Manufacturing method for graphite thin film

Abstract

The present invention addresses the problem of providing a method by which a graphite film having a lowered surface roughness can be easily produced.　The present invention pertains to a method for producing a graphite film, said method comprising a step for subjecting a carbonization frame having a carbonization temperature Ta with an aromatic polyimide film or with a carbonized film obtained by carbonizing the aromatic polyimide film at a carbonization temperature Tb to integration and carbonization at a carbonization temperature Td followed by graphitization, wherein Ta>Tb and Tb<Td, and the graphite film has a surface roughness (arithmetic mean height Sa) of less than 18 nm, a thickness of 5 nm or more and less than 10 μm and an area of 1.0 cm2 or more and less than 500 cm2.

Description

[Technical Field]

[0001] The present invention relates to a method for producing a graphite thin film (also called a graphite film) with low surface roughness. [Background technology]

[0002] Graphite films are expected to be used in a wide range of fields, such as diaphragms in the MEMS field, light intensity distribution measurement using synchrotron radiation, charge conversion films, energy degraders, and fine wiring circuits (Non-Patent Documents 1 to 3, etc.). As the graphite film, for example, a film obtained by carbonizing an aromatic polymer film such as polyimide and then graphitizing it is known (Non-Patent Document 4, etc.). However, graphite films obtained from aromatic polymer films shrink during carbonization and expand during graphitization, which can lead to wrinkles and the formation of small irregularities on the surface, making it difficult to reduce the surface roughness (arithmetic mean height Sa). Patent Document 1 discloses a method for producing a thin, large-area graphite film with excellent surface smoothness by applying a force that pulls the polymer film outward along the film surface during baking. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] WO2016 / 129442 issue [Non-patent literature]

[0004] [Non-Patent Document 1] Micromachines, 2018, 9(2), 64 [Non-patent document 2] IPAC19 SX-MRPRM [Non-patent document 3] AIP Conference Proceedings 1962, 03005 (2018) [Non-patent document 4] Carbon 145, (2019) 23-30 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the method of Patent Document 1, the polymer film and its carbonized film are easily torn or damaged by applying tension as a physical external force, making it difficult to produce extremely thin graphite films or resulting in insufficient yields.

[0006] Patent Document 1 also discloses a method in which a carbonization frame and a carbonized film are produced under the same carbonization conditions, and then the carbonized film is bonded to the carbonization frame and baked at the graphitization temperature to convert the carbonized film into a graphite film (Example 65). However, with this method of graphitizing the integrated carbonization frame and carbonized film, it is difficult to apply a large tension, and the surface roughness Ra is about 18 nm (as shown in Comparative Example 4 of the present application, the arithmetic mean roughness Sa is about 30 nm).

[0007] Therefore, an object of the present invention is to provide a method for easily producing a graphite thin film having even smaller surface roughness. More specifically, an object of the present invention is to produce a graphite thin film with even smaller surface roughness without applying a physical external force that pulls the polymer film outward along the film surface during firing. [Means for solving the problem]

[0008] As a result of extensive research into solving the above problems, the inventors have discovered that if a carbonization frame and a film having expansion / contraction properties different from those of the frame are integrated and then carbonized or graphitized, the film can be graphitized while applying tension more appropriately to the film, and a graphite thin film with small surface roughness can be easily produced, leading to the present invention.

[0009] That is, the method for producing a graphite thin film according to the present invention, which has been able to solve the above-mentioned problems, has the following constituent features. [1] A method for producing a carbonized product comprising the steps of: integrating a carbonization frame having a carbonization temperature of Ta with an aromatic polyimide film or a carbonized film obtained by treating the aromatic polyimide film at a carbonization temperature of Tb; carbonizing the resulting carbonized film at a temperature of Td; and then graphitizing the resulting carbonized film; Ta>Tb and Tb <Tdであり、 Surface roughness (arithmetic mean height Sa) less than 18 nm, thickness 5 nm or more, less than 10 μm, area 1.0 cm 2 More than 500cm 2 A method for producing a graphite thin film that is less than 1000 nm in diameter. [2] The method for producing a graphite thin film according to [1], wherein the aromatic polyimide film has a thickness of 10 nm or more and less than 20 μm. [3] A carbonization frame having a carbonization temperature of Ta and a graphite film obtained by treatment at a graphitization temperature of Tc are integrated, and the resulting integrated carbonization frame and graphitized at a temperature of Te; Tc <Teであり、 Surface roughness (arithmetic mean height Sa) less than 18 nm, thickness 5 nm or more, less than 10 μm, area 1.0 cm 2 More than 500cm 2 A method for producing a graphite thin film that is less than 1000 nm in diameter. [4] The method for producing a graphite thin film according to [3], wherein the graphitization temperature Tc is 2000°C or higher and 2800°C or lower. [5] The method for producing a graphite thin film according to any one of [1] to [4], wherein the carbonization temperature Ta is 500°C or higher and lower than 2000°C. [6] The method for producing a graphite thin film according to any one of [1] to [5], wherein the electric conductivity in the film surface direction is 8000 S / cm or more and 26000 S / cm or less. [7] The method for producing a graphite thin film according to any one of [1] to [6], wherein the carbonization frame is obtained by carbonizing an aromatic polyimide film having a thickness of 10 to 100 μm in an inert gas. [8] The method for producing a graphite thin film according to any one of [1] to [7], wherein a load is applied to the frame when the carbonization frame and the aromatic polyimide film, the carbonized film, or the graphite film integrated together are carbonized or graphitized. [9] The method for producing a graphite thin film according to any one of [1] to [8], wherein in the graphitization step, the carbonization frame is expanded more than before graphitization. [Effects of the Invention]

[0010] According to the present invention, a graphite thin film with even smaller surface roughness can be easily produced. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic perspective view showing an example of a carbonization frame used in the present invention. [Figure 2] FIG. 2 is a schematic perspective view showing another example of the carbonization frame. [Figure 3] FIG. 3 is a schematic exploded perspective view showing an example of an integrated product of a carbonized frame and a film (aromatic polyimide film, low carbon film, low graphitization film). DETAILED DESCRIPTION OF THE INVENTION

[0012] The present invention relates to a method for integrating a carbonization frame with a film having different expansion / contraction properties than the frame, followed by firing (carbonization, graphitization, etc.). There are two methods, depending on the type of film. The first method uses an aromatic polyimide film or a carbonized aromatic polyimide film with a lower carbonization degree than the carbonization frame (or a film having a carbonization temperature Tb lower than the carbonization temperature Ta of the carbonization frame) (hereinafter sometimes referred to as a low-carbonized film). The integrated product of the film and the carbonization frame is carbonized and then graphitized. During carbonization, the carbonization frame does not expand or contract, whereas the aromatic polyimide film or low-carbonized film contracts. This allows for a stable application of large tension to the film, thereby reducing the film's surface roughness. Furthermore, during subsequent graphitization, both the carbonization frame and the carbonized film expand in the same way, allowing the resulting graphite thin film to maintain a low surface roughness.

[0013] The second method uses a partially graphitized film (hereinafter sometimes referred to as a low-graphitization film) as the film to be integrated with the carbonized frame, and graphitizes the integrated product of this film and the carbonized frame. When the integrated product is graphitized, the carbonized frame expands more than the low-graphitization film, so a large tension can be stably applied to the low-graphitization film, and the surface roughness of the resulting graphite film can be reduced. The first and second methods will be described in more detail below.

[0014] 1. Method of integrating a carbonized frame with an aromatic polyimide film or a low-carbon film (Method 1) 1.1 Aromatic polyimide film The aromatic polyimide film is a polymer obtained from an acid dianhydride and a diamine, where the acid dianhydride is an aromatic acid dianhydride, the diamine is an aromatic diamine, or both.

[0015] 1.1.1 Acid dianhydrides Examples of acid dianhydrides that can be used in the synthesis of the aromatic polyimide include pyromellitic dianhydride (PMDA), 2,3,6,7-naphthalenetetracarboxylic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, 2,2',3,3'-biphenyltetracarboxylic dianhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 2,2-bis(3,4-dicarboxyphenyl)propane dianhydride, 3,4,9,10-perylenetetracarboxylic dianhydride, bis(3,4-dicarboxyphenyl)propane dianhydride, 1, Examples of suitable polyimide dianhydrides include 1-bis(2,3-dicarboxyphenyl)ethane dianhydride, 1,1-bis(3,4-dicarboxyphenyl)ethane dianhydride, bis(2,3-dicarboxyphenyl)methane dianhydride, bis(3,4-dicarboxyphenyl)ethane dianhydride, oxydiphthalic dianhydride, bis(3,4-dicarboxyphenyl)sulfone dianhydride, p-phenylene bis(trimellitic acid monoester anhydride), ethylene bis(trimellitic acid monoester anhydride), and bisphenol A bis(trimellitic acid monoester anhydride). These may be used alone or in any mixture. The more rigid the polymer structure, the higher the orientation of the polyimide film, making it easier to obtain graphite with excellent crystallinity. Furthermore, from the standpoint of availability, pyromellitic acid dianhydride and 3,3',4,4'-biphenyltetracarboxylic acid dianhydride are preferred.

[0016] 1.1.2 Diamines Diamines include 4,4'-diaminodiphenyl ether (ODA), p-phenylenediamine (PDA), 4,4'-diaminodiphenylpropane, 4,4'-diaminodiphenylmethane, benzidine, 3,3'-dichlorobenzidine, 4,4'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl sulfone, 4,4'-diaminodiphenyl sulfone, 4,4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl ether, and 3,4'-diaminodiphenyl ether. Examples of suitable polyimide polymers include 4,4'-diaminodiphenyl ether (ODA), 1,5-diaminonaphthalene, 4,4'-diaminodiphenyldiethylsilane, 4,4'-diaminodiphenylsilane, 4,4'-diaminodiphenylethylphosphine oxide, 4,4'-diaminodiphenyl-N-methylamine, 4,4'-diaminodiphenyl-N-phenylamine, 1,4-diaminobenzene (p-phenylenediamine), 1,3-diaminobenzene, and 1,2-diaminobenzene, which can be used alone or in any mixture. From the standpoint of availability and the fact that they increase the orientation of the polyimide film and make it easier to obtain graphite with excellent crystallinity, 4,4'-diaminodiphenyl ether (ODA), p-phenylenediamine (PDA), and the like are preferred.

[0017] 1.1.3 Preparation method of polyamic acid The polyamic acid can be prepared by any known method, and the following polymerization method is preferred: 1) A method in which an aromatic diamine is dissolved in a polar organic solvent and reacted with an aromatic tetracarboxylic dianhydride in a substantially equimolar amount to polymerize the resulting solution; 2) A method in which an aromatic tetracarboxylic dianhydride is reacted with an aromatic diamine compound in a molar amount that is insufficient relative to the aromatic tetracarboxylic dianhydride in a polar organic solvent to obtain a prepolymer having acid anhydride groups at both ends, and then polymerized using an aromatic diamine compound so that the aromatic tetracarboxylic dianhydride and the aromatic diamine compound are substantially equimolar in all steps; 3) A method in which an aromatic tetracarboxylic dianhydride is reacted with an excess molar amount of an aromatic diamine compound in a polar organic solvent to obtain a prepolymer having amino groups at both ends, and then an aromatic diamine compound is added to the prepolymer, followed by polymerization using the aromatic tetracarboxylic dianhydride so that the amounts of the aromatic tetracarboxylic dianhydride and the aromatic diamine compound are substantially equimolar throughout the entire process; 4) A method in which an aromatic tetracarboxylic dianhydride is dissolved and / or dispersed in a polar organic solvent, and then polymerized using an aromatic diamine compound in a substantially equimolar amount. 5) A method of polymerizing a mixture of substantially equimolar amounts of an aromatic tetracarboxylic dianhydride and an aromatic diamine by reacting them in a polar organic solvent. The methods are as follows:

[0018] For example, a typical method for preparing polyamic acid from an acid dianhydride and a diamine involves dissolving at least one aromatic acid dianhydride and at least one diamine in an organic solvent and stirring the resulting organic solvent solution of polyamic acid under controlled temperature conditions until polymerization of the acid dianhydride and diamine is complete. The concentration of these polyamic acid solutions is typically 5 to 35 wt %, preferably 10 to 30 wt %. A concentration within this range can achieve appropriate molecular weight and solution viscosity. If the concentration of the polyamic acid solution is too low, the molecular weight may be insufficient, resulting in a polyimide film with insufficient strength, or if the viscosity is too low, it may be difficult to form a polyimide film. On the other hand, if the concentration of the polyamic acid solution is too high, the viscosity may be too high, making it difficult to form a polyimide film.

[0019] The acid dianhydride and diamine in the polyamic acid solution are preferably in substantially equimolar amounts, and the molar ratio (acid dianhydride:diamine) is, for example, 1.5:1 to 1:1.5, preferably 1.2:1 to 1:1.2, and more preferably 1.1:1 to 1:1.1.

[0020] Preferred solvents for synthesizing polyamic acid are amide solvents, such as N,N-dimethylformamide (DMF), N,N-dimethylacetamide, and N-methyl-2-pyrrolidone, with N,N-dimethylformamide and N,N-dimethylacetamide being particularly preferred.

[0021] Polyimide production methods include a thermal curing method in which the precursor polyamic acid is imidized by heating, and a chemical curing method in which a dehydrating agent, such as an acid anhydride such as acetic anhydride, or a tertiary amine such as picoline, quinoline, isoquinoline, or pyridine, is used as an imidization accelerator to imidize the polyamic acid. Either method may be used in the present invention, or a combination of several methods may be used. The chemical curing method is preferred because the resulting polyimide film is less likely to break even when tension is applied during baking, and it is easier to obtain a high-quality graphite film with high electrical conductivity. On the other hand, the thermal curing method is relatively easy to use even when a polyimide film is to be formed over a long period of time, since imidization is less likely to occur unless the polyamic acid is heated. It is also easily applicable to various polyimide film formation methods, such as spin coating, and has the advantage of providing a high degree of flexibility in the production process.

[0022] For example, a method for producing a polyimide film by chemical cure is as follows. First, a stoichiometric or greater amount of dehydrating agent and a catalytic amount of imidization promoter are added to the organic solvent solution of the polyamic acid. The mixture is then cast or coated onto a support substrate such as aluminum foil, a polymer film such as PET, a drum, or an endless belt to form a film. The organic solvent is then dried by heating to obtain a self-supporting film. The film is then further heated and dried while being imidized to obtain a polyimide film. The heating temperature is preferably in the range of 150°C or higher and lower than 500°C. As described above, the imidization may be carried out simply by heating to obtain a polyimide film (thermal cure) without adding an imidization accelerator. In this case, the heating temperature is preferably in the range of 150°C or higher and lower than 500°C.

[0023] Furthermore, it is preferable to include a step of fixing or stretching the film during the polyimide production process. Fixing or stretching the film can prevent polyimide shrinkage and increase the orientation of polymer chains in the film plane direction. Using a polyimide film with high orientation in the film plane direction tends to increase the crystallinity of graphite, making it easier to obtain a graphite film with excellent electrical conductivity.

[0024] 1.1.4 Aromatic polyimide film thickness The thickness of the aromatic polyimide film is, for example, 10 nm or more and less than 20 μm. The thickness of the finally obtained graphite film is about 50% of that of the aromatic polyimide film, and by keeping the thickness of the aromatic polyimide film within this range, the thickness of the graphite film can be controlled within a desired range. In the present invention, the film can be graphitized while applying tension without causing stress concentration in the film, so even extremely thin films can be produced. From this perspective, the thickness of the aromatic polyimide film is preferably 1 μm or less, more preferably 300 nm or less, even more preferably 100 nm or less, and particularly preferably 50 nm or less.

[0025] 1.2 Low-carbon membrane 1.2.1 Production of low-carbon membranes The low-carbon film can be obtained by heating the aromatic polyimide film in an inert gas or in a vacuum to carbonize it. The inert gas is preferably nitrogen, argon, or a mixture of argon and nitrogen. The low-carbonized film is preferably a film carbonized at a temperature lower than the carbonization temperature of the carbonization frame and the carbonization temperature of the integrated product of the carbonization frame and the carbonized film.

[0026] The carbonization temperature (Tb) is lower than the carbonization temperature (Ta) when manufacturing the carbonization frame described later. By setting Tb < Ta, when carbonizing the integrated product of the carbonization frame and the low-carbonization film, the shrinkage of the low-carbonization film can be made larger than that of the frame body, and a large tension can be applied to the low-carbonization film. The value of Tb - Ta is, for example, less than 0°C to 1100°C or more, preferably less than 0°C to 800°C or more, more preferably -100°C or less, still more preferably -300°C or less, and particularly preferably -500°C or less.

[0027] Also, the carbonization temperature (Tb) during the production of the low-carbonization film is lower than the carbonization temperature (Td) of the integrated product described later. By setting Tb < Td, the low-carbonization film can be shrunk during the carbonization of the integrated product, and a large tension can be applied to the low-carbonization film.

[0028] The carbonization temperature (Tb) is, for example, about 500°C to 1500°C. The carbonization temperature (Tb) is preferably 520°C or more, more preferably 550°C or more, still more preferably 560°C or more, even more preferably 570°C or more, and particularly preferably 58°C or more, and preferably 1300°C or less, more preferably 1000°C or less, still more preferably 900°C or less, particularly preferably 700°C or less, and most preferably 600°C or less. Note that those with a carbonization temperature (Tb) of less than 400°C are not considered carbonized and are considered to be aromatic polyimide films. <UNK>

[0029] [[ID=十一]] The heating rate up to the carbonization temperature (Tb) is, for example, about 2 to 30°C / min, preferably about 5 to 20°C / min, and the holding time at the carbonization temperature (Tb) is, for example, 20 minutes or more and 5 hours or less, preferably 40 minutes or more and 3 hours or less.

[0030] 1.2.2 Thickness of the low-carbonization film The thickness of the low-carbon film is preferably 78 to 100% of the thickness of the aromatic polyimide film, more preferably 80 to 99%, even more preferably 85 to 98%, even more preferably 90 to 97%, particularly preferably 92 to 96%, and most preferably 94 to 95%. That is, the thickness of the low-carbon film is preferably 7.8 nm or more and less than 20 μm, more preferably 8.0 nm or more and 19.8 μm or less, even more preferably 8.5 nm or more and 19.6 μm or less, still more preferably 9.0 nm or more and 19.4 μm or less, particularly preferably 9.2 nm or more and 19.2 μm or less, and most preferably 9.4 nm or more and 19.0 μm or less.

[0031] 1.3 Carbonization frame The carbonization frame may be any frame that surrounds the outer periphery of the aromatic polyimide film, low-carbon film, or low-graphitization film. As illustrated in the schematic perspective view of FIG. 1, the frame (carbonization frame) 1 refers to a member that surrounds the space 2. Frame 1 typically has a hollow space 2 within it, but as shown in FIG. 2, it may also be frame 3, in which at least one side of the frame or the inside of the frame is solid 4. Whether the inside is space 2 or solid 4, the frames 1 and 3 and the film (aromatic polyimide film, low-carbon film, or low-graphitization film) are integrated, while the frames 1 and 3 and the film are not integrated within it. This allows the film to contract and expand independently of the contraction and expansion of the frame, thereby reducing the surface roughness of the film. A hollow frame is preferable because it reduces interference with the film and avoids adverse effects during firing. The frame shape can be square, rectangular, hexagonal, circular, elliptical, or the like, with circular being preferred. In the case of squares, rectangles, hexagons, etc., the corners may be rounded.

[0032] The carbonized frame refers to a frame obtained by carbonizing an aromatic polyimide. The aromatic polyimide may be any combination of the components and conditions of the aromatic polyimide described for the aromatic polyimide film. The carbonized frame may be obtained by carbonizing a frame-shaped aromatic polyimide, or may be obtained by carbonizing a planar aromatic polyimide and then cutting it into a frame shape.

[0033] The carbonization temperature (Ta) of the aromatic polyimide to obtain the carbonized frame is, for example, 500° C. or higher, preferably 800° C. or higher, more preferably 900° C. or higher, and for example, less than 2000° C., preferably 1800° C. or lower, more preferably 1500° C. or lower, and even more preferably 1200° C. or lower. The carbonization conditions other than the carbonization temperature (Ta) (such as atmosphere, heating rate, and holding time) are the same as those for the low-carbon film described above.

[0034] The thickness of the aromatic polyimide to be used for the carbonization frame is, for example, 10 μm or more, preferably 15 μm or more, more preferably 20 μm or more, and for example, 100 μm or less, preferably 60 μm or less, more preferably 40 μm or less. The thickness of the carbonization frame is, for example, 9 μm or more, preferably 13.5 μm or more, more preferably 18 μm or more, and for example, 90 μm or less, preferably 54 μm or less, more preferably 36 μm or less.

[0035] The size of the carbonized frame (the size of the outer periphery (e.g., diameter, side length, etc.)) may be equal to or greater than the size of the aromatic polyimide film, low-carbon film, or low-graphitization film (the size of the outer periphery (e.g., diameter, side length, etc.)). The width of the outer and inner dimensions of the carbonization frame is, for example, 0.5 to 12 cm, preferably 1 to 10 cm, more preferably 2 to 8 cm, and even more preferably 3 to 6 cm.

[0036] 1.4 Integration Examples of methods for integrating an aromatic polyimide film or a low-carbon film with a carbonization frame include a method of sandwiching the film between the frames, a method of sewing with graphite string, a method of inserting graphite pins, a method of attaching with an adhesive, a method of using a molten polymer as an adhesive, a method of applying a polymer solution and drying it to use as an adhesive, and a method of applying a polyamic acid, drying it, and heating it to imidize it to use as an adhesive. In particular, it is preferable that the aromatic polyimide film or low-carbon film is integrated with the carbonization frame by direct contact between the film and the carbonization frame without the use of an adhesive layer such as an adhesive or other material, and that the film is a laminate consisting of the aromatic polyimide film or low-carbon film and the carbonization frame. As shown in Figure 3, frames 1 may be placed on both the front and back surfaces of the film 5 (aromatic polyimide film, low-carbon film, low-graphitization film, etc.), and the film 5 may be sandwiched between the frames 1, and the film may be integrated by applying a load to the frames 1 in particular. If the integrated body is carbonized and graphitized while a load is applied to the frame 1, distortion of the frame can be prevented. The load applied to the frame is, for example, 0.1 to 10 kgf / cm. 2 , preferably 0.3 to 5 kgf / cm 2 , more preferably 0.5 to 3 kgf / cm 2 is. The number of aromatic polyimide films or low-carbon films may be one or two or more as long as the predetermined thickness is satisfied, but one film is preferred.

[0037] 1.5 Carbonization of the integrated material The integrated product obtained as described above is carbonized at a predetermined carbonization temperature (Td). In this carbonization process, carbonization of the aromatic polyimide film or the low-carbon film proceeds more rapidly than that of the carbonization frame, resulting in greater shrinkage (film shrinkage). This applies tension to the film, thereby reducing the surface roughness of the final graphite film.

[0038] The carbonization temperature (Td) of the integrated product is, for example, 800°C or higher, more preferably 900°C or higher, and, for example, 1800°C or lower, more preferably 1500°C or lower, and even more preferably 1200°C or lower. It is preferable that the carbonization temperature (Td) of the integrated product is not too high compared with the carbonization temperature (Ta) of the carbonization frame. The smaller the value of Td - Ta, the more the carbonization frame can be prevented from shrinking during carbonization of the integrated product, and sufficient tension can be applied to the aromatic polyimide film or low-carbon film. The value of Td - Ta is, for example, 300°C or lower, preferably 200°C or lower, more preferably 100°C or lower, and particularly preferably 0°C or lower. Td - Ta is not particularly limited as long as Td is a predetermined temperature or higher and the predetermined carbonization proceeds, and may be a negative value. Td - Ta is, for example, -800°C or higher, preferably -500°C or higher, more preferably -200°C or higher, and particularly preferably -100°C or higher. The carbonization conditions (atmosphere, temperature rise rate, holding time, etc.) other than the carbonization temperature (Td) are the same as those for the low-carbon film described above.

[0039] 1.6 Graphitization of monoliths The carbonized integrated body is placed in a graphitization furnace and graphitized. During the graphitization process, the carbonized film expands, but the carbonization frame also expands. This prevents wrinkles and surface irregularities from forming on the film during graphitization.

[0040] Graphitization is carried out in an inert gas. Argon is the most suitable inert gas, and adding a small amount of helium to argon is even more preferable. The pressure (gauge pressure) of the inert gas atmosphere is, for example, 0.01 MPa or more, preferably 0.03 MPa or more, more preferably 0.05 MPa or more, and for example, 1 MPa or less, preferably 0.5 MPa or less, more preferably 0.3 MPa or less.

[0041] The graphitization temperature (Te) is, for example, 2200°C or higher, preferably 2600°C or higher, more preferably 2800°C or higher, and for example, 3300°C or lower, preferably 3200°C or lower, more preferably 3000°C or lower.

[0042] The heating rate up to the graphitization temperature (Te) is, for example, about 5 to 40 °C / min, preferably about 10 to 30 °C / min, and the holding time at the graphitization temperature (Te) is, for example, 5 minutes or more and 3 hours or less, preferably 15 minutes or more and 1 hour or less.

[0043] 2. Method for integrating the carbonization frame and the low-graphitization film (second method) 2.1 Low-graphitization film The low-graphitization film is a film obtained by carbonizing the aromatic polyimide film and then graphitizing it. The carbonization temperature (Tb’) can be set, for example, from the range of about 800 to 1800 °C. The carbonization conditions (atmosphere, heating rate, holding time, etc.) other than the carbonization temperature (Tb’) are the same as those of the above-mentioned low-carbonization film. The low-graphitization film refers to a film graphitized at a temperature lower than the graphitization temperature of the integrated product of the carbonization frame and the low-graphitization film.

[0044] The graphitization temperature (Tc) during the production of the low-graphitization film is carried out at a temperature lower than the graphitization temperature (Te) of the integrated product. Since Tc < Te, the graphitization of the low-graphitization film can proceed in the graphitization process of the integrated product. At this time, the low-graphitization film expands, but the carbonization frame expands more. Therefore, graphitization can proceed while applying tension to the low-graphitization film, and the surface roughness of the obtained graphite film can be reduced. The value of Tc - Te is, for example, -100 °C or lower and -800 °C or higher, preferably -200 °C or lower, more preferably -300 °C or lower, and even more preferably -400 °C or lower.

[0045] The graphitization temperature (Tc) is, for example, 2000 °C or higher, preferably 2200 °C or higher, more preferably 2300 °C or higher, and is, for example, 2800 °C or lower, preferably 2600 °C or lower, more preferably 2500 °C or lower. The graphitization conditions (atmosphere, pressure, heating rate, holding time, etc.) other than the graphitization temperature (Tc) are the same as those for the graphitization of the integrated material.

[0046] The thickness of the low-graphitization film is, for example, 5 μm or less, preferably 1 μm or less, more preferably 500 nm or less, even more preferably 250 nm or less, still more preferably 100 nm or less, particularly preferably 50 nm or less, and for example, 1 nm or more, preferably 2 nm or more, more preferably 5 nm or more.

[0047] 2.2 Graphitization of the integrated carbon frame and low-graphitization film The carbonization frame used in the second method is the same as the carbonization frame used in the first method. The carbonization frame and the low-graphitization film can be integrated using the same method as in the first method. The graphitization of the integrated product in the second method is the same as in the first method. It is also preferable to apply a load to the frame during graphitization.

[0048] 3. Graphite thin film (graphite film) The graphite film obtained in this manner has significantly reduced surface roughness. The arithmetic mean height Sa of the graphite film is less than 18 nm, preferably 15 nm or less, more preferably 12 nm or less, even more preferably 9 nm or less, and particularly preferably 6 nm or less. There is no particular restriction on the lower limit (limit) of the arithmetic mean height Sa, but according to the present invention, it is possible to set it to about 1 nm, particularly about 0.1 nm. The arithmetic mean height Sa may be calculated based on, for example, ISO 25178, and the measuring instrument may be a stylus surface roughness meter, a laser microscope, a scanning tunneling microscope (STM), an atomic force microscope (AFM), a scanning probe microscope (SPM), or the like.

[0049] The area of ​​the graphite film is, for example, 1.0 cm 2 More than 500cm 2 less than 5 to 400 cm 2and more preferably 10 to 300 cm 2 The shape of the graphite film may be square, rectangular, hexagonal, circular, elliptical, etc., and is preferably circular.

[0050] The thickness of the graphite film is 5 nm or more and less than 10 μm. In the present invention, the film can be graphitized while applying tension without causing stress concentration in the film, so even extremely thin graphite films can be produced. From this perspective, the thickness of the graphite film is preferably 500 nm or less, more preferably 150 nm or less, even more preferably 50 nm or less, and particularly preferably 25 nm or less.

[0051] The electrical conductivity of the graphite film in the film surface direction is, for example, 8000 to 26000 S / cm, preferably 16000 to 26000 S / cm, and more preferably 20000 to 26000 S / cm. The electrical conductivity may be measured by the van der Pauw method, for example, using a resistivity / DC & AC Hall measurement system, RESI Test 8300, manufactured by Toyo Technica Corporation.

[0052] This application claims the benefit of priority to Japanese Patent Application No. 2020-057574, filed on March 27, 2020. The entire content of the specification of Japanese Patent Application No. 2020-057574, filed on March 27, 2020, is incorporated herein by reference. [Example]

[0053] The present invention will be described in more detail below with reference to examples. However, the present invention is not limited to the following examples, and it is possible to carry out the invention by making appropriate modifications within the scope of the above and below-described aims, and all such modifications are included in the technical scope of the present invention.

[0054] 1. Evaluation Method The properties of the graphite films obtained in the following examples and comparative examples were evaluated as follows.

[0055] (1) Electrical conductivity The electrical conductivity of the graphite film was measured by the van der Pauw method. 5 The sample was cut into a square shape, silver paste electrodes were attached to the four corners, and the electrical conductivity was measured using a resistivity / DC & AC Hall measurement system, RESI Test 8300, manufactured by Toyo Technica Corporation.

[0056] (2) Surface roughness and thickness The graphite film was transferred onto the glass substrate by gently pressing it against the substrate. The surface roughness (arithmetic mean height Sa; ISO 25178) and the step height between the graphite film and the glass substrate (graphite film thickness) were measured using a scanning probe microscope (SPM).

[0057] 2. Preparation of Polyimide Film Manufacturing Example 1 Polyimide films were prepared using the following method. 100 g of an 18 wt. % dimethylformamide (DMF) solution of polyamic acid, synthesized from pyromellitic anhydride and 4,4'-diaminodiphenyl ether in a 1:1 molar ratio, was mixed with a curing agent consisting of 20 g of acetic anhydride and 10 g of isoquinoline, stirred, and degassed by centrifugation. The mixture was then cast onto aluminum foil, and a polyamic acid film with a uniform thickness ranging from 0.04 μm to 25 μm was prepared on the aluminum foil using a spin coater. The thickness was adjusted by changing the concentration of the amic acid solution and the rotation speed of the spin coater. The polyamic acid film was heated at 120°C for 150 seconds, 250°C, and 450°C for 60 seconds each, and then the aluminum foil was removed to produce five polyimide films with different thicknesses (0.04 μm, 0.4 μm, 2.2 μm, 4.0 μm, and 25 μm, respectively): (A-0.04), (A-0.4), (A-2.2), (A-4.0), and (A-25).

[0058] 3. Fabrication of Carbonized Frame Manufacturing Example 2 Polyimide film (A-25) cut into rings with an outer diameter of 8 cm and an inner diameter of 4 cm was heated in an electric furnace in nitrogen gas at a rate of 10°C / min to 750°C, 1000°C, and 1500°C, respectively, and maintained at the maximum temperature for 1 hour to obtain three types of carbonized frames (B-750), (B-1000), and (B-1500).

[0059] 4. Graphite Film Preparation Example 1: Preparation of graphite film (C-1) A 0.04 μm thick polyimide film (A-0.04) cut into a circle with a diameter of 8 cm was sandwiched between carbonization frames (B-1000) and subjected to a pressure of 1.0 kgf / cm. 2 The sample was heated to 1000°C at a rate of 10°C / min in nitrogen gas using an electric furnace, and then kept at 1000°C for 1 hour to be carbonized.

[0060] Next, the obtained carbonized film was placed inside a graphitization furnace together with a carbonization frame, and the furnace was heated in an argon atmosphere at a gauge pressure of 0.10 MPa (1.0 kgf / cm 2 The temperature was increased to 2900°C at a rate of 20°C / min under pressure. The temperature was maintained at 2900°C for 30 minutes, and then the temperature was decreased at a rate of 40°C / min to produce a graphite film (C-1).

[0061] Example 2: Preparation of graphite film (C-2) A 0.04 μm thick polyimide film (A-0.04) cut into a circle with a diameter of 8 cm was heated to 500°C at a rate of 10°C / min in nitrogen gas using an electric furnace, and after maintaining at 500°C for 1 hour, the temperature was lowered. The obtained film was sandwiched on both sides between carbonization frames (B-750) and subjected to a pressure of 1.0 kgf / cm. 2 The sample was heated to 1000°C at a rate of 10°C / min in nitrogen gas using an electric furnace, and then kept at 1000°C for 1 hour to be carbonized.

[0062] Next, the obtained carbonized film was placed inside a graphitization furnace together with a carbonization frame, and the furnace was heated in an argon atmosphere at a gauge pressure of 0.10 MPa (1.0 kgf / cm 2The temperature was increased to 2900°C at a rate of 20°C / min under pressure. The temperature was maintained at 2900°C for 30 minutes, and then the temperature was decreased at a rate of 40°C / min to produce a graphite film (C-2).

[0063] Example 3: Preparation of graphite film (C-3) A 0.04 μm thick polyimide film (A-0.04) cut into a circle with a diameter of 8 cm was heated to 500°C at a rate of 10°C / min in nitrogen gas using an electric furnace, and after maintaining at 500°C for 1 hour, the temperature was lowered. The obtained film was sandwiched on both sides between carbonization frames (B-1000) and subjected to a pressure of 1.0 kgf / cm. 2 The sample was heated to 1000°C at a rate of 10°C / min in nitrogen gas using an electric furnace, and then kept at 1000°C for 1 hour to be carbonized.

[0064] Next, the obtained carbonized film was placed inside a graphitization furnace together with a carbonization frame, and the furnace was heated in an argon atmosphere at a gauge pressure of 0.10 MPa (1.0 kgf / cm 2 The temperature was increased to 2900°C at a rate of 20°C / min under pressure. The temperature was maintained at 2900°C for 30 minutes, and then the temperature was decreased at a rate of 40°C / min to produce a graphite film (C-3).

[0065] Example 4: Preparation of graphite film (C-4) A 0.04 μm thick polyimide film (A-0.04) cut into a circle with a diameter of 8 cm was heated to 500°C at a rate of 10°C / min in nitrogen gas using an electric furnace, and after maintaining at 500°C for 1 hour, the temperature was lowered. The obtained film was sandwiched on both sides between carbonization frames (B-1500) and subjected to a pressure of 1.0 kgf / cm. 2 The sample was heated to 1000°C at a rate of 10°C / min in nitrogen gas using an electric furnace, and then kept at 1000°C for 1 hour to be carbonized.

[0066] Next, the obtained carbonized film was placed inside a graphitization furnace together with a carbonization frame, and the furnace was heated in an argon atmosphere at a gauge pressure of 0.10 MPa (1.0 kgf / cm 2The temperature was increased to 2900°C at a rate of 20°C / min under pressure. The temperature was maintained at 2900°C for 30 minutes, and then the temperature was decreased at a rate of 40°C / min to produce a graphite film (C-4).

[0067] Example 5: Preparation of graphite film (C-5) A 0.04 μm thick polyimide film (A-0.04) cut into a circle with a diameter of 8 cm was heated to 600°C at a rate of 10°C / min in nitrogen gas using an electric furnace, and after maintaining at 600°C for 1 hour, the temperature was lowered. The obtained film was sandwiched on both sides between carbonization frames (B-1000) and subjected to a pressure of 1.0 kgf / cm. 2 The sample was heated to 1000°C at a rate of 10°C / min in nitrogen gas using an electric furnace, and then kept at 1000°C for 1 hour to be carbonized.

[0068] Next, the obtained carbonized film was placed inside a graphitization furnace together with a carbonization frame, and the furnace was heated in an argon atmosphere at a gauge pressure of 0.10 MPa (1.0 kgf / cm 2 The temperature was increased to 2900°C at a rate of 20°C / min under pressure. The temperature was maintained at 2900°C for 30 minutes, and then the temperature was decreased at a rate of 40°C / min to produce a graphite film (C-5).

[0069] Example 6: Preparation of graphite film (C-6) A 0.04 μm thick polyimide film (A-0.04) cut into a circle with a diameter of 8 cm was heated to 800°C at a rate of 10°C / min in nitrogen gas using an electric furnace, and after maintaining at 800°C for 1 hour, the temperature was lowered. The obtained film was sandwiched on both sides between carbonization frames (B-1000) and subjected to a pressure of 1.0 kgf / cm. 2 The sample was heated to 1000°C at a rate of 10°C / min in nitrogen gas using an electric furnace, and then kept at 1000°C for 1 hour to be carbonized.

[0070] Next, the obtained carbonized film was placed inside a graphitization furnace together with a carbonization frame, and the furnace was heated in an argon atmosphere at a gauge pressure of 0.10 MPa (1.0 kgf / cm 2The temperature was increased to 2900°C at a rate of 20°C / min under pressure. The temperature was maintained at 2900°C for 30 minutes, and then the temperature was decreased at a rate of 40°C / min to produce a graphite film (C-6).

[0071] Example 7: Preparation of graphite film (C-7) A 0.40 μm thick polyimide film (A-0.4) cut into a circle with a diameter of 8 cm was heated to 500°C at a rate of 10°C / min in nitrogen gas using an electric furnace, and after maintaining at 500°C for 1 hour, the temperature was lowered. The obtained film was sandwiched on both sides between carbonization frames (B-1000) and subjected to a pressure of 1.0 kgf / cm. 2 The sample was heated to 1000°C at a rate of 10°C / min in nitrogen gas using an electric furnace, and then kept at 1000°C for 1 hour to be carbonized.

[0072] Next, the obtained carbonized film was placed inside a graphitization furnace together with a carbonization frame, and the furnace was heated in an argon atmosphere at a gauge pressure of 0.10 MPa (1.0 kgf / cm 2 The temperature was increased to 2900°C at a rate of 20°C / min under pressure. The temperature was maintained at 2900°C for 30 minutes, and then the temperature was decreased at a rate of 40°C / min to produce a graphite film (C-7).

[0073] Example 8: Preparation of graphite film (C-8) A 4.00 μm thick polyimide film (A-4.0) cut into a circle with a diameter of 8 cm was heated to 500°C at a rate of 10°C / min in nitrogen gas using an electric furnace, and after maintaining at 500°C for 1 hour, the temperature was lowered. The obtained film was sandwiched on both sides between carbonization frames (B-1000) and subjected to a pressure of 1.0 kgf / cm. 2 The sample was heated to 1000°C at a rate of 10°C / min in nitrogen gas using an electric furnace, and then kept at 1000°C for 1 hour to be carbonized.

[0074] Next, the obtained carbonized film was placed inside a graphitization furnace together with a carbonization frame, and the furnace was heated in an argon atmosphere at a gauge pressure of 0.10 MPa (1.0 kgf / cm 2The temperature was increased to 2900°C at a rate of 20°C / min under pressure. The temperature was maintained at 2900°C for 30 minutes, and then the temperature was decreased at a rate of 40°C / min to produce a graphite film (C-8).

[0075] Example 9: Preparation of graphite film (C-9) A 0.04 μm thick polyimide film (A-0.04) cut into a circle with a diameter of 8 cm was heated to 1000°C at a rate of 10°C / min in nitrogen gas using an electric furnace, maintained at 1000°C for 1 hour, and then cooled down to carbonize. The obtained film was heated to 2500°C at a rate of 20°C / min in nitrogen gas using a graphitization furnace, and maintained at 2500°C for 1 hour to reduce the graphitization.

[0076] Next, the obtained low-graphitization film was sandwiched on both sides between carbonization frames (B-1000) and placed again inside the graphitization furnace, and heated in an argon atmosphere at a gauge pressure of 0.10 MPa (1.0 kgf / cm 2 The temperature was increased to 2900°C at a rate of 20°C / min under pressure. The temperature was maintained at 2900°C for 30 minutes, and then the temperature was decreased at a rate of 40°C / min to produce a graphite film (C-9).

[0077] Comparative Example 1: Preparation of graphite film (D-1) A 0.04 μm thick polyimide film (A-0.04) cut into a circle with a diameter of 8 cm was heated to 1000°C at a rate of 10°C / min in nitrogen gas using an electric furnace, and after being held at 1000°C for 1 hour, the temperature was lowered. The obtained film was sandwiched on both sides between carbonization frames (B-1500) and subjected to a pressure of 1.0 kgf / cm. 2 The sample was heated to 1000°C at a rate of 10°C / min in nitrogen gas using an electric furnace, and then kept at 1000°C for 1 hour to be carbonized.

[0078] Next, the obtained carbonized film was placed inside a graphitization furnace together with a carbonization frame, and the furnace was heated in an argon atmosphere at a gauge pressure of 0.10 MPa (1.0 kgf / cm 2The temperature was increased to 2900°C at a rate of 20°C / min under pressure. The temperature was maintained at 2900°C for 30 minutes, and then the temperature was decreased at a rate of 40°C / min to produce a graphite film (D-1).

[0079] Comparative Example 2: Preparation of graphite film (D-2) A 2.20 μm thick polyimide film (A-2.2) cut into a circle with a diameter of 8 cm was heated to 1000°C at a rate of 10°C / min in nitrogen gas using an electric furnace, and after being held at 1000°C for 1 hour, the temperature was lowered. The obtained film was sandwiched on both sides between carbonization frames (B-1000) and subjected to a pressure of 1.0 kgf / cm. 2 The sample was heated to 1000°C at a rate of 10°C / min in nitrogen gas using an electric furnace, and then kept at 1000°C for 1 hour to be carbonized.

[0080] Next, the obtained carbonized film was placed inside a graphitization furnace together with a carbonization frame, and heated in an argon atmosphere at a gauge pressure of 0.10 MPa (1.0 kgf / cm 2 The temperature was increased to 2900°C at a rate of 20°C / min under pressure. The temperature was maintained at 2900°C for 30 minutes, and then the temperature was decreased at a rate of 40°C / min to produce a graphite film (D-2).

[0081] Comparative Example 3: Preparation of graphite film (D-3) A 0.04 μm thick polyimide film (A-0.04) cut into a circle with a diameter of 8 cm was heated to 1000°C at a rate of 10°C / min in nitrogen gas using an electric furnace, and after maintaining at 1000°C for 1 hour, the temperature was lowered. The obtained film was sandwiched on both sides between carbonization frames (B-750) and subjected to a pressure of 1.0 kgf / cm. 2 The sample was heated to 1000°C at a rate of 10°C / min in nitrogen gas using an electric furnace, and then kept at 1000°C for 1 hour to be carbonized.

[0082] Next, the obtained carbonized film was placed inside a graphitization furnace together with a carbonization frame, and the furnace was heated in an argon atmosphere at a gauge pressure of 0.10 MPa (1.0 kgf / cm 2The temperature was increased to 2900°C at a rate of 20°C / min under pressure. The temperature was maintained at 2900°C for 30 minutes, and then the temperature was decreased at a rate of 40°C / min to produce a graphite film (D-3).

[0083] Comparative Example 4: Preparation of graphite film (D-4) A 0.04 μm thick polyimide film (A-0.04) cut into a circle with a diameter of 8 cm was sandwiched on both sides between a ring-shaped polyimide frame (A-25) cut into an outer diameter of 8 cm and an inner diameter of 4 cm, and subjected to a pressure of 1.0 kgf / cm 2 The sample was heated to 1000°C at a rate of 10°C / min in nitrogen gas using an electric furnace, and then kept at 1000°C for 1 hour to be carbonized.

[0084] Next, the obtained carbonized film was placed inside a graphitization furnace together with a carbonization frame, and the furnace was heated in an argon atmosphere at a gauge pressure of 0.10 MPa (1.0 kgf / cm 2 The temperature was increased to 2900°C at a rate of 20°C / min under pressure. The temperature was maintained at 2900°C for 30 minutes, and then the temperature was decreased at a rate of 40°C / min to produce a graphite film (D-4).

[0085] Comparative Example 5: Preparation of graphite film (D-5) A 0.04 μm thick polyimide film (A-0.04) cut into a circle with a diameter of 8 cm was heated to 800°C at a rate of 10°C / min in nitrogen gas using an electric furnace, and after being kept at 800°C for 1 hour, the temperature was lowered. The obtained film was sandwiched on both sides between polyimide frames (A-25) cut into ring shapes with an outer diameter of 8 cm and an inner diameter of 4 cm, and then subjected to a pressure of 1.0 kgf / cm. 2 The sample was heated to 1000°C at a rate of 10°C / min in nitrogen gas using an electric furnace, and then kept at 1000°C for 1 hour to be carbonized.

[0086] Next, the obtained carbonized film was placed inside a graphitization furnace together with a carbonization frame, and the furnace was heated in an argon atmosphere at a gauge pressure of 0.10 MPa (1.0 kgf / cm 2The temperature was increased to 2900°C at a rate of 20°C / min under pressure. The temperature was maintained at 2900°C for 30 minutes, and then the temperature was decreased at a rate of 40°C / min to produce a graphite film (D-5).

[0087] Table 1 shows the film thickness (μm), surface roughness Sa (nm), and electrical conductivity (S / cm) of the graphite films (C-1) to (C-9) obtained in Examples 1 to 9 and the graphite films (D-1) to (D-5) obtained in Comparative Examples 1 to 5.

[0088] [Table 1] [Industrial Applicability]

[0089] Graphite films can be used in a wide range of fields, such as diaphragms in the MEMS field, light intensity distribution measurement using synchrotron radiation, charge conversion films, energy degraders, and fine wiring circuits. [Explanation of symbols]

[0090] 1 frame (carbonization frame) 2 space 3 Frame (Carbonization Frame) 4 Solid Body 5. Films (aromatic polyimide films, low-carbon films, low-graphitized films)

Claims

1. A method for producing a carbonized product comprising the steps of: integrating a carbonization frame in which aromatic polyimide has been carbonized at a carbonization temperature Ta with an aromatic polyimide film, or a carbonized film obtained by treating the aromatic polyimide film at a carbonization temperature Tb; carbonizing the resulting carbonized film at a temperature Td; and then graphitizing the resulting carbonized film; Ta>Tb and Tb<Td, The value of Tb-Ta is −100°C or less and −1100°C or more, The carbonization frame is held at the carbonization temperature Ta for 20 minutes or more, Surface roughness (arithmetic mean height Sa) less than 18 nm, thickness 5 nm or more and less than 10 μm, area 1.0 cm ２ Above, 500cm ２ A method for producing a graphite thin film that is less than 1000 nm in diameter.

2. A method for producing a graphite thin film as described in claim 1, wherein the Ta, Tb, and Td satisfy the following ranges. Ta: 500℃ or more and 1800℃ or less Tb: 500℃ or more and 1500℃ or less Td: 800℃ or more and 1800℃ or less Td-Ta: Below 300℃ - Above 800℃

3. The heating rate to the carbonization temperature Ta is 2°C / min or more, The heating rate up to the carbonization temperature Tb is 30° C. / min or less, 3. The method for producing a graphite thin film according to claim 1, wherein the holding time at the carbonization temperature Tb is 5 hours or less.

4. 4. The method for producing a graphite thin film according to claim 1, wherein the aromatic polyimide film has a thickness of 10 nm or more and less than 20 μm.

5. A method for producing a carbonized polyimide film, comprising: integrating a carbonization frame obtained by carbonizing an aromatic polyimide at a carbonization temperature Ta with a graphite film obtained by treating the carbonized polyimide at a graphitization temperature Tc; and graphitizing the resulting carbonized polyimide film at a temperature Te; Tc<Te, Ta is 1800°C or less, Tc is 2000°C or higher, the graphite film is held at the graphitization temperature Tc for 15 minutes or more; Surface roughness (arithmetic mean height Sa) less than 18 nm, thickness 5 nm or more and less than 10 μm, area 1.0 cm ２ Above, 500cm ２ A method for producing a graphite thin film that is less than 1000 nm in diameter.

6. A method for producing a graphite thin film as described in claim 5, wherein Ta, Tc, and Te satisfy the following ranges. Ta: 500℃ or more Tc: 2800℃ or less Te: 2200℃ or more and 3300℃ or less Tc-Te: -100℃ or less -800℃ or more

7. The heating rate to the carbonization temperature Ta is 2°C / min or more, The retention time at the carbonization temperature Ta is 20 minutes or more, the heating rate up to the graphitization temperature Tc is 5 to 40°C / min; 7. The method for producing a graphite thin film according to claim 5, wherein the holding time at the graphitization temperature Tc is 3 hours or less.

8. 8. The method for producing a graphite thin film according to claim 1, wherein the electric conductivity in the film surface direction is 8,000 S / cm or more and 26,000 S / cm or less.

9. 9. The method for producing a graphite thin film according to claim 1, wherein the carbonized frame is obtained by carbonizing an aromatic polyimide film having a thickness of 10 to 100 μm in an inert gas.

10. 10. The method for producing a graphite thin film according to claim 1, wherein a load is applied to the frame when the carbonization frame and the aromatic polyimide film, the carbonized film, or the graphite film integrated together are carbonized or graphitized.

11. 11. The method for producing a graphite thin film according to claim 1, wherein in the graphitization step, the carbonized frame is expanded more than before graphitization.

Images