JP2024047203A - Curable polymer compound and resin composition containing said compound - Google Patents

Abstract

[Problem] To provide a curable polymer compound that can be molded into a film. [Solution] A polymer compound obtained by reacting a random copolymer represented by formula (2) as an intermediate raw material with (meth)acrylic acid chloride or (meth)acrylic acid. TIFF2024047203000012.tif57101 (In the formula, R1 represents a hydrogen atom or a methyl group. R3, R4 and R5 each independently represent a hydrogen atom or an alkyl group. l, m and n each independently represent the average number of repeating units and are in the range of 1 to 2,000.) [Selected Figure] None

Description

The present invention relates to a novel polymer compound that can be easily molded into a film by casting an organic solvent solution containing the polymer compound onto a substrate, and the resin composition that is used in combination with a radical initiator can be cured with heat or light, and the cured product has excellent dielectric properties, adhesiveness, and heat resistance.

Phenoxy resin is a polymeric compound with a very large molecular weight obtained by polymerizing a difunctional epoxy resin and a difunctional phenolic compound. By adding this phenoxy resin, it is possible to turn general epoxy resin compositions and radically polymerizable compositions into a film, and it is therefore used in a wide range of fields as an important component of film-type adhesives, and is particularly used in the electrical and electronic fields for interlayer insulation layers in printed wiring boards and resin-coated copper foils.

Although the cured product of the resin composition containing the phenoxy resin has excellent adhesion and film-forming ability, it has low heat resistance and a high dielectric constant and dielectric dissipation factor (generally, the dielectric constant is about 3.5 and the dielectric dissipation factor is about 0.03 at a frequency of 1 GHz), so it cannot be used in electronic devices, which have become faster in signal response speed in recent years. Polymeric fluorine compounds such as polytetrafluoroethane (PTFE) (Patent Document 1) and liquid crystal polymers (Patent Document 2) are generally known as resins with excellent dielectric properties, but these resins have extremely low compatibility with other resins and insufficient adhesion. Patent Document 3 describes a curable polymer compound obtained by esterifying a monomer having one or more ethylenically unsaturated groups and one carboxyl group with an aliphatic hydroxyl group in a random copolymer of a monomer having one ethylenically unsaturated group of 70% or less by weight and a (meth)acrylate having one or more aliphatic hydroxyl groups of 30% or more by weight. However, when the present inventors conducted further tests, the cured product of the curable polymer compound obtained by the structural formula in the document had a dielectric loss tangent of about 0.005 at 10 GHz, which does not fully meet the low dielectric characteristics required for current high-frequency circuit board applications.

JP 2005-001274 A JP 2014-060449 A Japanese Patent Application Laid-Open No. 10-017812

The present invention has been made in consideration of the above points, and aims to provide a curable polymer compound that has sufficient flexibility to be formed into a film, and when used in combination with a radical initiator, the cured product of the composition has high heat resistance, high adhesion to low-roughness copper foil, and low dielectric constant and dielectric tangent.

As a result of intensive research, the present inventors have found that the above-mentioned problems can be solved by a compound in which one hydroxyl group of a dihydroxybenzene compound is (meth)acrylated, and a polymer compound which is a dehydrochlorination condensation product of a hydroxyl group of a copolymer of styrene and an N-phenylmaleimide compound and a chloride group of (meth)acrylic acid chloride, and have completed the present invention.
That is, the present invention is
(1) The following formula (1)

(wherein _R1 and _R2 each independently represent a hydrogen atom or a methyl group; _R3 , _R4 and _R5 each independently represent a hydrogen atom or an alkyl group; and l, m and n each independently represent the average number of repeating units, each independently ranging from 1 to 2,000.)
(2) A resin composition comprising the polymer compound according to the above item (1) and a radical initiator.
(3) The resin composition according to the above item (2), further comprising a compound having a radical reactive group.
(4) a film-like adhesive comprising the resin composition according to the preceding item (2) or (3); and (5) a cured product of the resin composition according to the preceding item (2) or (3).
Regarding.

The polymer compound of the present invention has sufficient flexibility to be formed into a film, and by curing a resin composition in which the polymer compound is used in combination with a radical initiator using heat or light energy, a cured product with excellent dielectric properties, adhesiveness, and heat resistance can be obtained.

Hereinafter, an embodiment of the present invention will be described.
The polymer compound represented by formula (1) of the present invention is obtained by reacting a random copolymer represented by the following formula (2) as an intermediate material with (meth)acrylic acid chloride or (meth)acrylic acid, where R ₁ , R ₃ , R ₄ , R ₅ , l, m and n in formula (2) have the same meanings as R ₁ , R ₃ , R ₄ , R ₅ , l, m and n in formula (1).

First, the intermediate raw material represented by the above formula (2) (a random copolymer of a (meth)acrylate having a phenolic hydroxyl group, styrene and an N-phenylmaleimide compound, hereinafter simply referred to as the "copolymer") will be described.
The (meth)acrylate having a phenolic hydroxyl group, which is a raw material for the copolymer, is not particularly limited as long as it is a compound having a phenolic hydroxyl group and a (meth)acryloyl group in one molecule, and examples thereof include 4-hydroxyphenyl methacrylate, 2-hydroxyphenyl methacrylate, 3-hydroxyphenyl methacrylate, 4-hydroxyphenyl acrylate, 2-hydroxyphenyl acrylate, and 3-hydroxyphenyl acrylate, with 4-hydroxyphenyl methacrylate being preferred.
In this specification, the term "(meth)acrylate" means both "acrylate and methacrylate".

Examples of N-phenylmaleimide compounds that are used as raw materials for the copolymer include N-phenylmaleimide, N-(4-methylphenyl)maleimide, N-(3-methylphenyl)maleimide, N-(2-methylphenyl)maleimide, N-(2,6-dimethylphenyl)maleimide, N-(2,4-dimethylphenyl)maleimide, and N-(4-t-butylphenyl)maleimide, with N-phenylmaleimide being particularly versatile and preferred.

The method for copolymerizing the (meth)acrylate having a phenolic hydroxyl group, styrene, and N-phenylmaleimide compound is not particularly limited as long as it is a known copolymerization method, and examples thereof include bulk polymerization, solution polymerization, emulsion polymerization, and suspension polymerization.
Solvents that can be used in solution polymerization include toluene, xylene, methyl ethyl ketone, methyl isobutyl ketone, cyclopentanone, cyclohexanone, propylene glycol monomethyl ether acetate, N-methylpyrrolidone, N,N-dimethylformamide, γ-butyrolactone, etc. In emulsion polymerization and suspension polymerization, water and a surfactant are usually used, and the copolymerization reaction is carried out in a state where the raw material components are emulsified or suspended in water.

The copolymerization reaction may be any of radical polymerization, cationic polymerization, and anionic polymerization. In the case of radical polymerization, it is preferable to use a radical polymerization initiator. Specific examples of the radical polymerization initiator include 2,2'-azobisisobutyronitrile, 2,2'-azobis(2-methylbutyronitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), 1,1'-azobis(cyclohexane-1-carbonitrile, 2,2'-azobis[2-(2-imidazolin-2-yl)propane]dihydrochloride, hydrogen peroxide, di-t-butyl peroxide, dicumyl peroxide, dilauroyl peroxide, and benzoyl peroxide. Also, living radical polymerization can be performed by adding a free radical such as a TEMPO reagent to form a dormant species.
The amount of the radical polymerization initiator is usually 0.001 to 5 parts by mass per 100 parts by mass of the raw material components of the copolymer. The polymerization temperature is usually 50 to 250° C., preferably 60 to 200° C., and the polymerization time is usually 0.5 to 30 hours, preferably 1 to 20 hours. The radical polymerization reaction is preferably carried out under a nitrogen gas atmosphere to prevent polymerization inhibition by oxygen in the air.

Specific examples of cationic polymerization initiators include inorganic acids such as sulfuric acid and hydrochloric acid, organic acids such as CF ₃ COOH and CCl ₃ COOH, and super strong acids such as CF ₃ SO ₃ H and HClO _4. Specific examples of anionic polymerization initiators include butyl lithium, Na-naphthalene complexes, alkali metals, alkyl lithium compounds, sodium amides, Grignard reagents, and lithium alkoxides. However, since there is a concern that ionic initiators used in cationic polymerization and anionic polymerization remain in the copolymer even after the polymerization reaction and adversely affect the dielectric properties and insulating properties, it is preferable to synthesize the copolymer that is the intermediate raw material of the polymer compound of the present invention by radical polymerization.
The amount of the cationic polymerization initiator or anionic polymerization initiator is usually 0.01 to 5 parts by mass per 100 parts by mass of the raw material components of the copolymer. The polymerization temperature is usually 40 to 150° C., preferably 50 to 120° C., and the polymerization time is usually 0.5 to 20 hours, preferably 1 to 15 hours.

The number average molecular weight of the copolymer serving as the intermediate raw material for the polymer compound of the present invention is usually 3,000 to 300,000, and preferably 5,000 to 200,000.
In order to obtain a copolymer having a number average molecular weight within the above range, it is preferable to adjust the amount of initiator used when synthesizing the copolymer to an appropriate amount. The amount of initiator required to obtain a copolymer having a number average molecular weight within the above range depends on the type of (meth)acrylate having a phenolic hydroxyl group and the amount of (meth)acrylate having a hydroxyl group, styrene, and N-phenylmaleimide compound used in the copolymerization reaction, so it cannot be generally stated, but it is generally known that a copolymer having a large molecular weight can be obtained by reducing the amount of initiator, and it is only necessary to select the amount of initiator that can obtain a copolymer having a desired molecular weight within the above range of the amount of initiator.

The proportions of the (meth)acrylate having a phenolic hydroxyl group, styrene and N-phenylmaleimide compound used in synthesizing the copolymer serving as the intermediate raw material of the polymer compound of the present invention are not particularly limited, but the total amount (mass) of styrene and N-phenylmaleimide compound used is usually 4 to 99.5 times, preferably 4.5 to 99.7 times, the mass of the (meth)acrylate having a phenolic hydroxyl group. The preferred proportion (mass ratio) of styrene and N-phenylmaleimide compound used is usually 99.9:0.1 to 50:50, preferably 99.8:0.2 to 60:40.
By setting the usage ratios of the (meth)acrylate having a phenolic hydroxyl group, styrene and N-phenylmaleimide compound, which are raw materials for the copolymer, within the above-mentioned ranges, it is possible to obtain the polymer compound of the present invention, the cured product of which exhibits excellent dielectric properties (low dielectric constant and low dielectric tangent).

The polymer compound of the present invention is obtained by a dehydrochlorination reaction between the phenolic hydroxyl group of the above copolymer (this hydroxyl group is the hydroxyl group of the raw material (meth)acrylate having a phenolic hydroxyl group) and the chloride group of (meth)acrylic acid chloride, or by a dehydration condensation reaction between the phenolic hydroxyl group of the above copolymer and the carboxyl group of (meth)acrylic acid.

The ratio of the copolymer and (meth)acrylic acid chloride or (meth)acrylic acid used when synthesizing the polymer compound of the present invention is not particularly limited, but if there is an excess or shortage of (meth)acrylic acid chloride or (meth)acrylic acid relative to the phenolic hydroxyl groups of the copolymer, the (meth)acrylic acid chloride or (meth)acrylic acid remaining unreacted in the polymer compound and the phenolic hydroxyl groups remaining in the copolymer without reacting with (meth)acrylic acid chloride or methacrylic acid may adversely affect the properties of the cured product, so it is preferable to use an equivalent amount of (meth)acrylic acid chloride or (meth)acrylic acid to the hydroxyl groups of the copolymer.

The reaction between the copolymer and (meth)acrylic acid chloride may be carried out by adding (meth)acrylic acid chloride to an organic solvent solution of the copolymer under stirring. The organic solvent that can be used here is not particularly limited as long as it can dissolve the copolymer and (meth)acrylic acid chloride. When the copolymer that is the intermediate raw material is synthesized in a solvent, the copolymer solution after the polymerization reaction may be used as it is. The concentration of the copolymer solution to be reacted with (meth)acrylic acid chloride is usually 10 to 90% by mass, preferably 20 to 80% by mass. The reaction temperature is usually 30 to 120°C, preferably 40 to 110°C, and the reaction time is usually 0.5 to 4 hours, preferably 1 to 3 hours.

Since the reaction between the copolymer and (meth)acrylic acid chloride is a dehydrochlorination reaction, it is preferable to add a tertiary amine such as triethylamine or pyridine to the reaction solution in advance in order to trap the hydrochloric acid generated and further promote the reaction. The amount of the tertiary amine used is preferably equimolar to 4 times the number of moles of the (meth)acrylic acid chloride, and more preferably equimolar to 3 times the number of moles. The hydrochloric acid generated during the reaction precipitates as the hydrochloride salt of the amine, and can be removed by filtration after the reaction. In addition, the excess tertiary amine can be distilled out of the system after filtration under heating and reduced pressure.

The reaction of the copolymer with (meth)acrylic acid may be a conventionally known esterification reaction, and the reaction may be carried out, for example, by heating and stirring the copolymer with (meth)acrylic acid in the presence of a catalyst. Since the reaction of the copolymer with (meth)acrylic acid is a dehydration reaction, it is preferable to carry out the reaction while distilling off water from the reaction system by azeotropy, and therefore it is preferable to carry out the reaction using a solvent that is not completely miscible with water, such as toluene, xylene, ethyl acetate, butyl acetate, and methyl isobutyl ketone. The amount of the solvent used is preferably an amount that makes the concentration of the raw material component of the polymer compound represented by formula (1) 20 to 80 mass %.
Examples of the catalyst used in the esterification reaction include acid catalysts such as sulfuric acid, methanesulfonic acid, and p-toluenesulfonic acid, and the amount used is preferably 0.1 to 5 mass % based on the total mass of the raw material components of the polymer compound represented by formula (1) used in the reaction, the solvent, etc. The reaction temperature is usually 50 to 150° C., preferably 60 to 140° C., and the reaction time is usually 0.5 to 4 hours, preferably 1 to 3 hours.

In addition, in order to prevent polymerization reactions between (meth)acryloyl groups in the polymer compound of the present invention and to improve the storage stability of the polymer compound, it is preferable to add a small amount of a polymerization inhibitor to the polymer compound solution after completion of the synthesis reaction. Specific examples of polymerization inhibitors include hydroquinone, paramethoxyphenol, methylhydroquinone, di-t-butylhydroxytoluene, t-butylhydroquinone, 2-t-butyl-1,4-benzoquinone, 1,4-benzoquinone, 1,1-diphenyl-2-picrylhydrazyl free radical, 6-t-butyl-2,4-xylenol, 4-t-butylpyrocatechol, 2,6-di-t-butylphenol, 2,6-di-t-butyl-p-cresol, and phenothiazine.

The number average molecular weight of the polymer compound of the present invention thus obtained is preferably in the range of 11,000 to 300,000, more preferably 15,000 to 200,000. If the molecular weight is smaller than the above range, the adhesion to low-roughness copper foil will be reduced, and if it is larger, the viscosity will be high, making coating and the like difficult.
In this specification, the molecular weight refers to a value calculated in terms of polystyrene based on the results of GPC measurement.

The resin composition of the present invention contains the polymer compound of the present invention and a radical initiator. As the radical initiator, either a thermal radical initiator or a photoradical initiator can be used.
Preferred thermal radical initiators include peroxides such as benzoyl peroxide, cumene hydroperoxide, 2,5-dimethylhexane-2,5-dihydroperoxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hexyne-3, di-t-butyl peroxide, t-butylcumyl peroxide, α,α-bis(t-butylperoxy-m-isopropyl)benzene, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, dicumyl peroxide, di-t-butylperoxyisophthalate, t-butylperoxybenzoate, 2,2-bis(t-butylperoxy)butane, 2,2-bis(t-butylperoxy)octane, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, di(trimethylsilyl)peroxide, and trimethylsilyltriphenylsilyl peroxide.

Examples of preferred photoradical initiators include benzoin and its alkyl ethers such as benzoin, benzoin methyl ether, and benzoin ethyl ether; acetophenones such as acetophenone, 2,2-dimethoxy-2-phenylacetophenone, and 1,1-dichloroacetophenone; anthraquinones such as 2-methylanthraquinone, 2-amyl anthraquinone, 2-t-butyl anthraquinone, and 1-chloro anthraquinone; thioxanthones such as 2,4-dimethylthioxanthone, 2,4-diisopropylthioxanthone, and 2-chlorothioxanthone; ketals such as acetophenone dimethyl ketal and benzyl dimethyl ketal; benzophenones such as benzophenone; 2-methyl-1-[4-(methylthio)phenyl]-2-morpholino-propan-1-one and 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone-1; acylphosphine oxides, and xanthones.

The content of the radical initiator in the resin composition of the present invention is usually 0.1 to 10 parts by mass, preferably 0.1 to 8 parts by mass, per 100 parts by mass of the polymer compound and the resin components such as the optional compound having a radical reactive group described below.

The resin composition of the present invention may be used in combination with a compound having a radical polymerizable group. The compound having a radical polymerizable group that may be used in combination with the resin composition of the present invention may be either a radical polymerizable monomer having a number average molecular weight of approximately less than 1,000 or a radical polymerizable polymer having a number average molecular weight of approximately 1,000 or more, or both may be used in combination.

Specific examples of radically polymerizable monomers having a radically polymerizable group include acenaphthylene, N-phenylmaleimide, N-vinyl-2-pyrrolidone, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, 1,4-butanediol dimethacrylate, neopentyl glycol dimethacrylate, 1,6-hexanediol dimethacrylate, 1,9-nonanediol dimethacrylate, glycerin dimethacrylate, 2-hydroxy-3-acryloyloxypropyl methacrylate, and ethylene oxide adduct methacrylate of bisphenol A. , trimethylolpropane trimethacrylate, tricyclodecane dimethanol dimethacrylate, glycerin dimethacrylate, trimethylolpropane trimethacrylate, ethoxylated isocyanuric acid triacrylate, ε-caprolactone modified tris-(2-acryloxyethyl)isocyanurate, pentaerythritol triacrylate, ditrimethylolpropane tetraacrylate, ethoxylated pentaerythritol tetraacrylate, pentaerythritol tetraacrylate, dipentaerythritol polyacrylate, dipentaerythritol hexaacrylate, triallyl isocyanurate ester, triallyl cyanurate, divinylbenzene, divinyl isophthalate, N-phenyl-maleimide, N-phenyl-methylmaleimide, N-phenyl-chloromaleimide, N-p-chlorophenyl-maleimide, N-p-methoxyphenyl-maleimide, N-p-methylphenyl-maleimide, N-p-nitrophenyl-maleimide, N-p-phenoxyphenyl-maleimide, N-p-phenylaminophenyl-maleimide, N-p-phenoxycarbonylphenyl-maleimide, 1-maleimido-4-acetoxysuccinimide-benzene, 4-maleimido-4'-acetoxysuccinimide-diphenyl Examples of the monomers include N-ethylmaleimide, N-2.6-xylylmaleimide, N-cyclohexylmaleimide, N-2,3-xylylmaleimide, xylylmaleimide, 2,6-xylylenemaleimide, and 4,4'-bismaleimidediphenylmethane, but those having a maleimide group as a functional group are preferred. These radical polymerizable monomers may be used alone or in combination of two or more.
By using a radically polymerizable monomer in combination with the resin composition of the present invention, the reactivity of the resin composition of the present invention and the heat resistance of the cured product can be improved.
The content of the radical polymerizable monomer in the resin composition of the present invention is usually 50% by mass or less, preferably 2 to 40% by mass, based on the polymer compound represented by formula (1).

Specific examples of radically polymerizable polymers (monomers) having a radical reactive group include polyphenylene ether modified with methacryloyl groups at both ends represented by the following formula (3) (product name SA-9000, manufactured by SABIC LLC), polyphenylene ether modified with styroyl groups at both ends represented by the following formula (4) (product name OPE-2St, manufactured by Mitsubishi Gas Chemical Company, Inc.), polyfunctional styrene resin represented by the following formula (5) (product name STR, manufactured by Nippon Kayaku Co., Ltd.), and styrene-butadiene copolymer. In the formulas (3) to (5), n is the average number of repeats, and is usually 2 to 100, preferably 4 to 80.
The number average molecular weight of the radical polymerizable polymer represented by any one of formulas (3) to (5) is preferably 1,000 to 3,000. In addition, it is also a preferred embodiment to use in combination with the resin composition of the present invention a radical polymerizable monomer represented by any one of formulas (3) to (5) and having a number average molecular weight of 500 or more and less than 1,000.
By using a radically polymerizable polymer in combination with the resin composition of the present invention, the reactivity of the resin composition of the present invention and the heat resistance of the cured product can be improved.
The content of the radical polymerizable polymer in the resin composition of the present invention is usually 80% by mass or less, preferably 5 to 70% by mass, based on the polymer compound represented by formula (1).

The resin composition of the present invention may be used in combination with an organic solvent. Specific examples of organic solvents include aromatic solvents such as toluene and xylene, ether solvents such as diethylene glycol dimethyl ether, diethylene glycol diethyl ether, propylene glycol, propylene glycol monomethyl ether, propylene glycol monomethyl ether monoacetate, propylene glycol monobutyl ether, and anisole, ketone solvents such as methyl ethyl ketone, methyl isobutyl ketone, cyclopentanone, and cyclohexanone, lactones such as γ-butyrolactone and γ-valerolactone, amide solvents such as N-methylpyrrolidone (NMP), N,N-dimethylformamide (DMF), N,N-dimethylacetamide, and N,N-dimethylimidazolidinone, and sulfones such as tetramethylene sulfone. The content of the organic solvent in the resin composition of the present invention is usually 90% by mass or less, preferably 30 to 80% by mass in the resin composition.

The resin composition of the present invention may be used in combination with a polymerization inhibitor to improve storage stability. There are no particular limitations on the polymerization inhibitor that may be used in combination, so long as it is a commonly known one, and examples of such inhibitors include quinones such as hydroquinone, methylhydroquinone, p-benzoquinone, chloranil, and trimethylquinone, aromatic diols, and di-t-butylhydroxytoluene.

The resin composition of the present invention can be used by blending fillers and additives in amounts that do not impair the original performance, in order to impart the desired performance depending on the application. The fillers may be in the form of fibers or powders, and examples of such fillers include silica, carbon black, alumina, talc, mica, glass beads, and glass hollow spheres.

The resin composition of the present invention can also be used in combination with flame-retardant compounds, additives, and the like. These are not particularly limited as long as they are commonly used. For example, flame-retardant compounds include bromine compounds such as 4,4-dibromobiphenyl, phosphate esters, melamine phosphate, phosphorus-containing epoxy resins, nitrogen compounds such as melamine and benzoguanamine, oxazine ring-containing compounds, silicon-based compounds, and the like. Additives include ultraviolet absorbers, antioxidants, photopolymerization initiators, fluorescent brighteners, photosensitizers, dyes, pigments, thickeners, lubricants, defoamers, dispersants, leveling agents, gloss agents, and the like, and can be used in appropriate combination as desired.

The resin composition of the present invention can be applied or impregnated on various substrates. For example, when a thermal radical initiator is used, the resin composition can be applied to a PET film, and the organic solvent can be dried as necessary, and then the PET film can be peeled off to obtain a film-like adhesive. The film-like adhesive can be applied to a polyimide film and the organic solvent can be dried as necessary to obtain a polyimide film having the film-like adhesive, which can be used as a coverlay. The resin composition can also be applied to a copper foil and the organic solvent can be dried as necessary to obtain a copper foil having the film-like adhesive, which can be used as a resin-coated copper foil. In addition, the resin composition can be impregnated into glass cloth, glass paper, carbon fiber, various nonwoven fabrics, etc., and used as a printed wiring board or a prepreg for CFRP. Furthermore, the resin composition can be used as various resists by using a photoradical initiator.

The interlayer insulating layer, coverlay, resin-coated copper foil, prepreg, etc. of the present invention can be made into a cured product by heating and pressurizing it using a hot press or the like.

The present invention will be described in more detail below with reference to examples and comparative examples. Note that the present invention is not limited to these examples.

Example 1 (Synthesis of the polymer compound of the present invention)
(Step 1) Synthesis of copolymer 1, which is an intermediate raw material of the polymer compound of the present invention 96 parts of styrene, 2 parts of 4-hydroxyphenyl methacrylate, 2 parts of N-phenylmaleimide, 0.122 parts of dilauroyl peroxide and 25 parts of anisole were added to a flask equipped with a thermometer, a cooling tube, a nitrogen gas inlet tube and a stirrer, and reacted for 6 hours at 120 to 130°C under a nitrogen atmosphere to obtain an anisole solution of copolymer 1 represented by the following formula (6). When a part of this solution was analyzed by gas chromatography, it was found that no unreacted 4-hydroxyphenyl methacrylate or N-phenylmaleimide remained. In addition, a part of this solution was heated under reduced pressure to remove the solvent and unreacted styrene, and the dry mass was calculated as the solid content, and the amount of copolymer 1 obtained was 61 parts. Considering that the amount of unreacted styrene was 39 parts, the obtained copolymer was a copolymer of 57 parts of styrene, 2 parts of 4-hydroxyphenyl methacrylate and 2 parts of N-phenylmaleimide. The number average molecular weight of the sample subjected to the dry mass measurement was 45,000, and the weight average molecular weight was 172,000. From the copolymerization ratio of styrene and 4-hydroxyphenyl methacrylate and the number average molecular weight, the value of l in formula (6) was calculated to be 9, the value of m to be 397, and the value of n to be 8.

(Step 2) Synthesis of Polymer Compound 1 of the Present Invention From the anisole solution of copolymer 1 obtained in step 1, unreacted styrene was distilled off together with anisole under heating and reduced pressure, and then toluene was added to obtain 244 parts of a 25% by weight solution of copolymer 1. After adding 1.48 parts of triethylamine to this solution, 1.17 parts of methacrylic acid chloride were added under stirring at 60° C. and reacted for 1 hour. The reaction solution was pressure-filtered with a filter paper having a capture particle size of 1 micron to remove triethylamine hydrochloride, and then excess triethylamine and toluene were distilled off from the filtrate using a rotary evaporator, and the amount of toluene was adjusted again to obtain 244 parts of a solution containing 25% by weight of the polymer compound of the present invention (polymer compound 1) represented by the following formula (7). The number average molecular weight of the obtained polymer compound 1 was 47,000, and the weight average molecular weight was 178,000.

Comparative Example 1 (Synthesis of Comparative Compound)
(Step 3) Synthesis of copolymer 2, an intermediate raw material of the comparative compound A solution of copolymer 2 represented by the following formula (8) was obtained in the same manner as in step 1, except that the amount of styrene charged was changed to 98 parts and the amount of N-phenylmaleimide charged was changed to 0 parts. When a part of this solution was analyzed by gas chromatography, no unreacted 4-hydroxyphenyl methacrylate remained. In addition, a part of this solution was heated under reduced pressure to remove the solvent and unreacted styrene, and the dry mass was calculated as the solid content. The amount of copolymer 2 obtained was 59 parts. Considering that the amount of unreacted styrene was 39 parts, the obtained copolymer was a copolymer of 57 parts of styrene and 2 parts of 4-hydroxyphenyl methacrylate. In addition, the number average molecular weight of the sample subjected to the measurement of the dry mass was 51,000, and the weight average molecular weight was 182,000. From the copolymerization ratio of styrene and 4-hydroxyphenyl methacrylate and the number average molecular weight, the value of m in formula (8) was calculated to be 471, and the value of n was calculated to be 10.

(Step 4) Synthesis of Comparative Compound 242 parts of a solution containing 25% by mass of a comparative compound (polymer compound 2) represented by the following formula (9) was obtained in the same manner as in step 2, except that the anisole solution of copolymer 1 obtained in step 1 was changed to the anisole solution of copolymer 2 obtained in step 3. The number average molecular weight of the obtained polymer compound 2 was 53,000 and the weight average molecular weight was 185,000.

Example 2 (Preparation of Resin Composition of the Present Invention)
To 10 parts of the solution of the polymer compound 1 of the present invention obtained in Example 1, 0.05 parts of dicumyl peroxide as a radical initiator was added and mixed uniformly to obtain a resin composition 1 of the present invention.

Comparative Example 2 (Preparation of Comparative Resin Composition)
Comparative resin composition 1 was obtained in the same manner as in Example 2, except that the solution of polymer compound 1 of the present invention obtained in Example 1 was changed to the solution of polymer compound 2 obtained in Comparative Example 1.

(Evaluation of dielectric properties and heat resistance of cured resin composition)
The resin composition 1 of the present invention and the resin composition 1 of the comparative example obtained in Example 2 and Comparative Example 2 were applied to a thickness of 280 μm on the mirror surface of a copper foil having a thickness of 18 μm using an applicator, and the solvent was dried by heating at 90 ° C for 10 minutes. The film-like adhesive on the copper foil obtained above was heated and cured at 180 ° C for 1 hour using a vacuum oven, and then immersed in an etching solution to remove the copper foil. Since a cured product having a thickness of 70 μm that can be handled as a film was obtained from the film-like adhesive consisting of the resin composition 1 of the present invention and the resin composition 1 of the comparative example, the dielectric properties were evaluated using the cured product obtained above. The dielectric properties were evaluated based on the results of measuring the dielectric constant and dielectric loss tangent at 10 GHz using a network analyzer 8719ET (manufactured by Agilent Technologies) by a cavity resonance method. The glass transition temperature of the film was also measured using a TMA (thermomechanical measuring device). The results are shown in Table 1.

(Evaluation of Adhesive Strength of Cured Resin Composition)
Using an applicator, the resin composition 1 of the present invention obtained in Example 2 and Comparative Example 2 and the resin composition 1 of Comparative Example were applied to a matte surface of a 12 μm thick high frequency low roughness copper foil (CF-T4X-SV: manufactured by Fukuda Metal Foil Powder Co., Ltd.) to a thickness of 50 μm, and the solvent was dried by heating at 90 ° C for 10 minutes to obtain a copper foil having a film-like adhesive made of the resin composition. The matte surface of the same copper foil as above was placed on the adhesive surface of the copper foil obtained above, and the copper foil was heated and cured at a pressure of 3 MPa for 1 hour in a vacuum press, and then the 90 ° peel strength (adhesive strength) between the copper foils was measured using an autograph AGX-50 (manufactured by Shimadzu Corporation). The results are shown in Table 1.

As described above, the polymer compound of the present invention, when cured using a radical initiator, formed a flexible film and further exhibited excellent dielectric properties, adhesiveness and heat resistance.

Claims (5)

The following formula (1)

(In the formula, _R1 and _R2 each independently represent a hydrogen atom or a methyl group. _R3 , _R4 and _R5 each independently represent a hydrogen atom or an alkyl group. l, m and n each independently represent the average number of repeating units and are in the range of 1 to 2,000.)
A polymer compound represented by the formula: A resin composition comprising the polymer compound according to claim 1 and a radical initiator. The resin composition according to claim 2, further comprising a compound having a radical reactive group. A film-like adhesive comprising the resin composition according to claim 2 or 3. A cured product of the resin composition according to claim 2 or 3.