Metal member and metal-rubber composite

Abstract

To provide a metal member having superior adhesion to rubber members such as tires.SOLUTION: A metal member comprises an iron-based substrate containing iron and a cobalt layer disposed on the iron-based substrate, wherein the cobalt layer has a surface having a developed interfacial area ratio (Sdr) of at least 0.7.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a metal member and a metal-rubber composite.

Background Art

[0002] M. Yoshikawa et al., New Adhesion Technology with the Dry Plated Thin Films of Cobalt Alloys, Society of Vacuum Coaters., 505 / 298-7624, 35th Annual Technical Conference Proceedings(1992), 1-878068-11-3(Non-Patent Document 1) discloses a steel plate and a brass plate in which a cobalt layer is formed by sputtering film formation on a target material such as a steel material. The above steel plate and brass plate are said to be good in terms of initial performance and wet heat deterioration performance when joined to rubber.

Prior Art Documents

Non-Patent Documents

[0003]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the technical field related to the above-mentioned metal members such as steel plates and brass plates, and metal-rubber composites using the above-mentioned metal members, the development of improved technologies contributing to further improvement in the adhesiveness between the metal members and rubber has been underway. The steel plate or brass plate disclosed in Non-Patent Document 1 has a smooth surface of the cobalt layer formed by sputtering film formation, so it is difficult to expect further improvement in adhesiveness due to the anchor effect with rubber. In the first place, in this technical field, since low cost in manufacturing is severely required, it is difficult to apply expensive sputtering film formation.

[0005] In view of the above circumstances, an object of the present disclosure is to provide a metal member capable of improving the adhesiveness with rubber, and a metal-rubber composite using the above-mentioned metal member.

Means for Solving the Problems

[0006] The metal member according to one aspect of the present disclosure includes an iron base material containing iron and a cobalt layer provided on the iron base material, and the cobalt layer has a surface with a developed interface area ratio Sdr of 0.7 or more.

Effects of the Invention

[0007] According to the present disclosure, a metal member capable of improving the adhesiveness with rubber, and a metal-rubber composite using the above-mentioned metal member are provided.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Embodiments for Carrying Out the Invention

[0009] [Description of Embodiments of the Present Disclosure] The inventor has intensively studied to solve the above problems and reached the present disclosure. Specifically, the inventor focused on forming a cobalt layer having a surface roughness that can obtain a sufficient anchor effect with rubber on the surface of an iron substrate by appropriately adjusting plating conditions. In particular, by adjusting the plating conditions so as to have a surface roughness with a developed interfacial area ratio Sdr of 0.7 or more, a cobalt layer was plated on the iron substrate to obtain a metal member including the cobalt layer. As a result, it was found that the adhesiveness of the metal member with rubber used for tires and the like is improved.

[0010] First, it will be described by listing the embodiments of the present disclosure. [1] A metal member according to an aspect of the present disclosure includes an iron substrate containing iron and a cobalt layer provided on the iron substrate, and the cobalt layer has a surface with a developed interfacial area ratio Sdr of 0.7 or more. A metal member having such characteristics can improve adhesiveness with rubber.

[0011] [2] In the above [1], the surface is 500 μm 2It preferably has 200 or more and 1000 or less protrusions per unit area, and the protrusions preferably have a height of 0.01 μm or more and 0.5 μm or less and a width of 0.1 μm or more and 2 μm or less. In this case, the metal member can further improve the adhesiveness with rubber.

[0012] [3] In [1] or [2] above, the cobalt layer preferably contains sulfur. In this case, the metal member can further improve the adhesiveness with rubber.

[0013] [4] In [3] above, the sulfur content contained in the cobalt layer is preferably 1 ppb or more and 500 ppm or less. In this case, the metal member can further improve the adhesiveness with rubber.

[0014] [5] In any one of [1] to [4] above, the cobalt layer is preferably a crystal layer. In this case, the metal member can further improve the adhesiveness with rubber.

[0015] [6] In any one of [1] to [5] above, the thickness of the cobalt layer is preferably 10 nm or more and 2 μm or less. In this case, the metal member can further improve the adhesiveness with rubber.

[0016] [7] The metal-rubber composite according to one aspect of the present disclosure includes a rubber member and the metal member according to any one of [1] to [6] encapsulated in the rubber member. The metal-rubber composite having such characteristics can improve both the adhesion between the rubber and the metal member immediately after vulcanization and the adhesion between the rubber and the metal member after a predetermined damp heat test based on the characteristics of the metal member.

[0017] [8] In [7] above, the metal-rubber composite has a cobalt-sulfur layer, the cobalt-sulfur layer is disposed between the rubber member and the metal member, the cobalt-sulfur layer consists of sulfur, carbon, the balance of cobalt and inevitable impurities, and it is preferable that any two points X and Y existing on the interface where the surface of the cobalt layer in the metal member contacts the cobalt-sulfur layer satisfy the following Condition I and Condition II. Condition I: The straight-line distance between X and Y is 1 μm. Condition II: The distance along the interface from X to Y is 1.10 μm or more and 2.50 μm or less.

[0018] In this case, the metal-rubber composite can further improve both the adhesion between the rubber immediately after vulcanization and the metal member and the adhesion between the rubber and the metal member after a predetermined damp heat test.

[0019] [9] In [8] above, it is preferable that the cobalt-sulfur layer is an amorphous layer. In this case, the metal-rubber composite can further improve both the adhesion between the rubber immediately after vulcanization and the metal member and the adhesion between the rubber and the metal member after a predetermined damp heat test.

[0020]

[10] In [8] or [9] above, it is preferable that the sulfur content in the cobalt-sulfur layer is 10 atomic % or more and 90 atomic % or less. In this case, the metal-rubber composite can further improve both the adhesion between the rubber immediately after vulcanization and the metal member and the adhesion between the rubber and the metal member after a predetermined damp heat test.

[0021]

[11] In any of [8] to

[10] above, the sulfur contained in the cobalt-sulfur layer has a concentration distribution in the thickness direction, and it is preferable that the concentration distribution shows a tendency for the sulfur concentration to decrease in the direction from the rubber member side to the metal member side. In this case, the metal-rubber composite can further improve both the adhesion between the rubber immediately after vulcanization and the metal member and the adhesion between the rubber and the metal member after a predetermined damp heat test.

[0022]

[12] In any one of the above [8] to

[11] , the thickness of the cobalt sulfur layer is preferably 300 nm or less. In this case, the metal-rubber composite can further improve both the adhesion between the rubber immediately after vulcanization and the metal member, and the adhesion between the rubber and the metal member after a predetermined damp heat test.

[0023]

[13] In any one of the above [8] to

[12] , the cobalt sulfur layer contains oxygen as the inevitable impurity, and the oxygen content contained in the cobalt sulfur layer is preferably 1 atomic % or more and 50 atomic % or less. In this case, the metal-rubber composite can improve both the adhesion between the rubber immediately after vulcanization and the metal member, and the adhesion between the rubber and the metal member after a predetermined damp heat test.

[0024]

[14] In any one of the above [7] to

[13] , the metal member is a wire rod having a circular cross section, and the diameter of the wire rod is preferably 0.05 mm or more and 3 mm or less. In this case, the metal-rubber composite can improve both the adhesion between the rubber immediately after vulcanization and the metal member, and the adhesion between the rubber and the metal member after a predetermined damp heat test in a metal-rubber composite using a wire rod having a circular cross section widely used in rubber products as the metal member.

[0025] [Details of Embodiments of the Present Disclosure] Hereinafter, specific examples of the metal member and the metal-rubber composite of the embodiment of the present disclosure (hereinafter referred to as "the present embodiment") will be described with reference to the drawings. In the drawings of the present disclosure, the same reference numerals represent the same or corresponding parts. Also, in the above drawings, dimensional relationships such as length, width, thickness, depth, etc. have been appropriately changed for clarity and simplification of the drawings, and do not necessarily represent actual dimensional relationships.

[0026] In this specification, the notation in the form of "A to B" means the upper and lower limits of the range (i.e., A or more and B or less). When there is no unit description for A and there is a unit description only for B, the units of A and B are the same. When a compound or the like is represented by a chemical formula in this specification, the compound includes all conventionally known atomic ratios when the atomic ratio is not particularly limited, and should not necessarily be limited only to the atomic ratio within the stoichiometric range.

[0027] [Metal member] The metal member according to this embodiment includes an iron base material containing iron and a cobalt layer provided on the iron base material. The cobalt layer has a surface with a spreading interface area ratio Sdr of 0.7 or more. A metal member having such characteristics can improve the adhesiveness with rubber.

[0028] FIG. 1 is a cross-sectional explanatory view schematically showing an example of the metal member according to this embodiment. As shown in FIG. 1, the metal member 1 exemplified as this embodiment can include an iron base material 10 containing iron and a cobalt 12 layer provided on the iron base material 10 so as to cover the surface of the iron base material 10. In particular, a brass plating layer 11 as described later can be interposed between the iron base material 10 and the cobalt 12 layer in the metal member 1. In this case, the surface of the iron base material 10 of the metal member 1 is covered with the brass plating layer 11 by known so-called brass plating. Further, the surface of the brass plating layer 11 of the metal member 1 is covered with the cobalt 12 layer by cobalt plating using a known cobalt plating bath. The cobalt 12 layer may be directly provided on the iron base material 10 in the metal member 1 without interposing the brass plating layer 11.

[0029] The shape of the metal member 1 is not particularly limited. The metal member 1 may be, for example, a steel cord which is a linear member or a steel plate which is a plate-shaped member.

[0030] Among them, steel cords are preferably used as reinforcing members such as tires. That is, the metal member 1 is preferably a wire rod (steel cord) with a circular cross-section. Furthermore, the diameter of the wire rod is preferably 0.05 mm or more and 3 mm or less. The steel cord may be a single wire (plain wire), or may be a stranded wire formed by twisting the single wires together. When the steel cord is a single wire, the diameter of the single wire is more preferably 0.15 to 0.40 mm in particular. The number of single wires constituting one stranded wire is preferably 3 to 30, for example.

[0031] <Iron base material> The metal member 1 includes an iron base material 10 containing iron as described above. The iron base material 10 is not particularly limited as long as it is a member composed of a material containing iron. The material containing iron is preferably steel (a material containing iron and carbon). The content of carbon contained in this steel is preferably 0.04 to 2% by mass, and more preferably 0.5 to 1% by mass.

[0032] The shape of the iron base material 10 is also not particularly limited, similar to the metal member 1. For example, the iron base material 10 may be linear or plate-shaped. When the iron base material 10 is linear, the metal member 1 may be preferably used as a steel cord as described above.

[0033] <Brass plating layer> The metal member 1 can be provided by coating the surface of the iron base material 10 with a brass plating layer 11 as described above. The brass plating layer 11 preferably consists of an alloy of copper (Cu) and at least one of zinc (Zn) and tin (Sn) (Cu-Zn alloy, Cu-Sn alloy, or Cu-Zn-Sn alloy). The content of Cu in the brass plating layer 11 is preferably 60 to 95% by mass. The thickness of the brass plating layer 11 is, for example, 0.01 to 1 μm. By providing the brass plating layer 11, the metal member 1 is expected to have improved workability in the wire drawing process for manufacturing the metal member 1 and improved adhesiveness to rubber.

[0034] The brass plating layer 11 is coated on the surface of the iron base material 10 by, for example, a known method. The surface of the brass plating layer 11 (the surface opposite to the iron base material 10) may contain zinc oxide (ZnO), zinc hydroxide (Zn(OH) 2 ), etc. generated by natural oxidation or the like.

[0035] <Cobalt layer> The metal member 1 according to the present embodiment includes a cobalt 12 layer provided on the iron base material 10 as described above. More specifically, the metal member 1 can include a cobalt 12 layer so as to cover the surface of the brass plating layer 11 on the iron base material 10 whose surface is covered with the brass plating layer 11. The cobalt 12 layer may be provided on the iron base material 10 without interposing the brass plating layer 11 as described above. The cobalt 12 layer is provided on the iron base material 10, for example, by immersing the iron base material 10 or the iron base material 10 covered with the brass plating layer 11 in a cobalt plating bath having a known composition (for example, a plating bath containing a 50 mass% cobalt sulfamate solution) and performing cobalt plating under predetermined conditions (current density, bath temperature, pH, plating time, etc.).

[0036] (sulfur) The cobalt layer 12 preferably contains at least cobalt (Co) and further contains sulfur (S). In particular, when the cobalt layer 12 contains S, the content of S contained in the cobalt layer 12 is preferably 1 ppb or more and 500 ppm or less. Since the metal member 1 contains S in the cobalt layer 12 and the content of S contained in the cobalt layer 12 is in the range of 1 ppb or more and 500 ppm or less, the adhesiveness with rubber can be more remarkably improved. The content of S contained in the cobalt layer 12 is more preferably 1 ppb or more and 100 ppm or less. When the content of S contained in the cobalt layer 12 is less than 1 ppb, the metal member 1 may not sufficiently obtain the effect of improving the adhesiveness with rubber. When the content of S contained in the cobalt layer 12 exceeds 500 ppm, since Co stably exists as a plating layer in the metal member 1, it tends to be difficult to combine with S in the rubber. The cobalt layer 12 may contain materials other than the above Co and S as long as the effects of the present disclosure are maintained. For example, it may be contained in the cobalt layer 12 due to the diffusion of the components contained in the brass plating layer 11. In addition, components contained in the cobalt plating bath or the like may be contained in the cobalt layer 12.

[0037] Whether S is contained in the cobalt layer 12 and the content of S contained in the cobalt layer 12 are measured by, for example, a scanning transmission electron microscope (Scanning Transmission Electron Microsope: STEM) equipped with an energy dispersive X-ray detector (Energy Dispersive X-ray Spectroscopy: EDX) (hereinafter also referred to as "STEM-EDX") used for the analysis of the cross-section of the metal-rubber composite described later. That is, first, the metal member 1 is cut so that the cobalt layer 12 appears on the cross-section, whereby a cross-section to be measured of the metal member 1 for analyzing the composition of the cobalt layer 12 is obtained. Next, an image for composition analysis is obtained from the observation by the STEM of the cross-section to be measured. By performing composition analysis based on the EDX on this image for composition analysis, the content of S in the cobalt layer of the image is determined. The content of S contained in the cobalt layer 12 is the average value of the content of S in the cobalt layer analyzed from each of the two images for composition analysis obtained by line analysis with a width of 200 nm using the STEM-EDX.

[0038] (Thickness) The thickness of the cobalt layer 12 is preferably 10 nm or more and 2 μm or less. By including the cobalt layer 12 having a thickness in the range of 10 nm or more and 2 μm or less, the metal member 1 can further improve the adhesiveness with rubber. In particular, the thickness of the cobalt layer 12 is preferably 10 nm or more and 1 μm or less. When the thickness of the cobalt layer 12 is less than 10 nm, the metal member 1 may not sufficiently obtain the effect of improving the adhesiveness with rubber. When the thickness of the cobalt layer 12 exceeds 2 μm, the cost or labor for thickening the cobalt layer may increase rather than the effect of improving the adhesiveness between the metal member 1 and rubber. The thickness of the cobalt layer 12 can be controlled, for example, by adjusting the conditions (current density, plating time, etc.) of cobalt plating using a cobalt plating bath.

[0039] The thickness of the cobalt layer 12 is measured, for example, from the observation by STEM in the above STEM-EDX. That is, by identifying the site of the cobalt layer from the observation by the above STEM for the measured cross-section described above, the thickness of the cobalt layer can be determined. The thickness of the cobalt layer 12 is the average value of the thicknesses of the cobalt layers measured in the observation of each of the above measured cross-sections fabricated at three locations from the metal member 1.

[0040] (Crystal layer) The cobalt layer 12 is preferably a crystal layer from the viewpoint of improving the adhesiveness with rubber. For example, by applying cobalt plating to the surface of the iron base material 10 or the brass plating layer 11 using a known cobalt plating bath, the above surface is coated with the cobalt 12 layer which is a crystal layer.

[0041] (Sdr) The cobalt layer 12 has a surface with a developed interface area ratio Sdr of 0.7 or more. Thereby, the metal member 1 can improve the adhesiveness with rubber due to the anchor effect based on at least a part of the surface of the cobalt layer 12 being roughened. The surface of the cobalt layer 12 may have the Sdr of 0.8 or more, 1.0 or more, 1.5 or more, 2.0 or more, 3.0 or more, 4.0 or more, or 5.0 or more. The upper limit value of the Sdr on the surface of the cobalt layer 12 is realistically 10.0 or less. When the value of the Sdr is too large, it may cause a case where the rubber cannot flow into the unevenness of the roughened surface of the cobalt layer 12 due to the high viscosity of the rubber. The Sdr on the surface of the cobalt layer 12 may be 8.0 or less, or 6.0 or less.

[0042] The developed interface area ratio Sdr refers to one of the indexes for evaluating the surface roughness defined in JIS B 0681-2:2018 (ISO 25178-2:2022). The above Sdr is a composite parameter indicating the ratio of the difference between the area of the interface of the contour surface and the area of the reference area to the area of the reference area [{(area of the interface of the contour surface) - (area of the reference area)} / (area of the reference area)]. In the contour surface within the reference area to be evaluated, when there is no surface unevenness at all, the above Sdr is shown as 0%. This is because the area of the interface of the above contour surface becomes the same as the area of the above reference area.

[0043] In the present disclosure, the above Sdr of the surface of the cobalt layer 12 is measured by the following procedure. First, a single-wire metal member 1 is prepared. The cobalt layer 12 located on the surface of this metal member 1 is analyzed using a shape analysis laser microscope (trade name: "VK-X100 (trademark), manufactured by Keyence Corporation"), whereby the above Sdr of the cobalt layer 12 is measured.

[0044] Specifically, first, a measurement sample is prepared by cutting a single-wire metal member 1 so that the length in the longitudinal direction becomes 50 mm. Next, the surface of the cobalt layer 12 in the above measurement sample is divided into rectangular unit areas of 110 μm × 145 μm, and the above Sdr in the above unit areas is measured respectively using the above shape analysis laser microscope. Further, the percentage (N2 / N1)×100 of the number N2 of unit areas where the above Sdr is 0.7 or more with respect to the total number N1 of all unit areas is calculated. In the present disclosure, when the above percentage (N2 / N1)×100 is 70% or more, in the metal member 1 used as the measurement sample, the cobalt layer 12 is evaluated to have a surface where the above Sdr is 0.7 or more.

[0045] In the above measurement sample, when the surface of the cobalt layer 12 is divided into unit areas of 110 μm × 145 μm, it is preferable that the above Sdr of all the unit areas is 0.7 or more. In this case, since the above measurement sample is evaluated to have a uniform above Sdr over the entire surface of the cobalt layer 12, the adhesive force with rubber can be further improved.

[0046] When the surface of the cobalt layer 12 is divided into unit areas, the sample to be measured may not be divided into an integer number of unit areas depending on its size and shape, and there may be an area including the surface of the cobalt layer 12 and space outside the unit area. In such a case, only the unit area shall be the measurement target of the Sdr, and the area including the surface of the cobalt layer 12 and space shall be excluded from the measurement target.

[0047] (Protrusion on the surface) The surface of the cobalt layer 12 preferably has protrusions. Specifically, the surface preferably has 200 or more and 1000 or less protrusions per 500 μm. 2 In this case, the protrusions are defined as having a height of 0.01 μm or more and 0.5 μm or less and a width of 0.1 μm or more and 2 μm or less. Thereby, the metal member 1 can further improve the adhesiveness with rubber. On the surface of the cobalt layer 12, a convex portion having a height of less than 0.01 μm or a width of less than 0.1 μm is not defined as the above-described protrusion. This is because such a convex portion may not sufficiently obtain the above-described anchor effect. On the other hand, on the surface of the cobalt layer 12, a convex portion having a height exceeding 0.5 μm or a width exceeding 2 μm is difficult to conceive in view of the manufacturing method of the metal member 1 described later. This is because the metal member 1 having such a large convex portion on the surface of the cobalt layer 12 often has an oxidized plating film and is usually not selected as a good product.

[0048] The surface of the cobalt layer 12 is 500 μm 2 More preferably, it has protrusions in the range of 200 or more and 800 or less per. The surface of the cobalt layer 12 has protrusions of 500 μm 2 When the number of protrusions is less than 200 per 500 μm, there is a possibility that the anchor effect for further improving the adhesiveness with rubber cannot be sufficiently obtained. The surface of the cobalt layer 12 has protrusions of 500 μm 2When the number exceeds 1000 per unit area, the rubber cannot flow into the spaces between the protrusions (between the roughened unevenness), and the anchor effect for further improving the adhesiveness with the rubber may not be sufficiently obtained.

[0049] The number of protrusions on the surface of the cobalt layer 12 is measured as follows. That is, the surface of the cobalt layer 12 of the metal member 1 is observed at a magnification of 5000 times using a scanning electron microscope (SEM), and the number of the protrusions is measured. In this case, since one field of view of the above observation is 25 μm × 20 μm, the surface of 500 μm of the cobalt layer 12 can be observed by one such observation. 2 In the above observation, only the convex portions having a height of 0.01 μm or more and 0.5 μm or less and a width of 0.1 μm or more and 2 μm or less are counted as effective protrusions. The height of the convex portion (protrusion) is obtained by shifting the focus of the scanning electron microscope, that is, adjusting in the depth direction. The number of protrusions on the surface of the cobalt layer 12 is the average value of the number of protrusions obtained for each of the surfaces of three fields of view observed using the above SEM.

[0050] FIG. 2 is a microscopic image of the surface of the cobalt layer in the metal member according to the present embodiment. In FIG. 2, one field of view (25 μm × 20 μm) of the microscopic image of the surface of the cobalt layer 12 observed at a magnification of 5000 times using a scanning electron microscope (trade name: “FlexSEM 1000 II”, manufactured by Hitachi High-Technologies Corporation) is shown. In FIG. 2, the number of protrusions defined by the convex portions having a height of 0.01 μm or more and 0.5 μm or less and a width of 0.1 μm or more and 2 μm or less is 700. The Sdr of the surface of the cobalt layer 12 corresponding to the microscopic image in FIG. 2 is 2.5.

[0051] The cobalt layer 12 may be a single layer or may be composed of a plurality of layers. When the cobalt layer 12 is composed of a plurality of layers, it is preferable that the Sdr on the surface of the outermost cobalt layer farthest from the iron base material 10 is at least 0.7 or more. Further, when the cobalt layer 12 is composed of a plurality of layers, each of the plurality of layers may have a different crystal grain size from each other. Whether the cobalt layer 12 is composed of a single layer or a plurality of layers is confirmed by observing a measurement cross section used when measuring the thickness of the cobalt layer 12 with the above SEM at a magnification of 5000 times.

[0052] 〔Metal-rubber composite〕 The metal-rubber composite according to the present embodiment includes a rubber member and the metal member encapsulated in the rubber member. A metal-rubber composite having such characteristics can improve both the adhesion between the rubber (rubber member) and the metal member immediately after vulcanization and the adhesion between the rubber (rubber member) and the metal member after a predetermined damp heat test based on the anchor effect and the like obtained from the roughened surface of the cobalt layer of the above-described metal member.

[0053] In particular, it is preferable that the metal-rubber composite has a cobalt sulfur layer. In this preferred embodiment, the cobalt sulfur layer is disposed between the rubber member and the metal member. The cobalt sulfur layer is composed of sulfur, carbon, and the balance of cobalt and unavoidable impurities. Any two points X and Y existing on the interface where the surface of the cobalt layer in the metal member is in contact with the cobalt sulfur layer preferably satisfy the following condition I and condition II. Condition I: The linear distance between X and Y is 1 μm. Condition II: The distance along the interface from X to Y is 1.10 μm or more and 2.50 μm or less.

[0054] According to the above preferred embodiment, the metal-rubber composite can improve both the adhesion between the rubber member and the metal member immediately after vulcanization and the adhesion between the rubber member and the metal member after a predetermined damp heat test. Here, in this specification, the "predetermined damp heat test" refers to a test in which the metal-rubber composite is placed in an environment of 95 °C and a relative humidity (RH) of 95% for 5 days.

[0055] FIG. 3 is a cross-sectional explanatory view schematically showing an example of the metal-rubber composite according to this embodiment. As shown in FIG. 3, the metal-rubber composite 100 includes a rubber member 2 and a metal member 1 encapsulated in the rubber member 2. In particular, the metal-rubber composite 100 has a cobalt sulfur layer 31. The cobalt sulfur layer 31 is disposed between the rubber member 2 and the metal member 1.

[0056] Specific examples of the metal-rubber composite 100 include, for example, a carcass, a belt, or a bead in which a plurality of steel cords are embedded in rubber and processed into a sheet shape, or a bead in which steel is bundled and used. These are used as reinforcing members such as tires. In the metal-rubber composite 100, the characteristics of the metal member 1 encapsulated in the rubber member 2 are as shown in the above item of [Metal Member], and repeated descriptions will not be repeated. In the metal-rubber composite 100, the metal member 1 encapsulated in the rubber member 2 is a wire rod having a circular cross section as described above, and the diameter of the wire rod is preferably 0.05 mm or more and 3 mm or less. Hereinafter, the rubber member 2 and the cobalt sulfur layer 31 will be described in detail.

[0057] <Rubber member> The rubber member 2 is manufactured by molding the following rubber composition and vulcanizing it as necessary.

[0058] (Rubber composition) The rubber composition contains, for example, a rubber component, sulfur, and a vulcanization accelerator. The rubber component contains, for example, at least one of natural rubber (NR) and isoprene rubber (IR). The content of at least one of NR and IR in the rubber component is preferably 60% by mass or more, more preferably 70% by mass or more. In this case, the rubber composition can have excellent breaking strength.

[0059] In addition to NR and IR, the rubber component can contain, for example, styrene-butadiene rubber (SBR), butadiene rubber (BR), ethylene-propylene-diene rubber (EPDM), chloroprene rubber (CR), butyl rubber (IR), acrylonitrile-butadiene rubber (NBR), and the like. As the sulfur, for example, sulfur generally used in the rubber industry is used.

[0060] The content of sulfur in the rubber composition is preferably, for example, 3 to 10 parts by mass with respect to 100 parts by mass of the rubber component. When the content of sulfur is 3 parts by mass or more, an improvement in the crosslink density of the rubber and an improvement in the adhesiveness to the steel member are expected. Also, when the content of sulfur is 10 parts by mass or less, it is expected to uniformly disperse sulfur in the rubber and suppress the occurrence of blooming.

[0061] As a vulcanization accelerator, for example, sulfenamide-based accelerators are preferably used. Examples of sulfenamide-based accelerators include N,N'-dicyclohexyl-2-benzothiazolylsulfenamide, N-cyclohexyl-2-benzothiazolylsulfenamide, N-tert-butyl-2-benzothiazolylsulfenamide, N-oxydiethylene-2-benzothiazolylsulfenamide, and the like. As a vulcanization accelerator, for example, thiazole-based accelerators, thiuram-based accelerators, etc. may also be used. Examples of thiazole-based accelerators include 2-mercaptobenzothiazole, di-2-benzothiazolylsulfide, and the like. Examples of thiuram-based accelerators include tetrabenzylthiuram disulfide, tetramethylthiuram disulfide, tetraethylthiuram disulfide, tetrakis(2-ethylhexyl)thiuram disulfide, tetramethylthiuram monosulfide, and the like.

[0062] In addition to the above rubber component, sulfur, and vulcanization accelerator, the rubber composition can contain optional components. The rubber composition can contain, for example, well-known rubber additives such as reinforcing agents (carbon black, silica, etc.), waxes, antioxidants, and the like.

[0063] For example, the rubber composition is made into a kneaded product by kneading the above-mentioned respective components by a conventional method, and the kneaded product is heat-treated and extruded to be manufactured.

[0064] <Cobalt sulfur layer> The metal-rubber composite 100 preferably has the cobalt sulfur layer 31 as described above. In this case, the cobalt sulfur layer 31 is disposed between the rubber member 2 and the metal member 1. The cobalt sulfur layer 31 functions as an adhesion part (hereinafter, also referred to as "adhesion interface") where the rubber member 2 and the surface of the cobalt layer 12 of the metal member 1 adhere to each other. The cobalt sulfur layer 31 is composed of sulfur (S), carbon (C), the balance cobalt (Co), and inevitable impurities. The cobalt sulfur layer 31 may be an amorphous layer in terms of the manufacturing method of the metal-rubber composite 100.

[0065] (Flexural surface satisfying Condition I and Condition II) In the metal-rubber composite 100, it is preferable that any two points X and Y existing on the interface where the surface of the cobalt layer 12 in the metal member 1 is in contact with the cobalt sulfur layer 31 satisfy the following Condition I and Condition II. Condition I: The linear distance between the above X and the above Y is 1 μm. Condition II: The distance along the interface from the above X to the above Y is 1.10 μm or more and 2.50 μm or less.

[0066] The inventor has found that in the metal-rubber composite 100 according to the present embodiment, the cobalt sulfur layer 31 exhibits a flexural surface along the roughened surface with an Sdr of 0.7 or more of the cobalt layer 12, so that the points X and Y on the above interface satisfy the above Condition I and Condition II. That is, when the points X and Y on the above interface of the metal-rubber composite 100 satisfy the above Condition I and Condition II, since the cobalt sulfur layer 31 exhibits a flexural surface, the adhesion area between the rubber member 2 and the metal member 1 can be increased as compared with the case where it is smooth. Thereby, the metal-rubber composite 100 can exhibit an anchor effect, and it is expected that both the adhesion between the rubber member 2 and the metal member 1 immediately after vulcanization and the adhesion between the rubber member 2 and the metal member 1 after a predetermined damp heat test can be further improved.

[0067] Figure 4 is a microscopic image (the left figure is an ADF image and the right figure is a BF image) taken of the cross-section revealed by cutting the metal-rubber composite according to this embodiment, using a scanning transmission electron microscope (STEM-EDX) equipped with an energy-dispersive fluorescent X-ray detector. The microscopic image shown in Figure 4 is a microscopic image taken at a magnification of 200,000 times of the measured cross-section formed by cutting the metal-rubber composite 100 so that the cobalt sulfur layer 31 appears. In the above microscopic image, the cobalt layer 12 in the metal member 1, the rubber member 2, and the cobalt sulfur layer 31 formed between the metal member 1 and the rubber member 2 appear. The cobalt layer 12 appears white in the ADF image of Figure 4 and black in the BF image of Figure 4. The rubber member 2 appears black in the ADF image of Figure 4 and white in the BF image of Figure 4. The cobalt sulfur layer 31 appears gray in both the ADF image and the BF image of Figure 4.

[0068] In Figure 4, the cobalt sulfur layer 31 exhibits a curved surface. Further, in Figure 4, points X and Y on the interface between the surface of the cobalt sulfur layer 31 and the surface of the cobalt layer 12, and the line segment connecting points X and Y are added. The straight-line distance (the length of the line segment) between this point X and point Y is 1 μm. The distance along the interface from point X to point Y is 1.8 μm. Incidentally, the Sdr of the surface of the cobalt layer 12 constituting the metal-rubber composite 100 photographed in Figure 4 is 2.3. The protrusions on the surface of the cobalt layer 12 are 650 per 500 μm 2 per hit.

[0069] Therefore, it is understood that the metal-rubber composite 100 photographed in FIG. 4 has the following characteristics. That is, the cobalt sulfur layer 31 shown in FIG. 4 exhibits a curved surface along the roughened surface with an Sdr of 2.3 on the surface of the cobalt layer 12. As a result, points X and Y on the interface between the cobalt sulfur layer 31 and the surface of the cobalt layer 12 satisfy condition I (1 μm) and condition II (1.10 to 2.50 μm). From the above, it is suggested that the metal-rubber composite 100 photographed in FIG. 4 can improve both the adhesion between the rubber member 2 and the metal member 1 immediately after vulcanization and the adhesion between the rubber member 2 and the metal member 1 after a predetermined damp heat test. In particular, the metal-rubber composite 100 photographed in FIG. 4 has 650 protrusions per 500 μm 2 on the surface of the cobalt layer 12, so the anchor effect is more significantly exerted, which is more preferable.

[0070] In the metal-rubber composite 100, when the linear distance between point X and point Y on the interface between the cobalt sulfur layer 31 and the surface of the cobalt layer 12 is 1 μm (i.e., condition I is satisfied), it is more preferable that the distance along the interface from point X to point Y (condition II) is 1.50 μm or more and 2.50 μm or less. In this case, the anchor effect is more significantly exerted.

[0071] (thickness) The thickness of the cobalt sulfur layer 31 is preferably 300 nm or less. The thickness of the cobalt sulfur layer 31 is more preferably 100 nm or less. In terms of the manufacturing method of the metal-rubber composite 100, it is realistic that the thickness of the cobalt sulfur layer 31 is 10 nm or more. In this case, the cobalt sulfur layer 31 has an appropriate thickness as an adhesive interface, so that both the adhesion between the rubber member 2 and the metal member 1 immediately after vulcanization and the adhesion between the rubber member 2 and the metal member 1 after a predetermined damp heat test can be further improved.

[0072] The thickness of the cobalt sulfur layer 31 is measured, for example, from the observation by STEM in the above STEM-EDX. That is, by identifying the part of the cobalt sulfur layer 31 that is gray from the observation of the microscope image described above, the thickness of the cobalt sulfur layer is determined. The thickness of the cobalt sulfur layer is the average value of the thicknesses of the cobalt layers measured at each of the three measurement sites set in the above microscope image.

[0073] (Composition analysis) The cobalt sulfur layer 31 is composed of sulfur (S), carbon (C), the remaining cobalt (Co), and inevitable impurities as described above. The specific composition ratio (atomic %) of the cobalt sulfur layer 31 is preferably, for example, Co:S:C = 5 to 40:5 to 30:5 to 60. Examples of the inevitable impurities include oxygen (O) that is inevitably mixed in the production of the metal-rubber composite 100, iron (Fe) derived from the iron base material 10 of the metal member 1, Cu, Zn, etc. derived from the brass plating when the metal member 1 has a brass plating layer 11.

[0074] The composition of the cobalt sulfur layer 31 is measured by the following method. That is, the composition of the cobalt sulfur layer 31 is measured, for example, by the above STEM-EDX. First, the metal-rubber composite 100 is cut so that the cobalt sulfur layer 31 appears in the cross section, thereby obtaining a measurement cross section for analyzing the composition of the cobalt sulfur layer 31. Next, an image for composition analysis is obtained from the observation by the above STEM of the above measurement cross section. By performing composition analysis based on the above EDX on this image for composition analysis, the composition of the cobalt sulfur layer 31 in the image is determined. The above composition analysis specifically means identifying the composition of the metal-rubber composite by performing line analysis in a 250 nm width from the rubber member side through the cobalt sulfur layer to the cobalt layer side in the above image for composition analysis. As the above image for composition analysis, for example, a microscope image as shown in FIG. 4 is used.

[0075] FIG. 5 is a graph showing the result of line analysis of the composition of the metal-rubber composite at a width of 250 nm from the rubber member side through the cobalt sulfur layer to the cobalt layer side for the microscope image of FIG. 4. As shown in FIG. 5, when the microscope image of FIG. 4 is subjected to composition analysis based on the above-mentioned EDX of STEM-EDX, from the rubber member 2 side through the cobalt sulfur layer 31 to the cobalt layer 12 side, C, which is the main atom in the rubber member 2, is observed to have its concentration decreasing. On the other hand, from the rubber member 2 side through the cobalt sulfur layer 31 to the cobalt layer 12 side, Co, which is the main atom in the cobalt layer 12, is observed to have its concentration increasing. Since the cobalt sulfur layer 31 is the adhesion interface between the rubber member 2 and the surface of the cobalt layer 12 of the metal member 1, in FIG. 5, the position where the amounts of the concentration of C in the rubber member 2 and the concentration of Co in the cobalt layer 12 are reversed and its periphery correspond to the cobalt sulfur layer 31 (indicated by the arrow in FIG. 5). In FIG. 5, at the position corresponding to the cobalt sulfur layer 31, each atom of S, C, Co, and O is detected. Fe, Cu, and Zn are below the detection limit.

[0076] (Content of sulfur) The content of S contained in the cobalt sulfur layer 31 is preferably 10 atomic % or more and 90 atomic % or less. More preferably, the content of the above S is 20 atomic % or more and 50 atomic % or less. By the content of S contained in the cobalt sulfur layer 31 being within the above-mentioned range, the metal-rubber composite 100 can further improve both the adhesion between the rubber member 2 and the metal member 1 immediately after vulcanization and the adhesion between the rubber member 2 and the metal member 1 after a predetermined damp heat test. The content of S contained in the cobalt sulfur layer 31 is measured by the above-mentioned composition analysis method of the cobalt sulfur layer 31. For example, according to FIG. 5, the content of S contained in the cobalt sulfur layer 31 is observed to be about 30 atomic %.

[0077] The S contained in the cobalt sulfur layer 31 preferably has a concentration distribution in the thickness direction. In this case, it is more preferable that the concentration distribution shows a tendency for the concentration of the S to decrease in the direction from the rubber member 2 side toward the metal member 1 side. Thereby, the metal-rubber composite 100 can further improve both the adhesion between the rubber member 2 and the metal member 1 immediately after vulcanization and the adhesion between the rubber member 2 and the metal member 1 after a predetermined damp heat test. The above concentration distribution is also measured by the composition analysis method of the cobalt sulfur layer 31 described above. For example, according to FIG. 5, it is observed that the concentration distribution of the S contained in the cobalt sulfur layer 31 shows a tendency to decrease in the direction from the rubber member 2 side toward the metal member 1 (cobalt layer 12) side.

[0078] (Inevitable impurities) The cobalt sulfur layer 31 preferably contains oxygen (O) as the above inevitable impurity. In this case, the content of O contained in the cobalt sulfur layer 31 may be 1 atomic % or more and 50 atomic % or less. The content of the above O is preferably 2 atomic % or more and 20 atomic % or less. The content of O contained in the cobalt sulfur layer 31 is measured by the composition analysis method of the cobalt sulfur layer 31 described above. For example, according to FIG. 5, it is observed that the content of O contained in the cobalt sulfur layer 31 is about 8 atomic % at the peak top of O.

[0079] (Manufacturing method) The metal-rubber composite 100 can be produced by preparing the above-described metal member 1 and coating the metal member 1 with the rubber member 2 as described above by a known method. Therefore, the metal-rubber composite 100 can be obtained by a known manufacturing method if the metal member 1 according to the present embodiment is prepared.

[0080] <Tire> As described above, the metal-rubber composite 100 according to the present embodiment may be used as a reinforcing member of a tire, such as a carcass, a belt, or a bead, for example. That is, the metal-rubber composite 100 according to the present embodiment is preferably used for a tire. Hereinafter, the outline of the tire to which the metal-rubber composite 100 is applied will be described with reference to FIG. 6. FIG. 6 is an explanatory view schematically showing a cross section of a tire which is an application example of the metal-rubber composite according to the present embodiment. In FIG. 6, a cross section of the tire 40 cut along a plane perpendicular to the circumferential direction is shown. In FIG. 6, a cross section on the left side of the center line (CL) is shown, but actually, a similar structure exists on the right side of the CL with the CL as the reference axis.

[0081] As shown in FIG. 6, the tire 40 includes, for example, a tread portion 41, a sidewall portion 42, and a bead portion 43. The tread portion 41 is a portion that contacts the road surface. The bead portion 43 is provided on the inner diameter side of the tire 40 with respect to the tread portion 41. The bead portion 43 is a portion that contacts the rim of the wheel of the vehicle. The sidewall portion 42 connects the tread portion 41 and the bead portion 43. When the tread portion 41 receives an impact from the road surface, the sidewall portion 42 elastically deforms and absorbs the impact.

[0082] Furthermore, the tire 40 includes an inner liner 44, a carcass 45, a belt layer 46, and a bead wire 47. The inner liner 44 is made of a rubber material and seals the space between the tire 40 and the wheel. The carcass 45 forms the skeleton of the tire 40. The above metal-rubber composite may be applied as the carcass 45.

[0083] The bead wire 47 is provided in the bead portion 43. The bead wire 47 receives the tensile force acting on the carcass 45. The belt layer 46 tightens the carcass 45 and increases the rigidity of the tread portion 41. Note that the tire 40 shown in FIG. 6 has two belt layers 46. The two belt layers 46 can be stacked in the radial direction of the tire 40. The above metal-rubber composite may be applied as the belt layer 46.

[0084] In the tire 40 exemplified in this specification, the metal-rubber composite may be applied to at least one of the carcass 45 and the belt layer 46. Thereby, the tire 40 can exhibit excellent wet heat durability based on the metal-rubber composite.

Example

[0085] Hereinafter, the present disclosure will be described in more detail by way of examples, but the present disclosure is not limited thereto. In the following description, the metal members of Sample 1, Sample 2, and Sample 3, and the metal-rubber composites of Sample 101, Sample 102, and Sample 103 are examples. The metal member of Sample A and the metal-rubber composite of Sample 10A are comparative examples.

[0086] 〔Preparation of Samples〕 <Sample 1> First, a steel wire with a diameter of 0.46 mm having a brass plating layer (a plating formed by alloying copper and zinc) on the surface was prepared. This steel wire was immersed in a known cobalt plating bath (composition: cobalt sulfamate tetrahydrate 490 g / L, boric acid 25 g / L, pH adjusted with sulfamic acid). Subsequently, using this cobalt plating bath, cobalt plating was performed on the steel wire under plating conditions of a current density of 20 A (ampere) / dm 2 , a bath temperature of 50 °C, a pH of 4, and a holding time of 7 seconds. Thus, the required number of metal members of Sample 1 having a circular cross-section was produced. The diameter of the metal member of Sample 1 was 0.4 mm.

[0087] <Sample 101> As a rubber composition, a composition consisting of the following components was prepared. NR: 100 phr Carbon black (HAF): 60 phr Sulfur: 5 phr Vulcanization accelerator: 2 phr Zinc oxide: 10 phr Stearic acid: 2 phr

[0088] A part (length: 12.5 mm) of the metal member of Sample 1 was embedded in a rod-shaped rubber with a thickness of 12.5 mm, a width of 12.5 mm, and a length of 200 mm, which was made of the above rubber composition. In this state (in accordance with ASTM D2229-02), the rubber composition was vulcanized by heating at 165 °C for 18 minutes, thereby producing a metal-rubber composite of Sample 101. The pressure during vulcanization was 50 kgf / cm 2 was. The metal-rubber composite of Sample 101 had a cobalt sulfur layer. The cobalt sulfur layer was an amorphous layer. The cobalt sulfur layer contained 5 atm% of oxygen, which was an unavoidable impurity.

[0089] <Sample 2, Sample 102> Except for changing the value of the current density among the plating conditions to 25 A / dm 2 the required number of metal members of Sample 2 was produced in the same manner as Sample 1. Furthermore, by using the metal member of Sample 2, a metal-rubber composite of Sample 102 was produced in the same manner as Sample 101. The diameter of the metal member of Sample 2 was 0.4 mm. The metal-rubber composite of Sample 102 had a cobalt sulfur layer. The cobalt sulfur layer was an amorphous layer. The cobalt sulfur layer contained 10 atm% of oxygen, which was an unavoidable impurity.

[0090] <Sample 3, Sample 103> Except for changing the value of the current density among the plating conditions to 10 A / dm 2 the required number of metal members of Sample 3 was produced in the same manner as Sample 1. Furthermore, by using the metal member of Sample 3, a metal-rubber composite of Sample 103 was produced in the same manner as Sample 101. The diameter of the metal member of Sample 3 was 0.4 mm. The metal-rubber composite of Sample 103 had a cobalt sulfur layer. The cobalt sulfur layer was an amorphous layer. The cobalt sulfur layer contained 5 atm% of oxygen, which was an unavoidable impurity.

[0091] <Sample A, Sample 10A> Except for changing the value of the current density among the plating conditions to 2 A / dm 2Except for changing to , the required number of metal members of Sample A was produced in the same manner as Sample 1. Furthermore, by using the metal members of Sample A, a metal-rubber composite of Sample 10A was produced in the same manner as Sample 101.

[0092] <Measurement of Sdr on the surface of the cobalt layer> For the metal members of Samples 1 to 3 and Sample A, by using the above measurement method, the Sdr on the surface of the cobalt layer was determined. The results are shown in Table 1.

[0093] <Characteristic evaluation of the cobalt layer> For the metal members of Samples 1 to 3 and Sample A, by using the above measurement method, the number of protrusions on the surface of the cobalt layer, the concentration of S contained in the cobalt layer, and the thickness of the cobalt layer were measured. The results are shown in Table 1.

[0094] <Adhesion evaluation between the metal member and the rubber member in the metal-rubber composite> Regarding the metal-rubber composites of Samples 101 to 103 and Sample 10A, when the rubber member was peeled off from the metal member immediately after vulcanization by heating at 165°C for 18 minutes and after being placed in a damp heat environment at 80°C, relative humidity (RH) 95%, and for 5 days, the area ratio of the rubber member remaining on the metal member was evaluated in four grades. According to this test, rubber remains on the metal member at locations where the adhesion (adhesive strength) between the metal member and the rubber is stronger than the cohesive failure (failure strength) of the rubber. Specifically, for the above four-grade evaluation, when the area ratio of the rubber remaining on the metal member is 90% or more, it is rated as A. When the area ratio of the rubber remaining on the metal member is 75% or more, it is rated as B. When the area ratio of the rubber remaining on the metal member is 40% or more, it is rated as C. When the area ratio of the rubber remaining on the metal member is less than 40%, it is rated as D. The area ratio of the rubber remaining on the metal member was evaluated visually. The results are shown in Table 2.

[0095] <Characteristic evaluation of the cobalt sulfur layer, etc.> For the metal-rubber composites of Sample 101 to Sample 103 and Sample 10A, by using the above-described measurement method, the distance along the interface from point X to point Y on the interface (the straight-line distance between point X and point Y is 1 μm), the concentration of S contained in the cobalt-sulfur layer, and the thickness of the cobalt-sulfur layer were measured. The results are shown in Table 2. In the metal-rubber composites of Sample 101 to Sample 103 and Sample 10A, the concentration of S contained in the cobalt-sulfur layer had a concentration distribution in the thickness direction. In particular, the above concentration distribution showed a tendency that the concentration of S decreased in the direction from the rubber member side to the metal member side.

[0096]

Table 1

[0097]

Table 2

[0098] 〔Discussion〕 For the metal members of Sample 1 to Sample 3, the Sdr on the surface of the cobalt layer was 0.7 or more in all cases. In that case, the adhesion evaluation between the metal member and the rubber member in the metal-rubber composites of Sample 101 to Sample 103 was evaluated as A or B both immediately after vulcanization and after a predetermined damp heat test. From the above, it is suggested that the metal members of Sample 1 to Sample 3 and the metal-rubber composites of Sample 101 to Sample 103 using them can improve the adhesiveness with rubber.

[0099] As described above, the embodiments and examples of the present disclosure have been explained. However, it has also been initially planned that the configurations of the above-described embodiments and examples can be appropriately combined.

[0100] The embodiments and examples disclosed this time should be considered as illustrative in all respects and not restrictive. The scope of the present disclosure is shown not by the above-described embodiments but by the claims, and it is intended that all meanings equivalent to the claims and all modifications within the scope are included.

Description of Symbols

[0101] 1 Metal member 10 Iron base material 11 Brass plating layer 12 Cobalt layer 2 Rubber member 31 Cobalt sulfur layer 40 Tire 41 Tread portion 42 Sidewall portion 43 Bead portion 44 Inner liner 45 Carcass 46 Belt layer 47 Bead wire 100 Metal-rubber composite Points on the X,Y interface

Claims

1. An iron base material containing iron, and a cobalt layer provided on the iron base material, wherein the cobalt layer has a surface with a spreading interface area ratio Sdr of 0.7 or more, a metal member.

2. The surface is 500 μm 2 has 200 or more and 1000 or less protrusions per hit, The protrusion has a height of 0.01 μm or more and 0.5 μm or less and a width of 0.1 μm or more and 2 μm or less, the metal member according to claim 1.

3. The cobalt layer contains sulfur, the metal member according to claim 1 or claim 2.

4. The content of sulfur contained in the cobalt layer is 1 ppb or more and 500 ppm or less, the metal member according to claim 3.

5. The cobalt layer is a crystal layer, the metal member according to claim 1 or claim 2.

6. The thickness of the cobalt layer is 10 nm or more and 2 μm or less, the metal member according to claim 1 or claim 2.

7. A metal-rubber composite including a rubber member and the metal member according to claim 1 or claim 2 encapsulated in the rubber member.

8. The metal-rubber composite has a cobalt-sulfur layer, the cobalt-sulfur layer is disposed between the rubber member and the metal member, the cobalt-sulfur layer is composed of sulfur, carbon, the balance of cobalt, and inevitable impurities, any two points X and Y existing on the interface where the surface of the cobalt layer in the metal member is in contact with the cobalt-sulfur layer satisfy the following Condition I and Condition II, the metal-rubber composite according to claim 7. Condition I: The straight-line distance between X and Y is 1 μm. Condition II: The distance along the interface from X to Y is 1.10 μm or more and 2.50 μm or less.

9. The cobalt-sulfur layer is an amorphous layer, the metal-rubber composite according to claim 8.

10. The content of sulfur contained in the cobalt-sulfur layer is 10 atomic% or more and 90 atomic% or less, the metal-rubber composite according to claim 8.

11. The sulfur contained in the cobalt-sulfur layer has a concentration distribution in the thickness direction, the concentration distribution shows a tendency for the concentration of the sulfur to decrease in the direction from the rubber member side to the metal member side, the metal-rubber composite according to claim 8.

12. The thickness of the cobalt-sulfur layer is 300 nm or less, the metal-rubber composite according to claim 8.

13. The cobalt-sulfur layer contains oxygen as the inevitable impurity, The oxygen content in the cobalt sulfur layer is 1 atomic % or more and 50 atomic % or less, and the metal-rubber composite according to claim 8.

14. The metal member is a wire rod having a circular cross section, The diameter of the wire rod is 0.05 mm or more and 3 mm or less, and the metal-rubber composite according to claim 8.

15. A metal-rubber composite including a rubber member and the metal member according to claim 2 encapsulated in the rubber member, The metal-rubber composite has a cobalt sulfur layer, The cobalt sulfur layer is disposed between the rubber member and the metal member, The cobalt sulfur layer is composed of sulfur, carbon, and the balance of cobalt and inevitable impurities, The cobalt sulfur layer is an amorphous layer, The sulfur content in the cobalt sulfur layer is 10 atomic % or more and 90 atomic % or less, The sulfur contained in the cobalt sulfur layer has a concentration distribution in the thickness direction, The concentration distribution shows a tendency that the sulfur concentration decreases in the direction from the rubber member side to the metal member side, Any two points X and Y existing on the interface where the surface of the cobalt layer in the metal member is in contact with the cobalt sulfur layer satisfy the following Condition I and Condition II, The thickness of the cobalt sulfur layer is 300 nm or less, or the cobalt sulfur layer contains oxygen as the inevitable impurity, and the oxygen content in the cobalt sulfur layer is 1 atomic % or more and 50 atomic % or less, and the metal-rubber composite. Condition I: The straight-line distance between X and Y is 1 μm. Condition II: The distance along the interface from X to Y is 1.10 μm or more and 2.50 μm or less.

Images