JP7824751B2 - curable composition - Google Patents

Description

The present invention relates to a curable composition.

Curable compositions containing a (meth)acrylic polymer and an epoxy compound are known in the prior art. Patent Document 1 describes a method for purifying a vinyl polymer produced by atom transfer radical polymerization of a vinyl monomer. Patent Document 2 describes a curable composition whose essential components are a vinyl polymer having a specific terminal structure produced by living radical polymerization of a (meth)acrylic monomer using a copper complex as a catalyst, an epoxy compound and/or an oxetane compound, a photoradical polymerization initiator, a photocationic polymerization initiator, and a compound having an epoxy group and a (meth)acryloyl group in the molecule.

Japanese Patent Application Laid-Open No. 2004-155846 International Publication No. 2012/020545 WO 2005/092981

However, the above-mentioned conventional techniques leave room for further improvement in terms of realizing a curable composition with excellent electrical insulation properties.

One aspect of the present invention aims to provide a curable composition with excellent electrical insulation properties.

The curable composition according to one embodiment of the present invention comprises:
a (meth)acrylic polymer (A);
an epoxy compound and/or an oxetane compound (B);
a photoradical polymerization initiator (C);
an epoxy curing agent (D);
Contains
the weight ratio of the (meth)acrylic polymer (A) to the epoxy compound and/or oxetane compound (B) is (1:99) to (50:50);
The (meth)acrylic polymer (A) is
The molecular weight distribution (Mw/Mn) is 1.8 or less,
The total amount of bromine and potassium contained in the polymer is 0 ppm or more and 25 ppm or less, and
The compound has 1.0 or more (meth)acryloyl functional groups represented by the following general formula (a) per molecule.
-OC(O)C(R ¹ )=CH ₂ ...General formula (a)
(wherein ^R1 represents a hydrogen atom or an organic group having 1 to 20 carbon atoms).

One aspect of the present invention provides a curable composition with excellent electrical insulation properties.

One embodiment of the present invention is described below, but the present invention is not limited to this. Unless otherwise specified, "A to B" representing a numerical range means "A or more and B or less." In this specification, "(meth)acrylic" means acrylic and/or methacrylic.

[1. (Meth)acrylic polymer (A)]
The curable composition according to one embodiment of the present invention contains a (meth)acrylic polymer (A). The (meth)acrylic polymer (A) may be used alone or in combination of two or more.

[1.1. Main chain of (meth)acrylic polymer]
The (meth)acrylic monomer constituting the main chain of the (meth)acrylic polymer (A) is not particularly limited, and examples of the (meth)acrylic monomer include (meth)acrylic acid and (meth)acrylic acid esters. Examples of (meth)acrylic acid esters include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, n-pentyl (meth)acrylate, n-hexyl (meth)acrylate, cyclohexyl (meth)acrylate, n-heptyl (meth)acrylate, n-octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, dodecyl (meth)acrylate, phenyl (meth)acrylate, toluyl (meth)acrylate, benzyl (meth)acrylate, 2-methoxyethyl (meth)acrylate, 3-methoxybutyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, hydroxypropyl, stearyl (meth)acrylate, glycidyl (meth)acrylate, 2-aminoethyl (meth)acrylate, γ-(methacryloyloxypropyl)trimethoxysilane, ethylene oxide adduct of (meth)acrylic acid, trifluoromethyl (meth)acrylate, 2-trifluoromethylethyl (meth)acrylate, 2-perfluoroethylethyl (meth)acrylate, 2-perfluoroethyl-2-perfluorobutylethyl (meth)acrylate, 2-perfluoroethyl (meth)acrylate, perfluoromethyl (meth)acrylate, diperfluoromethylmethyl (meth)acrylate, 2-perfluoromethyl-2-perfluoroethylmethyl (meth)acrylate, 2-perfluorohexylethyl (meth)acrylate, 2-perfluorodecylethyl (meth)acrylate, and 2-perfluorohexadecylethyl (meth)acrylate.

From the viewpoint of the physical properties of the resulting (meth)acrylic polymer (A), among these monomers, acrylic acid esters and methacrylic acid esters are preferred, acrylic acid esters are more preferred, and one or more selected from the group consisting of n-butyl acrylate, ethyl acrylate, and 2-methoxyethyl acrylate are even more preferred.

The (meth)acrylic polymer (A) may be composed of units derived from only one of these monomers, or may be composed of units derived from two or more monomers. The (meth)acrylic polymer (A) may be a copolymer of units derived from the above-mentioned preferred monomers and units derived from other monomers. In this case, the proportion of units derived from preferred monomers in the (meth)acrylic polymer (A) is preferably 20% by weight or more, more preferably 50% by weight or more, and even more preferably 70% by weight or more.

[1.2. (Meth)acryloyl Functional Group in (Meth)acrylic Polymer (A)]
The (meth)acrylic polymer (A) has 1.0 or more (meth)acryloyl functional groups represented by the following general formula (a) per molecule: In the formula, ^R1 represents a hydrogen atom or an organic group having 1 to 20 carbon atoms. Since the (meth)acrylic polymer (A) has a (meth)acryloyl substituent, it is cured by light irradiation.
-OC(O)C(R ¹ )=CH ₂ ...General formula (a)

The (meth)acryloyl functional group represented by general formula (a) may be located in the middle of the main chain of the (meth)acrylic polymer (A) or at the end of the main chain. From the viewpoint of the resulting rubber elasticity, it is preferable that the (meth)acryloyl functional group be located at the end of the main chain.

In general formula (a), examples of the structure of R ¹ include -H, -CH ₃ , -CH ₂ CH ₃ , -(CH ₂ ) _n CH ₃ (n represents an integer of 2 to 19), -C ₆ H ₅ (phenyl group), -CH ₂ OH, and -CN. From the viewpoint of the reactivity of the (meth)acryloyl functional group, R ¹ is preferably -H or -CH ₃ .

The number of (meth)acryloyl functional groups contained in the (meth)acrylic polymer (A) is preferably 1.2 or more per molecule, more preferably 1.5 or more, and even more preferably 1.8 or more. The upper limit of the number of (meth)acryloyl functional groups contained in the (meth)acrylic polymer (A) can be, for example, 2.0 or less, 2.5 or less, or 3.0 or less per molecule.

[1.3. Molecular weight distribution of (meth)acrylic polymer (A)]
The molecular weight distribution of the (meth)acrylic polymer (A) is 1.8 or less. In this specification, the molecular weight distribution refers to the ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn). The weight average molecular weight and the number average molecular weight are measured by gel permeation chromatography (GPC). In one embodiment, the mobile phase used in the GPC measurement is chloroform or tetrahydrofuran. In one embodiment, the column used in the GPC measurement is a polystyrene gel column. The molecular weight value is determined as a polystyrene equivalent value.

The number average molecular weight of the (meth)acrylic polymer (A) is not particularly limited. The lower limit of the number average molecular weight is preferably 500 or more, more preferably 3,000 or more, even more preferably 5,000 or more, and most preferably 8,000 or more. The upper limit of the number average molecular weight is preferably 1,000,000 or less, more preferably 100,000 or less, even more preferably 80,000 or less, and most preferably 50,000 or less. If the number average molecular weight is too low, the desired properties of the (meth)acrylic polymer (A), such as tensile properties, tend to be less apparent. If the number average molecular weight is too high, the polymer tends to be difficult to handle.

The molecular weight distribution of the (meth)acrylic polymer (A) is preferably 1.7 or less, more preferably 1.6 or less, even more preferably 1.5 or less, particularly preferably 1.4 or less, and most preferably 1.3 or less. The theoretical lower limit of the molecular weight distribution is 1.

[1.4. Ionic elements contained in the (meth)acrylic polymer (A)]
The (meth)acrylic polymer (A) has a reduced content of ionic elements. In this specification, the ionic elements refer to bromine and potassium. These ionic elements are basically incorporated during the synthesis of the main chain of the (meth)acrylic polymer (A). However, potassium is also incorporated during the introduction of functional groups.

The total amount of bromine and potassium contained in the (meth)acrylic polymer (A) is 25 ppm or less. From the viewpoint of electrical insulation, the total amount of bromine and potassium contained in the (meth)acrylic polymer (A) is preferably 20 ppm or less, more preferably 15 ppm or less, and even more preferably 10 ppm or less. Since bromine and potassium are inevitably contained during the synthesis of the (meth)acrylic polymer (A), the lower limit of the total content of these elements is greater than 0 ppm. This lower limit may be, for example, 0.1 ppm or 0.5 ppm. When the total amount of bromine and potassium is within the above range, the resulting cured product exhibits good electrical insulation.

Between elemental bromine and elemental potassium, elemental bromine tends to be present in greater amounts in the (meth)acrylic polymer (A). Therefore, by reducing the amount of elemental bromine contained in the (meth)acrylic polymer (A), the amount of ionic elements contained in the (meth)acrylic polymer (A) can be efficiently reduced. The amount of elemental bromine contained in the (meth)acrylic polymer (A) is preferably 15 ppm or less, more preferably 10 ppm or less, and even more preferably 5 ppm or less. This lower limit may be, for example, 0.1 ppm or 0.5 ppm.

The content of ionic elements is measured using inductively coupled plasma mass spectrometry (ICP-MS).

In order to reduce the ionic element content of the (meth)acrylic polymer (A), it is preferable to include a purification step in the production process of the (meth)acrylic polymer (A). Examples of substances to be removed in the purification step include solvents (such as polymerization solvents) and insoluble components (such as polymerization catalysts). Specific examples of treatments in the purification step include liquid-liquid extraction using water and adsorption treatment using an adsorbent. To improve purification efficiency, a heat treatment may be performed in the purification step.

Another example of a method for reducing the ionic element content of (meth)acrylic polymer (A) is chemical modification. Specifically, one method involves introducing a functional group to eliminate the bromine groups contained in the polymer molecule.

For more detailed information about the purification process, see, for example, paragraphs [0040] to [0066] of JP 2004-002835 A and paragraphs [0117] to [0143] of JP 2013-241541 A.

Specific examples of preferred production methods for reducing the ionic element content of (meth)acrylic resin (A) include performing the adsorption-filtration purification described in paragraphs [0040] to [0066] of JP 2004-002835 A before the (meth)acryloyl functional group introduction step, and performing water purification described in paragraphs [0117] to [0143] of JP 2013-241541 A after the (meth)acryloyl functional group introduction step. The production method will be described in more detail in the production examples described below.

2. Method for producing (meth)acrylic polymer (A)
[2.1. Method for producing main chain]
The molecular weight distribution (Mw/Mn) of the (meth)acrylic polymer (A) is 1.8 or less. In order to achieve such a small molecular weight distribution, it is preferable to produce the (meth)acrylic polymer (A) by living polymerization. Examples of living polymerization include living radical polymerization, living anionic polymerization, and living cationic polymerization. From the viewpoints of raw material management, facility design, and the production process, living radical polymerization is preferred. Examples of living radical polymerization include ATRP (atom transfer radical polymerization), ARGET, ICAR, SET-LRP, RAFT, and NMP. From the viewpoints of raw material procurement and ease of purification, ATRP and ARGET are preferred. Each method will be briefly described below.

[2.1.1. ATRP]
Examples of initiators used in ATRP include organic halides and sulfonyl halide compounds. Among organic halides, organic halides having a highly reactive carbon-halogen bond are more preferred (carbonyl compounds having a halogen at the α-position, compounds having a halogen at the benzyl position, etc.). Specific examples of initiators are described in paragraphs [0040] to [0064] of JP-A-2005-232419.

As the initiator, a compound having two or more initiation points is preferred. Using such an initiator makes it easier to control the molecular structure of the (meth)acrylic resin (A) to be produced. Specifically, it is easy to obtain a (meth)acrylic resin (A) having a (meth)acryloyl functional group at the molecular end and having 1.0 or more such functional groups per molecule.

The (meth)acrylic monomer used in ATRP is not particularly limited. Any of the (meth)acrylic acid ester monomers exemplified in Section [1] can be suitably used.

The transition metal complex used as a polymerization catalyst in ATRP is not particularly limited. It is preferably a metal complex having an element of Group 7, 8, 9, 10, or 11 of the periodic table as the central metal. It is more preferably a transition metal complex having zero-valent copper, monovalent copper, divalent ruthenium, divalent iron, or divalent nickel as the central metal. It is even more preferably a complex having monovalent copper as the central metal. Examples of monovalent copper compounds used to form such complexes include cuprous chloride, cuprous bromide, cuprous iodide, cuprous cyanide, cuprous oxide, and cuprous perchlorate.

When a metal complex containing monovalent copper as the central metal is used as a polymerization catalyst, it is preferable to use a polydentate amine as a ligand, as this enhances catalytic activity. Examples of polydentate amines include 2,2'-bipyridine or its derivatives, 1,10-phenanthroline or its derivatives, tetramethylethylenediamine, pentamethyldiethylenetriamine, and hexamethyltris(2-aminoethyl)amine.

The ATRP polymerization reaction can be carried out in the absence of a solvent or in the presence of a solvent. Examples of solvents used in the polymerization are described in paragraph [0067] of JP-A-2005-232419. A single solvent may be used, or two or more solvents may be used in combination. The polymerization reaction can also be carried out in an emulsion system or a system using supercritical fluid _CO2 as a medium.

The polymerization temperature in ATRP is preferably 0 to 200°C, and more preferably room temperature (e.g., 20°C) to 150°C.

[2.1.2. ARGET]
ARGET is one aspect of ATRP. In ARGET, the metal catalyst is regenerated using a reducing agent, which significantly reduces the amount of metal catalyst used. This reduces the purification load after production and leads to cost reduction.

In one embodiment, ARGET uses monovalent copper, a polydentate amine, a base other than the polydentate amine, and a reducing agent. In this polymerization system, the monovalent copper coordinated with the polydentate amine functions as a polymerization catalyst. The base other than the polydentate amine removes acid, a by-product of the catalytic cycle, and prevents the polydentate amine from being poisoned. The reducing agent reduces the divalent copper complex to an active monovalent copper complex. By controlling the addition rate of the reducing agent, the polymerization rate and heat of polymerization can be controlled.

In a preferred embodiment of ARGET, copper atoms are used in an amount of 5 to 30 ppm by weight relative to the total amount of (meth)acrylic monomers charged. In this embodiment, the amount of polydentate amine used is 7 mmol% or less of the entire polymerization system, and 150 mol% or less of the total amount of copper atoms. This polymerization system also contains a base and a reducing agent in addition to the polydentate amine.

(polydentate amines)
Examples of the polydentate amine include the following: One type of polydentate amine may be used alone, or two or more types may be used in combination.
Bidentate polydentate amines: 2,2-bipyridine, 4,4'-di-(5-nonyl)-2,2'-bipyridine, N-(n-propyl)pyridylmethanimine, N-(n-octyl)pyridylmethanimine. Tridentate polydentate amines: N,N,N',N'',N''-pentamethyldiethylenetriamine, N-propyl-N,N-di(2-pyridylmethyl)amine. Tetradentate polydentate amines: hexamethyltris(2-aminoethyl)amine, N,N-bis(2-dimethylaminoethyl)-N,N'-dimethylethylenediamine, 2,5,9,12-tetramethyl-2,5,9,12-tetraazatetradecane, 2,6,9,13-tetramethyl N-2,6,9,13-tetraazatetradecane, 4,11-dimethyl-1,4,8,11-tetraazabicyclohexadecane, N',N''-dimethyl-N',N''-bis((pyridin-2-yl)methyl)ethane-1,2-diamine, tris[(2-pyridyl)methyl]amine, 2,5,8,12-tetramethyl-2,5,8,12-tetraazatetradecane; Pentadentate multidentate amine: N,N,N',N'',N''',N'''',N'''',N''''-heptamethyltetraethylenetetramine; Hexadentate multidentate amine: N,N,N',N'-tetrakis(2-pyridylmethyl)ethylenediamine; Polyamine: polyethyleneimine

Preferred polydentate amines are hexamethyltris(2-aminoethyl)amine and N,N,N',N'-tetrakis(2-pyridylmethyl)ethylenediamine. The use of these polydentate amines allows for a sufficient reaction rate to be achieved while reducing the amount of transition metal atoms used (approximately 30 ppm or less relative to the (meth)acrylic monomer). Furthermore, the molecular weight distribution of the resulting (meth)acrylic resin is narrow.

(Bases other than polydentate amines)
The base other than the polydentate amine may be a Bronsted base (a compound that accepts a proton) or a Lewis base (a compound that donates an unshared electron pair to form a coordinate bond). Examples of the base other than the polydentate amine include the following. Only one type of base other than the polydentate amine may be used, or two or more types may be used in combination.
Monoamines: Monoamines are compounds that contain only one amine moiety that acts as a base. Examples of monoamines include primary amines (methylamine, aniline, lysine, etc.), secondary amines (dimethylamine, piperidine, etc.), tertiary amines (trimethylamine, triethylamine, etc.), aromatic amines (pyridine, pyrrole, etc.), and ammonia.
Inorganic base: An inorganic base refers to an element or compound from Group 1 or 2 of the periodic table. Examples of elements include lithium, sodium, and calcium. Examples of compounds include sodium methoxide, potassium ethoxide, methyllithium, sodium hydroxide, potassium hydroxide, potassium carbonate, sodium bicarbonate, ammonium bicarbonate, trisodium phosphate, disodium hydrogen phosphate, tripotassium phosphate, dipotassium hydrogen phosphate, sodium acetate, potassium acetate, sodium oxalate, potassium oxalate, sodium phenoxy, potassium phenoxy, sodium ascorbate, and potassium ascorbate. In addition, salts of weak acids (such as ammonium hydroxide) with strong bases are also inorganic bases.

Bases other than polydentate amines may be added directly to the reaction system or may be generated in the reaction system.

Bases other than polydentate amines are usually removed by purification after production of the (meth)acrylic polymer (A). Therefore, amines with low boiling points or low costs are preferred. Examples of amines that meet these conditions include triethylamine and trimethylamine.

(reducing agent)
Examples of the reducing agent are described in paragraphs [0083] to [0095] of WO 2012/020545. One type of reducing agent may be used alone, or two or more types may be used in combination.

The reducing agent is usually removed by purification after production of the (meth)acrylic polymer (A). Therefore, a reducing agent that is easy to purify or low cost is preferred. Examples of reducing agents that meet these conditions include ascorbic acid, ascorbate salts, and organotin compounds.

The lower limit of the amount of reducing agent added is preferably 10 ppm or more relative to the total amount of (meth)acrylic acid monomer charged. The upper limit of the amount of reducing agent added is preferably 100,000 ppm or less, more preferably 10,000 ppm or less, even more preferably 1,000 ppm or less, and particularly preferably 500 ppm or less, relative to the total amount of (meth)acrylic acid monomer charged. If the amount of reducing agent added is within the above range, sufficient polymerization activity can be expected, and it can also be easily removed by purification.

If the reducing agent is a solid substance at room temperature, it is preferable to add a solution of the reducing agent dissolved in a good solvent to the polymerization system. This makes it easier for the reducing agent to exert its effect.

As mentioned above, the polymerization rate and heat of polymerization can be controlled by adjusting the rate at which the reducing agent is added. From a safety standpoint, it is preferable to add the reducing agent to the polymerization system in small amounts as the polymerization progresses. The lower limit of the rate at which the reducing agent is added is preferably 10 mol%/Hr or more, more preferably 20 mol%/Hr or more, and even more preferably 30 mol%/Hr or more, relative to the copper complex. The upper limit of the rate at which the reducing agent is added is preferably 1000 mol%/Hr or less, more preferably 700 mol%/Hr or less, and even more preferably 500 mol%/Hr or less, relative to the copper complex.

[2.2. Method for introducing a (meth)acryloyl-based functional group]
A known method can be used to introduce the (meth)acryloyl functional group represented by formula (a) into the main chain of the (meth)acrylic polymer, as described, for example, in paragraphs [0080] to [0091] of JP-A-2004-203932.

In particular, a method in which the terminal halogen groups of a (meth)acrylic polymer represented by the following general formula (b) are substituted with a compound having a (meth)acryloyl functional group represented by the following general formula (c) is preferred. This method makes it easy to control the reaction.

-CR ² R ³ X...General formula (b)
In the formula, ^R2 and ^R3 are groups bonded to the ethylenically unsaturated group of the (meth)acrylic monomer, and X represents chlorine, bromine, or iodine.

M ^+- OC(O)C(R ¹ )=CH ₂ ...General formula (c)
In the formula, ^R1 is as described for general formula (a). M ⁺ represents an alkali metal ion or a quaternary ammonium ion. Examples of alkali metal ions include lithium ions, sodium ions, and potassium ions. Examples of quaternary ammonium ions include tetramethylammonium ions, tetraethylammonium ions, tetrabenzylammonium ions, trimethyldodecylammonium ions, tetrabutylammonium ions, and dimethylpiperidinium ions. Preferred M ⁺ is one or more selected from sodium ions and potassium ions.

By using an organic halide or sulfonyl halide compound described in Section [2.1.1.] as an initiator and a transition metal complex as a catalyst, a (meth)acrylic polymer having a terminal structure represented by general formula (b) can be produced. Alternatively, a (meth)acrylic polymer having a terminal structure represented by general formula (b) can also be produced by using a halogen compound as a chain transfer agent. The former production method is preferred.

When reacting a polymer represented by general formula (b) with a compound represented by general formula (c), the ratio of the oxyanion in general formula (c) to the halogen group in general formula (b) is preferably set to 1.0 to 5.0 equivalents, more preferably 1.0 to 1.2 equivalents.

The solvent used in the introduction reaction is preferably a polar solvent. This is because the introduction reaction is a nucleophilic substitution reaction. Examples of polar solvents include tetrahydrofuran, dioxane, diethyl ether, acetone, dimethyl sulfoxide, dimethylformamide, dimethylacetamide, hexamethylphosphoric triamide, and acetonitrile.

The reaction temperature for the introduction reaction is preferably 0 to 150°C. From the viewpoint of maintaining the polymerizability of the (meth)acryloyl functional group, the reaction temperature is more preferably room temperature (e.g., 20°C) to 100°C.

[3. Epoxy Compound and/or Oxetane Compound (B)]
A curable composition according to one embodiment of the present invention contains an epoxy compound and/or an oxetane compound (B). The epoxy compound and the oxetane compound serve to improve the strength of the cured product. The oxetane compound also serves to reduce the viscosity of the curable composition, thereby improving workability. The epoxy compound and/or the oxetane compound (B) may be used alone or in combination of two or more types.

[3.1. Epoxy compounds]
The term "epoxy compound" generally refers to a compound having an epoxy group. Examples of the epoxy compound include aromatic epoxy compounds and alicyclic epoxy compounds. From the viewpoint of increasing the hardness of the cured product, aromatic epoxy compounds are preferred.

Furthermore, it is preferable that the epoxy compound has a radically reactive group. Such an epoxy compound forms crosslinks with the (meth)acryloyl functional group of the (meth)acrylic polymer. This results in a tough cured product with low elution in solvents. Examples of radically reactive groups include acryloyl groups, methacryloyl groups, and allyl groups. Epoxy compounds with radically reactive groups are available from Nippon Kayaku Co., Ltd., DIC Corporation, Showa Denko Materials Co., Ltd., and other companies.

Specific examples of aromatic epoxy compounds include bisphenol A epoxy compounds, bisphenol F epoxy compounds, bisphenol AD epoxy compounds, hydrogenated bisphenol A epoxy compounds, and hydrogenated bisphenol F epoxy compounds. An example of an aromatic epoxy compound is 2,2-bis(4-glycidyloxyphenyl)propane.

Examples of alicyclic epoxy compounds include compounds having a cyclohexene oxide group, a tricyclodecene oxide group, a cyclopentene oxide group, etc. More specific examples of alicyclic epoxy compounds include vinylcyclohexene diepoxide, vinylcyclohexene monoepoxide, 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate, 2-(3,4-epoxycyclohexyl 5,5-spiro-3,4-epoxy)cyclohexane-m-dioxane, bis(3,4-epoxycyclohexyl)adipate, and bis(3,4-epoxycyclohexylmethylene)adipate.

[3.2. Oxetane compounds]
Examples of the oxetane compound include 3-ethyl-3-hydroxymethyloxetane, 3-(meth)allyloxymethyl-3-ethyloxetane, (3-ethyl-3-oxetanylmethoxy)methylbenzene, 4-fluoro-[1-(3-ethyl-3-oxetanylmethoxy)methyl]benzene, 4-methoxy-[1-(3-ethyl-3-oxetanylmethoxy)methyl]benzene, [1-(3-ethyl-3-oxetanylmethoxy)ethyl]phenyl ether, isobutoxymethyl(3-ethyl-3-oxetanyl) 3-ethyl-3-oxetanylmethyl) ether, isobornyloxyethyl (3-ethyl-3-oxetanylmethyl) ether, isobornyl (3-ethyl-3-oxetanylmethyl) ether, 2-ethylhexyl (3-ethyl-3-oxetanylmethyl) ether, ethyl diethylene glycol (3-ethyl-3-oxetanylmethyl) ether, dicyclopentadiene (3-ethyl-3-oxetanylmethyl) ether, dicyclopentenyloxyethyl (3-ethyl-3-oxetanylmethyl) ether, dicyclopentenyl phenoxyethyl (3-ethyl-3-oxetanylmethyl) ether, tetrahydrofurfuryl (3-ethyl-3-oxetanylmethyl) ether, tetrabromophenyl (3-ethyl-3-oxetanylmethyl) ether, 2-tetrabromophenoxyethyl (3-ethyl-3-oxetanylmethyl) ether, tribromophenyl (3-ethyl-3-oxetanylmethyl) ether, 2-tribromophenoxyethyl (3-ethyl-3-oxetanylmethyl) ether, 2-hydroxyethyl (3-ethyl phenyl(3-ethyl-3-oxetanylmethyl) ether, 2-hydroxypropyl(3-ethyl-3-oxetanylmethyl) ether, butoxyethyl(3-ethyl-3-oxetanylmethyl) ether, pentachlorophenyl(3-ethyl-3-oxetanylmethyl) ether, pentabromophenyl(3-ethyl-3-oxetanylmethyl) ether, bornyl(3-ethyl-3-oxetanylmethyl) ether, 3,7-bis(3-oxetanyl)-5-oxa-nonane, 1,4-bis[(3-ethyl-3-oxetanylmethyl) ether] ... 1,2-bis[(3-ethyl-3-oxetanylmethoxy)methyl]benzene, 1,2-bis[(3-ethyl-3-oxetanylmethoxy)methyl]ethane, 1,2-bis[(3-ethyl-3-oxetanylmethoxy)methyl]propane, ethylene glycol bis(3-ethyl-3-oxetanylmethyl)ether, dicyclopentenyl bis(3-ethyl-3-oxetanylmethyl)ether, triethylene glycol bis(3-ethyl-3-oxetanylmethyl)ether, tetraethylene glycol bis(3-ethyl-3-oxetanylmethyl) bis(3-ethyl-3-oxetanylmethyl)ether, tricyclodecanediyldimethylenebis(3-ethyl-3-oxetanylmethyl)ether, 1,4-bis[(3-ethyl-3-oxetanylmethoxy)methyl]butane, 1,6-bis[(3-ethyl-3-oxetanylmethoxy)methyl]hexane, polyethylene glycol bis(3-ethyl-3-oxetanylmethyl)ether, EO-modified bisphenol A bis(3-ethyl-3-oxetanylmethyl)ether, PO-modified bisphenol A bis(3-ethyl-3-oxetanylmethyl)ether ) ether, EO-modified hydrogenated bisphenol A bis(3-ethyl-3-oxetanylmethyl) ether, PO-modified hydrogenated bisphenol A bis(3-ethyl-3-oxetanylmethyl) ether, EO-modified bisphenol F bis(3-ethyl-3-oxetanylmethyl) ether, trimethylolpropane tris(3-ethyl-3-oxetanylmethyl) ether, pentaerythritol tris(3-ethyl-3-oxetanylmethyl) ether, pentaerythritol tetrakis(3-ethyl-3-oxetanylmethyl) ether dipentaerythritol hexakis(3-ethyl-3-oxetanylmethyl) ether, dipentaerythritol pentakis(3-ethyl-3-oxetanylmethyl) ether, dipentaerythritol tetrakis(3-ethyl-3-oxetanylmethyl) ether, caprolactone-modified dipentaerythritol hexakis(3-ethyl-3-oxetanylmethyl) ether, and ditrimethylolpropane tetrakis(3-ethyl-3-oxetanylmethyl) ether.

The weight ratio of the (meth)acrylic polymer (A) to the epoxy compound and/or oxetane compound (B) in the curable composition is preferably 1:99 to 50:50, more preferably 2:98 to 40:60, and even more preferably 3:97 to 30:70. If the blending ratio of the two is within the above range, the cured product will have sufficient strength and elongation.

[4. Photoradical polymerization initiator (C)]
The curable composition according to one embodiment of the present invention contains a photoradical polymerization initiator (C). The photoradical polymerization initiator (C) serves to cure the curable composition when triggered by light irradiation (such as UV irradiation). The photoradical polymerization initiator (C) may be used alone or in combination of two or more types.

Examples of photoradical polymerization initiators (C) include acetophenone, propiophenone, benzophenone, xanthol, fluorene, benzaldehyde, anthraquinone, triphenylamine, carbazole, 3-methylacetophenone, 4-methylacetophenone, 3-pentylacetophenone, 2,2-diethoxyacetophenone, 4-methoxyacetophenone, 3-bromoacetophenone, 4-allylacetophenone, p-diacetylbenzene, 3-methoxybenzophenone, 4-methylbenzophenone, 4-chlorobenzophenone, 4,4'-dimethoxybenzophenone, 4-chloro-4'-benzylbenzophenone, 3-chloroxanthone, 3,9-dichloroxanthone, 3-chloro- 8-nonylxanthone, benzoyl, benzoin methyl ether, benzoin butyl ether, bis(4-dimethylaminophenyl)ketone, benzyl methoxyketal, 2-chlorothioxanthone, 2,2-dimethoxy-1,2-diphenylethan-1-one, 1-hydroxy-cyclohexyl-phenyl-ketone, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone-1, 2-(dimethylamino)-2-(4-methylbenzyl)-1-(4-morpholinophenyl)butan-1-one).

Further examples of the photoradical polymerization initiator (C) include acylphosphine oxide-based photopolymerization initiators. Acylphosphine oxide-based photopolymerization initiators are preferred due to their excellent deep curing properties when exposed to UV light. Examples of acylphosphine oxide-based photopolymerization initiators include 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, bis(2,6-dimethoxybenzoyl)-2,4,4-trimethyl-pentylphosphine oxide, bis(2,6-dimethylbenzoyl)-phenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)-isobutylphosphine oxide, bis(2,6-dimethoxybenzoyl)-isobutylphosphine oxide, and bis(2,6-dimethoxybenzoyl)-phenylphosphine oxide. Of these, 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, and bis(2,6-dimethoxybenzoyl)-2,4,4-trimethyl-pentylphosphine oxide are preferred.

Among the above-mentioned photoradical polymerization initiators (C), 1-hydroxycyclohexylphenylketone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 2,2-dimethoxy-1,2-diphenylethan-1-one, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, and bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide are preferred due to their high reactivity.

The amount of photoradical polymerization initiator (C) is preferably 0.01 to 5 parts by weight, based on 100 parts by weight of the total weight of the (meth)acrylic polymer (A) and the epoxy compound and/or oxetane compound (B). From the viewpoint of achieving both deep curing and optical transparency of the cured product, 0.05 to 1 part by weight is more preferable.

5. Epoxy Curing Agent (D)
The curable composition contains an epoxy curing agent (D). A wide variety of conventionally known epoxy curing agents can be used as the epoxy curing agent (D). Examples of the epoxy curing agent (D) include amine-based curing agents, imidazole-based curing agents, and acid anhydride-based curing agents. Only one type of epoxy curing agent (D) may be used, or two or more types may be used in combination.

Examples of amine-based curing agents include aliphatic amines (diethylenetriamine, triethylenetetraamine, tetraethylenepentamine, diethylaminopropylamine, hexamethylenediamine, methylpentamethylenediamine, trimethylhexamethylenediamine, guanidine, oleylamine, etc.); alicyclic amines (menthenediamine, isophoronediamine, norbornanediamine, piperidine, N,N'-dimethylpiperazine, N-aminoethylpiperazine, 1,2-diaminocyclohexane, bis(4-amino-3-methylcyclohexyl)methane, bis(4-aminocyclohexyl)methane, polycyclohexylpolyamine, 1,8-diazabicyclo[5.4.0]undecene-7 (DBU), etc.); amines with ether bonds (3 ,9-bis(3-aminopropyl)-2,4,8,10-tetraoxaspiro[5,5]undecane (ATU), morpholine, N-methylmorpholine, polyoxypropylenediamine, polyoxypropylenetriamine, polyoxyethylenediamine, etc.); hydroxyl group-containing amines (diethanolamine, triethanolamine, etc.); aromatic amines (tris-2,4,6-dimethylaminomethylphenol, etc.); aminosilanes (γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, γ-aminopropyltriisopropoxysilane, γ-aminopropylmethyldimethoxysilane, γ-aminopropylmethyldiethoxysilane, γ-(2-aminoethyl)aminopropyltrimethoxysilane, γ-(2-aminoethyl)aminopropyltriisopropoxy ... N-(2-aminoethyl)aminopropylmethyldimethoxysilane, γ-(2-aminoethyl)aminopropyltriethoxysilane, γ-(2-aminoethyl)aminopropylmethyldiethoxysilane, γ-(2-aminoethyl)aminopropyltriisopropoxysilane, γ-(2-(2-aminoethyl)aminoethyl)aminopropyltrimethoxysilane, γ-(6-aminohexyl)aminopropyltrimethoxysilane, 3-(N-ethylamino)-2-methylpropyltrimethoxysilane, 2-aminoethylaminomethyltrimethoxysilane, N-cyclohexylaminomethyltriethoxysilane, N-cyclohexylaminomethyldiethoxymethylsilane, γ-ureidopropyltrimethoxysilane, γ-ureidopropyltriethoxysilane, N-furan Examples include phenyl-γ-aminopropyltrimethoxysilane, N-phenylaminomethyltrimethoxysilane, N-benzyl-γ-aminopropyltrimethoxysilane, N-vinylbenzyl-γ-aminopropyltriethoxysilane, N-(3-triethoxysilylpropyl)-4,5-dihydroimidazole, N-cyclohexylaminomethyltriethoxysilane, N-cyclohexylaminomethyldiethoxymethylsilane, N-phenylaminomethyltrimethoxysilane, (2-aminoethyl)aminomethyltrimethoxysilane, N,N'-bis[3-(trimethoxysilyl)propyl]ethylenediamine, and ketimine silanes (such as N-(1,3-dimethylbutylidene)-3-(triethoxysilyl)-1-propanamine).

Examples of imidazole curing agents include 2-phenylimidazole, 2-ethyl-4(5)-methylimidazole, 2-phenyl-4-methylimidazole, 1-benzyl-2-methylimidazole, 1-benzyl-2-phenylimidazole, 1-cyanoethyl-2-undecylimidazole, 1-cyano-2-phenylimidazole, 1-cyanoethyl-2-undecylimidazole trimellitate, 1-cyanoethyl-2-phenylimidazolium trimellitate, 2,4-diamino-6 Examples of imidazole-based curing agents include 2,4-diamino-6-[2'-ethyl-4'-methylimidazolyl-(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-ethyl-4'-methylimidazolyl-(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine isocyanuric acid adduct, 2-phenylimidazole isocyanuric acid adduct, 2-phenyl-4,5-dihydroxymethylimidazole, and 2-phenyl-4-methyl-5-hydroxymethylimidazole. Adducts of epoxy compounds with the above-mentioned imidazole compounds are also examples of imidazole-based curing agents.

Examples of acid anhydride curing agents include phthalic anhydride, trimellitic anhydride, pyromellitic anhydride, tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride, methylnadic anhydride, hexahydrophthalic anhydride, and dodecylsuccinic anhydride.

Further examples of epoxy curing agents (D) include polyamidoamines (such as polyamides obtained by reacting dimer acid with polyamines (diethylenetriamine, triethylenetetramine, etc.), and polyamides obtained by reacting polycarboxylic acids other than dimer acid with polyamines); dicyandiamide; and modified amines (such as epoxy-modified amines obtained by reacting amines with epoxy compounds, Mannich-modified amines obtained by reacting amines with formalin or phenolic compounds, Michael addition-modified amines, and ketimines).

From the viewpoint of the curability of the epoxy compound and/or oxetane compound (B), an amine-based curing agent is preferred as the epoxy curing agent (D). Furthermore, from the viewpoint of the storage stability of the curable composition, a tertiary amine compound is preferred as the epoxy curing agent (D).

The amount of epoxy curing agent (D) is preferably 1 to 200 parts by weight, and more preferably 5 to 100 parts by weight, per 100 parts by weight of the epoxy compound and/or oxetane compound (B). When the amount of epoxy curing agent (D) is within the above range, the curability of the curable composition can be enhanced and the elution of components from the cured product can be reduced.

[6. Other Ingredients]
In addition to the above-described (A) to (D), the curable composition according to one embodiment of the present invention may contain various additives depending on the purpose. Examples of the additives include polymerizable monomers and/or oligomers, fillers, plasticizers, solvents, thixotropic agents, antioxidants, and other additives. Each of these additives may be used alone or in combination of two or more.

[6.1. Polymerizable Monomers and/or Oligomers]
Addition of a polymerizable monomer and/or oligomer can, for example, reduce the viscosity of the curable composition, improve the curability, and improve the mechanical properties of the cured product. Examples of the polymerizable monomer and/or oligomer include the substances described in [0110] to [0124] of JP-A-2006-274085.

The blend amount of the polymerizable monomer and/or oligomer is preferably 10 to 200 parts by weight, more preferably 20 to 150 parts by weight, and even more preferably 30 to 100 parts by weight, per 100 parts by weight of the (meth)acrylic polymer (A). A blend amount within the above range has the advantage of improving workability by reducing viscosity. Only one type of polymerizable monomer and/or oligomer may be used, or two or more types may be used in combination.

6.2. Fillers
Addition of a filler can adjust the thixotropy of the curable composition and impart mechanical strength and abrasion resistance to the cured product. Examples of fillers include the fillers and hollow microparticles described in [0134] to [0151] of JP-A-2006-291073.

Specific examples of fillers include reinforcing silica, such as finely powdered silica (fumed silica, wet-process silica, etc.), carbon black, wood flour, pulp, cotton chips, mica, walnut shell powder, rice husk flour, graphite, white clay, silica (crystalline silica, fused silica, dolomite, anhydrous silicic acid, hydrous silicic acid, etc.), heavy calcium carbonate, colloidal calcium carbonate, magnesium carbonate, diatomaceous earth, calcined clay, clay, talc, titanium oxide, bentonite, organic bentonite, ferric oxide, red iron oxide, fine aluminum powder, flint powder, zinc oxide, activated zinc white, zinc powder, zinc carbonate, shirasu balloons, beads (made of polyacrylic resin, polyacrylonitrile-vinylidene chloride resin, phenolic resin, polystyrene resin, etc.), and hollow particles thereof, inorganic hollow particles (glass balloons, shirasu balloons, fly ash balloons, etc.), and fibrous fillers (glass fiber, glass filament, carbon fiber, Kevlar fiber, polyethylene fiber, etc.). Among these, from the viewpoint of excellent reinforcing properties, one or more types selected from the group consisting of fumed silica, wet-process silica, carbon black, heavy calcium carbonate, and hard calcium carbonate are preferred.

The particle size of the fumed silica and wet-process silica is preferably 50 μm or less. The specific surface area of the fumed silica and wet-process silica is preferably 80 m ² /g or more. Such fumed silica and wet-process silica can sufficiently enhance reinforcing properties. In this specification, the specific surface area value represents a value measured by the BET method. As the silica used as a filler, surface-untreated silica is preferred to surface-treated silica (e.g., silica surface-treated with organosilane, organosilazane, diorganocyclopolysiloxane, etc.). Surface-untreated silica has the advantages of being easy to knead, improving the fluidity of the curable composition, and being economical.

An example of commercially available fumed silica is AEROSIL (manufactured by Nippon Aerosil Co., Ltd.). An example of commercially available wet-process silica is Nipsil (manufactured by Tosoh Silica Corporation).

Examples of carbon black include channel black, furnace black, acetylene black, and thermal black. From the standpoint of reinforcement and economy, furnace black is preferred.

The amount of filler blended is preferably 0.1 to 500 parts by weight, more preferably 0.5 to 200 parts by weight, and even more preferably 1 to 50 parts by weight, per 100 parts by weight of (meth)acrylic polymer (A). If the blending amount is within the above range, both the reinforcement properties of the cured product and the workability of the curable composition can be achieved. Only one type of filler may be used, or two or more types may be used in combination.

6.3. Plasticizers
The addition of a plasticizer can adjust the viscosity of the curable composition and the mechanical properties (tensile strength, elongation, etc.) of the cured product, and can also improve the transparency of the cured product.

Examples of plasticizers include phthalate esters (dibutyl phthalate, diheptyl phthalate, di(2-ethylhexyl) phthalate, butyl benzyl phthalate, etc.); aromatic esters of polyalkylene glycols (diethylene glycol dibenzoate, triethylene glycol dibenzoate, etc.); phosphate esters (tricresyl phosphate, tributyl phosphate, etc.); trimellitate esters; pyromellitate esters; polystyrene-based resins (polystyrene, poly-α-methylstyrene, etc.); ester-based plasticizers obtained by reacting saturated aliphatic alcohols and saturated fatty acids; polybutadiene; polybutene; polyisobutylene; butadiene -Acrylonitrile; polychloroprene; chlorinated paraffin; hydrocarbon oils (alkyldiphenyls, partially hydrogenated terphenyls, etc.); process oil; polyethers (polyether polyols (polyethylene glycol, polypropylene glycol, polytetramethylene glycol, etc.), derivatives of polyether polyols in which the hydroxyl groups have been converted to ester groups or ether groups, etc.); epoxy plasticizers (epoxidized soybean oil, epoxy benzyl stearate, etc.); (meth)acrylic polymers obtained by polymerizing vinyl monomers using various methods (acrylic plasticizers, etc.; commercially available products include the ARUFON series (manufactured by Toagosei Co., Ltd.)).

The amount of plasticizer blended is preferably 1 to 100 parts by weight, and more preferably 1 to 50 parts by weight, per 100 parts by weight of (meth)acrylic polymer (A). When the blending amount is within the above range, the workability of the curable composition is improved and the effect on the mechanical properties of the resulting cured product is minimal. Only one type of plasticizer may be used, or two or more types may be used in combination.

6.4. Solvents
Examples of the solvent include aromatic hydrocarbon solvents (toluene, xylene, etc.); ester solvents (ethyl acetate, butyl acetate, amyl acetate, cellosolve acetate, etc.); ketone solvents (acetone, methyl ethyl ketone, methyl isobutyl ketone, diisobutyl ketone, etc.); alcohol solvents (methanol, ethanol, isopropanol, etc.); and hydrocarbon solvents (hexane, cyclohexane, methylcyclohexane, heptane, octane, etc.).

The amount of solvent blended is preferably 50 parts by weight or less, and more preferably 30 parts by weight or less, per 100 parts by weight of the (meth)acrylic polymer (A). When the blending amount is within the above range, the workability of the curable composition is improved and the impact of cure shrinkage is small. Furthermore, from the viewpoint of minimizing the impact on the working environment, an amount of 10 parts by weight or less per 100 parts by weight of the (meth)acrylic polymer (A) is even more preferable. Only one type of solvent may be used, or two or more types may be used in combination.

[6.5. Thixotropy-imparting agents]
Addition of a thixotropic agent (anti-sagging agent) can prevent sagging and improve workability.

Examples of anti-thixotropy agents include hydrogenated castor oil derivatives, metal soaps with long-chain alkyl groups, ester compounds with long-chain alkyl groups, inorganic fillers (such as silica), and amide waxes.

The amount of the thixotropy-imparting agent is preferably 0.1 to 10 parts by weight, and more preferably 0.1 to 5 parts by weight, per 100 parts by weight of the (meth)acrylic polymer (A). When the amount is within the above range, the workability of the curable composition is improved. Only one type of thixotropy-imparting agent may be used, or two or more types may be used in combination.

6.6. Antioxidants
Addition of an antioxidant (anti-aging agent) can improve the heat resistance of the cured product.

Examples of antioxidants include primary antioxidants (hindered phenol antioxidants, amine antioxidants, lactone antioxidants, ethanolamine antioxidants, etc.) and secondary antioxidants (sulfur-based oxidants, phosphorus-based oxidants, etc.). Further examples of antioxidants include the substances described in [0232] to [0235] of JP 2007-308692 A and the substances described in [0089] to [0093] of WO 2005/116134 A.

The amount of antioxidant blended is preferably 0.1 to 5 parts by weight, and more preferably 0.1 to 3 parts by weight, per 100 parts by weight of (meth)acrylic polymer (A). A blending amount within the above range ensures sufficient heat resistance and is not economically disadvantageous.

6.7. Other Additives
Examples of other additives include compatibilizers, curing regulators, radical inhibitors, metal deactivators, antiozonants, phosphorus-based peroxide decomposers, lubricants, pigments, antifoaming agents, foaming agents, anti-termite agents, anti-fungal agents, ultraviolet absorbers, and light stabilizers. Further examples of other additives include those described in JP-A-63-006041, JP-A-63-006003, JP-A-63-254149, JP-A-64-022904, and JP-A-2001-072854.

[7. Curing method]
The curable composition according to one embodiment of the present invention is cured by both photoradical curing and thermal curing.

Photoradical curing is curing initiated by irradiation with active energy rays (such as UV or electron beams). The active energy ray source can be selected appropriately depending on the properties of the photoradical polymerization initiator (C). Examples of active energy ray sources include high-pressure mercury lamps, low-pressure mercury lamps, LEDs, electron beam irradiation devices, halogen lamps, light-emitting diodes, and semiconductor lasers.

Thermal curing is an effect initiated by heating. The thermal curing temperature is set appropriately depending on the type of epoxy compound and/or oxetane compound (B), epoxy curing agent (D), and other additives. The thermal curing temperature is preferably 15 to 300°C, and more preferably 15 to 250°C. This temperature range prevents deterioration of the cured product due to heat. Heating furnaces, ovens, heated conveyors, etc. can be used for thermal curing.

[8. Use]
The curable composition according to one embodiment of the present invention has good electrical insulation properties and is therefore suitable for use in electrical and electronic components, resist materials, etc. However, the use is not limited to these applications and can be used in a variety of applications.

Examples of electrical and electronic components include electrical insulating materials (such as insulating coatings for electric wires and cables), sealing materials, adhesives, pressure-sensitive adhesives, conformal coatings, potting agents for electrical and electronic applications, packing, O-rings, and belts. More specific examples include high-voltage thick-film resistors, hybrid IC circuit elements, HICs, electrical insulating components, semiconducting components, conductive components, modules, printed circuits, ceramic substrates, diodes, buffer materials for transistors or bonding wires, coating materials for optical fibers used in optical communications, high-voltage transformer circuits, printed circuit boards, high-voltage transformers with variable resistors, electrical insulating components, potting materials for solar cells (such as crystalline silicon solar cells, amorphous silicon solar cells, CI(G)S solar cells, perovskite solar cells, organic thin-film solar cells, dye-sensitized solar cells, and GaAs solar cells), flyback transformers for televisions, heavy electrical components, low-voltage electrical components, backside sealing materials for solar cells, and sealing materials for circuits and substrates of electrical and electronic devices.

Examples of resist materials include peripheral components for semiconductors and conductors. More specific examples include photomasks, photoresists, semiconductor surface protection tape, dicing tape, die bonding tape, die bonding materials, interlayer insulating materials (build-up materials), photosensitive dry film resists, liquid photosensitive resin materials, interposer materials, package substrate materials, solder resists, semiconductor encapsulation resins, underfill materials, sidefill materials, printed circuit board materials, and modifiers for these materials.

Further suitable applications include components that transmit light (ultraviolet light, visible light, infrared light, X-rays, lasers, etc.). Examples include display peripheral components and UV inks for 3D printing. More specific examples include flat panel displays and their encapsulants; peripheral materials for liquid crystal display devices (such as light guide plates, prism sheets, polarizing plates, retardation plates, viewing angle correction films, front glass protective films, polarizer protective films or adhesives, adhesives or fillers between panels or films, and liquid crystal films in the field of liquid crystal displays); encapsulants, anti-reflection films, optical correction films, front glass protective films or adhesives, adhesives or fillers between panels or films for color PDPs (plasma displays); molding materials for light-emitting elements used in light-emitting diode display devices, light-emitting diode (LED) encapsulants, front glass protective films or adhesives, adhesives or fillers between panels or films; and light guide plates, prism sheets, polarizing plates, retardation plates, and viewing angle correction films in plasma-addressed liquid crystal (PALC) displays. , polarizer protective films or adhesives, adhesives or fillers between panels or films; protective films or adhesives for front glass in organic EL (electroluminescence) displays, adhesives or fillers between panels or films; protective films or adhesives, adhesives or fillers between panels or films in organic TFT (organic thin film transistor) displays; various film substrates, protective films or adhesives for front glass, adhesives or fillers between panels or films in field emission displays (FEDs); protective films or adhesives, adhesives or fillers between panels or films in electronic paper; protective films or adhesives, adhesives or fillers between panels or films for touch panels, mobile phone displays, and car navigation displays; and peripheral materials for the above-mentioned display devices.

9. Summary
The present invention includes the following aspects.
<1>
a (meth)acrylic polymer (A);
an epoxy compound and/or an oxetane compound (B);
a photoradical polymerization initiator (C);
an epoxy curing agent (D);
Contains
the weight ratio of the (meth)acrylic polymer (A) to the epoxy compound and/or oxetane compound (B) is (1:99) to (50:50);
The (meth)acrylic polymer (A) is
The molecular weight distribution (Mw/Mn) is 1.8 or less,
The total amount of bromine and potassium contained in the polymer is 0 ppm or more and 25 ppm or less, and
The (meth)acryloyl functional group represented by the following general formula (a) has 1.0 or more per molecule:
-OC(O)C(R ¹ )=CH ₂ ...General formula (a)
(wherein ^R1 represents a hydrogen atom or an organic group having 1 to 20 carbon atoms)
Curable composition.
<2>
The curable composition according to <1>, wherein the (meth)acrylic polymer (A) has the (meth)acryloyl functional group at a molecular terminal.
<3>
The curable composition according to <1> or <2>, wherein the (meth)acrylic polymer (A) contains 0 ppm or more and 15 ppm or less of bromine element.
＜4＞
<4> The curable composition according to any one of <1> to <3>, wherein the epoxy compound and/or the oxetane compound (B) is an aromatic epoxy compound.
<5>
<4> The curable composition according to any one of <1> to <4>, wherein the epoxy compound and/or oxetane compound (B) is an epoxy compound having a radical reactive group.
＜6＞
<5> The curable composition according to any one of <1> to <5>, wherein the epoxy curing agent (D) is an amine compound.
＜７＞
a step of producing the (meth)acrylic polymer (A) using a copper complex, a polydentate amine, a base other than the polydentate amine, and a reducing agent;
a step of mixing the obtained (meth)acrylic polymer (A), the epoxy compound and/or oxetane compound (B), the photoradical polymerization initiator (C), and the epoxy curing agent (D);
<6> A method for producing the curable composition according to any one of <1> to <6>, comprising:

In addition to the above aspects, the present invention also includes the following aspects.
<A1>
The (meth)acrylic polymer (A) may be produced by a living polymerization method.
<A2>
The living polymerization method may be a living radical polymerization method.

Specific examples of the present invention are shown below. However, the present invention is not limited to the following examples.

[Method for measuring physical properties of (meth)acrylic resin]
[1. Number average molecular weight and molecular weight distribution]
The number average molecular weight and molecular weight distribution (ratio of weight average molecular weight to number average molecular weight) were calculated by a standard polystyrene conversion method using gel permeation chromatography (GPC).

The GPC column used was a column packed with cross-linked polystyrene gel (Shodex GPC K-804 and K-802.5, manufactured by Showa Denko K.K.). Chloroform was used as the GPC solvent.

[2. Content of ionic elements]
The content of ionic elements (bromine element and potassium element) was analyzed using ICP-MS (HP-4500, manufactured by Yokogawa Analytical Systems, Inc.).

[3. Number of functional groups introduced in the functionalization step]
The number of functional groups introduced per polymer molecule was calculated based on the concentration analysis by ¹ H-NMR and the number average molecular weight. The NMR apparatus used was ASX-400 (manufactured by Bruker). Deuterated chloroform was used as the solvent for NMR.

[Production Example of (Meth)acrylic Resin]
The reagents used in the production examples were mass-produced products with industrialization in mind, and were used without any treatment such as purification after being procured.

[Production Example 1]
<1. Polymerization process>
1. 100 parts by weight of n-butyl acrylate, 20 parts by weight of methanol, 1.76 parts by weight of diethyl 2,5-dibromoadipate, and 955 ppm of triethylamine (EtN) were charged and stirred at 45°C under a nitrogen stream. Triethylamine is an amine other than a polydentate amine.
2. A copper bromide solution was prepared by mixing 107 ppm of copper(II) bromide, 109 ppm of hexamethyltris(2-aminoethyl)amine (purity: 96%), and 0.43 parts by weight (0.54 parts by volume) of methanol. The copper content in the copper bromide solution was 30 ppm, and the content of hexamethyltris(2-aminoethyl)amine was equal to that of copper. Hexamethyltris(2-aminoethyl)amine is a polydentate amine.
3. An ascorbic acid solution was prepared by mixing 17 ppm ascorbic acid with 0.10 parts by weight (0.13 parts by volume) of methanol. Ascorbic acid corresponds to a reducing agent.
4. The copper bromide solution and ascorbic acid solution were added to the reaction system to initiate the reaction. During the reaction, the ascorbic acid solution was added appropriately, and the reaction solution was heated and stirred continuously so that the temperature was kept between 45°C and 70°C.
5. 153 minutes after the start of polymerization, the conversion of n-butyl acrylate reached 94 mol %. At this point, the volatile matter was removed by devolatilization under reduced pressure to obtain (meth)acrylic polymer X. The amount of ascorbic acid and the amount of methanol added to the reaction system up to this point were 432 ppm and 65.4 parts by weight (81.8 parts by volume), respectively.

The number average molecular weight of (meth)acrylic polymer X was 21,200, and the molecular weight distribution was 1.10.

<2. Adsorption filtration purification step (1)>
6. The (meth)acrylic polymer X obtained in the polymerization step was diluted with 100 parts by weight of butyl acetate to prepare a polymer solution.
7. An adsorbent was added to the polymer solution, and the mixture was heated and stirred for 1 hour at approximately 100° C. The adsorbents used were Kyoward 700SEN (adsorbent, manufactured by Kyowa Chemical Industry Co., Ltd.) and Kyoward 500SH (adsorbent, manufactured by Kyowa Chemical Industry Co., Ltd.), each in an amount of 1 part by weight.
8. The polymer slurry solution containing insoluble components (such as the adsorbent) was filtered to separate the solid and liquid, thereby obtaining a clear polymer solution.

<3. Functionalization process>
9. To the polymer solution obtained in the adsorption filtration purification step (1), 2.0 parts by weight of potassium acrylate, 0.3 parts by weight of tetrabutylammonium bromide, and 0.01 parts by weight of H-TEMPO were added.
10. Using an autoclave, the mixture was heated and stirred for 2 hours at an internal temperature of 120° C. This gave a (meth)acrylic polymer Y having a terminal functional group represented by “—OC(O)CH═CH ₂ ”.

In (meth)acrylic polymer Y, the number of terminal functional groups introduced was two per molecule.

<4a. Water purification process>
11a. 400 parts by weight of water was added to the polymer solution of (meth)acrylic polymer Y obtained in the functionalization step. After stirring for 5 minutes at an internal temperature of 80°C, the mixture was allowed to stand for 10 minutes. This step caused the solution to separate into two phases, with an organic phase (polymer solution) formed in the upper part and an aqueous phase in the lower part.
12a. The aqueous phase was removed from the bottom of the autoclave, and the organic phase was then devolatilized under reduced pressure at 130° C. to obtain a clear (meth)acrylic polymer (1).

The number average molecular weight of (meth)acrylic polymer (1) was 21,800, and the molecular weight distribution was 1.11. The bromine content of (meth)acrylic polymer (1) was 5 ppm, and the potassium content was 2 ppm.

[Production Example 2]
The polymerization step, the adsorption/filtration purification step (1), and the functionalization step were the same as those in Production Example 1. After the functionalization step, the following adsorption/filtration purification step (2) was carried out instead of the above-mentioned water purification step.

<4b. Adsorption filtration purification step (2)>
An adsorbent was added to the polymer solution of (meth)acrylic polymer Y obtained in the functionalization step, and the mixture was heated and stirred at 100° C. for 1 hour. Kyoward 700SEN (manufactured by Kyowa Chemical Industry Co., Ltd.) and Kyoward 500SH (manufactured by Kyowa Chemical Industry Co., Ltd.) were used as the adsorbent, in an amount of 1 part by weight each.
12b) The polymer slurry solution containing insoluble components (such as an adsorbent) was filtered, and then devolatilized under reduced pressure at 130°C to obtain a clear (meth)acrylic polymer (2).

The number average molecular weight of (meth)acrylic polymer (2) was 21,900, and the molecular weight distribution was 1.12. The bromine content of (meth)acrylic polymer (2) was 20 ppm, and the potassium content was 11 ppm. Therefore, (meth)acrylic polymer (2) does not fall under the category of (meth)acrylic polymer (A) as used herein.

[Preparation of evaluation samples]
Samples for evaluating physical properties were prepared by the following method.

[1. Preparation of curable composition]
The components according to the composition shown in Table 1 below were added to a disposable cup and stirred with a spatula. The mixture was then stirred at 1600 rpm for 1.5 minutes and degassed at 2200 rpm for 3 minutes using a planetary centrifugal mixer (Thinky Mixer). A curable composition was thus obtained.

The components contained in the curable composition are as follows:
(Meth)acrylic polymer (A)
(Meth)acrylic polymer (1): obtained in Production Example 1 (Meth)acrylic polymer (2): obtained in Production Example 2 Epoxy compound and/or oxetane compound (B)
Epoxy compound (B1): an epoxy compound having a glycidyl group and an acryloyl group. Epoxy compound (B2): 2,2-bis(4-glycidyloxyphenyl)propane (jER828, manufactured by Mitsubishi Chemical Corporation).
Photoradical polymerization initiator (C)
Photoradical polymerization initiator (C1): 2-hydroxy-2-methyl-1-phenyl-propan-1-one (Omnirad1173, manufactured by IGM Resins BV)
Photoradical polymerization initiator (C2): bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide (Ominirad819, manufactured by IGM Resins BV)
Epoxy hardener (D)
Epoxy curing agent (D1): Tris-2,4,6-dimethylaminomethylphenol (Ankamine K54, manufactured by EVONIK)

[2a. Preparation of sample for three-point bending test]
1. The curable composition was poured into a Teflon (registered trademark) mold (width 10 mm, length 100 mm, thickness 2 mm).
2. Preheating was performed at 80°C for 20 minutes. Thereafter, the curable composition was irradiated with UV light using a UV irradiation device (LIGHT HAMMER 6, manufactured by Fusion UV Systems). The irradiated light source was a mercury lamp, with a peak irradiance of 250 mW/ ^cm2 and an accumulated light dose of 2,000 mJ/ ^cm2 .
3. The composition was heated at 150°C for 60 minutes to obtain a cured product.

[2b. Preparation of sample for volume resistance measurement]
A cured product was prepared using the same procedure as for preparing the sample for the three-point bending test, except that the size of the Teflon (registered trademark) mold was changed to 100 mm wide, 100 mm long, and 2 mm thick.

[Method for evaluating physical properties of cured product]
[Three-point bending test]
A jig with an indenter radius of 5 mm and a fulcrum radius of 2 mm was used. The distance between the fulcrums was 32 mm. An autograph (AG-2000A, manufactured by Shimadzu Corporation) was used for the measurement. The measurement temperature was 23°C and the strain rate was 2 mm/min.

[Volume resistivity]
The specific volume resistivity was measured using an R8340 Ultra High Resistance Meter (manufactured by Advantest) according to a method in accordance with JIS K 6911. It can be said that the higher the specific volume resistivity, the more excellent the electrical insulation.

As can be seen from Table 1, the cured product containing (meth)acrylic polymer (1) had a higher volume resistivity and better electrical insulation than the cured product containing (meth)acrylic polymer (2). The difference between (meth)acrylic polymer (1) and (meth)acrylic polymer (2) is the total content of ionic elements (bromine and potassium).

A comparison of the Examples and Comparative Examples confirmed that the mechanical properties of the cured product were not affected even when the total content of bromine and potassium elements was reduced. Furthermore, a comparison of the Examples and Comparative Examples with the Reference Example confirmed that the mechanical properties of the cured product were improved even when a (meth)acrylic polymer with a reduced total content of bromine and potassium elements was blended.

One aspect of the present invention can be utilized in the field of curable compositions.

Claims (9)

a (meth)acrylic polymer (A);
an epoxy compound and/or an oxetane compound (B);
a photoradical polymerization initiator (C);
an epoxy curing agent (D);
Contains
the weight ratio of the (meth)acrylic polymer (A) to the epoxy compound and/or oxetane compound (B) is (1:99) to (50:50);
The (meth)acrylic polymer (A) is
The molecular weight distribution (Mw/Mn) is 1.8 or less,
The total amount of bromine and potassium contained in the polymer is 7 ppm or more and 15 ppm or less, and
The (meth)acryloyl functional group represented by the following general formula (a) has 1.0 or more per molecule:
-OC(O)C(R ¹ )=CH ₂ ...General formula (a)
(wherein ^R1 represents a hydrogen atom or an organic group having 1 to 20 carbon atoms)
Curable composition. The curable composition according to claim 1, wherein the (meth)acrylic polymer (A) has the (meth)acryloyl functional group at the molecular end. The curable composition according to claim 1 or 2, wherein the (meth)acrylic polymer (A) contains 5 ppm or more and 15 ppm or less of bromine element. The curable composition according to any one of claims 1 to 3, wherein the epoxy compound and/or oxetane compound (B) is an aromatic epoxy compound. The curable composition according to any one of claims 1 to 4, wherein the epoxy compound and/or oxetane compound (B) is an epoxy compound having a radical reactive group. The curable composition according to any one of claims 1 to 5, wherein the epoxy curing agent (D) is an amine compound. The curable composition according to any one of claims 1 to 6, wherein the (meth)acrylic polymer (A) contains 10 ppm or less of elemental bromine. The curable composition according to any one of claims 1 to 7, wherein the (meth)acrylic polymer (A) contains 10 ppm or less of elemental bromine and elemental potassium in total. A method for producing the curable composition according to any one of claims 1 to 8, comprising:
a step of producing the (meth)acrylic polymer (A) using a copper complex, a polydentate amine, a base other than the polydentate amine, and a reducing agent;
a step of mixing the obtained (meth)acrylic polymer (A), the epoxy compound and/or oxetane compound (B), the photoradical polymerization initiator (C), and the epoxy curing agent (D);
A method for producing a curable composition, comprising: