Inkjet ink and ink set

Abstract

To provide an inkjet ink capable of forming an image with suppressed bleeding and having excellent jetting properties.SOLUTION: Provided is an inkjet ink including: a colorant; a binder resin; water, and an organic solvent S, in which the amount of the water is in a range from 3.0 mass% to 10.0 mass%, relative to the total amount of the ink, and the organic solvent S includes an organic solvent A with a boiling point of 150°C or higher and lower than 200°C, in an amount of 90.0 mass% or more relative to the total amount of the organic solvent S.SELECTED DRAWING: None

Description

[Technical Field]

[0001] FIELD OF THE INVENTION Embodiments of the present invention relate to inkjet inks and ink sets. [Background technology]

[0002] Inkjet recording, in which highly fluid inkjet ink is ejected as droplets from minute nozzles to record an image on a substrate placed opposite the nozzle, has rapidly become popular in recent years due to its low-noise, high-speed printing capabilities. Inks used in inkjet recording include aqueous inks containing water as the primary solvent, ultraviolet-curable inks (UV inks) containing a high content of polymerizable monomers as the primary component, and hot-melt inks (solid inks) containing a high content of wax as the primary component, as well as so-called non-aqueous inks containing a non-aqueous solvent as the primary solvent. Non-aqueous inks can be classified into solvent-based inks, which contain a volatile organic solvent as the primary solvent, and oil-based inks, which contain a low-volatility or non-volatile organic solvent as the primary solvent. Solvent inks dry on the substrate primarily through the evaporation of the organic solvent, whereas oil-based inks dry primarily through penetration into the substrate.

[0003] Inkjet printing is sometimes performed on plastic substrates such as vinyl chloride resins and olefin resins. Conventionally, when printing on substrates that are difficult for ink to penetrate, highly volatile organic solvents are often used in the ink to prevent bleeding of the image. Furthermore, since plastic substrates such as vinyl chloride resins and olefin resins generally do not have very high heat resistance, it is desirable for the ink to dry quickly at low temperatures.

[0004] However, for example, when a solvent ink uses an organic solvent with a low boiling point and high volatility, nozzle clogging in the inkjet head and ejection defects due to ink adhesion near the nozzles may occur. Also, from the viewpoint of the working environment during printing, when using ink containing an organic solvent, it is desirable to use an organic solvent that is not too volatile and is highly safe.

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

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

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-233086 [Patent Document 2] Japanese Patent Application Laid-Open No. 2017-190373 Summary of the Invention [Problem to be solved by the invention]

[0008] An object of an embodiment of the present invention is to provide an inkjet ink that is capable of forming an image with little bleeding and has excellent ejection properties. [Means for solving the problem]

[0009] In some embodiments of the present invention, there is provided an inkjet ink comprising a colorant, a binder resin, water, and an organic solvent S, wherein the water is present in an amount of 3.0 to 10.0 mass % relative to the total amount of the ink, and the organic solvent S comprises an organic solvent A having a boiling point of 150°C or higher but lower than 200°C in an amount of 90.0 mass % or higher relative to the total amount of the organic solvent S.

[0010] One embodiment of the present invention relates to an inkjet ink comprising a colorant, a binder resin, water, and an organic solvent S, wherein the water accounts for 3.0 to 10.0% by mass of the total amount of the ink, the organic solvent S comprises organic solvent A having a boiling point of 150°C or higher but lower than 200°C in an amount of 90.0% by mass or more based on the total amount of the organic solvent S, and the organic solvent A comprises water-soluble organic solvent B having a boiling point of 150°C or higher but lower than 200°C in an amount of 50.0% by mass or more based on the total amount of the organic solvent S.

[0011] Another embodiment of the present invention relates to an ink-jet ink comprising a colorant, a binder resin, water, and an organic solvent S, wherein the water accounts for 3.0 to 10.0% by mass of the total amount of the ink, and the organic solvent S comprises an organic solvent A having a boiling point of 150°C or higher but lower than 200°C in an amount of 90.0% by mass or higher, relative to the total amount of the organic solvent S, and wherein, 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) at 23°C of a mixture Ma of the organic solvent S and water in a mass ratio (organic solvent S:water) of 99:1 to the viscosity b (mPa s) at 23°C of a mixture Mb of the organic solvent S and water in a mass ratio (organic solvent S:water) of 100-W:W is 0.95 or less.

[0012] Another embodiment of the present invention relates to an inkjet ink set comprising the inkjet ink of any of the above-described embodiments, and a pretreatment liquid containing a flocculant and water in an amount of more than 10.0 mass % relative to the total amount of the pretreatment liquid. [Effects of the Invention]

[0013] According to some embodiments of the present invention, it is possible to provide an inkjet ink that is capable of forming an image with little bleeding and has excellent ejection properties. DETAILED DESCRIPTION OF THE INVENTION

[0014] The present invention will be described below using embodiments. The examples in the following embodiments do not limit the present invention. In the following description, inkjet ink may be simply referred to as "ink."

[0015] <Inkjet ink> In some embodiments of the present invention, there is provided an inkjet ink comprising a colorant, a binder resin, water, and an organic solvent S, wherein the water is present in an amount of 3.0 to 10.0 mass % relative to the total amount of the ink, and the organic solvent S comprises an organic solvent A having a boiling point of 150° C. or higher but lower than 200° C. in an amount of 90.0 mass % or higher 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): (i) Organic solvent A contains 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 organic solvent S. (ii) When the amount of water relative to the total amount of ink is W mass %, the ratio a / b of the viscosity a (mPa·s) at 23°C of a mixture Ma of organic solvent S and water in a mass ratio (organic solvent S:water) of 99:1 to the viscosity b (mPa·s) at 23°C of a mixture Mb of organic solvent S and water in a mass ratio (organic solvent S:water) of 100-W:W is 0.95 or less.

[0016] An inkjet ink according to one embodiment includes a colorant, a binder resin, water, and an organic solvent S, wherein the water accounts for 3.0 to 10.0% by mass of the total amount of the ink, the organic solvent S includes organic solvent A having a boiling point of 150°C or higher but lower than 200°C in an amount of 90.0% by mass or more of the total amount of organic solvent S, and organic solvent A includes water-soluble organic solvent B having a boiling point of 150°C or higher but lower than 200°C in an amount of 50.0% by mass or more of the total amount of organic solvent S (hereinafter, this inkjet ink may be referred to as "inkjet ink Ia" or "ink Ia"). An inkjet ink according to another embodiment includes a colorant, a binder resin, water, and an organic solvent S, wherein the water accounts for 3.0 to 10.0% by mass of the total ink, and the organic solvent S includes organic solvent A having a boiling point of 150°C or higher but lower than 200°C in an amount of 90.0% by mass or higher, relative to the total amount of organic solvent S, and wherein, when the amount of water relative to the total amount of ink is W% by mass, the ratio a / b of the viscosity a (mPa·s) at 23°C of a mixture Ma of organic solvent S and water in a mass ratio (organic solvent S:water) of 99:1 to the viscosity b (mPa·s) at 23°C of a mixture Mb of organic solvent S and water in a mass ratio (organic solvent S:water) of 100-W:W is 0.95 or less (hereinafter, this inkjet ink may be referred to as "inkjet ink Ib" or "ink Ib").

[0017] For example, when a low-boiling organic solvent is used to improve the drying properties of solvent ink in order to prevent image bleeding, the ejection properties of the ink from the inkjet head may be impaired. The present inventors have found that, when an ink contains 3.0 to 10.0 mass% of water, relative to the total amount of ink, and organic solvent A having a boiling point of 150°C or more but less than 200°C, in an amount of 90.0 mass% or more, relative to the total amount of organic solvent S contained in the ink, and organic solvent A contains water-soluble organic solvent B having a boiling point of 150°C or more but less than 200°C, in an amount of 50.0 mass% or more, relative to the total amount of organic solvent S, and / or when the ratio a / b of the viscosity a (mPa·s) at 23°C of a mixture Ma of organic solvent S and water in a mass ratio (organic solvent S:water) of 99:1 to the viscosity b (mPa·s) at 23°C of a mixture Mb of organic solvent S and water in a mass ratio (organic solvent S:water) of 100-W:W, where the amount of water is W mass%, relative to the total amount of ink, is 0.95 or less, the ink ejection properties are excellent and images with reduced bleeding can be formed. Without being bound by any particular theory, the reason for this is presumed to be as follows.

[0018] By including 90.0% by mass or more of organic solvent A, which has a moderate boiling point (between 150°C and 200°C), relative to the total amount of organic solvents S in the ink, the ink's drying properties can be improved. Furthermore, by not using a large amount of low-boiling-point organic solvents, nozzle clogging and ejection defects due to ink adhesion near the nozzles can be reduced. Furthermore, by including 3.0% by mass or more of water, relative to the total amount of ink, the ink's drying properties can be improved. This is thought to be due to the azeotropic phenomenon between water and the organic solvent. Furthermore, by keeping the amount of water to 10.0% by mass or less relative to the total amount of ink, an increase in ink viscosity can be suppressed. Furthermore, by including 50.0% by mass or more of water-soluble organic solvent B, which has a boiling point between 150°C and 200°C, relative to the total amount of organic solvents S in the ink, as in Ink Ia, the ink can be more stably infused with water, thereby suppressing an increase in ink viscosity. Furthermore, as in the case of Ink Ib, where the amount of water relative to the total ink volume is W mass%, the ratio a / b between the viscosity a (mPa·s) at 23°C of a mixture Ma of organic solvent S and water in a mass ratio (organic solvent S:water) of 99:1 and the viscosity b (mPa·s) at 23°C of a mixture Mb of organic solvent S and water in a mass ratio (organic solvent S:water) of 100-W:W is 0.95 or less. This effectively prevents ink viscosity increases that may occur when the ink solids concentration increases due to the evaporation of low-boiling water. Ink Ia and Ink Ib can thus suppress nozzle clogging, ejection problems due to ink adhesion near the nozzles, and increased ink viscosity, thereby improving ink ejection performance. It is also believed that improving the ink's drying properties reduces image bleeding.

[0019] <Inkjet ink Ia> Inkjet ink Ia according to one embodiment contains a colorant, a binder resin, water, and an organic solvent S, wherein the water accounts for 3.0 to 10.0% by mass of the total amount of the ink, and organic solvent S contains organic solvent A having a boiling point of 150°C or higher but lower than 200°C in an amount of 90.0% by mass or more of the total amount of organic solvent S, and organic solvent A contains water-soluble organic solvent B having a boiling point of 150°C or higher but lower than 200°C in an amount of 50.0% by mass or more of the total amount of organic solvent S. Inkjet ink Ia will now be described.

[0020] The ink Ia may include a colorant, which may be a pigment, a dye, or a combination thereof.

[0021] Pigments can be used in the present invention, including organic pigments such as azo pigments, phthalocyanine pigments, polycyclic pigments, and dye lake pigments, as well as inorganic pigments such as carbon black and metal oxides. Examples of azo pigments include soluble azo lake pigments, insoluble azo pigments, and condensed azo pigments. Examples of phthalocyanine pigments include metal phthalocyanine pigments and metal-free phthalocyanine pigments. Examples of polycyclic pigments include quinacridone pigments, perylene pigments, perinone pigments, isoindoline pigments, isoindolinone pigments, dioxazine pigments, thioindigo pigments, anthraquinone pigments, quinophthalone pigments, metal complex pigments, and diketopyrrolopyrroles (DPPs). Examples of carbon black include furnace carbon black, lamp black, acetylene black, and channel black. Examples of metal oxides include titanium oxide and zinc oxide. These pigments can be used alone or in combination.

[0022] From the viewpoints of ejection stability and storage stability, the average particle size of the pigment particles in the ink is preferably 1 μm or less, more preferably 500 nm or less, and even more preferably 300 nm or less, as the volume-based average value in the particle size distribution measured by dynamic light scattering.

[0023] The pigment may be blended in the ink as a pigment dispersion. The pigment dispersion may be any one that allows the pigment to be dispersed in a solvent and maintains a dispersed state in the ink. For example, a pigment dispersed in a dispersion medium using a pigment dispersant, or a microencapsulated pigment coated with a resin and dispersed in a dispersion medium may be used.

[0024] The pigment dispersion form may be a so-called capsule pigment in which the pigment is coated with an oil-insoluble resin, or a dispersion in which colored resin particles are dispersed with a pigment dispersant, but a dispersion in which the pigment dispersant is directly adsorbed onto the pigment surface and dispersed is preferred.

[0025] Any dye commonly used in the art can be used as the dye, but it is preferable to use an oil-soluble dye because it has affinity for the non-aqueous solvent of the ink and therefore has better storage stability. Examples of oil-soluble dyes include azo dyes, metal complex 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. These may be used alone or in combination.

[0026] From the viewpoint of print density and ink viscosity, the content of the coloring material is preferably 0.1 to 20% by mass, more preferably 1 to 15% by mass, and even more preferably 5 to 10% by mass, based on the total amount of ink.

[0027] When ink Ia contains a pigment, a pigment dispersant can be used together with the pigment to stably disperse the pigment in the ink. The pigment dispersant is not particularly limited as long as it can stably disperse the pigment in a non-aqueous solvent, but preferred examples include hydroxyl group-containing carboxylic acid esters, salts of long-chain polyaminoamides and high-molecular-weight acid esters, salts of high-molecular-weight polycarboxylic acids, salts of long-chain polyaminoamides and polar acid esters, high-molecular-weight unsaturated acid esters, copolymers of vinylpyrrolidone and long-chain alkenes, modified polyurethanes, modified polyacrylates, polyether ester-type anionic surfactants, polyoxyethylene alkyl phosphate esters, and polyester polyamines.

[0028] As the pigment dispersant, it is preferable to use a polymer dispersant, which may be a synthesized polymer dispersant or a commercially available polymer dispersant. Examples of commercially available pigment dispersants include Solsperse J180, Solsperse J200, Solsperse 71000, Solsperse 74000, Solsperse 86000, Solsperse 87000, and Solsperse M387 manufactured by Lubrizol Japan Co., Ltd., and BYKJET-9151, BYKJET-9152, and BYKJET-9170 manufactured by BYK Japan Co., Ltd. (all trade names). These may be used alone or in combination of two or more.

[0029] The pigment dispersant is preferably contained in a mass ratio of 0.2 to 1.0 per pigment 1. The content of the pigment dispersant in the total amount of ink is preferably 0.5 to 15 mass%, and more preferably 1 to 5 mass%.

[0030] The ink Ia may include a binder resin. From the viewpoint of forming a uniform ink film and improving the adhesion of the image to the substrate, the binder resin is preferably a resin that dissolves in the organic solvent S contained in the ink.

[0031] Examples of binder resins include (meth)acrylic resins, styrene-(meth)acrylic resins, styrene-maleic acid resins, ethylene-(meth)acrylic resins, urethane resins, vinyl chloride resins, vinyl chloride-vinyl acetate resins, polyester resins, polyvinyl alcohol resins, epoxy resins, and polyvinylpyrrolidone resins.

[0032] From the viewpoint of improving the adhesion of the image to the substrate, a (meth)acrylic resin is preferred as the binder resin. A (meth)acrylic resin that is soluble in organic solvent S is more preferred as the binder resin. When a (meth)acrylic resin is used, 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 solvent of the ink, making it difficult to obtain adhesion of the image, but when a (meth)acrylic resin is used, it is easy to improve the adhesion of the image to the substrate.

[0033] The (meth)acrylic resin may be, for example, a resin containing at least one unit selected from the group consisting of units derived from (meth)acrylic acid and units derived from a (meth)acrylic acid ester. In the present disclosure, (meth)acrylic acid collectively refers to acrylic acid and methacrylic acid, (meth)acrylic acid ester collectively refers to acrylic acid ester and methacrylic acid ester, and (meth)acrylate collectively refers to acrylate and methacrylate.

[0034] Examples of (meth)acrylic acid esters include (meth)acrylic acid alkyl esters, benzyl (meth)acrylate, hydroxyalkyl (meth)acrylate, etc. Examples of (meth)acrylic acid alkyl esters include (meth)acrylic acid alkyl esters having an alkyl group having 1 to 8, 1 to 6, or 1 to 4 carbon atoms, and specific examples include methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, etc.

[0035] The (meth)acrylic resin may be, for example, a polymer of one or more monomers selected from the group consisting of (meth)acrylic acid and (meth)acrylic acid esters.

[0036] Examples of the (meth)acrylic resin include poly(meth)acrylic acid, poly(meth)acrylic acid esters (e.g., polymethyl(meth)acrylate, polyethyl(meth)acrylate, polybutyl(meth)acrylate, etc.), (meth)acrylic acid ester copolymer resins, and (meth)acrylic acid-(meth)acrylic acid ester copolymer resins.

[0037] The (meth)acrylic resin preferably contains, for example, units derived from a (meth)acrylic acid alkyl ester. The units derived from a (meth)acrylic acid alkyl ester may account for, for example, 50.0 mass % or more, 70.0 mass % or more, or 90.0 mass % or more of the total units of the (meth)acrylic resin.

[0038] Specific examples of the (meth)acrylic resin include a polymer of methyl (meth)acrylate, and a copolymer of methyl (meth)acrylate with 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, a copolymer of 100 parts by mass of methyl methacrylate with 0.1 to 200 parts by mass, 1 to 180 parts by mass, or 10 to 150 parts by mass of at least one selected from the group consisting of methacrylic acid, butyl methacrylate, and benzyl methacrylate).

[0039] The glass transition point (Tg) of the (meth)acrylic resin may 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, and more preferably 100°C or higher. The glass transition point of the (meth)acrylic resin may be, for example, 200°C or lower. The glass transition point of the (meth)acrylic resin may 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 an estimated value according to the FOX formula.

[0040] The weight average molecular weight of the (meth)acrylic resin is preferably 5,000 to 150,000, and 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, and more preferably 10,000 or more. From the viewpoints of ink viscosity and jetting performance, the weight average molecular weight of the (meth)acrylic resin is preferably 150,000 or less, and more preferably 100,000 or less. In the present disclosure, the weight average molecular weight is a value determined by a GPC method in terms of standard polystyrene.

[0041] As the (meth)acrylic resin, a synthesized resin or a commercially available resin may be used.

[0042] The synthesis method of 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)acrylic acid esters can be polymerized.

[0043] The polymerization solvent (reaction solvent) used in the solution polymerization is not particularly limited, but is preferably one that can dissolve the (meth)acrylic resin obtained by polymerization. From the viewpoint of compatibility between the obtained (meth)acrylic resin and the organic solvent in the ink, and thereby preparing an ink with low viscosity, the organic solvent S or organic solvent A contained in the ink may be used as the polymerization solvent. For example, when the ink contains two or more organic solvents as organic solvent S or organic solvent A, only one of them may be used as the polymerization solvent.

[0044] In the polymerization reaction, a polymerization initiator such as a radical polymerization initiator may be used. Examples of the radical polymerization initiator that can be used include known radical polymerization initiators such as azo compounds such as 2,2'-azobis(isobutyronitrile) (AIBN), 2,2'-azobis(2,4'-dimethylvaleronitrile), and 2,2'-azobisdimethylisobutyrate, and organic peroxides such as hydroperoxides, dialkyl peroxides, peroxyesters, and diallyl peroxides. These may be used alone or in combination of two or more.

[0045] From the viewpoint of achieving good compatibility between the (meth)acrylic resin and the solvent and thereby preparing a low-viscosity ink, the (meth)acrylic resin is preferably an acrylic resin obtained by solution polymerization of a radically polymerizable monomer with a radical polymerization initiator in the organic solvent S or organic solvent A used in the ink. For example, when the ink contains two or more organic solvents as the organic solvent S or organic solvent A, the (meth)acrylic resin may be a resin obtained by solution polymerization using only one of them as the polymerization solvent.

[0046] Commercially available (meth)acrylic resins include, for example, "Neocryl B-728" and "Neocryl B-801" manufactured by Covestro, and "Dianal BR-83," "Dianal BR-87," and "Dianal MB-7333" manufactured by Mitsubishi Chemical Corporation (all trade names).

[0047] The binder resin may be, for example, 1.0% by mass or more or 3.0% by mass or more relative to the total amount of ink. On the other hand, the binder resin may be, for example, 40.0% by mass or less, 30.0% by mass or less, or 20.0% by mass or less relative to the total amount of ink. The binder resin may 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 relative to the total amount of ink.

[0048] Ink Ia may include water. The water is not particularly limited, but is preferably one that contains as few ionic components as possible. In particular, from the viewpoint of ink storage stability, it is preferable that the content of polyvalent metal ions such as calcium is low. Examples of water that can be used include ion-exchanged water, distilled water, and ultrapure water.

[0049] From the viewpoint of reducing image bleeding, the water content is preferably 3.0% by mass or more, more preferably 4.0% by mass or more, and even more preferably 4.5% by mass or more, based on the total amount of ink. When the water content is 3.0% by mass or more, the ink drying property is improved, and when printing on roll paper, for example, image transfer during winding after printing can be suppressed. On the other hand, from the viewpoint of improving ink jetting properties, the water content is preferably 10.0% by mass or less, more preferably 9.0% by mass or less, and even more preferably 8.0% by mass or less, based on the total amount of ink. The water content is preferably 3.0 to 10.0% by mass, more preferably 4.0 to 9.0% by mass, and even more preferably 4.5 to 8.0% by mass, based on the total amount of ink.

[0050] The amount of water in the ink may be the same as the amount of water intentionally blended into the ink. On the other hand, when an organic solvent that has an affinity for water is blended into the ink, such an organic solvent may absorb water vapor contained in the atmosphere, etc., and in such cases, for example, the amount of water blended into the ink may not be the same as the amount of water in the ink. The amount of water in the ink may be measured, for example, using the Karl Fischer method.

[0051] Ink Ia may contain organic solvent S. Examples of organic solvent S include organic solvents having a boiling point of 150°C or higher but lower than 200°C (organic solvent A), as well as other organic solvents. Examples of other organic solvents include organic solvents having a boiling point of lower than 150°C and organic solvents having a boiling point of 200°C or higher. Examples of organic solvents having a boiling point of lower than 150°C include ethylene glycol monomethyl ether acetate. Examples of organic solvents having a boiling point of 200°C or higher include γ-butyrolactone and 2-pyrrolidone. The ink may contain one or more of these other organic solvents.

[0052] The organic solvent (organic solvent A) having a boiling point of 150° C. or higher and lower than 200° C. may be any of ketone-based organic solvents, alcohol-based organic solvents, glycol ether-based organic solvents, acetate-based organic solvents, etc. The organic solvent A may be used alone or in combination of two or more.

[0053] From the viewpoint of reducing image bleeding, the boiling point of organic solvent A is preferably less than 200° C., and more preferably 195° C. or less. On the other hand, from the viewpoint of improving ink ejection properties, the boiling point of organic solvent A is preferably 150° C. or more, more preferably 160° C. or more, and even more preferably 170° C. or more.

[0054] In ink Ia, organic solvent A can contain a water-soluble organic solvent (water-soluble organic solvent B) having a boiling point of 150°C or more and less than 200°C, but may also contain a water-insoluble organic solvent having a boiling point of 150°C or more and less than 200°C. Among the organic solvents 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. Among the organic solvents A, examples of water-insoluble organic solvents 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 solvents 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.

[0055] From the viewpoints of improving ink ejection properties and suppressing image bleeding, the organic solvent A is preferably 90.0% by mass or more, more preferably 95.0% by mass or more, and even more preferably 99.0% by mass or more, based on the total amount of organic solvent S in the ink. The organic solvent A may be 100% by mass based on the total amount of organic solvent S in the ink. The organic solvent A may be, for example, 90.0 to 100% by mass, 95.0 to 100% by mass, or 99.0 to 100% by mass, based on the total amount of organic solvent S in the ink.

[0056] From the viewpoint of improving ink ejection performance, the amount of water-soluble organic solvent B is preferably 50.0% by mass or more, more preferably 60.0% by mass or more, even more preferably 70.0% by mass or more, even more preferably 80.0% by mass or more, and even more preferably 90.0% by mass or more, based on the total amount of organic solvent S in the ink. The amount of water-soluble organic solvent B may be, for example, 100% by mass, based on the total amount of organic solvent S in the ink. The amount of water-soluble organic solvent B may be, for example, 50.0 to 100% by mass, 60.0 to 100% by mass, 70.0 to 100% by mass, 80.0 to 100% by mass, or 90.0 to 100% by mass, based on the total amount of organic solvent S in the ink.

[0057] In order to stabilize the binder resin in the ink, suppress an increase in the ink viscosity, and further improve the ejection properties, the water-soluble organic solvent B is selected to have a Hansen solubility parameter (HSP value) of 25.0 MPa. 1 / 2 and preferably contains a water-soluble organic solvent Bx having a boiling point of 150°C or higher and lower than 200°C.

[0058] The HSP value of the water-soluble organic solvent Bx is, for example, 23.0 MPa. 1 / 2 On the other hand, the HSP value of the water-soluble organic solvent Bx may be, for example, 10.0 MPa or less. 1 / 2 or above 15.0MPa 1 / 2 The HSP value of the water-soluble organic solvent Bx may be, for example, 10.0 to 25.0 MPa. 1 / 2 or 15.0 to 23.0 MPa 1 / 2 It may be.

[0059] The Hansen solubility parameter was proposed by Hansen in 1967 and is a solubility parameter introduced by Hildebrand, expressed as a dispersion term δ D , polar term δ P , hydrogen bond term δ H The dispersion term represents the effect of dispersion forces, the polar term represents the effect of dipole-dipole forces, and the hydrogen bond term represents the effect of hydrogen bonding forces. For more details, see POLYMER HANDBOOK, FOURTH EDITION (Editors: J. BRANDRUP, E. HIMMERGUT, and EA This is explained in, for example, .GRULKE. In the present disclosure, values calculated using the Hansen solubility parameter calculation software "HSPiP: Hansen Solubility Parameters in Practice" version 5.3 by Charles M. Hansen et al. are used.

[0060] 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 may be used alone or in combination of two or more.

[0061] From the viewpoint of further improving the ejection performance, the amount of the water-soluble organic solvent Bx is preferably 50.0% by mass or more, more preferably 75.0% by mass or more, even more preferably 80.0% by mass or more, and even more preferably 90.0% by mass or more, based on the total amount of the water-soluble organic solvent B. On the other hand, the amount of the water-soluble organic solvent Bx may be 100% by mass, based on the total amount of the water-soluble organic solvent B. The amount of the water-soluble organic solvent Bx may be, for example, 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, based on the total amount of the water-soluble organic solvent B.

[0062] For example, when the amount of water relative to the total amount of ink is W mass %, the ratio a / b of the viscosity a (mPa·s) at 23°C of a mixture Ma of organic solvent S and water in a mass ratio (organic solvent S:water) of 99:1 to the viscosity b (mPa·s) at 23°C of a mixture Mb of organic solvent S and water in a mass ratio (organic solvent S:water) of 100-W:W may be 0.95 or less. The ratio a / b may be, for example, 0.90 or less or 0.85 or less. On the other hand, the ratio a / b may be, for example, 0.50 or more, 0.55 or more, or 0.60 or more. The ratio a / b may be, for example, 0.50 to 0.95, 0.55 to 0.90, or 0.60 to 0.85. The viscosity measurement device may be, for example, a "Rheometer MCR302" manufactured by Anton Paar Japan Co., Ltd. Mixtures Ma and Mb may be prepared, for example, by the method described for ink Ib.

[0063] The ink Ia preferably contains a surfactant. For example, from the viewpoint of improving the wetting and spreading of the ink even on a hydrophobic substrate surface and increasing the drying speed to form a good image, the ink preferably contains a surfactant. Examples of surfactants include silicone-based surfactants, fluorine-based surfactants, and polyoxyethylene derivatives, which are nonionic surfactants.

[0064] Examples of silicone surfactants include polyester-modified silicone, polyether-modified silicone, etc. Examples of commercially available silicone surfactants include "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", and "BYK-SILCLEAN 3700" manufactured by BYK Japan Co., Ltd., and "Silface SAG005", "Silface SAG008", and "Silface SAG503A" manufactured by Nissin Chemical Industry Co., Ltd. (all trade names).

[0065] Examples of commercially available fluorine-based surfactants include "BYK-340" manufactured by BYK Japan Co., Ltd., and "Surflon S-241," "Surflon S-242," "Surflon S-242L," "Surflon S-243," "Surflon S-420," and "Surflon S-431" manufactured by AGC Inc. (all trade names).

[0066] As the polyoxyethylene derivative, an acetylene glycol surfactant is preferably used. Examples of commercially available acetylene glycol surfactants include "Surfynol 420", "Surfynol 440", "Surfynol 465", and "Surfynol 485" manufactured by Evonik Industries, Ltd., and "Olfine E-1004" and "Olfine-1010" manufactured by Nissin Chemical Industry Co., Ltd. (all trade names).

[0067] From the viewpoints of continuous ejection property during printing and color development of images, it is preferable that ink Ia contains a silicone surfactant.

[0068] The surfactant may be used alone or in combination of two or more. The surfactant content is preferably 0.05 to 2% by mass, and more preferably 0.1 to 1% by mass, based on the total amount of the ink.

[0069] The ink Ia may contain various additives depending on the application, etc. Examples of the additives include UV absorbers, light stabilizers, antioxidants, and plasticizers.

[0070] <Inkjet ink Ib> In one embodiment, inkjet ink Ib comprises a colorant, a binder resin, water, and an organic solvent S, wherein the water accounts for 3.0 to 10.0% by mass of the total ink, and the organic solvent S comprises organic solvent A having a boiling point of 150°C or higher but lower than 200°C in an amount of 90.0% by mass or higher of the total organic solvent S, and wherein, when the amount of water relative to the total ink is W% by mass, the ratio a / b of the viscosity a (mPa·s) at 23°C of a mixture Ma of organic solvent S and water in a mass ratio (organic solvent S:water) of 99:1 to the viscosity b (mPa·s) at 23°C of a mixture Mb of organic solvent S and water in a mass ratio (organic solvent S:water) of 100-W:W is 0.95 or less.

[0071] The ink Ib may contain a colorant, which may be a pigment, a dye, or a combination thereof. The explanation for ink Ia can be applied to the coloring materials and their contents in ink Ib.

[0072] When ink Ib contains a pigment, a pigment dispersant can be used together with the pigment to stably disperse the pigment in the ink. The explanation for ink Ia can be applied to the pigment dispersant and its content in ink Ib.

[0073] The ink Ib may contain a binder resin. The binder resin and its content in the ink Ib can be the same as those described for the ink Ia.

[0074] The ink Ib may contain water. The explanation for the ink Ia can be applied to the water content and other aspects of the ink Ib.

[0075] Ink Ib may contain organic solvent S. Examples of organic solvent S include organic solvents (organic solvent A) having a boiling point of 150°C or higher but lower than 200°C, as well as other organic solvents. Examples of other organic solvents include organic solvents having a boiling point of less than 150°C and organic solvents having a boiling point of 200°C or higher. Examples of organic solvents having a boiling point of less than 150°C include ethylene glycol monomethyl ether acetate. Examples of organic solvents having a boiling point of 200°C or higher include γ-butyrolactone and 2-pyrrolidone. The ink may contain one or more of these other organic solvents.

[0076] The organic solvent (organic solvent A) having a boiling point of 150° C. or higher and lower than 200° C. may be any of ketone-based organic solvents, alcohol-based organic solvents, glycol ether-based organic solvents, acetate-based organic solvents, etc. The organic solvent A may be used alone or in combination of two or more.

[0077] From the viewpoint of reducing image bleeding, the boiling point of organic solvent A is preferably less than 200° C., and more preferably 195° C. or less. On the other hand, from the viewpoint of improving ink ejection properties, the boiling point of organic solvent A is preferably 150° C. or more, more preferably 160° C. or more, and even more preferably 170° C. or more.

[0078] In ink Ib, organic solvent A may contain a water-soluble organic solvent B having a boiling point of 150° C. or higher but lower than 200° C., a water-insoluble organic solvent having a boiling point of 150° C. or higher but lower than 200° C., or a combination thereof. Among the organic solvents A, examples of the water-soluble organic solvent B include those exemplified in the description of ink Ia, etc. These may be used alone or in combination of two or more. Among the organic solvents A, examples of water-insoluble organic solvents having a boiling point of 150° C. or higher and lower than 200° C. include those mentioned in the description of ink Ia. The water-insoluble organic solvents 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.

[0079] From the viewpoints of improving ink ejection properties and reducing image bleeding, the organic solvent A is preferably 90.0% by mass or more, more preferably 95.0% by mass or more, and even more preferably 99.0% by mass or more, based on the total amount of organic solvent S in the ink. The organic solvent A may be 100% by mass based on the total amount of organic solvent S in the ink. The organic solvent A may be, for example, 90.0 to 100% by mass, 95.0 to 100% by mass, or 99.0 to 100% by mass, based on the total amount of organic solvent S in the ink.

[0080] The water-soluble organic solvent B may 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, based on the total amount of organic solvent S in the ink. The water-soluble organic solvent B may be, for example, 100% by mass, based on the total amount of organic solvent S in the ink. The water-soluble organic solvent B may be, for example, 20.0 to 100% by mass, 50.0 to 100% by mass, 60.0 to 100% by mass, 70.0 to 100% by mass, 80.0 to 100% by mass, or 90.0 to 100% by mass, based on the total amount of organic solvent S in the ink.

[0081] From the viewpoint of improving ink ejection performance, when the amount of water relative to the total amount of ink is W mass %, the ratio a / b of the viscosity a (mPa·s) at 23°C of a mixture Ma of organic solvent S and water in a mass ratio (organic solvent S:water) of 99:1 to the viscosity b (mPa·s) of a mixture Mb of organic solvent S and water in a mass ratio (organic solvent S:water) of 100-W:W is preferably 0.95 or less. The ratio a / b may be, for example, 0.90 or less or 0.85 or less. On the other hand, the ratio a / b may be, for example, 0.50 or more, 0.55 or more, or 0.60 or more. The ratio a / b may be, for example, 0.50 to 0.95, 0.55 to 0.90, or 0.60 to 0.85.

[0082] The mixture Ma can be obtained, for example, by measuring the amount of water contained in the organic solvent S by the Karl Fischer method and adjusting the amount of water to 1% by mass relative to the total amount of the organic solvent S and water. The mixture Mb can be obtained, for example, by measuring the amount of water contained in the organic solvent S by the Karl Fischer method and adjusting the amount of water relative to the total amount of the organic solvent S and water to W mass %, which is the same amount as the amount of water relative to the total amount of ink. Furthermore, when the water content of the organic solvent S is too high, for example, exceeding 1% by mass, dehydration may be carried out using various means. A preferred dehydration method is to use a porous material such as a molecular sieve. In this case, the porous material or dehydrating agent is added to the solvent and mixed by stirring or other means, dehydration is carried out, and then the porous material is removed by filtration or other means. As a viscosity measuring device, for example, "Rheometer MCR302" manufactured by Anton Paar Japan Co., Ltd. can be used.

[0083] There are no particular limitations on the method for achieving a ratio a / b of 0.95 or less. For example, a method can be used in which, when a mixture of water and an organic solvent has a specific mixing ratio, the viscosity of the mixture is higher than the viscosity of both water and the organic solvent, i.e., the viscosity of the mixture reaches a maximum value at a specific mixing ratio. Since the reason for this maximum value is often due to the intermolecular interaction between water and the organic solvent, it is advisable to select the organic solvent using, for example, the Hansen solubility parameter (HSP value) as an indicator. Specifically, by including an organic solvent with a small HSP value in the organic solvent S, the mixture of water and organic solvent S can reach a viscosity maximum value. Therefore, by adjusting the amount of water (W mass %) relative to the total amount of ink, the ratio a / b can be set to 0.95 or less.

[0084] In order to improve the storage stability of the ink and more effectively suppress the increase in the viscosity of the ink, organic solvent A is selected from organic solvents having a Hansen solubility parameter (HSP value) of 25.0 MPa. 1 / 2 It is preferable that the HSP value of the organic solvent Ax is 23.0 MPa or less and ... boiling point of the organic solvent Ax is 150° C. or more and less than 200° C. 1 / 2 The HSP value of the organic solvent Ax is preferably 10.0 MPa or less. 1 / 2 or above 15.0MPa1 / 2 The HSP value of the organic solvent Ax may be, for example, 10.0 to 25.0 MPa. 1 / 2 or 15.0 to 23.0 MPa 1 / 2 It may be.

[0085] As organic solvent Ax, the HSP value is 25.0 MPa 1 / 2 Water-soluble organic solvent Bx with a boiling point of 150°C or more and less than 200°C, HSP value of 25.0MPa or less 1 / 2 or less, a water-insoluble organic solvent having a boiling point of 150° C. or more and less than 200° C., or a combination thereof can be used. Among the organic solvents Ax, examples of the water-soluble organic solvents Bx include those given as examples of the water-soluble organic solvents Bx in the description of the ink Ia. These may be used alone or in combination of two or more. Among the organic solvents Ax, examples of water-insoluble organic solvents include 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. These may be used alone or in combination of two or more.

[0086] From the viewpoint of improving the storage stability of the ink, the organic solvent Ax is preferably an organic solvent having an ether bond. Examples of such organic solvents include those having an HSP value of 25.0 MPa. 1 / 2 Alkylene glycol monoalkyl ether with a boiling point of 150°C or more and less than 200°C, HSP value of 25.0MPa or less 1 / 2 Examples of such alkylene glycol dialkyl ethers include alkylene glycol dialkyl ethers having a boiling point of 150° C. or higher and lower than 200° C. Because ether bonds have relatively low reactivity, they tend to be less susceptible to reaction with water or hydrolysis, which can improve the storage stability of inks that contain water.

[0087] From the viewpoint of improving the storage stability of the ink, the organic solvent Ax has an HSP value of 25.0 MPa.1 / 2 or less, and the boiling point is 150°C or more and less than 200°C, and the HSP value is 25.0MPa 1 / 2 Preferably, the organic solvent Ax contains at least one selected from the group consisting of alkylene glycol dialkyl ethers having a boiling point of 150° C. or higher and lower than 200° C. in an amount of 50.0% by mass or higher relative to the organic solvent Ax.

[0088] The organic solvent Ax preferably accounts for 20% by mass or more, more preferably 40% by mass or more, and even more preferably 60% by mass or more, based on the total amount of organic solvent S. On the other hand, the organic solvent Ax may be, for example, 100% by mass, based on the total amount of organic solvent S. The organic solvent Ax preferably accounts for 20 to 100% by mass or more, more preferably 40 to 100% by mass or more, and even more preferably 60 to 100% by mass or more, based on the total amount of organic solvent S.

[0089] <Ink manufacturing method> Although there are no particular limitations on the method for producing inks Ia and Ib, one method is to prepare the ink by mixing and stirring the components all at once or in portions. Specifically, for example, the ink can be prepared by adding all the components all at once or in portions to a disperser such as a bead mill, dispersing the components, and, if desired, passing the mixture through a filter such as a membrane filter.

[0090] In the method for producing the ink, for example, a pigment dispersion may be prepared in advance by mixing and stirring the pigment with a pigment dispersant, an organic solvent, and the like to disperse the pigment.

[0091] <Ink viscosity> The suitable range of viscosity of inks Ia and Ib varies depending on the nozzle diameter of the ejection head of the inkjet recording system, the ejection environment, etc., but in general, it is preferably 3 to 30 mPa·s at 23°C, more preferably 3 to 15 mPa·s, and even more preferably 4 to 10 mPa·s. In the present disclosure, ink viscosity is a value measured at 23°C. As a viscosity measuring device, for example, a "Rheometer MCR302" manufactured by Anton Paar Japan Ltd. can be used.

[0092] <Printing method> The printing method using ink Ia and / or Ib is not particularly limited and may be any method, such as a piezoelectric method, an electrostatic method, or a thermal method. When an inkjet recording apparatus is used, it is preferable to eject the ink according to one embodiment from an inkjet head based on a digital signal and allow the ejected ink droplets to adhere to a substrate. The printing method may include a pretreatment step, a heating step, and other steps. The pretreatment step may involve applying a pretreatment liquid to the substrate prior to applying the ink to the substrate, and the pretreatment liquid described below can be used as the pretreatment liquid.

[0093] In this embodiment, the substrate is not particularly limited, and examples thereof include printing paper such as plain paper, coated paper, and specialty paper; cloth; inorganic sheets; films; and overhead projector sheets. These substrates may also be used as adhesive sheets with an adhesive layer on the backside. For example, the ink of this embodiment can also be used preferably on plastic substrates such as vinyl chloride resin and olefin resin. Examples of olefin resins include polypropylene resin. Such plastic substrates may be absorbent substrates capable of absorbing applied ink, such as substrates with an ink-receiving layer, or non-absorbent substrates without an ink-receiving layer. The ink of this embodiment can also be used preferably on substrates that are difficult for ink to penetrate. Furthermore, olefin resins tend to have low affinity with the organic solvents in the ink, making it difficult to achieve image adhesion to the substrate. However, when the ink of this embodiment is used, good image adhesion can be achieved even on substrates made of olefin resin. The ink of this embodiment can also be used preferably on synthetic paper made of olefin resin, such as polypropylene resin.

[0094] <Ink set> An ink set according to one embodiment can include the inkjet ink Ia or inkjet ink Ib described above, and a pretreatment liquid.

[0095] From the viewpoint of improving gradation reproducibility, the ink set preferably contains the inkjet ink Ia or inkjet ink Ib described above, and a pretreatment liquid containing an aggregating agent and water in an amount of more than 10.0 mass % relative to the total amount of the pretreatment liquid. The inkjet ink Ia or Ib described above has excellent ink drying properties, and when used, it is possible to form images with minimal bleeding. When this ink is used in conjunction with a pretreatment liquid containing a flocculant and more than 10.0% by mass of water relative to the total amount of the pretreatment liquid, image bleeding can be more effectively reduced, resulting in images with excellent gradation reproducibility. Without being bound by any particular theory, the reason for this is presumed to be as follows: When the pretreatment liquid contains more than 10.0% by mass of water, which is relatively highly volatile, the drying properties of the pretreatment liquid are improved, thereby more effectively reducing image bleeding. Furthermore, when the ink comes into contact with the pretreatment liquid, the flocculant in the pretreatment liquid and the water contained in the pretreatment liquid in an amount greater than 10.0% by mass effectively cause aggregation and thickening of the ink components. It is believed that this effectively reduces image bleeding, thereby enabling images with excellent gradation reproducibility to be obtained. Furthermore, when such an ink set is used, image bleeding is likely to be suppressed even when the ink is applied before the pretreatment liquid has completely dried. Therefore, even on printing substrates with low heat resistance that are difficult to dry at high temperatures, image bleeding can be reduced and images with excellent gradation reproducibility can be obtained.

[0096] The ink set may include one or a combination of two or more inks. The ink set may include either inkjet ink Ia or inkjet ink Ib, or a combination thereof.

[0097] The pretreatment liquid may contain a flocculant. The aggregating agent may be a component that has the effect of aggregating components such as coloring materials contained in the ink. Examples of aggregating agents include polyvalent metal salts, cationic water-soluble resins, and cationic water-dispersible resins, and these may be used alone or in combination of two or more.

[0098] From the viewpoint of more effective aggregation of ink components and further improving gradation reproducibility, the aggregating agent preferably contains a polyvalent metal salt, a cationic water-soluble resin, or a combination thereof.

[0099] Examples of polyvalent metal salts include halides, nitrates, sulfates, acetates, fatty acid salts, lactates, and chlorates of divalent or higher metals. Preferred halides include chlorides, bromides, and iodides. Examples of divalent or higher metals include divalent alkaline earth metals such as Mg, Ca, Sr, and Ba; divalent metals such as Ni, Zn, Cu, and Fe(II); and trivalent metals such as Fe(III) and Al. Specific examples of polyvalent metal salts include calcium chloride, calcium nitrate, magnesium chloride, magnesium sulfate hexahydrate, and magnesium acetate tetrahydrate. These salts may be used alone or in combination of two or more.

[0100] From the viewpoint of more effective aggregation of ink components and further improving gradation reproducibility, the content of the polyvalent metal salt is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, and even more preferably 1.0% by mass or more, and may be, for example, 2.0% by mass or more, relative to the total amount of the pretreatment liquid. The content of the polyvalent metal salt may be 20.0% by mass or less, or 10.0% by mass or less, relative to the total amount of the pretreatment liquid. For example, the content of 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, relative to the total amount of the pretreatment liquid. In the case of a hydrate, the amount of the polyvalent metal salt is the amount converted to the anhydrous form.

[0101] Examples of cationic water-soluble resins include polyethyleneimine, polyvinylamine, polyallylamine and salts thereof, polyvinylpyridine, cationic acrylamide copolymers, cationic modified polyvinyl alcohol, etc. These may be used alone or in combination of two or more.

[0102] The content of the cationic water-soluble resin is preferably 0.1% by mass or more, and more preferably 0.5% by mass or more, relative to the total amount of the pretreatment liquid. The content of 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, relative to the total amount of the pretreatment liquid. For example, the content of 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, relative to the total amount of the pretreatment liquid.

[0103] Cationic water-dispersible resins are resin particles whose surfaces are positively charged and can be dispersed in particulate form without dissolving in water to form an oil-in-water (O / W) emulsion. Like self-emulsifying resins, the resin may have cationic functional groups on the particle surface, or the resin may be surface-treated by attaching a cationic dispersant to the surface of the resin particles. Examples of cationic water-dispersible resins include conjugated diene resins such as styrene-butadiene copolymer, methyl methacrylate-butadiene copolymer, and vinyl chloride-vinyl acetate copolymer; acrylic resins such as polymers of acrylic acid esters and methacrylic acid esters or copolymers of these with styrene; vinyl resins such as ethylene-vinyl acetate copolymer, or functional group-modified resins of these resins with a functional group-containing monomer such as a carboxyl group; melamine resin, urea resin, polyurethane resin, polyester resin, polyolefin resin, silicone resin, polyvinyl butyral resin, and alkyd resin. Resin emulsions of these resins alone or hybrid resin emulsions may also be used. These may be used alone or in combination of two or more.

[0104] The content of the cationic water-dispersible resin is preferably 0.5% by mass or more, more preferably 1.0% by mass or more, and even more preferably 2.0% by mass or more, based on the total amount of the pretreatment liquid. The content of the cationic water-dispersible resin may 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 content of the cationic water-dispersible resin may 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.

[0105] The amount of the flocculant may 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 amount of the flocculant may 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 amount of the flocculant may 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.

[0106] The pretreatment liquid may contain water. The water to be added to the pretreatment liquid is not particularly limited, but may be, for example, ion-exchanged water, distilled water, or ultrapure water.

[0107] From the viewpoints of improving drying properties, reducing image bleeding, and improving tone reproducibility, the water content is preferably greater than 10.0% by mass, more preferably greater than 20.0% by mass, and even more preferably greater than 40.0% by mass, relative to the total amount of the pretreatment liquid. When the water content is greater than 10.0% by mass, the stability of the ink that comes into contact with the pretreatment liquid is effectively disrupted, making the ink components more likely to aggregate and thicken. Furthermore, by incorporating more than 10.0% by mass of water, which has relatively high volatility, in the pretreatment liquid, the drying properties of the pretreatment liquid are improved and image bleeding can be effectively reduced. The water content may be, for example, 99.9% by mass or less, or 99.0% by mass or less, relative to the total amount of the pretreatment liquid. The water content may be, for example, greater 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, relative to the total amount of the pretreatment liquid.

[0108] The amount of water in the pretreatment liquid may be the same as the amount of water intentionally blended into the pretreatment liquid. On the other hand, if the pretreatment liquid contains an organic solvent that has an affinity for water, the organic solvent may absorb water vapor contained in the atmosphere, etc., and in such cases, for example, the amount of water blended into the pretreatment liquid may not be the same as the amount of water in the ink. The amount of water in the pretreatment liquid may be measured, for example, by the Karl Fischer method.

[0109] The pretreatment liquid may contain a binder resin. Examples of the binder resin include the resins listed as examples of the binder resin for ink Ia. The binder resin may be present in an amount of 1 to 20% by mass, or 3 to 15% by mass, relative to the total amount of the pretreatment liquid.

[0110] The pretreatment liquid may contain a water-soluble organic solvent. The water-soluble organic solvent may be an organic compound that is liquid at room temperature and dissolves in water. It is preferable to use a water-soluble organic solvent that is uniformly mixed with an equal volume of water at 20°C under 1 atmosphere. Examples of the water-soluble organic solvent include lower alcohols such as methanol, ethanol, 1-propanol, isopropanol, 1-butanol, 2-butanol, isobutanol, and 2-methyl-2-propanol; glycols such as ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, and polypropylene glycol; glycerins such as glycerin, diglycerin, triglycerin, and polyglycerin; acetins such as monoacetin and diacetin; ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, diacetin, and the like. Examples of suitable water-soluble organic solvents include glycol ethers such as ethylene 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, and tetraethylene glycol diethyl ether; triethanolamine, 1-methyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, β-thiodiglycol, and sulfolane. The boiling point of the water-soluble organic solvent is preferably 100° C. or higher, and more preferably 150° C. or higher.

[0111] These water-soluble organic solvents may be used alone or in combination of two or more, as long as they form a single phase with water. The content of the water-soluble organic solvent in the pretreatment liquid may be, for example, 10 to 80 mass %.

[0112] The pretreatment liquid may contain a surfactant. For example, the surfactants exemplified for ink Ia can be used as the surfactant. The surfactant content may be approximately 0.1 to 5% by mass of the total amount of the pretreatment liquid.

[0113] The method for producing the pretreatment liquid is not particularly limited. The pretreatment liquid can be appropriately produced, for example, by a conventional method. For example, the pretreatment liquid can be produced by adding all the components at once or in portions to a stirrer such as a Three-One Motor, mixing or dispersing the components, and, if desired, passing the mixture through a filter such as a membrane filter.

[0114] <Manufacturing method for printed matter> A method for producing a printed matter according to one embodiment includes applying an ink to a substrate by an inkjet method. The ink may be the ink Ia or ink Ib of the above-described embodiment. The substrate may be any of the above-described substrates.

[0115] In the step of applying the ink to the 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, or a thermal method.

[0116] The amount of ink applied to the substrate is 1 to 500 g / m 2 is preferable, and 3 to 100 g / m 2 More preferably, 5 to 50 g / m 2 is more preferably 10 to 30 g / m 2 is most preferred.

[0117] The method for producing a printed matter may include steps such as a pretreatment step and a heating step.

[0118] For example, a method for producing a printed matter may include applying a pretreatment liquid to a substrate and applying an ink to the substrate by an inkjet method. The pretreatment liquid may be any of the above-described pretreatment liquids. When a pretreatment liquid containing the above-described flocculant and more than 10.0% by mass of water relative to the total amount of the pretreatment liquid is used, image bleeding can be more effectively reduced and gradation reproducibility can be improved.

[0119] The method for applying the pretreatment liquid is not particularly limited. For example, the pretreatment liquid may be applied uniformly to the surface of the printing substrate using a brush, roller, bar coater, air knife coater, or spray, or may be applied by printing an image by a printing method such as inkjet printing, gravure printing, or flexographic printing. That is, the pretreatment liquid may be applied to the entire surface of the substrate, or may be applied only to necessary areas, for example, only to areas where the ink is to be applied. The amount of pretreatment liquid applied to the substrate is 1 to 500 g / m 2 is preferable, and 3 to 100 g / m 2 More preferably, 5 to 50 g / m 2 is more preferable.

[0120] The present disclosure includes the following embodiments. <1> Contains colorant, binder resin, water, and organic solvent S, the water content 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 more and less than 200°C in an amount of 90.0% by mass or more based on 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 but 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 water-soluble organic solvent B has a Hansen solubility parameter (HSP value) of 25.0 MPa. 1 / 2 or less, and contains a water-soluble organic solvent Bx having a boiling point of 150°C or more and less than 200°C, <1> The inkjet ink according to claim 1. <3> The water-soluble organic solvent Bx is 75.0 mass% or more based on the total amount of the water-soluble organic solvent B. <2> The inkjet ink according to claim 1.

[0121] <4> Contains colorant, binder resin, water, and organic solvent S, the water content 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 more and less than 200°C in an amount of 90.0% by mass or more based on the total amount of the organic solvent S, an ink-jet ink, wherein the ratio a / b of the viscosity a (mPa·s) at 23°C of a mixture Ma of the organic solvent S and water in a mass ratio (organic solvent S:water) of 99:1 to the viscosity b (mPa·s) at 23°C of a mixture Mb of the organic solvent S and water in a mass ratio (organic solvent S:water) of 100-W:W is 0.95 or less, where W represents the amount of water relative to the total amount of the ink. <5> The organic solvent A has a Hansen solubility parameter (HSP value) of 25.0 MPa. 1 / 2 and containing an organic solvent Ax having a boiling point of 150°C or more and less than 200°C. <4> The inkjet ink according to claim 1. <6> The binder resin contains a (meth)acrylic resin. <1> ~ <5> 10. The ink-jet ink according to any one of claims 1 to 9.

[0122] <7> <1> ~ <6> and the inkjet ink according to any one of the preceding claims. An inkjet ink set comprising: a flocculant; and a pretreatment liquid containing more than 10.0% by mass of water relative to the total amount of the pretreatment liquid. <8> The flocculant contains at least one selected from the group consisting of polyvalent metal salts and cationic water-soluble resins. <7> 1. An inkjet ink set according to claim 1. [Example]

[0123] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples.

[0124] <Production of pigment dispersion> The materials listed in Table 1 were weighed into a beaker in the proportions shown in Table 1, premixed, and then transferred to a plastic container with a lid. Zirconia beads with a diameter of 0.8 mm were added and dispersed for 60 minutes using a rocking mill RM-05 (manufactured by Seiwa Giken Co., Ltd.), and the beads were then separated from the dispersion to produce pigment dispersions 1 to 5 with a pigment concentration of 20% by mass.

[0125] The materials listed in Table 1 will be described in detail below.

[0126] [Table 1]

[0127] <Synthesis of binder resin> Binder resins 1 and 2 were produced as follows. In the following, the weight average molecular weights of the produced binder resins 1 and 2 were determined by the GPC method in terms of standard polystyrene. A GPC measuring device manufactured by Shimadzu Corporation was used for the measurement. The glass transition temperature (Tg) was calculated using the FOX formula.

[0128] (Synthesis of binder resin 1) A mixture of 340.0 g of the radical polymerizable monomer methyl methacrylate and 5.1 g of the polymerization initiator 2,2'-azobis(isobutyronitrile) (AIBN) (Tokyo Chemical Industry Co., Ltd.) dissolved in 85.0 g of diethylene glycol diethyl ether was added dropwise over 2 hours to 317.8 g of diethylene glycol diethyl ether (Tokyo Chemical Industry Co., Ltd.) maintained at 90°C in a 1 L flask. After the addition, 1.1 g of AIBN was added 30 minutes and 1 hour later while maintaining the liquid temperature at 90°C. The mixture was further reacted at 90°C for 1 hour, and then diluted with diethylene glycol diethyl ether to obtain a binder resin solution with an active ingredient concentration of 40.0% by mass. This yielded a binder resin solution with an active ingredient concentration of 40% by mass. The Tg of binder resin 1 was 105°C and the weight-average molecular weight was 20,000.

[0129] (Synthesis of binder resin 2) A mixture of 17.0 g of radically polymerizable monomers (methacrylic acid, 153.0 g of methyl methacrylate, 170.0 g of butyl methacrylate), and 5.1 g of polymerization initiator (2,2'-azobis(isobutyronitrile) (AIBN) (Tokyo Chemical Industry Co., Ltd.) dissolved in 85.0 g of diethylene glycol diethyl ether was added dropwise over 2 hours to 317.3 g of diethylene glycol diethyl ether (Tokyo Chemical Industry Co., Ltd.) maintained at 90°C in a 1 L flask. After the addition, 1.1 g of AIBN was added 30 minutes and 1 hour later while maintaining the liquid temperature at 90°C. The mixture was further reacted at 90°C for 1 hour, and then diluted with diethylene glycol diethyl ether to obtain a binder resin with an active ingredient concentration of 40.0% by mass, yielding a binder resin 2 solution. The active ingredient concentration in the resulting binder resin 2 solution was 40.0% by mass. The Tg of binder resin 2 was 60° C. and the weight average molecular weight was 19,000.

[0130] <Ink manufacturing> Each material shown in Tables 2 to 5 was weighed out in the proportions shown in Tables 2 to 5, mixed and stirred with a three-one motor, and then filtered through a membrane filter with a pore size of 3 μm to give inks 1 to 28. Details of the raw materials listed in Tables 2 to 5 will be described later. In addition, Tables 2 to 5 show 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 with a boiling point of 150°C or more and less than 200°C, the amount of water-soluble organic solvent B in the ink with a boiling point of 150°C or more and less than 200°C, and the HSP value of the ink of 25.0 MPa. 1 / 2 The amount of the water-soluble organic solvent Bx having a boiling point of 150°C or more and less than 200°C, and the HSP value in the ink is 25.0 MPa or less 1 / 2 The amounts of organic solvent Ax having a boiling point of 150°C or higher and lower than 200°C are shown as percentages (mass%) relative to the total amount of ink. Tables 2 to 5 also show the amount (mass%) of water-soluble organic solvent B in organic solvent S, which is shown as percentages (mass%) relative to the total amount of organic solvent S. The amounts of water in the inks shown in Tables 2 to 5 were measured by the Karl Fischer method, and measurements were performed using a volumetric titration moisture measuring device, Model KF-31, manufactured by Nitto Seiko Analytech Co., Ltd.

[0131] In the table, viscosity a (mPa s) is the viscosity at 23°C of mixture Ma, where the mass ratio of organic solvent S to water (organic solvent S:water) is 99:1. Mixture Ma was obtained by measuring the amount of water contained in organic solvent S using the Karl Fischer method and adjusting the amount of water to 1 mass% of the total of organic solvent S and water. In the table, viscosity b (mPa·s) is the viscosity at 23°C of mixture Mb, where the mass ratio of organic solvent S to water (organic solvent S:water) is 100-W:W, where W is the mass% of water relative to the total amount of ink. Mixture Mb was obtained by measuring the amount of water contained in organic solvent S using the Karl Fischer method and adjusting the amount of water relative to the total amount of organic solvent S and water to W% by mass, the same amount as the amount of water relative to the total amount of ink.

[0132] [Table 2]

[0133] [Table 3]

[0134] [Table 4]

[0135] [Table 5]

[0136] Details of the materials listed in Tables 1 to 5 are shown below.

[0137] (pigment) Pigment 1: Carbon black, "MOGUL L" (trade name), manufactured by Cabot Corporation Pigment 2: Copper phthalocyanine, "Fastogen Blue LAS5380" (trade name), manufactured by DIC Corporation

[0138] (pigment dispersant) Polymer dispersant: "Solsperse J180" (trade name), manufactured by Lubrizol Japan, active ingredient 100% by mass

[0139] (Pigment dispersion) Pigment Dispersions 1 to 5: those prepared above, pigment 20% by mass, solvent 70% by mass

[0140] (binder resin) Binder resin 1 solution: The product prepared 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 Binder resin 2 solution: the one produced 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 Binder resin 3: "Hi-Loss-X RS-1190" (product name), manufactured by Seiko PMC Corporation, active ingredient ((meth)acrylic resin) 100% by mass, Tg 73°C Binder resin 4: "Hi-Loss-X X-1" (trade name), manufactured by Seiko PMC Corporation, active ingredient (styrene-(meth)acrylic resin) 100% by mass, Tg 52°C Binder resin 5: "XIRAN 1000P" (trade name), manufactured by Polyscope Polymers BV, active ingredient (styrene-maleic acid resin) 100% by mass, Tg 150°C

[0141] (organic solvent) 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 Water-soluble organic solvent 2: Diethylene glycol monomethyl ether, manufactured by Tokyo Chemical Industry Co., Ltd., boiling point 193°C, HSP value 22.7MPa 1 / 2 Water-soluble organic solvent 3: 3-methoxy-3-methyl-1-butanol, manufactured by Tokyo Chemical Industry Co., Ltd., boiling point 174°C, HSP value 19.5MPa 1 / 2 Water-soluble organic solvent 4: 1,2-propanediol, manufactured by Tokyo Chemical Industry Co., Ltd., boiling point 188°C, HSP value 29.8MPa 1 / 2 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 Water-soluble organic solvent 6:2-pyrrolidone, manufactured by Tokyo Chemical Industry Co., Ltd., boiling point 245°C, HSP value 23.6MPa 1 / 2 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 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 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 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 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

[0142] Non-water-soluble 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 Non-water-soluble organic solvent 2: ethylene glycol diacetate, manufactured by Tokyo Chemical Industry Co., Ltd., boiling point 190°C, HSP value 19.5 MPa 1 / 2

[0143] (surfactant) Surfactant: Silicone surfactant, "BYK-3550" (product name), manufactured by BYK Japan Co., Ltd.

[0144] <Evaluation> The inks produced above were used to carry out the following evaluations. Tables 6 to 9 show the inks used in Examples 1 to 19 and Comparative Examples 1 to 8, and the evaluation results.

[0145] (Dischargeability) For Examples 1-19 and Comparative Examples 1-8, the inks prepared, Inks 1-28, as shown in Tables 6-9, were introduced into the ink paths of a commercially available solvent inkjet printer (Mutoh Industries, Ltd., "ValueJet VJ-628" (product name)). Colorless Ink 23 was introduced into the color paths other than the paths into which the inks were introduced. For the black inks (Inks 1-8, 10-22, and 24-28), a 25 cm x 18 cm solid black image was printed on A4-sized polypropylene synthetic paper (Yupo Corporation, "New Yupo FGS110" (product name)). When the start of printing was defined as the top and the end of printing as the bottom, poor ejection performance would result in poor ejection during printing, resulting in a lower image density at the bottom compared to the top. Therefore, the difference in density between the top and bottom was used to evaluate ejection performance. The measurement area was a 3 cm area above the solid image and a 3 cm area below it. Five measurements were taken for each of these measurement areas, and the average OD value of the upper area and the average OD value of the lower area were calculated. The difference in OD values was calculated using the following formula: OD difference = (average OD value at top - average OD value at bottom)

[0146] The evaluation criteria are as follows: A: The difference in OD value is less than 0.05 B: The difference in OD value is 0.05 or more and less than 0.10 C: The difference in OD value is 0.10 or more but less than 0.20 D: The difference in OD value is 0.20 or more

[0147] (Image bleed) The prepared inks 1 to 22 and 24 to 28 were evaluated for image bleeding as follows. Using a commercially available inkjet printer ("ValueJet VJ-628" (trade name)), an image with single-color characters of 6 to 12 pt size was printed on A4-sized polypropylene synthetic paper ("New Yupo FGS110" (trade name) manufactured by Yupo Corporation). The resulting printed text image was visually inspected for bleeding and evaluated according to the following evaluation criteria. A: All letters of any size are clearly visible without blurring. B: The letters are slightly thick, but all letters are clearly visible and not crushed. C: The text is thick and anything smaller than 8pt is crushed. D: The letters are noticeably thicker and the bleeding is noticeable even at 12pt.

[0148] (Image adhesion to substrate) Tape was applied to the solid image portion of the printed matter having a solid image produced in the inkjet ejection property evaluation, and the image and tape were observed after the tape was peeled off, and the adhesion of the image to the substrate was evaluated according to the following evaluation criteria. A: No peeling on the image B: There is some color transfer to the tape after peeling, but no noticeable peeling in the image C: Part of the image is peeling off D: The image on the taped area has almost completely peeled off.

[0149] [Table 6]

[0150] [Table 7]

[0151] [Table 8]

[0152] [Table 9]

[0153] Examples 1 to 19 showed excellent results in both the evaluation of ejection properties and the evaluation of image bleeding.

[0154] In Comparative Examples 1 and 2, in which inks 16 and 17, respectively, containing small amounts of water, were used, poor results were obtained in the evaluation of image bleeding. It is believed that the low amount of water in the inks resulted in poor drying properties, causing image bleeding. Furthermore, in Comparative Example 3, in which ink 18, containing a large amount of water in the ink, was used, poor results were obtained in terms of ejection performance. It is believed that this is due to the high ink viscosity and poor ejection performance. In Comparative Examples 4 and 5, in which inks 19 and 20, respectively, containing high-boiling-point organic solvents in an amount exceeding 10% by mass relative to the total amount of organic solvents in the ink, poor results were obtained in terms of image bleeding. It is believed that this is due to the poor drying properties of the ink, resulting in worsening image bleeding. In Comparative Example 6, in which ink 21, containing low-boiling-point organic solvents in an amount exceeding 10% by mass relative to the total amount of organic solvents in the ink, was used, poor results were obtained in the evaluation of ejection performance. It is believed that the ink dried quickly on the nozzle surface of the inkjet head, causing nozzle clogging and other problems, resulting in poor ejection performance. In Comparative Examples 7 and 8, which used inks 22 and 28, respectively, in which the amount of water-soluble organic solvent B relative to the total amount of organic solvent S was small and the ratio a / b was not 0.95 or less, good results were not obtained in the ejection performance evaluation. In Comparative Examples 7 and 8, neither the effect of uniformly blending water into the ink to suppress an increase in ink viscosity nor the effect of suppressing an increase in ink viscosity due to volatilization of components near the nozzle was sufficiently obtained, which is thought to have resulted in the deterioration of ejection performance.

[0155] <Preparation of pretreatment solution> Each material shown in Table 10 was weighed out in the proportions shown in Table 10 and mixed to obtain pretreatment solutions 1 to 7. The amount of water (% by mass) in the pretreatment solution is shown as a percentage (% by mass) of the total amount of the pretreatment solution in Table 10. The amount of water in the pretreatment solution shown in Table 10 was measured by the Karl Fischer method, and a volumetric titration moisture analyzer, Model KF-31, manufactured by Nitto Seiko Analytech Co., Ltd. was used as the moisture meter.

[0156] Details of the materials listed in Table 10 are provided below. Flocculant 1: Calcium chloride, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. Flocculant 2: calcium nitrate tetrahydrate, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. Flocculant 3: cationic water-soluble resin, "Himax SC-100" (trade name), manufactured by HIMO Co., Ltd., active ingredient (cationic water-soluble resin) 35% by mass Flocculant 4: Resin emulsion (cationic water-dispersible acrylic resin), "Polysol AP-1350" (trade name), manufactured by Resonac Co., Ltd., active ingredient (cationic water-dispersible acrylic resin) 32% by mass

[0157] Binder resin: Polyvinyl alcohol resin, "JMR-10M" (product name), manufactured by Nippon Vaccination & Poval Co., Ltd., active ingredient content 100% by mass Surfactant: Silicone surfactant, "BYK-3550" (product name), manufactured by BYK Japan Co., Ltd.

[0158] [Table 10]

[0159] <Evaluation> Printed matter was produced as follows and evaluated for gradation reproducibility using the pretreatment liquids 1 to 7 and inks 1, 4 to 6, and 10 produced above. Tables 11 and 12 show the pretreatment liquids and inks used in Examples 20 to 30, and the evaluation results.

[0160] (Printed matter production) For Examples 20 to 30, the pretreatment solutions 1 to 7 prepared above were applied to an A4 size PET film using a bar coater in an amount of 20 g / m 2 After that, it was left at room temperature for 1 hour to obtain a pretreated printing substrate.

[0161] Using a commercially available inkjet printer ("ValueJet VJ-628" (trade name)), a gradation image composed of solid prints in 10% increments from 0% to 100% coverage using the inks shown in Tables 11 and 12 was printed on the pretreated printing substrate obtained above. The reproducibility of the gradation image on the obtained print was visually observed and evaluated according to the following evaluation criteria. A: All gradations have gradual differences in density, and the gradations are reproduced. B: It is difficult to see the density difference in the areas with high printing rate, but the gradation is generally reproduced. C: When the print ratio is 50% or more, the dots are crushed and the gradation is not reproduced.

[0162] [Table 11]

[0163] [Table 12]

[0164] As shown in the table, Examples 20 to 30 showed excellent results in the evaluation of image tone reproducibility.

Claims

1. A colorant, a binder resin, water, and an organic solvent S are included, the water content 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 higher based on 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 but lower than 200° C. in an amount of 50.0% by mass or higher based on the total amount of the organic solvent S.

2. The water-soluble organic solvent B has a Hansen solubility parameter (HSP value) of 25.0 MPa. １／２ The ink-jet ink according to claim 1 , further comprising a water-soluble organic solvent Bx having a boiling point of 150° C. or higher and lower than 200° C.

3. The ink-jet ink according to claim 2 , wherein the water-soluble organic solvent Bx is present in an amount of 75.0% by mass or more based on the total amount of the water-soluble organic solvent B.

4. A colorant, a binder resin, water, and an organic solvent S are included, the water content 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 higher based on the total amount of the organic solvent S, an ink-jet ink, wherein a ratio a / b of a viscosity a (mPa s) at 23°C of a mixture Ma of the organic solvent S and water in a mass ratio (organic solvent S:water) of 99:1 to a viscosity b (mPa s) at 23°C of a mixture Mb of the organic solvent S and water in a mass ratio (organic solvent S:water) of 100-W:W is 0.95 or less, where W % by mass represents the amount of water relative to the total amount of the ink.

5. The organic solvent A has a Hansen solubility parameter (HSP value) of 25.0 MPa. １／２ The ink-jet ink according to claim 4, further comprising an organic solvent Ax having a boiling point of 150°C or higher and lower than 200°C.

6. The ink-jet ink according to claim 1 or 4, wherein the binder resin comprises a (meth)acrylic resin.

7. The inkjet ink according to claim 1 or 4, An inkjet ink set comprising: a flocculant; and a pretreatment liquid containing more than 10.0% by mass of water relative to the total amount of the pretreatment liquid.

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

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