JPWO2006137332A1 - Method for producing diamond-like carbon film - Google Patents

Abstract

To provide a method for producing a highly practical DLC film, specifically, to provide a method for producing a DLC film having a low degree of vacuum and good adhesion to a substrate using a simple apparatus. A first step of forming a metal oxide thin film or a metal nitride thin film on a substrate; and a mixed gas containing at least a hydrocarbon gas and / or an alcohol and a hydrogen gas in the metal oxide thin film or the metal nitride thin film. Reduced by the pulse discharge-plasma chemical vapor deposition method used as the introduced gas to form a metal thin film, and at least the surface layer of the metal thin film is changed to metal carbide to form an intermediate layer, on this intermediate layer A method for producing a diamond-like carbon film having a second step of forming a diamond-like carbon film.

Description

  The present invention relates to a method for producing a diamond-like carbon film.

The diamond-like carbon film (hereinafter abbreviated as “DLC film”) is an amorphous film having both sp ³ bonds such as diamond and sp ² bonds such as graphite. The DLC film has an extremely smooth surface, high hardness, and excellent wear resistance and lubrication characteristics. Therefore, taking advantage of these characteristics, it is expected to be used as a hard coating on the surface of plastic working dies and jigs.

  However, as a problem at the time of forming the DLC film, there is a problem that the adhesion to the substrate is poor. In particular, it is difficult to directly form a DLC film on an iron-based substrate. As these causes, it is considered that the internal stress of the DLC film is large and the stability of the carbon bond with the substrate is not sufficient.

  Therefore, as a method for improving the adhesion to the base material, a method of sandwiching an intermediate layer between the base material and the DLC film has been proposed. As this kind of intermediate layer, a Ti film, a Cr film, a Si film, a SiC film and the like are known. Conventionally, all of these intermediate layers have a high degree of vacuum by a physical vapor deposition method (hereinafter abbreviated as “PVD method”) or a chemical vapor deposition method (hereinafter abbreviated as “CVD method”). It is formed below (see, for example, Japanese Patent Laid-Open No. 2000-256850). For this reason, there are many practical problems such as a low DLC film generation rate and high cost.

  By the way, Noda, one of the present inventors, has shown that a DLC film can be formed on the anode side under a low vacuum level up to 200 Torr in the pulse discharge-plasma CVD method (Japanese Patent Laid-Open No. 2004-169183). .

  Here, as shown in FIG. 1, the pulse discharge-plasma CVD method is a DC power supply, an intelligent power module for intermittently outputting the power, a pulse transmitter, a high voltage transformer, a resistor, and a high voltage side of the high voltage transformer. In this method, plasma is generated by pulse discharge from a discharge electrode composed of a cathode and an anode using a pulse power source including a diode for discharging a voltage from the cathode, and a source gas is decomposed to vapor-phase grow.

  The problem to be solved by the present invention is to provide a highly practical method for producing a DLC film. Specifically, a simple apparatus is used, the degree of vacuum is low, and the adhesion to a substrate is good. The object is to provide a method of manufacturing a DLC film.

  As a result of intensive studies to solve the above problems, the present inventors have formed a metal oxide thin film or a metal nitride thin film on a substrate and then used a pulse discharge-plasma CVD method. Using a very high reducing atmosphere by hydrogen radicals, which is a feature, a metal oxide thin film or metal nitride thin film is reduced to a metal thin film such as a Ti film or Si film, and in the reaction process of pulse discharge-plasma CVD method, The present inventors have found that a metal present in at least the surface layer of a metal thin film can be changed to a metal carbide such as TiC or SiC, and a DLC film having high adhesion can be formed on the metal carbide film.

  That is, the method for producing a DLC film according to the present invention includes a first step of forming a metal oxide thin film or a metal nitride thin film on a substrate, a metal oxide thin film or a metal nitride thin film, a hydrocarbon gas, and / Or reduced by pulse discharge-plasma chemical vapor deposition using a mixed gas containing at least alcohol and hydrogen gas as an introduction gas to form a metal thin film, and at least the metal present in the surface layer of the metal thin film is a metal carbide And a second step of forming a diamond-like carbon film on the intermediate layer. The thin film refers to a film having a thickness of 0.1 mm to 1 nm.

  Here, the pulse discharge-plasma CVD method basically uses a mixed gas containing at least a hydrocarbon gas and / or alcohol and hydrogen gas as an introduction gas, and in an atmosphere formed by the introduction gas. To be implemented.

Before introducing the introduced gas into the reaction chamber of the pulse discharge-plasma CVD method, the reaction chamber is evacuated to about 10 ⁻² Torr. However, it is also possible to carry out with a lower degree of vacuum.

  Specific examples of the hydrocarbon gas include methane gas and acetylene gas, but are not necessarily limited thereto. Moreover, the said hydrocarbon gas may be 1 type, or 2 or more types may be mixed.

  In the pulse discharge described above, the discharge start voltage is as high as about 10 times the effective discharge voltage, and thus plasma is strongly injected into the base material, and there is an effect of improving the adhesion between the intermediate layer and the base material.

  At this time, as the base material, a metal material such as iron, iron alloy, aluminum, aluminum alloy, copper, copper alloy, titanium, titanium alloy or the like can be used. These metal materials may be contained in one kind or two or more kinds.

  The present invention is particularly useful for forming a DLC film on an iron alloy. Iron alloys have many uses as practical materials such as tool materials, mold materials, and magnetic memory materials. By forming a DLC film, the wear resistance and lubricity of the above-mentioned practical materials are improved, and additional value is added. It is because it can improve.

  The metal component constituting the metal oxide thin film or metal nitride thin film is preferably one or more selected from titanium, silicon, vanadium, zirconium, and tungsten. Silicon is called a so-called semi-metal because it belongs to the middle of a metal and a non-metal due to its nature, but in the present invention, it is treated as a metal component for convenience.

  These metal components are excellent in compatibility between the iron alloy as the base material and the DLC film. When these metal components are contained in the intermediate layer, it becomes easy to form a DLC film having high adhesion on the iron alloy. .

  Further, as a method of forming the metal oxide thin film or metal nitride thin film, specifically, for example, CVD method, laser ablation method, liquid phase deposition method (LPD method), electrophoresis method (EPD method), A method such as a sol-gel method can be exemplified.

  Each of these methods has advantages and disadvantages, and may be selected in consideration of the shape of the base material, required film characteristics, cost, and the like. For example, the CVD method can form a dense thin film at a relatively high processing speed, but requires an expensive apparatus and is expensive. The laser ablation method can form a dense thin film relatively easily, but the processing speed is slow and the cost is high. The LPD method is advantageous for forming a thin film over a large area and saves energy. However, since a metal fluoro complex is used as a raw material, attention must be paid to solution management. The EPD method is also advantageous for forming a large area thin film, but has a high running cost.

  On the other hand, the sol-gel method uses metal alkoxide as a raw material, so the solution is likely to be affected by moisture in the atmosphere and may become unstable. It is suitable for forming a large-area metal oxide thin film and has a low running cost. Therefore, it can be suitably used in the present invention.

The pulse discharge is performed at least with a gas pressure of 1 to 800 Torr, a discharge current density of 0.001 to 1000 A / cm ² , a discharge time of 0.01 to 10 ms in each cycle of the pulse, and a discharge stop time of 0.01 to 10 ms. It is good if the conditions are met. This is because, if such discharge conditions are satisfied, an appropriate film formation speed is obtained, and it becomes easy to form a DLC film with high adhesion.

In the conventional method for manufacturing a DLC film, a high vacuum of 10 ⁻⁴ Torr or more is required at the time of film formation. On the other hand, in the method for producing a DLC film according to the present invention, in order to obtain a DLC film having good adhesion to a substrate, exhaust up to about 10 ⁻² Torr as a vacuum is sufficient, and pulse discharge-plasma During the execution of the CVD method, a low vacuum degree of about 1 to 200 Torr may be used. In addition, since direct current (DC) plasma discharge can be used, the apparatus is simpler than radio frequency (RF) sputtering. Furthermore, since the sol-gel method can be used when forming the intermediate layer, the running cost can be reduced as a whole.

It is the schematic of the power supply circuit used for a pulse discharge-plasma CVD method. It is the schematic which showed the apparatus structure for forming a DLC film by a pulse discharge-plasma CVD method. It is the figure which showed the discharge waveform in the pulse discharge-plasma CVD method. It is an optical microscope photograph after the scratch test about the untreated goods (Bare) which has not performed the coating process by a coating liquid. It is an optical microscope photograph after the scratch test about the processed goods which performed the coating process by the coating liquid (use of titanium alkoxide) of the dilution rate 10%. It is the SEM photograph which showed the surface state about the case where there is no intermediate layer in formation of a DLC film to a spinning needle. It is the SEM photograph which showed the surface state about the case where an intermediate layer exists in formation of a DLC film to a spinning needle. It is the figure which showed the result of the Raman spectroscopic analysis in the case of no intermediate | middle layer in formation of the DLC film | membrane to a spinning needle. It is the figure which showed the result of the Raman spectroscopic analysis in case of an intermediate | middle layer in formation of the DLC film | membrane to a spinning needle.

  In the present invention, the substrate on which the metal oxide thin film or the metal nitride thin film is formed is moved to the reaction chamber for the treatment by the pulse discharge-plasma CVD method, and then introduced into the reaction chamber as an introduced gas. A mixed gas containing at least hydrocarbon gas and / or alcohol and hydrogen gas is introduced.

  At this time, before introducing the mixed gas, first, only hydrogen gas may be introduced and discharged. In this case, the metal oxide or metal nitride can be more completely reduced to the metal. A metal thin film formed by introducing a mixed gas into the reaction chamber and reducing the metal oxide thin film or metal nitride thin film by pulse discharge-plasma CVD processing is a metal carbide such as TiC or SiC at least in the surface layer. The DLC film with high adhesion is formed on the intermediate layer.

  In the intermediate layer, metal carbide may be present in a gradient from the surface toward the substrate, or metal carbide may be present in stages. Furthermore, metal carbide may exist in the entire intermediate layer.

  When the metal oxide thin film or metal nitride thin film that is the precursor of the intermediate layer is formed by the sol-gel method, as the metal alkoxide that is the raw material, specifically, for example, at least one M-O-C ( M: metal, O :, C: represents carbon), and an organic metal compound in which H of alcohol R—O—H is substituted with metal can be exemplified. Hereinafter, metal alkoxides are illustrated more specifically, but are not necessarily limited thereto. Moreover, these can also be used 1 type or in mixture of 2 or more types.

  Specific examples of the silicon alkoxide include methyl orthosilicate, ethyl orthosilicate, butyl orthosilicate, phenyltriethoxysilane, allyltriethoxysilane, methyltriethoxysilane, and cyclopentyltriethoxysilane. .

  Specific examples of the titanium-based alkoxide include titanium tetraisopropoxide, titanium tetraethoxide, titanium tetrabutoxide, and cyclopentadinier titanium triisopropoxide.

  Specific examples of vanadium alkoxides include vanadium acetyl acetate, vanadium oxytriethoxide, vanadium triisopropoxide, and the like.

  Specific examples of the zirconium alkoxide include zirconium ethoxide, zirconium tetraethoxide, zirconium tetrapropoxide, zirconium tetrabutoxide and the like.

  Specific examples of the tungsten alkoxide include tungsten pentaethoxide.

  The sol-gel method may be performed by diluting the metal alkoxide with a solvent such as toluene or dichloroethylene to prepare a coating solution, and coating the coating solution on the substrate in the air. In this case, specific examples of the coating method on the substrate include a dipping method, a spraying method, and a spin coating method. What is necessary is just to select suitably considering the shape of a base material, a target film thickness, etc.

Thereafter, the substrate coated with the metal alkoxide is moved into an apparatus maintained at a low vacuum of 10 ⁻² Torr or less, and a pulse discharge-plasma CVD process is performed. Pulse discharge-Heating by a plasma CVD process and a reducing atmosphere reduce the metal oxide to a metal such as Ti and Si first, and then change it into a metal carbide such as TiC and SiC, which is suitable for forming a DLC film. It becomes an intermediate layer.

  Hereinafter, a preferred embodiment of the present invention will be described with reference to examples. The present invention is not limited to the following examples, and various modifications can be made without departing from the scope of the invention.

FIG. 2 shows a schematic diagram of the apparatus used in this experiment. The vacuum chamber is evacuated to about 10 ⁻² Torr by a rotary pump, and then a mixed gas of CH ₄ and H ₂ (CH ₄ concentration = 3 vol%) is injected to a predetermined gas pressure. The flow rate of the gas is 20 sccm (standard cc / min 1 atm (atmospheric pressure 760 Torr)).

  FIG. 1 shows a power supply unit. The voltage switched by the intelligent power module (IPM) is boosted by a high voltage transformer, rectified by a high voltage diode, and then applied to the cathode. Here, the discharge is generated between the substrate (anode side) which is the base material and the cathode, and a DLC film is generated on the substrate.

  The high voltage and current applied to the substrate have waveforms as shown in FIG. Here, Ip is the discharge current, Td is the discharge time, Tn is the discharge pause time, Vp is the peak voltage at the start of discharge, and Vg is the discharge voltage. In the following, DT is a film forming time.

  Tetra-i-propoxytitanium (made by 5N high-purity chemical) as titanium alkoxide and tetraethoxysilane (made by 3N Kanto Chemical) as silicate alkoxide were each diluted with toluene to prepare each coating solution. The dilution ratio of each coating solution was 50%, 10%, 5%, 2%, and 1%, respectively, in volume ratio. These coating liquids were coated on the substrate with a spin coater (rotation speed 3000 rpm to 1000 rpm, centrifugal force 2000 G to 200 G). The used substrate (length 5 mm × width 5 mm × thickness 0.5 mm) is obtained by quenching a hard steel wire (SW-B; 80C), and has a Vickers hardness Hv of 850 to 870. The substrate hardness after the DLC film treatment was at least 823 and a maximum of 982 in micro Vickers, and there was almost no change in the hardness of the substrate before and after the treatment, and the temperature rise by this treatment did not reach the annealing temperature of the substrate ( 180 ° C. or lower).

  A substrate made of SK5 (quenched steel C-0.85 wt%, Cr-0.13 wt%) was prepared as a sample. Further, tetra-i-propoxy titanium (5N high-purity chemical) was diluted with toluene as a titanium alkoxide to prepare a coating solution. The dilution ratio of the coating solution was 10%, 2%, and 1%, respectively, in volume ratio. Further, tetraethoxysilane (manufactured by 3N Kanto Chemical Co., Ltd.) as a silicate alkoxide was diluted with toluene to prepare a coating solution. The dilution rate of the coating solution was 2% by volume.

  Subsequently, each coating liquid was apply | coated to the said sample surface with the spin coater. For comparison, an untreated (Bare) solution in which each coating solution was not applied was also prepared.

  Subsequently, these were each processed by the pulse discharge-plasma CVD method. The conditions of the pulse discharge-plasma CVD method are: methane concentration Cm = 3%, gas pressure Pg = 10 Torr, discharge current Ip = 1 A, discharge time Td = 0.5 msec, discharge pause time Tn = 1.7 msec, film formation time DT = 2 hr.

  Each of the obtained samples was scratched with a diamond needle. At this time, the load on the diamond needle was 70 N at maximum, and the load was increased by 10 N per 1 mm.

  4 and 5 are diagrams showing the influence of the presence or absence of the intermediate layer formed by the scratch test. FIG. 4 is an optical micrograph after a scratch test on an untreated product (Bare) that has not been coated with a coating solution. FIG. 5 is an optical micrograph after a scratch test on a treated product that has been coated with a coating solution (using titanium alkoxide) at a dilution rate of 10%.

  The treated product had a hard DLC film, and no peeling of the DLC film was observed even at 70N. On the other hand, it was confirmed that the untreated product had poor adhesion of the DLC film and the underlying iron layer was exposed by a load of about 10N to 20N.

  A substrate made of SUS301H was prepared as a sample. Further, tetra-i-propoxytitanium (manufactured by 5N High-Purity Science) was diluted with toluene as a titanium alkoxide to prepare a coating solution. The dilution ratio of the coating solution was 10%, 2%, and 1%, respectively, in volume ratio.

  Subsequently, each coating liquid was apply | coated to the said sample surface with the spin coater. For comparison, an untreated (Bare) solution in which each coating solution was not applied was also prepared.

  Next, each of the obtained samples was partially covered with an insulating vinyl tape to produce a film thickness measurement sample.

  Next, these samples were each processed by a pulse discharge-plasma CVD method. The conditions of the pulse discharge-plasma CVD method are: methane concentration Cm = 3%, gas pressure Pg = 15 Torr, discharge current Ip = 0.6 A, discharge time Td = 0.3 msec, discharge pause time Tn = 1.2 msec, film formation Time DT = 2 hr.

  Next, for each of the obtained DLC films, the film thickness was measured under the same conditions using a contact-type surface roughness meter. As a result, each film thickness was 0.9 μm.

  A sample in which a coating liquid containing a titanium alkoxide having a dilution rate of 5% is spray-coated on the surface of a spinning needle (manufactured by Nakagawa Seisakusho, product number 855, quenched steel SK5 C-0.85 wt%, Cr-0.13 wt%) The untreated (Bare) samples were each treated by a pulse discharge-plasma CVD method. The conditions of the pulse discharge-plasma CVD method are methane concentration Cm = 3%, gas pressure Pg = 5 Torr, discharge current Ip = 1.5 A, discharge time Td = 0.3 msec, discharge pause time Tn = 1.2 msec, film formation Time DT was set to 1 hr.

  6 and 7 show SEM photographs showing the difference in surface state depending on the presence or absence of the intermediate layer in the formation of the DLC film on the spinning needle. 8 and 9 show the results of Raman spectroscopic analysis with and without an intermediate layer in the formation of the DLC film on the spinning needle.

As can be seen from the Raman spectroscopic analysis results, the untreated product (Bare) has a very thin film thickness, and the SEM observation image shows that the DLC film is only partially attached. On the other hand, the processed product in which the intermediate layer was formed was confirmed to have a peak at 1350 cm ⁻¹ due to sp ³ bonding (diamond structure) and a peak at 1550 cm ^{−1 due} to sp ² bonding (graphite structure). It was confirmed that was formed.

Claims (4)

A first step of forming a metal oxide thin film or a metal nitride thin film on a substrate;
The metal oxide thin film or metal nitride thin film,
Reduced by a pulse discharge-plasma chemical vapor deposition method using a mixed gas containing at least hydrocarbon gas and / or alcohol and hydrogen gas as an introduction gas to form a metal thin film, and exists in at least the surface layer of the metal thin film Change the metal to metal carbide to make an intermediate layer,
A second step of forming a diamond-like carbon film on the intermediate layer;
A method for producing a diamond-like carbon film, comprising: The substrate is made of an iron alloy, and
2. The metal component constituting the metal oxide thin film or metal nitride thin film is one or more selected from titanium, silicon, vanadium, zirconium, and tungsten. Method for producing a diamond-like carbon film.   The method for producing a diamond-like carbon film according to claim 1 or 2, wherein the metal oxide thin film is formed by a sol-gel method using a metal alkoxide as a raw material. The pulse discharge has at least discharge conditions of a gas pressure of 1 to 800 Torr, a discharge current density of 0.001 to 1000 A / cm ² , a discharge time of 0.01 to 10 ms in each cycle of the pulse, and a discharge stop time of 0.01 to 10 ms. The method for producing a diamond-like carbon film according to claim 1, wherein the diamond-like carbon film is satisfied.

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