Curable resin, curable resin composition, and cured product

Abstract

To provide a cured product excellent in heat resistance and dielectric characteristics (low dielectric characteristics).SOLUTION: A curable resin is represented by the following general formula (1) (where Ra and Rb each independently represent a C1-12 alkyl group, an aryl group, an aralkyl group or a cycloalkyl group; Rc and Rd each independently represent hydrogen, a C1-12 alkyl group, an aryl group, an aralkyl group or a cycloalkyl group; X represents a vinylbenzyl ether group, a (meth)acryloyloxy group or an allyl ether group; and m represents an integer of 0-3).SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a curable resin having a specific structure, a curable resin composition containing the curable resin, and a cured product obtained from the curable resin composition. [Background technology]

[0002] With the increase in the volume of information and communication in recent years, information and communication in the high frequency band has become more prevalent. This has created a demand for electrical insulating materials with better electrical properties, particularly low dielectric constant and low dielectric tangent, in order to reduce transmission loss in the high frequency band.

[0003] Furthermore, printed circuit boards and electronic components using these electrical insulating materials are exposed to high-temperature solder reflow during mounting, so materials with excellent heat resistance and a high glass transition temperature are required. In particular, lead-free solders with high melting points have recently been used from the perspective of environmental issues, so there has been an increasing demand for electrical insulating materials with higher heat resistance.

[0004] In response to these demands, vinyl group-containing curable resins having various chemical structures have been proposed. As such curable resins, for example, divinylbenzyl ether of bisphenol or polyvinylbenzyl ether of novolac has been proposed (see, for example, Patent Documents 1 and 2). However, these vinylbenzyl ethers cannot give a cured product with sufficiently small dielectric properties, and the obtained cured product has a problem in being used stably in a high frequency band, and further, divinylbenzyl ether of bisphenol does not have sufficiently high heat resistance.

[0005] In order to improve the dielectric properties of vinylbenzyl ethers having the above-mentioned improved properties, some polyvinylbenzyl ethers having specific structures have been proposed (see, for example, Patent Documents 3 to 9). Although attempts have been made to suppress the dielectric tangent and improve the heat resistance, the improvements in these properties are still not sufficient, and further improvements in properties are desired.

[0006] As described above, conventional vinyl group-containing curable resins including polyvinyl benzyl ether did not give a cured product having both a low dielectric tangent required for electrical insulating material applications, particularly for high-frequency electrical insulating material applications, and heat resistance sufficient to withstand lead-free soldering. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 63-68537 [Patent Document 2] Japanese Patent Application Publication No. 64-65110 [Patent Document 3] Special Publication No. 1-503238 [Patent Document 4] Japanese Patent Application Publication No. 5-43623 [Patent Document 5] Japanese Patent Application Publication No. 6-172242 [Patent Document 6] Japanese Patent Application Publication No. 9-31006 [Patent Document 7] JP 2005-281618 A [Patent Document 8] JP 2005-314556 A [Patent Document 9] JP 2015-030776 A [Patent Document 10] JP 2015-189925 A Summary of the Invention [Problem to be solved by the invention]

[0008] Therefore, the problem to be solved by the present invention is to provide a cured product having excellent heat resistance (high glass transition temperature) and low dielectric properties by using a curable resin having a specific structure. [Means for solving the problem]

[0009] Therefore, in order to solve the above problems, the inventors conducted intensive research and found that a curable resin that can contribute to heat resistance and low dielectric properties, and a cured product obtained from a curable resin composition containing the curable resin, have excellent heat resistance and low dielectric properties, and thus completed the present invention.

[0010] That is, the present invention relates to a curable resin represented by the following general formula (1). [ka] (In the formula, Ra and Rb each independently represent an alkyl group, an aryl group, an aralkyl group, or a cycloalkyl group having 1 to 12 carbon atoms. Rc and Rd each independently represent a hydrogen atom, an alkyl group, an aryl group, an aralkyl group, or a cycloalkyl group having 1 to 12 carbon atoms. X represents a vinylbenzyl ether group, a (meth)acryloyloxy group, or an allyl ether group. m represents an integer of 0 to 3.)

[0011] In the curable resin of the present invention, the above general formula (1) is preferably represented by the following general formula (2). [ka]

[0012] The present invention relates to a curable resin composition containing the curable resin.

[0013] The present invention relates to a cured product obtained by subjecting the curable resin composition to a curing reaction. Effect of the Invention

[0014] Since the curable resin of the present invention can contribute to heat resistance and low dielectric properties, a cured product obtained from a curable resin composition containing the curable resin has excellent heat resistance and low dielectric properties (particularly low dielectric tangent) and is useful. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] The present invention will be described in detail below.

[0016] <Curable resin> The present invention relates to a curable resin represented by the following general formula (1). [ka] (In the formula, Ra and Rb each independently represent an alkyl group, an aryl group, an aralkyl group, or a cycloalkyl group having 1 to 12 carbon atoms. Rc and Rd each independently represent a hydrogen atom, an alkyl group, an aryl group, an aralkyl group, or a cycloalkyl group having 1 to 12 carbon atoms. X represents a vinylbenzyl ether group, a (meth)acryloyloxy group, or an allyl ether group. m represents an integer of 0 to 3.)

[0017] In the above general formula (1), Ra and Rb each independently represent an alkyl group, an aryl group, an aralkyl group, or a cycloalkyl group having 1 to 12 carbon atoms, and are preferably an alkyl group, an aryl group, or a cycloalkyl group having 1 to 12 carbon atoms. When Ra and Rb are an alkyl group or the like having 1 to 12 carbon atoms, the molecular mobility of the polar group derived from the crosslinking group (X) is restricted, and the dielectric loss tangent is lowered, which is preferable.

[0018] In the above general formula (1), m represents an integer of 0 to 3, and preferably an integer of 1 to 2. When m is within the above range, the planarity in the vicinity of the benzene ring in the above general formula (1) is reduced, and the reduced crystallinity improves the solvent solubility and lowers the melting point, which is a preferred embodiment.

[0019] In the above general formula (1), Rc and Rd each independently represent hydrogen, an alkyl group having 1 to 12 carbon atoms, an aryl group, an aralkyl group, or a cycloalkyl group, and are preferably hydrogen, an alkyl group having 1 to 12 carbon atoms, an aryl group, or a cycloalkyl group. When Rc and Rd are hydrogen or the like, the structure is a hydrogen atom or a structure consisting of only hydrogen atoms and carbon atoms (hydrocarbon group), which is non-polar, and the dielectric constant and dielectric loss tangent of the obtained cured product are low, which is a preferred embodiment.

[0020] In the above general formula (1), X is a vinylbenzyl ether group, a (meth)acryloyloxy group, or an allyl ether group, preferably a vinylbenzyl ether group or a (meth)acryloyloxy group, more preferably a methacryloyloxy group or a vinylbenzyl ether group, and particularly preferably a vinylbenzyl ether group. By having the crosslinking group (X) in the curable resin, a cured product having a low dielectric tangent is obtained, which is a preferred embodiment. Although the detailed reason is not clear, in the present invention, the vinylbenzyl ether group is preferred because it can obtain a cured product having a lower dielectric tangent compared to other crosslinking groups (e.g., a (meth)acryloyloxy group or an allyl ether group). In addition, the crosslinking group X is also a polar group, but the substituents Ra and Rb are adjacent (particularly the Ra), which causes steric hindrance, suppressing the molecular mobility of X, and lowering the dielectric tangent of the obtained cured product, which is a preferred embodiment. In addition, the crosslinking group (X) located at the center of the curable resin also suppresses the molecular mobility of X due to the adjacent substituent Rd and a structure containing it, which lowers the dielectric tangent of the obtained cured product, which is a preferred embodiment.

[0021] When the number of crosslinking groups (X) in the curable resin is 3, multiple crosslinking groups are present, and the crosslinking density increases, and in particular, the crosslinking groups (X) are evenly arranged, so that the crosslinking points are uniform and the crosslinking density is high, and therefore the obtained cured product has excellent heat resistance, which is preferable. Note that, when the number of crosslinking groups (X) is less than 3, the heat resistance decreases, which is problematic in practical use, and when the number of crosslinking groups (X) is more than 3, the crosslinking density increases, and the molded product (cured product) becomes brittle, which is not preferable.

[0022] In the curable resin of the present invention, the above general formula (1) is preferably represented by the following general formula (2): In the curable resin represented by the above general formula (1), Rc is a methyl group and Rd is hydrogen, whereby the polarity of the entire molecular structure is suppressed, and the dielectric constant and dielectric loss tangent of the obtained cured product are reduced, which is a preferred embodiment. [ka]

[0023] In addition, in the above general formula (2), the same symbols, the same substituents, and the same functional groups (X, Ra, Rb, and m) as those in the above general formula (1) are common.

[0024] <Method for producing intermediate phenol compounds> As a method for producing the curable resin, first, a method for producing an intermediate phenol compound, which is a raw material (precursor) of the curable resin, will be described below.

[0025] The method for producing the intermediate phenol compound includes mixing a diol phenol compound represented by the following general formula (3-1), a divinyl phenol compound represented by the following general formula (3-2) (hereinafter sometimes referred to as "compound (a)"), and a phenol derivative represented by the following general formula (4) (hereinafter sometimes referred to as "compound (b)"), and reacting them in the presence of an acid catalyst to obtain an intermediate phenol compound represented by the following general formula (5). [ka] [ka] [ka] [ka]

[0026] In the general formula (3-1), Re each independently represents a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, an aryl group, an aralkyl group, or a cycloalkyl group, and is preferably a hydrogen atom, a methyl group, or an ethyl group. When Re is a hydrogen atom, a methyl group, an ethyl group, or the like, the purity of the intermediate phenol compound obtained is high, which is a preferred embodiment.

[0027] In the above general formulas (3-1), (3-2), (4), and (5), the same symbols, the same substituents, and the same functional groups (Ra, Rb, Rc, Rd, and m) as those in the above general formula (1) are considered to be common.

[0028] Specific examples of the compound (a) include 2,6-di(hydroxymethyl)phenol, 2,6-di(methoxymethyl)phenol, 2,6-divinyl-4-methyl)phenol, and phenol compounds in which the hydrogen at the 4-position of the phenol compound such as the 2,6-di(hydroxymethyl)phenol is replaced with a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tart-butyl group, a cyclopentyl group, a cyclohexyl group, a phenyl group, chlorine, or bromine. These compounds (a) may be used alone or in combination of two or more. Among them, from the viewpoint of industrial availability, the compound (a) is, for example, 2,6-di(hydroxymethyl)phenol or 2,6-di(hydroxymethyl)-p-cresol, and it is more preferable to use 2,6-di(hydroxymethyl)-p-cresol.

[0029] The compound (b) is not particularly limited, but specific examples thereof include cresols such as o-cresol, m-cresol, and p-cresol; xylenols such as 2,3-xylenol, 2,4-xylenol, 2,5-xylenol, and 2,6-xylenol (2,6-dimethylphenol), 3,4-xylenol, 3,5-xylenol, and 3,6-xylenol; 2,3,5-trimethylphenol and 2,3,6-trimethylphenol; ethylphenols such as o-ethylphenol (2-ethylphenol), m-ethylphenol, and p-ethylphenol; butylphenols such as isopropylphenol, butylphenol, and pt-butylphenol; alkylphenols such as p-pentylphenol, p-octylphenol, p-nonylphenol, and p-cumylphenol; and mono-substituted phenols such as o-phenylphenol, p-phenylphenol, 2-cyclohexylphenol, and 2-benzylphenol. Each of these compounds (b) may be used alone, or two or more of them may be used in combination. Among them, from the viewpoint of industrial availability, it is more preferable to use, for example, xylenol or 2,6-xylenol as compound (b).

[0030] In the method for producing the intermediate phenol compound, the compound (a) and the compound (b) are charged in a molar ratio of the compound (b) to the compound (a) (compound (b) / compound (a)) of preferably 2.5 / 1 to 1.05 / 1, more preferably 2 / 1 to 1.1 / 1, and reacted in the presence of an acid catalyst, thereby obtaining an intermediate phenol compound which is a reaction product (c) of the compound (a) and the compound (b).

[0031] Examples of the acid catalyst used in the reaction include inorganic acids such as phosphoric acid, hydrochloric acid, and sulfuric acid; organic acids such as oxalic acid, benzenesulfonic acid, toluenesulfonic acid, methanesulfonic acid, and fluoromethanesulfonic acid; solid acids such as activated clay, acid clay, silica alumina, zeolite, and strongly acidic ion exchange resins; and heteropolyacid salts. However, it is preferable to use oxalic acid, benzenesulfonic acid, toluenesulfonic acid, methanesulfonic acid, and fluoromethanesulfonic acid, which are homogeneous catalysts that can be easily removed by neutralization with a base and washing with water after the reaction.

[0032] The amount of the acid catalyst is within a range of 0.001 to 40 parts by mass relative to 100 parts by mass of the total amount of the compound (a) and the compound (b) that are the raw materials initially charged, and from the viewpoints of handleability and economy, a range of 0.001 to 25 parts by mass is preferred.

[0033] The reaction temperature is usually in the range of 40 to 80°C, but in order to suppress the formation of isomeric structures, avoid side reactions such as thermal decomposition, and obtain a high-purity intermediate phenol compound, a temperature of 40 to 45°C is preferred.

[0034] The reaction time is usually in the range of 0.5 to 24 hours in total under the above reaction temperature conditions, and preferably in the range of 0.5 to 15 hours in total, since the reaction does not proceed completely in a short time and side reactions such as thermal decomposition of the product occur in a long time.

[0035] In the method for producing the intermediate phenol compound, since the raw material may also serve as the solvent, it is not necessary to use other solvents, but it is possible to use a solvent. In addition, a method may be adopted in which the solvent (e.g., methanol, etc.) generated during the reaction is distilled off before the reaction is carried out within the above reaction temperature range.

[0036] Examples of organic solvents used to synthesize the intermediate phenol compound include ketones such as acetone, methyl ethyl ketone (MEK), methyl isobutyl ketone, cyclohexanone, and acetophenone; alcohols such as 2-ethoxyethanol and methanol; aprotic solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, N-methyl-2-pyrrolidone, acetonitrile, and sulfolane; cyclic ethers such as dioxane and tetrahydrofuran; esters such as ethyl acetate and butyl acetate; and aromatic solvents such as benzene, toluene, and xylene. These may be used alone or in combination.

[0037] <Method of manufacturing hardening resin> The method for producing the curable resin (introduction of a vinylbenzyl ether group, a (meth)acryloyloxy group, or an allyl ether group into an intermediate phenol compound) will be described below.

[0038] The curable resin can be obtained by a known method such as reacting the intermediate phenol compound (reaction product (c)) with (meth)acrylic anhydride, (meth)acrylic acid chloride, chloromethylstyrene, chlorostyrene, allyl chloride, allyl bromide, or the like (hereinafter sometimes referred to as "compound (d)") in the presence of a basic or acidic catalyst. By reacting these, a crosslinking group (X) can be introduced into the intermediate phenol compound, and the compound has a low dielectric constant, a low dielectric tangent, and is thermosetting, which is a preferred embodiment.

[0039] As the compound (d) (functions as a crosslinking group introduction agent), the (meth)acrylic anhydride includes acrylic anhydride and methacrylic anhydride, the (meth)acrylic chloride includes acrylic chloride and methacrylic chloride, the chloromethylstyrene includes, for example, p-chloromethylstyrene (4-chloromethylstyrene) and m-chloromethylstyrene, the chlorostyrene includes, for example, p-chlorostyrene and m-chlorostyrene, the allyl chloride includes, for example, 3-chloro-1-propene, and the allyl bromide includes, for example, 3-bromo-1-propene. These may be used alone or in combination. Among them, it is preferable to use methacrylic anhydride, methacrylic chloride, p-chlorostyrene, m-chlorostyrene, etc., since a cured product with a lower dielectric tangent can be obtained, and it is particularly preferable to use p-chloromethylstyrene.

[0040] Specific examples of the basic catalyst include dimethylaminopyridine, alkaline earth metal hydroxides, alkali metal carbonates, and alkali metal hydroxides. Specific examples of the acidic catalyst include sulfuric acid and methanesulfonic acid. Dimethylaminopyridine is particularly excellent in terms of catalytic activity.

[0041] The reaction between the intermediate phenol compound and the compound (d) can be carried out by adding 1 to 10 moles of the compound (d) per mole of hydroxyl groups contained in the intermediate phenol compound, and reacting the mixture at a temperature of 30 to 150° C. for 1 to 40 hours while adding 0.01 to 0.2 moles of a basic catalyst all at once or gradually.

[0042] In addition, the reaction rate in the synthesis of the curable resin can be increased by using an organic solvent in combination during the reaction with the compound (d) (introduction of a crosslinking group). Such organic solvents are not particularly limited, but examples thereof include ketones such as acetone and methyl ethyl ketone, alcohols such as methanol, ethanol, 1-propyl alcohol, isopropyl alcohol, 1-butanol, secondary butanol, and tertiary butanol, cellosolves such as methyl cellosolve and ethyl cellosolve, ethers such as tetrahydrofuran, 1,4-dioxane, 1,3-dioxane, and diethoxyethane, aprotic polar solvents such as acetonitrile, dimethyl sulfoxide, and dimethylformamide, and toluene. These organic solvents may be used alone, or two or more of them may be used in combination as appropriate to adjust the polarity.

[0043] After the reaction with the compound (d) (introduction of a crosslinking group) is completed, the reaction product is reprecipitated in a poor solvent, the precipitate is stirred in the poor solvent at a temperature of 20 to 100° C. for 0.1 to 5 hours, filtered under reduced pressure, and then dried at a temperature of 40 to 80° C. for 1 to 10 hours to obtain the target curable resin. Examples of the poor solvent include hexane.

[0044] The curable resin of the present invention is characterized by containing a curable resin having a structure of the above general formula (1) (or (2)). Even if the above production method contains a structure other than the above general formula (1) (or (2)) as a side reaction, there is no particular problem as long as it does not affect the properties of the curable resin in the present invention.

[0045] <Curable resin composition> The present invention relates to a curable resin composition containing the curable resin. The curable resin can contribute to heat resistance and low dielectric properties, so that a cured product obtained by using the curable resin composition containing the curable resin has excellent heat resistance and low dielectric properties, which is a preferred embodiment.

[0046] [Other resins, etc.] In the curable resin composition of the present invention, in addition to the curable resin, other resins, curing agents, curing accelerators, etc. can be used without particular limitation within the scope of not impairing the object of the present invention. As described later, the curable resin can obtain a cured product by heating or the like without blending a curing agent, but for example, when blending other resins, etc., they can be used by blending a curing agent, a curing accelerator, etc. The curable resin composition of the present invention contains the curable resin. However, among the curable resins, when X is an allyl ether group, unlike when X is a vinylbenzyl ether group or a (meth)acryloyloxy group, the curable resin cannot homopolymerize (crosslink) (cannot obtain a cured product by itself), and therefore, when X is an allyl ether group, it is necessary to use a curing agent, a curing accelerator, or the like.

[0047] [Other resins] Examples of the other resins that can be added include alkenyl group-containing compounds such as bismaleimides, allyl ether compounds, allyl amine compounds, triallyl cyanurate, alkenyl phenol compounds, vinyl group-containing polyolefin compounds, etc. In addition, other thermosetting resins such as thermosetting polyimide resins, epoxy resins, phenolic resins, active ester resins, benzoxazine resins, cyanate resins, etc. can also be appropriately blended depending on the purpose.

[0048] [Hardening agent] Examples of the curing agent include amine compounds, amide compounds, acid anhydride compounds, phenol compounds, cyanate ester compounds, etc. These curing agents may be used alone or in combination of two or more kinds.

[0049] [Curing Accelerator] As the curing accelerator, various types can be used, including, for example, phosphorus compounds, tertiary amines, imidazoles, organic acid metal salts, Lewis acids, amine complex salts, etc. In particular, when used as a semiconductor encapsulation material, phosphorus compounds such as triphenylphosphine or imidazoles are preferred because of their excellent curability, heat resistance, electrical properties, and moisture resistance reliability. These curing accelerators can be used alone or in combination of two or more.

[0050] [Flame retardant] The curable resin composition of the present invention may contain a flame retardant to exhibit flame retardancy, if necessary, and preferably contains a non-halogen flame retardant that does not substantially contain halogen atoms. Examples of the non-halogen flame retardant include phosphorus-based flame retardants, nitrogen-based flame retardants, silicone-based flame retardants, inorganic flame retardants, and organic metal salt-based flame retardants, and these flame retardants may be used alone or in combination of two or more.

[0051] [Filler] The curable resin composition of the present invention may contain an inorganic filler as required. Examples of the inorganic filler include fused silica, crystalline silica, alumina, silicon nitride, and aluminum hydroxide. When the amount of the inorganic filler is particularly large, it is preferable to use fused silica. The fused silica may be either crushed or spherical, but in order to increase the amount of fused silica and suppress the increase in the melt viscosity of the molding material, it is preferable to mainly use spherical silica. In order to further increase the amount of spherical silica, it is preferable to appropriately adjust the particle size distribution of the spherical silica. In addition, when the curable resin composition is used for applications such as a conductive paste described in detail below, a conductive filler such as silver powder or copper powder can be used.

[0052] [Other compounding agents] To the curable resin composition of the present invention, various compounding agents such as a silane coupling agent, a release agent, a pigment, an emulsifier, etc. may be added, if necessary.

[0053] <Cured product> The present invention relates to a cured product obtained by subjecting the curable resin composition to a curing reaction. The curable resin composition can be obtained by uniformly mixing the curable resin alone or the curable resin and each component such as the curing agent described above, and can be easily cured by a method similar to a conventionally known method. Examples of the cured product include molded cured products such as laminates, cast products, adhesive layers, coatings, and films.

[0054] The curing reaction includes heat curing and ultraviolet curing reaction, among which heat curing reaction is easily carried out even without a catalyst, but when it is desired to react more quickly, it is effective to add a polymerization initiator such as an organic peroxide or an azo compound, or a basic catalyst such as a phosphine compound or a tertiary amine. For example, benzoyl peroxide, dicumyl peroxide, azobisisobutyronitrile, triphenylphosphine, triethylamine, imidazoles, etc.

[0055] <Application> The cured product obtained by the curable resin composition of the present invention has excellent heat resistance and low dielectric properties, and therefore can be suitably used for heat-resistant members and electronic members. In particular, it can be suitably used for prepregs, circuit boards, semiconductor encapsulants, semiconductor devices, build-up films, build-up boards, adhesives, resist materials, etc. It can also be suitably used for matrix resins of fiber-reinforced resins, and is particularly suitable as highly heat-resistant prepregs. In addition, the curable resin contained in the curable resin composition exhibits excellent solubility in various solvents, and can be made into paint. The heat-resistant members and electronic members thus obtained can be suitably used for various applications, such as industrial machine parts, general machine parts, automobile, railway, vehicle parts, space and aviation related parts, electronic and electrical parts, building materials, containers and packaging materials, daily necessities, sports and leisure goods, and housing members for wind power generation, but are not limited thereto. EXAMPLES

[0056] The present invention will be described in detail below with reference to examples and comparative examples, in which "parts" and "%" are by mass unless otherwise specified. Curable resins and cured products obtained by using the curable resins were synthesized under the conditions shown below, and the obtained cured products were measured and evaluated under the conditions shown below.

[0057] < 1 H-NMR measurement> 1 H-NMR: “JNM-ECA400” manufactured by JEOL RESONANCE Magnetic field strength: 400MHz Number of times: 16 Solvent: chloroform-d1 Sample concentration: 1% by mass The above 1 From the results of the H-NMR chart, a peak derived from the target product was confirmed, and it was confirmed that the target product was obtained in each reaction (see FIG. 1 of Example 1 and FIG. 2 of Example 2). 1 H-NMR measurement was performed to confirm the synthesis of the target product (no figures).

[0058] Example 1 34.5g (0.28mol) of 2,6-dimethylphenol, 15g of methanol, 6.5g of water and 1.83g of 96% sulfuric acid were charged into a 200mL flask equipped with a thermometer, a condenser and a stirrer, and heated to 45°C while stirring. Then, 9.6g (0.57mol) of 2,6-bis(hydroxymethyl)-p-cresol was added for 1 hour, and the mixture was reacted at 45°C for 5 hours. After the reaction was completed, the reaction mixture was cooled to room temperature, 90g of water was added to the reaction liquid, and the mixture was neutralized with an aqueous sodium hydroxide solution. The mixture was then stirred at 40°C for 4 hours, and the precipitated solid was filtered off, washed with hot water, and then dried in vacuum. 15.4g (0.041mol) of intermediate phenol compound was obtained. In a 1L flask equipped with a thermometer, a condenser, and a stirrer, 15.4g (0.041mol) of the intermediate phenol compound obtained, 40g of N,N-dimethylformamide, 34.3g (0.228mol) of 4-chloromethylstyrene, and 22.4g of 48% potassium hydroxide aqueous solution were charged, and the mixture was heated to 60°C with stirring and reacted for 20 hours. The reaction liquid was poured into 300g of methanol, and the precipitated solid was filtered and dried in vacuum. A curable resin with the following structural formula was obtained. 1 The structure of the product was determined by H-NMR measurement (see Figure 1). [ka]

[0059] Example 2 34.5g (0.28mol) of 2,6-dimethylphenol, 15g of methanol, 6.5g of water and 1.83g of 96% sulfuric acid were charged into a 200mL flask equipped with a thermometer, a condenser and a stirrer, and heated to 45°C while stirring. Then, 9.6g (0.57mol) of 2,6-bis(hydroxymethyl)-p-cresol was added for 1 hour, and the mixture was reacted at 45°C for 5 hours. After the reaction was completed, the reaction mixture was cooled to room temperature, 90g of water was added to the reaction liquid, and the mixture was neutralized with an aqueous sodium hydroxide solution. The mixture was then stirred at 40°C for 4 hours, and the precipitated solid was filtered off, washed with hot water, and then dried in vacuum. 15.4g (0.041mol) of intermediate phenol compound was obtained. In a 200 mL flask equipped with a thermometer, a condenser, and a stirrer, 20 g of toluene and 15.4 g (0.041 mol) of the intermediate were mixed and heated to about 85°C. 0.92 g (0.0075 mol) of dimethylaminopyridine was added. When it appeared that all the solids had dissolved, 38.5 g (0.25 mol) of methacrylic anhydride was gradually added. The resulting solution was maintained at 85°C for 3 hours with continuous mixing. The solution was then cooled to room temperature and added dropwise over 30 minutes to 360 g of hexane in a 1 L beaker that was vigorously stirred with a magnetic stirrer. The resulting precipitate was filtered under reduced pressure and dried to obtain 11.6 g of a curable resin of the following structural formula. 1The structure of the product was determined by H-NMR measurement (see Figure 2). [ka]

[0060] Example 3 A curable resin having the following structural formula was obtained by carrying out synthesis in the same manner as in Example 1, except that the methacrylic anhydride in Example 2 was changed to 31.5 g (0.25 mol) of acrylic anhydride. [ka]

[0061] Example 4 The synthesis was carried out in the same manner as in Example 1, except that the 2,6-dimethylphenol in Example 1 was changed to 47.7 g (0.28 mol) of o-phenylphenol, to obtain a curable resin having the following structural formula. [ka]

[0062] Example 5 The synthesis was carried out in the same manner as in Example 1, except that the 2,6-dimethylphenol in Example 1 was changed to 49.3 g (0.28 mol) of 2-cyclohexylphenol, to obtain a curable resin having the following structural formula. [ka]

[0063] Example 6 The synthesis was carried out in the same manner as in Example 2, except that the 2,6-dimethylphenol in Example 2 was changed to 49.3 g (0.28 mol) of 2-cyclohexylphenol, to obtain a curable resin having the following structural formula. [ka]

[0064] Example 7 The synthesis was carried out in the same manner as in Example 1, except that 2,6-dimethylphenol in Example 1 was changed to 51.6 g (0.28 mol) of 2-benzylphenol, to obtain a curable resin having the following structural formula. [ka]

[0065] Example 8 The synthesis was carried out in the same manner as in Example 1, except that the 2,6-bis(hydroxymethyl)-p-cresol in Example 1 was changed to 134.7 g (0.57 mol) of 5-cyclohexyl-2-hydroxy-1,3-phenylenedimethanol, to obtain a curable resin with the following structural formula. [ka]

[0066] Example 9 The synthesis was carried out in the same manner as in Example 1, except that 2,6-bis(hydroxymethyl)-p-cresol in Example 1 was changed to 91.3 g (0.57 mol) of (2,6-divinyl-4-methyl)phenol, to obtain a curable resin with the following structural formula. [ka]

[0067] Example 10 The synthesis was carried out in the same manner as in Example 1, except that 4-chloromethylstyrene in Example 1 was changed to 17.4 g (0.228 mol) of allyl chloride, to obtain a curable resin having the following structural formula. [ka]

[0068] Comparative Example 1 Synthesis was carried out in the same manner as in Example 1, except that the 2,6-dimethylphenol in Example 1 was changed to 26.4 g (0.28 mol) of phenol, to obtain a curable resin having the following structural formula. [ka]

[0069] Comparative Example 2 The synthesis was carried out in the same manner as in Example 1, except that the 2,6-dimethylphenol in Example 2 was changed to 26.4 g (0.28 mol) of phenol, to obtain a curable resin having the following structural formula. [ka]

[0070] Comparative Example 3 The synthesis was carried out in the same manner as in Example 1, except that the intermediate phenol compound 15.4 g (0.041 mol) in Example 1 was changed to 2,2-bis(4-hydroxy-3,5-dimethylphenyl)propane 11.7 g (0.041 mol), to obtain a curable resin having the following structural formula. [ka]

[0071] <Creating resin film (cured product)> The curable resin (solid powder) obtained in the examples and comparative examples was placed in a 5 cm square mold, sandwiched between stainless steel plates, and set in a vacuum press. It was pressurized to 1.5 MPa at normal pressure and room temperature. Next, the pressure was reduced to 10 torr, and the temperature was heated to a temperature 50°C higher than the heat curing temperature over 30 minutes. After leaving it to stand for another 2 hours, it was gradually cooled to room temperature. As a result, a uniform resin film (cured product) with an average film thickness of 100 μm was produced. In addition, in the curable resin obtained in Example 10 (X is an allyl ether group), homopolymerization (crosslinking) of the curable resin alone does not proceed, so only the production confirmation of the curable resin was performed, and the following evaluation based on the resin film (cured product) was not performed.

[0072] <Evaluation of dielectric properties> The dielectric properties of the obtained resin film (cured product) in the in-plane direction were measured using a Keysight Technologies network analyzer N5247A by the split post dielectric resonator method at a frequency of 10 GHz, including the dielectric constant and dielectric loss tangent. The dielectric loss tangent was 10.0×10 -3 If it is less than this, there is no practical problem, and preferably, it is 5.0 × 10 -3 More preferably, it is 3.0×10 or less. -3 More preferably, it is 2.5×10 -3 Furthermore, as for the dielectric constant, there is no practical problem if it is 3 or less, and it is preferably 2.7 or less, and more preferably 2.5 or less.

[0073] <Evaluation of heat resistance (glass transition temperature)> The obtained resin film (cured product) was measured using a PerkinElmer DSC device (Pyris Diamond) at a temperature rise of 20°C / min from room temperature to observe the exothermic peak temperature (thermosetting temperature), and then held at a temperature 50°C higher than that for 30 minutes. The sample was then cooled to room temperature at a temperature drop of 20°C / min, and then heated again at a temperature rise of 20°C / min to measure the glass transition temperature (Tg) (°C) of the resin film (cured product). Note that as long as the glass transition temperature (Tg) is 100°C or higher, there is no practical problem, and it is preferably 150°C or higher.

[0074] [Table 1]

[0075] From the evaluation results in Table 1 above, it was confirmed that in Examples 1 to 9, the cured products obtained by using the desired curable resins were able to achieve both heat resistance and low dielectric properties, and were at a level that was not problematic for practical use.

[0076] On the other hand, from the evaluation results in Table 1 above, in Comparative Example 1, a curable resin that does not have a hydrocarbon group corresponding to Ra and Rb contained in the structure of the desired curable resin was used, so the molecular mobility of the crosslinking group (X) was not restricted, and the dielectric tangent and dielectric constant of the obtained cured product were higher than those of the Examples, and it was confirmed that the dielectric properties (low dielectric properties) were poor. In Comparative Example 2, a curable resin that does not have a hydrocarbon group corresponding to Ra and Rb contained in the structure of the desired curable resin was used, so the molecular mobility of the crosslinking group (X) was not restricted, and the dielectric tangent and dielectric constant of the obtained cured product were higher than those of the Examples, and it was confirmed that the dielectric properties (low dielectric properties) were poor. In Comparative Example 3, an intermediate phenolic compound as used in the Examples was not used, and a curable resin with a small number of crosslinking groups (X) was used for synthesis, so the glass transition temperature of the obtained cured product was very low, and it was confirmed that the heat resistance was poor. [Industrial Applicability]

[0077] The cured product obtained by using the cured resin of the present invention has excellent heat resistance and dielectric properties (low dielectric properties), and therefore can be suitably used for heat-resistant parts and electronic parts, and in particular, can be suitably used for prepregs, semiconductor encapsulants, circuit boards, build-up films, build-up boards, adhesives, resist materials, etc. It can also be suitably used as a matrix resin for fiber-reinforced resins, and is suitable as a highly heat-resistant prepreg. [Brief description of the drawings]

[0078] [Figure 1] 1 is a 1H-NMR spectrum of the curable resin obtained in Example 1. [Diagram 2] 1 is a 1H-NMR spectrum of the curable resin obtained in Example 2.

Claims

1. A curable resin represented by the following general formula (1): 【Chemistry 1】 (In the formula, Ra and Rb each independently represent an alkyl group, an aryl group, an aralkyl group, or a cycloalkyl group having 1 to 12 carbon atoms. Rc and Rd each independently represent a hydrogen atom, an alkyl group, an aryl group, an aralkyl group, or a cycloalkyl group having 1 to 12 carbon atoms. X represents a vinylbenzyl ether group, a (meth)acryloyloxy group, or an allyl ether group. m represents an integer of 0 to 3.)

2. The curable resin according to claim 1, characterized in that the general formula (1) is represented by the following general formula (2): 【Chemistry 2】

3. A curable resin composition comprising the curable resin according to claim 1 or 2.

4. A cured product obtained by subjecting the curable resin composition according to claim 3 to a curing reaction.

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