Coating composition, coating layer, and coated article

Abstract

To provide a coating composition, a coating layer, and a coated article that can form a coating layer that has excellent adhesion to the substrate and does not impair the transparency of the coated article. [Solution] A coating composition, coating layer, and coated article comprising a (meth)acrylic copolymer comprising a constituent unit (a) derived from an alkyl (meth)acrylate monomer, a constituent unit (b) derived from a monomer having an amino group, and a constituent unit (c) having a urethane bond and a (meth)acryloyl group, and which includes a constituent unit (a) different from the above constituent unit (a) and the above constituent unit (b), wherein the content of the above constituent unit (b) is in the range of 1.0% by mass or more and 2.5% by mass or less of the total constituent units, the content of the above constituent unit (c) is in the range of 20 mol% or more and 40 mol% or less of the total constituent units, and the weight-average molecular weight is in the range of 20,000 or more and 100,000 or less, and a photoinitiator.

Description

Technical Field

[0001] The present disclosure relates to a coating composition, a coat layer, and a coated article.

Background Art

[0002] Polycarbonate resins are widely used in various electrical appliances, various optical products, vehicle interior parts, various building materials, etc. because of their high transparency, excellent impact resistance and heat resistance. It is known to provide a coat layer on the surface of an article made of polycarbonate resin for the purpose of scratch resistance, solvent resistance, etc., and reports have been made on compositions for forming the coat layer.

[0003] For example, in Patent Document 1, a (meth)acrylic polymer (A) having a hydroxyl value of 10 mgKOH / g to 350 mgKOH / g, a (meth)acrylic equivalent of 100 g / eq to 800 g / eq, a weight average molecular weight of 10,000 to 200,000, a glass transition point of 50°C to 110°C, and having a photopolymerizable group and a hydroxyl group in the side chain, an inorganic particle (B) having an average particle diameter of 10 nm to 500 nm, an organic particle (C) having an average particle diameter of 10 nm to 500 nm, and a photopolymerizable polyfunctional compound (D) having two or more photopolymerizable groups in one molecule, and the content of the (meth)acrylic polymer (A) is 10% by weight to 40% by weight, the content of the inorganic particle (B) is 5% by weight to 40% by weight, the content of the organic particle (C) is 0.5% by weight to 10% by weight, and the content of the photopolymerizable polyfunctional compound (D) is 20% by weight to 70% by weight with respect to the total weight of the (meth)acrylic polymer (A), the inorganic particle (B), the organic particle (C), and the photopolymerizable polyfunctional compound (D). A photocurable resin composition has been reported.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

[0005] The coating layer formed on the surface of a substrate requires not only high transparency but also high adhesion to the substrate. However, conventional coating layers have room for improvement in their adhesion to the substrate (especially substrates containing polycarbonate resin). On the other hand, if the effect of the coating layer on the substrate is strengthened to improve adhesion between the substrate and the coating layer, the transparency of the coated substrate (so-called coated article) may be impaired.

[0006] This disclosure is made in light of the circumstances described above. One embodiment of this disclosure aims to solve the problem of providing a coating composition that can form a coating layer that has excellent adhesion to a substrate and does not impair the transparency of the coated article. Other embodiments of this disclosure aim to solve the problem of providing a coated layer formed by the above-mentioned coating composition, and a coated article comprising the above-mentioned coating layer. [Means for solving the problem]

[0007] The following are examples of specific means for solving the problem: <1> A (meth)acrylic copolymer comprising a constituent unit (a) derived from an alkyl (meth)acrylate monomer, a constituent unit (b) derived from a monomer having an amino group, and a constituent unit (c) having a urethane bond and a (meth)acryloyl group, and which includes a constituent unit (c) different from the above constituent units (a) and (b), wherein the content of the above constituent unit (b) is in the range of 1.0% by mass or more and 2.5% by mass or less of the total constituent units, the content of the above constituent unit (c) is in the range of 20 mol% or more and 40 mol% or less of the total constituent units, and the weight-average molecular weight is in the range of 20,000 or more and 100,000 or less, Photoinitiator and A coating composition containing the following: <2> The monomer having the above amino group is a monomer having at least one of a dimethylamino group and a diethylamino group. <1> The coating composition described above. <3> The monomer having the above amino group comprises at least one selected from the group consisting of dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, and N-(3-dimethylaminopropyl)methacrylamide. <1> The coating composition described above. <4> The alkyl (meth)acrylate monomer is at least one selected from the group consisting of methyl (meth)acrylate and ethyl (meth)acrylate, and the content of the above constituent unit (a) is in the range of 40.0% by mass or more and 60.0% by mass or less relative to the total constituent units of the above (meth)acrylic copolymer. <1> ~ <3> A coating composition as described in any one of the following. <5> The above alkyl (meth)acrylate monomer is methyl methacrylate. <4> The coating composition described above. <6> <1> ~ <5> A coating layer formed by any one of the coating compositions described in the preceding paragraph. <7> A base material containing polycarbonate resin, Provided on the surface of the substrate containing the above polycarbonate resin <6> The coating layer described above, A covering article equipped with the following features. [Effects of the Invention]

[0008] According to one embodiment of the present disclosure, a coating composition is provided that can form a coating layer that has excellent adhesion to a substrate and does not impair the transparency of the coated article. Other embodiments of the present disclosure provide a coated layer formed by the above-mentioned coating composition, and a coated article comprising the above-mentioned coating layer. [Modes for carrying out the invention]

[0009] The coating compositions, coating layers, and coated articles of this disclosure will be described in detail below. The descriptions of requirements below may be based on typical embodiments of this disclosure, but this disclosure is not limited to such embodiments and may be modified as appropriate within the scope of the purposes of this disclosure.

[0010] In this disclosure, a numerical range indicated using "~" means a range that includes the numbers written before and after "~" as the lower limit and upper limit, respectively. In the numerical ranges described in stages in this disclosure, the upper or lower limit stated in one numerical range may be replaced with the upper or lower limit of another numerical range described in stages. Furthermore, in the numerical ranges described in this disclosure, any upper or lower limit values ​​described within a numerical range may be replaced with the values ​​shown in the examples.

[0011] In this disclosure, a combination of two or more preferred embodiments is a more preferred embodiment.

[0012] In this disclosure, the amount of each component in the composition means the total amount of any multiple substances present in the composition, unless otherwise specified, if there are multiple substances corresponding to each component in the composition.

[0013] In this disclosure, unless otherwise specified, "solids" means components other than the solvent contained in the composition, and "solvent" means water and organic solvents. For example, if the solvent in the composition is only water, then the solids content refers to the components other than water in the composition; if the solvent in the composition is only an organic solvent, then the solids content refers to the components other than the organic solvent in the composition; and if the solvent in the composition is both water and an organic solvent, then the solids content refers to the components other than water and the organic solvent in the composition.

[0014] In the present disclosure, the “(meth)acrylic copolymer” means a copolymer that contains structural units derived from (meth)acrylic monomers and in which the proportion of the structural units derived from (meth)acrylic monomers is 50% by mass or more. In the present disclosure, the “(meth)acrylic monomer” means a monomer having a (meth)acryloyl group.

[0015] In the present disclosure, “(meth)acrylic” is a term encompassing both “acrylic” and “methacrylic”, “(meth)acrylate” is a term encompassing both “acrylate” and “methacrylate”, and “(meth)acryloyl” is a term encompassing both “acryloyl” and “methacryloyl”.

[0016] In the present disclosure, “n-” means normal, “i-” means iso, “s-” means secondary, and “t-” means tertiary.

[0017] In the present disclosure, “monomer” and “monomeric unit” are synonymous, and “polymer” and “polymeric substance” are synonymous.

[0018] In the present disclosure, “% by mass” and “% by weight” are synonymous, and “parts by mass” and “parts by weight” are synonymous.

[0019] In the present disclosure, the “structural unit derived from a monomer” means a structural unit formed by the addition polymerization of a monomer.

[0020] In the present disclosure, the term “step” includes not only an independent step but also a step that cannot be clearly distinguished from other steps, provided that the intended purpose of the step is achieved.

[0021] [Coating composition] The coating composition of this disclosure comprises a (meth)acrylic copolymer comprising a constituent unit (a) derived from an alkyl (meth)acrylate monomer, a constituent unit (b) derived from a monomer having an amino group, and a constituent unit (c) having a urethane bond and a (meth)acryloyl group, and being different from the above constituent units (a) and (b), wherein the content of the above constituent unit (b) is in the range of 1.0% by mass or more and 2.5% by mass or less relative to the total constituent units, the content of the above constituent unit (c) is in the range of 20 mol% or more and 40 mol% or less relative to the total constituent units, and the weight-average molecular weight is in the range of 20,000 or more and 100,000 or less, and a photoinitiator.

[0022] The coating layer formed on the surface of a substrate is required to have excellent adhesion to the substrate being coated, as well as not impairing the transparency of the substrate. Conventional coating layers have room for improvement in terms of adhesion to the substrate. However, if the effect of the coating layer on the substrate is strengthened in order to improve the adhesion between the substrate and the coating layer, the transparency of the coated substrate (so-called coated article) may be impaired. In particular, polycarbonate resin tends to undergo accelerated hydrolysis when exposed to basic compounds, and if a basic coating composition is used on a substrate containing polycarbonate resin, the transparency of the substrate is easily impaired. For example, if the coating composition contains a (meth)acrylic copolymer having amino groups, the coating composition exhibits basicity, and the transparency of the substrate containing polycarbonate resin tends to decrease. However, on the other hand, if the coating composition contains a (meth)acrylic copolymer having amino groups, the amino groups of the coating layer act on the substrate when the coating layer is formed, which can have the effect of improving the adhesion between the coating layer and the substrate. The coating composition of this disclosure, having the above-described structure, has excellent adhesion to the substrate, high transparency, and, despite containing an amino group-containing (meth)acrylic copolymer, does not impair the transparency of the substrate; in other words, it can form a coating layer that does not impair the transparency of the coated article.

[0023] The substrates to which the coating compositions of this disclosure are applied are not particularly limited. The shape of the substrate is not particularly limited and can be set as appropriate depending on the purpose. The substrate may have a planar shape (e.g., a plate or film) or a three-dimensional shape. The substrate may have a curved surface or an uneven surface. The size of the substrate is not particularly limited and can be set as appropriate depending on the purpose.

[0024] Examples of substrate materials include resin, glass, and metal. Examples of resins include polycarbonate resin, acrylic resin, polyolefin resin [e.g., polyethylene (PE) and polypropylene (PP)], polyester resin [e.g., polyethylene terephthalate (PET)], acetate resin [e.g., triacetylcellulose (TAC)], and vinyl chloride resin. When the material of the base material is resin, the base material may contain one type of resin alone or two or more types of resin. For example, in order to better demonstrate the effects of the coating composition of this disclosure, the substrate preferably contains a polycarbonate resin, and more preferably is a polycarbonate resin.

[0025] In this disclosure, a "(meth)acrylic copolymer comprising a constituent unit (a) derived from an alkyl (meth)acrylate monomer, a constituent unit (b) derived from a monomer having an amino group, and a constituent unit having a urethane bond and a (meth)acryloyl group, and comprising a constituent unit (c) different from the above constituent unit (a) and the above constituent unit (b), wherein the content of the above constituent unit (b) is in the range of 1.0% by mass or more and 2.5% by mass or less of the total constituent units, the content of the above constituent unit (c) is in the range of 20 mol% or more and 40 mol% or less of the total constituent units, and the weight-average molecular weight is in the range of 20,000 or more and 100,000 or less" is also referred to as a "specific (meth)acrylic copolymer".

[0026] In this disclosure, "(meth)acrylate alkyl ester monomer-derived constituent unit (a)" is also simply referred to as "constituent unit (a)," and "(b) monomer-derived amino group-containing constituent unit (b)" is also simply referred to as "constituent unit (b)." Furthermore, in this disclosure, "constituent unit (c) having a urethane bond and a (meth)acryloyl group, and being different from constituent unit (a) and constituent unit (b)" is also simply referred to as "constituent unit (c)."

[0027] [Specific (meth)acrylic copolymer] The coating composition of this disclosure includes a (meth)acrylic copolymer [i.e., a specific (meth)acrylic copolymer] comprising a constituent unit (a) derived from an alkyl (meth)acrylate monomer, a constituent unit (b) derived from a monomer having an amino group, and a constituent unit (c) having a urethane bond and a (meth)acryloyl group, and different from the above constituent units (a) and (b), wherein the content of the above constituent unit (b) is in the range of 1.0% by mass or more and 2.5% by mass or less of the total constituent units, the content of the above constituent unit (c) is in the range of 20 mol% or more and 40 mol% or less of the total constituent units, and the weight-average molecular weight is in the range of 20,000 or more and 100,000 or less. The coating composition of this disclosure may contain one specific (meth)acrylic copolymer alone, or two or more specific (meth)acrylic copolymers.

[0028] <Constituent unit (a)> The specific (meth)acrylic copolymer contains a constituent unit (a) derived from an alkyl (meth)acrylate monomer. In this disclosure, "(meth)acrylate alkyl ester monomer" refers to an (meth)acrylate alkyl ester monomer that does not have any amino group, hydroxyl group, or carboxyl group. In other words, for example, in this disclosure, "(meth)acrylate alkyl ester monomer having an amino group" is classified as a monomer having an amino group, "(meth)acrylate alkyl ester monomer having a hydroxyl group" is classified as a monomer having a hydroxyl group, and "(meth)acrylate alkyl ester monomer having a carboxyl group" is classified as a monomer having a carboxyl group.

[0029] The type of alkyl (meth)acrylate monomer is not particularly limited. The alkyl (meth)acrylate monomer may be an alkyl acrylate monomer or an alkyl methacrylate monomer. The alkyl group in the alkyl (meth)acrylate monomer may be unsubstituted or may have substituents (excluding amino groups, hydroxyl groups, and carboxyl groups), but it is preferable that it be unsubstituted. The alkyl group of the alkyl (meth)acrylate monomer may be linear, branched, or cyclic. The number of carbon atoms in the alkyl moiety of the (meth)acrylate alkyl ester monomer is preferably 1 to 18, more preferably 1 to 8, even more preferably 1 to 4, and particularly preferably 1 to 2.

[0030] Specific examples of alkyl (meth)acrylate monomers include methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, i-butyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, n-octyl (meth)acrylate, i-octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-nonyl (meth)acrylate, i-nonyl (meth)acrylate, n-decyl (meth)acrylate, stearyl (meth)acrylate, lauryl (meth)acrylate, cyclohexyl (meth)acrylate, and isobornyl (meth)acrylate.

[0031] The alkyl (meth)acrylate monomer preferably contains at least one selected from the group consisting of methyl (meth)acrylate and ethyl (meth)acrylate, for example, from the viewpoint of adhesion between the coating layer and the substrate and suppression of coating unevenness, more preferably at least one selected from the group consisting of methyl (meth)acrylate and ethyl (meth)acrylate, and even more preferably methyl methacrylate. The above-mentioned alkyl (meth)acrylate monomer has a small number of carbon atoms in the alkyl portion, making it less likely to cause steric hindrance during polymerization. Therefore, when a specific (meth)acrylic copolymer contains a structural unit derived from the above-mentioned alkyl (meth)acrylate monomer, polymerization curing tends to proceed relatively quickly, and the adhesion between the coating layer and the substrate tends to be improved. Furthermore, specific (meth)acrylic copolymers containing constituent units derived from the above-mentioned alkyl (meth)acrylate monomers tend to have a relatively high glass transition temperature, resulting in good coating properties for the coating composition and a reduced likelihood of uneven coating.

[0032] The specific (meth)acrylic copolymer may contain one type of constituent unit (a) alone, or it may contain two or more types.

[0033] The content of constituent unit (a) in the specific (meth)acrylic copolymer is not particularly limited, but is preferably 35.0% by mass or more, and more preferably 40.0% by mass or more, relative to the total constituent units of the specific (meth)acrylic copolymer. When the content of constituent unit (a) in a specific (meth)acrylic copolymer is 35.0% by mass or more relative to the total constituent units of the specific (meth)acrylic copolymer, the resulting coating layer tends to exhibit high transparency. The upper limit of the content of constituent unit (a) in the specific (meth)acrylic copolymer is preferably 60.0% by mass or less relative to the total constituent units of the specific (meth)acrylic copolymer. In one embodiment, the content of constituent unit (a) in the specific (meth)acrylic copolymer may be in the range of 35.0% by mass or more and 60.0% by mass or less, or in the range of 40.0% by mass or more and 60.0% by mass or less, relative to the total constituent units of the specific (meth)acrylic copolymer.

[0034] As for the configuration of the constituent unit (a) in the specific (meth)acrylic copolymer, for example, from the viewpoint of adhesion between the coating layer and the substrate, high transparency of the coating layer, and suppression of coating unevenness, the following configuration (1) is preferred and configuration (2) is more preferred. Embodiment (1): The alkyl (meth)acrylate monomer is at least one selected from the group consisting of methyl (meth)acrylate and ethyl (meth)acrylate, and the content of constituent unit (a) [i.e., the total content of constituent units derived from methyl acrylate, constituent units derived from methyl methacrylate, constituent units derived from ethyl acrylate, and constituent units derived from ethyl methacrylate] is in the range of 40.0% by mass or more and 60.0% by mass or less with respect to all constituent units of the (meth)acrylic copolymer. Embodiment (2): The alkyl (meth)acrylate monomer is methyl methacrylate, and the content of constituent unit (a) [i.e., the content of constituent units derived from methyl methacrylate] is in the range of 40.0% by mass or more and 60.0% by mass or less with respect to the total constituent units of the (meth)acrylic copolymer.

[0035] <Constituent unit (b)> The specified (meth)acrylic copolymer contains a constituent unit (b) derived from a monomer having an amino group, and the content of constituent unit (b) is in the range of 1.0% by mass or more and 2.5% by mass or less relative to the total constituent units.

[0036] The type of monomer having an amino group is not particularly limited. Examples of monomers having an amino group include monomers having at least one amino group and an ethylenically unsaturated group in one molecule. The amino group may be a primary amino group, a secondary amino group, or a tertiary amino group. That is, the amino group may be an unsubstituted amino group, or a substituted amino group in which a hydrogen atom of the amino group is replaced by a substituent. The amino group is preferably a substituted amino group (i.e., a secondary or tertiary amino group), and more preferably a tertiary amino group, from the viewpoint of maintaining the transparency of the coated article. When the amino group acts on the substrate, hydrolysis of the substrate may occur. In particular, in substrates containing polycarbonate resin, hydrolysis due to the action of the amino group is likely to occur, which can be a factor in the decrease in transparency. Since substituted amino groups are less reactive than unsubstituted amino groups, hydrolysis of the substrate is less likely to occur, and the decrease in the transparency of the substrate tends to be less likely. If an amino group has multiple substituents, these substituents may be the same or different. The substituent on the amino group is preferably an alkyl group, and this alkyl group may have further substituents.

[0037] Examples of ethylenically unsaturated groups include vinyl groups, allyl groups, vinylphenyl groups, (meth)acrylamide groups, and (meth)acryloyl groups.

[0038] The monomer having an amino group is preferably a monomer having at least one of a dimethylamino group and a diethylamino group, for example, from the viewpoint of maintaining the transparency of the coated article. Because dimethylamino and diethylamino groups have lower reactivity compared to other amino groups, they tend to be less likely to cause a decrease in the transparency of the substrate (especially substrates containing polycarbonate resin) that can occur when amino groups interact with the substrate. Examples of monomers having a dimethylamino group include dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate, N-(3-dimethylaminopropyl)acrylamide, and N-(3-dimethylaminopropyl)methacrylamide [DMAPMA]. Examples of monomers having a diethylamino group include diethylaminoethyl acrylate, diethylaminoethyl methacrylate, N-(3-diethylaminopropyl)acrylamide, and N-(3-diethylaminopropyl)methacrylamide.

[0039] The monomer having an amino group preferably includes at least one selected from the group consisting of dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, and N-(3-dimethylaminopropyl)methacrylamide, and more preferably at least one selected from the group consisting of dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, and N-(3-dimethylaminopropyl)methacrylamide, from the viewpoint of not excessively reacting with the substrate (particularly a substrate containing polycarbonate resin) and not impairing the transparency of the substrate.

[0040] The specific (meth)acrylic copolymer may contain one type of constituent unit (b) alone, or it may contain two or more types.

[0041] The content of constituent unit (b) in the specified (meth)acrylic copolymer is, for example, in the range of 1.0% by mass or more and 2.5% by mass or less relative to the total constituent units of the specified (meth)acrylic copolymer, from the viewpoint of adhesion between the coating layer and the substrate and maintaining the transparency of the coated article. When the content of constituent unit (b) in the specific (meth)acrylic copolymer is 1.0% by mass or more relative to the total constituent units of the specific (meth)acrylic copolymer, the amino groups act sufficiently on the substrate, and the adhesion of the coating layer to the substrate tends to be excellent. When the content of constituent unit (b) in a specific (meth)acrylic copolymer is 2.5% by mass or less relative to the total constituent units of the specific (meth)acrylic copolymer, the amino groups do not excessively act on the substrate, and therefore, a decrease in the transparency of the substrate due to the action of the amino groups tends to be less likely. The content of constituent unit (b) in the specific (meth)acrylic copolymer is preferably in the range of 1.1% by mass or more and 2.3% by mass or less, and more preferably in the range of 1.2% by mass or more and 2.0% by mass or less, relative to the total constituent units of the specific (meth)acrylic copolymer.

[0042] <Constituent unit (c)> The specified (meth)acrylic copolymer is a constituent unit having a urethane bond and a (meth)acryloyl group, and includes a constituent unit (c) that is different from constituent units (a) and (b), with the content of constituent unit (c) being in the range of 20 mol% to 40 mol% relative to the total number of constituent units. In this disclosure, the "constituent unit having a urethane bond and a (meth)acryloyl group" may be, for example, a constituent unit formed by the reaction of a hydroxyl group in a constituent unit derived from a monomer having a hydroxyl group with an isocyanate group in a compound having a (meth)acryloyl group and an isocyanate group.

[0043] The constituent unit (c) is a constituent unit having a urethane bond and a (meth)acryloyl group, and its form is not particularly limited as long as it is a different constituent unit from constituent units (a) and (b). Examples of constituent units (c) include the constituent units represented by (c-1), (c-2), (c-3), and (c-4) below.

[0044] [ka]

[0045] The specific (meth)acrylic copolymer may contain one type of constituent unit (c) alone, or it may contain two or more types.

[0046] The content of constituent unit (c) in the specific (meth)acrylic copolymer is, for example, in the range of 20 mol% to 40 mol% of the total constituent units of the specific (meth)acrylic copolymer, from the viewpoint of adhesion between the coating layer and the substrate. When the content of constituent unit (c) in a specific (meth)acrylic copolymer is 20 mol% or more relative to the total constituent units of the specific (meth)acrylic copolymer, the curing of the coating composition proceeds sufficiently, and the adhesion of the coating layer to the substrate tends to be excellent. When the content of constituent unit (c) in a specific (meth)acrylic copolymer is 40 mol% or less relative to the total constituent units of the specific (meth)acrylic copolymer, the curing of the coating composition does not proceed excessively, and as a result, a decrease in the adhesion of the coating layer to the substrate due to excessive cohesive force of the formed coating layer is less likely to occur. The content of constituent unit (c) in the specific (meth)acrylic copolymer is preferably in the range of 22 mol% to 38 mol%, and more preferably in the range of 25 mol% to 35 mol%, relative to the total constituent units of the specific (meth)acrylic copolymer.

[0047] The content of constituent unit (c) in the (meth)acrylic copolymer is determined by the method described in the examples below.

[0048] <Other constituent units> The specific (meth)acrylic copolymer may, as necessary, include any constituent units that do not fall under any of constituent units (a), (b), and (c) (so-called other constituent units), to the extent that they do not impair the effects of the coating composition of the present disclosure. If a specific (meth)acrylic copolymer contains other constituent units, these other constituent units may consist of one type alone or two or more types.

[0049] Other constituent units include, for example, constituent units derived from monomers having a hydroxyl group, and constituent units derived from monomers having a carboxyl group.

[0050] The type of monomer having a hydroxyl group is not particularly limited. Examples of monomers having a hydroxyl group include monomers having at least one hydroxyl group and an ethylenically unsaturated group in one molecule. Examples of ethylenically unsaturated groups include vinyl groups, allyl groups, vinylphenyl groups, (meth)acrylamide groups, and (meth)acryloyl groups.

[0051] Specific examples of monomers containing hydroxyl groups include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, 12-hydroxylauryl (meth)acrylate, 3-methyl-3-hydroxybutyl (meth)acrylate, and 1,1-dimethyl-3-hydroxybutyl (meth)acrylate. Examples include methyl(meth)acrylate, 1,3-dimethyl-3-hydroxybutyl(meth)acrylate, 2,2,4-trimethyl-3-hydroxypentyl(meth)acrylate, 2-ethyl-3-hydroxyhexyl(meth)acrylate, N-hydroxyethyl(meth)acrylamide, glycerin mono(meth)acrylate, polypropylene glycol mono(meth)acrylate, polyethylene glycol mono(meth)acrylate, and poly(ethylene glycol-propylene glycol) mono(meth)acrylate.

[0052] The specific (meth)acrylic copolymer is preferably, for example, from the viewpoint of maintaining the transparency of the coated article, free from constituent units derived from monomers having hydroxyl groups, or the content of constituent units derived from monomers having hydroxyl groups is in the range of more than 0% by mass and 10% by mass or less relative to the total constituent units; more preferably, free from constituent units derived from monomers having hydroxyl groups, or the content of constituent units derived from monomers having hydroxyl groups is in the range of more than 0% by mass and 5% by mass or less relative to the total constituent units; even more preferably, free from constituent units derived from monomers having hydroxyl groups, or the content of constituent units derived from monomers having hydroxyl groups is in the range of more than 0% by mass and 2% by mass or less relative to the total constituent units; particularly preferably, free from constituent units derived from monomers having hydroxyl groups, or the content of constituent units derived from monomers having hydroxyl groups is in the range of more than 0% by mass and 1% by mass or less relative to the total constituent units; and most preferably, free from constituent units derived from monomers having hydroxyl groups. When a specific (meth)acrylic copolymer contains constituent units derived from monomers having hydroxyl groups, the coating composition and / or coating layer tend to absorb water. When a specific (meth)acrylic copolymer does not contain constituent units derived from monomers having hydroxyl groups, or when the content of constituent units derived from monomers having hydroxyl groups in the specific (meth)acrylic copolymer is 10% by mass or less relative to the total constituent units of the specific (meth)acrylic copolymer, clouding of the coating layer due to water content in the coating composition and / or coating layer tends to be prevented or suppressed.

[0053] The type of monomer having a carboxyl group is not particularly limited. Examples of monomers having a carboxyl group include monomers having at least one carboxyl group and an ethylenically unsaturated group in one molecule. Examples of ethylenically unsaturated groups include vinyl groups, allyl groups, vinylphenyl groups, (meth)acrylamide groups, and (meth)acryloyl groups.

[0054] Specific examples of monomers having a carboxyl group include (meth)acrylic acid, crotonic acid, maleic acid, fumaric acid, itaconic acid, glutaconic acid, citraconic acid, ω-carboxy-polycaprolactone mono(meth)acrylate [e.g., ω-carboxy-polycaprolactone (n≒2) monoacrylate], and succinic acid derivatives (e.g., 2-acryloyloxyethyl succinic acid). The monomer having a carboxyl group preferably contains (meth)acrylic acid, and more preferably contains methacrylic acid, and even more preferably is methacrylic acid, from the viewpoint of the coating layer's resistance to blocking. Certain (meth)acrylic copolymers containing constituent units derived from methacrylic acid tend to have a relatively high glass transition temperature, which makes them less susceptible to blocking phenomena caused by the coating layer.

[0055] When a specific (meth)acrylic copolymer contains constituent units derived from monomers having carboxyl groups as other constituent units, the content of constituent units derived from monomers having carboxyl groups in the specific (meth)acrylic copolymer is not particularly limited, but for example, from the viewpoint of adhesion between the coating layer and the substrate and the blocking resistance of the coating layer, it is preferably in the range of 0.01% by mass or more and 1% by mass or less, more preferably in the range of 0.01% by mass or more and 0.5% by mass or less, even more preferably in the range of 0.01% by mass or more and 0.2% by mass or less, and particularly preferably in the range of 0.01% by mass or more and 0.1% by mass or less, relative to the total constituent units of the specific (meth)acrylic copolymer. When the content of constituent units derived from monomers having carboxyl groups in a specific (meth)acrylic copolymer is 0.01% by mass or more relative to the total constituent units of the specific (meth)acrylic copolymer, the polarity of the coating composition increases, and thus the adhesion between the coating layer and the substrate tends to improve. When the content of constituent units derived from monomers having carboxyl groups in a specific (meth)acrylic copolymer is 1% by mass or less relative to the total constituent units of the specific (meth)acrylic copolymer, the tack of the formed coating layer is suppressed, and blocking phenomena caused by the coating layer tend to be less likely to occur.

[0056] <<Weight-average molecular weight of specific (meth)acrylic copolymers>> The weight-average molecular weight (also known as "Mw") of a specific (meth)acrylic copolymer is, for example, in the range of 20,000 to 100,000, from the viewpoint of preventing blocking in the coating layer and suppressing coating unevenness. Certain (meth)acrylic copolymers, when their weight-average molecular weight is 20,000 or higher, tend to have a relatively high glass transition temperature, which makes them less susceptible to blocking phenomena caused by the coating layer. When the weight-average molecular weight of a specific (meth)acrylic copolymer is 100,000 or less, the coating composition tends to have good coatability and is less prone to uneven coating. The weight-average molecular weight of the specific (meth)acrylic copolymer is preferably in the range of 25,000 to 80,000, and more preferably in the range of 30,000 to 65,000.

[0057] The weight-average molecular weight of a specific (meth)acrylic copolymer is a value measured by the following method. Specifically, it is measured according to (1) to (3) below. (1) A solution of the specific (meth)acrylic copolymer is applied to release paper, and then dried at 100°C for 1 minute to obtain a film-like specific (meth)acrylic copolymer. (2) Using the film-like specific (meth)acrylic copolymer obtained in (1) above and tetrahydrofuran, a sample solution with a solid content concentration of 0.2% by mass is obtained. Here, "solid content concentration" refers to the mass ratio of the specific (meth)acrylic copolymer in the sample solution. (3) The weight-average molecular weight of the specific (meth)acrylic copolymer is determined as a standard polystyrene equivalent by gel permeation chromatography (GPC) under the following conditions.

[0058] ~Conditions~ Measurement device: High-speed GPC [Model number: HLC-8420 GPC, manufactured by Tosoh Corporation] Detector: Differential Refractometer (RI) [Integrated into HLC-8420, manufactured by Tosoh Corporation] Column: TSKgel GMH XL Two columns were used [Column size: 7.8mmφ x 30cm, manufactured by Tosoh Corporation]. Column temperature: 40℃ Eluent: Tetrahydrofuran Sample solution injection volume: 100 μL Flow rate: 0.8mL / min

[0059] The weight-average molecular weight of a specific (meth)acrylic copolymer can be adjusted to a desired value, for example, when producing the specific (meth)acrylic copolymer by the production method X described later, by adjusting the polymerization temperature, polymerization time, amount of organic solvent used, type of polymerization initiator, amount of polymerization initiator used, etc., when polymerizing the monomer in the production of the pre-polymer.

[0060] <<Glass transition temperature of specific (meth)acrylic copolymers>> The glass transition temperature (also called "Tg") of a specific (meth)acrylic copolymer is not particularly limited, but is preferably in the range of 50°C to 100°C, and more preferably in the range of 52°C to 90°C. When the glass transition temperature of a specific (meth)acrylic copolymer falls within the above range, blocking phenomena caused by the coating layer tend to be less likely to occur.

[0061] The glass transition temperature of a specific (meth)acrylic copolymer is measured by the following method. Specifically, a differential scanning calorimetry (DSC) is used, and the measurement is performed in a nitrogen atmosphere with a sample of 5 mg, under conditions of a starting temperature of -10°C, an ending temperature of 150°C, and a heating rate of 10°C / min. The inflection point of the resulting DSC curve is defined as the glass transition temperature of the specific (meth)acrylic copolymer. As a differential scanning calorimetry device, for example, a differential scanning calorimeter (product name: Discovery DSC 2500) manufactured by T.A. Instrument Japan Co., Ltd. can be suitably used. However, the differential scanning calorimetry device is not limited to this.

[0062] The glass transition temperature of a specific (meth)acrylic copolymer can be set to a desired value, for example, by appropriately selecting the type and ratio of monomers that form the constituent units of the specific (meth)acrylic copolymer.

[0063] <<Content of specific (meth)acrylic copolymer>> The content of the specific (meth)acrylic copolymer in the coating composition of this disclosure is not particularly limited, but is preferably in the range of 50% to 99.5% by mass, more preferably in the range of 60% to 99% by mass, and even more preferably in the range of 70% to 98.5% by mass, based on the total solid content in the coating composition.

[0064] In this disclosure, "total solid content in the coating composition" means the total mass of the coating composition if the coating composition does not contain a solvent, and the mass of the residue remaining after removing the solvent from the coating composition if the coating composition contains a solvent.

[0065] [Meth)acrylic copolymer manufacturing method] The method for producing the specific (meth)acrylic copolymer is not particularly limited. The specific (meth)acrylic copolymer is preferably manufactured by the manufacturing method X described below, for example, because it is relatively easy to control the content of the constituent unit (c) in the specific (meth)acrylic copolymer, and it is easy to produce the desired specific (meth)acrylic copolymer.

[0066] -Manufacturing method X- Manufacturing method X involves polymerizing an alkyl (meth)acrylate monomer, a monomer having an amino group, and a monomer having a hydroxyl group to obtain a prepolymer. Then, a monomer having an isocyanate group and a (meth)acryloyl group [a so-called (meth)acrylic monomer having an isocyanate group] is added to the obtained prepolymer, and the hydroxyl group of the prepolymer reacts with the isocyanate group of the above monomer to introduce a (meth)acryloyl group into the copolymer, thereby obtaining a specific (meth)acrylic copolymer.

[0067] <<Manufacturing of prepolymers>> In manufacturing method X, an alkyl (meth)acrylate monomer, a monomer having an amino group, and a monomer having a hydroxyl group are polymerized to obtain a prepolymer. Prepolymers can be produced by polymerizing alkyl (meth)acrylate monomers, monomers having amino groups, and monomers having hydroxyl groups using known polymerization methods such as solution polymerization, emulsion polymerization, suspension polymerization, and bulk polymerization. The polymerization method for the prepolymer is preferably a solution polymerization method, for example, from the viewpoint of adjusting the molecular weight.

[0068] In solution polymerization, a predetermined organic solvent, monomers, a polymerization initiator, and a chain transfer agent (if necessary) are generally charged into a polymerization tank, and the reaction is carried out by heating for several hours at, for example, the reflux temperature of the organic solvent while stirring. In this case, at least a portion of the organic solvent, monomers, polymerization initiator, and the chain transfer agent (if necessary) may be added sequentially. Alternatively, the reaction may be carried out under a nitrogen atmosphere.

[0069] Examples of organic solvents used in polymerization reactions include aromatic hydrocarbon compounds, aliphatic hydrocarbon compounds, alicyclic hydrocarbon compounds, ester compounds, and ketone compounds. More specifically, organic solvents used in polymerization reactions include aromatic hydrocarbon compounds such as benzene, toluene, ethylbenzene, n-propylbenzene, t-butylbenzene, o-xylene, m-xylene, p-xylene, tetralin, decalin, and aromatic naphtha; aliphatic or alicyclic hydrocarbon compounds such as n-hexane, n-heptane, n-octane, i-octane, n-decane, dipentene, petroleum spirits, petroleum naphtha, and turpentine oil; methyl acetate, ethyl acetate, n-butyl acetate, n-amyl acetate, n-butyl carbitol acetate (diethylene Examples include ester compounds such as glycol monobutyl ether acetate (also known as "propylene glycol methyl ether acetate"), 2-methoxy-1-methylethyl acetate (also known as "propylene glycol methyl ether acetate"), dipropylene glycol methyl ether acetate, 2-hydroxyethyl acetate, 2-butoxyethyl acetate (also known as "butyl cellosolve acetate"), 3-methoxybutyl acetate, and methyl benzoate, as well as ketone compounds such as acetone, methyl ethyl ketone, methyl-i-butyl ketone, isophorone, cyclohexanone, and methylcyclohexanone.

[0070] In the production of prepolymers, it is preferable to use organic solvents that do not easily cause chain transfer during polymerization reactions, such as aromatic hydrocarbon compounds, ester compounds, and ketone compounds.

[0071] During the polymerization reaction, one organic solvent may be used alone, or two or more may be used.

[0072] Examples of polymerization initiators include organic peroxides and azo compounds commonly used in conventional solution polymerization methods. Specific examples of organic peroxides include t-butylperoxy-2-ethylhexanoate, t-butylhydroperoxide, cumenehydroperoxide, dicumylperoxide, benzoylperoxide, lauroylperoxide, caproylperoxide, di-i-propylperoxydicarbonate, di-2-ethylhexylperoxydicarbonate, t-butylperoxypivalate, and 2,2-bis(4,4-di-t-butylperoxy). Examples include chlorohexyl)propane, 2,2-bis(4,4-di-t-amylperoxycyclohexyl)propane, 2,2-bis(4,4-di-t-octylperoxycyclohexyl)propane, 2,2-bis(4,4-di-α-cumylperoxycyclohexyl)propane, 2,2-bis(4,4-di-t-butylperoxycyclohexyl)butane, and 2,2-bis(4,4-di-t-octylperoxycyclohexyl)butane. Specific examples of azo compounds include 2,2'-azobisisobutyronitrile [AIBN], 2,2'-azobis(2,4-dimethylvaleronitrile) [ABVN], 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), 1,1'-azobis(cyclohexane-1-carbonitride), and 2,2'-azobis(isobutyric acid)dimethyl.

[0073] During the polymerization reaction, one polymerization initiator may be used alone, or two or more may be used.

[0074] The amount of polymerization initiator used is not particularly limited and can be appropriately determined, for example, depending on the molecular weight of the target specific (meth)acrylic copolymer.

[0075] In the production of prepolymers, chain transfer agents may be used as needed. Examples of chain transfer agents include cyanoacetic acid, alkyl ester compounds of cyanoacetic acid with 1 to 8 carbon atoms, bromoacetic acid, alkyl ester compounds of bromoacetic acid with 1 to 8 carbon atoms, aromatic compounds represented by α-methylstyrene, anthracene, phenanthrene, fluorene, and 9-phenylfluorene, aromatic nitro compounds represented by p-nitroaniline, nitrobenzene, dinitrobenzene, p-nitrobenzoic acid, p-nitrophenol, and p-nitrotoluene, benzoquinone derivatives represented by benzoquinone and 2,3,5,6-tetramethyl-p-benzoquinone, borane derivatives represented by tributylborane, carbon tetrabromide, and tetra- Examples include halogenated hydrocarbon compounds represented by carbon chloride, 1,1,2,2-tetrabromoethane, tribromoethylene, trichloroethylene, bromotrichloromethane, tribromomethane, and 3-chloro-1-propene; aldehyde compounds represented by chloral and furaldihydes; alkyl mercaptan compounds having 1 to 18 carbon atoms; aromatic mercaptan compounds represented by thiophenol and toluene mercaptan; mercaptoacetic acid; alkyl ester compounds of mercaptoacetic acid having 1 to 10 carbon atoms; hydroxyalkyl mercaptan compounds having 1 to 12 carbon atoms; and terpene compounds represented by pinene and terpinolene.

[0076] When using a chain transfer agent in the production of a prepolymer, the amount of the chain transfer agent used is not particularly limited and can be appropriately determined, for example, depending on the molecular weight of the target specific (meth)acrylic copolymer.

[0077] The polymerization temperature is not particularly limited and can be set appropriately depending on the molecular weight of the target specific (meth)acrylic copolymer.

[0078] The amount of monomer containing hydroxyl groups used is appropriately determined, for example, according to the proportion of (meth)acryloyl groups introduced into the copolymer.

[0079] <<Introduction of (meth)acryloyl group>> In manufacturing method X, an isocyanate group-containing (meth)acrylic monomer is added to the prepolymer obtained above, and a (meth)acryloyl group is introduced into the copolymer by reacting the hydroxyl group of the prepolymer with the isocyanate group of the (meth)acrylic monomer.

[0080] The (meth)acrylic monomers having an isocyanate group are not particularly limited, and examples include 2-isocyanate ethyl acrylate, 2-isocyanate ethyl methacrylate, and various derivatives thereof. Here, a derivative means a compound having an acryloyl group and an isocyanate group at the molecular termini, such as Karenz MOI-EG [component: 2-(2-methacryloyloxyethyloxy)ethyl isocyanate, manufactured by Resonaq Co., Ltd.]. In manufacturing method X, one (meth)acrylic monomer having an isocyanate group may be used alone, or two or more may be used. Commercially available (meth)acrylic monomers containing isocyanate groups can be used. Examples of commercially available (meth)acrylic monomers having an isocyanate group include Karenz AOI [component: 2-isocyanate ethyl acrylate, manufactured by Resonaq Corporation], Karenz MOI [component: 2-isocyanate ethyl methacrylate, manufactured by Resonaq Corporation], Karenz MOI-EG [component: 2-(2-methacryloyloxyethyl oxy)ethyl isocyanate, manufactured by Resonaq Corporation], and Karenz BEI [component: 1,1-(bisacryloyloxymethyl)ethyl isocyanate, manufactured by Resonaq Corporation].

[0081] The amount of (meth)acrylic monomer having an isocyanate group used is appropriately determined, for example, according to the proportion of (meth)acryloyl groups introduced into the copolymer. The amount of (meth)acrylic monomer having an isocyanate group used is preferably in the range of 30 parts by mass or more and 60 parts by mass or less, more preferably in the range of 35 parts by mass or more and 55 parts by mass or less, and even more preferably in the range of 40 parts by mass or more and 50 parts by mass or less, per 100 parts by mass of the prepolymer.

[0082] The specific (meth)acrylic copolymer obtained after the reaction of hydroxyl groups with isocyanate groups is preferably free of residual hydroxyl groups, for example, from the viewpoint of maintaining the transparency of the coated article. If hydroxyl groups remain in the specific (meth)acrylic copolymer, the coating composition and / or the coating layer may become more susceptible to water absorption, and the coating layer may become cloudy. In manufacturing method X, it is preferable to use a crosslinking catalyst from the viewpoint of promoting the reaction between hydroxyl groups and isocyanate groups and suppressing the residue of hydroxyl groups. The crosslinking catalyst is not particularly limited and includes, for example, imidazole compounds represented by 1,2-dimethylimidazole, 1-benzyl-2-methylimidazole, 1-benzyl-2-phenylimidazole, and 2,3-dihydro-1H-pyrrolo[1,2-a]benzimidazole; organometallic compounds represented by dioctyl tin dilaurate (DOTDL), dibutyl tin dilaurate, bismuth carboxylate, and 1,3-diacetoxytetrabutylstanoxane; and tertiary amine compounds represented by triethylenediamine and N-methylmorpholine. In manufacturing method X, when a crosslinking catalyst is used, one type of crosslinking catalyst may be used alone, or two or more types may be used. Commercially available products can be used as crosslinking catalysts. Examples of commercially available crosslinking catalysts include "DBU" from Sunapro Co., Ltd., "ADEKA Stab OT-1" from ADEKA Corporation, and "Curesol 1B2MZ," "Curesol 1B2PZ," "Curesol TBZ," and "Curesol 1,2DMZ" (all are trade names) from Shikoku Chemicals, Inc. The above terms, "Adekastab" and "Curezol," are both registered trademarks.

[0083] In manufacturing method X, when a crosslinking catalyst is used, the amount of the crosslinking catalyst used is not particularly limited and can be appropriately set depending on, for example, the reaction temperature and the amount of (meth)acrylic monomer having an isocyanate group used.

[0084] Furthermore, in manufacturing method X, it is preferable to use (meth)acrylic acid for polymerization of the prepolymer, and more preferable to use methacrylic acid, from the viewpoint of promoting the reaction between hydroxyl groups and isocyanate groups and suppressing the persistence of hydroxyl groups.

[0085] In manufacturing method X, for example, the amount of monomer having a hydroxyl group used for polymerization of the prepolymer and the amount of (meth)acrylic monomer having an isocyanate group used for introducing (meth)acryloyl groups into the copolymer can be adjusted to a range of 20 mol% to 40 mol% relative to the total constituent units of the specific (meth)acrylic copolymer. More specifically, increasing the amount of monomers containing hydroxyl groups in the prepolymer and increasing the amount of (meth)acrylic monomers containing isocyanate groups used to introduce (meth)acryloyl groups into the prepolymer can increase the content of constituent unit (c) in a specific (meth)acrylic copolymer. Conversely, decreasing the amount of monomers containing hydroxyl groups in the prepolymer and decreasing the amount of (meth)acrylic monomers containing isocyanate groups used to introduce (meth)acryloyl groups into the prepolymer can decrease the content of constituent unit (c) in a specific (meth)acrylic copolymer.

[0086] The temperature at which the hydroxyl groups of the prepolymer react with the isocyanate groups of the (meth)acrylic monomer is not particularly limited and can be set appropriately depending on the reaction time and the amount of (meth)acrylic monomer having isocyanate groups used.

[0087] [Photoinitiator] The coating composition of this disclosure comprises a photoinitiator. When a coating composition applied to a substrate is irradiated with active light (e.g., ultraviolet light), the photoinitiator absorbs the light and generates initiator species such as radicals and cations. The generated initiator species react with (meth)acryloyl groups, and further reactions occur between (meth)acryloyl groups, leading to polymerization and curing to form a coating layer.

[0088] The type of photoinitiator is not particularly limited. The photoinitiator may be a photoradical initiator or a photocationic initiator, but a photoradical initiator is preferred. Examples of photoinitiators include photopolymerization initiators having an oxime ester structure (so-called oxime-based photopolymerization initiators), photopolymerization initiators having an α-aminoalkylphenone structure (so-called α-aminoalkylphenone-based photopolymerization initiators), photopolymerization initiators having an α-hydroxyalkylphenone structure (so-called α-hydroxyalkylphenone-based polymerization initiators), photopolymerization initiators having an acylphosphine oxide structure (so-called acylphosphine oxide-based photopolymerization initiators), and photopolymerization initiators having an N-phenylglycine structure (so-called N-phenylglycine-based photopolymerization initiators).

[0089] Commercially available photoinitiators can be used. Examples of commercially available photoinitiators include Omnirad 184 (components: 1-hydroxycyclohexylphenyl ketone, alkylphenone-based photopolymerization initiator, manufactured by IGM Resins BV), Omnirad 651 (components: 2,2-dimethoxy-2-phenylacetophenone, alkylphenone-based photopolymerization initiator, manufactured by IGM Resins BV), and Omnirad TPO N (components: 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, acylphosphine oxide-based photopolymerization initiator, manufactured by IGM Resins BV). Please note that "Omnirad" is a registered trademark.

[0090] The coating compositions of this disclosure may contain one photoinitiator alone or two or more photoinitiators.

[0091] The photoinitiator content in the coating composition of this disclosure is not particularly limited, but for example, from the viewpoint of the blocking resistance of the coating layer, it is preferably in the range of 0.5 parts by mass to 15 parts by mass, and more preferably in the range of 1 part by mass to 7 parts by mass, per 100 parts by mass of the specific (meth)acrylic copolymer.

[0092] [Organic solvents] The coating compositions of this disclosure preferably contain an organic solvent. The coating composition of this disclosure may have improved coating properties by including an organic solvent.

[0093] The type of organic solvent is not particularly limited. Examples of organic solvents include those similar to those used in the polymerization reaction of the prepolymer mentioned above. If the substrate on which the coating layer is formed is a substrate with poor solvent resistance, such as a polycarbonate substrate, it is preferable that the organic solvent used has little effect on the substrate. For example, when the substrate forming the coating layer is a polycarbonate substrate, the organic solvent is preferably at least one selected from the group consisting of propylene glycol methyl ether acetate, butyl cellosolve acetate, butyl carbitol acetate, cyclohexanone, isophorone, propylene glycol methyl ether acetate, and dipropylene glycol methyl ether acetate.

[0094] If the coating composition of this disclosure contains an organic solvent, it may contain one organic solvent alone or two or more organic solvents.

[0095] If the coating composition of this disclosure contains an organic solvent, the content of the organic solvent is not particularly limited and can be set as appropriate depending on the purpose.

[0096] [Other ingredients] The coating composition of this disclosure may, if necessary, contain components other than those described above (so-called other components), as long as they do not impair its effect. Other components include various additives such as antistatic agents.

[0097] If the coating composition of this disclosure contains other components, the content of these other components can be set as appropriate, as long as it does not impair the effects of the coating composition of this disclosure.

[0098] [Coating layer] The coating layer of this disclosure is a coating layer formed by the coating composition of this disclosure. The coating layer of this disclosure includes a cured product of the coating composition of this disclosure. The coating layer of this disclosure is formed by the coating composition of this disclosure and therefore exhibits excellent adhesion to the substrate. Furthermore, because the coating layer of this disclosure is formed by the coating composition of this disclosure, it is less likely to impair the transparency of the coated article. Moreover, because the coating layer of this disclosure is formed by the coating composition of this disclosure, it has a dense crosslinked structure, and for example, even if hand cream adheres to it, the penetration of urea, glycerin, benzoic acid, or their derivatives contained in the hand cream into the layer is suppressed, so transparency tends not to decrease easily.

[0099] The thickness of the coating layer of this disclosure is not particularly limited. For example, the thickness of the coating layer of this disclosure can be appropriately set depending on the material, shape, etc., of the substrate to be coated. Examples of the thickness of the coating layer in this disclosure include 1 μm to 20 μm.

[0100] In this disclosure, "coat layer thickness" refers to the average thickness of the coat layer. The average thickness of the coating layer is determined by the following method. The thickness of the coating layer is measured at 10 randomly selected locations in the thickness direction using a film thickness gauge. The arithmetic mean of the measured values ​​is calculated, and this value is taken as the average thickness of the coating layer.

[0101] The method for forming the coating layer in this disclosure is the same as the method for forming the coating layer in the coated article of this disclosure described later, so a detailed explanation is omitted here.

[0102] [Covered articles] The coated article of this disclosure comprises a substrate containing a polycarbonate resin and a coating layer of this disclosure provided on the surface of the substrate containing the polycarbonate resin. That is, the coated article of this disclosure comprises a coating layer formed by the coating composition of this disclosure on the surface of a substrate containing a polycarbonate resin. The coated articles of this disclosure have excellent adhesion between the substrate and the coated layer, as well as excellent transparency, because the coated layer provided on the surface of a substrate containing polycarbonate resin is formed from the coating composition of this disclosure.

[0103] In the coated articles of this disclosure, the coating layer may be provided on one side of the substrate or on both sides of the substrate. Furthermore, in the coated articles of this disclosure, the coating layer may be provided on a part of the surface of the substrate or on the entire surface of the substrate.

[0104] The base material in the coated article of this disclosure includes a polycarbonate resin. The proportion of polycarbonate resin in the substrate is not particularly limited, but for example, in order to better exhibit the effects of the coating composition of this disclosure, it is preferably 50% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, and may be 100% by mass.

[0105] The substrate in the coated article of this disclosure may contain various additives other than polycarbonate resin, such as plasticizers, colorants (e.g., dyes and pigments), heat stabilizers, light stabilizers, antistatic agents, flame retardants, antioxidants, and fillers.

[0106] The shape and size of the base material in the coated article of this disclosure are not particularly limited and may be set as appropriate depending on the purpose. The base material may have a planar shape or a three-dimensional shape.

[0107] Specific examples of substrates in the coated articles of this disclosure include various electrical equipment, various optical products, vehicle interior parts, and various building materials.

[0108] [Method for manufacturing coated articles] The method for manufacturing the coated article of this disclosure is not particularly limited. The coated articles of this disclosure can be suitably manufactured, for example, by the following methods. A coating composition of the present disclosure is applied to the surface of a substrate containing polycarbonate resin to form a coating film. After drying the formed coating film, it is irradiated with active light. By doing so, a coated article of the present disclosure can be manufactured, having a coating layer of the present disclosure on the surface of a substrate containing polycarbonate resin.

[0109] The method for applying the coating composition is not particularly limited and includes, for example, spin coating, roller coating, bar coating, dip coating, spray coating, curtain coating, die coating, flow coating, gravure coating, and screen printing. Among these, screen printing is preferred because it allows for a thicker application of the coating composition compared to other application methods, enabling the formation of a relatively thick coating layer.

[0110] The amount of coating composition applied is not particularly limited and can be set appropriately, for example, according to the desired thickness of the coating layer.

[0111] The method for drying the coating film is not particularly limited. Examples of drying methods for the coating film include natural drying, heat drying, hot air drying, and vacuum drying. For example, a hot air circulating dryer can be suitably used to dry the coating film. The drying temperature and drying time of the coating film are not particularly limited and are set appropriately according to the thickness of the coating film, the type and amount of solvent contained in the coating film, etc. Drying conditions include, for example, using a hot air circulation dryer and drying at 70°C to 100°C for 30 to 90 minutes.

[0112] Examples of active light include ultraviolet light, visible light, and X-rays, with ultraviolet light being preferred, for example, because the irradiation device is relatively inexpensive. Examples of light sources include low-pressure mercury lamps, medium-pressure mercury lamps, high-pressure mercury lamps, ultra-high-pressure mercury lamps, chemical lamps, metal halide lamps, and light-emitting diodes (LEDs). The irradiation intensity is not particularly limited, but for example, an irradiation intensity of 100 mW / cm² of light in the wavelength range effective for activating the photoinitiator is... 2 ~150mW / cm 2 It is preferable that this be the case. The irradiation time is not particularly limited and can be set as appropriate depending on, for example, the irradiation intensity, the composition of the coating composition, etc. For example, the irradiation time can be expressed as the product of irradiation intensity and irradiation time, resulting in an integrated light quantity of 500 mJ / cm². 2 ~1000 mJ / cm 2 It is preferable to set it so that it is as follows. [Examples]

[0113] The coating compositions, coating layers, and coated articles of this disclosure will be described in more detail below with reference to examples. This disclosure is not limited to the following examples unless it exceeds the spirit of the disclosure.

[0114] [Production of (meth)acrylic copolymers] <Manufacturing example A-1b> (1) Production of prepolymer A-1a 80 parts by mass of propylene glycol methyl ether acetate [organic solvent] were added to a reactor equipped with a thermometer, a stirrer, and a reflux condenser. Next, 63.1 parts by mass of methyl methacrylate [MMA], an alkyl (meth)acrylate monomer, 35.0 parts by mass of 2-hydroxyethyl acrylate [2HEA], a monomer having a hydroxyl group, and 1.9 parts by mass of dimethylaminoethyl methacrylate [DM], a monomer having an amino group were added to another container and mixed to obtain a monomer mixture. Next, 1.20 parts by mass of 2,2'-dimethyl 2,2'-azobis(isobutyrate) [polymerization initiator] and 20 parts by mass of propylene glycol methyl ether acetate [organic solvent] were added to another container and mixed to obtain a polymerization initiator solution. Next, after raising the temperature of the reactor to 90°C, the monomer mixture and the polymerization initiator solution were added dropwise to the reactor over 150 minutes while stirring the organic solvent in the reactor. After dropwise addition, the contents of the reactor were reacted for 210 minutes to obtain prepolymer A-1a.

[0115] (2) Production of (meth)acrylic copolymer A-1b Next, (meth)acryloyl groups were introduced into the side chains of the copolymer. To the reactor containing prepolymer A-1a, 0.019 parts by mass of dioctyl tin dilaurate [product name: ADEKA Stab OT-1, manufactured by ADEKA Corporation] was added as a crosslinking catalyst. Next, while stirring the contents of the reactor, 45.4 parts by mass of 2-isocyanate ethyl methacrylate [product name: Karenz MOI, manufactured by Resonac Corporation], a (meth)acrylic monomer having an isocyanate group, was added dropwise to the reactor over 60 minutes. After the dropwise addition, the contents of the reactor were reacted for 90 minutes to obtain a solution of (meth)acrylic copolymer A-1b.

[0116] <Manufacturing example A-2b> (1) Production of prepolymer A-2a Except for changing the monomer composition of the prepolymer to the monomer composition shown in Table 1, the same procedure as in the production of prepolymer A-1a was performed to obtain prepolymer A-2a.

[0117] (2) Production of (meth)acrylic copolymer A-2b The same procedure as for the production of (meth)acrylic copolymer A-1b was followed to obtain a solution of (meth)acrylic copolymer A-2b, except that precopolymer A-2a was used instead of precopolymer A-1a.

[0118] <Manufacturing example A-3b> (1) Production of prepolymer A-3a Except for changing the monomer composition of the prepolymer to the monomer composition shown in Table 1, the same procedure as in the production of prepolymer A-1a was performed to obtain prepolymer A-3a.

[0119] (2) Production of (meth)acrylic copolymer A-3b The same procedure as for the production of (meth)acrylic copolymer A-1b was followed to obtain a solution of (meth)acrylic copolymer A-3b, except that precopolymer A-3a was used instead of precopolymer A-1a.

[0120] <Manufacturing example A-4b> (1) Production of prepolymer A-3a Except for changing the monomer composition of the prepolymer to the monomer composition shown in Table 1, the same procedure as in the production of prepolymer A-1a was performed to obtain prepolymer A-3a.

[0121] (2) Production of (meth)acrylic copolymer A-4b A solution of (meth)acrylic copolymer A-4b was obtained by performing the same procedure as for the production of (meth)acrylic copolymer A-1b, except that precopolymer A-3a was used instead of precopolymer A-1a, and the amount of (meth)acrylic monomer having an isocyanate group used per 100 parts by mass of precopolymer was changed to the amount shown in Table 2.

[0122] <Manufacturing example A-5b> (1) Production of prepolymer A-3a Except for changing the monomer composition of the prepolymer to the monomer composition shown in Table 1, the same procedure as in the production of prepolymer A-1a was performed to obtain prepolymer A-3a.

[0123] (2) Production of (meth)acrylic copolymer A-5b A solution of (meth)acrylic copolymer A-5b was obtained by performing the same procedure as for the production of (meth)acrylic copolymer A-1b, except that precopolymer A-3a was used instead of precopolymer A-1a, and the amount of (meth)acrylic monomer having an isocyanate group used per 100 parts by mass of precopolymer was changed to the amount shown in Table 2.

[0124] <Manufacturing example A-6b> (1) Production of prepolymer A-3a Except for changing the monomer composition of the prepolymer to the monomer composition shown in Table 1, the same procedure as in the production of prepolymer A-1a was performed to obtain prepolymer A-3a.

[0125] (2) Production of (meth)acrylic copolymer A-6b A solution of (meth)acrylic copolymer A-6b was obtained by performing the same procedure as for the production of (meth)acrylic copolymer A-1b, except that precopolymer A-3a was used instead of precopolymer A-1a, and the amount of (meth)acrylic monomer having an isocyanate group used per 100 parts by mass of precopolymer was changed to the amount shown in Table 2.

[0126] <Manufacturing example A-7b> (1) Production of prepolymer A-4a Except for changing the monomer composition of the prepolymer to the monomer composition shown in Table 1, the same procedure as in the production of prepolymer A-1a was performed to obtain prepolymer A-4a.

[0127] (2) Production of (meth)acrylic copolymer A-7b The same procedure as for the production of (meth)acrylic copolymer A-1b was followed to obtain a solution of (meth)acrylic copolymer A-7b, except that precopolymer A-4a was used instead of precopolymer A-1a.

[0128] <Manufacturing example A-8b> (1) Production of prepolymer A-5a Except for changing the monomer composition of the prepolymer to the monomer composition shown in Table 1, the same procedure as in the production of prepolymer A-1a was performed to obtain prepolymer A-5a.

[0129] (2) Production of (meth)acrylic copolymer A-8b The same procedure as for the production of (meth)acrylic copolymer A-1b was followed to obtain a solution of (meth)acrylic copolymer A-8b, except that precopolymer A-5a was used instead of precopolymer A-1a.

[0130] <Manufacturing example A-9b> (1) Production of prepolymer A-6a Except for changing the monomer composition of the prepolymer to the monomer composition shown in Table 1, the same procedure as in the production of prepolymer A-1a was performed to obtain prepolymer A-6a.

[0131] (2) Production of (meth)acrylic copolymer A-9b Except for using prepolymer A-6a instead of prepolymer A-1a, and changing the amount of (meth)acrylic monomer having an isocyanate group per 100 parts by mass of prepolymer to the amount shown in Table 2, the same procedure as for the production of (meth)acrylic copolymer A-1b was followed to obtain a solution of (meth)acrylic copolymer A-9b.

[0132] <Manufacturing example A-10b> (1) Production of prepolymer A-7a Except for changing the monomer composition of the prepolymer to the monomer composition shown in Table 1, the same procedure as in the production of prepolymer A-1a was performed to obtain prepolymer A-7a.

[0133] (2) Production of (meth)acrylic copolymer A-10b A solution of (meth)acrylic copolymer A-10b was obtained by performing the same procedure as for the production of (meth)acrylic copolymer A-1b, except that precopolymer A-7a was used instead of precopolymer A-1a, and the amount of (meth)acrylic monomer having an isocyanate group used per 100 parts by mass of precopolymer was changed to the amount shown in Table 2.

[0134] <Manufacturing example A-11b> (1) Production of prepolymer A-8a Except for changing the monomer composition of the prepolymer to the monomer composition shown in Table 1, and adjusting at least one of the amounts of organic solvent and polymerization initiator used so that the weight-average molecular weight of the (meth)acrylic copolymer is as shown in Table 2, the same procedure as for the production of prepolymer A-1a was performed to obtain prepolymer A-8a.

[0135] (2) Production of (meth)acrylic copolymer A-11b A solution of (meth)acrylic copolymer A-11b was obtained by performing the same procedure as for the production of (meth)acrylic copolymer A-1b, except that precopolymer A-8a was used instead of precopolymer A-1a.

[0136] <Manufacturing example A-12b> (1) Production of prepolymer A-9a Except for changing the monomer composition of the prepolymer to the monomer composition shown in Table 1, and adjusting at least one of the amounts of organic solvent and polymerization initiator used so that the weight-average molecular weight of the (meth)acrylic copolymer is as shown in Table 2, the same procedure as for the production of prepolymer A-1a was performed to obtain prepolymer A-9a.

[0137] (2) Production of (meth)acrylic copolymer A-12b The same procedure as for the production of (meth)acrylic copolymer A-1b was followed to obtain a solution of (meth)acrylic copolymer A-12b, except that precopolymer A-9a was used instead of precopolymer A-1a.

[0138] <Manufacturing example A-13b> (1) Production of prepolymer A-10a Except for changing the monomer composition of the prepolymer to the monomer composition shown in Table 1, the same procedure as in the production of prepolymer A-1a was performed to obtain prepolymer A-10a.

[0139] (2) Production of (meth)acrylic copolymer A-13b A solution of (meth)acrylic copolymer A-13b was obtained by performing the same procedure as for the production of (meth)acrylic copolymer A-1b, except that precopolymer A-10a was used instead of precopolymer A-1a, and the amount of (meth)acrylic monomer having an isocyanate group used per 100 parts by mass of precopolymer was changed to the amount shown in Table 2.

[0140] <Manufacturing example A-14b> (1) Production of prepolymer A-11a Except for changing the monomer composition of the prepolymer to the monomer composition shown in Table 1, the same procedure as in the production of prepolymer A-1a was performed to obtain prepolymer A-11a.

[0141] (2) Production of (meth)acrylic copolymer A-14b A solution of (meth)acrylic copolymer A-14b was obtained by performing the same procedure as for the production of (meth)acrylic copolymer A-1b, except that precopolymer A-11a was used instead of precopolymer A-1a.

[0142] <Manufacturing example A-15b> (1) Production of prepolymer A-12a Except for changing the monomer composition of the prepolymer to the monomer composition shown in Table 1, the same procedure as in the production of prepolymer A-1a was performed to obtain prepolymer A-12a.

[0143] (2) Production of (meth)acrylic copolymer A-15b A solution of (meth)acrylic copolymer A-15b was obtained by performing the same procedure as for the production of (meth)acrylic copolymer A-1b, except that precopolymer A-12a was used instead of precopolymer A-1a, and the amount of (meth)acrylic monomer having an isocyanate group used per 100 parts by mass of precopolymer was changed to the amount shown in Table 2.

[0144] Table 1 shows the monomer compositions of precopolymers A-1a to A-12a. Table 2 shows the types of prepolymers used in the production of (meth)acrylic copolymers A-1b to A-15b, the amount of (meth)acrylic monomers having isocyanate groups used per 100 parts by mass of prepolymer in the production of (meth)acrylic copolymers A-1b to A-15b, the content of constituent unit (c) in (meth)acrylic copolymers A-1b to A-15b, and the weight-average molecular weight (denoted as "Mw") of (meth)acrylic copolymers A-1b to A-15b.

[0145] The weight-average molecular weights of (meth)acrylic copolymers A-1b to A-15b were measured using the same method as described above for measuring the weight-average molecular weight of the specific (meth)acrylic copolymers.

[0146] The content of constituent unit (c) in (meth)acrylic copolymers A-1b to A-15b was calculated from the formulations described in the corresponding manufacturing examples. Below, the method for determining the content of constituent unit (c) in (meth)acrylic copolymers will be explained in detail, using (meth)acrylic copolymer A-1b as an example.

[0147] The monomer composition of the precopolymer A-1a of (meth)acrylic copolymer A-1b is 63.1 parts by mass of MMA (formula weight: 100.12), 35.0 parts by mass of 2HEA (formula weight: 116.12), and 1.9 parts by mass of DM (formula weight: 157.21). When the parts by mass of each monomer are converted to grams, that is, when 100 g of precopolymer A-1a is obtained, the number of moles of each constituent unit is 0.6302 moles for MMA, 0.3014 moles for 2HEA, and 0.0121 moles for DM, for a total of 0.9437 moles. From this, when the proportion of constituent units derived from each monomer contained in precopolymer A-1a is converted to mole percent, it is 66.8 mol% for MMA, 31.9 mol% for 2HEA, and 1.3 mol% for DM.

[0148] Next, the composition obtained when 2-isocyanate ethyl methacrylate [MOI], a (meth)acrylic monomer having an isocyanate group, is reacted with prepolymer A-1a will be examined in terms of parts by mass, moles, and mole percent. (Meth)acrylic copolymer A-1b was obtained by adding 45.4 parts by mass of MOI (formula weight: 155.15) to 100 parts by mass of precopolymer A-1a. In other words, 45.4 g of MOI (0.2926 moles (≒45.4 / 155.15)) was reacted with 100 g of precopolymer A-1a (of which 0.301 moles are constituent units derived from 2HEA). Here, the reaction between 2HEA and MOI proceeds almost 100% in the presence of a crosslinking catalyst. Therefore, of the 0.3014 moles of constituent units derived from 2HEA contained in precopolymer A-1a, 0.2926 moles reacted with MOI, and the remainder remained as constituent units derived from 2HEA in the copolymer. Therefore, while MOI reacted 100%, 2HEA reacted 97% [≒(0.2926 / 0.3014)×100]. As mentioned above, the proportion of constituent units derived from 2HEA in precopolymer A-1a is 31.9 mol%, of which 97% react with MOI.

[0149] (Meth)acrylic copolymer A-1b includes a constituent unit derived from MMA, a constituent unit derived from 2HEA (i.e., a constituent unit derived from 2HEA that has not reacted with MOI), a constituent unit derived from DM, and a constituent unit derived from a monomer having a site where the hydroxyl group of 2HEA reacts with the isocyanate group of MOI (a so-called urethane bond) and a (meth)acryloyl group. The above constituent unit derived from the monomer having a urethane bond and a (meth)acryloyl group corresponds to constituent unit (c) in this disclosure. The formula weight of the constituent unit derived from the monomer having a urethane bond and a (meth)acryloyl group is 271.27. When the parts by mass of each constituent unit contained in (meth)acrylic copolymer A-1b are determined, for 100 parts by mass of precopolymer A-1a, the constituent units derived from MMA are 63.1 parts by mass, the constituent units derived from 2HEA are 1.02 parts by mass [≒(0.3014-0.2926)×116.12], the constituent units derived from DM are 1.9 parts by mass, and the constituent units derived from monomers having urethane bonds and (meth)acryloyl groups are 79.37 parts by mass [≒0.2926×271.27]. From these sums, it can be seen that when 100 parts by mass of precopolymer A-1a is reacted with MOI, 145.36 parts by mass of (meth)acrylic copolymer A-1b is obtained.

[0150] As mentioned above, the amount of constituent unit (a) contained in (meth)acrylic copolymer A-1b, i.e., the constituent unit derived from MMA, is 63.1 parts by mass. Therefore, (meth)acrylic copolymer A-1b contains 43.4% by mass (≒63.1 / 145.36) of constituent unit (a). Similarly, the amount of constituent unit (b) contained in (meth)acrylic copolymer A-1b, i.e., the constituent unit derived from DM, is 1.9 parts by mass, as described above. Therefore, (meth)acrylic copolymer A-1b contains 1.3% by mass (≒1.9 / 145.36) of constituent unit (b).

[0151] When the number of moles of each constituent unit contained in (meth)acrylic copolymer A-1b is determined, the constituent units derived from MMA amount to 0.6302 moles [≒63.1 / 100.12], the constituent units derived from 2HEA amount to 0.0088 moles [≒1.02 / 116.12], the constituent units derived from DM amount to 0.0121 moles [≒1.9 / 157.21], and the constituent units derived from monomers having urethane bonds and (meth)acryloyl groups amount to 0.2926 moles [≒79.37 / 271.27]. From these sums, the total number of moles of constituent units contained in 145.36 parts by mass of (meth)acrylic copolymer A-1b is 0.9437 moles. Therefore, the content of constituent unit (c) in (meth)acrylic copolymer A-1b is 31 mol% [≒0.2926 / 0.9437].

[0152] Of the (meth)acrylic copolymers A-1b to A-15b, (meth)acrylic copolymers A-1b to A-12b correspond to the specified (meth)acrylic copolymers in this disclosure.

[0153] [Table 1]

[0154] Details of each monomer listed in Table 1 are as follows: <(meth)acrylate alkyl monomer> "MMA": Methyl methacrylate "EA": Ethyl acrylate <Monomers containing an amino group> "DM": Dimethylaminoethyl methacrylate "DE": Diethylaminoethyl methacrylate "DMAPMA": N-(3-dimethylaminopropyl)methacrylamide <Monomers containing hydroxyl groups> "2HEA": 2-hydroxyethyl acrylate <Monomers containing a carboxyl group> "MAA": Methacrylic acid

[0155] In Table 1, a "-" in the monomer composition column indicates that the monomer corresponding to that column was not used.

[0156] [Table 2]

[0157] [Preparation of coating composition] [Example 1] To the solution of (meth)acrylic copolymer A-1b obtained above, 3.7 parts by mass of a photoinitiator (trade name: Omnirad 184, manufactured by IGM Resins BV) and 40 parts by mass of propylene glycol methyl ether acetate (organic solvent) were added per 100 parts by mass of (meth)acrylic copolymer A-1b (i.e., the solid content of the solution of (meth)acrylic copolymer A-1b), and the mixture was stirred to obtain the coating composition of Example 1.

[0158] [Examples 2-12] In Examples 2 to 12, the same procedure as in Example 1 was followed, except that the type of (meth)acrylic copolymer was changed to the types shown in Table 3, to obtain each of the coating compositions in Examples 2 to 12.

[0159] [Comparative Examples 1-3] In Comparative Examples 1 to 3, the same procedure as in Example 1 was followed, except that the type of (meth)acrylic copolymer was changed to the types shown in Table 3, to obtain each of the coating compositions in Comparative Examples 1 to 3.

[0160] [Preparation of test specimens] A coating composition was applied to the surface of a polycarbonate resin sheet (product name: Panlight® PC-1151, size: 5cm x 7cm, thickness: 0.5mm, manufactured by Teijin Limited) using a doctor blade with a gap of 30μm to form a coating film. The formed coating film was then dried in a hot air circulation dryer at a drying temperature of 80°C for 60 minutes. After drying, the film was illuminated with a high-pressure mercury lamp at an illuminance of 120mW / cm².2 and integrated light intensity 700 mJcm 2 Ultraviolet light was irradiated under these conditions. Based on the above, a test specimen was obtained having a coating layer on the surface of a substrate containing polycarbonate resin. The following evaluation tests were performed using the obtained test specimen.

[0161] [evaluation] 1. Adhesion (cross-cut test) A cross-cut test was performed on the coating layer of the test specimens obtained above, in accordance with JIS K 5600-5-6:1999. In the cross-cut test, cuts were made in the coating layer at 1 mm intervals to form 100 1 mm square grids. After the test, the number of detached grids was measured and evaluated according to the evaluation criteria below. The evaluation results are shown in Table 3. If the evaluation result is "A" or "B", it is judged that the coating layer has excellent adhesion to the substrate. An evaluation result of "A" is most preferable.

[0162] -Evaluation Criteria- A: The number of detached grids was 0. B: The number of detached grids was in the range of 1 to 10. C: The number of detached grids was 11 or more.

[0163] 2. Transparency (boiling water test) The test specimens obtained as described above were immersed in boiling water for 30 minutes and then removed from the water. The haze (in %) of these removed test specimens was measured using a haze meter (model number: NDH 5000SP, manufactured by Nippon Denshoku Industries Co., Ltd.) and evaluated according to the evaluation criteria below. The evaluation results are shown in Table 3. If the evaluation result was "A", it was determined that the coating layer was unlikely to impair the transparency of the coated article.

[0164] -Evaluation Criteria- A: The haze was less than 3%. B: The haze level was 3% or higher.

[0165] [Table 3]

[0166] The results shown in Table 3 clearly demonstrate that the coating layers formed by the coating compositions of Examples 1 to 12 exhibit excellent adhesion to the substrate. Furthermore, test specimens (so-called coated articles) with coating layers formed by the coating compositions of Examples 1 to 12 on their surfaces exhibited low haze values, indicating that the coating layer did not significantly impair the transparency of the test specimen. On the other hand, it was found that the coating layers formed by the coating compositions of Comparative Examples 1 and 3 had inferior adhesion to the substrate compared to the coating layers formed by the coating compositions of the Examples. Furthermore, it was found that the coating layer formed by the coating composition of Comparative Example 2 was more likely to impair the transparency of the test specimen compared to the coating layer formed by the coating composition of the Examples.

Claims

1. A (meth)acrylic copolymer comprising a constituent unit (a) derived from an alkyl (meth)acrylate monomer, a constituent unit (b) derived from a monomer having an amino group, and a constituent unit (c) having a urethane bond and a (meth)acryloyl group, and which is different from constituent units (a) and (b), wherein the content of constituent unit (b) is in the range of 1.0% by mass or more and 2.5% by mass or less of the total constituent units, the content of constituent unit (c) is in the range of 20 mol% or more and 40 mol% or less of the total constituent units, and the weight-average molecular weight is in the range of 20,000 or more and 100,000 or less, Photoinitiator and A coating composition containing the following:

2. The coating composition according to claim 1, wherein the monomer having an amino group is a monomer having at least one of a dimethylamino group and a diethylamino group.

3. The coating composition according to claim 1, wherein the monomer having an amino group comprises at least one selected from the group consisting of dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, and N-(3-dimethylaminopropyl)methacrylamide.

4. The coating composition according to claim 1, wherein the alkyl (meth)acrylate monomer is at least one selected from the group consisting of methyl (meth)acrylate and ethyl (meth)acrylate, and the content of the constituent unit (a) is in the range of 40.0% by mass or more and 60.0% by mass or less with respect to the total constituent units of the (meth)acrylic copolymer.

5. The coating composition according to claim 4, wherein the alkyl (meth)acrylate monomer is methyl methacrylate.

6. A coating layer formed by the coating composition according to any one of claims 1 to 5.

7. A base material containing polycarbonate resin, A coating layer according to claim 6 provided on the surface of the substrate containing the polycarbonate resin, A covering article equipped with the following features.

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