JP6593100B2 - Ink, ink manufacturing method, ink cartridge - Google Patents

Description

  The present invention relates to a water-based ink using a novel copolymer effective as a binder resin or pigment-dispersing resin for water-based ink, a method for producing the same, and an ink cartridge using the ink.

The inkjet recording method is popular because it has the advantage that the process is simple and full color can be easily achieved compared to other recording methods, and even a device with a simple configuration can obtain a high-resolution image. To the field of office use, commercial printing and industrial printing. However, water-based inks that use water-soluble dyes as color materials used in inkjet recording systems have the disadvantage of being inferior in water resistance and light resistance, and therefore pigment inks that use water-insoluble pigments are being developed. ing.
In inkjet printing for office use, plain paper is mainly used as a recording medium, and high image density is required. In general, when pigment ink is printed on plain paper, the pigment penetrates into the paper without staying on the paper surface, so the pigment density on the paper surface is lowered and the image density is lowered. If the pigment concentration in the ink is increased, the image density is increased, but the viscosity of the ink is increased and the ejection stability is lowered.

Further, immediately after the pigment ink droplets land on the plain paper, there is a problem that the paper surface is swollen by water in the ink, the difference in elongation between the front and back is increased, and curling occurs. Such a phenomenon did not cause a problem in low-speed printing, but as the printing speed increased, it was necessary to transport the recording medium without eliminating curling after printing, and a paper jam problem occurred. As a countermeasure, there is a method of adding a penetrant so that water can permeate the paper quickly. However, since the ink becomes hydrophobic, it is difficult to ensure the storage stability of the ink, and at the same time, the pigment penetrates into the recording medium. As a result, the image density also decreases, and the image density further decreases.
In order to solve the above problems, various methods have been proposed so that the pigment stays on the paper surface. For example, in Patent Document 1, a polymer having at least one functional group having a specific calcium index value is contained in the ink. However, ink storage stability is low.
In Patent Document 2, a receiving liquid containing Ca salt is attached to paper and printing is performed using ink containing a pigment having a phosphorus-containing group bonded thereto. However, when recorded on plain paper, the image density is improved. The effect is not enough.

In the field of commercial printing and industrial printing, there is a need for a technique for stably creating an image with higher resolution and sharpness at a higher speed. As the recording medium, plain paper, coated paper, art paper, non-permeable film such as PET film, and the like are used, and high adaptability of the ink to the recording medium is required.
In particular, when an image having excellent resolution and sharpness is formed at high speed on a poorly permeable medium such as coated paper or art paper or a non-permeable film, beading (mottle) tends to occur.
As a countermeasure, Patent Document 3 proposes an ink having a minimum film forming temperature of 40 ° C. or higher and containing at least a wax emulsion, a resin emulsion, a latex, organic ultrafine particles, and inorganic ultrafine particles as a fixing agent. . Patent Document 4 proposes an ink in which the high molecular compound contained in the ink or the ink after evaporation of a part of the water in the ink exhibits UCST phase separation in the range of 0 ° C. to 100 ° C. ing. Patent Document 5 proposes an ink containing a jettable vehicle, a plurality of pigment solids self-dispersed in the vehicle, and a styrene maleic anhydride (SMA) half ester dispersed in the vehicle. Has been.
Furthermore, Patent Document 6 proposes a method of changing the rheology of an ink by changing the pH using a pH-responsive polymer.
However, with the above conventional ink, it has been difficult to form images on various recording media at high speed without causing beading.

Similar to the above-described ink jet recording method, in a writing instrument such as a sign pen, ballpoint pen, or plotter pen, the aqueous pigment ink has a problem that the color density on plain paper, particularly white plain paper, is inferior to that of dye ink.
In response to this problem, Patent Document 7 discloses a water-insoluble (meth) acrylic resin and / or a styrene- (meth) acrylic acid copolymer having an average particle diameter of 50 to 200 nm and a minimum film-forming temperature of 50 ° C. or higher. An aqueous pigment ink containing an O / W emulsion, urea or a derivative thereof, a phosphate ester surfactant, or the like has been proposed, but the effect of improving color density is not sufficient.

In addition, water-based pigment inks used in the above ink jet recording methods and writing instruments, unlike water-based dye inks, need to stably disperse pigments that do not dissolve in water for a long period of time, so various pigment dispersants have been developed. Has been.
For example, in Patent Document 8, by using a graft polymer containing an aromatic ring in the side chain as a pigment dispersant, ink storage stability for 3 days at 70 ° C. is ensured. Is not enough.
In addition, in the ink jet recording method, in order to prevent paper curl that occurs when printing on plain paper, or when printing on coated paper or art paper, the ink permeability is increased, drying is accelerated and beading is performed. In order to prevent this, there is a method of adding a hydrophilic organic solvent to the water-based ink. However, when the graft polymer of Patent Document 8 is applied to this method, the pigment dispersibility is lowered and long-term storage stability cannot be ensured. Moreover, in patent document 8, there is neither a specific illustration nor an Example about the copolymer used by this invention.

  An object of the present invention is to provide an ink having a high image density and high storage stability even when recorded on plain paper.

（上記式中、Ｒは水素原子又はメチル基を表し、Ｘは炭素数２〜４のアルキレン基を表し、Ｙは芳香環を含む炭化水素基を表し、該炭化水素基の炭素数は置換基も含めて６〜１５である。） The above problem is solved by the following invention 1).
1) An ink comprising water, a coloring material, and a copolymer, wherein the copolymer has a structural unit represented by the general formula (1) and a structural unit having an anionic group.
General formula (1)

(In the above formula, R represents a hydrogen atom or a methyl group, X represents an alkylene group having 2 to 4 carbon atoms, Y represents a hydrocarbon group containing an aromatic ring, and the carbon number of the hydrocarbon group is a substituent. Including 6 to 15)

  According to the present invention, a high image density can be obtained even when recording on plain paper, and an ink having high storage stability can be provided.

Schematic which shows an example of the ink bag of an ink cartridge. FIG. 2 is a schematic diagram illustrating an ink cartridge in which the ink bag of FIG. 1 is accommodated in a cartridge case.

（上記式中、Ｒは水素原子又はメチル基を表し、Ｘは炭素数２〜４のアルキレン基を表し、Ｙは芳香環を含む炭化水素基を表し、該炭化水素基の炭素数は置換基も含めて６〜１５である。）
６） １）〜４）のいずれかに記載のインクを容器に収容したインクカートリッジ。 Hereinafter, the present invention 1) will be described in detail, but the following 2) to 6) are also included in the embodiment, and these will also be described together.
2) The ink according to 1), wherein the structural unit having an anionic group has a carboxyl group.
3) The ink according to 1) or 2), wherein the content of the structural unit represented by the general formula (1) in the copolymer is 75 to 90% by weight.
4) The ink according to any one of 1) to 3), wherein the copolymer has a weight average molecular weight of 15,000 to 40,000.
5) 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 general formula (2) and a monomer having an anionic group. An ink production method comprising a step of synthesis by radical polymerization.
General formula (2)

(In the above formula, R represents a hydrogen atom or a methyl group, X represents an alkylene group having 2 to 4 carbon atoms, Y represents a hydrocarbon group containing an aromatic ring, and the carbon number of the hydrocarbon group is a substituent. Including 6 to 15)
6) An ink cartridge containing the ink according to any one of 1) to 4) in a container.

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

<Structural unit represented by general formula (1)>
In the said General formula (1), Y represents the hydrocarbon group containing an aromatic ring, and carbon number of this hydrocarbon group is 6-15 including a substituent. Examples of the substituent include a lower alkyl group such as a methyl group, a methoxy group, a halogen, and a functional group containing a halogen.

Although the specific example of the structural unit represented by General formula (1) below is given, it is not limited to these.

In the general formula (1), the naphthyl group present at the terminal via Y has an excellent pigment adsorbing power due to π-π stacking with the pigment which is a coloring material in the ink. When preparing the pigment dispersion in which the pigment is dispersed in water, if the copolymer is used, since the adsorptive power with the pigment is high, the dispersion stability is increased and a dispersion having high storage stability is obtained. Furthermore, even when a hydrophilic organic solvent is added to the ink, the dispersibility is maintained and an ink having high storage stability can be obtained.
Further, when the copolymer is used for ink, a high image density can be obtained even when recording on plain paper. The mechanism is not clear, but is presumed as follows.
That is, since the ink using the copolymer has a high dispersion stability of the pigment, it is considered that it is difficult to form coarse particles even when adhering to the plain paper surface. When 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 lowered. On the other hand, the ink using the copolymer can uniformly coat the plain paper surface with a pigment, and a high image density can be obtained.

<Structural unit having an 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 unsaturated carboxylic acid monomers, unsaturated sulfonic acid monomers, and unsaturated phosphoric acid monomers.
Examples of the unsaturated carboxylic acid monomer include acrylic acid, methacrylic acid, itaconic acid, maleic acid, and fumaric acid. Examples of the unsaturated sulfonic acid monomer include styrene sulfonic acid and 2-acrylamido-2-methylpropane sulfonic acid. Examples of unsaturated phosphoric acid monomers include vinylphosphonic acid, vinyl phosphate, bis (methacryloxyethyl) phosphate, diphenyl-2-acryloyloxyethyl phosphate, diphenyl-2-methacryloyloxyethyl phosphate, dibutyl-2-acrylic acid. And leuoxyethyl phosphate.
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 invention is not limited thereto.

The monomer 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.
Examples of the base include 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 Xoxide, nonyltrimethylammonium hydroxide, decyltrimethylammonium hydroxide, dodecyltrimethylammonium hydroxide, tetradecyltrimethylammonium hydroxide, hexadecyltrimethylammonium hydroxide, octadecyltrimethylammonium hydroxide, didodecyldimethylammonium hydroxide, ditetradecyl Dimethylammonium hydroxide, dihexadecyldimethylammonium hydroxide, dioctadecyldimethylammonium hydroxide, ethylhexadecyldimethylammonium hydroxide, aqueous ammonia, dimethylamine, trimethylamine, monoethylamine, diethylamine, triethylamine, monoethanolamine, diethanolamine, Examples include ethanolamine, methylethanolamine, methyldiethanolamine, dimethylethanolamine, monopropanolamine, dipropanolamine, tripropanolamine, isopropanolamine, morpholine, N-methylmorpholine, N-methyl-2-pyrrolidone, and 2-pyrrolidone. It is done.
The base as the neutralizing agent may be used alone or in combination of two or more.
The neutralization treatment may be performed when the monomer having an anionic group is copolymerized or may be performed when the copolymer is dissolved.

<Composition ratio>
There is no restriction | limiting in particular in the content rate of the structural unit represented by the said General formula (1), Although it can select suitably according to the objective, 60 to 90 weight% is preferable with respect to the said copolymer whole quantity, More preferably, it is 75 to 90% by weight. When the content is within the above range, it is advantageous in that the image density and storage stability are improved when used in ink.

<Molecular weight>
The weight average molecular weight of the copolymer is preferably 5000 to 50000, more preferably 15000 to 40000, in terms of polystyrene. When the weight average molecular weight is within the above range, it is advantageous in that image density and storage stability are improved when used in ink.

<Other monomers>
In addition to the structural unit represented by the general formula (1) and the structural unit having an anionic group, the copolymer may have a structural unit composed of other polymerizable monomers.
The other polymerizable monomer is not particularly limited and may 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, 4-chloromethylstyrene; methyl (meth) acrylate, (Meth) ethyl acrylate, (meth) acrylate-n-butyl, 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 acrylate (C20), helicosyl (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 , Unsaturated ethylene monomers having an alkyl group such as 1-octadecene, 1-nonadecene, 1-eicocene and 1-docosene. These may be used alone or in combination of two or more.

Examples of the polymerizable hydrophilic monomer include (meth) acrylic acid-2-hydroxyethyl, 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 a single type or a mixture of two or more types, a structural unit represented by the general formula (1), and a structural unit having an anionic group. What is necessary is just to use 5 to 100 weight% with respect to the total amount of the monomer to form.

<Synthesis of copolymer>
The copolymer is obtained by copolymerizing the monomer represented by the general formula (2) with a monomer having an anionic group in the presence of a radical polymerization initiator.
In the said General formula (2), Y represents the hydrocarbon group containing an aromatic ring, and carbon number of this hydrocarbon group is 6-15 including a substituent. Examples of the substituent include a lower alkyl group such as a methyl group, a methoxy group, a halogen, and a functional group containing a halogen.

Although the specific example of a monomer represented by General formula (2) below is given, it is not limited to these.

（反応式２）

The monomer represented by the general formula (2) can be synthesized and used as follows. That is, as shown in the following (Reaction Formula 1) to (Reaction Formula 2), first, the diisocyanate compound (A-1) and naphthol (A-2) are reacted in the presence of an acid acceptor such as amine or pyridine. To obtain a reaction intermediate (A-3). Next, the monomer represented by the general formula (2) can be obtained by reacting the hydroxyalkyl methacrylate (A-4) with the (A-3).
(Reaction Formula 1)

(Reaction Formula 2)

As another method, (A-1) and (A-4) are reacted first, and then reacted with (A-2) to obtain the monomer represented by the general formula (2). You can also.
As another method, as shown in the following reaction formula (3), by reacting the diisocyanate compound (A-1), naphthol (A-2), and hydroxyalkyl methacrylate (A-4), The monomer represented by (2) can also be obtained.
(Reaction Formula 3)

The compound represented by (A-1) is particularly limited if it is a diisocyanate in which Y is a hydrocarbon group containing an aromatic ring and the hydrocarbon group has 6 to 15 carbon atoms including substituents. There is no. Examples thereof include the following.
4,4'-diphenylmethane diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, m-phenylenebis (1-methylethane-1,1-diyl) diisocyanate, hexamethylene diisocyanate, m-xylylene diyl 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 dii Cyanate, 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) diisocyanate, naphthalene-1,4-diylbis (methylene) diisocyanate, naphthalene-1,5-diylbis (methylene) diisocyanate, 4-ethyl-1 , 3-fe Range isocyanate, 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- (Trofluoromethyl) 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, methylenebis (3-methyl-4,1-phenylene) diisocyanate, 4-[(4-isocyanatophenyl) methyl] -2-methoxyphenyl isocyanate, 3-[(4-isocyanato Phenyl) methyl] -2,4,6-trimethylphenyl isocyanate, isopropylidenebis (4,1-phenylene) diisocyanate, [(tetralin) -1,5-diyl] diisocyanate, 9H-fluorene-2,7-diyl diisocyanate 9H-Cal Zole-3,6-diyl diisocyanate Among these, methylene diphenyl-4,4'-diisocyanate, m-xylylene diisocyanate, m-phenylene bis (1-methylethane) from the viewpoint of image density and storage stability when ink is prepared. -1,1-diyl) diisocyanate, naphthalene-1,5-diyl diisocyanate, and 2,4-tolylene diisocyanate are preferred.

As the method for synthesizing the copolymer, a method using a radical polymerization initiator is preferable because the polymerization operation and the molecular weight are easily adjusted, and a solution polymerization method in which a polymerization reaction is performed in a solution is more preferable.
Preferred solvents for 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 carbonization such as benzene, toluene and xylene. Examples thereof include hydrogen solvents, isopropanol, ethanol, cyclohexane, tetrahydrofuran, dimethylformamide, dimethyl sulfoxide, hexamethylphosphoamide, and the like, and more preferred are ketone solvents, acetate solvents, and alcohol solvents.

The radical polymerization initiator is not particularly limited and may be appropriately selected depending on the purpose. Examples thereof include peroxyketals, hydroperoxides, dialkyl peroxides, diacyl peroxides, peroxydicarbonates, peroxy esters, cyano azobisisobutyronitrile, azobis (2-methylbutyronitrile), And 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.
There is no restriction | limiting in particular in content of the said radical polymerization initiator, Although it can select suitably according to the objective, 1 to 10 weight% is preferable with respect to the total amount of a polymerizable monomer.

In order to adjust the molecular weight of the copolymer, 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, dodecyl mercaptan, 1-dodecanethiol, thioglycerol, and the like.
The polymerization temperature is not particularly limited and may be appropriately selected depending on the intended purpose, but is preferably 50 ° C to 150 ° C, more preferably 60 ° C to 100 ° C. The polymerization time is not particularly limited and may be appropriately selected depending on the intended purpose, but is preferably 3 to 48 hours.

<Content of copolymer>
The content of the copolymer in the ink of the present invention is not particularly limited and can be appropriately selected according to the purpose. However, the solid content is preferably 0.05 to 10% by weight, and 0.3 to 5% by weight. More preferred. If the content is 0.05% by weight or more, an effect of improving dispersibility and storage stability is recognized. If the content is 10% by weight or less, it is possible to make the viscosity range suitable for discharging ink from the head. Become.
The copolymer can be used as a pigment dispersant or as an additive to the pigment dispersion. When used as a pigment dispersant, a further improvement in storage stability is observed in inks having a high water-soluble organic solvent content.
The content in the case of using the copolymer as a pigment dispersant is not particularly limited and can be appropriately selected according to the purpose, but is preferably 1 to 100 parts by weight with respect to 100 parts by weight of the pigment, 5-80 weight part is more preferable. When the content is in the more preferable range, it is advantageous in that the image density and storage stability are improved.

<Water>
Examples of the water used in the ink of the present invention include pure water such as ion exchange water, ultrafiltration water, reverse osmosis water, and distilled water, and ultrapure water.
The content of water in the ink is not particularly limited and may be appropriately selected according to the purpose. However, it is preferably 10 to 90% by weight from the viewpoint of ink drying property and ejection reliability, and 20 to 60% by weight. Is more preferable.

<Color material>
As the coloring material of the ink of the present invention, a pigment or a dye can be used. However, the adsorption ability of the copolymer to the coloring material is superior to that of the dye, and the water resistance and light resistance. From this point, a pigment is preferable.

<Pigment>
There is no restriction | limiting in particular in a pigment, According to the objective, it can select suitably, For example, the inorganic pigment, organic pigment, etc. for black or color are mentioned. These may be used alone or in combination of two or more.
There is no restriction | limiting in particular in content of the pigment in an ink, Although it can select suitably according to the objective, 0.5 to 20 weight% is preferable and 1 to 10 weight% is more preferable.

(Inorganic pigment)
Examples of the inorganic pigment include titanium oxide, iron oxide, calcium carbonate, barium sulfate, aluminum hydroxide, barium yellow, cadmium red, chrome yellow, and carbon black.
Examples of black pigments include carbon blacks (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).
There are various types of carbon black, which are manufactured by the furnace method and the channel method, the primary particle size is 15 to 40 nm, the specific surface area by the BET method is 50 to 300 m ² / g, and the DBP oil absorption is 40. Those having ~ 150 mL / 100 g, volatile content of 0.5 to 10%, and 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, chelate azo pigments), polycyclic pigments (eg, phthalocyanine pigments, perylene pigments, perinone pigments, anthraquinone pigments, quinacridone). Pigments, dioxazine pigments, indigo pigments, thioindigo pigments, isoindolinone pigments, quinofullerone pigments, etc.), dye chelates (eg basic dye chelate, acid dye chelate), nitro pigment, nitroso pigment, aniline black, etc. it can.
Of these pigments, those having particularly good affinity with water are preferable.
Examples of the azo pigments include azo lakes, insoluble azo pigments, condensed azo pigments, and chelate azo pigments.
Examples of the polycyclic pigment include a phthalocyanine pigment, a perylene pigment, a perinone pigment, an anthraquinone pigment, a quinacridone pigment, a dioxazine pigment, an indigo pigment, a thioindigo pigment, an isoindolinone pigment, a quinofullerone pigment, and a rhodamine B lake pigment. Is mentioned.
Examples of the dye chelates include basic dye chelates and acidic dye chelates.

  There is no restriction | limiting in particular as a pigment for yellow, According to the objective, it can select suitably. 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 magenta pigment is not particularly limited and may 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 cyan pigment is not particularly limited and may 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; C.I. 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 and C.I. I. By using CI Pigment Blue 15: 3, a well-balanced ink having excellent color tone and light resistance 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 color developability of the obtained image, a self-dispersing pigment may be used, and an anionic self-dispersing pigment is preferable. An anionic self-dispersing pigment refers to a pigment that has been dispersed and stabilized by introducing an anionic functional group directly on the pigment surface or via another atomic group.
As the pigment before dispersion stabilization, various conventionally known pigments such as those listed in, for example, International Publication No. 2009/014242 can be used.
In addition, an anionic functional group means the functional group which half or more of 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 these, a carboxyl group or a phosphonic acid group is preferable from the viewpoint of increasing the optical density of the obtained image.

Examples of the method for introducing an anionic functional group into the surface of the pigment include a method for oxidizing carbon black.
Specific examples of the oxidation treatment method include a method of treating with hypochlorite, ozone water, hydrogen peroxide, chlorite, nitric acid, etc., Patent No. 3808504, Special Table 2009-515007, And a surface treatment method using a diazonium salt as described in JP-A-2009-506196.
Examples of commercially available pigments having a hydrophilic functional group introduced on the surface include CW-1, CW-2, and CW-3 (above, manufactured by Orient Chemical Industry Co., Ltd.); CAB-O-JET200, CAB- O-JET300, CAB-O-JET400 (manufactured by Cabot Corporation) and the like can be mentioned.

The ink of the present invention is produced by, for example, dispersing or dissolving water, a pigment, a water-soluble organic solvent, a coloring material, the copolymer, and other components as necessary in an aqueous medium, and stirring and mixing them. However, the manufacturing method is not particularly limited. In addition, the copolymer may be used as a pigment dispersion resin when preparing 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, etc., and stirring and mixing are performed by a stirrer using a normal stirring blade, a magnetic stirrer, a high-speed disperser, or the like. be able to.
In the production, it is preferable to deaerate coarse particles by filtering them with a filter, a centrifugal separator or the like, if necessary.

<Dye>
As the dye, dyes classified in the color index into acid dyes, direct dyes, basic dyes, reactive dyes, and food dyes 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, as a direct dye, 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, 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, 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, etc. are mentioned.

The pigment dispersant in the pigment dispersion is preferably a copolymer containing the structural unit represented by the general formula (1) and a structural unit having an anionic group.
Other usable dispersants include, for example, various surfactants such as anionic surfactants, cationic surfactants, amphoteric surfactants, nonionic surfactants, naphthalenesulfonic acid Na formalin condensate, polymer type 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-acyl methyl taurates, polyoxyalkyl ethers. Sulfate, polyoxyethylene alkyl ether phosphate, rosin acid soap, castor oil sulfate, lauryl alcohol sulfate, alkylphenol phosphate, naphthalenesulfonate formalin condensate, alkyl phosphate, alkylallylsulfone hydrochloride, Examples include diethylsulfosuccinate, diethylhexylsulfosuccinate, dioctylsulfosuccinate, and the like.
Examples of the cationic surfactant 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 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, polyoxyethylene alkyl ether, Ether type surfactants such as oxyallylalkyl alkyl ethers; polyoxyethylene oleic acid, polyoxyethylene oleate, polyoxyethylene distearate, sorbitan laurate, sorbitan monostearate, sorbitan monooleate, sorbitan sesquioleate Ester surfactants such as polyoxyethylene monooleate and polyoxyethylene stearate; 2,4,7,9-tetramethyl Acetylene glycol surfactants such as lu-5-decyne-4,7-diol, 3,6-dimethyl-4-octyne-3,6-diol, 3,5-dimethyl-1-hexyn-3-ol, Etc.

<Water-soluble organic solvent>
The water-soluble organic solvent used in the ink of the present invention has at least one of an effect as a wetting agent that prevents drying of the ink and an effect as a penetrating agent.
There is no restriction | limiting in particular as said water-soluble organic solvent, According to the objective, it can select suitably. Examples thereof include ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, polypropylene glycol, 1,3-butanediol, 3-methyl-1,3- Butanediol, 1,5-pentanediol, 1,6-hexanediol, glycerin, isopropylideneglycerol, trimethylolethane, trimethylolpropane, 1,2,4-butanetriol, 1,2,3-butanetriol, 1 Polyhydric alcohols such as 1,2,6-hexanetriol and petriol; ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether Polyhydric alcohol alkyl ethers such as diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, tetraethylene glycol monomethyl ether and propylene glycol monoethyl ether; polyhydric alcohol aryl ethers such as ethylene glycol monophenyl ether and ethylene glycol monobenzyl ether Nitrogen-containing heterocyclic compounds such as 2-pyrrolidone, N-methyl-2-pyrrolidone, N-hydroxyethyl-2-pyrrolidone, 1,3-dimethylimidazolidinone, ε-caprolactam, γ-butyrolactone; formamide, N -Methylformamide, N, N-dimethylformamide, N, N-dimethyl-β-methoxypropionamide, N, N-dimethyl-β-butoxypropionamide, etc. Amides; Amines such as monoethanolamine, diethanolamine, triethanolamine, monoethylamine, diethylamine, triethylamine; sulfur-containing compounds such as dimethyl sulfoxide, sulfolane, thiodiethanol; 3-ethyl-3-hydroxymethyloxetane, propylene carbonate , Ethylene carbonate, and the like. These may be used alone or in combination of two or more.

Among these, 3-ethyl-3-hydroxymethyloxetane, isopropylideneglycerol, N, N-dimethyl-β-methoxypropionamide, N, N-dimethyl-β-butoxypropionamide from the viewpoint of curling prevention in plain paper Is particularly preferred.
In addition, 1,3-butanediol, diethylene glycol, 2,2,4-trimethyl-1,3-pentanediol, triethylene glycol, and glycerin are excellent in preventing ejection failure due to water evaporation.
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)] and the like.

As other polyol compounds, as aliphatic diols, for example, 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 ink and adjusted to desired physical properties, and can be appropriately selected according to the purpose. Examples thereof include alkyls and aryls of polyhydric alcohols such as diethylene glycol monophenyl ether, ethylene glycol monophenyl ether, ethylene glycol monoallyl ether, diethylene glycol monophenyl ether, diethylene glycol monobutyl ether, propylene glycol monobutyl ether, and tetraethylene glycol chlorophenyl ether. And ethers, lower alcohols such as ethanol, and the like.

In addition, saccharides can be contained as a wetting agent that is not a water-soluble organic solvent. Examples of the saccharide include monosaccharides, disaccharides, oligosaccharides (including trisaccharides and tetrasaccharides), and polysaccharides. 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 a substance that exists widely in nature such as α-cyclodextrin and cellulose. The derivatives of these saccharides are represented by the reducing sugars of the saccharides described above [for example, sugar alcohol [general formula: HOCH ₂ (CHOH) _n CH ₂ OH (where n represents an integer of 2 to 5)). The ], Oxidized sugars (eg, aldonic acid, uronic acid, etc.), amino acids, thioic acids and the like. Among these, sugar alcohol is preferable, and examples of the sugar alcohol include maltitol and sorbit.

The ratio of the pigment and the water-soluble organic solvent greatly affects the ejection stability of the ink from the head when used as an inkjet recording ink. 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 progress and cause ejection failure.
The content of the water-soluble organic solvent in the ink is not particularly limited and may be appropriately selected depending on the intended purpose, but is preferably 10 to 60% by weight, and more preferably 20 to 60% by weight. When the content is 10% by weight or more, ink ejection stability can be secured, and when the content is 60% by weight or less, the drying property is improved. The ink having the content in the more preferable range has an advantage that drying property and ejection reliability are very good.

<Other ingredients>
The other components used in the ink of the present invention are not particularly limited and may be appropriately selected as necessary. For example, a surfactant, a pH adjuster, a water-dispersible resin, an antiseptic / antifungal agent, and a rust inhibitor , Antioxidants, ultraviolet absorbers, oxygen absorbers, light stabilizers, and the like.

-Surfactant-
There is no restriction | limiting in particular as said surfactant, According to the objective, it can select suitably, Anionic surfactant, cationic surfactant, nonionic surfactant, amphoteric surfactant, fluorine-type surfactant , Etc. Among these, nonionic surfactants and fluorine surfactants are particularly preferable.
Examples of the anionic surfactant include alkyl allyl sulfonate, alkyl naphthalene sulfonate, alkyl phosphate, alkyl sulfate, alkyl sulfonate, alkyl ether sulfate, alkyl sulfosuccinate, alkyl ester sulfate. Salt, alkylbenzene 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 phosphorus Acid salt, polyoxyethylene alkyl ether sulfate ester salt, ether carboxylate, sulfosuccinate, α-sulfo fatty acid ester, fatty acid salt, condensation of higher fatty acid and amino acid , Naphthenic acid salts, 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, Etc.
Examples of the nonionic surfactant include acetylene glycol surfactants, polyoxyethylene alkyl ethers, polyoxyethylene alkyl phenyl ethers, polyoxyethylene alkyl esters, polyoxyethylene sorbitan fatty acid esters, and the like.
Examples of the amphoteric surfactant include imidazoline derivatives such as imidazolinium betaine, dimethylalkyl lauryl betaine, alkyl glycine, alkyl di (aminoethyl) glycine, and the like.

（上記式中、ｍは、０〜１０の整数を表す。ｎは、１〜４０の整数を表す。）

（上記式中、Ｒｆはフッ素含有基を表し、ｍ、ｎ、及びｐは整数を表す。）
前記フッ素含有基としてはパーフルオロアルキル基が好ましく、特に炭素数が１〜１０のものが好ましく、炭素数１〜３のものがより好ましい。その例としては、Ｃ_jＦ_２j−１（ただし、jは１〜１０の整数を表す）が挙げられ、具体例としては、ＣＦ_３、ＣＦ_２ＣＦ_３、Ｃ_３Ｆ_７、Ｃ_４Ｆ_９、などが挙げられる。これらの中でも、ＣＦ_３、ＣＦ_２ＣＦ_３が特に好ましい。また、ｎは１〜４、ｍは６〜２５、ｐは１〜４が好ましい。 Examples of the fluorosurfactant include materials represented by the following general formulas (I) to (III).

(In the above formula, m represents an integer of 0 to 10. n represents an integer of 1 to 40.)

(In the above formula, Rf represents a fluorine-containing group, and m, n, and p represent integers.)
The fluorine-containing group is preferably a perfluoroalkyl group, particularly preferably having 1 to 10 carbon atoms, and more preferably having 1 to 3 carbon atoms. Examples thereof include C _j F _2j-1 (where j represents an integer of 1 to 10), and specific examples include CF ₃ , CF ₂ CF ₃ , C ₃ F ₇ , C ₄ F _9. , Etc. Among these, CF ₃ and CF ₂ CF ₃ are particularly preferable. N is preferably 1-4, m is preferably 6-25, and p is preferably 1-4.

（上記式中、Ｒｆはフッ素含有基を表し、ｑは整数を表す。）
前記フッ素含有基としては、前記一般式（II）と同様のパーフルオロアルキル基が好ましく、例えば、ＣＦ_３、ＣＦ_２ＣＦ_３、Ｃ_３Ｆ_７、Ｃ_４Ｆ_９などが挙げられる。Ｒ_２ ^＋はカチオン基を表し、例えば、第４級アンモニウム基；ナトリウム、カリウム等のアルカリ金属イオン；トリエチルアミン、トリエタノールアミン、などが挙げられる。これらの中でも、第４級アンモニウム基が特に好ましい。Ｒ_１ ⁻はアニオン基を表し、例えば、ＣＯＯ⁻、ＳＯ_３ ⁻、ＳＯ_４ ⁻、ＰＯ_４ ^―、などが挙げられる。ｑは、１〜６が好ましい。

(In the above formula, Rf represents a fluorine-containing group, and q represents an integer.)
The fluorine-containing group is preferably a perfluoroalkyl group similar to the general formula (II), and examples thereof include CF ₃ , CF ₂ CF ₃ , C ₃ F ₇ , and C ₄ F ₉ . R ₂ ⁺ represents a cationic group, and examples thereof include quaternary ammonium groups; alkali metal ions such as sodium and potassium; triethylamine, triethanolamine, and the like. Among these, a quaternary ammonium group is particularly preferable. R ₁ ⁻ represents an anionic group, and examples thereof include COO ⁻ , SO ₃ ⁻ , SO ₄ ⁻ and PO ₄ ⁻ . q is preferably 1-6.

As said fluorosurfactant, what was synthesize | combined suitably may be used and a commercial item 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.); FC-93, FC-95, FC-98, FC-129, FC-135, FC-170C, FC-430, FC-431 (all manufactured by Sumitomo 3M); Megafac F-470, F1405, F -474 (all manufactured by DIC); 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); PF-151N (Solutions Corporation) Manufactured by de Corporation); UNIDYNE DSN-403N (manufactured by Daikin Industries, Ltd.) and the like. Among these, Zonyl FS-300, FSN, FSN-100, FSO (all manufactured by DuPont) and Unidyne DSN-403N (manufactured by Daikin Industries) are particularly preferable from the viewpoint of improving reliability and color developability.

  The content of the surfactant in the ink is not particularly limited and may be appropriately selected depending on the intended purpose, but is preferably 0.01 to 5.0% by weight, more preferably 0.5 to 3% by weight. . When the content is 5.0% by weight or less, the permeability to the recording medium is good, and the reduction of the image density and the occurrence of show-through can 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 ink to be prepared, and can be appropriately selected according to the purpose.
Examples thereof include alcohol amines, alkali metal 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 alkali metal hydroxide include lithium hydroxide, sodium hydroxide, and potassium hydroxide.
Examples of the ammonium hydroxide include ammonium hydroxide and quaternary ammonium hydroxide.
Examples of the phosphonium hydroxide include 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 has high water resistance and high image density (high color development). Useful for.
Examples thereof include condensation-type synthetic resins, addition-type synthetic resins, natural polymer compounds, and the like.
Examples of the condensed synthetic resin include polyester resin, polyurethane resin, polyepoxy resin, polyamide resin, polyether resin, poly (meth) acrylic resin, acrylic-silicone resin, and fluorine-based resin.
Examples of the addition type synthetic resin include polyolefin resins, polystyrene resins, polyvinyl alcohol resins, polyvinyl ester resins, polyacrylic acid resins, unsaturated carboxylic acid resins, and the like.
Examples of the natural polymer compound include celluloses, rosins, natural rubber, and the like.
Among these, polyurethane resin fine particles, acrylic-silicone resin fine particles, and fluorine-based resin fine particles are preferable.

The average particle size (D50) of the water-dispersible resin is related to the viscosity of the dispersion, and for the same composition, the viscosity at the same solid content increases as the particle size decreases.
The average particle diameter (D50) of the water-dispersible resin is not particularly limited and can be appropriately selected according to the purpose, but is preferably 50 nm or more so that the ink does not have an excessively high viscosity.
Further, when the particle diameter is several tens of μm, it cannot be used because it becomes larger than the nozzle opening of the ink jet head, and if particles having a large particle diameter exist in the ink even if smaller than the nozzle opening, the ejection stability is deteriorated. Therefore, the average particle diameter (D50) is more preferably 200 nm or less in order not to impair ink ejection stability.

The water-dispersible resin preferably has a function of fixing the water-dispersible colorant on the paper surface, and has a function of forming a film at room temperature to improve the fixability of the color material.
Therefore, the minimum film forming temperature (MFT) of the water dispersible resin is preferably 30 ° C. or less.
In addition, when the glass transition temperature of the water-dispersible resin is -40 ° C or lower, the resin film becomes more viscous and the printed matter is tacked. Therefore, the glass transition temperature is preferably about -30 ° C or higher.
The content of the water-dispersible resin in the ink is not particularly limited and may be appropriately selected depending on the intended purpose. However, the solid content is preferably 1 to 15% by weight, and more preferably 2 to 7% by weight.

-Antiseptic and fungicide-
Examples of the antiseptic / antifungal agent include sodium dehydroacetate, sodium sorbate-2-pyridinethiol-1-oxide sodium, sodium benzoate, sodium pentachlorophenol, and the like.
-Antirust agent-
Examples of the rust preventive agent include acidic sulfite, sodium thiosulfate, ammonium thiodiglycolate, diisopropylammonium nitrite, pentaerythritol tetranitrate, dicyclohexylammonium nitrite, and the like.
-Antioxidant-
Examples of the antioxidant include phenolic antioxidants (including hindered phenolic antioxidants), amine-based antioxidants, sulfur-based antioxidants, phosphorus-based antioxidants, and the like.
-UV absorber-
Examples of the ultraviolet absorber include benzophenone ultraviolet absorbers, benzotriazole ultraviolet absorbers, salicylate ultraviolet absorbers, cyanoacrylate ultraviolet absorbers, and nickel complex salt ultraviolet absorbers.

<Use of ink>
The ink of the present invention can be used for inkjet recording, spray coating, relief printing, intaglio printing, stencil printing, writing instruments, stamps, and the like, and is particularly suitable for inkjet recording.

<Ink cartridge>
The ink cartridge of the present invention contains the ink in a container and further includes other members appropriately selected as necessary.
The container is not particularly limited, and its shape, structure, size, material, etc. can be appropriately selected according to the purpose. For example, the container has an ink bag formed of an aluminum laminate film, a resin film, etc. , Etc. are preferred.
The ink cartridge will be described with reference to FIGS.
FIG. 1 is a diagram illustrating an example of an 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 ink from the ink inlet 242 and exhausts it, and then closes the ink inlet 242 by fusing. In use, the needle of the apparatus main body is pierced into the ink discharge port 243 made of a rubber member and supplied to the apparatus. The ink bag 241 is formed of a packaging member such as a non-permeable aluminum laminate film. As shown in FIG. 2, it is usually housed in a plastic cartridge case 244 and used as an ink cartridge 200 detachably mounted on various ink jet recording apparatuses.

  EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated further more concretely, this invention is not limited by these Examples. In the examples, “parts” and “%” are “parts by weight” and “% by weight” unless otherwise specified, including those in Table 1. The numerical values in Tables 2 and 3 are also “parts by weight”.

<Molecular weight measurement of copolymer>
The molecular weights of the copolymers obtained in the examples and comparative examples were determined as follows.
Using GPC (Gel Permeation Chromatography), 1 mL of a 0.5% concentration copolymer was injected, and the molecular weight was measured under the following conditions.
-Equipment: GPC-8020 (manufactured by Tosoh Corporation)
Column: TSK G2000HXL and G4000HXL (manufactured by Tosoh Corporation)
・ Temperature: 40 ℃
・ Solvent: THF (tetrahydrofuran)
・ Flow rate: 1.0 mL / min

Subsequently, from the molecular weight distribution of the copolymer obtained by measurement, the weight average molecular weight Mw and the number average molecular weight Mn of the copolymer were calculated using a molecular weight calibration curve prepared with a monodisperse polystyrene standard sample.

[Example 1]
--Synthesis of copolymer CP-1--
(Synthesis of Monomer M-1)
27.2 parts of 2-hydroxyethyl methacrylate, 71.6 parts of methylenediphenyl-4,4'-diisocyanate, and 41.2 parts of 2-naphthol are put into a reaction vessel, and mixed in a mixed solvent of 550 parts of 2-butanone and 250 parts of toluene. It was dissolved by heating. Thereto was added 0.15 part of dibutyldilauryltin, and the mixture was reacted at 60 ° C. for 3 hours, then returned to room temperature, diluted with 300 parts of toluene, and then filtered to obtain colorless crystals. Further, 1000 parts of n-hexane was added to the filtrate, and the precipitated colorless crystals were collected by filtration. The obtained crystals were combined and 1200 parts of acetone was added and dissolved by stirring. Insoluble matter was removed by filtration, and 1500 parts of n-hexane was added for precipitation. The precipitate was collected by filtration to obtain 63.5 parts of a coarse product. Next, the mixture was further purified by chromatography on silica gel using a mixture of toluene and ethyl acetate (volume ratio 5: 1) as a developing solvent to obtain 50.8 parts of [monomer M-1] as the target product.

(Synthesis of copolymer CP-1: Synthesis example 1)
A monomer solution was prepared by dissolving 18.0 parts of acrylic acid (AA) and 82.0 parts of [Monomer M-1] in 30 mL of dry methyl ethyl ketone.
After heating 10% of the monomer solution to 75 ° C. under an argon stream, a solution obtained by dissolving 3.9 parts of a polymerization initiator 2,2′-azoisobutyronitrile (AIBN) in the remaining monomer solution was 1. The solution was added dropwise over 5 hours and stirred at 75 ° C. for 6 hours. Subsequently, it cooled to room temperature and thrown the obtained reaction solution into hexane. The precipitated copolymer was filtered off and dried under reduced pressure to obtain 97.9 parts of [Copolymer CP-1] (Mw: 23000).

--Preparation of pigment dispersion PD-1--
[Copolymer CP-1] 4.0 parts was dissolved in an aqueous tetraethylammonium hydroxide (TEAOH) solution so that the copolymer concentration was 2.5% and pH 8.0, and the resulting aqueous solution 84 was obtained. To this part, 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 (Shinmaru Enterprises Co., Ltd., KDL type, media: zirconia balls having a diameter of 0.1 mm). The mixture was filtered through a 2 μm membrane filter, and an adjusted amount of pure water was added to obtain 97.0 parts of [Pigment dispersion PD-1] (pigment solid content concentration: 16%).

--- Preparation of ink GJ-1--
[Pigment Dispersion PD-1] 40.0 parts, 10.0 parts of glycerin, 20.0 parts of 1,3-butanediol, 1.0 part of 2-ethyl-1,3-hexanediol, 2,2,4 -1.0 part of trimethyl-1,3-pentanediol, 1.0 part of Unidyne DSN-403N (manufactured by Daikin Industries) and 27.0 parts of pure water were mixed and stirred for 1 hour, and then the pore diameter was 1.2 μm. [Ink GJ-1] of the present invention.

[Examples 2 to 26]
(Synthesis of monomers M-2 to 5)
In order to synthesize M-2 to 5 instead of methylenediphenyl-4,4′-diisocyanate in the synthesis of the monomer M-1, the same procedure was performed except that the following diisocyanates were used [Monomer M-2 to 5] was obtained.
For M-2: m-xylylene diisocyanate (XDI)
For M-3: m-phenylenebis (1-methylethane-1,1-diyl) diisocyanate (TMXID)
For M-4: Naphthalene-1,5-diyl diisocyanate (NDI)
For M-5: 2,4-tolylene diisocyanate (TDI)

(Synthesis of copolymer CP-2 to 21: Synthesis examples 2 to 21)
The monomer and the number of parts in the synthesis of the copolymer CP-1 are changed to the monomers M-2 to 5, the anionic monomer, other monomers and the parts shown in the respective columns of Synthesis Examples 2 to 21 in Table 1, and AIBN and chain [Copolymer CP-2 to 21] was obtained in the same manner except that the transfer modifier thioglycerol was used as shown in the above-mentioned columns and the polymerization temperatures shown in Table 1 were used.
Mw of each copolymer is as shown in Table 1. In the column of anionic monomer in Table 1, AA is acrylic acid, and MAA is methacrylic acid.

(Preparation of pigment dispersion PD-2 to 26)
The pH adjuster in the preparation of the pigment dispersion PD-1 was changed to that shown in each column of Synthesis Examples 2 to 21 in Table 1, and the types and blending amounts of the copolymer and the pigment were changed from PD-2 to Table 2 in Table 2. [Pigment dispersion PD-2 to 26] were obtained in the same manner except that the points were changed as indicated in each column of No. 26.
In Table 1, TEAOH is tetraethylammonium hydroxide, NaOH is sodium hydroxide, and DEA is diethanolamine.

(Preparation of inks GJ-2 to 26)
Except that the pigment dispersion, the water-soluble solvent, and the surfactant were used in the preparation of the ink GJ-1, and the types and amounts thereof were changed as shown in the columns of Examples 2 to 26 in Table 3. Thus, [inks GJ-2 to 26] were obtained.

次いで、前記顔料分散体ＰＤ−１の調製における共重合体ＣＰ−１に代えて、共重合体ＲＣＰ−１を用いた点以外は同様にして、顔料分散体ＲＰＤ−１を得た。
次いで、前記インクＧＪ−１の作製における顔料分散体ＰＤ−１に代えて、顔料分散体ＲＰＤ−１を用いた点以外は同様にして、比較例１の［インクＲＧＪ−１］を得た。 [Comparative Example 1; Preparation of Ink RGJ-1]
Copolymer RCP-1 (Mw: 7500, Mn: 2800) 4 except that the monomer M-1 in the synthesis of the copolymer CP-1 was changed to the monomer of the following structural formula (7). .82 g was obtained.

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

[Comparative Examples 2 to 4; Preparation of Ink RGJ-2 to 4]
Instead of the copolymer CP-1 in the preparation of the pigment dispersion PD-24 to 26, a copolymer RCP-1 was used, the amount of the copolymer was 4.0 parts, and the amount of the pigment was 76. Pigment dispersions RPD-2 to 4 were obtained in the same manner except for changing to 0.0 parts.
Next, in place of the pigment dispersion PD-24 to 26 in the production of the ink GJ-24 to 26, the same procedure as in Comparative Examples 2 to 4 was performed except that the pigment dispersion RPD-2 to 4 was used. RGJ-2-4] were obtained.

[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, 0.3 g of 2,2-azobis (2,4-dimethylvaleronitrile) as an initiator are dissolved in 160 mL of THF, Under a nitrogen atmosphere, the mixture was heated to 65 ° C. and reacted for 7 hours. The obtained solution was allowed to cool, 80 mg of dibutyltin dilaurate (IV) and a catalytic amount of hydroquinone were added, and 10.0 g of 2-methacryloyloxyethyl isocyanate was added dropwise. Next, the temperature was raised to 50 ° C. and reacted for 2.5 hours, and then purified by reprecipitation with a mixed solvent of methanol and water to obtain 71 g of macromonomer MM-1 (Mw: 4000, Mn: 1900). .
Next, 20 g of methyl ethyl ketone was heated to 75 ° C. under a nitrogen atmosphere, and then 40 g of methyl ethyl ketone was added to 1.16 g of dimethyl-2,2′-azobisisobutyrate, 9 g of macromonomer MM-1, 1.8 g of A solution in which p-styrenesulfonic acid and 49.2 g of methyl methacrylate were dissolved was dropped over 3 hours. Next, after further reacting for 1 hour, a solution of 0.2 g of dimethyl-2,2′-azobisisobutyrate dissolved in 0.6 g of methyl ethyl ketone was added, the temperature was raised to 80 ° C., and the mixture was stirred for 4 hours. did. Further, a solution of 0.2 g of dimethyl-2,2′-azobisisobutyrate dissolved in 0.6 g of methyl ethyl ketone was added and stirred for 6 hours with heating. Next, the mixture was cooled, and the resulting reaction solution was added to hexane, and the precipitated graft polymer was filtered and dried to obtain a copolymer RCP-2.
Next, a pigment dispersion RPD-5 was obtained in the same manner except that the copolymer RCP-2 was used instead of the copolymer CP-1 in the preparation of the pigment dispersion PD-1.
Next, [Ink RGJ-5] was obtained in the same manner except that Pigment Dispersion RPD-5 was used instead of Pigment Dispersion PD-1 in the preparation of Ink GJ-1.

[Comparative Example 6; Preparation of Ink RGJ-6]
(Synthesis of monomer of structural formula X)
72.0 g (500 mmol) of 2-naphthol and 125.0 g (1000 mmol) of ethylene glycol-mono-2-chloroethyl ether were dissolved in 500 mL of N-methyl-2-pyrrolidinone and stirred at room temperature for 1 hour. Furthermore, after stirring at 110 degreeC for 10 hours, it cooled to room temperature, 2500 mL of pure waters were added to the obtained reaction solution, and it stirred at room temperature for 1 hour. The precipitated solid was filtered off and dried under reduced pressure.
70.0 g of the solid obtained in the above reaction and 45.0 g (450 mmol) of triethylamine were dissolved in 250 mL of tetrahydrofuran and stirred for 30 minutes in an ice bath. 36.6 g (350 mmol) of methacryloyl chloride was slowly added dropwise thereto, and the mixture was further stirred for 3 hours in an ice bath. To the obtained solution, 250 mL of ethyl acetate and 100 mL of pure water were added and washed with water. Next, the ethyl acetate layer was isolated and washed with a saturated saline solution. The ethyl acetate layer was isolated and 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 of the following structural formula X.

(Synthesis of copolymer RCP-3)
In a 100 mL three-necked flask equipped with a stirrer and a condenser, 12.0 g of methyl ethyl ketone was placed and heated to 72 ° C. under an argon stream. Next, to 6.0 g of methyl ethyl ketone, 2.4 g (8.00 mmol) of the monomer of the above structural formula X, 1.2 g (13.9 mol) of methacrylic acid, 8.4 g (47.6 mmol) of benzyl methacrylate, 2,2 ′ -A solution in which 0.128 g (0.56 mmol) of azobis (isobutyric acid) dimethyl was dissolved was added dropwise over 3 hours. After completion of the dropwise addition, the mixture was further reacted for 1 hour, and a solution prepared by dissolving 0.06 g (0.26 mmol) of 2,2′-azobis (isobutyric acid) dimethyl in 2.0 g of methyl ethyl ketone was added and heated to 78 ° C. for 4 hours. Stir. Then, reprecipitation was repeated 5 times using hexane, and the copolymer was purified. Subsequently, the copolymer was separated by filtration and dried under reduced pressure to obtain 311.6 g of a copolymer RCP (yield: 96.6%, Mn: 16,200, Mw: 34000).

(Preparation of aqueous solution for pigment dispersion of copolymer RCP-3)
Next, 4.0 g of copolymer RCP-3 was added to a mixed solution of 1.9 g of 35% aqueous solution of tetraethylammonium hydroxide, 50.0 g of 3-methoxy-N, N′-dimethylpropionamide, and 28.1 g of pure water. By dissolving, an aqueous solution for dispersing the pigment of the copolymer RCP-3 was prepared.

(Preparation of pigment dispersion RPD-6)
To an aqueous solution of 84.0 parts of 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 for 1 hour at a peripheral speed of 10 m / s using a disk-type bead mill (Shinmaru Enterprises Co., Ltd., KDL type, media: using zirconia balls with a diameter of 0.1 mm), and then the pore size was 1 The mixture was filtered through a 2 μm membrane filter, and an adjusted amount of pure water was added to obtain 95.0 parts of pigment dispersion RPD-6 (pigment solid content concentration: 16%).

(Preparation of ink RGJ-6)
45.0 parts of pigment dispersion RPD-6, 10.0 parts of 1,3-butanediol, 10.0 parts of glycerol, 1.0 part of Unidyne DSN-403N (manufactured by Daikin Industries, Ltd., solid content 100%), and 34.0 parts of pure water was mixed and stirred for 1 hour, and then filtered through a membrane filter having a pore size of 1.2 μm to obtain [Ink RGJ-6].

The storage stability of the pigment dispersions according to the above Examples and Comparative Examples was measured and evaluated as follows.

<Storage stability of pigment dispersion>
Each pigment dispersion was filled in a glass container and stored at 70 ° C. for 2 weeks. The rate of change in viscosity after storage with respect to the viscosity before storage was determined from the following formula and evaluated according to the following criteria. C or higher is practical.
For measurement of the viscosity, a viscometer (RE80L, manufactured by Toki Sangyo Co., Ltd.) was used, and the viscosity at 25 ° C. was measured at 50 revolutions.
Viscosity change rate (%) = [(viscosity of pigment dispersion after storage−viscosity of pigment dispersion before storage)
/ Viscosity of pigment dispersion before storage] × 100

〔Evaluation criteria〕
A: Change rate of viscosity is within ± 5% B: Change rate of viscosity exceeds ± 5% and within ± 8% C: Change rate of viscosity exceeds ± 8% and within ± 10% D: Change in viscosity Rate exceeds ± 10% and within ± 30% E: Viscosity change rate exceeds ± 30% (cannot be evaluated due to gelation)

The physical properties of the inks of the above examples and comparative examples were measured and evaluated as follows.

<Ink storage stability>
Each ink was filled in an ink cartridge and stored at 70 ° C. for 1 week. The change rate of the viscosity after storage with respect to the viscosity before storage was obtained from the following formula and evaluated according to the following criteria. C or higher is practical.
For measurement of the viscosity, a viscometer (RE80L, manufactured by Toki Sangyo Co., Ltd.) was used, and the viscosity at 25 ° C. was measured at 50 revolutions.
Viscosity change rate (%) = [(Viscosity of ink after storage−Ink viscosity before storage)
/ Ink viscosity before storage] × 100

〔Evaluation criteria〕
A: Change rate of viscosity is within ± 5% B: Change rate of viscosity exceeds ± 5% and within ± 8% C: Change rate of viscosity exceeds ± 8% and within ± 10% D: Change in viscosity Rate exceeds ± 10% and within ± 30% E: Viscosity change rate exceeds ± 30% (cannot be evaluated due to gelation)

<Image density>
General symbols of 64 points JIS X 0208 (1997), 2223 created by Microsoft Word 2000 (Microsoft), each ink filled in an ink jet printer (Ricoh, IPSiO GX5000) in an environment of 23 ° C. and 50% RH Is printed on plain paper 1 (XEROX 4200, manufactured by XEROX) and plain paper 2 (MyPaper, manufactured by Ricoh), and the symbol part on the printed surface is printed by X-Rite 938 (manufactured by X-Rite). The color was measured and evaluated according to the following criteria. C or higher is practical.
As the print mode, a mode in which the “plain paper-standard fast” mode is changed to “no color correction” from the user setting of plain paper by a driver attached to the printer.
Note that JIS X 0208 (1997), 2223 is a symbol whose outer shape is a regular square and the entire surface of the symbol is filled with ink.

〔Evaluation criteria〕
A: 1.25 or more B: 1.20 or more, less than 1.25 C: 1.10 or more, less than 1.20 D: less than 1.10 E: The pigment gels and cannot be dispersed in the ink and cannot be printed.

As can be seen from the above results, the pigment dispersions prepared using the copolymers having the naphthyl group at the end of the side chain according to the present invention in Examples 1 to 26 are the side chain of Comparative Examples 1 to 5. Compared to a pigment dispersion prepared using a copolymer having no naphthyl group at the terminal, it had excellent storage stability. This is presumably because the adsorptivity to the pigment was increased by the π-π interaction between the naphthyl group of the copolymer and the pigment.
In addition, when a copolymer having a structural unit different from the structural unit of the general formula (1) is used in that it has a naphthyl group at the end of the side chain, a sufficient amount of ink Storage stability cannot be obtained, and it is difficult to ensure stable quality over a long period of time. (See Comparative Example 6)

200 Ink cartridge 241 Ink bag 242 Ink inlet 243 Ink outlet 244 Cartridge case

Japanese Patent No. 5001291 Japanese Patent No. 4956666 Japanese Patent No. 2867491 Japanese Patent No. 4687110 JP 2008-536963 A JP 2012-52027 A Japanese Patent No. 4722462 JP 2011-105866 A

Claims (6)

An ink comprising water, a coloring material, and a copolymer, wherein the copolymer has a structural unit represented by the general formula (1) and a structural unit having an anionic group.
General formula (1)

(In the above formula, R represents a hydrogen atom or a methyl group, X represents an alkylene group having 2 to 4 carbon atoms, Y represents a hydrocarbon group containing an aromatic ring, and the carbon number of the hydrocarbon group is a substituent. Including 6 to 15)   The ink according to claim 1, wherein the structural unit having an anionic group has a carboxyl group.   The ink according to claim 1 or 2, wherein the content of the structural unit represented by the general formula (1) in the copolymer is 75 to 90% by weight.   The ink according to any one of claims 1 to 3, wherein the copolymer has a weight average molecular weight of 15,000 to 40,000. In the method for producing an ink containing water, a coloring material, and a copolymer, radical polymerization of a polymerizable material in which the copolymer includes at least a monomer represented by the general formula (2) and a monomer having an anionic group A method for producing ink, comprising the step of:
General formula (2)

(In the above formula, R represents a hydrogen atom or a methyl group, X represents an alkylene group having 2 to 4 carbon atoms, Y represents a hydrocarbon group containing an aromatic ring, and the carbon number of the hydrocarbon group is a substituent. Including 6 to 15)   An ink cartridge containing the ink according to claim 1 in a container.

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