JP7012393B2 - Graphite thin film, graphite thin film laminate, and their manufacturing method - Google Patents

Description

The present invention relates to a graphite thin film, a graphite thin film laminate, and a method for producing them.

Graphite composed of carbon atoms (C) bonded to SP ² has excellent heat resistance, chemical resistance, high conductivity and high thermal conductivity, and occupies an important position as an industrial material. As such graphite, artificially manufactured graphite is generally used. For example, a method of producing sheet-shaped graphite by using an aromatic polymer such as polyimide as a starting material and firing it is industrially used (see Patent Document 1, Non-Patent Documents 1 and 2). ). This artificial graphite sheet is currently widely used as a high heat conductive sheet for heat dissipation of small personal devices such as mobile phones and smartphones. Recently, a method has been developed in which a graphene oxide integrated film obtained by filtering a graphene oxide solution with a filter is reduced by high-temperature treatment to increase the thermal conductivity.

The conventional graphite thin film and its manufacturing process as described above have the problems shown in the following (1) to (3).
(1) Graphite thin films have been commercialized up to a thickness of about 10 μm, and are widely used as heat management materials for electronic devices and the like. In order to utilize the graphite thin film for more sophisticated thermal management such as Thermal Interface Material (TIM), it is preferable to realize a thinness of 1 μm or less. A sheet-shaped graphite thin film produced by firing an aromatic polymer such as polyimide or graphene oxide as a starting material can be made thinner than several μm in thickness due to its manufacturing method. It's very difficult.
(2) In the production method using aromatic polymers such as polyimide as a starting material, carbonization by heat treatment at about 1000 ° C and graphitization by heat treatment at a temperature of 2000 ° C to 3000 ° C or higher are multiple high temperatures. A process is required. Even when reducing the graphene oxide integrated film, a high temperature of 3000 ° C. or higher is required to achieve high thermal conductivity. Therefore, only batch production has been realized so far. Industrially, a high-throughput production method using a continuous production method such as roll-to-roll has been long-awaited, but it has not yet been established.
(3) The problems of (1) and (2) above are major obstacles to the development of the excellent properties of graphite in a wider range of applications.

Japanese Patent No. 1991824

M. Murakami, K. Watanabe, and S. Yoshimura: “High-quality pyrographite films”, Appl. Phys. Lett. Vol.48, No. 23, pp.1594-1596 (1986) M. Murakami, N. Nishiki, K. Nakamura, J. Ehara, H. Okada, T. Kouzaki, K. Watanabe, T. Hoshi and S. Yoshimura, Carbon 30 (1992), pp.255-262.

Therefore, an object of the present invention is to provide a high-quality graphene thin film having an average film thickness of 300 to 400 nm, and a manufacturing method for manufacturing the graphene thin film at a relatively low temperature.
Another object of the present invention is, on one aspect, a graphene thin film laminate containing a high-quality graphene thin film having an average film thickness of 300 to 400 nm and a nickel foil film supporting the graphene thin film, and a method for producing them. Is to provide.

As a result of diligent research to solve the above problems, the present inventors have found that a graphite thin film having a thickness of 1 μm or less can be produced in a simple process and at a low temperature as compared with the conventional method for producing a graphite thin film. Got Furthermore, it was found that this method is suitable as a continuous production method such as roll-to-roll.

The following inventions are disclosed in this application.
<1> A graphite thin film having an average film thickness of 300 to 400 nm, which has peaks in the vicinity of 1580 cm ^-1 and 2680 cm ^-1 in its Raman spectroscopic spectrum, and has no peak in the vicinity of 1350 cm ^-1 . A graphite thin film having a peak whose peak intensity is 5% or less of the peak near 1580 cm ^-1 .
<2> The graphite thin film according to <1>, which has a sheet resistance of 0.5 to 5Ω and / or a thermal conductivity of 1500 to 1700 W / mK.
<3> In the 2θ-θ measurement spectrum of X-ray diffraction, the 2θ angle has a strong and clear peak of (002) diffraction at 26.54 °, and the 2θ angle has a small peak of (004) diffraction at 54.64 °. In the 2θ measurement spectrum in which the θ angle is fixed at 0.5 °, the peak intensity of the 2θ angle is 26.54 ° is 2% of the peak intensity of the 2θ-θ measurement spectrum of 26.54 °. The graphite thin film according to <1> below.
<4> The graphite thin film according to <1>, which is a self-supporting thin film.
<5> A graphite thin film laminate comprising the graphite thin film according to any one of <1> to <4> and a nickel foil supporting the graphite thin film.
<6> The graphite thin film laminate according to <5>, wherein the graphite thin film is provided on both surfaces of the nickel foil.

<7> The nickel foil is heated under vacuum to raise the temperature to a temperature of 1250 to 1350 ° C., the nickel foil is heated and subjected to plasma treatment of carbon-containing gas, and then the nickel foil is continuously subjected to plasma treatment. A method for producing a graphite thin film or a graphite thin film laminate, which is cooled to 830 to 870 ° C. to form a graphite thin film on the surface of the nickel foil.
<8> In the graphite thin film, the carbon produced by decomposing the carbon-containing gas by plasma treatment melts into the nickel foil, and then during the cooling process from 830 to 870 ° C. and / or the plasma treatment at that temperature, the graphite thin film is described. The method for producing a graphite thin film or a graphite thin film laminate according to <7>, wherein the melted carbon is deposited on the surface of the nickel foil and crystallized to be formed on the nickel foil.
<9> The method for producing a graphite thin film or a graphite thin film laminate according to <7> or <8>, wherein the graphite thin film or the graphite thin film laminate is produced by using roll-to-roll.
<10> In the method for producing a graphite thin film or a graphite thin film laminate according to any one of <7> to <9>, a method for producing a graphite thin film from which a nickel foil is removed from the produced graphite thin film laminate.

The graphite thin film of the present invention is of high quality with an average film thickness of about 300 to 400 nm.
Further, according to the manufacturing method of the present invention, a high-quality graphite thin film having an average film thickness of about 300 to 400 nm is manufactured at a significantly lower temperature (about 1300 ° C.) than the conventional method without including a stacking step. It is possible. Therefore, by using this method, it is possible to produce an ultra-thin graphite thin film by a continuous production method such as roll-to-roll.

FIG. 1 is a schematic cross-sectional view of a graphite thin film according to an embodiment of the present invention. FIG. 2 is a schematic cross-sectional view of a graphite thin film / nickel foil / graphite thin film laminate according to the embodiment of the present invention. FIG. 3 is a diagram showing a process of manufacturing a graphite thin film / nickel foil / graphite thin film laminate using plasma irradiation in the embodiment of the present invention. FIG. 4 is a diagram showing a manufacturing process without plasma irradiation in a comparative example for comparison with the manufacturing process in the embodiment of the present invention. The left figure of FIG. 5 is a diagram showing the positions (1) to (5) where Raman spectroscopy was performed on the sample of the example prepared by plasma irradiation, and the right figure of FIG. 5 shows the Raman spectroscopy spectrum of each position. It is a figure which shows. The left figure of FIG. 6 is a diagram showing the positions (1) to (5) where Raman spectroscopy was performed on the sample of the comparative example prepared without plasma irradiation, and the right figure of FIG. 5 is the Raman spectroscopy spectrum of each position. It is a figure which shows. FIG. 7 is a diagram showing an X-ray diffraction spectrum (2θ-θ measurement) of the graphite thin film according to the embodiment of the present invention. FIG. 8 is a diagram showing the results of thermal diffusivity measurement by the periodic heating method of the graphite thin film according to the embodiment of the present invention, and FIG. 8 (a) shows the response temperature positions at heating frequencies 70, 140, 200 and 400 Hz. The relationship between the phase difference θ and the distance L from the heating point (laser light irradiation position) is shown, and FIG. 8B is a diagram showing the relationship between the thermal diffusivity α and the heating frequency f.

Hereinafter, the graphite thin film, the graphite thin film laminate, and the method for producing them will be described with reference to the embodiments and examples. Duplicate explanations will be omitted as appropriate. In addition, when "-" is described between two numerical values to represent a numerical range, these two numerical values are also included in the numerical range.

FIG. 1 shows a graphite thin film 10 according to an embodiment of the present invention. Further, FIG. 2 shows the graphite thin film / nickel foil / graphite thin film laminate 12 according to the embodiment of the present invention. The graphite thin film / nickel foil / graphite thin film laminate (hereinafter, may be simply referred to as “graphite thin film laminate”) includes the graphite thin film 10 and the nickel foil 11.

The graphite thin film according to the embodiment of the present invention has an average film thickness of 300 to 400 nm and is of high quality. High quality means that the Raman spectroscopic spectrum has peaks near 1580 cm ^-1 and 2680 cm ^-1 , and does not have peaks in the defective D band (observed near 1350 cm ^-1 ). Alternatively, even if it has a peak, it can be confirmed that the peak intensity is 5% or less of the peak near 1580 cm ^-1 .

It can be said that the graphite thin film according to the embodiment of the present invention is of high quality because it has orientation. The orientation can be confirmed by satisfying the following (1) to (3) in the X-ray diffraction spectrum.
(1) In the 2θ-θ measurement spectrum of X-ray diffraction, there is a strong and clear peak at a 2θ angle of 26.54 ° (002).
(2) In the 2θ-θ measurement spectrum of X-ray diffraction, the 2θ angle is small at 54.64 ° (004), but there is a clear peak. (The peak intensity with a 2θ angle of 54.64 ° is 2% or more of the peak intensity with a 2θ angle of 26.54 °).
(3) In the 2θ measurement spectrum in which the θ angle is fixed at 0.5 °, the peak intensity of the 2θ angle of 26.54 ° is 2% or less of the peak intensity of the 2θ-θ measurement spectrum of the 2θ angle of 26.54 °. Is.

The nickel foil is used as a base material or support during formation or use of the graphite thin film, and as a base material or support for facilitating handling, transportation, etc. until the graphite thin film is peeled off from the nickel foil and used. It is used as a body.
The nickel of the nickel foil may be pure nickel or may contain an alloy component of 50% by mass or less (preferably 20% by mass or less, more preferably 10% by mass or less). The thickness of the nickel foil is not limited, but is usually about 1 to 100 μm, preferably about 1 to 50 μm. When the nickel foil is removed by etching or the like, the thinner one is preferably 1 to 50 μm, and more preferably about 2 to 30 μm.

The graphite thin film according to the embodiment of the present invention is preferably a self-supporting film. The self-supporting film means a film that can retain its shape even in the absence of a support (or a base material) such as a nickel foil. Even if the film is formed and fixed on the support, the thin film that can retain its shape even after the support is removed by various means such as etching removal is a self-supporting film.

As shown in FIG. 2, it is desirable to form a graphite thin film 10 on both the front and back surfaces of the nickel foil 11 to produce a graphite thin film laminate 12, but one surface of the nickel foil is covered with an appropriate material. It is also possible to obtain a graphite thin film laminate in which a graphite thin film is formed only on the other surface.
The graphite thin film laminate 12 is obtained by the following steps using plasma treatment (see FIG. 3). That is, a nickel foil is installed in the plasma processing apparatus, and vacuum exhaust is once performed to 10 ^-3 Pa or less (preferably about 10 ^-4 Pa or less). Next, by heating the nickel foil in such a vacuum state (for example, energization heating), the temperature rises from room temperature to 1250 to 1350 ° C. (preferably 1280 to 1320 ° C.) over 3 to 8 minutes (preferably 4 to 6 minutes). Warm (Fig. 3, (1)). While heating at the heated temperature, a carbon-containing gas (preferably methane, ethane, or acetylene) is introduced at 20 to 40 SCCM (preferably 25 to 35 SCCM) to increase the pressure to 10 to 30 Pa (preferably 15 to 25 Pa). After adjustment, plasma treatment of a carbon-containing gas such as methane is carried out for 20 to 40 minutes (preferably 25 to 35 minutes) (FIGS. 3, (2)). After that, it is cooled to 800 to 900 ° C. (preferably 830 to 880 ° C.) over 10 to 20 minutes at a rate of about 20 to 40 ° C. (preferably 25 to 35 ° C.) per minute while performing plasma irradiation (FIG. 3). , (3)). Plasma treatment is continued at that cooling temperature for 3 to 8 minutes (preferably 4 to 6 minutes) (FIGS. 3, (4)). After that, the plasma treatment and the heating of the nickel foil are completed. At the same time, the supply of the carbon-containing gas is stopped, and the mixture is cooled to room temperature in about 3 to 8 minutes (preferably 4 to 6 minutes) while evacuating (FIGS. 3 and 5). The entire process of producing the graphite thin film laminate is about 1 hour.

Methane, which is a carbon-containing gas for plasma treatment, is decomposed by plasma, and the carbon component decomposed and generated by the decomposition is once dissolved in a nickel foil maintained at a temperature rise temperature of about 1300 ° C. After that, carbon melted in the cooling process up to a cooling temperature of about 850 ° C. and the process of maintaining the cooling temperature precipitates on the surface of the nickel foil and crystallizes to form a graphite thin film. As a result, both the front and back surfaces of the nickel foil or one surface is covered with the graphite thin film. It was visually confirmed that the nickel foil had a metallic luster before the formation of the graphite thin film, but had a black color after the formation of the graphite thin film. Since the production of a graphite thin film by a conventional resin carbonization method such as polyimide requires two steps of a carbonization step of about 1000 ° C. and a crystallization (graphitization) step of about 3000 ° C., it is compared with the method according to the embodiment of the present invention. It is much more laborious, time consuming and requires high temperature. On the other hand, according to the method according to the embodiment of the present invention, a high-quality graphite thin film laminate can be produced in a short time of about 1 hour as a whole and at a low temperature of about 1300 ° C. In addition, since the production of the graphite thin film laminate by this method is completed in the process of plasma irradiation ((2), (3) and (4) in FIG. 3), the nickel foil, which is the substrate for film formation, is continuously wound up. By irradiating with plasma, it is possible to continuously form a graphite thin film laminate. That is, this method can be applied to the continuous production of graphite thin film laminates by roll-to-roll, which was not possible with the conventional resin carbonization method, and can be developed as an industrially very advantageous high-throughput production method. can. In addition, roll-to-roll is a processing method in which a sheet material wound in a roll shape is unwound, and while performing necessary processing while intermittently or continuously transporting the sheet material, the processed material is wound up again in a roll shape. Means.

By removing the nickel foil from the produced graphite thin film laminate, one or two graphite thin films can be obtained. The nickel foil removing means includes, but is not limited to, etching removal. Examples of the etching solution used for etching removal include, but are not limited to, an aqueous solution of ferric chloride and dilute nitric acid.

The graphite thin film separated from the nickel foil has a sheet resistance of about 0.5 to 5Ω and a thermal conductivity of about 1500 to 1700 W / mK.

Hereinafter, the present invention will be described in more detail based on Examples and Comparative Examples, but the present invention is not limited to these Examples.

(Manufacturing of graphite thin film or graphite thin film laminate using nickel foil)
A nickel foil was installed in the plasma processing device, and vacuum exhaust was once performed to about ^10-4 Pa. Next, the nickel foil was energized and heated in such a vacuum state to raise the temperature from room temperature to 1300 ° C. over 5 minutes (FIG. 3, (1)). While heating at 1300 ° C., 30 SCCM of methane as a carbon-containing gas was introduced to adjust the pressure to 20 Pa, and plasma treatment of methane was performed for 30 minutes (FIGS. 3 and 2). Then, while continuing plasma irradiation, the mixture was cooled to 850 ° C. at a rate of about 30 ° C. per minute for about 15 minutes (FIGS. 3 and 3). Plasma treatment was continued at 850 ° C. for 5 minutes (FIGS. 3 and 4), after which plasma treatment and heating of the nickel foil were completed. At the same time, the supply of methane was stopped, and the mixture was cooled to room temperature in about 5 minutes while evacuating (Fig. 3, (5)) to form a graphite thin film or graphite thin film laminate formed on both the front and back surfaces of the nickel foil. Obtained.

(Raman spectroscopic measurement of graphite thin film)
In order to evaluate the crystal quality of the graphite thin film, Raman spectroscopy of the graphite thin film formed on the nickel foil after plasma treatment was performed. The wavelength of the excitation laser used is 638 nm, and the spot diameter of the laser beam is 1 μm. As shown in FIG. 5, the measurement was performed at 5 points along the diagonal line of the sample of 10 mm × 10 mm. FIG. 5 shows Raman spectroscopic spectra measured at five points. Thus, spectra with peaks at 1578 cm ^-1 and 2678 cm ^-1 were observed. The peak of 1578 cm ^{-1 is the G band of graphite and the peak of 2678 cm -1 is} the 2D band, which is a typical Raman spectroscopic spectrum obtained from high quality graphite. No D band showing defects (observed near 1350 cm ^-1 ) was observed. This indicates that the graphite thin film produced by this method has very good and high crystal quality.

(Comparative experiment example, no plasma irradiation)
For comparison, as shown in FIG. 4, in the process shown in FIG. 3, the portion ((2), (3) and (4) in FIG. 3) to be irradiated with plasma of methane gas for 10 minutes is not irradiated with plasma. ((2), (3) and (4) in FIG. 4). Other steps are the same as those shown in FIG. According to this step, the surface of the nickel foil did not exhibit black color, and it was not possible to visually confirm that the graphite thin film was formed. That is, it was not possible to produce a graphite thin film or a graphite thin film laminate without plasma irradiation.
For comparison, Raman spectroscopy of the surface of the nickel foil treated in the process without plasma irradiation shown in FIG. 4 was also performed. FIG. 6 is a Raman spectroscopic spectrum showing the measurement results, but neither G band nor 2D band was observed at all. This indicates that the graphite thin film was not formed on the surface of the nickel foil in the process without plasma irradiation shown in FIG.

(Preparation of graphite thin film separated from nickel foil)
Next, a nickel foil having a graphite thin film formed on both the front and back surfaces shown in FIG. 2, that is, a graphite thin film laminate was immersed in a ferric chloride solution, and nickel was dissolved to separate the graphite thin film from the nickel foil. Furthermore, the graphite thin film separated from the nickel foil was scooped up with a stainless washer, held in the same container as Bencot (registered trademark) soaked with pure water, and gradually dried under high humidity. The dried graphite thin film could be picked up from the washer using tweezers. In this way, a graphite thin film separated from the nickel foil was produced.

(Measurement of thickness of graphite thin film)
As the film thickness of the graphite thin film separated from the above nickel foil, measurement with a stylus type step meter (surface roughness measuring device) and cross-sectional observation with a scanning electron microscope (SEM) were carried out. In carrying out the measurement with a profilometer, first, a graphite thin film was adhered to quartz glass via isopropyl alcohol and ethanol, and then the cutoff value was 0.08 mm and the stylus feed rate was 0.05 mm / sec. Measurements were carried out from three directions. The average height of the measured graphite thin film from the quartz substrate was taken as the thickness of the graphite thin film measured by a step meter. Next, the prepared graphite thin film was cross-sectionally observed by SEM to measure the film thickness. The film thickness of the graphite thin film determined from the measurement by the stylus type step meter and SEM was in the range of 300 nm to 400 nm, and the average film thickness was about 350 nm. The average film thickness is the average value when the film thickness is measured in a predetermined range of about 1 to 5 mm with a stylus type step meter, or the film thickness of about 10 to 20 places randomly selected by SEM. It means the average value when measured.

(Measurement of electrical conductivity of graphite thin film)
The sheet resistance of the graphite thin film separated from the above nickel foil was measured using the four-probe method. A gold alloy probe was used, and the distance between the probes was 300 μm. Measurements were performed at 10 points on a sample with a diameter of 6 mm. Since the electrical resistivity σ has a reciprocal relationship with the electrical resistivity ρ, it was calculated using the value of the average film thickness obtained by the stylus type step meter and the value of the sheet resistance Rs obtained by the four-probe method. The electrical resistivity ρ is given by ρ = Rs × t from the thickness t of the graphite thin film and the sheet resistance Rs, and the electrical resistivity σ is given by σ = 1 / (Rs × t). Since the average sheet resistance of the graphite thin film obtained in the present invention was 3.2 ± 0.3Ω and the film thickness was about 350 nm, the electric conductivity was about 9000 S / cm.

(XRD measurement (2θ-θ measurement))
The X-ray diffraction measurement of the above-mentioned self-supporting graphite thin film was performed. The details of the measurement are described below. The X-ray diffractometer used was an X-ray diffractometer RINT2100XRD-DSCII manufactured by Rigaku Co., Ltd., and the goniometer was an UltraIII horizontal goniometer manufactured by Rigaku Co., Ltd. A multipurpose sample table for thin film standard is attached to this goniometer. The measured sample is a graphite thin film separated from the above nickel foil adhered to a thin quartz glass. The size of the sample was about 10 mm square. As the X-ray, Kα1 ray of copper (Cu) was used. The applied voltage and current of the X-ray tube were 40 kV and 40 mA. A scintillation counter was used as the X-ray detector. First, the scattering angle (2θ angle) was calibrated using a standard silicon sample. The deviation of the 2θ angle was ± 0.02 ° or less. Next, the sample for measurement is fixed on the sample table, and the X-ray incident direction is parallel to the sample surface under the condition that the 2θ angle is 0 °, that is, the X-ray is directly incident on the detector. Adjusted so that half was blocked by the sample. In this way, the incident angle (θ angle) of X-rays with respect to the sample surface was determined to be 0 °. From this state, rotate the goniometer, change the 2θ angle from 10 ° to 90 ° in 0.02 ° increments, and irradiate X-rays while changing the θ angle to half the 2θ angle, and each 2θ. The intensity of X-rays scattered from the sample was measured at the −θ angle. The computer program used for the measurement is the RINT2000 / PC software Window (registered trademark) version manufactured by Rigaku Co., Ltd.

The measured X-ray diffraction spectrum is shown in FIG. It can be seen that the 2θ angle has a strong and clear peak at 26.54 °. Furthermore, the 2θ angle is as small as 54.64 °, but there is a clear peak. From the 2θ angles of these peaks, it was found that they were graphite (002) and (004) diffraction peaks, respectively.

Next, the θ angle is fixed at 0.5 °, and X-rays are irradiated while changing the 2θ angle from 21 ° to 30 ° in 0.02 ° increments, and the X-rays scattered from the sample at each 2θ angle. The intensity was measured. The intensity of the peak having a 2θ angle of 26.54 ° obtained by this measurement was less than one-hundredth of the (002) diffraction peak intensity of the 2θ-θ measurement in FIG. This indicates that the crystal planes of the measurement sample are very well aligned with the sample membrane plane, and the graphite thin film produced by this method has high orientation.

この関係を使い、Ｌの正および負の領域それぞれから熱拡散率αを求める。これにより得た熱拡散率αは加熱周波数ｆの関係を図８（ｂ）に示す。熱拡散率αは加熱周波数ｆが７０、１４０、２００、４００Ｈｚのそれぞれにおいて、１．１×１０^-3、９．３×１０^-4、９．１×１０^-4、９．２×１０^-4ｍ²／ｓであった。
また熱伝導率ｋは、熱拡散率α、密度ρ、比熱ｃを用いて以下のように与えられる。
ｋ＝αρｃ （２）
ここでグラファイトの密度２．２６ｇ／ｃｍ³、比熱７１０Ｊ／（ｋｇＫ）を用いて、本発明の実施例に係るグラファイト薄膜の熱伝導率はおよそ１５７０Ｗ／ｍＫであった。(Measurement of thermal diffusivity of graphite thin film by periodic heating method)
The thermal diffusivity of the graphite thin film separated from the nickel foil was measured by the periodic heating method. The periodic heating method is a method in which heat flow energy in which the intensity is periodically modulated is given to a measurement sample, and the heat diffusion rate is obtained from the amplitude or phase difference of the temperature response at a position separated from the heating region by a certain distance. Laser light or Joule heat of the heater is used as heat flow energy, and this is periodically modulated and given to the sample. In this measurement, heating by laser irradiation was used. In addition, temperature sensors (thermocouples, etc.) and thermoreflectance methods are used to detect the temperature response, but in this measurement, temperature was detected by non-contact using a radiation thermometer. For details on thermal diffusivity measurement by periodic heating method, refer to the literature (H.Kato, T.Baba, M.Okaji, “Anisotropic thermal-diffusivity measurements by a new laser-spot-heating technique”, Meas. Sci. Technol. See Vol. 12 (2001) pp.2074-2080).
The measured graphite thin film had a diameter of 6 mm. The average film thickness was about 350 nm. FIG. 8A shows the measurement results. The horizontal axis is the distance L from the heating point (laser light irradiation position), and the vertical axis is the phase difference θ of the temperature response. The heating frequencies f are 70, 140, 200 and 400 Hz, and the laser output for heating is 30 mW. The thermal diffusivity α and the phase difference θ have the relationship as shown below.

Using this relationship, the thermal diffusivity α is obtained from each of the positive and negative regions of L. The relationship between the thermal diffusivity α obtained thereby and the heating frequency f is shown in FIG. 8 (b). The thermal diffusivity α is 1.1 × 10 ^-3 , 9.3 × 10 ^-4 , 9.1 × 10 ^-4 , 9.2 × 10- ^, respectively, at heating frequencies f of 70, 140, 200, and 400 Hz. It was ⁴ m ² / s.
Further, the thermal conductivity k is given as follows by using the thermal diffusivity α, the density ρ, and the specific heat c.
k = αρc (2)
Here, using a graphite density of 2.26 g / cm ³ and a specific heat of 710 J / (kgK), the thermal conductivity of the graphite thin film according to the embodiment of the present invention was about 1570 W / mK.

Claims (10)

A graphite thin film with an average film thickness of 300 to 400 nm, which has peaks near 1580 cm ^-1 and 2680 cm ^-1 and no peaks near 1350 cm ^-1 in the Raman spectroscopic spectrum of the graphite thin film . A graphite thin film having a peak whose peak intensity is 5% or less of the peak near 1580 cm ^-1 . The graphite thin film according to claim 1, wherein the sheet resistance is 0.5 to 5Ω and / or the thermal conductivity is 1500 to 1700 W / mK. In the 2θ-θ measurement spectrum of X-ray diffraction, the 2θ angle has a strong and clear peak of (002) diffraction at 26.54 °, and the 2θ angle has a small peak of (004) diffraction at 54.64 °. In the 2θ measurement spectrum in which the θ angle is fixed at 0.5 °, the peak intensity of the 2θ angle of 26.54 ° is 2% or less of the peak intensity of the 2θ-θ measurement spectrum of the 2θ angle of 26.54 °. The graphite thin film according to claim 1. The graphite thin film according to claim 1, which is a self-supporting thin film. A graphite thin film laminate comprising the graphite thin film according to any one of claims 1 to 4 and a nickel foil supporting the graphite thin film. The graphite thin film laminate according to claim 5, wherein the graphite thin film is provided on both surfaces of the nickel foil. The nickel foil is heated under vacuum to raise the temperature to a temperature of 1250 to 1350 ° C., the nickel foil is heated and subjected to plasma treatment of carbon-containing gas, and then the nickel foil is heated from 830 to 830 while continuing the plasma treatment. A method for producing a graphite thin film or a graphite thin film laminate, which is cooled to 870 ° C. to form a graphite thin film on the surface of the nickel foil. In the graphite thin film, the carbon generated by decomposing the carbon-containing gas by plasma treatment melts into the nickel foil, and then during the cooling process from 830 to 870 ° C. and / or the plasma treatment at that temperature, the melted carbon The method for producing a graphite thin film or a graphite thin film laminate according to claim 7, wherein is deposited on the surface of the nickel foil and crystallized to be formed on the nickel foil. The method for producing a graphite thin film or a graphite thin film laminate according to claim 7 or 8, wherein the graphite thin film or the graphite thin film laminate is manufactured by using roll-to-roll. The method for producing a graphite thin film or a graphite thin film laminate according to any one of claims 7 to 9, wherein the nickel foil is removed from the produced graphite thin film laminate.

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