WO2025047299A1 - Resin composition, prepreg, resin-bearing film, resin-bearing metal foil, metal-clad laminate sheet, and wiring board - Google Patents

Abstract

One aspect of the present invention relates to a resin composition containing a thermosetting compound (A) and an inorganic filler (B), wherein: the thermosetting compound (A) contains at least one radically polymerizable compound (A1) selected from the group consisting of polyphenylene ether compounds having a reactive unsaturated group, hydrocarbon compounds having a reactive unsaturated group, and maleimide compounds having two or more maleimide groups; the inorganic filler (B) contains a boron nitride filler (B1); and a polydopamine (C) having a functional group (X) that reacts with the radically polymerizable compound (A1) adheres to the surface of the boron nitride filler (B1).

Description

Resin composition, prepreg, resin-coated film, resin-coated metal foil, metal-clad laminate, and wiring board

The present invention relates to a resin composition, a prepreg, a resin-coated film, a resin-coated metal foil, a metal-clad laminate, and a wiring board.

As the amount of information processed increases in various electronic devices, mounting technologies such as higher integration of the semiconductor devices mounted thereon, higher density wiring, and multi-layering are advancing. Furthermore, wiring boards used in various electronic devices are required to be high-frequency compatible wiring boards, such as millimeter wave radar boards for in-vehicle applications. In order to increase the signal transmission speed, wiring boards used in various electronic devices are required to reduce loss during signal transmission, and this is especially true for wiring boards that are high-frequency compatible. To meet this requirement, the substrate material that constitutes the substrate for the wiring boards used in various electronic devices is required to have a low dielectric constant and dielectric tangent.

As such a substrate material, for example, a PPE-containing resin composition containing PPE (polyphenylene ether), a crosslinked curable compound, and a phosphaphenanthrene derivative has been reported to have excellent low dielectric properties (Patent Document 1).

On the other hand, electronic materials used in PA (power amplifier) boards for base stations are required to have high thermal conductivity in addition to low dielectric properties. One method that has been reported so far is to use boron nitride as an inorganic filler as a method for improving the thermal conductivity of resin compositions (Patent Document 2).

The boron nitride filler described in Patent Document 2 does indeed improve the thermal conductivity of the resin composition. However, when the resin composition is used as a molding material for substrate materials, etc., even better adhesion is also required. In this regard, it has been found that boron nitride does not have sufficient adhesion to resins. When the adhesion between the inorganic filler and the resin is poor, breaks are likely to occur in the cured product of the resin composition, and when a resin composition containing the inorganic filler is used as a substrate material for metal-clad laminates, the adhesion to the metal foil will also be poor. In the technology described in Patent Document 2, an aldehyde compound is used as a surface modifier for the inorganic filler to increase the thermal conductivity, but the above-mentioned adhesion problem is not resolved.

JP 2015-67700 A JP 2020-73422 A

The present invention has been made in consideration of these circumstances, and aims to provide a resin composition that can give a cured product with low dielectric properties, high thermal conductivity, and excellent adhesion. The present invention also aims to provide a prepreg, a resin-coated film, a resin-coated metal foil, a metal-clad laminate, and a wiring board that are obtained using the resin composition.

After extensive investigation, the inventors discovered that the above object can be achieved by the following configuration, and after further investigation, they achieved the present invention.

The resin composition according to one embodiment of the present invention is a resin composition containing a thermosetting compound (A) and an inorganic filler (B), characterized in that the thermosetting compound (A) contains at least one radically polymerizable compound (A1) selected from the group consisting of polyphenylene ether compounds having reactive unsaturated groups, hydrocarbon compounds having reactive unsaturated groups, and maleimide compounds having two or more maleimide groups, the inorganic filler (B) contains a boron nitride filler (B1), and polydopamine (C) having a functional group (X) that reacts with the radically polymerizable compound (A1) is attached to the surface of the boron nitride filler (B1).

FIG. 1 is a schematic cross-sectional view showing an example of a prepreg according to an embodiment of the present invention. FIG. 2 is a schematic cross-sectional view showing an example of a metal-clad laminate according to an embodiment of the present invention. FIG. 3 is a schematic cross-sectional view showing an example of a wiring board according to an embodiment of the present invention. FIG. 4 is a schematic cross-sectional view showing an example of a resin-coated metal foil according to an embodiment of the present invention. FIG. 5 is a schematic cross-sectional view showing an example of a resin-coated film according to an embodiment of the present invention.

　The following describes specific embodiments of the present invention, but the present invention is not limited to these.

[Resin composition]
The resin composition according to the embodiment of the present invention is a resin composition containing a thermosetting compound (A) and an inorganic filler (B). The thermosetting compound (A) contains at least one radical polymerizable compound (A1) selected from the group consisting of a polyphenylene ether compound having a reactive unsaturated group, a hydrocarbon-based compound having a reactive unsaturated group, and a maleimide compound having two or more maleimide groups. The inorganic filler (B) contains a boron nitride filler (B1), and a polydopamine (C) having a functional group (X) that reacts with the radical polymerizable compound (A1) is attached to the surface of the boron nitride filler (B1).

The above-mentioned configuration makes it possible to provide a resin composition that can give a cured product with low dielectric properties, high thermal conductivity, and excellent adhesion. In addition, it is possible to provide a prepreg, a resin-coated film, a resin-coated metal foil, a metal-clad laminate, and a wiring board that are obtained using the resin composition and have excellent properties.

First, we will explain each component of the resin composition of this embodiment.

(Thermosetting compound (A))
The thermosetting resin compound (A) of this embodiment is a thermosetting compound containing a radically polymerizable compound (A1). The radically polymerizable compound (A1) used in this embodiment is a compound having radical polymerizability, such as a compound having a reactive unsaturated group, a compound having a maleimide group, etc. More specifically, for example, a polyphenylene ether compound, a cyanate ester compound, an active ester compound, a compound having an unsaturated group, etc. can be mentioned. Examples of the compound having an unsaturated group include an acrylic compound, a methacrylic compound, a vinyl compound, an allyl compound, a propenyl compound, a maleimide compound, a hydrocarbon-based compound having an unsaturated double bond, etc.

Among these, the thermosetting resin compound (A) of this embodiment contains at least one radically polymerizable compound (A1) selected from the group consisting of polyphenylene ether compounds having reactive unsaturated groups, hydrocarbon-based compounds having reactive unsaturated groups, and maleimide compounds having two or more maleimide groups. By containing these radically polymerizable compounds (A1), it is possible to obtain a resin composition having excellent low dielectric properties in the cured product. Each of these will be described in more detail below.

Polyphenylene ether compound The polyphenylene ether compound that can be used in this embodiment is not particularly limited as long as it is a polyphenylene ether compound having a reactive unsaturated group in the molecule. In this specification, the term "reactive unsaturated group" refers to, for example, a group having an unsaturated double bond. Specific examples of polyphenylene ether compounds having a reactive unsaturated group include polyphenylene ether compounds having a group represented by the following formula (3) or formula (4). It is believed that the inclusion of such a modified polyphenylene ether compound results in a resin composition that can obtain a cured product with low dielectric properties and high heat resistance.

In formula (3), s represents an integer of 0 to 10. Z represents an arylene group. R ₁ to R ₃ are each independent. That is, R ₁ to R ₃ may be the same group or different groups. R ₁ to R ₃ represent a hydrogen atom or an alkyl group.

In addition, in formula (3), when s is 0, this indicates that Z is directly bonded to the end of the polyphenylene ether.

The arylene group of Z is not particularly limited. Examples of the arylene group include monocyclic aromatic groups such as phenylene groups, and polycyclic aromatic groups in which the aromatic ring is not monocyclic but is polycyclic aromatic such as naphthalene rings. The arylene group also includes derivatives in which the hydrogen atom bonded to the aromatic ring is replaced with a functional group such as an alkenyl group, an alkynyl group, a formyl group, an alkylcarbonyl group, an alkenylcarbonyl group, or an alkynylcarbonyl group. The alkyl group is not particularly limited, and is preferably an alkyl group having 1 to 18 carbon atoms, more preferably an alkyl group having 1 to 10 carbon atoms. Specific examples include a methyl group, an ethyl group, a propyl group, a hexyl group, and a decyl group.

In formula (4), _R4 represents a hydrogen atom or an alkyl group. The alkyl group is not particularly limited, and is preferably, for example, an alkyl group having 1 to 18 carbon atoms, and more preferably an alkyl group having 1 to 10 carbon atoms. Specific examples include a methyl group, an ethyl group, a propyl group, a hexyl group, and a decyl group.

Preferred specific examples of the substituent represented by formula (3) include, for example, a substituent containing a vinylbenzyl group. Examples of the substituent containing a vinylbenzyl group include, for example, a substituent represented by formula (5) below. Examples of the substituent represented by formula (4) include, for example, an acrylate group and a methacrylate group.

More specifically, examples of the substituent include vinylbenzyl groups (ethenylbenzyl groups) such as p-ethenylbenzyl and m-ethenylbenzyl groups, vinylphenyl groups, acrylate groups, and methacrylate groups.

The polyphenylene ether compound has a polyphenylene ether chain in the molecule, and preferably has, for example, a repeating unit represented by the following formula (6) in the molecule.

In formula (6), t represents 1 to 50. R ₅ to R ₈ are each independent. That is, R ₅ to R ₈ may be the same group or different groups. R ₅ to R ₈ represent a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, a formyl group, an alkylcarbonyl group, an alkenylcarbonyl group, or an alkynylcarbonyl group. Among these, a hydrogen atom and an alkyl group are preferred.

Specific examples of the functional groups mentioned for R ₅ to R ₈ include the following.

The alkyl group is not particularly limited, but for example, an alkyl group having 1 to 18 carbon atoms is preferable, and an alkyl group having 1 to 10 carbon atoms is more preferable. Specific examples include a methyl group, an ethyl group, a propyl group, a hexyl group, and a decyl group.

The alkenyl group is not particularly limited, but for example, an alkenyl group having 2 to 18 carbon atoms is preferable, and an alkenyl group having 2 to 10 carbon atoms is more preferable. Specific examples include a vinyl group, an allyl group, and a 3-butenyl group.

The alkynyl group is not particularly limited, but for example, an alkynyl group having 2 to 18 carbon atoms is preferable, and an alkynyl group having 2 to 10 carbon atoms is more preferable. Specific examples include an ethynyl group and a prop-2-yn-1-yl group (propargyl group).

The alkylcarbonyl group is not particularly limited as long as it is a carbonyl group substituted with an alkyl group, but for example, an alkylcarbonyl group having 2 to 18 carbon atoms is preferred, and an alkylcarbonyl group having 2 to 10 carbon atoms is more preferred. Specific examples include an acetyl group, a propionyl group, a butyryl group, an isobutyryl group, a pivaloyl group, a hexanoyl group, an octanoyl group, and a cyclohexylcarbonyl group.

The alkenylcarbonyl group is not particularly limited as long as it is a carbonyl group substituted with an alkenyl group, but for example, an alkenylcarbonyl group having 3 to 18 carbon atoms is preferred, and an alkenylcarbonyl group having 3 to 10 carbon atoms is more preferred. Specific examples include an acryloyl group, a methacryloyl group, and a crotonoyl group.

The alkynylcarbonyl group is not particularly limited as long as it is a carbonyl group substituted with an alkynyl group, but for example, an alkynylcarbonyl group having 3 to 18 carbon atoms is preferred, and an alkynylcarbonyl group having 3 to 10 carbon atoms is more preferred. Specific examples include a propioloyl group.

The weight average molecular weight (Mw) of the polyphenylene ether compound is not particularly limited. Specifically, it is preferably 500 to 5000, more preferably 800 to 4000, and even more preferably 1000 to 3000. The weight average molecular weight may be measured by a general molecular weight measurement method, and specifically, it may be a value measured using gel permeation chromatography (GPC). In addition, when the polyphenylene ether compound has a repeating unit represented by the formula (6) in the molecule, t is preferably a value that causes the weight average molecular weight of the polyphenylene ether compound to be within this range. Specifically, t is preferably 1 to 50.

When the weight average molecular weight of the polyphenylene ether compound is within this range, it has the excellent low dielectric properties of polyphenylene ether, and the heat resistance of the cured product is excellent, as well as the moldability. This is believed to be due to the following. When the weight average molecular weight of a normal polyphenylene ether is within this range, the heat resistance of the cured product tends to decrease because the molecular weight is relatively low. In this regard, since the polyphenylene ether compound according to this embodiment has one or more unsaturated double bonds at the terminal, it is believed that the heat resistance of the cured product is sufficiently high. In addition, when the weight average molecular weight of the polyphenylene ether compound is within this range, it is believed that the moldability is excellent because the molecular weight is relatively low. Therefore, it is believed that such a polyphenylene ether compound not only has excellent heat resistance, but also has excellent moldability.

The average number of the substituents (number of terminal functional groups) at the molecular ends per molecule of the polyphenylene ether compound is not particularly limited. Specifically, it is preferably 1 to 5, more preferably 1 to 3, and even more preferably 1.5 to 3. If the number of terminal functional groups is too small, it tends to be difficult to obtain a cured product with sufficient heat resistance. Furthermore, if the number of terminal functional groups is too large, the reactivity becomes too high, and there is a risk of problems occurring, such as a decrease in the storage stability of the resin composition or a decrease in the fluidity of the resin composition.

The number of terminal functional groups of a polyphenylene ether compound may be, for example, a numerical value representing the average number of the above-mentioned substituents per molecule of all modified polyphenylene ether compounds present in 1 mole of the polyphenylene ether compound. The number of terminal functional groups can be measured, for example, by measuring the number of hydroxyl groups remaining in the obtained modified polyphenylene ether compound and calculating the reduction from the number of hydroxyl groups of the polyphenylene ether before modification. This reduction from the number of hydroxyl groups of the polyphenylene ether before modification is the number of terminal functional groups. The number of hydroxyl groups remaining in the modified polyphenylene ether compound can be measured by adding a quaternary ammonium salt (tetraethylammonium hydroxide) that associates with hydroxyl groups to a solution of the modified polyphenylene ether compound and measuring the UV absorbance of the mixed solution.

Examples of the polyphenylene ether compound of this embodiment include a modified polyphenylene ether compound represented by the following formula (7) and a modified polyphenylene ether compound represented by the following formula (8). In addition, as the polyphenylene ether compound of this embodiment, these modified polyphenylene ether compounds may be used alone, or these two types of modified polyphenylene ether compounds may be used in combination.

In formula (7) and formula (8), R ₉ to R ₁₆ and R ₁₇ to R ₂₄ each independently represent a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, a formyl group, an alkylcarbonyl group, an alkenylcarbonyl group, or an alkynylcarbonyl group. X ₁ and X ₂ each independently represent a substituent having a carbon-carbon unsaturated double bond. A and B each represent a repeating unit represented by the following formula (9) and formula (10), respectively. In addition, in formula (8), Y represents a linear, branched, or cyclic hydrocarbon having 20 or less carbon atoms.

In formula (9) and formula (10), m and n each represent an integer of 0 to 20. R ₂₅ to R ₂₈ and R ₂₉ to R ₃₂ each independently represent a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, a formyl group, an alkylcarbonyl group, an alkenylcarbonyl group, or an alkynylcarbonyl group.

The modified polyphenylene ether compound represented by the formula (7) and the modified polyphenylene ether compound represented by the formula (8) are not particularly limited as long as they satisfy the above-mentioned constitution. Specifically, in the formula (7) and the formula (8), R ₉ to R ₁₆ and R ₁₇ to R ₂₄ are each independent as described above. That is, R ₉ to R ₁₆ and R ₁₇ to R ₂₄ may be the same group or different groups. In addition, R ₉ to R ₁₆ and R ₁₇ to R ₂₄ represent a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, a formyl group, an alkylcarbonyl group, an alkenylcarbonyl group, or an alkynylcarbonyl group. Among these, a hydrogen atom and an alkyl group are preferred.

In formula (9) and formula (10), m and n each preferably represent 0 to 20 as described above. Moreover, m and n each preferably represent a numerical value such that the sum of m and n is 1 to 30. Therefore, it is more preferable that m represents 0 to 20, n represents 0 to 20, and the sum of m and n represents 1 to 30. Moreover, R ₂₅ to R ₂₈ and R ₂₉ to R ₃₂ are each independent. That is, R 25 to R 28 and R ₂₉ to R ₃₂ may each be the same group or different groups. Moreover, R ₂₅ to R ₂₈ and _{R 29 to R 32 represent a} hydrogen atom, an alkyl group, an alkenyl _group , an alkynyl group, a formyl group, an alkylcarbonyl group, an alkenylcarbonyl group, or an alkynylcarbonyl group. Among these, a hydrogen atom and an alkyl group are preferable.

R ₉ to R ₃₂ are the same as R ₅ to R ₈ in the above formula (6).

In the formula (8), Y is, as described above, a linear, branched, or cyclic hydrocarbon having 20 or less carbon atoms. Examples of Y include a group represented by the following formula (11).

In the formula (11), R ₃₃ and R ₃₄ each independently represent a hydrogen atom or an alkyl group. Examples of the alkyl group include a methyl group. Examples of the group represented by the formula (11) include a methylene group, a methylmethylene group, and a dimethylmethylene group, and among these, a dimethylmethylene group is preferred.

In the formula (7) and the formula (8), X ₁ and X ₂ are each independently a substituent having a carbon-carbon unsaturated double bond. The substituents X ₁ and X ₂ are not particularly limited as long as they are a substituent having a carbon-carbon unsaturated double bond. Examples of the substituents X ₁ and X ₂ include the substituents represented by the formula (3) and the substituents represented by the formula (4). In the modified polyphenylene ether compound represented by the formula (7) and the modified polyphenylene ether compound represented by the formula (8), X ₁ and X ₂ may be the same or different substituents.

A more specific example of the modified polyphenylene ether compound represented by the formula (7) is, for example, a modified polyphenylene ether compound represented by the following formula (12).

More specific examples of the modified polyphenylene ether compound represented by formula (8) include the modified polyphenylene ether compound represented by formula (13) below and the modified polyphenylene ether compound represented by formula (14) below.

In the above formulas (12) to (14), m and n are the same as m and n in the above formulas (9) and (10). In addition, in the above formulas (12) and (13), R ₁ to R ₃ , p and Z are the same as R ₁ to R ₃ , s and Z in the above formula (3), respectively. In addition, in the above formulas (13) and (14), Y is the same as Y in the above formula (8). In addition, in the above formula (14), R ₄ is the same as R ₄ in the above formula (4).

By using the modified polyphenylene ether compounds described above, it is believed that it is possible to maintain low dielectric properties such as low dielectric tangent and excellent heat resistance, while also improving high Tg and adhesion.

The modified polyphenylene ether compounds can be used alone or in combination of two or more.

The polyphenylene ether compound used in the resin composition of this embodiment can be synthesized by a known method, or a commercially available product can be used. Examples of commercially available products include "OPE-2st 1200" and "OPE-2st 2200" manufactured by Mitsubishi Gas Chemical Company, Inc., and "SA9000" manufactured by SABIC Innovative Plastics.

Hydrocarbon-Based Compound Having a Reactive Unsaturated Group The hydrocarbon-based compound that can be used in the present embodiment is not particularly limited as long as it is a hydrocarbon-based compound having a reactive unsaturated group in the molecule. Preferred examples of the hydrocarbon-based compound include hydrocarbon resins such as polyfunctional vinyl aromatic polymers, cyclic polyolefin resins, and vinyl aromatic compound-conjugated diene compound copolymers.

The polyfunctional vinyl aromatic polymer is preferably a polymer containing at least a polyfunctional vinyl aromatic compound and/or a derivative thereof polymerized therein, and is not particularly limited as long as it is a polymer containing a structure derived from a polyfunctional vinyl aromatic compound and/or a derivative thereof, and may be a polymer containing one or more polyfunctional vinyl aromatic compounds and/or a structure derived from their derivatives.

In addition to the polyfunctional vinyl aromatic compound and/or its derivative structural unit, one or more structural units derived from a reactive monomer may be further included. The reactive monomer is not particularly limited, but may be, for example, a polyfunctional vinyl aromatic copolymer having a structural unit derived from a monovinyl aromatic compound such as styrene.

More specifically, examples of the polyfunctional vinyl compounds include those having two or more vinyl groups in the molecule. Further examples of the polyfunctional vinyl compounds include divinylbenzene, divinylnaphthalene, divinylbiphenyl, and polybutadiene.

Maleimide Compound The maleimide compound that can be used in this embodiment is not particularly limited as long as it has two or more maleimide groups in the molecule. Specifically, the maleimide compound includes a polyfunctional maleimide compound having two or more maleimide groups in the molecule, and a modified maleimide compound thereof. Examples of the modified maleimide compound include a modified maleimide compound in which a part of the molecule is modified with an amine compound, a modified maleimide compound in which a part of the molecule is modified with a silicone compound, and a modified maleimide compound in which a part of the molecule is modified with an amine compound and a silicone compound.

More specifically, examples of such compounds include maleimide compounds having two or more N-substituted maleimide groups in one molecule, maleimide compounds having an indane structure, maleimide compounds having at least one group selected from an alkyl group having 6 or more carbon atoms and an alkylene group having 6 or more carbon atoms, and maleimide compounds having a benzene ring in the molecule.

The maleimide compound used in this embodiment may be a commercially available product, such as MIR-3000 and MIR-5000 manufactured by Nippon Kayaku Co., Ltd.; BMI-4000, BMI-2300, BMI-TMH, BMI-4000, BMI-5100, etc. manufactured by Daiwa Kasei Kogyo Co., Ltd.; and BMI-689, BMI-1500, BMI-3000J, BMI-5000, etc. manufactured by Designer Molecules Inc.

・Other thermosetting compounds (hardeners)
The resin composition of the present embodiment may further contain a thermosetting compound other than the radically polymerizable compound (A1) as described above. In that case, the thermosetting compound is preferably a thermosetting compound that acts as a curing agent capable of reacting with the radically polymerizable compound as described above.

Specific examples of preferred thermosetting compounds include phenolic resins, benzoxazine compounds, styrene compounds, styrene derivatives, compounds having an acryloyl group in the molecule, compounds having a methacryloyl group in the molecule, compounds having a vinyl group in the molecule, compounds having an allyl group in the molecule, compounds having an acenaphthylene structure in the molecule, isocyanurate compounds having an isocyanurate group in the molecule, and monomaleimide compounds. These can be used alone, or the above-mentioned radical polymerizable compound (A1) can be used in combination with two or more types of curing agents.

As a benzoxazine compound, for example, a benzoxazine compound represented by the following general formula (15) can be used.

In formula (15), R ^a represents a k-valent group, and R ^b each independently represents a halogen atom, an alkyl group, or an aryl group, k represents an integer of 2 to 4, and l represents an integer of 0 to 4.

Commercially available products include "JBZ-OP100D" and "ODA-BOZ" manufactured by JFE Chemical Corporation; "P-d", "F-a", and "ALP-d" manufactured by Shikoku Chemical Industry Co., Ltd.; and "HFB2006M" manufactured by Showa Polymer Co., Ltd.

The styrene compound is not particularly limited as long as it has a styrene skeleton in the molecule, but a preferred example is a resin compound whose terminals are modified with a styrene skeleton.

Examples of the styrene derivatives include bromostyrene and dibromostyrene.

The compound having an acryloyl group in the molecule is an acrylate compound. Examples of the acrylate compound include monofunctional acrylate compounds having one acryloyl group in the molecule, and polyfunctional acrylate compounds having two or more acryloyl groups in the molecule. Examples of the monofunctional acrylate compounds include methyl acrylate, ethyl acrylate, propyl acrylate, and butyl acrylate. Examples of the polyfunctional acrylate compounds include tricyclodecane dimethanol diacrylate.

The compound having a methacryloyl group in the molecule is a methacrylate compound. Examples of the methacrylate compound include monofunctional methacrylate compounds having one methacryloyl group in the molecule, and polyfunctional methacrylate compounds having two or more methacryloyl groups in the molecule. Examples of the monofunctional methacrylate compounds include methyl methacrylate, ethyl methacrylate, propyl methacrylate, and butyl methacrylate. Examples of the polyfunctional methacrylate compounds include tricyclodecane dimethanol dimethacrylate.

The compound having a vinyl group in the molecule is a vinyl compound. Examples of the vinyl compound include a monofunctional vinyl compound (monovinyl compound) having one vinyl group in the molecule.

The compound having an allyl group in the molecule is an allyl compound. Examples of the allyl compound include monofunctional allyl compounds having one allyl group in the molecule, and polyfunctional allyl compounds having two or more allyl groups in the molecule. Examples of the polyfunctional allyl compounds include diallyl phthalate (DAP).

The compound having an acenaphthylene structure in the molecule is an acenaphthylene compound. Examples of the acenaphthylene compound include acenaphthylene, alkyl acenaphthylenes, halogenated acenaphthylenes, and phenyl acenaphthylenes. Examples of the alkyl acenaphthylenes include 1-methyl acenaphthylene, 3-methyl acenaphthylene, 4-methyl acenaphthylene, 5-methyl acenaphthylene, 1-ethyl acenaphthylene, 3-ethyl acenaphthylene, 4-ethyl acenaphthylene, and 5-ethyl acenaphthylene. Examples of the halogenated acenaphthylenes include 1-chloroacenaphthylene, 3-chloroacenaphthylene, 4-chloroacenaphthylene, 5-chloroacenaphthylene, 1-bromoacenaphthylene, 3-bromoacenaphthylene, 4-bromoacenaphthylene, and 5-bromoacenaphthylene. Examples of the phenylacenaphthylenes include 1-phenylacenaphthylene, 3-phenylacenaphthylene, 4-phenylacenaphthylene, and 5-phenylacenaphthylene. The acenaphthylene compound may be a monofunctional acenaphthylene compound having one acenaphthylene structure in the molecule as described above, or a polyfunctional acenaphthylene compound having two or more acenaphthylene structures in the molecule.

The compound having an isocyanurate group in the molecule is an isocyanurate compound. Examples of the isocyanurate compound include compounds further having an alkenyl group in the molecule (alkenyl isocyanurate compounds), such as triallyl isocyanurate (TAIC) and other trialkenyl isocyanurate compounds.

Among the above, it is preferable to use, for example, benzoxazine compounds, isocyanurate compounds having an isocyanurate group in the molecule, N-phenylmaleimide, and resin compounds whose ends are modified with a styrene skeleton.

The thermosetting compounds used as curing agents as described above may be used alone or in combination of two or more.

In the resin composition of this embodiment, the content of the thermosetting compound (A) is preferably 15 to 60 parts by mass, and more preferably 20 to 55 parts by mass, per 100 parts by mass of the total of the thermosetting compound (A) and the inorganic filler (B). If the content of the thermosetting compound (A) is within the above range, it is believed that a resin composition that can produce a cured product with low dielectric properties and high heat resistance can be more reliably obtained.

When the resin composition of this embodiment contains a thermosetting compound (which acts as a curing agent) in addition to the radically polymerizable compound (A1), the content ratio of the radically polymerizable compound (A1):other thermosetting compound is preferably about 95:5 to 50:50 by mass. If the content ratio is within this range, the resin composition will have better heat resistance in the cured product. This is thought to be because the curing reaction between the resin component of this embodiment and the curing agent proceeds smoothly.

(Inorganic Filler (B))
Boron nitride filler (B1)
The resin composition according to this embodiment further includes an inorganic filler (B) including a boron nitride filler (B1). The boron nitride filler is not particularly limited as long as it can be used as an inorganic filler contained in the resin composition. In this embodiment, as the boron nitride filler (B1), hexagonal boron nitride (h-BN) having a graphite-type layered structure, diamond-type cubic boron nitride (c-BN), and amorphous boron nitride (a-BN) can be used. h-BN is particularly useful because it can be synthesized relatively easily and has excellent thermal conductivity, electrical insulation, chemical stability, and heat resistance. In addition, boron nitride particles can be used as the boron nitride filler (B1). The boron nitride particles are usually white in color. The shape of the boron nitride particles is not particularly limited. The shape of the boron nitride particles may be, for example, scale-like, spherical, elliptical, rod-like, or the like.

The average particle size of the boron nitride particles is not particularly limited. The average particle size of the boron nitride particles may be, for example, 0.05 μm or more and 100 μm or less, or 0.1 μm or more and 50 μm or less. In this embodiment, the average particle size of the boron nitride particles means the median diameter. The median diameter means the particle size (d50) when the cumulative volume in the volume-based particle size distribution is equal to 50%. The volume-based particle size distribution is measured, for example, by a laser diffraction measuring device.

In this embodiment, polydopamine (C) having a functional group (X) that reacts with the radically polymerizable compound (A1) is attached to the surface of the boron nitride filler (B1). The polydopamine (C) may cover at least a portion of the surface of the boron nitride filler (B1). In this case, the polydopamine (C) may cover the entire surface of the boron nitride filler (B1), or may cover only a portion of the surface of the boron nitride filler (B1).

Polydopamine Polydopamine is a polymer of dopamine and may have a repeating unit represented by the following formula (16), for example: In the following formula (16), the indoline skeleton may be an indole skeleton.

In the above composition formula (16), n is an integer of 1 or more, particularly 2 or more.

As shown in formula (16) above, polydopamine may have an indoline skeleton and/or an indole skeleton. However, polydopamine may include those that are not completely cyclized. In other words, polydopamine may contain a mixture of primary and secondary amines. In addition, in formula (16), the 5,6-dihydroxyindoline structure may contain any of the quinone structures shown in the following structural formulas.

The polydopamine (C) of this embodiment is obtained by introducing a functional group (X) into such polydopamine. That is, the polydopamine (C) of this embodiment has a functional group (X) that reacts with the radical polymerizable compound (A1). By attaching the polydopamine (C) having the functional group (X) that reacts with the radical polymerizable compound (A1) to the boron nitride filler (B1), the adhesion between the radical polymerizable compound (A1) and the boron nitride filler (B1) is improved. As a result, peeling between the inorganic filler (B) and the thermosetting resin (A) can be suppressed, and the adhesion between the resin composition and metal foil or the like is improved. In addition, the functional group (X) derived from dopamine in the polydopamine (C) may be partially changed.

The polydopamine (C) may be in the form of a thin film on the surface of the boron nitride filler (B1). The thickness of the thin film of polydopamine (C) is, for example, 0.1 nm to 300 nm, and more preferably 0.1 nm to 100 nm. The thin film of polydopamine (C) may cover at least a portion of the surface of the boron nitride filler (B1), or may cover the entire surface of the boron nitride filler (B1).

The functional group (X) is not particularly limited as long as it reacts with the radical polymerizable compound (A1) and the thermosetting compound (which acts as a curing agent).

For example, it is preferable that the functional group (X) of the polydopamine (C) contains at least one selected from the group consisting of an epoxy group, a phenylamino group, a vinyl group, an acrylic group, a methacrylic group, an allyl group, a styrene structure, and a maleimide group.

In this specification, the term "styrene structure" refers to the structure shown in the following formula (S).

- Manufacturing method of boron nitride filler (B1) having attached thereto polydopamine (C) having a functional group (X) that reacts with radical polymerizable compound (A1) The boron nitride filler (B1) of this embodiment can be obtained by, for example, attaching polydopamine to the surface of the boron nitride filler and then introducing a functional group (X) to the attached polydopamine to obtain a boron nitride filler (B1) having attached thereto polydopamine (C) having a functional group (X). Note that, before introducing the functional group (X) to the polydopamine, the boron nitride filler having attached thereto polydopamine may be heat-treated.

The method for attaching polydopamine to the surface of the boron nitride filler is not particularly limited, and polydopamine can be attached to the surface of the boron nitride filler by contacting the boron nitride filler with a dopamine solution and oxidizing and polymerizing the dopamine.

The dopamine solution can be obtained, for example, by adding dopamine hydrochloride to a Tris-HCl solution whose pH has been adjusted to 8.5, and stirring the mixture. There is no particular limit to the concentration of the dopamine solution, and it is, for example, in the range of 0.01 mg/mL to 30 mg/mL. The pH of the dopamine solution is in the range of pH 6 to pH 11, and may be in the range of pH 8 to pH 10. The pH of the dopamine solution can be adjusted by mixing with a Tris-HCl solution or the like. The temperature of the dopamine solution during oxidative polymerization is, for example, 10°C to 100°C. The polymerization time is, for example, 1 hour to 48 hours.

In addition, when at least a portion of the surface of the boron nitride filler is coated to form a polydopamine layer (a thin film of polydopamine), the maximum thickness of the polydopamine layer is preferably, for example, 0.1 nm or more and 100 nm or less. This has the advantage of being able to increase adhesion to the thermosetting resin while maintaining the low dielectric tangent of boron nitride. The thickness of the polydopamine layer can be controlled by the polymerization time.

After attaching polydopamine to the surface, the boron nitride filler may be heat-treated. This will result in a polydopamine film with even higher purity. There are no particular limitations on the method of heat treatment. Heat treatment can be carried out using known heat treatment devices such as a sintering device, electric furnace, or hot plate. In particular, it is desirable to carry out the heat treatment using a sintering device or electric furnace, as this makes it easy to control the temperature.

The heat treatment can be carried out by heating the ambient temperature of the boron nitride filler to a range of 100°C to 400°C. The heating time is, for example, 1 hour to 48 hours.

Then, a functional group (X) is introduced into the polydopamine attached to the surface of the boron nitride filler. As a result, a polydopamine layer is formed by polydopamine (C). The introduction of the functional group (X) is not particularly limited, but can be carried out, for example, by acylation treatment or treatment with a silane coupling agent.

The acylation treatment of polydopamine (C) can introduce functional groups (X) by reacting polydopamine with an acylating agent in the presence of a catalyst to acylate at least a portion of the hydroxyl groups of polydopamine.

The acylating agent is not particularly limited as long as it is capable of reacting with polar functional groups such as hydroxyl groups contained in polydopamine to acylate them. The acylating agent may be an acid anhydride. Examples of known acylating agents include carboxylic acid anhydrides. More specifically, examples of such agents include methacrylic acid anhydride, acetic anhydride, benzoic acid anhydride, and propanoic acid anhydride. The acid anhydride may include at least one selected from the group consisting of methacrylic acid anhydride, acrylic acid anhydride, acetic anhydride, and benzoic acid anhydride. When the acylating agent has a double bond at the end, this double bond reacts with the reactive residue of the resin of the insulating layer to form a bond, thereby improving the adhesion between the thermosetting compound (A) and the inorganic filler (B). From this perspective, the acylating agent is preferably methacrylic acid anhydride or acetic anhydride.

In addition to the above-mentioned acylation treatment, functional groups (X) can be introduced into polydopamine (C) by treating it with a silane coupling agent having various functional groups.

Examples of silane coupling agents include methacryl silane coupling agents, vinyl silane coupling agents, styryl silane coupling agents, acrylic silane coupling agents, phenylamino silane coupling agents, epoxy silane coupling agents, maleimide silane coupling agents, etc. The method of treatment with a silane coupling agent is not particularly limited, but for example, polydopamine (C) in which at least a portion of the hydroxyl groups contained in the polydopamine are substituted with the functional group (X) as described above can be obtained by mixing the boron nitride filler to which polydopamine is attached in an aqueous solution containing a silane coupling agent having a functional group (X) and then drying.

When the above-mentioned acylation treatment or the treatment of introducing the functional group (X) using the above-mentioned silane coupling agent is performed, the polydopamine (C) of this embodiment may further have at least one structure selected from the structures represented by the following formula (1) and the following formula (2).

It is believed that having such a structure has the advantage that the bond between the cured thermosetting resin (A) and the boron nitride filler to which the polydopamine film (C) is attached is stronger.

Other Inorganic Fillers The resin composition of the present embodiment may contain only the boron nitride filler (B1) as the inorganic filler (B), or may contain an inorganic filler other than the boron nitride filler (B1).

The inorganic filler other than the boron nitride filler (B1) is not particularly limited as long as it can be used as an inorganic filler contained in the resin composition. For example, boron nitride filler other than the boron nitride filler (B1), silica filler, alumina filler, titanium oxide filler, metal oxide filler such as magnesium oxide and mica, aluminum hydroxide filler, metal hydroxide filler such as magnesium hydroxide, talc filler, aluminum borate filler, barium sulfate filler, aluminum nitride filler, silicon nitride filler, magnesium carbonate filler such as anhydrous magnesium carbonate, and calcium carbonate filler. Among these, preferred inorganic fillers other than the boron nitride filler (B1) include silica filler, anhydrous magnesium carbonate filler, alumina filler, silicon nitride filler, boron nitride filler with no dopamine attached to the surface, and the like. The silica filler is not particularly limited, and examples thereof include crushed silica filler and silica particle filler, and silica particle filler is preferred. The magnesium carbonate filler is not particularly limited, but anhydrous magnesium carbonate (synthetic magnesite) filler is preferred.

The inorganic filler other than the boron nitride filler (B1) may be a surface-treated inorganic filler or an inorganic filler that has not been surface-treated. In addition, examples of the surface treatment include treatment with a silane coupling agent.

The content of the inorganic filler (B) is preferably 40 to 85 parts by weight per 100 parts by weight of the total of the thermosetting compound (A) and the inorganic filler (B). More preferably, it is 40 to 80 parts by weight. The content of the boron nitride filler (B1) in the inorganic filler (B) is preferably 10 to 90 mass% and more preferably 10 to 70 mass% with respect to the total amount of the inorganic filler (B). It is believed that having the content of the boron nitride filler (B1) in the above range has the advantage of ensuring high thermal conductivity and adhesion.

(Silane coupling agent)
The resin composition of the present embodiment may further contain a silane coupling agent, which is believed to more reliably substitute the hydroxyl groups in the polydopamine (C) with the functional groups (X), thereby further improving the adhesion between the resin component and boron nitride.

The silane coupling agent may, for example, be a silane coupling agent having at least one functional group selected from the group consisting of a vinyl group, a styryl group, a methacryloyl group, an acryloyl group, and a phenylamino group. In other words, the silane coupling agent may be a compound having at least one of a vinyl group, a styryl group, a methacryloyl group, an acryloyl group, and a phenylamino group as a reactive functional group, and further having a hydrolyzable group such as a methoxy group or an ethoxy group.

The silane coupling agent has a vinyl group, and examples thereof include vinyltriethoxysilane and vinyltrimethoxysilane. The silane coupling agent has a styryl group, and examples thereof include p-styryltrimethoxysilane and p-styryltriethoxysilane, which have a styrene structure represented by the above formula (S). The silane coupling agent has a methacryloyl group, and examples thereof include 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, and 3-methacryloxypropylethyldiethoxysilane. The silane coupling agent has an acryloyl group, and examples thereof include 3-acryloxypropyltrimethoxysilane and 3-acryloxypropyltriethoxysilane. Examples of the silane coupling agent that has a phenylamino group include N-phenyl-3-aminopropyltrimethoxysilane and N-phenyl-3-aminopropyltriethoxysilane.

When the resin composition of this embodiment contains a silane coupling agent, the content is preferably about 0.1 to 10 parts by mass per 100 parts by mass of the thermosetting compound (A).

(Reaction initiator)
The resin composition of the present embodiment may further contain a reaction initiator. The radical polymerization (curing) reaction of the resin composition may proceed even without a reaction initiator. However, depending on the process conditions, it may be difficult to raise the temperature to a level where curing proceeds, so a reaction initiator may be added.

The reaction initiator is not particularly limited as long as it can accelerate the curing reaction of the resin composition. Specific examples include metal oxides, azo compounds, and peroxides, and preferably includes at least one of peroxides and azo compounds.

Specific examples of metal oxides include metal carboxylates.

Organic peroxides include α,α'-di(t-butylperoxy)diisopropylbenzene, 2,5-dimethyl-2,5-di(t-butylperoxy)-3-hexyne, benzoyl peroxide, 3,3',5,5'-tetramethyl-1,4-diphenoquinone, chloranil, 2,4,6-tri-t-butylphenoxyl, t-butylperoxyisopropyl monocarbonate, azobisisobutyronitrile, etc.

Specific examples of azo compounds include 2,2'-azobis(2,4,4-trimethylpentane), 2,2'-azobis(N-butyl-2-methylpropionamide), and 2,2'-azobis(2-methylbutyronitrile).

The above-mentioned reaction initiators may be used alone or in combination of two or more.

When the resin composition of this embodiment contains the reaction initiator, its content is not particularly limited, but for example, it is preferably 0.1 to 5.0 parts by mass, more preferably 0.5 to 3.0 parts by mass, and even more preferably 0.5 to 2.0 parts by mass, relative to 100 parts by mass of the thermosetting compound (A).

(Other ingredients)
The resin composition according to the present embodiment may contain components other than the above-mentioned components (other components) as necessary within a range that does not impair the effects of the present invention. The other components contained in the resin composition according to the present embodiment may further contain additives such as, for example, a flame retardant, an antifoaming agent, an antioxidant, a heat stabilizer, an antistatic agent, an ultraviolet absorber, a dye or pigment, a dispersant, and a lubricant.

(Production method)
The method for producing the resin composition of the present embodiment is not particularly limited, and examples thereof include a method in which the thermosetting compound (A) is mixed with other organic components as necessary, and then the inorganic filler (B) is added, etc. Specifically, in the case of obtaining a varnish-like composition containing an organic solvent, the method described in the description of the prepreg described later can be used.

In addition, by using the resin composition according to this embodiment, it is possible to obtain prepregs, metal-clad laminates, wiring boards, metal foils with resin, and films with resin, as described below.

The cured product of the resin composition preferably has a thermal conductivity of 1.0 W/m·K or more and a dielectric loss tangent of 0.003 or less at a frequency of 10 GHz. By using the resin composition of this embodiment in this way, it is possible to achieve both high thermal conductivity and low dielectric properties in the cured product, and excellent adhesion can also be obtained. There is no particular upper limit to the thermal conductivity, but from the viewpoint of the filling ability of the inorganic filler in the resin composition, it is preferable that it is 50 W/m·K or less.

[Prepreg]
1 is a schematic cross-sectional view showing an example of a prepreg 1 according to an embodiment of the present invention. In the following description, each reference symbol indicates the following: 1 prepreg, 2 resin composition or semi-cured resin composition, 3 fibrous base material, 11 metal-clad laminate, 12 insulating layer, 13 metal foil, 14 wiring, 21 wiring board, 31 resin-attached metal foil, 32, 42 resin layer, 41 resin-attached film, 43 support film.

As shown in Figure 1, the prepreg 1 according to this embodiment comprises the resin composition or a semi-cured product of the resin composition 2, and a fibrous base material 3. This prepreg 1 comprises the resin composition or a semi-cured product of the resin composition 2, and the fibrous base material 3 present in the resin composition or the semi-cured product of the resin composition 2.

In this embodiment, the semi-cured product refers to a resin composition that has been partially cured to the extent that it can be further cured. In other words, the semi-cured product is a resin composition that has been semi-cured (B-staged). For example, when the resin composition is heated, the viscosity first gradually decreases, and then curing begins, and then curing begins and the viscosity gradually increases. In such a case, the semi-cured product can be described as the state between when the viscosity starts to increase and when it is completely cured.

The prepreg obtained using the resin composition according to this embodiment may comprise a semi-cured product of the resin composition as described above, or may comprise the uncured resin composition itself. That is, it may be a prepreg comprising a semi-cured product of the resin composition (the resin composition in B stage) and a fibrous base material, or a prepreg comprising the resin composition before curing (the resin composition in A stage) and a fibrous base material. The resin composition or the semi-cured product of the resin composition may be the resin composition that has been dried or heat-dried.

When manufacturing prepregs, the resin composition 2 is often prepared in a varnish form and used to impregnate the fibrous base material 3, which is the base material for forming the prepreg. In other words, the resin composition 2 is usually often a resin varnish prepared in a varnish form. Such a varnish-like resin composition (resin varnish) is prepared, for example, as follows.

First, each component of the resin composition that is soluble in an organic solvent is added to the organic solvent and dissolved. Heating may be performed if necessary. Then, components that are not soluble in the organic solvent (e.g., inorganic fillers, etc.) are added as necessary, and the varnish-like resin composition is prepared by dispersing the components until a predetermined dispersion state is reached using a ball mill, bead mill, planetary mixer, roll mill, etc. The organic solvent used here is not particularly limited as long as it dissolves the modified polyphenylene ether compound and the curing agent, etc., and does not inhibit the curing reaction. Specific examples include toluene and methyl ethyl ketone (MEK).

The method for producing the prepreg is not particularly limited as long as it is capable of producing the prepreg. Specifically, when producing the prepreg, the resin composition used in the present embodiment described above is often prepared in a varnish form and used as a resin varnish, as described above.

Specific examples of the fibrous substrate include glass cloth, aramid cloth, polyester cloth, glass nonwoven fabric, aramid nonwoven fabric, polyester nonwoven fabric, pulp paper, and linter paper. When glass cloth is used, a laminate with excellent mechanical strength is obtained, and flattened glass cloth is particularly preferable. A specific example of the flattening process is a method in which glass cloth is continuously pressed with a press roll at an appropriate pressure to compress the yarns flat. The thickness of the fibrous substrate that is generally used is, for example, 0.01 mm or more and 0.3 mm or less.

The method for producing the prepreg is not particularly limited as long as it is capable of producing the prepreg. Specifically, when producing the prepreg, the resin composition according to the present embodiment described above is often prepared in a varnish form as described above and used as a resin varnish.

The method of manufacturing the prepreg 1 includes, for example, a method of impregnating the fibrous base material 3 with the resin composition 2, for example, a resin composition 2 prepared in a varnish form, and then drying the resin composition 2. The resin composition 2 is impregnated into the fibrous base material 3 by immersion, coating, or the like. Impregnation can be repeated multiple times as necessary. In this case, it is also possible to adjust the composition and impregnation amount to the final desired one by repeating the impregnation using multiple resin compositions with different compositions and concentrations.

The fibrous substrate 3 impregnated with the resin composition (resin varnish) 2 is heated under the desired heating conditions, for example, at 80°C to 180°C for 1 minute to 10 minutes. By heating, a prepreg 1 in an uncured (A stage) or semi-cured (B stage) state is obtained. The heating can also volatilize the organic solvent from the resin varnish, thereby reducing or removing the organic solvent.

The prepreg comprising the resin composition according to this embodiment or a semi-cured product of this resin composition is a prepreg that can suitably produce a cured product with low dielectric properties, high thermal conductivity, and excellent adhesion.

[Metal-clad laminate]
FIG. 2 is a schematic cross-sectional view showing an example of a metal-clad laminate 11 according to an embodiment of the present invention.

As shown in FIG. 2, the metal-clad laminate 11 is composed of an insulating layer 12 containing the cured product of the prepreg 1 shown in FIG. 1, and a metal foil 13 laminated together with the insulating layer 12. That is, the metal-clad laminate 11 has an insulating layer 12 containing a cured product of a resin composition, and a metal foil 13 provided on the insulating layer 12. The insulating layer 12 may be made of the cured product of the resin composition, or may be made of the cured product of the prepreg. The thickness of the metal foil 13 varies depending on the performance required for the final wiring board, and is not particularly limited. The thickness of the metal foil 13 can be appropriately set depending on the desired purpose, and is preferably, for example, 0.2 to 70 μm. Examples of the metal foil 13 include copper foil and aluminum foil, and when the metal foil is thin, it may be a carrier-attached copper foil having a release layer and a carrier to improve handling.

The method for producing the metal-clad laminate 11 is not particularly limited as long as the metal-clad laminate 11 can be produced. Specifically, a method for producing the metal-clad laminate 11 using the prepreg 1 can be mentioned. This method includes a method in which one or more prepregs 1 are stacked, and then a metal foil 13 such as copper foil is stacked on both sides or one side of the prepreg 1, and the metal foil 13 and the prepreg 1 are heated and pressurized to laminate and integrate them, thereby producing a laminate 11 with metal foil on both sides or one side. That is, the metal-clad laminate 11 is obtained by stacking the metal foil 13 on the prepreg 1 and heating and pressurizing it. In addition, the heating and pressurizing conditions can be appropriately set depending on the thickness of the metal-clad laminate 11 to be produced and the type of composition of the prepreg 1. For example, the temperature can be 170 to 230°C, the pressure can be 3 to 4 MPa, and the time can be 60 to 150 minutes. The metal-clad laminate may also be produced without using a prepreg. For example, a method is used in which a varnish-like resin composition is applied onto a metal foil, a layer containing the resin composition is formed on the metal foil, and then the layer is heated and pressurized.

The metal-clad laminate having an insulating layer containing the cured product of the resin composition according to this embodiment is a metal-clad laminate having an insulating layer that has low dielectric properties, high thermal conductivity, and excellent adhesion to the metal foil.

[Wiring board]
FIG. 3 is a schematic cross-sectional view showing an example of a wiring board 21 according to an embodiment of the present invention.

As shown in FIG. 3, the wiring board 21 according to this embodiment is composed of an insulating layer 12 used by curing the prepreg 1 shown in FIG. 1, and wiring 14 laminated together with the insulating layer 12 and formed by partially removing the metal foil 13. That is, the wiring board 21 has an insulating layer 12 containing a cured product of a resin composition, and wiring 14 provided on the insulating layer 12. Furthermore, the insulating layer 12 may be made of a cured product of the resin composition, or may be made of a cured product of the prepreg.

The method for manufacturing the wiring board 21 is not particularly limited as long as the wiring board 21 can be manufactured. Specifically, a method for manufacturing the wiring board 21 using the prepreg 1 can be mentioned. For example, the method includes a method for manufacturing the wiring board 21 in which wiring is provided as a circuit on the surface of the insulating layer 12 by etching the metal foil 13 on the surface of the metal-clad laminate 11 manufactured as described above. That is, the wiring board 21 is obtained by forming a circuit by partially removing the metal foil 13 on the surface of the metal-clad laminate 11. In addition to the above methods, other methods for forming a circuit include, for example, a semi-additive process (SAP) or a modified semi-additive process (MSAP). The wiring board 21 has an insulating layer 12 that has low dielectric properties, high heat resistance, and can favorably maintain its low dielectric properties even after water absorption treatment.

Such a wiring board has an insulating layer that has low dielectric properties, high thermal conductivity, and excellent adhesion to the metal foil.

[Metal foil with resin]
FIG. 4 is a schematic cross-sectional view showing an example of a resin-coated metal foil 31 according to the present embodiment.

As shown in FIG. 4, the resin-coated metal foil 31 according to this embodiment comprises a resin layer 32 containing the resin composition or a semi-cured product of the resin composition, and a metal foil 13. This resin-coated metal foil 31 has the metal foil 13 on the surface of the resin layer 32. That is, this resin-coated metal foil 31 comprises the resin layer 32 and the metal foil 13 laminated together with the resin layer 32. The resin-coated metal foil 31 may also comprise another layer between the resin layer 32 and the metal foil 13.

The resin layer 32 may contain the semi-cured product of the resin composition as described above, or may contain the uncured resin composition. That is, the resin-attached metal foil 31 may include a resin layer containing the semi-cured product of the resin composition (the resin composition in the B stage) and a metal foil, or may be a resin-attached metal foil including a resin layer containing the resin composition before curing (the resin composition in the A stage) and a metal foil. The resin layer may contain the resin composition or the semi-cured product of the resin composition, and may or may not contain a fibrous substrate. The resin composition or the semi-cured product of the resin composition may be the resin composition that has been dried or heated. The fibrous substrate may be the same as the fibrous substrate of the prepreg.

The metal foil may be any metal foil used in metal-clad laminates, without any limitations. Examples of metal foil include copper foil and aluminum foil.

The resin-coated metal foil 31 and the resin-coated film 41 may be provided with a cover film or the like as necessary. By providing a cover film, it is possible to prevent the inclusion of foreign matter. The cover film is not particularly limited, but examples thereof include polyolefin film, polyester film, polymethylpentene film, and films formed by providing a release agent layer on these films.

The method for producing the resin-coated metal foil 31 is not particularly limited as long as the resin-coated metal foil 31 can be produced. Examples of the method for producing the resin-coated metal foil 31 include a method in which the varnish-like resin composition (resin varnish) is applied to the metal foil 13 and heated. The varnish-like resin composition is applied to the metal foil 13, for example, by using a bar coater. The applied resin composition is heated, for example, under conditions of 80° C. or higher and 180° C. or lower, and 1 minute or longer and 10 minutes or shorter. The heated resin composition is formed on the metal foil 13 as an uncured resin layer 32. The organic solvent can be volatilized from the resin varnish by the heating, thereby reducing or removing the organic solvent.

The resin-coated metal foil having a resin layer containing the resin composition according to this embodiment or a semi-cured product of this resin composition is a resin-coated metal foil that is suitable for producing a cured product that has low dielectric properties, high thermal conductivity, and excellent adhesion to the metal foil.

[Resin-coated film]
FIG. 5 is a schematic cross-sectional view showing an example of a resin-attached film 41 according to the present embodiment.

As shown in FIG. 5, the resin-attached film 41 according to this embodiment includes a resin layer 42 containing the resin composition or a semi-cured product of the resin composition, and a support film 43. This resin-attached film 41 includes the resin layer 42 and a support film 43 laminated together with the resin layer 42. The resin-attached film 41 may also include other layers between the resin layer 42 and the support film 43.

The resin layer 42 may contain the semi-cured product of the resin composition as described above, or may contain the uncured resin composition. That is, the resin-attached film 41 may include a resin layer containing the semi-cured product of the resin composition (the resin composition in the B stage) and a support film, or may be a resin-attached film including a resin layer containing the resin composition before curing (the resin composition in the A stage) and a support film. The resin layer may contain the resin composition or the semi-cured product of the resin composition, and may or may not contain a fibrous substrate. The resin composition or the semi-cured product of the resin composition may be the resin composition that has been dried or heated. The fibrous substrate may be the same as the fibrous substrate of the prepreg.

Furthermore, as the support film 43, any support film used for a resin-coated film can be used without any restrictions. Examples of the support film include electrically insulating films such as polyester film, polyethylene terephthalate (PET) film, polyimide film, polyparabanic acid film, polyether ether ketone film, polyphenylene sulfide film, polyamide film, polycarbonate film, and polyarylate film.

The resin-coated film 41 may be provided with a cover film or the like as necessary. By providing a cover film, it is possible to prevent the intrusion of foreign matter. The cover film is not particularly limited, but examples thereof include polyolefin film, polyester film, and polymethylpentene film.

The support film and cover film may be subjected to surface treatments such as matte treatment, corona treatment, release treatment, and roughening treatment, as necessary.

The method for producing the resin-attached film 41 is not particularly limited as long as the resin-attached film 41 can be produced. Examples of the method for producing the resin-attached film 41 include a method in which the varnish-like resin composition (resin varnish) is applied to the support film 43 and heated. The varnish-like resin composition is applied to the support film 43 by using a bar coater, for example. The applied resin composition is heated, for example, at 80° C. or higher and 180° C. or lower, for 1 minute or longer and 10 minutes or shorter. The heated resin composition is formed on the support film 43 as an uncured resin layer 42. The organic solvent can be volatilized from the resin varnish by the heating, thereby reducing or removing the organic solvent.

The resin-attached film having a resin layer containing the resin composition according to this embodiment or a semi-cured product of this resin composition is a resin-attached film that can suitably produce a cured product with low dielectric properties, high thermal conductivity, and excellent adhesion.

This specification discloses various aspects of the technology as described above, but the main technologies are summarized below.

The resin composition according to the first aspect of the present invention is a resin composition containing a thermosetting compound (A) and an inorganic filler (B), characterized in that the thermosetting compound (A) contains at least one radically polymerizable compound (A1) selected from the group consisting of polyphenylene ether compounds having reactive unsaturated groups, hydrocarbon compounds having reactive unsaturated groups, and maleimide compounds having two or more maleimide groups, the inorganic filler (B) contains a boron nitride filler (B1), and polydopamine (C) having a functional group (X) that reacts with the radically polymerizable compound (A1) is attached to the surface of the boron nitride filler (B1).

The resin composition according to the second embodiment is the resin composition according to the first embodiment, wherein the functional group (X) contains at least one selected from the group consisting of an epoxy group, a phenylamino group, a vinyl group, an acrylic group, a methacrylic group, an allyl group, a styrene structure, and a maleimide group.

The resin composition according to the third aspect is the second resin composition, in which the polydopamine (C) further has at least one structure selected from the structures represented by the above formula (1) and the above formula (2).

The resin composition according to the fourth aspect is the resin composition according to any one of the first to third aspects, in which the polydopamine (C) forms a polydopamine layer on the surface of the boron nitride filler (B1), and the maximum thickness of the dopamine layer is 0.1 nm or more and 100 nm or less.

The resin composition according to the fifth aspect is a resin composition according to any one of the first to fourth aspects, in which the thermal conductivity of the cured product of the resin composition is 1 W/mK or more and 50 W/mK or less.

The resin composition according to the sixth aspect is the resin composition according to any one of the first to fifth aspects, in which the content of the inorganic filler (B) is 40 to 85 parts by weight per 100 parts by weight of the total of the thermosetting compound (A) and the inorganic filler (B).

The resin composition according to the seventh aspect is the resin composition according to any one of the first to sixth aspects, in which the content of the boron nitride filler (B1) is 10 to 90 mass% relative to the inorganic filler (B).

The resin composition according to the eighth aspect is the resin composition according to any one of the first to seventh aspects, further comprising a silane coupling agent.

The prepreg according to the ninth aspect of the present invention is characterized by comprising the resin composition according to any one of the first to eighth aspects or a semi-cured product of the resin composition, and a fibrous base material.

The resin-coated film according to the tenth aspect of the present invention is characterized by comprising a resin layer containing the resin composition according to any one of the first to eighth aspects or a semi-cured product of the resin composition, and a support film.

The resin-coated metal foil according to the eleventh aspect of the present invention is characterized by comprising a resin layer containing the resin composition according to any one of the first to eighth aspects or a semi-cured product of the resin composition, and a metal foil.

The metal-clad laminate according to the twelfth aspect of the present invention is characterized by comprising an insulating layer containing a cured product of the resin composition according to any one of the first to eighth aspects or a cured product of the prepreg according to the ninth aspect, and a metal foil.

The wiring board according to the thirteenth aspect of the present invention is characterized by having an insulating layer containing a cured product of the resin composition according to any one of the first to eighth aspects or a cured product of the prepreg according to the ninth aspect, and wiring.

The present invention will be explained in more detail below with reference to examples, but the scope of the present invention is not limited to these examples.

In this example, we will explain each component used in preparing the resin composition.

(Radically polymerizable compound (A1))
Modified polyphenylene ether compound (modified PPE): polyphenylene ether compound having a methacryloyl group at the end ("SA9000" manufactured by SABIC Innovative Plastics, weight average molecular weight Mw 2000, number of terminal functional groups 2)
Hydrocarbon compound: Polybutadiene (Cray Valley Corporation's "Ricon (registered trademark)")
Maleimide compound: bismaleimide ("MIR-5000" manufactured by Nippon Kayaku Co., Ltd.)

(Other thermosetting compounds)
Curing agent 1: Triallyl isocyanurate (TAIC manufactured by Nippon Kasei Chemical Industry Co., Ltd.)
Hardener 2: Benzoxazine compound ("P-d" manufactured by Shikoku Chemical Industry Co., Ltd.)
Other thermosetting compounds: Unmodified polyphenylene ether compounds (SA90 manufactured by SABIC Innovative Plastics)

(Reaction initiator)
Peroxide initiator: PBP (1,3-bis(butylperoxyisopropyl)benzene; Perbutyl P manufactured by NOF Corporation)

(Inorganic filler)
Untreated boron nitride filler (BN): h-BN ("SGP" manufactured by Denka Co., Ltd. (average particle size: 18 μm)
・Silica filler: "FB-7SDC" manufactured by Denka Co., Ltd.
Alumina filler: "DAW-03AC" manufactured by Denka Co., Ltd.

Surface-treated boron nitride filler 1: Polydopamine-treated boron nitride filler (no functional groups)
As boron nitride (BN), h-BN (manufactured by Denka, "SGP") was used. Dopamine hydrochloride was added to a Tris-HCl solution whose pH had been adjusted to 8.5, and the mixture was stirred to obtain a dopamine solution (concentration: 23 mg/mL). 4.5 g of the boron nitride was added to the obtained dopamine solution. The solution temperature was set to 80°C, and the mixture was stirred with a magnetic stirrer for 1 hour. Thereafter, a solid was obtained by filtration. The obtained solid was washed with water and then dried. In this way, boron nitride particles having polydopamine attached thereto were obtained. Next, the obtained particles were heat-treated in an electric furnace at 200°C for 24 hours to obtain a polydopamine-treated boron nitride filler (surface-treated boron nitride filler 1, no functional group). The thickness of the polydopamine layer was 2 nm.

The thickness of the polydopamine layer was measured using X-ray photoelectron spectroscopy (XPS). Specifically, XPS was used to detect the amounts of B, C, N, and O in the boron nitride in the depth direction from the surface, and areas where the amounts of C and O derived from the polydopamine film were increased compared to untreated boron nitride were identified, and these areas were defined as the polydopamine layer and measurements were carried out.

(Boron nitride filler (B1))
Surface-treated boron nitride filler 2: Polydopamine (C)-treated boron nitride filler (functional group (X): methacryl group)
50 mL of a methacrylsilane coupling agent ("KBM-503" manufactured by Shin-Etsu Chemical Co., Ltd.) was added to 1 L of toluene. 300 g of the surface-treated boron nitride filler 1 was added thereto. The liquid temperature was adjusted to 100°C in a heated oil bath, and the mixture was stirred at 500 rpm for 3 hours. The resulting solid was then cooled in toluene, filtered, washed with toluene, and dried to obtain surface-treated boron nitride filler 2 (containing methacryl groups).

Surface-treated boron nitride filler 3: Polydopamine (C)-treated boron nitride filler (functional group (X): vinyl group)
Surface-treated boron nitride filler 3 (containing vinyl groups) was obtained in the same manner as for surface-treated boron nitride filler 2, except that the methacryl silane coupling agent (manufactured by Shin-Etsu Chemical Co., Ltd., "KBM-503") was changed to a vinyl silane coupling agent (manufactured by Shin-Etsu Chemical Co., Ltd., "KBM-1003").

Surface-treated boron nitride filler 4: Polydopamine (C)-treated boron nitride filler (functional group (X): styrene structure)
Surface-treated boron nitride filler 4 (containing a styrene structure) was obtained in the same manner as for surface-treated boron nitride filler 2, except that the methacryl silane coupling agent ("KBM-503" manufactured by Shin-Etsu Chemical Co., Ltd.) was changed to a styryl silane coupling agent ("KBM-1403" manufactured by Shin-Etsu Chemical Co., Ltd.).

Surface-treated boron nitride filler 5: Polydopamine (C)-treated boron nitride filler (functional group (X): acrylic group)
Surface-treated boron nitride filler 5 (containing acrylic groups) was obtained in the same manner as for surface-treated boron nitride filler 2, except that the methacryl silane coupling agent ("KBM-503" manufactured by Shin-Etsu Chemical Co., Ltd.) was changed to an acrylic silane coupling agent ("KBM-5103" manufactured by Shin-Etsu Chemical Co., Ltd.).

Surface-treated boron nitride filler 6: Polydopamine (C)-treated boron nitride filler (functional group (X): methacryl group)
Surface-treated boron nitride filler 6 (containing methacrylic groups, dopamine layer thickness 20 nm) was obtained in the same manner as for surface-treated boron nitride filler 2, except that the stirring time using a magnetic stirrer after adding boron nitride to the dopamine solution was changed from 1 hour to 4 hours.

Surface-treated boron nitride filler 7: Polydopamine (C)-treated boron nitride filler (functional group (X): methacryl group)
Surface-treated boron nitride filler 7 (containing methacryl groups, dopamine layer thickness 100 nm) was obtained in the same manner as for surface-treated boron nitride filler 2, except that the stirring time using a magnetic stirrer after adding boron nitride to the dopamine solution was changed from 1 hour to 12 hours.

Surface-treated boron nitride filler 8: Polydopamine (C)-treated boron nitride filler (acylated)
2.0 g of the surface-treated boron nitride filler 1 was added to 20 ml of deionized water, and 0.1 g of DMAP was added as a catalyst to dissolve it. Next, 2 ml of methacrylic anhydride was added as an acylating agent to obtain a mixed solution. The temperature of the mixed solution was set to 25°C, and the mixture was stirred for 24 hours using a magnetic stirrer. The mixed solution was then filtered to obtain a solid. The obtained solid was washed with toluene and then dried. This resulted in a surface-treated boron nitride filler 8 (acylated, containing methacrylic groups, dopamine layer thickness 2 nm) (a boron nitride filler to which polydopamine having a structure represented by formula (1) was attached).

(Silane coupling agent)
- Methacrylic silane coupling agent ("KBM-503" manufactured by Shin-Etsu Chemical Co., Ltd.)

[Examples 1 to 20 and Comparative Examples 1 to 4]
(Preparation Method)
First, each organic resin component other than the inorganic filler was added to toluene as a solvent and mixed in the composition (parts by mass) shown in Tables 1 and 2 so that the solid content concentration was about 40 to 80 mass%. The mixture was stirred for 60 minutes. Thereafter, each inorganic filler and coupling agent was added to the obtained liquid in the formulation (parts by mass) shown in Tables 1 and 2, and the inorganic filler was dispersed using a bead mill. By doing so, a varnish-like resin composition (varnish) was obtained.

Next, an evaluation board (cured prepreg) was obtained as follows.

The resulting varnish was impregnated into a fibrous substrate (glass cloth: Asahi Kasei Corporation's #1078 type, L glass), which was then heated and dried at 110°C for 3 minutes to produce prepregs. One, two, or four of the resulting prepregs were then stacked on top of each other, and copper foil (Furukawa Electric Co., Ltd.'s "FV-WS" copper foil thickness: 18 μm) was attached to both sides of each stack. The stack was heated to 200°C at a heating rate of 4°C/min, and heated and pressed at 200°C for 120 minutes at a pressure of 3 MPa to produce copper-clad laminates of three different thicknesses.

The copper-clad laminate prepared as described above was used as the evaluation substrate and was evaluated by the method described below. In the thermal conductivity measurement described below, a cured product of one prepreg, a copper-clad laminate of two prepregs from which the copper foil had been removed, and a copper-clad laminate of four prepregs from which the copper foil had been removed (cured prepreg) were used, and in the evaluation test of dielectric properties (dielectric constant), a copper-clad laminate of four prepregs from which the copper foil had been removed (cured prepreg) was used.

[Thermal conductivity]
The thermal conductivity of the obtained evaluation board (cured prepreg) was measured by a method conforming to ASTM D5470. Specifically, a thermal property evaluation device (T3Ster DynTIM Tester manufactured by Mentor Graphics) was used to measure the thermal resistance and thickness of the obtained evaluation board (cured product of one prepreg, cured product of two prepregs, and cured product of four prepregs), and the measured values were plotted on a graph and approximated by a straight line, and the thermal conductivity was calculated from the increase in thermal resistance and thickness. The pass standard for thermal conductivity in this example was set to 1.0 W/m·K or more.

[Dielectric properties (dielectric constant)]
The dielectric loss tangent (Df) of the evaluation board (cured prepreg) at 10 GHz was measured by a cavity resonator perturbation method. Specifically, the dielectric loss tangent of the evaluation board at 10 GHz was measured using a network analyzer (N5230A manufactured by Keysight Technologies, Inc.). The pass criterion in this example was set to Df≦0.003.

[Copper foil peel strength]
First, for the peel strength (copper foil peel) test, a copper clad laminate (CCL) was prepared using the prepregs of each Example and Comparative Example. Specifically, four prepregs were stacked, and 18 μm thick copper foil (FV-WS manufactured by Furukawa Electric Co., Ltd.) was attached to both surfaces of the stacked prepregs, and the stacked prepregs were heated and pressed for 120 minutes under vacuum conditions at a temperature of 200° C. and a pressure of 3 MPa to obtain a copper clad laminate (CCL) (evaluation board) having a thickness of 510 μm and copper foil attached to both surfaces.

Then, using the obtained CCL, the peel strength of the copper foil from the insulating layer was measured in accordance with JIS C 6481. A pattern 10 mm wide and 100 mm long was formed, and the copper foil was peeled off at a speed of 50 mm/min using a tensile tester, and the peel strength at that time was measured. The unit of measurement is kN/m. The pass standard in this example was set to 0.40 kN/m or more.

The results of each of the above evaluations are shown in Tables 1 and 2.

(Discussion)
As can be seen from Tables 1 and 2, it was confirmed that in all of the examples using the resin composition of the present invention, cured products having low dielectric properties, high thermal conductivity, and excellent adhesion were obtained.

On the other hand, as shown in Table 2, the sample of Comparative Example 1, which does not contain the radical polymerizable compound (A1), was unable to obtain sufficient dielectric properties and adhesion. Furthermore, the samples of Comparative Examples 2 and 3, which used boron nitride filler that was not surface-treated via a polydopamine film as an inorganic filler, resulted in poor adhesion. Comparing Comparative Examples 2 and 3, it was confirmed that increasing the content of boron nitride filler improves the thermal conductivity, but also leads to poorer adhesion. Furthermore, Comparative Example 4, which used a boron nitride filler that was surface-treated with polydopamine but did not have a functional group (X), also failed to obtain sufficient adhesion.

This application is based on Japanese Patent Application No. 2023-140937, filed on August 31, 2023, the contents of which are incorporated herein by reference.

　In order to express the present invention, the present invention has been properly and sufficiently described above through embodiments with reference to specific examples and drawings, etc., but it should be recognized that a person skilled in the art could easily modify and/or improve the above-mentioned embodiments. Therefore, as long as the modifications or improvements implemented by a person skilled in the art are not at a level that deviates from the scope of the rights of the claims described in the claims, the modifications or improvements are interpreted as being included in the scope of the rights of the claims.

The present invention has wide industrial applicability in technical fields such as electronic materials, electronic devices, and optical devices.

Claims (15)

A resin composition comprising a thermosetting compound (A) and an inorganic filler (B),
the thermosetting compound (A) contains at least one radically polymerizable compound (A1) selected from the group consisting of a polyphenylene ether compound having a reactive unsaturated group, a hydrocarbon-based compound having a reactive unsaturated group, and a maleimide compound having two or more maleimide groups;
The inorganic filler (B) contains a boron nitride filler (B1),
A resin composition comprising the boron nitride filler (B1) and a polydopamine (C) having a functional group (X) reactive with the radical polymerizable compound (A1) attached to the surface of the boron nitride filler (B1). The resin composition according to claim 1, wherein the functional group (X) includes at least one selected from the group consisting of an epoxy group, a phenylamino group, a vinyl group, an acrylic group, a methacrylic group, an allyl group, a styrene structure, and a maleimide group. The resin composition according to claim 2, wherein the polydopamine (C) further has at least one structure selected from structures represented by the following formula (1) and the following formula (2).

The polydopamine (C) forms a polydopamine layer on the surface of the boron nitride filler (B1);
The resin composition according to claim 1 , wherein the maximum thickness of the dopamine layer is 0.1 nm or more and 100 nm or less. The resin composition according to claim 1, wherein the thermal conductivity of the cured product of the resin composition is 1 W/mK or more and 50 W/mK or less. The resin composition according to claim 1, wherein the content of the inorganic filler (B) is 40 to 85 parts by weight per 100 parts by weight of the total of the thermosetting compound (A) and the inorganic filler (B). The resin composition according to claim 1, wherein the content of the boron nitride filler (B1) is 10 to 90 mass% relative to the inorganic filler (B). The resin composition according to claim 1, further comprising a silane coupling agent. A prepreg comprising the resin composition according to any one of claims 1 to 8 or a semi-cured product of said resin composition and a fibrous base material. A resin-coated film comprising a resin layer containing the resin composition according to any one of claims 1 to 8 or a semi-cured product of the resin composition, and a support film. A resin-coated metal foil comprising a resin layer containing the resin composition according to any one of claims 1 to 8 or a semi-cured product of the resin composition, and a metal foil. A metal-clad laminate comprising an insulating layer containing a cured product of the resin composition according to any one of claims 1 to 8, and a metal foil. A wiring board comprising an insulating layer containing a cured product of the resin composition according to any one of claims 1 to 8, and wiring. A metal-clad laminate comprising an insulating layer containing the cured prepreg according to claim 9 and a metal foil. A wiring board comprising an insulating layer containing the cured prepreg according to claim 9 and wiring.

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