JP7476612B2 - Thermally conductive sheet and method for producing same - Google Patents

Description

The present invention relates to a thermally conductive sheet and a method for manufacturing the thermally conductive sheet.

In recent years, the amount of heat generated by electronic components such as plasma display panels (PDPs) and integrated circuit (IC) chips has increased as their performance has improved. As a result, electronic devices that use electronic components need to take measures to prevent malfunctions caused by temperature increases in the electronic components.

Generally, measures to prevent functional failures due to temperature rise are taken by attaching a heat sink, heat sink plate, heat sink fin, or other heat sink made of metal to a heat source such as an electronic component to promote heat dissipation. When using a heat sink, the heat source and heat sink are attached to each other via a sheet-like member (heat conductive sheet) with high thermal conductivity in order to efficiently transfer heat from the heat source to the heat sink. For this reason, the heat conductive sheet that is sandwiched between the heat source and heat sink is required to have high thermal conductivity and high flexibility. Furthermore, from the standpoint of safety, the heat conductive sheet is also required to have high flame retardancy and excellent durability.

For example, Patent Document 1 reports that a thermally conductive sheet containing a resin, a particulate carbon material, and a fibrous carbon material can simultaneously achieve high levels of flame retardancy, durability, and thermal conductivity.

International Publication No. 2016/185688

Here, when the thermally conductive sheet is used in a heated state sandwiched between a heating element and a heat sink, repeated cycles of pressure and decompression can cause the thermally conductive sheet to tear at the parts where strong pressure is applied, causing it to protrude from between the heating element and the heat sink. Because protruding thermally conductive sheets can cause short circuits inside electronic devices, thermally conductive sheets are required to be difficult to tear when in use.

However, the thermally conductive sheets of the above-mentioned conventional technology left room for improvement in terms of resistance to tearing during use.

Therefore, the present invention aims to provide a thermally conductive sheet that is less likely to tear during use.

The inventors conducted extensive research to achieve the above object. They discovered that by mixing a dispersion liquid in which the dispersant coverage rate of the fibrous carbon material is within a predetermined range, a resin, and a particulate filler, it is possible to manufacture a thermally conductive sheet that is less likely to tear during use, and thus completed the present invention.

That is, the present invention aims to advantageously solve the above problems, and the manufacturing method of the thermal conductive sheet of the present invention is a manufacturing method of a thermal conductive sheet containing a resin, a particulate filler, and a fibrous carbon material, and is characterized in that it includes a step of mixing a dispersion liquid containing the fibrous carbon material and a dispersant, the resin, and the particulate filler, and the dispersant coverage of the fibrous carbon material in the dispersion liquid is 30 mass% or more and 160 mass% or less. In this way, according to the manufacturing method of the thermal conductive sheet including the step of mixing a dispersion liquid in which the dispersant coverage of the fibrous carbon material is within a predetermined range, a resin, and a particulate filler, it is possible to manufacture a thermal conductive sheet that is difficult to tear during use.
In the present invention, the coverage of the dispersant on the fibrous carbon material in the dispersion can be measured by the method described in the Examples of this specification.

Here, in the method for producing a thermally conductive sheet of the present invention, it is preferable that the content of the fibrous carbon material in the dispersion is 0.01 parts by mass or more and 3.00 parts by mass or less per 100 parts by mass of the resin used. If the content of the fibrous carbon material in the dispersion is within the above-mentioned specified range, the thermal resistance of the thermally conductive sheet produced can be reduced while further increasing the resistance to tearing during use.

In addition, in the method for producing a thermally conductive sheet of the present invention, it is preferable that the mass ratio (particulate filler/fibrous carbon material) between the amount of the particulate filler used and the content of the fibrous carbon material in the dispersion liquid is 50 or more and 20,000 or less. If the mass ratio (particulate filler/fibrous carbon material) between the amount of the particulate filler used and the content of the fibrous carbon material in the dispersion liquid is within the above-mentioned specified range, the produced thermally conductive sheet can be further prevented from tearing during use.

Furthermore, in the method for producing a thermally conductive sheet of the present invention, it is preferable that the dispersant has an amine value. In this way, if the dispersant has an amine value, the produced thermally conductive sheet can be made even more resistant to tearing during use.

In addition, in the method for producing a thermally conductive sheet of the present invention, it is preferable that the mass ratio of the dispersant to the fibrous carbon material in the dispersion liquid (dispersant/fibrous carbon material) is 0.5 or more and 8 or less. If the mass ratio of the dispersant to the fibrous carbon material in the dispersion liquid (dispersant/fibrous carbon material) is within the above-mentioned specified range, the produced thermally conductive sheet can be made even more resistant to tearing during use.

Furthermore, in the method for producing a thermally conductive sheet of the present invention, it is preferable that the BET specific surface area of the fibrous carbon material is 400 ^m2 /g or more. If the BET specific surface area of the fibrous carbon material is equal to or greater than the above-mentioned predetermined value, the produced thermally conductive sheet can be made more resistant to tearing during use and the thermal conductivity of the thermally conductive sheet can be improved.
In the present invention, the "BET specific surface area" refers to a nitrogen adsorption specific surface area measured by the BET method.

The present invention also aims to solve the above-mentioned problems in an advantageous manner, and provides a thermally conductive sheet comprising a resin, a particulate filler, and a fibrous carbon material, the thermal conductivity of the thermally conductive sheet in a thickness direction being 12 W/m·K or more, and wherein, when a thickness of the thermally conductive sheet is pressed in the thickness direction at 0.9 MPa is T0.9, and a thickness of the thermally conductive sheet is pressed in the thickness direction at 0.1 MPa is T0.1, the thermal conductivity of the thermally conductive sheet in a thickness direction being T0.9 is _{T0.9, and the thermal conductivity of the thermally conductive sheet in a thickness direction is T0.1, the thermal conductivity of the thermally conductive sheet being T0.9 is T0.9, and the thermal conductivity of the thermally conductive sheet in a thickness direction being T0.1 is T0.1, and the thermal conductivity of the thermally conductive sheet in a thickness direction being T0.9} is T0.9, and the thermal conductivity of the thermally conductive sheet in a thickness direction being _T0.1 , is
C = 100 × {1 - (T _0.9 /T _0.1 )} [%] (1)
In this way, the thermal conductive sheet containing the resin, the particulate filler, and the fibrous carbon material, having a thermal conductivity in the thickness direction equal to or greater than a predetermined value, and having a compressibility calculated by a predetermined method equal to or less than a predetermined value, is unlikely to tear during use.
In the present invention, the thermal conductivity in the thickness direction of the thermally conductive sheet can be measured by the method described in the Examples of this specification.

Here, the thermal conductive sheet of the present invention preferably has a content of the fibrous carbon material of 0.01 parts by mass or more and 3.00 parts by mass or less per 100 parts by mass of the resin. If the content of the fibrous carbon material is within the above-mentioned specified range, the thermal resistance of the thermal conductive sheet can be reduced while further increasing the resistance of the thermal conductive sheet to tearing during use.

In addition, the heat conductive sheet of the present invention preferably has a mass ratio between the particulate filler and the fibrous carbon material (particulate filler/fibrous carbon material) of 50 or more and 20,000 or less. If the mass ratio between the particulate filler and the fibrous carbon material (particulate filler/fibrous carbon material) is within the above-mentioned specified range, the heat conductive sheet can be made even more resistant to tearing during use.

Furthermore, it is preferable that the thermally conductive sheet of the present invention further contains a dispersant, and the dispersant has an amine value. If the thermally conductive sheet further contains a dispersant having an amine value, the thermally conductive sheet can be made even more resistant to tearing during use.

The thermally conductive sheet of the present invention preferably further contains a dispersant, and the mass ratio of the dispersant to the fibrous carbon material (dispersant/fibrous carbon material) is 0.5 or more and 8 or less. If the mass ratio of the dispersant to the fibrous carbon material (dispersant/fibrous carbon material) is within the above-mentioned specified range, the thermally conductive sheet can be made more resistant to tearing during use.

Furthermore, in the thermal conductive sheet of the present invention, the BET specific surface area of the fibrous carbon material is preferably 400 ^m2 /g or more. If the BET specific surface area of the fibrous carbon material is equal to or greater than the above-mentioned predetermined value, the thermal conductive sheet is more resistant to tearing during use and has improved thermal conductivity.

The present invention provides a thermally conductive sheet that is less likely to tear during use.

1A to 1C are explanatory diagrams showing a process for producing a thermally conductive sheet using an example of a method for producing a thermally conductive sheet according to the present invention.

Hereinafter, an embodiment of the present invention will be described in detail.
The thermally conductive sheet of the present invention can be used, for example, by being sandwiched between a heat generating body and a heat sink when attaching the heat sink to the heat generating body. That is, the thermally conductive sheet of the present invention can constitute a heat dissipation device together with a heat sink, a heat sink plate, a heat sink fin, or other heat sink. The thermally conductive sheet of the present invention can be manufactured, for example, by using the manufacturing method of the thermally conductive sheet of the present invention.

(Method of manufacturing thermally conductive sheet)
The method for producing a thermally conductive sheet of the present invention is a method for producing a thermally conductive sheet containing a resin, a particulate filler, and a fibrous carbon material, and is characterized in that it includes a step (mixing step) of mixing a dispersion liquid containing the fibrous carbon material and a dispersant with a resin and a particulate filler, and the dispersant coverage rate of the fibrous carbon material in the dispersion liquid is within a predetermined range. According to the method for producing a thermally conductive sheet of the present invention, it is possible to produce a thermally conductive sheet that is difficult to tear during use.
The method for producing a thermally conductive sheet of the present invention may further include a step (other step) other than the above-mentioned mixing step.

<Mixing step>
In the mixing step, a dispersion liquid having a dispersant coverage rate of the fibrous carbon material within a predetermined range, a resin, and a particulate filler are mixed. By mixing a dispersion liquid having a dispersant coverage rate of the fibrous carbon material within a predetermined range, a resin, and a particulate filler, the thermal conductive sheet produced can be made less likely to tear during use.

Here, the reason why mixing a dispersion liquid in which the dispersant coverage rate of the fibrous carbon material is within a predetermined range with a resin and a particulate filler makes the thermal conductive sheet produced less likely to tear during use is not clear, but is presumed to be as follows.
First, in a dispersion liquid containing a fibrous carbon material with a dispersant coverage rate within a predetermined range, the fibrous carbon material is well dispersed. Therefore, by mixing the dispersion liquid, a resin, and a particulate filler, the fibrous carbon material can be well dispersed in the resulting mixture. As a result, it is presumed that the fibrous carbon material forms a three-dimensional mesh structure in the produced thermally conductive sheet. And, since the strength of the thermally conductive sheet is increased by the three-dimensional mesh structure of the fibrous carbon material, it is considered that the thermally conductive sheet can be well prevented from being crushed even when, for example, the thermally conductive sheet is sandwiched between a heating body and a heat dissipating body and cycles of heating and cooling and/or cycles of pressurization and decompression are repeated. Therefore, it is presumed that the thermally conductive sheet can be made difficult to tear even during use.

In addition, in the mixing process, components other than the above-mentioned dispersion liquid, resin, and particulate filler may be further mixed.

<<Dispersion>>
The dispersion liquid used in the mixing process contains a fibrous carbon material and a dispersant. Here, the dispersion liquid is a dispersion liquid in which the fibrous carbon material is dispersed in a solvent (dispersion medium). At least a portion of the dispersant contained in the dispersion liquid adheres to the fibrous carbon material. As a result, at least a portion of the surface of the fibrous carbon material is coated with the dispersant in the dispersion liquid. By coating at least a portion of the surface of the fibrous carbon material with the dispersant, an effect of suppressing entanglement of the fibers is achieved, and the fibrous carbon material can be well dispersed in the dispersion liquid.

[Carbon fiber materials]
The fibrous carbon material is a material that makes the produced thermally conductive sheet less likely to tear during use and can impart properties such as flame retardancy and thermal conductivity to the thermally conductive sheet.
The fibrous carbon material is not particularly limited, and examples thereof include carbon nanotubes, vapor-grown carbon fibers, carbon fibers obtained by carbonizing organic fibers, and cut products thereof. These may be used alone or in combination of two or more.

Among the above, it is preferable to use fibrous carbon nanostructures such as carbon nanotubes as the fibrous carbon material, and it is more preferable to use fibrous carbon nanostructures containing carbon nanotubes. By using fibrous carbon nanostructures such as carbon nanotubes, the thermal conductive sheet produced can be made more resistant to tearing during use, and the thermal conductivity of the thermal conductive sheet can be improved.

- Fibrous carbon nanostructures including carbon nanotubes -
Here, the fibrous carbon nanostructure containing carbon nanotubes that can be suitably used as the fibrous carbon material may consist only of carbon nanotubes (hereinafter sometimes referred to as "CNTs"), or may be a mixture of CNTs and fibrous carbon nanostructures other than CNTs.
The CNTs in the fibrous carbon nanostructure are not particularly limited, and single-walled carbon nanotubes and/or multi-walled carbon nanotubes can be used, but the CNTs are preferably single-walled to five-walled carbon nanotubes, and more preferably single-walled carbon nanotubes.

The average diameter of the fibrous carbon nanostructures containing CNTs 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. If the average diameter of the fibrous carbon nanostructures is 0.5 nm or more, the aggregation of the fibrous carbon nanostructures is suppressed and the dispersibility of the fibrous carbon nanostructures is increased, thereby making the manufactured heat conductive sheet more resistant to tearing during use. On the other hand, if the average diameter of the fibrous carbon nanostructures is 15 nm or less, the strength of the manufactured heat conductive sheet is increased, making the manufactured heat conductive sheet more resistant to tearing during use. In addition, if the average diameter of the fibrous carbon nanostructures is 15 nm or less, the thermal conductivity of the manufactured heat conductive sheet can be further improved.

Furthermore, it is preferable that the fibrous carbon nanostructures containing CNTs have an average length of 100 μm or more and 5000 μm or less. If the average length of the fibrous carbon nanostructures containing CNTs is within the above-mentioned specified range, the manufactured thermal conductive sheet will be more resistant to tearing during use, and the thermal conductivity of the thermal conductive sheet can be further improved.

The "average diameter of fibrous carbon nanostructures" and the "average length of fibrous carbon nanostructures" can be determined by measuring the diameter (outer diameter) and length, respectively, of 100 randomly selected fibrous carbon nanostructures using a transmission electron microscope. The average diameter and average length of fibrous carbon nanostructures containing CNTs may be adjusted by changing the manufacturing method or manufacturing conditions of the fibrous carbon nanostructures containing CNTs, or by combining multiple types of fibrous carbon nanostructures containing CNTs obtained by different manufacturing methods.

And, the fibrous carbon nanostructure containing CNT having the above-mentioned properties can be efficiently manufactured, for example, by supplying a raw material compound and a carrier gas onto a substrate having a catalyst layer for producing carbon nanotubes on its surface, synthesizing CNT by chemical vapor deposition (CVD), and by making a trace amount of an oxidizing agent (catalyst activation material) present in the system, thereby dramatically improving the catalytic activity of the catalyst layer (super growth method; see International Publication No. 2006/011655). Note that, hereinafter, carbon nanotubes obtained by the super growth method may be referred to as "SGCNT".
Here, the fibrous carbon nanostructure containing CNT produced by the super-growth method may be composed only of SGCNT, or may contain, in addition to SGCNT, other carbon nanostructures, such as non-cylindrical carbon nanostructures.

- BET specific surface area of fibrous carbon material -
The BET specific surface area of the fibrous carbon material is preferably 400 m ² /g or more, more preferably 600 m ² /g or more, even more preferably 800 m ² /g or more, preferably 2500 m ² /g or less, and more preferably 1200 m ² /g or less. If the BET specific surface area of the fibrous carbon material is 400 m ² /g or more, the resistance to tearing during use of the produced heat conductive sheet can be further increased, and the thermal conductivity of the heat conductive sheet can be improved. In addition, if the BET specific surface area of the fibrous carbon material is 2500 m ² /g or less, the aggregation of the fibrous carbon nanostructures can be suppressed and the dispersibility of the fibrous carbon nanostructures can be increased, thereby further increasing the resistance to tearing during use of the produced heat conductive sheet.

- Concentration of fibrous carbon materials -
The concentration of the fibrous carbon material in the dispersion is preferably 0.01% by mass or more, preferably 0.05% by mass or more, more preferably 0.10% by mass or more, more preferably 0.20% by mass or more, preferably 2.00% by mass or less, more preferably 1.00% by mass or less, and more preferably 0.50% by mass or less. If the concentration of the fibrous carbon material in the dispersion is equal to or higher than the lower limit, the amount of dispersion added during the production of the thermal conductive sheet can be reduced, and the production efficiency of the thermal conductive sheet can be improved by reducing the amount of solvent to be removed. On the other hand, if the concentration of the fibrous carbon material in the dispersion is equal to or lower than the upper limit, the fibrous carbon material can be easily dispersed in the dispersion.

-Content of fibrous carbon material-
The content of the fibrous carbon material in the dispersion used in the mixing step is preferably 0.01 parts by mass or more, more preferably 0.05 parts by mass or more, even more preferably 0.10 parts by mass or more, and preferably 3.00 parts by mass or less, more preferably 2.00 parts by mass or less, even more preferably 1.00 parts by mass or less, even more preferably 0.60 parts by mass or less, and even more preferably 0.40 parts by mass or less, relative to 100 parts by mass of the resin used. If the content of the fibrous carbon material in the dispersion is the above lower limit or more relative to 100 parts by mass of the resin used, the resistance to tearing during use of the produced thermal conductive sheet can be further increased. On the other hand, if the content of the fibrous carbon material in the dispersion is the above upper limit or less relative to 100 parts by mass of the resin used, the hardness of the produced thermal conductive sheet is suppressed from increasing excessively, and the thermal conductive sheet and the adherend (such as a heat sink and a heat generating body) can be well adhered to each other, so that the thermal resistance of the thermal conductive sheet can be reduced.

[Dispersant]
The dispersant is a component that adheres to the above-mentioned fibrous carbon material, coats the surface of the fibrous carbon material, and provides a physical distance between the fibers, thereby suppressing entanglement of the fibers, thereby enabling the fibrous carbon material to be well dispersed in the dispersion liquid.

The dispersant is not particularly limited as long as it can achieve the desired effect of the present invention, but from the viewpoint of improving the dispersibility of the fibrous carbon material and further increasing the resistance of the produced thermal conductive sheet to tearing, it is preferable to use a polymer, and it is more preferable to use a polymer containing an amine value (e.g., a polymer containing a basic group, etc.).

From the viewpoint of improving the dispersibility of the fibrous carbon material and further increasing the resistance of the produced thermally conductive sheet to tearing during use, it is preferable that the dispersant has an amine value.
The amine value of the dispersant is preferably 5 mgKOH/g or more, more preferably 10 mgKOH/g or more, and is preferably 50 mgKOH/g or less, and more preferably 20 mgKOH/g or less. If the amine value of the dispersant is within the above-mentioned range, the produced thermal conductive sheet can be made more resistant to tearing during use.
In the present invention, the amine value of the dispersant can be measured by titration with potassium hydroxide (KOH).

In order to improve the dispersibility of the fibrous carbon material and to make the produced thermal conductive sheet more resistant to tearing during use, the dispersant preferably has an acid value.
The acid value of the dispersant is preferably 3 mgKOH/g or more, more preferably 5 mgKOH/g or more, and is preferably 80 mgKOH/g or less, and more preferably 50 mgKOH/g or less. If the acid value of the dispersant is within the above-mentioned range, the produced thermal conductive sheet can be made more resistant to tearing during use.
In the present invention, the acid value of the dispersant can be measured by titration with potassium hydroxide (KOH).

As a dispersant, commercially available products can also be used, such as "Ajisper PB821" (manufactured by Ajinomoto Fine-Techno Co., Ltd.) and "BYK-2013" (manufactured by BYK-Chemie Co., Ltd.).

-Dispersant coverage of fibrous carbon material-
The dispersant coverage of the fibrous carbon material in the dispersion must be 30% by mass or more, preferably 35% by mass or more, must be 160% by mass or less, preferably 140% by mass or less, more preferably 120% by mass or less, and even more preferably 100% by mass or less. If the dispersant coverage of the fibrous carbon material in the dispersion is less than 30% by mass, the dispersibility of the fibrous carbon material is insufficient, so that the thermal conductive sheet produced is easily torn during use. On the other hand, if the dispersant coverage of the fibrous carbon material in the dispersion is 30% by mass or more, the dispersibility of the fibrous carbon material is sufficiently increased, so that the thermal conductive sheet produced is less likely to tear during use. In addition, if the dispersant coverage of the fibrous carbon material in the dispersion exceeds 160% by mass, the amount of dispersant that can adhere to the fibrous carbon material is saturated, and the amount of dispersant that is not adhered to the fibrous carbon material also becomes excessive, so that the thermal conductive sheet produced becomes excessively soft and easily torn during use. On the other hand, if the dispersant coverage rate of the fibrous carbon material in the dispersion liquid is 160 mass % or less, the thermally conductive sheet produced can be prevented from becoming excessively soft, making the thermally conductive sheet less likely to tear during use.

The dispersant coverage of the fibrous carbon material in the dispersion can be adjusted by the type and properties of the fibrous carbon material, the type of dispersant, the concentrations of the fibrous carbon material and dispersant in the dispersion, the mass ratio of the dispersant to the fibrous carbon material, and the preparation method and preparation conditions of the dispersion.

- Dispersant concentration -
The concentration of the dispersant in the dispersion is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, and even more preferably 0.10% by mass or more, and is preferably 4.00% by mass or less, more preferably 2.00% by mass or less, and even more preferably 0.50% by mass or less. If the concentration of the dispersant in the dispersion is within the above-mentioned range, the produced thermal conductive sheet can be further improved in resistance to tearing during use.

-Dispersant content-
The content of the dispersant in the dispersion used in the mixing step is preferably 0.005 parts by mass or more, more preferably 0.025 parts by mass or more, even more preferably 0.050 parts by mass or more, and preferably 2.000 parts by mass or less, more preferably 1.500 parts by mass or less, even more preferably 1.000 parts by mass or less, even more preferably 0.800 parts by mass or less, and even more preferably 0.400 parts by mass or less, relative to 100 parts by mass of the resin used. If the content of the dispersant in the dispersion is equal to or greater than the lower limit above relative to 100 parts by mass of the resin used, the resistance to tearing during use of the thermal conductive sheet produced can be further increased. On the other hand, if the content of the dispersant in the dispersion is equal to or less than the upper limit above relative to 100 parts by mass of the resin used, the thermal conductive sheet produced can be prevented from becoming excessively soft, thereby further increasing the resistance to tearing during use of the thermal conductive sheet.

--Mass ratio of dispersant to fibrous carbon material (dispersant/fibrous carbon material)--
The mass ratio of the dispersant to the fibrous carbon material in the dispersion (dispersant/fibrous carbon material) is preferably 0.5 or more, more preferably 0.7 or more, even more preferably 0.9 or more, preferably 10 or less, more preferably 8 or less, and even more preferably 4 or less. If the mass ratio of the dispersant to the fibrous carbon material in the dispersion (dispersant/fibrous carbon material) is equal to or greater than the above lower limit, the thermal conductive sheet produced can be further improved in resistance to tearing during use. On the other hand, if the mass ratio of the dispersant to the fibrous carbon material in the dispersion (dispersant/fibrous carbon material) is equal to or less than the above upper limit, the thermal conductive sheet produced can be prevented from becoming excessively soft, thereby further improving the resistance to tearing during use.

〔solvent〕
The solvent (dispersion medium) used in the dispersion is not particularly limited, and either water or an organic solvent can be used, but it is preferable to use an organic solvent. If an organic solvent is used as the solvent, the dispersion and the resin are well mixed during the mixing process, and the fibrous carbon material is well dispersed in the resulting mixture, so that the manufactured thermal conductive sheet is more difficult to break during use.
The organic solvent may be appropriately selected from polar organic solvents such as ketones such as methyl ethyl ketone (MEK), alcohols such as ethanol and isopropyl alcohol, and non-polar organic solvents such as hydrocarbon solvents including cyclohexane and toluene, depending on the type of resin used. These solvents may be used alone or in combination of two or more in any ratio.

[Method of preparing dispersion]
The method for preparing the dispersion is not particularly limited, but for example, a method can be used in which the above-mentioned fibrous carbon material, the dispersion, and a solvent are mixed to prepare a crude dispersion, and then a process (cycle) of sending the crude dispersion into a capillary flow passage of a jet mill while applying pressure using an apparatus equipped with a jet mill is carried out once or multiple times.

Here, in the above process, the pressure applied when feeding the crude dispersion liquid into the capillary flow path is preferably 5 MPa or more, more preferably 10 MPa or more, even more preferably 20 MPa or more, preferably 200 MPa or less, more preferably 150 MPa or less, and even more preferably 120 MPa or less. If the pressure applied when feeding the crude dispersion liquid into the capillary flow path is equal to or higher than the above lower limit, the dispersant coverage of the fibrous carbon material in the prepared dispersion liquid can be increased, and the fibrous carbon can be well dispersed. On the other hand, if the pressure applied when feeding the crude dispersion liquid into the capillary flow path is equal to or lower than the above, cutting of the fibrous carbon material can be suppressed.

The processing temperature in the above process is not particularly limited, but can be, for example, 0°C or higher and 50°C or lower.

In order to prevent clogging of the capillary flow passage and to satisfactorily disperse the carbon material in the dispersion liquid, for example, the above process can be carried out once or multiple times using a first capillary flow passage, and then the above process can be carried out once or multiple times using a second capillary flow passage having a diameter smaller than that of the first capillary flow passage.

Here, the diameter of the first capillary passage portion is not particularly limited, but is preferably 50 μm or more, more preferably 100 μm or more, and preferably 1000 μm or less, and more preferably 500 μm or less. If the diameter of the first capillary passage portion is 50 μm or more, clogging of the capillary passage portion can be effectively prevented. On the other hand, if the diameter of the first capillary passage portion is 1000 μm or less, the fibrous carbon can be more effectively dispersed in the dispersion liquid.
The diameter of the second capillary passage portion is not particularly limited as long as it is smaller than the diameter of the first capillary passage portion, but is preferably 50 μm or more, more preferably 60 μm or more, and preferably less than 150 μm, and more preferably 100 μm or less. If the diameter of the second capillary passage portion is 50 μm or more, clogging of the capillary passage portion can be effectively prevented. On the other hand, if the diameter of the second capillary passage portion is less than 150 μm, the fibrous carbon can be more effectively dispersed in the dispersion liquid.

The number of times of treatment using the first capillary channel section may be at least one, preferably at least two, more preferably at least three, preferably no more than 20, more preferably no more than 10, and even more preferably no more than 5. When the number of times of treatment using the first capillary channel section is at least the lower limit, clogging of the capillary channel section can be effectively prevented. On the other hand, when the number of times of treatment using the first capillary channel section is at most the upper limit, cutting of the fibrous carbon material can be suppressed.
The number of times of treatment using the second capillary flow passage section may be 0, preferably 1 or more, more preferably 2 or more, even more preferably 3 or more, preferably 20 or less, more preferably 10 or less, and even more preferably 5 or less. If the number of times of treatment using the second capillary flow passage section is equal to or greater than the lower limit, the carbon material can be dispersed in the dispersion liquid more satisfactorily. On the other hand, if the number of times of treatment using the second capillary flow passage section is equal to or less than the upper limit, cutting of the fibrous carbon material can be suppressed.

As devices equipped with a jet mill, for example, "Nanoveita" (manufactured by Yoshida Kikai Kogyo Co., Ltd.), "BERYU SYSTEM PRO" (manufactured by Biryu Co., Ltd.), ultra-high pressure wet type micronization device (manufactured by Yoshida Kogyo Co., Ltd.), "Nanomizer" (manufactured by Nanomizer Co., Ltd.), "Starburst" (manufactured by Sugino Machine Co., Ltd.), etc. can be used.

<<Resin>>
The resin is not particularly limited, and any resin can be used. For example, the resin can be either a liquid resin or a solid resin. The resin may be used alone or in combination of two or more types. For example, from the viewpoint of achieving both improved tear resistance during use of the produced thermal conductive sheet and reduced thermal resistance, it is preferable to use both a liquid resin and a solid resin.

[Liquid resin]
The liquid resin is not particularly limited as long as it is liquid at room temperature and normal pressure, and for example, a thermoplastic resin that is liquid at room temperature and normal pressure can be used.
In the present invention, "normal temperature" refers to 23° C., and "normal pressure" refers to 1 atm (absolute pressure).

Examples of liquid resins include fluororesins, silicone resins, acrylic resins, and epoxy resins. These may be used alone or in combination of two or more. Among them, silicone resins and fluororesins are preferred as liquid resins, and fluororesins are more preferred. If at least one of silicone resins and fluororesins is used as the liquid resin, the flame retardancy of the thermal conductive sheet can be improved. Furthermore, if a fluororesin is used as the liquid resin, the heat resistance, oil resistance, and chemical resistance of the resulting thermal conductive sheet can be improved.

[Solid Resin]
The solid resin is not particularly limited as long as it is not liquid at room temperature and normal pressure. For example, a thermoplastic resin that is solid at room temperature and normal pressure, or a thermosetting resin that is solid at room temperature and normal pressure can be used.

- Thermoplastic resin that is solid at room temperature and pressure -
Examples of thermoplastic resins that are solid at room temperature and pressure include acrylic resins such as poly(2-ethylhexyl acrylate), a copolymer of acrylic acid and 2-ethylhexyl acrylate, polymethacrylic acid or its ester, and polyacrylic acid or its ester; silicone resins; fluororesins; polyethylene; polypropylene; ethylene-propylene copolymers; polymethylpentene; polyvinyl chloride; polyvinylidene chloride; polyvinyl acetate; ethylene-vinyl acetate copolymers; polyvinyl alcohol; polyacetal; polyethylene terephthalate; polybutylene terephthalate; polyethylene naphthalate; polystyrene; and polyacrylonitrile. Examples of the polymerizable compound include styrene-acrylonitrile copolymers, acrylonitrile-butadiene copolymers (nitrile rubbers), acrylonitrile-butadiene-styrene copolymers (ABS resins), styrene-butadiene block copolymers or hydrogenated products thereof, styrene-isoprene block copolymers or hydrogenated products thereof, polyphenylene ethers, modified polyphenylene ethers, aliphatic polyamides, aromatic polyamides, polyamideimides, polycarbonates, polyphenylene sulfides, polysulfones, polyethersulfones, polyethernitriles, polyetherketones, polyketones, polyurethanes, liquid crystal polymers, and ionomers. These may be used alone or in combination of two or more.
In the present invention, rubber is included in the "resin".

- Thermosetting resin that is solid at room temperature and pressure -
Examples of thermosetting resins that are solid at room temperature and normal pressure include natural rubber, butadiene rubber, isoprene rubber, nitrile 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, benzocyclobutene resin, phenolic resin, unsaturated polyester, diallyl phthalate resin, polyimide silicone resin, polyurethane, thermosetting polyphenylene ether, thermosetting modified polyphenylene ether, etc. These may be used alone or in combination of two or more.

[Liquid resin content]
The content of the liquid resin in the resin (in other words, the proportion of the liquid resin in the total of the solid resin and the liquid resin) is not particularly limited, but is preferably 30% by mass or more, more preferably 40% by mass or more, even more preferably 50% by mass or more, particularly preferably 60% by mass or more, preferably 95% by mass or less, more preferably 90% by mass or less, even more preferably 85% by mass or less, and particularly preferably 80% by mass or less. If the content of the liquid resin in the resin is within the above-mentioned specified range, the produced thermal conductive sheet can be made even more difficult to tear during use.

<<Particulate filler>>
The particulate filler is not particularly limited, and examples thereof include alumina particles, zinc oxide particles, boron nitride particles, aluminum nitride particles, silicon nitride particles, silicon carbide particles, magnesium oxide particles, and particulate carbon materials.
These particulate fillers may be used alone or in combination of two or more kinds in any desired ratio.

In order to increase the thermal conductivity of the thermally conductive sheet to be manufactured, it is preferable to use a particulate carbon material as the particulate filler.

[Carbon material particles]
The particulate carbon material is not particularly limited, and examples thereof include graphite such as artificial graphite, scaly graphite, exfoliated graphite, natural graphite, acid-treated graphite, negative electrode active material, expandable graphite, and expanded graphite; carbon black; etc. These may be used alone or in combination of two or more kinds.

Among the above, it is preferable to use expanded graphite as the particulate carbon material. By using expanded graphite, the thermal conductivity of the thermal conductive sheet to be manufactured can be further improved. Here, expanded graphite can be obtained by, for example, chemically treating graphite such as flake graphite with sulfuric acid or the like to obtain expandable graphite, which is then expanded by heat treatment and then refined. Examples of expanded graphite include EC1500, EC1000, EC500, EC300, EC100, and EC50 (all trade names) manufactured by Ito Graphite Industries Co., Ltd.

[Properties of particulate filler]
The volume average particle diameter of the particulate filler is preferably 10 μm or more, preferably 20 μm or more, more preferably 30 μm or more, even more preferably 40 μm or more, preferably 180 μm or less, more preferably 160 μm or less, and even more preferably 140 μm or less. If the volume average particle diameter of the particulate filler is equal to or greater than the above lower limit, it is presumed that the heat transfer path of the particulate filler can be well formed in the heat conductive sheet produced, and the thermal conductivity of the heat conductive sheet can be improved. On the other hand, if the volume average particle diameter of the particulate filler is equal to or less than the above upper limit, the thickness accuracy of the heat conductive sheet produced can be sufficiently high. In addition, if the volume average particle diameter of the particulate filler is within the above-mentioned predetermined range, the resistance to tearing during use of the heat conductive sheet produced can be further improved.
In the present invention, the "volume average particle size" can be measured in accordance with JIS Z8825, and represents a particle size at which the cumulative volume calculated from the small diameter side is 50% in a particle size distribution (volume basis) measured by a laser diffraction method.

The particulate filler preferably has an aspect ratio (major axis/minor axis) of more than 1 and not more than 10, more preferably more than 1 and not more than 5. If the particulate filler has an aspect ratio of more than 1 and not more than 10, it is presumed that the particulate filler is easily oriented well in the thickness direction in the thermal conductive sheet, and the thermal conductivity in the thickness direction of the thermal conductive sheet can be increased.
In the present invention, the "aspect ratio" can be determined by observing the particulate filler with a SEM (scanning electron microscope), measuring the maximum diameter (long diameter) and the particle diameter (short diameter) in a direction perpendicular to the maximum diameter for any 50 particulate fillers, and calculating the average value of the ratio of the long diameter to the short diameter (long diameter/short diameter). In the above, for example, when the particulate filler is scaly, the "long diameter" refers to the length in the direction of the long axis of the main surface of the scaly shape, and the "short diameter" refers to the length in the direction perpendicular to the long axis of the main surface.

[Amount of particulate filler used]
The amount of particulate filler used in the mixing step is preferably 20 parts by mass or more, more preferably 30 parts by mass or more, even more preferably 40 parts by mass or more, and preferably 150 parts by mass or less, more preferably 120 parts by mass or less, and even more preferably 100 parts by mass or less, relative to 100 parts by mass of the resin used. If the amount of particulate filler used is equal to or greater than the lower limit relative to 100 parts by mass of the resin used, the thermal conductivity of the thermal conductive sheet produced can be improved. On the other hand, if the amount of particulate filler used is equal to or less than the upper limit relative to 100 parts by mass of the resin used, the softness of the thermal conductive sheet produced can be sufficiently maintained, and as a result, the thermal resistance can be reduced. In addition, if the amount of particulate filler used is within the above-mentioned predetermined range relative to 100 parts by mass of the resin used, the resistance to tearing during use of the thermal conductive sheet produced can be further increased.

[Mass ratio of particulate filler to fibrous carbon material (particulate filler/fibrous carbon material)]
In addition, the mass ratio (particulate filler/fibrous carbon material) between the amount of particulate filler used in the mixing step and the content of the fibrous carbon material in the dispersion liquid described above is preferably 50 or more, more preferably 80 or more, even more preferably 100 or more, even more preferably 150 or more, even more preferably 200 or more, preferably 20,000 or less, more preferably 10,000 or less, even more preferably 3,000 or less, even more preferably 1,600 or less, and even more preferably 800 or less. If the mass ratio (particulate filler/fibrous carbon material) between the amount of particulate filler used in the mixing step and the content of the fibrous carbon material in the dispersion liquid is within the above-mentioned predetermined range, the resistance to tearing during use of the manufactured thermal conductive sheet can be further increased.
The mass ratio of the amount of the particulate filler used in the mixing step to the amount of the fibrous carbon material contained in the dispersion liquid (particulate filler/fibrous carbon material) may be 100 or less.

<<Other ingredients>>
In the mixing step, components other than the above-mentioned dispersion, resin, and particulate filler (other components) may be further mixed, if necessary.
The other components are not particularly limited as long as they are components that can be used to form a thermally conductive sheet, and examples thereof include plasticizers such as fatty acid esters, such as sebacic acid esters; flame retardants, such as red phosphorus flame retardants and phosphate ester flame retardants; toughness improvers, such as urethane acrylates; moisture absorbents, such as calcium oxide and magnesium oxide; adhesion improvers, such as silane coupling agents, titanium coupling agents and acid anhydrides; wettability improvers, such as nonionic surfactants and fluorine surfactants; ion trapping agents, such as inorganic ion exchangers; etc. The additives may be used alone or in combination of two or more.
The amounts of other components used in the mixing step can be appropriately adjusted within the range in which the desired effects of the present invention can be obtained.

<<Mixing method>>
The mixing of the dispersion containing the above-mentioned fibrous carbon material and dispersant, the resin, the particulate filler, and other components added as necessary can be carried out using a known mixing device such as a Hobart, stirring blade, mixer, etc., without any particular limitation.
The above mixing is usually carried out while heating. By carrying out the mixing while heating, the solvent (dispersion medium) contained in the dispersion liquid can be removed. The mixing temperature can be appropriately set according to the type of the solvent contained in the dispersion liquid, and can be, for example, 70° C. or higher and 100° C. or lower. The removal of the solvent may be carried out under reduced pressure.
The mixing time can be, for example, from 5 minutes to 60 minutes.

The mixture obtained in the mixing step may be subjected to processes such as degassing and crushing, if necessary.

<Other processes>
The method for producing a thermally conductive sheet of the present invention may further include a step other than the above-mentioned mixing step.
For example, the method for producing a thermally conductive sheet of the present invention preferably further includes, as other steps, (1) a step of forming the mixture obtained in the mixing step into a sheet to obtain a primary sheet (primary sheet forming step), (2) a step of stacking a plurality of the obtained primary sheets in the thickness direction, or folding or rolling the pre-thermally conductive sheet, to obtain a laminate (laminate forming step), and (3) a step of slicing the obtained laminate (slicing step).

<<Primary sheet molding process>>
In the primary sheet forming step, the mixture obtained in the mixing step is formed into a sheet to obtain a primary sheet.
The mixture is usually formed into a sheet by pressing (primary pressing). Here, the method of forming the mixture into a sheet is not particularly limited as long as it is a molding method in which pressure is applied, and known molding methods such as press molding, rolling molding, and extrusion molding can be used. Among them, it is preferable to use rolling molding, and it is more preferable to use a method in which the mixture is sandwiched between protective films and passed between rolls to form it into a sheet. The protective film is not particularly limited, and a polyethylene terephthalate (PET) film that has been subjected to sandblasting treatment can be used. The roll temperature can be 5°C or more and 150°C or less.

[Characteristics of the primary sheet]
In the primary sheet, since the particulate filler is mainly oriented in the in-plane direction, it is presumed that the thermal conductivity in the in-plane direction in particular is improved.
The thickness of the primary sheet is not particularly limited and can be, for example, 0.05 mm or more and 2 mm or less.

The tensile strength of the primary sheet is preferably 0.52 MPa or more, more preferably 0.54 MPa or more, and even more preferably 0.56 MPa or more, and is preferably 1.00 MPa or less, more preferably 0.90 MPa or less, and even more preferably 0.85 MPa or less. If the tensile strength of the primary sheet is within the above-mentioned range, the manufactured thermal conductive sheet can be further improved in resistance to tearing during use.
The tensile strength of the primary sheet can be measured by the method described in the Examples of this specification.

In addition, the breaking elongation of the primary sheet is preferably 2.60 mm or more, more preferably 2.70 mm or more, and even more preferably 2.75 mm or more, and is preferably 3.15 mm or less, more preferably 3.10 mm or less, and even more preferably 3.05 mm or less. If the breaking elongation of the primary sheet is within the above-mentioned range, the manufactured thermal conductive sheet can be further improved in resistance to tearing during use.
The breaking elongation of the primary sheet can be measured by the method described in the Examples of this specification.

<<Laminate Forming Process>>
In the laminate formation step, a plurality of the primary sheets obtained in the primary sheet molding step are laminated in the thickness direction, or the primary sheets are folded or rolled to obtain a laminate.

Here, in order to further increase the adhesive strength between the surfaces of the primary sheets in the laminate obtained in the laminate formation process and sufficiently suppress delamination of the laminate, the laminate formation process may be performed with the surfaces of the primary sheets slightly dissolved in a solvent, or with an adhesive applied to the surfaces of the primary sheets or with an adhesive layer provided on the surface of the pre-thermal conductive sheet, or the laminate with the primary sheets stacked may be further pressed (secondary pressure) in the stacking direction.

From the viewpoint of efficiently suppressing delamination, it is preferable to apply a secondary pressure to the obtained laminate in the lamination direction. The conditions for the secondary pressure application are not particularly limited, and can be a pressure of 0.05 MPa or more and 0.5 MPa or less in the lamination direction, a temperature of 80°C or more and 170°C or less, and a pressure application time of 10 seconds or more and 30 minutes or less.

And in the laminate obtained by stacking, folding or rolling the primary sheet, it is presumed that the particulate filler is aligned in a direction approximately perpendicular to the stacking direction.

[Properties of the laminate]
The Asker C hardness of the laminate at 25° C. is preferably 70 or more, more preferably 75 or more, and even more preferably 80 or more, and is preferably 100 or less, more preferably 95 or less, and even more preferably 90 or less. If the Asker C hardness of the laminate at 25° C. is within the above-mentioned predetermined range, the produced thermal conductive sheet can be further prevented from tearing during use.
Furthermore, the Asker C hardness of the laminate at 70° C. is preferably 20 or more, more preferably 25 or more, and even more preferably 30 or more, and is preferably 55 or less, more preferably 50 or less, and even more preferably 45 or less. If the Asker C hardness of the laminate at 70° C. is within the above-mentioned predetermined range, the produced thermal conductive sheet can be further prevented from tearing during use.
The Asker C hardness of the laminate can be measured by the method described in the Examples of this specification.

<<Slicing process>>
In the slicing step, the laminate obtained in the laminate forming step is sliced, thereby obtaining thermally conductive sheets made of sliced pieces of the laminate.

The method for slicing the laminate is not particularly limited, and for example, a slicing method using a cutting tool equipped with a blade can be used. Here, the shape of the blade is not particularly limited, and it may be a single-edged, double-edged, or asymmetrical blade, but from the viewpoint of ensuring sufficient thickness precision of the obtained thermal conductive sheet, a double-edged blade is preferable. In addition, the material of the blade is not particularly limited, but it is preferably made of metal. Examples of cutting tools equipped with such blades include a cutter, a plane, a slicer, etc.

The angle at which the laminate is sliced is preferably 45° or less with respect to the direction in which the primary sheets are stacked (hereinafter, sometimes simply referred to as the "stacking direction"). More preferably, it is 30° or less with respect to the stacking direction, and even more preferably, it is 15° or less with respect to the stacking direction. It is particularly preferable that the angle is approximately 0° with respect to the stacking direction (i.e., along the stacking direction). Here, it is presumed that the particulate filler is oriented in a direction approximately perpendicular to the stacking direction inside the laminate formed by stacking the above-mentioned primary sheets in the thickness direction. If such a laminate is sliced at an angle of 45° or less with respect to the stacking direction, the thermal conductivity in the thickness direction of the thermal conductive sheet can be improved. The reason why the thermal conductivity in the thickness direction of the thermal conductive sheet is improved by slicing the laminate at an angle of the above-mentioned predetermined value or less with respect to the stacking direction is presumed to be that the particulate filler is oriented in the thickness direction (i.e., in a direction approximately perpendicular to the stacking direction of the primary sheets) in the obtained thermal conductive sheet, and the heat transfer path formed by the contact of the particulate filler is mainly well formed in the thickness direction of the thermal conductive sheet.

From the viewpoint of slicing the laminate easily, the temperature of the laminate during slicing is preferably -20°C or higher and 80°C or lower, and more preferably -10°C or higher and 50°C or lower.
Furthermore, from the viewpoint of slicing the laminate easily, it is preferable to fix the laminate by applying pressure or the like when slicing. In such a pressurization, the surface to which the pressure is applied is not particularly limited. For example, the laminate can be sliced while applying a pressure of 0.05 MPa or more and 0.5 MPa or less in the stacking direction.

In addition, in the thermally conductive sheet obtained in the slicing process, the particulate filler is oriented in a direction that is approximately perpendicular to the in-plane direction (i.e., the thickness direction of the thermally conductive sheet). Therefore, it is presumed that the thermally conductive sheet can exhibit excellent thermal conductivity, especially in the thickness direction.

(Thermal Conduction Sheet)
The thermally conductive sheet of the present invention is characterized in that it contains a resin, a particulate filler, and a fibrous carbon material, has a thermal conductivity in the thickness direction equal to or greater than a predetermined value, and has a compression ratio calculated by a predetermined method equal to or less than a predetermined value. The thermally conductive sheet of the present invention is also difficult to tear during use. For example, the thermally conductive sheet of the present invention is unlikely to tear even when it is sandwiched between a heat generating body and a heat dissipating body and is subjected to repeated cycles of heating and cooling and/or pressurization and decompression. Therefore, the thermally conductive sheet of the present invention has excellent durability.
The thermally conductive sheet of the present invention can be efficiently produced by the above-mentioned method for producing a thermally conductive sheet of the present invention.

Here, the resin, particulate filler, and fibrous carbon material contained in the thermal conductive sheet of the present invention can be, for example, the resin and particulate filler described above in the section "Method for manufacturing a thermal conductive sheet," and the fibrous carbon material contained in the dispersion liquid.
In addition, the preferred range of the particulate filler content per 100 parts by mass of resin in the thermal conductive sheet can be the same as the preferred range of the particulate filler usage per 100 parts by mass of resin in the mixing process described above in the section ``Method for manufacturing thermal conductive sheet.''
In addition, the preferred range of the content of the fibrous carbon material per 100 parts by mass of resin in the thermal conductive sheet can be the same as the preferred range of the content of the fibrous carbon material in the dispersion per 100 parts by mass of resin used in the mixing process described above in the section ``Method for manufacturing a thermal conductive sheet.''
Furthermore, the preferred range of the mass ratio of the particulate filler to the fibrous carbon material in the thermal conductive sheet (particulate filler/fibrous carbon material) can be the same as the preferred range of the mass ratio of the amount of particulate filler used in the mixing process described above in the section "Method for manufacturing a thermal conductive sheet" to the content of the fibrous carbon material in the dispersion liquid (particulate filler/fibrous carbon material).

The thermal conductive sheet of the present invention may further contain a dispersant. As the dispersant, for example, the dispersant contained in the dispersion liquid described above in the section "Method of manufacturing a thermal conductive sheet" can be used.
In addition, the preferred range of the dispersant content per 100 parts by mass of resin in the thermal conductive sheet can be the same as the preferred range of the dispersant content in the dispersion per 100 parts by mass of resin used in the mixing process described above in the section ``Method of manufacturing thermal conductive sheet.''
In addition, the preferred range of the mass ratio of the dispersant to the fibrous carbon material in the thermal conductive sheet (dispersant/fibrous carbon material) can be the same as the preferred range of the mass ratio of the dispersant to the fibrous carbon material (dispersant/fibrous carbon material) in the dispersion liquid used in the mixing process described above in the section ``Method for manufacturing a thermal conductive sheet.''
The content of the dispersant in the thermally conductive sheet can be measured by extraction utilizing the difference in solubility, or by thermogravimetry (TGA measurement) utilizing the difference in combustion temperature.

The thermal conductive sheet of the present invention may further contain components (other components) other than the above-mentioned resin, particulate filler, fibrous carbon material, and dispersant. Examples of other components that may be contained in the thermal conductive sheet include other components that may be mixed in the mixing step described above in the section "Method for manufacturing a thermal conductive sheet."
The contents of other components in the thermally conductive sheet can be appropriately adjusted within the range in which the desired effects of the present invention can be obtained.

<Thermal Conductivity>
The thermal conductivity of the thermal conductive sheet in the thickness direction must be 12 W/m·K or more, preferably 13 W/m·K or more, and more preferably 15 W/m·K or more. If the thermal conductivity of the thermal conductive sheet in the thickness direction is less than 12 W/m·K, the thermal conductive sheet cannot exhibit sufficient thermal conductivity in the thickness direction. On the other hand, if the thermal conductivity of the thermal conductive sheet in the thickness direction is 12 W/m·K or more, the thermal conductive sheet can exhibit sufficient thermal conductivity in the thickness direction.
The upper limit of the thermal conductivity value in the thickness direction of the thermally conductive sheet is not particularly limited, but is, for example, 45 W/m·K or less.
The thermal conductivity of the thermal conductive sheet in the thickness direction can be adjusted by the types and proportions of materials and components (resin, particulate filler, fibrous carbon material, dispersant, etc.) contained in the thermal conductive sheet, as well as the manufacturing method and manufacturing conditions of the thermal conductive sheet.

<Compression ratio>
The thickness of the thermally conductive sheet when pressed in the thickness direction at 0.9 MPa is T0.9, and the thickness of the thermally conductive sheet when pressed in the thickness direction at 0.1 MPa is _T0.1 , and the thickness of the thermally conductive sheet when pressed in the thickness direction at 0.1 MPa is _T0.9 , the following formula (1):
C = 100 × {1 - (T _0.9 /T _0.1 )} [%] (1)
The compression ratio C calculated by the above formula must be 10% or less, preferably 9% or less, and more preferably 7% or less. If the compression ratio C of the thermal conductive sheet exceeds 10%, the thermal conductive sheet becomes easily torn during use. On the other hand, if the compression ratio C of the thermal conductive sheet is 10% or less, the thermal conductive sheet becomes less likely to tear during use.
In addition, the lower limit of the compressibility C of the thermal conductive sheet is not particularly limited, but is preferably 3% or more, and more preferably 5% or more. If the compressibility C of the thermal conductive sheet is equal to or higher than the lower limit, the thermal conductive sheet can be well adhered to the adherend (such as a heat sink and a heat generator), thereby reducing the thermal resistance of the thermal conductive sheet.
The compression ratio C of the thermal conductive sheet can be adjusted by the types and proportions of materials and components (resin, particulate filler, fibrous carbon material, dispersant, etc.) contained in the thermal conductive sheet, as well as the manufacturing method and manufacturing conditions of the thermal conductive sheet (e.g., the dispersant coverage rate of the fibrous carbon material in the dispersion liquid used).

<Thermal resistance>
The thermal resistance of the thermally conductive sheet when pressed in the thickness direction is not particularly limited, but for example, the thermal resistance of the thermally conductive sheet when pressed in the thickness direction at 0.1 MPa is preferably 0.25° C./W or less, more preferably 0.20° C./W or less, and even more preferably 0.15° C./W or less. If the thermal resistance of the thermally conductive sheet when pressed in the thickness direction at 0.1 MPa is equal to or less than the above-mentioned predetermined value, the thermal conductivity of the thermally conductive sheet in the thickness direction can be increased.
The thermal resistance of the thermally conductive sheet when pressed in the thickness direction at 0.5 MPa is preferably 0.15° C./W or less, more preferably 0.12° C./W or less, and even more preferably 0.10° C./W or less. If the thermal resistance of the thermally conductive sheet when pressed in the thickness direction at 0.5 MPa is equal to or less than the above-mentioned predetermined value, the thermal conductivity of the thermally conductive sheet in the thickness direction can be increased.
Furthermore, the thermal resistance of the thermally conductive sheet when pressed in the thickness direction at 0.9 MPa is preferably 0.15° C./W or less, more preferably 0.12° C./W or less, and even more preferably 0.10° C./W or less. If the thermal resistance of the thermally conductive sheet when pressed in the thickness direction at 0.9 MPa is equal to or less than the above-mentioned predetermined value, the thermal conductivity of the thermally conductive sheet in the thickness direction can be increased.
The thermal resistance of the thermally conductive sheet when pressed in the thickness direction can be measured by the method described in the examples of this specification.

<Thickness>
The thickness of the thermal conductive sheet of the present invention is not particularly limited, but is preferably 200 μm or less, more preferably 150 μm or less, even more preferably 100 μm or less, preferably 50 μm or more, more preferably 60 μm or more, and more preferably 70 μm or more. If the thickness of the thermal conductive sheet is equal to or less than the upper limit, the thermal conductivity of the thermal conductive sheet in the thickness direction can be increased. On the other hand, if the thickness of the thermal conductive sheet is equal to or more than the lower limit, the thermal conductive sheet does not become too thin, so that the flame retardancy, strength, and handleability of the thermal conductive sheet can be sufficiently high.

The present invention will be specifically described below based on examples, but the present invention is not limited to these examples. In the following description, "%" and "parts" expressing amounts are based on mass unless otherwise specified.
In the production examples, examples, and comparative examples, the dispersant coverage of CNT (fibrous carbon material) in the dispersion, the tensile strength and breaking elongation of the primary sheet, the Asker C hardness of the laminate, and the thermal resistance, thickness, compressibility, thermal conductivity, and resistance to tearing during use of the thermally conductive sheet were each measured or evaluated by the following methods.

<CNT Dispersant Coverage Rate>
An arbitrary amount of CNT was taken out from the CNT dispersion liquid produced in each production example by filtration and wrapped in filter paper. The edge of the filter paper was folded so that the CNT would not come out of the filter paper, and the periphery was further sealed with a metal clip. The package thus obtained was immersed in an excess amount of solvent (methyl ethyl ketone) for 12 hours. This dissolved and removed the dispersant that did not interact with the CNT.
Thereafter, the package was removed from the solvent and vacuum dried to isolate the CNTs. When removing the package, the CNTs were appropriately washed with the same solvent as above.
The CNTs isolated in this manner were subjected to thermogravimetry (TGA measurement) in an air atmosphere at a temperature range of 30 to 600° C. at a heating rate of 10° C./min. In this case, the amount of decomposed material that had been decomposed by the time the temperature was raised to 500° C. was defined as A mass %, and the amount of undecomposed material that was not decomposed even when the temperature was raised to 500° C. was defined as B mass %, and the dispersant coverage of the CNTs in the CNT dispersion was calculated by the following formula.
Dispersant coverage (mass%) = 100 x A/B
The isolated CNT described above is CNT coated with a dispersant, and the amount of decomposed material (A mass%) that decomposed before the temperature was raised to 500°C represents the amount of dispersant that had coated the CNT, and the amount of undecomposed material that did not decompose even when heated to 500°C represents the amount of CNT that did not have any dispersant attached (B mass%).

<Tensile strength and elongation at break>
The primary sheets produced in each of the Examples and Comparative Examples were punched out with a dumbbell No. 2 in accordance with JIS K6251 to prepare test pieces. Using a tensile tester (manufactured by Shimadzu Corporation, product name "AG-IS20kN"), the test pieces were pinched at points 1 cm from both ends and pulled at a temperature of 23°C in a direction perpendicular to the normal line extending from the surface of the test piece at a pulling speed of 500 mm/min to measure the breaking strength (tensile strength) and breaking elongation.

<Asker C hardness of laminate>
The Asker C hardness of the laminates produced in each of the Examples and Comparative Examples was measured in accordance with the Asker C method of the Society of Rubber Industry, Japan (SRIS) using a hardness tester (manufactured by Kobunshi Keiki Co., Ltd., product name "ASKER CL-150LJ") at temperatures of 25°C and 70°C. Specifically, the obtained laminates were left to stand in a thermostatic chamber maintained at a temperature of 25°C or 70°C for 48 hours or more to prepare test specimens. Next, a hardness tester was placed so that the needle tip was 2 cm away from the laminate surface, and a damper was lowered to cause the laminate and the damper to collide. The Asker C hardness of the laminate 60 seconds after the collision was measured twice using a hardness tester (manufactured by Kobunshi Keiki Co., Ltd., product name "ASKER CL-150LJ"), and the average value of the measurement results was used.

<Thermal resistance, thickness and compressibility>
The thermal resistance and thickness of the thermally conductive sheets manufactured in each Example and Comparative Example when pressed in the thickness direction were measured using a thermal resistance tester (manufactured by Hitachi Technology & Services Co., Ltd., product name "Resin Material Thermal Resistance Measuring Device"). Here, the thermally conductive sheets cut into approximately 1 cm squares were used as samples, and the thermal resistance (°C/W) and thickness of the thermally conductive sheets were measured when pressures of 0.1 MPa, 0.5 MPa, and 0.9 MPa were applied at a sample temperature of 50°C. The smaller the thermal resistance value, the better the thermal conductivity of the thermally conductive sheet, and for example, the better the heat dissipation characteristics when interposed between a heat generating body and a heat sink.
In addition, the thickness of the thermally conductive sheet when pressed in the thickness direction at 0.9 MPa is defined as T _0.9 , and the thickness of the thermally conductive sheet when pressed in the thickness direction at 0.1 MPa is defined as T _0.1 , and the thickness of the thermally conductive sheet when pressed in the thickness direction at 0.1 MPa is defined as T 0.9 .
C = 100 × [1 - (T _0.9 /T _0.1 )] [%] ... (1)
The compressibility (%) of the thermal conductive sheet was calculated by the above formula.

<Thermal Conductivity>
For the thermal conductive sheets produced in each of the Examples and Comparative Examples, the thermal diffusivity α (m ² /s) in the thickness direction, the specific heat at constant pressure Cp (J/g·K) and the specific gravity ρ (g/m ³ ) were measured by the following methods.
[Thermal diffusivity α]
The measurements were made using a thermal diffusion/thermal conductivity measuring device (manufactured by Ai-Phase Corporation, product name "Ai-Phase Mobile 1u") in accordance with the provisions of ISO 22007-3.
[Constant pressure specific heat Cp]
The specific heat was measured at 25° C. under a temperature increase rate of 10° C./min using a differential scanning calorimeter (manufactured by Rigaku, product name "DSC8230").
[Specific gravity ρ (density)]
The measurement was performed using an automatic specific gravity meter (manufactured by Toyo Seiki Co., Ltd., product name "DENSIMETER-H").
The obtained measured values are then used to calculate the following formula (I):
λ=α×Cp×ρ (I)
The thermal conductivity λ (W/m·K) in the thickness direction of the thermally conductive sheet at a temperature of 25° C. was determined by the above method.

<Heat conductive sheet is difficult to tear when in use>
The thermally conductive sheets produced in each of the Examples and Comparative Examples were sized to 10 mm x 10 mm and placed on a first metal plate (heating element) heated to 120°C.
A smooth second metal plate (heat sink) sized to 12 mm x 12 mm was placed on top of the thermally conductive sheet so that its center overlapped with the thermally conductive sheet. A cyclic test was performed in which a pressure of 250 N was applied from above for 10 seconds and then released for 10 seconds, and this was repeated 50 times.
The thermal conductive sheet was observed from directly above after the cycle test to see how much it protruded from the second metal plate, and the thermal conductive sheet was evaluated for its resistance to tearing during use according to the following criteria. When the thermal conductive sheet was sandwiched between a heat generating body and a heat dissipating body and heated, and pressure and decompression cycles were repeated, the thermal conductive sheet, which is prone to tearing, broke at the part where a particularly strong pressure was applied, and protruded from between the heat generating body and the heat dissipating body. Therefore, the smaller the protruding part of the thermal conductive sheet, the less likely it is to tear during use.
A: The thermally conductive sheet protrudes, with at least one side being 0 mm or more and less than 1 mm.
B: The thermally conductive sheet protrudes, with at least one side being 1 mm or more and less than 3 mm.
C: The thermal conductive sheet protrudes, with at least one side being 3 mm or more and less than 6 mm.

(Production Example 1)
Single-walled CNT (manufactured by Zeon Nanotechnology Inc., product name "ZEONANANO SG101", SGCNT, average diameter: 3.5 nm, average length: 400 μm, BET specific surface area: 1050 ^m2 /g) as a fibrous carbon material was added to a methyl ethyl ketone solvent so that the concentration was 0.2%, and 1 equivalent (same amount) of a basic group-containing polymer (product name "AJISPER PB821", manufactured by Ajinomoto Fine-Techno Co., Ltd., amine value: 10 mg KOH/g, acid value: 17 mg KOH/g) was further added as a dispersant relative to the amount of CNT added, and the mixture was stirred with a magnetic stirrer for 1 hour to obtain a crude dispersion.
Next, the above-mentioned crude dispersion was filled into a multistage step-down high-pressure homogenizer (manufactured by BERYU SYSTEM PRO, manufactured by BIRYU Co., Ltd.) having a multistage pressure control device (multistage step-down device) connected to a high-pressure dispersion processing unit (jet mill) having a capillary flow path with a diameter of 170 μm, and a pressure of 100 MPa was intermittently and instantaneously applied to the crude dispersion at a temperature of 25° C. and sent to the capillary flow path, which constituted one cycle. This was repeated three times.
Next, the previous capillary flow passage was replaced with a capillary flow passage having a diameter of 90 μm, and the same dispersion treatment was repeated for one cycle. This cycle was repeated three times to obtain a CNT dispersion liquid (1).
When measured according to the above-mentioned method, the coverage of the CNTs (fibrous carbon material) with the dispersant in the obtained CNT dispersion (1) was 72%.

(Production Example 2)
A CNT dispersion (2) was obtained in the same manner as in Production Example 1, except that the amount of the basic group-containing polymer added as a dispersant was changed from 1 equivalent (the same amount) to 5 equivalents relative to the amount of CNT added.
When measured according to the above-mentioned method, the coverage of the CNTs (fibrous carbon material) with the dispersant in the obtained CNT dispersion (2) was 138%.

(Production Example 3)
A CNT dispersion liquid (3) was obtained in the same manner as in Production Example 1, except that only three cycles of the dispersion treatment using the capillary flow path portion having a diameter of 170 μm were performed, and three cycles of the dispersion treatment using the capillary flow path portion having a diameter of 90 μm were not performed.
When measured according to the above-mentioned method, the coverage of the CNTs (fibrous carbon material) with the dispersant in the obtained CNT dispersion (3) was 37%.

(Production Example 4)
A CNT dispersion (4) was obtained in the same manner as in Production Example 1, except that the amount of the basic group-containing polymer added as a dispersant was changed from 1 equivalent (the same amount) to 8 equivalents relative to the amount of CNT added.
When measured according to the above-mentioned method, the coverage of the CNTs (fibrous carbon material) with the dispersant in the obtained CNT dispersion (4) was 152%.

(Production Example 5)
A CNT dispersion liquid (5) was obtained in the same manner as in Production Example 1, except that no basic group-containing polymer was added as a dispersant, and only three cycles of dispersion treatment using a capillary flow channel portion having a diameter of 170 μm were performed, and three cycles of dispersion treatment using a capillary flow channel portion having a diameter of 90 μm were not performed.
When measured according to the above-mentioned method, the coverage of the CNTs (fibrous carbon material) with the dispersant in the obtained CNT dispersion (5) was 0%.

(Production Example 6)
A CNT dispersion (6) was obtained in the same manner as in Production Example 1, except that the fibrous carbon material was changed from SGCNT (single-walled CNT) to multi-walled CNT (manufactured by Nanocyl S.A., product name "Nanosil NC7000", average diameter: 9.5 nm, average length: 1.5 μm, BET specific surface area: 216 ^m2 /g) and the amount of the basic group-containing polymer added as a dispersant was changed from 1 equivalent (the same amount) to 5 equivalents relative to the amount of CNT added.
When measured according to the above-mentioned method, the coverage of the CNTs (fibrous carbon material) with the dispersant in the obtained CNT dispersion (6) was 28%.

(Production Example 7)
A CNT dispersion (7) was obtained in the same manner as in Production Example 1, except that the amount of the basic group-containing polymer added as a dispersant was changed from 1 equivalent (the same amount) to 10 equivalents relative to the amount of CNT added.
When measured according to the above-mentioned method, the coverage of the CNTs (fibrous carbon material) with the dispersant in the obtained CNT dispersion (7) was 170%.

Example 1
<Mixing step>
100 parts of the CNT dispersion (1) produced in Production Example 1 (0.2 parts in terms of CNT), 50 parts of expanded graphite (manufactured by Ito Graphite Industries Co., Ltd., trade name "EC-300", volume average particle size: 50 μm) as a particulate filler, 70 parts of a thermoplastic fluororesin (manufactured by Daikin Industries, Ltd., trade name "Daiel G-101") that is liquid at room temperature as a resin, and 30 parts of a thermoplastic fluororesin (manufactured by 3M Japan Ltd., trade name "Dyneon FC2211") that is solid at room temperature were heated to 80 ° C. in a Hobart mixer (manufactured by Kodaira Manufacturing Co., Ltd., trade name "ACM-5LVT type", capacity: 5 L), and mixed for 30 minutes while removing the solvent (methyl ethyl ketone) contained in the CNT dispersion. The resulting mixture was put into a Wonder Crush Mill (manufactured by Osaka Chemical Co., Ltd., trade name "D3V-10") and crushed for 1 minute.

<Primary sheet molding process>
50 g of the crushed mixture was sandwiched between 50 μm thick polyethylene terephthalate (PET) films (protective films) that had been sandblasted, and rolled (primary pressurization) was performed under the conditions of a roll gap of 550 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 primary sheet with a thickness of 0.5 mm. The tensile strength and breaking elongation of the obtained primary sheet were measured according to the above-mentioned method. The results are shown in Table 1.

<Laminate Forming Process>
The obtained primary sheet was cut into a size of 150 mm length x 150 mm width x 0.5 mm thickness, and 120 sheets were stacked in the thickness direction of the primary sheet. The stacked sheets were then pressed (secondary pressurization) in the stacking direction at a temperature of 120°C and a pressure of 0.1 MPa for 3 minutes to obtain a laminate (block body) with a height of about 60 mm. The Asker C hardness of the obtained laminate was then measured. The results are shown in Table 1.

<Slicing process>
Thereafter, the entire upper surface of the obtained laminate was pressed with a metal plate, leaving a length required for slicing, and a pressure of 0.1 MPa was applied in the lamination direction (i.e., from above) to fix the laminate. Note that the side and back of the laminate were not fixed. At this time, the temperature of the laminate was 25°C.
Next, a blade 10 (double-edged, blade angle 2θ: 20°, maximum thickness of blade: 3.5 mm, material: super steel, Rockwell hardness: 91.5, silicon processing of blade surface: none, total length: 200 mm) having the shape shown in FIG. 1 was attached to the press part of a servo press (manufactured by Electric Discharge Precision Machining Research Institute), and sliced in the stacking direction of the laminate 20 (in other words, in the direction that coincides with the normal line of the main surface of the stacked primary sheets) under the conditions of a slice width of 100 μm and a slice speed of 200 mm/sec to obtain a thermally conductive sheet 30 having a main surface of 150 mm length x 80 mm width. Note that the orientation of the blade during slicing was such that the angle α shown in FIG. 1 was 10°, and the extension direction of the blade surface 11 was parallel to the slice surface 21 of the laminate 20.
The thermal resistance, thickness, compressibility, thermal conductivity, and tear resistance during use of the obtained thermally conductive sheet were measured or evaluated according to the methods described above. The results are shown in Table 1.

Example 2
In the mixing step of Example 1, a primary sheet, a laminate, and a thermally conductive sheet were produced in the same manner as in Example 1, except that a CNT dispersion (2) having a dispersant coverage rate of 138% was used instead of a CNT dispersion (1) having a dispersant coverage rate of 72% in the mixing step of Example 1. Various measurements and evaluations were performed. The results are shown in Table 1.

Example 3
In the mixing step of Example 1, a primary sheet, a laminate, and a thermally conductive sheet were produced in the same manner as in Example 1, except that a CNT dispersion (3) having a dispersant coverage rate of 37% was used instead of a CNT dispersion (1) having a dispersant coverage rate of 72% in the mixing step of Example 1. The results are shown in Table 1.

Example 4
In the mixing step of Example 1, a primary sheet, a laminate, and a thermally conductive sheet were produced in the same manner as in Example 1, except that a CNT dispersion (4) having a dispersant coverage rate of 152% was used instead of a CNT dispersion (1) having a dispersant coverage rate of 72% in the mixing step of Example 1. The results are shown in Table 1.

Example 5
A primary sheet, a laminate, and a thermally conductive sheet were produced in the same manner as in Example 1, except that the amount of CNT dispersion (1) used in the mixing step of Example 1 was changed from 100 parts by mass to 250 parts by mass, and various measurements and evaluations were performed. The results are shown in Table 1.

(Comparative Example 1)
In the mixing step of Example 1, a primary sheet, a laminate, and a thermally conductive sheet were produced in the same manner as in Example 1, except that a CNT dispersion (5) having a dispersant coverage rate of 0% was used instead of a CNT dispersion (1) having a dispersant coverage rate of 72%. Various measurements and evaluations were performed. The results are shown in Table 1.

(Comparative Example 2)
In the mixing step of Example 1, a primary sheet, a laminate, and a thermally conductive sheet were produced in the same manner as in Example 1, except that a CNT dispersion (6) having a dispersant coverage rate of 28% was used instead of a CNT dispersion (1) having a dispersant coverage rate of 72% in the mixing step of Example 1. Various measurements and evaluations were performed. The results are shown in Table 1.

(Comparative Example 3)
A primary sheet, a laminate, and a thermally conductive sheet were produced in the same manner as in Example 1, except that the CNT dispersion liquid (1) was not used in the mixing step of Example 1, and various measurements and evaluations were performed. The results are shown in Table 1.

(Comparative Example 4)
In the mixing step of Example 1, a primary sheet, a laminate, and a thermally conductive sheet were produced in the same manner as in Example 1, except that a CNT dispersion (7) having a dispersant coverage rate of 170% was used instead of a CNT dispersion (1) having a dispersant coverage rate of 72%. Various measurements and evaluations were performed. The results are shown in Table 1.

From Table 1, it can be seen that the thermal conductive sheet manufacturing method of Examples 1 to 5, which includes a step of mixing a dispersion liquid in which the dispersant coverage rate of the fibrous carbon material (CNT) is within a predetermined range, a resin, and a particulate filler, can produce a thermal conductive sheet that is difficult to tear during use.
On the other hand, it is found that the thermal conductive sheet manufactured by the thermal conductive sheet manufacturing method of Comparative Example 1 using a dispersion liquid that does not contain a dispersant (i.e., the dispersant coverage rate of the fibrous carbon material (CNT) is 0 mass%) is easily torn during use.
It was also found that the thermal conductive sheet manufactured by the thermal conductive sheet manufacturing method of Comparative Example 2, which used a dispersion liquid in which the dispersant coverage rate of the fibrous carbon material (CNT) did not fall within the specified range, was also prone to tearing during use.
Furthermore, it was found that the thermal conductive sheet manufactured by the thermal conductive sheet manufacturing method of Comparative Example 3, in which no dispersion liquid containing fibrous carbon material (CNT) and a dispersant was used, also easily tore during use.
It was also found that the thermal conductive sheet manufactured by the thermal conductive sheet manufacturing method of Comparative Example 4, which used a dispersion in which the dispersant coverage rate of the fibrous carbon material (CNT) exceeded the specified range, was also prone to tearing during use.

The present invention provides a thermally conductive sheet that is less likely to tear during use.

10 Blade 11 Blade surface 20 Laminate 21 Slicing surface 30 Heat conductive sheet

Claims (8)

A method for producing a thermally conductive sheet containing a resin, a particulate filler, and a fibrous carbon material, comprising:
mixing a dispersion liquid containing the fibrous carbon material and a dispersant, the resin, and the particulate filler;
a dispersant coverage rate of the fibrous carbon material in the dispersion liquid is 30% by mass or more and 160% by mass or less,
the content of the fibrous carbon material in the dispersion is 0.01 parts by mass or more and 3.00 parts by mass or less with respect to 100 parts by mass of the resin used,
A method for producing a thermal conductive sheet , wherein the mass ratio (particulate filler/fibrous carbon material) of the amount of the particulate filler used to the content of the fibrous carbon material in the dispersion is 50 or more and 20,000 or less . The method for producing a thermal conductive sheet according to claim 1 , wherein the dispersant has an amine value. The method for producing a thermal conductive sheet according to claim 1 , wherein a mass ratio of the dispersant to the fibrous carbon material in the dispersion (dispersant/fibrous carbon material) is 0.5 or more and 10 or less. 4. The method for producing a thermal conductive sheet according to claim 1 , wherein the fibrous carbon material has a BET specific surface area of 400 m ² /g or more. A thermally conductive sheet comprising a resin, a particulate filler, and a fibrous carbon material,
The thermal conductivity of the thermal conductive sheet in the thickness direction is 12 W/m K or more,
The thickness of the thermally conductive sheet when pressed in the thickness direction at 0.9 MPa is _T0.9 , and the thickness of the thermally conductive sheet when pressed in the thickness direction at 0.1 MPa is T0.1, and the thickness of the thermally conductive sheet when pressed in the thickness direction at _{0.1 MPa} is T0.1.
C = 100 × {1 - (T _0.9 / T _0.1 )} [%] (1)
The compression ratio C calculated by is 10% or less,
The content of the fibrous carbon material is 0.01 parts by mass or more and 3.00 parts by mass or less with respect to 100 parts by mass of the resin,
A thermally conductive sheet , wherein the mass ratio of the particulate filler to the fibrous carbon material (particulate filler/fibrous carbon material) is 50 or more and 20,000 or less . Further comprising a dispersant,
The thermal conductive sheet according to claim 5 , wherein the dispersant has an amine value. Further comprising a dispersant,
The thermal conductive sheet according to claim 5 , wherein a mass ratio of the dispersant to the fibrous carbon material (dispersant/fibrous carbon material) is 0.5 or more and 10 or less. The thermal conductive sheet according to any one of claims 5 to 7 , wherein the fibrous carbon material has a BET specific surface area of 400 m ² /g or more.

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