Patent Application
20130058640
This application claims the benefit of priorities of Japanese Patent Application No. 2010-106928 filed on May 7, 2010 and International Patent Application No. PCT/JP2011/060909 filed on May 6, 2011, and the disclosures of Japanese Patent Application No. 2010-106928 and International Patent Application No. PCT/JP2011/060909 are incorporated herein by reference in their entities.
The present teaching relates to a conductive sliding film which can be formed on a surface of a member which is movable slidably and relatively (relative to other member), a member such as a mount member for a camera having the conductive sliding film formed therein, and a method for producing the conductive sliding film.
With respect to a member which is movable slidably relative to other member and a member (referred to as “connection member”) which is movable slidably on and relative to a contact surface of another member and is connectable to the contact surface, there exists a large number of members each having a coating film formed on a surface thereof. Such a member is exemplified by a packaging (exterior) material for an optical device, etc., and such a connection member is exemplified by a connection member referred to as a bayonet-type mount (hereinafter referred to simply as “mount”) provided on a body side and a lens side in a camera system configured so that a lens unit is detachable (removable) and interchangeable with respect to a camera body. Such a mount is generally constructed of a substrate made of brass and a protective coating film which has conductivity (which is conductive) and which is made of metal chrome and formed on a surface of the brass substrate (see, for example, Japanese Patent Application Laid-open No. 2006-225686).
The reason that the metal chrome has been selected as a material for a surface processing (treatment) material for the mount is that the metal chrome is a metal which has a high reflectance with a beautiful metallic luster, which is relatively hard, which has the conductivity, and which can be produced with a relatively low production cost because of not being a rare metal. Namely, a mount in which a body-side mount and a lens-side mount are moved slidably and relative to each other so that the mounts are engaged with and connected to each other is required to have not only the sliding performance (slidability) or slidable moving performance (low friction coefficient) and the wear resistance (surface hardness), but also required to have the conductivity in order that the camera body and the lens unit have the same ground potential and/or that the mount is used as a signal current channel allowing the electricity to be passed between the camera body and lens unit. In addition, the mount is required to have beautiful metallic luster and corrosion resistance so as to ensure external appearance quality. In particular, the slidability (low friction coefficient) and the wear resistance (surface hardness) are correlative, and thus each of the slidability (low friction coefficient) and the wear resistance (surface hardness) needs to be adjusted to have a value in an appropriate range. For example, in a case that the surface hardness of the mount is too high, the friction coefficient becomes high, thus lowering the operability when attaching the lens unit to the camera body. On the other hand, in a case that the mount does not have a predetermined surface hardness, the surface processing or treatment (film) is damaged and/or is easily exfoliated or peeled off. Accordingly, the friction coefficient and the surface hardness are each required to have a value such that, when the lens unit is attached/detached with respect to the camera body, the mount can endure the attachment/detachment for a predetermined number of times, while maintaining a satisfactory operability. As described above, a camera mount is directly touched and operated by a user and is also a product in which user preference should be taken into consideration. Therefore, the camera mount is required to have characteristics which are not required for a sliding component of an automobile and/or for a machine for which only the operation performance and/or function is/are important.
If a material such as a metallic compound which is hard but has low reflectance is used instead of the metal chrome, it is not possible to obtain a desired external appearance quality. On the other hand, if a metal which has a high reflectance but is soft is used, there is a fear that any flaw might be generated after performing the lens exchange only for a small number of times, which in turn easily lower the external appearance quality, and further that the wear might progress to such an extent that the lens cannot be fixed at an accurate position, as well. The conventional technique to apply metal chrome plating on a surface of the brass substrate has been used as a technique to realize the above-described requirements in a relatively well-balanced manner.
However, even in the conventional mount using the metal chrome coating film, there is a problem such that a layer of metal chrome is worn by a repeated exchange of the lens by the user, thus exposing the brass in the back layer, any damage such as a flaw (scar) is generated, etc., in some cases, and that the surface hardness and/or the durability are/is not necessarily sufficient.
Further, in view of the increased severity of the environmental problem, it has become a social mission to avoid any wet-type plating process using hexavalent chromium that is a hazardous chemical substance to human body; and there is desired a new film-forming technique capable of satisfying a predetermined requirement with a dry process.
As a coating material for a sliding material (slidably moving material), there is known a film of hard carbon having wear resistance and low-frictional/sliding properties. For example, Japanese Patent Application Laid-open No. H06-212429 discloses a method for forming a film of hard carbon from methane gas with the plasma-enhanced CVD method, the sputtering method or the ion plating method while using an impurity element such as Ti and/or Mo, for the purpose of providing a film of hard carbon which has both of excellent wear resistance and high conductivity. Although Japanese Patent Application Laid-open No. H06-212429 does not disclose the structure of the obtained film of hard carbon, it is appreciated, from the results of the experiments performed by the present inventor (to be described later on), that the obtained film of hard carbon in Japanese Patent Application Laid-open No. H06-212429 has a structure close to that of a diamond-like carbon mainly comprised of sp2 bond (hybrid orbital) or has a structure mainly composed of sp3 bond (hybrid orbital) containing a large amount of hydrogen.
In a case of the carbon film of the sp3 bond containing a large amount of hydrogen, however, there are a problem associated with the corrosion resistance, and such a problem that the adhesiveness of the carbon film is lowered since hydrogen is vaporized under high-temperature atmosphere. Further, the diamond-like carbon mainly composed of sp2 bond is not suitable for the application to the camera mount in view of the wear resistance and the hardness.
In the recent years, there is known a technique of producing a low-friction sliding member from tetrahedral amorphous carbon (ta-C) which does not contain hydrogen and contains the sp3 bond in a relatively greater extent with respect to the sp2 bond, by using the Filtered Cathodic Vacuum Arc method (FCVA method) (Japanese Patent Application Laid-open No. 2008-297477).
The present teaching is made in view of such a situation, an object of which is to provide a conductive sliding film for a connection member which is suitable in particular for surface treatment (processing) for a camera mount, which has high wear resistance and satisfactory slidability and which has conductivity to enable transmission of electric signal, and a connection member having the conductive sliding film formed therein; and to provide a method capable of producing such a connection member with a dry process. Further, another object of the present teaching is to provide a member such as a camera mount, a camera body and a lens unit each provided with such a conductive sliding film and such a connection member.
According to a first aspect, there is provided a conductive sliding film which is applied on a surface of a member moving slidably relative to other member, the conductive sliding film being formed of tetrahedral amorphous carbon which is doped with a metal, wherein resistivity of the conductive sliding film is in a range of 102 to 10−4 [Ωcm].
In this aspect, the metal for doping is titanium; and a content (content ratio) of the titanium may be 1 to 33 [at %], in particular, may be 1 to 20 [at %].
According to a second aspect, there is provided a member having the conductive sliding film of the first aspect formed on a surface of the member. The member may be a member having the conductive sliding film of the first aspect formed on a connection surface of the member, the connection surface being movable slidably relative to and connectable to a connection surface of the other member. The member may be comprised of a substrate made of a metal material and the above-described conductive sliding film formed on a surface of the substrate.
The member may be at least one of a first connection member and a second connection member which move slidably relative to each other and are connected to each other, wherein when a connection surface of the first connection member and a connection surface of the second connection member move slidably relative to reach other and are engaged with and connected to each other, the first and second connection members may be mechanically connected and electrically connected.
According to a third aspect, there is provided a mount member used for a camera system and provided on a side of a body and/or a lens of the camera system configured so that a lens unit is detachable and interchangeable with respect to a camera body, the mount member including: a substrate; and a conductive sliding film which is formed on the substrate; wherein the conductive sliding film is formed of tetrahedral amorphous carbon doped with a metal and which has resistivity of 10−2 to 10−4 [Ω·cm], surface hardness of 10 to 30 [Gpa] and dynamic friction coefficient of less than 0.15.
According to a fourth aspect, there is provided a camera body provided with the mount member for camera of the third aspect.
According to a fifth aspect, there is provided a lens unit provided with the mount member for camera of the third aspect.
According to a sixth aspect, there is provided a method for producing a conductive sliding film, the method including: arranging a member, which moves slidably relative to other member, in a vacuum chamber; and forming, on a surface of the member, a film of metal-doped tetrahedral amorphous carbon (ta-C:M) having resistivity in a range of 102 to 10−4 [Ωcm] and surface hardness in a range of 10 to 30 [GPa] with Filtered Cathodic Vacuum Arc method (hereinafter referred to as “FCVD” method, as appropriate) by using, as a raw material, a graphite target in which a metal or a metal carbide is contained. It is preferable that the target substantially does not contain hydrogen. Note that in the present application, the FCVA method encompasses not only a FCVA method in a narrow sense but also a cathodic vacuum arc method or vacuum arc method having a function (filter function) which classifies elements such as a specific ionized carbon, etc., and a method similar to the cathodic vacuum arc method or the vacuum arc method, for example, Arc Ion Plating method (AIP method).
Embodiments of the present teaching will be explained below with reference to the drawings.
An explanation will be given about tetrahedral amorphous carbon which is used in the present teaching.
In this phase diagram, each of the apexes in the triangle is a pure single element (and bond) substance, wherein the sp3-bonded carbon sp3-C positioned in the upper apex is diamond; the sp2-bonded carbon sp2-C positioned in the lower left apex is graphite (black lead); and H positioned in the lower right apex is hydrogen. The sp3-C diamond and the sp2-C graphite are both composed of carbon as the composition element, but are clearly different from each other in the crystalline structure due to the difference in inter-atomic bond state.
Compounds on the respective sides in the triangle, except for those at the apexes, are each amorphous of two-component (binary) system; and on the left side connecting the upper apex (sp3-C) and the lower left apex (sp2-C), carbon compounds in which sp3-C and sp2-C are mixed randomly in a composition ratio based on a position thereof on the axis (the left side) are formed. Each of the carbon compounds which does not contain hydrogen is referred to as “amorphous carbon” and indicated as “a-C”.
Among the amorphous carbons a-C, a carbon compound with a high composition ratio of sp3-C (approximately 50 to 90%) is particularly referred to as “tetrahedral amorphous carbon” and indicated as “ta-C”. Tetrahedral amorphous carbon does not substantially contain hydrogen, and is composed of sp3-C and sp2-C. The phrase that “does not substantially contain hydrogen” means that containing hydrogen only in an amount smaller than a detected amount of hydrogen originated from a measurement device (for example, not more than 0.3 at %). When attempt is made to measure the composition of an amorphous carbon film, hydrogen originated from a measurement device (for example, hydrogen adhered to the measurement device), as the background, is detected in some cases. In such a case, it is considered that the hydrogen is not substantially contained. Such a tetrahedral amorphous carbon can be produced by the FCVA method, but cannot be produced by the conventional CVD method.
Carbon-hydrogen compounds of the ternary system in which sp3-C, sp2-C and hydrogen are randomly mixed, respectively, are formed in an area inside the triangle surrounded by the three sides. The carbon compounds containing hydrogen as described above are referred to as “hydrogenated amorphous carbon”, and indicated as “a-C:H”. Among the a-C:H hydrogenated amorphous carbons, a carbon-hydrogen compound with a high composition ratio of sp3-C (in an upper inner area in the triangle in the phase diagram) is referred to as “hydrogenated tetrahedral amorphous carbon”, and is indicated as “ta-C:H”. Since ta-C:H contains hydrogen, it is known that ta-C:H has slidability (friction coefficient) needed for a sliding material inferior to that of ta-C which does not contain hydrogen. Further, it is known that ta-C:H has inferior hardness and heat resistance than those of ta-C.
As are well known, the diamond as sp3-C has such characteristics as extremely high hardness, transparent in the visible light range, and electrically insulating. On the other hand, the graphite as sp2-C has such characteristics as being soft, opaque (black color) in the visible light range, and self-lubricating (has low friction coefficient). Namely, the diamond (sp3-C) and the graphite (sp2-C) have mutually contrastive characteristics, although both being carbon compounds.
In the phase diagram, amorphous carbon a-C located on the line connecting sp3-C (diamond) and sp2-C (graphite) has an intermediate characteristic or property having both the characteristics of diamond and the characteristics of graphite, either of which being more dominant depending on the composition ratio thereof. Accordingly, it is assumed that a film of tetrahedral amorphous carbon ta-C containing a large amount of sp3-C may have wear resistance based on the high hardness, and may obtain satisfactory slidability based on the low friction coefficient. For a reference purpose,
Provided that even it is possible to obtain the wear resistance and satisfactory slidability with the amorphous carbon a-C by combining the characteristics of both of the sp3-C and sp2-C, it has been considered to be impossible to impart the conductivity so as to enable transmission/receipt of electric signals such realized by the metal chrome; further, it has been also considered as being difficult to obtain a desired metallic external appearance by an a-C film for the following reasons. Namely, the reason of the extremely high hardness of diamond is realized by the covalent bond between carbon atoms not having any free electrons, whereas the conductivity and metallic luster are realized by having a large number of free electrons. The present teaching has successfully produced a sliding film provided with a satisfactory wear resistance, slidability and conductivity by doping in particular tetrahedral amorphous carbon, among such amorphous carbons a-C as described above, with a metal.
A metal with which tetrahedral amorphous carbon is doped is exemplified by Ti, Ni, Cr, Al, Mg, Cu, Fe, Ag, Au, Pt, etc., in view of the wear resistance, slidability and conductivity, in particular the conductivity, of the sliding film. Among these metals, Ti, Cr, Ni, Fe are preferable. The content (dope amount) of metal in the sliding film may be 1 at % to 33 at %, in particular may be 1 at % to 20 at %, in order to appropriately maintain the wear resistance, slidability and conductivity of the sliding film. In a case that the content is less than 1 at %, the conductivity is not sufficient and the electric resistance of the sliding film becomes high. In a case that the content exceeds 20 at %, the hardness of the sliding film tends to be lowered, which in turn deteriorates the wear resistance.
A sliding film according to an embodiment of the present teaching achieves the resistance value in a range of 102 to 10−4 [Ωcm], in particular in range of 10−2 to 10−4 [Ωcm], further in range of 10−3 to 10−4 [Ωcm]. Accordingly, by using the sliding film, for example, in a mount (camera mount) for a camera capable of automatically controlling the lens such as an auto-focus camera, it is possible to realize transmission of electric signal between a lens section and a camera body of the camera, via the sliding film. Further, in a case that the sliding film is used in the mount of such a camera, a certain user attaches and detaches such as the lens section and/or a strobe frequently to and from (with respect to) the camera body in some cases, and such repeated frequent attachment/detachment causes the sliding film provided on a sliding portion of the mount to be exfoliated or peeled off in some cases. However, if such an exfoliation of the sliding film is occurred, it is not possible to realize the conduction between the lens section and the camera body via the sliding film as described above. Therefore, the sliding film is required to have also the wear resistance and the hardness. Further, the detachment/attachment of the lens section with respect to the camera body is performed manually by the user, and thus it is necessary that the attachment/detachment of the lens section with respect to the camera body via the sliding film is performed smoothly, thereby making it necessary to lower the dynamic friction of the sliding film. Thus, a sliding section or sliding portion used in a camera mount is required to have, at the same time, (i) low electrical resistivity, (ii) appropriate hardness (wear resistance); and (iii) low dynamic friction coefficient. However, when the metal dope amount (amount of metal dopant) is increased for the purpose of lowering the electrical resistivity, the hardness is lowered, which makes the film likely to be exfoliated. On the other hand, when the hardness of the film is increased too much, the dynamic friction coefficient also becomes high, which in turn lowers the slidability. For these reasons, the sliding film of the camera mount is required to satisfy the above-described three characteristics in a well-balance manner.
According to the experiments performed by the present inventor, it is appreciated that, in a case of using a sliding film mainly composed of tetrahedral amorphous carbon in the camera mount, the lens unit has a durability enduring attachment/detachment with respect to the camera body exceeding 5,000 times when the sliding film has the resistivity in a range of 10−2 to 10−4 [Ωcm], the surface hardness in a range of 10 to 30 GPa, and the dynamic friction coefficient of less than 0.15. In particular, it is appreciated, through the examples (to be described later on) that in a case that Ti is used as the metal for doping and when the content of Ti is 1 to 25 at %, it is possible to satisfy the above-described resistivity, surface hardness and dynamic friction coefficient suitable for the camera mount.
An explanation will be given about FCVA (Filtered Cathodic Vacuum Arc) method as an example of a film-forming method for forming a conductive sliding film on a substrate, and the schematic structure of a film-forming apparatus 1 for practicing the method, with reference to
The film-forming apparatus 1 is mainly constructed of an arc plasma producing section 10, a filter section 20 and a film-forming chamber 30. The arc plasma producing section 10 and the film-forming chamber 30 are connected by the filter section 20 having a duct shape, and the pressure of the film-forming chamber 30 is set to have vacuum to an extent of about 10−5 [Torr] by an un-illustrated vacuum device.
The arc plasma producing section 10 is provided with an anode (striker) and a cathode while sandwiching a target 11 therebetween, and the striker is brought into contact with the target 11 and then immediately is separated from the target 11 so as to produce arc discharge. In a case of forming a ta-C film, graphite is used as the target 11 and arc plasma (carbon plasma) is generated by the arc discharge. Neutral particle(s) and positively ionized carbon produced by the arc plasma fly in the filter section 20 toward the film-forming chamber 30. In order to produce a sliding film composed of a metal-doped ta-C film of the above-described embodiment, a target of graphite containing a metal but not containing hydrogen is used. The kinds of metal are exemplified by Ti, Ni, Cr, Al, Mg, Cu, Fe, Ag, Au, Pt, etc., as described above.
A duct 23 around which a double-bend electromagnetic coil 21 is wound and a coil 25 for scanning ion (ion-scanning coil 25) are provided on the filter section 20. The duct 23 is bent twice, in two directions perpendicular to each other, between the arc plasma producing section 10 and the film-forming chamber 30; and the double-bend electromagnetic coil 21 is wound around the outer circumference portion of the duct 23. Since the duct 23 has such a bend structure (double-bend structure), the particles flowing in the duct 23 collide with the inner wall surface thereof or flow along the wall surface thereof. By passing an electric current through the double-bend electromagnetic coil 21, the Lorentz force acts on the charged particles flowing inside the duct 23 to change a flying path of the charged particles.
Therefore, by optimizing electric power applied to the double-bend electromagnetic coil 21 with respect to the mass of ionized carbon, it is possible to accumulate charged particles which are lighter and/or heavier than the ionized carbon and neutral particles which are not bent by the Lorentz force on the inner wall of the duct 23 to be removed, and thereby to introduce only the ionized carbon to the film-forming chamber 30 with high efficiency. That is, the double-bend electromagnetic coil 21 and the duct 23 function as a narrow-band electromagnetic spatial filter through which only the target particles are passed with high efficiency.
The ion-scanning coil 25 scans a beam of ionized carbon which passes through the double-bend electromagnetic coil 21 and then enters into the film-forming chamber 30 as described above, and uniformly forms an a-C film (ta-C film, ta-C:M film) on a surface of each of substrates 32, 33 held by a holder 31. As the substrate, it is possible to use a material having an arbitrary shape and formed, for example, of an organic material such as a resin, etc.; an inorganic material such as a metal, ceramics, etc.; and the like. In a case of using the sliding film for the sliding portion of the camera mount, a plastic such as a resin or a metal such as brass is used.
The film-forming chamber 30 is provided with the holder 31 having a plate-shape and facing or opposite to the outlet of the filter section 20, and the substrates 32, 33 are set on a surface of the holder 31. The holder 31 is rotatable around the revolution axis thereof by a motor 35. Arbitrary bias can be set for the holder 31 by a power source 37. For example, by applying appropriate negative bias voltage in accordance with the desired composition ratio of a target ta-C film (ratio of sp3-C to sp2-C), it is possible to form a ta-C film with arbitrary composition ratio with high efficiency.
According to this embodiment, a member having the above-described sliding film is also provided. Although the sliding film of the embodiment can be used in members or parts (components) of variety of kinds of usage, in view of the high wear resistance, satisfactory slidability and conductivity (low resistivity) possessed by the sliding film, the sliding film is particularly suitable for a member which moves slidably relative to another member and/or a member which is connected to or joined to another member while moving slidably relative to the another member. Further, the sliding film of the embodiment is also suitable for a pair of members slidably moving relative to each other; and/or a member set and/or a member kit connected to or joined to each other while slidably moving relative to each other. In particular, the sliding film is suitable for a mount member, disposed on a side of a lens unit of a camera, in which the lens unit is attachable/detachable with respect to a camera body, and/or a mount member disposed on a side of the camera body of said camera. An explanation will be briefly made about these mount members with reference to
In order to attach the interchangeable lens 42 to the camera body 41, the claw portion 53 of the male mount 52 is inserted into the insertion portion 54 of the female mount 51; a contact surface 56 of the male mount 52 is brought in contact with a receiving surface 57 of the female mount 51; and the interchangeable lens 42 is rotated with respect to the camera body 41. In this situation, the contact surface 56 and the receiving surface 57 slidably move with respect to each other in a state that the contact surface 56 and the receiving surface 57 make contact with each other. Then, the interchangeable lens 42 is further rotated to engage the claw portion 53 of the male mount 52 with the engaging portion 55 of the female mount 51, and the attachment of the interchangeable lens 42 is completed. In this situation, a surface of the claw portion 53 and a surface of the engaging portion 55 slidably move with each other while making contact with each other. Further, in a case that the interchangeable lens 42 is detached or removed from the camera body 41, the processes described above are performed in a reversed order to the order described above. Therefore, the female mount 51 of the camera body 41 and the male mount 52 of the interchangeable lens 42 slidably move with respect to each other in a state that the female mount 51 and the male mount 52 make contact with each other every time when the interchangeable lens 42 is exchanged.
In the female mount 51 and the male mount 52, a sliding film 50 of the embodiment is formed on a surface of each of substrates 60 having the shapes of the female and male mounts 51, 52, respectively as shown in
This embodiment also encompasses the camera body and/or the lens unit as shown in
In the following, the conductive sliding film of the present teaching and a method for producing a member using the conductive sliding film of the present teaching will be described. However, the present teaching is not limited to the examples described below.
The following shows Examples 1-8 by which conductive sliding films were formed by using the FCVA film-forming apparatus 1 as shown in
The typical operating conditions for the FCVA film-forming apparatus 1 (see
With respect to the film formed on the Si substrate as described above in the respective examples, measurement was performed with the Rutherford backscattering spectrometry method to obtain the content amounts of carbon (C), titanium (Ti), oxygen (O) and hydrogen (H) contained in the film. The measurement results are shown in the table of
Next, regarding the obtained films, the ratio of sp2-C bond (hybrid orbital) and sp3-C bond (hybrid orbital) of the carbon contained in the film was analyzed with X-ray photoelectron spectroscopy method. The analysis results are shown in the table of
Film-formation was performed under the same condition as that of Example 1, except that a sintered graphite target containing 2.15 [at %] of Ti without any dewatering treatment was used as the target 11 containing the metal element, and that the operating conditions of the FCVA film-forming apparatus 1 were changed to the values shown in
With respect to the film obtained in Example 9, the components composing the film were analyzed with the Rutherford backscattering spectrometry method, in a similar manner as in Example 1. The analysis result is shown in the table of
A film having a thickness of 300 nm was formed in a similar manner as in Example 1, except that a sintered graphite target not containing Ti was used as the target 11 containing the metal element and that the operating condition (bias voltage) of the FCVA film-forming apparatus 1 was changed to the value shown in
The film formed on a Si substrate as described above was analyzed with the Rutherford backscattering spectrometry method, and it is appreciated that 99.9 at % of carbon was contained in the film (see the table of
Next, with respect to the obtained film, the ratio of the sp2-C and sp3-C bonds of the carbon contained in the film was analyzed with the X-ray photoelectron spectroscopy. As shown in the table of
Film-formation was performed with the ion plating method by using benzene vapor (C6H6) as the raw material to form an amorphous carbon film having a thickness of 300 nm on a substrate heated to 400 degrees Celsius. In order to individually evaluate the hardness and elastic modulus, the film composition, the friction coefficient, etc., of the film (to be described later on), the film-formation was performed a plurality of times, under a same condition except for selectively using the different kinds of substrate, respectively, in a similar manner as in Example 1.
The film formed on a Si substrate as described above in Comparative Example 2 was analyzed with the Rutherford backscattering spectrometry method, and it is appreciated that the film contained 99.6 at % of carbon and 0.4 at % of hydrogen (see the table of
Next, with respect to the obtained film, the ratio of the sp2-C and sp3-C bonds of the carbon contained in the film was analyzed with the infrared spectroscopy. As shown in the table of
Film-formation was performed by using the ion plating method in a similar manner as Comparative Example 2, except that the temperature of the substrate was changed to 200 degrees Celsius. The film formed on a Si substrate was measured by the Rutherford backscattering spectrometry method, and the film contained 75.2 at % of carbon and 24.8 at % of hydrogen. The ratio of the sp2-C and sp3-C bonds of the carbon contained in the film was analyzed with the X-ray photoelectron spectroscopy. As shown in the table of
Film-formation was performed with the plasma-enhanced CVD method using methane gas (CH4) as the raw material to form a carbon film having a thickness of 300 nm on a substrate heated to 100 degrees Celsius. In order to individually evaluate the hardness and elastic modulus, the film composition, the friction coefficient, etc. of the film (to be described later on), the film-formation was performed a plurality of times, under a same condition except for selectively using the different kinds of substrate, respectively, in a similar manner as in Example 1.
The film formed on a Si substrate as described above was measured by the Rutherford backscattering spectrometry method, and it is appreciated that the film contained 58.8 at % of carbon and 41.2 at % of hydrogen (see the table in
Next, the ratio of the sp2-C and sp3-C bonds of the carbon contained in the film was analyzed with the X-ray photoelectron spectroscopy. As shown in the table of
With respect to the films obtained in Examples 1 to 9 and Comparative Examples 1 to 4, the resistivity, the hardness and elastic modulus, the friction coefficient, etc. as the physical properties of the films were measured as follows.
The resistivity (volume resistivity) of ta-C:Ti films, etc. formed on a SiO2 glass substrate. was measured by the 4-point probe method. The measured values are shown in the table of
The hardness and elastic modulus were measured regarding each of the ta-C:Ti films formed on the Si substrates with the nanoindentation method at a plurality of sampling positions. The measured hardness and elastic modulus of the film of each of Examples 1 to 9 and Comparative Examples 1 to 4 are shown in the table of
Next, with respect to the film formed on the Si substrate in each of Examples 1 to 9 and Comparative Examples 1 to 4, the wear characteristic (abrasion characteristic) was measured by the ball-on-disk method. An alumina ball was used for the measurement with the following conditions of load: 200 [gf]; radius of rotation: 2 [mm]; and rotation speed: 100 [rpm]. With respect to the films of Examples 1 to 9 and Comparative Examples 1 to 4, the average value of the dynamic friction coefficients with respect to the time was measured and shown in the table of
With respect to the film formed on the Si substrate in each of Examples 1 to 9 and Comparative Examples 1 to 4, the sliding durability was measured with the ball-on-disk method. A SUS420J2 ball was used with the following conditions of load: 1,000 [gf]; radius of rotation: 2 [mm]; and rotation speed: 100 [rpm], and the time until occurrence of film exfoliation was measured. The results are shown in the table of
The internal stress was measured regarding the films obtained in the examples and the comparative examples. The internal stress was obtained by measuring the curvature radiuses of each of the substrates with a stylus type profilometer before and after the film formation on each of the substrates, and then calculating based on the Young modulus, etc. of each of the substrates. The results are shown in the table of
With respect to the films obtained in Examples 1 to 9 and Comparative Examples 1 to 4, the heat resistance was evaluated with the thermal desorption method. In each of Examples 1 to 9 and Comparative Example 1, the heat resistance was high that was 850 degrees Celsius due to the structure of tetrahedral amorphous carbon. On the other hand, in each of Comparative Examples 2 to 4, the heat resistances were less than 700 degrees Celsius, less than 400 degrees Celsius, and less than 300 degrees Celsius, respectively.
In Examples 10 to 14, ta-C:Ti films having different Ti/C atomic ratios were formed in a similar manner as in Example 1, except that the operating conditions of the FCVA apparatus were made to have values as shown in the table of
Next, the performance as the sliding film for camera bayonet was evaluated in the following manner. Under the operating conditions of the FCVA apparatus in Examples 6, 9 and 10-14, a ta-C:Ti film was formed (applied) to have a thickness of 2 microns on each of a brass mount on the lens side and on a mount on the camera body side. Further as a comparative example, a metallic Cr film was formed (applied) to have a thickness of 4 microns on each of a brass mount on the lens side and on a mount on the camera body side with the hexavalent chromium plating method (Comparative Example 5). The actual device test was performed by repeatedly attaching and detaching the ta-C:Ti film and metallic Cr film with respect to the camera body and the lens unit (exchange lens); and the number of attachment/detachment times until the film was completely exfoliated (peeled off) and the substrate was exposed were counted. The results are shown in the table of
As shown by the evaluation results described above, the ta-C:Ti films of the examples have the wear resistance based on the high hardness similar to that of a ta-C film, have the satisfactory slidability based on the low friction coefficient, further have the satisfactory conductivity capable of transmitting electric signals as well, and are provided with the metallic luster suitably ensuring external appearance quality. Namely, there is successfully realized a new conductive sliding film (thin film which is conductive and with high hardness and low friction coefficient) suitably ensuring the above characteristics, at the same time, that have been conventionally considered as being mutually contradicting and hardly achievable at the same time.
A member having such a conductive sliding film formed on a surface thereof has a high external appearance quality realized by the metallic luster, and is capable of maintaining the external appearance quality for a long period of time owing to the high wear resistance. In addition, a connection member, which has the conductive sliding film formed on a contact surface thereof and which is movable slidably on and relative to a contact surface of another member and is connectable to the contact surface of the another member, is easily subjected to the attachment/detachment operation due to the satisfactory slidability, and it is possible to suppress the connection member from being worn and/or damaged due to the high wear resistance, even if the connection member is subjected to the repeated attachment/detachment accompanying the relative sliding movement. According to such a configuration that the conductive sliding film is formed on a surface of a substrate made of a metal material, it is possible to easily form a connection member having a complex structure and/or requiring high precision, while making it possible to obtain a connection member having a high-hardness connection surface which cannot be realized with a metal film (metal coating film). On the other hand, according to such a configuration that the conductive sliding film is formed on a surface of a substrate made of a resin material, it is possible to easily and inexpensively provide a connection member having a connection surface which has a high hardness and conductivity that cannot be realized with a resin part or component.
The configuration, wherein the connection member is formed of a first connection member and a second connection member which slidably move relative to each other and which are connected detachably with respect to each other; and the first and second connection members are connected mechanically and electrically when the first and second connection members slidably move relative to each other and engaged and connected to each other, can enjoy great effect by suitably using the properties such as the high hardness, low friction coefficient and conductivity realized by the conductive sliding film of the examples described above. For example, a mount member provided on the body side, a mount member provided on the lens side, a hot shoe (bracket, etc.) to and from which a flash, etc. is engaged and disengaged, etc. in a camera system configured so that a lens unit is detachable or removable and interchangeable with respect to a camera body, are representative examples to which the conductive sliding films of the examples are most suitable, including the external appearance quality.
The conductive sliding film of the embodiments can be practiced by the FCVA method that is a dry process without using any chemical substance hazardous for the human body in the film-forming process. Therefore, the conductive sliding film can be produced without damaging the environment. In particular, according to the FCVA method, it is possible to form a conductive sliding film having the predetermined composition in which the resistivity is in the range of 102 to 10−4 [Ωcm] and the surface hardness is in the range of 10 to 30 [GPa], on a variety of kinds of substrates such as those formed of a metal material, resin material, inorganic material, etc. with high efficiency. In particular, it is possible to form a conductive sliding film provided with such characteristics that the resistivity is in the range of 10−2 to 10−4 [Ωcm], the surface hardness is in the range of 10 to 30 [GPa] and the dynamic friction coefficient is less than 0.15, which is suitable for a mount for a camera.
The foregoing explanation has been made regarding preferable embodiments of the present teaching. However, the present teaching is not limited to these embodiments. For example, although titanium is described as an example of a metal dope element for the ta-C:M, it is sufficient that the metal dope element serves to impart the conductivity to the film based on ta-C, as will be understood by a person skilled in the art from the foregoing explanation; and the dope metal may be other metal element such as, for example, Ni, Cr, Al, Mg, Cu, Fe, Ag, Au, Pt, etc.
Further, although a mount for a system camera in which a lens unit is attachable/detachable with respect to the camera body (still camera such as silver halide camera or digital camera, video camera, etc.) is exemplified as a specific application example of the connection member movable slidably relative to other member, the present teaching is not limited to such an aspect, and is applicable to a wide variety of applications. The applications are exemplified, for example, by an electrical connector, a slip-ring, a connection device, a packaging (exterior) material for a device such as a camera, mobile phone, etc., and it is possible to obtain a similar effect also in these applications.
According to the aspects as described above, it is possible to provide a conductive sliding film and a member each having a high wear resistance, a satisfactory slidability and a conductivity capable of electric signal transmission, in particular, a member suitable for a camera mount. In addition, such a member is produced by the FCVA method, without using any plating method, and thus causing any environmental problem.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2010-106928 | May 2010 | JP | national |
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/JP2011/060609 | May 2011 | US |
| Child | 13666523 | US |
