JP3254969B2 - Ink jet ink and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet ink having excellent water resistance and a method for producing the ink.

[0002]

2. Description of the Related Art Conventionally, ink jet recording liquids are disclosed in JP-A-53-61412 and JP-A-54-89.
As disclosed in JP-A-811 and JP-A-55-65269, those obtained by dissolving a water-soluble dye such as an acid dye, a direct dye or a basic dye in a glycol-based solvent and water are often used. However, as the water-soluble dyes, those having high solubility in water are generally used in order to obtain the stability of the recording liquid. There has been a problem that the dye of the recording portion is blurred.

In order to improve such poor water resistance,
As disclosed in JP-A-56-57862, attempts have been made to change the structure of the dye or to prepare a recording solution having a strong basicity. Also, Japanese Patent Application Laid-Open Nos. 50-49004, 57-36692, and 59-2
As disclosed in JP-A No. 0696 and JP-A-59-146889, the water resistance is improved by making good use of the reaction between the recording paper and the recording liquid. These methods have a remarkable effect on certain types of recording paper. However, since various recording papers are used in the ink jet system, sufficient water resistance of the recorded matter can be obtained with a recording liquid using a water-soluble dye. Often not.

As recording liquids having good water resistance, there are those in which an oil-soluble dye is dispersed or dissolved in a high boiling point solvent, and those in which an oil-soluble dye is dissolved in a volatile solvent. Environmentally disliked the emission of
Depending on the case where a large amount of data is recorded or where the apparatus is installed, the necessity of solvent recovery may be a problem. Therefore, in order to improve the water resistance of the recorded matter, a recording liquid in which a pigment is dispersed in an aqueous medium has been developed. However, pigments, unlike dyes, are insoluble in a recording medium, and it is very difficult to disperse them as fine particles and to maintain a stable dispersion state. In addition, while exhibiting the characteristics of pigments with excellent water and light resistance, adjustment of recording liquid ejection conditions, long-term storage stability, fixing to recording media such as paper, image color, bleeding, etc. At present, further improvement is required in order to obtain properties comparable to or better than dyes.

[0005] Further, in the recording liquid for ink jet, as the nozzle diameter becomes smaller due to the higher resolution of the printer, it is necessary to make the particle diameter of the colorant finer. In addition, the recording liquid in which the pigment is dispersed is required to have conflicting properties such as resolubility in the recording liquid and water resistance on paper, but using a water-soluble resin is superior in resolubility. However, it was difficult to obtain sufficient characteristics in terms of water resistance on paper. Further, when a water-dispersible resin is used from the viewpoint of water resistance, the water resistance on paper is good, but when ink adheres to the head portion or the like, the ink has no resolubility and there is a restriction in use.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide an ink-jet ink which has sufficient water resistance on paper, excellent re-dissolution of the ink at the head, and good ejection stability at the nozzle. Is to do.

[0007]

That is, according to the present invention, carbon black is dispersed in an aqueous liquid by using a terpolymer composed of acrylic acid, styrene and α-methylstyrene, and the dispersion is dispersed in an aqueous liquid. The present invention relates to a method for producing an ink-jet ink, which comprises performing a heat treatment at a temperature of from about 80C to about 80C. Furthermore, the present invention relates to the above-mentioned production method, wherein a concentrated aqueous dispersion in which carbon black is dispersed is prepared, and then diluted by adding water and additives, followed by heat treatment. Further, the present invention relates to the above production method, wherein the heating time is 5 to 48 hours.

[0008]

DETAILED DESCRIPTION OF THE INVENTION The ink-jet ink of the present invention generally contains 1 to 5% by weight of carbon black,
-1% by weight, antifungal agent 0.03-0.5% by weight, terpolymer of acrylic acid, styrene, α-methylstyrene 0.5-10% by weight, aqueous solvent 0-25% by weight, water 50
９５95% by weight.

The terpolymer composed of acrylic acid, styrene and α-methylstyrene contributes to the extremely stable dispersion of carbon black, and 0.5 to 10%
It is preferable to use 10% by weight. If it is less than this, the conductivity due to the carbon black increases, and the possibility of short-circuiting at the deflection electrode or the like in the continuous type multi-head increases. On the other hand, if the amount is larger than this, it is difficult to set the viscosity of the ink to be low, and it is impossible to generate droplets sufficiently. The molecular weight of the terpolymer composed of acrylic acid, styrene and α-methylstyrene is 2000
It is preferably from 8,000 to 5,000, and more preferably from 2,000 to 5,000, in view of the dispersibility of the pigment and the ejection stability of the ink, the resistance value of the ink solid printing surface, and the like. Further, the acid value of the terpolymer is preferably from 90 to 130 in view of water resistance on paper, resolubility of the ink in the head portion, resistance value of the ink solid printing surface, and the like.

A terpolymer composed of acrylic acid, styrene and α-methylstyrene can be obtained by copolymerizing acrylic acid, styrene and α-methylstyrene by a known method. It is preferable that the copolymer is a total of 3 to 5 mol of α-methylstyrene.
Further, styrene 2.0 mole per mole of acrylic acid
To 4.0 mol, preferably 2.2 to 3.5 mol, α-methylstyrene 0.3 to 1.5 mol, preferably 0.5 to
Preferably, it is a 1.2 mol copolymer. By this copolymerization ratio, a copolymer having a good balance of dispersion stability, water resistance, resolubility, and high resistance value on a solid image forming surface can be obtained.

In the ink-jet ink of the present invention, in order to stably dissolve the terpolymer in the liquid component of the ink, hydroxides of alkali metals such as sodium and potassium, aliphatic amine and ethanolamine are used. , Propanolamine, alcoholamines such as methylethanolamine, morpholine, N-methylmorpholine, dimethylaminoethanol, diethylaminoethanol and the like are used as neutralizing agents. By using an equimolar or excessive amount of the neutralizing agent with the above terpolymer, maintenance of solubility, maintenance of water resistance, and maintenance of resolubility are performed well.

As the carbon black, any of neutral, basic and acidic carbon blacks can be used. Specifically, Mitsubishi Kasei's MA7, MA100, MA8,
MA11, NO50, NO2300, No950. No
850, MCF88, Printex9 manufactured by Degussa
5,90,85,75,55,45,40, Color
Black FW18, S160, Special B
rack 550, 350, RAVEN 1030, 850, 760, 780, 50 manufactured by Columbia Carbon Co.
0,1255,1250,1500, Black PEAR, VULCAN XC, P, RE manufactured by Cabot Corporation
Examples include GAL 550R, 330I, ELFEX8, and SEAST 5H, 3H manufactured by Tokai Carbon Co., Ltd., and a commercially available dispersion previously dispersed may be used.

Carbon black is dispersed together with a binder resin in an aqueous medium, or is dispersed in advance with a binder resin and then diluted with an aqueous medium to produce an ink jet ink. The preferred particle size of the carbon black after dispersion is 0.2 μm or less, more preferably 0.1 μm or less, in terms of the average particle size determined by a laser scattering method. With such a particle diameter, the ejection of the ink at the time of recording is stabilized, and the filtration operation in the production of the ink is easy, and the sedimentation of the ink over time is less likely to occur. Carbon black is preferably used in the range of 1 to 5% by weight of the ink. If it is less than this, the image density and color reproduction will be insufficient. On the other hand, if it is more than this, the stability of the discharge is remarkably reduced, and the nozzle is liable to be frequently clogged. Also, it may be difficult to adjust the viscosity of the ink.

A dye may be used in the ink-jet ink of the present invention in such a manner that there is no problem in water resistance and light resistance for the purpose of adjusting the hue, imparting the density, and adjusting the characteristics of the ink. However, the use of the dye may degrade the dispersion stability of the carbon black, so the amount of the dye used is 40% by weight or less of the pigment, preferably 2% by weight.
It must be kept below 5% by weight. Dyes include acid dyes, basic dyes, direct dyes, reactive dyes, disperse dyes,
A metal-containing dye or the like is used. The dye is preferably a purified dye from which inorganic salts have been removed.

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, Food Blacks 1, 2 and their lithium or potassium substitutes, CI Acid Blue 9, 22, 40, 59, 93, 102, 104, 11
3,117,120,167,229,234, CI Basic Blue 1,3,5,7,9,24,25,2
6, 28, 29 and the like.

The liquid component in the ink-jet ink of the present invention includes water and an aqueous solvent. As the water used as the ink medium, ion-exchanged water or distilled water from which metal ions and the like have been removed is 50 to 95% by weight of the ink.
It is preferable to use within the range. The aqueous solvent prevents drying and solidification of the ink at the nozzle portion, prevents stable ejection of the ink and prevents the nozzle from drying over time, and also functions as a humectant. ~ 2
Used in the range of 5% by weight.

As the aqueous 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,
Examples thereof include ethylene glycol monoethyl ether, 1,2-hexanediol, N-methyl-2-pyrrolidone, substituted pyrrolidone, 2,4,6-xantriol, tetrafurfuryl alcohol, and 4-methoxy-4-methyl petanone. Further, alcohols such as methanol, ethanol and isopropyl alcohol can be used for the purpose of speeding up the drying of the ink on paper.

If the ink substrate is a permeable material such as paper, a penetrant may be added to stop the ink from penetrating into the paper and speed up the apparent dryness. Examples of such penetrants include glycol ethers such as diethylene glycol monobutyl ether and the like exemplified as aqueous solvents, alkylene glycol, polyethylene glycol monolauryl ether, sodium lauryl sulfate, sodium dodecylbenzenesulfonate, sodium oleate, sodium dioctylsulfosuccinate, and the like. Can be used. These have sufficient effects when used in an amount of 5% by weight or less of the ink. If the amount is more than 5% by weight, bleeding of the print and paper loss (print through) occur, which is not preferable.

The antifungal agent is for preventing the generation of mold on the ink, and includes sodium dehydroacetate, sodium benzoate, sodium pyridinethione-1-oxide, zinc pyridinethion-1-oxide, 1,2-benzisothiazoline. For example, amine salts of -3-one and 1-benzisothiazolin-3-one are used. These are used in the range of about 0.03 to 0.5% by weight of the ink. The chelating agent blocks metal ions in the ink and prevents the deposition of metal at the nozzle portion and the deposition of insoluble substances in the ink. The chelating agent is ethylenediaminetetraacetic acid, ethylenediaminetetraacetic acid. And the ammonium salt of ethylenediaminetetraacetic acid, the tetraammonium salt of ethylenediaminetetraacetic acid, and the like.
These are used in the range of 0 to 0.5% by weight of the ink.

In order to adjust the pH of the ink and obtain stability of the ink or stability with the ink pipe in the recording apparatus, a pH adjuster such as an amine, an inorganic salt or ammonia, or a buffer solution such as phosphoric acid is used. be able to. Further, an antifoaming agent can be added in order to prevent the circulation and movement of the ink or the generation of bubbles during the production of the ink. Furthermore, for the purpose of carbon black dispersion and image quality improvement,
Surfactants such as anionic, nonionic, cationic and amphoteric surfactants and dispersants can be used.

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, and alkyl phosphoric acids. Salt, polyoxyethylene 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, etc. Can be illustrated.

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 amphoteric surfactants include alkyl betaines, alkylamine oxides, phosphadylcholines, and the like.

As other additives, urea, dimethyl urea and the like can be added. In addition, other conventionally known various solvents, additives, salts, synthetic and natural resins and the like can be used in combination. For ink production, mix carbon black, water, and if necessary, dispersant and aqueous solvent.
After dispersing with a sand mill, a homogenizer, a ball mill, a paint shaker, an ultrasonic disperser or the like, a solution of the terpolymer is added and mixed. Alternatively, carbon black, a terpolymer, water, a dispersant, and an aqueous solvent are mixed as necessary, and the mixture is dispersed with a sand mill, a homogenizer, a ball mill, a paint shaker, an ultrasonic disperser, or the like. Alternatively, carbon black and terpolymer are kneaded well in advance with a two-roll mill, further dispersed in a sand mill or the like, diluted appropriately with water, and mixed with other additives.

The terpolymer may be used after being sufficiently dissolved in a neutralizing agent in advance, and it is also effective to heat the terpolymer for dissolution. It is also effective to add a heat treatment after dispersion to improve the stability of the ink. Mixing and stirring can be performed by using a high-speed disperser,
It can be performed by an emulsifier or the like. Before or after dilution, the mixed ink is sufficiently filtered through a filter having a pore size of 3 μ or less, preferably a filter of 1.0 μ or less, and more preferably a filter of 0.45 μ or less.
Prior to filtration, filtration by centrifugation may be performed, thereby reducing clogging in filter filtration and reducing filter replacement.

The ink is adjusted as a liquid having a viscosity of 0.8 to 15 cps (at 25 ° C.), depending on the type of the recording apparatus. The surface tension is 25-60 dyn / cm. pH
Is in the range of 7 to 12, though not particularly restricted, and is in the range of 7 to 1
A weak alkalinity of 0 is preferred. The ink of the present invention can be used for both a continuous type printer and an on-demand type printer. In a continuous type printer, the conductivity of the ink is adjusted so that the droplets are appropriately charged.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on embodiments.
In the examples, parts and% represent parts by weight and% by weight, respectively. A terpolymer having the following monomer composition (molar ratio) was synthesized according to an acrylic resin synthesis method. Acrylic acid Styrene α-Methylstyrene Acid value Molecular weight Synthesis Example 1 1 2.5 0.7 105 3500 21 2 0.9 0.9 100 5000 3 1 2.3 0.7 102 2500 2500 13.0 1.0 95 4500 5 1 3.4 0.7 90 4000 6 1 2.1 1.2 120 3000

Example 1 The following materials were placed in a sand mill and dispersed to prepare a dispersion. Carbon black ("MA7", manufactured by Mitsubishi Kasei Co., Ltd.) 30 parts Terpolymer of Synthesis Example 1 3.0 parts Dimethylaminoethanol 0.4 part Surfactant (Emulgen 420, manufactured by Kao Corporation) 1.0 part Purification Water 50.0 parts Glycerin 6.0 parts

After dispersion, they were mixed with: After mixing
The mixture was filtered through a 0.45 μm membrane filter to produce an ink. The particle size distribution of the obtained ink is measured by a laser diffraction type particle size distribution meter (“DSL-700” manufactured by Otsuka Electronics Co., Ltd.).
As a result, the average particle size was 80 nm. The above dispersion 13.5 parts Surfactant ("Emulgen 420" manufactured by Kao Corporation) 0.2 part The terpolymer of Synthesis Example 1 3.8 parts Ethylene glycol 10.0 parts Antifungal agent (manufactured by Ohrin Co., Ltd.) Sodium omadine ") 0.15 parts Sodium salt of ethylenediaminetetraacetic acid 0.02 parts Purified water 63.53 parts

Example 2 The following materials were placed in a sand mill and dispersed to produce a dispersion. Carbon black (“Printex 40” manufactured by Degussa) 4.0 parts Blue pigment dispersant (P- [CH ₂ NH (CH ₂ ) ₄ N (CH ₃ ) ₂ ] ₃ ) P is a copper phthalocyanine residue 0.6 part Synthesis 3.0 parts of the terpolymer of Example 2 3.0 parts of diethylaminoethanol 0.3 parts of a surfactant ("Emulgen 420" manufactured by Kao Corporation) 0.5 parts of a dispersant ("Solsperse 27000" manufactured by Zeneca) 0.5 part Purification Water 50.0 parts Diethylene glycol monobutyl ether 1.0 part

After dispersion, they were mixed with: After mixing
The mixture was filtered through a 0.45 μm membrane filter to produce an ink. The average particle size of the obtained ink was 85 nm. The above dispersion 13.5 parts Surfactant ("Emulgen 420" manufactured by Kao Corporation) 0.2 part Terpolymer of Synthesis Example 1 4.3 parts Ethylene glycol 10.0 parts Antifungal agent (manufactured by Ohlin Co., Ltd.) Sodium omadine ") 0.15 parts Sodium salt of ethylenediaminetetraacetic acid 0.02 parts Purified water 63.53 parts

Example 3 The following materials were placed in a sand mill, dispersed, filtered through a 1 μm membrane filter, and further filtered through a 0.45 μm membrane filter to produce an ink. The average particle size of the obtained ink is 94 nm.
Met. 9.5 parts of carbon black dispersion (“Hostafine TS” manufactured by Hoechst, solid content 33%) Blue pigment dispersant (P- [CH ₂ NH (CH ₂ ) ₄ N (CH ₃ ) ₂ ] ₃ P is copper Phthalocyanine residue 0.1 part Dye (CI Direct Black 154) 0.5 part Terpolymer of Synthesis Example 2 3.9 parts Diethylaminoethanol 0.6 part Surfactant ("Emulgen 420" manufactured by Kao Corporation) 0.4 part Dispersant ("Solsperse 27000" manufactured by Zeneca) 0.5 part Diethylene glycol monobutyl ether 1.0 part Ethylene glycol 1.0 part Fungicide ("Sodium Omazine" manufactured by Ohlin) 0.15 part Ethylenediaminetetra Acetic acid sodium salt 0.02 parts Purified water 83.53 parts

[Comparative Examples 1 to 10 and Examples 4 to 10]
The following resin was used instead of the terpolymer of Synthesis Example 2,
An ink was produced in the same manner as in Example 3.

Resin Acid Value Molecular Weight (Solid Content) Comparative Example 1 A-St 150 6800 4 parts 2 A-St 195 10000 5 parts 3 A-St 200 5000 5 parts 4 A-St 200 7000 4 parts 5 A-St 200 7500 5 parts 6 A-St 235 1600 5 parts 7 A-emulsion 1 4 parts 8 A-emulsion 2 5 parts 9 Polyester 5 parts Example 4 Synthesis Example 3 102 2500 5 parts 5 4 95 5 4000 5 parts 6 5 90 4000 5 parts 7 3 102 2500 4 parts 8 4 95 4000 4 parts 9 5 90 4000 4 parts 10 6 120 3000 4 parts

A-St is a styrene acrylic resin, and A-emulsion 1 is an acrylic resin emulsion ("Riocryl PFX030" manufactured by Nippon Polymer Industries Co., Ltd.).
2)) and A-emulsion 2 is an acrylic resin emulsion ("Torkuril S74" manufactured by Nippon Polymer Industries Co., Ltd.).
0 "), and polyester represents a water-soluble polyester resin (" Z-446 "manufactured by Ryogo Chemical Industry Co., Ltd.).

The inks obtained in Examples and Comparative Examples were evaluated for water resistance, resolubility, filterability, viscosity, jetting characteristics, resistance and dispersibility. Table 1 shows the results. When the ink obtained in the example was stored at −40 ° C. for one week and then naturally thawed, the initial viscosity was maintained and stable ejection characteristics were exhibited. In addition, when stored in a 60 ° C constant temperature bath for one month, the initial viscosity was maintained.
It showed stable injection characteristics. Further, when a cycle of −40 ° C. for 7 hours, room temperature for 7 hours, and 50 ° C. for 7 hours was repeated three times, the initial printing characteristics and physical properties of the ink were maintained.

The evaluation was performed as follows. (1) Water resistance After printing the ink on the cartridge of an inkjet printer (“GXII” manufactured by Hitachi, Ltd.) and printing on plain paper (“K” manufactured by Xerox Corporation), immerse the ink in water for 1 minute after drying. Was visually evaluated (good: no bleeding, poor: bleeding). Further, the change in the printed portion when the solid printed on the art paper was rubbed three times with a wet cotton swab was visually evaluated (good: no change, defective: changed).

(2) Resolubility The ink was dropped on a nickel plate, dried 2 days later, and visually evaluated for solubility when immersed in the same ink (good: dissolved, poor: insoluble). (3) Filterability The amount of filtration with a 90 mm diameter membrane filter was examined. (4) Viscosity 25 ° C with a vibrating viscometer (“VM-1A” manufactured by Yamaichi Electric Co., Ltd.)
Was measured.

(5) Ejection Characteristics Injection failure of nozzles during continuous printing was evaluated based on the presence or absence of defects in printed matter (good: no defect, defective: defective). (6) Resistance value Ink was applied to coated paper (“NPI coated paper” manufactured by Nippon Paper Industries). 6 with a bar coater, and the resistance of the coated surface after drying is measured with a resistivity meter (“MCP-T40” manufactured by Mitsubishi Yuka Co., Ltd.).
0]). The same resistance value was measured at 70 ° C. 12
The test was also performed on the ink that had been subjected to the heat treatment for a long time. (7) Dispersibility The ink was evaluated for dispersibility from changes in particle diameter before and after storage at 50 ° C. for 7 days (good: less than 15 nm, bad: 15 nm or more).

[0039]

[Table 1]

[0040]

The ink-jet ink of the present invention provides water-resistant recorded matter regardless of the type of the recording medium while using water as a medium.
It can be used in fields such as cardboard marking and numbering. Further, since the ink of the present invention is excellent in resolubility, even when ink adheres to the deflection electrode, troubles due to adhesion and accumulation of the ink are reduced. Furthermore, in the case of ink using carbon black in particular, there is a possibility that a short circuit of current due to the ink at the deflecting electrode may be a problem. However, since the ink of the present invention has a high resistance value after drying, such an ink is used. Trouble is reduced.

────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-4-126780 (JP, A) JP-A-2-276875 (JP, A) JP-A-2-276873 (JP, A) JP-A-2-27687 276872 (JP, A) JP-A-8-253716 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C09D 11/00-11/20

Claims (5)

(57) [Claims] 1. Carbon black is dispersed in an aqueous liquid using a terpolymer of acrylic acid, styrene and α-methylstyrene, and the dispersion is heated at a temperature of 60 to 80 ° C. A method for producing an inkjet ink, comprising: 2. The production method according to claim 1, wherein a concentrated aqueous dispersion in which carbon black is dispersed is prepared, and then water and additives are added thereto for dilution, followed by heat treatment. 3. The heating time is 5 to 48 hours.
Or the production method according to 2. 4. A terpolymer having a molecular weight of 2,000 to 80.
The method according to any one of claims 1 to 3 , wherein the acid value is 90 to 130 . 5. A terpolymer The method according to any one of claims 1 to 4 polymer used from 0.5 to 10 wt%.