JP2021075661A - Interface heat conductive sheet - Google Patents

Abstract

To provide an interfacial heat conductive sheet composed of a polymer material as a base material exhibiting high interfacial heat conductivity, and capable of producing with ease.SOLUTION: The interfacial heat conductive sheet includes a porous polymer sheet, and a carbon particle filled in pores of the porous polymer sheet. As the carbon particle, at least one of a flaky graphite, and a fibrous graphite is preferable. When the average pore diameter of the porous polymer sheet is D1, and the average value of maximum diameters of carbon particles is D2 it is preferable to be D1≥D2×2 . The interfacial heat conductive sheet ca be produced by impregnating the porous polymer sheet with a dispersion of carbon particles.SELECTED DRAWING: None

Description

The present invention relates to an intersurface heat conductive sheet that is suitably used for various electronic devices, lighting devices, and the like.

In various electronic devices or lighting devices, if the device is exposed to high temperature for a long time due to the heat generated by the elements used, it will lead to malfunction or failure. Therefore, a heat conductive member is widely used to prevent the temperature of the device from rising. The heat conductive member has the effect of preventing the temperature rise of the device by diffusing the heat generated by the element or transmitting it to the heat radiating member for discharging it to the outside of the system such as the atmosphere.

When metal or ceramics is used as the heat conductive member, problems such as difficulty in weight reduction, poor workability, and low flexibility may occur. In many cases, these problems can be solved by using a polymer material made of resin or rubber as a base material. Therefore, for example, one in which ceramic fine particles are dispersed in a resin is used.

As the heat conductive member made of a polymer material, a sheet-shaped polymer material is used as a substrate, and heat is transferred in a direction perpendicular to the main surface of the polymer sheet (interplanetary direction, that is, sheet thickness direction). There is an inter-face heat conduction sheet. Specific examples thereof include a thermal interface material (TIM) that fills a minute gap between a heat source such as an electronic circuit and a heat sink so that heat can flow smoothly between the two. TIM is described in, for example, Patent Document 1. Since the TIM is required to have flexibility to fill these gaps, a TIM mainly made of a polymer material is used.

In addition, the polymer material is a printed circuit board on which electronic components are mounted, and the surface of the printed circuit board is used to transmit the heat generated by the electronic components to the heat radiating member provided on the surface opposite to the mounting surface of the printed circuit board. A structure that transfers heat in the inter-direction may be used (for example, Patent Document 2). In this case, a fine through hole is provided in the lower part of the electronic component of the printed circuit board, and a metal member such as copper is inserted into the through hole to obtain thermal conductivity in the interplane direction.

Special Table 2010-538111 Japanese Unexamined Patent Publication No. 2014-170835

The problem with the heat conductive sheet using a polymer material as the base material is that high thermal conductivity cannot be obtained. For example, the thermal conductivity of silicone rubber, which is often used as a TIM, is as small as about 0.2 to 5 W / m · K, and the thermal conductivity is not sufficient. Therefore, a silicone rubber having a higher thermal conductivity is required. Further, a structure in which a metal member is inserted into a through hole of a polymer material has a drawback that it is difficult to manufacture because high precision is required for processing and insertion process.

An object of the present invention is to provide a face-to-face heat conduction sheet using a polymer material as a base material, which exhibits high face-to-face heat conductivity and can be easily manufactured. And.

As a result of repeated studies to solve the above problems, the present inventor has found that the above problems can be solved by using a composite material in which the pores of the porous polymer sheet are filled with carbon particles.
That is, the gist of the present invention is as follows.

[1] An interplanetary heat conductive sheet having a porous polymer sheet and carbon particles filled in the pores of the porous polymer sheet.

[2] The interplane heat conduction sheet according to [1], wherein the carbon particles are at least one of flaky graphite and fibrous graphite.

[3] The face-to-face heat conduction sheet according to [2], wherein the carbon particles are flaky graphite.

[4] The face-to-face heat conductive sheet according to [3], wherein the flaky graphite has a thickness of 100 nm or less.

[5] The surface according to any one of [1] to [4], where D1 ≧ D2 × 2 when the average pore diameter of the porous polymer sheet is D1 and the average value of the maximum diameters of the carbon particles is D2. Interheat conduction sheet.

[6] The surface according to any one of [1] to [5], where D1 ≦ D2 × 3000, where D1 is the average pore diameter of the porous polymer sheet and D2 is the average value of the maximum diameters of the carbon particles. Interheat conduction sheet.

[7] The face-to-face heat conductive sheet according to any one of [1] to [6], wherein the pores of the porous polymer sheet are formed perpendicular to the main surface of the porous polymer sheet.

[8] The method for producing an interplanar heat conductive sheet according to any one of [1] to [7], which comprises a step of impregnating a porous polymer sheet with a dispersion of carbon particles. Production method.

The face-to-face heat conductive sheet of the present invention, which is made of a composite material in which the pores of the porous polymer sheet are filled with carbon particles, is derived from carbon particles and has high heat conductivity in the face-to-face direction, and is a porous base material. Since it can have both the flexible and lightweight properties of the polymer sheet, it is suitable for various applications such as TIM.
Further, since the face-to-face heat conduction sheet of the present invention can be produced only by filling the pores of the porous polymer sheet with carbon particles, the production thereof is very easy.

Since the heat conduction sheet of the present invention mainly allows heat to flow through the carbon particles filled in the pores of the porous polymer sheet, the density, size, etc. of the pores of the porous polymer sheet filled with the carbon particles can be determined. By changing it, the thermal conductivity can be adjusted arbitrarily.
Further, by changing the distribution of pores in the porous polymer sheet, it is possible to locally provide portions having different thermal conductivity. According to the face-to-face heat-conducting sheet having portions having locally different thermal conductivity, for example, by arranging the face-to-face heat-conducting sheet on a heat source having a uniform temperature distribution in the plane direction. It is possible to arbitrarily form a non-uniform temperature distribution. On the contrary, by arranging the face-to-face heat conduction sheet on a heat source having a non-uniform temperature distribution, the temperature distribution can be made uniform.

Since the porous polymer sheet containing carbon particles in the present invention also has electromagnetic wave shielding performance and sound absorbing performance, the surface heat conductive sheet of the present invention can also have performances such as electromagnetic wave shielding and sound absorption. ..

Embodiments of the present invention will be described in detail below.

The face-to-face heat conductive sheet of the present invention is characterized by having a porous polymer sheet and carbon particles filled in the pores of the porous polymer sheet.

[Perforated polymer sheet]
The porous polymer sheet is a porous sheet made of a polymer material.
Examples of the polymer material constituting the porous polymer sheet used in the present invention include resin and rubber.
Since the porous polymer sheet is used in contact with or close to a heat source, the polymer material constituting the porous polymer sheet preferably has a heat resistant temperature of 100 ° C. or higher. A more preferable heat resistant temperature of the polymer material is 150 ° C. or higher, and more preferably 200 ° C. or higher.
The heat resistant temperature of a polymer material is defined by Tg (glass transition point) in the case of resin, and is defined by the heat resistant limit temperature in the case of rubber.

Preferred resins as a constituent material of the porous polymer sheet used in the present invention include, for example, polyesters such as nylon, fluororesin, silicone resin, polyethylene terephthalate (PET), and polyethylene naphthalate (PEN), polyimide, epoxy resin, and phenol resin. Can be mentioned.
Further, preferred rubbers include natural rubber, styrene-butadiene rubber, acrylic rubber, silicone rubber, fluororubber and the like. Of these rubbers, silicone rubber and fluororubber are particularly preferable materials from the viewpoint of heat resistance and flexibility.
Only one kind of these resins and rubbers may be used, or two or more kinds thereof may be mixed and used.
Reinforcing materials such as glass fibers, other additives, and the like may be blended with these polymer materials constituting the porous polymer sheet.

The porous polymer sheet used in the present invention has a porosity of preferably 10% or more, more preferably 20% or more, still more preferably 30% or more in order to contain a sufficient amount of carbon particles. .. On the other hand, in order to secure the mechanical strength, the porosity of the porous polymer sheet is preferably 98% or less, more preferably 95% or less.

Here, the porosity of the porous polymer sheet is as follows from the mass M (g) of the porous polymer sheet, the apparent volume V (cm ³ ), and the specific gravity D (g / cm ³ ) of the constituent material of the porous polymer sheet. Calculated by the formula.
Porosity (%) = [1- {M ÷ (V × D)}] × 100

Further, from the viewpoint of securing the pore size of the porous polymer sheet to some extent and facilitating filling with carbon particles, the average value D1 of the pore size of the porous polymer sheet is preferably 0.05 mm or more, preferably 0.08 mm or more. It is more preferably 0.12 mm or more, particularly preferably 0.12 mm or more, and most preferably 0.14 mm or more. On the other hand, from the viewpoint of ensuring the strength of the porous polymer sheet, and if D1 is too large, the carbon particles cannot be retained in the pores of the porous polymer sheet, and defects occur due to the carbon particles peeling off. Therefore, D1 Is preferably 5 mm or less, more preferably 4 mm or less, and particularly preferably 3 mm or less.
Here, the average value D1 of the pore diameters of the porous polymer sheet is 20 pore diameters measured for the pores observed when the porous polymer sheet is viewed in a plan view with an optical microscope or a scanning electron microscope (SEM). Arithmetic mean.

It is preferable that at least a part of the pores of the porous polymer sheet is perpendicular to the main surface of the sheet. This is because when the carbon particles are brought into close contact with the wall surface of the pores in parallel by an intermolecular force, the direction of the basal surface of the carbon particles faces the interplanetary direction, and heat can be easily transferred in this direction.

Further, in order for the carbon particles filled in the pores of the porous polymer sheet to easily transfer heat in the inter-plane direction, one surface (one sheet surface) of the main surface of the porous polymer sheet is opposed to the other surface (the other). It is preferable that the holes penetrate or almost penetrate to the sheet surface). Here, "almost penetrates" means that holes are present in 90% or more of the thickness (inter-plane distance) of the porous polymer sheet.

The shape of the holes seen from the upper surface of the porous polymer sheet (the shape of the holes in a plan view) may be circular, or may be another shape such as a quadrangle or a honeycomb.
The porous polymer sheet may have holes in the inter-plane direction of the polymer sheet, or may be a form in which fine polymer wires are bonded. It may also be in the form of a mesh. In the case of a mesh-like porous polymer sheet made of fine polymer wires, the line width (fiber diameter) is preferably 10 to 1000 μm, and the numerical aperture per inch is preferably about 10 to 200 mesh.

When the pores are formed perpendicular to the main surface of the porous polymer sheet and penetrate the pores, the porosity matches the aperture ratio.

The shape and dimensions of the face-to-face heat conductive sheet of the present invention vary depending on the application (applicable object), and are not particularly limited. It is preferable to have. If the intermolecular heat conductive sheet is TIM, the thickness must be sufficient to fill the gap between the heat source and the heat dissipation member, and if it is too thin, the carbon particles in the pores of the porous polymer sheet will be porous. It is preferably 50 μm or more because it cannot be held by the intermolecular force between the polymer sheet and the polymer sheet.
Therefore, the thickness of the porous polymer sheet used in the present invention is preferably 50 μm or more and 5 mm or less so as to obtain an inter-plane heat conductive sheet having such a thickness.

The method for producing such a porous polymer sheet is not particularly limited, but a method in which a foaming agent is put in a polymer material and heated to foam, a method in which fibrous polymer materials are combined to form a mesh, and a high molecular weight material are used. Examples thereof include a method of making holes in a molecular sheet by mechanical cutting, laser, water flow, etching, etc., and a method of forming a porous polymer sheet using a mold having cores and protrusions for forming holes.

[Carbon particles]
As the carbon particles, it is preferable to use at least one of flaky and fibrous graphite. In particular, by using flaky graphite, the carbon particles and the wall surface of the pores of the porous polymer sheet are bonded by an intermolecular force, and the carbon particles can be stably filled even if the pores are through holes. Further, the thermal conductivity can be improved by binding the basal surfaces of the carbon particles by the intermolecular force. Since this intermolecular force becomes stronger as the thickness of the carbon particles becomes thinner, it is preferable to use thin flake graphite in order to obtain a sufficiently strong intermolecular force, and the average value of the thickness is preferably 100 nm or less. 50 nm or less is more preferable, 25 nm or less is particularly preferable, and so-called graphene having a thickness of 10 nm or less is most preferable. Among the graphenes, the average thickness is preferably 8 nm or less, more preferably 6 nm or less, and most preferably 4 nm or less. However, the lower limit of the thickness of flaky graphite is about 0.3 nm due to the atomic size of carbon.

Examples of fibrous graphite include carbon nanotubes. The preferable diameter (fiber diameter) of the fibrous graphite is 10 to 1000 nm, and the diameter is preferably about the same as the thickness of the flaky graphite in order to obtain a strong intermolecular force.

In order for the carbon particles to enter the pores of the above-mentioned porous polymer sheet, it is preferable that the average pore diameter D1 of the porous polymer sheet is sufficiently larger than the average value D2 of the maximum diameters of the carbon particles. It is preferably 2, more preferably D1 ≧ D2 × 3, further preferably D1 ≧ D2 × 5, and particularly preferably D1 ≧ D2 × 10. On the other hand, when the average pore size D1 of the porous polymer sheet is excessively large with respect to the average value D2 of the maximum diameters of the carbon particles, the intermolecular force between the pore wall surface of the porous polymer sheet and the carbon particles is inside the pores. The carbon particles cannot be supported, and the carbon particles may easily come off and cause defects. Therefore, D1 ≦ D2 × 3000 is preferable, D1 ≦ D2 × 2000 is more preferable, D1 ≦ D2 × 1000 is more preferable, and D1 ≦ D2 × 500 is particularly preferable. Most preferably, D1 ≦ D2 × 200.

Further, since the joints between carbon particles cause thermal resistance, the average value D2 of the maximum diameters of the carbon particles is 0. From the viewpoint that it is better to reduce the number of joints between the particles by using large carbon particles. It is preferably 1 μm or more, more preferably 1 μm or more, further preferably 3 μm or more, particularly preferably 5 μm or more, and most preferably 10 μm or more. On the other hand, from the viewpoint of inserting into the pores of the porous polymer sheet, D2 is preferably 500 μm or less, more preferably 200 μm or less, further preferably 100 μm or less, and further preferably 50 μm or less. Is particularly preferable, and 20 μm or less is most preferable.

Here, the maximum diameter of the carbon particles corresponds to the size of the interval of the portion where the interval between the two parallel plates is the largest when the carbon particles are sandwiched between the two parallel plates. For example, in the case of flaky graphite, it refers to the length of the largest diameter portion of the basal surface. In the case of fibrous graphite, it refers to the fiber length. The average value D2 of the maximum diameters of carbon particles is determined as an arithmetic mean value of values measured by observing, for example, 20 or more carbon particles with a scanning electron microscope (SEM) or a scanning probe microscope (SPM).
Similarly, for the average value of the graphene thickness, the thickness of 20 or more graphene particles is determined as the arithmetic mean value of the values measured by observing with a scanning electron microscope (SEM) or a scanning probe microscope (SPM). be able to.

In order to obtain a surface heat conductive sheet having high thermal conductivity, it is preferable that the carbon particles filled in the pores of the porous polymer sheet occupy 50% or more of the void volume of the porous polymer sheet, and more. It is preferably 60% or more, more preferably 70% or more, and particularly preferably 80% or more.

In order to obtain sufficient thermal conductivity, the carbon atoms in the carbon particles are preferably 90 atomic% or more, more preferably 95 to 100 atomic% of the total carbon particles.

[Manufacturing method of intersurface heat conduction sheet]
The method for producing the interplanetary heat conductive sheet of the present invention by filling the pores of the porous polymer sheet with carbon particles is not particularly limited, but the porous polymer sheet is prepared in a dispersion in which carbon particles are dispersed in a dispersion medium. A method of removing the dispersion medium from the porous polymer sheet (cast method, dip coating method, etc.) after impregnating with the dispersion liquid by immersing the particles, and a dispersion liquid in which carbon particles are dispersed in the dispersion medium is used as a porous polymer sheet. (Spin coat, blade coat, bar coat, die coat, etc.) and then the dispersion medium is removed. Alternatively, a porous polymer sheet is placed on a filter (for example, filter paper), a dispersion liquid in which carbon particles are dispersed in a dispersion medium is supplied onto the porous polymer sheet, and vacuum suction is performed from below the filter paper to disperse the particles. A vacuum filtration method for removing the medium may be used. It is also possible to supply the carbon particle dispersion liquid only to the pore portion by a printing method such as an inkjet method.

Water, alcohols, acetone, N-methylpyrrolidone (NMP), etc. are used as the dispersion medium, but water, ethanol, isopropyl alcohol, etc., which are inexpensive, highly safe, and have no risk of dissolving the porous polymer sheet. Alcohols and mixtures thereof are preferred.
The concentration of carbon particles in the dispersion is not particularly limited, but 0.1 to 5% by mass from the viewpoint of efficiently infiltrating the dispersion into the pores of the porous polymer sheet and filling the carbon particles with a high filling rate. It is preferable to set the degree.

A dispersant for assisting dispersion (for example, Pluronic P123 manufactured by BASF) can also be added to the dispersion liquid. A binder for binding carbon particles (for example, carboxymethyl cellulose) can also be added. However, when these organic substances are added, the portion where the organic matter was present becomes a void due to the subsequent removal of the organic matter by heating and firing, and thermal conductivity cannot be obtained in that portion. Therefore, from the viewpoint of thermal conductivity, from the viewpoint of thermal conductivity, It is preferable not to use these dispersants or binders.

The dispersion medium after impregnation with the dispersion liquid may be naturally dried, but a method such as heat drying or vacuum drying is used to remove the dispersion medium in a short time.
After removing the dispersion medium, the porous polymer sheet can be heated at a temperature equal to or lower than the melting point in order to remove organic impurities such as a dispersant. This heating temperature is usually about 100 to 300 ° C.

If the carbon particles remain in close contact with each other other than the pores of the porous polymer sheet, the basal surface of the carbon particles faces the in-plane direction (the direction parallel to the main surface of the sheet), which hinders heat conduction in the interplane direction. .. In order to prevent this, it is preferable to perform a step of filling the porous polymer sheet with carbon particles and then wiping off the carbon particles other than the pores to remove them.

[Contact layer]
When applying the face-to-face heat conduction sheet of the present invention, in order to reduce the thermal resistance at the time of contact between the face-to-face heat conduction sheet and the heat source, the heat radiation member, etc., between the heat source or the heat radiation member and the face heat conduction sheet. A contact layer may be provided. The contact layer preferably has high flexibility and relatively high thermal conductivity in order to reduce the thermal resistance with the adjacent member. The preferable thermal conductivity of the contact layer is 1 W / m · K or more. Further, the contact layer preferably has a tack property. When the heat radiating member comes into contact with an electric member that uses electricity such as an LED or an IC, the contact layer is preferably an insulating one in order to prevent a short circuit of the electric member.

Examples of the material of the contact layer include silicone resin, acrylic resin, EPDM (ethylene propylene diene rubber) and the like. If a conductive material can be used, the contact layer may be a metal thin film such as aluminum, copper, or silver. After filling the porous polymer sheet with carbon particles, the surface of the porous polymer sheet is melted to cover the entire surface to form a contact layer.

Since the contact layer has a lower thermal conductivity than the heat radiating member, if it is too thick, the effect of the heat radiating member will be reduced. The thickness of the contact layer is preferably 1/30 or more and 1/5 or less of the thickness of the heat radiating member.

[Reason why the present invention is effective]
The reason why the interplane heat conductive sheet of the present invention exerts the effect of in-plane heat conductivity is presumed as follows.
That is, the carbon particles adhere to the wall surface of the porous polymer sheet facing the inter-plane direction by intermolecular force, and the carbon particles are laminated in the same direction, so that the basal surface of the carbon particles is mainly in the inter-plane direction. As a result of good flow of heat in the inter-plane direction, high inter-plane thermal conductivity can be obtained.

Hereinafter, the present invention will be described in more detail with reference to examples.

[Example 1]
<Manufacturing of face-to-face heat conduction sheet>
200 mg of graphene powder (maximum diameter average value: 12 μm, average thickness: 2.5 nm) manufactured by STREM CHEMICALS, 60 mL of pure water and 40 mL of isopropyl alcohol as dispersion media are placed in a container and ultrasonically bathed. It was dispersed by applying ultrasonic waves for 10 minutes.
As the porous polymer sheet, a nylon mesh (average pore diameter: 0.45 mm) having 53 mesh (53 openings per inch), a line width of 190 μm, an aperture ratio of 49%, and a thickness of 220 μm was used. This nylon mesh is a combination of nylon wires having a circular cross section in a grid pattern, and the hole surface is perpendicular to the main surface of the sheet at the narrowest portion of the hole (opening).

A PTFE membrane filter having a pore size of 0.2 μm was set on the bottom of the container of the vacuum filtration device, and a nylon mesh of 20 mm × 20 mm was placed on the membrane filter. The graphene dispersion was placed in a container and exhausted with a diaphragm pump from the opposite side of the nylon mesh of the membrane filter to remove the dispersion medium. After the dispersion medium was completely removed, the nylon mesh was taken out. The excess graphene on the nylon mesh was then removed with a cotton swab impregnated with isopropyl alcohol.

As a result, it was possible to obtain an interfaceted heat conductive sheet in which the openings of the nylon mesh were filled with graphene. This face-to-face heat conductive sheet was flexible and could be easily bent by hand.

With respect to this face-to-face heat conduction sheet, the mass ratio of graphene in the face-to-face heat conduction sheet was calculated to be about 43%, which was calculated from the mass difference between the nylon mesh before and after graphene filling. The pores were completely filled with graphene, that is, graphene occupied 100% of the void volume. The density of this face-to-face heat conductive sheet was 0.9 g / cm ³ , which was even lighter than that of nylon 1.1 g / cm ^3.

<Measurement of thermal conductivity>
When the thermal conductivity of the manufactured interplane heat conduction sheet was measured with the Thermowave Analyzer TA3 manufactured by Bethel Co., Ltd., it was 5 W / m · K in the in-plane direction of the sheet and 78 W / m · K in the face-to-face direction. Thermal conductivity was obtained.
Since the thermal conductivity of a flat sheet containing only nylon is 0.2 W / m · K, the thermal conductivity is improved in both the in-plane direction and the inter-plane direction, and in particular, the thermal conductivity in the inter-plane direction is improved. It can be seen that the rate has improved dramatically.

<Evaluation of filling property in holes>
The filling property of the graphene powder into the pores of the porous polymer sheet can be confirmed by visually observing the transmitted light of the manufactured face-to-face heat conductive sheet, and the following peeling test is performed to perform the graphene powder. The peeled state of was confirmed and evaluated according to the following criteria.
<Peeling test>
This was done by adhering a mending tape (12 mm width) manufactured by 3M Japan Ltd. to the surface of the interstitial heat conductive sheet and then peeling it off at once.
<Evaluation criteria>
◯: Graphene powder can be filled without defects, and after filling, it does not peel off in a peeling test.
Δ: The graphene powder can be filled without any defects, but after filling, a part of the graphene powder is peeled off in a peeling test.
X: The graphene powder is not sufficiently filled inside the pores.
The results of these evaluations are shown in Table 1.

[Example 2]
An interfaced heat conductive sheet was prepared and carried out in the same manner as in Example 1 except that the graphene powder was product number 900413 manufactured by Sigma-Aldrich (average maximum diameter: 25 μm, average thickness: 7.1 nm). Similar to Example 1, the thermal conductivity was measured and the filling property into the pores was evaluated. The pores were completely filled with graphene, that is, graphene occupied 100% of the void volume. The results are shown in Table 1.

[Example 3]
An interfaced heat conductive sheet was prepared in the same manner as in Example 1 except that the graphene powder was iGraphen-α manufactured by Aitec (average value of maximum diameter: 120 μm, average thickness: 1200 nm), and the same as in Example 1. The thermal conductivity was measured and the filling property into the pores was evaluated. The pores were completely filled with graphene, that is, graphene occupied 100% of the void volume. The results are shown in Table 1.

[Example 4]
An interplanetary heat conductive sheet was prepared in the same manner as in Example 1 except that the graphene powder was GNH-XZ manufactured by Graphene Platform Co., Ltd. (average value of maximum diameter: 2 μm, average thickness: 130 nm), and Example 1 In the same manner as above, the thermal conductivity was measured and the filling property into the pores was evaluated. The pores were completely filled with graphene, that is, graphene occupied 100% of the void volume. The results are shown in Table 1.

[Example 5]
An interplanar heat conductive sheet was prepared in the same manner as in Example 1 except that the graphene powder was XGnP C-500 manufactured by XG SCIENCES (average value of maximum diameter: 0.12 μm, average thickness: 2.8 nm). Then, the thermal conductivity was measured and the filling property into the hole was evaluated in the same manner as in Example 1. The pores were completely filled with graphene, that is, graphene occupied 100% of the void volume. The results are shown in Table 1.

[Comparative Example 1]
An attempt was made to prepare an interplane heat conductive sheet in the same manner as in Example 1 except that the graphene powder was manufactured by Luxor (no model number) (average maximum diameter: 330 μm, average thickness: 1.6 nm). However, the graphene powder was not filled in the pores of the nylon mesh.

[Example 6]
Polytetrafluoroethylene having an aperture ratio of 40%, in which circular holes having a thickness of 0.49 mm and a hole diameter of 0.75 mm are opened at a pitch of 1.1 mm perpendicular to the main surface of the sheet. An interplanar thermal conductivity sheet was prepared in the same manner as in Example 1 except that the punching sheet was made of PTFE), and the thermal conductivity was measured and the filling property into the hole was evaluated in the same manner as in Example 1. .. The pores were completely filled with graphene, that is, graphene occupied 100% of the void volume. The results are shown in Table 1.
The face-to-face heat conductive sheet was flexible and could be easily bent by hand. In addition, the density of this face-to-face heat conduction sheet was 1.5 g / cm ³ , which was even lighter than the 2.2 g / cm ^{3 of PTFE.}

[Example 7]
A porous polymer sheet is formed with a silicone rubber punching sheet having an opening ratio of 25%, in which circular holes having a thickness of 0.7 mm and a hole diameter of 1.2 mm are opened perpendicularly to the main surface of the sheet at a pitch of 2.3 mm. An inter-plane heat conduction sheet was prepared in the same manner as in Example 1, and the heat conductivity was measured and the filling property into the pores was evaluated in the same manner as in Example 1. The pores were completely filled with graphene, that is, graphene occupied 100% of the void volume. The results are shown in Table 1.
The face-to-face heat conductive sheet was flexible and could be easily bent by hand. In addition, the density of this interfaceted heat conductive sheet was 0.6 g / cm ³ , which was even lighter than the 0.97 g / cm ^{3 of silicone rubber.}

The face-to-face heat conduction sheet of the present invention has high heat conductivity in the face-to-face direction and is excellent in flexibility. Therefore, it can be suitably used as a so-called TIM that thermally connects the heat source and the heat radiating member. Further, it can be used as a substrate on which an electronic element is arranged to transmit heat generated from the electronic element to a heat radiating member. Further, it can be suitably used for applications such as housing of electronic devices such as smartphones and PCs, electronic circuit boards, LED lighting devices, heat dissipation from motors and the like.

Claims (8)

An interplanetary heat conductive sheet having a porous polymer sheet and carbon particles filled in the pores of the porous polymer sheet. The interplane heat conduction sheet according to claim 1, wherein the carbon particles are at least one of flaky graphite and fibrous graphite. The interplane heat conduction sheet according to claim 2, wherein the carbon particles are flaky graphite. The interplane heat conductive sheet according to claim 3, wherein the flaky graphite has a thickness of 100 nm or less. The face-to-face heat conduction according to any one of claims 1 to 4, where D1 ≧ D2 × 2 when the average pore diameter of the porous polymer sheet is D1 and the average value of the maximum diameters of the carbon particles is D2. Sheet. The interplane heat conduction according to any one of claims 1 to 5, where D1 ≦ D2 × 3000, where D1 is the average pore diameter of the porous polymer sheet and D2 is the average value of the maximum diameters of the carbon particles. Sheet. The interplane heat conduction sheet according to any one of claims 1 to 6, wherein the pores of the porous polymer sheet are formed perpendicular to the main surface of the porous polymer sheet. The method for producing an interplanar heat conductive sheet according to any one of claims 1 to 7, further comprising a step of impregnating a porous polymer sheet with a dispersion of carbon particles.