Post-treatment solution for oil-based ink, ink set, and method for manufacturing printed matter

Abstract

To provide a post-treatment agent for oil-based ink with which it is possible to obtain a printed surface having a high image concentration by inhibiting bleed-through of the ink.SOLUTION: A post-treatment solution for oil-based ink is a water-in-oil emulsion and includes silica in both an oil phase and a water phase.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to a post-treatment liquid for oil-based inks, an ink set, and a method for producing printed matter. [Background technology]

[0002] There are various types of printing inks, including aqueous inks containing water as the primary solvent, ultraviolet-curable inks (UV inks) primarily composed of polymerizable monomers, hot-melt inks (solid inks) primarily composed of wax, and non-aqueous inks containing non-aqueous solvents as the primary solvent. Non-aqueous inks can be classified into solvent inks (solvent-based inks) whose primary solvent is a volatile organic solvent, and oil-based inks (oil-based inks) whose primary solvent is a low-volatility or non-volatile organic solvent. Solvent inks dry on the substrate primarily due to the evaporation of the organic solvent, while oil-based inks dry primarily due to penetration into the substrate.

[0003] As mentioned above, oil-based inks dry mainly due to the penetration of low-volatility or non-volatile non-aqueous solvents into the substrate. Therefore, in oil-based inks, the colorant penetrates into the substrate together with the non-aqueous solvent, reducing the amount of colorant remaining on the substrate surface, which can cause a decrease in the surface density of the printed material.

[0004] As a technology related to oil-based inks, Patent Document 1 describes a printing method that uses a non-aqueous pigment ink together with a non-aqueous post-treatment liquid containing silica and an organic solvent, blends a water-soluble resin having an amino group into either the non-aqueous pigment ink or the post-treatment liquid, and ejects a non-aqueous post-treatment liquid containing silica and an organic solvent onto dots formed by ejecting the non-aqueous pigment ink, thereby improving print density. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-123747 Summary of the Invention [Problem to be solved by the invention]

[0006] The printing method described in Patent Document 1 did not provide sufficient image density on the printed surface, and also caused ink bleed-through. One of the objectives of the present disclosure is to provide a post-treatment liquid for oil-based inks, an ink set, and a method for producing printed matter that can obtain a printed surface with high image density and suppress ink bleed-through. [Means for solving the problem]

[0007] One embodiment of the present disclosure relates to a post-treatment liquid for oil-based ink, which is a water-in-oil emulsion and contains silica in both the oil phase and the water phase.

[0008] Another embodiment of the present disclosure relates to a post-treatment liquid for oil-based ink, which is a water-in-oil emulsion and contains both hydrophobic silica and hydrophilic silica. [Effects of the Invention]

[0009] According to the present disclosure, it is possible to provide a post-treatment liquid for oil-based ink, an ink set, and a method for producing a printed matter that can obtain a printed surface with high image density while suppressing ink strike-through. DETAILED DESCRIPTION OF THE INVENTION

[0010] Several embodiments of the present invention will be described in detail below, but the present disclosure is not limited to these embodiments.

[0011] In this disclosure, acrylic resin is a general term for resins obtained by polymerizing acrylic acid, methacrylic acid, and derivatives thereof, either singly or in combination. (Meth)acrylic acid is a general term for acrylic acid and methacrylic acid, and (meth)acrylic acid ester is a general term for acrylic acid ester and methacrylic acid ester.

[0012] One embodiment of the post-treatment liquid for oil-based inks (hereinafter sometimes referred to as "post-treatment liquid (1)") is a water-in-oil emulsion containing silica in both the oil phase and the water phase. In post-treatment liquid (1), silica aggregates on the substrate surface, which causes aggregation of the pigment in the oil-based ink, thereby suppressing penetration of the pigment into the substrate. As a result, the pigment remains on the substrate surface, resulting in a printed surface with high image density and suppressing ink strike-through.

[0013] When the post-treatment liquid contains silica only in the aqueous phase, the silica has a relatively high dispersion stability in water, so that the silica does not sufficiently aggregate on the substrate surface, and the effect of causing pigment aggregation is not sufficiently achieved.On the other hand, when the post-treatment liquid contains silica only in the oil phase, the silica easily penetrates into the substrate together with the non-aqueous solvent in the oil phase, and the effect of retaining the pigment on the substrate surface is not sufficiently achieved.

[0014] The post-treatment liquid (1) is a water-in-oil emulsion, and because the oil phase contains silica, structural viscosity occurs between the silica in the oil phase and the aqueous phase when the post-treatment liquid is applied to a printing substrate, making it easier for the post-treatment liquid to remain on the substrate surface. Furthermore, because the aqueous phase contains silica, the thickening effect due to structural viscosity is enhanced. Furthermore, when the substrate is cellulose-derived paper, it is believed that the hydroxyl groups contained in the cellulose form hydrogen bonds with water and the silanol groups of the silica, thereby inhibiting penetration of the post-treatment liquid into the substrate and enhancing its retention on the substrate surface.

[0015] Another embodiment of the post-treatment liquid for oil-based inks (hereinafter sometimes referred to as "post-treatment liquid (2)") is a water-in-oil emulsion containing both hydrophobic and hydrophilic silica. As with post-treatment liquid (1), silica aggregates on the substrate surface, which causes the pigment in the oil-based ink to aggregate, thereby suppressing the penetration of the pigment into the substrate. As a result, the pigment remains on the substrate surface, resulting in a printed surface with high image density and suppressing ink strike-through. By including hydrophobic silica in post-treatment liquid (2), structural viscosity is generated between the hydrophobic silica and the aqueous phase when the post-treatment liquid is applied to the printing substrate, making it easier for the post-treatment liquid to remain on the substrate surface. Furthermore, by including hydrophilic silica in post-treatment liquid (2), the thickening effect due to structural viscosity is enhanced.

[0016] The post-treatment liquid (1) will now be described. The silica contained in the oil phase of the post-treatment liquid (1) (hereinafter, this may be referred to as "silica (S)") may be used alone or in combination of two or more types. The specific surface area of ​​silica (S) is set to 10 m2 as measured by the BET method of JIS Z 8830:2013, since this has a more pronounced effect of increasing image density. 2 / g or more, and 2 / g or more is more preferable, and 50m 2 / g or more is particularly preferable. 2 / g or less, and 2 / g or less is more preferable, and 150m 2 The specific surface area of ​​silica (S) is preferably 10 to 400 m / g or less as measured by the BET method. 2 / g, and may be in the range of 50 to 150m 2 / g.

[0017] The silica (S) may be either so-called hydrophobic silica having hydrophobic groups on the silica surface, or so-called hydrophilic silica having hydrophilic groups such as silanol groups on the silica surface. These may also be used in combination. From the viewpoint of the storage stability of the post-treatment liquid (1), it is preferable that the silica (S) contains hydrophobic silica. The proportion of hydrophobic silica in the entire silica (S) may be 50% by mass or more, 70% by mass or more, or 90% by mass or more, or may even be 100% by mass.

[0018] Examples of the hydrophobic group contained in the hydrophobic silica include (poly)alkylsilyl groups such as dimethylsilyl, trimethylsilyl, and octylsilyl; dialkylpolysiloxane structures such as dimethylpolysiloxane; and polymerizable groups such as methacrylsilyl.

[0019] Examples of hydrophobic silica include Evonik's "Aerosil NX90G," "Aerosil NX90S," "Aerosil R972," "Aerosil NX130," "Aerosil RY200S," "Aerosil R202," "Aerosil R974," "Aerosil R9200," "Aerosil RX200," "Aerosil R8200," "Aerosil RY200," "Aerosil RY200L," and "Aerosil R805."

[0020] Examples of hydrophilic silica include "Aerosil OX50," "Aerosil 50," "Aerosil 90G," "Aerosil 130," "Aerosil 150," "Aerosil 200," "Aerosil 300," and "Aerosil 380," manufactured by Evonik.

[0021] The content of silica (S) in the oil phase is not particularly limited and is adjusted appropriately depending on the desired viscosity, etc., but may be, for example, 0.5% by mass or more, 1% by mass or more, or 3% by mass or more. It may also be 10% by mass or less, 8% by mass or less, or 5% by mass or less. The content of silica (S) in the oil phase may be in the range of 0.5 to 10% by mass.

[0022] The oil phase contains a non-aqueous solvent. The non-aqueous solvent may be either a non-polar organic solvent or a polar organic solvent. One type of non-aqueous solvent may be used alone, or two or more types may be used in combination. The oil phase may also contain other organic solvents to the extent that they can form a single phase with the non-aqueous solvent used. As the non-aqueous solvent, it is preferable to use a water-insoluble organic solvent that is not uniformly miscible with the same volume of water at 1 atmosphere and 20°C.

[0023] Examples of non-polar organic solvents include petroleum-based hydrocarbon solvents such as aliphatic hydrocarbon solvents, alicyclic hydrocarbon solvents, and aromatic hydrocarbon solvents. Examples of aliphatic hydrocarbon solvents and alicyclic hydrocarbon solvents include non-aqueous solvents such as paraffin-based, isoparaffin-based, and naphthenic solvents. Commercially available products include "No. 0 Solvent L," "No. 0 Solvent M," "No. 0 Solvent H," "Cactus normal paraffin N-10," "Cactus normal paraffin N-11," "Cactus normal paraffin N-12D," "Cactus normal paraffin N-13," "Cactus normal paraffin N-14," "Cactus normal paraffin YHNP," "Cactus normal paraffin SHNP," "Isozol 300," "Isozol 400," "Teclain N16," "Teclain N20," "Teclain N22," "AF Solvent No. 4," "AF Solvent No. 5," "AF Solvent No. 6," "AF Solvent No. 7," "Naphtesol 160," "Naphtesol 200," and "Naphtesol 220," manufactured by ENEOS Corporation; and "Isozol G" and "Isozol H" manufactured by ExxonMobil Corporation. Examples of suitable solvents include "BHT," "Isopar L," "Isopar M," "Exsor D40," "Exsor D60," "Exsor D80," "Exsor D110," and "Exsor D130" manufactured by MORESCO Corporation; and "Moresco White P-60," "Moresco White P-70," "Moresco White P-80," "Moresco White P-100," "Moresco White P-120," "Moresco White P-150," "Moresco White P-200," "Moresco White P-260," and "Moresco White P-350P" manufactured by MORESCO Corporation. Examples of suitable aromatic hydrocarbon solvents include "Solvesso 100," "Solvesso 150," "Solvesso 200," and "Solvesso 200ND" manufactured by ExxonMobil Corporation. The initial boiling point of petroleum-based hydrocarbon solvents is preferably 100°C or higher, more preferably 150°C or higher, and particularly preferably 200°C or higher. The initial boiling point of distillation can be measured according to JIS K0066, "Test Method for Distillation of Chemical Products."

[0024] Preferred examples of polar organic solvents include fatty acid ester solvents, higher alcohol solvents, and higher fatty acid solvents. For example, isononyl isononanoate, isodecyl isononanoate, isotridecyl isononanoate, methyl laurate, isopropyl laurate, hexyl laurate, isopropyl myristate, isopropyl palmitate, hexyl palmitate, isooctyl palmitate, isostearyl palmitate, methyl oleate, ethyl oleate, isopropyl oleate, butyl oleate, hexyl oleate, methyl linoleate, ethyl linoleate, isobutyl linoleate, butyl stearate, hexyl stearate, isooctyl stearate, isopropyl isostearate, 2-octyldecyl pivalate, soybean oil fatty acid methyl esters, soybean Examples of such solvents include fatty acid ester solvents having 13 or more carbon atoms per molecule, preferably 16 to 30, such as oil fatty acid isobutyl ester, tall oil fatty acid methyl ester, and tall oil fatty acid isobutyl ester; higher alcohol solvents having 6 or more carbon atoms per molecule, preferably 12 to 20, such as isomyristyl alcohol, isopalmityl alcohol, isostearyl alcohol, oleyl alcohol, isoeicosyl alcohol, and decyltetradecanol; and higher fatty acid solvents having 12 or more carbon atoms per molecule, preferably 14 to 20, such as lauric acid, isomyristic acid, palmitic acid, isopalmitic acid, α-linolenic acid, linoleic acid, oleic acid, and isostearic acid. The boiling points of polar organic solvents such as fatty acid ester solvents, higher alcohol solvents, and higher fatty acid solvents are preferably 150°C or higher, more preferably 200°C or higher, and even more preferably 250°C or higher. Non-aqueous solvents having a boiling point of 250°C or higher also include non-aqueous solvents that do not exhibit a boiling point.

[0025] The content of the non-aqueous solvent in the oil phase is not particularly limited and is adjusted appropriately depending on the desired viscosity, etc., but may be, for example, 70% by mass or more, 80% by mass or more, or 85% by mass or more. Also, it may be 99% by mass or less, 97% by mass or less, or 95% by mass or less. The content of the non-aqueous solvent in the oil phase may be in the range of 70 to 99% by mass.

[0026] The oil phase may contain a non-aqueous dispersant to improve the dispersion stability of the silica (S). A wide variety of common non-aqueous dispersants can be used as pigment dispersants for non-aqueous solvents. One type of non-aqueous dispersant may be used alone, or two or more types may be used in combination.

[0027] Examples of commercially available non-aqueous dispersants include Solsperse 11200, Solsperse 13940, Solsperse 16000, Solsperse 17000, Solsperse 18000, Solsperse 19000, Solsperse 24000, Solsperse 32000, Solsperse 38500, Solsperse 39000, Solsperse 71000, Solsperse 22000, and Solsperse 28000 manufactured by Lubrizol Japan Co., Ltd.; Disperbyk109 manufactured by BYK Japan Co., Ltd.; Acetamine 24 and Acetamine 86 manufactured by Kao Corporation; and Hypermer KD3 and Hypermer 28000 manufactured by Croda Japan Co., Ltd. KD11" manufactured by Ajinomoto Fine-Techno Co., Ltd.; "Ajisper PB-821" manufactured by Ashland Japan Co., Ltd.; "Antaron V-216" and "Antaron V-220" manufactured by Ashland Japan Co., Ltd.; "Disparon KS-860" and "Disparon KS-873N4" manufactured by Kusumoto Chemicals Co., Ltd.

[0028] The content of the non-aqueous dispersant in the oil phase is not particularly limited, but may be, for example, 0.5% by mass or more, 1% by mass or more, or 3% by mass or more. It may also be 10% by mass or less, 8% by mass or less, or 5% by mass or less. The content of the non-aqueous dispersant in the oil phase may be in the range of 0.5 to 10% by mass.

[0029] The silica contained in the aqueous phase of the post-treatment liquid (1) (hereinafter sometimes referred to as "silica (W)") may be used alone or in combination of two or more types. The specific surface area of ​​silica (W) is set to 10 m2 as measured by the BET method of JIS Z 8830:2013, since this has a more pronounced effect of increasing image density.2 / g or more, and 2 / g or more is more preferable, and 80m 2 / g or more is particularly preferable. 2 / g or less, and 2 / g or less is more preferable, and 350m 2 The specific surface area of ​​the silica (2) is preferably 10 to 500 m / g or less as measured by the BET method. 2 / g, and 2 / g.

[0030] The silica (W) may be either so-called hydrophobic silica having hydrophobic groups on the silica surface, or so-called hydrophilic silica having hydrophilic groups such as silanol groups on the silica surface. These may also be used in combination. From the viewpoint of the storage stability of the post-treatment liquid (1), it is preferable that the silica (W) contains hydrophilic silica. The proportion of hydrophilic silica in the entire silica (W) may be 50% by mass or more, 70% by mass or more, or 90% by mass or more, or may even be 100% by mass.

[0031] Specific examples of hydrophobic silica and hydrophilic silica used as silica (W) include the same as those exemplified as silica (S).

[0032] The content of silica (W) in the aqueous phase is not particularly limited and is adjusted appropriately depending on the desired viscosity, etc., but may be, for example, 0.5% by mass or more, 1% by mass or more, or 3% by mass or more. It may also be 10% by mass or less, 8% by mass or less, or 5% by mass or less. The content of silica (W) in the aqueous phase may be in the range of 0.5 to 10% by mass.

[0033] Examples of water used in the aqueous phase include ion-exchanged water, distilled water, and ultrapure water. The water content in the aqueous phase is not particularly limited and is adjusted appropriately depending on the desired viscosity, etc., but may be, for example, 70% by mass or more, 75% by mass or more, or 80% by mass or more. It may also be 99% by mass or less, 95% by mass or less, or 90% by mass or less. The water content in the aqueous phase may be in the range of 70 to 99% by mass.

[0034] The aqueous phase may contain an aqueous dispersant to improve the dispersion stability of the silica (W). A wide variety of common aqueous dispersants can be used as aqueous pigment dispersants. One type of aqueous dispersant may be used alone, or two or more types may be used in combination. Examples of aqueous dispersants include polymer dispersants and surfactant-type dispersants.

[0035] Among these, surfactant-type dispersants that are dispersible or soluble in water are preferred. For example, the Griffin HLB value of the surfactant-type dispersant may be 9.0 or more, or 16.0 or more.

[0036] Examples of polymer dispersants include the TEGO Disperse series manufactured by EVONIK (such as "TEGO Disperse 740W," "TEGO Disperse 750W," "TEGO Disperse 755W," "TEGO Disperse 757W," and "TEGO Disperse 760W"), and the Solsperse series manufactured by Lubrizol Japan Co., Ltd. (such as "Solsperse 20000," "Solsperse 27000," "Solsperse 41000," "Solsperse 41090," "Solsperse 43000," "Solsperse 44000," and "Solsperse 46000"). etc.), the JONCRYL series manufactured by BASF Japan Ltd. ("JONCRYL 57", "JONCRYL 60", "JONCRYL 62", "JONCRYL 63", "JONCRYL 71", "JONCRYL 501", etc.), "DISPERBYK-102", "DISPERBYK-185", "DISPERBYK-190", "DISPERBYK-193", "DISPERBYK-199", etc. manufactured by BYK Japan Co., Ltd., and "Polyvinylpyrrolidone K-30" and "Polyvinylpyrrolidone K-90" manufactured by Daiichi Kogyo Seiyaku Co., Ltd.

[0037] Examples of surfactant-type dispersants include anionic surfactants such as the Demol series manufactured by Kao Corporation ("Demol P", "Demol EP", "Demol N", "Demol RN", "Demol NL", "Demol RNL", "Demol T-45", etc.), and nonionic surfactants such as the Emulgen series manufactured by Kao Corporation ("Emulgen A-60", "Emulgen A-90", "Emulgen A-500", "Emulgen B-40", "Emulgen L-40", "Emulgen 420", "Emulgen 1118S-70", etc.).

[0038] The content of the aqueous dispersant in the aqueous phase is not particularly limited, but may be, for example, 0.5% by mass or more, 1% by mass or more, or 5% by mass or more. It may also be 20% by mass or less, 15% by mass or less, or 10% by mass or less. The content of the aqueous dispersant in the aqueous phase may be in the range of 0.5 to 20% by mass.

[0039] The post-treatment liquid (1) may contain other components in addition to the components described above, specifically, silica (S), non-aqueous solvent, non-aqueous dispersant, silica (W), water, and aqueous dispersant. Examples of other components include aqueous solvents, electrolytes, humectants, water-soluble polymers, preservatives, and antifreeze agents. In a post-treatment liquid that is a water-in-oil emulsion, these other components may be contained in either the oil phase or the aqueous phase.

[0040] The method for producing a water-in-oil emulsion from an oil phase and an aqueous phase is not particularly limited, and any method may be used. For example, a method may be used in which silica is dispersed in each of the oil phase and the aqueous phase using a dispersing machine such as a bead mill, and then the aqueous phase is added to the oil phase and emulsified.

[0041] During emulsification, an emulsifier may be used as needed. One type of emulsifier may be used alone, or two or more types may be used in combination. Examples of emulsifiers include anionic surfactants, cationic surfactants, amphoteric surfactants, and nonionic surfactants. Of these, nonionic surfactants are preferred from the viewpoint of the emulsifiability and storage stability of the water-in-oil emulsion. Examples of nonionic surfactants include sorbitan fatty acid esters such as sorbitan monolaurate, sorbitan monopalmitate, sorbitan monooleate, sorbitan sesquioleate, and sorbitan monoisostearate; (poly)glycerin fatty acid esters such as glyceryl monostearate, hexaglyceryl tetraoleate, hexaglyceryl pentaoleate, decaglyceryl decaoleate, decaglyceryl pentahydroxystearate, decaglyceryl pentaisostearate, and decaglyceryl condensed ricinoleate; polyoxyethylene sorbitan fatty acid esters, polyoxyethylene glycerin fatty acid esters, polyoxyethylene sorbit fatty acid esters, propylene glycol fatty acid esters, (poly)ethylene glycol fatty acid esters, polyoxyethylene alkyl ethers, polyoxyethylene polyoxypropylene alkyl ethers, polyoxyethylene alkylphenyl ethers, and polyoxyethylene (hydrogenated) castor oil. Examples of emulsifiers include the Rheodol series manufactured by Kao Corporation (such as "Rheodol MS50," "Rheodol MS60," "Rheodol MO60," and "Rheodol AO-10V"), and "NIKKOL MGO" manufactured by Nikko Chemicals Co., Ltd.

[0042] The amount of emulsifier used may be 0.5% by mass or more, 1% by mass or more, or 3% by mass or more, based on the total mass of the oil phase and the aqueous phase. It may also be 15% by mass or less, 10% by mass or less, or 8% by mass or less. The amount of emulsifier used may be in the range of 0.5 to 15 parts by mass, based on the total mass of the oil phase and the aqueous phase.

[0043] When an emulsifier is used, it is preferable to blend the emulsifier with the oil phase beforehand and then add the aqueous phase. The aqueous phase may be added all at once, in portions, or by dropwise addition. Furthermore, the emulsification treatment may be carried out after the entire amount of the aqueous phase has been added to the oil phase, or may be carried out after each portion addition, or while adding the aqueous phase dropwise to the oil phase, etc.

[0044] The ratio of the oil phase to the aqueous phase is preferably 50% by mass or more, more preferably 60% by mass or more, and particularly preferably 70% by mass or more, relative to the total mass of the oil and aqueous phases, in order to obtain a printed surface with high image density and to more significantly suppress ink strike-through. The ratio is also preferably 90% by mass or less, more preferably 85% by mass or less, and particularly preferably 80% by mass or less. The ratio of the oil phase to the total mass of the oil and aqueous phases may be in the range of 50 to 90% by mass.

[0045] Furthermore, the ratio of silica (S) to silica (W) is preferably 50% by mass or more, more preferably 60% by mass or more, and particularly preferably 70% by mass or more, based on the fact that a printed surface with high image density and the effect of suppressing ink strike-through are more pronounced. Also, the ratio is preferably 90% by mass or less, more preferably 85% by mass or less, and particularly preferably 80% by mass or less. The ratio of silica (S) to the total mass of silica (S) and silica (W) may be in the range of 50 to 90% by mass.

[0046] The post-treatment liquid (2) will now be described. The hydrophobic silica contained in the post-treatment liquid (2) may be used alone or in combination of two or more types. Specific examples of hydrophobic silica include those exemplified in the description of silica (S).

[0047] The specific surface area of ​​hydrophobic silica is 10m2 as measured by the BET method of JIS Z 8830:2013, because this has a more pronounced effect on increasing image density. 2 / g or more, and 2 / g or more is more preferable, and 50m 2 / g or more is particularly preferable. 2 / g or less, and 2 / g or less is more preferable, and 150m 2 The specific surface area of ​​the hydrophobic silica is preferably 10 to 400 m / g as measured by the BET method. 2 / g, and may be in the range of 50 to 150m 2 / g.

[0048] The hydrophilic silica contained in the post-treatment liquid (2) may be used alone or in combination of two or more types. Specific examples of hydrophilic silica include those exemplified in the description of silica (S).

[0049] The specific surface area of ​​hydrophilic silica is 10m2 as measured by the BET method of JIS Z 8830:2013, because this has a more pronounced effect on increasing image density. 2 / g or more, and 2 / g or more is more preferable, and 80m 2 / g or more is particularly preferable. 2 / g or less, and 2 / g or less is more preferable, and 350m 2 The specific surface area of ​​the hydrophilic silica is preferably 10 to 500 m / g as measured by the BET method. 2 / g, and 2 / g.

[0050] In the post-treatment liquid (2), the ratio of hydrophobic silica to hydrophilic silica relative to the total mass of both is preferably 50% by mass or more, more preferably 60% by mass or more, and particularly preferably 70% by mass or more, in order to obtain a printed surface with high image density and to more significantly suppress ink strike-through. Also, the ratio is preferably 90% by mass or less, more preferably 85% by mass or less, and particularly preferably 80% by mass or less. The ratio of hydrophobic silica relative to the total mass of hydrophobic silica and hydrophilic silica may be in the range of 50 to 90% by mass.

[0051] The post-treatment liquid (2) is a water-in-oil emulsion, and in the post-treatment liquid (2), the hydrophobic silica and the hydrophilic silica may be present in either the oil phase or the aqueous phase, or may be present in both the oil phase and the aqueous phase. Furthermore, the post-treatment liquid (2) may be produced in any manner. One example of a method for producing the post-treatment liquid (2) is a method for producing a water-in-oil emulsion from an oil phase containing hydrophobic silica and an aqueous phase containing hydrophilic silica.

[0052] The oil phase contains a non-aqueous solvent in addition to hydrophobic silica. Specific examples of the non-aqueous solvent include those exemplified in the description of post-treatment liquid (1). The content of hydrophobic silica in the oil phase is not particularly limited and is adjusted appropriately depending on the desired viscosity, etc., but may be, for example, 0.5% by mass or more, 1% by mass or more, or 3% by mass or more. It may also be 10% by mass or less, 8% by mass or less, or 5% by mass or less. The content of hydrophobic silica in the oil phase may be in the range of 0.5 to 10% by mass.

[0053] The content of the non-aqueous solvent in the oil phase is not particularly limited and is adjusted appropriately depending on the desired viscosity, etc., but may be, for example, 70% by mass or more, 80% by mass or more, or 85% by mass or more. Also, it may be 99% by mass or less, 97% by mass or less, or 95% by mass or less. The content of the non-aqueous solvent in the oil phase may be in the range of 70 to 99% by mass.

[0054] The oil phase is obtained by dispersing hydrophobic silica in a non-aqueous solvent using a dispersing machine such as a bead mill. In this case, a non-aqueous dispersant may be contained to improve the dispersion stability of the hydrophobic silica. Examples of non-aqueous dispersants include those exemplified as non-aqueous dispersants that may be contained in the oil phase of the post-treatment liquid (1). One type of non-aqueous dispersant may be used alone, or two or more types may be used in combination. The content of the non-aqueous dispersant in the oil phase is not particularly limited and is adjusted appropriately depending on the desired viscosity, etc., but may be, for example, 0.5% by mass or more, 1% by mass or more, or 3% by mass or more. It may also be 10% by mass or less, 8% by mass or less, or 5% by mass or less. The content of the non-aqueous dispersant in the oil phase may be in the range of 0.5 to 10% by mass.

[0055] Examples of water used in the aqueous phase include ion-exchanged water, distilled water, and ultrapure water. The content of hydrophilic silica in the aqueous phase is not particularly limited and is adjusted appropriately depending on the desired viscosity, etc., but may be, for example, 0.5% by mass or more, 1% by mass or more, or 3% by mass or more. It may also be 10% by mass or less, 8% by mass or less, or 5% by mass or less. The content of hydrophilic silica in the aqueous phase may be in the range of 0.5 to 10% by mass.

[0056] The water content in the aqueous phase is not particularly limited and is adjusted appropriately depending on the desired viscosity, etc., but may be, for example, 70% by mass or more, 75% by mass or more, or 80% by mass or more. It may also be 99% by mass or less, 95% by mass or less, or 90% by mass or less. The water content in the aqueous phase may be in the range of 70 to 99% by mass.

[0057] The aqueous phase can be obtained by dispersing hydrophilic silica in the aqueous phase using a dispersing machine such as a bead mill. In this case, an aqueous dispersant may be contained to improve the dispersion stability of the hydrophilic silica. Examples of aqueous dispersants include those exemplified as aqueous dispersants that may be contained in the aqueous phase of the post-treatment liquid (1). One type of aqueous dispersant may be used alone, or two or more types may be used in combination. The content of the aqueous dispersant in the aqueous phase is not particularly limited and is adjusted appropriately depending on the desired viscosity, etc., but may be, for example, 0.5% by mass or more, 1% by mass or more, or 5% by mass or more. It may also be 20% by mass or less, 15% by mass or less, or 10% by mass or less. The content of the aqueous dispersant in the aqueous phase may be in the range of 0.5 to 20% by mass.

[0058] The post-treatment liquid (2) may contain other components in addition to the components described above, specifically, hydrophobic silica, non-aqueous solvent, non-aqueous dispersant, hydrophilic silica, water, and aqueous dispersant. Examples of other components include aqueous solvents, electrolytes, humectants, water-soluble polymers, preservatives, and antifreeze agents. In a post-treatment liquid that is a water-in-oil emulsion, these other components may be contained in either the oil phase or the aqueous phase.

[0059] The method for producing a water-in-oil emulsion from an oil phase and an aqueous phase is not particularly limited, and any method may be used. One example is a method in which the aqueous phase is added to the oil phase and emulsified.

[0060] An emulsifier may be used during emulsification, if necessary. One type of emulsifier may be used alone, or two or more types may be used in combination. Examples of emulsifiers include those exemplified in the description of the production method for post-treatment liquid (1). The amount of emulsifier used may be 0.5% by mass or more, 1% by mass or more, or 3% by mass or more, relative to the total mass of the oil phase and the aqueous phase. Also, it may be 15% by mass or less, 10% by mass or less, or 8% by mass or less. The amount of emulsifier used may be in the range of 0.5 to 15 parts by mass, relative to the total mass of the oil phase and the aqueous phase.

[0061] When an emulsifier is used, it is preferable to blend the emulsifier with the oil phase beforehand and then add the aqueous phase. The aqueous phase may be added all at once, in portions, or by dropwise addition. Furthermore, the emulsification treatment may be carried out after the entire amount of the aqueous phase has been added to the oil phase, or may be carried out after each portion addition, or while adding the aqueous phase dropwise to the oil phase, etc.

[0062] The ratio of the oil phase to the aqueous phase is preferably 50% by mass or more, more preferably 60% by mass or more, and particularly preferably 70% by mass or more, relative to the total mass of the oil and aqueous phases, in order to obtain a printed surface with high image density and to more significantly suppress ink strike-through. The ratio is also preferably 90% by mass or less, more preferably 85% by mass or less, and particularly preferably 80% by mass or less. The ratio of the oil phase to the total mass of the oil and aqueous phases may be in the range of 50 to 90% by mass.

[0063] An ink set according to one embodiment includes the oil-based ink post-treatment agent (1) or (2) described above and an oil-based ink. Regardless of the type of oil-based ink, the use of the post-treatment agent described above allows for a printed surface with high image density to be obtained and also suppresses ink strike-through.

[0064] Oil-based inks mainly contain pigments, pigment dispersants, and non-aqueous solvents.

[0065] Examples of pigments include organic pigments such as azo pigments, phthalocyanine pigments, polycyclic pigments, and dye lake pigments; and 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 diketopyrrolopyrrole (DPP). 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. One type of pigment may be used alone, or two or more types may be used in combination.

[0066] The average particle size of the pigment can be adjusted appropriately depending on the type of oil-based ink, printing method, etc., but may be, for example, in the range of 50 to 300 nm. The content of the pigment in the oil-based ink can be adjusted appropriately depending on the type of oil-based ink, printing method, etc., but may be, for example, in the range of 1 to 30 mass %.

[0067] Examples of pigment dispersants include the same non-aqueous dispersants that can be contained in the oil phase described above. One type of pigment dispersant may be used alone, or two or more types may be used in combination. The content of the pigment dispersant in the oil-based ink can be adjusted appropriately depending on the type of oil-based ink, printing method, etc., but may be, for example, in the range of 1 to 20 mass%.

[0068] Examples of non-aqueous solvents include those similar to the non-aqueous solvents contained in the oil phase described above. One type of non-aqueous solvent may be used alone, or two or more types may be used in combination. Furthermore, other organic solvents may be contained to the extent that a single phase can be formed with the non-aqueous solvent used. The content of the non-aqueous solvent in the oil-based ink can be adjusted appropriately depending on the type of oil-based ink, printing method, etc., but may be, for example, in the range of 50 to 99% by mass.

[0069] The oil-based ink may contain other components in addition to the pigment, pigment dispersant, and non-aqueous solvent depending on the type of ink, printing method, etc. Examples of other components include resins, antioxidants, conductivity modifiers, viscosity modifiers, surface tension modifiers, oxygen absorbers, etc. The specific types of these other components are not particularly limited, and those used in the relevant field can be used.

[0070] The oil-based ink may be, for example, an oil-based inkjet ink. In this case, the viscosity of the oil-based ink is preferably 5 to 30 mPa·s at 23°C, and more preferably 5 to 15 mPa·s, although the appropriate range varies depending on the nozzle diameter of the ejection head of the inkjet recording system, the ejection environment, and the like.

[0071] A method for producing a printed matter according to one embodiment includes printing an image using oil-based ink and applying a post-treatment liquid for oil-based ink.

[0072] The substrate to be printed may be any substrate that is permeable to the non-aqueous solvent, and may include printing paper such as plain paper, coated paper, and special paper, cloth, porous sheet, etc., or an adhesive sheet having an adhesive layer on the back surface of the substrate made of any of these. Among these, printing paper such as plain paper and coated paper is preferably used from the viewpoint of permeability of the non-aqueous solvent.

[0073] Here, plain paper refers to paper on which no ink-receiving layer or film layer is formed. Examples of plain paper include fine paper, medium-quality paper, PPC paper, wood paper, recycled paper, etc. Plain paper has paper fibers with a thickness of several μm to several tens of μm that form voids of several tens to several hundreds of μm, making it easy for non-aqueous solvents to penetrate.

[0074] Furthermore, as the coated paper, inkjet coated paper such as matte paper, glossy paper, and semi-glossy paper, as well as so-called coated printing paper, can be preferably used. Here, coated printing paper refers to printing paper that has traditionally been used in letterpress printing, offset printing, gravure printing, and the like, and is printing paper in which a coating layer is provided on the surface of fine or medium-quality paper using a paint containing an inorganic pigment such as clay or calcium carbonate and a binder such as starch. Coated printing paper is classified into lightly coated paper, fine lightweight coated paper, medium lightweight coated paper, fine coated paper, medium coated paper, art paper, cast coated paper, and the like, depending on the amount of paint applied and the coating method.

[0075] The method for printing an image using oil-based ink is not particularly limited, and various printing methods can be used, such as screen printing, roller printing, gravure printing, flexographic printing, inkjet printing, etc. Printing an image using oil-based ink may be performed by inkjet printing.

[0076] The printing method using oil-based inkjet ink is not particularly limited, and may be any method such as a piezoelectric method, an electrostatic method, a thermal method, etc. When an inkjet recording device is used, it is preferable to eject oil-based ink from an inkjet head based on a digital signal and allow the ejected ink droplets to adhere to a substrate.

[0077] The method for applying the post-treatment liquid is not particularly limited, and various printing methods such as screen printing, roller printing, gravure printing, flexographic printing, inkjet printing, etc. may be used, or the post-treatment liquid may be applied by a brush, a bar coater, an air knife coater, a spray, etc. The post-treatment liquid may be applied by inkjet printing.

[0078] The post-treatment liquid is preferably applied to an area including at least a part of an image formed by oil-based ink, and more preferably to an area including the entire image. The amount of post-treatment liquid applied is adjusted appropriately depending on the type of ink, printing method, substrate, etc. -1 ~10 -5 ml / cm 2 may be in the range of

[0079] Some embodiments of the present disclosure are set forth below. <1> A post-treatment liquid for oil-based inks, which is a water-in-oil emulsion and contains silica in both the oil phase and the water phase.

[0080] <2> The specific surface area of ​​the silica contained in the oil phase by the BET method is 50 to 150 m 2 / g <1> A post-treatment liquid for oil-based inks according to the present invention.

[0081] <3> The specific surface area of ​​the silica contained in the aqueous phase by the BET method is 80 to 350 m 2 / g <1> or <2> A post-treatment liquid for oil-based inks according to the present invention.

[0082] <4> A post-treatment liquid for oil-based inks, which is a water-in-oil emulsion and contains both hydrophobic silica and hydrophilic silica.

[0083] <5> The aforementioned <1> ~ <4> 1. An ink set comprising the oil-based ink post-treatment liquid according to any one of items 1 to 8 above and an oil-based ink.

[0084] <6> Printing an image using oil-based ink, and <1> ~ <4> and applying the oil-based ink post-treatment liquid according to any one of the preceding items. [Example]

[0085] 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. Unless otherwise specified, common components are the same throughout the following Examples and Comparative Examples. Unless otherwise specified, "%" indicates "% by mass."

[0086] [Examples 1 to 7 and Comparative Example 1: Preparation of post-treatment liquid] The oil and water phase components were mixed in the proportions shown in Table 1 and dispersed in a bead mill to obtain an oil phase and a water phase. The emulsifier and water phase were added to the oil phase in that order, and the mixture was irradiated with ultrasonic waves for 10 minutes under ice-cooled conditions using an ultrasonic homogenizer ("Ultrasonic processor VC-750" manufactured by Sonics Corporation) to obtain a post-treatment liquid that is a water-in-oil emulsion.

[0087] [Oil-based ink manufacturing] An oil-based ink was obtained by blending 10 parts by weight of pigment, 8 parts by weight of pigment dispersant, and 82 parts by weight of non-aqueous solvent, and dispersing the mixture in a bead mill. Pigment: Asahi Carbon Co., Ltd. "SB335", carbon black Pigment dispersant: Ashland Japan Co., Ltd.'s "Antaron V220," a copolymer of vinylpyrrolidone and eicosene Non-aqueous solvent: Isononyl isononanoate (Kyukyu Alcohol Kogyo Co., Ltd.)

[0088] [Printed material production] Oil-based ink and post-treatment liquid were loaded into a line-type inkjet printer "Comphis GD9630" (manufactured by Riso Kagaku Corporation), and 1,000 solid images were continuously printed on plain paper "Riso Paper Thin" (manufactured by Riso Kagaku Corporation) to obtain printed matter. The printing conditions were 30 pL of oil-based ink and 20 pL of post-treatment liquid.

[0089] [Evaluation of image density] Five prints were randomly selected from the prints obtained above and left at room temperature for 24 hours. The OD values ​​of the surfaces of the prints were then measured using an optical densitometer (Macbeth RD920). The print with the highest OD value was evaluated according to the following criteria. The results are shown in Table 1. A:OD value is 1.33 or more B:OD value is 1.30 or more and less than 1.33 C:OD value is less than 1.30

[0090] [Evaluation of bleed-through] Five prints were randomly selected from the prints obtained above and left at room temperature for 24 hours. The OD values ​​of the backsides of the prints were measured using an optical densitometer (Macbeth "RD920"), and the print with the lowest OD value was evaluated according to the following criteria. The results are shown in Table 1. A:OD value is less than 0.28 B:OD value is 0.28 or more

[0091] [Table 1]

[0092] Silica (1): "Aerosil R972" manufactured by Nippon Aerosil Co., Ltd., a hydrophobic silica having a dimethylsilyl group, a specific surface area of ​​90 to 130 m according to the BET method of JIS Z 8830:2013 2 / g Silica (2): "Aerosil RY200S" manufactured by Nippon Aerosil Co., Ltd., a hydrophobic silica having a dimethylpolysiloxane group, a specific surface area of ​​65 to 95 m according to the BET method of JIS Z 8830:2013 2 / g Non-aqueous solvent: Isononyl isononanoate (Kyukyu Alcohol Kogyo Co., Ltd.) Non-aqueous dispersant: "Antaron V220" manufactured by Ashland Japan Co., Ltd. Silica (3): "Aerosil 130" manufactured by Nippon Aerosil Co., Ltd., hydrophilic silica, specific surface area 105 to 155 m according to the BET method of JIS Z 8830:2013 2 / g Silica (4): "Aerosil 300" manufactured by Nippon Aerosil Co., Ltd., hydrophilic silica, specific surface area of ​​270 to 330 m according to the BET method of JIS Z 8830:2013 2 / g Water-based dispersant: Kao Corporation's "Emulgen 1118S-70" Emulsifier (1): "Rheodol MS60" manufactured by Kao Corporation Emulsifier (2): "Rheodol MS50" manufactured by Kao Corporation Emulsifier (3): "Rheodol MO60" manufactured by Kao Corporation Emulsifier (4): "NIKKOL MGO" manufactured by Nikko Chemicals Co., Ltd.

[0093] As shown in Table 1, by using the post-treatment liquid of each Example, ink strike-through was effectively suppressed, and a printed surface with high image density was obtained. On the other hand, in Comparative Example 1, which used a silica dispersion in a non-aqueous solvent as the post-treatment liquid, ink strike-through occurred and the image density was low.

Claims

1. A post-treatment liquid for oil-based inks, which is a water-in-oil emulsion and contains silica in both the oil phase and the water phase.

2. The specific surface area of ​​the silica contained in the oil phase as measured by the BET method is 50 to 150 m ２ The oil-based ink post-treatment liquid according to claim 1, wherein the water content is in the range of 1 / g.

3. The specific surface area of ​​the silica contained in the aqueous phase as measured by the BET method is 80 to 350 m ２ The oil-based ink post-treatment liquid according to claim 1, wherein the water content is in the range of 1 / g.

4. A post-treatment liquid for oil-based inks, which is a water-in-oil emulsion and contains both hydrophobic silica and hydrophilic silica.

5. An ink set comprising the oil-based ink post-treatment liquid according to any one of claims 1 to 4 and an oil-based ink.

6. A method for producing a printed matter, comprising: printing an image using an oil-based ink; and applying the oil-based ink post-treatment liquid according to any one of claims 1 to 4 onto the image.

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