WO2024004526A1 - Boron nitride material and application of same - Google Patents

Abstract

A boron nitride material (10) according to the present disclosure comprises: a hexagonal boron nitride which has a thickness of 5 nm or more in the c-axis direction; and a polymer (2) which adheres to the hexagonal boron nitride. The solubility parameter of the boron nitride material 10 as determined by a methanol titration method is less than 47.9 MPa^0.5. A boron nitride material (10) according to the present disclosure is used in applications such as a filler, a resin composition, a prepreg, a film with a resin, a metal foil with a resin, a metal-clad laminate and a wiring board.

Description

Boron nitride materials and their applied products

The present disclosure relates to boron nitride materials and applied products thereof.

In recent years, in the electronics field, the level of performance required of electronic devices has been increasing in order to expand the use of the 5th generation mobile communication system (5G). For example, 5G uses higher frequency bands to provide faster communication speeds than previous generations. Therefore, high frequency compatible wiring boards are required for electronic devices.

The transmission loss in the transmission path of the wiring board depends on the frequency. The higher the signal frequency, the greater the transmission loss. Furthermore, transmission loss depends on dielectric constant and dielectric loss tangent. Therefore, in order to reduce the transmission loss of high-frequency signals, the substrate material constituting the insulating layer of the wiring board is required to have a low dielectric constant and a low dielectric loss tangent. Particularly in high frequency bands, the dielectric loss tangent largely depends on the orientational polarization of organic molecules contained in the substrate material. Therefore, it is required to reduce polar groups such as hydroxyl groups and amino groups contained in the substrate material.

Furthermore, in large-capacity communications such as 5G, the transmission distance of radio waves is short because high frequency bands are used. Therefore, it is necessary to increase the output of electronic devices. In addition, with the realization of high integration and miniaturization, the packaging density of circuits will also increase. Attempting to satisfy these needs increases the amount of heat generated per unit area of the wiring board. Therefore, wiring boards are required to have high heat dissipation properties. In order to improve the heat dissipation of a wiring board, a filler having excellent thermal conductivity is included in a substrate material constituting an insulating layer of the wiring board to increase the thermal conductivity of the wiring board.

Patent No. 5530318

In the prior art, it is desirable to reduce the dielectric loss tangent of boron nitride materials under high humidity.

This disclosure:
hexagonal boron nitride having a thickness in the C-axis direction of 5 nm or more;
a polymer attached to the hexagonal boron nitride;
A boron nitride material comprising:
the solubility parameter of the boron nitride material measured by methanol titration is less than 47.9 MPa ^0.5 ;
Provides boron nitride materials.

According to the present disclosure, the dielectric loss tangent of a boron nitride material under high humidity can be reduced.

FIG. 1 is a diagram showing a schematic configuration of a boron nitride material in Embodiment 1. FIG. 2 is a graph showing the relationship between the HSP distance between a polymer and water and the dielectric loss tangent of a boron nitride material during humidification. FIG. 3 is a diagram showing a schematic structure of a resin composition in Embodiment 4. FIG. 4 is a cross-sectional view of a resin-coated film in Embodiment 6. FIG. 5 is a cross-sectional view of the resin-coated metal foil in Embodiment 7. FIG. 6 is a cross-sectional view of a metal-clad laminate in Embodiment 8. FIG. 7 is a cross-sectional view of a wiring board in Embodiment 9.

(Findings that formed the basis of this disclosure)
Boron nitride is a material with high thermal conductivity and excellent electrical insulation. In particular, boron nitride, which has a hexagonal crystal structure, has a layered structure similar to graphite, can be synthesized relatively easily, and has excellent properties such as thermal conductivity, electrical insulation, chemical stability, and heat resistance. It has the following characteristics. Therefore, boron nitride is promising as a filler for resin compositions used in heat dissipation sheets, thermally conductive insulating substrates, and the like.

However, boron nitride has a hydrophilic surface and absorbs moisture under high humidity. Therefore, when boron nitride is used as a filler, the amount of water contained in the insulating substrate increases, and there is a concern that the dielectric loss tangent may deteriorate. Since the C-plane occupies most of the surface area of scale-like hexagonal boron nitride, surface modification of the C-plane to make the C-plane hydrophobic suppresses water adsorption and reduces the dielectric loss tangent. It is particularly effective for

However, the amount of functional groups present on the C-plane of boron nitride particles is extremely small compared to other surfaces. In other words, the C-plane of boron nitride is chemically inert. Therefore, it is difficult to form a direct covalent bond between a known surface modifier such as a silane coupling agent and the C-plane of boron nitride to suppress water adsorption to the C-plane.

Patent Document 1 discloses surface modification of aggregate-like hexagonal boron nitride with a silane coupling agent having a vinyl group. The silane coupling agent is considered to be chemically bonded to boron nitride by dehydration condensation with hydroxyl groups present on the surface of boron nitride. However, the amount of hydroxyl groups present on the C-plane of scale-like hexagonal boron nitride is small. Therefore, it is unlikely that a sufficient amount of the silane coupling agent can be adsorbed on the C-plane of boron nitride. In other words, according to the method of Patent Document 1, it is thought that surfaces other than the C-plane that are rich in hydroxyl groups are modified with the silane coupling agent. In this case, the effect of suppressing water adsorption to the C-plane is limited. Moreover, the silyl group contained in the silane coupling agent is easily converted into a silanol group having a hydroxyl group by a hydrolysis reaction. Therefore, the silane coupling agent can be a direct cause of deterioration of the dielectric loss tangent.

Incidentally, the dopamine-containing protein secreted from the byssus gland of the mussel, a type of bivalve, is known as a natural adhesive that exhibits stable adhesive strength even in seawater. According to Non-Patent Document 1, dopamine adheres to the surfaces of various materials under basic conditions and undergoes oxidative polymerization to form a polydopamine film.

For example, Non-Patent Document 2 discloses coating the C-plane of boron nitride with polydopamine. However, water is easily adsorbed on surfaces treated with a hydrophilic surface modifier such as polydopamine. Polydopamine itself also has a large amount of hydroxyl groups. Therefore, when polydopamine is used as a surface modifier for boron nitride, the dielectric loss tangent of boron nitride deteriorates.

Non-Patent Document 3 discloses surface modification of the C-plane of boron nitride nanosheets with polystyrene moieties of a block copolymer of polystyrene and PMMA.

However, the thickness of the boron nitride nanosheet in the C-axis direction is only a few nm. The surface area of boron nitride nanosheets per unit mass is several tens to hundreds of times larger than that of ordinary scale-like boron nitride. Therefore, when boron nitride nanosheets are formed, the area where water can be adsorbed increases, and it is expected that hygroscopicity and dielectric loss tangent will deteriorate under high humidity conditions. Furthermore, isolation of boron nitride nanosheets requires complicated procedures and has a low yield, which poses challenges for industrial use.

Furthermore, as a result of studies conducted by the present inventors, it was not possible to sufficiently modify the surface of flaky boron nitride, which is not a nanosheet, with polystyrene. The boron nitride nanosheet has a structure in which scale-like boron nitride is thinly exfoliated along the C-plane. The thickness of the boron nitride nanosheet in the C-axis direction is several nm, which corresponds to a monoatomic layer to several atomic layers. Therefore, the structure of boron nitride nanosheets is thermodynamically unstable compared to flaky boron nitride, which has a thickness of several tens of nanometers to several hundreds of nanometers in the C-axis direction. This is considered to be the reason why organic molecules are easily adsorbed on the surface of boron nitride nanosheets.

Therefore, none of the preceding examples can reduce the hygroscopicity of hexagonal boron nitride under high humidity, nor can it reduce the dielectric loss tangent of boron nitride.

The present inventors have conducted intensive studies on polymers that enable surface modification of hexagonal boron nitride. As a result, the present disclosure was completed by discovering that the above problems can be solved by attaching a polymer that can achieve a specific solubility parameter (SP value) to the surface of boron nitride.

(Summary of one aspect of the present disclosure)
The boron nitride material according to the first aspect of the present disclosure includes:
hexagonal boron nitride having a thickness in the C-axis direction of 5 nm or more;
a polymer attached to the hexagonal boron nitride;
A boron nitride material comprising:
The solubility parameter (SP value) of the boron nitride material measured by methanol titration is less than 47.9 MPa ^0.5 .

According to the present disclosure, the dielectric loss tangent of a boron nitride material under high humidity can be reduced.

In the second aspect of the present disclosure, for example, in the boron nitride material according to the first aspect, the polymer may be attached to the C-plane of the hexagonal boron nitride. Since the polymer is attached to the C-plane of hexagonal boron nitride, a sufficient surface modification effect can be obtained.

In a third aspect of the present disclosure, for example, in the boron nitride material according to the first or second aspect, the polymer may include a polyvinyl aromatic polymer, and the polyvinyl aromatic polymer It may also contain a side chain containing an aromatic ring. Having such a structure allows the polymer to strongly adsorb to the surface of boron nitride.

In a fourth aspect of the present disclosure, for example, in the boron nitride material according to any one of the first to third aspects, the polymer may include a repeating unit represented by formula (1). In formula (1), n represents a positive integer, X is represented by formula (2), and any one of R ¹ to R ⁵ in formula (2) is directly connected to the main chain contained in the repeating unit. The other four from R ¹ to R ⁵ independently represent a group consisting of H, B, C, N, O, Si, F, P, S, Cl, I and Br. Contains at least one atom selected from Having such a structure allows the polymer to strongly adsorb to the surface of boron nitride.

In the fifth aspect of the present disclosure, for example, in the boron nitride material according to the fourth aspect, in the formula (2), the other four R ¹ to R ⁵ are independently H atoms or hydrocarbon groups. It may be. It is desirable that the other four of R ¹ to R ⁵ be H atoms or hydrocarbon groups from the viewpoint of increasing the hydrophobicity of the polymer.

In the sixth aspect of the present disclosure, for example, in the boron nitride material according to the fourth aspect, X in formula (1) may be represented by formula (3). Any one of R ¹¹ to R ¹⁹ in formula (3) represents a direct bond to the main chain, and the other eight of R ¹¹ to R ¹⁹ independently represent H, B, C , N, O, Si, F, P, S, Cl, I and Br. Having such a structure allows the polymer to strongly adsorb to the surface of boron nitride.

In the seventh aspect of the present disclosure, for example, in the boron nitride material according to the sixth aspect, in the formula (3), the other eight of R ¹¹ to R ¹⁹ are independently H atoms or hydrocarbon groups. It may be. It is desirable that the other eight of R ¹¹ to R ¹⁹ be H atoms or hydrocarbon groups from the viewpoint of increasing the hydrophobicity of the polymer.

In the eighth aspect of the present disclosure, for example, in the boron nitride material according to the first aspect, the polymer may include a repeating unit containing at least one selected from the group consisting of a carbazole skeleton and a fluorene skeleton. Since the repeating unit of the polymer includes at least one selected from the group consisting of a carbazole skeleton and a fluorene skeleton, the polymer can be strongly adsorbed on the surface of boron nitride.

In the ninth aspect of the present disclosure, for example, in the boron nitride material according to the eighth aspect, the fluorene skeleton may include at least one substituent.

In the tenth aspect of the present disclosure, for example, in the boron nitride material according to the first aspect, the polymer may include a repeating unit containing a polyphenylene ether skeleton. Since the repeating unit of the polymer contains a polyphenylene ether skeleton, the polymer can be strongly adsorbed on the surface of boron nitride.

In the eleventh aspect of the present disclosure, for example, in the boron nitride material according to the tenth aspect, the polyphenylene ether skeleton may include at least one substituent.

The filler according to the twelfth aspect of the present disclosure includes the boron nitride material according to any one of the first to eleventh aspects. According to the filler of the present disclosure, the heat resistance of the filler can be improved. Generation of bubbles when heating the filler can also be suppressed.

The resin composition according to the thirteenth aspect of the present disclosure includes the filler according to the twelfth aspect. According to the thirteenth aspect, it is possible to provide a resin composition that exhibits a low dielectric loss tangent and has excellent heat resistance.

The prepreg according to the fourteenth aspect of the present disclosure includes the resin composition of the thirteenth aspect or a semi-cured product of the resin composition.

The resin-coated film according to the fifteenth aspect of the present disclosure is
A resin layer containing the resin composition of the thirteenth aspect or a semi-cured product of the resin composition,
a support film;
It is equipped with

The resin-coated metal foil according to the sixteenth aspect of the present disclosure includes:
A resin layer containing the resin composition of the thirteenth aspect or a semi-cured product of the resin composition,
metal foil and
It is equipped with

The metal clad laminate according to the seventeenth aspect of the present disclosure includes:
an insulating layer comprising a cured product of the resin composition of the thirteenth aspect or a cured product of the prepreg of the fourteenth aspect;
metal foil and
It is equipped with

The wiring board according to the eighteenth aspect of the present disclosure,
an insulating layer comprising a cured product of the resin composition of the thirteenth aspect or a cured product of the prepreg of the fourteenth aspect;
wiring and
We are prepared.

According to the fourteenth to eighteenth aspects, various applied products suitable for high frequencies can be provided.

(Embodiment 1)
FIG. 1 is a diagram showing a schematic configuration of a boron nitride material 10 in the first embodiment. Boron nitride material 10 comprises boron nitride 1 and polymer 2. Polymer 2 is attached to boron nitride 1.

[Boron nitride]
Boron nitride 1 is hexagonal boron nitride (h-BN). Hexagonal boron nitride is suitable for the boron nitride material 10 of the present disclosure because it can be synthesized relatively easily and has excellent properties such as thermal conductivity, electrical insulation, chemical stability, and heat resistance. .

Boron nitride 1 has a particle shape. The shape of the particles of boron nitride 1 is not particularly limited as long as the C-plane to be modified is exposed on the surface. Since the area of the C-plane is large, it is desirable that the shape of the particles of boron nitride 1 is scaly.

The thickness of the boron nitride 1 in the C-axis direction is, for example, 5 nm or more. When boron nitride 1 has a thickness of 5 nm or more, the surface area per unit mass of boron nitride 1 can be reduced. This is advantageous in reducing the amount of moisture adsorbed by boron nitride 1 under high humidity and keeping the dielectric loss tangent of boron nitride material 10 low. The upper limit of the thickness of boron nitride 1 in the C-axis direction is not particularly limited. The thickness of boron nitride 1 in the C-axis direction may be 10 μm or less. The thickness of boron nitride 1 in the C-axis direction may be 10 nm or more and 10 μm or less.

The thickness of boron nitride 1 in the C-axis direction can be measured using a scanning electron microscope image (SEM image) of boron nitride 1. The widest plane of hexagonal boron nitride is the C-plane. Therefore, the thickness of the side surface of boron nitride 1 in the SEM image can be regarded as the thickness in the C-axis direction.

The average particle size of boron nitride 1 is not particularly limited. The average particle size of boron nitride 1 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 the present disclosure, the average particle size of boron nitride particles means the median diameter. The median diameter means the particle diameter (d50) when the cumulative volume in the volume-based particle size distribution is equal to 50%. The volume-based particle size distribution is measured using, for example, a laser diffraction measuring device.

[polymer]
Polymer 2 is an organic compound that serves as a surface modifier for boron nitride 1. Polymer 2 is attached to the C-plane of boron nitride 1. Since most of the surface area of hexagonal boron nitride is the C-plane, a sufficient surface modification effect can be obtained by adhering the polymer 2 to the C-plane.

The polymer 2 may form a film on the C-plane of the boron nitride 1. The polymer 2 may be attached to the entire C-plane or only to a part of the C-plane. The polymer 2 may be attached to a surface other than the C-plane. Modification of the C-plane is effective for improving hygroscopicity, but hygroscopicity can also be improved when both the C-plane and surfaces other than the C-plane are modified.

The polymer 2 may be a polymer having an aromatic ring within the repeating unit. Since the C-plane of hexagonal boron nitride is inert, it is not easy to chemically modify the C-plane. In this embodiment, polymer 2 is physically adsorbed onto boron nitride 1. "Physical adsorption" means adsorption mainly by van der Waals forces.

The polymer 2 may be physically adsorbed to the C-plane of the boron nitride 1 by π-π interaction. The π-π interaction that acts on aromatic rings is known to be a particularly strong interaction among van der Waals forces. A sufficient amount of polymer 2 can be attached to the C-plane of boron nitride 1 by van der Waals forces including π-π interactions.

In this embodiment, the HSP (Hansen solubility parameter) distance between the polymer 2 and water is greater than 39.5 MPa ^0.5 . The HSP distance is calculated by the atomic group contribution method (Hansen method). A sufficiently large HSP distance between polymer 2 and water means that polymer 2 has high hydrophobicity. Since the polymer 2 has high hydrophobicity, the hygroscopicity of the boron nitride material 10 can be reduced. Thereby, the dielectric loss tangent of the boron nitride material 10 under high humidity can be reduced. The upper limit of the HSP distance between polymer 2 and water is not particularly limited. The upper limit of the HSP distance is, for example, 54.8 MPa ^0.5 .

Generally, when forming a covalent bond between a surface modifier and boron nitride through a chemical reaction such as dehydration condensation, a compound containing a highly reactive polar group is used as the surface modifier. Since a compound containing a polar group has high hydrophilicity, the HSP distance between the compound and water is likely to be 39.5 MPa ^0.5 or less. Therefore, in surface modification using a hydrophobic compound, surface modification by physical adsorption is more preferable than forming a covalent bond by chemical reaction.

Whether or not the amount of polymer 2 attached to boron nitride 1 is sufficient, that is, whether the surface modification is sufficient is determined by the solubility parameter (SP value) of boron nitride material 10 measured by methanol titration method. can. In this embodiment, it is determined that the surface modification is sufficient when the SP value is less than 47.9 MPa ^0.5 . When the surface of the boron nitride material is hydrophilic, its SP value is 47.9 MPa ^0.5 or more. By sufficiently adhering the polymer 2 to the surface of the boron nitride 1, the surface of the boron nitride material changes to be hydrophobic, and its SP value becomes less than 47.9 MPa ^0.5 . When the SP value is suppressed to less than 47.9 MPa ^0.5 , the boron nitride material 10 exhibits a low dielectric loss tangent even under high humidity. The lower limit of the SP value of the boron nitride material 10 is not particularly limited. The lower limit of the SP value of the boron nitride material 10 is, for example, 34.1 MPa ^0.5 .

The polymer 2 may include a polyvinyl aromatic polymer, and the polyvinyl aromatic polymer may include a side chain containing a heteroaromatic ring. Having such a structure allows the polymer 2 to strongly adsorb to the surface of the boron nitride 1.

Polymer 2 may have a repeating unit represented by formula (1). In formula (1), n represents a positive integer. X is represented by formula (2). Any one of R ¹ to R ⁵ in formula (2) represents a direct bond to the main chain contained in the repeating unit represented by formula (1). The other four R ¹ to R ⁵ are each independently at least one atom selected from the group consisting of H, B, C, N, O, Si, F, P, S, Cl, I, and Br. including. "The other four from R ¹ to R ⁵ " means a site that does not form a bond to the main chain. The main chain is an ethylene skeleton in formula (1). Having such a structure allows the polymer 2 to strongly adsorb to the surface of the boron nitride 1.

The other four R ¹ to R ⁵ are each independently a hydrogen atom, a halogen atom, a hydrocarbon group, a halogenated hydrocarbon group, a group containing an oxygen atom, a group containing a nitrogen atom, and a group containing a sulfur atom. , a group containing a silicon atom, a group containing a phosphorus atom, or a group containing a boron atom.

Examples of halogen atoms include F, Cl, Br and I.

Examples of the hydrocarbon group include an aliphatic saturated hydrocarbon group, an alicyclic hydrocarbon group, and an aliphatic unsaturated hydrocarbon group.

A halogenated hydrocarbon group means a group in which at least one hydrogen atom contained in the hydrocarbon group is substituted with a halogen atom. The halogenated hydrocarbon group may be a group in which all hydrogen atoms contained in the hydrocarbon group are substituted with halogen atoms. Examples of the halogenated hydrocarbon group include a halogenated alkyl group and a halogenated alkenyl group.

The group containing an oxygen atom is, for example, a substituent having at least one selected from the group consisting of a hydroxyl group, a carboxyl group, an aldehyde group, an ether group, an acyl group, and an ester group.

The nitrogen atom-containing group is, for example, a substituent having at least one selected from the group consisting of an amino group, an imino group, a cyano group, an azide group, an amide group, a carbamate group, a nitro group, a cyanamide group, an isocyanate group, and an oxime group. It is the basis.

Groups containing a sulfur atom include, for example, a thiol group, a sulfide group, a sulfinyl group, a sulfonyl group, a sulfino group, a sulfonic acid group, an acylthio group, a sulfenamide group, a sulfonamide group, a thioamide group, a thiocarbamide group, and a thiocyano group. It is a substituent having at least one member selected from the group consisting of:

The group containing a silicon atom is, for example, a substituent having at least one selected from the group consisting of a silyl group and a siloxy group.

The group containing a phosphorus atom is, for example, a substituent having at least one selected from the group consisting of a phosphino group and a phosphoryl group.

The group containing a boron atom is, for example, a substituent having a boronic acid group. Examples of the substituent having a boronic acid group include the boronic acid group itself and a hydrocarbon group having a boronic acid group.

The other four R ¹ to R ⁵ may be independently H atoms or hydrocarbon groups. H atoms or hydrocarbon groups do not increase the polarity of polymer 2. Therefore, from the viewpoint of increasing the hydrophobicity of the polymer 2, it is desirable that the other four of R ¹ to R ⁵ are H atoms or hydrocarbon groups.

Examples of the hydrocarbon group include an aliphatic saturated hydrocarbon group, an alicyclic hydrocarbon group, and an aliphatic unsaturated hydrocarbon group. The aliphatic saturated hydrocarbon group may be an alkyl group. Examples of aliphatic saturated hydrocarbon groups include -CH ₃ , -CH ₂ CH ₃ , -CH ₂ CH ₂ CH ₃ , -CH(CH ₃ ) ₂ , -CH(CH ₃ )CH ₂ CH ₃ , -C(CH ₃ ) ₃ , _-CH2CH ( _CH3 ) _{2 ,} -( _CH2 ) _3CH3 , -( _CH2 ) _{4CH3 ,} -C( _{CH2CH3 )} ( _CH3 ) ₂ , _-CH2C (CH ₃ ) ₃ , -(CH ₂ ) ₅ CH ₃ , -(CH ₂ ) ₆ CH ₃ , -(CH ₂ ) ₇ CH ₃ , -(CH ₂ ) ₈ CH ₃ , -(CH ₂ ) ₉ CH ₃ , -(CH ₂ ) ₁₀ CH ₃ , -(CH ₂ ) ₁₁ CH ₃ , -(CH ₂ ) ₁₂ CH ₃ , -(CH ₂ ) ₁₃ CH ₃ , -(CH ₂ ) ₁₄ CH ₃ , -(CH ₂ ) ₁₅ CH ₃ , -(CH ₂ ) ₁₆ CH ₃ , -(CH ₂ ) ₁₇ CH ₃ , -(CH ₂ ) ₁₈ CH ₃ , -(CH ₂ ) ₁₉ CH ₃ and the like. Examples of the alicyclic hydrocarbon group include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, and an adamantyl group. Examples of aliphatic unsaturated hydrocarbon groups include -CH=CH ₂ , -C≡CH, -C≡CCH ₃ , -C(CH ₃ )=CH ₂ , -CH=CHCH ₃ , -CH ₂ CH=CH ₂ Examples include.

The number of carbon atoms in the hydrocarbon group is not particularly limited, and is, for example, 1 or more and 20 or less, may be 1 or more and 10 or less, or may be 1 or more and 5 or less. The hydrocarbon group may be linear, branched, or cyclic.

In formula (1), X may be represented by formula (3). Any one of R ¹¹ to R ¹⁹ in formula (3) represents a direct bond to the main chain contained in the repeating unit represented by formula (1). The other eight R ¹¹ to R ¹⁹ are each independently at least one atom selected from the group consisting of H, B, C, N, O, Si, F, P, S, Cl, I, and Br. including. "The other eight from R ¹¹ to R ¹⁹ " means sites that do not form a bond to the main chain. Having such a structure allows the polymer 2 to strongly adsorb to the surface of the boron nitride 1.

The other eight R ¹¹ to R ¹⁹ are, independently of each other, a hydrogen atom, a halogen atom, a hydrocarbon group, a halogenated hydrocarbon group, a group containing an oxygen atom, a group containing a nitrogen atom, a group containing a sulfur atom. , a group containing a silicon atom, a group containing a phosphorus atom, or a group containing a boron atom. The examples explained above regarding R ¹ to R ⁵ can be applied to specific examples of R ¹¹ to R ¹⁹ .

The other eight of R ¹¹ to R ¹⁹ may be independently H atoms or hydrocarbon groups. H atoms or hydrocarbon groups do not increase the polarity of polymer 2. Therefore, from the viewpoint of increasing the hydrophobicity of the polymer 2, it is desirable that the other eight atoms from R ¹¹ to R ¹⁹ are H atoms or hydrocarbon groups.

Polymer 2 may be a polymer represented by formula (4). That is, the polymer 2 may have a structure other than the repeating unit represented by formula (1). In formula (1), n represents a positive integer, and m represents an integer of 0 or more. X is represented by formula (2) or formula (3). R ⁶ contains at least one atom selected from the group consisting of H, B, C, N, O, Si, F, P, S, Cl, I and Br. Having such a structure allows the polymer 2 to strongly adsorb to the surface of the boron nitride 1.

The examples described above regarding R ¹ to R ⁵ can be applied to specific examples of R ⁶ .

R ⁶ may be an H atom or a hydrocarbon group. H atoms or hydrocarbon groups do not increase the polarity of polymer 2. It is desirable that R ⁶ be an H atom or a hydrocarbon group from the viewpoint of increasing the hydrophobicity of the polymer 2.

In formula (4), m may be zero.

Furthermore, the polymer 2 may have a repeating unit containing at least one selected from the group consisting of a carbazole skeleton and a fluorene skeleton. When polymer 2 has a carbazole skeleton and a fluorene skeleton, it can exhibit strong adhesion to the C-plane of boron nitride 1. The carbazole skeleton and fluorene skeleton may be included in the main chain of the polymer 2, or may be included in the side chain. The carbazole skeleton and the fluorene skeleton may each have at least one substituent. At least one substituent can be a group containing at least one atom selected from the group consisting of H, B, C, N, O, Si, F, P, S, Cl, I and Br. Examples of such groups include the groups described above for formula (1).

Polymer 2 may have a repeating unit containing a polyphenylene ether skeleton. When having a polyphenylene ether skeleton, the polymer 2 can exhibit strong adhesion to the C-plane of the boron nitride 1. The polyphenylene ether skeleton may be included in the main chain of the polymer 2, or may be included in the side chain. Each polyphenylene ether skeleton may have at least one substituent. At least one substituent can be a group containing at least one atom selected from the group consisting of H, B, C, N, O, Si, F, P, S, Cl, I and Br. Examples of such groups include the groups described above for formula (1).

By having a carbazole skeleton, a fluorene skeleton, or a polyphenylene ether skeleton, the polymer 2 can strongly adsorb to the surface of the boron nitride 1.

Note that in order to reduce the hygroscopicity of the boron nitride material 10, it is desirable that the HSP distance between the polymer 2 and water be large. When the content of polar groups such as hydroxyl groups, carboxyl groups, unsubstituted amino groups, thiol groups, sulfonic acid groups, and silanol groups is small, the HSP distance between the polymer 2 and water can become large. Moreover, when the content of polar groups is small, the dielectric loss tangent of the polymer 2 itself can also be suppressed. Therefore, polymer 2 does not need to have these polar groups. Further, it is desirable that the polymer 2 does not generate these polar groups through reactions such as hydrolysis when absorbing moisture.

The molecular weight of polymer 2 is not particularly limited. Polymer 2 has, for example, a number average molecular weight Mn of 100 or more. The upper limit of the number average molecular weight Mn of the polymer 2 is not particularly limited, and is, for example, 500,000.

The thermal decomposition temperature and boiling point of the polymer 2 are, for example, 200°C or higher, and may be 250°C or higher. The boron nitride material 10 is used, for example, as a filler in an insulating layer of a wiring board. When the thermal decomposition temperature of the polymer 2 is sufficiently high, thermal decomposition or evaporation of the polymer 2 can be suppressed in a solder reflow process when electronic components are mounted on a wiring board. This can prevent air bubbles from forming between the wiring board and the resin layer. Furthermore, according to the present embodiment, since the amount of moisture adsorbed by the boron nitride material 10 is suppressed, the generation of bubbles due to evaporation of adsorbed water in the solder reflow process can also be suppressed.

The amount of polymer 2 attached to boron nitride 1 is not particularly limited. For example, the ratio of the mass of polymer 2 to the mass of boron nitride 1 is 10% or less. By appropriately adjusting the amount of the polymer 2 attached, the amount of gas generated during thermal decomposition of the boron nitride material 10 can be suppressed. This is particularly significant when using boron nitride material 10 as a filler. As long as the surface of boron nitride 1 can be sufficiently modified, the lower limit of the ratio of the mass of polymer 2 to the mass of boron nitride 1 is not particularly limited. The lower limit of the ratio is, for example, 0.01%.

The method of surface modification of boron nitride 1 with polymer 2 is not particularly limited. For example, boron nitride material 10 is obtained by mixing a solution containing polymer 2 and boron nitride 1, and filtering, washing, and drying the solid matter.

The temperature at which the surface of boron nitride 1 is modified with polymer 2 is not particularly limited as long as it is below the boiling point of the solvent. Surface modification may be performed at room temperature (20°C±15°C). The type of solvent is not particularly limited as long as it can dissolve the polymer 2. The amount of polymer 2 used is also not particularly limited. The ratio of the mass of polymer 2 to the mass of boron nitride 1 may be 0.01% or more and 10% or less, or 0.75% or more and 5% or less.

[Boron nitride material]
The boron nitride material 10 has a configuration that is advantageous in reducing the dielectric loss tangent under high humidity. For example, the ratio of the dielectric loss tangent of the boron nitride material 10 at 1 GHz in an atmosphere with 90% humidity to the dielectric loss tangent of boron nitride 1 at 1 GHz is less than 1. Therefore, the boron nitride material 10 is suitable for applications requiring a low dielectric loss tangent, for example, as a filler for wiring boards. The lower limit of the ratio of the dielectric loss tangent of the boron nitride material 10 to the dielectric loss tangent of the boron nitride 1 is not particularly limited. The lower limit of the ratio is, for example, 0.001. Note that in this specification, "humidity" means relative humidity.

The boron nitride material 10 has a configuration that is advantageous in reducing the amount of water adsorption. For example, the ratio of the amount of moisture adsorbed by the boron nitride material 10 in an atmosphere with a humidity of 90% to the amount of moisture adsorbed by the boron nitride 1 in an atmosphere with a humidity of 90% is less than 1. By reducing the amount of water adsorption, the dielectric loss tangent can be reduced, and the generation of bubbles in the solder reflow process can also be suppressed. The lower limit of the ratio of the amount of moisture adsorbed by the boron nitride material 10 to the amount of moisture adsorbed by the boron nitride 1 is not particularly limited. The lower limit of the ratio is, for example, 0.01.

(Embodiment 2)
The heat dissipation gap filler according to the present embodiment includes the boron nitride material 10 according to the first embodiment.

In the present disclosure, a heat dissipation gap filler is a filler used to dissipate heat from an electronic component by applying it to an electronic component such as a substrate material to fill air pockets or gaps. The heat dissipation gap filler is a hardening type heat dissipation paste that hardens from a paste form to a sheet form. According to the heat dissipation gap filler according to the present embodiment, the heat resistance of the filler can be improved. Generation of bubbles during heating can also be suppressed.

The heat dissipation gap filler according to the present embodiment is produced by, for example, kneading the boron nitride material 10 according to the first embodiment with an epoxy resin, a silicone resin, or a non-silicone acrylic resin or a ceramic resin. It can be manufactured by

(Embodiment 3)
The filler for thermal grease according to the present embodiment includes the boron nitride material 10 according to the first embodiment.

In the present disclosure, a filler for heat-radiating grease is a filler used for heat-radiating grease. Thermal grease is a non-hardening thermal paste used to dissipate heat from electronic components by applying them to electronic components, such as substrate materials, to fill air pockets or gaps. According to the filler for thermal grease according to the present embodiment, the heat resistance of the filler can be improved. Generation of bubbles during heating can also be suppressed.

The heat dissipation grease filler according to the present embodiment is produced by, for example, kneading the boron nitride material 10 according to Embodiment 1 with an epoxy resin, a silicone resin, or a non-silicone acrylic resin or ceramic resin. It can be manufactured by

(Embodiment 4)
FIG. 3 is a diagram showing a schematic configuration of a resin composition 20 in Embodiment 4. The resin composition 20 includes, for example, a filler 22 and a curable resin 24.

The filler 22 includes the boron nitride material 10 described in the first embodiment. According to this embodiment, it is possible to provide a resin composition 20 that exhibits a low dielectric loss tangent and has excellent heat resistance. As the filler 22, the boron nitride material 10 alone may be used, or other filler materials such as silica particles may be used in combination with the boron nitride material 10.

Examples of the curable resin 24 include epoxy resins, cyanate ester compounds, maleimide compounds, phenol resins, acrylic resins, polyamide resins, polyamideimide resins, thermosetting polyimide resins, and polyphenylene ether resins. As the curable resin 24, one kind or a combination of two or more kinds selected from these can be used.

The resin composition 20 may contain other components. Other ingredients include curing agents, flame retardants, ultraviolet absorbers, antioxidants, reaction initiators, silane coupling agents, optical brighteners, photosensitizers, dyes, pigments, thickeners, lubricants, and erasers. Examples include foaming agents, dispersants, leveling agents, brighteners, antistatic agents, polymerization inhibitors, and organic solvents. If necessary, the resin composition 20 can use one type or a combination of two or more types selected from these.

(Embodiment 5)
The prepreg according to Embodiment 5 includes the resin composition 20 of Embodiment 4 shown in FIG. 3 or a semi-cured product thereof, and a fibrous base material. The fibrous base material is present in the matrix of the resin composition 20 or semi-cured material. Prepreg is a composite material of the resin composition 20 and a fibrous base material. According to this embodiment, it is possible to provide a prepreg suitable for high-frequency wiring boards.

In this embodiment, the semi-cured material refers to a material that is partially cured to the extent that the resin composition 20 can be further cured. That is, the semi-cured material is a material obtained by semi-curing the resin composition 20. For example, when the resin composition 20 is heated, its viscosity gradually decreases. If heating is continued, curing will then begin and its viscosity will gradually increase. In such a case, the semi-cured state includes the state of the resin composition 20 during the period from the time when the viscosity starts to increase until the time when it is completely cured.

As the fibrous base material, known materials used in various electrically insulating material laminates can be used. Examples of the fibrous base material include glass cloth, aramid cloth, polyester cloth, glass nonwoven fabric, aramid nonwoven fabric, polyester nonwoven fabric, pulp paper, and linter paper.

The resin composition 20 is impregnated into the fibrous base material through treatments such as dipping and coating. By heating the fibrous base material impregnated with the resin composition 20 under predetermined heating conditions, a pre-cured or semi-cured prepreg according to the present embodiment can be obtained.

(Embodiment 6)
FIG. 4 is a cross-sectional view of a resin-coated film 30 in Embodiment 6. The resin-coated film 30 includes a resin layer 32 containing the resin composition 20 or a semi-cured product thereof, and a support film 34. According to this embodiment, a resin-coated film 30 suitable for an insulating layer can be provided. The resin layer 32 is supported by a support film 34. In the example of FIG. 4, a support film 34 is placed on the surface of the resin layer 32. However, another layer such as an adhesive layer may be provided between the resin layer 32 and the support film 34.

The resin layer 32 contains the resin composition 20 of Embodiment 4 shown in FIG. 3 or a semi-cured product thereof, and may or may not contain a fibrous base material. As the fibrous base material, the same material as the fibrous base material of the prepreg can be used. The resin layer 32 hardens and changes into an insulating layer. An example of such an insulating layer is an insulating layer of a wiring board.

As the support film 34, any support film used for resin-coated films can be used without limitation. Examples of the support film 34 include resin films such as polyester films and polyethylene terephthalate films.

(Embodiment 7)
FIG. 5 is a cross-sectional view of resin-coated metal foil 40 in Embodiment 7. The resin-coated metal foil 40 includes a resin layer 42 containing the resin composition 20 or a semi-cured product thereof, and a metal foil 44. A resin layer 42 is supported by a metal foil 44. According to this embodiment, a resin-coated metal foil 40 suitable for electronic circuit components such as wiring boards can be provided. In the example of FIG. 5, a metal foil 44 is placed on the surface of the resin layer 42. However, another layer such as an adhesive layer may be provided between the resin layer 42 and the metal foil 44.

The resin layer 42 contains the resin composition of Embodiment 4 shown in FIG. 3 or a semi-cured product thereof, and may or may not contain a fibrous base material. As the fibrous base material, the same material as the fibrous base material of the prepreg can be used. The resin layer 42 hardens and changes into an insulating layer. An example of such an insulating layer is an insulating layer of a wiring board.

As the metal foil 44, resin-coated metal foil and metal foil used for metal-clad laminates can be used without limitation. Examples of the metal foil include copper foil and aluminum foil.

(Embodiment 8)
FIG. 6 is a cross-sectional view of a metal-clad laminate 50 in Embodiment 8. Metal-clad laminate 50 includes an insulating layer 52 and at least one metal foil 54 . According to this embodiment, a metal-clad laminate 50 suitable for a wiring board can be provided. The insulating layer 52 includes a cured product of the resin composition 20 of the fourth embodiment shown in FIG. 3 or a cured product of the prepreg of the fifth embodiment. Metal foil 54 is placed on the surface of insulating layer 52. In this embodiment, metal foils 54 are placed on each of the front and back surfaces of the insulating layer 52.

The metal-clad laminate 50 is typically manufactured using the prepreg of Embodiment 5. For example, a laminate is formed by stacking 1 to 20 sheets of prepreg. A metal-clad laminate 50 is obtained by placing metal foil on one or both sides of the prepreg laminate and heating and pressurizing the prepreg laminate. Examples of the metal foil 54 include copper foil, aluminum foil, and the like.

For example, the molding conditions for manufacturing a laminate for electrically insulating materials and a multilayer board can be applied to the molding conditions for manufacturing the metal-clad laminate 50.

(Embodiment 9)
FIG. 7 is a cross-sectional view of wiring board 60 in the ninth embodiment. Wiring board 60 includes an insulating layer 62 and wiring 64. According to this embodiment, a wiring board 60 suitable for high frequencies can be provided. The insulating layer 62 includes a cured product of the resin composition 20 of the fourth embodiment shown in FIG. 3 or a cured product of the prepreg of the fifth embodiment. The wiring 64 is supported by the insulating layer 62. Specifically, the wiring 64 is arranged on the insulating layer 62. Wiring 64 may be formed by partially removing the metal foil.

By patterning the metal foil 54 on the surface of the metal-clad laminate 50 shown in FIG. 6 by a method such as etching, a wiring board 60 in which wiring 64 forming a circuit is provided on the surface of the insulating layer 62 is obtained. That is, the wiring board 60 is obtained by partially removing the metal foil 54 on the surface of the metal-clad laminate 50 so that a circuit is formed.

A new laminate may be formed by laminating the prepreg of Embodiment 5 on at least one surface of the wiring board 60 and applying heat and pressure. A multilayer wiring board can be obtained by patterning the metal foil on the surface of the obtained laminate to form wiring.

Hereinafter, details of the present disclosure will be explained using Examples and Comparative Examples. Note that the present disclosure is not limited to the following examples.

Hereinafter, scaly hexagonal boron nitride (manufactured by Denka, GP grade) was used as boron nitride.

[Example 1]
A solution was obtained by dissolving 15 mg of poly(9-vinylcarbazole) represented by formula (5) (manufactured by Aldrich, number average molecular weight Mn 25,000 to 50,000) in 1 mL of toluene. 200 mg of boron nitride was suspended in the solution and stirred at 100°C overnight. After isolation of boron nitride by suction filtration, it was washed with toluene and vacuum dried at room temperature. As a result, about 200 mg of powder of the boron nitride material of Example 1 was obtained.

[Example 2]
A solution was obtained by dissolving 15 mg of poly(N-ethyl-2-vinylcarbazole) (manufactured by Aldrich) represented by formula (6) in 1 mL of toluene. 200 mg of boron nitride was suspended in the solution and stirred at 100°C overnight. After isolation of boron nitride by suction filtration, it was washed with toluene and vacuum dried at room temperature. As a result, about 200 mg of powder of the boron nitride material of Example 2 was obtained.

[Example 3]
A solution was obtained by dissolving 15 mg of Poly(9,9-di-n-dodecylfluorenyl-2,7-diyl) (LT-A1016, manufactured by Luminescence Technology) represented by formula (7) in 1 mL of toluene. 200 mg of boron nitride was suspended in the solution and stirred at 100°C overnight. After isolation of boron nitride by suction filtration, it was washed with toluene and vacuum dried at room temperature. As a result, about 200 mg of powder of the boron nitride material of Example 3 was obtained.

[Example 4]
PFOTBT (Poly[2,7-(9,9-di-octyl-fluorene)-alt-4,7-bis(thiophen-2-yl)benzo-2,1,3- thiadiazole] (manufactured by Luminescence Technology, LT-S9419) was dissolved in 1 mL of toluene to obtain a solution. 200 mg of boron nitride was suspended in the solution and stirred at 100°C overnight. After isolation of boron nitride by suction filtration, it was washed with toluene and vacuum dried at room temperature. As a result, about 200 mg of powder of the boron nitride material of Example 4 was obtained.

[Example 5]
A solution was obtained by dissolving 15 mg of polyphenylene ether represented by formula (9) (manufactured by SABIC Japan) in 1 mL of toluene. 200 mg of boron nitride was suspended in the solution and stirred at 100°C overnight. After isolation of boron nitride by suction filtration, it was washed with toluene and vacuum dried at room temperature. As a result, about 200 mg of powder of the boron nitride material of Example 5 was obtained.

[Comparative example 1]
Hexagonal boron nitride (manufactured by Denka, GP grade) was used as it was as boron nitride in Comparative Example 1.

[Comparative example 2]
A solution was obtained by dissolving 15 mg of poly(4-vinylpyridine) represented by formula (10) (manufactured by Aldrich, weight average molecular weight Mw less than 60,000) in 1 mL of chloroform. 200 mg of boron nitride was suspended in the solution and stirred at 50°C overnight. Boron nitride was isolated by suction filtration, washed with chloroform, and dried under vacuum at room temperature. As a result, about 200 mg of powder of the boron nitride material of Comparative Example 2 was obtained.

[Comparative example 3]
Boron nitride was added to a dopamine solution (23 mg/mL) whose pH was adjusted to 8.5 with Tris-HCl. The solution temperature was set at 80° C., and the solution was stirred using a magnetic stirrer for 24 hours to advance the polymerization reaction of dopamine to form polydopamine. After the reaction, the boron nitride was filtered, washed with water, and then dried. Thereby, a powder of boron nitride material of Comparative Example 3 was obtained.

[Comparative example 4]
A solution was obtained by dissolving 15 mg of polystyrene (manufactured by Aldrich, weight average molecular weight Mw 35000) in 1 mL of toluene. 200 mg of boron nitride was suspended in the solution and stirred at 100°C overnight. After isolation of boron nitride by suction filtration, it was washed with toluene and vacuum dried at room temperature. As a result, about 200 mg of powder of the boron nitride material of Comparative Example 4 was obtained.

<Calculation of HSP distance>
The HSP distance between the polymer used in Examples and Comparative Examples and water was calculated by the following method.

Using the atomic group contribution method (Hansen method), the dispersion term δ _d , polarity term δ _p and hydrogen bond term δ _h of the HSP value were calculated from the molecular structure of the polymer. By substituting these values into formula (A1), the HSP distance (MPa ^0.5 ) between the polymer and water was calculated. 15.5 MPa ^0.5 , 16.0 MPa ^0.5 and 42.3 MPa ^0.5 were used as the dispersion term δ _d , polar term δ _p and hydrogen bond term δ _h of the HSP value of water, respectively. The results are shown in Table 1.

HSP distance = [4(δ _d -15.5) ² +(δ _p -16.0) ² +(δ _h -42.3) ² ] ^1/2 ...(A1)

Polydopamine used in Comparative Example 3 is known to be a mixture having multiple molecular structures. In this specification, the HSP distance was calculated assuming that polydopamine has a single structure described in formula (11). Actual polydopamine is known as a highly hydrophilic polymer. Even if polydopamine has a structure other than formula (11), its HSP distance will not be less than 39.5 MPa ^0.5 .

The HSP distance is used as an index representing the ease of solubility and dispersibility between solvents or organic molecules. Therefore, the HSP distance between water and a polymer can be used as a standard for quantitatively determining the degree of hydrophobicity or hydrophilicity of a polymer. As can be understood from the measurement results described later in Example and Comparative Example 2, a polymer having an HSP distance of more than 39.5 MPa ^0.5 has sufficient hydrophobicity to reduce the dielectric loss tangent during humidification of boron nitride. I can judge.

<Measurement of dielectric loss tangent during humidification>
The boron nitride materials of Examples and Comparative Examples were humidified by the following method. The boron nitride material was placed in a container with an open lid. The container was placed in a transparent plastic bag along with the hygrometer. The boron nitride material was humidified by flowing air at 25° C. whose humidity was adjusted to 90% into the plastic bag and leaving it in that state for 15 hours. A hygrometer was used to confirm that the humidity inside the plastic bag was maintained at 90% during humidification. The boron nitride material after humidification was taken out from the plastic bag.

After humidification, the dielectric loss tangent of the boron nitride material at a frequency of 1 GHz was measured. A cavity resonator (manufactured by AET, MS46122B) was used to measure the dielectric loss tangent. During the period from the end of humidification to the start of measurement of dielectric loss tangent, the boron nitride material was exposed to outside air at room temperature (25° C.). The measurement was performed 20 minutes after the end of humidification. The results are shown in Table 1. In Table 1, the dielectric loss tangent during humidification indicates a value normalized by setting the dielectric loss tangent during humidification of Comparative Example 1 to 1.

This measurement was carried out to determine the quality of the dielectric loss tangent during humidification. The dielectric loss tangent of the boron nitride material was normalized by setting the dielectric loss tangent of unmodified boron nitride (Comparative Example 1) to 1. That is, the ratio of the dielectric loss tangent of the boron nitride material to the dielectric loss tangent of unmodified boron nitride was calculated. If the calculated value is less than 1, it can be determined that the dielectric loss tangent is good.

<Measurement of water adsorption amount>
The boron nitride materials of the Examples and Comparative Examples were humidified in the manner described above. The amount of moisture adsorbed by the humidified boron nitride material was measured using the Karl Fischer method. For the measurement, a Karl Fischer moisture meter (manufactured by Kyoto Electronics Industry Co., Ltd., MKC-610) and a vaporizer (manufactured by Kyoto Electronics Industry Co., Ltd., ADP-611) were used. The vaporization temperature was 150°C. The end point was when the drift value reached +0.1 μg/sec. Nitrogen (200 mL/min) was used as the carrier gas. The measurement was performed twice, and the average value of the two measurements was used as the result. During the period from the end of humidification to the start of measurement, the boron nitride material was stored in a gas displacement desiccator filled with air with a humidity of 90%, and the boron nitride material was not exposed to outside air until the start of measurement. The results are shown in Table 1. In Table 1, the amount of water adsorption during humidification is a value normalized with the amount of water adsorption during humidification of Comparative Example 1 taken as 1.

This measurement was conducted to determine the amount of moisture adsorbed by the boron nitride material during humidification. The moisture adsorption amount of the boron nitride material was standardized by setting the moisture adsorption amount of unmodified boron nitride (Comparative Example 1) during humidification to 1. That is, the ratio of the amount of moisture adsorbed by the boron nitride material to the amount of moisture adsorbed by unmodified boron nitride was calculated. If the calculated value is less than 1, it can be determined that the amount of water adsorption is good.

<Measurement of SP value (methanol titration method)>
The SP values of the boron nitride materials of Examples and Comparative Examples were measured by the method shown below. 50 mL of ion exchange water was placed in a 200 mL beaker, and 50 mg of the boron nitride material was floated on the water surface. Thereafter, the mixture was stirred for 3 minutes using a magnetic stirrer at a rotation speed of 300 rpm to obtain a dispersion. The tip of a buret containing methanol was placed in the dispersion liquid, methanol was added dropwise under stirring, and the amount of methanol added Y (mL) required for all the particles of the boron nitride material to settle into the liquid was measured. . The SP value was calculated by substituting the measured addition amount Y into formula (A2). In this example, 47.9 MPa ^0.5 was used as the SP value (literature value) of water. 29.6 MPa ^0.5 was used as the SP value (literature value) of methanol. The results are shown in Table 1.

SP value = (47.9×50+29.6×Y)/(50+Y)...(A2)

This measurement was carried out to determine whether the surfaces of the boron nitride materials of Examples and Comparative Examples were sufficiently hydrophobic. If the calculated SP value is less than 47.9 MPa ^0.5 , which is the SP value of water, it can be determined that the material has hydrophobicity. When the amount of polymer attached to boron nitride is insufficient, or when the polymer is hydrophilic, the surface of the boron nitride material has insufficient hydrophobicity, and the SP value becomes 47.9 MPa ^0.5 or more. .

<Measurement of weight loss at 500°C>
When the boron nitride materials of Examples and Comparative Examples were heated from room temperature to 500° C., the weight loss was measured. A thermal analyzer (TG/DTA7200, manufactured by Hitachi High-Tech Science Co., Ltd.) was used for the measurement. Thermogravimetric measurements were performed under a nitrogen atmosphere. The amount of weight decrease from room temperature to 500° C. can be evaluated as the amount of adsorption of the polymer. The results are shown in Table 1.

As shown in Table 1, in Examples 1 to 5, the HSP distance between the polymer and water was greater than 39.5 MPa ^0.5 . The SP values of the boron nitride materials of Examples 1 to 5 were less than 47.9 MPa ^0.5 , and the surfaces of the particles of the boron nitride materials had sufficient hydrophobicity. From this, it can be concluded that in Examples 1 to 5, the surface of boron nitride was sufficiently modified with the polymer. The dielectric loss tangent (ratio to Comparative Example 1) of the boron nitride materials of Examples 1 to 5 was less than 1. In other words, Examples 1 to 5 exhibited lower dielectric loss tangents than hexagonal boron nitride under high humidity. The moisture adsorption amount (ratio to Comparative Example 1) of the boron nitride materials of Examples 1 to 5 was less than 1, which was lower than that of Comparative Examples 1 and 3.

FIG. 2 is a graph showing the relationship between the HSP distance between a polymer and water and the dielectric loss tangent of a boron nitride material during humidification. The horizontal axis shows the HSP distance between the polymers used in Examples 1 to 5 and Comparative Example 2 and water. The vertical axis indicates the dielectric loss tangent of the boron nitride materials of Examples 1 to 5 and Comparative Example 2 during humidification. A total of six points in Examples 1 to 5 and Comparative Example 2 were subjected to linear approximation using the least squares method to obtain an approximate straight line shown in FIG. The approximate straight line is expressed as y = -0.0565x + 3.2323, and the coefficient of determination R ² is 0.7061.

The HSP distance when the dielectric loss tangent during humidification was 1 was calculated from the approximate straight line. The HSP distance when the dielectric loss tangent during humidification was 1 was 39.5 MPa ^0.5 . Therefore, it is considered that if the surface of boron nitride is sufficiently modified with a polymer whose HSP distance to water is greater than 39.5 MPa ^0.5 , the dielectric loss tangent during humidification can be lowered than before the surface modification.

The polymers used in the boron nitride materials of Comparative Examples 2 and 3 had HSP distances of 38.7 MPa ^0.5 and 27.2 MPa ^0.5 , respectively. Therefore, it is considered that in Comparative Examples 2 and 3, the dielectric loss tangent during humidification exceeded the dielectric loss tangent of hexagonal boron nitride (Comparative Example 1).

Comparative Example 2 showed a small amount of water adsorption, but a high dielectric loss tangent. It is presumed that the main reason for this result is that there is a discrepancy between the amount of water measured by the Karl Fischer method and the amount of water measured by the dielectric loss tangent. The dielectric loss tangent was measured 20 minutes after the boron nitride material was transferred from an environment with a humidity of 90% to the atmosphere. In other words, "dielectric loss tangent during humidification" represents the dielectric loss tangent in a state where moisture desorption has progressed to some extent. In Examples 1 to 5, moisture desorption progressed sufficiently, but in Comparative Example 2, it is presumed that moisture desorption did not proceed sufficiently.

The measured values of Comparative Example 3 were not used to calculate the approximate straight line. This is because the polymer contained in the boron nitride material of Comparative Example 3 is polydopamine. Polydopamine does not have a single molecular structure, making it impossible to accurately calculate the HSP distance, and the large amount of hydroxyl groups contained within its structure directly causes deterioration of the dielectric loss tangent. The data of Comparative Example 3 was judged to be inappropriate for discussing the influence of moisture absorption on the dielectric loss tangent and was therefore excluded.

In Comparative Example 4, the HSP distance between the polymer (polystyrene) and water was sufficiently large. However, the SP value of the boron nitride material of Comparative Example 4 exceeded 47.9 MP ^0.5 . In other words, in Comparative Example 4, sufficient surface modification was not performed.

The reason why the polymers of Comparative Examples 2 to 4 were not able to achieve sufficient surface modification is not necessarily clear, but it is speculated that steric hindrance of the molecular chain, low adsorption energy of the polymer to boron nitride, etc. had an effect. be done.

Although the present disclosure has been adequately and fully described through the embodiments above to express the present disclosure, those skilled in the art will readily be able to modify and/or improve the above-described embodiments. It should be recognized that Therefore, unless the modification or improvement made by a person skilled in the art does not go beyond the scope of the claims stated in the claims, the modifications or improvements are within the scope of the claims. It is interpreted as encompassing.

The boron nitride material of the present disclosure exhibits a low dielectric loss tangent even under high humidity, so it is suitable for wiring boards of electronic devices used for large-capacity communications.

1 Boron nitride 2 Polymer 10 Boron nitride material 20 Resin composition 22 Filler 24 Curable resin 30 Resin-coated film 32 Resin layer 34 Support film 40 Resin-coated metal foil 42 Resin layer 44 Metal foil 50 Metal-clad laminate 52 Insulating layer 54 Metal Foil 60 Wiring board 62 Insulating layer 64 Wiring

Claims (18)

1. hexagonal boron nitride having a thickness in the C-axis direction of 5 nm or more;
   a polymer attached to the hexagonal boron nitride;
   A boron nitride material comprising:
   the solubility parameter of the boron nitride material measured by methanol titration is less than 47.9 MPa ^0.5 ;
   Boron nitride material.
2. the polymer is attached to the C-plane of the hexagonal boron nitride;
   The boron nitride material according to claim 1.
3. The polymer includes a polyvinyl aromatic polymer,
   The polyvinyl aromatic polymer includes a side chain containing a heteroaromatic ring.
   The boron nitride material according to claim 1.
4. The polymer includes a repeating unit represented by formula (1),
   In formula (1),
   n represents a positive integer,
   X is represented by formula (2),
   Any one of R ¹ to R ⁵ in formula (2) represents a direct bond to the main chain contained in the repeating unit,
   The other four R ¹ to R ⁵ are each independently at least one atom selected from the group consisting of H, B, C, N, O, Si, F, P, S, Cl, I, and Br. including,
   The boron nitride material according to claim 1.
   
5. In the formula (2), the other four R ¹ to R ⁵ are independently H atoms or hydrocarbon groups,
   The boron nitride material according to claim 4.
6. In the above formula (1),
   X is represented by formula (3),
   Any one of R ¹¹ to R ¹⁹ in formula (3) represents a direct bond to the main chain,
   The other eight R ¹¹ to R ¹⁹ are each independently at least one atom selected from the group consisting of H, B, C, N, O, Si, F, P, S, Cl, I, and Br. including,
   The boron nitride material according to claim 4.
   
7. In the formula (3), the other eight from R ¹¹ to R ¹⁹ are independently H atoms or hydrocarbon groups,
   The boron nitride material according to claim 6.
8. The polymer includes a repeating unit containing at least one selected from the group consisting of a carbazole skeleton and a fluorene skeleton.
   The boron nitride material according to claim 1.
9. The fluorene skeleton includes at least one substituent,
   The boron nitride material according to claim 8.
10. The polymer includes a repeating unit containing a polyphenylene ether skeleton,
    The boron nitride material according to claim 1.
11. The polyphenylene ether skeleton includes at least one substituent,
    The boron nitride material according to claim 10.
12. comprising the boron nitride material according to claim 1;
    filler.
13. comprising the filler according to claim 12;
    Resin composition.
14. comprising the resin composition according to claim 13 or a semi-cured product of the resin composition,
    prepreg.
15. A resin layer comprising the resin composition according to claim 13 or a semi-cured product of the resin composition,
    a support film;
    Film with resin.
16. A resin layer comprising the resin composition according to claim 13 or a semi-cured product of the resin composition,
    comprising a metal foil and
    Metal foil with resin.
17. An insulating layer comprising a cured product of the resin composition according to claim 13 or a cured product of the prepreg according to claim 14,
    comprising a metal foil and
    Metal-clad laminate.
18. An insulating layer comprising a cured product of the resin composition according to claim 13 or a cured product of the prepreg according to claim 14,
    Wiring and equipped,
    wiring board.