JP5896318B2 - Black ink composition - Google Patents

Description

Background of the Invention

The present invention relates to a black ink composition comprising a pigment.

BACKGROUND ART An 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 print density of the recorded matter, the ink viscosity may increase rapidly accordingly.

  In order to solve this problem, a certain amount or more of surface active hydrogen or a salt thereof is introduced to the pigment surface and dispersed in an aqueous solvent alone without a dispersant such as a surfactant or a polymer dispersant. Self-dispersing pigment dispersions that can be used have been proposed.

  In JP-A-10-237349 (Patent Document 1), JP-A-8-3498 (Patent Document 2), and International Publication No. 01/94476 (Patent Document 3), a dispersant as described above is required. In other words, so-called self-dispersing pigments are said to have characteristics such as an increase in the OD value (optical density) of an image when used in ink as a colorant.

  In addition, as an ink set having high color developability, an ink set comprising a black ink composition containing a self-dispersing pigment having a hydrophilic group on the pigment surface is disclosed in JP-A-2009-256605 (Patent Document 4). It is disclosed.

  On the other hand, there is a problem that an image using an ink having such a self-dispersing pigment as a colorant generally has poor fixability. When the image is rubbed with a finger, a line marker, paper, or the like, a recorded matter may not be obtained with sufficient scratch resistance that the image becomes dirty. Therefore, in order to improve the fixability of the self-dispersing pigment to the recording medium, proposals have been made to add a resin having a binding effect to the recording medium.

  JP-A-2001-81366 (Patent Document 5) and JP-A-2002-80761 (Patent Document 6) disclose, as an ink composition containing resin particles, a recording liquid comprising a colorant, resin fine particles, and water, A recording liquid for an ink printer composed of an aqueous dispersion of pigment and resin fine particles is proposed.

  In JP 2009-256606 A (Patent Document 7), the black ink composition contains a self-dispersing pigment having a hydrophilic group on its surface, and the color ink composition has a hydrophilic group via a phenyl group on its surface. An ink set is disclosed that includes a self-dispersing pigment having a water content and includes a resin emulsion in all ink compositions.

  However, it can be said that there is still a need for an ink composition that can achieve an image that achieves both high color developability and suppression of change in printing density over time due to good pigment sedimentation and further improves the fixability of plain paper.

On the other hand, in Japanese Patent Application Laid-Open No. 2006-104452 (Patent Document 8), the number of coarse particles having an average particle diameter of 0.08 to 0.25 μm and a particle diameter of 1 μm or more is 6. An actinic radiation curable inkjet ink is disclosed that is less than 0 × 10 ⁵ / μL. However, it is completely different from the black ink composition of the present invention.

Japanese Patent Laid-Open No. 10-237349 JP-A-8-3498 WO 01/94476 pamphlet JP 2009-256605 A JP 2001-81366 A Japanese Patent Laid-Open No. 2002-80761 JP 2009-256606 A JP 2006-104452 A

  The present inventors are now a black ink composition comprising a pigment, and the value calculated from the average particle size, the particle size distribution width, and the ink viscosity of the pigment contained in the ink composition is within a certain range. And having a good ink storage stability when the black ink composition comprises a resin emulsion in which the number of coarse particles contained in the ink composition is equal to or less than a certain value. In addition, the inventors have obtained knowledge that both the color developability of plain paper during high-speed printing and the suppression of changes in print density over time due to pigment sedimentation can be achieved, and in particular, an image with improved fixability of plain paper can be realized. The present invention is based on these findings.

  Therefore, the present invention has good ink storage stability, and at the same time, achieves both the color developability of plain paper especially during high-speed printing and the suppression of changes in print density over time due to pigment sedimentation, and more particularly fixing of plain paper. The object is to provide an ink composition capable of realizing an image with improved properties.

The composition according to the present invention is a black ink composition comprising a pigment, wherein the average particle diameter (nm) of the pigment contained in the ink composition is D50%, and the particle diameter of the pigment contained in the ink composition. When the distribution width (nm) is D90% -D10% and the ink viscosity (mPa · s) at 20 ° C. is η, the value of X represented by the following formula (I) is in the range of 2500-4500,
X = {D50% × (D90% −D10%)} / η (I)
In addition, the number of coarse particles having a pigment particle size of 0.5 μm or more contained in the ink composition is 7.0 × 10 ⁹ or less per mL of the ink composition, and the black ink composition comprises a resin emulsion.

  According to the present invention, the ink has good ink storage stability, and is compatible with both the color development of plain paper, particularly during high-speed printing, and the suppression of changes in print density over time due to pigment sedimentation, and more particularly fixing of plain paper. An ink composition capable of realizing an image with improved properties can be provided.

Detailed description of the invention

The ink composition according to the present invention is a black ink composition comprising a pigment, wherein the average particle diameter (nm) of the pigment contained in the ink composition is D50%, and the particle diameter distribution of the pigment contained in the ink composition When the width (nm) is D90% -D10% and the ink viscosity (mPa · s) at 20 ° C. is η, the value of X represented by the above formula (I) is in the range of 2500-4500, and The number of coarse particles having a pigment particle size of 0.5 μm or more contained in the ink composition is 7.0 × 10 ⁹ or less per mL of the ink composition, and comprises a resin emulsion. Hereinafter, the black ink composition according to the present invention will be described.

Black ink composition In the black ink composition of the present invention, the value of X represented by the above formula (I) is in the range of 2500 to 4500, and the particle size of the pigment contained in the ink composition is 0.5 μm. The number of the coarse particles is 7.0 × 10 ⁹ or less per 1 mL of the ink composition. By setting it within these ranges, it is possible to realize an image in which the color developability of plain paper particularly during high-speed printing and the suppression of change in print density with time due to pigment sedimentation are both compatible, and the fixability of plain paper is particularly improved. Here, “plain paper” in the present invention refers to paper represented by PPC paper that does not particularly take into consideration ink jet recording characteristics.

According to a preferred embodiment of the present invention, in the black ink composition of the present invention, η (ink viscosity) is 7.0 mPa · s or more, and the value of X represented by the above formula (I) is in the range of 2500 to 4500. And the number of coarse particles having a particle diameter of 0.5 μm or more contained in the ink composition is 7.0 × 10 ⁹ or less per 1 mL of the ink composition. From the viewpoint of ink viscosity, η is more preferably 8.0 mPa · s or more. By setting these ranges, it is possible to realize an image in which the color developability of plain paper is further improved particularly during high-speed printing.

According to another preferred embodiment of the present invention, in the black ink composition of the present invention, D50% (average particle diameter) is 150 nm or more, and the value of X represented by the above formula (I) is 2500-4500. The number of coarse particles having a particle diameter of 0.5 μm or more in the ink composition is 7.0 × 10 ⁹ or less per mL of the ink composition. From the viewpoint of the average particle diameter, D50% is more preferably 160 nm or more. By setting these ranges, it is possible to realize an image in which the color developability of plain paper is further improved particularly during high-speed printing.

According to another preferred embodiment of the present invention, in the black ink composition of the present invention, D90% -D10% (particle size distribution width) is 230 nm or less, and the value of X represented by the above formula (I) is The number of coarse particles having a particle diameter of 0.5 μm or more in the ink composition in the range of 2500 to 4500 is 7.0 × 10 ⁹ or less per mL of the ink composition. By setting it as these ranges, the image which further suppressed the printing density change with time by pigment sedimentation is realizable.

According to a more preferred embodiment of the present invention, in the black ink composition of the present invention, η (ink viscosity) is 7.0 mPa · s or more, D90% -D10% (particle size distribution width) is 230 nm or less, The value of X represented by the above formula (I) is in the range of 2500 to 4500, and the number of coarse particles having a pigment particle size of 0.5 μm or more contained in the ink composition is 7.0 × per mL of the ink composition. 10 is ⁹ or less. From the viewpoint of ink viscosity, η is more preferably 8.0 mPa · s or more. By setting it within these ranges, it has good ink storage stability, and more particularly achieves both the color development of plain paper during high-speed printing and the suppression of changes in printing density over time due to pigment sedimentation, and more particularly ordinary An image with improved paper fixability can be realized.

According to a further preferred embodiment of the present invention, in the black ink composition of the present invention, the value of X represented by the formula (I) is in the range of 3200 to 4000, and the pigment contained in the ink composition The number of coarse particles having a particle diameter of 0.5 μm or more is 2.0 × 10 ⁹ or less per mL of the ink composition. By setting these ranges, the ink has good ink storage stability, and more particularly achieves both the color development of plain paper during high-speed printing and the suppression of changes in printing density over time due to pigment sedimentation. It is possible to realize an image with improved fixing properties of plain paper.

According to still another preferred embodiment of the present invention, in the black ink composition of the present invention, η (ink viscosity) is 7.0 mPa · s or more, and the value of X represented by the above formula (I) is 3200 to The number of coarse particles having a particle diameter of 0.5 μm or more within the range of 4000 and a pigment contained in the ink composition is 2.0 × 10 ⁹ or less per mL of the ink composition. From the viewpoint of ink viscosity, it is even more preferable that η is 8.0 mPa · s or more. By setting these ranges, the ink has good ink storage stability, and more particularly achieves both the color development of plain paper during high-speed printing and the suppression of changes in printing density over time due to pigment sedimentation. It is possible to realize an image with improved fixing properties of plain paper.

According to still another preferred embodiment of the present invention, in the black ink composition of the present invention, η (ink viscosity) is 7.0 mPa · s or more, and D90% -D10% (particle size distribution width) is 230 nm or less. Yes, the value of X represented by the above formula (I) is in the range of 3200 to 4000, and the number of coarse particles having a pigment particle size of 0.5 μm or more contained in the ink composition is 1 mL of the ink composition. No more than 2.0 × 10 ⁹ per hit. From the viewpoint of ink viscosity, it is even more preferable that η is 8.0 mPa · s or more. By setting these ranges, the ink has good ink storage stability, and more particularly achieves both the color development of plain paper during high-speed printing and the suppression of changes in printing density over time due to pigment sedimentation. It is possible to realize an image with improved fixing properties of plain paper.

  Here, the average particle diameter D50% is a volume average particle diameter that can be measured by a dynamic light scattering method, and can be measured using, for example, Microtrac UPA150 (Microtrac Inc.).

  Further, D90% and D10% used in the particle size distribution range D90% -D10% of the pigment contained in the ink composition are the same as the average particle size D50%, but the microtrack UPA150 (using dynamic light scattering method) Microtrac Inc.) or the like. D90% and D10% are the particle diameters at which the cumulative curves are 90% and 10%, respectively, when the total curve of the pigment population is 100% in the obtained particle size distribution.

  Furthermore, the number of coarse particles having a pigment particle size of 0.5 μm or more contained in the ink composition can be measured using, for example, a number counting particle size distribution measuring device Accusizer 780 (manufactured by Particle Sizing Systems).

  Further, the ink viscosity can be measured using a known viscosity measuring device such as a B-type viscometer, an E-type viscometer, or a vibration type viscometer.

  The pigment in the black ink composition according to the present invention is preferably a self-dispersing pigment having a hydrophilic group on the pigment surface.

  Self-dispersing pigments are pigments that can be dispersed and / or dissolved in an aqueous medium without a dispersant. Here, “dispersed and / or dissolved in an aqueous medium without a dispersing agent” means that the surface is stably present in the aqueous medium due to the hydrophilic group on the surface without using a dispersing agent for dispersing the pigment. The state that is.

  The ink containing the self-dispersing pigment as a colorant does not need to contain a dispersant as described above in order to disperse a normal pigment. Therefore, there is almost no foaming due to a decrease in defoaming property due to the dispersant, and an ink excellent in ejection stability can be easily prepared. In addition, since a significant increase in viscosity due to the dispersant can be suppressed, it is possible to contain more pigment, and the printing density can be sufficiently increased.

Black ink composition of the present invention is a self-dispersion pigment having a hydrophilic group on the pigment surface, the hydrophilic group, -OM, -COOM, -CO -, - SO 3 M, -SO 2 M, - SO ₂ NH ₂ , —RSO ₂ M, —PO ₃ HM, —PO ₃ M ₂ , —SO ₂ NHCOR, —NH ₃ , and —NR ₃ (wherein M is a hydrogen atom, an alkali metal, ammonium, or Represents organic ammonium, and R represents an alkyl group having 1 to 12 carbon atoms, a phenyl group which may have a substituent, or a naphthyl group which may have a substituent. One or more hydrophilic groups are preferred.

  The self-dispersing pigment of the black ink composition is produced, for example, by bonding (grafting) the hydrophilic group to the surface of the pigment by subjecting the pigment to physical treatment or chemical treatment. Examples of the physical treatment include vacuum plasma treatment. Examples of the chemical treatment include a wet oxidation method in which oxidation is performed with an oxidizing agent in water, a method in which p-aminobenzoic acid or the like is bonded to the pigment surface, and a carboxyl group is bonded through a phenyl group. . Among these, it is preferable that the hydrophilic group on the surface of the pigment is bonded by oxidizing the pigment.

  In the present invention, the self-dispersion of the black ink composition surface-treated by oxidation treatment with hypohalous acid and / or hypohalite, oxidation treatment with ozone, or oxidation treatment with persulfuric acid and / or persulfate. Type pigments are preferred in terms of high color development. The black pigment dispersion surface-treated as described above is concentrated in a separation membrane, if necessary, filtered using a metal filter or membrane filter, classified by centrifugation, alkali metal salt hydroxide or amine. Neutralization can be performed.

  Moreover, as a pigment used as the raw material of the self-dispersing pigment of the black ink composition, for example, carbon black produced by a known method such as a contact method, a furnace method, or a thermal method can be used. Specific examples of preferred carbon black in the present invention include No. 2300, 900, MCF88, no. 20B, no. 33, no. 40, no. 45, no. 52, MA7, MA8, MA100, No2200B (Mitsubishi Chemical Corporation), Color Black FW1, FW2, FW2V, FW18, FW200, S150, S160, S170, Pretex 35, U, V, 140U, Special Black 6 5, 4A, 4, 250 (above Degussa), Conductex SC, Raven 1255, 5750, 5250, 5000, 3500, 1255, 700 (above Columbia Carbon), Regal 400R, 330R, 660R, Mogul L , Monarch 700, 800, 880, 900, 1000, 1100, 1300, 1400, Elftex 12 (manufactured by Cabot Corporation), and the like. These carbon blacks may be used alone or as a mixture of two or more.

  In addition, a commercially available product can be used as the self-dispersing pigment in the black ink composition according to the present invention, and a preferred example is Microjet CW1 (manufactured by Orient Chemical Industries, Ltd.).

The pigment in the black ink composition according to the present invention is preferably contained in an amount of 6% by mass or more.
When the pigment concentration in the black ink composition is 6% by mass or more, the recorded matter is highly colored.

  The self-dispersing pigment preferably has an average particle size in the range of 50 to 250 nm from the viewpoints of ink storage stability and prevention of nozzle clogging.

  The black ink composition according to the present invention preferably comprises 60 to 10% by mass of water, a water-soluble organic solvent, and a surfactant with respect to the ink composition.

  By defining the water content contained in the black ink composition within the above range, the amount of water absorbed by the cellulose in the coated paper is less than in conventional ink compositions, resulting in cockling and curling. Swelling of cellulose considered to be the cause can be suppressed. Therefore, the ink composition of the present embodiment is also useful for a recording medium having an absorbent layer of a paper support having poor ink absorbability, such as plain paper or coated paper for printing (printing paper).

  The water contained in the black ink composition according to the present invention is a main solvent, and it is preferable to use pure water or ultrapure water such as ion exchange water, ultrafiltration water, reverse osmosis water, or distilled water. In particular, it is preferable to use water sterilized by ultraviolet irradiation or addition of hydrogen peroxide in order to prevent the generation of mold and bacteria and to enable long-term storage of the ink composition.

  In the present invention, examples of the water-soluble organic compound include glycerin, 1,2,6-hexanetriol, trimethylolpropane, ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, pentaethylene glycol, diethylene Propylene glycol, 2-butene-1,4-diol, 2-ethyl-1,3-hexanediol, 2-methyl-2,4-pentanediol, 1,2-octanediol, 1,2-hexanediol, 1,2 -Polyhydric alcohols such as pentanediol and 4-methyl-1,2-pentanediol, glucose, mannose, fructose, ribose, xylose, arabinose, galactose, aldonic acid, glucitol, (sorbitol), maltose Sugars such as cellobiose, lactose, sucrose, trehalose, maltotriose, so-called solid wetting agents such as sugar alcohols, hyaluronic acids, ureas, etc., alkyl alcohols having 1 to 4 carbon atoms such as ethanol, methanol, butanol, propanol, isopropanol , Ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol monomethyl ether acetate, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol mono-n-propyl ether, ethylene glycol mono-iso-propyl ether, Diethylene glycol mono-iso-propyl ether, ethylene glycol mono- -Butyl ether, ethylene glycol mono-t-butyl ether, diethylene glycol mono-t-butyl ether, 1-methyl-1-methoxybutanol, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol mono-t-butyl ether, propylene glycol mono- Glycol ethers such as n-propyl ether, propylene glycol mono-iso-propyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol mono-n-propyl ether, dipropylene glycol mono-iso-propyl ether 2-pyrrolidone, N-methyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone Formamide, acetamide, dimethyl sulfoxide, sorbitol, sorbitan, acetin, diacetin, triacetin, sulfolane, and the like, may be used alone or in combination. These water-soluble organic solvents may be contained in the black ink composition in an amount of 10 to 90% by mass from the viewpoint of ensuring appropriate physical properties (such as viscosity) of the black ink composition, printing quality, and reliability. preferable. By including these water-soluble organic solvents in the black ink composition of the present invention, the storage stability and ejection stability are good even at high solids content.

  Furthermore, in the present invention, at least a polyhydric alcohol, a butyl ether of glycol, and a pyrrolidone are used in combination as a water-soluble organic solvent, thereby providing excellent reliability such as print quality, ejection stability, and clogging recovery. This is preferable because a black ink composition can be provided. This is because polyhydric alcohols are suitable for controlling water retention (humidity) and penetrability of black ink compositions into recording media such as plain paper, and glycol butyl ethers are suitable for ejection stability and recording media. It is suitable for controlling the permeability of the ink composition, and it has been found that pyrrolidones greatly contribute to ejection stability, storage stability and color development of the ink composition, polyhydric alcohols and glycol butyl ethers By using together with pyrrolidones, it is possible to provide a highly reliable black ink composition such as print quality, ejection stability, and clogging recovery.

  Furthermore, in the embodiment of the present invention, the water-soluble organic solvent preferably contains 5% by mass or more of polyhydric alcohol monoalkyl ether and / or nitrogen-containing cyclic compound and contains polyhydric alcohols. By using such a water-soluble organic solvent, cockling and curling can be suppressed, and printing quality such as bleeding and unevenness can be ensured.

  Here, as the polyhydric alcohol monoalkyl ether, among the above glycol ethers, for example, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, diethylene glycol monoisobutyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoisopropyl ether, dipropylene Examples thereof include glycol monoisopropyl ether, dipropylene glycol monobutyl ether, triethylene glycol monomethyl ether, triethylene glycol monobutyl ether, tripropylene glycol monomethyl ether, and tripropylene glycol monobutyl ether. Examples of the nitrogen-containing cyclic compound include 1 , 3-Dimethyl-2-imidazolidinone, 2-pyrrolide , N- methyl-2-pyrrolidone, .epsilon.-caprolactam, and the like.

  In addition, the polyhydric alcohol can be any of the above polyhydric alcohols, and in particular, 1,2-pentanediol, 1,2-hexanediol, 1,2-octanediol, etc. Of 1,2-alkanediol.

  As the surfactant contained in the black ink composition of the present invention, an anionic surfactant, a cationic surfactant, an amphoteric surfactant, and a nonionic surfactant can be contained. A nonionic surfactant is particularly preferable from the viewpoint of obtaining an ink composition with less foaming and foaming.

  Further specific examples of nonionic surfactants include acetylene glycol surfactants, acetylene alcohol surfactants, polyoxyethylene nonyl phenyl ether, polyoxyethylene octyl phenyl ether, polyoxyethylene dodecyl phenyl ether, polyoxyethylene alkyl Ethers such as allyl ether, polyoxyethylene oleyl ether, polyoxyethylene lauryl ether, polyoxyethylene alkyl ether, polyoxyalkylene alkyl ether; polyoxyethylene oleic acid, polyoxyethylene oleic acid ester, polyoxyethylene distearic acid ester , Sorbitan laurate, sorbitan monostearate, sorbitan monooleate, sorbitan sesquioleate, polyoxy Esters such as ethylene monooleate and polyoxyethylene stearate, polyether-modified siloxane surfactants such as dimethylpolysiloxane, and other fluorine-containing surfactants such as fluorine alkyl esters and perfluoroalkyl carboxylates Can be mentioned. A nonionic surfactant can also be used 1 type or in combination of 2 or more types.

  According to a preferred embodiment of the present invention, among the nonionic surfactants described above, an ink set comprising an acetylene glycol surfactant and / or a polyether-modified siloxane surfactant has particularly low foaming and is excellent. It is preferable in that it has a defoaming performance.

  Further specific examples of the acetylene glycol surfactant include 2,4,7,9-tetramethyl-5-decyne-4,7-diol, 3,6-dimethyl-4-octyne-3,6-diol. 3,5-dimethyl-1-hexyne-3ol, etc., but are also available commercially, for example, Surfynol 104, 82, 465, 485 manufactured by Air Products, manufactured by TG and Nisshin Chemical Co., Ltd. Olfin STG, Olfin E1010 and the like. Specific examples of the polyether-modified siloxane surfactant include BYK-345, BYK-346, BYK-347, BYK-348, UV3530, and the like manufactured by Big Chemie Japan. A plurality of these may be used in the ink composition, and the surface tension is preferably adjusted to 20 to 40 mN / m, and 0.1 to 3.0% by mass is contained in the ink composition.

The black ink composition according to the present invention preferably contains a pH adjuster. As the pH adjuster, alkali hydroxides such as lithium hydroxide, potassium hydroxide and sodium hydroxide and / or alkanolamines such as ammonia, triethanolamine, tripropanolamine, diethanolamine and monoethanolamine can be used. .
In particular, it is preferably adjusted to pH 6 to 10 including at least one pH adjusting agent selected from alkali metal hydroxide, ammonia, triethanolamine, and tripropanolamine. When the pH is out of this range, the material constituting the ink jet printer is adversely affected, and the clogging recovery property is deteriorated.

  If necessary, collidine, imidazole, phosphoric acid, 3- (N-morpholino) propanesulfonic acid, tris (hydroxymethyl) aminomethane, boric acid and the like can be used as a pH buffering agent.

  Furthermore, an antifoaming agent, an antioxidant, an ultraviolet absorber, an antiseptic / antifungal agent, and the like can be added to the black ink composition used in the present invention as necessary.

  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 ( Avecia's Proxel CRL, Proxel BDN, Proxel GXL, Proxel XL-2, Proxel TN) and the like.

<Resin emulsion>
The resin emulsion has the effect of improving the fixability of the image portion of the recorded matter because the resin particles and the resin particles and the coloring component are fused to each other as the ink is dried to fix the colorant to the recording medium. .

  These resin particles are preferably one or more selected from the group consisting of acrylic resins, methacrylic resins, styrene resins, urethane resins, acrylamide resins, and epoxy resins. These resins may be used as homopolymers or as copolymers.

  In the present invention, resin particles having a single particle structure can be used. On the other hand, in the present invention, it is also possible to use resin particles having a core / shell structure including a core portion and a shell portion surrounding the core portion. In the present invention, the “core / shell structure” means “a form in which two or more polymers having different compositions are present in phase separation in the particles”. Therefore, the shell portion may not only cover the core portion completely, but may cover a portion of the core portion. Further, a part of the shell polymer may form a domain or the like in the core particle. Further, it may have a multilayer structure of three or more layers including one or more layers having different compositions between the core portion and the shell portion.

  The resin particles used in the present invention can be obtained by known emulsion polymerization. That is, it can be obtained by emulsion polymerization of an unsaturated vinyl monomer (unsaturated vinyl monomer) in water in the presence of a polymerization catalyst and an emulsifier.

  As unsaturated vinyl monomers, acrylic acid ester monomers, methacrylic acid ester monomers, aromatic vinyl monomers, vinyl ester monomers, vinyl, which are generally used in emulsion polymerization Cyanide monomers, halogenated monomers, olefin monomers, diene monomers and the like can be mentioned.

  Further, 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, dodecyl acrylate. Acrylates such as 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, vinyl esters such as vinyl acetate, vinyl such as acrylonitrile, methacrylonitrile, etc. Cyanogen compounds, halogenated monomers such as vinylidene chloride and vinyl chloride, aromatic vinyl monomers such as styrene, α-methylstyrene, vinyltoluene, t-butylstyrene, chlorostyrene, vinylanisole and vinylnaphthalene , Olefins such as ethylene and propylene, dienes such as butadiene and chloroprene, vinyl ether, vinyl ketone, vinyl pyrrolidone Vinyl monomers such as acrylic acid, methacrylic acid, itaconic acid, fumaric acid, maleic acid and other unsaturated carboxylic acids, acrylamide and N, N′-dimethylacrylamide and other acrylamides, 2-hydroxyethyl acrylate, 2 -Hydroxypropyl acrylate, 2-hydroxyethyl methacrylate, and hydroxyl group-containing monomers such as 2-hydroxypropyl methacrylate.

Moreover, in this invention, what has the structure bridge | crosslinked by the crosslinkable monomer which has two or more polymerizable double bonds can be used as a molecule | numerator derived from the said monomer.
Examples of the crosslinkable monomer having two or more polymerizable double bonds include polyethylene glycol diacrylate, triethylene glycol diacrylate, 1,3-butylene glycol diacrylate, 1,6-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 di Methacrylate, 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 Methacrylate, 2, Examples include dimethacrylate compounds such as 2′-bis (4-methacryloxydiethoxyphenyl) propane, trimethacrylate compounds such as trimethylolpropane trimethacrylate and trimethylolethane trimethacrylate, methylenebisacrylamide, and divinylbenzene. Or 2 or more types can be mixed and used.

  Moreover, the polymerization initiator, the emulsifier, and the molecular weight modifier used in the emulsion polymerization can be used according to a conventional method.

  As the polymerization initiator, those used for normal radical polymerization are used, for example, potassium persulfate, ammonium persulfate, hydrogen peroxide, azobisisobutyronitrile, benzoyl peroxide, dibutyl peroxide, Examples include peracetic acid, cumene hydroperoxide, t-butyl hydroxy peroxide, paramentane hydroxy peroxide, and the like. In particular, as described above, when the polymerization reaction is performed in water, a water-soluble polymerization initiator is preferable.

  Examples of the emulsifier include sodium lauryl sulfate, those generally used as anionic surfactants, nonionic surfactants, or amphoteric surfactants, and mixtures thereof. These may be used alone or in combination of two or more. Can be used as a mixture.

  When the resin particles are produced by emulsion polymerization, particularly when a polymer emulsion composed of anionic resin particles is produced by emulsion polymerization, negative polar groups such as carboxyl groups and sulfonic acid groups are formed on the resin particle surface. Is present, the pH is inclined to the acidic side, and viscosity increases and aggregation tends to occur. Therefore, neutralization with a basic substance is usually performed. As this basic substance, ammonia, organic amines, inorganic hydroxides and the like can be used. Of these, monovalent inorganic hydroxides (potassium hydroxide, sodium hydroxide, lithium hydroxide) are particularly preferred from the viewpoints of long-term storage stability and ejection stability of the polymer emulsion and aqueous ink composition. The addition amount of the neutralizing agent is appropriately determined so that the pH of the polymer emulsion is in the range of 7.5 to 9.5, preferably in the range of 7.5 to 8.5.

  From the viewpoints of long-term storage stability and ejection stability of the ink composition, the resin particles preferably used in the present invention have a particle size in the range of 5 to 400 nm, more preferably in the range of 50 to 200 nm.

  The addition amount of these resin emulsions may be appropriately determined in consideration of fixability and the like, but it is preferable that the black ink composition according to the present invention contains 2% by mass or more in terms of solid content.

Ink Set In addition to the black ink composition according to the present invention, a color ink composition and / or another black ink composition (hereinafter, black ink compositions other than the black ink composition are referred to as “other black ink compositions”). Can also be used as an ink set. The color ink composition may contain either a self-dispersing pigment and / or a pigment that is dispersible in water via a resin.

As pigments contained in the color ink composition, pigment yellow, pigment red, pigment violet, pigment blue and the like described in the color index, phthalocyanine, azo, anthraquinone, azomethine, condensed ring systems, etc. The pigments can be exemplified. Further, organic pigments such as yellow No. 4, No. 5, 205, 401; orange No. 228, No. 405, blue No. 1, 404, etc., titanium oxide, zinc oxide, zirconium oxide, iron oxide, ultramarine blue, bitumen, Examples thereof include inorganic pigments such as chrome oxide. I. Pigment Yellow 1, 3, 12, 13, 14, 17, 24, 34, 35, 37, 42, 53, 55, 74, 81, 83, 95, 97, 98, 100, 101, 104, 108, 109, 110, 117, 120, 128, 138, 150, 153, 155, 174, 180, 198, C.I. I. Pigment red 1,3,5,8,9,16,17,19,22,38,57: 1,90,112,122,123,127,146,184, C.I. I. Pigment Bio Red 1,3,5: 1, 16, 19, 23, 38, C.I. I. And CI pigment blue 1, 2, 15, 15: 1, 15: 2, 15: 3, 15: 4, and 16.
In particular, the organic pigment contained in the yellow ink composition is C.I. I. Pigment Yellow 74, 109, 110, 128, 138, 147, 150, 155, 180, and 188. The organic pigment contained in the magenta ink composition contains at least one selected from the group consisting of C.I. I. Pigment red 122, 202, 207, 209, and C.I. I. The organic pigment containing at least one selected from the group consisting of CI pigment violet 19 and contained in the cyan ink composition is C.I. I. It is preferable to include at least one selected from the group consisting of CI Pigment Blue 15, 15: 1, 15: 2, 15: 3, 15: 4, and 16.

  Various known surface treatment means can be applied as the surface treatment means for bonding the functional group which is a hydrophilic group or a salt thereof to the pigment surface via a phenyl group, such as sulfanilic acid and p-aminobenzoic acid. Examples thereof include a method of bonding a hydrophilic group via a phenyl group by bonding 4-aminosalicylic acid or the like to the pigment surface.

  Commercially available products can also be used as the self-dispersing pigment of the color ink composition, such as CAB-O-JET250C, CAB-O-JET260M, CAB-O-JET270Y (manufactured by Cabot). It is done.

  The pigment in the color ink composition and / or other black ink composition is preferably contained in an amount of 6% by mass or more, as in the case of the black ink composition. When the pigment concentration is 6% by mass or more, the recorded matter is highly colored.

  Further, the pigment in the color ink composition and / or the other black ink composition has an average particle size from the viewpoint of storage stability of the ink and prevention of nozzle clogging, as in the case of the black ink composition. The diameter is preferably in the range of 50 to 250 nm.

  The color ink composition and / or other black ink composition contains at least 60 to 10% by mass of water, a water-soluble organic solvent, and a surfactant, as in the case of the black ink composition. Preferably it comprises. These specific examples and the addition amount thereof may be the same as those of the black ink composition.

Further, the color ink composition and / or other black ink composition includes, as necessary, a pH adjusting agent, a pH buffering agent, an antifoaming agent, an antioxidant, an ultraviolet ray, as in the case of the black ink composition. Absorbers, antiseptic / antifungal agents, resin emulsions and the like can be added.
Specific examples thereof may be the same as those of the black ink composition.

  The ink set according to the present invention can be configured in the same manner as a conventionally known ink set, and can be used as various conventionally known inks for recording methods. In particular, in the present invention, a high-resolution and high-quality image can be printed at a high speed with a relatively inexpensive apparatus, so that a small droplet of ink is ejected and adhered to a recording medium such as paper. Therefore, it is suitable for an application for printing.

Inkjet recording method An inkjet recording method using the black ink composition of the present invention or an ink set comprising the black ink composition of the present invention ejects droplets of the ink composition and attaches the droplets to a heated recording medium. Printing. As an example of a method for ejecting droplets of each ink composition, for example, an electrostrictive element is used to convert an electrical signal into a mechanical signal, and ink stored in the nozzle head portion is intermittently ejected to record the surface of the recording medium. A method for recording characters and symbols on the surface of the recording medium, by rapidly heating the ink stored in the nozzle head part at a location very close to the ejection part, generating bubbles, and ejecting them intermittently by the volume expansion caused by the bubbles. There is a method of recording characters and symbols. According to a preferred embodiment of the present invention, the black ink composition according to the present invention or the ink set containing the black ink composition according to the present invention is preferably used in an ink jet recording method using an electrostrictive element. The droplets of the black ink composition according to the present invention or the ink set containing the black ink composition according to the present invention are preferably ejected by a recording head that ejects ink droplets using the mechanical action of a piezoelectric element.

  The recorded matter recorded on the recording medium using the black ink composition according to the present invention or the ink set containing the black ink composition according to the present invention has good ink storage stability and is particularly high-speed printing. It is possible to realize an image in which the color developability of plain paper at the same time and the suppression of the change in printing density over time due to pigment sedimentation are improved, and further the fixability of plain paper is improved.

  Various recording media can be used, and examples thereof include ink jet dedicated paper (matte paper, glossy paper, etc.), plain paper, printing paper, and film.

  The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

Preparation of Black Pigment Dispersion 1 500 g of commercially available carbon black MA600 (Mitsubishi Chemical Corporation) was added to 3750 g of ion-exchanged water, and the temperature was raised to 50 ° C. while stirring with a dissolver. Thereafter, 5300 g of an aqueous solution 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. did. Subsequently, pulverization was continued for 30 minutes with a sand mill to obtain a reaction liquid containing modified carbon black. The reaction solution was filtered through a 400-mesh wire mesh to separate the zirconia beads and unreacted carbon black from the reaction solution. A potassium hydroxide 5% aqueous solution was added to the reaction solution obtained by the separation to adjust the pH to 7.5. Desalination and purification were performed with an ultrafiltration membrane until the electric conductivity of the liquid reached 1.5 mS / cm. Further desalting and purification were performed using an electrodialyzer until the conductivity of the liquid reached 1.0 mS / cm. The liquid was concentrated until the carbon black concentration was 22% by mass. This concentrated solution was treated with a continuous centrifuge at a centrifugal force of 15000 G and a flow rate of 200 ml / min, and further subjected to three stages of filtration with filters of 1 μm, 0.6 μm, and 0.3 μm. Ion-exchanged water was added to the obtained filtrate, and the resultant was diluted and dispersed until the carbon black solid content concentration became 20% by mass to obtain a black pigment dispersion 1.

The black pigment dispersion 2 was prepared in the same manner as the black pigment dispersion 1, except that MA8 (manufactured by Mitsubishi Chemical), which is a commercially available carbon black, was used instead of MA600 as a pigment. Of 20% by weight of black pigment dispersion 2 was obtained.

Preparation of Black Pigment Dispersion 3 The filtration treatment was performed in the same manner as the Black Pigment Dispersion 1 except that the filtration process was performed in two stages of 1 μm and 0.6 μm filters, and the carbon black solid concentration was 20% by mass. A pigment dispersion 3 was obtained.

Color Black which is a commercially available carbon black instead of MA600 as a preparation pigment for the black pigment dispersion 4
A black pigment dispersion 4 having a carbon black solid content concentration of 20% by mass was prepared in the same manner as the black pigment dispersion 1 except that S170 (manufactured by Degussa Huls) was used.

Preparation of Black Pigment Dispersion Liquid 5 A black pigment dispersion liquid having a carbon black solid content concentration of 20% by mass was prepared in the same manner as the black pigment dispersion liquid 1, except that the filtration treatment was performed in only one stage of a 1 μm filter. 5 was obtained.

The black pigment dispersion 6 was prepared in the same manner as the black pigment dispersion 1, except that commercially available carbon black # 44 (manufactured by Mitsubishi Chemical) was used instead of MA600 as a pigment. A black pigment dispersion 6 having a concentration of 20% by mass was obtained.

Preparation of Black Pigment Dispersion 7 Centrifugation was performed in the same manner as in Black Pigment Dispersion 1 except that the centrifugal separation was performed under the conditions of a centrifugal force of 10000 G and a flow rate of 200 ml / min, and the carbon black solid content concentration was 20% by mass. A black pigment dispersion 7 was obtained.

Preparation of resin emulsion 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. Maintaining the internal temperature at 70 ° C., adding 4 g of potassium persulfate as a polymerization initiator, dissolving, and previously stirring 450 g of ion exchange water, 3 g of sodium lauryl sulfate, 20 g of acrylamide, 365 g of styrene, 545 g of butyl acrylate, and 30 g of methacrylic acid The emulsion prepared by adding below was continuously dropped into the reaction solution over 4 hours. After completion of dropping, aging was performed for 3 hours. The obtained resin emulsion was cooled to room temperature, and then ion-exchanged water and an aqueous sodium hydroxide solution were added to adjust the solid content to 40% by mass and pH 8. The glass transition temperature of the resin particles in the obtained aqueous emulsion was −6 ° C.

Preparation of each ink composition Each ink composition was prepared by mixing each component according to the composition of Table 1 below and filtering with a 10 μm membrane filter. In addition, the numerical value in following Table 1 represents content (mass%) in an ink. The viscosity of each ink composition obtained was measured at 20 ° C. using a vibration type viscometer VM-100 (manufactured by Yamaichi Denki Co., Ltd.). The average particle size (D50%) and particle size distribution width (nm) (D90% -D10%) are measured and calculated by the particle size distribution measurement of Microtrac UPA150 (manufactured by Microtrac), and the number of coarse particles of 0.5 μm or more is The measurement was performed using Accusizer 780 (manufactured by Particle Sizing Systems), and the values are shown in Table 1.

Evaluation method
Evaluation of Colorability of Plain Paper Each black ink composition prepared was filled in an ink jet printer PX-A550 (manufactured by Seiko Epson Corporation), and 100% solid printing was performed. The recording medium was printed using Xerox 4024 and XeroxP (Fuji Xerox Co., Ltd.), and the obtained sample was left in a general environment for 1 hour. After standing, the OD value of the solid part was measured using a Gretag densitometer (manufactured by Gretag Macbeth). The average OD value was determined based on the following criteria. The results are shown in Table 2 below.
A: OD value is 1.40 or more B: OD value is 1.30 or more and less than 1.40 C: OD value is 1.20 or more and less than 1.30 D: OD value is less than 1.20

Evaluation of OD change over time Each prepared black ink composition was filled in an ink cartridge and centrifuged under the following conditions.
・ Rotating radius: 20cm
-Centrifugal acceleration: 600 rpm
-Centrifugation time: 15 hours-Centrifugal direction: the same direction as the direction when it is installed in the printer The obtained ink cartridge after centrifuging is attached to the ink jet recording apparatus PX-A550 (Seiko Epson) without shaking, 100% solid printing was performed continuously.
The recording medium was XeroxP (manufactured by Fuji Xerox Co., Ltd.), and printing was performed until the ink in the cartridge was finished 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. The obtained ΔOD value was determined based on the following criteria. The results are shown in Table 2 below.
A: ΔOD value is less than 0.08 B: ΔOD value is 0.08 or more and less than 0.13 C: ΔOD value is 0.13 or more and less than 0.18 D: ΔOD value is 0.18 or more

Evaluation of ink storage stability 60 g of each prepared black ink composition was put in a 100 g plastic bottle, sealed, and allowed to stand in a 70 ° C. environment for 1 week. The viscosity of each ink composition before and after being allowed to stand was measured with a vibratory viscometer (manufactured by Yamaichi Electronics Co., Ltd.), and the storage stability was determined from the change rate based on the following criteria. The results are shown in Table 2 below.
A: Viscosity change rate is less than ± 5% B: Viscosity change rate is ± 5% or more and less than ± 10% C: Viscosity change rate is ± 10% or more

Evaluation of fixing property of plain paper In the same manner as the evaluation of coloring property of plain paper, a pattern including solid and characters was printed. The obtained recorded matter was naturally dried for 24 hours, and then a yellow aqueous fluorescent pen ZEBRA manufactured by Zebra Corporation was used.
Using PEN2 (trademark), the printed characters were rubbed with a writing pressure of 300 g / 15 mm2, and the presence or absence of dirt adhered to the pen tip was visually observed. The result was determined based on the following criteria. The results are shown in Table 2 below.
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.

Claims (11)

A black ink composition comprising a pigment, wherein the average particle diameter (nm) of the pigment contained in the ink composition is D50%, and the particle diameter distribution width (nm) of the pigment contained in the ink composition is D90. % −D10%, when the ink viscosity (mPa · s) at 20 ° C. is η, the value of X represented by the following formula (I) is in the range of 2500-4500, and D50% is 150-171 nm. D90% -D10% is 171 to 244 nm, η is 10.2 mPas or less,
X = {D50% × (D90% −D10%)} / η (I)
And the number of coarse particles having a particle diameter of 0.5 μm or more contained in the ink composition is 7.0 × 10 ⁹ or less per 1 mL of the ink composition;
A black ink composition comprising a resin emulsion.   The ink composition according to claim 1, wherein the pigment in the ink composition is contained in an amount of 6% by mass or more based on the ink composition.   The ink composition according to claim 1 or 2, wherein the resin emulsion is contained in the ink composition in an amount of 2% by mass or more.   The ink composition according to any one of claims 1 to 3, wherein the pigment in the ink composition is a self-dispersing pigment having a hydrophilic group on the pigment surface.   The ink composition according to claim 4, wherein hydrophilic groups on the surface of the pigment in the ink composition are bonded by oxidizing the pigment.   The ink composition according to claim 5, wherein the oxidation treatment is oxidation treatment with hypohalous acid and / or hypohalite, oxidation treatment with ozone, or oxidation treatment with persulfuric acid and / or persulfate. . The hydrophilic group is, -OM, -COOM, -CO -, - SO 3 M, -SO 2 M, -SO 2 NH 2, -RSO 2 M, -PO 3 HM, -PO 3 M 2, -SO 2 NHCOR, —NH ₃ , and —NR ₃ (wherein M represents a hydrogen atom, an alkali metal, ammonium, or organic ammonium, and R has an alkyl group having 1 to 12 carbon atoms and a substituent). The ink according to any one of claims 4 to 6, which is one or more functional groups selected from the group consisting of a phenyl group which may be substituted or a naphthyl group which may have a substituent. Composition.   8. The ink composition according to claim 1, wherein the ink composition comprises at least 60 to 10% by mass of water, a water-soluble organic solvent, and a surfactant with respect to the ink composition. Ink composition.   The ink according to claim 8, wherein the ink composition contains 5% by mass or more of a polyhydric alcohol monoalkyl ether and / or a nitrogen-containing cyclic compound as the water-soluble organic solvent, and a polyhydric alcohol. Composition.   The ink composition according to claim 8 or 9, wherein the surfactant is an acetylene glycol surfactant and / or a polyether-modified siloxane surfactant.   An inkjet recording method for performing printing by discharging droplets of an ink composition and attaching the droplets to a recording medium, wherein the inkjet composition uses the ink composition according to any one of claims 1 to 10. Recording method.