Resin molded body

A resin molded body includes a body having a surface, and a decorative sheet adhered to the surface of the body. The decorative sheet has a metallic luster layer, a transparent protective layer positioned on an outer side of the metallic luster layer, and a welding layer adhered to the surface of the body. The body is formed from a fiber-reinforced resin having reinforcing fibers defining an anchor structuring layer such that the reinforcing fibers of the body bite into the welding layer at a boundary portion between the welding layer and the body such that the boundary portion has an uneven shape.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to Japanese Patent Application No. 2018-183642, filed on Sep. 28, 2018. The entire disclosure of Japanese Patent Application No. 2018-183642 is hereby incorporated herein by reference.

BACKGROUND

Field of the Invention

The present invention relates to a resin molded body in which a decorative sheet having a metallic luster is adhered to the surface.

Background Art

A resin molded body having a metallic luster is lighter than metal articles. Japanese Laid-Open Patent Application No. S61(1986)-352169 proposes a method in which a sheet having a metallic luster is placed in an injection mold and is integrally molded with a resin as a method for imparting a metallic luster to a resin molded body.

SUMMARY

The object of the present invention is to provide a resin molded body that exhibits sufficient strength to withstand a large force and high sheet adhesiveness.

The resin molded body according to the present invention comprises a body and a decorative sheet that is adhered to a surface of the body, the decorative sheet having a metallic luster layer, a transparent protective layer positioned on the outer side of the metallic luster layer, and a welding layer positioned on the inner side of the metallic luster layer and that is welded on the surface of the body. The body is formed from fiber-reinforced resin having reinforcing fibers. An anchor structuring layer is configured at boundary between the welding layer and the body, and has an uneven shape such that the reinforcing fibers of the body bite into the welding layer.

Because the body is formed from fiber-reinforced resin, the resin molded body exhibits high strength, and even if a large force acts on the resin molded body, the resin molded body is capable of withstanding the force. In addition, since the body has the anchor structuring layer in which the reinforcing fibers of the body bite into the welding layer at boundary between the welding layer and the body such that the anchor structuring layer has an uneven shape, there is significant adhesion between the decorative sheet and the body. Therefore, even if a large force acts on the resin molded body, the metallic luster is maintained as well as the adhesion of the decorative sheet to the body.

Preferably, in one embodiment, the reinforcing fibers of the body bite into the welding layer randomly in the anchor structuring layer, which improves the anchoring effect.

Preferably, in one embodiment, the anchor structuring layer has a height difference greater than the fiber diameter of the reinforcing fibers, which improves the anchoring effect.

In addition, the anchor structuring layer preferably has a height difference of 20 μm or more, which improves the anchoring effect.

In particular, the resin molded body is suitable for a structural member of a bicycle or fishing gear.

As described above, since the body is formed from the fiber-reinforced resin which defines an anchor structuring layer such that the reinforcing fibers thereof bite into the welding layer side of the decorative sheet, it is possible for the decorative sheet to have a high connection strength that can withstand a large force and has high adhesion. Therefore, it is possible to use the resin molded body as an alternative to a metal article for which high strength and precision design are required, and it is possible to reduce the weight of the article.

DETAILED DESCRIPTION OF THE EMBODIMENT

A resin molded body according to one embodiment of the present invention is described below with reference toFIGS. 1 to 7. The resin molded body can be used for various purposes. In particular, the resin molded body is suitable for a structural member of a bicycle or of fishing gear. Examples include bicycle brake levers, cranks, rims, interior sprocket components, bicycle shoe soles, reel main bodies, reel spools, reel seats, and the like. The resin molded body is suitable for products having a metallic luster, and that are lightweight and strong.

As shown inFIG. 1, the resin molded body comprises a body1and a decorative sheet2that is adhered to the surface of the body1. The body1is formed from a fiber-reinforced resin. The reinforcing fibers10of the body1are carbon fibers or glass fibers, for example. The reinforcing fibers10can be cut to several millimeters or to several tens of millimeters, or be long fibers. The body1can be formed by various molding methods. Examples of the molding method for the body1include injection molding that uses the reinforcing fibers10cut to several millimeters, SMC molding that uses the reinforcing fibers10cut to several tens of millimeters, molding by a prepreg that uses long fibers, and the like. The material of the resin of the body1can be a material suitable for various moldings. The material of the resin of the body1can be various thermoplastic resins or thermosetting resins. The material of the resin of the body1can be, for example, various resins for injection molding in the case of injection molding, thermoplastic resins such as epoxy resin in the case of using a prepreg, and nylon resin, epoxy resin, vinyl ester resin, or the like in the case of SMC molding. The body1of the present embodiment is molded by injection molding. Short fibers cut to a length of several millimeters, in particular, to a length of 1 mm or less, are used as the reinforcing fibers10. Polyamide resin (nylon) is used as the resin.

The decorative sheet2is adhered to the surface of the body1. The decorative sheet2can be integrated with the surface of the body1when the body1is molded. One example of the decorative sheet2is shown inFIG. 2. The decorative sheet2has a protective layer20, a first adhesive layer21, a support layer22, a metallic luster layer23, a second adhesive layer24, and a welding layer25. The protective layer20is positioned on the outermost surface of the decorative sheet2. The protective layer20is the outermost layer of the decorative sheet2. The protective layer20can be transparent and can have a transparency of a degree that allows at least visual recognition of the metallic luster layer23. The protective layer20preferably has excellent wear resistance and weather resistance. The protective layer20can be composed of various resin films. The thickness of the film of the protective layer20can be several tens of μm, for example. Examples of the resin of the film of the protective layer20include acrylic resins such as polymethyl methacrylate (PMMA) resin and polycarbonate (PC) resin. The first adhesive layer21can be a layer for bonding the protective layer20and the support layer22. The protective layer20can be stacked on the outer side (surface side) of the support layer22with the first adhesive layer21interposed therebetween. Various adhesives are used for the first adhesive layer21. The first adhesive layer21can be transparent and can have a transparency of a degree that enables at least visual recognition of the metallic luster layer23. The first adhesive layer21may be colorless and transparent, or colored and transparent.

The support layer22is a layer for holding the metallic luster layer23. The support layer22can be composed of various resin films. The thickness of the film of the support layer22can be several tens of μm, for example, and the film of the support layer22is generally thinner than the film of the protective layer20. The resin of the film of the support layer22is a polyester resin, such as PET. The metallic luster layer23is a metal vapor deposition layer, a metal foil, a metal-colored coating film, or the like. A metal-colored coating film can be composed of metal nanoparticles. Examples of the metal nanoparticles include silver, gold, copper, nickel, chromium, platinum, palladium, titanium, tin, and alloys thereof, and any one or a mixture thereof is used. The metal-colored coating film can be formed by various printing methods, such as coater coating, gravure printing, inkjet printing, or the like. The metallic luster layer23according to the present embodiment is a metal vapor deposition layer formed on one side of the support layer22. The metal vapor deposition layer is formed on one side of the resin film as the support layer22, and the protective layer20is stacked on the outer side of the resin film with the metal vapor deposition layer, with the first adhesive layer21interposed therebetween.

The second adhesive layer24is a layer for bonding the metallic luster layer23and the welding layer25. Various adhesives are used for the second adhesive layer24, in the same manner as the first adhesive layer21. The welding layer25is stacked on the inner side (back side) of the metallic luster layer23with the second adhesive layer24interposed therebetween. The welding layer25is a layer that serves as the base of the decorative sheet2and is a thermoplastic resin layer. The welding layer25is the thickest layer of the layers constituting the decorative sheet2. The thickness of the welding layer25is several hundred μm, for example. The welding layer25is the innermost layer of the decorative sheet2. The welding layer25is adhered to the surface of the body1when the body1is molded. The welding layer25can be composed of various resins and/or composed of various resin films. For example, the welding layer25can be composed of a film of ABS resin, polypropylene resin, polycarbonate resin, or the like.

For example, the decorative sheet2is placed in a molding die for injection molding, etc., after being preformed by sheet molding, such as vacuum pressure forming. In addition, the decorative sheet2with a flat plate shape can be set in a molding die for injection molding, etc., the decorative sheet2can be formed into a prescribed shape in the molding die so as to match the shape of the molding die, and the resin for the body1may be subsequently injected into the molding die to thereby form the body1.

As shown in the enlarged view ofFIG. 3, the resin molded body has an anchor structuring layer30in a boundary portion3between the body1and the decorative sheet2. The boundary portion3between the body1and the decorative sheet2is the interface between the body1and the decorative sheet2and is the adhesion surface. The anchor structuring layer30is a structure in which the reinforcing fibers10of the body1bite into the welding layer25such that the boundary portion3has an uneven shape. The reinforcing fibers10bite randomly into the welding layer25. Therefore, the unevenness of the anchor structuring layer30is not regular but irregular. If the welding layer25is convex; the size, orientation, and shape of the convex portion31of the anchor structuring layer30are not constant. Some of the convex portions31of the anchor structuring layer30are themselves complex in shape with small irregularities. The convex portion31of the anchor structuring layer30is formed by the biting of the reinforcing fibers10into the welding layer25. Therefore, the convex portion31of the anchor structuring layer30includes the reinforcing fibers10. The reinforcing fibers10are positioned at the distal end portion of the convex portion31of the anchor structuring layer30.

The unevenness of the anchor structuring layer30preferably has a height difference greater than the fiber diameter of the reinforcing fibers10. In particular, the unevenness of the anchor structuring layer30preferably has a height difference approximately several times the fiber diameter of the reinforcing fibers10. The fiber diameter of the reinforcing fibers10is about 10 μm, for example. The unevenness of the anchor structuring layer30preferably has a height difference of 20 μm or more, and particularly preferably a height difference of 50 μm or more. For example, when the thickness of the welding layer25is about 200-300 μm, the unevenness of the height difference of the anchor structuring layer30is about 10%, but can be 10% or more. Even when the thickness of the welding layer25is greater, the unevenness of the height difference of the anchor structuring layer30is often not that different.

FIGS. 4 to 7show enlarged photographs of the cut sections of the resin molded body. ABS resin film is used for the welding layer25. The body1is formed by mixing short fibers, obtained by cutting carbon fibers to a length of 1 mm or less, with polyamide resin and carrying out injection molding. The magnification inFIG. 4is 200×, the magnification inFIG. 5is 500×, and the magnification inFIG. 6is 1500×.FIG. 7is a photograph in which a line is drawn on the boundary portion3between the welding layer25and the body1in the photograph ofFIG. 6. In the photograph, the reinforcing fibers10of the body1have a white, shiny appearance.

As shown inFIG. 4, the boundary portion3between the welding layer25and the body1undulates considerably. As shown inFIGS. 6 and 7, the reinforcing fibers10of the body1bite into the welding layer25of the decorative sheet2randomly, and the form of the biting of the reinforcing fibers10is the undulation, i.e., the unevenness, of the boundary portion3. The location shown in the photograph exhibits the formation of an uneven shape having a height difference of about 30-50 μm.

FIGS. 8 to 10show enlarged photographs of the cut sections of a resin molded body as a comparative example. With respect to the resin molded body shown inFIGS. 4 to 7above, the resin molded body of this comparative example has the same decorative sheet102but the material of the resin of a body101is different. The body101of the resin molded body in the comparative example is injection-molded from ABS resin, and does not contain the reinforcing fibers10. The magnifications ofFIGS. 8 to 10are, respectively, 200×, 500×, and 1500×, which are the same asFIGS. 4 to 6. In the resin molded body of the comparative example, a boundary portion103between the body101and an welding layer125of the decorative sheet102is flat, and has a planar shape with extremely small irregularities.

As stated above, since the body1of the resin molded body of the present embodiment is made up of fiber-reinforced resin, high strength can be obtained. Therefore, even if a large force acts on the resin molded body, the resin molded body can withstand such a force. In addition, since the anchor structuring layer30in which the reinforcing fibers10bite into the welding layer25is disposed at the boundary portion3between the welding layer2and the body1, there is significant adhesions between the decorative sheet2and the body1. Therefore, even when a large force acts on the resin molded body, the metallic luster as well as the adhesion of the decorative sheet2to the body1are maintained. In this manner, since high strength and metallic luster due to the high adhesiveness of the decorative sheet2can be obtained, it is possible to use the resin molded body as an alternative to a metal article, and it is possible to reduce the weight of the article. In particular, if the resin molded body is configured as a structural member of a bicycle or fishing gear on which a large force acts, it is be possible to reduce the weight of the structural member while maintaining the strength and the aesthetic appearance of the structural member.