WO2025239130A1 - Organopolysiloxane and photocurable coating composition - Google Patents

Abstract

The present invention is photocurable (meth)acrylic group-containing organopolysiloxane characterized by being represented by general formula (1). Thus, provided are an organopolysiloxane having a photocurable (meth)acrylic group and a photocurable coating composition that contains the organopolysiloxane and yields a cured film having excellent appearance, transparency, scratch resistance, adhesion, water repellency, antifouling properties, and weather resistance.

Description

Organopolysiloxane and photocurable coating composition

The present invention relates to an organopolysiloxane and a photocurable coating composition.

In recent years, there has been a demand for curable compositions that can form cured films having excellent coatability, appearance, transparency, scratch resistance, surface slippage, low curling, adhesion, chemical resistance, and the like, and that are capable of forming cured films having excellent weather resistance, as protective coating agents for the surfaces of various substrates such as various plastics (polycarbonate, polymethyl methacrylate, polystyrene, polyester, polyolefin, epoxy resin, melamine resin, triacetyl cellulose resin, ABS resin, AS resin, norbornene-based resin, etc.), metal, wood, etc.
Furthermore, it is desirable to have the above properties satisfied by a photocurable composition that can be cured in a short time with less energy than a heat-curable composition that takes a relatively long time to cure and requires a lot of energy.

A well-known example of a common photocurable coating composition is a photocurable (meth)acrylic composition that uses a multifunctional (meth)acrylate. Photocurable (meth)acrylic compositions contain one or more multifunctional (meth)acrylates and a photopolymerization initiator, and form a coating through crosslinking via photopolymerization of the (meth)acrylic groups in the multifunctional (meth)acrylate, thereby exhibiting excellent curability, scratch resistance, hardness, and chemical resistance.

By blending these photocurable (meth)acrylic coating compositions with a fluorine-based additive having perfluoropolyether groups and (meth)acrylic groups as water-repellent and stain-resistant groups, it is possible to obtain a coating that has the above properties as well as water-repellent and stain-resistant properties (Patent Documents 1 and 2). Also known as a fluorine-based additive is a compound in which cyclic polysiloxanes are linked by divalent perfluoropolyether chains (Patent Document 3).

In recent years, the use of some of the perfluoroalkyl and polyfluoroalkyl compounds (PFAS) that make up fluorine-based additives has been restricted worldwide due to their persistence and high bioaccumulation potential. Polysiloxane-based additives have been proposed as an alternative to fluorine-based additives, and it is known that blending polysiloxane-based additives into (meth)acrylic coating compositions can impart smoothness, slipperiness, water repellency, water slippage, and the ability to wipe off fingerprints and oil-based dyes (Patent Documents 4 to 9).

However, while these examples disclose various organopolysiloxanes that have (meth)acryloyl groups at one end, both ends, or in the side chain of the polysiloxane, there are almost no known examples that, when incorporated into a photocurable (meth)acrylic coating composition, satisfy all of the following requirements: appearance, transparency, scratch resistance, adhesion, water repellency, stain resistance, and weather resistance.

JP 2010-053114 A JP 2010-138112 A Japanese Patent Application Laid-Open No. 2010-285501 JP 2010-121013 A JP 2013-023547 A Japanese Patent Application Laid-Open No. 2015-196748 International Publication No. 2015/152288 International Publication No. 2018/181645 International Publication No. 2018/181650

The present invention has been made in consideration of the above circumstances, and aims to provide an organopolysiloxane having a photocurable (meth)acrylic group, and a photocurable coating composition containing the organopolysiloxane that provides a cured film with excellent appearance, transparency, scratch resistance, adhesion, water repellency, stain resistance, and weather resistance.

In order to solve the above problems, the present invention provides a photocurable (meth)acrylic group-containing organopolysiloxane represented by the following general formula (1):
(In the formula, R1 ^'s are each independently a group selected from an alkyl group having 1 to 4 carbon atoms and an aryl group having 6 to 10 carbon atoms; R2 ^'s are each an alkyl group having 1 to 8 carbon atoms; X's are each a divalent or trivalent saturated hydrocarbon group which may have one or more atoms selected from oxygen and nitrogen atoms inserted in the molecular chain; Q's are each independently an (a+1)-valent saturated hydrocarbon group which may have an oxygen atom or nitrogen atom inserted in the molecular chain; Z's are each independently an acryloyloxy group or a methacryloyloxy group; a and b are each independently 1 or 2, provided that a and b are not both 1; when b is 1, a is 2; and when b is 2, a is 1 or 2; and n is an integer from 0 to 200.)

Since such organopolysiloxanes have multiple photocurable (meth)acrylic groups at one end, cured films obtained from compositions containing them have excellent appearance, transparency, scratch resistance, adhesion, water repellency, stain resistance, and weather resistance.

In the present invention, in the general formula (1), it is preferable that X is a group represented by the following formula (2) or (3), and Q is a group represented by any one of the following formulas (4), (5), and (6):
(In the formula, * ¹ represents a bond to the silicon atom of the general formula (1), and * ² represents a bond to the oxygen atom in the urethane group of the general formula (1).)
(In the formula, * ⁵ represents a bond to Z in the general formula (1), and * ⁶ represents a bond to the nitrogen atom in the urethane group in the general formula (1).)

Such organopolysiloxanes are preferred because they are easy to synthesize and the raw materials are readily available.

In this case, it is preferable that in the general formula (1), X is a group represented by the formula (2), Q is a group represented by the formula (6), a is 2, and b is 1.

In this case, it is preferable that in the general formula (1), X is a group represented by the formula (3), Q is a group represented by the formula (4), a is 1, and b is 2.

In this case, it is preferable that in the general formula (1), X is a group represented by the formula (3), Q is a group represented by the formula (6), a is 2, and b is 2.

These are more preferred organopolysiloxanes for the present invention.

The present invention also provides a photocurable coating composition, comprising:
(A) an organopolysiloxane represented by the following general formula (1):
(B) a polyfunctional (meth)acrylate compound other than the component (A), and (C) a photopolymerization initiator;
wherein the content of component (A) is 0.01 to 20% by mass relative to the total amount of compounds having a photocurable reactive group in the composition.
(In the formula, R1 ^'s are each independently a group selected from an alkyl group having 1 to 4 carbon atoms and an aryl group having 6 to 10 carbon atoms; R2 ^'s are each an alkyl group having 1 to 8 carbon atoms; X's are each a divalent or trivalent saturated hydrocarbon group which may have one or more atoms selected from oxygen and nitrogen atoms inserted in the molecular chain; Q's are each independently an (a+1)-valent saturated hydrocarbon group which may have an oxygen atom or nitrogen atom inserted in the molecular chain; Z's are each independently an acryloyloxy group or a methacryloyloxy group; a and b are each independently 1 or 2, provided that a and b are not both 1; when b is 1, a is 2; and when b is 2, a is 1 or 2; and n is an integer from 0 to 200.)

Such a photocurable coating composition will produce a cured film with excellent appearance, transparency, scratch resistance, adhesion, water repellency, stain resistance, and weather resistance.

In the present invention, in the general formula (1), it is preferable that X is a group represented by the following formula (2) or (3), and Q is a group represented by any one of the following formulas (4), (5), and (6):
(In the formula, * ¹ represents a bond to the silicon atom of the general formula (1), and * ² represents a bond to the oxygen atom in the urethane group of the general formula (1).)
(In the formula, * ⁵ represents a bond to Z in the general formula (1), and * ⁶ represents a bond to the nitrogen atom in the urethane group in the general formula (1).)

Such photocurable coating compositions are preferred because they are easy to synthesize and the raw materials are readily available.

Furthermore, in the present invention, it is preferable that the composition further contains (D) an ultraviolet absorber.

Such photocurable coating compositions are preferable because they improve the weather resistance of the cured film.

In this case, it is preferable that the component (D) has a hydroxyphenyltriazine structure.

In this case, it is more preferable that the component (D) has a hydroxyphenyltriazine structure and a (meth)acryloyloxy group.

Such component (D) forms crosslinks with the components (A) and (B) above, and is incorporated into the cured film without bleeding or falling off, thereby achieving long-term weather resistance.

In this case, it is preferable that the content of component (D) is 1 to 30 mass% relative to the total amount of compounds having a photocurable reactive group in the composition.

Such photocurable coating compositions can produce cured films with excellent coating appearance and weather resistance.

Furthermore, in the present invention, it is preferable that the composition does not contain a compound containing a fluorine atom.

Such photocurable coating compositions are also preferable from an environmental perspective because they do not contain fluorine atoms.

According to the present invention, by adding a specific photocurable (meth)acrylic group-containing organopolysiloxane, it is possible to obtain a photocurable coating composition that gives a cured film with excellent appearance, transparency, scratch resistance, adhesion, water repellency, stain resistance, and weather resistance.

1 is ^{a 1} H-NMR spectrum chart of the photocurable (meth)acrylic group-containing organopolysiloxane synthesized in Synthesis Example 1.

As described above, there has been a need for the development of a photocurable coating composition that provides a cured film with excellent appearance, transparency, scratch resistance, adhesion, water repellency, stain resistance, and weather resistance, as well as an organopolysiloxane contained in said composition.

As a result of extensive research to achieve the above objective, the inventors discovered that a coating composition containing an organopolysiloxane containing a specific photocurable (meth)acrylic group produces a cured film with the above-mentioned excellent properties, leading to the completion of the present invention.

That is, the present invention is a photocurable (meth)acrylic group-containing organopolysiloxane characterized by being represented by the following general formula (1):
(In the formula, R1 ^'s are each independently a group selected from an alkyl group having 1 to 4 carbon atoms and an aryl group having 6 to 10 carbon atoms; R2 ^'s are each an alkyl group having 1 to 8 carbon atoms; X's are each a divalent or trivalent saturated hydrocarbon group which may have one or more atoms selected from oxygen and nitrogen atoms inserted in the molecular chain; Q's are each independently an (a+1)-valent saturated hydrocarbon group which may have an oxygen atom or nitrogen atom inserted in the molecular chain; Z's are each independently an acryloyloxy group or a methacryloyloxy group; a and b are each independently 1 or 2, provided that a and b are not both 1; when b is 1, a is 2; and when b is 2, a is 1 or 2; and n is an integer from 0 to 200.)

The present invention also provides a photocurable coating composition, comprising:
(A) an organopolysiloxane represented by the following general formula (1):
(B) a polyfunctional (meth)acrylate compound other than the component (A), and (C) a photopolymerization initiator;
and the content of component (A) is 0.01 to 20 mass % relative to the total amount of compounds having a photocurable reactive group in the composition.
(In the formula, R1 ^'s are each independently a group selected from an alkyl group having 1 to 4 carbon atoms and an aryl group having 6 to 10 carbon atoms; R2 ^'s are each an alkyl group having 1 to 8 carbon atoms; X's are each a divalent or trivalent saturated hydrocarbon group which may have one or more atoms selected from oxygen and nitrogen atoms inserted in the molecular chain; Q's are each independently an (a+1)-valent saturated hydrocarbon group which may have an oxygen atom or nitrogen atom inserted in the molecular chain; Z's are each independently an acryloyloxy group or a methacryloyloxy group; a and b are each independently 1 or 2, provided that a and b are not both 1; when b is 1, a is 2; and when b is 2, a is 1 or 2; and n is an integer from 0 to 200.)

The present invention is described in detail below, but is not limited to these.

[Organopolysiloxane]
The organopolysiloxane of the present invention is a photocurable (meth)acrylic group-containing organopolysiloxane represented by the following general formula (1).
(In the formula, R1 ^'s are each independently a group selected from an alkyl group having 1 to 4 carbon atoms and an aryl group having 6 to 10 carbon atoms; R2 ^'s are each an alkyl group having 1 to 8 carbon atoms; X's are each a divalent or trivalent saturated hydrocarbon group which may have one or more atoms selected from oxygen and nitrogen atoms inserted in the molecular chain; Q's are each independently an (a+1)-valent saturated hydrocarbon group which may have an oxygen atom or nitrogen atom inserted in the molecular chain; Z's are each independently an acryloyloxy group or a methacryloyloxy group; a and b are each independently 1 or 2, provided that a and b are not both 1; when b is 1, a is 2; and when b is 2, a is 1 or 2; and n is an integer from 0 to 200.)

The organopolysiloxane of the present invention has two or more (meth)acryloyl groups at one end, and can react with a radically polymerizable compound to form a three-dimensional crosslinked structure.

In the general formula (1), ^R1 's are each independently a group selected from an alkyl group having 1 to 4 carbon atoms and an aryl group having 6 to 10 carbon atoms, and specific examples include alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, and tert-butyl; and aryl groups such as phenyl, tolyl, and xylyl, with a methyl group or phenyl group being preferred, and a methyl group being more preferred. ^R2 's are an alkyl group having 1 to 8 carbon atoms, and are preferably a methyl group or n-butyl group, and a n-butyl group being more preferred.

In the above general formula (1), X is a divalent or trivalent saturated hydrocarbon group. One or more atoms selected from oxygen atoms and nitrogen atoms may be present in the molecular chain, and the group may be linear, branched, or cyclic. A divalent or trivalent saturated hydrocarbon group having 1 to 20 carbon atoms is preferred. Among these, considering ease of synthesis and availability of raw materials, it is more preferred that X be a group represented by the following formula (2) or (3).

(In the formula, * ¹ represents a bond to the silicon atom of the general formula (1), and * ² represents a bond to the oxygen atom in the urethane group of the general formula (1).)

In the general formula (1), each Q is independently an (a+1)-valent saturated hydrocarbon group. An oxygen atom or a nitrogen atom may be present in the molecular chain, _and the group may be linear, branched, or _cyclic . Examples include linear or branched _{divalent or trivalent} saturated hydrocarbon groups having ₁ to _{10 carbon} atoms _, such as _-CH2CH2- , -CH2CH2CH2-, -CH( _CH3 ) _{CH2- , -CH2CH2CH2CH2-} , _-CH2CH2 -O _- CH2CH2-, -CH<, -CH2CH<, -CH( _CH3 )CH<, -C( _CH3 )( _CH2- ) ₂ , and -C( _CH3 )[( _CH2 )-] ₂ . Note that "<" indicates two bonds. Among these, in consideration of ease of synthesis and availability of raw materials, Q is preferably a group represented by any one of the following formulas (4), (5), and (6), and more preferably a group represented by the following formula (4) or (6).

(In the formula, * ⁵ represents a bond to Z in the general formula (1), and * ⁶ represents a bond to the nitrogen atom in the urethane group in the general formula (1).)

In the above general formula (1), each Z is independently an acryloyloxy group or a methacryloyloxy group. Of these, an acryloyloxy group is preferred because of its excellent photocurability.

In the above general formula (1), a represents the number of Z's bonded to Q, and b represents the number of groups containing a urethane group bonded to X. a and b are each independently 1 or 2, but a and b cannot both be 1 at the same time; when b is 1, a is 2, and when b is 2, a is 1 or 2. If n is outside this range, three-dimensional crosslinking will not occur during curing of the coating film, resulting in a cured film with inferior scratch resistance and water-repellent durability, as well as inferior crack resistance. n is an integer between 0 and 200, preferably between 3 and 100, and more preferably between 8 and 60. If n is outside this range, the water repellency, stain resistance, and appearance of the cured coating film may be poor.

In the general formula (1), it is preferable that X is a group represented by formula (2), Q is a group represented by formula (6), a is 2, and b is 1; in the general formula (1), X is a group represented by formula (3), Q is a group represented by formula (4), a is 1, and b is 2; or in the general formula (1), X is a group represented by formula (3), Q is a group represented by formula (6), a is 2, and b is 2.

Examples of organopolysiloxanes of the above general formula (1) preferably have easy availability of raw materials, compatibility with relatively highly polar binders such as polyfunctional (meth)acrylates, and excellent photocurability, and include compounds represented by the following formulas (8) to (13):

(wherein n is the same as above.)

(wherein n is the same as above.)

The method for producing the organopolysiloxane of general formula (1) above is not particularly limited. For example, it can be obtained by a general urethane reaction. Among these, the preferred production method is described below.

First, an organopolysiloxane precursor having a carbinol group at one end of the molecular chain, represented by the following general formula (14), is prepared.
(wherein R ¹ , R ² , X, b, and n are the same as above.)

Next, it is preferable to react the hydroxyl group bonded to X in the precursor of general formula (14) above with an isocyanate group of a compound represented by the following general formula (15) to obtain the organopolysiloxane of the present invention represented by general formula (1) above.
(In the formula, Q, Z, and a are the same as above.)

Specific examples of the above general formula (15) include 2-acryloyloxyethyl isocyanate (trade name "Karenz AOI" (manufactured by Resonac Co., Ltd.)), 2-methacryloyloxyethyl isocyanate (trade name "Karenz MOI" (manufactured by Resonac Co., Ltd.)), 2-(2-methacryloyloxyethyloxy)ethyl isocyanate (trade name "Karenz MOI-EG" (manufactured by Resonac Co., Ltd.)), and 1,1-bis(acryloyloxymethyl)ethyl isocyanate (trade name "Karenz BEI" (manufactured by Resonac Co., Ltd.)).

In the above reaction, the temperature at which the general formula (14) and the general formula (15) are reacted is preferably in the range of 10 to 120°C, more preferably 40 to 100°C, in order to prevent polymerization of the (meth)acryloyl group during the reaction and to promote the reaction.

There are no particular restrictions on the reaction time, but it is preferably 1 to 12 hours, and more preferably 2 to 8 hours.

The above reaction may be carried out in the presence of a catalyst, if necessary. Examples of such catalysts include di-n-octyltin oxide, dibutyltin dilaurate, iron(III) acetylacetonate, bismuth(III) octoate, titanium(IV) 2-ethylhexyloxide, 1,4-diazabicyclo[2.2.2]octane, 2,2'-dimorpholinodiethyl ether, and triethylamine. These catalysts can be used alone or in combination of two or more.

The amount of catalyst used is preferably in the range of 0 to 10,000 ppm, and more preferably 100 to 5,000 ppm, relative to the total amount of compounds represented by general formula (14) and general formula (15). Within this range, the reaction proceeds more easily, side reactions are less likely to occur, and the product is less discolored.

The above reaction may also be carried out in the presence of a solvent, if necessary. The solvent preferably does not have a group reactive with an isocyanate group, and examples include hydrocarbons (toluene, xylene, n-hexane, cyclohexane, etc.), ethers (diethyl ether, tetrahydrofuran, 1,4-dioxane, etc.), esters (ethyl acetate, butyl acetate), and ketones (methyl ethyl ketone, methyl isobutyl ketone). These solvents can be used alone or in combination of two or more.

Furthermore, to suppress the polymerization of the (meth)acryloxy group, the above reaction may be carried out with the addition of a polymerization inhibitor, if necessary. Any polymerization inhibitor conventionally used for acrylic compounds may be used. Examples of polymerization inhibitors include phenolic polymerization inhibitors such as hydroquinone, methylhydroquinone, hydroquinone monomethyl ether, 2-tert-butylhydroquinone, 4-methoxyphenol, and 2,6-di-tert-butyl-p-cresol. These polymerization inhibitors may be used alone or in combination of two or more. There are no particular restrictions on the amount of polymerization inhibitor, but an amount that is 5 to 1,000 ppm, and more preferably 20 to 500 ppm, based on the mass of the resulting compound is preferred.

Polymerization can also be suppressed by carrying out the reaction in air or nitrogen containing 4% oxygen, and these may be used in combination.

It is desirable to react the above general formula (14) and the above general formula (15) in equimolar amounts, but this is not a limitation. The amount of the above general formula (15) to be reacted can be adjusted depending on the number of hydroxyl groups that can react with the isocyanate groups in the above general formula (14). However, considering the storage stability of the resulting coating composition, it is preferable to adjust the ratio of the above general formula (14) to the above general formula (15) so that no isocyanate groups remain in the reaction product.

Photocurable Coating Composition
The present invention provides a photocurable coating composition comprising:
(A) an organopolysiloxane represented by the above general formula (1),
(B) a polyfunctional (meth)acrylate compound other than the component (A), and (C) a photopolymerization initiator;
wherein the content of component (A) is 0.01 to 20% by mass relative to the total amount of compounds having a photocurable reactive group in the composition.

The content of component (A) is in the range of 0.01 to 20% by mass, preferably 0.1 to 20% by mass, and more preferably 1 to 16% by mass, relative to the total amount of compounds having a photocurable reactive group in the entire composition. Examples of compounds having a photocurable reactive group include acrylic compounds and methacrylic compounds. For example, among components (A) to (C), components (A) and (B) are compounds having a photocurable reactive group. If the content of component (A) is outside this range, the resulting cured film will have poor water repellency and stain resistance, will not exhibit the durability of these properties, and may also have poor scratch resistance and adhesion to the substrate.

Furthermore, in the present invention, in the general formula (1), it is preferable that X is a group represented by the formula (2) or (3), and Q is a group represented by any of the following formulas (4), (5), and (6):

[(B) Component]
Component (B) is a polyfunctional (meth)acrylate compound other than component (A) that functions as a binder.

Specific examples of component (B) include neopentyl glycol di(meth)acrylate, ethylene glycol di(meth)acrylate, polyethylene glycol (number of repeating units (hereinafter referred to as "k") = 2 to 15) di(meth)acrylate, polypropylene glycol (k = 2 to 15) di(meth)acrylate, polybutylene glycol (k = 2 to 15) di(meth)acrylate, 2,2-bis(4-(meth)acryloxyethoxyphenyl)propane, 2,2-bis(4-(meth)acryloxydiethoxyphenyl)propane, trimethylolpropane diacrylate, Bis(2-(meth)acryloxyethyl)hydroxyethylisocyanurate, trimethylolpropane tri(meth)acrylate, tris(2-(meth)acryloxyethyl)isocyanurate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, epoxy di(meth)acrylate obtained by reacting bisphenol A diepoxy with (meth)acrylic acid urethane tri(meth)acrylate obtained by reacting 2-hydroxyethyl (meth)acrylate with a trimer of 1,6-hexamethylene diisocyanate; urethane di(meth)acrylate obtained by reacting isophorone diisocyanate with 2-hydroxypropyl (meth)acrylate; urethane hexa(meth)acrylate obtained by reacting isophorone diisocyanate with pentaerythritol tri(meth)acrylate; urethane di(meth)acrylate obtained by reacting dicyclomethane diisocyanate with 2-hydroxyethyl (meth)acrylate. ) acrylate; urethane poly(meth)acrylates such as urethane di(meth)acrylate obtained by reacting a urethane reaction product of dicyclomethane diisocyanate and poly(k=6-15)tetramethylene glycol with 2-hydroxyethyl (meth)acrylate; polyester poly(meth)acrylates such as polyester (meth)acrylate obtained by reacting trimethylolethane with succinic acid and (meth)acrylic acid; and polyester poly(meth)acrylates such as polyester (meth)acrylate obtained by reacting trimethylolpropane with succinic acid, ethylene glycol, and (meth)acrylic acid.

The content of component (B) is preferably 10 to 99% by mass, and more preferably 15 to 90% by mass, based on the total amount of compounds having photocurable reactive groups in the entire composition. Within this range, a cured film with excellent coating appearance, scratch resistance, substrate adhesion, and weather resistance is obtained.

[(C) Component]
The photopolymerization initiator of component (C) may be appropriately selected from those having excellent compatibility and curability in the photocurable coating composition. Specific examples include carbonyl compounds such as benzoin, benzoin monomethyl ether, benzoin isopropyl ether, acetoin, benzil, benzophenone, p-methoxybenzophenone, diethoxyacetophenone, benzil dimethyl ketal, 2,2-diethoxyacetophenone, 1-hydroxycyclohexyl phenyl ketone, methylphenyl glyoxylate, and 2-hydroxy-2-methyl-1-phenylpropan-1-one; tetrahydrofuran; Examples of suitable organic solvents include sulfur compounds such as tetramethylthiuram monosulfide and tetramethylthiuram disulfide; phosphate compounds such as 2,4,6-trimethylbenzoyldiphenylphosphine oxide, 2,4,6-trimethylbenzoylphenylethoxyphosphine oxide, bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide and bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide; 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)butanone-1 and camphorquinone. These may be used alone or in combination of two or more, and can be combined as desired depending on the required coating film performance.

The content of component (C) is preferably an amount that allows for an appropriate curing rate for the resulting coating film, improves the scratch resistance and adhesion to the substrate of the cured film, and prevents discoloration and a decrease in weather resistance. It is preferably 0.1 to 20% by mass, and more preferably 1 to 15% by mass, based on the total amount of compounds having a photocurable reactive group in the composition.

[(D) Component]
The photocurable coating composition of the present invention preferably further contains (D) an ultraviolet absorber, as needed, in order to improve the weather resistance of the cured film. The component (D) can be used alone or in combination of two or more.

Component (D) is not particularly limited as long as it absorbs ultraviolet light, but examples include hydroxybenzophenones, hydroxybenzotriazoles, cyanoacrylates, and hydroxyphenyltriazines. Specific examples include 2,4-dihydroxybenzophenone, 2,2',4,4'-tetrahydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-methoxybenzophenone-5-sulfonic acid, 2-hydroxy-4-n-octoxybenzophenone, 2-hydroxy-4-n-dodecyloxybenzophenone, 2-hydroxy-4-n-benzyloxybenzophenone, and 2,2'-dihydroxy-4,4'-dimethoxybenzophenone. hydroxybenzophenones such as 2-(2-hydroxybenzophenone), 2,2'-dihydroxy-4,4'-diethoxybenzophenone, 2,2'-dihydroxy-4,4'-dipropoxybenzophenone, 2,2'-dihydroxy-4,4'-dibutoxybenzophenone, 2,2'-dihydroxy-4-methoxy-4'-propoxybenzophenone, 2,2'-dihydroxy-4-methoxy-4'-butoxybenzophenone, and 2,3,4-trihydroxybenzophenone; hydroxybenzotriazoles such as 2-(2-hydroxy-5-t-octylphenyl)benzotriazole, 2-(2-hydroxy-3,5-di-t-butylphenyl)benzotriazole; cyanoacrylates such as ethyl-2-cyano-3,3-diphenylacrylate and 2-ethylhexyl-2-cyano-3,3-diphenylacrylate; 2-(2-hydroxy-4-hexyloxyphenyl)-4,6 Examples of hydroxyphenyl triazines include 2-[4-[(2-hydroxy-3-(2'-ethyl)hexyl)oxy]-2-hydroxyphenyl]-4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine, and 2-[2-hydroxy-4-(1-octyloxycarbonylethoxy)phenyl]-4,6-bis(4-phenylphenyl)-1,3,5-triazine, with hydroxyphenyl triazines being preferred. These can be used alone or in combination of two or more.

Component (D) is preferably an ultraviolet absorber having a hydroxyphenyltriazine structure, and even more preferably an ultraviolet absorber having a hydroxyphenyltriazine structure and a (meth)acryloyloxy group. Such ultraviolet absorbers form crosslinks with components (A) and (B) above, and are incorporated into the cured film without bleeding or falling off, thereby achieving long-term weather resistance.

Specific examples of hydroxybenzophenones having a (meth)acryloyloxy group include 2-hydroxy-4-(2-(meth)acryloxyethoxy)benzophenone, 2-hydroxy-4-(4-(meth)acryloxybutoxy)benzophenone, 2,2'-dihydroxy-4-(2-(meth)acryloxyethoxy)benzophenone, 2,4-dihydroxy-4'-(2-(meth)acryloxyethoxy)benzophenone, 2,2',4-trihydroxy-4'-(2-(meth)acryloxyethoxy)benzophenone, 2-hydroxy-4-(3-(meth)acryloxy-2-hydroxypropoxy)benzophenone, and 2-hydroxy-4-(3-(meth)acryloxy-1-hydroxypropoxy)benzophenone.

Specific examples of hydroxybenzotriazoles having a (meth)acryloyloxy group include 2-(2'-hydroxy-5'-(meth)acryloxyphenyl)-2H-benzotriazole, 2-(2'-hydroxy-3'-tert-butyl-5'-(meth)acryloxymethylphenyl)-2H-benzotriazole, 2-[2'-hydroxy-5'-(2-(meth)acryloxyethyl)phenyl]-2H-benzotriazole, 2-[2'-hydroxy-3'-tert-butyl-5'-(2-(meth)acryloxyethyl)phenyl]-5-chloro-2H-benzotriazole, and 2-[2'-hydroxy-3'-methyl-5'-(8-(meth)acryloxyoctyl)phenyl]-2H-benzotriazole.

Specific examples of hydroxyphenyltriazines having a (meth)acryloyloxy group include the reaction product of 2-[4-[(2-hydroxy-3-(2'-ethyl)hexyl)oxy]-2-hydroxyphenyl]-4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine with 2-acryloyloxyethyl isocyanate (for example, Synthesis Example 1 in Japanese Patent No. 6354665), and the reaction product of 2-[4-[(2-hydroxy-3-(2'-ethyl)hexyl)oxy]-2-hydroxyphenyl]-4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine with 1,1-bis(acryloyloxy). Examples include a reaction product of 2-[4-{(hydroxy-3-dodecyloxypropyl)oxy}-2-hydroxyphenyl]-4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine with 2-acryloyloxyethyl isocyanate, and a reaction product of 2-[4-{(hydroxy-3-dodecyloxypropyl)oxy}-2-hydroxyphenyl]-4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine with 1,1-bis(acryloyloxymethyl)ethyl isocyanate (for example, Synthesis Example 1 in Japanese Patent No. 6156214).

The content of component (D) relative to the total amount of compounds having a photocurable reactive group in the composition is preferably 1 to 30 mass%, and more preferably 5 to 20 mass%. Within this range, a cured film with excellent coating appearance and weather resistance will be obtained.

[(E) component]
The photocurable coating composition of the present invention may optionally contain one or more components selected from (E) organopolysiloxanes having (meth)acryloyl groups but not urethane bonds, and silica particles surface-modified with alkoxysilanes having (meth)acryloyl groups but not urethane bonds, in order to improve the transparency, scratch resistance, substrate adhesion, durability, etc. of the cured film.

Organopolysiloxanes that have (meth)acryloyl groups but no urethane bonds can be obtained, for example, by (co)hydrolytic condensation of alkoxysilanes that have (meth)acryloyl groups but no urethane bonds, or mixtures with other silanes.

Furthermore, silica particles surface-modified with an alkoxysilane having a (meth)acryloyl group but no urethane bond can be obtained by (co)hydrolytic condensation of an alkoxysilane having a (meth)acryloyl group but no urethane bond, or a mixture with other silanes, in the presence of colloidal silica, or by dry-treating silica powder with such an alkoxysilane.

Specific examples of alkoxysilanes that have a (meth)acryloyl group but no urethane bond include 3-(meth)acryloxypropylmethyldimethoxysilane, 3-(meth)acryloxypropyltrimethoxysilane, 2-(meth)acryloxyethyltrimethoxysilane, 2-(meth)acryloxyethyltriethoxysilane, (meth)acryloxymethyltrimethoxysilane, (meth)acryloxymethyltriethoxysilane, 3-(meth)acryloxypropylmethyldiethoxysilane, 3-(meth)acryloxypropyltriethoxysilane, 8-(meth)acryloxyoctyltrimethoxysilane, and 8-(meth)acryloxyoctyltriethoxysilane.

In consideration of obtaining a cured film that has excellent compatibility with other components, heat resistance, chemical resistance, durability, and adhesion to the substrate, the preferred component (E) is 3-(meth)acryloxypropyltrimethoxysilane alone or its (co)hydrolyzed condensation product with other silanes, or a product obtained by (co)hydrolyzed condensation of 3-(meth)acryloxypropyltrimethoxysilane alone or with other silanes in the presence of colloidal silica. These may be used alone or in combination of two or more, and can be combined as desired depending on the required cured film performance.

When component (E) is used, its amount is preferably more than 0 to 30 mass% or less, and more preferably 1 to 25 mass%, based on the total amount of compounds having photocurable reactive groups in the composition, taking into consideration the transparency, scratch resistance, substrate adhesion, and durability of the cured film. When component (E) is incorporated into the photocurable coating composition of the present invention, component (E) is also treated as a compound having photocurable reactive groups, and the above amount is calculated accordingly.

The photocurable coating composition of the present invention may contain a monofunctional (meth)acrylate compound as needed to improve the transparency, flexibility, and substrate adhesion of the cured film. Specific examples of monofunctional (meth)acrylate compounds include methyl (meth)acrylate, ethyl (meth)acrylate, s-butyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, i-butyl (meth)acrylate, t-butyl (meth)acrylate, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, morpholyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, glycidyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, Examples of mono(meth)acrylates include diethylaminoethyl (meth)acrylate, tricyclodecane (meth)acrylate, polyethylene glycol mono(meth)acrylate, cyclohexyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclopentenyl (meth)acrylate, isobornyl (meth)acrylate, allyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, benzyl (meth)acrylate, phenoxyethyl (meth)acrylate, and phenyl (meth)acrylate; and mono(meth)acrylate compounds such as an adduct of phthalic anhydride and 2-hydroxyethyl (meth)acrylate.

In addition, other additives may be added to the photocurable coating composition of the present invention depending on the purpose of the present invention. Examples include antifouling agents, water repellents, leveling agents, colorants, pigments, antioxidants, anti-yellowing agents, bluing agents, defoamers, thickeners, anti-settling agents, antistatic agents, surfactants, adhesion promoters, infrared absorbers, light stabilizers, flexibility-imparting agents, curing catalysts, metal oxide particles, etc.

Furthermore, in the present invention, it is preferable that the composition does not contain a compound containing a fluorine atom.

The photocurable coating composition of the present invention may be used as is, or may be diluted with an organic solvent. It is preferable to select the organic solvent depending on the coating method. For example, when used for spray coating, it is preferable to use any combination of alcohol-based solvents such as isobutanol, glycol-based solvents such as propylene glycol monomethyl ether, ester-based solvents such as n-butyl acetate, ketone-based solvents such as methyl isobutyl ketone, and aromatic solvents such as toluene, to achieve a viscosity of 20 mPa·s or less. When used for application by shower flow coating or dip coating, it is preferable to achieve a viscosity of 100 mPa·s or less.

A cured film can be produced by applying the photocurable coating composition of the present invention to various substrates and curing it. During photocuring, the photocurable coating composition is applied to the substrate to form a specified film thickness, and then, after volatilizing the solvent as necessary, the coating is irradiated with ultraviolet light, electron beams, or the like using a high-pressure mercury lamp, metal halide lamp, LED lamp, or the like. The irradiation atmosphere can be air or an inert gas such as nitrogen or argon.

Substrates include organic resins such as plastic molded bodies, wood-based products, fibers, ceramics, glass, metals, and composites thereof, and although there are no particular limitations, the coating composition of the present invention can be suitably used on various plastic materials.

In particular, it can be used effectively with polycarbonate resin, polystyrene resin, acrylic resin, modified acrylic resin, urethane resin, thiourethane resin, polycondensation product of halogenated bisphenol A and ethylene glycol, acrylic urethane resin, halogenated aryl group-containing acrylic resin, sulfur-containing resin, polyalkylene terephthalate resin, cellulose resin, amorphous polyolefin resin, and composite resins thereof.

Furthermore, these resin substrates may be used with their surfaces treated, specifically with chemical conversion treatment, corona discharge treatment, flame treatment, plasma treatment, or acid or alkaline solution treatment, or laminates may be used in which the surface layer is coated with a different type of resin than the substrate itself.

Specific examples of laminates include laminates manufactured by co-extrusion or lamination, in which an acrylic resin layer or urethane resin layer is present on the surface of a polycarbonate resin substrate, and laminates in which an acrylic resin layer is present on the surface of a polyester resin substrate.

The photocurable coating composition may be applied directly to the surface of the substrate, or, if necessary, may be applied via a primer layer, ultraviolet absorbing layer, printing layer, recording layer, heat-shielding layer, adhesive layer, inorganic vapor deposition film layer, etc.

The coating method can be appropriately selected from known coating methods such as spin coater, comma coater, lip coater, roll coater, die coater, knife coater, blade coater, rod coater, kiss coater, gravure coater, screen coating, dip coating, and cast coating.

There are no particular restrictions on the thickness of the cured film produced from the photocurable coating composition of the present invention, but in order to prevent coating film damage and provide sufficient scratch resistance, as well as to maintain stable adhesion over the long term and prevent cracking, a thickness of 0.1 to 50 μm is preferred, and 1 to 30 μm is even more preferred.

Furthermore, if necessary, other coating layers such as an adhesive layer, ultraviolet absorbing layer, printing layer, recording layer, heat ray shielding layer, adhesive layer, inorganic vapor deposition film layer, water- and oil-repellent layer, and hydrophilic antifouling layer may be formed on the surface of the cured film of the photocurable coating composition of the present invention.

As described above, the cured film obtained from the photocurable coating composition of the present invention has excellent scratch resistance. To achieve even greater scratch resistance, an inorganic vapor deposition film layer may be coated onto the cured film.

The inorganic vapor deposition film layer is not particularly limited as long as it is formed by a dry film formation method, and examples include layers whose main component is at least one metal containing elements such as Si, Ti, Zn, Al, Ga, In, Ce, Bi, Sb, B, Zr, Sn, and Ta, or oxides, nitrides, and sulfides of these metals. Other examples include diamond-like carbon film layers, which have high hardness and excellent insulating properties.

The method for laminating the inorganic vapor deposition film layer is not particularly limited as long as it is a dry film formation method, and examples include physical vapor deposition methods such as resistance heating evaporation, electron beam evaporation, molecular beam epitaxy, ion beam deposition, ion plating, and sputtering, and chemical vapor deposition methods such as thermal CVD, plasma CVD, photo CVD, epitaxial CVD, atomic layer CVD, and cat CVD.

Coated articles coated with a cured film of the photocurable coating composition of the present invention obtained in this manner can have excellent water repellency, stain resistance, scratch resistance, and weather resistance, particularly weather crack resistance.

The photocurable coating composition of the present invention is preferably used as a photocurable coating composition for articles to be used outdoors.

In particular, it is preferred to use it for surface coating of automobile headlamp lenses, vehicle sensor covers, and plastic glass. The substrate for these is polycarbonate, which is commonly used because it combines high impact resistance, heat resistance, transparency, and lightness. However, polycarbonate lacks performance in areas such as chemical resistance, weather resistance, and scratch resistance, so it is preferable to coat the surface with the coating composition of the present invention to improve these performances.

Furthermore, polycarbonate coated with a coating film made from the photocurable coating composition of the present invention can prevent yellowing and weather-resistant cracking of the coating film, and further exhibits excellent water repellency and stain resistance, is lightweight, and is easily moldable, making it suitable for a wide range of uses, including automobile headlamp lenses, vehicle sensors, vehicle windows, outdoor signs, window glass for greenhouses and outdoor buildings, terrace and garage roofs, balconies, and instrument covers.

The present invention will be explained in more detail below with reference to examples and comparative examples, but the present invention is not limited to these examples.
In the following examples, unless otherwise specified, "parts" and "%" mean "parts by mass" and "% by mass", respectively. The devices used in the examples are as follows.

(1) GPC Measurement Conditions Apparatus: HLC-8320GPC manufactured by Tosoh Corporation
Column: TSKgel G4000HXL + G3000HXL + G2000HXL + G2000HXL (inner diameter 6 mm, length 150 mm) manufactured by Tosoh Corporation
Developing solution: tetrahydrofuran Column bath temperature: 40°C
Flow rate: 1mL/min
Detector: Refractive Index (RI)
Standard: Monodisperse polystyrene (2) Proton nuclear magnetic resonance spectrum ( ¹ H-NMR) measurement conditions Apparatus: AVANCE III 400 manufactured by BRUKER
Solvent: _CDCl3
Internal standard: tetramethylsilane (TMS)
(3) Infrared absorption spectrum (IR) measurement conditions Apparatus: Nicolet 6700 manufactured by Thermo Fisher
(4) Kinematic viscosity measurement conditions: This is a value measured at 25°C using a Cannon-Fenske viscometer in accordance with JIS Z 8803:2011.
(5) Average particle diameter measurement conditions Device: Nikkiso Co., Ltd. UPA-EX150
Method: The particle dispersion was diluted with methanol to a particle concentration of 1% by mass, and after irradiating with ultrasound for 10 minutes, measurements were taken to calculate the volume-based median particle diameter (D50).

[1] Synthesis of organopolysiloxane (component (A)) [Synthesis Example 1]
A 500 mL brown glass reactor equipped with a stirrer, thermometer, reflux condenser, and dropping funnel was charged with 53.4 g of a mono-end-carbinol-modified dimethylpolysiloxane (hydroxyl value 21.0 mgKOH/g) represented by the following formula (16), 0.02 g of t-butylhydroxytoluene as a polymerization inhibitor, and 0.02 g of di-n-octyltin oxide as a urethanization catalyst, and the mixture was heated and stirred until the internal temperature reached 70°C. 4.8 g of 1,1-(bisacryloyloxymethyl)ethyl isocyanate (manufactured by Resonac Corporation, Karenz BEI, molecular weight 239) was then added. The mixture was then reacted at 80°C for 5 hours. After cooling to 25°C, IR spectroscopy revealed that the absorption peak (2,260 cm ⁻¹ ) derived from the isocyanate group had almost completely disappeared, confirming the consumption of the raw material Karenz BEI. Next, 0.3 g of silica gel (trade name: Silica Gel 60N (spherical, neutral) particle size 40-100 μm, manufactured by Kanto Chemical Co., Inc.) was added, and the mixture was stirred at room temperature for 1 hour to adsorb the tin catalyst, which was then removed by filtration, yielding 56.8 g of colorless, transparent organopolysiloxane A-1. The kinematic viscosity of organopolysiloxane A-1 was 87.3 mm ² /s, and the nonvolatile content was 99.5%. The structure of A-1 confirmed by ¹ H-NMR measurement is shown in formula (17) below. Figure 1 shows the ¹ H-NMR spectrum of organopolysiloxane A-1.

[Synthesis Example 2]
A 500 mL brown glass reactor equipped with a stirrer, thermometer, reflux condenser, and dropping funnel was charged with 44.5 g of a one-end dicarbinol-modified dimethylpolysiloxane (hydroxyl value 126 mg KOH/g) represented by the following formula (18), 0.02 g of t-butylhydroxytoluene as a polymerization inhibitor, and 0.02 g of di-n-octyltin oxide as a urethanization catalyst, and the mixture was heated and stirred until the internal temperature reached 70°C. To this was added dropwise 14.1 g of 2-acryloyloxyethyl isocyanate (manufactured by Resonac Corporation, Karenz AOI, molecular weight 141) over 30 minutes. The mixture was then allowed to react at 80°C for 5 hours. After cooling to 25°C, IR spectroscopy revealed that the absorption peak (2,260 cm ⁻¹ ) derived from the isocyanate group had almost completely disappeared, confirming the consumption of the raw material Karenz AOI. Next, 0.3 g of silica gel (trade name: Silica Gel 60N (spherical, neutral) particle size 40-100 μm, manufactured by Kanto Chemical Co., Inc.) was added, and the mixture was stirred at room temperature for 1 hour to adsorb the tin catalyst, which was then removed by filtration, yielding 54.0 g of colorless, transparent organopolysiloxane A-2. The kinematic viscosity of organopolysiloxane A-2 was 474 mm ² /s, and the nonvolatile content was 99.4%. The structure of A-2 confirmed by ¹ H-NMR measurement is shown in formula (19) below.

[Synthesis Example 3]
A 500 mL brown glass reactor equipped with a stirrer, thermometer, reflux condenser, and dropping funnel was charged with 50.5 g of a one-end dicarbinol-modified dimethylpolysiloxane (hydroxyl value 37.0 mgKOH/g) represented by the following formula (20), 0.02 g of t-butylhydroxytoluene as a polymerization inhibitor, and 0.02 g of di-n-octyltin oxide as a urethanization catalyst, and the mixture was heated and stirred until the internal temperature reached 70°C. To this was added 8.0 g of 1,1-(bisacryloyloxymethyl)ethyl isocyanate (manufactured by Resonac Corporation, Karenz BEI, molecular weight 239) dropwise over 30 minutes. The mixture was then allowed to react at 80°C for 5 hours. After cooling to 25°C, IR spectroscopy revealed that the absorption peak (2,260 cm ⁻¹ ) derived from the isocyanate group had almost completely disappeared, confirming the consumption of the raw material Karenz BEI. Next, 0.3 g of silica gel (trade name: Silica Gel 60N (spherical, neutral) particle size 40-100 μm, manufactured by Kanto Chemical Co., Inc.) was added, and the mixture was stirred at room temperature for 1 hour to adsorb the tin catalyst, which was then removed by filtration, yielding 55.2 g of colorless, transparent organopolysiloxane A-3. The kinematic viscosity of organopolysiloxane A-3 was 2241 mm ² /s, and the nonvolatile content was 99.6%. The structure of A-3 confirmed by ¹ H-NMR measurement is shown in formula (21) below.

Synthesis Example 4 Synthesis of Urethane-Free Acryloyl Group-Containing Organopolysiloxane E-1 142 g of acryloyloxypropyltrimethoxysilane (KBM5103, manufactured by Shin-Etsu Chemical Co., Ltd.), 500 g of isopropyl alcohol, 0.1 g of p-methoxyphenol, 1.0 g of tetramethylammonium hydroxide, and 20 g of deionized water were combined and reacted at 20° C. for 24 hours to obtain a colorless, transparent liquid. The mixture was concentrated by distillation under reduced pressure to obtain colorless, transparent liquid organopolysiloxane E-1.

Synthesis Example 5 Synthesis of Silica Particles E-2 Surface-Treated with Acryloyl Group-Containing Silane A mixture of 2.8 g of acryloyloxypropyltrimethoxysilane (KBM5103, manufactured by Shin-Etsu Chemical Co., Ltd.), 95.6 g of methyl ethyl ketone-dispersed silica sol (MEK-ST, average particle size 45 nm, silica concentration 30%), and 0.1 g of ion-exchanged water was stirred at 80°C for 3 hours, and then 1.4 g of trimethyl orthoformate was added. The mixture was heated and stirred at the same temperature for an additional hour to obtain a dispersion of surface-treated silica particles E-2. The solids content of the resulting dispersion was 32% by mass, and the average particle size of the surface silica particles E-2 was 45 nm.

[2] Preparation of coating compositions and production of coated articles [Examples 1-1 to 1-7, Comparative Examples 1-1 to 1-6]
The following components (A) to (F) were mixed with stirring at room temperature in the amounts shown in Tables 1 and 2, and then filtered through a filter paper to prepare coating compositions (X1 to X7, R1 to R6).

(A) Component A-1: Organopolysiloxane obtained in Synthesis Example 1. A-2: Organopolysiloxane obtained in Synthesis Example 2. A-3: Organopolysiloxane obtained in Synthesis Example 3. A'-4 (comparison component): Organopolysiloxane modified with methacrylic acid at one end, represented by the following formula (22):
A'-5 (comparative component): acryl-modified organopolysiloxane at both ends represented by the following formula (23):
A'-6 (comparative component): A mixture containing 80% by mass of a one-terminal acrylic-modified organopolysiloxane of the following formula (24), 15% by mass of a diacrylate represented by the following formula (25), and 5% by mass of a non-functional organosiloxane represented by the following formula (26).
A'-7 (comparative component): acryl-modified organopolysiloxane at both ends represented by the following formula (27):

(B) Component B-1: Pentaerythritol triacrylate (A-TMM-3L, manufactured by Shin-Nakamura Chemical Co., Ltd.)
B-2: 1,6-hexanediol diacrylate (A-HD-N, manufactured by Shin-Nakamura Chemical Co., Ltd.)

(C) Component C-1: 2,4,6-trimethylbenzoyldiphenylphosphine oxide (manufactured by IGM, Omnirad TPO)
C-2: 1-hydroxycyclohexyl phenyl ketone (manufactured by IGM, Omnirad 184)

(D) Component D-1: 2-[4-[(2-hydroxy-3-(2'-ethyl)hexyl)oxy]-2-hydroxyphenyl]-4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine (manufactured by BASF, Tinuvin 405)
D-2: A hydroxyphenyltriazine derivative represented by the following formula (28):

(E) Component E-1: acryloyl group-containing organopolysiloxane obtained in Synthesis Example 4 E-2: surface-treated silica particles obtained in Synthesis Example 5 (32% by mass methyl ethyl ketone dispersion)

(F) Additive F-1: Polyether silicone leveling agent (manufactured by Shin-Etsu Chemical Co., Ltd., Leveling Agent A)

The coating compositions obtained in the above Examples and Comparative Examples were applied by flow coating to the surface of a polycarbonate NF-2000 sheet (2 mm thick × 15 cm long × 10 cm wide) manufactured by Mitsubishi Engineering-Plastics Corporation, followed by air drying for 5 minutes and heating at 60°C for 3 minutes. The coating film was then cured by irradiating it with light from a high-pressure mercury lamp at an exposure dose of 2,500 mJ/ ^cm2 , and the resulting test pieces were evaluated as follows. The results are shown in Tables 1 and 2. Furthermore, to evaluate weather resistance, a 100-hour test was conducted using an Iwasaki Electric Co., Ltd. Eye Super UV Tester W-151 under the following conditions: [black panel temperature 63°C, humidity 50% RH, illuminance 50 mW/ ^cm2 , rainfall 10 seconds per hour for 5 hours] → [black panel temperature 30°C, humidity 95% RH for 1 hour]. After the weather resistance test, the coating film was evaluated for the following evaluation items: coating film appearance, haze, water contact angle, and ease of wiping with a marker.

(1) Appearance of Coating Film The coating film was visually observed to determine whether there were any abnormalities.
○: No abnormalities △: Slight unevenness ×: Abnormalities such as foreign matter, unevenness, cracks, or peeling

(2) Haze The haze of the coating film was measured using a haze meter NDH5000SP manufactured by Nippon Denshoku Industries Co., Ltd. A haze of 1.5 or less was considered to be acceptable.

(3) Water Contact Angle A 2 μL droplet of pure water was brought into contact with the coating film and the contact angle was measured using a fully automatic contact angle meter DM-701 manufactured by Kyowa Interface Science Co., Ltd. A contact angle of 95° or more was deemed to be acceptable.

(4) Marker Wiping Ability A line of approximately 2 cm was written on the coating film using Zebra Corporation's Hi-Mackey (registered trademark) black, and then wiped twice with Nippon Paper Crecia Co., Ltd.'s Kaydry (registered trademark), and the appearance was visually observed and evaluated according to the following criteria.
○: No traces left, wiped off cleanly △: Mostly wiped off, but traces can be seen ×: Almost no wiped off

(5) Scratch Resistance Using a Gakushin-type abrasion tester AB-301 manufactured by Tester Sangyo Co., Ltd., steel wool No. 0000 was attached, and the haze was measured after 11 reciprocal movements under a load of 500 g. The difference in haze value before and after the test was taken as the scratch resistance. A haze difference of 7 or less was considered to be acceptable.

(6) Adhesion Using a razor blade, 25 grids were made in the coating film by cutting six cuts vertically and six cuts horizontally at 2 mm intervals, and after firmly adhering the grid with Cellotape (registered trademark) (manufactured by Nichiban Co., Ltd.), the grid was rapidly peeled off in a 90° direction toward the user. The number of grids (X) that remained without peeling of the coating film was recorded as X/25.

The coating films obtained from the coating compositions (X1 to X7) of the present invention in Examples 1-1 to 1-7 were excellent in initial appearance, haze, SW resistance, adhesion, water contact angle, and marker wiping ability. In particular, the water contact angle after the weathering test was high at over 95°, and no deterioration in marker wiping ability was observed. This result is presumably due to the fact that the organopolysiloxane (component A) contains multiple acrylic groups at one end, which creates a gradient structure with the multifunctional acrylate binder (component B) in the wet coating film, resulting in concentration at the coating film surface and strong three-dimensional crosslinking between component A and the binder, making the film less susceptible to deterioration. Furthermore, the reaction of only one end of the organopolysiloxane (component A) with the binder results in a structure in which siloxane chains stand up on the coating film surface, resulting in a high concentration of the siloxane component at the coating film surface.

On the other hand, the coating film made from Comparative Example 1-1 (R1), which did not contain the organopolysiloxane of the present invention as component (A), naturally had poor water contact angle and marker wipeability. Furthermore, because R1 did not contain the UV absorber (component (D)), cracks occurred in the coating film after the weather resistance test.

Furthermore, in Comparative Example 1-2 (R2), in which the organopolysiloxane (A) was blended at 25% of the total amount of compounds having photocurable reactive groups in the composition, the blended amount was too high, resulting in unevenness in the appearance of the coating film and high haze.

Comparative Examples 1-3 to 1-6 (R3 to R6), which used an (A) component other than the organopolysiloxane of the present invention, exhibited coating unevenness, high haze, poor SW resistance, low water contact angle, and poor marker wiping ability, and also exhibited a significant decrease in water contact angle after weather resistance testing. R3 uses an organopolysiloxane with one terminal monofunctional group as component (A), and the functional group is a methacrylic group, which has lower UV reactivity than an acryloyl group. This is thought to be why crosslinking with the binder was insufficient, causing phase separation with the binder and easily resulting in the removal of component (A) during SW resistance and weather resistance testing. R4 uses an organopolysiloxane with acrylic groups at both ends as component (A), and although initial evaluation was good, the water contact angle and marker wiping ability decreased after weather resistance testing. This is presumably because component (A) has acrylic groups at both ends, preventing siloxane chains from rising up on the coating surface, making thickening difficult. R5 contains an organopolysiloxane that does not contain (meth)acrylic groups, which likely resulted in slight unevenness in the coating appearance and high haze. The water contact angle and wipeability with a marker were also poor. R6 uses an organopolysiloxane with acryloyl groups at both ends as component (A), resulting in low water contact angles and wipeability with a marker. This is presumably due to the low content of dimethylpolysiloxane units in component (A). The water contact angle also decreased after the weathering test, which is presumably due to the presence of acrylic groups at both ends, preventing siloxane chains from rising up on the coating surface, making thickening difficult.

The present specification includes the following aspects.
[1]: A photocurable (meth)acrylic group-containing organopolysiloxane, characterized in that it is represented by the following general formula (1):
(In the formula, R1 ^'s are each independently a group selected from an alkyl group having 1 to 4 carbon atoms and an aryl group having 6 to 10 carbon atoms; R2 ^'s are each an alkyl group having 1 to 8 carbon atoms; X's are each a divalent or trivalent saturated hydrocarbon group which may have one or more atoms selected from oxygen and nitrogen atoms inserted in the molecular chain; Q's are each independently an (a+1)-valent saturated hydrocarbon group which may have an oxygen atom or nitrogen atom inserted in the molecular chain; Z's are each independently an acryloyloxy group or a methacryloyloxy group; a and b are each independently 1 or 2, provided that a and b are not both 1; when b is 1, a is 2; and when b is 2, a is 1 or 2; and n is an integer from 0 to 200.)
[2]: The organopolysiloxane of [1] above, characterized in that, in the general formula (1), the X is a group represented by the following formula (2) or (3), and the Q is a group represented by any one of the following formulas (4), (5), and (6):
(In the formula, * ¹ represents a bond to the silicon atom of the general formula (1), and * ² represents a bond to the oxygen atom in the urethane group of the general formula (1).)
(In the formula, * ⁵ represents a bond to Z in the general formula (1), and * ⁶ represents a bond to the nitrogen atom in the urethane group in the general formula (1).)
[3]: The organopolysiloxane of [2] above, wherein, in the general formula (1), X is a group represented by the formula (2), Q is a group represented by the formula (6), a is 2, and b is 1.
[4]: The organopolysiloxane of [2] above, wherein, in the general formula (1), X is a group represented by the formula (3), Q is a group represented by the formula (4), a is 1, and b is 2.
[5]: The organopolysiloxane of [2] above, wherein, in the general formula (1), X is a group represented by the formula (3), Q is a group represented by the formula (6), a is 2, and b is 2.
[6]: A photocurable coating composition,
(A) an organopolysiloxane represented by the following general formula (1):
(B) a polyfunctional (meth)acrylate compound other than the component (A), and (C) a photopolymerization initiator;
and the content of component (A) is 0.01 to 20 mass% relative to the total amount of compounds having a photocurable reactive group in the composition.
(In the formula, R1 ^'s are each independently a group selected from an alkyl group having 1 to 4 carbon atoms and an aryl group having 6 to 10 carbon atoms; R2 ^'s are each an alkyl group having 1 to 8 carbon atoms; X's are each a divalent or trivalent saturated hydrocarbon group which may have one or more atoms selected from oxygen and nitrogen atoms inserted in the molecular chain; Q's are each independently an (a+1)-valent saturated hydrocarbon group which may have an oxygen atom or nitrogen atom inserted in the molecular chain; Z's are each independently an acryloyloxy group or a methacryloyloxy group; a and b are each independently 1 or 2, provided that a and b are not both 1; when b is 1, a is 2; and when b is 2, a is 1 or 2; and n is an integer from 0 to 200.)
[7]: The photocurable coating composition according to [6] above, characterized in that, in the general formula (1), X is a group represented by the following formula (2) or (3), and Q is a group represented by any one of the following formulas (4), (5), and (6):
(In the formula, * ¹ represents a bond to the silicon atom of the general formula (1), and * ² represents a bond to the oxygen atom in the urethane group of the general formula (1).)
(In the formula, * ⁵ represents a bond to Z in the general formula (1), and * ⁶ represents a bond to the nitrogen atom in the urethane group in the general formula (1).)
[8]: The photocurable coating composition according to the above [6] or [7], further comprising (D) an ultraviolet absorber.
[9]: The photocurable coating composition according to the above [8], wherein the component (D) has a hydroxyphenyltriazine structure.
[10]: The photocurable coating composition according to the above [9], wherein the component (D) has a hydroxyphenyltriazine structure and a (meth)acryloyloxy group.
[11]: The photocurable coating composition according to any one of [8] to [10] above, wherein the content of component (D) relative to the total amount of compounds having a photocurable reactive group in the composition is 1 to 30 mass%.
[12]: The photocurable coating composition according to any one of [6] to [11] above, characterized in that the composition does not contain a compound containing a fluorine atom.

The present invention is not limited to the above-described embodiments. The above-described embodiments are merely examples, and anything that has substantially the same configuration as the technical concept described in the claims of the present invention and exhibits similar effects is included within the technical scope of the present invention.

Claims (12)

A photocurable (meth)acrylic group-containing organopolysiloxane, characterized in that it is represented by the following general formula (1):
(In the formula, R1 ^'s are each independently a group selected from an alkyl group having 1 to 4 carbon atoms and an aryl group having 6 to 10 carbon atoms; R2 ^'s are each an alkyl group having 1 to 8 carbon atoms; X's are each a divalent or trivalent saturated hydrocarbon group which may have one or more atoms selected from oxygen and nitrogen atoms inserted in the molecular chain; Q's are each independently an (a+1)-valent saturated hydrocarbon group which may have an oxygen atom or nitrogen atom inserted in the molecular chain; Z's are each independently an acryloyloxy group or a methacryloyloxy group; a and b are each independently 1 or 2, provided that a and b are not both 1; when b is 1, a is 2; and when b is 2, a is 1 or 2; and n is an integer from 0 to 200.) 2. The organopolysiloxane according to claim 1, wherein, in the general formula (1), X is a group represented by the following formula (2) or (3), and Q is a group represented by any one of the following formulas (4), (5), and (6):
(In the formula, * ¹ represents a bond to the silicon atom of the general formula (1), and * ² represents a bond to the oxygen atom in the urethane group of the general formula (1).)
(In the formula, * ⁵ represents a bond to Z in the general formula (1), and * ⁶ represents a bond to the nitrogen atom in the urethane group in the general formula (1).) The organopolysiloxane according to claim 2, characterized in that, in the general formula (1), X is a group represented by the formula (2), Q is a group represented by the formula (6), a is 2, and b is 1. The organopolysiloxane according to claim 2, characterized in that, in the general formula (1), X is a group represented by the formula (3), Q is a group represented by the formula (4), a is 1, and b is 2. The organopolysiloxane according to claim 2, characterized in that, in the general formula (1), X is a group represented by the formula (3), Q is a group represented by the formula (6), a is 2, and b is 2. 1. A photocurable coating composition comprising:
(A) an organopolysiloxane represented by the following general formula (1):
(B) a polyfunctional (meth)acrylate compound other than the component (A), and (C) a photopolymerization initiator;
and the content of component (A) is 0.01 to 20 mass% relative to the total amount of compounds having a photocurable reactive group in the composition.
(In the formula, R1 ^'s are each independently a group selected from an alkyl group having 1 to 4 carbon atoms and an aryl group having 6 to 10 carbon atoms; R2 ^'s are each an alkyl group having 1 to 8 carbon atoms; X's are each a divalent or trivalent saturated hydrocarbon group which may have one or more atoms selected from oxygen and nitrogen atoms inserted in the molecular chain; Q's are each independently an (a+1)-valent saturated hydrocarbon group which may have an oxygen atom or nitrogen atom inserted in the molecular chain; Z's are each independently an acryloyloxy group or a methacryloyloxy group; a and b are each independently 1 or 2, provided that a and b are not both 1; when b is 1, a is 2; and when b is 2, a is 1 or 2; and n is an integer from 0 to 200.) The photocurable coating composition according to claim 6, characterized in that, in the general formula (1), X is a group represented by the following formula (2) or (3), and Q is a group represented by any one of the following formulas (4), (5), and (6):
(In the formula, * ¹ represents a bond to the silicon atom of the general formula (1), and * ² represents a bond to the oxygen atom in the urethane group of the general formula (1).)
(In the formula, * ⁵ represents a bond to Z in the general formula (1), and * ⁶ represents a bond to the nitrogen atom in the urethane group in the general formula (1).) The photocurable coating composition according to claim 6, further comprising (D) an ultraviolet absorber. The photocurable coating composition according to claim 8, characterized in that component (D) has a hydroxyphenyltriazine structure. The photocurable coating composition according to claim 9, characterized in that component (D) has a hydroxyphenyltriazine structure and a (meth)acryloyloxy group. The photocurable coating composition according to claim 8, characterized in that the content of component (D) is 1 to 30 mass% relative to the total amount of compounds having a photocurable reactive group in the composition. The photocurable coating composition according to any one of claims 6 to 11, characterized in that the composition does not contain a compound containing a fluorine atom.