JP6331794B2 - Ink for inkjet recording - Google Patents

Description

  The present invention relates to an ink for ink jet recording (hereinafter sometimes simply referred to as “ink”) ink cartridge and recording apparatus.

  The inkjet recording method is popular because it has the advantage that the process is simpler than other recording methods, full color is easy, and even high-resolution images can be obtained even with a simple configuration. Have been doing. In this ink jet recording method, a small amount of ink is ejected by pressure generated using bubbles generated by heat, piezo or electrostatic, and the ink is attached to a recording medium such as paper and dried quickly (or recording). This is a method of forming an image by infiltrating the medium). This ink jet recording system has been expanded in use to personal and industrial printers and printing.

In such an ink jet recording system, a water-based ink using a water-soluble dye as a colorant is mainly used. However, the dye ink has a defect that it is inferior in weather resistance and water resistance. For this reason, research on pigment inks that use water-insoluble pigments instead of water-soluble dyes is underway. However, the pigment ink is still inferior in color development, ink ejection stability, and storage stability to the dye ink.
In addition, with the improvement of image quality improvement technology of OA printers, high image density is required even when plain paper is used as a recording medium in pigment ink. However, when the plain ink is used as the recording medium, the pigment ink has a problem that the pigment density on the paper surface is lowered by permeating into the paper and the image density is lowered.

  In recent years, the demand for industrial applications has increased, and high-speed printing is desired. An ink jet printer equipped with a line head has been proposed along with such high-speed printing. In order to achieve high-speed printing, in order to increase the drying speed of the ink adhering to the recording medium, means for increasing the drying speed by adding a penetrant to the ink and allowing water to penetrate into the recording medium has been tried. In addition to this, there is a problem that the permeability of the pigment into the recording medium is increased and the image density is lowered.

In addition, when plain paper is used as a recording medium, there is a problem that immediately after printing, the surface of the plain paper is swollen by water as an ink solvent, the difference in elongation between the front and back is increased, and curling occurs. Since such a phenomenon disappears as the drying progresses, there was no problem in low-speed printing.
However, with the increase in printing speed, it is necessary to transport the recording medium without eliminating curling after printing, which may cause a paper jam problem. As for curling, a means for increasing the content of the organic solvent in the ink is effective, but since the ink is more hydrophobic, it is difficult to ensure the storage stability of the ink.

  In order to solve the above problems, for example, an ink-jet ink composition containing a liquid vehicle, a colorant, and a polymer having at least one functional group having a specific calcium index value has been proposed (see Patent Document 1). In this proposal, 4-methacrylamide-1-hydroxybutane-1,1-diphosphonic acid is shown as a monomer constituting the polymer, and when the colorant comes into contact with the paper, the diphosphonic acid group of the polymer and the paper It is said that the printed image can be improved by making it unstable with the Ca salt therein.

  In addition, an ink jet recording method has been proposed in which a receiving liquid containing a Ca salt is attached to paper, and an ink containing a pigment having a phosphorus-containing group bonded thereto, a resin emulsion, and a surfactant is printed (see Patent Document 2). This proposal describes that bisphosphonic acid is preferable as the phosphorus-containing group, and describes that the Ca salt of the receiving solution reacts with the phosphorus-containing group and has an effect of improving feathering and fixing properties. Yes. However, in the proposed technique, a phosphonic acid group-containing polymer is not used as a dispersant and an additive for a pigment dispersion, but a pigment bonded with phosphoric acid is used, and an image when recorded on plain paper is used. The effect of increasing the concentration is not sufficient. In addition, in the case of this method, since it is necessary to chemically modify the pigment surface in advance, there is a problem that versatility in pigment selection is low.

Further, an aqueous ink containing a colorant, water, a water-soluble organic solvent, a surfactant, and a chelating agent has been proposed (see Patent Document 3). In this proposal, hydroxyethylidene diphosphonic acid or a salt thereof, which is a low molecular compound, is used as the chelating agent. The chelating agent is said to be able to remove calcium and the like contained in a dispersion such as a pigment and improve discharge stability and storage stability. However, the proposal only describes a low molecular weight compound, hydroxyethylidene diphosphonic acid, and does not describe a polymer containing phosphonic acid, and improves the image density when recorded on a chelating agent and plain paper. It also does not describe the relationship with effects.
Therefore, it is desired to provide an ink for ink jet recording using a general-purpose pigment, which can obtain a high image density even when recorded on plain paper, has excellent storage stability even when the content of the water-soluble organic solvent is increased. ing.

An object of the present invention is to solve the above-described problems and achieve the following objects.
That is, an object of the present invention is to provide an ink for ink jet recording which can obtain a high image density and has excellent storage stability even when a pigment without chemical modification of a phosphorus-containing group is used.

  The ink for ink jet recording of the present invention as means for solving the above problems is (1) “an ink for ink jet recording having a copolymer containing at least water, a water-soluble solvent, a pigment, and a salt of a diphosphonic acid group”. The copolymer containing the salt of the diphosphonic acid group has at least a structural unit (1) represented by the following general formula (1) and a structural unit (2) represented by the general formula (2). Ink for inkjet recording, characterized by

(R ₁ in the general formula (1) represents a hydrogen atom or a methyl group, and M + represents an alkali metal ion, an organic ammonium ion or a proton. However, an alkali metal and a proton and an organic ammonium ion and a proton are mixed. More than half of M + in the copolymer is an alkali metal ion or an organic ammonium ion, and X in the general formula (1) represents an alkylene group having 1 to 3 carbon atoms.)

(R ₂ in the general formula (2) represents a hydrogen atom or a methyl group, and Z ₁ represents a hydrocarbon group having 6 to 22 carbon atoms).

  According to the present invention, the conventional problems can be solved, the object can be achieved, a high image density can be obtained even when a pigment without chemical modification of a phosphorus-containing group is used, and the storage stability is excellent. Ink for ink jet recording can be provided.

FIG. 3 is a schematic plan view for explaining an example of the ink container of the present invention. FIG. 2 is a schematic plan view including a case (exterior) of the ink container of the present invention shown in FIG. 1. 1 is a perspective view showing an example of a serial type ink jet recording apparatus of the present invention. FIG. 4 is a partially enlarged sectional view of the ink jet recording apparatus shown in FIG. 3. FIG. 4 is another partially enlarged cross-sectional view of the ink jet recording apparatus shown in FIG. 3.

Hereinafter, the present invention will be described in detail.
As described above, the present invention includes "a copolymer containing at least water, a water-soluble solvent, a pigment, and a salt of a diphosphonic acid group, wherein the copolymer containing the salt of the diphosphonic acid group includes: This relates to an ink for inkjet recording having at least the structural unit (1) represented by (1) and the structural unit (2) represented by the general formula (2). The “ink-jet recording ink” further includes “ink-jet recording ink” having an aspect as described in the following (2) to (7). Further, the present invention also includes the “ink cartridge” and the “inkjet recording apparatus” described in the following (8) to (9) using such “inkjet recording ink”. The “ink-jet recording ink”, “ink cartridge”, and “ink-jet recording apparatus” described in (2) to (9) will also be described in detail.
(2) In the inkjet recording ink having a copolymer containing at least water, a water-soluble solvent, a pigment, and a salt of a diphosphonic acid group, the copolymer containing the salt of the diphosphonic acid group has at least the following general formula ( An ink for inkjet recording, which is a radical copolymer including a portion derived from the monomer represented by 4) and a portion derived from the monomer represented by the general formula (5);

(R ₁ in the general formula (4) represents a hydrogen atom or a methyl group, M + represents an alkali metal ion, an organic ammonium ion, or a proton. X in the general formula (4) has 1 to 3 carbon atoms. Represents an alkylene group of

(R ₂ in the general formula (5) represents a hydrogen atom or a methyl group, and Z ₂ represents a hydrocarbon group having 6 to 22 carbon atoms). "
(3) “Z _{1 in} the structural unit (2) of the general formula (2) in the copolymer containing a salt of the diphosphonic acid group is a benzyl group, a phenethyl group, or an alkyl group having 12 to 22 carbon atoms. The inkjet recording ink according to (1) or (2), characterized in that it is characterized.
(4) The above-mentioned (1) to (1), wherein the content of the structural unit (1) of the general formula (1) in the copolymer containing a salt of the diphosphonic acid group is 30% by mass to 70% by mass. The ink for inkjet recording according to any one of (3). "
(5) In the above (4), the content of the structural unit (1) of the general formula (1) in the copolymer containing a salt of the diphosphonic acid group is 40% by mass to 60% by mass. The inkjet recording ink described. "
(6) The above-mentioned (1) to (1), wherein the aqueous solution viscosity (concentration: 10% by mass, 25 ° C.) of the copolymer containing a salt of the diphosphonic acid group is 1.5 to 4.0 mPa · s. The ink for inkjet recording according to any one of 5). "
(7) “M + is an alkyl group having 1 to 5 carbon atoms in the site derived from the structural unit (1) of the general formula (1) or the monomer of the general formula (4) in the copolymer containing a salt of the diphosphonic acid group. The ink for inkjet recording according to any one of (1) to (6), wherein the ink is a tetraalkylammonium ion comprising:
(8) “An ink cartridge comprising the ink for inkjet recording according to any one of (1) to (7)” contained in a container.
(9) “At least an ink flying step of recording an image by applying a stimulus to the ink for ink jet recording according to any one of (1) to (7) and causing the ink for ink jet recording to fly. Inkjet recording apparatus. "

--Copolymer containing salt of phosphonic acid group--
The copolymer containing a salt of a phosphonic acid group in the present invention is a copolymer having at least a structural unit represented by the general formula (1) and a structural unit represented by the general formula (2).

Examples of the alkali metal in the M ⁺ alkali metal ion in the general formula (1) include lithium, sodium, and potassium.
Examples of the organic amine in the M ⁺ organic ammonium ion include alkylamines such as mono-, di- or trimethylamine, mono-, di- or triethylamine; ethanolamine, diethanolamine, triethanolamine, methylethanolamine, methyldiethanolamine, dimethylethanol Alcohol amines such as amine, monopropanolamine, dipropanolamine, tripropanolamine, isopropanolamine, trishydroxymethylaminomethane, 2-amino-2-ethyl-1,3propanediol (AEPD); choline, morpholine, N -Cyclic amines such as methylmonoformin, N-methyl-2-pyrrolidone and 2-pyrrolidone.
Further, a quaternary organic ammonium ion can also be suitably used as the M ⁺ organic ammonium ion. For example, tetramethylammonium ion, tetraethylammonium ion, tetrapropylammonium ion, tetrabutylammonium ion, tetraamylammonium ion, benzyltrimethylammonium ion, hydroxyethyltrimethylammonium ion, methyltrioctylammonium ion, trimethylstearylammonium ion, etc. It is done.
In particular, potassium ion, sodium ion, and alkylammonium ion are desirable from the viewpoint of both image density and storage stability.
Among the alkylammonium ions, the use of a tetraalkylammonium ion composed of an alkyl group having 1 to 5 carbon atoms is particularly preferable because an ink having low viscosity and excellent storage stability can be provided.
Specific examples of tetraalkylammonium ions comprising an alkyl group having 1 to 5 carbon atoms include tetraethylammonium ion, tetrabutylammonium ion, methyltributylammonium ion, methyltriamylammonium ion, triethylmethylammonium ion, ethyltrimethylammonium ion, and the like. Can be mentioned.
As M ⁺ , more than half or all of them are preferably alkali metal ions or organic ammonium ions, and the rest are preferably hydrogen ions (protons).
Examples of the alkylene group having 1 to 3 carbon atoms of X in the general formula (1) include a methylene group, an ethylene group, and a propylene group. In the present invention, a propylene group is mentioned to explain the effect.

The hydrocarbon group of 6 to 22 carbon atoms represented by Z ₁ in formula (2), a phenyl group, an aromatic hydrocarbon group such as a naphthyl group, a cyclic saturated hydrocarbon group such as cyclohexyl group , Chain saturated hydrocarbon groups such as dodecyl group, stearyl group and isostearyl group, aralkyl groups such as benzyl group and phenethyl group, and chain unsaturated hydrocarbon groups such as 9-octadecenyl group.
In particular, a benzyl group, a phenethyl group, and an alkyl group having 12 to 22 carbon atoms are preferable.
The alkyl group having 12 to 22 carbon atoms is not particularly limited as long as it is within the range. For example, linear or branched such as dodecyl group, tetradecanyl group, hexadecanyl group, octadecanyl group, icosanyl group, docosanyl group, A chain alkyl group.

The mass ratio of the structural unit represented by the general formula (1) is not particularly limited and can be appropriately selected depending on the purpose. 30 mass%-70 mass% is preferable with respect to the said polymer whole quantity, 40 mass%-60 mass% are more preferable, 45 mass%-55 mass% are still more preferable.
When the mass ratio is within the more preferable range, it is advantageous in that when used for an ink jet recording ink, a high image density is obtained, and dispersion stability and storage stability are improved.

  The copolymer containing a salt of a phosphonic acid group used in the present invention can be produced by the polymer production method of the present invention described below. The copolymer containing the structural units represented by the general formula (1) and the general formula (2) includes a pigment dispersant, a pigment concentration improver, a pigment binder resin, and a viscosity modifier in an inkjet recording ink. It can use suitably as.

<Method for producing polymer>
In the method for producing a polymer used in the present invention, a polymerizable raw material containing at least the compound (monomer) represented by the general formula (4) and the general formula (5) is radical-polymerized, and then the obtained polymer is alkalinized. It can be synthesized by neutralizing with either a metal base and an organic amine base or an organic ammonium base.
In the neutralization treatment, the amount of neutralization from 0 to 4 of the 4 acid groups in the general formula (1) can be adjusted. The number of neutralized acid groups, that is, the number of M + in the general formula (1) is preferably 2 to 4, more preferably 2 or 3.

Specific examples of the monomer (1) represented by the general formula (4) include sodium hydrogen-1-hydroxy-4-methacrylamide-1-phosphonobutylphosphonate, sodium 1-hydroxy-4-methacrylamidebutane-1 , 1-diylbis (hydrogen phosphonate), sodium 1- (hydrogen phosphonate) -1-hydroxy-4-methacrylamide butylphosphonate, sodium 1-hydroxy-4-methacrylamide butane-1,1-diyl diphosphonate, etc. Is mentioned.
Furthermore, the case where these methacryl is an acryl, and the case where sodium is potassium and an organic ammonium ion can be mentioned.
Further, in the case of 1-hydroxy-4-methacrylamideamidane-1,1-diyldiphosphonic acid or the like when all are protons, it can be used as a monomer.
As a method for synthesizing the monomer (1) represented by the general formula (4), when X in the general formula (4) is propylene (that is, 1-hydroxy-4- (meth) acrylamide butane-1,1 -Salt of diyl diphosphonic acid) As an example, alendronic acid is neutralized with an alkali metal base, organic amine base or organic ammonium base in the range of 1 equivalent to 3 equivalents in advance, and then methacrylic acid. It can be obtained by reacting with chloride or acrylic acid chloride.
Further, after the reaction, the number of salts can be adjusted by neutralization treatment.

In the general formula (5), as the hydrocarbon group having 6 to 22 carbon atoms represented by Z ₂ , an aromatic hydrocarbon group such as a phenyl group or a naphthyl group, a cyclic saturated hydrocarbon group such as a cyclohexyl group, A chain saturated hydrocarbon group such as dodecyl group, stearyl group or isostearyl group, an aralkyl group such as benzyl group or phenethyl group, or a chain unsaturated hydrocarbon group such as 9-octadecenyl group is represented.
Examples of the monomer in which the hydrocarbon group having 6 to 22 carbon atoms represented by Z ₂ is an aromatic hydrocarbon group such as a phenyl group or a naphthyl group include phenyl (meth) acrylate and naphthyl (meth) acrylate. It is done. Examples of the monomer in which the hydrocarbon group having 6 to 22 carbon atoms represented by Z ₂ is a chain saturated hydrocarbon group such as a cyclohexyl group include cyclohexyl (meth) acrylate.

Examples of the monomer (2) in which the hydrocarbon group having 6 to 22 carbon atoms represented by Z ₂ is a chain saturated hydrocarbon group such as a dodecyl group, a stearyl group, or an isostearyl group include hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, octyl (meth) acrylate, nonyl (meth) acrylate, decyl (meth) acrylate, dodecyl (meth) acrylate, hexadecyl (meth) acrylate, octadecyl (meth) acrylate, docosyl (meth) acrylate, etc. Is mentioned.
Examples of the monomer in which the hydrocarbon group having 6 to 22 carbon atoms represented by Z ₂ is an aralkyl group such as a benzyl group or a phenethyl group include benzyl (meth) acrylate and phenethyl (meth) acrylate.
Examples of the monomer in which the hydrocarbon group having 6 to 22 carbon atoms represented by Z ₂ is a chain unsaturated hydrocarbon group such as a 9-octadecenyl group include oleyl (meth) acrylate.
The (meth) acrylate represents both methacrylate and acrylate.

  Specific examples of the monomer (2) represented by the general formula (5) include benzyl acrylate, benzyl methacrylate, phenethyl acrylate, phenethyl methacrylate, cyclohexyl acrylate, cyclohexyl methacrylate, dodecyl acrylate, dodecyl methacrylate, hexadecanyl acrylate, hexadeca Nyl methacrylate, octadecanyl acrylate, octadecanyl methacrylate, icosanyl acrylate, icosanyl methacrylate, docosanyl acrylate, docosanyl methacrylate and the like can be mentioned.

The polymer containing the structural units (1) and (2) represented by the general formula (1) and the general formula (2) is a known polymer such as a bulk polymerization method, a solution polymerization method, a suspension polymerization method, and an emulsion polymerization method. Polymerized by a polymerization method.
Although not limited to these polymerization methods, a method using a radical polymerization initiator is preferable because polymerization operation and molecular weight adjustment are easy, and a solution polymerization method in which polymerization is performed in a mixed solvent of an organic solvent and water is more preferable.
The operation for performing radical polymerization by the solution polymerization method is not particularly limited, but the monomer, initiator, chain transfer agent, and solvent may be charged all at once into the polymerization reaction vessel or continuously using a dropping funnel. May be supplied. Moreover, you may add an initiator during a polymerization reaction as needed.

There is no restriction | limiting in particular as a solvent at the time of performing radical polymerization by the said solution polymerization method. It is preferable to perform polymerization while supplying the monomer (1) of the general formula (4) as an aqueous solution and dissolving and supplying the monomer (2) of the general formula (5) in an organic solvent. Are preferred.
For example, alcohol solvents such as methanol and ethanol, ether solvents such as tetrahydrofuran, and amide solvents such as N, N-dimethylformamide are preferable.

There is no restriction | limiting in particular as said radical polymerization initiator, According to the objective, it can select suitably. For example, 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 from the viewpoint of easy control of molecular weight and low decomposition temperature.
The content of the polymerization initiator is not particularly limited and may be appropriately selected depending on the intended purpose, but is preferably 1% by mass to 20% by mass with respect to the total mass 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, nonyl mercaptan, 1-dodecanethiol, α-thioglycerol, and the like.
There is no restriction | limiting in particular in superposition | polymerization temperature, Although it can select suitably according to the objective, 50 to 150 degreeC is preferable and 60 to 100 degreeC is more preferable.
The polymerization time is not particularly limited and may be appropriately selected depending on the intended purpose, but is preferably 3 hours to 48 hours.

The obtained polymer is neutralized with either an alkali metal base or an organic amine base.
The neutralization treatment can be performed by neutralizing some or all of the phosphonic acid groups of the polymer with an alkali metal base or an organic amine base.
When neutralization is completed in the monomer (1) production process of the general formula (4), this neutralization process can be omitted, but usually 1 to 2 equivalents in the monomer (1) production process The remaining acid groups are neutralized after neutralization and polymerization.

The neutralization treatment of the alkali metal base or organic amine base can also be performed in a state where the pigment and the polymer are mixed in the ink production process.
More specifically, an aqueous solution in which the monomer (1) of the general formula (4) is dissolved in a flask equipped with a stirrer, a thermometer, an inert gas (nitrogen or argon) introduction tube, and a condenser, and the general formula ( 5) The organic solvent solution in which the monomer (2) is dissolved, and the solution in which the polymerization initiator, the molecular weight modifier and the like are dissolved are batched or continuously stirred under an inert gas at 60 ° C to 150 ° C. After reacting at a temperature, it can be synthesized by neutralizing with either an alkali metal base or an organic amine base.
The neutralization degree can be controlled by measuring the acid value of the resin in advance and performing neutralization treatment accordingly. The acid value is measured by dissolving or dispersing the weighed resin in water or a water-soluble organic solvent or a mixed solvent thereof, and neutralizing and titrating with a potassium hydroxide methanol solution having a specified concentration using thymolphthalein as an indicator.
In the bisphosphonic acid compound of the present invention, it is known that three of the four acid groups are neutralized when the color of thymolphthalein changes (pH = 8 to 9). Therefore, when the acid value is obtained using thymolphthalein as an indicator and neutralized by adding a base accordingly, a structure in which three acid groups are neutralized can be prepared.
30-70 mass% is preferable, as for the ratio of the monomer (1) represented by the said General formula (4) with respect to the polymerizable monomer gross weight at the time of a synthesis | combination, 40-60 mass% is more preferable, 45-55 mass% Is more preferable.

The obtained polymer (copolymer) has a molecular weight distribution depending on the degree of polymerization. Usually, the molecular weight can be easily measured by gel permeation chromatography (GPC), but the present polymer is a dissociative polymer and is difficult to measure due to adsorption to the GPC column.
Therefore, in the present invention, the viscosity when the polymer is a solution having a constant concentration is used as a substitute characteristic of molecular weight. The measuring method of a viscosity can be performed as follows. Using a viscometer (RE500L, manufactured by Toki Sangyo Co., Ltd.), it is adjusted to 50 or 100 rotations according to the viscosity of the sample.
The aqueous solution viscosity (10% by mass, 25 ° C.) of the copolymer containing the phosphonic acid group salt of the present invention is preferably in the range of 1.5 mPa · s to 4.0 mPa · s, and is preferably 1.7 mPa · s. More preferably, it is -3.0 mPa * s.
When the aqueous solution viscosity of the polymer is 1.5 mPa · s or more, the molecular weight is moderate, the dispersion stability is good, and the image density is not lowered due to a decrease in calcium reactivity. If this is the case, the molecular weight does not become excessive, and therefore, the increase in ink viscosity can be suppressed, and it becomes easy to avoid clogging of the head and ejection failure, and the pigment dispersion and ink are caused by a decrease in dispersibility and dispersibility stability. It becomes difficult for deterioration of storage stability to occur.
When it is in the range of 1.7 mPa · s to 3.0 mPa · s, image density reduction and ink storage stability are more unlikely to occur. Deterioration of ink storage stability may lead to head clogging or ejection failure.

The molecular weight of the polymer containing the structural units (1) and (2) represented by the general formula (1) and the general formula (2) can be controlled to some extent by the polymerization temperature, the polymerization initiator amount, and the monomer concentration during the reaction. It is.
Regarding the polymerization temperature, a low molecular weight polymer tends to be obtained when polymerized at a high temperature in a short time, and a high molecular weight polymer tends to be obtained when polymerized at a low temperature for a long time.
As for the content of the polymerization initiator, a larger amount tends to obtain a low molecular weight polymer, and a smaller amount tends to obtain a high molecular weight polymer.
As for the monomer concentration during the reaction, a high concentration tends to provide a low molecular weight polymer, and a low concentration tends to provide a high molecular weight polymer.
Further, as described above, the molecular weight of the copolymer in the present invention can be controlled by adjusting the amount of the chain transfer agent used. As is known, chain transfer agents receive radicals from the grown polymer chain and stop polymer elongation, but chain transfer agents that receive radicals can attack the monomer and start polymerization again, It also contributes to the adjustment of molecular weight distribution and the average molecular weight.

<Copolymer containing structural units represented by general formula (1) and general formula (2)>
The polymer containing the structural unit (1) represented by the general formula (1) in the inkjet recording ink of the present invention has a dibasic acid structure in which a phosphonic acid group is adjacent. Differently, it has many diphosphonic acid groups in the molecule. As a result, more hydrophilic groups can be added in the polymer molecule than in the case of a monobasic acid, and good hydrophilicity is exhibited. Moreover, since it has a phosphonic acid group that easily reacts with Ca ions, and the phosphonic acid group is a dibasic acid, it has the effect of chelating Ca ions, and shows stronger bonds when contacted with Ca ions. Can be hydrophobized.

  The structural unit (2) represented by the general formula (2) brings hydrophobicity to the polymer, improves wettability and adsorbability with the pigment, improves dispersion stability, and is hydrophilic in the general formula (1). It functions to improve the cohesiveness of the resin when in contact with Ca ions due to the balance with the functional phosphonic acid group.

Although the reason is not clear, it has the effect of preventing the association of phosphonic acid groups in the polymer, and has the effect of further improving the storage stability in aqueous ink. These functions can be used as a dispersant.
Therefore, when the polymer containing the structural units (1) and (2) represented by the general formula (1) and the general formula (2) is used for the ink for ink jet recording, good ink dispersion stability and Shows storage stability. Further, when ink is printed on paper, the copolymer is hydrophobized by Ca ions eluted from the paper into the ink even if the plain paper has a small Ca ion content, and the general formula (2) The structural unit represented by is highly adsorbable with respect to the pigment, so that the pigment stays on the paper surface by aggregating and aggregating the pigment, so that a higher image density can be realized.

  The content of the polymer containing the structural units (1) and (2) represented by the general formula (1) and the general formula (2) in the ink for inkjet recording is not particularly limited and is appropriately selected depending on the purpose. can do. The solid content is preferably 0.05% by mass to 10% by mass, more preferably 0.5% by mass to 5% by mass, and particularly preferably 1% by mass to 3% by mass. The effect of improving the image density is recognized when the content is 0.05% by mass or more. When the content is 10% by mass or less, it is possible to make the viscosity range suitable for ejecting ink from the head.

  If a polymer containing the structural units represented by the general formula (1) and the general formula (2) is used as a pigment dispersant, the image density of plain paper and the water-soluble organic solvent A further improvement in storage stability is observed with ink having a high content.

  The content of the polymer containing the structural units (1) and (2) represented by the general formula (1) and the general formula (2) is not particularly limited when used as a pigment dispersant. It can be appropriately selected depending on the case. 1-100 mass parts is preferable with respect to 100 mass parts of said pigments, 5-80 mass parts is more preferable, 10-50 mass parts is still more preferable. When the content is within the more preferable range, it is advantageous in that a high image density is obtained and dispersion stability and storage stability are improved.

<Water>
As said water, pure water, such as ion-exchange water, ultrafiltration water, reverse osmosis water, distilled water, or ultrapure water can be used, for example.
There is no restriction | limiting in particular in content in the said ink for inkjet recording of the said water, According to the objective, it can select suitably.

<Pigment>
There is no restriction | limiting in particular as said 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.
Examples of the inorganic pigment include titanium oxide, iron oxide, calcium carbonate, barium sulfate, aluminum hydroxide, barium yellow, cadmium red, and chrome yellow, as well as a known method such as a contact method, a furnace method, and a thermal method. Carbon black can be used.
Examples of the organic pigment include azo pigments, azomethine pigments, polycyclic pigments, dye chelates, nitro pigments, nitroso pigments, and aniline black. Among these, azo pigments and polycyclic pigments are more 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.
Examples of black materials include carbon blacks (CI pigment black 7) such as furnace black, lamp black, acetylene black, channel black, copper, iron (CI pigment black 11), titanium oxide, and the like. And organic pigments such as aniline black (CI Pigment Black 1).
As the carbon black, a furnace method, a carbon black produced by the channel method, primary particle diameter of 15Nm～40nm, the BET specific surface area of ^{50m 2 / g~300m 2 / g,} DBP oil absorption amount 40 mL / 100 g Those having ~ 150 mL / 100 g, volatile content of 0.5% to 10%, and pH of 2 to 9 are preferred.
Commercially available products can be used as the carbon black. Examples of the commercially available products include Color Black FW1, Printex 35, Special Black 6 (all manufactured by Degussa), and the like.
There is no restriction | limiting in particular as a pigment which can be used for yellow ink as the thing for said colors, According to the objective, it can select suitably, for example, C.I. I. Pigment yellow 74, C.I. I. Pigment yellow 154, C.I. I. Pigment yellow 174, and the like.
There is no restriction | limiting in particular as a pigment which can be used for a magenta ink, According to the objective, it can select suitably, For example, C.I. I. Pigment red 122, C.I. I. Pigment red 202, pigment violet 19, and the like.
The pigment that can be used in the cyan ink is not particularly limited and may be appropriately selected depending on the intended purpose. I. Pigment blue 15: 3, C.I. I. Pigment blue 15: 4, C.I. I. Bat Blue 60 and the like.
In addition, the pigment used in the present invention may be newly produced for the present invention.
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.
The volume average particle diameter (D50) of the pigment is not particularly limited and may be appropriately selected depending on the intended purpose, but is preferably 150 nm or less, and more preferably 100 nm or less. When the volume average particle diameter (D50) is 150 nm or less, ejection stability is improved, and occurrence of nozzle clogging and ink bending may be prevented.
Here, the 50% average particle diameter of the pigment indicates a value of D50% measured by a dynamic light scattering method with Microtrac UPA manufactured by Nikkiso Co., Ltd. in an environment of 23 ° C. and 55% RH.
The content of the pigment in the ink for inkjet recording is not particularly limited and may be appropriately selected depending on the intended purpose, but is preferably 0.1% by mass to 20% by mass, and 1% by mass to 20% by mass. More preferred.

The pigment is preferably mixed with water, a pigment, and, if necessary, a dispersant, dispersed with a disperser to adjust the particle size, and then the pigment dispersion is contained in the ink.
The pigment dispersion is obtained by mixing water, a pigment, a pigment dispersant, and, if necessary, other components, and then dispersing the mixture with a disperser and adjusting the particle size.
The obtained pigment dispersion is preferably degassed by filtering coarse particles with a filter, a centrifugal separator or the like, if necessary.
There is no restriction | limiting in particular in content of the pigment at the time of producing the said pigment dispersion, Although it can select suitably according to the objective, 0.1 mass%-50 mass% are preferable, 0.1 mass%- 30 mass% is more preferable.
The pigment dispersion is preferably degassed by filtering coarse particles with a filter, a centrifugal separator or the like, if necessary.
The pigment dispersant in the pigment dispersion is preferably a polymer containing the structural unit (1) represented by the general formula (1). 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.
Among these, naphthalenesulfonic acid Na formalin condensate is particularly preferable.
The total content of naphthalenesulfonic acid dimer, trimer, and tetramer in the naphthalenesulfonic acid Na formalin condensate is not particularly limited and can be appropriately selected according to the purpose. It is preferable that it is -80 mass%. When the content is 20% by mass or more, the dispersibility is improved and the storage stability of the ink is improved. As a result, the occurrence of nozzle clogging can be prevented. On the other hand, when the content is 80% by mass or less, the viscosity range of the ink is appropriate and the dispersibility may be good.

<Water-soluble organic solvent>
The water-soluble organic solvent has at least one of an effect as a wetting agent for preventing ink drying 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. For example, glycerin, ethylene glycol, diethylene glycol, isopropylideneglycerol, 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 ester 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 compounds; 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; dimethyl sulfoxide, sulfolane, thiodiethanol and the like Sulfur-containing compounds: 3-ethyl-3-hydroxymethyloxetane, propylene carbonate, ethylene carbonate, and the like. These may be used individually by 1 type and may use 2 or more types together.

Among these, 3-ethyl-3-hydroxymethyloxetane, isopropylideneglycerol, 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 are excellent in preventing discharge failure due to moisture 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 the ink and adjusted to desired physical properties, and can be appropriately selected according to the purpose. For example, alkyl and aryl ethers 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, tetraethylene glycol chlorophenyl ether, And lower alcohols such as ethanol.

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), polysaccharides, and the like. 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 to the water-soluble organic solvent has a great influence on the ink ejection stability from the head. If the content of the water-soluble organic solvent is low 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 inkjet recording ink is not particularly limited and may be appropriately selected depending on the intended purpose, but is preferably 10% by mass to 60% by mass, and more preferably 20% by mass to 60% by mass. Is more preferable. When the content is 10% by mass or more, the ink ejection stability may be improved, and when it is 60% by mass or less, the drying property may be improved. The ink having the content in the more preferable numerical range has an advantage that the drying property and the ejection reliability are very good.

<Other ingredients>
There is no restriction | limiting in particular as said other component, It can select suitably as needed, For example, surfactant, pH adjuster, water-dispersible resin, antiseptic / antifungal agent, rust inhibitor, antioxidant , Ultraviolet absorbers, oxygen absorbers, light stabilizers, and the like.

-Surfactant-
The surfactant is not particularly limited and may be appropriately selected depending on the intended purpose. Anionic surfactants, cationic surfactants, nonionic surfactants, amphoteric surfactants, fluorine-based surfactants Agents, etc. Among these, nonionic surfactants and fluorine surfactants are particularly preferable.
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 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 phosphate, Polyoxyethylene alkyl ether sulfate ester salt, ether carboxylate, sulfosuccinate, α-sulfo fatty 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, 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.
Examples of the fluorosurfactant include materials represented by the following general formulas (I) to (III).

ただし、前記一般式（Ｉ）中、ｍは、０〜１０の整数を表す。ｎは、１〜４０の整数を表す。

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

前記一般式（II）において、Ｒｆはフッ素含有基を表し、パーフルオロアルキル基が好ましい。

In the general formula (II), Rf represents a fluorine-containing group, 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) Etc. Examples of the perfluoroalkyl group, _{e.g., -CF 3, -CF 2 CF 3} , -C 3 F 7, -C 4 F 9, and the like. Among these, —CF ₃ and —CF ₂ CF ₃ are particularly preferable.
m, n, and p each represent an integer, n is preferably 1-4, m is preferably 6-25, and p is preferably 1-4.

In the general formula (III), Rf represents a fluorine-containing group, and is preferably a perfluoroalkyl group similar to the above general formula (II). For example, CF ₃ , CF ₂ CF ₃ , C ₃ F ₇ , C ₄ such as F ₉ are preferably exemplified.
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.); Fullrad 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 (Solue) ®-made lens Inc. Co., Ltd.) and the like. Among these, Zonyl FS-300, FSN, FSN-100, and FSO (all manufactured by DuPont) are particularly preferable from the viewpoint of improving reliability and color developability.
The content of the surfactant in the inkjet recording ink is not particularly limited and may be appropriately selected depending on the intended purpose, but is preferably 0.01% by mass to 5.0% by mass, and 0.5% by mass. % To 3% by mass is more preferable. When the content is 5.0% by mass or less, the permeability to the recording medium is improved, and it may be possible to prevent a decrease in image density and occurrence of show-through.

-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. For example, alcohol amines, alkali metal hydroxides, ammonium hydroxides, phosphonium hydroxides, alkali metal carbonates, and the like can be given.
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, quaternary ammonium hydroxide, quaternary phosphonium hydroxide, and the like.
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 used for image recording with high water resistance and high image density (high color development). Useful.
Examples of the water-dispersible resin 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 so that the ink does not have an excessively high viscosity, and can be appropriately selected according to the purpose, but is preferably 50 nm or more.
Further, when the particle size is several tens of μm, it becomes larger than the nozzle opening of the ink jet head and cannot be used. If particles having a large particle diameter are present in the ink even though they are 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 disturb the ink ejection stability.
The water-dispersible resin has a function of fixing the water-dispersed colorant on the paper surface, and is preferably formed into 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 not particularly limited and can be appropriately selected according to 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 resin film becomes more viscous and the printed matter is tacky. Therefore, the water-dispersible resin has a glass transition temperature of −30 ° C. or higher. It is preferable.
The content of the water-dispersible resin in the inkjet recording ink is not particularly limited and may be appropriately selected depending on the intended purpose. However, the solid content is preferably 1% by mass to 15% by mass, and preferably 2% by mass. -7 mass% is more preferable.

-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 inhibitor include acidic sulfite, sodium thiosulfate, diammonium thiodiglycolate, diisopropylammonium nitrite, pentaerythritol tetranitrate, and dicyclohexylammonium nitrite.

-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 a benzophenone ultraviolet absorber, a benzotriazole ultraviolet absorber, a salicylate ultraviolet absorber, a cyanoacrylate ultraviolet absorber, and a nickel complex ultraviolet absorber.

<Method for producing ink for inkjet recording>
The ink jet recording ink production method of the present invention includes, for example, water, a water-soluble organic solvent, a pigment, and the structural units (1) and (2) represented by the general formula (1) and the general formula (2). The polymer and, if necessary, other components can be dispersed or dissolved in an aqueous medium and mixed by stirring.
The ink is preferably degassed by filtering coarse particles with a filter, a centrifugal separator or the like, if necessary.
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.

<Ink physical properties>
The physical properties of the ink for ink jet recording of the present invention are not particularly limited and may be appropriately selected depending on the intended purpose. For example, the viscosity, surface tension and the like are preferably in the following ranges.
There is no restriction | limiting in particular in the viscosity at 25 degrees C of the said ink for inkjet recording, Although it can select suitably according to the objective, 3 mPa * s-20 mPa * s are preferable. When the ink viscosity is 3 mPa · s or more, the effect of improving the printing density and the character quality can be obtained. On the other hand, when the ink viscosity is 20 mPa · s or less, ink ejection properties may be secured.
The viscosity can be measured at 25 ° C. using, for example, a viscometer (RE500L, manufactured by Toki Sangyo Co., Ltd.).
There is no restriction | limiting in particular as surface tension of the said ink for inkjet recording, Although it can select suitably according to the objective, 40 mN / m or less is preferable at 25 degreeC.

(Inkjet recording method and inkjet recording apparatus)
The ink jet recording apparatus of the present invention records information or an image on the recording medium using the ink of the present invention with an ink jet head. This recording apparatus has at least ink flying means for ejecting ink, and further has other means appropriately selected as necessary, for example, stimulus generation means, control means, and the like.
The ink flying means is a means for forming an image by applying a stimulus to the ink of the present invention and causing it to fly. The ink flying means is not particularly limited, and examples thereof include various nozzles for ejecting ink.
The stimulus can be generated by, for example, the stimulus generating means, and the stimulus is not particularly limited and can be appropriately selected according to the purpose, such as heat (temperature), pressure, vibration, light, etc. Can be mentioned. These may be used individually by 1 type and may use 2 or more types together. Of these, heat and pressure are preferred. Examples of the stimulus generating means include a superheating device, a pressurizing device, a piezoelectric element, a vibration generating device, an ultrasonic oscillator, and a light. Specifically, a piezoelectric actuator such as a piezoelectric element such as a piezoelectric element, a thermal actuator that uses a phase change due to liquid film boiling using an electrothermal transducer such as a heating resistor, a shape that uses a metal phase change due to a temperature change Memory alloy actuators, electrostatic actuators using electrostatic force, and the like can be mentioned.

There is no particular limitation on the mode of the ink flight, and it varies depending on the type of the stimulus.
For example, when the stimulus is “heat”, thermal energy corresponding to a recording signal is applied to the ink in the recording head using, for example, a thermal head, and bubbles are generated in the ink by the thermal energy. Examples include a method of ejecting and ejecting the ink as droplets from the nozzle holes of the recording head by the pressure of the bubbles. When the stimulus is “pressure”, for example, by applying a voltage to a piezoelectric element bonded to a position called a pressure chamber in an ink flow path in the recording head, the piezoelectric element is bent, For example, a method of reducing the volume and ejecting and ejecting the ink as droplets from the nozzle holes of the recording head can be used.
The control means is not particularly limited as long as the movement of each means can be controlled, and can be appropriately selected according to the purpose. Examples thereof include devices such as sequencers and computers.

Here, an outline of the ink jet recording apparatus of the present invention used in the examples and an ink jet recording method using the recording apparatus will be described.
FIG. 3 is a perspective view showing an example of the serial type ink jet recording apparatus of the present invention. The recording apparatus includes an apparatus main body 101, a paper feed tray 102 for loading paper loaded in the apparatus main body 101, and paper discharge for stocking paper on which an image is recorded (formed) mounted on the apparatus main body 101. The tray 103 has an ink container loading portion 104 that protrudes forward from the front surface 112 and is lower than the upper cover 111 on one end of the front surface 112 of the apparatus main body 101. An operation unit 105 such as operation keys and a display is arranged on the upper surface of the ink container loading unit 104. The ink storage container loading unit 104 has a front cover 115 that can be opened and closed for detaching the ink storage container 200.
In the apparatus main body 101, as shown in FIGS. 4 and 5 (partially enlarged sectional view of the recording apparatus in FIG. 3), a guide rod 131 which is a guide member horizontally mounted on left and right side plates, not shown, The carriage 132 holds the carriage 133 slidably in the main scanning direction, and moves and scans in the direction of the arrow as shown in FIG. 5 by the main scanning motor.

The carriage 133 is provided with a plurality of ink ejection heads 134 including four inkjet recording heads that eject ink droplets of each color of yellow (Y), cyan (C), magenta (M), and black (Bk). The outlets are arranged so as to cross the main scanning direction, and the ink droplet ejection direction is directed downward.
As the ink jet recording head constituting the recording head 134, a piezoelectric actuator such as a piezoelectric element, a thermal actuator using phase change due to liquid film boiling using an electrothermal transducer such as a heating resistor, a metal phase due to temperature change, etc. A shape memory alloy actuator using a change, an electrostatic actuator using an electrostatic force, or the like provided as energy generating means for discharging ink can be used. In addition, the carriage 133 is equipped with a sub tank 135 for each color for supplying ink of each color to the recording head 134. The sub tank 135 is supplied with ink from the ink container 200 of the present invention loaded in the ink container loading unit 104 via an ink supply tube (not shown) and is replenished.

On the other hand, as a paper feeding unit for feeding the paper 142 stacked on the paper stacking unit (pressure plate) 141 of the paper feed tray 102, a half-moon roller (feeding) that separates and feeds the paper 142 one by one from the paper stacking unit 141 A separation pad 144 made of a material having a large coefficient of friction is provided facing the paper roller 143) and the paper feed roller 143, and the separation pad 144 is urged toward the paper feed roller 143 side.
As a transport unit for transporting the paper 142 fed from the paper feed unit below the recording head 134, a transport belt 151 for transporting the paper 142 by electrostatic adsorption and a guide 145 from the paper feed unit. The counter roller 152 for transporting the paper 142 fed via the transport belt 151 with the transport belt 151 and the paper 142 fed substantially vertically upward are changed by approximately 90 ° so as to follow the transport belt 151. For this purpose, a conveyance guide 153 and a tip pressure roller 155 urged toward the conveyance belt 151 by a pressing member 154 are provided.

In addition, a charging roller 156 that is a charging unit for charging the surface of the conveyance belt 151 is provided. The conveyance belt 151 is an endless belt, is stretched between the conveyance roller 157 and the tension roller 158, and can circulate in the belt conveyance direction. The transport belt 151 includes, for example, a surface layer serving as a sheet adsorbing surface formed of a resin material (for example, a copolymer of tetrafluoroethylene and ethylene (ETFE)) having a thickness of about 40 μm that is not subjected to resistance control, and the surface layer. And a back layer (medium resistance layer, grounding layer) that is controlled by carbon with the same material. On the back side of the conveyance belt 151, a guide member 161 is disposed corresponding to the printing area by the recording head 134.
Note that, as a paper discharge unit for discharging the paper 142 recorded by the recording head 134, a separation claw 171 for separating the paper 142 from the conveyance belt 151, a paper discharge roller 172, and a paper discharge roller 173 are provided. The paper discharge tray 103 is disposed below the paper discharge roller 172.
A double-sided paper feeding unit 181 is detachably mounted on the back surface of the apparatus main body 101.
The double-sided paper feeding unit 181 takes in the paper 142 returned by the reverse rotation of the transport belt 151, reverses it, and feeds it again between the counter roller 152 and the transport belt 151. A manual paper feed unit 182 is provided on the upper surface of the duplex paper feed unit 181.

In this ink jet recording apparatus, the paper 142 is separated and fed one by one from the paper feed unit, and the paper 142 fed substantially vertically upward is guided by the guide 145 and between the transport belt 151 and the counter roller 152. It is sandwiched and conveyed. Further, the leading end is guided by the conveying guide 153 and pressed against the conveying belt 151 by the leading end pressure roller 155, and the conveying direction is changed by approximately 90 °. At this time, the conveyance belt 157 is charged by the charging roller 156, and the sheet 142 is conveyed by being electrostatically attracted to the conveyance belt 151. Therefore, by driving the recording head 134 according to the image signal while moving the carriage 133, ink droplets are ejected onto the stopped paper 142 to record one line, and after the paper 142 is conveyed by a predetermined amount, Record the next line.
Upon receiving a recording end signal or a signal that the trailing edge of the sheet 142 has reached the recording area, the recording operation is terminated, and the sheet 142 is discharged onto the discharge tray 103. When a near-end remaining amount of ink in the sub tank 135 is detected, a required amount of ink is supplied from the ink container 200 to the sub tank 135.

In this ink jet recording apparatus, when the ink in the ink container 200 is used up, the casing of the ink container 200 can be disassembled and only the ink container inside can be replaced. In addition, the ink container 200 can supply ink stably even when the ink container 200 is placed vertically and has a front loading configuration. Accordingly, even when the upper portion of the apparatus main body 101 is closed and installed, for example, when stored in a rack, or when an object is placed on the upper surface of the apparatus main body 101, the ink container 200 can be easily exchanged.
In addition, although it demonstrated in the example applied to the serial type (shuttle type) inkjet recording device which a carriage scans, it can apply similarly to the line type inkjet recording device provided with the line type head.
The ink jet recording apparatus of the present invention can be applied to various types of recording by the ink jet recording method, and is particularly preferably applied to, for example, an ink jet recording printer, a facsimile apparatus, a copying apparatus, a printer / fax / copier multifunction machine, and the like. Can do.

-Ink recordings-
The ink recorded matter recorded by the ink jet recording method of the present invention is the ink recorded matter of the present invention. The ink recorded matter of the present invention has an image recorded on the recording medium by the ink recording ink of the present invention.
The recording medium used in the present invention is not particularly limited as long as the ink for ink jet recording of the present invention is landed and an image can be formed. For example, plain paper, coated paper for printing, glossy paper, special paper and the like can be mentioned. The paper exemplified above contains calcium carbonate, talc, kaolin, aluminum sulfate (sulfuric acid band), and the like. When the ink jet recording ink of the present invention lands on the paper, the polyvalent metal ions, In the sample, divalent or trivalent metal ions such as calcium, magnesium and aluminum are eluted.
As mentioned above, the present invention can be used with any paper, but plain paper is particularly preferred. Here, “plain paper” means an image forming apparatus for office use, home use or personal use using hard copy forming technology such as an electrophotographic copying machine, a simple offset printing machine, a printer, or a conventional diazo copying machine. In general, it refers to all paper media for supporting images with paper-passability and transportability. Plain paper seems to be the reason for Plain Paper, but today the mainstream of Plain Paper is high-quality paper. Therefore, high-quality paper is often referred to as plain paper, and an electrophotographic image medium as a typical image forming technique using the high-quality paper is popularly abbreviated as PPC (plain paper copy).

The ink for ink jet recording in the present invention reacts with the above polyvalent metal ions to aggregate the pigment, and a high image density is obtained. However, it is difficult to achieve high image density, for example, with plain paper among the papers exemplified above.
Many of the fillers and sizing agent fixing agents contained in plain paper are poorly water-soluble metal salts. Moreover, even if a water-soluble metal salt is contained, the content is small. Therefore, plain paper has less elution of polyvalent metal ions compared to paper processed with water-soluble polyvalent metal salt or the like on the paper surface, and the prior art cannot provide an effect of improving image density.
In the present invention, a high image density can be realized not only on the processed paper but also on paper with less elution of polyvalent metal ions such as plain paper. Examples of commercially available plain paper include high-quality paper My Paper (manufactured by Ricoh Co., Ltd.), Xerox 4024 (manufactured by Fuji Xerox Co., Ltd.), and the like.

The ink of the present invention is preferably used for paper having an amount of Ca ions eluted from the paper of 1.0 × 10 ^{−4 to} 5.0 × 10 ⁻⁴ [g / g]. When the Ca ion amount is 1.0 × 10 ⁻⁴ [g / g] or more, the effect of improving the image density by reaction aggregation with the pigment dispersant is improved. Further, since the Ca ion amount is 5.0 × 10 ⁻⁴ [g / g] or less, the ink permeation into the paper is not inhibited, so that the drying property of the ink is improved, and the scratch resistance and the marker resistance are also improved. improves.
The amount of Ca ions eluted from the paper is calculated by the following method.
That is, the paper is filtered into a 2.5 cm (± 0.5 cm) × 3.5 cm (± 0.5 cm) square piece of paper, and the pure water is filtered through a 0.8 μm cellulose acetate filter (manufactured by Advantech Co., Ltd.). Then, the Ca ions contained in the immersion liquid are quantified by an ICP emission spectroscopic analyzer. The Ca ion concentration [ppm] obtained here is multiplied by 200 g, which is the weight of high-purity water, and is further divided by 16 g, which is the weight of the immersed paper. The amount of Ca ions eluted from the paper [g / g ] Is calculated.
For example, the amount of Ca ions of MyPaper (manufactured by Ricoh Co., Ltd.) is 4.3 × 10 ⁻⁴ [g / g], and the amount of Ca ions of Xerox 4024 (manufactured by Fuji Xerox Co., Ltd.) is 1.7 × 10 ⁻⁴ [ g / g].

  Examples of the present invention will be described below, but the present invention is not limited to the following examples. “Part” represents “part by mass” unless otherwise specified. “%” Represents “% by mass” unless otherwise specified.

<Synthesis of Monomer (1) of General Formula (4)>
<Monomer No. (1) -1: Sodium 1-hydroxy-4-methacrylamidebutane-1,1-diylbis (hydrogen phosphonate)>
25 parts of alendronic acid (manufactured by Tokyo Chemical Industry Co., Ltd.) was placed in the flask, and then an aqueous solution in which 17.1 parts of sodium hydroxide was dissolved in 200 parts of ion-exchanged water was added and completely dissolved while stirring. Next, 13.32 parts of methacrylic acid chloride (manufactured by Tokyo Chemical Industry Co., Ltd.) was slowly added dropwise while cooling the flask to 5 ° C. After completion of the dropwise addition, the mixture was further stirred for 30 minutes, and then 14.53 parts of concentrated hydrochloric acid was added dropwise while cooling. The reaction solution was extracted and washed with methylene chloride three times, and the remaining aqueous solution was dropped into 800 parts of methanol to precipitate the desired product. Filtration gave 35 parts of the desired product.
1.7 parts of this target product was dissolved in 176 parts of ion-exchanged water, neutralized with a 0.1N KOH methanol solution using thymolphthalein (manufactured by Kanto Chemical Co.) as an indicator, and the acid value was determined to be 155 ( It was in good agreement with the calculated value 155 (mgKOH / g) when two of the OH groups of phosphonic acid were replaced with Na salt by comparing with the titration result of alendronic acid.

<Monomer No. (1) -2: Potassium 1-hydroxy-4-methacrylamidebutane-1,1-diylbis (hydrogen phosphonate)>
Monomer No. 40 parts of the desired product were obtained in the same manner except that 24 parts of potassium hydroxide was used instead of 17.1 parts of sodium hydroxide in the synthesis of (1) -1.

<Monomer No. (1) -3: Sodium 4-acrylamido-1-hydroxybutane-1,1-diylbis (hydrogen phosphonate)>
Monomer No. Instead of using 13.32 parts of methacrylic acid chloride in the synthesis of (1) -1, 33 parts of the target product was obtained in the same manner except that 11.53 parts of acrylic acid chloride (manufactured by Tokyo Chemical Industry Co., Ltd.) was used. .

<Monomer No. (1) -4: Triethylammonium 4-acrylamido-1-hydroxybutane-1,1-diylbis (hydrogen phosphonate)>
Monomer No. Instead of using 13.32 parts of methacrylic acid chloride in the synthesis of (1) -1, 11.53 parts of acrylic acid chloride are used, and triethylamine (manufactured by Kanto Chemical Co., Inc.) 43 instead of 17.1 parts of sodium hydroxide 44 parts were obtained in the same manner except that 3 parts were used.

<Monomer No. (1) -5: Tetraethylammonium 1-hydroxy-4-methacrylamidebutane-1,1-diylbis (hydrogen phosphonate)>
Monomer No. In the synthesis of (1) -1, 179.8 parts of tetraethylammonium hydroxide (manufactured by Tokyo Chemical Industry Co., Ltd., 35% aqueous solution) instead of 17.1 parts of sodium hydroxide and 200 parts of ion-exchanged water and 83.1 of ion-exchanged water 55 parts were obtained in the same manner except that the parts were used.

<Monomer No. (1) -6: Tetrabutylammonium 1-hydroxy-4-methacrylamidebutane-1,1-diylbis (hydrogen phosphonate)>
Monomer No. In the synthesis of (1) -1, 277.2 parts of tetrabutylammonium hydroxide (manufactured by Tokyo Chemical Industry Co., Ltd., 40% aqueous solution) instead of 17.1 parts of sodium hydroxide and 200 parts of ion-exchanged water and 33. ion-exchanged water. 76 parts of the target product were obtained in the same manner except that 7 parts were used.

<Polymer synthesis example 1; synthesis of copolymer (polymer 1) containing a salt of phosphonic acid group>
In a reaction vessel equipped with a gas introduction tube, a thermometer, and a reflux condenser, 450 parts of N, N-dimethylformamide (DMF) was placed under an argon atmosphere and heated to 75 ° C. Thereto, 75 parts of monomer No. 464 parts of a DMF solution prepared by mixing 558 parts of (1) -1 aqueous solution, 525 parts of DMF solution of 75 parts of cyclohexyl methacrylate, 4.5 parts of 2,2′-azobisisobutyronitrile, and 9 parts of α-thioglycerol. Each was divided into 12 portions and added every 30 minutes. Stirring was continued for an additional 4 hours after all had been added, and then the polymerization was stopped by cooling.
The precipitate was collected by filtration, washed with hexane, and dried to obtain 136 parts of a copolymer (Polymer 1).
When 1 part of this resin (copolymer) was dissolved in 120 parts of ion-exchanged water and titrated with 0.1N KOH methanol solution using thymolphthalein as an indicator, the acid value was determined to be 78 mgKOH / g. Monomer No. It was in good agreement with the value 77.7 mgKOH / g calculated from the acid value of (1) -1 as copolymerized according to the charge ratio.
Based on this acid value, a 10% by mass resin aqueous solution was prepared while neutralizing with sodium hydroxide. The viscosity of this solution measured at 25 ° C. was 1.84 mPa · s.
The 10% by mass resin aqueous solution thus obtained was used for preparing a pigment dispersion. From the titration result of the monomer raw material alendronic acid, it can be seen that three of the four OH groups of phosphonic acid are neutralized at the time of discoloration of thymolphthalein. Of the four OH groups, three are neutralized with sodium ions.

<Polymer synthesis example 2; synthesis of copolymer containing phosphonic acid group salt (polymer 2)>
As shown in Table 1-1, as the monomer of the general formula (4), the monomer No. The same treatment as in Synthesis Example 1 was conducted except that 558 parts of an aqueous solution containing 75 parts of (1) -2 was used and 525 parts of a DMF solution containing 75 parts of cyclohexyl methacrylate was used as the monomer of the general formula (5). 136 parts of a copolymer (polymer 2) were obtained.
While neutralizing this copolymer (polymer 2) resin aqueous solution using potassium hydroxide instead of sodium hydroxide, a 10% by mass resin aqueous solution was prepared. The viscosity of this solution was 1.82 mPa · s (25 ° C.). The resin obtained by neutralization is obtained by neutralizing three of the four OH groups with potassium ions. The results are shown in Table 1-1.

<Polymer Synthesis Example 3 (Synthesis of Polymer 3) to Synthesis Example 33 (Synthesis of Polymer 33), Comparative Synthesis Example 1 (Synthesis of Polymer 34) to Comparative Synthesis Example 2 (Synthesis of Polymer 35)>
The reaction conditions shown in Table 1-2 were changed to mass% of monomer (1) of general formula (4) and mass% of monomer (2) of general formula (5) as shown in Table 1-1, respectively. Other than the synthesis, in the same manner as in the synthesis of polymer 1, each of polymers 3 to 31 having a solution viscosity shown in Table 1-1 was synthesized, and a salt composition (general) as shown in Table 1-1. Neutralized to M) of formula (1), or used as it was without neutralization for the preparation of the pigment dispersion.

<Comparative Synthesis Example 3; Preparation of 2-hydroxyethylidene diphosphonic acid neutralized salt>
2-Hydroxyethylidene-1,1-diphosphonic acid was neutralized with 2 equivalents of potassium hydroxide in methanol, and the methanol was distilled off and used as it was.
The viscosity at 25 ° C. of a 10% by mass aqueous solution of 1-hydroxyethylidene-1,1-diphosphonic acid salt was 1.9 mPa · s.

  In the table, for 3Na, 1H, etc., M + represents 3 Na ions and 1 proton. Similarly, 2K and 2H represent two K ions and two protons. TEtA represents triethylammonium ion. TetraEtA represents tetraethylammonium ion and TetraBuA represents tetrabutylammonium ion. MA represents methacrylate, and A represents acrylate.

<Preparation of pigment dispersion>
(Pigment dispersion preparation example 1)
After premixing the following mixture 1, it was circulated and dispersed for 10 minutes at a peripheral speed of 10 m / s with a disk-type bead mill (Kymal Enterprises, KDL type, media: 0.1 mm diameter zirconia ball used), and the pore size The pigment dispersion 1 was obtained by filtering through a 1.2 μm membrane filter.
"Mixture 1"
・ Carbon black (NIPEX150, manufactured by Degussa) ・ ・ ・ ・ ・ ・ 20.0 mass parts ・ Naphthalenesulfonic acid Na formalin condensate (solid content 10 mass%) ・ 13.0 mass parts ・ pure water ・ ・ ・ ・... 67.0 parts by mass

(Pigment Dispersion Preparation Example 2 (Preparation of Pigment Dispersion 2))
As shown in Table 2, pigment dispersion 2 was obtained by treating in the same manner as pigment dispersion preparation example 1 except that the mixture in pigment dispersion preparation example 1 was replaced with mixture 2 having the following composition.
"Mixture 2"
Carbon black (NIPEX150, manufactured by Degussa) ... 20.0 parts by mass Polymer 1 (solid content 10% by mass) ... 50 0 parts by mass, pure water ... 30.0 parts by mass

(Pigment Dispersion Preparation Example 3 (Preparation of Pigment Dispersion 3) to Pigment Dispersion Preparation Example 40 (Preparation of Pigment Dispersion 40))
Pigment Dispersion 3 to Pigment Dispersion 40 were treated in the same manner as Pigment Dispersion Preparation 1 except that the mixture in Pigment Dispersion Preparation 1 was replaced with one having the composition shown in Table 2. Obtained. As understood from Table 2, Pigment Dispersion 1 contains naphthalenesulfonic acid Na formalin condensate, but does not contain Pigment Dispersion 2 to Pigment Dispersion 40. The pigment dispersion 40 does not contain a copolymer (polymer) containing a salt of a phosphonic acid group, but contains a low-molecular bisphosphonate.

<Preparation of ink for ink jet recording>

[Example 1]
The following materials were mixed, stirred for 1.5 hours, and filtered through a membrane filter having a pore size of 1.2 μm to obtain an ink.
・ Pigment Dispersion 1 (Pigment solid content 20% by mass) ... 40.0 parts by mass-1,3-butanediol (water-soluble solvent) ... 20.0 parts by mass Glycerin (water-soluble solvent) 10.0 parts by mass 2-ethyl-1,3 -Hexanediol (water-soluble solvent) ... 1.0 parts by mass2,2,4-trimethyl-1,3-pentadiol (water-soluble solvent) ... 1.0 parts by mass Surfactant (solid content 40% by mass) ... 2.0 parts by mass (DuPont, Zonyl FS-300)
・ Aqueous solution of polymer 14 (solid content 10% by mass) 20.0 parts by mass Distilled water ... ... 6.0 parts by mass

[Example 2]
In place of pigment dispersion 1 used in Example 1, pigment dispersion 2 (Bk dispersion containing polymer 1) was used, and the aqueous solution of polymer 14 used in Example 1 was not added, but distillation in Example 1 was performed. Ink of Example 2 was obtained in the same manner as Example 1 except that 26.0 parts by mass of distilled water was used instead of 6.0 parts by mass of water.

[Example 3]
Ink of Example 3 was obtained in the same manner as Example 2 except that Pigment Dispersion 3 (Bk dispersion containing polymer 2) was used instead of Pigment Dispersion 2 used in Example 2.

[Example 4]
Ink of Example 4 was obtained in the same manner as in Example 2 except that Pigment Dispersion 4 (Bk dispersion containing Polymer 3) was used instead of Pigment Dispersion 2 used in Example 2.

[Example 5]
Ink of Example 5 was obtained in the same manner as in Example 2, except that Pigment Dispersion 5 (Bk dispersion containing polymer 4) was used instead of Pigment Dispersion 2 used in Example 2.

[Example 6]
Ink of Example 6 was obtained in the same manner as in Example 2 except that Pigment Dispersion 6 (Bk dispersion containing polymer 5) was used instead of Pigment Dispersion 2 used in Example 2.

[Example 7]
Ink of Example 7 was obtained in the same manner as in Example 2 except that Pigment Dispersion 7 (Bk dispersion containing polymer 6) was used instead of Pigment Dispersion 2 used in Example 2.

[Example 8]
Ink of Example 8 was obtained in the same manner as in Example 2, except that Pigment Dispersion 8 (Bk dispersion containing polymer 7) was used instead of Pigment Dispersion 2 used in Example 2.

[Example 9]
Ink of Example 9 was obtained in the same manner as in Example 2 except that Pigment Dispersion 9 (Bk dispersion containing polymer 8) was used instead of Pigment Dispersion 2 used in Example 2.

[Example 10]
Ink of Example 10 was obtained in the same manner as in Example 2 except that Pigment Dispersion 10 (Bk dispersion containing polymer 9) was used instead of Pigment Dispersion 2 used in Example 2.

[Example 11]
Ink of Example 11 was obtained in the same manner as Example 2 except that Pigment Dispersion 11 (Bk dispersion containing polymer 10) was used instead of Pigment Dispersion 2 used in Example 2.

[Example 12]
Ink of Example 12 was obtained in the same manner as in Example 2, except that Pigment Dispersion 12 (Bk dispersion containing polymer 11) was used instead of Pigment Dispersion 2 used in Example 2.

[Example 13]
Ink of Example 13 was obtained in the same manner as Example 2 except that Pigment Dispersion 13 (Bk dispersion containing polymer 12) was used instead of Pigment Dispersion 2 used in Example 2.

[Example 14]
Ink of Example 14 was obtained in the same manner as Example 2, except that Pigment Dispersion 14 (Bk dispersion containing polymer 13) was used instead of Pigment Dispersion 2 used in Example 2.

[Example 15]
Ink of Example 15 was obtained in the same manner as in Example 2 except that Pigment Dispersion 15 (Bk dispersion containing polymer 14) was used instead of Pigment Dispersion 2 used in Example 2.

[Example 16]
Ink of Example 16 was obtained in the same manner as Example 2 except that Pigment Dispersion 16 (Cy Dispersion Containing Polymer 14) was used instead of Pigment Dispersion 2 used in Example 2.

[Example 17]
Ink of Example 17 was obtained in the same manner as Example 2 except that Pigment Dispersion 17 (Ma Dispersion Containing Polymer 14) was used instead of Pigment Dispersion 2 used in Example 2.

[Example 18]
Ink of Example 18 was obtained in the same manner as Example 2 except that Pigment Dispersion 18 (Ye Dispersion containing Polymer 14) was used instead of Pigment Dispersion 2 used in Example 2.

[Example 19]
Ink of Example 19 was obtained in the same manner as in Example 2 except that Pigment Dispersion 19 (Bk dispersion containing polymer 15) was used instead of Pigment Dispersion 2 used in Example 2.

[Example 20]
Ink of Example 20 was obtained in the same manner as Example 2 except that Pigment Dispersion 20 (Bk dispersion containing polymer 16) was used instead of Pigment Dispersion 2 used in Example 2.

[Example 21]
Ink of Example 21 was obtained in the same manner as in Example 2 except that Pigment Dispersion 21 (Bk dispersion containing polymer 17) was used instead of Pigment Dispersion 2 used in Example 2.

[Example 22]
Ink of Example 22 was obtained in the same manner as Example 2 except that Pigment Dispersion 22 (Bk dispersion containing polymer 18) was used instead of Pigment Dispersion 2 used in Example 2.

[Example 23]
Ink of Example 23 was obtained in the same manner as in Example 2 except that Pigment Dispersion 23 (Bk dispersion containing polymer 19) was used instead of Pigment Dispersion 2 used in Example 2.

[Example 24]
Ink of Example 24 was obtained in the same manner as in Example 2, except that Pigment Dispersion 24 (Bk dispersion containing polymer 20) was used instead of Pigment Dispersion 2 used in Example 2.

[Example 25]
Ink of Example 25 was obtained in the same manner as in Example 2 except that Pigment Dispersion 25 (Bk dispersion containing polymer 21) was used instead of Pigment Dispersion 2 used in Example 2.

[Example 26]
Ink of Example 26 was obtained in the same manner as in Example 2 except that Pigment Dispersion 26 (Bk dispersion containing polymer 22) was used instead of Pigment Dispersion 2 used in Example 2.

[Example 27]
Ink of Example 27 was obtained in the same manner as in Example 2 except that Pigment Dispersion 27 (Bk dispersion containing polymer 23) was used instead of Pigment Dispersion 2 used in Example 2.

[Example 28]
Ink of Example 28 was obtained in the same manner as in Example 2 except that Pigment Dispersion 28 (Bk dispersion containing polymer 24) was used instead of Pigment Dispersion 2 used in Example 2.

[Example 29]
Ink of Example 29 was obtained in the same manner as Example 2 except that Pigment Dispersion 29 (Bk dispersion containing polymer 25) was used instead of Pigment Dispersion 2 used in Example 2.

[Example 30]
Ink of Example 30 was obtained in the same manner as in Example 2 except that Pigment Dispersion 30 (Bk dispersion containing polymer 26) was used instead of Pigment Dispersion 2 used in Example 2.

[Example 31]
Ink of Example 31 was obtained in the same manner as in Example 2 except that Pigment Dispersion 31 (Bk dispersion containing polymer 27) was used instead of Pigment Dispersion 2 used in Example 2.

[Example 32]
Ink of Example 32 was obtained in the same manner as Example 2 except that Pigment Dispersion 32 (Bk dispersion containing polymer 28) was used instead of Pigment Dispersion 2 used in Example 2.

[Example 33]
Ink of Example 33 was obtained in the same manner as in Example 2 except that Pigment Dispersion 33 (Bk dispersion containing polymer 29) was used instead of Pigment Dispersion 2 used in Example 2.

[Example 34]
Ink of Example 34 was obtained in the same manner as in Example 2, except that Pigment Dispersion 34 (Bk dispersion containing polymer 30) was used instead of Pigment Dispersion 2 used in Example 2.

[Example 35]
Ink of Example 35 was obtained in the same manner as Example 2 except that Pigment Dispersion 35 (Bk dispersion containing Polymer 31) was used instead of Pigment Dispersion 2 used in Example 2.

[Example 36]
Ink of Example 36 was obtained in the same manner as Example 2 except that Pigment Dispersion 36 (Bk dispersion containing polymer 32) was used instead of Pigment Dispersion 2 used in Example 2.

[Example 37]
Ink of Example 37 was obtained in the same manner as Example 2 except that Pigment Dispersion 37 (Bk dispersion containing polymer 33) was used instead of Pigment Dispersion 2 used in Example 2.

[Comparative Example 1]
Ink of Comparative Example 1 was obtained in the same manner as in Example 2 except that Pigment Dispersion 38 (Bk dispersion containing polymer 34) was used instead of Pigment Dispersion 2 used in Example 2.

[Comparative Example 2]
Ink of Comparative Example 2 was obtained in the same manner as in Example 2, except that Pigment Dispersion 39 (Bk dispersion containing polymer 35) was used instead of Pigment Dispersion 2 used in Example 2.

[Comparative Example 3]
The same procedure as in Example 2 was conducted except that pigment dispersion 40 (Bk dispersion containing a salt of 1-hydroxyethylidene-1,1-bisphosphonic acid) was used instead of pigment dispersion 2 used in Example 2. Thus, an ink of Comparative Example 3 was obtained.
These results are summarized in Table 3.
In the above description, Bk is black, Cy is cyan, Ma is magenta, and Ye is yellow.

[Evaluation results]
Next, the inkjet inks of Examples 1 to 37 and Comparative Examples 1 to 3 were evaluated by the following evaluation method. The results are shown in Table 4 below.

<Image density>
In the environment of 23 ° C. and 50% RH, the ink prepared in an inkjet printer (manufactured by Ricoh Co., Ltd., IPSiO GX5000) was filled, and 64 point characters “JIS X0208 (1997), 2223” prepared by Microsoft Word 2000 (manufactured by Microsoft). ”Is printed on plain paper 1 (XEROX 4200, manufactured by XEROX) and plain paper 2 (MyPaper, manufactured by Ricoh Co., Ltd.), and“ JIS X0208 (1997), The color “■” part of “2223” was measured with X-Rite 938 (manufactured by X-Rite Co., Ltd.) and judged according to the following evaluation criteria.
The printing mode used was a driver attached to the printer, in which the “plain paper-standard fast” mode was changed to “no color correction” from the user setting for plain paper.

〔Evaluation criteria〕
(black)
A: 1.25 or more B: 1.20 or more and less than 1.25 C: 1.10 or more and less than 1.20 D: less than 1.10 E: The pigment gelled and could not be dispersed in the ink, and printing was not possible (yellow )
A: 0.80 or more B: 0.75 or more and less than 0.80 C: 0.70 or more and less than 0.75 D: Less than 0.70 E: The pigment is gelled and cannot be dispersed in the ink and cannot be printed (magenta )
A: 0.95 or more B: 0.85 or more and less than 0.95 C: 0.75 or more and less than 0.85 D: Less than 0.75 E: The pigment gelates and cannot be dispersed in the ink, and printing cannot be performed (cyan) )
A: 1.05 or more B: 0.95 or more and less than 1.05 C: 0.85 or more and less than 0.95 D: Less than 0.85 E: The pigment is gelled and cannot be dispersed in the ink and cannot be printed.

<Storage stability of pigment dispersion>
Each pigment dispersion was put in a polyethylene container, sealed, stored at 60 ° C. for 1 week, the change rate 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.
Viscosity change rate (%) = (viscosity of pigment dispersion after storage / viscosity of pigment dispersion before storage) × 100

  The viscosity was measured using a viscometer (RE500L, manufactured by Toki Sangyo Co., Ltd.), adjusted to 50 or 100 rotations according to the viscosity of the sample, and evaluated based on the following criteria. .

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

<Ink storage stability>
Each ink was filled in an ink cartridge and stored at 60 ° 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.
Viscosity change rate (%) = (ink viscosity after storage / ink viscosity before storage) × 100
The viscosity was measured using a viscometer (RE500L, manufactured by Toki Sangyo Co., Ltd.), adjusted to 50 or 100 rotations according to the viscosity of the sample, and evaluated based on the following criteria. .
[Evaluation criteria]
A: Change rate of viscosity is within ± 5% B: Change rate of viscosity is over ± 5% and within ± 8% C: Change rate of viscosity is over ± 8% and within ± 10% D: Change rate of viscosity is Over ± 10% and within ± 30% E: Viscosity change rate exceeds ± 30% (cannot be evaluated due to gelation)

  From the results shown in Table 4, the ink of the example can obtain a higher image density even on general plain paper than the ink of the comparative example, and the ink can be used even if the content of the water-soluble organic solvent exceeds 20% by mass. It was found that the storage stability of was excellent.

DESCRIPTION OF SYMBOLS 101 Device main body 102 Paper feed tray 103 Paper discharge tray 104 Ink storage container loading part 105 Operation part 111 Upper cover 112 Front surface 115 Front cover 131 Guide rod 132 Stay 133 Carriage 134 Recording head 135 Sub tank 141 Paper mounting part 142 Paper 143 Paper feed Roller 144 Separation pad 145 Guide 151 Conveying belt 152 Counter roller 153 Conveying guide 154 Holding member 155 Tip pressure roller 156 Charging roller 157 Conveying roller 158 Densation roller 161 Guide member 171 Separating claw 172 Discharging roller 173 Discharging roller 181 Double-sided feeding Paper unit 182 Manual paper feed unit 200 Ink container 241 Ink container 242 Ink inlet 243 Ink outlet 244 Case (exterior)

Special table 2009-513802 JP 2012-51357 A JP 2004-123904 A

Claims (10)

An ink for inkjet recording having a copolymer containing at least water, a water-soluble solvent, a pigment, and a salt of a diphosphonic acid group, wherein the copolymer containing the salt of a diphosphonic acid group is represented by the following general formula (1). An inkjet recording ink comprising at least the structural unit (1) and the structural unit (2) represented by the general formula (2).

(R ₁ in the general formula (1) represents a hydrogen atom or a methyl group, and M ⁺ represents an alkali metal ion, an organic ammonium ion, or a proton. However, an alkali metal and a proton, and an organic ammonium ion and a proton are mixed. And more than half of M ^{+ in} the copolymer is an alkali metal ion or an organic ammonium ion, and X in the general formula (1) represents an alkylene group having 1 to 3 carbon atoms.)

(R ₂ in the general formula (2) represents a hydrogen atom or a methyl group, and Z ₁ represents an aralkyl group or an alkyl group having 12 to 22 carbon atoms .) In an inkjet recording ink having a copolymer containing at least water, a water-soluble solvent, a pigment, and a salt of a diphosphonic acid group, the copolymer containing the salt of the diphosphonic acid group is represented by at least the following general formula (4). An ink for ink jet recording, which is a radical copolymer including a monomer-derived site and a monomer-derived site represented by the general formula (5).

(R ₁ in the general formula (4) represents a hydrogen atom or a methyl group, M ⁺ represents an alkali metal ion, an organic ammonium ion, or a proton. 3 represents an alkylene group.)

(R ₂ in the general formula (5) represents a hydrogen atom or a methyl group, and Z ₂ represents an aralkyl group or an alkyl group having 12 to 22 carbon atoms .) Z _{1 in} the structural unit (2) of the general formula (2) in the copolymer containing a salt of the diphosphonic acid group is a benzyl group, a phenethyl group, or an alkyl group having 12 to 22 carbon atoms. Item 3. The ink for inkjet recording according to Item 1 or 2.   The content of the structural unit (1) of the general formula (1) in the copolymer containing a salt of the diphosphonic acid group is 30% by mass to 70% by mass, according to any one of claims 1 to 3. The ink for inkjet recording as described.   The content of the structural unit (1) of the general formula (1) in the copolymer containing a salt of the diphosphonic acid group is 40% by mass to 60% by mass, for inkjet recording according to claim 4, ink.   6. The aqueous solution viscosity (concentration: 10 mass%, 25 ° C.) of the copolymer containing a salt of the diphosphonic acid group is 1.5 to 4.0 mPa · s. 6. Ink jet recording ink. In the copolymer containing the salt of the diphosphonic acid group, M ⁺ is a tetramer composed of an alkyl group having 1 to 5 carbon atoms at the site derived from the structural unit (1) of the general formula (1) or the monomer of the general formula (4). The ink for ink jet recording according to any one of claims 1 to 6, wherein the ink is an alkyl ammonium ion. Z is a moiety derived from the monomer represented by the general formula (5). ₂ The ink for inkjet recording according to claim 2, wherein is a benzyl group, a phenethyl group, or an alkyl group having 12 to 22 carbon atoms. An ink cartridge comprising the ink for ink jet recording according to claim 1 contained in a container. 9. An ink jet recording apparatus comprising at least ink flying means for recording an image by applying a stimulus to the ink for ink jet recording according to claim 1 and causing the ink for ink jet recording to fly.

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