JP4784817B2 - Black ink composition, recording method and recorded matter using the same - Google Patents

Description

  The present invention relates to a black ink composition, a recording method using the black ink composition, and a recorded matter. More specifically, the print quality such as optical density value (hereinafter referred to as “OD value”), fixing property, etc. The present invention relates to an excellent black ink composition, a recording method using the same, and a recorded matter.

  The ink jet recording method is a printing method in which printing is performed by causing ink droplets to fly and adhere to a recording medium such as paper. As the ink, generally, various water-soluble dyes dissolved in water or water and a water-soluble organic solvent are used. It has been generally pointed out that an image formed with an ink containing such a water-soluble dye is inferior in water resistance and light resistance.

  On the other hand, an ink obtained by dispersing a pigment in an aqueous medium is excellent in water resistance and light resistance. For example, an aqueous pigment ink in which a pigment 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 OD value of the recorded matter, the ink viscosity may increase rapidly accordingly. In addition, in order to disperse the pigment stably in the ink, an excessive surfactant or polymer dispersant is required, which may cause deterioration of printing stability due to generation of bubbles or deterioration of defoaming property. It was.

Generally, there is a trade-off relationship between the sedimentation characteristics of a pigment and the OD value. In order to make these characteristics compatible, a carbon black dispersion liquid that defines the relationship between carbon black as a raw material and a resin is provided. For example, in an inkjet ink in which at least a colorant and an emulsion resin are dispersed in an aqueous medium, by setting the average particle diameter of the emulsion resin to ½ or less of the average particle diameter of the colorant, It is disclosed that an ink-jet ink excellent in light resistance, water resistance, fixing property, ejection stability and storage stability can be obtained (Patent Document 1). Further, in an ink containing at least water, a pigment, and one or more types of resin particles, the size of the resin particles is 1 to 1.5 times the size of the pigment particles. In addition, it is disclosed that a high print quality and a high OD value are imparted to plain paper, and an ink composition having glossiness and good fixability can be obtained on glossy media for inkjet (Patent Document 2).
JP 2003-12975 A Japanese Patent Laid-Open No. 2004-238445

  Conventional ink compositions have the problem that there is still room for improvement in the rub resistance when printed. Also, depending on the pigment used, the OD value may be low and the desired print quality may not be satisfied.

  However, when a pigment having a specific parameter capable of securing a high OD value is used, there is a problem that the pigment is liable to settle and a stable print quality cannot be secured.

  With respect to the rub resistance, a fixing agent such as a resin may be used for the purpose of improving the rub resistance of the printed matter. In particular, resin emulsions mainly composed of an insoluble polymer prepared by an emulsion polymerization method have been used for reasons such as easy handling without increasing the viscosity of the ink.

  However, it has been found that when the pigment dispersion and the resin emulsion are simply used in combination for the purpose of obtaining an ink composition having both excellent OD value and abrasion resistance, the sedimentation rate of the pigment may increase. Although the cause is not clear, it is presumed that the resin emulsion alone does not precipitate, and therefore the precipitation of the pigment is promoted by some interaction with the pigment.

  Accordingly, the present invention provides a black ink composition having excellent printing quality such as OD value and fixability without promoting pigment sedimentation even when a pigment dispersion and a resin emulsion are used in combination. With the goal.

As a result of intensive studies, the present inventors have determined that by using a combination of a resin emulsion having a particle size ratio with a pigment in a specific range in a black ink composition using carbon black having a specific parameter and a dispersion thereof. The present inventors have found that the above problems can be solved, and have reached the present invention. The present invention has been made based on such findings, and is a black ink composition containing at least water, carbon black, and a resin emulsion, and the carbon black has a primary particle diameter of 10 to 30 nm, and DBP. Oil absorption is 180 to 250 ml / 100 g, BET specific surface area (m ² / g) / DBP oil absorption (ml / 100 g) is 0.3 to 2.5, 50% volume average in dispersion The particle size is 100 to 250 nm, the resin emulsion has a glass transition point (Tg) of 0 ° C. or less, and the value of volume average particle size of the resin emulsion / 50% volume average particle size of the carbon black is The present invention provides a black ink composition characterized by being 0.7 or less.

  With such a configuration, sufficient fixability of a recorded matter having a high OD value can be secured, and the sedimentation rate of the pigment in the ink, that is, the change in the OD value can be suppressed. An ink composition that can ensure quality can be obtained.

  Preferred embodiments of the invention are as follows. The content of the resin emulsion is preferably 1 to 10% by weight based on the total amount of the black ink composition (100% by weight).

  The carbon black content is preferably 2 to 15% by weight based on the total amount of the black ink composition (100% by weight).

  The black ink composition is preferably used in an ink jet recording system.

  In addition, the present invention provides a recording method characterized in that printing is performed by attaching the black ink composition to a recording medium.

  The present invention also provides an ink jet recording method characterized in that printing is performed by discharging droplets of the black ink composition and attaching the droplets to a recording medium.

  The present invention also provides a recorded matter recorded by the above recording method.

Next, a preferred embodiment of the present invention will be described in more detail. As described above, the present invention is a black ink composition containing at least water, carbon black, and a resin emulsion. The carbon black has a primary particle size of 10 to 30 nm and a DBP oil absorption of 180 nm. ˜250 ml / 100 g, BET specific surface area (m ² / g) / DBP oil absorption (ml / 100 g) is 0.3 to 2.5, and 50% volume average particle size in the dispersion is 100 The resin emulsion has a glass transition point (Tg) of 0 ° C. or less, and the volume average particle size of the resin emulsion / 50% volume average particle size of the carbon black is 0.7 or less. It is.

[Carbon black]
Carbon black used for the black ink composition in the present embodiment has a primary particle size of 10 to 30 nm, a DBP oil absorption of 180 to 250 ml / 100 g, and a BET specific surface area (m ² / g) / DBP oil absorption. Those having a value of (ml / 100 g) of 0.3 to 2.5 are used. By using carbon black having these parameters, a black ink composition capable of obtaining a recorded material having a high OD value can be realized. Hereinafter, each parameter will be described.

  Carbon black having a primary particle diameter of 10 to 30 nm is used. As the primary particle size of carbon black, it can be generally produced in the range of 10 to 100 nm because of its production method, but if it is 30 nm or less, precipitation of pigment particles in the black ink composition can be suppressed, which is preferable. It is.

  In the present embodiment, the “primary particle diameter” refers to the size of particles formed by collecting single crystals or crystallites close thereto. The primary particle size of the pigment is measured by electron microscopy. This is to measure the size of pigment particles from an electron micrograph, and is more reliable by dispersing the pigment in an organic solvent, fixing it to a support film, and performing image processing and measurement from a transmission electron micrograph. The value can be determined. Specifically, the minor axis diameter and the major axis diameter of each primary particle diameter are measured, and the diameter of a circle equal to the area is arithmetically determined as the primary particle diameter, and 50 or more pigments from a fixed visual field. Particles are randomly selected and an average value is obtained. Other measurement methods can be used as long as the same reliability can be obtained, but when there is a substantial difference in numerical values, the value obtained by the above method is adopted.

  Carbon black having a DBP oil absorption of 180 to 250 ml / 100 g is used from the viewpoint of increasing the OD value of the recorded matter, preferably 180 to 230 ml / 100 g, and 180 to 210 ml / 100 g. It is more preferable that

  When the DBP oil absorption of carbon black is less than 180 ml / 100 g, there is a possibility that a sufficient OD value of a recorded matter cannot be obtained when an aqueous dispersion is used as an ink composition. Further, the higher the DBP oil absorption amount of carbon black, the higher the OD value of the recorded material when the aqueous dispersion is used as an ink composition. On the other hand, when the DBP oil absorption amount exceeds 250 ml / 100 g, it is obtained. The resulting ink composition is unfavorably high in viscosity. The DBP oil absorption is measured according to JIS K-6221.

Carbon black has a BET specific surface area (m ² / g) / DBP oil absorption (ml / 100 g) value of 0.3 to 2.5 from the viewpoint of increasing the OD value of the recorded matter. More preferably, it is 3 to 1.75.

  In the present embodiment, “BET specific surface area” refers to a value measured using GEMINI 2360 (BET specific surface area measuring device manufactured by Micromeritics). Other models that can obtain equivalent measurement values may be used, but if there is a difference in measurement values, the values obtained from the above models shall be adopted. In the measurement method, a pigment is put in a sample cell in advance and replaced with nitrogen gas, and dried at 150 ° C. for 1.5 hours to remove moisture. More specifically, the mass of the pigment and the atmospheric pressure at the time of measurement are measured, and 0.1 g, 0.15, 0.2, 0.25, and 0.3 times the atmospheric pressure per 5 g of relative pressure. Measure the amount of nitrogen adsorption. The specific surface area is calculated from the five points of nitrogen absorption by the BET method.

  In the present embodiment, when the BET specific surface area of carbon black is referred to, the BET specific surface area based on the carbon black in any of the surface-treated pigment described later and the unmodified surface pigment used as the raw material is also used. Shall be included. Further, it is estimated that the BET specific surface area of the surface-treated pigment and the BET specific surface area of the surface unmodified pigment are substantially the same and show almost the same value.

  The DBP oil absorption (ml / 100 g) is a value expressed as the amount of dibutyl phthalate (DBP) absorbed by 100 g of carbon black, and can be obtained according to the measurement method defined in JIS K6221. In addition, according to the said measuring method, the absorption amount of DBP per 100g calculated | required from 70% of the maximum torque when using DBP to carbon black using an absolute meter is calculated | required.

[Pigment dispersion]
As a particularly preferred pigment dispersion in the present embodiment, a large number of hydrophilic functional groups and / or salts thereof (hereinafter referred to as dispersibility-imparting groups) are directly or alkyl groups on the surface of carbon black having the specific parameters described above. And a pigment dispersion using a so-called surface-treated pigment indirectly bonded via an alkyl ether group, an aryl group or the like.

  The surface-treated pigment can be dispersed and / or dissolved in water without a dispersant, and carbon black is stably present with a minimum particle size that can be dispersed in an aqueous medium without using a dispersant. Examples of the dispersibility-imparting group bonded to the surface of the carbon black include a carboxyl group, a lactone group, a carbonyl group, a hydroxyl group, a sulfone group, a phosphoric acid group and a quaternary ammonium, and salts thereof.

  When the surface-treated pigment dispersion is used as an ink composition, it is not necessary to include a dispersant to be contained in order to disperse a normal pigment, so that almost no defoaming or foaming is caused by the dispersant. Ink is easy to handle, and it is easy to prepare an ink having excellent printing stability when used for printing. Further, not only the blackness of carbon black itself is high, but also a significant increase in viscosity due to the dispersant can be suppressed, so that more pigment can be contained and the OD value can be further increased.

  In the present embodiment, the 50% volume average particle size in the carbon black dispersion is 100 to 250 nm, preferably 100 to 200 nm, and preferably 120 to 200 nm, from the viewpoint of high OD value and suppression of sedimentation. It is more preferable. If the 50% volume average particle size in the carbon black dispersion is less than 100 nm, the desired OD value of the recorded matter may not be ensured when used as an ink composition. On the other hand, when the 50% volume average particle size in the carbon black dispersion exceeds 250 nm, there is a problem that pigment particles are liable to settle.

[Resin emulsion]
In the present embodiment, a resin emulsion having a glass transition point (Tg) of 0 ° C. or less is used from the viewpoint of fixability of recorded matter. By using such a resin emulsion, the resin spreads on the recording medium, and carbon black as a pigment can be satisfactorily fixed on the recording medium. As described above, the glass transition point (Tg) of the resin emulsion is 0 ° C. or lower, but in order to effectively exhibit the effect, 0 ° C. or lower, −80 ° C. or higher, particularly −10 It is preferable that it is below 80 degreeC and -80 degreeC or more.

  In the present embodiment, the glass transition point (Tg) can be measured using a usual method, for example, a thermal analyzer such as a differential scanning calorimeter (DSC). An example of the thermal analyzer is SSC5000 manufactured by Seiko Electronics. Further, when the resin emulsion is a copolymer, the glass transition point (Tg) and the evaluation methodology are as follows. The glass transition point (Tg) of a copolymer having a specific monomer composition can be determined by the Fox equation. Here, the Fox formula is for calculating the Tg of the copolymer based on the Tg of the homopolymer of the monomer for each monomer forming the copolymer, Details thereof are described in Bulletin of the American Society, Series 2, Vol. 1, No. 3, p. 123 (1956). The Tg of the homo-copolymer for various monomers as the basis for calculating the Tg of the copolymer according to the Fox formula is described in, for example, pages 525 to 546 of Polymer Data Handbook Fundamentals (Edition of Polymer Society). The measured numerical value or the actual measurement value measured by a normal method can be adopted.

  Examples of the resin applicable to the resin emulsion used in the present embodiment include an acrylic resin, a urethane resin, an epoxy resin, and a polyolefin resin, but are not particularly limited. These resins can be used alone or in combination of two or more.

  The resin emulsion used in the present embodiment is blended in the ink composition in the form of an emulsion of resin particles obtained by emulsion polymerization of unsaturated monomers (for example, so-called “acrylic emulsion”). Is preferred. The reason is that, even if the resin particles are added to the ink composition as they are, dispersion of the resin particles may be insufficient, so that the emulsion form is preferable for the production of the ink composition. The resin emulsion is preferably an acrylic emulsion from the viewpoint of storage stability of the ink composition.

  A resin emulsion (such as an acrylic emulsion) can be obtained by a known emulsion polymerization method. For example, it can be obtained by emulsion polymerization of an unsaturated monomer (such as an unsaturated vinyl monomer) in water containing a polymerization initiator and a surfactant.

  Examples of unsaturated monomers include acrylic acid ester monomers, methacrylic acid ester monomers, aromatic vinyl monomers, vinyl ester monomers, vinyl cyanide compounds generally used in emulsion polymerization. Examples include monomers, halogenated monomers, olefin monomers, and diene monomers. Furthermore, specific examples include methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, n-amyl acrylate, isoamyl acrylate, n-hexyl acrylate, 2-ethylhexyl acrylate, octyl acrylate, decyl acrylate. Acrylic acid esters such as dodecyl acrylate, octadecyl acrylate, cyclohexyl acrylate, phenyl acrylate, benzyl acrylate, glycidyl acrylate, methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-amyl methacrylate, isoamyl Methacrylate, n-hexyl methacrylate, 2-ethyl Hexyl methacrylate, octyl methacrylate, decyl methacrylate, dodecyl methacrylate, octadecyl methacrylate, cyclohexyl methacrylate, methacrylic esters such as phenyl methacrylate, benzyl methacrylate, glycidyl methacrylate, and vinyl esters such as vinyl acetate; vinyl such as acrylonitrile and methacrylonitrile Cyanides; halogenated monomers such as vinylidene chloride and vinyl chloride; simple aromatic vinyl such as styrene, α-methylstyrene, vinyltoluene, 4-t-butylstyrene, chlorostyrene, vinylanisole, vinylnaphthalene Olefins such as ethylene and propylene; dienes such as butadiene and chloroprene; vinyl ether, vinyl ketone, vinyl pyrrolide Vinyl monomers such as ethylene; unsaturated carboxylic acids such as acrylic acid, methacrylic acid, itaconic acid, fumaric acid and maleic acid; acrylamides such as acrylamide, methacrylamide and N, N′-dimethylacrylamide; 2-hydroxy Examples thereof include hydroxyl group-containing monomers such as ethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxyethyl methacrylate and 2-hydroxypropyl methacrylate, and these can be used alone or in combination of two or more.

  A crosslinkable monomer having two or more polymerizable double bonds can also be used. Examples of the crosslinkable monomer having two or more polymerizable double bonds include polyethylene glycol diacrylate, triethylene glycol diacrylate, 1,3-butylene glycol diacrylate, 1,4-butylene glycol diacrylate, 1,6-hexanediol diacrylate, neopentyl glycol diacrylate, 1,9-nonanediol diacrylate, polypropylene glycol diacrylate, 2,2′-bis (4-acryloxypropyloxyphenyl) propane, 2,2 ′ -Diacrylate compounds such as bis (4-acryloxydiethoxyphenyl) propane, triacrylate compounds such as trimethylolpropane triacrylate, trimethylolethane triacrylate, tetramethylolmethane triacrylate , Tetraacrylate compounds such as ditrimethylol tetraacrylate, tetramethylol methane tetraacrylate, pentaerythritol tetraacrylate, hexaacrylate compounds such as dipentaerythritol hexaacrylate, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, polyethylene glycol Dimethacrylate, 1,3-butylene glycol dimethacrylate, 1,4-butylene glycol dimethacrylate, 1,6-hexanediol dimethacrylate, neopentyl glycol dimethacrylate, dipropylene glycol dimethacrylate, polypropylene glycol dimethacrylate, polybutylene glycol Dimethacrylate, , 2′-bis (4-methacryloxydiethoxyphenyl) propane and other dimethacrylate compounds, trimethylolpropane trimethacrylate, trimethylolethane trimethacrylate and other trimethacrylate compounds, methylenebisacrylamide, divinylbenzene and the like. Can be used alone or in admixture of two or more.

  In addition to the polymerization initiator and surfactant used in emulsion polymerization, a chain transfer agent, further a neutralizing agent, and the like may be used according to a conventional method. In particular, ammonia and inorganic alkali hydroxides such as sodium hydroxide and potassium hydroxide are preferred as the neutralizing agent.

  In the present embodiment, the content of the resin emulsion is preferably 1 to 10% by weight, based on the total amount of the black ink composition of the present embodiment (100% by weight), and preferably 0.5 to 7%. More preferably, it is 1 weight%, and it is still more preferable that it is 1 to 6 weight%.

  The preferred range for the content of the resin emulsion is to define an upper limit value from the viewpoint of the proper ink jet physical properties and reliability (clogging, ejection stability, etc.) of the black ink composition, and the effects of the present invention (high OD value, fixing) The lower limit is specified from the viewpoint of more effectively obtaining the property.

  The resin emulsion preferably has an average particle size of 30 to 175 nm, particularly 30 to 120 nm, from the viewpoint of dispersion stability in the black ink composition.

  Moreover, as a resin particle of a resin emulsion, any of a single phase structure and a multiphase structure (core shell type) can be used.

  In this embodiment, the “resin particles” are those in which a water-insoluble resin is dispersed in a particle form in a dispersion medium mainly composed of water, or a water-insoluble resin is mainly dispersed in a dispersion medium mainly composed of water. It means what is dispersed in the form of particles, and further includes the dried product.

  In the present embodiment, the term “resin emulsion” means a solid / liquid dispersion called dispersion, latex, or suspension.

  The resin emulsion is preferably anionic from the viewpoint of improving the dispersion stability of carbon black. From the same point of view, when a pigment having a cationic surface (for example, one dispersed with a cationic group by surface treatment) is used, the emulsion is preferably cationic.

  In the present embodiment, from the viewpoint of preventing the carbon black as a pigment from settling in the pigment dispersion, the value of the volume average particle diameter of the resin emulsion in the pigment dispersion / the value of 50% volume average particle diameter of the carbon black. Is 0.7 or less, preferably 0.2 to 0.6, and more preferably 0.3 to 0.6. When the volume average particle diameter of the resin emulsion in the pigment dispersion / the 50% volume average particle diameter of the carbon black exceeds 0.7, the precipitation rate of the pigment increases due to some interaction between the resin emulsion and the pigment. There's a problem.

  In addition, said value shall be a value when the volume average particle diameter of resin emulsion is 30-175 nm and the 50% volume average particle diameter of carbon black is 100-250 nm.

[Other ink components]
The black ink composition in the present embodiment 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, the use of water sterilized by ultraviolet irradiation or addition of hydrogen peroxide is preferable because the generation of mold and bacteria can be prevented when the black ink composition is stored for a long period of time.

In a preferred aspect of this embodiment, the black ink composition comprises the above-described pigment dispersion, and when the amount of the black ink composition applied to the recording medium is 1 mg / cm ² , It is preferable that the composition has permeability so that the penetration time of the composition is less than 1 second.

Here, the permeability that the penetration time is less than 1 second when the coating amount is 1 mg / cm ² is specifically, for example, an ink composition of 50 ng in an area of 360 dpi (dots / inch) × 360 dpi. When an object is applied to plain paper, the time until the ink composition is not soiled by touching the printed surface is less than 1 second. At this time, neutral plain paper such as Xerox-P (trade name, manufactured by Fuji Xerox Co., Ltd.) is used as the plain paper.

  The penetrability of such a black ink composition is improved by improving the wettability to a recording medium by adding a penetration accelerator such as a water-soluble organic solvent or a surfactant that lowers the surface tension of the aqueous solution. Obtainable.

  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, carbitols such as diethylene glycol monomethyl ether and diethylene glycol monoethyl ether, and 1,2-alkyldiols such as 1,2-hexanediol and 1,2-octanediol.

  In a further preferred aspect of the present embodiment, the water-soluble organic solvent used as the penetration enhancer is more preferably a glycol butyl ether-based water-soluble organic solvent. Examples of such a water-soluble organic solvent based on glycol butyl ether include ethylene glycol mono-n-butyl ether, diethylene glycol-n-butyl ether, and triethylene glycol-n-butyl ether.

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

  More preferable surfactants include nonionic surfactants such as polyoxyethylene alkyl ether and polyoxyethylene phenyl ether. These are advantageous in that the foaming of the ink can be reduced as compared with the ionic surfactant. Specific examples of such nonionic surfactants include Nissan Nonion K-211, K-220, P-213, E-215, E-220, S-215, S-220, HS-220, NS- 212 and NS-220 (all of which are trade names, manufactured by NOF Corporation) and the like. Examples of more preferable surfactants include Surfinol 61, 82, 104, 440, 465, and 485 (all are trade names, manufactured by Air Products and Chemicals) among nonionic surfactants, and the like. And acetylene glycol surfactants. When these are added to the ink composition, foaming hardly occurs, so that the ink composition is particularly suitable for use in the ink jet recording method.

  In this embodiment, the surface tension of the black ink composition is set to 40 mN / m by using the water-soluble organic solvent or surfactant as described above alone or in combination as a penetration accelerator. It is desirable to adjust to less than, preferably less than 35 mN / m.

  When used in the inkjet recording method, the black ink composition according to the present embodiment can further include a humectant for the purpose of preventing ink drying at the tip of the nozzle that ejects the ink.

  Such a humectant is usually selected from water-soluble and highly hygroscopic materials. Specifically, for example, glycerin, ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentane Diols, 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, Examples include ureas such as ethylene urea and 1,3-dimethylimidazolidinone, and sugars such as maltitol, sorbitol, gluconolactone, and maltose.

  These humectants can be added to the black ink composition of the present embodiment in an amount such that the viscosity of the black ink composition is 25 mPa · s or less at 25 ° C. when used in combination with other ink additives. it can.

  If necessary, the black ink composition according to the present embodiment may further contain a fixing agent, a pH adjuster, an antioxidant, an ultraviolet absorber, a preservative, an antifungal agent, and the like.

  As the fixing agent, water-soluble resins can be used. Examples of such a fixing agent include water-soluble rosins, alginic acids, polyvinyl alcohol, hydroxypropylcellulose, carboxymethylcellulose, hydroxyethylcellulose, methylcellulose, styrene-acrylic acid resin, styrene-acrylic acid-acrylic acid ester resin, and styrene. -Maleic acid resin, styrene-maleic acid half ester resin, acrylic acid-acrylic acid ester resin, isobutylene-maleic acid resin, rosin modified maleic acid resin, polyvinylpyrrolidone, gum arabic starch, polyallylamine, polyvinylamine, polyethyleneimine, etc. Can be mentioned.

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

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

  Examples of antiseptics and fungicides include sodium benzoate, sodium pentachlorophenol, sodium 2-pyridinethiol-1-oxide, sodium sorbate, sodium dehydroacetate, 1,2-dibenzisothiazoline-3-one (Proxel CRL, Proxel BDN, Proxel GXL, Proxel XL-2, Proxel TN from ICI) and the like.

  The ink composition of the present embodiment can be prepared in the same manner as the conventional ink composition using a conventionally known apparatus such as a ball mill, a sand mill, an attritor, a basket mill, a roll mill, or the like. In the preparation, it is preferable to remove coarse particles from the viewpoint of preventing nozzle clogging. The coarse particles are removed by, for example, filtering the ink obtained by mixing the above components using a filter such as a membrane filter or a mesh filter, and removing particles of preferably 10 μm or more, more preferably 5 μm or more. Done.

[Recording method]
The black ink composition in the present embodiment 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 other various printing methods. Therefore, the black ink composition according to the present embodiment can be preferably used for applications such as writing instruments such as a water-based pen, an ink jet recording method, printing, and a stamp.

  According to another aspect of the present embodiment, there is provided an ink jet recording method for performing printing by discharging droplets of the black ink composition of the present embodiment and attaching the droplets to a recording medium. As the ink jet recording method according to the present embodiment, any method can be used as long as the black 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, methods of various modes are known.

  An example of such a method 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 in the form of droplets from the nozzle, and printing information is printed while the ink droplets fly between the deflection electrodes. A signal is applied to the deflection electrode and recorded. In this method, if necessary, ink droplets may be ejected in response to a print information signal without being deflected.

  As another aspect, there is a method of forcibly ejecting ink droplets by applying pressure to the ink liquid with a small pump and mechanically vibrating the nozzle with a crystal resonator or the like. In this method, the ejected ink droplet is charged simultaneously with the ejection, and a printing information signal is applied to the deflection electrode and recorded while the ink droplet flies between the deflection electrodes.

  Another embodiment includes a method using a piezoelectric element. In this method, pressure and a print information signal are simultaneously applied to ink liquid by a piezoelectric element, and ink droplets are ejected to perform recording.

  As yet another aspect, there is a method in which the volume of ink is rapidly expanded by the action of thermal energy. In this method, ink is heated and foamed with a microelectrode in accordance with a print information signal, ink droplets are ejected, and recording is performed.

  The recording medium is not particularly limited, and various recording media such as plain paper, ink jet exclusive paper, plastic, film, metal and the like can be used.

[Recordings]
Furthermore, according to this embodiment, the recorded matter recorded by these recording methods is also provided. This recorded matter was recorded by discharging at least droplets of the black ink composition and attaching the droplets to a recording medium. Since the recorded matter recorded by the above recording method was recorded using the black ink composition, it has a high OD value and sufficient fixability. As a specific example of the recording medium, the recording medium described above can be used.

(Preparation of pigment dispersion A)
Primary particle size prepared by furnace method = 17 nm, BET specific surface area (indicated as “BET” in Table 1) = 215 m ² / g, DBP oil absorption (indicated as “DBP” in Table 1) = 210 mL / 100 g, 500 g of BET specific surface area / DBP oil absorption (denoted as “BET / DBP” in Table 1) = 1.02 500 g of carbon black bulk powder is added to 3750 g of ion-exchanged water, stirred with a dissolver, and raised to 50 ° C. Warm up. Thereafter, an aqueous solution of 6600 g of sodium hypochlorite (effective chlorine concentration = 12%) was added dropwise at 50-60 ° C. over 3.5 hours while being pulverized by a sand mill using zirconia beads having a diameter of 0.8 mm. Crushing was continued for 30 minutes with a sand mill to obtain a reaction liquid containing carbon black. The reaction solution was filtered through a 400 mesh wire mesh to separate zirconia beads and unreacted carbon black from the reaction solution. The reaction solution obtained by fractionation was adjusted to pH = 7.5 by adding a 5% aqueous solution of KOH, and then desalted and purified with an ultrafiltration membrane until the conductivity reached 1.5 mS / cm. Concentrated to 17 wt%. The concentrated solution was centrifuged to remove coarse particles and filtered through a 0.6 μm filter. Ion exchange water was added to the obtained filtrate, and carbon black was diluted to a concentration of 13% by weight to obtain pigment dispersion A.

  2.31 g of this pigment dispersion A was precisely weighed and a dispersion (0.30 g / L in terms of carbon black concentration) diluted with a 1000 mL volumetric flask was prepared, and a particle size analyzer MICROTRAC 9340-UPA (manufactured by Microtrac) When 50% volume average particle diameter was measured using, it was 240 nm.

(Preparation of pigment dispersion B)
Ion-exchanged water was added to 200 g of carbon black powder having a primary particle size of 18 nm, a BET specific surface area of 185 m ² / g, a DBP oil absorption of 200 mL / 100 g, and a BET specific surface area / DBP oil absorption of 0.93 prepared by a furnace method. In addition to 1500 g, the temperature was raised to 50 ° C. while stirring with a dissolver. Thereafter, an aqueous solution of 2220 g of sodium hypochlorite (effective chlorine concentration: 12%) was dropped at 50-60 ° C. over 3.5 hours, and glass beads having a diameter of 3 mm were added immediately after the dropping, and the mixture was stirred at 50 ° C. for 30 minutes. As a result, a reaction liquid containing carbon black was obtained. The reaction solution was filtered through a 400 mesh wire mesh to separate the glass beads and unreacted carbon black from the reaction solution. The reaction solution obtained by fractionation was adjusted to pH = 7.5 by adding NaOH 5% aqueous solution, and then desalted and purified with an ultrafiltration membrane until the conductivity reached 1.5 mS / cm, and the carbon black concentration was further increased. Concentrated to 17 wt%. The concentrated solution was centrifuged to remove coarse particles and filtered through a 0.6 μm filter. Ion exchange water was added to the obtained filtrate, and carbon black was diluted to a concentration of 13% by weight to obtain pigment dispersion B.

  2.31 g of this pigment dispersion B was precisely weighed and a dispersion (0.30 g / L in terms of carbon black concentration) diluted with a 1000 mL volumetric flask was prepared, and a particle size analyzer MICROTRAC 9340-UPA (manufactured by Microtrac) When 50% volume average particle diameter was measured using, it was 190 nm.

(Preparation of pigment dispersion C)
200 g of carbon black bulk powder prepared by the furnace method with a primary particle size = 16 nm, a BET specific surface area = 250 m ² / g, a DBP oil absorption = 155 mL / 100 g, and a BET specific surface area / DBP oil absorption = 1.61 In addition to 1500 g, the temperature was raised to 50 ° C. while stirring with a dissolver. Thereafter, an aqueous solution of 2220 g of sodium hypochlorite (effective chlorine concentration: 12%) was dropped at 50-60 ° C. over 3.5 hours, and glass beads having a diameter of 3 mm were added immediately after the dropping, and the mixture was stirred at 50 ° C. for 30 minutes. As a result, a reaction liquid containing carbon black was obtained. The reaction solution was filtered through a 400 mesh wire mesh to separate the glass beads and unreacted carbon black from the reaction solution. The reaction solution obtained by fractionation was adjusted to pH = 7.5 by adding NaOH 5% aqueous solution, and then desalted and purified with an ultrafiltration membrane until the conductivity reached 1.5 mS / cm, and the carbon black concentration was further increased. Concentrated to 17 wt%. The concentrated solution was centrifuged to remove coarse particles and filtered through a 0.6 μm filter. Ion exchange water was added to the obtained filtrate, and carbon black was diluted to a concentration of 13% by weight to obtain pigment dispersion C.

  2.31 g of this pigment dispersion C was precisely weighed and a dispersion (0.30 g / L in terms of carbon black concentration) diluted with a 1000 mL volumetric flask was prepared, and a particle size analyzer MICROTRAC 9340-UPA (manufactured by Microtrac) When the 50% volume average particle diameter was measured using, it was 120 nm.

(Preparation of pigment dispersion D)
500 g of carbon black bulk powder prepared by the channel method and having a primary particle size = 20 nm, BET specific surface area = 125 m ² / g, DBP oil absorption = 170 mL / 100 g, BET specific surface area / DBP oil absorption = 0.74, In addition to 3750 g, the mixture was stirred with a dissolver and heated to 50 ° C. Thereafter, an aqueous solution of 6600 g of sodium hypochlorite (effective chlorine concentration = 12%) was added dropwise at 50-60 ° C. over 3.5 hours while being pulverized by a sand mill using zirconia beads having a diameter of 0.8 mm. Crushing was continued for 30 minutes with a sand mill to obtain a reaction liquid containing carbon black. The reaction solution was filtered through a 400 mesh wire mesh to separate zirconia beads and unreacted carbon black from the reaction solution. The reaction solution obtained by separation was adjusted to PH = 7.5 by adding 5% aqueous KOH solution, and then desalted and purified with an ultrafiltration membrane until the conductivity reached 1.5 mS / cm. Concentrated to 17 wt%. The concentrated solution was centrifuged to remove coarse particles and filtered through a 0.6 μm filter. Ion exchange water was added to the obtained filtrate, and carbon black was diluted to a concentration of 13% by weight to obtain pigment dispersion D.

  2.31 g of this pigment dispersion D was precisely weighed and a dispersion (0.30 g / L in terms of carbon black concentration) diluted with a 1000 mL volumetric flask was prepared, and a particle size analyzer MICROTRAC 9340-UPA (manufactured by Microtrack) When the 50% volume average particle diameter was measured using, it was 220 nm.

(Preparation of resin emulsion A)
A reaction vessel equipped with a stirrer, a reflux condenser, a dropping device, and a thermometer was charged with 1000 g of ion-exchanged water and 2.5 g of sodium lauryl sulfate, and the temperature was raised to 70 ° C. while purging with nitrogen under stirring. The internal temperature was kept at 70 ° C., 4 g of potassium persulfate was added as a polymerization initiator, and after dissolution, 450 g of ion exchange water, 2 g of sodium lauryl sulfate, 20 g of acrylamide, 300 g of styrene, 640 g of butyl acrylate, 30 g of methacrylic acid, and ethylene An emulsion prepared by adding 2 g of glycol dimethacrylate under stirring was continuously dropped into the reaction solution over 4 hours. After completion of the dropwise addition, aging was performed for 3 hours. The obtained aqueous emulsion was cooled to room temperature, and then ion-exchanged water and ammonia water were added to adjust the solid content to 40% by weight and pH 8.

  The volume average particle diameter of the resin particles in the obtained resin emulsion was 80 nm, and the glass transition temperature (Tg) was −15 ° C.

(Preparation of resin emulsion B)
A reaction vessel equipped with a stirrer, a reflux condenser, a dropping device, and a thermometer was charged with 800 g of ion-exchanged water and 1 g of sodium lauryl sulfate, and the temperature was raised to 75 ° C. while purging with nitrogen under stirring. The internal temperature was kept at 75 ° C., 6 g of potassium persulfate was added as a polymerization initiator, and after dissolution, 450 g of ion exchange water, 2 g of sodium lauryl sulfate, 20 g of acrylamide, 300 g of styrene, 640 g of butyl acrylate, 30 g of methacrylic acid, and ethylene An emulsion prepared by adding 2 g of glycol dimethacrylate under stirring was continuously dropped into the reaction solution over 4 hours. After completion of the dropwise addition, aging was performed for 3 hours. The obtained aqueous emulsion was cooled to room temperature, and then ion-exchanged water and ammonia water were added to adjust the solid content to 40% by weight and pH 8.

  The volume average particle diameter of the resin particles in the obtained resin emulsion was 130 nm, and the glass transition temperature (Tg) was −15 ° C.

(Preparation of resin emulsion C)
A reaction vessel equipped with a stirrer, a reflux condenser, a dropping device, and a thermometer was charged with 800 g of ion-exchanged water and 0.48 g of sodium dodecyl diphenyl ether disulfonate, and the temperature was raised to 75 ° C. while purging with nitrogen under stirring. The internal temperature is kept at 75 ° C., 5 g of potassium persulfate is added as a polymerization initiator, and after dissolution, 450 g of ion exchange water, 2 g of sodium lauryl sulfate, 20 g of acrylamide, 300 g of styrene, 640 g of butyl acrylate, 30 g of methacrylic acid, and ethylene An emulsion prepared by adding 2 g of glycol dimethacrylate under stirring was continuously dropped into the reaction solution over 4 hours. After completion of the dropwise addition, aging was performed for 3 hours. The obtained aqueous emulsion was cooled to room temperature, and then ion-exchanged water and ammonia water were added to adjust the solid content to 40% by weight and pH 8.

  The volume average particle diameter of the resin particles in the obtained resin emulsion was 200 nm, and the glass transition temperature (Tg) was −15 ° C.

(Preparation of resin emulsion D)
A reaction vessel equipped with a stirrer, a reflux condenser, a dropping device, and a thermometer was charged with 900 g of ion-exchanged water and 1 g of sodium lauryl sulfate, and the temperature was raised to 70 ° C. while purging with nitrogen under stirring. The internal temperature was kept at 70 ° C., 6 g of potassium persulfate was added as a polymerization initiator, and after dissolution, 450 g of ion exchange water, 3 g of sodium lauryl sulfate, 20 g of acrylamide, 615 g of styrene, 295 g of butyl acrylate, 30 g of methacrylic acid, and ethylene An emulsion prepared by adding 2 g of glycol dimethacrylate to a stirrer was continuously dropped into the reaction solution over 4 hours. After completion of the dropwise addition, aging was performed for 3 hours. The obtained aqueous emulsion was cooled to room temperature, and then ion-exchanged water and ammonia water were added to adjust the solid content to 40% by weight and pH 8.

  The volume average particle diameter of the resin particles in the obtained resin emulsion was 130 nm, and the glass transition temperature (Tg) was 36 ° C.

(Preparation of black ink composition)
8 parts of each pigment dispersion shown in Table 3 (in terms of solid content), 3 parts of each resin emulsion (in terms of solid content), 5 parts of glycerin, 5 parts of 2-pyrrolidone, 2 parts of ethanol, Olphine E1010 (Nisshin Chemical) Kogyo Co., Ltd.) 1 part, triethylene glycol mono-n-butyl ether 3 parts, 1,2-hexanediol 5 parts, Proxel XL-2 (AVECIA) 0.3 part, and then the pH is 7.5. Triethanolamine was added to the solution, and ultrapure water was added so that the total amount was 100 parts. The mixture was stirred at room temperature for 2 hours, then filtered through a membrane filter (manufactured by Millipore) made of polytetrafluoroethylene and having a pore size of 5 μm, and inks 1 to 9 (Examples 1 to 4 and Comparative Examples 1 to 5). ) Black ink composition was obtained.

[Test Example 1] Evaluation of optical density value (OD value) Each of the prepared black ink compositions was filled in an ink jet recording apparatus PX-V700 (manufactured by Seiko Epson Corporation), and 100% solid printing was performed. There are four types of recording media: Xerox P as neutral plain paper, Xerox 4024 (manufactured by Fuji Xerox), EPP as acidic plain paper (manufactured by Seiko Epson), and Xerox R (made by Fuji Xerox) as recycled paper. Used to obtain a recorded material. After printing, each recorded matter was allowed to stand in a general environment for 1 hour, and then the OD value of the solid portion was measured using a Gretag densitometer (manufactured by Gretag Macbeth). And the average value of four types of recorded matter was calculated | required, and the optical density value (OD value) was evaluated by the following evaluation criteria about the calculated average OD value. The results are shown in Table 3. The types of pigment dispersions (A to D), the types of resin emulsions (A to D), the volume average particle size of the resin emulsion / 50% volume average particle size of carbon black (in Table 3, “EMφ / pigment φ” The value of “)” is also shown.
A: OD value is 1.35 or more B: OD value is 1.30 or more and less than 1.35 C: OD value is less than 1.30

[Test Example 2] Evaluation of Fixability Each prepared black ink composition was filled into an ink jet recording apparatus PX-V700 (manufactured by Seiko Epson Corporation), and a pattern including solid and letters was printed. The obtained recorded matter was air-dried for 24 hours, and then the printed characters were rubbed at a writing pressure of 300 g / 15 mm ² using a yellow aqueous fluorescent pen ZEBRA PEN2 (trademark) manufactured by Zebra Corporation. The presence or absence was visually observed. The results were evaluated based on the following criteria. The results are shown in Table 3.
A: No dirt is produced even if the same part is rubbed twice. B: No dirt is produced until one rubbing, but dirt is produced by two rubbing. C: Dirt is produced by one rubbing.

[Test Example 3] Evaluation of storage stability (1)
30 g of each prepared black ink composition was sealed in a settling tube and subjected to a centrifugal separation treatment at a gravitational acceleration of 11000 G for 10 minutes. After precisely weighing 4 g of the supernatant, it was diluted in a 1 L volumetric flask. Further, this diluted solution was measured into a 5 mL whole pipette and diluted with a 100 mL volumetric flask. The absorbance W1 at a wavelength of 500 nm of this liquid and the absorbance W0 when the black ink composition before centrifugal treatment was similarly diluted were measured, and the sedimentation rate S was calculated by the following formula.
Sedimentation rate S (%) = [1− (absorbance W1) / (absorbance W0)] × 100

Then, the storage stability of the black ink composition was evaluated based on the following evaluation criteria for the calculated sedimentation rate S (%). The results are shown in Table 3.
A: Less than 20% B: 20% or more and less than 30% C: 30% or more

[Test Example 4] Evaluation of storage stability (2)
Each prepared black ink composition was filled in an ink cartridge and centrifuged under the following conditions.
・ Rotating radius: 20cm
Centrifugal acceleration: 600 r. p. m.
-Centrifugal time: 15 hours-Centrifugal direction: the same direction as when attached to the printer

The obtained centrifuged ink cartridge was mounted on an ink jet recording apparatus PX-V700 (manufactured by Seiko Epson Corporation) without shaking, and 100% solid printing was continuously performed. The recording medium was Xerox P (manufactured by Fuji Xerox Co., Ltd.), which is neutral plain paper, and printing was performed until the ink in the cartridge was completed and printing was completely impossible. After printing, the recorded material is allowed to stand for 1 hour in a general environment, and then the OD value of each page of the obtained printed material is measured using a Gretag densitometer (made by Gretag Macbeth Co., Ltd.). A graph in which the measured OD values were plotted was obtained. From the graph, the number of pages giving the highest / lowest OD value and the OD value at that time were read and recorded. The ΔOD value (maximum OD value−minimum OD value) obtained here is the maximum OD value fluctuation generated in one cartridge due to sedimentation. Then, with respect to the obtained ΔOD value, the storage stability of the black ink composition was evaluated based on the following evaluation criteria. The results are shown in Table 3.
A: Less than 0.10 B: 0.10 or more and less than 0.15 C: 0.15 or more

As described above, the present invention uses carbon black and resin emulsion having specific parameters, and by specifying the volume average particle size of the resin emulsion and the value of 50% volume average particle size of the carbon black, it is high. Sufficient fixability of a recorded matter having an optical density value (OD value) can be secured, and the storage stability of the ink is excellent, and stable printing quality can be secured.

Claims (7)

A black ink composition comprising at least water, carbon black, and a resin emulsion,
The carbon black is
The primary particle size is 10-30 nm,
DBP oil absorption is 180-250ml / 100g,
The value of BET specific surface area (m ² / g) / DBP oil absorption (ml / 100 g) is 0.3 to 2.5,
The 50% volume average particle size in the dispersion is 100-250 nm,
The resin emulsion is
The glass transition point (Tg) is 0 ° C. or lower,
The black ink composition, wherein a value of volume average particle diameter of the resin emulsion / 50% volume average particle diameter of the carbon black is 0.7 or less.   2. The black ink composition according to claim 1, wherein the content of the resin emulsion is 1 to 10% by weight, based on the total amount of the black ink composition (100% by weight).   2. The black ink composition according to claim 1, wherein the content of the carbon black is 2 to 15% by weight based on the total amount of the black ink composition (100% by weight).   The black ink composition according to claim 1, wherein the black ink composition is used in an ink jet recording system.   5. A recording method comprising printing by attaching the black ink composition according to claim 1 to a recording medium.   An ink jet recording method, wherein printing is performed by discharging a droplet of the black ink composition according to any one of claims 1 to 4 and attaching the droplet to a recording medium. A recorded matter recorded by the recording method according to claim 5.