WO2017081867A1 - Method for producing composite material sheet and method for producing heat conductive sheet - Google Patents

Abstract

Provided is a method for producing a composite material sheet which achieves a good balance among high thermal conductivity, high strength and good hardness. A method for producing a composite material sheet according to the present invention comprises: a preparation step of composite particles for pressurization; and a pressurization step for applying a pressure to the composite particles for pressurization. The preparation step comprises: (A) a step for preparing composite particles, each of which contains a particulate carbon material and a resin; (B) a step for classifying the composite particles into at least two composite particle groups including specific composite particle groups A and B; and (C) a step for preparing the composite particles for pressurization with use of composite particles that are contained in composite particle groups other than the composite particle group A.

Description

COMPOSITE MATERIAL SHEET AND METHOD FOR PRODUCING HEAT CONDUCTIVE SHEET

The present invention relates to a method for manufacturing a composite material sheet and a method for manufacturing a heat conductive sheet.

In recent years, a sheet-like member (composite material sheet) using a composite material having functions such as thermal conductivity and conductivity has been used for various applications.

For example, the temperature of an electronic component may rise due to an increase in the amount of heat generated by the electronic component due to the high performance of the electronic device, resulting in a functional failure in the electronic device. As a countermeasure against such functional failure due to temperature rise, a method of promoting heat dissipation by attaching a heat sink such as a metal heat sink, heat sink, heat sink or the like to a heat generator such as an electronic component is adopted. ing. And when using a heat radiator, in order to transmit heat | fever efficiently from a heat generating body to a heat radiator, the heat generating body and the heat radiator are closely_contact | adhered via the heat conductive sheet with high heat conductivity. Here, the sheet | seat shape | molded using the composite material sheet | seat excellent in heat conductivity is used as the said heat conductive sheet.

Also, for example, electromagnetic noise generated by mutual interference between electronic devices or static electricity may cause a functional failure in the electronic device. As a countermeasure against such a functional failure, a highly conductive composite material sheet may be used as a member that is directly attached to an electronic device or an electronic component, or a member that contacts the electronic device or the electronic component (such as a packing material). it can. By using the composite material sheet having high conductivity, it is possible to prevent noise propagation generated between electronic devices and prevent charging.

Therefore, the composite material sheet is required to exhibit high thermal conductivity and / or high conductivity, preferably with orientation according to the application and use location.

For example, in Patent Document 1, a conductive curable resin composition obtained by kneading an elastomer component, a radical reactive resin, and a heat conductive material is press-molded with a roll, thereby being excellent in heat conductivity and conductivity. A technique for obtaining a sheet made of a composite material is disclosed. Here, in Patent Document 1, as the thermally conductive material, coke is pulverized in advance and classified as necessary, and then particles having a particle diameter of 5 μm or less are removed, and then the coke is graphitized. Is used. And in patent document 1, the high electroconductivity (low resistance) in a sheet surface and high are used by using together the elastomer component with the boron containing graphite fine powder which grind | pulverized and classified the coke beforehand and made it the desired particle size in this way. A sheet having high heat dissipation (high thermal conductivity) and high thickness accuracy is realized even if the carbon material is highly filled.

JP 2003-176327 A

Here, in addition to high thermal conductivity and / or conductivity, the composite material sheet has high flexibility to make good contact with a non-contacting body without any gap when attached, and thinning of the sheet. There is also a need to have a high strength that can be made possible. However, the conventional sheets described in Patent Document 1 and the like have not been sufficient in strength and flexibility.

Therefore, the present invention provides a method for manufacturing a composite material sheet and a method for manufacturing a heat conductive sheet, in which high thermal conductivity is ensured and high strength and good flexibility (low hardness) are arranged side by side. Objective.

The present inventors have intensively studied to achieve the above object. The inventors of the present invention focused on classifying the composite particles including the heat conductive material and the resin, not the heat conductive material itself, and removing the composite particle group including at least coarse composite particles. Then, by applying pressure to the composite particles contained in the remaining composite particle group to form a sheet, high thermal conductivity, high strength, and low Asker C hardness (hereinafter simply referred to as “hardness”) may be used. ), The present invention has been completed. In addition, the present inventors have found that a heat conductive sheet having excellent heat conductivity can be produced using the composite material sheet, and have completed the present invention.
In the present invention, “good hardness”, “excellent hardness”, “improvement of hardness” and the like mean that the Asker C hardness is a low value.

That is, the present invention aims to advantageously solve the above-mentioned problems, and the method for producing a composite material sheet of the present invention comprises a step of preparing a composite particle for pressurization to obtain a composite particle for pressurization, A method of producing a composite material sheet comprising a pressurizing step of obtaining a composite material sheet by pressurizing the composite particles for pressure, wherein the preparatory step of the composite particles for pressurization includes a particulate carbon material and a resin. And the prepared composite particles are classified into at least two composite particle groups including a composite particle group A having a maximum volume average particle diameter and a composite particle group B having a minimum volume average particle diameter. A step (B) and a step (C) of preparing the pressurizing composite particles using composite particles contained in a composite particle group other than the composite particle group A among the composite particle groups. .
Thus, after classifying the composite particles, by pressurizing the composite particles for press obtained using the composite particles contained in the composite particle group other than the composite particle group A having the maximum volume average particle diameter, A composite material sheet having excellent conductivity, strength, and hardness can be provided.
In the present invention, the “volume average particle diameter” represents a particle diameter (D50) at which the cumulative volume calculated from the small diameter side is 50% in the particle diameter distribution (volume basis) measured by the laser diffraction method. In the present invention, the “volume average particle size” can be measured using a laser diffraction / scattering particle size distribution measuring apparatus.

Here, in the method for producing a composite material sheet of the present invention, the volume average particle diameter of the composite particle group including the composite particles used in the step (C) is preferably 500 μm or less. This is because if a composite particle for pressurization is prepared using composite particles contained in a composite particle group having a volume average particle diameter of 500 μm or less, a composite material sheet with further improved thermal conductivity, strength, and hardness can be obtained. .

In the method for producing a composite material sheet of the present invention, it is preferable that the pressurizing composite particles have a content of composite particles having a particle diameter of 500 μm or more of less than 40% by volume. This is because if the ratio of the composite particles having a particle diameter of 500 μm or more in the composite particles for pressurization is less than 40% by volume, a composite material sheet with further improved thermal conductivity, strength, and hardness can be obtained.
In the present invention described above, the “composite particle content” in the composite particles for pressurization is calculated from the volume-based particle size distribution obtained using the laser diffraction / scattering particle size distribution measuring device described above. Can do.

Moreover, in the method for producing a composite material sheet of the present invention, it is preferable that the composite particles contain 50 parts by mass or more and 150 parts by mass or less of the resin with respect to 100 parts by mass of the particulate carbon material. This is because a composite material sheet having good thermal conductivity, strength, and hardness can be easily obtained by controlling the resin content in the composite particles within the above range.

In the method for producing a composite material sheet of the present invention, the step (A) includes a kneading step in which the particulate carbon material and the resin are kneaded to obtain a kneaded product, and the kneaded product is pulverized to form the composite particles. It is preferable to include a pulverizing step. This is because the composite particles used in the method for producing a composite material sheet of the present invention can be easily prepared through the kneading step and the pulverization step.

Moreover, this invention aims at solving the said subject advantageously, The manufacturing method of the heat conductive sheet of this invention is thickness of the said composite material sheet obtained by one of the manufacturing methods mentioned above. Laminating the laminated body by laminating a plurality of sheets in the direction or by folding or winding the composite material sheet obtained by any of the manufacturing methods described above to obtain a laminated body And a slicing step of obtaining a heat conductive sheet by slicing at an angle of 45 ° or less with respect to the direction. Thus, by performing a lamination | stacking process and a slicing process with respect to the obtained composite material sheet | seat, the heat conductive sheet which has high thermal conductivity of the thickness direction, and has high intensity | strength and favorable hardness can be manufactured.

According to the present invention, it is possible to provide a method for producing a composite material sheet in which high thermal conductivity, high strength, and good hardness are arranged side by side. Moreover, according to this invention, the manufacturing method of the heat conductive sheet which made parallel high heat conductivity, high intensity | strength, and favorable hardness can be provided.

Hereinafter, embodiments of the present invention will be described in detail.
The method for producing a composite material sheet of the present invention can be used when producing a composite material sheet containing a resin and a particulate carbon material. And the composite material sheet manufactured using the manufacturing method of the composite material sheet of this invention is not specifically limited, It can use for various uses as a sheet-like member excellent in heat conductivity and electroconductivity.
Moreover, the composite material sheet produced by the method for producing a composite material sheet of the present invention can be used when producing a heat conductive sheet according to the method for producing a heat conductive sheet of the present invention. And the heat conductive sheet manufactured using the manufacturing method of the heat conductive sheet of this invention can be used by inserting | pinching between a heat generating body and a heat radiator when attaching a heat radiator to a heat generating body. That is, the heat conductive sheet manufactured using the manufacturing method of the heat conductive sheet of this invention can comprise a heat radiating device with heat sinks, such as a heat sink, a heat sink, and a heat radiating fin.

In addition, the composite material sheet and the heat conductive sheet manufactured according to the manufacturing method of the present invention are excellent in heat conductivity, strength, hardness, and conductivity. Therefore, the composite material sheet and the heat conductive sheet are suitable as, for example, a heat radiating material, a heat radiating component, a cooling component, a temperature adjusting component, and an electromagnetic shielding component used in various devices and apparatuses. Here, various devices and devices are not particularly limited, and are electronic devices such as servers, server personal computers, and desktop personal computers; portable electronic devices such as notebook computers, electronic dictionaries, PDAs, mobile phones, and portable music players. Liquid crystal display (including backlight), plasma display, LED, organic EL, inorganic EL, liquid crystal projector, display device such as clock; ink jet printer (ink head), electrophotographic device (developing device, fixing device, heat roller, Image forming apparatuses such as heat belts; semiconductor-related components such as semiconductor elements, semiconductor packages, semiconductor encapsulating cases, semiconductor die bonding, CPUs, memories, power transistors, power transistor cases; rigid wiring boards, flexible wiring boards, ceramic wirings Board, Wiring board such as a folded-up wiring board and multilayer board (the wiring board includes a printed wiring board); manufacturing equipment such as vacuum processing equipment, semiconductor manufacturing equipment, display equipment manufacturing equipment; heat insulating material, vacuum heat insulating material, radiation heat insulating material Thermal insulation equipment for materials, etc .; DVD (optical pickup, laser generator, laser receiver), data recording equipment such as hard disk drive, etc .; Camera, video camera, digital camera, digital video camera, microscope, CCD, etc. image recording equipment; Examples thereof include battery devices such as devices, lithium ion batteries, and fuel cells.

(Production method of composite material sheet)
In the method for producing a composite material sheet of the present invention, composite particles containing a resin and a particulate carbon material are pressurized and formed into a sheet shape to produce a composite material sheet. Here, the manufacturing method of the composite material sheet of the present invention includes a step of preparing pressurizing composite particles using predetermined composite particles obtained through the classification operation (preparing step of pressurizing composite particles), and the pressurizing composite. And a step of pressurizing the particles (pressurizing step). And in the manufacturing method of the composite material sheet of the present invention, since the composite material sheet is molded by applying pressure to the composite particles for pressurization prepared using the predetermined composite particles, high thermal conductivity, high strength, and good A composite material sheet with parallel hardness is obtained. The reason why a composite material sheet having excellent thermal conductivity, strength, and hardness can be obtained by using the pressurizing composite particles is not clear, but as will be described in detail later, the pressurizing composite particles are formed into a sheet shape. In the composite material sheet obtained by pressurization, it is presumed that the particulate carbon material is well oriented during pressurization and the heat transfer path is well formed by contact between the particulate carbon materials.
Hereinafter, each step will be specifically described.

<Preparation process of composite particles for pressurization>
The step of preparing composite particles for pressurization included in the method for producing a composite material sheet of the present invention includes a step (A) of preparing composite particles containing a particulate carbon material and a resin, and at least two of the obtained composite particles. Step (B) for classifying into composite particle groups, and Step (C) for preparing composite particles for pressurization using composite particles contained in a predetermined composite particle group among the composite particle groups obtained by classification including. The pressurizing composite particles prepared in the pressurizing composite particle preparation step are used for forming a composite material sheet by pressurization.

[Step (A)]
Here, in the step (A), composite particles containing a particulate carbon material and a resin are prepared as a material (composite material) when the composite material sheet is manufactured according to the manufacturing method of the present invention.

[[Composite particles]]
The composite particles prepared in the step (A) contain a particulate carbon material and a resin. Further, the composite particles prepared in the step (A) can contain a known additive that can be generally blended with the fibrous carbon material and the composite material used for molding the composite material sheet, if necessary. .

-Particulate carbon material-
Here, the particulate carbon material of the composite particles is not particularly limited. For example, graphite such as artificial graphite, scale-like graphite, exfoliated graphite, natural graphite, acid-treated graphite, expandable graphite, and expanded graphite. Carbon black; and the like can be used. These may be used individually by 1 type and may use 2 or more types together. Among them, it is preferable to use expanded graphite as the particulate carbon material. This is because if expanded graphite is used, the thermal conductivity of the composite material sheet produced using the composite particles can be further improved.

= Expanded graphite =
Here, the expanded graphite that can be suitably used as the particulate carbon material is, for example, finely expanded after heat-treating expandable graphite obtained by chemically treating graphite such as scaly graphite with sulfuric acid or the like. Can be obtained. Examples of expanded graphite include EC1500, EC1000, EC500, EC300, EC100, and EC50 (all are product names) manufactured by Ito Graphite Industries. Moreover, as expanded graphite, scaly expanded graphite is preferable. By using scale-like expanded graphite as the particulate carbon material, the particulate carbon material is more favorably oriented in the produced composite material sheet, and the contact between the particulate carbon materials is facilitated. This is because it is easy to form a heat transfer path.

= Property of particulate carbon material =
Here, the particle diameter of the particulate carbon material contained in the composite particles is not particularly limited, but is preferably 150 μm or more, preferably 500 μm or less, and preferably 300 μm or less in volume conversion mode diameter. It is more preferable. When the particle diameter of the particulate carbon material is not less than the above lower limit, the particulate carbon materials are in good contact with each other, and the composite material sheet is likely to exhibit high thermal conductivity. Moreover, if the particle diameter of a particulate carbon material is below the said upper limit, a contact area with resin combined together will become large and it will be easy to make a composite material sheet exhibit favorable intensity | strength and hardness.
The aspect ratio (major axis / minor axis) of the particulate carbon material contained in the composite particles of the present invention is preferably 1 or more and 10 or less, and more preferably 1 or more and 5 or less.
In the present invention, the “mode diameter in terms of volume” can be measured using a laser diffraction / scattering particle size distribution measuring apparatus. Specifically, the “volume-converted mode diameter” of the particulate carbon material is obtained as the particle diameter at the maximum value of the particle diameter distribution curve obtained using a suspension in which the particulate carbon material is dispersed in a solvent. be able to.
Further, in the present invention, the “aspect ratio” refers to the maximum diameter (major axis) and the particle diameter (in the direction perpendicular to the maximum diameter) using an SEM (scanning electron microscope) for any 50 particulate carbon materials ( (Minor axis) is measured and the average value of the ratio of the major axis to the minor axis (major axis / minor axis) is calculated.
Here, the measurement of the “particle diameter” and the “aspect ratio” of the particulate carbon material contained in the composite particle is, for example, dissolving the resin using a good solvent for the resin contained in the composite particle, etc. The particulate carbon material can be taken out from the composite particles using any of the above methods.

= Content of particulate carbon material =
And it is preferable that content (mass conversion) of a particulate carbon material is 0.6 times or more with respect to resin, and, as for composite particles, it is preferable that it is 2.0 times or less. When the content of the particulate carbon material relative to the resin is 0.6 times or more, the thermal conductivity of the composite material sheet manufactured using the composite particles can be sufficiently increased. Further, if the content of the particulate carbon material relative to the resin is 2.0 times or less, the sheet can be formed while giving high strength to the composite material sheet, and the composite material sheet produced using the composite particles It is possible to suppress an increase in hardness (that is, a decrease in flexibility).

-Fibrous carbon material-
Here, the composite particles can further contain a fibrous carbon material in addition to the above-mentioned particulate carbon material. The fibrous carbon material is not particularly limited, and any fibrous carbon material having thermal conductivity can be used. Specifically, examples of the fibrous carbon material include cylindrical shapes such as vapor-grown carbon fiber, carbon fiber obtained by carbonizing organic fiber, and carbon nanotube (hereinafter sometimes referred to as “CNT”). Carbon nanostructures, non-cylindrical carbon nanostructures such as carbon materials in which a carbon six-membered ring network is formed in a flat cylindrical shape, and their cuts can be used. These may be used individually by 1 type and may use 2 or more types together.

Among them, as the fibrous carbon material used in combination with the particulate carbon material, a fibrous carbon material containing CNT is used from the viewpoint of further improving the thermal conductivity of the composite material sheet by forming a better heat transfer path. Is preferably used. The CNT is not particularly limited, and single-walled carbon nanotubes and / or multi-walled carbon nanotubes can be used. From the viewpoint of further improving the thermal conductivity of the composite material sheet, More preferably, it mainly contains single-walled carbon nanotubes, and more preferably only single-walled carbon nanotubes.
In the present invention, “mainly containing” single-walled carbon nanotubes means that the content of single-walled carbon nanotubes is 90% by mass or more.

= Method for producing fibrous carbon material =
The fibrous carbon material containing CNT is not particularly limited, and is a chemical vapor deposition method including an arc discharge method, a laser ablation method, or a super-growth method (see International Publication No. 2006/011655) ( It can be produced using a known CNT synthesis method such as a CVD method. Hereinafter, the carbon nanotube obtained by the super growth method may be referred to as “SGCNT”.

= Property of fibrous carbon material =
Here, the average diameter of the fibrous carbon material is preferably 0.5 nm or more, and preferably 15 nm or less. If the average diameter of the fibrous carbon material is 0.5 nm or more, aggregation of the fibrous carbon material can be suppressed and the thermal conductivity of the composite material sheet can be further improved. Moreover, if the average diameter of a fibrous carbon material is 15 nm or less, the thermal conductivity which was excellent in the fibrous carbon material can be exhibited, and the thermal conductivity of a composite material sheet can further be improved.

Further, the fibrous carbon material preferably has an average length of 1 μm or more at the time of synthesis. If the average length of the fibrous carbon material at the time of synthesis is 1 μm or more, the heat transfer path can be satisfactorily formed in the composite material sheet. In addition, the longer the fibrous carbon material during synthesis, the easier it is to cause damage such as breakage and cutting in the process of preparing composite particles, so the average length of the fibrous carbon material during synthesis The thickness is preferably 5000 μm or less.
The fibrous carbon material usually has an aspect ratio of more than 10.

From the viewpoint of obtaining a composite material sheet having excellent thermal conductivity, the fibrous carbon material preferably has a BET specific surface area of 200 m ² / g or more, and preferably 2500 m ² / g or less. If the BET specific surface area of a fibrous carbon material is 200 m < ² > / g or more, the thermal conductivity which was excellent in the fibrous carbon material can be exhibited, and the thermal conductivity of a composite material sheet can fully be improved. Moreover, if the BET specific surface area of a fibrous carbon material is 2500 m < ² > / g or less, aggregation of a fibrous carbon material can be suppressed and the thermal conductivity of a composite material sheet can further be improved.

Here, in the present invention, the “average diameter”, “aspect ratio”, and “average length” of the fibrous carbon material are measured using a microscope such as TEM (transmission electron microscope) or SEM (scanning electron microscope). It can be obtained by measuring the diameter (outer diameter) and length of 100 randomly selected fibrous carbon materials. In the present invention, the “BET specific surface area” of the fibrous carbon material refers to a nitrogen adsorption specific surface area measured using the BET method.

= Blending amount of fibrous carbon material =
And content of the fibrous carbon material in a composite particle can be 0.05 mass part or more per 100 mass parts of resin, and can be 5.0 mass parts or less. When the content of the fibrous carbon material per 100 parts by mass of the resin is 0.05 parts by mass or more, the thermal conductivity of the composite material sheet can be sufficiently increased. Further, if the content of the fibrous carbon material per 100 parts by mass of the resin is 5.0 parts by mass or less, the hardness of the composite material sheet is increased by mixing the fibrous carbon material (that is, the flexibility is decreased). It is possible to satisfactorily mold the composite material sheet while sufficiently suppressing the above.

-resin-
The resin contained in the composite particle is not particularly limited, and a known resin that can be used for manufacturing a composite material sheet can be used. Specifically, a thermoplastic resin or a thermosetting resin can be used as the resin. In the present invention, rubber and elastomer are included in “resin”. Moreover, you may use together a thermoplastic resin and a thermosetting resin.

= Thermoplastic resin =
Examples of the thermoplastic resin include poly (2-ethylhexyl acrylate), a copolymer of acrylic acid and 2-ethylhexyl acrylate, polymethacrylic acid or an ester thereof, and an acrylic resin such as polyacrylic acid or an ester thereof. Silicone resin; polyvinylidene fluoride, polytetrafluoroethylene, acrylic modified polytetrafluoroethylene, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, vinylidene fluoride-tetrafluoroethylene-hexafluoropropylene copolymer, etc. Fluorine resin; Polyethylene; Polypropylene; Ethylene-propylene copolymer; Polymethylpentene; Polyvinyl chloride; Polyvinylidene chloride; Polyvinyl acetate; Ethylene-vinyl acetate copolymer; Polyacetal; Polyethylene terephthalate; Polybutylene terephthalate; Polyethylene naphthalate; Polystyrene; Polyacrylonitrile; Styrene-acrylonitrile copolymer; Acrylonitrile-butadiene-styrene copolymer (ABS resin); Styrene-butadiene block copolymer or its hydrogen Additives; Styrene-isoprene block copolymer or hydrogenated product thereof; Polyphenylene ether; Modified polyphenylene ether; Aliphatic polyamides; Aromatic polyamides; Polyamideimide; Polycarbonate; Polyphenylene sulfide; Polysulfone; Nitrile; polyetherketone; polyketone; polyurethane; liquid crystal polymer; ionomer; These may be used individually by 1 type and may use 2 or more types together.

= Thermosetting resin =
Examples of the thermosetting resin include natural rubber, butadiene rubber, isoprene rubber, nitrile rubber, hydrogenated nitrile rubber, chloroprene rubber, ethylene propylene rubber, chlorinated polyethylene, chlorosulfonated polyethylene, butyl rubber, and halogenated butyl rubber. Polyisobutylene rubber; Epoxy resin; Polyimide resin; Bismaleimide resin; Benzocyclobutene resin; Phenolic resin; Unsaturated polyester; Diallyl phthalate resin; Polyimide silicone resin; Polyurethane; Thermosetting polyphenylene ether; Is mentioned. These may be used individually by 1 type and may use 2 or more types together.

Among the above, as the resin of the composite particles, it is preferable to use a thermoplastic resin, more preferably a fluororesin, and a binary fluororesin or a ternary fluororesin composed of different monomers. More preferred. For example, as the ternary fluororesin, a vinylidene fluoride-tetrafluoroethylene-hexafluoropropylene copolymer can be used. This is because the fluororesin is excellent in mechanical properties and the like, and if a thermoplastic resin such as a fluororesin is used, the strength and hardness (flexibility) of the composite material sheet can be further improved.

= Resin content =
Here, the content of the resin contained in the composite particles can be any blending amount. For example, from the viewpoint of satisfactorily combining the particulate carbon material and the resin with the resin, the resin contained in the composite particle is preferably 50 parts by mass or more with respect to 100 parts by mass of the particulate carbon material contained in the composite particle. More than mass part is more preferable, 150 mass parts or less are preferable, 100 mass parts or less are more preferable, and 70 mass parts or less are still more preferable. If the content of the resin per 100 parts by mass of the particulate carbon material is 150 parts by mass or less, the thermal conductivity of the composite material sheet can be sufficiently increased. Further, if the content of the resin per 100 parts by mass of the particulate carbon material is 50 parts by mass or more, the sheet can be molded while giving high strength to the composite material sheet, and the hardness of the composite material sheet increases. (That is, flexibility is reduced) can be sufficiently suppressed.

-Additive-
Additives that can be optionally blended in the composite particles are not particularly limited, and include, for example, red phosphorus flame retardants, phosphate ester flame retardants, and the like; sebacic acid and other plasticizers; calcium oxide, oxidation Hygroscopic agents such as magnesium; Adhesive strength improvers such as silane coupling agents, titanium coupling agents, acid anhydrides; wettability improvers such as nonionic surfactants and fluorosurfactants; inorganic ion exchangers, etc. Ion trapping agents; and the like. Among these, it is preferable to add a phosphate ester flame retardant such as a phosphate ester.

-Preparation method of composite particles-
And in a process (A), a composite particle can be obtained by compounding the above-mentioned particulate carbon material, resin, and optionally a fibrous carbon material and an additive using a known technique. . Specifically, in the step (A), the composite particles can be prepared using, for example, the following method (I) or (II) without any particular limitation.
(I) After kneading a particulate carbon material, a resin, an arbitrary fibrous carbon material and an additive (kneading stage), the obtained kneaded product is pulverized (pulverizing stage) to obtain composite particles.
(II) A dispersion containing a particulate carbon material, a resin, an arbitrary fibrous carbon material and an additive is dried and granulated to obtain composite particles.
Among these, the method (I) is desirable from the viewpoint of satisfactorily combining the particulate carbon material and the resin and from the viewpoint of ease of work.

= Kneading stage =
In the kneading stage that can be included in the step (A), the particulate carbon material, the resin, the arbitrary fibrous carbon material and the additive are kneaded, the particulate carbon material and the resin are contained, and optionally the fibrous shape A kneaded material further containing a carbon material and an additive is obtained.

Here, the kneaded product obtained in the kneading step is usually a lump having a diameter of about 1 mm to 200 mm.
The “particulate carbon material”, “resin”, and any “fibrous carbon material” and “additive” contained in the kneaded product obtained in the kneading stage can be contained in the composite particles described above. Since it is the same as the “particulate carbon material”, “resin”, “fibrous carbon material” and “additive”, the type, properties, blending amount, production method, etc. are also the same, so the description is omitted below. To do.

Here, the kneading method is not particularly limited, and a kneader; a mixer such as a Hobart mixer, a Banbury mixer, a high-speed mixer; a twin-screw kneader; a roll; it can. And kneading | mixing time can be made into 5 minutes or more and 60 minutes or less, for example. Moreover, kneading | mixing temperature can be 5 degreeC or more and 150 degrees C or less, for example.
The kneading may be performed in the presence of a solvent such as ethyl acetate. When a solvent is used at the time of kneading, it is preferable to move to the pulverization stage described below after removing the solvent. The solvent can be removed by a known drying method.

= Grinding stage =
In the pulverization stage that can be included in the step (A), for example, the kneaded product obtained in the above-described kneading stage is appropriately pulverized by an arbitrary technique to obtain composite particles containing the particulate carbon material and the resin.

Here, the composite particles obtained in the pulverization stage are not particularly limited and are preferably pulverized to a particle diameter of less than 1000 μm.

Here, the pulverization method is not particularly limited, and can be performed using a known pulverization apparatus utilizing a shearing action or a grinding action or a known stirring pulverization apparatus. Examples of known crushing devices using shearing action or grinding action or stirring type include, for example, a cutter mill, a hammer mill, a bead mill, a vibration mill, a meteor type ball mill, a sand mill, a ball mill, a roll mill, a three-roll mill, and a jet mill. And a high-speed rotary crusher. Among these, it is desirable to use a cutter mill or a hammer mill.
The pulverization conditions may be adjusted as appropriate according to the desired pulverized particle size, such as the pulverization apparatus and pulverization time. For example, when using a cutter mill, the pulverization time is preferably from 10 seconds to 60 seconds, and when using a hammer mill, the pulverization time is preferably from 5 seconds to 30 seconds.

[Step (B)]
In the step (B), the composite particles prepared in the step (A) include at least two composite particle groups including the composite particle group A having the maximum volume average particle size and the composite particle group B having the minimum volume average particle size. Classify. That is, in the step (B), only the composite particle group A having the maximum volume average particle diameter and the composite particle group B having the minimum volume average particle diameter may be obtained. In the step (B), the composite particle group A having the maximum volume average particle diameter, the composite particle group B having the minimum volume average particle diameter, and the maximum volume average particle diameter and the minimum volume average particle diameter Any other composite particle group having a volume average particle diameter may be obtained. Here, the other composite particle group may be one or plural.
The number of composite particle groups and the volume average particle diameter of each composite particle group can be adjusted by changing the classification method and classification conditions of the composite particles in the step (B).

[[Composite Particle Group A and Composite Particle Group B]]
The composite particle group A obtained in the step (B) needs to have a maximum volume average particle size, and the composite particle group B obtained in the step (B) needs to have a minimum volume average particle size. For example, when the composite particles are classified using a sieve, the top of the sieve having the largest opening is the composite particle group A, and the bottom of the sieve having the smallest opening is the composite particle group B.
Here, the “maximum / minimum volume average particle diameter” means the maximum / minimum of the volume average particle diameters measured for each composite particle group of at least two composite particle groups obtained by classifying the composite particles. Pointing is a relative concept.

That is, for example, if there are two composite particle groups obtained by classification and the respective volume average particle diameters are α μm and β μm (where αμm <β μm), the volume average particle diameter is β μm. A certain composite particle group becomes the composite particle group A, and a composite particle group whose volume average particle diameter is α μm becomes the composite particle group B. Specifically, if the volume average particle diameters of the two composite particle groups obtained by classification are 100 μm and 800 μm, respectively, the composite particle group having a volume average particle diameter of 800 μm becomes the composite particle group A, and the volume average particle A composite particle group having a diameter of 100 μm becomes a composite particle group B <Group 1>. Further, for example, when the obtained composite particle group is three and each volume average particle diameter is 200 μm, 400 μm, and 800 μm, the composite particle group having a volume average particle diameter of 800 μm becomes the composite particle group A. The composite particle group having a volume average particle diameter of 200 μm becomes the composite particle group B <Group 2>. Furthermore, for example, when the obtained composite particle groups are four and each volume average particle diameter is 200 μm, 400 μm, 800 μm, and 1000 μm, the composite particle group having a volume average particle diameter of 1000 μm is the composite particle group A composite particle group having a volume average particle diameter of 200 μm and A is a composite particle group B <Group 3>. Thus, the volume average particle size of the composite particle group A and the composite particle B varies depending on the particle size range to be classified.
The “volume average particle diameter” of the composite particle group refers to the above-described D50, and can be measured using the above-described laser diffraction / scattering particle diameter distribution measuring apparatus.

[[Other complex particles]]
Other composite particle groups that can be obtained in the step (B) are any number of composite particle groups having a volume average particle diameter between the maximum volume average particle diameter and the minimum volume average particle diameter.
That is, in the above <Group 1>, no other composite particle group exists, and in the above <Group 2>, the composite particle group having a volume average particle diameter of 400 μm becomes the other composite particle group. In the above <Group 3>, the two composite particle groups having a volume average particle diameter of 400 μm and 800 μm are the other composite particle groups, respectively.

-Classification method-
Here, the classification is not particularly limited as long as the obtained composite particles can be separated. For example, sieve classification, forced vortex type centrifugal classifier (micron separator, turboplex, turbo classifier, super separator) ), An air classifier such as an inertia classifier (an improved virtual impactor, elbow jet) can be used. A wet sedimentation method, a centrifugal classification method, or the like can also be used. Among these, from the viewpoint of easy work, a sieving method having a desired mesh opening is preferable, and the sieving method is more preferably performed manually.
From the viewpoint of obtaining a good composite particle for pressurization, when classifying the composite particles using a sieve, it is preferable to classify using one or more sieves having a sieve opening of 500 μm or less. It is more preferable to classify using one or more sieves having an opening of 250 μm or less, and the opening of the sieve to be used is preferably 150 μm or more.
Here, the classification temperature is not particularly limited, and can be performed, for example, at 25 ° C.

[Step (C)]
In the step (C), the composite particles for pressurization are prepared by using the composite particles contained in the composite particle groups other than the composite particle group A among the composite particle groups obtained in the step (B).

Here, “use composite particles contained in a composite particle group other than the composite particle group A” is included in the composite particle group B obtained by classification in the above <Group 1>, for example. This refers to preparing composite particles for pressurization using only composite particles (that is, removing composite particle group A from the entire composite particles obtained in step (A)).

Further, for example, in the above <Group 2>, at least one of the composite particles contained in the composite particle group B and other composite particle groups is used (that is, at least the composite particle group A is used in the step (A)). A composite particle for pressurization is prepared by removing from the entire composite particle obtained). That is, in the above <Group 2>, the composite particles for pressurization may be prepared using the composite particles contained in the composite particle group B and other composite particle groups, or included in the composite particle group B. The composite particles for pressurization may be prepared using only the composite particles that are present, or the composite particles for pressurization may be prepared using only the composite particles contained in other composite particle groups.
Thus, in the step (C), it is necessary to remove at least the composite particle group A from the composite particle group used for preparing the pressurizing composite particles. Further, the step (C) is to remove the composite particle group (composite particle group B and / or other composite particle group) other than the composite particle group A from the composite particle group used for preparing the composite particles for pressurization. Do not limit.
In <Group 2> described above, when preparing the composite particles for pressurization using the composite particles contained in the composite particle group B and the other composite particle groups, the composite particle group B and the other composite particles are prepared. Particle groups can be mixed and used at an arbitrary ratio. Moreover, the mixing of the composite particles at that time can be performed using a known mixing method.

Similarly to the above, for example, in <Group 3>, composite particles contained in at least one of the composite particle group B and two other composite particle groups are used (that is, at least the composite particle group A is converted into the step (A). Remove from the whole composite particles obtained in step)) to prepare composite particles for pressurization. That is, in the above <Group 3>, the composite particles for pressurization may be prepared using the composite particles contained in the composite particle group B and the two other composite particle groups. In the above <Group 3>, the composite particles for pressurization may be prepared using the composite particles contained in any one of the composite particle group B and two other composite particle groups. You may prepare the pressurization composite particle only using the composite particle contained in two other composite particle groups. Furthermore, in <Group 3> described above, the composite particles for pressurization may be prepared using only the composite particles contained in any one of the composite particle group B and two other composite particle groups.
Here, it is the same as in the case of <Group 2> that the composite particle group B and / or other composite particle groups used for preparing the composite particles for pressurization can be mixed at an arbitrary ratio.

Thus, the pressurizing composite particles obtained in the pressurizing composite particle preparation step including the steps (A), (B), and (C) described above are predetermined composite particles excluding at least a coarse composite particle group. Since it is prepared using the composite particles contained in the group, when the composite particles for pressurization are pressed, the manufactured composite material sheet can exhibit excellent thermal conductivity. In addition, the manufactured composite material sheet can exhibit excellent strength and hardness. The reason for this is not clear, but is presumed to be as follows.
That is, generally, in a molded body such as a sheet formed by pressurizing a composite material containing a particulate carbon material and a resin, the particulate carbon materials are in contact with each other to form a heat transfer path with excellent thermal conductivity. As a result, the thermal conductivity is improved. Here, in the case where composite particles that are a composite material containing a particulate carbon material and a resin are used without being classified, an aggregate of composite particles having a large particle size difference in which large particle size particles and small particle size particles are mixed Will be pressurized. Usually, when an aggregate of particles having a large particle size difference is pressurized, it is difficult to apply a uniform pressure to each particle. Further, since the small particle diameter particles easily flow through the gaps between the large particle diameter particles during pressurization, it is difficult to apply a large shear force to the aggregate of the particles.
On the other hand, when a composite particle group obtained by classifying composite particles containing a particulate carbon material and a resin and removing a composite particle group having a coarse particle diameter is used, it is easy to apply a uniform pressure to each particle, A large shearing force is easily applied to the aggregate of particles during pressurization. In addition, the area of mutual contact between the particles is relatively large with relatively small particles.
Accordingly, in the composite material sheet produced by pressurizing the composite particles for pressurization including the predetermined composite particle group that has undergone the above-described steps (A) to (C), the particulate carbon materials are in good contact with each other, In addition, the contact is easily aligned in the in-plane direction of the sheet due to the uniform shearing force. As a result, the manufactured composite material sheet has a good heat transfer path along the in-plane direction, and can exhibit high thermal conductivity particularly having in-plane orientation.

Further, in the composite particles included in the composite particle group from which the composite particle group having a coarse particle diameter is removed, the particulate carbon material and the resin are uniformly combined. Therefore, when the above-mentioned uniform pressure is applied to the composite particles, not only the granular carbon materials but also the resins come into contact with each other in a good blended state, so that the manufactured composite material sheet has excellent strength and flexibility. It can be demonstrated.

Here, the volume average particle diameter of the composite particle group including the composite particles used in the step (C) is preferably 500 μm or less, more preferably 400 μm or less, further preferably 350 μm or less, and 300 μm or less. It is more preferable that the thickness is 150 μm or more. If pressurizing composite particles for pressurization obtained using composite particles contained in a relatively small composite particle group whose volume average particle diameter is not more than the above upper limit, as described above, thermal conductivity, strength, and hardness are further increased. This is because an improved composite material sheet can be produced. In addition, if the volume average particle diameter of the composite particle group is 150 μm or more, it is possible to suppress the formation of heat transfer paths that are difficult to contact with each other in an excessively small particle, so that good thermal conductivity is achieved. It is because it is obtained.

[[Composite particles for pressurization]]
The composite particles for pressurization obtained in the step (C) constitute a composite material sheet through a pressurization step described later. Moreover, the composite particle for pressurization obtained at a process (C) is prepared using the composite particle contained in composite particle groups other than the composite particle group A as above-mentioned. And by pressurizing the composite particles for press obtained using the composite particles contained in a relatively small composite particle group other than the composite particle group A, the composite material sheet to be manufactured has high thermal conductivity, high strength, and Good hardness can be given.

-Properties of pressurized composite particles-
Here, in the composite particles for pressurization, the content of the composite particles having a particle diameter of 500 μm or more is preferably less than 40% by volume, more preferably less than 35% by volume, and further preferably less than 25% by volume. preferable. By removing a relatively large group of classified composite particles and pressurizing composite particles for pressurization with a content of composite particles having a particle diameter of 500 μm or more to less than 40% by volume in a pressurizing step described later, thermal conductivity This is because a composite material sheet with further improved strength and hardness can be produced.
The particle size distribution of the pressurizing composite particles can be adjusted by changing the method of classifying the composite particles in the step (B) and the method of combining the composite particle groups used for preparing the pressurizing composite particles.

<Pressurization process>
And the manufacturing method of the composite material sheet | seat of this invention is a pressurization process which obtains a composite material sheet | seat by pressurizing the composite particle for pressurization prepared by the preparatory process of the composite particle for pressurization mentioned above, and shape | molding in a sheet form. Need to contain. If pressure is applied to the above-mentioned predetermined composite particles for pressurization, it is possible to produce a composite material sheet having excellent thermal conductivity in the in-plane direction and having high strength and good hardness arranged side by side.

[Pressurization method]
Here, pressurization is not particularly limited as long as it is a molding method in which pressure is applied to the pressurizing composite particles, and a known molding method such as press molding, rolling molding or extrusion molding can be performed. Especially, it is preferable to shape | mold the composite particle for pressurization in a sheet form by rolling, and it is more preferable to pass between rolls in the state pinched | interposed into the protective film, and to shape | mold into a sheet form. In addition, as a protective film, it does not specifically limit, The polyethylene terephthalate (PET) film which performed the sandblasting process, the PET film which performed the silicone mold release process, etc. can be used. The roll temperature is 5 ° C. or more and 150 ° C. or less, the roll gap is 50 μm or more and 2500 μm or less, the roll linear pressure is 1 kg / cm or more and 3000 kg / cm or less, and the roll speed is 0.1 m / min or more and 20 m / min or less. it can.

And in the composite material sheet | seat manufactured through the pressurization process, it is guessed that a particulate carbon material arranges mainly in a sheet surface direction as above-mentioned. Furthermore, in the said composite material sheet, a heat-transfer path | route is favorably formed in an in-plane direction by contact between particulate carbon materials. Therefore, it is presumed that the composite material sheet manufactured using the above-described manufacturing method improves the thermal conductivity particularly in the in-plane direction. Moreover, the composite material sheet manufactured using the said manufacturing method is excellent also in intensity | strength and hardness as above-mentioned.
In addition, the thickness of a composite material sheet is not specifically limited, For example, it can be 0.05 mm or more and 2 mm or less. Further, from the viewpoint of further improving the thermal conductivity of the composite material sheet, the thickness of the composite material sheet is more than 1 time and not more than 5000 times the volume standard mode diameter of the particulate carbon material used for manufacturing the composite material sheet. It is preferable.

(Method for producing heat conductive sheet)
In the manufacturing method of the heat conductive sheet of this invention, the process (lamination process) of obtaining a laminated body using the composite material sheet manufactured by the manufacturing method of the composite material sheet of this invention, and the process of slicing a laminated body (for example) Through the slicing step, a heat conductive sheet can be manufactured. By subjecting the above-mentioned composite material sheet to a laminating step and a slicing step, it is possible to produce a heat conductive sheet excellent in all of the heat conductivity, strength, and hardness in the sheet thickness direction.
Hereinafter, each step will be specifically described.

<Lamination process>
In the step of obtaining a laminate (lamination step), a plurality of composite material sheets manufactured using the above-described composite material sheet manufacturing method are stacked in the thickness direction, or the above-described composite material sheet manufacturing method is used. The manufactured composite material sheet is folded or wound to obtain a laminate. Here, formation of the laminated body by lamination | stacking of a composite material sheet | seat is not specifically limited, You may carry out using a lamination apparatus, and may carry out manually. Moreover, formation of the laminated body by folding of a composite material sheet is not specifically limited, It can carry out by folding a composite material sheet by fixed width using a folding machine. Furthermore, the formation of the laminate by winding the composite material sheet is not particularly limited, and can be performed by winding the composite material sheet around an axis parallel to the short side direction or the long side direction of the composite material sheet. it can.

Here, usually, in the laminate obtained in the lamination step, the adhesive force between the surfaces of the composite material sheet is sufficiently obtained by the pressure at the time of laminating the composite material sheet and the pulling force at the time of folding or winding. . However, if the adhesive force is insufficient or if it is necessary to sufficiently suppress delamination of the laminate, the lamination step may be performed in a state where the surface of the composite material sheet is slightly dissolved with a solvent, The laminating step may be performed in a state where an adhesive is applied to the surface of the composite material sheet or an adhesive layer is provided on the surface of the composite material sheet.

The solvent used for dissolving the surface of the composite material sheet is not particularly limited, and a known solvent (for example, methyl ethyl ketone) that can dissolve the resin contained in the composite material sheet is used. Can do.

Moreover, it does not specifically limit as an adhesive agent apply | coated to the surface of a composite material sheet, A commercially available adhesive agent and adhesive resin can be used. The adhesive layer provided on the surface of the composite material sheet is not particularly limited, and a double-sided tape or the like can be used. Especially, as an adhesive layer, it is preferable to provide the adhesive layer which has an acrylic adhesive which is excellent in adhesiveness. And the thickness of the adhesive agent apply | coated to the surface of a composite material sheet or the contact bonding layer provided in the surface of a composite material sheet can be 1 micrometer or more and 1000 micrometers or less, for example.
Here, the heat conductive filler may be mix | blended with the adhesive agent or the contact bonding layer in the range by which the heat conductive sheet obtained does not become hard too much.

From the viewpoint of suppressing delamination, the obtained laminate is heated at 50 ° C. or more and 170 ° C. or less for 10 minutes to 8 hours while being pressed at a pressure of 0.1 MPa or more and 0.5 MPa or less in the lamination direction. Also good.

And in the laminate obtained by laminating, folding or winding the composite material sheet, it is presumed that the particulate carbon material and any fibrous carbon material are arranged in a direction substantially perpendicular to the laminating direction. In the laminate, the heat transfer path formed by the good contact between the particulate carbon materials or between the particulate carbon material and the fibrous carbon material is arranged mainly in a direction substantially orthogonal to the lamination direction. It is guessed.

<Slicing process>
In the slicing step, the laminated body obtained in the above-described laminating step is sliced at an angle of 45 ° or less with respect to the laminating direction to obtain a heat conductive sheet composed of sliced pieces of the laminated body. Here, the method for slicing the laminate is not particularly limited, and examples thereof include a wire saw method, a multi-blade method, a laser processing method, a water jet method, and a knife processing method. Especially, the knife processing method is preferable at the point which makes the thickness of a heat conductive sheet uniform. The cutting tool for slicing the laminate is not particularly limited, and includes a slice member (for example, a sharp blade) having a smooth board surface having a slit and a blade portion protruding from the slit portion. Cutter, canna, slicer) can be used.

In addition, from the viewpoint of increasing the thermal conductivity of the heat conductive sheet, the angle at which the laminate is sliced is preferably 30 ° or less with respect to the stacking direction, and more preferably 15 ° or less with respect to the stacking direction. Preferably, it is substantially 0 ° with respect to the stacking direction (that is, a direction along the stacking direction).

Further, from the viewpoint of easily slicing the laminate, the temperature of the laminate when slicing is preferably −20 ° C. or more and 80 ° C. or less, and more preferably −10 ° C. or more and 50 ° C. or less. Further, for the same reason, the laminated body to be sliced is preferably sliced while applying a pressure in a direction perpendicular to the lamination direction, and a pressure of 0.05 MPa to 0.5 MPa in a direction perpendicular to the lamination direction. It is more preferable to slice while loading.

And in the heat conductive sheet obtained through the slicing step, the particulate carbon material and any fibrous carbon material are substantially orthogonal to the thickness direction of the heat conductive sheet (that is, the lamination direction of the composite material sheet as the pre heat conductive sheet). It is inferred that they are arranged in the direction of Moreover, in the said heat conductive sheet, the heat-transfer path | route formed by the favorable contact of particulate carbon materials or a particulate carbon material and a fibrous carbon material has mainly arranged in the thickness direction of the heat conductive sheet. It is guessed. Therefore, the said heat conductive sheet is excellent in the heat conductivity of the thickness direction.
Moreover, since the composite material sheet mentioned above is excellent also in intensity | strength and hardness, it is guessed that the heat conductive sheet manufactured using the said composite material sheet is also excellent in intensity | strength and hardness.

EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, this invention is not limited to these Examples. In the following description, “%” and “part” representing amounts are based on mass unless otherwise specified.
In Examples and Comparative Examples, the particle diameter of expanded graphite in the heat conductive sheet, the volume average particle diameter of the composite particles and the composite particles for pressurization, the content of composite particles having a particle diameter of 500 μm or more in the composite particles for pressurization, The strength of the composite material sheet, the hardness of the composite material sheet, and the thermal conductivity of the heat conductive sheet were measured, calculated, or evaluated using the following methods, respectively.

<Particle size of expanded graphite in heat conductive sheet>
3 g of the manufactured heat conductive sheet was stirred for 5 minutes in 6 g of methyl ethyl ketone solvent using a stirrer, and then visually confirmed that there was no sheet-like material in the methyl ethyl ketone solvent, and contained in the heat conductive sheet. A suspension containing expanded graphite as a particulate carbon material was obtained. The particle diameter of the expanded graphite contained in the obtained suspension was measured using a laser diffraction / scattering particle size distribution measuring apparatus (manufactured by Horiba, model number “LA-960”). Then, a particle size distribution curve is obtained in which the horizontal axis is the particle size and the vertical axis is the abundance ratio of expanded graphite (volume basis), and the particle size at the maximum value of the particle size distribution curve is determined based on the volume basis of the expanded graphite. The mode diameter (μm) was obtained. The results are shown in Table 1.

<Volume average particle diameter of composite particle group and composite particle for pressurization>
Each composite particle group and 100 mg of composite particles for pressurization were used as samples, and each composite particle group and pressurization composite were measured using a laser diffraction / scattering particle size distribution measuring device (manufactured by Nikkiso, model number “Microtrack MT3300EX-II”). A particle size distribution of the particles was obtained. Then, in the obtained particle diameter distribution (volume basis), the central particle diameter (D50) at which the cumulative volume calculated from the small diameter side becomes 50% is determined as the volume average particle diameter (μm) of the composite particles included in the composite particle group. ) And the volume average particle diameter (μm) of the composite particles for pressurization. The results are shown in Table 1.

<Content of composite particles having a particle diameter of 500 μm or more in the composite particles for pressurization>
Using 100 mg of each composite particle for pressurization as a sample, a particle size distribution of each composite particle for pressurization was obtained using a laser diffraction / scattering particle size distribution measuring device (manufactured by Nikkiso, model number “Microtrack MT3300EX-II”). And the content rate (volume%) of the composite particle with a particle diameter of 500 micrometers or more was computed from the obtained particle diameter distribution. The results are shown in Table 1.

<Strength of composite material sheet>
The manufactured composite material sheet was punched out in a size of 20 mm × 80 mm to obtain a test body. Using a small tabletop testing machine (manufactured by Nidec Sympo, model number “FGS-500TV”, using FGP-50 as a digital force gauge), the test specimen obtained was pulled at a speed of 20 mm / min and the distance between chucks was 60 mm. By carrying out a tensile test, the breaking distance (mm) was measured as the maximum tensile strength (N) and the maximum elongation. It shows that the intensity | strength of a composite material sheet is so high that the obtained tensile strength and breaking distance are large. The results are shown in Table 1.

<Hardness of composite material sheet>
The hardness of the composite material sheet was evaluated as the hardness of a specimen (composite material sheet layer) in which a plurality of composite material sheets were stacked. Here, the hardness was measured according to the Asker C method of the Japan Rubber Association Standard (SRIS).
Specifically, the composite material sheets obtained in Examples and Comparative Examples were cut into a size of 25 mm wide × 50 mm long × 0.5 mm thick, and a test piece was obtained by stacking 24 sheets. The obtained test piece was allowed to stand in a temperature-controlled room maintained at a temperature of 23 ° C. for 48 hours or longer to obtain a composite material sheet layer as a test body. Next, the height of the damper was adjusted so that the pointer became 95 to 98, and the composite material sheet layer and the damper were made to collide with each other. The Asker C hardness of the composite material sheet layer 60 seconds after the collision was measured twice using a hardness meter (product name “ASKER CL-150LJ” manufactured by Kobunshi Keiki Co., Ltd.), and the average value of the measurement results was adopted. did. The smaller the Asker C hardness, the more flexible and excellent the composite sheet. The results are shown in Table 1.

<Thermal conductivity of thermal conductive sheet>
About the heat conductive sheet manufactured by the Example and the comparative example, thermal diffusivity (alpha) (m < ² > / s) of thickness direction, constant-pressure specific heat Cp (J / g * K), and specific gravity (rho) (g / m < ³ >) are the following methods. Measured with
[Thermal diffusivity]
The thermal diffusivity at a temperature of 25 ° C. was measured using a thermophysical property measuring apparatus (product name “Thermo Wave Analyzer TA35” manufactured by Bethel Co., Ltd.).
[Specific pressure specific heat]
Using a differential scanning calorimeter (manufactured by Rigaku, product name “DSC8230”), the specific heat at a temperature of 25 ° C. was measured under a temperature rising condition of 10 ° C./min.
[specific gravity]
The measurement was made using an automatic hydrometer (product name “DENSIMTER-H” manufactured by Toyo Seiki Co., Ltd.).
And the following formula (I):
λ = α × Cp × ρ (I)
Further, the thermal conductivity λ (W / m · K) of the thermal conductive sheet at a temperature of 25 ° C. was determined. It represents that it is a heat conductive sheet excellent in the heat conductivity of the thickness direction, so that (lambda) value is large. The results are shown in Table 1.

Example 1
<Preparation process of composite particles for pressurization>
[Step (A)]
[[Kneading stage]]
130 parts of expanded graphite (product name “EC-50”, average particle size: 250 μm) as a particulate carbon material, 1 part of a CNT easy dispersion aggregate as a fibrous carbon material, 80 parts of fluororesin (made by Daikin Industries, product name “DAIEL G-912”) as resin, and 10 parts of phosphoric ester (product name “LEOFOS 65”, manufactured by Ajinomoto Fine Techno Co., Ltd.) as flame retardant The mixture was stirred and kneaded at 50 ° C. for 30 minutes using a kneader (manufactured by Inoue Seisakusho) to obtain a kneaded product containing expanded graphite, CNT, fluororesin, and phosphate ester.
In addition, the used CNT easy-dispersed aggregate was prepared by the following method.

-Preparation of CNT easily dispersed aggregate-
A fibrous carbon material containing SGCNT was obtained by the above-described super-growth method. The obtained fibrous carbon material had a BET specific surface area of 800 m ² / g. Further, as a result of measuring the diameter and length of 100 randomly selected fibrous carbon materials using a transmission electron microscope, the average diameter was 3.3 nm and the average length was 100 μm. Furthermore, the obtained fibrous carbon material was mainly composed of single-walled CNTs.
Next, by removing the solvent from the dispersion obtained by dispersing the obtained fibrous carbon material in methyl ethyl ketone as a dispersion medium using a filter paper (Kiriyama Co., No. 5A) under reduced pressure. As a fibrous carbon material, a CNT easy-dispersed aggregate containing SGCNT was obtained. Since a fibrous carbon material such as CNT is generally easily aggregated, mixing with other components can be facilitated by setting it in such a state of an easily dispersible aggregate.

[[Crushing stage]]
The kneaded material obtained above was pulverized for about 30 seconds at 25 ° C. using a coffee mill (manufactured by Carita, model number “CM-50”), and expanded graphite, CNT, fluororesin, and phosphoric acid. Composite particles containing ester were obtained.

[Step (B)]
The composite particles obtained above are classified at 25 ° C. using sieves (manufactured by Tokyo Screen, openings: 150 μm, 250 μm), so that each of composite particle groups A (on a sieve having openings of 250 μm), composite particles Three composite particle groups were obtained: Group B (under a sieve having an opening of 150 μm) and other composite particles (aperture: above a sieve of 150 μm and under a sieve of 250 μm).

[Step (C)]
Of the three composite particle groups obtained above, the composite particle group A and the composite particle group B were removed, and only the composite particles contained in the other composite particle groups were directly employed as the pressurizing composite particles.
Then, the volume average particle size of the employed composite particle group (that is, the composite particle for pressurization) and the content ratio of the composite particle having a particle size of 500 μm or more in the obtained composite particle for pressurization were calculated. The results are shown in Table 1.

<Pressurization process>
10 g of the composite particles for pressurization obtained as described above were subjected to sandblast treatment and a PET film (protective film A) having a thickness of 50 μm and PET film (protective film B) having a thickness of 75 μm subjected to one-side silicone release treatment. Was rolled and formed under the conditions of a roll gap of 350 μm, a roll temperature of 50 ° C., a roll linear pressure of 50 kg / cm, and a roll speed of 1 m / min, to obtain a composite material sheet having a thickness of 0.5 mm.
And the intensity | strength and hardness (Asker C hardness) of the obtained composite material sheet were measured. The results are shown in Table 1.

<Lamination process>
A double-sided tape (manufactured by Nichiei Kako, product name “NeoFix10”, thickness: 10 μm) was attached to any one side of the composite material sheet obtained above. Next, by combining the surface side of the composite material sheet on which the double-sided tape is applied and the surface side of another composite material sheet on which the double-sided tape is not applied, and repeating the same operation for 120 sheets, the thickness is increased. A laminate of about 6 cm was obtained. The obtained laminate was compressed by hand, and the adhesive surfaces of the composite material sheet were brought into close contact with each other.

<Slicing process>
After that, while pressing the laminate of the composite material sheet with a pressure of 0.3 MPa, the slicer for woodworking (manufactured by Marunaka Co., Ltd., product name “Super-finished plane super mechanism”, the protruding length of the blade is 0.11 mm) at a speed of 2 mm / min and sliced at an angle of 0 degrees with respect to the stacking direction (in other words, sliced in the normal direction of the main surface of the laminated composite material sheet) A heat conductive sheet having a thickness of 0.50 mm was obtained.
And the particle diameter of the expanded graphite in the obtained heat conductive sheet and the heat conductivity of the heat conductive sheet were calculated. The results are shown in Table 1.

(Example 2)
In step (B), classification is performed using sieves having mesh openings of 150 μm, 250 μm, and 500 μm, so that composite particle group A (on a sieve having an opening of 500 μm) and composite particle group B (a sieve having an opening of 150 μm) are obtained. Lower), four composite particle groups of other composite particle group C (upper and 150 μm sieve openings) and other composite particle group D (up and 250 μm sieve openings) Got.
In step (C), among the obtained four composite particle groups, composite particle group A and composite particle B were removed, and other composite particle group C and other composite particle group D were employed. And the composite particle for pressurization was obtained by mixing the composite particle contained in the said 2 composite particle group by mass ratio 1: 1.
Except for the above, in the same manner as in Example 1, a kneaded product, composite particles, composite particle group, composite particles for pressurization, composite material sheet, and heat conductive sheet were produced. Measurement, calculation, or evaluation was performed in the same manner as in Example 1. The results are shown in Table 1.

(Example 3)
In the step (B), classification is performed using a sieve having mesh openings of 250 μm and 500 μm, so that composite particle group A (on a sieve having an opening of 500 μm) and composite particle group B (under a sieve having an opening of 250 μm), respectively. , And other composite particle groups (upper sieve having a sieve opening of 250 μm and lower sieve of 500 μm) were obtained.
Further, in the step (C), among the obtained three composite particle groups, the composite particle group A and the composite particle B are removed, and only the composite particles contained in the other composite particle groups are employed as they are. Composite particles for pressurization were obtained.
Except for the above, in the same manner as in Example 1, a kneaded product, composite particles, composite particle group, composite particles for pressurization, composite material sheet, and heat conductive sheet were produced. Measurement, calculation, or evaluation was performed in the same manner as in Example 1. The results are shown in Table 1.

(Comparative Example 1)
The composite particles for pressurization were obtained by directly adopting the composite particles obtained after the pulverization stage (that is, not classified) without performing the steps (B) and (C).
Except for the above, a kneaded product, composite particles, composite particles for pressurization, a composite material sheet, and a heat conductive sheet were produced in the same manner as in Example 1.
Measurement, calculation, or evaluation was performed in the same manner as in Example 1. The results are shown in Table 1.

(Comparative Example 2)
In the step (B), by classifying using a sieve having a mesh opening of 500 μm, each of composite particle group A (on a sieve having an opening of 500 μm) and composite particle group B (below a sieve having an opening of 500 μm) Two composite particle groups were obtained.
Further, in step (C), among the obtained two composite particle groups, the composite particle group B was removed, and only the composite particles contained in the composite particle group A were employed to obtain composite particles for pressurization. .
Except for the above, a kneaded product, composite particles, composite particle group, composite particles for pressurization, composite material sheet, and heat conductive sheet were produced in the same manner as in Example 1. Measurement, calculation, or evaluation was performed in the same manner as in Example 1. The results are shown in Table 1.

(Comparative Example 3)
In step (B), classification is performed using sieves having mesh openings of 150 μm, 250 μm, and 500 μm, so that composite particle group A (on a sieve having an opening of 500 μm) and composite particle group B (a sieve having an opening of 150 μm) are obtained. Lower), four composite particle groups of other composite particle group C (upper sieve of 150 μm opening and under 250 μm sieve) and composite particle group D (upper sieve of 250 μm opening and under 500 μm sieve) are obtained. It was.
Further, in the step (C), among the obtained four composite particle groups, the composite particle group B and the other composite particle group D were removed, and the composite particle group A and the other composite particle group C were adopted. And the composite particle for pressurization was obtained by mixing the composite particle contained in the said 2 composite particle group by mass ratio 1: 1.
Except for the above, in the same manner as in Example 1, a kneaded product, composite particles, composite particle group, composite particles for pressurization, composite material sheet, and heat conductive sheet were produced. Measurement, calculation, or evaluation was performed in the same manner as in Example 1. The results are shown in Table 1.

(Comparative Example 4)
In the step (B), by classifying using a sieve having a mesh opening of 250 μm and 500 μm, composite particle group A (on a sieve having an opening of 500 μm) and other composite particle groups (on a sieve having an opening of 250 μm) And a composite particle group B of a composite particle group B (under a sieve having an opening of 250 μm) was obtained.
In step (C), only the composite particle group B was removed from the obtained three composite particle groups, and the composite particle group A and the other composite particle groups were employed. And the composite particle for pressurization was obtained by mixing the composite particle contained in the said 2 composite particle group by mass ratio 1: 1.
Except for the above, in the same manner as in Example 1, a kneaded product, composite particles, composite particle group, composite particles for pressurization, composite material sheet, and heat conductive sheet were produced. Measurement, calculation, or evaluation was performed in the same manner as in Example 1. The results are shown in Table 1.

(Comparative Example 5)
In step (B), classification is performed using sieves having mesh openings of 150 μm, 250 μm, and 500 μm, so that composite particle group A (on a sieve having an opening of 500 μm) and composite particle group B (a sieve having an opening of 150 μm) are obtained. Lower), four composite particle groups of other composite particle group C (upper sieve of 150 μm opening and under 250 μm sieve) and composite particle group D (upper sieve of 250 μm opening and under 500 μm sieve) are obtained. It was.
Further, in the step (C), among the obtained four composite particle groups, the composite particle group B and the other composite particle group D were removed, and the composite particle group A and the other composite particle group C were adopted. And the composite particle for pressurization was obtained by mixing the composite particle contained in the said 2 composite particle group by composite particle group A: composite particle group C = 9: 1 (mass ratio).
Except for the above, in the same manner as in Example 1, a kneaded product, composite particles, composite particle group, composite particles for pressurization, composite material sheet, and heat conductive sheet were produced. Measurement, calculation, or evaluation was performed in the same manner as in Example 1. The results are shown in Table 1.

From Table 1, composite particles obtained by classifying / excluding the composite particle group A having a coarse particle diameter by going through all the steps (A), (B) and (C) in the step of preparing the composite particles for pressurization. In Examples 1 to 3 using groups, compared with Comparative Example 1 in which the classification / exclusion was not performed, favorable characteristics were exhibited in all of thermal conductivity, strength, and hardness.
In addition, the composite particle group obtained by classifying and excluding the composite particle group A having a coarse particle diameter by going through all the steps (A), (B) and (C) in the step of preparing the composite particles for pressurization. In Examples 1 to 3 used, high thermal conductivity, high strength and good hardness could be juxtaposed as compared with Comparative Examples 2 to 5 using the composite particle group A without performing the above exclusion. .
Therefore, the composite material sheet / thermal conductive sheet having excellent thermal conductivity, strength, and hardness can be provided by the composite material sheet manufacturing method / thermal conductive sheet manufacturing method of the present invention.

ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the composite material sheet which paralleled high thermal conductivity, high intensity | strength, and favorable hardness can be provided.
Moreover, according to this invention, the manufacturing method of the heat conductive sheet which made parallel high heat conductivity, high intensity | strength, and favorable hardness can be provided.

Claims (6)

1. A method for producing a composite material sheet, comprising: a step of preparing composite particles for pressurization to obtain composite particles for pressurization; and a pressurization step of obtaining a composite material sheet by pressurizing the composite particles for pressurization,
   The step of preparing the composite particles for pressurization includes:
   Preparing a composite particle containing a particulate carbon material and a resin (A);
   Classifying the prepared composite particles into at least two composite particle groups including a composite particle group A having a maximum volume average particle diameter and a composite particle group B having a minimum volume average particle diameter (B);
   (C) preparing the pressurizing composite particles using composite particles contained in a composite particle group other than the composite particle group A among the composite particle groups;
   A method for producing a composite material sheet, comprising:
2. The method for producing a composite material sheet according to claim 1, wherein the volume average particle diameter of the composite particle group containing the composite particles used in the step (C) is 500 µm or less.
3. The method for producing a composite material sheet according to claim 1 or 2, wherein the composite particles for pressurization have a content of composite particles having a particle diameter of 500 µm or more of less than 40% by volume.
4. The method for producing a composite material sheet according to any one of claims 1 to 3, wherein the composite particles contain 50 parts by mass or more and 150 parts by mass or less of the resin with respect to 100 parts by mass of the particulate carbon material.
5. The step (A) includes a kneading step of kneading the particulate carbon material and the resin to obtain a kneaded product, and a pulverizing step of crushing the kneaded product to obtain the composite particles. The manufacturing method of the composite material sheet of any one of these.
6. The manufacturing method according to any one of claims 1 to 5, wherein a plurality of the composite material sheets obtained by the manufacturing method according to any one of claims 1 to 5 are laminated in the thickness direction, or the manufacturing method according to any one of claims 1 to 5. Folding or winding the composite material sheet obtained in step to obtain a laminate;
   Slicing the laminate at an angle of 45 ° or less with respect to the lamination direction to obtain a heat conductive sheet;
   The manufacturing method of the heat conductive sheet containing this.