JP2005264080A - Aqueous ink composition, ink jet recording method using the same, and recorded matter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an aqueous ink composition suitable for an ink for ink jet recording that has a high long-term storing stability at a high temperature, a high injection stability when used for ink jet printers, and excellent color developing and color fixing properties irrespective of the types of recording media. <P>SOLUTION: This aqueous ink composition comprises a colorant, resin emulsion, humectant, and water. The colorant is a surface-treated pigment obtained by introducing at least one hydrophilic, dispersing property providing group onto the pigment surface directly and/or via a multivalent group, and is thermally treated at a temperature not less than the glass transition temperature (Tg) of a resin component constituting the resin emulsion before the resin emulsion is added to the aqueous ink composition. <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 colorant and a humectant such as glycerin for the purpose of preventing 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, water-soluble dyes may be inferior in various properties such as light resistance and water resistance. Therefore, printed matter printed with a 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, it is necessary to prepare it as an ink composition after being stably dispersed in water in advance.

  As a method for stably dispersing a pigment in an aqueous system, it has been conventionally studied that a dispersing agent such as a water-soluble resin or a surfactant is adsorbed on a pigment surface and dispersed as pigment particles in water. (Hereinafter, this type of pigment is referred to as “dispersant type pigment”). For example, an aqueous pigment ink in which carbon black is dispersed as a pigment and a surfactant or a polymer dispersant is dispersed as a 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). Also, 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).

  In addition to the above, various techniques have been proposed for providing self-dispersion pigments by imparting dispersibility in water to the pigments themselves. For example, “self-dispersing carbon black” in which a hydrophilic group such as a carboxyl group, a carbonyl group, a sulfone group, or a hydroxyl group is bonded to the surface of carbon black directly or via a polyvalent group has been proposed. (See Patent Document 7 and Patent Document 8). In addition, it has been proposed to improve dispersibility by oxidizing the surface of carbon black (see Patent Document 9, Patent Document 10, and Patent Document 11). In addition, “surface-treated pigments” in which sulfone groups are introduced on the surface of organic pigments have been proposed (see Patent Document 12, Patent Document 13, and Patent Document 14), and ink compositions for ink jet recording using the same have also been proposed. (See Patent Document 15). Further, it is described that an organic pigment mass having a surface positively charged is prepared by treating an organic pigment mass having a sulfonic acid group introduced thereto with a monovalent metal ion, and the surface positively charged organic pigment is further described. An aqueous ink composition containing pigment fine particles prepared from a lump, a dispersant, and water and having excellent storage stability is described (see Patent Document 16). In addition, by using a benzene ring introduced into carbon black, “an ink having pigment particles (macromolecular chromophore) having a water-solubilizing functional group and a polymer on the surface as a colorant” has been proposed (Patent Literature). 17).

  In addition, for the purpose of improving the fixability, water resistance, color development, etc. of ink on a recording medium, or suppressing bleeding, it has been studied to add a resin emulsion having a specific structure to ink containing a pigment. For example, there has been proposed an ink containing a pigment dispersed with a branched polymer dispersant, and an emulsion polymer composed of acrylic and / or methacrylic and / or vinyl monomers (see Patent Document 18 and Patent Document 19). Further, inks containing charged pigments and resin emulsions and having the same charge polarity have been proposed (see Patent Document 20 and Patent Document 21).

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 Japanese Patent Laid-Open No. 10-195360 Japanese Patent Laid-Open No. 10-330665 JP-A-8-3498 JP-A-10-195331 Japanese Patent Laid-Open No. 10-237349 JP-A-8-283598 JP-A-10-110110 JP-A-10-110111 Japanese Patent Laid-Open No. 10-110129 JP-A-11-49974 JP 2000-53902 A Japanese Patent Laid-Open No. 10-195354 JP-A-10-195355 JP 2000-351931 A JP 2000-81366 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. Some of these solvents affect the dispersibility by affecting the dispersed colorant, particularly the dispersant-type pigment, and thus may impair the storage stability of the ink composition. In particular, there is a problem that these effects 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 dispersant. In addition, when such an effect occurs, 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, ejection from the printer head becomes unstable. There was a problem of end.

  Used in water-based inks using a dispersion polymer in which 60 mol% or more of the acid groups of the dispersion polymer are neutralized with an alkaline neutralizing agent, as described in the above prior art (Patent Documents 5 and 6). Depending on the type of the water-soluble organic solvent, there has been 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.

  Further, in the above-described conventional technology (Patent Document 1 to Patent Document 6), a part of the dispersant for dispersing the pigment is dissolved in the ink, and it acts as a penetrant for the ink. The penetration into the recording medium has been increased more than necessary. For this reason, the pigment particles may be dragged into the recording medium and soak into the recording medium, resulting in poor color development of the image. The effect is particularly noticeable with plain paper and recycled paper, and in some cases, it causes bleeding due to excessive penetration and back-through where ink penetrates to the back side of the paper, causing deterioration in image quality. It was.

  On the other hand, since the above-mentioned self-dispersing surface-treated pigment (Patent Documents 7 to 17) has a dispersing group chemically bonded to the pigment surface, the above-mentioned water-soluble organic solvent is added to the ink. Even so, no dissociation of the dispersing group occurs. Therefore, it is excellent in storage stability such as dispersion stability. However, only the surface-treated pigment as the colorant has a problem that the fixing property of the image is poor because there is no fixing component on the pigment surface.

  For the purpose of preventing such harmful effects, various additions of a resin emulsion have been studied as shown in Patent Documents 18 to 21, and a certain effect can be obtained. Patent Document 15 also describes that the above-mentioned problems of the surface-treated pigment can be improved by adding a resin emulsion. However, as a result of detailed studies by the present inventors, it has been found that simply adding a resin emulsion to a pigment ink is not sufficient as an ink for inkjet recording. Specifically, when the ink is left for a long period of time or at a high temperature, there is an increase in viscosity, particle size, or agglomeration that appears to be due to the interaction between the pigment particles and the resin emulsion. It has been found that problems such as unstable ejection, clogging of the head nozzle, and reduction in density occur.

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

  The water-based ink composition of the present invention is a water-based ink composition comprising a colorant, a resin emulsion, a humectant, and water, wherein the colorant directly and directly contains at least one hydrophilic dispersibility-imparting group. Glass transition temperature (Tg) of the resin component which is a surface-treated pigment introduced to the pigment surface via a polyvalent group and which constitutes the resin emulsion before the resin emulsion is added to the aqueous ink composition The heat treatment is performed at the above temperature.

  The aqueous ink composition of the invention further comprises a penetrating solvent.

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

  The water-based ink composition of the invention further includes an acetylene glycol surfactant.

  Further, the water-based ink composition of the present invention is characterized in that it contains at least one kind of resin emulsion in which the resin component constituting the resin emulsion has a glass transition temperature (Tg) of 30 ° C. or higher.

  In the water-based ink composition of the present invention, in the surface-treated pigment, the hydrophilic dispersibility-imparting group introduced into the pigment surface is selected from the group consisting of a functional group represented by the following formula or a salt thereof. One or more than one is characterized.

-OM, -COOM, -CO -, - SO 3 M, -SO 2 M, -SO 2 NH 2, -RSO 2 M, -PO 3 HM, -PO 3 M 2, -SO 2 NHCOR, -NH 3 , -NR ₃
(In the formula, M represents a hydrogen atom, an alkali metal, ammonium, or organic ammonium. R represents an alkyl group having 1 to 12 carbon atoms, an optionally substituted phenyl group, or a substituted group. Represents a naphthyl group which may have a group.)
The aqueous ink composition of the present invention is characterized in that the surface-treated pigment is carbon black.

  The aqueous ink composition of the present invention is characterized in that the surface-treated pigment is an organic pigment.

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

  The aqueous 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 colorant, a resin emulsion, a humectant, and water as essential components, and the colorant has at least one hydrophilic dispersibility-imparting group directly and / or multivalently. The surface-treated pigment introduced on the surface of the pigment through the group of the resin, and the resin emulsion is heated at a temperature equal to or higher than the glass transition temperature (Tg) of the resin component constituting the resin emulsion before being added to the aqueous ink composition. Has been processed.

  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 and ejection stability, and excellent color developability and fixability for the inkjet recording method.

In the water-based ink composition of the present invention, it is essential to use the self-dispersing surface-treated pigment as described above as the colorant. As a result, it is possible to add as many "penetrating solvent species and their addition amount", which are restricted in use in the conventional dispersant-type pigments to inhibit the dispersion stability.
Accordingly, a quick-drying ink with increased permeability to the recording medium can be obtained, and a printed image with less bleeding can be realized. In addition, the content of the pigment as the colorant can be increased by the amount that the dispersant is no longer added, and even at the same pigment concentration, the printing density is higher than that of the conventional dispersant-type pigment ink. Therefore, it is easy to cope with high image quality with improved color development.

The resin emulsion, which is an essential component of the water-based ink composition of the present invention, improves the color developability by inhibiting the surface treated pigment from penetrating into the recording medium, and further improves the color developability as the resin emulsion is further dried. In addition, the resin emulsion is fused to the surface-treated pigment, and the pigment particles are fixed on the recording medium, thereby improving the water resistance and fixability.
Here, when the resin emulsion is added to the water-based ink composition of the present invention, the resin emulsion is previously converted to a glass transition temperature of the resin component constituting the resin emulsion (hereinafter abbreviated as “Tg”) or higher. It is essential to heat-treat with. The present inventors have found that by performing this treatment, the storage stability of the water-based ink composition is dramatically improved (particularly, the rate of change in viscosity and the rate of change in particle size are reduced). In particular, the improvement effect by this treatment was large in a resin emulsion composed of a resin component having a Tg of room temperature or higher (approximately 30 ° C. or higher). The present inventors have made various studies for the purpose of improving color developability on a recording medium, particularly on plain paper and recycled paper, but a resin emulsion is essential to achieve the purpose. It has been found that the Tg of the resin component constituting the resin emulsion has an influence on the existence and the effect, and that the effect is more effective when the Tg is room temperature or higher (approximately 30 ° C. or higher). However, at the same time, if an aqueous ink composition to which a resin emulsion having a Tg of the resin component of room temperature or higher is added is left for a long period of time or at a high temperature, problems such as increased particle size, increased viscosity, and generation of sediment frequently occur. I also found out. Therefore, as a result of various studies to achieve both improvement in color development and ensuring storage stability, it is possible to solve the problem by heat-treating the resin emulsion at Tg or more of the resin component constituting it before adding it to the ink. And the present invention has been established.

  The reason why the color developability is improved by adding the resin emulsion, and the reason why the storage stability is improved by heat-treating the resin emulsion at a temperature equal to or higher than the Tg of the resin component before adding the resin emulsion to the ink, has not yet been determined. Not estimated, but estimated as follows. In other words, when a water-based ink composition containing a resin emulsion adheres to plain paper, recycled paper, etc., the resin emulsion first adheres to the paper fibers or on the surface, preventing the colorant in the ink from seeping into the paper. To do. As the colorant suitable for the water-based ink composition of the present invention, as described above, a surface-treated pigment in which at least one hydrophilic dispersibility-imparting group is introduced directly and / or via a polyvalent group is used. Used. The pigment is present on the paper surface and has a characteristic of developing color by reflecting light of a specific wavelength. However, if the pigment penetrates into the paper, it is hidden by the paper fiber and cannot sufficiently reflect the light. Therefore, when a resin emulsion is added to the ink, the resin emulsion first fills the gap between the paper fibers and puts pigment particles on top of it, resulting in the presence of many pigment particles on the paper surface, resulting in plain paper or recycled paper We believe that the color development on paper will be improved. Further, when a resin emulsion is prepared, a dissociation group is obtained by neutralizing an unneutralized portion (specifically, a carboxylic acid group, a sulfonic acid group, etc.) of an acid group in a resin component constituting the resin emulsion with an alkaline compound. As a result, it is possible to stably disperse in water. However, not a few unneutralized groups remain in the resin emulsion particles. If this is added to the ink as it is and stored for a long time or at a high temperature, the unneutralized groups inside the resin emulsion particles will come out on the surface of the resin emulsion particles due to the molecular movement of the resin components, consuming the alkali components in the ink. As a result, the ink itself becomes a neutralizing group, and as a result, the pH of the ink is inclined toward the acidic side. As a result, dispersion of the surface-treated pigment particles contained in the ink becomes unstable on the acidic side, resulting in interactions between the pigment particles or the resin emulsion, resulting in increased particle size, thickening, aggregate generation, etc. It is possible that this problem will occur. However, if the resin emulsion is heat-treated at Tg or higher of the resin component before being added to the ink, unneutralized groups inside the resin emulsion particles come out on the surface of the resin emulsion particles and stabilize at that stage. Thus, once the non-neutralized groups come out on the surface of the resin emulsion particles by the heat treatment and are stabilized, even if they are added to the ink and allowed to stand for a long time or at a high temperature, there are no more unneutralized groups. Since the ink does not come out on the surface, the pH of the ink is not inclined toward the acidic side from the initial state, and the above-described problem may not occur.

The components of the water-based ink composition of the present invention are described below.
In the present specification, the “self-dispersing pigment” means “a pigment that can be dispersed in a solvent solely by pigment particles”, and a dispersing agent such as a resin is adsorbed on the surface of the pigment particles, and the dispersing agent. Not a “dispersant-type pigment” that is dispersed only by the effect of the “self-dispersing surface”, which is made possible by chemically bonding a hydrophilic dispersibility-imparting group to the pigment particle surface to enable dispersion in water. Treated pigment (sometimes referred to simply as “surface treated pigment” in the present specification) ”and“ pigment particles ”described herein below basically refers to“ pigment secondary particles ”. .

<Water-based ink composition>
[Colorant]
It is essential that the colorant used in the aqueous ink composition of the present invention is a self-dispersing surface-treated pigment. Examples of pigments that can be used for the surface-treated pigment include organic pigments and carbon black.

  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, 15: 1, 15: 2, 15: 3, 15: 4, 15:34, 15: 6, 16, 17: 1, 18, 19, 21, 22, 25, 56, 60, 64, 65, 66, etc., 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 about 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 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 14, 15, 16, 17, 18, 19, 21, 22, 23, 30, 31, 32, 37, 38, 40, 41, 42, 48 (Ca), 48 (Mn), 57 (Ca), 57: 1, 112, 122, 123, 144, 146, 149, 150, 166, 168, 170, 171 175, 176, 177, 178, 179, 184, 185, 187, 188, 189, 190, 194, 202, 209, 214, 216, 219, 220, 224, 242, 245, C.I. I. Pigment violet 19, 23, 31, 32, 33, 36, 38, 43, 50, etc., 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, 4, 5, 6, 7, 10, 11, 12, 13, 14, 16, 17, 24, 55, 61, 61: 1, 65, 73, 74, 75, 81, 83, 93, 94, 95, 97, 98, 99, 100, 108, 109, 110, 113, 114, 117, 119, 120, 123, 124, 128, 129, 133, 138, 139, 147, 150, 151, 153, 154, 155, 156, 167, 168, 172, 173, 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, 138 and 180. 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 1, 2, 5, 7, 13, 14, 15, 16, 24, 31, 34, 36, 38, 40, 42, 43, 51, 60, 62, 63, etc., preferably 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, 10, 36, 37, 47, etc., preferably 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.

[Surface treatment pigment (self-dispersing pigment)]
The surface-treated pigment essential as a colorant in the water-based ink composition of the present invention introduces a functional group or a salt thereof as a hydrophilic dispersibility-imparting group directly or via a polyvalent group on the surface of the pigment particle. By being (chemically bonded), it can be dispersed in water without a dispersant.

  In the surface-treated pigment used in the aqueous ink composition of the present invention, the functional group introduced into one pigment particle may be a single type or a plurality of types. The type and degree of the functional group to be introduced may be appropriately determined in consideration of the dispersion stability in the aqueous ink composition, the color density, the drying property on the front surface of the inkjet head, and the like.

Examples of the functional group introduced as the hydrophilic dispersibility-imparting group include one or two or more functional groups selected from the group consisting of functional groups represented by the following formula or salts thereof.
-OM, -COOM, -CO -, - SO 3 M, -SO 2 M, -SO 2 NH 2, -RSO 2 M, -PO 3 HM, -PO 3 M 2, -SO 2 NHCOR, -NH 3 , -NR ₃
(However, M in the formula represents a hydrogen atom, an alkali metal, ammonium or organic ammonium, and R represents an alkyl group having 1 to 12 carbon atoms, an optionally substituted phenyl group, or a substituted group. Represents a naphthyl group which may have a group.)
When the hydrophilic dispersibility-imparting group is introduced into the pigment via a polyvalent group, the polyvalent group to which the dispersibility-imparting group is bonded has an alkylene group having 1 to 12 carbon atoms and a substituent. An optional phenylene group, an optionally substituted naphthylene group, and the like can be given.

Various known surface treatment means are applied as the surface treatment means for introducing the above-mentioned functional group or a salt thereof, which is a hydrophilic dispersibility-imparting group, directly or via a polyvalent group into the surface of the pigment particles. be able to.
For example, (a) a means for applying ozone or sodium hypochlorite solution to commercially available oxidized carbon black to further oxidize the carbon black to make the surface more hydrophilic (for example, JP-A-7-258578) JP, 8-3498, JP-A-10-120958, JP-A-10-195331, JP-A-10-237349), (b) carbon black with 3-amino-N-alkyl substituted pyri Means for treating with bromide (for example, JP-A-10-195360, JP-A-10-330665), (c) a sulfonating agent by dispersing the organic pigment in a solvent in which the organic pigment is insoluble or hardly soluble Thus, means for introducing a sulfone group onto the surface of the pigment particles (for example, JP-A-8-283596, JP-A-10-110110, JP-A-10 No. 110111), (d) The organic pigment is dispersed in a basic solvent that forms a complex with sulfur trioxide, and the surface of the organic pigment is treated by adding sulfur trioxide, so that a sulfone group or a sulfonamino group is formed. Means for introducing (for example, JP-A-10-110114), (e) Means for introducing a water-solubilizing functional group and a polymer onto the pigment surface through a phenylene group bonded to carbon black by an azo coupling reaction (For example, JP 2000-53902 A) and the like.

  However, the preparation means for the surface-treated pigment used in the present invention is not limited to the means (a) to (e).

In the present invention, the sulfur-containing dispersibility-imparting group used as the hydrophilic dispersibility-imparting group is not particularly limited as long as it is a functional group containing a sulfur atom and imparting dispersibility in water. Specifically, a sulfinic acid group (SO ₂ ⁻ ) or a sulfonic acid group (SO ₃ ⁻ ) can be mentioned.

  The hydrophilic dispersibility-imparting group introduced into the surface-treated pigment as described above may be present at least on the particle surface, and may be contained inside the particle.

In the surface-treated pigment used in the aqueous ink composition of the present invention, a polymer substance can be introduced (chemically bonded) to the surface of pigment particles directly or via a polyvalent group. The introduction of the polymer substance to the pigment surface can be relatively easily performed via a polyvalent group. This reaction is realized by an acylation reaction or a nucleophilic substitution reaction of an ester group.
Specific examples of such a polymer substance include polyethylene glycol, polypropylene glycol, polytetramethylene glycol, and their homologs (polyethylene glycol having 1 to 10 carbon atoms in the alkyl group, polypropylene glycol, and polytetramethylene glycol). Monoalkyl ethers or monoaryl ethers, amines of methoxypolyethylene glycol, polyvinyl alcohol, copolymers of polyvinyl alcohol and polyvinyl acetate, and the like. These polymer materials desirably have at least one amine group or hydroxyl group at the terminal.

  In the aqueous ink composition of the present invention, the particle diameter of the surface-treated pigment particles at the time of dispersion is such that the maximum particle diameter when measured by a dynamic light scattering method is less than 500 nm and the average particle diameter is 300 nm or less, more preferably The average particle size is 200 nm or less.

[Resin emulsion]
It is essential that the water-based ink composition of the present invention comprises a resin emulsion. This resin emulsion suppresses the surface treated pigment particles from penetrating into the recording medium to improve the color developability. Further, as the resin emulsion is further dried, both the resin emulsions and the resin emulsion and the surface treated pigment particles are both. Adhering and fixing the pigment particles on the recording medium has an effect of improving the fixing property. Examples of the resin component constituting the resin emulsion having such characteristics include acrylic resins, methacrylic resins, styrene resins, urethane resins, acrylamide resins, epoxy resins, and the like, and a mixture of these resins. A system may be used. Among these resin components, a styrene-acrylic acid copolymer, a styrene-acrylic acid-acrylic acid alkyl ester copolymer, a styrene-maleic acid copolymer, and a styrene-maleic acid-acrylic acid alkyl ester copolymer are more preferable. Examples thereof include a polymer, a styrene-methacrylic acid copolymer, a styrene-methacrylic acid-acrylic acid alkyl ester copolymer, and a styrene-maleic acid-half ester copolymer.

These resin components are required to have both a hydrophobic part and a hydrophilic part as a 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 nonionic functional groups and neutralization groups, such as a hydroxyl group and a carboxylic amide 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.

  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.

  The resin component constituting the resin emulsion has the above-mentioned structure, so that the hydrophobic part exists inside the resin emulsion particles and is isolated from the water, and the hydrophilic part exists on the surface of the particles, so that it is compatible with water. Therefore, a resin emulsion that is stably dispersed in water can be obtained. Further, when adhering on the recording medium, the resin emulsions can be fused and filmed to surround the surface-treated pigment, and the hydrophobic part can cover the film surface. This film is insoluble in water and does not re-disperse, and is firmly fixed on the recording medium together with the surface-treated pigment, so that the image fixability and water resistance are good.

  Examples of the alkaline compound that neutralizes the unneutralized group of the resin emulsion 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 and morpholine, diethanolamine, triethanolamine, tripropanolamine and other highly volatile compounds. Examples include salts of boiling 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.

  Such resin emulsions may be synthesized and used so as to satisfy various characteristics, but commercially available products may also be used. Specifically as a commercial item, mobile 701 (Tg: -19 degreeC), mobile 743 (Tg: 39 degreeC), mobile 745 (Tg: 21 degreeC), mobile 940 (Tg: 1 degreeC), mobile 1930 (Tg: 1 ° C), mobile 664 (Tg: 6 ° C), mobile DM5 (Tg: -3 ° C), mobile 700 (Tg: -2 ° C), mobile 792 (Tg: -2 ° C), mobile DM772 (Tg: 3 ° C) ), Mobile 865 (Tg: 1 ° C), Mobile 870 (Tg: 19 ° C), Mobile 928 (Tg: 5 ° C), Mobile 1750T (Tg: 16 ° C), Mobile 1751 (Tg: 16 ° C), Mobile 1760 ( Tg: 7 ° C), mobile LDM6316 (Tg: 17 ° C), mobile 7200 (Tg: 24 ° C), mobile 727 ( g: 5 ° C), mobile 752 (Tg: 16 ° C), mobile 837 (Tg: 10 ° C), mobile 860 (Tg: 3 ° C), mobile 864 (Tg: 4 ° C), mobile 864M (Tg: 4 ° C) , Mobile DM60 (Tg: 0 ° C.), Mobile DM 765 (Tg: −19 ° C.), Mobile 937 (Tg: −42 ° C.), Mobile 1906 (Tg: −45 ° C.), Mobile LDM 6300 (Tg: 10 ° C.), Mobile 742N (Tg: 37 ° C.), mobile 749E (Tg: 25 ° C.), mobile 752 (Tg: 16 ° C.), mobile 916 (Tg: −5 ° C.), mobile 1700A (Tg: 37 ° C.), mobile 7210 (Tg: 16 ° C), mobile 747 (Tg: 42 ° C), mobile 6520 (Tg: 40 ° C), mobile 7 02 (Tg: −35 ° C.), mobile LDM7010 (Tg: 34 ° C.), mobile VDM7410 (Tg: −4 ° C.), mobile DM 772 (Tg: 3 ° C.), mobile DM 774 (Tg: 10 ° C.), mobile 947 (Tg) : -55 ° C), mobile LDM6481 (Tg: -22 ° C), mobile LDM6880 (Tg: 9 ° C), mobile DM758 (Tg: -60 ° C), mobile DM765 (Tg: -19 ° C), mobile 650 (Tg: −37 ° C.), mobile 760H (Tg: −17 ° C.), mobile 761HG (Tg: −35 ° C.), mobile 763 (Tg: −18 ° C.), mobile 412 (Tg: −62 ° C.), mobile 490 (Tg: −53 ° C.), mobile S-71 (Tg: −53 ° C.), mobile 987 (Tg: -2 ° C), Mobile 1410 (Tg: -8 ° C), Mobile 630 (Tg: 27 ° C), Mobile 620 (Tg: -22 ° C), Mobile 730L (Tg: -13 ° C), Mobile 735 (Tg: 14) ° C), mobile 747 (Tg: 42 ° C), mobile 767 (Tg: 25 ° C), mobile 790 (Tg: 102 ° C), mobile 9000 (Tg: 46 ° C), mobile 880 (Tg: 3 ° C), mobile DM60 (Tg: 3 ° C), mobile 8020 (Tg: -22 ° C), mobile 8030 (Tg: 17 ° C), mobile 8055 (Tg: 78 ° C), mobile 8201 (Tg: 8 ° C), mobile 787 (Tg: 14) ° C), mobile 710 (Tg: 9 ° C), mobile 718 (Tg: -6 ° C), mobile 776 (Tg: -2) ° C), Mobile 952 (Tg: -38 ° C), Mobile 963A (Tg: -19 ° C), Mobile DM772 (Tg: 6 ° C), Mobile 975A (Tg: 27 ° C), Mobile 3200 (Tg: -21 ° C) Apletan 760H (Tg: −17 ° C.), apletan 2200 (Tg: 19 ° C.), apletan 2000 (Tg: 19 ° C.), apletan 3510 (Tg: 0 ° C.), apletan 3410 (Tg: −32 ° C.) (all above) Trade name, manufactured by Clariant Japan Co., Ltd.), PCL series 0619 (Tg: -4 ° C), PCL series 0623A (Tg: -6 ° C), PCL series 0640 (Tg: 55 ° C), PCL series 0693 (Tg: 20 ° C) ), PCL series 0695 (Tg: -4 ° C), PCL series 0696 (Tg: -12 ° C) PCL series 0850 (Tg: 7 ° C), PCL series 0890 (Tg: -17 ° C), SB series 0561 (Tg: -63 ° C), SB series 0589 (Tg: 0 ° C), SB series 0602 (Tg: 40 ° C) ), SB series 2108 (Tg: −66 ° C.), SB series 0533 (Tg: −20 ° C.), SB series 0545 (Tg: −31 ° C.), SB series 0548 (Tg: −49 ° C.), SB series 0568 ( −23 ° C.), SB series 0569 (Tg: −4 ° C.), SB series 0573 (Tg: −9 ° C.), SB series 0597C (Tg: 28 ° C.), AE series AE116 (Tg: 50 ° C.), AE series AE119 (Tg: 55 ° C.), AE series AE120 (Tg: −10 ° C.), AE series AE121 (Tg: 58 ° C.), AE series AE125 (Tg: 60 ° C), AE series AE134 (Tg: 48 ° C), AE series AE137 (Tg: 48 ° C), AE series AE140 (Tg: 53 ° C), AE series AE173 (Tg: 60 ° C), AE series AE200 (Tg: -45 ° C), AE series AE311 (Tg: -50 ° C), AE series AE318 (Tg: 5 ° C), AE series AE337 (Tg: -30 ° C), AE series 343 (Tg: 0) ° C), AE series 362 (Tg: -5 ° C), AE series AE373B (Tg: 10 ° C), AE series AE379A (Tg: 20 ° C), AE series AE513A (Tg: -48 ° C), AE series AE517 (Tg) : -48 ° C), AE series AE604 (Tg: 5 ° C), AE series AE610C Tg: -62 ° C), AE series AE815 (Tg: 5 ° C), AE series AE945 (Tg: -17 ° C), AE series AE950 (Tg: -20 ° C), AE series AE986A (Tg: 2 ° C) (above) All trade names, manufactured by JSR Corporation), Jonkrill 7100 (Tg: -10 ° C), Jonkrill 390 (Tg: -5 ° C), Jonkrill 1674 (Tg: -4 ° C), Jonkrill 711 (Tg: 0) ), Jonkrill 1695 (Tg: 5 ° C), Jonkrill 511 (Tg: 9 ° C), Jonkrill 7001 (Tg: 12 ° C), Jonkrill 632 (Tg: 12 ° C), Jonkrill 741 (Tg: 15) ° C), Jonkrill 450 (Tg: 16 ° C), Jonkrill 840 (Tg: 16 ° C), Jonkrill 74J (Tg: 22 ° C), PDX-71 1B (Tg: 19 ° C.), HRC-1645 (Tg: 21 ° C.), Jonkrill 734 (Tg: 30 ° C.), Jonkrill 852 (Tg: 31 ° C.), Jonkrill 7600 (Tg: 35 ° C.), Jonkrill 775 (Tg: 37 ° C.), Jonkrill 537 (Tg: 49 ° C.), Jonkrill 1535 (Tg: 50 ° C.), PDX-7630A (Tg: 53 ° C.), Jonkrill 352 (Tg: 56 ° C.), Jonkrill 352D (Tg: 56 ° C.), PDX-7145 (Tg: 56 ° C.), Jonkrill 538 (Tg: 66 ° C.) (all are trade names, manufactured by Johnson Polymer Co., Ltd.) and the like.

  One or a plurality of these resin emulsions can be used in the aqueous ink composition of the present invention, and at least one of them is preferable that the Tg of the resin component constituting it is 30 ° C. or higher. The reason is that by including a resin emulsion having a resin Tg of 30 ° C. or more, a large amount of the surface-treated pigment can be present on the surface of the recording medium, and as a result, there is an effect of increasing the color developability.

  The addition amount of these resin emulsions may be appropriately determined in consideration of fixability, color developability and the like, but is preferably in the range of 0.1% by weight to 20% by weight in terms of solid content in the aqueous ink composition. If the amount of the resin emulsion added is less than 0.1% by weight, the color developability of the image may be poor. On the other hand, if it exceeds 20% by weight, the ink viscosity becomes high and becomes unsuitable as an ink for an ink jet recording system, and the solid content concentration in the ink becomes high, so that clogging of the head nozzle is likely to occur. .

  Here, it is essential that the resin emulsion used in the water-based ink composition of the present invention is previously heat-treated at a temperature equal to or higher than Tg of the resin component constituting the resin emulsion. The reason for this is as described above, because the storage stability (change in particle size, change in viscosity, etc.) of the aqueous ink composition for a long period of time or at a high temperature is dramatically improved. The method of heating the resin emulsion can be performed, for example, by sealing the resin emulsion dispersion in a sample bottle or the like and putting it in a thermostatic chamber set at a temperature equal to or higher than Tg of the resin component. If this heat treatment is not performed, unneutralized groups (for example, carboxylic acid groups, sulfonic acid groups, etc.) remaining inside the resin emulsion particles come out on the surface of the resin emulsion particles due to the molecular motion of the resin component and are neutralized. For this reason, the ink system is made acidic. If it does so, the dispersibility of the surface-treated pigment particle | grains mentioned above will become unstable, and as a result, bad effects, such as thickening, a granule increase, and sediment generation, will arise in ink.

[Humectant]
It is essential that the aqueous ink composition according to the present invention comprises a humectant. The humectant is added to suppress drying of the water-based ink composition, and has an effect of preventing aggregation and solidification of the water-based ink composition by suppressing water evaporation due to drying at the tip of the printer head nozzle.

  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, 2-ethyl-1,3-hexanediol, 1,2,6- Polyols such as hexanetriol and pentaerythritol, lactams such as 2-pyrrolidone and N-methyl-2-pyrrolidone, and ureas such as 1,3-dimethylimidazolidinone can be used.

  Furthermore, a water-soluble solid humectant can be used in combination and added for the purpose of assisting the ability of the above materials. Specifically, diols such as 1,6-hexanediol, 1,8-octanediol, 2,2-dimethyl-1,3-propanediol, and 2,2-diethyl-1,3-propanediol, trimethylolethane , 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 the reducing sugars, oxidized sugars, amino acids, thio sugars, etc. It is done. 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.

[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 is a surface-treated pigment in which at least one hydrophilic dispersibility-imparting group described above is introduced directly and / or via a polyvalent group onto the pigment surface, and has a Tg of the resin component in advance. The resin emulsion, humectant, and water heat-treated at the above temperature are essential components, and if composed of such components, the storage stability and ejection stability of the ink are good, and depending on the type of recording medium However, if necessary, various properties 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 further comprise a penetrating solvent. 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. Of these, 1,6-hexanediol, 1,2-heptanediol, and 1,2-octanediol having 6 to 8 carbon atoms are particularly preferable 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 a mixture of two or more. In particular, when a plurality of types of penetrating solvents having different structures are used in combination, the same image quality can be obtained for various recording medium types exhibiting different penetrability and color developability, which is preferable from the viewpoint of compatibility with recording medium types.

  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.

The penetrating solvent described above has almost no dissolving action on the resin emulsion, and has the action of stably dispersing and holding the dispersion in which the resin emulsion is dispersed. For this reason, the water-based ink composition of the present invention has an advantage that high storage stability and ejection stability can be ensured even when the penetrating solvent as described above is contained, since there is almost no dissolved resin component.
These penetrating solvents have excellent properties as penetrating components, and water-based ink compositions containing them have excellent penetrability and drying properties because they improve wettability and penetration speed regardless of the type of recording medium. Show. 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 further comprise an acetylene glycol surfactant. 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-based 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. Preferable specific examples of the acetylene glycol surfactants preferable in the present invention include Surfynol 61, 82, 104, 440, 465, 485, or TG (all trade names, manufactured by Air Products and Chemicals, Inc.), Orphine STG, Olphine E1010, etc. (all trade names, manufactured by Nissin Chemical Industry Co., Ltd.) are included.

  The addition amount of the acetylene glycol 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 surfactant described above has almost no dissolving action on the resin emulsion, and has an action of stably dispersing and holding the dispersion in which the resin emulsion is dispersed. Therefore, even if the water-based ink composition of the present invention contains the acetylene glycol surfactant as described above, since there is almost no dissolved resin component, it is possible to ensure high storage stability and ejection stability. There is.

  In addition, these acetylene glycol surfactants have excellent properties as penetrating components, and aqueous ink compositions containing them have improved wettability and penetration speed regardless of the type of recording medium. Shows excellent properties. Furthermore, since it also has a function of exhibiting high color developability regardless of the colorant type, it has an effect that a clear printed image with higher color developability can be realized without selecting a paper type.

[Weak alkalinizing agent]
In the ink jet recording apparatus, when a metal is used in the flow path of the water-based ink composition, the water-based ink composition of the present invention may be used because the metal may corrode if the water-based ink composition is acidic. It is desirable to be adjusted to be alkaline or alkaline.

  In order to adjust to neutral or alkaline, according to another aspect, the water-based ink composition preferably further contains a weak alkalinizing agent.

  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, surfactants, 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.

  The surfactant is an additive for further accelerating the ink permeability to the recording medium. Suitable materials include anionic surfactants such as fatty acid salts and alkyl sulfate ester salts, polyoxyethylene alkyl ethers, polyoxyethylenes. Nonionic surfactants such as ethylene phenyl ether, acetylene glycol-based nonionic surfactants, cationic surfactants, amphoteric surfactants, silicon-based surfactants, phosphorus-based surfactants, boron-based surfactants Etc. can be used as needed.

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

[Physical properties of water-based ink composition]
The water-based ink composition of the present invention may be used in the flow path of the water-based ink composition in the viewpoint of ensuring storage stability (change in particle size, change in viscosity, etc.) and dispersion stability, and in an inkjet recording apparatus. From the viewpoint of preventing corrosion of metal parts, the pH is preferably adjusted to neutral or alkaline. More desirably, the pH of the aqueous ink composition at 25 ° C. is in the range of 7.0 to 11.0. Deviating from this range tends to cause problems in terms of storage stability, dispersion stability, and corrosion.

  In addition, the water-based ink composition of the present invention preferably has a viscosity of 25 cPs or less at 25 ° C. from the viewpoint of ensuring ejection stability in an ink jet recording apparatus. More preferably, it is 15 cPs or less.

[Method for producing surface-treated pigment]
"Pigment surface treatment method"
Next, the manufacturing method of the surface treatment pigment used for the water-based ink composition of the present invention will be described.

  As a method for producing the surface-treated pigment, first, a step of surface-treating the pigment is performed. In this step, the pigment is subjected to a surface treatment (introduction of a dispersibility-imparting group) by mixing the pigment and the surface treatment agent in an aqueous or non-aqueous solvent, or by heating the mixture. . After the surface treatment, the obtained reaction product is repeatedly washed with water, ultrafiltration, reverse osmosis, centrifugation and / or filtration to remove residual unreacted substances, reaction byproducts, residual treatment agents, etc. Thus, a surface-treated pigment can be obtained.

In addition, it is desirable that the pigment used in the surface treatment step is pulverized and atomized in advance before introducing the hydrophilic dispersibility-imparting group. As a means for pulverizing the pigment, pulverization media such as zirconia beads, glass beads, and inorganic salts can be used, and wet pulverization or dry pulverization can be used. Examples of the pulverizer include an attritor, a ball mill, and a vibration mill. After the pulverization treatment, it is desirable to remove contaminant components generated from the pulverization media and the pulverizer by washing the pigment, ultrafiltration and the like.
In particular, a pulverization treatment method (salt milling method) combining dry pulverization and an inorganic salt can be easily removed by washing with water because the contaminant component generated from the pulverization medium is a water-soluble inorganic salt.

Here, as an example of a method for producing a surface-treated pigment used in the aqueous ink composition of the present invention, an example of a method for producing a surface-treated pigment having a sulfur-containing dispersibility-imparting group on the surface will be described below in more detail. To do.
First, in the step of surface-treating the pigment, a fine particulate or powdery pigment is placed in an aprotic solvent (for example, N-methyl-2-pyrrolidone or sulfolane) 3 to 200 times the amount of the pigment, Treat with a sulfonating agent while adjusting the size of the pigment. As the sulfonating agent, for example, sulfonated pyridine salt, sulfamic acid, amidosulfuric acid, fluorosulfuric acid, chlorosulfuric acid, sulfur trioxide, fuming sulfuric acid or sulfuric acid can be used alone or in combination of two or more. The treatment with the sulfonating agent can be performed under heating (about 60 to 200 ° C.) and under stirring, and the heating can be performed before or after the addition of the sulfonating agent.
After the sulfonation treatment, the aprotic solvent and the remaining sulfonating agent are removed from the obtained pigment slurry. The removal treatment can be carried out by repeatedly washing with water, ultrafiltration, reverse osmosis, centrifugation, and / or filtration. Moreover, the contaminant component mixed in the above-mentioned sizing and dispersing treatment and sulfonation treatment is also removed together with the aprotic solvent and the sulfonating agent.

  The amount of the dispersibility-imparting group introduced into the surface-treated pigment in the aqueous ink composition of the present invention is preferably 10 × 10 −6 equivalents or more, more preferably 15 × 10 −6 equivalents or more per 1 g of pigment particles. . When the amount of the dispersibility-imparting group introduced is less than 5 × 10 −6 equivalents per 1 g of pigment particles, aggregation of dispersed pigment particles and the like occur, resulting in thickening and dispersion of the dispersion / aqueous ink composition. In some cases, the storage stability of the pigment dispersion or the water-based ink composition may decrease due to, for example, an increase in the particle size of the pigment particles.

  For example, in the case of a sulfur-containing dispersibility-imparting group, the amount of the dispersibility-imparting group introduced can be measured by treating the pigment aqueous dispersion with an oxygen flask combustion method and absorbing it in an aqueous hydrogen peroxide solution, followed by ion chromatography. It can be measured by quantifying sulfate ions (divalent) and converting them to sulfonic acid groups and sulfinic groups.

  Further, the zeta potential of the surface-treated pigment particles in the aqueous ink composition of the present invention is measured as a diluted solution obtained by diluting the surface-treated pigment particles with ion-exchanged water so that the pigment concentration is 0.001 to 0.01% by weight. In this case, the absolute value of the zeta potential of the pigment particles at 20 ° C. and pH 8 to pH 9 is preferably 30 mV or more. More preferably, it is 40 mV or more, and an even more preferable absolute value of the zeta potential is 50 mV or more. When the absolute value of the zeta potential of the pigment particles is 20 mV or less, the storage stability of the pigment dispersion or water-based ink composition is reduced as in the case where the amount of the dispersibility-imparting group introduced is insufficient.

"Method for producing dispersion of surface-treated pigment"
In the aqueous ink composition of the present invention, the surface-treated pigment can be added to the aqueous ink composition as it is, but it is preferable to use it in the form of a pigment dispersion described below because it is easy to handle.

In the production of the pigment dispersion, first, the surface treatment pigment obtained in the above-described pigment surface treatment process, or the slurry of the surface treatment pigment, the wet cake, etc., has a pigment concentration (weight conversion) of about 5 to 50% by weight. So that it may be added to a water-based medium (particularly ion-exchanged water or distilled water) together with a neutralizing agent or the like as necessary. Subsequently, a surface-treated pigment dispersion can be obtained by dispersing the pigment particles in an aqueous medium by applying an appropriate shearing force using a stirrer or a dispersing device.
In the dispersion step, it is preferable to add a small amount of the above-described penetrating solvent and / or acetylene glycol surfactant and disperse. The reason is that these penetrating solvents and / or acetylene glycol surfactants have the effect that the pigment particles are easy to adapt (wet easily) to the aqueous medium, and are dispersed between the pigment particles and the pigment in the aqueous medium. This is because there is an effect of increasing the dispersion efficiency by increasing the contact resistance with the media. As a result, the shearing conditions of the apparatus in the dispersion treatment step can be relaxed (the shear force applied from the apparatus to the pigment dispersion can be reduced), and the time required for the dispersion treatment can be shortened. In such a case, the contamination component (particularly polyvalent metal ions such as Si, Ca, Mg, Fe, Cr, Ni, etc.) due to the dispersion media and the dispersion device is reduced. This has the effect of improving the dispersion stability and storage stability of the aqueous ink composition used. These penetrating solvents and / or acetylene glycol surfactants may be mixed with at least the pigment in the dispersion step, and the addition time to the pigment may be before the dispersion step or in the middle of the dispersion step. It doesn't matter.

  Examples of the apparatus that can be used in the dispersion treatment include a stirrer, paint shaker, ball mill, sand mill, roll mill, speed line mill, homomixer, ultrasonic homogenizer, nanomizer, and microfluidizer.

  The neutralizing agent is added to dissociate the salt-forming group of the dispersibility-imparting group on the surface of the surface-treated pigment, and the alkaline compound shown in the above resin emulsion can be suitably used.

  The above-described pigment surface treatment step and this surface treatment pigment dispersion step may be carried out continuously. In particular, when the surface treatment of the pigment is carried out with an aqueous solvent, the reaction solvent in the surface treatment step and the dispersion medium in the dispersion step can be made the same aqueous system, so that it is easy to assemble continuous steps. However, the removal of residual unreacted substances, reaction by-products and the like in the surface treatment step is easier to obtain a pigment dispersion having better final dispersion stability if carried out before the dispersion step. On the other hand, when the solvent in the surface treatment step is a non-aqueous solvent, it may be easier to separate and remove residual unreacted substances from the target surface-treated pigment.

<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 surface-treated pigment used for the water-based ink composition of the present invention and a dispersion using the same were prepared by the following method.

<Preparation of surface treatment pigment>
(1) Preparation of surface-treated pigment 1; carbon black 15 parts of carbon black (“MA-7” manufactured by Mitsubishi Chemical Corporation) were mixed in 200 parts of sulfolane, and beads were used with Eiger Motor Mill M250 type (manufactured by Eiger Japan). Dispersed for 1 hour under conditions of a filling rate of 70% and a rotational speed of 5,000 rpm, the dispersed pigment paste and solvent mixture was transferred to an evaporator and heated to 120 ° C. while reducing the pressure to 30 mmHg or less. After the contained water was distilled off as much as possible, the temperature was controlled at 150 ° C.

Next, 25 parts of sulfur trioxide was added and reacted for 6 hours. After completion of the reaction, the mixture was washed several times with excess sulfolane, poured into water and filtered to obtain a sulfinic acid group (SO ₂ ⁻ ) or a sulfonic acid group (SO ₂ ). ₃ ^-) a sulfur-containing dispersibility-imparting group such as was introduced directly to the pigment surface, to obtain a surface-treated carbon black pigment slurry.

(2) Preparation of surface-treated pigment 2; C.I. I. Pigment Blue 15: 3
20 parts of phthalocyanine blue pigment (CI Pigment Blue 15: 3) is mixed with 500 parts of quinoline, and the conditions are 70% bead filling and 5,000 rpm with Eiger Motor Mill M250 (Eiger Japan). For 2 hours, transfer the mixture of dispersed pigment paste and solvent to an evaporator, heat to 120 ° C while reducing the pressure to 30 mmHg or less, and distill off as much water as possible in the system, then control the temperature to 160 ° C. did. Next, 20 parts of a sulfonated pyridine complex was added and reacted for 8 hours. After completion of the reaction, the mixture was washed several times with excess quinoline, poured into water, and filtered to obtain a sulfinic acid group (SO ₂ ⁻ ) or a sulfonic acid group ( A slurry of a surface-treated phthalocyanine blue pigment in which a sulfur-containing dispersibility-imparting group such as SO ₃ ⁻ ) was directly introduced onto the pigment surface was obtained.

(3) Preparation of surface-treated pigment 3; C.I. I. Pigment Yellow 110
20 parts of isoindolinone pigment (CI Pigment Yellow 110) are mixed with 500 parts of quinoline and 2 in a condition of 70% bead filling and 5000 rpm with an Eiger Motor Mill M250 (manufactured by Eiger Japan). The mixture of the pigment paste and the solvent, which was dispersed for a time and finished, was transferred to an evaporator, heated to 120 ° C. while reducing the pressure to 30 mmHg or less, and the water contained in the system was distilled off as much as possible, and then the temperature was controlled to 160 ° C. . Next, 20 parts of a sulfonated pyridine complex is added as a reactant and reacted for 4 hours. After completion of the reaction, the mixture is washed several times with excess quinoline, poured into water, and filtered to obtain a sulfinic acid group (SO ₂ ⁻ ) or sulfone. Surface-treated isoindolinone pigment particles in which a sulfur-containing dispersibility-imparting group such as an acid group (SO ₃ ⁻ ) was directly introduced onto the pigment surface were obtained.

(4) Preparation of surface-treated pigment 4; I. Pigment Red 122
20 parts of dimethyl quinacridone pigment (CI Pigment Red 122) is mixed with 500 parts of quinoline and 2 in a condition of 70% bead filling and 5,000 rpm with Eiger Motor Mill M250 (manufactured by Eiger Japan). The mixture of the pigment paste and the solvent, which was dispersed for a time and finished, was transferred to an evaporator, heated to 120 ° C. while reducing the pressure to 30 mmHg or less, and the water contained in the system was distilled off as much as possible, and then the temperature was controlled to 160 ° C. . Next, 20 parts of a sulfonated pyridine complex is added as a reactant and reacted for 4 hours. After completion of the reaction, the mixture is washed several times with excess quinoline, poured into water, and filtered to obtain a sulfinic acid group (SO ₂ ⁻ ) or sulfone. A slurry of a surface-treated dimethylquinacridone pigment in which a sulfur-containing dispersibility-imparting group such as an acid group (SO ₃ ⁻ ) was directly introduced onto the pigment surface was obtained.

(5) Preparation of surface-treated pigment 5; I. Pigment Violet 19
20 parts of quinacridone pigment (CI Pigment Violet 19) atomized in advance by pulverization was mixed with 500 parts of quinoline, and sufficiently stirred and mixed with a magnetic stirrer. The obtained pigment paste and solvent mixture was transferred to an evaporator, heated to 120 ° C. while reducing the pressure to 30 mmHg or less, and water contained in the system was distilled off as much as possible, and the temperature was controlled at 160 ° C. Next, 20 parts of a sulfonated pyridine complex was added and reacted for 8 hours. After completion of the reaction, the mixture was washed several times with excess quinoline, poured into water, and filtered to obtain a sulfinic acid group (SO ₂ ⁻ ) or a sulfonic acid group ( A slurry of a surface-treated quinacridone pigment in which a sulfur-containing dispersibility-imparting group such as SO ₃ ⁻ ) was directly introduced onto the pigment surface was obtained.

(6) Preparation of surface-treated pigment 6; I. Pigment Yellow 128
20 parts of condensed azo yellow pigment (CI Pigment Yellow 128) is mixed with 500 parts of quinoline, and Eiger Motor Mill M250 type (manufactured by Eiger Japan) under the conditions of 70% bead filling and 5,000 rpm. The mixture of the pigment paste and the solvent, which has been sized and dispersed for 2 hours and finished sized and dispersed, is transferred to an evaporator and heated to 120 ° C. while reducing the pressure to 30 mmHg or less. The temperature was controlled to ° C. Next, 20 parts of a sulfonated pyridine complex is added as a reactant and allowed to react for 4 hours. After completion of the reaction, it is washed several times with excess quinoline, poured into water, and filtered to give a sulfinic acid group (SO ₂ ⁻ ) or A slurry of a surface-treated condensed azo yellow pigment in which a sulfur-containing dispersibility-imparting group such as a sulfonic acid group (SO ₃ ⁻ ) was directly introduced onto the pigment surface was obtained.

(7) Preparation of surface-treated pigment 7; carbon black 25 parts of carbon black pigment (Degussa “Special Black 4”) were mixed in 250 parts of sulfolane, and beads were used with Eiger Motor Mill M250 (Eiger Japan). The mixture is sized and dispersed for 1 hour under conditions of a filling rate of 70% and a rotational speed of 5,000 rpm, and the mixed liquid of the sized and dispersed pigment paste and solvent is transferred to an evaporator and heated to 120 ° C. while reducing the pressure to 30 mmHg or less. After the water contained in the system was distilled off as much as possible, the temperature was controlled at 150 ° C. Next, 25 parts of sulfur trioxide was added and allowed to react for 6 hours. After completion of the reaction, the mixture was washed several times with excess sulfolane, poured into water, and filtered to obtain a sulfinic acid group (SO ₂ ⁻ ) or a sulfonic acid group ( A slurry of a surface-treated carbon black pigment in which a sulfur-containing dispersibility-imparting group such as SO ₃ ⁻ ) was directly introduced onto the pigment surface was obtained.

  Next, 5 parts of ethyl p-aminobenzoate and 3 parts of concentrated nitric acid were added to 400 parts of water and cooled to 5 ° C. with stirring. The surface-treated carbon black pigment is added to this suspension, an aqueous solution consisting of 50 parts of water and 2 parts of sodium nitrite is slowly added, stirred for 10 hours, and repeatedly washed with water and filtered, further through a phenyl group. Thus, a slurry of a surface-treated carbon black pigment having an ethyl carboxylate group introduced therein was obtained.

  Next, 40 parts of polyethylene glycol (Mw: 5,000) and 0.5 part of diazabicycloundecene (DBU) were dissolved in 200 parts of ethanol, and the surface-treated carbon black pigment synthesized above was slowly added and stirred. After adjusting the pH of the mixture to 10 and refluxing for 24 hours, the resulting mixture was repeatedly washed with ethanol and filtered to finally introduce a sulfur-containing dispersibility-imparting group directly onto the surface, and further via a phenyl group. Thus, a surface-treated carbon black pigment into which polyethylene oxide propylene oxide benzamide was introduced was obtained.

(8) Preparation of surface-treated pigment 8; I. Pigment Red 177
25 parts of dianthraquinolyl red pigment (CI Pigment Red 177) previously atomized by pulverization was mixed with 480 parts of quinoline, and sufficiently stirred and mixed with a magnetic stirrer. The obtained pigment paste and solvent mixture was transferred to an evaporator, heated to 120 ° C. while reducing the pressure to 30 mmHg or less, and water contained in the system was distilled off as much as possible, and the temperature was controlled at 160 ° C. Next, 20 parts of a sulfonated pyridine complex was added and reacted for 8 hours. After completion of the reaction, the mixture was washed several times with excess quinoline, poured into water, and filtered to obtain a sulfinic acid group (SO ₂ ⁻ ) or a sulfonic acid group (SO _{2 3} ^-) a sulfur-containing dispersibility-imparting group such as to obtain surface treated Jian tiger quinolyl red pigment was introduced directly to the pigment surface.

  Next, 5 parts of ethyl p-aminobenzoate and 3 parts of concentrated nitric acid were added to 450 parts of water and cooled to 5 ° C. with stirring. The surface-treated dianthraquinolyl red pigment was added to this suspension, an aqueous solution consisting of 50 parts of water and 2 parts of sodium nitrite was slowly added, stirred for 10 hours, repeated washing with water and filtration to further add phenyl groups. A slurry of a surface-treated dianthraquinolyl red pigment having ethyl carboxylate groups introduced therein was obtained.

  Next, 35 parts of polyethylene glycol (Mw: 2,000) and 0.4 part of diazabicycloundecene (DBU) were dissolved in 200 parts of ethanol, and the surface-treated dianthraquinolyl red pigment synthesized above was slowly added and stirred. . After adjusting the pH of the mixture to 10 and refluxing for 24 hours, the resulting mixture was repeatedly washed with ethanol and filtered to finally introduce a sulfur-containing dispersibility-imparting group directly onto the surface, and further via a phenyl group. Thus, a surface-treated dianthraquinolyl red pigment into which polyethylene oxide propylene oxide benzamide was introduced was obtained.

(9) Production of surface-treated pigment 9: carbon black 35 parts of carbon black (“FW-18” manufactured by Degussa) were mixed in 1,000 parts of water and pulverized with a ball mill. To this crushed stock solution, 400 parts of sodium hypochlorite was added and stirred at 90 to 110 ° C. for 10 hours. Washing with water and filtration were repeated to obtain a slurry of a surface-treated carbon black pigment in which carboxylic acid groups were directly introduced on the pigment surface.

(10) Preparation of surface-treated pigment 10; carbon black 20 parts of carbon black (“FW-200” manufactured by Degussa) were mixed in 200 parts of water and pulverized with a ball mill. 7 parts of p-aminobenzenesulfonic acid and 3 parts of nitric acid were added to the pulverized stock solution and stirred at 75 ° C. for several hours. A 20% sodium nitrite aqueous solution was added thereto, and the mixture was further stirred for 1 hour. Washing with water and filtration were repeated to obtain a slurry of a surface-treated carbon black pigment having a carboxyl group introduced through a phenyl group.

(11) Preparation of surface-treated pigment 11; I. Pigment Green 7
20 parts of phthalocyanine green pigment (CI Pigment Green 7) previously atomized by pulverization was mixed with 5 parts of p-aminobenzenesulfonic acid and heated to 70 ° C. An aqueous solution of 80 parts of water and 2 parts of sodium nitrite was rapidly added to this mixture to form a pigment slurry. An aqueous hydrogen chloride solution was added to the resulting slurry until the pH reached 2, and the mixture was stirred for 1 hour, washed with water and filtered repeatedly to obtain a slurry of a surface-treated phthalocyanine green pigment into which a sulfonic acid group was introduced via a phenyl group.

(12) Preparation of surface-treated pigment 12; I. Pigment Red 149
50 parts of perylene scarred pigment (CI Pigment Red 149) previously atomized by pulverization was mixed with 6 parts of p-aminobenzoic acid. To this mixture, 1.5 parts of concentrated nitric acid and 200 parts of water were added and cooled to 5 ° C., and an aqueous solution consisting of 1.2 parts of sodium nitrite and 50 parts of water was slowly added and stirred. Next, this mixture was heated and stirred at 70 ° C. for 8 hours to react, and then washed with water and filtered to obtain a pigment slurry.

  By further adding 6 parts of ethyl p-aminobenzoate, 1.5 parts of concentrated nitric acid, 1.2 parts of sodium nitrite, and 200 parts of water to the above pigment slurry and reacting in the same manner as above, repeating washing with water and filtration. Then, a slurry of a surface-treated perylene scarred pigment into which a carboxylic acid and an ethyl carboxylate group were introduced via a phenyl group was obtained.

  Next, 40 parts of polyethylene glycol (Mw: 2,000) and 0.3 part of diazabicycloundecene (DBU) were dissolved in 100 parts of ethanol, and the surface-treated perylene pigment synthesized above was slowly added and stirred. Subsequently, the pH of the mixture was adjusted to 10 and refluxed for 24 hours.

  The resulting mixture was repeatedly washed with ethanol and filtered to finally obtain a surface-treated perylene scarred pigment into which carboxylic acid and polyethylene oxide propylene oxide benzamide were introduced via a phenyl group.

(13) Preparation of surface-treated pigment 13; I. Pigment Orange 36
20 parts of benzimidazolone orange pigment (CI Pigment Orange 36) previously atomized by pulverization is mixed and dispersed in 150 parts of water in 62 parts of p-amino-N-ethylpyridinium bromide. Nitric acid (32 parts) was added dropwise and stirred at 75 ° C. for 5 minutes. An aqueous solution of sodium nitrite was added, and the mixture was further stirred for 2 hours. Washing with water and filtration were repeated to obtain a slurry of a surface-treated benzimidazolone orange pigment into which an N-ethylpyridyl group was finally introduced via a phenyl group.

<Preparation of pigment dispersion>
(1) Dispersion 1
To 20 parts of the surface-treated pigment 1 (carbon black) obtained by the preparation of the above-mentioned (1) surface-treated pigment 1, 3 parts of triethanolamine and 72.5 parts of ion-exchanged water are added as a neutralizing agent. Glass beads used; bead filling ratio 60%; media diameter 1.7 mm), and dispersed until the average particle diameter (secondary particle diameter) of the pigment reaches 100 nm, and sulfinic acid groups (SO ₂ ⁻ ) or A dispersion 1 of surface-treated pigment 1 (carbon black) having a pigment concentration of 20% by weight in which a sulfur-containing dispersibility-imparting group such as a sulfonic acid group (SO ₃ ⁻ ) was directly introduced onto the pigment surface was obtained.

(2) Dispersion 2
Surfynol 465 (trade name, Air), which is an acetylene glycol surfactant, was added to 20 parts of the surface-treated pigment 2 (CI Pigment Blue 15: 3) obtained by the preparation of the surface-treated pigment 2 (2). 2 parts of Products and Chemicals Inc.), 4 parts of triethanolamine as a neutralizing agent and 67 parts of ion-exchanged water are added, and a paint shaker (using glass beads; bead filling rate 60%, media diameter 1.7 mm) is added. The pigment is dispersed using a sulfur-containing dispersibility-imparting group such as a sulfinic acid group (SO ₂ ⁻ ) or a sulfonic acid group (SO ₃ ⁻ ) until the average particle size (secondary particle size) of the pigment is 95 nm. A dispersion 2 of surface-treated pigment 2 (CI Pigment Blue 15: 3), which was directly introduced on the surface and had a pigment concentration of 20% by weight, was obtained.

(3) Dispersion 3
(3) 20 parts of the surface-treated pigment 3 (CI Pigment Yellow 110) obtained by the preparation of the surface-treated pigment 3 are mixed with 10 parts of triethylene glycol monobutyl ether as a penetrating solvent and ammonia as a neutralizing agent. Add 2 parts of 30% aqueous solution and 60 parts of ion-exchanged water, and use paint shaker (using glass beads; bead filling rate 60%, media diameter 1.7 mm), the average particle diameter (secondary particle diameter) of the pigment is 90 nm. The surface-treated pigment 3 having a pigment concentration of 20% by weight, in which a sulfur-containing dispersibility-imparting group such as a sulfinic acid group (SO ₂ ⁻ ) or a sulfonic acid group (SO ₃ ⁻ ) is directly introduced to the pigment surface. A dispersion 3 of (C.I. Pigment Yellow 110) was obtained.

(4) Dispersion 4
Surfynol 465 (trade name, Air Products and Chemicals) as an acetylene glycol surfactant was added to 20 parts of the surface-treated pigment 4 (CI Pigment Red 122) obtained in the preparation of the above-mentioned (4) surface-treated pigment 4. Inc.) 5 parts, 10 parts of 1,2-hexanediol as penetrating solvent, 1 part of 30% aqueous ammonia and 64 parts of ion-exchanged water as neutralizing agent, paint shaker (using glass beads; filled with beads) The pigment is dispersed until the average particle diameter (secondary particle diameter) of the pigment becomes 100 nm using a media diameter of 1.7 mm, and sulfinic acid groups (SO ₂ ⁻ ) or sulfonic acid groups (SO ₃ ⁻ ). The surface-treated pigment 4 (CI pigment pigment having a pigment concentration of 20% by weight, in which a sulfur-containing dispersibility-imparting group such as 122) to obtain a dispersion liquid 4.

(5) Dispersion 5
Surfynol 465 (trade name, manufactured by Air Products and Chemicals, Inc.) as an acetylene glycol surfactant was added to 20 parts of the surface-treated pigment 9 (carbon black) obtained by the preparation of the above-mentioned (9) surface-treated pigment 9. ) 2 parts, 2 parts of sodium hydroxide as neutralizing agent and 76 parts of ion-exchanged water, and using a paint shaker (using glass beads; bead filling rate 60%, media diameter 1.7 mm), the average particle diameter of the pigment ( Dispersion solution 5 of surface-treated pigment 9 (carbon black) having a pigment concentration of 20% by weight was obtained by dispersing until the secondary particle diameter) reached 100 nm and introducing carboxyl groups directly on the pigment surface.

<Preparation of water-based ink composition>
(Example 1)
In Example 1, Johncrill 734 (trade name, Tg: 30 ° C., solid content: 42% by weight, manufactured by Johnson Polymer Co., Ltd.) was used. The heat treatment method was performed by sealing Joncrill 734 in a sample bottle and leaving it at 40 ° C. 19.1 g of this heat-treated Jonkrill 734, 4.0 g of surface-treated pigment 1 (using carbon black) obtained by the above-mentioned materials and methods, 15.0 g of glycerin, 7.0 g of triethylene glycol, trimethylol Propane (5.0 g), 2-pyrrolidone (5.0 g), and addition of ultrapure water to make the total amount 100 g, using a paint shaker (glass beads used; bead filling rate 60%, media diameter 1.7 mm) Were dispersed until the average particle size (secondary particle size) of the particles became 100 nm. Thereafter, the mixture was filtered through a membrane filter (trade name, manufactured by Nippon Millipore Limited) having a pore diameter of about 1.2 μm to prepare an aqueous ink composition.

(Examples 2 to 13)
A water-based ink composition was prepared in the same manner as in Example 1 except that the additive and amount were changed to those shown in Table 1. The resin emulsion and heat treatment method used here are shown below.
<Resin emulsion 1>
Resin emulsion; John Krill 734 (trade name, Tg: 30 ° C., solid content: 42% by weight, manufactured by Johnson Polymer Co., Ltd.)
Heat treatment method: left at 40 ° C.
<Resin emulsion 2>
Resin emulsion; Mobile 742N (trade name, Tg: 37 ° C., solid content: 43% by weight, manufactured by Clariant Polymer Co., Ltd.)
Heat treatment method: left at 40 ° C.
<Resin emulsion 3>
Resin emulsion; AE series AE140 (trade name, Tg: 53 ° C., solid content: 48% by weight, manufactured by JSR Corporation)
Heat treatment method: left at 60 ° C.
<Resin emulsion 4>
Resin emulsion; John Krill 538 (trade name, Tg: 66 ° C., solid content: 45% by weight, manufactured by Johnson Polymer Co., Ltd.)
Heat treatment method: left at 90 ° C.
<Resin emulsion 5>
Resin emulsion; Mobile 937 (trade name, Tg: -42 ° C., solid content: 60% by weight, manufactured by Clariant Polymer Co., Ltd.)
Heat treatment method: left at 40 ° C.
<Resin emulsion 6>
Resin emulsion; AE series AE343 (trade name, Tg: 0 ° C., solid content: 55% by weight, manufactured by JSR Corporation)
Heat treatment method: left at 40 ° C.
<Resin emulsion 7>
Resin emulsion; Johncrill 631 (trade name, Tg: 87 ° C., solid content: 49.5 wt%, manufactured by Johnson Polymer Co., Ltd.)
Heat treatment method; no heat treatment.

(Example 14)
In Example 14, mobile 742N (trade name, Tg: 37 ° C., solid content: 43% by weight, manufactured by Clariant Polymer Co., Ltd.) and mobile 937 (trade name, Tg: −42 ° C., solid content: 60) subjected to heat treatment. % By weight, manufactured by Clariant Polymer Co., Ltd.). The heat treatment method was carried out by sealing mobile 742N and mobile 937 in respective sample bottles and leaving them at 40 ° C. 9.3 g of this heat-treated mobile 742N, 6.7 g of mobile 937, 53.3 g of dispersion 1 obtained by the above-mentioned materials and methods, 5.0 g of glycerin, 2.0 g of 2-pyrrolidone, trimethylol Propane 10.0g, 2-pyrrolidone 5.0g, ultrapure water is added and the total amount is 100g. After stirring and mixing for 2 hours, the membrane filter (trade name, manufactured by Nihon Millipore Limited) with a pore size of about 1.2μm is used. The aqueous ink composition was prepared by filtration.

(Examples 15 to 18)
A water-based ink composition was prepared in the same manner as in Example 14 except that the additive and amount were changed to those shown in Table 2. The resin emulsion and the heat treatment method used here are the same as those used in Examples 1 to 13 described above. Moreover, the addition amount of each additive in Table 2 also shows what is contained in the pigment dispersion.

(Comparative Example 1)
A water-based ink composition was prepared in the same manner as in Example 2 except that the resin emulsion 2 was not added to the composition of Example 2.

(Comparative Example 2)
A water-based ink composition was prepared in the same manner as in Example 7 except that 14.1 g of resin emulsion 7 was added instead of resin emulsion 1 and resin emulsion 5 to the composition of Example 7.

  Each composition of the said Example and a comparative example is put together in Table 1-Table 3, and is shown.

<Evaluation method>
(Storage stability)
The aqueous ink compositions of Examples 1 to 18 and Comparative Examples 1 and 2 were allowed to stand at 60 ° C. for 2 weeks, left for 1 month, and frozen for 1 week. Compared. Judgment criteria are as follows.
・ Viscosity judgment AA: Change width is less than ± 3% A: Change width is ± 3% or more, less than ± 6% B: Change width is ± 6% or more, less than ± 10% C: Change width is ± 10% or more Particle size determination AA: Change width is less than ± 5% A: Change width is ± 5% or more, less than ± 10% B: Change width is ± 10% or more, less than ± 20% C: Change width is ± 20% or more

(Discharge stability)
The aqueous ink compositions of Examples 1 to 18 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 18 and Comparative Examples 1 to 2 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. Further, 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 the uneven density and the back-through state 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 identified [Filled image quality]
Evaluation AA: Almost no shading is observed in all filled images. There is no breakthrough.
A: Slight shading unevenness is recognized in an image with a fill density of 100%, but it is a level that causes no problem in practical use. There is almost no see-through.
B: Light and dark unevenness is observed in an image having a fill density of 50% or more. The show-through is also noticeable.
C: Light and shade unevenness is observed in all filled images. Print-through is remarkable and printing density is low.

(Evaluation of image robustness on plain paper and recycled paper)
The aqueous ink compositions of Examples 1 to 18 and Comparative Examples 1 to 2 were mounted on PX-V700 (trade name, manufactured by Seiko Epson Corporation), which is an inkjet printer. When the print setting is “paper type; plain paper, print quality: fine”, and 20 points of Gothic characters are printed on plain paper / recycled paper. The ink bleeding and character disturbance (water resistance) were evaluated. Furthermore, the disorder of a character (line marker-proof property) at the time of marking a line on a printed character with a 200-300g load with a highlighter pen (brand name: Fluorescent Sparky 1, Zebra Co., Ltd.) 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.
〔water resistant〕
Evaluation AA: No ink oozes out in the water drop dripping part, and no character disturbance is observed A: There is a slight ink oozing out in the water drop dripping part, but no character disturbance is observed B: In the water drop dripping part Ink oozes out and characters are distorted. C: Ink oozes out in the area where water drops are dropped, making the characters distorted and unreadable. [Line marker resistance]
Evaluation AA: Characters are not distorted even if marking is performed twice or more at the same location. A: Characters are distorted slightly when marking is performed twice at the same location. B: Characters are distorted slightly after one marking C: Marking Character disorder is significant at one time

As shown in Tables 4 and 5, the aqueous ink compositions of Examples 1 to 18 containing the heat-treated resin emulsion have good storage stability (change in viscosity and change in particle size) when left under the above conditions. In addition, there was no problem with ejection stability in the ink jet printer. Also, the printing quality (character quality, filled image quality) and image fastness (water resistance, line marker resistance) were good regardless of the paper type.
On the other hand, in Comparative Example 1 in which the resin emulsion was not added to Example 2, the printing quality was filled and unevenness in density was caused by the image quality, and the printing density was lowered. Furthermore, the image fastness was poor in both water resistance and line marker resistance.
In Comparative Example 2 in which a resin emulsion that was not heat-treated was added, the storage stability was poor when left under the above conditions. In addition, there was a paper type in which the print quality bleeds at the character quality and the density unevenness occurs at the filled image quality. Furthermore, in terms of image fastness, some paper types were inferior in water resistance and line marker resistance.

  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 color development and fixability regardless of the type of recording medium, and is particularly suitable for use as an ink for ink jet recording.

Claims (12)

  An aqueous ink composition comprising a colorant, a resin emulsion, a humectant, and water, wherein the colorant has at least one hydrophilic dispersibility-imparting group directly and / or via a polyvalent group. A surface-treated pigment introduced on the surface of the pigment, and is heat-treated at a temperature equal to or higher than the glass transition temperature (Tg) of the resin component constituting the resin emulsion before the resin emulsion is added to the aqueous ink composition. A water-based ink composition characterized by the above.   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 aqueous composition according to any one of claims 1 to 4, comprising at least one kind of resin emulsion having a glass transition temperature (Tg) of a resin component constituting the resin emulsion of 30 ° C or higher. Ink composition. In the surface-treated pigment, the hydrophilic dispersibility-imparting group introduced into the pigment surface is one or more selected from the group consisting of a functional group represented by the following formula or a salt thereof. The water-based ink composition according to any one of claims 1 to 5.
_{-OM, -COOM, -CO -, -} SO 3 M, -SO 2 M, -SO 2 NH 2, -RSO 2 M, -PO 3 HM, -PO 3 M 2, -SO 2 NHCOR, -NH 3 , -NR ₃
(In the formula, M represents a hydrogen atom, an alkali metal, ammonium, or organic ammonium. R represents an alkyl group having 1 to 12 carbon atoms, an optionally substituted phenyl group, or a substituted group. Represents a naphthyl group which may have a group.)   The water-based ink composition according to any one of claims 1 to 6, wherein the surface-treated pigment is carbon black.   The water-based ink composition according to any one of claims 1 to 6, wherein the surface-treated pigment 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.