JP2026000680A - Curable resin composition - Google Patents

Abstract

The present invention provides a curable resin composition that can achieve both dielectric properties and melt viscosity.
[Solution] The curable resin composition according to one embodiment comprises a linear copolymer (A) having a repeating unit corresponding to a monovinyl aromatic compound and a repeating unit corresponding to a divinylaromatic compound, and a copolymer (B) containing, as constituent monomers, a styrene-based monomer and an aliphatic diene monomer having 4 to 7 carbon atoms and/or a hydrogenated product thereof, the copolymer having a number average molecular weight of 50,000 or less. The content of repeating units corresponding to the divinylaromatic compound in 100 mol % of all repeating units in the copolymer (A) is less than 40 mol %. The amount of the copolymer (B) is 80 parts by mass or less per 100 parts by mass of the total of the copolymers (A) and (B).
[Selection diagram] None

Description

An embodiment of the present invention relates to a curable resin composition.

In recent years, electronic devices have become smaller and more powerful, and as a result, the performance requirements for the various materials used are improving. For example, there is a demand for printed circuit board materials with low dielectric loss tangents that can be used for high-frequency communications.

Patent Document 1 discloses a thermosetting resin composition with excellent dielectric properties, heat resistance, adhesion, and moisture resistance, which contains a copolymer containing acenaphthylene-based structural units and hydroxystyrene-based structural units, a compound having at least two epoxy groups in one molecule, and a curing agent. Patent Document 1 also discloses a specific example of the copolymer, which is a copolymer of styrene, p-t-butoxystyrene, divinylbenzene, and acenaphthylene.

Patent Document 2 discloses a curable composition having excellent heat resistance, compatibility, dielectric properties, moist heat reliability, and resistance to thermal oxidative degradation, which contains a copolymer including structural units derived from a divinyl aromatic compound, structural units derived from a monovinyl aromatic compound, and structural units derived from a cycloolefin compound.

Patent Document 3 discloses a thermosetting resin composition having a high glass transition temperature, low water absorption, excellent dielectric properties, and excellent moisture and heat resistance, which contains a polyfunctional vinyl aromatic copolymer having structural units derived from a divinyl aromatic compound and an ethylvinyl aromatic compound, and an olefin resin having a styrene structure and a butadiene structure.

Japanese Patent Application Laid-Open No. 2001-192539 Japanese Patent Application Laid-Open No. 2018-039995 Special Publication No. 2020-515701

Conventional curable resin compositions are not necessarily satisfactory in terms of dielectric properties, and even those with excellent dielectric properties have problems such as high melt viscosity and poor processability, so there is a need to achieve both good dielectric properties and good melt viscosity.

The polyfunctional vinyl aromatic copolymer described in Patent Document 3 is obtained by polymerizing a divinyl aromatic compound and an ethyl vinyl aromatic compound as raw material monomers, and therefore branches are inevitably formed by the divinyl aromatic compound, making it not a linear copolymer. Furthermore, because the content of structural units derived from the divinyl aromatic compound is high, the effects of improving melt viscosity and dielectric properties are not necessarily sufficient.

In view of the above, an embodiment of the present invention aims to provide a curable resin composition that can achieve both dielectric properties and melt viscosity.

The present invention includes the embodiments shown below.
[1] A curable resin composition comprising: a linear copolymer (A) having a repeating unit corresponding to a monovinyl aromatic compound and a repeating unit corresponding to a divinylaromatic compound, wherein the content of the repeating unit corresponding to the divinylaromatic compound in 100 mol% of all repeating units is less than 40 mol%; and a copolymer (B) containing a styrene-based monomer and an aliphatic diene monomer having 4 to 7 carbon atoms as constituent monomers and/or a hydrogenated product thereof, the copolymer having a number average molecular weight of 50,000 or less, wherein the amount of the copolymer (B) is 80 parts by mass or less per 100 parts by mass of the total of the copolymer (A) and the copolymer (B).

[2] The curable resin composition according to [1], wherein the copolymer (B) contains a copolymer of a styrene-based monomer and butadiene and/or a hydrogenated product thereof.
[3] The curable resin composition according to [1] or [2], wherein the content of the repeating unit corresponding to the divinyl aromatic compound is less than 20 mol% in 100 mol% of all repeating units of the copolymer (A).
[4] The curable resin composition according to any one of [1] to [3], wherein the copolymer (A) further has a repeating unit corresponding to an aromatic ring-fused cyclic olefin compound having three rings.
[5] The curable resin composition according to any one of [1] to [4], wherein the content of repeating units corresponding to the monovinyl aromatic compound is 50 mol% or more in 100 mol% of all repeating units of the copolymer (A).
[6] The curable resin composition according to any one of [1] to [5], which is a printed circuit board material.
[7] Use of the curable resin composition according to any one of [1] to [5] as a printed circuit board material.

When the curable resin composition according to an embodiment of the present invention is used, it is possible to achieve both dielectric properties and melt viscosity.

The curable resin composition according to this embodiment includes (a) a linear copolymer (A) having repeating units corresponding to a monovinyl aromatic compound and (b) a repeating unit corresponding to a divinyl aromatic compound, and (B) a copolymer (B) containing, as constituent monomers, a styrene-based monomer and an aliphatic diene monomer having 4 to 7 carbon atoms.

Copolymer (A) has (a) repeating units corresponding to a monovinyl aromatic compound and (b) repeating units corresponding to a divinyl aromatic compound, and in one embodiment, may further have (c) repeating units corresponding to an aromatic ring-fused cyclic olefin compound.

The repeating unit corresponding to the monovinyl aromatic compound (a) above (hereinafter also referred to as the "monovinyl aromatic compound unit") is a constituent unit of the copolymer (A) and has a structure formed by addition polymerization of a monovinyl aromatic compound as a monomer. That is, the (a) monovinyl aromatic compound unit is a repeating unit having a structure in which the vinyl group of the monovinyl aromatic compound becomes a single bond through addition polymerization. The (a) monovinyl aromatic compound unit is not necessarily limited to one obtained by polymerization using the monovinyl aromatic compound, as long as it has a structure corresponding to the monovinyl aromatic compound, and may also be one that is further reacted after polymerization to form a structure corresponding to the monovinyl aromatic compound.

As the (a) monovinyl aromatic compound unit, a repeating unit represented by the following general formula (1) is preferred.

In formula (1), ^R1 represents a monovalent aromatic hydrocarbon group having 6 to 30 carbon atoms and therefore does not contain a heteroatom. More specifically, ^R1 is preferably a monovalent aromatic hydrocarbon group having 6 to 30 carbon atoms (more preferably 6 to 20 carbon atoms) selected from the group consisting of a phenyl group which may have a hydrocarbon group as a substituent, a biphenylyl group which may have a hydrocarbon group as a substituent, a naphthyl group which may have a hydrocarbon group as a substituent, and a terphenylyl group which may have a hydrocarbon group as a substituent. Here, the number of carbon atoms in ^R1 refers to the total number of carbon atoms in ^R1 , including the number of carbon atoms contained in the substituent, if any, such as an alkyl group.

The monovinyl aromatic compound forming such a repeating unit may be any aromatic compound having one vinyl group, and examples thereof include vinyl aromatic compounds such as styrene, vinylnaphthalene, and vinylbiphenyl, and nuclear alkyl-substituted vinyl aromatic compounds such as alkylstyrenes (e.g., o-methylstyrene, m-methylstyrene, p-methylstyrene, o-ethylstyrene, m-ethylstyrene, p-ethylstyrene, and 4-tert-butylstyrene), dialkylstyrenes (e.g., 3,5-dimethylstyrene, 2,5-dimethylstyrene, and 2,5-diethylstyrene), alkylvinylbiphenyls (e.g., ethylvinylbiphenyl), and alkylvinylnaphthalenes (e.g., ethylvinylnaphthalene), and any of these may be used alone or in combination of two or more.

In one embodiment, the monovinyl aromatic compound preferably contains at least one (a1) selected from the group consisting of styrene, vinylnaphthalene, vinylbiphenyl, alkylstyrene, dialkylstyrene, alkylvinylbiphenyl, and alkylvinylnaphthalene. More preferably, the monovinyl aromatic compound contains styrene. That is, the (a) monovinyl aromatic compound unit preferably contains a repeating unit corresponding to the (a1) (hereinafter also referred to as an "(a1) unit"), and more preferably contains a repeating unit corresponding to styrene (hereinafter also referred to as a "styrene unit").

The amount of repeating units of the above formula (1) (preferably (a1) units, more preferably styrene units) in 100 mol% of (a) monovinyl aromatic compound units is preferably 70 mol% or more, more preferably 80 mol% or more, even more preferably 90 mol% or more, and may be 100 mol%.

The repeating unit corresponding to the above (b) divinylaromatic compound (hereinafter also referred to as "divinylaromatic compound unit") is a structural unit of copolymer (A) that has a structure containing one vinyl group and is formed by addition polymerization of a divinylaromatic compound as a monomer. That is, the (b) divinylaromatic compound unit is a repeating unit that has a structure in which one vinyl group of the divinylaromatic compound has become a single bond through addition polymerization, and also has one vinyl group. The (b) divinylaromatic compound unit is not necessarily limited to one that is obtained by polymerization using the divinylaromatic compound, as long as it has a structure corresponding to the divinylaromatic compound; it may also be one that is further reacted after polymerization to form a structure corresponding to the divinylaromatic compound.

The (b) divinyl aromatic compound unit is preferably a repeating unit represented by the following general formula (2).

In formula (2), ^R2 represents a divalent aromatic hydrocarbon group having 6 to 30 carbon atoms and therefore does not contain a heteroatom. More specifically, ^R2 is preferably a divalent aromatic hydrocarbon group having 6 to 30 carbon atoms (more preferably 6 to 20 carbon atoms) selected from the group consisting of a phenylene group which may have a hydrocarbon group as a substituent, a biphenyldiyl group which may have a hydrocarbon group as a substituent, a naphthylene group which may have a hydrocarbon group as a substituent, and a terphenyldiyl group which may have a hydrocarbon group as a substituent. Here, the number of carbon atoms in ^R2 refers to the total number of carbon atoms in ^R2 , including the number of carbon atoms contained in the substituent, if any, such as an alkyl group.

The divinyl aromatic compound may be any aromatic compound having two vinyl groups, such as divinylbenzene (including each positional isomer or a mixture thereof), divinylnaphthalene (including each positional isomer or a mixture thereof), and divinylbiphenyl (including each positional isomer or a mixture thereof), and these may be used alone or in combination of two or more.

In one embodiment, the divinylaromatic compound preferably contains at least one (b1) selected from the group consisting of divinylbenzene, divinylnaphthalene, and divinylbiphenyl. More preferably, the divinylaromatic compound contains divinylbenzene (m-isomer, p-isomer, or a positional isomeric mixture thereof). That is, the (b) divinylaromatic compound unit preferably contains a repeating unit corresponding to the (b1) (hereinafter also referred to as a "(b1) unit"), and more preferably contains a repeating unit corresponding to divinylbenzene (hereinafter also referred to as a "divinylbenzene unit").

The amount of repeating units of the above formula (2) (preferably (b1) units, more preferably divinylbenzene units) in 100 mol% of (b) divinyl aromatic compound units is preferably 70 mol% or more, more preferably 80 mol% or more, even more preferably 90 mol% or more, and may be 100 mol%.

The repeating unit (hereinafter also referred to as "cyclic olefin unit") corresponding to the above-mentioned (c) aromatic ring-fused cyclic olefin compound is a constituent unit of copolymer (A) and has a structure formed by addition polymerization of an aromatic ring-fused cyclic olefin compound as a monomer. That is, the (c) cyclic olefin unit is a repeating unit having a structure in which the double bond of the cyclic olefin of the aromatic ring-fused cyclic olefin compound has become a single bond through addition polymerization. The (c) cyclic olefin unit is not necessarily limited to one obtained by polymerization using the aromatic ring-fused cyclic olefin compound, as long as it has a structure corresponding to the aromatic ring-fused cyclic olefin compound; it may also be one that has been further reacted after polymerization to form a structure corresponding to the aromatic ring-fused cyclic olefin compound.

Aromatic ring-fused cyclic olefin compounds are cyclic olefin compounds in which aromatic rings are fused, and more specifically, compounds having a fused ring of an aromatic ring and an aliphatic ring having a carbon-carbon double bond. The condensation may be ortho-condensation or ortho-peri-condensation. Examples of aromatic ring-fused cyclic olefin compounds include indene-based compounds, acenaphthylene-based compounds, phenalene-based compounds, acephenanthrylene-based compounds, aceanthrylene-based compounds, benzofuran-based compounds, and benzothiophene-based compounds, and these can be used alone or in combination of two or more.

Among these, aromatic ring-fused cyclic olefin compounds with three or fewer rings are preferred. Specifically, compounds with two rings include indene-based compounds, benzofuran-based compounds, and benzothiophene-based compounds; compounds with three rings include acenaphthylene-based compounds and phenalene-based compounds, with indene-based compounds and/or acenaphthylene-based compounds being more preferred. Furthermore, from the perspective of increasing the glass transition temperature of the cured product, it is preferable to use aromatic ring-fused cyclic compounds with three rings.

In one embodiment, the aromatic ring-fused cyclic olefin compound preferably contains at least one compound (c1) selected from the group consisting of indene-based compounds, acenaphthylene-based compounds, phenalene-based compounds, acephenanthrylene-based compounds, aceanthrylene-based compounds, benzofuran-based compounds, and benzothiophene-based compounds. In this case, the amount of repeating units corresponding to the at least one compound (c1) in 100 mol% of (c) cyclic olefin units is preferably 70 mol% or more, more preferably 80 mol% or more, even more preferably 90 mol% or more, and may be 100 mol%.

Examples of indene-based compounds include at least one selected from the group consisting of indene, alkyl indene, halogenated indene, arylindene, and alkoxyindene.

Examples of acenaphthylene compounds include at least one selected from the group consisting of acenaphthylene, alkylacenaphthylene, halogenated acenaphthylene, arylacenaphthylene, and alkoxyacenaphthylene.

Phenalene-based compounds, acephenanthrylene-based compounds, aceanthrylene-based compounds, benzofuran-based compounds, and benzothiophene-based compounds include phenalene, acephenanthrylene, aceanthrylene, benzofuran, and benzothiophene, as well as compounds having the same substituents as the indene-based compounds described above.

In one embodiment, the (c) cyclic olefin unit is preferably a repeating unit represented by the following general formula (3).

In formula (3), ^R3 and ^R4 each independently represent a monovalent saturated hydrocarbon group having 1 to 20 carbon atoms, a halogen atom, a monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms, or an alkoxy group having 1 to 20 carbon atoms. Here, the monovalent saturated hydrocarbon group may be a linear or branched alkyl group or a cycloalkyl group, and is preferably an alkyl group. The monovalent aromatic hydrocarbon group may be an aryl group or an aralkyl group, and is preferably an aryl group. The monovalent saturated hydrocarbon group preferably has 1 to 10 carbon atoms, and more preferably has 1 to 5 carbon atoms. The monovalent aromatic hydrocarbon group preferably has 6 to 10 carbon atoms. The alkoxy group preferably has 1 to 10 carbon atoms, and more preferably has 1 to 5 carbon atoms.

In formula (3), m and n each independently represent an integer of 0 to 3. When m and n are 2 or greater, R ³ and R ⁴ in one repeating unit may be the same or different.

The aromatic ring-fused cyclic olefin compound forming the repeating unit of formula (3) is an acenaphthylene-based compound represented by the following general formula (4).
R ³ , R ⁴ , m, and n in formula (4) are the same as R ³ , R ⁴ , m, and n in formula (3).

In one embodiment, the aromatic ring-fused cyclic olefin compound preferably contains an acenaphthylene-based compound represented by formula (4) above, and more preferably contains acenaphthylene. That is, the (c) cyclic olefin unit preferably contains a repeating unit of formula (3), and more preferably contains a repeating unit corresponding to acenaphthylene (hereinafter also referred to as an "acenaphthylene unit").

(c) The amount of repeating units (preferably repeating units of formula (3), more preferably acenaphthylene units) corresponding to an aromatic ring-fused cyclic compound having three rings in 100 mol% of cyclic olefin units is preferably 70 mol% or more, more preferably 80 mol% or more, even more preferably 90 mol% or more, and may be 100 mol%.

As described above, copolymer (A) is linear. The linear structure results in entanglement of molecular chains, improving moldability. Here, "linear" refers to a structure in which the repeating units constituting the copolymer are linked together in a one-dimensional chain, and does not have branches such as cross-linked structures.

In copolymer (A), the arrangement order of (a) monovinyl aromatic compound units, (b) divinylaromatic compound units, and (c) cyclic olefin units as an optional component may be regular or random. Copolymer (A) is preferably a random copolymer in which (a) monovinyl aromatic compound units, (b) divinylaromatic compound units, and (c) cyclic olefin units as an optional component are randomly arranged.

In addition to (a) monovinyl aromatic compound units, (b) divinyl aromatic compound units, and (c) cyclic olefin units, copolymer (A) may also contain repeating units corresponding to other monomers, provided that the effects of these units are not impaired. Examples of such other monomers include trivinyl aromatic compounds, trivinyl aliphatic compounds, divinyl aliphatic compounds, and monovinyl aliphatic compounds.

In copolymer (A), the content of (b) divinylaromatic compound units is less than 40 mol% based on 100 mol% of all repeating units constituting copolymer (A). A content of less than 40 mol% reduces the melt viscosity of the curable resin composition and improves the dielectric properties of the cured product. The content of (b) divinylaromatic compound units is preferably less than 20 mol% based on 100 mol% of all repeating units. From the viewpoint of improving thermosetting properties and glass transition temperature, the lower limit of this content is preferably 3 mol%. The content is more preferably 5 to 19 mol%, and even more preferably 10 to 18 mol%.

In this specification, 100 mol% of all repeating units does not include structures derived from the polymerization initiator or chain transfer agent present at the end of the copolymer.

In copolymer (A), the content of (a) monovinyl aromatic compound units is not particularly limited, but from the viewpoint of melt viscosity, it is preferably 50 mol% or more out of 100 mol% of all repeating units constituting copolymer (A). The content of (a) monovinyl aromatic compound units is more preferably 50 to 90 mol%, more preferably 60 to 85 mol%, and even more preferably 65 to 80 mol%.

In copolymer (A), the content of (c) cyclic olefin units is not particularly limited, and may be 30 mol% or less, 3 to 25 mol%, or 5 to 20 mol% relative to 100 mol% of all repeating units constituting copolymer (A).

In copolymer (A), the total content of (a) monovinyl aromatic compound units and (b) divinylaromatic compound units is preferably 70 mol% or more, more preferably 75 mol% or more, and even more preferably 80 mol% or more, based on 100 mol% of all repeating units constituting copolymer (A).

The linear copolymer (A) may have a structure derived from the polymerization initiator at its terminal. Examples of the polymerization initiator include radical initiators such as azo compounds and organic peroxides. Preferably, the polymerization initiator does not contain a heteroatom in the structure derived from the polymerization initiator introduced at the terminal. Examples of such polymerization initiators include azo compounds in which the organic groups on both sides of the azo group (-N=N-) are hydrocarbon groups. For example, a polymerization initiator represented by the following general formula (5) is preferred. In this case, R ⁵ - and/or R ⁶ - is introduced at the terminal of the copolymer (A).
R ⁵ -N=NR ⁶ (5)

In formula (5), ^R5 and ^R6 each independently represent a monovalent saturated hydrocarbon group or a monovalent aromatic hydrocarbon group, and therefore do not contain heteroatoms. Here, the monovalent saturated hydrocarbon group may be a branched or linear alkyl group or a cycloalkyl group. The monovalent aromatic hydrocarbon group may be an aryl group or an aralkyl group. The number of carbon atoms in the monovalent saturated hydrocarbon group is not particularly limited, and may be, for example, 1 to 23 or 4 to 13. The number of carbon atoms in the monovalent aromatic hydrocarbon group is not particularly limited, and may be, for example, 6 to 23 or 6 to 13.

The linear copolymer (A) may have a structure derived from a chain transfer agent at its terminal. The chain transfer agent is not particularly limited, but it is preferable to use α-methylstyrene dimer (i.e., 2,4-diphenyl-4-methyl-1-pentene).

Since copolymer (A) is highly effective in improving dielectric properties, it is preferable that it contains substantially no heteroatoms (i.e., atoms other than carbon and hydrogen atoms), i.e., that it consists essentially of hydrocarbons. The heteroatom content in 100% by mass of copolymer (A) is preferably 3.0% by mass or less, more preferably 2.0% by mass or less, more preferably 1.0% by mass or less, and even more preferably it contains no heteroatoms.

The weight-average molecular weight Mw of copolymer (A) is not particularly limited and may be, for example, 1,000 to 100,000, 1,200 to 20,000, 1,300 to 10,000, 1,500 to 7,000, or 2,000 to 5,000. A weight-average molecular weight Mw of 1,000 or more can improve moldability and glass transition temperature. A weight-average molecular weight Mw of 100,000 or less can reduce melt viscosity. Here, the weight-average molecular weight Mw is the weight-average molecular weight in terms of polystyrene measured by gel permeation chromatography (GPC).

There are no particular limitations on the method for producing copolymer (A). In one preferred embodiment, a method for synthesizing a linear copolymer involves copolymerizing a vinylbenzyl phosphonium salt, a monovinyl aromatic compound, and, as an optional component, an aromatic ring-fused cyclic olefin compound, and then reacting the resulting copolymer with formaldehyde. However, the present invention is not limited to this production method.

Vinylbenzyl phosphonium halides are preferably used as the vinylbenzyl phosphonium salt. Examples of the phosphonium group in the vinylbenzyl phosphonium salt include quaternary phosphonium groups such as trialkylphosphonium, triarylphosphonium, and trialalkylphosphonium. Examples of halogens that form salts with the phosphonium group include chlorine and bromine.

A known vinyl polymerization method can be used to copolymerize a vinylbenzyl phosphonium salt with a monovinyl aromatic compound. For example, by charging a vinylbenzyl phosphonium salt, a monovinyl aromatic compound, an optional aromatic-ring-fused cyclic olefin compound, a polymerization initiator, and a chain transfer agent into an organic solvent and allowing them to react, a copolymer is obtained that has repeating units derived from the vinylbenzyl phosphonium salt, repeating units derived from the monovinyl aromatic compound, and optional repeating units derived from the aromatic-ring-fused cyclic olefin compound, and that has a structure derived from the polymerization initiator and/or a structure derived from the chain transfer agent at its terminal.

The resulting copolymer can be reacted with formaldehyde using the well-known Wittig reaction. By treating the copolymer with a base and then reacting it with formaldehyde, the phosphonium groups are removed and vinyl groups are introduced. This results in copolymer (A).

With this manufacturing method, the vinylbenzyl phosphonium salt is monovinyl in the copolymerization step, resulting in a linear copolymer with no branches. After copolymerization, a vinyl group is introduced into the repeating units derived from the vinylbenzyl phosphonium salt, resulting in a linear copolymer with no branches, even though it has repeating units corresponding to the divinyl aromatic compound.

Copolymer (B) is a copolymer containing a styrene-based monomer and an aliphatic diene monomer having 4 to 7 carbon atoms as constituent monomers, and/or a hydrogenated product thereof. Therefore, the copolymer has repeating units derived from the styrene-based monomer and repeating units derived from the aliphatic diene monomer having 4 to 7 carbon atoms. The hydrogenated product of the copolymer refers to a copolymer in which, when carbon-carbon double bonds are contained in the copolymer molecule, at least some of the carbon-carbon double bonds have been hydrogenated.

In this embodiment, the copolymer (B) used has a number-average molecular weight Mn of 50,000 or less. By including such a copolymer (B) with a relatively small molecular weight, the melt viscosity of the curable resin composition can be reduced while maintaining the excellent dielectric properties of the copolymer (A). The number-average molecular weight Mn of the copolymer (B) is preferably 1,000 to 50,000, more preferably 2,000 to 30,000, more preferably 3,000 to 20,000, and even more preferably 5,000 to 10,000. Here, the number-average molecular weight Mn is the number-average molecular weight in terms of polystyrene measured by gel permeation chromatography (GPC).

The styrene-based monomer includes styrene or a derivative thereof, such as styrene, α-methylstyrene, alkylstyrene (e.g., o-methylstyrene, m-methylstyrene, p-methylstyrene, o-ethylstyrene, m-ethylstyrene, p-ethylstyrene, 4-tert-butylstyrene), and dialkylstyrene (e.g., 3,5-dimethylstyrene, 2,5-dimethylstyrene, 2,5-diethylstyrene). These can be used alone or in combination of two or more. Of these, styrene is preferred as the styrene-based monomer.

As the aliphatic diene monomer having 4 to 7 carbon atoms, an aliphatic hydrocarbon having 4 to 7 carbon atoms and having two carbon-carbon double bonds in the molecule is used, and preferably an aliphatic conjugated diene monomer having 4 to 7 carbon atoms is used. Examples of such aliphatic conjugated diene monomers include isoprene, 1,3-butadiene, 2,4-dimethyl-1,3-butadiene, piperylene, 3-methyl-1,3-pentadiene, 2,4-hexadiene, 2,4-heptadiene, cyclopentadiene, and methylcyclopentadiene. These can be used alone or in combination of two or more. Among these, the aliphatic diene monomer is preferably a chain aliphatic conjugated diene monomer, and more preferably 1,3-butadiene.

Copolymer (B) may contain only styrene-based monomers and aliphatic diene monomers having 4 to 7 carbon atoms as constituent monomers, but may also contain other monomers. The total amount of styrene-based monomers and aliphatic diene monomers having 4 to 7 carbon atoms in 100% by mass of all constituent monomers of copolymer (B) is not particularly limited, but is preferably 80% by mass or more, and more preferably 90% by mass or more.

Copolymer (B) may be a random copolymer or a block copolymer. A random copolymer is preferred.

In one embodiment, copolymer (B) preferably contains (B1) a copolymer of a styrene-based monomer and butadiene and/or a hydrogenated product thereof. More preferably, copolymer (B) contains (B2) a styrene-butadiene copolymer and/or a hydrogenated styrene-butadiene copolymer. The amount of (B1) (more preferably (B2)) in 100% by mass of copolymer (B) is preferably 50% by mass or more, more preferably 70% by mass or more, more preferably 90% by mass, and even more preferably 100% by mass.

The content of styrene-based monomers in all constituent monomers of copolymer (B) is not particularly limited, but from the viewpoint of further enhancing the effect of achieving both dielectric properties and melt viscosity, it is preferably 10% by mass or more and 90% by mass or less, more preferably 15% by mass or more and 80% by mass or less, and even more preferably 20% by mass or more and 70% by mass or less.

It is preferable to use a copolymer (B) that is liquid at room temperature (23°C). This further enhances the effect of reducing melt viscosity. Here, "liquid at room temperature" means that the copolymer has fluidity at 23°C.

The glass transition temperature Tg of copolymer (B) is not particularly limited and may be, for example, -70 to 0°C, -65 to -5°C, or -60 to -15°C. Here, the glass transition temperature is measured using a differential scanning calorimeter in accordance with JIS K6240:2011.

Commercialized products of this type of copolymer (B) include, but are not limited to, polystyrene butadiene random polymers manufactured by Kuraray Co., Ltd., such as "L-SBR-820," "L-SBR-841," "L-SBR-870," "L-SBR-822," and "L-SBR-841N."

The curable resin composition according to this embodiment contains the above-described copolymer (A) and copolymer (B). Because copolymer (A) contains vinyl groups in its molecular chain, crosslinking by polymerization is possible, and a cured product can be obtained by thermal curing. Therefore, the curable resin composition according to this embodiment can be said to be a thermosetting resin composition.

The amount of copolymer (A) in the curable resin composition is not particularly limited, as long as the composition has the property of being cured by heat or the like. For example, it may be 1 to 99.9% by mass, or 10 to 95% by mass, relative to 100% by mass of the solids content of the curable resin composition. Here, the solids content refers to the amount excluding the organic solvent if the curable resin composition contains an organic solvent, or the amount of the entire composition if the curable resin composition does not contain an organic solvent.

The amount of copolymer (B) in the curable resin composition is 80 parts by mass or less per 100 parts by mass of the total of copolymer (A) and copolymer (B). By keeping the amount of copolymer (B) 80 parts by mass or less, it is possible to suppress a decrease in the dielectric properties of the cured product. Even a small amount of copolymer (B) has the effect of reducing the melt viscosity according to the amount, so the lower limit is not particularly limited, but it may be, for example, 0.1 parts by mass or more. The amount of copolymer (B) is preferably 0.1 to 80 parts by mass, more preferably 1 to 50 parts by mass, more preferably 3 to 40 parts by mass, and more preferably 5 to 30 parts by mass per 100 parts by mass of the total of copolymer (A) and copolymer (B).

In addition to copolymer (A) and copolymer (B), the curable resin composition may contain various components such as other thermosetting resins (thermosetting crosslinking agents), thermoplastic resins, fillers, flame retardants, curing accelerators, polymerization initiators, chain transfer agents, defoamers, heat stabilizers, antistatic agents, UV absorbers, colorants such as dyes and pigments, lubricants, and dispersants.

The curable resin composition may also contain an organic solvent to adjust its viscosity, and the curable resin composition may be a solution containing copolymer (A) and copolymer (B). The organic solvent used may be one that can dissolve copolymer (A) and copolymer (B). Examples of the organic solvent include ketones such as acetone, methyl ethyl ketone, and methyl isobutyl ketone; esters such as ethyl acetate, propyl acetate, and butyl acetate; amides such as dimethylacetamide and dimethylformamide; and aromatic hydrocarbons such as toluene and xylene. Any one of these may be used alone or in combination of two or more.

The cured product obtained by curing the curable resin composition has a low dielectric tangent and excellent dielectric properties, and can therefore be used in electronic materials such as printed circuit board materials and semiconductor encapsulation materials. In other words, the curable resin composition according to one embodiment is a curable resin composition for electronic materials.

Printed circuit board materials include rigid printed circuit board materials such as single-sided boards, double-sided boards, multilayer boards, and build-up boards, as well as film- or sheet-like flexible printed circuit board materials. Furthermore, due to their excellent dielectric properties, they are ideally suited for use as high-frequency circuit board materials in high-frequency communication equipment.

The following provides a more detailed explanation using examples, but the present invention is not limited to these examples.

<Measurement and evaluation methods>
[Molar ratio of styrene/divinylbenzene/acenaphthylene]
The products obtained in Examples 1 to 3, 8 to 12, and Comparative Example 1 (products before mixing with copolymer (B); the same applies to the measurements of other molar ratios below) were dissolved in deuterated chloroform and subjected to ^1H -NMR measurement using a nuclear magnetic resonance apparatus (manufactured by JEOL) to determine the molar ratios of repeating units corresponding to styrene, repeating units corresponding to divinylbenzene, and repeating units relative to acenaphthylene, and the content of repeating units corresponding to styrene (styrene ratio), the content of repeating units corresponding to divinylbenzene (divinylbenzene ratio), and the content of repeating units corresponding to acenaphthylene (acenaphthylene ratio), relative to 100 mol% of all repeating units, were calculated.

[4-vinylbiphenyl/divinylbenzene/acenaphthylene molar ratio]
The product obtained in Example 4 was dissolved in deuterated chloroform and subjected to ^1H -NMR measurement using a nuclear magnetic resonance spectrometer (manufactured by JEOL) to determine the molar ratios of repeating units corresponding to 4-vinylbiphenyl, repeating units corresponding to divinylbenzene, and repeating units relative to acenaphthylene, and the content of repeating units corresponding to 4-vinylbiphenyl (4-vinylbiphenyl ratio), the content of repeating units corresponding to divinylbenzene (divinylbenzene ratio), and the content of repeating units corresponding to acenaphthylene (acenaphthylene ratio) relative to 100 mol% of all repeating units were calculated.

[4-tert-butylstyrene/divinylbenzene/acenaphthylene molar ratio]
The product obtained in Example 5 was dissolved in deuterated chloroform and subjected to ^1H -NMR measurement using a nuclear magnetic resonance apparatus (manufactured by JEOL) to determine the molar ratios of repeating units corresponding to 4-tert-butylstyrene, repeating units corresponding to divinylbenzene, and repeating units relative to acenaphthylene, and the content of repeating units corresponding to 4-tert-butylstyrene (4-tert-butylstyrene ratio), the content of repeating units corresponding to divinylbenzene (divinylbenzene ratio), and the content of repeating units corresponding to acenaphthylene (acenaphthylene ratio) relative to 100 mol% of all repeating units were calculated.

[Molar ratio of styrene/divinylbenzene/indene]
The product obtained in Example 6 was dissolved in deuterated chloroform and subjected to ^1H -NMR measurement using a nuclear magnetic resonance apparatus (manufactured by JEOL) to determine the molar ratios of repeating units corresponding to styrene, repeating units corresponding to divinylbenzene, and repeating units relative to indene, and the content of repeating units corresponding to styrene (styrene ratio), the content of repeating units corresponding to divinylbenzene (divinylbenzene ratio), and the content of repeating units corresponding to indene (indene ratio) relative to 100 mol% of all repeating units were calculated.

[Molar ratio of styrene/divinylbenzene]
The product obtained in Example 7 was dissolved in deuterated chloroform and subjected to ^1H -NMR measurement using a nuclear magnetic resonance spectrometer (manufactured by JEOL Ltd.) to determine the molar ratios of repeating units corresponding to styrene and repeating units corresponding to divinylbenzene, and the content of repeating units corresponding to styrene relative to 100 mol% of all repeating units (styrene ratio) and the content of repeating units corresponding to divinylbenzene (divinylbenzene ratio) were calculated.

[Mw of copolymer (A), Mn of copolymer (B)]
The sample was dissolved in tetrahydrofuran, and the weight-average molecular weight (Mw) or number-average molecular weight (Mn) in terms of polystyrene was measured using gel permeation chromatography (GPC) (Prominence, manufactured by Shimadzu Corporation) connected to four columns (Shodex GPC columns KF-601, KF-602, KF-603, and KF-604, manufactured by Showa Denko) packed with polystyrene gel. The column oven temperature was 40°C, the THF flow rate was 0.6 mL/min, the sample concentration was 0.1% by mass, and the sample injection volume was 10 μL. A differential refractive index detector (Shodex RI-504, manufactured by Showa Denko) was used.

[Melt viscosity]
The compositions obtained in Examples 1 to 12 and Comparative Example 1, as well as the products of Reference Example 1 and Comparative Examples 2 and 3, were used as samples. Using a manual hydraulic pump: P-1B (manufactured by Riken), 0.4 g of sample was pressed at a pressure of 10 MPa for 1 minute to produce pellets with a diameter of 20 mm and a thickness of 1 mm. Using the obtained pellets as samples, a dynamic viscoelasticity measuring device: Rheosol-G5000NT (manufactured by UBM Corporation) was used to raise the temperature from 50°C to 200°C at a heating rate of 5°C/min. The minimum value of the complex viscosity was taken as the minimum melt viscosity, and a minimum melt viscosity of less than 1000 poise was rated "A" (good), 1000 poise or more but less than 10,000 poise was rated "B" (fair), and 10,000 poise or more was rated "C" (poor).

[Moldability]
Using the compositions obtained in Examples 1 to 12 and Comparative Example 1, and the products of Reference Example 1 and Comparative Examples 2 and 3 as samples, 1.5 g of the sample was pressed for 15 minutes at a pressure of 10 Pa and a temperature of 220°C using a testing single-action compression molding machine (manufactured by Yasuda Seiki Seisakusho). Those that gave flat plates of 30 mm x 30 mm x 1 mm in thickness were rated as "A" (good moldability), and those that gave flat plates with cracks were rated as "B" (average moldability).

[Dielectric loss tangent]
The flat plate obtained in [Moldability] was cut to prepare test pieces with a width of 2 mm, a thickness of 1 mm, and a length of 30 mm, and the dielectric loss tangent at 10 GHz was measured using a cavity resonator dielectric constant measuring device (manufactured by KEYSIGHT). Dielectric loss tangents of less than 0.0008 were rated "A" (good), those of 0.0008 or more but less than 0.0015 were rated "B" (fair), and those of 0.0015 or more were rated "C" (poor).

[Glass transition temperature Tg]
The flat plate obtained in [Moldability] was cut to prepare a test piece with a width of 5 mm, a thickness of 1 mm, and a length of 25 mm. The glass transition temperature of this test piece was measured using a dynamic viscoelasticity measuring device: Rheogel-E4000 (manufactured by UBM Corporation). The maximum value of the loss tangent (tan δ) measured for this test piece under conditions of a tensile sine wave, a frequency of 1 Hz, and a heating rate of 3°C/min was determined as the glass transition temperature. Glass transition temperatures of 160°C or higher were rated "A" (good), those of 140°C or higher but less than 160°C were rated "B" (fair), and those of less than 140°C were rated "C" (poor).

(Synthesis Example 1) Synthesis of Compound 1: Triphenylvinylbenzylphosphonium chloride (Quaternized CMS) 1.5 moles (228.9 g) of vinylbenzyl chloride (trade name: CMS-14, manufactured by AGC Seimi Chemical Co., Ltd.), 1.8 moles (472.1 g) of triphenylphosphine, and 622.4 g of dimethylformamide were placed in a 2.0 L reactor and reacted at 70°C for 3 hours under nitrogen conditions, resulting in the precipitation of a white solid. The solid was thoroughly washed with acetone and then dried under reduced pressure at 92°C, and 490 g of Compound 1 was recovered.

Example 1
51.4 g of styrene, 40.2 g of Compound 1, 8.4 g of acenaphthylene, 27.6 g of α-methylstyrene dimer, 3.80 g of 2,2'-azobis(2,4,4-trimethylpentane) (product name: VR-110, Fujifilm Wako Pure Chemical Industries, Ltd.), and 233.3 g of dimethylformamide were charged into a reactor and reacted for 3 hours at 120°C under nitrogen conditions to obtain a copolymer as a dimethylformamide solution. This dimethylformamide solution was diluted with an equal amount of toluene, and 37% by mass formalin and 28% by mass aqueous potassium hydroxide were added so that the formaldehyde and potassium hydroxide amounts were 12 and 6 equivalents relative to Compound 1, respectively, and the reaction was carried out at room temperature for 4 hours. The reaction solution was diluted with toluene, and the organic layer was washed with distilled water and isopropyl alcohol. After dehydration and concentration of the organic layer, anhydrous magnesium chloride was added in an amount of 6 equivalents relative to Compound 1, and the mixture was stirred at 65°C for 2 hours. The solid matter was removed by filtration, and the filtrate diluted with toluene was reprecipitated in methanol. The solid matter was then removed by filtration, and the product (copolymer (A)) was recovered by drying under reduced pressure at 60 ° C. 92.5 parts by mass of this product and 7.5 parts by mass of SBR1 as copolymer (B) (3.52 parts by mass per 100 parts by mass of the monomer of copolymer (A)) were dissolved and mixed in toluene, and the toluene was distilled off by drying under reduced pressure at 60 ° C. to obtain the composition of Example 1.

(Examples 2 to 12 and Comparative Example 1)
The compositions of Examples 2 to 12 and Comparative Example 1 were obtained in the same manner as in Example 1, except that the type and amount of the monomer of copolymer (A), the amount of α-methylstyrene dimer, and the type and amount of copolymer (B) were changed as shown in the formulations (parts by mass) in Tables 1 to 3 below.

(Reference Example 1 and Comparative Examples 2 and 3)
The copolymers (A) obtained in Examples 1, 4 and 5 were directly used for evaluation as the products of Reference Example 1 and Comparative Examples 2 and 3, respectively.

Details of the copolymer (B) used in Examples 1 to 12 and Comparative Example 1 are as follows.
SBR1: styrene-butadiene copolymer, manufactured by Kuraray Co., Ltd., "L-SBR-870", number average molecular weight Mn: 6000, glass transition temperature: -18°C
SBR2: styrene-butadiene copolymer, manufactured by Kuraray Co., Ltd., "L-SBR-822", number average molecular weight Mn: 8800, glass transition temperature: -60°C

The weight-average molecular weight of copolymer (A) and the content of each repeating unit were measured for the compositions of Examples 1 to 12 and Comparative Example 1, and the products of Reference Example 1 and Comparative Examples 2 and 3. The melt viscosity, dielectric loss tangent, glass transition temperature, and moldability were also evaluated. The results are shown in Tables 1 to 3 below. Note that the "content (mass%) of copolymer (B)" in Tables 1 to 3 corresponds to the parts by mass of copolymer (B) per 100 parts by mass of the total of copolymer (A) and copolymer (B).

Copolymer (A) obtained in Example 1 had a weight-average molecular weight of 3,200, a styrene ratio of 72.4 mol%, a divinylbenzene ratio of 17.4 mol%, and an acenaphthylene ratio of 10.2 mol%. The composition of Example 1 contained copolymer (B) in addition to copolymer (A), and had a low melt viscosity, a low dielectric dissipation factor, a high glass transition temperature, and excellent moldability. In Reference Example 1, which serves as a comparison, copolymer (A) itself was the same as in Example 1, but did not contain copolymer (B). As a result, the melt viscosity was higher than that of Example 1. This demonstrates that by combining copolymer (A) with copolymer (B), the melt viscosity can be reduced without compromising the excellent dielectric properties, glass transition temperature, and moldability.

The copolymer (A) obtained in Example 2 differs from the copolymer (A) obtained in Example 1 in that it has a smaller weight-average molecular weight. Therefore, the composition of Example 2 was inferior to the composition of Example 1 in moldability and glass transition temperature, but like Example 1, it had excellent dielectric properties and melt viscosity.

The copolymer (A) obtained in Example 3 differs from the copolymer (A) of Example 1 in that it has a larger weight-average molecular weight. As a result, the melt viscosity of the composition of Example 3 was higher than that of the composition of Example 1. However, in Example 3, due to the inclusion of copolymer (B), the weight-average molecular weight of copolymer (A) was higher than that of Reference Example 1, and the melt viscosity was evaluated to be the same as that of Reference Example 1, and the dielectric properties were also excellent.

The copolymer (A) obtained in Example 4 had a weight-average molecular weight of 3,200, a 4-vinylbiphenyl ratio of 76.1 mol %, a divinylbenzene ratio of 14.9 mol %, and an acenaphthylene ratio of 9.0 mol %. In Comparative Example 2, which was used for comparison, the copolymer (A) itself was the same as in Example 4, but did not contain copolymer (B), resulting in a high melt viscosity. In contrast, in Example 4, copolymer (B) was blended with copolymer (A), thereby enabling a reduction in melt viscosity compared to Comparative Example 2 without compromising dielectric properties, glass transition temperature, or moldability.

The copolymer (A) obtained in Example 5 had a weight-average molecular weight of 3,200, a 4-tert-butylstyrene ratio of 72.4 mol%, a divinylbenzene ratio of 17.4 mol%, and an acenaphthylene ratio of 10.2 mol%. In Comparative Example 3, which was used for comparison, the copolymer (A) itself was the same as in Example 5, but did not contain copolymer (B), resulting in a high melt viscosity. In contrast, in Example 5, copolymer (B) was blended with copolymer (A), thereby enabling a reduction in melt viscosity compared to Comparative Example 3 without compromising dielectric properties, glass transition temperature, or moldability.

The copolymer (A) obtained in Example 6 had a weight-average molecular weight of 3,600, a styrene ratio of 71.8 mol%, a divinylbenzene ratio of 17.5 mol%, and an indene ratio of 10.7 mol%. Example 6 differs from Example 1 in that acenaphthylene was replaced with indene in copolymer (A). Although Example 6 had inferior moldability and glass transition temperature compared to Example 1, it had excellent dielectric properties and melt viscosity, similar to Example 1.

The copolymer (A) obtained in Example 7 had a weight-average molecular weight of 3,200, a styrene ratio of 83.1 mol %, and a divinylbenzene ratio of 16.9 mol %. Example 7 was obtained by removing acenaphthylene from the copolymer (A) of Example 1, and had an inferior glass transition temperature compared to Example 1. However, like Example 1, it had excellent dielectric properties, melt viscosity, and moldability.

The copolymer (A) obtained in Example 8 had a weight-average molecular weight of 3,200, a styrene ratio of 56.5 mol%, a divinylbenzene ratio of 33.7 mol%, and an acenaphthylene ratio of 9.7 mol%. In Example 8, the divinylbenzene ratio in copolymer (A) was higher than in Example 1, and the dielectric properties and melt viscosity were inferior to those of Example 1; however, the use of copolymer (B) in combination maintained these within the acceptable range. In contrast, in Comparative Example 1, the divinylbenzene ratio was 53.9 mol%, which was too high, resulting in significant deterioration in the dielectric properties and melt viscosity.

The copolymer (A) obtained in Example 9 had a weight-average molecular weight of 3,200, a styrene ratio of 77.3 mol%, a divinylbenzene ratio of 17.4 mol%, and an acenaphthylene ratio of 5.2 mol%. Compared to Example 1, Example 9 had a higher styrene ratio and a lower acenaphthylene ratio in the copolymer (A), and thus had an inferior glass transition temperature to Example 1. However, like Example 1, it had excellent dielectric properties, melt viscosity, and moldability.

The copolymer (A) obtained in Example 10 had a weight-average molecular weight of 3,200, a styrene ratio of 62.9 mol%, a divinylbenzene ratio of 16.9 mol%, and an acenaphthylene ratio of 20.2 mol%. Compared to Example 1, the styrene ratio in the copolymer (A) of Example 10 was lower and the acenaphthylene ratio was higher. Although the melt viscosity was inferior to that of Example 1, it was within the acceptable range, and the dielectric properties, glass transition temperature, and moldability were as excellent as those of Example 1.

Example 11 contained a larger amount of copolymer (B) than Example 1. Although the dielectric properties were inferior to those of Example 1, they were within the acceptable range, and the melt viscosity, glass transition temperature, and moldability were as excellent as those of Example 1.

The various numerical ranges described in this specification can each be combined with any upper and lower limit, and all such combinations are considered to be preferred numerical ranges and are described in this specification. Furthermore, a numerical range described as "X to Y" means greater than or equal to X and less than or equal to Y.

Although several embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be embodied in a variety of other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their omissions, substitutions, modifications, etc. are included within the scope and spirit of the invention, as well as within the scope of the inventions and their equivalents as set forth in the claims.

Claims (6)

a linear copolymer (A) having a repeating unit corresponding to a monovinyl aromatic compound and a repeating unit corresponding to a divinyl aromatic compound, wherein the content of the repeating unit corresponding to the divinyl aromatic compound in 100 mol % of all repeating units is less than 40 mol %;
a copolymer (B) containing a styrene-based monomer and an aliphatic diene monomer having 4 to 7 carbon atoms as constituent monomers and/or a hydrogenated product thereof, the copolymer having a number average molecular weight of 50,000 or less;
Including,
the amount of the copolymer (B) is 80 parts by mass or less relative to 100 parts by mass of the total of the copolymer (A) and the copolymer (B);
Curable resin composition. The curable resin composition according to claim 1, wherein the copolymer (B) comprises a copolymer of a styrene-based monomer and butadiene and/or a hydrogenated product thereof. The curable resin composition according to claim 1 or 2, wherein the content of repeating units corresponding to the divinyl aromatic compound is less than 20 mol % based on 100 mol % of all repeating units in the copolymer (A). The curable resin composition according to claim 1 or 2, wherein the copolymer (A) further has a repeating unit corresponding to an aromatic ring-fused cyclic olefin compound having three rings. The curable resin composition according to claim 1 or 2, wherein the content of repeating units corresponding to the monovinyl aromatic compound is 50 mol % or more based on 100 mol % of all repeating units in the copolymer (A). The curable resin composition according to claim 1 or 2, which is a material for a printed circuit board.