JP2006219584A - Water-based carbon black dispersion, method for producing the same and water-based ink - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a water-based carbon black dispersion imparting a high O. D. (optical density) value to a regular paper, also imparting a high luster to a single-purpose paper, especially paper including a material having the luster, or a film, and not changing the properties largely even after leaving the product for a long period, i.e. having excellent temporal stability; and to provide a method for producing the carbon black dispersion. <P>SOLUTION: The water-based carbon black dispersion comprises at least (A) a surface-modified carbon black, and (B) a nonionic surfactant having an HLB value within a range of 7-18, and an acetylene skeleton. The 50%-average particle diameter of the surface-modified carbon black is within the range of 40-90 nm, the content of solid components of the surface-modified carbon black is 10-30 wt.%, and the surface tension at 25°C is within the range of 30-55 mN/m. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a surface-modified aqueous carbon black dispersion and a method for producing the same. More specifically, a high OD value is given to plain paper, a high gloss is given to special paper, particularly paper or film having a glossy base material, and the paper is left for a long time. Further, the present invention relates to a surface-modified aqueous carbon black dispersion having no significant change in physical properties, that is, excellent in stability over time, and a method for producing the same. The present invention also relates to a water-based ink prepared using the water-based carbon black dispersion, and a recording method and recorded matter characterized by being made using the ink.

  Carbon black for color is widely used for writing instruments, transfer recording, inkjet inks, electrophotographic toners, and the like, but improvements for obtaining more favorable characteristics are being continued for each application. For example, when carbon black used as a colorant for ink jet recording is taken as an example, various developments and practical applications have been made for the purpose of dramatically improving water resistance and weather resistance with respect to dye ink. For example, an aqueous pigment ink in which carbon black is dispersed with a surfactant or a polymer dispersant has been proposed. However, in these inks, when the ink content of the colorant is increased in order to increase the print density of the recorded matter, the ink viscosity may increase rapidly accordingly. In addition, in order to stably disperse carbon black in the ink, an excessive surfactant or polymer dispersant is required, which may cause deterioration in printing stability due to foaming or defoaming deterioration. There is a problem of being.

  On the other hand, a certain amount or more of surface active hydrogen or a salt thereof is introduced on the surface of carbon black, and carbon black alone can be dispersed in an aqueous solvent without a dispersant such as a surfactant or a polymer dispersant. Also disclosed are surface-modified carbon black dispersions and methods for introducing sulfonic acid groups into the surface of carbon black (see, for example, Patent Documents 1 to 3). A so-called self-dispersing pigment that does not require such a dispersant, when used in an ink as a colorant, exhibits an O.D. D. The value (optical density) is high, the viscosity in the ink is easily adjusted to an appropriate range, and handling is easy.There is no need to consider the compatibility between the dispersant and various added solvents. large. As hydrophilic functional groups formed on the surface of carbon black, carbonyl groups, carboxyl groups, hydroxyl groups, sulfone groups, ammonium groups, and the like have been proposed.

  On the other hand, in recent years, there has been a demand for inks that give high gloss to not only high OD value of plain paper but also special paper, particularly paper or film having a glossy base material. In general, when an aqueous pigment dispersion dispersed with the above-described polymer dispersant is used, high glossiness is easily obtained due to the film-forming property, but conversely, the OD value of plain paper is likely to decrease. . Further, even in the case of a surface modified pigment, the average particle size of the pigment particles is set to 120 nm or less, more preferably 90 nm or less, thereby giving gloss without greatly reducing the OD value of plain paper. It is known.

  Reducing the average particle size of the pigment particles in the surface-modified pigment increases the surface area per unit weight, and as a result, the abundance per unit surface area of surface functional groups that play an important role in aqueous dispersion. It means to decline. Therefore, the surface modified pigment having a low particle diameter tends to be unstable in dispersion, and may cause problems such as thickening, granulating and sedimentation over time. In particular, in the case of carbon black applied to ink-jet inks in recent years, the pigment concentration in the ink tends to increase as a measure for the demand for high OD value on plain paper. In this case, since the average distance between the carbon black particles is rapidly reduced, there is a problem that dispersion tends to become unstable.

Japanese Patent Publication No. 6-8437 Japanese Patent Publication No. 8-30200 JP-A-4-261476

  The present invention has been made to solve the above-described problems. That is, the object of the present invention is to give a high OD value to plain paper and to give high gloss to special paper, especially paper or film having a glossy base material. An object of the present invention is to provide a surface-modified carbon black dispersion that is suitably applied to an aqueous ink, and a method for producing the same. The carbon black dispersion of the present invention exhibits excellent temporal stability despite the small average particle diameter of pigment particles being 40 to 90 nm.

  As a result of intensive studies, the inventors have at least a surface-modified carbon black having an average particle size in a specific range and a surfactant having specific requirements, and adjusting the surface tension to a specific range. The present inventors have found that a carbon black dispersion that can solve the above problems can be produced. The present invention is based on such knowledge. That is, the configuration of the present invention is as follows.

  (1) The aqueous carbon black dispersion of the present invention contains at least A) surface-modified carbon black, B) a nonionic surfactant having an HLB value in the range of 7 to 18 and having an acetylene skeleton. An aqueous carbon black dispersion, wherein the surface-modified carbon black has a 50% average particle size in the range of 40 to 90 nm, the surface-modified carbon black has a solid content of 10 to 30 wt%, and The surface tension at 25 ° C. is in the range of 30 to 55 mN / m.

  (2) The aqueous carbon black dispersion of the present invention is the aqueous carbon black dispersion described in (1) above, wherein the nonionic surfactant has a repeating structure of ethylene oxide in its molecule, And the content rate in the molecule | numerator of the ethylene oxide is 35-90 wt%, It is characterized by the above-mentioned.

  (3) The aqueous carbon black dispersion of the present invention is the aqueous carbon black dispersion according to the above (1) or (2), wherein the weight ratio of the surface-modified carbon black to the nonionic surfactant is It is the range of 90: 1-3: 2.

  (4) The aqueous carbon black dispersion of the present invention is the aqueous carbon black dispersion described in the above (1) to (3), and one kind selected from the group consisting of glycerin, alkylene glycol, and alkylene glycol alkyl ether. Or it contains the 2 or more types of water-soluble organic solvent further.

  (5) The method for producing an aqueous carbon black dispersion according to the present invention is a method for producing an aqueous carbon black dispersion, wherein at least a) a step of oxidizing the surface of carbon black to modify the surface, b) obtained A step of adjusting the pigment concentration by concentrating or diluting the slurry, and c) a step of adding and mixing a nonionic surfactant having an HLB value in the range of 7 to 18 and having an acetylene skeleton, or It is characterized by being performed in parallel.

  (6) The water-based ink of the present invention is a water-based ink produced using the water-based carbon black dispersion described in the above (1) to (4), and the blending amount of the surface-modified carbon black with respect to the total ink amount Is in the range of 1 to 12 wt%.

  (7) The water-based ink of the present invention is the water-based ink as described in (6) above, and is for inkjet recording.

  (8) The recording method of the present invention is a recording method for printing on a recording medium by attaching ink, wherein the water-based ink according to any one of (6) and (7) is used as the ink. And

  (9) The ink jet recording method of the present invention is an ink jet recording method in which ink droplets are ejected and the droplets are attached to a recording medium for printing, and the water-based ink described in (7) above It is characterized by using.

  (10) The recording method of the present invention is the recording method according to (8) or (9), wherein the recording medium is a paper or a film having a glossy base material.

  (11) The recorded matter of the present invention is characterized in that recording is performed by the recording method according to any one of (8) to (10).

  Hereinafter, the present invention will be described in detail based on preferred embodiments thereof.

  The aqueous carbon black dispersion of the present invention comprises at least A) a surface-modified carbon black, and B) a nonionic surfactant having an HLB value in the range of 7 to 18 and having an acetylene skeleton. A dispersion, wherein the surface-modified carbon black has a 50% average particle size in the range of 40 to 90 nm, the solid content of the surface-modified carbon black is 10 to 30 wt%, and at 25 ° C. The surface tension is in the range of 30 to 55 mN / m.

  Hereinafter, each component will be described in detail.

  The surface-modified carbon black in the present invention is contained in an aqueous dispersion as a colorant, and has a number of hydrophilic functional groups and / or salts thereof (hereinafter referred to as dispersibility-imparting groups) on the surface of the carbon black. Is a carbon black that can be directly or indirectly bonded via an alkyl group, an alkyl ether group, an aryl group or the like, and can be dispersed and / or dissolved in an aqueous medium without a dispersant. Here, “dispersed and / or dissolved in an aqueous medium without a dispersant” means that the pigment is stably present at the minimum particle size that can be dispersed in an aqueous medium without using a dispersant as described above. State. Here, the “minimum particle size that can be dispersed” refers to the particle size of the pigment that does not become smaller even if the dispersion time is increased.

  Examples of the dispersibility-imparting group bonded to the surface of the surface-modified carbon black include a carboxyl group, a carbonyl group, a hydroxyl group, a sulfone group, a phosphoric acid group, a quaternary ammonium, and salts thereof. As the carbon black used as the raw material for the surface-modified carbon black, those generally commercially available as color carbon black can be used. Specifically, acidic carbon black, neutral carbon black, and basic carbon black are classified according to pH, and furnace type carbon black, channel type carbon black, acetylene type carbon black, and thermal type carbon are classified according to manufacturing method. Any of black can be used. The surface-modified carbon black in the present invention is preferably obtained by oxidizing acidic carbon black among the above-mentioned classification of carbon black. Usually, the oxidation treatment of carbon black is performed continuously or almost simultaneously with the step of pulverizing the raw material carbon black and the step of oxidizing the pulverized carbon black, and an oxidant is required in both steps. Since acidic carbon black has many hydrophilic groups such as carboxyl groups on its surface, it is easily compatible with aqueous media and pulverized easily. Therefore, an oxidizing agent at the time of pulverization is unnecessary, and the amount of the oxidizing agent used for the oxidation treatment can be reduced.

  Moreover, it is preferable that the surface modified carbon black of the present invention has a 50% average particle diameter adjusted to a range of 40 to 90 nm. The 50% average particle diameter is measured as follows, for example. That is, the particle size distribution meter MICROTRAC UPA-150 was prepared using a dilute water dispersion obtained by diluting and adjusting the aqueous carbon black dispersion with ion-exchanged water so that the concentration of the surface-modified carbon black was about 0.02% by weight. The particle size distribution is measured with (Microtrac). In the obtained particle size distribution, the particle diameter when the cumulative fraction is 50% is determined, and the value is taken as the 50% average particle diameter. When the 50% average particle diameter is less than 40 nm, the OD value when recording on plain paper, recycled paper, etc. is lowered, which is not preferable. In addition, since the relative surface area per unit weight of carbon black increases rapidly, it may be difficult to keep the dispersion in a stable state. In this case, there may be a serious problem that the physical properties greatly change over time or the nozzle pores are clogged when applied to ink jet ink. On the other hand, when the 50% average particle diameter exceeds 90 nm, there is a possibility that sufficient glossiness may not be obtained when recording is performed on special paper, particularly paper or film having a glossy base material. . That is, by adjusting the 50% average particle size within the range of 40 to 90 nm, the OD value on plain paper and the glossiness on special paper can be balanced. Further, as described later, by further containing a surfactant having specific requirements and adjusting the surface tension within a specific range, in addition to the above-mentioned recording quality compatibility, the dispersion stability of carbon black is at a high level. It becomes possible to grant.

  Adjustment of 50% average particle size of surface-modified carbon black depends on the type of carbon black powder to be surface-modified, dispersion conditions such as dispersion model, dispersion strength, dispersion time, surface modification agent type and amount, etc. This can be achieved by appropriately adjusting the reforming conditions and the like. In particular, it is considered that the parameters of the carbon black bulk powder, among others, the primary particle diameter, specific surface area, oil absorption amount and the like are the major factors. Specific examples of carbon black powder suitably used in the present invention include # 45, # 45L, # 47 (manufactured by Mitsubishi Chemical Corporation), Printex 75 (manufactured by Degussa), and the like. Can be mentioned. These descriptions are examples of the raw material of carbon black that can be suitably used in the present invention, and the present invention is not limited to these examples.

  The solid content of the surface-modified carbon black contained in the aqueous carbon black dispersion of the present invention is preferably in the range of 10 to 30 wt%. When this value is as low as less than 10 wt%, when adjusting the aqueous ink composition by using the dispersion and other additives described later in combination, the amount of other additives added due to restrictions on the solid content concentration This may cause a problem that it is difficult to mix a preferable ink that matches the purpose. On the other hand, when this value is larger than 30 wt%, sufficient stability is exhibited even if the dispersion stabilizing effect of the acetylene skeleton nonionic surfactant having an HLB value in a specific range described later is provided. It becomes difficult to cause problems such as aggregation and sedimentation.

  The aqueous dispersion containing the surface-modified carbon black as a colorant does not need to contain the above-described dispersant added to disperse ordinary carbon black, and therefore has a defoaming property caused by the dispersant. It is easy to handle with almost no drop or foaming.

  The surface-modified carbon black, for example, bonds (grafts) the dispersibility-imparting group or the active species having the dispersibility-imparting group to the surface of the pigment by subjecting the carbon black to physical treatment or chemical treatment. Manufactured by. Examples of the physical treatment include vacuum plasma treatment. Examples of the chemical treatment include a wet oxidation method in which the pigment surface is oxidized with an oxidizing agent in water, a dry oxidation method in which the surface is oxidized with an oxidizing agent such as ozone in the gas phase, and p-aminobenzoic acid is added to the pigment surface. Examples thereof include a method of bonding a carboxyl group via a phenyl group by bonding to a carbonyl group.

  In the present invention, the content of the surface-modified carbon black in the aqueous dispersion is more preferably 12 to 30 wt%. A more preferable content is in the range of 15 to 25 wt%. In recent years, there has been a demand for higher quality and higher quality ink, but as one of these measures, there has been an increasing demand to achieve higher OD values with less ink usage. With this requirement, the carbon black content in the ink tends to gradually increase. On the other hand, ordinary water-based inks are mixed by adding functional materials such as a humectant, a penetration accelerator, a pH adjuster, and a viscosity adjuster to an aqueous pigment dispersion having a specific pigment concentration in consideration of handling properties and the like. It is manufactured by. As the carbon black content in the ink increases as described above, the carbon black content in the pigment dispersion is required to be higher. When the content of the surface-modified carbon black in the aqueous dispersion is 12% or more, it is easy to meet the above requirements. On the other hand, when the content of surface-modified carbon black in the aqueous dispersion is high, the dispersion state becomes unstable due to a rapid decrease in the average distance between carbon black particles, and problems such as thickening, granulation and sedimentation occur. It becomes easy. In the present invention, a surfactant having specific requirements described later is used in combination and the surface tension is adjusted within a specific range to solve this problem. However, the carbon black content is 30 wt%. When exceeding, the effect is hard to be exhibited, and in some cases, there is a concern of causing problems such as clogging of the discharge nozzle.

  According to the aspect of the present invention, the aqueous carbon black dispersion of the present invention preferably contains a nonionic surfactant having an HLB value in the range of 7 to 18 and having an acetylene skeleton. More preferably, the nonionic surfactant has a repeating structure of ethylene oxide in the molecule, and the content of the ethylene oxide in the molecule is 35 to 90 wt%. Examples of such surfactants include, for example, compounds represented by the general formulas of Formula (1) to Formula (4), but the present invention is not limited to these examples.

  The factor that these nonionic surfactants having a specific structure greatly contribute to dispersion stability in the surface-modified carbon black dispersion of the present invention is not clear, but is presumed as follows. That is, the nonionic surfactant of the present invention has an HLB of 7 to 18 and a relatively high hydrophilicity as a compound despite having a very hydrophobic acetylene skeleton in its molecular structure. Show. That is, one of the major features is that very high hydrophilic units and hydrophobic units are relatively clearly separated in the molecular structure. The surface-modified carbon black contained as a colorant in the present invention does not particularly require a dispersant, and the interaction between the hydrophilic functional group on the surface of the carbon black and surrounding water molecules and / or on the surface of the carbon black. It is thought that dispersion stability is maintained in the aqueous system by the action of electrostatic repulsion between particles due to electric charges. In the surface-modified carbon black of the present invention having a 50% average particle size in the range of 40 to 90 nm, the nonionic surfactant of the present invention is efficiently adsorbed on the carbon black surface due to its characteristic molecular structure, It is considered that the interaction between carbon black and surrounding water molecules and / or between carbon black particles assists in stabilizing. Another structural feature of the nonionic surfactant is that it has a very low molecular weight compared to general polymer dispersants. For this reason, it is easy to move in the dispersion, and it is expected that it contributes to efficient adsorption to the carbon black surface. As a result, even in the dispersion system of the present invention, a stable dispersion state can be maintained, and problems such as thickening / granulation / sedimentation with time can be effectively eliminated. In the present invention, a surfactant satisfying the requirements can be used alone, or two or more kinds of compounds may be used in combination.

  As the nonionic surfactant applied to the present invention, a commercially available product can be used as it is. Preferable examples include Surfynol 440, 465, 485 (Air Products), Orphine E1004, E1010 (Nisshin Chemical).

  According to the aspect of the present invention, the aqueous carbon black dispersion of the present invention is preferably adjusted to have a surface tension at 25 ° C. of 30 to 55 mN / m. By adjusting the surface tension within this range, the dispersion stabilizing effect of the acetylene glycol surfactant is more effectively expressed. The adjustment of the surface tension within the above range may be performed by adding only the acetylene glycol surfactant of the present invention, and a surfactant used for the purpose of adjusting the surface tension in an aqueous system is generally used. Furthermore, you may apply. The surfactant used for adjusting the surface tension can be selected from general anionic surfactants, cationic surfactants, amphoteric surfactants and nonionic surfactants. Nonionic surfactants are particularly preferred from the viewpoint of obtaining an aqueous dispersion having a low content. Further specific examples of nonionic surfactants include acetylene alcohol surfactants, polyoxyethylene nonyl phenyl ether, polyoxyethylene octyl phenyl ether, polyoxyethylene dodecyl phenyl ether, polyoxyethylene alkyl allyl ether, polyoxyethylene oleyl. Ethers such as ether, polyoxyethylene lauryl ether, polyoxyethylene alkyl ether, polyoxyalkylene alkyl ether, polyoxyethylene oleic acid, polyoxyethylene oleate, polyoxyethylene distearate, sorbitan laurate, sorbitan mono Stearate, sorbitan monooleate, sorbitan sesquioleate, polyoxyethylene monooleate, polyoxy Esters such as ethylene stearate-based, silicon-based surfactants dimethylpolysiloxane, other fluorine alkyl esters, fluorine-containing surfactants such as perfluoroalkyl carboxylic acid salts, and the like.

  According to the aspect of the present invention, the weight ratio of the surface-modified carbon black and the nonionic surfactant in the aqueous carbon black dispersion of the present invention is preferably in the range of 90: 1 to 3: 2. . When the ratio of the nonionic surfactant is smaller than 90: 1 with respect to carbon black, the above-mentioned dispersion stabilization effect may be difficult to express. In addition, when the ratio is larger than 3: 2, the effect expected even when added more often reaches the peak, and the composition of the aqueous ink produced using the aqueous dispersion of the present invention can be limited. There is sex.

  The aqueous carbon black dispersion of the present invention preferably further contains one or more water-soluble organic solvents selected from the group consisting of glycerin, alkylene glycol, and alkylene glycol alkyl ether. By further containing these water-soluble organic solvents, the effect of stabilizing the dispersion of the surface-modified carbon black can be further enhanced. This is presumably because these water-soluble organic solvents cause the above-described nonionic surfactant to move more efficiently in the aqueous system and adsorb on the pigment surface. On the other hand, in general, when a system in which particles are dispersed in water is left in a sub-freezing environment, the dispersion becomes extremely unstable in the process of freezing and / or thawing, and problems such as thickening and particle size increase after thawing. Often occurs. However, in the present invention, by further containing the above-mentioned water-soluble organic solvent, even when the aqueous dispersion of the present invention is left in a sub-freezing environment, it is difficult to freeze, and even if it is frozen, the dispersion is unstable. The effect which suppresses becoming can be expected.

  Specific examples of the water-soluble organic solvent that can be preferably used in the present invention include glycerins, solid glycerin such as glycerin, trimethylolpropane, and triethylolpropane, and alkylene glycols such as ethylene glycol, propylene glycol, diethylene glycol, and triethylene. Examples thereof include glycol, tetraethylene glycol, and dipropylene glycol. Examples of the alkylene glycol alkyl ethers include diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, and dipropylene glycol monobutyl ether.

  The amount of the water-soluble organic solvent added to the present invention is not particularly limited, and is appropriately determined in consideration of the expected dispersion stability effect, restrictions on the composition of the aqueous ink produced using the dispersion, and the like. sell.

  In the present invention, a preferred method for producing aqueous carbon black is also disclosed. That is, the method for producing an aqueous carbon black dispersion of the present invention includes at least a) a step of oxidizing carbon black to modify the surface, b) a step of adjusting the pigment concentration by concentrating or diluting the obtained slurry, c) The step of adding and mixing the nonionic surfactant having an HLB value in the range of 7 to 18 and having an acetylene skeleton is performed separately or in parallel.

  a) In the step of surface modification by oxidizing carbon black, for example, an oxidation method by contact with air, a gas phase oxidation method by reaction with nitrogen oxides, ozone, nitric acid, potassium permanganate, potassium dichromate Illustrative examples include liquid phase oxidation methods using oxidants such as chlorous acid, perchloric acid, hypohalite, hydrogen peroxide, aqueous bromine solution, and aqueous ozone solution, methods for modifying the surface by plasma treatment, etc. Any of them can be used suitably. In this step, a disperser or a high-speed stirrer having a high load can be used to pulverize and surface-modify carbon black more uniformly. Specific examples of the disperser or pulverizer include a jet mill, a ball mill, an attritor, a furo jet mixer, an impeller mill, a colloidal mill, and a sand mill (for example, “super mill”, “agitator mill”, “dyno mill”, “bead mill”. (Commercially available product name) and the like. The obtained dispersion may be purified using metal mesh filtration, ultrafiltration, a centrifuge, a filter, or the like in order to remove coarse particles and impurities. In particular, when producing a water-based carbon black dispersion for the purpose of producing a water-based ink for inkjet, it is preferable to carry out such a purification step because it may cause problems such as fine nozzle clogging. Further, the surface of the obtained surface-modified carbon black has many ionic functional groups such as carboxyl groups and sulfonic acid groups. For the purpose of pH adjustment of the obtained dispersion and neutralization of the ionic functional group, alkali metal hydroxides (for example, sodium hydroxide, potassium hydroxide and lithium hydroxide), ammonia (water), various types It is also useful to continue the neutralization step using an amine compound (diethanolamine, triethanolamine, tripropanolamine, etc.).

  b) In the step of adjusting the pigment concentration by concentrating or diluting the obtained slurry, in the aqueous phase oxidation method, the obtained water dispersion is concentrated or diluted to obtain carbon black in the final carbon black dispersion. Adjust the concentration to be in the desired range. In the gas phase oxidation method, the obtained surface-modified carbon black can be dispersed in water and adjusted to a desired concentration. It is also possible to carry out the neutralization step described in step a) above in this step b).

  c) In the step of adding and mixing the nonionic surfactant having an HLB value in the range of 7 to 18 and having an acetylene skeleton, the above-mentioned specific surfactant is sufficiently added to the produced aqueous dispersion. Mix. Thereby, also in the surface-modified carbon black of the present invention having a 50% average particle size in the range of 40 to 90 nm, it is possible to suppress problems such as thickening / granulation / sedimentation with time. One of the specific nonionic surfactants may be used alone, or two or more of them may be used in combination. As a mixer used here, in addition to a mixer such as a dissolver, a dispersing machine such as a jet mill, a ball mill, an attritor, a furo jet mixer, an impeller mill, a colloidal mill, or a sand mill, or a pulverizer can be suitably used. . Conditions such as mixing time and temperature are appropriately determined depending on the combination of the type of carbon black and the surfactant used, the production scale, and the like.

  The steps a), b) and c) described in detail above may be performed separately or in parallel. In any case, the preferred surface-modified carbon black dispersion of the present invention can be suitably produced.

  In the present invention, preferred aqueous inks are also disclosed. That is, the water-based ink of the present invention is a water-based ink produced using the surface-modified carbon black dispersion liquid described in detail above, and the blending amount of the surface-modified carbon black with respect to the total ink amount is 1 to 12 wt%. It is the range of these. By using the aqueous dispersion of the present invention, it is possible to easily design and adjust an aqueous ink having a surface-modified carbon black content of 1 to 12 wt%. In the present invention, by adjusting the blending amount of the surface-modified carbon black in the range of 1 to 12 wt%, the OD value on the plain paper and the glossiness on the special paper can be balanced. . Here, when the amount of carbon black in the ink is less than 1 wt%, the O.D. D. The value is low and may not meet the desired quality. Moreover, when larger than 12 wt%, even if carbon black is increased further, O.D. D. The value may reach a peak and may not increase, and the glossiness when recorded on dedicated paper may be greatly degraded. In addition, problems such as unstable ejection during printing due to a sudden increase in the initial viscosity of ink may occur.

  The water-based ink of the present invention comprises the above-described surface-modified carbon black dispersion of the present invention, if necessary, a moisturizing agent, a penetration accelerator, a fixing agent, a pH adjusting agent, a viscosity adjusting agent, an antioxidant, and an ultraviolet absorber. It is manufactured by adding and mixing preservatives and the like as appropriate.

  A humectant is generally a material added for the purpose of suppressing clogging resistance and ejection failure during intermittent printing, and is generally selected from water-soluble and highly hygroscopic materials. Examples of the humectant include glycerins such as glycerin, trimethylolpropane and triethylolpropane as described above, and alkylenes such as ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol and dipropylene glycol. Glycols are known to function effectively for this purpose, and 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1 , 2,6-hexanetriol, polyols such as pentaerythritol, lactams such as 2-pyrrolidone, N-methyl-2-pyrrolidone, and ε-caprolactam, urea, thiourea, ethyleneurea, 1,3-dimethylimidazolide Non-type urine S, maltitol, sorbitol, gluconolactone, maltose, etc., etc. may be exemplified. The amount of these humectants used is not particularly limited, but is generally in the range of 0.5 to 50% by weight.

  Penetration accelerator is a material added for the purpose of speeding up the penetration by improving the wettability to the recording medium, and is generally selected from water-soluble organic solvents and surfactants that reduce the surface tension of the aqueous solution. It is. In addition to being able to cope with high-speed printing by the addition of a penetration accelerator, it is possible to provide ink that gives excellent print quality to various paper types such as plain paper and recycled paper. As examples of penetration enhancers, alkylene glycol alkyl ethers such as diethylene glycol monobutyl ether, triethylene glycol monobutyl ether and dipropylene glycol monobutyl ether described above are known to function effectively for this purpose. And lower alcohols such as ethanol and propanol, 1,2-alkyldiols such as 1,2-hexanediol and 1,2-octanediol, and the like. In addition, as surfactants, nonionic surfactants having an acetylene skeleton, which is a requirement of the present invention, are known to function effectively for this purpose, as well as fatty acid salts, alkyl sulfate esters, etc. Anionic surfactants, nonionic surfactants such as polyoxyethylene alkyl ether and polyoxyethylene phenyl ether, cationic surfactants, amphoteric surfactants, and the like can also be used.

  The fixing agent is a material added for the purpose of improving the water resistance, friction resistance, solvent resistance, etc. of the printed matter when printing using the ink of the present invention, and is generally a water-soluble resin or water-based resin. It is selected from emulsion, aqueous polymer fine particles and the like. Water-soluble resins include water-soluble rosins, alginic acids, polyvinyl alcohol, hydroxypropyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, methyl cellulose, styrene-acrylic acid resin, styrene-acrylic acid-acrylic acid ester resin, styrene-maleic acid. Examples include acid resins, styrene-maleic acid half ester resins, acrylic acid-acrylic acid ester resins, isobutylene-maleic acid resins, rosin-modified maleic acid resins, polyvinyl pyrrolidone, gum arabic starch, polyallylamine, polyvinylamine, and polyethyleneimine. . Examples of the aqueous emulsion and aqueous polymer fine particles include styrene-acrylic acid emulsion and acrylic acid emulsion. The amount of these fixing agents used is not particularly limited, but is generally in the range of 0.5 to 50% by weight.

  The pH adjuster is a material added for the purpose of setting the pH of the ink within a desired range, and those conventionally used for water-based inks can be used without particular limitation. Specific examples include hydroxides of alkali metals such as lithium hydroxide, potassium hydroxide and sodium hydroxide, and amines such as ammonia, triethanolamine, triisopropanolamine and diethanolamine. These are the same examples as the materials used in the above-described pigment neutralization step, but the same materials may be used, or different materials may be used in combination. For this purpose, in addition to the above-mentioned materials, collidine, imidazole, phosphoric acid, 3- (N-morpholino) propanesulfonic acid, tris (hydroxymethyl) aminomethane, which are generally known as pH buffering agents, Boric acid or the like can also be suitably used. The pH of the ink adjusted using these materials is appropriately determined in consideration of matching with other members, print quality, 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 ( Avicia's Proxel CRL, Proxel BDN, Proxel GXL, Proxel XL-2, Proxel TN) and the like can be selected.

  The water-based ink of the present invention is also used as various inks for writing instruments, stamps and the like. In particular, when used as a writing ink composition such as a water-based ballpoint pen, the recording / writing characteristics are good and writing can be performed without unevenness of writing, and characters are not faded when written quickly. The water-based ink of the present invention can be more suitably used as an ink for ink jet recording in which ink droplets are ejected and the droplets are adhered to a recording medium for recording.

  The ink jet recording method of the present invention can use any method in which ink is ejected as droplets from a fine nozzle and the droplets are attached to a recording medium.

  Some of them will be explained. First, there is an electrostatic suction method. In this method, a strong electric field is applied between the nozzle and the acceleration electrode placed in front of the nozzle, ink is continuously ejected from the nozzle in the form of droplets, and a print information signal is output while the ink droplets fly between the deflection electrodes. There is a method of recording by applying to the deflecting electrode, or a method of ejecting ink droplets corresponding to the print information signal without deflecting.

  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 droplets are charged simultaneously with the ejection, and a printing information signal is applied to the deflection electrodes and recorded while the ink droplets fly between the deflection electrodes.

  The third method is a method using a piezoelectric element, in which pressure and a print information signal are simultaneously applied to ink with a piezoelectric element, and ink droplets are ejected and recorded.

  The fourth method is a method in which the ink is rapidly volume-expanded by the action of heat energy, and is a method in which ink is heated and foamed with a microelectrode in accordance with a print information signal, and ink droplets are ejected and recorded.

  Any of the above methods can be used in the ink jet recording method using the water-based ink of the present invention.

  The recording method of the present invention is more preferably carried out using a recording medium made of paper or film having a glossy base material. The surface-modified carbon black having an average particle diameter in the range of 40 to 90 nm applied to the present invention is excellent in gloss when recorded on the glossy recording medium.

  The recorded matter of the present invention is obtained by recording at least using the water-based ink. By using the water-based ink of the present invention, this recorded matter shows a high OD value when it is plain paper, and is a special paper, particularly a paper or film having a glossy base material. Indicates high gloss.

<Example>
Hereinafter, the water-based carbon black dispersion and the water-based ink of the present invention will be described in detail using examples, but the present invention is not limited to these examples.

  (Production of aqueous carbon black dispersion)

(Carbon black dispersion 1; carbon black dispersion within the scope of the present invention)
400 g of Printex75 (manufactured by Degusa), which is a commercially available acidic carbon black, was added to 4400 g of ion-exchanged water, and the mixture was stirred for 30 minutes with a dissolver. Thereafter, while increasing the stirring speed, ozone gas adjusted to a concentration of 5.5 to 6.0 wt% was injected into the container at a flow rate of 4.5 liters per minute, and the reaction was performed for about 3 hours. After adding and stirring NaOH to this reaction liquid and adjusting pH to about 7, it was circulated by a microfluidizer (made by Microfluidics) for about 5 hours, and was disperse | distributed. After further adding NaOH to the dispersion obtained here to adjust the pH to around 7, it was purified by a metal mesh filter (400 mesh) and an ultrafiltration membrane, and then concentrated until the pigment concentration became 13 wt%. did. 1.95 parts and 28.05 parts of Surfinol 465 (produced by Air Products) and ion-exchanged water were added and stirred to 100 parts of this concentrated solution, respectively, to obtain a pigment concentration of 10 wt% and a Surfinol 465 concentration of 1. A final dispersion of 5 wt% was obtained. This is designated as carbon black dispersion 1. It was 39 mN / m when the surface tension of the dispersion liquid 1 was measured in a 25 degreeC environment. Moreover, it was 71 nm when the 50% average particle diameter was measured by the above-mentioned method. Surfynol 465 used here is a nonionic surfactant having an acetylene skeleton containing a repeating structure of ethylene oxide in the molecule at a ratio of 65 wt% and an HLB value of 13.

(Carbon black dispersion 2; carbon black dispersion within the scope of the present invention)
A concentrated solution having a pigment concentration of 20 wt% was obtained by the same production method as in the carbon black dispersion 1 until the concentration step of the reaction solution. 6.67 parts, 2.00 parts, 4.00 parts, 20.66 parts of glycerin, Surfynol 465, triethylene glycol monobutyl ether, and ion-exchanged water were added to 100 parts of the concentrated solution and stirred. Thus, a final dispersion having a pigment concentration of 15 wt%, a glycerin concentration of 5 wt%, a surfinol 465 concentration of 1.5 wt%, and a triethylene glycol monobutyl ether concentration of 3 wt% was obtained. This is designated as carbon black dispersion 2. It was 33 mN / m when the surface tension of the dispersion liquid 2 was measured in a 25 degreeC environment. Moreover, it was 70 nm when the 50% average particle diameter was measured by the above-mentioned method.

(Carbon black dispersion 3; carbon black dispersion within the scope of the present invention)
100 g of commercially available acidic carbon black # 45 (manufactured by Mitsubishi Chemical Corporation) 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 added dropwise to this pulverized stock solution, reacted for 5 hours while pulverizing with a ball mill, and further boiled for 4 hours with stirring to perform wet oxidation. The obtained dispersion stock solution was filtered with glass fiber filter paper GA-100 (trade name, manufactured by Advantech Toyo Co., Ltd.) and further washed with water. This wet cake was redispersed in 5 kg of water, desalted and purified to a conductivity of 2 mS / cm with a reverse osmosis membrane, and further concentrated to a pigment concentration of 13 wt%. 6.50 parts, 1.30 parts, 22.2 parts of triethylene glycol, Surfynol 485 and ion-exchanged water were added and stirred to 100 parts of this concentrated solution, respectively, and the pigment concentration was 10 wt%, triethylene glycol. A final dispersion having a concentration of 5 wt% and Surfynol 485 concentration of 1.0 wt% was obtained. This is designated as carbon black dispersion 3. It was 42 mN / m when the surface tension of the dispersion liquid 3 was measured in a 25 degreeC environment. Moreover, it was 55 nm when the 50% average particle diameter was measured by the above-mentioned method. Surfynol 485 used here is a nonionic surfactant having an acetylene skeleton containing an ethylene oxide repeating structure in the molecule at a ratio of 85 wt% and an HLB value of 17.

(Carbon black dispersion 4; carbon black dispersion within the scope of the present invention)
25 g of commercially available acidic carbon black # 45 (manufactured by Mitsubishi Chemical Corporation) was mixed in 250 g of sulfolane, and granulated and dispersed with an Eiger motor mill (Eiger Japan) for about 1 hour. After removing water from this mixed solution with an evaporator, 250 g of sulfur trioxide was added in the reaction vessel and reacted for 6 hours. The reaction solution was washed with excess sulfolane and ion-exchanged water and then filtered to obtain a surface-modified pigment slurry having sulfine groups or sulfonic acid groups on the surface of carbon black. Next, 5 g of ethyl p-aminobenzoate and 3 g of concentrated nitric acid were added to 400 g of ion-exchanged water and cooled to 5 ° C. with stirring. The above pigment slurry is added to this suspension, an aqueous solution consisting of 50 g of water and 2 g of sodium nitrite is slowly added and stirred for 10 hours. A slurry of surface-modified carbon black pigment into which was introduced was obtained. Furthermore, 40 g of polyethylene glycol (Mw: 5,000) and 0.5 g of diazabicycloundecene (DBU) were dissolved in 200 g of ethanol, and the surface-modified carbon black 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-modified carbon black into which polyethylene oxide propylene oxide benzamide was introduced was obtained. This surface-modified carbon black was dispersed in ion-exchanged water and the concentration was adjusted to obtain a dispersion having a pigment concentration of 13 wt%. 1.95 parts, 3.90 parts, 24.15 parts of Orphine E1010 (manufactured by Nissin Chemical Co., Ltd.), triethylene glycol monobutyl ether, and ion-exchanged water are added to 100 parts of this dispersion and stirred. Thus, a final dispersion having a pigment concentration of 10 wt%, an orphine E1010 concentration of 1.5 wt%, and a triethylene glycol monobutyl ether concentration of 3 wt% was obtained. This is designated as carbon black dispersion 4. It was 34 mN / m when the surface tension of the dispersion liquid 4 was measured in a 25 degreeC environment. Moreover, it was 58 nm when the 50% average particle diameter was measured by the above-mentioned method. Note that Olfine E1010 used here is a nonionic surfactant having an acetylene skeleton containing a repeating structure of ethylene oxide at a ratio of 65 wt% in the molecule and an HLB value of 13.

(Carbon black dispersion 5; carbon black dispersion within the scope of the present invention)
300 g of commercially available acidic carbon black # 47 (manufactured by Mitsubishi Chemical Corporation) was added to 4400 g of ion-exchanged water and stirred with a dissolver for 30 minutes. Thereafter, while increasing the stirring speed, ozone gas adjusted to a concentration of 5.5 to 6.0 wt% was injected into the container at a flow rate of 4.5 liters per minute, and the reaction was performed for about 3 hours. After adding and stirring NaOH to this reaction liquid and adjusting pH to about 7, it was circulated by a microfluidizer (made by Microfluidics) for about 5 hours, and was disperse | distributed. After further adding NaOH to the dispersion obtained here to adjust the pH to around 7, it is refined with a metal mesh filter (400 mesh) and an ultrafiltration membrane, and then concentrated until the pigment concentration reaches 20 wt%. did. 5.56 parts, 1.67 parts, 3.33 parts, 0.55 parts of glycerin, Surfynol 465, triethylene glycol monobutyl ether, and ion-exchanged water are added to 100 parts of the concentrated solution and stirred. Thus, a final dispersion having a pigment concentration of 18 wt%, a glycerin concentration of 5 wt%, a surfinol 465 concentration of 1.5 wt%, and a triethylene glycol monobutyl ether concentration of 3 wt% was obtained. This is designated as carbon black dispersion 5. It was 33 mN / m when the surface tension of the dispersion liquid 5 was measured in a 25 degreeC environment. Moreover, it was 84 nm when the 50% average particle diameter was measured by the above-mentioned method.

[Comparative Example 1]
(Carbon black dispersion 6; carbon black dispersion outside the scope of the present invention)
400 g of commercially available acidic carbon black MA600 (manufactured by Mitsubishi Chemical Corporation) was added to 4400 g of ion-exchanged water, and the mixture was stirred for 30 minutes with a dissolver. Thereafter, while increasing the stirring speed, ozone gas adjusted to a concentration of 5.5 to 6.0 wt% was injected into the container at a flow rate of 4.5 liters per minute, and the reaction was performed for about 3 hours. After adding and stirring NaOH to this reaction liquid and adjusting pH to about 7, it was circulated by a microfluidizer (made by Microfluidics) for about 5 hours, and was disperse | distributed. After further adding NaOH to the dispersion obtained here to adjust the pH to around 7, it was purified by a metal mesh filter (400 mesh) and an ultrafiltration membrane, and then concentrated until the pigment concentration became 13 wt%. did. 1.95 parts and 28.05 parts of Surfinol 465 (produced by Air Products) and ion-exchanged water were added and stirred to 100 parts of this concentrated solution, respectively, to obtain a pigment concentration of 10 wt% and a Surfinol 465 concentration of 1. A final dispersion of 5 wt% was obtained. This is designated as carbon black dispersion liquid 6. It was 39 mN / m when the surface tension of the dispersion 6 was measured in a 25 ° C. environment. Moreover, it was 172 nm when the 50% average particle diameter was measured by the above-mentioned method.

[Comparative Example 2]
(Carbon black dispersion 7; carbon black dispersion outside the scope of the present invention)
A concentrated solution having a pigment concentration of 10 wt% was obtained by the same production method as in the carbon black dispersion 1 until the concentration step of the reaction solution. This concentrated liquid is designated as carbon black dispersion liquid 7. The surface tension of the dispersion 7 was measured in an environment of 25 ° C. and found to be 69 mN / m. Moreover, it was 71 nm when the 50% average particle diameter was measured by the above-mentioned method.

(Evaluation of storage stability of dispersion)
60 g of each of the carbon black dispersions 1 to 7 prepared in Examples 1 to 5 and Comparative Examples 1 and 2 were put into 100 g plastic bottles, sealed, and left in a 50 ° C. environment for 1 month. The viscosity and average particle size of the carbon black dispersion before and after standing were measured, and the storage stability was judged from the rate of change based on the following criteria.
Judgment A: When the change in viscosity and average particle diameter are both within ± 5% Judgment B; When both the change in viscosity and average particle diameter are within ± 10% Judgment C; Viscosity after leaving When any one of the change rates of the average particle diameter exceeds ± 10%, the evaluation results are shown in Table 1.

  As is clear from Table 1, carbon black dispersions 1 to 5 (Examples 1 to 5) which are within the scope of application of the present invention give a judgment A or B, and show excellent storage stability. Among them, the carbon black dispersions 2 to 5 further comprising one or two or more water-soluble organic solvents selected from the group consisting of glycerin, alkylene glycol, and alkylene glycol alkyl ethers give judgment A, and further excellent storage stability. Showing gender. On the other hand, the carbon black dispersion liquid 7 (Comparative Example 2) that has an HLB value of 7 to 18 as a requirement of the present invention and does not contain a nonionic surfactant having an acetylene skeleton gives a judgment C, and is stable in storage. The result was inferior.

  (Adjustment of water-based ink)

(Water-based ink 1; water-based ink within the scope of the present invention)
After mixing and stirring 60 parts of carbon black dispersion 1 prepared in Example 1, 12 parts of glycerin, 1 part of triethanolamine, 10 parts of triethylene glycol monobutyl ether, and 17 parts of ion-exchanged water, polytetrafluoroethylene And filtered through a membrane filter (made by Millipore) having a pore diameter of 5 μm to obtain an aqueous ink having a carbon black concentration of 6 wt%. This is referred to as water-based ink 1.

(Water-based ink 2; water-based ink within the scope of the present invention)
After mixing and stirring 40 parts of the carbon black dispersion 2 prepared in Example 2, 9.5 parts of glycerin, 1 part of triethanolamine, 8.5 parts of diethylene glycol monobutyl ether, and 41 parts of ion-exchanged water, polytetrafluoro The resultant was filtered through a membrane filter (manufactured by Millipore) made of ethylene and having a pore diameter of 5 μm to obtain an aqueous ink having a carbon black concentration of 6 wt%. This is referred to as water-based ink 2.

(Water-based ink 3; water-based ink within the scope of the present invention)
After mixing and stirring 60 parts of the carbon black dispersion liquid 3 prepared in Example 3, 10 parts of glycerin, 1 part of triisopropanolamine, 10 parts of triethylene glycol monobutyl ether, and 19 parts of ion-exchanged water, polytetrafluoroethylene And filtered through a membrane filter (made by Millipore) having a pore diameter of 5 μm to obtain an aqueous ink having a carbon black concentration of 6 wt%. This is designated as water-based ink 3.

(Water-based ink 4; water-based ink within the scope of the present invention)
After mixing and stirring 60 parts of carbon black dispersion 4 prepared in Example 4, 12 parts of glycerin, 1 part of triethanolamine, 10 parts of triethylene glycol monobutyl ether, and 17 parts of ion-exchanged water, polytetrafluoroethylene And filtered through a membrane filter (made by Millipore) having a pore diameter of 5 μm to obtain an aqueous ink having a carbon black concentration of 6 wt%. This is designated as water-based ink 4.

(Water-based ink 5; water-based ink within the scope of the present invention)
After mixing and stirring 50 parts of carbon black dispersion 5 prepared in Example 5, 10 parts of glycerin, 1 part of triethanolamine, 2 parts of triethylene glycol monobutyl ether, and 37 parts of ion-exchanged water, polytetrafluoroethylene And filtered through a membrane filter (made by Millipore) having a pore diameter of 5 μm to obtain an aqueous ink having a carbon black concentration of 9 wt%. This is designated as water-based ink 5.

[Comparative Example 3]
(Water-based ink 6; water-based ink outside the scope of the present invention)
After mixing and stirring 60 parts of carbon black dispersion 6 prepared in Comparative Example 1, 12 parts of glycerin, 1 part of triethanolamine, 10 parts of triethylene glycol monobutyl ether, and 17 parts of ion-exchanged water, polytetrafluoroethylene And filtered through a membrane filter (made by Millipore) having a pore diameter of 5 μm to obtain an aqueous ink having a carbon black concentration of 6 wt%. This is designated as water-based ink 6.

[Comparative Example 4]
(Water-based ink 7; water-based ink outside the scope of the present invention)
After mixing and stirring 760 parts of the carbon black dispersion liquid prepared in Comparative Example 2, 12 parts of glycerin, 1 part of triethanolamine, 10 parts of triethylene glycol monobutyl ether, and 17 parts of ion-exchanged water, polytetrafluoroethylene And filtered through a membrane filter (made by Millipore) having a pore diameter of 5 μm to obtain an aqueous ink having a carbon black concentration of 6 wt%. This is referred to as water-based ink 7.

(Evaluation of water-based ink)
After filling the water-based inks 1 to 7 prepared in Examples 6 to 10 and Comparative Examples 3 and 4 into an on-demand type ink jet printer PX-V700 (manufactured by Seiko Epson Corporation), plain paper-fast mode 100% solid printing was performed. As recording media, Xerox P and Xerox 4024 (made by Fuji Xerox Co., Ltd.) as neutral plain paper, EPP (made by Seiko Epson Corporation) as acidic plain paper, and Xerox R (made by Fuji Xerox Co., Ltd.) as recycled paper. A recorded material was obtained using four types of paper. After printing, the recorded matter is allowed to stand for 1 hour in a general environment, and then a solid portion O.D. is measured using a Gretag densitometer (manufactured by Gretag Macbeth). D. The value was measured. The measurement results were judged based on the following criteria.
Determination A; D. When the value is 1.35 or more Decision B; D. When the value is not less than 1.25 and less than 1.35: Determination C; D. If the value is less than 1.25

Further, each of the water-based inks 1 to 7 was filled in the printer PX-V700, and then printed in MC glossy paper-clean mode. As a recording medium, photographic paper <glossy> (manufactured by Seiko Epson Corporation) was used to obtain a recorded matter. After printing, the recorded material was allowed to stand in a general environment for 1 hour, and then the sharpness of transfer (mapping) onto the surface of the recorded material and the favorableness of gloss were visually evaluated. The evaluation result was determined based on the following criteria.
Judgment A: When the edge of the mapping object looks sharp and gives a favorable glossiness Judgment B: When the edge of the mapping object looks slightly blurred but gives a relatively favorable glossiness Judgment C: The edge of the mapping object is unclear When gloss is not preferred, the above O.D. D. Table 2 summarizes the values and evaluation results of glossiness.

  As is apparent from Table 2, aqueous inks 1 to 5 (Examples 6 to 10) that are within the scope of application of the present invention gave a determination A or B, and had excellent O.D. D. Shows value and gloss. On the other hand, the water-based ink 6 (Comparative Example 3) in which the 50% average particle diameter of the surface-modified carbon black is outside the scope of application of the present invention gave a judgment C in the glossiness evaluation. Thus, when the 50% average particle diameter of the surface-modified carbon black exceeds 90 nm, it is difficult to obtain a preferable glossiness.

  As described in detail above, according to the present invention, a high OD value is given for plain paper, and high for special paper, particularly paper or film having a glossy base material. Provided are a surface-modified carbon black dispersion that is suitably applied to water-based inks that impart gloss, and a method for producing the same. In addition, the carbon black dispersion of the present invention exhibits excellent temporal stability although the average particle diameter of the pigment particles is as small as 40 to 90 nm.

Claims (11)

  An aqueous carbon black dispersion containing at least A) a surface-modified carbon black and B) a nonionic surfactant having an HLB value in the range of 7 to 18 and having an acetylene skeleton, The 50% average particle diameter of carbon black is in the range of 40 to 90 nm, the solid content of the surface-modified carbon black is 10 to 30 wt%, and the surface tension at 25 ° C. is in the range of 30 to 55 mN / m. An aqueous carbon black dispersion characterized by   2. The aqueous solution according to claim 1, wherein the nonionic surfactant has a repeating structure of ethylene oxide in the molecule, and the content of ethylene oxide in the molecule is 35 to 90 wt%. Carbon black dispersion.   3. The aqueous carbon black dispersion according to claim 1, wherein a weight ratio of the surface-modified carbon black to the nonionic surfactant is in a range of 90: 1 to 3: 2.   The aqueous carbon according to any one of claims 1 to 3, further comprising one or more water-soluble organic solvents selected from the group consisting of glycerin, alkylene glycol, and alkylene glycol alkyl ethers. Black dispersion.   A method for producing an aqueous carbon black dispersion, wherein at least a) a step of oxidizing carbon black to modify the surface, b) a step of adjusting the pigment concentration by concentrating or diluting the resulting slurry, c) Production of an aqueous carbon black dispersion characterized in that the step of adding and mixing a nonionic surfactant having an HLB value of 7 to 18 and having an acetylene skeleton is performed separately or in parallel. Method.   A water-based ink produced using the water-based carbon black dispersion according to claim 1, wherein the amount of the surface-modified carbon black based on the total ink amount is in the range of 1 to 12 wt%. Water-based ink.   The water-based ink according to claim 6, which is for inkjet recording.   A recording method for performing printing on a recording medium by attaching ink, wherein the water-based ink according to claim 6 is used as the ink.   An inkjet recording method for performing printing by ejecting ink droplets and attaching the droplets to a recording medium, wherein the water-based ink according to claim 7 is used as the ink.   10. The recording method according to claim 8, wherein the recording medium is a paper or a film having a glossy base material. A recorded matter recorded by the recording method according to claim 8.