JP2008214171A - Graphite film and method for producing it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a graphite film of which the surface has an improved wettability and is excellent in adhesiveness to an adhesive, a pressure-sensitive adhesive, and an inorganic substance layer, and a method for producing it. <P>SOLUTION: The surface of a graphite film is subjected to a surface treatment, typified by a corona treatment, to introduce oxygen-derived functional groups on the surface of the graphite film and to form micro-irregularity on the surface. Thus is improved the adhesiveness of the graphite film surface to the adhesive, the pressure-sensitive adhesive, and an inorganic substance layer. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a heat dissipation film for electronic equipment, precision equipment and the like, and a graphite film used as a heat spreader material, and particularly relates to a graphite film having improved wettability and improved adhesion to adhesives, pressure-sensitive adhesives, inorganic substances, and the like. .

  As a generally available graphite film, a graphite film produced by a polymer pyrolysis method or an expanding method is known. Graphite film is known to have excellent properties in thermal conductivity, electrical conductivity, heat resistance, cold resistance, chemical resistance, mechanical strength, etc., but particularly excellent in thermal conductivity and electrical conductivity. As a method for obtaining a graphite film, a polymer film such as polyoxadiazole, polyimide, polyphenylene vinylene, polybenzimidazole, polybenzoxazole, polythiazole, or polyamide is heat-treated in an inert atmosphere such as argon or helium or under reduced pressure. A polymer pyrolysis method (Patent Document 1) is known. The graphite film thus produced is excellent in crystallinity and very excellent in thermal conductivity and electrical conductivity. Therefore, the example used as a heat radiating member of an electronic device is increasing.

As a concrete usage example,
1. 1. a heat dissipation spacer sandwiched between the CPU and the cooling fan or heat sink; Examples include a heat spreader that diffuses heat to the DVD optical pickup and the housing. When used as such a heat radiating member, in order to exhibit the excellent thermal conductivity of graphite, it is necessary to sufficiently adhere to the heat source, and the graphite film and the heat source are made of epoxy resin, acrylic resin or polyimide resin. May be bonded using a suitable adhesive or pressure sensitive adhesive. Specifically, it is common to use a graphite composite film in which an adhesive layer or an adhesive layer is formed on at least one surface of the graphite film, instead of separately preparing a graphite film and an adhesive, an adhesive, and the like.

Specifically, a film (Patent Document 2) including a sheet made of a graphite material and an adhesive layer having a thickness of 100 microns or less provided on the surface of the sheet is known. These heat dissipating materials can easily achieve thermal coupling to a heat generating source and a heat dissipating plate to some extent without causing a decrease in thermal conductivity.
JP 61-275116 A JP 11-317480 A

<1> Release properties of release liner of graphite composite film As described above, various types of graphite composite films (graphite film / adhesive, adhesive, etc./release liner) are known. Due to the high chemical resistance, the adhesive strength with various pressure-sensitive adhesives and adhesives was often insufficient. In fact, until now, depending on the type of pressure-sensitive adhesive, adhesive, etc., peeling may be seen from the interlayer of the pressure-sensitive adhesive, adhesive, etc. and the graphite film. Specifically, even a weak force at the time of peeling the release liner from the graphite composite film, sometimes peeled from the interlayer such as graphite and pressure-sensitive adhesive. Moreover, when the nip pressure at the time of bonding an adhesive tape and a graphite film is too weak, the same peeling may be seen. As described above, the graphite film as described in the prior art has poor handling properties when the release liner is peeled off, and may not be easily attached to an electronic device or a precision device.

<2> Adhesiveness between graphite film and pressure-sensitive adhesive In addition, the adhesion between the graphite layer and the pressure-sensitive adhesive (acrylic resin type, silicone resin type, etc.) is weak. Peeling may occur. For this reason, the adhesion between the sheet and the heat generating member is deteriorated, and sufficient heat dissipation capability cannot be exhibited. In particular, the heat generation density of electronic devices has increased in recent years, and peeling due to heat has become serious.

<3> Adhesiveness between graphite film and adhesive When a graphite film is combined with a plastic film or a plate-like support, various adhesives (epoxy resin, phenol resin, acrylic resin, silicone resin) In some cases, the graphite film has a poor adhesion to various adhesives due to its chemical structure and high chemical resistance.

<4> Adhesiveness between graphite film and inorganic layer In addition, for the purpose of contributing to electrical insulation and high emissivity to graphite, a flexible inorganic heat radiation film having an infrared radiation effect may be formed on the graphite surface. As a method of forming a heat radiation film, a liquid material in which a silanol-containing substance is dispersed with isopropyl alcohol, for example, HYPER COAT-HR (MicroCotech) is sprayed directly on one or both sides of graphite by spraying, and then It is formed by a dried film. However, conventional graphite films have very poor wettability due to their chemical structure and high chemical resistance, making it difficult to apply uniformly. Moreover, even if the inorganic layer could be formed, it was clear that the adhesion between the graphite film and the inorganic layer was very small, such as when the sheet was bent, the inorganic layer was peeled off from the graphite layer.

  The present invention was made to solve the above problems <1> to <4>, and provides a graphite film excellent in adhesiveness of an adhesive, a pressure-sensitive adhesive, and an inorganic layer.

That is, the present invention relates to (1) a graphite film in which the ratio of O / C element by surface element analysis in XPS measurement is 0.01 or more and 0.30 or less and the contact angle with water is 50 degrees or less (2) The graphite film according to (1), wherein unevenness having a shortest diameter of 0.1 to 5 μm is present on the surface of 5 pieces / 25 μm ² or more, (3) corona treatment, flame treatment, ultraviolet treatment, The graphite film according to (1) or (2), which has been subjected to at least one treatment of a group of film surface treatments consisting of alkali treatment, primer treatment, sandblast treatment, and plasma treatment,
(4) The graphite film is a graphite film obtained by heat-treating a raw material film composed of a polymer film and / or a carbonized polymer film at a temperature of 2000 ° C. or higher (1) to (3) The graphite film according to any one of the above, (5) the polymer film is polyimide, polyamide, polyoxadiazole, polybenzothiazole, polybenzobisthiazole, polybenzoxazole, polybenzobisoxazole, The graphite film according to (4), comprising at least one polymer selected from polyparaphenylene vinylene, polybenzimidazole, polybenzobisimidazole, and polythiazole, 6) The graphite film Wherein the planar direction of the thermal diffusivity is 8.0 × ¹⁰ -4 ^m 2 / s or more, a graphite film according to any one of (1) to (5), (7) the graphite The graphite film according to any one of (1) to (6), wherein the density of the film is 1.5 g / cm ³ or more, and (8) the thickness of the graphite film is 100 μm or less. It is related with the graphite film in any one of (1)-(7) characterized by the above-mentioned.

Also, (9) processing the power density of the corona treatment is 200W · min / ^{m 2} or more 50000W · min / ^{m 2} or less (3) be a method for producing a graphite film according to any one of the - (8) (10) The method for producing a graphite film according to (9), wherein in the corona treatment, the treatment is performed using an electrode coated with a dielectric.

  Provided is a graphite film having improved release properties of a release liner and excellent adhesion to an adhesive, an adhesive, and an inorganic layer.

The first of the present invention is a graphite film in which the ratio of O / C element by surface element analysis in XPS measurement is 0.01 or more and 0.30 or less and the contact angle with water is 50 degrees or less. More specifically, it is a graphite film in which irregularities having a shortest diameter of 0.1 to 5 μm of 5 pieces / 25 μm ² or more exist on the surface of the graphite film, and a graphite film subjected to a surface treatment represented by corona treatment. . The second is the present invention, the processing power density of the corona treatment is a 200W · min / ^{m 2} or more 50000W · min / ^{m 2} or less is a manufacturing method of the graphite film, and further, coated with a dielectric It is a method for producing a graphite film, wherein the treatment is performed using an electrode.

<Corona treatment>
Corona treatment is widely used in the plastics industry as a means of solving the difficulty of bonding. The manifestation of the effect is that a functional group having electrical polarity is formed on the surface by a chemical reaction to improve hydrophilicity and adhesion (eg, Patent Document 3). Corona treatment is usually applied to polymer films, and the electrodes are molded to the length that should be corona treated, in other words, approximately the width of the polymer film, and the polymer film is highly insulated. It runs along the roll between the formed roll and the corona electrode of the filament. And a high energy is made to act on the said corona electrode, and a corona discharge process can be given to a polymer film by raise | generating a corona discharge.
JP-A-2004-51712 <Coating of corona-treated electrode with dielectric> However, the corona treatment is usually limited to the purpose of improving the adhesiveness of an insulating material such as a polymer film, and exhibits electrical conductivity. Little is known about corona treatment of materials. When there is conductivity, a hole may be formed in the film and the film may be damaged, or corona generation may be difficult. The normal corona treatment as described above is usually limited to an insulator such as a polymer film and cannot be performed on a conductive film. Until now, the corona treatment to the electroconductive substance was hardly performed. For example, when corona treatment is performed on a material having conductivity such as graphite as in the present invention, a corona treatment machine having a structure in which a dielectric is coated on an electrode as shown in FIG. 2). If a tube made of silicone rubber, fluororubber, natural rubber or the like is used as the material to be coated, it may be easily attached to the electrode. Silicone tubes are particularly good because they have heat resistance. <Power Density of Corona Discharge Treatment> The power density of the corona discharge treatment at this time is 200 [W · min / m 2] or more and 50000 [W · min / m 2] or less, preferably 500 [W · min / m 2] or more and 30000 [W · min / m2] or less, more preferably 1000 [W · min / m2] or more and 10000 [W · min / m2] or less, but considering the type, thickness, storage period, and productivity of the graphite film It is set as appropriate based on experience. When the power density is smaller than 200 [W · min / m 2], the wettability of the graphite surface is not greatly improved, and only graphite having low adhesion to the adhesive and adhesive can be obtained. Moreover, when the power density is small, the wettability and adhesion of the surface may deteriorate in about several hours. Usually, the power density of corona discharge treatment to a polymer film such as a polyimide film is about 200 to 300 [W · min / m 2]. However, when corona treatment is applied to a graphite film, the power density is higher than that of the polymer film. The power density is better. This is because the graphite film has a very high chemical structure, so that a very high energy is required to contribute the functional group. On the other hand, however, it is not preferable that the processing power density is excessive in some respects described below. Therefore, there is an upper limit value of power density. Specifically, when the processing power density is larger than 50000 [W · min / m 2], the following problems occur. The first point is that the corona treatment requires a very high electric power, and therefore the cost is wasted due to excessive treatment. Second, the effect reaches its peak when the corona treatment power density is increased to a certain degree. Third, if the power density is too high, the graphite film may be damaged and the strength of the film may be deteriorated. Fourth, the durability of the corona treatment machine is very poor. From the above viewpoint, it is not good if the power density is too high. The material of the electrode is not particularly limited, and is appropriately selected and set empirically. The corona discharge treatment may be performed once or a plurality of times. The corona treatment may be performed only on one side of the graphite film, but it may be performed on both sides, and is not limited at all. <Ratio of O / C element on the surface of graphite film> In the present invention, it was found that functional groups derived from oxygen elements (carbonyl group, carboxyl group, etc.) were introduced to the surface by subjecting the graphite film to corona treatment. . As will be described later, the introduced functional group improves adhesion with an adhesive, an adhesive, and the like. The ratio of the O / C element on the surface of the graphite film of the present invention is 0.01 or more and 0.30 or less, preferably 0.05 or more and 0.25 or less, and more preferably 0.1 or more and 0.20 or less. If the O / C element ratio on the surface of the graphite film is 0.01 or more, the concentration of oxygen functional groups (carbonyl group, carboxyl group, etc.) present on the surface is high, and the adhesion between the adhesive layer, the adhesive layer, etc. and the graphite Will improve. On the other hand, if the O / C element ratio on the surface is less than 0.01, the concentration of oxygen functional groups present on the surface is low, and peeling between the adhesive layer, the adhesive layer, etc. and the graphite layer is likely to occur. Further, when the O / C element ratio on the surface of the graphite film is larger than 0.30, the improvement of the surface adhesion has reached its peak. Therefore, considering the cost of corona treatment, it is better to be 0.30 or less.

  The ratio of the O / C element on the graphite surface can be measured by XPS measurement (manufactured by ULVAC-PHI Co., Ltd., ESCA5800 type). Details are described in the Examples column.

<Contact angle with water>
The contact angle of the graphite film of the present invention with respect to water is 50 degrees or less, preferably 21 degrees or less, and more preferably 12 degrees or less. When the contact angle with water, which is also an index for improving wettability, is small, the adhesion with the pressure-sensitive adhesive and adhesive is increased. Further, even when a liquid material in which a substance containing silanol is dispersed in isopropyl alcohol or the like is applied to the graphite surface to form an inorganic layer or the like, uniform application is possible. If the contact angle with water is larger than 50 degrees, the adhesion between the pressure-sensitive adhesive and the adhesive is weak, so that it is difficult to combine graphite with various materials.

  The method for measuring the contact angle with water on the surface of the graphite film is shown below.

  The contact angle of the graphite film subjected to the corona treatment was measured 60 minutes after the treatment. Ion exchange water was used as a dropping liquid for contact angle measurement. As a measuring device for the contact angle, CA-DT • A type manufactured by Kyowa Interface Science Co., Ltd., and a 15 gauge gauge needle manufactured by Kyowa Interface Science Co., Ltd. was used. The liquid diameter in the droplet dropping direction was about 2.0 mm, 5 points were dropped per sample surface at 23 ° C., and the contact angle after 30 seconds was measured. The average value of the three contact angles excluding the maximum and minimum one of the five contact angles was rounded off and shown in the table.

<Irregular shape pattern with the shortest diameter of 0.1 to 5 μm on the surface of the graphite film>
As in the present invention, irregularities (patterns with an irregular shape) having a shortest diameter of 0.1 to 5 μm shown in FIG. 5 are observed on the surface of the graphite film. Specifically, 5 pieces / 25 μm ² or more, preferably 10 pieces / 25 μm ² or more, and more preferably 15 pieces / 25 μm ² or more. When the irregularities are present on the surface of the graphite film, the adhesion with adhesives, pressure-sensitive adhesives, etc. increases. The mechanism is as follows.

  In general, the SEM image of the graphite film surface obtained by the polymer decomposition method shows large wrinkles when observed at a low magnification (FIG. 3). When each individual wrinkle is observed at a high magnification, as shown in FIG. Is very smooth. However, unevenness as shown in FIG. 5 is observed on the surface of the graphite film subjected to the corona treatment at high magnification. It is not clear what the irregularities on the surface of the graphite film after the corona treatment are, but it is probably a micro irregularity on the surface formed by corona discharge accompanying the corona treatment.

  In addition to the contribution of the surface functional group as described above, it is considered that the adhesion effect with the adhesive, the pressure-sensitive adhesive, and the inorganic layer is strengthened by an increase in the anchor effect on the surface of the graphite film due to these irregularities.

On the other hand, when the number of irregular shapes having a shortest diameter of 0.1 to 5 μm on the graphite film surface is less than 5/25 μm ^{2, the} anchor effect as described above tends to be small.

  The surface of the graphite film can be observed using a Hitachi scanning electron microscope S-4500 type. Details are described in the Examples column.

<Other surface treatment methods for graphite films>
In addition to corona treatment, there are flame treatment, ultraviolet treatment, alkali treatment, primer treatment, sandblast treatment, plasma treatment and the like as methods for improving the contact angle and adhesion of graphite film to water. By treating these methods in combination, the wettability and adhesion of the graphite film can be improved. Further, when the graphite surface is treated with sandpaper or the like, the adhesion with the pressure-sensitive adhesive, adhesive, or inorganic layer can be improved by the anchor effect.

<Graphite film used in the present invention>
A commercially available graphite film can be used without any particular restriction on the structure and performance of the graphite film used in the present invention. As the graphite film of the present invention, a graphite film obtained by heat treating a polymer, a graphite film obtained by expanding using natural graphite as a raw material, and the like are suitable. Polymer pyrolysis is a heat treatment of polymer films such as polyoxadiazole, polyimide, polyphenylene vinylene, polybenzimidazole, polybenzoxazole, polythiazole or polyamide under an inert atmosphere such as argon or helium or under reduced pressure. It is a method to do. The expanding method is a method in which expanded graphite obtained by expanding a graphite layer by heating after immersing powdered and flake shaped natural graphite in an acid is roll-pressed.

<Graphite film obtained by polymer decomposition method>
Examples of the graphite film that is subjected to corona treatment, improves wettability, and particularly increases the adhesion to the pressure-sensitive adhesive, adhesive, and inorganic layer include a graphite film obtained by a polymer decomposition method. The graphite film obtained by the polymer decomposition method has extremely poor surface wettability due to a highly oriented chemical structure (contact angle with water is close to 90 degrees). Therefore, it has been difficult to combine with various substances so far. However, it has been found that wettability can be greatly improved by applying corona treatment.

  In addition, the graphite film obtained by the polymer decomposition method has a high molecular structure in which aromatic rings are regularly arranged on the horizontal surface of the film surface. Can withstand. For this reason, the graphite film obtained by the polymer decomposition method can be said to be a graphite film suitable for corona treatment.

  On the other hand, the graphite film obtained by the expanding method is less effective than the graphite film obtained by the polymer decomposition method as the graphite used in the present invention. The graphite film originally obtained by the expand method has better wettability than the graphite film obtained by the polymer decomposition method (water wettability is around 60 degrees). Is smaller than the polymer decomposition method. Further, although the wettability of the graphite film by the expanding method is improved by corona treatment, it is easily peeled off when used even if combined with a pressure-sensitive adhesive or an adhesive. This is because the purity of the graphite film itself is poor, so outgassing occurs when used at high temperatures, and peeling occurs between the pressure-sensitive adhesive or adhesive and the graphite layer. In addition, graphite by the expanding method is very weak because graphite powder is processed into a film by high-pressure pressing together with a binder, and the film may be broken by corona treatment.

  However, the graphite film to be subjected to the corona treatment in the present invention is not limited only to the graphite film obtained by the polymer pyrolysis method, and even in the graphite film obtained by the expanding method, wettability, pressure-sensitive adhesive, etc. The adhesion is improved and the effect can be sufficiently expected.

<Thermal diffusivity of graphite film>
Since a graphite film has a highly oriented chemical structure, it requires a lot of energy to destroy its molecular structure and introduce functional groups. Moreover, since the graphite film is a conductive substance, the energy of the corona discharge is dispersed by the film itself. Therefore, it is more difficult to introduce a functional group than a normal plastic film.

  Corona treatment for graphite films often requires higher energy than corona treatment for ordinary plastic films. Further, as described above, since the electrode is covered with a dielectric, heat is accumulated in the electrode portion, and the temperature tends to be high. When the thermal diffusivity of the graphite film is high, the heat accumulated in the electrode portion is dissipated through the graphite film, so that the heat accumulation is alleviated. For these reasons, it is better that the thermal diffusivity of the graphite film subjected to the corona treatment is higher.

The thermal diffusivity in the plane direction of the graphite film of the present invention is 5.2 × 10 ⁻⁴ m ² / s or more, preferably 7.3 × 10 ⁻⁴ m ² / s or more, and more preferably 9.0 × 10. ^-4 m ² / s or better. When it becomes 7.3 × 10 ⁻⁴ m ² / s or more, the heat generated by the electrode generated during the corona treatment can be dissipated and deterioration of the electrode can be suppressed. On the other hand, if it is less than 5.2 × 10 ⁻⁴ m ² / s, the thermal diffusibility is inferior, and the corona-treated electrode is likely to deteriorate.

<Thickness of graphite film>
As the graphite film that is easily corona-treated and easily improves the adhesion to the pressure-sensitive adhesive and adhesive, a thin film is preferable. The specific level of the thickness of the graphite film used in the present invention is 100 μm or less, preferably 70 μm or less, more preferably 50 μm or less. By subjecting the graphite film of 100 μm or less to corona treatment, a composite sheet that is difficult to peel off from the adhesive layer, the adhesive layer, etc. and the graphite layer can be obtained when the heat generating part of an electronic device or the like is used. On the other hand, if the thickness is greater than 100 μm, it tends to peel off during use. This is because the graphite film discharges impurities or absorbed moisture as outgas when the temperature becomes high. When the thickness is large, the amount of this outgas increases, and it becomes easy to peel from the interlayer between the adhesive and the graphite film.

  However, the graphite film that is subjected to corona treatment to improve wettability is not limited to a thin film, and the effect can be sufficiently expected even with a thick graphite film.

  As a method for measuring the thickness of the graphite film, a film of 50 mm × 50 mm was used with a thickness gauge (“thickness gauge” available from HEIDENHAIN Co., Ltd.), and any 10 points in a constant temperature room at 25 ° C. Were measured and averaged to obtain a measured value. The heat radiation film layer took the difference between the thickness of the heat radiation sheet and the thickness of the heat conduction layer.

<Density of graphite film>
As the graphite film that is easily corona-treated and easily improves the adhesiveness with the pressure-sensitive adhesive, the adhesive, and the inorganic layer, a high-density film is preferable. The specific level of the density of the graphite film used in the present invention is 1.5 g / cm ³ or more, preferably 1.6 g / cm ³ or more, more preferably 1.7 g / cm ³ or more. In general, a graphite film with a high density has less irregularities on the surface of the graphite, so that corona treatment can be performed more densely, and a graphite having a very large adhesion to an adhesive (adhesive) and an inorganic layer can be obtained. Can do. On the other hand, when the density is smaller than 1.5 g / cm ³ , the adhesive force between the adhesive and the pressure-sensitive adhesive and the graphite film may be small and peel off. This is because if the density is low, the amount of moisture absorbed by the graphite itself increases, and it tends to peel off due to outgassing during use. In addition, a graphite film having a low density generally has large surface irregularities, and a surface that is not subjected to corona treatment is generated, so that the adhesion with the adhesive is reduced.

<Excellent graphite film>
Furthermore, since thermal conductivity and strength are superior to conventional commercially available graphite films, it is more preferable to use the following graphite film for film surface treatment such as corona treatment. This is because excellent thermal conductivity and strength are suitable for film surface treatment such as corona treatment.

  (1) The graphite film is a graphite film characterized in that the cross-sectional pattern of the surface layer and the cross-sectional pattern other than the surface layer have at least different portions.

  (2) The graphite film is a graphite film having a substantially rectangular shape with a short side of 5 μm or more formed as a result of laminating a substantially rectangular shape having a thickness of less than 1 μm in a part of the cross-sectional pattern of the surface layer. It is a graphite film characterized by this.

  (3) The graphite film is a graphite film in which an irregularly shaped pattern having a shortest diameter of 0.1 to 50 μm is observed inside.

  (4) The graphite film is a graphite film obtained by heat-treating a raw material film comprising a polymer film and / or a carbonized polymer film at a temperature of 2000 ° C. or higher.

  (5) The graphite film is made of a polymer film and / or a carbonized polymer film, which is brought into contact with a substance containing a metal before and / or during heat treatment at a temperature of 2000 ° C. or higher. It is a graphite film characterized by being a graphite film obtained by heat treatment.

  (6) A step of holding a raw material film made of a polymer film and / or a carbonized polymer film in a container that can be directly energized by applying a voltage, and graphitizing while energizing by applying a voltage to the container. It is a graphite film characterized by being obtained by the manufacturing method characterized by including.

  (7) The graphite film holds the raw material film in a container (A) capable of energizing the raw material film (FIG. 6), and further the container (B) capable of energizing the container (A) (FIG. 7). The graphite film is obtained by a production method characterized by including a step of graphitizing while being encapsulated and energizing the whole.

  (8) The polymer film is polyimide, polyamide, polyoxadiazole, polybenzothiazole, polybenzobisthiazole, polybenzoxazole, polybenzobisoxazole, polyparaphenylene vinylene, polybenzimidazole, polybenzobisimidazole A graphite film comprising at least one polymer selected from polythiazole.

  (9) The graphite film is characterized in that the polyimide film is a polyimide film prepared by imidizing a precursor polyamic acid with a dehydrating agent and an imidization accelerator.

<Partner material to be bonded to graphite film>
The graphite film of the present invention may be bonded to a resin material (including an adhesive, an adhesive, etc.) and an inorganic material. Examples of the resin include polyimide resin, epoxy resin, phenol resin, acrylic resin, silicone resin, polyethylene resin, polypropylene resin, polyamide resin, and polyester resin. Examples of the inorganic material include ceramic materials such as silicon oxide, titanium oxide, and alumina, and metal materials such as copper, aluminum, magnesium, iron, and SUS.

<Applications>
Since the graphite film of the present invention has high wettability on the film surface and excellent adhesion to an adhesive and a pressure-sensitive adhesive, it can be combined with various materials using the pressure-sensitive adhesive or the adhesive. Moreover, since the graphite film and graphite composite film which concern on this invention are excellent in heat conductivity, it is possible to use it for the use in connection with all the heat | fever. Furthermore, since it is excellent in flexibility and electrical conductivity, it is particularly suitable for applications utilizing this feature. The characteristics of graphite film that excel in heat conduction are that it is necessary for applications that need to transfer heat, escape heat, spread heat, make heat uniform, make heat response faster, warm faster, cool faster. Is suitable. By spreading the heat instantaneously, it is possible to prevent and mitigate sudden temperature changes, or to avoid local heat concentration. On the other hand, it can be used for applications that cause sudden changes or detect slight changes in heat. By relaxing the heat, strength and adhesiveness can be ensured even in a high temperature environment. In addition, by transferring heat uniformly and accurately, characteristics such as high accuracy, high quality, and high image quality can be improved. When used in manufacturing equipment, it is possible to improve productivity by shortening tact time, improving heating / cooling efficiency, improving drying efficiency, speeding up, and shortening waiting time by taking advantage of the ability to transport heat quickly and in large quantities. . In addition, it is possible to reduce defects and enhance the heat retaining function by uniformizing heat and quick transportation. In addition, by adopting it in various devices, it is possible to save space, thin film, reduce weight, simplify the mechanism, improve the degree of freedom of installation, and eliminate unnecessary parts to save power and reduce noise. It becomes possible. In addition, since heat can be released, there is no deterioration in characteristics even in heat cycle environmental tests and annealing treatments, solder heat resistance, adhesive layer adhesion, heat resistance, reliability, durability can be improved, and heat insulation can be improved. It can also be increased and protected from heat-sensitive parts. As a result, maintenance can be reduced, cost can be reduced, and safety can be improved.

  Specific applications include the following. For example, electronic devices such as servers, server personal computers, desktop personal computers, word processors, keyboards, and games, portable electronic devices such as notebook computers, electronic dictionaries, PDAs, mobile phones, portable game devices, and portable music players. Liquid crystal display, transmissive liquid crystal display device, reflective LCD panel, plasma display, SED, LED, organic EL, inorganic EL, liquid crystal projector, rear projector, liquid crystal panel, backlight device (variation prevention, temperature unevenness improvement), TFT substrate , Electron emission devices, electron source substrates and face plates (weight reduction), display panel frame composites, light emitting devices, charge injection light emitting devices, optical and display devices such as watches, and parts thereof. Light emitting / illuminating devices such as lasers, semiconductor lasers, light emitting diodes, fluorescent lamps, incandescent bulbs, light emitting dots, issuing element arrays, lighting units, flat light emitting devices, and document lighting devices. Single or multiple recording heads (heater, heat insulating material, heat storage layer, etc.) for inkjet (spreading ink using thermal energy), line heads, long ink heads, solid ink jet devices, heat dissipation for ink jet heads Ink jet printer (ink head) devices such as plates, ink cartridges, ink jet head silicon substrates, ink jet drive drivers, and heating sources (halogen lamp heaters) for heating ink jet recording paper, and parts thereof. Toner cartridge, device having laser light source, scanning optical device (light emitting unit, deflection scanning polygon mirror, polygon mirror rotation driving motor, optical component leading to photosensitive drum), exposure device, developing device (photosensitive drum, light receiving member, Development roller, development sleeve, cleaning device), transfer device (transfer roll, transfer belt, intermediate transfer belt, etc.), fixing device (fixing roll (core, outer peripheral member, halogen heater, etc.), surf heater, electromagnetic induction heater, ceramic Electrophotographic equipment consisting of heater, fixing film, film heating device, heating roller, pressure roller / heating body, pressure member, belt nip), sheet cooling device, sheet loading device, sheet discharge device, sheet processing device, etc. Image forming apparatus and parts thereof. In the fixing device, the effect of improving the thermal characteristics due to the use of graphite film is remarkable, including uneven image quality in the width direction, image quality defects, image quality variation in continuous paper feeding, rise / fall time, real-time support, high temperature followability, paper feeding The temperature difference, wrinkle, strength, power saving, on-demand heating, high temperature offset and low temperature offset, overheating of the heater peripheral member, and heater cracking can be greatly improved. Other recording devices such as thermal transfer recording devices (ribbons), dot printers, sublimation printers. Semiconductor-related parts such as semiconductor elements, semiconductor packages, semiconductor sealing cases, semiconductor die bonding, liquid crystal display element driving semiconductor chips, CPUs, MPUs, memories, power transistors, and power transistor cases. Printed circuit board, rigid wiring board, flexible wiring board, ceramic wiring board, build-up wiring board, mounting board, high-density mounting printed circuit board, (tape carrier package), TAB, hinge mechanism, sliding mechanism, through hole, resin packaging Wiring boards such as sealing materials, multilayer resin moldings, and multilayer boards. CD, DVD (optical pickup, laser generator, laser receiver), Blu-ray disc, DRAM, flash memory, hard disk drive, optical recording / reproducing device, magnetic recording / reproducing device, magneto-optical recording / reproducing device, information recording medium, optical recording disc , Magneto-optical recording medium (translucent substrate, optical interference layer, domain wall motion layer, intermediate layer, recording layer, protective layer, heat dissipation layer, information track), light receiving element, photodetector element, optical pickup device, magnetic head, optical Magnetic recording magnetic heads, semiconductor laser chips, laser diodes, laser drive ICs and other recording devices, recording / reproducing devices, and parts thereof. Digital camera, analog camera, digital single-lens reflex camera, analog single-lens reflex camera, digital camera, digital video camera, camera-integrated VTR, camera-integrated VTR IC, video camera light, electronic flash device, imaging device, imaging tube cooling Apparatus, imaging apparatus, imaging element, CCD element, lens barrel, image sensor and information processing apparatus using the same, X-ray absorber pattern, X-ray mask structure, X-ray imaging apparatus, X-ray exposure apparatus, X-ray Flat detector, X-ray digital imaging device, X-ray area sensor substrate, electron microscope sample cooling holder, electron beam drawing device (electron gun, electron gun, electron beam drawing device), radiation detection device and radiation imaging system, scanner, Image reading device, moving image pickup device and still image pickup device, image recording device such as a microscope, and parts thereof. Primary batteries such as alkaline batteries and manganese batteries, secondary batteries such as lithium ion batteries, nickel metal hydride and lead storage batteries, electric double layer capacitors, electrolytic capacitors, assembled batteries, solar cells, solar cell module installation structures, photoelectric conversion substrates, Heat dissipation materials for battery devices such as photovoltaic element arrays, power generation elements, and fuel cells (power generation cells, outside the housing, inside the fuel tank). Power supplies (rectifier diodes, transformers), DC / DC converters, switching power supply devices (forward type), current leads, superconducting device systems, etc. and their components. Motors and parts such as motors, linear motors, planar motors, vibration wave motors, motor coils, circuit units for rotational control drive, motor drivers, inner rotor motors, vibration wave actuators, etc. Vacuum processing equipment, semiconductor manufacturing equipment, vapor deposition equipment, thin film single crystal semiconductor layer manufacturing equipment, plasma CVD, microwave plasma CVD, sputtering equipment, vacuum chambers, vacuum pumps, vacuum pumps, cryotraps, cryopumps, etc., electrostatic chucks , Vacuum vacuum chucks, pin chuck type wafer chucks, sputtering targets, semiconductor exposure devices, lens holding devices and projection exposure devices, photomasks, and other deposited film manufacturing devices (temperature constant, quality stable) and parts thereof. Heat treatment equipment by resistance heating / induction heating / infrared heating, dryer, annealing equipment, laminating equipment, reflow equipment, heat bonding (crimping) equipment, injection molding equipment (nozzles / heating section), resin molding dies, LIM molding, rollers Molding equipment reformed gas production (reforming part, catalyst part, heating part, etc.) stamper, (film, roll, recording medium), bonding tool, catalyst reactor, chiller, color filter substrate coloring device, resist Various manufacturing devices such as heating / cooling devices, welding equipment, magnetic induction heating films, anti-condensation glass, liquid remaining amount detection devices, heat exchange devices, and parts thereof. Heat insulation devices such as heat insulation materials, vacuum heat insulation materials, and radiation heat insulation materials. Chassis, housing, and exterior cover for various electronic and electrical equipment and manufacturing equipment. Heat dissipation components such as radiators, openings, heat pipes, heat sinks, fins, fans, and heat dissipation connectors. Cooling parts such as Peltier elements, electrothermal conversion elements, and water-cooled parts. Temperature control device, temperature control device, temperature detection device and parts. Heater related parts such as thermistors, thermo switches, thermostats, thermal fuses, overvoltage protection elements, thermo protectors, ceramic heaters, flexible heaters, composites of heaters, heat conduction plates and insulation materials, heater connectors and electrode terminal parts. Suitable for radiating parts with high emissivity, electromagnetic shielding parts such as electromagnetic shielding and electromagnetic wave absorbers, composites with metals such as aluminum, copper and silicon, and composites with ceramics such as silicon nitride, boron nitride and alumina is there.

<Usage etc.>
When the graphite film according to the present invention is actually applied to a heating element, a heat sink, a heat pipe, a water-cooled cooling device, a Peltier element, a casing, a hinge, etc., fixing with them, thermal diffusibility, heat dissipation, handling In order to improve the properties, it is preferable to form an adhesive layer, a resin layer, a ceramic layer, a metal layer, an insulating layer, a conductive layer or the like on one side and / or both sides.

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

<Graphite films A, B, C, D, E>
[Production Method of Polyimide 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.

  The drying conditions for film production when the finished thickness is 75 μm are shown below. The mixed solution layer on the aluminum foil was dried in a hot air oven at 120 ° C. for 240 seconds to form a self-supporting gel film. The gel film was peeled off from the aluminum foil and fixed to the frame. Furthermore, the gel film was heated stepwise in a hot air oven at 120 ° C. for 30 seconds, 275 ° C. for 40 seconds, 400 ° C. for 43 seconds, 450 ° C. for 50 seconds, and a far infrared heater at 460 ° C. for 23 seconds. And dried.

As described above, a polyimide film having a thickness of 75 μm (polyimide film A: elastic modulus 3.1 GPa, water absorption 2.5%, birefringence 0.10, linear expansion coefficient 3.0 × 10 ⁻⁵ / ° C.) Manufactured. In addition, when producing films with other thicknesses, the firing time was adjusted in proportion to the thickness. For example, in the case of a film having a thickness of 50 μm, the baking time was set to 2/3 times that in the case of 75 μm, and in the case of a film having a thickness of 175 μm, it was set to 7/3 times. When the thickness is large, it is necessary to take a sufficient baking time at a low temperature in order to prevent foaming due to evaporation of the solvent or imidization catalyst of the polyimide film.

[Method for producing carbonized film A]
A 75 μm-thick polyimide film A was sandwiched between graphite plates, heated to 1000 ° C. in a nitrogen atmosphere using an electric furnace, and then heat-treated at 1000 ° C. for 1 hour for carbonization treatment (carbonization treatment). This carbonized film was designated as carbonized film A.

[Production Method of Carbonized Film B]
A polyimide film B having a thickness of 50 μm was sandwiched between graphite plates, heated to 1000 ° C. in a nitrogen atmosphere using an electric furnace, and then heat-treated at 1000 ° C. for 1 hour for carbonization treatment (carbonization treatment). This carbonized film was designated as carbonized film B.
[Production Method of Carbonized Film C]
A polyimide film A having a thickness of 175 μm was sandwiched between graphite plates, heated to 1000 ° C. in a nitrogen atmosphere using an electric furnace, and then heat-treated at 1000 ° C. for 1 hour for carbonization treatment (carbonization treatment). This carbonized film was designated as carbonized film C.

[Production Method of Graphite Film A]
Carbonized film A (400 cm ² (length 200 mm × width 200 mm)) obtained by carbonization treatment is sandwiched from above and below by plate-like smooth graphite of length 270 mm × width 270 mm × thickness 3 mm, and length 300 mm × shown in FIG. It was held in a graphite container (container (A)) having a width of 300 mm and a thickness of 60 mm and capable of direct current application.

  As schematically shown in FIG. 7, the container (A) is a cylindrical container (B) that can be directly energized in the surface direction of the raw material film (more specifically, specifically shown in FIG. Such a directly energizable cylindrical container (B) with a lid is held so as to be parallel to the height direction of the cylinder, and the outer periphery of the container (A) is covered with carbon powder (container (A) And the container (B) were filled with carbon powder), and the container (A) was held so as not to contact the container (B) as shown in FIG. As shown in FIG. 9, with the outer periphery of the container (B) covered with carbon powder, a voltage was applied parallel to the surface direction of the raw material film (in the diameter direction of the cylinder of the container (B)) and turned on. The container (A) was heated to 3000 ° C. to produce a graphite film. In addition, the angle which the straight line which shows the electricity supply direction to a raw material film and the normal line with respect to the surface direction of a raw material film make is 90 degree | times.

  Moreover, FIG. 7 mentioned above is a schematic diagram before covering a container (B).

The heat-treated graphite was compressed in the thickness direction with a single plate press to obtain a graphite film A (thickness 40 μm).
[Production Method of Graphite Film B]
A graphite film B (25 μm) was produced in the same manner as the graphite A except that the carbonized film B obtained by the carbonization treatment was set.

[Production Method of Graphite Film C]
After applying a 10 wt% methanol solution of iron nitrate to carbonized film C obtained by carbonization treatment, it was sandwiched between graphite plates, set in a graphite container (container (A)), and not compressed after energization heating. A graphite film C (85 μm) was produced in the same manner as the graphite film A.

[Graphite film D]
The graphite film D is a PGS graphite film “EYGS182310” manufactured by Matsushita Electric Industrial Co., Ltd.

[Method for producing graphite film E]
In the presence of an oxidizing agent (hydrogen peroxide, perchloric acid, etc.), sulfuric acid, nitric acid, etc. are inserted between natural scaly graphite layers, and the formed intercalation compound is rapidly heated at a high temperature of about 900 to 1200 ° C. It was decomposed and gasified, and the graphite was expanded by expanding the graphite layer by the gas pressure at this time. The expanded graphite obtained as described above was compression-preformed and then rolled with a roll to obtain a graphite film E having a thickness of 250 μm and a density of 1.0 g / cm ³ .

<Surface element analysis by XPS measurement of graphite film>
The surface state of the graphite film was analyzed by XPS (manufactured by ULVAC-PHI Co., Ltd., ESCA5800 type). Mg was used for the counter cathode at an output of 400 W, and measurement was performed under a vacuum of 10 ⁻⁶ Pa or less. Based on the measurement results, the composition ratio of the surface elements was derived by comparing the peak areas with the strongest intensity of each element. Specifically, the composition ratio of the surface elements was derived from the ratio of the peak areas of C (near 280 eV) and O (near 540 eV).

<SEM observation of graphite film>
The surface of the graphite film was observed using a scanning electron microscope (SEM) (product name: S-4500 manufactured by Hitachi) at an acceleration voltage of 10 kV.

<Measurement of thermal diffusivity in the film surface direction by the optical alternating current method>
The progress of graphitization was determined by measuring the thermal diffusivity in the film surface direction. The higher the thermal diffusivity, the more remarkable the graphitization. The thermal diffusivity was measured by cutting a graphite film into a 4 × 40 mm sample shape using a thermal diffusivity measuring device (“LaserPit” available from ULVAC-RIKO Co., Ltd.) by an optical alternating current method, Measurements were taken at 10 Hz.

<Density measurement of graphite film>
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.

<Thickness measurement 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.

<Peelability of release liner>
As for the peelability of the release liner, the graphite film and acrylic adhesive (Nitto Denko, trade name: 5601) are bonded together, and when the release liner is peeled off, the peeling is observed from the graphite layer to the adhesive layer. It was observed visually. A sample in which peeling was confirmed as a whole was indicated as “x”, a sample partially confirmed as “Δ”, and a sample having no peeling as “◯”. Note that a laminator (GL835PRO) available from Nippon BG Co., Ltd. was used for bonding the pressure-sensitive adhesive and the graphite film, and a peeling test was conducted after 3 hours of bonding.

<Adhesion with acrylic adhesive>
Measurement of adhesion with acrylic adhesive was performed by bonding graphite film and polyimide film (Apical AH 50 μm, manufactured by Kaneka Corporation) via acrylic adhesive (trade name: Pyralux LF0100, manufactured by DuPont). It was. The lamination was performed by laminating at a temperature of 150 ° C. using a laminator (GL835PRO) available from Nippon BG Co., Ltd. after lamination, and curing was carried out in an oven at 185 ° C. for 1 hour.

  For the evaluation of adhesion, a sample immediately after being bonded to a 50 mm square was visually observed to confirm whether the graphite layer and the adhesive layer were separated from each other. A sample in which peeling was confirmed as a whole was indicated as “x”, a sample partially confirmed as “Δ”, and a sample having no peeling as “◯”.

<Adhesion with inorganic layer having infrared radiation effect>
The surface of the graphite film A was roughened with sandpaper as a pretreatment, and HYPER COAT-HR manufactured by MicroCotec was applied by spray coating. The film thickness was adjusted to 20 μm. Drying was performed in an oven at 120 ° C. for 40 minutes to produce a heat dissipation sheet.

  For the evaluation of adhesion, a sample immediately after the formation of a 50 mm square inorganic layer was visually observed, and the presence or absence of peeling from the interlayer between the graphite layer and the inorganic layer was confirmed. A sample in which peeling was confirmed as a whole was indicated as “x”, a sample partially confirmed as “Δ”, and a sample having no peeling as “◯”.

Table 1 summarizes the thickness and density of the graphite films used in Examples and Comparative Examples, the contact angle with water, the peelability of the release liner, the adhesion with various adhesives, and the adhesion with the inorganic layer.

(Example 1)
The graphite film A was subjected to a corona discharge treatment with a corona discharge density of 3000 W · min / m ² using a corona master PS-10S available from Shinko Electric Instrument Co., Ltd.

(Example 2)
A graphite film was produced in the same manner as in Example 1 except that the graphite film B was used.

(Example 3)
A graphite film was produced in the same manner as in Example 1 except that the graphite film C was used.

Example 4
A graphite film was produced in the same manner as in Example 1 except that the graphite film D was used.

(Example 5)
A graphite film was produced in the same manner as in Example 1 except that the graphite film E was used.

(Example 6)
A graphite film was produced in the same manner as in Example 1 except that the corona discharge density was 500 W · min / m ² .

(Example 7)
A graphite film was produced in the same manner as in Example 1 except that a corona discharge treatment with a corona discharge density of 180 W · min / m ² was performed.

(Comparative Example 1)
This is a graphite film A that has not been pretreated.

(Comparative Example 2)
Graphite film B that has not been pretreated.

(Comparative Example 3)
This is a graphite film C that has not been pretreated.

(Comparative Example 4)
This is a graphite film D that has not been pretreated.

(Comparative Example 5)
The graphite film E is not pretreated.

<O / C element ratio on the surface of the graphite film>
As a result of measuring the ratio of the O / C element on the surface of the graphite film for Examples 1 to 7 and Comparative Examples 1 to 5, in Examples 1 to 7 after the corona treatment, oxygen was highly concentrated at 0.01 or more. It can be seen that is given. On the other hand, in Comparative Examples 1-5, all were 0.010 or less, and most of the surface elements were carbon.

  Moreover, when Example 1, Example 6, and Example 7 were compared, as the processing power density was larger, more oxygen was applied to the surface, and wettability and adhesiveness were improved. In Example 7, although the ratio of the O / C element was larger than that before the corona treatment, the treatment power density was small, so the concentration of the surface O was small.

  Moreover, when Examples 1-3 and Examples 4-5 are compared, although the corona treatment density is the same, Examples 1-3 have a larger O / C ratio, and much oxygen is provided. I found out. This is because graphite A, B, and C have a higher density and a smoother surface than graphites D and E, and thus the corona-treated area was large.

<Water contact angle>
About Examples 1-7 and Comparative Examples 1-5, as a result of measuring the contact angle with respect to water, in Examples 1-7, all showed very excellent wettability with 50 degrees or less. On the other hand, in Comparative Examples 1-5, all were larger than 50 degree | times and the wettability was inferior. In particular, the graphite films A, B, C, and D of Comparative Examples 1 to 4 that were not pretreated showed large contact angles and very poor wettability. Moreover, when Example 1, Example 6, and Example 7 were compared, it turned out that wettability is improved, so that a corona treatment density is large. Moreover, in Example 7, although the wettability was improved as compared with that before the corona treatment, the wettability was not improved so much as compared with Examples 1 to 6 because the processing power density was small.

  Further, the O / C ratio on the surface of the graphite film and the water contact angle have a correlation. The larger the O / C ratio, the smaller the water contact angle and the better the wettability.

<Existence of irregular pattern>
As a result of performing SEM observation of the surface for Examples 1 to 7 and Comparative Examples 1 to 5, in Examples 1 to 7 after the corona treatment, an irregular pattern as shown in FIG. 5 was observed at high magnification. It was. This is considered that micro unevenness | corrugation was formed in the graphite film surface by corona discharge.

<Adhesion test>
Also in the adhesiveness test with various adhesives and inorganic layers, Examples 1 to 7 showed very high adhesive strength with respect to Comparative Examples 1 to 5. Details are shown below.

(Peelability of release liner)
As a result of investigating the peelability of the release liner for Examples 1 to 7 and Comparative Examples 1 to 5, in Examples 1 to 7, the release liner is peeled from the interlayer between the graphite film and the adhesive material. There was no. On the other hand, in Comparative Examples 1-5, some peeling was confirmed. This is considered to be because the adhesiveness of the graphite film was improved by corona treatment in Examples 1-7.

(Adhesion with acrylic adhesive)
In Examples 1 to 6, peeling was not confirmed immediately after bonding, but in Comparative Examples 1 to 5, peeling was confirmed from between the graphite layer and the adhesive layer over almost the entire surface. This is because the corona treatment improved the wettability of the graphite surface and increased the adhesion. Further, in Example 7, although the adhesion was improved as compared with that before the corona treatment, partial peeling could be confirmed because the corona treatment power density was small.

(Adhesion with inorganic layers)
Next, the adhesion with the inorganic layer will be described.

  In Examples 1-6, peeling was not confirmed, but in Comparative Examples 1-5, peeling was able to be confirmed from between the graphite layer and the adhesive layer over almost the entire surface. This is also because the wettability of the graphite surface was improved by the corona treatment, and the adhesion was increased. Further, in Example 7, although the adhesion was improved as compared with that before the corona treatment, partial peeling could be confirmed because the corona treatment power density was small.

<Thermal diffusivity>
Since the thermal diffusivity of the graphite film E was small, the silicone tube covering the electrode was broken during the corona treatment in Example 5. As described above, the amount of heat generated by the corona treatment is very large, and when a graphite film having a small thermal diffusivity is subjected to corona treatment, the electrode may be burdened. Therefore, a graphite film having a thermal diffusivity as large as possible is suitable for corona treatment.

<Increase of Si>
From XPS measurement of the graphite film after the corona treatment, Si was contributed to the surface with a slight amount. This is because the electrode of Coronamaster PS-10S manufactured by Shinko Electric Instrument Co., Ltd. used this time is coated with silicone resin, and Si contained in this resin is scattered by corona discharge and added to the graphite surface. We were able to estimate that it was done. Although the addition of Si does not directly contribute to the improvement of the adhesion of the graphite film, detection of Si on the graphite surface can be one method for investigating the presence or absence of corona treatment (finding infringement of other companies). .

<Summary>
As described above, by performing corona treatment on the graphite film, it was possible to improve the adhesion with the adhesive material, the adhesive, and the inorganic layer. This is because, as can be seen from the XPS measurement and the measurement of the water contact angle, the functional group derived from oxygen could be contributed to the graphite surface by performing the corona treatment. Moreover, it can be confirmed from SEM observation that micro unevenness is formed on the graphite surface after the corona treatment, and this is considered to be one reason that the adhesion can be improved as described above.

Corona treatment electrode Corona-treated electrode (cross section) Graphite surface before corona treatment by SEM observation (low magnification) Graphite surface before corona treatment by SEM observation (high magnification) Graphite surface after corona treatment by SEM observation (high magnification) Method of holding raw material film in container (A) Holding method of container (A) to container (B) Holding method of container (A) to container (B) Drawing which shows the relationship between the holding method of container (A) and container (B) and the surface direction of the raw material film and the energizing direction (consisting of a straight line indicating the energizing direction to the raw material film and a normal to the surface direction of the raw material film Angle is 90 degrees. Container (A) and container (B) are non-contact.)

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Metal electrode 2 Coating | covering material 11 Smooth flat electricity supply flat plate 12 container (A) for hold | maintaining a raw material film
13 Container holding raw material film (A)
21 Cylindrical container (B)
22 Lid 31 Carbon particles filled between container (A) and container (B) 32 Carbon particles filled around the outside of container (B)

Claims (10)

  A graphite film having an O / C element ratio of 0.01 or more and 0.30 or less by surface element analysis in XPS measurement, and a contact angle with water of 50 degrees or less. The graphite film according to claim 1, wherein the surface has 5 or 25 μm ² or more irregularities having a shortest diameter of 0.1 to 5 μm.   3. The graphite film according to claim 1, wherein at least one treatment of a group of film surface treatments including corona treatment, flame treatment, ultraviolet treatment, alkali treatment, primer treatment, sandblast treatment, and plasma treatment is performed.   The graphite film is a graphite film obtained by heat-treating a raw material film composed of a polymer film and / or a carbonized polymer film at a temperature of 2000 ° C or higher. The graphite film described in 1.   The polymer film is polyimide, polyamide, polyoxadiazole, polybenzothiazole, polybenzobisthiazole, polybenzoxazole, polybenzobisoxazole, polyparaphenylene vinylene, polybenzimidazole, polybenzobisimidazole, polythiazole. The graphite film according to claim 4, comprising at least one polymer selected from the group consisting of polymers. The graphite film according to claim 1, wherein a thermal diffusivity in a plane direction of the graphite film is 8.0 × 10 ⁻⁴ m ² / s or more. The graphite film according to claim 1, wherein the graphite film has a density of 1.5 g / cm ³ or more. The graphite film according to claim 1, wherein the graphite film has a thickness of 100 μm or less. The processing power density of corona treatment, a manufacturing method of the graphite film according to any one of 200W · min / ^{m 2} or more 50000W · min / ^{m 2} or less is claims 3-8.   The method for producing a graphite film according to claim 9, wherein in the corona treatment, the treatment is performed using an electrode coated with a dielectric.