ink

Abstract

To provide an ink capable of providing a printed matter having excellent scratch resistance.SOLUTION: In an SEM-reflected electron image of a surface after being subjected to electronic staining with a heavy metal for a solid printed matter prepared using Barcoater No. 3, there is provided an ink where the area ratio of a part not subjected to electronic staining is 25% or more and 60% or less relative to the total area.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an ink, a printed matter, and an inkjet recording method. [Background technology]

[0002] The recording method using an inkjet printer (inkjet recording method) is one of the most common recording methods. This method involves generating small droplets of ink and depositing them onto various recording media (paper, film, fabric, etc.). Advances in inkjet technology have led to inkjet recording being used in the field of high-resolution printing, which previously had been achieved using silver halide photography and offset printing.

[0003] In recent years, inkjet recording apparatuses have been increasingly used in the fields of commercial printing and office printing, where printed matter with excellent abrasion resistance is in demand. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2021-021042 [Patent Document 2] Japanese Patent Publication No. 2022-146196 [Patent Document 3] Patent No. 6560846 [Patent Document 4] Patent No. 6391721 [Non-patent literature]

[0005] [Non-Patent Document 1] KWSuh,DHClarke,J.Polym.Sci.,1671,1967 [Non-patent document 2] KWSuh,JMCorbett.J.Appl.Poym.Sci.,2359,1968 Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present invention is to provide an ink that provides excellent abrasion resistance to printed matter. [Means for solving the problem]

[0007] As a result of extensive research aimed at solving the above-mentioned problems, the present inventors have found that the above-mentioned problems can be solved by using an ink that, in a backscattered electron image of the surface of a solid print produced using a No. 3 bar coater and then subjected to an electronic staining treatment with a heavy metal, results in an area that is not electronically stained being 25% or more and 60% or less of the total area, and have thus completed the present invention. That is, the present invention relates to the following 1) to 3).

[0008] That is, the present invention relates to the following 1) to 3). 1) In a backscattered electron image of the surface of a solid print made using the No. 3 bar coater after electronic staining with heavy metals, the ratio of the area of ​​the non-electron-stained area to the total area is 25% or more and 60% or less. 2) 1) The ink according to 1), which contains a binder. 3) A printed matter printed using the ink described in 1) or 2). [Effects of the Invention]

[0009] The present invention has made it possible to provide an ink that provides excellent abrasion resistance to printed matter. DETAILED DESCRIPTION OF THE INVENTION

[0010] The printed matter of the present invention will be described in detail below. In this specification, "CI" is an abbreviation for Color Index. Furthermore, in this specification, "%" and "parts" are all based on mass, including in the examples, unless otherwise specified.

[0011] When the ink of the present invention is used on a solid print produced using a No. 3 bar coater, the proportion of the area of ​​the non-electron-stained portion of the surface in a backscattered electron image taken with a scanning electron microscope (SEM) after the surface has been subjected to an electron staining treatment with a heavy metal is 25% or more and 60% or less of the total area.

[0012] [ink] The ink is not particularly limited as long as it is one in which, in an SEM backscattered electron image of the surface of a solid printed item produced using a No. 3 bar coater after electronic staining treatment with a heavy metal, the proportion of the area of ​​the portion not electronically stained relative to the total area is 25% or more and 60% or less. In this specification, the ink may be abbreviated as "ink" when, in an SEM backscattered electron image of the surface of a solid printed item produced using a No. 3 bar coater after electronic staining treatment with a heavy metal, the proportion of the area of ​​the portion not electronically stained relative to the total area is 25% or more and 60% or less. The ink will now be described in detail.

[0013] [Solid print] The ink was printed using a No. 3 bar coater so that the ink was applied to the printing surface without any gaps, and this was defined as the "solid print." By binarizing the SEM backscattered electron image using image analysis, it is possible to determine whether an area is stained (stained area) or not (unstained area). The mode method is used to determine the threshold value. Areas that become white as a result of binarization are judged to be stained areas, and areas that become black are judged to be unstained areas.

[0014] [Electron staining area ratio] The "electronic dyeing treatment" refers to the process of immersing the above-mentioned "solid print" in an aqueous solution of a heavy metal or placing it in a vapor atmosphere of the aqueous solution of the heavy metal, thereby allowing the heavy metal to penetrate into the interior of the print. Examples of the heavy metal include osmium tetroxide, ruthenium tetroxide, and phosphotungstic acid, with ruthenium tetroxide being preferred. A specific example of the aqueous solution of the heavy metal is a 0.5% aqueous solution of ruthenium tetroxide. Specific examples of the "electronic dyeing treatment" include immersing the "solid print" in a 0.5% aqueous solution of ruthenium tetroxide. The "solid print" that has been subjected to the "electron staining treatment" is subjected to SEM reflectance measurement, and the area of ​​the part that has been electronically stained by the heavy metal and the part that has not been electronically stained by the heavy metal (hereinafter sometimes abbreviated as "part that has not been electronically stained") can be determined from the electronic image. There are two types of images that can be obtained from an SEM: images obtained by detecting backscattered electrons (reflection measurement) and images obtained by detecting secondary electrons. In this invention, images obtained by SEM reflection measurement are used because they can reveal differences in the composition of the sample in more detail. Specifically, each area can be calculated by using images obtained by SEM reflectance measurement and performing binarization through image analysis. Binarization is also called two-level gradation and refers to the process of converting an image into two colors, black and white. The modal method is used to determine the threshold value for image analysis. White areas resulting from binarization are considered to be stained areas, and black areas are considered to be unstained areas. In the electronic dyeing of the ink, the ratio of the area of ​​the portion not electronically dyed to the total area of ​​the solid print is 25% or more and 60% or less of the total area.

[0015] The ink preferably contains a polymer material composed of hydrogen, carbon, nitrogen, oxygen, and the like. A compound having another element may be contained within a range that does not impair the effects of the present invention. Specific examples of the polymer material include polyethylene, polypropylene, polyamide, polyacetal, polyester, polyphenylene sulfide, polyether ether ketone, liquid crystal polymer, polytetrafluoroethylene, polyacrylates or polymethacrylates having as a constituent a monomer that can impart crystallinity to the polymer material, such as lauryl methacrylate or stearyl methacrylate, and preferred are polyethylene, polypropylene, polyesters having as a constituent an aliphatic carboxylic acid monomer, polytetrafluoroethylene, polyacrylates or polymethacrylates having as a constituent a monomer that exhibits crystallinity, such as lauryl methacrylate or stearyl methacrylate.

[0016] The polymer material is preferably in the form of a water dispersion, and the average particle size thereof is preferably 50 nm to 5 μm, more preferably 100 nm to 1 μm, in order to prevent clogging of the inkjet head.

[0017] The amount of the polymeric material is 0.01 to 5.0% by mass, preferably 0.05 to 2.0% by mass, more preferably 0.1 to 1.5% by mass, and particularly preferably 0.5 to 1.25% by mass, based on the total weight of the ink. The amount of the polymeric material added represents the solid content of emulsion particles made of the polymeric material contained in the ink.

[0018] To obtain the ink, for example, the specific gravity of the polymer material is set to be lower than the specific gravity of the ink, a hydrophobic solvent is added to the ink, or a binder, which will be described later, is made hydrophilic, or other design steps can be performed. When the specific gravity of the polymer material is set to be lower than the specific gravity of the ink, it is preferably set to be lower than the specific gravity of the binder described below, and more preferably to be lower than the specific gravity of water, 1.00. A preferred method for measuring the specific gravity is to measure the specific gravity of a 20% diluted aqueous dispersion of the polymeric material using a hydrometer. The specific gravity of the polymeric material can be calculated from the value obtained by this method using the following formula (a). In formula (a), the value of A is 1.00 because the solvent is water. Y = (X - 0.8A) ÷ 0.2 Equation (a) In the above formula (a), Y represents the specific gravity of the polymer material in the aqueous dispersion, X represents the specific gravity obtained by measurement, and A represents the specific gravity of the solvent used in the measurement.

[0019] The ink preferably contains a binder. The binder is not particularly limited, and examples thereof include one or more selected from condensation polymers such as polyurethane and polyester, and vinyl polymers such as (meth)acrylic resins, styrene resins, acrylic-styrene resins, butadiene resins, styrene-butadiene resins, vinyl chloride resins, vinyl acetate resins, and acrylic silicone resins. From the viewpoints of ejection stability, drying properties, and abrasion resistance, it is preferred that the binder be a vinyl resin and that the constituent monomer be a (meth)acrylic monomer.

[0020] The (meth)acrylic monomer is not particularly limited, but examples thereof include (meth)acrylic acid, carboxylic acids having a carbon-carbon double bond such as β-carboxyethyl acrylate, (meth)acrylic acid esters such as methyl (meth)acrylate, butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and cyclohexyl (meth)acrylate, (meth)acrylic acid esters having a hydroxyl group such as 2-hydroxyethyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate, (meth)acrylates having an allyl group such as allyl acrylate and allyl methacrylate, ethylene glycol di(meth)acrylate, 1,3-butylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, and the like. di(meth)acrylate compounds bonded with alkyl chains such as polyoxyethylene (2)-2,2-bis(4-hydroxyphenyl)propane di(meth)acrylate, 1,5-pentanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, and neopentyl glycol di(meth)acrylate; di(meth)acrylate compounds bonded with chains containing aromatic groups and ether compounds such as polyoxyethylene (2)-2,2-bis(4-hydroxyphenyl)propane di(meth)acrylate, and polyoxyethylene (4)-2,2-bis(4-hydroxyphenyl)propane di(meth)acrylate; and polyfunctional (meth)acrylic acid esters such as pentaerythritol tri(meth)acrylate, trimethylolpropane tri(meth)acrylate, tetramethylolmethane tetra(meth)acrylate, and oligoester (meth)acrylate; The binder preferably contains a C1-C4 hydroxyalkyl (meth)acrylate as a constituent monomer.

[0021] The SP value of the binder is in the range of 10.0 or more and 12.3 or less, more preferably in the range of 10.1 or more and 11.3 or less, and even more preferably in the range of 10.3 or more and 11.0 or less.

[0022] The SP value (solubility parameter) was introduced by Hildebrand and is a value defined by regular solution theory, and is a physical property that serves as a measure of compatibility. The evaporation energy per mole of liquid is ΔE V [Unit: kcal mol -1 ] and its molar volume is Vm [unit: cm 3 mol -1 ], the SP value δ [unit: (cal / cm 3 ) 0.5 ] is defined by the following formula (b). δ = (ΔE V / Vm) 1 / 2 (b)

[0023] The δ value (SP value) is used as a physicochemical constant that indicates the magnitude of intermolecular interactions in liquids. δ values ​​at room temperature calculated from measured ΔEv values ​​have been reported for many compounds (e.g., Hoy, KL, The Hoy Tables of Solubility Parameters, Union Carbide Corporation, Solvents and Coatings Materials Division, South Charlston, WV, 1985).

[0024] On the other hand, for substances that do not sublimate, such as resin particles, or for substances whose boiling points are not substantially observable, such as thermally decomposable compounds, the cohesion can be estimated using the group contribution method proposed by Hoy (Allan F.M. Barton, CRC Handbook of Solubility Parameters and Other Cohesion Parameters, 2nd ed., CRC Press (1991), pp. 165-167).

[0025] The SP value can also be experimentally measured by turbidimetric titration, which is proposed in Non-Patent Documents 1 and 2, among others.

[0026] According to the above turbidimetric titration method, the SP value can be measured, for example, in accordance with the following procedure (procedures 1 and 2).

[0027] [Step 1]: Hydrogenation of hydrophilic groups of resin particles (preparation of SP value measurement sample) (1) 200 mL of the resin particle dispersion was placed in a dialysis membrane (product name "MWCO's 0.5 m of 3.5-5 kD Biotech RC", manufactured by Spectrum Laboratories, Inc.) and immersed in 10 L of hydrochloric acid (pH 3 ± 0.5). The membrane was left to immerse for 24 hours with magnetic stirring to replace cations such as amines and alkali metals with hydrogen ions. (2) The resin particles, still in the dialysis membrane, are immersed in 12 L of ion-exchange water (pH 7±0.5) for 24 hours with magnetic stirring to neutralize the resin particles. (3) After replacing the ion-exchanged water, immerse the sample for an additional 6 hours with magnetic stirring, and confirm that the pH of the ion-exchanged water is 7±0.5. (4) Immerse in 2 L of ethanol for 8 hours and remove water with magnetic stirring. (5) The resin particles removed from the dialysis membrane are placed in a dry 500 mL beaker and dried under reduced pressure for 6 hours while maintaining the temperature at 80°C to remove the ethanol. (6) The completely dried resin particles are ground to obtain a powder, which is used as a dry resin particle sample.

[0028] [Step 2]: Measuring the SP value (1) Weigh out 0.500 g ± 0.005 g of dry resin particle sample into a 50 mL Erlenmeyer flask. (2) Add 10 mL of tetrahydrofuran (THF) and dissolve the dried resin particle sample to prepare a sample solution. (3) The prepared sample solution is cooled with magnetic stirring, and titrated with n-hexane to the cloudy point (mL) while maintaining the temperature at 25°C. Specifically, an Erlenmeyer flask containing the sample solution is kept at 25°C and placed on a piece of Mincho font (12pt) printed on plain paper by electrophotography. When viewed from above, the liquid layer becomes cloudy and the letters become blurred and illegible. This is the titration point. (4) Using the same procedure, titrate the turbidity point (mL) of ion-exchanged water. (5) The SP value δ (cal / cm) of the resin particles is calculated according to the following formulas (1) to (9): 3 ) 1 / 2 Calculate.

[0029] (formula) TIFF2025167710000001.tif161170

[0030] The meaning and value of each variable are as follows: L: Titration volume (mL) of low polarity solvent (n-hexane) H: Titration volume of highly polar solvent (water) (mL) φ SL : Volume fraction of the dissolving solvent (THF) to the sum of the dissolving solvent (THF) and the titration solvent (n-hexane) φ L : Volume fraction of the titration solvent (n-hexane) to the sum of the dissolving solvent (THF) and the titration solvent (n-hexane) φ SH : Volume fraction of the dissolving solvent (THF) to the sum of the dissolving solvent (THF) and the titration solvent (ion-exchanged water) φ H : Volume fraction of titration solvent (ion-exchanged water) to the sum of dissolving solvent (THF) and titration solvent (ion-exchanged water) V S : Molar volume of dissolving solvent (THF) [mL / mol] = 81.0 V L Molar volume of titration solvent (n-hexane) [mL / mol] = 132 V H Molar volume of titration solvent (ion-exchanged water) [mL / mol] = 18.0 δ S : SP value of dissolving solvent (THF) [(cal / cm 3 ) 1 / 2 〕=9.54 δ L : SP value of titration solvent (n-hexane) [(cal / cm 3 ) 1 / 2 〕=7.24 δ H: SP value of titration solvent (ion-exchanged water) [(cal / cm 3 ) 1 / 2 〕=23.5 δ SL : SP value of the mixed solution when titrated with the titration solvent (n-hexane) δ SH : SP value of the mixed solution when titrated with the titration solvent (ion-exchanged water) δ: SP value of resin particles (cal / cm 3 ) 1 / 2 〕

[0031] [Step 1]: The purpose of hydrogenating the hydrophilic groups of resin particles (preparing the sample for SP value measurement) is to obtain a dry powder of resin particles, so if this purpose can be achieved, the dry powder can also be obtained by the following method: A resin particle dispersion is dropped into a poor solvent to precipitate resin fine particles, which are then filtered and dried, and a dry powder of resin particles is obtained by freeze-drying.

[0032] The SP value is 9.0 (cal / cm 3 ) 1 / 2 ] In the case of resin particles that are not easily soluble in THF, as shown below, p-xylene or toluene can be used instead of THF as a solvent to dissolve the dry resin particle sample. In this case, the variables change as shown below.

[0033] φ SL : Volume fraction of the dissolving solvent (p-xylene / toluene) relative to the sum of the dissolving solvent (p-xylene / toluene) and the titration solvent (n-hexane) φ L : Volume fraction of the titration solvent (n-hexane) to the sum of the dissolving solvent (p-xylene / toluene) and the titration solvent (n-hexane) φ SH : Volume fraction of the dissolving solvent (p-xylene / toluene) relative to the sum of the dissolving solvent (p-xylene / toluene) and the titration solvent (ion-exchanged water) φ H : Volume fraction of the titration solvent (ion-exchanged water) relative to the sum of the dissolution solvent (p-xylene / toluene) and the titration solvent (ion-exchanged water) V SMolar volume of dissolving solvent (p-xylene / toluene) [mL / mol] = 123 / 106 δ S : SP value of dissolving solvent (p-xylene / toluene) [(cal / cm 3 ) 1 / 2 〕=8.80 / 8.91 The SP value in the present invention is affected not only by the type of resin and constituent monomers, but also by a variety of factors such as the resin skeleton, which varies depending on the molecular weight and branching structure, the type and amount of initiator used, the type and amount of chain transfer agent, etc. Therefore, the SP value cannot be accurately derived by calculation, and an experimentally measured value must be used.

[0034] The glass transition temperature (Tg) of the binder is preferably 35 to 150° C., and more preferably 55 to 120° C. The glass transition temperature (Tg) of the resin is a value measured by a method such as differential scanning calorimetry (DSC).

[0035] The weight-average molecular weight of the binder is preferably 30,000 to 120,000. The weight-average molecular weight of the binder can be measured by gel permeation chromatography (GPC). Specifically, the measurement can be performed using an HLC-8320GPC (manufactured by Tosoh Corporation) as a GPC device, two TSK gel Super Multipore HZ-H columns (manufactured by Tosoh Corporation, inner diameter 4.6 mm × 15 cm), tetrahydrofuran as an eluent, and TSK Standard (manufactured by Tosoh Corporation) as a standard sample.

[0036] The acid value of the binder is preferably 5 to 150 mgKOH / g, more preferably 10 to 120 mgKOH / g, and even more preferably 15 to 75 mgKOH / g. The acid value of a polymer represents the number of mg of KOH required to neutralize 1 g of the polymer, and can be measured according to JIS-K3054.

[0037] Examples of the binder having the SP value, glass transition temperature (Tg), and weight-average molecular weight within the above ranges include those containing, as constituent monomers, C1-C4 alkyl (meth)acrylate, C1-C4 hydroxyalkyl (meth)acrylate, and C6-C10 alkyl (meth)acrylate, etc. Examples of the binder having an acid value of 5 to 150 mgKOH / g include those containing, as constituent monomers, carboxylic acid having a carbon-carbon double bond.

[0038] The alkyl portion of the C1-C4 alkyl (meth)acrylate may be linear or branched, preferably linear. Two or more C1-C4 alkyl (meth)acrylates may be mixed and used. As the C1-C4 alkyl (meth)acrylate, C1-C3 alkyl (meth)acrylate is preferred, C1-C2 alkyl (meth)acrylate is more preferred, and methyl methacrylate is even more preferred.

[0039] The hydroxyalkyl moiety of the C1-C4 hydroxyalkyl (meth)acrylate may be linear or branched, preferably linear. Two or more C1-C4 hydroxyalkyl (meth)acrylates may be mixed and used. As the C1-C4 hydroxyalkyl (meth)acrylate, C1-C3 hydroxyalkyl (meth)acrylate is preferred, C1-C2 hydroxyalkyl (meth)acrylate is more preferred, and 2-hydroxyethyl (meth)acrylate is even more preferred.

[0040] The alkyl moiety of the C6-C10 alkyl acrylate may be linear or branched, preferably branched. As the C6-C10 alkyl acrylate, C7-C9 alkyl acrylate is preferred, C8 alkyl acrylate is more preferred, and 2-ethylhexyl acrylate is even more preferred.

[0041] Examples of the carboxylic acid having a carbon-carbon double bond include acrylic acid, methacrylic acid, and β-carboxyethyl acrylate, with methacrylic acid being more preferred.

[0042] When the binder contains, as constituent monomers, C1-C4 alkyl (meth)acrylate, C1-C4 hydroxyalkyl (meth)acrylate, C6-C10 alkyl (meth)acrylate, and a carboxylic acid having a carbon-carbon double bond, the proportions of the four constituent monomers, C1-C4 alkyl (meth)acrylate, C1-C4 hydroxyalkyl (meth)acrylate, C6-C10 alkyl (meth)acrylate, and a carboxylic acid having a carbon-carbon double bond, are each 55 to 90% by weight. The content is preferably 5 mass%, 0.1 to 25 mass%, 0 to 45 mass%, and 2 to 15 mass%, and more preferably 65 to 90 mass%, 3 to 10 mass%, 0 to 31 mass%, and 4 to 10 mass%, and it is preferable that the total amount be within these ranges to 100 mass%. When the mass content of methyl methacrylate is X and the mass content of 2-hydroxyethyl (meth)acrylate is Y, out of the total mass of the constituent monomers, the value represented by X / Y is preferably in the range of 2.5 to 75.0, and more preferably in the range of 5.5 to 35.0.

[0043] The binder preferably contains, as constituent monomers, a C1-C4 alkyl (meth)acrylate and a C6-C10 alkyl (meth)acrylate, the respective contents of which are 55 to 95 mass % and 0.1 to 45 mass % relative to the total mass of the binder solid content.

[0044] The constituent monomers of the binder may include non-(meth)acrylic monomers such as propylene, butadiene, styrene chloride, maleic acid, styrene, chlorostyrene, and α-methylstyrene. For example, there are crosslinkable vinyl monomer units, specifically aromatic divinyl compounds such as divinylbenzene and divinylnaphthalene; (meth)acrylates having an allyl group such as allyl acrylate and allyl methacrylate; diacrylate compounds bonded by alkyl chains such as ethylene glycol diacrylate, 1,3-butylene glycol diacrylate, 1,4-butanediol diacrylate, 1,5-pentanediol diacrylate, 1,6-hexanediol diacrylate, neopentyl glycol diacrylate, and compounds in which the acrylate in the above compounds is replaced with methacrylate; diacrylate compounds bonded by alkyl chains containing ether bonds such as diethylene glycol diacrylate, triethylene glycol diacrylate, tetraethylene glycol diacrylate, and polyethylene glycol. 400 diacrylate, polyethylene glycol #600 diacrylate, dipropylene glycol diacrylate, and compounds in which the acrylate in the above compounds is replaced with methacrylate; diacrylate compounds linked by chains containing aromatic groups and ether compounds, such as polyoxyethylene (2)-2,2-bis(4-hydroxyphenyl)propane diacrylate, polyoxyethylene (4)-2,2-bis(4-hydroxyphenyl)propane diacrylate, and compounds in which the acrylate in the above compounds is replaced with methacrylate; polyfunctional crosslinking agents include pentaerythritol triacrylate, trimethylolpropane triacrylate, tetramethylolmethane tetraacrylate, oligoester acrylate, and compounds in which the acrylate in the above compounds is replaced with methacrylate; triallyl cyanurate, triallyl trimellitate, and the like.

[0045] The binder is preferably a water dispersion, and the average particle size thereof is preferably 50 nm to 5 μm, more preferably 100 nm to 1 μm, in order to prevent clogging of the inkjet head.

[0046] The content of the binder (content as solid content) is usually 0.1 to 14% by mass, preferably 0.5 to 12% by mass, and more preferably 2 to 10% by mass, relative to the total mass of the ink.

[0047] The ink may contain a colorant. The colorant is not particularly limited, but examples thereof include pigments and disperse dyes.

[0048] Examples of the pigment include inorganic pigments, organic pigments, extender pigments, and hollow particles. Examples of inorganic pigments include carbon black, metal oxides, metal hydroxides, metal sulfides, metal ferrocyanides, and metal chlorides.

[0049] When the ink according to this embodiment is a black ink and the colorant is an inorganic pigment, the inorganic pigment contained in the black ink is preferably a carbon black such as thermal black, acetylene black, oil furnace black, gas furnace black, lamp black, gas black, or channel black. Specific examples of carbon black include the Raven series manufactured by Columbia Carbon; the Monarch series, Regal series, and Mogul series manufactured by Cabot Corporation; the HiBlack series, ColorBlack series, Printex series, SpecialBlack series, and Nerox series manufactured by Orion Engineered Carbons; and the MA series, MCF series, No. 25, No. 33, No. 40, No. 47, No. 52, No. 900, and No. 2300 manufactured by Mitsubishi Chemical Corporation.

[0050] When the ink according to this embodiment is a white ink and the colorant is an inorganic pigment, examples of the inorganic pigment contained in the white ink include oxides, nitrides, and oxynitrides of metals such as zinc, silicon, aluminum, titanium, strontium, and zirconium; inorganic compounds such as glass and silica; etc. Among these, titanium dioxide and zinc oxide are preferred.

[0051] Examples of organic pigments include various pigments such as azo, disazo, phthalocyanine, quinacridone, isoindolinone, dioxazine, perylene, perinone, thioindigo, anthraquinone, and quinophthalone.

[0052] Specific examples of organic pigments include yellow pigments such as CI Pigment Yellow 1, 2, 3, 12, 13, 14, 16, 17, 24, 55, 73, 74, 75, 83, 93, 94, 95, 97, 98, 108, 114, 128, 129, 138, 139, 150, 151, 154, 155, 180, 185, 193, 199, 202, and 213; Red pigments such as 5, 7, 12, 48, 48:1, 57, 88, 112, 122, 123, 146, 149, 150, 166, 168, 177, 178, 179, 184, 185, 202, 206, 207, 254, 255, 257, 260, 264, 269, and 272; blue pigments such as CI Pigment Blue 1, 2, 3, 15, 15:1, 15:2, 15:3, 15:4, 15:6, 16, 22, 25, 60, 66, and 80; violet pigments such as CI Pigment Violet 19, 23, 29, 37, 38, and 50; orange pigments such as CI Pigment Orange 13, 16, 43, 68, 69, 71, and 73; and CI Pigment Green green pigments such as CI Pigment Black 1, CI Pigment Blue 15:4, etc., and black pigments such as CI Pigment Black 1. Of these, CI Pigment Blue 15:4 is preferred.

[0053] Examples of extender pigments include silica, calcium carbonate, talc, clay, barium sulfate, white carbon, etc. Extender pigments are often used in combination with other colorants.

[0054] As the hollow particles, known hollow particles described in, for example, U.S. Pat. No. 4,880,465, Japanese Patent No. 3,562,754, Japanese Patent No. 6,026,234, Japanese Patent No. 5,459,460, JP-A-2003-268694, Japanese Patent No. 4,902,216, etc. can be used, and they are particularly preferably used as white pigments.

[0055] As the disperse dye, for example, a dye selected from CI Dispers is preferred. Specific examples thereof include yellow dyes such as CI Dispers Yellow 9, 23, 33, 42, 49, 54, 58, 60, 64, 66, 71, 76, 79, 83, 86, 90, 93, 99, 114, 116, 119, 122, 126, 149, 160, 163, 165, 180, 183, 186, 198, 200, 211, 224, 226, 227, 231, and 237; red dyes such as CI Dispers Red 60, 73, 88, 91, 92, 111, 127, 131, 143, 145, 146, 152, 153, 154, 167, 179, 191, 192, 206, 221, 258, and 283; and CI Dispers Orange. Orange dyes such as 9, 25, 29, 30, 31, 32, 37, 38, 42, 44, 45, 53, 54, 55, 56, 61, 71, 73, 76, 80, 96, and 97; violet dyes such as CI Dispers Violet 25, 27, 28, 54, 57, 60, 73, 77, 79, and 79:1; blue dyes such as CI Dispers Blue 27, 56, 60, 79:1, 87, 143, 165, 165:1, 165:2, 181, 185, 197, 202, 225, 257, 266, 267, 281, 341, 353, 354, 358, 364, 365, and 368; and the like.

[0056] The average particle size of the colorant is preferably 30 to 300 nm, more preferably 50 to 250 nm. In this specification, the average particle size refers to the average particle size of particles measured using a laser light scattering method.

[0057] The content of the colorant relative to the total mass of the ink according to this embodiment is preferably 1 to 30 mass %, more preferably 1 to 10 mass %, and even more preferably 2 to 8 mass %.

[0058] The colorant may further contain other dyes in addition to the pigments and disperse dyes, such as solvent dyes, direct dyes, acid dyes, and reactive dyes.

[0059] When the ink contains multiple types of colorants, the blending ratio of the colorants can be set arbitrarily depending on the purpose. Furthermore, when the ink contains other dyes in addition to the colorants, the blending ratio of the total amount of the colorants to the total amount of the other dyes can also be set arbitrarily.

[0060] The ink may contain water. The water preferably contains a small amount of impurities such as metal ions, such as ion-exchanged water or distilled water. The water content is 60 to 90% by mass, and preferably 70 to 90% by mass, of the total mass of the ink according to this embodiment.

[0061] The ink may contain a water-soluble organic solvent. The water-soluble organic solvent is not particularly limited, and examples thereof include C1-C6 alcohols such as methanol, ethanol, propanol, isopropanol, butanol, isobutanol, secondary butanol, and tertiary butanol; carboxylic acid amides such as N,N-dimethylformamide and N,N-dimethylacetamide; lactams such as 2-pyrrolidone and N-methyl-2-pyrrolidone; cyclic ureas such as 1,3-dimethylimidazolidin-2-one and 1,3-dimethylhexahydropyrimid-2-one; acetone, 2-methyl-2-hydroxypentan-4-one; ketones or keto alcohols such as ethylene carbonate, tetrahydrofuran, dioxane, and the like; cyclic ethers such as ethylene glycol, diethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,4-butanediol, diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, polyethylene glycol (preferably those with a molecular weight of 400, 800, 1540, or more), polypropylene glycol, thiodiglycol, or dithiodiglycol mono-, oligo-, or polyalkylene glycols or thioglycols having a C2-C6 alkylene unit, such as glycerin, diglycerin, hexane-1,2,6-triol, and trimethylolpropane; C3-C9 polyols (triols), such as glycerin, diglycerin, hexane-1,2,6-triol, and trimethylolpropane; glycol ethers, such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monoallyl ether, ethylene glycol monoisopropyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether (butyl carbitol), triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monobutyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, and dipropylene glycol monomethyl ether (preferably glycol ethers selected from the group consisting of C3-C10 mono-, di-, or triethylene glycol ethers, and C4-C13 mono-, di-, or tripropylene glycol ethers);C5-C9 alkanediols such as 1,2-pentanediol, 1,5-pentanediol, 1,2-hexanediol, 1,6-hexanediol, 2-methyl-2,4-pentanediol, 2-ethyl-1,3-hexanediol, and 2,4-diethyl-1,5-pentanediol; γ-butyrolactone, dimethyl sulfoxide, and the like; The total content of the water-soluble organic solvents relative to the total mass of the ink is usually 0% to 60%, preferably 5% to 60%, and more preferably 10% to 50%.

[0062] The ink may contain a dispersant. The dispersant for dispersing the colorant is not particularly limited, and known dispersants such as polymeric dispersants can be used. Examples of polymeric dispersants include those other than the binders mentioned above, such as copolymers composed of at least two monomers (preferably at least one of which is a hydrophilic monomer) selected from the following monomers: styrene and its derivatives; vinylnaphthalene and its derivatives; aliphatic alcohol esters of α,β-ethylenically unsaturated carboxylic acids; (meth)acrylic acid and its derivatives; maleic acid and its derivatives; itaconic acid and its derivatives; faric acid and its derivatives; vinyl acetate, vinyl alcohol, vinylpyrrolidone, acrylamide, and their derivatives. Examples of such copolymers include styrene-(meth)acrylic acid copolymers, styrene-(meth)acrylic acid-(meth)acrylic acid ester copolymers, (meth)acrylic acid ester-(meth)acrylic acid copolymers, polyethylene glycol (meth)acrylate-(meth)acrylic acid copolymers, and styrene-maleic acid copolymers. Among these, styrene-(meth)acrylic acid copolymer, styrene-(meth)acrylic acid-(meth)acrylic acid ester copolymer, and (meth)acrylic acid ester-(meth)acrylic acid copolymer are preferred, (meth)acrylic acid ester-(meth)acrylic acid copolymer is more preferred, and methacrylic acid ester-methacrylic acid copolymer is even more preferred. Examples of copolymer types include block copolymers, random copolymers, and graft copolymers. These copolymers may be in the form of a salt. One type of dispersant may be used, or two or more types of dispersants may be used in combination. Another embodiment of the present invention involves using a self-dispersing colorant as the colorant, thereby enabling dispersion without the use of a dispersant.

[0063] Dispersants can be commercially available or synthesized.

[0064] Examples of commercially available dispersants include Joncyrl 62, 67, 68, 678, and 687 (styrene-acrylic copolymers manufactured by BASF); Movinyl S-100A (modified vinyl acetate copolymer manufactured by Japan Coating Resins Co., Ltd.); and Jurymer AT-210 (polyacrylic acid ester copolymer manufactured by Toa Gosei Co., Ltd.).

[0065] Examples of dispersants obtained by synthesis include the AB block polymer disclosed in WO 2013 / 115071. The monomer constituting the A block of the AB block polymer disclosed in WO 2013 / 115071 is at least one monomer selected from (meth)acrylic acid and linear or branched C4 alkyl (meth)acrylates, preferably at least one monomer selected from methacrylic acid and n-butyl methacrylate, and more preferably a combination of these two monomers. Furthermore, the monomer constituting the B block of the AB block polymer disclosed in WO 2013 / 115071 is at least one monomer selected from benzyl methacrylate and benzyl acrylate, preferably benzyl methacrylate. Specific examples of AB block polymers include the block copolymers disclosed in Synthesis Examples 3 to 8 of WO 2013 / 115071.

[0066] The acid value of the dispersant is usually 90 to 200 mgKOH / g, preferably 100 to 150 mgKOH / g, and more preferably 100 to 120 mgKOH / g.

[0067] A neutralizing agent may be used to uniformly disperse the dispersant in water. Examples of neutralizing agents include ammonia, alkali metal hydroxides, alkaline earth metal hydroxides, aliphatic amine compounds, and alkanolamine compounds. Among these, ammonia and alkali metal hydroxides are preferred, and ammonia is more preferred. The amount of neutralizing agent used is typically 30 to 300% neutralization, preferably 50 to 200%, with 100% neutralization being defined as neutralization with the theoretical equivalent of the acid value of the dispersant.

[0068] The mass-average molecular weight of the dispersant is usually 10,000 to 60,000, preferably 10,000 to 40,000, more preferably 15,000 to 30,000, and even more preferably 20,000 to 25,000. The mass-average molecular weight of the dispersant can be measured by gel permeation chromatography (GPC). Specifically, the measurement can be performed using an HLC-8320GPC (manufactured by Tosoh Corporation) as the GPC device, two TSK gel Super Multipore HZ-H columns (manufactured by Tosoh Corporation, inner diameter 4.6 mm × 15 cm), tetrahydrofuran as the eluent, and TSK Standard (manufactured by Tosoh Corporation) as the standard sample.

[0069] The PDI (mass average molecular weight / number average molecular weight) of the dispersant is preferably about 1.29 to 1.49. By setting the PDI within this range, the dispersibility and storage stability of the first ink composition tend to be improved.

[0070] The dispersant can be used in a state where it is mixed with the colorant, or in a state where the surface of the colorant is partially or entirely coated with the dispersant, or both of these states can be used in combination.

[0071] The ratio of the total mass of the dispersants to the total mass of the colorants is usually 0.01 to 1.0, preferably 0.05 to 0.6, and more preferably 0.1 to 0.5.

[0072] The ink may further contain ink modifiers such as a hydrophobic solvent, a humectant, an antiseptic / fungal agent, a pH adjuster, a chelating agent, a rust inhibitor, a water-soluble ultraviolet absorber, a water-soluble polymer compound, an antioxidant, and / or a surfactant.

[0073] The hydrophobic solvent is not particularly limited as long as it has a water-octanol partition coefficient of 1.25 to 3.90. The water-octanol partition coefficient of the hydrophobic solvent is preferably 2.00 or more but less than 3.50, more preferably 2.40 to 3.00. In this specification, the term "water-octanol partition coefficient" refers to the ClogP value calculated using ChemDraw Professional ver. 16.0 manufactured by Perkin Elmer. The number of decimal places calculated in this manner varies. Therefore, in this specification, the value is rounded to two decimal places and reported to two decimal places. When the calculated value has two decimal places, the value is reported as is. When the calculated value does not have two decimal places, the values ​​up to the second decimal place are considered to be "zero," and all values ​​are reported to two decimal places. Hereinafter, the "water-octanol partition coefficient" may be referred to as the "ClogP value." Examples of organic solvents having a ClogP value of 2.00 or more and less than 3.50 include 1,2-nonanediol (2.11), 2-propylheptane-1,3-diol (2.31), ethylene glycol monoheptyl ether (2.43), ethylene glycol diisobutyl ether (2.55), dibutyl diglycol (2.63), 1,2-decanediol (2.64), 2-[2-(2-ethylhexyloxy)ethoxy]ethanol (2.65), diisobutyl Examples include ethylene glycol dibutyl ether (2.81), 2,6-dimethyl-4-heptanol (2.99), 3,5,5-trimethyl-1-hexanol (3.08), 2-butoxyethyl benzoate (3.43), and diethylene glycol monobutyl ether adipate (3.49). The values ​​in parentheses are ClogP values. When other organic compound components of the binder are made hydrophilic, the SP value of the organic compound components is in the range of 9.8 to 12.3, and more preferably in the range of 10.0 to 11.3.

[0074] Specific examples of moisturizers include polyols such as glycerin, ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,2,6-hexanetriol, and pentaerythritol; cyclic amides such as 2-pyrrolidone and N-methyl-2-pyrrolidone; ureas such as urea, thiourea, ethyleneurea, and 1,3-dimethylimidazolidinones; lactams such as ε-caprolactam; solid glycerins such as trimethylolpropane and trimethylolethane; and sugars such as maltitol, sorbitol, gluconolactone, and maltose.

[0075] Specific examples of antiseptic and antifungal agents include organic sulfur-based, organic nitrogen sulfur-based, organic halogen-based, haloarylsulfone-based, iodopropargyl-based, haloalkylthio-based, nitrile-based, pyridine-based, 8-oxyquinoline-based, benzothiazole-based, isothiazolin-based, dithiol-based, pyridine oxide-based, nitropropane-based, organic tin-based, phenol-based, quaternary ammonium salt-based, triazine-based, thiazine-based, anilide-based, adamantane-based, dithiocarbamate-based, brominated indanone-based, benzyl bromoacetate-based, and inorganic salt-based compounds.

[0076] A specific example of the organic halogen compound is sodium pentachlorophenol, and a specific example of the pyridine oxide compound is sodium 2-pyridinethiol-1-oxide.

[0077] Examples of isothiazoline compounds include 1,2-benzisothiazolin-3-one, 2-n-octyl-4-isothiazolin-3-one, 5-chloro-2-methyl-4-isothiazolin-3-one, 5-chloro-2-methyl-4-isothiazolin-3-one magnesium chloride, 5-chloro-2-methyl-4-isothiazolin-3-one calcium chloride, and 2-methyl-4-isothiazolin-3-one calcium chloride.

[0078] Other specific examples of antiseptic and antifungal agents include anhydrous sodium acetate, sodium sorbate, sodium benzoate, p-hydroxybenzoic acid ethyl ester, and Arch Chemical's trade names Proxel GXL(S) and Proxel XL-2(S).

[0079] Any substance can be used as the pH adjuster as long as it can control the pH of the ink within the above range without adversely affecting the ink being prepared. Specific examples include the neutralizing agents mentioned above; alkali metal carbonates such as lithium carbonate, sodium carbonate, sodium bicarbonate, and potassium carbonate; alkali metal salts of organic acids such as sodium silicate and potassium acetate; and inorganic bases such as disodium phosphate.

[0080] Specific examples of the chelating agent include disodium ethylenediaminetetraacetate, sodium nitrilotriacetate, sodium hydroxyethylethylenediaminetriacetate, sodium diethylenetriaminepentaacetate, and sodium uracildiacetate.

[0081] Specific examples of the rust inhibitor include acid sulfite, sodium thiosulfate, ammonium thioglycolate, diisopropylammonium nitrite, pentaerythritol tetranitrate, and dicyclohexylammonium nitrite.

[0082] Examples of the water-soluble ultraviolet absorber include sulfonated benzophenone compounds, benzotriazole compounds, salicylic acid compounds, cinnamic acid compounds, and triazine compounds.

[0083] Specific examples of the water-soluble polymer compound are those other than the above-mentioned binders, waxes, and dispersants, and include, for example, polyethylene glycol, polyvinyl alcohol, cellulose derivatives, polyamines, and polyimines.

[0084] Examples of the antioxidant include various organic and metal complex anti-fading agents, such as hydroquinones, alkoxyphenols, dialkoxyphenols, phenols, anilines, amines, indanes, chromans, alkoxyanilines, and heterocycles.

[0085] Examples of the surfactant include known anionic, cationic, amphoteric, nonionic, silicone-based, and fluorine-based surfactants, and one or more of these can be selected and used.

[0086] Examples of anionic surfactants include alkyl sulfocarboxylates, α-olefin sulfonates, polyoxyethylene alkyl ether acetates, N-acylamino acids or salts thereof, N-acylmethyl taurines, alkyl sulfates, polyoxyalkyl ether sulfates, alkyl sulfates, polyoxyethylene alkyl ether phosphates, rosin acid soaps, castor oil sulfates, lauryl alcohol sulfates, alkylphenol phosphates, alkyl phosphates, alkylaryl sulfonates, diethyl sulfosuccinates, diethylhexyl sulfosuccinates, and dioctyl sulfosuccinates.

[0087] Examples of cationic surfactants include 2-vinylpyridine derivatives and poly(4-vinylpyridine) derivatives.

[0088] Examples of amphoteric surfactants include lauryl dimethylaminoacetic acid betaine, 2-alkyl-N-carboxymethyl-N-hydroxyethyl imidazolinium betaine, coconut oil fatty acid amidopropyl dimethylaminoacetic acid betaine, polyoctyl polyaminoethyl glycine, and imidazoline derivatives.

[0089] Examples of nonionic surfactants include ether surfactants such as polyoxyethylene nonylphenyl ether, polyoxyethylene octylphenyl ether, polyoxyethylene dodecylphenyl ether, polyoxyethylene oleyl ether, polyoxyethylene lauryl ether, and polyoxyethylene alkyl ether; polyoxyethylene oleate, polyoxyethylene distearate, sorbitan laurate, sorbitan monostearate, sorbitan monooleate, sorbitan sesquioleate, and polyoxyethylene Examples include ester-based surfactants such as monooleate and polyoxyethylene stearate; acetylene glycol (alcohol)-based surfactants such as 2,4,7,9-tetramethyl-5-decyne-4,7-diol, 3,6-dimethyl-4-octyne-3,6-diol, and 3,5-dimethyl-1-hexyn-3-ol; Surfynol 104, 105PG50, 82, 420, 440, 465, 485, and Olfine STG, both manufactured by Nissin Chemical Industry Co., Ltd.; and polyglycol ether-based surfactants such as Tergitol 15-S-7, manufactured by SIGMA-ALDRICH.

[0090] Examples of silicone surfactants include polyether-modified siloxanes and polyether-modified polydimethylsiloxanes, etc. Examples include Dynol 960 and Dynol 980 manufactured by Air Products Co., Ltd., Silface SAG001, Silface SAG002, Silface SAG003, Silface SAG005, Silface SAG503A, Silface SAG008, Silface SAG009, and Silface SAG010 manufactured by Nissin Chemical Industry Co., Ltd., and BYK-345, BYK-347, BYK-348, BYK-349, BYK-3450, BYK-3451, and BYK-3455 manufactured by BYK-Chemie, and a wide variety of such products are readily available for purchase.

[0091] Examples of fluorine-based surfactants include perfluoroalkyl sulfonic acid compounds, perfluoroalkyl carboxylic acid compounds, perfluoroalkyl phosphate ester compounds, perfluoroalkyl ethylene oxide adducts, and polyoxyalkylene ether polymer compounds having perfluoroalkyl ether groups on the side chains, such as Zonyl TBS, FSP, FSA, FSN-100, FSN, FSO-100, FSO, FS-300, and Capstone, manufactured by DuPont. Examples of such surfactants include FS-30 and FS-31; PF-151N and PF-154N manufactured by Omnova; F-114, F-410, F-444, EXP.TF-2066, EXP.TF-2148, EXP.TF-2149, F-430, F-477, F-552, F-553, F-554, F-555, F-556, F-557, F-558, F-559, F-561, F-562, R-40, R-41, RS-72-K, RS-75, RS-76-E, RS-76-NS, RS-77, EXP.TF-1540, and EXP.TF-1760 manufactured by DIC; and BYK-3440 and BYK-3441 manufactured by BYK-Chemie.

[0092] Among these, it is preferable to select at least one surfactant selected from nonionic or silicone surfactants.

[0093] The pH of the ink is usually 5 to 11, preferably 7 to 10, in order to improve storage stability. The surface tension of the ink is usually 10 to 50 mN / m, preferably 20 to 40 mN / m. The viscosity of the ink is usually 30 mPa·s or less, preferably 20 mPa·s or less. The pH and surface tension of the ink can be adjusted appropriately by using ink adjusters such as pH adjusters and surfactants.

[0094] When the ink is used as an inkjet ink, it is preferable to reduce the content of inorganic impurities such as chlorides of metal cations (e.g., sodium chloride) and sulfates (e.g., sodium sulfate). The content of inorganic impurities is preferably 1% or less based on the total mass of the colorant, and the lower limit may be below the detection limit of analytical equipment, i.e., 0%. Methods for producing colorants with reduced inorganic impurities include, for example, a method of exchanging and adsorbing inorganic impurities with an ion exchange resin.

[0095] In all of the above-mentioned components, contents, content ratios, etc., a combination of preferred components is more preferable, and a combination of more preferred components is even more preferable. The same applies to a combination of a preferred component and a more preferred component.

[0096] The ink can be used in various printing applications, such as writing instruments, various printing applications, information printing, and textile printing, and is particularly preferably used in inkjet printing.

[0097] The method for preparing the ink is not particularly limited, and one example is a method in which a dispersion is prepared from a colorant and a dispersant, and the binder, emulsion particles composed of the polymer material, and the water-soluble organic solvent are added to the dispersion, and water and the ink preparation agent are further added as necessary to prepare the ink.

[0098] The ink may be prepared using only one type of dispersion liquid, or two or more types of dispersion liquid may be used.

[0099] When the ink contains a colorant, methods for dispersing the colorant to prepare a dispersion include methods using a sand mill (bead mill), a roll mill, a ball mill, a paint shaker, an ultrasonic disperser, a microfluidizer, etc., and among these, a sand mill (bead mill) is preferred. Furthermore, when preparing a colorant dispersion using a sand mill (bead mill), it is desirable to use small beads (0.01 to 1 mm in diameter) and treat under conditions that increase dispersion efficiency by increasing the bead packing rate, for example. By carrying out dispersion under these conditions, the particle size of the colorant can be reduced, resulting in a dispersion with good dispersibility. Furthermore, after preparing the dispersion, it is also preferable to remove components such as pigments with large particle sizes by filtration and / or centrifugation. Furthermore, to suppress foaming during the preparation of the dispersion, a trace amount of an antifoaming agent such as the silicone-based or acetylene glycol-based antifoaming agent may be added. However, some antifoaming agents inhibit dispersion and microparticulation, so it is preferable to use an antifoaming agent that does not affect dispersion or post-dispersion stability.

[0100] The colorant in the dispersion may be a microencapsulated colorant in which the surface of the colorant is coated with a dispersant, or may not be microencapsulated, but is preferably a microencapsulated colorant in which the dispersant is uniformly coated.

[0101] Methods for uniformly coating a dispersant on the surface of a colorant to form microencapsulated particles can be broadly divided into two categories: physical / mechanical methods and chemical methods. Among the latter, chemical methods, surface precipitation, kneading, and interfacial polymerization methods have been proposed. Surface precipitation is a method for precipitating a dispersant on the surface of a colorant by adjusting the pH or utilizing differences in solubility in the medium, and includes acid precipitation and phase inversion emulsification. Interfacial polymerization is a method in which a monomer, oligomer, or pigment derivative is adsorbed onto the surface of the colorant and then polymerized, and is also known as surface polymerization. While either method may be used in the present invention, the surface precipitation method is preferred, and a colored dispersion obtained by phase inversion emulsification is even more preferred.

[0102] The phase inversion emulsification method is a method in which a colorant, a dispersant, and an organic solvent are mixed and dispersed, and water is further added to uniformly adsorb the dispersant onto the surface of the colorant. Specific known production methods include the following five types of production methods:

[0103] 1. A manufacturing method in which a solution of a colorant dispersed in a hydrophilic organic solvent and a dispersant that disperses or dissolves in water is mixed with a liquid whose main component is water, and then the solvent is removed. 2. A manufacturing method in which a solution of a colorant dispersed in a hydrophilic organic solvent and a dispersant that disperses or dissolves in water upon neutralization is mixed with a mixed liquid containing water and a neutralizing agent, and then the solvent is removed. 3. A manufacturing method in which a mixed solution of a hydrophilic organic solvent and a hydrophobic organic solvent, in which a colorant is dispersed and a dispersant that disperses or dissolves in water, is mixed with a liquid whose main component is water, and then the solvent is removed. 4. A manufacturing method in which a solution of a mixed solvent of a hydrophilic organic solvent and a hydrophobic organic solvent, in which a colorant is dispersed and the dispersant disperses or dissolves in water by neutralization, is mixed with a mixed liquid containing water and a neutralizing agent, and then the solvent is removed. 5. A manufacturing method in which a colorant is mixed with a solution of a mixed solvent whose main components are water and a hydrophilic organic solvent of a dispersant that disperses or dissolves in water, the pigment is dispersed in the solution, and then the solvent is removed.

[0104] The dispersion can be obtained by the above-mentioned manufacturing method, but a coated colorant dispersion can also be obtained by a different manufacturing method. An example of such a manufacturing method is a method in which a solution of a hydrophobic organic solvent in which a dispersant is dissolved is mixed with a liquid containing a neutralizing agent and whose main component is water to form an emulsion (emulsion or microemulsion), a colorant is added thereto and mixed and dispersed, and then water is added to remove the solvent.

[0105] Although a dispersion liquid composed of colorant particles whose surfaces are coated with a dispersant has been described in detail above, by using the above method, a dispersion liquid composed of colorant particles having a dispersant on their surfaces and an average particle size of 200 nm or less can be easily obtained. In particular, it is more preferable to set the average particle size to 50 to 180 nm by selecting the type of colorant and dispersant used, the acid value, the molecular weight, etc. Here, in this specification, the average particle size refers to the average particle size of the particles measured using a laser light scattering method.

[0106] In preparing the dispersion, a neutralizing agent can be used, such as an alkali metal hydroxide, an alkaline earth metal hydroxide, an aliphatic amine compound, or an alcohol amine compound. These neutralizing agents can be used alone or in combination. In preparing the dispersion, the amount of neutralizing agent is not limited. The degree of neutralization is 100% when the neutralization is carried out in an amount theoretically equivalent to the acid value of the dispersant, but it is also possible to use a neutralizing agent in an amount exceeding the theoretical amount. The degree of neutralization is usually 0 to 150%, preferably 30 to 100%, and more preferably 50 to 70%.

[0107] Alkali metal hydroxides include, for example, lithium hydroxide, sodium hydroxide, and potassium hydroxide. Examples of the hydroxides of alkaline earth metals include beryllium hydroxide, magnesium hydroxide, calcium hydroxide, and strontium hydroxide. Of these, lithium hydroxide or sodium hydroxide is preferred.

[0108] Examples of the alcoholamine compound include monoethanolamine, diethanolamine, triethanolamine, monopropanolamine, dipropanolamine, tripropanolamine, methylethanolamine, dimethylethanolamine, and N-methyldiethanolamine. Among these, tertiary amines are preferred, and triethanolamine is more preferred.

[0109] Examples of the aliphatic amine compound include ammonia, monomethylamine, dimethylamine, trimethylamine, monoethylamine, dimethylamine, and trimethylamine. Of these, ammonia or triethylamine is preferred.

[0110] The inkjet recording method includes a step of ejecting droplets of the ink and depositing them on a recording medium to form an image. The step of forming an image can be performed using an inkjet system. The present invention also includes an inkjet recording method including an ink depositing step of ejecting the ink from an inkjet and depositing it on a recording medium, which will be described later.

[0111] Known inkjet methods can be used. Specific examples of inkjet methods include charge control methods, drop-on-demand (pressure pulse) methods, acoustic inkjet methods, and thermal inkjet methods, with the drop-on-demand method being preferred. Inkjet methods also include methods that improve image quality by ejecting a large number of inks with a low pigment content in a small volume, methods that improve image quality by using multiple inks with substantially the same hue but different pigment concentrations, and methods that improve pigment fixation by using colorless, transparent ink.

[0112] Inkjet heads with or without an ink circulation mechanism can be used. From the viewpoint of suppressing pigment particle sedimentation, inkjet heads with an internal circulation mechanism are preferred. An inkjet head with a circulation mechanism refers to, for example, a mechanism having multiple droplet ejection elements, a common flow path communicating with each of the droplet ejection elements via a supply path, and a common circulation path communicating with the droplet ejection elements via a return path, and an ink circulation device that supplies ink to the droplet ejection elements from the common flow path and circulates it in the common circulation path. There are no particular restrictions on the ink circulation flow rate, but a rate of 10 mL / min to 1000 mL / min is preferred, and a rate of 20 mL / min to 500 mL / min is more preferred. Linehead-type industrial inkjet printers are known, which use an array of inkjet heads as a circulation mechanism. Therefore, the preferred range refers to the circulation flow rate per inkjet. Examples of inkjet heads equipped with a circulation mechanism include the SambaG3L manufactured by Fujifilm, the S series manufactured by Canon, and the KJ4B-EX1200 print head manufactured by Kyocera.

[0113] <Printed material> The present invention also includes printed matter printed using the above ink. Specifically, it refers to a printed matter obtained by recording on a recording material described below using the ink. The recording material is preferably a material that is non-absorbent or poorly absorbent to ink. Specific examples include coated paper such as lightly coated paper, art paper, coated paper, matte paper, and cast paper. Coated paper is paper whose surface is coated with a paint to enhance its aesthetic appeal and smoothness. Examples of such paint include various clays such as talc, pyrophyllite, and kaolin; mixtures of titanium oxide, magnesium carbonate, calcium carbonate, etc. with starch and / or polyvinyl alcohol; and the like. The paint can be applied to paper using a coater during the paper manufacturing process, for example. Coaters include an in-line system in which papermaking and coating are performed in a single process by being directly connected to a papermaking machine, and an offline system in which papermaking and coating are performed separately. Lightly coated paper is paper with a paint coating weight of 12 g / m2. 2 Art paper refers to the following paper: High-quality paper made from 100% chemical pulp with a thickness of 40 g / m 2 This refers to paper that has been coated with paint on both sides. Coated paper and matte paper are 20-40g / m 2 This refers to paper coated with a coating of a certain degree of gloss. Cast paper refers to art paper or coated paper that has been finished by applying pressure to the surface with a machine such as a casting drum to enhance gloss and recording effect. The above inks exhibit the effects of the present invention extremely well when used on such non-absorbent or poorly absorbent recording materials.

[0114] Examples of the recording material include plain paper having no ink-receiving layer, media used in gravure printing, offset printing, etc.; inkjet paper, inkjet film, glossy paper, glossy film, etc., having an inkjet-receiving layer; fibers and cloths such as cellulose, nylon, and wool; leather; and color filter substrates. Among plain papers having no ink-receiving layer, there are some that have low ink receptivity, similar to the non- or poorly absorbent non-recording materials. Even when such plain paper is used, the effects of the present invention are most effectively achieved.

[0115] The recording material is preferably liner paper. Liner paper is paper that forms the outside of cardboard and is made primarily from recycled paper or kraft pulp. Liner paper is liner paper for cardboard as described in the Japanese Industrial Standard JIS P3902:2011 "Corrugated cardboard liners." The recording method of this embodiment is applicable to recording not only on the liner itself but also on the liner after it has been processed into cardboard.

[0116] Furthermore, the object of recording using the recording method of this embodiment may be the liner paper on the surface of a cardboard sheet before processing, or, for example, the liner paper on the surface after it has been processed and / or formed into a cardboard box. The liner paper may be non-white. As described above, liner paper is often made from recycled paper and is often not white. Such non-white liner paper tends to have poor whiteness in the image formed on its surface, but the recording method of this embodiment allows for the formation of an image with good color development. The surface of the liner paper may be coated or surface-treated. Examples of surface treatments include water-repellent treatment, anti-fouling treatment, and coloring treatment. In particular, if the surface of the liner paper is water-repellent, it repels water-based liquids, and therefore inks, resulting in unevenness in the image. According to the recording method using the ink of this embodiment, good images can be formed even on liner paper treated as described above. The reason for this, as will be described in detail later, is believed to be due to the suppression of ink repelling due to the effects of the organic solvents, surfactants, and the like contained in the ink. Furthermore, in a preferred recording method using an aqueous treatment liquid according to the present invention, the coagulant contained in the aqueous treatment liquid thickens and solidifies the components in the ink, including the colorant, thereby further suppressing ink repelling and making unevenness less likely to occur. Therefore, it is believed that clear, good images can be obtained. Water-repellent treatment can be achieved by applying a water-repellent agent, and commercially available products, such as cardboard, containing water-repellent liner paper are also available. The liner paper is preferably cardboard liner paper.

[0117] The present invention also includes an ink set containing at least the above ink. Examples of the ink set include an ink set containing two or more of the above inks, an ink set containing one or more of the above inks and one or more of other inks other than the above inks, etc. The other inks other than the above inks are not particularly limited as long as they have a different composition from the above inks, but it is preferable that they have a different hue from the above inks.

[0118] For all of the above, combinations of preferred items are more preferred, and combinations of more preferred items are even more preferred. The same applies to combinations of preferred items and more preferred items, and combinations of more preferred items and even more preferred items. Furthermore, unless otherwise specified, all of the above-mentioned components can be used alone or in combination of two or more types.

[0119] The ink is excellent in circulation stability, storage stability, ejection stability, wet spreadability on a recording material, and drying properties, and printed matter obtained using the ink of the present invention is excellent in abrasion resistance, adhesion, color development, etc. Furthermore, in terms of abrasion resistance, it is excellent in both dry abrasion resistance and wet abrasion resistance. [Example]

[0120] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. The average particle size was measured using a dynamic light scattering particle size distribution analyzer, Nanotrac Wave, manufactured by Nikkiso Co., Ltd. The solid content in the aqueous solution was measured by the dry weight method using an MS-70 manufactured by A&D Co., Ltd.

[0121] [Preparation Example 1]: Preparation of Dispersion 1 A block copolymer was prepared as described in Synthesis Example 3 of WO 2013 / 115071. 5.4 parts of the resulting polymeric dispersant was dissolved in 20.0 parts of 2-butanone to form a homogeneous solution. A solution of 0.2 parts sodium hydroxide, 0.45 parts ROCIMA 640 (Dow Chemical Company), and 0.06 parts BYK1770 (BYK Japan Co., Ltd.) dissolved in 56.0 parts of ion-exchanged water was added to this solution and stirred for 1 hour to prepare an emulsified solution. 18.0 parts of CI Pigment Red 122 (Clariant Japan Co., Ltd. Ink Jet Magenta E02) was added to this solution and dispersed using a sand grinder. Dispersion was carried out for 6 hours at 1500 rpm. Subsequently, 100.0 parts of ion-exchanged water was added dropwise, and the dispersion beads were separated by filtration. Furthermore, 2-butanone and water were distilled off under reduced pressure using an evaporator so that the pigment solid content became 12.2%, to obtain a dispersion liquid having an average pigment particle size of 150 nm. This is designated as "Dispersion Liquid 1."

[0122] [Preparation Example 2]: Synthesis of Binder 1 A glass reaction vessel (500 mL) equipped with a stirrer was fitted with a condenser, thermometer, and nitrogen inlet, and 152.09 parts of ion-exchanged water and 7.46 parts of Neopelex G-65 (Kao Corporation) were added. The air inside was replaced with nitrogen, and the internal temperature was adjusted to 65°C while stirring. A separate 500 mL beaker was prepared and 130.22 parts of ion-exchanged water, 0.23 parts of Neopelex G-65 (Kao Corporation), 162.19 parts of methyl methacrylate, 14.14 parts of 2-ethylhexyl acrylate, 9.21 parts of methacrylic acid, 6.96 parts of 2-hydroxyethyl methacrylate, and 1.00 parts of 1-dodecanethiol were added. The mixture was stirred at 3,000 rpm for 5 minutes using a homogenizer to produce an emulsion. An aqueous solution of 1.50 parts ammonium persulfate dissolved in 15.00 parts ion-exchanged water in a 30 ml beaker was added to a glass reactor. Immediately afterwards, the resulting emulsion was continuously added dropwise to the glass reactor over 3 hours using a diaphragm pump. During the addition, the reaction was carried out at 65°C while introducing nitrogen. After the addition was completed, the mixture was stirred at 65°C for an additional 2 hours. After the reaction was completed, the mixture was cooled to below 40°C. After cooling, the mixture was filtered through a 325-mesh wire screen (opening: 0.043 mm) to obtain a Binder 1 aqueous dispersion with a solids concentration of 40% and the physical properties shown in Table 2. The specific gravity of Binder 1 in the Binder 1 aqueous dispersion was 1.20, and the SP value was 10.52.

[0123] [Preparation Example 3]: Synthesis of polymer material dispersion 1 A 1.5L emulsification system equipped with a stirrer, thermometer, and temperature controller was charged with 300.0 parts of oxidized polyethylene resin (melting point 105°C, acid value 16 mgKOH / g), 650.0 parts of ion-exchanged water, 50.0 parts of Rheodol MS-50 (Kao Corporation), and 10.0 parts of 48% potassium hydroxide aqueous solution. After purging with nitrogen, the system was sealed and stirred at 800 rpm for 1 hour at 150°C. After cooling to 130°C, the mixture was passed through a high-pressure homogenizer (Econizer Lab 02, Sanmaru Machinery Co., Ltd.) at 40 MPa and cooled to 40°C, yielding Polymer Dispersion 1 with a melting point of 105°C and a solids concentration of 35.1%. The specific gravity of the oxidized polyethylene resin in Polymer Dispersion 1 was 0.99.

[0124] [Preparation Example 4]: Synthesis of polymer material dispersion 2 A reactor equipped with a stirrer, thermometer, heater, cooling device, and distillation condenser was charged with 399.0 parts of terephthalic acid, 157.0 parts of 1,4-cyclohexanedicarboxylic acid, 210.0 parts of adipic acid, 813.0 parts of 1,4-butanediol, and 0.50 parts of tin(II) oxide. The mixture was heated to 220°C and subjected to an esterification reaction over 4 hours. After the esterification reaction, the pressure in the system was increased to 250°C while the pressure was reduced to 10 torr over 60 minutes. The pressure was then further reduced to a vacuum of 1 torr or less, and the polycondensation reaction was carried out at 250°C until the desired viscosity was reached. After the reaction, the crystalline polyester resin was removed and cooled to obtain a crystalline polyester resin with a melting point of 123°C. The resulting crystalline polyester resin was dispersed in water according to the following procedure. 100.0 parts of the resulting crystalline polyester resin and 120.0 parts of methyl ethyl ketone were charged into a reaction vessel equipped with a stirrer, condenser, and thermometer, and the resin was dissolved with stirring at 75°C. After confirming complete dissolution of the resin, 30.0 parts of isopropyl alcohol was charged and stirred for an additional 30 minutes. Next, 3.60 parts of dimethylaminoethanol was added and stirred for 30 minutes. Next, 300.0 parts of warm water was added and stirred for 1 hour. The internal temperature was then raised to 100°C, and the methyl ethyl ketone and isopropyl alcohol were distilled off to obtain Polymer Material Dispersion 2, which contained no organic solvent and had a solids concentration of 25.7%. The specific gravity of the crystalline polyester resin in Polymer Material Dispersion 2 was 1.15.

[0125] [Preparation Example 5]: Synthesis of polyester resin dispersion 1 A reaction vessel equipped with a stirrer, condenser, and thermometer was charged with 318.0 parts of terephthalic acid, 318.0 parts of isophthalic acid, 7.7 parts of trimellitic anhydride, 447.0 parts of ethylene glycol, and 70.0 parts of 2-methyl-1,3-propanediol. Under a nitrogen atmosphere at 2 atmospheres, the esterification reaction was carried out over 3 hours at temperatures ranging from 160°C to 230°C. After the pressure was released, 0.42 parts of tetrabutyl titanate was added. The system was then gradually depressurized to 5 mmHg over 20 minutes, and then further depressurized to 0.3 mmHg or less, at 260°C for 40 minutes. The mixture was cooled to 220°C under a nitrogen stream, and 23.0 parts of trimellitic anhydride were added, followed by a 30-minute reaction. After the reaction was complete, the polyester resin was removed and cooled to obtain a polyester resin with no melting point. 100.0 parts of the resulting polyester resin was placed in a vessel equipped with a stirrer, condenser, and thermometer, followed by the addition of 145.0 parts of methyl ethyl ketone and 40.0 parts of isopropyl alcohol, and the polyester was dissolved at 70°C. The vessel was then cooled, and when the internal temperature reached 55°C, 10.0 parts of 2.8% aqueous ammonia was added. 370.0 parts of 55°C ion-exchanged water was added at 25.0 parts per minute over a total of 15 minutes to obtain an aqueous dispersion containing residual solvent. The vessel was then gradually heated, and approximately 333.0 g of solvent and water were distilled off. The vessel was then cooled and removed when the temperature reached 35°C. Finally, the mixture was filtered through a 200-mesh nylon mesh to obtain Polyester Resin Dispersion 1 with a solids concentration of 30.0%. The specific gravity of the polyester resin in Polyester Resin Dispersion 1 was 1.35.

[0126] [Examples 1 and 2, Comparative Examples 1 and 2]: Preparation of ink Dispersion 1 obtained in Preparation Example 1, Binder 1 obtained in Preparation Example 2, the polymer material dispersion obtained in Preparation Example 3 or Preparation Example 4, and the polyester resin dispersion obtained in Preparation Example 5 were blended and stirred to obtain the compositions shown in Table 1 below, and the resulting liquids were filtered through a membrane filter with a pore size of 3 μm to obtain the inks of Examples 1 and 2 and Comparative Examples 1 and 2. Subsequently, 50 μl of each of the resulting inks was measured out and coated with OK Topcoat+ 127.9 g / m2 (manufactured by Oji Paper Co., Ltd.) using a No. 3 bar coater in a PI-1210 automatic coating device (manufactured by Tester Sangyo Co., Ltd.) at a speed of 200 mm / sec. 2 A solid print was made on coated paper. The resulting solid print was stained with ruthenium using a 0.5% aqueous solution of ruthenium tetroxide, and then a thin layer of platinum was coated onto the sample surface using an ion sputtering device. The coated sample was observed under a scanning electron microscope (SEM), and the resulting backscattered electron image was binarized using the mode method in Photoshop version 12.1 (Adobe Inc.) software. The percentage of the area of ​​the blackened portion was calculated and used as the percentage of the area of ​​the unstained portion. The results are shown in Table 1 below. The abbreviations in Table 1 below represent the following: In addition, blank spaces in Table 1 indicate 0 parts. TEX: 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate (also known as Texanol). PG: Propylene glycol. DEGMBE: Diethylene glycol monobutyl ether. BYK349: BYK-349 (manufactured by BYK Japan Co., Ltd.). In Table 1, the numerical value of each component represents the number of parts, and "balance" indicates that the total amount of the ink composition was adjusted to 100 parts by adding ion-exchanged water.

[0127] [Table 1]

[0128] [Abrasion resistance] The printed matter obtained in the examples and comparative examples was subjected to a 900g load using a Gakushin tester manufactured by Yasuda Seiki Seisakusho Co., Ltd., and the test printed matter and an uncoated OK top coat + 127.9g / m2 2 The test print (coated paper) was rubbed 13 times. The rubbed and unrubbed areas of the test print were visually compared and rated on a 5-point scale as follows. The evaluation results are shown in Table 2 below. -Evaluation criteria- A: Almost no discoloration can be seen. B: Very slight discoloration is observed. C: Slight discoloration is observed. D: Discoloration is clearly observed. E: The color of the abraded area has peeled off.

[0129] [Table 2]

[0130] As is clear from the results in Table 2, it was confirmed that the prints obtained using the example inks had good scratch resistance. [Industrial Applicability]

[0131] The ink of the present invention provides excellent scratch resistance to printed matter.

Claims

1. In a backscattered electron image of the surface of a solid print produced using the No. 3 bar coater after electronic staining treatment with a heavy metal, the ratio of the area of ​​the portion not electronically stained to the total area is 25% or more and 60% or less.

2. 10. The ink of claim 1, further comprising a binder.

3. A printed matter printed using the ink according to claim 1 or 2.

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