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WO2024048377A1 - Method for producing sheet, and sheet - Google Patents

Method for producing sheet, and sheet Download PDF

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Publication number
WO2024048377A1
WO2024048377A1 PCT/JP2023/030202 JP2023030202W WO2024048377A1 WO 2024048377 A1 WO2024048377 A1 WO 2024048377A1 JP 2023030202 W JP2023030202 W JP 2023030202W WO 2024048377 A1 WO2024048377 A1 WO 2024048377A1
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WO
WIPO (PCT)
Prior art keywords
boron nitride
sheet
cells
region
boron
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/JP2023/030202
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French (fr)
Japanese (ja)
Inventor
建治 宮田
麻菜 山本
祐輔 佐々木
遼 戎▲崎▼
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Denka Co Ltd
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Denka Co Ltd
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Publication date
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Priority to JP2024544159A priority Critical patent/JPWO2024048377A1/ja
Publication of WO2024048377A1 publication Critical patent/WO2024048377A1/en
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B21/00—Nitrogen; Compounds thereof
    • C01B21/06—Binary compounds of nitrogen with metals, with silicon, or with boron, or with carbon, i.e. nitrides; Compounds of nitrogen with more than one metal, silicon or boron
    • C01B21/064—Binary compounds of nitrogen with metals, with silicon, or with boron, or with carbon, i.e. nitrides; Compounds of nitrogen with more than one metal, silicon or boron with boron
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
    • C08J5/18—Manufacture of films or sheets
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K3/00—Use of inorganic substances as compounding ingredients
    • C08K3/38—Boron-containing compounds
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L101/00—Compositions of unspecified macromolecular compounds

Definitions

  • the present invention relates to a sheet manufacturing method and a sheet.
  • boron nitride powder As a ceramic powder, boron nitride powder, which has characteristics such as high thermal conductivity, high insulation, and low dielectric constant, is attracting attention.
  • Boron nitride powder is generally composed of agglomerated particles (lump particles) formed by agglomerating scale-like boron nitride particles (primary particles).
  • agglomerated particles lump particles
  • primary particles agglomerating scale-like boron nitride particles
  • the shape of the aggregated particles is made more spherical to improve the filling property, and the powder strength is also improved.
  • a hexagonal boron nitride powder is disclosed which is said to have improved and stabilized withstand voltage.
  • a resin composition containing boron nitride powder and a resin is pressurized and formed into a sheet shape, but in this case, the nitride in the resin composition is The aggregated boron particles collapse, and the boron nitride particles (primary particles) that constituted the aggregated particles tend to be oriented parallel to the main surface of the sheet (perpendicular to the pressing direction). If the boron nitride particles are oriented in a direction parallel to the main surface of the sheet, the thermal conductivity in the thickness direction of the sheet may decrease, which may make the sheet unsuitable for use as a heat transfer sheet.
  • the main object of the present invention is to produce a sheet in which the orientation of boron nitride particles in the direction parallel to the main surface of the sheet is suppressed.
  • the present inventors formed a sheet using boron nitride powder obtained by a manufacturing method including hot isostatic pressing (HIP method), thereby forming boron nitride in a direction parallel to the main surface of the sheet. It has been discovered that it is possible to produce a sheet with suppressed particle orientation.
  • the present invention provides the following [1] to [3].
  • a method for manufacturing a sheet comprising: [2] Contains boron nitride particles and a resin, A sheet whose average value X calculated by the following steps (1) to (8) is 0.01 or more. (1) Obtain an observation image of an arbitrary cross section of the sheet observed with a SEM at a magnification of 1000 times.
  • the one cell is a boron nitride region, and if the area ratio is less than 20%, it is determined that the one cell is a resin region.
  • n is 1 to 200, calculate the ratio of the number of cells determined to be the boron nitride region.
  • n is 1 to 5
  • FIG. 1 is a flow diagram of steps (1) to (7).
  • FIG. 2(a) is a reference diagram when area A included in the binarized image is divided into a plurality of cells.
  • FIG. 2(b) is a schematic diagram when each of the plurality of cells in FIG. 2(a) is determined to be either a boron nitride region or a resin region. It is a SEM image of a cross section of the sheet of Example 1-1.
  • 3 is a SEM image of a cross section of a sheet of Comparative Example 1. Graph showing the relationship between the length of one side of one cell and the ratio of the number of cells determined to be boron nitride regions when the sheet of Example 4-1 and the sheet of Comparative Example 4 are divided into a plurality of cells. It is.
  • a method for manufacturing a sheet according to an embodiment of the present invention includes a step of nitriding boron carbide powder while hot isostatic pressing (also referred to as "hot isostatic pressing") to obtain boron carbonitride powder. (nitriding step), a step of decarburizing boron carbonitride powder to obtain boron nitride powder (decarburizing step), and a step of mixing boron nitride powder with resin to obtain a resin composition (mixing step). , a step of molding the resin composition into a sheet shape by applying pressure (molding step).
  • Boron carbide powder (boron carbide particles) can be produced, for example, by a known production method. For example, boric acid and acetylene black are mixed and then heated in an inert gas atmosphere at 1800 to 2400° C. for 1 to 10 hours to obtain coarse boron carbide powder containing lumpy boron carbide particles. Boron carbide powder is obtained by appropriately performing pulverization, sieving, washing, impurity removal, drying, etc. on the obtained boron carbide coarse powder.
  • the average particle diameter of the boron carbide powder may be, for example, 5 ⁇ m or more, 10 ⁇ m or more, or 15 ⁇ m or more, and 80 ⁇ m or less, 60 ⁇ m or less, or 40 ⁇ m or less.
  • the average particle size of boron carbide powder means the particle size (D50) at which the volume cumulative particle size distribution is 50%, and can be measured by a laser diffraction scattering method.
  • boron carbide powder is nitrided to obtain boron carbonitride powder by heating the container filled with boron carbide powder under hot isostatic pressure in an atmosphere that allows the nitriding reaction to proceed.
  • the container may be, for example, a carbon crucible.
  • the hot isostatic pressing can be performed using, for example, a hot isostatic pressing device (for example, manufactured by Kobe Steel, Ltd.).
  • the atmosphere in which the nitriding reaction proceeds in the nitriding step may be a nitriding gas atmosphere that nitrides boron carbide powder.
  • the nitriding gas may be nitrogen gas, ammonia gas, etc. Nitrogen gas may be used from the viewpoint of ease of nitriding boron carbide powder and from the viewpoint of cost.
  • the nitriding gas may be used alone or in combination of two or more, and the proportion of nitrogen gas in the nitriding gas may be 95% by volume or more, 99% by volume or more, or 99.9% by volume or more.
  • the pressure in the nitriding step may be 10 MPa or more, 30 MPa or more, or 100 MPa or more.
  • the pressure in the nitriding step may be 200 MPa or less or 150 MPa or less.
  • the heating temperature in the nitriding step may be 1600° C. or higher or 1700° C. or higher from the viewpoint of sufficiently nitriding the boron carbide powder.
  • the heating temperature in the nitriding step may be 2200°C or lower or 2000°C or lower.
  • the time for pressurizing and heating in the nitriding step may be 3 hours or more, 5 hours or more, or 8 hours or more from the viewpoint of sufficiently nitriding the boron carbide powder.
  • the time for pressurizing and heating in the nitriding step may be 30 hours or less, 20 hours or less, or 10 hours or less.
  • a mixture containing boron carbonitride powder (boron carbonitride particles) obtained in the nitriding step and a boron source is filled in a container and heated to decarburize the boron carbonitride powder.
  • the container may be, for example, a boron nitride crucible.
  • Boron sources include boric acid, boron oxide, or mixtures thereof.
  • the mixture may further contain other additives used in the art, if necessary.
  • the mixing ratio of boron carbonitride powder and boron source is selected as appropriate.
  • boric acid or boron oxide is used as a boron source, the proportion of boric acid or boron oxide may be, for example, 50 parts by mass or more or 80 parts by mass or more, and 300 parts by mass or less, based on 100 parts by mass of boron carbonitride. Or it may be 200 parts by mass or less.
  • the atmosphere in the decarburization process may be a normal pressure (atmospheric pressure) atmosphere or a pressurized atmosphere.
  • the pressure in the decarburization step may be, for example, 0.5 MPa or less or 0.3 MPa or less, and may be 0.01 MPa or more or 0.03 MPa or more.
  • the temperature is raised to a predetermined temperature (a temperature at which decarburization can start), and then the temperature is further raised to a holding temperature at the predetermined temperature.
  • the predetermined temperature temperature at which decarburization can start
  • the rate of temperature increase from a predetermined temperature (temperature at which decarburization can be started) to the holding temperature may be, for example, 5° C./min or less, 4° C./min or less, 3° C./min or less, or 2° C./min or less.
  • the holding temperature may be 1800° C. or higher or 2000° C. or higher from the viewpoint of facilitating good particle growth.
  • the holding temperature may be 2200°C or less or 2100°C or less.
  • the holding time at the holding temperature may be, for example, 0.5 hours or more, 1 hour or more, 3 hours or more, or 5 hours or more, from the viewpoint of facilitating particle growth.
  • the holding time at the holding temperature may be, for example, 40 hours or less, 30 hours or less, or 20 hours or less.
  • the boron nitride powder (boron nitride agglomerated particles) obtained as described above may be classified using a sieve (classification step) so as to obtain boron nitride powder having a desired particle size.
  • the boron nitride agglomerated particles are composed of, for example, a plurality of boron nitride pieces (boron nitride primary particles).
  • the boron nitride pieces are made of boron nitride and may have, for example, a scale-like shape.
  • the plurality of boron nitride pieces may be in physical contact with each other or may be chemically bonded.
  • the fact that the plurality of boron nitride pieces are chemically bonded to each other can be confirmed by using SEM, since no boundaries between the boron nitride pieces are observed at the joints between the boron nitride pieces.
  • the average thickness of the boron nitride pieces may be 0.5 ⁇ m or more, 1.0 ⁇ m or more, or 3.0 ⁇ m or more, and 10 ⁇ m or less.
  • the average length of the boron nitride pieces in the longitudinal direction may be, for example, 1 ⁇ m or more and 10 ⁇ m or less.
  • the average thickness and average length in the longitudinal direction of the boron nitride pieces can be determined using an SEM image of the cross section of the boron nitride agglomerated particles observed at a magnification of 1000 times using image analysis software (for example, "Mac" manufactured by Mountech Co., Ltd.). -view'') and is defined as the average value of the thickness and longitudinal length of 40 boron nitride pieces measured in the SEM image.
  • the boron nitride agglomerated particles may have a cross section that includes a region in which a plurality of boron nitride pieces are stacked.
  • the fact that multiple boron nitride pieces were stacked was confirmed by observing the cross section of the boron nitride agglomerated particles using SEM, and it was found that the multiple boron nitride pieces were arranged side by side in the thickness direction of the boron nitride pieces. You can check it.
  • the average particle diameter of the boron nitride powder may be, for example, 10 ⁇ m or more, 20 ⁇ m or more, or 30 ⁇ m or more, and 100 ⁇ m or less, 80 ⁇ m or less, or 60 ⁇ m or less.
  • the average particle size of boron nitride powder means the particle size (D50) at which the volume cumulative particle size distribution is 50%, and can be measured by a laser diffraction scattering method.
  • the bulk density of the boron nitride powder may be 0.7 g/ml or more, 0.72 g/ml or more, 0.74 g/ml or more, or 0.75 g/ml or more, and 0.9 g/ml or less, 0. It may be 8 g/ml or less, or 0.75 g/ml or less.
  • the boron nitride agglomerated particles may consist essentially only of boron nitride. It can be confirmed that the boron nitride aggregate particles are substantially composed only of boron nitride by detecting only a peak derived from boron nitride in X-ray diffraction measurement.
  • a resin composition is obtained by mixing the boron nitride powder obtained in the decarburization step and a resin.
  • the resin examples include epoxy resin, silicone resin, silicone rubber, acrylic resin, phenol resin, melamine resin, urea resin, unsaturated polyester, fluororesin, polyimide, polyamideimide, polyetherimide, polybutylene terephthalate, polyethylene terephthalate, Polyphenylene ether, polyphenylene sulfide, fully aromatic polyester, polysulfone, liquid crystal polymer, polyether sulfone, polycarbonate, maleimide modified resin, ABS (acrylonitrile-butadiene-styrene) resin, AAS (acrylonitrile-acrylic rubber/styrene) resin, and AES ( Examples include acrylonitrile, ethylene, propylene, diene rubber (styrene) resin.
  • the content of the boron nitride powder is 50 volume% or more, 55 volume% or more, based on the total volume of the resin composition, from the viewpoint of improving the thermal conductivity of the resin composition and easily obtaining excellent heat dissipation performance. It may be 60% by volume or more, 65% by volume or more, or 70% by volume or more.
  • the content of the boron nitride powder is 85% by volume or less, 80% by volume or less, based on the total volume of the resin composition, from the viewpoint of suppressing the generation of pores during molding and the decrease in insulation and mechanical strength. Alternatively, it may be 75% by volume or less.
  • the content of the resin may be 15% by volume or more, 20% by volume or more, or 25% by volume or more, and 50% by volume or less, 45% by volume or less, 40% by volume or less, based on the total volume of the resin composition. , 35% by volume or less, or 30% by volume or less.
  • the resin composition may further contain a curing agent for curing the resin.
  • the curing agent is appropriately selected depending on the type of resin.
  • examples of the curing agent include phenol novolac compounds, acid anhydrides, amino compounds, and imidazole compounds.
  • the content of the curing agent may be, for example, 0.5 parts by mass or more or 1.0 parts by mass or more, and 15 parts by mass or less or 10 parts by mass or less, based on 100 parts by mass of the resin.
  • the resin composition may further contain other components.
  • Other components may include a curing accelerator (curing catalyst), a coupling agent, a wetting and dispersing agent, a surface conditioner, and the like.
  • curing accelerators examples include phosphorus curing accelerators such as tetraphenylphosphonium tetraphenylborate and triphenyl phosphate, imidazole curing accelerators such as 2-phenyl-4,5-dihydroxymethylimidazole, and trifluorocarbon curing accelerators.
  • phosphorus curing accelerators such as tetraphenylphosphonium tetraphenylborate and triphenyl phosphate
  • imidazole curing accelerators such as 2-phenyl-4,5-dihydroxymethylimidazole
  • trifluorocarbon curing accelerators examples include amine curing accelerators such as boron monoethylamine.
  • Examples of the coupling agent include silane coupling agents, titanate coupling agents, and aluminate coupling agents.
  • Chemical bonding groups contained in these coupling agents include vinyl groups, epoxy groups, amino groups, methacrylic groups, mercapto groups, and the like.
  • wetting and dispersing agents include phosphoric acid ester salts, carboxylic acid esters, polyesters, acrylic copolymers, block copolymers, and the like.
  • surface conditioners examples include acrylic surface conditioners, silicone surface conditioners, vinyl surface conditioners, fluorine surface conditioners, and the like.
  • the boron nitride powder and the resin can be mixed by a known method.
  • the resin composition obtained in the mixing step may further contain a solvent (for example, a solvent for dissolving the resin) as necessary, and may further contain the other components mentioned above.
  • Examples of the solvent include alcohol solvents, glycol ether solvents, aromatic solvents, ketone solvents, and the like.
  • Examples of alcoholic solvents include isopropyl alcohol and diacetone alcohol.
  • Examples of glycol ether solvents include ethyl cellosolve, butyl cellosolve, and the like.
  • Examples of aromatic solvents include toluene and xylene.
  • Examples of ketone solvents include methyl ethyl ketone and methyl isobutyl ketone.
  • the resin composition obtained in the mixing step is molded into a sheet by applying pressure to obtain a sheet.
  • the molding step may be, for example, a step of molding the resin composition into a sheet shape by applying the resin composition onto the base material using a film applicator and applying pressure.
  • the pressing force in the molding step may be, for example, 1 MPa or more or 5 MPa or more, or 100 MPa or less or 50 MPa or less.
  • a step (curing step) of curing part or all of the resin in the resin composition may be performed simultaneously with or after the molding.
  • the method for curing the resin is appropriately selected depending on the type of resin (and the curing agent used as necessary).
  • the resin when the resin is an epoxy resin and the above-mentioned curing agent is used together, the resin can be cured by heating in the curing step. In this case, the resin can be semi-cured by adjusting the heating temperature and heating time.
  • the resin composition contains a solvent, the resin may be cured and the solvent may be volatilized in the curing step.
  • boron nitride powder (boron nitride agglomerated particles) obtained by nitriding boron carbide powder under hot isostatic pressure to obtain boron carbonitride powder and then decarburizing the boron carbonitride powder is: Constructed from a relatively thick piece of boron nitride. Such boron nitride agglomerated particles tend to easily maintain their shape even when external force is applied.
  • each of the boron nitride pieces constituting the boron nitride aggregate particles is relatively thick, and the boron nitride aggregate particles have high density (low porosity).
  • the amount of boron nitride per particle is larger than that of conventional boron nitride agglomerated particles.
  • the amount per unit volume of the sheet is Since the number of boron nitride aggregated particles (or boron nitride pieces) is reduced, the frequency of compressive deformation of the boron nitride aggregated particles (or boron nitride pieces) during sheet formation is reduced.
  • Boron nitride agglomerated particles are difficult to break down and compressively deform less frequently during sheet formation, making it difficult for boron nitride pieces (boron nitride primary particles) to line up in a direction parallel to the main surface of the sheet, resulting in the formation of boron nitride particles in the sheet. It is presumed that the orientation is suppressed.
  • the mechanism of the present invention is not limited to the above reasons.
  • the sheet obtained by the above manufacturing method has a plurality of regions made of boron nitride particles and other regions in the cross section of the sheet.
  • the sheet obtained by the above manufacturing method is such that the boron nitride agglomerated particles maintain their shape to some extent in the sheet, so that the area of the region made of boron nitride particles in the cross section of the sheet (multiple regions made of boron nitride particles The area of each region of boron nitride particles tends to be larger than the area of the region of boron nitride particles in the cross section of a sheet made with the same content using conventional boron nitride agglomerated particles.
  • FIG. 1 shows a flow diagram of steps (1) to (7). (1) An observation image of an arbitrary cross section of the sheet is obtained by observing it at a magnification of 1000 times using an SEM.
  • the one cell is a boron nitride region, and if the area ratio is less than 20%, it is determined that the one cell is a resin region.
  • (6) In the steps (3) to (5) above, when n is 1 to 200, calculate the ratio of the number of cells determined to be the boron nitride region.
  • n is 1 to 5
  • the image format of the observation image to be acquired is bmp.
  • the image to be acquired may be one that is sharp enough to be binarized into a region made of boron nitride particles and other regions.
  • step (2) the observed image is imported into image processing software "imageJ” and filtered using a median filter (3x3 pixels). Thereafter, the region made of boron nitride particles and the other regions (for example, the region made of resin) are subjected to binarization processing using the Otsu method to obtain a binarized image.
  • step (3) the entire region A is included in the binarized image.
  • Area A is an area with a short side of 50 ⁇ m x a long side of 100 ⁇ m. Note that due to image processing, it is difficult to accurately specify the short side (50 ⁇ m ⁇ 5 ⁇ m) x long side (100 ⁇ m ⁇ 10 ⁇ m) as area A. , the influence on the calculation result of the average value X can be ignored, so this region can be regarded as region A.
  • step (3) area A is divided into a plurality of cells by dividing the short side of area A into n equal parts and dividing the long side of area A into 2n equal parts, where n is an integer greater than or equal to 1. .
  • the area A is divided into 2n2 cells, and each cell is a square with one side of 50/n ( ⁇ m).
  • FIG. 2(a) is a reference diagram when area A included in the binarized image is divided into a plurality of cells.
  • area A is divided into four equal parts along the short side and eight equal parts along the long side, and is divided into 32 square cells.
  • step (4) one cell among the plurality of cells is focused on, and the area ratio of the region made of boron nitride particles is calculated based on the total area of one cell.
  • the area ratio of the region consisting of boron nitride particles is 80% or more, it can be determined that the cell is an area occupied by boron nitride particles, and the area ratio of the area consisting of boron nitride particles is If it is less than 20%, it can be determined that the cell is an area occupied by components other than boron nitride particles (area not occupied by boron nitride particles).
  • region A by dividing region A into a plurality of cells and determining whether each cell is a region made of boron nitride particles (boron nitride region) or a region made of something else (resin region), it is possible to , it can be determined whether the area of each region among the plurality of regions made of boron nitride particles is relatively large.
  • FIG. 2(b) is a schematic diagram when each of the plurality of cells in FIG. 2(a) is determined to be either a boron nitride region or a resin region.
  • FIG. 2B cells determined to be boron nitride regions are shown as black cells, and cells determined to be resin regions are shown as white cells.
  • step (5) the determination in step (4) is performed for each of the plurality of cells, and the ratio of the number of cells determined to be boron nitride regions based on the total number of the plurality of cells is calculated. That is, the ratio of the number of cells determined to be boron nitride regions is calculated by dividing the total number of cells determined to be boron nitride regions by the total number of a plurality of cells.
  • the total value is calculated from the ratio of the number of cells determined to be boron nitride regions when n is 1 to 5. If the boron nitride agglomerated particles do not easily collapse during sheet production and the boron nitride agglomerated particles can maintain their shape to some extent in the sheet, since the area of the region made of boron nitride particles in the sheet cross section is relatively large, n Even when is 1 to 5 (that is, when area A is roughly divided), each cell is more likely to be determined to be a boron nitride area, and the proportion of cells determined to be boron nitride areas is large. There is a tendency to
  • step (8) obtain observation images of a total of 5 cross sections of the sheet, calculate the total value from each observation image according to steps (1) to (7), and calculate from each of the total 5 cross sections.
  • the average value X is calculated from the total value.
  • the average value X is 0.01 or more, 0.03 or more, 0.01 or more, 0.03 or more, from the viewpoint of suppressing the orientation of the boron nitride particles even when the boron nitride particles are packed in a large amount and easily obtaining a sheet with excellent heat dissipation performance. It may be 05 or more, 0.07 or more, 0.08 or more, 0.09 or more, or 0.10 or more, and from the viewpoint of suppressing a decrease in insulation properties and mechanical strength, 5 or less, 3 or less, 2 or less , 1.8 or less, 1.6 or less, 1.2 or less, 1 or less, 0.8 or less, 0.5 or less, 0.3 or less, or 0.2 or less.
  • the average value Y of the proportion of each boron nitride region is set to 0.0. It may be 5 or more, 0.52 or more, or 0.54 or more.
  • the average value Y may be 0.8 or less, 0.75 or less, 0.7 or less, or 0.65 or less from the viewpoint of suppressing a decrease in insulation properties and mechanical strength.
  • the orientation index of the sheet may be 15 or less, 13 or less, or 11.5 or less from the viewpoint of suppressing the orientation of boron nitride particles in a direction parallel to the main surface of the sheet.
  • the orientation index of the sheet may be 1 or more, 3 or more, or 5 or more.
  • the thickness of the sheet may be 50 ⁇ m or more, 80 ⁇ m or more, or 100 ⁇ m or more, and may be 500 ⁇ m or less, 400 ⁇ m or less, or 300 ⁇ m or less.
  • Example 1-1 Boron carbide powder with an average particle diameter (D50) of 26 ⁇ m was filled in a carbon crucible, and heated at 1800°C in a nitrogen gas atmosphere using a hot isostatic press device (manufactured by Kobe Steel, Ltd., 02-SYSTEM15X). The boron carbide powder was heated and pressurized under the conditions of 196 MPa for 1.5 hours using the HIP method to nitride the boron carbonitride powder (B 4 CN 4 ).
  • a naphthalene type epoxy resin manufactured by DIC Corporation, HP4032
  • an imidazole compound manufactured by Shikoku Kasei Co., Ltd., 2E4MZ-CN
  • a resin composition was obtained by mixing the powders so that the powder filling rate was 70% by volume. This resin composition was degassed under reduced pressure of 500 Pa for 10 minutes, and then applied onto a PET sheet to a thickness of 1.0 mm. Thereafter, press heating and pressing was performed for 60 minutes at a temperature of 150° C. and a pressure of 30 MPa to produce a sheet with a thickness of 0.5 mm.
  • Example 1-2 The procedure was repeated in the same manner as in Example 1, except that the amount of boric acid was changed to 100 parts by mass (50 mass%) to obtain boron nitride powder (average particle size 44.7 ⁇ m, bulk density 0.75 g/ml). A sheet was produced.
  • Example 1-3 Same as Example 1 except that the amount of boric acid was changed to 81.8 parts by mass (45% by mass) to obtain boron nitride powder (average particle size 51.5 ⁇ m, bulk density 0.74 g/ml). A sheet was prepared.
  • boron carbide powder is obtained by heating and pressurizing in a nitrogen gas atmosphere using a resistance heating furnace at 2000 ° C. and 0.85 MPa for 25 hours.
  • Boron nitride powder (average particle size 42.3 ⁇ m, bulk density 0.67 g/ml) was obtained in the same manner as in Example 1-1, except that boron carbonitride powder was obtained by nitriding, and a sheet was produced. did.
  • Example 2-1 A sheet was produced in the same manner as in Example 1-1, except that the sheet was produced by press heating and pressing for 60 minutes at a temperature of 150° C. and a pressure of 15 MPa.
  • Example 2-2 A sheet was produced in the same manner as in Example 1-2, except that the sheet was produced by press heating and pressing for 60 minutes at a temperature of 150° C. and a pressure of 15 MPa.
  • Comparative example 2 A sheet was produced in the same manner as in Comparative Example 1, except that the sheet was produced by press heating and pressing for 60 minutes at a temperature of 150° C. and a pressure of 15 MPa.
  • Example 3-1 A sheet was produced in the same manner as in Example 2-1, except that the filling rate of boron nitride powder was changed to 65% by volume to obtain a resin composition.
  • Example 3-2 A sheet was produced in the same manner as in Example 2-2, except that the filling rate of boron nitride powder was changed to 65% by volume to obtain a resin composition.
  • Example 3-3 A sheet was produced in the same manner as in Example 2-3, except that the filling rate of boron nitride powder was changed to 65% by volume to obtain a resin composition.
  • Comparative example 3 A sheet was produced in the same manner as Comparative Example 2 except that the filling rate of boron nitride powder was changed to 65% by volume to obtain a resin composition.
  • Example 4-1 A sheet was produced in the same manner as in Example 2-1, except that the filling rate of boron nitride powder was changed to 60% by volume to obtain a resin composition.
  • Example 4-2 A sheet was produced in the same manner as in Example 2-2, except that the filling rate of boron nitride powder was changed to 60% by volume to obtain a resin composition.
  • Example 4-3 A sheet was produced in the same manner as in Example 2-3, except that the filling rate of boron nitride powder was changed to 60% by volume to obtain a resin composition.
  • Comparative example 4 A sheet was produced in the same manner as Comparative Example 2 except that the filling rate of boron nitride powder was changed to 60% by volume to obtain a resin composition.
  • the X-ray diffraction peak was measured using an X-ray diffraction device (Ultima IV-N), and the peak intensity of the (002) plane/the peak intensity of the (100) plane was calculated as follows: It was measured as the orientation index of boron nitride particles in the sheet. The measurement results of the orientation index are shown in Tables 1 to 4.
  • Average values X and Y were calculated by the following procedure. The calculation results of the average values X and Y are shown in Tables 1 to 4. (1) The cross sections of the sheets produced in each of the Examples and Comparative Examples were observed using a SEM at a magnification of 1000 times to obtain observation images in bmp format. (2) The obtained observation image was imported into image processing software "imageJ" and filtered using a median filter (3 ⁇ 3 pixels). Next, the region made of boron nitride particles and the other region (resin region) were subjected to binarization processing using the Otsu method to obtain a binarized image.
  • area A of 50 ⁇ m on the short side x 100 ⁇ m on the long side in the obtained binarized image, draw a straight line that divides the short side of area A into n equal parts and the long side into 2n equal parts, and divide the area A into multiple cells. (However, n is an integer of 1 or more).
  • the calculated area ratio was 80% or more, it was determined that the one cell was a boron nitride region, and if the area ratio was less than 20%, it was determined that the one cell was a resin region.
  • the determination in (4) above was made for each of the two cells, and the ratio of the number of cells determined to be boron nitride regions based on the total number of cells (2) was calculated.
  • n was 2 to 200, the above (4) and (5) were performed, and the ratio of the number of cells determined to be in the boron nitride region was calculated.
  • a total value was calculated from the ratio of the number of cells determined to be in each boron nitride region when n was 1 to 5.
  • FIG. 3 shows a SEM image of the cross section of the sheet of Example 1-1
  • FIG. 4 shows a SEM image of the cross section of the sheet of Comparative Example 1.
  • the measurement result of the thermal conductivity of Example 1-2 was 24.4 W/(m K), and the measurement result of the thermal conductivity of Comparative Example 1 was 17.2 W/(m K). .

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Abstract

A method for producing a sheet which comprises a step in which a boron carbide powder is nitrided while being pressed by hot isotactic pressing to obtain a boron carbonitride powder, a step in which the boron carbonitride powder is decarburized to obtain a boron nitride powder, a step in which the boron nitride powder is mixed with a resin to obtain a resin composition, and a step in which the resin composition is formed into a sheet by pressing.

Description

シートの製造方法及びシートSheet manufacturing method and sheet

　本発明は、シートの製造方法及びシートに関する。 The present invention relates to a sheet manufacturing method and a sheet.

　パワーデバイス、トランジスタ、サイリスタ、ＣＰＵ等の電子部品においては、使用時に発生する熱を効率的に放熱することが課題となっている。この課題に対して、熱伝導率が高いセラミックス粉末を含有する放熱部材が用いられる。 In electronic components such as power devices, transistors, thyristors, and CPUs, it is a challenge to efficiently dissipate the heat generated during use. To solve this problem, a heat dissipation member containing ceramic powder with high thermal conductivity is used.

　セラミックス粉末としては、高熱伝導率、高絶縁性、低比誘電率等の特性を有している窒化ホウ素粉末が注目されている。窒化ホウ素粉末は、一般的に、鱗片状の窒化ホウ素粒子（一次粒子）が凝集してなる凝集粒子（塊状粒子）で構成されている。例えば、特許文献１には、凝集粒子の形状を一層球状化して充填性を高めると共に、粉末強度の向上を図り、さらには高純度化により、当該粉末を充填した伝熱シート等の絶縁性の向上および耐電圧の安定化を達成したとされる六方晶窒化ホウ素粉末が開示されている。 As a ceramic powder, boron nitride powder, which has characteristics such as high thermal conductivity, high insulation, and low dielectric constant, is attracting attention. Boron nitride powder is generally composed of agglomerated particles (lump particles) formed by agglomerating scale-like boron nitride particles (primary particles). For example, in Patent Document 1, the shape of the aggregated particles is made more spherical to improve the filling property, and the powder strength is also improved. A hexagonal boron nitride powder is disclosed which is said to have improved and stabilized withstand voltage.

特開２０１１－９８８８２号公報JP2011-98882A

　窒化ホウ素粉末を用いたシートを得る場合、一般的に、窒化ホウ素粉末と樹脂とを含有する樹脂組成物を加圧してシート状に成形するが、この場合、加圧により樹脂組成物中の窒化ホウ素の凝集粒子が崩れ、凝集粒子を構成していた窒化ホウ素粒子（一次粒子）がシートの主面と平行（加圧方向と垂直）になるように配向しやすい。窒化ホウ素粒子がシートの主面と平行な方向に配向すると、シートの厚み方向への熱伝導率が低下し得ることから、伝熱シートとして使用するのに適さないおそれがある。 When obtaining a sheet using boron nitride powder, generally a resin composition containing boron nitride powder and a resin is pressurized and formed into a sheet shape, but in this case, the nitride in the resin composition is The aggregated boron particles collapse, and the boron nitride particles (primary particles) that constituted the aggregated particles tend to be oriented parallel to the main surface of the sheet (perpendicular to the pressing direction). If the boron nitride particles are oriented in a direction parallel to the main surface of the sheet, the thermal conductivity in the thickness direction of the sheet may decrease, which may make the sheet unsuitable for use as a heat transfer sheet.

　そこで、本発明の主な目的は、シートの主面と平行な方向への窒化ホウ素粒子の配向が抑制されたシートを製造することである。 Therefore, the main object of the present invention is to produce a sheet in which the orientation of boron nitride particles in the direction parallel to the main surface of the sheet is suppressed.

　本発明者らは、熱間等方圧加圧法（ＨＩＰ法）を含む製造方法により得られた窒化ホウ素粉末を用いてシートを成形することにより、シートの主面と平行な方向への窒化ホウ素粒子の配向が抑制されたシートを製造できることを見出した。
　本発明は、いくつか側面において、以下の［１］～［３］を提供する。
［１］炭化ホウ素粉末を熱間等方圧加圧しながら窒化して、炭窒化ホウ素粉末を得る工程と、
　前記炭窒化ホウ素粉末を脱炭して、窒化ホウ素粉末を得る工程と、
　前記窒化ホウ素粉末を樹脂と混合して、樹脂組成物を得る工程と、
　前記樹脂組成物を加圧によりシート状に成形する工程と、
を備える、シートの製造方法。
［２］窒化ホウ素粒子と、樹脂と、を含有し、
　下記（１）～（８）の手順で算出される平均値Ｘが０．０１以上である、シート。
（１）前記シートの任意の断面をＳＥＭにより倍率１０００倍で観察した観察画像を取得する。
（２）前記観察画像において前記窒化ホウ素粒子からなる領域とそれ以外の領域とに二値化して、二値化画像を取得する。
（３）前記二値化画像において短辺５０μｍ×長辺１００μｍの領域Ａの短辺方向をｎ等分、長辺方向を２ｎ等分して、複数のセルに区分する（但し、ｎは１以上の整数）。
（４）前記複数のセルのうちの１個のセルにおいて、前記１個のセルの全面積を基準とした前記窒化ホウ素粒子からなる領域の面積割合を算出し、前記面積割合が８０％以上であれば前記１個のセルが窒化ホウ素領域であると判断し、前記面積割合が２０％未満であれば前記１個のセルが樹脂領域であると判断する。
（５）前記複数のセルのそれぞれにおいて前記（４）の判断を行い、前記複数のセルの総数を基準とした前記窒化ホウ素領域と判断されたセルの数の割合を算出する。
（６）前記（３）～前記（５）の手順において、ｎが１～２００のときの前記窒化ホウ素領域と判断されたセルの数の割合をそれぞれ算出する。
（７）ｎが１～５のときのそれぞれの前記窒化ホウ素領域と判断されたセルの数の割合の合計値を算出する。
（８）前記シートの合計５個の断面において前記（１）～（７）の手順で算出されるそれぞれの前記合計値から平均値Ｘを算出する。
［３］前記シートの前記合計５個の断面において、ｎが２００のときのそれぞれの前記窒化ホウ素領域と判断されたセルの数の割合の平均値Ｙが０．５以上である、［２］に記載のシート。 The present inventors formed a sheet using boron nitride powder obtained by a manufacturing method including hot isostatic pressing (HIP method), thereby forming boron nitride in a direction parallel to the main surface of the sheet. It has been discovered that it is possible to produce a sheet with suppressed particle orientation.
In some aspects, the present invention provides the following [1] to [3].
[1] Nitriding boron carbide powder while hot isostatic pressing to obtain boron carbonitride powder;
decarburizing the boron carbonitride powder to obtain boron nitride powder;
mixing the boron nitride powder with a resin to obtain a resin composition;
a step of molding the resin composition into a sheet shape by applying pressure;
A method for manufacturing a sheet, comprising:
[2] Contains boron nitride particles and a resin,
A sheet whose average value X calculated by the following steps (1) to (8) is 0.01 or more.
(1) Obtain an observation image of an arbitrary cross section of the sheet observed with a SEM at a magnification of 1000 times.
(2) Obtaining a binarized image by binarizing the observed image into a region made of the boron nitride particles and other regions.
(3) In the binarized image, the short side direction of the region A of 50 μm on the short side x 100 μm on the long side is divided into n equal parts, and the long side direction is divided into 2n equal parts to divide it into a plurality of cells (where n is 1 (integer greater than or equal to).
(4) In one cell of the plurality of cells, calculate the area ratio of the region made of the boron nitride particles based on the total area of the one cell, and if the area ratio is 80% or more. If so, it is determined that the one cell is a boron nitride region, and if the area ratio is less than 20%, it is determined that the one cell is a resin region.
(5) Perform the determination in (4) above for each of the plurality of cells, and calculate the ratio of the number of cells determined to be the boron nitride region based on the total number of the plurality of cells.
(6) In the steps (3) to (5) above, when n is 1 to 200, calculate the ratio of the number of cells determined to be the boron nitride region.
(7) When n is 1 to 5, calculate the total value of the ratio of the number of cells determined to be the boron nitride region.
(8) Calculate the average value X from the respective total values calculated in the steps (1) to (7) for a total of five cross sections of the sheet.
[3] In the total of five cross sections of the sheet, when n is 200, the average value Y of the ratio of the number of cells determined to be the boron nitride region is 0.5 or more, [2] Sheet listed in.

　本発明の一側面によれば、シートの主面と平行な方向への窒化ホウ素粒子の配向が抑制されたシートを製造することができる。 According to one aspect of the present invention, it is possible to produce a sheet in which orientation of boron nitride particles in a direction parallel to the main surface of the sheet is suppressed.

図１は、手順（１）～（７）のフロー図である。FIG. 1 is a flow diagram of steps (1) to (7). 図２（ａ）は、二値化画像に含まれる領域Ａを複数のセルに区分したときの参考図である。図２（ｂ）は、図２（ａ）において、複数のセルのそれぞれを窒化ホウ素領域と樹脂領域とのいずれかに判断したときの模式図である。FIG. 2(a) is a reference diagram when area A included in the binarized image is divided into a plurality of cells. FIG. 2(b) is a schematic diagram when each of the plurality of cells in FIG. 2(a) is determined to be either a boron nitride region or a resin region. 実施例１－１のシートの断面のＳＥＭ画像である。It is a SEM image of a cross section of the sheet of Example 1-1. 比較例１のシートの断面のＳＥＭ画像である。3 is a SEM image of a cross section of a sheet of Comparative Example 1. 実施例４－１のシート及び比較例４のシートを複数のセルに区分したときの１個のセルの一辺の長さと、窒化ホウ素領域と判断されたセルの数の割合との関係を示すグラフである。Graph showing the relationship between the length of one side of one cell and the ratio of the number of cells determined to be boron nitride regions when the sheet of Example 4-1 and the sheet of Comparative Example 4 are divided into a plurality of cells. It is.

　以下、本発明の実施形態について詳細に説明する。 Hereinafter, embodiments of the present invention will be described in detail.

　本発明の一実施形態に係るシートの製造方法は、炭化ホウ素粉末を熱間等方圧加圧（「熱間静水圧加圧」とも呼ばれる）しながら窒化して、炭窒化ホウ素粉末を得る工程（窒化工程）と、炭窒化ホウ素粉末を脱炭して、窒化ホウ素粉末を得る工程（脱炭工程）と、窒化ホウ素粉末を樹脂と混合して、樹脂組成物を得る工程（混合工程）と、樹脂組成物を加圧によりシート状に成形する工程（成形工程）と、を備える。 A method for manufacturing a sheet according to an embodiment of the present invention includes a step of nitriding boron carbide powder while hot isostatic pressing (also referred to as "hot isostatic pressing") to obtain boron carbonitride powder. (nitriding step), a step of decarburizing boron carbonitride powder to obtain boron nitride powder (decarburizing step), and a step of mixing boron nitride powder with resin to obtain a resin composition (mixing step). , a step of molding the resin composition into a sheet shape by applying pressure (molding step).

　炭化ホウ素粉末（炭化ホウ素粒子）は、例えば公知の製造方法により製造することができる。例えば、ホウ酸とアセチレンブラックとを混合した後、不活性ガス雰囲気中で、１８００～２４００℃にて、１～１０時間加熱し、塊状の炭化ホウ素粒子を含む炭化ホウ素粗粉末を得る。得られた炭化ホウ素粗粉末に対して、粉砕、篩分け、洗浄、不純物除去、及び乾燥等を適宜行うことによって炭化ホウ素粉末が得られる。炭化ホウ素粉末の平均粒子径は、例えば、５μｍ以上、１０μｍ以上、又は１５μｍ以上であってよく、８０μｍ以下、６０μｍ以下、又は４０μｍ以下であってよい。炭化ホウ素粉末の平均粒子径は、体積累積粒度分布が５０％となる粒子径（Ｄ５０）を意味し、レーザー回折散乱法により測定できる。 Boron carbide powder (boron carbide particles) can be produced, for example, by a known production method. For example, boric acid and acetylene black are mixed and then heated in an inert gas atmosphere at 1800 to 2400° C. for 1 to 10 hours to obtain coarse boron carbide powder containing lumpy boron carbide particles. Boron carbide powder is obtained by appropriately performing pulverization, sieving, washing, impurity removal, drying, etc. on the obtained boron carbide coarse powder. The average particle diameter of the boron carbide powder may be, for example, 5 μm or more, 10 μm or more, or 15 μm or more, and 80 μm or less, 60 μm or less, or 40 μm or less. The average particle size of boron carbide powder means the particle size (D50) at which the volume cumulative particle size distribution is 50%, and can be measured by a laser diffraction scattering method.

　窒化工程では、窒化反応を進行させる雰囲気下で、炭化ホウ素粉末を容器に充填した状態で熱間等方圧加圧しながら加熱することにより、炭化ホウ素粉末を窒化して炭窒化ホウ素粉末を得る。容器は、例えば、カーボンルツボであってよい。熱間等方圧加圧は、例えば、熱間等方圧加圧装置（例えば、神戸製鋼所製）を用いて行うことができる。 In the nitriding step, boron carbide powder is nitrided to obtain boron carbonitride powder by heating the container filled with boron carbide powder under hot isostatic pressure in an atmosphere that allows the nitriding reaction to proceed. The container may be, for example, a carbon crucible. The hot isostatic pressing can be performed using, for example, a hot isostatic pressing device (for example, manufactured by Kobe Steel, Ltd.).

　窒化工程における窒化反応を進行させる雰囲気は、炭化ホウ素粉末を窒化する窒化ガス雰囲気であってよい。窒化ガスとしては、窒素ガス、アンモニアガス等であってよく、炭化ホウ素粉末を窒化しやすい観点及びコストの観点から、窒素ガスであってよい。窒化ガスは、１種単独又は２種以上を組合せて用いてよく、窒化ガス中の窒素ガスの割合は、９５体積％以上、９９体積％以上又は９９．９体積％以上であってよい。 The atmosphere in which the nitriding reaction proceeds in the nitriding step may be a nitriding gas atmosphere that nitrides boron carbide powder. The nitriding gas may be nitrogen gas, ammonia gas, etc. Nitrogen gas may be used from the viewpoint of ease of nitriding boron carbide powder and from the viewpoint of cost. The nitriding gas may be used alone or in combination of two or more, and the proportion of nitrogen gas in the nitriding gas may be 95% by volume or more, 99% by volume or more, or 99.9% by volume or more.

　窒化工程における圧力は、１０ＭＰａ以上、３０ＭＰａ以上、又は１００ＭＰａ以上であってよい。窒化工程における圧力は、２００ＭＰａ以下又は１５０ＭＰａ以下であってよい。 The pressure in the nitriding step may be 10 MPa or more, 30 MPa or more, or 100 MPa or more. The pressure in the nitriding step may be 200 MPa or less or 150 MPa or less.

　窒化工程における加熱温度は、炭化ホウ素粉末を充分に窒化させる観点から、１６００℃以上又は１７００℃以上であってよい。窒化工程における加熱温度は、２２００℃以下又は２０００℃以下であってよい。 The heating temperature in the nitriding step may be 1600° C. or higher or 1700° C. or higher from the viewpoint of sufficiently nitriding the boron carbide powder. The heating temperature in the nitriding step may be 2200°C or lower or 2000°C or lower.

　窒化工程における加圧及び加熱を行う時間は、炭化ホウ素粉末を充分に窒化させる観点から、３時間以上、５時間以上又は８時間以上であってよい。窒化工程における加圧及び加熱を行う時間は、３０時間以下、２０時間以下又は１０時間以下であってよい。 The time for pressurizing and heating in the nitriding step may be 3 hours or more, 5 hours or more, or 8 hours or more from the viewpoint of sufficiently nitriding the boron carbide powder. The time for pressurizing and heating in the nitriding step may be 30 hours or less, 20 hours or less, or 10 hours or less.

　脱炭工程では、窒化工程にて得られた炭窒化ホウ素粉末（炭窒化ホウ素粒子）と、ホウ素源とを含む混合物を容器に充填した状態で加熱することにより、炭窒化ホウ素粉末を脱炭する。容器は、例えば、窒化ホウ素ルツボであってよい。 In the decarburization step, a mixture containing boron carbonitride powder (boron carbonitride particles) obtained in the nitriding step and a boron source is filled in a container and heated to decarburize the boron carbonitride powder. . The container may be, for example, a boron nitride crucible.

　ホウ素源としては、ホウ酸、酸化ホウ素、又はその混合物が挙げられる。混合物は、必要に応じて当技術分野で用いられるその他の添加物を更に含有していてもよい。炭窒化ホウ素粉末とホウ素源との混合割合は、適宜選定される。ホウ素源としてホウ酸又は酸化ホウ素を用いる場合、ホウ酸又は酸化ホウ素の割合は、炭窒化ホウ素１００質量部に対して、例えば５０質量部以上又は８０質量部以上であってよく、３００質量部以下又は２００質量部以下であってよい。 Boron sources include boric acid, boron oxide, or mixtures thereof. The mixture may further contain other additives used in the art, if necessary. The mixing ratio of boron carbonitride powder and boron source is selected as appropriate. When boric acid or boron oxide is used as a boron source, the proportion of boric acid or boron oxide may be, for example, 50 parts by mass or more or 80 parts by mass or more, and 300 parts by mass or less, based on 100 parts by mass of boron carbonitride. Or it may be 200 parts by mass or less.

　脱炭工程における雰囲気は、常圧（大気圧）の雰囲気又は加圧された雰囲気であってよい。脱炭工程における圧力は、例えば０．５ＭＰａ以下又は０．３ＭＰａ以下であってよく、０．０１ＭＰａ以上又は０．０３ＭＰａ以上であってよい。 The atmosphere in the decarburization process may be a normal pressure (atmospheric pressure) atmosphere or a pressurized atmosphere. The pressure in the decarburization step may be, for example, 0.5 MPa or less or 0.3 MPa or less, and may be 0.01 MPa or more or 0.03 MPa or more.

　脱炭工程では、例えば、まず、所定の温度（脱炭開始可能な温度）まで昇温した後に、所定の温度で保持温度まで更に昇温する。所定の温度（脱炭開始可能な温度）は、例えば、１０００℃以上であってよく、１５００℃以下又は１２００℃以下であってよい。所定の温度（脱炭開始可能な温度）から保持温度へ昇温する速度は、例えば５℃／分以下、４℃／分以下、３℃／分以下、又は２℃／分以下であってよい。 In the decarburization process, for example, first, the temperature is raised to a predetermined temperature (a temperature at which decarburization can start), and then the temperature is further raised to a holding temperature at the predetermined temperature. The predetermined temperature (temperature at which decarburization can start) may be, for example, 1000°C or higher, 1500°C or lower, or 1200°C or lower. The rate of temperature increase from a predetermined temperature (temperature at which decarburization can be started) to the holding temperature may be, for example, 5° C./min or less, 4° C./min or less, 3° C./min or less, or 2° C./min or less. .

　保持温度は、粒子成長が良好に起こりやすい観点から、１８００℃以上又は２０００℃以上であってよい。保持温度は、２２００℃以下又は２１００℃以下であってよい。 The holding temperature may be 1800° C. or higher or 2000° C. or higher from the viewpoint of facilitating good particle growth. The holding temperature may be 2200°C or less or 2100°C or less.

　保持温度における保持時間は、粒子成長が良好に起こりやすい観点から、例えば、０．５時間以上、１時間以上、３時間以上、又は５時間以上であってよい。保持温度における保持時間は、例えば４０時間以下、３０時間以下、又は２０時間以下であってよい。 The holding time at the holding temperature may be, for example, 0.5 hours or more, 1 hour or more, 3 hours or more, or 5 hours or more, from the viewpoint of facilitating particle growth. The holding time at the holding temperature may be, for example, 40 hours or less, 30 hours or less, or 20 hours or less.

　以上のようにして得られる窒化ホウ素粉末（窒化ホウ素凝集粒子）に対して、篩によって所望の粒子径を有する窒化ホウ素粉末が得られるように分級する工程（分級工程）を実施してもよい。 The boron nitride powder (boron nitride agglomerated particles) obtained as described above may be classified using a sieve (classification step) so as to obtain boron nitride powder having a desired particle size.

　窒化ホウ素凝集粒子は、例えば、複数の窒化ホウ素片（窒化ホウ素一次粒子）により構成されている。窒化ホウ素片は、窒化ホウ素により形成されており、例えば鱗片状の形状を有していてよい。 The boron nitride agglomerated particles are composed of, for example, a plurality of boron nitride pieces (boron nitride primary particles). The boron nitride pieces are made of boron nitride and may have, for example, a scale-like shape.

　複数の窒化ホウ素片同士は、物理的に接触していてもよく、化学的に結合していてもよい。複数の窒化ホウ素片同士が化学的に結合していることは、ＳＥＭを用いて、窒化ホウ素片同士の結合部分に窒化ホウ素片間の境界が観察されないことにより確認できる。 The plurality of boron nitride pieces may be in physical contact with each other or may be chemically bonded. The fact that the plurality of boron nitride pieces are chemically bonded to each other can be confirmed by using SEM, since no boundaries between the boron nitride pieces are observed at the joints between the boron nitride pieces.

　窒化ホウ素片の平均厚さは、０．５μｍ以上、１．０μｍ以上、又は３．０μｍ以上であってよく、１０μｍ以下であってよい。窒化ホウ素片の長手方向の平均長さは、例えば、１μｍ以上であってよく、１０μｍ以下であってよい。窒化ホウ素片の平均厚さ及び長手方向の平均長さは、ＳＥＭを用いて、倍率１０００倍で窒化ホウ素凝集粒子の断面を観察したＳＥＭ画像を画像解析ソフトウェア（例えば、株式会社マウンテック製の「Ｍａｃ－ｖｉｅｗ」）に取り込み、当該ＳＥＭ画像において測定される４０個の窒化ホウ素片の厚さ及び長手方向の長さの平均値として定義される。 The average thickness of the boron nitride pieces may be 0.5 μm or more, 1.0 μm or more, or 3.0 μm or more, and 10 μm or less. The average length of the boron nitride pieces in the longitudinal direction may be, for example, 1 μm or more and 10 μm or less. The average thickness and average length in the longitudinal direction of the boron nitride pieces can be determined using an SEM image of the cross section of the boron nitride agglomerated particles observed at a magnification of 1000 times using image analysis software (for example, "Mac" manufactured by Mountech Co., Ltd.). -view'') and is defined as the average value of the thickness and longitudinal length of 40 boron nitride pieces measured in the SEM image.

　窒化ホウ素凝集粒子は、複数の窒化ホウ素片が積層している領域を有する断面を有していてもよい。複数の窒化ホウ素片が積層していていることは、ＳＥＭを用いて窒化ホウ素凝集粒子の断面を観察し、複数の窒化ホウ素片が窒化ホウ素片の厚さ方向に並んで配置されていることにより確認できる。 The boron nitride agglomerated particles may have a cross section that includes a region in which a plurality of boron nitride pieces are stacked. The fact that multiple boron nitride pieces were stacked was confirmed by observing the cross section of the boron nitride agglomerated particles using SEM, and it was found that the multiple boron nitride pieces were arranged side by side in the thickness direction of the boron nitride pieces. You can check it.

　窒化ホウ素粉末の平均粒子径は、例えば、１０μｍ以上、２０μｍ以上、又は３０μｍ以上であってよく、１００μｍ以下、８０μｍ以下、又は６０μｍ以下であってよい。窒化ホウ素粉末の平均粒子径は、体積累積粒度分布が５０％となる粒子径（Ｄ５０）を意味し、レーザー回折散乱法により測定できる。 The average particle diameter of the boron nitride powder may be, for example, 10 μm or more, 20 μm or more, or 30 μm or more, and 100 μm or less, 80 μm or less, or 60 μm or less. The average particle size of boron nitride powder means the particle size (D50) at which the volume cumulative particle size distribution is 50%, and can be measured by a laser diffraction scattering method.

　窒化ホウ素粉末の嵩密度は、０．７ｇ／ｍｌ以上、０．７２ｇ／ｍｌ以上、０．７４ｇ／ｍｌ以上、又は０．７５ｇ／ｍｌ以上であってよく、０．９ｇ／ｍｌ以下、０．８ｇ／ｍｌ以下、又は０．７５ｇ／ｍｌ以下であってよい。 The bulk density of the boron nitride powder may be 0.7 g/ml or more, 0.72 g/ml or more, 0.74 g/ml or more, or 0.75 g/ml or more, and 0.9 g/ml or less, 0. It may be 8 g/ml or less, or 0.75 g/ml or less.

　窒化ホウ素凝集粒子は、実質的に窒化ホウ素のみからなってよい。窒化ホウ素凝集粒子が実質的に窒化ホウ素のみからなることは、Ｘ線回折測定において、窒化ホウ素に由来するピークのみが検出されることにより確認できる。 The boron nitride agglomerated particles may consist essentially only of boron nitride. It can be confirmed that the boron nitride aggregate particles are substantially composed only of boron nitride by detecting only a peak derived from boron nitride in X-ray diffraction measurement.

　混合工程では、脱炭工程にて得られた窒化ホウ素粉末と、樹脂とを混合することにより、樹脂組成物を得る。 In the mixing step, a resin composition is obtained by mixing the boron nitride powder obtained in the decarburization step and a resin.

　樹脂としては、例えば、エポキシ樹脂、シリコーン樹脂、シリコーンゴム、アクリル樹脂、フェノール樹脂、メラミン樹脂、ユリア樹脂、不飽和ポリエステル、フッ素樹脂、ポリイミド、ポリアミドイミド、ポリエーテルイミド、ポリブチレンテレフタレート、ポリエチレンテレフタレート、ポリフェニレンエーテル、ポリフェニレンスルフィド、全芳香族ポリエステル、ポリスルホン、液晶ポリマー、ポリエーテルスルホン、ポリカーボネート、マレイミド変性樹脂、ＡＢＳ（アクリロニトリル－ブタジエン－スチレン）樹脂、ＡＡＳ（アクリロニトリル－アクリルゴム・スチレン）樹脂、及びＡＥＳ（アクリロニトリル・エチレン・プロピレン・ジエンゴム－スチレン）樹脂が挙げられる。 Examples of the resin include epoxy resin, silicone resin, silicone rubber, acrylic resin, phenol resin, melamine resin, urea resin, unsaturated polyester, fluororesin, polyimide, polyamideimide, polyetherimide, polybutylene terephthalate, polyethylene terephthalate, Polyphenylene ether, polyphenylene sulfide, fully aromatic polyester, polysulfone, liquid crystal polymer, polyether sulfone, polycarbonate, maleimide modified resin, ABS (acrylonitrile-butadiene-styrene) resin, AAS (acrylonitrile-acrylic rubber/styrene) resin, and AES ( Examples include acrylonitrile, ethylene, propylene, diene rubber (styrene) resin.

　窒化ホウ素粉末の含有量は、樹脂組成物の全体積を基準として、樹脂組成物の熱伝導率を向上させ、優れた放熱性能が得られやすい観点から、５０体積％以上、５５体積％以上、６０体積％以上、６５体積％以上、又は７０体積％以上であってよい。窒化ホウ素粉末の含有量は、樹脂組成物の全体積を基準として、成形時に細孔の発生、並びに、絶縁性及び機械強度の低下を抑制できる観点から、８５体積％以下、８０体積％以下、又は７５体積％以下であってよい。 The content of the boron nitride powder is 50 volume% or more, 55 volume% or more, based on the total volume of the resin composition, from the viewpoint of improving the thermal conductivity of the resin composition and easily obtaining excellent heat dissipation performance. It may be 60% by volume or more, 65% by volume or more, or 70% by volume or more. The content of the boron nitride powder is 85% by volume or less, 80% by volume or less, based on the total volume of the resin composition, from the viewpoint of suppressing the generation of pores during molding and the decrease in insulation and mechanical strength. Alternatively, it may be 75% by volume or less.

　樹脂の含有量は、樹脂組成物の全体積を基準として、１５体積％以上、２０体積％以上、又は２５体積％以上であってよく、５０体積％以下、４５体積％以下、４０体積％以下、３５体積％以下、又は３０体積％以下であってよい。 The content of the resin may be 15% by volume or more, 20% by volume or more, or 25% by volume or more, and 50% by volume or less, 45% by volume or less, 40% by volume or less, based on the total volume of the resin composition. , 35% by volume or less, or 30% by volume or less.

　樹脂組成物は、樹脂を硬化させる硬化剤を更に含有していてよい。硬化剤は、樹脂の種類によって適宜選択される。例えば、樹脂がエポキシ樹脂である場合、硬化剤としては、フェノールノボラック化合物、酸無水物、アミノ化合物、及びイミダゾール化合物が挙げられる。硬化剤の含有量は、樹脂１００質量部に対して、例えば、０．５質量部以上又は１．０質量部以上であってよく、１５質量部以下又は１０質量部以下であってよい。 The resin composition may further contain a curing agent for curing the resin. The curing agent is appropriately selected depending on the type of resin. For example, when the resin is an epoxy resin, examples of the curing agent include phenol novolac compounds, acid anhydrides, amino compounds, and imidazole compounds. The content of the curing agent may be, for example, 0.5 parts by mass or more or 1.0 parts by mass or more, and 15 parts by mass or less or 10 parts by mass or less, based on 100 parts by mass of the resin.

　樹脂組成物は、その他の成分を更に含有してもよい。その他の成分は、硬化促進剤（硬化触媒）、カップリング剤、湿潤分散剤、表面調整剤等であってよい。 The resin composition may further contain other components. Other components may include a curing accelerator (curing catalyst), a coupling agent, a wetting and dispersing agent, a surface conditioner, and the like.

　硬化促進剤（硬化触媒）としては、テトラフェニルホスホニウムテトラフェニルボレート、トリフェニルフォスフェイト等のリン系硬化促進剤、２－フェニル－４，５－ジヒドロキシメチルイミダゾール等のイミダゾール系硬化促進剤、三フッ化ホウ素モノエチルアミン等のアミン系硬化促進剤などが挙げられる。 Examples of curing accelerators (curing catalysts) include phosphorus curing accelerators such as tetraphenylphosphonium tetraphenylborate and triphenyl phosphate, imidazole curing accelerators such as 2-phenyl-4,5-dihydroxymethylimidazole, and trifluorocarbon curing accelerators. Examples include amine curing accelerators such as boron monoethylamine.

　カップリング剤としては、シラン系カップリング剤、チタネート系カップリング剤、及びアルミネート系カップリング剤等が挙げられる。これらのカップリング剤に含まれる化学結合基としては、ビニル基、エポキシ基、アミノ基、メタクリル基、メルカプト基等が挙げられる。 Examples of the coupling agent include silane coupling agents, titanate coupling agents, and aluminate coupling agents. Chemical bonding groups contained in these coupling agents include vinyl groups, epoxy groups, amino groups, methacrylic groups, mercapto groups, and the like.

　湿潤分散剤としては、リン酸エステル塩、カルボン酸エステル、ポリエステル、アクリル共重合物、ブロック共重合物等が挙げられる。 Examples of wetting and dispersing agents include phosphoric acid ester salts, carboxylic acid esters, polyesters, acrylic copolymers, block copolymers, and the like.

　表面調整剤としては、アクリル系表面調整剤、シリコーン系表面調整剤、ビニル系調整剤、フッ素系表面調整剤等が挙げられる。 Examples of surface conditioners include acrylic surface conditioners, silicone surface conditioners, vinyl surface conditioners, fluorine surface conditioners, and the like.

　窒化ホウ素粉末と樹脂とは、公知の方法により混合することができる。混合工程で得られる樹脂組成物は、必要に応じて溶媒（例えば樹脂を溶解させる溶媒）を更に含んでよく、上述したその他の成分を更に含んでもよい。 The boron nitride powder and the resin can be mixed by a known method. The resin composition obtained in the mixing step may further contain a solvent (for example, a solvent for dissolving the resin) as necessary, and may further contain the other components mentioned above.

　溶媒としては、アルコール系溶媒、グリコールエーテル系溶媒、芳香族系溶剤、ケトン系溶剤等が挙げられる。アルコール系溶媒としては、イソプロピルアルコール、ジアセトンアルコール等が挙げられる。グリコールエーテル系溶媒としては、エチルセロソルブ、ブチルセロソルブ等が挙げられる。芳香族系溶剤としては、トルエン、キシレン等が挙げられる。ケトン系溶剤としては、メチルエチルケトン、メチルイソブチルケトン等が挙げられる。 Examples of the solvent include alcohol solvents, glycol ether solvents, aromatic solvents, ketone solvents, and the like. Examples of alcoholic solvents include isopropyl alcohol and diacetone alcohol. Examples of glycol ether solvents include ethyl cellosolve, butyl cellosolve, and the like. Examples of aromatic solvents include toluene and xylene. Examples of ketone solvents include methyl ethyl ketone and methyl isobutyl ketone.

　成形工程では、混合工程にて得られた樹脂組成物を加圧によりシート状に成形し、シートを得る。成形工程は、例えば、フィルムアプリケーターを用いて、樹脂組成物を基材上に塗工し、加圧することにより、樹脂組成物をシート状に成形する工程であってよい。 In the molding step, the resin composition obtained in the mixing step is molded into a sheet by applying pressure to obtain a sheet. The molding step may be, for example, a step of molding the resin composition into a sheet shape by applying the resin composition onto the base material using a film applicator and applying pressure.

　成形工程における加圧力は、例えば、１ＭＰａ以上又は５ＭＰａ以上であってもよく、１００ＭＰａ以下又は５０ＭＰａ以下であってもよい。 The pressing force in the molding step may be, for example, 1 MPa or more or 5 MPa or more, or 100 MPa or less or 50 MPa or less.

　成形工程においては、成形と同時又は成形後に、樹脂組成物中の樹脂を一部又は全部を硬化させる工程（硬化工程）が行われてもよい。 In the molding step, a step (curing step) of curing part or all of the resin in the resin composition may be performed simultaneously with or after the molding.

　樹脂を硬化させる方法は、樹脂（及び必要に応じて用いられる硬化剤）の種類に応じて適宜選択される。例えば、樹脂がエポキシ樹脂であり、上述した硬化剤が共に用いられる場合、硬化工程では、加熱により樹脂を硬化させることができる。この場合、加熱温度及び加熱時間を調整することにより、樹脂を半硬化させることができる。樹脂組成物が溶媒を含む場合は、硬化工程において、樹脂を硬化させると共に、当該溶媒を揮発させてもよい。 The method for curing the resin is appropriately selected depending on the type of resin (and the curing agent used as necessary). For example, when the resin is an epoxy resin and the above-mentioned curing agent is used together, the resin can be cured by heating in the curing step. In this case, the resin can be semi-cured by adjusting the heating temperature and heating time. When the resin composition contains a solvent, the resin may be cured and the solvent may be volatilized in the curing step.

　上記の製造方法により得られるシートは、シートの主面と平行な方向への窒化ホウ素粒子の配向が抑制されている。その理由について本発明者らは以下のように推察する。すなわち、炭化ホウ素粉末を熱間等方圧加圧しながら窒化して炭窒化ホウ素粉末を得た後、当該炭窒化ホウ素粉末を脱炭することによって得られる窒化ホウ素粉末（窒化ホウ素凝集粒子）は、比較的分厚い窒化ホウ素片で構成される。このような窒化ホウ素凝集粒子は、外力が加わってもその形状を維持しやすい傾向がある。そのため、このような窒化ホウ素凝集粒子を用いて樹脂組成物を作製し、樹脂組成物を加圧してシートを形成した場合、シート中の一部の窒化ホウ素凝集粒子は加圧されても崩れにくく、その形状をある程度維持できる。また、このような窒化ホウ素凝集粒子は、窒化ホウ素凝集粒子を構成する窒化ホウ素片のそれぞれが比較的分厚く、窒化ホウ素凝集粒子は高い緻密性（低い空隙率）を有するようになり、窒化ホウ素凝集粒子１粒あたりの窒化ホウ素の量が従来の窒化ホウ素凝集粒子と比べて多くなる。このような窒化ホウ素凝集粒子を用いてシートを形成する場合、従来の窒化ホウ素凝集粒子を用いて同じ充填量（質量基準の仕込み量）でシートを形成する場合と比べて、シートの単位体積当たりの窒化ホウ素凝集粒子（又は窒化ホウ素片）が少なくなるため、シートの形成時に、窒化ホウ素凝集粒子（又は窒化ホウ素片）が圧縮変形する頻度が少なくなる。窒化ホウ素凝集粒子が崩れにくく、シート形成時に圧縮変形する頻度が少ないことにより、窒化ホウ素片（窒化ホウ素一次粒子）がシートの主面と平行な方向に並びにくくなり、シート中で窒化ホウ素粒子の配向が抑制されると推察される。但し、本発明のメカニズムは、上記の理由に限定されない。 In the sheet obtained by the above manufacturing method, the orientation of the boron nitride particles in the direction parallel to the main surface of the sheet is suppressed. The present inventors conjecture the reason as follows. That is, boron nitride powder (boron nitride agglomerated particles) obtained by nitriding boron carbide powder under hot isostatic pressure to obtain boron carbonitride powder and then decarburizing the boron carbonitride powder is: Constructed from a relatively thick piece of boron nitride. Such boron nitride agglomerated particles tend to easily maintain their shape even when external force is applied. Therefore, when a resin composition is prepared using such aggregated boron nitride particles and a sheet is formed by pressurizing the resin composition, some of the aggregated boron nitride particles in the sheet do not easily collapse even under pressure. , can maintain its shape to some extent. In addition, in such boron nitride aggregate particles, each of the boron nitride pieces constituting the boron nitride aggregate particles is relatively thick, and the boron nitride aggregate particles have high density (low porosity). The amount of boron nitride per particle is larger than that of conventional boron nitride agglomerated particles. When forming a sheet using such boron nitride agglomerated particles, compared to forming a sheet using conventional boron nitride agglomerated particles at the same filling amount (filling amount based on mass), the amount per unit volume of the sheet is Since the number of boron nitride aggregated particles (or boron nitride pieces) is reduced, the frequency of compressive deformation of the boron nitride aggregated particles (or boron nitride pieces) during sheet formation is reduced. Boron nitride agglomerated particles are difficult to break down and compressively deform less frequently during sheet formation, making it difficult for boron nitride pieces (boron nitride primary particles) to line up in a direction parallel to the main surface of the sheet, resulting in the formation of boron nitride particles in the sheet. It is presumed that the orientation is suppressed. However, the mechanism of the present invention is not limited to the above reasons.

　上記の製造方法により得られるシートは、シートの断面において、窒化ホウ素粒子からなる複数の領域と、それ以外の領域とを有する。上記の製造方法により得られるシートは、シート中で窒化ホウ素凝集粒子がその形状をある程度維持していることにより、シートの断面における窒化ホウ素粒子からなる領域の面積（窒化ホウ素粒子からなる複数の領域のうちのそれぞれの領域）が、従来の窒化ホウ素凝集粒子を用いて同じ含有量で作製したシートの断面における窒化ホウ素粒子からなる領域の面積よりも大きくなる傾向がある。 The sheet obtained by the above manufacturing method has a plurality of regions made of boron nitride particles and other regions in the cross section of the sheet. The sheet obtained by the above manufacturing method is such that the boron nitride agglomerated particles maintain their shape to some extent in the sheet, so that the area of the region made of boron nitride particles in the cross section of the sheet (multiple regions made of boron nitride particles The area of each region of boron nitride particles tends to be larger than the area of the region of boron nitride particles in the cross section of a sheet made with the same content using conventional boron nitride agglomerated particles.

　シートの断面における窒化ホウ素粒子からなる領域の面積が比較的大きいことは、下記（１）～（８）の手順で算出される平均値Ｘが０．０１以上であることにより確認することができる。すなわち、本発明の他の一実施形態は、窒化ホウ素粒子と、樹脂と、を含有し、下記（１）～（８）の手順で算出される平均値Ｘが０．０１以上である、シートである。図１に手順（１）～（７）のフロー図を示す。
（１）シートの任意の断面をＳＥＭにより倍率１０００倍で観察した観察画像を取得する。
（２）観察画像において窒化ホウ素粒子からなる領域とそれ以外の領域とに二値化して、二値化画像を取得する。
（３）前記二値化画像において短辺５０μｍ×長辺１００μｍの領域Ａの短辺方向をｎ等分、長辺方向を２ｎ等分して、複数のセルに区分する（但し、ｎは１以上の整数）。
（４）前記複数のセルのうちの１個のセルにおいて、前記１個のセルの全面積を基準とした前記窒化ホウ素粒子からなる領域の面積割合を算出し、前記面積割合が８０％以上であれば前記１個のセルが窒化ホウ素領域であると判断し、前記面積割合が２０％未満であれば前記１個のセルが樹脂領域であると判断する。
（５）前記複数のセルのそれぞれにおいて前記（４）の判断を行い、前記複数のセルの総数を基準とした前記窒化ホウ素領域と判断されたセルの数の割合を算出する。
（６）前記（３）～前記（５）の手順において、ｎが１～２００のときの前記窒化ホウ素領域と判断されたセルの数の割合をそれぞれ算出する。
（７）ｎが１～５のときのそれぞれの前記窒化ホウ素領域と判断されたセルの数の割合の合計値を算出する。
（８）前記シートの合計５個の断面において前記（１）～（７）の手順で算出されるそれぞれの前記合計値から平均値Ｘを算出する。 That the area of the region made of boron nitride particles in the cross section of the sheet is relatively large can be confirmed by the fact that the average value X calculated by the following steps (1) to (8) is 0.01 or more. . That is, another embodiment of the present invention is a sheet containing boron nitride particles and a resin, and having an average value X calculated by the following steps (1) to (8) of 0.01 or more. It is. FIG. 1 shows a flow diagram of steps (1) to (7).
(1) An observation image of an arbitrary cross section of the sheet is obtained by observing it at a magnification of 1000 times using an SEM.
(2) Obtain a binarized image by binarizing the observed image into a region made of boron nitride particles and other regions.
(3) In the binarized image, the short side direction of the region A of 50 μm on the short side x 100 μm on the long side is divided into n equal parts, and the long side direction is divided into 2n equal parts to divide it into a plurality of cells (where n is 1 (integer greater than or equal to).
(4) In one cell of the plurality of cells, calculate the area ratio of the region made of the boron nitride particles based on the total area of the one cell, and if the area ratio is 80% or more. If so, it is determined that the one cell is a boron nitride region, and if the area ratio is less than 20%, it is determined that the one cell is a resin region.
(5) Perform the determination in (4) above for each of the plurality of cells, and calculate the ratio of the number of cells determined to be the boron nitride region based on the total number of the plurality of cells.
(6) In the steps (3) to (5) above, when n is 1 to 200, calculate the ratio of the number of cells determined to be the boron nitride region.
(7) When n is 1 to 5, calculate the total value of the ratio of the number of cells determined to be the boron nitride region.
(8) Calculate the average value X from the respective total values calculated in the steps (1) to (7) for a total of five cross sections of the sheet.

　手順（１）において、取得する観察画像の画像形式は、ｂｍｐとする。取得する画像は、窒化ホウ素粒子からなる領域と、それ以外の領域とに二値化できる程度の鮮明さを有するものであればよい。 In step (1), the image format of the observation image to be acquired is bmp. The image to be acquired may be one that is sharp enough to be binarized into a region made of boron nitride particles and other regions.

　手順（２）において、観察画像を画像処理ソフトウェア「ｉｍａｇｅＪ」に取り込み、Ｍｅｄｉａｎフィルタ（３×３ｐｉｘｃｅｌ）によりフィルタ処理を行う。その後、窒化ホウ素粒子からなる領域と、それ以外の領域（例えば、樹脂からなる領域）とに大津法による二値化処理を行い、二値化画像を取得する。 In step (2), the observed image is imported into image processing software "imageJ" and filtered using a median filter (3x3 pixels). Thereafter, the region made of boron nitride particles and the other regions (for example, the region made of resin) are subjected to binarization processing using the Otsu method to obtain a binarized image.

　手順（３）において、領域Ａの全体は、二値化画像中に含まれる。領域Ａは、短辺５０μｍ×長辺１００μｍの領域である。なお、画像処理の都合上、領域Ａとして正確に短辺５０μｍ×長辺１００μｍの範囲を指定することは難しいため、短辺（５０μｍ±５μｍ）×長辺（１００μｍ±１０μｍ）の領域であれば、平均値Ｘの算出結果への影響は無視できることから、当該領域を領域Ａとみなすことができる。 In step (3), the entire region A is included in the binarized image. Area A is an area with a short side of 50 μm x a long side of 100 μm. Note that due to image processing, it is difficult to accurately specify the short side (50 μm ± 5 μm) x long side (100 μm ± 10 μm) as area A. , the influence on the calculation result of the average value X can be ignored, so this region can be regarded as region A.

　手順（３）において、領域Ａは、ｎを１以上の整数として、領域Ａの短辺方向をｎ等分し、領域Ａの長辺方向を２ｎ等分することにより複数のセルに区分される。言い換えると、領域Ａは２ｎ２個のセルに区分され、各セルは、一辺が５０／ｎ（μｍ）の正方形である。例えば、ｎ＝１のとき、領域Ａは、領域Ａの短辺方向を１等分され（すなわち、領域Ａの短辺方向には分割せず）、領域Ａの長辺方向を２等分され、２個の正方形（５０μｍ×５０μｍ）のセルに区分される。 In step (3), area A is divided into a plurality of cells by dividing the short side of area A into n equal parts and dividing the long side of area A into 2n equal parts, where n is an integer greater than or equal to 1. . In other words, the area A is divided into 2n2 cells, and each cell is a square with one side of 50/n (μm). For example, when n=1, area A is divided into two equal parts in the short side direction of area A (that is, not divided in the short side direction of area A), and divided into two equal parts in the long side direction of area A. , divided into two square (50 μm x 50 μm) cells.

　図２（ａ）は、二値化画像に含まれる領域Ａを複数のセルに区分したときの参考図である。図２（ａ）において、領域Ａは短辺方向を４等分され、長辺方向を８等分されており、３２個の正方形のセルに区分されている。 FIG. 2(a) is a reference diagram when area A included in the binarized image is divided into a plurality of cells. In FIG. 2A, area A is divided into four equal parts along the short side and eight equal parts along the long side, and is divided into 32 square cells.

　手順（４）において、複数のセルのうちの１個のセルに着目し、１個のセルの全面積を基準とした窒化ホウ素粒子からなる領域の面積割合を算出する。１個のセルにおいて、窒化ホウ素粒子からなる領域の面積割合が８０％以上であれば、当該セルは窒化ホウ素粒子により占有される領域であると判断でき、窒化ホウ素粒子からなる領域の面積割合が２０％未満であれば、当該セルは窒化ホウ素粒子以外の成分により占有される領域（窒化ホウ素粒子により占有されていない領域）であると判断できる。このように、領域Ａを複数のセルに区分し、各セルについて窒化ホウ素粒子からなる領域（窒化ホウ素領域）か、それ以外からなる領域（樹脂領域）かを判断することにより、シートの断面において、窒化ホウ素粒子からなる複数の領域のうちのそれぞれの領域の面積が、比較的大きいか否かを判断することができる。 In step (4), one cell among the plurality of cells is focused on, and the area ratio of the region made of boron nitride particles is calculated based on the total area of one cell. In one cell, if the area ratio of the region consisting of boron nitride particles is 80% or more, it can be determined that the cell is an area occupied by boron nitride particles, and the area ratio of the area consisting of boron nitride particles is If it is less than 20%, it can be determined that the cell is an area occupied by components other than boron nitride particles (area not occupied by boron nitride particles). In this way, by dividing region A into a plurality of cells and determining whether each cell is a region made of boron nitride particles (boron nitride region) or a region made of something else (resin region), it is possible to , it can be determined whether the area of each region among the plurality of regions made of boron nitride particles is relatively large.

　図２（ｂ）は、図２（ａ）において、複数のセルのそれぞれを窒化ホウ素領域と樹脂領域とのいずれかに判断したときの模式図である。図２（ｂ）において、窒化ホウ素領域と判断されたセルを黒色のセルで示し、樹脂領域と判断されたセルを白色のセルで示している。 FIG. 2(b) is a schematic diagram when each of the plurality of cells in FIG. 2(a) is determined to be either a boron nitride region or a resin region. In FIG. 2B, cells determined to be boron nitride regions are shown as black cells, and cells determined to be resin regions are shown as white cells.

　手順（５）において、複数のセルのそれぞれについて手順（４）の判断を行い、複数のセルの総数を基準とした窒化ホウ素領域と判断されたセルの数の割合を算出する。すなわち、窒化ホウ素領域と判断されたセルの数の割合は、窒化ホウ素領域と判断されたセルの総数を複数のセルの総数で除することにより算出される。 In step (5), the determination in step (4) is performed for each of the plurality of cells, and the ratio of the number of cells determined to be boron nitride regions based on the total number of the plurality of cells is calculated. That is, the ratio of the number of cells determined to be boron nitride regions is calculated by dividing the total number of cells determined to be boron nitride regions by the total number of a plurality of cells.

　手順（６）において、手順（３）～（５）により、ｎが１～２００のときの窒化ホウ素領域と判断されたセルの数の割合を算出する。すなわち、領域Ａを２個のセル、８個のセル、１８個のセル、３２個のセル、５０個のセル、…８００００個のセルに区分したときのそれぞれの窒化ホウ素領域と判断されたセルの数の割合を算出する。例えば、図２（ｂ）においては、セルの総数は３２個であり、窒化ホウ素領域と判断されたセルの数は１２個であるから、窒化ホウ素領域と判断されたセルの数の割合は、０．３７５（＝１２／３２）である。 In step (6), calculate the ratio of the number of cells determined to be boron nitride regions when n is 1 to 200 according to steps (3) to (5). That is, when region A is divided into 2 cells, 8 cells, 18 cells, 32 cells, 50 cells, ... 80,000 cells, the cells determined to be in each boron nitride region Calculate the ratio of the number of. For example, in FIG. 2(b), the total number of cells is 32, and the number of cells determined to be boron nitride regions is 12, so the ratio of the number of cells determined to be boron nitride regions is: It is 0.375 (=12/32).

　手順（７）において、ｎが１～５のときのそれぞれの窒化ホウ素領域と判断されたセルの数の割合から合計値を算出する。シートの作製時に窒化ホウ素凝集粒子が崩れにくく、シート中で窒化ホウ素凝集粒子がその形状をある程度維持できている場合、シートの断面において窒化ホウ素粒子からなる領域の面積が比較的大きいことから、ｎが１～５のとき（すなわち、領域Ａが粗く区分されているとき）であっても、各セルにおいて窒化ホウ素領域と判断されやすくなり、窒化ホウ素領域と判断されたセルの数の割合が大きくなる傾向がある。 In step (7), the total value is calculated from the ratio of the number of cells determined to be boron nitride regions when n is 1 to 5. If the boron nitride agglomerated particles do not easily collapse during sheet production and the boron nitride agglomerated particles can maintain their shape to some extent in the sheet, since the area of the region made of boron nitride particles in the sheet cross section is relatively large, n Even when is 1 to 5 (that is, when area A is roughly divided), each cell is more likely to be determined to be a boron nitride area, and the proportion of cells determined to be boron nitride areas is large. There is a tendency to

　手順（８）において、シートの合計５個の断面の観察画像を取得し、それぞれの観察画像から（１）～（７）の手順により合計値を算出し、合計５個の断面のそれぞれから算出される合計値から平均値Ｘを算出する。 In step (8), obtain observation images of a total of 5 cross sections of the sheet, calculate the total value from each observation image according to steps (1) to (7), and calculate from each of the total 5 cross sections. The average value X is calculated from the total value.

　平均値Ｘは、窒化ホウ素粒子の充填量が多いときでも窒化ホウ素粒子の配向が抑制され、優れた放熱性能を有するシートが得られやすい観点から、０．０１以上、０．０３以上、０．０５以上、０．０７以上、０．０８以上、０．０９以上、又は０．１０以上であってもよく、絶縁性及び機械強度の低下を抑制できる観点から、５以下、３以下、２以下、１．８以下、１．６以下、１．２以下、１以下、０．８以下、０．５以下、０．３以下、又は０．２以下であってもよい。 The average value X is 0.01 or more, 0.03 or more, 0.01 or more, 0.03 or more, from the viewpoint of suppressing the orientation of the boron nitride particles even when the boron nitride particles are packed in a large amount and easily obtaining a sheet with excellent heat dissipation performance. It may be 05 or more, 0.07 or more, 0.08 or more, 0.09 or more, or 0.10 or more, and from the viewpoint of suppressing a decrease in insulation properties and mechanical strength, 5 or less, 3 or less, 2 or less , 1.8 or less, 1.6 or less, 1.2 or less, 1 or less, 0.8 or less, 0.5 or less, 0.3 or less, or 0.2 or less.

　シートの合計５個の断面において、ｎが２００のときのそれぞれの窒化ホウ素領域の割合の平均値Ｙは、シートの熱伝導率を向上させ、優れた放熱性能が得られやすい観点から、０．５以上、０．５２以上、又は０．５４以上であってもよい。平均値Ｙは、絶縁性及び機械強度の低下を抑制できる観点から、０．８以下、０．７５以下、０．７以下、又は０．６５以下であってもよい。 In a total of five cross sections of the sheet, when n is 200, the average value Y of the proportion of each boron nitride region is set to 0.0. It may be 5 or more, 0.52 or more, or 0.54 or more. The average value Y may be 0.8 or less, 0.75 or less, 0.7 or less, or 0.65 or less from the viewpoint of suppressing a decrease in insulation properties and mechanical strength.

　シートの配向性指数は、シートの主面と平行な方向への窒化ホウ素粒子の配向を抑制する観点から、１５以下、１３以下、又は１１．５以下であってもよい。シートの配向性指数は、１以上、３以上、又は５以上であってもよい。 The orientation index of the sheet may be 15 or less, 13 or less, or 11.5 or less from the viewpoint of suppressing the orientation of boron nitride particles in a direction parallel to the main surface of the sheet. The orientation index of the sheet may be 1 or more, 3 or more, or 5 or more.

　シートの厚さは、５０μｍ以上、８０μｍ以上、又は１００μｍ以上であってよく、５００μｍ以下、４００μｍ以下、又は３００μｍ以下であってよい。 The thickness of the sheet may be 50 μm or more, 80 μm or more, or 100 μm or more, and may be 500 μm or less, 400 μm or less, or 300 μm or less.

　以下、実施例により本発明を具体的に説明する。ただし、本発明は下記の実施例に限定されるものではない。 Hereinafter, the present invention will be specifically explained with reference to Examples. However, the present invention is not limited to the following examples.

（実施例１－１）
　平均粒子径（Ｄ５０）が２６μｍである炭化ホウ素粉末をカーボンルツボに充填し、熱間等方圧加圧装置（神戸製鋼所製、０２－ＳＹＳＴＥＭ１５×）を用いて窒素ガス雰囲気で、１８００℃、１９６ＭＰａの条件で１．５時間ＨＩＰ法により加熱及び加圧し、炭化ホウ素粉末を窒化して炭窒化ホウ素粉末（Ｂ４ＣＮ４）を得た。得られた炭窒化ホウ素粉末１００質量部と、ホウ酸１５０質量部（ホウ酸６０質量％）とをヘンシェルミキサーを用いて混合した後、混合物を窒化ホウ素ルツボに充填し、抵抗加熱炉を用いて、常圧、窒素ガス雰囲気で、保持温度２０００℃、０．０３ＭＰａの条件で、保持時間５時間で加熱することにより、粗大な粒子を含む粉末（粗粉末）を得た。粗粉末を乳鉢により１０分間解砕した後、篩目１７５μｍのナイロン篩にて分級を行った。これにより、粒子の集合体（粉末）を得た。得られた粉末の一部を回収し、Ｘ線回折装置（株式会社リガク製、「ＵＬＴＩＭＡ－ＩＶ」）を用いてＸ線回折測定したところ、窒化ホウ素に由来するピークのみが検出され、得られた粉末が窒化ホウ素粉末（平均粒子径４２．３μｍ、嵩密度０．７５ｇ／ｍｌ）であることを確認した。 (Example 1-1)
Boron carbide powder with an average particle diameter (D50) of 26 μm was filled in a carbon crucible, and heated at 1800°C in a nitrogen gas atmosphere using a hot isostatic press device (manufactured by Kobe Steel, Ltd., 02-SYSTEM15X). The boron carbide powder was heated and pressurized under the conditions of 196 MPa for 1.5 hours using the HIP method to nitride the boron carbonitride powder (B 4 CN 4 ). After mixing 100 parts by mass of the obtained boron carbonitride powder and 150 parts by mass of boric acid (60% by mass of boric acid) using a Henschel mixer, the mixture was filled into a boron nitride crucible and heated using a resistance heating furnace. Powder containing coarse particles (coarse powder) was obtained by heating at normal pressure and nitrogen gas atmosphere at a holding temperature of 2000° C. and 0.03 MPa for a holding time of 5 hours. After crushing the coarse powder in a mortar for 10 minutes, it was classified using a nylon sieve with a mesh size of 175 μm. As a result, a particle aggregate (powder) was obtained. When a part of the obtained powder was collected and subjected to X-ray diffraction measurement using an X-ray diffraction device (Rigaku Co., Ltd., "ULTIMA-IV"), only a peak derived from boron nitride was detected. It was confirmed that the powder was boron nitride powder (average particle size: 42.3 μm, bulk density: 0.75 g/ml).

　ナフタレン型エポキシ樹脂（ＤＩＣ社製、ＨＰ４０３２）１００質量部と、硬化剤としてイミダゾール化合物（四国化成社製、２Ｅ４ＭＺ－ＣＮ）１０質量部とを混合し、次いで、得られた窒化ホウ素粉末を窒化ホウ素粉末の充填率が７０体積％となるように混合して樹脂組成物を得た。この樹脂組成物を、５００Ｐａの減圧脱泡を１０分間行い、ＰＥＴ製シート上に厚さが１．０ｍｍになるように塗布した。その後、温度１５０℃、圧力３０ＭＰａの条件で６０分間のプレス加熱加圧を行って、厚さ０．５ｍｍのシートを作製した。 100 parts by mass of a naphthalene type epoxy resin (manufactured by DIC Corporation, HP4032) and 10 parts by mass of an imidazole compound (manufactured by Shikoku Kasei Co., Ltd., 2E4MZ-CN) as a hardening agent were mixed, and then the obtained boron nitride powder was mixed with boron nitride. A resin composition was obtained by mixing the powders so that the powder filling rate was 70% by volume. This resin composition was degassed under reduced pressure of 500 Pa for 10 minutes, and then applied onto a PET sheet to a thickness of 1.0 mm. Thereafter, press heating and pressing was performed for 60 minutes at a temperature of 150° C. and a pressure of 30 MPa to produce a sheet with a thickness of 0.5 mm.

（実施例１－２）
　ホウ酸の量を１００質量部（５０質量％）に変更して窒化ホウ素粉末（平均粒子径４４．７μｍ、嵩密度０．７５ｇ／ｍｌ）を得たこと以外は、実施例１と同様にしてシートを作製した。 (Example 1-2)
The procedure was repeated in the same manner as in Example 1, except that the amount of boric acid was changed to 100 parts by mass (50 mass%) to obtain boron nitride powder (average particle size 44.7 μm, bulk density 0.75 g/ml). A sheet was produced.

（実施例１－３）
　ホウ酸の量を８１．８質量部（４５質量％）に変更して窒化ホウ素粉末（平均粒子径５１．５μｍ、嵩密度０．７４ｇ／ｍｌ）を得たこと以外は、実施例１と同様にしてシートを作製した。 (Example 1-3)
Same as Example 1 except that the amount of boric acid was changed to 81.8 parts by mass (45% by mass) to obtain boron nitride powder (average particle size 51.5 μm, bulk density 0.74 g/ml). A sheet was prepared.

（比較例１）
　炭化ホウ素粉末をＨＩＰ法により窒化して炭化ホウ素粉末を得るのに代えて、抵抗加熱炉を用いて窒素ガス雰囲気で、２０００℃、０．８５ＭＰａの条件で２５時間加熱及び加圧し、炭化ホウ素粉末を窒化して炭窒化ホウ素粉末を得たこと以外は、実施例１－１と同様にして窒化ホウ素粉末（平均粒子径４２．３μｍ、嵩密度０．６７ｇ／ｍｌ）を得て、シートを作製した。 (Comparative example 1)
Instead of nitriding boron carbide powder by HIP method to obtain boron carbide powder, boron carbide powder is obtained by heating and pressurizing in a nitrogen gas atmosphere using a resistance heating furnace at 2000 ° C. and 0.85 MPa for 25 hours. Boron nitride powder (average particle size 42.3 μm, bulk density 0.67 g/ml) was obtained in the same manner as in Example 1-1, except that boron carbonitride powder was obtained by nitriding, and a sheet was produced. did.

（実施例２－１）
　温度１５０℃、圧力１５ＭＰａの条件で６０分間のプレス加熱加圧を行って、シートを作製したこと以外は実施例１－１と同様にしてシートを作製した。 (Example 2-1)
A sheet was produced in the same manner as in Example 1-1, except that the sheet was produced by press heating and pressing for 60 minutes at a temperature of 150° C. and a pressure of 15 MPa.

（実施例２－２）
　温度１５０℃、圧力１５ＭＰａの条件で６０分間のプレス加熱加圧を行って、シートを作製したこと以外は実施例１－２と同様にしてシートを作製した。 (Example 2-2)
A sheet was produced in the same manner as in Example 1-2, except that the sheet was produced by press heating and pressing for 60 minutes at a temperature of 150° C. and a pressure of 15 MPa.

（比較例２）
　温度１５０℃、圧力１５ＭＰａの条件で６０分間のプレス加熱加圧を行って、シートを作製したこと以外は比較例１と同様にしてシートを作製した。 (Comparative example 2)
A sheet was produced in the same manner as in Comparative Example 1, except that the sheet was produced by press heating and pressing for 60 minutes at a temperature of 150° C. and a pressure of 15 MPa.

（実施例３－１）
　窒化ホウ素粉末の充填率を６５体積％に変更して樹脂組成物を得たこと以外は実施例２－１と同様にしてシートを作製した。 (Example 3-1)
A sheet was produced in the same manner as in Example 2-1, except that the filling rate of boron nitride powder was changed to 65% by volume to obtain a resin composition.

（実施例３－２）
　窒化ホウ素粉末の充填率を６５体積％に変更して樹脂組成物を得たこと以外は実施例２－２と同様にしてシートを作製した。 (Example 3-2)
A sheet was produced in the same manner as in Example 2-2, except that the filling rate of boron nitride powder was changed to 65% by volume to obtain a resin composition.

（実施例３－３）
　窒化ホウ素粉末の充填率を６５体積％に変更して樹脂組成物を得たこと以外は実施例２－３と同様にしてシートを作製した。 (Example 3-3)
A sheet was produced in the same manner as in Example 2-3, except that the filling rate of boron nitride powder was changed to 65% by volume to obtain a resin composition.

（比較例３）
　窒化ホウ素粉末の充填率を６５体積％に変更して樹脂組成物を得たこと以外は比較例２と同様にしてシートを作製した。 (Comparative example 3)
A sheet was produced in the same manner as Comparative Example 2 except that the filling rate of boron nitride powder was changed to 65% by volume to obtain a resin composition.

（実施例４－１）
　窒化ホウ素粉末の充填率を６０体積％に変更して樹脂組成物を得たこと以外は実施例２－１と同様にしてシートを作製した。 (Example 4-1)
A sheet was produced in the same manner as in Example 2-1, except that the filling rate of boron nitride powder was changed to 60% by volume to obtain a resin composition.

（実施例４－２）
　窒化ホウ素粉末の充填率を６０体積％に変更して樹脂組成物を得たこと以外は実施例２－２と同様にしてシートを作製した。 (Example 4-2)
A sheet was produced in the same manner as in Example 2-2, except that the filling rate of boron nitride powder was changed to 60% by volume to obtain a resin composition.

（実施例４－３）
　窒化ホウ素粉末の充填率を６０体積％に変更して樹脂組成物を得たこと以外は実施例２－３と同様にしてシートを作製した。 (Example 4-3)
A sheet was produced in the same manner as in Example 2-3, except that the filling rate of boron nitride powder was changed to 60% by volume to obtain a resin composition.

（比較例４）
　窒化ホウ素粉末の充填率を６０体積％に変更して樹脂組成物を得たこと以外は比較例２と同様にしてシートを作製した。 (Comparative example 4)
A sheet was produced in the same manner as Comparative Example 2 except that the filling rate of boron nitride powder was changed to 60% by volume to obtain a resin composition.

［窒化ホウ素粉末の平均粒子径の測定］
　各実施例及び比較例で得られた窒化ホウ素粉末の平均粒子径は、ＩＳＯ１３３２０：２００９に準拠し、レーザー回折散乱法粒度分布測定装置（ベックマン・コールター株式会社製、「ＬＳ－１３　３２０」）を用いて測定した。ただし、測定処理の前に試料にホモジナイザーをかけずに測定した。粒度分布測定に際し、窒化ホウ素粉末を分散させる溶媒には水を用い、分散剤にはヘキサメタリン酸を用いた。このとき水の屈折率には１．３３を用い、また、窒化ホウ素粒子の屈折率については１．７の数値を用いた。 [Measurement of average particle size of boron nitride powder]
The average particle diameter of the boron nitride powder obtained in each Example and Comparative Example was measured using a laser diffraction scattering particle size distribution analyzer (manufactured by Beckman Coulter, Inc., "LS-13 320") in accordance with ISO13320:2009. It was measured using However, the measurement was performed without applying a homogenizer to the sample before the measurement process. When measuring the particle size distribution, water was used as a solvent for dispersing the boron nitride powder, and hexametaphosphoric acid was used as a dispersant. At this time, a value of 1.33 was used for the refractive index of water, and a value of 1.7 was used for the refractive index of boron nitride particles.

［配向性指数の測定］
　各実施例及び比較例で作製したシートについて、Ｘ線回折装置（Ｕｌｔｉｍａ　ＩＶ－Ｎ）を用いてＸ線回折ピークを測定し、（００２）面のピーク強度／（１００）面のピーク強度を、シートにおける窒化ホウ素粒子の配向性指数として測定した。配向性指数の測定結果を表１～４に示す。 [Measurement of orientation index]
For the sheets produced in each example and comparative example, the X-ray diffraction peak was measured using an X-ray diffraction device (Ultima IV-N), and the peak intensity of the (002) plane/the peak intensity of the (100) plane was calculated as follows: It was measured as the orientation index of boron nitride particles in the sheet. The measurement results of the orientation index are shown in Tables 1 to 4.

［平均値Ｘ、Ｙの算出］
　以下の手順により平均値Ｘ、Ｙを算出した。平均値Ｘ、Ｙの算出結果を表１～４に示す。
（１）各実施例及び比較例で作製したシートの断面をＳＥＭにより倍率１０００倍で観察し、ｂｍｐ形式の観察画像を得た。
（２）得られた観察画像を画像処理ソフトウェア「ｉｍａｇｅＪ」に取り込み、Ｍｅｄｉａｎフィルタ（３×３ｐｉｘｃｅｌ）によりフィルタ処理をした。次いで、窒化ホウ素粒子からなる領域と、それ以外の領域（樹脂領域）とに大津法による二値化処理を行い、二値化画像を得た。
（３）得られた二値化画像における短辺５０μｍ×長辺１００μｍの領域Ａにおいて、領域Ａの短辺方向をｎ等分、長辺方向を２ｎ等分する直線を作図し、複数のセルに区分した（但し、ｎは１以上の整数）。
（４）まず、ｎ＝１として領域Ａを２個の５０μｍ×５０μｍのセルに区分した。２個のセルのうちの１個のセルにおいて、１個のセルの全面積（２５００μｍ２）を基準とした窒化ホウ素粒子からなる領域の面積割合を算出した。算出した面積割合が８０％以上であれば当該１個のセルが窒化ホウ素領域であると判断し、面積割合が２０％未満であれば当該１個のセルが樹脂領域であると判断した。
（５）２個のセルのそれぞれにおいて上記の（４）の判断を行い、セルの総数（２個）を基準とした窒化ホウ素領域と判断されたセルの数の割合を算出した。
（６）ｎが２～２００のときに、上記の（４）、（５）を行い、窒化ホウ素領域と判断されたセルの数の割合をそれぞれ算出した。
（７）ｎが１～５のときのそれぞれの窒化ホウ素領域と判断されたセルの数の割合から合計値を算出した。
（８）シートの合計５個の断面において上記の（１）～（７）の手順を行い、各断面において合計値を算出した。合計５個の断面から算出した合計値から平均値Ｘを算出した。また、合計５個の断面からｎが２００のとき（領域Ａの短辺方向を２００等分、長辺方向を４００等分したとき）のそれぞれの窒化ホウ素領域と判断されたセルの数の割合の平均値Ｙを算出した。実施例１－１のシートの断面のＳＥＭ画像を図３に、比較例１のシートの断面のＳＥＭ画像を図４にそれぞれ示す。また、実施例４－１のシート及び比較例４のシートを複数のセルに区分したときの１個のセルの一辺の長さと、窒化ホウ素領域と判断されたセルの数の割合との関係を示すグラフを図５に示す。 [Calculation of average values X and Y]
Average values X and Y were calculated by the following procedure. The calculation results of the average values X and Y are shown in Tables 1 to 4.
(1) The cross sections of the sheets produced in each of the Examples and Comparative Examples were observed using a SEM at a magnification of 1000 times to obtain observation images in bmp format.
(2) The obtained observation image was imported into image processing software "imageJ" and filtered using a median filter (3×3 pixels). Next, the region made of boron nitride particles and the other region (resin region) were subjected to binarization processing using the Otsu method to obtain a binarized image.
(3) In area A of 50 μm on the short side x 100 μm on the long side in the obtained binarized image, draw a straight line that divides the short side of area A into n equal parts and the long side into 2n equal parts, and divide the area A into multiple cells. (However, n is an integer of 1 or more).
(4) First, area A was divided into two 50 μm×50 μm cells with n=1. In one of the two cells, the area ratio of the region made of boron nitride particles was calculated based on the total area of one cell (2500 μm 2 ). If the calculated area ratio was 80% or more, it was determined that the one cell was a boron nitride region, and if the area ratio was less than 20%, it was determined that the one cell was a resin region.
(5) The determination in (4) above was made for each of the two cells, and the ratio of the number of cells determined to be boron nitride regions based on the total number of cells (2) was calculated.
(6) When n was 2 to 200, the above (4) and (5) were performed, and the ratio of the number of cells determined to be in the boron nitride region was calculated.
(7) A total value was calculated from the ratio of the number of cells determined to be in each boron nitride region when n was 1 to 5.
(8) The above procedures (1) to (7) were performed on a total of five cross sections of the sheet, and the total value was calculated for each cross section. The average value X was calculated from the total value calculated from a total of five cross sections. In addition, when n is 200 from a total of 5 cross sections (when the short side direction of area A is divided into 200 equal parts and the long side direction is divided into 400 equal parts), the ratio of the number of cells determined to be each boron nitride region. The average value Y was calculated. FIG. 3 shows a SEM image of the cross section of the sheet of Example 1-1, and FIG. 4 shows a SEM image of the cross section of the sheet of Comparative Example 1. In addition, when the sheet of Example 4-1 and the sheet of Comparative Example 4 were divided into a plurality of cells, the relationship between the length of one side of one cell and the ratio of the number of cells determined to be boron nitride regions was determined. A graph is shown in FIG.

Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001

Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000002

Figure JPOXMLDOC01-appb-T000003
Figure JPOXMLDOC01-appb-T000003

Figure JPOXMLDOC01-appb-T000004
Figure JPOXMLDOC01-appb-T000004

［熱伝導率の測定］
　実施例１－２及び比較例１で作製したそれぞれのシートから１０ｍｍ×１０ｍｍの大きさの測定用試料を切り出し、キセノンフラッシュアナライザ（ＮＥＴＺＳＣＨ社製、ＬＦＡ４４７ＮａｎｏＦｌａｓｈ）を用いたレーザーフラッシュ法により、測定用試料の熱拡散率Ａ（ｍ２／秒）を測定した。また、測定用試料の比重Ｂ（ｋｇ／ｍ３）をアルキメデス法により測定した。また、測定用試料の比熱容量Ｃ（Ｊ／（ｋｇ・Ｋ））を、示差走査熱量計（株式会社リガク製、ＴｈｅｒｍｏＰｌｕｓＥｖｏＤＳＣ８２３０）を用いて測定した。これらの各物性値を用いて、熱伝導率Ｈ（Ｗ／（ｍ・Ｋ））をＨ＝Ａ×Ｂ×Ｃの式から求めた。実施例１－２の熱伝導率の測定結果は、２４．４Ｗ／（ｍ・Ｋ）であり、比較例１の熱伝導率の測定結果は、１７．２Ｗ／（ｍ・Ｋ）であった。

  [Measurement of thermal conductivity]
Measurement samples with a size of 10 mm x 10 mm were cut out from each of the sheets prepared in Example 1-2 and Comparative Example 1, and measured using a laser flash method using a xenon flash analyzer (manufactured by NETZSCH, LFA447NanoFlash). The thermal diffusivity A (m 2 /sec) was measured. Further, the specific gravity B (kg/m 3 ) of the measurement sample was measured by the Archimedes method. Further, the specific heat capacity C (J/(kg·K)) of the measurement sample was measured using a differential scanning calorimeter (ThermoPlusEvoDSC8230, manufactured by Rigaku Co., Ltd.). Using these physical property values, the thermal conductivity H (W/(m·K)) was determined from the formula H=A×B×C. The measurement result of the thermal conductivity of Example 1-2 was 24.4 W/(m K), and the measurement result of the thermal conductivity of Comparative Example 1 was 17.2 W/(m K). .

Claims (3)

　炭化ホウ素粉末を熱間等方圧加圧しながら窒化して、炭窒化ホウ素粉末を得る工程と、
　前記炭窒化ホウ素粉末を脱炭して、窒化ホウ素粉末を得る工程と、
　前記窒化ホウ素粉末を樹脂と混合して、樹脂組成物を得る工程と、
　前記樹脂組成物を加圧によりシート状に成形する工程と、
を備える、シートの製造方法。 nitriding boron carbide powder while hot isostatically pressing to obtain boron carbonitride powder;
decarburizing the boron carbonitride powder to obtain boron nitride powder;
mixing the boron nitride powder with a resin to obtain a resin composition;
a step of molding the resin composition into a sheet shape by applying pressure;
A method for manufacturing a sheet, comprising: 　窒化ホウ素粒子と、樹脂と、を含有し、
　下記（１）～（８）の手順で算出される平均値Ｘが０．０１以上である、シート。
（１）前記シートの任意の断面をＳＥＭにより倍率１０００倍で観察した観察画像を取得する。
（２）前記観察画像において前記窒化ホウ素粒子からなる領域とそれ以外の領域とに二値化して、二値化画像を取得する。
（３）前記二値化画像において短辺５０μｍ×長辺１００μｍの領域Ａの短辺方向をｎ等分、長辺方向を２ｎ等分して、複数のセルに区分する（但し、ｎは１以上の整数）。
（４）前記複数のセルのうちの１個のセルにおいて、前記１個のセルの全面積を基準とした前記窒化ホウ素粒子からなる領域の面積割合を算出し、前記面積割合が８０％以上であれば前記１個のセルが窒化ホウ素領域であると判断し、前記面積割合が２０％未満であれば前記１個のセルが樹脂領域であると判断する。
（５）前記複数のセルのそれぞれにおいて前記（４）の判断を行い、前記複数のセルの総数を基準とした前記窒化ホウ素領域と判断されたセルの数の割合を算出する。
（６）前記（３）～前記（５）の手順において、ｎが１～２００のときの前記窒化ホウ素領域と判断されたセルの数の割合をそれぞれ算出する。
（７）ｎが１～５のときのそれぞれの前記窒化ホウ素領域と判断されたセルの数の割合の合計値を算出する。
（８）前記シートの合計５個の断面において前記（１）～（７）の手順で算出されるそれぞれの前記合計値から平均値Ｘを算出する。 Contains boron nitride particles and a resin,
A sheet whose average value X calculated by the following steps (1) to (8) is 0.01 or more.
(1) Obtain an observation image of an arbitrary cross section of the sheet observed with a SEM at a magnification of 1000 times.
(2) Obtaining a binarized image by binarizing the observed image into a region made of the boron nitride particles and other regions.
(3) In the binarized image, the short side direction of the region A of 50 μm on the short side x 100 μm on the long side is divided into n equal parts, and the long side direction is divided into 2n equal parts to divide it into a plurality of cells (where n is 1 (integer greater than or equal to).
(4) In one cell of the plurality of cells, calculate the area ratio of the region made of the boron nitride particles based on the total area of the one cell, and if the area ratio is 80% or more. If so, it is determined that the one cell is a boron nitride region, and if the area ratio is less than 20%, it is determined that the one cell is a resin region.
(5) Perform the determination in (4) above for each of the plurality of cells, and calculate the ratio of the number of cells determined to be the boron nitride region based on the total number of the plurality of cells.
(6) In the steps (3) to (5) above, when n is 1 to 200, calculate the ratio of the number of cells determined to be the boron nitride region.
(7) When n is 1 to 5, calculate the total value of the ratio of the number of cells determined to be the boron nitride region.
(8) Calculate the average value X from the respective total values calculated in the steps (1) to (7) for a total of five cross sections of the sheet. 　前記シートの前記合計５個の断面において、ｎが２００のときのそれぞれの前記窒化ホウ素領域と判断されたセルの数の割合の平均値Ｙが０．５以上である、請求項２に記載のシート。

  3. The average value Y of the ratio of the number of cells determined to be the boron nitride region in each of the five cross sections of the sheet when n is 200 is 0.5 or more. sheet.
PCT/JP2023/030202 2022-08-30 2023-08-22 Method for producing sheet, and sheet Ceased WO2024048377A1 (en)

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2013543834A (en) * 2010-11-10 2013-12-09 イーエスケイ セラミクス ゲーエムベーハー アンド カンパニー カーゲー Boron nitride agglomerates, process for their production and their use
WO2020004600A1 (en) * 2018-06-29 2020-01-02 デンカ株式会社 Aggregate boron nitride particles, boron nitride powder, production method for boron nitride powder, resin composition, and heat dissipation member
WO2021079912A1 (en) * 2019-10-23 2021-04-29 デンカ株式会社 Boron nitride powder and production method therefor, boron carbonitride powder, composite material, and heat dissipating member
JP2022106113A (en) * 2021-01-06 2022-07-19 デンカ株式会社 Boron nitride powder, heat conductive resin composition, heat dissipation sheet and electronic component structure

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2013543834A (en) * 2010-11-10 2013-12-09 イーエスケイ セラミクス ゲーエムベーハー アンド カンパニー カーゲー Boron nitride agglomerates, process for their production and their use
WO2020004600A1 (en) * 2018-06-29 2020-01-02 デンカ株式会社 Aggregate boron nitride particles, boron nitride powder, production method for boron nitride powder, resin composition, and heat dissipation member
WO2021079912A1 (en) * 2019-10-23 2021-04-29 デンカ株式会社 Boron nitride powder and production method therefor, boron carbonitride powder, composite material, and heat dissipating member
JP2022106113A (en) * 2021-01-06 2022-07-19 デンカ株式会社 Boron nitride powder, heat conductive resin composition, heat dissipation sheet and electronic component structure

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