JPH01201095A - Diamond carbon film and production thereof - Google Patents

Abstract

PURPOSE:To easily obtain the above film having excellent mechanical strength and improved adhesivity owing to the stepwise or continuously varied bonded hydrogen content in the film and usable as a top-coating film of various products, by varying the reaction condition in the synthesis of the film continuously or stepwise at regular time intervals. CONSTITUTION:A matrix material 1 made of a metal, ceramics, plastics, etc., and useful for various products ranging from rocket to razor is placed in a reaction chamber. A carbon source gas (e.g., methane, CO or CO2) for forming a diamond carbon film 2 or a gaseous mixture of the source gas and a carrier gas (e.g., H2 or Ar) is supplied to the reaction chamber and a high-frequency potential is applied to a cathode while heating the matrix material 1 at room temperature-600 deg.C and varying the reaction condition stepwise or continuously to gradually decrease the bonded hydrogen content in the grown film. A glow discharge is formed between the cathode and an anode by this process to excite the carbon source (mixed) gas and generate a plasma. The objective film 2 having stepwise or continuously varied bonded hydrogen content can be produced by the above high-frequency plasma CVD process.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a diamond-like carbon film that can be used as a top coat film for various products, from rockets to razors, and a method for producing the same.

[Prior Art] In recent years, thin diamond-like carbon films have been synthesized from the gas phase in low-pressure regions, and the various properties of diamond-like carbon can be utilized to create cutting tools.

It is expected to be applied in various fields such as wear-resistant and slip-resistant materials, speaker materials, optical components, and electronics materials.

Among these, diamond-like carbon has the highest hardness.

Chemical stability, 71! One way to take advantage of its lubricity is to apply coach ink as a top coat on the surface of the base material, such as as an abrasion-resistant lubricant film for magnetic recording media or a wear-resistant film for cutting tools. .

[Problems to be solved] However, when a diamond-like carbon film is directly coated as a top coat film on a base material made of metal, ceramics, plastic, etc., the hardness 1 elastic coefficient and thermal expansion of the base material and the diamond-like carbon film are The difference in coefficients generates stress, which has the disadvantage of causing film peeling and cracks.

Therefore, although the diamond-like carbon film has the advantage of being highly hard and suitable for a top coat film, it has had the problem that it cannot be put to practical use as a top coat film.

The present invention has been made in view of the above problems. First, it improves the adhesion to the base material made of metal, ceramics, plastic, etc., prevents film peeling and cracks, and improves the adhesion of the top coat to the base material. The object of the present invention is to provide a diamond-like carbon film that can be practically used as a film, and a second object is to provide an easy manufacturing method for the diamond-like carbon film that can be practically used as a top coat film.

[Means for Solving Problems] In order to achieve the above object, the diamond-like carbon film of the present invention has a structure in which the amount of bound hydrogen in the film is varied stepwise or continuously.

Further, the method for producing a diamond-like carbon film of the present invention includes a method in which the reaction conditions during film synthesis are changed stepwise for a certain period of time, and films having different amounts of bound hydrogen are stacked in steps;
Another method is to continuously change the reaction conditions during membrane synthesis and to continuously vary the amount of bonded hydrogen.

Hereinafter, the present invention will be explained with reference to the drawings.

Figure 1 shows a conceptual diagram when the diamond-like carbon film of the present invention is used as a top coat film. In the figure, l is the base material as the material to be coated, and 2 is the diamond-like carbon film as the coating material. .

Base materials that require coating include a variety of products, from rockets to razors, and the materials may include metals,
Various materials such as ceramics and plastics can be used.

The diamond-like carbon film coating the base material 1 is formed on the surface of the base material 1 to a thickness of 100A or more, preferably 400A or more.

This diamond-like carbon film 2 is formed by a low-pressure vapor phase synthesis method such as an RF plasma CVD method, a DC plasma CVD method, an ion blasting method, or a sputtering method.

For example, when forming the diamond-like carbon film 2 by RF (radio frequency) plasma CVD method, a carbon source gas or a mixed gas of a carbon source gas and a carrier gas is supplied into the reaction chamber in which the base material l is placed, While heating the material 1, a high frequency is applied to the cathode to generate a glow discharge between the cathode and the anode, thereby exciting the carbon source gas or mixed gas and generating plasma. A diamond-like carbon film 2 is formed.

In this case, the carbon source gas includes, for example, alkanes such as methane, ethane, propane, butane, pentane, and hexane, ethylene, and propylene.

Alkenes such as butene, pentene, butadiene, alkynes such as acetylene, aromatic hydrocarbons such as benzene, toluene, xylene, indene, naphthalene, phenanthrene, cycloparaffins such as cyclopropane, cyclohexane, cyclopentene, cyclohexene, etc. Cycloolefins etc. are used.

Further, as the carbon source gas, carbon oxide, carbon dioxide, oxygen-containing carbon compounds such as methyl alcohol and ethyl alcohol, and nitrogen-containing carbon compounds such as methylamine, ethylamine and aniline can also be used. moreover,
Is it a single substance?It is classified as a Class 4 dangerous substance under the Fire Service Act, such as gasoline.
Class 1 petroleum, class 2 petroleum such as kerosene, turpentine oil, camphor oil, pine oil, etc., class 2 petroleum such as heavy oil, and class 4 petroleum such as gear oil and cylinder oil can also be effectively used. Moreover, the various carbon compounds mentioned above can also be used in combination.

Among the above carbon source gases, methane, carbon oxide, carbon dioxide, etc. are preferred.

The carrier gas is important not only as a carrier for introducing the carbon source gas into the plasma reaction system, but also in stably generating and sustaining plasma. As such a carrier gas, hydrogen gas, argon gas, neon gas, helium gas, xenon gas, nitrogen gas, etc. are used.

These may be used alone or in combination of two or more.

Among the above carrier gases, hydrogen gas, nitrogen gas, argon gas, etc. are preferred.

This diamond-like carbon film 2 has a structure in which the amount of bound hydrogen inside it is reduced stepwise or continuously from the base material l side to the surface side.

In other words, when the amount of bonded hydrogen in the film is large, the hardness of the film becomes low and the internal stress becomes small, and conversely, when the amount of bound hydrogen in the film is small, the hardness of the film becomes high and the internal stress becomes large. , the amount of bonded hydrogen on the base material l side is increased and the amount of bonded hydrogen on the surface side is decreased. This increases the hardness of the surface side of the top coat film, reduces the stress on the side that contacts the base material l, and improves adhesion, preventing peeling and cracking caused by differences in elastic modulus, thermal expansion coefficient, etc. is prevented.

Figure 2 shows a cross-sectional view of a diamond-like carbon film in which the amount of bound hydrogen 1 in the film differs in stages is used as a top coat film for base material 1. Different thin film layers 2-1゜2-2.2-3 (Amount of bonded hydrogen:
2-1>2-2>2-3). In this case, the number of thin film layers depends on the purpose of use of the base material l or the number of thin film layers.
Depending on the material, thickness, etc., the number of layers is two or more.

Further, FIG. 3 shows a cross-sectional view when a diamond-like carbon film 2 having a continuously different amount of bound hydrogen in the film is used as a top coat film for the base material l. In this case, the rate at which the amount of bound hydrogen changes continuously does not have to be uniform;
For example, the rate of change in the middle portion can be increased.

The amount of bonded hydrogen to be changed (reduced) stepwise or continuously is within the range of approximately 30 atomic % to several atomic %, or rotationally.

Next, a method for manufacturing a diamond-like carbon film will be described.

For example, when using the RF plasma CVD method, the reaction conditions for synthesizing the diamond-like carbon film 2 are controlled by changing the reaction gas concentration, pressure, base material temperature, and/or high-frequency input power.

In other words, when producing a diamond-like carbon film in which the amount of bound hydrogen changes stepwise by RF plasma CVD, in the first step, the reaction gas concentration, pressure, base material temperature, and/or temperature are adjusted so that the amount of bound hydrogen increases. Alternatively, set the conditions for high-frequency input power and perform arbitrary time synthesis.In the second stage, set the conditions such that the amount of bound hydrogen is smaller than in the first stage and perform arbitrary time synthesis, and then further In the third step, conditions are set such that the amount of bound hydrogen is smaller than in the second step, and synthesis is performed for an arbitrary time.As a result, thin film layers 2-1゜2-2.2-3 with different amounts of combined hydrogen are formed. It can also be formed by laminating (amount of bonded books X: 2-1>2-2>2-3).

In addition, when manufacturing a diamond-like carbon film in which the amount of bound hydrogen changes continuously, during membrane synthesis, the setting conditions of reaction gas concentration, pressure, base material temperature, and/or high-frequency input power should be changed sequentially depending on the amount of bound hydrogen. This is done by changing it continuously so that it decreases.

In the case of the RF plasma CVD method, the carbon source gas is supplied at a flow rate of, for example, 0.1 to 500 cc/min, and the carrier gas is supplied at a flow rate of 1 to 1,000 cc/min. In addition, the reaction stress, that is, the pressure inside the reaction chamber, is usually 10-5 to 10 Torr, preferably 10
-3~lO"Torr.This reaction pressure is 10-'
If the temperature is lower than Torr, the formation rate of the diamond-like carbon film may be significantly slowed down. On the other hand, 10'T
If it is higher than orr, a diamond-like carbon film may not be formed.

Furthermore, the heating temperature of the base material l is usually room temperature to 1.000
°C1 Preferably, it is room temperature to 900 °C. If this temperature is lower than room temperature, a diamond-like carbon film may not be formed. Further, it is preferable that the high-frequency input power be equal to IKW, because even if the high-frequency input power exceeds IKW, the corresponding effect may not be obtained.

[Example] The results of Examples and Comparative Examples are shown below.

・Base material: A1 substrate ・Diamond-like carbon layer: Formed by RF plasma CVD method of CH, +H2.

(Conditions)・Reaction pressure 10-'Torr・Substrate temperature,
100°C ・RF power + 120 W Example Three thin film layers were synthesized under the following conditions, and the base material l as a whole was
A diamond-like carbon film was formed in which the amount of bonded hydrogen decreased from the side to the surface side (thickness of each layer Comparative Example 1) Except that the diamond-like carbon film was formed under the same reaction conditions as the “base material side layer” in the above example, It was formed under the same conditions as in the example (diamond-like carbon film thickness: 6000A).

Comparative Example 2 A diamond-like carbon film was formed under the same conditions as in the example except that the diamond-like carbon film was formed under the same conditions as the "surface side layer" in the above example.The thickness of the diamond-like carbon film was 6000A.

The surface hardness of the rainbow glass was measured using a Knoop hardness meter, and the peeling state was measured using an optical microscope. The results are shown in the table below.

As a result, the samples of Examples had sufficient surface hardness, and no cracks or film peeling occurred. In contrast,
In Comparative Example 1, cracks and film peeling did not occur, or the surface hardness was insufficient, and the film was easily scratched. Furthermore, the surface hardness of Comparative Example 2 was not sufficient, and cracks and film peeling occurred.

[Effects of the Invention] As described above, according to the present invention, by changing the amount of hydrogen in the diamond-like carbon film, it is possible to improve adhesion, prevent film peeling, and improve mechanical strength. This will enable the practical use of diamond-like carbon films as top coat films for various products.

Another advantage is that these diamond-like carbon films can be easily synthesized using ordinary low-pressure vapor phase synthesis techniques.

[Brief explanation of the drawing]

Fig. 1 is a conceptual diagram when the diamond-like carbon film of the present invention is used as a top coat film, Fig. 2 is a cross-sectional view of the first embodiment of the present invention in which the amount of bonded hydrogen is changed stepwise, and Fig. 3 The figure shows a cross-sectional view of a second embodiment of the present invention in which the amount of bound hydrogen is continuously changed. l: Base material 2, diamond-like carbon film

Claims (3)

[Claims] (1) A diamond-like carbon film characterized in that the amount of bound hydrogen in the film is varied stepwise or continuously. (2) A method for producing a diamond-like carbon film, which is characterized in that the reaction conditions during film synthesis are changed in stages over a certain period of time, and films with different amounts of bonded hydrogen are stacked in stages. (3) A method for producing a diamond-like carbon film, characterized by continuously changing the reaction conditions during film synthesis and continuously varying the amount of bound hydrogen.