WO2024106490A1 - Sliding member and method for producing sliding member - Google Patents

Abstract

The sliding member according to one aspect of the present disclosure comprises a base and a sliding layer formed directly or indirectly on at least some of a surface of the base, wherein the sliding layer comprises, as a main component, a product of crosslinking of polytetrafluoroethylene, a tetrafluoroethylene/hexafluoropropylene copolymer, or a tetrafluoroethylene/perfluoro(alkyl vinyl ether) copolymer and wherein the surface of the sliding layer which directly or indirectly faces the base is a plasma-treated surface or a silane-coupling-treated surface.

Description

SLIDE MEMBER AND METHOD FOR MANUFACTURING SLIDE MEMBER

The present disclosure relates to a slide member and a method for manufacturing a slide member.
This application claims priority based on Japanese Application No. 2022-182609 filed on November 15, 2022, and incorporates by reference all of the contents of the above-mentioned Japanese application.

Sliding parts are required to have excellent sliding properties such as high abrasion resistance, low coefficient of friction, and low adhesion, and in particular excellent abrasion resistance from the viewpoint of improving durability. Fluororesins such as polytetrafluoroethylene have excellent heat resistance, chemical resistance, and weather resistance, and also have excellent sliding properties with low adhesion and coefficient of friction. For this reason, fluororesins are considered useful as coatings for various substrates and as sliding parts. However, because fluororesins have relatively low abrasion resistance and thermal conductivity, when used as sliding parts, the surface is easily worn, and wear is particularly accelerated by the rise in temperature of the sliding surface due to continuous operation.

In contrast, when fluororesin is irradiated with an electron beam, the molecules are cross-linked, improving its wear resistance. From this perspective, it has been proposed to use cross-linked fluororesin, which has excellent wear resistance, as a material for sliding components (see Patent Document 1).

JP 2014-089382 A

The sliding member according to one embodiment of the present disclosure comprises a substrate and a sliding layer laminated directly or indirectly on at least a portion of the surface of the substrate, the sliding layer being mainly composed of a crosslinked product of polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer, or tetrafluoroethylene-perfluoroalkylvinyl ether copolymer, and the surface of the sliding layer directly or indirectly facing the substrate is a plasma-treated surface.

FIG. 1 is a schematic cross-sectional view showing a slide member according to a first embodiment of the present disclosure. FIG. 2 is a schematic cross-sectional view showing a sliding layer of the sliding member according to the first embodiment of the present disclosure. FIG. 3 is a schematic cross-sectional view showing a sliding member according to a second embodiment of the present disclosure. FIG. 4 is a schematic cross-sectional view showing a sliding member according to a third embodiment of the present disclosure. FIG. 5 is a schematic exploded cross-sectional view of a sliding member according to a third embodiment of the present disclosure.

[Problem to be solved by this disclosure]
When adhering a crosslinked fluorine sheet to a substrate, it is necessary to use an abrasion-resistant and heat-meltable fluorine resin (e.g., tetrafluoroethylene-perfluoroalkylvinylether copolymer (PFA)) and press at a very high temperature (e.g., 340°C or higher) above the crystalline melting point of the fluorine resin, which may reduce the strength and other performance properties of the substrate. In addition, even when adhering a crosslinked fluorine sheet to a resin substrate, the heat resistance is very low, so the above method cannot be applied. Therefore, in order to avoid the deterioration of the performance of the substrate due to the process under high-temperature heating, a method has been proposed in which a fluorine paint is applied to a highly heat-resistant polyimide film, and then the laminate is baked at a high temperature and crosslinked by irradiation with an electron beam is adhered to the substrate using an adhesive under relatively low temperature conditions in the temperature range of 20°C to 150°C. However, in the case of such a method, there is a problem that the polyimide film is significantly warped, reducing workability.

The present disclosure has been made based on these circumstances, and aims to provide a sliding member that has a sliding layer mainly composed of a crosslinked product of polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer, or tetrafluoroethylene-perfluoroalkylvinyl ether copolymer, and that has good abrasion resistance as well as good adhesion between the sliding layer and the substrate.

[Effects of the present disclosure]
The sliding member of the present disclosure has a sliding layer mainly composed of a crosslinked product of polytetrafluoroethylene, a tetrafluoroethylene-hexafluoropropylene copolymer, or a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, and has good adhesion between the sliding layer and a substrate as well as good wear resistance.

[Description of the embodiments of the present disclosure]
First, the embodiments of the present disclosure will be listed and described.

A slide member according to one aspect of the present disclosure includes:
(1) A substrate and a sliding layer laminated directly or indirectly on at least a portion of a surface of the substrate, the sliding layer being composed mainly of a crosslinked product of polytetrafluoroethylene, a tetrafluoroethylene-hexafluoropropylene copolymer, or a tetrafluoroethylene-perfluoroalkylvinyl ether copolymer, and the surface of the sliding layer directly or indirectly facing the substrate is a plasma-treated surface.

In a sliding member according to one embodiment of the present disclosure, the surface of the sliding layer, which is mainly composed of a crosslinked body of polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer, or tetrafluoroethylene-perfluoroalkylvinylether copolymer, that directly or indirectly faces the substrate is a plasma-treated surface, so that functional groups such as carboxy groups, hydroxy groups, and amino groups are generated on the surface of the sliding layer that directly or indirectly faces the substrate. As a result, the contact angle of the surface of the sliding layer that directly or indirectly faces the substrate is reduced, improving wettability, and improving adhesion between the surface of the sliding layer and the substrate.
Furthermore, although the reason is not clear, it is presumed that the adhesive strength of the sliding layer is improved because the main component of the sliding layer is a crosslinked product of polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer, or tetrafluoroethylene-perfluoroalkylvinyl ether copolymer, which reduces the crystalline regions of the sliding layer and increases the areas that are susceptible to plasma treatment.
Furthermore, in this sliding member, in order to avoid deterioration of the performance of the base, it is not necessary to adhere the sliding layer to the base using a film obtained by applying a fluorine paint to a heat-resistant polyimide film which is prone to significant warping.
Therefore, the sliding member has a sliding layer mainly composed of a crosslinked product of polytetrafluoroethylene, a tetrafluoroethylene-hexafluoropropylene copolymer, or a tetrafluoroethylene-perfluoroalkylvinyl ether copolymer, and has good adhesion between the sliding layer and the substrate as well as good wear resistance without causing a decrease in the performance of the substrate. Here, the "plasma-treated surface" refers to a surface that has been subjected to a plasma treatment.

(2) In the above (1), an adhesive layer may be laminated between the substrate and the sliding layer, the adhesive layer may contain a main component resin, and the glass transition temperature of the main component resin may be 130°C or higher. In this way, by further providing an adhesive layer laminated between the substrate and the plasma-treated surface of the sliding layer, functional groups such as carboxyl groups, hydroxyl groups, and amino groups are generated on the surface of the sliding layer facing the adhesive layer. Therefore, the contact angle of the surface of the sliding layer facing the adhesive layer is reduced, and wettability is improved, so that adhesion between the surface of the sliding layer and the adhesive layer is improved. Since the sliding member can obtain high adhesion between the surface of the sliding layer and the adhesive layer, pressing at high temperatures is not necessary, and deterioration of the performance of the substrate due to pressing at high temperatures can be suppressed. In addition, although the sliding layer may become hot due to frictional heat, the adhesive layer has excellent heat resistance and can maintain high adhesive strength even at high temperatures because the glass transition temperature of the main component resin of the adhesive layer is 130°C or higher.

(3) In the above (1), the sliding layer may be laminated directly on at least a part of the surface of the substrate, and the surface of the substrate facing the sliding layer may be a plasma-treated surface or a silane coupling-treated surface. In this embodiment, the opposing surfaces of the sliding layer and the substrate are plasma-treated surfaces or silane coupling-treated surfaces, so that the sliding member has better adhesion between the sliding layer and the substrate. Furthermore, due to chemical bonding between the functional group of the plasma-treated surface of the sliding layer and the functional group of the plasma-treated surface or the silane coupling-treated surface of the substrate, the sliding member can further strengthen the adhesion between the sliding layer and the substrate by press processing at low temperatures without using an adhesive. In addition, since the sliding layer is laminated directly on at least a part of the surface of the substrate, there is no need to consider the adhesive layer protruding when the adhesive layer is laminated, and a high adhesive force can be obtained between the sliding layer and the substrate with a simpler configuration. Here, the "silane coupling-treated surface" refers to a surface on which a silane coupling treatment has been applied.

(4) In any of (1) to (3) above, the limit PV value of the outer surface of the sliding layer may be 200 MPa·m/min or more. When the limit PV value of the outer surface of the sliding layer is 200 MPa·m/min or more, the sliding layer has high wear resistance and can improve the sliding performance of the sliding member.

(5) A method for producing a sliding member according to another aspect of the present disclosure includes a step of crosslinking a sliding layer-forming film mainly composed of polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer, or tetrafluoroethylene-perfluoroalkylvinylether copolymer by irradiation, a step of performing plasma treatment on one side of the sliding layer-forming film after the crosslinking step, and a step of directly or indirectly laminating the sliding layer formed after the plasma treatment step on at least a part of the surface of a substrate, and the surface of the sliding layer directly or indirectly facing the substrate is the plasma-treated surface.

In the method for producing the sliding member, one side of the film for forming the sliding layer after electron beam crosslinking is subjected to plasma treatment, and the sliding layer is laminated directly or indirectly on at least a part of the surface of the substrate so that the plasma-treated surface of the sliding layer formed after the plasma treatment faces the substrate. This allows for strong adhesion between the substrate and the sliding layer, the main component of which is a crosslinked product of polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer, or tetrafluoroethylene-perfluoroalkylvinylether copolymer. In addition, the method for producing the sliding member does not require pressing at high temperatures, such as above the crystalline melting point of polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer, or tetrafluoroethylene-perfluoroalkylvinylether copolymer, and therefore can suppress deterioration of the performance of the substrate. Furthermore, in order to avoid deterioration of the performance of the substrate, it is not necessary to adhere the sliding layer to the substrate using a heat-resistant polyimide film that is prone to warping. Therefore, the manufacturing method for the sliding member can manufacture a sliding member that has good abrasion resistance as well as good adhesion between the sliding layer and the substrate, without reducing the performance of the substrate, in a sliding layer whose main component is a crosslinked product of polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer, or tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer.

(6) In the above (5), the method may further include a step of laminating an adhesive layer between the substrate and the sliding layer, the adhesive layer containing a main component resin, and the glass transition temperature of the main component resin may be 130°C or higher. The method for producing a sliding member includes laminating the sliding layer on the surface of the adhesive layer so that the plasma-treated surface of the sliding layer faces the adhesive layer, so that a high adhesive strength can be obtained between the surface of the sliding layer and the adhesive layer. Therefore, the sliding layer mainly composed of a crosslinked body of polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer, or tetrafluoroethylene-perfluoroalkylvinylether copolymer and the substrate can be firmly bonded. Since the glass transition temperature of the main component resin of the adhesive layer is 130°C or higher, the method has excellent heat resistance and can maintain a high adhesive strength even at high temperatures. In addition, the method for producing a sliding member does not require pressing at a high temperature, such as above the crystalline melting point of polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer, or tetrafluoroethylene-perfluoroalkylvinylether copolymer, so that the deterioration of the performance of the substrate due to pressing at high temperatures can be suppressed. Furthermore, in order to avoid a decrease in the performance of the substrate, it is not necessary to adhere the sliding layer to the substrate using a film obtained by applying a fluororesin paint to a heat-resistant polyimide film that is prone to significant warping. Therefore, the method for manufacturing the sliding member can suppress the occurrence of significant warping of the film for forming the sliding layer without causing a decrease in the performance of the substrate, and can manufacture a sliding member that has good adhesion between the substrate and the sliding layer, the main component of which is a crosslinked product of polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer, or tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer.

(7) In the above (5), the method may further include a step of performing a plasma treatment or a silane coupling treatment on one side of the substrate, the sliding layer being directly laminated on at least a part of the surface of the substrate after the step of performing the plasma treatment or the silane coupling treatment, and the surface of the substrate facing the sliding layer may be a plasma-treated surface or a silane coupling-treated surface. In the method for producing the sliding member, the sliding layer is laminated so that the surface of the sliding layer that has been subjected to the plasma treatment faces the surface of the substrate that has been subjected to the plasma treatment or the silane coupling treatment. This allows the sliding layer, which is mainly composed of a crosslinked body of polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer, or tetrafluoroethylene-perfluoroalkylvinylether copolymer, to be firmly bonded to the substrate. In addition, the method for producing the sliding member does not require pressing at a high temperature, such as above the crystalline melting point of polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer, or tetrafluoroethylene-perfluoroalkylvinylether copolymer, and therefore the deterioration of the performance of the substrate can be suppressed. Furthermore, in order to avoid a decrease in the performance of the substrate, it is not necessary to adhere the sliding layer to the substrate using a heat-resistant polyimide film that is prone to warping. Therefore, the method for producing the sliding member can produce a sliding member that has good adhesion between the sliding layer and the substrate as well as good wear resistance, without causing a decrease in the performance of the substrate, in a sliding layer that is mainly composed of a crosslinked product of polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer, or tetrafluoroethylene-perfluoroalkylvinyl ether copolymer.

In this disclosure, the term "main component" refers to the component with the largest content by mass, for example, a component with a content exceeding 50% by mass.

[Details of the embodiment of the present disclosure]
Hereinafter, a slide member and a method for manufacturing a slide member according to each embodiment of the present disclosure will be described in detail with reference to the drawings.

<Sliding Member>
The sliding member includes a substrate and a sliding layer laminated directly or indirectly on at least a portion of the surface of the substrate. The surface of the sliding layer facing the substrate is a plasma-treated surface. The sliding member can be suitably used for bearings of automobile engines and other industrial machine engines, driving parts in the automobile field, and piston packings.

[First embodiment]
The sliding member 10 according to the first embodiment shown in Fig. 1 includes a base 6, an adhesive layer 4, and a sliding layer 5 in this order. As shown in Fig. 2, the sliding layer 5 has a plasma-treated surface 2 on one side. The adhesive layer 4 is laminated between the base 6 and the plasma-treated surface 2 of the sliding layer 5. Although Fig. 1 illustrates a planar sheet-like configuration, the shape of the sliding member 10 is not particularly limited, and may be, for example, a shape having a curved surface such as a cylindrical shape or an arch shape, or may be a shape other than a sheet shape.

[Base]
Materials used for the substrate 6 include, for example, metals, resins, ceramics, and inorganic solid materials. Examples of the metals include aluminum, aluminum alloys, iron, iron alloys (stainless steel, etc.), nickel, copper, copper alloys, titanium, titanium alloys, and steel. Examples of the resins include polyetherketone, polybutylene naphthalate, polybenzimidazole, polyphenylene sulfide, polyetherimide, polyamideimide, polysulfone, polychlorotrifluoroethylene, polyarylate, polyimide, polyethersulfone, acrylic resins, polystyrene, acrylonitrile butadiene styrene, polyethylene, polyvinyl chloride, unsaturated polyester resins, urea resins, melamine resins, and phenolic resins. Examples of the ceramics include metal oxides and carbides. Examples of the inorganic solid materials include glass.

The substrate may be in a solid form at 80°C. "At 80°C" means that in the dry ring-on-disk abrasion test for evaluating abrasion resistance described in the examples below, at the step where the PV value reaches 200 MPa·m/min, the temperature of the substrate rises to 80°C due to frictional heat, and the substrate must be in a solid form at this temperature.

The average thickness of the substrate 6 can be set appropriately depending on the intended use of the sliding member 10, but is generally in the range of 20 μm to 10 cm. Here, the "average thickness" in this disclosure refers to the average value of the average thickness measured at any five points.

(Sliding layer)
The sliding layer 5 is mainly composed of a crosslinked body of polytetrafluoroethylene, a tetrafluoroethylene-hexafluoropropylene copolymer, or a tetrafluoroethylene-perfluoroalkylvinyl ether copolymer. The sliding layer 5 also has a resin layer 1 and a plasma-treated surface 2, which will be described later. The sliding layer 5 can enhance its wear resistance by having the crosslinked structure of the main component, polytetrafluoroethylene, a tetrafluoroethylene-hexafluoropropylene copolymer, or a tetrafluoroethylene-perfluoroalkylvinyl ether copolymer.

Polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer, or tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer may contain polymerization units derived from other copolymerizable monomers, for example, polymerization units of perfluoro(alkyl vinyl ether), (perfluoroalkyl)ethylene, and chlorotrifluoroethylene, to the extent that the effects of the present disclosure are not impaired. The upper limit of the content of polymerization units derived from the other copolymerizable monomers can be, for example, 3 mol%.

The lower limit of the content of polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer, or tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer in the sliding layer 5 may be 60 mass%, 85 mass%, or 98 mass%. The content may be 100 mass%. By making the content 60 mass% or more, it is possible to improve properties such as wear resistance and heat resistance.

The sliding layer 5 may contain other optional components within a range that does not impair the effects of the present disclosure. Examples of such optional components include solid lubricants and reinforcing materials. When the sliding layer 5 contains a solid lubricant and a reinforcing material, the sliding properties can be further improved. Examples of the solid lubricant include molybdenum disulfide. Examples of the reinforcing material include inorganic fillers such as calcium carbonate, talc, silica, alumina, and aluminum hydroxide, glass fillers such as glass fiber and spherical glass, and carbon fiber.

The lower limit of the average thickness of the sliding layer 5 may be 5 μm, 10 μm, 50 μm, or 100 μm. On the other hand, the upper limit of the average thickness of the sliding layer 5 may be 1000 μm, 700 μm, or 500 μm. By having the average thickness of the sliding layer 5 within the above range, the durability and flexibility of the sliding layer 5 can be improved.

The lower limit of the limit PV value of the outer surface of the sliding layer 5 may be 200 MPa·m/min, 250 MPa·m/min, 300 MPa·m/min, or 400 MPa·m/min. When the limit PV value of the outer surface of the sliding layer 5 is 200 MPa·m/min or more, the sliding layer 5 has high wear resistance and can improve the sliding performance of the sliding member 10. The upper limit of the limit PV value of the outer surface of the sliding layer 5 is not particularly limited, and may be, for example, 1500 MPa·m/min.

(Plasma-treated surface)
In the sliding member 10, the surface of the sliding layer 5 facing the adhesive layer 4 is the plasma-treated surface 2. In the sliding member 10, the surface of the sliding layer 5, which is mainly composed of a crosslinked body of polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer, or tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, facing the adhesive layer 4 is the plasma-treated surface 2, and thus functional groups such as carboxy groups, hydroxy groups, and amino groups are generated. Therefore, the contact angle of the surface of the sliding layer 5 facing the adhesive layer 4 is reduced, and wettability is improved, so that the adhesion between the surface of the sliding layer 5 and the adhesive layer 4 is improved. Therefore, the sliding member 10 can obtain high adhesion between the surface of the sliding layer 5 and the adhesive layer 4, so that a press treatment at high temperatures is not necessary, and the deterioration of the performance of the base 6 due to the press treatment at high temperatures can be suppressed.

(Adhesive Layer)
The adhesive layer 4 bonds the substrate 6 and the sliding layer 5. By further including the adhesive layer 4 laminated between the substrate 6 and the plasma-treated surface 2 of the sliding layer 5, the sliding member 10 has good adhesion between the sliding layer 5 and the substrate 6, and does not require a press treatment at a high pressure.

The lower limit of the glass transition temperature of the main component resin of the adhesive layer 4 is 130°C, and may be 140°C or 150°C. By setting the glass transition temperature of the main component resin of the adhesive layer 4 within the above range, the adhesive layer 4 has a moderate flexibility, and the heat resistance of the adhesive layer 4 is improved when the adjacent sliding layer 5 is heated to a high temperature due to frictional heat, so that high adhesive strength can be maintained even at high temperatures. The upper limit of the glass transition temperature of the adhesive layer 4 may be 250°C or 200°C from the viewpoint of flexibility. The "glass transition temperature" of the adhesive layer is a temperature measured by the following procedure. The adhesive composition is applied to the surface of a release PET film having a thickness of 25 μm so that the thickness after drying is 20 μm to 30 μm, and dried at 150°C for 2 minutes to form a semi-cured adhesive layer. This semi-cured adhesive layer is peeled off and heated and cured at 160°C for 40 minutes to form a measurement film. Using this measurement film, the temperature at the peak of Tan δ measured by dynamic mechanical analysis (DMA) (10°C/min) is taken as the glass transition temperature.

The main component resin of the adhesive layer 4 should have flexibility from the viewpoint of coatability, and since the sliding layer can reach high temperatures due to frictional heat, it is preferable that the adhesive layer adjacent to the sliding layer 5 has good heat resistance. From these viewpoints, examples of the main component resin of the adhesive layer 4 include epoxy resin-based, polyimide-based, and phenol-based adhesives. Among these, an epoxy resin that has flexibility and excellent heat resistance may be used.

Examples of epoxy resins include bisphenol A type epoxy resins, bisphenol F type epoxy resins, bisphenol S type epoxy resins, bisphenol AD type epoxy resins, bisphenol A type and bisphenol F type copolymer epoxy resins, naphthalene type epoxy resins, phenol novolac type epoxy resins, cresol novolac type epoxy resins, glycidylamine type epoxy resins, naphthol novolac type epoxy resins, biphenyl novolac type epoxy resins, phenol-biphenylene type epoxy resins, dicyclopentadiene type epoxy resins, trisphenolmethane type epoxy resins, naphthalene type epoxy resins, naphthol aralkyl type epoxy resins, and diphenyl ether type epoxy resins. These epoxy resins may be used alone or in combination.

The hardener contained in the epoxy resin can be one that is known as a hardener for epoxy resins, such as an acid anhydride hardener, a phenol hardener, or an amine hardener.

A curing accelerator can be added to the adhesive layer to accelerate the curing of the epoxy resin. Examples of the curing accelerator that can be used include imidazole-based curing accelerators and triazine-based curing accelerators.

The adhesive layer 4 may contain other optional components as long as they do not impair the effects of this disclosure.

The lower limit of the content of the main component resin in the adhesive layer 4 may be 60 mass%, 85 mass%, or 98 mass%. The content may be 100 mass%. When the content is within the above range, the adhesive strength between the base 6 and the adhesive layer 4 and between the sliding layer 5 and the adhesive layer 4 can be sufficiently increased.

The lower limit of the average thickness of the adhesive layer 4 may be 1 μm. On the other hand, the upper limit of the average thickness of the adhesive layer 4 may be 10 μm. By having the average thickness within the above range, the adhesive strength between the sliding layer 5 and the substrate 6 can be sufficiently increased and costs can be reduced.

The sliding member according to the first embodiment is provided with an adhesive layer laminated between the substrate and the plasma-treated surface of the sliding layer, so that a higher adhesive strength can be obtained between the sliding layer and the substrate, and press processing at high pressure is not required. The adhesive layer has a main component resin with a glass transition temperature of 130°C or higher, so that it has excellent heat resistance and can maintain a high adhesive strength even at high temperatures. Therefore, the sliding member has good abrasion resistance as well as adhesiveness without causing a decrease in the performance of the substrate in the sliding layer whose main component is a crosslinked product of polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer, or tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer.

[Second embodiment]
The sliding member according to the second embodiment includes a substrate and a sliding layer laminated directly on at least a part of the surface of the substrate. The sliding layer is mainly composed of a crosslinked product of polytetrafluoroethylene, a tetrafluoroethylene-hexafluoropropylene copolymer, or a tetrafluoroethylene-perfluoroalkylvinyl ether copolymer, and the surface of the sliding layer directly facing the substrate is a plasma-treated surface.

FIG. 3 is a schematic cross-sectional view showing a sliding member 15 according to the second embodiment. The sliding member 15 according to the second embodiment shown in FIG. 3 includes a substrate 6 and a sliding layer 5. The sliding layer 5 is the same as that in the first embodiment, and is therefore given the same number and will not be described. In the sliding member 15, the sliding layer 6 is mainly composed of a crosslinked body of polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer, or tetrafluoroethylene-perfluoroalkylvinylether copolymer, and the surface of the sliding layer 6 directly facing the substrate 5 is a plasma-treated surface. This allows a high adhesive force to be obtained between the sliding layer 5 and the substrate 6, and does not require a press treatment at high pressure. Therefore, the sliding member has good abrasion resistance as well as adhesiveness without causing a decrease in the performance of the substrate 6 in the sliding layer 6 mainly composed of a crosslinked body of polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer, or tetrafluoroethylene-perfluoroalkylvinylether copolymer.

[Third embodiment]
In the slide member according to the third embodiment, the slide layer is directly laminated on at least a part of the surface of the substrate, and the surface of the substrate facing the slide layer is a plasma-treated surface or a silane coupling-treated surface. That is, in the third embodiment, the plasma-treated surface of the slide layer faces the plasma-treated surface or the silane coupling-treated surface of the substrate.

4 is a schematic cross-sectional view showing a sliding member 20 according to the third embodiment, and FIG. 5 is a schematic exploded cross-sectional view of the sliding member 20. The sliding member 20 according to the third embodiment shown in FIG. 4 and FIG. 5 includes a base body 9 and a sliding layer 5. The sliding layer 5 is the same as that in the first embodiment, and the same number is used and the description is omitted. The base body 9 has a base material layer 7 and a plasma-treated surface or a silane coupling treatment surface 8. The sliding layer 5 is directly laminated on the base body 9, and the surface of the base body 9 facing the sliding layer 5 is the plasma-treated surface or the silane coupling treatment surface 8. That is, in the sliding member 20, the plasma-treated surface or the silane coupling treatment surface 8 of the base body 9 faces the plasma-treated surface 2 of the sliding layer 5. In the third embodiment, the plasma-treated surface 2 of the sliding layer 5 faces the plasma-treated surface or the silane coupling treatment surface 8 of the base body 9, so that the sliding member 20 has better adhesion between the sliding layer 5 and the base body 9. Furthermore, due to chemical bonding between the functional groups of the plasma-treated surface 2 of the sliding layer 5 and the functional groups of the plasma-treated surface or silane coupling-treated surface 8 of the substrate 9, the sliding member 20 can achieve stronger adhesion between the sliding layer 5 and the substrate 9 by press processing at low temperatures without using an adhesive. Therefore, the sliding member 20 can achieve stronger adhesion between the sliding layer 5 and the substrate 9. In addition, since the sliding layer 5 is directly laminated onto the substrate 9, there is no need to consider the adhesive layer protruding when the adhesive layer is laminated, and a high adhesive strength can be obtained between the sliding layer 5 and the substrate 9 with a simpler configuration.

(Plasma-treated surface and silane coupling-treated surface)
In the slide member 10, the surface of the substrate 9 facing the slide layer 5 is a plasma-treated surface or a silane coupling-treated surface 8. The plasma-treated surface is similar to the plasma-treated surface 2 of the slide layer 5 in the first embodiment, and therefore a description thereof will be omitted.

(Silane coupling treated surface)
Silane coupling treatment means forming a thin layer of silane coupling agent on the surface. For example, the treatment method of silane coupling agent includes a method of applying a solution of silane coupling agent on the surface, drying, and then heat-treating as necessary, and a method of immersing an object in a solution of silane coupling agent, drying, and then heat-treating as necessary. By performing silane coupling treatment using a silane compound containing a functional group, it is possible to impart uniform chemical properties to the surface of the substrate 9, and improve the adhesion at the laminated surface.

The silane coupling agent has, for example, an amino group or an epoxy group. Examples of silane coupling agents include N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-triethoxysilyl-N-(1,3-dimethylbutylidene)propylamine, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltriethoxysilane, vinyltrichlorosilane, vinyltrimethoxysilane, vinyltriethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyl Triethoxysilane, p-styryltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-acryloxypropyltrimethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane, N-(vinylbenzyl)-2-aminoethyl-3-aminopropyltrimethoxysilane hydrochloride, 3-ureidopropyltriethoxysilane, 3-chloropropyltrimethoxysilane, 3-mercaptopropylmethyldimethoxysilane, 3-mercaptopropyltrimethoxysilane, bis(triethoxysilylpropyl)tetrasulfide, 3-isocyanatepropyltriethoxysilane, tris-(3-trimethoxysilylpropyl)isocyanurate, chloromethylphenethyltrimethoxysilane, chloromethyltrimethoxysilane.

<Method of manufacturing slide member>
The method for producing the sliding member includes a step of crosslinking a film for forming a sliding layer, the main component of which is polytetrafluoroethylene, a tetrafluoroethylene-hexafluoropropylene copolymer, or a tetrafluoroethylene-perfluoroalkylvinylether copolymer, by irradiation, a step of performing a plasma treatment on one side of the film for forming a sliding layer after the crosslinking step, and a step of directly or indirectly laminating the sliding layer formed after the plasma treatment step on at least a part of the surface of a substrate. The surface of the sliding layer that directly or indirectly faces the substrate is the plasma-treated surface.

[Method of manufacturing slide member according to the first embodiment]
The method for producing a sliding member according to the first embodiment includes a step of crosslinking a sliding layer-forming film mainly composed of polytetrafluoroethylene, a tetrafluoroethylene-hexafluoropropylene copolymer, or a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer by electron beam irradiation (electron beam crosslinking step), a step of performing plasma treatment on one side of the sliding layer-forming film after the crosslinking step (plasma treatment step), and a step of laminating, in this order, an adhesive layer and the sliding layer formed after the plasma treatment step on at least a part of the surface of a base body (lamination step).

(Electron beam crosslinking process)
In this process, a film for forming a sliding layer, which is mainly composed of polytetrafluoroethylene, a tetrafluoroethylene-hexafluoropropylene copolymer, or a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, is irradiated with an electron beam in a low-oxygen atmosphere at a constant temperature. This irradiation causes the polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer, or tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, which is the main component of the film for forming a sliding layer, to have a crosslinked structure.

If the main component of the film for forming the sliding layer is polytetrafluoroethylene or a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, the heating temperature in this process is, for example, 280°C or higher and 420°C or lower.

If the main component of the film for forming the sliding layer is a tetrafluoroethylene-hexafluoropropylene copolymer, the heating temperature in this process is, for example, 180°C or higher and 265°C or lower.

By setting the heating temperature to be equal to or higher than the lower limit and equal to or lower than the upper limit, crosslinking of polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer, and tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer is sufficiently achieved, and decomposition of polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer, and tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer can be suppressed.

The heating time is, for example, from 5 minutes to 2 hours.

In this disclosure, a low-oxygen atmosphere specifically means a vacuum (5.0×10-4 Torr or less) or an inert gas atmosphere such as nitrogen. When electron beams are irradiated in a nitrogen atmosphere, the ratio of fluorine atoms on the outermost surface of the sliding layer decreases slightly, and the ratio of nitrogen atoms increases, so that the entire surface becomes hydrophilic and the adhesive strength of the sliding layer is presumably improved. The upper limit of the oxygen concentration in the low-oxygen atmosphere may be 100 ppm, 10 ppm, or 5 ppm. By keeping the oxygen concentration at 100 ppm or less, decomposition of polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer, and tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer due to electron beam irradiation can be suppressed.

The lower limit of the electron beam irradiation dose may be 50 kGy or 100 kGy. On the other hand, the upper limit of the irradiation dose may be 2,000 kGy or 1,000 kGy. When the irradiation dose is 50 kGy or more, the progress of the crosslinking reaction of polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer, and tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer can be improved. Furthermore, when the irradiation dose is 2,000 kGy or less, the main chains of polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer, and tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer can be prevented from being cleaved. Therefore, when the irradiation dose is within the above range, the electron beam crosslinking of the film for forming the sliding layer can be reliably performed while preventing the main chains of polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer, and tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer from being cleaved. The lower limit of the acceleration voltage may be 0.5 MeV, 0.7 MeV, or 1.0 MeV. The upper limit of the acceleration voltage may be 4.0 MeV or 2.5 MeV. By setting the acceleration voltage to 0.5 MeV or more, sufficient energy can be ensured for the electron beam to reliably perform cross-linking. By setting the acceleration voltage to 4.0 MeV or less, radiation can be reliably blocked.

(Plasma treatment process)
In this step, one side of the film for forming a sliding layer after the crosslinking step is subjected to a plasma treatment. The plasma treatment refers to a treatment performed by exposing the surface of the film for forming a sliding layer to a discharge that is initiated and sustained by applying a high DC or AC voltage between electrodes.

In the plasma treatment, a process gas corresponding to the functional group to be generated is supplied into the plasma treatment device. In the plasma treatment step of the film for forming a sliding layer in the method for producing the sliding member, functional groups such as a carboxy group (-COOH), a hydroxy group (-OH), and an amino group (-NH ₂ ) are generated as functional groups on one side of the film for forming a sliding layer. From this viewpoint, known gases such as argon, helium, ammonia, nitrogen, oxygen, air, carbon dioxide, and water vapor can be used as the process gas, but water vapor or an amino group-containing gas may be used from the viewpoint of improving the adhesiveness. Moreover, the water vapor or the amino group-containing gas may be diluted with a rare gas or an inert gas (argon, helium, nitrogen, etc.).

By the plasma treatment process, functional groups such as _--NH2 (amino group), --COOH (carboxy group), and --OH (hydroxy group) are generated on the plasma-treated surface of the film for forming a sliding layer. As a result, the contact angle of the surface is reduced and the wettability is improved, thereby improving the adhesion between the sliding layer and the adhesive layer.

(Lamination process)
In the lamination step, the adhesive layer and the sliding layer formed after the above-mentioned plasma treatment step are laminated in this order on at least a part of the surface of the substrate. This step results in the substrate, the adhesive layer containing a resin as a main component having a glass transition temperature of 130° C. or higher, and the sliding layer being laminated in this order. In this step, an adhesive composition containing a resin as a main component having a glass transition temperature of 130° C. or higher is first applied to at least a part of the surface of the substrate. Next, a film for forming a sliding layer is laminated on the surface of the coating layer of the adhesive composition so that the surface facing the adhesive layer is the plasma-treated surface. Then, the substrate, the adhesive layer, and the sliding layer are pressed under a heating condition of 20° C. to 150° C. at a pressure of 0.98 MPa to 2.94 MPa.

The specific configurations of the substrate, adhesive layer, and sliding layer are as described above.

The manufacturing method of the sliding member according to the first embodiment includes a step of laminating an adhesive layer and a sliding layer formed after the step of performing the plasma treatment on at least a part of the surface of the substrate in this order, and the sliding layer is laminated on the surface of the adhesive layer so that the plasma-treated surface of the sliding layer faces the adhesive layer, so that high adhesion can be obtained between the surface of the sliding layer and the adhesive layer. Therefore, the sliding layer, which is mainly composed of a crosslinked body of polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer, or tetrafluoroethylene-perfluoroalkylvinylether copolymer, can be firmly bonded to the substrate. Since the glass transition temperature of the main component resin of the adhesive layer is 130°C or higher, it has excellent heat resistance and can maintain high adhesive strength even at high temperatures. In addition, the manufacturing method of the sliding member does not require pressing at high temperatures such as above the crystalline melting point of polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer, or tetrafluoroethylene-perfluoroalkylvinylether copolymer, so that deterioration of the performance of the substrate due to pressing at high temperatures can be suppressed. Furthermore, in order to avoid a decrease in the performance of the substrate, it is not necessary to adhere the sliding layer to the substrate using a film obtained by applying a fluororesin paint to a heat-resistant polyimide film that is prone to significant warping. Therefore, the method for manufacturing the sliding member can manufacture a sliding member that has good adhesion between the sliding layer and the substrate as well as good wear resistance, without causing a decrease in the performance of the substrate, in a sliding layer that is mainly composed of a crosslinked product of polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer, or tetrafluoroethylene-perfluoroalkylvinyl ether copolymer.

[Method of manufacturing the slide member according to the second embodiment]
The method for producing a sliding member according to the second embodiment includes a step of crosslinking a sliding layer-forming film mainly composed of polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer, or tetrafluoroethylene-perfluoroalkylvinylether copolymer by irradiation (electron beam crosslinking step), a step of performing plasma treatment on one side of the sliding layer-forming film after the crosslinking step (plasma treatment step), and a step of directly laminating the sliding layer formed after the plasma treatment step on at least a part of the surface of a substrate (lamination step). The surface of the sliding layer directly facing the substrate is the plasma-treated surface. The electron beam crosslinking step and the plasma treatment step in the method for producing a sliding member according to the second embodiment are the same as those in the method for producing a sliding member according to the first embodiment, and therefore will not be described.

In the lamination process of this embodiment, the sliding layer formed after the plasma treatment process is laminated on the surface of the substrate so that the surface of the sliding layer facing the substrate becomes the plasma-treated surface. Then, the substrate and the sliding layer are pressed at a pressure of 2 MPa to 10 MPa under heating conditions of 150°C to 250°C.

The method for producing a sliding member according to the second embodiment includes a step of laminating a sliding layer formed after the step of performing the plasma treatment on at least a part of the surface of the substrate, and the sliding layer is laminated on the surface of the substrate so that the plasma-treated surface of the sliding layer faces the substrate, so that a high adhesive strength can be obtained between the surface of the sliding layer and the substrate. Therefore, the sliding layer, which is mainly composed of a crosslinked body of polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer, or tetrafluoroethylene-perfluoroalkylvinylether copolymer, and the substrate can be firmly bonded. In addition, the method for producing the sliding member does not require pressing at a high temperature, such as above the crystalline melting point of polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer, or tetrafluoroethylene-perfluoroalkylvinylether copolymer, so that the deterioration of the performance of the substrate can be suppressed. Furthermore, in order to avoid the deterioration of the performance of the substrate, it is not necessary to adhere the sliding layer to the substrate using a heat-resistant polyimide film that is prone to warping. Therefore, the manufacturing method for the sliding member can manufacture a sliding member that has good abrasion resistance as well as good adhesion between the sliding layer and the substrate, without reducing the performance of the substrate, in a sliding layer whose main component is a crosslinked product of polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer, or tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer.

[Method of manufacturing the slide member according to the third embodiment]
The method for producing a sliding member according to the third embodiment includes a step of crosslinking a sliding layer-forming film mainly composed of polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer, or tetrafluoroethylene-perfluoroalkylvinylether copolymer by irradiation (electron beam crosslinking step), a step of performing plasma treatment on one side of the sliding layer-forming film after the crosslinking step (plasma treatment step), a step of performing plasma treatment or silane coupling treatment on one side of the base (plasma treatment or silane coupling treatment step), and a step of directly laminating the sliding layer formed after the plasma treatment step on at least a part of the surface of the base formed after the plasma treatment or silane coupling treatment step (lamination step). The surface of the base facing the sliding layer is the plasma-treated surface or the silane coupling-treated surface. The electron beam crosslinking step and the plasma treatment step of the sliding layer-forming film in the method for producing a sliding member according to the third embodiment are the same as those in the method for producing a sliding member according to the second embodiment, and therefore will not be described.

In the plasma treatment or silane coupling treatment step, the surface of the substrate facing the sliding layer is subjected to plasma treatment or silane coupling treatment. The plasma treatment in this step can be performed by a known method, similar to the plasma treatment step of the film for forming the sliding layer. The silane coupling treatment means forming a thin layer of a silane coupling agent on the substrate surface. The plasma treatment or silane coupling treatment in this step can be performed by a known method. In the method for producing a sliding member according to the third embodiment, a sliding member having excellent adhesion between the sliding layer and the substrate can be produced by a press treatment at low temperature without using an adhesive, due to chemical bonding between the functional groups on the plasma-treated surface of the sliding layer and the functional groups on the plasma-treated surface or the silane coupling-treated surface of the substrate.

When the silane coupling treatment in the plasma treatment or silane coupling treatment step on the substrate is performed by immersing the substrate in a solution of a silane coupling agent, for example, the solvent that dissolves the silane coupling agent can be an organic solvent such as alcohols such as ethanol, ethers, or aromatic hydrocarbons such as benzene and toluene. The solution of the silane coupling agent can be a solution in which about 0.1 to 2 mass % of the silane coupling agent is dissolved in the above-mentioned solvent. Then, after the substrate is immersed in the solution of the silane coupling agent for a predetermined time, it is washed with methanol, toluene, or the like.

By the plasma treatment or silane coupling treatment step on the substrate, functional groups such as _--NH2 (amino group), --COOH (carboxy group), and --OH (hydroxy group) are generated on the plasma-treated or silane coupling-treated surface of the substrate, which has the effect of reducing the contact angle of the substrate surface and improving wettability, thereby improving adhesion between the sliding layer and the substrate.

In the lamination process of this embodiment, the sliding layer formed after the plasma treatment process is directly laminated onto at least a portion of the surface of the substrate formed after the plasma treatment or silane coupling treatment process. That is, the sliding layer is laminated onto the surface of the substrate so that the plasma-treated surface of the sliding layer faces the plasma-treated surface or silane coupling treatment surface of the substrate. Then, the substrate and the sliding layer are pressed at a pressure of 2 MPa to 10 MPa under heating conditions of 150°C to 250°C.

In the manufacturing method of the sliding member according to the third embodiment, the sliding layer is laminated so that the surface of the sliding layer that has been subjected to the plasma treatment faces the surface of the substrate that has been subjected to the plasma treatment or the silane coupling treatment. This allows the sliding layer, which is mainly composed of a crosslinked body of polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer, or tetrafluoroethylene-perfluoroalkylvinylether copolymer, to be firmly bonded to the substrate. In addition, the manufacturing method of the sliding member does not require pressing at a high temperature, such as above the crystalline melting point of polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer, or tetrafluoroethylene-perfluoroalkylvinylether copolymer, so that deterioration of the performance of the substrate can be suppressed. Furthermore, in order to avoid deterioration of the performance of the substrate, it is not necessary to bond the sliding layer to the substrate using a heat-resistant polyimide film that is prone to warping. Therefore, the manufacturing method for the sliding member can manufacture a sliding member that has good abrasion resistance as well as good adhesion between the sliding layer and the substrate, without reducing the performance of the substrate, in a sliding layer whose main component is a crosslinked product of polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer, or tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer.

[Other embodiments]
The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present disclosure is not limited to the configurations of the above-described embodiments, but is indicated by the scope of the claims, and is intended to include all modifications within the meaning and scope equivalent to the scope of the claims.

The present disclosure will be explained in more detail below with reference to examples, but the present disclosure is not limited to the following examples.

[Sliding member No. 1]
The sliding member No. 1 of the first embodiment was produced in the following procedure.
(Electron beam crosslinking process)
A sliding layer-forming film ("VALFLON (registered trademark)" manufactured by Nippon Valqua Industries Co., Ltd.) having an average thickness of 100 μm and mainly composed of uncrosslinked polytetrafluoroethylene (PTFE: melting point 327 ° C.) was placed in a chamber-type heating irradiation furnace. Next, the pressure in the furnace was repeatedly reduced and purged with nitrogen, and the oxygen concentration in the furnace was reduced to 5 ppm or less, and then the sliding layer-forming film was heated to 340 ° C. Thereafter, the heated sliding layer-forming film was irradiated with an electron beam (accelerating voltage 1,160 kV, irradiation amount 70 kGy) from one side using an electron beam accelerator (manufactured by NHV Corporation) to obtain a sliding layer-forming film No. 1. In this disclosure, the "melting point" refers to the melting point peak temperature measured by a differential scanning calorimeter (DSC) in accordance with JIS-K7121:2012 "Method for measuring transition temperature of plastics".

(Plasma treatment process of film for forming sliding layer)
Next, one side of the film for forming a sliding layer No. 1 was subjected to a surface modification treatment by providing an amino group by a high-frequency low-pressure plasma treatment under the plasma treatment conditions shown below. In this manner, a sliding layer was produced.
(1) Processing gas: _NH3
(2) Gas flow rate: 150 sccm
(3) Processing pressure: 50 Pa
(4) Frequency: 13.56 MHz
(5) Processing power: 750 W (0.19 W·cm ² )
(6) Treatment time: 5 minutes (7) Distance between electrodes: 80 mm

(Lamination process)
An aluminum plate-shaped substrate having an average thickness of 1200 μm, an adhesive layer made of an epoxy resin having a glass transition temperature of 170° C. ("Room temperature curing two-component epoxy resin TB2088E" manufactured by ThreeBond Co., Ltd., curing accelerator: polyamidoamine), and a sliding layer were laminated in this order under conditions of 100° C. The average thickness of the adhesive layer was 3 μm. Then, the substrate was pressed at a pressure of 2 MPa. At this time, the plasma-treated surface of the sliding layer was made to face the adhesive layer. In this manner, sliding member No. 1 was obtained.

[Sliding members No. 2 to No. 6]
Sliding members No. 2 to No. 6 were obtained in the same manner as in the process for sliding member No. 1, except that plates made of acrylic, PET (polyethylene terephthalate), PC (polycarbonate), alumina, or glass shown in Table 1 were used instead of the aluminum plate-shaped substrate No. 1 having an average thickness of 1,200 μm.

[Sliding members No. 7 to No. 12]
Sliding members No. 7 to No. 12 were obtained in the same manner as in the manufacturing process of No. 1 to No. 6, except that the electron beam crosslinking step was not performed.

[Sliding member No. 13]
A sliding member No. 13 was obtained in the same manner as in the production process of No. 1, except that a sliding layer-forming film having a main component of polytetrafluoroethylene (PTFE) in No. 1 was replaced with a sliding layer-forming film having an average thickness of 50 μm ("Neoflon FEP NF-0050" manufactured by Daikin Industries, Ltd.) having a main component of tetrafluoroethylene-hexafluoropropylene copolymer (FEP: melting point 267° C.) was used and heated to 240° C. before being irradiated with an electron beam.

[Sliding member No. 14]
A sliding member No. 14 was obtained in the same manner as in the production process of No. 1, except that the electron beam crosslinking step was not performed in the production process of No. 13.

[Sliding member No. 15]
(Electron beam crosslinking process)
A fluorine paint (Daikin Industries, Ltd.'s "Neoflon PFA AD2CREER") mainly composed of tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA: melting point 304-310 ° C.) was applied to a polyimide film (Toray DuPont Co., Ltd.'s "Kapton") having an average thickness of 25 μm so that the coating amount was 8 mg / cm ² , and then baked at 380 ° C. Next, the baked coating film was irradiated with an electron beam (accelerating voltage 1,160 kV, irradiation amount 300 kGy) in the same manner as in No. 1, and a laminate (average thickness 50 μm) of the polyimide film and the sliding layer of No. 15 was obtained.

(Lamination process)
An aluminum plate-shaped substrate having an average thickness of 1200 μm, an adhesive layer having an average thickness of 3 μm made of an adhesive mainly composed of epoxy resin ("Room temperature curing type two-part epoxy resin TB2088E" manufactured by ThreeBond Co., Ltd.), and a sliding layer made of a polyimide film coated with a fluorine paint were laminated in this order under a condition of 100° C. Then, the laminate was pressed under a pressure of 2.0 MPa. In this manner, a sliding member No. 15 was obtained.

[No. 16]
The same procedure was repeated as for No. 15 except that a fluororesin paint mainly composed of PTFE ("Polyflon PTFE EK-3700C21R" manufactured by Daikin Industries, Ltd.) was used instead of the PFA-based fluororesin paint used in No. 15. A sliding member No. 16 was obtained in the same manner as in the process for the member.

[Sliding member No. 17]
The sliding member No. 17 of the third embodiment was produced by the following procedure.
(Substrate Plasma Treatment Step)
One surface of an aluminum plate-shaped substrate having an average thickness of 1200 μm was subjected to plasma treatment under the following conditions.
First, one side of the substrate was subjected to a surface modification treatment by providing an amino group by a high-frequency low-pressure plasma treatment under the plasma treatment conditions shown below. In this manner, the surface treatment of one side of the substrate was performed.
(1) Processing gas: _NH3
(2) Gas flow rate: 150 sccm
(3) Processing pressure: 50 Pa
(4) Frequency: 13.56 MHz
(5) Processing power: 750 W (0.19 W·cm ² )
(6) Treatment time: 5 minutes (7) Distance between electrodes: 80 mm

(Lamination process)
The substrate after the plasma treatment step and the sliding layer of No. 1 were laminated under the condition of 200° C. Then, they were pressed at a pressure of 10.0 MPa. At this time, the plasma-treated surface of the sliding layer was made to face the plasma-treated surface of the substrate. In this way, the sliding member of No. 17 was obtained.

[Sliding member No. 18]
(Silane coupling treatment process for substrate)
One surface of an aluminum plate-shaped substrate having an average thickness of 1200 μm was subjected to a silane coupling treatment under the following conditions.
First, an aqueous solution of an amino-based silane coupling agent KBE903 (manufactured by Shin-Etsu Chemical Co., Ltd.) was prepared at a concentration of 1% by weight as a silane coupling agent, and the substrate surface was wiped with a cloth soaked in the solution, which was then dried at room temperature for 1 hour. In this manner, the surface was subjected to a silane coupling treatment.

(Lamination process)
The substrate after the silane coupling treatment step and the sliding layer of No. 17 were laminated under the condition of 200° C. Then, they were pressed at a pressure of 10.0 MPa. At this time, the plasma-treated surface of the sliding layer was made to face the silane coupling-treated surface of the substrate. In this way, the sliding member of No. 18 was obtained.

[Sliding member No. 19]
A sliding member No. 19 was obtained by carrying out the same steps as those for No. 17, except that a plate-shaped substrate made of aluminum and having an average thickness of 1,200 μm that had not been subjected to a surface treatment was used.

[Sliding member No. 20]
A sliding member No. 20 was obtained by carrying out the same steps as those for No. 18, except that a silane coupling treatment was carried out under the same conditions as those for No. 18 on one side of a plate-shaped substrate made of iron and having an average thickness of 1,200 μm.

[Sliding member No. 21]
A sliding member No. 21 was obtained by carrying out the same steps as those for No. 19, except that a plate-shaped substrate made of iron and having an average thickness of 1,200 μm that had not been subjected to a surface treatment was used.

[Sliding member No. 22]
A sliding member No. 22 was obtained by carrying out the same steps as those for No. 18, except that a silane coupling treatment was carried out under the same conditions as those for No. 18 on one side of a plate-shaped substrate made of stainless steel and having an average thickness of 1,200 μm.

[Sliding member No. 23]
A sliding member No. 23 was obtained by carrying out the same steps as those for No. 19, except that a plate-shaped substrate made of stainless steel and having an average thickness of 1,200 μm that had not been subjected to a surface treatment was used.

[Sliding member No. 24]
A sliding member No. 24 was obtained in the same manner as in the production process of No. 17, except that the electron beam crosslinking step was not performed.

[Sliding member No. 25]
A sliding member No. 25 was obtained in the same manner as in the production process of No. 18, except that the electron beam crosslinking step was not performed.

[Sliding member No. 26]
A sliding member No. 26 was obtained in the same manner as in the production process of No. 19, except that the electron beam crosslinking step was not performed.

[Sliding member No. 27]
A sliding member No. 27 was obtained in the same manner as in the manufacturing process of No. 26, except that a plate-shaped substrate made of stainless steel and having an average thickness of 1,200 μm that had not been subjected to a surface treatment was used.

[Sliding member No. 28]
A sliding member No. 28 was obtained in the same manner as in the production process of No. 17, except that a sliding layer-forming film having a main component of polytetrafluoroethylene (PTFE) in No. 17 was replaced with a sliding layer-forming film having an average thickness of 50 μm ("Neoflon FEP NF-0050" manufactured by Daikin Industries, Ltd.) having a main component of tetrafluoroethylene-hexafluoropropylene copolymer (FEP: melting point 267° C.) was used and heated to 240° C. before being irradiated with an electron beam.

[Sliding member No. 29]
A sliding member No. 29 was obtained in the same manner as in the production process of No. 18, except that a sliding layer-forming film having a main component of polytetrafluoroethylene (PTFE) in No. 18 was replaced with a sliding layer-forming film having an average thickness of 50 μm ("Neoflon FEP NF-0050" manufactured by Daikin Industries, Ltd.) having a main component of tetrafluoroethylene-hexafluoropropylene copolymer (FEP: melting point 267° C.) was used and heated to 240° C. before being irradiated with an electron beam.

[Sliding member No. 30]
A sliding member No. 30 was obtained by carrying out the same steps as those for No. 28, except that a plate-shaped substrate made of aluminum and having an average thickness of 1,200 μm that had not been subjected to a surface treatment was used.

[Sliding member No. 31]
A sliding member No. 31 was obtained in the same manner as in the production process of No. 20, except that a sliding layer-forming film having a main component of polytetrafluoroethylene (PTFE) in No. 20 was replaced with a sliding layer-forming film having an average thickness of 50 μm ("Neoflon FEP NF-0050" manufactured by Daikin Industries, Ltd.) having a main component of tetrafluoroethylene-hexafluoropropylene copolymer (FEP: melting point 267° C.) was used and heated to 240° C. before being irradiated with an electron beam.

[Sliding member No. 32]
A sliding member No. 32 was obtained by carrying out the same steps as those for No. 31, except that a plate-shaped substrate made of iron and having an average thickness of 1,200 μm that had not been subjected to a surface treatment was used.

[Sliding member No. 33]
A sliding member No. 33 was obtained by carrying out the same steps as in No. 31, except that a silane coupling treatment was carried out under the same conditions as in No. 31 on one side of a plate-shaped substrate made of stainless steel and having an average thickness of 1,200 μm.

[Sliding member No. 34]
A sliding member No. 34 was obtained by carrying out the same steps as those for No. 32, except that a plate-shaped substrate made of stainless steel and having an average thickness of 1,200 μm that had not been subjected to a surface treatment was used.

[Sliding member No. 35]
A sliding member No. 35 was obtained in the same manner as in the production process of No. 28, except that the electron beam crosslinking process of the film for forming a sliding layer was not performed.

[Sliding member No. 36]
A sliding member No. 36 was obtained in the same manner as in the production process of No. 29, except that the step of crosslinking the film for forming a sliding layer by electron beam was not performed.

[Sliding member No. 37]
A sliding member No. 37 was obtained in the same manner as in the production process of No. 30, except that the step of crosslinking the film for forming a sliding layer by electron beam was not performed.

[Sliding member No. 38]
A sliding member No. 38 was obtained by carrying out the same steps as those for No. 37, except that a plate-shaped substrate made of stainless steel and having an average thickness of 1,200 μm that had not been subjected to a surface treatment was used.

[Sliding member No. 39]
A sliding member No. 39 was obtained in the same manner as in the production process of No. 18, except that a sliding layer-forming film having a main component of polytetrafluoroethylene (PTFE) in No. 18 was replaced with a sliding layer-forming film having an average thickness of 50 μm ("AF-0050" manufactured by Daikin Industries, Ltd.) having a main component of tetrafluoroethylene-perfluoroalkylvinylether copolymer (PFA: melting point 305° C.) was used and heated to 290° C. before being irradiated with an electron beam.

[Sliding member No. 40]
A sliding member No. 40 was obtained by carrying out the same steps as those for No. 39, except that a plate-shaped substrate made of aluminum and having an average thickness of 1,200 μm that had not been subjected to a surface treatment was used.

[Sliding member No. 41]
A sliding member No. 41 was obtained by carrying out the same steps as those for No. 39, except that a plate-shaped substrate made of iron and having an average thickness of 1,200 μm was used.

[Sliding member No. 42]
A sliding member No. 42 was obtained by carrying out the same steps as those for No. 41, except that a plate-shaped substrate made of iron and having an average thickness of 1,200 μm that had not been subjected to a surface treatment was used.

[Sliding member No. 43]
A sliding member No. 43 was obtained by carrying out the same steps as those for No. 41, except that a plate-shaped substrate made of iron and having an average thickness of 1,200 μm was used.

[Sliding member No. 44]
A sliding member No. 44 was obtained by carrying out the same steps as those for No. 43, except that a plate-shaped substrate made of stainless steel and having an average thickness of 1,200 μm that had not been subjected to a surface treatment was used.

[Sliding member No. 45]
A sliding member No. 45 was obtained by carrying out the same steps as those for No. 19, except that a sliding layer was prepared without carrying out a surface treatment.

[Sliding member No. 46]
A sliding member No. 46 was obtained by carrying out the same steps as those for No. 17, except that a sliding layer was prepared without carrying out a surface treatment.

[Sliding member No. 47]
A sliding member No. 47 was obtained by carrying out the same steps as those for No. 18, except that a sliding layer was prepared without carrying out a surface treatment.

[Sliding member No. 48]
A sliding member No. 48 was obtained in the same manner as in the production process of No. 45, except that the step of crosslinking the film for forming a sliding layer by electron beam was not performed.

[Sliding member No. 49]
A sliding member No. 49 was obtained in the same manner as in the production process of No. 46, except that the step of crosslinking the sliding layer-forming film was not performed.

[Sliding member No. 50]
A sliding member No. 50 was obtained in the same manner as in the production process of No. 47, except that the step of crosslinking the film for forming a sliding layer by electron beam was not performed.

[Sliding member No. 51]
A sliding member No. 51 was obtained by carrying out the same steps as those for No. 30, except that a sliding layer was prepared without performing a surface treatment.

[Sliding member No. 52]
A sliding member No. 52 was obtained by carrying out the same steps as those for No. 28, except that a sliding layer was prepared without performing a surface treatment.

[Sliding member No. 53]
A sliding member No. 53 was obtained by carrying out the same steps as those for No. 29, except that a sliding layer was prepared without carrying out a surface treatment.

<Evaluation>
[Adhesion strength between sliding layer and adhesive layer]
The adhesive strength between the sliding layer and the adhesive layer was measured in terms of peel strength [N/10 mm] by the following procedure.
First, a 10 mm wide cut was made in each sliding member sample, the protruding portion of the sliding layer-forming film was gripped, and an evaluation was performed by a 90 degree peel test at a temperature of 25°C. In sliding members No. 1 to No. 16, peeling occurred at the interface between the sliding layer-forming film and the adhesive layer, so the adhesive strength at the interface between the sliding layer-forming film and the adhesive layer was evaluated. The results of the adhesive strength evaluation are shown in Tables 1 and 2. In Table 1, "-" means that the corresponding item is not included.

[Presence or absence of warping in sliding layer]
The appearance of the sliding layer before the lamination step was evaluated for the presence or absence of warping.

[Wear resistance performance: limit PV value by dry ring-on-disk wear test]
For sliding members No. 1 to No. 44, the limit PV value [MPa·m/min] of the outer surface of the sliding layer was measured by ring-on-disk type abrasion according to the following procedure. The measurement was performed under the condition that the load was constant at 10 MPa after adjusting the temperature at 23±2°C, and the speed was increased by one step every 3 minutes. Specifically, the material used as the ring-shaped mating material was S45C (carbon steel for mechanical construction) with ring dimensions (outer diameter/inner diameter) of φ11.6 mm/φ7.4 mm. Then, the test piece was rotated at a predetermined speed (rotation speed: V) with a load of 10 MPa (surface pressure: P) applied to the mating material under dry lubrication conditions, and the dynamic friction coefficient was measured by the reaction torque generated in the mating material. At this time, the speed was increased from 1 m/min in step (1) to 5 m/min in step (2) and 10 m/min in step (3), and thereafter the speed was increased by 10 m/min for each step, and the limit PV value was measured. In this disclosure, the PV value immediately before the substrate was exposed was taken as the limit PV value. For the above measurement, an "EFM-3-1010-S" test device manufactured by AND was used.
However, for sliding members No. 2 to No. 4 and No. 8 to No. 10, the measurement was stopped when the glass transition temperature of the substrate material was exceeded from the viewpoint of safety. The glass transition temperatures of the substrate materials in each member are as follows:
Acrylic: 70°C, PET: 75°C, PC: 150°C
For sliding members No. 45 to No. 53, the adhesive strength between the substrate and the sliding layer was not obtained, and therefore it was not possible to measure it.

(Slide member of the first embodiment)
As shown in Table 1, it can be seen that the sliding members No. 1 to No. 6 and No. 13 of the first embodiment, in which the sliding layer is mainly composed of a crosslinked body of polytetrafluoroethylene, a tetrafluoroethylene-hexafluoropropylene copolymer or a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, and the surface of the sliding layer facing the substrate via the adhesive layer is a plasma-treated surface, are free of warping of the sliding layer and have good peel strength between the sliding layer and the substrate as well as good limit PV value.

On the other hand, sliding members No. 7 to No. 12 and No. 14, whose sliding layers are mainly composed of uncrosslinked polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer or crosslinked tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, did not warp in the sliding layer, but compared with substrates of the same material, the limit PV value and peel strength between the sliding layer and substrate were inferior. Also, sliding members No. 15 and No. 16, which have sliding layers made of polyimide film coated with fluorine paint, had good limit PV values and peel strength, but significant warping was observed in the sliding layer.

(Slide Members of Second and Third Embodiments)
As shown in Table 2, the sliding members No. 19, No. 21, No. 23, No. 30, No. 32, No. 34, No. 40, No. 42 and No. 44 of the second embodiment in which the sliding layer is mainly composed of a crosslinked body of polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer or tetrafluoroethylene-perfluoroalkylvinylether copolymer and the surface of the sliding layer directly facing the substrate is a plasma-treated surface, were good in limit PV value and peel strength between the sliding layer and the substrate.
Furthermore, in the sliding members No. 17, No. 18, No. 20, No. 22, No. 28, No. 29, No. 31, No. 33, No. 39, No. 41 and No. 43 of the third embodiment in which the surface of the substrate facing the sliding layer is a plasma-treated surface or a silane coupling-treated surface, the limit PV value and the peel strength between the sliding layer and the substrate were good.

On the other hand, sliding members No. 24 to No. 27 and No. 35 to No. 38, whose sliding layers are mainly composed of crosslinked polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer, or tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, had low peel strength and limit PV value when compared with substrates of the same material. Also, sliding members No. 45 to No. 53, whose sliding layer surface directly facing the substrate was not plasma-treated, had no adhesive strength, regardless of whether the sliding layer was crosslinked or not, and it was impossible to measure the limit PV value.

As described above, the sliding member has a sliding layer mainly composed of a crosslinked product of polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer, or tetrafluoroethylene-perfluoroalkylvinyl ether copolymer, and it has been shown that the sliding layer has good abrasion resistance and good adhesion between the substrate and the substrate without causing a decrease in the performance of the substrate.

REFERENCE SIGNS LIST 1 resin layer 2 plasma-treated surface of sliding layer 4 adhesive layer 5 sliding layer 6, 9 substrate 7 base material layer 8 plasma-treated surface or silane coupling-treated surface of substrate 10, 15, 20 sliding member

Claims (7)

1. A substrate;
   a sliding layer laminated directly or indirectly on at least a part of the surface of the substrate,
   the sliding layer is mainly composed of a crosslinked material of polytetrafluoroethylene, a tetrafluoroethylene-hexafluoropropylene copolymer, or a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer,
   A sliding member, wherein the surface of the sliding layer which faces directly or indirectly the substrate is a plasma treated surface.
2. an adhesive layer is laminated between the substrate and the sliding layer;
   The adhesive layer contains a resin as a main component,
   2. The sliding member according to claim 1, wherein the main component resin has a glass transition temperature of 130° C. or higher.
3. the sliding layer is laminated directly on at least a part of the surface of the substrate,
   2. The sliding member according to claim 1, wherein the surface of the substrate facing the sliding layer is a plasma-treated surface or a silane coupling-treated surface.
4. The sliding member according to any one of claims 1 to 3, wherein the limit PV value of the outer surface of the sliding layer is 200 MPa·m/min or more.
5. A step of crosslinking a film for forming a sliding layer, the film mainly composed of polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer, or tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer by irradiation;
   a step of performing a plasma treatment on one surface of the film for forming a sliding layer after the crosslinking step;
   and a step of laminating the sliding layer formed after the step of performing the plasma treatment directly or indirectly on at least a part of the surface of the substrate,
   A method for producing a sliding member, wherein the surface of the sliding layer which directly or indirectly faces the substrate is a plasma treated surface.
6. further comprising a step of laminating an adhesive layer between the substrate and the sliding layer,
   The adhesive layer contains a resin as a main component,
   6. The method for producing a sliding member according to claim 5, wherein the main component resin has a glass transition temperature of 130[deg.] C. or higher.
7. The method further comprises a step of subjecting one surface of the substrate to a plasma treatment or a silane coupling treatment,
   the sliding layer is laminated directly on at least a part of the surface of the substrate after the step of performing the plasma treatment or silane coupling treatment,
   6. The method for producing a sliding member according to claim 5, wherein the surface of the substrate facing the sliding layer is a plasma-treated surface or a silane coupling-treated surface.
   

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