JP2000053885A - Carbon black and recording ink - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the dispersion stability of carbon black in an aqueous medium and to improve the storage stability of a recording ink using carbon black as the coloring material and to enable obtainment of good images with reduced occurrence of disturbance of images, nonuniformity of density and the like by preventing clogging of the ink in the nozzle to stably jet the ink in the case of using the recording ink in an ink recording apparatus. SOLUTION: This recording ink can be obtained by reacting a diamine having a terminal amino group with the surface of carbon black, further reacting this diamine with a polyoxyethylene and dispersing a coloring agent composed of the resulting carbon black having been reacted with the diamine and the polyoxy-ethylene in an aqueous medium.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a carbon black used as a coloring material such as an ink, and a recording ink using such a carbon black as a coloring material. It is characterized in that the dispersion stability of carbon black in an aqueous medium is improved, and the storage stability of a recording ink using carbon black as a coloring material is improved so that stable and good recording can be performed. Things.

[0002]

2. Description of the Related Art Conventionally, as inks used in ink recording devices such as ink jet printers, water-based inks have been widely used in addition to oil-based inks in terms of easy handling and safety.

Here, as a water-based ink, a water-soluble dye is generally used as a coloring material, and a water-soluble dye dissolved in an aqueous medium has been widely used.

[0004] However, such water-based inks have poor water resistance, and when supplied to a recording medium such as plain paper to form an image, bleeding of the ink called bleeding or feathering occurs. There is a problem that ink flows.

Therefore, in recent years, it has been studied to use a pigment such as carbon black as a coloring material in an ink and to use an ink in which the pigment such as carbon black is dispersed in an aqueous medium. .

However, when carbon black is dispersed in an aqueous medium as described above, the dispersion stability of the carbon black in the aqueous medium is not sufficient, and when such an ink is used in an ink recording apparatus such as an ink jet printer. The carbon black in the ink gradually aggregates, thereby clogging the nozzles of the ink recording device, deteriorating the ejection stability of the ink, disturbing the formed image, and the density of the formed image. However, there is a problem that good recording cannot be stably performed due to variations in the recording quality.

For this reason, conventionally, an alkyl ether derivative of a polyhydric alcohol such as triethylene glycol monobutyl ether or an ester derivative of a polyhydric alcohol such as glyceryl monoacetate is conventionally contained in the ink in which carbon black is dispersed as described above. Attempts have been made to improve the dispersion stability of carbon black in the ink by adding a dispersant such as

However, when a large amount of the above dispersant is added to improve the dispersion stability of carbon black in the ink, the dispersant tends to cause clogging of the ink in the nozzles of the ink recording device, and the On the contrary, there is a problem that the ejection stability is deteriorated, and there is also a problem that the concentration of the coloring material in the ink is reduced due to the addition of the dispersant, thereby lowering the density of the formed image.

In recent years, Japanese Patent Application Laid-Open No. 5-230
As disclosed in JP-A-410, in order to improve the storage stability of an ink using carbon black, carbon black that has been surface-treated by graft polymerization of an acrylamide derivative, or that disclosed in Japanese Unexamined Patent Application Publication No.
As shown in JP-A-339516 and JP-A-6-25572, in order to improve the storage stability and dispersibility of an ink using carbon black, a monomer having a vinyl group is graft-polymerized to carbon black. It has been proposed to use

However, as shown in these publications,
Even when carbon black obtained by polymerizing an acrylamide derivative or a monomer having a vinyl group on the surface of carbon black is used, the ink tends to clog the nozzles of the ink recording device, and the ink cannot be stably ejected. There was.

[0011]

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems when carbon black is used as a coloring material in a recording ink used in an ink recording device such as an ink jet printer. Is what you do.

That is, in the present invention, carbon black is modified, and in a recording ink using this carbon black as a coloring material, the carbon black is maintained in an appropriately dispersed state, and the storage stability of the ink is improved. When such a recording ink is used for an ink recording device such as an ink jet printer, the ink is prevented from being clogged in a nozzle of the ink recording device, and the ink is stably ejected. Accordingly, it is an object of the present invention to stably obtain a good image with less occurrence of image disturbance, density unevenness, and the like.

[0013]

In order to solve the above-mentioned problems, the carbon black according to the first aspect of the present invention is reacted with an amine having an amino group at a terminal on the surface of the carbon black. The amines were reacted with polyoxyethylenes.

Further, in the carbon black according to the second aspect of the present invention, the above-mentioned polyoxyethylenes having a hydroxyl group or a carboxyl group at the terminal are used.

Then, when an amine having an amino group at the terminal on the surface is reacted with the carbon black as described in claim 1 or 2, and the amine is further reacted with a polyoxyethylene, the reaction proceeds. The functional group bonded to the surface of the carbon black prevents the carbon blacks from aggregating in the aqueous medium.

Here, it is not clear why the functional groups bonded to the surface of the carbon black by the above-mentioned reaction prevent the carbon blacks from aggregating in the aqueous medium. This is considered to be because the carbon black has a hydrophilic property and the carbon black is stably dispersed in the aqueous medium by this functional group.

In the recording ink according to the third aspect, the color material comprising carbon black according to the first or second aspect is dispersed in an aqueous medium.

Here, when the coloring material composed of carbon black according to claim 1 or 2 is dispersed in an aqueous medium like the recording ink according to claim 3, the carbon blacks mutually disperse as described above. Agglomeration in an aqueous medium is suppressed, carbon black is maintained in a state of being sufficiently dispersed in the recording ink, and the storage stability of the recording ink is improved.

When this recording ink is used in an ink recording apparatus such as an ink jet printer,
The recording ink is prevented from clogging the nozzles of the ink recording apparatus, and the ink is stably ejected, so that a good image with little disturbance of the image and non-uniform density is obtained stably. Will be able to

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, carbon black and recording ink according to an embodiment of the present invention will be specifically described.

Here, as the carbon black used in the present invention, known carbon blacks such as furnace black, acetylene black and channel black can be used. As the furnace black, for example, Realgal 250 manufactured by Cabot Co., Ltd.
R, 415R, 330R, # 45L, D made by Mitsubishi Chemical Corporation
Egussa's Printex-35 and the like, as acetylene black, for example, D-Chemistry manufactured by Denki Kagaku Kogyo Co., Ltd.
For example, Neospectra II or the like manufactured by Columbia Carbon can be used as the channel black.

Examples of the amines to be reacted with the surface of carbon black include, for example,
The following structural formulas (1) and (2) can be used.

[0023]

Embedded image H ₂ N—R1-NH ₂ (1) H ₂ N—R2-NH—R3-NH ₂ (2)

In the above structural formulas (1) and (2), R1, R2 and R3 are each a straight-chain, branched or cyclic hydrocarbon group, an aryl group or a heterocyclic group, and And R1 and R2 and R3 may be the same or different groups.

In the above R1, R2 and R3,
Examples of the substituent bonded to the linear, branched, or cyclic hydrocarbon group, aryl group, or heterocyclic group include, for example, a halogen group, a linear, branched, or cyclic group. Hydrocarbon group, aryl group, heterocyclic group, -OR, -COR, -COOR,-
OCOR, -COONa, -COOK, -COO ^- NR
_{^{4 +, -CN, -NR 2,}} - (S) n, -SO 3 H, -S
_{O 3 Na, -SO 3 K,} -SO 3 - NR 4 +, -NR (CO
_{R), - CONR 2, -NO} 2, -PO 3 H 2, -PO
_{3 HNa, -PO 3 Na 2,} -N = NR, -N 2 + X -,
_{^{-NR 3 + X -, -PR 3}} + X - ( Note, R represents hydrogen, an alkyl group and an aryl group having a carbon number of 1 to 20, X is a halogen element, an anion of an inorganic or organic acid, n represents 1 And an integer of 8). In particular, in order to suppress aggregation of carbon black in an aqueous medium, the above substituent is preferably a hydrophilic group, for example,
_{-CH 2 CH 2 COOH, -CN,} -CH 2 OH, -O
_{H, -CHO, -OCOCH 3, -COOCH} 3, it is preferable to use an organic acid salt or the like.

The polyoxyethylenes to be reacted with the amines are as described in claim 2.
Polyoxyethylenes having a hydroxyl group or a carboxyl group at the end can be used, and polyoxyethylenes having a hydroxyl group at the end can be polyethylene glycol or the like, and polyoxyethylenes having a carboxyl group at the end can be used. For example, polyoxyethylene diglycolic acid or the like can be used.

The recording ink of this embodiment is made of carbon black obtained by reacting an amine having an amino group at a terminal on the surface thereof, and further reacting a polyoxyethylene with the amine as described above. The coloring material is dispersed in the aqueous medium.

Here, water or a water-soluble organic solvent is used as the aqueous medium in which the coloring material composed of carbon black is dispersed. Examples of the water-soluble organic solvent include methyl alcohol, ethyl alcohol, and n- An aliphatic alcohol having 1 to 5 carbon atoms such as propyl alcohol and isopropyl alcohol can be used.

In the recording ink according to this embodiment, in addition to the coloring material comprising carbon black in the aqueous medium, a viscosity adjusting agent, a surface tension adjusting agent, pH adjusters, humectants, chelating agents, penetrants, fungicides, quick-drying agents, stabilizers,
It is preferable to add a fixing agent and the like.

Here, the viscosity adjusting agent is used for adjusting the viscosity of the ink to improve the ejection property of the ink and for adjusting the permeability of the ink into a recording medium such as plain paper. Polyalkylene glycols such as glycol and polypropylene glycol can be used, and polyethylene glycol is particularly preferable. When the viscosity modifier is added to the ink, the amount of the viscosity modifier is 0 to 10% by weight, preferably 0.1 to 8% by weight, more preferably 1 to 10% by weight.
It should be in the range of 5% by weight.

The surface tension adjusting agent is used for adjusting the surface tension of the ink to improve the ejection property of the ink and for adjusting the permeability of the ink to the recording medium. Agents, various surfactants such as silicon-based, fluorine-based, and acetylene-based surfactants, and anionic and cationic surfactants can be used. Preferably, nonionic surfactants are used.
When the surface tension adjuster is added to the ink, the amount of addition is in the range of 0.1 to 5% by weight, preferably 0.1 to 3% by weight, more preferably 0.2 to 1% by weight. To be.

The pH adjuster is used to maintain the pH of the ink in an appropriate state and to suppress a decrease in the dispersion stability of carbon black due to a change in the pH. For example, NaHCO ₃ , Na ₂ B ₄ O ₇ , Na ₂ CO ₃ ,
KHCO ₃ , K ₂ CO ₃ , NaOH, CH ₃ COON
a, N (CH ₂ CH ₂ OH) ₃ or the like can be used;
In particular, it is preferable to use NaHCO ₃ . And
When such a pH adjuster is added to the ink, the amount of the pH adjuster is 0.1 to 1% by weight, preferably 0.1 to 1% by weight.
To 0.5% by weight, more preferably 0.2 to 0.5% by weight
Range.

The humectant is used to prevent the concentration and viscosity of the ink from changing due to the evaporation of water, which is the main component of the aqueous medium, and to prevent the ejection stability of the ink from deteriorating. 1,2-ethanediol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, , 5-pentanediol, 1,7-heptanediol, 2-methyl-
2,4-pentanediol, 2-ethyl-1,3-hexanediol, glycerin, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol 200, dipropylene glycol, 2,2′-thiodiethanol, 1,2,2 Alkylene glycols such as 6-hexanetriol; 1,2-dimethoxyethane, 1,2-diethoxyethane, 1,2-
Dibutoxyethane, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol dibutyl ether, 2-methoxyethanol, 2-ethoxyethanol, 2- (methoxymethoxy) ethanol, 2-butoxyethanol, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether , Triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, 1-
Use of lower alkyl ethers of polyhydric alcohols such as methoxy-2-propanol, 1-ethoxy-2-propanol, dipropylene glycol, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, and tripropylene glycol monomethyl ether. In particular, it is preferable to use diethylene glycol, triethylene glycol, glycerin and the like. When such a humectant is added to the ink, the added amount is 1 to 10% by weight,
It is preferably in the range of 3 to 10% by weight, more preferably 5 to 8% by weight.

The chelating agent is used to capture metal ions present in the ink and to prevent the loss of the dispersion stability of carbon black due to the metal ions. , Ethylenediaminetetraacetic acid, sodium nitrile triacetate, sodium hydroxyethylethylenediaminetriacetate, sodium diethylenetriaminepentaacetate, sodium uramil diacetate, and the like. When such a chelating agent is added to the ink, the added amount is 0.1 to 1% by weight, preferably 0.1 to 0.5% by weight, more preferably 0.2 to 0.5% by weight.
% By weight.

The penetrant is used to enhance the permeability of the ink into the recording medium. For example, a lower alkyne ether of a polyhydric alcohol such as diethylene glycol monobutyl ether or triethylene glycol monobutyl ether is used. Can be used. When such a penetrant is added to the ink, the amount added is 1 to 10% by weight, preferably 3 to 10% by weight.
%, More preferably in the range of 4 to 8% by weight.

The antifungal agent is used to prevent the occurrence of mold and the like in the ink. For example, imidazole-based agents such as thiabenzol (manufactured by Merck) and Mergar (manufactured by Hoechst) are used. Or isothiazoline-based ones such as Proxel (manufactured by Zeneca) and Amorden (manufactured by Daiwa Chemical Industries), Preventol series (manufactured by Bayer), sodium omazine, dioxin, sodium dihydroacetate, water glass, etc. be able to. When the antifungal agent is added to the ink, the amount of the antifungal agent is 0.01 to 0.5% by weight, preferably 0.05 to 0.4% by weight, and more preferably 0.1 to 0% by weight. To be in the range of 4% by weight.

The quick-drying agent is used to prevent the ink from quickly drying or penetrating after the ink has adhered to the recording medium, thereby preventing the ink from adhering to another recording medium and becoming soiled. For example, lower alcohols such as methanol, ethanol, propanol, 2-propanol, 1-butanol, and 2-butanol are used.

The stabilizer is used to prevent the dispersion stability of carbon black from decreasing in an aqueous medium. Examples of the stabilizer include alcohol amines such as monoethanolamine, diethanolamine and triethanolamine. 2-pyrrolidone, N-methyl-2-
Pyrrolidone, 1,3-dimethylimidazolidinone, 1,
Cyclic amide compounds such as 3-dimethyl-2-imidazolidinone, sulfolane, dimethyl sulfoxide, ε-caprolactam; imide compounds such as succinimide; formamide, sorbit, 1,3-bis (β-hydroxyethyl) urea and the like Preferably, triethanolamine is used. When such a stabilizer is added to the ink, the amount of the stabilizer is 0.1 to 1% by weight, preferably 0.1 to 0.5% by weight.
More preferably, it is in the range of 0.2 to 0.5% by weight.

The fixing agent improves the fixing property of the ink to the recording medium. Examples of the fixing agent include water-soluble polyesters, polyurethanes, polyamides, polyimides, polyacryls, and polyvinyl alcohols. Preferably, poly (meth) acrylates are used. When the fixing agent is added to the ink, the amount of the fixing agent is 0.1 to 1
It should be in the range of 5% by weight, preferably 1-10% by weight, more preferably 4-8% by weight.

[0040]

Hereinafter, the carbon black and the recording ink according to the embodiment of the present invention will be specifically described, and a comparative example will be given. In the recording ink using the carbon black according to the embodiment of the present invention, Comparative examples show that the dispersion stability of carbon black in an aqueous medium is excellent, the storage stability of ink and the ejection stability of ink are improved, and a good image is obtained.

(Example 1) In this example, furnace black having a particle size of 34 nm (available from Cabot: Realgal 250R) was used as carbon black.
On the other hand, ethylenediamine (manufactured by Wako Pure Chemical Industries, Ltd.) is used as an amine to react with the surface of the carbon black, and polyoxyethylene diglycol having a carboxyl group at the terminal is used for the polyoxyethylene to react with the amine. An acid was used.

Then, 3.9 of the above carbon black was placed in a 300 ml three-necked flask equipped with a reflux condenser.
g, 1.6 g (0.027 m
ol) and benzene at a rate of 70 ml and stirred at room temperature, and then 10 g of polyoxyethylene diglycolic acid.
(0.0033 mol) dissolved benzene solution in 15
0 ml was added, and these were allowed to react at room temperature for 24 hours.
This was filtered, and then the unreacted substances and by-products were removed by Soxhlet extraction using benzene as a solvent. Ethylenediamine was reacted on the surface, and carbon black was obtained by reacting polyoxyethylenediglycolic acid with this ethylenediamine. I got

Next, 5 parts by weight of the above carbon black, 19 parts by weight of glycerin, 75 parts by weight of distilled water and 1 part by weight of triethanolamine were mixed and stirred at room temperature for 3 hours, and then homogenized. The ink was prepared by filtering the particles with a 10 μm membrane filter.

Example 2 In this example, furnace black was used as the carbon black and ethylenediamine was used as the amine to be reacted with the carbon black, as in the case of Example 1 described above. For the polyoxyethylenes to be reacted with the compounds, polyethylene glycol having a hydroxyl group at a terminal (manufactured by Wako Pure Chemical Industries, Ltd.) is used.
In the same manner as in Example 1 above, ethylenediamine was reacted on the surface, and carbon black was obtained by reacting ethylenediamine with polyethylene glycol.

Using the carbon black thus obtained, an ink was prepared in the same manner as in Example 1 above.

Example 3 In this example, the same furnace black as in Example 1 was used as the carbon black, while diethylene triamine (Aldr) was used as the amine to be reacted with the carbon black.
In the same manner as in Example 1 described above, diethylene triamine was reacted on the surface, and carbon black was obtained by further reacting polyoxyethylene diglycolic acid with the diethylene triamine. .

Using the carbon black thus obtained, an ink was prepared in the same manner as in Example 1 above.

Example 4 In this example, the same furnace black as in Example 1 was used as the carbon black, while the amines reacted with this carbon black were used in Example 3 as described above. Using the same diethylenetriamine as above, and using the same polyethylene glycol as in Example 2 above for the polyoxyethylenes to be reacted with this diethylenetriamine, and otherwise using the same method as in Example 1 above Then, carbon black was obtained by reacting diethylene triamine on the surface and further reacting polyethylene glycol with the diethylene triamine.

Then, using the carbon black thus obtained, an ink was prepared in the same manner as in Example 1 above.

(Comparative Example 1) In this comparative example, the same furnace black as that of the above-mentioned Example 1 (Cagal, Realgal 250) was used as carbon black.
Using R), the carbon black was used as it was without bonding a functional group to the surface of the carbon black.

Then, 5 parts by weight of this carbon black, 19 parts by weight of glycerin, 75 parts by weight of distilled water, and 1 part by weight of triethanolamine were used, and ink was prepared in the same manner as in Example 1 above. Prepared.

(Comparative Example 2) In this comparative example, the same furnace black as that used in Example 1 was used as the carbon black, and the carbon black was irradiated with ultraviolet rays to surface-treat the surface of the carbon black. After that, the carbon black thus surface-treated is
7 parts by weight, 8 parts by weight of acrylamide and 75 parts by weight of distilled water were mixed, and the mixture was stirred at 65 ° C. while blowing nitrogen gas into the solution to carry out polymerization for 1 hour.

Then, the homopolymer was sufficiently removed by centrifugal separation, washed with hot water, and dried to obtain carbon black having acrylamide graft-polymerized on the surface.

Then, 3 parts by weight of the carbon black thus surface-treated, 10 parts by weight of glycerin, 1-
An ink was prepared in the same manner as in Example 1 above, using 4 parts by weight of propanol and 83 parts by weight of distilled water.

Next, Example 1 manufactured as described above was used.
For each of the carbon blacks and recording inks of Comparative Examples 1 to 4 and Comparative Examples 1 and 2, dispersion stability, storage stability, temperature change stability, print quality, density unevenness, and discharge stability were evaluated. The results are shown in Table 1.

Here, regarding the dispersion stability, a 10% by weight aqueous solution in which each of the carbon blacks of Examples 1 to 4 and Comparative Examples 1 and 2 was dispersed was placed in a 10 ml centrifugal sedimentation tube, and commercially available. Centrifuge (BECKMAN)
12000rpm using Avanti J25)
After centrifugation at 600 m for 1 hour, the absorbance of the supernatant at 600 nm was measured, and the concentration of carbon black in the supernatant was determined based on a previously determined calibration curve. %, At least 0.05 wt.% And less than 0.01 wt.%, And at least 0.005 wt.%, X.

Regarding the storage stability, a 10% by weight aqueous dispersion of each of the carbon blacks of Examples 1 to 4 and Comparative Examples 1 and 2 was placed in a 10 ml centrifugal sedimentation tube. The sedimentation tube was left at a temperature of 40 ° C. for 3 months, and thereafter, the dispersion aqueous solution was put into a 10 ml centrifugal sedimentation tube and centrifuged as in the case of measuring the dispersion stability. The concentration of carbon black in the medium was determined, and when the concentration was 0.01% by weight or more, ○, when 0.05% or more and less than 0.01% by weight, and when it was less than 0.005% by weight. Indicated by x.

As to the temperature change stability, each of the carbon blacks of Examples 1 to 4 and Comparative Examples 1 and 2 was dispersed in 10 ml of a 10% by weight aqueous solution.
And left the sample tube at a temperature of −10 ° C. for 1 hour, and then immediately left at a temperature of 50 ° C. for 1 hour. After the test was continued for 3 days, the shear rates were compared before and after the test, and the presence or absence of thixotropy of the ink and the stability of the physical properties were examined. The case where there was no change was indicated by ○, and the case where there was a change was indicated by x.

Regarding the print quality, a straight line having a width of 3 dots is printed on plain paper using each of the inks of Examples 1 to 4 and Comparative Examples 1 and 2, and TEP (showing the rattling state in the straight line) is used. Tangential Edge P
rofile) with the dot analyzer DA-5000S
(Oji Scientific Instruments), TEP is 60 μm
Is smaller than O, and X is TE when the TEP is 60 μm or more. Note that TEP indicates the backlash of a straight line as the amount of displacement from the originally expected straight line, and indicates the standard deviation value.

Further, regarding the density unevenness, Examples 1 to 4
Printing was performed on plain paper using the inks of Comparative Examples 1 and 2, and the image density (ID) of the solid printed portion was measured with a Sakura densitometer PDA65 (manufactured by Konica Corporation), and the image density of the printed portion was measured. Were determined, and the case where the density difference was less than 0.15 was indicated by ○, and the case where it was 0.15 or more was indicated by ×.

Regarding the ejection stability of the ink, printing was performed continuously for 10 hours using each of the inks of Examples 1 to 4 and Comparative Examples 1 and 2, and then the power of the ink recording apparatus was turned off. After leaving it for 14 hours and setting this as one cycle, after repeating 5 cycles, a straight line having a line width of 150 μm was printed, and the image density on this straight line was measured using a microdensitometer (PDM5, manufactured by Konica Corporation). ,
A point where the image density is less than 0.3 is defined as a missing portion of the ink ejection, and the distance of the missing portion is checked.
When the distance is less than 10 μm, the result is indicated by x.

[0062]

[Table 1]

As a result, as in the case of the carbon blacks shown in the above Examples 1 to 4, when an amine having an amino group at the terminal on its surface is reacted, and the amine is further reacted with a polyoxyethylene, Dispersion stability, storage stability, and temperature change stability of the carbon black in the aqueous medium are improved as compared with the carbon black in Comparative Example 1, and the temperature change is also higher than the carbon black in Comparative Example 2. Stability was improved.

When each of the inks of Examples 1 to 4 using carbon black as described above was used in the ink recording apparatus, the ink was used in the ink recording apparatus as compared with the case where the ink of Comparative Example 1 was used. The clogging of the nozzles is suppressed, the ink is stably ejected, the printing quality is excellent, and good recording with less density unevenness can be performed. Clogging of the nozzles of the ink recording apparatus with ink was suppressed, and the ink was stably ejected.

[0065]

As described in detail above, in the carbon black of the present invention, the amine having an amino group at the terminal is reacted on the surface of the carbon black, and the polyoxyethylene is reacted with the amine. In addition, the dispersion stability, storage stability, and temperature change stability of carbon black in an aqueous medium were improved.

In the recording ink according to the present invention, since the coloring material composed of carbon black as described above is dispersed in an aqueous medium, the aggregation of carbon black in the ink is suppressed.
The storage stability of the recording ink is improved, and when the recording ink is used in an ink recording device such as an inkjet printer, the recording ink is prevented from being clogged in the nozzles of the ink recording device, Ink has been stably ejected, and a good image with little disturbance of the image and non-uniform density has been stably obtained.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Kenichi Tabata 2-13-13 Azuchicho, Chuo-ku, Osaka City Inside Osaka International Building Minolta Co., Ltd. (72) Takamasa Ueda 2-3-3 Azuchicho, Chuo-ku, Osaka-shi No. 13 Osaka International Building Minolta Co., Ltd. F-term (reference) 4J037 AA02 CB16 CC25 EE02 EE04 EE28 EE43 FF05 FF15 FF23 4J039 BA04 BC34 BE01 BE22 BE24 CA03 EA41 EA44 EA46 GA24

Claims (3)

[Claims] 1. A carbon black obtained by reacting an amine having an amino group at a terminal on the surface of the carbon black, and further reacting a polyoxyethylene with the amine. 2. The carbon black according to claim 1, wherein the polyoxyethylene has a hydroxyl group or a carboxyl group at a terminal. 3. A recording ink comprising the coloring material comprising carbon black according to claim 1 or 2 dispersed in an aqueous medium.