Inkjet ink and ink set

Abstract

The invention relates to an inkjet ink and an ink set. Disclosed is an inkjet ink containing a coloring material, a binder resin, water, and an organic solvent S, the water being 3.0-10.0 mass% relative to the total amount of the ink, and the organic solvent S containing an organic solvent A having a boiling point of 150 DEG C or more and less than 200 DEG C in an amount of 90.0 mass% or more relative to the total amount of the organic solvent S. An ink kit is also disclosed.

Description

Technical Field

[0001] Embodiments of the present invention relate to inkjet inks and ink sets. Background Art

[0002] In the inkjet recording method, an inkjet ink with high fluidity is ejected in the form of droplets from a fine nozzle, and an image is recorded on a substrate disposed opposite to the nozzle. Since high-speed printing can be achieved with low noise, it has been rapidly popularized in recent years. As the ink used in such an inkjet recording method, an aqueous ink containing water as a main solvent, an ultraviolet curable ink (UV ink) containing a polymerizable monomer as a main component in a high content, a hot melt ink (solid ink) containing wax as a main component in a high content, and a so-called non-aqueous ink containing a non-aqueous solvent as a main solvent are known. The non-aqueous ink can be classified into a solvent ink (solvent-based ink) having a volatile organic solvent as a main solvent and an oil-based ink (oil-based ink) having a low-volatile or non-volatile organic solvent as a main solvent. The solvent ink is mainly dried on the substrate by evaporation of the organic solvent, and the penetration of the oil-based ink into the substrate is the main drying method.

[0003] Sometimes, inkjet printing is performed on plastic substrates such as vinyl chloride resin and olefin resin. Conventionally, in the case of printing on a substrate where ink hardly penetrates, in order to prevent bleeding of the image, a highly volatile organic solvent is often used for the ink. In addition, plastic substrates such as vinyl chloride resin and olefin resin generally do not have high heat resistance, so it is desirable that the ink dries quickly at a low temperature.

[0004] However, for example, when a low-boiling point and highly volatile organic solvent is used in the solvent ink, nozzle clogging of the inkjet head and ejection failure caused by ink sticking near the nozzle sometimes easily occur. In addition, from the viewpoint of the operating environment during printing, when using an ink containing an organic solvent, it is desirable to use an organic solvent with not too high volatility and high safety.

[0005] Patent Document 1 describes an inkjet recording ink containing at least one of diethylene glycol monomethyl ether or diethylene glycol monoethyl ether and containing diethylene glycol ethyl methyl ether.

[0006] Patent Document 2 describes a non-aqueous inkjet ink composition containing (poly)ethylene glycol dialkyl ether and containing (poly)alkylene glycol monoalkyl ether monoacetate and / or (poly)alkylene glycol diacetate.

[0007] Prior Art Documents

[0008] Patent Documents

[0009] Patent Document 1: Japanese Patent Application Laid-Open No. 2012-233086

[0010] Patent Document 2: Japanese Patent Application Laid-Open No. 2017-190373 Summary of the Invention

[0011] Problems to be Solved by the Invention

[0012] The subject of the embodiments of the present invention is to provide an inkjet ink capable of forming an image with less bleeding and having excellent ejection properties.

[0013] Solutions to the Problems

[0014] In some embodiments of the present invention, there is provided an inkjet ink containing a coloring material, a binder resin, water, and an organic solvent S, wherein the water is 3.0 to 10.0% by mass relative to the total amount of the ink, and the organic solvent S contains an organic solvent A having a boiling point of 150°C or higher and lower than 200°C in an amount of 90.0% by mass or more relative to the total amount of the organic solvent S.

[0015] One embodiment of the present invention relates to an inkjet ink containing a coloring material, a binder resin, water, and an organic solvent S, wherein the water is 3.0 to 10.0% by mass relative to the total amount of the ink, the organic solvent S contains an organic solvent A having a boiling point of 150°C or higher and lower than 200°C in an amount of 90.0% by mass or more relative to the total amount of the organic solvent S, and the organic solvent A contains a water-soluble organic solvent B having a boiling point of 150°C or higher and lower than 200°C in an amount of 50.0% by mass or more relative to the total amount of the organic solvent S.

[0016] Another embodiment of the present invention relates to an inkjet ink, which contains a coloring material, a binder resin, water, and an organic solvent S, wherein the water is 3.0 to 10.0% by mass relative to the total amount of the ink, the organic solvent S contains an organic solvent A having a boiling point of 150°C or higher and lower than 200°C in an amount of 90.0% by mass or more relative to the total amount of the organic solvent S. When the amount of the water relative to the total amount of the ink is W% by mass, the ratio a / b of the viscosity a (mPa·s) of the mixture Ma of the organic solvent S and water with a mass ratio of (organic solvent S: water) of 99:1 at 23°C to the viscosity b (mPa·s) of the mixture Mb of the organic solvent S and water with a mass ratio of (organic solvent S: water) of 100 - W:W at 23°C is 0.95 or less.

[0017] Another embodiment of the present invention relates to an inkjet ink kit, which includes: the inkjet ink according to any one of the above embodiments and a pretreatment liquid, and the pretreatment liquid contains a flocculant and water in an amount greater than 10.0% by mass relative to the total amount of the pretreatment liquid.

[0018] Advantages of the Invention

[0019] According to some embodiments of the present invention, it is possible to provide an inkjet ink capable of forming an image with less bleeding and having excellent ejection properties. Detailed Embodiments

[0020] Hereinafter, the present invention will be described using embodiments. The examples in the following embodiments do not limit the present invention. In the following description, the inkjet ink may sometimes be simply referred to as "ink".

[0021] <Inkjet Ink>

[0022] In some embodiments of the present invention, an inkjet ink is provided, which contains a coloring material, a binder resin, water, and an organic solvent S. The water is 3.0 to 10.0% by mass relative to the total amount of the ink. The organic solvent S contains an organic solvent A having a boiling point of 150°C or higher and lower than 200°C in an amount of 90.0% by mass or more relative to the total amount of the organic solvent S. In some embodiments, the inkjet ink satisfies at least one selected from the group consisting of the following (i) and (ii).

[0023] (i) The organic solvent A contains a water-soluble organic solvent B having a boiling point of 150°C or higher and lower than 200°C in an amount of 50.0% by mass or more relative to the total amount of the organic solvent S.

[0024] (ii) When the amount of water relative to the total amount of the ink is W% by mass, the ratio a / b of the viscosity a (mPa·s) of the mixture Ma of the organic solvent S and water with a mass ratio of (organic solvent S: water) 99:1 at 23°C to the viscosity b (mPa·s) of the mixture Mb of the organic solvent S and water with a mass ratio of (organic solvent S: water) 100 - W:W at 23°C is 0.95 or less.

[0025] An inkjet ink of one embodiment is the following inkjet ink (hereinafter, this inkjet ink may sometimes be referred to as "inkjet ink Ia" or "ink Ia"): It contains a coloring material, a binder resin, water, and an organic solvent S. The water is 3.0 to 10.0% by mass relative to the total amount of the ink. The organic solvent S contains an organic solvent A having a boiling point of 150°C or higher and lower than 200°C in an amount of 90.0% by mass or more relative to the total amount of the organic solvent S. The organic solvent A contains a water-soluble organic solvent B having a boiling point of 150°C or higher and lower than 200°C in an amount of 50.0% by mass or more relative to the total amount of the organic solvent S.

[0026] An inkjet ink of another embodiment is the following inkjet ink (hereinafter, this inkjet ink may sometimes be referred to as "inkjet ink Ib" or "ink Ib"): It contains a coloring material, a binder resin, water, and an organic solvent S. The water is 3.0 to 10.0% by mass relative to the total amount of the ink. The organic solvent S contains an organic solvent A having a boiling point of 150°C or higher and lower than 200°C in an amount of 90.0% by mass or more relative to the total amount of the organic solvent S. When the amount of water relative to the total amount of the ink is W% by mass, the ratio a / b of the viscosity a (mPa·s) of the mixture Ma of the organic solvent S and water with a mass ratio of (organic solvent S: water) 99:1 at 23°C to the viscosity b (mPa·s) of the mixture Mb of the organic solvent S and water with a mass ratio of (organic solvent S: water) 100 - W:W at 23°C is 0.95 or less.

[0027] For example, when a low-boiling organic solvent is used in a solvent ink to improve the drying property and thereby improve image bleeding, sometimes the discharge property of the ink from the inkjet head deteriorates. The present inventors have found that when the ink contains 3.0 to 10.0% by mass of water relative to the total amount of the ink, the organic solvent S contains an organic solvent A having a boiling point of 150°C or higher and lower than 200°C in an amount of 90.0% by mass or more relative to the total amount of the organic solvent S contained in the ink, and the organic solvent A contains a water-soluble organic solvent B having a boiling point of 150°C or higher and lower than 200°C in an amount of 50.0% by mass or more relative to the total amount of the organic solvent S, and / or when the amount of water relative to the total amount of the ink is W% by mass, the ratio a / b of the viscosity a (mPa·s) of the mixture Ma of the organic solvent S and water with a mass ratio of (organic solvent S: water) 99:1 at 23°C to the viscosity b (mPa·s) of the mixture Mb of the organic solvent S and water with a mass ratio of (organic solvent S: water) 100 - W:W at 23°C is 0.95 or less, the discharge property of the ink can be made good, and an image with suppressed bleeding can be formed. Without being bound by a specific theory, the reason is presumably as follows.

[0028] By making the ink contain, relative to the total amount of the organic solvent S in the ink, 90.0 mass% or more of an organic solvent A having a medium boiling point with a boiling point of 150°C or higher and lower than 200°C, the drying property of the ink can be improved. In addition, since a large amount of low-boiling organic solvent is not used, nozzle clogging can be reduced, and the occurrence of ejection failure caused by ink solidification near the nozzle can be reduced. In addition, the ink contains 3.0 mass% or more of water relative to the total amount of the ink, whereby the drying property can be improved. It is considered that this is due to the azeotropic phenomenon of water and the organic solvent. In addition, by making the amount of water 10.0 mass% or less relative to the total amount of the ink, an increase in ink viscosity can be suppressed. In addition, as in ink Ia, the organic solvent A contains, in an amount of 50.0 mass% or more relative to the total amount of the organic solvent S in the ink, a water-soluble organic solvent B having a boiling point of 150°C or higher and lower than 200°C, whereby water can be more stably contained in the ink, and an increase in ink viscosity can be suppressed. In addition, as in ink Ib, when the amount of water relative to the total amount of the ink is W mass%, when the ratio a / b of the viscosity a (mPa·s) of the mixture Ma with a mass ratio of organic solvent S to water (organic solvent S: water) of 99:1 at 23°C to the viscosity b (mPa·s) of the mixture Mb with a mass ratio of organic solvent S to water (organic solvent S: water) of 100 - W:W at 23°C is 0.95 or less, it becomes easier to suppress an increase in ink viscosity such as a situation where the ink solid component concentration becomes high due to the evaporation of low-boiling water. It is speculated that ink Ia and ink Ib can improve the ejection property of the ink by suppressing nozzle clogging, suppressing ejection failure caused by ink solidification near the nozzle, and suppressing an increase in ink viscosity, and in addition, by improving the drying property of the ink, bleeding of the image can be reduced.

[0029] <Inkjet ink Ia>

[0030] An inkjet ink Ia according to an embodiment is the following inkjet ink: It contains a coloring material, a binder resin, water, and an organic solvent S. Water is 3.0 to 10.0 mass% relative to the total amount of the ink. The organic solvent S contains, in an amount of 90.0 mass% or more relative to the total amount of the organic solvent S, an organic solvent A having a boiling point of 150°C or higher and lower than 200°C. The organic solvent A contains, in an amount of 50.0 mass% or more relative to the total amount of the organic solvent S, a water-soluble organic solvent B having a boiling point of 150°C or higher and lower than 200°C. Hereinafter, inkjet ink Ia will be described.

[0031] Ink Ia may contain a coloring material. Ink Ia may contain a pigment, a dye, or a combination thereof as the coloring material.

[0032] As the pigment, organic pigments such as azo pigments, phthalocyanine pigments, polycyclic pigments, and dye lakes, as well as inorganic pigments such as carbon black and metal oxides can be used. As azo pigments, soluble azo lake pigments, insoluble azo pigments, and condensed azo pigments can be cited. As phthalocyanine pigments, metal phthalocyanine pigments and metal-free phthalocyanine pigments can be cited. As polycyclic pigments, quinacridone-based pigments, perylene-based pigments, perinone-based pigments, isoindoline-based pigments, isoindolinone-based pigments, dioxazine-based pigments, thioindigo-based pigments, anthraquinone-based pigments, quinophthalone-based pigments, metal complex pigments, and diketopyrrolopyrrole (DPP) can be cited. As carbon black, furnace black, lamp black, acetylene black, channel black, etc. can be cited. As metal oxides, titanium oxide, zinc oxide, etc. can be cited. These pigments can be used alone or in combination of two or more.

[0033] Regarding the average particle diameter of the pigment particles in the ink, from the viewpoints of ejection stability and storage stability, the average value based on volume in the particle size distribution measured by the dynamic light scattering method is preferably 1 μm or less, more preferably 500 nm or less, and further preferably 300 nm or less.

[0034] The pigment can be incorporated into the ink in the form of a pigment dispersion. As the pigment dispersion, as long as the pigment can be dispersed in the solvent and the pigment is in a dispersed state in the ink. For example, those obtained by dispersing the pigment in a dispersion medium with a pigment dispersant, those obtained by dispersing microencapsulated pigments covered with a resin in a dispersion medium, etc. can be used.

[0035] The dispersion form of the pigment can be a dispersion in which so-called capsule pigments and colored resin particles covered with a non-oil-soluble resin by a pigment dispersant are dispersed, and preferably a dispersion in which the pigment dispersant is directly adsorbed on the surface of the pigment and dispersed.

[0036] As the dye, dyes commonly used in the art can be arbitrarily used. The dye shows affinity for the non-aqueous solvent of the ink, so that the storage stability becomes better. Therefore, an oil-soluble dye is preferably used.

[0037] As oil-soluble dyes, azo dyes, metal complex salts dyes, naphthol dyes, anthraquinone dyes, indigo dyes, carbonium dyes, quinoneimine dyes, xanthene dyes, cyanine dyes, quinoline dyes, nitro dyes, nitroso dyes, benzoquinone dyes, naphthoquinone dyes, phthalocyanine dyes, metal phthalocyanine dyes, etc. can be cited. These can be used alone or in combination of multiple.

[0038] Regarding the content of the coloring material, from the viewpoints of printing density and ink viscosity, it is preferably 0.1 to 20% by mass, more preferably 1 to 15% by mass, and further preferably 5 to 10% by mass relative to the total amount of the ink.

[0039] When the ink Ia contains a pigment, in order to stably disperse the pigment in the ink, a pigment and a pigment dispersant can be used simultaneously. As the pigment dispersant, as long as it can stably disperse the pigment in the ink, there is no particular limitation. For example, it is preferably a hydroxy-containing carboxylic acid ester, a salt of a long-chain polyaminoamide and a high-molecular-weight acid ester, a salt of a high-molecular-weight polycarboxylic acid, a salt of a long-chain polyaminoamide and a polar acid ester, a high-molecular-weight unsaturated acid ester, a copolymer of vinylpyrrolidone and a long-chain olefin, a modified polyurethane, a modified polyacrylate, a polyether ester type anionic surfactant, a polyoxyethylene alkyl phosphate ester, a polyester polyamine, etc.

[0040] As the pigment dispersant, a high-molecular dispersant is preferably used. As the high-molecular dispersant, a synthetic substance can be used, or a commercially available product can also be used.

[0041] Examples of commercially available products of the pigment dispersant include "Solsperse J180", "Solsperse J200", "Solsperse 71000", "Solsperse 74000", "Solsperse 86000", "Solsperse 87000", "Solsperse M387", etc. manufactured by Lubrizol Corporation (all are trade names). These can be used alone as one kind, or two or more kinds can be used in combination.

[0042] The pigment dispersant is preferably contained in a mass ratio of 0.2 to 1.0 relative to the pigment 1. As the content of the pigment dispersant in the total amount of the ink, it is preferably 0.5 to 15% by mass, more preferably 1 to 5% by mass.

[0043] The ink Ia may contain a binder resin.

[0044] From the viewpoint of forming a uniform ink film and improving the adhesion of the image to the substrate, as the binder resin, a resin that is soluble in the organic solvent S contained in the ink is preferably used.

[0045] As the binder resin, for example, (meth)acrylic resins, styrene-(meth)acrylic resins, styrene-maleic resins, ethylene-(meth)acrylic resins, urethane resins, vinyl chloride resins, vinyl chloride-vinyl acetate resins, polyester resins, polyvinyl alcohol resins, epoxy resins, polyvinylpyrrolidone resins, etc. can be cited.

[0046] From the viewpoint of improving the adhesion of the image to the substrate, as the binder resin, a (meth)acrylic resin is preferred. As the binder resin, a (meth)acrylic resin that is soluble in the organic solvent S is more preferred. When using a (meth)acrylic resin, the adhesion of the image to a plastic substrate such as an olefin resin can be improved. In particular, olefin resins tend to have low affinity for the organic solvents of inks, and it is sometimes difficult to obtain good adhesion of the image. However, when using a (meth)acrylic resin, it is easy to improve the adhesion of the image to the substrate.

[0047] (Meth)acrylic resins can be, for example, resins containing at least one unit selected from the group consisting of units derived from (meth)acrylic acid and units derived from (meth)acrylic esters.

[0048] In the present disclosure, (meth)acrylic acid refers to the general term for acrylic acid and methacrylic acid, and (meth)acrylate refers to the general term for acrylate and methacrylate.

[0049] Examples of (meth)acrylates include (meth)acrylic acid alkyl esters, (meth)acrylic acid benzyl esters, (meth)acrylic acid hydroxyalkyl esters, etc. Examples of (meth)acrylic acid alkyl esters include (meth)acrylic acid alkyl esters having an alkyl group with 1 to 8, 1 to 6, or 1 to 4 carbon atoms. Specifically, for example, methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, etc.

[0050] (Meth)acrylic resins can be, for example, polymers of one or more monomers selected from the group consisting of (meth)acrylic acid and (meth)acrylates.

[0051] Examples of (meth)acrylic resins include poly(meth)acrylic acid, poly(meth)acrylates (e.g., poly(methyl methacrylate), poly(ethyl methacrylate), poly(butyl methacrylate), etc.), (meth)acrylate copolymer resins, (meth)acrylic acid-(meth)acrylate copolymer resins, etc.

[0052] (Meth)acrylic resins preferably contain, for example, units derived from (meth)acrylic acid alkyl esters. The units derived from (meth)acrylic acid alkyl esters can be, for example, 50.0 mass% or more, 70.0 mass% or more, or 90.0 mass% or more relative to all the units of the (meth)acrylic resin.

[0053] As specific examples of the (meth)acrylic resin, for example, polymers of methyl (meth)acrylate, copolymers of methyl (meth)acrylate and at least one selected from the group consisting of (meth)acrylic acid, ethyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, and benzyl (meth)acrylate (for example, copolymers of 100 parts by mass of methyl methacrylate and at least one selected from the group consisting of methacrylic acid, butyl methacrylate, and benzyl methacrylate in an amount of 0.1 to 200 parts by mass, 1 to 180 parts by mass, or 10 to 150 parts by mass, etc.) can be mentioned.

[0054] The glass transition point (Tg) of the (meth)acrylic resin can be, for example, 60°C or higher, and from the viewpoint of improving the adhesion of the image to the substrate, it is preferably 80°C or higher, more preferably 100°C or higher. The glass transition point of the (meth)acrylic resin can be, for example, 200°C or lower. The glass transition point of the (meth)acrylic resin can be, for example, 60 to 200°C, 80 to 200°C, or 100 to 200°C. In the present disclosure, the glass transition point is a calculated value based on the FOX formula.

[0055] The weight-average molecular weight of the (meth)acrylic resin is preferably 5,000 to 150,000, more preferably 10,000 to 100,000. From the viewpoints of water resistance and durability, the weight-average molecular weight of the (meth)acrylic resin is preferably 5,000 or more, more preferably 10,000 or more. From the viewpoints of ink viscosity and dischargeability, the weight-average molecular weight of the (meth)acrylic resin is preferably 150,000 or less, more preferably 100,000 or less. In the present disclosure, the weight-average molecular weight is a value obtained by conversion with standard polystyrene by the GPC method.

[0056] As the (meth)acrylic resin, a synthetic resin can be used, and a commercially available resin can also be used.

[0057] The method for synthesizing the (meth)acrylic resin is not particularly limited. The (meth)acrylic resin can be obtained, for example, by polymerizing one or more radical polymerizable monomers by solution polymerization or the like. For example, at least one monomer selected from the group consisting of (meth)acrylic acid and (meth)acrylate can be polymerized.

[0058] The polymerization solvent (reaction solvent) used in solution polymerization is not particularly limited, and preferably can dissolve the (meth)acrylic resin obtained by polymerization. From the viewpoints of the compatibility between the obtained (meth)acrylic resin and the organic solvents in the ink and the preparation of an ink with low viscosity therefrom, the polymerization solvent can be the organic solvent S or the organic solvent A contained in the ink. For example, when the ink contains two or more organic solvents as the organic solvent S or the organic solvent A, only one of them can be used as the polymerization solvent.

[0059] When carrying out the polymerization reaction, a polymerization initiator such as a radical polymerization initiator can be used.

[0060] As the radical polymerization initiator, known radical polymerization initiators such as azo compounds such as 2,2'-azobis(isobutyronitrile) (AIBN), 2,2'-azobis(2,4'-dimethylvaleronitrile), 2,2'-azobisisobutyric acid dimethyl ester, hydrogen peroxide-based, dialkyl peroxide-based, peroxyester-based, diallyl peroxide-based and other organic peroxides can be used. These can be used alone or in combination of two or more.

[0061] As the (meth)acrylic resin, from the viewpoints of good compatibility between the (meth)acrylic resin and the solvent and the preparation of an ink with low viscosity therefrom, an acrylic resin obtained by solution polymerization of a radically polymerizable monomer using a radical polymerization initiator in the organic solvent S or the organic solvent A used for the ink is preferred. For example, when the ink contains two or more organic solvents as the organic solvent S or the organic solvent A, the (meth)acrylic resin can be a resin obtained by solution polymerization using only one of them as the polymerization solvent.

[0062] As commercially available products of the (meth)acrylic resin, for example, "Neocryl B-728", "Neocryl B-801" manufactured by Covestro, "Dianal BR-83", "Dianal BR-87", "Dianal MB-7333" manufactured by Mitsubishi Chemical Corporation, etc. (all are trade names) can be cited.

[0063] The binder resin can be, for example, 1.0% by mass or more or 3.0% by mass or more based on the total amount of the ink. On the other hand, the binder resin can be, for example, 40.0% by mass or less, 30.0% by mass or less, or 20.0% by mass or less based on the total amount of the ink. The binder resin can be, for example, 1.0 to 40.0% by mass, 1.0 to 30.0% by mass, or 3.0 to 20.0% by mass based on the total amount of the ink.

[0064] Ink Ia can contain water.

[0065] As for water, there is no particular limitation, and it is preferably as free of ionic components as possible. In particular, from the viewpoint of the storage stability of the ink, it is preferable that the content of polyvalent metal ions such as calcium is small. As water, for example, ion-exchanged water, distilled water, ultrapure water, etc. are suitable.

[0066] From the viewpoint of reducing bleeding of the image, water is preferably 3.0 mass% or more, more preferably 4.0 mass% or more, and still more preferably 4.5 mass% or more based on the total amount of the ink. When water is 3.0 mass% or more based on the total amount of the ink, the drying property of the ink is improved. For example, in the case of printing on a roll paper, transfer of the image during winding after printing can also be suppressed. On the other hand, from the viewpoint of improving the discharge property of the ink, water is preferably 10.0 mass% or less, more preferably 9.0 mass% or less, and still more preferably 8.0 mass% or less based on the total amount of the ink. Water is preferably 3.0 to 10.0 mass%, more preferably 4.0 to 9.0 mass%, and still more preferably 4.5 to 8.0 mass% based on the total amount of the ink.

[0067] The amount of water in the ink may sometimes be the same as the amount of water actively compounded into the ink. On the other hand, when an organic solvent having an affinity for water is compounded into the ink, such an organic solvent may absorb water vapor or the like contained in the atmosphere, etc. For example, in such a case, the amount of water compounded into the ink may be different from the amount of water in the ink.

[0068] The amount of water in the ink can be measured, for example, by the Karl Fischer method.

[0069] Ink Ia may contain an organic solvent S. As the organic solvent S, an organic solvent having a boiling point of 150°C or higher and lower than 200°C (organic solvent A), and other organic solvents can be cited. As other organic solvents, for example, organic solvents having a boiling point lower than 150°C, and organic solvents having a boiling point of 200°C or higher can be cited. As an organic solvent having a boiling point lower than 150°C, for example, ethylene glycol monomethyl ether acetate, etc. can be cited. As an organic solvent having a boiling point of 200°C or higher, for example, γ-butyrolactone, 2-pyrrolidone, etc. can be cited. The ink may contain one or two or more of these other organic solvents.

[0070] The organic solvent having a boiling point of 150°C or higher and lower than 200°C (organic solvent A) can be any solvent among ketone-based organic solvents, alcohol-based organic solvents, glycol ether-based organic solvents, acetate-based organic solvents, etc. The organic solvent A can be used alone or in combination of two or more.

[0071] Regarding the boiling point of the organic solvent A, from the viewpoint of reducing bleeding of the image, it is preferably lower than 200°C, more preferably 195°C or lower. On the other hand, regarding the boiling point of the organic solvent A, from the viewpoint of improving the discharge property of the ink, it is preferably 150°C or higher, more preferably 160°C or higher, and still more preferably 170°C or higher.

[0072] In Ink Ia, the organic solvent A may contain a water-soluble organic solvent (water-soluble organic solvent B) having a boiling point of 150°C or higher and lower than 200°C, and may also contain a water-insoluble organic solvent having a boiling point of 150°C or higher and lower than 200°C.

[0073] In the organic solvent A, examples of the water-soluble organic solvent B include diethylene glycol diethyl ether, diethylene glycol ethyl methyl ether, diethylene glycol isopropyl methyl ether, diethylene glycol dimethyl ether, ethylene glycol monobutyl ether, diethylene glycol monoethyl ether, diethylene glycol monomethyl ether, dipropylene glycol monomethyl ether, 3-methoxy-3-methyl-1-butanol, 3-methoxy-1-butanol, diethylene glycol monoethyl ether acetate, 1,2-propanediol, ethyl lactate, ethylene glycol, ethylene glycol monoacetate, etc. These may be used alone or in combination of two or more.

[0074] In the organic solvent A, examples of the water-insoluble organic solvent having a boiling point of 150°C or higher and lower than 200°C include ethylene glycol monobutyl ether acetate, ethylene glycol diacetate, dipropylene glycol dimethyl ether, propylene glycol 1-monobutyl ether, butyl lactate, hexyl propionate, ethyl 3-ethoxypropionate, etc. The water-insoluble organic solvent having a boiling point of 150°C or higher and lower than 200°C may be used alone or in combination of two or more.

[0075] For the organic solvent A, from the viewpoints of improving the ejection property of the ink and suppressing bleeding of the image, it is preferably 90.0 mass% or more, more preferably 95.0 mass% or more, and still more preferably 99.0 mass% or more, relative to the total amount of the organic solvent S in the ink. The organic solvent A may be 100 mass% relative to the total amount of the organic solvent S in the ink. The organic solvent A may be, for example, 90.0 to 100 mass%, 95.0 to 100 mass%, or 99.0 to 100 mass% relative to the total amount of the organic solvent S in the ink.

[0076] From the viewpoint of improving the ejection property of the ink, the water-soluble organic solvent B is preferably 50.0 mass% or more, more preferably 60.0 mass% or more, still more preferably 70.0 mass% or more, still more preferably 80.0 mass% or more, and still more preferably 90.0 mass% or more, relative to the total amount of the organic solvent S in the ink. The water-soluble organic solvent B may be 100 mass% relative to the total amount of the organic solvent S in the ink. The water-soluble organic solvent B may be, for example, 50.0 to 100 mass%, 60.0 to 100 mass%, 70.0 to 100 mass%, 80.0 to 100 mass%, or 90.0 to 100 mass% relative to the total amount of the organic solvent S in the ink.

[0077] From the viewpoint of stably maintaining the binder resin in the ink, suppressing the increase in the viscosity of the ink, and further improving the dischargeability, the water-soluble organic solvent B preferably contains a water-soluble organic solvent Bx having a Hansen solubility parameter (HSP value) of 25.0 MPa 1 / 2 or less and a boiling point of 150°C or higher and lower than 200°C.

[0078] The HSP value of the water-soluble organic solvent Bx can be, for example, 23.0 MPa 1 / 2 or less. On the other hand, the HSP value of the water-soluble organic solvent Bx can also be, for example, 10.0 MPa 1 / 2 or more or 15.0 MPa 1 / 2 or more. The HSP value of the water-soluble organic solvent Bx can be, for example, 10.0 to 25.0 MPa 1 / 2 or 15.0 to 23.0 MPa. 1 / 2

[0079] The Hansen solubility parameter was proposed by Hansen in 1967 and divides the solubility parameter introduced by Hildebrand into a dispersion term δ D , a polar term δ P , and a hydrogen bond term δ H These three components are represented in three-dimensional space. The dispersion term represents the effect based on the dispersion force, the polar term represents the effect based on the dipole-dipole force, and the hydrogen bond term represents the effect of the hydrogen bond force.

[0080] More specifically, it is described in POLYMER HANDBOOK.FOURTH EDITION.(Editors.J.BRANDRUP, E.H.IMMERGUT, and E.A.GRULKE.) and the like.

[0081] In the present disclosure, the value calculated using the Hansen solubility parameter calculation software "HSPiP: Hansen Solubility Parameters in Practice" ver. 5.3 based on Charles.M.Hansen et al. is adopted.

[0082] Examples of the water-soluble organic solvent Bx include diethylene glycol diethyl ether, diethylene glycol ethyl methyl ether, diethylene glycol isopropyl methyl ether, diethylene glycol dimethyl ether, ethylene glycol monobutyl ether, diethylene glycol monoethyl ether, diethylene glycol monomethyl ether, dipropylene glycol monomethyl ether, 3-methoxy-3-methyl-1-butanol, 3-methoxy-1-butanol, diethylene glycol monoethyl ether acetate, ethyl lactate, ethylene glycol monoacetate, etc. These can be used alone or in combination of two or more.

[0083] ​From the viewpoint of further improving the discharge property, the water-soluble organic solvent Bx is preferably 50.0% by mass or more, more preferably 75.0% by mass or more, still more preferably 80.0% by mass or more, and still more preferably 90.0% by mass or more with respect to the total amount of the water-soluble organic solvent B. On the other hand, the water-soluble organic solvent Bx can be 100% by mass with respect to the total amount of the water-soluble organic solvent B. For example, the water-soluble organic solvent Bx can be 50.0 to 100% by mass, 75.0 to 100% by mass, 80.0 to 100% by mass, or 90.0 to 100% by mass with respect to the total amount of the water-soluble organic solvent B.

[0084] For example, when the amount of water with respect to the total amount of the ink is W% by mass, the ratio a / b of the viscosity a (mPa·s) of the mixture Ma having a mass ratio of the organic solvent S to water (organic solvent S: water) of 99:1 at 23°C to the viscosity b (mPa·s) of the mixture Mb having a mass ratio of the organic solvent S to water (organic solvent S: water) of 100 - W:W at 23°C can be 0.95 or less. The ratio a / b can be, for example, 0.90 or less, or 0.85 or less. On the other hand, the ratio a / b can also be, for example, 0.50 or more, 0.55 or more, or 0.60 or more. The ratio a / b can be, for example, 0.50 to 0.95, 0.55 to 0.90, or 0.60 to 0.85.

[0085] As the viscosity measuring device, for example, "Rheometer MCR302" manufactured by Anton Paar Japan K.K. can be used. The mixtures Ma and Mb can be prepared, for example, by the method described in Ink Ib.

[0086] Ink Ia preferably contains a surfactant. For example, from the viewpoints of good wetting and spreading of the ink on the surface of a hydrophobic substrate, increased drying speed, and formation of a good image, the ink preferably contains a surfactant. Examples of the surfactant include silicone-based surfactants, fluorine-based surfactants, and polyoxyethylene derivatives as nonionic surfactants.

[0087] As the silicone-based surfactant, for example, polyester-modified silicone, polyether-modified silicone, etc. can be cited. As an example of a commercially available product of the silicone-based surfactant, for example, "BYK-307", "BYK-313", "BYK-330", "BYK-333", "BYK-342", "BYK-370", "BYK-377", "BYK-378", "BYK-3550", "BYK-3750", "BYK-3761", "BYK-3762", "BYK-3764", "BYK-SILCLEAN3700" manufactured by BYK-Chemie Japan K.K., "SILFACE SAG005", "SILFACE SAG008", "SILFACE SAG503A" manufactured by Nissin Chemical Industry Co., Ltd., etc. (all are trade names).

[0088] As an example of a commercially available product of the fluorine-based surfactant, "BYK-340" manufactured by BYK-Chemie Japan K.K., "Surflon S-241", "Surflon S-242", "Surflon S-242L", "Surflon S-243", "Surflon S-420", "Surflon S-431" manufactured by AGC Inc., etc. (all are trade names) can be cited.

[0089] As the polyoxyethylene derivative, an alkynediol-based surfactant is preferably used. As an example of a commercially available product of the alkynediol-based surfactant, for example, "SURFYNOL 420", "SURFYNOL 440", "SURFYNOL 465", "SURFYNOL 485" manufactured by Evonik Industries, "OLFINE E-1004", "OLFINE-1010" manufactured by Nissin Chemical Industry Co., Ltd., etc. (all are trade names).

[0090] From the aspects of continuous dischargeability during printing and color development of the image, Ink Ia preferably contains a silicone-based surfactant.

[0091] The surfactant can be used alone in one kind, or two or more kinds can be used in combination.

[0092] The surfactant is preferably 0.05 to 2% by mass, more preferably 0.1 to 1% by mass based on the total amount of the ink.

[0093] Ink Ia can contain various additives according to uses, etc. As the additives, for example, UV absorbers, light stabilizers, antioxidants, plasticizers, etc. can be cited.

[0094] <Inkjet Ink Ib>

[0095] Ink Ib of one embodiment is the following inkjet ink: it contains a coloring material, a binder resin, water, and an organic solvent S. The water is 3.0 to 10.0% by mass relative to the total amount of the ink. The organic solvent S contains, in an amount of 90.0% by mass or more relative to the total amount of the organic solvent S, an organic solvent A having a boiling point of 150°C or higher and lower than 200°C. When the amount of water relative to the total amount of the ink is W% by mass, the ratio a / b of the viscosity a (mPa·s) of the mixture Ma of the organic solvent S and water at a mass ratio (organic solvent S: water) of 99:1 at 23°C to the viscosity b (mPa·s) of the mixture Mb of the organic solvent S and water at a mass ratio (organic solvent S: water) of 100 - W:W at 23°C is 0.95 or less.

[0096] Ink Ib may contain a coloring material. Ink Ib may contain a pigment, a dye, or a combination thereof as the coloring material.

[0097] Regarding the coloring material in Ink Ib and its content, etc., the description in Ink Ia can be applied.

[0098] When Ink Ib contains a pigment, in order to stably disperse the pigment in the ink, a pigment and a pigment dispersant can be used simultaneously. Regarding the pigment dispersant in Ink Ib and its content, etc., the description in Ink Ia can be applied.

[0099] Ink Ib may contain a binder resin. Regarding the binder resin in Ink Ib and its content, etc., the description in Ink Ia can be applied.

[0100] Ink Ib may contain water. Regarding the water in Ink Ib and its content, etc., the description in Ink Ia can be applied.

[0101] Ink Ib may contain an organic solvent S. Examples of the organic solvent S include an organic solvent (organic solvent A) having a boiling point of 150°C or higher and lower than 200°C, and other organic solvents. Examples of the other organic solvents include organic solvents having a boiling point lower than 150°C and organic solvents having a boiling point of 200°C or higher. Examples of the organic solvent having a boiling point lower than 150°C include ethylene glycol monomethyl ether acetate, etc. Examples of the organic solvent having a boiling point of 200°C or higher include γ-butyrolactone, 2-pyrrolidone, etc. The ink may contain one or two or more of these other organic solvents.

[0102] As the organic solvent (organic solvent A) having a boiling point of 150°C or higher and lower than 200°C, it can be any solvent among ketone-based organic solvents, alcohol-based organic solvents, glycol ether-based organic solvents, acetate-based organic solvents, etc. The organic solvent A can be used alone or in combination of two or more.

[0103] Regarding the boiling point of organic solvent A, from the perspective of reducing bleeding of the image, it is preferably below 200 °C, more preferably 195 °C or lower. On the other hand, from the perspective of improving the ejection property of the ink, the boiling point of organic solvent A is preferably 150 °C or higher, more preferably 160 °C or higher, and further preferably 170 °C or higher.

[0104] In ink Ib, organic solvent A may contain a water-soluble organic solvent B having a boiling point of 150 °C or higher and lower than 200 °C, a water-insoluble organic solvent having a boiling point of 150 °C or higher and lower than 200 °C, or a combination thereof.

[0105] In organic solvent A, as examples of the water-soluble organic solvent B, for example, the examples exemplified in the description of ink Ia can be cited. These can be used alone or in combination of two or more.

[0106] In organic solvent A, as examples of the water-insoluble organic solvent having a boiling point of 150 °C or higher and lower than 200 °C, for example, the examples cited in the description of ink Ia can be cited. The water-insoluble organic solvent having a boiling point of 150 °C or higher and lower than 200 °C can be used alone or in combination of two or more.

[0107] Regarding organic solvent A, from the perspective of improving the ejection property of the ink and reducing bleeding of the image, it is preferably 90.0% by mass or more, more preferably 95.0% by mass or more, and further preferably 99.0% by mass or more, relative to the total amount of organic solvent S in the ink. Organic solvent A can be 100% by mass relative to the total amount of organic solvent S in the ink. For example, organic solvent A can be 90.0 - 100% by mass, 95.0 - 100% by mass, or 99.0 - 100% by mass relative to the total amount of organic solvent S in the ink.

[0108] The water-soluble organic solvent B can be, for example, 20.0% by mass or more, 50.0% by mass or more, 60.0% by mass or more, 70.0% by mass or more, 80.0% by mass or more, or 90.0% by mass or more, relative to the total amount of organic solvent S in the ink. The water-soluble organic solvent B can be 100% by mass relative to the total amount of organic solvent S in the ink. For example, the water-soluble organic solvent B can be 20.0 - 100% by mass, 50.0 - 100% by mass, 60.0 - 100% by mass, 70.0 - 100% by mass, 80.0 - 100% by mass, or 90.0 - 100% by mass relative to the total amount of organic solvent S in the ink.

[0109] From the viewpoint of improving the ejection property of the ink, when the amount of water relative to the total amount of the ink is W mass%, the ratio a / b of the viscosity a (mPa·s) of the mixture Ma of an organic solvent S and water at a mass ratio of (organic solvent S: water) 99:1 at 23°C to the viscosity b (mPa·s) of the mixture Mb of an organic solvent S and water at a mass ratio of (organic solvent S: water) 100 - W:W at 23°C is preferably 0.95 or less. The ratio a / b can be, for example, 0.90 or less, or 0.85 or less. On the other hand, the ratio a / b can also be, for example, 0.50 or more, 0.55 or more, or 0.60 or more. The ratio a / b can be, for example, 0.50 to 0.95, 0.55 to 0.90, or 0.60 to 0.85.

[0110] For the mixture Ma, for example, the amount of water contained in the organic solvent S can be measured by the Karl Fischer method, and adjusted so that the amount of water relative to the total amount of the organic solvent S and water becomes 1 mass% to obtain it.

[0111] For the mixture Mb, for example, the amount of water contained in the organic solvent S can be measured by the Karl Fischer method, and adjusted so that the amount of water relative to the total amount of the organic solvent S and water becomes the same amount as the amount of water relative to the total amount of the ink, that is, W mass% to obtain it.

[0112] In addition, when the amount of water contained in the organic solvent S is too high, for example, when it exceeds 1 mass%, various means can be used for dehydration. As a means of dehydration, for example, a method using a porous material such as a molecular sieve is preferably used. In this case, the porous material and the dehydrating agent can be added to the solvent and mixed by means such as stirring, and after dehydration, the porous material can be removed by means such as filtration.

[0113] As the viscosity measuring device, for example, "Rheometer MCR302" manufactured by Anton Paar Japan K.K. can be used.

[0114] The method of setting the ratio a / b to 0.95 or less is not particularly limited. For example, in a mixture of water and an organic solvent, when the mixing ratio is within a specific range, a method of using an organic solvent whose viscosity of the mixture is higher than the viscosity of water and the viscosity of the organic solvent, that is, an organic solvent whose viscosity of the mixture shows a maximum value at a specific mixing ratio, as the organic solvent S can be cited. For the reason for such a maximum value, it is mostly based on the intermolecular interaction between water and the organic solvent. Therefore, for example, an organic solvent can be selected using the Hansen solubility parameter (HSP value) as an index. Specifically, by making the organic solvent S contain an organic solvent with a small HSP value, the mixture of water and the organic solvent S can have a maximum value of viscosity. Therefore, the ratio a / b can be made 0.95 or less by adjusting the amount of water relative to the total amount of the ink (W mass%).

[0115] From the viewpoints of improving the storage stability of the ink and more effectively suppressing the increase in the viscosity of the ink, the organic solvent A preferably contains an organic solvent Ax having a Hansen solubility parameter (HSP value) of 25.0 MPa 1 / 2 or less and a boiling point of 150 °C or higher and lower than 200 °C. The HSP value of the organic solvent Ax is more preferably 23.0 MPa 1 / 2 or less. The HSP value of the organic solvent Ax can be, for example, 10.0 MPa 1 / 2 or more or 15.0 MPa 1 / 2 or more. The HSP value of the organic solvent Ax can be, for example, 10.0 to 25.0 MPa 1 / 2 or 15.0 to 23.0 MPa 1 / 2 .

[0116] As the organic solvent Ax, a water-soluble organic solvent Bx having an HSP value of 25.0 MPa 1 / 2 or less and a boiling point of 150 °C or higher and lower than 200 °C, a water-insoluble organic solvent having an HSP value of 25.0 MPa 1 / 2 or less and a boiling point of 150 °C or higher and lower than 200 °C, or a combination thereof can be used.

[0117] Among the organic solvents Ax, as examples of the water-soluble organic solvent Bx, for example, the examples cited as the water-soluble organic solvent Bx in the description of Ink Ia can be cited. These can be used alone or in combination of two or more.

[0118] Among the organic solvents Ax, as examples of the water-insoluble organic solvent, for example, ethylene glycol monobutyl ether acetate, ethylene glycol diacetate, propylene glycol diacetate, dipropylene glycol dimethyl ether, propylene glycol 1-monobutyl ether, butyl lactate, hexyl propionate, ethyl 3-ethoxypropionate, etc. can be cited. These can be used alone or in combination of two or more.

[0119] From the viewpoint of improving the storage stability of the ink, as the organic solvent Ax, an organic solvent having an ether bond is preferred. As examples of such an organic solvent, for example, an alkylene glycol monoalkyl ether having an HSP value of 25.0 MPa 1 / 2 or less and a boiling point of 150 °C or higher and lower than 200 °C, an alkylene glycol dialkyl ether having an HSP value of 25.0 MPa 1 / 2 or less and a boiling point of 150 °C or higher and lower than 200 °C, etc. can be cited. Since the reactivity of the ether bond is relatively low, there is a tendency that it is not easily reacted with water and not easily hydrolyzed, and the storage stability of the ink containing water can be improved.

[0120] From the viewpoint of improving the storage stability of the ink, the organic solvent Ax is preferably contained in an amount of 50.0% by mass or more based on the organic solvent Ax and is selected from alkylene glycol monoalkyl ethers having an HSP value of 25.0 MPa 1 / 2 or less and a boiling point of 150°C or higher and lower than 200°C, and alkylene glycol dialkyl ethers having an HSP value of 25.0 MPa 1 / 2 or less and a boiling point of 150°C or higher and lower than 200°C, and at least one selected from the group consisting of them.

[0121] The organic solvent Ax is preferably 20% by mass or more, more preferably 40% by mass or more, and still more preferably 60% by mass or more based on the total amount of the organic solvents S. On the other hand, the organic solvent Ax can be, for example, 100% by mass based on the total amount of the organic solvents S. The organic solvent Ax is preferably 20 to 100% by mass, more preferably 40 to 100% by mass, and still more preferably 60 to 100% by mass based on the total amount of the organic solvents S.

[0122] <Method for manufacturing ink>

[0123] The method for manufacturing the inks Ia and Ib is not particularly limited. As a method, each component can be mixed and stirred all at once or in portions to prepare the ink. Specifically, for example, all components can be added all at once or in portions to a disperser such as a bead mill and dispersed, and if desired, filtered through a filter such as a membrane filter to prepare the ink.

[0124] In the method for manufacturing the ink, for example, the pigment can be premixed and stirred with a pigment dispersant and an organic solvent or the like to disperse the pigment and prepare a pigment dispersion.

[0125] <Viscosity of ink>

[0126] The viscosities of the inks Ia and Ib vary depending on the nozzle diameter of the discharge head of the inkjet recording system, the discharge environment, etc., and the suitable range is different. Usually, at 23°C, it is preferably 3 to 30 mPa·s, more preferably 3 to 15 mPa·s, and still more preferably 4 to 10 mPa·s. In the present disclosure, the ink viscosity is a value measured at 23°C. As the viscosity measuring device, for example, "Rheometer MCR302" manufactured by Anton Paar Japan K.K. can be used.

[0127] <Printing method>

[0128] As a printing method using Ink Ia and / or Ib, there is no particular limitation, and it can be any method such as a piezoelectric method, an electrostatic method, a thermal method, etc. In the case of using an inkjet recording apparatus, it is preferable to discharge the ink of one embodiment from an inkjet head based on a digital signal and cause the discharged ink droplets to adhere to a substrate. The printing method may include processes such as a pre-treatment process and a heating process. As the pre-treatment process, it may be a process of causing a pre-treatment liquid to adhere to the substrate before the ink adheres to the substrate. As the pre-treatment liquid, the pre-treatment liquid described below may be used.

[0129] In this embodiment, the substrate is not particularly limited, and printing papers such as plain paper, coated paper, and special paper, cloth, inorganic sheets, films, OHP sheets, etc., adhesive sheets having these as substrates and having an adhesive layer provided on the back surface, etc. may be used. For example, the ink of the embodiment is preferably usable for plastic substrates such as vinyl chloride resin and olefin resin. As the olefin resin, for example, polypropylene resin etc. may be mentioned. Such a plastic substrate may be an absorbent substrate such as a substrate having an ink receiving layer that can absorb the applied ink, but may also be a non-absorbent substrate not having an ink receiving layer. The ink of the embodiment is preferably also usable for substrates where ink hardly penetrates. In addition, olefin resins tend to have a low affinity with the organic solvents of the ink, and sometimes it is not easy to obtain the adhesion of the image to the substrate, but in the case of using the ink of the embodiment, even for substrates using olefin resins, good image adhesion can be obtained. The ink of the embodiment is also preferably usable for synthetic papers etc. made of olefin resins such as polypropylene resin.

[0130] <Ink Kit>

[0131] An ink kit of one embodiment may contain the above-described inkjet ink Ia or inkjet ink Ib and contain a pre-treatment liquid.

[0132] From the viewpoint of improving gray-scale reproducibility, the ink kit preferably contains the above-described inkjet ink Ia or inkjet ink Ib and contains a pre-treatment liquid, and the pre-treatment liquid contains a coagulant and water in an amount greater than 10.0% by mass based on the total amount of the pre-treatment liquid.

[0133] The above inkjet ink Ia or Ib is an ink with excellent drying property of the ink. When it is used, an image with less bleeding can be formed. When this ink and a pretreatment liquid containing a coagulant and more than 10.0% by mass of water based on the total amount of the pretreatment liquid are used simultaneously, bleeding of the image can be reduced more effectively, and an image with excellent gray-scale reproducibility can be obtained. Without being bound by a specific theory, the reason is presumed as follows. By making the pretreatment liquid contain water with relatively high volatility in an amount greater than 10.0% by mass, the drying property of the pretreatment liquid is improved, and bleeding of the image can be reduced more effectively. In addition, when the ink comes into contact with the pretreatment liquid, due to the coagulant in the pretreatment liquid and the water contained in the pretreatment liquid in an amount greater than 10.0% by mass, coagulation and thickening of the ink components occur effectively. It is considered that bleeding of the image is reduced effectively in this way, and thus an image with excellent gray-scale reproducibility can be obtained.

[0134] In addition, when such an ink set is used, even when the ink is applied in a state where the pretreatment liquid is not completely dry, bleeding of the image is easily suppressed. Therefore, even for a printing substrate with low heat resistance that is difficult to dry under high heat, bleeding of the image can be reduced, and an image with excellent gray-scale reproducibility can be obtained.

[0135] The ink set may include a combination of one or more kinds of inks. The ink set may include any one of the inkjet ink Ia and the inkjet ink Ib, or may include a combination thereof.

[0136] The pretreatment liquid may contain a coagulant.

[0137] As the coagulant, a component having a function of coagulating components such as a coloring material contained in the ink can be used. As the coagulant, for example, polyvalent metal salts, cationic water-soluble resins, cationic water-dispersible resins, etc. can be cited, and one kind of these can be used or two or more kinds can be used in combination.

[0138] From the viewpoint of further improving the more effective coagulation of the ink components and gray-scale reproducibility, the coagulant preferably contains a polyvalent metal salt, a cationic water-soluble resin, or a combination thereof.

[0139] As the polyvalent metal salt, for example, halides, nitrates, sulfates, acetates, fatty acid salts, lactates, chlorates, etc. of metals with a valence of 2 or more can be cited. As the halide, chlorides, bromides, iodides, etc. are preferred. As the metal with a valence of 2 or more, divalent alkaline earth metals such as Mg, Ca, Sr, Ba, divalent metals such as Ni, Zn, Cu, Fe(II), trivalent metals such as Fe(III), Al, etc. can be cited. As specific examples of the polyvalent metal salt, for example, calcium chloride, calcium nitrate, magnesium chloride, magnesium sulfate hexahydrate, magnesium acetate tetrahydrate, etc. can be cited. One kind of these can be used alone or two or more kinds can be used in combination.

[0140] From the viewpoint of further improving the more effective aggregation of the ink components and the gray-scale reproducibility, the polyvalent metal salt is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, and still more preferably 1.0% by mass or more, based on the total amount of the pretreatment liquid. For example, it may be 2.0% by mass or more. The polyvalent metal salt may be 20.0% by mass or less or 10.0% by mass or less, based on the total amount of the pretreatment liquid. For example, the polyvalent metal salt may be 0.1 to 20.0% by mass, 0.5 to 10.0% by mass, 1.0 to 10.0% by mass, or 2.0 to 10.0% by mass. The amount of the polyvalent metal salt in the case of a hydrate is converted to the amount of the anhydride.

[0141] Examples of the cationic water-soluble resin include polyethyleneimine, polyvinylamine, polyallylamine and its salts, polyvinylpyridine, copolymers of cationic acrylamide, cationic-modified polyvinyl alcohol, etc. These may be used alone or in combination of two or more.

[0142] The cationic water-soluble resin is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, based on the total amount of the pretreatment liquid. The cationic water-soluble resin may be 10.0% by mass or less, 5.0% by mass or less, or 2.0% by mass or less, based on the total amount of the pretreatment liquid. For example, the cationic water-soluble resin may be 0.1 to 10.0% by mass, 0.1 to 5.0% by mass, or 0.2 to 2.0% by mass.

[0143] The cationic water-dispersible resin is a resin particle having a positive charge on its surface, and the positively charged resin particles are dispersed in a particulate form without dissolving in water, and can form an oil-in-water (O / W) type emulsion. As in the case of a self-emulsifying resin, the cationic functional groups possessed by the resin may be present on the particle surface, or surface treatment such as attaching a cationic dispersant to the resin particle surface may be performed.

[0144] Examples of the cationic water-dispersible resin include conjugated diene resins such as styrene-butadiene copolymer, methyl methacrylate-butadiene copolymer, vinyl chloride-vinyl acetate copolymer, etc.; acrylic resins such as polymers of acrylate and methacrylate, or copolymers thereof with styrene, etc.; vinyl-based resins such as ethylene-vinyl acetate copolymer, or functional group-modified resins of these various resins based on functional group-containing monomers such as carboxyl groups; melamine resin, urea resin, polyurethane resin, polyester resin, polyolefin resin, silicone resin, polyvinyl butyral resin, alkyd resin. The resin emulsion of these individual resins may be used, or a mixed resin emulsion may be used. These may be used alone or in combination of two or more.

[0145] The cationic water-dispersible resin is preferably 0.5% by mass or more, more preferably 1.0% by mass or more, and still more preferably 2.0% by mass or more based on the total amount of the pretreatment liquid. The cationic water-dispersible resin can be 20.0% by mass or less, or 15.0% by mass or less based on the total amount of the pretreatment liquid. For example, the cationic water-dispersible resin can be 0.5 to 20.0% by mass, 1.0 to 20.0% by mass, or 2.0 to 15.0% by mass based on the total amount of the pretreatment liquid.

[0146] The flocculant can be, for example, 0.1% by mass or more, 0.5% by mass or more, or 1.0% by mass or more based on the total amount of the pretreatment liquid. The flocculant can be, for example, 20.0% by mass or less, 15.0% by mass or less, or 10.0% by mass or less based on the total amount of the pretreatment liquid. The flocculant can be, for example, 0.1 to 20% by mass, 0.5 to 15.0% by mass, or 1.0 to 10.0% by mass based on the total amount of the pretreatment liquid.

[0147] The pretreatment liquid may contain water. There is no particular limitation on the water blended into the pretreatment liquid. For example, it is advisable to use ion-exchanged water, distilled water, ultrapure water, etc.

[0148] From the viewpoints of improving drying property, reducing ink bleeding of the image, and improving gray-scale reproducibility, the water is preferably more than 10.0% by mass, more preferably 20.0% by mass or more, and still more preferably 40.0% by mass or more based on the total amount of the pretreatment liquid. When the water content is more than 10.0% by mass based on the total amount of the pretreatment liquid, the stability of the ink in contact with the pretreatment liquid effectively collapses, making it easy to cause aggregation and thickening of the ink components. In addition, by making the pretreatment liquid contain more than 10.0% by mass of water with relatively high volatility, the drying property of the pretreatment liquid is also improved, and ink bleeding of the image can be effectively reduced. The water can be, for example, 99.9% by mass or less, or 99.0% by mass or less based on the total amount of the pretreatment liquid. The water can be, for example, more than 10.0% by mass and 99.5% by mass or less, 20.0 to 99.0% by mass, or 40.0 to 99.0% by mass based on the total amount of the pretreatment liquid.

[0149] The amount of water in the pretreatment liquid may sometimes be the same as the amount of water actively blended in the pretreatment liquid. On the other hand, when an organic solvent having an affinity for water is blended in the pretreatment liquid, such an organic solvent may absorb water vapor contained in the atmosphere, etc. For example, in such a case, the amount of water blended in the pretreatment liquid may not be the same as the amount of water in the ink.

[0150] The amount of water in the pretreatment liquid can be measured, for example, by the Karl Fischer method.

[0151] The pretreatment liquid may contain a binder resin. As the binder resin, for example, the resins exemplified as the binder resin in Ink Ia can be mentioned. The binder resin can be, for example, 1 to 20% by mass, or 3 to 15% by mass, relative to the total amount of the pretreatment liquid.

[0152] The pretreatment liquid may contain a water-soluble organic solvent. As the water-soluble organic solvent, an organic compound that is liquid at room temperature and soluble in water can be used. Preferably, a water-soluble organic solvent that is uniformly mixed with the same volume of water at 1 atm and 20 °C is used. For example, lower alcohols such as methanol, ethanol, 1-propanol, isopropyl alcohol, 1-butanol, 2-butanol, isobutanol, 2-methyl-2-propanol, etc.; glycols such as ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, polypropylene glycol, etc.; glycerols such as glycerol, diglycerol, triglycerol, polyglycerol, etc.; glycerol acetates such as monoglycerol acetate, diglycerol acetate, etc.; glycol ethers such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monopropyl ether, diethylene glycol monobutyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monopropyl ether, triethylene glycol monobutyl ether, tetraethylene glycol monomethyl ether, tetraethylene glycol monoethyl ether, tetraethylene glycol dimethyl ether, tetraethylene glycol diethyl ether, etc.; triethanolamine, 1-methyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, β-thiodiglycol, sulfolane, etc. The boiling point of the water-soluble organic solvent is preferably 100 °C or higher, more preferably 150 °C or higher.

[0153] These water-soluble organic solvents can be used alone, or two or more of them can be used in combination as long as they can form a single phase with water. The content of the water-soluble organic solvent in the pretreatment liquid can be, for example, 10 to 80% by mass.

[0154] The pretreatment liquid may contain a surfactant. For example, as the surfactant, the surfactants exemplified in Ink Ia can be used. The surfactant can be about 0.1 to 5% by mass relative to the total amount of the pretreatment liquid.

[0155] The manufacturing method of the pretreatment liquid is not particularly limited. The pretreatment liquid can be suitably manufactured by a usual method, for example. For example, the pretreatment liquid can be mixed or dispersed by being charged into a stirrer such as a three-in-one motor all at once or in portions, and can be prepared by filtering with a filter such as a membrane filter as desired.

[0156] <Method for manufacturing a printed matter>

[0157] A method for manufacturing a printed matter according to one embodiment may include applying ink to a substrate by an inkjet method. As the ink, Ink Ia or Ink Ib of the above embodiment can be used. In addition, as the substrate, the above substrate can be used.

[0158] In the step of applying ink to a substrate, the ink is preferably applied to the substrate by an inkjet method. The inkjet method is not particularly limited and may be any method such as a piezoelectric method, an electrostatic method, a thermal method, or the like.

[0159] The amount of ink applied to the substrate is preferably 1 to 500 g / m 2 and more preferably 3 to 100 g / m 2 and still more preferably 5 to 50 g / m 2 and most preferably 10 to 30 g / m 2 .

[0160] The method for manufacturing a printed matter may include steps such as a pretreatment step and a heating step.

[0161] For example, the method for manufacturing a printed matter may include: applying a pretreatment liquid to a substrate and applying ink to the substrate by an inkjet method. As the pretreatment liquid, the above-described pretreatment liquid can be used. When using a pretreatment liquid containing the above-described coagulant and water in an amount greater than 10.0% by mass based on the total amount of the pretreatment liquid, image bleeding can be more effectively reduced and gray-scale reproducibility can be improved.

[0162] The method for applying the pretreatment liquid is not particularly limited. For example, it can be carried out by uniformly coating the surface of the printing substrate with the pretreatment liquid using a brush, a roller, a bar coater, an air knife coater, or a sprayer, or it can also be carried out by printing an image using a printing means such as inkjet printing, gravure printing, or flexographic printing. That is, the pretreatment liquid can be applied to the entire surface of the substrate or only to the required parts, for example, only to the parts where the above-described ink is applied.

[0163] The amount of the pretreatment liquid applied to the substrate is preferably 1 to 500 g / m 2 and more preferably 3 to 100 g / m 2 and still more preferably 5 to 50 g / m 2 .

[0164] The present disclosure includes the following embodiments.

[0165] <1> An inkjet ink containing a coloring material, a binder resin, water, and an organic solvent S,

[0166] wherein the water is 3.0 to 10.0% by mass based on the total amount of the ink,

[0167] the organic solvent S contains an organic solvent A having a boiling point of 150°C or higher and lower than 200°C in an amount of 90.0% by mass or more based on the total amount of the organic solvent S,

[0168] The aforementioned organic solvent A contains a water-soluble organic solvent B having a boiling point of 150°C or higher and lower than 200°C in an amount of 50.0% by mass or more based on the total amount of the aforementioned organic solvent S.

[0169] <2>The inkjet ink according to <1>, wherein the aforementioned water-soluble organic solvent B contains a water-soluble organic solvent Bx having a Hansen solubility parameter (HSP value) of 25.0 MPa 1 / 2 or less and a boiling point of 150°C or higher and lower than 200°C.

[0170] <3>The inkjet ink according to <2>, wherein the aforementioned water-soluble organic solvent Bx is 75.0% by mass or more based on the total amount of the aforementioned water-soluble organic solvent B.

[0171] <4>An inkjet ink containing a coloring material, a binder resin, water, and an organic solvent S,

[0172] wherein the aforementioned water is 3.0 to 10.0% by mass based on the total amount of the ink,

[0173] the aforementioned organic solvent S contains an organic solvent A having a boiling point of 150°C or higher and lower than 200°C in an amount of 90.0% by mass or more based on the total amount of the aforementioned organic solvent S,

[0174] when the amount of the aforementioned water relative to the total amount of the ink is set to W% by mass, the ratio a / b of the viscosity a (mPa·s) of the mixture Ma of the aforementioned organic solvent S and water at a mass ratio (organic solvent S: water) of 99:1 at 23°C to the viscosity b (mPa·s) of the mixture Mb of the aforementioned organic solvent S and water at a mass ratio (organic solvent S: water) of 100 - W:W at 23°C is 0.95 or less.

[0175] <5>The inkjet ink according to <4>, wherein the aforementioned organic solvent A contains an organic solvent Ax having a Hansen solubility parameter (HSP value) of 25.0 MPa 1 / 2 or less and a boiling point of 150°C or higher and lower than 200°C.

[0176] <6>The inkjet ink according to any one of <1> to <5>, wherein the aforementioned binder resin contains a (meth)acrylic resin.

[0177] <7>An inkjet ink kit containing the inkjet ink according to any one of <1> to <6> and a pretreatment liquid, the pretreatment liquid containing a flocculant and water in an amount greater than 10.0% by mass based on the total amount of the pretreatment liquid.

[0178] <8>The inkjet ink kit according to <7>, wherein the aforementioned flocculant contains at least one selected from the group consisting of polyvalent metal salts and cationic water-soluble resins.

[0179] [Example]

[0180] Hereinafter, the present invention will be described in more detail by way of examples. The present invention is not limited to the following examples.

[0181] [Manufacture of Pigment Dispersion]

[0182] Measure each of the materials described in Table 1 in the proportions shown in Table 1 into a beaker. After premixing, transfer it into a plastic container with a lid. Add zirconia beads with a diameter of 0.8 mm thereto, and disperse for 60 minutes using a swing mill RM-05 (manufactured by Seiwa Giken Co., Ltd.). Then separate the beads from the dispersion liquid to manufacture pigment dispersions 1 to 5 with a pigment concentration of 20% by mass.

[0183] Details of the materials described in Table 1 will be described later.

[0184] [Table 1]

[0185]

[0186] [Synthesis of Binder Resin]

[0187] Binder resins 1 and 2 are manufactured as follows. In the following, the weight average molecular weights of the manufactured binder resins 1 and 2 are values obtained by conversion with standard polystyrene by the GPC method. The measurement is performed using a GPC measurement device manufactured by Shimadzu Corporation. In addition, the glass transition point (Tg) is calculated by the FOX formula.

[0188] [Synthesis of Binder Resin 1]

[0189] In a 1 L flask, a mixture in which 340.0 g of methyl methacrylate as a radically polymerizable monomer and 5.1 g of 2,2'-azobis(isobutyronitrile) (AIBN) (manufactured by Tokyo Chemical Industry Co., Ltd.) as a polymerization initiator are dissolved in 85.0 g of diethylene glycol diethyl ether is dropped into 317.8 g of diethylene glycol diethyl ether (manufactured by Tokyo Chemical Industry Co., Ltd.) maintained at 90°C over 2 hours. After the dropping is completed, the liquid temperature is maintained at 90°C, and 1.1 g of AIBN is added after 30 minutes and 1 hour, respectively. Further, the reaction is carried out at 90°C for 1 hour, and diluted with diethylene glycol diethyl ether so that the effective ingredient concentration of the binder resin becomes 40.0% by mass to obtain a solution of binder resin 1. In the obtained solution of binder resin 1, the effective ingredient concentration is 40% by mass. The Tg of binder resin 1 is 105°C, and the weight average molecular weight is 20,000.

[0190] [Synthesis of Binder Resin 2]

[0191] In a 1-L flask, over a period of 2 hours, a mixture prepared by dissolving 17.0 g of methacrylic acid, 153.0 g of methyl methacrylate, 170.0 g of butyl methacrylate as radically polymerizable monomers, and 5.1 g of 2,2'-azobis(isobutyronitrile) (AIBN) (manufactured by Tokyo Chemical Industry Co., Ltd.) as a polymerization initiator in 85.0 g of diethylene glycol diethyl ether was added dropwise to 317.3 g of diethylene glycol diethyl ether (manufactured by Tokyo Chemical Industry Co., Ltd.) maintained at 90°C. After completion of the dropwise addition, the liquid temperature was maintained at 90°C, and 1.1 g of AIBN was added after 30 minutes and 1 hour, respectively. Further, the reaction was carried out at 90°C for 1 hour, and the solution was diluted with diethylene glycol diethyl ether to make the effective ingredient concentration of the binder resin 40.0 mass%. A solution of binder resin 2 was obtained. In the obtained solution of binder resin 2, the effective ingredient concentration was 40.0 mass%. The Tg of binder resin 2 was 60°C, and the weight average molecular weight was 19,000.

[0192] <Manufacture of Ink>

[0193] The respective materials described in Tables 2 to 5 were measured in the proportions shown in Tables 2 to 5, mixed and stirred using a three-in-one motor, and then filtered through a membrane filter with a pore size of 3 μm to prepare Inks 1 to 28.

[0194] Details of the raw materials described in Tables 2 to 5 are described later.

[0195] In addition, the amount of water in the ink, the amount of organic solvent S in the ink, the amount of organic solvent A in the ink having a boiling point of 150°C or higher and lower than 200°C, the amount of water-soluble organic solvent B in the ink having a boiling point of 150°C or higher and lower than 200°C, the HSP value in the ink was 25.0 MPa 1 / 2 Hereinafter and the amount of water-soluble organic solvent Bx having a boiling point of 150°C or higher and lower than 200°C, and the HSP value in the ink was 25.0 MPa 1 / 2 Hereinafter and the amount of organic solvent Ax having a boiling point of 150°C or higher and lower than 200°C are shown in the form of the ratio (mass%) relative to the total amount of the ink. In addition, the amount of water-soluble organic solvent B in organic solvent S (mass%) is also shown in Tables 2 to 5, which is shown in the form of the ratio (mass%) relative to the total amount of organic solvent S.

[0196] The amount of water in the ink described in Tables 2 to 5 is a value measured by the Karl Fischer method, and a volumetric titration type moisture meter KF-31 manufactured by Nittoseiko Analytech Co., Ltd. was used as the moisture meter in the measurement.

[0197] In the table, the viscosity a (mPa·s) is the viscosity of the mixture Ma of the organic solvent S and water with a mass ratio of the organic solvent S to water (organic solvent S: water) of 99:1 at 23°C. The mixture Ma is obtained as follows: The water content in the organic solvent S is measured by the Karl Fischer method and adjusted so that the amount of water relative to the total amount of the organic solvent S and water is 1% by mass.

[0198] In the table, the viscosity b (mPa·s) is the viscosity of the mixture Mb of the organic solvent S and water with a mass ratio of the organic solvent S to water (organic solvent S: water) of 100 - W:W at 23°C when the amount of water relative to the total amount of the ink is W% by mass. The mixture Mb is obtained as follows: The water content in the organic solvent S is measured by the Karl Fischer method and adjusted so that the amount of water relative to the total amount of the organic solvent S and water is the same as the amount of water relative to the total amount of the ink, i.e., W% by mass.

[0199] [Table 2]

[0200]

[0201] [Table 3]

[0202]

[0203] [Table 4]

[0204]

[0205] [Table 5]

[0206]

[0207] The details of the materials described in Tables 1 to 5 are shown below.

[0208] (Pigment)

[0209] Pigment 1: Carbon black, "MOGUL L" (trade name), manufactured by Cabot Corporation

[0210] Pigment 2: Copper phthalocyanine, "Fastogen Blue LA5380" (trade name), manufactured by DIC Corporation (pigment dispersant)

[0211] Polymeric dispersant: "Solsperse J180" (trade name), manufactured by Lubrizol Corporation, active ingredient 100% by mass

[0212] (Pigment dispersion)

[0213] Pigment dispersions 1 to 5: The substances manufactured above, 20% by mass of pigment, 70% by mass of solvent

[0214] (Binder resin)

[0215] Solution of Binder Resin 1: The substance manufactured above, active ingredient ((meth)acrylic resin) 40% by mass, solvent (diethylene glycol diethyl ether) 60% by mass, resin Tg 105°C, resin weight average molecular weight 20,000

[0216] Solution of Binder Resin 2: The substance manufactured above, active ingredient ((meth)acrylic resin) 40% by mass, solvent (diethylene glycol diethyl ether) 60% by mass, resin Tg 60°C, resin weight average molecular weight 19,000

[0217] Binder Resin 3: "Hailos-XRS-1190" (trade name), manufactured by Seiko PMC Co., Ltd., active ingredient ((meth)acrylic resin) 100% by mass, Tg 73°C

[0218] Binder Resin 4: "Hailos-XX-1" (trade name), manufactured by Seiko PMC Co., Ltd., active ingredient (styrene-(meth)acrylic resin) 100% by mass, Tg 52°C

[0219] Binder Resin 5: "Xiran 1000P" (trade name), manufactured by Polyscope Polymers B.V., active ingredient (styrene-maleic resin) 100% by mass, Tg 150°C

[0220] (Organic solvent)

[0221] Water-soluble organic solvent 1: Diethylene glycol diethyl ether, manufactured by Tokyo Chemical Industry Co., Ltd., boiling point 188°C, HSP value 17.5 MPa 1 / 2

[0222] Water-soluble organic solvent 2: Diethylene glycol monomethyl ether, manufactured by Tokyo Chemical Industry Co., Ltd., boiling point 193°C, HSP value 22.7 MPa 1 / 2

[0223] Water-soluble organic solvent 3: 3-Methoxy-3-methyl-1-butanol, manufactured by Tokyo Chemical Industry Co., Ltd., boiling point 174°C, HSP value 19.5 MPa 1 / 2

[0224] Water-soluble organic solvent 4: 1,2-Propanediol, manufactured by Tokyo Chemical Industry Co., Ltd., boiling point 188°C, HSP value 29.8 MPa 1 / 2

[0225] Water-soluble organic solvent 5: γ-Butyrolactone, manufactured by Tokyo Chemical Industry Co., Ltd., boiling point 204°C, HSP value 25.6 MPa 1 / 2

[0226] Water-soluble organic solvent 6: 2-Pyrrolidone, manufactured by Tokyo Chemical Industry Co., Ltd., boiling point 245 °C, HSP value 23.6 MPa 1 / 2

[0227] Water-soluble organic solvent 7: Ethylene glycol monomethyl ether acetate, manufactured by Tokyo Chemical Industry Co., Ltd., boiling point 143 °C, HSP value 20.4 MPa 1 / 2

[0228] Water-soluble organic solvent 8: 3-Methoxy-1-butanol, manufactured by Tokyo Chemical Industry Co., Ltd., boiling point 161 °C, HSP value 21.2 MPa 1 / 2

[0229] Water-soluble organic solvent 9: Ethyl lactate, manufactured by Tokyo Chemical Industry Co., Ltd., boiling point 154 °C, HSP value 21.7 MPa 1 / 2

[0230] Water-soluble organic solvent 10: Ethylene glycol, manufactured by Tokyo Chemical Industry Co., Ltd., boiling point 197 °C, HSP value 33.0 MPa 1 / 2

[0231] Water-soluble organic solvent 11: Ethylene glycol monoacetate, manufactured by Tokyo Chemical Industry Co., Ltd., boiling point 182 °C, HSP value 24.6 MPa 1 / 2

[0232] Water-insoluble organic solvent 1: Ethylene glycol monobutyl ether acetate, manufactured by Tokyo Chemical Industry Co., Ltd., boiling point 192 °C, HSP value 18.4 MPa 1 / 2

[0233] Water-insoluble organic solvent 2: Ethylene glycol diacetate, manufactured by Tokyo Chemical Industry Co., Ltd., boiling point 190 °C, HSP value 19.5 MPa 1 / 2

[0234] (Surfactant)

[0235] Surfactant: Organosilicon surfactant, "BYK-3550" (trade name), manufactured by BYK-Chemie Japan K.K.

[0236] <Evaluation>

[0237] Using the ink manufactured above, the following evaluation was carried out. Tables 6 to 9 show the inks used in Examples 1 to 19 and Comparative Examples 1 to 8, and the evaluation results.

[0238] (Dischargeability)

[0239] For Examples 1 to 19 and Comparative Examples 1 to 8, the inks shown in Tables 6 to 9 of the prepared Inks 1 to 28 were introduced into the ink path of a commercially available solvent inkjet printer ("ValueJet VJ-628" (trade name) manufactured by Mutoh Industries, Ltd.). Colorless Ink 23 was introduced into the paths of colors other than the path into which the ink was introduced. On A4-sized polypropylene synthetic paper ("Yupo FGS110" (trade name) manufactured by Yupo Corporation), a solid black image with a length of 25 cm and a width of 18 cm was printed for black ink (Inks 1 to 8, 10 to 22, and 24 to 28), and a solid blue image with a length of 25 cm and a width of 18 cm was printed for cyan ink (Ink 9). When the start of printing was set at the upper part and the end of printing was set at the lower part, if the discharge property was poor, discharge failure occurred during printing, and the image density of the lower part was lower than that of the upper part. The difference in OD value between the upper part and the lower part was used as the difference in OD value, and the discharge property was evaluated based on the difference in OD value. It should be noted that the measurement parts were the ranges of 3 cm from the upper part and 3 cm from the lower part of the solid image. Five measurements were performed in each of these measurement parts, the average OD value of the upper part and the average OD value of the lower part were obtained, and the difference in OD value was calculated using the following formula.

[0240] Difference in OD value = (Average OD value of the upper part - Average OD value of the lower part)

[0241] The evaluation criteria are as follows.

[0242] A: The difference in OD value is less than 0.05

[0243] B: The difference in OD value is 0.05 or more and less than 0.10

[0244] C: The difference in OD value is 0.10 or more and less than 0.20

[0245] D: The difference in OD value is 0.20 or more

[0246] (Bleeding of the image)

[0247] For the prepared Inks 1 to 22 and 24 to 28, bleeding of the image was evaluated as follows.

[0248] Using a commercially available inkjet printer ("ValueJet VJ-628" (trade name)), an image with monochromatic text sized 6 to 12 pt was printed on A4-sized polypropylene synthetic paper ("Yupo FGS110" (trade name) manufactured by Yupo Corporation). The bleeding of the text image of the printed matter obtained by visual observation was evaluated according to the following evaluation criteria.

[0249] A: No bleeding was observed for text of any size, and it could be clearly seen

[0250] B: The text is slightly thickened, but text of any size can be clearly seen without being damaged.

[0251] C: The text is thickened, and text below 8 pt is damaged.

[0252] D: The text is significantly thick, and even at 12 pt, there is significant bleeding.

[0253] (Adhesion of the image to the substrate)

[0254] In the inkjet discharge property evaluation, a tape is pasted on the solid image portion of the printed matter having a solid image, and after peeling off the tape, the image and the tape are observed, and the adhesion of the image to the substrate is evaluated according to the following evaluation criteria.

[0255] A: The image is not peeled off.

[0256] B: The color is slightly transferred to the tape after peeling, but the image is not significantly peeled off.

[0257] C: A part of the image is peeled off.

[0258] D: The image of the portion where the tape is pasted is basically peeled off.

[0259] [Table 6]

[0260]

[0261] [Table 7]

[0262]

[0263] [Table 8]

[0264]

[0265] [Table 9]

[0266]

[0267] In Examples 1 to 19, excellent results were shown in both the discharge property evaluation and the bleeding evaluation of the image.

[0268] In Comparative Examples 1 and 2 where inks 16 and 17 with small amounts of water were used respectively, good results were not obtained in the evaluation of bleeding of the image. It is considered that since the amount of water in the ink is small, the drying property is low and the image bleeds. In addition, in Comparative Example 3 where ink 18 with a large amount of water in the ink was used, good results were not obtained in the ejection property. It is considered that the ink viscosity becomes high and the ejection property decreases. In Comparative Examples 4 and 5 where inks 19 and 20 containing a high-boiling organic solvent in an amount exceeding 10% by mass relative to the total amount of the organic solvents in the ink were used respectively, good results were not obtained in the bleeding of the image. It is considered that the drying property of the ink decreases and the bleeding of the image deteriorates. In Comparative Example 6 where ink 21 containing a low-boiling organic solvent in an amount exceeding 10% by mass relative to the total amount of the organic solvents in the ink was used, good results were not obtained in the evaluation of the ejection property. It is considered that the drying speed of the ink on the nozzle surface of the inkjet head becomes fast, nozzle clogging occurs, etc., and the ejection property deteriorates. In Comparative Examples 7 and 8 where inks 22 and 28 with a small amount of the water-soluble organic solvent B relative to the total amount of the organic solvent S and not having a ratio a / b of 0.95 or less were used respectively, good results were not obtained in the evaluation of the ejection property. It is considered that in Comparative Examples 7 and 8, the effect of suppressing the increase in ink viscosity by uniformly blending water into the ink was not sufficiently obtained, and the effect of suppressing the increase in ink viscosity accompanying the volatilization of components near the nozzle was not sufficiently obtained, and the ejection property deteriorated.

[0269] <Preparation of Pretreatment Liquid>

[0270] The respective materials described in Table 10 were measured in the proportions shown in Table 10 and mixed to obtain Pretreatment Liquids 1 to 7.

[0271] The amount of water (mass%) in the pretreatment liquid is shown in Table 10 in the form of a ratio (mass%) relative to the total amount of the pretreatment liquid. The amount of water in the pretreatment liquid described in Table 10 is a value measured by the Karl Fischer method, and a volumetric titration moisture meter KF-31 type manufactured by Nittoseiko Analytech Co., Ltd. was used for the measurement.

[0272] Details of the materials described in Table 10 are shown below.

[0273] Coagulant 1: Calcium chloride, manufactured by FUJIFILM Wako Pure Chemical Corporation

[0274] Coagulant 2: Calcium nitrate tetrahydrate, manufactured by FUJIFILM Wako Pure Chemical Corporation

[0275] Coagulant 3: Cationic water-soluble resin, "Himax SC-100" (trade name), manufactured by HYMO Co., Ltd., active ingredient (cationic water-soluble resin) 35% by mass

[0276] Coagulant 4: Resin emulsion (cationic water-dispersible acrylic resin), "Polyzol AP-1350" (trade name), manufactured by Resonac Corporation, active ingredient (cationic water-dispersible acrylic resin) 32% by mass

[0277] Binder resin: Polyvinyl alcohol resin, "JMR-10M" (trade name), manufactured by JAPAN VAM&POVAL CO., LTD., active ingredient content 100% by mass

[0278] Surfactant: Silicone-based surfactant, "BYK-3550" (trade name), manufactured by BYK-Chemie Japan K.K.

[0279] [Table 10]

[0280]

[0281] [Evaluation]

[0282] Using the pretreatment liquids 1 to 7 and inks 1, 4 to 6, and 10 manufactured above, a printed matter was manufactured as follows, and the gray-scale reproducibility was evaluated. Tables 11 and 12 show the pretreatment liquids, inks, and evaluation results used in Examples 20 to 30.

[0283] (Manufacture of Printed Matter)

[0284] For Examples 20 to 30, the pretreatment liquids 1 to 7 manufactured above were coated on an A4-sized PET film with an application amount of 20 g / m 2 by means of a bar coater. Thereafter, it was left at room temperature for 1 hour to obtain a pretreated printing substrate.

[0285] Using a commercially available inkjet printer ("ValueJet VJ-628" (trade name)), a gradient image composed of solids with a print ratio of 0% to 100% at 10% intervals based on the inks shown in Tables 11 and 12 was printed on the pretreated printing substrate obtained above. The reproducibility of the gradient image of the printed matter obtained by visual observation was evaluated according to the following evaluation criteria.

[0286] A: All gray scales have a stepwise density difference, and the gray scales are reproduced

[0287] B: It is difficult to distinguish the density difference in the part with a high print ratio, but the gray scales are roughly reproduced

[0288] C: When the print ratio is 50% or more, it is damaged and the gray scales are not reproduced

[0289] [Table 11]

[0290] Table 11 Example 20 Example 21 Example 22 Example 23 Example 24 Example 25 Ink Ink 1 Ink 4 Ink 10 Ink 5 Ink 6 Ink 1 Pretreatment Liquid Pretreatment Liquid 1 Pretreatment Liquid 1 Pretreatment Liquid 1 Pretreatment Liquid 1 Pretreatment Liquid 1 Pretreatment Liquid 4 Gray Scale Reproducibility A A A A B B

[0291] [Table 12]

[0292] Table 12 Example 26 Example 27 Example 28 Example 29 Example 30 Ink Ink 1 Ink 1 Ink 1 Ink 1 Ink 1 Pretreatment Liquid Pretreatment Liquid 5 Pretreatment Liquid 6 Pretreatment Liquid 7 Pretreatment Liquid 2 Pretreatment Liquid 3 Gray Scale Reproducibility A B B A A

[0293] As shown in the table, Examples 20 to 30 showed excellent results in terms of the evaluation of the gray-scale reproducibility of the image.

Claims

1. An inkjet ink, which comprises a coloring material, a binder resin, water, and an organic solvent S, wherein the water is 3.0 to 10.0% by mass relative to the total amount of the ink, the organic solvent S contains an organic solvent A having a boiling point of 150°C or higher and lower than 200°C in an amount of 90.0% by mass or more relative to the total amount of the organic solvent S, the organic solvent A contains a water-soluble organic solvent B having a boiling point of 150°C or higher and lower than 200°C in an amount of 50.0% by mass or more relative to the total amount of the organic solvent S, 2. The inkjet ink according to claim 1, wherein, The water-soluble organic solvent B contains a water-soluble organic solvent Bx having a Hansen solubility parameter (HSP value) of 25.0 MPa 1 / 2 or less and a boiling point of 150 °C or higher and lower than 200 °C.

3. The inkjet ink according to claim 2, wherein, the water-soluble organic solvent Bx is 75.0% by mass or more relative to the total amount of the water-soluble organic solvent B.

4. An inkjet ink, which comprises a coloring material, a binder resin, water, and an organic solvent S, wherein the water is 3.0 to 10.0% by mass relative to the total amount of the ink, the organic solvent S contains an organic solvent A having a boiling point of 150°C or higher and lower than 200°C in an amount of 90.0% by mass or more relative to the total amount of the organic solvent S, when the amount of the water relative to the total amount of the ink is set to W% by mass, the ratio a / b of the viscosity a of the mixture Ma having a mass ratio of the organic solvent S to water (organic solvent S: water) of 99:1 at 23°C to the viscosity b of the mixture Mb having a mass ratio of the organic solvent S to water (organic solvent S: water) of 100 - W:W at 23°C is 0.95 or less, and the units of the viscosity a and the viscosity b are mPa·s.

5. The inkjet ink according to claim 4, wherein, The organic solvent A includes an organic solvent Ax having a Hansen solubility parameter (HSP value) of 25.0 MPa 1 / 2 or less and a boiling point of more than 150°C and less than 200°C.

6. The inkjet ink according to claim 1 or 4, wherein, The binder resin contains a (meth)acrylic resin.

7. An inkjet ink kit, which comprises the inkjet ink according to any one of claims 1 to 6 and a pretreatment liquid, the pretreatment liquid containing a flocculant and water in an amount greater than 10.0% by mass relative to the total amount of the pretreatment liquid.

8. The inkjet ink kit according to claim 7, wherein, The flocculant contains at least one selected from the group consisting of polyvalent metal salts and cationic water-soluble resins.

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