JP2008069304A - Method for dispersing pigment for inkjet ink, pigment dispersion and inkjet ink using the pigment dispersion - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for dispersion of pigment dispersing pigment in a short time, pigment dispersion dispersed by the pigment dispersing method and to provide inkjet ink excellent in high temperature preservation obtained by using the dispersing method. <P>SOLUTION: The invention relates to the method for dispersing pigments for inkjet ink using a triplex-structured dispersing machine comprising a cylindrical vessel (4), a cylindrical rotor (15) located in the vessel, rotating disks (5) located in the cylindrical rotor (15), and a cylindrical separating mechanism (6) for crushing medium in the barrel of the cylindrical rotor (15) located to have a constant gap between itself and inner circumferential face of the barrel and having a large number of small pores on the surface, wherein each of the rotating disk (5) has blades (5a) with a protruding shape toward outside in the diameter direction in a plurality of regions in the outer periphery and has 0.91 to 0.95 of the ratio of the outer diameter of the disk (5) to the inner diameter of the vessel (4) as the shape of the disk (5) and 0.11 to 0.15 of the ratio of the height of the blades to the inner diameter of the vessel. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a high-efficiency pigment dispersion method for ink-jet ink having good high-temperature storage stability, a pigment dispersion, and ink-jet ink using the pigment dispersion, and the like. Applied to the dispersal of functional materials.

  A pigment-based ink-jet ink is usually prepared by mixing a pigment, a dispersant, water, etc., and dispersing the mixture with a disperser such as a medium mill to produce a pigment dispersion. Then, the pigment dispersion, water, a water-soluble organic solvent, an interface It is manufactured by mixing an activator and the like. Pigment inks tend to increase in particle diameter and viscosity due to pigment aggregation during storage at a high temperature as compared with conventional dye inks. When such inks are used, there is a risk of clogging of printer nozzles. In addition, pigment ink requires a pigment dispersion step during production as compared with dye ink, and the pigment dispersion step usually takes a long time, and thus the production cost tends to increase.

  As means for solving the above problems, Patent Document 1 (Japanese Patent Laid-Open No. 2006-16444) discloses an aqueous recording liquid for an ink jet printer in which a pigment is coated with a neutralized organic polymer compound having an anionic group. In the production method, a dispersion medium stirring type dispersion apparatus having a rotor and a separator in a cylindrical pulverizing section is used as a dispersion apparatus, and the dispersion medium efficiency in the dispersion apparatus is 0.1 to 1.2 kwh per 1 kg of pigment. A method for producing an aqueous recording liquid for an ink jet printer is disclosed, in which a suspension is supplied so that the amount of water / kg is reduced, and the pigment is finely dispersed to obtain a pigment dispersion. In the above production method, it is difficult to ensure the high temperature storage stability of the ink. In particular, Pigment Yellow 74, which is a yellow pigment, tends to have a large particle size when stored at high temperatures. No consideration is given to shortening the dispersion time.

  On the other hand, Patent Document 2 (Japanese Patent Application Laid-Open No. 2004-149632) discloses a method for producing an inkjet pigment dispersion in which the pigment dispersion comprises at least a pigment, a dispersant, and water, and the average particle diameter (D50) of the pigment particles. ) Is 100 nm or less, the particle size standard deviation in the particle size distribution of the pigment particles is smaller than the average particle size (D50), and when the production of the pigment dispersion is dispersed using a media mill, the liquid flow rate during dispersion is 300 ml. Although a method for producing a pigment dispersion for ink-jets is disclosed, characterized in that it can be at least 5 minutes per minute, depending on the type of pigment, high-temperature storage stability of the ink can be improved only by controlling the particle diameter of the pigment and the liquid flow rate during dispersion. It is difficult to secure. Furthermore, no consideration is given to shortening the dispersion time.

JP 2006-16444 A JP 2004-149632 A

  The present invention has been made in view of the circumstances as described above, a pigment dispersion method capable of being dispersed in a short time, a pigment dispersion dispersed by the pigment dispersion method, and excellent high-temperature storage stability using the pigment dispersion. It aims at providing the ink for inkjet.

  As a result of intensive studies to solve the above problems, the present inventors have found for the first time that the high-temperature storage stability of the ink and the pigment dispersion efficiency can be highly compatible by optimizing the shape of the disk used in the disperser. The present invention has been reached.

That is, the said subject is solved by the following this invention.
(1) "Cylindrical vessel (4), cylindrical rotor (15) disposed therein, rotating disk (5) disposed in the cylindrical rotor (15), and cylindrical rotor (15 Inkjet using a triple structure disperser having a cylindrical pulverizing medium separating mechanism (6) which is arranged in the cylinder with a certain gap from the cylinder inner peripheral surface and provided with many small holes on the surface. Ink pigment dispersion method, wherein each rotating disk (5) has blades (5a) protruding outward in the radial direction in a plurality of regions on the outer periphery thereof, and the shape of the disk (5) The ratio of the outer diameter of the disk (5) to the inner diameter of the vessel (4) is 0.91 or more and 0.95 or less, and the ratio of the height of the blade of the disk to the inner diameter of the vessel is 0.11 or more and 0.15 or less. For inkjet ink, characterized by using a disperser Fee dispersion method ",
(2) “The pigment dispersion method for inkjet ink according to the above item (1), wherein a dispersion having a dispersion time in a laboratory batch type disperser of 60 minutes to 300 minutes is dispersed”;
(3) “The pigment dispersion method for ink-jet ink according to the above item (1) or (2), wherein the dispersion having a viscosity of 30 mPa · s or less is dispersed while being circulated”;
(4) “The pigment dispersion method according to any one of (1) to (3) above, wherein the pigment is CI Pigment Yellow 74”;
(5) "The pigment dispersing method for inkjet ink according to any one of (1) to (4) above, wherein the dispersant is a surfactant-based dispersant";
(6) Any one of the above items (1) to (5), wherein the circulating flow rate (L / min) with respect to the vessel volume (L) is operated under a condition of 0.5 or more and 5 or less. The pigment dispersion method for inkjet inks ",
(7) “Pigment dispersion method for inkjet ink according to any one of (1) to (6) above, wherein the peripheral speed of the disk is 8 m / s or more and 20 m / s or less”,
(8) “Pigment dispersion for inkjet ink, characterized by being produced by the pigment dispersion method according to any one of (1) to (7)”,
(9) “The pigment dispersion for inkjet ink according to item (8), wherein D50 is 100 nm or less and D90 is 250 nm or less”,
(10) "Inkjet ink characterized by using the pigment dispersion for inkjet ink according to (8) or (9)",
(11) “A method for producing an inkjet ink, comprising mixing and stirring the inkjet ink pigment dispersion according to (8) or (9)” and an ink raw material ”.

  In the pigment dispersion method for inkjet ink of the present invention, the pigment can be dispersed in a short time, and the inkjet ink using the pigment dispersion for inkjet ink is excellent in high-temperature storage stability.

Hereinafter, the present invention will be described in detail.
The present invention includes a cylindrical vessel (4), a cylindrical rotor (15) disposed therein, a rotating disk (5) disposed in the cylindrical rotor (15), and the cylindrical rotor (15 Inkjet using a triple structure disperser having a cylindrical pulverizing medium separating mechanism (6) which is arranged in the cylinder with a certain gap from the cylinder inner peripheral surface and provided with many small holes on the surface. Ink pigment dispersion method, wherein each rotating disk (5) has blades (5a) protruding outward in the radial direction in a plurality of regions on the outer periphery thereof, and the shape of the disk (5) The ratio of the outer diameter of the disk (5) to the inner diameter of the vessel (4) is 0.91 or more and 0.95 or less, and the ratio of the height of the blade of the disk to the inner diameter of the vessel is 0.11 or more and 0.15 or less. Ink-jet ink using a disperser It is a pigment dispersion method.

Examples of the dispersing device in the present invention include a circulating type dispersing device having a premix tank (1), a disperser (3), and a pump (7) as shown in FIG.
The premix tank (1) may be provided with stirring means such as a stirring blade (2).
The disperser (3) includes a cylindrical vessel (4), a cylindrical rotor (15) disposed therein, a plurality of rotating disks (5) disposed in the cylindrical rotor (15), and a cylindrical rotor (15 ) And a grinding medium separation mechanism (6) such as a cylindrical gap separator provided with a large number of small holes on the surface, which is disposed with a constant gap (11) and a cylinder inner peripheral surface. In 4), grinding media (not shown) such as ceramic beads (zirconia beads, alumina beads, etc.), glass beads, steel beads, resin beads, etc. are introduced as grinding media. An annular gap (12) is provided between the cylindrical vessel (4) and the cylindrical rotor (15), and the grinding media such as ceramic beads are disposed on the inner wall of the vessel (4) and the inside thereof. It exists in both the gap (12) between the outer surface of the cylindrical rotor (15) and the gap (11) between the inner side of the cylindrical rotor (15) and the outer surface of the grinding medium separating mechanism (6). Therefore, the cylindrical rotor (15) is provided with pores or grooves for that purpose, for example, spiral grooves. The grinding medium separation mechanism (6) is provided with a small hole, but may also be a slit (reference numeral (A) in the figure). The rotating disk (5) is a flat plate in this example, and has a hole in the inner area as shown in the right figure of FIG. 1, and the material is ceramics (zirconia, etc.), urethane resin, nylon resin, metal (Wear-resistant steel, etc.). Moreover, although the rotating disk (5) is arrange | positioned along the cross-sectional direction orthogonal to the axial direction of the vessel (4), it is inserted in the outer surface of the cylindrical rotor (15) in this example.
A part to be dispersed (13) is provided on a part of the cylindrical vessel (4) (the upper end part in the example of the apparatus in this figure), and a part of the grinding medium separation mechanism (6) (to be dispersed in the example of the apparatus). A treated material discharge section (14) is provided on one end surface of the grinding medium separation mechanism (6) on the opposite side of the material introduction section.
A plurality of rotating disks (5) are provided on the cylindrical rotor (15) with a space between each other, and each rotating disk (5) has an outer direction (Bessel ( 4) The blade (5a) has a shape protruding in the direction of the inner wall).

  Prior to the operation of the disperser, the dispersant aqueous solution is charged into the premix tank (1) and then the pigment is charged. If necessary, the dispersion is predispersed with a homomixer, an ultrasonic homogenizer or the like (not shown). Do. Alternatively, a solid or paste-like dispersant and water may be placed in the premix tank (1) and stirred and dissolved by the stirring blade (2) to produce a dispersant aqueous solution. Then, if necessary, the mixture (= dispersion) of the pigment and dispersant aqueous solution is introduced to the disperser (3) with the pump (7) while the stirring blade (2) is operated, and the disperser is operated while circulating the dispersion. Then, the pigment is dispersed. The dispersion passes through the separation mechanism (6), is discharged from the disperser and returns to the premix tank (1), and the pulverization medium remains in the disperser (3).

  The disk shape of the disperser is such that both “ratio of disk outer diameter to vessel inner diameter” and “ratio of disk blade height to vessel inner diameter” shown in FIG. 2 are in a specific range. Can keep the shearing speed of the grinding media in the disperser high and reduce the dispersion of the grinding media to the limit, shorten the dispersion time, prevent primary particles from being crushed by overdispersion, and store the ink at high temperature. High balance of sex can be achieved. Such high-quality dispersion can be achieved by simply optimizing the dispersion conditions (disk peripheral speed, circulation flow rate, grinding medium filling rate, etc.), but cannot be compatible with shortening of the dispersion time. is there.

  The ratio of the disk outer diameter to the vessel inner diameter is preferably 0.91 or more and 0.95 or less. If it is less than 0.91, the movement of the grinding medium is insufficient, so that the dispersion efficiency is lowered. If it exceeds 0.95, the dispersion speed of the grinding medium in the disperser becomes large and the storage stability of the dispersion is lowered. Tend.

  The ratio of the height of the disk blade to the inner diameter of the vessel is preferably 0.11 or more and 0.15 or less. If it is less than 0.11, the dispersion efficiency is lowered because the movement of the grinding medium is insufficient, and if it exceeds 0.15, the movement of the grinding medium in the center of the disk becomes slow, so that the dispersion efficiency also tends to be lowered.

The dispersion method in the present invention is preferably applied to a dispersion in which the dispersion time in a laboratory batch type disperser is 60 minutes to 300 minutes, but the dispersion takes less than 60 minutes or longer than 300 minutes. But it is applicable. Even in the case of using a pigment having a dispersion time of 60 to 300 minutes in a laboratory batch type disperser, that is, a pigment having poor dispersibility, the present dispersion method enables efficient dispersion. In the case of a pigment having a dispersion time of less than 60 minutes, the dispersion method tends to cause a decrease in the high-temperature storage stability of the ink due to overdispersion. Tend to be difficult.
This “lab batch disperser” is a different type from the disperser of the type shown in FIG. 1, and as shown in FIG. 3, there is no premix tank or pump because it is a batch type. . The pigment dispersion (pre-dispersed) and the grinding medium are put from the upper part of the vessel, and taken out from the lower part after the dispersion is finished (the inlet and outlet are not shown in FIG. 3).
The dispersion time in a laboratory batch type disperser was filled with 0.3 mmφ zirconia beads at a filling rate of 85% with a Dino mill MULTI LAB (using 0.3 L glass container) manufactured by Shinmaru, and the peripheral speed of the disk was 10 m / s. This is the dispersion time required for the pigment to be reduced to a predetermined particle size when operated at.

The viscosity of the pigment dispersion applied to this dispersion method is preferably 30 mPa · s or less, and particularly preferably 20 mPa · s or less. If the viscosity exceeds 30 mPa · s, the pressure loss in the pulverizing medium separation mechanism increases when circulating and dispersing, making it difficult to ensure the flow rate. This may cause clogging of the mechanism.
The viscosity in the present invention is a value measured with a viscometer RE80L manufactured by Toki Sangyo Co., Ltd. using a rotor 1 ° 34 × R24 at a temperature of 25 ° C. and a rotation speed of 20 rpm.

  Examples of the pigment used in the present invention include organic pigments such as azo, phthalocyanine, anthraquinone, dioxazine, indigo, thioindigo, perylene, isoindolenone, aniline black, azomethine, rhodamine B lake pigment, and the like. Examples of the inorganic pigment include carbon black, iron oxide, titanium oxide, calcium carbonate barium sulfate, aluminum hydroxide, barium yellow, bitumen, cadmium red, chrome yellow, and metal powder.

  More specifically, as the black pigment, carbon blacks (CI pigment black 7) such as furnace black, lamp black, acetylene black, channel black, or copper oxide, iron oxide (CI pigment) Examples thereof include black 11), metals such as titanium oxide, and organic pigments such as aniline black (CI Pigment Black 1).

  Examples of yellow pigments include C.I. I. Pigment Yellow 1 (Fast Yellow G), 2, 3, 12 (Disazo Yellow AAA), 13, 14, 16, 17, 20, 23, 24, 34, 35, 37, 42 (Yellow Iron Oxide), 53, 55 73, 74, 75, 81, 83 (disazo yellow HR), 86, 93, 95, 97, 98, 100, 101, 104, 108, 109, 110, 114, 117, 120, 125, 128, 129, 137, 138, 139, 147, 148, 150, 151, 153, 154, 155, 166, 168, 180, 185 and the like.

  Examples of magenta pigments include C.I. I. Pigment Red 1, 2, 3, 5, 7, 9, 12, 17, 22 (Brilliant First Scarlet), 23, 31, 38, 48: 1 (Permanent Red 2B (Ba)), 48: 2 (Permanent Red 2B) (Ca)), 48: 3 (permanent red 2B (Sr)), 48: 4 (permanent red 2B (Mn)), 49: 1, 52: 2, 53: 1, 57: 1 (brilliant carmine 6B), 60: 1, 63: 1, 63: 2, 64: 1, 81 (Rhodamine 6G rake), 83, 88, 92, 97, 101 (Bengara), 104, 105, 106, 108 (Cadmium red), 112, 114, 122 (dimethylquinacridone), 123, 146, 149, 166, 168, 170, 172, 175, 176, 178, 179, 180 184,185,190,192,193,202,209,215,216,217,219,220,223,226,227,228,238,240,254,255,272, and the like.

  Examples of cyan pigments include C.I. I. Pigment Blue 1, 2, 3, 15 (copper phthalocyanine blue R), 15: 1, 15: 2, 15: 3 (phthalocyanine blue G), 15: 4, 15: 6 (phthalocyanine blue E), 16, 17: 1, 22, 56, 60, 63, 64, Bat Blue 4, Bat Blue 60, and the like.

  Also, red, green, and blue for intermediate colors are C.I. I. Pigment red 177, 194, 224, C.I. I. Pigment orange 16, 36, 43, 51, 55, 59, 61, 71, C.I. I. Pigment violet 3, 19, 23, 29, 30, 37, 40, 50, C.I. I. Pigment green 7, 36, and the like.

  Among the above pigments, C.I. I. Application to CI Pigment Yellow 74 is preferable. In the case of Pigment Yellow 74, if the dispersion is insufficient, the particle size tends to increase during high-temperature storage. In order to ensure high-temperature storage stability with conventional dispersers, it is necessary to take extremely long time for dispersion. The method can significantly reduce the dispersion time.

  In the pigment dispersion of the present invention, nonionic or anionic activator dispersants, polymer dispersants and the like used for dispersing pigments can be appropriately used. Nonionic surfactants include polyoxyethylene lauryl ether, polyoxyethylene myristyl ether, polyoxyethylene cetyl ether, polyoxyethylene stearyl ether, polyoxyethylene alkyl ether such as polyoxyethylene oleyl ether, and polyoxyethylene octylphenyl ether. , Polyoxyethylene alkyl phenyl ether such as polyoxyethylene nonyl phenyl ether, polyoxyethylene α-naphthyl ether, polyoxyethylene β-naphthyl ether, polyoxyethylene monostyryl phenyl ether, polyoxyethylene distyryl phenyl ether, polyoxyethylene alkyl Naphthyl ether, polyoxyethylene monostyryl naphthyl ether, polyoxyethylene distyle Examples include naphthyl ether, polyoxyethylene polyoxypropylene block copolymer, and the like. Also used are surfactants in which a part of polyoxyethylene in the above surfactant is replaced with polyoxypropylene, and surfactants condensed with a compound having an aromatic ring such as polyoxyethylene alkylphenyl ether with formalin. it can.

  The HLB of the nonionic surfactant is preferably from 12 to 19.5, more preferably from 13 to 19. If the HLB is less than 12, there is a tendency for the dispersion stability to deteriorate due to poor compatibility of the surfactant with the dispersion medium. If the HLB exceeds 19.5, the surfactant is difficult to adsorb on the pigment, so that the dispersion stability is also maintained. There is a tendency to deteriorate.

  Anionic surfactants include polyoxyethylene alkyl ether sulfate, polyoxyethylene alkyl phenyl ether sulfate, polyoxyethylene monostyryl phenyl ether sulfate, polyoxyethylene distyryl phenyl ether sulfate, polyoxyethylene alkyl ether phosphorus Acid salt, polyoxyethylene alkyl phenyl ether phosphate, polyoxyethylene monostyryl phenyl ether phosphate, polyoxyethylene distyryl phenyl ether phosphate, polyoxyethylene alkyl ether carboxylate, polyoxyethylene alkyl phenyl ether Carboxylate, polyoxyethylene monostyryl phenyl ether carboxylate, polyoxyethylene distyryl phenyl ether carboxylate, naphthalene Phosphonate formalin condensate, melanin sulfonate formalin condensate, dialkyl sulfosuccinate ester salt, sulfosuccinic acid alkyl disalt, polyoxyethylene alkyl sulfosuccinic acid disalt, alkyl sulfoacetate, α-olefin sulphonate, alkylbenzene sulfone Acid salts, alkylnaphthalene sulfonates, alkyl sulfonates, N-acyl amino acid salts, acylated peptides, soaps, and the like. Among these, polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, polyoxy Particularly preferred is the sulfate or phosphate of ethylene distyryl phenyl ether.

  As a polymer dispersant, it is an aqueous polymer. Animal polymers such as seaweed polymers, gelatin, casein, albumin, collagen, etc., microbial polymers such as xanthene gum, dextran, and fibers such as methylcellulose, ethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, carboxymethylcellulose in the semisynthetic system Organic polymers, starch polymers such as sodium starch glycolate and sodium starch phosphate, seaweed polymers such as sodium alginate and propylene glycol alginate, pure Polyacrylic acid, polymethacrylic acid, acrylic acid-acrylonitrile copolymer, vinyl acetate-acrylic acid ester copolymer, acrylic acid-acrylic acid alkyl ester copolymer, styrene-acrylic acid copolymer, styrene- Methacrylic acid copolymer, styrene-acrylic acid-alkyl acrylate copolymer, styrene-methacrylic acid-alkyl acrylate copolymer, styrene-α-methylstyrene-acrylic acid copolymer, styrene-α-methyl Styrene-acrylic acid copolymer-alkyl acrylate ester copolymer, styrene-maleic acid copolymer, vinyl naphthalene-maleic acid copolymer, vinyl acetate-ethylene copolymer, vinyl acetate-fatty acid vinyl ethylene copolymer , Vinyl acetate-maleic acid ester copolymer, vinegar Vinyl - crotonic acid copolymer, vinyl acetate - acrylic acid copolymer and the like.

  In the pigment dispersion method of the present invention, it is particularly preferable to use a surfactant-based dispersant as the dispersant. Since the dispersion using the surfactant-based dispersant is advantageous for atomization of the pigment, it is particularly advantageous for securing high-temperature stability of the ink using Pigment Yellow 74, and the dispersion speed tends to be high.

  The addition amount of the dispersant is preferably 10% by weight or more and 50% by weight or less of the pigment. When the added amount of the dispersant is less than 10% by weight of the pigment, the storage stability of the pigment dispersion and the ink is lowered or the dispersion takes an extremely long time. When the added amount exceeds 50% by weight, the viscosity of the ink becomes too high. Therefore, the discharge stability tends to decrease.

  In this dispersion method, the circulation flow rate (L / min) with respect to the vessel capacity (L) is preferably operated under the condition of 0.5 or more and 5 or less, particularly preferably 1 or more and 3 or less. If it is less than 0.5, the temperature in the vessel becomes too high, and there is a tendency for pigment aggregation and equipment damage to occur. If the value exceeds 5, the flow rate is too fast and the grinding media separation mechanism is easily clogged, and the pressure in the vessel increases. It tends to be easy.

  The disk peripheral speed is preferably 8 m / s or more and 20 m / s or less, and particularly preferably 10 m / s or more and 15 m / s or less. If it is less than 8 m / s, not only does it take a long time to disperse the pigment but also coarse particles tend to remain, so the particle size distribution tends to be broad. If it exceeds 20 m / s, the temperature in the vessel becomes too high and the pigment aggregates. It is easy to raise concerns about the damage to the disperser.

In the pigment dispersion of the present invention, the particle diameter of the pigment can be appropriately set in consideration of ink characteristics, but D50 is preferably 100 nm or less and D90 is preferably 250 nm or less. If D50 exceeds 100 nm or D90 exceeds 250 nm, the pigment particle size is too large and the storage stability of the ink tends to decrease.
In addition, D50 or D90 in the present invention uses a sample diluted with pure water so that the pigment concentration (weight concentration) in the measurement sample becomes 0.01% using Microtrac UPA-150 manufactured by Nikkiso Co., Ltd. The refractive index is 1.51, the particle density is 1.4 g / cm 3, and the solvent parameter is the particle diameter D50 or D90 measured at 23 ° C. using the parameters of pure water.

  The ink-jet ink of the present invention can be produced by stirring and mixing the above-described pigment dispersion and ink raw material, and subjecting to heat treatment, centrifugal treatment, ion exchange treatment, filtration and the like as necessary.

The ink-jet ink of the present invention can contain a nonionic or anionic surfactant in order to improve the permeability to paper and to impart quick drying properties to the ink.
Nonionic or anionic surfactants include polyoxyethylene alkyl ether acetates, dialkyl sulfosuccinates, polyoxyethylene alkyl ethers, polyoxyethylene alkyl ether acetates, nonionic or anionic surfactants used for dispersing the pigments. Examples thereof include oxyethylene alkylphenyl ether, polyoxyethylene polyoxypropylene block copolymer, acetylene glycol surfactant, and fluorine surfactant.

  The addition amount of the surfactant is preferably 0.05% by weight to 10% by weight, and more preferably 0.1% by weight to 5% by weight. If it is less than 0.05% by weight, sufficient penetrability cannot be obtained, so that blurring occurs at the boundary at the two-color overlapping portion, and if it exceeds 10% by weight, the compound itself may precipitate at a low temperature, resulting in poor reliability.

  In the present invention, it is possible to contain one or more resin emulsions. As the resin emulsion, acrylic acid (or methacrylic acid) or a derivative thereof (for example, methyl acrylate, ethyl acrylate, methacrylic acid, or methyl methacrylate) is a polymer or copolymer of an acrylic acid polymer, Styrene-acrylic resin, acrylic silicone resin, urethane resin, rubber-based polymer such as styrene-butadiene rubber (SBR), ethylene-vinyl acetate (EVA), or acrylonitrile-butadiene rubber (NBR), starch, modified starch, gelatin, Casein, natural polymer compounds such as soybean protein, or cellulose-modified polymers such as carboxymethylcellulose (CMC), hydroxyethylcellulose (HEC), or hydroxypropylcellulose (HPC) And polyvinyl alcohol (PVA), modified PVA, polyacrylamide, polyethylene, polyacetal resins, guar gum, polyesters, polyvinyl pyrrolidone, ethylene - and polyvinyl alcohol copolymers. Among these, acrylic resins, styrene-acrylic resins, acrylic silicon resins, and urethane resins are particularly preferable from the viewpoints of fixability, image quality, and storage stability.

  The pH of the ink is preferably 5 or more and 12 or less, more preferably 6 or more and 11 or less, and further preferably 7 or more and 10 or less. If the pH is less than 5 or more than 12, aggregation and thickening tend to occur during storage of the ink. In addition, pH in this invention is the value measured on 25 degreeC conditions with the pH meter HM-50V by Toa Denpa.

  The ink of the present invention mainly uses water as a liquid medium. In order to make the ink have desired physical properties, to prevent the ink from drying, and to stabilize the compound added to the ink of the present invention. The following water-soluble organic solvents can be used for the purpose of improving the properties.

  Alcohols such as methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, isobutyl alcohol, ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, 1,2-propanediol, 1, 2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 2-methyl-1,3-butanediol, 1,5-pentanediol, 1,6-hexanediol, Obtained by dehydration condensation of polyhydric alcohols such as glycerin, 1,2,6-hexanetriol, 1,2,4-butanetriol, 1,2,3-butanetriol, and petriol, and the polyhydric alcohol and the alcohol. Monoether derivatives and di Ether derivatives, polyhydric alcohol phenyl ethers such as ethylene glycol monophenyl ether, ethylene glycol monobenzyl ether, N-methyl-2-pyrrolidone, N-hydroxyethyl-2-pyrrolidone, 2-pyrrolidone, 1,3-dimethylimidazolide Non, nitrogen-containing heterocyclic compounds such as ε-caprolactam, amides such as formamide, N-methylformamide, N, N-dimethylformamide, ketones such as acetone and methylethylketone, monoethanolamine, diethanolamine, triethanolamine, triisopropanol Amines such as amine, monoethylamine, diethylamine, triethylamine, propylamine and butylamine; sulfur-containing compounds such as dimethylsulfoxyside, sulfolane and thiodiethanol; Lopylene carbonate, ethylene carbonate, and γ-butyrolactone. These solvents are used alone or in combination with water.

  Among these, particularly preferred are diethylene glycol, thiodiethanol, polyethylene glycol 200 to 600, triethylene glycol, glycerin, 1,2,6-hexanetriol, 1,2,4-butanetriol, petriol, 1,3- Butanediol, 2,3-butanediol, 1,4-butanediol, 2-methyl-1,3-butanediol, 1,5-pentanediol, N-methyl-2-pyrrolidone, N-hydroxyethylpyrrolidone, 2 -Pyrrolidone, 1,3 dimethylimidazolidinone, and by using these, excellent effects can be obtained with respect to the high solubility of the compound added to the ink of the present invention and the prevention of jetting characteristics failure due to water evaporation.

  The addition amount of the water-soluble organic solvent is preferably 10% or more and 50% or less. If the water-soluble organic solvent is less than 10%, the viscosity after drying increases, and if it exceeds 50%, not only the viscosity of the ink increases, but also the character quality tends to deteriorate when printed.

Further, as a penetrant added for the purpose of adjusting the surface tension other than the surfactant added to the ink of the present invention, diethylene glycol monophenyl ether, ethylene glycol monophenyl ether, ethylene glycol monoallyl ether, diethylene glycol monophenyl ether, Alkyl and aryl ethers of polyhydric alcohols such as diethylene glycol monobutyl ether, propylene glycol monobutyl ether, triethylene glycol monobutyl ether, tetraethylene glycol chlorophenyl ether, 2-ethyl-1,3-hexanediol, 2,2,4-trimethyl- Diols such as 1,3-pentanediol and 2,2-dimethyl-1,3-propanediol, polyoxyethylene polyoxypropylene block Polymers, lower alcohols such as ethanol and 2-propanol can be mentioned, and particularly preferred are diethylene glycol monobutyl ether as polyhydric alcohol alkyl ether, 2-ethyl-1,3-hexanediol as diol having 6 or more carbon atoms, and 2 2,4-trimethyl 1,3-pentanediol. Diols are preferred because they are less likely to cause aggregation of water-insoluble colorants.
The addition amount depends on the type and desired physical properties, but is added in the range of 0.1 wt% to 20 wt%, preferably 0.5 wt% to 10 wt%. If it is less than 0.1% by weight, the permeability is insufficient, and if it exceeds 20% by weight, the particle formation characteristics are adversely affected. In addition, the addition of these improves wettability to the ink jet head member and the recording device, improves the filling property, and makes it difficult for recording defects due to bubbles to occur.

In addition to the above materials, conventionally known additives can be added to the inkjet ink of the present invention.
For example, as a preservative and antifungal agent, sodium dehydroacetate, sodium sorbate, sodium 2-pyridinethiol-1-oxide, sodium benzoate, sodium pentachlorophenol, isothiazoline and the like can be used in the present invention.
Other chelating agents include, for example, sodium ethylenediaminetetraacetate, sodium nitrilotriacetate, sodium hydroxyethylethylenediaminetriacetate, sodium diethylenetriaminepentaacetate, sodium uramil diacetate, and the like.
Examples of the rust preventive include acidic sulfite, sodium thiosulfate, ammonium thiodiglycolate, diisopropyl ammonium nitrite, pentaerythritol tetranitrate, dicyclohexyl ammonium nitrite, and benzotriazole.
In addition, it is possible to add a water-soluble ultraviolet absorber, a water-soluble infrared absorber, an antifoaming agent, a pH buffering agent, etc. according to the purpose.
In addition, a dye can be used together as necessary. As a preferable dye, those having excellent water resistance and light resistance among dyes classified into acid dyes, direct dyes, basic dyes, reactive dyes, and food dyes in the color index are used.

  In the ink production method of the present invention, ink materials such as a coloring material, a water-soluble organic solvent, a surfactant, and water are mixed and stirred until they are uniform after being put into a tank, thereby producing an ink. Thereafter, the ink may be pressure-fed to the filtration device for filtration.

EXAMPLES Hereinafter, although this invention is demonstrated in detail based on an Example, this invention is not limited to a present Example. In addition, the number of parts in an Example represents a weight part.
<Example 1>
A schematic configuration diagram of the disperser is shown in FIG. A star mill LMZ4 (Bessel inner diameter 180 mmφ) manufactured by Ashizawa Finetech was used as a disperser, and a disk with an outer diameter of 168 mmφ and a blade height of 24 mm was mounted (ratio of the outer diameter of the disk to the inner diameter of the vessel = 0.93, the disk with respect to the inner diameter of the vessel) The blade height ratio = 0.13), and zirconia beads having a diameter of 0.3 mmφ were introduced into the vessel at a filling rate of 85%. The vessel capacity was 3.9L.
Next, 42,000 parts of pure water and 6000 parts of a surfactant-based dispersant (polyoxyethylene (n = 40) β-naphthyl ether) are placed in a premix tank, stirred with a stirring blade, dissolved, and 12000 parts of pigment (Pigment Yellow 74) are added. After the addition, premixing was performed with a stirring blade. Thereafter, the pump was operated to circulate at a liquid flow rate of 5 L / min (circulation flow rate (L / min) with respect to the vessel volume (L) = 1.3), and the disperser was operated at a disk peripheral speed of 12 m / s for 20 hours. The pigment was dispersed.
The liquid viscosity after dispersion was 6.5 mPa · s, the D50 of the pigment was 13.5 nm, and the D90 was 35.9 nm.
The dispersion time of the dispersion in a laboratory batch disperser was 120 minutes.

<Example 2>
In Example 1, except that a disk having an outer diameter of 164 mmφ and a blade height of 20 mm was mounted (ratio of disk outer diameter to vessel inner diameter = 0.91, ratio of disk blade height to vessel inner diameter = 0.11). The pigment was dispersed in the same manner as in Example 1.
The liquid viscosity after dispersion was 6.4 mPa · s, the D50 of the pigment was 13.9 nm, and the D90 was 43.6 nm.

<Example 3>
The dispersion formulation was 41940 parts pure water, 6000 parts surfactant-based dispersant (polyoxyethylene (n = 40) β naphthyl ether), 60 parts surfactant (sodium naphthalenesulfonate formalin condensate), pigment (pigment) Red Blue 15: 3) The pigment was dispersed in the same manner as in Example 1 except that the amount was changed to 12000 parts and the dispersion time was changed to 6 hours.
The liquid viscosity after dispersion was 6.0 mPa · s, the D50 of the pigment was 73.8 nm, and the D90 was 209.4 nm.
The dispersion time of the dispersion in a laboratory batch disperser was 8 minutes.

<Example 4>
In Example 1, the pigment was dispersed in the same manner as in Example 1 except that the circulation flow rate was changed to 7 L / min (circulation flow rate (L / min) with respect to the vessel volume (L) = 1.8).
The liquid viscosity after dispersion was 6.3 mPa · s, the D50 of the pigment was 12.0 nm, and the D90 was 27.7 nm.

<Example 5>
In Example 1, the pigment was dispersed in the same manner as in Example 1 except that the peripheral speed of the disk was changed to 10 m / s.
The liquid viscosity after dispersion was 6.2 mPa · s, the D50 of the pigment was 14.5 nm, and the D90 was 56.9 nm.

<Comparative Example 1>
In Example 1, a disk having an outer diameter of 160 mmφ and a blade height of 24 mm was mounted (ratio of disk outer diameter to vessel inner diameter = 0.89, ratio of disk blade height to vessel inner diameter = 0.13). Except for the above, the pigment was dispersed in the same manner as in Example 1.
The dispersion viscosity after dispersion was 6.4 mPa · s, the D50 of the pigment was 29.9 nm, and the D90 was 124.5 nm. The dispersion efficiency was worse than that of Example 1.

<Comparative example 2>
In Example 1, a disk having an outer diameter of 160 mmφ and a blade height of 12 mm was mounted (ratio of disk outer diameter to vessel inner diameter = 0.89, ratio of disk blade height to vessel inner diameter = 0.07). Except for the above, the pigment was dispersed in the same manner as in Example 1.
The liquid viscosity after dispersion was 3.9 mPa · s, the D50 of the pigment was 53.0 nm, and D90 was 166.3 nm. The dispersion efficiency was worse than that of Example 1.

  Next, using the pigment dispersions of Examples 1 to 5 and Comparative Examples 1 and 2, inks were prepared according to the formulations shown in Table 1 below. Table 2 shows the results of confirming the particle diameter of the ink before and after storage at 50 ° C. for 2 weeks.

  Inks using the dispersions of Examples 1 to 5 showed a small increase in average particle size even when stored at 50 ° C. for 2 weeks, whereas inks using the dispersions of Comparative Examples 1 and 2 were averaged in a storability test. The particle size is increasing.

It is a schematic block diagram of the disperser used by this invention. It is a figure for demonstrating the disk shape of a disperser. It is a figure which shows the batch type disperser for laboratories.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Premix tank 2 Stirring blade 3 Disperser 4 Vessel 5 Disc 5a Blade 6 Grinding medium separation mechanism 7 Pump 8 Vessel inner diameter 9 Disc outer diameter 10 Disc blade height 11 Gap 12 Gap 13 Dispersed material introduction part 14 Discharge part 15 Tubular rotor A Small hole

Claims (11)

A cylindrical vessel (4), a cylindrical rotor (15) disposed therein, a rotating disk (5) disposed in the cylindrical rotor (15), and a trunk of the cylindrical rotor (15) Of a pigment for ink-jet ink using a triple-structure disperser having a cylindrical pulverizing medium separating mechanism (6) which is arranged with a certain gap from the inner peripheral surface of the cylinder and provided with a large number of small holes on the surface. In the dispersion method, each rotating disk (5) has blades (5a) protruding outward in the radial direction in a plurality of regions on the outer periphery, and a vessel (4) is formed as the shape of the disk (5). A disperser is used in which the ratio of the outer diameter of the disk (5) to the inner diameter is 0.91 or more and 0.95 or less, and the ratio of the height of the blade of the disk to the inner diameter of the vessel is 0.11 or more and 0.15 or less. Pigment dispersion for inkjet ink Law. 2. The pigment dispersion method for inkjet ink according to claim 1, wherein a dispersion having a dispersion time of 60 minutes to 300 minutes in a laboratory batch type disperser is dispersed. The method for dispersing a pigment for inkjet ink according to claim 1 or 2, wherein a dispersion having a viscosity of 30 mPa · s or less is dispersed while being circulated. The pigment is C.I. I. The pigment dispersion method for inkjet ink according to any one of claims 1 to 3, which is CI Pigment Yellow 74. The method for dispersing a pigment for inkjet ink according to any one of claims 1 to 4, wherein the dispersant is a surfactant-based dispersant. The pigment dispersion method for inkjet ink according to any one of claims 1 to 5, wherein the circulating flow rate (L / min) with respect to the vessel volume (L) is operated under a condition of 0.5 or more and 5 or less. 7. The pigment dispersion method for inkjet ink according to claim 1, wherein the peripheral speed of the disk is 8 m / s or more and 20 m / s or less. A pigment dispersion for inkjet ink, which is produced by the pigment dispersion method for inkjet ink according to any one of claims 1 to 7. The pigment dispersion for inkjet ink according to claim 8, wherein D50 is 100 nm or less and D90 is 250 nm or less. An inkjet ink comprising the inkjet ink pigment dispersion according to claim 8. 10. A method for producing an inkjet ink, comprising mixing and stirring the pigment dispersion for inkjet ink according to claim 8 or 9 and an ink raw material.

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