JP2017132868A - Black pigment for inkjet printer and black pigment aqueous dispersant for inkjet printer - Google Patents

Abstract

Provided is a black pigment for an ink jet printer that exhibits excellent dispersibility and storage stability in an aqueous medium, and exhibits excellent blackness equal to or better than that of electrophotography by only one printing.
A nitrogen adsorption specific surface area _(N 2 SA) of ^{80m 2 / g~160m 2 / g,} DBP oil absorption amount 100ml / 100g~170ml / 100g, 24M4DBP absorption of 80ml / 100g~140ml / 100g, the DBP The oil absorption is larger than the 24M4DBP absorption, the difference expressed by DBP oil absorption−24M4DBP absorption is 10 ml / 100 g to 40 ml / 100 g, the coloring power (Tint) is 100 to 145, the mode diameter of the aggregate is Dst, A black pigment for an ink jet printer, comprising a hydrophilized product of carbon black having a ratio represented by ΔDst / Dst of 0.5 to 0.8, where ΔDst is the half width of the mode diameter of the aggregate It is.
[Selection figure] None

Description

  The present invention relates to a black pigment for an ink jet printer and a black pigment aqueous dispersion for an ink jet printer.

  In recent years, water-based inks have been widely used to replace organic solvent-based inks in a wide range of fields because of their safety and low environmental impact. Especially for business applications, water-free color materials that are odorless are essential as inks used for various printing in offices. For industrial applications, organic solvents can be used due to problems in the working environment, safety of ink and paint handling, and waste liquid treatment. There is an increasing tendency to use as little as possible. In addition, water-based colorants are also more popular than organic solvent-type colorants because they do not require special equipment such as explosion-proof equipment, exhaust equipment, and organic solvent recovery equipment during production. .

  As the water-based coloring material, two dyes and pigments are mainly used depending on the application. The dye has excellent gradation and easily forms a high-resolution image, but has low light resistance and has a practical problem. On the other hand, since pigments are extremely excellent in water resistance and light resistance, many pigment inks are now provided.

  Gravure inks that are printed via printing plate making and water-based liquid inks for offset printing have been developed, but the most popular recording method for offices that uses water-based inks is the ink jet recording method.

  The ink jet recording method is a method in which ink droplets are ejected from a fine nozzle head and characters and images are recorded on the surface of a recording medium such as paper. Since it can be easily printed on demand without making a full color printing plate on a simple recording medium, it has begun to spread widely.

  An ink jet printer that employs an ink jet recording method is a method in which ink droplets are ejected from a fine nozzle head and characters and images are recorded on the surface of a recording medium such as paper. (Registered trademark) method and piezo method. The former is a recording method that instantaneously heats the ink guided to the nozzle head with a heater to generate bubbles, and the ink expansion is intermittently ejected by volume expansion due to the bubbles, the latter is an electrostrictive element (piezoelectric element) Is a recording system that converts electrical signals into mechanical signals and intermittently ejects ink droplets stored in the nozzle head portion, and various pigments corresponding to such recording methods have been proposed. (For example, see Patent Document 1 (Japanese Patent Laid-Open No. 2001-81355)).

JP 2001-81355 A

  As such an ink jet printer ink, an aqueous dispersion of carbon black has been used. Conventionally, an aqueous carbon black dispersion for an ink jet printer is described in Patent Document 1 due to the influence of an ink jet printer head. Only carbon black having a small particle diameter as dispersed in water can be used. In the case of using such an aqueous dispersion containing carbon black having a small particle diameter, it was necessary to print (print) a plurality of times in order to develop blackness equal to or higher than that of electrophotography.

  However, recent inkjet printers do not print multiple times during high-speed printing, unlike conventional serial printers. Instead of printing only once (one-pass printing), the same print density, especially electrophotography. However, it has been difficult for the conventional black pigment aqueous dispersion for inkjet printers to exhibit the above blackness by only one printing. It turned out to be.

  Therefore, the present invention provides an ink jet that exhibits excellent dispersibility and storage stability in an aqueous medium, and exhibits excellent blackness equivalent to or better than that of electrophotography with only one printing when used in an ink jet ink. An object of the present invention is to provide a black pigment aqueous dispersion for printers and a black pigment for inkjet printers.

In order to solve the above technical problems, the present inventors have conducted intensive studies. As a result, nitrogen adsorption specific surface area (N ₂ SA), DBP oil absorption, 24M4DBP absorption, DBP oil absorption−24M4DBP absorption, coloring power (Tint) and The present inventors have found that the above technical problem can be solved by using carbon black having a ratio represented by ΔDst / Dst in a specific range, and have completed the present invention based on this finding.

That is, the present invention
(1) a nitrogen adsorption specific surface area _(N 2 SA) of ^{80m 2} / ^g~160m 2 / g,
DBP oil absorption is 100ml / 100g-170ml / 100g,
24M4DBP absorption is 80 ml / 100 g-140 ml / 100 g,
The DBP oil absorption amount is larger than the 24M4DBP absorption amount, and the difference expressed by DBP oil absorption amount−24M4DBP absorption amount is 10 ml / 100 g to 40 ml / 100 g,
Coloring power (Tint) is 100 to 145,
When the mode diameter of the aggregate is Dst and the half width of the mode diameter of the aggregate is ΔDst, the ratio represented by ΔDst / Dst is 0.5 to 0.8.
A black pigment for an ink jet printer, characterized by comprising a hydrophilized product of carbon black,
(2) In the cumulative frequency distribution curve of the agglomerate particle size obtained by irradiating laser light in the state of an aqueous dispersion and the frequency modulation degree of the scattered light, the value of the cumulative frequency 50% is the average particle size Dupa _50% , the cumulative frequency When the value of _90% is Dupa _90% ,
The carbon black agglomerate has an average particle size Dupa _50% of 130 nm to 160 nm,
Dupa _90% of the agglomerate of the carbon black is 210 nm to 280 nm
A black pigment for an inkjet printer according to the above (1),
(3) The black pigment for an ink jet printer according to the above (1) or (2), wherein the hydrogen-containing surface functional group amount of the hydrophilized product of carbon black is 3 μeq / m ² or more,
(4) Provided is a black pigment aqueous dispersion for an ink jet printer, comprising the black pigment for an ink jet printer according to any one of (1) to (3) above.

  According to the present invention, an ink jet exhibiting excellent dispersibility and storage stability in an aqueous medium, and exhibiting excellent blackness equivalent to or better than that of electrophotography with only one printing when used in an ink jet ink. Black pigment aqueous dispersions for printers and inkjet printers can be provided.

First, the black pigment for inkjet printers according to the present invention will be described.
The black pigment for inkjet printers according to the present invention is:
Nitrogen adsorption specific surface area _(N 2 SA) of ^{80m 2} / ^g~160m 2 / g,
DBP oil absorption is 100ml / 100g-170ml / 100g,
24M4DBP absorption is 80 ml / 100 g-140 ml / 100 g,
The DBP oil absorption is larger than the 24M4BP absorption, and the difference expressed by DBP oil absorption−24M4DBP absorption is 10 ml / 100 g to less than 40 ml / 100 g,
Coloring power (Tint) is 100 to 145,
When the mode diameter of the aggregate is Dst and the half width of the mode diameter of the aggregate is ΔDst, the ratio represented by ΔDst / Dst is 0.5 to 0.8.
It is characterized by comprising a carbon black hydrophilic treatment product.

Black pigment for ink jet printer according to the present invention, the nitrogen adsorption specific surface area of the hydrophilic treatment before _(N 2 SA) of carbon black ^is a ^{80m 2 / g~160m 2 / g,} 90m 2 / g~150m 2 / it is preferably ^g, and more preferably 100m ² / g~145m 2 / g.

In the black pigment for an ink jet printer according to the present invention, the nitrogen adsorption specific surface area (N ₂ SA) of carbon black before hydrophilization treatment is within the above range, so that it has excellent ejection stability when used in an ink jet ink. And paper fixing density can be exhibited.
When the nitrogen adsorption specific surface area (N ₂ SA) is less than 80 m ² / g, when used in inkjet ink, the precipitation residue rate increases, and the filterability and discharge stability tend to be remarkably lowered. This is because when the adsorption specific surface area (N ₂ SA) exceeds 160 m ² / g, the paper fixing density tends to be low when printing is performed using the inkjet ink.

Note that in the present application, the nitrogen adsorption specific surface area _(N 2 SA) of carbon black means a value measured according to the method defined in ASTM D6556.

In the black pigment for an ink jet printer according to the present invention, the DBP oil absorption amount of carbon black before hydrophilization is 100 ml / 100 g to 170 ml / 100 g, preferably 105 ml / 100 g to 165 ml / 100 g, and 110 ml / 100 g. More preferably, it is -160ml / 100g.
In the black pigment for an inkjet printer according to the present invention, when the DBP oil absorption amount of carbon black before the hydrophilization treatment is within the above range, excellent print density and filterability are exhibited when used for the preparation of inkjet ink. can do.
When the DBP oil absorption is less than 100 ml / 100 g, the printing density tends to be thin when used for inkjet ink, and when it exceeds 170 ml / 100 g, the precipitation residue rate tends to increase when used for preparation of inkjet ink. The filterability is likely to decrease.

  In addition, in this application document, DBP oil absorption means the value measured based on the method prescribed | regulated to ASTMD2414.

In the black pigment for an ink jet printer according to the present invention, the 24M4DBP absorption amount of carbon black before hydrophilization treatment is 80 ml / 100 g to 140 ml / 100 g, preferably 85 ml / 100 g to 135 ml / 100 g, preferably 90 ml / 100 g. More preferably, it is -130ml / 100g.
In the black pigment for an ink jet printer according to the present invention, the carbon black before hydrophilization treatment has a 24M4DBP absorption amount within the above range, so that it has excellent print density, filterability, and storage when used for preparation of ink jet ink. Stability can be demonstrated.
When the 24M4DBP absorption amount is less than 80 ml / 100 g, the printing density tends to decrease when used for the preparation of inkjet ink, and when it exceeds 140 ml / 100 g, the precipitation residue rate increases when used for the preparation of inkjet ink. As a result, filterability and storage stability tend to decrease.

  In addition, in this application document, 24M4DBP absorption amount means the value measured based on the method prescribed | regulated to ASTMD3493.

  In the black pigment for an inkjet printer according to the present invention, the carbon black before hydrophilization treatment has a DBP oil absorption amount larger than the 24M4BP absorption amount, and a difference expressed by DBP oil absorption amount−24M4DBP absorption amount is 10 ml / 100 g to 40 ml. / 100 g, preferably 12 ml / 100 g to 35 ml / 100 g, more preferably 15 ml / 100 g to 30 ml / 100 g.

In the black pigment for inkjet printers according to the present invention, the difference represented by the DBP oil absorption amount−24M4DBP absorption amount of carbon black before hydrophilization treatment is within the above range, which is excellent when used for the preparation of inkjet ink. Filterability, sedimentation and printing density can be exhibited.
When the difference expressed by the DBP oil absorption amount−24M4DBP absorption amount is less than 10, when used for the preparation of the inkjet ink, the filterability and sedimentation property are liable to decrease. In addition, since the agglomerates are easily broken and the particle diameter becomes too small, the print density tends to be lowered when used for the preparation of inkjet ink.

The DBP oil absorption amount and 24M4DBP absorption amount of the carbon black are characteristics indicating the structure of the carbon black. As described above, when these values are small, the blackness ( On the other hand, when these values are increased, the aggregated unit of carbon black also increases, so that it is easy to aggregate and settle in water, and storage stability and dispersion when used for the preparation of inkjet inks. Stability is likely to decrease.
The black pigment for an ink jet printer according to the present invention has a high structure structure because the carbon black DBP oil absorption amount before the hydrophilic treatment, 24M4 DBP absorption amount, and especially the difference between them is within the above predetermined range. The structure is less likely to collapse during the dispersion process, and a high print density can be easily achieved when used in inkjet ink.

In the black pigment for an ink jet printer according to the present invention, the coloring power (Tint) of the carbon black before the hydrophilic treatment is 100 to 145, preferably 110 to 140, and more preferably 115 to 135. .
In the black pigment for an ink jet printer according to the present invention, the coloring power (Tint) of carbon black before hydrophilization treatment is within the above range, so that it exhibits excellent filterability and viscosity when used for the preparation of ink jet ink. can do.
When the coloring power (Tint) is less than 100, the particle size distribution becomes too large, and the filterability tends to be lowered when used for preparing an inkjet ink. In addition, when the coloring power (Tint) exceeds 145, the distribution becomes too sharp and the viscosity is likely to increase greatly when used for the preparation of inkjet ink.

  In addition, in this application document, the coloring power (Tint) of carbon black means the value measured based on the method prescribed | regulated to ASTMD3265.

  In the black pigment for an ink jet printer according to the present invention, when the mode diameter of the aggregate constituting the carbon black before the hydrophilic treatment is Dst and the half width of the mode diameter of the aggregate is ΔDst, it is expressed by ΔDst / Dst. The ratio is 0.5 to 0.8, preferably 0.55 to 0.77, and more preferably 0.6 to 0.75.

In the black pigment for an inkjet printer according to the present invention, the ratio represented by the mode diameter Dst of the aggregate of carbon black before hydrophilization treatment / the half-value width ΔDst of the mode diameter of the aggregate is within the above range. When used for ink preparation, excellent filterability and viscosity can be exhibited.
When the ratio represented by the above-mentioned aggregate mode diameter Dst / half-value width ΔDst of the aggregate mode diameter is less than 0.5, the distribution becomes too sharp and the viscosity increases when used in the preparation of inkjet ink. When the ratio exceeds 0.8, the particle size distribution becomes wide, and the filterability tends to be lowered when used for preparing an inkjet ink.

  In the present application documents, the mode diameter Dst of the aggregate means the maximum frequency of the Stokes equivalent diameter in the Stokes equivalent diameter distribution of the aggregate measured by centrifugal sedimentation (DCF), and the mode diameter of the aggregate The full width at half maximum ΔDst means the full width at half maximum of the Stokes equivalent diameter distribution of the aggregate measured by centrifugal sedimentation (DCF).

In the black pigment for an ink jet printer according to the present invention, the carbon black after the hydrophilic treatment is irradiated with laser light in the state of an aqueous dispersion, and in the cumulative frequency distribution curve of the agglomerate particle diameter obtained from the frequency modulation degree of the scattered light. , the average particle diameter _{Dupa 50%} the value of the cumulative frequency of 50%, when the value of the cumulative frequency of 90% was _{Dupa 90%,} an average particle diameter _{Dupa 50%} of the agglomerate of the carbon black, it is 130nm~160nm Is preferable, 135 nm to 158 nm is more preferable, 140 nm to 155 nm is further preferable, and Dupa _90% of the agglomerate of the carbon black is preferably 210 nm to 280 nm, and is preferably 215 nm to 275 nm. More preferably, 22 And still more preferably from nm~270nm.

When the average particle diameter Dupa _50% or Dupa _90% of the agglomerate of the carbon black is within the above range, excellent print density, viscosity, and the like can be exhibited when used for the preparation of an inkjet ink.
When the carbon black agglomerate average particle size Dupa _50% is less than 130, the print density during one-pass printing tends to be low, and when the carbon black agglomerate average particle size Dupa _50% exceeds 160, inkjet When used in ink, the print density is good, but the particles are too large and are likely to settle naturally.
Further, if the Dupa _{90% of the} carbon black is less than 210, the difference from the Dupa _50% becomes small, so that the viscosity is likely to increase when used in an inkjet ink, and the Dupa _{90% of the} carbon black is 280. If it exceeds 1, the large particle size increases, and when used in inkjet ink, it becomes easy to close the nozzle.

In the present application documents, the average particle diameter Dupa _50% and Dupa _90% of the carbon black agglomerates are obtained from the degree of frequency modulation of scattered light by irradiating laser light in the state of an aqueous dispersion as described above. In the cumulative frequency distribution curve of the agglomerate particle size obtained, a value of 50% cumulative frequency means an average particle size Dupa _50%, and a value of 90% cumulative frequency means Dupa _90% .

In the black pigment for an ink jet printer according to the present invention, the hydrogen-containing surface functional group amount of the carbon black hydrophilized product is preferably 3 μeq / m ² or more, and is 3.5 to 3.8 μeq / m ² . More preferably, it is more preferably 3.9 to 4.5 μeq / m ² .

  In the black pigment for an ink jet printer according to the present invention, the hydrogen-containing surface functional group amount of the carbon black hydrophilized product is within the above range, so that the dispersibility becomes good when used in the ink jet ink, and the long term. A black pigment aqueous dispersion and an ink-jet ink that can withstand storage of the ink can be provided.

  In this application document, the hydrogen-containing surface functional group amount of the carbon black hydrophilized product means the total amount of the carboxyl group amount and hydroxyl group amount of the carbon black hydrophilized product, and the carboxyl group The amount and the hydroxyl group amount each mean a value calculated by the following method.

(Carboxyl group amount)
After adding 2 to 5 g of carbon black hydrophilized product in 50 ml of 0.976N sodium hydrogen carbonate and shaking for 6 hours, the carbon black hydrophilized product was filtered off from the reaction solution, and 0.05 N was added to the filtrate. After adding hydrochloric acid aqueous solution, neutralization titration test is performed with 0.05N sodium hydroxide aqueous solution until pH becomes 7.0, and the amount of carboxyl groups is measured, and the obtained measured value is treated with hydrophilic treatment of carbon black. The value obtained by dividing the product by the nitrogen adsorption specific surface area (N ₂ SA (m ² / g)) is defined as the amount of carboxyl groups (μeq / m ² ) formed per unit surface area of the hydrophilized product of carbon black.
In addition, the nitrogen adsorption specific surface area (N ₂ SA (m ² / g)) of the hydrophilized product of carbon black is measured according to the method defined in ASTM D6556.

(Hydroxyl group content)
2,2′-Diphenyl-1-picrylhydrazyl (DPPH) was dissolved in carbon tetrachloride to prepare a solution having a concentration of 5 × 10 ⁻⁴ mol / L. After adding 1-0.6g and stirring in a 60 degreeC thermostat for 6 hours, the carbon black hydrophilization processed material is separated from the reaction liquid, and the amount of hydroxyl groups in the filtrate is measured with an ultraviolet absorptiometer. . The value obtained by dividing the value measured in this way by the nitrogen adsorption specific surface area (N ₂ SA (m ² / g)) of the carbon black hydrophilized product is the amount of hydroxyl groups formed per unit surface area of the carbon black. (Μeq / m ² ).
In addition, the nitrogen adsorption specific surface area (N ₂ SA (m ² / g)) of the hydrophilized product of carbon black is measured according to the method defined in ASTM D6556.

  In the black pigment for an ink jet printer according to the present invention, the carbon black hydrophilized product can be produced by hydrophilizing the carbon black.

The method for hydrophilizing carbon black is not particularly limited, and examples thereof include alkali metal salts such as hypochlorite, chlorite, chlorate, persulfate, perborate, percarbonate, and ammonium salts. A method of oxidizing by adding carbon black into an aqueous oxidizing agent solution such as
Examples of the hydrophilic treatment method of carbon black include a method of treating with hydrogen peroxide, ozone, ozone water, M ₂ O ₂ (M is an alkali metal), dichromate, permanganate or the like. it can.
Furthermore, examples of the hydrophilic treatment method of carbon black include a method of performing a diazo coupling treatment. For example, p-nitrobenzoic acid is azotized with nitrous acid and azotized on the surface of carbon black. Can be mentioned.
In addition, examples of the hydrophilic treatment method of carbon black include a method of treating carbon black with a surfactant, or microcapsulating a polymer on the surface of carbon black and dispersing it in water.
The hydrophilic treatment method of carbon black may be any hydrophilic method as long as the obtained hydrophilized product can be well dispersed in an aqueous medium.

  According to the present invention, there is provided a black pigment for an ink jet printer that exhibits excellent dispersibility and storage stability in an aqueous medium, and exhibits excellent blackness equivalent to or better than that of electrophotography by only one printing. be able to.

Next, the black pigment aqueous dispersion for inkjet printers according to the present invention will be described.
The black pigment aqueous dispersion for inkjet printers according to the present invention is characterized in that it contains the black pigment for inkjet printers according to the present invention.

  The black pigment aqueous dispersion for inkjet printers according to the present invention includes at least the black pigment for inkjet printers according to the present invention and an aqueous medium.

The details of the black pigment for an ink jet printer according to the present invention are as described above.
Further, examples of the aqueous medium include water and those containing water as a main component and further containing a water-soluble organic solvent, and those consisting only of water are preferable.
Examples of water constituting the aqueous medium include purified water such as ion exchange water (deionized water) and distilled water.

  The black pigment aqueous dispersion for inkjet printers according to the present invention is obtained by dispersing the black pigment for inkjet printers according to the present invention in an aqueous medium.

  The method for dispersing the black pigment for an ink jet printer according to the present invention in an aqueous medium is not particularly limited, but it is preferably performed by a disperser.

  Examples of the disperser include a high-pressure homogenizer, a sand mill, a dyno mill, a ball mill, a paint shaker, an ultrasonic disperser, and a disperser that disperses by a cavitation effect in a high-pressure chamber. Further, the dispersion treatment may be performed by a stirrer using a normal stirring blade, a high-speed disperser, an emulsifier, or the like.

  In the black pigment aqueous dispersion for an ink jet printer according to the present invention, the content (solid content concentration) of the black pigment for an ink jet printer is preferably 4 to 10% by mass, and more preferably 5 to 9% by mass. Preferably, it is 6-8 mass%.

  When preparing an inkjet ink using the black pigment aqueous dispersion for inkjet printers according to the present invention, additives to be added to the black pigment aqueous dispersion for inkjet printers include wetting agents, preservatives, antifungal agents, and rust inhibitors. , PH adjusting agents, penetrants, fixing agents, antifoaming agents and the like.

Examples of the wetting agent include various water-soluble organic solvents. Specifically, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, propylene glycol, 1,3-butanediol, 1,3 -Propanediol, 2-methyl-1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, glycerin, 1,2,6-hexanetriol, 2 -Polyhydric alcohols such as ethyl-1,3-hexanediol, 1,2,4-butanol, 1,2,3-butanetriol, petriol, ethylene glycol monoethyl ether, ethylene glycol -Rumonobutyl ether, diethylene glycol monomethyl ether, diethyl Polyhydric alcohol alkyl ethers such as ethylene glycol monoethyl ether, diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, tetraethylene glycol monomethyl ether and propylene glycol monoethyl ether, ethylene glycol monophenyl ether, ethylene glycol monobenzyl ether Nitrogen-containing heterocyclic compounds such as monohydric alcohol aryl ethers, N-methyl-2-pyrrolidone, N-hydroxyethyl-2-pyrrolidone, 2-pyrrolidone, 1,3-dimethylimidazolidinone, ε-caprolactam, formamide Amides such as N-methylformamide, N, N-dimethylformamide, monoethanolamine, diethanolamine, triethanolamine, monoethylamine One or more selected from amines such as ethylene, diethylamine and triethylamine, sulfur-containing compounds such as dimethyl sulfoxide, sulfolane and thiodiethanol, propylene carbonate, ethylene carbonate, and γ-butyrolactone.
These water-soluble organic solvents can be used alone or in combination with water.

  As preservatives and antifungal agents, one or more selected from sodium dehydroacetate, sodium sorbate, sodium 2-pyridinethiol-1-oxide, isothiazoline compounds, sodium benzoate, sodium pentachlorophenol, proxel XL-2, etc. Can be mentioned.

  Examples of the rust inhibitor include one or more selected from acidic sulfites, sodium thiosulfate, ammonium thiodiglycolate, diisopropylammonium nitrite, pentaerythritol tetranitrate, dicyclohexylammonium nitrite, benzotriazole, and the like.

  Examples of the pH adjuster include hydroxides of alkali metal elements such as lithium hydroxide, sodium hydroxide, potassium hydroxide, ammonium hydroxide, quaternary ammonium hydroxide, quaternary phosphonium hydroxide, lithium carbonate, Examples include one or more selected from alkali metal carbonates such as sodium carbonate and potassium carbonate, amines such as diethanolamine and triethanolamine, boric acid, hydrochloric acid, nitric acid, sulfuric acid, acetic acid and the like.

  As the penetrant, polyhydric alcohol alkyl ethers having low odor and low vapor pressure are preferably used, and among polyhydric alcohol alkyl ethers, the ink penetration rate into a recording material such as paper can be effectively increased. Therefore, it is preferable to select and use a material that improves the quick drying property of the ink on the recording material, prevents bleeding due to the slow drying property, and hardly causes bleeding due to penetration. Specific examples of such polyhydric alcohol alkyl ether include, for example, diethylene glycol methyl ether, diethylene glycol butyl ether, diethylene glycol isobutyl ether, dipropylene glycol methyl ether, dipropylene glycol propyl ether, dipropylene glycol isopropyl ether, dipropylene glycol butyl ether, One or more selected from triethylene glycol methyl ether, triethylene glycol butyl ether, tripropylene glycol methyl ether, tripropylene glycol butyl ether and the like can be mentioned.

  When preparing an inkjet ink, for example, while stirring, adding a black pigment aqueous dispersion for an inkjet printer while stirring, a wetting agent, an antiseptic, an antifungal agent, a rust inhibitor, a pH adjuster, and a penetrating agent Add additives such as adhesives, fixing agents, antifoaming agents, etc., any known water-soluble resin, wax dispersed in water, resin emulsion, etc., stir, if necessary, viscosity with water, water-soluble organic solvent And can be produced by filtration by any known filtration method.

  When preparing an inkjet ink using the black pigment aqueous dispersion for an inkjet printer, the concentration of the carbon black hydrophilized product, that is, the mass ratio of the carbon black hydrophilized product in the dispersion can be appropriately selected. Usually, it is preferably about 4 to 10% by mass.

  Since the black pigment aqueous dispersion for inkjet printers according to the present invention contains the black pigment for inkjet printers according to the present invention, it exhibits excellent dispersibility and storage stability in an aqueous medium, and is used only once. It is possible to provide an inkjet ink that exhibits excellent blackness equivalent to or better than that of electrophotography in printing.

  The contents of the present invention will be described below with specific examples. However, the present invention is not limited to the contents of these examples.

Example 1
Nitrogen adsorption specific surface area (N ₂ SA), DBP oil absorption, 24M4DBP absorption, ΔDBP (DBP oil absorption−24M4DBP absorption), coloring power (Tint), aggregate mode diameter Dst, aggregate Carbon black having half-value widths ΔDst and ΔDst / Dst of mode diameters was used, and hydrophilization treatment was performed with a sodium persulfate aqueous solution.
Specifically, with respect to 1,000 g of carbon black having the physical properties shown in Table 1, while adjusting the concentration of aqueous sodium persulfate solution per unit surface area of the carbon black to 150 nmol / L / m ² , The temperature was raised from room temperature to 90 ° C. at a temperature rising rate of 1.5 ° C./min and maintained for 5 hours while being brought into contact with a sodium sulfate aqueous solution in a stirring tank and rotating the stirring blade at 70 rpm. Hydrophilic treatment was performed by cooling to room temperature at 5 ° C./min.
The above-mentioned carbon black subjected to hydrophilization is treated with AHV-3010 (fraction molecular weight 50,000) manufactured by Asahi Kasei Chemicals Corporation, and then sodium hydroxide is added until the pH becomes 9.0. The neutralizing agent was fixed by treating at 100 ° C. for 3 hours to obtain a carbon black hydrophilized slurry (solid content concentration: 3 mass%).
Next, a slurry of the carbon black hydrophilized product (solid content concentration 3) using a Heisin Mono pump (2NE20PM) manufactured by Hyojin Equipment Co., Ltd. against a centrifuge (model SJ-30G manufactured by Mitsubishi Chemical Corporation). Mass%) is passed through for 4 L / min to remove coarse particles, unreacted carbon black, grids, etc., and then purified again with an ultrafiltration membrane similar to the above to an electric conductivity of 0.3 mS / cm. Then, using the same ultrafiltration membrane, concentration treatment was performed to a carbon black concentration of 15% by mass to obtain an objective black pigment water dispersion for inkjet printers (hydrogen-containing surface functional group amount: 3.8 μeq) / M ² ).

In the obtained black pigment water dispersion for inkjet printers, the viscosity, average particle size Dupa _50% , cumulative frequency 90% particle size Dupa _90% , pH, surface tension, electrical conductivity and filterability were measured by the following methods. Asked.
The viscosity, average particle size Dupa _50% , cumulative frequency 90% particle size Dupa _90% , pH, surface tension, and electrical conductivity were set to 70 with the obtained black pigment aqueous dispersion for inkjet printers along with initial values. When stored at ° C. for 2 weeks, the value after 1 week and the value after 2 weeks were measured, respectively. The results are shown in Table 2.

(viscosity)
Using a rotary type B viscometer (TV-10 manufactured by Toki Sangyo Co., Ltd.), the viscosity of the black pigment aqueous dispersion for an ink jet printer at 25 ° C. was measured.

(Particle size)
In the cumulative frequency distribution curve of the agglomerate particle size obtained from the frequency modulation degree of the scattered light using a laser diffraction / scattering type particle size distribution measuring device UPA150 manufactured by Microtrac, the particle size (average particle size) Dupa having a cumulative frequency of 50% The particle size Dupa _90% of _50% and cumulative frequency _90% was measured.

(PH)
An electrode of a glass electrode type hydrogen ion concentration meter (manufactured by Toa Denpa Kogyo Co., Ltd., pH meter, HM-30G) is immersed in a black pigment aqueous dispersion for an ink jet printer, and the black pigment aqueous dispersion for an ink jet printer at 25 ° C. The pH was measured.

(surface tension)
Using an automatic surface tension meter (CBVP-Z manufactured by Kyowa Interface Science Co., Ltd.), the surface tension of black pigment aqueous dispersion for inkjet printer is measured after measuring the surface tension of pure water at a measurement temperature of 25 ° C. Tension was measured.

(Electrical conductivity)
Using an electric conductivity meter, the electric conductivity of the black pigment aqueous dispersion for an ink jet printer having a liquid temperature of 25 ° C. was measured.

(Filterability)
Membrane filter with a diameter of 47 mm and a pore diameter of 5 μm (manufactured by Advantech)
Using a membrane filter (manufactured by Advantech Co., Ltd.) with a diameter of 25 mm and a pore diameter of 0.8 μm, the filtration time when the entire amount of the black pigment aqueous dispersion for an ink jet printer with a sample amount of 100 g was passed under reduced pressure of an aspirator It was measured.

<Preparation of inkjet ink>
The resulting black pigment aqueous dispersion for inkjet printers was mixed so that the solid content concentration (carbon black hydrophilized treatment concentration) was 6% by mass, glycerin 14% by mass, diethylene glycol monobutyl ether 5% by mass, acetylene. 1% by weight of glycol (olefin E1010), 0.02% by weight of benzotriazole, 0.03% by weight of preservative (Lonza Proxel XL-2), 0.80% by weight of triethanolamine, 73.15% by weight of purified water An ink jet ink was prepared by stirring and mixing so that
Printing density and precipitation residue rate were measured by the following method using the obtained inkjet ink. The results are shown in Table 3.

(Print density)
EM-930C manufactured by Seiko Epson Corporation is injected into a predetermined ink cartridge, and five types of paper ((1) XEROX 4200, (2) Fuji XEROX P, (3) Hammer Milly Copy Plus, (4) EPSON double-sided high quality ordinary Paper (recycled paper) and (5) EPSON photographic paper light (thin gloss)) are printed in “fast” mode and “clean” mode, respectively. D. The average value when the value was measured with a reflection type optical densitometer (504, manufactured by X-Rite, USA) was determined.
The “fast” mode is a mode for printing only once, and the “clean” mode corresponds to a mode for printing a plurality of times. The results are shown in Table 3.

(Precipitation residue rate)
Based on the precipitation residue mass (M1) after centrifugal separation of the inkjet ink obtained by the above method at a gravitational acceleration of 20,000 G for 30 minutes, and the mass of carbon black (M0) before the centrifugal treatment, The precipitation residue ratio (mass%) obtained by (M1 / M0) × 100 was calculated. The results are shown in Table 3.
A lower precipitation residue rate value indicates better dispersion stability.

(Example 2)
A black pigment aqueous dispersion for an inkjet printer containing a black pigment for an inkjet inkjet printer having a hydrogen-containing surface functional group amount of 3.2 μeq / m ^{2 in} the same manner as in Example 1 except that carbon black having the physical properties shown in Table 1 was used. In the same manner as in Example 1, the viscosity, average particle size Dupa _50% , cumulative frequency 90% particle size Dupa _90% , pH, surface tension were prepared. The electrical conductivity and filterability were determined. The results are shown in Table 2.
In addition, an inkjet ink was prepared in the same manner as in Example 1 by using the obtained black pigment aqueous dispersion for an inkjet printer.
Printing density and precipitation residue rate were measured by the same method as in Example 1 using the obtained inkjet ink. The results are shown in Table 3.

(Comparative Examples 1 to 4)
A black pigment aqueous dispersion for an inkjet printer was prepared in the same manner as in Example 1 except that carbon black having the physical properties shown in Table 1 was used. In the same manner as above, viscosity, average particle diameter Dupa _50% , cumulative frequency 90% particle diameter Dupa _90% , pH, surface tension, electrical conductivity and filterability were determined. The results are shown in Table 2 (the black pigment aqueous dispersion for inkjet printers obtained in Comparative Example 3 and Comparative Example 4 requires a long time when a membrane filter having a pore diameter of 0.8 μm is used, and is filtered within a predetermined time. Since it was not possible, the description of the data in Table 2 is omitted).
In addition, an inkjet ink was prepared in the same manner as in Example 1 by using the obtained black pigment aqueous dispersion for an inkjet printer.
Printing density and precipitation residue rate were measured by the same method as in Example 1 using the obtained inkjet ink. The results are shown in Table 3.

From Tables 1 to 3, the black pigment aqueous dispersions for inkjet printers obtained in Examples 1 to 2 are the nitrogen adsorption specific surface area (N ₂ SA), DBP oil absorption, 24M4DBP absorption before hydrophilization treatment. , DBP oil absorption−24M4 DBP Carbon having a ratio (ΔDBP), tinting strength (Tint), aggregate mode diameter half-value width ΔDst / aggregate mode diameter Dst in a specific range Because it contains black, viscosity, Dupa _50% , Dupa _90% , pH, electrical conductivity hardly change over 2 weeks in an aqueous medium, and excellent filterability, so excellent dispersibility and storage stability In addition, the inkjet ink prepared using such a black pigment aqueous dispersion has a printing density of only once ( Even in the “fast” mode), it can be seen that the blackness is almost the same as or better than that of electrophotography by printing only once, almost the same as multiple times printing (“clean” mode). It can be seen that an ink-jet ink having can be provided.

On the other hand, from Tables 1 to 3, the black pigment aqueous dispersion for an inkjet printer obtained in Comparative Example 1 contains carbon black having a nitrogen adsorption specific surface area (N ₂ SA) before hydrophilization treatment outside the predetermined range. Therefore, the print density of the inkjet ink obtained from the black pigment aqueous dispersion is low for both one-time printing (“fast” mode) and multiple-time printing (“clean” mode). It was not reached.

Further, from Tables 1 to 3, the black pigment aqueous dispersion for an inkjet printer obtained in Comparative Example 2 has a nitrogen adsorption specific surface area (N ₂ SA) before hydrophilization treatment, and a DBP oil absorption amount before hydrophilization treatment— Since the difference (ΔDBP) and the coloring power (Tint) expressed by the 24M4DBP absorption amount include carbon black that is outside the predetermined range, the viscosity of the inkjet ink obtained from the black pigment aqueous dispersion is very high. The print density was low both for one-time printing (“fast” mode) and multiple times (“clean” mode), and did not reach the print density of electrophotography.

  Furthermore, as shown in Tables 1 to 3, the black pigment aqueous dispersion for inkjet printers obtained in Comparative Example 3 has a predetermined difference (ΔDBP) expressed by DBP oil absorption before hydrophilic treatment−24M4DBP absorption. Since it contains carbon black that is out of the range, when using a membrane filter having a pore diameter of 0.8 μm, it takes a long time and cannot be filtered within a predetermined time, and may have poor dispersibility. I understand.

As shown in Tables 1 to 3, the black pigment aqueous dispersion for inkjet printers obtained in Comparative Example 4 has a nitrogen adsorption specific surface area (N ₂ SA), a DBP oil absorption amount, a 24M4DBP absorption amount before hydrophilization treatment, DBP oil absorption amount −24M4 DBP Absorption amount (ΔDBP) and tinting strength (Tint) both include carbon black that is outside the predetermined range, so it is long when a membrane filter with a pore diameter of 0.8 μm is used. It takes time and is inferior in filterability that cannot be filtered within a predetermined time, and since the precipitation residue rate of the inkjet ink obtained from the black pigment aqueous dispersion is very high, the dispersion stability is inferior, It turns out that it cannot be put to practical use.

  As shown in Tables 1 to 3, the black pigment aqueous dispersion for an ink jet printer obtained in Comparative Example 5 is represented by the DBP oil absorption amount, 24M4DBP absorption amount and DBP oil absorption amount−24M4DBP absorption amount before hydrophilization treatment. Since the difference (ΔDBP) includes carbon black that is outside the predetermined range, the particle size of the carbon black is too small, and the print density of the inkjet ink obtained from the black pigment aqueous dispersion is only once. It can be seen that both the printing (“fast” mode) and the multiple printing (“clean” mode) are very low and do not reach the printing density of the electrophotographic image and cannot be put to practical use.

  According to the present invention, a black pigment for an inkjet printer and an inkjet printer that exhibit excellent dispersibility and storage stability in an aqueous medium, and exhibit excellent blackness equivalent to or better than that of an electrophotographic image by only one printing. An aqueous black pigment dispersion can be provided.

Claims (4)

Nitrogen adsorption specific surface area _(N 2 SA) of ^{80m 2} / ^g~160m 2 / g,
DBP oil absorption is 100ml / 100g-170ml / 100g,
24M4DBP absorption is 80 ml / 100 g-140 ml / 100 g,
The DBP oil absorption amount is larger than the 24M4DBP absorption amount, and the difference expressed by DBP oil absorption amount−24M4DBP absorption amount is 10 ml / 100 g to 40 ml / 100 g,
Coloring power (Tint) is 100 to 145,
When the mode diameter of the aggregate is Dst and the half width of the mode diameter of the aggregate is ΔDst, the ratio represented by ΔDst / Dst is 0.5 to 0.8.
A black pigment for an ink jet printer, comprising: a carbon black hydrophilized product. In the cumulative frequency distribution curve of the agglomerate particle size obtained by irradiating laser light in the state of an aqueous dispersion and the frequency modulation degree of the scattered light, the value of the cumulative frequency 50% is the average particle size Dupa _50% and the cumulative frequency 90%. When the value is Dupa _90% ,
The carbon black agglomerate has an average particle size Dupa _50% of 130 nm to 160 nm,
Dupa _90% of the agglomerate of the carbon black is 210 nm to 280 nm
The black pigment for an ink jet printer according to claim 1. 3. The black pigment for an ink jet printer according to claim 1, wherein a hydrogen-containing surface functional group amount of the carbon black hydrophilized product is 3 μeq / m ² or more.   An aqueous black pigment dispersion for an ink jet printer, comprising the black pigment for an ink jet printer according to any one of claims 1 to 3.