 60% of water in an amount of 0.6 to 4 mg / m ² per carbon black specific surface area. The average particle diameter of the carbon black pigment obtained by dispersing with a high-speed rotation media mill having a volume filling rate of 100% of the medium is in the range of 0.06 to 0.17 μm, and the maximum particle diameter is 0. A method for producing an aqueous pigment-based ink for inkjet, comprising mixing an organic solvent and an organic compound-based additive with a dispersion having a particle size of 0.6 μm or less. 2. The method according to claim 1, wherein the water is alkaline ionized water. 3. An aqueous pigment-based ink for inkjet obtained by the production method according to claim 1.