Hexagonal boron nitride filler, production method for hexagonal boron nitride filler, resin composition, and production method for resin composition

Abstract

Provided is a hexagonal boron nitride filler containing: hexagonal boron nitride particles; and a film (a) including a compound (A) that has a polyethyleneimine skeleton and a polyalkylene oxide chain and that has a weight-average molecular weight of 2,000-10,000.

Description

Hexagonal boron nitride filler, method for producing hexagonal boron nitride filler, resin composition, and method for producing the resin composition.

[0001] The present invention relates to hexagonal boron nitride filler, a method for producing hexagonal boron nitride filler, a resin composition, and a method for producing the resin composition.

[0002] Nitride fillers possess high thermal conductivity and excellent electrical insulation properties. Therefore, nitride fillers are promising as fillers for resin compositions used in products such as heat dissipation sheets and encapsulants for electronic components. Hexagonal boron nitride particles are known to be used as raw materials for such nitride fillers because they not only have high thermal conductivity but also do not suffer from moisture resistance problems like aluminum nitride particles, and they also have a low dielectric constant. Furthermore, modifying the surface of hexagonal boron nitride particles is being investigated depending on the application.

[0003] Patent Document 1 describes a boron nitride composition comprising boron nitride powder whose surface is treated with an organosilicon compound. Patent Document 2 describes a boron nitride composition comprising boron nitride powder, wherein the surface of the boron nitride powder is treated with an overcoating layer comprising at least one of silane, siloxane, carboxylic acid derivative, and mixtures thereof. Patent Document 3 describes surface-coated hexagonal boron nitride particles, in which a layer containing a condensate of the coupling agent is formed on at least a portion of the surface of the hexagonal boron nitride particles by mixing hexagonal boron nitride particles, a coupling agent, and a catalyst having polar groups and aromatic rings in a solvent.

[0004] Japanese Patent Publication No. 2008-94701, Japanese Patent Publication No. 2007-182369, Japanese Patent Publication No. 2022-183821

[0005] Hexagonal boron nitride particles have advantages such as high thermal conductivity, lack of moisture resistance issues like aluminum nitride particles, and low dielectric constant. However, the primary particles of hexagonal boron nitride are plate-like, have few active sites, and the active sites are localized at the end faces. Therefore, when hexagonal boron nitride particles are mixed with resins such as epoxy resins, the viscosity of the resulting resin composition tends to increase. In addition, hexagonal boron nitride particles are difficult to mix with resins, and it is difficult to significantly reduce the viscosity of the resin composition even when dispersion aids are added.

[0006] Furthermore, resin compositions used in products such as heat dissipation sheets and encapsulants for electronic components are required to have a long pot life in order to stably mold the products. In addition, these resin compositions are required to have good adhesive strength in order to be used in a variety of applications.

[0007] The present invention has been made in view of these circumstances, and aims to provide a hexagonal boron nitride filler, a method for producing the hexagonal boron nitride filler, a resin composition containing the hexagonal boron nitride filler, and a method for producing the resin composition, which can be obtained by suppressing the increase in viscosity when mixed with an epoxy resin to form a resin composition, having a long pot life, and suppressing the decrease in adhesive strength at the interface between the hexagonal boron nitride filler and the epoxy resin after curing.

[0008] As a result of diligent research by the inventors, we have found that hexagonal boron nitride particles and a hexagonal boron nitride filler having a coating containing a specific compound can solve the above problems, and have completed the present invention. That is, the present invention has the following configuration.

[0009] [1] A hexagonal boron nitride filler containing hexagonal boron nitride particles and a coating (a) containing compound (A) having a polyethyleneimine skeleton and polyalkylene oxide chains, and having a weight-average molecular weight of 2,000 or more and 10,000 or less. [2] The specific surface area (m²) of the hexagonal boron nitride particles obtained by the BET method. ２ Surface area per 1 m² calculated from ( / g) ２ In this case, compound (A) is divided into 5.0 × 10-4 g or more and less than 5.0×10 -2 g, the hexagonal boron nitride filler according to [1] above. [3] The hexagonal boron nitride filler according to [1] or [2] above, containing a silicon-containing oxide film (b). [4] The surface area per 1 m ２ calculated from the specific surface area (m ２ / g) determined by the BET method of the hexagonal boron nitride particles, the compound (A) and the silicon-containing oxide film (b) are 5.0×10 -4 g or more and less than 5.0×10 -2 g, the hexagonal boron nitride filler according to [3] above. [5] The hexagonal boron nitride filler according to any one of [1] to [4] above, containing an organosilicon compound film (c) having a silanol group. [6] The hexagonal boron nitride filler according to [5] above, in which the film (a) and the organosilicon compound film (c) are adjacent to each other. [7] The surface area per 1 m ２ calculated from the specific surface area (m ２ / g) determined by the BET method of the hexagonal boron nitride particles, the compound (A) and the organosilicon compound film (c) are 5.0×10 -4 g or more and less than 5.0×10 -2 g, the hexagonal boron nitride filler according to [5] or [6] above. [8] The hexagonal boron nitride filler according to any one of [1] to [7] above, containing a silicon-containing oxide film (b) and an organosilicon compound film (c) having a silanol group. [9] The surface area per 1 m ２ calculated from the specific surface area (m ２ / g) determined by the BET method of the hexagonal boron nitride particles, the compound (A), the silicon-containing oxide film (b), and the organosilicon compound film (c) are 5.0×10 -4 g or more and less than 5.0×10 -2[8] above, a hexagonal boron nitride filler containing less than g.

[10] A method for producing a hexagonal boron nitride filler, comprising a fourth step of forming the coating (a), wherein the hexagonal boron nitride particles and a coating (a) containing a compound (A) having a polyethyleneimine skeleton and a polyalkylene oxide chain and a weight-average molecular weight of 2,000 or more and 10,000 or less.

[11] A method for producing a hexagonal boron nitride filler, comprising a first step of coating with an organosilicone compound having active hydrogen and a second step of forming a silicon-containing oxide coating (b) by heating.

[12] A method for producing a hexagonal boron nitride filler, comprising a third step of coating with an organosilicone compound having active hydrogen by vapor deposition and treating the coated organosilicone compound with a basic substance to form an organosilicone compound coating (c) having a silanol group.

[13] A resin composition comprising a hexagonal boron nitride filler according to any one of [1] to [9] above and an epoxy resin.

[14] A method for producing the resin composition according to

[13] above, comprising step I of adding and mixing the hexagonal boron nitride filler with the epoxy resin.

[15] A method for producing the resin composition according to

[13] above, comprising step II-1 of obtaining a composition i comprising the compound (A) and the epoxy resin, and step II-2 of adding and mixing at least one particle selected from hexagonal boron nitride particles, a silicon-containing oxide film (b) and particles containing hexagonal boron nitride particles, an organosilicon compound film (c) having a silanol group and particles containing hexagonal boron nitride particles, and a silicon-containing oxide film (b) and an organosilicon compound film (c) having a silanol group and particles containing hexagonal boron nitride particles.

[0010] According to the present invention, it is possible to obtain a resin composition in which the viscosity increase when mixed with an epoxy resin to form a resin composition can be suppressed, the pot life is long, and the decrease in adhesive strength at the interface between the hexagonal boron nitride filler and the epoxy resin after curing is suppressed. The present invention provides a hexagonal boron nitride filler, a method for producing the hexagonal boron nitride filler, a resin composition containing the hexagonal boron nitride filler, and a method for producing the resin composition.

[0011] The present invention will now be described in detail. The present invention also includes embodiments in which any selection or combination of the provisions described herein is arbitrarily selected. In this specification, preferred provisions can be arbitrarily selected, and combinations of preferred provisions can be considered more preferred. In this specification, the notation "XX to YY" means "XX or more and YY or less." In this specification, the lower and upper limits described in steps for a preferred numerical range (e.g., a range of content, etc.) can be combined independently. For example, from the notation "preferably 10 to 90, more preferably 30 to 60," the "preferred lower limit (10)" and the "more preferred upper limit (60)" can be combined to arrive at "10 to 60."

[0012] In this specification, "50% cumulative volume particle size (D50)" refers to the particle size at which the cumulative volume of a given particle size distribution reaches 50%. D50 is determined from the particle size distribution by laser diffraction scattering. Specifically, it can be measured using a laser diffraction / scattering particle size distribution analyzer (Microtrac-Bell Co., Ltd., product name: Microtrac MT3300EX2), etc.

[0013] <Hexagonal Boron Nitride Filler> The hexagonal boron nitride filler of the present invention contains hexagonal boron nitride particles and a coating (a) containing compound (A), which has a polyethyleneimine skeleton and polyalkylene oxide chains and a weight-average molecular weight of 2,000 to 10,000. By containing a coating (a) containing compound (A) in the hexagonal boron nitride filler, the increase in viscosity when mixed with epoxy resin to form a resin composition can be suppressed, resulting in a resin composition with a long pot life and suppressed reduction in adhesive strength at the interface between the hexagonal boron nitride filler and the epoxy resin after curing. In particular, the hexagonal boron nitride filler of the present invention does not have the problem of moisture resistance like fillers using aluminum nitride, and also has the advantage of having a very high dielectric strength and dielectric constant compared to fillers using aluminum nitride.

[0014] [Hexagonal Boron Nitride Particles] In the hexagonal boron nitride particle filler of the present invention, the hexagonal boron nitride particles (hereinafter also referred to as h-BN particles) used as raw materials can be commercially available or other known products. The form of the h-BN particles used in the present invention is not particularly limited, and examples include needle-shaped, plate-shaped primary particles, and aggregates of these primary particles. h-BN particles can be used alone or in combination of two or more types.

[0015] The cumulative volume 50% particle size (D50) of the h-BN particles used in the present invention is not particularly limited, but is preferably 0.1 μm or more, more preferably 0.3 μm or more, even more preferably 0.4 μm or more, and even more preferably 0.5 μm or more, preferably 200.0 μm or less, more preferably 100.0 μm or less, and even more preferably 50.0 μm or less. That is, it is preferably 0.1 to 200.0 μm, more preferably 0.3 to 100.0 μm, even more preferably 0.4 to 50.0 μm, and even more preferably 0.5 to 50.0 μm.

[0016] If the D50 of h-BN particles is 0.1 μm or larger, the high heat dissipation performance inherent in h-BN particles can be expected to be realized. If it is 200.0 μm or smaller, even when using a resin composition containing hexagonal boron nitride filler as a heat dissipation material for mounting power system electronic components, it becomes possible to supply the thinnest possible heat dissipation material. Furthermore, the thinner the heat dissipation material, the smaller the power system electronic components can be made, increasing their versatility.

[0017] [Coating (a)] The coating (a) contained in the hexagonal boron nitride filler of the present invention contains compound (A) which has a polyethyleneimine skeleton and a polyalkylene oxide chain and a weight-average molecular weight of 2,000 or more and 10,000 or less. The content of compound (A) in coating (a) is not particularly limited, but from the viewpoint of further exhibiting the effects of the present invention, it is preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 98% by mass or more, and may be 100% by mass. That is, coating (a) may be formed from compound (A).

[0018] The coating (a) may be adjacent to the h-BN particles, or it may be formed on the h-BN particles via other layers, such as the silicon-containing oxide coating (b) described later, or the organic silicone compound coating (c) having silanol groups. That is, the coating (a) may be adjacent to the h-BN particles, adjacent to the silicon-containing oxide coating (b), or adjacent to the organic silicone compound coating (c) having silanol groups. From the viewpoint of effectively obtaining the effects of the present invention, it is preferable that the hexagonal boron nitride filler has the coating (a) as the outermost layer of the hexagonal boron nitride filler.

[0019] In addition to compound (A), the coating (a) may optionally contain dispersants such as surface treatment agents, tackifiers, etc. Examples of dispersants include DISPERBYK106, BYK-W9010, BYK-P104 (all manufactured by Bic Chemie Japan Co., Ltd.), and Floren G700 (Kyoeisha Chemical Co., Ltd.). Examples of tackifiers include the hydrogenated petroleum resin Alcon M-90 (Arakawa Chemical Industries, Ltd.), the terpene resin YS Resin TO-85, and YS Polystar T80 (both manufactured by Yasuhara Chemical Co., Ltd.).

[0020] (Compound (A)) Compound (A) contained in the coating (a) containing the hexagonal boron nitride filler of the present invention has a polyethyleneimine skeleton and a polyalkylene oxide chain, and its weight-average molecular weight is 2000 or more and 10000 or less. The polyethyleneimine skeleton has the following formula (I) as its constituent unit: -CH ２ CH ２ NR ａ - (I) In the above equation (I), R ａ This is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and the polyethyleneimine skeleton includes not only those having a complete linear structure, but also those having a branched chain structure containing primary, secondary, and tertiary amino nitrogens. From the viewpoint of better exhibiting the effects of the present invention, it is preferable that the polyethyleneimine skeleton has 3 to 10 nitrogen atoms per molecule.

[0021] The alkylene oxide contained in the polyalkylene oxide chain is preferably an alkylene oxide having 2 to 4 carbon atoms, such as ethylene oxide, propylene oxide, oxetane, butylene oxide, and tetrahydrofuran. Among these, propylene oxide is preferred from the viewpoint of better exhibiting the effects of the present invention.

[0022] From the viewpoint of further exhibiting the effects of the present invention, compound (A) preferably has 1 to 10 polyalkylene oxide chains having 8 to 15 repeating units as side chains.

[0023] When mixing hexagonal boron nitride particles or a filler containing hexagonal boron nitride particles with an epoxy resin, adding a general surfactant can suppress, to some extent, the increase in viscosity of the resulting resin composition. However, adding a general surfactant reduces the adhesive strength at the interface between the hexagonal boron nitride particles or the filler containing hexagonal boron nitride particles and the epoxy resin, thereby reducing the strength of the cured resin composition and the adhesive strength at the phase interface. On the other hand, in the present invention, because compound (A) has a polyethyleneimine skeleton and a polyalkylene oxide chain, it is possible to suppress the increase in viscosity when mixed with the epoxy resin to form a resin composition, as well as suppress the decrease in adhesive strength at the interface between the hexagonal boron nitride filler and the epoxy resin, and suppress the decrease in adhesive strength at the phase interface. Also, for the same reason, the resin composition obtained by mixing with the epoxy resin has a long pot life and makes it easier to obtain the desired molded product.

[0024] The weight-average molecular weight of compound (A) is not particularly limited as long as it is between 2,000 and 10,000, but from the viewpoint of better demonstrating the effects of the present invention, it is preferably between 2,500 and 9,000, more preferably between 3,000 and 7,000, and even more preferably between 3,500 and 6,000. In this specification, the weight-average molecular weight is the value measured by matrix-assisted laser desorption / ionization time-of-flight mass spectrometry (MALDI-TOF MS), and can be measured specifically by the method described in the examples.

[0025] When the hexagonal boron nitride filler contains h-BN particles and a coating (a), the specific surface area (m²) of the hexagonal boron nitride particles, determined by the BET method, is used to better demonstrate the effects of the present invention. ２ Surface area per 1 m² calculated from ( / g) ２ The correct compound (A) is 5.0 × 10 -４ g or more 5.0×10 -２ Preferably containing less than 10 g, and more preferably 2.0 × 10 -３ g or more 4.0×10 -２ g or less, more preferably 4.0 × 10 -３ g or more 4.0×10 -２It is less than or equal to g. In this specification, the specific surface area (m²) obtained from the BET method is used. ２ The value ( / g) is measured using the nitrogen adsorption BET single-point method based on gas flow. A Mountech Macsorb HM model-1220 can be used as the evaluation device.

[0026] When the hexagonal boron nitride filler contains h-BN particles, a coating (a), and a silicon-containing oxide coating (b), the specific surface area (m²) of the hexagonal boron nitride particles, determined by the BET method, is used to better demonstrate the effects of the present invention. ２ Surface area per 1 m² calculated from ( / g) ２ Each time, the compound (A) and the silicon-containing oxide film (b) are divided into 5.0 × 10 -４ g or more 5.0×10 -２ Preferably containing less than 10 g, and more preferably 2.0 × 10 -３ g or more 4.0×10 -２ g or less, more preferably 4.0 × 10 -３ g or more 4.0×10 -２ It is less than or equal to g.

[0027] When the hexagonal boron nitride filler contains h-BN particles, a coating (a), and an organosilicon compound coating (c) having silanol groups, the hexagonal boron nitride filler is determined from the viewpoint of further exhibiting the effects of the present invention by the specific surface area (m²) of the hexagonal boron nitride particles obtained by the BET method. ２ Surface area per 1 m² calculated from ( / g) ２ In each case, the compound (A) and the organic silicone compound coating (c) are divided into 5.0 × 10 -４ g or more 5.0×10 -２ Preferably containing less than 10 g, and more preferably 2.0 × 10 -３ g or more 4.0×10 -２ g or less, more preferably 4.0 × 10 -３ g or more 4.0×10 -２ It is less than or equal to g.

[0028] When the hexagonal boron nitride filler contains h-BN particles and a coating (a), a silicon-containing oxide coating (b), and an organosilicon compound coating (c) having silanol groups, the hexagonal boron nitride filler is determined from the viewpoint of exhibiting the effects of the present invention by the specific surface area (m²) of the hexagonal boron nitride particles obtained by the BET method. ２ Surface area per 1 m² calculated from ( / g) ２ Each time, the compound (A), the silicon-containing oxide film (b), and the organic silicone compound film (c) are distributed in a quantity of 5.0 × 10 -４ g or more 5.0×10 -２ Preferably containing less than 10 g, and more preferably 2.0 × 10 -３ g or more 4.0×10 -２ g or less, more preferably 4.0 × 10 -３ g or more 4.0×10 -２ It is less than or equal to g.

[0029] [Silicon-containing oxide coating (b)] The hexagonal boron nitride filler of the present invention may contain a silicon-containing oxide coating (b). Examples of the "silicon-containing oxide" in the silicon-containing oxide coating (b) include silica and composite oxides of silicon and boron. In this specification, oxides also include oxynitrides, oxycarbonitrides, and the like.

[0030] When the hexagonal boron nitride filler contains a silicon-containing oxide film (b), the content of the silicon-containing oxide film (b) in the hexagonal boron nitride filler is preferably 0.8 × 10¹⁶, from the viewpoint of increasing the affinity between the surface of the h-BN particles and compound (A). －５ ~2.5 x 10 －２ [SiO ２ Conversion g / m ２ ], more preferably 1.0 × 10 －４ ~2.0 x 10 －２ [SiO ２ Conversion g / m ２ ], more preferably 2.0 × 10 －４ ~1.5 x 10 －２ [SiO ２ Conversion g / m ２The silicon content of the silicon-containing oxide film (b) in the hexagonal boron nitride filler is calculated by multiplying the silicon atom content (ΔSi amount) measured by ICP emission spectroscopy by the specific surface area (m²) obtained from the BET method of the hexagonal boron nitride filler. ２ Surface area (m²) calculated from ( / g) ２ It can be found by dividing by ).

[0031] The silicon atom content (ΔSi amount) in the silicon-containing oxide film (b) is preferably 20 to 2000 ppm by mass, more preferably 30 to 1950 ppm by mass, and even more preferably 40 to 1900 ppm by mass, from the viewpoint of increasing the affinity between the surface of the h-BN particles and compound (A). The ΔSi amount can be measured by ICP emission spectroscopy.

[0032] When the hexagonal boron nitride filler contains a silicon-containing oxide film (b), it is preferable that the silicon-containing oxide film (b) is contained between the h-BN particles and the film (a), and it is more preferable that the silicon-containing oxide film (b) and the h-BN particles are adjacent to each other, with the film (a) being the outermost layer. Since the silicon-containing oxide film (b) has a high affinity for the h-BN particles and compound (A), containing the silicon-containing oxide film (b) between the h-BN particles and the film (a) can increase the affinity between the h-BN particles and compound (A). As a result, the adhesive strength between the resin contained in the resin composition described later and the hexagonal boron nitride filler is improved, and when the resin composition is laminated, the adhesive strength at the layer interface is improved.

[0033] The silicon-containing oxide film (b) can be formed by the method described later in the <Method for producing hexagonal boron nitride filler>. Furthermore, it is preferable that the silicon-containing oxide film (b) is formed using an organosilicon compound having active hydrogen, as described later, as a raw material.

[0034] [Organosilicone compound coating having silanol groups (c)] The hexagonal boron nitride filler of the present invention may contain an organosilicone compound coating having silanol groups (c) (hereinafter sometimes simply referred to as "organosilicone compound coating (c)"). Furthermore, the hexagonal boron nitride filler of the present invention may also contain a silicon-containing oxide coating (b) and an organosilicone compound coating (c).

[0035] The organosilicone compound coating (c) is preferably an organosilicone compound containing the structure shown in the following formula (i).

[0036]

[0037] (In formula (i), R １ (These are alkyl groups with 1 to 4 carbon atoms.)

[0038] The organosilicon compound containing the structure shown in formula (i) above may be linear, cyclic, or branched.

[0039] The content of the organic silicone compound containing the structure shown in formula (i) in the organic silicone compound coating (c) is not particularly limited, but from the viewpoint of suppressing a decrease in the interfacial adhesion strength between the resin contained in the resin composition and the hexagonal boron nitride filler, it is preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 98% by mass or more, and may be 100% by mass. In other words, the organic silicone compound coating (c) may be formed from an organic silicone compound containing the structure shown in formula (i). The content of the organic silicone compound containing the structure shown in formula (i) in the organic silicone compound coating (c) can be calculated by converting from the measured values ​​obtained by ICP emission spectrometry.

[0040] When the hexagonal boron nitride filler contains an organosilicon compound coating (c), the content of the organosilicon compound coating (c) in the hexagonal boron nitride filler is preferably 0.8 × 10¹⁶, from the viewpoint of suppressing a decrease in thermal conductivity. -５ ~2.5 x 10 -２ [SiO ２ Conversion g / m ２], more preferably 1.0 × 10 -４ ~2.0 x 10 -２ [SiO ２ Conversion g / m ２ ], more preferably 2.0 × 10 -４ ~1.5 x 10 -２ [SiO ２ Conversion g / m ２ The content of the organosilicone compound coating (c) can be determined by the same method as the content of the silicon-containing oxide coating (b) in the hexagonal boron nitride filler.

[0041] When the hexagonal boron nitride filler contains an organic silicone compound coating (c), it is preferable that the hexagonal boron nitride filler contains the organic silicone compound coating (c) between the h-BN particles and the coating (a). Furthermore, it is preferable that the coating (a) and the organic silicone compound coating (c) are adjacent to each other, and it is more preferable that the coating (a) is contained in the outermost layer. Since the organic silicone compound coating (c) has a high affinity for the h-BN particles and compound (A), when the hexagonal boron nitride filler contains the organic silicone compound coating (c) between the h-BN particles and the coating (a), the affinity between the h-BN particles and compound (A) can be further increased. As a result, the interfacial adhesion strength between the resin contained in the resin composition described later and the hexagonal boron nitride filler is improved, and when the resin composition is laminated, the adhesion strength of the layer interface is improved.

[0042] When the hexagonal boron nitride filler contains a silicon-containing oxide film (b) and an organosilicone compound film (c), from the viewpoint of effectively obtaining the effects of the present invention, it is preferable that the h-BN particles and the silicon-containing oxide film (b) are adjacent to each other, the organosilicone compound film (c) is adjacent to the surface of the silicon-containing oxide film (b) opposite to the surface in contact with the h-BN particles, and that film (a) is contained as the outermost layer. Furthermore, when the hexagonal boron nitride filler contains a silicon-containing oxide film (b) and an organosilicone compound film (c), the hexagonal boron nitride filler may have multiple layers of each of the silicon-containing oxide film (b) and the organosilicone compound film (c).

[0043] The organosilicone compound coating (c) can be formed by the method described later in the <Method for producing hexagonal boron nitride filler>.

[0044] <Method for producing hexagonal boron nitride filler> The method for producing hexagonal boron nitride filler of the present invention is a method for producing the hexagonal boron nitride filler described above. The method for producing hexagonal boron nitride filler of the present invention is a method for producing hexagonal boron nitride filler that contains h-BN particles and a coating (a) containing a compound (A) having a polyethyleneimine skeleton and a polyalkylene oxide chain and a weight-average molecular weight of 2000 or more and 10000 or less, and comprises a fourth step of forming the coating (a).

[0045] The method for producing hexagonal boron nitride filler of the present invention may, in addition to the fourth step, include a first step of coating with an organic silicone compound having active hydrogen, a second step of forming a silicon-containing oxide film (b) by heating, and a third step of coating with an organic silicone compound having active hydrogen by vapor deposition and treating with a basic substance to form an organic silicone compound film (c) having silanol groups. The method for producing hexagonal boron nitride filler of the present invention may, in addition to the fourth step, include a first step of coating with an organic silicone compound having active hydrogen and a second step of forming a silicon-containing oxide film (b) by heating. Furthermore, the method for producing hexagonal boron nitride filler of the present invention may, in addition to the fourth step, include a first step of coating with an organic silicone compound having active hydrogen, a second step of forming a silicon-containing oxide film (b) by heating, and a third step of forming an organic silicone compound film (c) having silanol groups by treating with a basic substance. Steps 1 to 4 will be described below.

[0046] [Step 1] This step involves coating with an organic silicone compound containing active hydrogen, and is performed to form a silicon-containing oxide film (b). The objects to be coated with the organic silicone compound containing active hydrogen are h-BN particles, particles coated with a silicon-containing oxide film (b) on h-BN particles, particles coated with an organic silicone compound film (c), and particles coated with both a silicon-containing oxide film (b) and an organic silicone compound film (c) on h-BN particles.

[0047] <Organosilicone Compounds Having Active Hydrogen> In the hexagonal boron nitride filler of the present invention, the organosilicone compound having active hydrogen (hereinafter sometimes simply referred to as "organosilicone compound") used as a raw material for the silicon-containing oxide film (b) is preferably an organosilicone compound containing the structure shown in the following formula (1) from the viewpoint of forming a more uniform film, and may be linear, cyclic, or branched. The structure represented by the following formula (1) is a hydrogen siloxane unit in which hydrogen is directly bonded to a silicon atom.

[0048]

[0049] (In formula (1), R is an alkyl group having 1 to 4 carbon atoms.)

[0050] In formula (1) above, R, which is an alkyl group having 1 to 4 carbon atoms, is preferably a methyl group, ethyl group, propyl group, t-butyl group, etc., from the viewpoint of volatilizing the silicone compound, and is particularly preferably a methyl group. In the hexagonal boron nitride filler of the present invention, the organosilicon compound used as a raw material is, for example, an oligomer or polymer containing the structure shown in formula (1).

[0051] As the organosilicon compound, at least one of the compounds represented by the following formula (2) and the compounds represented by the following formula (3) is preferred.

[0052]

[0053] (In formula (2), R1 and R2 are each independently a hydrogen atom or a methyl group, at least one of R1 and R2 is a hydrogen atom, and m is an integer from 0 to 10.)

[0054]

[0055] (In equation (3), n is an integer between 3 and 6.)

[0056] In particular, the cyclic hydrogensiloxane oligomer in formula (3) where n is 4 is excellent in that it can form a uniform silicon-containing oxide film (b) on the surface of the object to be coated. The weight-average molecular weight of the organosilicon compound containing the structure shown in formula (1) is preferably 100 to 2000, more preferably 150 to 1000, and even more preferably 180 to 500. It is presumed that using an organosilicon compound containing the structure shown in formula (1) with a weight-average molecular weight in this range makes it easier to form a thin and uniform silicon-containing oxide film (b) on the surface of the object to be coated. In formula (2), it is preferable that m is 1.

[0057] In the first step, the method is not particularly limited as long as the surface of the object to be coated can be covered with an organosilicone compound. Examples of methods for the first step include a dry mixing method in which the organosilicone compound is added by spraying or other means while stirring the object to be coated using a general powder mixing device, and then dry-mixed. Examples of powder mixing devices include Henschel mixers, container-rotating V-blenders, double-cone blenders, ribbon blenders with mixing blades, screw blenders, sealed rotary kilns, and stirring using a stirrer in a sealed container with a magnetic coupling. The temperature conditions in this case are not particularly limited, depending on the boiling point and vapor pressure of the organosilicone compound, but a preferred temperature is 10°C to 200°C, more preferably 20°C to 150°C, and even more preferably 40°C to 100°C.

[0058] Furthermore, as the first step, a gas-phase adsorption method can be used in which the vapor of the organosilicon compound alone or a mixed gas with an inert gas such as nitrogen gas is attached to or deposited onto the surface of the object to be coated while it is standing still. In this case, the temperature conditions depend on the boiling point and vapor pressure of the organosilicon compound, but the preferred temperature is in the range of 10°C to 200°C, more preferably 20°C to 150°C, and even more preferably 40°C to 100°C. The processing time is preferably 3 to 7 hours, and more preferably 3.5 to 5 hours. If necessary, the system can be pressurized or depressurized (sometimes called chemical vapor deposition (CVD)). In this case, a sealed system that allows for easy replacement of the gas in the system is preferred, such as a glass container, desiccator, or CVD apparatus. When coating the object to be coated with the organosilicon compound without stirring, the processing time needs to be longer. However, by intermittently placing the processing container on the vibrator, areas where powder particles are in contact and creating shadows, as well as powder particles far from the upper air layer, can be processed efficiently by moving the container's position.

[0059] The amount of organosilicone compound used in the first step is not particularly limited. When an organosilicone compound containing the structure shown in formula (1) is used as the organosilicone compound, the amount of organosilicone compound containing the structure shown in formula (1) used to coat the object is equal to the specific surface area (m²) of the object to be coated, determined by the BET method. ２ Surface area per 1 m² calculated from ( / g) ２ The amount is preferably 0.08 mg to 20.0 mg per unit, more preferably 0.09 mg to 15.0 mg, and even more preferably 1.0 mg to 10.0 mg. With the above coating amount, the decrease in thermal conductivity can be further suppressed and the affinity with compound (A) can be further increased. The specific surface area (m²) of the coated object obtained by the BET method is... ２ Surface area per 1 m² calculated from ( / g) ２ The amount of organic silicone compound coating per unit containing the structure shown in equation (1) is calculated by taking the difference in mass of the object to be coated with the organic silicone compound and the specific surface area (m²) of the object to be coated, obtained from the BET method. ２ Surface area (m²) calculated from ( / g)２ It can be found by dividing by ).

[0060] The timing of introducing the organosilicon compound can be any stage before heating, as long as the reaction amount of the organosilicon compound is maintained.

[0061] [Second Step] In this step, the coated organic silicone compound is heated to form a silicon-containing oxide film (b). That is, in this step, a silicon-containing oxide film (b) is formed by heating.

[0062] The heating temperature in the second step is preferably 500°C to 900°C, more preferably 550°C to 850°C, and even more preferably 600°C to 800°C. Any general heating furnace that can maintain the temperature within the above range can be used.

[0063] If the heating in this second step is at a low temperature, a silica film is formed on the surface of the object to be coated, and silica-coated boron nitride particles can be produced. In other words, the silicon-containing oxide film (b) is formed as a silica film. If the heating in this second step is at a high temperature, a composite oxide film of silicon and boron elements is formed on the surface of the object to be coated, and composite oxide-coated boron nitride particles of silicon and boron elements can be produced. In other words, the silicon-containing oxide film (b) is formed as a composite oxide film of silicon and boron elements. It is presumed that when the temperature in the second step is high, the boron contained in the object to be coated comes out onto the surface of the object to be coated, and together with the silicon derived from the organosilicon compound, a composite oxide film of silicon and boron elements is formed. From the viewpoint of producing hexagonal boron nitride fillers that maintain the high thermal conductivity of h-BN particles and have excellent moisture resistance, it is preferable that the silicon-containing oxide film (b) is a silica film.

[0064] Note that silica coating means that the material is coated with a thin film mainly composed of silica. However, since multiple inorganic composites may exist at the interface between the coated silica and the boron nitride particles, when analyzed by ToF-SIMS (Time of Flight Secondary Ion Mass Spectrometry, ION-TOF, TOF.SIMS5), the recombination of secondary ions and decomposition during ionization may also occur, resulting in AlSiO ４ In some cases, segments such as ions and SiNO ions may be detected simultaneously as minor components. These composite segments analyzed by ToF-SIMS can also be defined as partial detections of boron nitride when it is silicated. As a guideline, if the amount of secondary electrons in silica is greater than that of other fractions, silica can be considered the main component.

[0065] To further improve accuracy and confirm the purity of silica, a silica film was formed on a boron nitride polycrystalline substrate using the same method. The surface of this sample was measured using a photoelectron spectroscopy (XPS: X-ray Photoelectron Spectroscopy, ULVAC-PHIE, Quantera II). The kinetic energy of the detected Si-derived photoelectrons nearly matched the standard peak of silica, 103.7 eV, indicating that it is mostly SiO ２ It is presumed that this is the structure. Furthermore, depending on the heating temperature, organic components may remain. It is quite possible that organic siloxane components may be present, as long as it does not impair the effects of the present invention.

[0066] The carbon atom content can be measured using a carbon-sulfur analyzer employing a non-dispersive infrared absorption method in a tubular electric furnace. Specifically, it can be measured using a carbon-sulfur analyzer (Carbon Anlyzer EMIA-821: manufactured by Horiba, Ltd.).

[0067] When the heating temperature (heat treatment temperature) in the second step is 1000 °C or lower, the thermal conductivity of the hexagonal boron nitride filler becomes good, which is also effective in terms of energy cost. Further, when the heating temperature is 500 °C or higher, the silicon-containing oxide film (b) becomes excellent in insulation. Further, when the heating temperature is 500 °C or higher and 1000 °C or lower, the silicon-containing oxide film (b) is uniformly formed on the surface of the object to be coated.

[0068] As the heating time in the second step, it is preferably 2 hours or more and 10 hours or less, more preferably 2 hours or more and 8 hours or less, and still more preferably 2 hours or more and 7 hours or less. When the heat treatment time is 2 hours or more, there is no residue of the decomposition product of the organic group (alkyl group having 4 or less carbon atoms) of the organosilicon compound, and it is preferable in that a silicon-containing oxide film (b) having a very low carbon atom content can be obtained on the surface of the object to be coated. Further, setting the heating time to 7 hours or less is preferable in that the silicon-containing oxide film (b) can be formed with high production efficiency.

[0069] The atmosphere for the heat treatment in the second step is not particularly limited. For example, it may be under an inert gas atmosphere such as N ２ , Ar, He, etc., or may be under an atmosphere containing a reducing gas such as H ２ , CO, CH ４ , etc., or may be under an atmosphere containing oxygen gas, for example, in the atmosphere (in the air).

[0070] Further, in order to further increase the affinity with the compound (A) by increasing the thickness of the silicon-containing oxide film (b), after the heat treatment in the second step, the first step and the second step may be further performed in order. That is, the steps of performing the first step and the second step in order may be repeatedly executed. In the first step, the coating method of covering the surface of the object to be coated with an organosilicon compound by the vapor phase adsorption method is preferable because a uniform and thin silicon-containing oxide film (b) can be formed as compared with the coating method performed by liquid treatment. Therefore, even if the steps of performing the first step and the second step in order are repeated a plurality of times, for example, about 2 to 5 times, the good thermal conductivity of the h-BN particles can be exhibited.

[0071] [Third Step] In this step, an organosilicone compound having active hydrogen is coated onto the h-BN particles by vapor deposition, and an organosilicone compound film (c) having silanol groups is formed by treatment with a basic substance. The organosilicone compound film (c) may be formed adjacent to the h-BN particles, or a silicon-containing oxide film (b) may be formed on the surface of the h-BN particles, and then the organosilicone compound film (c) may be formed on the surface opposite to the surface where the silicon-containing oxide film (b) is in contact with the h-BN particles. The organosilicone compound film (c) may be formed on the surface of the h-BN particles, or it may be formed on particles containing the silicon-containing oxide film (b) and the h-BN particles. In other words, the objects to be coated with the organic silicone compound are h-BN particles, particles coated with a silicon-containing oxide film (b) on h-BN particles, particles coated with an organic silicone compound film (c), and particles coated with both a silicon-containing oxide film (b) and an organic silicone compound film (c) on h-BN particles. Furthermore, from the viewpoint of suppressing a decrease in the interfacial adhesion strength between the resin contained in the resin composition and the h-BN filler, it is preferable that the organic silicone compound film (c) is adjacent to film (a).

[0072] In this step, the method for coating with an organic silicone compound containing active hydrogen by vapor deposition is the same as the method for coating with an organic silicone compound by vapor deposition in the first step. Furthermore, if the h-BN filler contains a silicon-containing oxide film (b), the organic silicone compound used in this step may be the same as or different from the organic silicone compound used in the first step. From the viewpoint of improving adhesive strength, the organic silicone compound used in this step is preferably an organic silicone compound containing the structure shown in formula (1) above. Furthermore, when coating the h-BN particles with an organic silicone compound containing active hydrogen by vapor deposition, components other than the organic silicone compound containing active hydrogen may or may not be coated. That is, the coating film applied by vapor deposition may contain components other than the organic silicone compound containing active hydrogen, or it may be formed from an organic silicone compound.

[0073] In this process, after coating with an organosilicon compound by vapor deposition, the -Si-H groups (active hydrogen groups) of the organosilicon compound are converted to -Si-OH groups (silanol groups) by treatment with a basic substance. The basic substance is not particularly limited, ranging from weak bases to strong bases, from Brønsted bases to Lewis bases, except that a strong base aqueous solution that remains as a solid is not used, but examples include aqueous ammonia, monoethylamine, diethylamine, triethylamine, and 2-ethanolamine. Ammonia is preferred from the viewpoint of ease of separation.

[0074] Methods for treatment with a basic substance include immersion or vapor deposition.

[0075] (Immersion Method) The immersion method is a film formation method in which an organosilicon compound coated by vapor deposition is immersed in an aqueous solution of a basic substance, thereby allowing the basic substance to react with the organosilicon compound and convert the -Si-H groups (active hydrogen groups) to -Si-OH groups (silanol groups). The aqueous solution of the basic substance is preferably aqueous ammonia.

[0076] In the immersion method, there are no particular restrictions on the concentration of the basic substance, but for example, when aqueous ammonia is used as the basic substance, it is preferable that the concentration be 0.01 N or more and 10 N or less from the viewpoint of reaction rate, more preferable that it be 0.1 N or more and 5 N or less from the viewpoint of suppressing side reactions of residual organosilicon compounds and reducing the risk to the work environment, and even more preferable that it be 0.5 N or more and 1.5 N or less.

[0077] There are no particular restrictions on the amount of ammonia water used, but for example, if the particle size (D50) of the h-BN particles used in the reaction is 30 μm or more and 100 μm or less, it is preferable to treat with ammonia water in an amount of at least one-third of the particle mass and no more than the particle mass. Also, if the particle size (D50) is 0.1 μm or more and less than 30 μm, it is preferable to treat with ammonia water in an amount of at least half of the particle mass and no more than twice the particle mass. It is sufficient that the entire particles, such as the h-BN particles, silicon-containing oxide film (b), and particles containing h-BN particles, are immersed in the ammonia water, and there are no particular restrictions. As the particle size decreases, the wettability of the particle surface with the ammonia water immediately after immersion tends to be poor, so in such cases, it is preferable to add an amount of ethanol equal to the ammonia water. Adding ethanol improves the wettability of the particle surface with the ammonia water, so further ethanol should be added while stirring. The reaction may be carried out with constant stirring, but it will also react sufficiently under intermittent manual stirring and static conditions. There are no particular restrictions on the container used for manual mixing and stirring, but it is preferable to use a wide-mouthed polyethylene bottle with a volume approximately twice the total volume of the contents.

[0078] The processing temperature is preferably 20°C to 60°C, but since a large amount of hydrogen is generated immediately after processing, it is preferable to start processing at 20°C for safety reasons. The processing time is preferably 20 hours to 30 hours, and more preferably 22 hours to 27 hours.

[0079] After processing the basic substance, it is preferable to filter it off by suction filtration using filter paper, thoroughly wash the filtrate with distilled water, and then wash it with ethanol to facilitate drying. From the viewpoint of facilitating drying, the filtrate may also be washed with acetone. Alternatively, the filtrate may be dried by heating it at 90 to 120°C for 2 to 4 hours.

[0080] (Vapor Phase Deposition Method) The vapor phase deposition method is a film formation method in which a basic substance is vapor-deposited onto an organosilicon compound coated by vapor deposition using an aqueous solution of a basic substance, and the basic substance reacts with the organosilicon compound to convert -Si-H groups (active hydrogen groups) to -Si-OH groups (silanol groups). The aqueous solution of the basic substance is preferably aqueous ammonia.

[0081] In the vapor phase film deposition method, there are no particular restrictions on the concentration of the basic substance. However, if ammonia water is used as the basic substance, for example, it is preferable to carry out the process in an airtight container with a gas vent hole, in a location where local exhaust ventilation is possible. The concentration of ammonia water is preferably 0.01 N to 10.0 N, more preferably 0.10 N to 5.0 N, and even more preferably 0.50 N to 1.50 N, from the viewpoint of suppressing side reactions of residual organosilicon compounds and reducing risks to the work environment. In the vapor phase film deposition method, the reaction rate is lower compared to the immersion method using ammonia water. Therefore, the processing temperature is preferably 20°C to 80°C, more preferably 20°C to 70°C, and even more preferably 30°C to 60°C. The processing time for the vapor phase film deposition method using ammonia water is 24 to 48 hours when the processing temperature is 20°C, but the processing time can be shortened by increasing the processing temperature. For example, when processing at 50°C, sufficient silanol groups can be introduced in 4 to 5 hours.

[0082] Since this process eliminates filtration and drying steps and allows for efficient manufacturing, it is preferable to form an organic silicone compound coating (c) by a vapor phase deposition method.

[0083] [Step 4] In this step, a coating (a) is formed. The coating (a) is formed on h-BN particles, or particles containing a silicon-containing oxide coating (b) and h-BN particles, or particles containing an organosilicon compound coating (c) and h-BN particles, or particles containing a silicon-containing oxide coating (b), an organosilicon compound coating (c), and h-BN particles (hereinafter sometimes simply referred to as "particles"). For example, if the coating (a) is formed on h-BN particles, a hexagonal boron nitride filler containing h-BN particles and the coating (a) can be produced. There are no particular restrictions on the method of forming the coating (a), but it is preferably formed by the impregnation method and the integral method, and from the viewpoint of more effectively obtaining the effects of the present invention, it is more preferable to form it by the impregnation method.

[0084] (Impregnation Method) The impregnation method is a film-forming method that forms a film (a) on the surface of particles by immersing the particles in a solution containing compound (A). Examples of solvents that can be used in the solution containing compound (A) include isopropanol, 1-methoxy-2-propanol, ethylene glycol monomethyl ether, and dioxolane. Among these, isopropanol is preferred from the viewpoint of balancing volatility and solubility, and from the viewpoint of not having high toxicity. The content of compound (A) in the solution containing compound (A) is preferably 8 to 30% by mass, more preferably 10 to 25% by mass, and even more preferably 15 to 20% by mass, from the viewpoint of efficiently forming a film (a).

[0085] A solution containing compound (A) may also contain components other than compound (A).

[0086] In the impregnation method, the immersion time for the particles is preferably 10 to 60 minutes, more preferably 15 to 50 minutes, and even more preferably 20 to 40 minutes.

[0087] After immersion, the material may be heated at 100-150°C for 1-3 hours to remove the solvent.

[0088] (Integral Method) The integral method is a film-forming method in which a resin such as epoxy resin is mixed with compound (A), and then h-BN particles, or particles containing a silicon-containing oxide film (b) and h-BN particles, or particles containing an organic silicone compound film (c) and h-BN particles, or particles containing a silicon-containing oxide film (b), an organic silicone compound film (c), and h-BN particles are added and mixed to the mixture to form a film (a) on the surface of these particles. The resin to be mixed with compound (A) can be epoxy resin, phenolic resin, phenol novolac resin, urethane resin, acrylic resin, epoxyphenolic resin, epoxy urethane resin, epoxy acrylic resin, etc., but epoxy-based resins are mainly preferred.

[0089] From the viewpoint of more effectively obtaining the effects of the present invention, the content of compound (A) in the mixture obtained by mixing a resin such as epoxy resin with compound (A) is preferably 0.03 to 3.0% by mass, more preferably 0.05 to 1.5% by mass, and even more preferably 0.08 to 0.8% by mass. When the mixture obtained by mixing the resin such as epoxy resin with compound (A) is used as a resin composition as described later, from the viewpoint of more effectively obtaining the effects of the present invention, the content of compound (A) in the mixture obtained by mixing the resin such as epoxy resin with compound (A) is preferably 0.03 to 3.0% by mass, more preferably 0.05 to 1.5% by mass, and even more preferably 0.08 to 0.8% by mass.

[0090] From the viewpoint of more effectively obtaining the effects of the present invention, the amount of particles added is preferably such that the particle content in the resulting resin composition is 50 to 90% by mass, more preferably 55 to 85% by mass, and even more preferably 60 to 80% by mass.

[0091] When producing a hexagonal boron nitride filler containing h-BN particles, a coating (a), and a silicon-containing oxide coating (b), the method for producing the hexagonal boron nitride filler preferably includes a first step of coating with an organosilicone compound having active hydrogen, a second step of forming a silicon-containing oxide coating (b) by heating, and a fourth step of forming the coating (a). When producing a hexagonal boron nitride filler containing h-BN particles, a coating (a), and an organosilicone compound coating (c), the method for producing the hexagonal boron nitride filler preferably includes a third step of coating with an organosilicone compound having active hydrogen by vapor deposition and treating with a basic substance to form an organosilicone compound coating (c) having silanol groups, and a fourth step of forming the coating (a). When producing a hexagonal boron nitride filler containing h-BN particles, a coating (a), a silicon-containing oxide coating (b), and an organosilicone compound coating (c), the preferred method for producing the hexagonal boron nitride filler comprises: a first step of coating with an organosilicone compound having active hydrogen; a second step of forming a silicon-containing oxide coating (b) by heating; a third step of forming an organosilicone compound coating (c) having silanol groups by coating with an organosilicone compound having active hydrogen by vapor deposition and treating with a basic substance; and a fourth step of forming the aforementioned coating (a).

[0092] <Resin Composition> The resin composition of the present invention comprises the hexagonal boron nitride filler of the present invention and an epoxy resin. Because the resin composition of the present invention contains the hexagonal boron nitride filler of the present invention, viscosity increase is suppressed and the decrease in adhesive strength after curing is also suppressed.

[0093] The resin composition may also contain fillers other than the hexagonal boron nitride filler of the present invention, such as boron nitride, alumina, silica, and zinc oxide, which are commonly used.

[0094] Examples of epoxy resins include: difunctional glucidyl ether type epoxy resins such as bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, hydrogenated bisphenol A type epoxy resin, and biphenyl type epoxy resin; glucidyl ester type epoxy resins such as glycidyl hexahydrophthalate and glycidyl dimer acid; linear aliphatic epoxy resins such as epoxidized polybutadiene and epoxidized soybean oil; heterocyclic epoxy resins such as triglycidyl isocyanurate; and N,N,N',N'-tetraglycidyl-4,4'-dia Examples include glucidylamine-type epoxy resins such as minodiphenylmethane, N,N,N',N'-tetraglycidyl-1,3-benzenedi(methanamine), 4-(glycidyloxy)-N,N-diglycidylaniline, and 3-(glycidyloxy)-N,N-diglycidylaniline; polyfunctional glycidyl ether-type epoxy resins such as phenol novolac-type epoxy resins, cresol novolac-type epoxy resins, biphenyl aralkyl-type epoxy resins, naphthalene aralkyl-type epoxy resins, tetrafunctional naphthalene-type epoxy resins, and triphenylmethane-type epoxy resins. The epoxy resins described above can be used individually or in combination of two or more types. The coating (a) containing compound (A) most preferably provides a viscosity-reducing effect when used in combination with a bisphenol A-type epoxy resin. As the resin component in the resin composition, bisphenol A type epoxy resin may be used alone, or it may be used in combination with an epoxy resin other than bisphenol A type epoxy resin, or it may be used in combination with a phenol novolac resin.

[0095] When using the epoxy resin described above, a curing agent, curing accelerator, etc., may be added. Examples of curing agents include alicyclic acid anhydrides such as methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, and hymicic anhydride; aliphatic acid anhydrides such as dodecenyl succinic anhydride; aromatic acid anhydrides such as phthalic anhydride and trimellitic anhydride; bisphenols such as bisphenol A, bisphenol F, and bisphenol S; phenol resins such as phenol-formaldehyde resin, phenol-aralkyl resin, naphthol-aralkyl resin, and phenol-dicyclopentadiene copolymer resin; organic dihydrazides such as dicyandiamide and adipic acid dihydrazide; and examples of curing catalysts include amines such as tris(dimethylaminomethyl)phenol, dimethylbenzylamine, 1,8-diazabicyclo(5,4,0)undecene, and their derivatives; and imidazoles such as 2-methylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, and their derivatives. These can be used individually or in combination of two or more types.

[0096] The resin composition of the present invention may contain resins other than epoxy resins. Preferred resins other than epoxy resins include thermosetting resins and mixtures of thermosetting resins and thermoplastic resins, as these yield a resin composition with excellent heat resistance. Examples of thermosetting resins include silicone resins such as polydimethylsiloxane, phenolic resins, bismaleimide resins, cyanate resins, urethane resins, (meth)acrylic resins, vinyl ester resins, unsaturated polyester resins, and polyvinyl alcohol acetal resins, which can be used individually or in combination of two or more. Furthermore, a mixture of a thermosetting resin with a curing agent and a curing accelerator may also be used.

[0097] Silicone resins include addition-curing type silicone resins, condensation-curing type silicone resins, and organic peroxide-curing type silicone resins, and can be used individually or in combination of two or more types with different viscosities. In particular, when the resulting resin composition is used in applications where flexibility and adhesion are important, an addition-curing type liquid silicone resin that does not produce by-products that can cause bubbles, etc., can be used as the silicone resin. In this case, curing can be achieved by reacting an organopolysiloxane having alkenyl groups as the base polymer with an organopolysiloxane having Si-H groups as the crosslinking agent at room temperature or by heating in the presence of a curing agent. Specific examples of the organopolysiloxane as the base polymer include, for example, those having vinyl groups, allyl groups, propenyl groups, hexenyl groups, etc., as the alkenyl groups. Vinyl groups are particularly preferred as organopolysiloxanes. Furthermore, a platinum metal-based curing catalyst can be used as the curing catalyst, and the amount added can be adjusted to achieve the desired hardness of the cured resin.

[0098] The resin composition of the present invention may optionally contain additives such as flexibility-imparting agents like silicone, urethane acrylate, butyral resin, acrylic rubber, diene rubber and its copolymers, silane coupling agents, titanium coupling agents, inorganic ion scavengers, pigments, dyes, diluents, and solvents.

[0099] The total content of hexagonal boron nitride filler and other fillers in the resin composition is not particularly limited as long as it is in an amount that results in the desired resin composition, but is preferably 30% to 80% by volume, more preferably 35% to 75% by volume, and even more preferably 40% to 70% by volume. A total content of 30% by volume or more allows for better heat dissipation, and a total content of 80% by volume or less allows for better workability when using the resin composition.

[0100] The total content of hexagonal boron nitride filler and other fillers in the resin composition is not particularly limited as long as it is in an amount that results in the desired resin composition, but is preferably 50% by mass or more and 90% by mass or less, more preferably 60% by mass or more and 88% by mass or less, and even more preferably 70% by mass or more and 85% by mass or less. If the total content is 50% by mass or more, good heat dissipation can be achieved, and if it is 90% by mass or less, good workability can be obtained when using the resin composition.

[0101] Furthermore, the content of hexagonal boron nitride filler in the components other than the resin component (fillers) of the resin composition is preferably 30% to 100% by volume of the total content of the hexagonal boron nitride filler and other fillers, more preferably 40% to 100% by volume, and even more preferably 50% to 100% by mass. A total content of 30% by volume or more allows for better heat dissipation.

[0102] The total content of epoxy resin and other resins in the resin composition is not particularly limited as long as it is in an amount that results in the desired resin composition, but is preferably 1% by mass or more and 50% by mass or less, more preferably 3% by mass or more and 40% by mass or less, and even more preferably 5% by mass or more and 30% by mass or less. If the total content is 50% by mass or less, good heat dissipation can be achieved, and if it is 1% by mass or more, good workability can be obtained when using the resin composition.

[0103] Furthermore, the epoxy resin content in the resin composition is preferably 30% to 100% by mass of the total content of the epoxy resin and other resins, more preferably 35% to 100% by mass, and even more preferably 40% to 100% by mass. If the total content is 30% by mass or more, the increase in viscosity when mixed with the epoxy resin can be suppressed, and the decrease in adhesive strength after curing of the epoxy resin-containing resin composition can be suppressed.

[0104] <Method for Manufacturing the Resin Composition> The method for manufacturing the resin composition of the present invention preferably includes the following step I, or the following steps II-1 and II-2. Step I: A step of adding and mixing the hexagonal boron nitride filler with the epoxy resin. Step II-1: A step of obtaining a composition i containing the compound (A) and the epoxy resin. Step II-2: A step of adding and mixing at least one particle selected from h-BN particles, a silicon-containing oxide film (b) and particles containing h-BN particles, an organosilicon compound film (c) having silanol groups and particles containing h-BN particles, and a silicon-containing oxide film (b) and an organosilicon compound film (c) having silanol groups and particles containing h-BN particles. Steps I, II-1 and II-2 will be described below.

[0105] [Step I] This step involves adding and mixing the hexagonal boron nitride filler of the present invention with an epoxy resin. A resin composition can be obtained by going through this step. Examples of epoxy resins include the epoxy resins described in <Resin Composition> above. In this step, other components described in <Resin Composition> above, other than compound (A) and the epoxy resin, may also be added. The mixing method is not particularly limited, and examples include mixing, dissolving, and kneading the components such as the hexagonal boron nitride filler of the present invention, epoxy resin, resins other than epoxy resin, fillers such as boron nitride, alumina, silica, zinc oxide, and other additives all at once or in separate portions, using dispersion and dissolution devices such as a mixer, planetary mixer, rotation / revolution mixer, kneader, and roll mill, either individually or in appropriate combinations, and heating as necessary. From the viewpoint of efficiently forming a film (a), the method for producing the resin composition preferably includes step I.

[0106] [Step II-1] This step is to obtain composition i containing compound (A) and epoxy resin, and composition i is obtained by mixing compound (A) and epoxy resin. Examples of epoxy resin include the epoxy resin described in <Resin Composition> above. In this step, composition i may also be obtained by adding and mixing compound (A) and other components described in <Resin Composition> above other than epoxy resin. The mixing method in this step is not particularly limited, and examples include mixing, dissolving, and kneading compound (A), epoxy resin, resins other than epoxy resin, and other additives all at once or in separate parts, using dispersion and dissolution devices such as a turntable, planetary mixer, rotation / revolution mixer, kneader, and roll mill, either individually or in appropriate combinations, and heating as necessary.

[0107] [Step II-2] This step involves adding and mixing at least one selected from h-BN particles, particles containing a silicon-containing oxide film (b) and h-BN particles, particles containing an organosilicon compound film having silanol groups (c) and h-BN particles, and particles containing a silicon-containing oxide film (b), an organosilicon compound film having silanol groups (c) and h-BN particles to composition i. By adding and mixing at least one selected from the above particles to composition i, a film (a) can be formed on the surface of the particles. The mixing method in this step is not particularly limited, and examples include mixing, dissolving, and kneading the components to be mixed all at once or in separate parts, using dispersion and dissolution devices such as a mixer, planetary mixer, rotation / revolution mixer, kneader, and roll mill, either individually or in appropriate combinations, and heating as necessary.

[0108] <Applications of the Resin Composition> The resin composition obtained in step I, or in steps II-1 and II-2 below, can be molded into a sheet and reacted as needed to produce a heat dissipation sheet. The above-described resin composition and heat dissipation sheet can be suitably used for bonding applications such as semiconductor power devices and power modules.

[0109] Methods for manufacturing heat dissipation sheets include molding a resin composition by compression pressing or the like, sandwiching it between two base films, and coating a base film with a resin composition using equipment such as a bar coater, screen printer, blade coater, die coater, or comma coater. Furthermore, the heat dissipation sheet after molding and coating can be further processed with steps such as solvent removal, B-stage formation by heating, and complete curing. As described above, various forms of heat dissipation sheets can be obtained through different processes, making it possible to widely accommodate target application fields and usage methods.

[0110] When applying or forming a resin composition onto a substrate film, a solvent may be used to improve workability. The solvent is not particularly limited, but may be used individually or in combination of two or more of the following: ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclopentanone, and cyclohexanone; ether solvents such as 1,4-dioxane, tetrahydrofuran, and diglyme; glycol ether solvents such as methyl cellosolve, ethyl cellosolve, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monobutyl ether, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, and diethylene glycol methyl ethyl ether; and other solvents such as benzyl alcohol, N-methylpyrrolidone, γ-butyrolactone, ethyl acetate, and N,N-dimethylformamide.

[0111] To form a resin composition into a sheet, it is necessary to have sheet-forming properties that allow it to maintain its sheet shape. To obtain sheet-forming properties, high molecular weight components can be added to the resin composition. Examples include phenoxy resin, polyimide resin, polyamide resin, polycarbodiimide resin, cyanate ester resin, (meth)acrylic resin, polyester resin, polyethylene resin, polyethersulfone resin, polyetherimide resin, polyvinyl acetal resin, urethane resin, and acrylic rubber. Among these, phenoxy resin, polyimide resin, (meth)acrylic resin, acrylic rubber, cyanate ester resin, and polycarbodiimide resin are preferred from the viewpoint of excellent heat resistance and film-forming properties, and phenoxy resin, polyimide resin, (meth)acrylic resin, and acrylic rubber are more preferred. These can be used individually or as mixtures or copolymers of two or more types.

[0112] The weight-average molecular weight of the high molecular weight component is preferably 10,000 to 100,000, and more preferably 20,000 to 50,000.

[0113] Furthermore, a good sheet shape that is easy to handle can be maintained by adding weight-average molecular weight components within the range described above.

[0114] The amount of high molecular weight component added is not particularly limited, but in order to maintain sheet properties, it is preferably 0.1% to 20% by mass relative to the resin composition, more preferably 1% to 15% by mass, and even more preferably 2% to 10% by mass. An addition amount of 0.1% to 20% by mass provides good handling and allows for the formation of good sheets and films.

[0115] The base film used in the manufacture of the heat dissipation sheet is not particularly limited as long as it can withstand the process conditions such as heating and drying during manufacture. Examples include films made of polyester having aromatic rings such as polyethylene terephthalate (PET) and polybutylene terephthalate (PBT), polypropylene films, polyimide films, and polyetherimide films. The above-mentioned films may be multilayer films made by combining two or more types, and the surface may be treated with a release agent such as silicone. The thickness of the base film is preferably 10 μm to 100 μm.

[0116] The thickness of the heat dissipation sheet formed on the base film is preferably 20 μm to 500 μm, and more preferably 50 μm to 200 μm. A thickness of 20 μm or more allows for the acquisition of a heat dissipation sheet with a uniform composition, while a thickness of 500 μm or less allows for good heat dissipation.

[0117] The present invention will now be specifically described with reference to examples, but the present invention is not limited in any way by these examples.

[0118] [BET Value] The BET value (specific surface area) of h-BN particles was measured using a specific surface area measuring device (Mountec Co., Ltd., product name: Macsorb HM model-1220) by a single-point BET method using nitrogen adsorption via gas flow.

[0119] [Weight-average molecular weight] The weight-average molecular weight of compound (A) and the surface treatment agent was measured by matrix-assisted laser desorption / ionization time-of-flight mass spectrometry (MALDI-TOF MS). Specifically, the measurement was performed using "autoflex® max" (manufactured by Bruker Japan Ltd.) as the measuring instrument, and a tetrahydrofuran solution containing 1 mol / L sodium trifluoroacetate as the ionization reagent, with 1500 cumulative measurements.

[0120] [Surface coverage (a+b+c) and surface coverage (a'+b+c) (g / m ２The amount of surface coating (a + b + c) (total amount of coating (a) + silicon-containing oxide coating (b) + organosilicone compound coating (c)) and the amount of surface coating (a' + b + c) (total amount of coating (a') + silicon-containing oxide coating (b) + organosilicone compound coating (c)) were measured by the following methods. The amount of coating (a) was determined by dividing the amount of compound (A) used in the example or the amount of surface treatment agent (g) used in the comparative example by the BET specific surface area of ​​h-BN particles measured by the BET single-point method by nitrogen adsorption using the gas flow method, using a specific surface area measuring device (manufactured by Mountec Co., Ltd., product name: Macsorb HM model-1220). The amount of silicon-containing oxide film (b) in the hBN-filler containing film (a) and silicon-containing oxide film (b) was determined by subtracting the silicon atom content of the h-BN particles from the silicon atom content of the particles (hBN-filler) after the formation of the silicon-containing oxide film (b), determining the silicon atom content of the silicon-containing oxide film (b), and then dividing this by the BET specific surface area of ​​the h-BN particles measured by the BET single-point method by nitrogen adsorption. The amounts of silicon-containing oxide film (b) and organosilicone compound film (c) in hBN-filler containing film (a), silicon-containing oxide film (b), and organosilicone compound film (c) were determined by subtracting the silicon atom content of h-BN particles from the silicon atom content of particles (hBN-filler) after the formation of silicon-containing oxide film (b) and organosilicone compound film (c), and then dividing by the BET specific surface area of ​​h-BN particles measured by the BET single-point method using nitrogen adsorption. The adsorbed gases used during the measurement of specific surface area were 70% by volume of He and N ２ Using a 30% by volume mixed gas, the silicon atom content was measured by ICP emission spectroscopy using an ICP mass spectrometer (Shimadzu Corporation, product name: ICPMS-2030).

[0121] [Viscosity] The viscosity of the resin composition was measured using a flow tester (Shimadzu Corporation, model number: "CFT-EX") with a nozzle of φ2 × 2 mm L, at 30°C and under a 25 kg load.

[0122] [Thermal Conductivity] In Example 1, 20.00 g of hexagonal boron nitride filler, 4.74 g of bisphenol A type epoxy resin (product name: YD-128, manufactured by Nippon Steel & Sumitomo Metal Chemical Co., Ltd.), and 0.02 g of 2-ethyl-4-methylimidazole (product name: 2E4MZ, manufactured by Shikoku Chemicals Co., Ltd.) as a curing agent were weighed into a container (capacity 300 mL) for a rotation-and-revolution type mixer (product name: Awatori Rentaro Atmospheric Pressure Type ARE-310, manufactured by Thinky Co., Ltd.). The mixture was stirred at 2000 rpm for 30 seconds using the rotation-and-revolution type mixer, and then the manual mixing operation was repeated twice to prepare the raw material for pressing. After filling the raw material for pressing into a 30 mm x 30 mm x 0.3 mm mold, the top and bottom surfaces were sandwiched between 30 μm thick copper foils, and the sides were sandwiched between 5 mm thick SUS flat plates. The mold was then press-molded at 150°C for 30 minutes to create a flat plate sample with an h-BN particle content of 50 volume%. In Examples 2-8, Comparative Examples 1-4, and Comparative Examples 5-7, 20.00 g of the hexagonal boron nitride filler obtained in Examples 2-8, or the h-BN particles used in Comparative Examples 1-4, or the particles obtained in Comparative Examples 5-7, 0.02 g of 2-ethyl-4-methylimidazole (product name: 2E4MZ, manufactured by Shikoku Chemicals, Inc.) as a curing agent, and bisphenol A type epoxy resin (product name: YD-128, manufactured by Nippon Steel & Sumitomo Metal Chemical Co., Ltd.) were mixed to achieve the boron nitride content (volume%) shown in Table 3 or 4 to create a flat plate sample. The obtained flat plate samples were cut to a size of 10 mm x 10 mm and used as measurement samples. Subsequently, the thermal diffusivity was measured using the obtained measurement samples with a xenon laser flash thermal diffusivity measuring device (product name: LFA447 NanoFlash, manufactured by NETZSCH). The value calculated by multiplying the obtained thermal diffusivity by the theoretical values ​​of the specific heat and density of each measurement sample was defined as the thermal conductivity in the thickness direction of the measurement sample.

[0123] [Adhesive Strength] The resin compositions obtained in the examples and comparative examples were coated onto a 12 μm thick copper foil using an applicator with a coating gap of 350 μm, dried at 100°C for 10 minutes, then another 12 μm thick copper foil was placed on top, and both sides were sandwiched with 38 μm polyester sheets to create a pre-press sheet. This was then pressed at 180°C for 1 hour at a pressure of 5 MPa to cure it and create a copper-clad plate. Next, the polyester sheets were removed, and a 10 mm wide PET adhesive masking tape was firmly attached to the copper foil with a gap of 2 to 3 mm. This was then immersed in a 9% sodium peroxide aqueous solution at 75°C for 60 minutes to dissolve the copper, and then removed and thoroughly washed with distilled water. After wiping off the moisture with a laboratory wiper, it was air-dried and 10 mm wide strips were prepared. The PET adhesive masking tape was peeled off to create a peel test piece. One end of the copper foil of the peel test specimen was peeled off, and a 90-degree peeling jig was set on the desktop precision universal testing machine "Autograph AGS-X" (manufactured by Shimadzu Corporation). The adhesive strength was measured at a peeling speed of 50 mm / min.

[0124] [Pot Life] The hexagonal boron nitride filler obtained in Examples 1 to 8, or the h-BN particles used in Comparative Examples 1 to 4, or the particles obtained in Comparative Examples 5 to 7, were mixed with epoxy resin PG-207GS using a rotation-revolution type mixer (product name: Awatori Rentaro Atmospheric Pressure Type ARE-310) to produce resin compositions containing 10 volume% of the hexagonal boron nitride filler obtained in Examples 1 to 8, or the h-BN particles used in Comparative Examples 1 to 4, or the particles obtained in Comparative Examples 5 to 7, and were left to stand for 150 hours. After standing, each resin composition was evaluated according to the following criteria. VG: No separation of epoxy resin PG-207GS was confirmed. G: Separation of epoxy resin PG-207GS was confirmed to be less than 10 volume% of the total. B: Separation of epoxy resin PG-207GS was confirmed to be 10 volume% or more of the total.

[0125] [Materials] Table 1 shows the details of the h-BN particles used in the examples and comparative examples, and Table 2 shows the details of the compounds used for film formation.

[0126]

[0127]

[0128] Details of the epoxy resins used in the examples and comparative examples are as follows: • Epoxy resin YD-128: Bisphenol A type epoxy resin (Product name: YD-128, manufactured by Nippon Steel Chemical & Material Co., Ltd.) • Epoxy resin PG-207GS: Polypropylene glycol diglycidyl ether (Product name: PG-207GS, manufactured by Nippon Steel Chemical & Material Co., Ltd.)

[0129] [Example 1] (Production of hexagonal boron nitride filler) Compound a (Compound (A)) 0.85 g (Amount such that the content of coating (a) in the hexagonal boron nitride filler is 1.70 parts by mass per 100 parts by mass of h-BN particles I = surface area of ​​h-BN particles I of 1 m² ２ 6.3 x 10 －３ A mixed solution was prepared by dissolving (equivalent to 1 g) in 5 g of isopropanol. Subsequently, 50 g of h-BN particles I was weighed into a 500 mL evaporating dish, and the mixed solution was added in three portions, stirring and mixing after each addition. After these additions, stirring, and mixing were performed for approximately 3 minutes, the mixture was allowed to cure and air dry at room temperature for 2 hours. After that, it was heat-treated at 120°C for 2 hours to form a coating (a), and hexagonal boron nitride filler X-1 was obtained.

[0130] (Preparation of Resin Composition) 27.00 g of hexagonal boron nitride filler X-1 and 9.99 g of epoxy resin YD-128 were weighed into a container (capacity 150 mL) for a rotation-and-revolution type mixer (product name: Awatori Rentaro Atmospheric Pressure Type ARE-310, manufactured by Thinky Co., Ltd.). The mixture was stirred at 2000 rpm for 30 seconds using the rotation-and-revolution type mixer, and then manually stirred for 20 seconds using a spatula. The above stirring was repeated three times to obtain resin composition X-1 with an h-BN particle content of 50 volume%. The evaluation results of the physical properties of hexagonal boron nitride filler X-1 and resin composition X-1 are shown in Table 3.

[0131] [Examples 2 to 5] In Example 1, hexagonal boron nitride fillers X-2 to X-5 were obtained in the same manner except that the boron nitride particle species were those described in Table 3. Also, for the resin compositions X-2 to X-5, the resin compositions were obtained such that the boron nitride particle content in the resin composition was the amount (volume %) described in Table 3 (46% by volume in Example 2, 49% by volume in Example 3, 47% by volume in Example 4, and 50% by volume in Example 5). Table 3 shows the evaluation results of the physical properties of the hexagonal boron nitride fillers X-2 to X-5 and the resin compositions X-2 to X-5.

[0132] [Example 6] 9.99 g of epoxy resin YD-128 and 0.06 g of compound a (the content of the coating (a) in the hexagonal boron nitride filler is such that the amount is 1.70 parts by mass with respect to 100 parts by mass of h-BN particles I = the surface area of h-BN particles I 1 m ２ per 4.25 × 10 －３ g equivalent) were weighed into a container (capacity 150 mL) for a rotation / revolution type mixer (trade name: Aotori Rettaro atmospheric pressure type ARE-310, manufactured by Shinchi Co., Ltd.), and after stirring at 2000 rpm for 30 seconds using the rotation / revolution type mixer, 27.00 g of h-BN particles I were added, and stirring at 2000 rpm for 30 seconds was carried out 3 times to obtain a resin composition X-6 having a h-BN particle content of 46% by volume. Table 3 shows the evaluation results of the physical properties of the hexagonal boron nitride filler X-6 and the resin composition X-6.

[0133] [Example 7] (Production of hexagonal boron nitride filler) 27.00 g of h-BN particles I were spread uniformly on a stainless steel tray and left to stand in a large oven with a reaction vessel volume of 250 L. Next, 340 g of organosilicon compound (1) (trade name: 2,4,6,8-tetramethylcyclotetrasiloxane, manufactured by Tokyo Chemical Industry Co., Ltd.), in which n=4 in formula (3), was placed in a glass petri dish and left to stand in the reaction vessel, and the reaction vessel was closed. Since hydrogen gas is generated by the reaction, the reaction vessel was first evacuated until the oxygen concentration was below 8 volume%, which is the explosion limit, and then nitrogen gas was introduced into the reaction vessel to return the internal pressure to atmospheric pressure (0.1 MPa). After that, the reaction vessel was heated to 80°C for 7.5 hours to vaporize the organosilicon compound (1) and obtain particles coated with the organosilicon compound. The particles coated with the obtained organosilicon compound were placed in an alumina crucible and heated in air at 700°C for 3 hours to obtain particle X-7 containing one layer of h-BN particles and a silicon-containing oxide coating (b). Subsequently, a coating (a) was formed in the same manner as in Example 1, except that particle X-7 was used instead of h-BN particle I, to obtain hexagonal boron nitride filler X-2. The amount of compound a was such that the content of coating (a) in the hexagonal boron nitride filler was 1.70 parts by mass per 100 parts by mass of particle X-7 (surface area of ​​particle X-7 = 1 m²). ２ 6.3 x 10 －３ (An amount equivalent to gram) was used.

[0134] (Preparation of Resin Composition) Resin composition X-7 having an h-BN particle content of 50 volume% was obtained in the same manner as in Example 1, except that hexagonal boron nitride filler X-7 was used instead of hexagonal boron nitride filler X-1. The evaluation results of the physical properties of hexagonal boron nitride filler X-7 and resin composition X-7 are shown in Table 3.

[0135] [Example 8] (Production of hexagonal boron nitride filler) Particle X-8 containing h-BN particles and one layer of silicon-containing oxide film (b) was obtained in the same manner as in Example 7. 11.0 g of organosilicon compound (1) was placed in a φ50 glass petri dish at the bottom of an 8 L pressure vessel made of stainless steel. Next, 200 g of particle X-8 was placed in an aluminum foil tray and set on a stainless steel raised bottom grate on top of the 8 L pressure vessel made of stainless steel. The lid of the 8 L pressure vessel was closed and left in a sealed state in an oven maintained at 80°C for 10 minutes to release the pressure. Then, CVD treatment was performed again in a sealed state in an oven maintained at 80°C for 4.5 hours. Next, 200 g of 1N ammonia water was placed in a 1 L polyethylene wide-mouth bottle, and the entire amount of the CVD-treated sample was added. For the first 3 hours, it was stirred by hand every hour, and then left to stand at room temperature for 24 hours in a local exhaust ventilation system. During the standing period, the container was not sealed tightly, allowing the generated hydrogen to leak out through the gap in the lid. After 24 hours, the mixture was vacuum filtered using filter paper of a coarseness that could maintain the particle size, the filtrate was washed twice with distilled water and twice with ethanol, and dried at 90°C for 2 hours to form an organic silicone compound coating (c) having silanol groups, and particles X-8 containing the organic silicone compound coating (c) were obtained. Subsequently, coating (a) was formed in the same manner as in Example 1, except that particles X-8 were used instead of h-BN particles I, to obtain hexagonal boron nitride filler X-8. The amount of compound a was such that the content of coating (a) in the hexagonal boron nitride filler was 1.70 parts by mass per 100 parts by mass of particles X-8 (surface area of ​​particle X-8 = 1 m²). ２ 6.3 x 10 －３ (An amount equivalent to gram) was used.

[0136] (Preparation of Resin Composition) Resin composition X-8 having an h-BN particle content of 50 volume% was obtained in the same manner as in Example 1, except that hexagonal boron nitride filler X-8 was used instead of hexagonal boron nitride filler X-1. The evaluation results of the physical properties of hexagonal boron nitride filler X-8 and resin composition X-8 are shown in Table 3.

[0137] [Comparative Examples 1-4] Resin compositions were obtained in the same manner as in Example 1, except that the h-BN particle species listed in Table 4 was used instead of the hexagonal boron nitride filler X-1, and the boron nitride particle content in the resin composition was set to the amount (vol %) listed in Table 3 (50 vol % for resin composition Y-1, 46 vol % for Y-2, 49 vol % for Y-3, and 47 vol % for Y-4). The evaluation results of the physical properties of the h-BN particles and resin compositions Y-1 to Y-4 are shown in Table 4.

[0138] [Comparative Example 5] In Example 1, instead of using compound a, 0.06 g of surface treatment agent a' was used (the amount such that the content of the coating (a') in the hexagonal boron nitride filler (the coating consisting of surface treatment agent a') is 0.22 parts by mass per 100 parts by mass of h-BN particles I = surface area 1 m² ２ 1.79 x 10 －３ Hexagonal boron nitride filler Y-5 was obtained in the same manner as above, except that an equivalent amount (in grams) was used, and then resin composition Y-5 was obtained. The evaluation results of the physical properties of hexagonal boron nitride filler Y-5 and resin composition Y-5 are shown in Table 4.

[0139] [Comparative Example 6] In Example 7, instead of using compound a, 0.06 g of surface treatment agent a' was used (an amount such that the content of the coating (a') in the hexagonal boron nitride filler (the coating consisting of surface treatment agent a') is 0.22 parts by mass per 100 parts by mass of h-BN particles I = surface area 1 m² ２ 1.79 x 10 －３ Hexagonal boron nitride filler Y-6 was obtained in the same manner as in Example 7, except that an equivalent amount (in grams) was used. Subsequently, an attempt was made to mix hexagonal boron nitride filler Y-6 with epoxy resin YD-128, as in Example 7, but uniform mixing could not be achieved. The evaluation results of the physical properties of hexagonal boron nitride filler Y-6 are shown in Table 4.

[0140] [Comparative Example 7] In Example 8, instead of using compound a, 0.06 g of surface treatment agent a' was used (the amount such that the content of the coating (a') in the hexagonal boron nitride filler (the coating consisting of surface treatment agent a') is 0.22 parts by mass per 100 parts by mass of h-BN particles I = surface area 1 m² ２ 1.79 x 10 －３Hexagonal boron nitride filler Y-8 was obtained in the same manner as in Example 7, except that an equivalent amount (in grams) was used. Subsequently, an attempt was made to mix hexagonal boron nitride filler Y-7 with epoxy resin YD-128, similar to Example 7, but uniform mixing could not be achieved. The results of the evaluation of the physical properties of hexagonal boron nitride filler Y-7 are shown in Table 4.

[0141]

[0142]

[0143] From Example 1 and Comparative Example 1, Example 2 and Comparative Example 2, Example 3 and Comparative Example 3, and Example 4 and Comparative Example 4, it can be seen that the hexagonal boron nitride filler, by containing a coating (a) containing compound (A), can suppress the increase in viscosity when mixed with epoxy resin. Furthermore, Comparative Example 5, which uses compound a' that is not a compound having a polyethyleneimine skeleton and polyalkylene oxide chains and a weight-average molecular weight of 2000 to 10000, shows that the viscosity increases when mixed with epoxy resin. In addition, from Examples 1 to 8 and Comparative Examples 1 to 7, it can be seen that the coating (a) containing compound (A) does not impair the high thermal conductivity inherent in hexagonal boron nitride. Furthermore, from Example 1 and Comparative Example 1, Example 4 and Comparative Example 4, and Example 5 and Comparative Example 5, it can be seen that the hexagonal boron nitride filler, by containing a coating (a) containing compound (A), has good adhesive strength.

Claims

1. A hexagonal boron nitride filler containing hexagonal boron nitride particles and a coating (a) containing compound (A) having a polyethyleneimine skeleton and polyalkylene oxide chains, and having a weight-average molecular weight of 2,000 to 10,000.

2. Specific surface area (m²) of the hexagonal boron nitride particles obtained by the BET method. ２ Surface area per 1 m² calculated from ( / g) ２ In this case, compound (A) is divided into 5.0 × 10 -4 g or more 5.0×10 -2 The hexagonal boron nitride filler according to claim 1, including less than g.

3. The hexagonal boron nitride filler according to claim 1 or 2, comprising a silicon-containing oxide film (b).

4. Specific surface area (m²) of the hexagonal boron nitride particles obtained by the BET method. ２ Surface area per 1 m² calculated from ( / g) ２ In each case, the compound (A) and the silicon-containing oxide film (b) are divided into 5.0 × 10 -4 g or more 5.0×10 -2 The hexagonal boron nitride filler according to claim 3, including less than g.

5. The hexagonal boron nitride filler according to claim 1 or 2, comprising an organosilicon compound coating (c) having a silanol group.

6. The hexagonal boron nitride filler according to claim 5, wherein the coating (a) and the organosilicone compound coating (c) are adjacent to each other.

7. The surface area per 1 m ２ calculated from the specific surface area (m ２ / g) determined by the BET method for the hexagonal boron nitride particles, the compound (A) and the organosilicon compound film (c) are contained in an amount of 5.0 × 10 -4 g or more and less than 5.0 × 10 -2 g. The hexagonal boron nitride filler according to claim 5.

8. The hexagonal boron nitride filler according to claim 1 or 2, comprising a silicon-containing oxide film (b) and an organosilicon compound film having a silanol group (c).

9. Specific surface area (m²) of the hexagonal boron nitride particles obtained by the BET method. ２ Surface area per 1 m² calculated from ( / g) ２ Each time, the compound (A), the silicon-containing oxide film (b), and the organic silicone compound film (c) are distributed in a quantity of 5.0 × 10 -4 g or more 5.0×10 -2 The hexagonal boron nitride filler according to claim 8, including less than g.

10. A method for producing hexagonal boron nitride filler, comprising hexagonal boron nitride particles and a coating (a) containing a compound (A) having a polyethyleneimine skeleton and a polyalkylene oxide chain, and having a weight-average molecular weight of 2,000 or more and 10,000 or less, the method comprising a fourth step of forming the coating (a).

11. A method for producing a hexagonal boron nitride filler according to claim 10, comprising a first step of coating with an organosilicon compound having active hydrogen, and a second step of forming a silicon-containing oxide film (b) by heating.

12. A method for producing a hexagonal boron nitride filler according to claim 10 or 11, comprising a third step of coating with an organosilicon compound having active hydrogen by vapor deposition, and treating the coated organosilicon compound with a basic substance to form an organosilicon compound film (c) having silanol groups.

13. A resin composition comprising the hexagonal boron nitride filler according to claim 1 or 2 and an epoxy resin.

14. A method for producing the resin composition according to claim 13, comprising step I of adding and mixing the hexagonal boron nitride filler with the epoxy resin.

15. A method for producing a resin composition according to claim 13, comprising: step II-1 of obtaining a composition i comprising the compound (A) and the epoxy resin; and step II-2 of adding and mixing at least one particle selected from hexagonal boron nitride particles, a silicon-containing oxide film (b) and particles containing hexagonal boron nitride particles, an organosilicon compound film having silanol groups (c) and particles containing hexagonal boron nitride particles, and a silicon-containing oxide film (b) and an organosilicon compound film having silanol groups (c) and particles containing hexagonal boron nitride particles.

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