JP2026000040A - 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 divinyl aromatic compound, and a compound (B) represented by the following general formula (1): In formula (1), ^R1 and ^R2 each independently represent a monovalent saturated hydrocarbon group having 1 to 10 carbon atoms or a monovalent aromatic hydrocarbon group having 6 to 10 carbon atoms, and p and q each independently represent an integer of 0 to 5.
[Chemical formula 1]
[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, 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 such a copolymer, 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.

On the other hand, Patent Document 3 discloses that α-methylstyrene dimer is blended into a resin composition used as a printed circuit board material as a curl-reducing component to suppress curling during curing.

Japanese Patent Application Laid-Open No. 2001-192539 Japanese Patent Application Laid-Open No. 2018-039995 JP 2013-231132 A

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.

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 divinyl aromatic compound, and a compound (B) represented by the following general formula (1):
(In the formula, ^R1 and ^R2 each independently represent a monovalent saturated hydrocarbon group having 1 to 10 carbon atoms or a monovalent aromatic hydrocarbon group having 6 to 10 carbon atoms, and p and q each independently represent an integer of 0 to 5.)
[2] The amount of the compound (B) is 0.1 to 50 parts by mass relative to 100 parts by mass of the total amount of the copolymer (A) and the compound (B). [1] The curable resin composition according to [1].
[3] The curable resin composition according to [1] or [2], wherein the copolymer (A) further has a repeating unit corresponding to an aromatic ring-fused cyclic olefin compound having three rings.
[4] The curable resin composition according to any one of [1] to [3], wherein the content of repeating units corresponding to the monovinyl aromatic compound is 50 mol% or more in 100 mol% of all repeating units.
[5] The curable resin composition according to any one of [1] to [5], which is a printed circuit board material.
[6] Use of the curable resin composition according to any one of [1] to [4] 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 contains a linear copolymer (A) having repeating units corresponding to (a) a monovinyl aromatic compound and (b) a divinyl aromatic compound, as well as a compound (B).

The compound (B) is a vinylidene group-containing compound represented by the following general formula (1): When the curable resin composition contains the compound (B), the melt viscosity can be reduced while maintaining excellent dielectric properties.

In formula (1), ^R1 and ^R2 each independently represent a monovalent saturated hydrocarbon group having 1 to 10 carbon atoms or a monovalent aromatic hydrocarbon group having 6 to 10 carbon atoms, and therefore do not contain heteroatoms. 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 6 carbon atoms, and more preferably 1 to 3 carbon atoms. The monovalent aromatic hydrocarbon group preferably has 6 to 8 carbon atoms.

In formula (1), p and q each independently represent an integer from 0 to 5, preferably an integer from 0 to 3, more preferably an integer from 0 to 2, and even more preferably 0.

A specific example of compound (B) is α-methylstyrene dimer (i.e., 2,4-diphenyl-4-methyl-1-pentene).

As described above, copolymer (A) has (a) repeating units corresponding to a monovinyl aromatic compound and (b) repeating units corresponding to a divinyl aromatic compound. In one embodiment, copolymer (A) 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 (2) is preferred.

In formula (2), ^R3 represents a monovalent aromatic hydrocarbon group having 6 to 30 carbon atoms and therefore does not contain a heteroatom. More specifically, ^R3 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 ^R3 refers to the total number of carbon atoms in ^R3 , 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 (2) (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 (3).

In formula (3), ^R4 represents a divalent aromatic hydrocarbon group having 6 to 30 carbon atoms and therefore does not contain a heteroatom. More specifically, ^R4 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 ^R4 refers to the total number of carbon atoms in ^R4 , 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 (3) (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 (4).

In formula (4), ^R5 and ^R6 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 (4), m and n each independently represent an integer of 0 to 3. When m and n are 2 or greater, R ⁵ and R ⁶ in one repeating unit may be the same or different.

The aromatic ring-fused cyclic olefin compound forming the repeating unit of formula (4) is an acenaphthylene-based compound represented by the following general formula (5).
R ⁵ , R ⁶ , m, and n in formula (5) are the same as R ⁵ , R ⁶ , m, and n in formula (4).

In one embodiment, the aromatic ring-fused cyclic olefin compound preferably contains an acenaphthylene-based compound represented by the above formula (5), more preferably contains acenaphthylene. That is, the (c) cyclic olefin unit preferably contains a repeating unit of formula (4), 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 (4), 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 (a) monovinyl aromatic compound units is not particularly limited, but from the viewpoint of melt viscosity, it is preferably 50 mol% or more of the total 100 mol% of 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%. Note that, 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 terminals of the copolymer.

In copolymer (A), the content of (b) divinylaromatic compound units is not particularly limited, but is preferably 3 to 30 mol% based on 100 mol% of all repeating units constituting copolymer (A). A content of 3 mol% or more enhances thermosetting properties, resulting in a good cured product, and also improves the glass transition temperature. The content of (b) divinylaromatic compound units is more preferably 5 to 25 mol%, even more preferably 8 to 22 mol%, and even more preferably 10 to 20 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 (6) is preferred. In this case, R ⁷ - and/or R ⁸ - is introduced at the terminal of the copolymer (A).
R ⁷ -N=NR ⁸ (6)

In formula (6), ^R7 and ^R8 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. Compound (B) represented by the above general formula (1) can be used as a chain transfer agent, in which case a structure derived from compound (B) is introduced at the terminal of copolymer (A).

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.

The vinylbenzyl phosphonium salt can be copolymerized with a monovinyl aromatic compound using known vinyl polymerization methods. For example, by charging a vinylbenzyl phosphonium salt, a monovinyl aromatic compound, an optional aromatic-ring-fused cyclic olefin compound, a polymerization initiator represented by the above general formula (6), and compound (B) represented by the above general formula (1) into an organic solvent and allowing them to react, a copolymer having repeating units derived from the vinylbenzyl phosphonium salt, repeating units derived from the monovinyl aromatic compound, and an optional repeating unit derived from the aromatic-ring-fused cyclic olefin compound, and having a structure derived from the polymerization initiator and/or a structure derived from compound (B) at its terminal, can be obtained.

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.

The curable resin composition according to this embodiment contains a copolymer (A) and a compound (B). The presence of vinyl groups in the molecular chain of the copolymer (A) enables crosslinking by polymerization, 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 compound (B) in the curable resin composition is preferably 0.1 to 50 parts by mass, more preferably 0.5 to 30 parts by mass, more preferably 1.0 to 10 parts by mass, and even more preferably 1.2 to 5 parts by mass, per 100 parts by mass of the total amount of copolymer (A) and compound (B).

The compound (B) contained in the curable resin composition may be a chain transfer agent that was charged during the preparation of the copolymer (A) and remains unreacted, or it may be a compound added after the preparation of the copolymer (A).

In addition to the copolymer (A) and the compound (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, 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 the copolymer (A) and the compound (B). The organic solvent used may be one that can dissolve the copolymer (A) and the compound (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 and compositions obtained in Examples 1 to 3, 8 to 10, Reference Example 1, and Comparative Examples 1 and 4 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 products obtained in Example 4 and Comparative Example 2 were 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 products obtained in Example 5 and Comparative Example 3 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 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 relative to 100 mol% of all repeating units (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) 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) 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 (styrene ratio) and the content of repeating units corresponding to divinylbenzene (divinylbenzene ratio) relative to 100 mol% of all repeating units were calculated.

[Weight average molecular weight]
The products and compositions obtained in Examples 1 to 10, Reference Example 1, and Comparative Examples 1 to 4 were dissolved in tetrahydrofuran, and the weight-average molecular weight Mw 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) filled 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 amount was 10 μL, and a differential refractive index detector (Shodex RI-504, manufactured by Showa Denko) was used.

[Content of α-methylstyrene dimer or methyl α-bromomethylacrylate]
The products and compositions obtained in Examples 1 to 10, Reference Example 1, and Comparative Examples 1 to 4 were dissolved in tetrahydrofuran, and the mass ratio (mass%) of α-methylstyrene dimer (2,4-diphenyl-4-methyl-1-pentene) or α-bromomethyl methyl acrylate in the products and compositions was measured by gas chromatography (Agilent Technologies 8890 gas chromatograph system, column: "DB-1", inner diameter 0.32 mm x length 30 m, film thickness 0.25 μm). The inlet temperature was 300°C, the detection port temperature was 300°C, the sample concentration was 1 mass%, and the sample injection amount was 1 μL. After holding at 70°C for 3 minutes, the temperature was increased at 10°C/min and held at 300°C for 5 minutes. In this example, the mass ratio (mass%) corresponds to the parts by mass of compound (B) relative to 100 parts by mass of the total amount of copolymer (A) and compound (B).

[Melt viscosity]
The products and compositions obtained in Examples 1 to 10, Reference Example 1, and Comparative Examples 1 to 4 were used as samples. Using a manual hydraulic pump: P-1B (manufactured by Riken Co., Ltd.), 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 defined as the minimum melt viscosity, and a minimum melt viscosity of less than 5,000 poise was rated "A" (good), 5,000 poise or more but less than 20,000 poise was rated "B" (fair), and 20,000 poise or more was rated "C" (poor).

[Moldability]
Using the products and compositions obtained in Examples 1 to 10, Reference Example 1, and Comparative Examples 1 to 4 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 thick 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 as "A" (good), those of 0.0008 or more but less than 0.001 as "B" (fair), and those of 0.001 or more as "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) (trade 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 was diluted with toluene and reprecipitated in methanol. The solid matter was then removed by filtration and dried under reduced pressure at 60°C to recover the product.

(Examples 2 to 9, Reference Example 1, and Comparative Examples 1 to 3)
The types and amounts of monomers charged were changed as shown in the formulations (parts by mass) in Tables 1 to 3 below, and the other procedures were the same as in Example 1 to obtain the products of Examples 2 to 9, Reference Example 1, and Comparative Examples 1 to 3. However, in Reference Example 1 and Comparative Examples 1 to 3, reprecipitation was repeated until the content of α-methylstyrene dimer in the product fell below the detection limit.

Example 10
5.0 g of the product obtained in Example 1 was dissolved in 3.3 g of toluene, 0.21 g of α-methylstyrene dimer (1.8 parts by mass relative to 100 parts by mass of the total of the monomers) was added thereto, and the mixture was stirred. The mixture was then dried under reduced pressure at 60°C to distill off the toluene, and a composition was recovered.

(Comparative Example 4)
5.0 g of the product obtained in Reference Example 1 was dissolved in 3.3 g of toluene, 0.09 g of methyl α-bromomethylacrylate (0.78 parts by mass relative to 100 parts by mass of the total of the monomers) was added thereto, and the mixture was stirred. The mixture was then dried under reduced pressure at 60°C to distill off the toluene, and a composition was recovered.

The products and compositions of Examples 1 to 10, Reference Example 1, and Comparative Examples 1 to 4 were measured for the weight-average molecular weight of the copolymer, the content of each repeating unit, and the content of α-methylstyrene dimer or α-bromomethylmethyl acrylate ("Content of (B)" in the table). Additionally, the melt viscosity, dielectric loss tangent, moldability, and glass transition temperature were evaluated. The results are shown in Tables 1 to 3 below.

The copolymer 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%, and contained no heteroatoms. The product of Example 1 contained 1.8 mass% of α-methylstyrene dimer, and was therefore a composition containing copolymer (A) and compound (B). Example 1 had a low melt viscosity, a low dielectric dissipation factor, a high glass transition temperature, and excellent moldability. The product of Reference Example 1, which was used for comparison, was essentially the same copolymer as Example 1, but did not contain α-methylstyrene dimer and therefore had a higher melt viscosity than Example 1. This demonstrates that combining copolymer (A) with compound (B) can reduce melt viscosity without impairing excellent dielectric properties, glass transition temperature, and moldability.

The copolymer obtained in Example 2 had a weight-average molecular weight of 6,300, a styrene ratio of 72.4 mol%, a divinylbenzene ratio of 17.4 mol%, and an acenaphthylene ratio of 10.2 mol%, contained no heteroatoms, and contained 1.9 mass% of α-methylstyrene dimer in the product. The product of Comparative Example 1, which was used for comparison, was essentially the same copolymer as in Example 2, but did not contain α-methylstyrene dimer. Comparing Example 2 and Comparative Example 1, the inclusion of α-methylstyrene dimer in Example 2 enabled a reduction in melt viscosity without impairing the excellent dielectric properties, glass transition temperature, and moldability.

The copolymer obtained in Example 3 had a lower weight-average molecular weight than Example 1. Due to the lower molecular weight, it was inferior to Example 1 in moldability and glass transition temperature, but like Example 1, it had excellent dielectric properties and melt viscosity.

The copolymer 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%, and contained no heteroatoms. The product contained 1.8 mass% of α-methylstyrene dimer. The product of Comparative Example 2, which was used for comparison, was essentially the same copolymer as Example 4, but did not contain α-methylstyrene dimer, and therefore had a higher melt viscosity than Example 4.

The copolymer 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%, and contained no heteroatoms. The product contained 1.8 mass% of α-methylstyrene dimer. The product of Comparative Example 3, which was used for comparison, was essentially the same copolymer as Example 5, but did not contain α-methylstyrene dimer, and therefore had a higher melt viscosity than Example 5.

The copolymer 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%, and contained no heteroatoms. The product contained 1.8 mass% of α-methylstyrene dimer. Example 6 was obtained by replacing acenaphthylene with indene in Example 1, and was inferior to Example 1 in terms of moldability and glass transition temperature, but had excellent dielectric properties and melt viscosity, similar to Example 1.

The copolymer 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%, and contained no heteroatoms. The product contained 1.8 mass% of α-methylstyrene dimer. Unlike Example 1, Example 7 did not contain acenaphthylene, and had an inferior glass transition temperature to Example 1. However, like Example 1, it had excellent dielectric properties, melt viscosity, and moldability.

The copolymer obtained in Example 8 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%, contained no heteroatoms, and contained 1.8 mass% of α-methylstyrene dimer in the product. Example 8 had a higher styrene ratio and a lower acenaphthylene ratio than Example 1, and had an inferior glass transition temperature to Example 1. However, like Example 1, it had excellent dielectric properties, melt viscosity, and moldability.

The copolymer obtained in Example 9 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%, contained no heteroatoms, and contained 1.8 mass% of α-methylstyrene dimer in the product. Example 9 had a lower styrene ratio and a higher acenaphthylene ratio than Example 1, and was inferior in moldability to Example 1. However, like Example 1, it had excellent dielectric properties, melt viscosity, and glass transition temperature.

In Example 10, α-methylstyrene dimer was added to the product obtained in Example 1, and the amount of α-methylstyrene dimer in the composition was 6.0% by mass. Although Example 10 had a lower glass transition temperature than Example 1, it had excellent dielectric properties, melt viscosity, and moldability, just like Example 1.

In Comparative Example 4, methyl α-bromomethylacrylate was added to the product obtained in Comparative Example 1, and the composition did not contain α-methylstyrene dimer. Note that the "Content of (B)" in Table 3 refers to the amount of methyl α-bromomethylacrylate. When methyl α-bromomethylacrylate was added, the dielectric properties were inferior, and it was not possible to achieve both dielectric properties and melt viscosity.

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 (5)

a linear copolymer (A) having a repeating unit corresponding to a monovinyl aromatic compound and a repeating unit corresponding to a divinyl aromatic compound;
A compound (B) represented by the following general formula (1),
Including,
In the formula, ^R1 and ^R2 each independently represent a monovalent saturated hydrocarbon group having 1 to 10 carbon atoms or a monovalent aromatic hydrocarbon group having 6 to 10 carbon atoms, and p and q each independently represent an integer of 0 to 5.
Curable resin composition. The curable resin composition according to claim 1, wherein the amount of compound (B) is 0.1 to 50 parts by mass per 100 parts by mass of the total amount of copolymer (A) and compound (B). 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. The curable resin composition according to claim 1 or 2, which is a material for a printed circuit board.