JP6884634B2 - Resin molded products and their manufacturing methods - Google Patents

Description

The present invention relates to a resin molded product having an appearance equivalent to that of natural wood by embossing the surface, and a method for producing the same.

In recent years, from the viewpoint of conservation of the global environment, recycling of forest resources has been required, and attempts have been made to recycle waste wood such as pillars and flooring materials for houses. For example, in Patent Document 1, wood powder is produced by crushing wood that has been scrapped for various purposes, the wood powder is mixed with various thermoplastic synthetic resins, and the mixture is heated and smelted to form a resin. A technique for producing a molding material is disclosed. By reusing the resin molding material produced in this way for the above-mentioned various uses, it is expected that logging of new forest resources will be stopped.

Since the above resin molding material is made using wood powder, its appearance color tone is not inferior to that of natural wood, but the wood texture on its surface is still inferior to that of natural wood. At a glance, you can see the difference between the two. For this reason, natural wood is deeply popular in applications such as pillars, wall materials, and flooring for houses that are easily visible to the public, and the spread of recycled resin molding materials has not progressed yet.

In order to solve such a problem, for example, Patent Document 1 discloses a technique of imparting the texture of natural wood by decorating the surface layer of a resin molded product having a flat surface with a wood grain pattern. The resin molded product disclosed in Patent Document 1 has a base layer and a surface layer having a heat deformation temperature lower than that of the base layer on the surface of the base layer, and the surface of the surface layer is heated to heat the surface of the heated surface layer. While pressing the decorative roll against the surface, the decorative roll is rolled and the wood grain pattern applied to the surface of the decorative roll is transferred to the surface of the surface layer to form the wood grain pattern on the surface of the surface layer. By forming a wood grain pattern on the surface of the resin molded product having a flat surface in this way, it is possible to obtain a resin molded product having an appearance close to that of natural wood.

Japanese Unexamined Patent Publication No. 2008-120019

Even when the surface of the resin molded product is processed as described above, the surface of the portion where the wood grain pattern is not formed is a flat surface as it is processed by the resin molding. Since such a flat surface gives the impression that it is a material formed by resin molding, improvement for making it closer to the appearance of natural wood has been required.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a resin molded product having an appearance equivalent to that of natural wood and a method for producing the same.

In order to solve the above problems, in the resin molded product of the present invention, embossed portions and non-embossed non-embossed portions are alternately formed on the surface, and the non-embossed portions are roughened. A streak pattern is formed by processing, the arithmetic average roughness Ra of the non-embossed portion is set to 2 μm or more and 30 μm or less, and the embossed portion has a plurality of recesses and is adjacent to each recess so as to sandwich each recess from both sides. The maximum value of the depth of the concave portion is 50 μm or more and 1000 μm or less, and the maximum value of the height of the convex portion is 40 μm or more and 800 μm or less, and the depth of the concave portion. It is less than the maximum value (claim 1).

The resin molded product of the present invention looks like a wood grain pattern of natural wood due to the embossed portions and the non-embossed portions alternately formed on the surface thereof. Further, since the streaks are formed by the roughing process in the non-embossed portion, the plastic-like flat surface peculiar to resin molding disappears even in the non-embossed portion, and the wood texture can be produced. Moreover, by setting the arithmetic mean roughness Ra of the portion where the streak pattern is formed within the above range, the streak pattern formed on the surface of the resin molded product looks like a streak of natural wood. The combination of these embossed portions and the non-embossed portion of the streaks makes it possible to obtain a resin molded product having an appearance similar to that of natural wood.
In addition, a plurality of concave portions and convex portions are formed in the embossed portion, and convex portions are provided adjacent to each concave portion so as to sandwich each concave portion from both sides, thereby reproducing a texture similar to that of natural wood. Therefore, the texture of the resin molded product can be made closer to the texture of natural wood. Further, since the convex portion formed above the surface of the resin molded product, the anti-slip property of the resin molded product can be improved. Moreover, since the concave portions are provided on both sides of the concave portion, for example, even if a large amount of water adheres to the surface of the resin molded product, the adhered water flows from the convex portion to the concave portion and the concave portion. Water concentrates on the surface and easily drains to the outside through the recess. As a result, the upper surface of the resin molded product becomes easy to dry, and a resin molded product having good drainage property suitable for installation outdoors can be obtained.
Further, when the depth of the recess in the embossed portion is within the above numerical range, the embossed portion looks like an annual ring pattern appearing on the cross section of the natural wood cut in the vertical direction. You can get closer. Further, since the height of the convex portion in the embossed portion is less than the depth of the concave portion, the depth of the concave portion is appropriately emphasized by each convex portion, and the texture of natural wood can be enhanced. Moreover, since the height of the convex portion is within the above numerical range, the anti-slip property of the resin molded product can be enhanced, so that the resin molded product can be applied to the upper surface of the outdoor deck floor.

In the above configuration, a coating material is preferably applied to the embossed portion and the non-embossed portion (claim 2).

According to the above configuration, by applying a coating material to the surface of the resin molded product that has been roughened, fluffing that occurs on the surface of the resin molded product due to the roughing can be suppressed, and the surface of the resin molded product can be suppressed. It feels good on the skin and can be finished smoothly. By applying the coating material to the surface in this way, it is possible to prevent the surface of the resin molded product from getting dirty with hand stains or the like.

In the above configuration, preferably, the resin molded product has a base member and a surface layer formed on the surface of the base member, and the base member and the surface layer are each made of a synthetic resin mixed with wood powder. It is composed of a powder-blended resin, and the base member has a higher wood powder content than the surface layer (claim 3 ).

By increasing the content of wood powder in the base member as compared with the surface layer as in the above configuration, the content of the synthetic resin contained in the base member is relatively small, so that the base member can be made difficult to deform. it can. On the other hand, since the content of the synthetic resin contained in the surface layer is relatively large as compared with the base member, the surface layer can be easily deformed. By forming a easily deformable surface layer on the surface of the base member which is hard to be deformed in this way, the surface layer of the resin molded product is not deformed by the pressing by the embossing roll when the resin molded product is embossed. An embossed portion (unevenness) can be formed on the surface.

The method for producing a resin molded product of the present invention includes a first step of forming a streak pattern on the surface of the resin molded product by roughing, and the columnar roll body portion and the raised surface of the roll body portion outside the outer peripheral surface. By partially embossing the surface of the resin molded product using an embossed roll including the embossed portion, the embossed portion embossed on the surface of the resin molded product and the non-embossed non-embossed portion are embossed. includes a second step of forming a part alternately to, in the first step, performs the roughed as arithmetic average roughness Ra of the non-embossed portion is 2μm or more 30μm or less, the embossing roll The embossed portion is formed with irregularities rougher than the streak pattern, and in the second step, the embossed portion of the resin molded product is separated from the surface of the resin molded product while the surface of the roll main body is separated from the surface of the resin molded product. By pressing against the surface, a plurality of concave portions and a convex portion adjacent to each concave portion are formed in the embossed portion so as to sandwich each concave portion from both sides (claim 4 ).

According to the manufacturing method of the present invention, a resin molded product having an appearance similar to that of a natural wood grain pattern can be obtained by alternately forming embossed portions and non-embossed portions. Further, since the non-embossed portion has a streak pattern formed by roughing, it is possible to erase the plastic-like flat surface peculiar to resin molding and give a wood texture. Moreover, by setting the arithmetic mean roughness Ra of the portion where the streak pattern is formed within the above range, the streak pattern formed on the surface of the resin molded product looks like a streak of natural wood. A resin molded product having a texture similar to that of natural wood can be produced by combining the streaks of the non-embossed portion and the wood grain pattern of the embossed portion.
Further, since the convex portion is provided so as to sandwich each concave portion from both sides in the embossed portion, the depth of the concave portion can be made to stand out by the convex portion, and the appearance of the resin molded product can be made closer to the texture of natural wood. Further, the anti-slip property of the resin molded product can be improved by forming the convex portion raised above the surface of the resin molded product. Moreover, since the convex portions are provided on both sides of the concave portion, for example, even if a large amount of water adheres to the surface of the resin molded product, the adhered water flows from the convex portion to the concave portion and water enters the concave portion. Concentrate and easily drain to the outside through the recess. As a result, the upper surface of the resin molded product becomes easier to dry as compared with the case where the surface of the resin molded product is not formed with irregularities, and a resin molded product having good drainage property suitable for installation outdoors can be obtained. ..

In the above configuration, preferably, a third step of applying a coating material to the non-embossed portion and the embossed portion is further included (claim 5 ).

According to the above configuration, by applying the coating material, it is possible to suppress fluffing generated on the surface of the resin molded product due to the roughing process. As a result, the surface of the resin molded product can be finished smoothly and softly. Further, by applying the coating material, it is possible to prevent the surface of the resin molded product from being soiled by hand stains or the like.

In the above configuration, preferably, the embossing process and the roughing process are performed on the resin molded product in this order (claim 6 ).

According to the above configuration, after the unevenness is formed in the embossed portion by the embossing process, the streak pattern formed by the roughing process is formed to prevent the streak pattern formed by the roughing process from being crushed by the embossing process. Can be done.

In the above configuration, preferably, the roughing process and the embossing process are performed on the resin molded product in this order (claim 7 ).

According to the above configuration, by forming an embossed portion by embossing after roughing, a streak pattern can be formed on a portion (non-embossed portion) that has not been embossed.

In the above configuration, preferably, the maximum value of the depth of the concave portion is 50 μm or more and 1000 μm or less, the maximum value of the height of the convex portion is 40 μm or more and 800 μm or less, and the maximum depth of the concave portion is maximum. It is less than the value (Claim 8 ).

By forming the embossed portion satisfying the above configuration, the embossed portion looks like an annual ring pattern appearing on the cross section of the natural wood cut in the vertical direction, so that the resin molded product can be made closer to the texture of the natural wood. Further, since the height of the convex portion in the embossed portion is less than the depth of the concave portion, the depth of the concave portion is appropriately emphasized by the convex portion, so that the texture of natural wood can be brought out. Moreover, since the anti-slip property of the resin molded product can be enhanced by setting the height of the convex portion, it is possible to obtain a resin molded product applicable to the upper surface of the outdoor deck floor.

According to the present invention, it is possible to provide a resin molded product having an appearance equivalent to that of natural wood and a method for producing the same.

It is a perspective view of the resin molded article of Embodiment 1. FIG. FIG. 5 is an enlarged cross-sectional view of an embossed portion of a cut surface obtained by cutting the resin molded product of FIG. 1 vertically. FIG. 5 is an enlarged cross-sectional view of the unevenness of the embossed portion of FIG. It is a schematic diagram of the embossing apparatus used in Embodiment 1. It is a schematic diagram which shows the apparatus structure which arranges an embossing apparatus and a roll coater side by side, and continuously processes a resin molded article. It is a perspective view of the resin molded article of Embodiment 2.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. The following embodiments are examples that embody the present invention and do not limit the technical scope of the present invention.

<Embodiment 1>
FIG. 1 is a perspective view of the resin molded product of the present embodiment. The resin molded product 1 of the present embodiment is used for terraces, promenades (boardwalks), decorative boards, wall materials, flooring materials, natural wood decorative boards, furniture materials, building materials, automobile interior parts, and the like. As shown in FIG. 1, it is a hollow member having a plurality of cavities penetrating in the longitudinal direction inside. As shown in FIG. 1, the resin molded product 1 of the present embodiment has a rectangular parallelepiped shape extending in the longitudinal direction, and the embossed portion 3 on the surface thereof and the non-embossed portion 4 not embossed are alternately alternated. Have in. A streak pattern 4a is formed in the non-embossed portion 4 by roughing, and the arithmetic average roughness Ra of the non-embossed portion 4 is 2 μm or more and 30 μm or less.

As shown in FIG. 1, the embossed portion 3 has an annual ring pattern that appears on the cut surface when the natural wood is cut up and down, and the embossed portion 3 has a streak pattern 4a formed on the non-embossed portion 4. Rougher irregularities are formed. FIG. 2 is an enlarged cross-sectional view of the embossed portion 3 of the cut surfaces obtained by vertically cutting the resin molded product of FIG. 1, and FIG. 3 is an enlarged cross-sectional view of the unevenness of the embossed portion 3 of FIG. .. The embossed portion 3 is formed with a plurality of recesses 3a and convex portions 3b adjacent to the recesses 3a so as to sandwich the recesses 3a from both sides. The concave portion 3a is formed on the surface of the resin molded product 1 like a groove extending in substantially the same direction as the longitudinal direction of the streak pattern 4a, and the convex portions 3b raised on both sides of the concave portion 3a along the concave portion 3a are formed. It is formed. The convex portion 3b is formed by embossing the material existing inside the concave portion 3a and pushing it away from both sides of the concave portion 3a. Therefore, the height y of the convex portion 3b is less than the depth of the concave portion 3a.

The depth of the recess 3a is 50 μm or more and 1000 μm or less. The depth x of the recess 3a means the length from the surface 1c of the resin molded product 1 to the deepest position of the recess 3a as shown in FIG. The depth x of the recess 3a is preferably 100 μm or more and 1000 μm or less, and more preferably 150 μm or more and 500 μm or less. It is not necessary for all the recesses 3a of the recesses 3a formed in the embossed portion 3 to satisfy the above-mentioned numerical range, and the recesses 3a having a depth partially outside the above-mentioned numerical range may be formed. ..

The height y of the convex portion 3b is 40 μm or more and 800 μm or less. Here, the height y of the convex portion 3b means the length from the surface 1c of the resin molded product 1 to the highest position of the convex portion 3b. The height y of the convex portion 3b is preferably 80 μm or more and 800 μm or less, and more preferably 120 μm or more and 400 μm or less. It is not necessary that the heights y of all the convex portions 3b of the convex portions 3b formed on the embossed portion 3 satisfy the above-mentioned numerical range, and the convex portions 3b having a height partially outside the above-mentioned numerical range It may be formed. In such an embossed portion 3, the length (x + y) from the highest position of the convex portion 3b to the deepest position of the concave portion 3a is preferably 100 μm or more and 1500 μm or less, and more preferably 200 μm or more and 1000 μm or less. It is preferable, more preferably 300 μm or more and 600 μm or less.

As shown in FIG. 1, the resin molded product 1 has a two-layer structure integrally including a base member 1a and a surface layer 1b that integrally covers all surfaces (that is, four surfaces on the top, bottom, left, and right) except for both end faces in the longitudinal direction of the base member 1a. It is said that. Both the base member 1a and the surface layer 1b are made of a wood powder-blended resin in which wood powder is mixed with a synthetic resin. For example, as the surface layer 1b, a mixture of ASA resin and wood powder can be preferably used, and as the base member 1a, one or both of polyvinyl chloride (PVC) resin and ABS resin are mixed with wood powder. Can be preferably used.

The blending ratio of wood powder and synthetic resin is not particularly limited, but the higher the blending ratio of wood flour, the higher the rigidity, while the higher the blending ratio of wood flour, the lower the blending ratio of synthetic resin. The sex is reduced. Therefore, the base member 1a preferably has a higher wood powder content than the surface layer 1b. As a result, the moldability of the surface layer 1b can be increased, and the rigidity of the base member 1a can be increased. Therefore, unevenness can be easily formed on the surface layer 1b through embossing, and the base member 1a exists even if the convex portion of the embossing roll is pressed against the surface 1c of the resin molded product 1 during the embossing. The resin molded product is not easily deformed as a whole. The content of wood powder in the base member 1a is preferably 10% or more higher than the content of wood powder in the surface layer 1b, and more preferably 15% or more. For example, the blending ratio of wood powder in the surface layer 1b may be 10%, and the blending ratio of wood flour in the base member 1a may be 30%.

The types of synthetic resins listed here are merely preferred examples, and various other synthetic resins such as polyethylene, polypropylene, EVA resin, and polystyrene can be used. As for wood flour, any kind of finely divided wood can be used. The base member 1a and the surface layer 1b may not contain wood powder as an essential component, or may contain a coloring pigment for producing a wood texture in addition to the wood powder, or may be a foaming agent or a foaming agent. Various additives such as an ultraviolet absorber, a flame retardant, and an antistatic agent may be blended.

The resin molded product 1 having the above structure can be manufactured, for example, by coextrusion molding. That is, a resin having a two-layer structure having the base member 1a and the surface layer 1b integrally by extruding the melted raw material of the base member 1a and the raw material of the surface layer 1b into one mold from separate extrusion heads. Molded product 1 can be manufactured. The extrusion direction at this time coincides with the longitudinal direction of the resin molded product 1. The thickness of the surface layer 1b after extrusion molding (thickness before roughing) is set to 0.5 to 5 mm.

After the extrusion molding as described above, the entire surface of the surface layer 1b is roughened to form a streak pattern 4a on the entire surface (upper and lower surfaces and side surfaces) of the surface layer 1b. The streak pattern 4a referred to in the present specification is a pattern that appears due to a large number of fine streak-like irregularities generated by roughing along a specific direction. The surface of the resin molded product 1 on which such a streak pattern 4a is formed has a rough surface having an arithmetic average roughness Ra of 2 μm or more and 30 μm or less. This roughening process is performed on the upper, lower, left and right surfaces of the surface layer 1b by using, for example, a belt sander provided with an endless sanding belt (polishing sheet) that is driven by winding at high speed. At this time, the belt sander is used in a posture in which the sanding belt is in sliding contact with the surface layer 1b in parallel with the longitudinal direction.

The tool used for the roughing is not limited to the belt sander. For example, roughing may be performed using a buffing machine, a disc grinder, or the like. In particular, since the area of both end faces of the resin molded product 1 in the width direction is smaller than that of the upper surface, both end faces may be roughened using a rotary tool with a metal brush attached to the tip, or sandpaper may be used. Both end faces may be roughened by hand. When sand paper is used, it is preferable that the count of sand paper is # 40 to # 80.

Next, after the roughing process, the surface layer 1b of the resin molded product 1 is partially embossed using the embossing apparatus 10 shown in FIG. 4, so that the resin molded product is as shown in FIG. Embossed portions 3 and non-embossed portions 4 are alternately formed on the surface of 1. Such embossing is performed using the embossing apparatus 10 shown in FIG.

Specifically, first, two embossing rolls 11 in the embossing apparatus 10 shown in FIG. 4 are arranged one above and one below the thickness of the resin molded product 1. Each of these embossed rolls 11 has a cylindrical embossed roll main body 11a (roll main body) , an embossed portion 11b that rises outward from the outer peripheral surface of the embossed roll main body 11a, and an embossed roll main body 11a. It is provided with a shaft support portion 11c that rotatably supports the shaft. As shown in FIG. 4, the embossed portion 11b is provided on the outer peripheral surface of the embossed roll main body portion 11a so that a plurality of streaky patterns are separated from each other so as to look like a wood grain pattern. Is formed with irregularities that are coarser than the streak pattern 4a by roughing in order to produce an annual ring pattern that looks like a cut surface when the natural wood is cut up and down. The area of the embossed portion 11b occupies a region of 20% to 80% of the outer peripheral surface of the embossed roll main body portion 11a. Further, the height of the convex portion of the unevenness formed on the embossed portion 11b with respect to the surface of the embossed roll main body portion 11a is preferably 100 μm or more and 2 mm or less, and more preferably 150 μm or more and 1.5 mm or less. More preferably, it is 200 μm or more and 1 mm or less. Here, the height of the convex portion means the length from the surface of the embossed roll main body portion 11a to the upper end of the convex portion.

Then, each embossed roll 11 is heated to a temperature equal to or higher than the thermal deformation temperature of the resin constituting the surface layer 1b. The thermal deformation temperature here is preferably 90 ° C to 200 ° C. While pressing the embossed portions 11b of the heated upper and lower embossing rolls 11 against the upper and lower surfaces of the resin molded product 1, the resin molded product 1 is passed between the upper and lower embossed rolls 11. In this way, the wood grain-shaped embossed portion 3 is formed on the portion of the surface of the resin molded product 1 to which the embossed portion 11b is pressed. The unevenness formed on the embossed portion 11b is transferred to the embossed portion 3 instead of the streak pattern formed by the roughing process. Specifically, the heated embossed portion 11b enters the inside from the surface of the resin molded product 1 to form a recess 3a on the surface of the resin molded product 1, and the material existing inside the recess 3a. Is pushed away from both sides of the recess 3a to form convex portions 3b along both sides of the recess 3a. On the other hand, the surface portion of the resin molded product 1 other than the embossed portion 3 becomes the non-embossed portion 4. During the embossing process, the non-embossed portion 4 is roughened by passing the resin molded product 1 between the upper and lower embossed rolls 11 so that the outer peripheral surface of the embossed roll main body 11a does not come into contact with the surface of the resin molded product 1. I am trying to leave a streak pattern.

In the above embossing, it is preferable that the embossing is performed so that the embossed portion 3 is formed on an area of 20% or more and 80% or less of the entire surface of the surface layer 1b of the resin molded product 1. It is preferably 25% or more and 75% or less, and more preferably 30% or more and 70% or less. By forming the embossed portion 3 on the surface of the resin molded product 1 with such an area ratio, the entire embossed portion 3 looks like an annual ring pattern appearing on the cut surface when the natural wood is cut up and down, and the resin molded product 1 Can be brought closer to the appearance of natural wood. As described above, the resin molded product 1 of the present embodiment can be produced.

Various coating materials may be applied to the resin molded product 1 produced as described above. Examples of the coating material include a transparent paint containing no pigment, a wood grain paint containing a pigment for creating a pattern of natural wood, and a lacquer-like paint containing a pigment for creating a color tone of lacquer. The coating material preferably contains at least one selected from the group consisting of acrylic silicon-based resin, acrylic resin, urethane resin, silicon resin, and fluororesin, and the surface of the resin molded product 1 is required to have slipperiness. It is preferable to contain an acrylic resin in various applications.

The transparent paint and the wood grain paint are preferably applied by a roll coater 20 provided after the embossing apparatus 10 as shown in FIG. In FIG. 5, the roll coater 20 is a resin molded product in which a coating material is applied to the surface of the surface layer 1b of the resin molded product 1 in the process of transporting the resin molded product 1 from the left side to the right side. Each of the upper and lower decorative rolls 21 for sandwiching 1 is provided with a predetermined pressure.

The upper and lower decorative rolls 21 are rotatably supported by shaft branches (not shown), and when the resin molded product 1 is inserted from the left side between these decorative rolls 21 and pulled out to the right side, the resin molded product 1 is pulled out. The upper part and the lower part of 1 are pressed by the upper and lower decorative rolls 21, respectively, and pass between them. Since the coating material adheres to the surface of the decorative roll 21, the coating material adhered to the decorative roll 21 rolls on the surface of the resin molded product 1 so that the coating material adheres to the upper surface of the resin molded product 1. And transferred to the lower surface, a coating material is formed on the upper surface and the lower surface of the resin molded product 1. When the coating material contains a volatile solvent, a coating film is formed by drying the coating material after applying the coating material. These coating materials are not limited to the coating method of applying by the roll coater 20, and may be applied by an operator using a brush or by spray coating, for example. When a lacquer-like paint is used as the coating material, it is preferable that the operator applies it twice or more by brushing. By applying in this way, the texture of lacquer ware can be given to the resin molded product 1.

The coating amount of the coating material ^{is preferably set to 200 g / m 2} or less, more preferably 0.1 g / m ² or more and 100 g / m ² or less, and further preferably 0.2 g / m 2 or more and 50 ^{g / m 2.} It is m ² or less, particularly preferably 0.3 g / m ² or more and 10 g / m ² or less. The coating amount here means the weight of the solid content contained in the coating material, and when the coating material is diluted with a solvent to adjust the viscosity, it means the weight of the solid content excluding the weight of the solvent. The coating amount of the coating material is calculated based on the weight change before and after forming the coating film on the resin molded product 1. By forming the coating film with such a coating amount, the streaks 4a (unevenness) formed on the surface of the resin molded product 1 are not completely covered by the coating film, and the streaks 4a can be formed on the coating film. It can be seen, and this streak pattern 4a looks similar to the streak seen when the natural wood is cut in the longitudinal direction.

Moreover, since the fluffing caused by the roughing process can be suppressed by forming the coating film, it is possible to obtain the resin molded product 1 having a smooth surface texture and a smooth texture. Further, by forming the coating film with the above coating amount, the coating material can be appropriately placed on the streak pattern 4a to obtain a resin molded product having a unique wood texture.

Regarding the above coating amount, when the lacquer-like paint is applied, the coating amount is set higher than when the transparent paint and the wood grain paint are applied. That is, the coating amount of the lacquer-like paint ^{is preferably set to 200 g / m 2} or less, more preferably 50 g / m ² or more and 200 g / m ² or less, and further preferably 80 g / m ² or more and 195 g / m. ² or less, particularly preferably 100 g / m ² or more and 190 g / m ² or less.

The arithmetic average roughness Ra of the surface of the resin molded product 1 after the coating material is applied is preferably 2 μm or more and 30 μm or less, and more preferably 5 μm or more and 20 μm or less. By applying the coating material with a thickness that leaves appropriate irregularities on the surface in this way, the shine of the plastic-like flat surface can be suppressed, and a unique wood texture can be imparted to the surface of the resin molded product.

Further, the difference between the arithmetic mean roughness Ra of the surface of the resin molded product 1 before forming the coating film and the arithmetic mean roughness Ra of the surface of the resin molded product 1 after forming the coating film is 10 μm or less. The difference is preferably 8 μm or less, more preferably 5 μm or less. Normally, when the coating material is applied to a surface having irregularities, the coating material flows into the concave and convex recesses and the irregularities become smooth. However, the above condition is that the coating material is applied to the concave and convex recesses formed on the surface of the resin molded product 1. It stipulates what should be done so as not to flow too much.

As a condition for preventing the coating material from flowing too much into the recesses on the surface of the resin molded product 1, it is considered that a suitable numerical range of the viscosity and temperature of the coating material should be set, but it is blended in the coating material. Since the suitable viscosity and the suitable temperature differ depending on various components, it is difficult to uniformly set the suitable numerical range. Therefore, as a result of various studies by the present inventors, it is considered that the change in the arithmetic mean roughness before and after applying the coating film can be a parameter that can reproduce the unique wood texture, and the preferable numerical range is examined. By overlapping, the upper limit of the change in the arithmetic mean roughness described above was found. That is, by applying a coating material whose various parameters such as temperature and viscosity are adjusted so as to satisfy the difference in the arithmetic mean roughness Ra on the surface of the resin molded product 1, the coating material has irregularities on the surface of the resin molded product 1. The coating film can be formed to follow the above, and the unique wood texture can be reproduced by the surface of the natural wood. On the contrary, when the arithmetic mean roughness after applying the coating material does not satisfy the above numerical range, the coating material flows into the streaks (recesses) of the streaks and is formed by roughing the resin molded product 1. The unevenness of the surface is filled and the surface becomes smooth, and the unique wood texture is impaired.

Further, from the viewpoint of making the appearance of the resin molded product closer to that of natural wood, it is preferable that the maximum height Ry on the surface of the resin molded product 1 is within a predetermined range. Here, the maximum height Ry is the difference between the maximum value and the minimum value of the roughness curve of a predetermined section on the surface of the resin molded product, and when this value is large, it is locally localized in the surface roughness measurement region. It means that a raised convex portion or a locally deeply penetrated concave portion is formed. For example, when the maximum height Ry is large even though the arithmetic mean roughness Ra is low, a locally raised convex portion or a locally deeply penetrated concave portion is formed in the surface roughness measurement region. Therefore, those parts (that is, local uneven parts) may significantly impair the texture of natural wood. From this point of view, the surface of the resin molded product 1 after the coating material is applied preferably satisfies the above arithmetic mean roughness Ra, and further preferably has a maximum height Ry of 30 μm or more and 100 μm or less. It is preferably 60 μm or more and 95 μm or less, and more preferably 80 μm or more and 92 μm or less. By setting the maximum height Ry in such a range, it is possible to suppress the formation of excessively large protrusions and grooves on the surface, the appearance can be made to resemble natural wood, and the muscles have an appropriate depth equivalent to that of natural wood. A pattern is formed and the feel is good.

Further, the difference between the maximum height Ry of the surface of the resin molded product 1 before forming the coating film and the maximum height Ry of the surface of the resin molded product 1 after forming the coating film is 1 μm or more and 50 μm or less. Is preferable. The difference in the maximum height Ry before and after the formation of the coating film here indicates the degree to which the unevenness of the surface of the resin molded product 1 is leveled by the coating film, and the larger the difference in the maximum height Ry, the more the coating film causes. It means that the unevenness of the surface of the resin molded product 1 is smooth. The difference in the maximum height Ry before and after the formation of the coating film is more preferably 3 μm or more and 40 μm or less, and further preferably 8 μm or more and 35 μm or less. By forming the coating film so as to be within the range of the difference as described above, the maximum height and the minimum height on the surface of the resin molded product 1 are maintained even after the coating film is formed, and the wood like natural wood is maintained. You can leave the texture.

In order to further enhance the appearance of the natural wood, it is preferable to adjust the value of the ten-point average roughness Rz on the surface of the resin molded product 1. The ten-point average roughness Rz here is the sum of the average value of the heights of the upper five convex portions of the surface irregularities of the resin molded product in the predetermined section and the average value of the depths of the upper five concave portions. It means that the smaller the ten-point average roughness Rz is, the less the protruding protrusions or recesses are. The presence of the protruding concave portion or convex portion not only impairs the feel of the resin molded product 1, but also impairs the uniformity of the coating film, and thus may impair the appearance. From this point of view, the ten-point average roughness Rz of the surface of the resin molded product 1 before applying the coating film is preferably 30 μm or more and 80 μm or less, more preferably 40 μm or more and 70 μm or less, and further preferably 45 μm. It is 65 μm or more and 65 μm or less. If the value of the ten-point average roughness Rz is too small, the surface may be too smooth and the wood texture may not be obtained.

Further, the difference between the ten-point average roughness Rz of the surface of the resin molded product 1 before forming the coating film and the ten-point average roughness Rz of the surface of the resin molded product 1 after forming the coating film is 1 μm or more and 40 μm. The difference is preferably 3 μm or more and 30 μm or less, and further preferably 4 μm or more and 22 μm or less.

In this embodiment, not only the preferable numerical range of the arithmetic mean roughness Ra but also the preferable numerical range of the maximum height Ry and the ten-point average roughness Rz are focused on, and unevenness satisfying all of these conditions is formed on the surface. Therefore, an appropriate streak pattern 4a that is not too smooth can be formed on the surface of the resin molded product 1. It is considered that the streaks that satisfy all of these surface roughness conditions are as close as possible to those of natural wood, and by applying a coating material on such streaks, the streaks 4a disappear due to the coating material. The streaks are appropriately left on the surface of the resin molded product 1 without being lost, and the texture of natural wood can be obtained.

In the resin molded product 1 of the present embodiment, the embossed portion 3 is formed with a plurality of recesses 3a and convex portions 3b adjacent to the recesses 3a so as to sandwich the recesses 3a from both sides (claim 7). ).

By providing the convex portion 3b adjacent to each of the plurality of concave portions 3a as in the above configuration, the feel of the resin molded product 1 can be made closer to the texture of natural wood. Further, since the convex portion 3b that rises above the surface of the resin molded product 1 is formed, the anti-slip property of the resin molded product 1 can be improved. Moreover, since the convex portions 3b are provided on both sides of the concave portion 3a, for example, even if a large amount of water adheres to the surface of the resin molded product 1, the adhered water flows from the convex portion 3b into the concave portion 3a. Water concentrates in the recess 3a and is easily drained to the outside through the recess 3a. As a result, the upper surface of the resin molded product 1 becomes easy to dry, and the resin molded product 1 having good drainage property suitable for installation outdoors can be obtained.

The resin molded product 1 of the present embodiment has a base member 1a and a surface layer 1b formed on the surface of the base member 1a, and the base member 1a and the surface layer 1b are each made of a synthetic resin mixed with wood powder. Since the base member 1a is composed of a powder-blended resin and has a higher wood powder content than the surface layer 1b, the base member 1a can be made difficult to be deformed, and the surface layer 1b can be easily deformed. be able to. By forming the easily deformable surface layer 1b on the surface of the base member 1a which is hard to be deformed in this way, the entire resin molded product is deformed by pressing with the embossing roll when the resin molded product 1 is embossed. Instead, the embossed portion 3 (unevenness) can be formed on the surface layer 1b.

<Embodiment 2>
The resin molded product 31 of the present embodiment is the same as that of the first embodiment except that a lacquer-like paint is applied instead of the roughing process of the first embodiment as shown in FIG. That is, in the present embodiment, the resin molded product 31 is manufactured by applying a lacquer-like paint after embossing without roughening.

In the resin molded product 31 of the present embodiment, the streak pattern 4a is not formed in the non-embossed portion 4 because the roughening process is not performed, so that the plastic feeling peculiar to the resin molding remains on the surface. The plastic feeling can be hidden by repeatedly applying a lacquer-like paint to the non-embossed portion 4. As a result, it is possible to obtain a resin molded product having an appearance as if it were lacquered on natural wood. The amount of the lacquer-like paint applied is preferably the same as the amount described in the first embodiment.

<Embodiment 3>
The resin molded product of the present embodiment is the same resin molded product as that of the first embodiment except that the order of the roughing process and the embossing process is changed from that of the first embodiment. That is, in the first embodiment, a streak pattern and an embossed portion are formed on the surface of the resin molded product by performing the roughing process and then the embossing process. However, the embossing process is performed as in the present embodiment. Roughing may be performed later. By first embossing the resin molded product and then forming a streak pattern by the roughing process, it is possible to prevent the streak pattern due to the roughing process from being crushed by the embossing process. By performing the embossing process and then the roughing process in this way, the same product as the resin molded product of the first embodiment can be obtained.

When roughing is performed after forming the embossed portion as in the present embodiment, the depth of the concave portion formed in the embossed portion is 100 μm from the viewpoint of avoiding that the unevenness formed in the embossed portion becomes inconspicuous due to the roughing process. The above is preferable. Since the concave portion having such a depth is one size larger than the streak pattern obtained by the roughing process, the concave portion of the embossed portion does not disappear by the roughing process and becomes conspicuous.

Next, an experiment conducted to confirm the effect of improving the appearance of the resin molded product 1 of the above embodiment will be described. In Examples 1 to 6 and Comparative Examples 1 to 3 below, the resin molded product 1 was produced by changing the presence / absence of roughing, the presence / absence of embossing, and the area ratio of the embossed portion.

(Example 1)
As Example 1, a resin molded product 1 having a two-layer structure as shown in FIG. 1 was processed into a test piece having a width of 145 mm and a length of 1 m. The blending ratio of wood powder in the surface layer 1b was 10%, and the blending ratio of wood flour in the base member 1a was 30%. Then, the side surface and the upper and lower surfaces of the resin molded product 1 were roughened using sandpaper # 40.

Next, the resin molded product 1 of Example 1 was produced by embossing the surface of the resin molded product 1 after the roughening process using the embossing apparatus shown in FIG. The embossing was performed by heating the upper and lower embossing rolls 11 of the embossing apparatus 10 shown in FIG. 4 to 110 ° C. and then passing the resin molded product 1 between the upper and lower embossing rolls 11.

As the embossing roll 11 here, one in which the embossing portion 11b is provided in a region of 20% of the outer peripheral surface of the embossing roll main body portion 11a is used. The embossed portion 11b is formed with irregularities in which a plurality of convex portions are raised with respect to the outer peripheral surface of the embossed roll main body 11a, and the convex portions in the irregularities are formed on the outer peripheral surface of the embossed roll main body 11a. It had a height of 200 μm or more and 400 μm or less.

The resin molded product 1 is made so that only the upper portion of the convex portion formed on the embossed portion 11b is pressed against the surface of the resin molded product, that is, the outer peripheral surface of the embossed roll main body portion 11a does not come into contact with the resin molded product. The embossed portion 3 was formed on an area of 20% of the surface of the above. In the embossed portion 3, the streak pattern due to the roughing process disappeared, and unevenness having a coarser unevenness than the streak pattern due to the roughing process was formed. This rough unevenness had a concave portion and a convex portion adjacent to each concave portion so as to sandwich the concave portion from both sides. On the other hand, a region (region having an area ratio of 80%) other than the embossed portion 3 on the surface of the resin molded product 1 became the non-embossed portion 4. A streak pattern 4a due to roughing remained in the non-embossed portion 4.

In this way, the embossed portion 3 and the non-embossed portion 4 are formed on the surface of the resin molded product 1 of Example 1, and the surface roughness of the non-embossed portion 4 is referred to as "handysurf E-35A" manufactured by Tokyo Seimitsu Co., Ltd. The measurement was performed using the mobile surface roughness measuring device of the model. The measurement conditions are that the cutoff value is 2.5 mm, the evaluation length is 12.5 mm, and the pickup of the measuring instrument is moved along the direction orthogonal to the longitudinal direction of the streak pattern formed on the resin molded product 1. By performing the operation at five different locations in the non-embossed portion 4 of the resin molded product 1, the arithmetic mean roughness Ra, the maximum height Ry, and the ten-point average roughness Rz of the non-embossed portion 4 at the five locations are measured, respectively. did. When the average of the three measured values excluding the maximum value and the minimum value among these measured values was calculated, in Example 1, the arithmetic average roughness Ra of the non-embossed portion 4 after the roughing process was 16.5 μm. The maximum height Ry was 91.1 μm, and the ten-point average roughness Rz was 64.0 μm.

Next, the resin molded product 1 was cut on a plane perpendicular to the longitudinal direction, and the vicinity of the surface of the resin molded product 1 on the cut surface was magnified and observed with a microscope to obtain an enlarged image thereof. Based on the image, the depth of the concave portion and the height of the convex portion formed in the embossed portion of the resin molded product 1 were calculated. The concave portion in the unevenness had a depth of 50 μm or more and 250 μm or less with respect to the surface of the resin molded product 1, and the convex portion had a height of 40 μm or more and 200 μm or less with respect to the surface of the resin molded product 1. Further, the maximum value of the depth x of the concave portion was 250 μm, and the maximum value of the height y of the convex portion was 200 μm. The results are shown in the "Emboss" column of Table 1.

(Example 2)
Using the roll coater 20 shown in FIG. 5, the resin molded product of Example 2 was produced by applying an acrylic resin-based transparent paint to the surface of the resin molded product produced in Example 1. The application of the transparent paint here was carried out by passing a resin molded product between the upper and lower decorative rolls 21 of the roll coater 20. By volatilizing the solvent in the transparent paint applied in this way, a transparent coating film was formed on the surface of the resin molded product 1.

Further, the amount of the transparent coating film formed on the resin molded product 1 is calculated by measuring the weight change before and after applying the transparent paint on the surface of the resin molded product 1, and it is calculated by the area of the outer surface of the resin molded product 1. By dividing, the weight of the transparent coating film per ^{1 m 2 was calculated.} The amount of the transparent coating film applied was 20 g / m ² as shown in the “Film thickness” column of Table 1.

The surface roughness of the non-embossed portion was measured on the surface of the resin molded product 1 of Example 2 by the same measuring method as in Example 1 above. The arithmetic average roughness Ra of the resin molded product 1 after forming the transparent coating film was 15.4 μm, the maximum height Ry was 81.8 μm, and the ten-point average roughness Rz was 59.8 μm. Further, the maximum value of the depth x of the concave portion and the maximum value of the height y of the convex portion in the embossed portion were calculated by the same measurement method as in Example 1 above. In the following Examples 3, 4 and 6, similarly, the surface roughness of the resin molded product after forming the coating film, the amount of the coating film, the maximum value of the depth x of the concave portion, and the height y of the convex portion. The maximum value was measured. The results are shown in each column of Table 1.

(Example 3)
Using the roll coater shown in FIG. 5, the resin molded product of Example 3 was produced by applying an acrylic silicon resin-based wood paint to the surface of the resin molded product produced in Example 1. The application of the wood paint here was carried out in the same manner as the application of the transparent paint of Example 2 above. The wood paint used contains a pigment for creating a pattern of natural wood, and the wood paint is applied by a roll coater 20 so that the surface of the resin molded product 1 has a wood grain tone, and the solvent in the wood paint is applied. By volatilizing, a wood grain coating was formed on the surface of the resin molded product 1.

(Example 4)
A resin molded product was produced by applying a urethane resin-based lacquer-like paint to the surface of the resin molded product produced in Example 1. The lacquer-like paint used here contains a pigment for creating the color tone of lacquer, and the lacquer-like paint is applied to the surface of the resin molded product three times with a brush to give the texture of lacquer. The surface to be brewed.

(Example 5)
In Example 5, the embossing was performed using the embossing roll 11 in which the embossing portion 11b was provided in 80% of the outer peripheral surface of the embossing roll main body portion 11a, except that the embossing was performed. The resin molded product of Example 5 was produced in the same manner as in Example 1.

(Example 6)
In Example 6, a resin molded product was produced in the same manner as in Example 4, except that the roughing process was omitted in the step of producing the resin molded product of Example 4.

(Comparative Example 1)
A resin molded product of Comparative Example 1 was produced in the same manner as in Example 1 except that the roughing process was performed and then the embossing process was not performed. That is, Comparative Example 1 is a resin molded product 1 in which the surface is only roughened.

(Comparative Example 2)
A resin molded product of Comparative Example 2 was produced in the same manner as in Example 1 except that only embossing was performed without roughening. That is, Comparative Example 2 is a resin molded product 1 whose surface is only embossed.

(Comparative Example 3)
In Comparative Example 3, the embossing process was performed using the embossing roll 11 provided with the embossing processing portion 11b on the entire outer peripheral surface of the embossing roll main body portion 11a, except that the embossing process was performed in the same manner as in the first embodiment. A resin molded product was produced. In Comparative Example 3, by using such an embossing roll 11, a resin molded product in which the embossed portion 3 was formed on the entire surface was produced.

(Evaluation)
The appearance and water-drainability of the resin molded products of each Example and each Comparative Example produced in this manner were evaluated. The results are shown in the "Appearance" and "Water drainage" columns of Table 1 below. The water-drainability was evaluated in response to the need to dry the surface of the resin-molded product at an early stage when the resin-molded product is used as a deck material on which a person walks or sits, and the resin has good water-drainability. It means that the molded product is more suitable for use as a deck material. “⊚”, “〇”, “Δ”, and “×” described in “Appearance” in Table 1 above are evaluation results of the appearance of the resin molded product 1. The appearance is evaluated as "◎" when the appearance of the resin molded product is equivalent to that of natural wood, "○" when it can be seen that it is not natural wood, and "△" when it is inferior to natural wood. , The case where the wood is clearly different from the natural wood and the plastic feeling remains is evaluated as "x". Further, "○" and "×" described in the column of "water drainage" in Table 1 indicate good or bad water drainage. The water-drainability was evaluated by sprinkling water on the upper surface of the resin molded product for 30 minutes and observing the degree of dryness of the upper surface 1 hour after the completion of watering. Then, the water-drainability when almost no water was left (dry) from the upper surface after 1 hour was evaluated as "○" (good), and the water-drainability when a large amount of water remained was evaluated as "x" (impossible).

(Discussion)
The reason why the evaluation results in Table 1 above were obtained will be considered. First, comparing Examples 1 to 5 with Comparative Examples 1 and 2, even though resin molded products having the same material and structure are used, only one of roughing and embossing is lacking. It can be seen that the appearance is significantly deteriorated.

For example, the appearance of the resin molded products of Examples 1 to 5 that have been subjected to both roughing and embossing is "◎" or "○", whereas the appearance of the resin molded product that has not been embossed is "◎" or "○". Both the resin molded product and the resin molded product of Comparative Example 2 which has not been roughened have an appearance of "x". From this, it can be seen that in order to produce a resin molded product having an appearance equivalent to that of natural wood, it is essential to perform both roughing and embossing in this order. However, when the lacquer-like paint is applied as in Example 6, the appearance equivalent to that of natural wood can be obtained without exceptionally roughening. The reason for this is probably that the lacquer-like paint is applied to the thick film as compared with other coating materials, and the lacquer-like coating film hides the flat surface having a plastic feeling peculiar to resin molding. ..

Further, from the results of Comparative Example 3, even if both roughing and embossing are performed, good evaluation results cannot be obtained in appearance when embossing is performed on the entire surface of the resin molded product. I understood. It is considered that the reason for this is that when the entire surface of the resin molded product 1 is embossed, all the streak patterns 4a due to the roughing process are crushed by the embossing process and disappear. Therefore, in order to obtain a resin molded product having a good appearance, it can be said that it is necessary to perform embossing so that the streak pattern 4a due to the roughing process remains even a little. Then, as far as Examples 1 and 5 are compared with Comparative Examples 1 and 3, in order to obtain a good appearance, the area of the embossed portion (that is, the embossed portion 3) should be 20% or more and 80% or less. What to do is derived.

Further, in the resin molded products of Examples 1 to 5 and Comparative Example 3 in which both roughing and embossing were performed, the water drainage property was "○", whereas in Comparative Example 1 and only roughing. In the resin molded products of Example 6 and Comparative Example 2 in which only embossing is performed, the water drainage property is "x". The reason for this is that the streaks formed by the roughing process allow the water adhering to the surface of the resin molded product to become familiar with the surface and spread easily, and the unevenness formed by the embossing process causes the water to be discharged to the outside. It is considered that this is due to the fact that it became easier for water to remain on the surface of the resin molded product. From this, it was clarified that both the roughing process and the embossing process are indispensable in order to obtain a resin molded product having good water drainage property.

(Modification example)
In the above embodiment, the case where the paint is applied to the surface of the resin molded product by the roll coater has been described, but the method of applying the paint is not limited to the roll coater, and various types such as brush coating, gravure coater, spin coater, and spray coating are used. The coating method of can be used.

In each of the above embodiments, the resin molded product 1 having a ladder-shaped hollow cross section has been illustrated, but the resin molded product 1 of the present invention can have various cross-sectional shapes, for example, a resin having a solid cross section. It may be a molded product 1.

In each of the above embodiments, a resin molded product 1 having a two-layer structure having a base member 1a and a surface layer 1b has been exemplified, but the resin molded product 1 of the present invention is not limited to the two-layer structure, and is, for example, a single-layer structure. May be good.

In each of the above embodiments, the resin molded product 1 extending straight in the longitudinal direction has been illustrated, but the resin molded product of the present invention is not limited to a product that extends linearly, and may have a shape that extends while being curved along a curve, for example. Good. Further, the width dimension of the resin molded product 1 does not have to be constant, and may have different widths depending on the location.

In the above embodiment, the embossed portion is formed on the surface of the resin molded product 1 by heating the embossed roll 11, but the method is not limited to such an embossed portion forming method, and the surface layer 1b of the resin molded product 1 is heated. After making the surface of the surface layer 1b easily deformable, the embossed portion may be formed by rolling the embossed roll while pressing the embossed roll having the wood grain pattern on the surface.

1, 31 Resin molded product 1a Base member 1b Surface layer 3 Embossed part 3a Concave part 3b Convex part 4 Non-embossed part 4a Streak pattern 10 Embossing device 11 Embossed roll 11a Embossed roll body part 11b Embossed part 20 Roll coater 21 Decorative roll

Claims (8)

It is a resin molded product that imitates wood.
Embossed and non-embossed parts are alternately formed on the surface.
A streak pattern is formed on the non-embossed portion by roughing, and the arithmetic average roughness Ra of the non-embossed portion is set to 2 μm or more and 30 μm or less .
The embossed portion is formed with a plurality of recesses and convex portions adjacent to the recesses so as to sandwich the recesses from both sides.
The maximum value of the depth of the recess is 50 μm or more and 1000 μm or less.
A resin molded product in which the maximum value of the height of the convex portion is 40 μm or more and 800 μm or less, and less than the maximum value of the depth of the concave portion. The resin molded product according to claim 1, wherein a coating material is applied to the embossed portion and the non-embossed portion. The resin molded product has a base member and a surface layer formed on the surface of the base member.
The base member and the surface layer are each composed of a wood powder-blended resin in which wood powder is mixed with a synthetic resin.
The resin molded product according to claim 1 or 2 , wherein the base member has a higher content of wood powder than the surface layer. The first step of forming a streak pattern on the surface of a resin molded product by roughing,
The resin molding is performed by partially embossing the surface of the resin molded product using an embossed roll including a cylindrical roll main body portion and an embossed portion raised outward from the outer peripheral surface of the roll main body portion. Including a second step of alternately forming embossed portions and non-embossed non-embossed portions on the surface of the product.
In the first step, the roughing process is performed so that the arithmetic mean roughness Ra of the non-embossed portion is 2 μm or more and 30 μm or less.
The embossed portion of the embossed roll is formed with irregularities that are coarser than the streak pattern.
In the second step, the surface of the roll main body is separated from the surface of the resin molded product, and the embossed portion is pressed against the surface of the resin molded product so as to sandwich the plurality of recesses and the recesses from both sides. A method for manufacturing a resin molded product, in which a convex portion adjacent to each concave portion is formed in the embossed portion. The method for producing a resin molded product according to claim 4 , further comprising a third step of applying a coating material to the non-embossed portion and the embossed portion. The method for producing a resin molded product according to claim 4 or 5 , wherein the embossing process and the roughing process are performed on the resin molded product in this order. The method for producing a resin molded product according to claim 4 or 5 , wherein the roughing process and the embossing process are performed on the resin molded product in this order. The maximum value of the depth of the recess is 50 μm or more and 1000 μm or less.
The method for producing a resin molded product according to any one of claims 4 to 7, wherein the maximum value of the height of the convex portion is 40 μm or more and 800 μm or less, and less than the maximum value of the depth of the concave portion.

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