Electromagnetic interference suppression materials

Abstract

Provided is an electromagnetic interference-suppressing material containing a carbon composite material and a base material including at least one of an organic substance and an inorganic substance, wherein the carbon composite material is at least one substance selected from among core-shell particles in which the surface of inorganic particles is coated with a coating layer comprising an average of four layers or less of graphene and core-shell connected bodies in which the surface of connected bodies of inorganic particles is coated with a coating layer having an average of four layers or less of graphene, and the volume resistivity is 103 Ω·cm or more.

Description

[Technical Field]

[0001] This disclosure relates to electromagnetic interference suppression materials. [Background technology]

[0002] In recent years, various measures have been taken to reduce electromagnetic interference, such as equipment malfunctions due to electromagnetic noise, information leakage, and reductions in information communication speed due to interference. Methods proposed to reduce electromagnetic interference include methods of blocking electromagnetic waves by reflection or methods of absorbing electromagnetic waves.

[0003] For example, Patent Document 1 proposes an electromagnetic wave shielding material made by dispersing soft magnetic metal powder, such as powder of a metal selected from Fe, Ni, Co, and V, or an alloy composed of two or more of these metals, in a rubber or plastic matrix and forming it into a sheet. Patent Document 2 proposes a sheet-like radio wave absorber in which a radio wave absorbing layer formed of a radio wave absorbing material, which is made by dispersing silicon carbide powder in a matrix resin, is laminated on the surface of a metal body. Patent Document 3 proposes an electromagnetic wave absorbing sheet for the 5-7 GHz frequency band, having a dielectric layer made of a matrix containing carbon material, a divided conductive film layer laminated on one side of the dielectric layer, and an electromagnetic wave reflective layer laminated on the other side of the dielectric layer. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2001-68889 [Patent Document 2] Japanese Patent Publication No. 2005-57093 [Patent Document 3] Japanese Patent Publication No. 2012-209515 [Overview of the project] [Problems that the invention aims to solve]

[0005] Conventionally, many proposals have been made to reduce electromagnetic interference, such as the electromagnetic shielding materials, radio wave absorbers, and electromagnetic wave absorbing sheets described in the above-mentioned Patent Documents 1 to 3. However, with the increasing performance and diversification of communication equipment in recent years, the reduction of electromagnetic interference is sometimes insufficient, and further improvements have been required. Furthermore, methods that block electromagnetic waves by reflecting them with metals or other materials had the drawback of inevitably causing autointoxication.

[0006] This disclosure is made in view of these circumstances and aims to provide an electromagnetic interference suppression material that has good electromagnetic wave absorption performance and electromagnetic interference suppression performance, and is capable of reducing electromagnetic interference even more effectively. [Means for solving the problem]

[0007] As a result of diligent research to solve the above-mentioned problems, the inventors of the present invention have found that an electromagnetic interference suppression material comprising a base material containing at least one selected from organic and inorganic materials, and a predetermined carbon composite material, has high electromagnetic wave absorption performance and electromagnetic interference suppression performance, and is more effective in reducing electromagnetic interference. This disclosure is based on such findings.

[0008] In other words, this disclosure relates to the following: [1] An electromagnetic interference suppression material comprising a base material containing at least one selected from organic and inorganic materials, and a carbon composite material, The carbon composite material is at least one selected from core-shell particles, in which the surface of inorganic particles is coated with a coating layer of graphene with an average number of 4 or fewer layers, and core-shell assemblies, in which the surface of an assembly of inorganic particles is coated with a coating layer of graphene with an average number of 4 or fewer layers. Volume resistance is 10 3 Electromagnetic interference suppression material with an impedance of Ω·cm or greater. [2] The electromagnetic interference suppression material according to [1] above, wherein the average particle size of the inorganic particles having the core-shell particles and the inorganic particles having the core-shell assembly is 100 μm or less. [3] The electromagnetic interference suppression material according to any one of [1] or [2] above, wherein the content of graphene in the electromagnetic interference suppression material is 0.001 to 30% by mass based on the entire electromagnetic interference suppression material. [4] The electromagnetic interference suppression material according to any one of [1] to [3] above, wherein the inorganic particles included in the core-shell particles and the inorganic particles included in the core-shell connector include at least one selected from alumina, silica, magnesium oxide, tungsten carbide, and aluminum nitride. [5] The electromagnetic interference suppression material according to any one of [1] to [3] above, wherein the inorganic particles included in the core-shell particles and the inorganic particles included in the core-shell connector are magnetic materials. [6] The electromagnetic interference suppression material according to [5] above, wherein the magnetic material includes at least one selected from magnetic metals, magnetic metal alloys, and magnetic oxides, and the magnetic oxide is at least one selected from ferrite and magnetite. [7] The electromagnetic interference suppression material according to [6] above, wherein the magnetic metal and the magnetic metal alloy are in a flat shape. [8] The electromagnetic interference suppression material according to any one of [1] to [7] above, wherein the organic substance is a thermosetting resin. [9] The electromagnetic interference suppression material according to any one of [1] to [7] above, wherein the organic substance is a thermoplastic resin.

[10] The electromagnetic interference suppression material according to any one of [1] to [9] above, wherein the inorganic substance is ceramics.

Advantages of the Invention

[0009] According to the present disclosure, it is possible to provide an electromagnetic interference suppression material having high electromagnetic wave absorption performance and electromagnetic interference suppression performance and more excellent electromagnetic interference reduction performance.

Modes for Carrying Out the Invention

[0010] Hereinafter, the present disclosure will be described in detail with reference to one embodiment. In this specification, the notation "XX~YY" means "XX or more and YY or less." Furthermore, in this specification, the lower and upper limits of numerical ranges (e.g., ranges of content, etc.) described in stages can be combined independently. In addition, in numerical ranges described in this specification, the upper or lower limit of the numerical range may be replaced with the values ​​shown in the examples. In this specification, "electromagnetic interference suppression material" refers to a material that can attenuate near-field electromagnetic fields and electromagnetic waves by utilizing its loss characteristics (magnetic loss, dielectric loss, electrical resistance, etc.). In this specification, "graphene" means "a layer of 10 or fewer sp 2 It means "a sheet-like material of bonded carbon atoms." In this specification, the "average number of layers" of graphene is the value obtained by the following formula. Specifically, it is obtained by the method described in the examples below. Average number of graphene layers = amount of carbon supported per unit area (g / m²) 2 ) / (mass of graphene per unit area [g / m²] 2 ]) Note that "carbon load per unit area (g / m²)" 2 )" is the amount of carbon supported per unit mass of the carbon composite material (g) determined by thermogravimetric analysis, and the specific surface area (m²) of the inorganic particles in the core-shell particles or the inorganic particles in the core-shell linkage. 2 This value is obtained by dividing by ( / g). The carbon load (g) per unit mass of the carbon composite material, determined by thermogravimetric analysis, is specifically determined by the method described in the examples. The aforementioned specific surface area refers to the BET specific surface area, which is a value obtained by measuring using the BET multi-point method (e.g., 5-6 points) due to nitrogen adsorption. In this specification, "volume resistivity" refers to volume resistivity, which can be measured in accordance with JIS K-6911:2006, and specifically, can be measured by the method described in the examples.

[0011] [Electromagnetic interference suppression material] The electromagnetic interference suppression material of this disclosure comprises a matrix material containing at least one selected from organic and inorganic materials, and a carbon composite material. The carbon composite material is at least one selected from core-shell particles in which inorganic particles are coated with a coating layer of graphene with an average number of layers of 4 or less, and core-shell assemblies in which an assembly of inorganic particles is coated with a coating layer of graphene with an average number of layers of 4 or less, and the electromagnetic interference suppression material has a volume resistivity of 1.0 × 10⁻¹⁶ 3 It is greater than or equal to Ω·cm. If the carbon composite material is at least one selected from core-shell particles, in which inorganic particles are coated with a graphene coating layer having an average number of 4 or fewer layers on their surface, and core-shell assemblies, in which an inorganic particle assembly is coated with a graphene coating layer having an average number of 4 or fewer layers on its surface, the resulting electromagnetic interference suppression material will have high electromagnetic wave absorption performance and electromagnetic interference suppression performance, and will have better electromagnetic interference reduction performance. The reason for this is not clear, but it is thought to be as follows.

[0012] The carbon composite material of this disclosure has a coating layer made of graphene with an average number of layers of 4 or less covering the surface of inorganic particles. In other words, the carbon composite material of this disclosure has a three-dimensionally continuous graphene sheet (shell) with an average number of layers of 4 or less covering the surface of inorganic particles (core). Therefore, the carbon composite material has a large specific surface area and high radio wave absorption performance per unit volume compared to other carbon composite materials. Due to this large specific surface area, the carbon composite material of this disclosure can improve volume resistivity compared to other carbon composite materials containing the same amount. Because of this large specific surface area and the effect of improving volume resistivity, the carbon composite material of this disclosure is expected to have high electromagnetic wave absorption performance and electromagnetic interference suppression performance.

[0013] The coating layer on the core-shell particles and the coating layer on the core-shell assembly may be made of graphene. From the viewpoint of increasing the specific surface area of ​​the carbon composite material and further improving the electromagnetic wave absorption performance and electromagnetic interference suppression performance, the average number of graphene layers may be less than 4, 3 or less, 2.5 or less, 2.0 or less, or 1.9 or less.

[0014] The electromagnetic interference suppression material of the present disclosure has a volume resistivity of 1.0×10 3 Ω·cm or more. Electromagnetic interference suppression materials are generally said to be difficult to have both insulation, electromagnetic absorption performance, and electromagnetic interference suppression performance. However, the electromagnetic interference suppression material of the present disclosure contains the carbon composite material, so it has high insulation (volume resistivity), and its electromagnetic wave absorption performance and electromagnetic interference suppression performance are improved. In one aspect of the present disclosure, from the viewpoint of ensuring insulation, the volume resistivity may be 10 6 Ω·cm or more, may be 10 8 Ω·cm or more, and may be 10 10 Ω·cm or more. There is no particular upper limit provided, but it may be 1.0×10 16 Ωcm or less.

[0015] Some communication devices are accompanied by large heat generation, and generally a heat dissipation mechanism using a heat dissipation sheet or the like in combination is required. If the electromagnetic interference suppression material not only reduces electromagnetic interference but also has high thermal conductivity and heat dissipation properties, there is no need to use other mechanisms such as a heat dissipation sheet in combination. In addition to miniaturization and weight reduction of electronic components, it is useful because it can also reduce the number of assembly steps. From this perspective, the thermal conductivity of the electromagnetic interference suppression material may be 0.1 to 10.0 W / m·K, may be 0.5 to 8.0 W / m·K, or may be 1.0 to 6.0 W / m·K. The thermal conductivity can be obtained by a hot wire method in which the temperature gradient when heat flux energy is applied as a heat ray is compared with a sample having a known thermal conductivity, or a laser flash method in which a homogeneous substance is instantaneously given high energy by a laser or the like, and the thermal conductivity is calculated based on the thermal diffusivity and specific heat measured at that time. Specifically, it can be measured by the method described in the examples.

[0016] Communication devices are becoming smaller and lighter, which is creating a demand for packaging materials that utilize electromagnetic interference suppression materials. For example, some modular electronic component packages are asymmetrical, thin, and have a large surface area. In packaging processes such as FOWLP (Fan Out Wafer Level Package), where electronic components on a large substrate are sealed on one side as a whole before being separated into individual components, it is necessary to reduce warping. In such cases, it is useful to bring the thermal expansion of the electromagnetic interference suppression material as close as possible to that of an insert with a low thermal expansion coefficient, i.e., to reduce the thermal expansion of the electromagnetic interference suppression material. From this viewpoint, the thermal expansion coefficient of the electromagnetic interference suppression material (α1: thermal expansion coefficient from room temperature (25°C) to the glass transition temperature) may be 1 ppm / deg. or higher, or 3 ppm / deg. or higher. Furthermore, the thermal expansion coefficient of the electromagnetic interference suppression material may be 40 ppm / deg. or lower, or 35 ppm / deg. or lower. When the electromagnetic interference suppressing material is used as a sealing material, the thermal expansion coefficient of the electromagnetic interference suppressing material may be 22 ppm / deg. or less, or 20 ppm / deg. or less. The coefficient of thermal expansion can be determined from the slope of the tangent line between 25 and 60 degrees Celsius in a TMA chart obtained by thermomechanical analysis (TMA). Specifically, it can be measured by the method described in the examples.

[0017] <Carbon composite materials> The carbon composite material of this disclosure is at least one selected from core-shell particles, in which inorganic particles are coated with a coating layer of graphene having an average number of 4 or fewer layers, and core-shell assemblies, in which an assembly of inorganic particles is coated with a coating layer of graphene having an average number of 4 or fewer layers. Furthermore, the carbon composite materials disclosed herein include those in which the pores of inorganic particles are coated with carbon, and those in which the pores of inorganic particles are filled with carbon.

[0018] The average particle size of the core-shell particles may be 0.0005 to 100 μm, 0.1 to 50 μm, or 0.5 to 20 μm, from the viewpoint of ease of manufacturing and further improvement of electromagnetic wave absorption performance and electromagnetic interference suppression performance. The average particle size of the core-shell particles is calculated using the following formula, assuming a cylindrical pore. Average particle size (m) of core-shell particles = 6 / [specific surface area (m²)] 2 ( / g) × true density of core-shell particles (g / m³) 3 )] The aforementioned specific surface area refers to the BET specific surface area, which is a value obtained by measuring using the BET multi-point method (e.g., 5-6 points) due to nitrogen adsorption.

[0019] The average particle size of the core-shell assembly may be 0.0005 to 100 μm, 0.1 to 50 μm, or 0.5 to 20 μm, from the viewpoint of ease of manufacture and further improvement of electromagnetic wave absorption performance and electromagnetic interference suppression performance. The average particle size of the core-shell assembly can be estimated using a laser diffraction particle size analyzer.

[0020] The average particle size of the carbon composite material may be 100 μm or less, from the viewpoint of further improving electromagnetic wave absorption performance and electromagnetic interference suppression performance. In this specification, "average particle size of the carbon composite material" refers to the average particle size of primary particles when the carbon composite material is not aggregated and is composed of primary particles, and refers to the average particle size of secondary particles when the carbon composite material aggregates and forms secondary particles. The average particle size of the carbon composite material is calculated from the volume of the pores and the specific surface area, estimated using a laser diffraction particle size analyzer, or calculated as the average value of the particle sizes observed within 20 to 100 fields of view using a scanning electron microscope (SEM) or transmission electron microscope (TEM). Furthermore, "particle size" refers to the maximum distance between any two points passing through the center of the particle and along its contour line.

[0021] The specific surface area of ​​the carbon composite material is set to 800 m² from the viewpoint of further improving electromagnetic wave absorption performance and electromagnetic interference suppression performance. 2 It may be less than / g, and 780m 2 It may be less than / g, and 600m 2 It may be less than / g. There is no particular lower limit, but 1m 2 It may be more than / g, 5m 2 / g or more is also acceptable, 10m 2 It may be more than / g. The specific surface area mentioned above refers to the BET specific surface area, and is a value measured by the BET multi-point method due to nitrogen adsorption.

[0022] In this disclosure, the content (mass%) of the carbon composite material in the electromagnetic interference suppression material is not particularly limited, as it varies greatly depending on the application and the base material. From the viewpoint of further improving electromagnetic wave absorption performance and electromagnetic interference suppression performance, the content (mass%) of the carbon composite material in the electromagnetic interference suppression material may be 0.1 to 90% by mass, 0.5 to 35% by mass, or 1 to 30% by mass, relative to the total amount of the electromagnetic interference suppression material.

[0023] [Inorganic particles] The core-shell particles and core-shell assemblies of this disclosure have inorganic particles. The inorganic particles that the core-shell particles and the inorganic particles that the core-shell assemblies have (hereinafter collectively referred to as "inorganic particles") are not particularly limited. Examples include inorganic particles such as alumina, silica, magnesium oxide, tungsten carbide, aluminum nitride, cerium oxide, titanium oxide, and calcium carbonate; magnetic materials that are magnetic metals such as pure iron; magnetic materials that are magnetic metal alloys such as amorphous magnetic metal alloys, Ni-Fe alloys, mild steel, silicon steel (Fe-Si alloys), Fe-Al alloys, Fe-Si-Al alloys (Sendust), and Co-Fe alloys; and magnetic materials that are magnetic oxides such as carbonyl iron, magnetite, and ferrite.

[0024] Examples of the aforementioned ferrites include Mn-Zn ferrite, Ni-Zn ferrite, Cu-Zn ferrite, Cu-Zn-Mg ferrite, Mn-Mg-Al ferrite, Y-type hexagonal ferrite, Z-type hexagonal ferrite, and M-type hexagonal ferrite.

[0025] The magnetic metal and the magnetic metal alloy may be in a flattened shape.

[0026] The inorganic particles may be selected according to the application of the electromagnetic interference suppression material. The inorganic particles may include at least one selected from alumina, silica, magnesium oxide, tungsten carbide, and aluminum nitride, or they may include at least one selected from alumina, silica, and magnesium oxide, or they may include alumina. Furthermore, the inorganic particles may also contain silica from the viewpoint of thermal expansion coefficient. Furthermore, the inorganic particles may include one selected from alumina, magnesium oxide, and aluminum nitride from the viewpoint of thermal conductivity, and may also include alumina. Furthermore, the inorganic particles may be magnetic materials, from the viewpoint of improving thermal conductivity and electromagnetic wave absorption capacity over a wide frequency range. These magnetic materials may include at least one selected from magnetic metals, magnetic metal alloys, and magnetic oxides, amorphous magnetic metal alloys, at least one selected from Fe-Si-Al alloys (Sendust), ferrite, and magnetite, or at least one selected from ferrite and magnetite.

[0027] The inorganic particles may consist of only one type, or they may contain two or more types. The inorganic particles may be nanoparticles, from the viewpoint of further improving electromagnetic wave absorption performance and electromagnetic interference suppression performance.

[0028] [Graphene] The graphene of this disclosure is a sheet-like material having a hexagonal lattice structure in which carbon atoms are bonded. The graphene may be in a monolayer state with a thickness of one carbon atom, or in a multilayer state of two or more layers. In addition to carbon atoms, the graphene may contain oxygen atoms, hydrogen atoms, boron atoms, nitrogen atoms, sulfur atoms, phosphorus atoms, and the like.

[0029] The graphene content (mass%) in the core-shell particles and the core-shell assembly is not particularly limited. From the viewpoint of further improving electromagnetic wave absorption performance and electromagnetic interference suppression performance, it may be 0.1 to 70 mass%, 0.5 to 45 mass%, or 1 to 20 mass%.

[0030] The graphene content (mass%) in the electromagnetic interference suppression material is not particularly limited. From the viewpoint of further improving electromagnetic wave absorption performance and electromagnetic interference suppression performance, it may be 0.001 to 30 mass%, 0.01 to 20 mass%, or 0.05 to 15 mass%.

[0031] <Base material> The base material of this disclosure comprises at least one selected from organic and inorganic materials. The base material may consist solely of organic materials, solely of inorganic materials, or a mixture of organic and inorganic materials.

[0032] [Organic matter] The organic matter contained in the base material is not particularly limited, but examples include thermosetting resins and thermoplastic resins. Examples of thermosetting resins include epoxy resins, phenolic resins, and imide resins. Examples of thermoplastic resins include polyolefin resins, vinyl resins, styrene-acrylic resins, ethylene-acrylic ester resins, ethylene-methacrylic ester resins, diene resins, terpene resins, petroleum resins, cellulose resins, polyamide resins, polyurethane resins, polyester resins, polycarbonate resins, polyimide resins, and fluororesins.

[0033] The aforementioned organic material may be a thermosetting resin from the viewpoint of reliability of the molded article using the electromagnetic interference suppression material, and may be an epoxy resin or an imide resin from the viewpoint of electrical insulation and heat resistance of the molded article using the electromagnetic interference suppression material. From the viewpoint of ease of manufacture and ease of processing, it may be a thermoplastic resin, and from the viewpoint of durability and weather resistance, it may be a polyurethane, and for outdoor use, it may be a polycarbonate-based polyurethane with good hydrolysis resistance. Note that a molded article refers to a molded article manufactured by placing it in a mold such as a casting mold or a metal mold. The aforementioned organic material may be used individually, or two or more may be used in combination.

[0034] In this disclosure, the epoxy resin used as an organic material has two or more epoxy groups in one molecule and is commonly used in electronic components; however, its molecular structure, molecular weight, etc., are not particularly limited. Examples of epoxy resins include phenol novolac type epoxy resins, cresol novolac type epoxy resins, aliphatic epoxy resins such as dicyclopentadiene derivatives, and aromatic epoxy resins such as biphenyl type, biphenyl aralkyl type, naphthyl type, and bisphenol type. These epoxy resins may be used individually or in mixtures of two or more. There are no particular restrictions on their properties, and they may be liquid or solid at room temperature (25°C). For example, the epoxy resin may be a solid cresol novolac type epoxy resin. The solid cresol novolac type epoxy resin is available commercially, for example, N670 (manufactured by DIC Corporation). Alternatively, the epoxy resin may be a liquid epoxy resin, specifically bisphenol A type and bisphenol F type. The liquid epoxy resin may be a liquid bisphenol A type epoxy resin. Liquid bisphenol A type epoxy resin is available commercially, for example, Epomic® R140 (manufactured by Mitsui Chemicals, Inc.). In this disclosure, "liquid epoxy resin" refers to an epoxy resin that is liquid at 25°C.

[0035] The epoxy equivalent of the epoxy resin may be 140 or more from the viewpoint of the thermomechanical properties of the molded article. It may also be 200 or more from the viewpoint of electromagnetic wave absorption performance. The upper limit of the epoxy equivalent may be 400 or less, or 380 or less, from the viewpoint of thermomechanical properties.

[0036] The epoxy resin is (R 1 The polyoxyalkylene structure represented by O)m and (R 2 It may also be an epoxy resin having a polyoxyalkylene structure represented by O)n. Here, R 1 and R 2 Each of these independently represents an alkylene group having 1 or more carbon atoms. m+n may be between 1 and 50, or between 1 and 20. Also, m may be between 0 and 49, or between 0 and 19. n may be between 1 and 50, or between 1 and 20.

[0037] R 1 and R 2 Examples of alkylene groups represented by include alkylene groups having 1 to 6 carbon atoms, specifically methylene groups, ethylene groups, trimethylene groups, propylene groups, tetramethylene groups, hexamethylene groups, etc. From the viewpoint of electromagnetic wave absorption performance, the alkylene group may be a methylene group or an ethylene group. m R 1 In the O group, multiple R 1 These may be the same alkylene group, or they may be alkylene groups with different numbers of carbon atoms. Also, n R 2 In the O group, multiple R 2 These may be the same alkylene group or alkylene groups with different numbers of carbon atoms.

[0038] Examples of epoxy resins having the polyoxyalkylene structure include liquid epoxy resins having a bisphenol A skeleton and polyethylene glycol diglycidyl ether. A commercially available liquid epoxy resin having a bisphenol A skeleton is Ricaresin BEO-60E (manufactured by Shin-Nippon Rika Co., Ltd.), which is represented by the following general formula (1). A commercially available polyethylene glycol diglycidyl ether is Epolite 400E (manufactured by Kyoeisha Chemical Co., Ltd.), which has the compound represented by the following general formula (2) as its main component.

[0039] [ka]

[0040] [ka]

[0041] Examples of imide resins used as organic materials in this disclosure include bisallylnadiimide. Bisallylnadiimide is available commercially, and examples include BANI-M (manufactured by Maruzen Petrochemical Co., Ltd.) and BANI-X (manufactured by Maruzen Petrochemical Co., Ltd.).

[0042] In this disclosure, the content (mass%) of the organic substance in the electromagnetic interference suppression material may be 0.1 to 40 mass%, 1 to 30 mass%, 3 to 25 mass%, or 5 to 20 mass% of the total amount of the electromagnetic interference suppression material, from the viewpoint of further improving the electromagnetic wave absorption performance and electromagnetic interference suppression performance.

[0043] If the aforementioned organic material includes a thermosetting resin, the electromagnetic interference suppression material of this disclosure may further contain a curing agent and a curing accelerator, etc. Examples of the curing agent include aliphatic amines, aromatic amines, dicyandiamides, dihydrazide compounds, acid anhydrides, and phenolic resins. These may be used individually or in combination of two or more. Examples of the curing accelerators include organic peroxides such as dicumyl peroxide and dibutyl peroxide; imidazole compounds such as 2-methylimidazole and 2-ethylimidazole; organophosphorus compounds such as trimethylphosphine, triethylphosphine, tributylphosphine, and triphenylphosphine; diazabicycloalkene compounds such as 1,8-diazabicyclo[5,4,0]undecene-7 (DBU) and 1,5-diazabicyclo(4,3,0)nonene-5; and tetraphenylborone compounds such as 2-ethyl-4-methylimidazole tetraphenylborate. These may be used individually or in combination of two or more. In one embodiment of the present disclosure, if the electromagnetic interference suppression material of the present disclosure contains a curing agent, the content thereof may be 0 to 150% by mass, 0 to 120% by mass, or 0 to 100% by mass, based on 100% by mass of the thermosetting resin. In other embodiments of the present disclosure, if the electromagnetic interference suppression material of the present disclosure contains a curing agent, the amount thereof may be 1 to 20% by mass, 2 to 18% by mass, or 3 to 15% by mass, based on the total amount of the electromagnetic interference suppression material. Furthermore, if the electromagnetic interference suppression material of this disclosure contains a curing accelerator, the amount thereof may be 0.01 to 10% by mass, 0.05 to 5% by mass, or 0.1 to 3% by mass, based on the total amount of the electromagnetic interference suppression material.

[0044] The electromagnetic interference suppression material of this disclosure may further contain a dispersion aid. The dispersion aid is not particularly limited as long as it is a material that stably and highly disperses fine particles in a matrix resin. Generally, the dispersant used is a surfactant having functional groups of different reactivity in a single molecule, and a coupling agent. Examples of the dispersion aid include surfactants such as anionic surfactants such as carboxylate salts and cationic surfactants such as quaternary ammonium salts; coupling agents having amine functional groups and sulfide functional groups; and cellulose nanofibers.

[0045] The cellulose nanofibers are bipolar micro-solids that improve the dispersibility of fillers through their surfactant properties. The cellulose nanofibers may already be highly dispersed in a liquid such as water or a thermosetting resin oligomer. The average fiber length of the cellulose nanofibers may be 1 μm to 100 μm, or 5 μm to 50 μm, from the viewpoint of workability and fluidity. The average fiber diameter of the cellulose nanofibers, including aggregates, may be between 1 nm and 1000 nm, or between 4 nm and 500 nm. Having the average fiber diameter within this range improves the dispersibility of the carbon composite material, thereby further enhancing its electromagnetic interference suppression performance. Furthermore, the average fiber length and average fiber diameter of cellulose nanofibers can be measured using a scanning electron microscope (SEM) in the same manner as the average fiber length and average fiber diameter of carbon nanotubes described above.

[0046] Examples of commercially available coupling agents having the aforementioned amine-based functional group and sulfide-based functional group include SUMILINK® 100 (manufactured by Sumitomo Chemical Co., Ltd.). Examples of commercially available cellulose nanofibers include ELLEX-S (manufactured by Daio Paper Corporation).

[0047] If the electromagnetic interference suppression material of this disclosure contains the dispersion aid, the amount thereof may be 0.1 to 30% by mass, 0.2 to 10% by mass, or 0.3 to 5% by mass, based on the total amount of the electromagnetic interference suppression material, from the viewpoint of dispersibility and maintaining thermomechanical properties.

[0048] In addition to the components described above, the electromagnetic interference suppression material disclosed herein may optionally contain, without departing from the gist of this disclosure, other additives commonly used in this type of electromagnetic interference suppression material, such as: release agents such as synthetic waxes, natural waxes, higher fatty acids, and esters of higher fatty acids; colorants such as cobalt blue; modifiers such as silicone oil and silicone rubber; hydrotalcites; ion scavengers; charge control agents; and flame retardants such as phosphazenes. Each of these additives may be used individually or in combination of two or more.

[0049] The content of each of these additives in the electromagnetic interference suppression material of this disclosure may be 0.05 to 30% by mass or 0.2 to 20% by mass, based on the total amount of each additive in relation to the total amount of the electromagnetic interference suppression material.

[0050] [Inorganic substances] The inorganic substances included in the base material are not particularly limited as long as they are inorganic substances used in electronic components, but examples include inorganic substances (A) and inorganic substances (B) described below. These may be used individually, or in combination of two or more types.

[0051] (Inorganic substances (A)) Inorganic material (A) is at least one selected from inorganic fillers such as silica, alumina, magnesium oxide, titanium oxide, barium titanate, silicon nitride, aluminum nitride, silicon carbide, and tungsten carbide; amorphous magnetic metal alloys; Ni-Fe alloys; pure iron, mild steel, silicon steel (Fe-Si alloys), Fe-Al alloys, Fe-Si-Al alloys, Co-Fe alloys, carbonyl iron; magnetic materials such as magnetite and ferrite; and is an inorganic material other than inorganic material (B) described below. The inorganic material (A) may be used together with an organic material. From the viewpoint of reducing the coefficient of thermal expansion and improving the thermal conductivity of the electromagnetic interference suppression material, it may be at least one selected from silica and alumina, or it may be silica. Furthermore, from the viewpoint of further improving the electromagnetic wave absorption performance and electromagnetic interference suppression performance, it may be at least one selected from ferrite and amorphous magnetic metal alloys.

[0052] The shape of the inorganic substance (A) is not particularly limited, but examples include spherical, flake-shaped, fibrous, etc. The shape of the inorganic substance may be spherical or other than spherical.

[0053] The average particle size of the inorganic substance (A) is not particularly limited, but may be 0.1 μm or more and 100 μm or less, 0.2 μm or more and 75 μm or less, or 0.2 μm or more and 50 μm or less. In this specification, the average particle size refers to the volume-average particle diameter, and the average particle size of inorganic material (A) can be calculated as the average value of the major axis of the particles measured using a laser diffraction particle size distribution analyzer.

[0054] If the electromagnetic interference suppression material of this disclosure contains the inorganic substance (A), from the viewpoint of further improving the electromagnetic wave absorption performance and electromagnetic interference suppression performance, the amount of the inorganic substance may be 20 to 95% by mass, 30 to 90% by mass, or 35 to 85% by mass, based on the total amount of the electromagnetic interference suppression material. When the electromagnetic interference suppression material of this disclosure is used as a semiconductor encapsulant, metal foreign matter is removed during the manufacturing process of the semiconductor encapsulant. When metal foreign matter is removed using a magnet, magnetic materials are considered foreign matter and removed, resulting in a lower yield. From this perspective, when the electromagnetic interference suppression material of this disclosure is used as a semiconductor encapsulant, the content of the magnetic material may be 1% by mass or less, 0.5% by mass or less, or 0% by mass, relative to the total amount of the electromagnetic interference suppression material. Furthermore, since the magnetic material has a high specific gravity, the content of the magnetic material may be less than or equal to the above values ​​from the viewpoint of reducing the weight of the resulting molded product.

[0055] (Inorganic substances (B)) Inorganic material (B) is ceramics. The aforementioned ceramics are not particularly limited, but specifically, examples include sintered bodies mainly composed of metal oxides, nitrides, carbides, etc. Examples of metal oxides include alumina, zirconia, and magnesium oxide. Examples of nitrides of the aforementioned metals include aluminum nitride, boron nitride, silicon nitride, and the like. Examples of the aforementioned metal carbides include silicon carbide and boron carbide. The ceramics may be at least one sintered body selected from alumina and aluminum nitride.

[0056] [Method for manufacturing carbon composite materials] The following describes one embodiment of the method for manufacturing the carbon composite material of this disclosure, but this disclosure is not limited to the embodiment described below.

[0057] The carbon composite material according to this disclosure can be manufactured, for example, by coating inorganic particles with a carbon layer.

[0058] (Inorganic particles) Examples of inorganic particles in this disclosure include the inorganic particles described above under [Inorganic Particles]. In this embodiment, when the inorganic particles are coated with a carbon layer by CVD treatment or the like, the original structure may be kept stable during the CVD treatment or the like. For this reason, they may have high heat resistance. The inorganic particles may be materials with uniform particle size, structure, and composition, and may also be materials that can control the average number of graphene layers obtained to four or less in order to achieve a high specific surface area. From this perspective, the inorganic particles may be at least one selected from alumina, silica, magnesium oxide, tungsten carbide, aluminum nitride, and magnetic materials such as magnetic metals, magnetic metal alloys, and magnetic oxides. Furthermore, from the viewpoint of improving electrical insulation performance, they may be alumina or silica, and from the viewpoint of improving thermal conductivity and heat dissipation, they may be magnetic materials, at least one selected from Fe-Si-Al alloys (Sendust), ferrite, and magnetite.

[0059] The average particle size of the inorganic particles is not particularly limited, but may be 0.0005 to 100 μm, 0.1 to 50 μm, or 0.5 to 20 μm. If the average particle size is 0.0005 μm or larger, it is easy to handle and has good carbon coating properties. In addition, the gas permeability of the carbon source is good when coating the carbon source, making uniform carbon coating easier. On the other hand, if the average particle size is 100 μm or smaller, a carbon composite material with a high specific surface area (BET specific surface area) can be obtained.

[0060] The inorganic particles may be used in combination with granular spacers. By using spacers, appropriate voids can be ensured between the particles, preventing the particles from becoming too densely packed and resulting in a large pressure drop. The spacers may be particles with an average particle size of, for example, 100 to 5000 μm. The material of the spacers is not particularly limited as long as it can be sieved after carbon coating, and may be a material that does not decompose at 900 to 1000°C.

[0061] The mixing ratio of the particles to the spacer is not particularly limited, but for example, the mass ratio of (particles:spacer) may be 0.1:10 to 10:10, or 1:10 to 10:10. Within this range, the carbon composite material can be obtained in high yield.

[0062] (Coating with a carbon layer) The method for coating the inorganic particle surface with a carbon layer is not particularly limited, and either a wet or dry method can be applied. From the viewpoint of keeping the average number of graphene layers to four or less, chemical vapor deposition (CVD) or a method in which naphthalene molecules are introduced to the surface of inorganic particles such as silica by chemical modification, followed by calcination, may be used.

[0063] CVD (Chemical Vapor Deposition) is an industrial method used to deposit a carbon layer on inorganic particles by introducing organic compounds. It creates thin films (for example, thin films made of carbon) consisting of specific elements or elemental compositions on substrates such as inorganic particles. Typically, this technique utilizes the fact that energy is supplied to a gas containing raw materials by heat or light, or by creating plasma with high frequency, causing the raw materials to become radicalized and highly reactive through chemical reactions or thermal decomposition, leading to their adsorption and deposition on the substrate.

[0064] The organic compounds used in the CVD method may be gaseous at room temperature or capable of vaporization. Methods of vaporization include heating above the boiling point or reducing the atmosphere. The organic compounds used can be appropriately selected from carbon source materials. In particular, compounds that decompose upon heating may be used, as may compounds that can deposit a carbon layer on the surface of inorganic particles.

[0065] Furthermore, the organic compound used may be an organic compound containing hydrogen, oxygen, nitrogen, boron, sulfur, phosphorus, etc. This organic compound may be an organic compound containing unsaturated or saturated hydrocarbons, or a mixture thereof. The organic compounds used may be unsaturated linear or branched hydrocarbons having double and / or triple bonds, saturated linear or branched hydrocarbons, saturated cyclic hydrocarbons, aromatic hydrocarbons such as benzene and toluene, etc. Alcohols such as methanol and ethanol, or nitrogen-containing compounds such as acetonitrile and acrylonitrile may also be used as organic compounds. Examples of organic compounds include acetylene, methylacetylene, ethylene, propylene, isoprene, cyclopropane, methane, ethane, propane, benzene, toluene, vinyl compounds, ethylene oxide, methanol, ethanol, acetonitrile, and acrylonitrile. One type of organic compound may be used alone, or two or more types may be used in combination. In particular, organic compounds that can penetrate the voids between particles, such as acetylene, ethylene, propylene, methane, and ethane, may be used. From the viewpoint of precipitating highly crystalline carbon, methane, propylene, and benzene may also be used. Furthermore, methane may be used from the viewpoint of obtaining highly crystalline carbon at a high thermal decomposition temperature. The organic compounds used for CVD at higher temperatures and those used for CVD at lower temperatures may be the same or different. For example, acetylene, ethylene, etc. may be used for CVD at low temperatures, while propylene, isoprene, benzene, etc. may be used for CVD at high temperatures.

[0066] When introducing an organic compound onto the inorganic particles, the inorganic particles may be subjected to reduced pressure beforehand, or the system itself may be subjected to reduced pressure. Any method of depositing carbon by CVD may be used. For example, carbon produced by a chemical reaction or thermal decomposition of an organic compound may be deposited (or adsorbed) onto alumina nanoparticles, thereby coating the alumina nanoparticles with a carbon layer.

[0067] The pressure used during CVD processing is not particularly limited and may be, for example, 1 kPa to 200 kPa or 50 to 150 kPa. The heating temperature during CVD processing should be such that a few or fewer carbon layers can be formed on the inorganic particles, and an appropriate temperature can be selected depending on the organic compound used. The heating temperature may be 400 to 1500°C, 450 to 1100°C, or 550 to 950°C. For example, when propylene is used as the organic compound, the temperature may be 700 to 900°C, and when methane is used, the temperature may be 900 to 1100°C. However, a temperature about 50 to 200°C lower than the decomposition temperature of the organic compound is preferable. Heating above the decomposition temperature of the organic compound will result in significant gas-phase carbon deposition, but by doing so as described above, it is possible to prevent uneven carbon deposition between the surface and interior of the inorganic particles, for example, and to deposit carbon uniformly. Furthermore, the heating temperature can be appropriately selected depending on the CVD processing time and / or the pressure in the reaction system. Alternatively, the product may be analyzed, and the temperature required to achieve the desired number of layers may be set based on the results.

[0068] The heating rate during CVD processing is not particularly limited, but it may be 1 to 50°C / min or 5 to 20°C / min. Processing time during CVD processing (predetermined) The CVD treatment time at the heating temperature should be any time required to obtain graphene with an average number of layers of 4 or less, and an appropriate time can be selected depending on the organic compound used and the temperature. For example, the treatment time in CVD may be 5 minutes to 8 hours, 0.5 to 6 hours, or 1 to 5 hours. Alternatively, the product may be analyzed, and the time required for sufficient carbon deposition may be set based on the results.

[0069] CVD treatment may be carried out under reduced pressure, under vacuum, under pressure, or in an inert gas atmosphere. When carried out in an inert gas atmosphere, examples of inert gases include nitrogen, helium, neon, and argon, and nitrogen may be used. In the CVD method, carbon can be easily deposited or adsorbed onto particles in the gas phase by heating while a gaseous organic compound is passed through the particles in contact with the particles together with a carrier gas. The type of carrier gas, flow rate, flow rate, and heating temperature are adjusted as appropriate depending on the type of organic compound used. Examples of carrier gases include the inert gases mentioned above, and may be nitrogen, or a mixture of oxygen gas or hydrogen gas.

[0070] From the viewpoint of keeping the average number of graphene layers to 4 or less, the carrier gas flow rate may be, for example, 0.05 to 1.0 m / min or 0.32 to 0.64 m / min. In addition, the amount of organic compound introduced may be 1 to 30 volume percent or 5 to 20 volume percent relative to the total amount of carrier gas and organic compound.

[0071] As a method for coating the inorganic particles with a carbon layer, an organic compound may be introduced by a wet method such as impregnation and then carbonized. Alternatively, the organic compound may be impregnated and carbonized before introducing the organic compound and performing CVD. As the organic compound to be impregnated, for example, a thermopolymerizable monomer such as furfuryl alcohol, which has a high carbonization yield, can be used. For the impregnation method of the organic compound, known means can be employed, such as using the organic compound as is or mixed with a solvent if it is a liquid, or dissolving it in a solvent and bringing it into contact with the inorganic particles if it is a solid.

[0072] After the first step, the carbon-coated inorganic particles may be heat-treated to carbonize the carbon layer and precipitate highly crystalline carbon on the surface of the inorganic particles. In this way, the resulting carbon composite material will have higher crystallinity and a higher specific surface area. Since carbonization of the carbon layer can also proceed by CVD treatment, the heat treatment may be performed during the CVD treatment or by other methods. The method of heat treatment is not particularly limited, and heat treatment may be performed using a high-frequency induction heating furnace or the like. By the above method, core-shell particles and core-shell connectives, i.e., carbon composite materials, can be obtained in which the surface of inorganic particles is coated with a coating layer made of graphene with an average number of layers of 4 or less.

[0073] [Method for manufacturing electromagnetic interference suppression material] The electromagnetic interference suppression material of this disclosure may be obtained by thoroughly and uniformly mixing a carbon composite material and other components as needed using a mixer or the like, and then kneading it using a disperser, kneader, three-roll mill, twin-screw heated roll, twin-screw heated extrusion kneading device, etc. The kneading process may also be carried out by heating. The temperature at which this occurs may be 70°C to 150°C or 75°C to 120°C.

[0074] The electromagnetic interference suppression material of this disclosure may, for example, be cooled and solidified after the kneading process, and then crushed to an appropriate size using a cutting mill, ball mill, cyclone mill, hammer mill, vibratory mill, cutter mill, grinder mill, speed mill, etc.

[0075] Alternatively, the mixture obtained after the kneading process may be pressed in a molding machine at a temperature of 50°C to 100°C and a pressure of 0.5 MPa to 1.5 MPa to form a sheet.

[0076] The electromagnetic interference suppression material of this disclosure can be used as a radio wave absorbing material, a noise suppression sheet, a semiconductor encapsulant, a encapsulation sheet, a wire coating material, and the like. As one embodiment of the present disclosure, for example, a resin-encapsulated electronic component can be obtained by encapsulating a semiconductor element fixed on a substrate with a semiconductor element encapsulant containing the electromagnetic interference suppression material of the present disclosure. Furthermore, known molding methods are not particularly limited and can be used to obtain electronic components. Low-pressure transfer molding is the most common molding method, but molding by injection molding, casting, compression molding, etc., is also possible.

[0077] For example, in the transfer molding method, a heat treatment may be performed in the molding die using a transfer molding machine at a temperature of 150°C to 200°C for a time of 20 seconds to 200 seconds, the molded product may be removed from the molding die, and a heat treatment to complete the hardening may be performed at a temperature of 150°C to 200°C for 2 hours to 12 hours.

[0078] In the case of compression molding, first, a substrate with a semiconductor element mounted on it is supplied to the upper mold of the molding die, and the electromagnetic interference suppression material of this disclosure is supplied to the cavity of the lower mold. Next, the upper and lower molds are clamped together with the required clamping pressure, thereby immersing the substrate with the semiconductor element mounted on it in the electromagnetic interference suppression material that has been heated and melted in the lower mold cavity. After that, the heated and melted electromagnetic interference suppression material in the lower mold cavity is pressed by the cavity bottom member, and compression molding is performed under reduced pressure and the required pressure is applied. The molding conditions may be a temperature of 120°C to 200°C and a pressure of 2 MPa to 20 MPa. [Examples]

[0079] The present disclosure will now be specifically illustrated by examples, but the present disclosure is not limited in any way by these examples.

[0080] [Manufacturing of carbon composite materials] The details of the inorganic particles listed in Tables 1 and 2 used in the manufacture of the carbon composite material are as follows: • Silica: SO-C1; manufactured by Admatex Co., Ltd., average particle size: 0.3 μm • Alumina: Puralox SBa-200; manufactured by Sasol, average particle size (primary particle diameter): 7nm • Mesoporous silica: SBA-15 (prepared by the method described below) Magnesium oxide: Manufactured by EM Japan Co., Ltd., average particle size (primary particle diameter): 10 nm • Sendust (Fe-Si-Al alloy): Sanyo Special Steel Co., Ltd., average particle size: 40 μm, flattened shape • Ferrite (Mn-Zn type): Powdertech Co., Ltd., average particle size: 5-10 μm

[0081] <Manufacturing Example 1> 2.3 g of 2,3-dihydroxynaphthalene (DN) was dissolved in 5 ml of acetone, and then 0.47 g of dried silica (SO-C1) was added to obtain a mixture. This mixture was stirred at room temperature for 2 hours, and then the acetone was evaporated at 95°C. The residue of the DN and silica mixture was heat-treated at 573°C under a nitrogen stream for 1 hour to react the silica surface with DN, and then heat-treated at 800°C under a nitrogen stream for 4 hours to obtain carbon-coated silica particles (A-1).

[0082] <Manufacturing Example 2> Alumina (Puralox SBa-200) and quartz sand (manufactured by Sendai Wako Pure Chemical Industries, Ltd.) as a spacer were mixed in a mass ratio of 3:20 (alumina nano:quartz sand). The quartz sand was prepared by immersing it in 1M hydrochloric acid for 12 hours, heating it in a muffle furnace in air at 800°C for 2 hours, and then sieving it through a 180 μm sieve. The alumina and quartz sand mixture prepared above was placed in a reaction tube (37 mm inner diameter), and chemical vapor deposition (CVD) using methane as the carbon source was performed. Specifically, under conditions where the N2 gas flow rate was adjusted to 224 ml / min, the alumina and quartz sand mixture prepared above was heated from room temperature to 900°C at a heating rate of 10°C / min, held at 900°C for 30 minutes, and then N2 gas (carrier gas) and methane gas were introduced into the reaction tube, and chemical vapor deposition (CVD) treatment was performed at 900°C for 2 hours. When introducing N2 gas and methane gas into the reaction tube, the amount of methane gas was adjusted to 20% by volume relative to the total amount of N2 gas and methane gas, the flow rate of methane gas was adjusted to 45 ml / min, and the flow rate of N2 gas was adjusted to 179 ml / min. After CVD treatment, the introduction of methane gas was stopped, and the N2 gas flow rate was adjusted to 224 ml / min. The mixture was then held at 900°C for 30 minutes and then cooled to obtain carbon-coated alumina particles (A-2).

[0083] <Manufacturing Example 3> Mesoporous silica (SBA-15) was prepared by the sol-gel method. Specifically, it was prepared by the following method: First, 15 g of surfactant (P-123) was dissolved in 360 mL of pure water in a 500 mL beaker, and 33 g of tetraethoxysilane (TEOS) was added and stirred for 5 minutes. Subsequently, 60 mL of 36% by mass hydrochloric acid was added dropwise over 30 minutes, stirred at 35°C for 20 hours, and then stirred at 95°C for 24 hours. The resulting white precipitate was dried at 80°C for 12 hours, and then calcined under air at 550°C for 6 hours to obtain SBA-15. Next, carbon-coated silica particles (A-3) were obtained using the same procedure as in Production Example 1, except that mesoporous silica (SBA-15) was used instead of silica as the inorganic particle.

[0084] <Manufacturing Example 4> In Production Example 2, carbon-coated magnesium oxide particles (A-4) were obtained using the same procedure as in Production Example 2, except that magnesium oxide was used instead of alumina as the inorganic particle.

[0085] <Manufacturing Example 5> To increase the degree of crystalline order and to form an oxide layer of Si and Al on the surface, Sendust was heated at 700°C for 5 hours in an Ar atmosphere, and then heated at 150°C for 5 hours in air. Next, carbon-coated Sendust particles (A-5) were obtained using the same procedure as in Production Example 1, except that Sendust obtained in the same way was used instead of silica as the inorganic particles.

[0086] <Manufacturing Example 6> In Production Example 2, carbon-coated ferrite particles (A-6) were obtained using the same procedure as in Production Example 2, except that ferrite was used instead of alumina as the inorganic particle.

[0087] [Measurement and evaluation of carbon composite materials] The obtained carbon composite material was subjected to measurement and evaluation of the following items. The results of these measurement and evaluation are summarized in Table 1.

[0088] <Specific surface area (BET specific surface area)> The obtained carbon composite material was vacuum-heated and dried at 150°C for 6 hours. The specific surface area was then determined using a multi-point method (5 points) from nitrogen adsorption isotherms measured with a high-precision automatic gas / vapor adsorption measurement device "BEL SORP MAX" (manufactured by Nippon Bell Co., Ltd.).

[0089] <Carbon load (carbon content in carbon composite materials)> The amount of carbon supported in the obtained carbon composite material was measured using the differential thermal and thermogravimetric simultaneous measurement device "DTG-60 / 60H" (manufactured by Shimadzu Corporation). Specifically, the obtained carbon composite material was heated to 120°C at a rate of 10°C / min under synthetic air flow (50 cc / min) while measuring its mass, held for 30 minutes, then heated to 800°C at a rate of 5°C / min and held for 1 hour, and cooled to 120°C at a rate of -10°C / min and held for 30 minutes. The amount of carbon supported per unit mass was determined from the difference between the average mass held at 120°C before heating to 800°C and the average mass held at 120°C after heating to 800°C.

[0090] <Average number of layers in graphene> The average number of graphene layers was determined using the following formula based on the specific surface area and carbon load obtained by the method described above. Average number of graphene layers = amount of carbon supported per unit area (g / m²) 2 ) / (mass of graphene per unit area [g / m²] 2 ]) Note that "carbon load per unit area (g / m²)" 2 )" is calculated by determining the amount of carbon supported per unit mass of the carbon composite material (g) using the method described above, and the specific surface area (m²) of the inorganic particles possessed by the core-shell particles or core-shell linkage. 2 This is the value obtained by dividing by ( / g).

[0091] <Carbon content (graphene content)> The carbon content in the carbon composite material was determined using the following formula. Carbon content (%) = Carbon surface density of graphene (g / m³) 2 ) × Specific surface area of ​​inorganic particles (m²) of core-shell particles or core-shell conjugates 2 (g) × average number of graphene layers The carbon surface density of graphene is 7.61 × 10⁻⁶. -4 g / m 2 That's what I decided.

[0092] [Table 1]

[0093] [Manufacturing of electromagnetic interference suppression materials] The details of each component listed in Table 2 used in the manufacture of the electromagnetic interference suppression material are as follows: [Organic matter] • Epoxy resin: EPICLON N670; Cresol novolac type epoxy resin; Manufactured by DIC Corporation; Epoxy equivalent: 210 • Phenolic resin: PC-25; Sumitomo Bakelite Co., Ltd. • Hardener: BRG-557; phenol novolac resin; manufactured by Aica Kogyo Co., Ltd. • Curing accelerator: Curazole C17Z; imidazole compound; manufactured by Shikoku Chemicals Co., Ltd. • Flame retardant: Rabitol (phosphophazene-based flame retardant) FP100; manufactured by Mitsui Chemicals Fine Co., Ltd. • Ethylene-ethyl acrylate copolymer: MB-870; manufactured by Nippon Unicar Co., Ltd. Lubricant: Stearic acid; manufactured by NOF Corporation [Inorganic substances] • Silica: FB105; manufactured by Denka Co., Ltd., average particle size: 12 μm • Alumina: DAW07; manufactured by Denka Co., Ltd., average particle size: 8 μm, maximum particle size: 50 μm [Carbon materials] • Carbon black (CB): TPK1227R; manufactured by Cabot, average particle size: 0.1 μm • Carbon nanotubes (CNTs): LUCAN; manufactured by LG, average fiber length: 30 μm, average fiber diameter: 0.02 μm, aspect ratio: 1500 〔others〕 ·Fe-based alloy powder: Fe content: 95wt% (remaining Si, Cr), BET specific surface area: 5m 2 / g

[0094] <Examples 1-7 and Comparative Examples 1-3> Each component, according to the type and amount listed in Table 2, was placed in a Henschel mixer and mixed. The mixture was then placed in a twin-screw roll kneader heated to 110°C and heated and kneaded until uniform. Next, the resulting heated and kneaded material was placed in a cold roll, stretched into a sheet, and then pulverized to obtain an electromagnetic interference suppression material composition. The obtained electromagnetic interference suppression material composition was compression-molded into molded bodies with a thickness of 0.5 mm, 1.0 mm, or 25 mm (temperature: 175°C, pressure: 10 MPa) to obtain an electromagnetic interference suppression material.

[0095] <Examples 8-10> Each component of the type and amount listed in Table 2 was extruded into a 0.5 mm thick tube using an extruder heated to 180°C, and then rolled into a plate using a rolling mill to obtain an electromagnetic interference suppression material composition. The obtained electromagnetic interference suppression material composition was compression molded into a molded body with a thickness of 0.5 mm, 1.0 mm, or 25 mm (temperature: 190°C, pressure: 15 MPa) to obtain an electromagnetic interference suppression material.

[0096] <Example 11> 56 parts by mass of carbon-coated alumina particles (A-2) obtained in Production Example 2 were mixed with 104 parts by mass (solid content concentration 43%) of a mixed solution containing phenolic resin, methanol, and acetone. A 0.15 mm thick sheet was then formed using the doctor blade method. Multiple sheets were laminated and pressed, and then heat-treated at 150°C for 2 hours to obtain a 0.5 mm thick sheet sample (20 mm × 20 mm).

[0097] <Example 12> In Example 11, a sheet sample was obtained using the same procedure as in Example 11, except that a 0.15 mm thick sheet was fabricated using the doctor blade method, multiple sheets were laminated and pressed, and then heat-treated at 150°C for 2 hours to obtain a 0.9 mm thick sheet sample (20 mm x 20 mm).

[0098] <Comparative Example 4> After mixing 70 parts by mass of Fe-based alloy powder with 150 parts by mass of a mixed solution containing phenolic resin, methanol, and acetone (solid content concentration 43%), a 0.15 mm thick sheet was formed using the doctor blade method. Multiple sheets were then laminated and pressed, and the mixture was heat-treated at 150°C for 2 hours to obtain a 0.5 mm thick sheet sample (20 mm × 20 mm). [Table 2]

[0099] [Measurement and evaluation of electromagnetic interference suppression materials] The electromagnetic interference suppression materials obtained in Examples 1-10 and Comparative Examples 1-3 were measured and evaluated for thermal conductivity, thermal expansion coefficient, volume resistivity, electromagnetic wave absorption performance (frequency 10 GHz, near-field measurement system), and electromagnetic wave absorption performance (frequency 5 GHz, far-field measurement system). The results of these measurements and evaluations are summarized in Table 3. For the sheet samples (electromagnetic interference suppression materials) obtained in Examples 11 and 12, and Comparative Example 4, surface resistance, transmission attenuation ratio (Rtp), and voltage standing wave ratio (VSWR) were measured and evaluated. The results of these measurements and evaluations are summarized in Table 4.

[0100] <Thermal conductivity> In the example, a 1.0 mm thick molded body of electromagnetic interference suppression material was obtained, and one side was irradiated with laser light to provide heat flow energy with periodically modulated intensity. A temperature sensor was used to detect the phase difference of the temperature response on the other side of the molded body, and the thermal diffusivity and specific heat were determined, and the thermal conductivity was calculated.

[0101] <Coefficient of thermal expansion> Using the electromagnetic interference suppression material, which is a molded body with a thickness of 1.0 mm obtained in the example, the temperature was raised from room temperature (25°C) to 300°C using the TMA method with a thermal analyzer "SSC / 5200" (manufactured by Seiko Instruments Inc.) at a heating rate of 5°C / min. From the resulting TMA chart, the slope of the part that is closest to a straight line between 25 and 60°C was taken as the coefficient of thermal expansion.

[0102] <Volume Resistivity> Using the 1.0 mm thick molded electromagnetic interference suppression material obtained in the examples, the volume resistivity at 150°C was measured in accordance with JIS K-6911:2006.

[0103] <Electromagnetic wave absorption performance (frequency 10 GHz, near-field measurement system)> An electromagnetic interference suppression material molded to a thickness of 0.5 mm was placed between a high-frequency oscillation device and a receiving antenna. When electromagnetic waves with a frequency of 10 GHz were generated, the electromagnetic wave intensity was measured with and without the molded material, and the ratio (electromagnetic wave intensity when electromagnetic waves are absorbed by the electromagnetic interference suppression material / electromagnetic wave intensity when the electromagnetic interference suppression material is not present) was defined as the electromagnetic wave absorption performance in dB units. The electromagnetic wave intensity was measured in accordance with "IEICE Transactions on Electronics, Information and Communication Engineers, Vol. J97-B, No. 3, pp. 279-285".

[0104] <Electromagnetic wave absorption performance (frequency 5GHz, far-field measurement system)> A 1mm thick copper plate (600mm x 600mm) was placed on top of an anti-reflective radio wave absorber, and a 25mm thick electromagnetic interference suppression material (440mm x 440mm) was placed on the metal plate. Next, an antenna was attached to a network analyzer via a cable, and electromagnetic waves with a frequency of 5GHz were transmitted from one antenna. The electromagnetic interference suppression material or the radio wave absorber and the metal plate placed beneath it were reflected, and the electromagnetic wave intensity was measured by receiving the signal with the other antenna. In addition, the electromagnetic wave intensity was measured by radiating electromagnetic waves in the same manner as above, without placing the electromagnetic interference suppression material on the metal plate. The ratio of these results (electromagnetic wave intensity when electromagnetic waves are absorbed by the electromagnetic interference suppression material / electromagnetic wave intensity when there is no electromagnetic interference suppression material) was defined as the electromagnetic wave absorption performance in dB. The electromagnetic wave intensity was measured in accordance with "Kagoshima Prefectural Industrial Technology Center Research Report No. 15 (2001), pp. 53-61".

[0105] <Surface resistance> In accordance with JIS K-6911:2006, the surface resistance was measured using a resistance meter probe at 1 cm intervals.

[0106] <Transmission attenuation rate (Rtp) and voltage standing wave ratio (VSWR)> In accordance with the IEC 62333-2 Transmission Attenuation Ratio measurement method, the Rtp and voltage standing wave ratio (VSWR) of sheet samples were measured in the frequency bands listed in Table 4, except that a coplanar transmission line with a line width of 0.6 mm was used instead of the microstrip line used in the method.

[0107] [Table 3]

[0108] [Table 4]

[0109] As shown in Table 3, the electromagnetic interference suppression materials of Examples 1 to 10 exhibit good radio wave absorption performance. Furthermore, their high volume resistivity indicates good electromagnetic interference suppression performance in the near field. In addition, they also possess high thermal conductivity.

[0110] As shown in Table 4, the sheet samples of Examples 11 and 12 showed low Rtp values ​​at 3 GHz, while their Rtp values ​​at 30 GHz and 45 GHz were both high, exceeding 20 dB. On the other hand, the sheet sample of Comparative Example 4 showed a larger Rtp at 3 GHz compared to the sheet samples of Examples 11 and 12, and a smaller value at 45 GHz compared to the sheet samples of Examples 11 and 12. While the voltage standing wave ratio (VSWR) was 1.5 or less for all samples, the values ​​for the sheet samples in Examples 11 and 12 at 30 GHz and 5 GHz were a very small 1.1. Based on these results, the sheet samples of Examples 11 and 12 exhibit excellent frequency selectivity and demonstrate a significant electromagnetic interference suppression effect in the high-frequency region above 30 GHz without deterioration of VSWR. Therefore, the configuration of this disclosure is an effective means for suppressing electromagnetic interference occurring in the microwave band (3 GHz to 30 GHz) and high-frequency regions exceeding 30 GHz, and can be said to be effective as a high-frequency noise suppression sheet for use in the near field, such as inside a mobile phone.

Claims

1. An electromagnetic interference suppression material comprising a base material containing organic and inorganic materials, and a carbon composite material, The aforementioned organic material is a thermosetting resin. The content of the aforementioned organic matter is 0.1 to 40% by mass. The carbon composite material is at least one selected from core-shell particles, in which the surface of inorganic particles is coated with a coating layer of graphene with an average number of 4 or fewer layers, and core-shell assemblies, in which the surface of an assembly of inorganic particles is coated with a coating layer of graphene with an average number of 4 or fewer layers. Volume resistance is 10 ３ Electromagnetic interference suppression material with an impedance of Ω·cm or greater.

2. The electromagnetic interference suppression material according to claim 1, wherein the average particle size of the inorganic particles in the core-shell particles and the inorganic particles in the core-shell assembly is 100 μm or less.

3. The electromagnetic interference suppressing material according to claim 1 or 2, wherein the graphene content in the electromagnetic interference suppressing material is 0.001 to 30% by mass relative to the entire electromagnetic interference suppressing material.

4. The electromagnetic interference suppression material according to claim 1 or 2, wherein the inorganic particles in the core-shell particles and the inorganic particles in the core-shell assembly include at least one selected from alumina, silica, magnesium oxide, tungsten carbide, and aluminum nitride.

5. The electromagnetic interference suppression material according to claim 1 or 2, wherein the inorganic particles in the core-shell particles and the inorganic particles in the core-shell assembly are magnetic materials.

6. The electromagnetic interference suppression material according to claim 5, wherein the magnetic material comprises at least one selected from magnetic metals, magnetic metal alloys, and magnetic oxides, and the magnetic oxide is at least one selected from ferrite and magnetite.

7. The electromagnetic interference suppression material according to claim 6, wherein the magnetic metal has a flattened shape.

8. The electromagnetic interference suppression material according to claim 1 or 2, wherein the inorganic material is a ceramic.

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