JP2020059783A - Ultraviolet curing-type coating material composition, cured film and article comprising cured film - Google Patents

Abstract

To provide an ultraviolet curing-type coating material composition for coloration that is excellent in ultraviolet curability and produces a cured film having good appearance.SOLUTION: The ultraviolet curing-type coating material composition includes (A) a (meth)acrylic resin, (B) a photopolymerization initiator and (C) pigment, in which the (meth)acrylic resin has a (meth)acryloyl group in the side chain; and the pigment includes at least one kind selected from the group consisting of coloring pigments and brilliant pigments. In the composition, the pigment is included so that a cured film having a film thickness of 5 μm has a total light transmittance of 0% to 60%; a content of the (meth)acryloyl group is 1 mmol to 10 mmol per 1 g of the (meth)acrylic resin; an acid value of the (meth)acrylic resin is 0 mgKOH/g to 10 mgKOH/g; a weight average molecular weight of the (meth)acrylic resin is 2,000 to 60,000; and the (meth)acrylic resin includes a (meth)acrylic copolymer having a first functional group in the side chain and a (meth)acrylic monomer having a second functional group reactive with the first functional group.SELECTED DRAWING: None

Description

The present invention relates to an ultraviolet curable coating composition.

When using a one-part thermosetting paint or a two-part thermosetting paint that requires a post-painting heating step in the application of colored paint, it takes a long heating time to dry and cure the coating film, and the process takes a long time. There is.

Therefore, in consideration of the environment, paints containing a color pigment or a bright pigment have recently been proposed which are curable by an active energy ray (mainly ultraviolet ray), which has a short process time.
However, UV-curable paints for coloring that contain color pigments and bright pigments, because the color pigments and bright pigments contained in the coating film reflect and absorb UV rays during UV curing, the UV rays reach deep inside the coating film. However, there is a tendency for problems such as insufficient curing to occur and curing failure to occur.
Further, since ultraviolet rays do not reach uniformly and the coating film surface is not uniformly cured, “curing unevenness” occurs, which causes a problem that a cured film has a poor appearance.

Patent Document 1 discloses a coating material containing a color pigment and a binder resin ((meth) acrylic resin) for dispersion in which the color pigment is dispersed.

Patent Document 2 contains at least one of mono-, bis- or polyvalent aliphatic or aromatic glycidyl ethers, titanium dioxide (pigment), an iodonium hexafluorophosphate salt as a photoinitiator, and a sensitizer compound. , UV curable cationically polymerizable compositions are disclosed.

Patent Document 3 discloses poly [(meth) acryloyloxyalkyl] isocyanurate (A), polyfunctional (meth) acrylate (B) having 4 or more (meth) acryloyl groups, acrylic resin (C), and An active energy ray-curable coating composition containing at least one pigment (D) selected from the group consisting of a coloring pigment and a bright pigment, wherein the acrylic resin (C) has a weight average molecular weight of 5 Active energy ray curable coating compositions having a solubility parameter in the range of 3,000 to 30,000 and a solubility parameter in the range of 9.0 to 11.5 are disclosed.

JP2012-92154A Special table 2002-513078 Patent 6279800

However, the inventions disclosed in the above-mentioned prior art documents require strong UV irradiation for sufficient curing (ultraviolet curability is insufficient), and increasing the addition amount of the pigment causes UV curing. There is a concern that it will be hindered (Patent Documents 1 and 3). Further, the cationically polymerizable energy ray-curable coating material has a slow reaction rate as compared with the radical polymerization reaction, and thus there is a concern that the curing step takes a long time (Patent Document 2). Incidentally, it goes without saying that such disadvantages are not described in the prior art documents.

As described above, the study of the ultraviolet curable coating composition for coloring has been actively conducted. However, it has been difficult to obtain a coating composition having excellent ultraviolet curability and a cured film having a good appearance.

The present invention provides an ultraviolet curable coating composition for coloring, which is excellent in ultraviolet curability and has a good appearance of a cured film obtained.

The inventors of the present invention have conducted extensive studies in order to achieve the above-mentioned object, and the ultraviolet-curable coating composition obtained by the means shown below has excellent ultraviolet curability and is a cured product obtained from the coating composition. It was found that the film had a good appearance. The present specification provides the following means based on such findings.

The present invention that can solve the above-mentioned problems is an ultraviolet-curable coating composition shown below.
The present invention
Contains a (meth) acrylic resin (A), a photopolymerization initiator (B) and a pigment (C),
The (meth) acrylic resin has a (meth) acryloyl group in the side chain,
The pigment contains at least one selected from the group consisting of a coloring pigment and a bright pigment,
It is an ultraviolet-curable coating composition.

Hereinafter, embodiments of the present invention will be described in detail.
In the present specification, the notation “a to b” in the description of the numerical range means a to b inclusive, unless otherwise specified. For example, “1 to 5 mass%” means “1 mass% or more and 5 mass% or less”.

In the description of the group (atomic group) in the present specification, the notation of whether it is substituted or unsubstituted includes both those having no substituent and those having a substituent. For example, the “alkyl group” includes not only an alkyl group having no substituent (unsubstituted alkyl group) but also an alkyl group having a substituent (substituted alkyl group).

The expression "(meth) acrylic" in the present specification represents a concept including both acrylic and methacrylic. The same applies to similar notations such as “(meth) acrylate”.

<Ultraviolet curable coating composition>
The ultraviolet curable coating composition of the present embodiment,
An ultraviolet curable coating composition,
Contains a (meth) acrylic resin (A), a photopolymerization initiator (B) and a pigment (C),
The (meth) acrylic resin has a (meth) acryloyl group in the side chain,
The pigment contains at least one selected from the group consisting of a coloring pigment and a bright pigment,
It is an ultraviolet-curable coating composition.

In addition, below, the (meth) acrylic resin which has a (meth) acryloyl group in a side chain is also described as "resin (A)." The photopolymerization initiator is also referred to as "initiator (B)", and the pigment containing at least one selected from the group consisting of color pigments and bright pigments is also referred to as "pigment (C)".

The ultraviolet-curable coating composition disclosed in the present specification (hereinafter, also referred to as the present coating composition) is a coating composition having good ultraviolet curability and a cured film having a good appearance. The reason for this is not entirely clear, but it can be explained as follows.

The coating composition contains a resin (A), an initiator (B) and a pigment (C). The resin (A) is a component for forming a cured film, and when a coating film obtained by applying the present coating composition is irradiated with ultraviolet rays, the initiator (B) forms an initiation radical and the resin (A) has a side chain. The (meth) acryloyl group contained in (3) radically polymerizes to form a cured film. Further, the pigment (C) contributes to coloring of the cured film.

On the other hand, as described above, generally, the ultraviolet curable coating composition for coloring has a problem in ultraviolet curability. The pigment reflects or absorbs light having a wavelength in the ultraviolet region, which is necessary for the initiator to form an initiation radical, and thus interferes with ultraviolet curing. In particular, when the amount of pigment is large, the ultraviolet curability tends to be poor.

In addition, in general, an ultraviolet curable coating composition for coloring has a problem that a cured film to be obtained is likely to have poor appearance. This is because the ultraviolet rays are reflected or absorbed by the pigment during ultraviolet curing, so even if the coating film is uniformly irradiated with ultraviolet rays, the parts that cure faster and the parts that cure slowly in the entire coating film. It is assumed that this is due to the occurrence of. That is, the pigment is extruded from the portion where the curing is fast, and the extruded pigment moves to the portion where the curing is slow. Then, a portion where the pigment concentration is low and a portion where the pigment concentration is high are generated in the coating film, and the curing reaction does not proceed uniformly in the entire coating film. As a result, so-called "curing unevenness" occurs and it is presumed that the appearance becomes poor.

Further, in the case of an ultraviolet-curable coating composition in which only a polyfunctional (meth) acrylate compound other than the resin (A) is a cured film forming component, curing contraction occurs during ultraviolet curing, and the pigment easily moves to cure. It is considered that the appearance of the film is apt to occur.

Therefore, in the present coating composition, the resin (A) is used to make it difficult for the pigment (C) to move due to a non-uniform curing reaction or curing shrinkage during ultraviolet curing. In other words, the resin (A) plays a role of preventing migration of the pigment (C) during ultraviolet curing. The mechanism is not entirely clear, but it can be explained as follows.

First, there is a pigment dispersion effect of the resin (A).
The resin (A) has an effect of improving the dispersed state of the pigment (C) as well as the role of the cured film forming component as described above. It is considered that the resin (A) is present around the pigment, prevents the pigments (C) from aggregating with each other, and improves the dispersed state of the pigment (C).
It is considered that the pigment (C) can be uniformly present in the coating film due to the pigment dispersion effect of the resin (A), and migration of the pigment can be prevented during ultraviolet curing. Therefore, it is considered that the pigment density in the coating film is unlikely to occur and the appearance defect is unlikely to occur.

Secondly, the curing characteristics of the resin (A) can be mentioned.
The resin (A) has a characteristic that curing shrinkage hardly occurs. This is because the distance between the (meth) acryloyl groups in the resin (A) is larger than the distance between the (meth) acryloyl groups in a so-called general polyfunctional (meth) acrylate compound other than the resin (A). This is because there is a tendency.
Therefore, it is considered that the components in the coating film are less likely to flow, and further, the pigment (C) is prevented from moving. Further, since the resin (A) has a (meth) acryloyl group in the side chain, it is presumed that the resin (A) is cured rapidly after being irradiated with ultraviolet rays and the pigment (C) can be made difficult to move.
Therefore, by using the resin (A), the migration of the pigment is suppressed, the density of the pigment concentration in the coating film is less likely to occur, and the appearance of the coating film is improved.

Each component of the coating composition of this embodiment will be described.
[(Meth) acrylic resin (A)]
(Characteristics of resin (A))
The coating composition of this embodiment contains a (meth) acrylic resin having a (meth) acryloyl group in its side chain. As described above, the (meth) acryloyl group described in the present specification includes the concept of both an acryloyl group and a methacryloyl group.

The (meth) acryloyl group contributes to the formation of a cured film by radical polymerization starting from the initiation radical formed from the initiator (B).
Since the acryloyl group has a faster reaction rate than the methacryloyl group, the resin (A) is a (meth) acrylic resin having an acryloyl group in its side chain from the viewpoint of ultraviolet curability and various physical properties of the cured film. Is more preferable.

The content of the (meth) acryloyl group in the resin (A) is 1 mmol to 10 mmol per 1 g of the resin (A), more preferably 1.2 mmol to 5 mmol, and further preferably 1.5 mmol to 4 mmol. Within such a numerical range, the coating composition has a good balance between the curing speed and the curing shrinkage, and a cured film having a good appearance can be obtained. In addition, by setting the value within such a range, the coating film is sufficiently cured, and a cured film having excellent chemical resistance can be obtained.

The content of the (meth) acryloyl group of the resin (A) described in the present specification is determined by isolating and purifying the resin (A) from the present coating composition, and determining the iodine value by a method according to JIS-K-0070. It can be obtained and calculated from the value, or can be calculated by H-NMR measurement.

The number average molecular weight and the weight average molecular weight of the resin (A) affect the dispersibility of the pigment (C) in the coating composition and the migration of the pigment (C) during curing.
The number average molecular weight of the resin (A) is not particularly limited, but is preferably 1,000 to 30,000, more preferably 2,000 to 20,000, and further preferably 3,000 to 10,000. Is. The weight average molecular weight of the resin (A) is not particularly limited, but is preferably 2,000 to 60,000, more preferably 4,000 to 40,000, and further preferably 6,000 to 20. 1,000.
Within such a numerical range, the pigment (C) is stably dispersed, so that the pigment can be prevented from moving during ultraviolet curing, and a cured film having a good appearance can be obtained.

The number average molecular weight and the weight average molecular weight can be measured as standard polystyrene conversion values by gel permeation chromatography (GPC) method.

The acid value of the resin (A) is not particularly limited, but is preferably 0 to 20 mgKOH / g, more preferably 0 to 10 mgKOH / g, and further preferably 0 to 3 mgKOH / g.
The acid value represents the amount of acidic groups of the resin (A). The acidic group has a high affinity for chemicals, especially highly polar chemicals such as sunscreen and cosmetics, and affects the chemical resistance of the cured film.
By setting the acid value within this numerical range, it is possible to obtain a cured film that is not easily affected by acidic groups, has a good cured film appearance, and has good chemical resistance.
The acid value of the resin (A) described in the present specification can be measured according to JIS-K-5601-2-1 by isolating and purifying the resin (A) from the present coating composition.

The content of the resin (A) in the coating composition is preferably 5 to 99% by mass, more preferably 10 to 96% by mass, and more preferably 20 to 20% by mass based on the whole nonvolatile components of the coating composition. It is more preferably 90% by mass.
Within such a numerical range, the pigment (C) in the coating film is prevented from migrating during ultraviolet curing, the coating composition has excellent ultraviolet curability, and a cured film having a good appearance can be obtained.

The resin (A) is not particularly limited as long as it is a (meth) acrylic resin having a (meth) acryloyl group in the side chain, but a commercially available resin or a resin produced by itself can be used. .

When the resin (A) is produced by itself, it is not particularly limited, but for example, it is obtained by introducing a (meth) acryloyl group into a (meth) acrylic copolymer obtained by polymerizing a (meth) acrylate compound. You can

As a method for introducing a (meth) acryloyl group into a side chain of the resin (A), a known method can be used and is not particularly limited, but a (meth) acryl copolymer having a first functional group in a side chain is used. It is preferably obtained by reacting the polymer with a (meth) acrylic monomer having a second functional group that reacts with the first functional group.
In addition, in this specification, a (meth) acrylic-type monomer represents the monomer of (meth) acrylic acid and a (meth) acrylic acid ester.

As an example only, the following general formula (1) shows a schematic diagram of a (meth) acrylic copolymer (a structural formula with a simplified chemical structure), and Table 1 shows a first functional group and a second functional group. An example of the combination of
(X in the general formula (1) represents a first functional group.)

(R ¹ in the table represents hydrogen or a methyl group. Two R ¹ may be the same or different from each other. In each general formula in the table, R ² is a substituted or unsubstituted hydrocarbon. Each of the general formulas in the table may or may not have R ² , and X represents a first functional group.)

In the present specification, the (meth) acrylic copolymer for obtaining the resin (A) means a polymer having a structural unit derived from a (meth) acrylic monomer.

The (meth) acrylic copolymer can be produced according to a known method.
For example, the (meth) acrylic copolymer used in the present invention can be obtained by polymerizing one or more (meth) acrylic monomers in a solvent in the presence of a polymerization initiator and under heating. To be

Further, the (meth) acrylic copolymer may partially contain a structural unit derived from a monomer that is not a (meth) acrylic monomer.

For example, styrene, a structural unit derived from a styrene monomer such as α-methylstyrene, a vinyl monomer such as vinyl acetate and vinyl propionate, an unsaturated carboxylic acid monomer such as itaconic acid, maleic acid, and fumaric acid may be included. Good.

However, from the viewpoint of sufficiently obtaining the effect derived from the (meth) acrylic structure, in the (meth) acrylic copolymer, 50% by mass or more of all structural units are structural units derived from the (meth) acrylic monomer. It is preferable that 80% by mass or more of all structural units are structural units derived from a (meth) acrylic monomer.

The glass transition temperature of the (meth) acrylic copolymer, that is, the glass transition temperature of the main chain of the resin (A) is preferably −20 to 100 ° C., more preferably 20 to 80 ° C. By setting the value within such a range, a cured film having a hardness that is practically no problem can be obtained.

The glass transition temperature in this specification represents the glass transition temperature of the (meth) acrylic copolymer, that is, the glass transition temperature of the main chain of the resin (A).
The glass transition temperature of the (meth) acrylic copolymer can be determined by various methods, for example, it can be determined based on the following formula (known as Fox's formula).
1 / Tg = (W1 / Tg1) + (W2 / Tg2) + (W3 / Tg3) + ... + (Wn / Tgn)

In the formula, Tg is the glass transition temperature (K) of the (meth) acrylic copolymer, W1, W2, W3 ... Wn are the mass fractions of the respective monomers, and Tg1, Tg2, Tg3 ... Tgn are , Glass transitions of homopolymers composed of (meth) acrylic monomers and monomers other than (meth) acrylic monomers corresponding to the mass fractions of the respective monomers other than (meth) acrylic monomers and (meth) acrylic monomers, respectively. The temperature (K) is shown.

(First functional group)
Examples of the first functional group include a glycidyl group, a hydroxyl group, an isocyanate group, and a carboxyl group. Among them, a glycidyl group, a hydroxyl group, and an isocyanate group are preferable from the viewpoint of chemical resistance and ease of synthesis. A (meth) acrylic resin (resin (A)) having a (meth) acryloyl group in its side chain can be obtained by using a (meth) acrylic copolymer having a first functional group such as these. .

The (meth) acrylic copolymer having a first functional group is a copolymer of a monomer having a copolymerizable unsaturated double bond and a first functional group together with a monomer capable of copolymerizing with the monomer. It can be obtained by polymerization. More specifically, a (meth) acrylic monomer having a first functional group represented by the general formula (2) is polymerized alone, or is copolymerized with a monomer or the like copolymerizable with the monomer. You can get it.

(R ¹ and X have the same meanings as in General Formula (1) and Table 1. R ³ represents a substituted or unsubstituted hydrocarbon group. General Formula (2) has R ³ . You may or may not have it.)

The monomer having both the copolymerizable unsaturated double bond and the first functional group may be used alone or in combination of two or more.

The (meth) acrylic copolymer having the first functional group will be specifically described.
The (meth) acrylic copolymer described below is merely an example and does not limit the constitution of the present invention.

First, as a first example, a (meth) acrylic copolymer having a glycidyl group as the first functional group can be mentioned.
The (meth) acrylic copolymer having a glycidyl group as the first functional group is obtained by copolymerizing a monomer having both a copolymerizable unsaturated double bond and a glycidyl group, and a monomer copolymerizable with the monomer. Can be obtained at. For example, it can be obtained by polymerizing a (meth) acrylic monomer having a glycidyl group represented by the following general formula (3) alone or by copolymerizing with a monomer copolymerizable with the monomer. You can

(R ¹ has the same meaning as in Table 1. R ³ has the same meaning as in General Formula (2). General Formula (3) may or may have R ³ . It doesn't have to be.)

Examples of the (meth) acrylic monomer having a glycidyl group (first functional group) include glycidyl (meth) acrylate, α-ethylglycidyl (meth) acrylate, α-n-propylglycidyl (meth) acrylate. , (Meth) acrylic acid α-n-butylglycidyl, (meth) acrylic acid 3,4-epoxybutyl, (meth) acrylic acid 3,4-epoxyheptyl, (meth) acrylic acid α-ethyl-6,7- Examples thereof include epoxyheptyl, 4-hydroxybutyl acrylate glycidyl ether (4-HBAGE), 3,4-epoxycyclohexyl methyl methacrylate, epoxidized cyclohexyl polylactone methacrylate, and 3,4-epoxycyclohexyl methyl acrylate.

Among these, ease of preparation of the (meth) acrylic copolymer, various properties of the resin (A) (weight average molecular weight, glass transition temperature of the main chain of the resin (A), inclusion of a (meth) acryloyl group) (Amount, acid value, etc.), it is preferable to use glycidyl (meth) acrylate, glycidyl α-ethyl (meth) acrylate, and glycidyl α-n-propyl (meth) acrylate from the viewpoint of ease of adjustment of (amount, acid value, etc.). Among them, it is more preferable to use glycidyl (meth) acrylate.

Next, as a second example, a (meth) acrylic copolymer having a hydroxyl group as the first functional group can be mentioned.
The (meth) acrylic copolymer having a hydroxyl group as the first functional group can be obtained by copolymerizing a monomer having both a copolymerizable unsaturated double bond and a hydroxyl group with a monomer copolymerizable with the monomer. Can be done. For example, it can be obtained by polymerizing a (meth) acrylic monomer having a hydroxyl group as represented by the following general formula (4) alone or by copolymerizing with a monomer copolymerizable with the monomer. it can.

(R ¹ has the same meaning as in Table 1. R ³ has the same meaning as in General Formula (2).)

Examples of the (meth) acrylic monomer having a hydroxyl group (first functional group) include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, and 3-hydroxypropyl (meth) acrylate. Examples thereof include hydroxybutyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, hydroxyphenyl (meth) acrylate, and hydroxybenzyl (meth) acrylate.

Among these, ease of preparation of the (meth) acrylic copolymer, various properties of the resin (A) (weight average molecular weight, glass transition temperature of the main chain of the resin (A), inclusion of a (meth) acryloyl group) It is preferable to use 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, and 3-hydroxypropyl (meth) acrylate from the viewpoint of easiness of adjusting the amount, acid value, and the like. Above all, it is more preferable to use 2-hydroxyethyl (meth) acrylate.

Next, as a third example, a (meth) acrylic copolymer having an isocyanate group as the first functional group can be mentioned.
The (meth) acrylic copolymer having an isocyanate group as the first functional group can be obtained by copolymerizing a monomer having both a copolymerizable unsaturated double bond and an isocyanate group with a monomer copolymerizable with the monomer. You can get it. For example, it can be obtained by polymerizing a (meth) acrylic monomer having an isocyanate group represented by the following general formula (5) alone or by copolymerizing with a monomer copolymerizable with the monomer. it can.

(R ¹ has the same meaning as in Table 1. R ³ has the same meaning as in General Formula (2). General Formula (5) may or may not have R ³ . It doesn't have to be.)

Examples of the (meth) acrylic monomer having an isocyanate group (first functional group) include isocyanate methyl (meth) acrylate, isocyanate ethyl (meth) acrylate, isocyanate propyl (meth) acrylate, isocyanate octyl (meth) acrylate, Examples thereof include p-methacryloxy-α, α'-dimethylbenzyl isocyanate, m-acryloxy-α, α'-dimethylbenzyl isocyanate, m- or p-isopropenyl-α, α'-dimethylbenzyl isocyanate. Moreover, the thing etc. which made a part of isocyanate of a polyisocyanate compound react with the compound which has a hydroxyl group and a (meth) acryloyl group are mentioned.

Among these, ease of preparation of the (meth) acrylic copolymer, various properties of the resin (A) (weight average molecular weight, glass transition temperature of the main chain of the resin (A), inclusion of a (meth) acryloyl group) From the viewpoint of ease of adjusting the amount, acid value, etc.), it is preferable to use isocyanate methyl (meth) acrylate or isocyanate ethyl (meth) acrylate, and it is more preferable to use isocyanate ethyl (meth) acrylate. .

A fourth example is a (meth) acrylic copolymer having a carboxyl group as the first functional group.
The (meth) acrylic copolymer having a carboxyl group as the first functional group is obtained by copolymerizing a monomer having both a copolymerizable unsaturated double bond and a carboxyl group with a monomer copolymerizable with the monomer. You can get it. For example, a (meth) acrylic monomer having a carboxyl group as represented by the following general formulas (6) and (7) may be polymerized alone, or may be copolymerized with a monomer copolymerizable with the monomer. You can get it by doing.

(R ¹ has the same meaning as in Table 1. R ³ has the same meaning as in General Formula (2). General Formula (7) may or may not have R ³ . It doesn't have to be.)

Examples of the (meth) acryl-based monomer having a carboxyl group (first functional group) include (meth) acrylic acid, β-carboxyethyl (meth) acrylate, carboxypentyl (meth) acrylate, and 2- (meth) acryl. Royloxyethyl hexahydrophthalic acid, 2- (meth) acryloyloxypropyl hexahydrophthalic acid, 2- (meth) acryloyloxyethyl phthalic acid, 2- (meth) acryloyloxyethyl succinic acid, 2- (meth ) Acryloyloxyethyl maleic acid, carboxypolycaprolactone mono (meth) acrylate, 2- (meth) acryloyloxyethyl tetrahydrophthalic acid and the like can be mentioned.

Among these, ease of preparation of the (meth) acrylic copolymer, various properties of the resin (A) (weight average molecular weight, glass transition temperature of the main chain of the resin (A), inclusion of a (meth) acryloyl group) (Meth), (acid value, etc.), it is preferable to use (meth) acrylic acid or β-carboxyethyl (meth) acrylate, and it is more preferable to use (meth) acrylic acid. .

A monomer that can be used for the production of a (meth) acrylic copolymer having each first functional group as exemplified above (having both a copolymerizable unsaturated double bond and a first functional group). The monomer copolymerizable with the monomer) is not particularly limited as long as it is a copolymerizable ethylenically unsaturated compound, and examples thereof include (meth) acrylic monomers and other vinyl monomers.

As described above, the (meth) acrylic monomer represents (meth) acrylic acid or (meth) acrylic acid ester. Not only one type of (meth) acrylic monomer or other vinyl type monomer that can be copolymerized with a monomer having both a copolymerizable unsaturated double bond and the first functional group, but a combination of a plurality of types is used. You may.

Examples of the (meth) acrylic acid ester include a (meth) acrylic acid ester having an alkyl group, a macromonomer, and a nitrogen-containing (meth) acrylic acid ester.

Examples of the (meth) acrylic acid ester having an alkyl group include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl. (Meth) acrylate, t-butyl (meth) acrylate, hexyl (meth) acrylate, cyclohexyl (meth) acrylate, octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, nonyl (meth) acrylate, decyl (meth) acrylate. , Dodecyl (meth) acrylate, 4-t-butylcyclohexyl (meth) acrylate, isobornyl (meth) acrylate, adamantyl (meth) acrylate and the like.

Examples of the macromonomer include one-terminal (meth) acrylate-modified polyalkylene glycol and one-terminal (meth) acrylate-modified polydimethylsiloxane.

Examples of the one-terminal (meth) acrylate-modified polyalkylene glycol include NK ester 20G, 40G, 90G, 230G manufactured by Shin-Nakamura Chemical Co., Ltd., NOF BLEMMER PE series and AE series manufactured by NOF CORPORATION.

Examples of the one-terminal (meth) acrylate-modified polydimethylsiloxane include Silaplane FM-0711, FM-0721, FM-0725 manufactured by JNC Co., Ltd., X-22-174DX and X-22-X manufactured by Shin-Etsu Chemical Co., Ltd. 2426, etc., and Toagosei Co., Ltd. AK-5, AK-32, etc. are mentioned.

Examples of the nitrogen-containing (meth) acrylic acid ester include various dialkylaminoalkyl (meth) acrylates such as dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, dimethylaminopropyl (meth) acrylate, and diethylaminopropyl (meth) acrylate. ) Acrylate and the like.

Examples of other vinyl-based monomers include vinyl acetate, various styrene-based aromatic monomers such as styrene, α-methylstyrene, vinyltoluene, and divinylbenzene (aromatic vinyl-based monomers) dimethyl maleate, diethyl. Examples thereof include maleates such as maleate, diethyl fumarate, dibutyl fumarate, and dibutyl itaconate, and diesters of various dicarboxylic acids represented by fumaric acid and itaconic acid with monohydric alcohols.

Among these, the (meth) acrylic monomer copolymerizable with the monomer having both a copolymerizable unsaturated double bond and the first functional group is a (meth) acrylic ester having an alkyl group. Is preferred. With the (meth) acrylic acid ester having an alkyl group, it becomes easy to adjust the glass transition temperature (Tg) of the (meth) acrylic copolymer (main chain of the resin (A)). Among (meth) acrylic acid esters having an alkyl group, methyl (meth) acrylate, n-butyl (meth) acrylate, t-butyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, isobornyl (meth) acrylate. ) More preferably, at least one selected from the group consisting of acrylates is included.

The method for producing the (meth) acrylic copolymer is not particularly limited, and known methods can be appropriately applied. For example, it is preferably produced by a polymerization reaction, and more preferably produced by radical polymerization. The polymerization may be any of known methods such as solution polymerization, suspension polymerization and emulsion polymerization. Of these, solution polymerization is preferable from the viewpoint of precise control of polymerization and the like.

As the polymerization initiator for radical polymerization, known compounds can be used. For example, azobisisobutyronitrile, 2,2-azobis (2-methylbutyronitrile), 2,2-azobis (2-methylpropionitrile), and 2,2-azobis (2,4-dimethylvalero). Nitrile) and other azo-based initiators, benzoyl peroxide, t-butyl peroxyoctanoate, diisobutyl peroxide, di (2-ethylhexyl) peroxypivalate, decanoyl peroxide, t-butylperoxy-2- Redox combining peroxides such as ethylhexanoate and t-butylperoxybenzoate, hydrogen peroxide and iron (II) salts, persulfates and sodium bisulfite, and oxidizing agents and reducing agents Examples include system initiators. These can be used alone or in combination of two or more.

The blending amount of the polymerization initiator is not particularly limited, but it is preferably 0.001 to 10 parts by mass when 100 parts by mass of the total liquid mixture of the monomers to be polymerized is used.

In the polymerization reaction, known chain transfer agents, polymerization inhibitors, molecular weight modifiers and the like may be used as appropriate. Furthermore, the polymerization reaction may be carried out in one step or in two or more steps. The temperature of the polymerization reaction is not particularly limited, but is typically in the range of 50 ° C to 200 ° C, preferably 80 ° C to 150 ° C.

The (meth) acrylic copolymer having a first functional group is a (meth) acrylic copolymer having a glycidyl group from the viewpoint of adjusting the content of the (meth) acryloyl group of the resin (A) and the acid value. It is preferable to use a polymer, a (meth) acrylic copolymer having a hydroxyl group, or a (meth) acrylic copolymer having an isocyanate group.

(Second functional group)
The second functional group is not particularly limited as long as it is a functional group that reacts with the first functional group.

When the (meth) acrylic copolymer in which the first functional group is a glycidyl group is used, the second functional group is preferably a carboxyl group.

Examples of the (meth) acrylic monomer having a carboxyl group as the second functional group include (meth) acrylic acid represented by the following general formula (8) and β-carboxyl represented by the following general formula (9). Ethyl (meth) acrylate, carboxypentyl (meth) acrylate, 2- (meth) acryloyloxyethyl hexahydrophthalic acid, 2- (meth) acryloyloxypropyl hexahydrophthalic acid, 2- (meth) acryloyloxy Ethyl phthalic acid, 2- (meth) acryloyloxyethyl succinic acid, 2- (meth) acryloyloxyethyl maleic acid, carboxypolycaprolactone mono (meth) acrylate, 2- (meth) acryloyloxyethyl tetrahydrphthalic acid Etc.

(R ¹ and R ² are as defined in Table 1. The general formula (9) may or may not have R ^2. )

Examples of the (meth) acrylic monomer having a carboxyl group as the second functional group other than the above-mentioned ones include a polyfunctional (meth) acrylic monomer having a carboxyl group. For example, succinic acid adduct of pentaerythritol tri (meth) acrylate, succinic acid adduct of dipentaerythritol penta (meth) acrylate, pentaerythritol tri (meth) acrylate maleic acid adduct, dipentaerythritol penta (meth) acrylate Maleic acid adduct, dicarboxylic acid adduct of dipentaerythritol tetra (meth) acrylate, maleic acid adduct of EO6 mol added pentaerythritol tri (meth) acrylate, cyclohexenyl carboxylic acid of EO10 mol added dipentaerythritol penta (meth) acrylate Examples thereof include acid addition products.

Among them, from the viewpoint of ease of preparation of the resin (A) and UV curing, (meth) acrylic acid, β-carboxyethyl (meth) acrylate, and a polyfunctional (meth) acrylic monomer having a carboxyl group are used. Among these, acrylic acid having an acryloyl group, β-carboxyethyl acrylate, and a polyfunctional acrylic monomer having a carboxyl group are more preferably used.

When the (meth) acrylic copolymer in which the first functional group has a hydroxyl group is used, the second functional group is preferably an isocyanate group.

Examples of the (meth) acrylic monomer having an isocyanate group as the second functional group include isocyanate methyl (meth) acrylate, isocyanate ethyl (meth) acrylate, and isocyanate propyl (meth) acrylate as represented by the following general formula (10). , Isocyanate octyl (meth) acrylate, p-methacryloxy-α, α'-dimethylbenzyl isocyanate, m-acryloxy-α, α'-dimethylbenzyl isocyanate, m- or p-isopropenyl-α, α'-dimethylbenzyl isocyanate , 1,1- (bisacryloyloxymethyl) ethyl isocyanate and the like.

(R ¹ and R ² have the same meanings as in Table 1. The general formula (10) may or may not have R ^2. )

Examples of the (meth) acryl-based monomer having an isocyanate group other than those described above include those obtained by reacting a part of the isocyanate of the polyisocyanate compound with a compound having a hydroxyl group and a (meth) acryloyl group.

Among them, isocyanate methyl (meth) acrylate, isocyanate ethyl (meth) acrylate, 1,1- (bisacryloyloxymethyl) ethyl isocyanate, polyisocyanate compound from the viewpoint of ease of preparation of the resin (A) and ultraviolet curing. It is preferable to use one obtained by reacting a part of the isocyanate with a compound having a hydroxyl group and a (meth) acryloyl group, and among them, isocyanate ethyl acrylate having an acryloyl group, 1,1- (bisacryloyloxymethyl) ethyl isocyanate It is more preferable to use a polyisocyanate compound obtained by reacting a part of isocyanate with a compound having a hydroxyl group and an acryloyl group.

When the (meth) acrylic copolymer in which the first functional group is an isocyanate group is used, the second functional group is preferably a hydroxyl group.

Examples of the (meth) acryl-based monomer having a hydroxyl group as the second functional group include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, and 3-hydroxy as represented by the general formula (11). Examples thereof include propyl (meth) acrylate, 3-hydroxybutyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, hydroxyphenyl (meth) acrylate and hydroxybenzyl (meth) acrylate.

(R ¹ and R ² have the same meanings as in Table 1.)

Examples of the (meth) acrylic monomer having a hydroxyl group as the second functional group other than those described above include a polyfunctional (meth) acrylic monomer having a hydroxyl group such as pentaerythritol tri (meth) acrylate.

Among them, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, and a polyfunctional (meth) acrylic monomer having a hydroxyl group are used from the viewpoint of ease of preparation of the resin (A) and ultraviolet curing. It is preferable to use, and it is more preferable to use 2-hydroxyethyl acrylate having an acryloyl group.

When the (meth) acrylic copolymer in which the first functional group is a carboxyl group is used, the second functional group is preferably a glycidyl group.

Examples of the (meth) acrylic monomer having a glycidyl group as the second functional group include, for example, glycidyl (meth) acrylate, α-ethylglycidyl (meth) acrylate, and (meth) represented by the general formula (12). Α-n-propylglycidyl acrylate, α-n-butylglycidyl (meth) acrylate, 3,4-epoxybutyl (meth) acrylate, 3,4-epoxyheptyl (meth) acrylate, (meth) acrylic acid α-Ethyl-6,7-epoxyheptyl, 4-hydroxybutyl acrylate glycidyl ether (4-HBAGE), 3,4-epoxycyclohexyl methyl methacrylate, epoxidized cyclohexyl polylactone methacrylate, 3,4-epoxycyclohexyl methyl acrylate, etc. Is mentioned.

(R ¹ and R ² have the same meanings as in the table. The general formula (12) may or may not have R ^2. )

Among them, glycidyl (meth) acrylate and 4-hydroxybutyl acrylate glycidyl ether are preferably used from the viewpoint of ease of preparation of the resin (A) and ultraviolet curing, and among them, glycidyl acrylate having an acryloyl group. More preferably, 4-hydroxybutyl acrylate glycidyl ether is used.

[Photopolymerization initiator (B)]
The coating composition contains an initiator (B). The photopolymerization initiator that can be used in the present coating composition is not particularly limited, and can be used properly according to the application and purpose. Specifically, acetophenone compounds, benzyl compounds, anthraquinone compounds, benzylmethyl ketal compounds, α-hydroxyalkylphenone compounds, α-aminoalkylphenone compounds, acylphosphine oxide compounds, oxime ester compounds, biimidazole. Examples thereof include system compounds and aryl iodonium salt compounds. You may use these by 1 type (s) or 2 or more types.

Examples of the acetophenone-based compound include acetophenone, 2-hydroxy-2-phenylacetophenone, 2-ethoxy-2-phenylacetophenone, 2-methoxy-2-phenylacetophenone, 2-isopropoxy-2-phenylacetophenone, 2-isobutoxy. 2-Phenylacetophenone and the like can be mentioned. Examples of benzyl compounds include benzyl and 4,4'-dimethoxybenzyl.

Examples of the anthraquinone compound include 2-ethylanthraquinone, 2-t-butylanthraquinone, 2-phenoxyanthraquinone, 2- (phenylthio) anthraquinone, and 2- (hydroxyethylthio) anthraquinone.

Examples of the benzylmethyl ketal compound include 2,2-dimethoxy-1,2-diphenylethan-1-one.

Examples of the α-hydroxyalkylphenone compound include 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1- [4- (2-hydroxyethoxy) -phenyl]. 2-Hydroxy-2-methyl-1-propan-1-one, 2-hydroxy-1- {4- [4- (2-hydroxy-2-methylpropionyl) -benzyl] phenyl} -2-methyl-1 -On.

Examples of the α-aminoalkylphenone compound include 2-methyl-1- (4-methylthiophenyl) -2-morpholinopropan-1-one and 2-benzylmethyl 2-dimethylamino-1- (4-morpholine. Rinophenyl) -1-butanone.

Examples of the acylphosphine oxide compound include 2,4,6-trimethylbenzoyl-diphenylphosphine oxide and bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide.

Examples of the oxime ester compound include (2E) -2- (benzoyloxyimino) -1- [4- (phenylthio) phenyl] octane-1-one oxime ester and O-acetyl-1- [6- (2 -Methylbenzoyl) -9-ethyl-9H-carbazol-3-yl] ethanone oxime.

Examples of the biimidazole compound include 2,2′-bis (2-chlorophenyl) -4,4 ′, 5,5′-tetraphenyl-1,2′-biimidazole and 2,2′-bis (2 ，
4-dichlorophenyl) -4,4 ', 5,5'-tetraphenyl-1,2'-biimidazole, 2,2'-bis (2,4,6-trichlorophenyl) -4,4', 5 5'-tetraphenyl-1,2'-biimidazole may be mentioned.

Examples of the aryliodonium salt-based compound include (4-methylphenyl) [4- (2-methylpropyl) phenyl] iodonium-hexafluorophosphate. Examples of the arylsulfonium salt compound include phenylthiophenyldiphenylsulfonium-hexafluorophosphate and phenylthiophenyldiphenylsulfonium-hexafluoroantimonate.

From the viewpoint of compatibility with other components, the initiator (B) is preferably an α-hydroxyalkylphenone compound having both a cyclic skeleton and a hydroxyl group, such as 1-hydroxycyclohexyl phenyl ketone and 2-hydroxy-1- {. More preferred is 4- [4- (2-hydroxy-2-methyl-propionyl) -benzyl] -phenyl} -2-methyl-propan-1-one.

From another point of view, when two or more initiators (B) are used in combination, it is preferable that the initiators (B) having different absorption wavelength ranges are included.

When two or more types of initiators (B) having different absorption wavelength regions are used in combination, it is less likely to be affected by the pigment (C) that reflects or absorbs light having a wavelength in the ultraviolet region, and the ultraviolet curability is improved. Tend.

In the present specification, “different in absorption wavelength range” means that the maximum absorption wavelength of the initiator (B) is different by 5 nm or more. The "maximum absorption wavelength" is a 0.2 mass% methanol solution of the initiator (B), and the absorption spectrum measured based on the absorbance measurement of the liquid based on JIS-K-0115-2004 is measured, and It refers to the wavelength corresponding to the absorption maximum appearing on the long wavelength side. The maximum absorption wavelengths are preferably different by 10 nm or more, more preferably 50 nm or more.
More specifically, it is preferable to combine one or more types of the initiator (B) having a maximum absorption wavelength in the range of 370 to 420 nm and the initiator (B) having a maximum absorption wavelength in the range of 360 nm or less.

Examples of the initiator (B) having a maximum absorption wavelength in the range of 370 to 420 nm include bis (2,6-dimethoxybenzoyl) -2,4,4-trimethyl-pentylphosphine oxide (maximum absorption wavelength: 390 nm), 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide (maximum absorption wavelength: 380 nm), bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide (maximum absorption wavelength: 380 nm) and the like can be mentioned.

Among them, 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide and bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide are preferable, and among them, bis (2,4,6-trimethyl) Benzoyl) -phenylphosphine oxide is more preferred.

Specific examples of the initiator (B) having a maximum absorption wavelength in the range of 360 nm or less include 1-hydroxycyclohexyl phenyl ketone (maximum absorption wavelength: 330 nm), 1- [4- (2-hydroxyethoxy)- Phenyl] -2-hydroxy-2-methyl-1-propan-1-one (maximum absorption wavelength: 340 nm), 2-hydroxy-1- {4- [4- (2-hydroxy-2-methyl-propionyl)- Benzyl] -phenyl} -2-methyl-propan-1-one (maximum absorption wavelength: 330 nm), 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butanone-1 (maximum absorption wavelength: 320 nm), 2-dimethylamino-2- (4-methyl-benzyl) -1- (4-morpholin-4-yl-phenyl) -butan-1-one ( Large absorption wavelength: 330 nm, 2-hydroxy-2-methyl-1-phenylpropan-1-one (maximum absorption wavelength: 330 nm), 2,2-dimethoxy-1,2-diphenylethan-1-one (maximum absorption) Wavelength: 340 nm), ethanone, 1- [9-ethyl-6- (2-methylbenzoyl) -9H-carbazol-3-yl]-, 1- (0-acetyloxime), oxy-phenyl-acetic acid 2 A mixture of-[2-oxo-2-phenyl-acetoxy-ethoxy] -ethyl ester and oxy-phenyl-acetic acid 2- [2-hydroxy-ethoxy] -ethyl ester (maximum absorption wavelength: 330 nm), phenylglyoxy Examples thereof include ric acid methyl ester (maximum absorption wavelength: 340 nm).

Among them, from the viewpoint of compatibility, 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-1- {4- [4- (2-hydroxy-2-methyl-propionyl) -benzyl] -phenyl} -2-methyl -Propan-1-one is preferred.

The amount of the initiator (B) contained in the present coating composition is not particularly limited as long as it is contained in an amount such that the composition can be appropriately cured.
For example, the content of the initiator (B) is preferably 1 part by mass to 10 parts by mass, and more preferably 2 parts by mass to 9 parts by mass with respect to 100 parts by mass of the resin (A). When the present coating composition contains a polyfunctional (meth) acrylate compound (D) described below, the content of the initiator (B) is the same as that of the resin (A) and the polyfunctional (meth) acrylate compound (D). It is preferably 1 part by mass to 10 parts by mass, and more preferably 2 parts by mass to 9 parts by mass with respect to 100 parts by mass in total.
When the content of the initiator (B) is 1 part by mass or more, it becomes possible to impart sufficient ultraviolet curability to the present coating composition, while the content of the photopolymerization initiator is 10 parts by mass or less. In that case, problems such as yellowing of the cured film and bleed-out of the photopolymerization initiator from the cured film are less likely to occur.

[Pigment (C)]
The coating composition contains a pigment (C) that contributes to coloring.
As described above, in general, the pigment may hinder ultraviolet curing and cause poor appearance of the cured film. Therefore, it has been difficult to add an amount of pigment necessary for coloring to the ultraviolet curable coating composition. However, the present coating composition can prevent migration of the pigment (C) by using the resin (A) and can obtain a good cured film appearance. Therefore, the coating composition can contain the pigment (C) in an amount necessary for sufficient coloring.

As the pigment (C), a known coloring pigment or bright pigment can be appropriately used.
By including the pigment (C), a colored article can be obtained.
The coating composition of this embodiment may contain two or more pigments (C).

Specific examples of the known coloring pigment include titanium white (titanium oxide), zinc white, lead white, basic lead sulfate, lead sulfate, lithopone, zinc sulfide, antimony white, and the like. Examples of black pigments include carbon black, acetylene black, lamp black, bone black, graphite, iron black and aniline black. Examples of the yellow pigment include naphthol yellow S, Hansa yellow, pigment yellow L, benzidine yellow, and permanent yellow, and examples of the yellow-brown pigment include chrome orange, chrome vermillion, and permanent orange.

Examples of red pigments include reddish brown pigments such as iron oxide and amber, red iron oxide, red lead, and permanent red quinacridone red pigment. Purple pigments such as cobalt purple, fast violet and methyl violet lake, blue pigments such as ultramarine blue, dark blue, cobalt blue, phthalocyanine blue and indigo, and green pigments such as chrome green, pigment green B and phthalocyanine green. Examples include green pigments, but are not limited to these.

As the bright pigment, a metallic pigment or a pearl pigment can be appropriately used.
Examples of the metallic pigment include aluminum flakes, copper bronze flakes, glass flakes, mica-like iron oxide, mica flakes, mica-like iron oxide coated with metal oxides, and mica flakes coated with metal oxides.

Examples of the pearl pigment include titanium oxide-coated mica, titanium oxide-coated mica, bismuth oxychloride, titanium oxide-coated bismuth oxychloride, titanium oxide, coated talc, fish scale foil, titanium oxide-coated colored mica and the like.

The pigment (C) is preferably dispersed in the coating composition using a dispersant.
The pigment (C) may be previously dispersed with a dispersant, or may be dispersed with a dispersant when the present coating composition is produced.
Further, as the pigment (C), a commercially available pigment paste containing the pigment (C) and a dispersant may be used, or one that is dispersed by itself using a dispersant may be used.

The method of dispersing the pigment (C) by itself is not particularly limited, but as the method of dispersing, for example, a homogenizer, a disper, a bead mill, a paint shaker, a kneader, a roll mill, a ball mill, an attritor, a sand mill or the like can be used. Is.

As a dispersant for dispersing the pigment, a pigment dispersant manufactured by Big Chemie Co. or (Anti-Terra-U, Disperbyk-101, 103, 106, 110, 161, 162, 164, 166, 167, 168, 170, 174, 182) is used. , 184 and 2020), pigment dispersants manufactured by Ajinomoto Fine-Techno Inc. (Azisper PB711, PB821, PB814, PN411, PA111, etc.), pigment dispersants manufactured by Lubrizol (Solspers 5000, 12000, 32000, 33000, 39000, etc.), etc. Is mentioned.

The resin (A) can also be used as a dispersant for dispersing the pigment.
When the resin (A) is used as the dispersant, the dispersant is also fixed to the cured film, so that the hardness of the cured film tends to improve and the chemical resistance tends to improve.

The content of the pigment (C) contained in the present coating composition is not particularly limited as long as it is contained in such an amount that it is colored.
For example, the content of the pigment (C) is preferably 0.5 to 100 parts by mass, more preferably 1 to 90 parts by mass with respect to 100 parts by mass of the resin (A).
When the coating composition contains a polyfunctional (meth) acrylate compound (D) described below, the content of the pigment (C) is the total amount of the resin (A) and the polyfunctional (meth) acrylate compound (D). It is preferably 0.5 to 100 parts by mass, and more preferably 1 to 90 parts by mass with respect to 100 parts by mass. When the content of the pigment (C) is in such a range, the coating composition has good ultraviolet curability and a sufficiently colored cured film is obtained.

On the other hand, the required amount for coloring the cured film differs depending on the type of pigment (C). For example, in general, carbon black (black) or the like is sufficiently colored even in a relatively small amount, but titanium oxide (white) or the like requires a relatively large amount in order to be sufficiently colored. As described above, since the degree of coloring differs depending on the type of pigment, it is difficult to adjust the degree of coloring simply by the content of the pigment.

Therefore, in order to adjust the degree of coloring, the present coating composition was designed with the "transparency" of the cured film as one index.
More specifically, the larger the amount of the pigment (C) added, the lower the "transparency" of the coating film and the lower the total light transmittance. In other words, it can be said that the lower the total light transmittance, the more sufficiently colored. Therefore, the degree of coloring was adjusted using the "transparency" (total light transmittance) of the cured film as an index.

The total light transmittance in the present specification is a value obtained by measuring the transmittance in the visible light region, and at first glance, it seems that the ultraviolet curability related to the ultraviolet light region is not affected.
However, the degree of apparent coloring (total light transmittance in the visible light region) tends to affect the ultraviolet curability. Generally, the lower the total light transmittance of the cured film, that is, the lower the "transparency" of the cured film, the more the ultraviolet rays do not reach the coating film sufficiently and the cured film tends not to be sufficiently cured. In addition, such a coating composition is likely to be affected by pigment migration during ultraviolet curing and tends to cause uneven curing due to the reasons described above.

However, the present coating composition has the effect of dispersing the pigment (C) of the resin (A) and the effect of preventing migration of the pigment (C). Even when the ratio is low, a coating composition having good ultraviolet curability can be obtained.

From the viewpoint of coloring, it is preferable to include the pigment (C) such that the cured film having a film thickness of 5 μm obtained from the present coating composition has a total light transmittance of 0 to 60%.
When the total light transmittance of the cured film is within the above range, the coating composition has good ultraviolet curability and a colored cured film is obtained.

The average particle diameter of the pigment (C) is preferably 0.01 to 50 μm, more preferably 0.015 to 40 μm, and further preferably 0.02 to 30 μm.
When the average particle diameter of the pigment (C) is in such a range, the coating composition has good ultraviolet curability, and a colored cured film can be obtained.

The average particle diameter can be typically measured by the dynamic light scattering method. Specifically, the pigment (C) was diluted with methanol and subjected to a cumulant analysis (ISO13321) from the light intensity distribution using a device "Zetasizer" of Malvern Instruments Ltd at 25 ° C, and the obtained Z-Average was obtained. The value of can be used as the average particle diameter.

[Polyfunctional (meth) acrylate compound (D)]
The coating composition contains, in addition to the resin (A), the initiator (B), the pigment (C), a polyfunctional (meth) acrylate compound (D) different from the resin (A), that is, a (meth) acrylic resin. A polyfunctional (meth) acrylate compound having no skeleton may be included. The polyfunctional (meth) acrylate compound (D) has different physical properties of the cured film of the resin (A) (for example, to obtain a cured film having a high hardness and to improve chemical resistance). (Physical properties derived from the (meth) acrylate compound (D)) can be imparted.

The polyfunctional (meth) acrylate compound (D) includes a polyfunctional (meth) acrylate having two or more (meth) acryloyl groups in one molecule as shown in the following general formula (13). By including the polyfunctional (meth) acrylate compound, a cured film having higher hardness and scratch resistance can be obtained.

(R ¹ has the same meaning as in formula (1), * represents a bond)

Again, in general, the polyfunctional (meth) acrylate compound (D) is more likely to undergo shrinkage by curing than the resin (A), and cannot prevent the pigment (C) from moving. Further, the effect of dispersing the pigment (C) is lower than that of the resin (A).
Therefore, the ultraviolet curable coating composition for coloring, in which only the polyfunctional (meth) acrylate compound (D) is a cured film forming component, tends to cause a defective appearance of the cured film. However, when used in combination with the resin (A), it is derived from the polyfunctional (meth) acrylate compound (D) while maintaining the effect of preventing the transfer of the pigment (C) of the resin (A) and the dispersing effect of the pigment (C). It can exhibit the physical properties of

The polyfunctional acrylate compound (D) is not particularly limited as long as it is a compound having two or more (meth) acryloyl groups represented by the general formula (13) in one molecule. A bifunctional (meth) acrylate monomer having two (meth) acryloyl groups, a polyfunctional (meth) acrylate monomer having three or more (meth) acryloyl groups in a molecule, a polyfunctional (meth) acrylate oligomer, and the like. To be The polyfunctional (meth) acrylate compound is not limited to one type, and a plurality of types may be used in combination.

Examples of the bifunctional (meth) acrylate monomer include triethylene glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, 1,9-nonanediol di ( Examples thereof include (meth) acrylate, dimethylol-tricyclodecanedi (meth) acrylate, 1,4-butanediol di (meth) acrylate, diethylene glycol di (meth) acrylate, and propylene glycol di (meth) acrylate.

Examples of polyfunctional (meth) acrylate monomers include dipentaerythritol hexa (meth) acrylate, dipentaerythritol penta (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol tetra (meth) acrylate, pentaerythritol triacrylate. (Meth) acrylate, dipentaerythritol tri (meth) acrylate, pentaerythritol glycidyl tri (meth) acrylate, trimethylolpropane tri (meth) acrylate, ditrimethylolpropane tetra (meth) acrylate, isocyanuric acid tri (meth) acrylate, tri Tri (meth) acrylate of 3 mol propylene oxide adduct of methylol propane and 6 mol ethylene oxide of trimethylol propane Polyalkylene glycol-modified trimethylolpropane tri (meth) acrylate tri (meth) acrylate side adduct, glycerin propoxy tri (meth) acrylate, hexa acrylate of caprolactone adduct of dipentaerythritol.

Examples of polyfunctional (meth) acrylate oligomers include urethane (meth) acrylate oligomers, epoxy (meth) acrylate oligomers, polyester (meth) acrylate oligomers, and the like.

Among them, from the viewpoint of obtaining a cured film having high hardness, it is preferable to use a polyfunctional (meth) acrylate compound having 3 or more (meth) acryloyl groups, and a polyfunctional compound having 3 or more (meth) acryloyl groups. It is more preferred to use (meth) acrylate monomers.

From the viewpoint of obtaining a cured film having high hardness, the content of the polyfunctional (meth) acrylate compound is preferably 0 to 90% by mass, more preferably 20 to 85% by mass, based on the whole nonvolatile components of the composition. 40-80 mass% is more preferable.
By setting the content of the polyfunctional (meth) acrylate compound in this range, a cured film having high hardness can be obtained and a good cured film appearance can be obtained.

[Other ingredients]
The coating composition may further contain components (hereinafter referred to as “other components”) other than the components (A) to (D) unless the effects of the present invention are impaired. Specific examples of the other components include pigments other than the pigment (C), matting agents, thermal polymerization inhibitors, antioxidants such as hindered phenol / phosphite, light stabilizers (HALS) such as hindered amines, and the like. Ultraviolet absorber (UVA), surfactant, heat ray reflection / absorption agent, flexibility agent, antistatic agent, antifouling agent, water repellent agent, defoaming agent, leveling agent, plasticizer, Examples include foaming agents, flame retardants, antistatic agents, antiaging agents, antibacterial and antifungal agents.

An extender pigment is mentioned as a pigment other than the pigment (C) which can be used for this coating composition. Examples of extender pigments include talc, calcium carbonate, precipitated barium sulfate, and silica. These may be used alone or in combination of two or more.
It should be noted that pigments other than these pigments (C) are less likely to absorb ultraviolet rays, and are less likely to affect the ultraviolet curability and the appearance of the cured film.

<Method for producing ultraviolet curable coating composition>
The method for producing the present coating composition is not particularly limited, and it can be produced by mixing the above-mentioned respective components by a known method. For example, it can be manufactured by mixing all of the above components all together and stirring with a known high speed disperser or the like.

<Cured film>
The cured film of the present invention is formed from a cured product of the present coating composition.
The method for forming the cured film is not particularly limited, and for example, it can be formed by coating the present coating composition on a substrate by a known method and irradiating with ultraviolet light to cure.

The base material is not particularly limited, and examples thereof include organic materials such as plastics and inorganic materials such as glass, ceramics and metals. Examples of the plastic include polyesters such as acrylic, polycarbonate, polyethylene terephthalate, polyethers, polyamides, polyimides, polyolefins such as polypropylene, polystyrene, polyalkylenes, ABS and mixtures thereof.

Examples of the coating method of the present coating composition include spray coating method, electrostatic coating method, curtain coating method, spin coating method, dipping coating method, gravure printing method, screen printing method, gravure offset printing method, flexo printing method. Method, inkjet printing method, and the like. The thickness of the cured film can be appropriately designed according to the application. The dry film thickness is preferably 1 to 100 μm, more preferably 3 to 50 μm, and further preferably 5 to 20 μm. By setting the dry film thickness to such a numerical range, it is possible to sufficiently perform ultraviolet curing and to obtain a sufficiently colored cured film.

At the time of ultraviolet curing, an ultraviolet irradiation device having a xenon lamp, a high-pressure mercury lamp, a medium-pressure mercury lamp, a low-pressure mercury lamp, a metal halide lamp, and an LED lamp is used as a light source, and the light amount, the arrangement of the light source, and the like are adjusted as necessary. Ultraviolet rays having a wavelength of 190 to 450 nm are preferable. The irradiation amount of ultraviolet rays is generally preferably 10~10,000mJ / cm ^2, more preferably 100~2,000mJ / cm ^2, more preferably 300~1,000mJ / cm ^2. By setting the irradiation amount of ultraviolet rays within such a numerical range, a sufficiently ultraviolet-cured cured film can be obtained.

<Article provided with cured film>
The coated article provided with the cured film obtained by the method as described above is not particularly limited, and examples thereof include various plastic molded articles such as mobile phones, electric appliances, and automobile bumpers. It can be used with any inorganic material.

The present coating composition can be directly applied to these target articles, or a film or sheet obtained by coating the present coating composition on another substrate in advance can be applied to the target article. It can also be attached.

The embodiments of the present invention have been described above, but these are examples of the present invention, and various configurations other than the above can be adopted. Further, the present invention is not limited to the above-described embodiment, and modifications, improvements, etc. within the scope of achieving the object of the present invention are included in the present invention.

Hereinafter, embodiments of the present invention will be described in detail based on Examples and Comparative Examples. The present invention is not limited to the examples.

<Synthesis of resin (A)>
(Synthesis of Resin (A-1))
A four-necked flask equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen inlet was prepared.
100 parts of butyl isoacetate was charged into this flask and heated to 115 ° C. in a nitrogen atmosphere while stirring. Then, 2 parts of a mixed solution prepared by mixing 25 parts of isobornyl methacrylate, 75 parts of glycidyl methacrylate, and 4 parts by mass of 1,1′-azobis-1-cyclohexanecarbonitrile (V-40 manufactured by Wako Pure Chemical Industries, Ltd.). It dripped at the said flask over time.

After completion of the dropping, the mixture was further stirred at 115 ° C. for 5 hours to cause a reaction. Then, heating was stopped and it cooled to room temperature, and the (meth) acryl copolymer composition containing the (meth) acryl copolymer which has a glycidyl group as a 1st functional group was obtained.
The glass transition temperature of the (meth) acrylic copolymer was 67 ° C., which was determined from the compounding ratio of the monomers used based on the Fox equation. The glass transition temperature of the acrylic copolymer obtained here represents the glass transition temperature of the main chain of the (meth) acrylic resin (A-1) described later.

Next, using the obtained (meth) acrylic copolymer, a second step reaction was carried out to synthesize a resin (A-1) as follows.

35 parts by mass of acrylic acid ((meth) acrylic monomer having a carboxyl group), 0.5 part by mass of hydroquinone monomethyl ether, and 1.0 part by mass of triphenylphosphine were added to the obtained (meth) acrylic copolymer composition. After mixing the parts, the mixture was heated to 105 ° C., and the glycidyl group of the first functional group was reacted with the carboxyl group of the second functional group while stirring for 8 hours. Then, the heating was stopped, the temperature was cooled to room temperature, and butyl isoacetate was added until the solid content became 40% by mass to obtain a (meth) acrylic resin composition containing the (meth) acrylic resin (A-1). .

The number average molecular weight of the obtained (meth) acrylic resin (A-1) was 6,500, and the weight average molecular weight was 11,000. Furthermore, the content of (meth) acryloyl group per 1 g of the resin was 3.6 mmol, and the acid value was 0 mgKOH / g.

The number average molecular weight and the weight average molecular weight were measured and calculated by gel permeation chromatography (GPC). The equipment and conditions used are as follows.
-Device used: HLC8220GPC (manufactured by Tosoh Corporation)
-Use column: TSKgel SuperHZM-M, TSKgel GMHXL-H, TSKgel G2500HXL, TSKgel G5000HXL (manufactured by Tosoh Corporation)
・ Column temperature: 40 ℃
Standard material: TSKgel standard polystyrene A1000, A2500, A5000, F1, F2, F4, F10 (manufactured by Tosoh Corporation)
・ Detector: RI (differential refraction) detector ・ Eluent: Tetrahydrofuran ・ Flow rate: 1 ml / min

The content of the (meth) acryloyl group per 1 g of the resin (A) is determined by purifying the resin (A) and removing the influence of residual monomers, and then determining the iodine value by a method according to JIS-K-0070. Calculated from the value.
Similarly, the acid value was measured by purifying the resin (A) and removing the influence of residual monomers by a method according to JIS-K-5601-2-1 (acid value titration method).

(Synthesis of Resins (A-2) to (A-6))
The (meth) acrylic resins (A-2) to (A-6) were also synthesized by a method similar to that of the resin (A-1).

(Synthesis of resin (A-7))
As for the resin (A-7), the raw materials shown in Table 2 are used as in the case of the resin (A-1), and the (meth) acryl copolymer contains a (meth) acryl copolymer having a hydroxyl group as the first functional group. A polymer composition was obtained.

Next, using the obtained (meth) acrylic copolymer, a second step reaction was performed to synthesize a resin (A-7) as follows.

In the (meth) acrylic copolymer composition containing the obtained (meth) acrylic copolymer, 26 parts by mass of isocyanate ethyl acrylate ((meth) acrylic monomer having an isocyanate group), hydroquinone monomethyl ether 0.5 After mixing by mass, the mixture was stirred at 70 ° C. for 6 hours to react the hydroxyl group as the first functional group with the isocyanate group as the second functional group. Then, the spectrum was measured by an infrared absorption spectrometer (FTIR Spectrum100 manufactured by Perkin Elmer), and it was confirmed that the isocyanate group was completely consumed. After this confirmation, the flask was cooled and butyl isoacetate was added until the solid content reached 40 mass% to obtain a (meth) acrylic resin composition containing the (meth) acrylic resin (A-7).

(Synthesis of resin (A-8))
As for the resin (A-8), the (meth) acryl copolymer containing a (meth) acryl copolymer having a carboxyl group as the first functional group using the raw materials in Table 2 as in the resin (A-1). A combined composition was obtained.

Next, using the obtained (meth) acrylic copolymer, a second step reaction was performed to synthesize a resin (A-8) as follows.

To the (meth) acrylic copolymer composition containing the obtained (meth) acrylic copolymer, 42 parts by mass of 4-hydroxybutyl acrylate glycidyl ether (manufactured by Mitsubishi Chemical Corporation, hereinafter "4HBAGE") (chrysidyl group was added). ((Meth) acrylic monomer), hydroquinone monomethyl ether (0.5 parts by mass), and triphenylphosphine (1.0 parts by mass) are mixed, heated to 105 ° C., and stirred for 8 hours to be the first functional group. The carboxyl group was reacted with the glycidyl group, which is the second functional group. The heating was stopped, the temperature was cooled to room temperature, and butyl isoacetate was added until the solid content became 40 mass% to obtain a (meth) acrylic resin composition containing the (meth) acrylic resin (A-8).

(Synthesis of Resin (A-9))
The (meth) acrylic resin (A-9) was also synthesized by a method similar to that of the (meth) acrylic resin (A-8).

(Synthesis of resin (A-10))
Regarding the (meth) acrylic resin (A-10), the reaction in the second stage was not performed, and the (meth) acrylic resin composition containing the (meth) acrylic resin (A-10) was prepared using the raw materials shown in Table 2. Got

The raw materials of the (meth) acrylic resins (A-1) to (A-10) and the charged amounts of the raw materials, and the acid value, number average molecular weight and weight average molecular weight are shown.
In addition, the unit of the numerical value of the compounding amount in the column of raw material in Table 2 is "part by mass".

Explanation of terms in Table 2 ・ GMA ・ ・ ・ Glycidyl methacrylate ・ HEMA ・ ・ ・ 2-Hydroxyethyl methacrylate ・ AA ・ ・ ・ Acrylic acid ・ MMA ・ ・ ・ Methyl (meth) acrylate ・ BMA ・ ・ ・ n-Butyl methacrylate・ IB-X ... Isobornyl methacrylate (Kyoeisha Chemical Co., Ltd., trade name Light Ester IB-X)
・ BA ・ ・ ・ n-butyl acrylate ・ AOI ・ ・ ・ Isocyanate ethyl acrylate (Showa Denko KK, trade name Karenz AOI)
・ 4HBAGE ... 4-hydroxybutyl acrylate glycidyl ether (manufactured by Mitsubishi Chemical Corporation)

[Example 1]
<Preparation of coating composition>
250 parts by mass of the (meth) acrylic resin composition containing the (meth) acrylic resin (A-1) synthesized above (100 parts by mass of the resin (A-1) contained) and a carbon black dispersion (Dainichi Seika) Industrial Co., Ltd., model number FPGS245S) 16 parts by mass (the carbon black contained is 1.3 parts by mass) and 4.5 parts by mass of Irgacure 184 are mixed, and isopropyl alcohol is further added to obtain a solid content of 30. A coating composition of mass% was prepared.

In the table, the amount of the (meth) acrylic resin is not the amount as the resin composition (solid content ratio: 40% by mass), but the amount of the resin (solid content) contained in the resin composition. . The same applies to carbon black, not the amount of carbon black dispersion but the amount of pigment (carbon black) contained in the dispersion.

[Examples 2-35]
Each coating composition was produced in the same manner as in Example 1 so that the blending ratios shown in Tables 3 to 7 were obtained.
As for the value of the aluminum paste in Table 6, the amount of the aluminum pigment contained in the aluminum paste is described instead of the amount of the aluminum paste as in the case of the carbon black.

<Preparation of test coated plate and evaluation film>
Each coating composition obtained in each of the examples and comparative examples was dried on a black ABS resin plate (manufactured by Engineering Test Service Co., Ltd., thickness 1.0 mm, side length 100 mm × 100 mm square) to obtain a film thickness after drying. Was sprayed with air spray so that it was 5 μm, and then dried at 80 ° C. for 5 minutes. Further, a high-pressure mercury lamp (manufactured by Eye Graphics Co., Ltd.) was used to irradiate the resin with ultraviolet rays under the condition of an integrated light amount of 500 mJ / cm ² to cure the resin plate, and a resin plate having a cured film with a thickness of 5 μm (hereinafter referred to as “test”). I got a coated plate).

In addition, No. The coating composition was applied to a polypropylene resin plate (100 mm in length x 100 mm in width x 2 mm in thickness, prepared according to JIS-K-6921) using a bar coater 12 and then dried at 80 ° C for 5 minutes. It was Further, a high pressure mercury lamp (manufactured by Eye Graphics Co., Ltd.) was used to perform ultraviolet irradiation under the condition of an integrated light amount of 500 mJ / cm ² to cure the resin plate, thereby obtaining a resin plate provided with a cured film. The cured film was peeled off from the obtained resin plate to obtain a cured film having a film thickness of 5 μm (hereinafter referred to as an evaluation film).

<Evaluation>
The following evaluation was performed on the test coated plate and the evaluation film (cured film) obtained from the various coating compositions obtained (the evaluation film (cured film) itself, only for the evaluation of the total light transmittance). Was used, and the test coated plate was used for other evaluations). The evaluation results are shown in Tables 3 to 6 together with the formulations of various coating compositions.

(Appearance of cured film)
On the cured film on the test coated plate, 26 lines were drawn at intervals of 2 mm in the grid pattern direction to draw a grid (25 squares × 25 squares). It was visually checked whether or not there was an abnormal appearance (whether there was uneven curing) for each grid, and the ratio of the area of the abnormal appearance was evaluated by the number of grids with an abnormal appearance.
5: No abnormal appearance of the cured film is seen in any of the lattices.
4 ... The ratio of the area of abnormal appearance (curing unevenness) is less than 10%. 3 ... The ratio of the area of abnormal appearance (curing unevenness) is 10% or more and less than 20%. 20% or more and less than 50% 1 ... Abnormal appearance (uneven curing) area 50% or more

(UV curability (curability))
The cured state of the cured film on the test coated plate was evaluated according to the following evaluation criteria.
The cured film was touched with a finger, and the degree of adhesion of the coating composition to the finger was evaluated according to the following evaluation criteria.
5 ... There is no change in the cured film even when the cured film is touched with a finger.
4 ... Touching the cured film with a finger leaves a slight trace of the finger.
3 ... When the cured film is touched with a finger, the mark of the finger is clearly left. 2 ... When the cured film is touched with the finger, the coating composition is slightly attached to the finger.
1 ... When the cured film is touched with a finger, it sticks to the finger.

(60 ° gloss)
The 60 ° gloss (gloss (60 °)) of the cured film on the test coated plate was measured by a gloss meter “Micro-Gloss” manufactured by BYK-Gardner GmbH. In a coating composition containing no matting agent, the higher the gloss value, the better the appearance of the cured film.

(Total light transmittance)
The total light transmittance of the evaluation film (cured film) was measured with a haze meter (Automatic Haze Meter TC-H3DPK / 2, manufactured by Tokyo Denshoku Co., Ltd.). The lower the total light transmittance, the more the film tends to be sufficiently colored.
As described above, only this evaluation is performed using the “evaluation film (cured film) itself” separated from the polypropylene resin plate.

(Pencil hardness)
JIS-K-5600-5-4 (using a test coated plate, a surface property measuring device (Shinto Kagaku Co., Ltd., Tribogear 14FW) and a pencil hardness measurement pencil (Mitsubishi Uni from Mitsubishi Pencil Co., Ltd.) 1999) Mechanical properties of cured film—scratch hardness (pencil method) ”. The measurement load was 750 g, the measurement speed was 30 mm / min, and the measurement distance was 5 mm. The measurement was carried out 5 times, and the hardness of the pencils that passed 4/5 was taken as the evaluation result.

<Table 3: Influence of resin (A)>

<Table 4: Combined use of polyfunctional (meth) acrylate compound (D)>

<Table 5: Effect of initiator (B)>

<Table 6: Influence of pigment (C)>

Explanation of terms in Tables 3 to 6-DPHA: manufactured by Shin Nakamura Chemical Co., Ltd., NK ester A-DPH, dipentaerythritol hexaacrylate-PETA: manufactured by Toagosei Co., Ltd., Aronix M-305, pentaerythritol tri- Acrylate-A-9300 ... Shin Nakamura Chemical Co., Ltd., NK ester A-9300, ethoxylated isocyanuric acid triacrylate-A-200 ... Shin Nakamura Chemical Co., Ltd., NK ester A-200, polyethylene glycol di Acrylate / carbon black ... Carbon black dispersion, model number FPGS245S, manufactured by Dainichiseika Kogyo Co., Ltd., average particle size 0.024 μm, pigment concentration 8% by mass
・ Titanium oxide CR-95 ... made by Ishihara Sangyo Co., Ltd., titanium oxide, average particle size 0.28 μm
・ Aluminum paste FZ-U75C ... manufactured by Toyo Aluminum Co., Ltd., aluminum paste, average particle diameter 30 μm, pigment concentration 43 mass%
・ Irgacure 184 ... manufactured by BASF Corporation, 1-hydroxycyclohexyl phenyl ketone, maximum absorption wavelength: 330 nm
-Irgacure 127 ... manufactured by BASF Corporation, 2-hydroxy-1- {4- [4- (2-hydroxy-2-methyl-propionyl) -benzyl] -phenyl} -2-methyl-propane-1-. ON, maximum absorption wavelength: 330 nm
・ Irgacure 819 ... manufactured by BASF Corporation, bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide, maximum absorption wavelength: 380 nm

As can be seen from the results shown in Tables 3 to 6, in Examples 1 to 29 having the constitution of the present invention, the ultraviolet curable coating composition had good ultraviolet curability, and the appearance of the cured film was good.
On the other hand, in the case where the (meth) acrylic resin having no (meth) acryloyl group in the side chain is used (Comparative Examples 1 to 4), the obtained cured film has a good appearance and ultraviolet rays having good ultraviolet curability. A curable coating composition could not be obtained. Further, in the case of using only the polyfunctional (meth) acrylate compound (D) without containing the resin (A) as the cured film forming component (Comparative Example 5), a good cured film appearance cannot be obtained. It was

This means that by using a (meth) acrylic resin (resin (A)) having a (meth) acryloyl group in the side chain, the resin (A) prevents migration of the pigment (C) in the coating film during ultraviolet curing. It is considered that this is due to suppression and uniform UV curing.

[Additional consideration]
In addition to the above various evaluations, chemical resistance was evaluated.
<Evaluation of chemical resistance>
(chemical resistance)
On the surface of the cured film of the test coated plate, a sunscreen agent [trade name: Ultra Sheer Dry Touch Sunblock SPF45, manufactured by Neutrogena, UV absorber: salicylic acid ester derivative (10% by mass) and benzophenone derivative (5% by mass)] Was applied at a rate of 0.1 g / 20 cm ² and then allowed to stand for 4 hours in a dryer without forced convection (temperatures are 40 ± 2 ° C. and 80 ± 2 ° C., respectively). Then, it was washed with water to remove the sunscreen, and the appearance of the cured film was visually determined according to the following evaluation criteria.
5: There is no change in the appearance of the cured film.
4: The gloss of the cured film is slightly reduced.
3 ... Slightly traces remain on the cured film 2 ... Clear traces remain on the cured film 1 ... Cured film peels from the substrate.

As can be seen from the results in Table 7, Examples 2, 11, 21, 23, 30, 31, 34, and 35 had good chemical resistance as well as cured film appearance and ultraviolet curability. .
The reason for this is that Example 2 and Example 21 have a higher content of the (meth) acryloyl group per 1 g of the resin (A) than those of Example 3, Example 8 and Example 32. It is considered that the film was densely cross-linked, which made it difficult for the chemical to permeate into the cured film, resulting in good chemical resistance.

Similarly, in Examples 11, 23, 30, 31, 34, and 35, it is considered that the cured film was more densely crosslinked and the chemical resistance was further improved by using the polyfunctional (meth) acrylate compound together. .
In more detail, Example 30 and Example 34 have better chemical resistance than Example 31 and Example 35. The reason for this is considered to be that the resin (A-8) used in these examples has a low acid value, which makes it difficult for chemicals to penetrate into the cured film.

In addition, among Examples 11, 23, 30, 31, 34, and 35, the resin (A-2) and the resin (A-8) having a low acid value are used, and the initiator (B) having a different absorption wavelength range is used. Examples 23 and 34, which used together, had particularly good chemical resistance. This is because by using together an initiator (B) with a different maximum absorption wavelength range, it is less susceptible to the influence of the pigment (C) (reflection and absorption of ultraviolet rays), the ultraviolet curability is good, and the chemical resistance is improved. It is thought to have been done.

Claims (14)

An ultraviolet curable coating composition,
Contains a (meth) acrylic resin (A), a photopolymerization initiator (B) and a pigment (C),
The (meth) acrylic resin is
Having a (meth) acryloyl group in the side chain,
The pigment contains at least one selected from the group consisting of a coloring pigment and a bright pigment,
UV-curable coating composition. The ultraviolet curable coating composition according to claim 1, wherein
A pigment is included so that the total light transmittance of a 5 μm-thick cured film obtained from the ultraviolet curable coating composition is 0% or more and 60% or less.
UV-curable coating composition. The ultraviolet curable coating composition according to claim 1 or 2, wherein
The content of the (meth) acryloyl group is
An ultraviolet curable coating composition, which is 1 mmol or more and 10 mmol or less per 1 g of the (meth) acrylic resin. The ultraviolet curable coating composition according to any one of claims 1 to 3,
An ultraviolet-curable coating composition in which the acid value of the (meth) acrylic resin is 0 mgKOH / g or more and 10 mgKOH / g or less. The ultraviolet curable coating composition according to any one of claims 1 to 4,
An ultraviolet-curable coating composition, wherein the (meth) acrylic resin has a weight average molecular weight of 2,000 or more and 60,000 or less. The ultraviolet curable coating composition according to any one of claims 1 to 5,
The (meth) acrylic resin is
A (meth) acrylic copolymer having a first functional group on the side chain,
Including a reaction product with a (meth) acrylic monomer having a second functional group that reacts with the first functional group,
UV-curable coating composition. The ultraviolet curable coating composition according to claim 6,
The first functional group is a glycidyl group,
The second functional group is a carboxyl group,
UV-curable coating composition. The ultraviolet curable coating composition according to claim 6,
The first functional group is a hydroxyl group,
The second functional group is an isocyanate group,
UV-curable coating composition. The ultraviolet curable coating composition according to claim 6,
The first functional group is an isocyanate group,
The second functional group is a hydroxyl group,
UV-curable coating composition. The ultraviolet curable coating composition according to claim 6,
The first functional group is a carboxyl group,
The second functional group is a glycidyl group,
UV-curable coating composition. The ultraviolet curable coating composition according to any one of claims 1 to 10,
The pigment is
Including a pigment having an average particle size of 0.01 μm or more and 50 μm or less,
UV-curable coating composition. The ultraviolet curable coating composition according to any one of claims 1 to 11,
Further comprising a polyfunctional (meth) acrylate compound (D) different from the (meth) acrylic resin,
UV-curable coating composition. A cured film of the ultraviolet curable coating composition according to any one of claims 1 to 12. An article comprising the cured film according to claim 13.