Coating agent and cured product

Abstract

To provide a coating agent that yields a cured product with high hardness and adhesion, as well as high transparency and environmental resistance; and also to provide a cured product of the coating agent.SOLUTION: A coating agent contains a copolymer (X), at least one particle selected from inorganic / organic pigment particles (Y), and a curing agent (Z). (X) is one selected from (i) a mixture of a copolymer (A) with (I) and without (II) and a copolymer (B) with (II) and without (I) and (ii) a copolymer (AB) with (I) and (II).SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a coating agent and a cured product thereof. [Background technology]

[0002] It has been known to disperse metal particles in a coating agent for the purpose of imparting various physical properties, such as mechanical properties, chemical resistance, a high refractive index, antistatic properties, ultraviolet and infrared blocking properties, and scratch resistance, to the cured film obtained by applying and curing the coating agent, or to use the metal particles as a pigment.

[0003] For example, Patent Document 1 describes a coating agent containing a metal particle dispersion liquid in which metal particles are dispersed by a dispersant made of a (meth)acrylic polymer having an ionic group and having a predetermined physical property. In the examples of Patent Document 1, a coating agent using a copolymer made of structural units derived from 2-hydroxyethyl methacrylate (hereinafter sometimes abbreviated as "HEMA") having only primary hydroxyl groups as the (meth)acrylic polymer is described. Patent Document 1 states that the dispersibility of metal particles can be improved by using the above dispersant. Although Patent Document 2 does not disclose a coating agent, it describes a composition used as an adhesive, which contains a (meth)acrylic copolymer containing a structural unit derived from a (meth)acrylic acid ester having a tertiary hydroxyl group. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2017 / 094394 [Patent Document 2] International Publication No. 2019 / 230407 Summary of the Invention [Problem to be solved by the invention]

[0005] Coating agents are required to have various properties depending on the application, and in addition to high hardness and adhesion, high transparency may be required. In addition, high humidity and heat resistance may be required, and in this case, it is required that the decrease in transparency is suppressed even when placed in a high-temperature and high-humidity environment. However, conventional coating agents, including the coating agent described in the above-mentioned Patent Document 1, do not fully satisfy all of these performances, and there is room for improvement. In particular, according to the study by the present inventors, it was found that when a (meth)acrylic copolymer having only a primary hydroxyl group is used as in the examples of Patent Document 1, the haze becomes large and the transparency cannot be increased.

[0006] The present invention has been made in consideration of the above-mentioned problems in the conventional art, and an object of the present invention is to provide a coating agent which can give a cured product having high hardness and adhesion, as well as excellent transparency and environmental resistance, and a cured product thereof. [Means for solving the problem]

[0007] The present inventors have found that the above-mentioned problems can be solved by having a primary hydroxyl group derived from a specific hydroxyl group-containing (meth)acrylic acid ester such as 2-hydroxyethyl methacrylate (hereinafter sometimes abbreviated as "HEMA") and a tertiary hydroxyl group derived from a specific hydroxyl group-containing (meth)acrylic acid ester such as 3-hydroxy-3-methylbutyl methacrylate (hereinafter sometimes abbreviated as "IPDMA") simultaneously present in a copolymer, and have conducted further research based on this finding, leading to the completion of the present invention.

[0008] The present invention relates to the following [1] to [7]. [1] A coating agent comprising: a copolymer (X); at least one type of particle (Y) selected from the group consisting of inorganic particles and organic pigment particles; and a curing agent (Z), The copolymer (X) is (i) a mixture of a copolymer (A) having a structural unit (1) represented by the following general formula (I) and not having a structural unit (2) represented by the following general formula (II) and a copolymer (B) having the structural unit (2) and not having the structural unit (1); and (ii) a copolymer (AB) having the structural unit (1) and the structural unit (2); At least one selected from the group consisting of Coating agent. [ka] [In general formula (I), R 1 represents an alkyl group having 1 to 3 carbon atoms, R 2 represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, R 3 represents a hydrogen atom or a methyl group, and n is an integer of 2 to 7. [ka] [In general formula (II), R 4 represents a hydrogen atom or a methyl group, and m is an integer of 2 to 7. [2] The coating agent according to the above [1], further comprising a solvent. [3] The coating agent according to the above [1] or [2], wherein the curing agent (Z) is a melamine derivative compound. [4] In the above general formula (I), R 1 , R 2 , and R 3 The coating agent according to any one of the above [1] to [3], wherein is a methyl group, and n is 2. [5] The coating agent according to any one of the above [1] to [4], wherein at least one of the copolymer (A), the copolymer (B), and the copolymer (AB) has an ionic group. [6] The coating agent according to any one of the above [1] to [5], wherein the particles (Y) are metal particles. [7] A cured product obtained by curing the coating agent according to any one of the above [1] to [6]. Effect of the Invention

[0009] According to the present invention, it is possible to provide a coating agent which gives a cured product having high hardness and adhesion, as well as excellent transparency and environmental resistance, and a cured product thereof. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, an embodiment of the present invention will be described. Any selected or combined embodiment of the items described in this specification is also included in the present invention. In this specification, preferred definitions may be selected arbitrarily, and combinations of preferred definitions may be considered more preferred. In this specification, the expression "XX to YY" means "at least XX and at most YY." In this specification, the lower limit and upper limit described in stages for the preferred numerical range (e.g., range of content, etc.) can be independently combined. For example, the description "preferably 10 to 90, more preferably 30 to 60" can be combined with the "preferable lower limit (10)" and the "more preferable upper limit (60)" to form "10 to 60."

[0011] [Coating agent] A coating agent according to an embodiment of the present invention is a coating agent comprising a copolymer (X), at least one type of particles (Y) selected from the group consisting of inorganic particles and organic pigment particles, and a curing agent (Z), wherein the copolymer (X) is (i) a mixture of a copolymer (A) having a structural unit (1) represented by the following general formula (I) and not having a structural unit (2) represented by the following general formula (II) and a copolymer (B) having the structural unit (2) and not having the structural unit (1); and (ii) at least one selected from the group consisting of a copolymer (AB) having the structural unit (1) and the structural unit (2). [ka] [In general formula (I), R1 represents an alkyl group having 1 to 3 carbon atoms, R 2 represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, R 3 represents a hydrogen atom or a methyl group, and n is an integer of 2 to 7. [ka] [In general formula (II), R 4 represents a hydrogen atom or a methyl group, and m is an integer of 2 to 7.

[0012] In the coating agent, a part of the copolymer (X) functions as a binder resin, so that good coatability is easily ensured and a good quality coating film is easily obtained. In addition, another part of the copolymer (X) functions as a dispersant, so that the particles (Y) can be well dispersed in the coating agent, and various physical properties such as surface hardness can be improved. In addition, the presence of the structural unit (1) having a tertiary hydroxyl group or a secondary hydroxyl group and the structural unit (2) having a primary hydroxyl group in the copolymer (X) is believed to moderate the reactivity of the copolymer (X) with respect to the curing agent (Z). In addition, the structural unit (1) has a tertiary hydroxyl group at a position farther from the polymer main chain than the structural unit derived from 2-hydroxy-2-methylpropyl methacrylate (hereinafter sometimes abbreviated as "HBMA"), and the structural unit (1) does not have a branched structure of the side chain contained in the structural unit derived from 4-hydroxy-4-methylpentan-2-yl methacrylate (hereinafter sometimes abbreviated as "HGMA"), so it is believed that the reactivity with respect to the curing agent (Z) is higher than the structural unit having a tertiary hydroxyl group derived from HBMA and the structural unit having a tertiary hydroxyl group derived from HGMA. From these facts, it is presumed that the generation of bubbles and the aggregation of particles (Y) are suppressed when the coating agent is cured, and as a result, a cured film excellent in transparency and environmental resistance is formed while ensuring hardness and adhesion. In this specification, a "tertiary hydroxyl group" means a "hydroxyl group bonded to a tertiary carbon atom," a "secondary hydroxyl group" means a "hydroxyl group bonded to a secondary carbon atom," and a "primary hydroxyl group" means a "hydroxyl group bonded to a primary carbon atom."

[0013] From the viewpoint of coatability, the coating agent preferably further contains a solvent, and more preferably, the copolymer (X) is dissolved in the solvent. Details of the solvent will be described later.

[0014] Each component contained in the coating agent will be described below.

[0015] <Copolymer (X)> As described above, the copolymer (X) is at least one selected from the group consisting of the following (i) and (ii): (i) A mixture of a copolymer (A) having a structural unit (1) represented by the following general formula (I) and not having a structural unit (2) represented by the following general formula (II), and a copolymer (B) having the structural unit (2) and not having the structural unit (1): (ii) Copolymer (AB) having structural unit (1) and structural unit (2) [ka] [ka]

[0016] The mixture of the copolymer (A) and the copolymer (B) may be a mixture prepared in advance before preparing the coating agent, or may be a mixture prepared by simultaneously or sequentially adding one of the copolymers (A) and (B) and the other to the coating agent during preparation of the coating agent, thereby causing both to coexist in the coating agent.

[0017] In general formula (I), R 1represents an alkyl group having 1 to 3 carbon atoms, and from the viewpoint of making it easier to prepare the coating agent and to make the reactivity with the curing agent (Z) appropriate, R 1 is preferably a methyl group or an ethyl group, and more preferably a methyl group.

[0018] In general formula (I), R 2 represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms. From the viewpoint of making it easier to prepare the coating agent and to make the reactivity with the curing agent (Z) appropriate, R 2 is preferably a methyl group or an ethyl group, and more preferably a methyl group.

[0019] In general formula (I), R 3 represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms. From the viewpoint of making it easier to prepare the coating agent and to make the reactivity with the curing agent (Z) appropriate, R 3 is preferably a methyl group.

[0020] In the general formula (I), n is an arbitrary integer of 2 to 7. From the viewpoint of making it easier to prepare the coating agent and to make the reactivity with the curing agent (Z) appropriate, n is preferably an integer of 5 or less, more preferably an integer of 3 or less, and most preferably 2.

[0021] In the general formula (I), in order to facilitate proper reactivity with the curing agent (Z), R 1 , R 2 , and R 3 It is preferred that n is a methyl group and n is 2.

[0022] In general formula (II), R 4 represents a hydrogen atom or a methyl group, and is preferably a methyl group from the viewpoint of making the reactivity with the curing agent (Z) more appropriate. In the general formula (II), m is an arbitrary integer of 2 to 7, and from the viewpoint of making the reactivity to the curing agent (Z) more appropriate, m is preferably an integer of 5 or less, more preferably an integer of 3 or less, and most preferably 2. In the general formula (II), in order to facilitate proper reactivity with the curing agent (Z), R 4 It is preferred that m is a methyl group and m is 2.

[0023] The copolymer (X) may consist only of a mixture of the copolymer (A) and the copolymer (B) (hereinafter also referred to as "copolymer mixture (X1)"), may consist only of the copolymer (AB), or may consist of a mixture of at least one of the copolymer (A) and the copolymer (B) and the copolymer (AB). When the copolymer (X) is a mixture of at least one of the copolymers (A) and (B) and the copolymer (AB), the ratio (W1 / W2) of the mass W1 of the former to the mass W2 of the latter is preferably 70 / 30 to 30 / 70, more preferably 60 / 40 to 40 / 60, and even more preferably 55 / 45 to 45 / 55, from the viewpoint of making the reactivity to the curing agent (Z) more appropriate.

[0024] Each of the copolymers (A) and (B) is preferably a copolymer of a first monomer (a) which is at least one (meth)acrylic acid ester containing a hydroxyl group, and a second monomer (b) which is different from the first monomer (a). Moreover, the copolymer (AB) is preferably a copolymer of at least two kinds of first monomers (a) and at least one kind of second monomer (b).

[0025] (Mixture of copolymers (X1)) As described above, the copolymer mixture (X1) is a mixture of the copolymer (A) having the structural unit (1) and not having the structural unit (2) and the copolymer (B) having the structural unit (2) and not having the structural unit (2). In the copolymer mixture (X1), the ratio (WA / WB) of the mass WA of the copolymer (A) to the mass WB of the copolymer (B) is preferably 70 / 30 to 30 / 70, more preferably 60 / 40 to 40 / 60, even more preferably 55 / 45 to 45 / 55, and still more preferably 55 / 45 to 50 / 50, from the viewpoint of making it easier to achieve an appropriate reactivity to the curing agent (Z).

[0026] (Copolymer (A)) The copolymer (A) is obtained by using at least one selected from the group consisting of a (meth)acrylic acid ester (a1) having a tertiary hydroxyl group (hereinafter also referred to as "monomer (a1)") and a (meth)acrylic acid ester (a2) having a secondary hydroxyl group (hereinafter also referred to as "monomer (a2)") as a first monomer (a), and copolymerizing the first monomer (a) with a second monomer (b). Note that, in producing the copolymer (A), the monomer (a3) ​​described below is not used. From the viewpoint of ease of production and making it easier to achieve appropriate reactivity with the curing agent (Z), it is preferred that the copolymer (A) is produced using the monomer (a1) as the first monomer (a) and thus contains a structural unit derived from the monomer (a1) as the structural unit (1).

[0027] ((Meth)acrylic acid ester having a tertiary hydroxyl group (monomer (a1))) The monomer (a1) may be a compound represented by the following general formula (I').

[0028] [ka]

[0029] In general formula (I'), R 1 , R 2 , R 3 and n are as defined in general formula (I) above.

[0030] Specific examples of the monomer (a1) include 3-hydroxy-3-methylbutyl methacrylate, 3-hydroxy-3-methylbutyl acrylate, etc. From the viewpoint of facilitating moderate relaxation of the reactivity to the curing agent (Z), 3-hydroxy-3-methylbutyl methacrylate is preferred. These may be used alone or in combination of two or more.

[0031] ((Meth)acrylic acid ester having a secondary hydroxyl group (monomer (a2))) The monomer (a2) may be a compound represented by the following general formula (I″). [ka]

[0032] In the general formula (I''), R 1 , R 3 and n are as defined in general formula (I) above.

[0033] Specific examples of the monomer (a2) include 3-hydroxybutyl methacrylate and 3-hydroxybutyl acrylate. These may be used alone or in combination of two or more.

[0034] (First monomer other than monomers (a1) and (a2)) The copolymer (A) may contain, as the first monomer (a), a (meth)acrylic acid ester containing a hydroxyl group other than the monomer (a1) and the monomer (a2). Examples of the first monomer other than monomer (a1) and monomer (a2) include 2-hydroxy-2-methylpropyl methacrylate (abbreviation "HBMA"), 4-hydroxy-4-methylpentan-2-yl methacrylate (abbreviation "HGMA"), 3-hydroxy-1,3-dimethylbutyl (meth)acrylate, ethylene glycol mono(2-hydroxyisobutyrate) mono(meth)acrylate, pinacol mono(meth)acrylate, 3-hydroxyphenyl (meth)acrylate, 3-hydroxy-1-adamantyl (meth)acrylate, 3-chloro-2-hydroxypropyl (meth)acrylate, and 2-hydroxypropyl (meth)acrylate.

[0035] (Amount of structural unit (1) in copolymer (A)) The amount of structural unit (1) in copolymer (A) (in other words, the total amount of structural units derived from monomer (a1) and structural units derived from monomer (a2)) is preferably 20% by mass or more, more preferably 30% by mass or more, even more preferably 40% by mass or more, and preferably 90% by mass or less, more preferably 80% by mass or less, and even more preferably 70% by mass or less. When the amount of structural unit (1) in copolymer (A) is within the above range, it is possible to more effectively prevent a decrease in adhesive strength after contact with water. From the viewpoint of making it easier to achieve a suitable reactivity with the curing agent (Z), the amount of the structural unit derived from the monomer (a1) in the structural unit (1) is preferably 50% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, still more preferably 90% by mass or more, and may be 100% by mass.

[0036] From the viewpoint of easily achieving the effects of the present invention, the structural units derived from the first monomers other than monomer (a1) and monomer (a2) are preferably 5 mass% or less, more preferably 3 mass% or less, even more preferably 1 mass% or less, and particularly preferably 0 mass%, relative to the total structural units derived from all the first monomers.

[0037] (Copolymer (B)) The copolymer (B) is obtained by using at least one kind of (meth)acrylic acid ester (a3) ​​having a primary hydroxyl group (hereinafter also referred to as "monomer (a3)") as a first monomer (a) and copolymerizing this monomer (a3) ​​with a second monomer (b). Note that, in producing the copolymer (B), the above-mentioned monomer (a1) and monomer (a2) are not used.

[0038] ((Meth)acrylic acid ester (a3) ​​having a primary hydroxyl group) The monomer (a3) ​​may be a compound represented by the following general formula (II'). [ka]

[0039] In general formula (II'), R 4 and m is as defined in general formula (II) above.

[0040] Specific examples of the monomer (a3) ​​include 2-hydroxyethyl (meth)acrylate, polyalkylene oxide mono(meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, etc. From the viewpoint of easily ensuring the necessary reactivity with the curing agent (Z), 2-hydroxyethyl methacrylate is preferred. These may be used alone or in combination of two or more.

[0041] (Copolymer (AB)) As described above, the copolymer (AB) is a copolymer having the structural unit (1) and the structural unit (2). The structural unit (1) constituting the copolymer (AB) is the same as that described for the copolymer (A), and the structural unit (1) constituting the copolymer (AB) is the same as that described for the copolymer (A). The copolymer (AB) is obtained by using at least one selected from the group consisting of the above-mentioned monomer (a1) and monomer (a2), and the above-mentioned monomer (a3) ​​as a first monomer (a), and copolymerizing the first monomer (a) with the above-mentioned second monomer (b). In the copolymer (AB), the structural unit (1) and the structural unit (2) may be arranged alternately, repeatedly in a block form, or randomly.

[0042] In the copolymer (AB), the ratio (M1 / M2) of the molar amount M1 of the structural unit (1) to the molar amount M2 of the structural unit (2) is preferably 70 / 30 to 30 / 70, more preferably 65 / 35 to 40 / 60, and even more preferably 60 / 40 to 50 / 50, from the viewpoint of making it easier to achieve an appropriate reactivity to the curing agent (Z).

[0043] (Second Monomer (b)) The second monomer (b) used to obtain the copolymers (A), (B), and (AB) is a monomer copolymerizable with the first monomer (a) and is used for the purposes of making it easier to ensure a predetermined hardness and adhesion in the cured product of the coating agent and for the purposes of introducing an ionic group. Examples of the second monomer (b) include (meth)acrylic ester compounds not containing a hydroxyl group, aromatic ethylenically unsaturated monomers, ionic group-containing monomers, itaconic acid esters such as dimethyl itaconate, maleic acid esters such as dimethyl maleate, fumaric acid esters such as dimethyl fumarate, acrylonitrile, methacrylonitrile, vinyl acetate, acrylamide, etc. The ionic group-containing monomers will be described later.

[0044] Examples of the (meth)acrylic ester compound not containing a hydroxyl group include methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and methoxypolyethylene glycol mono(meth)acrylate, etc. These may be used alone or in combination of two or more.

[0045] Examples of aromatic ethylenically unsaturated monomers include styrene, α-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, and p-tert-butylstyrene. By using an aromatic ethylenically unsaturated monomer, the glass transition point of the (meth)acrylic polymer can be adjusted to a desired range, and when a copolymer (X) is blended as a binder resin in a metal particle dispersion liquid described below, compatibility with the copolymer (X) can be improved. These monomers may be used alone or in combination of two or more.

[0046] (Ionic groups in copolymers (A), (B), and (AB)) Each of the copolymer (A), the copolymer (B), and the copolymer (AB) preferably has an ionic group from the viewpoint of facilitating adsorption of the particles (Y). The ionic group is not particularly limited, and examples thereof include known ionic groups. Specific examples of the ionic group include anionic groups such as a carboxyl group and a phosphate group, and cationic groups such as a tertiary amino group and a quaternary ammonium group.

[0047] The tertiary amino group is not particularly limited, and examples thereof include N,N-dialkylamino such as N,N-dimethylamino, N,N-diethylamino, N,N-dipropylamino, N,N-diisopropylamino, N,N-dibutylamino, N,N-di-isobutylamino, N,N-di-s-butylamino, and N,N-di-t-butylamino.

[0048] Furthermore, examples of the quaternary ammonium group include those obtained by reacting the above tertiary amino group with a quaternizing agent such as epihalohydrin, benzyl halide, or alkyl halide.

[0049] These ionic groups may be used alone or in combination of two or more kinds. As the ionic group, preferably, an anionic group is used, and more preferably, a carboxyl group is used. The average content of the ionic groups is appropriately set depending on the purpose and application.

[0050] In addition, when an anionic group is used as the ionic group, at least a part of the anionic group may be neutralized with a neutralizing agent (described later). If at least a part of the anionic group is neutralized with a neutralizing agent (described later), a salt of the anionic group is formed, so that the dispersibility in an aqueous dispersion medium can be improved.

[0051] At least one of the above-mentioned first monomer (a) and second monomer (b), preferably at least one of the second monomer (b), is a monomer having the above-mentioned ionic group (ionic group-containing monomer), and this ionic group-containing monomer is used to prepare a copolymer, whereby an ionic group can be introduced into the copolymer (A), the copolymer (B), and the copolymer (AB). In addition, when the first monomer (a) is an ionic group-containing monomer, the monomer is a hydroxyl group-containing (meth)acrylic acid ester having a structure different from the above-mentioned monomers (a1), (a2), and (a3), and is, for example, a half-esterification product of a hydroxyl group-containing (meth)acrylate and an acid anhydride.

[0052] Examples of the ionic group-containing monomer include anionic group-containing monomers such as carboxyl group-containing monomers and phosphate group-containing monomers, and cationic group-containing monomers such as tertiary amino group-containing monomers and quaternary ammonium group-containing monomers.

[0053] Examples of the carboxyl group-containing monomer include α,β-unsaturated carboxylic acids such as (meth)acrylic acid, itaconic acid, maleic acid, and fumaric acid, or salts thereof, and preferably, α,β-unsaturated carboxylic acids, and more preferably, (meth)acrylic acid.

[0054] Examples of the phosphate group-containing monomer include phosphate group-containing (meth)acrylates such as acid phosphooxyethyl (meth)acrylate and mono(2-hydroxyethyl (meth)acrylate) phosphate, and preferably mono(2-hydroxyethyl (meth)acrylate) phosphate.

[0055] Examples of the tertiary amino group-containing monomer include N,N-dialkylaminoalkyl (meth)acrylates such as N,N-dimethylaminoethyl (meth)acrylate, N,N-diethylaminoethyl (meth)acrylate, N,N-dimethylaminopropyl (meth)acrylate, N,N-di-t-butylaminoethyl (meth)acrylate, and N,N-dimethylaminobutyl (meth)acrylate; and N,N-dialkylaminoalkyl (meth)acrylamides such as N,N-dimethylaminoethyl (meth)acrylamide, N,N-diethylaminoethyl (meth)acrylamide, and N,N-dimethylaminopropyl (meth)acrylamide. Of these, N,N-dialkylaminoalkyl (meth)acrylates are preferred, and N,N-dimethylaminoethyl (meth)acrylate is more preferred.

[0056] The quaternary ammonium group-containing monomer is, for example, a tertiary amino group-containing monomer that has been reacted with a quaternizing agent (e.g., epihalohydrin, benzyl halide, alkyl halide, etc.), and specifically, for example, (meth)acryloyloxyalkyltrialkylammonium salts such as 2-(methacryloyloxy)ethyltrimethylammonium chloride, 2-(methacryloyloxy)ethyltrimethylammonium bromide, and 2-(methacryloyloxy)ethyltrimethylammonium dimethylphosphate, for example, methacryloylaminopropyltrimethylammonium chloride, ammonium bromide, (meth)acryloylaminoalkyl trialkyl ammonium salts such as methacryloylaminopropyl trimethyl ammonium bromide, tetraalkyl (meth)acrylates such as tetrabutyl ammonium (meth)acrylate, trialkyl benzyl ammonium (meth)acrylates such as trimethyl benzyl ammonium (meth)acrylate, etc., preferably, (meth)acryloyloxy alkyl trialkyl ammonium salts are used, and more preferably, 2-(methacryloyloxy) ethyl trimethyl ammonium chloride is used.

[0057] These ionic group-containing monomers can be used alone or in combination of two or more kinds. As the ionic group-containing monomer, preferably, an anionic group-containing monomer is used, and more preferably, a carboxyl group-containing monomer is used.

[0058] The amount of structural units derived from the second monomer (b) in the copolymers (A), (B) and (AB) is preferably from 50 to 95 mass%, more preferably from 55 to 90 mass%, and even more preferably from 60 to 88 mass%.

[0059] <Method for producing copolymers (A), (B), and (AB)> The method for producing the copolymers (A), (B), and (AB) is not particularly limited, and for example, they can be polymerized by radical polymerization, ionic polymerization, photopolymerization, etc., according to a method such as a solution polymerization method, a solution dispersion polymerization method, a bulk polymerization method, etc. Among these, from the viewpoint of simple polymerization, it is preferable to polymerize by a solution radical polymerization method.

[0060] Examples of the solvent used in the solution radical polymerization method include alcohol-based solvents such as methanol, ethanol, n-propanol, butanol, and isopropanol; hydrocarbon-based solvents such as toluene, xylene, cyclohexane, n-hexane, and octane; ester-based solvents such as methyl acetate, butyl acetate, amyl acetate, ethyl ethoxypropionate, 2-ethoxyethyl acetate, and methyl 2-hydroxyisobutyrate; ketone-based solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, methyl amyl ketone, and cyclohexanone; ether-based solvents such as dibutyl ether, 2-ethoxyethyl ether, 1,2-diethoxyethane, 1,2-dimethoxyethane, dimethoxymethane, and tetrahydrofuran; etc. These solvents may be used alone or in combination of two or more. Among these, alcohol-based solvents, ester-based solvents, ketone-based solvents, and ether-based solvents are preferred, and alcohol-based solvents are more preferred, since the coating agent according to the embodiment of the present invention can be prepared more easily and the manufacturing cost of the coating agent can be reduced by using the same medium as the particle dispersion liquid described above. After the polymerization reaction is completed, a hydrophilic solvent such as water may be additionally added as a diluting solvent.

[0061] The polymerization initiator used in the polymerization is not particularly limited and may be appropriately selected depending on the purpose and application. Specific examples of the polymerization initiator include radical polymerization initiators. Examples of the radical polymerization initiator include azo compounds, peroxide compounds, sulfides, sulfines, sulfinic acids, diazo compounds, and redox compounds, and preferably, azo compounds and peroxide compounds.

[0062] Examples of azo compounds include azobisisobutyronitrile, azobisdimethylvaleronitrile, azobiscyclohexanenitrile, 1,1'-azobis(1-acetoxy-1-phenylethane), dimethyl 2,2'-azobisisobutyrate, and 4,4'-azobis-4-cyanovaleric acid.

[0063] Examples of peroxide compounds include benzoyl peroxide, lauroyl peroxide, acetyl peroxide, capryl peroxide, 2,4-dichlorobenzoyl peroxide, isobutyl peroxide, acetylcyclohexylsulfonyl peroxide, t-butyl peroxybiparate, t-butylperoxy-2-ethylhexanoate, 1,1-di-t-butylperoxycyclohexane, 1,1-di-t-butylperoxy-3,3,5-trimethylcyclohexane, 1,1-di-t-hexylperoxy-3,3,5-trimethylcyclohexane, isopropyl peroxydicarbonate, isobutyl peroxydicarbonate, s-butyl peroxydicarbonate, n-butyl peroxydicarbonate, 2-ethylhexyl peroxydicarbonate, and bis(4-t-butylcyclohexyl)peroxy. dicarbonate, t-amylperoxy-2-ethylhexanoate, 1,1,3,3-tetramethylbutylperoxy-ethylhexanoate, 1,1,2-trimethylpropylperoxy-2-ethylhexanoate, t-butylperoxyisopropyl monocarbonate, t-amylperoxyisopropyl monocarbonate, t-butylperoxy-2-ethylhexyl carbonate, t-butylperoxyallyl carbonate, t-butylperoxyisopropyl carbonate, 1,1,3,3-tetramethylbutylperoxyisopropyl monocarbonate, 1,1,2-trimethylpropylperoxyisopropyl monocarbonate, 1,1,3,3-tetramethylbutylperoxyisononaate, 1,1,2-trimethylpropylperoxy-isononaate, and t-butylperoxybenzoate.

[0064] These polymerization initiators can be used alone or in combination of two or more kinds. The amount of the polymerization initiator used varies depending on the raw material monomer, solvent, and polymerization initiator, but is preferably 0.5 to 10 parts by mass, more preferably 1 to 9 parts by mass, and even more preferably 2 to 8 parts by mass, per 100 parts by mass of the raw material monomer. The polymerization temperature and polymerization time are not particularly limited, but it is preferable to carry out the reaction at about 30 to 100° C. for 1 to 10 hours.

[0065] When an anionic group-containing monomer is used as the ionic group-containing monomer, it is preferable to add a neutralizing agent after the above polymerization to neutralize at least a portion of the anionic groups and form a salt of the anionic groups.

[0066] The neutralizing agent may be a known basic compound, and specific examples thereof include amine compounds (monoamines such as ammonia, triethylamine, and diethylamine, and alkanolamines such as 2-amino-2-methyl-1-propanol, N,N-dimethylaminoethanol, N,N-diethylaminoethanol, 2-dimethylamino-2-methyl-1-propanol, monoisopropanolamine, diisopropanolamine, triisopropanolamine, monoethanolamine, diethanolamine, triethanolamine, N-ethyldiethanolamine, and N-methyldiethanolamine), hydroxides (sodium hydroxide, potassium hydroxide, etc.), and morpholine. These neutralizing agents can be used alone or in combination of two or more kinds.

[0067] When at least a portion of the anionic group is neutralized with a neutralizing agent, a salt of the anionic group is formed, and therefore dispersibility in the solvent serving as the dispersion medium can be improved. From the viewpoint of increasing the dispersibility of the particles (Y), the acid value of the copolymers (A), (B), and (AB) after the addition of the neutralizing agent is preferably 80 to 200 mgKOH / g, more preferably 90 to 170 mgKOH / g, and still more preferably 100 to 150 mgKOH / g. The acid value is measured in accordance with the titration method described in JIS-K-5601-2-1:1999, and more specifically, by the method described in the Examples.

[0068] This results in a dispersion of the copolymer (A), the copolymer (B), or the copolymer (AB). If necessary, the above-mentioned solvent can be added or removed to adjust the concentration of the dispersion of the copolymer (A), the copolymer (B), or the copolymer (AB).

[0069] <Weight average molecular weight of copolymers (A), (B), and (AB)> The weight average molecular weight of each of the copolymers (A), (B) and (AB) is preferably from 4,000 to 100,000, more preferably from 5,000 to 50,000, further preferably from 6,000 to 30,000, and even further preferably from 7,000 to 15,000.

[0070] <Glass transition temperatures of copolymers (A), (B), and (AB)> The glass transition temperature of the copolymers (A), (B) and (AB) is preferably from -20 to +50°C, more preferably from -10 to +45°C, further preferably from 0 to 40°C, and even further preferably from 10 to 40°C. When the glass transition temperatures of the (meth)acrylic copolymers (A), (B), and (AB) are within the above ranges, the adhesiveness under normal conditions is improved, and the adhesive strength after contact with water is also improved. Furthermore, the re-adhesion performance is also improved.

[0071] <Amount of copolymer (X) in the coating agent> The amount of copolymer (X) in the coating agent according to the embodiment of the present invention (when a plurality of types of copolymers (A), (B), and (AB) are contained, the total mass of them) is preferably 0.5 to 20 mass%, more preferably 1 to 15 mass%, and further preferably 1.5 to 10 mass%. When the amount of copolymer (X) is within the above range, the coating agent can be prepared more simply and the effects of the present invention can be more easily obtained.

[0072] <Particle (Y)> The particles (Y) are at least one type of particles selected from the group consisting of inorganic particles and organic pigment particles. The inorganic particles include metal particles, as well as particles of glass, talc, clay, mica, carbon black, white carbon, and the like. Examples of the organic pigment particles include phthalocyanine pigment particles and azo pigment particles.

[0073] The particles (Y) are preferably metal particles from the viewpoint of easily improving transparency, design properties, and coating strength. The metal particles are not particularly limited, and examples thereof include fine particles of metal oxides such as aluminum oxide, titanium oxide, zinc oxide, zirconium oxide, tin oxide, yttrium oxide, bismuth oxide, antimony oxide, cerium oxide, and indium oxide, and fine particles of heterogeneous element-doped metal oxides obtained by doping the metal oxides with heterogeneous elements such as gallium, antimony, tin, fluorine, phosphorus, and aluminum. The crystal structure of these metal oxides is not particularly limited, and may be, for example, any of a cubic system, a tetragonal system, an orthorhombic system, a monoclinic system, a triclinic system, a hexagonal system, and a trigonal system.

[0074] As the gold fine particles, preferably, aluminum oxide, titanium oxide, zinc oxide, zirconium oxide, gallium-doped zinc oxide, and antimony-doped tin oxide are used, and more preferably, aluminum oxide is used. Furthermore, the metal particles may be surface-treated by a known method, if necessary. These metal particles can be used alone or in combination of two or more kinds.

[0075] The shape of the metal particles is not particularly limited, and examples thereof include lump, spherical, hollow, porous, rod-like, plate-like, fibrous, irregular shapes, and mixtures thereof. The particle size of the metal particles is measured as the average primary particle size of the metal fine particles themselves, and is, for example, 200 nm or less, preferably 90 nm or less, and usually 1 nm or more, preferably 3 nm or more. When the average primary particle size of the metal particles is within the above range, the fine metal particles are easily available, and the storage stability of the metal particle dispersion and the transparency of the cured film can be improved.

[0076] When preparing the coating agent, it is preferable that the particles (Y) are dispersed in advance in a solvent together with a dispersant to form a particle dispersion. The details of the particle dispersion will be described later. The average particle size of the particles (Y) in the particle dispersion is, for example, 300 nm or less, preferably 150 nm or less, and usually 20 nm or more, preferably 30 nm or more.

[0077] The average particle size of the particles (Y) in the particle dispersion is measured by dynamic light scattering, specifically, by the method described in the Examples. The average primary particle size of the particles (Y) used in preparing the coating agent is calculated by a method of estimation from the specific surface area measured by the BET method. When using a commercially available product as the particles (Y), the catalog value may be used.

[0078] The content of the particles (Y) in the coating agent is preferably 1 to 30% by mass, more preferably 2 to 20% by mass, and even more preferably 3 to 10% by mass, from the viewpoint of easily ensuring transparency and desired physical properties.

[0079] <Hardening agent (Z)> The coating agent of this embodiment contains a curing agent (Z). Any curing agent (Z) can be used as long as it cures the coating film when the coating film of the coating agent is heated, for example by reacting with a resin. In other words, when the coating agent contains a curing agent (Z), the coating agent is usually thermosetting.

[0080] As the curing agent (Z), any agent known in the field of coating agents can be used appropriately. An appropriate curing agent (Z) can be selected taking into consideration the functional groups of the resin. An example of a preferred curing agent (Z) is a melamine derivative compound such as a melamine resin, etc. As the melamine derivative compound, those known in the field of coating agents can be used without particular limitation. Specifically, examples of the resin include those containing structural units derived from a compound having a hydroxymethyl group and / or an alkoxymethyl group, represented by the following general formula (M).

[0081] [ka]

[0082] In general formula (M), R 11 ~R 16 each independently represents a hydrogen atom, a hydroxymethyl group, or an alkoxymethyl group. However, usually, at least one of R1 to R6 is a hydroxymethyl group or an alkoxymethyl group, and preferably two or more of R1 to R6 are hydroxymethyl groups or alkoxymethyl groups. All of R1 to R6 may be hydroxymethyl groups or alkoxymethyl groups. Examples of the alkoxymethyl group for R1 to R6 include a methoxymethyl group, an ethoxymethyl group, an n-butoxymethyl group, and an isobutoxymethyl group.

[0083] Commercially available melamine resins include, for example, Cymel 300, Cymel 301, Cymel 303LF, Cymel 350, Cymel 370N, Cymel 771, Cymel 325, Cymel 327, Cymel 703, Cymel 712, Cymel 701, Cymel 266, Cymel 267, Cymel 285, Cymel 232, Cymel 235, Cymel 236, Cymel 238, Cymel 272, Cymel 212, Cymel 253, and Sa Imel 254, Cymel 202, Cymel 207, Mycoat 506 (all manufactured by Allnex Japan Co., Ltd.), Nikalac MW-30M, Nikalac MW-30, Nikalac MW-30HM, Nikalac MW-390, Nikalac MW-100LM, Nikalac MX-750LM, Nikalac MW-22, Nikalac MS-21, Nikalac MS-11, Nikalac MW-24X, Nikalac MS-001, Nikalac MX -002, Nikalac MX-730, Nikalac MX-750, Nikalac MX-708, Nikalac MX-706, Nikalac MX-042, Nikalac MX-035, Nikalac MX-45, Nikalac MX-43, Nikalac MX-417, Nikalac MX-410 (all manufactured by Sanwa Chemical Co., Ltd.), U-Ban 20SB, U-Ban 20SE60, U-Ban 21R, U-Ban 22R, U-Ban 122, U-Ban 125, Examples of the copolymer include U-ban 220, U-ban 225, U-ban 228, and U-ban 2020 (all manufactured by Mitsui Chemicals, Inc.), Amidea J-820-60, Amidea L-109-65, Amidea L-117-60, Amidea L-127-60, Amidea 13-548, Amidea G-821-60, Amidea L-110-60, Amidea L-125-60, and Amidea L-166-60B (all manufactured by DIC Corporation).

[0084] Another example of a preferred curing agent (Z) is an epoxy compound. The epoxy compound preferably has two or more epoxy groups in one molecule. Specific examples of the epoxy compound include known epoxy resins, such as cresol novolac epoxy resins, phenol novolac epoxy resins, biphenyl epoxy resins, bisphenol A epoxy resins, bisphenol F epoxy resins, naphthalene epoxy resins, dicyclopentadiene epoxy resins, linear aliphatic epoxy resins, alicyclic epoxy resins, heterocyclic epoxy resins, and spiro ring-containing epoxy resins.

[0085] The curing agent (Z) may also be an isocyanate compound (including a blocked isocyanate compound). The isocyanate compound has good curing properties, particularly when the resin has a hydroxyl group. In terms of storage stability, a blocked isocyanate compound is more preferred. The isocyanate compound is preferably a polyfunctional isocyanate. The polyfunctional isocyanate is preferably difunctional to hexafunctional (that is, having 2 to 6 reactive isocyanate groups per molecule), more preferably difunctional to tetrafunctional.

[0086] The coating agent of the present embodiment may contain only one type of curing agent (Z), or may contain two or more types. For example, by using a melamine resin and an epoxy compound in combination, the basic physical properties of the coating film can be further improved. The content of the curing agent (Z) in the coating agent is preferably 3 to 40 mass%, more preferably 5 to 30 mass%, and even more preferably 5 to 20 mass%, based on the total non-volatile components of the coating agent (100 mass%).

[0087] <Solvent> Examples of the solvent that may be contained in the coating agent include alcohol-based solvents such as methanol, ethanol, n-propanol, butanol, and isopropanol; hydrocarbon-based solvents such as toluene, xylene, cyclohexane, n-hexane, and octane; ester-based solvents such as methyl acetate, butyl acetate, amyl acetate, ethyl ethoxypropionate, 2-ethoxyethyl acetate, and methyl 2-hydroxyisobutyrate; ketone-based solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, methyl amyl ketone, and cyclohexanone; ether-based solvents such as dibutyl ether, 2-ethoxyethyl ether, 1,2-diethoxyethane, 1,2-dimethoxyethane, dimethoxymethane, and tetrahydrofuran; and water. These solvents may be used alone or in combination of two or more. Among these, alcohol-based solvents, ester-based solvents, ketone-based solvents, ether-based solvents, and water are preferred, and alcohol-based solvents and water are more preferred, because the coating agent can be prepared more easily. The same type of solvent as that used in producing the copolymer (A), (B) or (AB) may be used as the solvent in preparing the particle dispersion.

[0088] (Amount of solvent in coating agent) The amount of the solvent in the coating agent is preferably 10 to 95% by mass, more preferably 20 to 92% by mass, and even more preferably 30 to 90% by mass. When the amount of the solvent in the coating agent is within the above range, the viscosity can be easily adjusted and the coating agent can be easily handled.

[0089] <Optional ingredients>

[0090] Examples of tackifier resins include rosin-based resins such as rosin resin, rosin phenol resin, and ester compounds thereof; terpene-based resins such as terpene-based resin, terpene phenol-based resin, and aromatic modified terpene-based resin; and the like.

[0091] When the coating agent contains an optional component, the content of the optional component is preferably 10 parts by mass or less, more preferably 8 parts by mass or less, and even more preferably 5 parts by mass or less, based on 100 parts by mass of the copolymer (X).

[0092] <Method of manufacturing coating agent> The coating agent can be produced by appropriately mixing the copolymer (X), the particles (Y), and the curing agent (Z), as well as a solvent and optional components, if necessary. In producing the coating agent, as described above, it is preferable to prepare a particle dispersion by dispersing the particles (Y) in a solvent in advance, and then mix the particle dispersion with other components. By using the particle dispersion, it becomes easier to increase the dispersibility of the particles (Y) in the coating agent. It is preferable to use a dispersant when preparing the particle dispersion. It is more preferable to use any one of the above-mentioned copolymers (A), (B), and (AB) as the dispersant. The above-mentioned copolymer mixture (X1) may be obtained by including one of the copolymers (A) and (B) as a dispersant in the particle dispersion, and mixing the other of the copolymers (A) and (B) as a binder component with the particle dispersion together with the curing agent (Z) and other optional components.

[0093] [Cured product] The cured product according to the embodiment of the present invention is obtained by curing the above-mentioned coating agent. If the coating agent of the present embodiment contains a melamine derivative compound as the curing agent (Z), it can be crosslinked and cured as described below to obtain a cured film. Also, if the coating agent contains a binder resin, it can be dried and cured as described below to obtain a cured film with various excellent physical properties. As a method for obtaining a cured film from the above-mentioned coating agent, for example, when the coating agent contains the above-mentioned melamine derivative compound as the curing agent (Z), a method can be mentioned in which the coating agent is applied to a substrate by a known method, and then the coating film is heat-cured (crosslinked and cured).

[0094] The substrate is not particularly limited, and examples thereof include plastics such as polycarbonate, polymethyl methacrylate, polystyrene, polyester (such as polyethylene terephthalate), polyolefin, epoxy resin, melamine resin, triacetyl cellulose resin, ABS resin, AS resin, and norbornene resin, as well as metal, wood, paper, glass, and slate. The coating method is not particularly limited, and examples of the coating method that can be used include coating using equipment commonly used for coating, such as a roll coater, a bar coater, a doctor blade, a Mayer bar, and an air knife, and known coating methods such as screen printing, offset printing, flexographic printing, brush coating, spray coating, gravure coating, and reverse gravure coating.

[0095] The curing conditions are such that the heating temperature is, for example, 100° C. or more, preferably 110° C. or more, and for example, 200° C. or less, preferably 180° C. or less, and the heating time is, for example, 1 minute or more, preferably 3 minutes or more, and for example, 60 minutes or less, preferably 30 minutes or less. The coating film may be cured in one stage or in multiple stages. When the coating film is cured in multiple stages, the curing conditions in each stage may be the same or different. By such heating, the coating agent containing the melamine derivative compound crosslinks to form a cured film with a three-dimensional structure.

[0096] Furthermore, for example, when a curing agent other than the above-mentioned melamine derivative compound is used as the curing agent (Z), the coating agent is applied to the substrate by the above-mentioned method, and then the coating film is dried and cured. The drying conditions are a drying temperature of, for example, 100° C. or more, preferably 110° C. or more, and for example, 200° C. or less, preferably 180° C. or less, and a drying time of, for example, 3 minutes or more, preferably 5 minutes or more, and for example, 10 minutes or less, preferably 7 minutes or less. By such a method, the solvent volatilizes from the coating agent, and the metal particle dispersant and binder resin are dried and cured to form a cured film.

[0097] The cured film thus obtained is excellent in various physical properties such as surface hardness, adhesion, transparency, moist heat resistance, etc. Therefore, the cured film is suitably used in various industrial products, for example, optical films, and functional coatings for plastics, metals, etc.

[0098] <Characteristics of the cured product> The thickness of the coating film before curing to form the above cured product is preferably 2 to 30 μm, more preferably 3 to 20 μm, and even more preferably 4 to 15 μm, from the viewpoint of easily ensuring the required surface hardness and adhesion. The thickness of the cured product obtained by curing the coating is preferably 0.1 to 20 μm, more preferably 0.3 to 10 μm, and even more preferably 0.5 to 5 μm, from the viewpoint of easily ensuring the required surface hardness and adhesion. The haze of the cured product is preferably 2.0% or less, more preferably 1.5% or less, and even more preferably 1.3% or less, from the viewpoint of obtaining high transparency. The haze is measured in accordance with JIS-K7136:2000, specifically, by the method described in the examples.

[0099] The cured product is preferably excellent in environmental resistance, and the haze is preferably unlikely to decrease even when exposed to a high-humidity and high-temperature environment. Specifically, the cured film is exposed to conditions of 85°C and 85 RH% (relative humidity) for 250 hours, and then the cured product has a humidity and heat resistance haze of preferably 6.0% or less, more preferably 5.5% or less, and even more preferably 5.3% or less, from the viewpoint of easily suppressing a decrease in transparency. The above-mentioned wet heat resistant haze is specifically measured by the method described in the examples.

[0100] The surface hardness of the cured product is preferably a pencil hardness of F or more in order to ensure a high hardness. The surface hardness is measured in accordance with JIS-K5600-5-4:1999, specifically, by the method described in the Examples.

[0101] From the viewpoint of easily preventing peeling of the cured product, the adhesion of the cured product is preferably evaluated in accordance with JIS-K5600-5-6:1999 as a score of 3 or less, more preferably 2 or less, even more preferably 1 or less, and still more preferably 0. The adhesion is specifically measured by the method described in the Examples. EXAMPLES

[0102] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples.

[0103] [Properties of composition and ratio of components] Various physical properties of the compositions (particle dispersions) obtained in the production examples described below were measured according to the methods shown below.

[0104] <Average particle size of particles (Y) in particle dispersion> The average particle size of the particles (Y) in the particle dispersion was measured under the following conditions using a zeta potential / particle size measurement system ELS-Z2 (manufactured by Otsuka Electronics Co., Ltd.). Measuring cell: Particle size cell unit ·Scattering angle: 165° ·Measurement temperature: 25℃ Measurement sample: Particle dispersion diluted 50 times with the dispersion medium used to prepare the particle dispersion Measurement method: Dynamic light scattering (photon correlation method) ·Particle size analysis method: Contin method

[0105] <First monomer ratio> The molar ratio of the first monomer used in the synthesis of the copolymer in the cured film was calculated from the charged amount (first monomer ratio). When multiple copolymers were present, the molar ratio was calculated from the total amount of each monomer used.

[0106] <Acid value> The acid value (mgKOH / g) of the copolymer was measured using a potentiometric titrator AT-710 (Kyoto Electronics Manufacturing Co., Ltd.) in accordance with the titration method described in JIS-K-5601-2-1:1999.

[0107] [evaluation] Various evaluations of the polyethylene terephthalate (PET) films on which cured films were formed, obtained in the examples and comparative examples described below, were carried out according to the following methods.

[0108] <Surface hardness> The test was conducted in accordance with JIS-K5600-5-4:1999, and was evaluated based on the hardness of the pencil lead that caused scratches. The higher the pencil hardness, the harder the coating surface is, and the more resistant it is to scratches.

[0109] <Adhesion> The test was carried out in accordance with JIS-K5600-5-6:1999, and the peeling of the coating after the test was observed with a magnifying glass and evaluated according to the following criteria. The smaller the number, the better the adhesion. Evaluation criteria 0: The edges of the cut are completely smooth and there are no peeling marks on any of the grids. 1: Small peeling of the coating at the intersections of the cuts. The cross-cut area affected does not appreciably exceed 5%. 2: The coating has flaked along the edges of the cuts and / or at the intersections. The cross-cut area is clearly more than 5% but not more than 15% affected. 3: The coating has suffered partial or complete flaking along the edges of cuts and / or has suffered partial or complete flaking in various areas of the mesh. Cross-cut areas are affected in areas significantly exceeding 15% but not exceeding 35%. 4: The coating is partially or completely flaked along the edges of cuts and / or partially or completely flaked in several sections. Cross-cut areas are clearly more than 35% but not more than 65% affected. 5: The degree of peeling exceeds level 4.

[0110] <Haze> The evaluation was performed using a cloudiness tester NDH2000 (manufactured by Nippon Denshoku Industries Co., Ltd.) in accordance with JIS-K7136:2000. The smaller the value, the more excellent the transparency.

[0111] <Heat and humidity haze resistance> The cured film was exposed to conditions of 85° C. and 85 RH% (relative humidity) for 250 hours, after which the haze of the cured film was measured in the same manner as above, and was taken as the moist heat haze resistance.

[0112] [Each component] <1> The components used in the copolymer production examples are as follows: <First monomer> Monomer (a1): 2-hydroxyethyl methacrylate (hereinafter, HEMA): manufactured by Kanto Chemical Co., Ltd. Monomer (a3): 3-hydroxy-3-methylbutyl methacrylate (hereinafter, IPDMA): manufactured by Kuraray Co., Ltd. Other monomers 1: 2-hydroxy-2-methylpropyl methacrylate (hereinafter referred to as HBMA): manufactured by Kuraray Co., Ltd. Other monomer 2: 4-hydroxy-4-methylpentan-2-yl methacrylate (HGMA): Kuraray Co., Ltd.

[0113] <Second Monomer> Methacrylic acid (hereinafter referred to as MAA): Manufactured by Kanto Chemical Co., Ltd. Methyl methacrylate (MMA): Kanto Chemical Co., Ltd. Styrene (hereinafter St): Kanto Chemical Co., Ltd. -Butyl acrylate (hereinafter referred to as n-BA): Kanto Chemical Co., Ltd. <Solvent> Isopropanol (hereinafter referred to as IPA): Manufactured by Kanto Chemical Co., Ltd. <Polymerization initiator> Perbutyl (registered trademark) O: 2-(ethylhexanoyl) (tert-butyl) peroxide, manufactured by NOF Corporation <Neutralizing agent> N,N-Dimethylethanolamine: Kanto Chemical Co., Ltd.

[0114] The components used in the production examples of the composition (fine particle dispersion) are as follows: <Copolymer> Copolymers 1 to 7 prepared in Preparation Examples 1 to 7 <particle> Aluminum oxide: Trade name AEROXIDE (registered trademark) AluC, average primary particle size 13 nm, manufactured by EVONIK <Solvent (dispersion medium)> Isopropanol (hereinafter referred to as IPA): Manufactured by Kanto Chemical Co., Ltd.

[0115] <3> The components used in the examples and comparative examples relating to coating agents and cured films are as follows. <Copolymer> Copolymers 1 to 7 prepared in Preparation Examples 1 to 7 <Particle dispersion> Compositions 1 to 5 prepared in Preparation Examples 8 to 12 <Hardening agent> Nikalac (registered trademark) MX-706: Melamine-formaldehyde-alkyl monoalcohol (C1-C12) polycondensate, manufactured by Nippon Carbide Industries Co., Ltd. <Solvent> ·water

[0116] <Production of copolymer> [Production Example 1] Synthesis of Copolymer 1 In a reactor equipped with a stirrer, a thermometer, and a reflux tube, 150.0 g of IPA was placed under a nitrogen stream and heated to 80°C. A mixture of 22.5 g of HEMA, 30.0 g of MAA, 7.5 g of MMA, 7.5 g of St, 82.5 g of n-BA, and 9.0 g of Perbutyl O was bubbled with dry nitrogen and added dropwise over 120 minutes. One hour after the end of the dropwise addition, 1.5 g of Perbutyl O was added and aged at 80°C for 180 minutes. Then, the mixture was cooled, and 24.0 g of N,N-dimethylethanolamine was added and stirred. Then, 51.0 g of water was added as a dilution solvent to prepare a solution containing copolymer 1 (hereinafter also referred to as "copolymer solution 1"). The copolymer 1 corresponds to the above-mentioned copolymer (B).

[0117] [Production Examples 2 to 7] Synthesis of Copolymers 2 to 7 Copolymer solutions 2 to 7 containing copolymers 2 to 7 were obtained in the same manner as in Production Example 1, except that the formulations were as shown in Table 1. Copolymer 2 corresponds to the above-mentioned copolymer (A), and copolymer 3 corresponds to the above-mentioned copolymer (AB).

[0118] The composition of the copolymer in each production example is shown in Table 1.

[0119] [Table 1]

[0120] <Production of composition> [Production Example 8] Preparation of Composition 1 6.75 g of the copolymer solution 1 obtained in Production Example 1 as a dispersant, 9.00 g of aluminum oxide as particles, 1.35 g of IPA as a dispersion medium, 51.8 g of water, and 103.0 g of zirconia beads with a particle size of 50 μm as a dispersion medium were placed in an automatic stirring and defoaming machine (AR-250, manufactured by Thinky Corporation), and stirring was performed for 3 minutes three times. After that, the mixture was stirred for 7 days with a shaker, and the zirconia beads were removed by filtration. The filtrate was dispersed for 40 minutes with an ultrasonic homogenizer Sonifier Model 450D (manufactured by BRANSON) to obtain composition 1, which is a particle dispersion liquid.

[0121] [Production Examples 9 to 12] Preparation of Compositions 2 to 5 Compositions 2 to 5, which are particle dispersions, were obtained in the same manner as in Production Example 8, except that the formulations shown in Table 2 were used.

[0122] Table 2 shows the composition of each production example and the average particle size of the particles in the particle dispersion.

[0123] [Table 2]

[0124] <Production of coating agents and cured products> [Example 1] 16.0 g of Composition 2, which is the particle dispersion obtained in Production Example 9, 1.5 g of Copolymer Solution 1 obtained in Production Example 1 as a binder resin, and 40.0 g of water as a solvent were placed in a flask, and dispersed for 5 minutes using an ultrasonic homogenizer Sonifier Model 450D (manufactured by Branson Co., Ltd.). Then, 2.66 g of Nikalac (registered trademark) MX-706 as a curing agent was placed in the flask, and dispersed for 3 minutes using an ultrasonic homogenizer Sonifier Model 450D (manufactured by Branson Co., Ltd.) to prepare a coating agent. The obtained coating agent was applied to a PET film (product name A4300, manufactured by Toyobo Co., Ltd.) using a bar coater to a film thickness of 9 μm, and the coating film was cured by heating at 120° C. for 10 minutes to form a cured film with a thickness of 0.7 μm on the PET film.

[0125] [Examples 2 to 4, Comparative Examples 1 to 10] A coating agent and a cured film having the same thickness as in Example 1 were obtained in the same manner as in Example 1, except that the formulations shown in Tables 3 and 4 were used.

[0126] The measurement results of each of the examples and comparative examples are shown in Tables 3 and 4 together with the composition.

[0127] [Table 3]

[0128] [Table 4]

[0129] As shown in Tables 3 and 4, in Examples 1 to 4, cured films with small haze and excellent transparency were obtained. In addition, the values ​​of moist heat resistance haze were smaller than those of the comparative examples, and cured films with excellent moist heat resistance were obtained. The surface hardness and adhesion were also good. The cured films of Examples 1 to 4 contain primary hydroxyl groups derived from HEMA and tertiary hydroxyl groups derived from IPDMA, and the appropriate reactivity with the curing agent is believed to prevent the generation of bubbles and the aggregation of particles, forming cured films with excellent transparency.

[0130] On the other hand, a cured film with insufficient transparency was obtained in Comparative Example 1. This result is believed to be due to the fact that only primary hydroxyl groups derived from HEMA were present in the cured film of Comparative Example 1, which resulted in excessively high reactivity between the copolymer and the curing agent, leading to the generation of bubbles and aggregation of particles during curing. Moreover, a cured film with insufficient transparency was obtained in Comparative Example 2. This result is believed to be due to the fact that only tertiary hydroxyl groups derived from IPDMA were present in the cured film of Comparative Example 2, which resulted in insufficient reactivity between the copolymer and the curing agent, leading to aggregation of particles. Furthermore, the cured films obtained in Comparative Examples 3 to 6 had insufficient transparency. This result is believed to be due to the fact that the tertiary hydroxyl group derived from HBMA in the cured films of Comparative Examples 3 to 6 is located closer to the polymer main chain than the tertiary hydroxyl group derived from IPDMA, which reduces the reactivity between the copolymer and the curing agent and causes the particles to aggregate. Furthermore, the cured films obtained in Comparative Examples 7 to 10 had insufficient transparency. This result is believed to be due to the presence of a branched structure of the side chain derived from HGMA in the cured films of Comparative Examples 7 to 10, which reduces the reactivity between the copolymer and the curing agent, causing the particles to aggregate.

Claims

1. A coating agent comprising a copolymer (X), at least one kind of particles (Y) selected from the group consisting of inorganic particles and organic pigment particles, and a curing agent (Z), The copolymer (X) is (i) a mixture of a copolymer (A) having a structural unit (1) represented by the following general formula (I) but not having a structural unit (2) represented by the following general formula (II), and a copolymer (B) having the structural unit (2) but not having the structural unit (1); (ii) a copolymer (AB) having the structural unit (1) and the structural unit (2); At least one selected from the group consisting of Coating agent. 【Chemistry 1】 [In general formula (I), R １ represents an alkyl group having 1 to 3 carbon atoms, and R ２ represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and R ３ represents a hydrogen atom or a methyl group, and n is an integer of 2 to 7. 【Chemistry 2】 [In general formula (II), R ４ represents a hydrogen atom or a methyl group, and m is an integer of 2 to 7.

2. The coating agent of claim 1 further comprising a solvent.

3. 2. The coating agent according to claim 1, wherein the curing agent (Z) is a melamine derivative compound.

4. In the general formula (I), R １ , R ２ , and R ３ 2. The coating agent according to claim 1, wherein is a methyl group and n is 2.

5. The coating agent according to claim 1, wherein at least one of the copolymer (A), the copolymer (B), and the copolymer (AB) has an ionic group.

6. 2. The coating agent according to claim 1, wherein the particles (Y) are metal particles.

7. A cured product obtained by curing the coating agent according to any one of claims 1 to 6.

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