Water-repellent object, water-repellent component, and method for producing water-repellent object

Abstract

A water-repellent object (1) comprises: a base material (metal film (3)) having a dip-and-bump structure (30); and a coating film (4) covering the dip-and-bump structure (30). The coating film (4) has a water-repellent part (6) containing a fluorine compound, and an adhesion part (5) firmly adhering to the base material (metal film (3)). The adhesion part (5) is a mixture containing silica and yttria.

Description

Water-repellent body, water-repellent part, and method for manufacturing water-repellent body

[0001] The present disclosure relates to a water-repellent body, a water-repellent part, and a method for manufacturing a water-repellent body.

[0002] Conventionally, water-repellent bodies have been known in which a water-repellent coating is formed on the surface of an article to prevent adhesion of water droplets, dust, etc. to the surface of the article (for example, Patent Document 1). Such water-repellent bodies have a large contact angle with water and can easily repel water droplets, etc., and are therefore used in automobile bodies, camera lenses, and other applications requiring water repellency.

[0003] Patent Document 1 describes a water-repellent body in which a coating containing a fluororesin, hydrophilic silica particles, and hydrophobic silica particles is formed on a substrate. The fluororesin and hydrophilic silica particles serve to bond the substrate and the coating.

[0004] International Publication No. 2016 / 181676

[0005] The water-repellent body of Patent Document 1 has a problem in that the adhesion between the water-repellent coating and the substrate is weak, so the coating is easily peeled off from the substrate due to friction or the like, and the water-repellent properties are easily lost.

[0006] Therefore, there is a demand for a highly durable water-repellent body that has high water repellency and can prevent the coating (water-repellent portion) from peeling off.

[0007] One embodiment of a water-repellent body according to the present disclosure comprises a substrate having a concave-convex structure and a coating covering the concave-convex structure, the coating having a water-repellent portion containing a fluorine compound and an adhesion portion that adheres to the substrate, the adhesion portion being a mixture containing silica and yttria.

[0008] One embodiment of a water-repellent part according to the present disclosure includes a water-repellent body and a coating target material on whose surface the water-repellent body is formed.

[0009] One embodiment of a method for manufacturing a water-repellent body according to the present disclosure includes a concave-convex structure forming step of forming a concave-convex structure on the surface of a substrate, a contact portion forming step of forming an adhesion portion made of a mixture containing silica and yttria on the surface of the concave-convex structure, and a water-repellent portion forming step of forming a water-repellent portion containing a fluorine compound on the surface of the adhesion portion.

[0010] According to the embodiments of the present disclosure, it is possible to provide a highly durable water-repellent body that has high water repellency and can suppress peeling of the water-repellent portion, a water-repellent part that includes a water-repellent body, and a method for manufacturing a water-repellent body.

[0011] 1 is a longitudinal cross-sectional view of a water-repellent part; 2 is an SEM image showing a surface with a concave-convex structure; 3 is an SEM image showing a longitudinal cross-section of a metal coating; 4 is a diagram showing a method for manufacturing a water-repellent body and a water-repellent part; 5 is a longitudinal cross-sectional view of a water-repellent body; 6 is a diagram showing a method for manufacturing a water-repellent body; 7 is a diagram showing the contact angle of water in an example; 8 is a diagram showing the sliding angle of water in an example.

[0012] Hereinafter, embodiments of a water-repellent body according to the present disclosure will be described with reference to the drawings. Note that the embodiments described below are examples for explaining the present disclosure, and the present disclosure is not limited to these embodiments. Therefore, the present disclosure can be implemented in various forms without departing from the gist thereof.

[0013] [First embodiment] Fig. 1 is a longitudinal cross-sectional view of a water-repellent part 100 according to this embodiment. The water-repellent part 100 includes a water-repellent body 1 and a material to be coated 2. The water-repellent part 100 is, but is not limited to, a component of various products that require water repellency. The material to be coated 2 may be a metal such as aluminum or iron, glass, ceramics, or the like. While the material to be coated 2 in Fig. 1 is a single layer, the present invention is not limited thereto and may be a laminate of multiple layers, in which case the layers may be the same or different. The material to be coated 2 may be, for example, an automobile body or a door handle. The water-repellent body 1 is formed on the surface of the material to be coated 2.

[0014] The water-repellent body 1 includes a metal coating 3 (an example of a substrate) and a coating 4. The metal coating 3 is formed of a metal such as titanium or chromium, and has a film thickness of 1 μm to 5 μm. The metal coating 3 has an uneven structure 30, which is formed on the surface of the metal coating 3 opposite to the surface that comes into contact with the coating target material 2.

[0015] Fig. 2 is a scanning electron microscope (SEM) image showing the surface of the uneven structure 30, and Fig. 3 is an SEM image showing a vertical cross section of the metal coating 3. As shown in Figs. 2 and 3, the metal coating 3 is made of columnar crystals with pointed tips, and these tip portions are defined as the uneven structure 30. The metal coating 3 in Figs. 2 and 3 is made of chromium, but may be made of other metals.

[0016] The height difference between the convex portions and concave portions in the uneven structure 30 may be, for example, 10 nm to 5 μm. Specifically, the height difference between the convex portions and concave portions is the difference between the height of the apex of the convex portion and the height of the bottom of the concave portion. If the height difference between the convex portions and concave portions is too large, the strength of the uneven structure 30 decreases and the uneven structure 30 becomes more likely to collapse. On the other hand, if the height difference between the convex portions and concave portions is too small, the high water-repellent performance described below cannot be obtained, so this difference is preferably 100 nm to 3 μm. Because such an uneven structure 30 is a fine structure, it is easily collapsed by contact with a human hand, etc. However, by forming the uneven structure 30 from metal, the hardness is increased compared to uneven structures conventionally formed from resin, etc., and therefore durability can be improved.

[0017] As shown in Fig. 1, the concave-convex structure 30 is covered with a coating 4. The coating 4 has an adhesive portion 5 that adheres to the concave-convex structure 30 and a water-repellent portion 6 formed on the surface of the adhesive portion 5. Therefore, the coating 4 is formed on the surface of the concave-convex structure 30 so that the adhesive portion 5 and the water-repellent portion 6 are laminated in this order.

[0018] The adhesion portion 5 is a mixture containing silica and yttria. The silicon contained in the adhesion portion 5 has a high affinity with the fluorine contained in the water-repellent portion 6, which will be described later, and thus a stable bond is formed between them, resulting in adhesion between the adhesion portion 5 and the water-repellent portion 6. This makes it possible to prevent the water-repellent portion 6 from peeling off from the uneven structure 30.

[0019] The yttria contained in the adhesion portion 5 can be added to silica to improve hardness. Therefore, compared to hydrophilic silica particles commonly used as adhesives, the adhesion portion 5 has a higher hardness and durability. Therefore, by covering the surface of the uneven structure 30 with the adhesion portion 5, the uneven structure 30 can be protected by the adhesion portion 5. This further improves the durability of the uneven structure 30. The yttria content in the adhesion portion 5 is not particularly limited, but, for example, the lower limit is preferably 1.0 mol% or more, more preferably 1.1 mol% or more, and the upper limit is preferably less than 10 mol%, more preferably less than 6 mol%, from the viewpoint of the adhesion of the uneven structure 30. The adhesion portion 5 preferably has a thickness of 5 nm to 90 nm, and is preferably uniformly formed on the surface of the uneven structure 30.

[0020] A portion of the yttrium atoms contained in the adhesion portion 5 may be substituted with atoms of a Group 4A element. The Group 4A element is not particularly limited, but may be, for example, at least one element selected from the group consisting of titanium, zirconium, and hafnium, with zirconium being particularly preferred. These elements may be used alone or in combination. By substituting a portion of the yttrium atoms with these atoms, the atomic bonds in the adhesion portion 5 are strengthened. Therefore, it is believed that the hardness of the adhesion portion 5 is higher than when a portion of the yttrium atoms is not substituted. This makes it possible to impart scratch resistance and the like to the concave-convex structure 30 and improve durability.

[0021] In the adhesion portion 5, the substitution rate of yttrium atoms with atoms of the Group 4A element (content of atoms of the Group 4A element) is not particularly limited as long as it exceeds 0, but the upper limit may be, for example, 20 mol%, 15 mol%, 10 mol%, or 5 mol%.

[0022] Furthermore, some of the oxygen atoms in the yttria may be substituted with nitrogen atoms. Since the bonding strength between nitrogen atoms and yttrium atoms is stronger than that between oxygen atoms and yttrium atoms, the strength of the adhesion portion 5 is improved by substituting some of the oxygen atoms in the yttria with nitrogen atoms. This also improves the strength of the water-repellent body 1 having the adhesion portion 5.

[0023] In the adhesion portion 5, the substitution rate (nitrogen atom content) at which some of the oxygen atoms in the yttria are replaced with nitrogen atoms is not particularly limited as long as it exceeds 0, but may be 1 atomic %, and the upper limit may be, for example, 10 atomic %, 5 atomic %, 3 atomic %, or 2 atomic %.

[0024] A water-repellent portion 6 is formed on the surface of the adhesion portion 5. The water-repellent portion 6 contains a fluorine compound. The fluorine compound may have a difluoromethyl group and may contain silicon, oxygen, or the like. As described above, the silicon atoms of the adhesion portion 5 and the fluorine atoms of the water-repellent portion 6 form stable bonds, causing the water-repellent portion 6 to adhere to the adhesion portion 5. Furthermore, because the bonds between the fluorine atoms and carbon atoms contained in the water-repellent portion 6 are stable, the force acting between these molecules is weak and the surface free energy of the water-repellent portion 6 is low. Therefore, the water-repellent portion 6 exhibits water repellency. The water-repellent portion 6 preferably has a thickness of 5 nm to 90 nm and is preferably formed uniformly on the surface of the adhesion portion 5 (or the uneven structure 30).

[0025] Here, when a water droplet adheres to the surface of the water-repellent body 1, the contact area between the water-repellent body 1 and the water droplet is the contact area between the tip of the concave-convex structure 30 and the water droplet. Therefore, by having the concave-convex structure 30, the water-repellent body 1 can reduce the contact area between the water droplet and the water-repellent body 1. Furthermore, by forming the water-repellent water-repellent portion 6 on the surface of the concave-convex structure 30, high water repellency is imparted to the water-repellent body 1. In other words, the high water repellency of the water-repellent body 1 in this embodiment is achieved by the combination of the concave-convex structure 30 and the water-repellent portion 6. The water-repellent body 1 has the effect of suppressing the wetting and spreading of water on its surface, and can therefore be applied to, for example, the surface of a glass lens or the surface of a motion sensor installed in an automobile.

[0026] [Method for Manufacturing Water-Repellent Body] Next, a method for manufacturing the water-repellent part 100 and the water-repellent body 1 will be described with reference to FIG. 4 . First, a concave-convex structure forming step is performed to form a metal coating 3 and a concave-convex structure 30 on the surface of the material to be coated 2. The concave-convex structure forming step is performed by sputtering, and titanium, chromium, or the like can be used as the target. If the gas pressure of the sputtering gas in the concave-convex structure forming step is too low, a smooth metal coating 3 is formed on the surface of the material to be coated 2, and the concave-convex structure 30 cannot be obtained. Therefore, in the concave-convex structure forming step, it is recommended to form the concave-convex structure 30 under medium to high pressure (e.g., 1 Pa or higher). In this way, by forming the concave-convex structure 30 using the sputtering method, the strength of the concave-convex structure 30 can be increased.

[0027] In the uneven structure forming step, the method of performing sputtering other than the above-mentioned methods is not particularly limited, and may be the same as or similar to a general sputtering method, for example.

[0028] Next, an adhesion portion forming process is performed to form adhesion portions 5 on the surface of the concave-convex structure 30. The adhesion portion forming process is not particularly limited, and can be performed, for example, by vacuum deposition, sputtering, ion plating, or ion beam deposition, which are classified as physical vapor deposition, or atomic layer deposition or plasma CVD, which are classified as chemical vapor deposition. Vapor deposition has a high film formation rate but tends to produce a film with low hardness (soft). Sputtering has a low film formation rate but tends to produce a film with high hardness (hard). In the adhesion portion forming process of this embodiment, it is preferable to use sputtering from the viewpoint of improving the strength of the concave-convex structure 30. Furthermore, sputtering allows the adhesion portions 5 to be formed uniformly on the surface of the concave-convex structure 30.

[0029] In the adhesion portion forming step, a mixture of silica and yttria can be used as a target. This allows the adhesion portion 5 to be formed uniformly on the surface of the concave-convex structure 30, thereby enabling the water-repellent portion 6 to be closely attached to the concave-convex structure 30. Note that some of the yttrium atoms in the mixture may be substituted with atoms of a Group 4A element such as zirconium atoms.

[0030] Furthermore, in order to further replace some of the oxygen atoms in the yttria contained in the adhesion portion 5 with nitrogen atoms, a film may be formed by, for example, sputtering in an atmosphere of argon plus nitrogen (reactive sputtering method).

[0031] In the adhesion portion forming step, the method of performing sputtering is not particularly limited, and may be the same as or equivalent to a general sputtering method. From the viewpoint of production efficiency, it is preferable that the film formation rate by the sputtering method is not too slow, and from the viewpoint of the hardness of the adhesion portion 5, it is preferable that the film formation rate by the sputtering method is not too fast.

[0032] Finally, a water-repellent portion forming step is carried out to form a water-repellent portion 6 on the surface of the contact portion 5. The water-repellent portion forming step is not particularly limited, but can be carried out by, for example, a plasma gas treatment method. As the plasma gas treatment method, atmospheric pressure plasma treatment, corona treatment, etc. can be used.

[0033] Examples of fluorine compounds that can be used in the water-repellent portion forming step include perfluorocarbons such as carbon tetrafluoride and perfluorocyclobutane, hydrofluorocarbons such as trifluoromethane and difluoromethane, sulfur hexafluoride, and nitrogen trifluoride. Fluorine-based active species are formed by converting these gases into plasma, and the surface free energy of the water-repellent body 1 is reduced by a coating derived from the fluorine-based active species held in the contact portion 5. This makes it possible to impart high water repellency to the water-repellent body 1.

[0034] The method of performing the plasma gas treatment in the water-repellent portion forming step is not particularly limited, and may be the same as or equivalent to a general plasma gas treatment. Furthermore, the uneven structure forming step, the adhesion portion forming step, and the water-repellent portion forming step may be performed in a single process.

[0035] Second Embodiment A water-repellent body 1 according to a second embodiment will be described with reference to Fig. 5. The resin film 7 (an example of a substrate) having an uneven structure 70 is a flexible resin film. As shown in Fig. 5, the uneven structure 70 in this embodiment is continuously formed on the surface of the resin film 7. An adhesion portion 5 and a water-repellent portion 6 are formed in this order on the surface of the uneven structure 70. The other configurations are the same as those in the first embodiment, and therefore a description of the similar configurations will be omitted.

[0036] The concave-convex structure 70 formed by the resin film 7 is weaker and more likely to collapse than the concave-convex structure 30 formed by metal or the like in the first embodiment. Therefore, in this embodiment, the strength of the concave-convex structure 70 is maintained by the adhesion portion 5 that covers the concave-convex structure 70.

[0037] The resin film 7 is not particularly limited as long as it is a flexible resin, and examples thereof include thermoplastic resins, thermosetting resins, and photocurable resins. Examples of thermoplastic resins include polyester resins such as polyethersulfone resins, polycarbonate resins, acrylic resins, polyethylene terephthalate resins, and polyethylene naphthalate resins; unsaturated polyester resins, polyolefin resins, and cycloolefin resins such as norbornene resins; polyimide resins, polyamide resins, polyimideamide resins, polyarylate resins, polysulfone resins, and polyetherimide resins. Examples of thermosetting resins include phenolic resins, epoxy resins, and urethane resins. Examples of photocurable resins include acrylic resins and epoxy resins. From the perspective of formability of the concave-convex structure 70, it is preferable to use thermoplastic resins, thermosetting resins, photocurable resins, and the like for the resin film 7. Furthermore, a heat-resistant resin may be selected depending on the performance of the water-repellent body 1.

[0038] The thickness of the resin film 7 is, for example, 100 nm to 1 mm. By adhering such a thin resin film 7 to the surface of an article (coating target) to which water repellency is to be imparted, it is possible to impart water repellency to even coating target materials with complex shapes. Since high water repellency can be imparted to objects with large areas, it is possible to impart water repellency to a variety of articles. Furthermore, by continuously connecting multiple resin films 7, high water repellency can be imparted to the roll-shaped film itself.

[0039] The resin film 7 may or may not be colored. By coloring the resin film 7, it is possible to color the water-repellent body 1, thereby increasing the options for the appearance design of the water-repellent body 1. The resin film 7 may also be permeable. By being permeable, fixing the resin film 7 to the surface of the material to be coated does not inhibit the color development of the material to be coated. Therefore, the water-repellent body 1 can be easily applied to pre-made products, etc., making it possible to impart water repellency to a variety of items.

[0040] The resin film 7 may be fixed to the surface of the object to be coated with an adhesive. The adhesive is not particularly limited as long as it can fix the resin film 7, but for example, an acrylic resin or a polyester resin may be used.

[0041] [Method for manufacturing water-repellent body] Next, a method for manufacturing the water-repellent body 1 will be described with reference to Fig. 6. First, a concave-convex structure forming step is performed to form a concave-convex structure 70 on the surface of the resin film 7. The concave-convex structure forming step is performed by pressing a molding die 8 against the resin film 7 to transfer the concave-convex structure 70.

[0042] The forming die 8 is, for example, a metal mold, and is formed so that the concave-convex structure 70 can be transferred. The forming die 8 is processed by etching, laser, electroforming, or the like so that the concave-convex structure 70 similar to the concave-convex structure 30 can be formed. Because the concave-convex structure 70 is an extremely fine structure, it is preferable to create the forming die 8 using electroforming, which can form such a concave-convex structure 70 with high precision. To create the forming die 8, it is preferable to use the concave-convex structure 30 formed by sputtering in the first embodiment.

[0043] The transfer can be performed by a thermal imprinting method, a UV imprinting method, a nanocasting method, a reversal imprinting method, a roll-to-roll method, or the like. The thermal imprinting method involves a heat cycle, which results in poor production efficiency, but it can process a variety of materials. The UV imprinting method has the advantage of enabling efficient transfer in a short time. Any of these methods can be used in this embodiment.

[0044] When producing the resin film 7 using a thermoplastic resin, the thermoplastic resin that has been heated and softened is clamped in a mold 8 (the mold 8 is pressed against the thermoplastic resin). The thermoplastic resin is then cooled and the mold is opened to obtain the resin film 7 having the concave-convex structure 70. When producing the resin film 7 using a thermosetting resin, the liquid thermosetting resin may be clamped in the mold 8 and then heated. After the thermosetting resin has hardened by heating, the mold is opened to obtain the resin film 7 having the concave-convex structure 70. When producing the resin film 7 using a photocurable resin, the liquid thermosetting resin may be applied to the surface of the material to be coated, and the photocurable resin may be hardened by irradiating it with light while clamped in a transparent mold 8. The mold is then opened to obtain the resin film 7. Alternatively, the liquid photocurable resin may be irradiated with light, and the partially hardened photocurable resin may be clamped in an opaque mold 8, the mold is opened, and further irradiated with light to completely harden it.

[0045] Next, a contact portion forming step is performed to form contact portions 5 on the surface of the uneven structure 70, and then a water-repellent portion forming step is performed to form water-repellent portions 6 on the surface of the contact portions 5. The contact portion forming step and the water-repellent portion forming step are the same as those in the first embodiment, and therefore detailed explanations thereof will be omitted.

[0046] The water-repellent body 1, in which the adhesive portion 5 and the water-repellent portion 6 are formed on the resin film 7, may be fixed to the surface of the material to be coated. Fixing may be performed by applying an adhesive, such as an acrylic resin or polyester resin, to the surface of the material to be coated and fixing the water-repellent body 1 to that surface. In this way, the adhesive bonds the material to be coated and the water-repellent body 1, fixing the water-repellent body 1 to the surface of the material to be coated, and imparting the high water repellency of the water-repellent body 1 to the material to be coated. The adhesive may also be applied to the surface of the water-repellent body 1 that comes into contact with the material to be coated. Note that if the mold is clamped with a liquid thermosetting resin or photocurable resin applied to the material to be coated and the resin is cured by heating or light irradiation, the resin film 7 is fixed to the surface of the material to be coated as the resin hardens, eliminating the need for fixing with an adhesive or the like.

[0047] Examples of the present disclosure will be described below, although the present disclosure is not limited to the following examples.

[0048] Example 1 Example 1 was produced using the manufacturing method of a water-repellent body according to the present disclosure. First, in the uneven structure forming step, a sputtering device (E-200S, Canon Anelva Corporation) was used to form a metal coating 3 having an uneven structure 30 on the surface of a coating target material 2 by sputtering. In the uneven structure forming step, a DC power supply was used, and the input power was 150 W. Chromium was used as the target for forming the metal coating 3, and argon was used as the sputtering gas. Sputtering was performed under medium to high pressure, and the substrate was heated in the range of room temperature to 200°C to obtain the metal coating 3 and the uneven structure 30. The film thickness of the obtained metal coating 3 was 2.5 μm.

[0049] Next, in the adhesion portion forming process, a sputtering device (E-200S, Canon Anelva Corporation) was used to form adhesion portions 5 on the surface of the uneven structure 30 by sputtering. In the adhesion portion forming process, a high-frequency power supply was used, and the input power was 75 W. A ceramic mixture of silica and yttria (sintered density: 65% to 98%) was used as the target for forming the adhesion portions 5. The ceramic was obtained by hot pressing using a multipurpose high-temperature furnace (Hi-Multi 5000, Fuji Denpa Kogyo Co., Ltd.). Argon was used as the sputtering gas, and film formation was performed at room temperature under low pressure, thereby obtaining the adhesion portions 5. The film thickness of the obtained adhesion portions 5 was 30 nm.

[0050] Finally, in the water-repellent portion forming step, a reactive ion etching apparatus (RIE-400iPB, Samco Inc.) was used to form a water-repellent portion 6 on the surface of the adhesion portion 5 by plasma gas treatment. The ICP power was set to 100 to 1000 W, and perfluorocyclobutane and oxygen were used as the gases. The gas pressure was set to 1 to 10 Pa, and treatment was carried out in the temperature range of room temperature to 70°C, thereby obtaining the water-repellent portion 6. The film thickness of the obtained water-repellent portion 6 was 50 nm.

[0051] Example 2 A water-repellent body 1 was obtained in the same manner as in Example 1, except that in the adhesion portion forming step, a ceramic mixture of silica, zirconia, and yttria was used as the target for forming the adhesion portion 5, and argon and nitrogen were used as the sputtering gas. In Example 2, the substitution rate of yttrium atoms with zirconium atoms was 5 to 20 mol %. In addition, some of the oxygen atoms in the yttria were substituted with nitrogen atoms. The ceramic (sintered density: 65% to 98%) used in producing Example 2 was produced in the same manner as in Example 1.

[0052] Comparative Example 1 A water-repellent body 1 was obtained in the same manner as in Example 2, except that a ceramic mixture of zirconia and yttria was used as the target for forming the adhesion portion 5. In Comparative Example 1, the substitution rate of yttrium atoms with zirconium atoms was 5 mol %. In addition, some of the oxygen atoms in the yttria were substituted with nitrogen atoms. The ceramic (sintered density: 65% to 98%) used in producing Comparative Example 1 was produced in the same manner as in Example 1.

[0053] Comparative Example 2 A water-repellent body 1 was obtained in the same manner as in Comparative Example 1, except that the substitution rate of yttrium atoms with zirconium atoms was set to 10 mol %.

[0054] Comparative Example 3 A water-repellent body 1 was obtained in the same manner as in Comparative Example 1, except that the substitution rate of yttrium atoms with zirconium atoms was set to 20 mol %.

[0055] Comparative Example 4 A commercially available water-repellent film (Leafy LF-4362, Soken Chemical & Engineering Co., Ltd.) was used as Comparative Example 4.

[0056] The ceramic mixture of zirconia and yttria used as the target for forming the adhesion portion 5 in Comparative Examples 1 to 3 is also used as a target for coating CBN tools, for example. CBN is an abbreviation for Cubic Boron Nitride, a sintered body made of boron and nitrogen. CBN tools have hardness second only to diamond, high thermal conductivity, and stability at high temperatures, and are therefore used as cutting tools for hardened steels and the like. CBN tools have high wear resistance, but further extension of their lifespan is desired. Therefore, by forming a coating of a mixture containing zirconia and yttria on the surface of the CBN tool, it is possible to impart further oxidation resistance to the CBN tool and extend its lifespan. For example, by forming the above coating on a φ1.0 radius end mill, the tool life can be improved by 128% for HRC50 materials (e.g., SKD11), 143% for HRC55 materials (e.g., STAVAX), and 155% for HRC60 materials (e.g., ELMAX). The formation of the above coating on a CBN tool may be carried out in the same manner as in the adhesion portion forming step in Example 1, and in this case, the sputtering temperature should be set to 200°C or higher.

[0057] To investigate the durability of each of Examples 1 and 2 and Comparative Examples 1 to 4, a reciprocating friction test was conducted in which the surface of the water-repellent body 1 was rubbed back and forth, and the contact angle and sliding angle of water were measured before and after the reciprocating friction test. The reciprocating friction test was conducted by applying a load of 500 g to the surface of the water-repellent body 1 and moving a canvas cloth back and forth 1,000 times at a speed of 50 mm / s.

[0058] The contact angle was measured by dropping a 2 μL droplet of water onto the surfaces of Examples 1 and 2 and Comparative Examples 1 to 4. The sliding angle was measured by dropping a 20 μL droplet of water onto the surfaces of Examples 1 and 2 and Comparative Examples 1 to 4, changing the tilt angle of each water-repellent body 1 from 0° to 90° at a rate of 5° / s, and measuring the angle at which the droplet slid down. These measurement results are shown in FIGS. 7 and 8.

[0059] As shown in Figure 7, the contact angles of Examples 1 and 2 and Comparative Examples 1 to 4 before the reciprocating friction test exceeded 140°, indicating that all of them exhibited high water repellency. However, while the contact angles of Examples 1 and 2 did not change significantly before and after the reciprocating friction test, the contact angles of Comparative Examples 1 to 4 changed significantly before and after the reciprocating friction test, with the contact angles after the reciprocating friction test being approximately half of the values ​​before the reciprocating friction test. This indicates that the water-repellent body 1 of the present disclosure has high durability and does not lose its water-repellent properties due to friction.

[0060] As shown in Figure 8, the sliding angles in Examples 1 and 2 did not change significantly before and after the reciprocating friction test, with Example 1 showing a value of approximately 30° and Example 2 showing a value of approximately 25°. In other words, it was found that the water-repellent bodies 1 in Examples 1 and 2, even after the reciprocating friction test, did not allow water droplets to adhere to their surfaces as long as they had an inclination of approximately 25 to 30°. On the other hand, the sliding angles in Comparative Examples 1 to 4 changed significantly before and after the reciprocating friction test, with the sliding angle after the reciprocating friction test for Comparative Example 1 being approximately five times that before the reciprocating friction test, and the sliding angle after the reciprocating friction test for Comparative Examples 2 and 3 being approximately twice that before the reciprocating friction test. This indicates that the inclusion of silica in the contact portion 5 improves the abrasion resistance of the water-repellent body 1. In Comparative Example 4, the sliding angle, which was 1° before the reciprocating friction test, increased to over 90° after the reciprocating friction test, and no sliding occurred. These results demonstrate that the water-repellent body 1 of the present disclosure has high durability and does not lose its water-repellent properties due to friction.

[0061] [Outline of the above embodiment] The following provides an outline of the water-repellent body 1, the water-repellent part 100, and the method for manufacturing the water-repellent body 1 described in the above embodiment.

[0062] (1) The water-repellent body (1) is characterized by comprising a substrate (metal coating (3), resin film (7)) having an uneven structure (30, 70), and a coating (4) covering the uneven structure (30, 70), the coating (4) having a water-repellent portion (6) containing a fluorine compound and an adhesion portion (5) that adheres to the substrate (metal coating (3), resin film (7)), and the adhesion portion (5) is a mixture containing silica and yttria.

[0063] According to this configuration, the uneven structure (30, 70) reduces the contact area between the substrate (metal coating (3), resin film (7)) and water droplets, etc., and the water-repellent portion (6) containing a fluorine compound reduces the surface free energy of the uneven structure (30, 70), thereby imparting high water repellency to the substrate (metal coating (3), resin film (7)). While the water-repellent portion (6) is prone to peeling from the substrate (metal coating (3), resin film (7)) due to friction, etc., the adhesion portion (5) that adheres to the substrate (metal coating (3), resin film (7)) contains silica, and therefore easily bonds with the fluorine compound contained in the water-repellent portion (6). This improves adhesion between the water-repellent portion (6) and the adhesion portion (5), thereby preventing peeling of the water-repellent portion (6). Furthermore, the adhesion portion (5) contains yttria, which provides high hardness and improves the durability of the uneven structure (30, 70). This makes it possible to provide a highly durable water-repellent body (1).

[0064] (2) In the water-repellent body (1) described in (1) above, the mixture may have some of the yttrium atoms substituted with atoms of a Group 4A element.

[0065] According to this configuration, by substituting some of the yttrium atoms with atoms of a Group 4A element that forms an oxide harder than yttria, it is possible to strengthen the bonds of the atoms that make up the adhesion portion (5), increase the hardness of the adhesion portion (5), and improve the durability of the uneven structure (30, 70).

[0066] (3) In the water-repellent body (1) described in (2) above, the atom of the 4A group element may be a zirconium atom.

[0067] According to this configuration, by substituting some of the yttrium atoms with zirconium atoms that form zirconia, which is harder than yttria, the bonds between the atoms that make up the adhesion portion (5) are strengthened, the hardness of the adhesion portion (5) is increased, and the strength of the uneven structure (30, 70) can be further improved.

[0068] (4) In the water-repellent body (1) according to any one of (1) to (3), the uneven structure (30, 70) may contain chromium.

[0069] According to this configuration, the uneven structure (30, 70) contains chromium, which can improve the strength of the uneven structure (30, 70), thereby increasing the durability of the water-repellent body (1).

[0070] (5) In the water-repellent body (1) according to any one of (1) to (3), the substrate may be a resin film (7).

[0071] According to this configuration, by forming an uneven structure (70) on the surface of the flexible resin film (7), it is possible to impart permeability and flexibility to the water-repellent body (1). This increases the options for the exterior design of the water-repellent body (1). Furthermore, since the resin film (7) can be fixed to the surface of any object, it is possible to impart high water repellency to objects with large areas or various shapes. As a result, high water repellency can be imparted to a variety of articles.

[0072] (6) In the water-repellent body (1) according to any one of (1) to (5), the fluorine compound may contain a difluoromethyl group.

[0073] According to this configuration, the bond between the fluorine atom and the carbon atom in the difluoromethyl group is stable, so the force acting between these molecules is weak and the surface free energy of the water-repellent portion (6) is low. Therefore, the water-repellent portion (6) exhibits water repellency. Furthermore, a stable bond is likely to form between the fluorine atom contained in the water-repellent portion (6) and the silicon atom contained in the adhesion portion (5), so the water-repellent portion (6) adheres to the adhesion portion (5). This makes it possible to suppress peeling of the water-repellent portion (6).

[0074] (7) The water-repellent part (100) is characterized by comprising a water-repellent body (1) described in any one of (1) to (5) and a coating target material (2) on the surface of which the water-repellent body (1) is formed.

[0075] According to this configuration, a highly durable water-repellent body (1) is formed on the surface of the material to be coated (2), thereby obtaining a water-repellent part (100) that is resistant to losing its water-repellent properties. This makes it possible to maintain the water-repellent properties for a long period of time even for a water-repellent part (100) that is easily touched by human hands and is subject to friction.

[0076] (8) The manufacturing method of the water-repellent body (1) is characterized in that it includes a concave-convex structure forming step of forming a concave-convex structure (30) on the surface of the substrate (metal coating (3), resin film (7)), an adhesion part forming step of forming an adhesion part (5) consisting of a mixture containing silica and yttria on the surface of the concave-convex structure (30), and a water-repellent part forming step of forming a water-repellent part (6) containing a fluorine compound on the surface of the adhesion part (5).

[0077] According to this configuration, by forming a concave-convex structure (30, 70) on the surface of the substrate (metal coating (3), resin film (7)) in the concave-convex structure forming step, it is possible to reduce the contact area between the substrate (metal coating (3), resin film (7)) and water droplets, etc. Furthermore, since the contact portion (5) formed in the contact portion forming step contains yttria, the durability of the concave-convex structure (30, 70) can be further improved by covering and protecting the concave-convex structure (30, 70) with the contact portion (5). Furthermore, by forming a water-repellent portion (6) containing a fluorine compound on the surface of the contact portion (5) in the water-repellent portion forming step, it is possible to reduce the surface free energy of the substrate (metal coating (3), resin film (7)) and obtain high water repellency. Furthermore, since the silicon contained in the contact portion (5) has a high affinity with the fluorine contained in the water-repellent portion (6), a stable bond is formed between them, resulting in adhesion between the contact portion (5) and the water-repellent portion (6). Therefore, the water-repellent portion (6) is less likely to peel off from the substrate (metal coating (3), resin film (7)), making it possible to manufacture a highly durable water-repellent body (1).

[0078] (9) In the method for producing the water-repellent body (1) described in (8) above, the mixture may have some of the yttrium atoms substituted with atoms of a Group 4A element.

[0079] According to this configuration, by substituting some of the yttrium atoms with atoms of a Group 4A element that forms an oxide harder than yttria, it is possible to strengthen the bonds of the atoms that make up the adhesion portion (5), increase the hardness of the adhesion portion (5), and improve the durability of the uneven structure (30, 70).

[0080] (10) In the method for producing the water-repellent body (1) described in (9) above, the atom of the Group 4A element may be a zirconium atom.

[0081] According to this configuration, by substituting some of the yttrium atoms with zirconium atoms that form zirconia, which is harder than yttria, the bonds between the atoms that make up the adhesion portion (5) are strengthened, the hardness of the adhesion portion (5) is increased, and the durability of the uneven structure (30, 70) can be improved.

[0082] (11) In the method for producing the water-repellent body (1) according to any one of (8) to (10), the uneven structure forming step may be carried out by a sputtering method.

[0083] According to this configuration, the uneven structure forming step is carried out by sputtering, so that the uneven structure (30) can be formed simultaneously with the formation of the substrate (metal coating (3)).

[0084] (12) In the method for producing the water-repellent body (1) described in (11) above, the uneven structure forming step may use chromium as a target.

[0085] According to this configuration, since the concave-convex structure (30) contains chromium, it is possible to improve the strength of the concave-convex structure (30).

[0086] (13) In the method for manufacturing the water-repellent body (1) described in any one of (8) to (10), the uneven structure forming step may be performed by transferring the uneven structure (70) to a flexible resin film (7).

[0087] According to this configuration, by pressing a mold (8) capable of forming a concave-convex structure (70) against a flexible resin film (7) to transfer the concave-convex structure (70), it is possible to efficiently form the concave-convex structure (70) even on a resin film (7) with a large surface area. Furthermore, for example, by fixing the resin film (7) to the surface of an article to which water repellency is to be imparted, water repellency can be imparted to articles on which the concave-convex structure (70) cannot be directly formed. This makes it possible to impart water repellency to objects with large areas or various shapes, thereby broadening the range of applications of the water-repellent body (1). Furthermore, since the resin film (7) can be made permeable and flexible, it is possible to increase the options for the exterior design of the water-repellent body (1).

[0088] (14) In the method for producing the water-repellent body (1) according to any one of (8) to (13), the fluorine compound may contain a difluoromethyl group.

[0089] According to this configuration, the bond between the fluorine atom and the carbon atom in the difluoromethyl group is stable, so the force acting between these molecules is weak and the surface free energy of the water-repellent portion (6) is low. Therefore, the water-repellent portion (6) exhibits water repellency. Furthermore, a stable bond is likely to form between the fluorine atom contained in the water-repellent portion (6) and the silicon atom contained in the adhesion portion (5), so the water-repellent portion (6) adheres to the adhesion portion (5). This makes it possible to suppress peeling of the water-repellent portion (6).

[0090] (15) The water-repellent body (1) may be produced by the method for producing the water-repellent body (1) according to any one of (8) to (14).

[0091] According to this configuration, it is possible to provide a highly durable water-repellent body (1) that has high water repellency and can prevent the water-repellent portion (6) from peeling off.

[0092] The present disclosure is applicable to a water-repellent body, a water-repellent part including a water-repellent body, and a method for manufacturing a water-repellent body.

[0093] 1: Water-repellent body 2: Coating target material 3: Metal coating (substrate) 4: Coating 5: Adhesion part 6: Water-repellent part 7: Resin film (substrate) 30: Uneven structure 70: Uneven structure 100: Water-repellent part

Claims

1. A substrate having a concavo-convex structure, and a coating covering the concavo-convex structure, wherein the coating has a water-repellent part containing a fluorine compound and an adhesion part adhering to the substrate, and the adhesion part is a water-repellent body which is a mixture containing silica and yttria.

2. The water-repellent body according to claim 1, wherein a part of the yttrium atoms in the mixture is substituted with atoms of a Group 4A element.

3. The water-repellent body according to claim 2, wherein the atoms of the Group 4A element are zirconium atoms.

4. The water-repellent body according to any one of claims 1 to 3, wherein the concavo-convex structure contains chromium.

5. The water-repellent body according to any one of claims 1 to 4, wherein the substrate is a flexible resin film.

6. The water-repellent body according to any one of claims 1 to 5, wherein the fluorine compound contains a difluoromethyl group.

7. A water-repellent component comprising the water-repellent body according to any one of claims 1 to 6, and a film target material on which the water-repellent body is formed on the surface.

8. A method for manufacturing a water-repellent body, comprising: a concavo-convex structure forming step of forming a concavo-convex structure on the surface of a substrate; an adhesion part forming step of forming an adhesion part made of a mixture containing silica and yttria on the surface of the concavo-convex structure; and a water-repellent part forming step of forming a water-repellent part containing a fluorine compound on the surface of the adhesion part.

9. The method for manufacturing a water-repellent body according to claim 8, wherein a part of the yttrium atoms in the mixture is substituted with atoms of a Group 4A element.

10. The method for manufacturing a water-repellent body according to claim 9, wherein the atoms of the Group 4A element are zirconium atoms.

11. The method for manufacturing a water-repellent body according to any one of claims 8 to 10, wherein the concavo-convex structure forming step is performed by a sputtering method.

12. The method for manufacturing a water-repellent body according to claim 11, wherein chromium is used as a target in the concavo-convex structure forming step.

13. The method for manufacturing a water-repellent body according to any one of claims 8 to 10, wherein the concavo-convex structure forming step is performed by transferring the concavo-convex structure to a flexible resin film.

14. The method for manufacturing a water-repellent body according to any one of claims 8 to 10, wherein the fluorine compound contains a difluoromethyl group.

15. A water-repellent body manufactured by the manufacturing method according to any one of claims 8 to 14.

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