WO2020162270A1

WO2020162270A1 - Ink, inkjet recording method and recording media

Info

Publication number: WO2020162270A1
Application number: PCT/JP2020/003047
Authority: WO
Inventors: 径明武田; 阿衣子松村; 麻衣子岩見
Original assignee: 日本化薬株式会社
Priority date: 2019-02-06
Filing date: 2020-01-28
Publication date: 2020-08-13
Also published as: JPWO2020162270A1; JP7408585B2

Abstract

Provided is an ink which contains carbon black, a dispersing agent, an organic solvent, a resin and water. The BET specific surface area of the carbon black is 80 m²/g or more. The water/octanol partition coefficient of the organic solvent is not less than -0.05 and less than 3.50. The resin is a compound which is different from the dispersing agent and which has an acid value of more than 0 mg KOH/g and less than 100 mg KOH/g. Also provided are: an inkjet recording method that uses the ink; recording media to which the ink is adhered; an ink tank that contains the ink; and an inkjet printer provided with the ink tank.

Description

Ink, inkjet recording method and recording medium

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

A recording method using an inkjet printer (inkjet recording method) is a method in which small droplets of ink are generated and attached to various recording media (paper, film, cloth, etc.) for recording. In recent years, the demand for inkjet printing for industrial use is also increasing.

Black ink is the ink most often used for printing recorded images containing characters. Further, a high print density is required for the recorded image. Here, the colorant contained in the inkjet ink is roughly classified into a water-soluble dye and a water-insoluble dye or pigment. Of these, the latter aqueous ink containing a colorant is a dispersion ink in which the colorant is dispersed without being dissolved in the ink. Carbon black is widely used as a water-insoluble colorant contained in black ink.

In industrial inkjet printing that uses paper as the recording medium, recording media such as coated paper that does not have an ink receiving layer, such as art paper and coated paper, are usually used. The recording medium having no ink receiving layer can absorb less ink than the recording medium having an ink receiving layer. Therefore, it is difficult to improve the print density in a recording medium having no ink receiving layer, which is a serious problem.

The print density can be improved to some extent by increasing the content of the colorant in the ink. However, in a dispersion ink containing a water-insoluble colorant, if the content of the colorant that is a solid content is increased, the dispersion stability of the ink is reduced. Therefore, there is a strong demand for a dispersed ink containing a water-insoluble colorant and capable of obtaining a higher print density.

Patent Documents 1 to 3 disclose inks containing carbon black.

JP, 2011-184540, A JP, 2010-065131, A JP 2005-263771 A

The present invention provides an aqueous ink containing carbon black as a water-insoluble colorant and having a high black print density, particularly a high black print density when recorded on a recording medium having no ink receiving layer. It is an issue.

The present inventors have completed the present invention described in 1) to 7) below as a result of intensive studies to solve the above problems.

1)
Contains carbon black, dispersant, organic solvent, resin, and water,
The BET specific surface area of the carbon black is 80 m ² /g or more,
The water-octanol partition coefficient of the organic solvent is -0.05 or more and less than 3.50,
The above resin is a compound different from the above dispersant, and has an acid value of more than 0 mgKOH/g and less than 100 mgKOH/g.
2)
The ink according to 1) above, further containing a viscosity modifier.
3)
The ink according to 1) or 2) above, which further contains a surfactant.
4)
An ink jet recording method for performing recording by ejecting an ink droplet of the ink according to any one of the above 1) to 3) from an ink jet printer and adhering it to a recording medium.
5)
A recording medium to which the ink according to any one of 1) to 3) above is attached.
6)
An ink tank containing the ink according to any one of 1) to 3) above.
7)
An inkjet printer comprising the ink tank according to 6) above.

According to the present invention, there is provided an aqueous ink containing carbon black as a water-insoluble colorant and having a high black print density, particularly a high black print density when recorded on a recording medium having no ink receiving layer. be able to.

Hereinafter, embodiments of the present invention will be described in detail. However, the present invention is not limited to the following embodiments.
In the present specification, “%” and “part” are described on a mass basis, including examples, unless otherwise specified. In addition, in the present specification, when the content rate is described, it means the content rate with respect to the total mass of the ink, unless otherwise specified.

<Ink>
The ink according to the present embodiment contains carbon black, a dispersant, an organic solvent, a resin, and water, and the BET specific surface area of the carbon black is 80 m ² /g or more, and the water-octanol partition coefficient of the organic solvent. Is −0.05 or more and less than 3.50, the resin is a compound different from the dispersant, and the acid value is greater than 0 mgKOH/g and less than 100 mgKOH/g.

Each component contained in the ink according to this embodiment will be described below. Each of the components described below may be used alone or in combination of two or more.

[Carbon black]
The carbon black contained in the ink according to the present embodiment has a BET specific surface area of 80 m ² /g or more, preferably 85 m ² /g or more, more preferably 90 m ² /g or more. By using such carbon black, a high print density can be obtained. Carbon black tends to have a higher print density as the BET specific surface area increases. Therefore, the upper limit of the BET specific surface area is not particularly limited. However, even if the BET specific surface area is continuously increased, the print density reaches a peak in the middle, and the print density does not permanently increase. The BET specific surface area when the printing density reaches a peak is usually 300 m ² /g or less, preferably 250 m ² /g or less, and more preferably 200 m ² /g or less. Therefore, the upper limit of the optimum BET specific surface area of carbon black is sufficient.

The type of carbon black is not particularly limited, and may be any of thermal black, acetylene black, oil furnace black, gas furnace black, lamp black, gas black, channel black and the like.

Specific examples of the carbon black include, for example, PRINTEX 60, 85, 75, 50L, alpha, P, 55, FP, F alpha, L, HIBLACK 30, 30L, 40L, 45LB manufactured by Orion Engineered Carbons. , NEROX 505, 510, 600, 605, SPECIAL BLACK 550, 4, 4A; MA77, MA7, MA8, MA100, MA100R, MA100S, MCF88, MA600, #1000, 1000N, 750B, 650B, 52 manufactured by Mitsubishi Chemical Corporation. , 47, 45, 45L, 44, 40; Raven 2350 Ultra, 2000, 1300 Ultra, 1255, 1250, 1200, 1190 Ultra, 1185 Ultra, 1180, 1170, 1100 Ultra, FC1; manufactured by BIRLA CARBON. ..

The above carbon black does not include chemically modified carbon black, that is, self-dispersing carbon black.

The total content of the above carbon black is usually 1% to 20%, preferably 2% to 10%, more preferably 3% to 8%.

[Dispersant]
A known dispersant can be used as the dispersant contained in the ink according to the present embodiment. The dispersant is used for the purpose of dispersing carbon black in the ink. As the dispersant, a dispersant having a functional group that exhibits acidity in a free form, such as a carboxy group, a sulfo group, or a phosphoric acid group, is preferable. Among them, monomers selected from styrene, (meth)acrylate, and (meth)acrylic acid (preferably 2 or more types of monomers, more preferably 2 to 6 types of monomers, and further preferably 2 to 4 types of monomers). Polymers composed of monomers, particularly preferably 2 to 3 types of monomers) are preferred.
In addition, in this specification, (meth)acrylate is used to mean both acrylate and methacrylate, and (meth)acrylic acid and the like are also the same.

As the (meth)acrylate, a monomer selected from alkyl(meth)acrylate and arylalkyl(meth)acrylate is preferable, and a monomer selected from alkylmethacrylate and arylalkylmethacrylate is more preferable.
The alkyl(meth)acrylate is preferably C1-C4 alkyl(meth)acrylate, more preferably C1-C4 alkyl methacrylate, further preferably alkyl(meth)acrylate selected from methyl methacrylate and butyl methacrylate, and n-butyl methacrylate. Is particularly preferable.
The arylalkyl(meth)acrylate is preferably C6-C10 aryl C1-C4 alkyl(meth)acrylate, more preferably C6-C10 aryl C1-C4 alkyl methacrylate, further preferably phenyl C1-C4 alkyl methacrylate, and benzyl methacrylate. Particularly preferred.

Examples of the above polymer include a polymer composed of at least one monomer selected from alkyl (meth)acrylate, arylalkyl (meth)acrylate, and (meth)acrylic acid; and a styrene-(meth)acrylic-based polymer. Coalescence is preferred.

The polymer composed of at least one selected from alkyl(meth)acrylate, arylalkyl(meth)acrylate, and (meth)acrylic acid is a block A and a block B. -B block polymers are preferred.
The A block is preferably composed of arylalkyl (meth)acrylate and can include (meth)acrylic acid. The content of (meth)acrylic acid at this time is usually 0 mol% to 5 mol%, preferably 0 mol% to 3 mol%, and more preferably 0 mol% to 1 with respect to the arylalkyl (meth)acrylate. Mol%, and more preferably 0 mol% to 0.1 mol%.
The B block is preferably a copolymer composed of alkyl (meth)acrylate and (meth)acrylic acid.

A water-insoluble polymer is preferable as the AB block polymer. In the present specification, the “water-insoluble polymer” means that the solubility in 1 liter of water at 25° C. is usually 5 g or less, preferably 3 g or less, more preferably 1 g or less, still more preferably 0.5 g or less. The lower limit of solubility includes 0 g.

Examples of the AB block polymer include AB block polymers obtained by the living radical polymerization method disclosed in WO 2013/115071. Preferred and international publications include WO 2013/115071. It may be similar to the issue. For the production method of the AB block polymer and the like, reference can be made to WO 2013/115071.

On the other hand, as the styrene-(meth)acrylic polymer, the Joncryl series manufactured by BASF is preferable.

The acid value of the dispersant is usually 80 mgKOH/g to 140 mgKOH/g, preferably 90 mgKOH/g to 130 mgKOH/g, and more preferably 100 mgKOH/g to 120 mgKOH/g. By setting the acid value within these ranges, dispersibility and storage stability tend to be good.

The above dispersant can be used in a state of being mixed with carbon black. Further, the surface of carbon black can be used in a state of being coated with a dispersant. Also, both of them can be used together. In the present specification, “coating” means both a state in which the entire surface of carbon black is covered with a dispersant, and a state in which a part of the surface of carbon black is covered with a dispersant.

The average particle diameter (D50) of the particles in the dispersion is usually 50 nm to 250 nm, preferably 60 nm to 150 nm. When the particle size is within such a range, the dispersion stability and the ejection stability are improved, and the print density of a recorded image tends to be high. In the present specification, the “average particle diameter” means the average particle diameter of particles in a liquid, which is measured using a laser light scattering method.

The ratio of the total mass of the dispersant to the total mass of carbon black is usually 0.1 to 1.0, preferably 0.1 to 0.6, more preferably 0.2 to 0.5.

[Organic solvent]
The organic solvent contained in the ink according to the present embodiment has a water-octanol distribution coefficient of −0.05 or more and less than 3.50, preferably −0.02 or more and less than 3.50, and more preferably −0. It is 01 or more and less than 3.50, and more preferably 0.00 or more and 3.49 or less.

In the present specification, the “water-octanol partition coefficient” is a value obtained by calculation. Specifically, ChemDraw Professional ver. manufactured by Perkin Elmer. It means the numerical value of "ClogP" calculated using 16.0. The numbers calculated in this way do not have a fixed number of decimal places. Therefore, in this specification, the third digit after the decimal point is rounded off and the second digit after the decimal point is described. If the calculated value is up to the second digit after the decimal point, enter the numerical value as it is. When the calculated value does not have two digits after the decimal point, the numerical value of each digit up to the second digit after the decimal point is regarded as “zero”, and the second digit after the decimal point is described in each case. In the present specification, the “water-octanol partition coefficient” may be described as “ClogP”.

Examples of the organic solvent include tripropylene glycol monomethyl ether, ethylene glycol monoallyl ether, isopropyl glycol, 3-methoxy-3-methyl-1-butanol, butyl triglycol, diethylene glycol monoisobutyl ether, propyl propylene glycol (propylene glycol). Monopropyl ether), butyl diglycol, dipropylene glycol-n-propyl ether, hexyl diglycol, and other glycol monoethers, preferably glycol mono C1-C6 alkyl ethers, and more preferably C1-C3 alkyl groups. A mono-, di-, or tri-C2-C3 alkylene glycol mono-C1-C6 alkyl ether which can have as a substituent; a straight chain such as 1,2-pentanediol, 1,2-hexanediol, or 1,2-octanediol Alkanediol, preferably linear 1,2-alkanediol, more preferably linear 1,2-(C5-C8)alkanediol; 2,2-diethyl-1,3-propanediol, 2-methyl-2, Branched chain alkanes such as 4-pentanediol, 2,2,4-trimethyl-1,3-pentanediol, 2-ethyl-1,3-hexanediol, 2-butyl-4-ethyl-1,6-hexanediol A diol, preferably a branched chain alkanediol having a total carbon number of C6-C12, more preferably a branched chain C3-C6 alkanediol having an alkyl group having a total carbon number of C1-C6 as a substituent; diethylene glycol ethyl methyl ether , Glycol diethers such as diethylene glycol diethyl ether, dibutyl diglycol and dipropylene glycol dimethyl ether, preferably glycol di C1-C4 alkyl ether, more preferably mono or di C2-C3 alkylene glycol di C1-C4 alkyl ether; diethylene glycol monobutyl ether. Dicarboxylic acid diesters such as adipate [bis(2-(2-butoxyethoxy)ethyl)adipate], preferably C6 dicarboxylic acid diesters, more preferably C6 dicarboxylic acid di(alkoxyalkoxyalkyl)esters, and further preferably C6 dicarboxylic acid diesters. (C4 alkoxy C2 alkoxy C2 alkyl) ester; C8 alkane diol mono C1-C4 acylate, preferably C8 alkane diol mono C4 acylate, more preferably Is a branched chain C8 alkanediol mono-C4 acylate, more preferably branched chain C8 alkanediol monoisobutyrate, and particularly preferably texanol (2,2,4-trimethyl-1,3-pentanediol-1-isobutyrate and 2,2). , 4-trimethyl-1,3-pentanediol-3-isobutyrate, preferably a mixture thereof); and the like.

Among the above organic solvents, preferable examples include, for example, tripropylene glycol monomethyl ether (-0.03), 2-methyl-2,4-pentanediol (-0.02), 1,2-pentanediol (0. 00), ethylene glycol monoallyl ether (0.03), isopropyl alcohol (0.07), isopropyl glycol (0.09), diethylene glycol ethyl methyl ether (0.13), dipropylene glycol dimethyl ether (0.36), 3-methoxy-3-methyl-1-butanol (0.42), butyltriglycol (0.49), diethylene glycol diethyl ether (0.52), 1,2-hexanediol (0.53), diethylene glycol monoisobutyl Ether (0.54), propyl propylene glycol (0.62), butyl diglycol (0.67), dipropylene glycol-n-propyl ether (0.75), 2,2-diethyl-1,3-propane Diol (0.82), 2,2,4-trimethyl-1,3-pentanediol (1.00), 2-ethyl-1,3-hexanediol (1.26), 1,2-octanediol ( 1.58), hexyldiglycol (1.72), 2-butyl-4-ethyl-1,6-hexanediol (2.55), dibutyldiglycol (2.63), texanol (2.74), Diethylene glycol monobutyl ether adipate (3.49) and the like can be mentioned. The numbers in parentheses are ClogP numbers.

The total content of the above organic solvents is usually 1% to 12%, preferably 1.5% to 11%, more preferably 2% to 10%.

[resin]
The resin contained in the ink according to this embodiment is a compound different from the dispersant. The "compound different from the dispersant" means, for example, when the dispersant is an AB block polymer composed of a specific monomer, a random copolymer composed of the same monomer, an ABA block polymer, etc. Since it is a compound different from the agent, it means that it can be used as a resin. Further, when the dispersant is an AB block polymer composed of a specific monomer, even if the resin is also an AB block polymer, polymers having different types of monomers, polymers having different ratios of monomers, etc. It is a compound different from the dispersant and can be used as a resin. That is, even the compounds described above as the dispersant, compounds other than the compound used as the dispersant can be used as the resin.

The above resin has an acid value. The acid value of the resin is more than 0 mgKOH/g and less than 100 mgKOH/g, preferably 1 mgKOH/g to 90 mgKOH/g, more preferably 3 mgKOH/g to 80 mgKOH/g, further preferably 6 mgKOH/g to 70 mgKOH/g, Particularly preferred is 10 mgKOH/g to 70 mgKOH/g, and most preferred is 13 mgKOH/g to 65 mgKOH/g.

The acid value of the above resin can be measured by a known method such as a titration method. Further, when the acid value is described in the manufacturer's catalog, the numerical value can be adopted.

Specific examples of the resin include, for example, (meth)acrylic copolymer, styrene/(meth)acrylic copolymer, polystyrene resin, (meth)acrylamide copolymer, styrene/maleic anhydride copolymer, polyurethane resin. Resins selected from polyethylene resins, vinyl acetate/ethylene copolymers, vinyl chloride/ethylene copolymers, polybutadiene resins, epoxy resins, silicone resins, and the like.

The above resin can be obtained as a commercially available product or by synthesizing by a known method. Examples thereof include (meth)acrylic acid, (meth)acrylic acid ester, acrylonitrile, cyanoacrylate, acrylamide, olefin, styrene, vinyl acetate, vinyl chloride, vinyl alcohol, vinyl ether, vinylpyrrolidone, vinylpyridine, vinylcarbazole. , Vinyl imidazole, vinylidene chloride, and the like may be used. When the resin is a copolymer, it may be in any form of a random copolymer, a block copolymer, an alternating copolymer and a graft copolymer.

The above resin can be used as an aqueous solution or an aqueous emulsion. Among these, it is preferable to use as an aqueous resin emulsion.

Among the above resins, those obtained by synthesis include, for example, the resin emulsions disclosed as Preparation Examples 3 to 5 in WO 2015/147192.

Commercially available products of the resin include, for example, Jonkryl PDX-7430 (30), PDX-7145 (32), PDX-7326 (38), 537J (40), 780 (46), 7610 (manufactured by BASF). 50), 352J(51), 352D(51), 775(55), PDX-7341(51), 74J(51), 7100(51), 390(54), PDX-7511(54), 7641(60). ), PDX-7700(60), 7600(60), 538J(61), PDX-7538(62), PDX-7643(64), PDX-6102B(65), PDX-6124(65) and the like. .. The numerical value in parentheses indicates the acid value, and the unit is "mgKOH/g".

The total content of the above resin is usually 0.1% to 15%, preferably 0.5% to 10%, and more preferably 2% to 8% as solid content.

[water]
As water contained in the ink according to the present embodiment, it is preferable to use water containing few impurities such as metal ions and inorganic salts. Examples of such water include ion-exchanged water and distilled water.

Water is the balance excluding the above components, the viscosity modifier, the surfactant, and the ink preparation agent, which will be described later, and the content thereof is usually 30% to 80%, preferably 40% to 75%. It is preferably about 50% to 70%.

[Viscosity modifier]
The ink according to this embodiment may further contain a viscosity modifier. In an industrial inkjet printer, the viscosity range of ink that can be ejected is usually determined based on the specifications of a printer head (head that ejects ink) to be mounted. Therefore, it is possible to add a viscosity modifier to the ink and adjust the viscosity within an appropriate range.

The viscosity modifier is not particularly limited as long as it is a substance that can adjust the viscosity of the ink, and known substances can be used. Specific examples thereof include water-soluble organic solvents (excluding the above organic solvents), sugars and the like. Among these, water-soluble organic solvents having a Clog P value of usually less than −0.05, preferably −0.06 or less, more preferably −0.07 or less, and further preferably −0.08 or less are mentioned. .. The lower limit of the value of Clog P of the water-soluble organic solvent is not particularly limited, but is usually −4.00 or more, preferably −3.00 or more, more preferably −2.00 or more, further preferably −1.50 or more. is there.

Examples of such water-soluble organic solvents include isopropyl diglycol (-0.08), dipropylene glycol monomethyl ether (-0.16), ethanol (-0.24), 3-methyl-1,5- Pentanediol (-0.24), diethylene glycol dimethyl ether (-0.26), propylene glycol monomethyl ether (-0.30), 3-methyl-1,3-butanediol (-0.33), trimethylolpropane ( -0.39), N-methyl-2-pyrrolidone (-0.40), 1,2-butanediol (-0.53), 3-ethyl-3-hydroxymethyloxetane (-0.58), 1 ,5-Pentanediol (-0.64), 2-methyl-1,3-propanediol (-0.64), dipropylene glycol (-0.69), 1,3-butanediol (-0.73) ), methyldiglycol (-0.78), methyltriglycol (-0.96), 2-pyrrolidone (-0.97), propylene glycol (-1.06), 1,4-butanediol (-1) .16), diethylene glycol (-1.30), ethylene glycol (-1.37), triethylene glycol (-1.48), glycerin (-1.54), diglycerin (-2.96), Aoki oil and fat Examples thereof include Glyceres-3 (-3.49) and Glyceres-20 (-5.42) manufactured by Kogyo Co., Ltd. The numbers in parentheses are ClogP numbers.

The total content of the water-soluble organic solvent is usually 0% to 55%, preferably 5% to 40%, more preferably 10% to 30%.

[Surfactant]
The ink according to this embodiment may further contain a surfactant. The printing speed of industrial inkjet printers is usually variable. Therefore, it is preferable to properly adjust the surface tension of the ink based on the printing speed. The surface tension of the ink can be adjusted by adding a surfactant to the ink.

Examples of the surfactant include anionic, cationic, amphoteric, nonionic, silicone-based, and fluorine-based surfactants, and one or more of these can be selected and used. Among these, surfactants selected from nonionic and silicone type are preferable, and it is more preferable to select one or more kinds of surfactants from nonionic and silicone type, and one or more kinds selected from silicone type. It is further preferred to select a surfactant.

Examples of the anionic surfactant include alkyl sulfocarboxylate, α-olefin sulfonate, polyoxyethylene alkyl ether acetate, N-acyl amino acid and its salt, N-acyl methyl taurine salt, alkyl sulfate polyoxy. Alkyl ether sulfate, alkyl sulfate polyoxyethylene alkyl ether phosphate, rosin acid soap, castor oil sulfate ester salt, lauryl alcohol sulfate ester salt, alkylphenol type phosphate ester, alkyl type phosphate ester, alkylaryl sulfonate, diethyl sulfo Examples include succinate, diethylhexylsylsulfosuccinate, dioctylsulfosuccinate, and the like.

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

Examples of the amphoteric surfactant include lauryldimethylaminoacetic acid betaine, 2-alkyl-N-carboxymethyl-N-hydroxyethylimidazolinium betaine, coconut oil fatty acid amidopropyldimethylaminoacetic acid betaine, polyoctylpolyaminoethylglycine, and imidazoline. Examples thereof include derivatives.

Examples of nonionic surfactants include ethers such as polyoxyethylene nonylphenyl ether, polyoxyethylene octyl phenyl ether, polyoxyethylene dodecyl phenyl ether, polyoxyethylene oleyl ether, polyoxyethylene lauryl ether, and polyoxyethylene alkyl ether. System: Polyoxyethylene oleate, polyoxyethylene distearate, sorbitan laurate, sorbitan monostearate, sorbitan monooleate, sorbitan sesquioleate, polyoxyethylene monooleate, polyoxyethylene stearate, etc. System; 2,4,7,9-tetramethyl-5-decyne-4,7-diol, 3,6-dimethyl-4-octyne-3,6-diol, 3,5-dimethyl-1-hexyne-3 -Acetylene glycol (alcohol) type such as all; Surfinol 104, 105PG50, 82, 420, 440, 465, 485, manufactured by Nissin Chemical Co., Ltd. Olphin STG; polyglycol ether type (for example, SIGMA-ALDRICH TergItol 15-S-7 etc.); and the like. Among these, acetylene glycol-based surfactants are preferable.

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

As the fluorine-based surfactant, for example, a perfluoroalkyl sulfonic acid compound, a perfluoroalkyl carboxylic acid compound, a perfluoroalkyl phosphoric acid ester compound, a perfluoroalkyl ethylene oxide adduct, a perfluoroalkyl ether group in the side chain. Examples thereof include polyoxyalkylene ether polymer compounds. Examples include Dupont's Zonyl TBS, FSP, FSA, FSN-100, FSN, FSO-100, FSO, FS-300, Capstone FS-30, FS-31; OMNOVA's PF-151N, PF. -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 manufactured by BYK Chemie, and the like can be mentioned.

[Ink preparation]
The ink according to the present embodiment may further contain a component other than the above as an ink preparation agent, if necessary. Examples of the ink preparation agent include antifungal agents, preservatives, pH adjusters, chelating agents, rust preventives, water-soluble ultraviolet absorbers, water-soluble polymer compounds, antioxidants and the like. The total content of the ink preparation agent is usually 0% to 30%, preferably 0% to 10%, more preferably 0% to 5%.

Examples of the mildew-proofing agent include sodium dehydroacetate, sodium benzoate, sodium pyridinethione-1-oxide, p-hydroxybenzoic acid ethyl ester, 1,2-benzisothiazolin-3-one and salts thereof.

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

As the pH adjustor, any substance can be used as long as it can control the pH of the ink within the 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). Examples thereof include 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.

Examples of the chelating agent include disodium ethylenediaminetetraacetate, sodium nitrilotriacetate, sodium hydroxyethylethylenediaminetriacetate, sodium diethylenetriaminepentaacetate, sodium uracildiacetate, and the like.

Examples of rust preventives include acidic sulfite, sodium thiosulfate, ammonium thioglycolate, diisopropylammonium nitrite, pentaerythritol tetranitrate, dicyclohexylammonium nitrite and the like.

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

Examples of water-soluble polymer compounds include polyethylene glycol, polyvinyl alcohol, cellulose derivatives, polyamines and polyimines.

As the antioxidant, for example, various organic type and metal complex type anti-fading agents can be used. Specific examples of the organic anti-fading agent include, for example, hydroquinones, alkoxyphenols, dialkoxyphenols, phenols, anilines, amines, indanes, chromanes, alkoxyanilines, heterocycles and the like. Can be mentioned.

[Ink preparation method, etc.]
The ink according to this embodiment can be prepared by a known method. An example thereof is a method in which a dispersion liquid of carbon black is prepared, and an organic solvent and, if necessary, various ink preparation agents are added to the dispersion liquid and mixed.

When preparing a dispersion, for example, the 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. Next, carbon black is added to the obtained emulsion to carry out dispersion treatment to obtain a liquid. By distilling off the organic solvent and a part of water from the liquid thus obtained under reduced pressure, a dispersion liquid containing carbon black can be obtained.

The dispersion treatment can be performed, for example, by stirring a solution or emulsion of a dispersant and carbon black with a sand mill (beads mill), a roll mill, a ball mill, a paint shaker, an ultrasonic disperser, a microfluidizer, or the like. When using a sand mill, beads having a particle diameter of about 0.01 mm to 3 mm can be used. The efficiency of the dispersion treatment can be adjusted by adjusting the filling rate of beads, the dispersion time, the amount of carbon black added, and the like. By filtering and/or centrifuging the dispersion liquid obtained as described above, the particle size of the contained particles can be made uniform within a certain range.

When the ink according to this embodiment is used for ink jet recording, it is preferable to use a material having a low content of inorganic impurities such as metal cation chloride (for example, sodium chloride) and sulfate (for example, sodium sulfate). .. The standard of the content of inorganic impurities is about 1% or less with respect to the total mass of carbon black, and the lower limit can be set to the detection limit of the analytical instrument, that is, 0%. As a method for obtaining an ink having a small amount of inorganic impurities, for example, a method of purifying the ink with a reverse osmosis membrane; a method of suspending and purifying carbon black in a mixed solvent of C1-C4 alcohol such as methanol and water; And a method of exchanging and adsorbing inorganic impurities in the ink.

The pH of the ink according to this embodiment 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 according to this embodiment is usually about 10 mN/m to 50 mN/m, preferably about 20 mN/m to 40 mN/m. The viscosity of the ink according to this embodiment is usually 30 mPa·s or less, preferably 20 mPa·s or less, and the lower limit is about 0.1 mPa·s.

The ink according to this embodiment can be used in various fields. Examples thereof include aqueous inks for writing, aqueous printing inks, information recording inks, textile printing, and the like. In the field where inkjet recording is possible, it is preferably used as an inkjet ink.

<Inkjet recording method, recording medium, ink tank, inkjet printer>
The inkjet recording method according to the present embodiment performs recording by ejecting the ink droplets from an inkjet printer and adhering them to a recording medium.

There is no particular limitation on the ink nozzles used for recording, and it 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 inkjet method, a thermal inkjet method, and the like.

The recording medium is not particularly limited as long as it is a substance that can be colored with ink. Examples thereof include paper, films, fibers or cloths (cellulose, nylon, wool, etc.), leather, substrates for color filters, and the like.

The recording medium is roughly classified into a recording medium having an ink receiving layer and a recording medium having no ink receiving layer. Examples thereof include fibers; paper having an ink receiving layer; ink-absorptive or non-ink-absorbing recording media having no ink receiving layer; and the like.
As the paper having the ink receiving layer, a paper for exclusive use of ink jet is mentioned.
Examples of the recording medium having poor ink absorbability include plain paper; recording media used for gravure printing, offset printing, etc.; coated paper such as lightly coated paper, art paper, coated paper, matte paper, cast paper, etc. Are listed.
Examples of non-ink absorbing recording media include vinyl chloride sheets, polymer sheets, glass and rubber.
Among these, a recording medium which does not have an ink receiving layer and is hardly absorbable to ink is preferable.

The ink receiving layer is formed, for example, by a method of impregnating or coating a recording medium with a cationic polymer; inorganic fine particles such as porous silica, alumina sol, and special ceramics that can absorb dyes in the ink, polyvinyl alcohol, polyvinyl pyrrolidone, It can be provided by a method of coating the surface of the substrate together with the hydrophilic polymer.

When the recording medium is a fiber, the fiber includes a fiber selected from the group consisting of polyester, cellulose, polyamide, and a natural fiber, and a mixed fiber containing these fibers. These fibers can have an ink receiving layer. The ink receiving layer can be provided on the fiber by a known method. Fibers having an ink receiving layer are commercially available, for example, in the form of cloth.
Examples of polyester fibers include polyethylene terephthalate fibers.
Examples of the cellulose fibers include fibers of 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 inkjet recording method according to the present embodiment, an ink tank containing the above ink is loaded in a predetermined position of an inkjet printer and recording is performed by the above recording method. An ink tank containing the above ink and an inkjet printer provided with the ink tank are also included in the scope of the present invention.

In the ink jet recording method according to the present embodiment, if necessary, full color recording is performed by using together with an ink containing a colorant selected from pigments or dyes such as yellow, blue, red, green, violet and orange. Can also

For the purpose of increasing the printing speed, industrial inkjet printers are preferably line-head inkjet printers, and single-pass printing is also preferably performed. With the above ink, it is possible to obtain a print image having a high black print density, particularly a high black print density when recorded on a recording medium having no ink receiving layer, even under such printing conditions.

Regarding all the above-mentioned matters, the preferable combination of the preferable ones is more preferable, and the preferable combination of the preferable ones is further preferable. The same applies to combinations of preferable and more preferable ones, combinations of more preferable and more preferable ones, and the like.

The ink is capable of forming minute droplets and has good ejection properties. Further, the redispersibility is good even when the ink is dried, and the wettability with respect to the recording medium is also good. Further, the above ink has good storage stability, and the dispersion state of the carbon black fine particles in the dispersion is also good.
Further, the image recorded with the above ink does not cause a mottling phenomenon, and solid filling is good. Further, the image recorded with the above ink has no bleeding and is excellent in scratch resistance.

Hereinafter, the present invention will be specifically described with reference to Examples, but the present invention is not limited to the following Examples.
Unless otherwise specified, all the synthetic reactions and operations such as crystallization were carried out under stirring.
When it was necessary to measure the solid content of the pigment, it was determined by the dry weight method using MS-70 manufactured by A&D Co., Ltd. The pigment solid content in the examples is a conversion value obtained by calculating the content of only the pigment solid content from the measured value obtained by the dry weight method.

[Synthesis Example 1: Synthesis of dispersant]
According to “Synthesis Example 3 Synthesis of Block Copolymer A” of International Publication No. 2013/115071, 138 g of a dispersant having a mass average molecular weight of 24300 and a PDI of 1.49 was obtained. The obtained dispersant is an AB block polymer, and the monomers constituting the A block are benzyl methacrylate and the monomers constituting the B block are methacrylic acid and butyl methacrylate.

[Synthesis Example 2: Synthesis of resin emulsion]
A resin emulsion having an acid value of 13 mgKOH/g and a solid content of 25% was obtained in accordance with "[Preparation Example 3] Preparation of Polymer Emulsion 2" of International Publication No. WO 2015/147192. The resin emulsion thus obtained is designated as Resin 1.

[Example 1: Preparation of ink]
The dispersant (6 parts) obtained in Synthesis Example 1 was dissolved in 2-butanone (15 parts) to obtain a liquid. A liquid prepared by dissolving 0.45 part of sodium hydroxide in ion-exchanged water (60 parts) was added to this liquid, and the mixture was stirred for 1 hour to prepare an emulsion. This emulsion and NEROX 605 (20 parts) were placed in a sand grinder and dispersed for 10 hours at 1500 rpm to obtain a liquid. Ion-exchanged water (100 parts) was added dropwise to the obtained solution, followed by filtration with a glass fiber filter (GA-100 manufactured by ADVANTEC) to obtain a filtrate. The obtained filtrate was put in an evaporator, 2-butanone and a part of water were distilled off under reduced pressure, and ion-exchanged water was added so that the pigment concentration became 12% to obtain a dispersion liquid. 1,2-hexanediol (5 parts), Resin 1 (3 parts) obtained in Synthesis Example 2, propylene glycol (20 parts), BYK-349 (0.5 parts), and triethanolamine were added to the resulting dispersion. (0.5 parts), Proxel GXL(s) and water to make a total amount of 100 parts were stirred for about 1 hour, and then filtered with a membrane filter having a pore size of 3 μm to obtain the ink of Example 1. It was The ink was prepared so that the carbon black content in the ink was 5%.

[Examples 2 to 10 and Comparative Examples 1 to 3; Preparation of Ink]
Inks of Examples 2 to 10 and Comparative Examples 1 to 3 were prepared in the same manner as in Example 1 except that the compositions shown in Tables 1 and 2 below were used. The content of carbon black in each ink was adjusted to 5%, which is the same as in Example 1.

Abbreviations and the like in Tables 1 and 2 below have the following meanings. Moreover, the numerical value in each table means content, and the unit is "part".
N305: NEROX 305 (carbon black having a BET specific surface area of 78 m ² /g)
N505: NEROX 505 (carbon black having a BET specific surface area of 97 m ² /g)
N605: NEROX 605 (carbon black having a BET specific surface area of 123 m ² /g)
#1000: (carbon black having a BET specific surface area of 180 m ² /g)
Dp1: Dispersant 1 obtained in Synthesis Example 1
1,2-HD: 1,2-hexanediol (Clog P: 0.53)
1,2-PD:1,2-pentanediol (Clog P:0.00)
IPDg: Isopropyl diglycol (Clog P: -0.08)
TEX: Texanol (Clog P:2.74)
DGBEA: Diethylene glycol monobutyl ether adipate (Clog P: 3.49)
2-Et-1,3-HD:2-ethyl-1,3-hexanediol (Clog P:1.26)
Resin 1: Resin emulsion obtained in Synthesis Example 2 PDX-7538: Jonkryl PDX-7538 (acid value: 62 mgKOH/g)
PDX-7611: John Cryl PDX-7611 (acid value: 145 mg KOH/g)
PG: Propylene glycol BYK: BYK-349
TEA: Triethanolamine GXL(s): Proxel GXL(s)
Water: Ion exchange water

The following [print density test] was carried out on each of the inks of Examples and Comparative Examples obtained as described above.
[Print density test]
Using an inkjet printer (PX-205, manufactured by EPSON Co., Ltd.), a 100% duty image of each ink of Examples and Comparative Examples was solidly printed on OK top coat (manufactured by Oji Paper Co., Ltd.). A test piece was obtained by drying the obtained image at room temperature for 24 hours. The solid image of the obtained test piece was subjected to color measurement with a densitometer manufactured by X-rite, eXact Advance. The color measurement conditions were ISO status T, a viewing angle of 2°, and a light source D50 as the density standard. Colorimetric values of print density are shown in Tables 1 and 2 above. The larger the print density value, the higher the print density.

As is clear from Tables 1 and 2, it was found that the inks of the respective examples had a clearly larger colorimetric value of the print density and a higher black print density than the inks of the comparative examples. From this result, it was confirmed that, by setting the ink to a specific composition, an image having a high black print density can be obtained even if the carbon black content is the same.

Claims

Contains carbon black, dispersant, organic solvent, resin, and water,
The BET specific surface area of the carbon black is 80 m 2 /g or more,
The water-octanol partition coefficient of the organic solvent is -0.05 or more and less than 3.50,
The resin is a compound different from the dispersant and has an acid value of more than 0 mgKOH/g and less than 100 mgKOH/g.
The ink according to claim 1, further comprising a viscosity modifier.
The ink according to claim 1 or 2, further containing a surfactant.
An inkjet recording method for performing recording by ejecting an ink droplet of the ink according to any one of claims 1 to 3 from an inkjet printer and adhering it to a recording medium.
A recording medium to which the ink according to any one of claims 1 to 3 is attached.
An ink tank containing the ink according to any one of claims 1 to 3.
An inkjet printer including the ink tank according to claim 6.