JP2002322555A - Diamond-like carbon multilayered film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a diamond-like carbon multilayered film which is excellent in wear resistance and further has low friction coefficient and excellent sliding characteristic. SOLUTION: A low density carbon layer 4 formed of diamond-like carbon with low film density and a high density carbon layer 5 formed of diamond-like carbon with high film density are alternatively laminated. The low density carbon layer 4 has average film density of <=2.2 g/cm<3> and meanwhile the high density carbon layer 5 has average film density of 2.3 to 3.2 g/cm<3> . The high density carbon layer 5 contains <=5 at.% of hydrogen component in the film. Layer thickness T1 of the low density carbon layer 4 is 0.4 to 30 nm, layer thickness T2 of the high density carbon layer 5 is 0.4 to 10 nm and T1/T2 is made to be 5 to 0.2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wear-resistant member such as a tool or a mold, an industrial or general household mechanical member / sliding member typified by an automobile part and a home appliance part, and an automatic card / ticket member. The present invention relates to a diamond-like carbon multilayer film which is used as a protective film for a write / read head of a reader or a printer, and is particularly suitable as a surface protective film requiring abrasion resistance and high sliding characteristics.

[0002]

2. Description of the Related Art A hard carbon film is generally made of diamond-like carbon (hereinafter sometimes abbreviated as DLC).
Called membrane. DLC uses various names such as hard amorphous carbon, amorphous carbon, hard amorphous carbon, i-carbon, and diamond-like carbon, but there is no particular distinction between these terms. The essence of DLC, in which these various terms are used, is that it has a structurally intermediate structure between diamond and graphite, and, like diamond, hardness, wear resistance, Because of its excellent solid lubricity, thermal conductivity, chemical stability, etc., for example, various members such as sliding members, dies, cutting tools, wear-resistant mechanical parts, abrasives, magnetic and optical parts, etc. It is being used as a surface protective film.

A characteristic of the DLC film is that it has a small friction coefficient (hereinafter sometimes referred to as μ) in contact with various mating materials such as metals such as iron and aluminum and ceramics such as glass. Can be But DLC
It is known that the coefficient of friction of the film varies greatly depending on the measurement environment and the mating material. In general, for example, in the case of an iron-based mating material, it is 0.15 to 0.4 in the atmosphere, in a vacuum or in a dry state. In a nitrogen atmosphere, it is 0.1 or less. Numerous studies have been made on the mechanism of reducing the μ of the DLC film. However, generally, carbon atoms adhere to the partner material from the DLC film, which is graphitized, and slip deformed on the c-plane (π-bonded plane) of the graphite. However, it is considered that μ is reduced by acting as a self-lubricating material.

When a DLC film is put into practical use as a hard coating film, it is required to realize a low friction coefficient of about 0.1 with respect to an iron-based counterpart material, to secure a thin film hardness which influences abrasion resistance, and to relate to coating reliability. Ensuring the adhesion to the substrate is an essential condition, and many proposals have been made for these conditions. Particularly effective methods include the addition of alloying elements to the DLC and the formation of a laminated film. Regarding the addition of alloy elements, for example, when Si is added,
μ is 0.1 to 0.15, and the hardness is reported to be about 30 GPa. The layered structure of DLC contributes to reduction of internal stress and improvement of adhesion, improvement of durability by thickening, improvement of corrosion resistance, and is recognized as a powerful means of controlling electric resistance. The following technologies are known.

(1) Japanese Patent Application Laid-Open No. 5-65625 discloses that a hard carbon film and a material having a high affinity for the hard carbon film, such as silicon, germanium, silicon carbide, silicon nitride, silicon dioxide, 1 selected from glass and alumina
A laminate is described in which more than one kind of buffer layers are alternately laminated and the outermost layer is a hard carbon film. (2) JP-A-10-237827 discloses a hard carbon film or a hard carbon film to which at least one kind of metal element is added, and at least one kind of metal or metal carbide, metal nitride or metal carbonitride. It describes a laminate in which objects are repeatedly laminated alternately, or a laminate in which at least two or more types of hard carbon films to which different types of metal elements or different amounts of metal elements are added are repeatedly and alternately laminated. . (3) JP-A-10-226874 describes a laminate in which hard carbon films having electric resistivity different by at least two orders are alternately laminated. (4) JP-A-11-1013 discloses that a carbon layer containing carbon as a main component, Si,
A metal layer mainly composed of a semimetal or a metal alloy of at least one or at least two selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo and W; A laminated film is described. (5) JP-A-10-72288 discloses that a raw material gas for film formation containing a carbon compound gas is turned into plasma by applying a voltage under vacuum to form a carbon layer unit comprising a thin-film carbon layer and a fine-particle carbon layer. It is described that stress is reduced by one or two or more carbon films formed, and durability is improved by improving adhesion and increasing the film thickness. (6) Japanese Patent Application Laid-Open No. 9-298097 discloses that in a DLC laminated film, at least three or more layers of a conductive film and a film having a higher hardness than the conductive film are alternately laminated, and the outermost layer is made of a conductive film. A laminate as a film is described.

[0006]

The high sliding property of a hard carbon film represented by DLC is caused by the slip of the π-bonded surface of the graphite crystal contained in the hard carbon film or formed at the sliding interface during sliding. It is believed to be due to lubrication. Therefore, graphite itself is easily deformed, and a film in which fine carbon particles are included in the hard carbon film itself has a low coefficient of friction and good slidability, but because the film hardness itself is low, wear due to sliding is low. Intense. That is, high hardness cannot be obtained when a low friction coefficient is to be obtained, or wear resistance is insufficient if the hardness is low even with a low friction coefficient, and in any case, the durability of the coating film is insufficient. Occurs. Conversely, when the graphite component in the DLC film is reduced, the film hardness is increased and the wear resistance can be secured, but the reduction in the coefficient of friction due to the self-lubricating property of graphite is not sufficiently achieved. For this reason, even in a conventional DLC having a single-layer structure or a laminated structure, a low friction coefficient of at least about 0.1 to 0.15, which is practically required, is stably realized, and high wear resistance is achieved. DLC with
No membrane was obtained.

In the case of metal nitrides such as TiN, TiAlN, and CrN which have been conventionally used as a hard coating film material, splashing powder called macroparticles generated at the time of film formation and friction with a partner material are caused. The friction coefficient is reduced by using abrasion powder generated by attacking the material or being attacked by the partner material as a lubricant. However, when such a hard material is used, troubles such as wear of the sliding member, an increase in the friction coefficient over time, and clogging by wear powder occur.

The present invention has been made in view of such a problem, and provides a diamond-like carbon film having excellent abrasion resistance, a low coefficient of friction, and a low aggressiveness to a counterpart material, and excellent sliding characteristics. The purpose is to:

[0009]

Means for Solving the Problems The present inventors have paid attention to the fact that the development of the coefficient of friction and the hardness of the thin film are greatly affected by the fine structure of DLC, and functionally laminate ultra-thin DLC films having different fine structures. The relationship between the microstructure and the sliding characteristics was examined. As a result, it has been found that by controlling the film density of the DLC film and laminating two types of DLC films having different film densities with an appropriate film thickness and cycle, excellent wear resistance and sliding characteristics can be obtained. Thus, the present invention has been completed.

That is, the diamond-like carbon multilayer film according to the present invention has a low-density carbon layer formed of diamond-like carbon having a low film density and a high-density carbon layer formed of diamond-like carbon having a high film density alternately. The low density carbon layer has an average film density of 2.2 g / cm ³ or less, while the high density carbon layer has an average film density of 2.3 to 3.2 g / cm ³ , The high-density carbon layer has a hydrogen component contained in the film of 5 at% or less, the low-density carbon layer has a thickness of 0.4 to 30 nm, and the high-density carbon layer has a thickness of 0.4 to 30 nm. 10 nm, and the ratio T of the layer thickness T1 of the low density carbon layer to the layer thickness T2 of the high density carbon layer.
1 / T2 is 5 to 0.2. In the multilayer film, the outermost layer is preferably formed of the low-density carbon layer, and the thickness thereof is preferably set to 2 to 200 nm.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS DLC according to an embodiment of the present invention
As shown in FIG. 1, the multilayer film is formed on the surface of the substrate 1 by the intermediate layer 2.
, A low-density carbon layer 4 formed by DLC having a low film density and a high-density carbon layer 5 formed by DLC having a high film density are alternately stacked. And a top layer 6 made of the same low-density carbon layer as the layer 4 is formed thereon.

Here, the technical significance of changing the density of the carbon layer formed by DLC in the multilayer film 3 and stacking it will be described in detail. In order to improve the wear resistance of the DLC film, it is necessary to avoid plastic deformation of the film on the friction surface. That is, it is desirable to reduce the plasticity index. This plasticity index is determined by the elastic constant E, the film hardness H, and the ratio E / H of the material properties together with the shape of the material surface.
It is considered that a material having a large E and H and a small E / H is good as a material ("Thin Film Tribology", Enomoto and Miyake, published by The University of Tokyo Press, p5
8). In the case of a metal material, the E / H is almost constant irrespective of the type, but ceramics having a small E / H as compared to metal have high wear resistance, which is a reason suitable as a hard coating film. The wear rate of the material is inversely proportional to H. On the other hand, the coefficient of friction depends on the resistance to shear stress on the friction surface, which has a close correlation with the hardness of the coating film surface. For example, graphite, molybdenum disulfide, silver, indium, and the like used as a solid lubricating film have low hardness and low resistance to shear force, and thus have a low friction coefficient.

From the above description, it is essentially impossible to simultaneously achieve wear resistance and a low coefficient of friction as long as a single material is used even with a DLC film. On the other hand, the present inventor has conducted intensive studies on the mechanical properties of the DLC film and the abrasion resistance and sliding sliding properties correlated therewith. As a result, these properties have a close relationship with the film density of the DLC film, and are referred to as film density. It was found that control was possible with macro parameters. Therefore, in the process of forming the carbon layer, a certain difference is given to the film density, which contributes to the slidability by reducing the friction coefficient, and the high wear resistance contributes to the improvement of the friction durability. By continuously forming the high-density carbon layer into a multilayer under predetermined conditions, a DLC film satisfying both characteristics was successfully obtained. Hereinafter, the required film density will be further described.

The average film density of DLC of the low density carbon layer 4 is 2.2 g / cm ³ or less, preferably 2.0 g / cm ^3.
It is better to do the following. By setting the average film density to 2.2 g / cm ³ or less, the elastic constant is smaller than 200 GPa, the film hardness is smaller than 30 GPa, and the film is easily deformed by shear stress on the friction surface, and the friction coefficient is reduced. be able to. On the other hand, the average film density of the high-density carbon layer is 2.3 g / cm ³ or more, preferably 2.5 g / cm ³ or more. By setting the average film density to 2.3 g / cm ³ or more, the elastic constant becomes larger than 300 GPa, the film hardness becomes larger than 50 GPa, and sufficient abrasion resistance is provided. However, if the film density becomes too high,
Intrinsic stress of film becomes excessive, reduces the deformability due to load stress at the time of use, since such problems such as peeling and film breakdown occurs, 3.2 g / cm ³ or less, preferably 3.0 g / cm ³
It is better to keep the amount below 2.7 g / cm ³ , more preferably.

The above-mentioned film density means an average value in the carbon layer, regardless of the form of the density distribution in the thickness direction of the carbon layer. For example, as shown in FIG. 2, not only the form (A) in which the film density in each carbon layer is constant, but also the form (B) or (C) in which the film density changes in the layer in a tilted manner in the thickness direction. You may take it. In addition, the film density is measured by Rutherford back scattering (RBS) method, X-ray reflectivity method,
Or Sink-Float method (ASTMD729) or Density
It can be measured by the Gradient Column method (ASTMD1505) or the like.

The hydrogen content in the high-density carbon layer 5 is preferably as small as possible, and it is desirable to keep the hydrogen content at 5 at% or less. By controlling the impurity hydrogen to 5 at% or less,
The film hardness and elastic constant under a high film density can be easily increased, and the wear resistance can be further improved. Scheibe et al. Reported the relationship between the film density of the carbon layer and the hydrogen contained therein (IEEE Tran. On Plasma Sci., Vo
It is known that the DLC film density is closely correlated with the elastic constant E and the film hardness H, as described in I.25 (1997), p685). That is, when the film density is high, both E and H increase, and when the film density is low, both E and H decrease. This is because the rate of increase / decrease differs depending on the impurity element contained in the DLC. In particular, when hydrogen is contained at less than 5 at%, the degree of correlation increases, and both E and H take large values under a high film density. The plasticity index is reduced, and the wear resistance can be further improved.

The low-density carbon layer 4 has a thickness of 0.4 nm.
As described above, the thickness is preferably 30 nm or less, and the layer thickness of the high-density carbon layer 5 is preferably 0.4 nm or more and 10 nm or less. If each of the low-density carbon layer 4 and the high-density carbon layer 5 is less than 0.4 nm, it becomes difficult for each layer to maintain its characteristics. When the low-density carbon layer 4 exceeds 30 nm,
Since this layer has low resistance to shear stress, the amount of wear due to friction increases, which causes trouble. On the other hand, when the high-density carbon layer 5 exceeds 10 nm, the friction in this layer affects the overall sliding characteristics in the portion exposed on the friction surface and the sliding surface, and this layer has a resistance to shear stress. Due to the high performance, the coefficient of friction increases.

The thickness of the low-density carbon layer 4 is T1,
When the layer thickness of the high-density carbon layer 5 is T2, the layer thickness ratio T
It is desirable that 1 / T2 be 5 to 0.2. In determining the layer thickness ratio, it is necessary that the low-density carbon layer 4 is not too thick and the high-density carbon layer 5 is not too thin, so that the resistance of the entire coating film to the shear stress of friction is balanced. . When the layer thickness ratio T1 / T2 exceeds 5, and the low-density carbon layer 4 is significantly thicker than the high-density carbon layer 5, the low-density carbon layer 4 has a small amount of deformation due to low frictional resistance, In addition, the high-density carbon layer 5 is relatively thin, which causes a decrease in wear resistance. On the other hand, the ratio T1
If / T2 is less than 0.2 and the high-density carbon layer 5 is significantly thicker than the low-density carbon layer 4, the amount of deformation with respect to friction decreases, leading to an increase in the coefficient of friction.

Although the outermost layer 6 is not always required, by providing a low-density carbon layer as the outermost layer 6, the surface can be easily deformed in the initial stage of sliding, and furthermore, the outermost layer 6 can be used as a mating material. The adhesion of carbon atoms can be promoted, and a reduction in the coefficient of friction can be realized, especially at the beginning of the sliding test. However, the thickness of the outermost layer 6 is 2 nm.
If it is less than 200 nm, the effect is too small.On the other hand, if it exceeds 200 nm, the amount of wear due to friction increases, and the generation of wear powder in the sliding portion prevents the friction from occurring smoothly, that is, the friction coefficient becomes unstable. Therefore, the thickness of the outermost layer 6 is preferably set to 2 to 200 nm, because it causes troubles such as an increase in the amount of friction.

It is desirable that the repetition period of one set of the low-density carbon layer 4 and the high-density carbon layer 5 in the layer direction is 30 nm or less, preferably 10 nm or less. 3 laminated films
By using an ultrathin film having a thickness of 0 nm or less, the characteristics of both layers can be efficiently exhibited against the friction phenomenon on the sliding surface, and excellent wear resistance and a low friction coefficient can be stably realized. When the outermost layer 6 is provided, it is preferable that the thickness of the laminated portion 7 inside the outermost layer 6 be at least 500 nm or more than the outermost layer 6. When the outermost layer 6 is formed to be thicker than the low-density carbon layer 4 in the laminated portion 7,
The numerical values of T1, T2, T1 / T2, and the repetition period mean recommended values for the low-density carbon layer 4 and the high-density carbon layer 5 in the laminated portion 7.

As the substrate 1 on which the multilayer film 3 is formed, ceramics such as cemented carbide, iron alloy, titanium alloy, aluminum alloy, copper alloy, glass, alumina, etc.
An appropriate metal material such as Si or a resin material, or a nonmetal material can be used. The intermediate layer 2 provided between the base material 1 and the multilayer film 3 serves to ensure the adhesion between the base material 1 and the multilayer film 3, and has a metal such as tungsten having such an effect. Or a mixture of metal and carbon described in, for example, JP-A-10-29718, a metal or metalloid carbide for protecting a substrate, or a metal or metalloid nitride, or a metal or metalloid Can be used. The intermediate layer 2 is not limited to a single layer, but may be a multilayer.

The method for forming the multilayer film of the present invention is not particularly limited. However, the method for forming the multilayer film by sputtering using solid carbon as an evaporation source (target) is nanometer (n).
m) It is preferable because the layer thickness and the film density can be easily controlled on the order. Also, from the viewpoint of reducing hydrogen in the carbon film, a method of forming a carbon film using a hydrocarbon gas such as methane as a film forming source gas is inappropriate, and sputtering using solid carbon as a target is not appropriate. preferable.

When the low density carbon layer 4 is formed, it is not necessary to apply a negative bias voltage to the substrate, but when the high density carbon layer 5 is formed, it is preferable to apply a negative bias voltage. That is, a negative DC voltage, a DC pulse voltage or a high-frequency bias voltage is applied to the substrate, and the applied voltage irradiates the ions simultaneously with the deposition of the film at the time of film formation, thereby increasing the film density by the ion implantation effect. It is preferable to control. In general, it is difficult to form a hard carbon film having a film density of more than 2.6 g / cm ³ by a method of applying a bias voltage in the ordinary sputtering, but an inductively coupled plasma (IPC) method or a high-frequency plasma (rf) method is used. Hard carbon film exceeding 2.6 g / cm ³ can be easily formed by sputtering by increasing the ionization rate of carbon by adding it to sputtering or adding arc ion plating or laser ablation. can do.

By the way, as mentioned above,
Japanese Patent No. 226874 describes a DLC film in which two types of hard carbon films having electric resistivity different by at least two digits are alternately laminated, but there is essentially no relation between electric resistivity and film density. Further, when a film is formed using a hydrocarbon gas as a raw material gas as in Examples 1, 2 and 4 described in the same publication, even if the density is high, a large amount of hydrogen is contained, and the elastic modulus E and the hardness H are low. Therefore, the wear resistance cannot be improved. In the cathode arc ion plating method as in Example 3, the substrate voltage was increased from 600 V to 60 V.
It is presumed that a low-density film of 2.1 g / cm ³ or less cannot be formed even if V is changed to V. Further, in the above-mentioned Japanese Patent Application Laid-Open No. 10-72288, a DLC film in which a thin-film carbon layer and a fine-particle carbon layer are alternately laminated is described, but the particulate carbon layer is not essential in the present invention, and It is described that these carbon layers use a hydrocarbon gas as a source gas for film formation, and as described above, as long as the hydrocarbon gas is used as a source gas to form a film, the wear resistance according to the present invention is excellent. It is difficult to form a high density carbon layer. JP-A-9-298097 discloses a DL in which a conductive film and an insulating film having a higher hardness are alternately laminated.
Although the C film is described, the insulating film is formed by using methane gas as a source gas. As described above, as long as such a hydrocarbon gas is used as a source gas, the abrasion resistance according to the present invention is reduced. It is difficult to form a high-density carbon layer having a good quality.

Next, the present invention will be described more specifically with reference to examples, but the present invention is not construed as being limited by the following examples.

[0026]

EXAMPLE First, a SKH (high-speed steel) substrate having a diameter of 50 mm and a thickness of about 8 mm for measuring the coefficient of friction and abrasion resistance, and a diameter of about 2 inches and a thickness of about 20 for measuring the film density and the amount of hydrogen in the film.
A 0 μm Si wafer substrate was prepared. These substrates were degreased with acetone as a pretreatment for film formation, ultrasonically cleaned for 20 minutes, and then sufficiently dried by spraying compressed air. The substrate subjected to such a treatment was set in a sputtering chamber and evacuated to 3 × 10 ⁻⁶ torr or less. afterwards,
Ar gas as an operating gas was introduced into the chamber to a pressure of 3 mtorr, a high-frequency power source was applied to generate Ar plasma, and sputter etching of the substrate surface with Ar ions was performed at a rf power of 200 W for 5 minutes.

As a sample for measuring a coefficient of friction and abrasion resistance, the surface of the SKH substrate was coated with a multilayer film or a single layer film shown in FIG. 1 in the following manner. In the case of a multilayer film, the outermost layer 6 is formed of a low density carbon layer. Table 1 shows the layer thickness T1 of the low-density carbon layer 4, the layer thickness T2 of the high-density carbon layer 5, the layer thickness ratio T1 / T2, the number of layers, and the layer thickness of the outermost layer 6, which constitute the laminated portion 7 excluding the outermost layer. Show. Table 1 shows layers 4 and 5
And the lamination cycle and the number of laminations as one set. (1) Except for sample No. 23 On the SKH base material, first, a W metal layer was formed to a thickness of about 50 nm as a first intermediate layer, and then a second intermediate layer was formed by spin deposition.
A 200-nm thick W-carbon mixed amorphous layer as an intermediate layer
Formed. Further, a low-density carbon layer 4 and a high-density carbon layer 5 were alternately formed thereon, and finally an outermost layer 6 was formed. (2) On a sample No. 23 SKH base material, first, a TiAlN layer was formed as a base intermediate layer to a thickness of 1 μm by an arc ion plating film forming apparatus, and a Ti layer of a first intermediate layer was formed thereon by sputtering. A metal layer is formed to a thickness of about 50 nm, and a Ti—carbon mixed amorphous layer as a second intermediate layer is formed to a thickness of about 20 nm by spin film formation.
It was formed at 0 nm. Further, a low-density carbon layer 4 and a high-density carbon layer 5 were alternately formed thereon, and finally an outermost layer 6 was formed.

The intermediate layer, the low-density carbon layer, the high-density carbon layer and the outermost layer were all formed by dc magnetron sputtering using a HSM-752 sputtering system manufactured by Shimadzu Corporation. As common film forming conditions, a target / substrate distance is 55 mm, a substrate temperature is room temperature, a normal cathode structure (hereinafter abbreviated as CM) is used for a metal target, and an UBM (unbalanced) is used for a carbon target. (Demagnetron) cathode structure. The film forming power was 500 W for the first intermediate layer, and the power for the metal target was smoothly reduced from 500 W to 0 W for the second intermediate layer. In the carbon target, the power was smoothly increased from 0 W to 1 kW to provide a gradient layer whose composition continuously changed. Low density carbon layer 4
(Including the outermost layer 6), no bias voltage was applied to the substrate, while a predetermined dc bias voltage was applied to the formation of the high-density carbon layer 5. Further, in Nos. 16 to 18 and 34, the deposition of the laminated portion was performed by adding the coupling induction plasma during the deposition of the high-density carbon layer. In Nos. 20 to 22, methane gas was introduced into the chamber only during the formation of the low-density carbon layer 4 in order to confirm that there was no adverse effect of hydrogenation on the low-density carbon layer 4, and the amount of methane gas relative to Ar gas was reduced. The low density carbon layer 4 was hydrogenated at a pressure of 5 to 20%.

On the other hand, as a sample for measuring the film density and the amount of hydrogen in the film, a single-layer low-density film was formed under the same conditions as when forming each layer of the multilayer film without forming an intermediate layer on the Si wafer substrate. A carbon layer or a high-density carbon layer was formed.

[0030]

[Table 1]

The prepared samples were measured and evaluated for the coefficient of friction, wear resistance, film density and hydrogen content by the following methods. (1) Friction coefficient The friction coefficient was measured using a HEIDON reciprocating sliding tester. At this time, the sample was fixed on the stage and the diameter was about 8 mm.
Using a SUJ2 steel ball, a sliding test was performed on the sample surface with a load of 4.9 N, a sliding speed of 20 mm / sec, and a sliding width of 10 mm, and an integrated sliding distance of 0 to 5 m, 50 to 150 m, 15
Average friction coefficient at 0-200m and lamination sliding distance is 1k
The coefficient of friction when m was reached was measured. The test environment was controlled in the atmosphere at a temperature of 20 to 26 ° C. and a humidity of 40 to 80%. (2) Abrasion resistance After the HEIDON type reciprocating sliding test, the depth of the sliding mark was measured with a stylus type surface roughness meter, the worn volume was measured, and the sliding distance and load were measured. Was calculated and the wear resistance was evaluated. (3) Film density and hydrogen content Film density and hydrogen content in a single layer of low-density carbon layer or high-density carbon layer formed on a Si wafer substrate by Rutherford back scattering (RBS) method Was measured. Table 2 shows the measurement results. Although the hydrogen content is not shown in the table, the hydrogen content of the low-density carbon layer was 6 at% for No. 20 and 21 and 22 for No. 20.
Was less than 10 at%, and the other samples were less than 1 at%. The density of the high-density carbon layer was also less than 1 at%.

[0032]

[Table 2]

As shown in Table 2, the DLC hard multilayer film (N
According to o. 1-26), although the coefficient of friction at the initial stage of sliding is slightly high, a coefficient of friction of 0.15 or less can be obtained stably thereafter, and it has excellent abrasion resistance. It can be seen that the aggression is also very small. However, when the outermost layer is too thick, such as No. 26, having a thickness of 300 nm, the amount of wear increases and the friction coefficient becomes unstable.

On the other hand, a single-layer film having only a high-density carbon layer (No. 3)
In the case of 1) or a single-layer film composed of only a low-density single-layer film (No. 32), problems such as the friction coefficient at the initial stage of sliding exceeding 0.2 and the increase of the friction coefficient as the sliding distance is increased. Yes,
Further, it can be seen that the specific wear amount is large and a problem occurs in durability. Further, even in the case of a DLC multilayer film, No. 33-40
When the average film density, the layer thickness, the layer thickness ratio, and the layer thickness of the outermost layer of each hard carbon layer are out of the range of the invention as described above, a good friction coefficient of 0.15 or less cannot be obtained stably, It can be seen that the abrasion is insufficient and the resulting multilayer film lacks both high abrasion resistance and high slidability.

[0035]

The DLC hard multilayer film of the present invention has a thickness of 0.1 to
Since a low friction coefficient of about 0.15 can be stably obtained, the wear resistance is excellent, and the aggressiveness to the counterpart material is small, so that a protective film for various sliding members, particularly automobile parts, tools, machine parts, etc. Also, it can be suitably used for a protective film of a magnetic head such as an automatic reader of a card or a ticket or a printer.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating a cross section of a main part of a member including a DLC multilayer film according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating a density distribution form in a thickness direction for clarifying the meaning of an average film density.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Base material 2 Intermediate layer 3 Multilayer film 4 Low density carbon layer 5 High density carbon layer 6 Outermost layer 7 Lamination part

Claims (2)

[Claims] A diamond-like carbon multilayer film in which a low-density carbon layer formed of diamond-like carbon having a low film density and a high-density carbon layer formed of diamond-like carbon having a high film density are alternately laminated. The low-density carbon layer has an average film density of 2.2 g / cm ³ or less, while the high-density carbon layer has an average film density of 2.3 to
3.2 g / cm ³ , the high-density carbon layer has a hydrogen content of 5 at% or less in the film, the low-density carbon layer has a thickness of 0.4 to 30 nm, The layer thickness of the low density carbon layer is 0.4 to 10 nm;
1 and the thickness T2 of the high-density carbon layer, T1 / T2, is 5 to 0.5.
2, a diamond-like carbon multilayer film. 2. An outermost layer is formed of the low density carbon layer,
The diamond-like carbon multilayer film according to claim 1, wherein the layer thickness is 2 to 200 nm.