JP2013224258A - Method for producing graphite composite film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a graphite composite film which can be peeled off from a housing etc. of electronic equipment, where the graphite does not cause delamination.SOLUTION: A graphite composite film includes at least an adhesive layer at least on one side of the graphite film, wherein (1) the adhesion of the adhesive layer is 1 N/20 mm or more and 11 N/20 mm or less, and the surface roughnesses Ra of the graphite film is 0.2 μm or more and 3.0 μm or less. It is preferred that the thermal conductivity of the graphite film in the film surface direction is 200 W/mK or more, and that the thermal conductivity of the graphite film in the vertical direction to the film surface is 20 W/mK or less.

Description

  The present invention relates to a heat dissipation film for electronic equipment, precision equipment and the like, and a graphite composite film used as a heat spreader material, and more particularly to a graphite composite film having excellent reworkability.

  In recent years, semiconductor elements of electronic devices have been improved in performance while being reduced in size, and a material capable of diffusing heat in a small space and a small size is required. The graphite film that occupies an important position as such a material is lightweight and excellent in thermal conductivity. Such a graphite film has a highly developed layered graphite structure in the plane direction of the film, and has anisotropy in thermal conductivity and electrical conductivity based on the anisotropy of such a structure. In heat diffusion applications, high thermal conductivity in the surface direction is used, but the graphite layer is easily peeled off.

  As a generally available method for producing a highly heat-conductive graphite film, there are an expanding method in which expanded graphite is rolled into a sheet, or a polymer pyrolysis method. In the polymer pyrolysis method in which a polymer film such as a polyimide film is heat-treated and rolled, a graphite film having high quality, strong bending resistance and high flexibility can be obtained. In addition, the graphite film thus prepared is very excellent in crystallinity, electrical conductivity, and thermal conductivity (Patent Document 1). Therefore, the use as a heat radiating member of electronic equipment is increasing.

  However, when a graphite film is used as a heat dissipation member, it is necessary to prevent an electrical short circuit between electronic components because the graphite film has electrical conductivity. Therefore, a method is used in which the graphite surface is protected with an epoxy resin, an acrylic resin, a PET resin, or the like and an insulation treatment is performed.

  In order to exhibit the excellent thermal conductivity of the graphite film, it is also known that the graphite film is bonded to the casing using an adhesive such as an epoxy resin or an acrylic resin or an adhesive. For example, in a graphite composite film (Patent Document 2) in which a pressure-sensitive adhesive is applied to the surface of a graphite layer (Patent Document 2), the resistance value of the contact portion between the graphite film and the heating element is reduced, and the high thermal conductivity of the graphite film is exhibited. Can be made. However, in the case where the pressure-sensitive adhesive is formed like this, there is a problem that it cannot be sufficiently fixed to the heating element and is easily peeled off. There are also patents in which an adhesive layer is provided on the entire surface and adhered to a housing or the like (Patent Documents 3 and 4).

  On the other hand, when a graphite film is joined through an adhesive layer in an assembly process of an electronic device or the like, if a wrong attachment or the like occurs, it is necessary to remove the graphite film and attach it again. This is defined as reworkability. However, when the graphite is peeled off, the graphite is easily peeled off on the flakes because of the structure in which the graphene layers are stacked, so that the graphite is delaminated and reworked in the case of the conventional graphite composite film (Patent Documents 3 and 4). The problem of being unable to happen was happening.

JP 61-275116 A JP 2002-319653 A JP-A-11-317480 JP 2007-261087 A

  An object of the present invention is to solve the above problems and to provide a graphite composite film excellent in reworkability that can be peeled off from a casing of an electronic device or the like without causing delamination of graphite.

  (1) In the method for producing a graphite composite film according to the present invention, the graphite composite film is a graphite composite film having at least an adhesive layer on at least one side of the graphite film, and the adhesive layer measured based on JIS Z 0237. Is a graphite composite film having an adhesive strength of 1 N / 20 mm or more and 11 N / 20 mm or less, wherein the graphite film is compressed, and the surface roughness Ra is 0.2 μm or more and 3.0 μm or less on the graphite surface during the compression process. Is a method for producing a graphite composite film. The graphite film used for the purpose of the present invention is flexible, and in order to form irregularities on its surface, it is preferable to compress the graphite and provide irregularities on the graphite surface in the process.

  (2) In the method for producing a graphite composite film according to the present invention, the method for forming irregularities of the graphite film may transfer the irregularities of the slip sheet to the graphite during the compression process. Desirable irregularities can be easily provided on the surface of the graphite by compressing with the interleaving paper interposed therebetween.

  (3) In the method for producing a graphite composite film according to the present invention, the thermal conductivity in the film surface direction of the graphite film is 200 W / mK or more, and the thermal conductivity in the direction perpendicular to the film surface is 20 W / mK or less. May be. For heat conduction, it is preferable that the heat conduction in the surface direction of the graphite film is 200 W / mK or more. In such a graphite film, a graphite layer structure is developed in parallel with the film surface.

  (4) In the method for producing a graphite composite film according to the present invention, the adhesive layer may be a material containing an acrylic adhesive and / or a silicone adhesive. Adhesive strength is important for the purpose of the present invention, and an acrylic adhesive and / or a silicone-based adhesive is preferable in order to realize the fine adhesion of the present invention.

  (5) In the method for producing a graphite composite film according to the present invention, the adhesive layer may have a thickness of 30 μm or less. One method is to reduce the thickness of the pressure-sensitive adhesive layer in order to achieve the fine adhesive strength within the range of the present invention. By using the acrylic pressure-sensitive adhesive material and / or the silicone-based pressure-sensitive adhesive material and making the thickness of the pressure-sensitive adhesive layer 30 μm or less, the fine pressure-sensitive adhesive force within the range of the present invention can be realized.

  (6) In the method for producing a graphite composite film according to the present invention, the pressure-sensitive adhesive layer may have a three-layer structure or more composed of at least an adhesive layer / polymer layer / adhesive layer. Rework work can be remarkably facilitated by adopting a three-layer structure of adhesive layer / polymer layer / adhesive layer.

  (7) In the method for producing a graphite composite film according to the present invention, the polymer layer includes a polyimide resin, a polyethylene terephthalate (PET) resin, a polyphenylene sulfide (PPS) resin, and a polyethylene naphthalate (PEN) resin. In addition, at least one kind of a group of polyester resins may be included.

  (8) In the manufacturing method of the graphite composite film which concerns on this invention, you may use what was produced using the expanded graphite as a graphite film used for the manufacturing method of the graphite composite film of this invention. A graphite film produced using expanded graphite is preferred as the graphite film used for the purpose of the present invention.

  (9) In the method for producing a graphite composite film according to the present invention, the graphite film is polyimide, polyamide, polyoxadiazole, polybenzothiazole, polybenzobisthiazole, polybenzoxazole, polybenzobisoxazole, polyparaphenylene. It may be obtained by heat treatment of at least one polymer selected from the group consisting of vinylene, polybenzimidazole, polybenzobisimidazole, and polythiazole. These polymers become graphite having excellent thermal conductivity by heat treatment and are preferable as the graphite for the purpose of the present invention.

  Provided is a graphite composite film that can be peeled off from a casing of an electronic device without causing delamination of graphite.

<Graphite film>
Examples of the graphite film of the present invention include a graphite film obtained by sheeting graphite powder such as natural graphite and artificial graphite, and a graphite film obtained by heat-treating a polymer film. Graphite film has high thermal conductivity in the plane direction, large anisotropy in the thermal conductivity in the plane direction and thermal conductivity in the thickness direction, and heat is high at spots like electronic equipment and precision equipment. In the electronic member, heat can be effectively diffused.

  The first production method of the graphite film used in the present invention is a graphite film obtained by pressing graphite powder into a sheet. In order for the graphite powder to be formed into a film, the powder needs to be in the form of flakes or flakes. The most common method for producing such graphite powder is a method called an expanded (expanded graphite) method. In this method, graphite is immersed in an acid such as sulfuric acid to produce a graphite intercalation compound, which is then heat treated and foamed to separate the graphite layers. After peeling, the graphite powder is washed to remove the acid to obtain a thin film graphite powder. The graphite powder obtained by such a method is further subjected to rolling roll molding to obtain film-like graphite. The graphite film produced using expanded graphite obtained by such a method is flexible and has a high thermal conductivity in the film surface direction, so that it is preferably used for the purpose of the present invention.

  A second method for producing a graphite film preferably used for the purpose of the present invention is one in which film-like graphite is produced by heat treatment of a polymer film such as a polyimide resin.

  The raw material film of the graphite film used in the second method is polyimide, polyamide, polyoxadiazole, polybenzothiazole, polybenzobisthiazole, polybenzoxazole, polybenzobisoxazole, polyparaphenylene vinylene, polybenzimidazole, It is at least one polymer film selected from polybenzobisimidazole and polythiazole.

  In particular, a polyimide film is preferable as a raw material film for the graphite film of the present invention. Polyimide film is more prone to carbonization and graphitization of film than raw film made from other organic materials, so the thermal diffusivity, thermal conductivity, and electrical conductivity of the film are likely to increase uniformly at low temperatures. In addition, the thermal diffusivity, thermal conductivity, and electrical conductivity itself tend to be high. Further, in addition to the case where the thickness is thin, even when it is thick, the graphite has high thermal conductivity. In addition, the resulting graphite has excellent crystallinity, excellent heat resistance and bendability, and when bonded to a protective film, it is easy to obtain a graphite film in which graphite does not easily fall from the surface.

  In order to obtain a graphite film from a polymer, the polymer film as a starting material is first carbonized by preheating treatment under reduced pressure or in an inert gas. This carbonization is usually performed at a temperature of about 1000 ° C., and for example, when the temperature is raised at a rate of 10 ° C./min, it is desirable to hold the temperature for about 30 minutes in the temperature range of 1000 ° C. The graphitization step is performed under reduced pressure or in an inert gas, and argon and helium are suitable as the inert gas. In the method for producing a graphite film of the present invention, the heat treatment temperature is required to be at least 2000 ° C., finally 2400 ° C. or more, more preferably 2600 ° C. or more, more preferably 2800 ° C. or more. By setting the heat treatment temperature to be high, it is possible to obtain graphite having excellent thermal conductivity. The higher the heat treatment temperature is, the higher the quality can be converted to graphite, but from the viewpoint of economy, it is preferable that the conversion to high quality graphite is possible at the lowest possible temperature. In order to obtain an ultra-high temperature of 2500 ° C. or higher, usually, a current is directly applied to the graphite heater, and heating using the Joule heat is performed.

<Thermal conductivity of graphite film>
The graphite film used in the present invention preferably has a thermal conductivity in the plane direction of the film of 200 W / mK or more and a thermal conductivity in the direction perpendicular to the film plane of 20 W / mK or less. When the thermal conductivity in the surface direction of the film is 200 W / m · K or more, the thermal conductivity of the graphite composite film is increased even as a composite product in which an adhesive layer or a protective film layer is formed. Further, in order to quickly move the heat from the heat-generating component, the thermal conductivity in the thickness direction of the graphite film needs to be sufficiently small. For example, when there is no thermal conductivity anisotropy in the plane direction and thickness direction and the thermal conductivity is inferior, and even if there is anisotropy in thermal conductivity in the plane direction and thickness direction, the thickness direction compared to the plane direction If the heat conductivity of the heat generating portion is excellent, the heat from the heat generating portion cannot be sufficiently diffused, so that a heat spot is generated in which the heat is high at the spot of the heat generating portion. When this heat spot is generated, for example, when it occurs in a notebook computer or a mobile phone, it causes a low temperature burn. However, the graphite film has thermal conductivity anisotropy in the plane direction and the thickness direction, and the plane direction is more excellent in thermal conductivity than the thickness direction, so priority is given to heat from the heat generation part. In particular, it is possible to diffuse in the surface direction, and heat spots can be suppressed. Therefore, it can be seen that (1) high thermal conductivity in the plane direction and (2) sufficiently small thermal conductivity in the thickness direction are necessary to achieve rapid thermal diffusion from the heat generating portion. Therefore, the thermal conductivity in the thickness direction of the present invention is preferably 20 W / mK or less. Thus, graphite has anisotropy, and has a characteristic that thermal conductivity is large in the plane direction of graphite and small in the thickness direction. Therefore, the capability of diffusing heat in the plane direction is high. In particular, the higher the thermal conductivity in the plane direction, the lower the thermal conductivity in the thickness direction, and the higher the capability of diffusing heat. On the other hand, however, graphite has a structure in which graphene layers are stacked, so that it is easy to peel off on the flakes, and there is a problem that graphite easily causes delamination.

The thermal diffusivity in the plane direction of the graphite film of the present invention is preferably 7.5 × 10 ⁻⁴ m ² / s or more. When it is 7.5 × 10 ⁻⁴ m ² / s or more, since heat conductivity is high, it becomes easy to release heat from the heat generating device, and it becomes possible to suppress the temperature rise of the heat generating device. Moreover, when it is set as the graphite composite film in which the adhesion layer and the protective film layer were formed, sufficiently high thermal conductivity can be exhibited. The thermal diffusivity can be measured at 10 Hz in an atmosphere of 20 ° C. using a thermal diffusivity measuring apparatus (trade name “LaserPit” available from ULVAC-RIKO Co., Ltd.) by an optical alternating current method.

<Adhesive layer>
The present invention is a graphite composite film having at least an adhesive layer on at least one side of a graphite film, and the adhesive strength of the adhesive layer measured based on JIS Z 0237 is 1 N / 20 mm or more and 11 N / 20 mm or less. However, it is more preferably 1 N / 20 mm or more and 10 N / 20 mm or less, and further preferably 1 N / 20 mm or more and 8 N / 20 mm. On the other hand, when the adhesive strength of the adhesive layer is stronger than 11 N / 20 mm, the graphite tends to cause delamination during peeling, and the reworkability is deteriorated. On the other hand, if it is weaker than 1 N / 20 mm, the adhesive force is too weak, so that it does not adhere well to the housing or peels off during use. Furthermore, since the adhesiveness is poor, the heat of the heat source does not transfer well to the graphite, and the heat dissipation effect is lost.

Examples of the material for the adhesive layer that realizes such slight adhesion include acrylic adhesives, silicone adhesives, etc. These materials have excellent heat resistance and are used in combination with heat-generating parts and heat-dissipating parts. In addition, sufficient long-term reliability can be obtained. In addition, these materials are excellent in reusability and removability because they are excellent in repeated use and long-term reliability.
The thickness of the pressure-sensitive adhesive layer is 30 μm or less, preferably 10 μm or less. Generally, as the thickness of the adhesive layer increases, the adhesive strength increases. When the thickness exceeds 30 μm, the adhesive strength increases, so that it cannot be peeled off successfully from the housing and the like, and graphite is likely to cause delamination. Become.

<Base material for adhesive layer>
The adhesive layer preferably contains a substrate. Here, including a base material means that the pressure-sensitive adhesive layer has a three-layer structure or more composed of at least an adhesive layer / polymer layer / adhesive layer. By using a graphite composite film having such a structure, the rework work can be remarkably facilitated. By including the base material, the stiffness of the graphite composite film increases, and when the graphite film once attached is re-peeled, the delamination of the graphite film can be suppressed. In particular, in the case of a graphite film having excellent crystallinity and thermal diffusibility as in the present invention, the film may be easily peeled in layers, but the presence of a substrate may improve the peelability. It becomes possible.

The material of the substrate of the present invention is preferably a polymer film. As an example, a polymer film including at least one selected from the group consisting of a polyimide resin, a polyethylene terephthalate (PET) resin, a polyphenylene sulfide (PPS) resin, a polyethylene naphthalate (PEN) resin, a polyester resin, and the like. It is done.
Among these, polyimide and polyethylene terephthalate are excellent in heat resistance, strength, and dimensional stability, and when combined, they become a graphite composite film that is excellent in peelability and scratch resistance without degrading thermal conductivity.

<Surface roughness of graphite>
An object of the present invention is to provide a graphite composite film excellent in reworkability. To achieve the object, (1) a slightly sticky adhesive layer is used, (2) the adhesive layer is thinned, (3 (4) In addition to the three methods of adding a polymer substrate to the adhesive layer, (4) it is also beneficial to control the roughness of the graphite surface. In the case of a graphite composite film having at least an adhesive layer on at least one surface of the graphite film, the surface of the graphite when the adhesive force of the adhesive layer measured based on JIS Z 0237 is 1 N / 20 mm or more and 11 N / 20 mm or less The roughness Ra is preferably 0.2 μm to 3.0 μm. More preferably, when the adhesive strength of the adhesive layer is 8 N / 20 mm or more, the preferable surface roughness of graphite is Ra 1.2 μm or more and 3.0 μm or less. When the adhesive strength of the adhesive layer is 8 N / 20 mm or more, the adhesive strength with the housing or the like is too strong, and when the surface roughness Ra is less than 1.2 μm, the adhesiveness when adhered is too good. When peeling off, the adhesive layer and the housing are not peeled off, and the graphite is liable to delaminate. However, when the surface roughness of graphite is 1.2 μm or more, the adhesion between the casing and the adhesive layer is somewhat lowered, and peeling is possible. On the other hand, when the surface roughness Ra of the graphite is 3.0 μm or more, the surface is too rough, so that the adhesion is poor when bonded to a housing or the like, and the heat of the heat source is not transmitted well to the graphite, and the heat dissipation effect is lost. End up.

  As a method for providing irregularities on the graphite surface, a graphite film can be compressed, and irregularities having a surface roughness Ra of 0.2 μm or more and 3.0 μm or less can be provided on the graphite surface in the compression process. The graphite film used for the purpose of the present invention is flexible, and in order to form irregularities on its surface, it is preferable to compress the graphite and provide irregularities on the graphite surface in the process. Furthermore, the method for forming irregularities of the graphite film transfers the irregularities of the slip sheet to the graphite during the compression process. Desirable irregularities can be easily provided on the surface of the graphite by compressing with the interleaving paper interposed therebetween.

  The present invention can also be configured as follows.

  (1) In a graphite composite film having at least an adhesive layer on at least one side of the graphite film, the adhesive strength of the adhesive layer measured based on JIS Z 0237 is set to be 1 N / 20 mm or more and 11 N / 20 mm or less. It is.

  (2) A graphite composite film having a thermal conductivity in the film surface direction of the graphite film of 200 W / mK or more and a thermal conductivity in a direction perpendicular to the film surface of 20 W / mK or less. For heat conduction, it is preferable that the heat conduction in the surface direction of the graphite film is 200 W / mK or more. In such a graphite film, a graphite layer structure is developed in parallel with the film surface.

  (3) A graphite composite film having at least an adhesive layer on at least one side of the graphite film, wherein the adhesive strength of the adhesive layer measured based on JIS Z 0237 is 1 N / 20 mm or more and 11 N / 20 mm or less. The graphite composite film according to (1) to (2), wherein the graphite film has a surface roughness Ra of 0.2 μm or more and 3.0 μm or less.

  (4) The graphite composite film according to (3), wherein the graphite film is compressed, and irregularities having a surface roughness Ra of 0.2 μm or more and 3.0 μm or less are provided on the graphite surface during the compression process. It is a manufacturing method. The graphite film used for the purpose of the present invention is flexible, and in order to form irregularities on its surface, it is preferable to compress the graphite and provide irregularities on the graphite surface in the process.

  (5) The method for producing a graphite composite film according to (4), wherein the method for forming irregularities of the graphite film is to transfer the irregularities of the slip sheet to the graphite in the compression process. Desirable irregularities can be easily provided on the surface of the graphite by compressing with the interleaving paper interposed therebetween.

  (6) The graphite composite film according to any one of (1) to (3), wherein the adhesive layer is a material including an acrylic adhesive and / or a silicone adhesive. Adhesive strength is important for the purpose of the present invention, and an acrylic adhesive and / or a silicone-based adhesive is preferable in order to realize the fine adhesion of the present invention.

  (7) The graphite composite film according to any one of (1), (2), (3), and (6), wherein the adhesive layer has a thickness of 30 μm or less. One method is to reduce the thickness of the pressure-sensitive adhesive layer in order to achieve the fine adhesive strength within the range of the present invention. By using the acrylic pressure-sensitive adhesive material and / or the silicone-based pressure-sensitive adhesive material and making the thickness of the pressure-sensitive adhesive layer 30 μm or less, the fine pressure-sensitive adhesive force within the range of the present invention can be realized.

  (8) The pressure-sensitive adhesive layer is a graphite composite film having at least a three-layer structure comprising an adhesive layer / polymer layer / adhesive layer. Rework work can be remarkably facilitated by adopting a three-layer structure of adhesive layer / polymer layer / adhesive layer.

  (9) The polymer layer includes at least one selected from the group consisting of a polyimide resin, a polyethylene terephthalate (PET) resin, a polyphenylene sulfide (PPS) resin, a polyethylene naphthalate (PEN) resin, and a polyester resin. The graphite composite film according to any one of (1) to (8), characterized in that it includes types.

  (10) The graphite film used in the graphite composite film of the present invention is one prepared using expanded graphite. A graphite film produced using expanded graphite is preferred as the graphite film used for the purpose of the present invention.

  (11) The graphite film is polyimide, polyamide, polyoxadiazole, polybenzothiazole, polybenzobisthiazole, polybenzoxazole, polybenzobisoxazole, polyparaphenylene vinylene, polybenzimidazole, polybenzobisimidazole, and The graphite composite film according to any one of (1) to (9), wherein the graphite composite film is obtained by heat treatment of at least one polymer selected from the group consisting of polythiazoles. These polymers become graphite having excellent thermal conductivity by heat treatment and are preferable as the graphite for the purpose of the present invention.

  Embodiments and effects of the present invention will be described below with reference to examples, but the present invention is not limited thereto.

<Graphite film>
As an example, six types of graphite films A, B, C, D, E, and F were used.
[Graphite film A]
In a DMF (dimethylformamide) solution in which 1 equivalent of 4,4′-oxydianiline was dissolved, 1 equivalent of pyromellitic dianhydride was dissolved to obtain a polyamic acid solution (18.5 wt%). While this solution was cooled, an imidation catalyst containing 1 equivalent of acetic anhydride, 1 equivalent of isoquinoline, and DMF was added to the carboxylic acid group contained in the polyamic acid to degas. Next, this mixed solution was applied onto an aluminum foil so as to have a predetermined thickness after drying. The mixed solution layer on the aluminum foil was dried using a hot air oven and a far infrared heater. As described above, a polyimide film A having a thickness of 50 μm (elasticity 3.1 GPa, water absorption 2.5%, birefringence 0.10, linear expansion coefficient 3.0 × 10 ⁻⁵ / ° C.) was produced.

A polyimide film having a thickness of 50 μm was sandwiched between graphite plates and heated to 1000 ° C. using an electric furnace to perform carbonization (carbonization). This carbonized film was designated as carbonized film A. The carbonized film A obtained by the carbonization treatment was sandwiched between graphite plates, and was graphitized by raising the temperature to 2900 ° C. or higher using a graphitization furnace. Graphite A (thickness 25 μm, density 1.86 g / cm ³ , thermal diffusivity) is obtained by sandwiching the heat-treated graphite with a single plate press with a slip sheet having a surface roughness Ra of 0.3 μm and compressing it in the thickness direction. 9.1 cm ² / s, thermal conductivity 1200 W / m · K, surface roughness Ra 0.3 μm).
[Graphite film B]
Graphite film B (thickness 25 μm, density 1.86 g / cm ³ , thermal diffusivity 9.1 cm ² / s), except that it was compressed using a slip sheet having a surface roughness Ra of 1.2 μm. , Thermal conductivity 1200 W / m · K, surface roughness Ra 1.2 μm).
[Graphite film C]
Graphite film C (thickness 25 μm, density 1.86 g / cm ³ , thermal diffusivity 9.1 cm ² / s), except that it was compressed using interleaving paper having a surface roughness Ra of 3.0 μm. , Thermal conductivity 1200 W / m · K, surface roughness Ra 3.0 μm).
[Graphite film D]
A polyimide film D was obtained so that the finished thickness was 75 μm. The obtained polyimide film was carbonized and graphitized in the same manner to produce a graphite film D, and compressed with a slip sheet having a surface roughness Ra of 0.3 μm (thickness 40 μm, density 1.86 g). / Cm ³ , thermal diffusivity 9.5 cm ² / s, thermal conductivity 1200 W / m · K, surface roughness Ra 0.3 μm).
[Graphite film E]
Graphite film E (thickness 40 μm, density 1.86 g / cm ³ , thermal diffusivity 9.5 cm ² / s), similar to graphite film D, except that it was compressed using interleaving paper having a surface roughness Ra of 3.0 μm. , Thermal conductivity 1200 W / m · K, surface roughness Ra 3.0 μm).

[Graphite film F]
In the presence of an oxidizing agent (hydrogen peroxide, perchloric acid, etc.), sulfuric acid, nitric acid, etc. are inserted between the layers of natural scaly graphite, and the formed intercalation compound is rapidly heated at 5 high temperatures of about 900 to 1200 ° C. The gas was decomposed and gas was expanded to expand the graphite layer by the gas pressure at this time. The expanded graphite obtained as described above is compression-preformed, and then rolled with a roll to obtain a graphite film F (thickness 75 μm, density 1.67 g / cm ³ , thermal diffusivity 3.0 cm ² / s, thermal conductivity 400 W / m · K, surface roughness Ra 1.0 μm).

<Measurement of properties of graphite film>
As a method for measuring the thickness of the graphite film, a film of 50 mm × 50 mm was measured at any 10 points in a constant temperature room at 25 ° C. using a thickness gauge (HEIDENHAIN-CERTO, manufactured by HEIDENHAIN Co., Ltd.). The average value was taken as the measured value.

The density of the graphite film was calculated by dividing the weight (g) of the graphite film by the volume (cm ³ ) calculated by the product of the vertical, horizontal and thickness of the graphite film. In addition, the average value measured by arbitrary 10 points | pieces was used for the thickness of a graphite film. The higher the density, the more remarkable the graphitization.
The thermal diffusivity of the graphite film was measured by cutting the graphite film into a 4 × 40 mm sample shape using a thermal diffusivity measuring apparatus (“LaserPit” available from ULVAC-RIKO Co., Ltd.) by an optical alternating current method, The measurement was performed at 10 Hz under the atmosphere of The progress of graphitization was determined by measuring the thermal diffusivity in the film surface direction. Higher thermal diffusivity means more remarkable graphitization. The thermal conductivity of the graphite film was calculated from the thermal diffusivity, density, and specific heat as shown in the following equation.
λ = αdC
λ: thermal conductivity (W / mK)
α: Thermal diffusivity (m ² / s)
d: Density (kg / m ³ )
C: Specific heat (J / kg · K)
Data of thermal conductivity and thickness of graphite films used in Examples and Comparative Examples are summarized in Table 1. The surface roughness Ra of the graphite film is a value obtained in accordance with JIS B 0601. Specifically, the surface roughness Ra was measured using a surface roughness measuring instrument SE3500 (manufactured by Kosaka Laboratory Ltd.). The surface roughness Ra of the graphite film is cut into a size of 100 mm length × 3 mm width, a chart is drawn with a cut-off of 0.8 mm and a feed rate of 2 mm / s, and a portion of the reference length L is cut out. When the center line of the portion is the X axis, the vertical direction is the Y axis, and the roughness curve is represented by Y = f (X), the value obtained by the following equation is represented by μm.

In this measurement, the reference length (L) is set to 80 mm, three values are calculated, and the average value is calculated. Hereinafter, the “surface roughness Ra” in this specification refers to this measured value.

<Adhesive layer>
Five types of double-sided tapes having different adhesive forces were prepared by controlling the components and thickness using an acrylic adhesive material. The structure of the double-sided tape is: adhesive layer / PET (1 μm) / adhesive layer. Each sample was cut to a width of 20 mm, a 2 kg roller was reciprocated once on a stainless steel plate, and left at 23 ° C. for 30 minutes, and then pulled using a tensile tester under conditions of a pulling speed of 300 mm / min and a peeling angle of 180 °. The adhesive strength was measured. (JIS Z 0237) The thickness and adhesive strength of the adhesive layer of each double-sided tape are as follows.
[Double-sided tape A] Adhesive strength 2N / 20mm, PET thickness 1μm
[Double-sided tape B] Adhesive strength 5N / 20mm, PET thickness 1μm
[Double-sided tape C] Adhesive strength 8.3 N / 20 mm, PET thickness 2 μm, total thickness 10 μm
[Double-sided tape D] Adhesive strength 10.4 N / 20 mm, PET thickness 12 μm, total thickness 30 μm
[Double-sided tape E] Adhesive strength 20 N / 20 mm, PET thickness 25 μm, total thickness 100 μm
Example 1
A graphite film B (20 mm width) was placed on the adhesive surface of a PET (polyethylene terephthalate) tape (Teraoka Seisakusho 631S: PET 12 μm / acrylic 18 μm). Next, this composite film and double-sided tape A were bonded together with a laminator to produce a graphite composite film in which a PET insulating layer was formed on one side of the graphite film and an adhesive layer was formed on one side. Thereafter, a sample having a shape of 20.5 mm wide × 20.5 mm long (0.5 mm around the graphite film was covered with an insulating layer and an adhesive layer) was cut. The results are summarized in Table 1.

(Example 2)
A graphite film A (20 mm width) was placed on the adhesive surface of a PET (polyethylene terephthalate) tape (Teraoka Seisakusho 631S: PET 12 μm / acrylic 18 μm). Next, this composite film and double-sided tape A were bonded together with a laminator to produce a graphite composite film in which a PET insulating layer was formed on one side of the graphite film and an adhesive layer was formed on one side. Thereafter, a sample having a shape of 20.5 mm wide × 20.5 mm long (0.5 mm around the graphite film was covered with an insulating layer and an adhesive layer) was cut. The results are summarized in Table 1.

(Example 3)
A graphite film B (20 mm width) was placed on the adhesive surface of a PET (polyethylene terephthalate) tape (Teraoka Seisakusho 631S: PET 12 μm / acrylic 18 μm). Next, this composite film and double-sided tape B were bonded together with a laminator to produce a graphite composite film in which a PET insulating layer was formed on one side of the graphite film and an adhesive layer was formed on one side. Thereafter, a sample having a shape of 20.5 mm wide × 20.5 mm long (0.5 mm around the graphite film was covered with an insulating layer and an adhesive layer) was cut. The results are summarized in Table 1.

Example 4
A graphite film A (20 mm width) was placed on the adhesive surface of a PET (polyethylene terephthalate) tape (Teraoka Seisakusho 631S: PET 12 μm / acrylic 18 μm). Next, this composite film and double-sided tape B were bonded together with a laminator to produce a graphite composite film in which a PET insulating layer was formed on one side of the graphite film and an adhesive layer was formed on one side. Thereafter, a sample having a shape of 20.5 mm wide × 20.5 mm long (0.5 mm around the graphite film was covered with an insulating layer and an adhesive layer) was cut. The results are summarized in Table 1.

(Example 5)
A graphite film B (20 mm width) was placed on the adhesive surface of a PET (polyethylene terephthalate) tape (Teraoka Seisakusho 631S: PET 12 μm / acrylic 18 μm). Next, this composite film and double-sided tape C were bonded together with a laminator to produce a graphite composite film in which a PET insulating layer was formed on one side of the graphite film and an adhesive layer was formed on one side. Thereafter, a sample having a shape of 20.5 mm wide × 20.5 mm long (0.5 mm around the graphite film was covered with an insulating layer and an adhesive layer) was cut. The results are summarized in Table 1.

(Example 6)
A graphite film A (20 mm width) was placed on the adhesive surface of a PET (polyethylene terephthalate) tape (Teraoka Seisakusho 631S: PET 12 μm / acrylic 18 μm). Next, this composite film and double-sided tape C were bonded together with a laminator to produce a graphite composite film in which a PET insulating layer was formed on one side of the graphite film and an adhesive layer was formed on one side. Thereafter, a sample having a shape of 20.5 mm wide × 20.5 mm long (0.5 mm around the graphite film was covered with an insulating layer and an adhesive layer) was cut. The results are summarized in Table 1.

(Example 7)
Graphite film C (20 mm width) was placed on the adhesive surface of PET (polyethylene terephthalate) tape (Teraoka Seisakusho 631S: PET 12 μm / acrylic 18 μm). Next, this composite film and double-sided tape D were bonded together with a laminator to produce a graphite composite film in which a PET insulating layer was formed on one side of the graphite film and an adhesive layer was formed on one side. Thereafter, a sample having a shape of 20.5 mm wide × 20.5 mm long (0.5 mm around the graphite film was covered with an insulating layer and an adhesive layer) was cut. The results are summarized in Table 1.

(Example 8)
A graphite film B (20 mm width) was placed on the adhesive surface of a PET (polyethylene terephthalate) tape (Teraoka Seisakusho 631S: PET 12 μm / acrylic 18 μm). Next, this composite film and double-sided tape D were bonded together with a laminator to produce a graphite composite film in which a PET insulating layer was formed on one side of the graphite film and an adhesive layer was formed on one side. Thereafter, a sample having a shape of 20.5 mm wide × 20.5 mm long (0.5 mm around the graphite film was covered with an insulating layer and an adhesive layer) was cut. The results are summarized in Table 1.

Example 9
A graphite film A (20 mm width) was placed on the adhesive surface of a PET (polyethylene terephthalate) tape (Teraoka Seisakusho 631S: PET 12 μm / acrylic 18 μm). Next, this composite film and double-sided tape D were bonded together with a laminator to produce a graphite composite film in which a PET insulating layer was formed on one side of the graphite film and an adhesive layer was formed on one side. Thereafter, a sample having a shape of 20.5 mm wide × 20.5 mm long (0.5 mm around the graphite film was covered with an insulating layer and an adhesive layer) was cut. The results are summarized in Table 1.

(Example 10)
A graphite film D (20 mm width) was placed on the adhesive surface of a PET (polyethylene terephthalate) tape (Teraoka Seisakusho 631S: PET 12 μm / acrylic 18 μm). Next, this composite film and double-sided tape A were bonded together with a laminator to produce a graphite composite film in which a PET insulating layer was formed on one side of the graphite film and an adhesive layer was formed on one side. Thereafter, a sample having a shape of 20.5 mm wide × 20.5 mm long (0.5 mm around the graphite film was covered with an insulating layer and an adhesive layer) was cut. The results are summarized in Table 1.

(Example 11)
A graphite film D (20 mm width) was placed on the adhesive surface of a PET (polyethylene terephthalate) tape (Teraoka Seisakusho 631S: PET 12 μm / acrylic 18 μm). Next, this composite film and double-sided tape B were bonded together with a laminator to produce a graphite composite film in which a PET insulating layer was formed on one side of the graphite film and an adhesive layer was formed on one side. Thereafter, a sample having a shape of 20.5 mm wide × 20.5 mm long (0.5 mm around the graphite film was covered with an insulating layer and an adhesive layer) was cut. The results are summarized in Table 1.

(Example 12)
A graphite film D (20 mm width) was placed on the adhesive surface of a PET (polyethylene terephthalate) tape (Teraoka Seisakusho 631S: PET 12 μm / acrylic 18 μm). Next, this composite film and double-sided tape C were bonded together with a laminator to produce a graphite composite film in which a PET insulating layer was formed on one side of the graphite film and an adhesive layer was formed on one side. Thereafter, a sample having a shape of 20.5 mm wide × 20.5 mm long (0.5 mm around the graphite film was covered with an insulating layer and an adhesive layer) was cut. The results are summarized in Table 1.

(Example 13)
A graphite film E (20 mm width) was placed on the adhesive surface of a PET (polyethylene terephthalate) tape (Teraoka Seisakusho 631S: PET 12 μm / acrylic 18 μm). Next, this composite film and double-sided tape D were bonded together with a laminator to produce a graphite composite film in which a PET insulating layer was formed on one side of the graphite film and an adhesive layer was formed on one side. Thereafter, a sample having a shape of 20.5 mm wide × 20.5 mm long (0.5 mm around the graphite film was covered with an insulating layer and an adhesive layer) was cut. The results are summarized in Table 1.

(Example 14)
A graphite film D (20 mm width) was placed on the adhesive surface of a PET (polyethylene terephthalate) tape (Teraoka Seisakusho 631S: PET 12 μm / acrylic 18 μm). Next, this composite film and double-sided tape D were bonded together with a laminator to produce a graphite composite film in which a PET insulating layer was formed on one side of the graphite film and an adhesive layer was formed on one side. Thereafter, a sample having a shape of 20.5 mm wide × 20.5 mm long (0.5 mm around the graphite film was covered with an insulating layer and an adhesive layer) was cut. The results are summarized in Table 1.

(Example 15)
A graphite film F (20 mm width) was placed on the adhesive surface of a PET (polyethylene terephthalate) tape (Teraoka Seisakusho 631S: PET 12 μm / acrylic 18 μm). Next, this composite film and double-sided tape B were bonded together with a laminator to produce a graphite composite film in which a PET insulating layer was formed on one side of the graphite film and an adhesive layer was formed on one side. Thereafter, a sample having a shape of 20.5 mm wide × 20.5 mm long (0.5 mm around the graphite film was covered with an insulating layer and an adhesive layer) was cut. The results are summarized in Table 1.

(Comparative Example 1)
A graphite film A (20 mm width) was placed on the adhesive surface of a PET (polyethylene terephthalate) tape (Teraoka Seisakusho 631S: PET 12 μm / acrylic 18 μm). Next, this composite film and the double-sided tape E were bonded together with a laminator to prepare a graphite composite film in which a PET insulating layer was formed on one side of the graphite film and an adhesive layer was formed on one side. Thereafter, a sample having a shape of 20.5 mm wide × 20.5 mm long (0.5 mm around the graphite film was covered with an insulating layer and an adhesive layer) was cut. The results are summarized in Table 1.

(Comparative Example 2)
A graphite film D (20 mm width) was placed on the adhesive surface of a PET (polyethylene terephthalate) tape (Teraoka Seisakusho 631S: PET 12 μm / acrylic 18 μm). Next, this composite film and the double-sided tape E were bonded together with a laminator to prepare a graphite composite film in which a PET insulating layer was formed on one side of the graphite film and an adhesive layer was formed on one side. Thereafter, a sample having a shape of 20.5 mm wide × 20.5 mm long (0.5 mm around the graphite film was covered with an insulating layer and an adhesive layer) was cut. The results are summarized in Table 1.

(Comparative Example 3)
A graphite film C (20 mm width) was placed on the adhesive surface of a PET (polyethylene terephthalate) tape (Teraoka Seisakusho 631S: PET 12 μm / acrylic 18 μm). Next, this composite film and the double-sided tape E were bonded together with a laminator to prepare a graphite composite film in which a PET insulating layer was formed on one side of the graphite film and an adhesive layer was formed on one side. Thereafter, a sample having a shape of 20.5 mm wide × 20.5 mm long (0.5 mm around the graphite film was covered with an insulating layer and an adhesive layer) was cut. The results are summarized in Table 1.

<Evaluation of reworkability>
Each sample was attached to a stainless steel plate and then peeled off. It was visually confirmed whether or not the graphite film was delaminated at that time. The test was conducted 5 times. When the graphite could be reworked 4 times or more without causing delamination, “◎”, 3 times “○”, 2 times “△”, 1 time or less Was marked “x”.
Examples 1 to 6 and Examples 10 to 12 showed excellent reworkability. On the other hand, in Comparative Examples 1 to 3, graphite caused delamination during rework, and rework could not be performed. For this reason, when the graphite composite film is peeled off from the housing, etc., if the adhesive layer is too strong, the strength at which the graphite layer is peeled off becomes weaker than the strength at which the housing-adhesive layer peels off. Furthermore, it can be said that the graphite causes delamination before the casing-adhesive layer is peeled off.

  Moreover, Example 9 and Example 14 resulted in a slightly inferior rework property. On the other hand, Examples 7, 8, and 13 using the same double-sided tapes as these and using a graphite film having a surface roughness Ra of 1.2 or more showed improvement in reworkability. This is thought to be due to the fact that the adhesive surface of the adhesive layer to the housing or the like is somewhat reduced by roughening the surface, thereby lowering the adhesion, thereby improving the peeling.

Claims (9)

A method for producing a graphite composite film, comprising:
The graphite composite film is a graphite composite film having at least one adhesive layer on at least one side of the graphite film, and the adhesive strength of the adhesive layer measured based on JISZ 0237 is 1 N / 20 mm or more and 11 N / 20 mm or less. A film,
A method for producing a graphite composite film, wherein the graphite film is compressed, and irregularities having a surface roughness Ra of 0.2 μm or more and 3.0 μm or less are provided on the graphite surface during the compression process.   2. The method for producing a graphite composite film according to claim 1, wherein the method of forming the unevenness of the graphite film is to transfer the unevenness of the slip sheet to the graphite during the compression process.   The method for producing a graphite composite film according to claim 1 or 2, wherein the thermal conductivity in the film surface direction of the graphite film is 200 W / mK or more and the thermal conductivity in the direction perpendicular to the film surface is 20 W / mK or less.   The method for producing a graphite composite film according to any one of claims 1 to 3, wherein the adhesive layer is a material containing an acrylic adhesive and / or a silicone adhesive.   The thickness of the said adhesion layer is 30 micrometers or less, The manufacturing method of the graphite composite film of any one of Claims 1-4 characterized by the above-mentioned.   The method for producing a graphite composite film according to any one of claims 1 to 5, wherein the pressure-sensitive adhesive layer has a three-layer structure or more comprising at least an adhesive layer / polymer layer / adhesive layer.   The polymer layer includes at least one selected from the group consisting of polyimide resin, polyethylene terephthalate (PET) resin, polyphenylene sulfide (PPS) resin, polyethylene naphthalate (PEN) resin, and polyester resin. A method for producing a graphite composite film according to claim 6.   The method for producing a graphite composite film according to claim 1, wherein the graphite film is produced using expanded graphite.   The graphite film is made of polyimide, polyamide, polyoxadiazole, polybenzothiazole, polybenzobisthiazole, polybenzoxazole, polybenzobisoxazole, polyparaphenylene vinylene, polybenzimidazole, polybenzobisimidazole, and polythiazole. The method for producing a graphite composite film according to any one of claims 1 to 8, wherein the graphite composite film is obtained by heat treatment of at least one polymer selected from the group consisting of: