WO2025225088A1 - Coating composition, coat film, and base material - Google Patents

Abstract

The present invention provides: a coating composition containing a compound represented by formula (1); a coat film obtained by curing the coating composition; and a base material comprising the coat film. In formula (1), R1-R3 each independently represent a hydrogen atom or a monovalent organic group, a-d represent molar ratios, a and b each independently represent a positive number, and c and d each independently represent 0 or a positive number.

Description

Coating composition, coating film, and substrate

This disclosure relates to a coating composition, a coating film, and a substrate.

BACKGROUND ART Flexible devices such as foldable devices that can be bent and rollable devices that can be rolled up are becoming popular.
The displays of these devices are required to have flexibility, transparency, surface hardness, and the like.
When a plastic film is used in a flexible display, a coating film layer with high surface hardness is often provided to prevent scratches.
Ultra-thin glass, which is hard and bendable, is sometimes used as the substrate. In this case, too, a coating film layer is provided to maintain the surface hardness and prevent cracking or shattering when subjected to impact.

Foldable display shapes include, for example, an infold shape (inward bending) where the coated film surface is on the inside, an outfold shape (outward bending) where the coated film surface is on the outside, and a tri-fold shape where the coated film surface is on both the inside and outside (folded in a Z-shape).

Examples of coating compositions with high surface hardness include acrylates, epoxy resins, and silsesquioxane derivatives.
In addition to various resin films, tempered glass may be used as the substrate. In the case of tempered glass, cationic or anionic curing systems may cause polymerization inhibition and may not be usable.

As conventional coating compositions, several coating compositions have been disclosed which produce cured films that are excellent in abrasion resistance and flexible.
Patent Document 1 discloses a bendable film comprising a substrate, a coating film layer, and an abrasion-resistant layer.
Furthermore, Patent Document 2 discloses a scratch-resistant coating made of a silsesquioxane compound formed by the reaction of a polymerizable functional group with an active hydrogen atom.
Patent Document 3 discloses an anti-scratch coating containing a cationically polymerizable compound and a radically polymerizable compound.

Japanese Patent Application Laid-Open No. 2023-113598 International Publication No. 2021/060055 International Publication No. 2019/146659

Patent Document 1 describes excellent scratch resistance and flexibility, but to achieve this, it is necessary to apply at least two types of coatings in sequence, which makes the process complicated and increases the risk of thickening the film. Furthermore, the outermost surface contains a fluorine-containing compound, which has low surface free energy, making it difficult to process onto upper layers, and there are also concerns about the environmental impact.
The invention described in Patent Document 2 can withstand continuous bending at a bending radius of 2 mm, but the scratch resistance is only 200 g load, which may result in insufficient scratch resistance. In addition, the outermost surface has a fluorine-containing compound, which has low surface free energy, which may make processing onto upper layers difficult, and there are also concerns about the environmental impact.
The invention described in Patent Document 3 is evaluated at a bending radius of 2.5 mm, and there is a concern that it cannot be applied to thin modules.

The present disclosure has been made in light of the above, and aims to provide a coating composition that produces a coating film with excellent scratch resistance, a coating film obtained by curing the coating composition, and a substrate provided with the coating film.

The means for solving the above problems include the following aspects.
<1> A coating composition containing a compound represented by the following formula (1):

In formula (1), R ¹ to R ³ each independently represent a hydrogen atom or a monovalent organic group, a to d each independently represent a molar ratio, a and b each independently represent a positive number, and c and d each independently represent 0 or a positive number.

<2> The coating composition according to <1>, wherein R ¹ contains a group having a polymerizable functional group, and the relationship a/b satisfies 0.4<a/b<1.5.
<3> The coating composition according to <1> or <2>, which is capable of forming a film having an average indentation hardness of 0.40 GPa or more at a surface depth of 200 nm to 400 nm as measured with a nanoindenter.
<4> The coating composition according to any one of <1> to <3>, further comprising inorganic particles and a polymerization initiator.
<5> The coating composition according to <4>, wherein the inorganic particles have an average particle size of less than 1 μm.
<6> The coating composition according to <4> or <5>, wherein the inorganic particles are silica particles.
<7> The coating composition according to any one of <4> to <6>, wherein the mass ratio of the inorganic particles in the coating composition excluding the solvent and the polymerization initiator is 50 mass % or less.
<8> The coating composition according to any one of <1> to <7>, further comprising a di- or higher functional (meth)acrylate compound or a di- or higher functional epoxy compound.
<9> The coating composition according to <8>, wherein a mass ratio of the di- or higher functional (meth)acrylate compound or the di- or higher functional epoxy compound in the coating composition excluding the solvent and the polymerization initiator is more than 0 mass% and less than 35 mass%.
<10> The coating composition according to any one of <1> to <9>, wherein a film having a thickness of less than 10 μm obtained by curing the coating composition does not break even when bent inward 200,000 times continuously at a bending radius R of 1.5 mm.
<11> A coating film obtained by curing the coating composition according to any one of <1> to <10>.
<12> A substrate provided with the coating film according to <11>.

The present disclosure provides a coating composition that produces a coating film with excellent scratch resistance, a coating film obtained by curing the coating composition, and a substrate that includes the coating film.

Hereinafter, embodiments for carrying out the present disclosure will be described in detail. However, the present disclosure is not limited to the following embodiments. In the following embodiments, components (including element steps, etc.) are not essential unless otherwise specified. The same applies to numerical values and their ranges, and do not limit the present disclosure.
In this specification, when a numerical range is indicated using "to", the numerical values before and after "to" are included as the minimum and maximum values, respectively.
In the present specification, the upper or lower limit of one numerical range may be replaced with the upper or lower limit of another numerical range. In addition, in the present specification, the upper or lower limit of a numerical range may be replaced with a value shown in the examples.
Also, in this specification, a combination of two or more preferred embodiments is a more preferred embodiment.

In the present specification, R ¹ to R ³ in formula (1) may each independently be partially substituted with a substituent or a halogen atom. For example, R ¹ to R ³ may each independently be partially substituted with an alkyl group, an aryl group, an aralkyl group, a vinyl group, an epoxy group, an oxetanyl group, a hydroxyl group, an amino group, an alkylamino group, an arylamino group, an aralkylamino group, an ammonium group, a thiol group, an isocyanurate group, a ureido group, an isocyanate group, a carboxy group, an acid anhydride group, or a halogen atom.

[Coating composition]
The coating composition according to the present disclosure is a coating composition containing a compound represented by the following formula (1):

In formula (1), R ¹ to R ³ each independently represent a hydrogen atom or a monovalent organic group, a to d each independently represent a molar ratio, a and b each independently represent a positive number, and c and d each independently represent 0 or a positive number.

As described above, conventional coating compositions have not provided sufficient scratch resistance in the cured products thereof.
As a result of extensive investigations, the present inventors have found that by adopting the above-mentioned constitution, it is possible to provide a coating composition which gives a coating film having excellent scratch resistance.
It is presumed that when a and b in the formula (1) are positive numbers, an appropriate crosslinked structure can be obtained after curing, and therefore a coating film with excellent scratch resistance can be produced.

Furthermore, the coating film obtained by curing the coating composition according to the present disclosure also has excellent resistance to continuous bending.
Furthermore, the coating film obtained by curing the coating composition according to the present disclosure has excellent hardness while maintaining the aforementioned resistance to continuous bending, thereby making it possible to obtain a display or lens with high durability.

(Compound represented by formula (1))
The coating composition according to the present disclosure contains the compound represented by formula (1).

The structural units that may be contained in the silsesquioxane derivatives used in this disclosure are referred to as structural units (a) to (d) as follows:

In the compound represented by formula (1), a and b each independently represent a positive number, and c and d each independently represent 0 or a positive number. In other words, the compound represented by formula (1) contains, of the structural units (a) to (d) described above, structural unit (a) and structural unit (b), and may optionally contain at least one of structural unit (c) and structural unit (d).

In formula (1), a to d represent the molar ratio of the structural units (a) to (d). In formula (1), a to d represent the relative molar ratio of the structural units (a) to (d) that may be contained in the compound represented by formula (1). The molar ratio can be determined, for example, from the NMR (nuclear magnetic resonance) analysis value of the compound represented by formula (1). Furthermore, when the reaction rate of each raw material for the compound represented by formula (1) is known, or when the yield is 100%, the molar ratio can be determined from the amount of the raw material charged.
For example, the molar ratio of each constitutional unit of the compound represented by formula (1) may be calculated by subjecting a sample dissolved in deuterated chloroform or the like to ¹ H-NMR analysis, and, if necessary, further subjecting the sample to ²⁹ Si-NMR analysis.
The structure of the original compound represented by formula (1) may be estimated from the ratio of the constituent units after decomposing the compound into constituent units with an alkali or the like.
If necessary, the molar ratio of each structural unit of the compound represented by formula (1) may be determined by a combination of known techniques such as mass spectrometry and IR (infrared absorption spectroscopy) analysis.

Each of the structural units (b) to (d) in formula (1) may be of only one type, or may be of two or more types. Furthermore, the order of arrangement in formula (1) indicates the composition of the structural units, but does not refer to the order of arrangement of the compound represented by formula (1). Therefore, the condensation form of the structural units in the compound represented by formula (1) does not necessarily have to be the same as the order of arrangement in formula (1).
The structural units (a) to (d) and the other structural unit (e) will be described in detail below.

(Structural Unit (a))
The structural unit (a) is a Q unit having four O _0.5 (two oxygen atoms) per silicon atom. Note that the Q unit refers to a unit having four O _0.5 per silicon atom.

The proportion of structural unit (a) in the compound represented by formula (1) is not particularly limited, but from the viewpoints of abrasion resistance, continuous bending resistance, and hardness, it is preferably 1% by mass to 80% by mass, more preferably 5% by mass to 65% by mass, and particularly preferably 10% by mass to 50% by mass, relative to the total mass of the compound represented by formula (1).

(Structural unit (b))
The structural unit (b) is a T unit having three O _0.5 (1.5 oxygen atoms) per silicon atom and a monovalent organic group bonded to the silicon atom. Note that the T unit means a unit having three O _0.5 per silicon atom.

The compound represented by formula (1) may contain one type of R ¹ alone or two or more types.
From the viewpoints of abrasion resistance, continuous bending resistance, and hardness, R ¹ preferably contains a group having a polymerizable functional group, and more preferably is a group having a radically polymerizable functional group or a cationically polymerizable functional group.
As the radical polymerizable group, from the viewpoints of reactivity, scratch resistance, resistance to continuous bending, and hardness, an ethylenically unsaturated group is preferred, and a (meth)acrylate group is more preferred, and as the cationically polymerizable functional group, an epoxy group or an oxetanyl group is preferred.
When R ¹ contains a radical polymerizable group, from the viewpoints of abrasion resistance, continuous flex resistance, and hardness, it preferably contains a group represented by the following formula (R1-1), and is more preferably a group represented by the following formula (R1-1). Furthermore, when R ¹ contains a cationically polymerizable group, from the viewpoints of abrasion resistance, continuous flex resistance, and hardness, it preferably contains a group represented by the following formula (R1-2), and is more preferably a group represented by the following formula (R1-2).

In formula (R1-1) and formula (R1-2), ^Rb represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, ^L1 represents an alkylene group having 1 to 10 carbon atoms, a cycloalkylene group having 3 to 10 carbon atoms, an arylene group having 6 to 10 carbon atoms, or an aralkylene group having 7 to 12 carbon atoms, and * represents the bonding position to the silicon atom.

^L1 is preferably an alkylene group having 1 to 10 carbon atoms or a cycloalkylene group having 3 to 10 carbon atoms, and more preferably an alkylene group having 1 to 10 carbon atoms.
The alkylene group having 1 to 10 carbon atoms is preferably an alkylene group having 1 to 6 carbon atoms, more preferably an alkylene group having 2 to 4 carbon atoms, and even more preferably a propylene group. The alkylene group having 1 to 10 carbon atoms may be linear or branched.
The cycloalkylene group having 3 to 10 carbon atoms is preferably a cycloalkylene group having 3 to 6 carbon atoms, and more preferably a cycloalkylene group having 4 to 6 carbon atoms. The cycloalkylene group having 3 to 10 carbon atoms may be branched.
Examples of the alkyl group having 1 to 6 carbon atoms for R ^b include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, and a hexyl group, with a methyl group and an ethyl group being preferred, and a methyl group being more preferred.

Furthermore, ^R1 is preferably a hydrogen atom, a saturated or unsaturated chain hydrocarbon group having 1 to 20 carbon atoms, a saturated or unsaturated cyclic hydrocarbon group having 3 to 8 carbon atoms, an aryl group having 6 to 20 carbon atoms, or an aralkyl group having 7 to 20 carbon atoms.

The saturated or unsaturated chain hydrocarbon group having 1 to 20 carbon atoms may be linear or branched. The saturated or unsaturated chain hydrocarbon group having 1 to 20 carbon atoms is preferably a saturated or unsaturated chain hydrocarbon group having 1 to 10 carbon atoms, and more preferably a saturated chain hydrocarbon group having 1 to 10 carbon atoms.

Examples of saturated chain hydrocarbon groups having 1 to 10 carbon atoms include methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, and decyl groups. From the standpoint of heat resistance and hardness of the cured product, methyl or ethyl groups are preferred, with methyl groups being more preferred.

Examples of unsaturated chain hydrocarbon groups having 1 to 10 carbon atoms include vinyl groups, 2-propenyl groups, and ethynyl groups.

The saturated or unsaturated cyclic hydrocarbon group having 3 to 8 carbon atoms may be branched. The saturated or unsaturated cyclic hydrocarbon group having 3 to 8 carbon atoms is preferably a saturated or unsaturated cyclic hydrocarbon group having 4 to 6 carbon atoms.

The aryl group having 6 to 20 carbon atoms is preferably an aryl group having 6 to 10 carbon atoms.

Examples of aryl groups having 6 to 20 carbon atoms include phenyl groups, groups in which one or more hydrogen atoms of a phenyl group are substituted with an alkyl group having 1 to 10 carbon atoms, and naphthyl groups. From the standpoint of heat resistance and hardness of the cured product, phenyl groups are preferred.

The aralkyl group having 7 to 20 carbon atoms is preferably an aralkyl group having 7 to 10 carbon atoms.

Examples of aralkyl groups having 7 to 20 carbon atoms include groups in which one hydrogen atom of an alkyl group having 1 to 10 carbon atoms is substituted with an aryl group such as a phenyl group. Examples include benzyl groups and phenethyl groups, with benzyl groups being preferred from the standpoint of heat resistance and hardness of the cured product.

When part of the groups in ^R1 is substituted with a substituent or a halogen atom, examples of ^R1 include a 3-glycidoxypropyl group, a 2-(3,4-epoxycyclohexyl)ethyl group, a 3-(3-ethyloxetan-3-yl)methoxypropyl group, a 3-hydroxypropyl group, a 3-aminopropyl group, a 3-dimethylaminopropyl group, a 3-hydroxypropyl group, a 3-aminopropyl hydrochloride salt, a 3-dimethylaminopropyl hydrochloride salt, a p-styryl group, an N-2-(aminoethyl)-3-aminopropyl group, an N-phenyl-3-aminopropyl group, an N-(vinylbenzyl)-2-aminoethyl-3-aminopropyl hydrochloride salt, a 3-ureidopropyl group, a 3-mercaptopropyl group, a 3-isocyanatopropyl group, a 3-carboxypropyl group, and a 3-chloropropyl group.

The proportion of structural unit (b) in the compound represented by formula (1) is not particularly limited, but from the viewpoints of abrasion resistance, continuous bending resistance, and hardness, it is preferably 20% by mass or more, more preferably 30% by mass or more, and particularly preferably 30% by mass to 90% by mass, relative to the total mass of the compound represented by formula (1).

Furthermore, from the viewpoints of abrasion resistance, continuous bending resistance, and hardness, the value of a/b preferably satisfies 0.2<a/b<2.0, more preferably 0.4<a/b<1.5, and particularly preferably 0.5<a/b<1.3.

(Structural unit (c))
The structural unit (c) is a D unit having two O _0.5 (one oxygen atom) per silicon atom, and two R ⁵ 's bonded to the silicon atom. The D unit refers to a unit having two O _0.5 per silicon atom.

In the structural unit (c), each ^R2 is preferably independently a hydrogen atom, a saturated or unsaturated chain hydrocarbon group having 1 to 20 carbon atoms, a saturated or unsaturated cyclic hydrocarbon group having 3 to 8 carbon atoms, an aryl group having 6 to 20 carbon atoms, or an aralkyl group having ⁷ to 20 carbon atoms. In the structural unit (c), multiple ^R2s may be the same or different. Preferred embodiments of the saturated or unsaturated chain hydrocarbon group having 1 to 20 carbon atoms, saturated or unsaturated cyclic hydrocarbon group having 3 to 8 carbon atoms, aryl group having 6 to 20 carbon atoms, and aralkyl group having 7 to 20 carbon atoms in ^R2 are the same as the preferred embodiments of the saturated or unsaturated chain hydrocarbon group having 1 to 20 carbon atoms, saturated or unsaturated cyclic hydrocarbon group having 3 to 8 carbon atoms, aryl group having 6 to 20 carbon atoms, and aralkyl group having 7 to 20 carbon atoms in R1.

From the viewpoints of abrasion resistance, continuous bending resistance, and hardness, the proportion of structural unit (c) in the compound represented by formula (1) is preferably 10% by mass or less, more preferably 5% by mass or less, even more preferably 1% by mass or less, and particularly preferably 0% by mass, relative to the total mass of the compound represented by formula (1).

Furthermore, from the viewpoints of abrasion resistance, continuous bending resistance, and hardness, the value of c/b preferably satisfies 0≦c/b<0.1, more preferably 0≦c/b<0.05, and particularly preferably 0≦c/b<0.01.

(Structural unit (d))
The structural unit (d) is an M unit having one O _0.5 (0.5 oxygen atoms) per silicon atom, and three R ^3s bonded to the silicon atom. Note that the M unit refers to a unit having one O _0.5 per silicon atom.

Each ^R3 is preferably independently an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms, or an aralkyl group having 7 to 10 carbon atoms. In the structural unit (d), multiple ^R3s may be the same or different. Preferred aspects of ^R3 are the same as those of ^R2 in the structural unit (c).

From the viewpoints of abrasion resistance, continuous bending resistance, and hardness, the proportion of structural unit (d) in the compound represented by formula (1) is preferably 10% by mass or less, more preferably 5% by mass or less, even more preferably 1% by mass or less, and particularly preferably 0% by mass, relative to the total mass of the compound represented by formula (1).

Furthermore, from the viewpoints of abrasion resistance, continuous bending resistance, and hardness, the value of d/b preferably satisfies 0≦d/b<0.1, more preferably 0≦d/b<0.05, and particularly preferably 0≦d/b<0.01.

(Other structural units (e))
The silsesquioxane derivative represented by formula (1) may further contain (R ⁴ O _1/2 ) as a structural unit not containing Si (hereinafter also referred to as structural unit (e)).
Here, ^R4 is a hydrogen atom or an alkyl group having 1 to 6 carbon atoms. The alkyl group having 1 to 6 carbon atoms may be either an aliphatic group or an alicyclic group, and may be either linear or branched. Specific examples of the alkyl group having 1 to 6 carbon atoms include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, and a hexyl group.

The structural unit (e) is an alkoxy group, which is a hydrolyzable group contained in the silicon compound described below, or an alkoxy group formed when an alcohol contained in the reaction solvent substitutes for a hydrolyzable group in the silicon compound, and may be one that remains in the molecule without being hydrolyzed or polycondensed, or it may be a hydroxyl group that remains in the molecule after hydrolysis without being polycondensed.

The weight average molecular weight (hereinafter also referred to as "Mw") of the compound represented by formula (1) is not particularly limited, and may be, for example, 300 to 50,000, 500 to 25,000, 700 to 20,000, or 1,000 to 15,000.
In the present disclosure, Mw refers to a value obtained by converting the molecular weight measured by GPC (gel permeation chromatography) using polystyrene as a standard substance. The measurement conditions for Mw can be, for example, the measurement conditions in the Examples described below.

(Method for producing a compound represented by formula (1))
The compound represented by formula (1) can be produced by a known method. A method for producing a silsesquioxane derivative is disclosed in detail in WO 2013/031798 and the like as a method for producing a polysiloxane.

Among these, the method for producing the compound represented by formula (1) preferably comprises a step of hydrolyzing at least one organosilicon compound represented by R _n SiX _p (n represents an integer of 0 to 3, p represents an integer of 1 to 4, n+p=4, R represents a group bonded to a silicon atom in the silsesquioxane derivative via a carbon atom, and X represents a hydrolyzable group) using an organic solvent and adding 1.5 molar equivalents or more of water relative to the total amount of hydrolyzable groups possessed by the organosilicon compound (hereinafter also referred to as the "hydrolysis step").
Suitable examples of R include groups bonded to the silicon atom in the silsesquioxane derivative via a carbon atom (H ₂ C═CHCOO—R ¹ —, H ₂ C═C(R ³ )COO—R ² —, and R ⁴ to R ^8, etc.).
X is preferably an alkoxy group, a silyloxy group, or a halogen atom, and more preferably an alkoxy group or a silyloxy group.

In the hydrolysis step, it is preferable to carry out not only the hydrolysis of the organosilicon compound but also the hydrolysis and polycondensation reaction of the organosilicon compound and, if necessary, other silicon compounds.
In the hydrolysis step, the organosilicon compound and, if necessary, other silicon compounds may be subjected to hydrolysis and polycondensation reactions to obtain a silsesquioxane derivative as an intermediate product, and then the obtained intermediate product may be further subjected to hydrolysis and polycondensation reactions with the organosilicon compound and the like.

When obtaining an intermediate product as described above, after carrying out hydrolysis and polycondensation reactions of the organosilicon compound and, if necessary, other silicon compounds, it is possible to further carry out hydrolysis and polycondensation reactions of the obtained intermediate product with a compound in which n is 3 and p is 1 in the organosilicon compound. This makes it possible to suitably synthesize a compound represented by formula (1) whose terminal portions are blocked with structural unit (e) derived from the compound in which n is 3 and p is 1 in the organosilicon compound, thereby suppressing an increase in viscosity of the silsesquioxane derivative and improving storage stability.

The method for producing the compound represented by formula (1) preferably includes a distillation step in which, after hydrolysis and polycondensation of a silicon compound in the presence of a reaction solvent, the reaction solvent, by-products, residual monomers, water, etc. are distilled off from the reaction liquid.

Among the above-mentioned organosilicon compounds, examples of those containing an acryloyl group include (3-acryloyloxypropyl)trimethoxysilane, (3-acryloyloxypropyl)triethoxysilane, (8-acryloyloxyoctyl)trimethoxysilane, and (3-acryloyloxypropyl)trichlorosilane.

Among the above-mentioned organosilicon compounds, examples of those containing a methacryloyl group include (3-methacryloyloxypropyl)trimethoxysilane, (3-methacryloyloxypropyl)triethoxysilane, (8-methacryloyloxyoctyl)trimethoxysilane, and (3-methacryloyloxypropyl)trichlorosilane.

Among the above organosilicon compounds, examples of those containing an oxetanyl group include (3-ethyl-3-oxetanylmethoxypropyl)trimethoxysilane, (3-ethyl-3-oxetanylmethoxypropyl)triethoxysilane, (3-methyl-3-oxetanylmethoxypropyl)trimethoxysilane, and (3-oxetanylmethoxypropyl)trichlorosilane.

Among the above organosilicon compounds, those containing epoxy groups include, for example, (glycidyloxypropyl)trimethoxysilane, (glycidyloxypropyl)triethoxysilane, and 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane.

Examples of silicon compounds that give structural unit (a) upon hydrolysis include tetramethoxysilane, tetraethoxysilane, and tetrapropoxysilane.

Examples of the organosilicon compounds where n is 3 and p is 1 include methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, propyltrimethoxysilane, octyltrimethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, benzyltrimethoxysilane, cyclohexyltrimethoxysilane, vinyltrimethoxysilane, allyltrimethoxysilane, p-styryltrimethoxysilane, ethynyltrimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, and 3-aminopropyltrimethoxysilane. Examples include trimethoxysilane, 3-triethoxysilyl-N-(1,3-dimethyl-butylidene)propylamine, N-phenyl-3-aminopropyltrimethoxysilane, N-(vinylbenzyl)-2-aminoethyl-3-aminopropyltrimethoxysilane hydrochloride, 3-ureidopropyltrimethoxysilane, 3-ureidopropyltriethoxysilane, 3-isocyanatepropyltriethoxysilane, tris(trimethoxysilylpropyl)isocyanurate, 3-mercaptopropyltrimethoxysilane, 3-ethyl-3-[{3-(trimethoxysilyl)propoxy}methyl]oxetane, and 3-ethyl-3-[{3-(triethoxysilyl)propoxy}methyl]oxetane.

Examples of the organosilicon compounds where n is 2 and p is 2 include dimethyldimethoxysilane, dimethyldiethoxysilane, diethyldidiethoxysilane, propylmethyldimethoxysilane, octylmethyldimethoxysilane, phenylmethyldimethoxysilane, diphenyldiethoxysilane, benzylmethyldimethoxysilane, cyclohexylmethyldimethoxysilane, vinylmethyldimethoxysilane, allylmethyldimethoxysilane, p-styrylmethyldimethoxysilane, ethynylmethyldimethoxysilane, 2-(3,4-epoxycyclohexyl)ethylmethyldimethoxysilane, Examples include silane, 3-glycidoxypropylmethyldimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, 3-aminopropylmethyldimethoxysilane, N-phenyl-3-aminopropylmethyldimethoxysilane, N-(vinylbenzyl)-2-aminoethyl-3-aminopropylmethyldimethoxysilane hydrochloride, 3-ureidopropylmethyldialkoxysilane, 3-isocyanatopropylmethyldiethoxysilane, (3-acryloxypropyl)methyldimethoxysilane, and (3-methacryloxypropyl)methyldiethoxysilane.

Examples of the organosilicon compound where n is 1 and p is 3 include hexamethyldisiloxane, trimethylmethoxysilane, trimethylethoxysilane, trimethylchlorosilane, and dimethylphenylmethoxysilane.

In the hydrolysis step, the reaction solvent is not particularly limited, but it is preferable to use an alcohol as the organic solvent. The alcohol is an alcohol in the narrow sense represented by the general formula R—OH, and is a compound having no functional groups other than an alcoholic hydroxyl group.
The alcohol is not particularly limited, and examples thereof include methanol, ethanol, 1-propanol, 2-propanol, 2-butanol, 2-pentanol, 3-pentanol, 2-methyl-2-butanol, 3-methyl-2-butanol, cyclopentanol, 2-hexanol, 3-hexanol, 2-methyl-2-pentanol, 3-methyl-2-pentanol, 2-methyl-3-pentanol, 3-methyl-3-pentanol, 2-ethyl-2-butanol, 2,3-dimethyl-2-butanol, and cyclohexanol. Among these, secondary alcohols such as 2-propanol, 2-butanol, 2-pentanol, 3-pentanol, 3-methyl-2-butanol, cyclopentanol, 2-hexanol, 3-hexanol, 3-methyl-2-pentanol, and cyclohexanol are preferred.
In the hydrolysis step, these alcohols may be used alone or in combination of two or more.

The organic solvent used in the hydrolysis step may be alcohol alone or may be a mixed solvent containing at least one auxiliary solvent, which may be either a polar solvent or a non-polar solvent, or a combination of both.
Examples of organic solvents other than alcohol include xylene, toluene, methyl ethyl ketone, methyl isobutyl ketone, and propylene glycol monomethyl ether.

The hydrolysis and condensation reactions in the hydrolysis step proceed in the presence of water.
In the hydrolysis step, it is preferred to add water in an amount of 0.5 to 30 molar equivalents relative to the total amount of hydrolyzable groups possessed by the organosilicon compound to carry out hydrolysis, followed by further condensation.
Furthermore, in the hydrolysis step, the amount of water added is preferably 0.6 molar equivalents or more, more preferably 0.7 molar equivalents or more, even more preferably 0.8 to 8 molar equivalents, particularly preferably 0.9 to 7 molar equivalents, and most preferably 1.0 to 6 molar equivalents, relative to the total amount of hydrolyzable groups in the organosilicon compound, from the viewpoints of the cure shrinkage rate, hardness, storage stability, and curl suppression during curing of the resulting compound represented by formula (1).

The hydrolysis and polycondensation reaction of the silicon compound may be carried out without a catalyst or with a catalyst. When a catalyst is used, preferred catalysts include inorganic acids such as sulfuric acid, nitric acid, hydrochloric acid, and phosphoric acid; organic acids such as formic acid, acetic acid, oxalic acid, and paratoluenesulfonic acid; and base catalysts such as ammonia, tetramethylammonium hydroxide, sodium hydroxide, potassium hydroxide, sodium carbonate, and potassium carbonate.
The amount of catalyst used is preferably an amount corresponding to 0.01 mol % to 20 mol %, and more preferably an amount corresponding to 0.1 mol % to 10 mol %, based on the total amount (mol) of silicon atoms contained in the silicon compound.

The completion of the hydrolysis and polycondensation reaction in the hydrolysis step can be appropriately detected using methods described in various publications. Note that an auxiliary agent can be added to the reaction system in the hydrolysis step of the method for producing the compound represented by formula (1).

By including the aforementioned distillation step after the hydrolysis step in the production of the compound represented by formula (1), the stability of the resulting silsesquioxane derivative of the present disclosure can be improved. Distillation can be carried out under normal pressure or reduced pressure, at room temperature or under heating, or under cooling.

The method for producing the compound represented by formula (1) can include a neutralization step for neutralizing the catalyst prior to the distillation step. It can also include a step for removing the salt produced by neutralization by washing with water, etc.

The compound represented by formula (1) may contain, among the side-chain functional groups derived from the silicon compound used as a raw material in its production, a group formed by ring-opening upon addition of an acid or the like to an oxetanyl group or an epoxy group, a hydroxyalkyl group formed by decomposition of an organic group having a (meth)acryloyl group, or a group formed by addition of an acid or the like to an unsaturated hydrocarbon group. Specific examples include those in which a structure represented by formula (A) and/or a structure represented by formula (B) below is included as part of formula (1). The content of these groups is sufficient for implementing the present disclosure as long as it is 50 mol% or less relative to the amount corresponding to the original organic group having an oxetanyl group or an epoxy group, the original organic group having a (meth)acryloyl group, or the original organic group having an unsaturated hydrocarbon group derived from the silicon compound as a raw material. A content of 30 mol% or less is preferred, and a content of 10 mol% or less is more preferred. In both formulas (A) and (B), T units are exemplified, but similar D units, M units, etc. may also be used.

(Polymerization initiator)
The coating composition according to the present disclosure preferably further contains a polymerization initiator, and more preferably contains a radical polymerization initiator.
The polymerization initiator is not particularly limited, and examples thereof include a photopolymerization initiator and a thermal polymerization initiator. Examples of the photopolymerization initiator include a photoradical polymerization initiator.
The thermal polymerization initiator may be, for example, a thermal radical polymerization initiator.
As the photopolymerization initiator and the thermal polymerization initiator, known compounds may be used.

Photopolymerization initiators include 4-methylphenyl-4-(1-methylethyl)phenyliodonium tetrakis(pentafluorophenyl)borate, 2,2-dimethoxy-1,2-diphenylethan-1-one, 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-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one, and 2-benzyl-2- Acetophenone compounds such as dimethylamino-1-(4-morpholinophenyl)-butan-1-one, diethoxyacetophenone, oligo[2-hydroxy-2-methyl-1-[4-(1-methylvinyl)phenyl]propanone] and 2-hydroxy-1-{4-[4-(2-hydroxy-2-methyl-propionyl)benzyl]phenyl}-2-methyl-propan-1-one; benzophenone compounds such as benzophenone, 4-phenylbenzophenone, 2,4,6-trimethylbenzophenone and 4-benzoyl-4'-methyldiphenyl sulfide α-ketoester compounds such as methyl benzoyl formate, oxyphenylacetic acid 2-[2-oxo-2-phenylacetoxyethoxy]ethyl ester and oxyphenylacetic acid 2-[2-hydroxyethoxy]ethyl ester; phosphine oxide compounds such as 2,4,6-trimethylbenzoyldiphenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide and bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide; benzoin, benzoyl These include benzoin-based compounds such as benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, and benzoin isobutyl ether; titanocene-based compounds; acetophenone/benzophenone hybrid photoinitiators such as 1-(4-(4-benzoylphenylsulfanyl)phenyl)-2-methyl-2-(4-methylphenylsulfinyl)propan-1-one; oxime ester photopolymerization initiators such as 1-(4-phenylthiophenyl)-2-(O-benzoyloxime)-1,2-octanedione; and camphorquinone. These may be used alone or in combination of two or more.

There are no particular restrictions on the thermal radical polymerization initiator, and examples include peroxides and azo-based initiators.

Examples of peroxides include hydrogen peroxide; inorganic peroxides such as sodium persulfate, ammonium persulfate, and potassium persulfate; 1,1-bis(t-butylperoxy)2-methylcyclohexane, 1,1-bis(t-hexylperoxy)-3,3,5-trimethylcyclohexane, 1,1-bis(t-hexylperoxy)cyclohexane, 1,1-bis(t-butylperoxy)-3,3,5-trimethylcyclohexane, 1,1-bis(t-butylperoxy)cyclohexane, and 2,2-bis(4,4-dimethylcyclohexane). -butylperoxycyclohexyl)propane, 1,1-bis(t-butylperoxy)cyclododecane, t-hexylperoxyisopropyl monocarbonate, t-butylperoxymaleic acid, t-butylperoxy-3,5,5-trimethylhexanoate, t-butylperoxylaurate, 2,5-dimethyl-2,5-di(m-toluoylperoxy)hexane, t-butylperoxyisopropyl monocarbonate, t-butylperoxy 2-ethylhexyl monocarbonate, t- Hexyl peroxybenzoate, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, t-butyl peroxyacetate, 2,2-bis(t-butylperoxy)butane, t-butyl peroxybenzoate, n-butyl-4,4-bis(t-butylperoxy)valerate, di-t-butylperoxyisophthalate, α,α'-bis(t-butylperoxy)diisopropylbenzene, dicumyl peroxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane Examples of organic peroxides include hexane, t-butylcumyl peroxide, di-t-butyl peroxide, p-menthane hydroperoxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hexyne-3, diisopropylbenzene hydroperoxide, t-butyltrimethylsilyl peroxide, 1,1,3,3-tetramethylbutyl hydroperoxide, cumene hydroperoxide, t-hexyl hydroperoxide, and t-butyl hydroperoxide.
These may be used alone or in combination of two or more.

Examples of the azo initiator include azo compounds such as 2,2'-azobisisobutyronitrile, 1,1'-azobis(cyclohexane-1-carbonitrile), 2-(carbamoylazo)isobutyronitrile, 2-phenylazo-4-methoxy-2,4-dimethylvaleronitrile, azodi-t-octane, and azodi-t-butane. These may be used alone or in combination of two or more.
Alternatively, a redox reaction can be carried out by combining a peroxide with a redox polymerization initiation system that uses a reducing agent such as ascorbic acid, sodium ascorbate, sodium erythorbate, tartaric acid, citric acid, a metal salt of formaldehyde sulfoxylate, sodium thiosulfate, sodium sulfite, sodium bisulfite, sodium metabisulfite, or ferric chloride.

The content of the polymerization initiator in the coating composition according to the present disclosure is preferably 0.01 to 20 parts by mass, more preferably 0.1 to 10 parts by mass, and even more preferably 1 to 5 parts by mass, per 100 parts by mass of the compound represented by formula (1).

(Inorganic particles)
The coating composition according to the present disclosure preferably contains inorganic particles, and more preferably contains inorganic particles having an average particle size of less than 1 μm.
Examples of materials for the inorganic particles include glass, silica, alumina, mica, ceramics, silicone rubber powder, calcium carbonate, aluminum nitride, carbon powder, kaolin clay, dried clay minerals, and dried diatomaceous earth.
Among these, silica particles are preferred as inorganic particles.

The average particle size (median diameter on a volume basis unless otherwise specified) of the inorganic particles is preferably 0.05 μm or more and less than 1 μm, and more preferably 0.1 μm to 0.5 μm.
The average particle size of inorganic particles in the present disclosure refers to a particle size corresponding to a cumulative 50% by volume from the fine particle side in the volume-based particle size distribution of the inorganic material measured using a particle size distribution measuring device based on a laser light diffraction scattering method.

The inorganic particles may be surface-treated.
Among these, inorganic particles having polymerizable groups on the surface are preferred, inorganic particles having ethylenically unsaturated groups on the surface are more preferred, and inorganic particles having (meth)acrylate groups on the surface are particularly preferred.
The method for treating the surface of the inorganic particles is not particularly limited, and known methods can be used.

In the coating composition according to the present disclosure, the mass ratio of the inorganic particles in the coating composition, excluding the solvent and polymerization initiator, is preferably 50 mass% or less, more preferably 5 to 50 mass%, and even more preferably 10 to 40 mass%, from the viewpoints of abrasion resistance, continuous bending resistance, and hardness.

(Other polymerizable compounds)
From the viewpoints of abrasion resistance, continuous flex resistance, and hardness, the coating composition according to the present disclosure preferably contains a polymerizable compound other than the compound represented by formula (1) (hereinafter also referred to as “other polymerizable compounds”).
The other polymerizable compound is not particularly limited as long as it is a compound capable of undergoing a polymerization reaction in the presence of the compound represented by formula (1) and a polymerization initiator. Examples of the other polymerizable compound include silsesquioxane derivatives other than the compound represented by formula (1), (meth)acrylate compounds, compounds having an ethylenically unsaturated group, epoxy compounds (compounds having an epoxy group), compounds having an oxetanyl group (oxetanyl group-containing compounds), and compounds having a vinyl ether group (vinyl ether compounds).

Among these, from the viewpoints of abrasion resistance, continuous bending resistance, and hardness, the other polymerizable compounds preferably include a bifunctional polymerizable compound, and more preferably include at least one compound selected from the group consisting of a bifunctional (meth)acrylate compound and a bifunctional epoxy compound.
Furthermore, from the viewpoints of abrasion resistance, continuous bending resistance, and hardness, the bifunctional (meth)acrylate compound is preferably an alkylene glycol di(meth)acrylate compound, and more preferably a linear alkylene glycol di(meth)acrylate compound.
The alkylene glycol preferably has 4 to 8 carbon atoms, more preferably 5 to 7 carbon atoms, from the viewpoints of scratch resistance, continuous bending resistance, and hardness.

There are no particular restrictions on the (meth)acrylate compound, and examples include compounds having one (meth)acryloyl group (hereinafter also referred to as "monofunctional (meth)acrylates") and compounds having two or more (meth)acryloyl groups (hereinafter also referred to as "polyfunctional (meth)acrylates").

Examples of monofunctional (meth)acrylates include:
alkyl (meth)acrylates such as methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate;
monofunctional (meth)acrylates having an alicyclic group, such as cyclohexyl (meth)acrylate, tert-butylcyclohexyl (meth)acrylate, isobornyl (meth)acrylate, and tricyclodecanemethylol (meth)acrylate;
Monofunctional (meth)acrylates having an aromatic group, such as benzyl (meth)acrylate and phenyl (meth)acrylate;
(meth)acrylates of alkylene oxide adducts of phenol derivatives, such as (meth)acrylate of phenol ethylene oxide adduct, (meth)acrylate of phenol propylene oxide adduct, (meth)acrylate of modified nonylphenol ethylene oxide adduct, (meth)acrylate of nonylphenol propylene oxide adduct, (meth)acrylate of alkylene oxide adduct of paracumylphenol, (meth)acrylate of alkylene oxide adduct of orthophenylphenol (meth)acrylate, and (meth)acrylate of alkylene oxide adduct of orthophenylphenol;
Monofunctional (meth)acrylates having an alkoxyalkyl group, such as 2-ethylhexyl carbitol (meth)acrylate;
Monofunctional (meth)acrylates having a heterocycle, such as tetrahydrofurfuryl (meth)acrylate and N-(2-(meth)acryloxyethyl)hexahydrophthalimide;
hydroxylalkyl (meth)acrylates such as hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxybutyl (meth)acrylate, and hydroxyhexyl (meth)acrylate;
Monofunctional (meth)acrylates having a hydroxyl group and an aromatic group, such as 2-hydroxy-3-phenoxypropyl (meth)acrylate;
Examples of the alkylene glycol mono(meth)acrylate include diethylene glycol mono(meth)acrylate, dipropylene glycol mono(meth)acrylate, triethylene glycol mono(meth)acrylate, and tripropylene glycol mono(meth)acrylate; and monofunctional (meth)acrylates having a carboxy group, such as ω-carboxypolycaprolactone mono(meth)acrylate and monohydroxyethyl phthalate (meth)acrylate.

Examples of polyfunctional (meth)acrylates include:
polyethylene glycol di(meth)acrylates such as diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, and tetraethylene glycol di(meth)acrylate;
polypropylene glycol di(meth)acrylates such as dipropylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, and tetrapropylene glycol di(meth)acrylate;
Examples of the di(meth)acrylate include 1,4-butanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, ethylene oxide-modified neopentyl glycol di(meth)acrylate, ethylene oxide-modified bisphenol A di(meth)acrylate, propylene oxide-modified bisphenol A di(meth)acrylate, ethylene oxide-modified hydrogenated bisphenol A di(meth)acrylate, trimethylolpropane di(meth)acrylate, trimethylolpropane allyl ether di(meth)acrylate, trimethylolpropane tri(meth)acrylate, ethylene oxide-modified trimethylolpropane tri(meth)acrylate, propylene oxide-modified trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, and dipentaerythritol hexaacrylate.

As the polyfunctional (meth)acrylate, urethane (meth)acrylate can also be used.
Examples of urethane (meth)acrylates include compounds obtained by addition reaction of organic polyisocyanate with hydroxyl group-containing (meth)acrylate, and compounds obtained by addition reaction of organic polyisocyanate, polyol, and hydroxyl group-containing (meth)acrylate.
The monofunctional (meth)acrylates, polyfunctional (meth)acrylates, etc. may be used alone or in combination of two or more kinds, or different kinds may be used in combination.

Examples of the polyol include low molecular weight polyol, polyether polyol, polyester polyol, and polycarbonate polyol.
Low molecular weight polyols include ethylene glycol, propylene glycol, neopentyl glycol, cyclohexanedimethylol, and 3-methyl-1,5-pentanediol.
Examples of polyether polyols include polypropylene glycol and polytetramethylene glycol.
Examples of polyester polyols include reaction products of these low molecular weight polyols and/or polyether polyols with acid components such as dibasic acids such as adipic acid, succinic acid, phthalic acid, hexahydrophthalic acid, and terephthalic acid, or anhydrides thereof.
These may be used alone or in combination of two or more kinds, or different kinds may be used in combination.

Examples of organic polyisocyanates include tolylene diisocyanate, xylylene diisocyanate, tetramethylxylylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, hexamethylene diisocyanate, and isophorone diisocyanate.
Examples of the hydroxyl group-containing (meth)acrylate include hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate; and hydroxyl group-containing polyfunctional (meth)acrylates such as pentaerythritol tri(meth)acrylate, di(meth)acrylate of an adduct of 3 moles of alkylene oxide with isocyanuric acid, and dipentaerythritol penta(meth)acrylate.
These may be used alone or in combination of two or more kinds, or different kinds may be used in combination.

A compound having one ethylenically unsaturated group in one molecule other than the (meth)acrylate compound may be added to the curable composition.
The ethylenically unsaturated group is preferably a (meth)acryloyl group, a maleimide group, a (meth)acrylamide group, or a vinyl group.
Specific examples of the compound having an ethylenically unsaturated group include (meth)acrylic acid, a Michael addition dimer of acrylic acid, N-(2-hydroxyethyl)citraconimide, N,N-dimethylacrylamide, acryloylmorpholine, N-vinylpyrrolidone, and N-vinylcaprolactam.
These may be used alone or in combination of two or more.

Examples of the epoxy compound include a monofunctional epoxy compound and a polyfunctional epoxy compound.
Examples of the oxetanyl group-containing compound include monofunctional oxetane compounds and polyfunctional oxetane compounds.
Examples of the vinyl ether compound include monofunctional vinyl ether compounds and polyfunctional vinyl ether compounds.
As these compounds, for example, compounds described in JP-A-2011-42755 may be used.
The silicone is not particularly limited, and known silicones can be used, such as polydimethylsilicone, polydiphenylsilicone, and polymethylphenylsilicone, and preferably has a functional group at its end and/or side chain. The functional group is not particularly limited, and examples thereof include (meth)acryloyl group, epoxy group, oxetanyl group, vinyl group, hydroxyl group, carboxy group, amino group, and thiol group.

The mass ratio of the other polymerizable compounds in the coating composition excluding the solvent and the polymerization initiator in the coating composition according to the present disclosure is preferably 0 mass % or more and 50 mass % or less, more preferably more than 0 mass % and less than 35 mass %, and even more preferably 10 mass % to 30 mass %, from the viewpoints of abrasion resistance, continuous bending resistance, and hardness.
Furthermore, the mass ratio of the bifunctional (meth)acrylate compound in the coating composition excluding the solvent and the polymerization initiator in the coating composition according to the present disclosure is preferably 0 mass % or more and 50 mass % or less, more preferably more than 0 mass % and less than 35 mass %, and even more preferably 10 mass % to 30 mass %, from the viewpoints of abrasion resistance, continuous bending resistance, and hardness.
The mass proportion of the bifunctional (meth)acrylate compound relative to the total mass of the other polymerizable compounds in the coating composition according to the present disclosure is, from the viewpoints of abrasion resistance, continuous bending resistance, and hardness, preferably 50 mass % or more, more preferably 80 mass % or more, even more preferably 90 mass % or more, and particularly preferably 100 mass %.

(Other ingredients)
The coating composition according to the present disclosure may further contain other components in addition to the compound represented by formula (1), the polymerization initiator, the inorganic particles, and the other polymerizable compound.
The other components are not particularly limited and include, for example, solvents, resins, silicones, monomers, fillers, surfactants, antistatic agents (e.g., conductive polymers), leveling agents, photosensitizers, ultraviolet absorbers, antioxidants, heat resistance improvers, stabilizers, lubricants, pigments, dyes, plasticizers, suspending agents, adhesion imparting agents, nanoparticles, nanofibers, nanosheets, etc. The curable composition of the present disclosure may also contain silane-based reactive diluents such as tetraalkoxysilanes, trialkoxysilanes, dialkoxysilanes, monoalkoxysilanes, and disiloxanes.

The coating composition according to the present disclosure may or may not contain a solvent.
Examples of the solvent include various organic solvents such as aliphatic hydrocarbon solvents, aromatic hydrocarbon solvents, chlorinated hydrocarbon solvents, alcohol solvents, ether solvents, amide solvents, ketone solvents, ester solvents, and cellosolve solvents.

(Average indentation hardness of cured film)
From the viewpoints of abrasion resistance, continuous bending resistance, and hardness, the coating composition according to the present disclosure is preferably capable of forming a film having an average indentation hardness of 0.45 GPa or more at a surface depth of 200 nm to 400 nm as measured with a nanoindenter, more preferably 0.50 GPa or more, even more preferably 0.48 GPa to 1.5 GPa, and particularly preferably 0.48 GPa to 1.0 GPa.

The method for measuring the average indentation hardness of the cured film in the present disclosure is as follows.
A photocured film is prepared in the same manner as in the measurement of the indentation elastic modulus.
The indentation hardness of the obtained photocured film is measured using a nanoindenter (Nano Indenter G200 manufactured by Agilent Technologies, using a Berkovich indenter) at 23°C and a strain rate of 0.05/s. The hardness values at indentation depths of 200 nm to 400 nm are averaged to calculate the hardness.

(Resistant to breakage due to repeated bending of the cured film)
It is preferable that a film having a thickness of less than 10 μm obtained by curing the coating composition according to the present disclosure does not break even when bent inwardly 200,000 times continuously at a bending radius R of 1.5 mm, more preferably does not break even when bent inwardly 100,000 times continuously at a bending radius R of 1.0 mm, and particularly preferably does not break even when bent inwardly 200,000 times continuously at a bending radius R of 1.0 mm.

The method for measuring the resistance to breakage due to continuous bending in the present disclosure is as follows.
A photocured film is prepared in the same manner as in the measurement of the indentation elastic modulus.
The obtained photocured film is set in a durability testing machine DMLHP-CS manufactured by Yuasa System Equipment Co., Ltd. with the coated film surface facing inward, and a repeated bending test is carried out at a bending radius of 1 mm or 1.5 mm, at a rate of 1 cycle per 2 seconds, 100,000 or 200,000 times, and the presence or absence of fractures or cracks is confirmed visually.

(Method for producing coating composition)
The method for producing the coating composition according to the present disclosure is not particularly limited, and any known method can be used, but it is preferable that the method comprises a step of hydrolyzing at least one organosilicon compound represented by R _n SiX _p (n represents an integer of 0 to 3, p represents an integer of 1 to 4, n+p=4, R represents a group bonded to a silicon atom in the silsesquioxane derivative via a carbon atom, and X represents a hydrolyzable group) using an organic solvent and adding 1.5 molar equivalents or more of water relative to the total amount of hydrolyzable groups in the organosilicon compound.
The hydrolysis step in the method for producing a coating composition according to the present disclosure is the same as the hydrolysis step in the method for producing a compound represented by formula (1), and preferred embodiments are also the same.

[Coating film]
The coating film according to the present disclosure is obtained by curing the coating composition according to the present disclosure. For example, the coating film according to the present disclosure can be obtained by irradiating the coating composition according to the present disclosure with active energy rays or by heating the coating composition according to the present disclosure.

The coating composition according to the present disclosure may be cured after the coating composition according to the present disclosure has been applied to a substrate.
The coating composition according to the present disclosure may or may not contain a solvent. When the coating composition contains a solvent, it is preferable to remove the solvent before curing.

When the coating composition according to the present disclosure is applied to a substrate, the method for applying the coating composition is not particularly limited, and examples of the application method include common coating methods such as inkjet coating, casting, spin coating, bar coating, dip coating, spray coating, roll coating, flow coating, and gravure coating.
There are no particular limitations on the thickness to which the coating composition according to the present disclosure is applied, and it may be appropriately set depending on the purpose.
The substrate to which the coating composition according to the present disclosure is applied is not particularly limited, and examples thereof include wood, metal, inorganic materials, plastics, paper, fibers, and fabrics.
Examples of metals include copper, silver, iron, aluminum, silicon, silicon steel, and stainless steel.
Examples of inorganic materials include metal oxides such as aluminum oxide, silicon oxide, magnesium oxide, zirconium oxide, zinc oxide, indium tin oxide, and gallium oxide; metal nitrides such as aluminum nitride, gallium nitride, and silicon nitride; ceramics such as silicon carbide and boron nitride; mortar, concrete, and glass.
Specific examples of plastics include acrylic resins such as polymethyl methacrylate, polyester resins such as polyethylene terephthalate, polyvinyl chloride resins, polycarbonate resins, epoxy resins, polyamide resins such as nylon and aramid, polyimide resins, polyamideimide resins, fluororesins such as tetrafluoroethylene resins, polyolefin resins such as cross-linked polyethylene resins, vinylidene chloride resins, acrylonitrile-butadiene-styrene (ABS) resins, polystyrene resins, polyacrylonitrile resins, cycloolefin polymers (COP), cycloolefin copolymers (COC), acetate resins, polyarylate, cellophane, norbornene resins, acetyl cellulose resins such as triacetyl cellulose (TAC), polychloroprene, polyphenylene sulfide, polysulfone, polyethersulfone, polyetheretherketone, polyurethane resins, and composite resins such as glass epoxy resins, and various fiber-reinforced resins.
Examples of fibers include natural fibers, regenerated fibers, semi-synthetic fibers, metal fibers, glass fibers, carbon fibers, ceramic fibers, and known chemical fibers. The fabric may be a woven fabric or a nonwoven fabric, and can be made using, for example, the above-mentioned fibers.
These materials may be used alone, or two or more of them may be used in combination, mixed, or composite form.
The shape of the substrate is not particularly limited, and examples thereof include plate-like, sheet-like, film-like, rod-like, spherical, fibrous, powder-like, lenticular, and other regular or irregular shapes.

(Curing method)
In the present disclosure, the curing method and curing conditions are selected depending on whether the coating composition is active energy ray-curable and/or thermosetting. Furthermore, the curing conditions (e.g., the type of light source and the amount of light irradiation in the case of active energy ray-curable coatings, and the heating temperature and heating time in the case of thermosetting coatings) are appropriately selected depending on the type and amount of polymerization initiator and the types of other polymerizable compounds contained in the coating composition.

(1) Active Energy Ray Curing Method When the coating composition according to the present disclosure is an active energy ray-curable composition, the curing method may involve irradiating the composition with active energy rays using a known active energy ray irradiation device, etc. Examples of active energy rays include electron beams, and light such as ultraviolet rays, visible light, and X-rays. Light is preferred, and ultraviolet rays are more preferred from the viewpoint of being able to use inexpensive equipment.
Examples of ultraviolet irradiation devices include low-pressure mercury lamps, medium-pressure mercury lamps, high-pressure mercury lamps, ultra-high-pressure mercury lamps, metal halide lamps, ultraviolet (UV) electrodeless lamps, chemical lamps, black light lamps, microwave-excited mercury lamps, and light-emitting diodes (LEDs).
The light irradiation intensity of the coating film coated with the coating composition according to the present disclosure may be selected depending on the purpose, application, etc., and the light irradiation intensity in the light wavelength range effective for activating the active energy ray polymerization initiator (referred to as a photopolymerization initiator in the case of photocurable materials) (this varies depending on the type of photopolymerization initiator, but light with a wavelength of 220 nm to 460 nm is preferably used) is preferably 0.1 mW/cm ² to 1000 mW/cm ² .
Furthermore, the irradiation energy should be appropriately set depending on the type of active energy ray, the formulation, etc. The light irradiation time of the coating may also be selected depending on the purpose, application, etc., and it is preferable to set the light irradiation time so that the cumulative light dose, expressed as the product of the light irradiation intensity in the light wavelength region and the light irradiation time, is 10 mJ/cm ² to 7,000 mJ/cm ^2. The cumulative light dose is more preferably 200 mJ/cm ² to 5,000 mJ/cm ² , and even more preferably 500 mJ/cm ² to 4,000 mJ/cm ^2. When the cumulative light dose is within the above range, curing of the composition proceeds smoothly, and a uniform cured product can be easily obtained.

Furthermore, heat curing may be carried out before and/or after photocuring, as appropriate.
For example, a two-stage curing process can be performed by impregnating a substrate having a shaded area with the present composition, irradiating the substrate with light to first cure the composition in the area exposed to light, and then applying heat to cure the composition in the area not exposed to light. There are no particular limitations on the substrate, and examples include substrates with complex shapes such as fabric, fiber, powder, porous, and uneven, and may also include a shape that combines two or more of these shapes.

The coating film according to the present disclosure is preferably further heated before or after UV curing. By performing the additional heating, the hardness is improved, and the scratch resistance and continuous bending resistance are also improved.
The heating temperature of the coating film after curing is preferably 60° C. to 200° C., more preferably 80° C. to 180° C., and even more preferably 100° C. to 150° C. The curing temperature may be constant or may be increased. A combination of temperature increase and temperature decrease may also be used.
The heating time for the cured coating film is preferably 1 to 360 minutes, more preferably 5 to 120 minutes, and even more preferably 5 to 60 minutes.

(2) Thermal Curing Method When the coating composition according to the present disclosure is a thermosetting composition, the curing method and curing conditions are not particularly limited.
The curing temperature is preferably 80° C. to 200° C., more preferably 100° C. to 180° C., and even more preferably 110° C. to 150° C. The curing temperature may be constant or may be increased. A combination of temperature increase and temperature decrease may also be used.
The curing time is appropriately selected depending on the type of thermal polymerization initiator, the content of other components, etc., and is preferably 10 to 360 minutes, more preferably 30 to 300 minutes, and even more preferably 60 to 240 minutes. By curing the composition under the above-mentioned preferred conditions, a uniform cured film free from blistering, cracks, etc. can be formed.

(Applications such as coating films)
The coating composition according to the present disclosure has excellent hardness and can therefore be suitably applied to hard coat films. Furthermore, by curing the coating composition according to the present disclosure, a hard coat film with excellent flex resistance can be obtained. The coating composition according to the present disclosure may be provided on a substrate; for example, a substrate having a hard coat film can be obtained by curing the coating composition applied to the substrate. The coating composition according to the present disclosure may contain various components as needed.
The hard coat film according to the present disclosure and the substrate having the coat film according to the present disclosure have excellent flex resistance, and therefore can be suitably used in flexible devices such as bendable foldable devices and rollable rollable devices, displays such as electronic paper and bendable flexible displays, and optical components such as lenses.

Next, the present disclosure will be described in detail based on examples and comparative examples. The present disclosure is not limited to the following examples.

<Synthesis Example 1>
38.1 g (0.25 mol) of tetramethoxysilane and 43.4 g of 1-propanol were weighed into a 200 mL four-neck flask equipped with a dropping funnel and a stirrer. While stirring at room temperature (25°C, the same applies below), 12.8 g (0.035 mol) of a 25% by weight tetramethylammonium hydroxide methanol solution was added dropwise from the dropping funnel to obtain a tetraalkoxysilane solution. Separately, 62.8 g (0.25 mol) of 3-methacryloyloxypropyltrimethoxysilane, 74.5 g of 1-propanol, and 31.5 g of pure water were weighed into a 500 mL four-neck flask equipped with a dropping funnel and a stirrer. The mixture was stirred thoroughly, and the tetraalkoxysilane solution was added dropwise while heating to 60°C. The mixture was then stirred at 60°C for 2 hours. 2.5 g (0.04 mol) of nitric acid was added to neutralize the mixture, and the 1-propanol was distilled off under reduced pressure. 50 g of propylene glycol monobutyl ether was added thereto, and the mixture was transferred to a separatory funnel. The aqueous phase was removed to obtain 101 g of a 50% by mass propylene glycol monobutyl ether solution of the silsesquioxane derivative S1.

<Synthesis Example 2>
102 g of a 50% by mass propylene glycol monobutyl ether solution of silsesquioxane derivative S2 was obtained in the same manner as in Synthesis Example 1, except that the amount of tetramethoxysilane was changed to 45.7 g (0.3 mol) and the amount of 3-methacryloyloxypropyltrimethoxysilane was changed to 49.7 g (0.2 mol).

<Synthesis Example 3>
106 g of a 50% by mass propylene glycol monobutyl ether solution of silsesquioxane derivative S3 was obtained in the same manner as in Synthesis Example 1, except that the amount of tetramethoxysilane was changed to 42.6 g (0.28 mol) and the amount of 3-methacryloyloxypropyltrimethoxysilane was changed to 54.6 g (0.22 mol).

<Synthesis Example 4>
98 g of a 50% by mass propylene glycol monobutyl ether solution of silsesquioxane derivative S4 was obtained in the same manner as in Synthesis Example 1, except that the amount of tetramethoxysilane was changed to 24.4 g (0.16 mol) and the amount of 3-methacryloyloxypropyltrimethoxysilane was changed to 59.6 g (0.24 mol).

<Synthesis Example 5>
24.8 g (1 mol) of 3-methacryloyloxypropyltrimethoxysilane and 407 g of 2-propanol were weighed into a 500 mL four-neck flask equipped with a stirrer and a dropping funnel and stirred at room temperature. While heating this mixture to 50°C, a mixed aqueous solution of 1.3 g (0.012 mol) of 35% by weight hydrochloric acid aqueous solution and 53 g of pure water was added dropwise, followed by cooling to room temperature and stirring for 12 hours. The solvent and water were removed from the resulting solution under reduced pressure to obtain 181 g of silsesquioxane derivative S5.

<Synthesis Example 6>
102 g of a 50% by mass propylene glycol monobutyl ether solution of silsesquioxane derivative S6 was obtained in the same manner as in Synthesis Example 1, except that the amount of tetramethoxysilane was changed to 18.3 g (0.12 mol) and the amount of 3-methacryloyloxypropyltrimethoxysilane was changed to 69.5 g (0.28 mol).

<Synthesis Example 7>
50.2 g (0.33 mol) of tetramethoxysilane, 69.6 g (0.25 mol) of 3-[(3-ethyloxetan-3-yl)methoxy]propyl(trimethoxy)silane, and 89.8 g of 1-propanol were weighed into a 500 mL four-neck flask equipped with a dropping funnel and a stirrer and stirred at 40°C. 14.8 g (0.04 mol) of a 25% by mass tetramethylammonium hydroxide methanol solution was added dropwise, followed by the dropwise addition of a mixture of 37.3 g of pure water and 37.3 g of 1-propanol, and the mixture was stirred at 70°C for 6 hours. 2.5 g (0.04 mol) of nitric acid was added to the mixture to neutralize it, and the 1-propanol was distilled off under reduced pressure. 50 g of propylene glycol monobutyl ether was added thereto, and the mixture was transferred to a separatory funnel. The aqueous phase was removed to obtain 135 g of a 50% by mass propylene glycol monobutyl ether solution of silsesquioxane derivative S6.

<Synthesis Example 8>
278.4 g (1 mol) of 3-[(3-ethyloxetan-3-yl)methoxy]propyl(trimethoxy)silane and 246 g of 2-propanol were weighed into a 1000 mL four-neck flask equipped with a stirrer and a dropping funnel and stirred at 80 °C for 1 hour. A separately prepared mixed solution of 9.1 g (0.025 mol) of 25% by mass tetramethylammonium hydroxide aqueous solution and 47.3 g of pure water was added dropwise from the dropping funnel over approximately 1 hour while stirring the reaction solution, and then the mixture was stirred at 80 °C for 1 hour. The reaction solution was neutralized with a mixed solution of concentrated sulfuric acid (1.3 g, 0.013 mol) and pure water (25.7 g), and the solvent and other components were removed by distillation under reduced pressure. Further, diisopropyl ether was added, the mixture was transferred to a separatory funnel, washed with pure water, dehydrated, and the solvent and other components were removed by distillation under reduced pressure, yielding 209.3 g of silsesquioxane derivative S7.

Example 1
<Preparation of Photocurable Coating Composition>
To 1 part by mass of the silsesquioxane derivative S1 solution obtained in Synthesis Example 1, 0.05 parts by mass of 1-hydroxycyclohexyl phenyl ketone was added, and the mixture was stirred with a planetary centrifugal mixer to prepare a photocurable coating composition 1.

(Examples 2 to 23)
Each component was added so as to obtain the composition shown in Table 1, and 0.05 parts by mass of 1-hydroxycyclohexyl phenyl ketone was added to 1 part by mass of the solution of the compound represented by formula (1). The mixture was stirred using a planetary centrifugal mixer to prepare each photocurable coating composition.

(Example 24)
Each component was added so as to obtain the composition shown in Table 1, and 0.02 parts by mass of 4-methylphenyl-4-(1-methylethyl)phenyliodonium tetrakis(pentafluorophenyl)borate was added to 1 part by mass of the solution of the compound represented by formula (1). The mixture was stirred using a planetary centrifugal mixer to prepare each photocurable coating composition.

(Comparative Example 1)
A photocurable coating composition was prepared by adding 0.05 parts by mass of 1-hydroxycyclohexyl phenyl ketone and 1 part by mass of propylene glycol monobutyl ether to 1 part by mass of the silsesquioxane derivative S5 obtained in Synthesis Example 5, and stirring the mixture with a planetary centrifugal mixer.

(Comparative Example 2)
A photocurable coating composition was prepared by adding 0.05 parts by mass of 1-hydroxycyclohexyl phenyl ketone to 1 part by mass of silica in a silica/propylene glycol monobutyl ether dispersion (silica mass 40% by mass), and stirring the mixture with a planetary centrifugal mixer.

(Comparative Examples 3 to 5)
Each component was added so as to obtain the composition shown in Table 1, and 0.05 parts by mass of 2-hydroxy-2-methyl-1-phenylpropan-1-one was added per 1 part by mass of the (meth)acrylate compound used. The mixture was stirred with a planetary centrifugal mixer to prepare each photocurable coating composition.

(Comparative Example 6)
Each component was added so as to obtain the composition shown in Table 1, and 0.02 parts by mass of 4-methylphenyl-4-(1-methylethyl)phenyliodonium tetrakis(pentafluorophenyl)borate was added per 1 part by mass of the (meth)acrylate compound used, and the mixture was stirred with a planetary centrifugal mixer to prepare each photocurable coating composition.

<Preparation of photocured film>
Each of the coating compositions prepared as described above was applied to a 50 μm thick polyethylene terephthalate (PET) film (Cosmoshine A4300, manufactured by Toyobo Co., Ltd.). Specifically, each coating composition was applied using a No. 5 or 8 bar coater, and then the applied coating composition was dried at 60°C for 10 minutes, after which it was irradiated with ultraviolet light under the following conditions to cure, producing a photocured film (coated film). The film thickness was approximately 3 μm or 5 μm.
-Ultraviolet irradiation conditions-
Lamp: High-pressure mercury lamp (Eye Graphics Co., Ltd. ECS-4011GX)
Lamp height: 10cm
Conveyor speed: 5.75 m/min
Accumulated light amount per pass: 360 mJ/cm ² (UV-A, measured value using UV POWER PUCK II manufactured by EIT)
Atmosphere: Nitrogen Number of passes: 10

<Measurement of indentation hardness>
The indentation hardness of the photocured film prepared as described above was measured as follows. Specifically, the indentation hardness was measured at 23°C and a strain rate of 0.05/s using a nanoindenter (Nano Indenter G200 manufactured by Agilent Technologies, Inc., using a Berkovich indenter). The hardness was calculated by averaging the hardness values at indentation depths of 200 nm to 400 nm. The results are shown in Table 1.

<Evaluation of continuous bending resistance>
The photocured film prepared as described above was set in a durability testing machine DMLHP-CS manufactured by Yuasa System Co., Ltd. with the coated film surface facing inward, and a repeated bending test was performed 200,000 times at a bending radius of 1 mm or 1.5 mm and a speed of 1 bending/2 seconds. A rating of A was given if no cracks were observed in the coating film layer even after 200,000 bendings, a rating of B was given if cracks were observed after 50,000 to 200,000 bendings, and a rating of C was given if cracks were observed after less than 50,000 bendings. The results are shown in Table 1. The test was performed in a constant temperature and humidity environment set at a temperature of 23°C and a humidity of 50%.

<Evaluation of Scratch Resistance>
The photocured film prepared as described above was placed in a flat abrasion tester PAS-400 manufactured by Daiei Scientific Instruments Co., Ltd. with the coated surface facing up, and steel wool #0000 (manufactured by Japan Steel Wool Co., Ltd.) was brought into contact with the film so that the pressure was 1.5 kg/ ^cm² . The coated surface was abraded 1,000 times at an abrasion rate of 80 reciprocations/min with a stroke length of 140 mm. The coated surface after abrasion was visually observed and rated as A if there were no scratches, B if there were less than 20 scratches, and C if there were 20 or more scratches or peeling.

Details of each component listed in Table 1 other than those mentioned above are shown below.
Silica A: acryloyl group-modified silica (average particle size 12 nm)
Silica B: Epoxy group-modified silica (average particle size 12 nm)
Epoxy: 3,4-epoxycyclohexylmethyl-3',4'-epoxycyclohexanecarboxylate Acrylic A: 1,6-hexanediol diacrylate Acrylic B: bifunctional urethane acrylate (weight average molecular weight 1,600)
Acrylic C: Trifunctional urethane acrylate having a hexamethylene diisocyanate skeleton (weight average molecular weight 940)
Acrylic D: polyethylene glycol (n≒4) diacrylate Acrylic E: polyethylene glycol (n=9) diacrylate Acrylic F: isocyanuric acid ethylene oxide modified di- and triacrylate Acrylic G: pentaerythritol tri- and tetraacrylate

The coating film of Comparative Example 2 was brittle, and in the scratch resistance evaluation, many scratches and peeling occurred after less than 100 abrasions.

As shown in Table 1, the coating compositions of Examples 1 to 24 provided coating films superior in scratch resistance compared to Comparative Examples 1 to 6.
Furthermore, the coating compositions of Examples 1 to 11 and 15 to 24 provided coating films that were excellent in terms of resistance to continuous bending and hardness.

The disclosure of Japanese Patent Application No. 2024-69329, filed on April 22, 2024, is incorporated herein by reference in its entirety.
All publications, patent applications, and technical standards mentioned in this specification are herein incorporated by reference to the same extent as if each individual publication, patent application, or technical standard was specifically and individually indicated to be incorporated by reference.

Claims (12)

A coating composition comprising a compound represented by the following formula (1):


In formula (1), R ¹ to R ³ each independently represent a hydrogen atom or a monovalent organic group, a to d each independently represent a molar ratio, a and b each independently represent a positive number, and c and d each independently represent 0 or a positive number. The coating composition according to claim 1, wherein R ¹ contains a group having a polymerizable functional group, and the relationship a/b satisfies 0.4<a/b<1.5. The coating composition according to claim 1 is capable of forming a film having an average indentation hardness of 0.40 GPa or more at a surface depth of 200 nm to 400 nm as measured with a nanoindenter. The coating composition according to claim 1, further comprising inorganic particles and a polymerization initiator. The coating composition according to claim 4, wherein the inorganic particles have an average particle size of less than 1 μm. The coating composition according to claim 4, wherein the inorganic particles are silica particles. The coating composition according to claim 4, wherein the mass ratio of the inorganic particles in the coating composition excluding the solvent and polymerization initiator is 50 mass% or less. The coating composition according to claim 1, further comprising a difunctional or higher functional (meth)acrylate compound or a difunctional or higher functional epoxy compound. The coating composition according to claim 8, wherein the mass ratio of the difunctional or higher (meth)acrylate compound or difunctional or higher epoxy compound in the coating composition excluding the solvent and polymerization initiator is greater than 0 mass% and less than 35 mass%. The coating composition according to claim 1, wherein a film of less than 10 μm thick formed by curing the coating composition does not break even when bent continuously inward 200,000 times at a bending radius R of 1.5 mm. A coating film obtained by curing the coating composition described in any one of claims 1 to 10. A substrate provided with the coating film described in claim 11.