Electromagnetic Interference Suppression Materials

Abstract

The present invention provides an electromagnetic interference suppressing material which comprises a powdered carbon material and a base material containing at least one substance that is selected from among organic materials and inorganic materials, wherein: the powdered carbon material is composed of at least one shell-like body that is selected from among a first shell-like body which is a hollow particle having one or more pores, and a second shell-like body which has a plurality of pores, while having a shape where hollow particles are connected with each other; and respective shell parts of the first shell-like body and the second shell-like body are formed of a graphene that has an average number of layers of 4 or less.

Description

[Technical field]

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

[0002] In recent years, various measures have been taken to reduce electromagnetic interference, such as malfunction of equipment due to electromagnetic noise, information leakage, and reduced information communication speed due to interference. Methods of blocking electromagnetic waves by reflecting them or absorbing electromagnetic waves have been proposed as means of reducing electromagnetic interference.

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

[0004] [Patent Document 1] JP 2001-68889 A [Patent Document 2] JP 2005-57093 A [Patent Document 3] JP 2012-209515 A Summary of the Invention [Problem to be solved by the invention]

[0005] Conventionally, many proposals have been made for the purpose of reducing electromagnetic interference, such as the electromagnetic wave shielding materials, radio wave absorbers, and electromagnetic wave absorbing sheets described in the above Patent Documents 1 to 3. However, with the recent increase in performance and diversification of communication devices, there are cases where the reduction in electromagnetic interference is insufficient, and further improvements have been required. Furthermore, the method of blocking electromagnetic waves by reflecting them using metal or the like has the problem that auto-poisoning is unavoidable.

[0006] The present disclosure has been made in view of the above circumstances, and has an object to provide an electromagnetic interference suppression material that has excellent electromagnetic wave absorption performance and electromagnetic interference suppression performance, and is more effective at reducing electromagnetic interference. [Means for solving the problem]

[0007] As a result of intensive research aimed at solving the above problems, the present inventors have found that an electromagnetic interference suppression material containing a base material containing at least one type selected from an organic substance and an inorganic substance, and a specified powdered carbon material, has good electromagnetic wave absorption performance and electromagnetic interference suppression performance, and is more effective at reducing electromagnetic interference. The present disclosure was completed based on this finding.

[0008] That is, the present disclosure relates to the following: [1] An electromagnetic interference suppression material comprising a base material containing at least one selected from an organic material and an inorganic material, and a powdered carbon material, the powdered carbon material is at least one selected from a first shell-shaped body which is a hollow particle having one hole, and a second shell-shaped body which is a shape in which hollow particles are connected and has a plurality of holes; an electromagnetic interference suppression material, wherein the shell portions of the first shell-shaped bodies and the second shell-shaped bodies are made of graphene having an average number of layers of 4 or less; [2] The specific surface area of ​​the powdered carbon material is 1300 m 2 / g or more. [3] The electromagnetic interference suppression material according to [1] or [2] above, in which the pores of the first shell-shaped bodies and the pores of the second shell-shaped bodies each have a volume of 1.3 cc / g or more. [4] Volume resistivity is 10 3 The electromagnetic interference suppressing material according to any one of the above [1] to [3], which has a resistivity of Ω·cm or more. [5] The electromagnetic interference suppressing material according to any one of the above [1] to [4], wherein the powdered carbon material has an average particle size of 200 μm or less. [6] The electromagnetic interference suppressing material according to any one of the above [1] to [5], wherein the organic matter is an epoxy resin. [7] The electromagnetic interference suppressing material according to any one of the above [1] to [5], wherein the inorganic material is a ceramic. [8] The electromagnetic interference suppressing material according to any one of the above [1] to [7], wherein the organic material or the inorganic material is a foam. [9] The electromagnetic interference suppressing material according to any one of the above [1] to [8], wherein the powdered carbon material content is 0.01 to 95 mass %.

[10] The electromagnetic interference suppressing material according to any one of the above [1] to [9], wherein the powdery carbon material is present on the surface of a base material containing at least one selected from the group consisting of organic substances and inorganic substances.

[11] A semiconductor element encapsulation material comprising the electromagnetic interference suppression material according to any one of the above [1] to [7]. Effect of the Invention

[0009] According to the present disclosure, it is possible to provide an electromagnetic interference suppression material that has excellent electromagnetic wave absorption performance and electromagnetic interference suppression performance, and is more effective at reducing electromagnetic interference. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, the present disclosure will be described in detail with reference to one embodiment. In this specification, the expression "XX to YY" means "XX or more and YY or less." In addition, in this specification, the lower limit value and the upper limit value described in stages for a numerical range (for example, a range of content, etc.) can be independently combined. In addition, in the numerical range described in this specification, the upper limit value or the lower limit value of the numerical range may be replaced with a value shown in the examples. In this specification, the term "electromagnetic interference suppressing material" refers to a material that can attenuate nearby electromagnetic fields and electromagnetic waves by utilizing loss characteristics (magnetic loss, dielectric loss, electrical resistance, etc.). In this specification, "graphene" means "a graphene having 10 or fewer layers of sp 2 "A sheet-like substance of bonded carbon atoms." In this specification, the "average number of layers" of graphene is a value calculated by the following formula. Specifically, it is calculated by the method described in the examples below. Average number of graphene layers = 2627 (m 2 / g) / specific surface area (m 2 / g) The specific surface area refers to a BET specific surface area, and is a value obtained by measurement by a multipoint BET method using nitrogen adsorption. In this specification, a hollow particle refers to a particle having a shell, the inside of which is surrounded by the shell and has a cavity.

[0011] [Electromagnetic interference suppression materials] The electromagnetic interference suppression material of the present disclosure includes a base material containing at least one selected from an organic material and an inorganic material, and a powdered carbon material, the powdered carbon material being at least one selected from first shell-shaped bodies which are hollow particles having one hole, and second shell-shaped bodies which are in the form of connected hollow particles and have multiple holes, and the shells of the first shell-shaped bodies and the second shell-shaped bodies are made of graphene with an average number of layers of 4 or less. When the powdered carbon material is at least one selected from the first shell-shaped bodies and the second shell-shaped bodies, and the shells of the first shell-shaped bodies and the second shell-shaped bodies are made of graphene with an average number of layers of 4 or less, the resulting electromagnetic interference suppression material has good electromagnetic wave absorption performance and electromagnetic interference suppression performance, and is better at reducing electromagnetic interference. The reason for this is unclear, but is thought to be as follows.

[0012] The powdered carbon material of the present disclosure is a hollow particle, and the shell of the hollow particle is made of graphene having an average number of layers of 4 or less. In other words, the powdered carbon material of the present disclosure is a shell-shaped graphene laminate composed of three-dimensionally continuous graphene sheets having an average number of layers of 4 or less. Therefore, the powdered carbon material has a large specific surface area as a carbon material, and has high radio wave absorption performance per unit volume. Furthermore, the powdered carbon material can improve the volume resistance compared to the case where the same amount of other carbon materials is contained. It is considered that the powdered carbon material of the present disclosure has a large specific surface area and has an effect of improving volume resistance, and thus, by containing the powdered carbon material of the present disclosure, the electromagnetic wave absorption performance and the electromagnetic interference suppression performance are improved.

[0013] From the viewpoint of increasing the specific surface area of ​​the powdered carbon material and further improving the electromagnetic wave absorption performance and the electromagnetic interference suppression performance, the shell portions of the first shell-shaped body and the second shell-shaped body may be made of graphene having an average layer number of less than 4, may be made of graphene having an average layer number of 3 or less, may be 2.5 or less, may be 2.0 or less, or may be 1.9 or less.

[0014] In one embodiment of the present disclosure, the electromagnetic interference suppression material has a volume resistivity of 10 3 It may be 10 Ω·cm or more. 6 It may be 10 Ω·cm or more. 7 The upper limit is not particularly set, but it is preferably 10 16 It may be Ω·cm or less.

[0015] The powdered carbon material of the present disclosure may be present in an electromagnetic interference suppressing material, or may be present on the surface of a base material containing at least one selected from the organic and inorganic substances described above.

[0016] <Powdered carbon materials> The powdered carbon material of the present disclosure is at least one type selected from first shell-shaped bodies which are hollow particles having one hole, and second shell-shaped bodies which are hollow particles connected together and have a plurality of holes, and the shells of the first shell-shaped bodies and the second shell-shaped bodies are made of graphene having an average number of layers of 4 or less.

[0017] The first shell of the present disclosure is a hollow particle having one pore. The average pore size of the pores in the first shell-shaped bodies may be 0.5 to 100 nm, 0.7 to 50 nm, or 1.0 to 20 nm. The average pore size of the pores in the first shell-shaped body and the second shell-shaped body is a value calculated from the following formula, assuming cylindrical pores. Average pore size = 4 × pore volume / specific surface area (m 2 / g) The pore volume is the value per mass of material obtained by measuring a nitrogen adsorption isotherm and determining the amount of adsorption at a relative pressure (P / P0) of 0.96. The specific surface area refers to the BET specific surface area, and is the value obtained by measuring with the BET multipoint method using nitrogen adsorption.

[0018] The second shell of the present disclosure has a shape of interconnected hollow particles and has a plurality of pores. The number of holes in the second shell-shaped body is not particularly limited as long as there are multiple holes. The average pore size of each pore in the second shell-shaped body may be 0.5 to 100 nm, 0.7 to 50 nm, or 1.0 to 20 nm.

[0019] The average particle size of the first shell-like bodies may be considered to be the same as the average pore size of the pores of the first shell-like bodies described above, since the shell thickness is very thin.

[0020] From the viewpoint of ease of manufacture, the average particle size of the second shell-shaped bodies may be 1.0 nm or more, 2.0 nm or more, or 5.0 nm or more, and from the viewpoint of further improving the electromagnetic wave absorption performance and electromagnetic interference suppression performance, it may be 1000 nm or less, 500 nm or less, or 200 nm or less. The average particle size of the second shell-shaped bodies can be estimated by using a laser diffraction particle size distribution analyzer.

[0021] The average particle size of the powdered carbon material may be 200 μm or less from the viewpoint of further improving the electromagnetic wave absorption performance and the electromagnetic interference suppression performance. In this specification, the "average particle size of the powdered carbon material" refers to the average particle size of the primary particles when the powdered carbon material is not aggregated and is in the form of primary particles, and refers to the average particle size of the secondary particles when the powdered carbon material is aggregated and forms secondary particles. The average particle size of the powdered carbon material is measured by calculation from the pore volume and specific surface area, by estimation using a laser diffraction particle size distribution analyzer, or by calculation as the average particle size of particles observed in 20 to 100 fields of view using a scanning electron microscope (SEM) or a transmission electron microscope (TEM). The term "particle size" refers to the maximum distance between any two points on the contour of a particle that passes through the center of the particle.

[0022] When the powdered carbon material is not aggregated and is in the form of primary particles, the average particle size (primary particles) of the powdered carbon material may be 1 nm or more, 5 nm or more, or 10 nm or more from the viewpoint of ease of production, and may be 1000 nm or less, 500 nm or less, or 100 nm or less from the viewpoint of further improving the electromagnetic wave absorption performance and the electromagnetic interference suppression performance.

[0023] When the powdered carbon material aggregates to form secondary particles, the average particle size (secondary particles) of the powdered carbon material may be 0.1 μm or more, 1.0 μm or more, or 5.0 μm or more from the viewpoint of ease of production, and may be 200 μm or less, 100 μm or less, 50 μm or less, or 20 μm or less from the viewpoint of further improving the electromagnetic wave absorption performance and the electromagnetic interference suppression performance.

[0024] The specific surface area of ​​the powdered carbon material is set to 657 m from the viewpoint of further improving the electromagnetic wave absorption performance and the electromagnetic interference suppression performance. 2 / g or more, and 2 / g or more, and 2 / g or more, and 2 / g or more, and 2 From the viewpoint of ease of manufacture, 2627m 2 / g or less, and 2 / g or less, and 2 / g or less, and 2 / g or less. The specific surface area refers to a BET specific surface area, and is a value measured by a BET multipoint method using nitrogen adsorption.

[0025] From the viewpoint of further improving the electromagnetic wave absorption performance and the electromagnetic interference suppression performance, the volume of the pores of the first shell-shaped body and the pores of the second shell-shaped body may be 1.0 cc / g or more, 1.3 cc / g or more, 1.6 cc / g or more, 10.0 cc / g or less, 9.0 cc / g or less, or 8.0 cc / g or less. If the pore volume is 1.0 cc / g or more, a higher specific surface area can be obtained. The pore volume is a value obtained by performing nitrogen adsorption isotherm measurement and determining from the amount of adsorption at a relative pressure (P / P0) of 0.96.

[0026] The powdered carbon material of the present disclosure is mainly composed of carbon. Here, "mainly composed of carbon" means that the carbon content in the powdered carbon material is 50 mass% or more. The carbon content in the powdered carbon material may be 80 mass% or more, 95 mass% or more, or 98 mass% or more.

[0027] In the present disclosure, the content (mass %) of the powdered carbon material in the electromagnetic interference suppression material is not particularly limited because it varies greatly depending on the application and the base material, but may be 0.01 to 95 mass % based on the total amount of the electromagnetic interference suppression material from the viewpoint of further improving the electromagnetic wave absorption performance and the electromagnetic interference suppression performance.

[0028] When the electromagnetic interference suppression material of the present disclosure is in the form of a molded body, the content (mass %) of the powdered carbon material in the electromagnetic interference suppression material may be 0.01 to 95 mass %, 0.01 to 20 mass %, or 0.05 to 10 mass % relative to the total amount of the electromagnetic interference suppression material, from the viewpoint of further improving the electromagnetic wave absorption performance and the electromagnetic interference suppression performance. The molded body refers to a molded body produced by putting the material in a mold such as a casting mold or a metal die.

[0029] When the electromagnetic interference suppression material of the present disclosure is in the form of a foam, the content (mass %) of the powdered carbon material in the electromagnetic interference suppression material may be 0.05 to 20 mass %, 0.1 to 10 mass %, or 0.2 to 5 mass %, relative to the total amount of the electromagnetic interference suppression material, from the viewpoint of further improving the electromagnetic wave absorption performance and the electromagnetic interference suppression performance.

[0030] [Graphene] The graphene of the present disclosure is a sheet-like substance having a hexagonal lattice structure in which carbon atoms are bonded. The graphene may be in a single-layer state having a layer thickness of one carbon atom, or in a multi-layer state of two or more layers. In addition to carbon atoms, the graphene may contain oxygen atoms, hydrogen atoms, nitrogen atoms, boron atoms, etc.

[0031] The graphene content in the first shell-shaped body and the second shell-shaped body is not particularly limited, but from the viewpoint of further improving the electromagnetic wave absorption performance and the electromagnetic interference suppression performance, it may be 90% by mass or more, 95% by mass or more, or 98% by mass or more.

[0032] <Base material> The base material of the present disclosure contains at least one selected from an organic material and an inorganic material. The base material may contain only an organic material, may contain only an inorganic material, or may contain an organic material and an inorganic material.

[0033] [Organic matter] The organic matter contained in the base material is not particularly limited, but examples thereof include thermosetting resins and thermoplastic resins. Examples of the thermosetting resin include epoxy resin, phenol resin, and imide resin. Examples of the thermoplastic resin include polyamide resin and polycarbonate. In one embodiment of the present disclosure, the organic matter may be a molded body from the viewpoint of reducing moisture permeability, and in another embodiment, it may be a foam from the viewpoint of improving electromagnetic absorption ability and reducing weight due to an increase in surface area. Examples of foams include foamed polyurethane, foamed polystyrene, foamed polyvinyl chloride, foamed polyethylene, foamed polypropylene, and foamed polyethylene terephthalate. From the viewpoint of improving electromagnetic absorption ability and reducing weight due to an increase in surface area, it may be foamed polyurethane.

[0034] The organic matter may be a thermosetting resin from the viewpoint of the reliability of the molded article using the electromagnetic interference suppression material, or may be an epoxy resin or an imide resin from the viewpoint of the electrical insulation and heat resistance of the molded article using the electromagnetic interference suppression material. From the viewpoints of ease of production, durability, weather resistance, etc., the organic matter may be a polyurethane, or in the case of outdoor use, a polycarbonate-based polyurethane having good hydrolysis resistance. The organic substances may be used alone or in combination of two or more.

[0035] In the present disclosure, the epoxy resin used as the organic substance is not particularly limited in terms of molecular structure, molecular weight, etc., so long as it has two or more epoxy groups in one molecule and is generally used in electronic components. Examples of the epoxy resin include aliphatic epoxy resins such as phenol novolac epoxy resins, cresol novolac epoxy resins, and dicyclopentadiene derivatives, and aromatic epoxy resins such as biphenyl, biphenyl aralkyl, naphthyl, and bisphenol. These epoxy resins may be used alone or in combination of two or more. There is no particular restriction on the nature of the epoxy resin, and it may be liquid or solid at room temperature (25°C). For example, the epoxy resin may be a solid cresol novolac epoxy resin. The solid cresol novolac epoxy resin is available as a commercially available product, and examples of the solid cresol novolac epoxy resin include N670 (manufactured by DIC Corporation). For example, the epoxy resin may be a liquid epoxy resin, and specific examples of the liquid bisphenol A epoxy resin include bisphenol F epoxy resin. The liquid bisphenol A epoxy resin is available as a commercially available product, and examples of the liquid bisphenol A epoxy resin include Epomic (registered trademark) R140 (manufactured by Mitsui Chemicals, Inc.). In the present disclosure, a liquid epoxy resin refers to an epoxy resin that is liquid at 25°C.

[0036] The epoxy equivalent of the epoxy resin may be 140 or more from the viewpoint of thermomechanical properties of an article formed using the electromagnetic interference suppression material. Also, from the viewpoint of electromagnetic wave absorption performance, it may be 200 or more. The upper limit of the epoxy equivalent may be 400 or less, or 380 or less from the viewpoint of thermomechanical properties.

[0037] The epoxy resin is (R 1 and a polyoxyalkylene structure represented by (R 2 The epoxy resin may be an epoxy resin having a polyoxyalkylene structure represented by the formula (I)n. Here, R 1 and R 2each independently represents an alkylene group having one or more carbon atoms. m+n may be 1 or more and 50 or less, or 1 or more and 20 or less. m may be 0 or more and 49 or less, or 0 or more and 19 or less. n may be 1 or more and 50 or less, or 1 or more and 20 or less.

[0038] R 1 and R 2 Examples of the alkylene group represented by the formula (I) include alkylene groups having 1 to 6 carbon atoms, specifically, methylene, ethylene, trimethylene, propylene, tetramethylene, hexamethylene, 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 may be the same alkylene group or may be alkylene groups having different carbon numbers. 2 In the O group, multiple R 2 may be the same alkylene group or may be alkylene groups having different carbon numbers.

[0039] Examples of epoxy resins having a polyoxyalkylene structure include liquid epoxy resins having a bisphenol A skeleton, polyethylene glycol diglycidyl ether, etc. Commercially available liquid epoxy resins having a bisphenol A skeleton include Likaresin BEO-60E (manufactured by New Japan Chemical Co., Ltd.) represented by the following general formula (1), and commercially available polyethylene glycol diglycidyl ethers include Epolite 400E (manufactured by Kyoeisha Chemical Co., Ltd.), which contains as its main component a compound represented by the following general formula (2).

[0040] [ka]

[0041] [ka]

[0042] In the present disclosure, examples of imide resins used as organic substances include bisallylnadimide, etc. Bisallylnadimide is available as a commercially available product, and examples of such products include BANI-M (manufactured by Maruzen Petrochemical Co., Ltd.) and BANI-X (manufactured by Maruzen Petrochemical Co., Ltd.).

[0043] In the present disclosure, the polyurethane used as the organic material is not particularly limited in terms of molecular structure, etc., as long as it is one that is generally used in electronic components. In addition, foamed polyurethane is generally obtained by reacting and foaming polyols, polyisocyanates, and a foaming agent as essential components and adding a catalyst, a foaming assistant, etc. to these.

[0044] Examples of the polyol component include polyester polyol, polyether polyol, polycarbonate polyol, polymer polyol, etc. These polyols may be used alone or in combination of two or more kinds. Examples of the polyester polyol include polyester polyols having an aliphatic dicarboxylic acid having 4 to 20 carbon atoms, such as adipic acid, suberic acid, sebacic acid, or brassylic acid, or an aromatic dicarboxylic acid, such as terephthalic acid or isophthalic acid, as an acid component, and an aliphatic diol having 1 to 6 carbon atoms, such as ethylene glycol, or an ether glycol, such as diethylene glycol or dipropylene glycol, as a polyol component (alcohol component).

[0045] As the isocyanate component, various known polyfunctional aliphatic, alicyclic and aromatic isocyanates can be used. For example, tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), dicyclohexylmethane diisocyanate, triphenyl diisocyanate, xylene diisocyanate (XDI), polymethylene polyphenylene polyisocyanate, hexamethylene diisocyanate, isophorone diisocyanate (IPDI), orthotoluidine diisocyanate, naphthylene diisocyanate, xylylene diisocyanate, lysine diisocyanate, etc. can be mentioned, and these may be used alone or in combination of two or more. Examples of the foaming agent include water, fluorocarbon, and pentane.

[0046] In one embodiment of the present disclosure, when the organic material is in the form of a molded body, the content (mass %) of the organic material in the electromagnetic interference suppression material may be 1 to 40 mass %, 3 to 30 mass %, 4 to 25 mass %, or 5 to 20 mass %, relative to the total amount of the electromagnetic interference suppression material, from the viewpoint of further improving the electromagnetic wave absorption performance and the electromagnetic interference suppression performance.

[0047] In another embodiment of the present disclosure, when the organic material is a foam, the content (mass %) of the organic material in the electromagnetic interference suppression material may be 80 to 99.95 mass %, 90 to 99.9 mass %, or 95 to 99.8 mass %, relative to the total amount of the electromagnetic interference suppression material, from the viewpoint of further improving the electromagnetic wave absorption performance and the electromagnetic interference suppression performance.

[0048] When the organic substance contains a thermosetting resin, the electromagnetic interference suppressing material of the present disclosure may further contain a curing agent, a curing accelerator, and the like. Examples of the curing agent include aliphatic amines, aromatic amines, dicyandiamide, dihydrazide compounds, acid anhydrides, phenolic resins, etc. These may be used alone or in combination of two or more. Examples of the curing accelerator include organic peroxides such as dicumyl peroxide and dibutyl peroxide; imidazole compounds such as 2-methylimidazole and 2-ethylimidazole; organic phosphorus 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 tetraphenylboron compounds such as 2-ethyl-4-methylimidazole tetraphenylborate. These may be used alone or in combination of two or more. In one embodiment of the present disclosure, when the electromagnetic interference suppression material of the present disclosure contains a curing agent, the content of the curing agent may be from 0% by mass to 150.0% by mass, from 0% by mass to 120% by mass, or from 0% by mass to 100% by mass, relative to 100% by mass of the thermosetting resin. In another embodiment of the present disclosure, when the electromagnetic interference suppression material of the present disclosure contains a curing agent, the content of the curing agent may be from 1.0 mass % to 20.0 mass % inclusive, from 2.0 mass % to 18.0 mass % inclusive, or from 3.0 mass % to 15.0 mass % inclusive, relative to the total amount of the electromagnetic interference suppression material. Furthermore, when the electromagnetic interference suppression material of the present disclosure contains a curing accelerator, the amount of the curing accelerator may be from 0.01% by mass to 10.0% by mass, from 0.05% by mass to 5.0% by mass, or from 0.1% by mass to 3.0% by mass, relative to the total amount of the electromagnetic interference suppression material.

[0049] The electromagnetic interference suppression material of the present disclosure may further include a dispersion aid. The dispersion aid may be any material capable of stably dispersing fine particles in a matrix resin, and generally includes a surfactant having functional groups with different reactivity in one molecule and a coupling agent. Examples of the dispersion aid include surfactants such as anionic surfactants such as carboxylates and cationic surfactants such as quaternary ammonium salts; coupling agents having amine functional groups and sulfide functional groups, and cellulose nanofibers.

[0050] The cellulose nanofibers are bipolar, extremely small solids that act as surfactants to improve the dispersibility of the filler. 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 from 1 μm to 100 μm, or from 5 μm to 50 μm, from the viewpoints of workability and fluidity. The average fiber diameter of the cellulose nanofibers, including aggregates, may be 1 nm or more and 1000 nm or less, or 4 nm or more and 500 nm or less. When the average fiber diameter is in the above range, the dispersibility of the powdered carbon material can be increased, and the electromagnetic interference suppression performance can be further improved. 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 for measuring the average fiber length and average fiber diameter of carbon nanotubes described above.

[0051] An example of a commercially available coupling agent having an amine functional group and a sulfide functional group is SUMILINK (registered trademark) 100 (manufactured by Sumitomo Chemical Co., Ltd.). An example of a commercially available cellulose nanofiber is ELLEX-S (manufactured by Daio Paper Corporation).

[0052] When the electromagnetic interference suppression material according to the present disclosure contains the dispersion aid, the content thereof may be 0.1 to 30 mass %, 0.2 to 10 mass %, or 0.3 to 5 mass %, relative to the total amount of the electromagnetic interference suppression material, from the viewpoints of dispersibility and retention of thermomechanical properties.

[0053] In addition to the above components, the electromagnetic interference suppression material of the present disclosure may contain additives, as necessary, that are generally blended into 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 oils and silicone rubbers; hydrotalcites; ion scavengers; charge control agents; and flame retardants, such as phosphazene, within the scope of the gist of the present disclosure. Each of these additives may be used alone or in combination of two or more.

[0054] The content of each of these additives in the electromagnetic interference suppressing material of the present disclosure may be, in terms of the total amount of the additives, 0.05 to 30.0 mass %, or 0.2 to 20.0 mass %, relative to the total amount of the electromagnetic interference suppressing material.

[0055] [Inorganic substances] The inorganic substance contained in the base material is not particularly limited as long as it is an inorganic substance used in electronic components, and examples of the inorganic substance include inorganic substance (A) and inorganic substance (B) described below. These may be used alone or in combination of two or more.

[0056] (Inorganic substances (A)) The inorganic substance (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; soft magnetic materials such as 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, and carbonyl iron; and magnetic materials such as magnetite and ferrite, and is an inorganic substance other than the inorganic substance (B) described below. The inorganic material (A) may be used together with an organic material. From the viewpoint of reducing the expansion coefficient or increasing 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 the electromagnetic interference suppression performance, it may be at least one selected from ferrite and amorphous magnetic metal alloys.

[0057] The shape of the inorganic material (A) is not particularly limited, and examples thereof include powder, spheres, flakes, fibers, etc. The shape of the inorganic material may be powder or spheres.

[0058] The average particle size of the inorganic material (A) is not particularly limited, but may be from 0.1 μm to 100 μm, from 0.2 μm to 75 μm, or from 0.2 μm to 50 μm. In this specification, the average particle size refers to the volume average particle size, and the average particle size of the inorganic substance (A) can be calculated as the average value of the long diameter of the particles measured using a laser diffraction particle size distribution measuring device.

[0059] When the electromagnetic interference suppression material of the present disclosure contains the inorganic substance (A), from the viewpoint of further improving the electromagnetic wave absorption performance and the electromagnetic interference suppression performance, the content of the inorganic substance (A) may be 30 to 92 mass %, 40 to 90 mass %, or 50 to 88 mass % of the total amount of the electromagnetic interference suppression material.

[0060] When the electromagnetic interference suppression material of the present disclosure is used as a semiconductor encapsulant, metal foreign matter removal is performed during the process of manufacturing the semiconductor encapsulant. When the metal foreign matter removal is performed using a magnet, the magnetic material is regarded as a foreign matter and is removed, resulting in poor yield. From this viewpoint, when the electromagnetic interference suppression material of the present disclosure contains the magnetic material, the content of the magnetic material may be 1 mass % or less, 0.5 mass % or less, or even 0 mass % relative to the total amount of the electromagnetic interference suppression material. In addition, since the magnetic material has a large specific gravity, the content of the magnetic material may be the above value or less from the viewpoint of reducing the weight of the resulting molded body.

[0061] (Inorganic substances (B)) The inorganic material (B) is a ceramic. The ceramics are not particularly limited, but specific examples include sintered bodies containing metal oxides, nitrides, carbides, etc. as main components. Specific examples of the metal oxide include alumina, zirconia, and magnesium oxide. Specific examples of the metal nitrides include aluminum nitride, boron nitride, and silicon nitride. Specific examples of the metal carbides include silicon carbide and boron carbide. The ceramic may be at least one sintered body selected from alumina and aluminum nitride. The ceramic may be a molded body, or may be a porous alumina foam.

[0062] [Method of manufacturing powdered carbon material] Hereinafter, one embodiment of the method for producing a powdered carbon material according to the present disclosure will be described, but the present disclosure is not limited to the following embodiment.

[0063] The powdered carbon material according to the present disclosure can be produced by a method including a first step of using particles of alumina, magnesium oxide, or the like as a template, coating the template with a carbon layer to prepare carbon-coated particles, a second step of dissolving and removing the template, and a third step of performing a heat treatment. By using such a method, a powdered carbon material having a high specific surface area and an average number of graphene layers of 4 or less can be easily obtained.

[0064] <1st process> (template) The template used in synthesizing the powdered carbon material of this embodiment must be capable of introducing an organic substance into the surface and inside the pores, must be capable of stably maintaining the original structure during CVD treatment, and must be capable of being easily separated from the produced powdered carbon material. For this reason, the template may be one that has good heat resistance and can be removed using an acid or alkali. The resulting powdered carbonaceous material has pores that reflect the shape of the template itself. In other words, the carbonaceous material is synthesized in a state where the shape of the template is transferred. For this reason, the template may be a material with a uniform structure and composition with uniform particle size, and by using such a material, a powdered carbonaceous material having pores of controlled size can be prepared. In addition, in order to obtain a high specific surface area, the template may be a material that can control the average number of layers of the resulting graphene to 4 or less.

[0065] Examples of such templates include particles of alumina, silica, magnesium oxide, tungsten carbide, aluminum nitride, cerium oxide, titanium oxide, calcium carbonate, etc. These particles may be nanoparticles. From the viewpoint of the material properties that the template should have and the properties of the powdery carbon material to be obtained, the particles may be at least one type selected from alumina and magnesium oxide, alumina particles, or alumina nanoparticles. The type of alumina is not particularly limited, but may be θ-alumina or γ-alumina.

[0066] The average particle size of the particles used in the template is not particularly limited, but may be 4 to 100 nm, or 5 to 20 nm. If the average particle size is 4 nm or more, the particles are easy to handle and have good carbon coverage. In addition, the gas permeability of the carbon source is good when covering the carbon source, so that uniform carbon coverage is easy. On the other hand, if the average particle size is 100 nm or less, a powdered carbon material with a high specific surface area (BET specific surface area) can be obtained. In addition, the decrease in the yield of the powdered carbon material caused by the relative increase in the amount of the template dissolved in the subsequent process can be reduced.

[0067] The particles may be mixed with granular spacers. By using the spacers, it is possible to secure an appropriate amount of void between the particles, and to reduce pressure loss due to the particles being too densely packed. The spacers may be particles having an average particle size of, for example, 100 to 5000 μm. The material of the spacer is not particularly limited as long as it can be sieved after carbon coating, and may be one that does not decompose at 900 to 1000 ° C. Alternatively, it may be one that can be dissolved and removed at the same time as the mold. Examples of the spacer include quartz sand, silica, alumina, silica-alumina, titania, etc. For example, when using quartz sand, it may be washed with an acid in advance, fired at 600 to 1000 ° C. for 1 to 5 hours, and controlled to the above particle size.

[0068] The compounding ratio of the particles and the spacer is not particularly limited, but for example, the mass ratio of (particles:spacer) may be 0.1:10 to 10:10, or may be 1:10 to 10:10. When it is within the above range, the powdery carbon material can be obtained in a high yield.

[0069] (Carbon layer coating) There is no particular limitation on the method for coating the surface of the particle serving as the template with a carbon layer, and either a wet method or a dry method can be applied. However, from the viewpoint of setting the average number of graphene layers to 4 or less, a chemical vapor deposition (CVD) method may also be used.

[0070] The CVD method, which is used to introduce organic compounds and deposit a carbon layer on a template, is an industrial technique for producing a thin film (e.g., a thin film made of carbon) of a specific element or element composition on a substrate such as a template. Usually, this technique utilizes the fact that a gas containing a raw material is energized by heat or light, or turned into plasma by high frequency, causing the raw material to undergo a chemical reaction or thermal decomposition to become radicalized and highly reactive, and the raw material is then adsorbed and deposited on the substrate.

[0071] The organic compound used in the CVD method may be a gas at room temperature or may be vaporizable. Vaporization may be performed by heating to above the boiling point or by reducing the pressure of the atmosphere. The organic compound used may be appropriately selected from carbon source substances. In particular, it may be a compound that decomposes thermally by heating, or a compound that can deposit a carbon layer on the surface of particles used as a template.

[0072] The organic compound used may be an organic compound containing hydrogen. The organic compound may be an organic compound containing unsaturated or saturated hydrocarbons, or a mixture thereof. The organic compound used may be an unsaturated straight-chain or branched-chain hydrocarbon having a double bond and / or a triple bond, a saturated straight-chain or branched-chain hydrocarbon, or an aromatic hydrocarbon such as saturated cyclic hydrocarbon, benzene, or toluene. As the organic compound, alcohols such as methanol and ethanol, or nitrogen-containing compounds such as acetonitrile and acrylonitrile may be used. Examples of the organic compound 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. Among them, the organic compound used may be one that can enter the gap between particles, such as acetylene, ethylene, propylene, methane, and ethane. From the viewpoint of precipitating carbon with high crystallinity, methane, propylene, and benzene may be used. In addition, methane may be used from the viewpoint of obtaining carbon with high crystallinity due to its high pyrolysis temperature. The organic compounds used in the higher temperature CVD and the lower temperature CVD may be the same or different, for example, acetylene, ethylene, etc. may be used in the lower temperature CVD and propylene, isoprene, benzene, etc. may be used in the higher temperature CVD.

[0073] When the organic compound is introduced onto the particles, the particles may be decompressed in advance, or the system itself may be decompressed. Any method that deposits carbon by CVD may be used. For example, carbon produced by chemical reaction or thermal decomposition of an organic compound may be deposited (or adsorbed) on alumina particles to coat the alumina particles with a carbon layer.

[0074] The pressure when carrying out the CVD treatment is not particularly limited, and may be, for example, 1 kPa to 200 kPa, or 50 to 150 kPa. The heating temperature when carrying out the CVD treatment may be any condition that allows the formation of a carbon layer of several layers or less on the 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 heating temperature may be 700 to 900°C, and when methane is used, the heating temperature may be 900 to 1100°C. However, the temperature may be about 50 to 200°C lower than the decomposition temperature of the organic compound. When heated to a temperature equal to or higher than the decomposition temperature of the organic compound, gas phase carbon deposition becomes prominent, but by doing as described above, for example, the unevenness of the carbon deposition amount between the surface and the inside of the particle can be reduced, and the carbon can be deposited uniformly. The heating temperature can be appropriately selected depending on the CVD processing time and / or the pressure in the reaction system. The product may be analyzed, and the temperature required to obtain the desired number of layers may be set based on the results.

[0075] The heating rate during the CVD treatment is not particularly limited, and may be 1 to 50° C. / min, or 5 to 20° C. / min. The CVD treatment time at the heating temperature (a) may be any time that allows graphene with an average number of layers of 4 or less to be obtained, and an appropriate time can be selected depending on the organic compound or temperature used. For example, the treatment time in the CVD treatment may be 5 minutes to 8 hours, 0.5 to 6 hours, or 1 to 5 hours. The product may be analyzed, and the time required for sufficient carbon deposition may be set based on the results of the analysis.

[0076] The CVD treatment may be carried out under reduced pressure, vacuum, or pressure, or may be carried out under an inert gas atmosphere. When the CVD treatment is carried out under an inert gas atmosphere, examples of the inert gas include nitrogen, helium, neon, and argon, and nitrogen may be used. In the CVD method, carbon can be easily deposited or adsorbed on particles in the gas phase by heating a gaseous organic compound together with a carrier gas while flowing the gaseous organic compound so as to contact the particles. The type, flow rate, flow rate and heating temperature of the carrier gas are appropriately adjusted depending on the type of organic compound used. The carrier gas may be, for example, the inert gases mentioned above, and may be nitrogen or a mixture with oxygen gas or hydrogen gas.

[0077] From the viewpoint of setting the average number of graphene layers to 4 or less, the flow rate of the carrier gas may be, for example, 0.05 to 1.0 m / min or 0.32 to 0.64 m / min. The amount of the organic compound introduced may be 1 to 30 volume % or 5 to 20 volume % with respect to the total amount of the carrier gas and the organic compound.

[0078] As a method for coating the particles with a carbon layer, an organic compound may be introduced by a wet method such as an impregnation method and carbonized. Alternatively, the organic compound may be introduced and carbonized before CVD. As the organic compound to be impregnated, for example, a thermally polymerizable monomer such as furfuryl alcohol, which has a high carbonization yield, may be used. As a method for impregnating the organic compound, a known method may be adopted, such as contacting the particles with the organic compound as it is or mixed with a solvent if the organic compound is liquid, or dissolving the organic compound in a solvent if the organic compound is solid.

[0079] After the first step, the carbon-coated particles may be heat-treated to carbonize the carbon layer and precipitate highly crystalline carbon on the particle surface, resulting in a powdered carbon material with higher crystallinity and a larger specific surface area.

[0080] Since the carbonization of the carbon layer can also proceed by a CVD treatment, the heat treatment may be carried out during the CVD treatment or by another method.

[0081] The method for the heat treatment is not particularly limited, and the heat treatment may be performed using a high-frequency induction heating furnace or the like.

[0082] <Second process> The second step of this embodiment, a step of dissolving and removing the template, is a step of dissolving and removing the template from the carbon-coated particles to obtain shell-shaped bodies. For dissolving and removing the template, an alkaline solution such as NaOH, KOH, LiOH, RbOH, or CsOH may be used. The alkaline solution may have a concentration of, for example, 1 to 5M. The alkaline solution may be 30 times or more, or 50 times or more, of the stoichiometric ratio with respect to the particles. If the alkaline solution is 30 times or more of the stoichiometric ratio, the remaining particles serving as the template can be suppressed. When dissolving and removing the template, for example, the carbon-coated particles may be placed in the alkaline solution and heat-treated at a heat treatment temperature of 200 to 300°C. In this case, the sample of the carbon-coated particles may be crushed in advance in order to uniformly contact the sample with the alkaline solution. The temperature rise rate during the heat treatment is not particularly limited, and is, for example, 200 to 300°C / hour. The heat treatment time (the holding time at a predetermined heat treatment temperature) is not particularly limited, and is, for example, 1 to 5 hours. This dissolving and removing process may be performed multiple times. The product may be analyzed, and the conditions required for sufficient template removal may be set based on the results.

[0083] After dissolving and removing the mold, the shells may be collected by filtration, or may be dried by vacuum heat drying. The conditions for vacuum heat drying are not particularly limited, and the vacuum heat drying temperature may be, for example, 100 to 200° C. The vacuum heat drying time may be, for example, 1 to 10 hours.

[0084] <3rd process> The third step is a heat treatment step. By passing through the third step after the second step, the crystallinity of the coated carbon is increased and stabilized. Therefore, the powdered carbon material has higher levels of electrical conductivity, corrosion resistance, and a large specific surface area. The heat treatment temperature is not particularly limited, but may be 1100 to 1850° C. or 1550 to 1830° C. If the heat treatment temperature is 1550° C. or higher, the effects of the present invention can be more significantly obtained. Also, if the heat treatment temperature is 1850° C. or lower, the reaction between the remaining template and carbon can be prevented. The heat treatment time (the holding time at a predetermined heat treatment temperature) may be 0.1 to 10 hours, 0.2 to 5 hours, or 0.5 to 2 hours. The heat treatment step may be carried out under reduced pressure. By the method including the above first to third steps, graphene having an average number of layers of 4 or less can be obtained.

[0085] [Method of manufacturing electromagnetic interference suppression material] In one embodiment of the present disclosure, when a molded body (not a foamed body) is used as the organic material, the electromagnetic interference suppression material may be obtained by thoroughly and uniformly mixing a base material containing at least one organic material, a powdered carbon material, and other components that are added as necessary using a mixer or the like, and then kneading the mixture using a disperse, kneader, three-roll mill, twin-screw heating roll, twin-screw heating extrusion kneader, or the like. The kneading process may be performed with heating. The temperature at that time may be 70°C or higher and 150°C or lower, or 75°C or higher and 120°C or lower.

[0086] The electromagnetic interference suppression material of the present disclosure may be used, for example, after the kneading treatment, by cooling and solidifying, and then pulverizing to an appropriate size using a cutting mill, ball mill, cyclone mill, hammer mill, vibration mill, cutter mill, grinder mill, speed mill, or the like.

[0087] The mixture obtained after the kneading treatment may be pressed in a molding machine under conditions of a temperature of 50° C. to 100° C. and a pressure of 0.5 MPa to 1.5 MPa to form a sheet.

[0088] The electromagnetic interference suppression material of the present disclosure can be used as a radio wave absorber, a noise suppression sheet, a semiconductor encapsulant, an encapsulating sheet, a wire covering material, and the like. As one embodiment of the present disclosure, for example, a resin-sealed electronic component can be obtained by sealing a semiconductor element fixed on a substrate with a semiconductor element encapsulant containing the electromagnetic interference suppression material of the present disclosure. To obtain electronic components, any known molding method can be used without any particular limitation. The most common molding method is low pressure transfer molding, but molding by injection molding, cast molding, compression molding, etc. is also possible.

[0089] For example, in the case of transfer molding, a heat treatment may be performed in a mold using a transfer molding machine at a temperature of 150°C or higher and 200°C or lower for a time period of 20 seconds or higher and 200 seconds or lower, and the molded product may then be removed from the mold and a heat treatment to complete curing may be performed at a temperature of 150°C or higher and 200°C or lower for a time period of 2 hours or higher and 12 hours or lower.

[0090] In the case of compression molding, a substrate on which a semiconductor element is mounted is first supplied to the upper mold of a molding die, and the electromagnetic interference suppression material of the present disclosure is supplied to the cavity of the lower mold. Next, the upper and lower molds are clamped with a required clamping pressure, so that the substrate on which the semiconductor element is mounted is immersed in the electromagnetic interference suppression material that has been heated and melted in the lower mold cavity. Thereafter, the heated and melted electromagnetic interference suppression material in the lower mold cavity is pressed by the cavity bottom member, and a required pressure is applied under reduced pressure to perform compression molding. Molding conditions may be a temperature of 120°C or higher and 200°C or lower, and a pressure of 2 MPa or higher and 20 MPa or lower.

[0091] In another embodiment of the present disclosure, when an inorganic substance (B) is used as the base material, the electromagnetic interference material can be obtained by the following method. A suitable organic binder, a solvent, etc. are added and mixed with a ceramic raw material powder to produce a slurry. This slurry is formed into a sheet using a conventionally known doctor blade method or the like to produce a ceramic green sheet. This ceramic green sheet is then fired to obtain the material. The material may also be obtained by dispersing a powdered carbon material in a solvent and immersing the resulting ceramic in a mixed dispersion containing other components as necessary. The material may also be obtained by firing a component capable of becoming a ceramic green sheet and a powdered carbon material. The conditions for firing the ceramic-potential component and the powdered carbon material are not particularly limited and may be appropriately adjusted depending on the ceramic-potential component. The firing may be performed in an inert gas atmosphere. The firing temperature may be 600°C to 1800°C, or 1000°C to 1600°C.

[0092] In yet another embodiment of the present disclosure, an electromagnetic interference suppression material containing a foam as an organic or inorganic substance may be obtained by dispersing a powdered carbon material in a solvent and immersing the foam in a mixed dispersion containing other components as necessary. Alternatively, the material may be obtained by foaming a component capable of forming a foam, a powdered carbon material, and other components that are mixed as necessary using a foaming machine, or by foaming by molding using a pressure press and then baking in air. The conditions for foaming these are not particularly limited, and may be appropriately adjusted depending on the components that can be foamed. EXAMPLES

[0093] The present disclosure will now be described in detail with reference to examples, but the present disclosure is not limited to these examples in any way.

[0094] [Production of powdered carbon materials] <Production Example 1> (Production of carbon-coated alumina nanoparticles) Alumina nanoparticles (TM300 manufactured by Taimei Chemical Industry Co., Ltd., crystal phase: γ-alumina, average particle size: 7 nm, specific surface area: 220 m 2 Alumina nanoparticles (alumina nanoparticles / g) and quartz sand (Sendai Wako Pure Chemical Industries, Ltd.) as a spacer were mixed in a mass ratio of 3:20 (alumina nanoparticles:quartz sand). The quartz sand used here was soaked in 1M hydrochloric acid for 12 hours, heated in air at 800°C for 2 hours in a muffle furnace, and sieved to 180 μm intervals. The mixture of alumina nanoparticles and quartz sand prepared above was placed in a reaction tube (inner diameter 37 mm), and CVD (methane CVD) was performed using methane as a carbon source.

[0095] In the methane CVD, alumina nanoparticles were heated from room temperature to 900°C at a heating rate of 10°C / min under conditions where the flow rate of N2 gas was adjusted to 224ml / min, and held at 900°C for 30 minutes. Then, N2 gas was used as a carrier gas, and 20% by volume of methane relative to the total amount of carrier gas and methane was introduced into the reaction tube, and chemical vapor deposition (CVD) processing was performed at 900°C for 2 hours. At this time, the flow rate of methane gas was adjusted to 45ml / min and the flow rate of N2 gas was adjusted to 179ml / min. Then, the introduction of methane gas was stopped, and the flow rate of N2 gas was adjusted to 224ml / min under conditions where the temperature was held at 900°C for 30 minutes, and then cooled to obtain carbon-coated alumina nanoparticles.

[0096] (Dissolving and removing the mold) The carbon-coated alumina nanoparticles and 5M NaOH (50 times or more the stoichiometric ratio) were placed in a Teflon (registered trademark) autoclave vessel, and the mixture was heated at a rate of 250°C / hour using a muffle furnace and held at 250°C for 2 hours. After natural cooling, the mixture was collected by filtration and dried by vacuum heating at 150°C for 6 hours to obtain shell-shaped bodies.

[0097] (Heat treatment) The shell-shaped body obtained in the above (dissolving and removing the mold) was crushed, and several pieces were collected and placed in a graphite crucible, which was then set in an induction heating furnace. In order to remove the air from inside the reaction tube, the reaction tube was evacuated with an oil pump and left for 30 minutes. Thereafter, water was run through the water-cooled jacket of the reaction tube, and the system was heated by induction heating, and a heat treatment was performed to obtain a powdered carbon material. The heat treatment was performed under vacuum. The heat treatment conditions were as follows: first, the temperature was raised from room temperature to 1000°C at 16.7°C / min over 60 minutes, then the temperature was raised to 1800°C at 5°C / min over 160 minutes, and then the temperature was heated at 1800°C for 60 minutes, and then the material was naturally cooled to room temperature to obtain a powdered carbon material 1 (second shell-shaped body).

[0098] <Production Example 2> (Production of carbon-coated alumina nanoparticles) Alumina nanoparticles (TM300 manufactured by Taimei Chemical Industry Co., Ltd., crystal phase: γ-alumina, average particle size: 7 nm, specific surface area: 220 m 2 Alumina nanoparticles (alumina nanoparticles / g) and quartz sand (Sendai Wako Pure Chemical Industries, Ltd.) as a spacer were mixed in a mass ratio of 3:20 (alumina nanoparticles:quartz sand). The quartz sand used here was soaked in 1M hydrochloric acid for 12 hours, heated in air at 800°C for 2 hours in a muffle furnace, and sieved to 180 μm intervals. The mixture of alumina nanoparticles and quartz sand prepared above was placed in a reaction tube (inner diameter 37 mm), and CVD (methane CVD) was performed using methane as a carbon source.

[0099] In the methane CVD, alumina nanoparticles were heated from room temperature to 900°C at a heating rate of 10°C / min under conditions where the flow rate of N2 gas was adjusted to 224ml / min, and held at 900°C for 30 minutes. Then, N2 gas was used as a carrier gas, and 20% by volume of methane relative to the total amount of carrier gas and methane was introduced into the reaction tube, and chemical vapor deposition (CVD) processing was performed at 900°C for 6 hours. At this time, the flow rate of methane gas was adjusted to 45ml / min and the flow rate of N2 gas was adjusted to 179ml / min. Then, the introduction of methane gas was stopped, and the flow rate of N2 gas was adjusted to 224ml / min under conditions where the temperature was held at 900°C for 30 minutes, and then cooled to obtain carbon-coated alumina nanoparticles.

[0100] (Dissolving and removing the mold) The same procedure as in Preparation Example 1 was carried out.

[0101] (Heat treatment) By the same procedure as in Production Method 1, powdered carbon material 2 (second shell bodies) was obtained.

[0102] <Comparative Manufacturing Example 1> (Production of carbon-coated alumina nanoparticles) Alumina nanoparticles (TM300 manufactured by Taimei Chemical Industry Co., Ltd., crystal phase: γ-alumina, average particle size: 7 nm, specific surface area: 220 m 2 Alumina nanoparticles (alumina nanoparticles / g) and quartz sand (Sendai Wako Pure Chemical Industries, Ltd.) as a spacer were mixed in a mass ratio of 3:20 (alumina nanoparticles:quartz sand). The quartz sand used here was soaked in 1M hydrochloric acid for 12 hours, heated in air at 800°C for 2 hours in a muffle furnace, and sieved to 180 μm intervals. The mixture of alumina nanoparticles and quartz sand prepared above was placed in a reaction tube (inner diameter 37 mm), and CVD (methane CVD) was performed using methane as a carbon source.

[0103] In the methane CVD, alumina nanoparticles were heated from room temperature to 950°C at a heating rate of 10°C / min under conditions where the flow rate of N2 gas was adjusted to 224ml / min, and held at 950°C for 30 minutes. Then, N2 gas was used as a carrier gas, and 20% by volume of methane relative to the total amount of carrier gas and methane was introduced into the reaction tube, and chemical vapor deposition (CVD) processing was performed at 950°C for 20 hours. At this time, the flow rate of methane gas was adjusted to 45ml / min and the flow rate of N2 gas was adjusted to 179ml / min. Then, the introduction of methane gas was stopped, and under conditions where the flow rate of N2 gas was adjusted to 224ml / min, the mixture was held at 950°C for 30 minutes, and then cooled to obtain carbon-coated alumina nanoparticles.

[0104] (Dissolving and removing the mold) The same procedure as in Preparation Example 1 was carried out.

[0105] (Heat treatment) The same procedure as in Production Method 1 was carried out to obtain powdered carbon material 3 (second shell bodies).

[0106] [Measurement and evaluation of powdered carbon materials] The obtained powdered carbon material was subjected to the following measurement and evaluation. The measurement and evaluation results are summarized in Table 1.

[0107] <Specific surface area (BET specific surface area)> The obtained powdered carbon material was vacuum heated and dried at 150°C for 6 hours, and then the specific surface area was calculated by the multi-point method from the nitrogen adsorption isotherm measured using a high-precision automatic gas / vapor adsorption measuring device "BEL SORP MAX" (manufactured by BEL Japan Co., Ltd.).

[0108] <Average number of graphene layers> From the specific surface area obtained by the above-mentioned method, the average number of graphene layers was calculated by the following formula. Average number of graphene layers = 2627 (m 2 / g) / specific surface area (m 2 / g)

[0109] <Pore volume> The obtained powdered carbon material was vacuum heated and dried at 150°C for 6 hours, after which a nitrogen adsorption isotherm was measured using a high-precision automatic gas / vapor adsorption measuring device "BEL SORP MAX" (manufactured by BEL Japan, Inc.) and the pore volume per mass of material was calculated from the adsorption amount at a relative pressure (P / P0) of 0.96.

[0110] [Table 1]

[0111] [Manufacturing of electromagnetic interference suppression materials] Details of each component used in the production of the electromagnetic interference suppression material and shown in Tables 2 and 3 are as follows: [Organic matter] Epoxy resin: EPICLON N670; cresol novolac type epoxy resin; manufactured by DIC Corporation; epoxy equivalent: 210 [Inorganic substances] Silica: FB105; Denka Co., Ltd., average particle size: 12 μm [Carbon Materials] Carbon black (CB): TPK1227R; manufactured by Cabot Corporation; average particle size: 0.1 μm Carbon nanotubes (CNTs): LUCAN; LG: average fiber length: 30 μm, average fiber diameter: 0.02 μm [Additives] Hardener: BRG-557; phenol novolac resin; manufactured by Aica Kogyo Co., Ltd. Curing accelerator: Curesol C11Z; imidazole compound; manufactured by Shikoku Kasei Co., Ltd. Flame retardant: Rabitol (phosphazene flame retardant) FP100; manufactured by Mitsui Chemicals Fine Co., Ltd. The powdered carbon materials 1 to 3 shown in Tables 2 and 3 used in the production of the electromagnetic interference suppression material were pulverized products of the powdered carbon materials 1 to 3 obtained in Production Examples 1 and 2, and Comparative Production Example 1, respectively. All of the powdered carbon materials 1 to 3 were pulverized and classified to have an average particle size of 10 μm.

[0112] <Examples 1 to 3 and Comparative Examples 1 to 5> The components of the types and amounts shown in Table 2 were charged into a Henschel mixer and mixed, then charged into a twin-screw roll kneader heated to 110°C, and heated and kneaded until homogenous. The heated and kneaded mixture was then charged into a cold roll, stretched into a sheet, and pulverized to obtain an electromagnetic interference suppression material composition. The electromagnetic interference suppression material composition was compression molded into a molded body having 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.

[0113] <Example 4> Adipic acid, diethylene glycol, and trimethylolpropane were placed in a flask and mixed by heating at 120° C., after which triisopropyl titanate was added and the mixture was dehydrated under reduced pressure at 240° C. to prepare an adipic acid-based polyester polyol. A polyol mixture was obtained by mixing 10 parts by mass of the above adipic acid-based polyester polyol, 70 parts by mass of terephthalic acid-based polyester polyol "Terrol 250" (manufactured by OXID Corporation), 20 parts by mass of ethylenediamine-based polyether polyol "AE-300" (manufactured by Mitsui Chemical Polyurethanes Co., Ltd.), 15 parts by mass of flame retardant "TMCPP" (manufactured by Daihachi Chemical Industry Co., Ltd.), 1 part by mass of foam stabilizer "L-5340" (manufactured by Nippon Unicar Co., Ltd.), 2.5 parts by mass of catalyst "KL-31" (manufactured by Kao Corporation), 35 parts by mass of blowing agent "HFC-245fa", and 1.5 parts by mass of water. The obtained polyol mixture and isocyanate "Sumidur 44V20" (manufactured by Sumika Bayer Urethane Co., Ltd.) were mixed and stirred so that the urethane index was 105, and the obtained mixture was placed in a mold and molded into a size of 440mm x 440mm x 25mm to obtain a rigid polyurethane foam (polyurethane foam). Separately, rigid polyurethane foam was molded into a size of 440mm x 440mm x 25mm by the same operation, and this was cut into 440mm x 440mm x 0.5mm or 440mm x 440mm x 1.0mm. Next, 1 part by mass of the powdered carbon material 1 obtained in Production Example 1 was mixed with 10,000 mL of urethane emulsion "Superflex" (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) to prepare mixed dispersion 1. The polyurethane foam obtained was immersed in mixed dispersion 1 at room temperature for 30 minutes and then heated and dried at 120°C for 120 minutes, thereby obtaining an electromagnetic interference suppression material in which the powdered carbon material is localized on the surface of the polyurethane foam.

[0114] <Example 5 and Comparative Examples 6 to 8> In Example 5, instead of using the powdered carbon material 1 in Example 4, An electromagnetic interference suppressing material in which a carbon material is localized on the surface of a polyurethane foam was obtained by the same procedure except that powdered carbon material 2 was used, powdered carbon material 3 was used in Comparative Example 6, carbon black (CB) was used in Comparative Example 7, and carbon nanotubes (CNT) were used in Comparative Example 8.

[0115] <Example 6> 50 parts by mass of the polyol mixture produced in Example 4, 50 parts by mass of the isocyanate "Sumidur 44V20" (manufactured by Sumika Bayer Urethane Co., Ltd.), and 1 part by mass of the powdered carbon material 1 obtained in Production Example 1 were charged into an automatic mixing type injection foaming machine (type: MU-203S, model number: 6-018, manufactured by Polyurethane Engineering Co., Ltd.) and foamed under the same molding conditions as in Example 4, to obtain an electromagnetic interference suppression material that was a polyurethane foam containing the powdered carbon material and had dimensions of 440 mm × 440 mm × 0.5 mm, 440 mm × 440 mm × 1.0 mm, or 440 mm × 440 mm × 25 mm.

[0116] <Comparative Examples 9 to 11> Electromagnetic interference suppressing materials were obtained by the same procedures as in Example 6, except that, instead of using powdered carbon material 1, in Comparative Example 9, powdered carbon material 3 was used, in Comparative Example 10, carbon black (CB) was used, and in Comparative Example 11, carbon nanotubes (CNT) were used.

[0117] <Example 7> An electromagnetic interference suppression material in which a powdered carbon material is localized on the surface of a sintered ceramic porous body (foam) was obtained by the same procedure as in Example 4, except that a sintered ceramic porous body "FA120" (manufactured by Fuji Chemical Co., Ltd., alumina material, average pore size 100 μm, average porosity 45-50%) was used instead of the polyurethane foam.

[0118] <Comparative Example 12> An electromagnetic interference suppressing material in which a carbon material was localized on the surface of a sintered porous ceramic body was obtained by the same procedure as in Example 7, except that carbon nanotubes (CNTs) were used instead of the powdered carbon material 1.

[0119] [Measurement and evaluation of electromagnetic interference suppression materials] The electromagnetic interference suppressing material thus obtained was subjected to measurement and evaluation for the following items. The measurement and evaluation results are summarized in Tables 2 and 3. In the "area where carbon material is present" column in Table 3, "surface" indicates that the carbon material is localized on the surface of the electromagnetic interference suppression material, and "entire" indicates that the carbon material is present both inside and on the surface of the electromagnetic interference suppression material (entire electromagnetic interference suppression material).

[0120] <Content of powdered carbon material (mass%)> The content of the powdered carbon material was determined from the blending ratio when the "area where the carbon material is present" is the "whole" (Examples 1 to 3, Example 6, Comparative Examples 1 to 5, and Comparative Examples 9 to 11), and from the mass increase before and after the introduction of the carbon material to the surface when the "area where the carbon material is present" is the "surface" (Example 4, Example 5, Example 7, Comparative Examples 6 to 8, and Comparative Example 12).

[0121] <Volume resistance> Using an electromagnetic interference suppression material molded to a thickness of 1.0 mm, the volume resistivity at 150°C was measured in accordance with JIS K-6911:2006.

[0122] <Electromagnetic wave absorption performance (frequency 10GHz, 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, and the electromagnetic wave intensity when electromagnetic waves with a frequency of 10 GHz were generated was measured with and without the molded article, and the ratio (electromagnetic wave intensity when electromagnetic waves are absorbed by the electromagnetic interference suppression material / electromagnetic wave intensity without the electromagnetic interference suppression material) was defined as the electromagnetic wave absorption performance in dB. The electromagnetic wave intensity was measured in accordance with the Transactions of the Institute of Electronics, Information and Communication Engineers, Vol. J97-B, No. 3, pp. 279-285.

[0123] <Electromagnetic wave absorption performance (frequency 5GHz, far-field measurement system)> A copper plate (600mm x 600mm) with a thickness of 1mm was placed on the anti-reflection wave absorber, and an electromagnetic interference suppression material (440mm x 440mm) molded to a thickness of 25mm was placed on the metal plate. Next, an antenna was attached to a network analyzer via a cable, and an electromagnetic wave with a frequency of 5GHz was transmitted from one antenna, reflected by the electromagnetic interference suppression material and the metal plate placed below it, and received by the other antenna to measure the electromagnetic wave intensity. In addition, the electromagnetic interference suppression material was not placed on the metal plate, and an electromagnetic wave was radiated and the electromagnetic wave intensity was measured by the same operation as above. The ratio of these (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 taken as the electromagnetic wave absorption performance in dB units. The electromagnetic wave intensity was measured in accordance with "Kagoshima Prefectural Industrial Technology Center Research Report No. 15 (2001), pp. 53-61."

[0124] [Table 2]

[0125] [Table 3]

[0126] As shown in Table 2, the electromagnetic interference suppression materials of Examples 1 to 3 have good radio wave absorption performance. In addition, because they have high volume resistivity, they also have good electromagnetic interference suppression performance in the near field. Furthermore, as shown in Table 3, the electromagnetic interference suppressing materials of Examples 4 to 7 have good radio wave absorbing performance.

Claims

1. An electromagnetic interference suppression material comprising a base material containing an organic substance and an inorganic substance, and a powdered carbon material, the organic material is a thermosetting resin, The inorganic substance is at least one selected from silica and alumina, the powdered carbon material is at least one selected from a first shell-shaped body which is a hollow particle having one hole, and a second shell-shaped body which is a shape in which hollow particles are connected and has a plurality of holes; The electromagnetic interference suppression material, wherein the shell portions of the first shell-shaped bodies and the second shell-shaped bodies are made of graphene having an average number of layers of 4 or less.

2. The powdered carbon material has a specific surface area of ​​1300 m ２ 2. The electromagnetic interference suppressing material of claim 1, wherein the MnO2 content is 1 / g or more.

3. 3 . The electromagnetic interference suppressing material according to claim 1 , wherein the pores of the first shell-shaped bodies and the pores of the second shell-shaped bodies each have a volume of 1.3 cc / g or more.

4. Volume resistance is 10 ３ 3. The electromagnetic interference suppressing material according to claim 1, having a resistivity of Ω·cm or more.

5. 3. The electromagnetic interference suppression material according to claim 1, wherein the powdered carbon material has an average particle size of 200 μm or less.

6. 3. The electromagnetic interference suppressing material according to claim 1, wherein the organic material is an epoxy resin.

7. 3. The electromagnetic interference suppressing material according to claim 1, wherein the organic material or the inorganic material is a foam.

8. 3. The electromagnetic interference suppressing material according to claim 1, wherein the powdered carbon material has a content of 0.01 to 95 mass %.

9. An electromagnetic interference suppression material as described in claim 1 or 2, wherein the powdered carbon material is present on the surface of the base material.

10. A semiconductor element encapsulation material comprising the electromagnetic interference suppression material according to claim 1 or 2.

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