Aqueous dispersion of acrylic resin particle containing pigment

Abstract

To provide an aqueous dispersion of acrylic resin particles containing a pigment which is excellent in base material adhesion (resistance against tape peelability) of an ink coating film of obtained printed matter when being used for printing a hydrophobic and non-absorbing resin film, and aqueous ink containing the aqueous dispersion.SOLUTION: There are provided [1] an aqueous dispersion of acrylic resin particles containing a pigment, wherein an acrylic resin A constituting the acrylic resin particles includes a structural unit derived from a (meth)acrylic acid (a-1), a structural unit derived from cycloalkyl acrylate (a-2) and a structural unit derived from alkyl (meth)acrylate (a-3) having a glass transition temperature (Tg) when being converted into a single polymer of 10°C or lower, and [2] aqueous ink containing an aqueous dispersion of acrylic resin particles containing a pigment described in [1], and a water-soluble organic solvent.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to an aqueous dispersion of pigment-containing acrylic resin particles, and an aqueous ink containing the aqueous dispersion. [Background technology]

[0002] Inkjet printing is a method of ejecting ink droplets from fine nozzles and depositing them directly on a printing substrate to obtain printed matter with characters and images. This method has become extremely popular due to its many advantages, including the ease and low cost of full color printing, the ability to use a variety of printing substrates such as plain paper, label paper, and resin film, and the fact that it does not come into contact with the substrate to be printed. In particular, from the viewpoint of the weather resistance and water resistance of printed matter, the use of pigments as colorants has become mainstream.

[0003] For example, Patent Document 1 discloses an inkjet recording ink containing a carbon black pigment dispersed using a polymer having an acid value of 50 mgKOH / g or more and 120 mgKOH / g or less and a weight average molecular weight of 20,000 or more and 120,000 or less, the polymer being polymerized with at least 50% by weight of benzyl acrylate or cyclohexyl acrylate or a mixture thereof and 15% by weight or less of (meth)acrylic acid as components of water and a polymer, for the purpose of providing an inkjet recording ink that has both high color development on plain paper and glossy paper and high gloss on glossy paper. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2008-222944 A Summary of the Invention [Problem to be solved by the invention]

[0005] Meanwhile, in the industrial printing market, such as packaging printing for food products, resin films are mainly used as printing substrates from the viewpoint of durability. A particular problem with using a resin film as a printing substrate is the substrate adhesion, particularly tape peel resistance, of the ink coating of the resulting printed matter. If the tape peel resistance of the ink coating of the printed matter is insufficient, the ink coating is likely to peel off from the resin film, impairing the aesthetic quality of the printed matter and reducing the shelf life of the contents, such as food products. Therefore, there is a demand for improving the substrate adhesion (tape peel resistance) of the ink coating of the printed matter obtained when printing on a resin film. In particular, when printing on a resin film using a water-based ink, the ink coating formed by the water-based ink needs to adhere sufficiently to the resin film. However, when the inkjet recording ink of Patent Document 1 was used for printing on a hydrophobic, non-liquid-absorbing resin film, it was found that the adhesion of the ink coating film of the obtained printed matter to the substrate (tape peel resistance) was insufficient. An object of the present invention is to provide an aqueous dispersion of pigment-containing acrylic resin particles, which, when used for printing on a hydrophobic, non-liquid-absorbing resin film, gives an ink coating film of the resulting printed matter excellent in substrate adhesion (tape peel resistance), and an aqueous ink containing the aqueous dispersion. [Means for solving the problem]

[0006] The present inventors have found that the above-mentioned problems can be solved by providing an aqueous dispersion of pigment-containing acrylic resin particles, in which the acrylic resin constituting the acrylic resin particles contains a structural unit derived from (meth)acrylic acid, a structural unit derived from a cycloalkyl acrylate, and a structural unit derived from an alkyl (meth)acrylate, the glass transition temperature (Tg) of which when made into a homopolymer is equal to or lower than a specific value. That is, the present invention provides the following [1] and [2]. [1] An aqueous dispersion of pigment-containing acrylic resin particles, The aqueous dispersion of pigment-containing acrylic resin particles is provided, in which the acrylic resin A constituting the acrylic resin particles contains a structural unit derived from (meth)acrylic acid (a-1), a structural unit derived from a cycloalkyl acrylate (a-2), and a structural unit derived from an alkyl (meth)acrylate (a-3) having a glass transition temperature (Tg) of 10°C or lower when made into a homopolymer. [2] A water-based ink comprising an aqueous dispersion of acrylic resin particles containing the pigment described in [1] above, and a water-soluble organic solvent. Effect of the Invention

[0007] According to the present invention, it is possible to provide an aqueous dispersion of pigment-containing acrylic resin particles, which, when used for printing on a hydrophobic, non-liquid-absorbing resin film, gives an ink coating film of the resulting printed matter with excellent substrate adhesion (tape peel resistance), and an aqueous ink containing the aqueous dispersion. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] [Water-based dispersion of pigment-containing acrylic resin particles] An aqueous dispersion (hereinafter also referred to as "aqueous dispersion of the present invention" or "aqueous dispersion") of acrylic resin particles containing the pigment of the present invention (hereinafter also referred to as "pigment-containing acrylic resin particles") is an aqueous dispersion of acrylic resin particles containing a pigment, in which an acrylic resin A (hereinafter also referred to as "acrylic resin A") constituting the acrylic resin particles contains a structural unit derived from (meth)acrylic acid (a-1), a structural unit derived from a cycloalkyl acrylate (a-2), and a structural unit derived from an alkyl (meth)acrylate (a-3) having a glass transition temperature (Tg) of 10°C or lower when made into a homopolymer. In the present invention, the pigment-containing acrylic resin particles are dispersed in an aqueous medium. In the present invention, the term "aqueous-based" means that water accounts for the largest proportion by mass of the liquid components. As the water in the aqueous medium, deionized water, ion-exchanged water, or distilled water is preferably used. The aqueous medium may further contain an organic solvent, such as aliphatic alcohols having 1 to 4 carbon atoms, such as methanol, ethanol, and 2-propanol, ketones having 3 to 8 carbon atoms, such as acetone and methyl ethyl ketone, and ethers, such as tetrahydrofuran, that dissolve in water. From the viewpoint of environmental friendliness, the water content in the aqueous medium is preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 90% by mass or more, and still more preferably 95% by mass or more.

[0009] In the present invention, the term "(meth)acrylic acid" refers to acrylic acid and / or methacrylic acid, and the term "alkyl (meth)acrylate" refers to alkyl acrylate and / or alkyl methacrylate. The term "non-liquid absorbing" in the context of the printing substrate of the present invention means that the amount of water absorbed by the printing substrate when it is in contact with pure water for 100 ms is 1 g / m 2 This means that: The term "hydrophobic" in the context of the printing substrate according to the present invention means that the surface free energy (wetting tension) is 45 mN / m or less. The surface free energy (wetting tension) of the printing substrate is measured using a mixture for wetting tension testing (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.) in accordance with the wetting tension testing method of JIS K6768. In the present invention, "adhesion to substrate" refers to the tape peel resistance of the ink coating film of the printed matter obtained when used for printing on a hydrophobic and non-liquid-absorbing resin film, and may be simply referred to as "adhesion to substrate".

[0010] According to the present invention, it is possible to provide an aqueous dispersion of pigment-containing acrylic resin particles, which, when used for printing on a hydrophobic and liquid-non-absorbent resin film, gives an ink coating film of the resulting printed matter excellent in substrate adhesion (tape peel resistance), and an aqueous ink containing the aqueous dispersion. The reason for this is not necessarily clear, but is thought to be as follows. The aqueous dispersion of the present invention is obtained by dispersing pigment-containing acrylic resin particles in an aqueous medium, and the acrylic resin constituting the pigment-containing acrylic resin particles contains a structural unit derived from a cycloalkyl acrylate. The cycloalkyl ester moiety of the cycloalkyl acrylate has a polarity value close to that of the polar functional group present on the surface of the resin film used as the printing substrate, which is considered to improve the wettability of the resin film when the aqueous dispersion of the present invention is used in an aqueous ink. Furthermore, hydrogen bonds are formed between the polar functional group and the cycloalkyl ester moiety, and van der Waals interactions can be efficiently expressed between the hydrophobic portion of the resin film and the cycloalkyl moiety of the cycloalkyl acrylate and the main chain of the acrylic resin containing the structural unit derived from the cycloalkyl acrylate, which is considered to improve the substrate adhesion of the ink coating film to the resin film. Furthermore, the alkyl (meth)acrylate-derived structural unit contained in the acrylic resin, which when made into a homopolymer has a glass transition temperature (Tg) of 10°C or less, contributes to increasing the conformational freedom of the cycloalkyl acrylate so that the cycloalkyl acrylate can strongly interact with the resin film, and can efficiently express a strong interaction. Furthermore, the alkyl (meth)acrylate-derived structural unit has the effect of plasticizing the acrylic resin and lowering the glass transition temperature of the acrylic resin, and also has the effect of alleviating stress when the ink coating film is peeled off from the printing substrate, and is therefore considered to be able to further improve the adhesion of the ink coating to the resin film.

[0011] <Acrylic resin particles containing pigment> The form of the pigment-containing acrylic resin particles in the aqueous dispersion of the present invention includes a form in which the acrylic resin A encapsulates the pigment, a form in which the pigment is uniformly dispersed in the acrylic resin A, a form in which the pigment is exposed from the surface of the acrylic resin A particles, a form in which the acrylic resin A is adsorbed to the pigment, and mixtures of these.

[0012] (Pigments) The pigment constituting the pigment-containing acrylic resin particles according to the present invention may be either an inorganic pigment or an organic pigment. Examples of inorganic pigments include carbon black and metal oxides, and carbon black is preferred for black inks. Examples of carbon black include furnace black, lamp black, acetylene black, and channel black. Examples of white inks include titanium dioxide, zinc oxide, silica, alumina, and metal oxides such as magnesium oxide. Examples of organic pigments include azo pigments, diazo pigments, phthalocyanine pigments, quinacridone pigments, isoindolinone pigments, dioxazine pigments, perylene pigments, perinone pigments, thioindigo pigments, anthraquinone pigments, and quinophthalone pigments. In the achromatic ink, achromatic pigments such as white, black, and gray can be used, while in the chromatic ink, chromatic pigments such as yellow, magenta, cyan, red, blue, orange, and green can be used. The above pigments can be used alone or in combination of two or more kinds.

[0013] (Acrylic resin A) The acrylic resin A constituting the pigment-containing acrylic resin particles according to the present invention contains, from the viewpoint of improving adhesion to a substrate, a structural unit derived from (meth)acrylic acid (a-1), a structural unit derived from a cycloalkyl acrylate (a-2), and a structural unit derived from an alkyl (meth)acrylate (a-3) having a glass transition temperature (Tg) of 10°C or lower when made into a homopolymer. The monomers (a-1) to (a-3) contained in each component can be used alone or in combination of two or more kinds.

[0014] [(Meth)acrylic acid (a-1)] The (meth)acrylic acid (a-1) is at least one selected from the group consisting of acrylic acid and methacrylic acid, preferably acrylic acid, from the viewpoint of improving adhesion to a substrate.

[0015] [Cycloalkyl acrylate (a-2)] From the viewpoint of improving adhesion to a substrate, the number of carbon atoms in the cycloalkyl group of the cycloalkyl acrylate (a-2) is preferably 4 or more, more preferably 5 or more, and preferably 12 or less, more preferably 8 or less, and even more preferably 7 or less. From the viewpoint of improving adhesion to the substrate, the cycloalkyl acrylate is preferably at least one selected from the group consisting of cyclopentyl acrylate, cyclohexyl acrylate, and cycloheptyl acrylate, and from the viewpoints of availability and economy, more preferably cyclohexyl acrylate.

[0016] [Alkyl (meth)acrylate (a-3)] As the alkyl(meth)acrylate (hereinafter also referred to as "alkyl(meth)acrylate (a-3)") having a glass transition temperature (Tg) of 10°C or less when made into a homopolymer, from the viewpoint of improving adhesion to a substrate, an alkyl(meth)acrylate having preferably 1 to 10 carbon atoms, more preferably 2 to 8 carbon atoms, can be mentioned. Specific examples thereof include one or more selected from the group consisting of methyl acrylate (Tg: 8°C), ethyl acrylate (Tg: -20°C), propyl acrylate (Tg: 3°C), isopropyl acrylate (Tg: -3°C), butyl acrylate (Tg: -55°C), isobutyl acrylate (Tg: -33°C), isopentyl acrylate (Tg: -45°C), hexyl acrylate (Tg: -57°C), octyl acrylate (Tg: -65°C), 2-ethylhexyl acrylate (Tg: -70°C), and benzyl acrylate (Tg: 6°C). Among these, from the viewpoint of improving adhesion to the substrate, more preferred is one or more selected from the group consisting of methyl acrylate, ethyl acrylate, butyl acrylate, isobutyl acrylate, and benzyl acrylate, and even more preferred is one or more selected from the group consisting of butyl acrylate and isobutyl acrylate. The values ​​in parentheses above indicate the glass transition temperature (Tg) when each monomer is made into a homopolymer. As the glass transition temperature (Tg) of the homopolymer of each monomer, for example, the values ​​described in Polymer Handbook Third Edition (Wiley-Interscience 1989) can be used.

[0017] The acrylic resin A may contain structural units derived from monomers other than the monomers (a-1) to (a-3) as long as the effects of the present invention are not impaired. Examples of the other monomers include ionic monomers other than the monomers (a-1) to (a-3), hydrophobic monomers having aromatic groups, and nonionic monomers.

[0018] (Content of each structural unit in acrylic resin A) The content of (meth)acrylic acid (a-1) in the raw material monomers constituting the acrylic resin A or the content of structural units derived from (meth)acrylic acid (a-1) in all structural units of the acrylic resin A is, from the viewpoint of improving adhesion to a substrate, preferably 13 mass% or more, more preferably 17 mass% or more, even more preferably 23 mass% or more, and is preferably 35 mass% or less, more preferably 33 mass% or less, even more preferably 30 mass% or less. The content of cycloalkyl acrylate (a-2) in the raw material monomers constituting the acrylic resin A, or the content of structural units derived from cycloalkyl acrylate (a-2) in all structural units of the acrylic resin A, is, from the viewpoint of improving adhesion to a substrate, preferably 25% by mass or more, more preferably 35% by mass or more, even more preferably 45% by mass or more, still more preferably 50% by mass or more, and is preferably 85% by mass or less, more preferably 75% by mass or less, even more preferably 70% by mass or less, still more preferably 65% ​​by mass or less, and still more preferably 60% by mass or less. The content of alkyl (meth)acrylate (a-3) in the raw material monomers constituting the acrylic resin A, or the content of structural units derived from alkyl (meth)acrylate (a-3) in all structural units of the acrylic resin A, is, from the viewpoint of improving adhesion to the substrate, preferably 0.5% by mass or more, more preferably 3% by mass or more, even more preferably 5% by mass or more, still more preferably 10% by mass or more, still more preferably 17% by mass or more, and is preferably 50% by mass or less, more preferably 47% by mass or less, and even more preferably 45% by mass or less.

[0019] The mass ratio of the content of alkyl (meth)acrylate (a-3) to the content of cycloalkyl acrylate (a-2) in the raw material monomers constituting the acrylic resin A, or the mass ratio of the content of structural units derived from alkyl (meth)acrylate (a-3) to the content of structural units derived from cycloalkyl acrylate (a-2) in all structural units of the acrylic resin A [alkyl (meth)acrylate (a-3) / cycloalkyl acrylate (a-2)] is preferably 0.01 or more, more preferably 0.03 or more, and even more preferably 0.05 or more, from the viewpoint of improving adhesion to the substrate, and from the same viewpoint as above, is preferably 1 or less, more preferably 0.95 or less, and even more preferably 0.90 or less.

[0020] The acrylic resin A can be produced by copolymerizing raw material monomers including the monomers (a-1) to (a-3) by a known polymerization method. From the viewpoint of improving adhesion to the substrate, the weight average molecular weight of the acrylic resin A is preferably 7,000 or more, more preferably 10,000 or more, even more preferably 15,000 or more, and is preferably 100,000 or less, more preferably 50,000 or less, even more preferably 30,000 or less. From the viewpoint of improving adhesion to a substrate, the acid value of the acrylic resin A is preferably 100 mgKOH / g or more, more preferably 140 mgKOH / g or more, even more preferably 180 mgKOH / g or more, and is preferably 260 mgKOH / g or less, more preferably 240 mgKOH / g or less, even more preferably 220 mgKOH / g or less. The weight average molecular weight and acid value of the acrylic resin A are measured by the method described in the examples.

[0021] From the viewpoint of improving adhesion to the substrate, the glass transition temperature (Tg) of the acrylic resin A is preferably -20°C or higher, more preferably -10°C or higher, even more preferably 0°C or higher, and is preferably 50°C or lower, more preferably 45°C or lower, even more preferably 40°C or lower, and still more preferably 35°C or lower. The glass transition temperature of the acrylic resin A, which is a copolymer, can be calculated from the mass ratio of each monomer constituting the acrylic resin A and the glass transition temperature of the homopolymer when each monomer is made into a homopolymer according to the following Fox equation. 1 / Tg=(W1 / Tg1)+(W2 / Tg2)+···+(W m / Tg m ) W1+W2+...W m =1 In the Fox formula, Tg is the glass transition temperature of acrylic resin A, and Tg1, Tg2, . . . , Tg m is the glass transition temperature of the homopolymer when each monomer is made into a homopolymer. The unit of temperature is K. Also, W1, W2, ..., W m represents the mass ratio of each monomer in acrylic resin A. As the glass transition temperature of a homopolymer of each monomer in the Fox formula, for example, the value described in Polymer Handbook Third Edition (Wiley-Interscience 1989) can be used.

[0022] (Neutralizer) The carboxy group of the acrylic resin A is preferably neutralized with a neutralizing agent, which increases the charge repulsive force of the carboxy group that appears after neutralization, and is believed to be able to suppress aggregation of the pigment-containing acrylic resin particles in the aqueous dispersion of the present invention, thereby improving the dispersion stability and storage stability. The neutralizing agent is preferably one or more selected from the group consisting of alkali metal hydroxides such as sodium hydroxide and potassium hydroxide, and amine compounds.

[0023] Among these, it is preferable that the carboxy group of the acrylic resin A is neutralized with an amine compound. The amine compound has the effect of plasticizing the acrylic resin A and lowering the glass transition temperature of the acrylic resin, and is considered to be able to improve the adhesion to the substrate (tape peel resistance) since it can relieve the stress when the ink coating film is peeled off from the printing substrate. Suitable examples of the amine compound include inorganic amines and organic amines. A suitable example of an inorganic amine is ammonia. Suitable examples of the organic amine include alkylamines, alkanolamines, aminoalkanediols, alkoxyamines, and heterocyclic amines. Examples of alkylamines include ethylamine (boiling point at 1 atmospheric pressure: 16.6°C), diethylamine (boiling point at 1 atmospheric pressure: 55.5°C), triethylamine (boiling point at 1 atmospheric pressure: 89.7°C), n-propylamine (boiling point at 48°C), di-n-propylamine (boiling point at 108°C), isopropylamine (boiling point at 33°C), diisopropylamine (boiling point at 84°C), n-butylamine (boiling point at 78°C), tert-butylamine (boiling point at 44.5°C), sec-butylamine (boiling point at 63°C), n-pentylamine (boiling point at 104°C), n-hexylamine (boiling point at 130°C), N,N-dimethylethylamine (boiling point at 37°C), N,N-diethylmethylamine (boiling point at 62°C), and N,N-dimethylbutylamine (boiling point at 93°C). Examples of alkanolamines include monoethanolamine (170°C), diethanolamine (217°C), triethanolamine (335°C), n-propanolamine (188°C), isopropanolamine (160°C), 2-amino-2-methyl-1-propanol (165°C), N-methylethanolamine (155°C), N-ethylethanolamine (169°C), N-butylethanolamine (199°C), N-methyldiethanolamine (1 34°C), N-ethyldiethanolamine (251°C), N,N-dimethylethanolamine (245°C), N,N-diethylethanolamine (162°C), N,N-dimethylpropanolamine (164°C), N,N-dimethylisopropanolamine (125°C), 2-(dimethylamino)-2-methyl-1-propanol (163°C), N-(2-aminoethyl)ethanolamine (125°C), and 2-(2-aminoethoxy)ethanol (223°C). Examples of aminoalkanediols include 2-amino-1,3-propanediol (same temperature: 302°C), 2-amino-2-ethyl-1,3-propanediol (same temperature: 294°C), 3-(methylamino)-1,2-propanediol (same temperature: 254°C), and 3-(dimethylamino)-1,2-propanediol (same temperature: 217°C). Examples of alkoxyamines include 3-methoxypropylamine (same: 116° C.) and 3-ethoxypropylamine (same: 132° C.). Examples of heterocyclic amines include pyrrolidine (same: 87°C), piperidine (same: 106°C), piperazine (same: 106°C), 1-(2-hydroxyethyl)piperazine (same: 246°C), and morpholine (same: 129°C).

[0024] From the viewpoint of improving the adhesion to the substrate, the boiling point of the amine compound at 1 atmospheric pressure is preferably 270° C. or lower, more preferably 260° C. or lower, even more preferably 250° C. or lower, and is preferably 40° C. or higher, more preferably 100° C. or higher, even more preferably 110° C. or higher, and still more preferably 120° C. or higher. When two or more organic amines are used, the boiling points of the organic amines are calculated as a weighted average value.

[0025] Among these, from the viewpoint of improving adhesion to the substrate, the neutralizing agent is more preferably one or more selected from the group consisting of ammonia and organic amines having a boiling point of 250° C. or less, even more preferably an organic amine having a boiling point of 250° C. or less, and even more preferably an alkanolamine having a boiling point of 250° C. or less.

[0026] From the viewpoint of improving adhesion to a substrate, the degree of neutralization of the carboxyl groups in the acrylic resin A is preferably 15 mol % or more, more preferably 20 mol % or more, even more preferably 25 mol % or more, and is preferably less than 100 mol %, more preferably 90 mol % or less, even more preferably 70 mol % or less, still more preferably 50 mol % or less, even more preferably 40 mol % or less. Here, the degree of neutralization can be calculated by the following formula (1) as the equivalent of the neutralizer used relative to the carboxyl groups of the acrylic resin A. When the equivalent of the neutralizer used is 100 mol% or less, it is synonymous with the degree of neutralization. When the equivalent of the neutralizer used exceeds 100 mol%, it means that the neutralizer is in excess relative to the carboxyl groups of the acrylic resin A, and in this case, the degree of neutralization of the acrylic resin A is considered to be 100 mol%. Equivalent amount of neutralizing agent used (mol%) = [{weight of neutralizing agent added (g) / equivalent amount of neutralizing agent} / [{acid value of acrylic resin A (mg KOH / g) × weight of vinyl polymer (g)} / (56 × 1000)]] × 100 (1)

[0027] (Production of aqueous dispersion of pigment-containing acrylic resin particles) The aqueous dispersion of the present invention can be efficiently produced by a method including a step of dispersing a pigment mixture containing a pigment, acrylic resin A, and water (hereinafter also referred to as "step 1"). Step 1 is preferably carried out by, for example, dispersing a pigment mixture containing a pigment, acrylic resin A, an organic solvent, water, and, as necessary, a neutralizing agent, a surfactant, and the like to obtain a pigment dispersion, and then removing the organic solvent from the pigment dispersion by a known method. The dispersion treatment in step 1 can be carried out by a known method using a kneading machine such as a roll mill or a kneader, a high-pressure homogenizer such as a Microfluidizer (manufactured by Microfluidics), a paint shaker, a media-type dispersing machine such as a bead mill, or the like.

[0028] (Content and properties of each component of aqueous dispersion) From the viewpoint of improving adhesion to a substrate, the solid content concentration of the aqueous dispersion of the present invention is preferably 5% by mass or more, more preferably 10% by mass or more, even more preferably 15% by mass or more, and is preferably 35% by mass or less, more preferably 30% by mass or less, even more preferably 25% by mass or less.

[0029] From the viewpoint of print density, the content of the pigment in the aqueous dispersion of the present invention is preferably 5% by mass or more, more preferably 7% by mass or more, even more preferably 10% by mass or more, and is preferably 20% by mass or less, more preferably 17% by mass or less, even more preferably 15% by mass or less.

[0030] The mass ratio of the content of the pigment to the total content of the pigment and acrylic resin A in the aqueous dispersion of the present invention [pigment / (pigment+acrylic resin A)] is, from the viewpoint of improving adhesion to a substrate, preferably 0.45 or more, more preferably 0.50 or more, even more preferably 0.55 or more, and is preferably 0.80 or less, more preferably 0.75 or less, even more preferably 0.70 or less, and still more preferably 0.65 or less.

[0031] From the viewpoint of reducing the environmental load, the water content in the aqueous dispersion of the present invention is preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, and is preferably 93% by mass or less, more preferably 87% by mass or less, even more preferably 82% by mass or less.

[0032] The average particle size of the pigment-containing acrylic resin particles in the aqueous dispersion of the present invention is, from the viewpoint of storage stability of the ink, preferably 50 nm or more, more preferably 70 nm or more, even more preferably 100 nm or more, and preferably 200 nm or less, more preferably 150 nm or less, even more preferably 130 nm or less. The average particle size of the pigment-containing acrylic resin particles in the aqueous dispersion of the present invention is measured by the method described in the Examples.

[0033] The aqueous dispersion of the present invention can be suitably used by being blended in aqueous inks for various printing applications such as inkjet printing, flexographic printing, gravure printing, etc. Among these, it is preferable to use the aqueous dispersion in an aqueous ink for inkjet printing from the viewpoints of ink jetting properties and substrate adhesion.

[0034] [Water-based ink] The water-based ink of the present invention (hereinafter also referred to as "the ink of the present invention") contains an aqueous dispersion of acrylic resin particles containing the pigment, and a water-soluble organic solvent.

[0035] <Water-soluble organic solvent> The water-soluble organic solvent is an organic solvent that can be mixed with water in any ratio. The water-soluble organic solvents can be used alone or in combination of two or more. The boiling point of the water-soluble organic solvent is preferably 90° C. or higher, more preferably 150° C. or higher, even more preferably 180° C. or higher, and preferably 260° C. or lower, more preferably 250° C. or lower, even more preferably 240° C. or lower, and even more preferably 230° C. or lower. When two or more water-soluble organic solvents are used, the boiling point value is a weighted average value weighted by the content (mass%) of each water-soluble organic solvent. Examples of the water-soluble organic solvent include polyhydric alcohols, polyhydric alcohol alkyl ethers, nitrogen-containing heterocyclic compounds, amides, amines, and sulfur-containing compounds. Among these, the water-soluble organic solvent preferably contains at least one selected from the group consisting of polyhydric alcohols and polyhydric alcohol alkyl ethers from the viewpoint of improving the adhesion to the substrate.

[0036] Examples of polyhydric alcohols include alkanediols such as ethylene glycol, propylene glycol, 1,2-pentanediol, 1,2-hexanediol, and 1,2-octanediol; polyalkylene glycols such as diethylene glycol and triethylene glycol; glycerin; and trimethylolpropane. Among these, the polyhydric alcohol is preferably one or more selected from the group consisting of propylene glycol, 1,2-hexanediol, triethylene glycol, and glycerin, and more preferably propylene glycol.

[0037] Examples of polyhydric alcohol ethers include (poly)alkylene glycol monoalkyl ethers such as monoalkylene glycol monoalkyl ethers, dialkylene glycol monoalkyl ethers, and trialkylene glycol monoalkyl ethers; and (poly)alkylene glycol dialkyl ethers such as monoalkylene glycol dialkyl ethers and dialkylene glycol dialkyl ethers. The alkylene oxide group of the polyhydric alcohol ether may be at least one selected from the group consisting of an ethylene oxide group and a propylene oxide group, with an ethylene oxide group being more preferred. The polyhydric glycol ether has at least one hydrocarbon group having 2 to 8 carbon atoms.

[0038] Examples of (poly)alkylene glycol monoalkyl ethers include ethylene glycol monoisopropyl ether (boiling point: 142°C), ethylene glycol mono-n-butyl ether (boiling point: 171°C), ethylene glycol monoisobutyl ether (boiling point: 161°C), and ethylene glycol mono-n-hexyl ether (boiling point: 208°C); diethylene glycol monoethyl ether (boiling point: 202°C), diethylene glycol monoisopropyl ether (boiling point: 207°C), diethylene glycol mono-n-butyl ether (boiling point: 231°C), and diethylene glycol monoisobutyl ether ( Preferred examples of the alkyl ethers include diethylene glycol monoalkyl ethers such as diethylene glycol mono-n-hexyl ether (boiling point: 220°C) and diethylene glycol mono-n-hexyl ether (boiling point: 259°C); triethylene glycol monoalkyl ethers such as triethylene glycol monobutyl ether (boiling point: 271°C); propylene glycol monoalkyl ethers such as propylene glycol mono-n-propyl ether (boiling point: 150°C); dipropylene glycol monoalkyl ethers; tripropylene glycol monoalkyl ethers; and ethylene glycol aryl ethers such as ethylene glycol monobenzyl ether (boiling point: 256°C). Examples of the (poly)alkylene glycol dialkyl ether include diethylene glycol dialkyl ethers such as diethylene glycol methyl ethyl ether (boiling point: 176° C.) and diethylene glycol diethyl ether (boiling point: 189° C.).

[0039] From the viewpoint of improving the adhesion to the substrate, the water-soluble organic solvent preferably contains one or more selected from diethylene glycol monoalkyl ether and diethylene glycol dialkyl ether, more preferably contains diethylene glycol monoalkyl ether, even more preferably contains one or more selected from the group consisting of diethylene glycol monoethyl ether (boiling point: 202°C), diethylene glycol monoisopropyl ether (boiling point: 207°C), diethylene glycol mono-n-butyl ether (boiling point: 231°C), diethylene glycol monoisobutyl ether (boiling point: 220°C), and diethylene glycol monohexyl ether (boiling point: 259°C), and even more preferably contains one or more selected from the group consisting of diethylene glycol monoisopropyl ether (boiling point: 207°C), diethylene glycol mono-n-butyl ether (boiling point: 231°C), and diethylene glycol monoisobutyl ether (boiling point: 220°C).

[0040] When the water-soluble organic solvent contains one or more selected from diethylene glycol monoalkyl ethers and diethylene glycol dialkyl ethers, the total content of diethylene glycol monoalkyl ethers and diethylene glycol dialkyl ethers in the water-soluble organic solvent is, from the viewpoint of improving adhesion to a substrate, preferably 3 mass % or more, more preferably 5 mass % or more, even more preferably 10 mass % or more, and is preferably 50 mass % or less, more preferably 40 mass % or less, even more preferably 30 mass % or less, and still more preferably 20 mass % or less.

[0041] When the water-soluble organic solvent contains diethylene glycol monoalkyl ether, the content of diethylene glycol monoalkyl ether in the water-soluble organic solvent is, from the viewpoint of improving adhesion to a substrate, preferably 3% by mass or more, more preferably 5% by mass or more, even more preferably 10% by mass or more, and preferably 50% by mass or less, more preferably 40% by mass or less, even more preferably 30% by mass or less, and still more preferably 20% by mass or less.

[0042] From the viewpoint of improving adhesion to a substrate, the water-soluble organic solvent preferably contains an alkanediol, and more preferably contains an alkanediol and one or more selected from diethylene glycol monoalkyl ethers and diethylene glycol dialkyl ethers. When the water-soluble organic solvent contains one or more selected from diethylene glycol monoalkyl ethers and diethylene glycol dialkyl ethers and an alkanediol, the mass ratio of the total content of diethylene glycol monoalkyl ethers and diethylene glycol dialkyl ethers to the content of alkanediol in the ink of the present invention [total content of diethylene glycol monoalkyl ethers and diethylene glycol dialkyl ethers / content of alkanediol] is, from the viewpoint of improving adhesion to the substrate, preferably 0.05 or more, more preferably 0.10 or more, even more preferably 0.15 or more, and is preferably 0.40 or less, more preferably 0.30 or less, even more preferably 0.25 or less, and still more preferably 0.20 or less.

[0043] The ink of the present invention may contain various additives, such as fixing resins, surfactants, humectants, wetting agents, wetting / penetrating agents, viscosity adjusters, defoamers, preservatives, antifungals, and rust inhibitors, as necessary. Examples of the surfactant include nonionic surfactants, anionic surfactants, and amphoteric surfactants. Among these, nonionic surfactants are preferred. Examples of nonionic surfactants include polyoxyalkylene alkyl ether surfactants, acetylene glycol surfactants, polyhydric alcohol surfactants, fatty acid alkanolamides, silicone surfactants, and fluorine-based surfactants.

[0044] The ink of the present invention can be produced by mixing an aqueous dispersion of pigment-containing acrylic resin particles, a water-soluble organic solvent, and, if necessary, water, various additives such as a surfactant, and the like.

[0045] (Content and properties of each component of water-based ink) From the viewpoint of improving adhesion to the substrate, the content of the pigment-containing acrylic resin particles in the ink of the present invention is preferably 3% by mass or more, more preferably 5% by mass or more, even more preferably 10% by mass or more, and is preferably 20% by mass or less, more preferably 17% by mass or less, even more preferably 15% by mass or less.

[0046] From the viewpoint of print density, the pigment content in the ink of the present invention is preferably 4.5% by mass or more, more preferably 5.0% by mass or more, even more preferably 5.5% by mass or more, and preferably 8.5% by mass or less, more preferably 8.0% by mass or less, even more preferably 7.5% by mass or less.

[0047] The mass ratio of the content of the pigment to the total content of the pigment and acrylic resin A in the ink of the present invention [pigment / (pigment+acrylic resin A)] is, from the viewpoint of improving adhesion to the substrate, preferably 0.45 or more, more preferably 0.50 or more, even more preferably 0.55 or more, and is preferably not more than 0.75, even more preferably 0.70 or less, and still more preferably 0.65 or less.

[0048] From the viewpoint of reducing the environmental load, the water content in the ink of the present invention is preferably 45% by mass or more, more preferably 50% by mass or more, even more preferably 55% by mass or more, still more preferably 55% by mass or more, still more preferably 60% by mass or more, and is preferably 80% by mass or less, more preferably 75% by mass or less, and even more preferably 70% by mass or less.

[0049] The content of the water-soluble organic solvent in the ink of the present invention is preferably 10% by mass or more, more preferably 15% by mass or more, even more preferably 20% by mass or more, and is preferably 40% by mass or less, more preferably 35% by mass or less, even more preferably 30% by mass or less.

[0050] When the ink of the present invention contains a surfactant, the content of the surfactant in the ink is preferably 0.3% by mass or more, more preferably 0.5% by mass or more, even more preferably 0.7% by mass or more, and preferably 3% by mass or less, more preferably 2.5% by mass or less, even more preferably 2% by mass or less.

[0051] From the viewpoint of storage stability of the ink, the average particle size of the pigment-containing acrylic resin particles in the ink of the present invention is preferably 50 nm or more, more preferably 70 nm or more, even more preferably 100 nm or more, and is preferably 200 nm or less, more preferably 150 nm or less, even more preferably 130 nm or less. The average particle size of the pigment-containing acrylic resin particles in the ink of the present invention is measured by the method described in the Examples.

[0052] The viscosity of the ink of the present invention at 32°C is preferably 2 mPa·s or more, more preferably 3 mPa·s or more, even more preferably 4 mPa·s or more, and preferably 12 mPa·s or less, more preferably 9 mPa·s or less, even more preferably 7 mPa·s or less. The viscosity of the water-based ink can be measured using an E-type viscometer. The pH of the ink of the present invention is preferably 7.0 or more, more preferably 7.2 or more, and even more preferably 7.5 or more. From the viewpoint of member resistance and skin irritation, the pH is preferably 11 or less, more preferably 10 or less, and even more preferably 9.5 or less. The pH of the water-based ink can be measured by a conventional method.

[0053] The ink of the present invention can be used as a printing ink for various printing methods such as inkjet printing, gravure printing, and flexographic printing. From the viewpoints of ink jetting properties and substrate adhesion, it is preferably used as a water-based ink for inkjet printing. When the water-based ink of the present invention is used for inkjet printing, the water-based ink can be loaded into a known inkjet printing device and ejected as ink droplets onto a printing substrate such as a resin film described below to print an image, etc. As the method for ejecting ink droplets, any of the piezo type, thermal type, and electrostatic type can be adopted.

[0054] From the viewpoint of substrate adhesion, a resin film is preferred as a printing substrate used in printing with the ink of the present invention. That is, the water-based ink of the present invention is preferably used in printing using a resin film as a printing substrate. Examples of the resin film include transparent synthetic resin films, such as polyester films such as polyethylene terephthalate films; vinyl chloride films; polyolefin films such as polypropylene films and polyethylene films; and polyamide films such as nylon films. These resin films may be stretched films such as biaxially stretched films and uniaxially stretched films, or non-stretched films. In addition, it is preferable to use these resin films that have been subjected to surface treatment such as corona discharge treatment, in order to impart polar functional groups to the resin film surface, improve the wettability of the water-based ink to the resin film, and form hydrogen bonds between the polar functional groups and the cycloalkyl ester moieties to improve adhesion to the substrate. Among these, a resin film having a surface free energy of 45 mN / m or less is preferred, with one or more selected from the group consisting of polyester film, oriented polypropylene film, and polyethylene film being more preferred, and one or more selected from the group consisting of corona discharge-treated polyethylene terephthalate (PET) film, corona discharge-treated biaxially oriented polypropylene (OPP) film, corona discharge-treated polyethylene (PE) film, etc. being even more preferred. EXAMPLES

[0055] In the following Production Examples, Examples and Comparative Examples, "parts" and "%" are "parts by mass" and "% by mass" unless otherwise specified. The methods for measuring and calculating each physical property are as follows.

[0056] (1) Measurement of weight average molecular weight of acrylic resin A The measurement was performed by gel permeation chromatography under the following conditions. GPC equipment: Tosoh Corporation "HLC-8320GPC" Columns: "TSKgel SuperAWM-H", "TSKgel SuperAW3000", and "TSKgel guardcolum Super AW-H" manufactured by Tosoh Corporation Eluent: N,N-dimethylformamide with phosphoric acid and lithium bromide dissolved at concentrations of 60mmol / L and 50mmol / L, respectively. Flow rate: 0.5mL / min Standard material: Monodisperse polystyrene kit with known molecular weight [PStQuick B (F-550, F-80, F-10, F-1, A-1000), PStQuick C (F-288, F-40, F-4, A-5000, A-500)] (manufactured by Tosoh Corporation) Measurement sample: 0.1 g of acrylic resin A was mixed with 10 mL of the eluent in a glass vial, stirred with a magnetic stirrer at 25° C. for 10 hours, and filtered with a syringe filter “DISMIC-13HP” (PTFE, 0.2 μm, Advantec Co., Ltd.) for use.

[0057] (2) Measurement of the acid value of acrylic resin A Acrylic resin A was dissolved in a titration solvent of toluene and acetone (2:1) in an automatic potentiometric titrator (Kyoto Electronics Manufacturing Co., Ltd., electric burette, model number: APB-610), and titrated with 0.1N potassium hydroxide / ethanol solution by potentiometric titration, with the inflection point on the titration curve as the end point. The acid value (mgKOH / g) was calculated from the titration amount of potassium hydroxide solution up to the end point.

[0058] (3) Calculation of the glass transition temperature of acrylic resin A The glass transition temperature of the acrylic resin A, which is a copolymer, can be calculated from the mass ratio of each monomer constituting the acrylic resin A and the glass transition temperature of the homopolymer when each monomer is made into a homopolymer according to the following Fox equation. 1 / Tg=(W1 / Tg1)+(W2 / Tg2)+···+(W m / Tg m ) W1+W2+...W m =1 In the Fox formula, Tg is the glass transition temperature of acrylic resin A, and Tg1, Tg2, . . . , Tg m is the glass transition temperature of the homopolymer when each monomer is made into a homopolymer. The unit of temperature is K. Also, W1, W2, ..., W m represents the mass ratio of each monomer in acrylic resin A. As the glass transition temperature of a homopolymer of each monomer in the Fox formula, for example, the value described in Polymer Handbook Third Edition (Wiley-Interscience 1989) can be used.

[0059] (4) Measurement of solids concentration 10.0 g of sodium sulfate, which had been kept constant in a desiccator, was weighed out into a 30 mL polypropylene container (φ=40 mm, height=30 mm), and about 1.0 g of the sample was added and mixed, then accurately weighed, and the mixture was kept at 105°C for 2 hours to remove volatile matter, and then left in the desiccator for 15 minutes, after which the mass was measured. The mass of the sample after removing the volatile matter was taken as the solid content, and divided by the mass of the sample added to obtain the solid content concentration (%).

[0060] (5) Measurement of the average particle size of pigment-containing acrylic resin particles in water-based dispersion or water-based ink Cumulant analysis was performed using a laser particle analysis system "ELS-8000" (manufactured by Otsuka Electronics Co., Ltd.), and the obtained cumulant average particle size was taken as the average particle size of the pigment-containing acrylic resin particles in the water-based dispersion or water-based ink. The measurement sample had a particle concentration of 5 × 10 -3% (solid content conversion) was used. The measurement conditions were a temperature of 25°C, an angle between the incident light and the detector of 90°, and 100 cumulative measurements. The refractive index of water (1.333) was entered as the refractive index of the dispersion solvent.

[0061] (6) Viscosity of Water-Based Dispersion and Water-Based Ink Using an E-type viscometer "TV-25" (manufactured by Toki Sangyo Co., Ltd., using a standard cone rotor 1°34'×R24, rotation speed 50 rpm), the aqueous dispersion was measured at 20°C, and the aqueous ink was measured at 32°C.

[0062] (Production of acrylic resin A) Manufacturing Example 1 As an initial charge, 0.98 parts of acrylic acid, 2.03 parts of cyclohexyl acrylate, 0.69 parts of methyl acrylate, 5.00 parts of methyl ethyl ketone (hereinafter, referred to as "MEK"), and 0.56 parts of water were charged into a reaction vessel equipped with a stirrer, a reflux condenser, and a dropping tank, and the temperature of the reaction vessel was maintained at 77°C and stirred for 10 minutes. Next, a mixture of 8.83 parts of acrylic acid, 18.34 parts of cyclohexyl acrylate, 6.17 parts of methyl acrylate, 45.03 parts of MEK, 5.00 parts of water, 0.56 parts of 4,4'-azobis(4-cyanovaleric acid) as a polymerization initiator, and 0.41 parts of 3-mercaptopropionic acid as a chain transfer agent was continuously added to the reaction vessel over 5 hours. After the addition was completed, the polymerization reaction was carried out for 1 hour, and then the polymerization reaction was terminated by cooling to room temperature to obtain a solution of acrylic resin A1' (resin solid concentration 40%). 28.60 parts of the obtained acrylic resin A1' solution was diluted with 3.68 parts of MEK so that the resin solid concentration was 35%. Next, 1.08 parts of N,N-dimethylethanolamine (hereinafter referred to as "DMAE") was added so that the degree of neutralization of the carboxyl group of the acrylic resin A1' was 30 mol%, and the mixture was stirred at 25°C. Then, 66.60 parts of water was added over 1 hour. After the addition was completed, MEK was distilled off with an evaporator to obtain an aqueous dispersion of acrylic resin A1 (DMAE neutralized) (resin solid concentration 25%). The physical properties of the acrylic resin A1 are shown in Table 1.

[0063] Production Examples 2 to 17 and Comparative Production Examples 1 to 3 In Production Example 1, the monomer composition and neutralizing agent constituting the acrylic resin A were changed to the conditions shown in Table 1, and the amount of the neutralizing agent was changed as necessary so that the neutralization degree of the acrylic resin A was 30 mol %. Except for this, the same procedure as in Production Example 1 was repeated to obtain each aqueous dispersion of the acrylic resin A (resin solid concentration: 25%). The notations in Table 1 are as follows: DMAE: N,N-dimethylethanolamine (boiling point 134°C) MDEA: N-methyldiethanolamine (boiling point 245°C) NH3: Ammonia NaOH: Sodium hydroxide

[0064] (Production of aqueous dispersion) Example 1-1 To 61.69 parts of the aqueous dispersion (resin solids concentration 25%) of acrylic resin A1 (neutralized with DMAE) obtained in Production Example 1, 2.95 parts of MEK and 12.78 parts of ion-exchanged water were added, and 22.58 parts of a cyan pigment (manufactured by DIC Corporation, product name: Fastogen Blue CA5380 15:3) was further added to obtain a pigment mixed liquid (ratio of the pigment mass to the total mass of the pigment and acrylic resin A [pigment / (pigment + acrylic resin A)]=0.59). The resulting pigment mixture was mixed for 1 hour at 7000 rpm and 20°C using a disperser blade, and then further dispersed for 10 passes at a pressure of 180 MPa using a Microfluidizer (high-pressure homogenizer, product name: M-140K, manufactured by Microfluidics) to obtain a pigment dispersion. From the obtained pigment dispersion, MEK was removed under reduced pressure at 60°C, and then some water was removed and centrifuged, after which the liquid layer was filtered through a membrane filter (manufactured by Sartorius, product name: Minisart Syringe Filter, pore size: 5 μm, material: cellulose acetate) to remove coarse particles, yielding an aqueous dispersion D1 of pigment-containing acrylic resin particles (total concentration of pigment and acrylic resin A: 22%). The average particle size of the pigment-containing acrylic resin particles in the obtained aqueous dispersion D1 and the viscosity of aqueous dispersion D1 at 20°C are shown in Table 1.

[0065] Examples 1-2 to 1-17 and Comparative Examples 1-1 to 1-3 Water-based dispersions D2 to D17 and DC1 to DC3 (each having a total concentration of 22% of pigment and acrylic resin A) of pigment-containing acrylic resin particles were obtained in the same manner as in Example 1-1, except that the type or amount of acrylic resin A in Example 1-1 was changed as shown in Table 1. The average particle size of the pigment-containing acrylic resin particles in each of the obtained water-based dispersions and the viscosity of each water-based dispersion at 20°C are shown in Table 1.

[0066] [Table 1]

[0067] (Preparation of Water-Based Ink) Example 2-1 To obtain the ink composition shown in Table 2, aqueous dispersion D1 of pigment-containing acrylic resin particles was mixed with 12 parts (pigment content 7 parts) in total of pigment and acrylic resin A, 22 parts of propylene glycol, 4 parts of diethylene glycol monoisobutyl ether, 1 part of an acetylene glycol surfactant (manufactured by Nissin Chemical Industry Co., Ltd., product name: Surfynol 440 (ethylene oxide (3.5 moles) adduct of 2,4,7,9-tetramethyl-5-decyne-4,7-diol, active content 100%)), and ion-exchanged water to a total of 100 parts, and the mixture was stirred, and then filtered through a membrane filter (product name: Minisart syringe filter, pore size: 5 μm, material: cellulose acetate) to obtain aqueous ink 1.

[0068] Examples 2-2 to 2-19 and Comparative Examples 2-1 to 2-3 Water-based inks 2 to 19 and C1 to C3 were obtained in the same manner as in Example 2-1, except that the ink composition in Example 2-1 was changed to that shown in Table 2. The average particle size and viscosity of each water-based ink are shown in Table 2.

[0069] The adhesion to substrates was evaluated by the method described below using the water-based inks 1 to 19 and C1 to C3 obtained in the above Examples and Comparative Examples. The results are shown in Table 2.

[0070] <Evaluation of adhesion to substrate> A printing evaluation device (Seiko Epson Corporation, inkjet printer, PX105, piezoelectric type) was used, and an A4-sized film heater (Kawai Electric Works, Ltd.) was fixed to the printing substrate discharge area so that the area where the ink was injected could be heated to 50°C. The printing substrate used was the resin film shown below cut to A4 size. In an environment of 25±1°C temperature and 30±5% relative humidity, the cartridge of the print evaluation device was filled with each of the water-based inks of the Examples and Comparative Examples, and a solid image of 50 mm x 50 mm was printed with 100% ink duty, and then the print was obtained by drying for 3 minutes on a film heater set to heat at 50°C. A 50 mm long, 15 mm wide tape "Nistack No. 4" (registered trademark) (manufactured by Nichiban Co., Ltd.) was attached to the printed surface of the obtained print, leaving a margin of 1 cm, and a T-type peel test was performed using a Tensilon universal material testing machine (manufactured by A & D Co., Ltd., product name: RTC-1150A) to measure the peel strength (N / 15 mm), which is an index of substrate adhesion, and the substrate adhesion was evaluated according to the following evaluation criteria. In the following evaluation criteria, A indicates excellent adhesion to the substrate, and E indicates poor adhesion to the substrate. (Printing base material) PET film: Corona discharge treated PET film (manufactured by Futamura Chemical Co., Ltd., product number: FE2001, film thickness: 20 μm) OPP film: Corona discharge treated OPP film (manufactured by Futamura Chemical Co., Ltd., product number: FOR-AQ, film thickness: 20 μm) LDPE film: Corona discharge treated LDPE film (manufactured by Sky Films Co., Ltd., product number: HR611, film thickness: 30 μm) (Evaluation Criteria) A:2.5N / 15mm or more B: 2.0N / 15mm or more, less than 2.5N / 15mm C: 1.5N / 15mm or more, less than 2.0N / 15mm D: 1.0N / 15mm or more, less than 1.5N / 15mm E: Less than 1.0N / 15mm

[0071] [Table 2]

[0072] From Table 2, it can be seen that the aqueous inks using the aqueous dispersions of the Examples have superior substrate adhesion (tape peel resistance) of the ink coating film of the resulting printed matter when printed on a hydrophobic, non-liquid-absorbing resin film compared to the aqueous inks using the aqueous dispersions of the Comparative Examples.

Claims

1. An aqueous dispersion of pigment-containing acrylic resin particles, The aqueous dispersion of pigment-containing acrylic resin particles is provided, wherein the acrylic resin A constituting the acrylic resin particles contains a structural unit derived from (meth)acrylic acid (a-1), a structural unit derived from a cycloalkyl acrylate (a-2), and a structural unit derived from an alkyl (meth)acrylate (a-3) that, when made into a homopolymer, has a glass transition temperature (Tg) of 10°C or lower.

2. 2. The aqueous dispersion of acrylic resin particles containing the pigment according to claim 1, wherein the carboxyl group of the acrylic resin A is neutralized with an amine compound.

3. 2. The aqueous dispersion of acrylic resin particles containing a pigment according to claim 1, wherein the acrylic resin A has an acid value of 100 mgKOH / g or more and 260 mgKOH / g or less.

4. 2. The aqueous dispersion of acrylic resin particles containing the pigment according to claim 1, wherein the content of structural units derived from cycloalkyl acrylate (a-2) in all structural units of the acrylic resin A is 25% by mass or more and 85% by mass or less.

5. 5. A water-based ink comprising an aqueous dispersion of acrylic resin particles containing the pigment according to claim 1 and a water-soluble organic solvent.

6. The water-based ink according to claim 5 , wherein the water-soluble organic solvent comprises an alkanediol.

7. The water-based ink according to claim 5, which is used in printing on a resin film as a printing substrate.

8. The water-based ink of claim 5 for ink-jet printing.

9. A pigment-containing acrylic resin particle, The acrylic resin particles contain a pigment, and the acrylic resin A constituting the acrylic resin particles contains a structural unit derived from (meth)acrylic acid (a-1), a structural unit derived from a cycloalkyl acrylate (a-2), and a structural unit derived from an alkyl (meth)acrylate (a-3) that has a glass transition temperature (Tg) of 10°C or lower when made into a homopolymer.

10. A method for producing acrylic resin particles containing the pigment according to claim 9, comprising a step of dispersing an acrylic resin A containing a constituent unit derived from (meth)acrylic acid (a-1), a constituent unit derived from a cycloalkyl acrylate (a-2), and a constituent unit derived from an alkyl (meth)acrylate (a-3) having a glass transition temperature (Tg) of 10°C or less when made into a homopolymer, a pigment, and a pigment mixed liquid containing water.

11. A water-based ink containing acrylic resin particles containing the pigment described in claim 9 and a water-soluble organic solvent.

12. A water-based ink as described in claim 11, used for printing using a resin film as the printing substrate.

13. The water-based ink of claim 11, for use in inkjet printing.