JP6662014B2 - Ink, container and method for producing ink - Google Patents

Description

  The present invention relates to an ink, a container, and a method for producing the ink.

  The inkjet recording method is popular because it has the advantage that the process is simpler than other recording methods, full color can be easily achieved, and an image having a high resolution can be obtained even with a device having a simple configuration. It is expanding from personal to office applications, commercial printing and industrial printing. In such an ink jet recording method, a water-based ink composition using a water-soluble dye as a coloring material is mainly used, but has a drawback that it has poor water resistance and light resistance. Pigment inks using the above pigments are being developed.

  In inkjet printing for office use, plain paper is mainly used as a recording medium, and a high image density is required. Generally, when a pigment ink is printed on plain paper, the pigment penetrates into the paper without remaining on the paper surface, so that the pigment density on the paper surface is reduced and the image density is reduced. Increasing the pigment concentration in the ink increases the image density, but increases the viscosity of the ink and decreases the ejection stability.

  Immediately after the pigment ink droplet lands on plain paper, the water in the ink swells the paper surface, increasing the difference in elongation between the front and back sides, resulting in curling. Such a phenomenon disappears as the drying proceeds, so that it is not a problem in low-speed printing. However, with the increase in printing speed, it is necessary to convey the recording medium without curling after printing, so that a paper jam problem may occur. In order to prevent this, it is effective to add a penetrant so that water permeates the paper quickly, but since the ink becomes hydrophobic, it becomes difficult to ensure the storage stability of the ink, The penetration of the pigment into the recording medium is also increased, and the image density is further reduced.

In order to solve the above problems, various methods have been proposed so that the pigment stays on the paper surface. For example, Patent Document 1 proposes an inkjet ink containing a liquid vehicle, a colorant, and a polymer having at least one functional group having a specific calcium index value. In this proposal, 4-methacrylamide-1-hydroxybutane-1,1-diphosphonic acid is shown as a monomer constituting the polymer, and when a colorant comes into contact with paper, the diphosphonic acid group of the polymer and the paper It is described that the coloring agent becomes unstable with the Ca salt therein, thereby improving the image. However, there is a problem that the storage stability of the ink is low.
Patent Document 2 proposes an ink jet recording method in which a receiving liquid containing a Ca salt is attached to paper, and an ink containing a pigment, a resin emulsion, and a surfactant bonded with a phosphorus-containing group is printed. This proposal states that the Ca salt of the receiving solution reacts with the phosphorus-containing group, and that feathering and fixability are improved. However, when recording is performed on plain paper, the effect of improving the image density is not sufficient.

In addition, the aqueous pigment ink used in the above-described ink jet recording system or writing instrument, unlike an aqueous dye ink prepared by dissolving a dye in water, it is necessary to stably disperse a pigment that does not dissolve in water in water for a long time. Therefore, various pigment dispersants have been developed. For example, Patent Document 3 proposes a graft polymer containing an aromatic ring in a side chain. By using this graft polymer as a pigment dispersant, the storage stability of the ink at 70 ° C. for 3 days is ensured, but the storage stability for a long period is insufficient. In addition, in the ink jet recording method, there is a method of adding a hydrophilic organic solvent to an aqueous ink in order to prevent paper curl generated when printing on plain paper.
When the graft polymer described in Patent Document 3 is applied to this method, the pigment dispersibility decreases, and long-term storage stability cannot be ensured. Further, Patent Literature 3 does not specifically describe the copolymer of the present invention in specific examples or examples.

An object of the present invention is to solve the above-described various problems in the related art and achieve the following objects.
That is, an object of the present invention is to provide an ink which can obtain high image density even when recorded on plain paper and has high storage stability.

The above problem is solved by the following invention.
An ink containing water, a coloring material, and a copolymer, wherein the copolymer has a structural unit represented by the following general formula (1) and a structural unit having an anionic group.

(In the general formula (1), R represents a hydrogen atom or a methyl group, X is an alkylene group having 2 to 4 carbon atoms, Y is a hydrocarbon group having 6 to 15 carbon atoms including an aromatic group, and Z is 2 carbon atoms. ~ 12 alkylene groups.)

  ADVANTAGE OF THE INVENTION According to this invention, even if it records on plain paper, a high image density is obtained and an ink with high storage stability can be provided.

It is a figure showing an example of an accommodation container of the present invention. FIG. 2 is a schematic view including a case (exterior) of the ink cartridge example of FIG. 1.

Hereinafter, the present invention will be described in detail, but the present invention includes inks of the embodiments described below.

[Copolymer]
The copolymer in the present invention has a structural unit represented by the following general formula (1) and a structural unit having an anionic group.

<Structural unit represented by general formula (1)>
In the general formula (1), R represents a hydrogen atom or a methyl group, X is an alkylene group having 2 to 4 carbon atoms, Y is a hydrocarbon group having 6 to 15 carbon atoms including aromatic, and Z is 2 carbon atoms. -12 represents an alkylene group.
If possible, the aromatic-containing hydrocarbon group having 6 to 15 carbon atoms may be independently substituted by a methyl group, a methoxycarbonyl group, a halogen or a functional group containing a halogen.

Specific examples of the structural unit represented by the general formula (1) are shown below, but the present invention is not limited to the following specific examples.

In the general formula (1), the terminal naphthyl group has excellent pigment adsorbing power due to π-π stacking with the pigment as a coloring material in the ink. When preparing the pigment dispersion in which the pigment is dispersed in water, the use of the copolymer according to the present invention increases the dispersion stability due to the high adsorptivity with the pigment, thereby obtaining a dispersion having high storage stability. Can be Furthermore, even when a hydrophilic organic solvent is added to the ink, dispersibility is maintained, and an ink having high storage stability is obtained.
When the copolymer of the present invention is used for the ink, a high image density can be obtained even when recording is performed on plain paper. The mechanism is not clear, but is presumed as follows.
That is, since the ink using the copolymer in the present invention has a high pigment dispersion stability, it is considered that it is difficult to form coarse particles even when the ink adheres to the plain paper surface. When the coarse particles are formed, an exposed portion where the pigment does not adhere to the plain paper surface is easily formed, and the image density is reduced. The ink using the copolymer according to the present invention can uniformly coat the surface of plain paper with the pigment, and can obtain a high image density.

<Structural unit having anionic group>
The structural unit having an anionic group is formed by copolymerizing a monomer having an anionic group. Examples of the monomer having an anionic group include an unsaturated carboxylic acid monomer, an unsaturated sulfonic acid monomer, and an unsaturated phosphoric acid monomer.
Examples of the unsaturated carboxylic acid monomer include acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, and the like. Examples of the unsaturated sulfonic acid monomer include styrene sulfonic acid and 2-acrylamido-2-methylpropane sulfonic acid. Examples of the unsaturated phosphoric acid monomer include vinyl phosphonic acid, vinyl phosphate, bis (methacryloxyethyl) phosphate, diphenyl-2-acryloyloxyethyl phosphate, diphenyl-2-methacryloyloxyethyl phosphate, and dibutyl-2-acrylic acid. Leuroxyethyl phosphate and the like can be mentioned.

  Among these, from the viewpoint of storage stability, a monomer having a carboxyl group is preferable, and acrylic acid or methacrylic acid is more preferable.

  Specific examples of the structural unit having an anionic group are shown below, but the present invention is not limited to the following specific examples.

The monomers having an anionic group may be used alone or in combination of two or more.
The structural unit having an anionic group may be neutralized with a base.
As the base, sodium hydroxide, potassium hydroxide, lithium hydroxide, tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, tetrapentylammonium hydroxide, tetrahexylammonium hydroxide , Triethylmethylammonium hydroxide, tributylmethylammonium hydroxide, trioctylmethylammonium hydroxide, 2-hydroxyethyltrimethylammonium hydroxide, tris (2-hydroxyethyl) methylammonium hydroxide, propyltrimethylammonium hydroxide, hexyltrimethylammonium Hydroxide, octyltrimethylammonium hydride Oxide, nonyltrimethylammonium hydroxide, decyltrimethylammonium hydroxide, dodecyltrimethylammonium hydroxide, tetradecyltrimethylammonium hydroxide, hexadecyltrimethylammonium hydroxide, octadecyltrimethylammonium hydroxide, didodecyldimethylammonium hydroxide, ditetradecyl Dimethyl ammonium hydroxide, dihexadecyl dimethyl ammonium hydroxide, dioctadecyl dimethyl ammonium hydroxide, ethyl hexadecyl dimethyl ammonium hydroxide, aqueous ammonia, dimethylamine, trimethylamine, monoethylamine, diethylamine, triethylamine, monoethanolamine, diethanolamine, Ethanolamine, methylethanolamine, methyldiethanolamine, dimethylethanolamine, monopropanolamine, dipropanolamine, tripropanolamine, isopropanolamine, morpholine, N-methylmorphone, N-methyl-2-pyrrolidone, 2-pyrrolidone and the like. .
The base as the neutralizing agent may be used alone or in combination of two or more.
The neutralization treatment may be performed when copolymerizing the monomer having an anionic group, or may be performed when dissolving the copolymer.

<Composition ratio>
The content of the structural unit represented by the general formula (1) is not particularly limited and can be appropriately selected depending on the purpose. However, the content is 60% by mass to 90% by mass based on the total amount of the copolymer. Is preferred. More preferably, it is 75 to 90% by mass. When the content is within the preferred range, it is advantageous in that when used in an ink, the image density and storage stability become good.
The content of the structural unit having an anionic group is not particularly limited and may be appropriately selected depending on the intended purpose. However, the content is preferably 5 to 60% by mass relative to the total amount of the copolymer. More preferably, it is 10 to 40% by mass. When the content is within the preferred range, it is advantageous in that when used in an ink, the image density and storage stability become good.

<Molecular weight>
The weight average molecular weight of the copolymer in the present invention is preferably 5,000 to 50,000 in terms of polystyrene. More preferably, it is 15,000 to 40,000. When the weight average molecular weight is within the preferred range, it is advantageous in that when used in an ink, the image density and storage stability are improved.

<Other monomers>
The copolymer in the present invention may have a structural unit composed of another polymerizable monomer in addition to the structural unit represented by the general formula (1) and the structural unit having an anionic group.
The other polymerizable monomer is not particularly limited and can be appropriately selected depending on the intended purpose. Examples thereof include a polymerizable hydrophobic monomer, a polymerizable hydrophilic monomer, and a polymerizable surfactant.

  Examples of the polymerizable hydrophobic monomer include unsaturated ethylene monomers having an aromatic ring such as styrene, α-methylstyrene, 4-t-butylstyrene, and 4-chloromethylstyrene; methyl (meth) acrylate; Ethyl (meth) acrylate, n-butyl (meth) acrylate, dimethyl maleate, dimethyl itaconate, dimethyl fumarate, lauryl (meth) acrylate (C12), tridecyl (meth) acrylate (C13), ( Tetradecyl (meth) acrylate (C14), pentadecyl (meth) acrylate (C15), hexadecyl (meth) acrylate (C16), heptadecyl (meth) acrylate (C17), nonadecyl (meth) acrylate (C19), ( Eicosyl (meth) acrylate (C20), Henicosyl (meth) acrylate ( 21), alkyl (meth) acrylates such as docosyl (meth) acrylate (C22); 1-heptene, 3,3-dimethyl-1-pentene, 4,4-dimethyl-1-pentene, 3-methyl-1 -Hexene, 4-methyl-1-hexene, 5-methyl-1-hexene, 1-octene, 3,3-dimethyl-1-hexene, 3,4-dimethyl-1-hexene, 4,4-dimethyl-1 -Hexene, 1-nonene, 3,5,5-trimethyl-1-hexene, 1-decene, 1-undecene, 1-dodecene, 1-tridecene, 1-tetradecene, 1-pentadecene, 1-hexadecene, 1-heptadecene And unsaturated ethylene monomers having an alkyl group such as 1-octadecene, 1-nonadecene, 1-eicosene and 1-docosene. These may be used alone or in combination of two or more.

  Examples of the polymerizable hydrophilic monomer include 2-hydroxyethyl (meth) acrylate, diethylene glycol mono (meth) acrylate, triethylene glycol mono (meth) acrylate, tetraethylene glycol mono (meth) acrylate, and polyethylene glycol. Mono (meth) acrylate, (meth) acrylamide, N-methylol (meth) acrylamide, N-vinylformamide, N-vinylacetamide, N-vinylpyrrolidone, acrylamide, N, N-dimethylacrylamide, Nt-butylacrylamide, Nonionic unsaturated ethylene monomers such as N-octylacrylamide and Nt-octylacrylamide are exemplified.

  The polymerizable hydrophobic monomer and the polymerizable hydrophilic monomer may be used alone or in combination of two or more to form a structural unit represented by the general formula (1) and a structural unit having an anionic group. It may be used in an amount of 5 to 100% by mass based on the total amount of the monomers.

<Synthesis of copolymer>
The copolymer in the present invention is obtained by copolymerizing a monomer represented by the following general formula (2) with a monomer having an anionic group in the presence of a radical polymerization initiator.

In the general formula (2), R represents a hydrogen atom or a methyl group, X is an alkylene group having 2 to 4 carbon atoms, Y is a hydrocarbon group having 6 to 15 carbon atoms including aromatic, and Z is 2 carbon atoms. -12 represents an alkylene group.
If possible, the hydrocarbon group containing an aromatic ring having 6 to 15 carbon atoms may be independently substituted with a methyl group, a methoxycarbonyl group, a halogen or a functional group containing a halogen, if possible.

  Specific examples of the monomer represented by the general formula (2) are shown below, but the present invention is not limited to the following specific examples.

The monomer represented by the general formula (2) can be synthesized and used as follows. That is, as shown in the following reaction formulas (1) to (3), first, a diol compound (A-1) and a naphthalene acid compound (A-2) are condensed to obtain a reaction intermediate (A-3). Next, the diisocyanate compound (A-4) is reacted with the above (A-3) in the presence of an acid acceptor such as an amine or pyridine or in the presence of a metal catalyst such as tin or titanium to form a reaction intermediate ( A-5) is obtained. Next, the monomer represented by the general formula (2) can be obtained by reacting the hydroxyalkyl (meth) acrylate (A-6) with the (A-5).
The compound represented by (A-2) is not particularly limited as long as it is a naphthalene acid compound capable of condensing with a hydroxy group, and the group represented by L is, for example, a carboxylic acid or a carboxylic acid such as a hydroxy group or an alkoxide group. Ester groups, or halogen-based leaving groups such as chlorine, bromine, and fluorine, or leaving groups such as tosyl groups, mesyl groups, and ammonium ions, but are not limited thereto. .

Another method is to react (A-4) with (A-6) first, then react with (A-1) and (A-2), and then react with (A-1). And the intermediate obtained by reacting (A-2) with (A-2) and the intermediate obtained by reacting (A-4) and (A-6) separately. The monomer represented by 2) can be obtained, but there is no particular limitation on the order in which (A-1), (A-2), (A-4), and (A-6) are reacted.
As another method, as shown in the following reaction formula (4), a diol compound (A-1), a naphthalene acid compound (A-2), a diisocyanate compound (A-4), a hydroxyalkyl (meth) acrylate ( The monomer represented by the general formula (2) can be obtained by reacting A-6).

The compound represented by the above (A-4) is not particularly limited as long as it is a diisocyanate comprising a hydrocarbon group having 6 to 15 carbon atoms including an aromatic ring. For example,
4,4′-diphenylmethane diisocyanate,
2,4-tolylene diisocyanate,
2,6-tolylene diisocyanate,
m-phenylenebis (1-methylethane-1,1-diyl) diisocyanate,
Hexamethylene diisocyanate,
m-xylylenediyl diisocyanate,
Naphthalene-1,5-diyl diisocyanate,
3,3′-dimethylbiphenyl-4,4′-diisocyanate,
1,4-phenylene diisocyanate,
2-methyl-1,4-phenylene diisocyanate,
Naphthalene-1,4-diisocyanate,
Naphthalene-2,6-diyl diisocyanate,
Naphthalene-2,7-diyl diisocyanate,
2,2′-dimethoxybiphenyl-4,4′-diyl diisocyanate,
5-methyl-1,3-phenylene diisocyanate,
Methylene bis (2,1-phenylene) diisocyanate,
4-[(2-isocyanatophenyl) methyl] phenyl isocyanate,
2,4,6-triisopropylbenzene-1,3-diyl diisocyanate,
Methylene bis (2-methyl-4,1-phenylene) diisocyanate,
4,4′-ethylenebis (1-isocyanatobenzene),
1- (trifluoromethyl) -2,2,2-trifluoroethylidenebis (4,1-phenylene) diisocyanate,
Biphenyl-4,4'-diyl diisocyanate,
1,4-phenylenebis (ethylene) diisocyanatenaphthalene-1,4-diylbis (methylene) diisocyanate,
Naphthalene-1,5-diylbis (methylene) diisocyanate,
4-ethyl-1,3-phenylene diisocyanate,
4-isopropyl-1,3-phenylene diisocyanate,
2,4-dimethyl-1,3-phenylene diisocyanate,
4,6-dimethyl-1,3-phenylene diisocyanate,
2,5-dimethyl-1,4-phenylene diisocyanate,
4-methyl-2,6-diethylbenzene-1,3-diyl diisocyanate,
2-methyl-4,6-diethylbenzene-1,3-diyl diisocyanate,
2,4,6-triethylbenzene-1,3-diyl diisocyanate,
4- (trifluoromethyl) benzene-1,2-diyl diisocyanate,
4-chlorobenzene-1,3-diyl diisocyanate,
2,4-dichlorobenzene-1,3-diisocyanate,
4,6-dichlorobenzene-1,3-diyl diisocyanate,
6-methyl-4-bromobenzene-1,3-diisocyanate,
4- (trifluoromethyl) benzene-1,3-diyl diisocyanate,
2,5-dichlorobenzene-1,4-diyl diisocyanate,
2- (trifluoromethyl) benzene-1,4-diyl diisocyanate,
2-methyl-6-bromobenzene-1,4-diyl diisocyanate,
2-nitrobenzene-1,4-diisocyanate,
2,6-dimethylbenzene-1,4-diyl diisocyanate,
2,6-diethylbenzene-1,4-diyl diisocyanate,
4-methoxybenzene-1,3-diyl diisocyanate,
4-ethoxybenzene-1,3-diisocyanate,
2-methoxybenzene-1,4-diyl diisocyanate,
2,5-dimethoxybenzene-1,4-diyl diisocyanate,
2,5-diethoxybenzene-1,4-diyl diisocyanate,
Biphenyl-2,4'-diyl diisocyanate,
2-nitrobiphenyl-4,4′-diyl diisocyanate,
Methylene bis (2-chloro-4,1-phenylene) diisocyanate,
Methylene bis (3-methyl-4,1-phenylene) diisocyanate,
4-[(4-isocyanatophenyl) methyl] -2-methoxyphenyl isocyanate,
3-[(4-isocyanatophenyl) methyl] -2,4,6-trimethylphenyl isocyanate,
Isopropylidenebis (4,1-phenylene) diisocyanate,
[(Tetralin) -1,5-diyl] diisocyanate,
9H-fluorene-2,7-diyl diisocyanate,
9H-carbazole-3,6-diyl diisocyanate,
And the like. Among these, 4,4'-diphenylmethane diisocyanate, m-xylylenediyl diisocyanate, m-phenylenebis (1-methylethane 1,1-diyl) diisocyanate, naphthalene- 1,5-diyl diisocyanate and 2,4-tolylene diisocyanate are preferred.

As a method for synthesizing the copolymer in the present invention, a method using a radical polymerization initiator is preferable because a polymerization operation and adjustment of molecular weight are easy, and a solution polymerization method in which a polymerization reaction is performed in a solution is more preferable.
Preferred solvents for performing radical polymerization by the solution polymerization method include ketone solvents such as acetone, methyl ethyl ketone, and methyl isobutyl ketone; acetate solvents such as ethyl acetate and butyl acetate; and aromatic hydrocarbons such as benzene, toluene, and xylene. Examples thereof include a hydrogen solvent, isopropanol, ethanol, cyclohexane, tetrahydrofuran, dimethylformamide, dimethyl sulfoxide, and hexamethylphosphamide, and more preferably a ketone solvent, an acetate solvent and an alcohol solvent.

The radical polymerization initiator is not particularly limited and can be appropriately selected depending on the purpose. Examples thereof include peroxyketal, hydroperoxide, dialkyl peroxide, diacyl peroxide, peroxydicarbonate, peroxyester, cyano-based azobisisobutyronitrile, azobis (2-methylbutyronitrile), Azobis (2,2′-isovaleronitrile), non-cyano dimethyl-2,2′-azobisisobutyrate, and the like. Among these, organic peroxides and azo compounds are preferable, and azo compounds are particularly preferable, because the molecular weight is easily controlled and the decomposition temperature is low.
The content of the radical polymerization initiator is not particularly limited and can be appropriately selected depending on the purpose. However, the content is preferably 1 to 10% by mass relative to the total amount of the polymerizable monomer.

In order to adjust the molecular weight of the polymer, an appropriate amount of a chain transfer agent may be added.
Examples of the chain transfer agent include mercaptoacetic acid, mercaptopropionic acid, 2-propanethiol, 2-mercaptoethanol, thiophenol, dodecylmercaptan, 1-dodecanethiol, and thioglycerol.

  The polymerization temperature is not particularly limited and may be appropriately selected according to the purpose. However, the polymerization temperature is preferably from 50C to 150C, and more preferably from 60C to 100C. The polymerization time is not particularly limited and may be appropriately selected depending on the purpose, but is preferably 3 to 48 hours.

<Amount of copolymer added>
The content of the copolymer of the present invention in the ink is not particularly limited and may be appropriately selected depending on the intended purpose. However, the solid content is preferably 0.05% by mass to 10% by mass, and It is more preferably from 5% by mass to 5% by mass.
When the content is 0.05% by mass or more, the effect of improving dispersibility and storage stability is recognized. When the content is 10% by mass or less, it is possible to set a viscosity range suitable for discharging ink from a head. Become.
The copolymer of the present invention is not particularly limited, and can be used both as a pigment dispersant and as an additive to a pigment dispersion. When used as a pigment dispersant, further improvement in storage stability in inks containing a large amount of a water-soluble organic solvent is recognized.

  When used as a pigment dispersant, the content of the copolymer of the present invention is not particularly limited, and can be appropriately selected depending on the purpose. And 1 mass part-100 mass parts are preferable with respect to the said pigment 100 mass parts, and 5 mass parts-80 mass parts are more preferable. When the content is within the more preferable range, it is advantageous in that the image density and the storage stability are improved.

<Water>
As the water, for example, pure water such as ion exchange water, ultrafiltration water, reverse osmosis water, and distilled water, or ultrapure water can be used.
The content of the water in the ink is not particularly limited, and can be appropriately selected depending on the purpose.

<Color material>
Pigments and dyes can be used as the coloring material of the ink of the present invention. Pigments are preferred in that pigments are superior to dyes in the ability of the copolymer to adsorb to colorants, and in terms of water resistance and light resistance.
The pigment is not particularly limited and can be appropriately selected depending on the purpose. Examples thereof include inorganic pigments and organic pigments for black or color. These may be used alone or in combination of two or more.

<Inorganic pigment>
As the inorganic pigment, for example, in addition to titanium oxide, iron oxide, calcium carbonate, barium sulfate, aluminum hydroxide, barium yellow, cadmium red, chrome yellow, contact method, furnace method, manufactured by known methods such as thermal method Carbon black can be used.
Examples of black pigments include carbon black (CI pigment black 7) such as furnace black, lamp black, acetylene black, and channel black; metals such as copper and iron (CI pigment black 11); Examples thereof include metal oxides such as titanium oxide, and organic pigments such as aniline black (CI pigment black 1).
The carbon black is a carbon black manufactured by a furnace method or a channel method, has a primary particle size of 15 to 40 nm, a specific surface area of 50 to 300 m ² / g by a BET method, and a DBP oil absorption of 40 to 150 mL / 100 g, Those having a volatile content of 0.5 to 10% and a pH of 2 to 9 are preferred.

<Organic pigment>
Examples of the organic pigment include azo pigments (including azo lakes, insoluble azo pigments, condensed azo pigments, chelated azo pigments, etc.) and polycyclic pigments (eg, phthalocyanine pigments, perylene pigments, perinone pigments, anthraquinone pigments, quinacridone Uses pigments, dioxazine pigments, indigo pigments, thioindigo pigments, isoindolinone pigments, quinoflurone pigments, etc., dye chelates (eg, basic dye chelates, acid dye chelates, etc.), nitro pigments, nitroso pigments, aniline black, etc. it can.
Among these pigments, those having good affinity for water are particularly preferably used.

Examples of the azo pigment include an azo lake, an insoluble azo pigment, a condensed azo pigment, a chelate azo pigment, and the like.
Examples of the polycyclic pigments include phthalocyanine pigments, perylene pigments, perinone pigments, anthraquinone pigments, quinacridone pigments, dioxazine pigments, indigo pigments, thioindigo pigments, isoindolinone pigments, quinoflurone pigments, rhodamine B lake pigments, and the like. Is mentioned.
Examples of the dye chelates include basic dye chelates and acid dye chelates.

  The pigment for yellow is not particularly limited and can be appropriately selected according to the purpose. Examples thereof include C.I. I. Pigment Yellow 1, C.I. I. Pigment Yellow 2, C.I. I. Pigment Yellow 3, C.I. I. Pigment Yellow 12, C.I. I. Pigment Yellow 13, C.I. I. Pigment Yellow 14, C.I. I. Pigment Yellow 16, C.I. I. Pigment Yellow 17, C.I. I. Pigment yellow 73, C.I. I. Pigment yellow 74, C.I. I. Pigment Yellow 75, C.I. I. Pigment yellow 83, C.I. I. Pigment Yellow 93, C.I. I. Pigment Yellow 95, C.I. I. Pigment Yellow 97, C.I. I. Pigment Yellow 98, C.I. I. Pigment yellow 114, C.I. I. Pigment yellow 120, C.I. I. Pigment Yellow 128, C.I. I. Pigment yellow 129, C.I. I. Pigment yellow 138, C.I. I. Pigment Yellow 150, C.I. I. Pigment yellow 151, C.I. I. Pigment yellow 154, C.I. I. Pigment yellow 155, C.I. I. Pigment yellow 174, C.I. I. Pigment Yellow 180, and the like.

  The pigment for magenta is not particularly limited and can be appropriately selected depending on the purpose. Examples thereof include C.I. I. Pigment Red 5, C.I. I. Pigment Red 7, C.I. I. Pigment Red 12, C.I. I. Pigment Red 48 (Ca), C.I. I. Pigment Red 48 (Mn), C.I. I. Pigment Red 57 (Ca), C.I. I. Pigment Red 57: 1, C.I. I. Pigment Red 112, C.I. I. Pigment Red 122, C.I. I. Pigment Red 123, C.I. I. Pigment Red 146, C.I. I. Pigment Red 168, C.I. I. Pigment red 176, C.I. I. Pigment Red 184, C.I. I. Pigment Red 185, C.I. I. Pigment Red 202, Pigment Violet 19, and the like.

The pigment for cyan is not particularly limited and can be appropriately selected depending on the purpose.
Examples thereof include C.I. I. Pigment Blue 1, C.I. I. Pigment Blue 2, C.I. I. Pigment Blue 3, C.I. I. Pigment Blue 15, C.I. I. Pigment Blue 15: 3, C.I. I. Pigment Blue 15: 4, C.I. I. Pigment blue 15:34, C.I. I. Pigment Blue 16, C.I. I. Pigment Blue 22, C.I. I. Pigment Blue 60, C.I. I. Pigment Blue 63, C.I. I. Pigment Blue 66; I. Bat Blue 4, C.I. I. Bat Blue 60, and the like.
In addition, C.I. I. Pigment Yellow 74, C.I. I. Pigment Red 122, C.I. I. Pigment Bio Red 19, C.I. I. By using Pigment Blue 15: 3, a well-balanced ink having excellent color tone and light fastness can be obtained.

<Self-dispersing pigment>
The pigments used in the present invention may be those newly produced for the present invention. Further, from the viewpoint of the coloring property of the obtained image, a self-dispersion pigment may be used, and an anionic self-dispersion pigment is preferable. The anionic self-dispersed pigment refers to a pigment which is dispersed and stabilized by introducing an anionic functional group directly or via another atomic group onto the surface of the pigment.
As the pigment before dispersion stabilization, various conventionally known pigments, for example, listed in WO 2009/014242 can be used.
The anionic functional group refers to a functional group at which half or more hydrogen ions dissociate at pH 7.0. Specific examples of the anionic functional group include a carboxyl group, a sulfo group, and a phosphonic acid group. Among them, a carboxyl group or a phosphonic acid group is preferable from the viewpoint of increasing the optical density of the obtained image.
As a method for introducing an anionic functional group on the surface of the pigment, for example, a method of oxidizing carbon black can be mentioned.
As specific examples of the oxidation treatment method, a method of treating with hypochlorite, ozone water, hydrogen peroxide, chlorite, nitric acid, or the like, Japanese Patent No. 3808504, Japanese Patent Publication No. 2009-515007, And a surface treatment method using a diazonium salt as described in JP-T-2009-506196.
Commercially available pigments having a hydrophilic functional group introduced on the surface include, for example, CW-1, CW-2, and CW-3 (all manufactured by Orient Chemical Co., Ltd.); CAB-O-JET200, CAB- O-JET300, CAB-O-JET400 (manufactured by Cabot) and the like.

  The content of the pigment in the ink is not particularly limited and may be appropriately selected depending on the intended purpose.

The ink of the present invention can be manufactured without being limited to the method described below.For example, water, a pigment, a water-soluble organic solvent, a coloring material, the copolymer, and if necessary, other components are aqueous. It can be manufactured by dispersing or dissolving in a medium and stirring and mixing. Further, the copolymer may be used as a pigment dispersion resin in producing a pigment dispersion.
The dispersion can be performed by, for example, a sand mill, a homogenizer, a ball mill, a paint shaker, an ultrasonic disperser, and the like, and the stirring and mixing is performed by a stirrer using a normal stirring blade, a magnetic stirrer, a high-speed disperser, and the like. be able to.
At the time of production, it is preferable to filter coarse particles with a filter, a centrifugal separator or the like and to deaerate the particles if necessary.

<Dye>
As the dye, dyes classified into acid dyes, direct dyes, basic dyes, reactive dyes and food dyes in a color index can be used.
Specifically, as acid dyes and food dyes, C.I. I. Acid Black 1, 2, 7, 24, 26, 94, C.I. I. Acid Yellow 17, 23, 42, 44, 79, 142, C.I. I. Acid Blue 9, 29, 45, 92, 249, C.I. I. Acid Red 1, 8, 13, 14, 18, 26, 27, 35, 37, 42, 52, 82, 87, 89, 92, 97, 106, 111, 114, 115, 134, 186, 249, 254, 289, C.I. I. Food black 1, 2, C.I. I. Food yellow 3, 4, C.I. I. Food red 7, 9, 14, C.I. I. Direct Black 19, 22, 32, 38, 51, 56, 71, 74, 75, 77, 154, (168), 171, C.I. I. Direct Yellow 1, 12, 24, 26, 33, 44, 50, 86, 120, 132, 142, 144, C.I. I. Direct Blue 1, 2, 6, 15, 22, 25, 71, 76, 79, 86, 87, 90, 98, 163, 165, 199, 202, C.I. I. Direct Red 1, 4, 9, 13, 17, 20, 28, 31, 39, 80, 81, 83, 89, 225, 227, C.I. I. Direct Orange 26, 29, 62, 102, as basic dyes, C.I. I. Basic Black 2, 8, C.I. I. Basic Yellow 1, 2, 11, 13, 14, 15, 19, 21, 23, 24, 25, 28, 29, 32, 36, 40, 41, 45, 49, 51, 53, 63, 64, 65, 67, 70, 73, 77, 87, 91, C.I. I. Basic Blue 1, 3, 5, 7, 9, 21, 22, 26, 35, 41, 45, 47, 54, 62, 65, 66, 67, 69, 75, 77, 78, 89, 92, 93, 105, 117, 120, 122, 124, 129, 137, 141, 147, 155, C.I. I. Basic Red 2, 12, 13, 14, 15, 18, 22, 23, 24, 27, 29, 35, 36, 38, 39, 46, 49, 51, 52, 54, 59, 68, 69, 70, 73, 78, 82, 102, 104, 109, 112, as reactive dyes, C.I. I. Reactive black 3, 4, 7, 11, 12, 17, C.I. I. Reactive yellow 1, 5, 11, 13, 14, 20, 21, 22, 25, 40, 47, 51, 55, 65, 67, C.I. I. Reactive blue 1, 2, 7, 14, 15, 23, 32, 35, 38, 41, 63, 80, 95, C.I. I. Reactive Red 1, 14, 17, 25, 26, 32, 37, 44, 46, 55, 60, 66, 74, 79, 96, 97 and the like.

As the pigment dispersant in the pigment dispersion, a copolymer containing a structural unit represented by the general formula (1) and a structural unit having an anionic group is preferable. Other usable dispersants include, for example, various surfactants such as anionic surfactants, cationic surfactants, amphoteric surfactants, and nonionic surfactants, naphthalenesulfonic acid Na-formalin condensate, and polymer type Dispersants, and the like.
These may be used alone or in combination of two or more.

Examples of the anionic surfactant include alkyl sulfocarboxylates, α-olefin sulfonates, polyoxyethylene alkyl ether acetates, N-acyl amino acids and salts thereof, N-acylmethyl taurine salts, polyoxyalkyl ethers Sulfate, polyoxyethylene alkyl ether phosphate, rosin acid soap, castor oil sulfate, lauryl alcohol sulfate, alkylphenol phosphate, naphthalene sulfonate formalin condensate, alkyl phosphate, alkyl allyl sulfonate, And diethylsulfosuccinate, diethylhexylsulfosuccinate, dioctylsulfosuccinate, and the like.
Examples of the cationic surfactant include a 2-vinylpyridine derivative and a poly-4-vinylpyridine derivative.
Examples of the amphoteric surfactant include betaine lauryl dimethylamino acetate, 2-alkyl-N-carboxymethyl-N-hydroxyethyl imidazolinium betaine, coconut oil fatty acid amide propyl dimethyl amino acetate betaine, polyoctyl polyaminoethyl glycine, And imidazoline derivatives.
Examples of the nonionic surfactant include polyoxyethylene nonyl phenyl ether, polyoxyethylene octyl phenyl ether, polyoxyethylene dodecyl phenyl ether, polyoxyethylene lauryl ether, polyoxyethylene oleyl ether, polyoxyethylene alkyl ether, and polyoxyethylene alkyl ether. Ether surfactants such as oxyallylalkyl alkyl ethers; polyoxyethylene oleic acid, polyoxyethylene oleate, polyoxyethylene distearate, sorbitan laurate, sorbitan monostearate, sorbitan monooleate, sorbitan sesquiolate Surfactants such as polyoxyethylene monooleate and polyoxyethylene stearate; 2,4,7,9-tetrame Acetylene glycol-based surfactants such as le-5-decyne-4,7-diol, 3,6-dimethyl-4-octyne-3,6-diol, and 3,5-dimethyl-1-hexyn-3-ol; And the like.

<Water-soluble organic solvent>
The water-soluble organic solvent has at least one of an effect as a wetting agent for preventing drying of the ink and an effect as a penetrating agent.
The water-soluble organic solvent is not particularly limited and can be appropriately selected depending on the purpose. For example, glycerin, ethylene glycol, diethylene glycol, isopropylidene glycerol, 1,3-butanediol, 3-methyl-1,3-butanediol, triethylene glycol, propylene glycol, dipropylene glycol, trimethylolpropane, trimethylolethane, Ethylene glycol, diethylene glycol, dipropylene glycol, tripropylene glycol, tetraethylene glycol, hexylene glycol, polyethylene glycol, polypropylene glycol, 1,5-pentanediol, 1,6-hexanediol, 1,2,6-hexanetriol, Polyhydric alcohols such as 1,2,4-butanetriol, 1,2,3-butanetriol and petriol; ethylene glycol monoethyl ether Polyhydric alcohol alkyl ethers such as ter, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, tetraethylene glycol monomethyl ether, propylene glycol monoethyl ether; ethylene glycol monophenyl ether, ethylene glycol monobenzyl Polyhydric alcohol aryl ethers such as ether; 2-pyrrolidone, N-methyl-2-pyrrolidone, N-hydroxyethyl-2-pyrrolidone, 1,3-dimethylimidazolidinone, ε-caprolactam, γ-butyrolactone, etc. Nitrogen-containing heterocyclic compound; formamide, N-methylformamide, N, N-dimethylformamide, N, N-dimethyl- Amides such as -methoxypropionamide and N, N-dimethyl-β-butoxypropionamide; amines such as monoethanolamine, diethanolamine, triethanolamine, monoethylamine, diethylamine and triethylamine; dimethylsulfoxide, sulfolane, thiodiethanol and the like And the like; 3-ethyl-3-hydroxymethyloxetane, propylene carbonate, ethylene carbonate, and the like. These may be used alone or in combination of two or more.

Among them, 3-ethyl-3-hydroxymethyloxetane, isopropylidene glycerol, N, N-dimethyl-β-methoxypropionamide, N, N-dimethyl-β-butoxypropion, from the viewpoint of preventing curling in plain paper. Amides are particularly preferred.
In addition, 1,3-butanediol, diethylene glycol, 2,2,4-trimethyl-1,3-pentanediol, triethylene glycol, and glycerin have excellent effects in preventing discharge failure due to evaporation of water.

Examples of the water-soluble organic solvent having relatively low wettability and permeability include 2-ethyl-1,3-hexanediol [solubility: 4.2% (25 ° C.)], 2,2,4 -Trimethyl-1,3-pentanediol [solubility: 2.0% (25 ° C)].
Examples of other polyol compounds include aliphatic diols such as 2-ethyl-2-methyl-1,3-propanediol, 3,3-dimethyl-1,2-butanediol, 2,2-diethyl-1, 3-propanediol, 2-methyl-2-propyl-1,3-propanediol, 2,4-dimethyl-2,4-pentanediol, 2,5-dimethyl-2,5-hexanediol, 5-hexene- 1,2-diol, and the like.

  Other penetrants that can be used in combination are not particularly limited as long as they can be dissolved in the ink and adjusted to desired physical properties, and can be appropriately selected depending on the purpose. For example, diethylene glycol monophenyl ether, ethylene glycol monophenyl ether, ethylene glycol monoallyl ether, diethylene glycol monophenyl ether, diethylene glycol monobutyl ether, propylene glycol monobutyl ether, alkyl and aryl ethers of polyhydric alcohols such as tetraethylene glycol chlorophenyl ether, And lower alcohols such as ethanol.

In addition, a saccharide can be contained as a wetting agent that is not a water-soluble organic solvent. Examples of the saccharide include a monosaccharide, a disaccharide, an oligosaccharide (including a trisaccharide and a tetrasaccharide), and a polysaccharide. Specific examples include glucose, mannose, fructose, ribose, xylose, arabinose, galactose, maltose, cellobiose, lactose, sucrose, trehalose, maltotriose, and the like. Here, the polysaccharide means a saccharide in a broad sense, and is used to include substances widely existing in nature such as α-cyclodextrin and cellulose. Further, derivatives of these saccharides are represented by reducing sugars of the above-mentioned saccharides [for example, sugar alcohols [general formula: HOCH ₂ (CHOH) _n CH ₂ OH (where n represents an integer of 2 to 5)]. You. ]], Oxidized sugars (eg, aldonic acid, uronic acid, etc.), amino acids, thioic acids and the like. Among them, sugar alcohols are preferable, and examples of the sugar alcohols include maltitol and sorbitol.

The ratio of the pigment to the water-soluble organic solvent, when used as an ink for ink-jet recording, greatly affects the stability of ink ejection from a head. If the content of the water-soluble organic solvent is small even though the pigment solid content is high, the evaporation of water near the ink meniscus of the nozzle may occur, resulting in poor ejection.
The content of the water-soluble organic solvent in the ink is not particularly limited and may be appropriately selected depending on the purpose. However, the content is preferably 10% by mass to 60% by mass, and more preferably 20% by mass to 60% by mass. . When the content is 10% by mass or more, the ejection stability of the ink may be improved, and when the content is 60% by mass or less, the drying property may be improved. An ink having the above-mentioned content within the more preferable numerical range has an advantage that drying property and ejection reliability are very good.

<Water>
The content of water in the ink is not particularly limited and may be appropriately selected depending on the purpose. However, from the viewpoint of drying properties and ejection reliability of the ink, the content is preferably from 10% by mass to 90% by mass, % To 60% by mass is more preferable.

<Other ingredients>
The other components are not particularly limited and may be appropriately selected as necessary. Examples thereof include a surfactant, a pH adjuster, a water-dispersible resin, an antiseptic / antifungal agent, a rust inhibitor, and an antioxidant. , An ultraviolet absorber, an oxygen absorber, a light stabilizer, and the like.

-Surfactant-
The surfactant is not particularly limited and can be appropriately selected depending on the intended purpose. Anionic surfactants, cationic surfactants, nonionic surfactants, amphoteric surfactants, fluorine surfactants Agents, and the like. Among these, nonionic surfactants and fluorine surfactants are particularly preferred.
Examples of the anionic surfactant include alkyl allyl, alkyl naphthalene sulfonate, alkyl phosphate, alkyl sulfate, alkyl sulfonate, alkyl ether sulfate, alkyl sulfosuccinate, alkyl ester sulfate, and alkyl benzene. Sulfonate, alkyl diphenyl ether disulfonate, alkyl aryl ether phosphate, alkyl aryl ether sulfate, alkyl aryl ether ester sulfate, olefin sulfonate, alkane olefin sulfonate, polyoxyethylene alkyl ether phosphate, Polyoxyethylene alkyl ether sulfate, ether carboxylate, sulfosuccinate, α-sulfofatty acid ester, fatty acid salt, condensate of higher fatty acid and amino acid, naphthene Salt, and the like.
Examples of the cationic surfactant include alkylamine salts, dialkylamine salts, aliphatic amine salts, benzalkonium salts, quaternary ammonium salts, alkylpyridinium salts, imidazolinium salts, sulfonium salts, phosphonium salts, And the like.
Examples of the nonionic surfactant include an acetylene glycol-based surfactant, polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene alkyl ester, and polyoxyethylene sorbitan fatty acid ester.
Examples of the amphoteric surfactant include imidazoline derivatives such as imidazolinium betaine, dimethyl alkyl lauryl betaine, alkyl glycine, and alkyl di (aminoethyl) glycine.
Examples of the fluorine-based surfactant include materials represented by the following general formulas (I) to (III).

  Here, in the general formula (I), m represents an integer of 0 to 10. n represents an integer of 1 to 40.

In the general formula (II), Rf represents a fluorine-containing group, and is preferably a perfluoroalkyl group.
Examples of the perfluoroalkyl group preferably has a carbon number of 1 to 10, more preferably those of 1 to 3, for _example, -C _{n F 2n-1} (where, n is an integer of 1 to 10) And the like. Examples of the perfluoroalkyl group, _{e.g., -CF 3, -CF 2 CF 3} , -C 3 F 7, -C 4 F 9, and the like. Of _{these, -CF 3,} -CF 2 CF 3 it is particularly preferred.
m, n, and p each represent an integer, and n is preferably 1 to 4, m is 6 to 25, and p is preferably 1 to 4.

In the general formula (III), Rf represents a fluorine-containing group, and is preferably a perfluoroalkyl group similar to the general formula (II), for example, CF ₃ , CF ₂ CF ₃ , C ₃ F ₇ , and C ₄ such as F ₉ are preferably exemplified.
R ₂ ⁺ represents a cationic group, for example, a quaternary ammonium group; an alkali metal ion such as sodium or potassium; triethylamine, triethanolamine, and the like. Among these, a quaternary ammonium group is particularly preferred. R ₁ ^— represents an anionic group, and examples thereof include COO ⁻ , SO ₃ ⁻ , SO ₄ ⁻ , and PO ₄ ⁻ . q is preferably 1 to 6.

As the fluorinated surfactant, an appropriately synthesized one may be used, or a commercially available product may be used.
Examples of the commercially available products include Surflon S-111, S-112, S-113, S-121, S-131, S-132, S-141, and S-145 (all manufactured by Asahi Glass Co., Ltd.); Fullard FC-93, FC-95, FC-98, FC-129, FC-135, FC-170C, FC-430, FC-431 (all manufactured by Sumitomo 3M Limited); Megafac F-470, F1405 , F-474 (all manufactured by DIC Corporation); Zonyl TBS, FSP, FSA, FSN-100, FSN, FSO-100, FSO, FS-300, UR (all manufactured by DuPont); FT-110 , FT-250, FT-251, FT-400S, FT-150, FT-400SW (all manufactured by Neos Corporation); PF-151N (Solution ® manufactured lens Inc. Co.); UNIDYNE DSN-403N (manufactured by Daikin Industries) and the like. Among these, Zonyl FS-300, FSN, FSN-100, and FSO (all manufactured by DuPont) and Unidyne DSN-403N (manufactured by Daikin Industries) are particularly preferable from the viewpoint of improvement in reliability and color development.

  The content of the surfactant in the ink is not particularly limited and may be appropriately selected depending on the intended purpose. The content is preferably 0.01% by mass to 5.0% by mass, and more preferably 0.5% by mass to 3% by mass. % Is more preferred. When the content is 5.0% by mass or less, the permeability to a recording medium is improved, and a decrease in image density and occurrence of strikethrough may be prevented.

-PH adjuster-
The pH adjuster is not particularly limited as long as it can adjust the pH to 8.5 to 11 without adversely affecting the prepared ink, and can be appropriately selected depending on the purpose.
Examples of the pH adjuster include alcohol amines, alkali metal element hydroxides, ammonium hydroxides, phosphonium hydroxides, alkali metal carbonates, and the like.
Examples of the alcohol amines include diethanolamine, triethanolamine, 2-amino-2-ethyl-1,3-propanediol, and the like. Examples of the hydroxide of the alkali metal element include lithium hydroxide, sodium hydroxide, and potassium hydroxide.
Examples of the ammonium hydroxide include ammonium hydroxide, quaternary ammonium hydroxide, and quaternary phosphonium hydroxide.
Examples of the alkali metal carbonate include lithium carbonate, sodium carbonate, and potassium carbonate.

-Water-dispersible resin-
The water-dispersible resin has excellent film-forming properties (image forming properties), and has high water repellency, high water resistance, and high weather resistance, and is suitable for high water resistance and high image density (high color development) image recording. Useful.
Examples of the water-dispersible resin include a condensation-type synthetic resin, an addition-type synthetic resin, and a natural polymer compound.
Examples of the condensation synthetic resin include a polyester resin, a polyurethane resin, a polyepoxy resin, a polyamide resin, a polyether resin, a poly (meth) acryl resin, an acryl-silicone resin, and a fluorine resin.
Examples of the additional synthetic resin include a polyolefin resin, a polystyrene resin, a polyvinyl alcohol resin, a polyvinyl ester resin, a polyacrylic acid resin, and an unsaturated carboxylic acid resin.
Examples of the natural polymer compound include celluloses, rosins, and natural rubber.
Among them, polyurethane resin fine particles, acryl-silicone resin fine particles and fluorine-based resin fine particles are preferable.
The average particle diameter (D50) of the water-dispersible resin is related to the viscosity of the dispersion liquid. When the composition is the same, the smaller the particle diameter, the higher the viscosity at the same solid content.
The average particle size (D50) of the water-dispersible resin is not particularly limited and may be appropriately selected depending on the purpose so that the ink does not have an excessively high viscosity, but is preferably 50 nm or more.
Further, when the particle size is several tens of μm, it cannot be used because it becomes larger than the nozzle opening of the ink jet head. If particles having a larger particle size than the nozzle opening are present in the ink, the ejection stability is deteriorated. Therefore, the average particle diameter (D50) is more preferably 200 nm or less so as not to impair the ink ejection stability.
Further, the water-dispersible resin has a function of fixing the water-dispersible colorant on the paper surface, and preferably forms a film at normal temperature to improve the fixability of the coloring material.
Therefore, the minimum film-forming temperature (MFT) of the water-dispersible resin is not particularly limited and may be appropriately selected depending on the purpose, but is preferably 30 ° C. or lower.
Further, when the glass transition temperature of the water-dispersible resin is −40 ° C. or lower, the viscosity of the resin film becomes strong, and tackiness occurs in printed matter, so that the glass transition temperature is −30 ° C. or higher. Is preferred.
The content of the water-dispersible resin in the ink for ink-jet recording is not particularly limited and may be appropriately selected depending on the intended purpose. -7 mass% is more preferable.

-Antiseptic / antifungal agent-
Examples of the antiseptic / antifungal agent include sodium dehydroacetate, sodium sorbate 2-pyridinethiol-1-oxide sodium, sodium benzoate, sodium pentachlorophenol, and the like.

-Rust inhibitor-
Examples of the rust preventive include acid sulfite, sodium thiosulfate, ammonium thiodiglycolate, diisopropylammonium nitrite, pentaerythritol tetranitrate, dicyclohexylammonium nitrite, and the like.

-Antioxidant-
Examples of the antioxidant include a phenol antioxidant (including a hindered phenol antioxidant), an amine antioxidant, a sulfur antioxidant, and a phosphorus antioxidant.

-UV absorber-
Examples of the ultraviolet absorber include a benzophenone ultraviolet absorber, a benzotriazole ultraviolet absorber, a salicylate ultraviolet absorber, a cyanoacrylate ultraviolet absorber, and a nickel complex salt ultraviolet absorber.

<Use of ink>
The ink of the present invention can be used for ink jet recording use, spray coating use, letterpress printing use, intaglio printing use, stencil printing use, writing instrument use, stamp use, etc., and particularly preferably used for ink jet recording use. .

<Container>
The container of the present invention means a container in which the ink of the present invention is stored, and the container in which the ink is stored can be used as an ink cartridge or an ink bottle. In the work such as replacement, it is not necessary to directly touch the ink, and it is possible to prevent fingers and clothes from being stained. Further, it is possible to prevent foreign substances such as dust from being mixed into the ink.
The container is not particularly limited, and its shape, structure, size, material, and the like can be appropriately selected according to the purpose. For example, an aluminum laminate film, a container having an ink bag formed of a resin film, or the like, or the like can be used. Is preferred.

The ink cartridge will be described with reference to FIGS.
FIG. 1 is a diagram illustrating an example of the ink cartridge, and FIG. 2 is a diagram including a case (exterior) of the ink cartridge of FIG. The ink cartridge 200 fills the ink bag 241 with the ink from the ink inlet 242 and exhausts the ink, and then closes the ink inlet 242 by fusion.
At the time of use, the ink is supplied to the apparatus by inserting a needle of the apparatus main body into the ink discharge port 243 made of a rubber member. The ink bag 241 is formed of a packaging member such as an air-impermeable aluminum laminate film. As shown in FIG. 2, the ink bag 241 is usually housed in a plastic cartridge case 244, and is used by being detachably attached to various inkjet recording apparatuses.

  Hereinafter, the present invention will be described more specifically with reference to Examples, but the present invention is not limited to these Examples. In the examples, “parts” and “%” are “parts by mass” and “% by mass” unless otherwise specified.

The molecular weights of the copolymers obtained in Examples and Comparative Examples were determined as follows.
<Measurement of molecular weight of copolymer>
The measurement was performed by GPC (Gel Permeation Chromatography) under the following conditions.
-Equipment: GPC-8020 (Tosoh Corporation)
-Column: TSK G2000HXL and G4000HXL (Tosoh Corporation)
・ Temperature: 40 ° C
-Solvent: THF (tetrahydrofuran)
-Flow rate: 1.0 mL / min. Inject 1 mL of the copolymer having a concentration of 0.5% by mass and use the molecular weight calibration curve prepared from the monodisperse polystyrene standard sample from the molecular weight distribution of the copolymer measured under the above conditions. To calculate the weight average molecular weight Mw of the copolymer.

-Synthesis example of copolymer-
[Monomer Synthesis Example 1: Synthesis of Monomer M-1]
62.0 parts of 1,6-hexanediol (manufactured by Tokyo Chemical Industry Co., Ltd.) was dissolved in 900 parts of methylene chloride, and 20.7 parts of pyridine were added. A solution obtained by dissolving 50.0 parts of 2-naphthalenecarbonyl chloride (manufactured by Tokyo Chemical Industry Co., Ltd.) in 130 parts of methylene chloride was added dropwise to the solution with stirring over 2 hours, and then stirred at room temperature for 6 hours. After washing the obtained reaction solution with water, the organic layer was isolated, dried over magnesium sulfate, and the solvent was distilled off. The residue was purified by silica gel column chromatography using a mixed solvent of methylene chloride / methanol (92/2 by volume) as an eluent to obtain 52.5 parts of 2-naphthoic acid-6-hydroxyhexyl ester. .
Next, 38.3 parts of 4,4'-diphenylmethane diisocyanate (manufactured by Tokyo Chemical Industry Co., Ltd.), 19.9 parts of 2-hydroxyethyl methacrylate (manufactured by Tokyo Chemical Industry Co., Ltd.), and 41.7 parts of 2-naphthoic acid -6-Hydroxyhexyl ester was dissolved in 50 parts of toluene and 10 parts of methyl ethyl ketone. Here, 0.04 parts of dibutyltin laurate (manufactured by Tokyo Chemical Industry Co., Ltd.) was added dropwise, and the mixture was stirred at 60 ° C. for 8 hours. The solvent was distilled off, and the residue was purified by silica gel column chromatography using a mixed solvent of toluene / ethyl acetate (volume ratio: 85/15) as an eluent to obtain 43.5 parts of a monomer M-1 as a target product I got

[Monomer Synthesis Example 2: Synthesis of Monomer M-2]
In Monomer Synthesis Example 1, 2-naphthalenecarbonyl chloride was used in place of 1-naphthalenecarbonyl chloride (manufactured by Tokyo Chemical Industry Co., Ltd.), and 43.0 parts of monomer M-2, which was the desired product, was used in the same manner except for the above. Obtained.

[Monomer Synthesis Example 3: Synthesis of Monomer M-3]
30.2 parts of 2,4-toluene diisocyanate (Tokyo Kasei Kogyo) was dissolved in 30 parts of toluene. A solution prepared by dissolving 22.5 parts of 2-hydroxyethyl methacrylate (manufactured by Tokyo Chemical Industry Co., Ltd.) in 10 parts of toluene was added dropwise to this solution at 40 ° C. with stirring over 2 hours. To the obtained solution, a solution prepared by dissolving 47.1 parts of 2-naphthoic acid-6-hydroxyhexyl ester obtained in the same manner as in Synthesis Example 1 of monomer in 80 parts of methyl ethyl ketone was added. To this, 0.04 parts of dibutyltin laurate (manufactured by Tokyo Chemical Industry Co., Ltd.) was added dropwise, and the mixture was stirred at 45 ° C. for 3 hours. The solvent was distilled off, and the residue was purified by silica gel column chromatography using a mixed solvent of toluene / ethyl acetate (volume ratio: 85/15) as an eluent to obtain 43.1 parts of a monomer M-3 as a target substance. I got

[Monomer Synthesis Example 4: Synthesis of Monomer M-5]
32.6 parts of meta-xylene diisocyanate (manufactured by Tokyo Chemical Industry Co., Ltd.) were dissolved in 30 parts of toluene. A solution of 24.9 parts of 4-hydroxybutyl acrylate (manufactured by Tokyo Chemical Industry Co., Ltd.) in 10 parts of toluene was added dropwise to this solution at 40 ° C. with stirring over 2 hours. To the obtained solution, a solution prepared by dissolving 47.1 parts of 2-naphthoic acid-6-hydroxyhexyl ester obtained in the same manner as in Synthesis Example 1 of monomer in 80 parts of methyl ethyl ketone was added. To this, 0.04 parts of dibutyltin laurate (manufactured by Tokyo Chemical Industry Co., Ltd.) was added dropwise, and the mixture was stirred at 45 ° C. for 3 hours. The solvent is distilled off, and the residue is purified by silica gel column chromatography using a mixed solvent of toluene / ethyl acetate (volume ratio: 85/15) as an eluent to obtain 40.0 parts of a monomer M-5 as a target substance. I got

[Monomer Synthesis Example 5: Synthesis of Monomer M-7]
106.12 parts of 1,12-dodecanediol (manufactured by Tokyo Chemical Industry Co., Ltd.) was dissolved in 900 parts of methylene chloride, and 20.7 parts of pyridine was added. A solution obtained by dissolving 50.0 parts of 2-naphthalenecarbonyl chloride (manufactured by Tokyo Chemical Industry Co., Ltd.) in 130 parts of methylene chloride was added dropwise to the solution with stirring over 2 hours, and then stirred at room temperature for 6 hours. After washing the obtained reaction solution with water, the organic layer was isolated, dried over magnesium sulfate, and the solvent was distilled off. The residue was purified by silica gel column chromatography using a mixed solvent of methylene chloride / methanol (92/2 by volume) as an eluent to obtain 68.3 parts of 2-naphthoic acid-12-hydroxydodecyl ester. .
Next, 36.4 parts of 1,5-diisocyanate naphthalene (manufactured by Tokyo Chemical Industry Co., Ltd.) was dissolved in 30 parts of toluene. A solution prepared by dissolving 22.5 parts of 2-hydroxyethyl methacrylate (manufactured by Tokyo Chemical Industry Co., Ltd.) in 10 parts of toluene was added dropwise to this solution at 40 ° C. with stirring over 2 hours. To the obtained solution, a solution in which 61.7 parts of 2-naphthoic acid-12-hydroxydodecyl ester was dissolved in 80 parts of methyl ethyl ketone was added. To this, 0.04 parts of dibutyltin laurate (manufactured by Tokyo Chemical Industry Co., Ltd.) was added dropwise, and the mixture was stirred at 45 ° C. for 3 hours. The solvent is distilled off, and the residue is purified by silica gel column chromatography using a mixed solvent of toluene / ethyl acetate (volume ratio: 85/15) as an eluent to obtain 50.2 parts of a monomer M-7 as an objective substance. I got

[Synthesis Example 1; Synthesis of Copolymer CP-1]
A monomer solution was prepared by dissolving 15.0 parts of acrylic acid (manufactured by Tokyo Chemical Industry Co., Ltd.) and 85.0 parts of monomer M-1 in 600 parts of methyl ethyl ketone. After heating 10% by mass of the monomer solution to 75 ° C. under an argon stream, 4.0 parts of 2,2′-azobis (isobutyronitrile) (AIBN, manufactured by Tokyo Chemical Industry Co., Ltd.) was added to the remaining monomer solution. A solution in which 0.5 part of α-thioglycerol (manufactured by Tokyo Chemical Industry Co., Ltd.) was dissolved was added dropwise over 2.5 hours, and the mixture was stirred at 75 ° C. for 6 hours. After cooling to room temperature, the obtained reaction solution was dropped into hexane. The precipitated copolymer was separated by filtration and dried under reduced pressure to obtain 96.0 parts of [Copolymer CP-1] (weight average molecular weight (Mw): 23000).

[Synthesis Examples 2 to 17; Synthesis of Copolymers CP-2 to 17]
In the synthesis of the copolymer CP-1 of Synthesis Example 1, the monomer represented by the general formula (2), the anionic monomer and the other monomer in the number of parts shown in Table 1 were used. [Copolymers CP-2 to 17] were obtained in the same manner except that AIBN and thioglycerol were used and the polymerization temperature was as shown in Table 1.
The weight average molecular weight Mw of each of the obtained copolymers CP-2 to 17 is as shown in Table 1.

  In Table 1, dodecyl methacrylate and styrene used were those manufactured by Tokyo Chemical Industry Co., Ltd. AA indicates acrylic acid, and MAA indicates methacrylic acid.

-Preparation example of pigment dispersion-
[Preparation of pigment dispersion 1; preparation of pigment dispersion PD-1]
4.0 parts of the copolymer CP-1 was dissolved in 80.0 parts of an aqueous solution of tetraethylammonium hydroxide so that the pH became 8.0. To 84.0 parts of the obtained aqueous copolymer solution, 16.0 parts of carbon black (NIPEX150, manufactured by Degussa) was added and stirred for 12 hours.
The obtained mixture was circulated and dispersed for 1 hour at a peripheral speed of 10 m / s using a disk-type bead mill (KDL type, manufactured by Shinmaru Enterprises Co., Ltd., medium: using zirconia balls having a diameter of 0.1 mm). The mixture was filtered through a 0.2 μm membrane filter, and an adjusted amount of ion-exchanged water was added to obtain 97.0 parts of [Pigment Dispersion PD-1] (pigment solid content: 16%).

[Preparation of Pigment Dispersion 2: Preparation of Pigment Dispersions PD-2 to 24]
In the preparation of the pigment dispersion PD-1, the copolymers CP-2 to 17 were used in the number of parts shown in Table 2, the neutralizing agent aqueous solution shown in Table 2 was used, and the pigment shown in Table 2 was used. Similarly, pigment dispersions PD-2 to PD-24 were obtained.

In Table 2, the following abbreviations were used for the neutralizing agent, and the following products were used.
・ TEAOH tetraethylammonium hydroxide, manufactured by Tokyo Kasei Kogyo Co., Ltd., 35% aqueous solution ・ NaOH sodium hydroxide, manufactured by Kishida Chemical Co., Ltd. ・ DEA diethanolamine, manufactured by Kanto Kagaku Co., Ltd. used.
-Pigment Blue 15: 3 Chromofine Blue A-220JC, manufactured by Dainichi Seika Co., Ltd.-Pigment Red 122 Toner Magenta EO02, manufactured by Clariant-Pigment Yellow 74 First Yellow 531, manufactured by Dainichi Seika

-Preparation example of ink-
Example 1 Preparation of Ink GJ-1
40.0 parts of pigment dispersion PD-1, 10.0 parts of glycerin, 20.0 parts of 1,3-butanediol, 1.0 part of 2-ethyl-1,3-hexanediol, 1.0 part of After mixing 2 parts of 2,2,4-trimethyl-1,3-pentanediol, 1.0 part of Unidyne DSN-403N (manufactured by Daikin Industries), and 27.0 parts of ion-exchanged water, and stirring for 1 hour, The mixture was filtered through a membrane filter having a pore size of 1.2 μm to obtain Ink GJ-1 of the present invention.

[Examples 2 to 24; Preparation of Inks GJ-2 to 24]
Using the same preparation method as that of Example 1, inks GJ-2 to 24 of Examples 2 to 23 were prepared according to the formulations shown in Table 3.

[Comparative Example 1: Preparation of ink RGJ-1]
1.20 g of acrylic acid and 7.12 g of a monomer having a structure represented by the following structural formula (14) were dissolved in 40 ml of dry methyl ethyl ketone to prepare a monomer solution. After heating 10% by mass of the monomer solution to 75 ° C. under a stream of argon, a solution obtained by dissolving 0.273 g of 2,2-azobis (isobutyronitrile) in the remaining monomer solution is taken for 1.5 hours. The mixture was added dropwise and stirred at 75 ° C. for 6 hours. After cooling to room temperature, the obtained reaction solution was poured into hexane. The precipitated copolymer was separated by filtration and dried under reduced pressure to obtain 4.82 g of a copolymer (weight average molecular weight (Mw): 7500).

Next, using this, an aqueous solution of the comparative copolymer RCP-1 was prepared in the same manner as in Example 1.
That is, a comparative pigment dispersion RPD-1 was obtained in the same manner except that the comparative copolymer RCP-1 was used instead of the copolymer CP-1 in the preparation of the pigment dispersion of Example 1.
Next, a comparative ink RGJ-1 was obtained in the same manner except that the comparative pigment dispersion RPD-1 was used instead of the pigment dispersion 1 in the production of the ink of Example 1.

[Comparative Example 2: Preparation of ink RGJ-2]
Comparative pigment dispersion RPD-2 was obtained in the same manner except that comparative copolymer RCP-1 was used instead of copolymer CP-1 in the preparation of pigment dispersion of Example 21.
Next, a comparative ink RGJ-2 was obtained in the same manner except that the comparative pigment dispersion RPD-2 was used instead of the pigment dispersion PD-21 in the production of the ink of Example 21.

[Comparative Example 3: Preparation of ink RGJ-3]
Comparative pigment dispersion RPD-3 was obtained in the same manner except that comparative copolymer RCP-1 was used instead of copolymer CP-1 in the preparation of pigment dispersion of Example 22.
Next, a comparative ink RGJ-3 was obtained in the same manner except that the comparative pigment dispersion RPD-3 was used instead of the pigment dispersion PD-22 in the production of the ink of Example 22.

[Comparative Example 4: Preparation of ink RGJ-4]
Comparative pigment dispersion RPD-4 was obtained in the same manner except that comparative copolymer RCP-1 was used instead of copolymer CP-1 in the preparation of pigment dispersion of Example 23.
Next, a comparative ink RGJ-4 was obtained in the same manner except that the comparative pigment dispersion RPD-4 was used instead of the pigment dispersion PD-23 in the ink preparation of Example 23.

[Comparative Example 5: Preparation of ink RGJ-5]
80 g of 2-phenoxyethyl methacrylate as a monomer, 3.7 g of 3-mercapto-1-propanol as a chain transfer agent, and 0.3 g of 2,2-azobis (2,4-dimethylvaleronitrile) as an initiator in 160 mL of THF. The mixture was dissolved, heated to 65 ° C. in a nitrogen atmosphere, and reacted for 7 hours. The resulting solution was allowed to cool, 80 mg of dibutyltin (IV) dilaurate and a catalytic amount of hydroquinone were added, and 10.0 g of 2-methacryloyloxyethyl isocyanate was added dropwise. After heating to 50 ° C. and reacting for 2.5 hours, purification was performed by reprecipitation with a mixed solvent of methanol and water, and 71 g of macromonomer MM-1 (weight average molecular weight (Mw): 4000, number average) Molecular weight (Mn): 1900).
Next, after heating 20 g of methyl ethyl ketone to 75 ° C. under a nitrogen atmosphere, 1.16 g of dimethyl 2,2′-azobisisobutyrate, 9 g of the macromonomer MM-1 obtained above and 1.8 g of A solution of p-styrenesulfonic acid and 49.2 g of methyl methacrylate dissolved in 40 g of methyl ethyl ketone was added dropwise over 3 hours. After the completion of the dropwise addition, the mixture was further reacted for 1 hour. Then, a solution prepared by dissolving 0.2 g of dimethyl 2,2′-azobisisobutyrate in 0.6 g of methyl ethyl ketone was added, the temperature was raised to 80 ° C., and the mixture was heated and stirred for 4 hours. did. Further, a solution obtained by dissolving 0.2 g of dimethyl 2,2′-azobisisobutyrate in 0.6 g of methyl ethyl ketone was added, and the mixture was stirred with heating for 6 hours. After cooling, the obtained reaction solution was dropped into hexane, and the precipitated graft polymer was separated by filtration and dried to obtain a comparative copolymer RCP-2.
Next, a comparative pigment dispersion RPD-5 was obtained in the same manner except that the comparative copolymer RCP-2 was used instead of the copolymer CP-1 in the preparation of the pigment dispersion of Example 1.
Next, a comparative aqueous ink RGJ-5 was obtained in the same manner except that the comparative pigment dispersion RPD-5 was used instead of the pigment dispersion PD-1 in the preparation of the ink of Example 1.

[Comparative Example 6: Preparation of ink RGJ-6]
(Synthesis of copolymer RCP-3)
72.0 g (500 mmol) of 2-naphthol (manufactured by Tokyo Chemical Industry Co., Ltd.) and 125.0 g (1000 mmol) of ethylene glycol mono-2-chloroethyl ether (manufactured by Tokyo Chemical Industry Co., Ltd.) were added to 500 ml of N-methyl-2. -Dissolved in pyrrolidinone (manufactured by Kanto Chemical Co.) and stirred at room temperature for 1 hour. Further, the mixture was stirred at 110 ° C. for 10 hours. After cooling to room temperature, 2500 ml of pure water was added to the obtained reaction solution, followed by stirring at room temperature for 1 hour. The precipitated solid was separated by filtration and dried under reduced pressure.
70.0 g of the solid obtained in the above reaction and 45.0 g (450 mmol) of triethylamine (manufactured by Tokyo Chemical Industry Co., Ltd.) were dissolved in 250 ml of tetrahydrofuran, and the mixture was stirred in an ice bath for 30 minutes. Here, 36.6 g (350 mmol) of methacryloyl chloride (manufactured by Wako Pure Chemical Industries, Ltd.) was slowly added dropwise, and the mixture was further stirred in an ice bath for 3 hours. 250 ml of ethyl acetate and 100 ml of pure water were added to the obtained solution, and the mixture was washed with water. Next, the ethyl acetate layer was isolated and washed with a saturated saline solution. The ethyl acetate layer was isolated, dried over magnesium sulfate, and the solvent was distilled off. The residue was purified by silica gel column chromatography to obtain 80.5 g of a monomer represented by the following structural formula (15).

  Next, 12.0 g of methyl ethyl ketone was added to a 100 ml three-necked flask equipped with a stirrer and a cooling tube, and heated to 72 ° C. under an argon stream. Here, 2.4 g (8.00 mmol) of the monomer represented by the structural formula (15), 1.2 g (13.9 mol) of methacrylic acid (manufactured by Tokyo Chemical Industry Co., Ltd.), and 8.4 g (47.6 mmol) of benzyl methacrylate A solution prepared by dissolving 0.128 g (0.56 mmol) of 2,2′-azobis (isobutyric acid) dimethyl (manufactured by Wako Pure Chemical Industries, Ltd.) in 6.0 g of methyl ethyl ketone (manufactured by Tokyo Chemical Industry Co., Ltd.) for 3 hours. It dripped over. After the completion of the dropwise addition, the mixture was further reacted for 1 hour. A solution of 0.06 g (0.26 mmol) of dimethyl 2,2′-azobis (isobutyrate) in 2.0 g of methyl ethyl ketone was added. Stirred for hours. Thereafter, reprecipitation was repeated twice using hexane to purify the copolymer. After the purification treatment, the copolymer was separated by filtration and dried under reduced pressure to obtain 11.6 g of a copolymer RCP-3 (weight average molecular weight (Mw): 34000).

(Preparation of pigment dispersion RPD-6)
4.0 parts of copolymer RCP-3 was replaced with 1.9 parts of a 35% aqueous solution of tetraethylammonium hydroxide (manufactured by Tokyo Chemical Industry Co., Ltd.) and 50.0 parts of 3-methoxy-N, N′-dimethylpropionamide. , 28.1 parts of ion-exchanged water.
To an aqueous solution of 84.0 parts of the copolymer RCP-3, 16.0 parts of carbon black (NIPEX150, manufactured by Degussa) was added and stirred for 12 hours. The obtained mixture was circulated and dispersed at a peripheral speed of 10 m / s for 1 hour using a disk type bead mill (KDL type, manufactured by Shinmaru Enterprises Co., Ltd., using zirconia balls having a diameter of 0.1 mm) for 1 hour. The mixture was filtered through a 0.2 μm membrane filter, and an adjusted amount of ion-exchanged water was added to obtain 95.0 parts of a pigment dispersion RPD-6 (pigment solid content concentration: 16%).

(Preparation of ink RGJ-6)
40.0 parts of pigment dispersion RPD-6, 10.0 parts of 1,3-butanediol, 10.0 parts of glycerin, 1.0 part of 2-ethyl-1,3-hexanediol, 1.0 part of Of 2,2,4-trimethyl-1,3-pentanediol, 1.0 part of Unidyne DSN-403N (manufactured by Daikin Industries, 100% solids), and 37.0 parts of ion-exchanged water. After stirring for 1 hour, the mixture was filtered through a membrane filter having a pore size of 1.2 μm to obtain Comparative Ink RGJ-6.

[Evaluation results]
Next, the inks of Examples 1 to 24 and Comparative Examples 1 to 6 were evaluated by the evaluation methods described below. The results are shown in Table 4 below.

<Storage stability of pigment dispersion>
Each pigment dispersion was filled in a glass container and stored at 70 ° C. for 2 weeks, and the rate of change of the viscosity after storage with respect to the viscosity before storage was determined from the following formula and evaluated according to the following criteria.
Change rate of viscosity (%) = (viscosity of pigment dispersion after storage / viscosity of pigment dispersion before storage) × 100
The viscosity was measured using a viscometer (RE80L, manufactured by Toki Sangyo Co., Ltd.) at 25 ° C. at 50 rotations.
〔Evaluation criteria〕
A: Change rate of viscosity is within ± 5% B: Change rate of viscosity exceeds ± 5%, within ± 8% C: Change rate of viscosity exceeds ± 8%, within ± 10% D: Change of viscosity The ratio exceeds ± 10% and is within ± 30% E: The rate of change in viscosity exceeds ± 30% (becomes gelled and cannot be evaluated)
C and above are practical.

<Storage stability of ink>
Each ink was filled in an ink cartridge and stored at 70 ° C. for one week, and the rate of change of the viscosity after storage with respect to the viscosity before storage was determined from the following formula, and evaluated according to the following criteria.
Change rate of viscosity (%) = (viscosity of ink after storage / viscosity of ink before storage) × 100
The viscosity was measured using a viscometer (RE80L, manufactured by Toki Sangyo Co., Ltd.) at 25 ° C. at 50 rotations.
〔Evaluation criteria〕
A: Change rate of viscosity is within ± 5% B: Change rate of viscosity exceeds ± 5%, within ± 8% C: Change rate of viscosity exceeds ± 8%, within ± 10% D: Change of viscosity The ratio exceeds ± 10% and is within ± 30% E: The rate of change in viscosity exceeds ± 30% (becomes gelled and cannot be evaluated)
C and above are practical.

<Image density>
Under an environment of 23 ° C. and 50% RH, an ink jet printer (manufactured by Ricoh, IPSiO GX5000) is filled with each ink, and a 64 point JIS X 0208 (1997), 2223 general symbol prepared by Microsoft Word 2000 (manufactured by Microsoft) is used. Is printed on plain paper 1 (XEROX4200, manufactured by XEROX) and plain paper 2 (MyPaper, manufactured by Ricoh), and the above-described symbol portion on the printing surface is converted to X-Rite 938 (manufactured by X-Rite). And evaluated according to the following criteria.
The print mode used was a mode in which the "plain paper-standard fast" mode was changed to "no color correction" from the plain paper user setting by the driver attached to the printer.
The above JIS X 0208 (1997), 2223 is a symbol whose outer shape is a square and whose entire surface is filled with ink.
〔Evaluation criteria〕
A: 1.25 or more B: 1.25 or more, less than 1.25 C: 1.10 or more, less than 1.20 D: less than 1.10 E: Pigment gelled and could not be dispersed in ink, and printing was not possible .
C and above are practical.

The pigment dispersions prepared using the copolymers having a naphthyl group at the terminal of the side chain of the present invention of Examples 1 to 24 are the same as those of Comparative Examples 1 to 5, having no naphthyl group at the terminal of the side chain. It had excellent storage stability as compared with the pigment dispersion prepared by using the union. The details of the expression mechanism are unknown, but are presumed as follows.
In order to achieve good pigment dispersion and dispersion stability, it is necessary to prevent the reaggregation of particles due to steric hindrance of the resin between pigment particles while the copolymer resin is firmly adsorbed on the pigment. It is presumed that the copolymer of the present invention is excellent in these properties. In the water-based ink, the adsorption of the copolymer and the pigment is attracted by the hydrophobic interaction and the aromatic stacking interaction (π-π interaction). The copolymer of the present invention comprises a structural part of the general formula (1), which is a hydrophobic part, and a structural part of an anionic group, which is a hydrophilic part. A certain structural part of the general formula (1) can be contained at a high concentration while securing water solubility, and a large hydrophobic interaction can be obtained. In addition, the hydrophobic portion has a naphthyl group, so that a large π-π interaction can be obtained. It is presumed that these are combined to strongly adsorb to the pigment. In addition, it is presumed that the copolymer of the present invention can continue to maintain repulsion between pigment particles and electrostatic repulsion due to steric hindrance due to its structural characteristics.
In addition, even if it has a naphthyl group, the storage stability of the ink cannot be made sufficient performance depending on the selection of other monomers used in the synthesis of the copolymer, and it is difficult to ensure long-term stable quality. (Comparative Example 6). It is presumed that the monomer in the present invention has an aromatic moiety also in the linker connecting the naphthyl group and the acrylic moiety, so that the effect of adsorbing the pigment by the aromatic stacking interaction was stronger.

200 ink cartridge 241 ink bag 242 ink inlet 243 ink outlet 244 cartridge case

Japanese Patent No. 5001291 Japanese Patent No. 4956666 JP 2011-105866 A

Claims (5)

Water, coloring material, and the ink containing a copolymer, the structural unit of the copolymer is represented by the following general formula (1), and, have a structural unit having an anionic group, said anionic group Is a structural unit derived from acrylic acid or methacrylic acid .

(In the general formula (1), R represents a hydrogen atom or a methyl group, X is an alkylene group having 2 to 4 carbon atoms, Y is a hydrocarbon group having 6 to 15 carbon atoms including an aromatic group, and Z is 2 carbon atoms. ~ 12 alkylene groups.) The ink according to claim 1 , wherein the content of the structural unit represented by the general formula (1) in the copolymer is 75 to 90% by mass. The ink according to claim 1 or 2 weight-average molecular weight of the copolymer is characterized in that it is a 15000-40000. A container containing the ink according to any one of claims 1 to 3 in a container. In the method for producing an ink containing water, a coloring material, and a copolymer, the copolymer is a polymerizable material containing at least a monomer represented by the following general formula (2) and a monomer having an anionic group. A method for producing an ink , comprising a step of being synthesized by radical polymerization , wherein the monomer having an anionic group is acrylic acid or methacrylic acid .

(In the general formula (2), R represents a hydrogen atom or a methyl group, X is an alkylene group having 2 to 4 carbon atoms, Y is a hydrocarbon group having 6 to 15 carbon atoms including an aromatic group, and Z is 2 carbon atoms. ~ 12 alkylene groups.)

Images