Water-based inkjet ink composition and ink set

Abstract

This water-based inkjet ink composition forms an image by being applied on a recording medium. The water-based inkjet ink composition contains a silicone compound and a polyolefin. The silicone compound is in particulate form and constitutes a silicone emulsion. The average particle diameter of the particulate silicone compound is in the range from 70 to 350 nm. The recording medium is a non-absorbent substrate.

Description

Aqueous inkjet ink composition and ink set

[0001] The present invention relates to an aqueous inkjet ink composition and an ink set, and more particularly to an aqueous inkjet ink composition that has excellent coating adhesion and abrasion resistance to non-absorbent substrates and is capable of forming high-quality images.

[0002] In recent years, inkjet printing technology for packaging materials for food, beverages, daily necessities, etc. has advanced, and inks compatible with non-absorbent substrates such as plastic films have been developed. Polypropylene substrates used in packaging materials are non-polar and crystalline, making it difficult for ink to adhere to them. Therefore, non-absorbent substrates such as polypropylene substrates are also referred to as low-adhesion substrates. Patent Document 1 discloses an inkjet recording method using a polyolefin resin in the ink, which has good adhesion to polypropylene substrates. However, while polyolefin has high adhesion to non-absorbent substrates such as polypropylene, the soft nature of the resin poses a problem of poor abrasion resistance of the ink coating.

[0003] Patent Document 2 discloses an inkjet composition that has excellent adhesion and abrasion resistance to non-absorbent substrates by employing a urethane resin having a polyolefin polyol structure and a silicone emulsion in the ink. The urethane resin having a polyolefin polyol structure has high adhesion to polypropylene substrates that have been surface-treated by corona discharge treatment or the like. However, the urethane resin having a polyolefin polyol structure exhibits insufficient adhesion of the ink coating to polypropylene substrates that have not been surface-treated.

[0004] Patent Literature 3 discloses an inkjet recording method that achieves both high image quality and good adhesion to polypropylene substrates by employing a two-component inkjet recording method with an ink containing polyolefin. However, although the employment of a two-component method improves image quality on non-absorbent substrates, the ink coating film lacks abrasion resistance because the only resin type in the ink is polyolefin.

[0005] JP 2013-193324 A JP 2021-155557 A JP 2014-024944 A

[0006] The present invention has been made in view of the above problems and circumstances, and an object of the present invention is to provide an aqueous inkjet ink composition and an ink set that are excellent in coating adhesion and abrasion resistance and can form high-quality images on non-absorbent substrates such as polypropylene substrates.

[0007] The present inventors have investigated the causes of the above problems in order to solve them. As a result, they have found that an aqueous inkjet ink composition contains a polyolefin and a silicone compound, and the silicone compound is made into a silicone emulsion. Furthermore, the average particle size of the silicone compound particles in the silicone emulsion is set within a specific range. They have found that this makes it possible to provide an aqueous inkjet ink composition and an ink set that are excellent in coating adhesion and abrasion resistance and can form high-quality images on non-absorbent substrates, and have arrived at the present invention. That is, the above problems of the present invention are solved by the following means.

[0008] 1. An aqueous inkjet ink composition for application to a recording medium to form an image, the aqueous inkjet ink composition comprising a silicone compound and a polyolefin, the silicone compound being in particulate form and constituting a silicone emulsion, the particulate silicone compound having an average particle diameter within the range of 70 to 350 nm, and the recording medium being a non-absorbent substrate.

[0009] 2. The aqueous ink-jet ink composition according to item 1, wherein the silicone emulsion is an amino group-containing silicone emulsion.

[0010] 3. The aqueous ink-jet ink composition according to claim 1, wherein the silicone emulsion is a self-crosslinking silicone emulsion.

[0011] 4. The aqueous ink-jet ink composition according to claim 1, wherein the polyolefin is an acid-modified polyolefin.

[0012] 5. The aqueous ink-jet ink composition according to item 1, wherein the mass ratio of the polyolefin to the silicone compound (mass of polyolefin:mass of silicone compound) is within a range of 4:1 to 1:1.

[0013] 6. The aqueous ink-jet ink composition according to item 1, wherein the polyolefin particles in the polyolefin have an average particle size in the range of 100 to 300 nm.

[0014] 7. An ink set comprising the aqueous inkjet ink composition according to any one of items 1 to 6 and a treatment liquid containing a flocculant.

[0015] 8. The ink set according to item 7, wherein the static surface tension of the treatment liquid is within a range of 18 to 25 mN / m at 25°C, and the dynamic surface tension of the treatment liquid at a surface life of 50 msec is within a range of 25 to 35 mN / min at 25°C.

[0016] The above-described means of the present invention can provide an aqueous inkjet ink composition and ink set that can form high-quality images on non-absorbent substrates with excellent coating adhesion and abrasion resistance. While the mechanism of action or effect of the present invention is unclear, it is speculated as follows: By using a polyolefin and a silicone emulsion in the ink, an ink coating can be formed that has excellent adhesion and abrasion resistance on non-absorbent substrates such as polypropylene. The technique of blending two or more polymers is widely used as a method for modifying polymeric materials. By controlling different polymer species to form a phase-separated structure, such as a sea-island structure, a polymeric material can be obtained that possesses the characteristics of each polymer. Although the mechanism of action of the present invention is not clear, by dispersing a silicone compound with high slip properties in an aqueous dispersion medium to form a silicone emulsion, the polyolefin and silicone compound form a phase-separated structure without uniformly mixing in the dried ink coating. It is believed that this results in adhesion to non-absorbent substrates and the slipperiness of the silicone compound. Coating adhesion can be imparted to non-absorbent substrates regardless of whether or not surface treatment such as corona discharge treatment is performed. In particular, it was found that the above effects can be effectively achieved by controlling the average particle size of the particulate silicone compound in the silicone emulsion to within the range of 70 to 350 nm. In the comparative examples described below, when a silicone compound with high slip properties that was dissolved in a dispersion medium and did not form an emulsion was used, the adhesion of the ink coating to non-absorbent substrates and the abrasion resistance both resulted in poor results. This is presumably because the polyolefin and silicone compound were mixed uniformly and did not form a phase-separated structure in the coating, resulting in the respective properties being averaged out.

[0017] FIG. 1 is a diagram for explaining the state in which the treatment liquid and ink are united in the present invention. FIG. 2 is a diagram for explaining the state in which the treatment liquid and ink are united in the present invention. FIG. 3 is a diagram for explaining the state in which the treatment liquid and ink are united in the present invention. Schematic diagram showing an example of a recording apparatus preferred for the present invention.

[0018] The aqueous inkjet ink composition of the present invention is an aqueous inkjet ink composition to be applied to a recording medium to form an image, the aqueous inkjet ink composition comprising a silicone compound and a polyolefin, the silicone compound being in particulate form and constituting a silicone emulsion, the particulate silicone compound having an average particle diameter within a range of 70 to 350 nm, and the recording medium being a non-absorbent substrate. This feature is a technical feature common to or corresponding to each of the following embodiments.

[0019] In one embodiment of the present invention, the silicone emulsion is preferably an amino group-containing silicone emulsion, since this can impart good water repellency to the coating film.

[0020] The silicone emulsion is preferably a self-crosslinking silicone emulsion, as this increases the hardness of the coating film and improves the abrasion resistance.

[0021] The polyolefin is preferably an acid-modified polyolefin, since high character reproducibility can be obtained.

[0022] In the aqueous inkjet ink composition, it is preferable that the mass ratio of the polyolefin to the silicone emulsion (mass of polyolefin:mass of silicone emulsion) is within a range of 4:1 to 1:1, in order to achieve both good adhesion and abrasion resistance of the coating film.

[0023] The average particle size of the polyolefin particles in the polyolefin is preferably within the range of 100 to 300 nm. When the average particle size is 100 nm or more, the film-forming properties of the resin do not become too high when the ink dries, preventing nozzle clogging. When the average particle size is 300 nm or less, the particle size does not become too large, resulting in good ejection properties from an inkjet head. As a result, good film-forming properties and good substrate adhesion are achieved.

[0024] The ink set of the present invention comprises the aqueous inkjet ink composition of the present invention and a treatment liquid containing an aggregating agent, and thereby provides an ink set that has excellent coating film adhesion and abrasion resistance on non-absorbent substrates and is capable of forming high-quality images.

[0025] It is preferable that the static surface tension of the treatment liquid is in the range of 18 to 25 mN / m at 25° C., and that the dynamic surface tension of the treatment liquid at a surface life of 50 msec is in the range of 25 to 35 mN / min at 25° C. By setting the static surface tension and dynamic surface tension of the treatment liquid within the above ranges, it is possible to prevent the treatment liquid from spreading and wetting too much, which would result in poor character reproducibility. Furthermore, the treatment liquid is not repelled by the substrate, resulting in good character reproducibility.

[0026] The present invention, its components, and embodiments and modes for carrying out the present invention will be described below. In this application, the symbol "to" is used to mean that the numerical values ​​before and after it are included as the lower limit and upper limit.

[0027] [Summary of Aqueous Inkjet Ink Composition of the Present Invention] The aqueous inkjet ink composition of the present invention is an aqueous inkjet ink composition to be applied to a recording medium to form an image, and contains a silicone compound and a polyolefin, the silicone compound is in particulate form and constitutes a silicone emulsion, the particulate silicone compound has an average particle diameter within the range of 70 to 350 nm, and the recording medium is a non-absorbent substrate.

[0028] Hereinafter, the "aqueous inkjet ink composition" may be simply referred to as "ink." The ink according to the present invention contains a polyolefin and a silicone compound, and the silicone compound is in particulate form and forms a silicone emulsion. The ink preferably further contains a water-soluble solvent, wax, water, a pigment, a pigment dispersant, etc.

[0029] <Polyolefin> Examples of the polyolefin that can be used include polyethylene, polypropylene, ethylene-propylene copolymers, and random or block copolymers of ethylene and / or propylene with other comonomers (e.g., ethylene-propylene-butene copolymers). Examples of the other comonomers include 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, and 1-nonene, each of which has two or more carbon atoms, and α-olefin comonomers having two to six carbon atoms. It is also possible to use copolymers of two or more of the above other comonomers, and mixtures of two or more of the above polymers.

[0030] Commercially available polyolefins may also be used. Examples of commercially available polyolefins include Arrowbase SB-1200 (manufactured by Unitika Ltd., "Arrowbase" is a registered trademark of the company), Auroren 150A, Auroren AE-301 (manufactured by Nippon Paper Industries Co., Ltd., "Auroren" is a registered trademark of the company), Superchlor E-415 (manufactured by Nippon Paper Industries Co., Ltd., "Superchlor" is a registered trademark of the company), and Hardren Na-1001 (manufactured by Toyobo Co., Ltd., "Hardren" is a registered trademark of the company).

[0031] In the present invention, the polyolefin is preferably a chlorinated polyolefin or an acid-modified polyolefin. The polyolefin is particularly preferably an acid-modified polyolefin, since it provides excellent character reproducibility in a two-liquid ink-jet recording system.

[0032] Examples of chlorinated polyolefins include chlorinated polyethylene, chlorinated polypropylene, chlorinated polybutylene, etc. The weight average molecular weight of the chlorinated polyolefin is preferably within a range of 5,000 to 200,000, more preferably within a range of 10,000 to 100,000, and even more preferably within a range of 10,000 to 50,000.

[0033] The chlorinated polyolefin may be a commercially available product. Examples of the commercially available product include trade names: Superchlor L-206 (manufactured by Nippon Paper Industries Co., Ltd., weight average molecular weight: 9000), trade name: Superchlor 370M (manufactured by Nippon Paper Industries Co., Ltd., weight average molecular weight: 10000), trade name: Superchlor 814HS (manufactured by Nippon Paper Industries Co., Ltd., weight average molecular weight: 20000), trade name: Hardlen 14-LWP (manufactured by Toyobo Co., Ltd., number average molecular weight: 40000), trade name: Hardlen DX-530P (manufactured by Toyobo Co., Ltd., number average molecular weight: 100000), trade name: Hardlen 15-LP (manufactured by Toyobo Co., Ltd., number average molecular weight: 150000), and trade name: Hardlen 13-LP (manufactured by Toyobo Co., Ltd., number average molecular weight: 200000). These may be used alone or in combination of two or more types.

[0034] Acid-modified polyolefins are resins obtained by modifying polyolefins such as polyethylene and polypropylene with unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid, maleic anhydride, fumaric acid, itaconic acid, etc. Among these acid-modified polyolefins, it is preferable to use polyolefins modified with maleic anhydride.

[0035] The polyolefin preferably contains polyolefin particles having an average particle size in the range of 100 to 300 nm. In particular, the polyolefin preferably contains polyolefin particles having an average particle size in the range of 10 to 80 nm and polyolefin particles having an average particle size in the range of 100 to 300 nm. Mixing resin particles having two different particle sizes is preferable in that it provides good film-forming properties and prevents coating cracks. Hereinafter, the polyolefin particles having an average particle size in the range of 10 to 80 nm are also referred to as small-diameter polyolefin particles. Furthermore, the polyolefin particles having an average particle size in the range of 100 to 300 nm are also referred to as large-diameter polyolefin particles.

[0036] The ratio of the content (mass%) of the small-diameter polyolefin particles to the content (mass%) of the large-diameter polyolefin particles in the polyolefin (content of large-diameter polyolefin particles:content of small-diameter polyolefin particles) is preferably within a range of 10:90 to 90:10. The content of large-diameter polyolefin particles:content of small-diameter polyolefin particles is more preferably within a range of 30:70 to 70:30, and particularly preferably 50:50.

[0037] The average particle size of the polyolefin particles can be measured using a commercially available particle size measuring device that uses dynamic light scattering, electrophoresis, or the like. In particular, measurement using dynamic light scattering is simple and can accurately measure the particle size range. Specifically, the average particle size of the polyolefin particles is a value calculated using the cumulant method. The average particle size of the polyolefin particles can be measured using a Zataizer Nano S90 manufactured by Melvern.

[0038] The content of polyolefin (total content of small-diameter and large-diameter polyolefin particles) in the ink is preferably within a range of 1 to 10% by mass. The ink of the present invention preferably contains large-diameter polyolefin particles and small-diameter polyolefin particles, but may also contain other resin particles in addition to these polyolefin particles. Examples of other resin particles include acrylic resin particles, polyester particles, and polyurethane particles, with acrylic resin particles being preferred.

[0039] Commercially available acrylic resins can be used, including NeoCryl A-1127 manufactured by Kusumoto Chemicals Co., Ltd., Mowinyl 6899D, 6969D, 6800, and 6810 manufactured by Japan Coating Resins Co., Ltd., and TOCRYL W-7146, W-7150, and W-7152 manufactured by Toyochem Co., Ltd.

[0040] <Silicone Emulsion> The ink of the present invention contains a silicone emulsion. The silicone emulsion is formed by dispersing a particulate silicone compound in an aqueous dispersion medium. A surfactant (emulsifier) ​​may be contained to form an emulsion of the silicone compound.

[0041] Silicone compounds contained in known mold release agents can be used as the silicone compound. Silicones are polymers collectively known as organopolysiloxanes, which have a main chain (silicone skeleton) in which organic groups such as alkyl groups or phenyl groups are bonded to siloxane bonds. Polydimethylsiloxane (PDMS) is a suitable organopolysiloxane. Preferred examples of the silicone compound include dimethylsilicone, methylphenylsilicone, and methylhydrogensilicone, which are classified as straight silicones; reactive silicones such as amine-modified silicone, epoxy-modified silicone, and carboxy-modified silicone, which are classified as modified silicones; and non-reactive silicones such as polyether-modified silicone and alkyl-modified silicone. It is preferable for the kinematic viscosity of the silicone compound to be within the range of 5,000 to 1,000,000 cS in terms of achieving small particle size and stability of the silicone emulsion.

[0042] The average particle size of the particulate silicone compound in the silicone emulsion is within a range of 70 to 350 nm, and preferably within a range of 100 to 250 nm. The particulate silicone compound is also referred to as silicone compound particles. The average particle size of the silicone compound particles in the silicone emulsion is a value calculated by the cumulant method. The average particle size of the silicone compound particles can be measured using a Zataizer Nano S90 manufactured by Melvern.

[0043] The surfactant (emulsifier) ​​that functions to disperse the silicone compound in an aqueous dispersion medium is selected from nonionic surfactants, anionic surfactants, cationic surfactants, and amphoteric surfactants. Examples of nonionic surfactants include polyoxyalkylene alkyl ethers such as polyoxyethylene alkyl ethers and polyoxyethylene propylene alkyl ethers, and polyoxyethylene fatty acid esters. Preferred examples of nonionic surfactants include polyoxyethylene lauryl ether and polyoxyethylene nonylphenyl ether. Examples of cationic surfactants include quaternary ammonium salts and alkylamine acetates. Examples of anionic surfactants include alkyl sulfates, alkylbenzene sulfonates, alkyl sulfosuccinates, polyoxyethylene alkyl ether sulfates, and polyoxyethylene alkyl phenyl ether sulfates. These surfactants may be used alone or in combination. When using anionic surfactants or amphoteric surfactants, it is preferable to use them in combination with nonionic surfactants or cationic surfactants. Among the above, nonionic surfactants are particularly preferred. A nonionic surfactant may be used in combination with one or more selected from anionic surfactants, cationic surfactants, and amphoteric surfactants.

[0044] The aqueous dispersion medium may be any medium that can disperse the particulate silicone compound and form an emulsion, and examples thereof include ion-exchanged water (purified water).

[0045] Examples of methods for producing silicone emulsions include those described in JP-A-5-32788, JP-A-7-70327, JP-A-63-125530, etc. Commercially available silicone emulsions include KM-9782, KM-9783, and POLON-MF-33 manufactured by Shin-Etsu Chemical Co., Ltd., and DOWSIL manufactured by Dow-Toray Industries, Inc. TM HV 496 Emulsrion, DOWSIL TM SM 7036 EX Emulsion, DOWSIL TM DK Q2-2003 and the like.

[0046] Silicone emulsions having a reactive functional group in part of the polydimethylsiloxane are also preferred. Examples of reactive functional groups include amino groups, epoxy groups, and carboxy groups. In particular, amino group-containing silicone emulsions are known to be able to impart good water repellency to coating films. Examples of methods for producing amino group-containing silicone emulsions include Japanese Patent No. 3532538 and Japanese Patent Laid-Open No. 2003-26922. Commercially available amino group-containing silicone emulsions include KM-9771 and KM-9794 manufactured by Shin-Etsu Chemical Co., Ltd., and DOWSIL® manufactured by Dow-Toray Industries, Inc. TM FZ-4634 EX, DOWSIL TM FZ-4658, DOWSIL TM SM 8709 SR Emulsion and the like.

[0047] Self-crosslinking silicone emulsions that cure to form a film are also preferred as silicone emulsions. Crosslinking silicone emulsions may be either addition-curing silicone emulsions or condensation-curing silicone emulsions. Crosslinking silicone emulsions cure by forming a three-dimensional crosslinked structure upon reaction. Examples of addition-curing silicone emulsions include linear polymers having siloxane bonds, including polydimethylsiloxane with vinyl groups at both ends of the linear chain, and hydrogen silane. A platinum-based curing catalyst may be used to accelerate curing. Examples of methods for producing addition-curing silicone emulsions include JP 2003-192896, JP 2021-121684, and JP 2021-24952. Commercially available addition-curing silicone emulsions include KM-3951, X-52-6068, X-52-151, and X-52-6069 manufactured by Shin-Etsu Chemical Co., Ltd.

[0048] Condensation-curable silicone emulsions include those containing an organopolysiloxane with a condensable reactive group and a hydrolyzable silane compound. A condensation catalyst such as a tin compound may be used to promote the reaction. Methods for producing condensation-curable silicone emulsions include JP 2021-28353, JP 2018-16909, and JP 2007-231030. Commercially available condensation-curable silicone emulsions include KM-2002-T-2, KM-9772, and KM-9749 manufactured by Shin-Etsu Chemical Co., Ltd.

[0049] The content of the silicone compound in the ink of the present invention is preferably in the range of 0.3 to 8 mass%, and more preferably in the range of 0.8 to 4 mass%. In the ink of the present invention, the mass ratio of the polyolefin to the silicone compound (mass of polyolefin:mass of silicone compound) is preferably in the range of 4:1 to 1:1. More preferably, the mass ratio of the polyolefin to the silicone compound (mass of polyolefin:mass of silicone compound) is in the range of 2:1 to 1:1.

[0050] <Pigment> The pigment contained in the ink of the present invention is preferably an anionic dispersed pigment, for example, a self-dispersed pigment having anionic groups on its surface, a pigment dispersed using an anionic polymer dispersant, or a pigment dispersed while its surface is coated with an anionic resin. In particular, it is preferable to use a pigment dispersed using an anionic polymer dispersant, as it has excellent dispersibility and reacts appropriately with the treatment liquid to form pinning.

[0051] As the pigment, any conventionally known pigment can be used without any particular limitation. For example, organic pigments such as insoluble pigments and lake pigments, and inorganic pigments such as titanium oxide can be preferably used.

[0052] In the case of titanium oxide, for which it is generally difficult to ensure ink ejection stability and adhesiveness, the present invention is particularly advantageous in that bleeding is prevented from occurring and adhesiveness can be improved.

[0053] Titanium oxide has three crystalline forms: anatase, rutile, and brookite, but the most commonly used can be broadly classified into anatase and rutile. While not particularly limited, rutile is preferred, as it has a high refractive index and high hiding power. Specific examples include the TR series from Fuji Titanium Industry Co., Ltd., the JR series from Teika Corporation, and Typepaque from Ishihara Sangyo Kaisha, Ltd.

[0054] The insoluble pigment is not particularly limited, but examples thereof include azo, azomethine, methine, diphenylmethane, triphenylmethane, quinacridone, anthraquinone, perylene, indigo, quinophthalone, isoindolinone, isoindoline, azine, oxazine, thiazine, dioxazine, thiazole, phthalocyanine, and diketopyrrolopyrrole.

[0055] Specific examples of organic pigments that can be preferably used include the following pigments: Pigments for magenta or red include, for example, C.I. Pigment Red 2, C.I. Pigment Red 3, C.I. Pigment Red 5, C.I. Pigment Red 6, C.I. Pigment Red 7, C.I. Pigment Red 15, C.I. Pigment Red 16, C.I. Pigment Red 48:1, C.I. Pigment Red 53:1, C.I. Pigment Red 57:1, C.I. Pigment Red 122, C.I. Pigment Red 123, C.I. Pigment Red 139, C.I. Pigment Red 144, C.I. Pigment Red 149, C.I. Pigment Red 166, C.I. Examples of pigments that can be used include C.I. Pigment Red 177, C.I. Pigment Red 178, C.I. Pigment Red 202, C.I. Pigment Red 222, and C.I. Pigment Violet 19.

[0056] Examples of orange or yellow pigments include C.I. Pigment Orange 31, C.I. Pigment Orange 43, C.I. Pigment Yellow 12, C.I. Pigment Yellow 13, C.I. Pigment Yellow 14, C.I. Pigment Yellow 15, C.I. Pigment Yellow 15:3, C.I. Pigment Yellow 17, C.I. Pigment Yellow 74, C.I. Pigment Yellow 93, C.I. Pigment Yellow 128, C.I. Pigment Yellow 94, C.I. Pigment Yellow 138, and C.I. Pigment Yellow 155. In particular, C.I. Pigment Yellow 155 is preferred in terms of the balance between color tone and lightfastness.

[0057] Examples of pigments for green or cyan include C.I. Pigment Blue 15, C.I. Pigment Blue 15:2, C.I. Pigment Blue 15:3, C.I. Pigment Blue 16, C.I. Pigment Blue 60, and C.I. Pigment Green 7.

[0058] Examples of black pigments include carbon black, C.I. Pigment Black 1, C.I. Pigment Black 6, and C.I. Pigment Black 7.

[0059] <Pigment Dispersant> The ink of the present invention preferably contains a pigment dispersant for dispersing the pigment. The pigment dispersant is not particularly limited, but is preferably a polymer dispersant having an anionic group, and one having a molecular weight in the range of 5,000 to 200,000 can be suitably used.

[0060] Examples of polymer dispersants include block copolymers and random copolymers having a structure derived from two or more monomers selected from styrene, styrene derivatives, vinylnaphthalene derivatives, acrylic acid, acrylic acid derivatives, maleic acid, maleic acid derivatives, itaconic acid, itaconic acid derivatives, fumaric acid, and fumaric acid derivatives, as well as salts thereof, polyoxyalkylenes, and polyoxyalkylene alkyl ethers.

[0061] The polymer dispersant preferably has an acryloyl group and is preferably neutralized with a neutralizing base before addition. The neutralizing base is not particularly limited, but is preferably an organic base such as ammonia, monoethanolamine, diethanolamine, triethanolamine, or morpholine. In particular, when the pigment is titanium oxide, the titanium oxide is preferably dispersed with a polymer dispersant having an acryloyl group.

[0062] The amount of polymer dispersant added is preferably within a range of 10 to 100% by mass, more preferably within a range of 10 to 40% by mass, based on the pigment.

[0063] It is particularly preferred that the pigment be in the form of a so-called capsule pigment, in which the pigment is coated with the polymer dispersant. Various known methods can be used to coat the pigment with the polymer dispersant. Preferred examples of such methods include a phase inversion emulsification method, an acid precipitation method, or a method in which the pigment is dispersed in a polymerizable surfactant, a monomer is supplied thereto, and the monomer is coated while polymerizing.

[0064] A particularly preferred method is as follows: A water-insoluble resin is dissolved in an organic solvent such as methyl ethyl ketone, and the acidic groups in the resin are partially or completely neutralized with a base. Thereafter, a pigment and ion-exchanged water are added and dispersed, and the organic solvent is removed, and water is added as necessary to prepare the dispersion.

[0065] The average particle size of the dispersed pigment particles contained in the ink is preferably within a range of 40 to 200 nm. The average particle size is particularly preferably within a range of 50 to 100 nm. This can improve the dispersion stability of the pigment and the storage stability of the ink. The particle size of the pigment can be measured using a commercially available particle size measuring device that uses dynamic light scattering, electrophoresis, or the like. Measurement by dynamic light scattering is particularly simple and can accurately measure the particle size range.

[0066] The pigment can be dispersed in a dispersing machine together with a dispersant and other additives required for various desired purposes.

[0067] As the dispersing machine, a conventionally known ball mill, sand mill, line mill, high-pressure homogenizer, etc. can be used. Among them, dispersing the pigment using a sand mill is preferable because it results in a sharp particle size distribution. Furthermore, the material of the beads used for sand mill dispersion is not particularly limited, but from the viewpoint of preventing the generation of bead fragments and contamination of ionic components, zirconia or zircon is preferred. Furthermore, the diameter of the beads is preferably within the range of 0.3 to 3 mm.

[0068] The content of the pigment in the ink is not particularly limited, but for titanium oxide, the content is preferably in the range of 7 to 18% by mass, and for organic pigments, the content of the pigment in the ink is preferably in the range of 0.5 to 7% by mass.

[0069] <Water-soluble solvent> The water-soluble solvent contained in the ink of the present invention is preferably a water-soluble solvent having a boiling point in the range of 150 to 250° C. Examples of such water-soluble solvents include alcohols, polyhydric alcohols, amines, amides, glycol ethers, and 1,2-alkanediols having 4 or more carbon atoms. Further, examples of the water-soluble solvent include those exemplified for the treatment liquid described below.

[0070] The ink may contain one or a combination of two or more selected from the water-soluble solvents described above.

[0071] The content of the water-soluble solvent in the ink is not particularly limited, but is preferably in the range of 10 to 60% by mass.

[0072] <Water> The water contained in the ink of the present invention is not particularly limited, and may be ion-exchanged water, distilled water, or pure water.

[0073] <Surfactant for controlling surface tension> The ink of the present invention preferably contains a surfactant in addition to the surfactant that functions as an emulsifier in the silicone emulsion. By including the surfactant in the ink, the surface tension of the ink can be controlled. This improves the ejection stability of the ink and controls the spread (dot diameter) of droplets that land on a recording medium. Hereinafter, a surfactant that is included in addition to the surfactant in the silicone emulsion is also referred to as a "surfactant for controlling surface tension."

[0074] The surfactant for controlling the surface tension is not particularly limited as long as it does not adversely affect the storage stability of the ink. However, as will be described later, it is preferable that the treatment liquid does not contain the same surfactant as that contained in the ink.

[0075] When the ink contains an anionic compound as another component, the surfactant for controlling surface tension is preferably anionic, nonionic, or betaine. In the present invention, preferred surfactants include fluorine-based or silicone-based surfactants with high static surface tension reduction capabilities, anionic surfactants such as dioctyl sulfosuccinate with high dynamic surface tension reduction capabilities, and nonionic surfactants such as relatively low-molecular-weight polyoxyethylene alkyl ethers, polyoxyethylene alkylphenyl ethers, acetylene glycols, Pluronic surfactants (Pluronic is a registered trademark), and sorbitan derivatives. It is also preferred to use a fluorine-based or silicone-based surfactant in combination with a surfactant with high dynamic surface tension reduction capabilities. Examples of polyoxyethylene alkyl ethers include TRITON HW-1000 (TRITON is a registered trademark) manufactured by The Dow Chemical Company. Examples of acetylene glycols include Olfine E1010 manufactured by Nissin Chemical Industry Co., Ltd.

[0076] It is preferable to add a silicone-based or fluorine-based surfactant as the surfactant for controlling surface tension. This can further suppress ink mixing on recording media made of various hydrophobic resins, such as vinyl chloride sheets, and recording media with low ink absorption capacity, such as printing paper. As a result, high-quality printed images can be obtained. This ink mixing is also known as beading.

[0077] The silicone surfactant is preferably a polyether-modified silicone. Examples of polyether-modified silicones include siloxanes having alkylene oxide groups on the side chains and / or both ends of a polydimethylsiloxane chain. Specific examples of silicone surfactants include BYK-331, BYK-333, BYK-345, BYK-3450, BYK-3451, BYK-3455, BYK-346, BYK-347, BYK-348, and BYK-349 manufactured by BYK-Chemie, and TEGOWet KL245, TEGOWet 250, TEGOWet 260, and TEGOWet 270 manufactured by Evonik. , TEGOWet 280, and Shin-Etsu Chemical Co., Ltd.'s KF-351A, KF-352A, KF-353, KF-354L, KF-355A, KF-615A, KF-640, KF-642, KF-643, KF-644, KF-945, KF-6011, KF-6012, KF-6015, KF-6017, KF-6020, KF-6204, and X-22-4515.

[0078] As the polyether-modified silicone, trisiloxane having alkylene oxide groups at the side chain and / or both ends of the polydimethylsiloxane chain is particularly preferred. By using trisiloxane, the dynamic surface tension of the treatment liquid can be effectively reduced, and an image with good adhesion to the substrate can be obtained. The trisiloxane preferably has a structure represented by the following general formula (1):

[0079]

[0080] In the general formula (1), "EO" represents a repeating unit structure of polyethylene oxide. That is, it represents a structure in which ethylene oxide, a three-membered cyclic ether, is ring-opened. Furthermore, "PO" represents a repeating unit structure of polypropylene oxide. That is, it represents a structure in which propylene oxide, a three-membered cyclic ether, is ring-opened. Here, the phrase "the order of [EO]m and [PO]n may be either" means that in the compound molecule represented by the general formula (1), the order of the bonding positions to the parent siloxane skeleton may be changed as appropriate.

[0081] In the general formula (1), X is preferably an alkylene group having 3 carbon atoms. The alkylene group having 3 carbon atoms is a propylene group. In addition, in the general formula (1), m is preferably an integer of 5 to 20, and n is preferably an integer of 0 to 6.

[0082] Specific examples of silicone surfactants having the structure represented by the general formula (1) are shown below as S-1 to S-8, but are not limited to these. (S-1): In the general formula (1), R = methyl group, X = alkylene group having 3 carbon atoms, m = 9, n = 0. (S-2): In the general formula (1), R = butyl group, X = alkylene group having 3 carbon atoms, m = 25, n = 6. (S-3): In the general formula (1), R = hydrogen atom, X = alkylene group having 3 carbon atoms, m = 3, n = 0. (S-4): In the general formula (1), R = hydrogen atom, X = alkylene group having 3 carbon atoms, m = 33, n = 0. (S-5): In the general formula (1), R = hydrogen atom, X = alkylene group having 3 carbon atoms, m = 22, n = 16. (S-6): In the general formula (1), R = hydrogen atom, X = alkylene group having 3 carbon atoms, m = 9, n = 0. (S-7): In the general formula (1), R = hydrogen atom, X = alkylene group having 3 carbon atoms, m = 12, n = 3. (S-8): In the general formula (1), R = hydrogen atom, X = alkylene group having 3 carbon atoms, m = 1, n = 0.

[0083] Examples of the trisiloxane include BYK-3450 and BYK-3451 manufactured by BYK Japan, and TEGOWET-KL245, TEGOWET-250, and TEGOWET-260 manufactured by Evonik. The content of the polyether-modified silicone in the ink is preferably in the range of 0.5 to 2% by mass, and more preferably in the range of 0.5 to 1.5% by mass.

[0084] The fluorine-based surfactants mentioned above refer to surfactants in which the hydrogen atoms bonded to the carbon atoms of the hydrophobic groups of ordinary surfactants have been partially or entirely substituted with fluorine atoms. Among these, surfactants having a perfluoroalkyl group in the molecule are preferred.

[0085] Some of the above fluorine-based surfactants are commercially available under the following trade names: Trade name: Megafac F (Dainippon Ink and Chemicals, Inc.) Trade name: Surflon (Asahi Glass Co., Ltd.) Trade name: Fluorad FC (Minnesota Mining and Manufacturing Company) Trade name: Monflor (Imperial Chemical Industries, Inc.) Trade name: Zonyls (E.I. duPont Nemelas and Company) Trade name: Licowet VPF (Falbewerke-Hoechst)

[0086] The content of the surface tension controlling surfactant in the ink is not particularly limited, but may be any amount that does not impair the storage stability of the ink, and is preferably in the range of 0.1 to 5.0% by mass, and more preferably in the range of 0.1 to 2.0% by mass.

[0087] <Wax> The wax contained in the ink of the present invention is preferably a polyolefin wax. When the ink contains a polyolefin wax, the water resistance and abrasion resistance of the resulting recorded matter are improved.

[0088] The polyolefin wax is not particularly limited, and examples thereof include waxes produced from olefins such as ethylene, propylene, and butylene, or derivatives thereof, and copolymers thereof, specifically polyethylene-based waxes, polypropylene-based waxes, and polybutylene-based waxes. Among these, polyethylene-based waxes are preferred from the viewpoint of more effectively reducing the occurrence of cracks in images. The polyolefin waxes can be used alone or in combination of two or more.

[0089] The polyolefin wax is preferably used in the form of a polyolefin wax emulsion in which solid wax particles are dispersed in water using the above-mentioned surfactant.

[0090] An example of a polyolefin wax emulsion is a method for producing a polyethylene wax emulsion. Polyethylene wax is produced by polymerizing ethylene, synthesizing it from hydrocarbon compounds, or thermally decomposing polyethylene for general molding to reduce its molecular weight. This polyethylene wax is then oxidized to add carboxyl groups or hydroxyl groups. A surfactant is then used to emulsify the wax, resulting in a highly stable aqueous wax emulsion.

[0091] Commercially available polyolefin waxes include the Chemipearl series, such as "Chemipearl W4005" (manufactured by Mitsui Chemicals, Inc., polyethylene wax, particle size 200 to 800 nm, ring and ball softening point 110°C, needle penetration hardness 3, solids content 40%). Other examples include the AQUACER series, such as AQUACER 513 (polyethylene wax, particle size 100 to 200 nm, melting point 130°C, solids content 30%), AQUACER 497, AQUACER 513, and AQUACER 517 (all manufactured by BYK Additives & Instruments); the Hitec series, such as Hitec E-7025P, Hitec E-2213, Hitec E-9460, Hitec E-9015, Hitec E-4A, Hitec E-5403P, and Hitec E-8237 (all manufactured by Toho Chemical Industry Co., Ltd.); and Nopcoat PEM-17 (manufactured by San Nopco Ltd., polyethylene emulsion, particle size 40 nm). These are commercially available in the form of aqueous emulsions in which polyolefin wax is dispersed in water by conventional methods. Therefore, it can be added directly to the ink in the form of an aqueous emulsion.

[0092] In addition to the above, the ink used in the present invention may contain various known additives, such as polysaccharides, viscosity modifiers, resistivity modifiers, film-forming agents, ultraviolet absorbers, antioxidants, anti-fading agents, anti-mold agents, and anti-rust agents, which may be appropriately selected and used as needed to improve ejection stability, compatibility with print heads and ink cartridges, storage stability, image storage stability, and other performances. Examples of such additives include oil droplet fine particles such as liquid paraffin, dioctyl phthalate, tricresyl phosphate, and silicone oil; 193, the same No. 57-87988, the same No. 62-261476, etc. ultraviolet absorbers, JP-A-57-74192, the same No. 57-87989, the same No. 60-72785, the same No. 61-146591, JP-A-1-95091, the same No. 3-13376, etc., anti-fading agents, JP-A-59-42993, the same No. 59-52689, the same No. 62-280069, the same No. 61-242871, JP-A-4-219266, etc., fluorescent brightening agents and the like can be mentioned.

[0093] The ink of the present invention having the above-mentioned composition preferably has a viscosity of 1 to 40 mPa·s at 25° C., more preferably 2 to 10 mPa·s.

[0094] [Ink Set] The ink set of the present invention comprises the aqueous inkjet ink composition described above and a treatment liquid containing an aggregating agent. In the ink set, it is preferable that the static surface tension of the treatment liquid is in the range of 18 to 25 mN / m at 25°C, and the dynamic surface tension of the treatment liquid at a surface life of 50 msec is in the range of 25 to 35 mN / min at 25°C.

[0095] The ink set forms an image by applying the ink and the treatment liquid to a recording medium and allowing them to coalesce. In the present invention, the terms "treatment liquid" and "ink" refer to a "treatment liquid (also referred to as a "pretreatment liquid" or "primer")" and "ink (also referred to as a "water-based ink" or "aqueous ink")" that use at least water or a water-soluble solvent as a solvent. In both cases, it is preferable that 60% by mass or more of the solvent used is water. In the present invention, "coalescence" refers to the process of causing droplets of the treatment liquid and the ink to overlap or come into contact with each other on the recording medium, mixing their respective components into a single liquid, and ultimately forming a single pixel that constitutes an image. For example, as shown in FIG. 1A , before the ink lands on the recording medium, droplets 12 of the treatment liquid are deposited on the recording medium F via an inkjet head. After the treatment liquid lands, droplets 22 of the ink are deposited on the recording medium F on which the treatment liquid has landed, as shown in FIG. 1B . 1C, the treatment liquid droplets 12 and the ink droplets 22 mix, and the pigment P in the ink aggregates and precipitates due to the aggregating agent in the treatment liquid. An image layer G is then formed on the recording medium F. Note that the ink may be first landed on the recording medium, and then the treatment liquid may be landed.

[0096] <Static Surface Tension> In the present invention, the term "static surface tension" refers to the surface tension at the time when the liquid surface approaches equilibrium as the components of the ink or treatment liquid diffuse over the course of its surface life. The static surface tension of the ink or treatment liquid can be measured using an automatic surface tensiometer with a platinum plate. An example of an automatic surface tensiometer is the "CBVP-Z" model manufactured by Kyowa Interface Science Co., Ltd. Unless otherwise specified, the static surface tension in this specification is measured at 25°C.

[0097] In the ink set of the present invention, the static surface tension of the treatment liquid is preferably within the range of 18 to 25 mN / m at 25°C. The reason why the static surface tension of the treatment liquid is set within this range is that if it is lower than 18 mN / m, the treatment liquid will expand and wet and spread too much, resulting in poor character reproducibility. On the other hand, if the static surface tension of the treatment liquid is higher than 25 mN / m, the treatment liquid will be repelled by the substrate, resulting in poor character reproducibility. Furthermore, in the ink set of the present invention, the static surface tension of the ink is preferably within the range of 25 to 35 mN / m at 25°C. By setting the static surface tension of the ink within this range, the storage stability of the ink is improved, allowing it to be ejected stably onto a recording medium.

[0098] <Dynamic Surface Tension> In the present invention, "dynamic surface tension" refers to the surface tension immediately after the formation of a liquid surface (gas-liquid interface) when the liquid surface is in a non-equilibrium state. It is a value measured at 25°C using the maximum bubble pressure method. Furthermore, "surface lifetime" refers to the time elapsed since the liquid surface was formed, i.e., the lifetime of the bubbles generated using the maximum bubble pressure method, and is also called bubble lifetime. Specifically, it refers to the time from the time a new interface is generated within the tip of the probe of the dynamic surface tensiometer until the maximum bubble pressure is reached. The dynamic surface tension of a treatment liquid or ink can be measured using a dynamic surface tensiometer. Examples of dynamic surface tensiometers include a bubble pressure dynamic surface tensiometer (manufactured by KRUSS, model "BP100"). Unless otherwise specified, the dynamic surface tension in this specification refers to the dynamic surface tension measured at 25°C for 15 ms using the maximum bubble pressure method.

[0099] In the ink set of the present invention, the dynamic surface tension of the treatment liquid at a surface life of 50 msec is preferably in the range of 25 to 35 mN / m at 25°C. The dynamic surface tension of the treatment liquid is set within this range because, if it is lower than 25 mN / m, the treatment liquid will expand and spread too much, resulting in poor character reproducibility. On the other hand, if the dynamic surface tension of the treatment liquid is higher than 35 mN / m, the treatment liquid will be repelled by the substrate, resulting in poor character reproducibility. In the ink set of the present invention, the dynamic surface tension of the ink at a surface life of 50 msec is preferably in the range of 35 to 45 mN / min at 25°C. By setting the static surface tension of the ink within this range, the storage stability of the ink is improved, allowing it to be ejected stably onto a recording medium.

[0100] In order to set the static surface tension and dynamic surface tension of the treatment liquid within the above ranges, the type and content of the surfactant, the type and content of the water-soluble solvent, and the type and content of the flocculant can be controlled. Specifically, it is preferable to use various polyether-modified silicone and / or acetylene glycol surfactants as the surfactant contained in the treatment liquid. In particular, it is preferable to use a trisiloxane surfactant. It is also preferable to set the content of the surfactant within the range of 0.1 to 2.0 mass % relative to the treatment liquid. Furthermore, it is preferable to use a water-soluble solvent having an SP value of 24 (J / cm 3 ) 1 / 2 It is preferable to use a water-soluble solvent having a boiling point in the range of 150°C to 250°C, with its content in the range of 5 to 40% by mass. Furthermore, as the flocculant, for example, an organic acid, a polyvalent metal salt, or a dissolved cationic polymer, as described below, is used, with the content of the flocculant in the treatment liquid being in the range of 1 to 8% by mass. Furthermore, it is preferable to set the content in the range of 1 to 4% by mass. By setting the content in this range, anionic components in the ink can be effectively flocculated. As a result, a good balance between image quality and hot water resistance is achieved.

[0101] In order to set the static surface tension and dynamic surface tension of the ink within the above ranges, the type and content of the surfactant for controlling surface tension, the type and content of the water-soluble solvent, the type and content of the pigment dispersant, the type and content of the polyolefin particles, and the type and content of the additives can be controlled. The surfactant for controlling surface tension is one that does not impair the storage stability of the ink, or is used in an amount that does not impair the storage stability. Specifically, it is preferable to use various polyether-modified silicones and / or acetylene glycol-based surfactants as the surfactant for controlling surface tension contained in the ink. It is preferable to set the content of the surfactant for controlling surface tension within the range of 0.1 to 2.0% by mass relative to the ink. The water-soluble solvent should have an SP value of 24 (J / cm 3 ) 1 / 2 It is preferable to use a water-soluble solvent having a boiling point in the range of 150°C to 250°C, with its content in the range of 5 to 40% by mass. Furthermore, it is preferable to use various low-molecular-weight dispersants, nonionic polymer dispersants, anionic polymer dispersants, or resin-coated pigment dispersions as appropriate as the pigment dispersant. Furthermore, it is preferable to use acid-modified polyolefins or chlorinated polyolefins as the type of polyolefin. The content of the polyolefin is preferably in the range of 1 to 10% by mass relative to the ink. The polyolefin preferably contains polyolefin particles having an average particle size in the range of 10 to 80 nm and polyolefin particles having an average particle size in the range of 100 to 300 nm. It is also preferable to use a wax as an additive, with its content preferably in the range of 0.1 to 5% by mass relative to the ink.

[0102] The treatment liquid contained in the ink set will be described below. [Treatment Liquid] The treatment liquid according to the present invention can accelerate ink image formation by aggregating or thickening the ink when recording an image on a substrate by inkjet printing. The treatment liquid according to the present invention contains at least an aggregating agent. Furthermore, the treatment liquid preferably contains a water-soluble solvent, a surfactant, and water.

[0103] <Aggregating Agent> The treatment liquid according to the present invention contains a material that generates aggregates when it comes into contact with ink, i.e., an aggregating agent which is a polyvalent metal salt. The aggregating agent enhances the interaction with the ink, thereby enabling the ink dots to be more firmly fixed.

[0104] (Polyvalent Metal Salt) The polyvalent metal salt can aggregate anionic components (usually coloring materials, pigments, etc.) in the ink, which will be described later, by salting out. As the polyvalent metal salt, a salt of a metal having a valence of 2 or more can be used. The type of metal (cation) constituting the polyvalent metal salt is not particularly limited. The type of the cation can be, for example, Ca ２＋ , Cu ２＋ , Ni ２＋ , Mg ２＋ , Zn ２＋ , Ba ２＋ + and other divalent metal ions, Al ３＋ , Fe ３＋ , Cr ３＋ , Y ３＋ trivalent metal ions such as Zr ４＋ Examples of the polyvalent metal salt include tetravalent metal ions such as tetravalent metal ions, ...

[0105] (Organic Acid) In addition to the polyvalent metal salt, the treatment liquid according to the present invention may further contain an organic acid as an aggregating agent. The organic acid contained in the treatment liquid as an aggregating agent is capable of aggregating the coloring material contained in the ink, and preferably has a first dissociation constant of 3.5 or less. In particular, it is preferable that the first dissociation constant is within the range of 1.5 to 3.5. When the first dissociation constant is within this range, liquid segregation in low-concentration regions is further prevented, and ink mixing (beading) in high-concentration regions is improved.

[0106] Furthermore, the use of an organic acid makes it easier to maintain the storage stability of the treatment liquid, and makes it less likely that blocking will occur after the treatment liquid has been applied and dried. From the above perspectives, preferred organic acids to be contained in the flocculant include formic acid, acetic acid, propionic acid, isobutyric acid, oxalic acid, fumaric acid, malic acid, citric acid, malonic acid, succinic acid, maleic acid, benzoic acid, 2-pyrrolidone-5-carboxylic acid, lactic acid, acrylic acid and derivatives thereof, methacrylic acid and derivatives thereof, acrylamide and derivatives thereof, and other compounds having a carboxy group, sulfonic acid derivatives, and phosphoric acid and derivatives thereof.

[0107] It is preferable to use an organic acid that is not completely neutralized with a base. Neutralized with a base means that the acidic group of the acid is ionic bonded to another positively charged element or compound (e.g., an inorganic compound such as a metal). In addition, not completely neutralized means that among the acidic groups possessed by the organic acid, there are acidic groups that do not form the above-mentioned ionic bond. Furthermore, the use of an organic acid makes it easier to maintain the storage stability of the treatment liquid, and blocking is less likely to occur after the treatment liquid is applied and dried. From the above viewpoint, preferred organic acids include formic acid, acetic acid, propionic acid, benzoic acid, etc.

[0108] (Inorganic Acid) In addition to the polyvalent metal salt, the treatment liquid according to the present invention may further contain an inorganic acid as a flocculating agent. The inorganic acid can flocculate the anionic components in the ink by changing the pH.

[0109] The inorganic acid is capable of aggregating pigments that may be contained in the ink, which will be described later. Examples of the inorganic acid include hydrochloric acid, nitric acid, sulfuric acid, and sulfamic acid.

[0110] Alternatively, a dissolving cationic polymer may be used as the flocculant. Examples of dissolving cationic polymers contained in the treatment liquid include polyallylamine, polyvinylamine, polyethyleneimine, and polydiallyldimethylammonium chloride. Examples of commercially available dissolving cationic polymers include KHE100L and FPA100L manufactured by Senka Corporation, and PAS-92A, PAS-M-1A, and PAS-21CL manufactured by Nittobo Medical Co., Ltd.

[0111] The content of the polyvalent metal salt is preferably in the range of 0.5 to 20% by mass, more preferably 1 to 10% by mass, relative to the total mass of the treatment liquid (100% by mass). This allows the anionic components in the ink to effectively aggregate, which is preferable from the viewpoint of balancing image quality and hot water resistance. Furthermore, when an organic acid is contained, the content of the organic acid is preferably in the range of 0.1 to 10% by mass, more preferably 1 to 3% by mass, relative to the total mass of the treatment liquid (100% by mass). Furthermore, when an inorganic acid is contained, the content of the inorganic acid is preferably in the range of 0.1 to 10% by mass, more preferably 1 to 3% by mass, relative to the total mass of the treatment liquid (100% by mass).

[0112] The content of the polyvalent metal salt or organic acid in the aqueous solution can be measured by a known method. For example, the content of the polyvalent metal salt can be measured by ICP emission spectrometry, and the content of the organic acid can be measured by high performance liquid chromatography (HPLC).

[0113] When an organic acid is used, the amount of the organic acid applied is preferably an amount that adjusts the pH of the treatment liquid to be equal to or less than the neutralization equivalent of the anionic component contained in the ink. Furthermore, when the anionic component is a compound having a carboxy group, the first dissociation constant of the organic acid is preferably 3.5 or less, from the viewpoint of making the image less susceptible to bleeding.

[0114] <Water-soluble solvent> The water-soluble solvent contained in the treatment liquid according to the present invention is preferably a water-soluble solvent having a boiling point in the range of 150 to 250°C. Examples of such water-soluble solvents include alcohols, polyhydric alcohols, amines, amides, glycol ethers, and 1,2-alkanediols having 4 or more carbon atoms. In addition, the water-soluble solvent should have an SP value of 24 (J / cm 3 ) 1 / 2 It is preferable to use a water-soluble solvent having an SP value of 24 (J / cm 3 ) 1 / 2 The use of such a water-soluble solvent lowers the cloud point of the treatment liquid, which allows the treatment liquid to be heated to a temperature equal to or higher than its cloud point during the ink drying process, thereby producing an image with particularly good adhesion to non-absorbent substrates.

[0115] In the present invention, the SP value is referred to as the solubility parameter. The SP value in the present invention is a value calculated by the Fedors method. It is determined from the molar heat of vaporization of the water-soluble solvent and the molar volume of the water-soluble solvent at 25°C. Although the unit of the SP value is generally cal, when converting to the SI unit system, (cal / cm 3 ) 1 / 2 = 2.046 x 10 3 (J / m 3 ) 1 / 2 In the following description, the unit of the SP value may be omitted, but the SP value is expressed as (J / cm 3 ) 1 / 2 It is a value expressed in units of .

[0116] The SP value is 24 (J / cm 3 ) 1 / 2 Examples of the water-soluble solvent having the above properties and a boiling point of 150° C. to 250° C. include polyhydric alcohols having 2 to 8 carbon atoms and polyalkylene glycols.

[0117] Examples of polyhydric alcohols having 2 to 8 carbon atoms include 1,2-ethanediol (SP value: 30.3, boiling point: 197°C), 1,2-propanediol (SP value: 28.0, boiling point: 188°C), 1,3-propanediol (SP value: 32.9, boiling point: 213°C), 1,2-butanediol (SP value: 26.1, boiling point: 192°C), 1,3-butanediol (SP value: 30.3, boiling point: 207°C), 1,4-butanediol (SP value: 30.7, boiling point: 230°C), and 2,3-butanediol (SP value: 2 9.9, boiling point: 177°C), 2-methyl-1,3-propanediol (SP value: 30.3, boiling point: 214°C), 1,2-pentanediol (SP value: 25.0, boiling point: 210°C), 1,5-pentanediol (SP value: 29.0, boiling point: 242°C), 1,2-hexanediol (SP value: 24.1, boiling point: 223°C), 1,6-hexanediol (SP value: 27.7, boiling point: 249°C), 2-methylpentane-2,4-diol (SP value: 26.8, boiling point: 197°C), and the like.

[0118] Examples of polyalkylene glycols include diethylene glycol (SP value: 30.6, boiling point: 244°C) and dipropylene glycol (SP value: 27.2, boiling point: 230°C).

[0119] The treatment liquid may contain one or a combination of two or more selected from these water-soluble solvents.

[0120] The ink may contain at least one water-soluble solvent having a boiling point of 150 to 250° C. The water-soluble solvent may also include alcohols other than those mentioned above, polyhydric alcohols, amines, amides, glycol ethers, and 1,2-alkanediols having 4 or more carbon atoms.

[0121] Examples of solvents other than water-soluble solvents having a boiling point of 150°C to 250°C include glycerin (SP value: 33.5, boiling point: 290°C), trimethylolpropane (SP value: 32.5, boiling point: 295°C), triethylene glycol (SP value: 27.8, boiling point: 287°C), and tetraethylene glycol (SP value: 26.1, boiling point: 275°C).

[0122] The total content of the water-soluble solvent is preferably in the range of 5 to 40% by mass, and more preferably in the range of 10 to 40% by mass, relative to 100% by mass of the total mass of the treatment liquid.

[0123] <Surfactant> The surfactant contained in the treatment liquid according to the present invention can improve the ejection stability of the treatment liquid from the nozzle and can control the spreading of droplets that have landed on a recording medium. The spreading of droplets is also referred to as an increase in dot diameter.

[0124] The surfactant is not particularly limited, and the surfactants exemplified for the ink can be used. However, the treatment liquid according to the present invention preferably contains a surfactant not contained in the ink, and the following two patterns can be mentioned. When the surfactant contained in the ink is defined as surfactant S1, (i) the surfactant contained in the treatment liquid is preferably surfactant S2, which is different from surfactant S1 contained in the ink. (ii) The surfactant contained in the treatment liquid preferably contains surfactant S2 in addition to surfactant S1. Specifically, preferred surfactant combinations include polyether-modified silicone and trisiloxane-based surfactants as surfactants contained in the treatment liquid. Furthermore, acetylene glycol-based surfactants and polyether-modified silicone are preferred as surfactants contained in the ink. Adding a surfactant not contained in the ink to the treatment liquid as described above can further enhance cohesion. A surfactant not contained in the ink is a surfactant that destabilizes the dispersion stability of the ink.

[0125] The content of the surfactant in the treatment liquid is not particularly limited, but is preferably in the range of 0.1 to 5.0 mass % of the total mass of the treatment liquid, and more preferably in the range of 0.1 to 2.0 mass %.

[0126] <Water> The treatment liquid according to the present invention may contain water, and there are no particular limitations on the type of water that can be used. Examples of the water that can be used include ion-exchanged water, distilled water, and pure water.

[0127] The treatment liquid may contain other components such as a crosslinking agent, an antifungal agent, a bactericide, etc., as appropriate, within the range that does not impair the effects of the present invention.

[0128] Further, the processing solution may contain, for example, ultraviolet absorbers described in JP-A Nos. 57-74193, 57-87988 and 62-261476, anti-fading agents described in JP-A Nos. 57-74192, 57-87989, 60-72785, 61-146591, 1-95091 and 3-13376, etc., aniline, It is also possible to contain various known additives such as various ionic, cationic or nonionic surfactants, fluorescent brightening agents described in JP-A Nos. 59-42993, 59-52689, 62-280069, 61-242871 and 4-219266, antifoaming agents, lubricants such as diethylene glycol, preservatives, thickeners, antistatic agents and the like.

[0129] It is preferable to prepare a treatment liquid layer by directly applying the treatment liquid according to the present invention as a coating liquid onto a substrate and drying the applied coating liquid. The additives preferably used in the treatment liquid are preferably thoroughly dissolved before use as a coating liquid.

[0130] The treatment liquid is applied by an inkjet method.

[0131] [Inkjet Recording Method] In the inkjet recording method, an image is formed by applying an ink set containing the treatment liquid and ink to the surface of a recording medium by a droplet ejection means and allowing them to coalesce. As such, the inkjet recording method is a so-called two-liquid recording method. According to this recording method, for example, a single inkjet printer can be used to continuously and efficiently apply the treatment liquid to the surface of a substrate (recording medium) and print with the ink. Furthermore, the treatment liquid and ink can be coalesced on the substrate, reducing variations in dot diameter between substrates. As a result, characters, designs, and the like can be printed with excellent image quality.

[0132] Specifically, the recording method first applies the treatment liquid to a substrate, and then applies the ink while the treatment liquid is wet to the area to which the treatment liquid has been applied, without going through a heat drying process. That is, the inkjet recording method comprises a treatment liquid application process and an ink application process. The treatment liquid application process is a process of applying the treatment liquid to the recording area of ​​the substrate. The ink application process is a process of applying the ink while the treatment liquid is wet to the area to which the treatment liquid has been applied in the treatment liquid application process, by inkjet recording.

[0133] In addition to the above steps, the inkjet recording method preferably includes an ink heating and drying step in which the treatment liquid and ink applied to the substrate after the ink application step are heated and dried to form an image (image layer).

[0134] In the ink application step, it is preferable to apply ink to the area to which the treatment liquid has been applied when the drying rate of the treatment liquid is 30% or less. It is also preferable to carry out the ink application step within 10 seconds after the treatment liquid application step. It is particularly preferable to carry out the ink application step within 0.1 to 5 seconds after the treatment liquid application step when the drying rate of the treatment liquid is in the range of 1 to 10%.

[0135] <Substrate> The substrate (recording medium) applicable to the inkjet recording method is a non-absorbent substrate made of a non-absorbent material. The non-absorbent substrate may or may not be surface-treated by corona discharge treatment or the like. In particular, in the present invention, it is preferable to use an untreated non-absorbent substrate that has not been surface-treated by corona discharge treatment or the like, in order to effectively exhibit the effects of the present invention.

[0136] In the present invention, a "non-absorbent substrate" is a substrate having a water absorption rate of 10 mL / m2 or less within 30 msec from the start of contact in the Bristow method. ２ The non-absorbent substrate refers to a recording substrate (medium) that is: Details of the test method are described, for example, in Standard No. 51 "Paper and Paperboard - Liquid Absorbency Test Method - Bristow Method" of "JAPAN TAPPI Paper and Pulp Test Method 2000 Edition." Known plastic films can be used as the non-absorbent substrate.

[0137] Specific examples of known plastic films include polyester films such as polyethylene terephthalate, polyethylene films, polypropylene films, polyamide films such as nylon, polystyrene films, polyvinyl chloride films, polycarbonate films, polyacrylonitrile films, and biodegradable films such as polylactic acid films. Furthermore, films coated with polyvinylidene chloride on one or both sides are preferred to impart gas barrier properties, moisture resistance, and aroma retention. Other preferred plastic films include films vapor-deposited with metal oxides. Non-absorbent films can be either unstretched or stretched. The thickness of the substrate, in the case of plastic films, is preferably within the range of 10 to 120 μm, more preferably 12 to 60 μm.

[0138] Furthermore, metal substrates such as tinplate for three-piece cans and tin-free steel plates (TFS plates, thickness 0.1 to 0.6 μm) are also preferably used as non-absorbent substrates. For example, packaging materials for canned foods, which have a coating layer of a thermosetting resin, can be suitably used as non-absorbent substrates. For example, the following materials are commonly used as packaging materials for canned foods to block air, moisture, and light and seal the food inside: Epoxy-phenolic paints or polyester-based laminating agents are used on the food side, and polyester-based or acrylic-based thermosetting paints are used on the outside.

[0139] Each step of the inkjet recording method will be described below. <Treatment liquid application step> In the treatment liquid application step, the treatment liquid described above is applied onto a recording medium, which is a non-absorbent substrate. The method for applying the treatment liquid onto the recording medium is an inkjet method. In the treatment liquid application step, the amount of treatment liquid applied (also referred to as the "application amount") per unit area on which an image is formed is 5.0 g / m 2 It is particularly preferable that the density is 0.3 to 5.0 g / m or less. 2 This allows high character reproducibility to be achieved in a two-liquid ink jet recording method.

[0140] <Ink Application Step> The ink application step is a step in which the ink of the ink set described above is applied by an inkjet method simultaneously with or immediately after the application of the treatment liquid onto a recording medium, which is a non-absorbent substrate. In particular, it is preferable to apply the ink to the area to which the treatment liquid has been applied after the treatment liquid application step, when the drying rate of the treatment liquid is 30% or less. It is also preferable to apply the ink to the area to which the treatment liquid has been applied within 10 seconds after the treatment liquid has been applied to the substrate. The drying rate of the treatment liquid is defined by the following formula: (Drying rate of treatment liquid) = 1 - ((Mass (g) of treatment liquid after drying)) / (Mass (g) of treatment liquid before drying) By applying the ink when the drying rate of the treatment liquid is 30% or less, the ink and the treatment liquid coalesce and mix. Furthermore, by applying the ink within 10 seconds after the application of the treatment liquid to the substrate, it is possible to suppress penetration of the treatment liquid into the absorbent substrate and repellency of the treatment liquid on the non-absorbent substrate, thereby achieving higher image quality.

[0141] In order to keep the drying rate of the treatment liquid at 30% or less, as described above, the time between the application of the treatment liquid and the application of the ink can be adjusted, or the temperature of the recording medium can be appropriately adjusted.

[0142] Furthermore, in the ink application step, it is preferable to adjust the amount of ink droplets so that the amount of ink applied (also referred to as the "application amount") per unit area is within a range of 2 to 25 times the amount of treatment liquid applied, in order to achieve higher image quality, and a more preferable range for the application amount is 2.5 to 8 times.

[0143] The inkjet method is not particularly limited, and a printer equipped with an inkjet head loaded with ink can be used. Specifically, ink is ejected as droplets from the nozzles of the inkjet head based on a digital signal, and these droplets land on the treatment liquid layer of the substrate to perform printing.

[0144] The inkjet head may be either an on-demand type or a continuous type. Examples of on-demand type inkjet heads include electro-mechanical conversion type inkjet heads, including single-cavity type, double-cavity type, bender type, piston type, shear mode type, and shared wall type inkjet heads, and electro-thermal conversion type inkjet heads, including thermal inkjet type and bubble jet type inkjet heads ("Bubble Jet" is a registered trademark of Canon Inc.).

[0145] Of the above ink jet heads, ink jet heads using a piezoelectric element as the electromechanical conversion element used in the electromechanical conversion system (also called piezo type ink jet heads) are preferred.

[0146] The inkjet printer may be of either a scan type or a single pass type, and in the case of a single pass type, it is preferable to use a line head type inkjet head.

[0147] A line head type inkjet head is an inkjet head having a length equal to or greater than the width of the printing range. A single line head type inkjet head having a length equal to or greater than the width of the printing range may be used. Alternatively, a line head type inkjet head may be configured by combining multiple heads so that the length is equal to or greater than the width of the printing range. Furthermore, multiple heads may be arranged side by side with their nozzles in a staggered arrangement to increase the overall resolution of the heads.

[0148] The conveying speed of the recording medium, which is the substrate, can be set, for example, within the range of 1 to 120 m / min. The faster the conveying speed, the faster the image formation speed. According to the present invention, it is possible to obtain high-resolution images with high ink fixation even at a very high linear speed of 50 to 120 m / min, which is applicable to a single-pass inkjet image formation method.

[0149] Ink Heating and Drying Process In the ink heating and drying process, the ink applied to the recording medium, which is a non-absorbent substrate, i.e., the area where the ink is applied, is heated, thereby drying the ink and the treatment liquid.

[0150] In the ink heating and drying step, the heating temperature of the area where the ink has been applied is preferably within the range of 60 to 200° C. The heating time of the ink is adjusted appropriately according to the type of recording medium and the amount of ink applied.

[0151] By heating the ink-applied area in this manner, the solvent components of the treatment liquid and ink, such as water and water-soluble solvents, are removed. Simultaneously with this removal, particularly in the case of metal substrates, the polyvalent metal salt is dried at a temperature equal to or higher than its thermal decomposition temperature, thereby thermally decomposing it. This also improves the abrasion resistance of the image and adhesion to the substrate.

[0152] Heat drying may be performed using a non-contact heating drying device such as a drying oven or a hot air blower. Alternatively, heat drying may be performed using a contact heating drying device such as a hot plate or a heated roller. The drying temperature can be obtained by measuring any one of the following over the entire drying period of the treatment liquid: (a) when a non-contact heating drying device such as a drying oven or a hot air blower is used, the ambient temperature such as the furnace temperature or the hot air temperature; (b) when a contact heating drying device such as a hot plate or a heated roller is used, the temperature of the contact heating section; or (c) the surface temperature of the surface to be dried. As the measurement location, it is more preferable to measure (c) the surface temperature of the surface to be dried.

[0153] The thickness of the image layer obtained as described above is preferably in the range of 0.3 to 3.0 μm, and more preferably in the range of 0.3 to 2.0 μm. When the thickness of the image layer is 0.3 μm or more, the adhesion and abrasion resistance of the image are easily improved. When the thickness of the image layer is 3.0 μm or less, the deformation stress applied to the image layer can be reduced, so the adhesion of the image layer is less likely to be impaired.

[0154] [Recording Apparatus] Figure 2 is a schematic diagram of a recording apparatus preferred for the present invention. However, the present invention is not limited to this. The recording apparatus 1 is mainly composed of a treatment liquid application unit 10 and an ink application unit 20. The treatment liquid application unit 10 applies a treatment liquid onto the substrate F, and the ink application unit 20 applies ink. The treatment liquid application unit 10 is an inkjet head 11 capable of ejecting a treatment liquid onto the substrate. The ink application unit 20 is an inkjet head 21 capable of ejecting ink onto the substrate.

[0155] In this recording apparatus 1, treatment liquid droplets 12 are ejected from the inkjet head 11 onto the substrate F fed from the delivery roller 30, forming a treatment liquid layer C. Next, ink droplets 22 are ejected from the inkjet head 21 onto the treatment liquid layer C, and the treatment liquid and the ink are combined. Thereafter, the drying section 23 heats and dries the area to which the ink has been applied, forming an image layer G. Next, the substrate F on which the image layer G has been formed is wound up by the winding roller 40, obtaining a recorded image.

[0156] 2 shows an apparatus configured to apply ink after applying a treatment liquid onto a substrate, but an apparatus configured to simultaneously apply the treatment liquid and ink may also be used. Alternatively, it is preferable to eject ink from the inkjet head when the drying rate of the treatment liquid layer is 30% or less. Furthermore, after applying ink, the treatment liquid may be applied before the ink dries.

[0157] As an apparatus other than the recording apparatus shown in FIG. 2, a flatbed printer is also preferably used to apply the treatment liquid and ink. In a flatbed printer, the substrate is fixed, and the inkjet head can be moved in the main scanning direction and the sub-scanning direction that intersects with the main scanning direction. Therefore, printing can be performed without transporting the substrate. Examples of such flatbed printers include the printers described in FIG. 1 of JP-A-2015-74161 and FIG. 1 of JP-A-2017-177578.

[0158] The present invention will be specifically described below with reference to examples, but the present invention is not limited thereto. In the following examples, unless otherwise specified, operations were performed at room temperature (25°C). Furthermore, unless otherwise specified, "%" and "parts" mean "% by mass" and "parts by mass", respectively. Furthermore, in the following tables, "wt%" means "% by mass".

[0159] [Preparation of Black Ink]

[0160] The abbreviations in Tables I to X below are as follows. <Commercially available silicone emulsions> "POLON-MF-33" (manufactured by Shin-Etsu Chemical Co., Ltd.): dimethyl silicone emulsion "KM-9771" (manufactured by Shin-Etsu Chemical Co., Ltd.): amino group-containing silicone emulsion "KM-9772" (manufactured by Shin-Etsu Chemical Co., Ltd.): self-crosslinking silicone emulsion "KM-2002-T-2" (manufactured by Shin-Etsu Chemical Co., Ltd.): self-crosslinking silicone emulsion "POLON-MF-14EC" (manufactured by Shin-Etsu Chemical Co., Ltd.): amino group-containing silicone emulsion "TEGO GLIDE 490" (manufactured by Evonik): polyether-modified silicone emulsion <Commercially available silicone compounds> "DOWSIL TM 29 Additive (manufactured by Dow-Toray Industries, Inc.): polyether-modified silicone Silsurf C208 (manufactured by GSI Creos Co., Ltd.): polyether-modified silicone

[0161] <Preparation of Silicone Emulsions A and D> 40 g of polyoxyethylene lauryl ether as a surfactant (emulsifier) ​​and 30 g of ion-exchanged water were thoroughly mixed in advance. 200 g of dimethyl silicone (kinematic viscosity: 5000 cS (centistokes)) was added to this and mixed with stirring. After the mixture became viscous and transparent, 230 g of ion-exchanged water was added and mixed again to obtain a silicone emulsion. At this time, the addition amount and reaction conditions were changed to obtain the target average particle size, and silicone emulsions A and D were obtained, respectively. The average particle size of the silicone compound particles in these silicone emulsions was 53 nm for silicone emulsion D and 74 nm for silicone emulsion A.

[0162] <Preparation of Silicone Emulsion B> 40 g of polyoxyethylene nonylphenyl ether as a surfactant (emulsifier) ​​and 10 g of ion-exchanged water were thoroughly mixed in advance. 200 g of dimethyl silicone (kinematic viscosity: 7000 cS) was added to this and mixed by stirring. After the mixture became viscous and transparent, 250 g of ion-exchanged water was added and mixed again to obtain Silicone Emulsion B. The average particle size of the silicone compound particles in Silicone Emulsion B was 147 nm.

[0163] <Preparation of Silicone Emulsions C and E> 40g of polyoxyethylene lauryl ether as surfactant (emulsifier) ​​and 30g of ion-exchanged water were mixed thoroughly in advance. 200g of dimethyl silicone (kinematic viscosity: 10000cS) was added thereto and stirred and mixed. After the mixture became viscous and transparent, 230g of ion-exchanged water was added and mixed again to obtain a silicone emulsion. At this time, the addition amount and reaction conditions were changed to obtain the target average particle size, and silicone emulsions C and E were obtained, respectively. The average particle size of the silicone compound particles in these silicone emulsions was 342nm for silicone emulsion C and 365nm for silicone emulsion E.

[0164] <Surfactants for controlling surface tension> "Olfine E1010" (manufactured by Nissin Chemical Co., Ltd.): acetylene glycol "KF351A" (manufactured by Shin-Etsu Chemical Co., Ltd.): polyether-modified silicone

[0165] <Preparation of Dispersion of Black Pigment A> A mixture was premixed by adding 20% ​​by mass of black pigment (carbon black), 8% by mass of an anionic polymer dispersant ("Joncryl 819" manufactured by BASF), 20% by mass of propylene glycol, 0.1% by mass of the antifungal agent Proxel GXL(S), and ion-exchanged water. The mixture was then dispersed using a bead mill filled with 50% by volume of 0.3 mm zirconia beads to prepare a pigment dispersion with a pigment content of 20% by mass, thereby obtaining a dispersion of Black Pigment A. The average particle diameter of the pigment particles contained in the dispersion of Black Pigment A was 80 nm.

[0166] <Commercially available polyolefin> Auroren AE-301 (manufactured by Nippon Paper Industries Co., Ltd.; "Auroren" is a registered trademark of the company)

[0167] <Preparation of chlorinated polyolefins A and B> 100 g of a propylene-based random copolymer (propylene component 96 mol%, ethylene component 4 mol%, weight average molecular weight = 100,000, Tm = 125°C), 4 g of maleic anhydride, and 3 g of dicumyl peroxide were thoroughly mixed in advance. Then, a kneading reaction was carried out using a twin-screw extruder set at 180°C. The mixture was degassed under reduced pressure in the extruder to remove any remaining unreacted material, thereby obtaining a maleic anhydride-modified polyolefin. 2 kg of this resin was placed in a 50 L reactor, and 20 L of chloroform was added, followed by 2 kg / cm ２ Under a pressure of 1000 kJ / cm 2 , gaseous chlorine was blown into the bottom of the reactor while irradiating with ultraviolet light to chlorinate the mixture. This yielded a sample with a chlorine content of 18% by mass. Next, the chloroform solvent was distilled off using an evaporator, and the solids content was adjusted to 30% by mass. 1.5% by mass of a stabilizer (t-butylphenyl glycidyl ether) was added to the chloroform solution, and the mixture was solidified using a twin-screw extruder with a barrel temperature set to 90°C. The resulting chlorinated modified polyolefin had a weight-average molecular weight of 92,000, a maleic anhydride graft mass of 3.5% by mass, a chlorine content of 15.5% by mass, and a melting point of 85°C.

[0168] Next, a four-neck flask was equipped with a stirrer, a condenser, a thermometer, and a funnel. 100 g of the obtained chlorinated modified polyolefin, 20 g of a surfactant (N,N-polyoxyalkylene-alkylamine), 18 g of 25% aqueous ammonia (neutralizing agent), and 25 g of toluene were added to this four-neck flask and kneaded at 120°C for 30 minutes. Then, 290 g of deionized water at 90°C was added over 60 minutes. Subsequently, the solvent was removed under reduced pressure, and the mixture was cooled to room temperature with stirring. At this time, the reaction conditions were changed so as to achieve the target average particle size, and a dispersion of chlorinated polyolefin A and a dispersion of chlorinated polyolefin B were obtained, respectively. The average particle sizes of the resin particles contained in these resin dispersions were 96 nm for the dispersion of chlorinated polyolefin A and 110 nm for the dispersion of chlorinated polyolefin B.

[0169] <Preparation of Acid-Modified Polyolefins A and B> A four-neck flask was equipped with a stirrer, a condenser, a thermometer, and a dropping funnel. In this four-neck flask, 300 g of a propylene-based random copolymer (propylene component 96 mol%, ethylene component 4 mol%, weight average molecular weight = 100,000, Tm = 125 °C) was heated and dissolved in 700 g of toluene. Thereafter, 13 g of maleic anhydride and 12 g of di-t-butyl peroxide as a radical generator were each added dropwise over 2 hours while stirring while maintaining the temperature of the system at 115 °C. The mixture was then aged for 3 hours. After the reaction, the mixture was cooled to room temperature and then poured into 20 L of acetone for purification, yielding a maleic anhydride graft copolymer (average molecular weight 18,500) with a graft amount of 2.1% by mass. 100 g of the obtained maleic anhydride graft copolymer (modified polyolefin) was placed in a reactor equipped with a stirrer, thermometer, condenser, and dropping funnel, and heated to 120 ° C. to melt. Then, 6 g of morpholine was added as a basic substance while stirring, and 40 g of polyethylene oxide was added as a surface active component. After stirring until homogeneous, 600 g of water was added in small amounts to obtain a hydrophilic product by phase inversion. At this time, the reaction conditions were changed to obtain the target average particle size, and a dispersion of acid-modified polyolefin A and a dispersion of acid-modified polyolefin B were obtained, respectively. The average particle size of the resin particles contained in these resin dispersions was 93 nm for the dispersion of acid-modified polyolefin A and 105 nm for the dispersion of acid-modified polyolefin B.

[0170] <Measurement of Average Particle Diameter> (Measurement of Average Particle Diameter of Pigment Particles) The average particle diameter of the pigment particles in the pigment dispersion obtained above was calculated by the cumulant method. This average particle diameter is also referred to as the Z-average diameter. The average particle diameter of the pigment particles was measured using a Zataizer Nano S90 manufactured by Melvern.

[0171] (Measurement of average particle size of resin particles in resin dispersion) The average particle size of the chlorinated or acid-modified polyolefin in the resin dispersion obtained above was also calculated by the cumulant method. The average particle size of the resin particles was measured using a Zataizer Nano S90 manufactured by Melvern.

[0172] (Measurement of the average particle size of silicone compound particles in silicone emulsion) The average particle size of the silicone compound particles in the silicone emulsion obtained above was also calculated by the cumulant method. The average particle size of the silicone compound particles was measured using a Zataizer Nano S90 manufactured by Melvern. TM The average particle size of "29 Additive" (manufactured by Dow-Toray) and "Silsurf C208" (manufactured by GSI Creos) could not be measured because they are silicone compounds that dissolve in water and do not form an emulsion.

[0173] <Preparation of Black Ink K1> The following materials were added to a 20.0% by mass dispersion of Black Pigment A while stirring. Dispersion of black pigment A (amount added was adjusted so that the pigment concentration in the ink was 4.0% by mass) Dispersion of chlorinated polyolefin A (amount added was adjusted so that the resin particles (solid content) in the ink was 4.0% by mass) Water-soluble solvent: propylene glycol 27.0% by mass Water-soluble solvent: 2-methyl-1,3-propanediol 5.0% by mass Silicone emulsion: silicone emulsion A (amount added was adjusted so that the silicone compound (solid content) in the ink was 0.8% by mass) Surfactant: E1010 (manufactured by Nissin Chemical Co., Ltd.) 1% by mass Surfactant: KF351A (manufactured by Shin-Etsu Chemical Co., Ltd.) 0.2% by mass Antifungal agent: 1,2-benzisothiazolin-3-one (Proxel GXL(S), manufactured by SC Johnson) 0.1% by mass Ion-exchanged water (the remainder was added so that the total amount of the raw materials constituting the ink was 100% by mass) The resulting mixture was filtered through a 1 μm filter to obtain black ink K1. There was no substantial change in composition before and after filtration. The solid mass ratios of the chlorinated polyolefin A dispersion and the silicone emulsion A were calculated from the amount of nonvolatile matter remaining when each solution was heat-treated at 105° C. for 3 hours. The solid mass ratios of the chlorinated polyolefin A and the silicone emulsion A in the ink were adjusted by adjusting the amounts of the above raw materials added.

[0174] <Preparation of Black Inks K2 to K28> In the preparation of black ink K1, the types and blend amounts (mass%) of the pigment dispersion, resin dispersion, silicone emulsion, and surfactant were changed as shown in Tables I to X below. Furthermore, treatment liquids K2 to K28 were prepared in the same manner, except that the amount of ion-exchanged water added (the balance) was also changed accordingly. Note that the water-soluble solvent, antifungal agent, and ion-exchanged water are not listed in the tables below.

[0175] [Preparation of Treatment Liquid] The abbreviations in Tables I to X below are as follows: <Surfactants> "Olfine E1010" (manufactured by Nissin Chemical Co., Ltd.): acetylene glycol "KF351A" (manufactured by Shin-Etsu Chemical Co., Ltd.): polyether-modified silicone "TORITON HW-1000" (manufactured by The Dow Chemical Company): polyoxyethylene alkyl ether "BYK3450" (manufactured by BYK-Chemie): trisiloxane polyoxyalkylene "Surflon S-211" (manufactured by AGC Sei Chemical Co., Ltd.): perfluoroalkyl carboxylate

[0176] <Preparation of Treatment Solution T1> To 3.0 mass% of calcium acetate hydrate as a flocculant, 28.0 mass% of propylene glycol and 5.0 mass% of 2-methyl-1,3-propanediol as water-soluble solvents, 1 mass% of Olfine E1010 (manufactured by Nissin Chemical Co., Ltd.) and 0.2 mass% of KF351A (manufactured by Shin-Etsu Chemical Co., Ltd.) as surfactants, 0.1 mass% of 1,2-benzisothiazolin-3-one (Proxel GXL(S), manufactured by SC Johnson) as an antifungal agent, and ion-exchanged water (balance; amount such that the total amount was 100 mass%) were added with stirring. The resulting mixture was filtered through a 1 μm filter to obtain Treatment Solution T1.

[0177] <Preparation of Treatment Solutions T2 and T3> In the preparation of treatment solution T1, the type and amount of surfactant added was changed as shown in Tables I to X below. Treatment solutions T2 and T3 were prepared in the same manner except that the amount of ion-exchanged water added (the remainder) was also changed accordingly. Note that the water-soluble solvent, antifungal agent, and ion-exchanged water are not listed in the tables below.

[0178] [Physical Properties] The static surface tension and dynamic surface tension of the resulting treatment liquid were measured by the following method. <Static Surface Tension> The static surface tension of the treatment liquid prepared above was measured at 25°C using a static surface tensiometer (CBVP-Z: manufactured by Kyowa Interface Science Co., Ltd.) using the Wilhelmy method. The measured values ​​(unit: mN / m) are shown in Tables I to X below.

[0179] <Dynamic Surface Tension> The dynamic surface tension of the treatment liquid prepared above was measured after a surface life of 50 msec using a dynamic surface tensiometer (BP-100: manufactured by KRUSS) using the maximum bubble pressure method. The measurement temperature was adjusted to 25°C. The dynamic surface tensions (unit: mN / m) after a surface life of 50 msec are shown in Tables I to X below.

[0180] [Printing Test] Using the treatment liquid and ink prepared above, a printing test was conducted using the one-liquid or two-liquid method as follows. A polypropylene substrate (#20 FOR, manufactured by Futamura Chemical Co., Ltd., 20 μm thick, corona-untreated surface) was prepared as a recording medium. A scanning printer equipped with two independently driven inkjet heads (360 npi, ejection volume 6 pL, 1024 nozzles) manufactured by Konica Minolta was prepared. For the two-liquid method, the head to be recorded first was filled with each treatment liquid, and the head to be recorded second was filled with each ink. An image with a resolution of 720 × 720 dpi was then divided into two in the scanning direction X and the transport direction Y to create four images (180 × 180 dpi). Printing was conducted in one direction, always with the treatment liquid being recorded first, using a four-pass mode in which one print area was printed four times. The carriage transport speed was set to 300 mm / sec, and no drying process was performed between the recording of the treatment liquid and the ink. The printing test was carried out under an environment of 25°C and 50% RH. The maximum printing rate for the treatment liquid was set to 33%, and the treatment liquid was applied in accordance with the ink image area. For the ink recording, the amount of each ink applied was 18 g / m. ２ The printing conditions were set to solid and printed. The time from when the treatment liquid was applied until the ink was applied was measured and calculated to be 0.2 seconds. In the case of the one-liquid method, the head was filled with only ink without using the treatment liquid, and ink recording was performed under the same printing conditions as for the two-liquid method.

[0181] [Drying of Recorded Material] In the above printing test, after applying the ink, the polypropylene film was placed in a dryer set at 90°C and dried by heating for 5 minutes to obtain an image recorded material. Printing was carried out under the same conditions as above to prepare each evaluation sample (image recorded material).

[0182] [Evaluation] <Image quality (character reproducibility)> Character reproducibility of each evaluation sample created was evaluated according to the following criteria. "A" and "B" in the criteria below were determined to be acceptable for practical use. (Criteria) A: 8 pt characters are clearly reproduced and can be recognized without problems. B: 10 pt characters are clearly reproduced and can be recognized without problems. C: Some 10 pt characters are cut off, making some characters difficult to recognize.

[0183] <Image Quality (Solid Uniformity)> The solid portion of each evaluation sample prepared was visually evaluated, and the reflection density was measured and evaluated according to the following criteria. The reflection density was measured under a D50 light source using a fluorescent spectrodensitometer (FD-7 manufactured by Konica Minolta). The following criteria, "A" and "B," were determined to be acceptable for practical use. (Criteria) A: No streaks or the like were present in the solid, and the reflection density was 1.5 or more. B: No streaks or the like were present in the solid, and the reflection density was 1.3 or more but less than 1.5. C: Streaks were visible to the naked eye, and the reflection density was less than 1.3.

[0184] <Tape peeling> An adhesion test (cross-cut method) according to JIS-K5600 was carried out on the solid area of ​​each evaluation sample prepared using Nichiban Cellotape (Cellotape is a registered trademark), and the degree of peeling was evaluated. The following criteria "A, B, C" were determined to be acceptable for practical use. (Criteria) A: No peeling B: Less than 20% of the squares peeled off C: 20% or more but less than 50% of the squares peeled off D: 50% or more of the squares peeled off

[0185] <Rubbing resistance (dry)> The rubbing resistance of the ink coating film was evaluated on the solid area of ​​each evaluation sample prepared using a Gakushin-type rubbing fastness tester "AB-301" manufactured by Tester Sangyo Co., Ltd. The evaluation conditions were test load: 200 gf, abrader: white cotton cloth (Kanakin No. 3), and number of reciprocating strokes: 10 times. The degree of peeling of the ink coating film after the rubbing resistance test was evaluated. The following criteria "A, B, C" were determined to be acceptable for practical use. (Criteria) A: No peeling B: Peeling area is less than 20% C: Peeling of 20% to less than 50% of the area D: Peeling of 50% or more of the area

[0186] <Rubbing resistance (wet)> The rubbing resistance of the ink coating film was evaluated on the solid area of ​​each evaluation sample prepared using a Gakushin-type rubbing fastness tester "AB-301" manufactured by Tester Sangyo Co., Ltd. The evaluation conditions were: test load: 200 gf, friction element: water-moistened white cotton cloth (Kanakin No. 3), number of reciprocating strokes: 10. The degree of peeling of the ink coating film after the rubbing resistance test was evaluated. The following criteria "A, B, C" were determined to be acceptable for practical use. (Criteria) A: No peeling B: Peeling area is less than 20% C: Peeling of 20% or more but less than 50% of the area D: Peeling of 50% or more of the area

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[0197] As shown by the above results, the ink of the present invention has better character reproducibility, uniformity in solid areas, and coating film adhesion than the ink of the comparative example, and is also superior in abrasion resistance.

[0198] The present invention can be used for aqueous inkjet ink compositions and ink sets that have excellent coating film adhesion and abrasion resistance and can form high-quality images on non-absorbent substrates.

[0199] REFERENCE SIGNS LIST 1 Recording apparatus 10 Treatment liquid application section 11 Inkjet head 12 Treatment liquid droplets 20 Ink application section 21 Inkjet head 22 Ink droplets 23 Drying section 30 Delivery roller 40 Take-up roller C Treatment liquid layer G Image layer F Base material (recording medium) P Pigment

Claims

1. An aqueous inkjet ink composition for application to a recording medium to form an image, comprising a silicone compound and a polyolefin, wherein the silicone compound is in particulate form and forms a silicone emulsion, the particulate silicone compound has an average particle diameter within the range of 70 to 350 nm, and the recording medium is a non-absorbent substrate.

2. The aqueous ink-jet ink composition according to claim 1, wherein the silicone emulsion is an amino group-containing silicone emulsion.

3. The aqueous ink-jet ink composition according to claim 1, wherein the silicone emulsion is a self-crosslinking silicone emulsion.

4. The aqueous ink-jet ink composition according to claim 1, wherein the polyolefin is an acid-modified polyolefin.

5. The aqueous ink-jet ink composition according to claim 1, wherein the mass ratio of the polyolefin to the silicone compound in the aqueous ink-jet ink composition (mass of polyolefin:mass of silicone compound) is within the range of 4:1 to 1:

1.

6. The aqueous ink-jet ink composition according to claim 1, wherein the average particle size of the polyolefin particles in the polyolefin is within the range of 100 to 300 nm.

7. An ink set comprising the aqueous inkjet ink composition according to any one of claims 1 to 6 and a treatment liquid containing a coagulant.

8. The ink set according to claim 7, wherein the static surface tension of the treatment liquid is within the range of 18 to 25 mN / m at 25°C, and the dynamic surface tension of the treatment liquid at a surface life of 50 msec is within the range of 25 to 35 mN / min at 25°C.

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