JP2000319572A - Aqueous pigment dispersion, aqueous ink composition, and recording by using the ink composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an aqueous pigment dispersion capable of providing high printing density, and further to provide an ink composition. SOLUTION: This aqueous pigment dispersion consists essentially of water and a surface-modified carbon black, and the surface-modified carbon black is the one capable of being dispersed and/or dissolved in the water without a dispersing agent, and having 5-30 μmol/m2 ratio of the amount of hydrophilic functional group to the value of a specific surface area.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aqueous pigment dispersion comprising surface-modified carbon black, and an aqueous ink composition comprising the aqueous pigment dispersion.

2. Description of the Related Art Conventionally, water-soluble dyes have been used as recording liquids for aqueous writing instruments and ink jet printers. In recent years, pigments such as carbon black have been used as colorants in order to improve the image quality and durability of recorded matters. For example, JP-A-64-6074 and JP-A-64-31881 describe aqueous pigment inks in which carbon black is dispersed with a surfactant or a polymer dispersant.

However, with these inks, if the ink content of the colorant is increased in order to increase the print density of the recorded matter, the viscosity of the ink may be rapidly increased. In addition, in order to stably disperse carbon black in the ink, an excess of a surfactant or a polymer dispersant is required, but since the presence of these causes the generation of bubbles and a decrease in defoaming property, particularly, In the case of the ink for inkjet recording, it was observed that the printing stability deteriorated.

In order to solve these problems, Japanese Patent Laid-Open No.
JP-A-3498 / 1998 and JP-A-10-120958 disclose that a certain amount or more of surface active hydrogen or a salt thereof is introduced into carbon black so that the carbon black alone can be used as an aqueous solvent without a surfactant or a polymer dispersant. Describes surface-modified carbon black dispersions that can be dispersed in water. Japanese Patent Application Laid-Open No. H10-110127 describes a method for introducing a sulfone group into carbon black. Further, JP-A-10-95941 proposes an inkjet ink containing the above-mentioned surface-modified carbon black and glycol ethers.

[0005]

SUMMARY OF THE INVENTION The present inventors have now realized that printing with a higher printing density can be realized by using a surface-modified carbon black having a ratio of hydrophilic functional group content / specific surface area in a specific range. And found that an ink composition capable of forming a higher-quality recorded matter was obtained. The present invention is based on such findings.

Accordingly, an object of the present invention is to provide an aqueous pigment dispersion and an aqueous ink composition which can perform printing with a high print density and can form a higher quality recorded matter.

[0007] The aqueous pigment dispersion of the present invention is an aqueous pigment dispersion comprising at least water and surface-modified carbon black, wherein the surface-modified carbon black is dissolved in water without a dispersant. It can be dispersed and / or dissolved, and has a value of hydrophilic functional group content / specific surface area of 5 to 30 μmol / m ² . Further, the aqueous ink composition of the present invention comprises at least the aqueous pigment dispersion.

[0008]

DETAILED DESCRIPTION OF THE INVENTION Aqueous pigment dispersion The aqueous pigment dispersion according to the present invention comprises at least water and surface-modified carbon black, which is dispersed in water without a dispersant. And / or dissolvable, and the value of the amount of hydrophilic functional group / specific surface area is in the range of 5 to 30 μmol / m ² .

The surface-modified carbon black of the present invention is a carbon black having a surface modified by introducing a large amount of hydrophilic functional groups into the carbon black, thereby maintaining the hydrophilicity of the carbon black itself. is there. For this reason, the surface-modified carbon black has a particle size capable of dispersing the carbon black (preferably the minimum particle size) so that the water-soluble dye is dissolved in water as a single molecule, and the aid of the dispersant is It is believed to be dispersed in water without. Such surface-modified carbon black is usually referred to as self-dispersed carbon black,
In the present invention, such carbon black is used.

[0010] By using the aqueous pigment dispersion according to the present invention, an ink composition can be prepared without a dispersant. As a result, even if the concentration of carbon black is increased, the viscosity of the ink composition does not significantly change, and high-concentration carbon black can be stably present in the ink composition. Therefore, a high-density print image can be realized. Further, the aqueous pigment dispersion according to the present invention uses a carbon black having a specific hydrophilic functional group amount / specific surface area value and having a specific surface modification, so that the carbon black that does not satisfy the requirements according to the present invention is used. This has an advantage that a remarkable improvement in image quality can be achieved.

In the present invention, the surface-modified carbon black refers to a hydrophilic functional group such as a carboxyl group, a carbonyl group, a hydroxyl group, a sulfone group, a phosphoric acid group, and a quaternary ammonium salt or a salt thereof, which is directly or alkylated. It means those bonded to the surface of carbon black as a pigment via a group, an alkyl ether group or an aryl group.

In the present invention, "dispersion and / or dissolution in water without a dispersing agent" means that carbon black can be dispersed in water without using a dispersing agent and has a particle diameter (preferably the minimum particle diameter) that is stable. Means the state that exists. The particle size that can be dispersed refers to a particle size at which the particles do not become smaller even if the dispersion time is increased.

The surface-modified carbon black contained in the aqueous pigment dispersion according to the present invention has a hydrophilic functional group content (μmol).
/ G) divided by the specific surface area (m ² / g) of carbon black, that is, the value of the amount of hydrophilic functional groups / specific surface area is 5
３０30 μmol / m ² , preferably 7.
It is in the range of 5 to 15 μmol / m ² . When the aqueous pigment dispersion is used as an aqueous ink for writing or ink jet recording, the above value is 7.5 to 15 μm.
It is particularly preferred that the range be 1 / m ² . An ink composition using an aqueous pigment dispersion containing a surface-modified carbon black having a value in this range can achieve higher print density and better dispersion stability and storage stability.

The term "hydrophilic functional group content" as used herein refers to the amount of a hydrophilic functional group such as a carboxyl group, a carbonyl group, a hydroxyl group, etc., which is generally measured by a vacuum heat for measuring the volatile content of carbon black. It can be determined by the decomposition gas method. The vacuum pyrolysis gas method is a method described in the Chemical Society of Japan, Vol. 88, No. 3 (1967), pp. 69-74, and is specifically the following method.

That is, the amount of the hydrophilic functional group in the surface-modified carbon black is measured by using a vacuum thermal analyzer equipped with an electric furnace and a gas chromatograph as shown in FIG. Here, the gas chromatograph is of the intermediate cell type, the column is silica gel in the first stage,
The second stage is filled with molecular sieves 13X, respectively.
Argon is used as carrier gas. 0.1 to 0.5 g of carbon black as a sample is weighed and placed in a quartz tube, loaded in an electric furnace, and evacuated at 120 ° C. for 2 hours to remove adsorbed moisture and air as a pretreatment. Next, the temperature controller of the electric furnace is set at 200 ° C. and maintained for 1 hour, and the generated gas is collected during that time, and the composition is analyzed by gas chromatography. Immediately, the generated gas was set at 300 ° C. for one hour, followed by collecting and analyzing the generated gas.
400 ° C, 500 ° C, 600 ° C, 700 ° C, 800 ° C,
The generated gas is collected at 900 ° C. and 1000 ° C. for 1 hour, and the composition is analyzed. The generated gas is mainly carbon monoxide and carbon dioxide. From the data of the composition in the generated gas under each temperature condition thus obtained, the amount of the hydrophilic functional group in the surface-modified carbon black is calculated.

In the present invention, the amount of the hydrophilic functional group in the surface-modified carbon black is preferably 1.5 mmol.
1 / g or more. When the amount of the hydrophilic functional group is such a value, it is advantageous in that the pigment dispersion can ensure good dispersion stability and storage stability.

In the present invention, the specific surface area (m ² / g)
Calculates the surface area of carbon black from the amount of gas adsorbed and the molecular cross-sectional area in the adsorbed state (known as the nitrogen adsorption method)
Can be determined by: In the present invention,
When the specific surface area of the carbon black is used, the specific surface area based on the carbon black in any aspect of the surface-modified carbon black and the unmodified surface black used as a raw material thereof is included. In addition, the specific surface area of the surface-modified carbon black and the specific surface area of the surface-unmodified carbon black are substantially the same, and are estimated to show substantially the same value.

As the carbon black used in the present invention, any carbon black generally available as a carbon black for color can be used. Specifically, when classified according to pH, acidic carbon black can be used. Any of black, neutral carbon black and basic carbon black can be used. Further, when classified by the production method, any of furnace carbon black, channel carbon black, acetylene carbon black, and thermal carbon black can be used.

According to a preferred embodiment of the present invention, the surface-modified carbon black is preferably one obtained by oxidizing acidic carbon black among the above-mentioned carbon blacks. Usually, when oxidizing carbon black, the step of pulverizing the raw carbon black and the step of oxidizing the pulverized carbon black are performed successively or almost simultaneously, and at this time, the oxidizing agent is used in both steps. Required. Since acidic carbon black has many hydrophilic groups such as carboxyl groups on its surface, it is easily compatible with aqueous media and is easily crushed. Therefore, an oxidizing agent can be made unnecessary at the time of pulverization, so that the amount of the oxidizing agent used for the oxidation treatment can be reduced. As a result, in the present invention, the value of the amount of the hydrophilic functional group / the specific surface area of the surface-modified carbon black can be easily controlled, for example, in the range of 5 to 30 μmol / m ² . Further, according to the present invention, since the amount of the oxidizing agent can be reduced, the target aqueous pigment dispersion can be produced relatively inexpensively.

Specific examples of the acidic carbon black suitably used in the present invention include # 50, MA8, MA
100 (manufactured by Mitsubishi Chemical Corporation); color black FW1, color black FW18, color black S170, special black 250 (manufactured by Degussa), etc .; raben 3500, raben 1080, raben C (above, Columbian carbon) And Monarch 1300 and Regal 400R (Cabot).

According to a further preferred aspect of the present invention, the surface-modified carbon black is preferably obtained by oxidizing a channel carbon black among the above-mentioned acidic carbon blacks. By using the channel carbon black, it is possible to obtain an aqueous pigment dispersion having a higher printing density than the conventional one. Here, the channel carbon black means carbon black for color manufactured by a channel method. The channel method is a method in which a raw material gas is burned in air, and the flame collides with a metal surface called a channel to produce carbon black. Natural gas is the most common source gas, but steam such as cleaning oil or naphthalene oil can also be used.

The reason why an aqueous pigment dispersion having a high print density can be obtained by using channel carbon black is presumed as follows. That is, in general, when obtaining a surface-modified carbon black, the step of pulverizing the raw carbon black and the step of oxidizing the pulverized carbon black are performed successively or almost simultaneously. An oxidizing agent is required in the process. The channel carbon black generally has a high volatile content, which is caused by a large number of hydrophilic groups on the surface. For this reason, even if untreated, the channel carbon black is easily compatible with the aqueous medium and is easily pulverized, so that an oxidizing agent is not required at the time of pulverizing, and the amount of the oxidizing agent used for the oxidizing treatment is reduced. Can be. As a result, an aqueous pigment dispersion having a high print density can be obtained.

In general, channel carbon black has a higher jetness of the pigment itself than furnace carbon black. Since such high jetness is also reflected in the aqueous pigment dispersion of surface-modified carbon black, it is considered that the print density at the time of printing can be further increased.

Further, the channel carbon black is
In many cases, when the pigment dispersion is deposited on a recording medium, the density of the carbon black particles on the recording medium can be increased because many of the particles have a small particle size and a small particle size distribution width as compared with furnace carbon black. . Therefore, by using channel carbon black,
It is considered that the print density can be increased.

The channel carbon black is generally made of high blackness channel black (HCC), depending on the blackness.
Intermediate blackness channel black (MCC; Medium)
Color Channel), standard blackness channel black (RCC; Regular Color C)
channel). In addition, depending on the ink characteristics, a long flow channel (LFC; Lo)
ng Flow Channel), Medium Flow Cha (MFC)
nnel) and the like. In the present invention, any of these classifications can be used.

Specific examples of the channel carbon black suitably used in the present invention include color black FW200, color black FW1, and color black F
W18, Special Black 74, Special Black 6, Special Black 5, Color Black S170,
Color Black S160, Printex U, Printex V (trade name; manufactured by Degussa Corporation) and the like.

According to the present invention, the aqueous pigment dispersion comprises a step of pulverizing carbon black in an aqueous medium having a surface tension of 50 mN / m or less, and a step of oxidizing the carbon black in an aqueous medium to form a hydrophilic functional group. To obtain an aqueous pigment dispersion containing a surface-modified carbon black. That is, the method for producing an aqueous pigment dispersion according to the present invention includes a step of pulverizing carbon black with an aqueous medium having a surface tension of 50 mN / m or less. Usually, in the oxidation treatment of carbon black, a step of pulverizing the raw carbon black and a step of oxidizing the pulverized carbon black are performed successively or almost simultaneously, and both steps require an oxidizing agent. On the other hand, when the surface tension is 5
In an aqueous medium of 0 mN / m or less, it easily penetrates into the carbon black aggregates, and as a result, the carbon black is easily pulverized, and an oxidizing agent is not required at the time of the pulverization. For this reason, the oxidizing agent used for the oxidation treatment of the carbon black is used only in the step of oxidizing the pulverized carbon black, and the amount of the oxidizing agent used and the amount of the hydrophilic functional group have a substantially 1: 1 relationship. Becomes For this reason, it is easy to control the value of the amount of the hydrophilic functional group / the specific surface area of the surface-modified carbon black to, for example, a range of 5 to 30 μmol / m ² . Furthermore, since it is used only in the step of oxidizing the oxidizing agent, the total amount of the oxidizing agent can be reduced, so that the target aqueous pigment dispersion can be produced relatively inexpensively.

In the method for producing an aqueous pigment dispersion according to the present invention, the main solvent of the aqueous medium is water. As the water, pure water such as ion exchange water, ultrafiltration water, reverse osmosis water, distilled water, or ultrapure water can be used. In addition, it is preferable to use water sterilized by ultraviolet irradiation or addition of hydrogen peroxide, since mold and bacteria can be prevented from being generated when the aqueous pigment dispersion is stored for a long period of time. The aqueous medium in the present invention may contain a water-soluble organic solvent and a surfactant, for example, those described below, in addition to water as a main solvent.

In the method for producing an aqueous pigment dispersion according to the present invention, the surface tension of the aqueous medium in the pulverizing step is adjusted to 5
In order to make the aqueous medium have a low surface tension, a water-soluble organic solvent or a surfactant can be added to make the aqueous medium have a surface tension of 0 mN / m or less.

For example, lower alcohols such as ethanol and propanol, cellosolves such as ethylene glycol monomethyl ether and ethylene glycol monoethyl ether, carbitols such as diethylene glycol monomethyl ether and diethylene glycol monoethyl ether, or nonionic, anionic and cationic By adding a surfactant or the like to water, the surface tension of the aqueous medium at the temperature of the pulverizing step can be adjusted to 50 mN / m or less. The surfactant used here is used only for the purpose of facilitating the penetration of the aqueous medium into the carbon black aggregate. That is, usually, it is necessary to select a surfactant that imparts dispersibility to the pigment, and a surfactant that adsorbs the pigment, but in the present invention, only the permeability may be considered, and a combination having no adsorptivity may be used. it can.

Further, the method for producing an aqueous pigment dispersion according to the present invention provides an aqueous pigment dispersion comprising a surface-modified carbon black by oxidizing carbon black in an aqueous medium to introduce a hydrophilic functional group. .

In the present invention, carbon black can be oxidized by a generally known oxidation treatment. Specifically, for example, it can be obtained by a method using nitric acid, ozone, aqueous hydrogen peroxide, nitrogen oxide, hypohalite or the like as an oxidizing agent under wet or dry conditions, or a method by plasma treatment or the like. it can.

In a preferred embodiment of the present invention, the oxidation of carbon black is preferably carried out using hypohalous acid and / or a salt thereof. Here, examples of the hypohalous acid or a salt thereof include sodium hypochlorite, potassium hypochlorite, sodium hypobromite, potassium hypobromite and the like. Among them, sodium hypochlorite is preferred in terms of reactivity and cost. Therefore, the surface-modified carbon black in the present invention is preferably obtained by oxidizing carbon black using hypohalous acid and / or a salt thereof.

In the method for producing an aqueous pigment dispersion according to the present invention, the value of the ratio of hydrophilic functional groups / specific surface area of the surface-modified carbon black contained in the aqueous pigment dispersion is 5 to 30 μm.
In order to adjust the molar ratio to the range of mol / m ² , it is preferable to adjust the amount ratio of carbon black to the oxidizing agent, the grinding and / or the oxidation time, and the like. For example, when acidic carbon black is treated with sodium hypochlorite as an oxidizing agent, sodium hypochlorite in an amount of 5 to 20 times the amount of carbon black as a raw material is used, and 10 to 15 hours, 95 to 95%.
By stirring at 105 ° C., the desired surface-modified carbon black can be obtained.

When the oxidation is carried out using hypohalous acid or a salt thereof, for example, carbon black and a hypohalite having an effective halogen concentration of 10 to 30% (for example, sodium hypochlorite) are used. Into an appropriate amount of water, 5 hours or more, preferably about 10 to 15 hours, 50 ° C
As described above, oxidation can be carried out preferably by stirring at 95 to 105 ° C. At that time, it is preferable that the carbon black is pulverized before the reaction, or that the carbon black is reacted at the same time as the pulverization. Examples of the pulverization method include pulverizing carbon black with beads such as glass, zirconia, alumina, stainless steel, or magnetism using a ball mill, an attritor, a colloid mill, or a sand mill. When the carbon black is easily disintegrated, the carbon black may be pulverized by a rotary homogenizer or an ultrasonic homogenizer.

After pulverizing and oxidizing the carbon black, beads and coarse particles are separated and removed from the obtained liquid, and then purification such as ultrafiltration for removing by-products and excessive ions is carried out. A pigment dispersion is obtained. If necessary, concentration with a separation membrane, filtration using a metal filter or a membrane filter, or classification by centrifugation may be performed, and neutralization with a hydroxide or amine of an alkali metal salt. May be performed.

Ink Composition The aqueous ink composition according to the present invention is used in a recording method using the ink composition. Examples of the recording method using the ink composition include an ink jet recording method, a recording method using a writing instrument such as a pen, and various other printing methods. Therefore, the aqueous ink composition according to the present invention can be preferably used for applications such as writing implements such as an aqueous pen, an ink jet recording method, printing, and a stamp.

The aqueous ink composition according to the present invention comprises at least the aqueous pigment dispersion described above.
Since the aqueous ink composition according to the present invention contains at least the aqueous pigment dispersion described above, high print density and good storage stability can be achieved.

The aqueous ink composition according to the present invention contains the surface-modified carbon black in an amount of preferably 1 to 15% by weight, more preferably 2 to 15% by weight, based on the ink composition.
-10% by weight. The fact that the ink composition contains the surface-modified carbon black in such a range is advantageous in that an ink composition having a viscosity usable in an ink jet recording system can be obtained while securing a sufficient print density. is there.

The aqueous ink composition according to the present invention preferably uses water as a main solvent. As the water, pure water such as ion exchange water, ultrafiltration water, reverse osmosis water, distilled water, or ultrapure water can be used. In addition, it is preferable to use water sterilized by ultraviolet irradiation, hydrogen peroxide addition, or the like, since mold and bacteria can be prevented from being generated when the aqueous ink composition is stored for a long period of time.

In a preferred embodiment of the present invention, the aqueous ink composition comprises the aqueous pigment dispersion described above, and the amount of the ink composition applied to the recording medium is 1 m.
When it is g / cm ² , it is preferable that the ink composition has permeability such that the penetration time of the ink composition is less than 1 second.

Here, the permeability such that the penetration time is less than 1 second when the application amount is 1 mg / cm ² is specifically, for example, 360 dpi (dot / inch) × 36.
When 50 ng of the ink composition is applied to plain paper in an area of 0 dpi, it takes less than 1 second until the ink composition does not become stained even when the printed surface is touched. At this time, as plain paper, neutral plain paper, for example, Xerox-
P (trade name, manufactured by Fuji Xerox Co., Ltd.) is used.

The permeability of the ink composition can be improved by adding a water-soluble organic solvent or a surfactant such as a surfactant which lowers the surface tension of the aqueous solution to improve the wettability to the recording medium. Can be obtained.

Examples of such water-soluble organic solvents include lower alcohols such as ethanol and propanol, cellosolves such as ethylene glycol monomethyl ether and ethylene glycol monoethyl ether, and carbitols such as diethylene glycol monomethyl ether and diethylene glycol monoethyl ether. Kind and 1,
Examples thereof include 1,2-alkyldiols such as 2-hexanediol and 1,2-octanediol.

In a more preferred embodiment of the present invention, the water-soluble organic solvent used as a penetration enhancer is more preferably a glycol butyl ether-based water-soluble organic solvent. Such glycol butyl ether-based water-soluble organic solvents include, for example, ethylene glycol mono-
Examples include n-butyl ether, diethylene glycol-n-butyl ether, and triethylene glycol-n-butyl ether. By combining such a water-soluble organic solvent and surface-modified carbon black, it is possible to provide a good printed matter with reduced bleeding during printing.

Examples of the above-mentioned surfactant include anionic surfactants such as fatty acid salts and alkyl sulfate salts, nonionic surfactants such as polyoxyethylene alkyl ether and polyoxyethylene phenyl ether, and cationic surfactants. And amphoteric surfactants and the like.

More preferred surfactants include nonionic surfactants such as polyoxyethylene alkyl ether and polyoxyethylene phenyl ether. These are advantageous in that foaming of the ink can be reduced as compared with ionic surfactants. Specific examples of such a nonionic surfactant include Nissan Nonion K
-211, K-220, P-213, E-215, E-
220, S-215, S-220, HS-220, NS
-212 and NS-220 (both are trade names,
Nippon Oils & Fats Co., Ltd.). Examples of more preferred surfactants include Surfynol 61, 82, 104, 440, and 46 among nonionic surfactants.
5,485 (both are brand names, Air Products, Inc.)
And Chemicals, Inc.). When these are added to the ink composition, foaming hardly occurs, and therefore, it is particularly preferable when the ink composition is used in an ink jet recording method.

The surface-modified carbon black of the present invention can be dispersed and / or dissolved in water without using a dispersant such as a surfactant.
These surfactants used in the ink composition according to the present invention can be selected for the sole purpose of promoting penetration. That is, usually, in order to impart dispersibility to the pigment, it is necessary to select in consideration of the combination in which the pigment and each material adsorb, but in the present invention, without considering such a combination The surfactant can be selected in consideration of only the penetration promoting effect.

In the present invention, the above-mentioned water-soluble organic solvent or surfactant is used alone or in combination as a penetration enhancer.
It is desirable to adjust the surface tension of the ink composition to less than 40 mN / m, preferably less than 35 mN / m.

The aqueous ink composition according to the present invention, when used in an ink jet recording method, can further comprise a humectant for the purpose of preventing ink drying at the tip of a nozzle for discharging ink.

[0051] Such humectants are usually selected from materials that are water-soluble and highly hygroscopic. Specifically, for example,
Glycerin, ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol,
Polyols such as polypropylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,2,6-hexanetriol, and pentaerythritol;
Lactams such as 2-pyrrolidone, N-methyl-2-pyrrolidone, ε-caprolactam, ureas such as urea, thiourea, ethylene urea, 1,3-dimethylimidazolidinone, maltitol, sorbitol, gluconolactone ,
Sugars such as maltose; These moisturizers
When used in combination with other ink additives, the ink composition can be added to the ink composition according to the present invention in an amount such that the viscosity of the ink composition at 25 ° C. is 25 mPa · s or less.

The aqueous ink composition according to the present invention may further contain, if necessary, a fixing agent, a pH adjusting agent, an antioxidant, an ultraviolet absorber, a preservative and a fungicide.

As the fixing agent, water-soluble resins can be used. Examples of such a fixing agent include water-soluble rosins, alginic acids, polyvinyl alcohol,
Hydroxypropyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, methyl cellulose, styrene-acrylic acid resin, styrene-acrylic acid-acrylate resin, styrene-maleic acid resin, styrene-maleic acid half-ester resin, acrylic acid-acrylic acid ester resin, Isobutylene-maleic acid resin, rosin-modified maleic resin, polyvinylpyrrolidone, gum arabic starch, polyallylamine, polyvinylamine, polyethyleneimine and the like. Since the surface-modified carbon black of the present invention is a colorant that can be dispersed and / or dissolved in water without using a dispersant composed of a water-soluble resin, the water-soluble resin used in the ink of the present invention is: It can be selected only for the purpose of the fixing effect. That is, in order to usually impart dispersibility to a pigment, it is necessary to select a combination in which the pigment and each material adsorb, but in the present invention, it is necessary to select only a fixing property without considering a combination. Can be.

Examples of the pH adjuster include alkali metal hydroxides and amines such as lithium hydroxide, sodium hydroxide, potassium hydroxide, triethanolamine and diethanolamine.

As the antioxidant and the ultraviolet absorber,
For example, alluhanates such as allohanate and methyl allohanate; biurets such as biuret, dimethyl biuret and tetramethyl biuret; L-ascorbic acid and salts thereof;
Vin 328, 900, 1130, 384, 292, 1
23, 144, 622, 770, 292, Irgaco
r252, 153, Irganox 1010, 107
6, 1035, MD1024, or oxides of lanthanides.

As the preservatives and fungicides, for example,
Sodium benzoate, sodium pentachlorophenol, sodium 2-pyridinethiol-1-oxide, sodium sorbate, sodium dehydroacetate,
1,2-dibenzisothiazolin-3-one (Proxel CRL, Proxel BDN, Proxel GX of ICI)
L, Proxel XL-2, Proxel TN) and the like.

The aqueous ink composition according to the present invention can be used for general writing instruments, printing, and stamping. However, the ink composition is ejected by droplets, and the droplets are adhered to a recording medium for printing. It is more preferable to use it as an ink composition for inkjet recording that performs the following. In the aqueous ink composition of the present invention as an ink for inkjet recording, the viscosity at 25 ° C. is 1.0 to 15
It is preferably in the range of mPa · s. If the viscosity of the ink composition is within the above range, the ink can be stably ejected in the ink jet recording method.

Recording Method The ink composition according to the present invention is used in a recording system for printing on a recording medium by attaching the ink composition.

According to another aspect of the present invention, there is provided an ink jet recording method for performing printing by discharging droplets of the ink composition according to the present invention and attaching the droplets to a recording medium. As the inkjet recording method according to the present invention, any method may be used as long as the ink composition is ejected as droplets from a fine nozzle and the droplets are attached to a recording medium. As specific examples of such a method, various embodiments of the method are known.

As an example of such a method, for example,
An electrostatic attraction system may be used. In this method, a strong electric field is applied between a nozzle and an accelerating electrode placed in front of the nozzle, ink is continuously ejected from the nozzle in the form of droplets, and printing information is printed while the ink droplet flies between the deflecting electrodes. A signal is applied to the deflection electrode and recorded. Further, in this method, if necessary, the ink droplet may be ejected in accordance with the print information signal without being deflected. As another mode, there is a method of forcibly ejecting ink droplets by applying pressure to an ink liquid with a small pump and mechanically vibrating a nozzle with a crystal oscillator or the like. According to this method, the ejected ink droplets are charged at the same time as the ejection, and a print information signal is applied to the deflecting electrodes while the ink droplets fly between the deflecting electrodes to record. Another embodiment includes a method using a piezoelectric element. In this method, a pressure and a print information signal are simultaneously applied to an ink liquid by a piezoelectric element, and an ink droplet is ejected to perform recording. As still another embodiment, there is a method of rapidly expanding the volume of an ink liquid by the action of thermal energy. In this method, recording is performed by causing an ink liquid to be heated and foamed by a microelectrode in accordance with a print information signal and ejecting ink droplets. According to the inkjet recording method of the present invention, inkjet recording can be performed stably.

Further, according to the present invention, a recorded matter recorded by these recording methods is also provided. This record is
By using the aqueous ink composition according to the present invention, high print density can be exhibited, and high water resistance, weather resistance, active gas resistance, and the like are obtained.

[0062]

The present invention will be described in more detail with reference to the following examples, but it should not be construed that the invention is limited thereto.

Preparation of Aqueous Pigment Dispersion Aqueous Pigment Dispersion 1 Color Black FW, a commercially available acidic carbon black
18 (trade name; manufactured by Degussa) (specific surface area: 260 m ² /
g) 100 g was mixed with 500 g of water and pulverized by a ball mill using zirconia beads. 1500 g of sodium hypochlorite (effective chlorine concentration 12%)
Was added dropwise, and the mixture was boiled for 10 hours to perform wet oxidation. The resulting undiluted dispersion was filtered through a glass fiber filter paper GA-100 (trade name, manufactured by Advantech Toyo Co., Ltd.), and further washed with water. The obtained wet cake is redispersed in 5 kg of water, desalted and purified by a reverse osmosis membrane until the electric conductivity becomes 2 mS / cm, and further concentrated until the pigment concentration becomes 10% by weight. 1 was prepared. The hydrophilic functional group content of the obtained surface-modified carbon black was measured by the above-described vacuum pyrolysis gas method, and was 2340 μmol.
/ G, and the value obtained by dividing this value by the specific surface area of the color black FW18 (that is, the value of the amount of the hydrophilic functional group / the specific surface area) was 9.0 μmol / m ² .

Aqueous pigment dispersion 2 Color black S1 which is a commercially available acidic carbon black
70 (trade name; manufactured by Degussa) (specific surface area: 200 m ² /
g) 100 g was mixed with 1 kg of water and pulverized by a ball mill using zirconia beads. 1400 g of sodium hypochlorite (effective chlorine concentration: 12%) was dropped into this ground stock solution, and reacted for 5 hours while grinding with a ball mill.
Further, the mixture was boiled for 4 hours with stirring to perform wet oxidation.
The resulting undiluted dispersion was filtered through a glass fiber filter paper GA-100 (trade name, manufactured by Advantech Toyo Co., Ltd.), and further washed with water. The obtained wet cake was re-dispersed in 5 kg of water, desalted and purified by a reverse osmosis membrane until the conductivity reached 2 mS / cm, and the pigment concentration was 10% by weight.
To obtain an aqueous pigment dispersion 2. The amount of the hydrophilic functional group of the obtained surface-modified carbon black was 2100 μmol / g as measured by the above method, and the value obtained by dividing this value by the specific surface area of the color black S170 was 10.5 μmol / m ² . there were.

Aqueous Pigment Dispersion 3 A commercially available acidic carbon black, MA8 (trade name; manufactured by Mitsubishi Chemical Corporation) (100 g, specific surface area: 137 m ² / g) was mixed with 500 g of water and pulverized by a ball mill using zirconia beads. . 500 g of sodium hypochlorite (effective chlorine concentration: 12%) was dropped into this ground stock solution, and the mixture was boiled for 10 hours to perform wet oxidation. The resulting undiluted dispersion was filtered through a glass fiber filter paper GA-100 (trade name, manufactured by Advantech Toyo Co., Ltd.), and further washed with water. The obtained wet cake is redispersed in 5 kg of water, desalted and purified by a reverse osmosis membrane until the electric conductivity becomes 2 mS / cm, and further concentrated until the pigment concentration becomes 10% by weight. 3 was prepared. The amount of the hydrophilic functional group of the obtained surface-modified carbon black was measured by the method described above, and was 1230 μmol / g, and the value obtained by dividing this value by the specific surface area of MA8 was 9.0 μmol / m ² . .

Aqueous pigment dispersion 4 Color black FW200 (trade name; manufactured by Degussa), a commercially available channel carbon black (specific surface area: 460)
(m ² / g) was mixed with 500 g of water and pulverized by a ball mill using zirconia beads. Sodium hypochlorite (effective chlorine concentration 12%) 10
00 g was added dropwise and the mixture was boiled for 10 hours to perform wet oxidation.
The resulting undiluted dispersion was filtered through a glass fiber filter paper GA-100 (trade name, manufactured by Advantech Toyo Co., Ltd.), and further washed with water. The obtained wet cake was re-dispersed in 5 kg of water, desalted and purified by a reverse osmosis membrane until the conductivity reached 2 mS / cm, and the pigment concentration was 10% by weight.
To obtain an aqueous pigment dispersion 4. The hydrophilic functional group content of the obtained surface-modified carbon black was 2600 μmol / g as measured by the above method, and the value obtained by dividing this value by the specific surface area of FW200 was 5.7 μmo.
1 / m ² .

Aqueous pigment dispersion 5 Special black 4 (trade name; manufactured by Degussa Co., Ltd.) which is a commercially available channel carbon black (specific surface area: 180 m ²
/ G) 100 g was mixed with 500 g of water and pulverized by a ball mill using zirconia beads. Sodium hypochlorite (effective chlorine concentration 12%) 1100
g was added dropwise and the mixture was boiled for 10 hours to perform wet oxidation. The obtained undiluted dispersion liquid was used as a glass fiber filter paper GA-100 (trade name,
(Advantech Toyo Co., Ltd.) and further washed with water. The obtained wet cake is redispersed in 5 kg of water, desalted and purified by a reverse osmosis membrane until the electric conductivity becomes 2 mS / cm, and further concentrated until the pigment concentration becomes 10% by weight. 5 was prepared. The amount of the hydrophilic functional group of the obtained surface-modified carbon black was 2500 μmol / g as measured by the above method, and the value obtained by dividing this value by the specific surface area of the special black 4 was 1
It was 3.9 μmol / m ² .

Aqueous Pigment Dispersion 6 (Comparative Example) 185 g of Color Black FW, which is an acidic carbon black described in Aqueous Pigment Dispersion 1, was added to 95 g of water, and sufficiently stirred with a homomixer. Then, when allowed to stand for several minutes, the carbon black aggregated and settled. The amount of the hydrophilic functional group of the obtained carbon black was 130 μmol / g as measured by the above method, and the value obtained by dividing this value by the specific surface area of the color black FW18 was 0.50 μm.
mol / m ² .

Aqueous Pigment Dispersion 7 (Comparative Example) 100 g of Color Black S170, which is an acidic carbon black described in Aqueous Pigment Dispersion 2, was mixed with 500 g of water and pulverized by a ball mill using zirconia beads. 350 g of sodium hypochlorite (effective chlorine concentration: 12%) was dropped into this ground stock solution, and the mixture was boiled for 10 hours to perform wet oxidation. The obtained undiluted dispersion solution is used as a glass fiber filter paper GA.
The mixture was filtered through -100 (trade name, manufactured by Advantech Toyo Co., Ltd.), and further washed with water. The obtained wet cake was redispersed in 5 kg of water, and the conductivity was set to 2 by a reverse osmosis membrane.
The resultant was desalted and purified to mS / cm, and further concentrated to a pigment concentration of 10% by weight to prepare an aqueous pigment dispersion liquid 7. The hydrophilic functional group content of the obtained surface-modified carbon black was measured by the method described above.
1 / g, and the value obtained by dividing this value by the specific surface area of Color Black S170 was 4.80 μmol / m ² .

Aqueous Pigment Dispersion 8 (Comparative Example) 100 g of the acidic carbon black MA8 described in Aqueous Pigment Dispersion 3 was mixed with 500 g of water and pulverized by a ball mill using zirconia beads. 70 g of sodium hypochlorite (effective chlorine concentration 12%)
Was added dropwise, and the mixture was boiled for 6 hours to perform wet oxidation. The resulting undiluted dispersion was filtered through a glass fiber filter paper GA-100 (trade name, manufactured by Advantech Toyo Co., Ltd.), and further washed with water. The obtained wet cake is redispersed in 5 kg of water, desalted and purified by a reverse osmosis membrane until the electric conductivity becomes 2 mS / cm, and further concentrated until the pigment concentration becomes 10% by weight. 8 was prepared. The amount of the hydrophilic functional group of the obtained surface-modified carbon black was 620 μmol / g as measured by the above method, and the value obtained by dividing this value by the specific surface area of MA8 was 4.53 μmol / m ^2.
Met.

Aqueous Pigment Dispersion 9 (Comparative Example) 100 g of Color Black FW18, which is an acidic carbon black described in Aqueous Pigment Dispersion 1, was mixed with 500 g of water and pulverized by a ball mill using zirconia beads. To this ground stock solution, 3840 g of sodium hypochlorite (effective chlorine concentration: 12%) was dropped, and the mixture was boiled for 10 hours to perform wet oxidation. The obtained undiluted dispersion liquid is used as a glass fiber filter paper G.
A-100 (trade name, manufactured by Advantech Toyo Corporation)
And further washed with water. The obtained wet cake is redispersed in 5 kg of water, desalted and purified by a reverse osmosis membrane until the electric conductivity becomes 2 mS / cm, and further concentrated until the pigment concentration becomes 10% by weight. 9
Was prepared. The amount of the hydrophilic functional group of the obtained surface-modified carbon black was measured by the above-mentioned method.
mol / g, and the value obtained by dividing this value by the specific surface area of the color black FW18 was 30.38 μmol / m ² .

Aqueous Pigment Dispersion 10 (Comparative Example) 100 g of Color Black S170, which is an acidic carbon black described in Aqueous Pigment Dispersion 2, was mixed with 1 kg of water and pulverized by a ball mill using zirconia beads.
Sodium hypochlorite (effective chlorine concentration)
2420 g of 12%) was added dropwise and reacted for 5 hours while being pulverized by a ball mill, and further boiled for 4 hours with stirring to perform wet oxidation. The resulting undiluted dispersion was filtered through a glass fiber filter paper GA-100 (trade name, manufactured by Advantech Toyo Co., Ltd.), and further washed with water. The obtained wet cake is redispersed in 5 kg of water, desalted and purified by a reverse osmosis membrane until the electric conductivity becomes 2 mS / cm, and further concentrated until the pigment concentration becomes 10% by weight. 10 was prepared. The obtained pigment dispersion was made acidic with aqueous hydrochloric acid, subjected to membrane purification again, concentrated, dried and pulverized to obtain a powder of oxidized carbon black. The hydrophilic functional group content of the obtained surface-modified carbon black was 6400 μmol / g as measured by the above method, and the value obtained by dividing this value by the specific surface area of the color black S170 was 3
It was 2.00 μmol / m ² .

Aqueous Pigment Dispersion Liquid 11 (Comparative Example) 100 g of MA8, which is an acidic carbon black described in Aqueous Pigment Dispersion Liquid 3, was mixed with 1 kg of water and pulverized by a ball mill using zirconia beads. 870 g of sodium hypochlorite (effective chlorine concentration 12%)
Was dropped and reacted for 5 hours while being pulverized by a ball mill, and further boiled for 4 hours with stirring to perform wet oxidation. The obtained undiluted dispersion liquid was used as a glass fiber filter paper GA-100.
(Trade name, manufactured by Advantech Toyo Co., Ltd.), and further washed with water. The obtained wet cake was redispersed in 5 kg of water, and the conductivity was 2 mS /
cm, desalting and purification until the pigment concentration reaches 1 cm.
The aqueous pigment dispersion liquid 11 was prepared by concentrating to 0% by weight. The obtained pigment dispersion was made acidic with aqueous hydrochloric acid, subjected to membrane purification again, concentrated, dried and pulverized to obtain a powder of oxidized carbon black. The amount of the hydrophilic functional group in the obtained oxidized carbon black was 4320 μmol / g as measured by the above method, and the value obtained by dividing this value by the specific surface area of MA8 was 31.53 μmol / m ² .

Aqueous Pigment Dispersion 12 (Comparative Example) 100 g of color black FW200 as a channel carbon black described in Aqueous Pigment Dispersion 4 and Joncryl J-62 (trade name, manufactured by Johnson Polymer Co., Ltd.) as a water-soluble resin dispersant ) 150 g, 6 g of sodium hydroxide, and 250 g of water were mixed and dispersed in a ball mill using zirconia beads for 10 hours. The resulting dispersion liquid was filtered through a stainless steel filter having a pore size of about 5 μm, and diluted with water until the pigment concentration became 10% by weight to prepare an aqueous pigment dispersion liquid 12 dispersed with a water-soluble resin.

Preparation of Water-based Ink Composition a Water-based ink composition 1a 20 g of water-based pigment dispersion 1, 5 g of glycerin and 5 g of 2-pyrrolidone as moisturizing components, and 4 g of ethanol as a permeation-promoting component were mixed to a total amount of 100 g. Ultrapure water was added. The mixture is stirred for 2 hours, and the pore size is about 5 μm.
Was filtered through a stainless steel filter to prepare aqueous ink composition 1a.

20 g of the aqueous pigment composition 2a, 6 g of triethylene glycol and 5 g of urea as moisturizing components and 4 g of ethanol as a permeation promoting component were mixed, and ultrapure water was added to a total amount of 100 g. The mixture is stirred for 2 hours to give a pore size of about 5μ.
The resulting mixture was filtered through a stainless steel filter of No. m to prepare an aqueous ink composition 2a.

Aqueous ink composition 3a Aqueous ink composition 1 except that aqueous pigment dispersion 3 was used
Aqueous ink composition 3a was prepared in the same manner as in a.

Aqueous ink composition 4a Aqueous ink composition 1 except that aqueous pigment dispersion 4 was used
Aqueous ink composition 4a was prepared in the same manner as in a.

Aqueous ink composition 5a An aqueous ink composition 1 was prepared except that the aqueous pigment dispersion 5 was used.
Aqueous ink composition 5a was prepared in the same manner as in a.

Aqueous Ink Composition 6a (Comparative Example) Aqueous ink composition 1a except that aqueous pigment dispersion 6 was used.
The aqueous ink composition 6a was prepared in the same manner as in the above.
However, the pigment in the ink settled immediately after stirring without being finely dispersed. Therefore, filtration and subsequent evaluation could not be performed.

Aqueous ink composition 7a (Comparative Example) Aqueous ink composition 2 was prepared except that aqueous pigment dispersion 7 was used.
A water-based ink composition 7a was prepared in the same manner as in a.

Aqueous Ink Composition 8a (Comparative Example) Aqueous ink composition 1 was prepared except that aqueous pigment dispersion 8 was used.
Aqueous ink composition 8a was prepared in the same manner as in a.

Aqueous ink composition 9a (Comparative Example) Aqueous ink composition 1 was prepared except that aqueous pigment dispersion 9 was used.
Aqueous ink composition 9a was prepared in the same manner as in a.

Aqueous Ink Composition 10a (Comparative Example) An aqueous ink composition 10a was prepared in the same manner as in the aqueous ink composition 2a except that the aqueous pigment dispersion 10 was used.

Aqueous Ink Composition 11a (Comparative Example) An aqueous ink composition 11a was prepared in the same manner as in the aqueous ink composition 1a except that the aqueous pigment dispersion liquid 11 was used.

Aqueous Ink Composition 12a (Comparative Example) An aqueous ink composition 12a was prepared in the same manner as in the aqueous ink composition 2a except that the aqueous pigment dispersion liquid 12 was used.

Preparation of Aqueous Ink Composition b Aqueous Ink Composition 1b 45 g of Aqueous Pigment Dispersion 1, 10 g of glycerin and 5 g of 2-pyrrolidone as moisturizing components, and te as a penetration promoting component
4 g of rt-pentanol and 1 g of nonionic surfactant Nissan Nonion NS-220 (trade name, manufactured by NOF CORPORATION) were mixed, and ultrapure water was added to make a total amount of 100 g. Triethanolamine was added to reach 5. The mixture was stirred for 2 hours and filtered with a stainless steel filter having a pore size of about 5 μm to prepare an aqueous ink composition 1b.

Aqueous ink composition 2b 45 g of aqueous pigment dispersion 2 and glycerin 1 as humectant
0 g, 5 g of diethylene glycol, and 7.5 g of diethylene glycol-mono-n-butyl ether as a penetration enhancer
g, add ultrapure water to make the total amount 100 g,
Further, triethanolamine was added until the ink pH reached 7.3. The mixture is stirred for 2 hours to give a pore size of about 5
The aqueous ink composition 2b was prepared by filtration through a μm stainless steel filter.

Aqueous ink composition 3b 45 g of aqueous pigment dispersion 3 and glycerin 1 as humectant
0 g and 5 g of diethylene glycol, 5 g of diethylene glycol-mono-n-butyl ether as a penetration enhancer and Surfynol 1 of an acetylene glycol-based surfactant
Then, 0.3 g of 04 and 1.5 g of Surfynol 485 were mixed, ultrapure water was added to make the total amount 100 g, and triethanolamine was further added until the ink pH reached 7.2. The mixture was stirred for 2 hours and filtered with a stainless steel filter having a pore size of about 5 μm to prepare an aqueous ink composition 3b.

Aqueous ink composition 4b was obtained in the same manner as for aqueous ink composition 1b, except that aqueous pigment dispersion 4 was used as the aqueous ink composition 4b dispersion.

An aqueous ink composition 5b was obtained in the same manner as the aqueous ink composition 3b, except that the aqueous pigment dispersion 5 was used as the aqueous ink composition 5b dispersion.

Aqueous Ink Composition 6b (Comparative Example) An aqueous ink composition 6b was prepared in the same manner as the aqueous ink composition 1b except that the aqueous pigment dispersion 6 was used as the dispersion. However, the pigment in the ink settled immediately after stirring without being finely dispersed. Therefore, filtration and subsequent evaluation could not be performed.

Aqueous Ink Composition 7b (Comparative Example) An aqueous ink composition 7b was obtained in the same manner as the aqueous ink composition 2b, except that the aqueous pigment dispersion 7 was used as the dispersion.

Aqueous Ink Composition 8b (Comparative Example) An aqueous ink composition 8b was obtained in the same manner as the aqueous ink composition 3b except that the aqueous pigment dispersion 8 was used as the dispersion.

Aqueous ink composition 9b (Comparative Example) An aqueous ink composition 9b was obtained in the same manner as the aqueous ink composition 1b, except that the aqueous pigment dispersion 9 was used as the dispersion.

Aqueous ink composition 10b (Comparative Example) Aqueous ink composition 10b was prepared in the same manner as aqueous ink composition 2b, except that aqueous pigment dispersion 10 was used as the dispersion.
I got

Aqueous ink composition 11b (Comparative Example) Aqueous ink composition 11b was prepared in the same manner as for aqueous ink composition 3b, except that aqueous pigment dispersion liquid 11 was used as the dispersion liquid.
I got

Aqueous ink composition 12b (Comparative Example) Aqueous ink composition 12b was prepared in the same manner as for aqueous ink composition 1b, except that aqueous pigment dispersion 12 was used as the dispersion.
I got

Evaluation of Pigment Dispersion A small amount of each of the aqueous pigment dispersions 1 to 12 was taken, and the dispersion state was observed at 400 times magnification using an optical microscope, and the presence or absence of aggregation was evaluated as follows. : There are no aggregates that can be seen at a magnification of 400 times, and the whole is uniform. ×: Coarse matter and aggregates are observed.

After standing for 1 hour, the aggregation of the aqueous pigment dispersion was observed with an optical microscope. The results were evaluated as follows. : No aggregate is generated. ×: Aggregates were generated or aggregates increased.

Further, each of the aqueous pigment dispersions 1 to 12 was placed in a sealed container, and left at 50 ° C. for one month.
Changes in the physical properties of these pigment dispersions before and after standing were evaluated as follows. : The change in the viscosity and the average particle diameter of the pigment dispersion is ± 50% or less of that before standing. X: The change in the viscosity or the average particle diameter of the pigment dispersion exceeded ± 50% of that before standing.

Further, the obtained pigment dispersion was coated with a coating thickness of 25.
Apply to neutral plain paper Xerox-P (trade name, manufactured by Fuji Xerox Co., Ltd.) using a μm applicator, dry and measure the OD value with a Macbeth densitometer TR-927 (trade name, manufactured by Colmorgen). did.

The results were as shown in Tables 1 and 2.

[0104]

[Table 1]

[0105]

[Table 2]

Evaluation of Ink Composition A Evaluation of Storage Stability Each of the aqueous ink compositions 1a to 12a was placed in a sealed container and left at 50 ° C. for one month. The viscosity and average particle size of the aqueous ink composition before and after standing were measured, and the storage stability was evaluated as follows. The results were as shown in Tables 3 and 4. : Change in viscosity and average particle size of the ink composition is ± 20% or less of that before leaving. ×: The change in the viscosity or average particle size of the ink composition exceeds ± 20% with respect to that before standing.

Evaluation of Print Density For the aqueous ink compositions 1a to 12a, a neutral plain paper Xerox-P (trade name; manufactured by Seiko Epson Corporation) was used by a piezoelectric element type on-demand ink jet recording apparatus MJ-500 (trade name, manufactured by Seiko Epson Corporation). (Trade name, manufactured by Fuji Xerox Co., Ltd.) to obtain a recorded matter. After drying the recorded matter, the print density (OD value) was measured by Macbeth densitometer TR-927 (trade name, manufactured by Colmorgen). The results were as shown in Tables 3 and 4.

[0108]

[Table 3]

[0109]

[Table 4]

Evaluation of Ink Composition B Evaluation of Storage Stability Each of the aqueous ink compositions 1b to 12b was placed in a sealed container and left at 50 ° C. for one month. The viscosity and average particle size of the aqueous ink composition before and after standing were measured, and the storage stability was evaluated as follows. The results were as shown in Tables 5 and 6. : Change in viscosity and average particle size of the ink composition is ± 20% or less of that before leaving. X: The change in the viscosity or the average particle diameter of the ink composition exceeds ± 20% with respect to before the standing.

Evaluation of Print Density For the aqueous ink compositions 1b to 12b having penetrability such that the permeation time of the ink is less than 1 second, the piezoelectric element type on-demand ink jet recording apparatus MJ-930C
Printing was performed on neutral plain paper Xerox-P (trade name; manufactured by Fuji Xerox Co., Ltd.) using (trade name; manufactured by Seiko Epson Corporation) to obtain a recorded matter. After drying the recorded matter, the print density (OD value) was measured by Macbeth densitometer TR-927 (trade name; manufactured by Colmorgen). The results were as shown in Tables 5 and 6.

[0112]

[Table 5]

[0113]

[Table 6]

Evaluation of Print Quality The recorded matter obtained in the evaluation of the print density was
The print quality was evaluated visually. In the recorded matter using the ink composition 2b to which glycol butyl ethers were added as a penetration enhancer, the bleeding at the peripheral portion of the print was small, and the print quality was particularly good. Ink compositions 3b and 5b further containing an acetylene glycol-based nonionic surfactant as a permeation enhancer had extremely little foaming, and were therefore excellent in handleability.

[Brief description of the drawings]

FIG. 1 is a diagram schematically showing a vacuum pyrolysis apparatus for measuring the amount of a hydrophilic functional group in a surface-modified carbon black.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Electric furnace 2 Quartz sample tube 3 Manometer 4 Cooling trap 5 Vacuum pump 6 Teppler pump 7 Gas buret 8 Gas chromatograph 9 Carrier gas inlet / outlet 10 Recorder

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme court ゛ (Reference) C09D 11/00 B41J 3/04 101Y (31) Priority claim number Japanese Patent Application No. 11-63523 (32) Priority date March 10, 1999 (March 10, 1999) (33) Priority country Japan (JP) (72) Inventor Masayuki Momose 3-5-3 Yamato, Suwa-shi, Nagano Pref. Seiko Epson Corporation (72) Inventor Hiroko Hayashi 3-5-5 Yamato, Suwa-shi, Nagano Seiko Epson Corporation (72) Inventor Soko Ito 8-1, Sanarahigashi-cho, Neyagawa-shi, Osaka Orient Chemical Industry Co., Ltd. In the first development center

Claims (18)

[Claims] 1. An aqueous pigment dispersion containing at least water and surface-modified carbon black, wherein the surface-modified carbon black can be dispersed and / or dissolved in water without a dispersant. And the value of the amount of the hydrophilic functional group / the specific surface area is 5 to 30 μmol / m
^2. An aqueous pigment dispersion, which is in the range of ² . 2. The aqueous pigment dispersion according to claim 1, wherein the surface-modified carbon black is obtained by oxidizing acidic carbon black. 3. The surface-modified carbon black is obtained by oxidizing a channel carbon black.
The aqueous pigment dispersion according to claim 1. 4. The aqueous pigment dispersion according to claim 1, wherein the surface-modified carbon black is obtained by oxidizing carbon black with hypohalous acid or a salt thereof. liquid. 5. The surface-modified carbon black is 1.5 m
The aqueous pigment dispersion according to any one of claims 1 to 4, wherein the aqueous pigment dispersion has a hydrophilic functional group of mol / g or more. 6. The method for producing an aqueous pigment dispersion according to claim 1, wherein the surface tension is 50 mN /
and a step of oxidizing the carbon black in an aqueous medium to introduce a hydrophilic functional group to obtain an aqueous pigment dispersion comprising a surface-modified carbon black. And a method comprising: 7. The method according to claim 6, wherein the oxidation of the carbon black is performed using hypohalous acid and / or a salt thereof. 8. An aqueous ink composition comprising at least the aqueous pigment dispersion according to any one of claims 1 to 5. 9. An ink composition applied to a recording medium having a coating amount of 1 m
When a g / cm ^2, penetration time of the ink composition has a permeability such as less than 1 second, the ink composition according to claim 8. 10. The ink composition has a surface tension of 40 mN / m.
The aqueous ink composition according to claim 8 or 9, wherein the aqueous ink composition is less than the aqueous ink composition. 11. The aqueous ink composition according to claim 8, further comprising a glycol butyl ether-based water-soluble organic solvent. 12. The aqueous ink composition according to claim 8, further comprising a nonionic surfactant. 13. The aqueous ink composition according to claim 12, wherein the nonionic surfactant is selected from acetylene glycol-based surfactants. 14. The amount of the surface-modified carbon black to be added is in the range of 1 to 15% by weight based on the total amount of the ink.
The aqueous ink composition according to any one of claims 8 to 13. 15. A recording method for printing on a recording medium by adhering an ink composition, wherein the aqueous ink composition according to any one of claims 8 to 14 is used as the ink composition. . 16. An ink jet recording method for ejecting droplets of an ink composition and attaching the droplets to a recording medium to perform printing, wherein the ink composition is any one of claims 8 to 14. An inkjet recording method using the aqueous ink composition described in the above. 17. A recorded matter recorded by the recording method according to claim 15 or 16. 18. A method for producing an aqueous pigment dispersion comprising at least water and surface-modified carbon black, comprising the steps of pulverizing carbon black in an aqueous medium having a surface tension of 50 mN / m or less; Oxidizing the carbon black in an aqueous medium to introduce hydrophilic functional groups to obtain an aqueous pigment dispersion comprising a surface-modified carbon black.