TW201835182A - Heat transfer sheet - Google Patents

Abstract

The thermally conductive sheet of the present invention includes a plurality of semi-finished thermally conductive sheets. The semi-finished thermally conductive sheet contains a particulate carbon material and a resin or a composite of multiple resins. A plurality of semi-finished thermally conductive sheets are stacked in the transverse direction with respect to the thickness direction of the thermally conductive sheets. The Mooney viscosity of all resin components is below 90 (ML _{1 + 4} , 100 ° C).

Description

Heat conductive sheet

The present invention relates to a heat conductive sheet.

In recent years, electronic components such as plasma display (PDP) and integrated circuit (IC) wafers have generated more heat with higher performance. As a result, electronic devices using electronic parts are beginning to seek countermeasures against malfunctions caused by the temperature rise of the electronic parts.

The countermeasures for abnormal functions caused by the temperature rise of electronic parts are generally to adopt the following methods: install heat sinks such as metal radiators, heat sinks, and heat dissipation fins on heat generating bodies such as electronic parts to promote heat dissipation. In addition, when the heat dissipation body is used, in order to efficiently conduct heat from the heat generating body to the heat dissipating body, the heat generating body and the heat dissipating body are closely adhered via a sheet member (heat conductive sheet) exhibiting good thermal conductivity. In addition, the heat conductive sheet disposed between the heat generating body and the heat dissipating body is required to have a high thermal conductivity in the thickness direction.

Here, as the heat conductive sheet, a sheet formed by using a compound mixture is usually used, and the compound mixture is mixed with a resin, a component exhibiting heat conductivity, and the like. In recent years, in order to improve the thermal conductivity of the thermally conductive sheet, many studies have been conducted on the constituent components of the thermally conductive sheet.

Specifically, in the past, there has been proposed a heat dissipation sheet (that is, "thermally conductive sheet") containing a specific rubber component and anisotropic graphite oriented in a certain direction (for example, refer to Patent Document 1: Japanese Patent No. 4743344). Patent Document 1 discloses a heat sink manufactured using a composition, wherein the composition is obtained by blending anisotropic graphite in a resin component, and the resin component includes a thermoplastic rubber component, a thermosetting rubber component, and a A thermosetting rubber hardener cross-linked to this thermosetting rubber component. When manufacturing a thermally conductive sheet, the prepared composition is sandwiched between two films and rolled, and the anisotropic graphite is oriented in a direction roughly parallel to the main surface of the rolled sheet to make a primary sheet . Next, this primary sheet is wound in a specified direction to obtain a shaped body, and this shaped body is sliced in a specified direction to make a thermally conductive sheet.

However, the thermally conductive sheet disclosed in Patent Document 1 has room for improvement in improving thermal conductivity.

Therefore, an object of the present invention is to provide a thermally conductive sheet excellent in thermal conductivity in the thickness direction.

In order to achieve the above object, the inventors of the present invention conducted intensive research. Furthermore, the present inventors have newly discovered that the Mooney viscosity of the resin component contained in the thermally conductive sheet greatly affects the thermal conductivity of the thermally conductive sheet, and completed the present invention.

That is, the object of the present invention is to effectively solve the above-mentioned problems. The thermally conductive sheet of the present invention is characterized by stacking a plurality of semi-finished thermally conductive sheets in a transverse direction with respect to the thickness direction of the thermally conductive sheet, wherein the semi-finished thermally conductive sheet includes a particulate carbon material and a resin or multiple types Compound of resin. The Mooney viscosity of all resin components made of the aforementioned resin or a combination of resins is 90 (ML _{1 + 4} , 100 ° C) or less. The heat conduction sheet of the specified structure whose Mooney viscosity of all resin components is 90 (ML _{1 + 4} , 100 ° C) or less has excellent heat conductivity in the thickness direction.

In addition, the "Muni viscosity (ML _{1 + 4} , 100 ° C)" described in this specification can be measured at 100 ° C according to JIS K6300.

Here, in the case where the Mooney viscosity of all the resin components is X and the thermal conductivity in the thickness direction of the thermally conductive sheet is Y, the thermally conductive sheet of the present invention satisfies Y> (-0.2X + 25) The relationship is better. The heat conductive sheet satisfying the above-mentioned specific relational expression is excellent in manufacturing efficiency because it is easy to select the resin used in manufacturing.

In addition, in this specification, the "thermal conductivity in the thickness direction" of the heat conductive sheet can be measured according to the method described in the embodiment.

In addition, the heat conductive sheet of the present invention preferably has an ASKER C hardness of 45 or more. When the ASKER C hardness of the heat conductive sheet is 45 or more, the heat conductive sheet has excellent handleability.

Here, "ASKER C hardness" can be measured using the hardness measurement at 23 ° C according to the ASKER C hardness method of the Japan Rubber Association Standard Specification (SRIS).

Furthermore, the thermally conductive sheet of the present invention preferably has a content ratio of the particulate carbon material of 35% by volume or more. A thermally conductive sheet containing more than 35% by volume of particulate carbon material has more excellent thermal conductivity.

According to the present invention, it is possible to provide a thermally conductive sheet excellent in thermal conductivity in the thickness direction.

Hereinafter, the present invention will be described in detail based on the embodiments of the present invention.

The heat conductive sheet of the present invention can be used by directly attaching to a heating body, or can be used by being sandwiched between a heating body and a cooling body when the cooling body is mounted on the heating body. At this time, one heat conductive sheet may be used alone, or a plurality of sheets may be used in combination. In addition, the heat conductive sheet of the present invention may constitute a heat dissipation device together with a heat dissipation body such as a heat generating body, a heat sink, a heat dissipation plate, and a heat dissipation fin.

The heat conductive sheet will be explained below.

The heat conductive sheet of the present invention is formed by stacking a plurality of semi-finished heat conductive sheets in a transverse direction with respect to the thickness direction of the heat conductive sheet. The thermally conductive sheet formed by stacking multiple semi-finished thermally conductive sheets in the transverse direction with respect to the thickness direction of the thermally conductive sheet has excellent thermal conductivity in the thickness direction. Furthermore, the semi-finished product of the thermal conductive sheet constituting the thermal conductive sheet of the present invention includes a particulate carbon material and a resin or a composite of multiple resins as the entire resin component. In the case where the semi-finished product of the thermally conductive sheet does not contain particulate carbon material, the thermal conductivity of the thermally conductive sheet becomes insufficient. In addition, in the case where the semi-finished heat conductive sheet does not contain a resin component, the flexibility of the heat conductive sheet becomes insufficient. Moreover, in the heat conductive sheet of the present invention, the Mooney viscosity of all resin components is 90 (ML _{1 + 4} , 100 ° C.) or less. The total resin content of the base material of the heat conductive sheet (hereinafter also referred to as "base resin") If it is not a resin with a Mooney viscosity of 90 (ML _{1 + 4} , 100 ° C) or less, the heat conductive sheet cannot be sufficiently improved Thermal conductivity.

In addition, since the heat conductive sheet of the present invention is formed by stacking the semi-finished products of the heat conductive sheet, the components of the semi-finished products of the heat conductive sheet are naturally included in the heat conductive sheet as a matter of course. Moreover, a plurality of semi-finished products of thermally conductive sheets are directly attached to each other, or preferably are attached via an extremely thin adhesive layer, wherein the adhesive layer is formed of resin or double-sided tape having the same composition as the base material resin of the thermally conductive sheet . Therefore, all the components and their ratios contained in the "heat conductive sheet semi-finished product constituting the heat conductive sheet of the present invention" are also applicable to the "heat conductive sheet of the present invention".

<Composition>

﹝ Particulate carbon material ﹞

Here, the particulate carbon material is not particularly limited. For example, graphite such as artificial graphite, flake graphite, exfoliated graphite, natural graphite, acid-treated graphite, expandable graphite, expanded graphite, etc .; carbon black, etc. can be used. Among these materials, one kind may be used alone, or two or more kinds may be used in combination.

Among them, it is preferable to use expanded graphite as the particulate carbon material. The reason is that if expanded graphite is used, the thermal conductivity of the thermally conductive sheet can be improved.

-Expanded graphite-

Here, expanded graphite as a particulate carbon material can be suitably used. For example, expanded graphite can be obtained by chemically treating graphite such as flake graphite with sulfuric acid, and then subjecting the expanded graphite to heat treatment After expansion, it is refined. Examples of expanded graphite include EC1500, EC1000, EC500, EC300, EC100, and EC50 (all are trade names) manufactured by Ito Black Lead Industry Co., Ltd.

-Properties and states of particulate carbon materials-

Here, the particle size of the particulate carbon material is preferably a volume-based mode diameter of 100 μm or more, preferably 150 μm or more, and preferably 300 μm or less, and preferably 250 μm or less. The reason is that if the particle size of the particulate carbon material is more than the above lower limit, the particulate carbon materials are in contact with each other to form a good heat transfer path in the thermally conductive sheet, so that the thermally conductive sheet can exhibit higher thermal conductivity . In addition, if the particle size of the particulate carbon material is equal to or less than the above upper limit, the thermally conductive sheet can be provided with higher flexibility, and when contacting the heating element, heat can be more favorably transferred from the heating element to the thermally conductive sheet.

In addition, the aspect ratio (long axis / short axis) of the particulate carbon material contained in the heat conductive sheet of the present invention is preferably 1 or more and 10 or less, and preferably 1 or more and 5 or less.

In addition, in the present invention, the "volume-based mode diameter" can be obtained using a laser diffraction / scattering type particle size distribution measuring device and according to the method described in the embodiments of the present specification.

In addition, in the present invention, the "aspect ratio of the particulate carbon material" can be obtained by dissolving and removing the resin in the heat conductive sheet in a solvent, and observing the obtained particulate carbon by SEM (scanning electron microscope) For any 50 particulate carbon materials, measure the maximum diameter (long diameter) and the particle diameter (short diameter) in the direction orthogonal to the maximum diameter, and calculate the ratio of long diameter to short diameter (long diameter / short diameter) Diameter).

-Content ratio of particulate carbon material-

The content ratio of the particulate carbon material in the heat conductive sheet of the present invention is preferably 35% by volume or more, preferably 45% by volume or more, more preferably 50% by volume or more, and usually 70% by volume or less. If the content ratio of the particulate carbon material in the thermally conductive sheet is greater than or equal to the above lower limit, the particulate carbon materials in the thermally conductive sheet can easily come into contact with each other, and a good heat transfer path can be easily formed. As a result, the thermally conductive sheet can exhibit higher thermal conductivity in the thickness direction. Furthermore, if the content ratio of the particulate carbon material in the thermally conductive sheet is within the above-mentioned range, the composite particles can easily receive the force due to pressure such as roll calendering. As a result, the particles in the thermally conductive sheet The carbon-like material is better aligned in the desired direction.

In addition, in the present invention, the "content ratio (volume%)" can be obtained from the theoretical value according to the method described in the examples of the present specification.

﹝ Fibrous carbon material ﹞

The heat conductive sheet of the present invention may further contain any fibrous carbon material. The inclusion of any fibrous carbon material is not particularly limited, and for example, nano carbon tubes, vapor-grown carbon fibers, carbon fibers obtained by carbonizing organic fibers, and cuts of these materials can be used. These materials can be used alone or in combination of two or more.

Furthermore, if the thermally conductive sheet of the present invention contains a fibrous carbon material, the thermal conductivity of the thermally conductive sheet can be further improved, and at the same time, the particulate carbon material can be prevented from being dusted. In addition, although the reason why the powdered carbon material can be prevented from being powdered by blending the fibrous carbon material is not clear, it is presumed that the fibrous carbon material forms a three-dimensional grid structure, thereby improving thermal conductivity and strength while preventing Particulate carbon material detachment.

In the above, it is better to use fibrous carbon nanostructures such as nanotubes as fibrous carbon materials, and use fibrous carbon nanostructures containing nanotubes as fibrous carbon The material is better. The reason for this is that if a fibrous carbon nanostructure such as a carbon nanotube is used, the thermal conductivity and strength of the thermally conductive sheet obtained by using the thermally conductive sheet can be further improved.

-Fibrous carbon nanostructures containing carbon nanotubes-

Here, the fibrous carbon nanostructures containing carbon nanotubes can be suitably used as fibrous carbon materials, and can be formed of only nanotubes (hereinafter also referred to as "CNT") or A mixture of CNT and fibrous carbon nanostructures other than CNT.

In addition, the CNT in the fibrous carbon nanostructure is not particularly limited, and single-layer nanotubes and ⁄ or multi-layer nanotubes can be used, but CNTs are preferably single-layer to five-layer nanotubes , Single-walled carbon nanotubes are preferred. The reason for this is that if a single-layer carbon nanotube is used, the thermal conductivity and strength of the thermally conductive sheet obtained by using the thermally conductive sheet can be further improved compared to the case of using a multilayered carbon nanotube.

For the fibrous carbon nanostructures containing CNTs, it is better to use carbon nanostructures with 3σ / Av exceeding 0.20 and less than 0.60, and it is better to use carbon nanostructures with 3σ / Av exceeding 0.25. It is better to use a carbon nanostructure with a 3σ / Av exceeding 0.50; where 3σ is the value obtained by multiplying the standard deviation σ of the diameter by 3, and 3σ / Av is the ratio of 3σ to the average diameter Av. The reason for this is that if a 3CNT / Av exceeding 0.20 and less than 0.60 CNT-containing fibrous carbon nanostructure is used, even if the amount of the carbon nanostructure is small, the heat conductive sheet can be sufficiently used The resulting thermal conductivity and strength of the thermally conductive sheet. Therefore, the situation that the hardness of the heat conductive sheet becomes excessively high due to the blending of the CNT-containing fibrous carbon nanostructure (that is, the softness is reduced) can be suppressed, and the heat conduction of the excellent heat conductive sheet can be sufficiently combined Sex and softness.

In addition, the "average diameter of the fibrous carbon nanostructure (Av)" and "the standard deviation of the diameter of the fibrous carbon nanostructure (σ: sample standard deviation)" can be used for transmission electron microscopy It was obtained by measuring the diameter (outer diameter) of 100 randomly selected fibrous carbon nanostructures. Moreover, the average diameter (Av) and standard deviation (σ) of the CNT-containing fibrous carbon nanostructure can also be performed by changing the manufacturing method or manufacturing conditions of the CNT-containing fibrous carbon nanostructure Adjustments can also be made by combining a variety of CNT-containing fibrous carbon nanostructures made by different manufacturing methods.

In addition, the following is generally used as a CNT-containing fibrous carbon nanostructure: the diameter measured as described above is used as the horizontal axis and the frequency is used as the vertical axis for plotting. Gaussian (Gaussian) is normally distributed when approximate.

Furthermore, when using Raman spectroscopy to evaluate CNT-containing fibrous carbon nanostructures, the peak with a radial breathing mode (Radial Breathing Mode, RBM) is preferred. In addition, if the fibrous carbon nanostructure includes only three or more multilayer carbon nanotubes, there is no RBM in its Raman spectrum.

In addition, the average diameter (Av) of the CNT-containing fibrous carbon nanostructure is preferably 0.5 nm or more, more preferably 1 nm or more, and preferably 15 nm or less, and more preferably 10 nm or less. The reason is that if the average diameter (Av) of the fibrous carbon nanostructure is 0.5 nm or more, the aggregation of the fibrous carbon nanostructure can be suppressed, and the dispersibility of the carbon nanostructure can be improved. In addition, if the average diameter (Av) of the fibrous carbon nanostructure is 15 nm or less, the thermal conductivity and strength of the thermally conductive sheet obtained by using the thermally conductive sheet can be sufficiently improved.

Further, a BET of carbon nano structure of the CNT-containing fibrous to 600m ² / g or more preferably to 800m ² / g or more is preferred specific surface area, and to 2500m ² / g or less preferably to 1200m ² / g or less is preferable. Furthermore, when the CNTs in the fibrous carbon nanostructure are mainly CNTs that have been opened, the BET specific surface area is preferably 1300 m ² / g or more. The reason is that if the BET specific surface area of the CNT-containing fibrous carbon nanostructure is 600 m ² / g or more, the thermal conductivity and strength of the thermally conductive sheet obtained by using the thermally conductive sheet can be sufficiently improved. In addition, if the BET specific surface area of the CNT-containing fibrous carbon nanostructure is 2500 m ² / g or less, the aggregation of the fibrous carbon nanostructure can be suppressed and the dispersion of CNTs in the thermally conductive sheet can be improved Sex.

In the present invention, the "BET specific surface area" refers to the nitrogen adsorption specific surface area measured by the BET method.

Furthermore, a CNT-containing fibrous carbon nanostructure having the above-mentioned properties and conditions can be efficiently manufactured according to the following method: on a substrate having a catalyst layer for manufacturing carbon nanotubes on the surface, Supply raw material compounds and carrier gas to synthesize CNT by chemical vapor deposition (CVD) method. At this time, the catalyst is activated by trace oxidant (activation catalyst substance) in the system. The catalytic activity of the layer is greatly improved (Super Growth Method, Super-Growth Method; refer to International Publication No. 2006/011655). In addition, the carbon nanotubes produced by the super growth method are also referred to as "SGCNT" below.

Here, the CNT-containing fibrous carbon nanostructure manufactured by the super growth method may be composed of SGCNT alone, or may include other non-cylindrical carbon nanostructures in addition to SGCNT Carbon nanostructures.

-Properties and states of fibrous carbon materials-

The average fiber diameter of the fibrous carbon material that can be contained in the heat conductive sheet is preferably 1 nm or more, preferably 3 nm or more, and preferably 2 μm or less, and preferably 1 μm or less. The reason for this is that if the average fiber diameter of the fibrous carbon material is within the above range, the resulting thermally conductive sheet can sufficiently have excellent thermal conductivity, flexibility and strength of the thermally conductive sheet.

Here, the aspect ratio of the fibrous carbon material is preferably more than 10.

In addition, in the present invention, the "average fiber diameter" can be obtained by dissolving and removing the resin in the heat conductive sheet in a solvent, using SEM (scanning electron microscope) or TEM (transmission electron microscope) Observe the obtained fibrous carbon material, and measure the fiber diameter for any 50 fibrous carbon materials, and calculate the average number of the measured fiber diameters. In particular, when the fiber diameter is small, it is more suitable for observation by TEM (transmission electron microscope) for the same cross section.

In addition, in the present invention, the "aspect ratio of the fibrous carbon material" can be obtained by dissolving and removing the resin in the thermally conductive sheet, and observing the obtained fibrous carbon material with a TEM (transmission electron microscope) , And measure the maximum diameter (long diameter) and the particle diameter (short diameter) in the direction orthogonal to the maximum diameter for any 50 fibrous carbon materials, and calculate the ratio of long diameter to short diameter (long diameter / short diameter) ) Average.

﹝ Resin ﹞

Here, the base material resin constituting the heat conductive sheet of the present invention must be a resin having a Mooney viscosity of 90 (ML _{1 + 4} , 100 ° C.) or less. This base material resin is not particularly limited as long as the Mooney viscosity is 90 (ML _{1 + 4} , 100 ° C.) or less, and it can be a known resin or a composite of multiple resins that can be used when manufacturing a thermally conductive sheet. Moreover, the base material resin whose Mooney viscosity is not particularly limited to 90 (ML _{1 + 4} , 100 ° C) or less may be an unvulcanized resin. In addition, in this specification, "resin" includes rubber and an elastomer (elastomer). In addition, in this specification, "uncured" means that no crosslinking reaction occurs when the resin or resin composition contains a vulcanizing agent (crosslinking agent), and the resin or resin composition is heated. status.

Furthermore, the base material resin is preferably a thermoplastic resin. In this specification, the so-called "thermoplastic" means a characteristic that it is softened by heating and becomes a formable state, and further hardened by cooling. Furthermore, in the case where the resin is "thermoplastic", the polymer structure of the resin in the cured state usually does not contain a cross-linked structure. Here, in general, resins are roughly classified into "thermoplastic resins" and "thermosetting resins". However, even if it is generally a resin that can be classified as a "thermosetting resin", if it is cured in the absence of a crosslinking agent, there may be a case where no crosslinking structure is formed in the polymer structure. Therefore, in this specification, regardless of whether they are generally classified as thermoplastic resins or thermosetting resins, resins having the above-defined "thermoplastic" are collectively referred to as "thermoplastic resins".

In addition, if the "thermoplastic resin" is blended into the thermally conductive sheet, the adhesion between the thermally conductive sheet and the heating element, heat sink, etc. can be improved. The reason is that the "thermoplastic resin" can improve the flexibility of the thermally conductive sheet in the high temperature environment when the thermally conductive sheet is used (at the time of heat dissipation).

In addition, the "thermoplastic resin" used as the base material resin is solid at normal temperature and pressure. If the resin used as the base material resin is solid at normal temperature and pressure, it can improve the flexibility of the heat conductive sheet and make the heat conductive sheet and the heat sink better under the high temperature environment during use (during heat dissipation) The ground is tightly sealed, and the handling property of the heat conductive sheet can be improved under normal temperature environment such as installation. In addition, in this specification, "normal temperature" means 23 degreeC, and "normal pressure" means 1 atmospheric pressure (absolute pressure).

In addition, as described above, the matrix resin may contain one kind of resin, or may be a composite obtained by mixing two or more kinds of resins. In the case of using the composite as the base material resin, various resins constituting the composite may be solid resins or liquid resins at normal temperature and pressure, but in the case of forming a composite, the composite must It becomes solid at normal temperature and pressure.

-Thermoplastic resin-

(1) Thermoplastic resin that is solid at normal temperature and pressure

The following are examples of resins with thermoplastic properties that can be used as base material resins, which are resins that are solid at room temperature and pressure: poly (2-ethylhexyl acrylate), acrylic acid and 2-ethylhexyl acrylate Acrylic resins such as copolymers, polymethacrylic acid or its esters, polyacrylic acid or its esters; silicone resins; fluororesins; polyethylene; polypropylene; ethylene-propylene copolymers; polymethylpentene; polyvinyl chloride; Polyvinylidene chloride; polyvinyl acetate; ethylene-vinyl acetate copolymer; polyvinyl alcohol; polyacetal; polyethylene terephthalate; polyethylene terephthalate; polybutylene terephthalate ); Polyethylene naphthalate; polystyrene; polyacrylonitrile; styrene-acrylonitrile copolymer; acrylonitrile-butadiene copolymer (nitrile rubber); acrylonitrile-butadiene- Styrene copolymer (ABS resin); styrene-butadiene block copolymer or its hydride; styrene-isoprene block copolymer or its hydride; polyphenylene ether (polyphenylene ether), modified Polyphenylene ether; Aliphatic polyamides; Aromatic polyamides; Polyamideimide; Polycarbonate; Polyphenylene sulfide; Polysulfide; Polyether sulfide; Polyether nitrile ; Polyether ketone; Polyketone; Polyurethane; Liquid crystal polymer; Ionic polymer and so on. These resins may be used alone or in combination of two or more.

Furthermore, it is preferable to use a "thermoplastic resin" that is a solid base material at room temperature and pressure, preferably a fluororesin. The reason is that if the base material resin is a fluororesin, the heat resistance, oil resistance, and chemical resistance of the heat conductive sheet can be improved. Specific examples include polymerized fluorine-containing monomers such as vinylidene fluoride-based fluororesins, tetrafluoroethylene-propylene-based fluororesins, tetrafluoroethylene-perfluorovinylether (tetrafluoroethylene-perfluorovinylether) fluororesins, etc. Elastomers, etc. More specifically, polytetrafluoroethylene, tetrafluoroethylene-perfluoroalkylvinyl ether copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, tetrafluoroethylene-ethylene copolymer , Polyvinylidene fluoride, polytrifluorochloroethylene, ethylene-chlorofluoroethylene copolymer (ethylene-chlorofluoroethylene copolymer), tetrafluoroethylene-perfluorodioxole copolymer (tetrafluoroethylene-perfluorodioxole copolymer), poly Ethylene fluoride, tetrafluoroethylene-propylene copolymer, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymer, polytetrafluoroethylene acrylic modified, polytetrafluoroethylene Ester modified products, epoxy modified products of polytetrafluoroethylene and silane modified products of polytetrafluoroethylene. Among these, from the viewpoint of processability, polytetrafluoroethylene, acrylic modification of polytetrafluoroethylene, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, vinylidene fluoride-hexafluoro Propylene copolymers and vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymers are preferred.

In addition, commercially available fluororesins that are solid and thermoplastic at room temperature and pressure include, for example, DAI-EL (registered trademark) manufactured by DAIKIN Industries Co., Ltd. G-300 series / G-700 series / G-7000 series (Binary copolymer of vinylidene fluoride-hexafluoropropylene), DAI-EL G-550 series / G-600 series (ternary copolymer of vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene), DAI-EL G-800 series (binary copolymer of vinylidene fluoride-hexafluoropropylene), DAI-EL G-900 series (ternary copolymer of vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene ); KYNAR (registered trademark) series (vinylidene fluoride-based fluororesin) and KYNAR FLEX (registered trademark) series (ternary copolymer of vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene) manufactured by ALKEMA; A-100 manufactured by Chemours (binary copolymer of vinylidene fluoride-hexafluoropropylene); Dyneon E-20575 (registered trademark) manufactured by 3M Japan (registered binary system of vinylidene fluoride-hexafluoropropylene) Copolymer) etc.

(2) Thermoplastic resin that is liquid at normal temperature and pressure

Moreover, as described above, when the composite becomes solid at normal temperature and pressure and does not significantly impair the effects of the present invention, it can also be combined at room temperature and normal pressure with a thermoplastic resin that is solid at normal temperature and pressure Used as a liquid thermoplastic resin. Examples of thermoplastic resins that are liquid at normal temperature and pressure include acrylic resins, epoxy resins, silicone resins, and fluororesins that are resins other than those that satisfy the above (1). These resins may be used alone or in combination of two or more.

Although it is not particularly limited to the viscosity of a thermoplastic resin that is liquid at normal temperature and pressure, in view of good kneadability, fluidity, crosslinking reactivity, and excellent moldability, this resin has a temperature of 105 ° C. The viscosity is preferably 500 mPa · s ~ 30,000 mPa · s, preferably 550 mPa · s ~ 25,000 mPa · s.

-Other resin-

The thermally conductive sheet may contain resins other than the above-mentioned resins without significantly impairing the effects of the present invention.

Other resins include various resins that can be generally classified as thermosetting resins, such as natural rubber; butadiene rubber; isoprene rubber; hydrogenated nitrile rubber; chloroprene rubber; ethylene propylene rubber; chlorinated polyethylene; Chlorosulfonated polyethylene; butyl rubber; halogenated butyl rubber; polyisobutylene rubber; epoxy resin; polyimide resin; bismaleimide resin; phenylcyclobutene resin; phenol resin; unsaturated polyester ; Diallyl phthalate resin (diallyl phthalate resin); polyimide silicone resin (polyimide silicone resin); polyurethane; thermosetting polyphenylene ether; thermosetting modified polyphenylene ether, etc. These resins may be used alone or in combination of two or more.

-Muni viscosity-

In addition, the Mooney viscosity (ML _{1 + 4} , 100 ° C) of the base material resin must be 90 (ML _{1 + 4} , 100 ° C) or less, and preferably 65 (ML _{1 + 4} , 100 ° C) or less, with 36 (ML _{1 + 4} , 100 ° C) The following is preferred. Usually above 3 (ML _{1 + 4} , 100 ℃). If the Mooney viscosity of the base material resin contained in the thermally conductive sheet is equal to or less than the above upper limit, the thermal conductivity of the thermally conductive sheet can be improved.

In addition, the Mooney viscosity of the base material resin contained in the heat conductive sheet can be obtained by the following steps: after dissolving the heat conductive sheet in a solvent that can dissolve the base material resin, the base material resin is separately separated and the mu The sample for measurement of Ni Viscosity, and then the Mooney viscosity (ML _{1 + 4} , 100 ℃) of the sample measured according to JIS-K6300. In addition, the Mooney viscosity value obtained by the above method is in principle slightly the same as the Mooney viscosity value of the base material resin in the material stage.

-Resin content-

Next, in the present invention, when the total volume of the heat conductive sheet is set to 100% by volume, the content ratio of all resin components in the heat conductive sheet is preferably 65% by volume or less, preferably 55% by volume or less, It is more preferably 50% by volume or less, and usually 30% by volume or more. If the content ratio of all resin components in the thermally conductive sheet is equal to or less than the above upper limit, the thermally conductive sheet can exhibit higher thermal conductivity. In addition, if the content ratio of all resin components in the thermally conductive sheet is equal to or higher than the above lower limit, the thermally conductive sheet can be provided with higher flexibility, and when it is in contact with the heating element, it can be transferred from the heating element to the thermal conductive sheet more favorably Heat transfer.

﹝additive﹞

The thermally conductive sheet of the present invention can optionally be blended with known additives that can be used when manufacturing the thermally conductive sheet. The additives that can be blended in the heat conductive sheet are not particularly limited, and examples include plasticizers such as fatty acid esters; flame retardants such as red phosphorus flame retardants and phosphate ester flame retardants; such as fluorine oil (fluorine oil, Demnum series manufactured by Daikin Industries Co., Ltd.) plasticizer and flame retardant additive; urethane acrylate and other toughening agents; calcium oxide, magnesium oxide and other hygroscopic agents; Adhesion promoters for silane coupling agents, titanium coupling agents, acid anhydrides, etc .; wettability promoters for non-ionic surfactants, fluorine-based surfactants; ion trapping agents for inorganic ion exchangers, etc.

<Nature and State>

﹝ ASKER C hardness ﹞

The heat conductive sheet of the present invention preferably has an ASKER C hardness of 45 or more, more preferably 55 or more, and even more than 60. The reason for this is that if the ASKER C hardness of the thermally conductive sheet is equal to or greater than the above lower limit, the handleability of the thermally conductive sheet can be improved. The ASKER C hardness value of the heat conductive sheet can be adjusted by selecting the content ratio of the particulate carbon material blended in the heat conductive sheet or the resin component used.

Conventionally, in order to improve the thermal conductivity of the thermally conductive sheet itself, a generally selected method is to increase the content ratio of thermally conductive materials such as particulate carbon materials. If the content of the heat conductive material is high, the heat conductive sheet tends to become hard. In the past, the hardness of the thermally conductive sheet affected the interface impedance between the thermally conductive sheet and other components (such as heating elements or heat sinks) equipped with the thermally conductive sheet (hereinafter also referred to as "interfacial impedance between components") as Under the premise, ASKER C hardness is used as the hardness index. In addition, in order to achieve a balance between improving the thermal conductivity of the thermally conductive sheet itself and suppressing the excessive increase of the ASKER C hardness, various studies have been conducted on methods for improving the thermal conductivity of the thermally conductive sheet. However, after re-examination by the present inventors, it was clearly found that there is no correlation between the ASKER C hardness of the heat conductive sheet and the interface impedance between the parts. Furthermore, as a result of further research, the present inventors have newly discovered that by blending a base material resin having a Mooney viscosity of less than a specified value, it is also beneficial to suppress the interfacial impedance between components. In addition, it is more clearly known that when the thermally conductive sheet contains a base material resin whose Mooney viscosity is below a specified value, the thermally conductive sheet has an appropriate ASKER C hardness value, and the thermal conductivity of the thermally conductive sheet is higher than the conventional thermal conductivity The value assumed by the relationship between the rate and ASKER C hardness.

﹝Thermal conductivity﹞

In the case where the Mooney viscosity of the base material resin is X (ML _{1 + 4} , 100 ° C.) and the thermal conductivity in the thickness direction of the thermally conductive sheet is Y, the thermally conductive sheet of the present invention satisfies Y> ( The relationship of -2.6X + 25) is better. The relationship of Y> (-2.6X + 42) is better, and the relationship of Y> (-2.6X + 120) is better. Using this relationship as an index, the resin material used as the base material resin can be easily selected and used, and the manufacturing efficiency of the heat conductive sheet can be improved by inversely calculating the heat conductivity as the purpose of the heat conductive sheet. On the contrary, since the thermal conductivity of the thermally conductive sheet can be estimated from the base material resin to be used, the design efficiency of the thermally conductive sheet can be improved.

More specifically, the thermal conductivity of the thermally conductive sheet is preferably 19 W / m · K or more, preferably 25 W / m · K or more, and more preferably 35 W / m · K or more. The reason for this is that if the thermal conductivity of the thermally conductive sheet is equal to or higher than the above lower limit, for example, when the thermally conductive sheet is used in close contact with the heating element, heat can be efficiently dissipated from the heating element.

﹝ Muni Viscosity ﹞

The Mooney viscosity (ML _{1 + 4} , 100 ° C) of the heat conductive sheet of the present invention is preferably 50 (ML _{1 + 4} , 100 ° C) or less, and preferably 30 (ML _{1 + 4} , 100 ° C) or less, Usually above 2 (ML _{1 + 4} , 100 ℃). It is considered here that if the Mooney viscosity of the thermally conductive sheet is below the above upper limit, in the case of using the thermally conductive sheet under high temperature conditions, the thermally conductive sheet and the heating element, heat sink, etc. can be improved The adhesion between the components, and can improve the heat dissipation efficiency.

﹝structure﹞

The thermally conductive sheet of the present invention has the following structure: a structure formed by stacking multiple semi-finished thermally conductive sheets in a transverse direction with respect to the thickness direction of the thermally conductive sheet, and the semi-finished thermally conductive sheet contains a particulate carbon material, a resin component, and any Additives, etc. Furthermore, in the semi-finished thermally conductive sheet, the particulate carbon material is preferably aligned along the surface direction of the semi-finished thermally conductive sheet (transversely with respect to the thickness direction of the semi-finished thermally conductive sheet). The reason for this is that if the particulate carbon material is aligned along the surface direction of the semi-finished product of the thermally conductive sheet, the thermal conductivity in the thickness direction of the thermally conductive sheet can be improved. The evidence of "the thermally conductive sheet is obtained by stacking and slicing a plurality of semi-finished thermally conductive sheets in the plane direction", for example, a method of observing the thickness direction of the thermally conductive sheet with a microscope or using a method to determine whether the thermal conductivity in the planar direction There is an anisotropic method to make a comprehensive judgment.

﹝thickness﹞

The thickness of the heat conductive sheet is not particularly limited, and may be 0.05 mm or more and 10 mm or less, for example. The reason for this is that, in general, if the thickness of the thermally conductive sheet is too thick, the thermal resistance of the thermally conductive sheet increases, so the thermal conductivity decreases, and when the thickness of the thermally conductive sheet is too small, it becomes impossible to fully utilize The thermal conductivity of the thermally conductive sheet.

Furthermore, a plurality of thermally conductive sheets with a certain thickness can be stacked in the thickness direction, and they can be integrated by standing for a specified time, and then use the integrated object as a thermally conductive sheet. In the thermally conductive sheet obtained as described above, it can be presumed that the particulate carbon material and any fibrous carbon material maintain alignment in the thickness direction of the thermally conductive sheet. Therefore, the thermal conductivity of a thick (thickness x) thermally conductive sheet obtained by stacking multiple thin thermally conductive sheets in the thickness direction is considered to have approximately the same thermal conductivity as a single thermally conductive sheet of the same thickness (thickness x) rate. Therefore, there is no need to prepare heat conductive sheets of various thicknesses, as long as multiple (thin) heat conductive sheets of specified thickness are prepared, a heat conductive sheet can be obtained, the thickness of which depends on the thickness of the portion where the heat conductive sheet is to be applied.

The method of manufacturing the heat conductive sheet will be described below.

The manufacturing method for manufacturing the thermally conductive sheet of the present invention is not particularly limited, and a manufacturing method that can be used when manufacturing the thermally conductive sheet can be adopted. The thermally conductive sheet is formed by stacking multiple semi-finished thermally conductive sheets in the plane direction. This manufacturing method may include, for example, a manufacturing method including the following steps: a step of preparing a composite mixture containing a particulate carbon material and a base material resin having a Mooney viscosity of 90 (ML _{1 + 4} , 100 ° C) or less; plus The step of pressing the composite particles to produce a semi-finished thermally conductive sheet; the step of obtaining a stack of semi-finished thermally conductive sheets; and the slicing step.

<Procedure for preparing compound mixture>

In the step of preparing the composite mixture, the composite mixture containing the particulate carbon material and the resin is prepared. Specifically, the step of preparing the composite mixture is not particularly limited, and a known technique can be used to compose arbitrary fibers with a particulate carbon material and a base material resin with a Mooney viscosity of 90 (ML _{1 + 4} , 100 ° C) or less Carbon material and / or additives to prepare a compound mixture. In addition, in the step of preparing the composite mixture, a commercially available composite mixture containing a particulate carbon material and a base material resin having a Mooney viscosity of 90 (ML _{1 + 4} , 100 ° C.) or lower may be purchased to prepare a composite mixture. In the case of preparing a compound mixture by the above compounding operation, more specifically, for example, the following methods (I) to (III) can be used.

(I) Mix and knead a particulate carbon material, a base material resin with a Mooney viscosity of 90 (ML _{1 + 4} , 100 ° C) or less, and any fibrous carbon material and / or additives to obtain a composite mixture.

(II) Drying and granulating a dispersion containing a particulate carbon material, a base material resin with a Mooney viscosity of less than 90 (ML _{1 + 4} , 100 ° C) and any fibrous carbon material and / or additives to obtain a composite mixture .

(III) The base material resin having a Mooney viscosity of 90 (ML _{1 + 4} , 100 ° C.) or less is sprayed on the particulate carbon material and any fibrous carbon material to obtain a composite mixture.

Among them, the method using (I) is preferred from the viewpoint of ease of work.

In addition, the particulate carbon material used in the step of preparing the composite mixture, the base material resin with a Mooney viscosity below 90 (ML _{1 + 4} , 100 ° C), and any fibrous carbon material and / or additives can be used with The above-mentioned thermally conductive sheet may contain the particulate carbon material, the base material resin having a Mooney viscosity of 90 (ML _{1 + 4} , 100 ° C) or less, any fibrous carbon material and / or additives having the same components, and preferably containing The ratio can also be set to the same.

﹝ Mixing and mixing methods ﹞

The method of mixing and kneading is not particularly limited, and it can be performed using a known mixing device such as a kneader, roller, Henschel mixer, and Hobart mixer. The mixing and kneading time can be, for example, 5 minutes or more and 6 hours or less. In addition, the mixing and kneading temperature can be set to, for example, 5 ° C or higher and 150 ° C or lower.

Here, although mixing and kneading may be performed in the presence of a solvent such as ethyl acetate, in the case where a solvent is used during mixing or kneading, it is preferable to remove the solvent before crushing / pulverizing the composite mixture described later. The solvent can be removed using a known drying method, or the solvent can be removed while defoaming the composite mixture at will. For example, if vacuum defoaming is used for defoaming, the solvent can also be removed while defoaming.

﹝ Composite mixture ﹞

The resulting composite mixture contains particulate carbon material and base material resin with a Mooney viscosity of 90 (ML _{1 + 4} , 100 ° C) or less, and further includes any fibrous carbon material and additives. In addition, the composite mixture is generally a block having a diameter of about 1 mm to 200 mm.

The pulverization step may be arbitrarily performed to pulverize the composite mixture into particles. In this case, in the pulverization step, the resulting composite mixture is pulverized by any method to obtain composite particles. In addition, in the step of obtaining composite particles, after the resulting composite mixture is pulverized, it may be classified by any method to obtain composite particles.

The pulverization of the composite mixture is not particularly limited as long as the resulting composite particles do not form a block of the composite mixture but become a powder fluid, and can be carried out by a known method. Also, the bulk can be crushed and dispersed before crushing. Furthermore, the crushing / pulverization of the composite mixture can be performed using, for example, a known crushing / pulverizing machine using shearing or grinding action, or a known crushing / pulverizing machine of stirring type. Examples of the above-mentioned known crusher / crusher include hammer crusher, cutting mill, hammer mill, bead mill, vibration mill, planetary ball mill, and sand mill. Machines, ball mills, roller mills, three-roll mills, jet mills, high-speed rotary mills, micro-mills / crushing and classifiers, nano jet mills (Nano Jetmizer), etc.

The type of crusher / crusher, energy and time during crushing / crushing, etc., can be selected as long as the desired state of the powdered fluid such as the state of the lumps of the composite mixture, the particle size of the composite particles, etc. is selected And adjustment.

Here, the composite mixture is not particularly limited, and it is preferably crushed to a particle size of less than 1000 μm classified by a sieve.

<Procedure for preparing semi-finished thermally conductive sheet>

In the step of producing the semi-finished product of the thermally conductive sheet, the composite mixture or composite particles prepared in the previous step are pressed into a sheet by any method.

﹝ Pressure method ﹞

The method of pressing the heat conductive sheet semi-finished product is not particularly limited as long as it is a load pressure forming method. The heat conductive sheet semi-finished product can be formed into a sheet shape using known forming methods such as press forming, calender forming, or extrusion forming. Among them, the heat conductive sheet is preferably formed into a sheet shape by calendering, and is preferably formed into a sheet shape by passing between rolls in a state of being sandwiched between protective films. In addition, the protective film is not particularly limited, and polyethylene terephthalate (PET) film subjected to sand blasting treatment or the like can be used. In addition, the roller temperature can be set to 5 ° C or higher and 150 ° C or lower.

In addition, the thickness of the semi-finished thermally conductive sheet is not particularly limited, and may be set to, for example, 0.05 mm or more and 2 mm or less. In addition, from the viewpoint of improving the thermal conductivity of the semi-finished thermally conductive sheet and improving the thermal conductivity of the thermally conductive sheet, the thickness of the semi-finished thermally conductive sheet is preferably 5,000 times or less the average particle diameter of the particulate carbon material.

<Steps to get the stack>

In the step of obtaining a stacked body, a plurality of semi-finished thermally conductive sheets obtained in the previous step are stacked in the thickness direction of the semi-finished thermally conductive sheet, or the semi-finished products of the thermally conductive sheet obtained in the previous step are folded or wound, thereby forming a stacked body.

﹝ Stacking method ﹞

The formation of the stacked body due to the stacking of the semi-finished thermally conductive sheets is not particularly limited, and it can be performed using a stacking device or manually. In addition, the formation of the stacked body due to the folding of the semi-finished thermally conductive sheet is not particularly limited, and can be performed by folding the thermally conductive primary sheet with a certain width using a folding machine. Furthermore, the formation of the stack due to the winding of the semi-finished thermally conductive sheet is not particularly limited, and it can be performed by winding the semi-finished thermally conductive sheet around an axis parallel to the short side direction or the long side direction of the semi-finished thermally conductive sheet.

Here, in the step of producing the stacked body, the surfaces of the semi-finished thermally conductive sheets can be fully obtained by the pressure when stacking the semi-finished thermally conductive sheets or the pressure when folding or winding the semifinished thermally conductive sheets. Adhesion. However, in the case of insufficient adhesion or when it is necessary to sufficiently suppress the delamination of the stack, the dissolution agent can also be used to form the stack in a state where the surface of the semi-finished thermally conductive sheet is slightly dissolved, or it can be The stacked body is formed in a state where an adhesive is applied on the surface or an adhesion layer is provided on the surface of the semi-finished heat conductive sheet.

In addition, the dissolving agent used when dissolving the surface of the semi-finished thermally conductive sheet is not particularly limited, and a known dissolving agent that can dissolve the resin component contained in the semi-finished thermally conductive sheet can be used.

In addition, the adhesive applied to the surface of the semi-finished heat conductive sheet is not particularly limited, and a commercially available adhesive or adhesive resin can be used. Among them, it is preferable to use a resin having the same composition as the resin component contained in the semi-finished product of the thermally conductive sheet. The thickness of the adhesive applied to the surface of the semi-finished thermally conductive sheet can be, for example, 10 μm or more and 1000 μm or less.

In addition, the adhesion layer provided on the surface of the semi-finished thermally conductive sheet is not particularly limited, and double-sided tape or the like can be used.

In addition, from the viewpoint of suppressing delamination, the resulting stacked body is continuously pressed at 20 ° C. or more and 150 ° C. or less for 1 minute or more and 30 minutes while applying a pressure of 0.05 MPa or more and 1.0 MPa or less in the stacking direction. The following is better.

In addition, in the stack obtained by stacking, folding, or winding the semi-finished thermally conductive sheets, it is presumed that the particulate carbon material and any fibrous carbon material are aligned in a direction approximately orthogonal to the stacking direction.

<Slicing step>

In addition, in the slicing step, the stacked body obtained in the above step is sliced at an angle of 45 ∘ or less with respect to the stacking direction, thereby obtaining a heat conductive sheet formed by slicing the stacked body.

﹝ Slicing method ﹞

The method of slicing the stacked body is not particularly limited, and examples thereof include a multi-blade method, a laser processing method, a water jet method, and a knife processing method. Among them, the knife processing method is preferred from the viewpoint of easily making the thickness of the heat conductive sheet uniform. Moreover, the cutting tool when slicing the stacked body is not particularly limited, and a slicing member having a smooth disk surface and a blade portion (for example, a planer or a slicer with a sharp blade) can be used, wherein the smooth disk surface has a slit, which The blade part is more protruding than this slit part.

In addition, from the viewpoint of improving the thermal conductivity of the thermally conductive sheet, the angle at which the stacked body is sliced is preferably 30 ∘ or less with respect to the stacking direction, and preferably 15 ∘ or less with respect to the stacking direction. It is better if the stacking direction is approximately 0∘ (that is, the direction along the stacking direction).

In addition, from the viewpoint of easily slicing the stacked body, the stacked body temperature during slicing is preferably -20 ° C or higher and 40 ° C or lower, and preferably 10 ° C or higher and 30 ° C or lower. In addition, for the same reason, it is better to perform slicing of the stacked body in a direction perpendicular to the stacking direction while carrying out slicing, in a direction perpendicular to the stacking direction of 0.1 MPa or more and 0.5 MPa or less. It is better to slice while pressing.

Since the heat conductive sheet obtained by the above manufacturing method is formed through the step of obtaining the stack and the slicing step, it can be presumed that the particulate carbon material and any fibrous carbon material will be aligned in the thickness direction of the heat conductive sheet. Therefore, for example, by allowing the heat sink to adhere well to the heat conductive sheet, the heat generated by the heat sink can be efficiently dissipated in the thickness direction of the heat conductive sheet.

The purpose of the heat conductive sheet will be explained below.

On the other hand, the thermally conductive sheet obtained by the manufacturing method of the present invention has excellent thermal conductivity, and generally has excellent strength and electrical conductivity. Therefore, this thermally conductive sheet is suitable for, for example, heat dissipation materials, heat dissipation elements, cooling elements, temperature adjustment elements, electromagnetic wave shielding members, electromagnetic wave absorption members, etc. used in various equipment and devices, etc. A rubber sheet for thermal compression bonding that is sandwiched between the object to be bonded and the thermal compression bonding device during connection.

Here, various devices and devices are not particularly limited, and examples include electronic devices such as servers, server computers, and desktop computers; notebook computers, electronic dictionaries, PDAs, mobile phones, and portable music players ( Portable electronic devices such as portable music players; liquid crystal displays (including backlights), plasma displays, LEDs, organic EL, inorganic EL, liquid crystal projectors, clocks and other display devices; inkjet printers (inkjet heads) , Electrophotography device (electrophotography device) (developing device, fixing device, heat roll (heat roll), heat belt (heat belt)) and other image forming devices; semiconductor elements, semiconductor packages, semiconductor sealed enclosures, semiconductor solid crystal ( die-bonding), CPU, memory, power transistors, power transistor housings and other semiconductor-related components; hard circuit boards, flexible circuit boards, ceramic circuit boards, build-up circuit boards, multilayer substrates and other circuit boards (The circuit board also includes printed circuit boards, etc.); vacuum processing equipment, semiconductor manufacturing equipment, display equipment manufacturing equipment and other manufacturing equipment; thermal insulation materials, vacuum thermal insulation materials, radiation thermal insulation materials and other thermal insulation devices; DVD (optical reading head, laser Generating device, laser light receiving device), hard disk drive and other information recording equipment; camera, video camera, digital camera, digital video camera, microscope, CCD and other image recording devices; charging device, lithium ion battery, fuel cell and other battery equipment Wait.

The embodiments will be described below.

Although the present invention will be specifically described below based on examples, the present invention is not limited to these examples. In addition, in the following description, "parts" indicating the amount, unless otherwise specified, are based on quality.

In the examples and comparative examples, the Mooney viscosity of the base material resin and the Mooney viscosity of the heat conductive sheet, the content ratio of the particulate carbon material in the heat conductive sheet and the volume-based mode diameter, the ASKER C of the heat conductive sheet The hardness and the thermal conductivity of the thermally conductive sheet are each measured and calculated using the following method.

＜ Muni viscosity】

The Mooney viscosity of the base material resin used in the manufacture of thermally conductive sheets is based on the base material resin cut and sliced, using a Mooney viscosity meter (Shimadzu Corporation, "MOONEY VISCOMETER SMV-202") based on JIS-K6300 Measure (ML _{1 + 4} , 100 ℃).

With respect to the obtained heat conductive sheet, the same slice was also cut out and measured in the same way.

<Content ratio of particulate carbon material>

The content ratio of the particulate carbon material in the heat conductive sheet is a theoretical value obtained using the volume fraction. Specifically, the volume (cm) is calculated from the density (g / cm ³ ) and the blending amount (g) for each component of the particulate carbon material, resin, and arbitrary fibrous carbon material and additives contained in the heat conductive sheet ³ ) After that, the content ratio of the particulate carbon material in the thermally conductive sheet is determined by the volume fraction (vol%).

<Volume-based mode diameter of the particulate carbon material in the thermally conductive sheet>

The volume-based mode diameter of the particulate carbon material in the thermally conductive sheet can be determined by the following steps: by adding 1 g of the thermally conductive sheet to the methyl ethyl ketone solvent to dissolve the resin component, a suspension is obtained, which The suspension separates and disperses the particulate carbon material; next, using the resulting suspension as a sample, a laser diffraction / scattering particle size distribution measurement device (made by HORIBA, model "LA960") is used for measurement The particle size of the particulate carbon material contained in the suspension; after that, the particle size distribution curve is drawn with the measured particle size as the horizontal axis and the volume of the particulate carbon material as the vertical axis, and the particle size distribution curve is taken The particle size of the maximum value is taken as the volume-based mode diameter (μm).

＜ ASKER C hardness of heat conductive sheet ＞

According to the ASKER C method of the Japan Rubber Association Standard Specification (SRIS), a hardness tester (manufactured by Macrometer Co., Ltd., trade name "ASKER CL-150LJ") was used to measure at a temperature of 23 ° C.

Specifically, 6 test pieces of thermally conductive sheets were superimposed. The size of these test pieces was adjusted to 30 mm in width × 60 mm in length × 1.0 mm in thickness, and the test pieces were allowed to stand in a constant temperature room maintained at 23 ° C. For more than 48 hours, use this material as a sample and measure the ASKER C hardness. After that, adjust the height of the damper so that the pointer becomes 95 to 98, measure the hardness of the test material and the damper after 20 seconds from the collision, perform this measurement 5 times, and take the average value as the ASKER C hardness of the sample.

<Thermal conductivity of the thermally conductive sheet>

When calculating the thermal conductivity of the thermally conductive sheet, first use a resin material thermal resistance tester (manufactured by Hitachi Technologies and Services, trade name "C47108") to measure the thermal resistance value. During the measurement, the heat conductive sheet is cut into squares with a side length of 1 cm and used as the measurement material. Next, the thermal resistance value R of the test material under the condition that the test temperature is 50 ° C. and the pressure is 0.50 MPa is measured. The smaller the thermal resistance value R, the better the thermal conductivity, and the more excellent the heat dissipation characteristics when used as a heat dissipation device between the heating body and the heat dissipation body.

Then, based on the following formula (I), the thermal conductivity is calculated from the measured thermal resistance value R and the thickness d of the thermally conductive sheet after pressing.

Thermal conductivity (W / m.K) = thickness of thermally conductive sheet d (m) / thermal resistance value R (m ² .K / W) ... (I)

Embodiment 1 will be described below.

<Preparation of fibrous carbon nanostructures containing CNTs>

According to the description of International Publication No. 2006/011655, a fibrous carbon nanostructure containing SGCNT is obtained by the super growth method.

The BET specific surface area of the obtained fibrous carbon nanostructure was 800 m ² / g. Furthermore, the diameter of 100 randomly selected fibrous carbon nanostructures was measured using a transmission electron microscope. The average diameter (Av) was 3.3 nm, and the sample standard deviation (σ) of the diameter was multiplied by three The value (3σ) is 1.9nm, and the ratio (3σ / Av) is 0.58. Furthermore, the resulting fibrous carbon nanostructure is mainly composed of a single layer of CNT (also known as "SGCNT").

<Preparation of easily dispersible aggregates of fibrous carbon nanostructures>

﹝ Modulation of dispersion liquid ﹞

Measure 400 mg of the fibrous carbon nanostructure obtained above as a fibrous carbon material, mix it with 2 L of methyl ethyl ketone as a solvent, and continue stirring for 2 minutes using a homogenizer to obtain a coarse dispersion liquid. Next, using a wet jet mill (manufactured by Changguang Co., Ltd., product name "JN-20"), the obtained crude dispersion liquid was passed through a 0.5 mm flow path of the wet jet mill at a pressure of 100 MPa 2 Circulate to disperse the fibrous carbon nanostructures in methyl ethyl ketone. Next, a dispersion liquid having a solid content concentration of 0.20% by mass was obtained.

﹝ Removal of solvent ﹞

After that, the dispersion liquid obtained above was filtered under reduced pressure using Tongshan filter paper (No. 5A) to obtain a sheet-shaped easily dispersible aggregate.

<Manufacture of heat conductive sheet>

﹝ Steps to prepare compound mixture ﹞

Using a kneader (manufactured by Inoue Manufacturing Co., Ltd.), the particulate carbon material, fibrous carbon material, base resin and flame retardant which are all resin components are mixed and kneaded while stirring for 15 minutes to obtain a particulate carbon material. , Base material resin, fibrous carbon material and flame retardant compound mixture. Among them, the constituent materials of the composite mixture and their parts by mass are as follows: the particulate carbon material is 130 parts of expanded graphite (manufactured by Ito Black Lead Industry Co., Ltd., trade name "EC-50", average particle diameter: 250 μm), The fibrous carbon material is 0.1 parts of easily dispersible aggregates of carbon nanostructures (in the table, marked as "SGCNT"), the base material of all resin components is 80 parts of the solid resin at room temperature and pressure is solid Thermoplastic fluororesin (manufactured by 3M Japan, trade name "Dyneon (registered trademark) E-20575", Mooney viscosity: 3.5ML _{1 + 4} , 100 ° C), and 10 parts of phosphate ester as flame retardant (Big Eight Made by Chemical Industry Corporation, trade name "PX-110").

﹝ Steps to prepare composite particles ﹞

Next, the composite mixture prepared as described above was put into a pulverizer (manufactured by Sanzhuang Industry Co., Ltd., product name "HAMMER CRUSHER HN34S") and pulverized for 60 seconds, thereby obtaining a particulate carbon material, base material resin, and fiber Composite particles of carbon material and flame retardant.

﹝ Steps to make semi-finished thermally conductive sheet ﹞

Next, 5 g of the composite particles obtained by the above steps were sandwiched with a PET film (protective film) subjected to sandblasting and having a thickness of 50 μm at a roll gap of 550 μm, a roll temperature of 50 ° C., and a roll linear pressure of 50 kg / cm. 1. Roll forming is performed under the condition of a roller speed of 1 m / min, thereby producing a semi-finished heat conductive sheet with a thickness of 0.5 mm.

﹝ Steps to get stacks ﹞

Furthermore, the semi-finished thermally conductive sheet obtained above was cut into a height of 6 cm × a width of 6 cm × a thickness of 0.5 mm, and 120 sheets were stacked in the thickness direction through a double-sided tape as an adhesive layer to obtain a stack of approximately 6 cm in thickness body.

﹝ Slicing procedure ﹞

Next, on the stacking section of the above-mentioned stack, pressurize with a pressure of 0.3 MPa, and use a woodworking slicer (made by Marukaka Iron Works, trade name "SUPER SURFACERS SUPER MECA-S, super-precision planer SUPER MECA-S ") sliced at an angle of 0 degrees relative to the stacking direction (in other words, sliced in the normal direction of the main surface of the stacked thermally conductive primary sheets) to obtain 6cm in height × 6cm in width × thickness 150μm heat conductive sheet. Here, the two blades used for the blade of the woodworking slicer are as follows. The two blades are two single blades, and the opposite sides of the cutting blades are in contact with each other. The front edge of the blade edge of the front blade is arranged 0.5 mm higher than the front edge of the blade edge of the inner blade and the protruding length from the slit is 0.11 mm The edge angle of the front blade is 22∘.

With respect to the obtained thermally conductive sheet, Mooney viscosity, volume-based mode diameter of the particulate carbon material, ASKER C hardness, and thermal conductivity were measured using the above method. The results are shown in Table 1-1.

Embodiment 2 will be described below.

In the step of preparing the composite mixture, except that the base material resin was changed to a different type of thermoplastic fluororesin solid at room temperature and pressure (made by Chemours Co., Ltd., trade name "A-100"), the Mooney viscosity Except 30.2ML _{1 + 4} , 100 degreeC), it carried out similarly to Example 1, and produced the heat conductive sheet. Next, various measurements similar to those in Example 1 were performed. The results are shown in Table 1-1.

Embodiment 3 will be described below.

In the step of preparing the composite mixture, the blending amount of the expanded graphite as the particulate carbon material was changed to 100 parts. In addition, the base material resin was changed to a different type of thermoplastic fluororesin solid at room temperature and pressure (made by Chemours Co., Ltd., trade name "A-100", Mooney viscosity: 30.2ML _{1 + 4} , 100 ° C), except for this, it carried out similarly to Example 1, and produced the heat conductive sheet. Next, various measurements similar to those in Example 1 were performed. The results are shown in Table 1-1.

Embodiment 4 will be described below.

In the step of preparing the composite mixture, except that the base material resin was changed to a different type of thermoplastic fluororesin solid at room temperature and pressure (made by DAIKIN Industries, under the trade name "DAI-EL (registered trademark) G -704BP ", except for Mooney viscosity: 62.4ML _{1 + 4} , 100 ° C), a thermally conductive sheet was produced in the same manner as in Example 1. Next, various measurements similar to those in Example 1 were performed. The results are shown in Table 1-2.

Embodiment 5 will be described below.

In the step of preparing the composite mixture, except that the base material resin was changed to a different type of thermoplastic fluororesin solid at room temperature and pressure (made by DAIKIN Industries, under the trade name "DAI-EL (registered trademark) G -912 ", except for the Mooney viscosity: 87.6ML _{1 + 4} , 100 ° C), a thermally conductive sheet was produced in the same manner as in Example 1. Next, various measurements similar to those in Example 1 were performed. The results are shown in Table 1-2.

Embodiment 6 will be described below.

In the step of preparing the composite mixture, the blending amount of the expanded graphite as the particulate carbon material was changed to 160 parts. In addition, the base material resin was changed to a thermoplastic silicone resin that was solid at normal temperature and pressure (manufactured by Shin-Etsu Chemical Co., Ltd., trade name "KE-931-U", Mooney viscosity: 18.0ML _{1 + 4} , 100 ° C), Except this, it carried out similarly to Example 1, and produced the heat conductive sheet. Thereafter, the same various measurements as in Example 1 were performed. The results are shown in Table 1-2.

Embodiment 7 will be described below.

In the step of preparing the composite mixture, the blending amount of the expanded graphite as the particulate carbon material was changed to 220 parts. In addition, the base material resin was changed to a thermoplastic nitrile rubber (manufactured by Ruion Corporation, trade name: "Nipol (registered trademark) DN3335" at room temperature and pressure), Mooney viscosity: 35.0ML _{1 + 4} , 100 ° C ) Except for this, a thermally conductive sheet was produced in the same manner as in Example 1. Thereafter, the same various measurements as in Example 1 were performed. The results are shown in Table 1-3.

Embodiment 8 will be described below.

In the step of preparing the composite mixture, the blending amount of the expanded graphite as the particulate carbon material was changed to 210 parts. In addition, the base material resin was changed to a thermoplastic acrylic resin that was solid at normal temperature and pressure (manufactured by Ruion Corporation, trade name: "AR-12", Mooney viscosity: 33.0ML _{1 + 4} , 100 ° C), except Except this, it carried out similarly to Example 1, and produced the heat conductive sheet. Thereafter, the same various measurements as in Example 1 were performed. The results are shown in Table 1-3.

Embodiment 9 will be described below.

In the step of preparing the composite mixture, the blending amount of the expanded graphite as the particulate carbon material was changed to 70 parts. In addition, the base material resin was changed to a different type of thermoplastic fluororesin solid at room temperature and pressure (made by Chemours Co., Ltd., trade name "A-100", Mooney viscosity: 30.2ML _{1 + 4} , 100 ° C), except for this, it carried out similarly to Example 1, and produced the heat conductive sheet. Next, various measurements similar to those in Example 1 were performed. The results are shown in Table 1-3.

Table 1-1 Table 1-2 Table 1-3

From Table 1-1, Table 1-2, and Table 1-3, it can be seen that a thermally conductive sheet formed by stacking multiple semi-finished thermally conductive sheets in the transverse direction with respect to the thickness direction has excellent thermal conductivity in the thickness direction. Among them, the semi-finished products of these heat conductive sheets include a particulate carbon material and a resin component having a Mooney viscosity of 90 (ML _{1 + 4} , 100 ° C) or less.

According to the present invention, it is possible to provide a thermally conductive sheet excellent in thermal conductivity in the thickness direction.

no.

no.

Claims (4)

A heat-conducting sheet includes: a plurality of semi-finished products of heat-conducting sheets, the semi-finished products of heat-conducting sheets include a granular carbon material and a resin or a composite of resins, and the thickness of the semi-finished products of the heat-conducting sheets relative to the heat-conducting sheets It is stacked in the transverse direction, and the Mooney viscosity of all the resin components made of the resin or the composite of multiple resins is less than 90 (ML _{1 + 4} , 100 ° C). The thermally conductive sheet according to claim 1, wherein when the Mooney viscosity of all the resin components is X and the thermal conductivity in the thickness direction of the thermally conductive sheet is Y, the relational expression is satisfied: Y > (-0.2X + 25). The heat conductive sheet according to claim 1 or 2, wherein the ASKER C hardness is 45 or more. The thermally conductive sheet according to claim 1, wherein the content ratio of the particulate carbon material is 35% by volume or more.