Metal oxide-attached hexagonal boron nitride particles, powder containing particles, resin composition containing particles, resin sheet, metal wiring board, and method for producing particles

Abstract

To provide metal oxide-attached hexagonal boron nitride particles capable of suppressing the increase in viscosity of a resin composition when used as a filler, capable of increasing the thermal conductivity of the resin composition, and capable of improving the peeling strength with a metal layer when used as a metal wiring board.SOLUTION: Metal oxide-attached hexagonal boron nitride particles have a metal oxide attached to the particle surface, wherein the area of the metal oxide attached to the plane of the hexagonal boron nitride particle is 10% or less and the area of the metal oxide attached to the end face of the hexagonal boron nitride particles is 30% or more.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to metal oxide-deposited hexagonal boron nitride particles, a powder containing the particles, a resin composition containing the particles, a resin sheet, a metal wiring board, and a method for producing the particles. [Background technology]

[0002] In recent years, electronic devices have rapidly become more compact and sophisticated. This has led to an increase in the power density of semiconductor devices, making it difficult to control the heat they generate. For this reason, thermally conductive materials are being used in mounting and surrounding components. Conventionally, high thermal conductivity compounds such as hexagonal boron nitride are often used as additives (fillers) for resins. In general, the higher the content of the thermally conductive filler, the higher the thermal conductivity of the resulting resin composition. However, since hexagonal boron nitride has a plate-like shape, it is poorly filled into resins, and there is a demand for improving the filling property in order to improve the thermal conductivity of the resulting resin composition and in order to improve the moldability of the resulting resin composition.

[0003] Furthermore, when the resin composition is used as a metal wiring substrate, it is necessary to improve the peel strength between the metal layer and the substrate made of the resin composition. However, since hexagonal boron nitride has few functional groups on the particle surface, it is difficult to improve the peel strength of the metal layer.

[0004] Patent Document 1 describes a method of mixing silica or the like with boron nitride to provide a thermally conductive material with reduced viscosity. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Special Publication No. 2022-546342 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in the method of Patent Document 1, as described in paragraph 0016, silica is uniformly dispersed on the surface of the platelet-shaped boron nitride, and in this case, the thermal conductivity of the resulting resin composition is insufficient.

[0007] In view of the above circumstances, an object of the present invention is to provide metal oxide-adhered hexagonal boron nitride particles which, when used as a filler, are capable of suppressing an increase in the viscosity of a resin composition, and of increasing the thermal conductivity of the resin composition, and further, when made into a metal wiring substrate, are capable of improving the peel strength from the metal layer; a powder containing the particles, a resin composition containing the particles, a resin sheet, a metal wiring substrate, and a method for producing the particles. [Means for solving the problem]

[0008] As a result of extensive investigations, the present inventors have completed the following invention. [1] Hexagonal boron nitride particles having a metal oxide attached to their surfaces, wherein the area adhesion rate of the metal oxide to the flat surfaces of the hexagonal boron nitride particles is 10% or less, and the area adhesion rate of the metal oxide to the end faces of the hexagonal boron nitride particles is 30% or more.

[0009] [2] The metal oxide-coated hexagonal boron nitride particles according to [1], wherein the hexagonal boron nitride particles have an aspect ratio of 12 or less and a particle diameter of 5 μm or more and 12 μm or less. [3] The metal oxide-coated hexagonal boron nitride particles according to [1] or [2], wherein the primary particle size of the metal oxide is 100 nm or more and 700 nm or less.

[0010] [4] A powder comprising the metal oxide-deposited hexagonal boron nitride particles according to any one of [1] to [3]. [5] A resin composition comprising a base resin and the metal oxide-adhered hexagonal boron nitride particles according to any one of [1] to [3].

[0011] [6] A resin sheet obtained by molding the resin composition of [5]. [7] A metal wiring board having metal wiring on the surface of the resin sheet of [6].

[0012] [8] A method for producing a powder containing hexagonal boron nitride particles with a metal oxide attached thereto, comprising a step of dry-mixing a powder containing hexagonal boron nitride particles having an average aspect ratio of 12 or less and an average particle size of 5 μm or more and 12 μm or less with a powder containing metal oxide particles having an average primary particle size of 100 nm or more and 700 nm or less. Effect of the Invention

[0013] When the metal oxide-attached hexagonal boron nitride particles of the present invention are used as a filler, it is possible to suppress an increase in viscosity of a resin composition and to increase the thermal conductivity of the resin composition. Furthermore, when used as a metal wiring substrate, it is possible to improve the peel strength from the metal layer. [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 is a conceptual diagram of a hexagonal boron nitride particle. [Diagram 2] FIG. 2 is an SEM image showing the state in which a metal oxide is adhered to a hexagonal boron nitride particle of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Next, the present invention will be described based on an embodiment, however, the present invention is not limited to the embodiment described below. In the present invention, when it is stated that "X or more" (X is any number), it includes the meaning of "preferably larger than X" unless otherwise specified, and when it is stated that "Y or less" (Y is any number), it also includes the meaning of "preferably smaller than Y" unless otherwise specified.

[0016] <Hexagonal boron nitride particles with metal oxide coating> The metal oxide-deposited hexagonal boron nitride particles of the present invention comprise hexagonal boron nitride particles and a metal oxide deposited on the surfaces of the hexagonal boron nitride particles.

[0017] (Hexagonal boron nitride particles) There are two types of boron nitride: hexagonal boron nitride (h-BN), which is stable at normal pressure, and cubic boron nitride (c-BN), which is stable at high pressure. The type used in the present invention is hexagonal boron nitride (h-BN).

[0018] The particle shape of the hexagonal boron nitride particles is flat, having a plane P1 and an end face P2, as conceptually shown in Figure 1. The hexagonal boron nitride particles may be secondary particles formed by agglomeration of primary particles, and the shape of the secondary particles is not particularly limited. Further, hexagonal boron nitride particles have thermal conductivity, but are characterized in that the thermal conductivity in the planar direction DR1 is higher than that in the thickness direction DR2 of the tabular particles.

[0019] Aspect ratio of hexagonal boron nitride particles The hexagonal boron nitride particles in the present invention are thick-walled, and the aspect ratio of the primary particles is preferably 12 or less, more preferably 10 or less, and even more preferably 8 or less. The lower limit of the aspect ratio is preferably 1 or more, and more preferably 2 or more. When the aspect ratio exceeds 12, adhesion of metal oxide particles to the end faces of the hexagonal boron nitride particles is limited. In addition, by setting the aspect ratio to 12 or less, it becomes easier to orient the planar direction DR1 of the hexagonal boron nitride particles in the thickness direction of the sheet, making it easier to improve the thermal conductivity in the thickness direction of the sheet.

[0020] The aspect ratio was measured by analyzing SEM images of metal oxide-coated hexagonal boron nitride particles using an image analyzer (A-Image-kun, manufactured by Asahi Kasei Engineering Co., Ltd.), measuring the length of the long axis and the length in the thickness direction, and calculating the aspect ratio as the long axis length / thickness length.

[0021] -Particle size of hexagonal boron nitride particles The primary particle size of the hexagonal boron nitride particles is preferably 5 μm or more and 12 μm or less, more preferably 6 μm or more and 10 μm or less, and further preferably 6.5 μm or more and 8 μm or less. The particle size of the hexagonal boron nitride particles is the length of the major axis obtained by analyzing the SEM observation image of the metal oxide-adhered hexagonal boron nitride particles using an image analyzer (A-Image-kun: manufactured by Asahi Kasei Engineering Co., Ltd.).

[0022] (Metal oxides) The metal oxide constituting the metal oxide-attached hexagonal boron nitride particles is preferably zirconium oxide, titanium oxide, zinc oxide, tin oxide, iron oxide, tungsten oxide, nickel oxide, copper oxide, magnesium oxide, manganese oxide, cerium oxide, aluminum oxide, silicon dioxide, and any mixture thereof. Among them, it is preferable to use silicon dioxide as the metal oxide, since it can be used for low dielectric applications, has high chemical stability, and is widely used as a resin filler.

[0023] The metal oxide may be a colloidal metal oxide formed via a colloid such as colloidal silica, a wet-process metal oxide formed using a wet process such as a sol-gel process, or a fumed metal oxide such as fumed silica obtained by burning a raw material. From the viewpoint of uniform control of the particle size, however, a wet-process metal oxide is preferred.

[0024] Primary particle size of metal oxide The primary particle diameter of the metal oxide is preferably 100 nm or more and 700 nm or less. The primary particle diameter of the metal oxide was determined by analyzing a plurality of metal oxide particles attached to the hexagonal boron nitride particles from the SEM image of the metal oxide-attached hexagonal boron nitride particles using an image analyzer (A-zo-kun: manufactured by Asahi Kasei Engineering Co., Ltd.), randomly selecting 100 different single particles, measuring the length of the major axis, and calculating the arithmetic average value. In addition, when there are less than 100 single particles whose major axis length can be measured, the arithmetic average value of the major axis length of all the single particles whose major axis length can be measured was determined as the primary particle diameter of the metal oxide. If the primary particle size of the metal oxide is less than 100 nm, the metal oxide will tend to adhere not only to the end faces of the hexagonal boron nitride particles but also to the flat surfaces, which may result in a decrease in thermal conductivity. Furthermore, if the primary particle size of the metal oxide exceeds 700 nm, adhesion of the metal oxide to the end faces of the hexagonal boron nitride particles is restricted.

[0025] (area deposition rate of metal oxide on the surface of hexagonal boron nitride particles) An SEM image showing the state of metal oxide particles adhering to hexagonal boron nitride particles is shown in Figure 2. The area adhesion rate of metal oxide R2 to plane P1 of hexagonal boron nitride particle R1 is preferably 10% or less, more preferably 9% or less, even more preferably 8% or less, even more preferably 7% or less, and particularly preferably 6% or less.

[0026] (Area deposition rate of metal oxide on the edge surface of hexagonal boron nitride particles) The area deposition rate of the metal oxide R2 on the end faces P2 of the hexagonal boron nitride particles R1 is preferably 30% or more, more preferably 40% or more, even more preferably 50% or more, still more preferably 60% or more, and particularly preferably 70% or more. The areal adhesion rate of metal oxide to the flat or end faces of hexagonal boron nitride particles is determined by analyzing the SEM images of the metal oxide-adhered hexagonal boron nitride particles using an image analyzer (A-Image-kun, manufactured by Asahi Kasei Engineering Co., Ltd.) and calculating the ratio of the area of ​​the flat or end face parts of the hexagonal boron nitride particles where the metal oxide is adhered to the area of ​​the flat or end face parts of the hexagonal boron nitride particles that can be confirmed in the SEM image (including the parts where the metal oxide is adhered).

[0027] <Powder> The above-mentioned metal oxide-attached hexagonal boron nitride particles can be made into a powder by mixing with other particles, such as hexagonal boron nitride particles not having a metal oxide attached, aluminum nitride particles, or aluminum oxide particles, or by itself, and can be used as a filler in applications requiring improved electrical insulation and thermal conductivity.

[0028] The content of the metal oxide-deposited hexagonal boron nitride particles in the powder is preferably 50 area % or more, more preferably 60 area % or more, and even more preferably 70 area % or more in order to exert the effect. The content is determined by the area ratio of the metal oxide-deposited hexagonal boron nitride particles of the present invention from a SEM image of the powder.

[0029] The average particle size of the hexagonal boron nitride particles constituting the metal oxide-deposited hexagonal boron nitride particles of the present invention contained in the powder is preferably 5 μm to 12 μm, more preferably 6 μm to 10 μm, and even more preferably 6.5 μm to 8 μm. The average particle size of the hexagonal boron nitride particles was determined by randomly selecting 100 different metal oxide-deposited hexagonal boron nitride particles from the SEM image of the powder, measuring the length of the major axis of the hexagonal boron nitride particles using the above-mentioned method, and calculating the arithmetic average value.

[0030] The average aspect ratio of the hexagonal boron nitride particles constituting the metal oxide-deposited hexagonal boron nitride particles of the present invention contained in the powder is preferably 12 or less, more preferably 10 or less, and even more preferably 8 or less. The lower limit of the aspect ratio is preferably 1 or more, more preferably 2 or more. The average aspect ratio of the hexagonal boron nitride particles was determined by randomly selecting 100 different metal oxide-deposited hexagonal boron nitride particles from an SEM image of the powder, measuring the aspect ratios of the hexagonal boron nitride particles using the above-mentioned method, and calculating the arithmetic average value.

[0031] In the metal oxide-attached hexagonal boron nitride particles of the present invention contained in the powder, the average area adhesion ratio of the metal oxide to the hexagonal boron nitride particle plane is preferably 10% or less, more preferably 9% or less, even more preferably 8% or less, even more preferably 7% or less, and particularly preferably 6% or less. The average area adhesion ratio of the metal oxide to the hexagonal boron nitride particle plane is preferably 30% or more, more preferably 40% or more, even more preferably 50% or more, even more preferably 60% or more, and particularly preferably 70% or more.

[0032] The average areal deposition rate of metal oxide on the flat surfaces of the hexagonal boron nitride particles of the present invention contained in the powder and the average areal deposition rate of metal oxide on the end faces were calculated by randomly selecting 100 different metal oxide-deposited hexagonal boron nitride particles from an SEM image of the powder, measuring the areal deposition rate of each particle using the method described above, and calculating the arithmetic average value.

[0033] The average particle size of the metal oxide constituting the metal oxide-adhered hexagonal boron nitride particles of the present invention contained in the powder is preferably 100 nm to 700 nm, more preferably 200 nm to 600 nm, and even more preferably 350 nm to 500 nm. The average particle size of the metal oxide particles was determined as the arithmetic average value by randomly selecting 100 different metal oxide-adhered hexagonal boron nitride particles from the SEM image of the powder and measuring the primary particle sizes of the multiple metal oxide particles adhered to the hexagonal boron nitride particles by the above-mentioned method.

[0034] <Resin composition> The above-mentioned metal oxide-adhered hexagonal boron nitride particles can be mixed with a base resin to form a resin composition. Examples of the base resin include thermoplastic resins such as polyolefin, vinyl chloride resin, methyl methacrylate resin, nylon resin, and fluororesin; thermosetting resins such as epoxy resin, phenol resin, urea resin, melamine resin, unsaturated polyester resin, and silicone resin; and synthetic rubber. The form of the resin composition may be a state in which the metal oxide-adhered hexagonal boron nitride particles are dispersed in the resin, or it may be a mixture of a particulate or powder-like base resin and the metal oxide-adhered hexagonal boron nitride particles. The amount of powder containing metal oxide-adhered hexagonal boron nitride particles in the resin composition is not particularly limited, but since high thermal conductivity is easily obtained, it is preferably 80 parts by volume or more, and more preferably 100 parts by volume or more, relative to 100 parts by volume of the base resin. The upper limit of the amount is not particularly limited, but is, for example, 1000 parts by volume or less.

[0035] <Resin sheet> The above-mentioned resin composition can be formed into a resin sheet by a known method, and can be used, for example, as a heat dissipation sheet or an insulating sheet. For example, it can be used as a heat dissipation sheet used between an electronic device such as a power transistor that generates heat and a heat sink. The thickness of the heat dissipation sheet may be, for example, 0.02 mm or more and 10 mm or less.

[0036] The surface of hexagonal boron nitride particles has relatively few functional groups, whereas metal oxide particles have relatively many functional groups, and the metal oxide-attached hexagonal boron nitride particles of the present invention have an increased number of functional groups on the surface due to the attachment of the metal oxide, which improves the affinity with the base resin and reduces the viscosity of the resin composition, thereby improving the moldability of the resin composition and enabling the resin sheet to be filled at a higher blending ratio and thus increasing the thermal conductivity.

[0037] In addition, as in the technology of Patent Document 1, when silica is uniformly attached to the surface of the small platelet boron nitride, the thermal conductivity of silica itself is lower than that of boron nitride, so the silica attached to the surface of the small platelet boron nitride becomes a thermal resistance, and the thermal conductivity of the small platelet boron nitride after silica attachment tends to be low. In contrast, in the metal oxide-attached hexagonal boron nitride particles of the present invention, the metal oxide is not attached to the entire surface of the metal oxide-attached hexagonal boron nitride particles, but the metal oxide is selectively attached to the end faces of the hexagonal boron nitride particles. Therefore, the thermal conductivity is improved compared to the technology of Patent Document 1. Furthermore, the filling viscosity of the metal oxide-adhered hexagonal boron nitride particles in the resin composition can be reduced, improving the moldability of the resin sheet, and the filling rate can be increased, further improving the thermal conductivity.

[0038] In addition, since the preferred embodiment comprises hexagonal boron nitride particles having a predetermined aspect ratio, it is possible to orient the planar direction of the hexagonal boron nitride particles close to the thickness direction of the resin sheet, which also makes it possible to increase the thermal conductivity of the resin sheet in the thickness direction. In addition, hexagonal boron nitride has a low dielectric constant, a low specific gravity, and high water resistance, and can therefore be suitably used in applications where such properties are required.

[0039] <Metal wiring board> The resin sheet can be suitably used as a metal wiring board having metal wiring on its surface by utilizing its heat dissipation and insulating properties. The metal wiring board can be produced by forming a metal layer on the surface of the resin sheet by a predetermined method and forming the metal layer into a wiring pattern by a method such as photolithography. The metal layer is not particularly limited, but may be made of, for example, copper. The resin sheet of the present invention has a form in which a metal oxide having a surface functional group is attached to the end faces of the metal oxide-adhered hexagonal boron nitride particles contained therein, so that it is possible to improve the peel strength between the resin sheet surface and the metal layer. Also, as described above, the content of the metal oxide-adhered hexagonal boron nitride particles in the resin sheet can be set high, so that the peel strength can be further improved.

[0040] <Method for producing metal oxide-attached hexagonal boron nitride particles> The method for producing metal oxide-coated hexagonal boron nitride particles of the present invention comprises a step of dry-mixing a powder containing hexagonal boron nitride particles (before metal oxide is coated) having an aspect ratio of 12 or less and a particle diameter of 5 μm or more and 12 μm or less, with a powder containing metal oxide particles (before coating) having a primary particle diameter of 100 nm or more and 700 nm or less.

[0041] The method of dry mixing is not particularly limited, and for example, the powder containing hexagonal boron nitride particles (before metal oxide adhesion) and the powder containing metal oxide particles (before adhesion) can be placed in a specified bag and shaken by hand, preferably for 10 seconds to 10 minutes.

[0042] (Hexagonal boron nitride particles (before metal oxide attachment)) The powder containing hexagonal boron nitride particles (before metal oxide is attached) as the raw material is not particularly limited, and any known powder can be used without limitation. For example, hexagonal boron nitride powder produced based on a known production method may be used. An example of the known production method is a method in which a mixture of a boron compound, a carbon source, and optionally a crystallization catalyst is heated under a nitrogen atmosphere to reduce and nitride the boron compound. In addition, a powder generally available on the market as hexagonal boron nitride powder may be used.

[0043] Aspect ratio of hexagonal boron nitride particles (before metal oxide deposition) The aspect ratio of the hexagonal boron nitride particles (before the metal oxide is attached) is more preferably equal to or less than 10, and even more preferably equal to or less than 8. The lower limit of the aspect ratio is preferably equal to or more than 1, and more preferably equal to or more than 2. Hexagonal boron nitride particles have more functional groups such as OH and NH2 on their end faces than on their flat faces. The hexagonal boron nitride particles (before metal oxide is attached) have the above-mentioned preferred aspect ratio, and are thick, flat particles, with a high proportion of end faces with many functional groups, making it easier for metal oxide to attach to the end faces. This makes it easy to achieve an area adhesion rate of metal oxide to the end faces of 30% or more.

[0044] The powder containing the raw material hexagonal boron nitride particles (before metal oxide is attached) preferably has an average aspect ratio of 12 or less, more preferably 10 or less, and even more preferably 8 or less. The lower limit of the average aspect ratio is preferably 1 or more, and more preferably 2 or more. By setting the average aspect ratio within the above range, the number of hexagonal boron nitride particles (before metal oxide is attached) having an aspect ratio within the above range can be increased, and the metal oxide-attached hexagonal boron nitride particles of the present invention can be efficiently produced.

[0045] - Particle size of hexagonal boron nitride particles (before metal oxide adhesion) The particle size of the hexagonal boron nitride particles (before the metal oxide is attached) is preferably 5 μm or more and 12 μm or less, more preferably 6 μm or more and 10 μm or less, and further preferably 6.5 μm or more and 8 μm or less.

[0046] The powder containing the raw material hexagonal boron nitride particles (before metal oxide is attached) preferably has an average particle size of 5 μm to 12 μm, more preferably 6 μm to 10 μm, and even more preferably 6.5 μm to 8 μm. By making the average particle size within the above range, the number of hexagonal boron nitride particles (before metal oxide is attached) having a particle size within the above range can be increased, and the metal oxide-attached hexagonal boron nitride particles of the present invention can be efficiently produced.

[0047] Specific surface area of ​​powder containing hexagonal boron nitride particles (before metal oxide adhesion) The powder containing the raw material hexagonal boron nitride particles (before metal oxide adhesion) has a specific surface area of ​​0.5 m 2 / g or more 3.0m 2 / g or less, and 0.7m 2 / g or more 2.0m 2 The specific surface area can be measured by a BET single point method using a Macsorb HM model-1201 manufactured by Mountech Co., Ltd., with nitrogen as the adsorbed species.

[0048] · Surface functional groups of hexagonal boron nitride particles (before metal oxide attachment) The hexagonal boron nitride particles (before metal oxide is attached) used in the present invention preferably have OH groups, NH2 groups, or both as surface functional groups. In general, the functional groups of hexagonal boron nitride particles are not present on the particle planes, but on the particle edge faces. By having such functional groups, the metal oxide is easily selectively attached to the edge faces of the hexagonal boron nitride particles due to the interaction between the hexagonal boron nitride particles (before metal oxide is attached) and the metal oxide.

[0049] Specifically, when the infrared absorption spectrum of the powder containing the raw material hexagonal boron nitride particles (before the metal oxide was attached) was measured, -1 ~3500cm -1 Symmetrical contraction vibration peak of the NH2 group in the range of 3530 cm -1 ~3590cm -1 NH2 group asymmetric shrinkage vibration peak in the range of 3600 cm -1 ~3750cm -1 It is preferable that any of the OH group peaks in the range of

[0050] In the infrared absorption spectrum, -1 ~3800cm -1 The highest absorption peak in the range is 3530 cm -1 ~3590cm -1 In the range of 3568 cm-1 It is preferable that the absorption peak is in the vicinity of the maximum absorption peak. The presence of the NH2 group at the particle edge at a high density indicates that such a powder can be produced, for example, by the method disclosed in WO2018 / 101241.

[0051] (Metal oxide particles (before attachment)) The powder containing metal oxide particles (before adhesion) having a primary particle diameter of 100 nm to 700 nm is not particularly limited, and any known powder can be used without limitation. For example, a metal oxide powder produced based on a known production method may be used, or a commercially available powder may be used.

[0052] Primary particle size of metal oxide particles (before deposition) The metal oxide particles (before adhesion) contained in the powder containing metal oxide particles (before adhesion) preferably have a primary particle diameter of 100 nm or more and 700 nm or less. The powder containing the metal oxide particles (before adhesion) has an average primary particle diameter of preferably 100 nm to 700 nm, more preferably 200 nm to 600 nm, and even more preferably 350 nm to 500 nm. By making the average primary particle diameter within the above range, the number of metal oxide particles (before metal oxide adhesion) having a primary particle diameter within the above range can be increased, and the metal oxide-adhered hexagonal boron nitride particles of the present invention can be efficiently produced.

[0053] Specific surface area of ​​powder containing metal oxide particles (before deposition) The powder containing metal oxide particles (before attachment) has a specific surface area of ​​4.0 m 2 / g or more 50m 2 / g or less, and 5.0m 2 / g or more 30m 2 It is more preferable that the molecular weight is not more than 1 / g. The ratio of the powder containing hexagonal boron nitride particles (before metal oxide adhesion) and the powder containing metal oxide particles (before adhesion) during mixing is not particularly limited, but for example, the powder containing metal oxide particles (before adhesion) can be 0.4 parts by mass or more and 15 parts by mass or less, preferably 0.6 parts by mass or more and 13 parts by mass or less, and more preferably 4 parts by mass or more and 12 parts by mass or less, per 100 parts by mass of the powder containing hexagonal boron nitride particles (before metal oxide adhesion). If the ratio is less than the lower limit, it is difficult to adhere a sufficient amount of metal oxide, and if the ratio exceeds the upper limit, the adsorption rate to the flat surface increases or the production efficiency decreases. EXAMPLES

[0054] The present invention will be described in detail below with reference to examples. However, the present invention is not limited to the following examples as long as it does not depart from the gist of the present invention. <Infrared absorption spectrum of hexagonal boron nitride powder> The hexagonal boron nitride powders obtained in the following examples and comparative examples were subjected to diffuse reflectance infrared spectroscopy measurement using an Agilent Technologies FTS-3000. The samples were pretreated by drying at 200°C under reduced pressure for 2 hours. The samples were packed into a measuring cup and measured. The resolution was 4 cm. -1 The number of accumulations was 64.

[0055] <Specific surface area (m) of hexagonal boron nitride powder and metal oxides 2 / g)> The specific surface area of ​​the hexagonal boron nitride powders obtained in the following Examples and Comparative Examples, and the metal oxides used therein, was measured using Macsorb HM model-1201 manufactured by Mountech Co., Ltd.

[0056] <Examples 1 to 10 and Comparative Examples 1 to 5> 195 g of boron oxide, 82 g of carbon black with a sulfur concentration of 3500 ppm, and 55 g of calcium carbonate were mixed using a ball mill. 100 g of the mixture was subjected to nitriding treatment in a graphite Tammann furnace by holding the mixture at 1500°C for 4 hours and at 1850°C for 5 hours under a nitrogen gas atmosphere to obtain boron nitride containing by-products.

[0057] Next, the obtained by-product-containing boron nitride was crushed and placed in a container, and hydrochloric acid (7 wt% HCl) was added in an amount 5 times the amount of the by-product-containing boron nitride, and the mixture was stirred at a rotation speed of 700 rpm for 24 hours. After the acid washing, the acid was filtered, and the resultant product obtained by filtration was dispersed in pure water in the same amount as the acid used, and filtered again. This operation was repeated five times, and then the mixture was vacuum dried at 200°C for 6 hours. After drying, the resulting powder was sieved through a 90μm mesh sieve to obtain white hexagonal boron nitride powder, "BN-A." The resulting white powder was identified as hexagonal boron nitride by X-ray diffraction measurement.

[0058] The diffuse reflectance infrared absorption spectrum and specific surface area of ​​the obtained hexagonal boron nitride powder were measured by the method described above. The specific surface area of ​​BN-A was 1.4 m 2 / g. BN-A was 3568 cm -1 The highest absorption peak was observed in the asymmetric contraction vibration of the NH2 group. BN-A (before the metal oxide was mixed) was analyzed from multiple SEM observation images using an image analyzer (A-image-kun: manufactured by Asahi Kasei Engineering Co., Ltd.), and it was confirmed that it contained hexagonal boron nitride particles (before the metal oxide was attached) with a particle diameter of 6.5 μm to 8 μm and an aspect ratio of 2 to 8. In addition, 100 different single particles were randomly selected, and the length of the long axis and the length in the thickness direction were measured. The aspect ratio was calculated as the long axis length / length in the thickness direction, and the average particle diameter D1 was 6.8 μm and the average aspect ratio was 5.7.

[0059] A powder containing hexagonal boron nitride particles with metal oxide attached was obtained by dry mixing BN-A and silicon dioxide manufactured by Tokuyama Corporation shown below as a metal oxide in the ratio shown in Table 1. For the dry mixing method, hexagonal boron nitride powder BN-A and the metal oxide were added to a Unipack (L-8) manufactured by Seisan Nippon Co., Ltd. so that the total amount was 100g, and mixed by hand for 1 minute.

[0060] 1: Sanseal SS-01 specific surface area 24m 2 / g Primary particle diameter 100nm 2: Sanseal SS-03, specific surface area 11m 2 / g Primary particle diameter 300nm 3: Sunseal SS-04, specific surface area 7m 2 / g Primary particle diameter 400nm 4: Sunsil SS-07 specific surface area 4m 2 / g Primary particle diameter 700nm 5: Sunseal SS-10, specific surface area 3m 2 / g Primary particle diameter 1000nm 6: Leoloseal QS-20, specific surface area 220m 2 / g Primary particle diameter 12nm

[0061] The powder containing metal oxide-adhered hexagonal boron nitride particles obtained in Example 1 was analyzed from SEM observation images using an image analyzer (A-zo-kun: manufactured by Asahi Kasei Engineering Co., Ltd.) and it was confirmed that metal oxide with a primary particle diameter of 100 nm or more and 700 nm or less was adhered to the surface of hexagonal boron nitride particles with a particle diameter of 6.5 μm or more and an aspect ratio of 2 to 8, and that metal oxide-adhered hexagonal boron nitride particles were present, with the area adhesion ratio of metal oxide adhered to the end faces being 30% or more and the area adhesion ratio of metal oxide adhered to the flat surfaces being 6% or less. The content of metal oxide-attached hexagonal boron nitride particles in the powder was 50% or more by area. Furthermore, 100 different metal oxide-attached hexagonal boron nitride particles were randomly selected, and the average particle diameter D2 of the metal oxide-attached hexagonal boron nitride particles, the average particle diameter D3 of the metal oxide, the average area attachment rate of the metal oxide attached to the end faces, and the average area attachment rate of the metal oxide attached to the flat surfaces were calculated. Hexagonal boron nitride and metal oxide were distinguished using SEM-EDX (Energy Dispersive X-ray Spectrometer Genesis2000: EDAX Corporation). The results are shown in Table 1.

[0062] For Examples 2 to 10 and Comparative Examples 1 to 5, metal oxide composite particles (metal oxide-adhered hexagonal boron nitride particles) were obtained in the same manner as in Example 1, except that silicon dioxide was dry-mixed in the ratio shown in Table 1, and measurements were performed in the same manner. The content of metal oxide-deposited hexagonal boron nitride particles in the powder was 50 area % or more in all Examples.

[0063] Furthermore, in Example 2, it was confirmed that metal oxide-attached hexagonal boron nitride particles exist, in which the surface of hexagonal boron nitride particles has a particle diameter of 6.5 μm or more and 8 μm or less and an aspect ratio of 2 or more and 8 or less, to which a metal oxide having a primary particle diameter of 100 nm or more and 700 nm or less is attached, and the area adhesion ratio of the metal oxide attached to the end faces is 40% or more, and the area adhesion ratio of the metal oxide attached to the flat surfaces is 6% or less.

[0064] In Examples 3 and 9, it was confirmed that metal oxide-attached hexagonal boron nitride particles having a particle diameter of 6.5 μm or more and 8 μm or less and an aspect ratio of 2 or more and 8 or less had a metal oxide with a primary particle diameter of 100 nm or more and 700 nm or less attached to the surface, and that the area adhesion ratio of the metal oxide attached to the end faces was 50% or more and the area adhesion ratio of the metal oxide attached to the flat surfaces was 6% or less.

[0065] In Examples 4, 5 and 10, it was confirmed that metal oxide-attached hexagonal boron nitride particles having a particle diameter of 6.5 μm or more and 8 μm or less and an aspect ratio of 2 or more and 8 or less had a metal oxide having a primary particle diameter of 100 nm or more and 700 nm or less attached to the surface, and the area adhesion ratio of the metal oxide attached to the end faces was 60% or more and the area adhesion ratio of the metal oxide attached to the flat surfaces was 6% or less.

[0066] In Examples 6 and 7, it was confirmed that metal oxide-attached hexagonal boron nitride particles were present, the surfaces of which had a particle diameter of 6.5 μm or more and 8 μm or less and an aspect ratio of 2 or more and 8 or less, with metal oxide having a primary particle diameter of 100 nm or more and 700 nm or less attached, and the area adhesion ratio of the metal oxide attached to the end faces was 70% or more and the area adhesion ratio of the metal oxide attached to the flat surfaces was 6% or less.

[0067] In Example 8, it was confirmed that metal oxide-attached hexagonal boron nitride particles were present, the surfaces of which had a particle diameter of 6.5 μm or more and 8 μm or less and an aspect ratio of 2 or more and 8 or less, to which metal oxide had a primary particle diameter of 100 nm or more and 700 nm or less was attached, and the area adhesion ratio of the metal oxide attached to the end faces was 60% or more and the area adhesion ratio of the metal oxide attached to the flat surfaces was 9% or less.

[0068] <Comparative Examples 6 to 10> Hexagonal boron nitride powder "BN-B" was obtained in the same manner as in Example 1, except that the sulfur concentration of the raw carbon black was 100 ppm and the amount of calcium carbonate was 20 g. The resulting white powder BN-B was identified as hexagonal boron nitride by X-ray diffraction measurement. The diffuse reflectance infrared absorption spectrum, specific surface area, average particle diameter D1, and average aspect ratio of the resulting hexagonal boron nitride powder were measured by the methods described above. The specific surface area of ​​BN-B was 2.0 m 2 / g, average particle diameter D1 = 6.8 μm, and average aspect ratio 15.7. Hexagonal boron nitride powder BN-B has a diffuse reflectance infrared spectrum (3100-3800 cm -1 ), no clear peak was observed.

[0069] Four types of silicon dioxide from Tokuyama Corporation were prepared as metal oxides for BN-B, and dry-mixed in the ratios shown in Table 1 in the same manner as in Example 1 to prepare composite particles of hexagonal boron nitride powder (BN-B) and metal oxides. The composite particles were observed with an SEM in the same manner as in Example 1, and the average particle diameter D2 of the hexagonal boron nitride particles with metal oxide attached and the average particle diameter D3 of the metal oxide, the average area adhesion ratio of the metal oxide attached to the end faces, and the average area adhesion ratio of the metal oxide attached to the flat surfaces were calculated. The results are shown in Table 1.

[0070] <Comparative Example 11> The BN-A obtained in Example 1 was heated in a graphite Tammann furnace under a nitrogen gas atmosphere at 1000°C for 5 hours to produce "BN-C", a hexagonal boron nitride powder. The resulting white powder "BN-C" was identified as hexagonal boron nitride by X-ray diffraction measurement. The diffuse reflectance infrared absorption spectrum, specific surface area, average particle diameter D1, and average aspect ratio of the resulting hexagonal boron nitride powder (BN-C) were measured using the methods described above. The specific surface area of ​​BN-C was 1.5 m 2 / g, average particle diameter D1 = 7.8 μm, and average aspect ratio 6.3. BN-C was measured by the diffuse reflectance infrared spectroscopy (3100-3800 cm -1 ), no clear peak was observed.

[0071] Silicon dioxide (SS-04) manufactured by Tokuyama Corporation described above was prepared as the metal oxide for BN-C, and dry-mixed in the ratio shown in Table 1 in the same manner as in Example 1 to prepare composite particles of hexagonal boron nitride powder and metal oxide. The composite particles were observed with an SEM in the same manner as in Example 1, and the average particle diameter D2 of the hexagonal boron nitride particles with metal oxide attached and the average particle diameter D3 of the metal oxide, the average area deposition rate of the metal oxide attached to the end faces, and the average area deposition rate of the metal oxide attached to the flat surfaces were calculated. The results are shown in Table 1.

[0072] [Table 1]

[0073] <Examples 11 to 20 and Comparative Examples 12 to 22> The powders obtained in Examples 1 to 10 and Comparative Examples 1 to 11 were filled into epoxy resin to prepare resin compositions, and their thermal conductivity was evaluated. The epoxy resin was prepared by mixing 100 parts by weight (JER806 manufactured by Mitsubishi Chemical Corporation) and 28 parts by weight of a curing agent (alicyclic polyamine curing agent, JER Cure 113 manufactured by Mitsubishi Chemical Corporation). Next, 42% by volume of each base resin and 58% by volume of each powder were mixed in a centrifugal mixer (MAZERUSTAR manufactured by Kurabo Industries, Ltd.) to obtain resin compositions.

[0074] <Evaluation of thermal conductivity> This was poured into a mold and cured using a heat press under conditions of temperature: 200°C, pressure: 5 MPa, and holding time: 30 minutes to produce a sheet with a diameter of 40 mm and a thickness of 0.22 mm. The sheet was analyzed using a temperature wave thermal analyzer (Ai-Phase Corporation) and the thermal conductivity was calculated and the results are shown in Table 2. The sheets filled with the composite particles of boron nitride powder and metal oxide produced in Examples 1 to 10 had a thermal conductivity of 10.0 W / m K or more, indicating high thermal conductivity.

[0075] <Evaluation of dielectric strength> Furthermore, the dielectric strength of the sheets filled with the powders obtained in Examples 1 to 10 and Comparative Examples 1 to 11 was measured using a voltage resistance tester (manufactured by Tama Densoku Co., Ltd.), and the results are shown in Table 2. The sheets filled with the composite particles of boron nitride powder and metal oxide produced in Examples 1 to 10 had a high dielectric strength of 90 kV / mm or more.

[0076] <Evaluation of peel strength> The copper foil peel strength between the copper foil and each of the obtained sheets was determined based on JIS C6481. The copper foil peel strength was determined as a relative value, with the value obtained using hexagonal boron nitride powder (BN-A not mixed with metal oxide) in Comparative Example 1 being set at 1. The copper foil peel strength of the sheets filled with the composite powder of boron nitride powder and metal oxide produced in Examples 1 to 10 showed a high relative value of 1.1 or more.

[0077] <Evaluation of Viscosity> Next, 80% by volume of each base epoxy resin and 20% by volume of powder containing composite particles from each Example and Comparative Example were mixed in a mortar under the same conditions for each test, and the viscosity was measured using a B-type viscometer TBA-10 (manufactured by Toki Kogyo Co., Ltd.) at a measurement temperature of 25°C. The viscosity was determined as a relative value, with the value obtained using the hexagonal boron nitride powder (BN-A not mixed with metal oxide) in Comparative Example 1 set at 1. The relative values ​​of the resin filling viscosity of the composite powders of boron nitride powder and metal oxide prepared in Examples 1 to 10 were low, being 0.8 or less.

[0078]

Table 2

Claims

1. Hexagonal boron nitride particles having a metal oxide attached to the particle surface, wherein the area adhesion rate of the metal oxide to the flat surfaces of the hexagonal boron nitride particles is 10% or less, and the area adhesion rate of the metal oxide to the end faces of the hexagonal boron nitride particles is 30% or more.

2. 2. The metal oxide-coated hexagonal boron nitride particles according to claim 1, wherein the hexagonal boron nitride particles have an aspect ratio of 12 or less and a particle size of 5 μm or more and 12 μm or less.

3. 3. The metal oxide-coated hexagonal boron nitride particles according to claim 1, wherein the primary particle size of the metal oxide is 100 nm or more and 700 nm or less.

4. A powder comprising the metal oxide-deposited hexagonal boron nitride particles of claim 1 or 2.

5. A resin composition comprising a base resin and the metal oxide-adhered hexagonal boron nitride particles according to claim 1 or 2.

6. A resin sheet obtained by molding the resin composition according to claim 5.

7. A metal wiring board comprising metal wiring on a surface of the resin sheet according to claim 6.

8. A method for producing a powder containing metal oxide-adhered hexagonal boron nitride particles, comprising a step of dry-mixing a powder containing hexagonal boron nitride particles having an average aspect ratio of 12 or less and an average particle size of 5 μm or more and 12 μm or less with a powder containing metal oxide particles having an average primary particle size of 100 nm or more and 700 nm or less.

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