Inkjet ink, ink set, image recording method, and method for manufacturing laminate

Abstract

Provided is an inkjet ink capable of recording an image having excellent adhesion to a substrate or the like (e.g., lamination strength to a lamination substrate disposed on an image surface of an image recording material), and use thereof. The inkjet ink contains water, a white pigment, and at least two types of resins, and has an acid value of 8.0 mgKOH / g or less.

Description

Technical Field

[0001] This invention relates to an inkjet ink, an ink assembly, an image recording method, and a method for manufacturing a laminate. Background Technology

[0002] In the past, various studies have been conducted on image recording using ink.

[0003] For example, Patent Document 1 discloses an ink composition containing resin particles and amino alcohols. The resin particles have an acid value of 10 mg KOH / g or less, and the amino alcohols have a standard boiling point of 320°C or less. The ink may or may not contain pigments, and the total content of the resin particles and pigments is 17% by mass or less relative to the total mass of the ink composition. Patent Document 2 discloses a water-based inkjet ink composition containing resin particles, a nonionic surfactant, a resin-soluble solvent, and water. The total acid value of the resin particles and the dispersant resin (in the case where the water-based inkjet ink composition contains a dispersant resin) is 200 mg KOH / 100g or less. Patent Document 3 discloses an inkjet ink composition containing pigments, water, an organic solvent, and resin particles. The resin particles contain resins with an elastic modulus of 400 MPa or more and 1000 MPa or less. The total content of pyrrolidones and glycol monoethers in the organic solvent is 1.5% by mass or less relative to the total mass of the inkjet ink composition.

[0004] Previous technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2021-91822

[0007] Patent Document 2: Japanese Patent Application Publication No. 2018-165314

[0008] Patent Document 3: Japanese Patent Application Publication No. 2017-190370 Summary of the Invention

[0009] The technical problem to be solved by the invention

[0010] Depending on the intended use, the images to be recorded are required to adhere to a variety of substrates.

[0011] After recording an image on a substrate to obtain an image recording, a laminating substrate is sometimes laminated onto the image of the image recording to create a laminate. Furthermore, there are times when it is required to increase the lamination strength between the image recording and the laminating substrate.

[0012] The present invention was made in view of this situation. The problem to be solved by the embodiments of the present invention is to provide an inkjet ink, an ink group and an image recording method capable of recording images with excellent adhesion to substrates such as substrates (e.g., lamination strength with a laminating substrate disposed on the image surface of an image recorder).

[0013] Another problem to be solved by an embodiment of the present invention is to provide a method for manufacturing a laminate that can produce a laminate with excellent lamination strength between a laminating substrate and an image recording material.

[0014] means for solving technical problems

[0015] The present invention includes the following methods.

[0016] <1> An inkjet ink comprising water, a white pigment, and at least two resins.

[0017] The acid value is below 8.0 mg KOH / g.

[0018] <2> according to <1> The inkjet ink, wherein,

[0019] The acid value ranges from 1.5 mg KOH / g to 4.0 mg KOH / g.

[0020] <3> according to <1> or <2> The inkjet ink, wherein,

[0021] The elastic modulus of the ink film formed by curing is 2.5 GPa to 5.0 GPa.

[0022] <4> according to <1> to <3> In any one of the inkjet inks, wherein,

[0023] The acid value of at least one of the two resins is below 40 mg KOH / g.

[0024] <5> according to <1> to <4> In any one of the inkjet inks, wherein,

[0025] At least one of the two resins exists in the form of resin particles.

[0026] <6> according to <5> The inkjet ink, wherein,

[0027] The content of resin particles relative to the total amount of inkjet ink is 3% to 8% by mass.

[0028] <7> An ink assembly comprising:

[0029] The first ink, for <1> to <6> The inkjet ink as described in any one of the following; and

[0030] The second ink is an inkjet ink containing pigments and resins other than water and white pigment.

[0031] <8> according to <7> The ink group, wherein,

[0032] The acid value of the second ink is below 8.0 mg KOH / g.

[0033] <9> according to <7> The ink group, wherein,

[0034] The acid value of the second ink is 1.0 mg KOH / g to 5.0 mg KOH / g.

[0035] <10> according to <7> to <9> In any one of the ink groups, wherein,

[0036] The absolute value of the difference between the acid value of the first ink and the acid value of the second ink is less than 2.0 mg KOH / g.

[0037] <11> according to <7> to <10> In any one of the ink groups, wherein,

[0038] The elastic modulus of the ink film formed by curing the second ink is 2.5 GPa to 5.0 GPa.

[0039] <12> according to <7> to <11> The ink group described in any one of the above statements further comprises a pretreatment solution containing water and resin.

[0040] <13> according to <12> The ink group, wherein,

[0041] The elastic modulus of the pretreatment liquid film formed by curing the pretreatment liquid is the same as or less than the elastic modulus of the ink film formed by curing the second ink.

[0042] <14> An image recording method that uses <1> to <6> The inkjet ink as described in any one of the following, wherein the image recording method includes a step of applying inkjet ink to a substrate by inkjet recording.

[0043] <15> An image recording method that uses <7> to <11> The ink group described in any one of the following statements,

[0044] The image recording method includes a process of applying a first ink and a second ink to a substrate by inkjet recording.

[0045] <16> An image recording method that uses <12> or <13> The ink group mentioned above,

[0046] The image recording method includes:

[0047] The process of applying a pretreatment liquid to a substrate; and

[0048] The process of applying the first ink and the second ink to a substrate that has been treated with a pretreatment liquid by inkjet recording.

[0049] <17> A method for manufacturing a laminate, comprising:

[0050] pass <14> to <16> The image recording method described in any one of the above describes the process of obtaining an image record having a substrate and an image disposed on the substrate; and

[0051] The process of laminating a laminating substrate onto the side of an image recorder containing the image to obtain a laminate.

[0052] Invention Effects

[0053] According to embodiments of the present invention, an inkjet ink, an ink group, and an image recording method are provided that are capable of recording images with excellent adhesion to substrates such as substrates (e.g., lamination strength with a laminating substrate disposed on the image surface of an image recorder).

[0054] According to another embodiment of the present invention, a method for manufacturing a laminate capable of producing a laminate with excellent lamination strength between a laminating substrate and an image recording material is provided. Attached Figure Description

[0055] Figure 1 This is a diagram illustrating the details of the character quality evaluation criteria in the embodiments. Detailed Implementation

[0056] The inkjet ink, ink assembly, image recording method, and method for manufacturing the laminate of the present invention will be described in detail below.

[0057] In this specification, the numerical range indicated by “~” represents the range of minimum and maximum values ​​recorded before and after “~”, respectively.

[0058] Within the numerical ranges described in this specification, the upper or lower limit of a certain numerical range can be replaced with the upper or lower limit of other numerical ranges described in different periods. Furthermore, within the numerical ranges described in this specification, the upper or lower limit of a certain numerical range can also be replaced with the values ​​shown in the embodiments.

[0059] In this specification, if a composition contains multiple substances corresponding to each component, unless otherwise specified, the amount of each component in the composition represents the total amount of the multiple substances present in the composition.

[0060] In this specification, a combination of two or more preferred methods is a more preferred method.

[0061] In this specification, the term "process" includes not only individual processes, but also processes that achieve the desired purpose of the process, even if they cannot be clearly distinguished from other processes.

[0062] In this specification, "image" refers to the entire film formed by sequentially applying a pretreatment solution and ink, and "image recording" refers to the formation of an image (i.e., the film).

[0063] Furthermore, the concept of "image" in this specification also includes solid images.

[0064] In this specification, "(meth)acrylate" is a concept that includes both acrylates and methacrylates. Furthermore, "(meth)acrylic acid" is a concept that includes both acrylic acid and methacrylic acid.

[0065] Inkjet ink

[0066] The inkjet ink of the present invention (hereinafter also referred to as "ink") contains water, white pigment and at least two kinds of resin, and has an acid value of less than 8.0 mg KOH / g.

[0067] The ink according to the present invention exhibits excellent adhesion between the image recorded with the ink and a substrate, etc. In particular, when a laminating substrate is disposed on the image surface of an image recorder, the lamination strength between the image and the laminating substrate is excellent when the laminating substrate is laminated onto the image recorded with the ink.

[0068] Here, lamination strength refers to the peel strength when peeling the laminate and image recording material from the laminate formed by the above-mentioned lamination [i.e., a laminate having a laminate structure of "laminated substrate / image recording material" (more specifically, a laminate structure of "laminated substrate / image / substrate").]

[0069] The reason why the ink of the present invention achieves the above-mentioned effects is speculated as follows.

[0070] The ink of the present invention has an acid value of 8.0 mg KOH / g or less, thus exhibiting excellent adhesion between the recorded image and the substrate. In the case of a laminate obtained by placing a laminating substrate on the image surface of an image recorder, it is necessary to improve the adhesion between the ink layer formed by the ink and the laminating substrate in order to improve the lamination strength of the laminate.

[0071] The ink of the present invention has an acid value of less than 8.0 mg KOH / g, which improves the adhesion between the ink layer and the substrate for lamination, and therefore it is speculated that the lamination strength will be improved.

[0072] On the other hand, Patent Documents 1 to 3 did not focus on the acid value of inks containing white pigments.

[0073] The components contained in the ink of the present invention will be described below.

[0074] (White pigment)

[0075] The ink of this invention contains a white pigment. The white pigment contained in the ink may be only one type, or it may be two or more types.

[0076] Examples of white pigments include titanium dioxide, barium sulfate, calcium carbonate, silicon dioxide, zinc oxide, zinc sulfide, mica, talc, and pearl.

[0077] The white pigment is preferably titanium dioxide, barium sulfate, calcium carbonate or zinc oxide, and more preferably titanium dioxide.

[0078] From the viewpoint of concealment, the average primary particle size of the white pigment is preferably 150 nm or more, more preferably 200 nm or more. Furthermore, from the viewpoint of ink sprayability, the average primary particle size of the white pigment is preferably 400 nm or less, more preferably 350 nm or less.

[0079] In this invention, the average primary particle size of the white pigment is a value measured using a transmission electron microscope (TEM). Specifically, it is obtained by selecting any 50 white pigments present within the field of view observed by the TEM, measuring the primary particle size of each of the 50 pigments, and then averaging the results. The transmission electron microscope can be a JEOL Ltd. 1200EX transmission electron microscope.

[0080] From the viewpoint of image density and ink sprayability, the content of white pigment in the ink is preferably 5% to 25% by mass relative to the total amount of ink, and more preferably 10% to 20% by mass.

[0081] (resin)

[0082] The ink of the present invention contains at least two resins. The ink may contain two or more resins.

[0083] The resin can be a dispersant that functions to disperse white pigments, or it can be a resin that is added separately to the ink along with the dispersant. Hereinafter, the resin that functions as a dispersant will also be referred to as a "dispersing resin." Furthermore, the resin other than the one that functions as a dispersant will also be referred to as an "additive resin." The at least two resins can be at least two dispersing resins, at least one dispersing resin and at least one additive resin, or at least two additive resins.

[0084] From the viewpoint of improving the adhesion between the substrate and the image, at least two resins are preferably at least one dispersion resin and at least one additive resin. Furthermore, as described later, from the viewpoint of improving the lamination strength of the image recorder, the additive resin is preferably present in the form of resin particles. Therefore, in the ink of the present invention, at least two resins are preferably at least one dispersion resin and at least one resin particle.

[0085] The type of resin is not particularly limited, and examples include acrylic resins, epoxy resins, urethane resins, polyethers, polyamides, phenolic resins, silicone resins, fluororesins, vinyl resins (e.g., vinyl chloride resins, vinyl acetate resins, vinyl alcohol resins, vinyl butyral resins), alkyd resins, polyester resins, melamine resins, melamine-formaldehyde resins, amino alkyd cocondensation resins, and urea resins. From the viewpoint of improving the adhesion between the image and the substrate (especially the lamination strength between the image and the substrate used for lamination), acrylic resins are preferred.

[0086] In this invention, acrylic resin refers to a polymer containing structural units derived from (meth)acrylic acid compounds having an acryloyl group (CH2=CH-C(=O)-) or a methacryloyl group (CH2=C(CH3)-C(=O)-). Examples of (meth)acrylic acid compounds include, for example, (meth)acrylic acid, (meth)acrylates, and (meth)acrylamide. In acrylic resins, structural units other than those derived from (meth)acrylic acid compounds include, for example, structural units derived from styrene. Styrene-acrylic resins are included in acrylic resins.

[0087] From a sprayability perspective, the total resin content in the ink is preferably 30% by mass or less, more preferably 20% by mass or less, and even more preferably 10% by mass or less, relative to the total amount of ink. The lower limit for the resin content is not particularly limited, for example, it is 0.1% by mass.

[0088] From the viewpoint of setting the acid value of the ink to 8 mg KOH / g or less, the acid value of at least one of the at least two resins contained in the ink is preferably 90 mg KOH / g or less, more preferably 60 mg KOH / g or less, even more preferably 40 mg KOH / g or less, and particularly preferably 20 mg KOH / g or less. The lower limit of the acid value is not particularly limited and can be 0 mg KOH / g. The acid value of the resin particles contained in the ink is preferably 1 mg KOH / g or more, more preferably 2 mg KOH / g or more.

[0089] In this invention, the acid value is a value determined by the method described in JIS K0070:1992.

[0090] - Resins that function as dispersants (dispersion resins) -

[0091] The dispersion resin is typically pre-mixed with the pigment and contained in the pigment dispersion. The dispersion resin can be appropriately selected from conventionally known dispersants and can be either a random copolymer or a block copolymer. Furthermore, the dispersion resin may also have a cross-linked structure.

[0092] The dispersion resin is preferably a random copolymer.

[0093] Random copolymers preferably contain structural units derived from hydrophobic monomers and structural units derived from monomers containing anionic groups (hereinafter referred to as "anionic monomers"). From the viewpoint of dispersion stability, the ratio (a:b) of structural unit a derived from hydrophobic monomers to structural unit b derived from anionic monomers is preferably 8:1 to 1:1.

[0094] The structural units derived from hydrophobic monomers contained in random copolymers can be of only one type or more types.

[0095] The structural units derived from anionic monomers contained in random copolymers can be of only one type or more types.

[0096] The hydrophobic monomer is preferably a monomer containing a hydrocarbon group having 4 or more carbon atoms, more preferably an olefinic unsaturated monomer containing a hydrocarbon group having 4 or more carbon atoms, and even more preferably a (meth)acrylate containing a hydrocarbon group having 4 or more carbon atoms. The hydrocarbon group can be any of a chain hydrocarbon group, an alicyclic hydrocarbon group, or an aromatic hydrocarbon group. The hydrocarbon group more preferably has 6 or more carbon atoms, and even more preferably 10 or more. The upper limit for the number of carbon atoms in the hydrocarbon group is, for example, 20.

[0097] Examples of (meth)acrylates having a chain-like hydrocarbon group having 4 or more carbon atoms include n-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, lauryl (meth)acrylate, and stearyl (meth)acrylate. The chain-like hydrocarbon group more preferably has 6 or more carbon atoms, further preferably 8 or more, and particularly preferably 12 or more. Among these, the olefinically unsaturated monomer having a chain-like hydrocarbon group having 4 or more carbon atoms is preferably lauryl (meth)acrylate or stearyl (meth)acrylate.

[0098] Examples of (meth)acrylates having an alicyclic hydrocarbon group having four or more carbon atoms include (meth)acrylate (bicyclo[2.2.1]heptyl-2) ester, (meth)acrylate 1-adamantyl ester, (meth)acrylate 2-adamantyl ester, (meth)acrylate 3-methyl-1-adamantyl ester, (meth)acrylate 3,5-dimethyl-1-adamantyl ester, (meth)acrylate 3-ethyladamantyl ester, (meth)acrylate 3-methyl-5-ethyl-1-adamantyl ester, (meth)acrylate 3,5,8-triethyl-1-adamantyl ester, (meth)acrylate 3,5-dimethyl-8-ethyl-1-adamantyl ester, and (meth)acrylate 2-methyl-2-adamantyl ester. Esters, 2-ethyl-2-adamantyl ester of (meth)acrylate, 3-hydroxy-1-adamantyl ester of (meth)acrylate, octahydro-4,7-menthol indene-5-yl ester of (meth)acrylate, octahydro-4,7-menthol indene-1-yl methyl ester of (meth)acrylate, 1-menthyl ester of (meth)acrylate, tricyclodecyl ester of (meth)acrylate, 3-hydroxy-2,6,6-trimethyl-bicyclo[3.1.1]heptyl ester of (meth)acrylate, 3,7,7-trimethyl-4-hydroxy-bicyclo[4.1.0]heptyl ester of (meth)acrylate, (nor)bornyl ester of (meth)acrylate, isobornyl ester of (meth)acrylate, 2,2,5-trimethylcyclohexyl ester of (meth)acrylate, and cyclohexyl ester of (meth)acrylate. The alicyclic hydrocarbon group preferably has 6 or more carbon atoms. Among them, the olefinic unsaturated monomer having an alicyclic hydrocarbon group with 4 or more carbon atoms is preferably isobornyl methacrylate or cyclohexyl methacrylate.

[0099] Examples of (meth)acrylates having an aromatic hydrocarbon group having 4 or more carbon atoms include 2-naphthyl (meth)acrylate, phenoxyethyl (meth)acrylate, and benzyl (meth)acrylate. Among these, the olefinic unsaturated monomer having an aromatic hydrocarbon group having 4 or more carbon atoms is preferably benzyl (meth)acrylate.

[0100] Hydrophobic monomers may also contain (meth)acrylates with a hydrocarbon group having 1 to 3 carbon atoms.

[0101] Examples of (meth)acrylates having a hydrocarbon group having 1 to 3 carbon atoms include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, and hydroxyethyl (meth)acrylate.

[0102] From the viewpoint of improving the dispersion stability of white pigments, the structural units derived from hydrophobic monomers contained in the dispersion resin preferably include structural units derived from (meth)acrylates with a chain hydrocarbon group having 4 or more carbon atoms and structural units derived from (meth)acrylates with an aromatic hydrocarbon group having 4 or more carbon atoms.

[0103] Examples of anionic groups in monomers containing anionic groups include carboxyl groups, salts of carboxyl groups, sulfonyl groups, salts of sulfonyl groups, phosphate groups, salts of phosphate groups, phosphonic acid groups, and salts of phosphonic acid groups.

[0104] As counterions in salts, examples include alkali metal ions such as sodium ions, potassium ions, and lithium ions; alkaline earth metal ions such as calcium ions and magnesium ions; and ammonium ions.

[0105] The anionic group is preferably a carboxyl group or a salt of a carboxyl group.

[0106] Examples of carboxyl-containing monomers include (meth)acrylic acid, β-carboxyethyl acrylate, fumaric acid, itaconic acid, maleic acid, and crotonic acid.

[0107] From the viewpoint of dispersion stability, monomers containing anionic groups are preferably (meth)acrylic acid or β-carboxyethyl acrylate, and more preferably (meth)acrylic acid.

[0108] The ratio of white pigment content to dispersion resin content, based on mass, is preferably 1:0.04 to 1:3, more preferably 1:0.05 to 1:1, and even more preferably 1:0.05 to 1:0.5.

[0109] From the viewpoint of dispersion stability, the acid value of the dispersion resin is preferably 100 mg KOH / g or more, and more preferably 120 mg KOH / g or more. On the other hand, from the viewpoint of setting the acid value of the ink to 8 mg KOH / g or less, the acid value of the dispersion resin is preferably 300 mg KOH / g or less, and more preferably 230 mg KOH / g or less.

[0110] When the ink contains a dispersing resin as a resin, the content of the dispersing resin relative to the total amount of ink is preferably 0.1% to 10% by mass, more preferably 0.3% to 5% by mass, and even more preferably 0.5% to 2.5% by mass.

[0111] - Resins other than resins that function as dispersants (added resins) -

[0112] Inks can be prepared, for example, by adding an additive resin to a pigment dispersion. Examples of additive resins include water-soluble resins and water-insoluble resins. Water-insoluble resins are dispersed in water and exist in the form of resin particles.

[0113] In this invention, "water solubility" refers to the property that the amount of water solubility in 100g of water at 25°C is 1g or more. Preferably, "water solubility" is the property that the amount of water solubility in 100g of water at 25°C is 3g or more (more preferably 10g or more).

[0114] In this invention, "water insoluble" refers to the property that the amount of water that can be dissolved in 100g of water at 25°C is less than 1g. Preferably, the property that the amount of water that can be dissolved in 100g of water at 25°C is less than 0.5g is preferred.

[0115] The added resin preferably exists in the form of resin particles, and at least one of the at least two resins contained in the ink preferably exists in the form of resin particles. That is, the ink preferably contains resin particles. If the ink contains resin particles, the strength of the ink film is improved, thereby improving the lamination strength of the image recorder. The resin particles are preferably acrylic resin particles or urethane resin particles.

[0116] The resin particles may contain only one type of resin or two or more types of resin.

[0117] The resin contained in the resin particles preferably has an aliphatic ring or an aromatic ring, more preferably an aromatic ring.

[0118] The aliphatic ring is preferably an alicyclic hydrocarbon with 5 to 10 carbon atoms, and is preferably a cyclohexane ring structure, a bicyclopentane ring structure, a bicyclopentene ring, or an adamantane ring.

[0119] As an aromatic ring, a naphthalene ring or a benzene ring is preferred, and a benzene ring is more preferred.

[0120] From the viewpoint of further improving the water dispersibility of resin particles, the resin contained in the resin particles preferably has ionic groups.

[0121] The ionic group can be either anionic or cationic, but from the viewpoint of easy introduction, anionic groups are preferred.

[0122] There are no particular limitations on the anionic group, but carboxyl or sulfonyl is preferred, and sulfonyl is more preferred.

[0123] The weight-average molecular weight 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.

[0124] From the viewpoint of spray stability, the average particle size 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. Furthermore, the average particle size of the resin particles is determined by measuring the volume average particle size using a particle size distribution measuring device (e.g., Nikkiso Co., Ltd., product name "NANOTRAC UPA-EX150") via dynamic light scattering.

[0125] From the viewpoint of setting the acid value of the ink to 8 mg KOH / g or less, the acid value of the resin particles is preferably 90 mg KOH / g or less, more preferably 60 mg KOH / g or less, even more preferably 40 mg KOH / g or less, and particularly preferably 20 mg KOH / g or less. The lower limit of the acid value of the resin particles is not particularly limited and can be 0 mg KOH / g. The acid value of the resin particles contained in the ink is preferably 1 mg KOH / g or more, more preferably 2 mg KOH / g or more.

[0126] The method for determining the acid value of resin particles is the same as the method for determining the acid value of the dispersed resin described above.

[0127] When the ink contains resin particles as resin, the content of resin particles relative to the total amount of ink is preferably 2% to 10% by mass, more preferably 3% to 8% by mass. If the content of resin particles is 2% by mass or more, the lamination strength of the image recorder is improved. On the other hand, if the content of resin particles is 10% by mass or less, the dispersion stability is improved.

[0128] (water)

[0129] The ink of this invention contains water. The water content is not particularly limited, for example, it is 40% to 70% by mass.

[0130] (Organic solvents)

[0131] The ink of the present invention preferably contains an organic solvent. The organic solvent contained in the ink may be one type or two or more types.

[0132] From the viewpoint of spray stability and lamination strength, the organic solvent preferably includes an organic solvent with a boiling point below 200°C, and more preferably an organic solvent with a boiling point of 120°C to 200°C.

[0133] The content of organic solvents with a boiling point of 200°C or higher is preferably 5% by mass or less, more preferably 2% by mass or less, and even more preferably 0% by mass relative to the total amount of ink. That is, it is preferable that the ink does not contain organic solvents with a boiling point of 200°C or higher. When the ink contains organic solvents, the organic solvents are preferably organic solvents with a boiling point of less than 200°C.

[0134] If the content of organic solvents with a boiling point above 200℃ is less than 5% by mass, the lamination strength of the image recorder will be improved.

[0135] In this invention, "boiling point" refers to the boiling point at 1 atmosphere (101325 Pa). The boiling point is determined by a boiling point meter, for example using a boiling point measuring instrument (product name "DosaTherm300", TITAN TECHNOLOGIES, KK).

[0136] Examples of organic solvents with boiling points below 200°C include:

[0137] Ethylene glycol (197℃), propylene glycol (187℃), and other alkylene glycols;

[0138] Diethylene glycol monomethyl ether (194℃), diethylene glycol dimethyl ether (162℃), diethylene glycol ethyl methyl ether (176℃), diethylene glycol isopropyl methyl ether (179℃), propylene glycol monomethyl ether (121℃), propylene glycol monobutyl ether (170℃), propylene glycol monopropyl ether (150℃), 3-methoxy-3-methyl-1-butanol (174℃), propylene glycol monomethyl ether propionate (160℃), methyl cellosolve (ethylene glycol monomethyl ether, 125℃), ethyl cellosolve (ethylene glycol monoethyl ether, 135℃), butyl cellosolve (ethylene glycol monobutyl ether, 171℃), ethylene glycol monotert-butyl ether (153℃), dipropylene glycol monomethyl ether (188℃), and other alkylene glycol alkyl ethers;

[0139] Esters such as ethylene glycol monomethyl ether acetate (145℃), ethyl acetate (154℃), ethyl lactate (154℃), and 3-methoxybutyl acetate (172℃); and ketones such as diacetone alcohol (169℃), cyclohexanone (156℃), and cyclopentanone (131℃). Additionally, the values ​​in parentheses indicate boiling points.

[0140] Examples of organic solvents with boiling points above 200°C include: 1,3-butanediol (207°C), 1,4-butanediol (228°C), benzyl alcohol (205°C), terpineol (217°C), etc.

[0141] Diethylene glycol (244℃), triethylene glycol (287℃), dipropylene glycol (230℃), and other alkylene glycols;

[0142] Diethylene glycol monoethyl ether (202°C), diethylene glycol monobutyl ether (231°C), triethylene glycol monomethyl ether (249°C), triethylene glycol dimethyl ether (216°C), diethylene glycol monohexyl ether (above 261°C), tripropylene glycol monomethyl ether (243°C), and other alkylene glycol alkyl ethers; and diethylene glycol monoethyl ether acetate (217°C). Additionally, the values ​​in parentheses indicate the boiling point.

[0143] In the ink, the content of organic solvent relative to the total amount of ink is preferably 5% to 40% by mass, more preferably 10% to 30% by mass.

[0144] (additive)

[0145] Depending on the requirements, inks may contain additives such as surfactants, co-sensitizers, UV absorbers, antioxidants, anti-fading agents, conductive salts, and alkaline compounds.

[0146] (physical properties)

[0147] The ink of the present invention has an acid value of 8 mg KOH / g or less, more preferably 1.5 mg KOH / g to 4.0 mg KOH / g. Because the ink has an acid value of 8 mg KOH / g or less, it exhibits excellent lamination strength.

[0148] If the acid value of the ink is below 8 mg KOH / g, it is believed that the adhesive used when laminating with the substrate will easily penetrate, thus increasing the lamination strength.

[0149] The acid value of the ink was determined by the method described in JIS K0070:1992.

[0150] In addition, when the ink contains dispersing resin and additive resin, the acid value and content of the dispersing resin and the acid value and content of the additive resin can be used to calculate the following formula.

[0151] The acid value of the ink = (acid value of the dispersion resin × content of the dispersion resin) / 100 + (acid value of the added resin × content of the added resin) / 100

[0152] The elastic modulus of the ink film formed by curing the ink of the present invention is preferably 2.5 GPa to 5.0 GPa, more preferably 2.5 GPa to 4.0 GPa. If the elastic modulus of the ink film is 2.5 GPa or higher, stress concentration at the interface of the ink film can be mitigated, thus further improving the lamination strength of the image recorder. On the other hand, if the elastic modulus of the ink film is 5.0 GPa or lower, stress concentration inside the ink film can be mitigated, thus further improving the lamination strength of the image recorder.

[0153] The ink film formed by curing represents the state of the water and organic solvents contained in the ink after the ink is applied to the substrate and then evaporated.

[0154] In this invention, the elastic modulus of the ink film is a value determined using nanoindentation. The measuring apparatus can be a Hysitron TI-950 nanoindenter. A cubic angle indenter is used as the nanoindentation head, and the measurement is performed at an indentation depth of 500 nm.

[0155] From the viewpoint of improving spraying stability, the pH of the ink is preferably 7 to 10, more preferably 7.5 to 9.5. The pH is measured using a pH meter at 25°C, for example using a pH meter (model "HM-31") manufactured by DKK-TOA CORPORATION.

[0156] The viscosity of the 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 using a viscometer at 25°C, for example, using a TV-22 type viscometer manufactured by Toki Sangyo Co., Ltd.

[0157] The surface tension of the ink is preferably below 60 mN / m, more preferably 20 mN / m to 50 mN / m, and even more preferably 30 mN / m to 45 mN / m. The surface tension is measured using a surface tension meter at 25°C, for example, using an automatic surface tension meter (product name "CBVP-Z") manufactured by Kyowa Interface Science Co., Ltd., measured by the plate method.

[0158] [Ink Set]

[0159] The ink assembly of the present invention preferably comprises: a first ink, which is the ink of the present invention; and a second ink, which is an inkjet ink containing water, a pigment other than a white pigment, and a resin. The details of the first ink are the same as those of the inks described above, and therefore the description is omitted.

[0160] -Second Ink-

[0161] The second ink contains water, pigments other than white pigment, and resin, and may also contain other ingredients.

[0162] (pigments other than white pigment)

[0163] The second ink contains pigments other than white pigment (hereinafter also referred to as "colored pigments"). There may be one or more colored pigments.

[0164] Colored pigments can be either commercially available organic or inorganic pigments. Examples of colored pigments include those described in Seishiro Itō's "Encyclopedia of Pigments" (published in 2000), W. Herbst and K. Hunger's "Industrial Organic Pigments," Japanese Patent Application Publication Nos. 2002-12607, 2002-188025, 2003-26978, and 2003-342503.

[0165] Furthermore, the colored pigment can be a water-insoluble pigment that can be dispersed in water by a dispersant, or it can be a self-dispersible pigment. A self-dispersible pigment is a pigment that can be dispersed in water even without the use of a dispersant. For example, a self-dispersible pigment is a compound formed by direct or chemical bonding to the surface of the pigment via other groups, including at least one hydrophilic group such as carbonyl, hydroxyl, carboxyl, sulfonyl, phosphate and their salts.

[0166] There are no particular limitations on the types of colored pigments; for example, cyan pigment, magenta pigment, yellow pigment, and black pigment can be mentioned.

[0167] From the viewpoint of image density and ink jetting properties, the content of colored pigment in the second ink is preferably 1% to 20% by mass relative to the total amount of the second ink, more preferably 1% to 15% by mass, and even more preferably 1% to 10% by mass.

[0168] (resin)

[0169] The resin can be a dispersant that functions to disperse colored pigments, or it can be a resin added separately to the ink along with a dispersant. Therefore, the ink may contain only a dispersing resin, or it may contain both a dispersing resin and an additive resin. Furthermore, in the case of a self-dispersing pigment, it may contain only an additive resin and no dispersant.

[0170] From the viewpoint of improving the adhesion between the substrate and the image, the second ink preferably contains two or more resins, and more preferably contains a dispersing resin and an additive resin.

[0171] The type of resin contained in the second ink is not particularly limited, and the same resin contained in the ink mentioned above (the first ink) can be cited as an example.

[0172] From a sprayability perspective, the resin content in the second ink is preferably 30% by mass or less, more preferably 20% by mass or less, and even more preferably 10% by mass or less, relative to the total amount of the second ink. The lower limit for the resin content is not particularly limited, for example, it is 0.1% by mass.

[0173] - Resins that function as dispersants (dispersion resins) -

[0174] The dispersion resin is typically pre-mixed with the pigment and contained in the pigment dispersion. The dispersion resin can be appropriately selected from conventionally known dispersants and can be either a random copolymer or a block copolymer. Furthermore, the dispersion resin may also have a cross-linked structure.

[0175] The dispersion resin contained in the second ink is preferably a random copolymer. Specific examples of the dispersion resin contained in the second ink are the same as those of the dispersion resin contained in the ink described above (the first ink).

[0176] From the viewpoint of improving the dispersion stability of colored pigments, the structural units derived from hydrophobic monomers contained in the dispersion resin contained in the second ink preferably include structural units derived from (meth)acrylates having an aromatic hydrocarbon group having 4 or more carbon atoms.

[0177] The ratio of the content of colored pigment to the content of dispersion resin, based on mass, is preferably 1:0.04 to 1:3, more preferably 1:0.05 to 1:1, and even more preferably 1:0.05 to 1:0.5.

[0178] From the viewpoint of dispersion stability, the acid value of the dispersion resin is preferably 80 mg KOH / g or more, more preferably 100 mg KOH / g or more. On the other hand, from the viewpoint of setting the acid value of the second ink to 8 mg KOH / g or less, the acid value of the dispersion resin is preferably 250 mg KOH / g or less, more preferably 200 mg KOH / g or less, and even more preferably 150 mg KOH / g or less.

[0179] When the second ink contains a dispersing resin as a resin, the content of the dispersing resin relative to the total amount of the second ink is preferably 0.1% to 10% by mass, more preferably 0.5% to 8% by mass, and even more preferably 1% to 5% by mass.

[0180] - Resins other than resins that function as dispersants (added resins) -

[0181] The second ink can be prepared, for example, by adding an additive resin to a pigment dispersion. Examples of additive resins include water-soluble resins and water-insoluble resins. Water-insoluble resins are dispersed in water and exist in the form of resin particles.

[0182] The second ink preferably contains resin particles. The preferred method for the resin particles contained in the second ink is the same as that for the resin particles contained in the first ink described above.

[0183] When the second ink contains resin particles as resin, the content of resin particles relative to the total amount of the second ink is preferably 2% to 10% by mass, more preferably 3% to 8% by mass. If the content of resin particles is 2% by mass or more, the lamination strength of the image recorder is improved. On the other hand, if the content of resin particles is 10% by mass or less, the dispersion stability is improved.

[0184] (water)

[0185] The second ink contains water. The water content is not specifically limited, for example, it can be 40% to 70% by mass.

[0186] (Organic solvents)

[0187] The second ink preferably contains an organic solvent. The organic solvent contained in the second ink may be one type or two or more types. The preferred method for the organic solvent contained in the second ink is the same as that for the organic solvent contained in the ink described above (the first ink).

[0188] (additive)

[0189] Depending on the requirements, the second ink may contain additives such as surfactants, co-sensitizers, UV absorbers, antioxidants, anti-fading agents, conductive salts, and alkaline compounds.

[0190] (physical properties)

[0191] The acid value of the second ink is preferably 8 mg KOH / g or less, more preferably 1.0 mg KOH / g to 5.0 mg KOH / g. If the acid value of the second ink is 8 mg KOH / g or less, the adhesion between the image and the substrate (especially the lamination strength between the image and the laminated substrate) is further improved.

[0192] The method for determining the acid value of the second ink is the same as that for determining the acid value of the first ink, which has already been described.

[0193] From the viewpoint of further improving the lamination strength, the absolute value of the difference between the acid value of the first ink and the acid value of the second ink is preferably 2.0 mg KOH / g or less, more preferably 1.5 mg KOH / g or less. The lower limit of the absolute value of the above difference is not particularly limited; for example, it is 0 mg KOH / g, preferably 0.1 mg KOH / g. The acid value of the first ink may be higher or lower than that of the second ink, but it is preferable to be lower.

[0194] If the absolute value difference between the acid values ​​of the first ink and the second ink is less than 2.0 mg KOH / g, the adhesion between the ink film formed by the first ink and the ink film formed by the second ink is improved. It is believed that the adhesion between the image and the substrate (especially the lamination strength between the image and the laminated substrate) is thus improved.

[0195] The elastic modulus of the ink film formed by curing the second ink is preferably 2.5 GPa to 5.0 GPa, more preferably 2.5 GPa to 4.0 GPa. If the elastic modulus of the ink film is 2.5 GPa or higher, stress concentration at the interface of the ink film can be mitigated, thus further improving the adhesion between the image recorder and the substrate (especially the lamination strength with the laminated substrate). On the other hand, if the elastic modulus of the ink film is 5.0 GPa or lower, stress concentration inside the ink film can be mitigated, thus further improving the adhesion between the image recorder and the substrate (especially the lamination strength with the laminated substrate).

[0196] From the viewpoint of further improving the lamination strength, the absolute value of the difference between the elastic modulus of the ink film formed by curing the first ink and the elastic modulus of the ink film formed by curing the second ink is preferably 2.0 GPa or less. The lower limit of the absolute value of the above difference is not particularly limited; for example, it is 0 GPa, and preferably 0.1 GPa. The elastic modulus of the first ink film may be higher or lower than that of the second ink film, but it is preferable to be higher.

[0197] The preferred methods for the pH, surface tension, and viscosity of the second ink are the same as those for the pH, surface tension, and viscosity of the first ink.

[0198] -Pretreatment solution-

[0199] The ink assembly of the present invention preferably further comprises a pretreatment liquid containing water and resin. When ink is applied to a substrate to which the pretreatment liquid has been applied, the resin contained in the ink comes into contact with the components in the pretreatment liquid, causing the dispersion to become unstable, thereby thickening the ink. As a result, interference between the falling ink droplets is suppressed, and image quality is improved.

[0200] (resin)

[0201] The pretreatment solution contains resin. The pretreatment solution may contain one type of resin or two or more types of resin.

[0202] The type of resin contained in the pretreatment solution is not particularly limited, and resins that are the same as those exemplified as resins contained in inks can be used. Preferably, the resin contained in the pretreatment solution includes polyester resin or acrylic resin, and more preferably polyester resin.

[0203] In this invention, polyester resin refers to a polymeric compound containing ester bonds in its main chain. Examples of polyester resins include condensation polymers of polycarboxylic acids (e.g., dicarboxylic acids) and polyols (e.g., diols).

[0204] From the viewpoint of improving image quality (especially character quality), the resin contained in the pretreatment solution preferably contains resin particles. There is no particular limitation on the type of resin particles that may be contained in the pretreatment solution; examples of resins similar to those exemplified as those contained in inks can be cited.

[0205] When preparing the pretreatment solution, commercially available aqueous dispersions of resin particles can be used.

[0206] Commercially available aqueous dispersions of resin particles include Pesthresin A124GP, Pesthresin A645GH, Pesthresin A615GE, Pesthresin A520 (manufactured by TAKAMAT SU OIL&FAT CO., LTD.), Eastek 1100, Eastek 1200 (manufactured by Eastman Chemical Company), plascoat RZ570, plascoat Z687, plascoat Z565, plascoat RZ570, plascoat Z690 (manufactured by GOO CHEMICAL CO., LTD.), Vylonal MD1200 (manufactured by TOYOBO CO., LTD.), and EM57DOC (manufactured by Daicel FineChem Ltd.).

[0207] From the viewpoint of sprayability, the resin content in the pretreatment solution is preferably 5% to 30% by mass relative to the total amount of the pretreatment solution, more preferably 1% to 20% by mass, and especially preferably 1% to 15% by mass.

[0208] (water)

[0209] The pretreatment solution contains water. The water content is not particularly limited, for example, it can be 50% to 90% by mass.

[0210] (Flocculant)

[0211] From the viewpoint of improving image quality (especially character quality), the pretreatment solution preferably contains a coagulant. The coagulant is not particularly limited to any component that causes the ink components to agglomerate. The coagulant is preferably selected from at least one of the group consisting of polyvalent metal compounds, organic acids, metal complexes, and cationic polymers, and more preferably contains an organic acid.

[0212] -Polyvalent metal compounds-

[0213] Examples of polyvalent metal compounds include salts of alkaline earth metals (e.g., magnesium, calcium) from Group 2 of the periodic table, transition metals (e.g., lanthanum) from Group 3 of the periodic table, metals (e.g., aluminum) from Group 13 of the periodic table, and lanthanides (e.g., neodymium).

[0214] Salts of these metals are preferably salts of organic acids, nitrates, chlorides, or thiocyanates, as described later.

[0215] The polyvalent metal compound is preferably a calcium or magnesium salt of an organic acid (e.g., formic acid, acetic acid, benzoic acid, etc.); a calcium or magnesium salt of nitric acid; or a calcium or magnesium salt of calcium chloride, magnesium chloride, or thiocyanate.

[0216] Preferably, at least a portion of the polyvalent metal compound dissociates into polyvalent metal ions and counterions in the pretreatment solution.

[0217] -Organic acids-

[0218] Organic acids can be exemplified by organic compounds having acidic groups.

[0219] Examples of acidic groups include phosphate, phosphonic acid, hypophosphonic acid, sulfate, sulfonic acid, sulfinic acid, and carboxyl groups.

[0220] From the viewpoint of ink agglomeration speed, the acidic group is preferably a phosphate group or a carboxyl group, and more preferably a carboxyl group.

[0221] Preferably, at least a portion of the acidic groups dissociate in the pretreatment solution.

[0222] Examples of organic compounds containing a carboxyl 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, pyrrolidone carboxylic acid, pyranone carboxylic acid, pyrrolic carboxylic acid, furan carboxylic acid, pyridine carboxylic acid, coumaric acid, thiophene carboxylic acid, and nicotinic acid.

[0223] From the viewpoint of ink agglomeration speed, organic compounds with carboxyl groups are preferably carboxylic acids with a valence of 2 or higher (hereinafter also referred to as polycarboxylic acids), and more preferably dicarboxylic acids.

[0224] 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.

[0225] The organic acid is preferably low in pKa (e.g., 1.0 to 5.0). Thus, by contacting with an organic acid with a lower pKa, the surface charge of particles such as pigments and resin particles in the ink, which are dispersed and stabilized by weakly acidic functional groups such as carboxyl groups, can be reduced, thereby reducing dispersion stability.

[0226] The organic acid preferably has a low pKa, high solubility in water, and a valence of 2 or higher. Furthermore, the organic acid is more preferably characterized by a high buffering capacity in a pH region lower than the pKa of the functional group (e.g., carboxyl group) that stabilizes the particle dispersion in the ink.

[0227] -Metal complex-

[0228] The metal complex preferably contains at least one metal element selected from the group consisting of zirconium, aluminum and titanium.

[0229] The metal complex is preferably a metal complex containing at least one ligand selected from the group consisting of acetate, acetylacetone, methyl acetoacetate, ethyl acetoacetate, octanediol, butoxyacetylacetone, lactate, ammonium lactate and triethanolamine.

[0230] Metal complexes are commercially available. Various organic ligands (especially multidentate ligands capable of forming metal chelating catalysts) are commercially available. Therefore, metal complexes can be prepared by combining commercially available organic ligands with metals.

[0231] Examples of metal complexes include zirconium tetraacetylacetone (e.g., ORGATIX ZC-150 manufactured by Matsumoto Fine Chemical Co., Ltd.), zirconium monoacetylacetone (e.g., ORGATIX ZC-540 manufactured by Matsumoto Fine Chemical Co., Ltd.), zirconium diacetylacetone (e.g., ORGATIX ZC-550 manufactured by Matsumoto Fine Chemical Co., Ltd.), zirconium monoacetylacetone (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.), diisopropoxybis(acetylacetone)titanium (e.g., ORGATIX TC-100 manufactured by Matsumoto Fine Chemical Co., Ltd.), and titanium tetraacetylacetone (e.g., ORGATIX manufactured by Matsumoto Fine Chemical Co., Ltd.). ORGATIX TC-401”, dioctyloxybis(octyl glycol) titanium (e.g., ORGATIX TC-200 manufactured by Matsumoto Fine Chemical Co., Ltd.), diisopropoxybis(ethyl acetoacetate) titanium (e.g., ORGATIX TC-750 manufactured by Matsumoto Fine Chemical Co., Ltd.), zirconium tetraacetylacetonate (e.g., ORGATIX ZC-700 manufactured by Matsumoto Fine Chemical Co., Ltd.), zirconium tributoxymonoacetylacetonate (e.g., ORGATIX ZC-540 manufactured by Matsumoto Fine Chemical Co., Ltd.), zirconium monobutoxyacetylacetonate bis(ethyl acetoacetate) (e.g., ORGATIX ZC-570 manufactured by Matsumoto Fine Chemical Co., Ltd.), dibutoxybis(ethyl acetoacetate) zirconium (e.g., ORGATIX ZC-570 manufactured by Matsumoto Fine Chemical Co., Ltd.) ZC-580”), aluminum triacetylacetonate (e.g., “ORGATIX AL-80” manufactured by Matsumoto Fine Chemical Co., Ltd.), ammonium titanium lactate (e.g., “ORGATIX TC-300” manufactured by Matsumoto Fine Chemical Co., Ltd.), titanium lactate (e.g., “ORGATIX TC-300” manufactured by Matsumoto Fine Chemical Co., Ltd.).Matsumoto Fine Chemical Co., Ltd. manufactures "ORGATIX TC-310, 315", triethanolamine titanium (Matsumoto Fine Chemical Co., Ltd. manufactures "ORGATIX TC-400"), and zirconium chloride compounds (e.g., Matsumoto Fine Chemical Co., Ltd. manufactures "ORGATIX ZC-126").

[0232] The metal complex is preferably titanium ammonium lactate (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 zirconium chloride compound (e.g., ORGATIX ZC-126 manufactured by Matsumoto Fine Chemical Co., Ltd.).

[0233] -Catonic polymer-

[0234] Furthermore, the pretreatment solution can be in the form of containing one or more cationic polymers as coagulation components. The cationic polymers are preferably homopolymers, copolymers, or condensation polymers of cationic monomers having primary to tertiary amino groups or quaternary ammonium groups. As cationic polymers, they can be used in any form, either as water-soluble polymers or water-dispersible latex particles.

[0235] Examples of cationic polymers include polyvinylpyridine salts, polyalkylaminoethyl acrylates, polyalkylaminoethyl methacrylates, polyvinylimazoles, polyethyleneimine, polybiguanidines, polyguanidines, polyallylamines, and their derivatives.

[0236] From the viewpoint of the viscosity of the pretreatment solution, a lower weight-average molecular weight of the cationic polymer is preferable. When the pretreatment solution is applied to the recording medium via inkjet printing, a weight-average molecular weight of 1,000 to 500,000 is preferred, 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 higher is advantageous from the viewpoint of agglomeration rate. A weight-average molecular weight of 500,000 or lower is advantageous from the viewpoint of jetting reliability. However, this is not a limitation when the pretreatment solution is applied to the recording medium by methods other than inkjet printing.

[0237] The pretreatment solution may contain only one type of coagulant or two or more types.

[0238] The content of the coagulant relative to the total amount of the pretreatment liquid is preferably 0.1% to 40% by mass, more preferably 0.1% to 30% by mass, even more preferably 1% to 20% by mass, and particularly preferably 1% to 10% by mass.

[0239] (Organic solvents)

[0240] The pretreatment solution preferably contains an organic solvent. The pretreatment solution may contain one or more organic solvents. The preferred method for the organic solvents in the pretreatment solution is the same as the preferred method for the organic solvents in the ink (first ink) described above.

[0241] (Other ingredients)

[0242] Depending on the requirements, the pretreatment solution may contain other components besides resin and water. Other components that may be contained in the pretreatment solution include surfactants, solid wetting agents, colloidal silica, inorganic salts, anti-fading agents, emulsion stabilizers, penetration enhancers, ultraviolet absorbers, preservatives, mildew inhibitors, pH adjusters, viscosity adjusters, rust inhibitors, chelating agents, and water-soluble polymers (e.g., the water-soluble polymers described in paragraphs 0026 to 0080 of Japanese Patent Application Publication No. 2013-001854).

[0243] (physical properties)

[0244] The elastic modulus of the pretreatment liquid film formed by curing the pretreatment liquid is preferably 2.5 GPa to 5.0 GPa, more preferably 2.5 GPa to 4.0 GPa. If the elastic modulus of the pretreatment liquid film is 2.5 GPa or higher, stress concentration at the interface of the pretreatment liquid film can be mitigated, thus further improving the lamination strength of the image recorder. On the other hand, if the elastic modulus of the pretreatment liquid film is 5.0 GPa or lower, stress concentration inside the pretreatment liquid film can be mitigated, thus further improving the lamination strength of the image recorder.

[0245] From the viewpoint of further improving the lamination strength of image recordings, the elastic modulus of the pretreatment liquid film is preferably the same as, or less than, the elastic modulus of the ink film formed by curing the second ink.

[0246] When the elastic modulus of the pretreatment liquid film is less than that of the ink film formed by curing the second ink, the difference between the elastic modulus of the pretreatment liquid film and the elastic modulus of the ink film formed by curing the second ink is preferably 0.1 GPa to 2.0 GPa.

[0247] From the viewpoint of ink agglomeration rate, the pH of the pretreatment solution is preferably 0.1 to 4.5, more preferably 0.2 to 4.0. The pH is measured using a pH meter at 25°C, for example using a pH meter (model "HM-31") manufactured by DKK-TOA CORPORATION.

[0248] From the viewpoint of ink agglomeration rate, the viscosity of the pretreatment solution is preferably 0.5 mPa·s to 10 mPa·s, more preferably 1 mPa·s to 5 mPa·s. The viscosity is the value measured using a viscometer at 25°C. Viscosity is measured using a viscometer at 25°C, for example, using a TV-22 type viscometer manufactured by Toki Sangyo Co., Ltd.

[0249] The surface tension of the pretreatment liquid is preferably below 60 mN / m, more preferably 20 mN / m to 50 mN / m, and even more preferably 30 mN / m to 45 mN / m. The surface tension is a value measured at 25°C. The surface tension is measured using a surface tension meter at 25°C, for example, using an automatic surface tension meter (product name "CBVP-Z") manufactured by Kyowa Interface Science Co., Ltd., measured by the plate method.

[0250] <Image Recording Methods>

[0251] -Method 1-

[0252] The first aspect of the image recording method of the present invention preferably uses the above-mentioned ink and includes a step of applying the above-mentioned ink to a substrate by inkjet recording.

[0253] (Substrate)

[0254] There are no particular limitations on the substrate material; any known substrate material can be used.

[0255] Examples of substrates include paper substrates, paper substrates laminated with resins (e.g., polyethylene, polypropylene, polystyrene, etc.), resin substrates, metal plates (e.g., plates of metals such as aluminum, zinc, copper, etc.), paper substrates laminated or vapor-deposited with the aforementioned metals, and resin substrates laminated or vapor-deposited with the aforementioned metals.

[0256] Furthermore, the substrate can be a textile substrate.

[0257] Examples of raw materials for textile substrates include natural fibers such as cotton, silk, hemp, and wool; chemical fibers such as viscose rayon and lyocell; synthetic fibers such as polyester, polyamide, and acrylic; and mixtures of at least two fibers selected from the group consisting of natural fibers, chemical fibers, and synthetic fibers. Textile substrates may also be those described in paragraphs

[0039] to

[0042] of International Publication No. 2015 / 158592.

[0258] The substrate is preferably a non-permeable substrate.

[0259] In this invention, the non-permeability of the non-permeable substrate refers to the property that the water absorption rate is less than 2.5% over 24 hours as measured according to ASTM D570-98 (2018). Here, the "%" used as the unit of water absorption rate is based on mass. The aforementioned water absorption rate is preferably less than 1.0%, more preferably less than 0.5%.

[0260] Materials that can be used as non-permeable substrates include, for example, 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 alcohol acetal, nylon, acrylic resin, etc.).

[0261] The preferred material for the non-permeable substrate is resin.

[0262] From a general perspective, the preferred materials for non-permeable substrates are polypropylene, polyethylene, polyethylene terephthalate, nylon, acrylic resin, or polyvinyl chloride.

[0263] The shape of the non-permeable substrate is preferably sheet (film) or plate. Examples of non-permeable substrates with this shape include glass plates, metal plates, resin sheets (resin films), paper laminated with plastic, paper laminated or deposited with metal, and plastic sheets (plastic films) laminated or deposited with metal.

[0264] As a resin-based non-permeable substrate, examples include resin sheets (resin films), and more specifically, flexible packaging materials for packaged foods and floor guide panels in large retail stores.

[0265] In addition to sheet-like (film-like) or plate-like non-permeable substrates, textiles (fabrics) and non-woven fabrics formed from non-permeable fibers can also be cited as examples of non-permeable substrates.

[0266] The thickness of the non-permeable 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.

[0267] Hydrophilic treatment can be applied to non-permeable substrates. Examples of hydrophilic treatments include corona treatment, plasma treatment, flame treatment, heat treatment, abrasion treatment, light irradiation treatment (e.g., UV treatment), but are not limited to these. Corona treatment can be performed, for example, using a corona master (product name "PS-10S", manufactured by Shinko Electric & Instrumentation Co., Ltd.). The conditions for corona treatment can be appropriately selected depending on the type of non-permeable substrate.

[0268] (Inkjet recording method)

[0269] There are no particular restrictions on the ink ejection method in inkjet recording. It can be any of the known methods, such as charge control method that uses electrostatic attraction to eject ink, on-demand inkjet method (pressure pulse method) that uses the vibration pressure of piezoelectric elements, acoustic inkjet method that converts electrical signals into sound beams that irradiate the ink and uses radiation pressure to eject ink, and thermal inkjet method (Bubble Jet (registered trademark)) that heats the ink to form bubbles and uses the resulting pressure.

[0270] As an inkjet recording method, the inkjet recording method described in Japanese Patent Application Publication No. 54-59936 can be used particularly effectively. In this inkjet recording method, the ink undergoes a rapid volume change under the influence of heat energy, and the ink is ejected from the nozzle by the force generated by this change in state. The method described in paragraphs 0093 to 0105 of Japanese Patent Application Publication No. 2003-306623 can also be used as an inkjet recording method.

[0271] Applying ink to a non-permeable substrate using inkjet recording is done by ejecting ink from the nozzles of an inkjet head.

[0272] As for inkjet head types, there are reciprocating methods where short, strip-shaped serial inkjet heads scan and record simultaneously in the width direction of the recorded medium, and line methods where recording elements are arranged in a row type inkjet head corresponding to the entire area of ​​one side of the recorded medium.

[0273] In line mode, by scanning the recording medium along a direction intersecting the arrangement direction of the recording elements, images can be recorded across the entire surface of the recording medium. In line mode, the transport system, such as the carriage used in reciprocating mode for scanning short, strip-shaped inkjet heads, is unnecessary. Furthermore, compared to reciprocating mode, line mode eliminates the need for complex scanning control between the carriage movement and the recording medium; only the recording medium is moved. Therefore, line mode increases image recording speed compared to reciprocating mode.

[0274] The ink is preferably applied using an inkjet head with a resolution of 300 dpi or higher (more preferably 600 dpi or higher, and even more preferably 800 dpi or higher). Here, dpi is an abbreviation for dots per inch, and linch (1 inch) is 2.54 cm.

[0275] From the viewpoint of obtaining high-definition images, the ink ejection volume is preferably 1 pL (picoliter) to 10 pL, more preferably 1.5 pL to 6 pL.

[0276] -Second Method-

[0277] The second aspect of the image recording method of the present invention preferably uses an ink group having the first ink and the second ink described above, and includes a step of applying the first ink and the second ink to a substrate by inkjet recording.

[0278] By using an ink set containing a first ink (i.e., white ink) containing white pigment and a second ink (i.e., colored ink) containing pigments other than white pigment, it is possible to record multiple color images.

[0279] There is no particular limitation on the order in which the first ink and the second ink are applied to the substrate, but it is preferable to apply the first ink after applying the second ink. For example, a multicolor image can be recorded on the substrate, in which a colored pattern image (characters, graphics, etc.) recorded using the second ink (i.e., colored ink) and a solid white image recorded using the first ink (i.e., white ink) to cover the pattern image are arranged sequentially. In this case, the pattern image can be visually recognized through the substrate from the back side (i.e., the side where no image is recorded).

[0280] The details of the substrate and inkjet recording method in Method 2 are the same as those in Method 1.

[0281] -Third Method-

[0282] The third aspect of the image recording method of the present invention preferably uses an ink group comprising the first ink, the second ink and the pretreatment liquid described above, and includes: a step of applying the pretreatment liquid to a substrate; and a step of applying the first ink and the second ink to the substrate on which the pretreatment liquid has been applied by inkjet recording.

[0283] By using an ink set comprising a first ink containing white pigment (i.e., white ink), a second ink containing pigment other than white pigment (i.e., colored ink), and a pretreatment liquid, high-definition multicolor images can be recorded.

[0284] The details of the substrate and inkjet recording method in Method 3 are the same as those in Method 1.

[0285] There are no particular limitations on the method of applying the pretreatment solution; known methods such as coating, immersion, and inkjet recording can be cited.

[0286] As a coating method, known coating methods include rod coating machines, extrusion coating machines, air knife coating machines, scraper coating machines, bar coating machines, doctor blade coating machines, extrusion coating machines, and reverse roller coating machines.

[0287] The pretreatment liquid can be heated and dried after being applied to the substrate. Examples of mechanisms for heating and drying the pretreatment liquid include known heating mechanisms such as heaters, known air supply mechanisms such as dryers, and mechanisms combining these.

[0288] Examples of methods for heating and drying pretreatment liquids include heating the substrate from the side opposite to the surface to which the pretreatment liquid is applied using a heater, blowing warm air or hot air onto the surface of the substrate to which the pretreatment liquid is applied, heating the substrate from the surface to which the pretreatment liquid is applied or from the side opposite to the surface to which the pretreatment liquid is applied using an infrared heater, and combining these methods together.

[0289] The heating temperature for heating and drying the pretreatment liquid 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.

[0290] There is no particular limitation on the heating and drying time, but it 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.

[0291] [Manufacturing method of laminate]

[0292] The method for manufacturing a laminate according to the present invention includes: a step of obtaining an image recorder having a substrate and an image disposed on the substrate by means of the image recording method of the present invention; and a step of laminating a laminating substrate to the side of the image recorder having the image disposed thereon to obtain a laminate.

[0293] According to the image recording method of the present invention, it is possible to manufacture an image recorder having a substrate and an image recorded on the substrate, and having excellent lamination strength after boiling treatment when a laminating substrate is laminated onto the image.

[0294] Therefore, the image recording method of the present invention is suitable for manufacturing a laminate having the above-described image recording object and a laminating substrate laminated to the image recording object on the side where the image is recorded.

[0295] According to the method for manufacturing the laminate of the present invention, it is possible to manufacture a laminate with excellent lamination strength between an image recorder and a substrate for lamination.

[0296] For the process of obtaining image recordings, please refer to the image recording method of the present invention.

[0297] The process of obtaining a laminate is to laminate a laminating substrate onto the image-containing side of an image recording. Lamination can be performed by methods such as: for example, bonding the laminating substrate to the image-containing side of the image recording via another layer (e.g., an adhesive layer); or bonding the image-containing side of the image recording while the laminating substrate is laminated to the image-containing side using a laminating machine. In the latter case, a commercially available laminating machine can be used.

[0298] There is no particular limitation on the lamination temperature during lamination. For example, when bonding image recording material and laminating substrate via other layers (e.g., adhesive layers), the temperature can be in the range of 20°C or higher. Furthermore, when using a laminator, the temperature of the laminating rollers can be set in the range of 20°C to 80°C. The pressing force of the laminating roller pair can be appropriately selected as needed.

[0299] The substrate for lamination is preferably a resin substrate. There are no particular limitations on the resin substrate; for example, a substrate made of thermoplastic resin can be cited.

[0300] Examples of resin substrates include substrates formed from thermoplastic resin in sheet form.

[0301] The resin substrate preferably contains polypropylene, polyethylene terephthalate, nylon, polyethylene or polyimide.

[0302] 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.

[0303] In the process of obtaining the laminate, the laminating substrate can be directly laminated to the side of the image recorder where the image is located, or it can be laminated to the side of the image recorder where the image is located via other layers (e.g., adhesive layers).

[0304] When a laminating substrate is directly laminated to the side of an image recorder containing an image, lamination can be performed using known methods such as hot pressing or hot welding.

[0305] Furthermore, the lamination of the laminating substrate to the side of the image recorder where the image is disposed via an adhesive layer can be carried out, for example, by applying an adhesive to the side of the image recorder where the image is disposed, placing the laminating substrate, and then bonding the image recorder and the laminating substrate together.

[0306] Furthermore, lamination when the image is attached to the side of the image recorder via an adhesive layer can also be performed by methods such as compression lamination (i.e., sandwich lamination).

[0307] 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, thus further enhancing the lamination strength.

[0308] Example

[0309] The present invention will be described in more detail below through embodiments, but the present invention is not limited to the following embodiments as long as it does not depart from its spirit.

[0310] In the preparation of ink, the dispersion resin is first synthesized.

[0311] -Synthesis of Dispersion Resin 1-

[0312] Add 100g of dipropylene glycol to a three-necked flask equipped with a stirrer and a cooling tube, and heat to 85°C under a nitrogen atmosphere.

[0313] Solution 1, consisting of 14.0 g of stearyl methacrylate, 35.3 g of benzyl methacrylate, 20.0 g of hydroxyethyl methacrylate, 30.7 g of methacrylic acid, and 0.55 g of 2-mercaptopropionic acid, and solution 2, consisting of 1.0 g of tert-butyl peroxy-2-ethylhexanoate ("PERBUTYL O", manufactured by NOF CORPORATION) dissolved in 20 g of dipropylene glycol, were prepared separately. Solution 1 was added dropwise to the three-necked flask over a period of 4 hours, and solution 2 was added dropwise over a period of 5 hours.

[0314] After the addition was complete, the mixture was allowed to react for another 2 hours, then heated to 95°C and stirred for 3 hours to ensure all unreacted monomers reacted. Nuclear magnetic resonance (NMR) was then used to analyze the reaction. 1 The disappearance of the monomer was confirmed by H-NMR.

[0315] The obtained reaction solution was heated to 70°C, and 12.0 g of dimethylethanolamine was added as an amine compound. Propylene glycol was then added and the mixture was stirred to obtain a 30% by mass solution of dispersion resin 1 as a polymer.

[0316] use 1 H-NMR confirmed the structural units of the obtained dispersion resin 1. Furthermore, the weight-average molecular weight (Mw) determined by GPC was 28,000.

[0317] Furthermore, the mass ratio of each structural unit in dispersion resin 1 is: structural unit derived from stearic acid methacrylate / structural unit derived from benzyl methacrylate / structural unit derived from hydroxyethyl methacrylate / structural unit derived from methacrylic acid = 14 / 35.3 / 20 / 30.7. Wherein, the above mass ratio does not include dimethylaminoethanol.

[0318] The acid value of dispersion resin 1 is 200 mg KOH / g.

[0319] -Synthesis of Dispersion Resin 2-

[0320] Add 100g of dipropylene glycol to a three-necked flask equipped with a stirrer and a cooling tube, and heat to 85°C under a nitrogen atmosphere.

[0321] Solution 1, consisting of 14.0 g of stearyl methacrylate, 43.0 g of benzyl methacrylate, 20.0 g of hydroxyethyl methacrylate, 23.0 g of methacrylic acid, and 0.55 g of 2-mercaptopropionic acid, and solution 2, consisting of 1.0 g of tert-butyl peroxy-2-ethylhexanoate ("PERBUTYL O", manufactured by NOF CORPORATION) dissolved in 20 g of dipropylene glycol, were prepared separately. Solution 1 was added dropwise to the three-necked flask over a period of 4 hours, and solution 2 was added dropwise over a period of 5 hours.

[0322] After the addition was complete, the mixture was allowed to react for another 2 hours, then heated to 95°C and stirred for 3 hours to ensure all unreacted monomers reacted. Nuclear magnetic resonance (NMR) was then used to analyze the reaction. 1 The disappearance of the monomer was confirmed by H-NMR.

[0323] The obtained reaction solution was heated to 70°C, and 12.0 g of dimethylethanolamine was added as an amine compound. Propylene glycol was then added and the mixture was stirred to obtain a 30% by mass solution of dispersion resin 2 as a polymer.

[0324] use 1 ¹H-NMR confirmed the structural units of the obtained dispersion resin 2. Furthermore, the weight-average molecular weight (Mw) determined by GPC was 26,000.

[0325] Furthermore, the mass ratio of each structural unit in dispersion resin 2 is: structural units derived from stearic acid methacrylate / structural units derived from benzyl methacrylate / structural units derived from hydroxyethyl methacrylate / structural units derived from methacrylic acid = 14 / 43 / 20 / 23. The above mass ratio does not include dimethylaminoethanol.

[0326] The acid value of dispersion resin 2 is 150 mg KOH / g.

[0327] -Synthesis of Dispersion Resin 3-

[0328] Add 100g of dipropylene glycol to a three-necked flask equipped with a stirrer and a cooling tube, and heat to 85°C under a nitrogen atmosphere.

[0329] Solution 1, consisting of 14.0 g of stearyl methacrylate, 27.6 g of benzyl methacrylate, 20.0 g of hydroxyethyl methacrylate, 38.4 g of methacrylic acid, and 0.55 g of 2-mercaptopropionic acid, and solution 2, consisting of 1.0 g of tert-butyl peroxy-2-ethylhexanoate ("PERBUTYL O", manufactured by NOF CORPORATION) dissolved in 20 g of dipropylene glycol, were prepared separately. Solution 1 was added dropwise to the three-necked flask over a period of 4 hours, and solution 2 was added dropwise over a period of 5 hours.

[0330] After the addition was complete, the mixture was allowed to react for another 2 hours, then heated to 95°C and stirred for 3 hours to ensure all unreacted monomers reacted. Nuclear magnetic resonance (NMR) was then used to analyze the reaction. 1 The disappearance of the monomer was confirmed by H-NMR.

[0331] The obtained reaction solution was heated to 70°C, and 12.0 g of dimethylethanolamine was added as an amine compound. Propylene glycol was then added and the mixture was stirred to obtain a 30% by mass solution of dispersion resin 3 as a polymer.

[0332] use 1 ¹H-NMR confirmed the structural units of the obtained dispersion resin 3. Furthermore, the weight-average molecular weight (Mw) determined by GPC was 22,000.

[0333] Furthermore, the mass ratio of each structural unit in dispersion resin 3 is: structural unit derived from stearate methacrylate / structural unit derived from benzyl methacrylate / structural unit derived from hydroxyethyl methacrylate / structural unit derived from methacrylic acid = 14 / 27.6 / 20 / 38.4. Wherein, the above mass ratio does not include dimethylaminoethanol.

[0334] The acid value of dispersion resin 3 is 250 mg KOH / g.

[0335] -Synthesis of Dispersion Resin 4-

[0336] 88 g of methyl ethyl ketone was added to a 1000 mL three-necked flask equipped with a stirrer and cooling tube. The flask was heated to 72 °C under a nitrogen atmosphere, and over 3 hours, a solution obtained by dissolving 0.85 g of dimethyl 2,2-azobisisobutyrate, 71.6 g of benzyl methacrylate, 18.4 g of methacrylic acid, and 10.0 g of methyl methacrylate in 50 g of methyl ethyl ketone was added dropwise. After the dropwise addition was complete, the mixture was allowed to react for another hour. Then, a solution obtained by dissolving 0.42 g of dimethyl 2,2-azobisisobutyrate in 2 g of methyl ethyl ketone was added, and the temperature was raised to 78 °C and heated for 4 hours. The resulting reaction solution was then precipitated twice in a large excess of hexane. The precipitated resin was dried to obtain dispersed resin 4.

[0337] use 1 H-NMR confirmed the structural units of the obtained dispersion resin 4. Furthermore, the weight-average molecular weight (Mw) calculated by GPC using polystyrene was 44,600.

[0338] In addition, the mass ratio of each structural unit in dispersion resin 4 is 71.6 / 10 / 18.4, which is the ratio of structural units derived from benzyl methacrylate to structural units derived from methyl methacrylate.

[0339] The acid value of dispersion resin 4 is 120 mg KOH / g.

[0340] -Synthesis of Dispersion Resin 5-

[0341] Add 88g of methyl ethyl ketone to a 1000mL three-necked flask equipped with a stirrer and cooling tube, heat to 72°C under a nitrogen atmosphere, and add dropwise a solution obtained by dissolving 0.85g of dimethyl 2,2-azobisisobutyrate, 62.4g of benzyl methacrylate, 27.6g of methacrylic acid, and 10.0g of methyl methacrylate in 50g of methyl ethyl ketone over a period of 3 hours. Dispersion resin 5 is obtained by the same method as dispersion resin 4.

[0342] use 1 H-NMR confirmed the structural units of the obtained dispersion resin 5. Furthermore, the weight-average molecular weight (Mw) calculated by GPC to polystyrene was 44,800.

[0343] In addition, the mass ratio of each structural unit in dispersion resin 5 is: structural unit derived from benzyl methacrylate / structural unit derived from methyl methacrylate / structural unit derived from methacrylic acid = 62.4 / 10 / 27.6.

[0344] The acid value of dispersion resin 5 is 180 mg KOH / g.

[0345] -Synthesis of Dispersion Resin 6-

[0346] 88 g of methyl ethyl ketone was added to a 1000 mL three-necked flask equipped with a stirrer and a cooling tube, and heated to 72 °C under a nitrogen atmosphere. The solution obtained by dissolving 0.85 g of dimethyl 2,2-azobisisobutyrate, 53.2 g of benzyl methacrylate, 36.8 g of methacrylic acid and 10.0 g of methyl methacrylate in 50 g of methyl ethyl ketone was added dropwise over 3 hours. Dispersion resin 6 was obtained by the same method as dispersion resin 4.

[0347] use 1 H-NMR confirmed the structural units of the obtained dispersion resin 6. Furthermore, the weight-average molecular weight (Mw) calculated by GPC to polystyrene was 42,000.

[0348] In addition, the mass ratio of each structural unit in dispersion resin 6 is 53.2 / 10 / 36.8, which is the ratio of structural units derived from benzyl methacrylate to structural units derived from methyl methacrylate.

[0349] The acid value of dispersion resin 6 is 240 mg KOH / g.

[0350] [Example 1]

[0351] -Preparation of Pigment Dispersion 1-

[0352] Pigment dispersion 1 was prepared using a Ready mill model LSG-4U-08 (manufactured by Aimex Co., Ltd.).

[0353] 45 parts by weight of titanium dioxide particles (average primary particle size: 210 nm, trade name "PF-690", manufactured by Ishihara Sanyo Kaisha, Ltd.) as a white pigment, 15 parts by weight of a 30% by weight solution of the above-mentioned dispersion resin 1, and 40 parts by weight of ultrapure water were added to a zirconia container. 40 parts by weight of 0.5 mm φ zirconia beads (manufactured by Toray, tracerambeads) were further added and lightly mixed with a spatula. The zirconia container containing the resulting mixture was placed in a Readymill and dispersed at 1000 rpm (revolutions per minute) for 5 hours. After dispersion, the mixture was filtered through a filter cloth to remove the beads, yielding a pigment dispersion 1 with a white pigment concentration of 45% by weight.

[0354] -Ink Preparation-

[0355] An ink having the following composition was prepared using pigment dispersion 1, 1,2-propanediol, propylene glycol monomethyl ether, surfactant (product name "OLFINE (registered trademark) F1010", manufactured by Nissin Chemical Industry Co., Ltd.) and water.

[0356] • White pigment…15% by weight

[0357] • Dispersion resin: 1…1.5% by mass of dispersion resin

[0358] ·1,2-Propanediol…15% by mass

[0359] ·Propylene glycol monomethyl ether…5% by mass

[0360] Surfactant…1% by mass

[0361] Water...total becomes 100% by mass surplus

[0362] [Examples 2 to 18, Comparative Examples 1 to 6]

[0363] In Examples 2 to 18 and Comparative Examples 1 to 6, pigment dispersions were prepared using the same method as in Example 1, with the types and amounts of dispersion resins as listed in Table 1. Inks were then prepared using the added resins listed in Table 1. The contents of white pigment, 1,2-propanediol, propylene glycol monomethyl ether, and surfactant were the same as in Example 1. Furthermore, resin 1, resin 2, and resin 3 in Table 1 represent the aforementioned dispersion resin 1, dispersion resin 2, and dispersion resin 3.

[0364] The details of the added resins listed in Table 1 are as follows. Emulsion refers to a dispersion containing resin, in which the resin exists in the form of resin particles. Water-soluble resin refers to an aqueous solution containing resin. Additionally, in the resin type column of Table 1, styrene-acrylic resin is simply referred to as "acrylic resin".

[0365] Neocryl A-1105: Acrylic resin emulsion, manufactured by DSM Japan KK.

[0366] Neocryl XK-12: Acrylic resin emulsion, manufactured by DSM Japan KK.

[0367] Neocryl A-1127: Acrylic resin emulsion, manufactured by DSM Japan KK.

[0368] Neocryl A-6092: Acrylic resin emulsion, manufactured by DSM Japan KK.

[0369] Neocryl A-1091: Styrene-acrylic resin emulsion, manufactured by DSM Japan KK.

[0370] VINYBLAN 715: Vinyl chloride emulsion, manufactured by Nissin Chemical Industry Co., Ltd.

[0371] PERMARIN UA-200: A urethane resin emulsion manufactured by SANYO CHEMICAL INDUSTRIES, LTD.

[0372] Joncryl JDX-6500: A water-soluble acrylic resin manufactured by BASF.

[0373] <Image Recording>

[0374] The prepared ink was used for image recording.

[0375] An inkjet recording device is prepared, which includes a conveying system for continuously conveying long strip-shaped substrates and an inkjet head for imparting ink.

[0376] Furthermore, as a substrate, a polyethylene terephthalate (PET) substrate (FUTAMURA CHEMICAL CO., LTD. "FE2001" (thickness 12μm, width 780mm, length 4000m) was prepared as a non-permeable substrate; hereinafter referred to as "non-permeable substrate A").

[0377] Using an inkjet recording device, a non-permeable substrate A is continuously conveyed at 50 m / min, and the ink is applied to form a solid image under the following conditions. The applied ink is then dried with warm air at 80°C for 30 seconds, thereby recording a solid image and obtaining an image record.

[0378] -Ink application conditions-

[0379] Inkjet head: 1200dpi / 30inch piezoelectric full-line inkjet head

[0380] Ink ejection volume from the printhead: 3.0 pL (picoli)

[0381] Drive frequency: 41kHz (substrate conveying speed: 50m / min)

[0382] [Measurement]

[0383] The acid value of the ink and the elastic modulus of the ink film formed after curing were measured for each embodiment and comparative example. The measurement methods are as follows. The measurement results are shown in Table 1.

[0384] (Acid value)

[0385] The acid value of the ink was determined according to the method described in JIS K0070:1992.

[0386] (Elastic modulus)

[0387] The elastic modulus of the surface of the image-recorded side of an image recorder was determined using nanoindentation. A Hysitron TI-950 nanoindenter was used as the measuring apparatus. A cubic angle indenter was used for nanoindentation, and the indentation depth was measured at 500 nm.

[0388] [evaluate]

[0389] The lamination strength, adhesion, preservation stability, and character quality of the image recordings in each embodiment and comparative example were evaluated. The evaluation methods are as follows. The evaluation results are shown in Table 1.

[0390] (Lamination strength)

[0391] A 500mm long × 200mm wide area with a solid image set on the entire surface of the image recorder is cut out as a sample for evaluating the lamination strength.

[0392] A dry laminating adhesive (TM-320 (isocyanate compound) / CAT-13B (alcohol compound), manufactured by Toyo-Morton, Ltd.) was applied to a solid image of the lamination strength evaluation sample using a rod coater. A linear low-density polyethylene film (trade name "LL-XMTN", manufactured by FUTAMURA CHEMICAL CO., LTD., 40 μm thick) was then layered on top as the lamination substrate. In this state, the lamination substrate and the lamination strength evaluation sample were bonded together to obtain the laminate.

[0393] The resulting laminate was aged at 40°C for 48 hours.

[0394] A sample piece measuring 100 mm in length and 15 mm in width was cut from the aged laminate.

[0395] Next, the laminating substrate and the lamination strength evaluation sample were manually peeled off from one end of the sample sheet along its length up to 30 mm. The remaining 70 mm section was left in the same state as the laminating substrate and the lamination strength evaluation sample.

[0396] Next, a tensile test was performed on the laminate substrate and the laminate strength evaluation sample of the peeled portion of the sample sheet, which were stretched in opposite directions. The stretching direction was set perpendicular to the remaining 70 mm length of the area (the area reserved to maintain the state of the laminate substrate and the laminate strength evaluation sample).

[0397] This tensile test was used to determine the peel strength of the laminate substrate and the laminate strength evaluation sample when peeling off the remaining 70mm length of the aforementioned area. The obtained peel strength was taken as the laminate strength. The evaluation criteria are as follows.

[0398] In addition, the above tensile tests were conducted using a tensile testing machine (product name "TENSILON RTM-25", manufactured by Orientec Co., Ltd.).

[0399] 6: The lamination strength between the image recording material and the substrate for lamination is ≥2.5N / 15mm.

[0400] 5: The lamination strength between the image recording material and the substrate for lamination is greater than 2 N / 15 mm and less than 2.5 N / 15 mm.

[0401] 4: The lamination strength between the image recording material and the substrate for lamination is greater than 1.5 N / 15 mm and less than 2 N / 15 mm.

[0402] 3: The lamination strength between the image recording material and the substrate for lamination is greater than 1 N / 15 mm and less than 1.5 N / 15 mm.

[0403] 2: The lamination strength between the image recording material and the laminating substrate is greater than 0.5 N / 15 mm and less than 1 N / 15 mm.

[0404] 1: The lamination strength between the image recording material and the laminating substrate is less than 0.5 N / 15 mm.

[0405] (Adhesion)

[0406] Adhesion was evaluated by pasting a sheet of transparent tape (registered trademark, No. 405, manufactured by NICHIBAN Co., Ltd., 12 mm wide, hereinafter also referred to as "tape") onto a solid image in an image recording, and then peeling off the tape.

[0407] Specifically, the application and removal of the tape are carried out using the following methods.

[0408] Remove the tape at a constant speed and cut it into pieces approximately 75mm in length to obtain tape sheets.

[0409] Overlay the obtained tape sheet onto the solid image, stick the tape sheet in the center of the tape sheet with your finger, measuring 12mm wide and 25mm long, and rub it vigorously with your fingertip.

[0410] Within 5 minutes of applying the tape, grasp the end of the tape and peel it off at an angle as close to 60° as possible for 0.5 to 1.0 seconds.

[0411] The presence of any additives or solid images on the peeled-off tape was visually inspected. The evaluation criteria are as follows.

[0412] 5: No material was found on the tape, nor was any image stripping detected.

[0413] 4: Some material was found on the tape, but no image peeling was found.

[0414] 3: Some material was found on the tape, and some image peeling was also found, but it is within the range that is permissible in practical applications.

[0415] 2: The material was found on the tape, and image stripping was also found, which exceeded the allowable range in practical applications.

[0416] 1: The material is identified on the tape, and the image is almost completely peeled off, making the substrate visually identifiable.

[0417] (Maintain stability)

[0418] The storage stability of the above inks was evaluated as follows.

[0419] The viscosity of the ink was measured after it was prepared and left to stand at 25°C for 1 hour (hereinafter referred to as "pre-storage viscosity") and the viscosity of the ink stored in a sealed state at 50°C for 14 days after preparation (hereinafter referred to as "post-storage viscosity"). Both pre-storage and post-storage viscosities were measured using a VISCOMETER TV-22 (manufactured by TokiSangyo Co., Ltd.) at 30°C and 100 rpm (revolutions per minute). Here, "sealed state" refers to the state where the contents are sealed in a container, and specifically, the state where the mass reduction of the contents is less than 1% by mass when stored at 50°C for 14 days.

[0420] The viscosity increase is calculated by subtracting the initial viscosity from the final viscosity after storage. A smaller viscosity increase indicates better storage stability. The evaluation criteria are as follows.

[0421] 5: The viscosity increase is less than 0.3 mPa·s.

[0422] 4: The viscosity increase is greater than 0.3 mPa·s and less than 0.5 mPa·s.

[0423] 3: The viscosity increase is greater than 0.5 mPa·s and less than 1.0 mPa·s.

[0424] 2: The viscosity increase is greater than 1.0 mPa·s and less than 2.0 mPa·s.

[0425] 1: The viscosity increase is above 2.0 mPa·s.

[0426] (Character quality)

[0427] An image recording with character images on a non-permeable substrate A was obtained using the same method as described above. The character images were printed at 4pt, 6pt, 8pt, and 10pt. Figure 1 The character shown is (Unicode: U+9DF9). Here, pt represents the DTP point, which indicates the font size; 1pt is 1 / 72 inch.

[0428] The character quality was evaluated by observing the images of each character on the image recording and determining whether they could be reproduced. "Reproducible" means that when confirmed from a distance of 0.5m, the characters are reproducible. Figure 1 In the character image, Figure 1 The horizontal line represented by 11 in the text is... Figure 1 The horizontal lines represented by 12 in the text are separated. The evaluation criteria are as follows.

[0429] The evaluation results are shown in Table 1 and Table 2.

[0430] 5: The 4pt character was reproduced.

[0431] 4: 6pt characters were reproduced, but 4pt characters were not reproduced.

[0432] 3: Reproduced 8pt characters, but failed to reproduce characters smaller than 6pt.

[0433] 2: Reproduced 10pt characters, but failed to reproduce characters smaller than 8pt.

[0434] 1: Failed to reproduce 10pt characters.

[0435] In Table 1, the unit for acid value is "mgKOH / g", and the unit for elastic modulus is "GPa", but these have been omitted. Furthermore, "-" is listed in the columns for items not measured or evaluated.

[0436] [Table 1]

[0437]

[0438] As shown in Table 1, it can be seen that in Examples 1 to 18, since the ink contains water, white pigment and at least two kinds of resin, the acid value of the ink is less than 8.0 mg KOH / g, so the lamination strength of the image recorder is excellent.

[0439] On the other hand, it can be seen that in Comparative Examples 1 to 6, the acid value of the ink exceeded 8.0 mg KOH / g, and the lamination strength of the image recorder was poor.

[0440] In Example 16, the acid value of the ink was 1.5 mg KOH / g or higher, resulting in higher lamination strength and better stability compared to Example 18. Furthermore, in Example 16, the acid value of the ink was 4.0 mg KOH / g or lower, resulting in higher lamination strength compared to Example 17.

[0441] In Example 3, the elastic modulus of the ink film is above 2.5 GPa, and the lamination strength is higher than that of Examples 4, 8 and 13.

[0442] In Example 2, resin particles were included, resulting in higher lamination strength and better adhesion compared to Example 1.

[0443] In Example 2, the acid value of the resin particles was below 40 mg KOH / g, and the lamination strength was higher than that in Examples 6 and 9.

[0444] In Example 14, the resin particle content was 3% by mass or more relative to the total ink content, resulting in superior adhesion compared to Example 13. In Example 14, the resin particle content was 8% by mass or less relative to the total ink content, resulting in superior stability compared to Example 15.

[0445] [Example 101]

[0446] <Preparation of the First Ink>

[0447] Pigment dispersion 1 was obtained in the same manner as in Example 1. First ink was prepared using the added resins listed in Table 2, in the same manner as in Example 1. The contents of white pigment, 1,2-propanediol, propylene glycol monomethyl ether, and surfactant were the same as in Example 1.

[0448] <Preparation of the Second Ink>

[0449] -Preparation of Pigment Dispersion 4-

[0450] A mixture of CI Pigment Blue 15:3 (manufactured by Dainichiseika Color & Chemicals Mfg. Co., Ltd.) as a cyan pigment (4 parts by mass), dispersion resin 4 (2 parts by mass), methyl ethyl ketone (42 parts by mass), a 1 mol / L NaOH aqueous solution (5.5 parts by mass), and water (87.2 parts by mass) was prepared. The mixture was dispersed for 6 hours using 0.1 mm φ zirconia beads in a bead mill at 2500 rpm. The dispersion was concentrated under reduced pressure at 55°C until the methyl ethyl ketone was completely distilled off, thereby removing some water. The mixture was then centrifuged for 30 minutes at 8000 rpm using a high-speed centrifuge 7550 (manufactured by Kubota Corporation) in 50 mL centrifuge tubes to remove precipitates and recover the supernatant.

[0451] Thus, a pigment dispersion 4 containing a portion of cyan pigment covered by the dispersion resin 4 is obtained.

[0452] -Preparation of the second ink-

[0453] An ink having the following composition was prepared using pigment dispersion 4, 1,2-propanediol, propylene glycol monomethyl ether, surfactant (product name "OLFINE (registered trademark) F1010", manufactured by Nissin Chemical Industry Co., Ltd.), added resins listed in Table 2, and water.

[0454] • Cyan pigment…5% by weight

[0455] • Dispersion resin: 4…2.5% by mass of dispersion resin

[0456] ·1,2-Propanediol…20% by mass

[0457] ·Propylene glycol monomethyl ether…5% by mass

[0458] Surfactant…1% by mass

[0459] • Added resin…6% by weight

[0460] Water...total becomes 100% by mass surplus

[0461] <Image Recording>

[0462] Image recording was performed using the prepared first and second inks.

[0463] An inkjet recording apparatus is prepared, comprising a transport system for continuously transporting a strip-shaped substrate, a first inkjet head for imparting a first ink, and a second inkjet head for imparting a second ink.

[0464] Furthermore, as a substrate, a polyethylene terephthalate (PET) substrate (FUTAMURA CHEMICAL CO., LTD. "FE2001" (thickness 12μm, width 780mm, length 4000m) was prepared as a non-permeable substrate; hereinafter referred to as "non-permeable substrate A").

[0465] Using an inkjet recording apparatus, a non-permeable substrate A is continuously conveyed at 50 m / min while a second ink is ejected from a second inkjet head to form a solid image. A first ink is then ejected from a first inkjet head onto the second ink, forming a solid image. The ink is dried with warm air at 80°C for 30 seconds, thereby recording the solid image and obtaining an image record.

[0466] -Ink application conditions-

[0467] Inkjet head: 1200dpi / 30inch piezoelectric full-line inkjet head

[0468] Ink ejection volume from the printhead: 3.0 pL (picoli)

[0469] Drive frequency: 41kHz (substrate conveying speed: 50m / min)

[0470] [Examples 102 to 120]

[0471] In Examples 102 to 120, pigment dispersions were prepared using the same method as in Example 101, with the types and amounts of dispersion resins as described in Table 2. Furthermore, using the added resins described in Table 2, a first ink and a second ink were prepared using the same method as in Example 101. In the first ink, the contents of white pigment, 1,2-propanediol, propylene glycol monomethyl ether, and surfactant were the same as in Example 101. In the second ink, the contents of cyan pigment, 1,2-propanediol, propylene glycol monomethyl ether, and surfactant were the same as in Example 101.

[0472] [Examples 121-122]

[0473] -Preparation of the first ink and the second ink-

[0474] The first ink and the second ink in Example 121 are the same as the first ink and the second ink in Example 101.

[0475] The first ink and the second ink in Example 122 are the same as the first ink and the second ink in Example 102.

[0476] -Preparation of pretreatment solution-

[0477] The following components are mixed to the following concentrations to prepare a pretreatment solution.

[0478] • Flocculant: glutaric acid…4.1% by mass

[0479] • Polyester resin: PESRESIN A-520 (manufactured by TAKAMATSU OIL&FAT CO.,LTD.)...6% by mass (content based on resin particles as solids).

[0480] Propylene glycol…10% by mass

[0481] Water…79.9% by mass

[0482] <Image Recording>

[0483] Image recording was performed using the prepared pretreatment solution, the first ink, and the second ink.

[0484] An inkjet recording apparatus is prepared, comprising a conveying system for continuously conveying a strip-shaped substrate, a wire bar coater for coating a pretreatment liquid onto the substrate, a first inkjet head for imparting a first ink, and a second inkjet head for imparting a second ink.

[0485] Furthermore, as a substrate, a polyethylene terephthalate (PET) substrate (FUTAMURA CHEMICAL CO., LTD. "FE2001" (thickness 12μm, width 780mm, length 4000m) was prepared as a non-permeable substrate; hereinafter referred to as "non-permeable substrate A").

[0486] The pretreatment solution was applied to a non-permeable substrate A using a wire rod coating machine to achieve a coating density of approximately 1.7 g / m². 2 Then it was dried at 50°C for 2 seconds.

[0487] Using an inkjet recording apparatus, a non-permeable substrate A is continuously conveyed at 50 m / min. Simultaneously, a second ink is ejected from a second inkjet head onto the surface of the substrate A coated with a pretreatment liquid, creating a solid image. A first ink is then ejected from a first inkjet head onto the second ink, creating a solid image. The applied ink is dried with warm air at 80°C for 30 seconds, thereby recording the solid image and obtaining an image record.

[0488] -Ink application conditions-

[0489] Inkjet head: 1200dpi / 30inch piezoelectric full-line inkjet head

[0490] Ink ejection volume from the printhead: 3.0 pL (picoli)

[0491] Drive frequency: 41kHz (substrate conveying speed: 50m / min)

[0492] [evaluate]

[0493] The acid values ​​and elastic moduli of the first ink, second ink, and pretreatment solution were measured for each embodiment, and the lamination strength and character quality of the image recordings were evaluated. The methods for measuring the acid values ​​of the first ink, second ink, and pretreatment solution, as well as the methods for evaluating the lamination strength and character quality, were the same as in Example 1. The methods for measuring the elastic moduli are as follows. The measurement results and evaluation results are shown in Table 2.

[0494] (Elastic modulus of the ink film formed by the curing of the first ink)

[0495] The elastic modulus of the surface of the image recorder on the image recording side obtained in the above image recording was determined using nanoindentation. A Hysitron TI-950 nanoindenter was used as the measuring apparatus. A cubic angle indenter was used as the nanoindentation indenter, and the indentation depth was measured at 500 nm.

[0496] (Elastic modulus of the ink film formed by the curing of the second ink)

[0497] Using an inkjet recording apparatus, a second ink was jetted from an inkjet head onto a non-permeable substrate A while continuously conveying the substrate at 50 m / min, thus imparting a solid image. The applied ink was dried with warm air at 80°C for 30 seconds, thereby recording the solid image to obtain an image recording. The elastic modulus was measured using this image recording through the same method described above.

[0498] (Elastic modulus of the pretreatment liquid film formed by the curing of the pretreatment liquid)

[0499] The pretreatment solution was applied to a non-permeable substrate A using a wire rod coating machine to achieve a coating density of approximately 1.7 g / m². 2 The pretreated liquid film was then dried at 80°C for 30 seconds. The elastic modulus of the resulting pretreated liquid film was measured using the same method as described above.

[0500] In Table 2, A1 represents the acid value of the first ink, and A2 represents the acid value of the second ink. The value obtained by subtracting the acid value of the second ink from the acid value of the first ink is recorded as "A1-A2". Furthermore, the elastic modulus of the ink film formed by curing the first ink is represented as B1, the elastic modulus of the ink film formed by curing the second ink is represented as B2, and the elastic modulus of the pretreatment liquid film formed by curing the pretreatment liquid is represented as B3. The value obtained by subtracting the elastic modulus of the second ink film from the elastic modulus of the first ink film is recorded as "B1-B2", and the value obtained by subtracting the elastic modulus of the pretreatment liquid film from the elastic modulus of the second ink film is recorded as "B2-B3".

[0501]

[0502] As shown in Table 2, it can be seen that in Examples 101 to 122, since the first ink contains water, white pigment and at least two kinds of resin and the second ink contains pigment and resin other than water and white pigment, the first ink has an acid value of less than 8 mg KOH / g, and therefore has high lamination strength.

[0503] It is known that in Examples 121 and 122, a pretreatment liquid is also included, resulting in excellent character quality. In particular, it is known that in Example 121, the elastic modulus of the pretreatment liquid film formed by curing the pretreatment liquid is less than the elastic modulus of the ink film formed by curing the second ink, resulting in excellent character quality and high lamination strength.

[0504] Symbol Explanation

[0505] 11, 12 - The horizontal line in the character.

Claims

1. An inkjet ink containing water, a white pigment, a dispersing resin, and an additive resin other than the dispersing resin, the acid value of the inkjet ink is 1.5 mgKOH / g to 8.0 mgKOH / g, the acid value of the dispersing resin is 100 mgKOH / g to 300 mgKOH / g, and the content of the dispersing resin is 0.1 mass% to 10 mass% relative to the total amount of the inkjet ink, the additive resin is present in the form of resin particles, the acid value of the resin particles is 0 mgKOH / g or more and 90 mgKOH / g or less, and the content of the resin particles is 2 mass% to 10 mass% relative to the total amount of the inkjet ink.

2. The inkjet ink according to claim 1, wherein the acid value of the inkjet ink is 1.5 mgKOH / g to 4.0 mgKOH / g.

3. The inkjet ink according to claim 1 or 2, wherein the elastic modulus of an ink film formed by curing is 2.5 GPa to 5.0 GPa.

4. The inkjet ink according to claim 1 or 2, wherein the acid value of the resin particles is 0 mgKOH / g to 40 mgKOH / g.

5. The inkjet ink according to claim 1, wherein the content of the resin particles is 3 mass% to 8 mass% relative to the total amount of the inkjet ink.

6. An ink set comprising: a first ink, which is the inkjet ink according to any one of claims 1 to 5; and a second ink, which is an inkjet ink containing water, a pigment other than a white pigment, and a resin.

7. The ink set according to claim 6, wherein the acid value of the second ink is 1.0 mgKOH / g to 8.0 mgKOH / g.

8. The ink set according to claim 6, wherein the acid value of the second ink is 1.0 mgKOH / g to 5.0 mgKOH / g.

9. The ink set according to claim 6, wherein the absolute value of the difference between the acid value of the first ink and the acid value of the second ink is 0 mgKOH / g to 2.0 mgKOH / g.

10. The ink set according to claim 6, wherein the elastic modulus of an ink film formed by curing of the second ink is 2.5 GPa to 5.0 GPa.

11. The ink set of claim 6, wherein, The ink set further comprises a pretreatment liquid containing water and a resin.

12. The ink set according to claim 11, wherein the elastic modulus of a pretreatment liquid film formed by curing of the pretreatment liquid is the same as or less than the elastic modulus of an ink film formed by curing of the second ink.

13. An image recording method in which the inkjet ink according to any one of claims 1 to 5 is used, the image recording method comprising a step of imparting the inkjet ink on a substrate by an inkjet recording method.

14. An image recording method in which the ink set according to claim 6 is used, the image recording method comprising a step of imparting the first ink and the second ink on a substrate by an inkjet recording method.

15. An image recording method in which the ink set according to claim 11 is used, The image recording method includes: The process of applying the pretreatment liquid to a substrate; and The process of applying the first ink and the second ink to a substrate having been treated with the pretreatment liquid using an inkjet recording method.

16. A method for manufacturing a laminate, comprising: The process of obtaining an image record having the substrate and an image disposed on the substrate by the image recording method according to claim 13; and The process of laminating a laminating substrate to the side of the image recorder where the image is disposed to obtain a laminate.

Images