Image recording method and method for manufacturing laminate

Abstract

Provided are an image recording method capable of recording an image having excellent lamination strength with a laminate base material, and an application thereof. This image recording method comprises: a step for preparing white ink containing a white pigment, and at least one type of base ink having a hue different from that of the white ink; a step for applying the base ink onto a base material to form a base layer; and a step for applying the white ink onto a surface of the base layer by an inkjet recording system to form a white ink layer. The base layer has a surface energy higher than a surface tension of the white ink.

Description

Image recording method and laminate manufacturing method

[0001] The present disclosure relates to an image recording method and a method for manufacturing a laminate.

[0002] Conventionally, various studies have been made on image recording using ink.

[0003] For example, Patent Document 1 describes an image forming method including an undercoat liquid application step of applying a substantially transparent undercoat liquid to an image forming body, the undercoat liquid having the function of preventing an aggregation reaction of a colorant contained in the ink liquid, to form an undercoat layer on the image forming body; an ink droplet ejection step of converting the ink liquid into droplets and ejecting them based on image data onto the image forming body on which the undercoat layer has been formed; a treatment liquid application step, after the ink droplet ejection step, of applying a treatment liquid to the image forming body that causes an aggregation reaction of the ink liquid; and a solvent removal step, after the treatment liquid application step, of removing the undercoat liquid, the ink liquid, and the liquid solvent of the treatment liquid from on the image forming body.

[0004] JP 2009-83325 A

[0005] The recorded image is required to have adhesion to various substrates depending on the mode of use. After recording an image on a substrate to obtain an image recorded product, a laminated product may be produced by laminating a substrate for lamination onto the image in the image recorded product. There are also cases where it is required to improve the lamination strength between the image recorded product and the substrate for lamination.

[0006] The present disclosure has been made in view of the above circumstances, and a problem to be solved by one embodiment of the present disclosure is to provide an image recording method capable of recording an image that has excellent lamination strength with a lamination substrate.A problem to be solved by another embodiment of the present disclosure is to provide a method for manufacturing a laminated body that can produce a laminated body that has excellent lamination strength with a lamination substrate.

[0007] The present disclosure includes the following aspects: <1> An image recording method including the steps of preparing a white ink containing a white pigment and at least one base ink having a hue different from that of the white ink, applying the base ink onto a substrate to form an base layer, and applying the white ink onto the surface of the base layer by inkjet recording to form a white ink layer, wherein the surface energy of the base layer is higher than the surface tension of the white ink. <2> The image recording method according to <1>, wherein at least one of the base inks is a first base ink containing a coagulant, the step of forming the base layer includes the step of applying the first base ink onto the substrate to form the first base layer, and the step of forming the white ink layer includes the step of applying the white ink onto the surface of the first base layer by inkjet recording, wherein the surface energy of the first base layer is 45 mN / m to 85 mN / m. <3> The image recording method according to <1> or <2>, wherein at least one of the undercoat inks is a second undercoat ink containing a colorant other than a white pigment, the step of forming the undercoat layer includes a step of applying the second undercoat ink onto a substrate to form the second undercoat layer, the step of forming the white ink layer includes a step of applying a white ink to the surface of the second undercoat layer by an inkjet recording method, and the surface energy of the second undercoat layer is 45 mN / m to 55 mN / m. <4> The image recording method according to <3>, wherein the surface tensions of the second undercoat ink and the white ink are both 40 mN / m or less. <5> The image recording method according to <3> or <4>, wherein the step of forming the undercoat layer includes a step of forming a undercoat layer and a step of forming a white ink layer in this order, and the step of forming the undercoat layer further includes a step of drying the second undercoat ink. <6> The second undercoat ink has an SP value of 24 MPa １／２ Does not contain the following organic solvents or has an SP value of 24 MPa １／２ The image recording method according to any one of <3> to <5>, wherein the content of the following organic solvent is more than 0% by mass and 5% by mass or less with respect to the total amount of the second base ink. <7> At the start of the step of forming the white ink layer, the remaining amount of the liquid component contained in the base layer is 0.1 g / m ２The image recording method according to any one of <1> to <6>, wherein: <8> the image recording method according to any one of <1> to <7>, wherein the difference between the surface energy of the underlayer and the surface tension of the white ink is 10 mN / m to 20 mN / m; <9> the image recording method according to any one of <1> to <8>, wherein the surface energy of the white ink layer is 45 mN / m to 55 mN / m; <10> a method for producing a laminated body, comprising: obtaining an image-recorded product comprising a substrate and an image disposed on the substrate by the image recording method according to any one of <1> to <9>; and laminating a lamination substrate onto the side of the image-recorded product on which the image is disposed to obtain a laminated body.

[0008] According to one embodiment of the present disclosure, there is provided an image recording method capable of recording an image having excellent lamination strength with a lamination substrate. According to another embodiment of the present disclosure, there is provided a method for manufacturing a laminated body capable of manufacturing a laminated body having excellent lamination strength with a lamination substrate.

[0009] The image recording method and laminate manufacturing method of the present disclosure will be described in detail below.

[0010] In the present disclosure, a numerical range indicated using "to" means a range that includes the numerical values ​​before and after "to" as the minimum and maximum values, respectively. In the numerical ranges described in stages in this specification, the upper or lower limit value described in a certain numerical range may be replaced with the upper or lower limit value of another numerical range described in stages. Furthermore, in the numerical ranges described in this specification, the upper or lower limit value described in a certain numerical range may be replaced with a value shown in the examples.

[0011] In the present disclosure, the amount of each component in a composition means the total amount of the components in the composition unless otherwise specified, when the composition contains multiple substances corresponding to each component. In the present disclosure, a combination of two or more preferred aspects is a more preferred aspect. In the present disclosure, the term "process" includes not only an independent process, but also a process that cannot be clearly distinguished from other processes, as long as the intended purpose of the process is achieved.

[0012] In this disclosure, the term "image" refers to a film formed by applying a base ink and a white ink in this order, and "image recording" refers to the formation of an image (i.e., a film). The concept of "image" in this disclosure also includes a solid image.

[0013] In the present disclosure, the term "(meth)acrylate" is a concept that encompasses both acrylate and methacrylate, and the term "(meth)acrylic" is a concept that encompasses both acrylic and methacrylic.

[0014] In the present disclosure, the expression "applying ink onto a substrate" encompasses an embodiment in which ink is applied directly to the surface of a substrate, and an embodiment in which, when, for example, layer A is formed on the substrate, ink is applied directly to the surface of layer A.

[0015] [Image Recording Method] The image recording method of the present disclosure includes a step of preparing a white ink containing a white pigment and at least one type of base ink different from the white ink (hereinafter also referred to as a "preparation step"), a step of applying the base ink onto a substrate to form a base layer (hereinafter also referred to as a "base layer forming step"), and a step of applying the white ink to the surface of the base layer by an inkjet recording method to form a white ink layer (hereinafter also referred to as a "white ink layer forming step"), wherein the surface energy of the base layer is higher than the surface tension of the white ink.

[0016] According to the image recording method of the present disclosure, an image recorded product is obtained that includes a substrate and an image recorded on the substrate, and that has excellent lamination strength when a substrate for lamination is laminated onto the image. Here, the lamination strength refers to the peel strength when the substrate for lamination and the image recorded product are peeled off in a laminated product formed by the lamination (i.e., a laminated product having a layered structure of "substrate for lamination / image recorded product" (more specifically, a layered structure of "substrate for lamination / image / substrate").

[0017] The reason why the image recording method of the present disclosure exhibits the above-mentioned effects is presumed to be as follows: In order to improve the lamination strength of the laminate, it is first necessary to improve the adhesion between the substrate and the underlayer, and between the underlayer and the white ink layer, and then it is necessary to improve the adhesion between the image (particularly the white ink layer) and the substrate for lamination.

[0018] In the image recording method of the present disclosure, a base ink and a white ink are applied in this order onto a substrate to record an image. Conventionally, when a white ink is applied to the surface of a base layer to form a white ink layer, the adhesion between the base layer and the white ink layer tends to decrease. In contrast, in the image recording method of the present disclosure, the surface energy of the base layer is higher than the surface tension of the white ink. Therefore, the white ink easily wets and spreads on the surface of the base layer, resulting in excellent adhesion between the base layer and the white ink layer, and as a result, an image recording product with excellent lamination strength is obtained.

[0019] On the other hand, Japanese Patent Laid-Open No. 2003-132996 does not pay attention to the relationship between the surface energy of the underlayer and the surface tension of the white ink.

[0020] Each step included in the image recording method of the present disclosure will be described below.

[0021] <Preparation Step> The image recording method of the present disclosure includes a step of preparing a white ink containing a white pigment and at least one type of base ink having a hue different from that of the white ink.

[0022] [White Ink] (White Pigment) The white ink prepared in the preparation step contains a white pigment.

[0023] The white pigment may be any pigment that exhibits a white color, and the type is not particularly limited. White refers to a color that does not absorb a specific wavelength or absorbs a specific wavelength to a small extent. Examples of white pigments include inorganic pigments such as titanium oxide, strontium titanate, barium titanate, zinc oxide, magnesium oxide, zirconium oxide, aluminum oxide, barium sulfate, silica, talc, mica, aluminum hydroxide, calcium silicate, aluminum silicate, and zinc sulfide. The white pigment is preferably a particle having titanium atoms, and more preferably titanium oxide.

[0024] The average particle size of the white pigment is preferably 10 nm to 550 nm, more preferably 100 nm to 450 nm, and even more preferably 150 nm to 400 nm. An average particle size of 550 nm or less improves color reproducibility and, further, improves ejection stability when recording images using an inkjet recording method. On the other hand, an average particle size of 10 nm or more improves lightfastness. The particle size distribution of the pigment is not particularly limited, and may be either a broad particle size distribution or a monodisperse particle size distribution. The average particle size and particle size distribution of the pigment are determined by measuring the volume-average particle size by dynamic light scattering using a particle size distribution analyzer (e.g., the Nanotrac UPA-EX150 manufactured by Nikkiso Co., Ltd.). When the pigment is coated with a pigment dispersant, the average particle size of the pigment refers to the average particle size of the pigment coated with the pigment dispersant.

[0025] From the viewpoint of hiding power, the content of the white pigment is preferably 5% by mass to 20% by mass, and more preferably 8% by mass to 15% by mass, relative to the total amount of the white ink.

[0026] (Water) The white ink prepared in the preparation step preferably contains water. The amount of water contained is not particularly limited, and is, for example, 40% by mass to 70% by mass relative to the total amount of the white ink.

[0027] (Pigment Dispersant) The white ink prepared in the preparation step preferably contains a pigment dispersant. In the present disclosure, the pigment dispersant has the function of dispersing the pigment. The pigment dispersant is adsorbed onto the surface of the pigment and coats at least a portion of the surface of the pigment, thereby enabling the pigment to be dispersed in water. Note that when a self-dispersing pigment that can be dispersed in water even in the absence of a pigment dispersant is used as the white pigment, the white ink does not need to contain a pigment dispersant.

[0028] The form of the pigment dispersant contained in the white ink is not particularly limited and may be any of a random polymer, a block polymer, and a graft polymer. Furthermore, the pigment dispersant contained in the white ink may also be a polymer having a crosslinked structure. In particular, the pigment dispersant contained in the white ink is preferably a polymer or block polymer having a crosslinked structure, and more preferably a block polymer. When the pigment dispersant is a polymer or block polymer having a crosslinked structure, it is believed that detachment of the pigment dispersant from the white pigment surface is more likely to be suppressed, thereby improving the dispersion stability of the white pigment. For example, when a first base ink containing a flocculant is used as the base ink, the white pigment uniformly aggregates when the white ink reacts with the flocculant contained in the first base ink, resulting in a uniform image, easier volatilization of the organic solvent, and improved laminate strength. Even when a first base ink is not used, the solvent ratio in the white ink increases as water evaporates after the white ink lands on the base layer, making the dispersion of the white pigment more unstable. In this case, if the pigment dispersant is a polymer or block polymer having a crosslinked structure, uneven aggregation of the white pigment is suppressed, the image becomes uniform, the organic solvent is easily volatilized, and the laminate strength is further improved.

[0029] In this disclosure, a polymer refers to a compound having a weight average molecular weight of 1000 or more.

[0030] In this disclosure, the weight average molecular weight (Mw) refers to a value measured by gel permeation chromatography (GPC). Measurements by gel permeation chromatography (GPC) are performed using an HLC (registered trademark)-8020GPC (manufactured by Tosoh Corporation) as a measuring device, three TSKgel (registered trademark) Super Multipore HZ-H columns (4.6 mm ID x 15 cm, manufactured by Tosoh Corporation), and THF (tetrahydrofuran) as an eluent. Measurements are performed using an RI detector at a sample concentration of 0.45% by mass, a flow rate of 0.35 ml / min, a sample injection volume of 10 μl, and a measurement temperature of 40°C. The calibration curve is prepared from eight samples of "Standard Sample TSK Standard, Polystyrene" manufactured by Tosoh Corporation: "F-40", "F-20", "F-4", "F-1", "A-5000", "A-2500", "A-1000", and "n-propylbenzene".

[0031] - Polymer Having a Crosslinked Structure - The polymer having a crosslinked structure is not particularly limited as long as it has at least one crosslinked structure in the molecule.

[0032] Whether or not the polymer contained in the ink has a crosslinked structure can be determined, for example, by the following method. First, the ink is subjected to a separation method such as solvent extraction to separate the polymer. The separated polymer is analyzed using various analytical methods such as nuclear magnetic resonance (NMR), infrared spectroscopy (IR), and thermal analysis, allowing a comprehensive determination of whether or not the polymer has a crosslinked structure.

[0033] A polymer having a crosslinked structure (hereinafter also referred to as a "crosslinked polymer") is formed, for example, by crosslinking an uncrosslinked polymer (hereinafter also referred to as an "uncrosslinked polymer") with a crosslinking agent. The uncrosslinked polymer is preferably a water-soluble polymer.

[0034] In the present disclosure, "water solubility" means the property of dissolving 1 g or more in 100 g of water at 25° C. Preferably, "water solubility" means the property of dissolving 3 g or more (more preferably 10 g or more) in 100 g of water at 25° C.

[0035] Even if the uncrosslinked polymer is water-soluble, the crosslinked polymer is not necessarily water-soluble.

[0036] Examples of the uncrosslinked polymer include vinyl resin, acrylic resin, urethane resin, and polyester resin, and among these, the uncrosslinked polymer is preferably an acrylic resin.

[0037] The uncrosslinked polymer is preferably a polymer having a functional group that can be crosslinked by a crosslinking agent. Examples of the crosslinkable functional group include a carboxy group or a salt thereof, an isocyanate group, and an epoxy group. Among these, from the viewpoint of improving the dispersibility of the pigment, the crosslinkable functional group is preferably a carboxy group or a salt thereof, and a carboxy group is particularly preferred. That is, the uncrosslinked polymer is preferably a polymer containing a carboxy group.

[0038] The uncrosslinked polymer is preferably a copolymer containing a structural unit derived from a monomer containing a carboxy group (hereinafter referred to as a "carboxy group-containing monomer"). The structural unit derived from the carboxy group-containing monomer contained in the copolymer may be of only one type, or may be of two or more types. The copolymer may be a random copolymer or a block copolymer, but is preferably a random copolymer.

[0039] Examples of carboxy group-containing monomers include (meth)acrylic acid, β-carboxyethyl acrylate, fumaric acid, itaconic acid, maleic acid, and crotonic acid.

[0040] From the viewpoint of crosslinkability and dispersibility, the carboxy group-containing monomer is preferably (meth)acrylic acid or β-carboxyethyl acrylate, and more preferably (meth)acrylic acid.

[0041] The content of the structural unit derived from the carboxy group-containing monomer is preferably 5% by mass to 40% by mass, more preferably 10% by mass to 35% by mass, and even more preferably 10% by mass to 30% by mass, based on the total amount of the uncrosslinked polymer.

[0042] The uncrosslinked polymer preferably contains a structural unit derived from a hydrophobic monomer in addition to a structural unit derived from a carboxy group-containing monomer. The structural unit derived from a hydrophobic monomer contained in the copolymer may be of one type or two or more types.

[0043] Examples of hydrophobic monomers include (meth)acrylates having an alkyl group having 1 to 20 carbon atoms, (meth)acrylates having an aromatic ring (for example, benzyl (meth)acrylate, phenoxyethyl (meth)acrylate, etc.), styrene, and styrene derivatives.

[0044] The content of the structural unit derived from the hydrophobic monomer is preferably 60% by mass to 95% by mass, more preferably 65% ​​by mass to 90% by mass, and even more preferably 70% by mass to 90% by mass, based on the total amount of the uncrosslinked polymer.

[0045] The uncrosslinked polymer is preferably a random copolymer containing a structural unit derived from a carboxy group-containing monomer and at least one of a structural unit derived from a (meth)acrylate having an alkyl group with 1 to 20 carbon atoms and a structural unit derived from a (meth)acrylate having an aromatic ring, more preferably a random copolymer containing a structural unit derived from (meth)acrylic acid and a structural unit derived from a (meth)acrylate having an aromatic ring, and even more preferably a copolymer containing a structural unit derived from (meth)acrylic acid and a structural unit derived from benzyl (meth)acrylate.

[0046] The weight average molecular weight (Mw) of the uncrosslinked polymer is not particularly limited, but from the viewpoint of dispersibility of the white pigment, it is preferably 3,000 to 300,000, more preferably 5,000 to 200,000, and even more preferably 7,000 to 100,000.

[0047] The preferred range of the weight average molecular weight of the crosslinked polymer is the same as the preferred range of the weight average molecular weight of the uncrosslinked polymer.

[0048] The crosslinking agent used to crosslink the uncrosslinked polymer is preferably a compound having two or more reactive sites with the uncrosslinked polymer (e.g., a polymer having a carboxy group). Only one type of crosslinking agent may be used, or two or more types may be used.

[0049] A preferred combination of a crosslinking agent and an uncrosslinked polymer is a combination of a compound having two or more epoxy groups (i.e., a bifunctional or higher epoxy compound) and a polymer having a carboxy group. In this combination, a crosslinked structure is formed by reaction between the epoxy group and the carboxy group. The formation of the crosslinked structure by the crosslinking agent is preferably carried out after the pigment has been dispersed by the uncrosslinked polymer.

[0050] Examples of difunctional or higher functional epoxy compounds include ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, diethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, dipropylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, and trimethylolpropane triglycidyl ether.

[0051] Among these, the difunctional or higher epoxy compound is preferably polyethylene glycol diglycidyl ether, diethylene glycol diglycidyl ether, or trimethylolpropane triglycidyl ether.

[0052] The crosslinking agent may be a commercially available product, such as Denacol EX-321, EX-821, EX-830, EX-850, and EX-851 (manufactured by Nagase ChemteX Corporation).

[0053] The molar ratio of the reactive site (e.g., epoxy group) in the crosslinking agent to the reactive site (e.g., carboxy group) in the uncrosslinked polymer is preferably 1:1.1 to 1:10, more preferably 1:1.1 to 1:5, and even more preferably 1:1.1 to 1:3, from the viewpoints of the crosslinking reaction rate and the dispersion stability after crosslinking.

[0054] -Block Polymer- A block polymer is also called a block copolymer, and is a copolymer in which at least two polymers are bonded in the molecule.

[0055] The block polymer preferably contains a structural unit derived from a hydrophobic monomer and a structural unit derived from a monomer containing an anionic group (hereinafter referred to as an "anionic group-containing monomer").

[0056] The structural unit derived from the hydrophobic monomer contained in the block polymer may be of only one type or may be of two or more types.The structural unit derived from the anionic group-containing monomer contained in the block polymer may be of only one type or may be of two or more types.

[0057] Examples of structural units derived from hydrophobic monomers include ethylenically unsaturated compounds having an aromatic ring structure or an alicyclic structure, and (meth)acrylates having an alkyl group having 1 to 20 carbon atoms.

[0058] The content of the structural unit derived from the hydrophobic monomer is preferably 35% by mass to 95% by mass, more preferably 50% by mass to 95% by mass, and even more preferably 70% by mass to 90% by mass, based on the total amount of the block polymer.

[0059] From the viewpoint of adsorption to the pigment, the hydrophobic monomer preferably contains an ethylenically unsaturated compound having an aromatic ring structure or an alicyclic structure, more preferably contains an ethylenically unsaturated compound having an alicyclic structure, and even more preferably contains an ethylenically unsaturated compound having an alicyclic structure having 6 or more carbon atoms.

[0060] The content of the structural unit derived from an ethylenically unsaturated compound having an aromatic ring structure or an alicyclic structure is preferably 10% by mass to 90% by mass, more preferably 20% by mass to 80% by mass, even more preferably 30% by mass to 70% by mass, and still more preferably 30% by mass to 60% by mass, relative to the total amount of the block polymer.

[0061] The structural unit derived from a hydrophobic monomer also preferably contains a (meth)acrylate having an alkyl group having 1 to 20 carbon atoms. The alkyl group may be either linear or branched.

[0062] Examples of (meth)acrylates having an alkyl group having 1 to 20 carbon atoms include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, n-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and octyl (meth)acrylate.

[0063] The content of the structural unit derived from a (meth)acrylate having an alkyl group having 1 to 20 carbon atoms is preferably 10% by mass to 90% by mass, more preferably 20% by mass to 80% by mass, even more preferably 30% by mass to 70% by mass, and particularly preferably 40% by mass to 60% by mass, based on the total amount of the block polymer.

[0064] In the structural unit derived from an anionic group-containing monomer, examples of the anionic group include a carboxy group, a salt of a carboxy group, a sulfo group, a salt of a sulfo group, a phosphate group, a salt of a phosphate group, a phosphonic acid group, and a salt of a phosphonic acid group.

[0065] Counter ions in salts include alkali metal ions such as sodium ion, potassium ion, and lithium ion; alkaline earth metal ions such as calcium ion and magnesium ion; and ammonium ion.

[0066] Of these, the anionic group is preferably a carboxy group or a salt of a carboxy group. Examples of the anionic group-containing monomer include (meth)acrylic acid, β-carboxyethyl acrylate, fumaric acid, itaconic acid, maleic acid, and crotonic acid. Of these, the anionic group-containing monomer is preferably (meth)acrylic acid.

[0067] The content of the structural unit derived from the anionic group-containing monomer is preferably 1% by mass to 30% by mass, more preferably 2% by mass to 25% by mass, and even more preferably 3% by mass to 20% by mass, based on the total amount of the block polymer.

[0068] Whether or not the polymer contained in the ink is a block polymer can be determined, for example, by the following method. First, the ink is subjected to a separation method such as solvent extraction to separate the polymer. The separated polymer is analyzed using various analytical methods such as nuclear magnetic resonance (NMR), infrared spectroscopy (IR), and thermal analysis, and physical properties such as the glass transition temperature are measured, allowing a comprehensive determination of whether or not the polymer is a block polymer.

[0069] The weight average molecular weight (Mw) of the block polymer is not particularly limited, but from the viewpoint of pigment dispersibility, it is preferably 3,000 to 100,000, more preferably 5,000 to 80,000, and even more preferably 10,000 to 60,000.

[0070] The mixing ratio of the white pigment to the pigment dispersant is preferably 1:0.02 to 1:2, more preferably 1:0.03 to 1:1.5, and even more preferably 1:0.04 to 1:1, on a mass basis.

[0071] As a dispersing device for dispersing the pigment, a known dispersing device can be used, and examples thereof include a ball mill, a sand mill, a bead mill, a roll mill, a jet mill, a paint shaker, an attritor, an ultrasonic disperser, and a disperser.

[0072] (Resin Particles) The white ink prepared in the preparation step preferably contains at least one type of resin particles, which are particles made of a resin, in addition to a pigment dispersant, from the viewpoint of improving the lamination strength of the image recorded product.

[0073] When a white ink is applied to a substrate to which the first base ink has been applied, the aggregating agent contained in the first base ink comes into contact with the resin particles contained in the white ink, destabilizing the dispersion of the resin particles and increasing the viscosity of the white ink, thereby fixing the white ink to the substrate and improving the lamination strength of the image recorded thereon.

[0074] The resin constituting the resin particles is preferably a water-insoluble polymer. The term "water-insoluble" in the context of a water-insoluble polymer means that the amount of the polymer that dissolves in 100 g of distilled water at 25° C. is less than 2 g.

[0075] The resin particles preferably include at least one of particles made of acrylic resin (hereinafter referred to as "acrylic resin particles") and particles made of urethane resin (hereinafter also referred to as "urethane resin particles"), and more preferably include acrylic resin particles.

[0076] The resin particles are preferably self-dispersing resin particles.

[0077] Examples of the self-dispersible resin particles include those described in paragraphs 0062 to 0076 of JP 2016-188345 A and paragraphs 0109 to 0140 of WO 2013 / 180074 A.

[0078] The weight average molecular weight (Mw) of the resin in the resin particles is preferably 1,000 to 300,000, more preferably 2,000 to 200,000, and even more preferably 5,000 to 100,000.

[0079] From the viewpoint of ejection stability, the average particle diameter of the resin particles is preferably 1 nm to 200 nm, more preferably 3 nm to 200 nm, and even more preferably 5 nm to 50 nm. The average particle diameter of the resin particles is determined by measuring the volume average particle diameter by dynamic light scattering using a particle size distribution measuring device (for example, the product name "Nanotrac UPA-EX150" manufactured by Nikkiso Co., Ltd.).

[0080] When the white ink contains resin particles, the content of the resin particles is preferably 0.1% by mass to 15% by mass, more preferably 0.5% by mass to 10% by mass, even more preferably 1% by mass to 8% by mass, and even more preferably 2% by mass to 5% by mass, relative to the total amount of the white ink.

[0081] (Surfactant) From the viewpoint of improving ejection stability, the white ink preferably contains at least one surfactant. Furthermore, in order to control the surface tension of the white ink to be lower than the surface energy of the underlayer, it is preferable to appropriately adjust the type and content of the surfactant.

[0082] The surfactant may be any of anionic surfactants, cationic surfactants, amphoteric surfactants, nonionic surfactants, and betaine surfactants. The surfactant may also be a fluorine-based surfactant or a silicone-based surfactant.

[0083] Among these, from the viewpoint of improving ejection stability, the surfactant preferably contains a nonionic surfactant, and more preferably contains an acetylene glycol-based surfactant. In particular, from the viewpoint of making the surface tension of the white ink lower than the surface energy of the underlayer, the surfactant preferably contains a silicone-based surfactant, and more preferably uses an acetylene glycol-based surfactant and a silicone-based surfactant in combination.

[0084] Examples of acetylene glycol surfactants include 2,4,7,9-tetramethyl-5-decyne-4,7-diol and alkylene oxide adducts of 2,4,7,9-tetramethyl-5-decyne-4,7-diol.

[0085] Commercially available acetylene glycol surfactants include Surfynol series such as Surfynol 104 manufactured by Nissin Chemical Industry Co., Ltd., and E series such as Olfine E1010 manufactured by Nissin Chemical Industry Co., Ltd.

[0086] Examples of silicone surfactants include polysiloxane compounds. The silicone surfactant is preferably a modified polysiloxane compound in which organic groups are introduced into some of the methyl groups of dimethylpolysiloxane. Modifications include polyether-modified, methylstyrene-modified, alcohol-modified, alkyl-modified, aralkyl-modified, fatty acid ester-modified, epoxy-modified, amine-modified, amino-modified, and mercapto-modified. Multiple types of organic groups may be introduced into some of the methyl groups of dimethylpolysiloxane. Among these, from the viewpoints of alkali removability and ejection stability, the silicone surfactant is preferably a polyether-modified polysiloxane compound.

[0087] The content of the surfactant is preferably 0.05% by mass to 4.0% by mass, more preferably 0.1% by mass to 2.0% by mass, and even more preferably 0.5% by mass to 1.5% by mass, relative to the total amount of the white ink.

[0088] The content of the acetylene glycol surfactant is preferably 0.1% by mass to 2.0% by mass, more preferably 0.2% by mass to 1.0% by mass, and even more preferably 0.3% by mass to 1.0% by mass, relative to the total amount of the white ink.

[0089] The content of the silicone surfactant is preferably 0.1% by mass to 2.0% by mass, more preferably 0.2% by mass to 1.0% by mass, and even more preferably 0.3% by mass to 1.0% by mass, relative to the total amount of the white ink.

[0090] (Additives) The white ink prepared in the preparation step may contain additives such as a co-sensitizer, an ultraviolet absorber, an antioxidant, an anti-fading agent, a conductive salt, and a basic compound, as needed.

[0091] (Physical Properties) From the viewpoint of improving ejection stability, the pH of the white ink is preferably 7 to 10, and more preferably 7.5 to 9.5. The pH is measured at 25°C using a pH meter, for example, a pH meter manufactured by Toa DKK Corporation (model number "HM-31")

[0092] The viscosity of the white ink is preferably 0.5 mPa·s to 30 mPa·s, more preferably 2 mPa·s to 20 mPa·s, more preferably 2 mPa·s to 15 mPa·s, and even more preferably 3 mPa·s to 10 mPa·s. The viscosity is measured at 25°C using a viscometer, for example, a TV-22 viscometer manufactured by Toki Sangyo Co., Ltd.

[0093] The surface tension of the white ink is preferably 50 mN / m or less, and more preferably 40 mN / m or less, from the viewpoint of making it lower than the surface energy of the underlayer. The lower limit of the surface tension of the white ink is preferably 30 mN / m or more, from the viewpoint of ejection properties. The surface tension is measured at 25°C by the plate method using a surface tensiometer, and can be measured using, for example, an automatic surface tensiometer (product name "CBVP-Z" manufactured by Kyowa Interface Science Co., Ltd.

[0094] [Base Ink] The base ink prepared in the preparation step is not particularly limited as long as it has a hue different from that of the white ink. Examples of inks having a hue different from that of the white ink include inks containing a colorant that exhibits a color other than white (e.g., black ink, chromatic ink, metallic ink, etc.) and colorless and transparent inks. The colorless and transparent ink is preferably an ink with a low colorant content, preferably an ink in which the colorant content relative to the solid content of the ink is less than 10% by mass, and more preferably an ink in which the colorant content relative to the solid content of the ink is less than 1% by mass. The lower limit is not particularly limited, but is, for example, greater than 0% by mass. Note that the colorless and transparent ink may not contain a colorant. In this case, the colorant content relative to the solid content of the ink is 0% by mass.

[0095] The base ink may be of one type or of two or more types.

[0096] From the viewpoint of improving the lamination strength, it is preferable to prepare a first base ink containing a coagulant as the base ink in the preparation step, and to obtain a desired color image, it is preferable to prepare a second base ink containing a colorant other than a white pigment as the base ink.

[0097] The base ink to be prepared may be only the first base ink, only the second base ink, or both the first and second base inks. Furthermore, each of the first base ink and the second base ink may be one type, or two or more types.

[0098] Preferred embodiments of the first base ink and the second base ink will be described below.

[0099] <<First Base Ink>> The first base ink is an ink containing a coagulant.

[0100] As will be described later, the first base ink is preferably applied to the surface of the substrate, and is also generally called a "pretreatment liquid."

[0101] (Aggregating Agent) The aggregating agent is not particularly limited as long as it is a component that aggregates components in the ink applied to the surface of the first base layer formed by the first base ink. When white ink is applied to the surface of the first base layer, the aggregating agent is preferably a component that aggregates components in the white ink.

[0102] The flocculant is preferably at least one selected from the group consisting of polyvalent metal compounds, organic acids, metal complexes, and cationic polymers, and more preferably contains an organic acid.

[0103] -Polyvalent Metal Compound- Examples of polyvalent metal compounds include salts of alkaline earth metals of Group 2 of the periodic table (e.g., magnesium, calcium), transition metals of Group 3 of the periodic table (e.g., lanthanum), metals of Group 13 of the periodic table (e.g., aluminum), and lanthanides (e.g., neodymium).

[0104] The metal salt is preferably a salt of an organic acid, a nitrate, a chloride, or a thiocyanate, as described below.

[0105] Among these, the polyvalent metal compound is preferably a calcium salt or magnesium salt of an organic acid (e.g., formic acid, acetic acid, benzoic acid, etc.); a calcium salt or magnesium salt of nitric acid; calcium chloride, magnesium chloride, or a calcium salt or magnesium salt of thiocyanic acid.

[0106] It is preferable that the polyvalent metal compound is at least partially dissociated into polyvalent metal ions and counter ions in the first base ink.

[0107] Organic Acids Examples of organic acids include organic compounds having an acidic group.

[0108] Acidic groups include phosphate groups, phosphonate groups, phosphinate groups, sulfate groups, sulfonate groups, sulfinate groups, and carboxy groups.

[0109] Among these, from the viewpoint of the aggregation speed of the ink, the acidic group is preferably a phosphate group or a carboxy group, and more preferably a carboxy group.

[0110] It is preferable that the acidic groups are at least partially dissociated in the first undercoat ink.

[0111] Examples of organic compounds having a carboxy group include (meth)acrylic acid, poly(meth)acrylic acid, acetic acid, formic acid, benzoic acid, glycolic acid, malonic acid, malic acid (preferably DL-malic acid), maleic acid, succinic acid, glutaric acid, pimelic acid, adipic acid, fumaric acid, citric acid, tartaric acid, phthalic acid, 4-methylphthalic acid, lactic acid, pyrrolidonecarboxylic acid, pyronecarboxylic acid, pyrrolecarboxylic acid, furancarboxylic acid, pyridinecarboxylic acid, coumaric acid, thiophenecarboxylic acid, and nicotinic acid.

[0112] Among these, from the viewpoint of the aggregation speed of the ink, the organic compound having a carboxy group is preferably a divalent or higher carboxylic acid (hereinafter also referred to as a polycarboxylic acid), and more preferably a dicarboxylic acid.

[0113] Specifically, the polycarboxylic acid is preferably malonic acid, malic acid, maleic acid, succinic acid, glutaric acid, pimelic acid, adipic acid, fumaric acid, tartaric acid, 4-methylphthalic acid, or citric acid, and more preferably malonic acid, malic acid, tartaric acid, succinic acid, glutaric acid, pimelic acid, adipic acid, or citric acid. It is also a preferred embodiment to use two or more of these organic acids in combination.

[0114] The organic acid preferably has a low pKa (for example, 1.0 to 5.0), which reduces the surface charge of particles such as pigments and resin particles in the ink, which are stabilized by weakly acidic functional groups such as carboxyl groups, by contacting them with an organic acid having an even lower pKa, thereby lowering dispersion stability.

[0115] The organic acid preferably has a low pKa, high solubility in water, and a valence of at least 2. Furthermore, the organic acid more preferably has a high buffering capacity in a pH range lower than the pKa of the functional group (e.g., carboxy group) that stabilizes the dispersion of the particles in the ink.

[0116] -Metal Complex- The metal complex preferably contains, as a metal element, at least one selected from the group consisting of zirconium, aluminum, and titanium.

[0117] The metal complex is preferably a metal complex containing, as a ligand, at least one selected from the group consisting of acetate, acetylacetonate, methylacetoacetate, ethylacetoacetate, octylene glycolate, butoxyacetylacetonate, lactate, lactate ammonium salt, and triethanolamine.

[0118] The metal complex may be a commercially available product. Various organic ligands, particularly various polydentate ligands capable of forming metal chelate catalysts, are commercially available. Therefore, the metal complex may be a metal complex prepared by combining a commercially available organic ligand with a metal.

[0119] Examples of the metal complex include zirconium tetraacetylacetonate (e.g., "Orgatix ZC-150" manufactured by Matsumoto Fine Chemical Co., Ltd.), zirconium monoacetylacetonate (e.g., "Orgatix ZC-540" manufactured by Matsumoto Fine Chemical Co., Ltd.), zirconium bisacetylacetonate (e.g., "Orgatix ZC-550" manufactured by Matsumoto Fine Chemical Co., Ltd.), zirconium monoethylacetoacetate (e.g., "Orgatix ZC-560" manufactured by Matsumoto Fine Chemical Co., Ltd.), zirconium acetate (e.g., "Orgatix ZC-115" manufactured by Matsumoto Fine Chemical Co., Ltd.), titanium diisopropoxybis(acetylacetonate) (e.g., "Orgatix TC-100" manufactured by Matsumoto Fine Chemical Co., Ltd.), and titanium tetraacetylacetonate (e.g., "Orgatix" manufactured by Matsumoto Fine Chemical Co., Ltd.). TC-401"), titanium dioctyloxybis(octylene glycolate) (e.g., Matsumoto Fine Chemical Co., Ltd.'s "Orgatix TC-200"), titanium diisopropoxybis(ethyl acetoacetate) (e.g., Matsumoto Fine Chemical Co., Ltd.'s "Orgatix TC-750"), zirconium tetraacetylacetonate (e.g., Matsumoto Fine Chemical Co., Ltd.'s "Orgatix ZC-700"), zirconium tributoxymonoacetylacetonate (e.g., Matsumoto Fine Chemical Co., Ltd.'s "Orgatix ZC-540"), zirconium monobutoxyacetylacetonate bis(ethyl acetoacetate) (e.g., Matsumoto Fine Chemical Co., Ltd.'s "Orgatix ZC-570")), zirconium dibutoxy Bis(ethylacetoacetate) (e.g., "Orgatix ZC-580" manufactured by Matsumoto Fine Chemical Co., Ltd.), aluminum trisacetylacetonate (e.g., "Orgatix AL-80" manufactured by Matsumoto Fine Chemical Co., Ltd.), titanium lactate ammonium salt (e.g., "Orgatix TC-300" manufactured by Matsumoto Fine Chemical Co., Ltd.), titanium lactate (e.g., "Orgatix TC-310, 315" manufactured by Matsumoto Fine Chemical Co., Ltd.), titanium triethanolamine (e.g., "Orgatix TC-400" manufactured by Matsumoto Fine Chemical Co., Ltd.), and zirconyl chloride compounds (e.g.,Matsumoto Fine Chemical Co., Ltd.'s "Orgatics ZC-126").

[0120] Among these, the metal complex is preferably a titanium lactate ammonium salt (e.g., "Orgatix TC-300" manufactured by Matsumoto Fine Chemical Co., Ltd.), titanium lactate (e.g., "Orgatix TC-310, 315" manufactured by Matsumoto Fine Chemical Co., Ltd.), titanium triethanolamine (e.g., "Orgatix TC-400" manufactured by Matsumoto Fine Chemical Co., Ltd.), or a zirconyl chloride compound (e.g., "Orgatix ZC-126" manufactured by Matsumoto Fine Chemical Co., Ltd.).

[0121] -Cationic Polymer- The first base ink may also contain one or more cationic polymers as aggregating components. The cationic polymer is preferably a homopolymer of a cationic monomer having a primary, secondary, or tertiary amino group or a quaternary ammonium salt group, or a copolymer or condensation polymer of a cationic monomer and a non-cationic monomer. The cationic polymer may be used in the form of either a water-soluble polymer or water-dispersible latex particles. Examples of cationic polymers include polyvinylpyridine salts, polyalkylaminoethyl acrylates, polyalkylaminoethyl methacrylates, polyvinylimidazole, polyethyleneimines, polybiguanides, polyguanides, polyallylamine, and derivatives thereof.

[0122] The weight-average molecular weight of the cationic polymer is preferably small from the viewpoint of the viscosity of the first base ink. When the first base ink is applied to a recording medium by inkjet recording, the weight-average molecular weight is preferably 1,000 to 500,000, more preferably 1,500 to 200,000, and even more preferably 2,000 to 100,000. A weight-average molecular weight of 1,000 or more is advantageous from the viewpoint of aggregation speed. A weight-average molecular weight of 500,000 or less is advantageous from the viewpoint of ejection reliability. However, this does not apply when the first base ink is applied to a recording medium by a method other than inkjet recording.

[0123] The first base ink may contain only one type of aggregating agent, or may contain two or more types of aggregating agents.

[0124] The content of the aggregating agent is preferably 0.1% by mass to 40% by mass, more preferably 0.1% by mass to 30% by mass, even more preferably 1% by mass to 20% by mass, and particularly preferably 1% by mass to 10% by mass, relative to the total amount of the first base ink.

[0125] (Water) The first base ink preferably contains water. There are no particular restrictions on the amount of water contained, and the amount is, for example, 40% by mass to 70% by mass relative to the total amount of the first base ink.

[0126] (Other Components) The first base ink may contain other components in addition to the flocculant and water, as necessary. Examples of other components that may be contained in the first base ink include known additives such as organic solvents, resin particles, surfactants, solid wetting agents, colorants, colloidal silica, inorganic salts, anti-fading agents, emulsion stabilizers, penetration enhancers, UV absorbers, preservatives, antifungal agents, pH adjusters, viscosity adjusters, rust inhibitors, chelating agents, and water-soluble polymer compounds (e.g., the water-soluble polymer compounds described in paragraphs 0026 to 0080 of JP 2013-001854 A). The first base ink preferably contains less than 10% by mass of colorant relative to the solid content of the first base ink, and more preferably less than 1% by mass. The lower limit is not particularly limited, but may be, for example, greater than 0% by mass. The first base ink may also be free of colorant. In this case, the colorant content relative to the solid content of the ink is 0% by mass.

[0127] (Physical Properties) From the viewpoint of the aggregation rate of the ink, the pH of the first base ink is preferably 0.1 to 4.5, and more preferably 0.2 to 4.0. The pH is measured at 25°C using a pH meter, for example, a pH meter manufactured by Toa DKK Corporation (model number "HM-31")

[0128] From the viewpoint of the ink aggregation speed, the viscosity of the first base ink is preferably 0.5 mPa·s to 10 mPa·s, and more preferably 1 mPa·s to 5 mPa·s. The viscosity is a value measured at 25°C using a viscometer, and can be measured using, for example, a TV-22 viscometer manufactured by Toki Sangyo Co., Ltd.

[0129] The surface tension of the first base ink is preferably 50 mN / m or less, and more preferably 40 mN / m or less, from the viewpoint of making it lower than the surface energy of the substrate. The lower limit of the surface tension of the first base ink is preferably 30 mN / m or more, from the viewpoint of ejection properties. The surface tension is measured at 25°C by the plate method using a surface tensiometer, and can be measured using, for example, an automatic surface tensiometer (product name "CBVP-Z" manufactured by Kyowa Interface Science Co., Ltd.

[0130] <<Second Base Ink>> The second base ink is an ink that contains a colorant other than a white pigment.

[0131] (Colorant) The colorant contained in the second base ink is not particularly limited as long as it is a white pigment, and may be a pigment or a dye.

[0132] Among these, the colorant is preferably a pigment from the viewpoint of durability (for example, water resistance, light resistance, etc.). Hereinafter, pigments other than white pigments will be simply referred to as "color pigments."

[0133] The color pigment may be a chromatic pigment, a black pigment, or a combination of one or more chromatic pigments and one or more black pigments.

[0134] The chromatic pigment is not particularly limited in type as long as it exhibits a chromatic color. A chromatic color refers to a color that has hue, lightness, and saturation.

[0135] The chromatic pigment is not particularly limited, and examples thereof include cyan pigments, magenta pigments, yellow pigments, blue pigments, red pigments, green pigments, orange pigments, and violet pigments.

[0136] Specific examples of chromatic pigments include organic pigments such as azo pigments, disazo pigments, condensed disazo pigments, phthalocyanine pigments, quinacridone pigments, quinacridonequinone pigments, anthraquinone pigments, aminoanthraquinone pigments, anthanthrone pigments, dioxazine pigments, indigo pigments, thioindigo pigments, perinone pigments, perylene pigments, isoindoline pigments, isoindolinone pigments, isoviolanthrone pigments, benzimidazolone pigments, indanthrone pigments, triarylcarbonium pigments, and diketopyrrolopyrrole pigments.

[0137] More specifically, examples of chromatic pigments include perylene pigments such as C.I. Pigment Red 190, C.I. Pigment Red 224, and C.I. Pigment Violet 29; perinone pigments such as C.I. Pigment Orange 43 and C.I. Pigment Red 194; quinacridone pigments such as C.I. Pigment Violet 19, C.I. Pigment Violet 42, C.I. Pigment Red 122, C.I. Pigment Red 192, C.I. Pigment Red 202, C.I. Pigment Red 207, and Pigment Red 209; quinacridonequinone pigments such as C.I. Pigment Red 206, C.I. Pigment Orange 48, and C.I. Pigment Orange 49; and C.I. Anthraquinone pigments such as C.I. Pigment Yellow 147; Anthanthrone pigments such as C.I. Pigment Red 168; C.I. Pigment Brown 25, C.I. Pigment Violet 32, C.I. Pigment Orange 36, C.I. Pigment Yellow 120, C.I. Pigment Yellow 180, Pigment Yellow 181, C.I. Pigment Orange 62, C.I. Benzimidazolone pigments such as Pigment Red 185; C.I. Pigment Yellow 93, C.I. Pigment Yellow 94, C.I. Pigment Yellow 95, C.I. Pigment Yellow 128, C.I. Pigment Yellow 166, C.I. Pigment Orange 34, C.I. Pigment Orange 13, C.I. C.I. Pigment Orange 31, C.I. Pigment Red 144, C.I. Pigment Red 166, C.I. Pigment Red 220, C.I. Pigment Red 221, C.I. Pigment Red 242, C.I. Pigment Red 248, C.I. Pigment Red 262, C.I. Pigment Brown 23 and other condensed disazo pigments; C.I. Pigment Yellow 13, C.I. Pigment Yellow 83, C.I. Pigment Yellow 188 and other disazo pigments; C.I. Pigment Red 187, C.I. Pigment Red 170, C.I. Pigment Yellow 74, C.I. Pigment Yellow 150, C.I. Pigment Red 48, C.I. Pigment Red 53, C.I. Pigment Orange 64, C.I. azo pigments such as C.I. Pigment Red 247; indanthrone pigments such as C.I. Pigment Blue 60;Phthalocyanine pigments such as C.I. Pigment Green 7, C.I. Pigment Green 36, C.I. Pigment Green 37, C.I. Pigment Green 58, C.I. Pigment Blue 16, C.I. Pigment Blue 75, and Pigment Blue 15; Triarylcarbonium pigments such as C.I. Pigment Blue 56 and C.I. Pigment Blue 61; Dioxazine pigments such as C.I. Pigment Violet 23 and C.I. Pigment Violet 37; Aminoanthraquinone pigments such as C.I. Pigment Red 177; C.I. Pigment Red 254, C.I. Pigment Red 255, C.I. Pigment Red 264, C.I. Pigment Red 272, C.I. Examples of pigments include diketopyrrolopyrrole pigments such as C.I. Pigment Orange 71 and C.I. Pigment Orange 73; thioindigo pigments such as C.I. Pigment Red 88; isoindoline pigments such as C.I. Pigment Yellow 139 and C.I. Pigment Orange 66; isoindolinone pigments such as C.I. Pigment Yellow 109 and C.I. Pigment Orange 61; pyranthrone pigments such as C.I. Pigment Orange 40 and C.I. Pigment Red 216; and isoviolanthrone pigments such as C.I. Pigment Violet 31.

[0138] The type of black pigment is not particularly limited as long as it exhibits black color, and examples of black pigments include carbon black and titanium black.

[0139] The average particle size of the color pigment is preferably 10 nm to 200 nm, more preferably 10 nm to 150 nm, and even more preferably 10 nm to 110 nm. An average particle size of 200 nm or less improves color reproducibility and, further, improves ejection stability when recording images using an inkjet recording method. On the other hand, an average particle size of 10 nm or more improves lightfastness. The particle size distribution of the pigment may be either a broad particle size distribution or a monodisperse particle size distribution. The average particle size and particle size distribution of the pigment are determined by measuring the volume average particle size by dynamic light scattering using a particle size distribution measuring device (for example, the Nanotrac UPA-EX150 manufactured by Nikkiso Co., Ltd.). When the pigment is coated with a pigment dispersant, the average particle size of the pigment refers to the average particle size of the pigment coated with the pigment dispersant.

[0140] From the viewpoints of image density, ejection properties, and re-ejection properties, the content of the color pigment is preferably 1% by mass to 15% by mass, and more preferably 2% by mass to 10% by mass, relative to the total amount of the second base ink.

[0141] (Organic Solvent) The second base ink preferably contains an organic solvent from the viewpoint of improving the ejection properties. In particular, from the viewpoint of further improving the ejection properties, the second base ink preferably contains an organic solvent having an SP value of 24 MPa or more. １／２ Does not contain the following organic solvents or has an SP value of 24 MPa １／２ The content of the organic solvent below is preferably 5% by mass or less relative to the total amount of the second base ink. There is no particular lower limit, but it may be, for example, more than 0% by mass.

[0142] In the present disclosure, the SP value refers to a value expressed as the square root of the molecular cohesive energy (solubility parameter), and is a value calculated by the method described in R. F. Fedors, Polymer Engineering Science, 14, pp. 147-154 (1974). The unit of the SP value is MPa. １／２ is.

[0143] Examples of organic solvents and their SP values ​​are given below. The values ​​in parentheses indicate the SP value. Propylene glycol (27.6 MPa１／２ ) Ethylene glycol (30.3 MPa １／２ ) Diethylene glycol (30.6 MPa １／２ ) Triethylene glycol (27.8 MPa １／２ ) Tripropylene glycol (24.7 MPa １／２ ) 2-methyl-1,3-butanediol (28.27 MPa １／２ ) 1,2-pentanediol (28.64 MPa １／２ ) 1,5-pentanediol (28.96 MPa １／２ ) 1,2-hexanediol (21.3 MPa １／２ ) 1,6-hexanediol (27.66 MPa １／２ ) Glycerin (33.5 MPa １／２ ) Dimethylformamide (30.62 MPa １／２ ) Methanol (28.17 MPa １／２ ) Isopropyl alcohol (28.69 MPa １／２ ) Triethanolamine (32.27 MPa １／２ ) Dipropylene glycol (27.1 MPa １／２ ) Ethylene glycol monoethyl ether (23.5 MPa １／２ ) Ethylene glycol monopropyl ether (21.8 MPa １／２ ) Ethylene glycol monobutyl ether (22.1 MPa １／２ ) Diethylene glycol monomethyl ether (22.98 MPa １／２ ) Diethylene glycol monoethyl ether (22.4 MPa １／２ ) Diethylene glycol monopropyl ether (21.9 MPa １／２ ) Diethylene glycol monobutyl ether (21.5 MPa １／２ ) Triethylene glycol monomethyl ether (22.1 MPa １／２ ) Triethylene glycol monoethyl ether (21.7 MPa １／２ ) Triethylene glycol monobutyl ether (21.1 MPa １／２ ) Propylene glycol monomethyl ether (23.0 MPa １／２) Propylene glycol monoethyl ether (22.3 MPa １／２ ) Propylene glycol monopropyl ether (21.8 MPa １／２ ) Propylene glycol monobutyl ether (21.4 MPa １／２ ) Dipropylene glycol monomethyl ether (21.3 MPa １／２ ) Dipropylene glycol monopropyl ether (20.69 MPa １／２ ) Dipropylene glycol monobutyl ether (20.45 MPa １／２ ) Dipropylene glycol t-butyl ether (19.98 MPa １／２ ) Tripropylene glycol monomethyl ether (20.4 MPa １／２ ) Diethylene glycol monohexyl ether (20.91 MPa １／２ ) Ethylene glycol mono-2-ethylhexyl ether (20.46 MPa １／２ ) Diethylene glycol mono-2-ethylhexyl ether (20.26 MPa １／２ )

[0144] The content of the organic solvent is preferably 10% by mass to 50% by mass, and more preferably 20% by mass to 40% by mass, relative to the total amount of the second base ink.

[0145] (Water) The second base ink preferably contains water. There are no particular restrictions on the amount of water contained, and the amount is, for example, 40% by mass to 70% by mass relative to the total amount of the second base ink.

[0146] (Pigment dispersant) When the second base ink contains a color pigment, it preferably contains a pigment dispersant. Note that when a self-dispersing pigment that can be dispersed in water even without a pigment dispersant is used as the color pigment, the second base ink does not need to contain a pigment dispersant.

[0147] The form of the pigment dispersant is not particularly limited, and may be any of a random polymer, a block polymer, and a graft polymer. The pigment dispersant may also be a polymer having a crosslinked structure. Of these, the pigment dispersant is preferably a polymer having a crosslinked structure. It is believed that when the pigment dispersant is a polymer having a crosslinked structure, the pigment dispersant is less likely to be detached from the surface of the colored pigment.

[0148] When the pigment dispersant contained in the second base ink is a polymer having a cross-linked structure, the preferred aspects of the polymer having a cross-linked structure are the same as the preferred aspects when the pigment dispersant contained in the above-mentioned white ink is a polymer having a cross-linked structure.

[0149] The mixing ratio of the color pigment to the pigment dispersant is preferably 1:0.06 to 1:3, more preferably 1:0.125 to 1:2, and even more preferably 1:0.125 to 1:1.5, on a mass basis.

[0150] (Resin Particles) From the viewpoint of improving the lamination strength of the image recorded product, the second base ink preferably contains at least one type of resin particles. The second base ink preferably contains resin particles, which are particles made of a resin, in addition to the pigment dispersant.

[0151] The preferred embodiments of the resin particles contained in the second base ink are the same as the preferred embodiments of the resin particles contained in the white ink.

[0152] When the second base ink contains resin particles, the content of the resin particles is preferably 0.1% by mass to 15% by mass, more preferably 0.5% by mass to 10% by mass, even more preferably 1% by mass to 8% by mass, and even more preferably 2% by mass to 6% by mass, relative to the total amount of the second base ink.

[0153] (Surfactant) From the viewpoint of improving ejection stability, the second base ink preferably contains at least one surfactant.

[0154] The surfactant may be the same as the surfactant that may be contained in the white ink.

[0155] The content of the surfactant is preferably 0.05% by mass to 4.0% by mass, more preferably 0.1% by mass to 2.0% by mass, and even more preferably 0.5% by mass to 1.5% by mass, relative to the total amount of the second base ink.

[0156] (Additives) The second base ink may contain additives such as co-sensitizers, ultraviolet absorbers, antioxidants, anti-fading agents, conductive salts, and basic compounds, as needed.

[0157] (Physical Properties) From the viewpoint of improving ejection stability, the pH of the second base ink is preferably 7 to 10, and more preferably 7.5 to 9.5. The pH is measured at 25°C using a pH meter, for example, a pH meter manufactured by Toa DKK Corporation (model number "HM-31")

[0158] The viscosity of the second base ink is preferably 0.5 mPa·s to 30 mPa·s, more preferably 2 mPa·s to 20 mPa·s, preferably 2 mPa·s to 15 mPa·s, and even more preferably 3 mPa·s to 10 mPa·s. The viscosity is measured at 25°C using a viscometer, and can be measured using, for example, a TV-22 viscometer manufactured by Toki Sangyo Co., Ltd.

[0159] The surface tension of the second base ink is preferably 50 mN / m or less, more preferably 40 mN / m or less, from the viewpoint of making it lower than the surface energy of the substrate or the first base layer. The surface tension of both the second base ink and the white ink is preferably 50 mN / m or less, more preferably 40 mN / m or less. From the viewpoint of ejection performance, the lower limit of the surface tension of the second base ink is preferably 25 mN / m or more, more preferably 30 mN / m or more. The surface tension is measured at 25°C by the plate method using a surface tensiometer, and can be measured using, for example, an automatic surface tensiometer (product name "CBVP-Z" manufactured by Kyowa Interface Science Co., Ltd.

[0160] <Undercoat Layer Forming Step> The image recording method of the present disclosure includes a step of applying an undercoat ink onto a substrate to form an undercoat layer.

[0161] A first embodiment of the base layer forming step is one in which at least one of the base inks is the first base ink. In this case, the base layer forming step preferably includes a step of applying the first base ink onto a substrate to form a first base layer. The first base ink may be applied to the surface of the substrate, or another layer may be formed on the substrate and then the first base ink may be applied to the surface of the other layer. The first base ink contains an aggregating agent and has the function of aggregating inks that are applied later, and is therefore preferably applied to the surface of the substrate.

[0162] A second embodiment of the base layer forming step is one in which at least one of the base inks is the second base ink. In this case, the base layer forming step preferably includes a step of applying the second base ink onto the substrate to form a second base layer. The second base ink may be applied to the surface of the substrate, or another layer may be formed on the substrate and then the second base ink may be applied to the surface of the other layer. From the viewpoint of further improving the laminate strength, the second base ink is preferably applied to the surface of the first base layer formed on the substrate.

[0163] (Substrate) The type of substrate is not particularly limited, and any known substrate can be used. The substrate may be a permeable substrate or a non-permeable substrate.

[0164] For the purpose of obtaining a laminate, the substrate is preferably an impermeable substrate.

[0165] In the present disclosure, the term "impermeability" in an impermeable substrate refers to a property in which the water absorption rate over 24 hours measured in accordance with ASTM D570-98 (2018) is 2.5% or less. Here, the unit of water absorption rate, "%", is based on mass. The water absorption rate is preferably 1.0% or less, and more preferably 0.5% or less.

[0166] Examples of materials for the impermeable substrate include glass, metals (e.g., aluminum, zinc, copper, etc.), and resins (e.g., polyvinyl chloride, cellulose diacetate, cellulose triacetate, cellulose propionate, cellulose butyrate, cellulose acetate butyrate, cellulose nitrate, polyethylene terephthalate, polyethylene, polystyrene, polypropylene, polycarbonate, polyvinyl acetal, nylon, acrylic resin, etc.).

[0167] The material of the impermeable substrate is preferably a resin. Among these, from the viewpoint of versatility, the material of the impermeable substrate is preferably polypropylene, polyethylene, polyethylene terephthalate, nylon, acrylic resin, or polyvinyl chloride.

[0168] The shape of the impermeable substrate is preferably a sheet (film) or plate, and examples of such a shape of the impermeable substrate include a glass plate, a metal plate, a resin sheet (resin film), a plastic-laminated paper, a metal-laminated or metal-deposited paper, and a metal-laminated or metal-deposited plastic sheet (plastic film).

[0169] Examples of impermeable resin substrates include resin sheets (resin films), and specific examples include flexible packaging materials for packaging foods and the like, and floor guide panels in mass retailers.

[0170] Examples of impermeable substrates include not only sheet-shaped (film-shaped) or plate-shaped impermeable substrates, but also textiles (woven fabrics) and nonwoven fabrics formed from impermeable fibers.

[0171] The thickness of the substrate is preferably 0.1 μm to 1,000 μm, more preferably 0.1 μm to 800 μm, and even more preferably 1 μm to 500 μm.

[0172] The substrate may be subjected to a hydrophilization treatment. Examples of hydrophilization treatments include, but are not limited to, corona treatment, plasma treatment, flame treatment, heat treatment, abrasion treatment, light irradiation treatment (e.g., UV treatment), and flame treatment. Corona treatment can be performed using, for example, a Corona Master (product name "PS-10S", manufactured by Shinko Electric Instrumentation Co., Ltd.). The conditions for the corona treatment may be appropriately selected depending on the type of substrate, etc.

[0173] (Method of Applying Base Ink) The method of applying the base ink is not particularly limited, and examples thereof include known methods such as a coating method, a dipping method, and an inkjet recording method.

[0174] Examples of the coating method include known coating methods using a bar coater, extrusion die coater, air doctor coater, blade coater, rod coater, knife coater, squeeze coater, reverse roll coater, and the like.

[0175] When the first base ink is used as the base ink, it is preferable to apply the first base ink to the entire surface of the substrate. Since the first base ink can be applied to the entire surface of the substrate, the method for applying the first base ink may be any of a coating method, a dipping method, and an inkjet recording method.

[0176] When the second base ink is used as the base ink, it is preferable that the second base ink is applied using an inkjet recording method, from the viewpoint of being able to record a high-definition image.

[0177] There are no particular limitations on the ink ejection method used in inkjet recording, and any of the well-known methods may be used, such as a charge control method that uses electrostatic attraction to eject ink, a drop-on-demand method (pressure pulse method) that uses the vibration pressure of a piezoelectric element, an acoustic inkjet method that converts an electric signal into an acoustic beam and irradiates the ink with it, thereby ejecting the ink using radiation pressure, and a thermal inkjet (Bubble Jet (registered trademark)) method that heats the ink to form bubbles and uses the resulting pressure.

[0178] As an inkjet recording method, in particular, the method described in JP-A-54-59936 can be effectively used, in which ink subjected to the action of thermal energy undergoes a sudden change in volume, and the ink is ejected from the nozzles by the force caused by this state change. As an inkjet recording method, the method described in paragraphs 0093 to 0105 of JP-A-2003-306623 can also be applied.

[0179] Ink application in inkjet recording is performed by ejecting ink from the nozzles of an inkjet head.

[0180] Inkjet recording methods include a shuttle method in which a short serial head is scanned across the width of the recording medium to perform recording, and a line method in which a line head is used in which recording elements are arranged to cover the entire area of ​​one side of the recording medium.

[0181] The line method allows for image recording over the entire surface of a recording medium by scanning the recording medium in a direction intersecting the arrangement direction of the recording elements. The line method eliminates the need for a transport system, such as a carriage that scans a short head, as in the shuttle method. Furthermore, compared to the shuttle method, the line method does not require complex scanning control of the carriage movement and the recording medium, and only the recording medium moves. Therefore, the line method achieves faster image recording speeds than the shuttle method.

[0182] The application of the base ink is preferably carried out using an inkjet head having a resolution of 300 dpi or more (more preferably 600 dpi or more, and even more preferably 800 dpi or more), where dpi stands for dots per inch, and 1 inch is 2.54 cm.

[0183] From the viewpoint of obtaining a high-resolution image, the droplet volume of the base ink is preferably 1 pL (picoliter) to 10 pL, and more preferably 1.5 pL to 6 pL. Also, from the viewpoint of improving image unevenness and continuous gradation, it is effective to eject different droplet volumes in combination.

[0184] (Drying Step) The base layer forming step preferably includes a step of applying the base ink and then heating and drying the base ink (hereinafter also referred to as the "drying step").

[0185] Drying means in the drying step include known heating means such as a heater, known air blowing means such as a dryer, and a combination of these.

[0186] Examples of drying methods in the drying step include a method of applying heat using a heater or the like from the side opposite to the surface of the substrate on which the base ink has been applied; a method of applying warm or hot air to the surface of the substrate on which the base ink has been applied; a method of applying heat using an infrared heater from the side opposite to the surface of the substrate on which the base ink has been applied or the surface on which the base ink has been applied; and a combination of these methods.

[0187] The heating temperature in the drying step is preferably 35° C. or higher, more preferably 40° C. or higher. There is no particular upper limit to the heating temperature, but it is preferably 100° C., more preferably 90° C., and even more preferably 70° C.

[0188] The heating time in the drying step is not particularly limited, but is preferably 0.5 seconds to 60 seconds, more preferably 0.5 seconds to 20 seconds, and even more preferably 0.5 seconds to 10 seconds.

[0189] Specifically, when the first base ink is used as the base ink, it is preferable to include a step of drying the first base ink after applying the first base ink.

[0190] By applying the first base ink and then drying the first base ink, the amount of liquid component contained in the first base layer (hereinafter also referred to as "remaining amount of liquid component") can be reduced. When applying white ink to the surface of the first base layer, the amount of remaining liquid component contained in the first base layer is 0.2 g / m at the time when the step of forming the white ink layer is started (i.e., the time when application of the white ink is started). ２ Preferably, the content is 0.15 g / m or less. ２Similarly, when the second base ink is applied to the surface of the first base layer, the remaining amount of the liquid component contained in the first base layer at the time when application of the second base ink starts is preferably 0.2 g / m or less. ２ Preferably, the content is 0.15 g / m or less. ２ The lower limit of the amount of the remaining liquid component contained in the first undercoat layer is not particularly limited, and is, for example, 0 g / m ２ is.

[0191] The remaining amount of liquid component contained in the first underlayer is 0.2 g / m ２ If the thickness is equal to or less than this, the adhesion to the ink layer (for example, the second undercoat layer or the white ink layer) formed on the first undercoat layer is improved, resulting in improved laminate strength.

[0192] Furthermore, when the second base ink is used as the base ink, it is preferable to include a step of drying the second base ink after applying the second base ink.

[0193] By applying the second base ink and then drying the second base ink, the amount of remaining liquid components in the second base layer can be reduced. When applying white ink to the surface of the second base layer, the amount of remaining liquid components in the second base layer is 0.2 g / m at the time when the step of forming the white ink layer is started (i.e., the time when application of the white ink is started). ２ Preferably, the content is 0.15 g / m or less. ２ More preferably, it is 0.1 g / m or less. ２ The lower limit of the amount of the remaining liquid component contained in the second undercoat layer is not particularly limited, and for example, it is 0 g / m ２ is.

[0194] The remaining amount of liquid component contained in the second underlayer is 0.2 g / m ２ If the thickness is not more than 100 nm, the adhesion to an ink layer (for example, a white ink layer) formed on the second underlayer is improved, resulting in improved laminate strength.

[0195] Here, the liquid components mean water and organic solvents.

[0196] The remaining amount of liquid component is calculated by the following method.

[0197] After applying the primer ink to the substrate, the primer ink is dried to form a primer layer. After the primer layer is formed, the substrate is cut to a certain size just before the white ink is applied. The primer layer is extracted with methanol. The amount of organic solvent contained in the extracted liquid is measured by gas chromatography. The amount of methanol used for extraction is removed and the remaining amount of liquid component is measured.

[0198] The image recording method of the present disclosure includes a step of applying a white ink to the surface of an underlayer by inkjet recording to form a white ink layer. Details of the inkjet recording method are the same as those of the inkjet recording method used in applying the underlayer ink.

[0199] A first embodiment of the white ink layer forming step includes applying a white ink to the surface of the first underlayer. In this case, the surface energy of the first underlayer is preferably 40 mN / m to 90 mN / m, more preferably 45 mN / m to 85 mN / m, and even more preferably 45 mN / m to 55 mN / m. When the surface energy of the first underlayer is within the above range, adhesion between the first underlayer and the white ink layer is improved, resulting in improved laminate strength.

[0200] A second embodiment of the white ink layer forming step is to apply a white ink to the surface of the second underlayer. In this case, the surface energy of the second underlayer is preferably 45 mN / m to 60 mN / m, more preferably 45 mN / m to 55 mN / m, and even more preferably 45 mN / m to 50 mN / m. When the surface energy of the second underlayer is within the above range, the adhesion between the second underlayer and the white ink layer is improved, resulting in improved laminate strength.

[0201] The surface energy of the white ink layer is preferably 40 mN / m to 60 mN / m, and more preferably 45 mN / m to 55 mN / m. When the surface energy of the white ink layer is in this range, the adhesion between the white ink layer and the laminate substrate is improved, resulting in improved laminate strength.

[0202] The surface energy is calculated by the Owens-Wendt method. Specific methods for calculating the surface energies of the base layer and the ink layer are as follows. Below, the method for calculating the surface energy of the base layer is described, and in the method for calculating the surface energy of the ink layer, the base layer is read as the ink layer.

[0203] Immediately after the formation of the primer layer on the substrate is completed, a sample of the substrate with the primer layer formed thereon is cut out. The completion of the formation of the primer layer refers to, for example, the completion of a drying process, if one has been performed. The contact angles of water and diiodomethane with the surface of the primer layer are measured using a contact angle meter within 30 minutes of the cut sample. For example, a contact angle meter with the product name "DM-501" manufactured by Kyowa Interface Science Co., Ltd. can be used. The surface energy of the primer layer is calculated by the Owens-Wendt method using the measured contact angles of water and diiodomethane with the surface of the primer layer and the dispersive and polar components of water and diiodomethane. The Owens-Wendt method is described in DK Owens and R.C. Wendt, Journal of Applied Polymer Science, Vol. 13, pp. 1741-1747, (1969).

[0204] A specific calculation method will be described below. When a liquid is dropped onto a solid surface (here, an underlayer), the following equations hold for each parameter at the interface between the solid surface and the liquid. Equation 1 below is known as Young's equation. Equation 2 below is known as Dupre's equation. Equations 3, 4, and 5 below are known as equations based on the Owens-Wendt method.

[0205] gamma Ｓ = γ Ｌcosθ+γ ＳＬ ... (1) W = γ Ｓ +γ Ｌ -γ ＳＬ …(2) γ Ｓ = γ Ｓ ｄ +γ Ｓ ｈ …(3) γ Ｌ = γ Ｌ ｄ +γ Ｌ ｈ ...(4) W = 2(γ Ｓ ｄ gamma Ｌ ｄ ) １／２ +2 (γ Ｓ ｈ gamma Ｌ ｈ ) １／２ …(5)

[0206] In the formulas 1 to 5, the details of each symbol are as follows: θ: contact angle of the liquid with respect to the surface of the underlayer γ: Ｓ …Surface energy of the base layer γ Ｌ ...surface energy of liquid γ ＳＬ …Interfacial energy between the base layer and the liquid W…Work of adhesion γ Ｓ ｄ …Dispersion component of the surface energy of the base layer γ Ｓ ｈ …polar component of the surface energy of the underlayer γ Ｌ ｄ ...dispersion component of the liquid surface energy γ Ｌ ｈ ...polar component of the liquid surface energy

[0207] From the above formulas 1 to 5, the following formula 6 is obtained: (γ Ｓ ｄ gamma Ｌ ｄ ) １／２ + (γ Ｓ ｈ gamma Ｌ ｈ ) １／２ = γ Ｌ (1+cosθ) / 2...(6)

[0208] As the liquid in Equation 6, water and diiodomethane are used, resulting in Equation 6A and Equation 6B. (γ Ｓ ｄ gamma Ｌ１ ｄ ) １／２ + (γ Ｓ ｈ gamma Ｌ１ ｈ ) １／２ = γ Ｌ１ (1+cosθ1) / 2...(6A) (γ Ｓ ｄ gamma Ｌ２ ｄ ) １／２ + (γ Ｓ ｈ gamma Ｌ２ ｈ ) １／２ = γ Ｌ２ (1+cosθ2) / 2...(6B)

[0209] In Formula 6A and Formula 6B, the details of each symbol are as follows: θ1: contact angle of water with respect to the surface of the underlayer θ2: contact angle of diiodomethane with respect to the surface of the underlayer γ Ｌ１ ...surface energy of water (72.8 mN / m) γ Ｌ１ ｄ ...dispersion component of water surface energy (21.8 mN / m) γ Ｌ１ ｈ ...polar component of water surface energy (51.0 mN / m) γ Ｌ２ ...Surface energy of diiodomethane (50.8 mN / m) γ Ｌ２ ｄ ...dispersion component of surface energy of diiodomethane (50.8 mN / m) γ Ｌ２ ｈ ...polar component of surface energy of diiodomethane (0 mN / m) The values ​​in parentheses are values ​​given in the literature.

[0210] In Equation 6A and Equation 6B, θ1, θ2, γ Ｌ１ , γ Ｌ１ ｄ , γ Ｌ１ ｈ , γ Ｌ２ , γ Ｌ２ ｄ , and γ Ｌ２ ｈBy substituting γ Ｓ ｄ and γ Ｓ ｈ The values ​​measured by the above measurement method are used as θ1 and θ2.

[0211] In Equation 3, the calculated γ Ｓ ｄ and γ Ｓ ｈ By substituting, the surface energy of the underlayer γ Ｓ Calculate.

[0212] <Relationship between Surface Energy of Base Layer and Surface Tension of White Ink> In the image recording method disclosed herein, the surface energy of the base layer is higher than the surface tension of the white ink. When a first base layer is formed on a substrate and white ink is applied to the surface of the first base layer, the surface energy of the first base layer is higher than the surface tension of the white ink. Also, when a first base layer and a second base layer are formed on a substrate in this order and white ink is applied to the surface of the second base layer, the surface energy of the second base layer is higher than the surface tension of the white ink. The white ink easily wets and spreads on the surface of the base layer, resulting in excellent adhesion between the base layer and the white ink layer, and as a result, an image recorded product with excellent lamination strength is obtained.

[0213] From the viewpoint of further improving the laminate strength, the difference between the surface energy of the underlayer and the surface tension of the white ink is preferably 3 mN / m to 60 mN / m, more preferably 5 mN / m to 50 mN / m, even more preferably 8 mN / m to 30 mN / m, and particularly preferably 10 mN / m to 20 mN / m. When a first underlayer is formed on a substrate and a white ink is applied to the surface of the first underlayer, the difference between the surface energy of the first underlayer and the surface tension of the white ink is preferably 3 mN / m to 60 mN / m, more preferably 5 mN / m to 50 mN / m, even more preferably 8 mN / m to 30 mN / m, and particularly preferably 10 mN / m to 20 mN / m. When a first underlayer and a second underlayer are formed in this order on a substrate and a white ink is applied to the surface of the second underlayer, the difference between the surface energy of the second underlayer and the surface tension of the white ink is preferably 3 mN / m to 60 mN / m, more preferably 5 mN / m to 50 mN / m, even more preferably 7 mN / m to 25 mN / m, and particularly preferably 10 mN / m to 20 mN / m.

[0214] [Method for manufacturing laminated body] According to the image recording method of the present disclosure, it is possible to produce an image recorded article comprising a substrate and an image recorded on the substrate, which has excellent lamination strength when a substrate for lamination is laminated on the image.

[0215] Therefore, the image recording method of the present disclosure is suitably used for producing a laminated body comprising the image recorded matter and a laminating substrate laminated on the side of the image recorded matter on which the image is recorded.

[0216] A method for manufacturing a laminated body, which is one embodiment of the present disclosure, includes a step of obtaining an image recorded matter having a substrate and an image disposed on the substrate by the image recording method described above, and a step of laminating a laminating substrate onto the side of the image recorded matter on which the image is disposed to obtain a laminated body.

[0217] According to the method for producing a laminate according to one embodiment of the present disclosure, a laminate having excellent lamination strength between an image-recorded material and a substrate for lamination can be produced.

[0218] For the step of obtaining an image recorded product, the image recording method of the present disclosure can be referred to. The step of obtaining a laminated body is a step of obtaining a laminated body by laminating a laminating substrate on the side on which the image is recorded.

[0219] The substrate for lamination is preferably a resin substrate, and is not particularly limited, but examples thereof include substrates made of thermoplastic resins.

[0220] The resin substrate may be, for example, a substrate formed by molding a thermoplastic resin into a sheet shape, and preferably contains polypropylene, polyethylene terephthalate, nylon, polyethylene, or polyimide.

[0221] The shape of the resin substrate is not particularly limited, but a sheet-like resin substrate is preferred. The thickness of the resin substrate is preferably 10 μm to 200 μm, more preferably 10 μm to 100 μm.

[0222] In the step of obtaining a laminate, the substrate for lamination may be laminated directly onto the side on which the image has been recorded, or may be laminated via another layer (for example, an adhesive layer).

[0223] When the substrate for lamination is directly laminated onto the side on which the image has been recorded, the lamination can be carried out by a known method such as thermocompression bonding or heat fusion bonding.

[0224] Furthermore, when laminating a substrate for lamination onto the side on which an image is recorded via an adhesive layer, the lamination can be carried out, for example, by applying an adhesive to the side on which the image is recorded, placing the substrate for lamination on the side, and then bonding the image-recorded material and the substrate for lamination together.

[0225] Furthermore, lamination on the image-recorded side via an adhesive layer can also be carried out by a method such as extrusion lamination (i.e., sandwich lamination).

[0226] The adhesive layer preferably contains an isocyanate compound. When the adhesive layer contains an isocyanate compound, the adhesion between the adhesive layer and the image is further improved, and therefore the lamination strength can be further improved.

[0227] Hereinafter, the present disclosure will be described more specifically with reference to examples, but the present disclosure is not limited to the following examples as long as it does not depart from the gist of the disclosure.

[0228] [Preparation of First Base Ink (Pretreatment Liquid)] In preparing the first base ink, an aqueous dispersion of resin particles A was prepared in advance.

[0229] Preparation of Aqueous Dispersion of Resin Particles A: 3.0 g of sodium dodecylbenzenesulfonate (62% by mass aqueous solution, manufactured by Tokyo Chemical Industry Co., Ltd.) and 376 g of water were placed in a 1000 ml three-neck flask equipped with a stirrer and a condenser, and heated to 90° C. under a nitrogen atmosphere. To the mixed solution in the heated three-neck flask, Solution A, prepared by dissolving 11.0 g of a 50% by weight aqueous solution of sodium 2-acrylamido-2-methylpropanesulfonate (manufactured by Aldrich) in 20 g of water, Solution B, prepared by mixing 12.5 g of 2-hydroxyethyl methacrylate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), 5.0 g of 2-(2-ethoxyethoxy)ethyl acrylate (manufactured by Tokyo Chemical Industry Co., Ltd.), 17.0 g of benzyl acrylate (manufactured by Tokyo Chemical Industry Co., Ltd.), and 10.0 g of styrene (St; Fujifilm Wako Pure Chemical Industries, Ltd.), and Solution C, prepared by dissolving 6.0 g of sodium persulfate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) in 40 g of water, were simultaneously added dropwise over 3 hours. After completion of the dropwise addition, the mixture was allowed to react for another 3 hours to obtain 500 g of an aqueous dispersion of resin particles A (solids concentration: 10.1% by weight). The resin particles A were acrylic resin particles, and had a glass transition temperature of 26° C. The weight average molecular weight of the resin particles A was 69,000.

[0230] (First base ink P11) The following components were mixed to prepare a first base ink P11. Flocculant: Malonic acid (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.) ... 2 mass% Flocculant: Glutaric acid (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.) ... 2 mass% Triisopropanolamine (TIPA) (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.) ... 0.5 mass% Aqueous dispersion of resin particles A ... 8 mass% as the solid content of resin particles A 1,2-propanediol (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.) ... 10 mass% Defoaming agent (product name "TSA-739", manufactured by Momentive Performance Materials Japan, LLC) ... 0.01 mass% as the solid content of the defoaming agent Acetylene glycol-based surfactant (product name "Olfine E1010", manufactured by Nissin Chemical Industry Co., Ltd.) ... 0.5 mass% Water ... the remaining amount to make the entire first base ink 100 mass%

[0231] (First base ink P12) First base ink P12 was prepared by adding 1.0% by mass of a silicone surfactant (product name "BYK-3450", manufactured by BYK Corporation) to the composition of first base ink P11 and reducing the water content.

[0232] (First base ink P13) First base ink P13 was prepared by adding 0.5% by mass of a silicone surfactant (product name "BYK-3450", manufactured by BYK Corporation) to the composition of first base ink P11 and reducing the water content.

[0233] (First base ink P14) The acetylene glycol surfactant contained in the first base ink P11 was changed to an acetylene glycol surfactant (product name "E1020", manufactured by Nissin Chemical Industry Co., Ltd.), and a first base ink P14 was prepared.

[0234] (First base ink P15) The acetylene glycol surfactant contained in the first base ink P11 was changed to a wetting and dispersing agent (product name "DISPERBYK-198", manufactured by BYK Japan KK) to prepare first base ink P15.

[0235] [Preparation of second base ink] Second base inks C21 to C25, each with a pigment concentration of 3% by mass, were prepared by mixing the components shown in Table 1 with water. The content (% by mass) of each component is as shown in Table 1. The water content is omitted in Table 1, but is the remaining amount required for the total content of the second base ink to be 100% by mass.

[0236] Details of each component shown in Table 1 are as follows.

[0237] Cyan pigment dispersion: a dispersion in which a cyan pigment (C.I. Pigment Blue 15:3) is dispersed in a crosslinked polymer (product name "APD4000Cyan", pigment concentration 20.0% by mass, manufactured by FUJIFILM Imaging Colorants) PG: propylene glycol PGmME: propylene glycol monomethyl ether Aqueous dispersion of resin particles: an aqueous dispersion of styrene acrylic resin particles (product name "Neocryl A1091", solid content concentration 45.0% by mass, manufactured by DSM) Acetylene glycol-based surfactant: product name "Olfine E1010", manufactured by Nissin Chemical Industry Co., Ltd. Silicone-based surfactant: product name "BYK-3450", manufactured by BYK Fluorine-based surfactant: product name "Capstone FS-50", manufactured by DuPont) Colloidal silica: product name "Snowtex XS", solid content 20% by mass, manufactured by Nissan Chemical Industries, Ltd.

[0238]

[0239] [Preparation of White Ink] In order to prepare the white ink, a white pigment dispersion was prepared in advance.

[0240] (Preparation of Block Polymer) 266 parts by mass of diethylene glycol dimethyl ether, 6.2 parts by mass of 2-iodo-2-cyanopropane, 120 parts by mass of methyl methacrylate (MMA), 28.8 parts by mass of acrylic acid (AA), 67.2 parts by mass of cyclohexyl methacrylate (CHMA), 7.9 parts by mass of azobisdimethylisovaleronitrile, and 0.7 parts by mass of 2-t-butyl-4,6-dimethylphenol were added to a 1 L separable flask reactor equipped with a stirrer, reflux condenser, thermometer, and nitrogen inlet tube, and the mixture was stirred while flowing nitrogen. Next, the temperature of the mixture in the reactor was raised to 70 ° C., and polymerization was carried out for 3 hours to obtain a polymerization solution A containing an MMA / AA / CHMA copolymer. After 3 hours, a portion of the polymerization solution A was sampled and the solids content was measured. It was found to be 42.0% by mass, confirming that most of the monomers had polymerized. The weight average molecular weight (Mw) of the MMA / AA / CHMA copolymer was measured by GPC and was found to be 7,500. The acid value of the MMA / AA / CHMA copolymer was 101.0 mgKOH / g.

[0241] Next, a mixture of 35.2 parts by mass of benzyl methacrylate (BzMA) and 0.3 parts by mass of 2,2'-azobis(2,4-dimethylvaleronitrile) (product name "V-65", manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was added to the polymerization solution A, and polymerization was carried out at 70°C for 3 hours to obtain polymerization solution B containing block polymer 1. Block polymer 1 is a block polymer containing an A block that is an MMA / AA / CHMA copolymer and a B block that is a BzMA homopolymer. The solids content of the obtained polymerization solution B was measured to be 43.2% by mass, confirming that most of the monomers had polymerized. Furthermore, the Mw of block polymer 1 was 8,500 and the acid value was 89.3 mgKOH / g. Block polymer 1 was used as a pigment dispersant.

[0242] <Preparation of White Pigment Dispersion> 136.4 parts by mass of polymerization solution B containing block polymer 1, 163.6 parts by mass of butyl carbitol, and 450 parts by mass of a white pigment, C.I. Pigment White 6 (trade name "JR-405", titanium dioxide particles, manufactured by Teica Corporation), were blended and stirred with a disperser. Next, the white pigment was thoroughly dispersed using a horizontal media disperser to obtain an oil-based pigment dispersion. The average particle diameter of the white pigment dispersed in the oil-based pigment dispersion was 290 nm. The viscosity (25°C) of the oil-based pigment dispersion was 86.3 mPa·s. Next, while stirring 700 parts by mass of the oil-based pigment dispersion using a disperser, a mixed liquid consisting of 4.0 parts by mass of potassium hydroxide and 341 parts by mass of water was gradually added thereto for neutralization. Thereafter, the white pigment was thoroughly dispersed using a horizontal media disperser to obtain a pigment dispersion. Next, the obtained pigment dispersion was subjected to ultrafiltration using an ultrafiltration device (cross-flow type ultrafilter (UF), manufactured by Sartorius) by passing ion-exchanged water through it at a flow rate of 600 mL per minute. The liquid temperature was maintained at 25°C, and ultrafiltration was performed 10 times, with one cycle being equal to one volume of the liquid charged. Ion-exchanged water was added, and white pigment dispersion 1 having a pigment concentration of 45% by mass and a pigment dispersant concentration of 3.7% by mass was obtained.

[0243] White inks W1 to W5, each with a pigment concentration of 14% by mass, were prepared by mixing the components shown in Table 2 with water. The content (% by mass) of each component is as shown in Table 2. The water content is omitted in Table 2, but is the remaining amount required to make the total content of the white ink 100% by mass.

[0244] Details of each component shown in Table 2 are as follows. Explanation of components common to Table 1 will be omitted. PGmPE: Propylene glycol monopropyl ether

[0245]

[0246] [Examples 1 to 14, Comparative Examples 1 and 2] <Image Recording> A polyethylene terephthalate (PET) substrate (product name "FE2001", manufactured by Futamura Chemical Co., Ltd., thickness 12 μm, width 100 mm, length 240 mm) was prepared as an impermeable substrate (hereinafter also simply referred to as "substrate").

[0247] An image recording device was prepared that included, in this order from the upstream side in the substrate transport direction, a conveying mechanism for conveying the substrate, a wire bar coater for applying the first base ink, a first inkjet head for applying the second base ink, and a second inkjet head for applying the white ink.

[0248] Both the first inkjet head and the second inkjet head were 1200 dpi / 20-inch wide piezo full-line heads, where dpi stands for dots per inch.

[0249] The first inkjet head and the second inkjet head were both arranged as line heads in a direction perpendicular to the transport direction of the substrate (i.e., the width direction of the substrate). As each of the inkjet heads, Samba (registered trademark) G3L (manufactured by FUJIFILM DIMATIX Corporation) was used.

[0250] The substrate, the first base ink, the second base ink, and the white ink were set in the image recording device.

[0251] (Examples 1 to 9, and Comparative Example 1) In Examples 1 to 9 and Comparative Example 1, the first base ink, the second base ink, and the white ink were applied in this order onto a substrate to obtain an image recorded thereon. The specific method is as follows.

[0252] While the substrate was being moved at a constant speed of 50 m / min, the first base ink was applied onto the substrate using a wire bar coater. The applied mass of the first base ink was 2.0 g / m ２ It was decided.

[0253] One second after the application of the first base ink was completed, a dryer was used to blow hot air at 60°C at a speed of 22 m / s for 3 seconds to dry the first base ink, thereby forming a first base layer on the substrate.

[0254] The substrate on which the first undercoat layer was formed was moved at a constant speed of 50 m / min, and the second undercoat ink was applied in a solid image on the surface of the first undercoat layer to form a second undercoat layer. The white ink was applied in a solid image on the surface of the second undercoat layer to form a white ink layer. The ejection conditions for both the second undercoat ink and the white ink were a resolution of 1200 dpi x 1200 dpi and an ejection frequency of 39.37 kHz.

[0255] In Example 5, after the second base ink was applied, the second base ink was dried by applying drying air at 120°C for 45 seconds at a speed of 100 m / s using a dryer on a hot plate at 65°C. In the other examples and Comparative Example 1, similar drying was not performed.

[0256] (Examples 10 to 14, and Comparative Example 2) In Examples 10 to 14, and Comparative Example 2, the first base ink and the white ink were applied in this order onto the substrate to obtain an image recorded thereon. The specific method is as follows.

[0257] While the substrate was being moved at a constant speed of 50 m / min, the first base ink was applied onto the substrate using a wire bar coater. The applied mass of the first base ink was 2.0 g / m ２ It was decided.

[0258] One second after the application of the first primer ink was completed, a dryer was used to blow hot air at 60°C at a speed of 22 m / s for 3 seconds to dry the first primer ink, thereby forming a first primer layer on the substrate. In Example 13, the hot air speed was changed to 10 m / s to dry the first primer ink.

[0259] While the substrate on which the first underlayer was formed was being moved at a constant speed of 50 m / min, a white ink was applied in a solid image form to the surface of the first underlayer, forming a white ink layer under the conditions of a resolution of 1200 dpi × 1200 dpi and a discharge frequency of 39.37 kHz.

[0260] A laminate was produced using the obtained image-recorded matter, and the laminate strength was evaluated. Furthermore, the continuous ejection property of the second base ink was evaluated. The evaluation method was as follows.

[0261] <Lamination Strength> A region of 200 mm length x 100 mm width (hereinafter also referred to as laminate strength evaluation region) having a solid image provided on the entire surface was cut out from the image recorded product to provide a laminate strength evaluation sample.

[0262] A dry laminating adhesive (main agent TM-320 (isocyanate compound) / curing agent CAT-13B (alcohol compound), manufactured by Toyo-Morton Co., Ltd.) was applied onto the solid image of the laminate strength evaluation sample using a bar coater and dried at 70°C for 10 seconds. Furthermore, a non-oriented polypropylene (CPP) film (trade name: Pylen P1128, manufactured by Toyobo Co., Ltd., thickness 25 μm) was overlaid as a laminating substrate. In this state, the laminating substrate and the laminate strength evaluation sample were bonded together to obtain a laminate. The obtained laminate was aged at 40°C for 48 hours.

[0263] A sample piece measuring 100 mm long x 15 mm wide was cut out from the aged laminate. Next, the laminating substrate and the laminate strength evaluation sample were manually peeled from a region extending from one longitudinal end of the sample piece to a length of 30 mm. The laminating substrate and the laminate strength evaluation sample were left attached to each other in the remaining 70 mm region. Next, a tensile test was conducted in which the laminating substrate and the laminate strength evaluation sample in the peeled portion of the sample piece were pulled in opposite directions. The pulling direction was perpendicular to the remaining 70 mm region (the region where the laminating substrate and the laminate strength evaluation sample remained attached). This tensile test determined the peel strength required to peel the laminating substrate and the laminate strength evaluation sample in the remaining 70 mm region, and the resulting peel strength was taken as the laminate strength. The tensile test was carried out at 25°C using a tensile tester (product name "TENSILON RTM-25", manufactured by Orientec Co., Ltd.). The evaluation criteria are as follows: AA: Laminate strength is 2.0 N / 15 mm or more. A: Laminate strength is 1.5 N / 15 mm or more and less than 2.0 N / 15 mm. B: Laminate strength is 1.0 N / 15 mm or more and less than 1.5 N / 15 mm. C: Laminate strength is 0.5 N / 15 mm or more and less than 1.0 N / 15 mm. D: Laminate strength is less than 0.5 N / 15 mm.

[0264] <Continuous Dischargeability> A Samba G3L (manufactured by FUJIFILM DIMATIX) was used as the inkjet head. The obtained second base ink was continuously discharged for 45 minutes from the 2,048 nozzles of the inkjet head under conditions of a droplet volume of 2 pL and a discharge frequency of 24 kHz. At the start of discharge, it was confirmed that ink was being discharged from all 2,048 nozzles. After the continuous discharge was completed, the number of nozzles that were able to discharge to the end without clogging (number of discharge nozzles) was counted. The number of discharge nozzles was used to calculate the ink discharge rate according to the following formula. The continuous dischargeability was evaluated based on the ink discharge rate. The evaluation criteria were as follows: Ink discharge rate (%) = (number of discharge nozzles / total number of nozzles) × 100. In the above formula, the total number of nozzles was 2,048. A: The ink discharge rate was 98% or more. B: The ink discharge rate was 92% or more but less than 98%. C: The ink discharge rate was less than 92%.

[0265] The evaluation results are shown in Table 3. Table 3 lists the types of first base ink, second base ink, and white ink used in each example and comparative example. It also lists the surface tensions (unit: mN / m) of the second base ink and white ink, and the surface energies (unit: mN / m) of the base layer and white ink layer. When the surface tension of the white ink is W and the surface energy of the base layer is E0, "E0-W" (unit: mN / m) means the value obtained by subtracting the surface tension of the white ink from the surface energy of the base layer. Furthermore, "at the start of application of white ink" refers to the remaining amount of liquid component (unit: g / m) at the time when application of white ink starts. ２ ) means

[0266]

[0267] As shown in Table 3, Examples 1 to 14 include a step of preparing a white ink and a base ink, a step of applying the base ink onto a substrate to form a base layer, and a step of applying white ink to the surface of the base layer by an inkjet recording method to form a white ink layer.It was found that the surface energy of the base layer was higher than the surface tension of the white ink, and therefore it was possible to record an image with excellent lamination strength with the lamination substrate.

[0268] On the other hand, in Comparative Example 1, the surface energy of the base layer and the surface tension of the white ink were the same, and in Comparative Example 2, the surface energy of the base layer was lower than the surface tension of the white ink, resulting in inferior laminate strength.

[0269] In Example 13, white ink was applied to the surface of the first base layer, and the surface energy of the first base layer was 85 mN / m or less, so it was found that the laminate strength was superior to Example 12. In Example 11, white ink was applied to the surface of the first base layer, and the surface energy of the first base layer was 45 mN / m or more, so it was found that the laminate strength was superior to Example 14.

[0270] In Example 5, white ink was applied to the surface of the second base layer, and the surface energy of the second base layer was 45 mN / m or more, so it was found that the laminate strength was superior to that of Example 9. In Example 5, white ink was applied to the surface of the second base layer, and the surface energy of the second base layer was 55 mN / m or less, so it was found that the laminate strength was superior to that of Example 4.

[0271] In Example 5, a process of drying the second base ink after applying the second base ink and before applying the white ink is included, and therefore it was found that the laminate strength was superior to that of Example 1.

[0272] In Example 1, the SP value of the second base ink is 24 MPa. １／２ It was found that the continuous discharge property was superior to that of Example 2 because the content of the following organic solvent was 5% by mass or less.

[0273] In Example 5, at the start of the step of forming the white ink layer, the remaining amount of the liquid component contained in the underlayer was 0.1 g / m ２ Since the results are as follows, it was found that the laminate strength was superior to that of Example 1.

[0274] In Example 1, the difference between the surface energy of the base layer and the surface tension of the white ink was 10 mN / m or more, and therefore it was found that the laminate strength was superior to Example 3. In Example 7, the difference between the surface energy of the base layer and the surface tension of the white ink was 20 mN / m or less, and therefore it was found that the laminate strength was superior to Example 8.

[0275] In Example 7, the surface energy of the white ink layer was 45 mN / m or more, and therefore it was found that the laminate strength was superior to that of Example 8. In Example 7, the surface energy of the white ink layer was 55 mN / m or less, and therefore it was found that the laminate strength was superior to that of Example 6.

Claims

1. preparing a white ink containing a white pigment and at least one type of base ink having a different hue from that of the white ink; applying the undercoat ink onto a substrate to form an undercoat layer; applying the white ink to a surface of the underlayer by an inkjet recording method to form a white ink layer; The image recording method, wherein the surface energy of the undercoat layer is higher than the surface tension of the white ink.

2. At least one of the base inks is a first base ink containing a coagulant; the step of forming the underlayer includes a step of applying the first underlayer ink onto the base material to form a first underlayer; the step of forming the white ink layer includes a step of applying the white ink to a surface of the first underlayer by an inkjet recording method; 2. The image recording method according to claim 1, wherein the first underlayer has a surface energy of 45 mN / m to 85 mN / m.

3. At least one of the base inks is a second base ink containing a colorant other than a white pigment, the step of forming the underlayer includes a step of applying the second underlayer ink onto the base material to form a second underlayer; the step of forming the white ink layer includes a step of applying the white ink to a surface of the second underlayer by an inkjet recording method; 2. The image recording method according to claim 1, wherein the second underlayer has a surface energy of 45 mN / m to 55 mN / m.

4. At least one of the base inks is a first base ink containing a coagulant; At least one of the base inks is a second base ink containing a colorant other than a white pigment, the step of forming the underlayer includes a step of applying the first underlayer ink onto the base material to form a first underlayer, and a step of applying the second underlayer ink onto a surface of the first underlayer to form a second underlayer, the step of forming the white ink layer includes a step of applying the white ink to a surface of the second underlayer by an inkjet recording method; 2. The image recording method according to claim 1, wherein the second underlayer has a surface energy of 45 mN / m to 55 mN / m.

5. 5. The image recording method according to claim 3, wherein the second base ink and the white ink each have a surface tension of 40 mN / m or less.

6. The method includes forming the undercoat layer and forming the white ink layer in this order, the step of forming the base layer further includes a step of drying the second base ink. The image recording method according to claim 3 or 4.

7. The second base ink has an SP value of 24 MPa. １／２ Does not contain the following organic solvents or has an SP value of 24 MPa or less １／２ The image recording method according to claim 3 or 4, wherein a content of the following organic solvent is more than 0% by mass and 5% by mass or less with respect to a total amount of the second base ink:

8. At the time when the step of forming the white ink layer is started, the amount of the remaining liquid component contained in the undercoat layer is 0.1 g / m ２ 3. The image recording method according to claim 1, wherein:

9. 3. The image recording method according to claim 1, wherein a difference between the surface energy of the underlayer and the surface tension of the white ink is 10 mN / m to 20 mN / m.

10. 3. The image recording method according to claim 1, wherein the white ink layer has a surface energy of 45 mN / m to 55 mN / m.

11. A step of obtaining an image recorded matter comprising the substrate and an image disposed on the substrate by the image recording method according to claim 1 or 2; a step of laminating a substrate for lamination onto the side of the image recorded product on which the image is disposed to obtain a laminate; A method for producing a laminate comprising the steps of:

12. Used in the image recording method according to claim 4, A conveying mechanism for conveying the base material is provided, a wire bar coater for applying the first base ink, a first inkjet head for applying the second base ink, and a second inkjet head for applying the white ink, in this order from an upstream side in a transport direction of the base material; Image recording device.