JP2018188573A - Dispersion liquid, ink, inkjet recording method and recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aqueous ink which contains carbon black as a pigment and has a high black printing density and good storage stability at high temperatures.SOLUTION: There is provided a dispersion liquid which contains carbon black, a polymer dispersant, an anionic surfactant and water, wherein the polymer dispersant is an A-B block polymer having a weight average molecular weight of 10000 or more and 20000 or less and the anionic surfactant is selected from a polyoxyethylene styrenated phenyl ether sulfate and a formalin condensate of naphthalene sulfonic acid.SELECTED DRAWING: None

Description

  The present invention relates to a dispersion containing carbon black, an ink containing the dispersion, an ink jet recording method using the ink, and a recording medium to which the ink is attached.

A recording method using an ink jet printer (ink jet recording method) is one of typical recording methods among various color recording methods. In this method, ink droplets are generated and recorded on various recording media (paper, film, fabric, etc.) for recording. Due to the advancement of ink jet technology, ink jet recording has come to be used in fields where silver salt photography and high-definition printing where offset printing has been used are required. Furthermore, in recent years, the demand for industrial applications is also increasing.
Black ink is the most frequently used ink for printing recorded images including characters. Further, a high print density is required for the recorded image. The colorant contained in the inkjet ink is roughly classified into a water-soluble dye and a water-insoluble dye or pigment. Among these, the aqueous ink containing the latter colorant is a dispersion ink in which the colorant is not dissolved. For this reason, ink containing carbon black as a colorant for black ink is strongly required to have good storage stability as well as high printing density.
Further, when a sand mill is used in the production of the dispersion, it is necessary to separate the dispersion beads and the dispersion. This separation is simple and inexpensive to carry out by filtration. For this reason, the dispersion liquid with favorable filterability is also calculated | required strongly.
Patent Documents 1 and 2 disclose inks containing carbon black.

JP 2010-066511 A JP 2005-054043 A

  The present invention contains carbon black as a colorant, has good filterability, and has excellent storage stability at high temperatures, and water dispersion containing the dispersion and giving a recorded image with high black print density The problem is to provide ink.

As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that the ink containing carbon black, a specific polymer dispersant, a specific anionic surfactant, and water can be used. The present inventors have found that the problem can be solved and completed the present invention.
That is, the present invention relates to the following 1) to 13).
1)
A dispersion containing carbon black, a polymer dispersant, an anionic surfactant, and water,
The polymer dispersant is an AB block polymer having a weight average molecular weight of 15,000 to 29000,
A dispersion in which the anionic surfactant is a surfactant selected from polyoxyalkylene styrenated phenyl ether sulfate and naphthalenesulfonic acid formalin condensate.
2)
In the AB block polymer, the monomer constituting the A block is a monomer selected from benzyl methacrylate and benzyl acrylate,
The dispersion according to 1) above, wherein the monomer constituting the B block is two or more types of monomers represented by the following formula (1).

[In Formula (1), R ¹ represents a hydrogen atom or an alkyl group, and R ² represents a hydrogen atom or a methyl group. ]
3)
The monomer constituting the A block is benzyl methacrylate,
Among the monomers represented by the formula (1), the monomer constituting the B block is:
A monomer in which R ¹ is a hydrogen atom and R ² is a methyl group;
The dispersion according to 2), wherein R ¹ is a C4 alkyl group and R ² is a monomer represented by a methyl group.
4)
The dispersion liquid as described in 1) above, wherein the carbon black has a primary particle size of 20 nm or less.
5)
The ink containing the dispersion liquid as described in any one of 1) to 4) and a penetrating agent.
6)
The ink according to 5) above, wherein the penetrant is C5-C9 alkanediol.
7)
The ink according to 5) above, wherein the penetrant is 1,2- (C5-C9) alkanediol.
8)
An ink jet recording method for performing recording by ejecting the ink droplets according to any one of 5) to 7) from an ink jet printer and attaching them to a recording medium.
9)
A recording medium to which the ink according to any one of 5) to 7) is attached.
10)
9. The recording medium according to 9) above, wherein the recording medium is a medium having an ink receiving layer.
11)
9. The recording medium according to 9) above, wherein the recording medium is a medium having no ink receiving layer.
12)
An ink tank containing the ink according to any one of 5) to 7).
13)
An ink jet printer having the ink tank according to 12).

  According to the present invention, a dispersion containing carbon black as a colorant, having good filterability and excellent storage stability at high temperatures, and an aqueous solution containing the dispersion and giving a recorded image with high black print density Ink was provided.

In this specification, “CI” is an abbreviation for color index.
Further, in the present specification, “%” and “part” are described on a mass basis unless otherwise specified, including examples.
In the present specification, when the content is described, it means the content relative to the total mass of the ink unless otherwise specified.

[Carbon black]
Examples of carbon black include thermal black, acetylene black, oil furnace black, gas furnace black, lamp black, gas black, and channel black. Of these, those having a primary particle diameter of 20 nm or less are preferred. By using such carbon black, the black print density can be increased. The primary particle diameter can be measured by a known method such as a dynamic light scattering method. In addition, the carbon black supplier may publish information on the primary particle size.
Specific examples thereof include, for example, COLOR BLACK FW1, FW2, FW18, FW200, FW285, S170, Special Black 6 manufactured by Degussa, NIPEX 160 IQ, 170 IQ, 180 IQ manufactured by Orion Engineered Carbon Co., Ltd. Monarch 800, 880, 1300 manufactured by Tokai Carbon Co., Ltd. # 75550, 8300, 8500; #MCF 88, MA 600, No. 850, no. 900, no. 950, no. 960, no. 980, no. 1000, no. 2300, no. 2350, no. 2600, no. 2650 or the like.

[Polymer dispersant]
The weight average molecular weight of the polymer dispersant is usually 15000 to 29000, preferably 16000 to 28000, more preferably 17000 to 27000. The polymer dispersant is an AB block polymer.
An AB block polymer in which the monomer constituting the A block is a monomer selected from benzyl methacrylate and benzyl acrylate, and the monomer constituting the B block is two or more monomers represented by the formula (1). preferable.
The monomer constituting the A block is benzyl methacrylate, and the monomer constituting the B block is a monomer represented by the formula (1), wherein R ¹ is a hydrogen atom and R ² is a methyl group. And an AB block polymer, which is two types of a monomer in which R ¹ is a C4 alkyl group and R ² is a methyl group, is more preferable.
As such AB block polymer, the dispersing agent disclosed by the international publication 2013/115071 gusset is mentioned, for example.

  The acid value of the polymer dispersant is usually 80 to 140 mgKOH / g, preferably 90 to 130 mgKOH / g, more preferably 100 to 120 mgKOH / g. By setting the acid value within these ranges, the dispersibility and the print density can be improved.

The dispersant can be used in a state mixed with a colorant. Moreover, it can also be used as the state which coat | covered the dispersing agent on the surface of a coloring agent. Moreover, both of these can also be used together.
When using a dispersant, the ratio of the amount of dispersant used relative to the total mass of the colorant is usually 0.1 to 1.0, preferably 0.1 to 0.6, more preferably 0.2 to 0.4. It is. When the ratio of the amount of the dispersant used is in this range, the stability is excellent and a good recorded image can be obtained.

[Anionic surfactant]
Examples of the anionic surfactant include surfactants selected from polyoxyalkylene styrenated phenyl ether sulfate and naphthalene sulfonic acid formalin condensate. Among these, examples of the polyoxyalkylene styrenated phenyl ether sulfate include a mixture of compounds represented by the following formula (2). Moreover, as a naphthalene sulfonic-acid formalin condensate, the mixture of the compound represented by following formula (3) is mentioned.

In formula (2), n1 represents an integer of usually 1 to 5, preferably 1 to 3.
m represents an integer of 3 to 30, preferably 5 to 18.
A represents an alkylene selected from ethylene, propylene and butylene, an alkylene selected from ethylene and propylene is preferable, and ethylene is more preferable.
M ¹ represents a cation, and includes a cation of an element selected from Group 1 elements and Group 2 elements of the periodic table of elements; quaternary ammonium; and ammonium (NH ₄ ⁺ ). Of these, ammonium is preferred.

In formula (3), n2 represents an integer of usually 7 to 200, preferably 7 to 100.
M ² each independently represents a cation, and includes cations of elements selected from Group 1 elements and Group 2 elements of the periodic table of elements; quaternary ammonium; and ammonium (NH ₄ ⁺ ). Among these, a cation of a group 1 element in the periodic table of elements is preferable; a cation of an element selected from lithium, sodium, and potassium is more preferable, and a cation of sodium is more preferable. Further, preferably a plurality of M ² are the same cation.

Specific examples of the mixture of the compound represented by the formula (2) include, for example, DEMAL N, DEMAL NL, DEMAL RN, DEMAL RN-L, DEMAL T, DEMAL T-45 and the like manufactured by Kao Corporation.
Specific examples of the mixture of compounds represented by the formula (3) include, for example, Hytenol NF-8, NF-0825, NF-13, NF-17 and the like manufactured by Daiichi Kogyo Seiyaku Co., Ltd.

The dispersion can be prepared by a known method.
As an example, a dispersant is dissolved in an organic solvent such as 2-butanone, and an aqueous solution of a neutralizing agent is added to prepare an emulsion. Carbon black is added to the obtained emulsion to perform a dispersion treatment to obtain a liquid. A dispersion containing a colorant can be obtained by distilling off the organic solvent and part of the water under reduced pressure from the liquid thus obtained.
In the dispersion treatment, for example, the dispersion or emulsion solution of the dispersant and carbon black are placed in a sand mill (bead mill), roll mill, ball mill, paint shaker, ultrasonic disperser, microfluidizer, or the like to perform dispersion. When using a sand mill, beads having a particle diameter of about 0.01 mm to 1 mm can be used. The efficiency of the dispersion treatment can be adjusted by adjusting the filling rate of beads, dispersion time, carbon black content, and the like.
The dispersion obtained as described above can be filtered and / or centrifuged to make the particle diameter of the contained particles uniform within a certain range.

  The average particle size of the particles contained in the dispersion is usually 50 nm to 150 nm, preferably 60 nm to 120 nm. By setting the particle diameter within this range, the dispersion stability and ejection stability are excellent, and the print density of the recorded image can be increased. In this specification, an average particle diameter means the average particle diameter of the particle | grains in a liquid measured using the laser light scattering method.

[Penetration agent]
The ink contains the dispersion liquid and a penetrant. Examples of penetrants include linear or branched C5-C9 alkanediols. Among them, straight chain is preferable, and 1,2- (C5-C9) alkanediol is more preferable.
Specific examples thereof include 1,2-pentanediol, 1,2-hexanediol, 1,2-heptanediol, 1,2-octanediol, 1,2-nonanediol, 2-methyl 2,4- Examples include pentanediol, 2-ethyl-1,3-hexanediol, and 2,4-diethyl-1,5-pentanediol. Of these, 1,2-hexanediol is preferred.
The content of the penetrant is usually 1% to 20%, preferably 3% to 18%.

  The ink may further contain one or more components other than those described above as ink preparation agents. Examples of the ink preparation agent include organic solvents, antifungal agents, preservatives, pH adjusters, chelating reagents, rust inhibitors, water-soluble ultraviolet absorbers, water-soluble polymer compounds, antioxidants, and surfactants. Is mentioned. The total content of the ink preparation agent excluding the organic solvent is usually 0% to 30%, preferably 0% to 10%, more preferably about 0% to 5%.

Examples of the organic solvent include a water-soluble organic solvent and a water-insoluble organic solvent.
Examples of the water-soluble organic solvent include C1-C6 alkanols such as methanol, ethanol, propanol, isopropanol, butanol, isobutanol, sec-butanol or tert-butanol, and trimethylolpropane; N, N-dimethylformamide or N, N A carboxylic acid amide such as dimethylacetamide; a lactam such as 2-pyrrolidone, N-methyl-2-pyrrolidone or N-methylpyrrolidin-2-one; 1,3-dimethylimidazolidin-2-one or 1,3-dimethyl Cyclic ureas such as hexahydropyrimido-2-one; ketones or ketoalcohols such as acetone, 2-methyl-2-hydroxypentan-4-one and ethylene carbonate; cyclic ethers such as tetrahydrofuran and dioxane; ethylene glycol , Diethylene Cole, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butylene glycol, 1,4-butylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, molecular weight 400, 800, 1540 Or more mono, oligo or polyalkylene glycols or thioglycols having C2-C4 alkylene units such as polyethylene glycol, polypropylene glycol, thiodiglycol or dithiodiglycol; glycerin, diglycerin, hexane-1,2,6- Polyols such as triols (triols); ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, diethylene glycol monoethyl ether, diethylene glycol Cole monobutyl ether (butyl carbitol), triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, ethylene glycol monoallyl ether, ethylene glycol monoisopropyl ether, diethylene glycol monomethyl ether, propylene glycol monopropyl ether, triethylene glycol monobutyl ether, etc. C1-C4 alkyl ether of polyhydric alcohol; γ-butyrolactone or dimethyl sulfoxide;
The total content of the water-soluble organic solvent is usually 0% to 55%, preferably 5% to 40%, more preferably about 10% to 30%.

  The water-insoluble organic solvent can be contained in a range that does not cause layer separation with the ink. The content is difficult to say in general due to the content of other components. The standard is usually 0.1 to 3%, preferably about 0.1 to 2%. Examples of the water-insoluble organic solvent include C8-C16 (preferably C8-12) alkyl having a hydroxy group and an acyloxy group. Specific examples thereof include texanol.

  Specific examples of the antifungal agent include sodium dehydroacetate, sodium benzoate, sodium pyridinethione-1-oxide, p-hydroxybenzoic acid ethyl ester, 1,2-benzisothiazolin-3-one or a salt thereof. .

  Examples of preservatives include, for example, organic sulfur, organic nitrogen sulfur, organic halogen, haloaryl sulfone, iodopropargyl, haloalkylthio, nitrile, pyridine, 8-oxyquinoline, benzothiazole , Isothiazoline, dithiol, pyridine oxide, nitropropane, organotin, phenol, quaternary ammonium salt, triazine, thiazine, anilide, adamantane, dithiocarbamate, brominated indanone, benzyl Examples thereof include bromoacetate-based or inorganic salt-based compounds. Specific examples of the organic halogen compound include, for example, sodium pentachlorophenol. Specific examples of the pyridine oxide compound include sodium 2-pyridinethiol-1-oxide. Examples of isothiazoline compounds include 1,2-benzisothiazolin-3-one, 2-n-octyl-4-isothiazolin-3-one, 5-chloro-2-methyl-4-isothiazolin-3-one, 5- Chloro-2-methyl-4-isothiazolin-3-one magnesium chloride, 5-chloro-2-methyl-4-isothiazolin-3-one calcium chloride, 2-methyl-4-isothiazolin-3-one calcium chloride and the like It is done. Specific examples of other antiseptic / antifungal agents include anhydrous sodium acetate, sodium sorbate or sodium benzoate, Proxel GXL (S), Proxel XL-2 (S) manufactured by Arch Chemical Co., etc.

  As the pH adjuster, any substance can be used as long as it can control the pH of the ink within a range of, for example, 5 to 11 without adversely affecting the prepared ink. Specific examples thereof include alkanolamines such as diethanolamine, triethanolamine and N-methyldiethanolamine; hydroxides of alkali metals such as lithium hydroxide, sodium hydroxide and potassium hydroxide; ammonium hydroxide (ammonia water); Alternatively, alkali metal carbonates such as lithium carbonate, sodium carbonate, sodium hydrogen carbonate, and potassium carbonate; alkali metal salts of organic acids such as sodium silicate and potassium acetate; inorganic bases such as disodium phosphate, and the like.

  Specific examples of the chelating reagent include, for example, disodium ethylenediaminetetraacetate, sodium nitrilotriacetate, sodium hydroxyethylethylenediaminetriacetate, sodium diethylenetriaminepentaacetate or sodium uracil diacetate.

  Specific examples of the rust inhibitor include acidic sulfite, sodium thiosulfate, ammonium thioglycolate, diisopropylammonium nitrite, pentaerythritol tetranitrate or dicyclohexylammonium nitrite.

  Examples of water-soluble UV absorbers include sulfonated benzophenone compounds, benzotriazole compounds, salicylic acid compounds, cinnamic acid compounds, and triazine compounds.

  Specific examples of the water-soluble polymer compound include polyethylene glycol, polyvinyl alcohol, cellulose derivatives, polyamine or polyimine.

  As examples of the antioxidant, for example, various organic and metal complex anti-fading agents can be used. Examples of the organic anti-fading agent include hydroquinones, alkoxyphenols, dialkoxyphenols, phenols, anilines, amines, indanes, chromans, alkoxyanilines or heterocyclic rings. .

  The ink may contain a surfactant other than the anionic surfactant. Examples of the surfactant include cationic, nonionic, amphoteric, silicone-based, and fluorine-based surfactants. Of these, surfactants selected from nonions and silicones are preferred.

  Examples of the cationic surfactant include 2-vinylpyridine derivatives and poly-4-vinylpyridine derivatives.

  Examples of amphoteric surfactants include lauryldimethylaminoacetic acid betaine, 2-alkyl-N-carboxymethyl-N-hydroxyethylimidazolinium betaine, coconut oil fatty acid amidopropyldimethylaminoacetic acid betaine, polyoctylpolyaminoethylglycine, and imidazoline derivatives. Can be mentioned.

Nonionic surfactants include ethers such as polyoxyethylene nonylphenyl ether, polyoxyethylene octylphenyl ether, polyoxyethylene dodecylphenyl ether, polyoxyethylene oleyl ether, polyoxyethylene lauryl ether, polyoxyethylene alkyl ether; Ester systems such as polyoxyethylene oleate, polyoxyethylene distearate, sorbitan laurate, sorbitan monostearate, sorbitan monooleate, sorbitan sesquioleate, polyoxyethylene monooleate, polyoxyethylene stearate; 2,4,7,9-tetramethyl-5-decyne-4,7-diol, 3,6-dimethyl-4-octyne-3,6-diol, 3,5-dimethyl Acetylene glycol (alcohol) system such as lu-1-hexyn-3-ol; Surfynol 104, 105PG50, 82, 420, 440, 465, 485 manufactured by Nissin Chemical Co., Ltd. Olfin STG; Polyglycol ether system (for example, SIGMA-ALDRICH TergItol 15-S-7 etc.);
Of these, acetylene glycol surfactants are preferred.

  Examples of the silicone surfactant include polyether-modified siloxane and polyether-modified polydimethylsiloxane. Examples thereof include BYK-345, BYK-348 (manufactured by Big Chemie, polyether-modified polydimethylsiloxane), BYK-347 (the same, polyether-modified siloxane), BYK-349, BYK-3455, and the like.

  Examples of the fluorosurfactant include a perfluoroalkyl sulfonic acid compound, a perfluoroalkyl carboxylic acid compound, a perfluoroalkyl phosphate ester compound, a perfluoroalkyl ethylene oxide adduct, and a perfluoroalkyl ether group as a side chain. And polyoxyalkylene ether polymer compounds. Examples include Zonyl TBS, FSP, FSA, FSN-100, FSN, FSO-100, FSO, FS-300, Capstone FS-30, FS-31 manufactured by DuPont; PF-151N, PF manufactured by Omninova -154N; F-114, F-410, F-444, EXP. TF-2066, EXP. TF-2148, EXP. TF-2149, F-430, F-477, F-552, F-553, F-554, F-555, F-556, F-557, F-558, F-559, F-561, F- 562, R-40, R-41, RS-72-K, RS-75, RS-76-E, RS-76-NS, RS-77, EXP. TF-1540, EXP. TF-1760; BYK-3440, BYK-3441, etc. manufactured by Big Chemie.

The ink is preferably prepared by obtaining a dispersion containing carbon black and a dispersant and then adding other components.
When the ink is used for ink jet recording, it is preferable to use an ink containing a small amount of inorganic impurities such as metal cation chloride (for example, sodium chloride) and sulfate (for example, sodium sulfate). The standard of the content of the inorganic impurities is about 1% or less with respect to the total mass of the carbon black, and the lower limit can be set below the detection limit of the analytical instrument, that is, 0%. Examples of a method for obtaining an ink having a small amount of inorganic impurities include a method of purifying the ink with a reverse osmosis membrane; a method of refining carbon black in a mixed solvent of C1-C4 alcohol such as methanol and water; and ion exchange. Examples thereof include a method of exchanging and adsorbing inorganic impurities in the ink using a resin.

The pH of the ink is usually pH 5 to pH 11, preferably pH 7 to pH 10, for the purpose of improving storage stability. The surface tension of the ink is usually 10 to 50 mN / m, preferably 20 to 40 mN / m. The viscosity of the ink is usually 30 mPa · s or less, preferably 20 mPa · s or less, and the lower limit is about 0.1 mPa · s.
The pH, surface tension, and viscosity of the ink can be adjusted, for example, with an ink preparation agent such as the above-described pH adjuster or surfactant.

  The ink can be used in various fields. Examples thereof include water-based ink for writing, water-based printing ink, information recording ink, textile printing, and the like, and it is preferably used for ink-jet recording.

  The ink jet recording method is a method of recording by ejecting ink droplets according to a recording signal and attaching them to a recording medium. There are no particular restrictions on the ink nozzles used during recording, and the ink nozzles can be selected according to the purpose.

  The recording method is not particularly limited, and a known method can be used. Examples thereof include a charge control method; a drop-on-demand method (pressure pulse method); an acoustic ink jet method; a thermal ink jet method.

  The recording medium is not particularly limited as long as it can be colored by the ink. Examples thereof include paper, film, fiber and cloth (cellulose, nylon, wool, etc.), leather, and a base material for a color filter.

Recording media are roughly classified into recording media having an ink receiving layer and recording media not having an ink receiving layer.
Examples thereof include fibers; paper having an ink-receiving layer; and recording media that do not have an ink-receiving layer and that are difficult to absorb or not absorb ink.
Examples of paper having an ink receiving layer include ink-jet dedicated paper.
Examples of the ink-absorptive recording medium include plain paper; media used for gravure printing and offset printing; and coated paper such as finely coated paper, art paper, coated paper, matte paper, and cast paper.
Examples of non-ink-absorbing recording media include vinyl chloride sheets, polymer sheets, glass, and rubber.
Among these, a recording medium that does not have an ink-receiving layer and is difficult to absorb ink is preferable.
The ink receiving layer is formed by, for example, impregnating or coating a recording medium with a cationic polymer; or inorganic fine particles capable of absorbing a pigment in ink such as porous silica, alumina sol, and special ceramics, such as polyvinyl alcohol and polyvinyl pyrrolidone. A method of coating the surface of the substrate together with a hydrophilic polymer;

When the recording medium is a fiber, a fiber selected from the group consisting of polyester, cellulose, polyamide, and natural fiber, and a blended fiber containing these fibers can be used. These fibers can have an ink receiving layer. The ink receiving layer can be provided on the fiber by a known method. The fiber having the ink receiving layer is commercially available, for example, in the form of a fabric.
Polyester fibers include polyethylene terephthalate fibers.
Examples of the cellulose fiber include cotton, cotton, rayon, triacetate, diacetate and the like.
Examples of polyamide fibers include nylon fibers.
Examples of natural fibers include silk and wool.

When recording on a recording medium by the ink jet recording method, an ink tank containing the ink is loaded at a predetermined position of the ink jet printer, and recording is performed by the recording method.
An ink tank containing the ink and an ink jet printer containing the ink tank are also included in the scope of the present invention.
The ink jet recording method can be used in combination with an ink containing a colorant selected from yellow, blue, red, green, violet, and orange pigments or dyes as necessary, and full color recording can also be performed.

  About all the above-mentioned matters, a combination of preferable ones is more preferable, and a combination of more preferable ones is further preferable. The same applies to a combination of a preferable one and a more preferable one, and a combination of a more preferable one and a more preferable one.

By recording with the ink, a high-density black image can be formed.
In addition, fine droplets can be formed, and an ink having good redispersibility and good wettability to a recording medium can be obtained even when the ink is dried.
In addition to the storage stability of the ink, the dispersion state of the carbon black fine particles in the dispersion can be stabilized.
Further, the image recorded with the ink does not cause a mottling phenomenon and has a good solid filling.
Further, the image has no blur and is excellent in scratching.

EXAMPLES The present invention will be specifically described with reference to examples, but the present invention is not limited to the following examples. In addition, operations such as each synthesis reaction and crystallization were performed under stirring unless otherwise specified.
The content of carbon black in each dispersion obtained in the examples was determined by dry weight method using MS-70 manufactured by A & D Corporation. The content of carbon black in each dispersion was adjusted to 12% as a conversion value from the total solid content.

[Synthesis Example 1]: Synthesis of a polymer dispersant.
In accordance with “[Synthesis Example 3] Synthesis of Block Copolymer A” of International Publication No. 2013/115071, 138 g of a dispersant having a weight average molecular weight of 24,300 and a PDI of 1.49 was obtained. In the obtained dispersant, the monomer constituting the A block is benzyl methacrylate, the monomer constituting the B block is a monomer represented by the formula (1), R ¹ is a hydrogen atom, and R ² is a methyl group And a monomer in which R ¹ is an n-butyl group as a C4 alkyl group and R ² is a methyl group.

Example 1 Preparation of Dispersion 1
The polymer dispersant (3 parts) obtained in Synthesis Example 1 was dissolved in 2-butanone (30 parts) to obtain a liquid. A solution obtained by dissolving 0.23 parts of sodium hydroxide in ion-exchanged water (41 parts) and hytenol NF13 (3 parts) were added to this liquid and stirred for 1 hour to prepare an emulsion. This emulsion and Toka Black # 8500 (20 parts) were placed in a sand grinder and subjected to a dispersion treatment at 1500 rpm for 15 hours to obtain a liquid. After ion-exchanged water (100 parts) was dropped into the obtained liquid, the filtrate was obtained by filtering with a glass fiber filter GA-100 manufactured by ADVANTEC. The obtained filtrate was put into an evaporator, and 2-butanone and a part of water were distilled off under reduced pressure to obtain dispersion 1 (130 parts).

[Example 2]: Preparation of dispersion 2.
Dispersion 2 (130 parts) was obtained in the same manner as in Example 1 except that Demol NL (3 parts) was used instead of Hightenol NF13 (3 parts).

[Comparative Example 1]: Preparation of dispersion 3.
A dispersion 3 (130 parts) was obtained in the same manner as in Example 1 except that Neugen EA-157 (polyoxyethylene styrenated phenyl ether: 3 parts) was used instead of Hytenol NF13 (3 parts).

[Comparative Example 2]: Preparation of dispersion 4.
Dispersion 4 (130 parts) was obtained in the same manner as in Example 1 except that Perex NBL (alkyl naphthalenesulfonic acid sodium salt: 3 parts) was used instead of Hytenol NF13 (3 parts).

[Comparative Example 3]: Preparation of dispersion 5.
The polymer dispersant (6 parts) obtained in Synthesis Example 1 was dissolved in 2-butanone (30 parts) to obtain a liquid. A solution prepared by dissolving 0.45 parts of sodium hydroxide in ion-exchanged water (41 parts) was added to this liquid, and an emulsion was prepared by stirring for 1 hour. This emulsion and Toka Black # 8500 (20 parts) were placed in a sand grinder and subjected to a dispersion treatment at 1500 rpm for 15 hours to obtain a liquid. After ion-exchanged water (100 parts) was dropped into the obtained liquid, filtration was attempted with a glass fiber filter GA-100 manufactured by ADVANTEC, but filtration could not be performed due to clogging of the filter. For this reason, the dispersion 5 could not be prepared.

The following “storage stability test (1)” was carried out on the dispersions of Examples and Comparative Examples obtained as described above. The test results are shown in Table 1 below.
As described above, since the dispersion 5 of Comparative Example 3 could not be prepared, the “storage stability test (1)” was not performed.

[Storage stability test (1)]
Each dispersion obtained in the above-mentioned Examples and Comparative Examples was diluted 600 times with ion exchange water to prepare a test sample, and the particle size distribution D90 was measured with Nanotrac Wave EX150 (manufactured by Microtrac Bell). did. This value is defined as “D90 before test”. 30 g of each test sample was put in a container, sealed, and allowed to stand for 3 days in a constant temperature and humidity machine at 70 ° C. After returning each container to room temperature, the particle size distribution D90 was measured in the same manner as described above to obtain “D90 after test”.
The change rate of the particle size distribution was calculated by the following formula. The smaller the change rate, the better the storage stability.
Rate of change (%) = | (D90 after test) − (D90 before test) | / (D90 before test) × 100.

Abbreviations and the like in the following Table 1 have the following meanings. Further, the components in Table 2 below are described by extracting only the carbon black, the polymer dispersant, and the anion dispersant and their contents. The numerical value of the content is “parts”.
# 8500: Talker Black # 8500.
Dp: the polymer dispersant obtained in Synthesis Example 1.
NF13: Haitenol NF13.
NL: Demall NL.
EA157: Neugen EA157.
NBL: Perex NBL.

[Comparative Example 4]: Preparation of dispersion 6.
Dispersion 6 (130 parts) is obtained in the same manner as in Example 1 except that NEROX 305 (primary particle diameter 28 nm: 20 parts) manufactured by Degussa is used instead of Toka Black # 8500 (20 parts). It was.

[Comparative Example 5]: Preparation of dispersion 7.
Except for using “6 parts” of polymer dispersing agent (3 parts), using NEROX 305 (20 parts) instead of Toka Black # 8500 (20 parts) and not adding Hightenol NF13 (3 parts). In the same manner as in Example 1, Dispersion 7 (130 parts) was obtained.

[Examples 3 to 4 and Comparative Examples 4 to 6]: Preparation of ink.
The components shown in Table 2 below were mixed, stirred for about 1 hour, and then filtered through a 3 μm membrane filter to obtain inks of Examples and Comparative Examples. The carbon black content in each ink was adjusted to 5%.
Abbreviations and the like in Table 1 represent the following meanings.
PG: Propylene glycol.
1,2-HD: 1,2-hexanediol.

[Inkjet recording]
Using each ink obtained in Examples and Comparative Examples, 100% Duty image was ink jet recorded on the following coated paper using an ink jet printer (trade name PX-205, manufactured by EPSON Corporation), and a test piece was obtained. Got. A colorimeter manufactured by X-rite, SpectroEye was used. The color measurement conditions are ANSI A, a viewing angle of 2 °, and a light source D50 as a density reference.
[Coated paper] Finese Gloss (manufactured by UPM).

[Print density test]
The print density of each test piece obtained as described above was measured using an X-rite colorimeter, SpectroEye. The color measurement conditions are ANSI A, a viewing angle of 2 °, and a light source D50 as a density reference. The color measurement results are shown in Table 3 below.

  The dispersion of the present invention has good storage stability at high temperatures. Further, the ink of the present invention containing the same can obtain a recorded image having a high black print density. For this reason, it is extremely useful as various recording inks, in particular, inkjet recording inks.

Claims (13)

A dispersion containing carbon black, a polymer dispersant, an anionic surfactant, and water,
The polymer dispersant is an AB block polymer having a weight average molecular weight of 15,000 to 29000,
A dispersion in which the anionic surfactant is a surfactant selected from polyoxyalkylene styrenated phenyl ether sulfate and naphthalenesulfonic acid formalin condensate. In the AB block polymer, the monomer constituting the A block is a monomer selected from benzyl methacrylate and benzyl acrylate,
The dispersion liquid of Claim 1 whose monomer which comprises B block is two or more types of monomers represented by following formula (1).

[In Formula (1), R ¹ represents a hydrogen atom or an alkyl group, and R ² represents a hydrogen atom or a methyl group. ] The monomer constituting the A block is benzyl methacrylate,
Among the monomers represented by the formula (1), the monomer constituting the B block is:
A monomer in which R ¹ is a hydrogen atom and R ² is a methyl group;
The dispersion according to claim 2, wherein R ¹ is a C4 alkyl group and R ² is a monomer represented by a methyl group.   The dispersion liquid according to claim 1, wherein a primary particle diameter of the carbon black is 20 nm or less.   An ink containing the dispersion according to any one of claims 1 to 4 and a penetrant.   The ink according to claim 5, wherein the penetrant is a C5-C9 alkanediol.   The ink according to claim 5, wherein the penetrant is 1,2- (C5-C9) alkanediol.   An ink jet recording method for performing recording by ejecting the ink droplets according to any one of claims 5 to 7 from an ink jet printer and attaching them to a recording medium.   A recording medium to which the ink according to any one of claims 5 to 7 is attached.   The recording medium according to claim 9, wherein the recording medium is a medium having an ink receiving layer.   The recording medium according to claim 9, wherein the recording medium is a medium having no ink receiving layer.   An ink tank containing the ink according to claim 5.   An ink jet printer having the ink tank according to claim 12.