Ink, image recording method, and method for producing laminate

Abstract

Provided are: an ink that contains a pigment, water, a water-soluble organic solvent having a boiling point of 200°C or lower, a water-soluble polymer A which contains an acid group, and a water-soluble polymer B which contains an ethylene oxide group and does not contain an acid group, the amount of the water-soluble organic solvent having a boiling point of 200°C or lower being 5-20 mass% relative to the total amount of the ink, the total amount of the water-soluble polymer A and the water-soluble polymer B being 3-8 mass% relative to the total amount of the ink, and the water-soluble polymer A and the water-soluble polymer B both being free within the ink without being adsorbed to the pigment; and the use of the aforementioned ink.

Description

Ink, Image Recording Method, and Method for Manufacturing a Laminate

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

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

[0003] For example, International Publication No. 2021 / 171875 and International Publication No. 2021 / 171876 describe an ink composition containing water, a pigment, a pigment-dispersing polymer A, and a water-soluble polymer B different from the pigment-dispersing polymer A. Japanese Patent Publication No. 2022-507624 describes a basic pH aqueous ink solvent containing water, a soluble base, and at least one water-soluble organic solvent, a pigment dispersant, and a polymer containing a base-neutralized carboxylic acid group having a glass transition temperature of 0°C to 150°C and an acid value of 50 to 1000 mgKOH / g dissolved in the solvent, and an inkjet ink containing the same.

[0004] When obtaining an image recording by applying ink onto a substrate, there may be a demand for achieving both good ejection properties of the ink and good scratch resistance of the obtained image.

[0005] The present disclosure has been made in view of such circumstances, and the problem to be solved by one embodiment of the present disclosure is to provide an ink capable of recording an image excellent in ejection properties and excellent in scratch resistance. Another problem to be solved by another embodiment of the present disclosure is to provide an image recording method capable of recording an image excellent in ejection properties and excellent in scratch resistance. Another problem to be solved by another embodiment of the present disclosure is to provide a method for manufacturing a laminate using the above image recording method.

[0006] This disclosure includes the following embodiments: <1> An ink comprising a pigment, water, a water-soluble organic solvent having a boiling point of 200°C or less, a water-soluble polymer A containing an acid group, and a water-soluble polymer B containing an ethylene oxide group but not an acid group, wherein the content of the water-soluble organic solvent having a boiling point of 200°C or less is 5% to 20% by mass of the total amount of ink, the total content of water-soluble polymer A and water-soluble polymer B is 3% to 8% by mass of the total amount of ink, and at least a portion of both water-soluble polymer A and water-soluble polymer B are free in the ink without being adsorbed to the pigment. <2> The ink according to <1>, wherein the mass ratio of the content of water-soluble polymer A to the content of water-soluble polymer B is greater than 1. <3> The ink according to <1> or <2>, wherein the water-soluble polymer A has a ClogP value of 0.5 or more. <4> The ink according to any one of <1> to <3>, wherein the water-soluble organic solvent having a boiling point of 200°C or lower includes a water-soluble organic solvent having a vapor pressure of 200 Pa or more at 20°C. <5> The ink according to <4>, wherein the proportion of the water-soluble organic solvent having a vapor pressure of 200 Pa or more at 20°C in the water-soluble organic solvent having a boiling point of 200°C or lower is 50% by mass or more, and the content of the water-soluble organic solvent having a boiling point exceeding 200°C is 2.5% by mass or less of the total amount of ink. <6> The ink according to any one of <1> to <5>, wherein both water-soluble polymer A and water-soluble polymer B have a weight-average molecular weight of 5000 to 35000. <7> The ink according to any one of <1> to <6>, wherein the proportion of the total content of pigment and water-soluble polymer A in relation to the total content of pigment, water-soluble polymer A, and water-soluble polymer B is 60% by mass or more. <8> An image recording method comprising the step of recording an image by applying an ink described in any one of <1> to <7> onto a substrate using an inkjet recording method. <9> A method for manufacturing a laminate, comprising the steps of: applying an ink described in any one of <1> to <7> onto a substrate using an inkjet recording method to record an image; and placing a laminating substrate on the image and laminating it.

[0007] According to one embodiment of the present disclosure, an ink is provided that can record an image with excellent ejection properties and excellent scratch resistance. According to another embodiment of the present disclosure, an image recording method is provided that can record an image with excellent ejection properties and excellent scratch resistance. According to another embodiment of the present disclosure, a method for manufacturing a laminate using the above image recording method is provided.

[0008] Hereinafter, the content of the present disclosure will be described in detail.

[0009] In the present disclosure, a numerical range indicated by using "~" means a range including the numerical values described before and after "~" as the minimum value and the maximum value, respectively. In the numerical ranges described stepwise in the present disclosure, the upper limit value or the lower limit value described in a certain numerical range may be replaced with the upper limit value or the lower limit value of the numerical range described in other stepwise descriptions. Also, in the numerical ranges described in the present disclosure, the upper limit value or the lower limit value described in a certain numerical range may be replaced with the value shown in the examples.

[0010] In the present disclosure, the amount of each component in the composition means the total amount of a plurality of substances present in the composition when there are a plurality of substances corresponding to each component in the composition, unless otherwise specified. In the present disclosure, a combination of two or more preferred embodiments is a more preferred embodiment. In the present disclosure, the term "step" includes not only an independent step but also a step that cannot be clearly distinguished from other steps, as long as the intended purpose of the step is achieved.

[0011] In the present disclosure, "image" means the entire film formed by applying ink, and "image recording" means the formation of an image (i.e., a film). Also, the concept of "image" in the present disclosure includes a solid image (solid image). In the present disclosure, the boiling point means the boiling point under 1 atm (101325 Pa). In the present disclosure, "water-soluble" means a property that the dissolution amount in 100 g of water at 25°C is 1 g or more. As "water-soluble", preferably, it is a property that the dissolution amount in 100 g of water at 25°C is 3 g or more (more preferably 10 g or more).

[0012] In this disclosure, "(meth)acrylate" is a concept that encompasses both acrylate and methacrylate. Similarly, "(meth)acrylic" is a concept that encompasses both acrylic and methacrylic.

[0013] <Ink> The ink of this disclosure comprises a pigment, water, a water-soluble organic solvent having a boiling point of 200°C or less, a water-soluble polymer A containing an acid group, and a water-soluble polymer B containing an ethylene oxide group but not an acid group, wherein the content of the water-soluble organic solvent having a boiling point of 200°C or less is 5% to 20% by mass of the total amount of ink, and the total content of water-soluble polymer A and water-soluble polymer B is 3% to 8% by mass of the total amount of ink, and both water-soluble polymer A and water-soluble polymer B are free in the ink without being adsorbed onto the pigment.

[0014] The inks disclosed herein exhibit excellent ejection properties and superior scratch resistance of the resulting images. The reason for this is not entirely clear, but it is presumed to be as follows.

[0015] In image recording, an ink film is typically formed on a substrate by applying ink to the substrate, thereby recording an image. The ink of this disclosure contains 5% to 20% by mass of a water-soluble organic solvent with a boiling point of 200°C or lower. As a result, the ink dries easily on the substrate, and less solvent remains in the ink film, thus increasing the strength of the ink film and providing excellent scratch resistance to the image. Furthermore, water-soluble polymer A is free in the ink and has the effect of increasing the strength of the ink film during its formation. Water-soluble polymer B contains ethylene oxide groups and has the effect of increasing viscosity. Since the total content of water-soluble polymer A and water-soluble polymer B is 3% to 8% by mass, both ink discharge performance and scratch resistance to the image can be achieved.

[0016] On the other hand, since International Publication No. 2021 / 171875, International Publication No. 2021 / 171876, and Japanese Patent Publication No. 2022-507624 do not contain any description of water-soluble polymer B, the combination of water-soluble polymer A and water-soluble polymer B has not been considered.

[0017] The following describes each component contained in the ink of this disclosure.

[0018] (Pigments) The inks of this disclosure contain at least one pigment. The pigment is included as a component for coloring the ink composition and can be appropriately selected from known pigments according to the desired hue. Pigments include organic pigments and inorganic pigments.

[0019] Examples of organic pigments include azo pigments, polycyclic pigments, dye chelates, nitro pigments, nitroso pigments, and aniline black. Among these, azo pigments or polycyclic pigments are preferred. Examples of azo pigments include azo lakes, insoluble azo pigments, condensed azo pigments, and chelated azo pigments. Examples of polycyclic pigments include phthalocyanine pigments, perylene pigments, perinone pigments, anthraquinone pigments, quinacridone pigments, dioxazine pigments, indigo pigments, thioindigo pigments, isoindolinone pigments, and quinophthalone pigments. Examples of dye chelates include basic dye-type chelates and acid dye-type chelates.

[0020] Examples of inorganic pigments include titanium dioxide, iron oxide, calcium carbonate, barium sulfate, aluminum hydroxide, barium yellow, cadmium red, chromium yellow, and carbon black.

[0021] Specific examples of pigments include those described in paragraphs 0142 to 0145 of Japanese Patent Publication No. 2007-100071.

[0022] The volume-average particle size of the pigment is preferably 10 nm to 200 nm, more preferably 10 nm to 150 nm, and even more preferably 10 nm to 100 nm. When the volume-average particle size is 200 nm or less, color reproducibility is good, and when recording images by inkjet method, droplet characteristics are good. Furthermore, when the volume-average particle size is 10 nm or more, lightfastness is good. There are no particular restrictions on the particle size distribution of the pigment in the ink; either a broad particle size distribution or a monodisperse particle size distribution is acceptable. In addition, two or more pigments with monodisperse particle size distributions may be mixed and used.

[0023] The volume-average particle size and particle size distribution of pigments in the ink are values ​​measured using a particle size distribution analyzer that employs light scattering (for example, the Microtrac UPA® EX150 manufactured by Nikkiso Co., Ltd.).

[0024] The pigment content is not particularly limited and can be appropriately selected according to the purpose and application. From the viewpoint of colorability and storage stability, the pigment content is preferably 1% to 20% by mass, and more preferably 1% to 10% by mass, based on the total mass of the ink.

[0025] (Water-soluble organic solvents with a boiling point of 200°C or less) The ink of this disclosure contains at least one water-soluble organic solvent with a boiling point of 200°C or less (hereinafter also referred to as "low-boiling point solvent").

[0026] This allows the ink applied to the substrate to dry easily. Low-energy drying is possible. In addition, because less solvent remains in the ink film, the scratch resistance of the resulting image is improved.

[0027] Examples of low-boiling point solvents include propylene glycol (boiling point 188°C), propylene glycol monomethyl ether (boiling point 120°C), ethylene glycol (boiling point 197°C), ethylene glycol monomethyl ether (boiling point 124°C), propylene glycol monoethyl ether (boiling point 133°C), ethylene glycol monoethyl ether (boiling point 135°C), propylene glycol monopropyl ether (boiling point 149°C), ethylene glycol monopropyl ether (boiling point 151°C), propylene glycol monobutyl ether (boiling point 170°C), ethylene glycol monobutyl ether (boiling point 171°C), 2-ethyl-1-hexanol (boiling point 187°C), dipropylene glycol monomethyl ether (boiling point 188°C), diethylene glycol dimethyl ether (boiling point 162°C), diethylene glycol diethyl ether (boiling point 188°C), and dipropylene glycol dimethyl ether (boiling point 175°C).

[0028] The low-boiling point solvent preferably contains a water-soluble organic solvent with a vapor pressure of 200 Pa or more at 20°C. Including a water-soluble organic solvent with a vapor pressure of 200 Pa or more at 20°C reduces the amount of solvent remaining in the ink film after drying, improving the scratch resistance of the resulting image.

[0029] In this disclosure, the vapor pressure at 20°C is measured using the static method. The static method is a method for directly or indirectly measuring the pressure of vapor in equilibrium with the solid of the sample, and is performed in accordance with OECD Guideline 104.

[0030] From the viewpoint of further improving the scratch resistance of the resulting image, the proportion of water-soluble organic solvent with a vapor pressure of 200 Pa or more at 20°C in the low-boiling point solvent is preferably 50% by mass or more, and more preferably 60% by mass or more. On the other hand, from the viewpoint of dischargeability, the proportion of water-soluble organic solvent with a vapor pressure of 200 Pa or more at 20°C in the low-boiling point solvent is preferably 90% by mass or less, and more preferably 80% by mass or less.

[0031] Examples of low-boiling point solvents with a vapor pressure of 200 Pa or higher at 20°C include propylene glycol monomethyl ether (vapor pressure 1200 Pa), propylene glycol monopropyl ether (vapor pressure 220 Pa), 1-propanol (vapor pressure 1900 Pa), and ethylene glycol monoethyl ether (vapor pressure 500 Pa).

[0032] The inks of this disclosure may contain a water-soluble organic solvent with a boiling point exceeding 200°C (hereinafter also referred to as "high-boiling point solvent"), to the extent that it does not significantly impair the effects of this disclosure. From the viewpoint of improving low-energy drying properties, the content of the high-boiling point solvent is preferably 10% by mass or less, more preferably 5% by mass or less, and even more preferably 2.5% by mass or less, based on the total amount of ink. Furthermore, it is particularly preferable that the inks of this disclosure do not contain high-boiling point solvents.

[0033] In particular, it is preferable that the proportion of a water-soluble organic solvent with a vapor pressure of 200 Pa or more at 20°C in the low-boiling-point solvent is 50% by mass or more, and that the content of the high-boiling-point solvent is 2.5% by mass or less relative to the total amount of ink.

[0034] The low-boiling-point solvent content is 5% to 20% by mass, preferably 5% to 10% by mass, relative to the total amount of ink. When the low-boiling-point solvent content is 5% by mass or more, ink drying at the nozzle is suppressed, resulting in excellent ejection performance. When the low-boiling-point solvent content is 20% by mass or less, the amount of solvent remaining in the ink film after the ink dries is reduced, resulting in excellent scratch resistance of the resulting image.

[0035] (Water-soluble polymer A containing acid groups) The ink of this disclosure contains at least one water-soluble polymer A containing acid groups (hereinafter also referred to as "water-soluble polymer A").

[0036] In this disclosure, "polymer" means a compound with a weight-average molecular weight of 1000 or more.

[0037] In this disclosure, the weight-average molecular weight (Mw) is to be measured by gel permeation chromatography (GPC). The GPC uses an HLC-8220GPC (manufactured by Tosoh Corporation), with three columns connected in series: TSKgeL Super HZ2000, TSKgeL Super HZ4000, and TSKgeL Super HZ-H (all manufactured by Tosoh Corporation, 4.6 mm × 15 cm). NMP (N-methylpyrrolidone) is used as the eluent. The sample concentration is 0.3% by mass, the flow rate is 0.35 mL / min, the sample injection volume is 10 μL, and the measurement temperature is 40°C. An RI (Refractive Index) detector (differential refractive index detector) is used as the detector. Furthermore, the calibration curve will be prepared using six samples from Tosoh Corporation's "Standard Samples TSK standard, polystyrene": "F-80", "F-20", "F-4", "F-2", "A-5000", and "A-1000".

[0038] Water-soluble polymer A is free in the ink without being adsorbed onto the pigment. Whether or not the polymer is free in the ink without being adsorbed onto the pigment can be confirmed by the following method.

[0039] In a centrifuge (product name "himac CS150FNX", manufactured by Koki Holdings Co., Ltd.), the ink is centrifuged using a rotor (S140AT) at a gravitational acceleration of 343,000Xg for 30 minutes. After centrifugation, the precipitate and supernatant are separated. Polymers contained in the recovered supernatant are considered to be polymers that are free in the ink and not adsorbed to the pigment. Polymers contained in the recovered precipitate are considered to be polymers that are adsorbed to the pigment in the ink. In other words, polymers that are not contained in the precipitate but are contained only in the supernatant are polymers that are free in the ink and not adsorbed to the pigment at all. Among these, polymers having acidic groups are water-soluble polymer A. On the other hand, polymers contained in both the precipitate and the supernatant are polymers that are partially adsorbed to the pigment and partially free in the ink. For example, the pigment-dispersing polymer described later falls into this category.

[0040] In the ink, it is preferable that 80% or more by mass of the water-soluble polymer A is free, and it is more preferable that all of the water-soluble polymer A is free.

[0041] The acidic groups contained in water-soluble polymer A may be acidic groups neutralized by a base (e.g., -COONa) or unneutralized acidic groups (i.e., -COOH). Water-soluble polymer A may contain both acidic groups neutralized by a base and unneutralized acidic groups.

[0042] Examples of acidic groups include phosphate groups, sulfo groups, and carboxyl groups. A carboxyl group is preferred as the acidic group.

[0043] The base is not limited as long as it can neutralize the acid group. Examples of bases include inorganic bases such as alkali metal hydroxides and alkaline earth metal hydroxides, and organic bases such as organic amines. Examples of alkali metals include potassium (K) and sodium (Na). Examples of alkaline earth metals include calcium (Ca) and magnesium (Mg).

[0044] Examples of alkali metal hydroxides include potassium hydroxide and sodium hydroxide. Examples of alkaline earth metal hydroxides include calcium hydroxide and magnesium hydroxide. Examples of organic amines include ammonia, primary amines (e.g., ethylamine, monoethanolamine), secondary amines (e.g., diethylamine, ethylenediamine), tertiary amines (e.g., triethylamine, triethanolamine, isopropylethylamine, pyrrolidine, piperidine), and quaternary ammonium salts. Among these, organic amines with a boiling point of 80°C or higher are preferred from the viewpoint of storage stability. From the viewpoint of storage stability, alkali metal hydroxides or organic amines are preferred as bases, and alkali metal hydroxides or organic amines with a boiling point of 80°C or higher are more preferred.

[0045] Examples of organic amines with a boiling point of 80°C or higher include ethylenediamine (117°C), triethylamine (90°C), monoethanolamine (170°C), triethanolamine (208°C), isopropylethylamine (127°C), pyrrolidine (87°C), and piperidine (106°C).

[0046] Acidic groups may be introduced into water-soluble polymer A by polymerizing monomers containing acidic groups. Preferably, water-soluble polymer A contains constituent units derived from monomers containing acidic groups.

[0047] Examples of monomers containing an acidic group include (meth)acrylic acid.

[0048] When the water-soluble polymer A is a copolymer containing constituent units derived from monomers containing acid groups, the content of constituent units derived from monomers containing acid groups is preferably 5% to 40% by mass, and more preferably 8% to 20% by mass, relative to the total amount of the water-soluble polymer A, from the viewpoint of scratch resistance.

[0049] When water-soluble polymer A is a copolymer containing constituent units derived from monomers containing acid groups, other constituent units other than those derived from monomers containing acid groups are not particularly limited.

[0050] From the viewpoint of improving the scratch resistance of the resulting image, it is preferable to include constituent units derived from monomers having an amide structure. The hydrogen bonding properties of the acid group and the amide structure increase the strength of the ink film, thereby improving the scratch resistance of the resulting image.

[0051] The constituent unit derived from monomers having an amide structure is preferably a constituent unit represented by the following formula (1).

[0052]

[0053] In formula (1), R １ represents a hydrogen atom or a methyl group.

[0054] In formula (1), R １１ R represents a hydrogen atom, a carboxyl group, or a carbamoyl group. The carbamoyl group may be substituted with an alkyl group (for example, an alkyl group having 1 to 4 carbon atoms). １１ A hydrogen atom is preferred as the element.

[0055] In formula (1), L １ and L ２ Each of these independently represents a divalent linking group which is one selected from group A consisting of alkylene groups, alkenylene groups, alkynylene groups, -O-, and -C(=O)-, a divalent linking group which is a combination of two or more selected from group A, or a single bond.

[0056] The alkylene group in Group A may be unsubstituted or may have a substituent, and an alkylene group having 1 to 8 carbon atoms is preferred, and an alkylene group having 1 to 4 carbon atoms is preferred. Examples of the alkylene group include a methylene group, an ethylene group, an i-propylene group, an n-butylene group, a t-butylene group, and the like. The alkenylene group in Group A may be unsubstituted or may have a substituent, and an alkenylene group having 2 to 8 carbon atoms is preferred, and an alkenylene group having 2 to 4 carbon atoms is preferred. Examples of the alkenylene group include vinylene, 1-methylvinylene, propenylene, 2-butenylene, 2-pentenylene group, and the like. The alkynylene group in Group A may be unsubstituted or may have a substituent, and an alkynylene group having 2 to 8 carbon atoms is preferred, and an alkynylene group having 2 to 4 carbon atoms is preferred. Examples of the alkynylene group include ethynylene, propynylene, butynylene, 1,3-butadiynylene, 2-pentynylene, 2,4-pentadiynylene, 2-hexynylene, 3-heptynylene, 4-octynylene, and the like.

[0057] Examples of the above-mentioned substituents in Group A include a halogen atom, an alkyl group, a carboxy group, a hydroxyl group, an amino group, etc. (hereinafter referred to as "substituent group X"). Examples of the halogen atom include chlorine, bromine, iodine, and the like. As the alkyl group, an alkyl group having 1 to 12 (preferably 1 to 8) carbon atoms is preferred, and examples thereof include a methyl group, an ethyl group, a propyl group, a butyl group, hexyl, and the like. The alkyl group may be unsubstituted or may have the same substituents as described above.

[0058] In formula (1), as the substituent, unless otherwise specified, the substituents in the above-mentioned substituent group X can be referred to.

[0059] L １ and L ２ In, examples of the divalent linking group formed by combining two or more selected from Group A include an alkyleneoxy group, an alkyl ester group, and the like. As the alkyleneoxy group, for example, -(C ２ H ４ O) ｎ -(n: an integer of 2 to 10), -(C ３ H ６ O)ｎ Examples include -(n: integer from 2 to 10). Examples of alkyl ester groups include caprolactone-modified acrylates.

[0060] Among the above, L １ and L ２ As for each, a single bond, an alkylene group, or an alkylene oxy group is preferred, a single bond, an alkylene group having 1 to 4 carbon atoms, or an alkylene oxy group having 2 to 3 carbon atoms is more preferred, and a single bond, an alkylene group having 1 to 4 carbon atoms, or an ethylene oxy group [-(C ２ H ４ O) ｎ - (n: integer from 2 to 10) is even more preferred. Examples of alkylene groups having 1 to 4 carbon atoms include methylene group, ethylene group, i-propylene group, n-butylene group, etc.

[0061] In formula (1), Y １ and Y ２ These are, independently, a hydrogen atom, -OH, and -R. ２ , -OR ２ , -NH ２ , - NHR ２ , -NR ２ R ３ R represents either -SH or -SH. ２ and R ３ Each of these independently represents an alkyl group, an alkenyl group, an alkynyl group, or an aryl group.

[0062] R ２ and R ３ The alkyl group in R may be unsubstituted or substituted, and is preferably an alkyl group having 1 to 8 carbon atoms, and preferably an alkyl group having 1 to 4 carbon atoms. Examples of alkyl groups include methyl group, ethyl group, propyl group, n-butyl group, t-butyl group, etc. ２ and R ３ The alkenyl group in may be unsubstituted or substituted, and is preferably an alkenyl group having 2 to 8 carbon atoms, and preferably an alkenyl group having 2 to 4 carbon atoms. Examples of alkenyl groups include vinyl, 1-methylvinyl, propenyl, 2-butenyl, and 2-pentenyl groups. ２ and R ３The alkynyl group in may be unsubstituted or substituted, and is preferably an alkynyl group having 2 to 8 carbon atoms, and preferably an alkynyl group having 2 to 4 carbon atoms. Examples of alkynyl groups include ethynyl, propynyl, butynyl, 1,3-butadiinyl, 2-pentynyl, 2,4-pentadinyl, 2-hexynyl, 3-heptynyl, and 4-octinyl. ２ and R ３ The aryl group in R may be unsubstituted or substituted. ２ and R ３ In this compound, a substituted or unsubstituted phenyl group is preferred as the aryl group.

[0063] In formula (1), Y １ and Y ２ They are bonded to each other, L １ , L ２ Together with N, a nitrogen-containing heterocycle may be formed. The formed nitrogen-containing heterocycle may contain heteroatoms other than nitrogen (e.g., oxygen atoms, sulfur atoms, etc.). A nitrogen-containing five-membered ring or a nitrogen-containing six-membered ring is preferred as the nitrogen-containing heterocycle. Examples of nitrogen-containing heterocycles include morpholine rings, piperidine rings, piperazine rings, pyrazolidine rings, pyrrolidine rings, imidazolidine rings, and the like.

[0064] Specific examples of the constituent units represented by equation (1) are shown below, but the constituent units represented by equation (1) are not limited to these specific examples.

[0065]

[0066]

[0067] The content of the constituent unit represented by formula (1) is preferably 3% to 45% by mass, more preferably 3% to 25% by mass, and even more preferably 5% to 20% by mass, based on the total amount of water-soluble polymer A.

[0068] When the content of the constituent unit represented by formula (1) is 3% by mass or more, the scratch resistance of the resulting image is improved. Furthermore, when the content of the constituent unit represented by formula (1) is 45% by mass or less, the adhesion of ink to the inside of the inkjet head is suppressed. As a result, the maintainability of the inkjet head is improved.

[0069] The total content of constituent units derived from monomers containing acid groups and constituent units represented by formula (1) is preferably 5% to 80% by mass, more preferably 10% to 60% by mass, and even more preferably 15% to 40% by mass, based on the total amount of water-soluble polymer A.

[0070] The constituent units derived from monomers containing acidic groups and the constituent units represented by formula (1) are hydrophilic constituent units, and when their total content is within the above range, the strength of the ink film increases, and the resulting image exhibits excellent scratch resistance.

[0071] Preferably, the water-soluble polymer A further contains at least one constituent unit selected from the group consisting of constituent units represented by the following formula (2A) and constituent units represented by the following formula (2B). The constituent unit represented by formula (2A) or formula (2B) is a hydrophobic constituent unit. The strength of the ink film can be appropriately adjusted by balancing the hydrophilic constituent units and the hydrophobic constituent units.

[0072]

[0073] In equations (2A) and (2B), R ４ Each of these independently represents either a hydrogen atom or a methyl group. In formula (2A), R ５ Each of these independently represents an alkyl group, an alkenyl group, or an alkynyl group, and m is an integer from 0 to 5. In formula (2B), A ２ represents a single bond or -O-, L ３ Y represents a divalent linking group which is one selected from group B consisting of alkylene group, alkenylene group, alkynylene group, -O-, and -C(=O)-, a divalent linking group which is a combination of two or more selected from group B, or a single bond. ３This represents an alkyl group having 4 to 22 carbon atoms, an alkenyl group having 4 to 22 carbon atoms, an alkynyl group having 4 to 22 carbon atoms, a cycloalkyl group having 4 to 22 carbon atoms, or an aryl group having 6 to 22 carbon atoms.

[0074] In equations (2A) and (2B), R ４ Each of these independently represents either a hydrogen atom or a methyl group, with the methyl group being preferred.

[0075] In equation (2A), R ５ In formula (1), the alkyl group, alkenyl group, or alkynyl group is R ２ and R ３ In this context, it is synonymous with alkyl group, alkenyl group, or alkynyl group, and the preferred embodiment is the same. Also, R ５ There are m such that R exists in the range m, where m is an integer from 0 to 5. In terms of composition suitability, m is preferably 0 or 1. If m is an integer of 2 or more, there are multiple R. ５ These may be the same group or different groups.

[0076] A in equation (2B) ２ It is preferable that it is -O-.

[0077] L in equation (2B) ３ L in equation (1) １ This is synonymous with the same as the term "desirable form."

[0078] Y in equation (2B) ３ This represents an alkyl group having 4 to 22 carbon atoms, an alkenyl group having 4 to 22 carbon atoms, an alkynyl group having 4 to 22 carbon atoms, a cycloalkyl group having 4 to 22 carbon atoms, or an aryl group having 6 to 22 carbon atoms.

[0079] C4-C22 alkyl groups may be unsubstituted or substituted, with C4-C18 alkyl groups being preferred, C4-C16 alkyl groups being more preferred, and C4-C10 alkyl groups being even more preferred. Examples of alkyl groups include n-butyl group, isobutyl group, 2-ethylhexyl group, isooctyl group, stearyl group, etc. C4-C22 alkenyl groups may be unsubstituted or substituted, with C4-C18 alkenyl groups being preferred, C4-C16 alkenyl groups being more preferred, and C4-C10 alkenyl groups being even more preferred. Examples of alkenyl groups include 2-methyl-propenyl group, 2-butenyl group, 3-methyl-2-butenyl group, etc. The alkynyl group having 4 to 22 carbon atoms may be unsubstituted or substituted, with a preference for an alkynyl group having 4 to 18 carbon atoms, a preference for an alkynyl group having 4 to 16 carbon atoms, and a preference for an alkynyl group having 4 to 10 carbon atoms. Examples of alkynyl groups include 4-methyl-1-pentynyl group and 3-3-dimethylbutynyl group.

[0080] Cycloalkyl groups having 4 to 22 carbon atoms may be unsubstituted or substituted, with cycloalkyl groups having 4 to 20 carbon atoms being preferred, cycloalkyl groups having 4 to 16 carbon atoms being more preferred, and cycloalkyl groups having 6 to 10 carbon atoms being even more preferred. Examples of cycloalkyl groups include cyclohexyl group, methylcyclohexyl group, dimethylcyclohexyl group, isobornyl group, dicyclopentanyl group, adamantane group, 2-methyladamantan-2-yl group, 2-ethyladamantan-2-yl group, 2-isopropyladamantan-2-yl group, norbornyl group, and methylnorbornyl group.

[0081] The aryl group having 6 to 22 carbon atoms may be unsubstituted or substituted, with aryl groups having 6 to 20 carbon atoms being preferred, aryl groups having 6 to 16 carbon atoms being more preferred, and aryl groups having 6 to 10 carbon atoms being even more preferred. Examples of aryl groups include phenyl group, tolyl group, xylyl group, ethylphenyl group, tert-butylphenyl group, adamantylphenyl group, biphenyl group, naphthyl group, and 2,6-diethylphenyl group.

[0082] From the viewpoint of further improving the scratch resistance of the resulting image, it is preferable that the water-soluble polymer A includes at least one constituent unit selected from the group consisting of the constituent unit represented by formula (a) below and the constituent units represented by any of the following formulas (b-1) to (b-4), among the constituent units represented by formula (2A) or formula (2B).

[0083]

[0084] In equation (a) and equations (b-1) to (b-4), R ５ Each of these independently represents either a hydrogen atom or a methyl group. In formula (a), R ５ A hydrogen atom is preferred, and R in formulas (b-1) to (b-4) ５ A methyl group is preferred.

[0085] In equation (a) and equations (b-1) to (b-2), R ６ R represents an alkyl group, m represents an integer from 0 to 5, and n represents an integer from 0 to 11. ６ Each of these is preferably a linear or branched alkyl group having 1 to 10 carbon atoms. ６ Each of these is preferably an alkyl group having 1 to 6 carbon atoms, and more preferably an alkyl group having 1 to 4 carbon atoms. m is preferably an integer from 0 to 2, and more preferably 0 or 1. n is preferably an integer from 0 to 3, and more preferably 0 or 1.

[0086] In equations (b-1) to (b-4), L ４ Each of these independently represents a divalent linking group which is one selected from group C consisting of an alkylene group having 1 to 18 carbon atoms, -O-, and -C(=O)-, a divalent linking group which is a combination of two or more selected from group C, or a single bond. ４ Each of these is independently preferably -O-, *-O-alkylene group- (* represents a bond that connects to a carbonyl group), or -O-alkylene group-O-. Furthermore, L ４ The number of carbon atoms in the alkylene group is preferably 1 to 12, more preferably 1 to 8, even more preferably 1 to 4, particularly preferably 1 or 2, and most preferably 1.

[0087] Specific examples of the constituent units represented by formula (a) and formulas (b-1) to (b-4) are shown below. Note that "*" in each structure represents a bond. Also, "nBu" represents "n-butyl", "iBu" represents "isobutyl", and "tBu" represents "tert-butyl".

[0088]

[0089] The content of at least one constituent unit selected from the group consisting of constituent units represented by formula (2A) and constituent units represented by formula (2B) is preferably 1% to 60% by mass, more preferably 3% to 50% by mass, and even more preferably 20% to 50% by mass, relative to the total amount of water-soluble polymer A.

[0090] Furthermore, the water-soluble polymer A may contain structural units derived from alkyl (meth)acrylates having 1 to 3 carbon atoms in the alkyl moiety. Examples of alkyl (meth)acrylates having 1 to 3 carbon atoms in the alkyl moiety include methyl (meth)acrylate, ethyl (meth)acrylate, and propyl (meth)acrylate. The content of structural units derived from alkyl (meth)acrylates having 1 to 3 carbon atoms in the alkyl moiety is preferably 10% to 80% by mass, more preferably 15% to 75% by mass, and even more preferably 30% to 60% by mass, based on the total amount of the water-soluble polymer A.

[0091] The weight-average molecular weight of water-soluble polymer A is preferably 5,000 to 35,000. When the weight-average molecular weight of water-soluble polymer A is 5,000 or more, dispensing curvature is further suppressed. When the weight-average molecular weight of water-soluble polymer A is 35,000 or less, dispensing delay is further suppressed. From the above viewpoint, the weight-average molecular weight of water-soluble polymer A is more preferably 10,000 to 30,000.

[0092] The water-soluble polymer A preferably has a ClogP value of 0.5 or higher. When the ClogP value of water-soluble polymer A is 0.5 or higher, the ink film becomes hydrophobic and its strength increases. As a result, the scratch resistance of the resulting image is improved. From the above viewpoint, the ClogP value of water-soluble polymer A is more preferably 0.6 or higher, and even more preferably 1.0 or higher. From the viewpoint of water solubility, the upper limit of the ClogP value of water-soluble polymer A is preferably 2.5 or lower.

[0093] A higher ClogP value indicates greater hydrophobicity. The ClogP value shall be calculated using ChemDraw® Professional (ver. 16.0.1.4) from PerkinElmer Infomatics.

[0094] The ClogP value of each polymer is calculated as the ClogP value of the monomers used to form that polymer. For polymers that are copolymers, the ClogP value of the copolymer is the weighted average of the ClogP values ​​of the monomers used to form the copolymer. For example, the ClogP value of polyacrylic acid is calculated as the ClogP value of acrylic acid. Also, the ClogP value of a polyacrylic acid-polymethacrylic acid copolymer (copolymerization mass ratio = 50:50) is calculated as the sum of the values ​​obtained by multiplying the ClogP values ​​of acrylic acid and methacrylic acid by the copolymerization mass ratio (in this case, 0.5 each). If a polymer contains a constituent unit that includes a neutralized acid group (e.g., -COONa), the ClogP value of the monomer used to form this constituent unit is calculated by taking the countercation (e.g., Na) from the monomer containing the neutralized acid group (e.g., -COONa). ＋ The ClogP values ​​of the anions excluding () are used. Furthermore, if the polymer contained in the ink is unknown, the structure and content ratio of the polymer are identified by performing a component analysis of the ink using spectroscopy or nuclear magnetic resonance (NMR) and the ClogP value of the polymer is calculated.

[0095] The content of water-soluble polymer A is adjusted so that the total content of water-soluble polymer A and water-soluble polymer B is between 3% by mass and 8% by mass.

[0096] The content of water-soluble polymer A is preferably 1% to 7% by mass, and more preferably 3% to 6% by mass, relative to the total amount of ink.

[0097] (Water-soluble polymer B containing ethylene oxide groups but not acidic groups) The ink of this disclosure contains at least one water-soluble polymer B (hereinafter also referred to as "water-soluble polymer B") which contains ethylene oxide groups but does not contain acidic groups. Water-soluble polymer B has the effect of increasing the viscosity of the ink. By appropriately adjusting the viscosity of the ink with water-soluble polymer B, the ink discharge performance is improved.

[0098] In the ink, it is preferable that 80% or more by mass of the water-soluble polymer B is free, and it is more preferable that all of the water-soluble polymer B is free.

[0099] The water-soluble polymer B is preferably represented by the following formula (B). ２１ O-(CH ２ CH ２ O) ｎ１ - (CH ２ CH (CH ３ )O) ｎ２ -H...(B) In formula (B), R ２１ represents a hydrogen atom or an alkyl group, with the average value of n1 being 1 to 1000 and the average value of n2 being 0 to 200.

[0100] R ２１ The alkyl group represented by is preferably an alkyl group having 1 to 12 carbon atoms (preferably 1 to 8 carbon atoms), and examples include a methyl group, an ethyl group, a propyl group, a butyl group, a hexyl group, and the like.

[0101] Among them, R ２１ It is preferable that it is a hydrogen atom. The average value of n1 is preferably 100 to 1000, and more preferably 100 to 500. The average value of n2 is preferably 0 to 100, and more preferably 0 to 50.

[0102] Examples of water-soluble polymer B include polyoxyethylene polyoxypropylene glycol and polyethylene glycol.

[0103] The weight-average molecular weight of water-soluble polymer B is preferably 5,000 to 35,000. That is, it is preferable that both water-soluble polymer A and water-soluble polymer B have a weight-average molecular weight of 5,000 to 35,000. If the weight-average molecular weight of water-soluble polymer B is 5,000 or more, dispensing curvature is further suppressed. If the weight-average molecular weight of water-soluble polymer B is 35,000 or less, dispensing delay is further suppressed. From the above viewpoint, it is more preferable that the weight-average molecular weight of water-soluble polymer B is 10,000 to 30,000.

[0104] The content of water-soluble polymer B is adjusted so that the total content of water-soluble polymer A and water-soluble polymer B is between 3% by mass and 8% by mass.

[0105] The content of water-soluble polymer B is preferably 1% to 7% by mass, and more preferably 1% to 4% by mass, relative to the total amount of ink.

[0106] -Total Content of Water-Soluble Polymer A and Water-Soluble Polymer B- The ink of this disclosure contains water-soluble polymer A and water-soluble polymer B, and the total content of water-soluble polymer A and water-soluble polymer B is 3% by mass to 8% by mass. By having the total content of water-soluble polymer A and water-soluble polymer B within the above range, the viscosity of the ink is appropriately adjusted and the strength of the ink film is obtained. As a result, the ink of this disclosure has excellent ejectability and scratch resistance of the obtained image.

[0107] From the above viewpoint, the total content of water-soluble polymer A and water-soluble polymer B is preferably 4% to 7% by mass.

[0108] -Mass ratio of water-soluble polymer A content to water-soluble polymer B content- The scratch resistance of the resulting image is improved by the balance of amounts of water-soluble polymer A and water-soluble polymer B in the ink of this disclosure.

[0109] Specifically, the mass ratio of the water-soluble polymer A to the water-soluble polymer B is preferably greater than 1, and more preferably 1.1 or greater. The above mass ratio is preferably 2 or less, and more preferably 1.5 or less.

[0110] - The ratio of the total content of pigment and water-soluble polymer A to the total content of pigment, water-soluble polymer A, and water-soluble polymer B - The ink of this disclosure improves adhesion when a laminating substrate is placed on an image and laminated, depending on the balance of amounts of pigment, water-soluble polymer A, and water-soluble polymer B.

[0111] Specifically, the ratio of the total content of pigment and water-soluble polymer A to the total content of pigment, water-soluble polymer A, and water-soluble polymer B is preferably 60% by mass or more, and more preferably 70% by mass or more. From the viewpoint of suppressing ejection curvature, the above ratio is preferably 90% by mass or less.

[0112] (Water) The inks of this disclosure contain water. The water content is preferably 10% by mass or more, more preferably 20% by mass or more, even more preferably 30% by mass or more, and particularly preferably 50% by mass or more, based on the total amount of ink. The upper limit of the water content may be adjusted as appropriate depending on the content of other components. For example, the water content is 90% by mass or less, preferably 85% by mass or less, and more preferably 80% by mass or less.

[0113] (Pigment Dispersant) Since the inks of this disclosure contain pigments, it is preferable that they contain a pigment dispersion polymer for dispersing the pigments in the ink.

[0114] Unlike the water-soluble polymers A and B described above, the pigment-dispersing polymer is adsorbed to the pigment in at least a portion of it. Even if a portion of the pigment-dispersing polymer is free from adsorption to the pigment in the ink, the free pigment-dispersing polymer does not fall under the categories of water-soluble polymers A and B. For example, when the ink contains two types of water-soluble polymers having acidic groups, the first type may be partially adsorbed to the pigment, with the remainder free from adsorption, while the second type may be free from adsorption to the pigment. In this case, the first type is the pigment-dispersing polymer, and the second type is water-soluble polymer A.

[0115] The pigment dispersion polymer preferably contains at least one acid group selected from the group consisting of phosphate groups, sulfo groups, and carboxyl groups. The pigment dispersion polymer preferably contains a carboxyl group as the acid group.

[0116] Acid groups may be introduced into the polymer by polymerizing monomers containing acid groups. It is preferable that the pigment-dispersed polymer contains constituent units derived from monomers containing acid groups.

[0117] Specific examples of constituent units derived from monomers containing acidic groups are shown below. However, this disclosure is not limited to these examples.

[0118]

[0119] When the pigment dispersion polymer is a copolymer containing constituent units derived from monomers containing acid groups, the content of constituent units derived from monomers containing acid groups is preferably 5% to 40% by mass, and more preferably 8% to 20% by mass, relative to the total amount of the pigment dispersion polymer, from the viewpoint of pigment dispersibility.

[0120] The pigment dispersion polymer preferably contains an aromatic ring. The aromatic ring may be introduced into the pigment dispersion polymer as a constituent unit derived from an aromatic ring-containing monomer by polymerizing the monomer containing the aromatic ring. When the pigment dispersion polymer contains an aromatic ring, the pigment dispersion polymer tends to become more hydrophobic. As a result, the pigment dispersion polymer is more easily adsorbed onto the pigment, and the storage stability of the ink is further improved.

[0121] Examples of aromatic rings include aromatic hydrocarbon rings such as benzene rings, naphthalene rings, anthracene rings, and pyrene rings; and heteroaromatic rings such as pyridine rings, pyrrole rings, furan rings, thiophene rings, imidazolyl rings, and acridone rings. Among these, aromatic hydrocarbon rings are preferred.

[0122] As monomers containing an aromatic ring, monomers containing an aromatic ring and an ethylenically unsaturated double bond are preferred, and vinyl monomers containing an aromatic ring are more preferred. Examples of monomers containing an aromatic ring include styrene, methylstyrene, divinylbenzene, vinylpyridine, diallyl phthalate, and (meth)acrylates containing an aromatic ring (e.g., benzyl acrylate, phenoxyethyl acrylate, etc.).

[0123] The monomer containing the aromatic ring may be unsubstituted or substituted with substituents. Examples of substituents include halogen atoms, alkyl groups, carboxylic acid groups, and hydroxyl groups. Examples of halogen atoms include chlorine, bromine, and iodine. Preferred alkyl groups are those having 1 to 12 carbon atoms (preferably 1 to 8 carbon atoms), such as methyl, ethyl, propyl, butyl, and hexyl groups. The alkyl group may be unsubstituted or may have substituents similar to those described above.

[0124] Specific examples of constituent units derived from monomers containing aromatic rings are shown below. This disclosure is not limited to these specific examples. In each structure, "*" indicates a bond. Also, "iBu" represents isobutyl, "nBu" represents n-butyl, and "tBu" represents tert-butyl.

[0125]

[0126] The content of monomer-derived structural units containing aromatic rings is preferably 50% to 85% by mass, and more preferably 60% to 80% by mass, relative to the total amount of the pigment dispersion polymer.

[0127] Pigment-dispersed polymers may contain constituent units derived from monomers that do not contain aromatic rings, in addition to constituent units derived from monomers that do contain aromatic rings. Suitable examples of monomer-derived constituent units that do not contain aromatic rings include alkyl (meth)acrylates.

[0128] As the alkyl (meth)acrylate, alkyl (meth)acrylates having 1 to 20 carbon atoms in the alkyl group are preferred. Examples of alkyl (meth)acrylates include methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, and stearyl (meth)acrylate.

[0129] Specific examples of pigment-dispersed polymers include the following copolymers. The mass ratio of monomers in the copolymer can be appropriately selected within the range that satisfies the weight-average molecular weight range. However, this disclosure is not limited to the following specific examples: • Benzyl methacrylate / acrylic acid copolymer • Benzyl methacrylate / methacrylic acid copolymer • Styrene / acrylic acid / stearyl acrylate copolymer • Styrene / acrylic acid / stearyl methacrylate copolymer • Benzyl methacrylate / methacrylic acid / stearyl methacrylate copolymer • Phenoxyethyl methacrylate / methacrylic acid / stearyl methacrylate copolymer • Phenoxyethyl methacrylate / methacrylic acid / stearyl methacrylate / hydroxyethyl methacrylate copolymer

[0130] The weight-average molecular weight of the pigment-dispersed polymer is preferably 1,000 to 100,000, and more preferably 1,000 to 50,000.

[0131] In the ink, the mass ratio of the pigment-dispersing polymer content to the pigment content is preferably 0.05 to 3, more preferably 0.05 to 2, even more preferably 0.05 to 1, and particularly preferably 0.05 to 0.7.

[0132] The inks of this disclosure may, as necessary, contain other components, provided that they do not significantly impair the effects of this disclosure.

[0133] Other ingredients include, for example, surfactants, drying inhibitors (swelling agents), color inhibitors, penetration enhancers, UV absorbers, preservatives, rust inhibitors, defoamers, viscosity modifiers, pH adjusters, and chelating agents.

[0134] The viscosity of the ink of this disclosure is preferably 5 mPa·s or higher, and more preferably 8 mPa·s or higher. The upper limit of the ink viscosity is, for example, 30 mPa·s, from the viewpoint of ink discharge performance.

[0135] The viscosity of the ink is measured at 25°C using a viscometer, for example, using a viscometer (product name "RE-85L," manufactured by Toki Sangyo Co., Ltd.).

[0136] The surface tension of the inks disclosed herein is preferably 20 mN / m to 40 mN / m, more preferably 23 mN / m to 38 mN / m, even more preferably 25 mN / m to 35 mN / m, and most preferably 25 mN / m to 32 mN / m.

[0137] The surface tension of the ink is measured at 25°C using a surface tensimeter, for example, using a surface tensimeter (product name "DY-700," manufactured by Kyowa Interface Chemical Co., Ltd.).

[0138] <Image Recording Method> The image recording method of the present disclosure includes a step of applying the ink of the present disclosure to a substrate using an inkjet recording method to record an image (hereinafter also referred to as the "ink application step"). The image recording method of the present disclosure may include other steps as necessary. Since the image recording method of the present disclosure records an image using the ink of the present disclosure, the same effects as those obtained by the ink of the present disclosure can be obtained by the image recording method of the present disclosure.

[0139] The type of substrate is not particularly limited, but the inks of this disclosure are suitable for image recording on cellulose-based printing paper (e.g., fine paper, coated paper, art paper).

[0140] As a base material, commercially available materials can be appropriately selected, for example, high-quality paper (A) such as "OK Prince Superior" from Oji Paper Co., Ltd., "Shiraoi" and "New NPI Superior" from Nippon Paper Industries Co., Ltd.; high-quality coated paper such as "Silver Diamond" from Nippon Paper Industries Co., Ltd.; lightly coated paper such as "OK Everlight Coat" from Oji Paper Co., Ltd. and "Aurora S" from Nippon Paper Industries Co., Ltd.; lightweight coated paper (A3) such as "OK Coat L" from Oji Paper Co., Ltd. and "Aurora L" from Nippon Paper Industries Co., Ltd.; coated paper (A2, B2) such as "OK Top Coat+" from Oji Paper Co., Ltd. and "Aurora Coat" from Nippon Paper Industries Co., Ltd.; art paper (A1) such as "OK Kinto+" from Oji Paper Co., Ltd. and "Tokuryo Art" from Mitsubishi Paper Mills Ltd.; and various types of photographic paper for inkjet recording can also be used.

[0141] In particular, coated paper, commonly used in offset printing, is preferred. Coated paper is made by applying a coating material to the surface of a base paper, such as a fine paper or acid-free paper that is not surface-treated and is mainly composed of cellulose, to create a coating layer. Coated paper is preferably made of a base paper and a coating layer containing kaolin and / or calcium bicarbonate, and art paper, coated paper, lightweight coated paper, or lightly coated paper is more preferred.

[0142] In the ink application process, the ink of this disclosure is applied to the substrate using an inkjet recording method to record an image.

[0143] There are no particular restrictions on the ink ejection method in an inkjet recording system, and any known method may be used, such as a charge control method that ejects ink using electrostatic attraction, a drop-on-demand method (pressure pulse method) that utilizes the vibration pressure of a piezoelectric element, an acoustic inkjet method that converts an electrical signal into an acoustic beam and irradiates the ink to eject ink using the radiation pressure, and a thermal inkjet (bubble jet®) method that heats the ink to form bubbles and utilizes the resulting pressure.

[0144] As an inkjet recording method, the method described in Japanese Patent Publication No. 54-59936 is particularly effective, as it involves the ink undergoing a rapid volume change due to the action of thermal energy, and the force resulting from this state change ejects the ink from the nozzle. As an inkjet recording method, the method described in paragraphs 0093 to 0105 of Japanese Patent Publication No. 2003-306623 can also be applied.

[0145] In inkjet printing, ink is applied by ejecting ink from the nozzles of the inkjet head.

[0146] Inkjet recording methods include the shuttle method, which uses a short serial head to scan the substrate in the width direction while recording, and the line method, which uses a line head in which recording elements are arranged to cover the entire area of ​​one side of the substrate.

[0147] In the line method, image recording can be performed across the entire surface of the substrate by scanning the substrate in a direction intersecting the arrangement direction of the recording elements. The line method eliminates the need for a transport system such as a carriage that scans the short head, which is required in the shuttle method. Furthermore, compared to the shuttle method, the line method eliminates the need for complex scanning control of the carriage movement and the substrate, as only the substrate moves. Therefore, the line method enables faster image recording compared to the shuttle method.

[0148] Ink application is preferably carried out using an inkjet head having 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 1 inch is equal to 2.54 cm.

[0149] From the viewpoint of obtaining high-definition images, the ink droplet size is preferably 1 pL (picoliters) to 10 pL, and more preferably 1.5 pL to 6 pL. Furthermore, from the viewpoint of improving image uniformity and the continuity of continuous gradations, it is also effective to dispense different droplet sizes in combination.

[0150] It is preferable to include a step of heating and drying the ink after applying it (hereinafter also referred to as the "drying step").

[0151] Drying methods in the drying process include known heating methods such as heaters, known air blowing methods such as dryers, and methods combining these.

[0152] Examples of drying methods in the drying process include: applying heat from the side of the substrate opposite to the side to which the ink is applied using a heater; applying warm air or hot air to the side of the substrate to which the ink is applied; applying heat from the side of the substrate to which the ink is applied using an infrared heater; and methods combining these methods.

[0153] The heating temperature in the drying process is preferably 35°C or higher, and more preferably 40°C or higher. There is no particular upper limit to the heating temperature, but 50°C is preferred, 70°C is more preferred, and 80°C is even more preferred.

[0154] The heating time in the drying process is not particularly limited, and can be, for example, 1 to 5 seconds.

[0155] The inks disclosed herein exhibit excellent low-energy drying properties, allowing for lower drying temperatures and shorter drying times compared to general image recording. Therefore, they can be applied to applications where strong drying is difficult.

[0156] <Method for manufacturing a laminated body> The method for manufacturing a laminated body according to the present disclosure includes the steps of: applying the ink of the present disclosure to a substrate using an inkjet recording method to record an image; and placing a laminating substrate on the image and laminating it (hereinafter also referred to as the "laminating step").

[0157] According to the method for manufacturing a laminate according to the present disclosure, a laminate can be manufactured that exhibits excellent adhesion between the image in an image recording obtained by the image recording method according to the present disclosure and the laminating substrate.

[0158] For the ink application process, refer to the image recording method disclosed herein.

[0159] In the lamination process, the laminating substrate may be placed directly on the image, or it may be placed via another layer.

[0160] Lamination can be performed by layering a laminating substrate onto the image, for example, via another layer (such as an adhesive layer), or by directly layering the laminating substrate onto the image and passing it through a laminator. In the latter case, a commercially available laminator can be used.

[0161] The lamination temperature is not particularly limited. For example, when laminating an image recording to a laminating substrate via another layer (e.g., an adhesive layer), a temperature of 20°C or higher is sufficient. When using a laminator, the temperature of the laminating rolls may be in the range of 20°C to 80°C. The bonding force of the laminating roll pair can be selected as appropriate as needed.

[0162] The laminating substrate is preferably a resin substrate. The resin substrate is not particularly limited, but examples include a substrate made of a thermoplastic resin.

[0163] Examples of resin substrates include substrates formed from thermoplastic resin into a sheet. Preferably, the resin substrate contains polypropylene, polyethylene terephthalate, nylon, polyethylene, or polyimide.

[0164] 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, and more preferably 10 μm to 100 μm.

[0165] When laminating a laminating substrate directly onto an image, lamination can be carried out by known methods such as heat bonding or heat fusion.

[0166] Furthermore, when laminating an image with a laminating substrate via an adhesive layer, the lamination can be carried out, for example, by applying adhesive to the side of the image recording material where the image is placed, then placing the laminating substrate on top, and then bonding the image recording material and the laminating substrate together.

[0167] Furthermore, when laminating a laminating substrate to an image via an adhesive layer, the lamination can also be carried out by methods such as extrusion lamination (i.e., sandwich lamination).

[0168] 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, thereby increasing the lamination strength.

[0169] The method for manufacturing laminates described herein is suitable for manufacturing beverage packaging.

[0170] The present invention will be described in more detail below with reference to examples. However, this disclosure is not limited to the following examples unless it exceeds the spirit of the invention.

[0171] <Preparation of Cyanide Pigment Dispersion> -Synthesis of Polymer Q1- A monomer composition is prepared by mixing 172 g of methacrylic acid (MAA), 828 g of benzyl methacrylate (BzMA), and 375 g of isopropanol. Separately, an initiator composition is prepared by mixing 22.05 g of 2,2-azobis(2-methylbutyronitrile) and 187.5 g of isopropanol. Next, 187.5 g of isopropanol is heated to 80°C under a nitrogen atmosphere, and the mixture of the monomer composition and the initiator composition is added dropwise over 2 hours. After the addition is complete, the resulting solution is kept at 80°C for a further 4 hours, and then cooled to 25°C. After cooling, the solvent is removed under reduced pressure to obtain polymer Q1 (BzMA:MAA = 82.8:17.2 [mass ratio]).

[0172] The composition of the obtained polymer Q1 is: １ Confirmed by 1H-NMR, polymer Q1 contains a carboxyl group in its molecule, and its acid value is 112 mgKOH / g. The Mw of polymer Q1 is 30,000.

[0173] - Preparation of Cyanide Pigment Dispersion - 0.8 equivalents of methacrylic acid in the polymer Q1 (150 g) obtained above are neutralized with an aqueous potassium hydroxide solution. After neutralization, ion-exchanged water is added to prepare an aqueous solution of polymer Q1 so that the concentration of polymer Q1 becomes 25% by mass. 124 parts of the aqueous solution of polymer Q1 are mixed with 48 g of cyanide pigment, pigment blue 15:3 (product name "Phthalocyanine Blue A220", manufactured by Dainichi Seika Co., Ltd.), 75 g of water, and 30 g of dipropylene glycol. The mixture is dispersed using zirconia beads (bead diameter 0.1 mmφ) in a bead mill until the desired volume-average particle size is obtained, to obtain a dispersion (uncrosslinked dispersion) with a pigment concentration of 15% by mass. Next, 1.3 g of trimethylolpropane polyglycidyl ether (product name "Denacol EX-321", manufactured by Nagase ChemteX Corporation), which is a crosslinking agent, and 14.3 g of an aqueous boric acid solution (boric acid concentration: 4% by mass) are added to 136 g of the above uncrosslinked dispersion, and the mixture is reacted at 50°C for 6.5 hours. After that, the mixture is cooled to 25°C to crosslink the water-soluble polymer Q1 with the crosslinking agent. This yields a dispersion (crosslinked dispersion) containing cyanide pigment and crosslinked polymer Q1. Next, ion-exchanged water is added to the above crosslinked dispersion, and ultrafiltration is performed using a stirred ultraholder (manufactured by ADVANTEC Corporation) and an ultrafiltration filter (manufactured by ADVANTEC Corporation, molecular weight cutoff 50,000, Q0500076E ultrafilter). Next, the crosslinked dispersion is purified to reduce the dipropylene glycol concentration in the crosslinked dispersion to 0.1% by mass or less. Subsequently, a cyan pigment dispersion is obtained by concentrating the mixture until the pigment concentration reaches 15% by mass. The cyan pigment dispersion contains cyan pigment and a pigment dispersion polymer (crosslinked polymer Q1), and at least a portion of the crosslinked polymer Q1 is adsorbed onto the cyan pigment.

[0174] [Examples 1-14, Comparative Examples 1-6] Each component is added to the cyan pigment dispersion to obtain the composition (mass%) shown in Tables 1 and 2 to prepare a mixed solution. After preparation, coarse particles are removed from the mixed solution using a 5 μm filter to prepare cyan ink. The water content is the amount remaining when the total cyan ink is 100% by mass.

[0175] Details of each component listed in Tables 1 and 2 are as follows:

[0176] <Water-soluble organic solvents> • 1,3-BD: 1,3-butanediol • PGmBE: propylene glycol monobutyl ether • PGmPE: propylene glycol monopropyl ether • PG: propylene glycol • PGmME: propylene glycol monomethyl ether

[0177] <Water-soluble polymers A1-A3> -Polymer A1- 82 g of propylene glycol is placed in a 500 ml three-necked flask equipped with a stirrer, thermometer, reflux condenser, and nitrogen gas inlet tube, and the temperature is raised to 90°C under a nitrogen stream. 1.57 g of perbutyl O (radical polymerization initiator; manufactured by NOF Corporation), 15 g of 2-methachlorooxyethyl acid phosphate (P-1M), 45 g of methyl methacrylate (MMA), isobornyl methacrylate (IBOMA), 10 g of acryloylmorpholine (ACMO), 1.84 g of dodecyl mercaptan, and 152 g of propylene glycol are added dropwise at a constant rate under dropwise conditions that complete the addition in 3 hours. After the addition of the mixed solution is complete, the mixture is stirred for 4 hours. Next, 12 g of a 24% by mass sodium hydroxide aqueous solution (alkali metal hydroxide) is added dropwise to the obtained reaction mixture using a dropper funnel to obtain a solution of polymer A1 (MAA:ACMO:IBOMA:MMA = 15:10:30:45 [mass ratio]).

[0178] The composition of the resulting polymer A1 is: １ Confirmation is performed by H-NMR. Polymer A1 contains a carboxyl group in its molecule, and its acid value is 98 mgKOH / g. Polymer A1 has a weight-average molecular weight (Mw) of 15,000 and a glass transition temperature (Tg) of 139°C.

[0179] -Polymer A2- A solution of polymer A2 (MAA:ACMO:IBOMA:MMA = 40:10:30:20 [mass ratio]) is obtained by the same method as for polymer A1. Polymer A2 contains carboxyl groups in its molecule, and its acid value is 261 mgKOH / g. Polymer A2 has a weight-average molecular weight (Mw) of 15,000 and a glass transition temperature (Tg) of 168°C.

[0180] -Polymer A3- A solution of polymer A3 (MAA:ACMO:IBOMA:MMA = 15:10:2:73 [mass ratio]) is obtained by the same method as for polymer A1. Polymer A3 contains a carboxyl group in its molecule, and its acid value is 98 mgKOH / g. Polymer A3 has a weight-average molecular weight (Mw) of 15,000 and a glass transition temperature (Tg) of 121°C.

[0181] Next, we will confirm whether polymers A1 to A3 are water-soluble polymers using the following method. First, prepare 1 g of sample (i.e., polymer) by drying the polymer solution under reduced pressure at 150°C for 6 hours. Add 100 g of 25°C water to the prepared 1 g of polymer and heat under reflux for 30 minutes. Cool the resulting liquid to 25°C and let it stand at 25°C for 1 hour. Visually observe the standing liquid. If all of the polymer is dissolved, it is determined that the polymer is a "water-soluble polymer." If some or all of the polymer does not dissolve, it is determined that the polymer is a "non-water-soluble polymer." Polymers A1 to A3 can be confirmed to be water-soluble polymers.

[0182] <Water-soluble polymers B1-B5> ・Polymer B1: Polyethylene glycol (product name "PEG4000", manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) ・Polymer B2: Polyethylene glycol (product name "PEG6000", manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) ・Polymer B3: Polyethylene glycol (product name "Alcox L-6", manufactured by Meisei Chemical Industry Co., Ltd.) ・Polymer B4: Polyoxyethylene polyoxypropylene glycol (product name "Newpol 75H-90000", manufactured by Sanyo Chemical Industries, Ltd.) ・Polymer B5: Polyoxyethylene polyoxypropylene glycol (product name "Newpol V-10-C", manufactured by Sanyo Chemical Industries, Ltd.)

[0183] Polymers B1 to B3 can be confirmed to be water-soluble polymers.

[0184] <Other polymers> ・PPG: Polypropylene glycol (product name "PPG4000", manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.)

[0185] In Tables 1 and 2, "low boiling point solvent" means a water-soluble organic solvent with a boiling point of 200°C or lower. "Percentage of solvents with a vapor pressure of 200 Pa or higher" means the percentage of water-soluble organic solvents with a vapor pressure of 200 Pa or higher at 20°C among water-soluble organic solvents with a boiling point of 200°C or lower. "Percentage of pigment and water-soluble polymer A" means the percentage of the total content of pigment and water-soluble polymer A relative to the total content of pigment, water-soluble polymer A, and water-soluble polymer B.

[0186] <Image Recording> OK Topcoat (manufactured by Oji Paper Co., Ltd.) is used as the recording medium. The image recording conditions are as follows: cyan ink droplet size of 5 pL, ejection frequency of 25.5 kHz, and resolution of 1200 dpi × 1200 dpi. Immediately after image recording, the substrate is placed on a 60°C hot plate with the side opposite to the image recording surface in contact with the plate, and drying is performed by applying 120°C hot air to the image recording surface for 10 seconds using a hairdryer.

[0187] The following evaluation will be performed using the above inks.

[0188] (Discharge Performance (Bending)) Ten line images parallel to the transport direction are recorded as images. The spacing between each line is 10 dots, and the length of each line is 2000 dots. The center value of the line is measured using a dot analyzer DA-6000 (product name, manufactured by Oji Instruments Co., Ltd.), the distance from the center value of the line image (amount of deviation) is determined, and the standard deviation (σ) is calculated. The calculated value of σ is used as an indicator to evaluate the discharge performance (discharge bending) based on the following evaluation criteria. A: σ < 4 μm B: 4 μm ≤ σ < 6 μm C: 6 μm ≤ σ ≤ 10 μm D: σ > 10 μm

[0189] (Ejection (Delay)) Ten line images perpendicular to the transport direction are recorded as an image. The spacing between each line is 10 dots, and the length of each line is 300 dots. First, confirm that ink is ejected from all nozzles. Next, leave the print head in the same state for 1 hour in an environment of 25°C and 80% relative humidity. Using a new recording medium, record an image again under the same conditions to create an image sample. Observe the obtained image sample visually. The evaluation criteria are as follows: A: Recording starts from the first line image. B: Recording starts from the second to fourth lines image. C: Recording starts from the fifth to eighth lines image. D: Recording starts from the ninth or tenth line image image, or none of the line images are recorded.

[0190] (Scratch Resistance) Record an image with a 100% duty cycle. A 100% duty cycle is defined as an image recorded under the condition that approximately 5.0 pL of ink is applied to one drop per unit area (1 pixel) of 1 / 1200 inch x 1 / 1200 inch at a resolution of 1200 dpi x 1200 dpi. One minute after the image recording material has dried, place a blank sheet of paper on top of the recorded image. Apply 2 kg / cm² of ink to the paper. ２ Apply a load and move the blank paper horizontally. After moving, visually check for ink transfer to the blank paper. A: No transfer at all. B: Transfer is observed in an area of ​​more than 0% but less than or equal to 25% of the entire image recording area. C: Transfer is observed in an area of ​​more than 25% but less than or equal to 50% of the entire image recording area. D: Transfer is observed in an area of ​​more than 50% of the entire image recording area.

[0191] (Adhesion) Record an image with a 100% duty cycle. Three hours after the image recording material has dried, apply polyethylene (PE) melted at 300°C to a thickness of approximately 10 μm. After application, leave it undisturbed for 24 hours at a temperature of 23°C and 50% humidity. Then, measure the adhesion force between the image recording material and the PE using a digital force gauge (IMADA). A: 0.80 N / m or more B: 0.60 N / m or more and less than 0.80 N / m C: 0.50 N / m or more and less than 0.60 N / m D: Less than 0.50 N / m

[0192] The results are shown in Tables 1 to 3.

[0193]

[0194]

[0195] As shown in Tables 1 and 2, Examples 1 to 14 contain a pigment, water, a water-soluble organic solvent with a boiling point of 200°C or less, a water-soluble polymer A containing an acid group, and a water-soluble polymer B containing an ethylene oxide group but not an acid group. The content of the water-soluble organic solvent with a boiling point of 200°C or less is 5% to 20% by mass of the total amount of ink, and the total content of water-soluble polymers A and B is 3% to 8% by mass of the total amount of ink. Since both water-soluble polymers A and B are free in the ink without being adsorbed to the pigment, it can be seen that the ejection properties are excellent and the resulting image has excellent scratch resistance. Whether or not water-soluble polymers A and B are free in the ink can be confirmed by centrifugation. Both water-soluble polymers A and B are 99% free in the ink.

[0196] On the other hand, in Comparative Example 1, the low-boiling point solvent content was more than 20% by mass, indicating inferior scratch resistance.

[0197] Comparative Example 2 shows that it does not contain a low-boiling point solvent and has poor discharge properties.

[0198] In Comparative Example 3, the total content of water-soluble polymer A and water-soluble polymer B exceeds 8% by mass, resulting in poor discharge properties and scratch resistance.

[0199] In Comparative Example 4, the total content of water-soluble polymer A and water-soluble polymer B is less than 3% by mass, and it can be seen that the dispensability and scratch resistance are inferior.

[0200] Comparative Example 5 does not contain water-soluble polymer B, and it can be seen that it is inferior in terms of dischargeability and scratch resistance.

[0201] Comparative Example 6 does not contain a low-boiling point solvent and exhibits inferior scratch resistance.

[0202] In Example 1, the mass ratio of the water-soluble polymer A content to the water-soluble polymer B content is greater than 1, and it can be seen that it has superior scratch resistance and adhesion compared to Example 2.

[0203] In Example 3, the ClogP value of water-soluble polymer A is 0.5 or higher, indicating superior scratch resistance compared to Example 4.

[0204] In Example 1, the proportion of a water-soluble organic solvent with a vapor pressure of 200 Pa or more at 20°C in the low-boiling point solvent was 50% by mass or more, and it can be seen that it has superior scratch resistance compared to Example 5.

[0205] In Example 1, both water-soluble polymer A and water-soluble polymer B have a weight-average molecular weight of 5,000 to 35,000, and it can be seen that they exhibit superior dispensability compared to Examples 6 and 10.

[0206] In Example 1, the total content of pigment and water-soluble polymer A relative to the total content of pigment, water-soluble polymer A, and water-soluble polymer B is 60% by mass or more, and it can be seen that it has superior scratch resistance and adhesion compared to Example 2.

[0207] Furthermore, the disclosure of Japanese Patent Application No. 2024-190049, filed on 29 October 2024, is incorporated herein by reference in its entirety. In addition, all documents, patent applications, and technical standards described herein are incorporated herein by reference to the same extent as if each individual document, patent application, and technical standard were specifically and individually indicated as being incorporated by reference.

Claims

1. An ink comprising a pigment, water, a water-soluble organic solvent having a boiling point of 200°C or less, a water-soluble polymer A containing an acid group, and a water-soluble polymer B containing an ethylene oxide group but not an acid group, wherein the content of the water-soluble organic solvent having a boiling point of 200°C or less is 5% to 20% by mass of the total amount of ink, the total content of water-soluble polymer A and water-soluble polymer B is 3% to 8% by mass of the total amount of ink, and at least a portion of both water-soluble polymer A and water-soluble polymer B are free in the ink without being adsorbed onto the pigment.

2. The ink according to claim 1, wherein the mass ratio of the content of water-soluble polymer A to the content of water-soluble polymer B is greater than 1.

3. The ink according to claim 1, wherein the water-soluble polymer A has a ClogP value of 0.5 or higher.

4. The ink according to claim 1, wherein the water-soluble organic solvent having a boiling point of 200°C or lower includes a water-soluble organic solvent having a vapor pressure of 200 Pa or more at 20°C.

5. The ink according to claim 4, wherein the proportion of the water-soluble organic solvent having a vapor pressure of 200 Pa or more at 20°C to the water-soluble organic solvent having a boiling point of 200°C or less is 50% by mass or more, and the content of the water-soluble organic solvent having a boiling point exceeding 200°C is 2.5% by mass or less of the total amount of the ink.

6. The ink according to claim 1, wherein both the water-soluble polymer A and the water-soluble polymer B have a weight-average molecular weight of 5,000 to 35,000.

7. The ink according to claim 1, wherein the ratio of the total content of the pigment and the water-soluble polymer A to the total content of the pigment, the water-soluble polymer A, and the water-soluble polymer B is 60% by mass or more.

8. An image recording method comprising the step of applying an ink described in any one of claims 1 to 7 onto a substrate using an inkjet recording method to record an image.

9. A method for manufacturing a laminate, comprising the steps of: applying an ink described in any one of claims 1 to 7 to a substrate using an inkjet recording method to record an image; and placing a laminating substrate on the image and laminating it.

Images