JP2017141387A - Oily inkjet recording liquid and method for producing oily inkjet recording liquid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an oily inkjet recording liquid that is excellent in storage stability and discharge stability by stably dispersing a pigment in a recording liquid, wherein the oily inkjet recording liquid with excellent wiping durability does not damage a nozzle face at the time of wiping in inkjet head cleaning, and an inkjet recording method.SOLUTION: An oily inkjet recording liquid has a pigment, an oily medium, and a resin. The pigment has a primary particle with an aspect ratio of 1.0 or more and 2.0 or less. The pigment has undergone surface treatment with a derivative of the pigment.SELECTED DRAWING: None

Description

  The present invention relates to an oil-based inkjet recording liquid and a method for producing an oil-based inkjet recording liquid.

  Development of office-use inkjet printers is ongoing. An office use printer is required to be capable of high-speed printing at high image quality on a recording medium such as plain paper, and to be able to handle a finisher such as bookbinding after printing. For this reason, as a characteristic required for the recording liquid used in this printer, it is possible to secure a high print density at a high speed for plain paper, and to prevent back-through to enable double-sided printing, Furthermore, it is required that paper deformation such as cockling and curling does not occur after high-speed printing. When an aqueous recording liquid containing an aqueous medium is used as the ink, paper deformation such as cockling and curling may occur after high-speed printing on plain paper. Development of recording liquid is also underway.

  In oil-based recording liquids, dyes or pigments are used as coloring materials, but pigments are preferred because of their good light resistance and water resistance. In many cases, the dye is dissolved in the solvent of the oil-based recording liquid, whereas the pigment is dispersed in the solvent of the oil-based recording liquid, so that the dispersion stability in the recording liquid is ensured. In addition, it is necessary to use in combination with a pigment dispersant or to use a self-dispersing pigment. Accordingly, there is a technique for improving the printing density by regulating the dispersed particle diameter and content of the pigment within a predetermined range, and further improving the discharge performance from the nozzle (for example, see Patent Document 1).

JP 2010-209188 A

  However, in the above technique, the pigment has a needle-like elongated shape, and the dispersed particle diameter of the pigment is defined, but no mention is made of the primary particle diameter of the pigment. The dispersed particle size of the pigment and the primary particle size do not necessarily correlate. If the primary particle size of the pigment is too small, the pigment is not stably dispersed in the recording liquid, and storage stability and ejection stability. On the other hand, when the primary particle diameter of the pigment is too large, nozzle clogging or the like may occur, resulting in poor discharge stability. Further, when the pigment has a needle-like elongated shape, the nozzle surface may be damaged at the time of wiping in the cleaning of the inkjet head.

  Accordingly, some aspects of the present invention solve at least a part of the above-described problems so that the pigment is stably dispersed in the recording liquid, and is excellent in storage stability and ejection stability. An object of the present invention is to provide an oil-based ink jet recording liquid and an ink jet recording method which do not damage the nozzle surface during wiping in head cleaning and have excellent wiping durability.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following aspects or application examples.

[Application Example 1]
One aspect of the oil-based inkjet recording liquid according to the present invention is:
In an oil-based inkjet recording liquid containing a pigment, an oil-based medium, and a resin,
The aspect ratio of the primary particles of the pigment is in the range of 1.0 or more and 2.0 or less.

  According to the application example, since the aspect ratio of the primary particles of the pigment is in the range of 1.0 or more and 2.0 or less, the pigment is stably dispersed in the recording liquid, and the storage stability and the ejection stability are improved. It is possible to provide an oil-based inkjet recording liquid that has excellent wiping durability and that does not damage the nozzle surface during wiping in cleaning an inkjet head.

[Application Example 2]
In the above application example,
The 90% integrated value (D90) of the primary particle size distribution of the pigment may be 100 nm or less.

[Application Example 3]
In the above application example,
The pigment may be at least one selected from the group consisting of quinacridone and copper phthalocyanine.

[Application Example 4]
In the above application example,
50 mass% or more of the oily medium may be a petroleum solvent.

[Application Example 5]
In the above application example,
The resin may be at least one selected from the group consisting of a urethane-modified acrylic resin, a fatty acid-modified alkyd resin, and a urethane-modified alkyd resin.

[Application Example 6]
One aspect of the method for producing an oil-based inkjet recording liquid according to the present invention is as follows.
A method for producing an oil-based ink jet recording liquid comprising a pigment, an oil-based medium, and a resin,
It includes a step of subjecting the pigment to a surface treatment using a derivative of the pigment.

  Hereinafter, preferred embodiments of the present invention will be described. The embodiment described below describes an example of the present invention. In addition, the present invention is not limited to the following embodiments, and includes various modifications that are implemented within a range that does not change the gist of the present invention.

1. Oil-based inkjet recording liquid The oil-based inkjet recording liquid according to the present embodiment (hereinafter also simply referred to as “oil-based recording liquid”) is an oil-based inkjet recording liquid containing a pigment, an oil-based medium, and a resin. The aspect ratio of the particles is in the range of 1.0 or more and 2.0 or less.

  Here, the “oil-based recording liquid” in the present specification is an ink containing an organic solvent as a main component and means an ink that does not substantially contain water. In addition, “substantially free of water” means that water is not intentionally added when the ink is produced, and a minute amount of water that inevitably mixes the oil-based recording liquid during production or storage. May be included.

  The specific water content of the “oil-based recording liquid substantially free of water” is preferably such that the water content in the oil-based recording liquid is 3% by mass or less, more preferably 1% by mass or less. More preferably, it is less than 0.05% by mass, more preferably less than 0.01% by mass, still more preferably less than 0.005% by mass, and most preferably less than 0.001% by mass.

  Hereinafter, components included in the oil-based inkjet recording liquid and components that can be included will be described.

1.1. Pigment The oil-based inkjet recording liquid according to the present embodiment contains a pigment. As the pigment, if the aspect ratio of the primary particles of the pigment is in the range of 1.0 or more and 2.0 or less, such as a colored inorganic pigment or a colored organic pigment usually used in conventional oil-based inkjet ink compositions Pigments can be used. These pigments may be used alone or in combination of two or more. Further, the hue of the pigment can be used without particular limitation as long as it is white, black, yellow, magenta, cyan, red, green, blue or orange. In addition, the pigment used by this embodiment is manufactured with the below-mentioned manufacturing method.

  Here, in this specification, the aspect ratio of the primary particles of the pigment is the average value of the aspect ratios of the primary particles of the individual pigments calculated by the ratio of (major axis length) / (minor axis length). It is. Specifically, the pigment powder is observed with a TEM (transmission electron microscope) or SEM (scanning electron microscope), and images of individual pigment particles are acquired. Then, the particle diameter (diameter) is measured at an interval of 1 ° from the angle 0 ° to 179 ° from the center of gravity of the acquired image of each pigment particle, and the maximum value of the 180 measured particle diameters is the long axis. The aspect ratio of the primary particle of each pigment is obtained by setting the minimum length to the length of the minor axis. Moreover, the average value of the aspect ratio of 100 or more pigment particles obtained in this way was used as the average value of the aspect ratio.

  When the aspect ratio of the primary particle of the pigment is in the range of 1.0 or more and 2.0 or less, since the shape of the pigment particle is pseudospherical, the interaction (aggregation attractive force) between the pigments is reduced, and In this case, it is possible to suppress the occurrence of unstable discharge due to flocculation at the nozzle. Further, since the pigment is stably dispersed in the ink, an increase in the ink viscosity due to the aggregation of the pigment can be suppressed. Thereby, the storage stability and ejection stability of the ink are excellent. In addition, since the nozzle surface can be prevented from being damaged by the polishing effect of the pigment at the time of wiping in the cleaning of the inkjet head, an oil-based inkjet recording liquid having excellent wiping durability is obtained.

  The aspect ratio of the primary particles of the pigment is preferably 1.1 or more and 1.9 or less, and more preferably about 1.2 or more and 1.8 or less. When the primary particles of the pigment have such an aspect ratio, the shape becomes closer to a sphere, so that each performance is improved.

  As for the primary particle diameter of the pigment in the oil-based recording liquid, the 90% integrated value (D90) of the number distribution of the primary particle diameter of the pigment is preferably 100 nm or less. In the present specification, the primary particle diameter of the pigment is obtained as follows. First, the pigment powder is observed with a TEM or SEM, and images of individual pigment particles are acquired. Next, the particle diameter (diameter) is measured from the center of gravity of the acquired image of each pigment particle at an interval of 1 ° in an angle range of 0 ° to 179 °, and the average value of the 180 measured particle sizes is the same. The primary particle diameter of pigment particles was used. Further, the 10% integrated value (D10) and 90% integrated value (D90) of the number distribution of the primary particle diameters of the pigments were determined from the measured primary particle diameters of 100 or more pigment particles thus obtained. .

  In this embodiment, the aspect ratio of the primary particles of the pigment is in the range of 1.0 to 2.0, and the 90% integrated value (D90) of the number distribution of the primary particle diameter of the pigment is 100 nm or less. In some cases, the cohesiveness of the pigment can be further reduced. Therefore, the storage stability and ejection stability of the ink are further improved. Further, since the polishing effect is also reduced, the wiping durability is further improved. D90 is more preferably 90 nm or less, and still more preferably 85 nm or less.

  The dispersed particle diameter often used as the particle diameter of the pigment means the diameter of dispersed particles (composite particles) formed from a pigment and a resin (dispersant) for dispersing the pigment in a medium. The composite particles of the pigment and the resin cannot reflect the size of the pigment because of the large resin adsorption amount, and may not correlate with various characteristics due to the pigment characteristics. Therefore, in the present invention, the aspect ratio of the primary particle of the pigment and the D90 of the primary particle diameter of the pigment are used as parameters, and by controlling these, the performance of the recording liquid including various characteristics due to the pigment is effectively improved. It becomes possible to design.

  Examples of pigments that can be used in the oil-based inkjet recording liquid according to the present embodiment include azo pigments such as azo lakes, insoluble azo pigments, condensed azo pigments, and chelate azo pigments; phthalocyanine pigments, perylene and perylene pigments, anthraquinone pigments, quinacridone pigments, Polycyclic pigments such as dioxazine pigments, thioindigo pigments, isoindolinone pigments, quinophthalone pigments; dye lakes such as basic dye type lakes and acid dye type lakes; nitro pigments, nitroso pigments, aniline black, daylight fluorescent pigments, etc. Organic pigments; inorganic pigments such as carbon black.

  More specifically, examples of the pigment when the oil-based inkjet recording liquid according to this embodiment is magenta or red ink include C.I. I. Pigment red 2, C.I. I. Pigment red 3, C.I. I. Pigment red 5, C.I. I. Pigment red 6, C.I. I. Pigment red 7, C.I. I. Pigment red 15, C.I. I. Pigment red 16, C.I. I. Pigment red 48: 1, C.I. I. Pigment red 53: 1, C.I. I. Pigment red 57: 1, C.I. I. Pigment red 122, C.I. I. Pigment red 123, C.I. I. Pigment red 139, C.I. I. Pigment red 144, C.I. I. Pigment red 149, C.I. I. Pigment red 166, C.I. I. Pigment red 170, C.I. I. Pigment red 177, C.I. I. Pigment red 178, C.I. I. Pigment red 194, C.I. I. Pigment red 209, C.I. I. Pigment red 222, C.I. I. Pigment red 224, C.I. I. Pigment violet 19 and the like.

  Examples of the pigment when the oil-based inkjet recording liquid according to the present embodiment is an orange or yellow ink include C.I. I. Pigment orange 31, C.I. I. Pigment orange 43, C.I. I. Pigment orange 64, C.I. I. Pigment yellow 12, C.I. I. Pigment yellow 13, C.I. I. Pigment yellow 14, C.I. I. Pigment yellow 15, C.I. I. Pigment yellow 17, C.I. I. Pigment yellow 74, C.I. I. Pigment yellow 93, C.I. I. Pigment yellow 94, C.I. I. Pigment yellow 128, C.I. I. Pigment yellow 138, C.I. I. Pigment yellow 150, C.I. I. And CI Pigment Yellow 180.

  Examples of the pigment when the oil-based inkjet recording liquid according to the present embodiment is green or cyan ink include C.I. I. Pigment blue 15, C.I. I. Pigment blue 15: 2, C.I. I. Pigment blue 15: 3, C.I. I. Pigment blue 15: 4, C.I. I. Pigment blue 16, C.I. I. Pigment blue 60, C.I. I. Pigment green 7, C.I. I. And CI Pigment Green 36.

  Examples of the pigment when the oil-based inkjet recording liquid according to the present embodiment is a black ink include carbon black.

  Examples of the pigment when the oil-based inkjet recording liquid according to this embodiment is white ink include C.I. I. Pigment white 6, C.I. I. Pigment white 18, C.I. I. And CI Pigment White 21.

  Among the pigments, when the pigment is quinacridone or copper phthalocyanine, the performance is improved by controlling the aspect ratio of the primary particle of the pigment and further the primary particle diameter of the pigment.

  The content of the pigment in the oil-based recording liquid according to the present embodiment can be appropriately selected depending on the application and printing characteristics. However, since excellent concealability and color reproducibility are obtained, the total mass (100 mass) of the recording liquid is obtained. %) Is preferably contained in the range of 0.01% by mass to 20% by mass, more preferably 0.5% by mass to 15% by mass, and particularly preferably 1% by mass to 10% by mass. It is as follows.

1.2. Oily medium The oily recording liquid according to this embodiment contains an oily medium. Here, the “oil-based medium” in this specification refers to a liquid medium in which a pigment or the like is dispersed contains an organic solvent, and refers to a liquid medium at normal temperature and pressure. Here, when the oil-based medium is an organic solvent-containing material composed of an organic solvent and a mixture other than the organic solvent, the organic solvent content exceeds 5% by mass.

  As the oil-based medium used in the oil-based recording liquid according to the present embodiment, any of various known vegetable oils and / or petroleum-based solvents can be used, and both nonpolar organic solvents and polar organic solvents are used. Is possible.

1.2.1. Nonpolar Organic Solvent Examples of the nonpolar organic solvent used in the oil-based recording liquid according to the present embodiment include petroleum solvents such as hydrocarbon solvents, fluorine solvents, and silicon solvents. Preferred examples of the petroleum solvent include an aliphatic hydrocarbon solvent, an alicyclic hydrocarbon solvent, and an aromatic hydrocarbon solvent. As the aliphatic hydrocarbon solvent and the alicyclic hydrocarbon solvent, commercially available ones may be used. For example, Nippon Oil Corporation Tclean N-16, Tclean N-20, Tclean N-22, Sun Stone Naphthezol L, Nisseki Naphthezol M, Nisseki Naphthezol H, No. 0 Solvent L, No. 0 Solvent M, No. 0 Solvent H, Nisseki Isosol 300, Nisseki Isosol 400, AF-4, AF-5, AF-6 , AF-7, Isopar G, IsoparH, IsoparL, IsoparM, ExxsolD40, ExxsolD80, ExxsolD100, ExxsolD130, ExxsolD140, etc., manufactured by ExxonMobil Co., Ltd. can be preferably exemplified. Examples of the aromatic hydrocarbon solvent include Nippon Oil Corporation Nisseki Cleansol G (alkylbenzene), ExxonMobil Corporation Solvesso 200, and the like.

1.2.2. Polar organic solvent Examples of the polar organic solvent used in the oil-based recording liquid according to this embodiment include ester solvents, alcohol solvents, amide solvents, fatty acid solvents, ether solvents, and the like.

  Examples of the ester solvent include higher fatty acid esters having 5 or more carbon atoms in one molecule, preferably 9 or more carbon atoms in one molecule, more preferably 12 to 32 carbon atoms in one molecule. For example, isodecyl isononanoate, isotridecyl isononanoate, isononyl isononanoate, methyl laurate, isopropyl laurate, isopropyl myristate, isopropyl palmitate, isooctyl palmitate, hexyl palmitate, isostearyl palmitate, isooctyl isopalmitate, olein Methyl acid, ethyl oleate, isopropyl oleate, butyl oleate, hexyl oleate, methyl linoleate, isobutyl linoleate, ethyl linoleate, butyl stearate, hexyl stearate, isotearic acid Octyl, isopropyl isostearate, 2-octyldodecyl pivalate, diisopropyl adipate, diisopropyl sebacate, diethyl sebacate, propylene glycol monocaprylate, trimethylolpropane tri-2-ethylhexanoate, glyceryl tri-2-ethylhexanoate, etc. Can be mentioned. In addition, soybean oil fatty acid methyl, soybean oil fatty acid isobutyl, linseed oil fatty acid methyl, linseed oil fatty acid butyl, linseed oil fatty acid propyl, linseed oil fatty acid 2-ethylhexyl, tung oil fatty acid methyl, tall oil fatty acid which are esters of drying oil fatty acid and alcohol Examples include methyl and tall oil fatty acid isobutyl.

  Examples of the cyclic ester include β-propiolactone, β-butyrolactone, γ-butyrolactone, γ-valerolactone, γ-caprolactone, σ-valerolactone, and ε-caprolactone.

  Examples of the alcohol solvent include methyl alcohol, ethyl alcohol, propyl alcohol, butyl alcohol, isopropyl alcohol, and fluorinated alcohol. In particular, the alcohol solvent is preferably an aliphatic higher alcohol having 12 or more carbon atoms in one molecule. For example, higher solvents such as hexadecanol, isomyristyl alcohol, isopalmityl alcohol, isostearyl alcohol, oleyl alcohol and the like. Alcohol etc. are mentioned.

  Examples of polyhydric alcohols include ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, polypropylene glycol, propylene glycol, butylene glycol, 1,2,6-hexanetriol, thioglycol, hexylene glycol, glycerin, Examples include trimethylolethane and trimethylolpropane.

  Examples of the amide solvent include acetamide, dimethylacetamide, N-methylpyrrolidinone and the like.

  Examples of the fatty acid solvent include fatty acids having 4 or more carbon atoms in one molecule, preferably 9 to 22 carbon atoms in one molecule. For example, isononanoic acid, isomyristic acid, hexadecanoic acid, isopalmitin Acid, oleic acid, isostearic acid and the like can be mentioned.

  Examples of the ether solvent include glycol ethers such as diethylene glycol monobutyl ether, ethylene glycol monobutyl ether, propylene glycol monobutyl ether, propylene glycol dibutyl ether, and acetates of glycol ethers.

  Examples of the ketone solvent include acetone, methyl ethyl ketone, and cyclohexanone.

  Amines may be blended, for example, hydroxylamines such as triethanolamine, tripropanolamine, tributanolamine, N, N-dimethyl-2-aminoethanol, N, N-diethyl-2-aminoethanol, etc. Can be mentioned.

  One or a plurality of the oily media exemplified here can be added to the oily recording liquid in an appropriate blending amount, but 50% by mass or more of the oily medium is preferably a petroleum solvent. In this case, since the pigment surface is coated with a solvent, the cohesiveness of the pigment is further reduced, and the slipperiness of the pigment surface is improved. For this reason, the pigment is further stably dispersed in the recording liquid, and the oil-based ink jet recording liquid is excellent in storage stability and ejection stability and excellent in wiping durability.

1.3. Resin The oil-based inkjet recording liquid according to the present embodiment contains a resin as a dispersant. As the resin, any dispersant used in a normal oil-based recording liquid can be used from the viewpoint of improving the dispersion stability of the pigment. The resin that can be used in the present invention is not particularly limited as long as the pigment is stably dispersed in the solvent. For example, Solsperse 5000, Solsperse 13940, Solsperse 11200, Solsperse 21000, Solsperse 28000 manufactured by Nippon Lubrizol Corporation. Etc.

  In particular, the resin is selected from a urethane-modified acrylic resin, a fatty acid-modified alkyd resin, and a urethane-modified alkyd resin in order to ensure the dispersion stability of the pigment by coating the pigment surface including a highly active site on the pigment surface. Resins are preferred. When the resin is any one of these, the resin adsorptivity to the pigment surface is improved, and the aggregation property of the pigment is greatly reduced. For this reason, storage stability and ejection stability are further improved. In addition, since the pigment is more stably dispersed in the ink, the droplet formability when ejected from the inkjet nozzle is improved. For this reason, the ejection stability is improved, and continuous stable ejection is possible particularly in high-speed line-type ink jet recording that requires high durability. Furthermore, since the adhesion of the pigment to the nozzle surface is reduced, the wiping durability is further improved.

  In the oil-based recording liquid according to this embodiment, the content of the resin can be appropriately selected depending on the pigment to be dispersed, but the content of the resin dissolved in the oil-based medium in the oil-based recording liquid is 0.1. The content is preferably from 10% by mass to 10% by mass, and more preferably from 1% by mass to 5% by mass. In this range, the pigment is more stably dispersed in the recording liquid, so that storage stability, ejection stability, and wiping durability are improved. The mass ratio of pigment to resin (pigment / resin) in the oil-based recording liquid is preferably in the range of 0.5 to 2.0, more preferably 1.0 to 1.5. is there.

1.4. Other Components Other additives contained in a normal oil-based recording liquid may be further added to the oil-based inkjet recording liquid according to the present embodiment. Examples of other additives include stabilizers such as antioxidants and ultraviolet absorbers, surfactants, binder resins, and the like.

<Antioxidant>
Examples of the antioxidant include BHA (2,3-butyl-4-oxyanisole), BHT (2,6-di-t-butyl-p-cresol) and the like.

<Ultraviolet absorber>
Examples of the ultraviolet absorber include benzophenone compounds and benzotriazole compounds.

<Binder resin>
In the oil-based inkjet recording liquid according to this embodiment, a binder resin may be added for the purpose of fixing the pigment to the recording medium or adjusting the viscosity of the recording liquid. Examples of the binder resin include acrylic resin, styrene acrylic resin, rosin modified resin, phenol resin, terpene resin, polyester resin, polyamide resin, epoxy resin, vinyl chloride vinyl acetate copolymer resin, cellulose acetate butyrate and the like. Resin, vinyltoluene-α-methylstyrene copolymer resin, and the like. These binder resins may be used alone or in combination of two or more. By containing these resins, the fixing property to the recording medium can be improved and the abrasion resistance is also improved.

  The solid content of the binder resin in the oil-based inkjet recording liquid according to this embodiment is preferably 0.05% by mass to 15% by mass, more preferably 0.1% by mass to 10% by mass, and still more preferably. It is 1 mass% or more and 5 mass% or less.

<Surfactant>
In the oil-based inkjet recording liquid according to the present embodiment, from the viewpoint of reducing surface tension and improving wettability with a recording medium, a silicon-based surfactant, a fluorine-based surfactant, or a nonionic surfactant is used. A certain polyoxyethylene derivative may be added.

  As the silicon surfactant, it is preferable to use polyester-modified silicon or polyether-modified silicon. Specific examples include BYK-315, 315N, 347, 348, BYK-UV3500, 3510, 3530, 3570 (all manufactured by Big Chemie Japan Co., Ltd.).

  As the fluorosurfactant, it is preferable to use a fluorine-modified polymer. Specific examples include BYK-340 (manufactured by BYK Japan), Surflon S-211, S-131, S-132, S-. 141, S-144, S-145 (manufactured by Asahi Glass Co., Ltd.), aftergent 100, 150, 251 (manufactured by Neos Co., Ltd.), Megafax F477 (manufactured by DIC Corporation), FC-170C, FC-430, Fluorard FC4430 (manufactured by Sumitomo 3M); FSO, FSO-100, FSN, FSN-100, FS-300 (manufactured by Dupont); FT-250, 251 (manufactured by Neos) and the like.

  As the polyoxyethylene derivative, it is preferable to use an acetylene glycol surfactant. Specific examples include Surfinol 82, 104, 465, 485, TG (all manufactured by Air Products Japan Co., Ltd.), Olphine STG, E1010 (all manufactured by Nissin Chemical Co., Ltd.), Nissan Nonion A-10R, A-. 13R (all manufactured by NOF Corporation), Floren TG-740W, D-90 (manufactured by Kyoeisha Chemical Co., Ltd.), Neugen CX-100 (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) and the like.

  The content of the surfactant in the oil-based inkjet recording liquid according to the present embodiment is preferably 0.05% by mass to 3% by mass, more preferably 0.1% by mass to 2% by mass, and still more preferably 0%. It is 5 mass% or more and 1 mass% or less.

  Furthermore, the oil-based inkjet recording liquid according to the present embodiment may include a pH adjuster, a chelating agent such as ethylenediaminetetraacetate (EDTA), an antiseptic / antifungal agent, and a rust preventive as required. Substances for imparting performance can be added.

1.5. Physical Properties The oil-based inkjet recording liquid according to this embodiment preferably has a surface tension at 20 ° C. of 20 mN / m or more and 50 mN / m from the viewpoint of the balance between recording quality and reliability as an inkjet ink composition. More preferably, it is 25 mN / m or more and 40 mN / m or less. The surface tension is measured by using an automatic surface tension meter CBVP-Z (manufactured by Kyowa Interface Science Co., Ltd.) by confirming the surface tension when the platinum plate is wet with ink in an environment of 20 ° C. can do.

  From the same viewpoint, the viscosity at 20 ° C. of the oil-based inkjet recording liquid according to this embodiment is preferably 2 mPa · s to 30 mPa · s, and more preferably 2 mPa · s to 20 mPa · s. preferable. The viscosity is measured by using a viscoelasticity tester MCR-300 (manufactured by Pysica Corporation), increasing the Shear Rate to 10 to 1000 in an environment of 20 ° C., and reading the viscosity at Shear Rate 200. Can be measured.

1.6. Application The oil-based inkjet recording liquid according to this embodiment is stored in an ink cartridge of a known inkjet recording apparatus, ejects ink droplets, and attaches the droplets to a recording medium such as paper to record an image. As the ink jet recording apparatus, an ink jet recording apparatus in which an electrostrictive element that can vibrate based on an electric signal is mounted and ink can be ejected by vibration of the electrostrictive element is preferable.

  As a method of discharging the oil-based inkjet recording liquid from the nozzle, for example, a strong electric field is applied between the nozzle and the acceleration electrode placed in front of the nozzle, and the droplet-shaped oil-based recording liquid is continuously discharged from the nozzle. A method in which droplets of oil-based recording liquid are ejected in response to recording information signals while flying between the deflection electrodes (electrostatic suction method); pressure is applied to the oil-based recording liquid with a small pump, and the nozzle is driven by a quartz crystal vibrator, etc. A method of forcibly ejecting oily recording liquid droplets by mechanical vibration; a method of simultaneously applying pressure and recording information signals to the oily recording liquid using a piezoelectric element, and ejecting and recording oily recording liquid droplets (Piezo method); a method (thermal jet method) in which an oil-based recording liquid is heated and foamed with a microelectrode according to a recording information signal, and droplets of the oil-based recording liquid are ejected and recorded.

  As the ink jet head, either a line type ink jet head or a serial type ink jet head can be used. The oil-based inkjet recording liquid according to the present embodiment enables continuous and stable ejection, particularly in a recording mode that requires high durability such as high-speed one-pass inkjet recording using an inkjet recording apparatus equipped with a line-type inkjet head. Highly effective. Further, since the pigment is more stably dispersed in the recording liquid, the color developability and fastness of the obtained image are ensured.

  In this embodiment, the recording medium to be printed is not particularly limited, and can be used for any type of recording medium such as plain paper, coated paper, plastic film, fabric, leather, etc., and has low ink absorption. Alternatively, a non-absorbable recording medium may be used.

In the present specification, the “ink-absorbing or non-absorbing recording medium” refers to a recording medium having a property of not absorbing or hardly absorbing an ink composition. Quantitatively, a non-ink-absorbing or low-absorbing recording medium is a “recording medium having a water absorption of 10 mL / m ² or less from the start of contact to 30 msec ^1/2 in the Bristow method”. Point to. This Bristow method is the most popular method for measuring the amount of liquid absorbed in a short time, and is also adopted by the Japan Paper Pulp Technology Association (JAPAN TAPPI). For details of the test method, refer to Standard No. of “JAPAN TAPPI Paper Pulp Test Method 2000”. 51 "Paper and paperboard-Liquid absorbency test method-Bristow method". On the other hand, an ink-absorbing recording medium refers to a recording medium that does not correspond to a non-ink-absorbing or low-absorbing recording medium.

  Examples of non-ink-absorbing recording media include plastic films that do not have an ink absorbing layer, those that are coated with plastic on a substrate such as paper, and those that have a plastic film adhered thereto. . Examples of the plastic here include polyvinyl chloride, polyethylene terephthalate, polycarbonate, polystyrene, polyurethane, polyethylene, and polypropylene.

  Examples of the recording medium with low ink absorption include a recording medium provided with a coating layer for receiving ink on the surface. For example, as the base material is paper, art paper, coated paper, mat For example, when the base material is a plastic film, a hydrophilic polymer is applied to the surface of polyvinyl chloride, polyethylene terephthalate, polycarbonate, polystyrene, polyurethane, polyethylene, polypropylene, etc. , Silica and titanium particles are coated with a binder. These recording media may be transparent recording media.

2. Method for Producing Oil-Based Inkjet Recording Liquid The oil-based inkjet recording liquid according to this embodiment can be produced by a known conventional method, and the production process includes a step of surface-treating the pigment using a pigment derivative. . That is, when preparing a pigment dispersion by adding a solvent to the pigment, a pigment dispersion is prepared by adding a pigment derivative and mixing by a ball mill, a bead mill, an ultrasonic wave, a jet mill or the like. By passing through this step, the shape of the primary particle of the pigment can be accurately controlled, and a pigment having an aspect ratio of the primary particle of the pigment in the range of 1.0 to 2.0 can be obtained. Furthermore, a pigment in which the primary particle aspect ratio of the pigment is in the range of 1.0 to 2.0 and the 90% integrated value (D90) of the number distribution of the primary particle diameter of the pigment is 100 nm or less is obtained. .

  The step is preferably salt milling using pulverized salt (salt), and it is preferable to wash the mixture after the salt milling. In the case of salt milling, since a large shearing force is applied to the pigment, the shape of the primary particles of the pigment can be controlled more accurately.

  To the obtained pigment dispersion, a resin as a dispersant, an oily medium, and other additives (for example, a surfactant and a binder resin) are added with stirring, and the oil-based inkjet recording liquid according to the present embodiment is obtained. can get.

  In the step of surface-treating the pigment using the pigment derivative, the control of the primary particle shape of the pigment depends on the amount ratio of the pigment to the pigment derivative. For this reason, in order to obtain the oil-based inkjet recording liquid according to the present embodiment, the primary particle shape control (pigment) / (pigment derivative) ratio of the pigment is preferably 10 or more and 30 or less, and 12 or more and 25. The following is more preferable.

3. Examples and Comparative Examples Examples and Comparative Examples are shown below to further illustrate the present invention, but the present invention is not limited to the following examples. “Part” and “%” in Examples and Comparative Examples are based on mass unless otherwise specified.

3.1. Sample preparation 3.1.1. Preparation of pigment (Pigment 1)
The following raw materials were filled in a 10 L double arm kneader (TK10 manufactured by Toshin Co., Ltd.), and salt milling was performed at 80 ° C. for 10 hours.
Fastens Super Magenta RTS (made by DIC Corporation)
500 parts by weight Quinacridone derivative (following (1)) 40 parts by weight Ground salt (salt) 3500 parts by weight Diethylene glycol 1000 parts by weight Wash the mixed product after salt milling with a filter press (manufactured by Kurita Machinery Co., Ltd., manual filter) A dehydration treatment was performed with a press SQ (PP), followed by drying and pulverization to obtain Pigment 1.

(Pigment 2)
In Pigment 1, the addition amount of the quinacridone derivative was 20 parts by mass, and the others were similarly obtained to obtain Pigment 2.

(Pigment 3)
In Pigment 2, the addition amount of pulverized salt (salt) was 2000 parts by mass, and the others were similarly obtained to obtain Pigment 3.

(Pigment 4)
In a 10 L autoclave container, 1000 parts by mass of phthalic anhydride, 1800 parts by mass of urea, 180 parts by mass of cuprous chloride, 5 parts by mass of ammonium molybdate, 1000 parts by mass of magnesium chloride, and 1000 parts by mass of sodium chloride were gradually added to 170 ° C. The mixture was heated and stirred for 4 hours to complete the reaction. After cooling, the reaction product was taken out, washed 10 times with 2% NaOH aqueous solution, 1% HCl aqueous solution and warm water in this order, repeatedly filtered, and then dried to obtain 780 parts of crude copper phthalocyanine. To 10 L double arm kneader (TK10 manufactured by Toshin Co., Ltd.), 500 parts by mass of the above crude copper phthalocyanine, 40 parts by mass of Solsperse 5000 (manufactured by Nippon Lubrizol Co., Ltd.), 3500 parts by mass of crushed salt (salt), and 1400 parts by mass of diethylene glycol were added. , Heated and ground at 90 ° C. for 7 hours. In the meantime, diethylene glycol was appropriately added so that the contents kept uniform viscosity. The obtained ground product was washed with 20 times hot water, filtered and dried to obtain Pigment 4.

(Pigment 5)
In the production method of Pigment 4, the amount of Solsperse 5000 added was 20 parts by mass, and the others were produced in the same manner.

(Pigment 6)
In Pigment 4, the addition amount of pulverized salt (sodium salt) was 2000 parts by mass, and the others were similarly obtained to obtain Pigment 6.

Table 1 shows the aspect ratio and 90% integrated value (D90) of the primary particle diameters of the obtained pigments 1 to 6.

3.1.2. Preparation of resin (Resin 1: Urethane-modified acrylic resin)
A separable flask having a capacity of 5 L was charged with a Dimroth condenser, a stirring blade, and a dropping funnel, and immersed in an oil bath at 60 ° C. for 1 hour while purging with nitrogen. A monomer solution (700 g of dodecyl methacrylate, 150 g of styrene, 100 g of Karenz MOI-BM manufactured by Showa Denko KK, 50 g of Blemmer ANP-300 manufactured by Nippon Oil & Fats Co., Ltd.), 500 g of isooctyl palmitate and a polymerization initiator (Wako Pure Chemical Industries, Ltd.) V-65) manufactured by Kogyo Co., Ltd. 10 g and 10 g of dodecyl mercaptan were added and filled in a dropping funnel, and the mixture was dropped over 2 hours. After dropping, stirring was continued for another hour, 2.0 g of V-65 was added, and stirring was further continued for 1 hour to obtain an acrylic trunk polymer. Thereafter, the temperature of the oil bath was raised to 150 ° C. while refluxing, and stirring was continued for 1 hour to deblock the isocyanate monomer, and the desorbed 1-methylpropylideneamine was distilled off. The temperature of the oil bath was set to 60 ° C., 94 g of dipropylene glycol and 238 g of Takenate 600 manufactured by Mitsui Chemicals, Inc. were mixed, filled in the dropping funnel, and dropped over 1 hour. Thereafter, 854 g of isooctyl palmitate was added and mixed and dissolved to obtain a resin 1 50% by mass solution. Using DMF as a developing solution, the molecular weight of Resin 1 was measured by GPC (HLC-8320GPC manufactured by Tosoh Corporation).

(Resin 2: Fatty acid-modified alkyd resin)
A 20-liter separable flask was charged with a Dimroth condenser and a stirring blade, and heated to 260 ° C. while being purged with nitrogen, and sufficiently purged with nitrogen and heated. 2960 g of phthalic anhydride, 1420 g of linseed oil fatty acid, 990 g of pentaerythritol, and 2100 g of glycerin were added and reacted while stirring. When the acid value became 30 or less, 10 g of paratoluenesulfonic acid was added and the acid value was 20 or less. The reaction was continued until Thereafter, the reaction system was adjusted so that the 33 mass% linseed oil viscosity was 8.0 Pa · S, and the pressure was reduced at 0.02 MPa for 10 minutes. Then, it cooled and the resin 2 was obtained. Further, a part of the resin 2 was dissolved in isooctyl palmitate to obtain a 50 mass% resin 2 solution.

(Resin 3: Urethane-modified alkyd resin)
A separable flask having a capacity of 5 L was charged with a Dimroth condenser, a stirring blade, and a dropping funnel, and immersed in an oil bath at 110 ° C. for 1 hour while purging with nitrogen, and was sufficiently purged with nitrogen and heated. Resin 2 (solid) 612.4g, propylene glycol 4.4g, diethanolamine 6.0g isooctyl palmitate 225.7g was added there, and it stirred and melt | dissolved, purging with nitrogen. Then, after maintaining at 110 ° C. for 2 hours, 0.4 g of dibutyltin dilaurate was added and stirred, and 22.5 g of Takenate 600 and 202.5 g of isooctyl palmitate were added to the solution over 30 minutes from the dropping funnel. Added inside. After dropping, the dropping funnel was washed with 184.2 g of isooctyl palmitate, and the washing liquid was filled in the flask. The temperature was maintained at 110 ° C., the reaction was performed for 6 hours, and the mixture was cooled to obtain a resin 3 solution (50 mass%).

(Resin 4: Acrylic resin)
A separable flask having a capacity of 5 L was charged with a Dimroth condenser, a stirring blade, and a dropping funnel, and immersed in an oil bath at 60 ° C. for 1 hour while purging with nitrogen. A monomer solution (700 g of dodecyl methacrylate, 250 g of styrene, 50 g of Blenmer Blenmer ANP-300 manufactured by Nippon Oil & Fats Co., Ltd.) was prepared, 500 g of isooctyl palmitate, and 10 g of a polymerization initiator (V-65 manufactured by Wako Pure Chemical Industries, Ltd.), 10 g of dodecyl mercaptan was added, filled in the dropping funnel, and dropped over 2 hours. Stirring was continued for an additional hour after the addition, 2.0 g of V-65 was added, and the mixture was further stirred for 1 hour to obtain acrylic resin 4. Thereafter, 500 g of isooctyl palmitate was added and mixed and dissolved to obtain a resin 4 50 mass% solution. The molecular weight of the resin 4 was measured by GPC (HLC-8320GPC manufactured by Tosoh Corporation) using DMF as a developing solution.

3.1.3. Ink Preparation (Example 1)
AF-4 (a naphthenic solvent manufactured by JX Energy Co., Ltd.) 5000 g, Pigment 1 500 g, and Resin 1 solution 700 g were placed in a 20 L stainless steel container and stirred for 1 hour with a dissolver manufactured by Inoue Manufacturing Co., Ltd. to prepare a mill base. The mill base was Star Mill LMZ (peripheral speed 12 m / s, beads used: zirconia φ0.1 mm, bead filling rate: 85%) manufactured by Ashizawa Finetech Co., Ltd., and a 5-pass dispersion treatment was performed in a pass operation. Thereafter, the mixture was subjected to a centrifugal treatment at an acceleration of 11,000 G for 20 minutes with a cooling centrifuge (CR7N) manufactured by Hitachi Koki Co., Ltd., and then filtered with a 3 μm filter. To the filtrate, 1000 g of AF-4, 1OP g of IOP (Isooctyl Palmitate manufactured by Higher Alcohol Industry Co., Ltd.), 1150 g of Hynol 14SS (Myristyl Alcohol manufactured by Higher Alcohol Industry Co., Ltd.) 1150 g were added and stirred sufficiently to obtain the ink of Example 1. It was.

(Example 2)
The ink of Example 2 was obtained in the same manner except that the resin 1 solution of Example 1 was changed to the resin 2 solution.

(Example 3)
The ink of Example 3 was obtained in the same manner except that the resin 1 solution of Example 1 was changed to the resin 3 solution.

Example 4
The ink of Example 4 was obtained in the same manner except that the resin 1 solution of Example 1 was changed to the resin 4 solution.

(Example 5)
4650 g of IOP, 500 g of pigment, and 700 g of resin 4 solution were placed in a 20 L stainless steel container and stirred for 1 hour with a dissolver manufactured by Inoue Seisakusho Co., Ltd. to produce a mill base. The mill base was Star Mill LMZ (peripheral speed 12 m / s, beads used: zirconia φ0.1 mm, bead filling rate: 85%) manufactured by Ashizawa Finetech Co., Ltd., and a 5-pass dispersion treatment was performed in a pass operation. Thereafter, the mixture was subjected to a centrifugal treatment at an acceleration of 11,000 G for 20 minutes with a cooling centrifuge (CR7N) manufactured by Hitachi Koki Co., Ltd., and then filtered with a 3 μm filter. 3000 g of AF-4 and 1150 g of Hynol 14SS were added to the filtrate, and the mixture was sufficiently stirred to obtain the ink of Example 5.

(Example 6)
Ink of Example 5 was obtained in the same manner except that Pigment 1 of Example 5 was changed to Pigment 2.

(Example 7)
Ink of Example 7 was obtained in the same manner except that Pigment 1 of Example 1 was changed to Pigment 4.

(Example 8)
Resin 1 of Example 7 was changed to Resin 2, and the ink of Example 8 was obtained in the same manner except that.

Example 9
The ink of Example 8 was obtained in the same manner except that the resin 1 of Example 7 was changed to the resin 3.

(Example 10)
The ink of Example 10 was obtained in the same manner except that the resin 1 of Example 7 was changed to the resin 4.

(Example 11)
Ink of Example 11 was obtained in the same manner except that Pigment 1 of Example 5 was changed to Pigment 4.

(Example 12)
Ink of Example 12 was obtained in the same manner except that Pigment 4 of Example 11 was changed to Pigment 5.

(Comparative Example 1)
Ink of Comparative Example 1 was obtained in the same manner except that Pigment 1 of Example 1 was changed to Pigment 3.

(Comparative Example 2)
Ink of Comparative Example 1 was obtained in the same manner except that Pigment 1 of Example 1 was changed to Pigment 6.

3.2. Evaluation test 3.2.1. Storage Stability Test Each ink obtained was put into a sample bottle and allowed to stand frozen at −20 ° C. for 1 week. The ink after standing was thawed and filtered to collect low-temperature precipitates. The storage stability of the ink was evaluated based on the appearance of the ink after standing and the number of low-temperature precipitates. The evaluation criteria are as follows.
(Evaluation criteria)
5: Low temperature precipitates are less than 50 pieces / mL.
4: Low temperature precipitates are 50 / 1mL or more and less than 100 / 1mL.
5: Low temperature precipitates are 100 / mL or more and less than 200 / 1mL.
2: The number of low-temperature precipitates is 200 / mL or more.
1: There is separation in the ink.

3.2.2. Ejection stability test Inkjet printer manufactured by Seiko Epson Corporation PX-7050 remodeled machine is filled with the above inks, and 2P character quality, 1 dot ruled line (vertical, horizontal) on plain paper (P paper A4 manufactured by Fuji Xerox Co., Ltd.) The test pattern including the ink was continuously printed on 1000 sheets and evaluated according to the following criteria. The evaluation criteria are as follows.
(Evaluation criteria)
5: Defect rate less than 0.1% 4: Defect rate 0.1% or more and less than 1% 3: Defect rate 1% or more and less than 5% 2: Defect rate 5% or more and less than 10% 1: Defect rate 10% or more

3.2.3. Wiping Durability Test Seiko Epson Corporation Inkjet Printer SC-S50650 Remodeling Machine Filled with the above inks, 2P character quality, 1 dot ruled line (vertical, horizontal) on plain paper (P paper A4 made by Fuji Xerox Co., Ltd.) The test pattern including it was continuously printed on 1000 sheets. Subsequently, the following wiping was performed on all nozzles.

For the absorbent body (cloth wiper), a cellulose continuous fiber non-woven fabric (trade name Benize) was used. In the wiping operation, the wiping means (absorber) is brought into contact with the nozzle plate and pressed on the surface from the back of the wiping means to the nozzle plate with a pressing member with a load of 350 gf in a direction perpendicular to the nozzle row. The sample was moved 20 cm from end to end and evaluated according to the following criteria. The wiping means was in the form of a roll, and a new part was pulled out and used for the next wiping. The evaluation criteria are as follows.
(Evaluation criteria)
5: The ink is wiped clean without damaging the nozzle surface.
4: Some scratches are observed on a part of the nozzle surface, and the printing state is not affected.
3: A streak-like flaw is recognized on a part of the nozzle surface, and a printing defect (ruled line shift) occurs.
2: A streak-like flaw is recognized on the entire nozzle surface, and printing failure (dot missing) occurs.
1: Partial peeling of the water-repellent film is observed on the nozzle surface, and printing failure (multiple nozzle missing) occurs.

3.3. Evaluation results Table 2 shows the above evaluation results.

  In Comparative Examples 1 and 2 in which the aspect ratio of the primary particles of the pigment deviated from the scope of the present invention, all evaluations were inferior. On the other hand, in the examples in which the aspect ratio of the primary particles of the pigment is within the range of the present invention, all the performances are improved as compared with the comparative example. In particular, when the primary particle diameter D90 of the pigment was 100 nm or less, the performance was improved. Further, the performance was improved when a urethane-modified acrylic resin, a fatty acid-modified alkyd resin or a urethane-modified alkyd resin was used as the resin, or when 50% by mass or more of the oily medium was a petroleum solvent. Thus, in the example which controlled the shape of the primary particle using the pigment derivative, all the performances were improving compared with the comparative example.

  The present invention is not limited to the embodiments described above, and various modifications are possible. For example, the present invention includes substantially the same configuration (for example, a configuration having the same function, method and result, or a configuration having the same purpose and effect) as the configuration described in the embodiment. In addition, the invention includes a configuration in which a non-essential part of the configuration described in the embodiment is replaced. In addition, the present invention includes a configuration that exhibits the same operational effects as the configuration described in the embodiment or a configuration that can achieve the same object. In addition, the invention includes a configuration in which a known technique is added to the configuration described in the embodiment.

Claims (6)

In an oil-based inkjet recording liquid containing a pigment, an oil-based medium, and a resin,
An oil-based inkjet recording liquid in which the primary particles have an aspect ratio of 1.0 or more and 2.0 or less.   2. The oil-based inkjet recording liquid according to claim 1, wherein a 90% integrated value (D90) of a number distribution of primary particle diameters of the pigment is 100 nm or less.   The oil-based inkjet recording liquid according to claim 1 or 2, wherein the pigment is at least one selected from the group consisting of quinacridone and copper phthalocyanine.   The oil-based inkjet recording liquid according to any one of claims 1 to 3, wherein 50% by mass or more of the oil-based medium is a petroleum solvent.   The oil-based inkjet recording liquid according to any one of claims 1 to 4, wherein the resin is at least one selected from the group consisting of a urethane-modified acrylic resin, a fatty acid-modified alkyd resin, and a urethane-modified alkyd resin. . A method for producing an oil-based ink jet recording liquid comprising a pigment, an oil-based medium, and a resin,
A method for producing an oil-based inkjet recording liquid, comprising a step of surface-treating the pigment using a derivative of the pigment.