JPS643801B2 - - Google Patents

Description

[Detailed description of the invention]

a. Field of Industrial Application The present invention relates to a method for manufacturing carbon films used as various electronic circuit elements, resistors, heating elements, etc. b. Prior Art Pure carbon films have excellent semimetallic properties and high stability, and are widely used as carbon film resistors and electric circuit elements. The conventional method for producing carbon films is to heat the porcelain body placed in a high-temperature vacuum furnace to over 1000℃, and then inject hydrocarbon gas into it to cause thermal decomposition.
A method of depositing a carbon film on the surface of porcelain is known. According to this method, in order to obtain a predetermined resistance value, it was necessary to adjust the heating temperature of the high-temperature vacuum furnace, the degree of vacuum, and the flow rate of the gas in a correlated manner. Usually 1100
℃ and a vacuum of 10 ^-5 Torr by adjusting the gas flow rate. Benzene was the most commonly used hydrocarbon, but propane and methane were also used. However, although this method is superior in producing a pure carbon film, (1) 1000
℃ or higher, (2) a carbon film with very high conductivity cannot be obtained, (3) the hardness of the obtained carbon film is relatively low, and (4) it cannot be uniformly spread on the carrier substrate. The drawback was that it was difficult to produce a carbon film with a certain thickness. For example, the conductivity of a carbon film formed on a substrate heated to 1000℃ using benzene is approximately
In order to obtain a film with higher conductivity than 500 S/cm, it is necessary to raise the substrate temperature or heat-treat the formed carbon film again. In experiments conducted by the present inventors, a temperature of 1400° C. was required to obtain a conductor of 1000 S/cm or more, and the hardness of the obtained carbon film was 7H on a pencil hardness value. In addition, in experiments conducted by the present inventor, when a carbon film was similarly created from a benzene raw material using a 10 cm x 5 cm ceramic substrate, the difference in film thickness distribution was usually 60 cm.
%, and it was difficult to keep it below 20% even under the best conditions. Of course, this tendency becomes more pronounced when the substrate becomes larger or when the carrier substrate is not flat but has a complicated shape. c. Purpose of the Invention The present invention aims to eliminate the above-mentioned drawbacks of the conventional method for producing a carbon film, and its purpose is to provide a carbon film that can be produced at a relatively low temperature and that also has high conductivity and high hardness. It is an object of the present invention to provide a method for producing a carbon film having a uniform film thickness distribution over the entire carrier substrate. d Structure of the Invention As a result of intensive research to achieve the above object, the present inventors have found that instead of hydrocarbons in the conventional method, a specific polymeric organic compound described below is coated on a carrier, or a polymeric film thereof is coated on a carrier. When sandwiched between carrier substrates and thermally decomposed in a vacuum or chemically inert gas atmosphere to generate a carbon film on the carrier, high conductivity and relatively high hardness values can be achieved at a low heating temperature of the carrier. It was discovered that it is possible to produce a carbon film having a constant thickness on a carrier, and based on this knowledge, the present invention was completed. The gist of the present invention is structured as follows. (1)
Polyparaphenylene oxide (hereinafter referred to as PPO), polyparaphenylene sulfide (hereinafter referred to as PPO)
PPS), polyparaxylene (hereinafter referred to as PPX), polysulfone (hereinafter referred to as PSF), polycarbonate (hereinafter referred to as PC), polyethylene terephthalate (hereinafter referred to as PET), aromatic polyimide (hereinafter referred to as PI), aromatic Polyamide-imide (hereinafter referred to as PAI), aromatic polyamide (hereinafter referred to as PAI)
), phenolic resin (hereinafter referred to as PHP),
Aromatic polymer compound selected from polymer compounds having polyoxadiazole (hereinafter referred to as POD), polybenzimidazole (hereinafter referred to as PBI), polybenzthiazole (hereinafter referred to as PBS), and polythiadiazole (PSD) structure. are coated on a carrier, or these polymer films are sandwiched between carrier substrates. (2) These carriers are heated to 700°C or higher in a vacuum or in an atmosphere of a chemically inert gas such as argon, helium, or nitrogen, or a gas mixture thereof to release the polymer compound. This method is characterized by thermal decomposition.
By cooling after thermal decomposition, taking out the carrier substrate, and physically removing the carbonized residual components of the polymer, a carbon thin film firmly adhered to the substrate can be obtained. Generally, when a polymeric organic compound is heated in an inert gas or vacuum, it thermally decomposes into a vaporized component and a carbonized residual component. However, this does not mean that any high-molecular organic compound can achieve the object of the present invention; rather, many are unsuitable. For example, polyethylene, a typical high-molecular organic compound, can be heated to generate hydrogen gas, ethylene gas, etc.
Although it decomposes into methane gas, etc., the resulting carbon film is essentially the same as a carbon film made from methane gas or the like as a raw material. In addition, polypropylene, polyvinyl alcohol, polyvinyl formal, polyvinyl ether, methyl methacrylate, vinyl chloride, vinylidene chloride, polyvinyl butyral, polyacetal, aliphatic polyamide, cellulose resin, etc. similarly cannot achieve the object of the present invention. When these polymers were used, an essentially soot-like film was precipitated, and the film had low electrical conductivity and hardness. Moreover, the film easily peeled off from the carrier, and the production efficiency of the film was significantly lower.
Furthermore, polyparaphenylene, which is a typical aromatic polymer compound, has a very small amount of components that gasify when heated, and almost no carbon film is formed even when heated to 1200°C. Examples of high-molecular organic compounds that belong to this category and cannot be used include urea resins and melamine resins. The polymeric organic compound used in the present invention has (1) a relatively large amount of components that are gasified by thermal decomposition. (2) It is necessary that the polymeric organic compound contains an aromatic ring such as a benzene ring. As a result of these considerations and experiments, the inventors found that PPO, PPS, PPX, PSF, PC, PET,
PI, PAT, PA, POD, PBI, PBS, PBD,
It turns out that PHP is ideal for creating carbon films. It was also found that derivatives of these compounds having an alkyl substituent on the aromatic ring have the same effect. By using these polymeric organic compounds, a carbon film with high conductivity can be obtained, and at temperatures of 700 to 900°C, where conventional materials such as benzene do not produce a carbon film.
A good carbon film can also be obtained. At the same time, a film with a high hardness value can be obtained, generally having a pencil hardness of 9H or more. The reason why a highly conductive carbon film is obtained is not clear, but thermal decomposition preferentially converts biradicals at the para-position of benzene.

[Formula] is generated, which is recombined on the substrate and is considered to be useful for improving the crystallinity and graphitization of the formed film. Although it is difficult to accurately estimate the graphitization rate of the film, laser Raman spectrum measurements indicate a high graphitization rate. The atmosphere in which the thermal decomposition and gasification components are precipitated is a vacuum or an atmosphere of argon, nitrogen, helium, or a mixed gas thereof. There is almost no difference in the characteristics of the carbon film produced in a vacuum or in an inert gas atmosphere such as argon. On the other hand, the presence of hydrogen gas generally tends to reduce the conductivity of the film, but the presence of less than 20% hydrogen gas does not significantly reduce the conductivity and may improve the adhesion of the film to the substrate. The presence of oxygen reduces the electrical conductivity, but if it is less than a few percent, it does not have much effect. The carrier substrate used in the present invention includes:
It must be able to withstand heating temperatures. For example, elements such as carbon, silicon, and boron, oxides such as alumina, silica, and magnesia, carbides such as silicon carbide, boron carbide, and tungsten carbide, nitrides such as silicon nitride, and boron nitride, Examples include borides such as tungsten boride and molybdenum boride, and silicides such as titanium silicide. Since the method according to the present invention is a method of applying the above-mentioned polymer onto a substrate and heat-treating it, a carbonaceous film can be essentially created on any carrier regardless of the shape of the carrier. In other words, even if the carrier has a complicated shape, it is sufficient to coat the surface of the carrier with a polymer and then heat-treat it. A film can also be formed on carriers having depressions that are difficult to form using the usual method of precipitating gasified components. Furthermore, since it is of course possible to continuously feed the carrier coated with the polymer into the furnace, this method is also suitable for continuous production of carbonaceous films. e Examples Example 1 Various polymer raw materials are dissolved in a solvent and 100×50×1
It was coated onto a 3 mm alumina ceramic substrate using a spinner. The film thickness is approximately the same for all polymers.
The thickness was set to 30 μm. The sample thus prepared was placed in a furnace and heated to 1000°C at a rate of 20°C per minute in an argon atmosphere. After holding at 1000°C for 1 hour, the temperature was lowered at a rate of 40°C per minute. After reaching room temperature, the sample was taken out and the remaining carbonized components on the substrate were removed with tweezers to obtain a carbon thin film firmly adhered to the substrate. For comparative evaluation, benzene,
The cases where polyparaphenylene and polyethylene were used are also shown. In the case of benzene, a carbon film was created by introducing benzene gas together with argon gas onto a ceramic substrate at 1000°C. Furthermore, since there is no suitable solvent for polyparaphenylene, polyparaphenylene in the form of pellets was sandwiched between ceramic substrates for evaluation. The film thickness distribution was measured at 9 locations on the substrate (3
The surface resistance was measured using the four-probe method (electrode spacing: 0.25 mm), and the film thickness distribution was calculated assuming that the conductivity was constant. Further, the conductivity value was calculated from the thickness measurement using Talystep and the above-mentioned surface resistance value. The results of the experiment are shown in Table 1. In the case of benzene, the conductivity was 600 s/cm and the film thickness distribution was 60%. Furthermore, it can be seen that polyparaphenylene and polyethylene have an extremely small amount of film deposited, making them practically unusable. On the other hand, the polymers used in the present invention all have higher electrical conductivity and higher hardness than benzene. It was also found that the film thickness distribution was 4% or less in all cases, and that a film with a very uniform thickness could be obtained.

【table】

【table】

[Table] Example 2 The relationship between electrical conductivity, film thickness, and film thickness distribution was measured in the same manner as in Example 1 by changing the treatment temperature and treatment time.
The results were as shown in Tables 2, 3 and 4 below.

【table】

【table】

[Table] As these results show, by using the method of the present invention, it is possible to create a carbon film at a temperature of 700°C or higher, and when compared under the same processing conditions, the film has a higher conductivity than benzene. I can do it. Also,
Furthermore, the resulting film has a significantly uniform thickness. The film thickness can be controlled by the treatment temperature and time as shown in Table 3. Example 3 A sample in which a polymer film was sandwiched between ceramic substrates was heat-treated in the same manner as in Example 1. It was observed that a carbon film similar to that of Example 1 was deposited, and its characteristics were almost the same. Therefore, it was found that the same effect can be obtained by sandwiching a polymer film between ceramics. Comparative Example 1 Using the apparatus shown in FIG. 1, a polymer raw material was placed in the pyrolysis furnace 1, and a substrate 6 made of quartz and alumina was placed in the substrate heating furnace 2. The polymer raw material placed in the pyrolysis furnace 1 is heated to 1000°C at a rate of 10°C per minute in an argon flow (0.4 liters per minute), and immediately after reaching 1000°C, the temperature is increased to 40°C per minute. The temperature dropped. The polymers in the pyrolysis furnace 1 are decomposed and gasified at a temperature specific to each polymer during heating, and the gasified components are conveyed to the substrate heating furnace together with argon gas.
The gasified components are precipitated on a substrate that has been previously heated to 1000°C. The resulting film was heat treated at 1000°C for 1 hour, and then the temperature was lowered at a rate of 40°C per minute. Table 5 shows the specific resistance value and condition of the carbon film thus obtained. Since the film thickness varies depending on the type of polymer used, we selected samples with a film thickness of approximately 1000 Å under the same conditions.

[Table] As is clear from the results in Table 5, the electrical conductivity value of the film obtained by the method of Comparative Example 1 is generally larger than that of the carbon film obtained using benzene as a raw material shown in Table 1. The value is almost the same as that of the carbon film obtained by the method of the present invention (Example 1, Table 1). In other words, it can be seen that the electrical conductivity of the carbon film is mainly determined by the starting materials. On the other hand, when comparing Example 1 of the present invention and this comparative example, the method of the comparative example yields a thick film, but it is far inferior to the method of the present invention in terms of uniformity of film thickness. There is. Using the method of this comparative example, a thinner film than the film shown in Table 5 (generally
200 to 400 Å), the film thickness distribution became even larger, reaching 300 to 100%. In other words, it can be seen that the method of applying a polymeric material in advance and then performing heat treatment as in the present invention is a much better method for creating a film of uniform thickness. f. Effects of the Invention As described above, according to the method of the present invention, the heating temperature of the substrate is lower than that of the conventional method of thermally decomposing hydrocarbons such as benzene and precipitating them on the substrate to create a carbon film. The film can be formed at a lower temperature, and the resulting carbon film has much higher conductivity and excellent hardness. Furthermore, the method of the present invention provides a much more uniform film thickness than the method of the present invention, in which a specific polymer compound is used as a raw material, and a gasified component obtained by thermal decomposition is precipitated on a heated substrate. A film is obtained. The present invention essentially allows the creation of a carbon film on a substrate of any size regardless of the size of the substrate, and is also suitable for continuous production of carbon films.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the principle of a carbon film manufacturing apparatus. 1: thermal decomposition furnace, 2: substrate heating furnace, 3: reaction tube, 4: carrier gas, 5: raw material polymeric organic compound, 6: substrate.

Claims (1)

[Claims] 1 Polyparaphenylene oxide, polyparaphenylene sulfide, polyparaxylylene, polysulfone, polycarbonate, polyethylene terephthalate, aromatic polyimide, aromatic polyamideimide, aromatic polyamide, phenolic resin polyoxadiazole, polybenzimidazole, An aromatic polymer compound selected from polybenzthiazole and polymer compounds having a polythiadiazole structure is coated on a carrier, or the polymer film is sandwiched between carrier substrates and heated at 700°C in an inert gas or vacuum. Pyrolyzed at temperatures above
A method for producing a carbon film, which comprises depositing a carbon film on the carrier.