JP5658782B2 - Method for producing carbonaceous film - Google Patents

Description

  The present invention relates to a method for producing a carbonaceous film used as a heat radiating member in electronic equipment, precision equipment, and the like.

  Graphite is widely used as a heat diffusion / heat dissipation material, heat-resistant sealing material, gasket, fuel cell separator, etc. because of its outstanding heat resistance, chemical resistance, thermal conductivity, electrical conductivity, and low gas permeability. Graphite has greatly different thermal and electrical properties in the ab plane direction and c axis direction, and the anisotropy of thermal conductivity in the ab plane direction and c axis direction reaches 50 to 400 times. The purpose of the graphite heat-dissipating film is to quickly diffuse a wide range of generated heat using such properties. There are two methods for producing graphite used for heat dissipation as described below.

  One of them is a method generally called an expanded graphite method. This is a sheet-like graphite film obtained by rolling expanded graphite produced when natural graphite lead is treated with a strong acid such as sulfuric acid to form an intercalation compound, which is heated and expanded (Non-Patent Document). 1). Such an expanded graphite film exhibits a thermal conductivity of about 100 to 400 W / (m · K) in the planar direction and is used as a heat dissipation material.

  Another method is to use a polymer film such as polyoxadiazole, polybenzothiazole, polybenzobisthiazole, polybenzoxazole, polybenzobisoxazole, polythiazole, polyimide, polyphenylene vinylene, or polyamide such as argon or helium. Polymer pyrolysis methods (Patent Documents 1, 2, and 3) in which heat treatment is performed in an inert atmosphere or in a vacuum are known. Specifically, these polymer films are preliminarily heated at, for example, about 1000 ° C. in an inert gas, preferably in a nitrogen gas to prepare a glassy carbonaceous film, and then the carbon prepared. A graphite film can be obtained by passing through two processes of the graphitization process which processes a quality film at the temperature of 2400 degreeC or more. The polymer graphite film viewed as a heat dissipation material has a very high thermal conductivity of 600 to 1800 W / (m · K), and is characterized in that a thin sheet can be produced and a sheet of 25 μm or less can be easily produced. . The method will be described in more detail as follows.

  Examples 1 and 2 of Patent Documents 1 and 2 disclose a method of heat-treating a raw material film with a sheet as follows. 25 micron PA film (poly (m-phenyleneisophthalamide)), PI (poly (pyromellitimide)), PBI (poly (m-phenylenebenzimidazole)), PBBI (poly (m-phenylenebenzobisimidazole)) Was fixed to a stainless steel frame and preheated from room temperature to 700 ° C. at a rate of 10 ° C. per minute in argon using an electric furnace. In the absence of a stainless steel frame, the PA film shrinks to 50% of its original size even in this temperature range, so fixing with the stainless steel frame means that a preheating treatment was applied while applying tension as a result. The film preliminarily heat-treated in this way was sandwiched between graphite plates, heated in an argon stream at a rate of 10 ° C. per minute, and heat-treated at a desired temperature (Tp) for 1 hour. After the heat treatment, the temperature was lowered at a rate of 20 ° C. per minute. The furnace used was an electric furnace using a carbon heater. The obtained black film was fragile and inflexible at Tp of 1400 ° C. or lower, but became flexible at 1800 ° C. or higher.

JP 61-275116 A JP-A 61-275117 JP-A-63-256508

New development of carbon materials, Japan Society for the Promotion of Science Carbon Material 117th Committee 60th anniversary publication

  The polyimide film, which is one of the raw material films used in the polymer pyrolysis method, shrinks with pyrolysis in the carbonization step, and the size is reduced to about 70 to 80% of the initial size. When a 200 mm square polyimide film is placed horizontally on a graphite material and subjected to heat treatment up to 1000 ° C. without applying any load from the top surface of the film, a carbonized film having a large undulating surface due to carbonization shrinkage is obtained. Come. In order to suppress the undulation of the carbonized film, it is possible to obtain a carbonized film with no undulation by sandwiching the polyimide film with graphite paper, expanded graphite gasket, etc., and fixing the polyimide film and carbonizing it. It becomes. However, when the polyimide film is fixed with interleaving paper and heat treatment is performed, small foreign matter is generated on the film or interleaving paper, which is thought to be derived from the decomposition gas of the film, and the foreign matter is caught when the film shrinks and scratches on the carbonized film There was a problem of making. This phenomenon appears more prominently when two polyimide films are directly stacked and carbonized by fixing the top and bottom with interleaving paper. There was a problem that the generation of foreign matter was further promoted between the films.

  In addition, when a number of films are stacked, or when carbonization is performed in a state where the load from the upper surface of the film is increased and the degree of adhesion between the films is increased, there is a problem that the films cause fusion. Once the carbonized film has been fused, it does not return to its original state in the subsequent graphitization process, and as a result, a cracked graphite film or a graphite film with an extremely poor surface state can be obtained.

  This problem can be solved by sandwiching interleaf paper such as expanded graphite gasket between the films. However, expanded graphite slip sheets are usually as thick as 200 to 250 μm, and there is a problem that the amount of carbonization treatment within a certain volume is extremely reduced. For example, when a 50 μm polyimide film is directly laminated on a container having an effective depth of 20 cm, 4000 sheets can be processed at a time, but when a 200 μm gasket is used as a slip sheet, the processing amount is about 800 sheets and 1 It will decrease to / 5.

  It is one of the objects of the present invention to produce a high-quality carbonaceous film with high productivity by directly laminating a polyimide film without sandwiching a slip sheet between the films and performing carbonization treatment.

  We have determined that the cause of the above foreign matter and fusion is that the decomposition gas from the polyimide film is carbonized and fixed without being discharged out of the system, and that the decomposition gas can be quickly removed from the system. The purpose of this study was to examine carbonization under reduced pressure conditions.

  The first of the present invention is a method for producing a carbonaceous film by heat-treating a polymer film, wherein the carbonization film is produced by performing at least a part of the carbonization step under reduced pressure. Here, “at least a part of the carbonization step is performed under reduced pressure” means that the gas pressure in the heating device (also referred to as a furnace) is made lower than that outside the heating device in at least a part of the carbonization step.

  The second of the present invention is the method for producing a carbonaceous film as described above, wherein in the step of carbonizing the laminated polyimide film, the step is performed under reduced pressure. Here, the “superimposed polyimide film” refers to a film in which polyimide films are directly laminated without sandwiching a graphite material or the like.

  A third aspect of the present invention is the method for producing a carbonaceous film as described above, wherein the number of the laminated polyimide film layers is 10 or more.

  A fourth aspect of the present invention is the above-described method for producing a carbonaceous film, wherein the polyimide film is heat-treated by applying a load from above.

  A fifth aspect of the present invention is the method for producing a carbonaceous film as described above, wherein the reduced pressure range is -0.001 kPa to -0.1 MPa. Here, “reduced pressure is −0.001 kPa” means that the pressure of the gas inside the heating apparatus is 0.001 kPa lower than the pressure of the gas outside the heating apparatus (usually considered to be atmospheric pressure). Similarly, “decompression is −0.1 kPa” means that the pressure of the gas in the heating device is 0.1 kPa lower than the pressure of the gas outside the heating device.

  The sixth of the present invention is the method for producing a carbonaceous film as described above, wherein the reduced pressure range is from -0.01 kPa to -0.08 MPa.

  7th of this invention is the manufacturing method of the said carbonaceous film characterized by depressurizing and carbonizing in the range of -0.01kPa--0.08MPa, introducing inert gas.

  In the eighth aspect of the present invention, the value of V / V1 (s) is 0.01 or more and 1000 or less when the volume of the treated product is V (L) and the amount of the inert gas to be introduced is V1 (L / s). The method for producing a carbonaceous film as described above, wherein Here, the “volume V of the processed material” represents the total volume of all members to be heated by being placed in a heating device, such as a polyimide film to be processed, a container of polyimide film, and a graphite material. The “inert gas amount V1” refers to the introduction rate (L / s) of the inert gas at the pressure of the gas outside the heating device (usually considered to be atmospheric pressure).

  The ninth of the present invention is the method for producing a carbonaceous film as described above, wherein the polymer film has a thickness of 10 μm to 250 μm.

The tenth aspect of the present invention is the method for producing a carbonaceous film as described above, wherein the area of the polymer film is 40000 mm ² or more.

  The eleventh aspect of the present invention is the method for producing a carbonaceous film as described above, wherein a carbonaceous film is produced from a laminate obtained by directly laminating two or more polymer films.

  A twelfth aspect of the present invention is the above-described carbonaceous film production method for producing a carbonaceous film from a laminate obtained by directly laminating 10 or more polymer films.

  By preventing the generation of foreign matter and fusion between raw material films in the carbonization process, it is possible to provide a high quality carbonaceous film with high productivity.

It is the schematic which shows an example of the processing method of the polymer film concerning this invention.

(Degree of decompression and thermal diffusivity)
When the polyimide film is treated under inert gas up to 1000 ° C, it gradually decomposes around 500 ° C, and low molecular gases such as carbon monoxide, carbon dioxide, nitrogen and ammonia, and low concentrations such as benzene, aniline, phenol and benzonitrile. Molecular organic matter is observed as a decomposition gas. When the temperature reaches about 900 ° C., the generation of these cracked gases almost converges, and after processing to 1000 ° C., a carbonaceous film having a weight reduced by about 60% can be obtained. In addition to the above components, many low molecular weight substances that are difficult to identify are observed, and these organic components are recovered as non-volatile tar components after carbonization.

  This tar component is present in the form of gas or fine mist immediately after being generated as a decomposition gas from the film. In the case where the film is sandwiched between graphite materials and processed, the gas may stay around the film under conditions where the decomposition gas does not escape easily. The staying gas causes aggregation and adheres to the film surface and the graphite material as tar. The adhering tar component is carbonized as the temperature rises as it is, and remains as a foreign substance on the film or interleaf. In order to suppress agglomeration of the gas component, carbonization in a reduced pressure atmosphere may be performed. By performing carbonization under reduced pressure, the decomposition gas can be prevented from agglomerating and the generation of foreign matter can be greatly suppressed. The suppression effect is higher as the degree of decompression is larger. For example, when a carbonization treatment is performed by sandwiching a polyimide film having a large area between graphite materials, it is expected that foreign substances are more likely to be generated due to a longer gas escape process than a polyimide film having a small area. Even in such a case, the occurrence of foreign matters can be suppressed by further increasing the degree of vacuum and performing carbonization.

In addition, when carbonizing a polyimide film under high vacuum (10 ¹ Pa or less) up to 1000 ° C., the weight per unit area is reduced compared to when carbonizing under an inert gas stream (atmospheric pressure). A carbonaceous film is obtained. This is considered to be because more outgas is generated from the inside of the film by heat treatment under high vacuum.

  The process of producing a graphite film from a polyimide film is divided into a carbonization process and a graphitization process. In order to obtain a graphite film with high thermal diffusion capability, it is necessary to orient the graphite layer neatly. In order to obtain a good quality graphite film having such a graphite layer, it is preferable to develop and orient the carbon plane to some extent after the carbonization treatment. The orientation of the carbon plane can be manipulated by adjusting the heating rate of carbonization. The lower the carbonization rate, the easier the carbon plane is oriented. For example, when the same polyimide film is processed up to 1000 ° C., a carbonized film having a good carbon orientation and a small thickness and a large area can be obtained when the carbonization rate is low as compared with the case where the carbonization rate is high.

On the other hand, when carbonization is performed under a high vacuum, more gas is generated from the inside of the film, so that a carbonized film having a partially broken carbon structure can be obtained. The structure-disturbed carbon plane hinders the growth of the graphite layer in the subsequent graphitization process, resulting in a graphite film with reduced thermal diffusion capacity. Foreign matter on the carbonized film can be removed by carbonization under reduced pressure conditions, but if the carbonization is performed under a high vacuum of about 10 ¹ Pa or less, the thermal diffusion capacity of the graphite film is reduced. End up.

  In order to solve the above problem, it is necessary to perform carbonization under reduced pressure that does not destroy the carbon surface. The degree of reduced pressure is preferably −0.001 kPa or more and −0.1 MPa or less, more preferably −0.01 kPa or more and −0.09 MPa or less, and further preferably −0.01 kPa or more and −0.08 MPa or less. If the degree of decompression is less than -0.001 kPa, the degree of decompression is too small, and the foreign matter removal effect may not be sufficiently exhibited. Conversely, if the degree of vacuum is greater than -0.1 MPa, the thermal diffusivity of the resulting graphite film may be reduced.

(Surface property of carbonized film)
The scratches on the carbonized film due to foreign materials will not disappear in the subsequent graphitization process, causing further problems such as the cracks spreading further and causing cracks or inducing cracks in the graphite film. . In addition, there is a problem that scratches on the carbon film inhibit the development of the graphite layer and cause a decrease in thermal diffusivity. When a graphite film is connected to a heat source for heat dissipation, if there is a scratch or tear on the graphite film, the portion becomes a large thermal resistance, and the heat dissipation performance of the graphite film is greatly reduced. In order to maximize the heat dissipation performance of graphite film, surface flaws must be suppressed as much as possible.

  Even in a carbonized film that appears to have no foreign matter at first glance, fine foreign matter that cannot be visually confirmed may adhere. These foreign substances are not lost in the graphitization step, and as a result, a graphite film having graphite fine particles adhered thereto is obtained. Since this graphite fine powder soars as fine dust during work, in addition to polluting the surroundings, there is also a danger that workers and the surrounding people will inhale dust. In addition, when using a graphite film for small equipment, etc., it is common to provide an adhesive layer or protective film layer, but in graphite films with fine graphite fine particles adhering to the surface, it may cause a decrease in adhesion There is. When the adhesion between the adhesive layer and the protective film layer and the graphite film is lowered, contact resistance is generated at the interface, and there is a possibility that the heat dissipation performance of the graphite film cannot be maximized as described above.

  If the foreign matter is removed by the carbonization method of the present invention, these problems can be solved, and a graphite film having a clean surface state and high heat dissipation performance can be obtained.

(Improvement of fusion)
From the viewpoint of increasing the amount of carbonization treatment, it is effective to perform carbonization treatment by directly laminating a large number of polyimide films. However, when two polyimide films are directly stacked and carbonized with a graphite material, a larger amount of decomposition gas is generated between the films than when only one sheet is processed, so that foreign matter is likely to be generated. . Even when such films are directly laminated, the occurrence of foreign matter can be greatly reduced by using the carbonization method of the present invention.

  When the number of directly laminated layers is increased, or when the load applied to the film is increased to suppress the undulation and the adhesion between the films is increased, a phenomenon occurs in which the carbonized films are fused to each other. When 10 sheets of 200mm square size polyimide film are directly laminated and carbonized to 1000 ° C under an inert gas stream (atmospheric pressure) without applying a load from above, a carbonized film with a large undulating surface is obtained. Although it is obtained, no fusion between the films occurs. When a certain amount of load is applied from above in order to suppress undulations, a part of the carbonized film will be fused, although the flatness will be high. This is thought to be due to the fact that the decomposition gas is difficult to escape due to the high adhesion between the films, and the tar content aggregated between the films works like an adhesive and solidifies as it is raised.

  As described above, since the polyimide film undergoes shrinkage in size in the carbonization process, when the heat treatment is performed in a free state where no weight is applied, a carbonized film having a largely undulated surface can be obtained. If the graphitization treatment is continued as it is, not only a distorted graphite film is obtained, but also the glassy film obtained after carbonization treatment has a very low mechanical strength, so that the workability is not good with a wavy carbonized film. The problem of becoming extremely bad also appears. Further, when carbonization treatment is performed by laminating a large number of polyimide films, the undulation is amplified between the overlapping films, and the undulation is further increased. This undulation can be suppressed by performing carbonization treatment while applying a load in a planar manner using means such as placing a weight on the film or caulking with a plate from above and below. As the number of polyimide films to be laminated increases, the force that causes undulations increases, so it is necessary to appropriately change the applied load according to the number of sheets to be overlaid.

  From the above, when the polyimide film is directly laminated and carbonized, it is necessary to perform the carbonization while applying a load to the polyimide film, but there is a problem that the films are likely to be fused. come. Even in such a case, the method of the present invention is extremely effective, and the carbonization treatment under reduced pressure prevents the decomposition gas from staying between the films, and also prevents the fusion even when plural sheets are directly laminated. It becomes possible to do.

(Introduction of inert gas)
When carbonizing a multilayer laminated polyimide film, foreign substances and fusion can be more effectively prevented by introducing the inert gas simultaneously with the treatment under reduced pressure. By introducing an inert gas from one of the firing sections and exhausting from the other at the same time, a flow path for the inert gas is generated in the firing section, and the decomposition gas staying between the films is removed more quickly from the system. I can do it. At this time, it is important to adjust the flow rate V1 (unit: L / s) of the inert gas and the displacement V2 (unit: L / s) to maintain the inside of the furnace in an appropriate reduced pressure state. The larger the amount of the inert gas introduced, the higher the effect. However, when the amount is too large, it is not preferable because the decomposition gas from the film becomes difficult to be emitted. There is also a problem that the cost increases when the use of inert gas increases. When the volume of the processed product is V, the volume of the processed product and the necessary amount of inert gas can be expressed in a proportional relationship. The volume V of the processed material referred to here does not indicate the volume of the firing part of the furnace, but includes all the members to be placed and heated in the heating device such as the polyimide film to be processed, the polyimide film container, and the interleaf. Represents the total volume. A value V / V1 (unit: s) obtained by dividing the flow rate V1 of the inert gas by the volume V of the processed material is preferably 0.01 or more and 1000 or less, more preferably 0.1 or more and 100 or less, and further preferably 1 It is 10 or less. When the value of V / V1 is less than 0.01, the amount of the inert gas to be introduced is too much for the processed material, which is not good. On the other hand, if the value of V / V1 is larger than 1000, the amount of inert gas is too small, and foreign matter and fusion may not be sufficiently prevented.

  Nitrogen, argon, helium etc. are mentioned regarding the kind of inert gas to be used. As long as the inert gas is used, no matter which gas is used, the film is not affected during carbonization, and the same quality can be obtained. Among these, nitrogen is preferably used from the viewpoint of cost.

  With respect to the atmospheric conditions, it is not always necessary to perform the treatment under the atmospheric conditions during the carbonization treatment, and at least the vicinity of 400 to 700 ° C. at which the most decomposition gas is generated may be the atmospheric conditions. For example, processing is performed under high vacuum up to around 400 ° C., and then an inert gas is introduced to maintain a predetermined degree of decompression, or the flow rate of the inert gas is reduced when 700 ° C. is exceeded. A method such as switching to the above processing is conceivable. By adopting such a treatment method, it is not necessary to constantly flow the inert gas during the treatment, and the consumption of the inert gas can be greatly reduced.

  In order to further exhibit the effects of the present invention, it is preferable to optimize the inert gas flow path in the furnace. It is more effective to design the inert gas introduction port and the exhaust port in accordance with the shape of the firing part and the container to be fired, and to make the container itself into which the polyimide film is put into a structure having good air permeability.

  The method of carbonizing under a reduced pressure atmosphere while introducing an inert gas is effective not only when processing a large number of laminated polyimide films but also when processing only one sheet. In particular, in the case of a polyimide film having a large area, it becomes difficult for gas to escape, and thus it may be impossible to completely remove foreign substances only by reducing the pressure. In such a case, it is possible to remove foreign substances more effectively by performing carbonization in a reduced pressure atmosphere while introducing an inert gas.

  When a large number of polyimide films are processed, it can be assumed that the inside of the furnace is temporarily at normal pressure or pressure when gas is generated. Predicting the amount of cracked gas and keeping the processing atmosphere in a reduced pressure state as much as possible is also a point for improving foreign matter and fusion.

(Regarding film thickness)
As the thickness of the raw material polyimide film increases, the amount of decomposition gas generated during the carbonization treatment increases, and the generation of foreign matter and fusion are more likely to occur. The thermal diffusion capacity of the graphite film itself is expressed by thermal conductivity (unit: W / (m · K)), but the ability to actually transport heat is obtained by multiplying the value of this thermal conductivity by the thickness of the graphite film. The value is an indicator. For example, even with a graphite film having the same thermal conductivity in the plane direction of 1000 W / (m · K), a 40 μm graphite film has a higher heat transport capability at a thickness of 25 μm and 40 μm. That is, when the same area is used, the 40 μm graphite film is more likely to diffuse the heat from the heat source. From the viewpoint of carrying out a large amount of heat transport with a minimum area, it is extremely effective to produce a thick graphite film.

  In general, in the case of producing a thick film with the polymer graphite method, it is necessary to use a thick polyimide film as a raw material. As described above, a thick polyimide film is more susceptible to foreign matters and fusion during carbonization. Further, since a thick polyimide film has a smaller number of processed sheets in the same volume than a thin film, it is preferable to use a slip sheet sandwiched between films as much as possible. By using the carbonization method under reduced pressure of the present invention, even a thick polyimide film can be carbonized without using a slip sheet. Also at this time, the reduced pressure carbonization treatment while flowing an inert gas is extremely effective. When processing a thick polyimide film, the flow rate of the inert gas may be further increased as compared with a thin film.

(Exhaust method)
Regarding the exhaust method, any known method can be used as long as it does not impair the safety of the firing furnace itself, such as a method using a vacuum pump or an exhaust fan. In particular, various types of vacuum pumps are commercially available from various companies and can be suitably used in the present invention because of their simple operation. Examples of the vacuum pump that can be used in the pressure range of -0.001 kPa to -0.1 MPa of the present invention include an aspirator (water flow pump), a dry vacuum pump, a mechanical booster pump, an oil rotary pump, a sorption pump, and an oil ejector pump. Is mentioned. The degree of decompression can be adjusted by attaching a valve to the exhaust part of the vacuum pump and adjusting the exhaust amount. Here, “pressure−0.001 kPa” means that the pressure is reduced by 0.001 kPa with a vacuum pump, and “pressure−0.1 kPa” means that the pressure is reduced by 0.1 kPa with a vacuum pump.

(Regarding treatment of outgas)
The cracked gas of the polyimide film contains various low molecular weight substances in addition to the above-described components, and these substances are obtained as nonvolatile tar-like substances when the polyimide film is carbonized. When a large number of polyimide films are carbonized at one time, the treatment of the generated tar becomes a problem. Many tar components are toxic, and it is necessary to treat the outgas efficiently considering the time and effort of cleaning and the danger to the human body. Further, if the continuous operation is continued with tar attached to the heater or the heat insulating material, there is a risk that deterioration will be accelerated. For this reason, it is necessary to quickly introduce the cracked gas during carbonization to the outside of the furnace after it is generated. When a polyimide film is processed in a high vacuum (10 ¹ Pa or less) with a vacuum pump, the outgas generated from the film diffuses in the furnace all at once. For this reason, the outgas is not guided well in the exhaust direction of the vacuum pump, but stays in the furnace and contaminates the furnace. In order to guide the gas out of the furnace successfully, do not perform carbonization under high vacuum, but introduce an inert gas from one side and exhaust from one side to create a flow of inert gas in the furnace. It ’s fine. By doing so, the generated gas is quickly discharged out of the furnace, and the risk of contaminating the furnace is greatly reduced. In the carbonization method of the present invention, the treatment of the cracked gas can be performed effectively.

(Regarding graphitization)
The carbonaceous film produced by the method of the present invention can be made into a higher quality carbonaceous film (graphite film) through a graphitization process in which heat treatment is performed at a high temperature of 2400 ° C. or higher. This graphitization process may be performed by once lowering the temperature of the furnace after carbonization and then increasing the temperature of the furnace again, or may be performed at once without passing through the temperature lowering process.

  Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. In addition, the flow volume of the nitrogen airflow in an Example and a comparative example represents the flow volume of the nitrogen gas in the atmospheric pressure outside an electric furnace.

(Preparation 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. Further, 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.

  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 125 μm, it was set to 5/3 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.

Example 1
A polyimide film A (PI-A) of 50 μm thickness prepared by the above method is sandwiched between graphite materials and carbonized by heating to 1000 ° C. at 2 ° C./min using an electric furnace. Was done. Carbonization was performed in a nitrogen stream (flow rate: 1 L / min), and the temperature was continuously raised while maintaining the internal pressure at -0.01 kPa with a vacuum pump. After cooling to room temperature, the thickness and surface state of the obtained carbonized film and the weight per unit area (g / m ² ) were measured. In addition, before and after the film processing, the contamination in the furnace was also evaluated. Subsequently, the carbonized film was sandwiched from above and below by an expanded graphite sheet having a length of 250 mm, a width of 250 mm, and a thickness of 250 μm, and a graphitization treatment was performed by raising the temperature to 2900 ° C. at 2 ° C./min using a graphitization furnace. After cooling to room temperature, the graphite film after heat treatment was sandwiched from above and below by a polyimide film having a length of 250 mm × width of 250 mm × thickness of 125 μm, and a back surface pressing step was performed using a compression molding machine. The applied pressure was 10 MPa. The thermal diffusivity of the finally obtained graphite film was measured using an optical AC method thermal diffusivity measuring apparatus (trade name “LaserPit” available from ULVAC-RIKO Co., Ltd.) in an atmosphere of 20 ° C. The measurement was performed at 10 Hz below. The results are summarized in Table 1. Here, “the internal pressure is −0.01 kPa with a vacuum pump” means that the internal pressure of the electric furnace is 0.01 kPa lower than the outside of the electric furnace.

(Example 2)
A polyimide film A (PI-A) of 50 μm thickness prepared by the above method is sandwiched between graphite materials and carbonized by heating to 1000 ° C. at 2 ° C./min using an electric furnace. Was done. Carbonization was performed in a nitrogen stream (flow rate: 1 L / min), and the temperature was continuously raised while maintaining the internal pressure at -0.1 kPa with a vacuum pump. Thereafter, the same process as in Example 1 was performed. The results are summarized in Table 1. Here, “the internal pressure is −0.1 kPa with a vacuum pump” means that the internal pressure of the electric furnace is 0.1 kPa lower than the outside of the electric furnace.

Example 3
A polyimide film A (PI-A) of 50 μm thickness prepared by the above method is sandwiched between graphite materials and carbonized by heating to 1000 ° C. at 2 ° C./min using an electric furnace. Was done. Carbonization was performed in a nitrogen stream (flow rate: 1 L / min), and the temperature was continuously increased while the internal pressure was kept at -0.5 kPa with a vacuum pump. Thereafter, the same process as in Example 1 was performed. The results are summarized in Table 1. Here, “the internal pressure is −0.5 kPa by a vacuum pump” means that the internal pressure of the electric furnace is 0.5 kPa lower than the outside of the electric furnace.

Example 4
A polyimide film A (PI-A) of 50 μm thickness prepared by the above method is sandwiched between graphite materials and carbonized by heating to 1000 ° C. at 2 ° C./min using an electric furnace. Was done. Carbonization was performed in a nitrogen stream (flow rate: 1 L / min), and the temperature was continuously increased while maintaining the internal pressure at -1 kPa with a vacuum pump. Thereafter, the same process as in Example 1 was performed. The results are summarized in Table 1. Here, “the internal pressure is −1 kPa by a vacuum pump” means that the internal pressure of the electric furnace is 1 kPa lower than the outside of the electric furnace.

(Example 5)
A polyimide film A (PI-A) of 50 μm thickness prepared by the above method is sandwiched between graphite materials and carbonized by heating to 1000 ° C. at 2 ° C./min using an electric furnace. Was done. Carbonization was performed in a nitrogen stream (flow rate: 1 L / min), and the temperature was continuously increased while maintaining the internal pressure at -10 kPa with a vacuum pump. Thereafter, the same process as in Example 1 was performed. The results are summarized in Table 1. Here, “the internal pressure is −10 kPa with a vacuum pump” means that the internal pressure of the electric furnace is 10 kPa lower than the outside of the electric furnace.

  It was found that a carbonized film without surface scratches can be obtained when carbonization is performed while flowing nitrogen under reduced pressure. It was also found that there was almost no contamination inside the furnace.

(Example 6)
A polyimide film A (PI-A) of 50 μm thickness prepared by the above method is sandwiched between graphite materials and carbonized by heating to 1000 ° C. at 2 ° C./min using an electric furnace. Was done. The carbonization was performed without flowing nitrogen, and the temperature was continuously raised while the internal pressure was kept at -10 kPa by a vacuum pump. Thereafter, the same process as in Example 1 was performed. The results are summarized in Table 1. Here, “the internal pressure is −10 kPa with a vacuum pump” means that the internal pressure of the electric furnace is 10 kPa lower than the outside of the electric furnace.

  In the case of treating one polyimide film, it was found that a carbonized film having no surface flaws can be obtained by performing carbonization under reduced pressure without flowing nitrogen. However, it was found that the inside of the furnace became slightly dirty as compared to when nitrogen was not flowed.

(Example 7)
A polyimide film A (PI-A) of 50 μm thickness prepared by the above method is sandwiched between graphite materials and carbonized by heating to 1000 ° C. at 2 ° C./min using an electric furnace. Was done. The carbonization treatment was performed without flowing nitrogen, and the temperature was continuously raised while maintaining the internal pressure at −80 kPa with a vacuum pump. Thereafter, the same process as in Example 1 was performed. The results are summarized in Table 1. Here, “the internal pressure is −80 kPa with a vacuum pump” means that the internal pressure of the electric furnace is 80 kPa lower than the outside of the electric furnace.

  It was found that a carbonized film having a high thermal diffusivity without surface flaws can be obtained even in a carbonization process under a relatively high reduced pressure.

(Comparative Example 1)
A polyimide film A (PI-A) of 50 μm thickness prepared by the above method is sandwiched between graphite materials and carbonized by heating to 1000 ° C. at 2 ° C./min using an electric furnace. Was done. Carbonization was performed in a nitrogen stream (flow rate: 1 L / min), and the temperature was continuously raised while the internal pressure was maintained at ± 0 kPa. Thereafter, the same process as in Example 1 was performed. The results are summarized in Table 1.

  The surface flaws of the carbonized film could not be removed completely only under conditions of nitrogen flow.

(Comparative Example 2)
A polyimide film A (PI-A) of 50 μm thickness prepared by the above method is sandwiched between graphite materials and carbonized by heating to 1000 ° C. at 2 ° C./min using an electric furnace. Was done. Carbonization was performed in a nitrogen stream (flow rate: 1 L / min), and the temperature was continuously increased while maintaining the internal pressure at +2 kPa. Thereafter, the same process as in Example 1 was performed. The results are summarized in Table 1. Here, “the internal pressure is +2 kPa by the vacuum pump” means that the internal pressure of the electric furnace is 2 kPa higher than the outside of the electric furnace.

  When carbonization was performed under the condition of nitrogen pressurization, the surface damage of the carbonized film was further increased as compared with the treatment under normal pressure. It was also found that the degree of contamination in the furnace also increased.

(Comparative Example 3)
A polyimide film A (PI-A) of 50 μm thickness prepared by the above method is sandwiched between graphite materials and carbonized by heating to 1000 ° C. at 2 ° C./min using an electric furnace. Was done. The carbonization treatment was performed without flowing nitrogen, and the temperature was continuously raised while maintaining the internal pressure at 10 ⁻¹ kPa with a vacuum pump. Thereafter, the same process as in Example 1 was performed. The results are summarized in Table 1. Here, “the internal pressure is 10 ⁻¹ kPa by a vacuum pump” means that the internal pressure of the electric furnace is 10 ⁻¹ kPa higher than the outside of the electric furnace.

  It was found that a carbonized film without scratches was obtained under high vacuum, but a graphite film having a low thermal diffusivity was obtained in the subsequent graphitization step. It was also found that the degree of contamination in the furnace also increased.

(Example 8)
A 75 μm thick polyimide film B (PI-B) (length 200 mm × width 200 mm) produced by the above method is sandwiched between graphite materials, and heated to 1000 ° C. at a rate of 2 ° C./min using an electric furnace. Was done. Carbonization was performed in a nitrogen stream (flow rate: 1 L / min), and the temperature was continuously raised while maintaining the internal pressure at -0.01 kPa with a vacuum pump. After cooling to room temperature, the thickness and surface state of the obtained carbonized film and the weight per unit area (g / m ² ) were measured. In addition, before and after the film processing, the contamination in the furnace was also evaluated. Subsequently, the carbonized film was sandwiched from above and below by an expanded graphite sheet having a length of 250 mm, a width of 250 mm, and a thickness of 250 μm, and a graphitization treatment was performed by raising the temperature to 2900 ° C. at 2 ° C./min using a graphitization furnace. After cooling to room temperature, the graphite film after heat treatment was sandwiched from above and below by a polyimide film having a length of 250 mm × width of 250 mm × thickness of 125 μm, and a back surface pressing step was performed using a compression molding machine. The applied pressure was 10 MPa. The thermal diffusivity of the finally obtained graphite film was measured using an optical AC method thermal diffusivity measuring apparatus (trade name “LaserPit” available from ULVAC-RIKO Co., Ltd.) in an atmosphere of 20 ° C. The measurement was performed at 10 Hz below. The results are summarized in Table 2. Here, “the internal pressure is −0.01 kPa with a vacuum pump” means that the internal pressure of the electric furnace is 0.01 kPa lower than the outside of the electric furnace.

Example 9
A 75 μm thick polyimide film B (PI-B) (length 200 mm × width 200 mm) produced by the above method is sandwiched between graphite materials, and heated to 1000 ° C. at a rate of 2 ° C./min using an electric furnace. Was done. Carbonization was performed in a nitrogen stream (flow rate: 1 L / min), and the temperature was continuously raised while maintaining the internal pressure at -0.1 kPa with a vacuum pump. Thereafter, the same process as in Example 8 was performed. The results are summarized in Table 2. Here, “the internal pressure is −0.1 kPa with a vacuum pump” means that the internal pressure of the electric furnace is 0.1 kPa lower than the outside of the electric furnace.

(Example 10)
A 75 μm thick polyimide film B (PI-B) (length 200 mm × width 200 mm) produced by the above method is sandwiched between graphite materials, and heated to 1000 ° C. at a rate of 2 ° C./min using an electric furnace. Was done. Carbonization was performed in a nitrogen stream (flow rate: 1 L / min), and the temperature was continuously increased while the internal pressure was kept at -0.5 kPa with a vacuum pump. Thereafter, the same process as in Example 8 was performed. The results are summarized in Table 2. Here, “the internal pressure is −0.5 kPa by a vacuum pump” means that the internal pressure of the electric furnace is 0.5 kPa lower than the outside of the electric furnace.

(Example 11)
A 75 μm thick polyimide film B (PI-B) (length 200 mm × width 200 mm) produced by the above method is sandwiched between graphite materials, and heated to 1000 ° C. at a rate of 2 ° C./min using an electric furnace. Was done. Carbonization was performed in a nitrogen stream (flow rate: 1 L / min), and the temperature was continuously increased while maintaining the internal pressure at -1 kPa with a vacuum pump. Thereafter, the same process as in Example 8 was performed. The results are summarized in Table 2. Here, “the internal pressure is −1 kPa by a vacuum pump” means that the internal pressure of the electric furnace is 1 kPa lower than the outside of the electric furnace.

(Example 12)
A 75 μm thick polyimide film B (PI-B) (length 200 mm × width 200 mm) produced by the above method is sandwiched between graphite materials, and heated to 1000 ° C. at a rate of 2 ° C./min using an electric furnace. Was done. Carbonization was performed in a nitrogen stream (flow rate: 1 L / min), and the temperature was continuously increased while maintaining the internal pressure at -10 kPa with a vacuum pump. Thereafter, the same process as in Example 8 was performed. The results are summarized in Table 2. Here, “the internal pressure is −10 kPa with a vacuum pump” means that the internal pressure of the electric furnace is 10 kPa lower than the outside of the electric furnace.

(Example 13)
A 75 μm thick polyimide film B (PI-B) (length 200 mm × width 200 mm) produced by the above method is sandwiched between graphite materials, and heated to 1000 ° C. at a rate of 2 ° C./min using an electric furnace. Was done. The carbonization was performed without flowing nitrogen, and the temperature was continuously raised while the internal pressure was kept at -10 kPa by a vacuum pump. Thereafter, the same process as in Example 8 was performed. The results are summarized in Table 2. Here, “the internal pressure is −10 kPa with a vacuum pump” means that the internal pressure of the electric furnace is 10 kPa lower than the outside of the electric furnace.

(Example 14)
A 75 μm thick polyimide film B (PI-B) (length 200 mm × width 200 mm) produced by the above method is sandwiched between graphite materials, and heated to 1000 ° C. at a rate of 2 ° C./min using an electric furnace. Was done. The carbonization treatment was performed without flowing nitrogen, and the temperature was continuously raised while maintaining the internal pressure at −80 kPa with a vacuum pump. Thereafter, the same process as in Example 8 was performed. The results are summarized in Table 2. Here, “the internal pressure is −80 kPa with a vacuum pump” means that the internal pressure of the electric furnace is 80 kPa lower than the outside of the electric furnace.

  It was found that when a 75 μm polyimide film was carbonized, foreign matter and scratches on the carbonized film were more likely to occur than when it was 50 μm. This is considered to be because the generation of decomposition gas increases as the thickness of the polyimide film increases. When carbonization is performed under reduced pressure, it is possible to reduce surface scratches on the carbonized film, but it cannot be completely eliminated. Further, it was found that if the treatment was performed in a nitrogen stream as in the case of 50 μm, the contamination in the furnace was reduced.

(Example 15)
A 75 μm thick polyimide film B (PI-B) (length 200 mm × width 200 mm) produced by the above method is sandwiched between graphite materials, and heated to 1000 ° C. at a rate of 2 ° C./min using an electric furnace. Was done. Carbonization was performed in a nitrogen stream (flow rate: 5 L / min), and the temperature was continuously increased while maintaining the internal pressure at -10 kPa with a vacuum pump. Thereafter, the same process as in Example 8 was performed. The results are summarized in Table 2. Here, “the internal pressure is −10 kPa with a vacuum pump” means that the internal pressure of the electric furnace is 10 kPa lower than the outside of the electric furnace.

  When the carbonization treatment was performed under reduced pressure by increasing the nitrogen flow rate, the surface foreign matter and scratches could be completely removed even with a 75 μm polyimide film.

(Comparative Example 4)
A polyimide film A (PI-A) of 50 μm thickness prepared by the above method is sandwiched between graphite materials and carbonized by heating to 1000 ° C. at 2 ° C./min using an electric furnace. Was done. Carbonization was performed in a nitrogen stream (flow rate: 1 L / min), and the temperature was continuously raised while the internal pressure was maintained at ± 0 kPa. Thereafter, the same process as in Example 8 was performed. The results are summarized in Table 2.

  The surface flaws of the carbonized film could not be removed only under conditions of nitrogen flow.

(Comparative Example 5)
A polyimide film A (PI-A) of 50 μm thickness prepared by the above method is sandwiched between graphite materials and carbonized by heating to 1000 ° C. at 2 ° C./min using an electric furnace. Was done. Carbonization was performed in a nitrogen stream (flow rate: 1 L / min), and the temperature was continuously increased while maintaining the internal pressure at +2 kPa. Thereafter, the same process as in Example 8 was performed. The results are summarized in Table 2. Here, “the internal pressure is +2 kPa by the vacuum pump” means that the internal pressure of the electric furnace is 2 kPa higher than the outside of the electric furnace.

  When carbonization was performed under the condition of nitrogen pressurization, the surface damage of the carbonized film was further increased as compared with the treatment under normal pressure. In addition, the amount of dirt in the furnace has increased.

(Comparative Example 6)
A polyimide film A (PI-A) of 50 μm thickness prepared by the above method is sandwiched between graphite materials and carbonized by heating to 1000 ° C. at 2 ° C./min using an electric furnace. Was done. The carbonization treatment was performed without flowing nitrogen, and the temperature was continuously raised while maintaining the internal pressure at 10 ⁻¹ kPa with a vacuum pump. Thereafter, the same process as in Example 8 was performed. The results are summarized in Table 2. Here, “the internal pressure is 10 ⁻¹ kPa by a vacuum pump” means that the internal pressure of the electric furnace is 10 ⁻¹ kPa higher than the outside of the electric furnace.

  It was found that a carbonized film with relatively few scratches was obtained under high vacuum, but a graphite film with a low thermal diffusivity was obtained in the subsequent graphitization step. In addition, the amount of dirt in the furnace has increased.

(Example 16)
A laminate of two 50 μm thick polyimide films A (PI-A) (length 200 mm × width 200 mm) produced directly by the above method was sandwiched between graphite materials, and an electric furnace was used up to 2 ° C./1000° C. The temperature was raised in min and carbonization was performed. Carbonization was performed in a nitrogen stream (flow rate: 1 L / min), and the temperature was continuously raised while maintaining the internal pressure at -0.01 kPa with a vacuum pump. After cooling to room temperature, whether or not the obtained carbonized film was fused was evaluated in three stages: ◯: no fusion, Δ: slight fusion, x: overall fusion. Evaluation was also made as to whether or not 10 sheets, 50 sheets, 75 sheets, and 100 sheets were directly laminated in the same process, after being carbonized. The results are summarized in Table 3. Here, “the internal pressure is −0.01 kPa with a vacuum pump” means that the internal pressure of the electric furnace is 0.01 kPa lower than the outside of the electric furnace.

(Example 17)
A laminate of two 50 μm thick polyimide films A (PI-A) (length 200 mm × width 200 mm) produced directly by the above method was sandwiched between graphite materials, and an electric furnace was used up to 2 ° C./1000° C. The temperature was raised in min and carbonization was performed. Carbonization was performed in a nitrogen stream (flow rate: 1 L / min), and the temperature was continuously raised while maintaining the internal pressure at -0.1 kPa with a vacuum pump. Thereafter, the same process as in Example 16 was performed. The results are summarized in Table 3. Here, “the internal pressure is −0.1 kPa with a vacuum pump” means that the internal pressure of the electric furnace is 0.1 kPa lower than the outside of the electric furnace.

(Example 18)
A laminate of two 50 μm thick polyimide films A (PI-A) (length 200 mm × width 200 mm) produced directly by the above method was sandwiched between graphite materials, and an electric furnace was used up to 2 ° C./1000° C. The temperature was raised in min and carbonization was performed. Carbonization was performed in a nitrogen stream (flow rate: 1 L / min), and the temperature was continuously increased while the internal pressure was kept at -0.5 kPa with a vacuum pump. Thereafter, the same process as in Example 16 was performed. The results are summarized in Table 3. Here, “the internal pressure is −0.5 kPa by a vacuum pump” means that the internal pressure of the electric furnace is 0.5 kPa lower than the outside of the electric furnace.

(Example 19)
A laminate of two 50 μm thick polyimide films A (PI-A) (length 200 mm × width 200 mm) produced directly by the above method was sandwiched between graphite materials, and an electric furnace was used up to 2 ° C./1000° C. The temperature was raised in min and carbonization was performed. Carbonization was performed in a nitrogen stream (flow rate: 1 L / min), and the temperature was continuously increased while maintaining the internal pressure at -1 kPa with a vacuum pump. Thereafter, the same process as in Example 16 was performed. The results are summarized in Table 3. Here, “the internal pressure is −1 kPa by a vacuum pump” means that the internal pressure of the electric furnace is 1 kPa lower than the outside of the electric furnace.

(Example 20)
A laminate of two 50 μm thick polyimide films A (PI-A) (length 200 mm × width 200 mm) produced directly by the above method was sandwiched between graphite materials, and an electric furnace was used up to 2 ° C./1000° C. The temperature was raised in min and carbonization was performed. Carbonization was performed in a nitrogen stream (flow rate: 1 L / min), and the temperature was continuously increased while maintaining the internal pressure at -10 kPa with a vacuum pump. Thereafter, the same process as in Example 16 was performed. The results are summarized in Table 3. Here, “the internal pressure is −10 kPa with a vacuum pump” means that the internal pressure of the electric furnace is 10 kPa lower than the outside of the electric furnace.

  When carbonization was performed while flowing nitrogen under reduced pressure, carbonization could be performed without causing fusion even when a large number of polyimide films were laminated.

(Example 21)
A laminate of two 50 μm thick polyimide films A (PI-A) (length 200 mm × width 200 mm) produced directly by the above method was sandwiched between graphite materials, and an electric furnace was used up to 2 ° C./1000° C. The temperature was raised in min and carbonization was performed. The carbonization was performed without flowing nitrogen, and the temperature was continuously raised while the internal pressure was kept at -10 kPa by a vacuum pump. Thereafter, the same process as in Example 16 was performed. The results are summarized in Table 3. Here, “the internal pressure is −10 kPa with a vacuum pump” means that the internal pressure of the electric furnace is 10 kPa lower than the outside of the electric furnace.

(Example 22)
A laminate of two 50 μm thick polyimide films A (PI-A) (length 200 mm × width 200 mm) produced directly by the above method was sandwiched between graphite materials, and an electric furnace was used up to 2 ° C./1000° C. The temperature was raised in min and carbonization was performed. The carbonization treatment was performed without flowing nitrogen, and the temperature was continuously raised while maintaining the internal pressure at −80 kPa with a vacuum pump. Thereafter, the same process as in Example 16 was performed. The results are summarized in Table 3. Here, “the internal pressure is −80 kPa with a vacuum pump” means that the internal pressure of the electric furnace is 80 kPa lower than the outside of the electric furnace.

  Even when a multi-layered polyimide film was processed only in a reduced-pressure atmosphere without flowing nitrogen, carbonization could be performed without causing fusion. However, when the number of laminated layers is large, the polyimide film can be carbonized without causing further fusion by performing carbonization while flowing nitrogen.

(Example 23)
A laminate of two 50 μm thick polyimide films A (PI-A) (length 200 mm × width 200 mm) produced directly by the above method was sandwiched between graphite materials, and an electric furnace was used up to 2 ° C./1000° C. The temperature was raised in min and carbonization was performed. Carbonization was performed in a nitrogen stream (flow rate: 5 L / min), and the temperature was continuously increased while maintaining the internal pressure at -10 kPa with a vacuum pump. Thereafter, the same process as in Example 16 was performed. The results are summarized in Table 3. Here, “the internal pressure is −10 kPa with a vacuum pump” means that the internal pressure of the electric furnace is 10 kPa lower than the outside of the electric furnace.

  When the flow rate of nitrogen was increased, fusion could be further prevented.

(Comparative Example 7)
A laminate of two 50 μm thick polyimide films A (PI-A) (length 200 mm × width 200 mm) produced directly by the above method was sandwiched between graphite materials, and an electric furnace was used up to 2 ° C./1000° C. The temperature was raised in min and carbonization was performed. Carbonization was performed in a nitrogen stream (flow rate: 1 L / min), and the temperature was continuously raised while the internal pressure was maintained at ± 0 kPa. Thereafter, the same process as in Example 16 was performed. The results are summarized in Table 3.

(Comparative Example 8)
A laminate of two 50 μm thick polyimide films A (PI-A) (length 200 mm × width 200 mm) produced directly by the above method was sandwiched between graphite materials, and an electric furnace was used up to 2 ° C./1000° C. The temperature was raised in min and carbonization was performed. Carbonization was performed in a nitrogen stream (flow rate: 1 L / min), and the temperature was continuously increased while maintaining the internal pressure at +2 kPa. Thereafter, the same process as in Example 16 was performed. The results are summarized in Table 3. Here, “the internal pressure is +2 kPa by the vacuum pump” means that the internal pressure of the electric furnace is 2 kPa higher than the outside of the electric furnace.

  When the internal pressure was normal pressure and pressurization, the films were fused.

(Example 24)
A laminate of two 75 μm-thick polyimide films B (PI-B) (length 200 mm × width 200 mm) directly produced by the above method was sandwiched between graphite materials, and an electric furnace was used up to 2 ° C./1000° C. The temperature was raised in min and carbonization was performed. Carbonization was performed in a nitrogen stream (flow rate: 1 L / min), and the temperature was continuously raised while maintaining the internal pressure at -0.01 kPa with a vacuum pump. After cooling to room temperature, whether or not the obtained carbonized film was fused was evaluated in three stages: ◯: no fusion, Δ: slight fusion, x: overall fusion. Evaluation was also made as to whether or not 10 sheets, 50 sheets, 75 sheets, and 100 sheets were directly laminated in the same process, after being carbonized. The results are summarized in Table 4. Here, “the internal pressure is −0.01 kPa with a vacuum pump” means that the internal pressure of the electric furnace is 0.01 kPa lower than the outside of the electric furnace.

(Example 25)
A laminate of two 75 μm-thick polyimide films B (PI-B) (length 200 mm × width 200 mm) directly produced by the above method was sandwiched between graphite materials, and an electric furnace was used up to 2 ° C./1000° C. The temperature was raised in min and carbonization was performed. Carbonization was performed in a nitrogen stream (flow rate: 1 L / min), and the temperature was continuously raised while maintaining the internal pressure at -0.1 kPa with a vacuum pump. Thereafter, the same process as in Example 24 was performed. The results are summarized in Table 4. Here, “the internal pressure is −0.1 kPa with a vacuum pump” means that the internal pressure of the electric furnace is 0.1 kPa lower than the outside of the electric furnace.

(Example 26)
A laminate of two 75 μm-thick polyimide films B (PI-B) (length 200 mm × width 200 mm) directly produced by the above method was sandwiched between graphite materials, and an electric furnace was used up to 2 ° C./1000° C. The temperature was raised in min and carbonization was performed. Carbonization was performed in a nitrogen stream (flow rate: 1 L / min), and the temperature was continuously increased while the internal pressure was kept at -0.5 kPa with a vacuum pump. Thereafter, the same process as in Example 24 was performed. The results are summarized in Table 4. Here, “the internal pressure is −0.5 kPa by a vacuum pump” means that the internal pressure of the electric furnace is 0.5 kPa lower than the outside of the electric furnace.

(Example 27)
A laminate of two 75 μm-thick polyimide films B (PI-B) (length 200 mm × width 200 mm) directly produced by the above method was sandwiched between graphite materials, and an electric furnace was used up to 2 ° C./1000° C. The temperature was raised in min and carbonization was performed. Carbonization was performed in a nitrogen stream (flow rate: 1 L / min), and the temperature was continuously increased while maintaining the internal pressure at -1 kPa with a vacuum pump. Thereafter, the same process as in Example 24 was performed. The results are summarized in Table 4. Here, “the internal pressure is −1 kPa by a vacuum pump” means that the internal pressure of the electric furnace is 1 kPa lower than the outside of the electric furnace.

(Example 28)
A laminate of two 75 μm-thick polyimide films B (PI-B) (length 200 mm × width 200 mm) directly produced by the above method was sandwiched between graphite materials, and an electric furnace was used up to 2 ° C./1000° C. The temperature was raised in min and carbonization was performed. Carbonization was performed in a nitrogen stream (flow rate: 1 L / min), and the temperature was continuously increased while maintaining the internal pressure at -10 kPa with a vacuum pump. Thereafter, the same process as in Example 24 was performed. The results are summarized in Table 4. Here, “the internal pressure is −10 kPa with a vacuum pump” means that the internal pressure of the electric furnace is 10 kPa lower than the outside of the electric furnace.

(Example 29)
A laminate of two 75 μm-thick polyimide films B (PI-B) (length 200 mm × width 200 mm) directly produced by the above method was sandwiched between graphite materials, and an electric furnace was used up to 2 ° C./1000° C. The temperature was raised in min and carbonization was performed. The carbonization was performed without flowing nitrogen, and the temperature was continuously raised while the internal pressure was kept at -10 kPa by a vacuum pump. Thereafter, the same process as in Example 24 was performed. The results are summarized in Table 4. Here, “the internal pressure is −10 kPa with a vacuum pump” means that the internal pressure of the electric furnace is 10 kPa lower than the outside of the electric furnace.

(Example 30)
A laminate of two 75 μm-thick polyimide films B (PI-B) (length 200 mm × width 200 mm) directly produced by the above method was sandwiched between graphite materials, and an electric furnace was used up to 2 ° C./1000° C. The temperature was raised in min and carbonization was performed. The carbonization treatment was performed without flowing nitrogen, and the temperature was continuously increased while maintaining the internal pressure at −80 kPa with a vacuum pump. The results are summarized in Table 4. Here, “the internal pressure is −80 kPa with a vacuum pump” means that the internal pressure of the electric furnace is 80 kPa lower than the outside of the electric furnace.

  It was found that when a 75 μm polyimide film was carbonized, fusion was more likely to occur than when it was 50 μm. This is considered to be because the generation of decomposition gas increases as the thickness of the polyimide film increases. When carbonization was performed under reduced pressure while flowing nitrogen, the fusion could be further suppressed.

(Example 31)
A laminate of two 75 μm-thick polyimide films B (PI-B) (length 200 mm × width 200 mm) directly produced by the above method was sandwiched between graphite materials, and an electric furnace was used up to 2 ° C./1000° C. The temperature was raised in min and carbonization was performed. Carbonization was performed in a nitrogen stream (flow rate 5 L / min), and the temperature was continuously increased while the internal pressure was kept at −80 kPa with a vacuum pump. Thereafter, the same process as in Example 24 was performed. The results are summarized in Table 4. Here, “the internal pressure is −80 kPa with a vacuum pump” means that the internal pressure of the electric furnace is 80 kPa lower than the outside of the electric furnace.

  When the flow rate of nitrogen was increased, fusion could be further prevented.

(Comparative Example 9)
A laminate of two 75 μm-thick polyimide films B (PI-B) (length 200 mm × width 200 mm) directly produced by the above method was sandwiched between graphite materials, and an electric furnace was used up to 2 ° C./1000° C. The temperature was raised in min and carbonization was performed. Carbonization was performed in a nitrogen stream (flow rate: 1 L / min), and the temperature was continuously raised while the internal pressure was maintained at ± 0 kPa. Thereafter, the same process as in Example 24 was performed. The results are summarized in Table 4.

(Comparative Example 10)
A laminate of two 75 μm-thick polyimide films B (PI-B) (length 200 mm × width 200 mm) directly produced by the above method was sandwiched between graphite materials, and an electric furnace was used up to 2 ° C./1000° C. The temperature was raised in min and carbonization was performed. Carbonization was performed in a nitrogen stream (flow rate: 1 L / min), and the temperature was continuously increased while maintaining the internal pressure at +2 kPa. Thereafter, the same process as in Example 24 was performed. The results are summarized in Table 4. Here, “the internal pressure is +2 kPa by the vacuum pump” means that the internal pressure of the electric furnace is 2 kPa higher than the outside of the electric furnace.

  When the internal pressure was normal pressure and pressurization, the films were fused.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

10 Graphite plate 20 Polyimide film

Claims (8)

A process for making a carbonaceous film was heat-treated polymer film, at least part of the step of carbonizing the polymer film is carried out in a vacuum range of -0.001kPa~-0.1MPa, in the vacuum A method for producing a carbonaceous film, characterized by introducing an inert gas simultaneously with the treatment . The value of V / V1 (s) is 0.01 or more and 1000 or less when the volume of the treated product is V (L) and the amount of inert gas introduced is V1 (L / s). Item 2. A method for producing a carbonaceous film according to Item 1 . The method for producing a carbonaceous film according to claim 1 or 2 , wherein the reduced pressure range is -0.01 kPa to -0.08 MPa. The method for producing a carbonaceous film according to any one of claims 1 to 3 , wherein the polymer film is heat-treated by applying a load from above. Method for producing a carbonaceous film according to any one of claims 1 to 4, wherein the thickness of the polymer film is 10μm or more 250μm or less. The method for producing a carbonaceous film according to any one of claims 1 to 5 , wherein the area of the polymer film is 40000 mm ² or more. The method for producing a carbonaceous film according to any one of claims 1 to 6 , wherein the polymer film is a polyimide film. After obtaining a carbonaceous film by the method according to any one of claims 1 to 7, characterized in that to produce a graphite film do graphitization process by heat treatment of the carbonaceous film at 2400 ° C. or higher A method for producing a graphite film.

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