JP2005146083A - Aqueous ink composition, inkjet recording method using the same and record - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an aqueous ink composition suitable for inkjet recording inks, which is high in storage stability when allowed to stand for a long time/at an elevated temperature, high in discharge stability in using an inkjet printer, and excellent in permeability/drying nature/color development irrespective of the kinds of recording media. <P>SOLUTION: The aqueous ink composition comprises a coloring component, 2-ethyl-1,3-hexane diol, and water. The coloring component is a dispersion in which a colorant is enveloped in a dispersing polymer to enable it to disperse into water, and the dispersing polymer is by itself insoluble in water. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an aqueous ink composition, an ink jet recording method, and a recorded matter.

  The ink jet recording method is a printing method in which printing is performed by causing a droplet of an ink composition to fly and adhere to a recording medium such as paper. This method has a feature that a high-resolution and high-quality image can be printed at a high speed with a relatively inexpensive apparatus.

  The ink composition used in the ink jet recording method generally contains water as a main component and contains a moisturizing agent such as glycerin for the purpose of preventing coloring components and clogging. As the colorant used in the ink composition for ink jet recording, many water-soluble dyes are used because of the high saturation of the colorant, the rich variety of colorants that can be used, and the solubility in water. Yes.

  However, the dye may be inferior in various properties such as light resistance and water resistance, and thus a printed matter printed with the dye-based ink composition is inferior in light resistance and water resistance. The water resistance is improved by an ink jet recording medium having an ink absorbing layer, but it is still not sufficient for plain paper.

  In contrast, pigments are superior in light resistance and water resistance compared to dyes, and in recent years, the use of pigments as colorants in ink compositions for ink jet recording has been studied for the purpose of improving light resistance and water resistance. Here, since the pigment is generally insoluble in water, when the pigment is used in the water-based ink composition, the pigment is mixed with a dispersant such as a water-soluble resin and stably dispersed in water. It is necessary to prepare as.

  In order to stably disperse the pigment in the water system, it is necessary to consider the type of pigment, particle size, type of dispersant used, and dispersion means, and so far, many dispersion methods and ink jet recording inks have been proposed. Has been. For example, an aqueous pigment ink in which carbon black is dispersed with a surfactant or a polymer dispersant is known (see Patent Document 1 and Patent Document 2).

  In addition, an ink composition comprising water, a styrene-maleic acid copolymer, ε-caprolactam, and a pigment has been proposed (see Patent Document 3).

  An ink composition containing an aqueous medium, a styrene-maleic acid copolymer, and a copper phthalocyanine pigment has been proposed (see Patent Document 4).

  Further, water-based inks using a resin in which 60 mol% or more of the acid groups of the dispersion polymer are neutralized with an alkaline neutralizing agent have been proposed (see Patent Documents 5 and 6).

  Furthermore, an ink composition using 2-ethyl-1,3-hexanediol has been proposed for the purpose of enhancing the permeability and drying property of the ink to the recording medium (see Patent Document 7).

JP-A 64-6074 JP-A 64-31881 Japanese Patent Laid-Open No. 3-252467 Japanese Patent Laid-Open No. 3-79680 JP-A-8-183920 Japanese Patent Laid-Open No. 9-40895 JP 2003-3100 A

  As described above, in order to use a pigment in an ink composition for ink jet recording, it is important to stably disperse it in water and hold it for a long time. 4) was not satisfactory.

  In addition to the colorant, various additives, particularly a water-soluble organic solvent, are added to the ink used in the ink jet recording method in order to optimize various characteristics in the ink jet recording method. The water-soluble organic solvent includes a moisturizing agent that prevents drying, a penetrating solvent or surfactant that controls the permeability to the recording medium by lowering the surface tension of the ink composition, and an organic amine that adjusts the pH of the ink composition. Etc. Among these solvents, there is a case where the dispersibility is affected by affecting the dispersed colorant and the storage stability of the ink composition is inhibited. In particular, there is a problem that these influences are likely to occur with a solvent having a strong affinity for the pigment surface having a hydrophobic surface and the hydrophobic portion in the dispersion polymer. In addition, when such an effect occurs, the dispersion polymer as the dispersant is released from the pigment surface and dissolved in the ink, and when this is used as an ink for ink jet recording, the discharge from the printer head is not possible. There was a problem of becoming stable.

  In aqueous inks using a resin in which 60 mol% or more of the acid groups of the dispersion polymer are neutralized with an alkaline neutralizing agent described in the prior art (Patent Documents 5 and 6), the water-soluble ink used is Depending on the type of water-soluble organic solvent, there is a problem that the storage stability and ejection stability of the ink are lowered due to the influence of the dispersion polymer and the water-soluble organic solvent. In particular, 2-ethyl-1,3-hexanediol used in the above-described conventional technology (Patent Document 7) has a large influence, and the ink using the dispersion of the conventional technology is stored in a long-term and high-temperature environment. In this case, there was a significant change in the physical property values and adverse effects such as aggregation and precipitation. About this point, even if it uses the pigment dispersion liquid described in patent document 7, it has not improved yet. When 2-ethyl-1,3-hexanediol is used as an additive to an ink for ink jet recording, it has excellent penetrability / drying / coloring properties with respect to the recording medium of the ink and clogging with respect to the printer head. Although it is a very useful solvent, it has not been fully used in the prior art due to the effects described above.

  Accordingly, an object of the present invention is to solve the above-mentioned problems and to provide a water-based ink composition suitable as an ink for ink jet recording having high storage stability, high ejection stability, and excellent color developability.

  The aqueous ink composition of the present invention is an aqueous ink composition comprising a coloring component, 2-ethyl-1,3-hexanediol, and water, and the coloring component includes a colorant as a dispersion polymer. The dispersion polymer is characterized in that it is a dispersion composed of a dispersion polymer that is dispersible in water and insoluble in water by itself.

  The water-based ink composition of the invention further comprises a penetrating solvent.

  The water-based ink composition of the invention is characterized in that the penetrating solvent is selected from the group consisting of monohydric alcohols, glycol monoether derivatives of polyhydric alcohols, and 1,2-alkyldiols.

  The aqueous ink composition of the present invention is characterized by further comprising an acetylene glycol surfactant.

  The water-based ink composition of the invention is characterized by further containing a water-soluble and / or water-dispersible additive resin.

  The water-based ink composition of the invention is characterized in that the additive resin alone is insoluble in water.

  The water-based ink composition of the invention is characterized in that the colorant is carbon black.

  The water-based ink composition of the invention is characterized in that the colorant is an organic pigment.

  The aqueous ink composition of the present invention further comprises a weak alkalinizing agent and is characterized by being alkaline.

  The water-based ink composition of the invention is characterized in that the weak alkalinizing agent comprises at least one compound selected from an organic acid salt and an organic buffer.

  The inkjet recording method of the present invention is characterized in that recording is performed by discharging droplets of the aqueous ink composition described above and attaching the droplets to a recording medium.

  The recorded matter of the present invention is characterized in that the above-described aqueous ink composition is printed by an inkjet recording method.

  The aqueous ink composition of the present invention comprises a coloring component, 2-ethyl-1,3-hexanediol, and water as essential components, and the coloring component includes a colorant as a dispersion polymer and is dispersed in water. A dispersion which is made possible and that the dispersion polymer alone is insoluble in water.

  Moreover, the water-based ink composition of the present invention according to another aspect further comprises a penetrating solvent in addition to the above components.

  Furthermore, the aqueous ink composition of the present invention according to another embodiment further comprises an acetylene alcohol surfactant in addition to the above components.

  With such a configuration, it is possible to obtain an aqueous ink composition suitable as an inkjet recording ink that has high storage stability, high ejection stability, and excellent color developability for the inkjet recording method.

  Here, it is essential that the dispersion polymer has both a hydrophobic part and a hydrophilic part as its polymer structure. If the dispersed polymer does not have a hydrophobic portion, the entire polymer is dissolved in water and does not become a dispersed polymer, and the 2-ethyl-1,3-hexanediol essential for the aqueous ink composition of the present invention is A stable colorant dispersion cannot be obtained. Further, the free polymer dissolved in water in this manner makes the discharge of the aqueous ink composition from the printer head unstable. On the other hand, if the dispersion polymer does not have a hydrophilic portion, the colorant cannot be stably dispersed by the polymer, and the colorant dispersion liquid aggregates and settles.

  Further, 2-ethyl-1,3-hexanediol is an essential component of the water-based ink composition according to the present invention, but if it is not used, ejection stability and storage stability are secured when used as an ink for ink jet recording. However, depending on the type of the recording medium, the penetrability / dryness is poor, and the image becomes unclear with poor color development.

The components of the water-based ink composition of the present invention are described below.
<Water-based ink composition>
[Dispersed polymer]
The dispersion polymer in the water-based ink composition of the present invention is insoluble in water alone and is soluble in an organic solvent (preferably a hydrophilic organic solvent such as acetone or methyl ethyl ketone) used in the method for producing a dispersion described later in the examples. Although there is no restriction | limiting in particular if it is a polymer, It is essential to have both a hydrophobic part and a hydrophilic part as the polymer structure.

Here, the hydrophobic portion refers to a repeating unit having an alkyl group, a cycloalkyl group, an aromatic ring, or an unneutralized group. An unneutralized group is a group that can be neutralized by a neutralizing agent, and examples thereof include an acid group and an alkaline group. Specific examples of the unneutralized group include a carboxylic acid group and a sulfonic acid group.
Moreover, as a hydrophilic part, the repeating unit which has a neutralizing group is shown. The neutralizing group is a group formed by neutralizing an unneutralized group, and is preferably an ionic group. The unneutralized group and the neutralized group are preferably anionic groups, and particularly suitable when the unneutralized group is a carboxylic acid group and the neutralized group is a carboxylic acid anion group (carboxylate group). Can be illustrated. Examples of the carboxylate include lithium carboxylate, sodium carboxylate, potassium carboxylate, and ammonium carboxylate.

  Since the dispersion polymer has the above-described structure, the hydrophobic polymer can be firmly adsorbed on the hydrophobic surface of the colorant described later and can include the colorant. Furthermore, since the hydrophilic part is compatible with water, it can be a dispersion that is stably dispersed in water.

  The dispersion polymer having an anionic group is obtained by polymerizing, for example, a monomer having an anionic group (hereinafter referred to as an anionic group-containing monomer) and, if necessary, another monomer that can be copolymerized with these monomers in a solvent. Is obtained. Examples of the anionic group-containing monomer include a monomer having a carboxylic acid group and a monomer having a sulfonic acid group.

  As the monomer having a carboxylic acid group, an acrylic monomer containing one or two carboxylic acid groups in the repeating unit is preferable.

  Specific examples of the monomer having a carboxylic acid group include acrylic acid, methacrylic acid, crotonic acid, ethacrylic acid, propylacrylic acid, isopropylacrylic acid, itaconic acid, fumaric acid, maleic acid and the like. Among these, acrylic acid, methacrylic acid, and maleic acid are preferable.

  Specific examples of the monomer having a sulfonic acid group include styrene sulfonic acid, isoprene sulfonic acid, sulfobutyl methacrylate, and allyl sulfonic acid. Furthermore, after polymerizing the resin, it is also preferable to sulfonate with a sulfonating agent such as sulfuric acid, fuming sulfuric acid, sulfamic acid and the like.

  Specific examples of other monomers that can be copolymerized with the anionic group-containing monomer include methyl acrylate, ethyl acrylate, isopropyl acrylate, acrylic acid-n-propyl, acrylic acid-n-butyl, and acrylic acid-t-. Butyl, 2-ethylhexyl acrylate, n-octyl acrylate, lauryl acrylate, benzyl acrylate, methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, methacrylic acid n-propyl, methacrylic acid n-butyl, (Meth) acrylic esters such as isobutyl methacrylate, tert-butyl methacrylate, 2-ethylhexyl methacrylate, n-octyl methacrylate, lauryl methacrylate, stearyl methacrylate, tridecyl methacrylate, benzyl methacrylate, etc. ; Steer Addition reaction product of oil fatty acid and (meth) acrylic acid ester monomer having oxirane structure such as addition reaction product of acid and glycidyl methacrylate; oxirane compound containing alkyl group having 3 or more carbon atoms and (meth) acrylic Addition reaction product with acid; styrene monomer such as styrene, α-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, p-tert-butylstyrene, etc .; such as benzyl itaconate Itaconic acid esters; maleic acid esters such as dimethyl maleate; fumaric acid esters such as dimethyl fumarate; acrylonitrile, methacrylonitrile, vinyl acetate, isobornyl acrylate, isobornyl methacrylate, aminoethyl acrylate, acrylic acid Aminopropyl, aqua Methylaminoethyl acrylate, methylaminopropyl acrylate, ethylaminoethyl acrylate, ethylaminopropyl acrylate, aminoethylamide acrylate, aminopropylamide acrylate, methylaminoethylamide acrylate, methylaminopropylamide acrylate, Acrylic acid ethylaminoethylamide, acrylic acid ethylaminopropylamide, methacrylic acid amide, aminoethyl methacrylate, aminopropyl methacrylate, methylaminoethyl methacrylate, methylaminopropyl methacrylate, ethylaminoethyl methacrylate, ethylamino methacrylate Propyl, methacrylic acid aminoethylamide, methacrylic acid aminopropylamide, methacrylic acid methylaminoethylamide, methacrylic acid methylaminoamide Pyramide, ethyl aminoethylamide methacrylate, ethyl aminopropyl amide methacrylate, hydroxymethyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, hydroxymethyl methacrylate, 2-hydroxyethyl methacrylate, Examples include 2-hydroxypropyl methacrylate, N-methylolacrylamide, and allyl alcohol.

  These dispersion polymers preferably have a number average molecular weight in the range of 1,000 to 200,000, particularly preferably in the range of 3,000 to 150,000. When the number average molecular weight of the dispersion polymer is within this range, the function as a coating film in the colorant or as a coating film in the aqueous ink composition can be sufficiently exhibited.

  Examples of the alkaline compound that neutralizes a part of the unneutralized group of the dispersion polymer having an anionic group include organic amines and alkali metal salt compounds. Specific examples of organic amines include salts with volatile amine compounds such as ammonia, triethylamine, tributylamine, dimethylethanolamine, diisopropanolamine, morpholine, and high boiling points that are difficult to volatilize such as diethanolamine, triethanolamine, tripropanolamine. And salts of organic amines. Specific examples of the alkali metal salt compound include compounds having lithium, sodium and potassium as the alkali metal, preferably an alkali metal hydroxide salt such as sodium hydroxide, potassium hydroxide and lithium hydroxide, more preferably potassium hydroxide. Can be mentioned.

  In the present invention, the hydrophobic part is preferably in the range of 1% to 67% in terms of molar ratio with respect to the sum of the repeating units of the hydrophobic part and the hydrophilic part. The range of 1% to 30% It is particularly preferred that Thereby, since the bad influence by 2-ethyl-1,3-hexanediol essential to the aqueous ink composition of the present invention does not occur, an aqueous ink composition having particularly high storage stability can be obtained. If there are too many hydrophobic parts, the dispersion of the colorant and the like by the dispersion polymer is unstable, and the colorant dispersion tends to aggregate and settle. Conversely, if there are too few hydrophobic parts, the entire dispersion polymer will be water-soluble and colored. There is a tendency that the amount of free polymer that does not adhere to the agent increases and the discharge of the aqueous ink composition from the printer head becomes unstable. Moreover, the bad influence by 2-ethyl- 1, 3- hexanediol will generate | occur | produce.

  The amount of the anionic group in the dispersion polymer is such that the acid value is about 30 KOHmg / g or more, preferably about 50 to 250 KOHmg / g. When the acid value of the dispersion polymer is in such a range, the storage stability of the colorant particles formed into a coating is improved, and the water resistance of the recorded image is improved.

  Although the dispersion polymer described above has little interaction with 2-ethyl-1,3-hexanediol, which will be described later, if a colorant dispersion dispersed with this polymer is used, the dispersion of the prior art described above and 2 -Since the trouble at the time of using together with ethyl-1, 3- hexanediol can be eliminated, the water-based ink composition suitable as an ink for inkjet recording excellent in storage stability and discharge stability is realizable.

[Colorant]
Examples of the colorant include organic pigments, carbon black, oil-soluble dyes, and disperse dyes as colorants that are insoluble or hardly soluble in an aqueous medium. In particular, carbon black, organic pigments, oil-soluble dyes, and disperse dyes are preferred because they have good color development and are difficult to settle during dispersion due to their low specific gravity.

  In the aqueous ink composition of the present invention, such a colorant is dispersed by the dispersion polymer (preferably a polymer having an anionic group).

  Specific examples of preferred carbon black in the present invention include No. 1 as carbon black manufactured by Mitsubishi Chemical Corporation. 2300, 900, MCF88, no. 20B, no. 33, no. 40, no. 45, no. 52, MA7, MA8, MA100, No2200B and the like. Examples of carbon blacks manufactured by Degussa include color blacks FW1, FW2, FW2V, FW18, FW200, S150, S160, S170, Pretex 35, U, V, 140U, Special Black 6, 5, 4A, 4, 250, etc. It is done. Examples of carbon black manufactured by Columbia Carbon include Conductex SC, Raven 1255, 5750, 5250, 5000, 3500, 1255, 700, and the like. Examples of the carbon black manufactured by Cabot include Regal 400R, 330R, 660R, Mogul L, Monarch 700, 800, 880, 900, 1000, 1100, 1300, 1400, Elftex 12 and the like manufactured by Cabot. Note that these are examples of carbon black suitable for the present invention, and the present invention is not limited to these. These carbon blacks may be used singly or as a mixture of two or more. These pigments are added in an amount of 0.5 to 15% by weight, preferably 1 to 10% by weight, based on the total amount of the aqueous ink composition.

  Preferred organic pigments in the present invention include quinacridone pigments, quinacridone quinone pigments, dioxazine pigments, phthalocyanine pigments, anthrapyrimidine pigments, ansanthrone pigments, indanthrone pigments, flavanthrone pigments, perylene pigments. , Diketopyrrolopyrrole pigments, perinone pigments, quinophthalone pigments, anthraquinone pigments, thioindigo pigments, benzimidazolone pigments, isoindolinone pigments, azomethine pigments or azo pigments.

  Specific examples of the organic pigment used in the water-based ink composition according to the present invention include the following.

  Examples of the pigment used in the cyan ink composition include C.I. I. Pigment blue 1, 2, 3, 15: 3, 15: 4, 15:34, 16, 22, 60, etc .; C.I. I. Bat blue 4, 60 and the like, preferably C.I. I. Pigment Blue 15: 3, 15: 4, and one or a mixture of two or more selected from the group consisting of 60. These pigments are contained in an amount of 0.5 to 15% by weight, preferably 1 to 10% by weight, based on the cyan ink composition.

  Examples of the pigment used in the magenta ink composition include C.I. I. Pigment Red 5, 7, 12, 48 (Ca), 48 (Mn), 57 (Ca), 57: 1, 112, 122, 123, 168, 184, 202, C.I. I. Pigment violet 19 and the like, preferably C.I. I. Pigment red 122, 202, and 209, C.I. I. One or a mixture of two or more selected from the group consisting of pigment violet 19. These pigments are contained in an amount of about 0.5 to 15% by weight, preferably about 1 to 10% by weight, based on the magenta ink composition.

  Examples of the pigment used in the yellow ink composition include C.I. I. Pigment Yellow 1, 2, 3, 12, 13, 14C, 16, 17, 73, 74, 75, 83, 93, 95, 97, 98, 119, 110, 114, 128, 129, 138, 150, 151, 154, 155, 180, 185, etc., preferably C.I. I. One or a mixture of two or more selected from the group consisting of CI Pigment Yellow 74, 109, 110, 128, and 138. These pigments are contained in an amount of about 0.5 to 15% by weight, preferably about 1 to 10% by weight, based on the yellow ink composition.

  Examples of the pigment used in the orange ink composition include C.I. I. Pigment Orange 36 or 43, or a mixture thereof. These pigments are contained in an amount of about 0.5 to 15% by weight, preferably about 1 to 10% by weight, based on the orange ink composition.

  Examples of the pigment used in the green ink composition include C.I. I. Pigment Green 7 or 36 or a mixture thereof. These pigments are contained in an amount of about 0.5 to 15% by weight, preferably about 1 to 10% by weight, based on the green ink composition.

  In the water-based ink composition of the invention, the ratio of the colorant to the dispersion polymer is preferably 10: 1 to 1:10, more preferably 4: 1 to 1: 3. Further, the particle size of the colorant at the time of dispersion is such that the maximum particle size when measured by a dynamic light scattering method is less than 500 nm and the average particle size is 300 nm or less, more preferably the average particle size is 200 nm or less.

[2-ethyl-1,3-hexanediol]
The aqueous ink composition of the present invention contains 2-ethyl-1,3-hexanediol as an essential component.

  2-ethyl-1,3-hexanediol has almost no dissolving action on the above-mentioned dispersion polymer, and has an action of stably dispersing and holding the dispersion liquid in which this polymer is dispersed. Therefore, in the water-based ink composition of the present invention, even when 2-ethyl-1,3-hexanediol is contained, there is almost no free dispersion polymer that is not adsorbed on the surface of the colorant such as pigment, so that high storage stability is obtained. -There is an advantage that discharge stability can be secured.

  In addition, 2-ethyl-1,3-hexanediol has excellent characteristics as a penetrating component, and an aqueous ink composition containing this has the effect of having substantially the same wettability and penetrating speed without being affected by the type of recording medium. Indicates. Furthermore, since it also has a function of exhibiting high color developability regardless of the colorant, it has an effect that a clear printed image with high color developability can be realized without selecting a paper type.

  Further, 2-ethyl-1,3-hexanediol also has an action as a humectant generally used in ink jet recording ink. Therefore, it can be used as a moisturizing component. Accordingly, since the total amount of the solvent in the aqueous ink composition can be reduced and the ink viscosity can be kept low, it is possible to obtain an aqueous ink composition exhibiting further high color developability by adding a large amount of a colorant or the like.

  The amount of 2-ethyl-1,3-hexanediol added is preferably 0.1% by weight to 20% by weight, more preferably 0.5% by weight to 15% by weight, based on the total amount of the aqueous ink composition. When the addition amount is less than 0.1% by weight, the penetrability and drying property of the water-based ink composition are poor, and it is difficult to obtain a clear image. Further, the effect as a moisturizing component is poor, and the printer head may be clogged. On the other hand, if it is added in an amount of more than 20% by weight, the viscosity of the water-based ink composition may increase and stable ejection may not be possible.

[water]
Water is a medium serving as the center of the aqueous ink composition of the present invention, and preferable water is ion-exchanged water, ultrafiltered water, reverse osmosis water, distilled water for the purpose of reducing ionic impurities as much as possible. Etc. or ultrapure water can be used.
Further, when water sterilized by ultraviolet irradiation or addition of hydrogen peroxide is used, it is preferable because generation of mold and bacteria can be prevented when the aqueous ink composition is stored for a long period of time.

  The water-based ink composition of the present invention includes the above-described colorant and colorant, and is capable of being dispersed in water and is a water-insoluble dispersion polymer, 2-ethyl-1,3-hexanediol, and water essential. As long as it is composed of these components, the storage stability and ejection stability of the ink are good, and an image with excellent colorability and excellent penetrability and drying properties can be obtained regardless of the type of recording medium. However, if necessary, various characteristics can be further improved by further including the following components. Hereinafter, the components will be described.

[Penetration solvent]
According to another aspect, the water-based ink composition according to the present invention can comprise a penetrating solvent together with the aforementioned 2-ethyl-1,3-hexanediol. The permeation solvent here is an additive for accelerating the ink permeability to the recording medium, and is appropriately selected depending on the desired ink drying time.

  As an example of the penetrating solvent, it is preferable to select from glycol monoether derivatives of polyhydric alcohols or 1,2-alkyldiols as having an action of lowering the surface tension of the aqueous ink composition.

  As the 1,2-alkyldiols, 1,2-alkyldiols having 4 to 8 carbon atoms such as butanediol, pentanediol, hexanediol, heptanediol, and octanediol are preferable. C6-C8 1,2-hexanediol, 1,2-heptanediol, and 1,2-octanediol are particularly preferred because of their high permeability to recording media. The addition amount of these 1,2-alkyl diols is preferably in the range of 0.25 wt% to 5 wt% with respect to the total amount of the aqueous ink composition.

  As the glycol monoether derivative of polyhydric alcohol, a derivative of polyhydric alcohol having 3 or more carbon atoms in alkyl is particularly preferable. Specifically, ethylene glycol monobutyl ether, diethylene glycol mono-n-propyl ether, ethylene glycol mono-iso-propyl ether, diethylene glycol mono-iso-propyl ether, ethylene glycol mono-n-butyl ether, ethylene glycol mono-t-butyl ether Diethylene glycol mono-n-butyl ether, triethylene glycol mono-n-butyl ether, diethylene glycol mono-t-butyl ether, 1-methyl-1-methoxybutanol, propylene glycol mono-t-butyl ether, propylene glycol mono-n-propyl ether, Propylene glycol mono-iso-propyl ether, propylene glycol mono-n-butyl ether, dipropylene Glycol mono -n- butyl ether, dipropylene glycol mono -n- propyl ether, dipropylene glycol monomethyl -iso- propyl ether. The addition amount of the glycol monoether derivative of the polyhydric alcohol is preferably in the range of 0.5 to 15% by weight with respect to the total amount of the aqueous ink composition.

  Moreover, as another example of the osmotic solvent, methanol, ethanol, n-propyl alcohol, iso-propyl alcohol, 2,2-dimethyl-1-propanol, n-butanol, 2-butanol, tert-butanol, iso-butanol Water-soluble ones such as 2-methyl-1-butanol, 3-methyl-1-butanol, 3-methyl-2-butanol, n-pentanol, 2-pentanol, 3-pentanol, tert-pentanol, etc. And monohydric alcohols. The addition amount of these monohydric alcohols is preferably in the range of 0.5 wt% to 10 wt% with respect to the total amount of the aqueous ink composition.

  These penetrating solvents may be used alone or in combination. In particular, by using a plurality of penetrating solvents having different structures, the same image quality can be obtained for various recording medium types exhibiting different penetrability / coloring properties, which is preferable from the viewpoint of compatibility with the recording medium type.

  In the case of an aqueous ink composition having a relatively long drying time, a moisturizing agent having a relatively small surface tension of an aqueous solution can be used as a substitute for the penetrating solvent. In this case, the above penetrating solvent is used. It can also be set as a water-based ink composition without adding.

  Like the 2-ethyl-1,3-hexanediol, the penetrating solvent described above has almost no dissolving action on the above-mentioned dispersion polymer, and acts to stably disperse and hold the dispersion in which this polymer is dispersed. have. Therefore, in the water-based ink composition of the present invention, there is almost no free dispersion polymer that is not adsorbed on the surface of the colorant such as a pigment even if it contains the penetrating solvent as described above together with 2-ethyl-1,3-hexanediol. Therefore, there is an advantage that high storage stability and ejection stability can be secured.

  Further, these penetrating solvents, when used together with 2-ethyl-1,3-hexanediol, have more excellent properties as penetrating components, and aqueous ink compositions containing these have wettability and penetrability regardless of the type of recording medium. Since the speed is improved, it has the characteristics of further excellent permeability and drying properties. Furthermore, since it also has a function of exhibiting high color developability regardless of the colorant, it also has an effect that a clear printed image with higher color developability can be realized without selecting a paper type.

[Acetylene glycol surfactant]
According to another aspect, the water-based ink composition according to the present invention can comprise an acetylene glycol surfactant together with the aforementioned 2-ethyl-1,3-hexanediol. The acetylene glycol-based surfactant here is an additive for accelerating the ink permeability to the recording medium, like the above-mentioned penetrating solvent. In addition, the acetylene glycol nonionic surfactant has characteristics with little or no foaming property, and is particularly useful when the aqueous ink composition of the present invention is used in an ink jet recording method. Specific examples of preferable acetylene glycol-based nonionic surfactants in the present invention include Air Products and Chemicals. Inc. Surfynol 61, 82, 104, 440, 465, 485 manufactured by the company, or TG, Olphine STG, Olphine E1010 manufactured by Nissin Chemical Industry Co., Ltd., and the like.

  The addition amount of the acetylene glycol-based nonionic surfactant may be appropriately determined depending on the desired ink drying time, but is preferably 0.01% by weight to 10% by weight with respect to the total amount of the aqueous ink composition.

  The acetylene glycol-based surfactant described above has almost no dissolving action on the above-mentioned dispersion polymer as in the case of 2-ethyl-1,3-hexanediol, and the dispersion in which this polymer is dispersed can be stably added. Has the effect of dispersing and holding. Therefore, in the water-based ink composition of the present invention, free dispersion that is not adsorbed on the surface of a colorant such as a pigment even if it contains the above-mentioned acetylene glycol surfactant together with 2-ethyl-1,3-hexanediol. Since there is almost no polymer, there is an advantage that high storage stability and ejection stability can be secured.

  These acetylene glycol surfactants have more excellent properties as penetrating components when used together with 2-ethyl-1,3-hexanediol, and aqueous ink compositions containing these have no relation to the type of recording medium. Since the wettability and penetration rate are improved, it has the characteristics of further excellent permeability and drying properties. Furthermore, since it also has a function of exhibiting high color developability regardless of the colorant, it also has an effect that a clear printed image with higher color developability can be realized without selecting a paper type.

  The aqueous ink composition of the present invention can further contain a water-soluble organic solvent as necessary. Examples of the water-soluble organic solvent include a humectant that controls the drying of the ink composition, and a surfactant that further increases the permeability to the recording medium. Each component will be described in detail below.

(Humectant)
The humectant is added to suppress drying of the aqueous ink composition. It is added in order to suppress moisture evaporation due to drying at the tip of the printer head nozzle and to prevent aggregation and solidification of the aqueous ink composition.

  The humectant is selected from water-soluble and highly hygroscopic materials such as glycerin, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, 1,3-propanediol. 1,4-butanediol, 1,5-pentanediol, 2,3-butanediol, 2-methyl-2,4-pentanediol, 1,2,6-hexanetriol, polyols such as pentaerythritol, 2 -Lacrams such as pyrrolidone and N-methyl-2-pyrrolidone, and ureas such as 1,3-dimethylimidazolidinone can be used.

  Furthermore, a water-soluble solid moisturizing agent can be used in combination and added for the purpose of assisting the ability of the above-described moisturizing organic solvent. Specifically, diols such as 1,6-hexanediol, 1,8-octanediol, 2,2-dimethyl-1,3-propanediol, and 2,2-diethyl-1,3-propanediol, trimethylolethane , Trimethylolpropane and the like, lactams such as ε-caprolactam, urea derivatives such as urea, thiourea and ethylene urea, glucose, mannose, fructose, ribose, xylose, arabinose, galactose, aldonic acid, glucitol, (sorbitol), maltose Monosaccharides such as cellobiose, lactose, sucrose, trehalose, maltotriose, disaccharides, oligosaccharides and polysaccharides and derivatives of these saccharides include reducing sugars, oxidized sugars, amino acids, thiosaccharides, etc. Can be mentioned. Sugar alcohol is particularly preferable, and specific examples include maltitol and sorbit.

  The addition amount of these humectants is preferably 1% by weight to 40% by weight, more preferably 1% by weight to 30% by weight, based on the total amount of the aqueous ink composition, alone or in combination. These humectants can be added together with other ink additives in an addition amount that results in an ink viscosity of 25 cPs or less at 25 ° C.

(Surfactant)
The surfactant is an additive for increasing the ink permeability to the recording medium.

  Suitable materials include anionic surfactants such as fatty acid salts and alkyl sulfate esters, nonionic surfactants such as polyoxyethylene alkyl ether and polyoxyethylene phenyl ether, acetylene glycol-based nonionic surfactants, and cationic surfactants. Surfactants, amphoteric surfactants, silicon surfactants, phosphorus surfactants, boron surfactants, and the like can be used.

  Examples of silicon surfactants include BYK-307, BYK-331, BYK-333, BYK-348 (trade names, all of which are manufactured by Big Chemie Co., Ltd.).

[Additive resin]
The additive resin is a resin that can be added to the aqueous ink composition separately from the dispersion polymer. Since the surface of the colorant used in the present invention is hydrophobic, a dispersant such as a surfactant or an aqueous resin is essential for stable dispersion in water. The colorant of the present invention has been described above in advance. Since the dispersion polymer is used for dispersion, the added resin added later does not require dispersibility. Therefore, the above-mentioned dispersion polymer can be added as a resin emulsion of a single resin, or a water-soluble resin and / or a water-dispersible resin having no dispersibility can be used.

  As the water-soluble resin and / or water-dispersible resin, an aqueous resin containing the above-mentioned dispersion polymer and the monomer of the dispersion polymer raw material, and polyvinyl alcohol, polyallyl alcohol, polyhydroxyethyl methacrylate, polyvinyl pyrrolidone, polyvinyl pyridine quaternary salt, Examples thereof include polyacrylamide, carboxymethylcellulose, hydroxypropylcellulose, starch, polylactic acid, shellac, modified rosin, phenol resin / alkali salt, and copolymers thereof.

  Furthermore, a resin obtained by hydrophilizing an oily resin having no water-soluble group in the molecule by oxidation, sulfonic acid addition, or the like can also be used.

[Weak alkaline agent]
In the ink jet recording apparatus, when a metal is used in the flow path of the ink composition, since the corrosion of the metal may occur if the ink composition is acidic, the aqueous ink composition of the present invention is neutral or It is desirable to adjust to alkalinity.

  In order to adjust to neutral or alkaline, the aqueous ink composition preferably further contains a weak alkalinizing agent. Here, when a strongly alkaline compound such as sodium hydroxide is used to adjust the water-based ink composition to neutral or alkaline, the unneutralized group is an acid group (such as a carboxylic acid group or a sulfonic acid group). There is a risk that neutralization of the acid group will proceed. In the present invention, by using a weak alkalinizing agent, the aqueous ink composition can be kept neutral or alkaline without greatly changing the neutralization rate of the dispersion polymer, and a more reliable aqueous ink composition is provided. can do.

  Examples of the weak alkalinizing agent include compounds selected from organic acid salts and organic buffering agents. The organic acid salt is preferably an alkyl carboxylic acid salt such as acetate or propionate, or a hydroxy acid salt such as lactate, glycolate or glycerate. Among these, alkali metal salts of alkylcarboxylic acids are preferable, such as sodium acetate, potassium acetate, sodium propionate, potassium propionate, and the like. As the organic buffer, tris (hydroxymethyl) aminomethane, tris-hydrochloride, tris-maleic acid, bis (2-hydroxyethyl) iminotris (hydroxymethyl) methane and the like are preferable.

  The addition amount of the weak alkalinizing agent can be appropriately set according to the desired ink pH, and is preferably in the range of 0.01 to 10% by weight.

[Other ingredients]
The water-based ink composition of the present invention may further contain additives that are usually used in ink jet recording inks, if necessary.

  Additives added as necessary include antioxidants, ultraviolet absorbers, preservatives, fungicides, and the like.

  Antioxidants and ultraviolet absorbers include allophanates such as allophanate and methyl allophanate, biurets such as biuret, dimethylbiuret and tetramethylbiuret, L-ascorbic acid and its salts, etc. Tinuvin 328, 900 manufactured by Ciba Geigy 1130, 384, 292, 123, 144, 622, 770, 292, Irgacor 252, 153, Irganox 1010, 1076, 1035, MD1024, or the like, or a lanthanide oxide or the like is used.

  Examples of antiseptics and fungicides include sodium benzoate, sodium pentachlorophenol, sodium 2-pyridinethiol-1-oxide, sodium sorbate, sodium dehydroacetate, 1,2-dibenzisothiazolin-3-one, etc. You can choose from.

[Colorant dispersion method and selection of water-soluble organic solvent and dispersion polymer]
In the present invention, a preferred method for dispersing a colorant with a dispersion polymer is to dissolve or disperse a polymer containing an anionic group in alkaline water containing an alkaline compound such as an organic amine or an alkali metal salt compound. And a colorant can be mixed and dispersed using a dispersing machine such as a ball mill, a sand mill, an attritor, a roll mill, an agitator mill, a Henschel mixer, a colloid mill, an ultrasonic homogenizer, a jet mill, or an ang mill. More preferably, in order to more firmly adhere the colorant and the sentence polymer to disperse and stabilize, JP-A-9-151342, JP-A-10-140065, JP-A-11-209672, JP-A-11-172180, It can also be produced by the methods disclosed in JP-A-10-25440, JP-A-11-43636, or JP-A-2001-247810. The manufacturing methods disclosed in these publications are outlined below.

  JP-A-2001-247810, JP-A-9-151342, and JP-A-10-140065 disclose “phase inversion method” and “acid precipitation method”.

a) "Phase inversion method"
In the present invention, the “phase inversion method” basically refers to a self-dispersion (phase inversion emulsification) method in which a mixed melt of a polymer having self-dispersing ability or solubility and a pigment is dispersed in water. . Here, the mixed melt means a mixed state without dissolving, a mixed state with dissolved, or a state including both of these states.

As one specific example,
(1) A step of preparing a solvent-based slurry by adding a pigment, a neutralizing agent and a small amount of water to a dispersion polymer precursor (a polymer containing an anionic group as described above) / solvent solution, (2) slurry (3) Remove the solvent used to dissolve the polymer from the water-based slurry and include the pigment in the water-dispersible polymer. And a step of producing a pigment-containing polymer particle dispersion.

b) "Acid precipitation"
In the present invention, the “acid precipitation method” refers to preparing a water-containing cake composed of a polymer and a pigment, and neutralizing a part of the unneutralized groups contained in the polymer in the water-containing cake with a neutralizing agent. This is a method for producing a colorant.

When the unneutralized group is an anionic acid group and the neutralizing agent is a basic compound, specifically, for example,
(1) A step of dispersing a polymer and a pigment in an alkaline aqueous medium, and subjecting the polymer to gelation by performing a heat treatment as necessary, and (2) neutralizing or acidifying the polymer by making the pH neutral or acidic. A step of hydrophobizing to strongly fix the polymer to the pigment, (3) a step of filtering and washing with water as necessary to obtain a water-containing cake, and (4) a polymer in which the water-containing cake is contained. A step of neutralizing a part or all of the anionic group with a basic compound and then redispersing in an aqueous medium; and (5) a step of gelling the polymer by performing heat treatment as necessary. Is included.

  More specific production methods of the above “phase inversion method” and “acid precipitation method” are the same as those disclosed in JP-A-9-151342 and JP-A-10-140065. Good.

Further, JP-A-11-209672 and JP-A-11-172180 disclose a method for producing a colorant. The outline of this production method basically comprises the following production steps.
(1) A polymer having an anionic group or a solution obtained by dissolving it in an organic solvent and a neutral compound are mixed and neutralized. (2) A pigment is mixed into this mixed solution to form a suspension. Later, the pigment is dispersed by a disperser or the like to obtain a pigment dispersion, (3) if necessary, the solvent is distilled off, and (4) a polymer having an anionic group by adding an acidic compound. By coating the pigment with a polymer having an anionic group, (5) filtering and washing with water as necessary, and (6) adding a basic compound to have an anionic group. Neutralizing anionic groups of the polymer and dispersing in an aqueous medium to obtain an aqueous dispersion.

  Moreover, it may be the same as that disclosed in JP-A-11-2096722 and JP-A-11-172180.

  In the aqueous dispersion of the colorant obtained as described above, the above-described 2-ethyl-1,3-hexanediol and water, and the above-described water-soluble organic solvent, weak alkali agent, and other components as necessary. By adding the aqueous ink composition, it can be suitably produced.

<Inkjet recording method and recorded matter>
As the ink jet recording method of the present invention, any method can be used as long as it is a system in which the above-described aqueous ink composition is ejected as droplets from a fine nozzle and the droplets adhere to a recording medium. To explain some of them, there is an electrostatic attraction method. In this method, a strong electric field is applied between the nozzle and the acceleration electrode placed in front of the nozzle, and ink is continuously ejected in the form of droplets from the nozzle. There are a method of recording by supplying a printing information signal to the deflection electrode while the ink droplet flies between the deflection electrodes, or a method of ejecting the ink droplet corresponding to the printing information signal without deflecting the ink droplet.

  The second method is a method in which ink droplets are forcibly ejected by applying pressure to the ink liquid with a small pump and mechanically vibrating the nozzle with a crystal resonator or the like. The ejected ink droplet is charged simultaneously with the ejection, and a printing information signal is given to the deflection electrode and recorded while the ink droplet flies between the deflection electrodes.

  The third method is a method using a piezoelectric element, in which a pressure and a print information signal are simultaneously applied to an ink liquid by a piezoelectric element to eject and record ink droplets.

  The fourth method is a method in which the ink liquid is rapidly expanded in volume by the action of heat energy, and the ink liquid is heated and foamed with a microelectrode in accordance with a print information signal to eject and record ink droplets.

  Of the various ink jet recording methods described above, in particular, by combining the printing method at a relatively low ink discharge speed of 10 m / s or less with the aqueous ink composition of the present invention, ink adhesion to the discharge nozzle is prevented. Ink jet recording can be performed stably, which is preferable.

  The recorded matter of the present invention can be obtained by printing the above-described aqueous ink composition by an ink jet recording method.

  The contents of the present invention will be clearly described by the following examples, but the scope of the present invention is not limited to the following examples. Moreover, the dispersion liquid used for the water-based ink composition of the present invention was prepared by the following method.

<Preparation of dispersion>
(1) Dispersion 1
75 g of MA100 (trade name, manufactured by Mitsubishi Chemical Corporation) as carbon black, Jonkrill 611 (trade name, Johnson Polymer Co., Ltd., average molecular weight 8,100) as a styrene-acrylic acid-based dispersion polymer having a carboxylic acid group as an anionic group , Acid value 53 KOH mg / g) 25 g, potassium hydroxide 1.0 g, and 250 g of ultrapure water purified by an ion exchange method and a reverse osmosis method were mixed and dispersed in a ball mill using zirconia beads for 10 hours. The obtained dispersion stock solution is filtered through a membrane filter having a pore size of about 8 μm (trade name, manufactured by Nihon Millipore Limited) to remove coarse particles, diluted to a pigment concentration of 15% by weight with ultrapure water, and dispersed with a dispersion polymer. Liquid 1 was prepared.

(2) Dispersion 2
A dispersion was prepared in the same manner as dispersion 1, except that carbon black was replaced with color black S160 (trade name, manufactured by Degussa) and the amount of potassium hydroxide added was changed to 1.20 g. This is Dispersion Liquid 2.

(3) Dispersion 3
For dispersion 1, carbon black was converted to C.I. I. A dispersion was prepared in the same manner except that Pigment Blue 15: 3 65 g, the addition amount of the dispersion polymer was changed to 35 g, and the addition amount of potassium hydroxide was changed to 1.70 g. This is Dispersion Liquid 3.

(4) Dispersion 4
For dispersion 1, carbon black was converted to C.I. I. A dispersion was prepared in the same manner except that Pigment Yellow 74 was used. This is Dispersion Liquid 4.

(5) Dispersion 5
75 g of MA100 (trade name, manufactured by Mitsubishi Chemical Corporation) as carbon black, Jonkrill 678 (trade name, Johnson Polymer Co., Ltd., average molecular weight 8,500) as a styrene-acrylic acid-based dispersion polymer having a carboxylic acid group as an anionic group , Acid value 215 KOH mg / g) 25 g, potassium hydroxide 1.80 g, and 250 g of ultrapure water purified by an ion exchange method and a reverse osmosis method were mixed and dispersed in a ball mill using zirconia beads for 10 hours. The obtained dispersion stock solution is filtered through a membrane filter having a pore size of about 8 μm (trade name, manufactured by Nihon Millipore Limited) to remove coarse particles, diluted to a pigment concentration of 15% by weight with ultrapure water, and dispersed with a dispersion polymer. Liquid 5 was prepared.

(6) Dispersion 6
A dispersion was prepared in the same manner as in dispersion 1, except that carbon black was replaced with color black S160 (trade name, manufactured by Degussa) and the amount of potassium hydroxide added was changed to 3.80 g. This is designated as Dispersion Liquid 6.

(7) Dispersion 7
For dispersion 1, carbon black was converted to C.I. I. A dispersion was prepared in the same manner except that 80 g of Pigment Red 122 was replaced with 20 g of the dispersion polymer and 3.44 g of potassium hydroxide. This is designated as Dispersion Liquid 7.

(8) Dispersion 8
[Synthesis of dispersion polymer]
A reaction vessel equipped with a stirrer, thermometer, reflux tube and dropping funnel was replaced with nitrogen, and then 25 g of styrene, 30 g of n-dodecyl methacrylate, 20 g of methoxypolyethylene glycol methacrylate, 15.5 g of butyl methacrylate, and 9.3 g of methacrylic acid were added to 100 g of methyl ethyl ketone. And was replaced with nitrogen gas.
The same monomer / methyl ethyl ketone solution was placed in the dropping funnel, and 0.2 g of 2,2′-azobis (2,4-isomethylvaleronitrile) was further added to perform nitrogen gas replacement.

  In a nitrogen atmosphere, the polymerization reaction was carried out while heating to 65 ° C. and adding the dropping funnel solution over 3 hours. The obtained copolymer solution was purified by repeatedly drying under reduced pressure, dissolving methyl ethyl ketone and filtering, and then diluted by adding methyl ethyl ketone so that the solid content of the dispersed polymer was 50% by weight. A dispersion polymer solution A having an acid value of about 70 KOH mg / g and an average molecular weight of 50,000 was obtained.

[Preparation of dispersion]
150 g of MA100 (trade name, manufactured by Mitsubishi Chemical Corporation) as carbon black and 100 g of the above dispersion polymer solution A were mixed and stirred to prepare a slurry. To this slurry, 50 g of a 10 wt% aqueous potassium hydroxide solution was added and dispersed with an ultrahigh pressure homogenizer.

  Subsequently, this dispersion solution is gradually added to 400 g of stirring pure water, and all of methyl ethyl ketone and a part of water are removed at 60 ° C. under reduced pressure to further increase the pigment concentration to 15% by weight. Pure water was added to obtain dispersion 8.

(9) Dispersion 9
A dispersion was prepared in the same manner as in dispersion 8, except that carbon black was replaced with color black S160 (trade name, manufactured by Degussa) and the addition amount of 10 wt% potassium hydroxide aqueous solution was changed to 47.5 g. . This is designated as Dispersion Liquid 9.

(10) Dispersion 10
C. of organic pigments I. Pigment Blue 15: 4 50 g and the above-mentioned dispersion polymer solution A 100 g were mixed and stirred to prepare a slurry. To this slurry, 47.5 g of a 10% by weight aqueous potassium hydroxide solution was added and dispersed with an ultrahigh pressure homogenizer.

  Subsequently, this dispersion solution was gradually added to 250 g of stirring pure water, and all of methyl ethyl ketone and a part of water were removed at 60 ° C. under reduced pressure to further increase the pigment concentration to 15% by weight. Pure water was added to obtain dispersion 10.

(11) Dispersion 11
For the dispersion 10, the pigment is an organic pigment C.I. I. Pigment Red 122 was 200 g, and a dispersion was prepared in the same manner except that the amount of 10 wt% potassium hydroxide aqueous solution was changed to 39.5 g. This is designated as Dispersion Liquid 11.

(12) Dispersion 12
For the dispersion 10, the pigment is an organic pigment C.I. I. Pigment Yellow 74 150 g was used, and a dispersion was prepared in the same manner except that the amount of 10 wt% potassium hydroxide aqueous solution was changed to 39.5 g. This is designated as Dispersion Liquid 12.

(13) Dispersion 13
[Synthesis of dispersion polymer]
Each component of n-butyl methacrylate 40% by weight, n-butyl acrylate 5% by weight, styrene 20% by weight, 2-hydroxyethyl methacrylate 15% by weight and methacrylic acid 20% by weight is mixed in a 1 L beaker so that the total amount becomes 500 g. Further, 4 g of tert-butyl peroxyoctoate was added as a polymerization initiator to obtain a polymer synthesis mixture.

  Next, 500 g of methyl ethyl ketone was put into a 1 L flask, and the temperature was raised to 75 ° C. while stirring in a nitrogen atmosphere. The polymer synthesis mixture was added dropwise over 3 hours with stirring at 75 ° C. The reaction was further continued for 8 hours at 75 ° C. with stirring. Thereafter, the reaction product was naturally cooled to 25 ° C., and diluted by adding methyl ethyl ketone so that the solid content was 50% by weight. A dispersion polymer solution B having an acid value of 150 KOH mg / g and an average molecular weight of 15,000 was obtained.

[Preparation of dispersion]
150 g of MA100 (trade name, manufactured by Mitsubishi Chemical Corporation) as carbon black, 100 g of the above-mentioned dispersion polymer solution B, 50 g of 10 wt% potassium hydroxide aqueous solution, and 700 g of ultrapure water purified by an ion exchange method and a reverse osmosis method are mixed. In a sand mill (manufactured by Yaskawa Seisakusho), the mixture was dispersed for 2 hours together with glass beads (diameter 1.7 mm, 1.5 times the amount (weight) of the mixture). Thereafter, the glass beads were removed, other components were added, and the mixture was stirred at room temperature for 20 minutes, followed by filtration through a 5 μm membrane filter.

  The obtained filtrate was distilled at 80 ° C. under normal pressure to distill all of methyl ethyl ketone and a part of water. Further, 1N hydrochloric acid solution was added dropwise with stirring to coagulate the dispersed polymer layer. This was subjected to suction filtration while washing with water to obtain a water-containing pigment cake. While stirring the water-containing cake, 1% by weight of potassium hydroxide aqueous solution was redispersed in 375 g, and ultrapure water was further added so that the pigment concentration was 15% by weight, whereby dispersion 13 was obtained.

(14) Dispersion 14
The dispersion liquid was prepared in the same manner as the dispersion liquid 13 except that the carbon black was color black S160 (trade name, manufactured by Degussa) and the amount of the 1 wt% potassium hydroxide aqueous solution added during redispersion was changed to 422 g. Produced. This is referred to as dispersion 14.

(15) Dispersion 15
For the dispersion 13, carbon black was changed to C.I. I. A dispersion was prepared in the same manner as in Pigment Red 122, except that 250 g of the 1% by weight aqueous potassium hydroxide solution was changed to 422 g. This is designated as dispersion 15.

(16) Dispersion liquid 16
[Preparation of dispersion polymer]
50 g of a styrene-methyl methacrylate polymer having an average molecular weight of 15,000 and a styrene molar ratio of 35%, 500 g of 2-pyrrolidone and 25 g of sulfamic acid were mixed and reacted at 80 ° C. for 3 hours to sulfonate some styrene, Purification by repeated dissolution in 2-pyrrolidone and precipitation with acidic water at pH 5.0 was followed by dissolution with methyl ethyl ketone so that the solid content was 50% by weight. A dispersion polymer solution C having an acid value of 70 KOH mg / g and an average molecular weight of 15,000 was obtained.

[Preparation of dispersion]
150 g of MA100 (trade name, manufactured by Mitsubishi Chemical Corporation) as carbon black, 100 g of the above-mentioned dispersion polymer solution C, 25 g of 10 wt% potassium hydroxide aqueous solution, and 700 g of ultrapure water purified by an ion exchange method and a reverse osmosis method are mixed. In a sand mill (manufactured by Yaskawa Seisakusho), the mixture was dispersed for 2 hours together with glass beads (diameter 1.7 mm, 1.5 times the amount (weight) of the mixture). Thereafter, the glass beads were removed, other components were added, and the mixture was stirred at room temperature for 20 minutes, followed by filtration through a 5 μm membrane filter.

  The obtained filtrate was distilled at 80 ° C. under normal pressure to distill all of methyl ethyl ketone and a part of water. Further, 1N hydrochloric acid solution was added dropwise with stirring to coagulate the dispersed polymer layer. This was subjected to suction filtration while washing with water to obtain a water-containing pigment cake. While stirring the water-containing cake, 1% by weight potassium hydroxide aqueous solution was redispersed in 310 g, and ultrapure water was further added so that the pigment concentration was 15% by weight, whereby dispersion 16 was obtained.

(17) Dispersion 17
For the dispersion 16, carbon black was changed to C.I. I. Pigment Blue 15: 3 A dispersion was prepared in the same manner except that 250 g was used. This is designated as Dispersion Liquid 17.

<Preparation of water-based ink>
[Example 1]
26.7 g of dispersion 1 (using carbon black) obtained by the above-mentioned materials and methods, 15 g of 2-ethyl-1,3-hexanediol, and ultrapure water were added for a total amount of 100 g, stirring for 2 hours, pore size An aqueous ink composition was prepared by filtration through a membrane filter (trade name, manufactured by Nihon Millipore Limited) of about 1.2 μm.

[Examples 2 to 26]
An ink was prepared in the same manner as in Example 1 except that the additive and amount were changed to the compositions shown in Tables 1 to 3.

  In Examples 21, 23, and 24, mobile vinyl 742N (trade name, manufactured by Clariant Polymer Co., Ltd.) was used as additive resin 1. In Examples 22, 25 and 26, dispersion polymer solution B was used as additive resin 2, and C.V. I. A resin emulsion of 20% by weight of a dispersed polymer is prepared in the same manner except that Pigment Red 122 is not added, and has a repeating unit having an unneutralized group, a neutralizing group, and is hydrated and / or dissolved in water. It was used in a state of having a repeating unit that can be used.

(Comparative Example 1)
With respect to the composition of Example 2, 2-ethyl-1,3-hexanediol was not added, instead, 2.6 g of a 1% by weight aqueous potassium hydroxide solution, 7 g of triethylene glycol, 4 g of 2-pyrrolidone, An aqueous ink composition was prepared by adding 1.5 g of Surfinol 465. As a result of adding potassium hydroxide during preparation of the aqueous ink composition, the amount of potassium hydroxide relative to the total amount of carboxylic acid groups in the dispersion polymer was about 125% in molar ratio, and all the carboxylic acid groups were in the state of potassium carboxylic acid. .

(Comparative Example 2)
An aqueous ink composition was prepared by adding 2.1 g of a 1% by weight aqueous potassium hydroxide solution to the composition of Example 11. As a result of adding potassium hydroxide during preparation of the aqueous ink composition, the amount of potassium hydroxide relative to the total amount of carboxylic acid groups in the dispersion polymer was about 125% in molar ratio, and all the carboxylic acid groups were in the state of potassium carboxylic acid. .

(Comparative Example 3)
A water-based ink composition was prepared by the same composition and method as in Example 1, except that the amount of 2-ethyl-1,3-hexanediol added was 22 g.

  Each said composition is put together in Table 1-Table 3, and is shown.

<Evaluation method>
(Storage stability)
The aqueous ink compositions of Examples 1 to 26 and Comparative Examples 1 to 3 were left at 60 ° C. for 2 weeks, left for 1 month, and frozen for 1 week to compare the viscosity immediately after ink preparation with the value after being left. . Judgment criteria are as follows.
Judgment AA: The fluctuation range is less than ± 3% A: The fluctuation range is ± 3% or more and less than ± 6% B: The fluctuation range is ± 6% or more and less than ± 10% C: The fluctuation range is ± 10% or more

(Discharge stability)
The aqueous ink compositions of Examples 1 to 26 and Comparative Examples 1 to 3 were mounted on PX-V700 (trade name, manufactured by Seiko Epson Corporation), which is an inkjet printer. A4 size Xerox P (trade name, manufactured by Fuji Xerox Office Supply Co., Ltd.) is used for printing paper, and images with mixed characters and fills are continuously printed in an environment of 20-25 ° C / 40-60% RH. Then, the image being printed was visually observed for defects such as flying bends and missing. Judgment criteria are as follows.
Judgment AA: Even if continuous printing is performed up to 200 sheets, no flying bend / missing occurs. A: Flying bend / missing does not occur when printing is performed up to 100 sheets. B: Flying bend / missing occurs after continuous printing up to 100 sheets. Has occurred, but there are less than 10 locations. C: Flying bends / misses occur at 10 locations or more during continuous printing of up to 100 sheets.

(Evaluation of print quality on plain paper and recycled paper)
The aqueous ink compositions of Examples 1 to 26 and Comparative Examples 1 to 3 were mounted on PX-V700 (trade name, manufactured by Seiko Epson Corporation), which is an inkjet printer. Print quality (character quality) due to character blurring when 1 to 20 points of Gothic characters are printed in 1 point increments on plain paper / recycled paper with the print setting “paper type; plain paper, print quality; fine” Evaluated. Furthermore, an image with a different fill density in 5% increments from 5% to 100% with the same print settings was printed, and the print quality (filled image quality) due to shading unevenness of the printed matter was evaluated. In this evaluation, Xerox Premium Multipurpose 4024 (trade name, manufactured by Xerox Corporation), Xerox P (trade name, manufactured by Fuji Xerox Office Supply Co., Ltd.), REYMAT (trade name, manufactured by Ausedat Ray Company), Hammermill Copy Plus (plain paper). Evaluation was carried out visually using Xerox R (trade name, manufactured by Fuji Xerox Office Supply Co., Ltd.) as a recycled paper using a product name (available from International Paper). The evaluation criteria are shown below.

[Character quality]
Evaluation AA: bleeding is not recognized in characters at all points A: Bleeding is slightly observed with characters of 5 points or less B: Characters of 5 points or less appear thick due to bleeding C: Bleeding is remarkable 5 points The following characters cannot be distinguished

[Filled image quality]
Evaluation AA: Almost no shading unevenness is observed in all filled images. A: Light shading unevenness is observed in an image with a filling density of 100%, but there is no practical problem. B: Shading unevenness in an image with a fill density of 50% or more Is recognized.
C: Light and shade unevenness is observed in all filled images.

  Table 4 summarizes the storage stability, ejection stability, and print quality results for each water-based ink composition.

  As shown in Table 4, regarding the storage stability of the ink composition, the aqueous ink compositions of Examples 1 to 26 each containing a dispersion liquid dispersed in a water-insoluble dispersion polymer alone in the aqueous ink composition. Even if the product contained 2-ethyl-1,3-hexanediol, which is essential in the present invention, the viscosity fluctuation before and after being left under the above conditions was as small as less than 6% and was stable. In contrast, Comparative Example 1 in which potassium hydroxide was further added to Example 2 to neutralize all unneutralized groups of the dispersion polymer, and further, potassium hydroxide was added to Example 11 to disperse the polymer. In Comparative Example 2 in which all of the unneutralized groups were neutralized, the viscosity fluctuated immediately after blending the material of the water-based ink composition, and the viscosity fluctuation before and after being left under the above conditions exceeded 10%. The sex was inferior.

  In addition, the ejection stability of the water-based ink composition in the ink jet printer is stable without causing problems such as flight bending and missing even when 100 or more sheets of the water-based ink composition of Examples 1 to 26 are continuously printed. It was. In particular, 2-ethyl-1,3-hexanediol and penetrating solvent, or 2-ethyl-1,3-hexanediol and acetylene glycol surfactant, or 2-ethyl-1,3-hexanediol and penetrating solvent, In Examples 3, 4, 6, 7, 8, 9, 10, 11, 12, 15, 16, 17, 18, 19, 20, 23, 24, 25, 26 in combination with an acetylene glycol surfactant Has a special effect that even if 200 sheets are continuously printed, it is stable without causing problems such as bent flight or missing. On the other hand, in Comparative Example 1 in which 2-ethyl-1,3-hexanediol was not added, flying bends and omissions occurred, and in Comparative Example 2 in which 2-ethyl-1,3-hexanediol was added, dispersion was observed. Since all the unneutralized groups of the polymer were neutralized with potassium hydroxide, it was more severe, and flight bending and omission occurred frequently immediately after the start of printing. In Comparative Example 3, the amount of 2-methyl-1,3-hexanediol added was too large, the viscosity of the water-based ink composition became unsuitable as an ink jet recording method, and flight bending and omission occurred.

  Furthermore, regarding the print quality of the aqueous ink composition in the ink jet printer, the aqueous ink compositions of Examples 1 to 26 all had good character quality and filled image quality regardless of the paper type. In particular, 2-ethyl-1,3-hexanediol and penetrating solvent, or 2-ethyl-1,3-hexanediol and acetylene glycol surfactant, or 2-ethyl-1,3-hexanediol and penetrating solvent, In Examples 8, 10, 11, 12, 19, and 20 in which an acetylene glycol surfactant was used in combination, clear character quality and filled image quality were obtained with all the recording papers evaluated, and additional resin was added here. In Examples 23, 24, 25, and 26 used in combination, there was a remarkable effect that clear character quality and filled image quality with higher color development were obtained. On the other hand, in Comparative Example 1, since 2-ethyl-1,3-hexanediol was not added, both the character quality and the filled image quality had a large amount of blur, and light and dark unevenness occurred. Even in Comparative Example 2 in which 2-ethyl-1,3-hexanediol was added, all of the unneutralized groups of the dispersed polymer were neutralized with potassium hydroxide. There has occurred. In Comparative Example 3, the amount of 2-methyl-1,3-hexanediol added was too large, and the penetrability of the aqueous ink composition became too high, and bleeding occurred depending on the paper type.

  Although the present invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention.

The water-based ink composition of the present invention has high storage stability and ejection stability and is excellent in permeability, drying and color development regardless of the type of recording medium, and is particularly suitable for use as an ink for inkjet recording. ing.

Claims (12)

  A water-based ink composition comprising a coloring component, 2-ethyl-1,3-hexanediol, and water, wherein the coloring component includes a colorant in a dispersion polymer so as to be dispersible in water. A water-based ink composition characterized by being a dispersion composed of a substance that is insoluble in water by itself.   The aqueous ink composition according to claim 1, further comprising a penetrating solvent.   The aqueous ink composition according to claim 2, wherein the penetrating solvent is selected from the group consisting of monohydric alcohols, glycol monoether derivatives of polyhydric alcohols, and 1,2-alkyldiols.   The aqueous ink composition according to any one of claims 1 to 3, further comprising an acetylene glycol surfactant.   The water-based ink composition according to any one of claims 1 to 4, further comprising a water-soluble and / or water-dispersible additive resin.   The aqueous ink composition according to claim 5, wherein the additive resin alone is insoluble in water.   The water-based ink composition according to claim 1, wherein the colorant is carbon black.   The water-based ink composition according to claim 1, wherein the colorant is an organic pigment.   The aqueous ink composition according to any one of claims 1 to 8, further comprising a weak alkalinizing agent and being alkaline.   10. The aqueous ink composition according to claim 9, wherein the weak alkalinizing agent comprises at least one compound selected from organic acid salts and organic buffering agents.   An ink jet recording method for performing recording by discharging droplets of the aqueous ink composition according to claim 1 and attaching the droplets to a recording medium. The recorded matter which printed the water-based ink composition as described in any one of Claims 1-10 with the inkjet recording method.