Water-based inkjet ink, method for producing printed matter, and ink set

Abstract

To provide aqueous inkjet ink which enables formation of an image that is excellent in color development property and is glossy, and obtains an image formed on a white base, which is glossy and has high image quality, when being used in white base printing of an image formation part.SOLUTION: Aqueous inkjet ink contains hollow resin particles A having a recess on its outer surface, water, and solid resin particles B, wherein a content of the hollow resin particles A is 5 mass% or more and less than 20 mass% with respect to the total amount of ink.SELECTED DRAWING: None

Description

[Technical Field]

[0001] SUMMARY OF THE INVENTION Embodiments of the present invention relate to aqueous inkjet inks, methods for producing printed matter, and ink sets. [Background technology]

[0002] In recent years, inkjet printing has come to be used not only on paper media such as plain paper and specialty paper, but also on substrates where ink easily spreads along the fibers, such as woven fabrics, knitted fabrics, nonwoven fabrics, and wood, functional porous materials that exhibit functionality through the voids in the substrate, and substrates where ink is difficult to penetrate, such as plastic substrates, synthetic paper, metal substrates, and glass. In order to perform high-quality printing on such a variety of substrates, in addition to high image quality, a beautiful appearance suited to the application may be required.

[0003] For example, there is a method in which, after a printed image is formed, an overcoat agent containing a resin with high gloss is spray coated. Patent Document 1 describes a method in which a clear ink containing resin particles is applied by an inkjet printer onto an image made of pigment ink. Furthermore, Patent Document 2 describes a method of using a binder resin containing flat particles in ink to reduce unevenness on the ink film surface and impart gloss to printed matter.

[0004] On the other hand, when printing an image on a dark-colored substrate, for example, there is a method in which a white ink is printed to form a white base, and then the desired image is formed on top of that. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-43559 [Patent Document 2] Japanese Patent Application Laid-Open No. 2015-10143 Summary of the Invention [Problem to be solved by the invention]

[0006] For example, when an overcoat agent is applied by spray coating to impart gloss to an image, the gloss is imparted to the entire area where the overcoat agent is spray coated. Furthermore, for example, in the case of a method using clear ink as in Patent Document 1, a step of applying clear ink is required. Furthermore, in the case of using ink capable of imparting gloss as in Patent Document 2, the gloss is imparted to the entire area where the ink is applied. An object of one embodiment of the present invention is to provide an aqueous inkjet ink that is capable of forming an image that has gloss and excellent color development, and that, when used for printing an image on a white base, makes the image formed on the white base glossy and of high quality. [Means for solving the problem]

[0007] One embodiment of the present invention relates to an aqueous inkjet ink comprising hollow resin particles A having recesses on their outer surfaces, water, and solid resin particles B, wherein the content of the hollow resin particles A is 5% by mass or more and less than 20% by mass of the total amount of the ink. Another embodiment of the present invention relates to a method for producing a printed matter, comprising the steps of applying the aqueous inkjet ink of the above-described embodiment to a substrate by an inkjet method, and applying, by an inkjet method, an aqueous inkjet ink containing water and a non-white colorant to the substrate to which the aqueous inkjet ink has been applied. Another embodiment of the present invention relates to an ink set comprising the aqueous inkjet ink of the above embodiment and an aqueous inkjet ink containing water and a non-white colorant. [Effects of the Invention]

[0008] According to one embodiment of the present invention, it is possible to provide an aqueous inkjet ink that is capable of forming an image that has gloss and excellent color development, and that, when used for printing a white base in an image formation area, makes the image formed on the white base glossy and of high quality. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is an SEM photograph (magnification: 30,000 times) of the surface of a calcium silicate board to which an example of an aqueous inkjet ink according to an embodiment has been applied. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, an embodiment of the present invention will be described in detail, but it goes without saying that the present invention is not limited to these embodiments and various modifications and changes may be made.

[0011] <Water-based inkjet ink> The aqueous inkjet ink according to one embodiment is an aqueous inkjet ink (hereinafter sometimes referred to as "white ink") that contains hollow resin particles A having recesses on their outer surfaces, water, and solid resin particles B, and the content of hollow resin particles A is 5% by mass or more and less than 20% by mass of the total amount of ink. When this white ink is used, it is possible to form an image that is glossy and has excellent color development. Furthermore, when this white ink is used for printing on a white base, it is possible to form an image on the white base that is glossy and of high quality.

[0012] Without being bound by theory, it is believed that this white ink may work as follows. The hollow resin particles A are hollow and have internal pores. In a liquid, the internal pores of the hollow resin particles A are filled with a solvent such as water, so the white ink does not develop a good white color immediately after being applied to a substrate. After the white ink is applied to the substrate, the solvent in the internal pores of the hollow resin particles A penetrates the substrate and / or volatilizes and is replaced by air. This causes light refraction and scattering due to the difference in refractive index between the interior of the hollow resin particles A and the outer shell resin of the particles, resulting in white color development. In addition to being hollow, the hollow resin particles A have recesses on their outer surfaces, which cause finer scattering and enable the white color development.

[0013] Figure 1 is an SEM photograph (magnification 30,000x) of the surface of a calcium silicate board where an example of a white ink has been applied by inkjet printing (white ink-printed area). When the white ink is applied to the substrate and the solvent in the ink penetrates and / or volatilizes, hollow resin particles A are laid out on the surface of the substrate in the white ink-printed area, as shown in Figure 1. Because hollow resin particles A have depressions on their outer surfaces, they are laid out to create a flatter surface, which results in a flatter coating surface that is more likely to produce a glossy surface.

[0014] Furthermore, when this white ink is used for white underprinting, the layer of hollow resin particles A on the substrate acts as a receptive layer for the ink applied thereon, fixing the ink. When the solvent penetrates or volatilizes into the substrate, the hollow resin particles A produce a good white color, allowing the ink image formed on the white ink-printed area to be of high quality. Furthermore, because the surface of the white ink-printed area is flat, the image formed on the white ink-printed area can be given a glossy finish.

[0015] Furthermore, the white ink printed area can give the image a glossy finish, while the areas where the white ink is not applied have a surface that retains the texture of the base material, making it possible to create printed items with varying textures in parts.

[0016] Furthermore, when the content of hollow resin particles A is 5.0% by mass or more relative to the total amount of the white ink, glossiness is easily obtained, and when the content of hollow resin particles A is less than 20.0% by mass relative to the total amount of the white ink, good inkjet ejection properties can be achieved, resulting in improved white color development and glossiness.

[0017] The white ink may contain hollow resin particles A that are hollow and have recesses on their outer surfaces.

[0018] The hollow resin particles A are hollow particles having an internal cavity and a recess on the outer surface. The hollow resin particles A are preferably not spherical or nearly spherical, and are preferably short in at least one direction when an orthogonal three-dimensional coordinate system is applied to the three-dimensional shape of the particles. The shape of the hollow resin particles A when viewed from one direction is not particularly limited, and may be, for example, a circle, an ellipse, a polygon such as a square or a hexagon, or a random (irregular) shape. Examples of the shape of the hollow resin particles A include shapes such as those illustrated in FIG. 1. When viewed from one direction, the hollow resin particles A preferably have a recess in the center. Examples of hollow resin particles A include those having a bowl-like shape due to the recess, and those having a disk-like shape with recesses formed in the center of both sides, like red blood cells.

[0019] The hollow resin particles A are preferably resin particles that can be dispersed in an aqueous solvent. The hollow resin particles A are preferably those that can be dispersed in water in a particulate form without dissolving in water, thereby forming an oil-in-water (O / W) emulsion. The hollow resin particles A are preferably contained in the white ink in a dispersed state as resin particles. The hollow resin particles A may be dispersed in an aqueous solvent by having a dispersible functional group on the particle surface, or may be dispersed by a dispersant or the like. In the white ink, the hollow resin particles A preferably contain a solvent within the hollow. The hollow resin particles A can be blended as a resin emulsion when producing the white ink.

[0020] It is preferable that the hollow resin particles A remain as individual particles even after the coating film has dried, do not form a film, and do not function as a binder. When the hollow resin particles A exist as particles on the substrate, they can easily function as a receiving layer that absorbs the ink applied thereon.

[0021] From the viewpoint of favorably functioning as an ink-receiving layer, the hollow resin particles A preferably have the property of not forming a film at room temperature and preferably have a relatively high glass transition point (Tg). More specifically, the glass transition point of the hollow resin particles A is preferably 50°C or higher, more preferably 60°C or higher, even more preferably 70°C or higher, and even more preferably higher than 80°C. The glass transition point of the hollow resin particles A is preferably 200°C or lower, more preferably 190°C or lower, and even more preferably 180°C or lower. The glass transition point of the hollow resin particles A is preferably 50 to 200°C, more preferably 60 to 190°C, even more preferably 70 to 180°C, and even more preferably higher than 80°C but not higher than 180°C.

[0022] The type of resin for the hollow resin particles A is not particularly limited, but resins that can be easily incorporated into aqueous inks, such as acrylic resins, polyester resins, polyurethane resins, epoxy resins, and vinyl resins, can be used. Examples of acrylic resins include polymers of acrylic acid esters and methacrylic acid esters, and copolymers of these with styrene or the like (e.g., styrene-acrylic resins). These may be used alone or in combination of two or more.

[0023] The particle size of the hollow resin particles A is preferably a size suitable for printing with an inkjet head and capable of achieving both white color development and gloss. The average particle diameter of the hollow resin particles A is preferably 250 nm or more, more preferably 300 nm or more. On the other hand, the average particle diameter of the hollow resin particles A is preferably 1 μm or less, more preferably 800 nm or less. The average particle diameter of the hollow resin particles A is preferably 250 nm or more and 1 μm or less, more preferably 300 nm or more and 800 nm or less.

[0024] Unless otherwise specified, the average particle size of hollow resin particles A and solid resin particles B (described later) in this specification refers to the volume-based particle size value (median size) in the particle size distribution measured by dynamic light scattering. A nanoparticle analyzer, nano Partica SZ-100 (Horiba, Ltd.), or the like, can be used as a dynamic light scattering particle size distribution measuring device. In the ink, hollow resin particles A and solid resin particles B (described later) may exist as independent particles or as aggregates of independent particles. However, the median size measured by dynamic light scattering will be defined as the "average particle size."

[0025] Commercially available resin emulsions containing hollow resin particles A include "FUJI SP WHITE 1185" (trade name) manufactured by Fuji Pigment Co., Ltd.

[0026] From the viewpoint of glossiness, the content (solids content) of hollow resin particles A in the white ink is preferably 5.0% by mass or more, and more preferably 10.0% by mass or more, based on the total amount of ink. On the other hand, from the viewpoints of image color development and glossiness, it is preferable that the white ink has good inkjet ejection properties, and from that viewpoint, the content (solids content) of hollow resin particles A is preferably less than 20.0% by mass, and more preferably 18.0% by mass or less, based on the total amount of ink. The content (solids content) of hollow resin particles A in the white ink is preferably 5.0% by mass or more and less than 20.0% by mass, and more preferably 10.0% by mass or more and 18.0% by mass or less, based on the total amount of ink.

[0027] The white ink may contain solid resin particles B. The solid resin particles B are not hollow particles, and unlike the hollow resin particles A, they do not have cavities inside. The solid resin particles B can function as a binder resin for fixing the hollow resin particles A to the substrate. The hollow resin particles A are preferably selected from the viewpoint of durability and flexibility of the printed surface. As the type of solid resin particles B, it is preferable to use a resin that forms a transparent coating film.

[0028] The solid resin particles B are preferably resin particles that can be dispersed in an aqueous solvent. The solid resin particles B are preferably those that can be dispersed in water without dissolving in water to form an oil-in-water (O / W) emulsion. The solid resin particles B are preferably contained in the white ink in a dispersed state as resin particles. The solid resin particles B can be blended as a resin emulsion when producing the white ink.

[0029] The average particle size of the solid resin particles B is preferably 250 nm or less, more preferably 200 nm or less, and even more preferably 150 nm or less. The average particle size of the solid resin particles B is preferably 1 nm or more, more preferably 5 nm or more, and even more preferably 10 nm or more. The average particle size of the solid resin particles B is, for example, preferably 1 to 250 nm, more preferably 5 to 200 nm, and even more preferably 10 to 150 nm.

[0030] The solid resin particles B may be those in which functional groups of the resin are present on the surface of the resin particles, such as a self-emulsifying resin, or may be those that have been subjected to a surface treatment such as attaching a dispersant to the surface of the resin particles. The solid resin particles B may be, for example, any of anionic, cationic, nonionic, or amphoteric water-dispersible resins.

[0031] The glass transition point (Tg) of the solid resin particles B is preferably 80° C. or lower, and from the viewpoint of better image gloss, more preferably 20° C. or lower, even more preferably 10° C. or lower, and even more preferably 0° C. or lower. The glass transition point of the resin of the solid resin particles B is preferably −50° C. or higher, and more preferably −35° C. or higher. The glass transition point of the resin of the solid resin particles B is, for example, preferably −50 to 80° C., more preferably −35 to 20° C., even more preferably −35 to 10° C., and even more preferably −35 to 0° C.

[0032] The type of resin for the solid resin particles B is, for example, Conjugated diene resins such as styrene-butadiene copolymer, methyl methacrylate-butadiene copolymer, vinyl chloride-vinyl acetate copolymer, etc.; acrylic resins such as polymers of acrylic acid esters and methacrylic acid esters, or copolymers thereof with styrene, etc.; vinyl resins such as ethylene-vinyl acetate copolymers, or functional group-modified resins of these various resins with a monomer containing a functional group such as a carboxyl group; Examples of the aqueous resin include melamine resin, urea resin, polyurethane resin, polyester resin, polyolefin resin, silicone resin, polyvinyl butyral resin, alkyd resin, etc. The resin particles may be made of a single resin or may be a hybrid type resin.

[0033] The solid resin particles B are preferably polyurethane resin particles, acrylic resin particles, or a combination thereof. Examples of polyurethane resins include ether type polyurethane, ester type polyurethane, ester-ether type polyurethane, and carbonate type polyurethane. Among these, from the viewpoint of flexibility and transparency, it is preferable that the solid resin particles B contain acrylic resin particles having a relatively low glass transition point (Tg). The glass transition point of the acrylic resin particles is preferably 80° C. or lower, more preferably 20° C. or lower, even more preferably 10° C. or lower, and even more preferably 0° C. or lower. The glass transition point of the acrylic resin particles is preferably −50° C. or higher, and more preferably −35° C. or higher. The glass transition point of the acrylic resin particles is, for example, preferably −50 to 80° C., more preferably −35 to 20° C., even more preferably −35 to 10° C., and even more preferably −35 to 0° C.

[0034] Commercially available resin emulsions of solid resin particles B include, for example, "Movinyl 966A" (product name) manufactured by Japan Coating Resins Co., Ltd., "Joncryl 7100" (product name) manufactured by BASF, and "Takelac W-635" manufactured by Mitsui Chemicals, Inc.

[0035] The solid resin particles B may be used alone or in combination of two or more.

[0036] When an appropriate amount of solid resin particles B is contained, the fixation to the substrate is improved and the flatness of the surface of the white ink layer can be improved. From the viewpoint of forming a good ink image when color printing is performed on a white ink layer, the content (solid content) of solid resin particles B in the white ink is preferably less than the content (solid content) of hollow resin particles A. The mass ratio of solid resin particles B to hollow resin particles A (solid resin particles B / hollow resin particles A) (both solid content) is preferably less than 1.0, more preferably 0.8 or less, and even more preferably 0.75 or less. On the other hand, from the viewpoint of imparting good gloss and fixing the hollow resin particles A to the substrate, the mass ratio of the solid resin particles B to the hollow resin particles A (solid resin particles B / hollow resin particles A) (both solid content) is preferably 0.1 or more, more preferably 0.25 or more, and even more preferably 0.4 or more. The mass ratio of solid resin particles B to hollow resin particles A (solid resin particles B / hollow resin particles A) (both solid content) is, for example, preferably 0.1 or more and less than 1.0, more preferably 0.25 or more and 0.8 or less, and even more preferably 0.4 or more and 0.75 or less.

[0037] The content (solid content) of the solid resin particles B in the white ink is preferably 0.5 to 20% by mass, and more preferably 1 to 10% by mass, relative to the total amount of the ink.

[0038] The white ink preferably contains water as an aqueous solvent, and the main solvent may be water. The water is not particularly limited, but it is preferable that the water contains as few ionic components as possible. In particular, from the viewpoint of storage stability of the ink, it is preferable that the content of polyvalent metal ions such as calcium is low. As the water, for example, ion-exchanged water, distilled water, ultrapure water, etc. may be used. From the viewpoint of adjusting the ink viscosity, the water content is preferably 20 to 90% by mass, more preferably 30 to 80% by mass, and even more preferably 40 to 70% by mass, of the total amount of the white ink.

[0039] It is preferable that a water-soluble organic solvent is blended into the white ink. As the water-soluble organic solvent, an organic compound that is liquid at room temperature and soluble in water can be used, and it is preferable to use a water-soluble organic solvent that is uniformly mixed with an equal volume of water at 20°C under 1 atmosphere. Examples of the water-soluble organic solvent include lower alcohols such as methanol, ethanol, 1-propanol, isopropanol, 1-butanol, 2-butanol, isobutanol, and 2-methyl-2-propanol; glycols such as ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, and polypropylene glycol; glycerins such as glycerin, diglycerin, triglycerin, and polyglycerin; acetins such as monoacetin and diacetin; ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monopropyl ether, diethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monopropyl ether, diethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monopropyl ether, diethylene glycol monobutyl ether, diethylene glycol monopropyl ... Examples of suitable water-soluble organic solvents include glycol ethers such as ethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monopropyl ether, diethylene glycol monobutyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monopropyl ether, triethylene glycol monobutyl ether, tetraethylene glycol monomethyl ether, tetraethylene glycol monoethyl ether, tetraethylene glycol dimethyl ether, and tetraethylene glycol diethyl ether; triethanolamine, 1-methyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, β-thiodiglycol, and sulfolane. The boiling point of the water-soluble organic solvent is preferably 100° C. or higher, and more preferably 150° C. or higher.

[0040] The water-soluble organic solvent preferably contains an alkylene glycol alkyl ether such as diethylene glycol monoethyl ether, a 1,2-alkanediol such as ethylene glycol, or a combination thereof. When an alkylene glycol alkyl ether and / or a 1,2-alkanediol is blended, it becomes easier to stably blend an acetylene glycol surfactant having an HLB value of 10.0 or less (described below) into the ink. This may further increase the likelihood of the hollow resin particles A remaining on the substrate surface.

[0041] The above-mentioned water-soluble organic solvents may be used alone or in combination of two or more kinds as long as they form a single phase with water. The content of the water-soluble organic solvent in the white ink is preferably 5 to 50% by mass, and more preferably 10 to 35% by mass, relative to the total amount of the ink.

[0042] The white ink preferably contains a surfactant. The surfactant may be an anionic surfactant, a cationic surfactant, an amphoteric surfactant, a nonionic surfactant, or a combination thereof, and more preferably a nonionic surfactant. In addition, either a low-molecular-weight surfactant or a high-molecular-weight surfactant may be used.

[0043] Examples of nonionic surfactants include ester surfactants such as glycerin fatty acid esters and fatty acid sorbitan esters; ether surfactants such as polyoxyethylene alkyl ethers, polyoxyethylene alkylphenyl ethers and polyoxypropylene alkyl ethers; ether ester surfactants such as polyoxyethylene sorbitan fatty acid esters; acetylene surfactants; silicone surfactants; fluorine surfactants; etc. Among these, acetylene surfactants and silicone surfactants are preferably used.

[0044] Examples of the acetylene surfactant include an acetylene glycol surfactant, an acetylene alcohol surfactant, and a surfactant having an acetylene group. The acetylene glycol surfactant is a glycol having an acetylene group, preferably a glycol having a symmetrical structure with the acetylene group located in the center, and may have a structure in which ethylene oxide is added to acetylene glycol. Commercially available acetylene surfactants include, for example, the Surfynol series manufactured by Evonik Industries, such as "Surfynol 104E," "Surfynol 104H," "Surfynol 420," "Surfynol 440," "Surfynol 465," and "Surfynol 485," and the Olfin series manufactured by Nissin Chemical Industry Co., Ltd., such as "Olfin E1004," "Olfin E1010," and "Olfin E1020" (all trade names).

[0045] Examples of silicone surfactants include polyether-modified silicone surfactants, alkyl-aralkyl-co-modified silicone surfactants, and acrylic silicone surfactants. Examples of commercially available silicone surfactants include "Silface SAG002," "Silface 503A," and "Silface SAG008" manufactured by Nissin Chemical Industry Co., Ltd. (all trade names). Other nonionic surfactants include polyoxyethylene alkyl ether surfactants such as those in the Emulgen series manufactured by Kao Corporation, including "Emulgen 102KG," "Emulgen 103," "Emulgen 104P," "Emulgen 105," "Emulgen 106," "Emulgen 108," "Emulgen 120," "Emulgen 147," "Emulgen 150," "Emulgen 220," "Emulgen 350," "Emulgen 404," "Emulgen 420," "Emulgen 705," "Emulgen 707," "Emulgen 709," "Emulgen 1108," "Emulgen 4085," and "Emulgen 2025G" (all trade names).

[0046] Examples of anionic surfactants include the Emeral series, manufactured by Kao Corporation, such as "Emeral 0," "Emeral 10," "Emeral 2F," "Emeral 40," and "Emeral 20C," the Neopelex series, such as "Neopelex GS," "Neopelex G-15," "Neopelex G-25," and "Neopelex G-65," the Pelex series, such as "Pelex OT-P," "Pelex TR," "Pelex CS," "Pelex TA," "Pelex SS-L," and "Pelex SS-H," and the Demol series, such as "Demol N," "Demol NL," "Demol RN," and "Demol MS" (all of which are trade names).

[0047] Examples of cationic surfactants include the Acetamine series (manufactured by Kao Corporation) such as "Acetamine 24" and "Acetamine 86," the Cortamine series (manufactured by Kao Corporation) such as "Cortamine 24P," "Cortamine 86P," "Cortamine 60W," and "Cortamine 86W," and the Sanisol series (manufactured by Kao Corporation) such as "Sanisol C" and "Sanisol B-50" (all trade names).

[0048] Examples of amphoteric surfactants include the Amphitol series manufactured by Kao Corporation, such as Amphitol 20BS, Amphitol 24B, Amphitol 86B, Amphitol 20YB, and Amphitol 20N (all trade names). The above surfactants may be used alone or in combination of two or more.

[0049] The HLB value of the surfactant used in the white ink is preferably 10.0 or less. The surfactant used in the white ink is preferably an acetylene-based surfactant such as an acetylene glycol-based surfactant, and more preferably an acetylene glycol-based surfactant. Here, the HLB value is one of the scales that indicate the properties of a surfactant, and is a numerical representation of the balance between hydrophilic groups and lipophilic groups in the molecule. The HLB value has been proposed by several calculation methods, but in this specification, it is a value calculated by the Griffin method, and is calculated by the following formula (1): HLB value = 20 × (formula weight of hydrophilic part) / (molecular weight of surfactant) Equation (1) Here, the "hydrophilic moiety" refers to a hydrophilic portion contained in the molecular structure of the surfactant, and is preferably a polyoxyalkylene group, an alcohol group having three or less carbon atoms in the main chain relative to the hydroxyl group, or a combination thereof. When the surfactant contains multiple hydrophilic moieties, the formula weight of the hydrophilic moiety in the above formula (1) is the total amount of these. The polyoxyalkylene group includes a polyoxyethylene group (polyethylene oxide; EO: -(CH2CH2O) n -), polyoxypropylene group (polypropylene oxide; PO: -(CH2CH(CH3)O) n -) etc. Examples of alcohol groups include groups derived from methanol, ethanol, propanol, isopropanol, glycerin, polyglycerin, trimethylolpropane, pentaerythritol, sorbitol, sorbitan, sucrose (cane sugar), mannitol, glycols, etc. (for example, —CH2CH2OH for ethanol). The "hydrophobic portion" refers to the hydrophobic portion contained in the molecular structure of the surfactant, and is, for example, an aliphatic hydrocarbon group or aromatic hydrocarbon group derived from an aliphatic alcohol, alkylphenol, fatty acid, etc., having four or more carbon atoms in the main chain relative to the hydroxyl group; a group derived from an organic siloxane, alkyl halide, etc.; or a combination thereof. From the viewpoint of increasing the speed at which the white ink wets the substrate and making it easier for the hollow resin particles A to remain on the substrate, it is preferable that the white ink contains an acetylene-based surfactant with an HLB of 10.0 or less, and it is more preferable that the white ink contains an acetylene glycol-based surfactant with an HLB of 10.0 or less.

[0050] The amount of surfactant blended in the white ink is preferably 0.1 to 5.0% by mass, and more preferably 0.5 to 3.0% by mass, based on the total amount of the white ink.

[0051] The white ink may contain other components as appropriate, such as a pH adjuster and a preservative.

[0052] The viscosity of the white ink at 23°C is preferably 3.0 to 20.0 mPa·s, more preferably 4.0 to 16.0 mPa·s, and even more preferably 6.0 to 14.0 mPa·s.

[0053] The method for preparing the white ink is not particularly limited, but the desired ink can be obtained by appropriately mixing the components. For example, a dispersing machine such as a bead mill may be used. The obtained composition may also be filtered using a filter. Various additives may also be added as appropriate. The white ink can be preferably used as a water-based white inkjet ink.

[0054] The white ink is preferably applied to, for example, substrates with large surface irregularities, substrates with many voids, etc. The white ink can impart a suitable gloss to the printed portion of substrates that do not have a glossy surface, such as substrates with large surface irregularities, substrates with many voids, etc. In particular, substrates with suitable liquid absorption and irregularities, such as calcium silicate boards, humidity-conditioning building materials, printing paper, wood, and cloth, are more preferred.

[0055] Examples of printing paper include plain paper and coated paper. Here, plain paper refers to ordinary paper on which no ink-receiving layer or film layer is formed. Examples of plain paper include fine paper, medium-quality paper, PPC paper, wood paper, recycled paper, etc.

[0056] Furthermore, as the coated paper, inkjet coated paper such as matte paper, glossy paper, and semi-glossy paper, as well as so-called coated printing paper, can be preferably used. Here, coated printing paper refers to printing paper that has traditionally been used in letterpress printing, offset printing, gravure printing, and the like, and is printing paper in which a coating layer is provided on the surface of fine or medium-quality paper with a paint containing an inorganic pigment such as clay or calcium carbonate and a binder such as starch. Coated printing paper is classified into lightly coated paper, fine lightweight coated paper, medium lightweight coated paper, fine coated paper, medium coated paper, art paper, cast coated paper, and the like, depending on the amount of paint applied and the coating method.

[0057] For example, a material that provides appropriate liquid absorption and unevenness, such as diatomaceous earth, may be applied to the surface of a smooth substrate such as a film or a metal plate, and used as the substrate. Furthermore, for example, by printing the white ink of one embodiment on a substrate obtained by applying a material that provides unevenness in this way, it is possible to obtain a printed product having a matte portion obtained by applying a material that provides unevenness to a substrate that originally has a smooth surface, and a glossy portion obtained by further printing white ink on the matte portion.

[0058] <Manufacturing method for printed matter> A method for producing a printed matter according to one embodiment includes the steps of: applying an aqueous inkjet ink to a substrate by inkjet printing; the aqueous inkjet ink contains hollow resin particles A having depressions on their outer surfaces, water, and solid resin particles B, with the hollow resin particles A content being 5% to less than 20% by mass of the total ink; and applying an aqueous inkjet ink (hereinafter sometimes referred to as a "color ink") containing water and a non-white colorant to the substrate to which the aqueous inkjet ink has been applied by inkjet printing. The aqueous inkjet ink containing hollow resin particles A having depressions on their outer surfaces, water, and solid resin particles B, with the hollow resin particles A content being 5% to less than 20% by mass of the total ink, can be the white ink according to the embodiment described above. The substrate can also be, for example, a substrate suitable for use with the white ink according to the embodiment described above. In the following description of the method for producing printed matter, an aqueous inkjet ink containing hollow resin particles A having depressions on their outer surfaces, water, and solid resin particles B, in which the content of hollow resin particles A is 5% by mass or more and less than 20% by mass of the total ink, may be referred to as a "white ink."

[0059] Examples of color inks include achromatic or chromatic inks other than white, such as magenta ink, cyan ink, yellow ink, and black ink. The color ink may contain a pigment, a dye, or a combination thereof as a non-white colorant, and more preferably contains a pigment.

[0060] The color ink preferably contains a non-white pigment. Non-white pigments include organic pigments such as azo pigments, phthalocyanine pigments, polycyclic pigments, and dye lake pigments, as well as inorganic pigments such as carbon black and metal oxides. Examples of azo pigments include soluble azo lake pigments, insoluble azo pigments, and condensed azo pigments. Examples of phthalocyanine pigments include metal phthalocyanine pigments and metal-free phthalocyanine pigments. Examples of polycyclic pigments include quinacridone pigments, perylene pigments, perinone pigments, isoindoline pigments, isoindolinone pigments, dioxazine pigments, thioindigo pigments, anthraquinone pigments, quinophthalone pigments, metal complex pigments, and diketopyrrolopyrrole (DPP). Examples of carbon black include furnace carbon black, lamp black, acetylene black, and channel black. These pigments may be used alone or in combination.

[0061] From the viewpoints of ejection stability and storage stability, the average particle size of the pigment particles in the color ink is preferably 300 nm or less, more preferably 150 nm or less, and even more preferably 100 nm or less, as the volume-based average value in the particle size distribution measured by dynamic light scattering.

[0062] A self-dispersing pigment may be used as the pigment. A self-dispersing pigment is a pigment in which a hydrophilic functional group has been introduced onto its surface by chemical or physical treatment. The hydrophilic functional group introduced into the self-dispersing pigment is preferably ionic. By charging the pigment surface anionically or cationic, the pigment particles can be stably dispersed in water due to electrostatic repulsion. Preferred anionic functional groups include carboxyl groups, sulfo groups, sulfino groups, sulfate ester groups, phosphate groups, phosphate ester groups, phosphite groups, and phosphite ester groups. Preferred cationic functional groups include quaternary ammonium groups and quaternary phosphonium groups.

[0063] These hydrophilic functional groups may be bonded directly to the pigment surface or via other atomic groups. Examples of such other atomic groups include, but are not limited to, alkylene groups, phenylene groups, and naphthylene groups. Examples of methods for treating the pigment surface include diazotization, sulfonation, hypochlorous acid treatment, humic acid treatment, and vacuum plasma treatment.

[0064] Preferred examples of self-dispersing pigments that can be used include the CAB-O-JET series manufactured by Cabot Corporation, such as "CAB-O-JET200," "CAB-O-JET300," "CAB-O-JET250C," "CAB-O-JET260M," "CAB-O-JET270," "CAB-O-JET450C," "CAB-O-JET465M," and "CAB-O-JET470Y," and products manufactured by Orient Chemical Industries Co., Ltd., such as "BONJET BLACK CW-1," "BONJET BLACK CW-2," "BONJET BLACK CW-3," and "BONJET BLACK CW-4" (all trade names). As the pigment, a microencapsulated pigment in which the pigment is coated with a resin may be used.

[0065] A pigment dispersion in which the pigment is dispersed in advance with a pigment dispersant may be used. Commercially available pigment dispersions dispersed with a pigment dispersant include, for example, the HOSTAJET series manufactured by Clariant and the FUJI SP series manufactured by Fuji Pigment Co., Ltd. A pigment dispersion dispersed with a pigment dispersant described below may also be used.

[0066] As non-white dyes, water-soluble dyes and water-soluble dyes made water-soluble by reduction or the like can be preferably used from among basic dyes, acid dyes, direct dyes, soluble vat dyes, acid mordant dyes, mordant dyes, reactive dyes, vat dyes, sulfur dyes, etc. Also preferably used are disperse dyes such as azo-based, anthraquinone-based, azomethine-based, and nitro-based dyes. These may be used alone or in combination.

[0067] From the viewpoint of print density and ink viscosity, the content of the color material is preferably 0.5 to 20.0 mass % of the total amount of color ink, more preferably 1.0 to 15.0 mass %, and even more preferably 2.0 to 10.0 mass %.

[0068] When the color ink contains a pigment, a pigment dispersant, such as a polymer dispersant or a surfactant-type dispersant, can be used to stably disperse the pigment in the ink. Examples of commercially available polymer dispersants include the TEGO Disperse series manufactured by EVONIK, such as "TEGO Disperse 740W," "TEGO Disperse 750W," "TEGO Disperse 755W," "TEGO Disperse 757W," and "TEGO Disperse 760W," and the Solsperse series manufactured by Lubrizol Japan, such as "Solsperse 20000," "Solsperse 27000," "Solsperse 41000," "Solsperse 41090," "Solsperse 43000," "Solsperse 44000," and "Solsperse 46000," and the Solsperse series manufactured by BASF Japan. Examples include the Johncryl series manufactured by Pan Co., Ltd., such as "Johncryl 57," "Johncryl 60," "Johncryl 62," "Johncryl 63," "Johncryl 71," and "Johncryl 501," as well as products manufactured by BYK Japan KK, such as "DISPERBYK-102," "DISPERBYK-180," "DISPERBYK-185," "DISPERBYK-190," "DISPERBYK-193," and "DISPERBYK-199," as well as products manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., such as "Polyvinylpyrrolidone K-30" and "Polyvinylpyrrolidone K-90" (all trade names). Examples of surfactant-type dispersants include anionic surfactants such as the Demol series manufactured by Kao Corporation, including "Demol P," "Demol EP," "Demol N," "Demol RN," "Demol NL," "Demol RNL," and "Demol T-45," and nonionic surfactants such as the Emulgen series manufactured by Kao Corporation, including "Emulgen A-60," "Emulgen A-90," "Emulgen A-500," "Emulgen B-40," "Emulgen L-40," and "Emulgen 420" (all trade names).

[0069] The above pigment dispersants may be used alone or in combination of two or more. When a pigment dispersant is used, the amount to be blended in the ink varies depending on the type and is not particularly limited, but in general, the mass ratio of the active ingredient (pigment concentration) to the pigment is preferably 0.01 to 1.0.

[0070] The color ink preferably contains water as an aqueous solvent, and the main solvent may be water. The water is not particularly limited, but it is preferable that the water contains as few ionic components as possible. In particular, from the viewpoint of storage stability of the ink, it is preferable that the content of polyvalent metal ions such as calcium is low. As the water, for example, ion-exchanged water, distilled water, ultrapure water, etc. may be used. From the viewpoint of adjusting the ink viscosity, the water content is preferably 20 to 90% by mass, and more preferably 30 to 80% by mass, of the total amount of the color ink.

[0071] The color ink may contain a water-soluble organic solvent. As the water-soluble organic solvent, an organic compound that is liquid at room temperature and dissolves in water may be used, and it is preferable to use a water-soluble organic solvent that is uniformly miscible with an equal volume of water at 20°C under 1 atmosphere. The water-soluble organic solvent can be selected from those described above for the white ink.

[0072] These water-soluble organic solvents may be used alone or in combination of two or more types as long as they form a single phase with water. The content of the water-soluble organic solvent in the color ink is preferably 5 to 50% by mass, and more preferably 10 to 35% by mass.

[0073] The color ink preferably contains a surfactant.

[0074] The surfactant may be an anionic surfactant, a cationic surfactant, an amphoteric surfactant, a nonionic surfactant, or a combination thereof, and more preferably a nonionic surfactant. In addition, either a low-molecular-weight surfactant or a high-molecular-weight surfactant may be used. The surfactant can be selected from those described above for the white ink.

[0075] The surfactant preferably has an active ingredient content of 0.05 to 5.0% by mass, more preferably 0.1 to 3.0% by mass, based on the total amount of the color ink.

[0076] The color ink preferably contains a water-dispersible resin, which is resin particles that can be dispersed in an aqueous solvent. The water-dispersible resin may be the same as or different from the solid resin particles B. The water-dispersible resin exhibits water dispersibility and can be dispersed in water without dissolving in water to form an oil-in-water (O / W) emulsion. The water-dispersible resin is preferably contained in the color ink in a dispersed state as resin particles. The water-dispersible resin can be blended as a resin emulsion when producing the color ink. As the type of water-dispersible resin, it is preferable to use a resin that forms a transparent coating film.

[0077] The average particle size of the water-dispersible resin is preferably 250 nm or less, more preferably 200 nm or less, and even more preferably 150 nm or less. The average particle size of the water-dispersible resin is preferably 1 nm or more, more preferably 5 nm or more, and even more preferably 10 nm or more. The average particle size of the water-dispersible resin is, for example, preferably 1 to 300 nm, more preferably 5 to 200 nm, and even more preferably 10 to 150 nm. Here, the average particle size of the water-dispersible resin is the volume-based particle size value (median size) in the particle size distribution measured by dynamic light scattering.

[0078] The water-dispersible resin may be a resin in which functional groups are present on the surface of the resin particles, such as a self-emulsifying resin, or may be a resin that has been subjected to a surface treatment such as attaching a dispersant to the surface of the resin particles. The water-dispersible resin may be an anionic, cationic, nonionic, or amphoteric water-dispersible resin, and preferably is an anionic, nonionic, or a combination thereof.

[0079] Examples of water-dispersible resins include: Conjugated diene resins such as styrene-butadiene copolymer, methyl methacrylate-butadiene copolymer, vinyl chloride-vinyl acetate copolymer, etc.; acrylic resins such as polymers of acrylic acid esters and methacrylic acid esters, or copolymers thereof with styrene, etc.; vinyl resins such as ethylene-vinyl acetate copolymers, or functional group-modified resins of these various resins with a monomer containing a functional group such as a carboxyl group; Examples of the resin include melamine resin, urea resin, polyurethane resin, polyester resin, polyolefin resin, silicone resin, polyvinyl butyral resin, alkyd resin, etc. A resin emulsion of one of these resins may be used, or a hybrid resin emulsion may be used.

[0080] Commercially available resin emulsions of water-dispersible resins include "Superflex 470" (trade name) manufactured by Daiichi Kogyo Seiyaku Co., Ltd.

[0081] These water-dispersible resins may be used alone or in combination of two or more. The content (solid content) of the water-dispersible resin in the color ink is preferably 0.5 to 20% by mass, and more preferably 1 to 10% by mass.

[0082] The color ink may contain other components as appropriate, such as a pH adjuster and a preservative.

[0083] The viscosity of the color ink at 23°C is preferably 1.0 to 20.0 mPa·s, more preferably 2.0 to 16.0 mPa·s, and even more preferably 3.0 to 14.0 mPa·s. The method for preparing the color ink is not particularly limited, but the desired ink can be obtained by appropriately mixing the components. For example, a dispersing machine such as a bead mill may be used to improve the dispersibility of the pigment. The obtained composition may also be filtered using a filter or the like. Various additives may also be added as appropriate. The color inks can be preferably used as aqueous color inkjet inks.

[0084] The method for producing a printed matter can include a step of applying white ink to a substrate by an inkjet method, and a step of applying color inks by an inkjet method to the substrate to which the white ink has been applied. The inkjet method is not particularly limited, and may be any of a piezoelectric method, an electrostatic method, a thermal method, etc. When an inkjet printing device is used, it is preferable to eject ink droplets from an inkjet head based on a digital signal and allow the ejected droplets to adhere to the substrate.

[0085] The process of applying the white ink to the substrate by the inkjet method will be described. The area to which the white ink is applied may be, for example, an area having the same shape as the image formed by the color inks, a wider area including the shape of the image formed by the color inks, only a part of the image formed by the color inks, or an area including a part of the image formed by the color inks and other parts. The area to which the white ink is applied may be, for example, the entire surface of the base material. It is preferable that the area where the white ink is applied and the area where the color ink is applied at least partially overlap each other.

[0086] The amount of white ink applied to the substrate is 10 to 400 g / m 2 is preferred, and 15 to 300 g / m2 More preferably, 20 to 200 g / m 2 is more preferred.

[0087] The process of applying color inks by an inkjet method to the substrate to which the white ink has been applied will be described. The area to which the color inks are applied may be, for example, an area of ​​the same shape as the white ink image, a wider area including the shape of the white ink image, only a part of the white ink image, or an area including a part of the white ink image and other areas. The area to which the color inks are applied may be, for example, the entire surface of the base material. It is preferable that the area where the color ink is applied and the area where the white ink is applied at least partially overlap each other.

[0088] The amount of color ink applied to the substrate is not particularly limited, but may be, for example, 5 to 50 g / m 2 is preferable, and 10 to 40 g / m 2 is more preferred.

[0089] One type of color ink may be applied, or two or more types of color ink may be applied.

[0090] The method for producing a printed matter may include other steps. For example, a step of drying the substrate may be included between a step of applying a white ink to the substrate by an inkjet method and a step of applying a color ink to the substrate to which the white ink has been applied by an inkjet method. The method of drying the substrate is not particularly limited, but examples include a method of leaving the substrate at room temperature for a certain period of time to dry, and the leaving time is preferably, for example, 1 minute to 24 hours. The method for producing a printed material preferably includes, for example, a step of applying color inks by an inkjet method to a substrate to which white ink has been applied, followed by a step of heat-treating the substrate. The heat-treatment temperature is, for example, preferably 30 to 250°C, more preferably 35 to 200°C. The heating device is not particularly limited, but examples of usable devices include a dryer, oven, and infrared heater. The heat-treatment time is, for example, preferably 30 seconds to 10 minutes, more preferably 1 to 5 minutes.

[0091] An ink set according to one embodiment may include an aqueous inkjet ink containing hollow resin particles A having recesses on their outer surfaces, water, and solid resin particles B, with the hollow resin particles A content being 5% by mass or more and less than 20% by mass of the total ink volume, and an aqueous inkjet ink containing water and a non-white coloring material. The aqueous inkjet ink containing hollow resin particles A having recesses on their outer surfaces, water, and solid resin particles B, with the hollow resin particles A content being 5% by mass or more and less than 20% by mass of the total ink volume, may be the white ink according to the embodiment described above. Furthermore, the aqueous inkjet ink containing water and a non-white coloring material may be the color ink described in the method for producing a printed material according to the embodiment described above. The ink set may contain only one type of color ink, or may contain two or more types of color inks. [Example]

[0092] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples. In the following explanation, "%" means "% by mass" unless otherwise specified. The content shown in each table indicates the total amount of raw materials blended as a solution or dispersion, and also indicates the percentage of non-volatile matter or active ingredients, etc.

[0093] <Production of Inorganic Particle Dispersions (Dispersions C to E)> Table 1 shows the formulations of hollow silica particle dispersion (Dispersion C), titanium oxide particle dispersion (Dispersion D), and flat mica particle dispersion (Dispersion E). The materials shown in Table 1 were weighed into a beaker in the proportions shown in Table 1 so that the total amount was 300 g, premixed, and then dispersed in an ultrasonic disperser for 5 minutes to produce Dispersions C to E.

[0094] The details of the raw materials listed in Table 1 are as follows:

[0095] Hollow silica particles: "Silinax" (trade name), manufactured by Nittetsu Mining Co., Ltd., hollow silica particles, average particle diameter 0.1 μm Titanium oxide particles: "A-100" (trade name), manufactured by Ishihara Sangyo Kaisha, Ltd., titanium oxide particles (solid), average particle size 0.15 μm Flat mica particles: "Pearl Glaze MM-100R" (product name), manufactured by Nihon Koken Kogyo Co., Ltd., solid flat mica particles, average particle diameter less than 15 μm Polymer dispersant: "DISPERBYK-180" (trade name), manufactured by BYK Japan Co., Ltd., non-volatile content 81.0% by mass

[0096] [Table 1]

[0097] <White ink production> Tables 2 to 5 show the formulations of White Inks 1 to 14. The materials listed in Tables 2 to 5 were mixed in the proportions shown in Tables 2 to 5, and then filtered through a membrane filter with a pore size of 5 μm to obtain White Inks 1 to 14. Note that White Ink 14 was not passed through the membrane filter due to its large particle size. Note that in Tables 2 to 5 and 7 to 9, W Inks 1 to 14 refer to White Inks 1 to 14.

[0098] Details of the raw materials listed in Tables 2 to 5 are as follows.

[0099] (dispersion) Dispersion A: "FUJI SP WHITE 1185" (trade name), manufactured by Fuji Pigment Co., Ltd., dispersion of hollow resin particles A having recesses on the outer surface, acrylic resin, average particle diameter 0.45 μm, non-volatile content 29.6% by mass Dispersion B: "SANSUI A-170" (trade name), manufactured by Sansui Co., Ltd., spherical hollow resin particle dispersion, non-volatile content 17.0% by mass, average particle diameter 1 μm Dispersion C: hollow silica particle dispersion prepared as above, nonvolatile content 20.0% by mass Dispersion D: Titanium oxide particle dispersion prepared as above, nonvolatile content 20.0% by mass Dispersion E: Produced as above, flat mica particle dispersion, nonvolatile content 20.0% by mass

[0100] The average particle size of each particle in Dispersions A and B represents the volume-based median size, and was measured under the following conditions using a nanoparticle analyzer "nano Partica SZ-100," a dynamic light scattering particle size distribution measuring device manufactured by HORIBA, Ltd. Sample: Prepared by diluting with water to a particle concentration of 0.5% by mass. Dispersion medium refractive index: 1.333. Sample refractive index: 1.600. Calculation conditions: polydispersity, narrow. Temperature: 25℃.

[0101] (Resin emulsion: Resin emulsion of solid resin particles B) "Joncryl 7100" (product name): BASF Japan Ltd., acrylic resin emulsion, glass transition temperature (Tg) = -10°C, non-volatile content 48.0% by mass "Movinyl 966A" (product name): manufactured by Japan Coating Resin Co., Ltd., acrylic resin emulsion, glass transition temperature (Tg) = -32°C, non-volatile content 45.0% by mass "Takelac W-635" (product name): manufactured by Mitsui Chemicals, Inc., carbonate-based polyurethane resin emulsion, glass transition temperature (Tg) = 70°C, non-volatile content 35.0% by mass

[0102] (Water-soluble organic solvent) Glycerin: Fujifilm Wako Pure Chemical Industries, Ltd. Ethylene glycol: Fujifilm Wako Pure Chemical Industries, Ltd. Diethylene glycol monoethyl ether: Fujifilm Wako Pure Chemical Industries, Ltd. Trimethylolpropane: manufactured by Tokyo Chemical Industry Co., Ltd.

[0103] (surfactant) "Surfynol 440" (trade name): manufactured by Nissin Chemical Industry Co., Ltd., acetylene glycol surfactant, HLB=8.1, active ingredient 100% by mass "Surfynol 485" (trade name): manufactured by Nissin Chemical Industry Co., Ltd., acetylene glycol surfactant, HLB=17.1, active ingredient 100% by mass "Silface SAG008" (product name): manufactured by Nissin Chemical Industry Co., Ltd., silicone surfactant, HLB=7, active ingredient 100% by mass

[0104] [Table 2]

[0105] [Table 3]

[0106] [Table 4]

[0107] [Table 5]

[0108] <Color ink manufacturing> Table 6 shows the formulations of four color inks (Ink K, Ink C, Ink M, and Ink Y), which are aqueous inkjet inks containing a non-white colorant. The materials listed in Table 6 were premixed in the proportions shown in Table 6, then dispersed in a homogenizer for 1 minute, and then filtered through a membrane filter with a pore size of 3 μm to obtain four color inks: Ink K, Ink C, Ink M, and Ink Y. The ink set containing Ink K, Ink C, Ink M, and Ink Y was designated as Water-Based Ink Set 1.

[0109] Details of the raw materials listed in Table 6 are as follows: (Pigment dispersion) "CAB-O-JET 300" (product name): manufactured by Cabot Corporation, water-based self-dispersing carbon black dispersion, pigment 15.0% by mass "CAB-O-JET 450C" (product name): Cabot Corporation, water-based self-dispersing pigment (cyan) dispersion, pigment 15.0% by mass "CAB-O-JET 465M" (product name): Cabot Corporation, water-based self-dispersing pigment (magenta) dispersion, pigment 24.0% by mass "CAB-O-JET 470Y" (product name): Cabot Corporation, water-based self-dispersing pigment (yellow) dispersion, pigment 15.0% by mass

[0110] (resin emulsion) "Superflex 470" (product name): Daiichi Kogyo Seiyaku Co., Ltd., water-based polyurethane resin emulsion, non-volatile content 38.0% by mass

[0111] (surfactant) "Surfynol 485" (product name): Nissin Chemical Industry Co., Ltd., acetylene glycol surfactant

[0112] (Water-soluble organic solvent) Glycerin: Fujifilm Wako Pure Chemical Industries, Ltd. Ethylene glycol: Fujifilm Wako Pure Chemical Industries, Ltd.

[0113] [Table 6]

[0114] <Production of white and color prints> (Target substrate) In the following, commercially available black fine paper (A4 size) was used as the substrate for producing white prints, and calcium silicate board (A4 size) was used as the substrate for producing color prints.

[0115] (Creating white prints) Tables 7 to 9 show the white inks used to prepare white printed matter in each of the Examples and Comparative Examples and the applied amounts of the white inks (wet applied amounts). Using the white inks shown in Tables 7 to 9 and black wood-free paper as a substrate, white printed matter of each example and comparative example was produced as follows.

[0116] For Examples 1 to 9 and Comparative Examples 1 to 5, which used White Inks 1 to 13 among the white inks, the white inks were introduced into a print head "RC1536M" (product name) manufactured by SII Printec Inc., and applied in the amount of coating (approximately 20 to 50 g / m) shown in Tables 7 to 9. 2 ) and left to dry for 1 hour to obtain a white printed matter with a white solid image printed thereon. In Comparative Example 6, which used White Ink 14, it was not possible to eject White Ink 14 using an inkjet head. Therefore, a 3 cm x 3 cm square mask was placed on the substrate, and a Wagner handheld sprayer "WAGNER W550" (product name) was used to apply a coating amount of 50 g / m. 2 A 3 cm x 3 cm square white solid image was printed so that the size of the printed white solid image was 3 cm x 3 cm, and the printed white solid image was left to dry for 1 hour to obtain a white printed matter.

[0117] (Production of color prints) The same white ink as used in producing the white printed matter described above was used in producing the color printed matter of each Example and Comparative Example. Tables 7 to 9 show the coating amounts (wet coating amounts) of the white ink and color inks used in producing the color printed matter of each Example and Comparative Example. Using the white ink and Ink Set 1 shown in Tables 7 to 9 and calcium silicate board as the substrate, the color printed matter of each Example and Comparative Example was produced as follows.

[0118] In Examples 1 to 9 and Comparative Examples 1 to 5, which used White Inks 1 to 13 among the white inks, the white ink was introduced into a print head "RC1536M" (product name) manufactured by SII Printec Inc., and applied to the substrate in an amount of about 20 to 50 g / m 2 A 3 cm x 3 cm square white solid image, a 3 cm x 3 cm square white gradation image, and white text were printed on the surface, and the surface was left to dry for 1 hour.

[0119] In Comparative Example 6, which used White Ink 14, since it was impossible to eject White Ink 14 using an inkjet head, a 3 cm x 3 cm square mask was placed on the substrate, and the ink was applied in an amount of 50 g / m using a Wagner handheld sprayer "WAGNER W550" (product name). 2 A 3 cm x 3 cm solid white image was printed on the surface, and the image was left to dry for 1 hour.

[0120] Ink Set 1 was loaded into a Mastermind inkjet printer "MMP845H" (product name), and solid images, gradation images, and text were printed using Ink Set 1 on the white ink-printed areas and non-printed areas of the calcium silicate board that had been previously white ink-printed. Specifically, using Ink Set 1, a 3 cm x 3 cm solid image (hereinafter sometimes referred to as "color ink solid image WC") was printed on a 3 cm x 3 cm white solid image, a 3 cm x 3 cm gradient image (hereinafter sometimes referred to as "color ink gradation image WC") on a 3 cm x 3 cm white gradation image, and the same text on white text (hereinafter sometimes referred to as "color ink text WC"). A similar 3 cm x 3 cm solid image (hereinafter sometimes referred to as "color ink solid image C"), a 3 cm x 3 cm gradation image, and text were also printed on the non-printed areas where white ink was not printed. After printing was completed, the board was dried at 90°C for 3 minutes to obtain a color print. In Comparative Example 6, a color print consisting of only a solid color ink image was produced.

[0121] <Evaluation> The white ink, white printed matter, and color printed matter prepared as described above were evaluated as follows. The results are shown in Tables 7 to 9.

[0122] 1. White ink inkjet ejection performance The prepared white inks (White Inks 1 to 14) were introduced into an inkjet head (print head "RC1536M" (trade name) manufactured by SII Printec Inc.), and ink was continuously ejected from all nozzles of the inkjet head for 1 minute. After leaving the head to stand for 1 minute, a nozzle check was performed and the number of nozzles that were unable to eject ink was counted. The evaluation criteria are shown below. X: Fewer than 5 nozzles failed to eject Y: 5 or more nozzles failed to eject The evaluation results for all of White Inks 1 to 12 were X, but the evaluation results for White Inks 13 and 14 were Y.

[0123] 2. Evaluation of white printed matter (Color development of white ink images) The color development of a solid white image on a white print made using black wood-free paper as a substrate was evaluated visually. The evaluation criteria are shown below. AA: The white color of the solid white image is clear and the background color is not visible. A: The white of the solid white image is a little dark, but clear. B: The white color of the solid white image is unclear and appears gray. C: The white color of the solid white image is not clear and is only faintly visible.

[0124] (Glossiness of white ink images) For white printed matter produced using black fine paper as the substrate, the 60° gloss of the solid white image and the non-printed areas where no white ink was printed was measured, and the difference between the 60° gloss of the solid white image and the 60° gloss of the non-printed areas (hereinafter sometimes referred to as the "gloss difference") was calculated using the following formula: The 60° gloss was measured using a gloss meter "VG7000" (product name) manufactured by Nippon Denshoku Industries Co., Ltd. Difference in glossiness = (60° glossiness of solid white image) - (60° glossiness of non-printed area where white ink is not printed)

[0125] Based on the gloss difference obtained by the above formula, the gloss of the white ink image was evaluated according to the following criteria. The greater the gloss difference, the better, as it allows for a change in texture within a single printed item. AA: The difference in gloss is +15 or more A: The difference in gloss is between +10 and +15. AB: The difference in gloss is +5 or more but less than +10 B: The difference in gloss is 0 or more and less than +5

[0126] 3. Evaluation of color prints (Color ink image quality) The color printed matter obtained above was visually evaluated for clarity of the color ink solid image WC printed on the white ink printed area, the color ink gradation image WC printed on the white ink printed area, and the color ink letters WC printed on the white ink printed area.

[0127] The evaluation criteria are shown below. AA: The colors are vivid, the text is clearly visible, and the gradation is clear. A: The color is slightly mixed with the base color (i.e. the color of the base material itself), but the color is natural, the letters are clearly visible, and the gradation is clear. B: The color is dark and uneven. The letters are a little hard to read, and the base color is mixed into the gradation, making it unclear. C: The image printed with color ink is difficult to see.

[0128] (Glossiness of color ink images) For the color printed matter obtained above, the 60° gloss of the color ink solid image WC printed in the white ink-printed area and the color ink solid image C printed in the non-printed area where no white ink was printed was measured, and the difference between the 60° gloss of the color ink solid image WC printed in the white ink-printed area and the 60° gloss of the color ink solid image C printed in the non-printed area where no white ink was printed (hereinafter sometimes referred to as the "difference in gloss of the color ink solid images") was calculated using the following formula. A gloss meter "VG7000" (trade name) manufactured by Nippon Denshoku Industries Co., Ltd. was used for the measurement. Difference in gloss level of color ink solid images = (60° gloss level of color ink solid image WC printed on white ink printed area) - (60° gloss level of color ink solid image C printed on non-printed area where white ink is not printed)

[0129] Based on the difference in glossiness of the color ink solid images obtained by the above formula, the glossiness of the color ink images was evaluated according to the following evaluation criteria. The greater the difference in glossiness of the color ink solid images, the better, as it is possible to impart a change in texture within a single printed item. AA: The difference in gloss level of the color ink solid image is +15 or more A: The difference in gloss level of the color ink solid image is between +10 and +15. B: The difference in gloss level of the color ink solid image is between +5 and +10 C: The difference in gloss level of the color ink solid image is 0 or more and less than +5

[0130] [Table 7]

[0131] [Table 8]

[0132] [Table 9]

[0133] As can be seen from the table, Examples 1 to 9 showed excellent results in all of the color development of the white ink image, the glossiness of the white ink image, the image quality of the color ink image, and the glossiness of the color ink image. Among them, Examples 1 to 3 showed even better results in all of the color development of the white ink image, the glossiness of the white ink image, the image quality of the color ink image, and the glossiness of the color ink image.

[0134] In Examples 4 and 5, white inks 5 and 6 were used, respectively, in which the solid resin particles B contained resin particles with a relatively high glass transition temperature (Tg). Comparing Examples 4 and 5 with Example 2, Example 2, in which the solid resin particles B had a relatively low glass transition temperature, showed better results in terms of glossiness of solid white images than Examples 4 and 5. In Examples 4 and 5, minute cracks occurred in the white ink film in the solid white images, which is thought to have caused the glossiness of the solid white images to be slightly lower than in Example 2.

[0135] In Example 6, white ink 8 was used, which contained a relatively small amount of solid resin particles B. Comparing Example 6 with Example 2, Example 2, which contained a relatively large amount of solid resin particles B, showed better results in terms of glossiness of the white ink image than Example 6.

[0136] Example 7 used white ink 4, which contained a relatively low amount of hollow resin particles A. Comparing Example 7 with Example 2, Example 2, which used white ink 2, which contained a relatively high amount of hollow resin particles A, showed better results than Example 7 in the color development of white ink images, the glossiness of white ink images, the image quality of color ink images, and the glossiness of color ink images.

[0137] White ink 7 containing a surfactant with a relatively high HLB was used in Example 8. In a comparison between Example 2 and Example 8, Example 2, which used white ink 2 containing a surfactant with a relatively low HLB, showed better results than Example 8 in the color development of white ink images, the glossiness of white ink images, the image quality of color ink images, and the glossiness of color ink images.

[0138] In Example 9, the amount of white ink 2 applied was less than the amount of white ink applied in Examples 1 to 8. In comparing Example 9 with Example 2, Example 2, in which the amount of white ink 2 applied was relatively greater, showed better results than Example 9 in the color development of the white ink image, the glossiness of the white ink image, the image quality of the color ink image, and the glossiness of the color ink image.

[0139] In Comparative Example 1, a white ink 9 containing spherical hollow resin particles with no recesses on the outer surface was used, but the color development of the white ink image, the image quality of the color ink image, and the glossiness of the color ink image were inferior to those of the Examples.

[0140] In Comparative Examples 2 and 3, white ink 10 containing spherical hollow silica particles and white ink 11 containing titanium oxide particles were used, respectively, but the color development of the white ink image, the image quality of the color ink image, and the gloss of the color ink image were inferior to those of the Examples. It is thought that the particles in the white ink penetrated into the substrate, resulting in insufficient color development of the white ink image and making the color ink image in the white ink-printed portion of the color printed product darker.

[0141] In Comparative Example 4, white ink 12 was used, which contained a small amount of hollow resin particles A in the ink, but the color development of the white ink image, the glossiness of the white ink image, and the image quality and glossiness of the color ink image were inferior to those of the Examples. It is thought that the white color development was insufficient, and as a result, the color ink images in the white ink-printed portions of the color printed matter also ended up being darker.

[0142] In Comparative Example 5, when white ink 13 containing a large amount of hollow resin particles A was introduced into the inkjet head, the ejection properties were very poor and clean printing was not possible. As a result, the color development and glossiness of the white ink image were inferior to those of the examples. In Comparative Example 6, white ink 14 containing flat mica particles was used, but the particle size of the flat mica particles was too large to be ejected using an inkjet head. Therefore, the ink was applied by spray coating and color printing was performed on top of it, but a good image could not be formed.

Claims

1. The present invention comprises hollow resin particles A having recesses on their outer surfaces, water, and solid resin particles B, the hollow resin particles A are not spherical or nearly spherical, but have a shape with a recess in the center when viewed from one direction, and the content of the hollow resin particles A is 5% by mass or more and less than 20% by mass with respect to the total amount of the ink, A water-based inkjet ink, which is a water-based white inkjet ink.

2. The aqueous inkjet ink according to claim 1 , wherein the solid resin particles B comprise acrylic resin particles having a glass transition point of 20° C. or lower.

3. 3. The aqueous inkjet ink according to claim 1, wherein the hollow resin particles A have an average particle diameter of 250 nm or more and 1 μm or less.

4. 4. The aqueous inkjet ink according to claim 1, further comprising an acetylene glycol surfactant having an HLB of 10.0 or less.

5. applying the aqueous inkjet ink according to any one of claims 1 to 4 to a substrate by an inkjet method; a step of applying, by an inkjet method, an aqueous inkjet ink containing water and a non-white colorant to the substrate to which the aqueous inkjet ink has been applied.

6. An ink set comprising the aqueous inkjet ink according to any one of claims 1 to 4, and an aqueous inkjet ink containing water and a non-white colorant.

Images